MODULE 13 INDUSTRIAL CHEMISTRY CHEMISTRY I. Industrial Chemistry By
Dr. Dr. Hele Helen n Nje Njeri ri Njen Njenga ga,, Uni Unive versi rsity ty of Nairob Nairobii and and William Wanasolo
II. rere!uisite C"urses "r #n"$led%e Module 5
Module 6
Module !
Module $
Unit I
Basic Organic Chemistry
Unit II
Hydrocarbons
Unit III
Alkyl halides
Unit IV
Amines
Unit I
Alcohols and ethers
Unit III
Carboxylic acids and their deriaties
Unit I
Ben"ene and its deriaties
Unit III
Heterocyclic com#ounds %hermodynamics Chemical #rinci#les o& ariable constituents
III. Time %his unit 'ill re(uire )*+ hours Unit Unit I, Introduc Introduction tion to industr industrial ial chemist chemistry ry and the chemica chemicall industr industry y -)5 hrs.
Unit *, Unit O#erations and Unit /rocesses -*+ hrs.
Unit 0, Industrial Inorganic Chemistry I -1xtractie Metallurgy. -)+ hrs.
Unit 2,Industrial Inorganic Chemistry II -Chlor3alkali4 Ammonia4 ul#huric Acid4 ertili"er ertili"er and and Cement. Cement. -*+ hrs. hrs.
1
Unit Unit 5, Industri Industrial al Organic Organic Chemist Chemistry ry I -/etrol -/etroleum4 eum4 /etroch /etrochemic emicals als and /olymers. -*5 hrs.
Unit Unit
6,
Indu Indust stri rial al
Orga Organi nic c
Chem Chemis istr try y
II
-er -erme ment ntat atio ion4 n4
1tha 1thano nol4 l4
/harmaceuticals4 oa#s and 7etergents. -*5 hrs.
I&. Materials 8ou 'ill re(uire the &ollo'ing tools and resources &or com#leting the module9 Com#uter4 C73:OM4 and e3library •
%o access this module4 exams and other releant material
•
%o access other suggested re&erence materials
•
or interactie discussions;chat sessions
:ecommended textbooks and re&erence materials •
%o assist learning and &urther understanding o& to#ics in the module
&. M"dule Rati"nale
Industrial chemistry deals 'ith commercial #roduction o& chemicals and related #roducts &rom natural ra' materials and their deriaties, It enables humanity to ex#erie ex#erience nce the bene&it bene&its s o& chemist chemistry ry 'hen 'hen 'e a##ly a##ly it in the ex#loitat ex#loitation ion o& materi materials als and and energ energy y,
2
inoled4 'e &ind it easier to study industrial inorganic and industrial organic chemistry se#arately4 %hrough the electrolysis o& brine4 'e obtain chlorine and sodium hydroxide both o& 'hich are im#ortant reactants in organic synthesis o& #roducts such as #etrochemicals and detergents res#ectiely, By &ixing nitrogen4 'e obtain ammonia4 &rom 'hich 'e can make &ertili"ers, rom sul#hur4 'e get sul#huric acid4 'hich 'e use4 in the manu&acture o& #hos#hate &ertili"ers, Mineral ores as 'ell as being ra' materials &or basic chemicals are the source o& #ure metals4 'hich 'e use else'here in building and construction4 manu&acture o& e(ui#ment4 machines and =e'ellery, %urning no' to organic chemical industry4 'e use use #etr #etrol oleu eum m as the the sour source ce o& #etr #etroc oche hemi mica cals ls and and synt synthe heti tic c #oly #olyme mers rs,, ermentation enables us to conert natural organic materials into chemicals4 some like #enicillin #enicillin being #harmaceutical #harmaceutical ingredients, ingredients, rom natural oils and &ats4 'e obtain soa#s and detergents,
VI, Oerie' %his module starts by de&ining industrial chemistry and then gies a ie' o& the chemical industry4 its #osition in the general economy4 and its classi&ication in terms o& the chemical #rocesses that characteri"e it, %o enable the study o& selected selected chemica chemicall #rocess #rocesses4 es4 unit o#erati o#erations ons and unit #rocess #rocesses4 es4 es#ecial es#ecially ly those that are releant in later learning actities4 actities4 are then coered in Unit *,
3
the study o& ethanol4 #harmaceuticals4 soa#s and detergents, %hese are high alue3added #roducts4 some o& 'hich are #roduced through the &ermentation route, '.1 (utline Unit 1) Intr"du*ti"n t" Industrial Chemistry +1, h"urs
Introduction to industrial chemistry
Classi&ication o& the chemical industry
:a' materials &or the chemical industry
Unit o#erations and unit #rocesses that make u# chemical #rocesses
lo' diagrams
Material and energy balances
Unit ) Unit "/erati"ns and unit /r"*esses +0 H"urs
i"e reduction and si"e enlargement
Magnetic and electrostatic se#aration
roth &lotation
ractional distillation
Unit #rocesses
Unit 3) In"r%ani* Industrial Chemi*al Industries art I) Etra*ti2e metallur%y +10 H"urs
Mineral ores
Ore dressing
/yro#rocessing
:e&ining
1xtractie metallurgy o& iron
1xtractie metallurgy o& aluminium
1xtractie metallurgy o& co##er
4
Unit ) In"r%ani* Chemi*al industries art II) Chl"r4al5ali6 Amm"nia6 Sul/huri* A*id6 7ertili8er6 Cement +, h"urs
odium hydroxide and Chlorine Ammonia
ul#huric acid
ertili"er
Cement
Unit ,) (r%ani* Chemi*al IndustriesI ) etr"leum6 etr"*hemi*als and "lymers +, h"urs
/etroleum #rocessing
/etrochemicals
/olymers
Unit
')
(r%ani*
Chemi*al
Industries
II
7ermentati"n6
Ethan"l6
harma*euti*als6 S"a/s and Deter%ents +, h"urs
ermentation
1thanol
/harmaceuticals
oa#s and detergents
'. 9ra/hi* (r%ani8er Industrial Chemistry
9eneral Industrial Chemistry
Industrial In"r%ani* Chemistry 5
Industrial (r%ani* *hemistry
Intr"du*ti"n
t" industrial *hemistry and *hemi*al
Unit "/erati"ns
industry
and unit /r"*esses
Etra*ti2e metallur%y
Chl"r4al5ali6 amm"nia6 sul/huri* a*id6
etr"leum6 /etr"*hemi*al s and /"lymers
7ermentati"n6 ethan"l6 /harma*euti*al s6 s"a/s and deter%ents
&II. 9eneral (:;e*ti2e+s At the end o& this module you should be able to9 i,
Classi&y the chemical industry in terms o& #roducts4 ra' materials4 scale and ty#es o& trans&ormations,
ii,
7escribe the o#eration #rinci#les o& selected unit o#erations and unit #rocesses,
iii,
7escribe metal extraction in general and the extractie metallurgy o& iron4 aluminium and co##er in #articular,
i,
7iscuss 'ith the hel# o& releant &lo' diagrams4 e(uations4 o#erating conditions and e(ui#ment #rinci#les4 the manu&acture o& chlorine4 sodium hydroxide4 ammonia4 sul#huric acid4 &ertili"er and cement,
,
1x#lain using &lo' diagrams and e(uations4 ho' crude oil is re&ined4 and ho' some #etrochemicals and #olymers are synthesi"ed,
i,
7iscuss &ermentation theory and its a##lication in ethanol manu&acture4 the #roduction o& some #harmaceuticals4 soa#s and detergents,
&III. S/e*i
At the end o& this unit4 you should be able to9 a, 7istinguish bet'een classical and industrial chemistry
6
b, Classi&y the chemical industry in terms o& scale4 ra' materials4 end use and alue addition c, 7istinguish bet'een unit o#erations and unit #rocesses d, 7escribe chemical #rocesses by means o& &lo' diagrams e, Carry out material balances &or a sim#le #rocess
Unit ) Unit (/erati"ns and Unit r"*esses
At the end o& this unit you should be able to9 a, >ist the arious reasons &or undertaking si"e reduction and enlargement in the chemical industry b, 7escribe the o#eration #rinci#les o& some si"e reduction e(ui#ment and si"e enlargement e(ui#ment c, 1x#lain ho' industrial materials can be se#arated on the basis o& their magnetic4 electrostatic4 hydro#hobic and olatility di&&erences res#ectiely d, 7iscuss
arious
organic
unit #rocesses
including
#olymeri"ation4
alkylation4 hydrolysis and their a##lication in the chemical industry, Unit 3) In"r%ani* Chemi*al Industries art I) Etra*ti2e Metallur%y
At the end o& this unit you should be able to9 a, 7escribe the arious stages mineral ores go through in a ty#ical mineral ore dressing #rocess, b,
Unit ) In"r%ani* *hemi*al Industries art II) Chl"r4al5ali6 Amm"nia6 Sul/huri* A*id6 7ertili8er6 Cement
At the end o& this unit you should be able to
7
a, 7escribe using e(uations and diagrams4 the electrolytic #rocess &or the #roduction o& sodium hydroxide and chlorine using mercury4 dia#hram and membrane cells b, 1x#lain ho' ammonia is manu&actured &rom methane and air by the Haber #rocess c, 7escribe the Contact #rocess &or the manu&acture o& sul#huric acid d, 7iscuss the arious ty#es o& &ertli"ers and the manu&acture o& #hos#hate &ertili"er e, 7escribe using diagrams4 e(uations and unit o#erations4 &or the manu&acture o& /ortland cement,
Unit ,) (r%ani* Chemi*al Industries art I) etr"leum6 etr"*hemi*als and "lymers
At the end o& this unit you should be able to9 a, 7iscuss the occurrence and extraction o& #etroleum b, 1x#lain the #ur#oses and a##lication o& &ractional distillation4 catalytic cracking and catalytic re&orming during #etroleum #rocessing c, 7escribe using e(uations and &lo' diagrams4 the manu&acture o& some #etrochemicals4 namely4 #hthalic anhydride and adi#ic acid d, Categori"e #lymeri"ation reactions4 #olymers and #olymer #roducts e, 7escribe the uses o& arious #lastics &, 1x#lain ho' #olyethylene and styrene butadiene rubber are manu&actured
Unit ') (r%ani* Chemi*al Industries art II) 7ermentati"n6 Ethan"l6 harma*euti*als 6 S"a/s and Deter%ents
At the end o& this unit you should be able to9 a, 7iscuss &actors that a&&ect the iability o& the &ermentation route and those that a&&ect &ermentation yield b, 7escribe the #rocess o& manu&acuring &ermentation ethanol c, ?ie a brie& history o& the #harmaceutical industry and the role #layed by antibiotics
8
d, 7escribe #roduction #rocess o& t'o #harmaceuticals9 #enicilin and as#irin e, Outline the soa# manu&acturing #rocess &, 7iscuss the arious ty#es o& sur&actants g, 1x#lain ho' detergents are manu&actured
I=. re4assessment Title "< reassessment) Industrail Chemistry /re3assessment %est
>.1 Rati"nale
%he #ur#ose o& this test is to assess your current chemistry kno'ledge that is a #rere(uisite &or success&ul learning o& this module, %o do this test4 you 'ill re(uire9 ), A calculator *, A list o& the elements 'ith symbols4 atomic numbers and atomic masses 0, Conersion tables &or scienti&ic units
?UESTI(NS
), Coert the &ollo'ing9 a. )2+ o to oC b. * atm to k/a c. 5+ kcal to k@ d. +,0 kmoles sodium carbonate to g sodium carbonate *, Calculate the nitrogen in each o& the &ollo'ing nitrogen &ertili"ers, a. Ammonium nitrate b. Ammonia c. 7iammonium #hos#hate 0,
*e*O0
b. Cl* D *EaBr
*EaCl D Br *
c. H* D Cl*
*HCl
9
2, +,)+0g sam#le o& EH 2EO0 re(uired )*,Fml o& +,)+)M EaOH &or neutrali"ation,
*GnO-s. D *O *-g.
Horxn 3F!$k@
-b. Calculate the molarity o& 05,2 mass;olume a(ueous solution o& #hos#horic acid -H 0/O2., F, 1x#lain ho' the #resence o& a catalyst aids the #rogress o& the &ollo'ing reaction9 A D B
CD7
$, -a.
/Cl0-g. D Cl * -g.
-b.
.. Ans$er 5ey ?uesti"n
), a b c d *, a b
Ans$er
Mar5s
6+oC *+*,65k/a *+$ k@ 0),Fkg
) ) ) )
05,++ F*,05
) )
10
c 0, a b c d 2, 5, 6, !, a b $,
)+, a, b )+ a, b, T(TAL
2+,6
)
O* Cl* * Cl* $$,5$ CaCO0 CaO CaO D H*O Ca-OH.* It has both acidic and basic #ro#erties
) ) ) ) 0 ) ) )
2,5)k@ 2,*)M %he catalyst lo'ers the actiation energy4 'hich is the minimum energy re(uired to initiate a chemical reaction
* * *
K/Cl0LKCl*L;K/Cl 5L +,+2
) *
*F+4+++ 2,))litres
) 0 30
=. #ey Concepts ), Al5ylati"n is the introduction o& an alkyl radical by substitution or addition into an organic com#ound, *, Anti:i"ti*s are chemical substances that can inhibit the gro'th o&4 and een destroy4 harm&ul microorganisms, 0, Catalyti* *ra*5in% is the breaking u# o& com#lex hydrocarbons into sim#ler molecules in order to increase the (uality and (uantity o& lighter4 more desirable #roducts and decrease the amount o& residuals, 2, Catalyti* re<"rmin% is a #rocess used to conert lo'3octane na#hthas into high3octane com#ounds such as toluene4 ben"ene4 xylene4 and other
11
aromatics 'hich are use&ul in gasoline blending and #etrochemical #rocessing, 5, Emulsi"n /"lymeri8ati"n is a &ree radical #olymeri"ation that take #lace in an emulsion consisting o& 'ater4 monomer4 sur&actant and other addities, 6, 7ermentati"n is a reaction 'herein a ra' material is conerted into a #roduct by the action o& micro3organisms or by means o& en"ymes, !, 7ertili8ers are chemical com#ounds gien to #lants to #romote gro'th F, Industrial *hemistry as the branch o& chemistry 'hich a##lies #hysical and chemical #rocedures to'ards the trans&ormation o& natural ra' materials and their deriaties to #roducts that are o& bene&it to humanity, $, Material :alan*e is the a##lication o& the la' o& conseration o& mass in the &orm o& e(uations to satis&y balances o& total masses4 com#onents and atomic s#ecies through a #rocess, )+, (re dressin% is the #re3treatment o& mineral ores by mainly #hysical #rocesses to e&&ect the concentration o& aluable minerals and to render the enriched material into the most suitable #hysical condition &or subse(uent o#erations, )), lasti* is a material that contains as an essential ingredient4 an organic substance o& a large molecular 'eight4 is solid in its &inished state4 and4 at some stage in its manu&acture or in its #rocessing into &inished articles4 can be sha#ed by &lo', )*, Sur
12
)0, Unit "/erati"ns are the #hysical treatment ste#s em#loyed in chemical #rocesses to trans&orm ra' materials and #roducts into re(uired &orms, )2, Unit /r"*esses are the chemical trans&ormations or conersions that are #er&ormed in a #rocess,
XI. Compulsory Readings Readin% @ 1 C"m/lete re
htt#9;;en,'iki#edia,org;Chemicalindustry
A:stra*t) %he chemical industry com#rises the com#anies that #roduce
industrial chemicals, It is central to modern 'orld economy4 conerting ra' materials -oil4 natural gas4 air4 'ater4 metals4 minerals. into ery many di&&erent #roducts, In this site chemical #roducts are categori"ed and can be searched by /roduct name4 /roduct Category4 %echnology etc, :elated links and re&erences are also gien,
Rati"nale) Unit I o& this module deals 'ith general classi&ication and com#osition
o& the chemical industry, Visits to this site 'ill enable you to see ho' 'ide is the &ield o& chemical manu&acturing,
Readin% @ C"m/lete re
encyclo#edia htt#9;;en,'iki#edia,org; 1mulsion#olymeri"ation A:stra*t) %his site gies the history4 theory4 manu&acturing #rocess and arious
ingredients -monomers4 co3monomers4 initiators4 sur&actants4 non3sur&actant stabili"ers4 other ingredients. and a##lications o& emulsion #olymeri"ation, In&ormation on arious #olymers #roduced by emulsion #olymeri"ation can be accessed &rom this site,
13
Rati"nale) 1mulsion #olymeri"ation theory is studied in Unit * and a##lied in
Unit 5 o& the manu&acture o& t'o #olymers, %his site 'ill ex#ose you to much more in&ormation on #olymeri"ation, Readin% @ 3 C"m/lete
re
1xtractie
metallurgy9
rom
the
&ree
encyclo#edia htt#9;;en,'iki#edia,org;1xtractiemetallurgy A:stra*t) %his site gies de&initions and brie& discussions on the basic
technologies used in metal extraction, %hese include mineral #rocessing #yrometallurgy and hydrometallurgy, 1xtractie metallurgy o& arious metals can be accessed &rom this site, Rati"nale) %he site and its links gie a good oerie' o& extractie metallurgy, It
su##lements in&ormation gien in Unit 0 on extractie metallurgy o& co##er4 aluminium and iron,
Readin% @ C"m/lete re
htt#9;;en,'iki#edia,org;ertili"er Des*ri/ti"n) Here you 'ill &ind the history o& the &ertili"er industry4 in&ormation on
macronutrients and micronutrients4 nitrogen &ertili"ers and organic &ertili"ers, >inks to related to#ics are gien, Rati"nale) %his reading 'ill su##lement 'hat is #roided in this module under
the sub=ect o& &ertili"er,
=II. C"m/uls"ry Res"ur*es C"m/lete re
/7 &iles9 aluminium,#d& chlor3alkali and aluminium electrolysis,#d& haber ammonia synthesis,#d& ammonia next ste#,#d&
14
cement,#d& nitric acid and adi#ic acid,#d& )+@ #olyethylene,#d& +$13B:/olymerummary@uly)6,#d& antibiotics #roduction,#d& soa#s and detergents,#d& A:stra*t) %he aboe &iles #roide reading materials4 'hich hel# you as
su##lementary resource materials &or this module, Rati"nale) %hese resource materials gie detailed ex#lanations on theory4
manu&acturing #rocesses and other in&ormation on some o& the #roducts coered in this module, %hese #roducts include aluminium4 ammonia4 cement4 adi#ic acid4 #olyethylene4 styrene butadiene rubber4 antibiotics4 soa#s and detergents,
=III. Use
7escri#tion9 This $e:site e*lusi2ely deals $ith /r"*ess
:ationale9 The site *an in*rease y"ur understandin% and a//re*iati"n "< h"$ /r"*ess des*ri/ti"ns are /resented in the <"rm "< dia%rams.
Use&ul >ink * Title) H"$ r"du*ts are made URL) ''',madeho',com
creen ca#ture
15
Des*ri/ti"n) %his site gies ex#lanations and details o& manu&acturing
#rocesses &or a 'ide ariety o& #roducts including some chemicals, %he site #roides ste# by ste# descri#tions o& the manu&acturing #rocess com#lemented 'ith illustrations and diagrams, 1ach #roduct also has related in&ormation such as background and history4 ho' the item 'orks4 ra' materials that are used4 #roduct a##lications4 by3#roducts generated4 #ossible &uture deelo#ments4 (uality control #rocedures4 etc, %here are seen olumes in 'hich in&ormation is arranged, Rati"nale) 8ou 'ill &ind use&ul in&ormation on as#irin in Volume)4 acrylic #lastics4
#olyester4 gasoline and soa# in Volume *4 antibiotics in Volume 2 and aluminium in Volume 5, %his in&ormation is releant to arious sections o& this module,
Use
creen ca#ture Des*ri/ti"n) Mine 1ngineer,Com has in&ormation on mining4 minerals4 coal4
mineral #rocessing4 coal #re#aration4 e(ui#ment used in the mining and #rocess industries, Other related to#ics are included, Rati"nale) In this 'ebsite in&ormation to su##lement 'hat is #resented in the
module 'ill be &ound on to#ics such as co##er4 aluminium4 cement4 #hos#hate ore #rocessing4 unit o#erations inoling si"e reduction and se#aration,
Use&ul >ink P 2 Title) 1lectrochemistry URL) htt#9;;''',cheresources,com
creen ca#ture
URL) htt#9;;electrochem,c'ru,ed;encycl Des*ri/ti"n) %his site gies use&ul in&ormation on industrial a##lication o&
electrochemistry,
16
Rati"nale) One article &rom this 'ebsite coers the history4 Bayer4 Hall3Heroult
and alternatie #rocesses &or aluminium #roduction,
Use&ul >ink P 5 Title) Cheresources URL) htt#9;;''',cheresources,com
creen ca#ture Des*ri/ti"n) Cheresources,com has been #roiding content and tools to
chemical engineers all oer the 'orld,
%he site has many &ree chemical
engineering resources as 'ell as #remium content and so&t'are &or isitors to choose &rom, ome o& the &ree articles are targeted &or students, Rati"nale) %his is a use&ul link to search &or detailed in&ormation on chemical
#rocess technology &or such #roducts as ammonia4 sul#huric acid and others coered in this module, ome o& the articles are &rom re&ereed =ournals,
Use&ul >ink P 6 Title) %he Contact /rocess URL) htt#9;;uk,encarta,msn,com;media!6)566$06;ul#huricAcid,html
creen ca#ture Des*ri/ti"n) %his #age describes the Contact /rocess &or the manu&acture o&
sul#huric acid Rati"nale9 %he article ex#lain the reasons &or the conditions used in the #rocess,
It looks at the e&&ect o& #ro#ortions4 tem#erature4 #ressure and catalyst on the com#osition o& the e(uilibrium mixture4 the rate o& the reaction and the economics o& the #rocess,
Use
creen ca#ture
17
Des*ri/ti"n) Chemical Intelligence is a directory o& chemicals #roiding
in&ormation on the chemicals coered by ICI, Chemicals A3G #age leads to in&ormation you may re(uire on any chemical, Rati"nale)
%he bulk industrial chemicals category includes those chemicals and materials #roduced in the chemical industry in large (uantities, %he site also ca#tures the main #etrochemical intermediates 'hich are #roduced &rom the #rimary ole&ins and aromatics building blocks 'hich are &urther #rocessed into monomers4 detergents4 adhesies4 solents4 #lastici"ers4 lubricants and #olymers,
Use
creen ca#ture Des*ri/ti"n) %his site has a 'ealth o& in&ormation on #etroleum re&ining, Rati"nale) %o#ics coered in this site include the history o& #etroleum re&ining4
crude oil extraction and com#osition4 re&ining #rocesses 'ith &lo' diagrams and detailed descri#tions, 8ou 'ill &ind this site use&ul as you study Unit 5,
Use Title) Access 1xcellence URL) htt#9;''',accessexcellence,org
creen ca#ture Des*ri/ti"n) %his site is a resource centre mainly &or li&e sciences including
biotechnology, One o& the sites4 Biotech Applied looks at the #ractical a##lications o& biotechnology and strategies &or introducing biotechnology into the classroom, It also gies one o##ortunity to interact and collaborate 'ith scientists4 teachers and others to ex#lore the cutting edge o& science, Rati"nale) One #articular site9
-htt#9;;''',accessexcellence,org;>C;;&ermbiogra#hy,html.4 &ermentation,
18
deals
'ith
Use
creen ca#ture Des*ri/ti"n) %his site is &or oa# and 7etergent Association 'ho re#resent
manu&acturers o& household4 industrial and institutional cleaning #roductsQ #roducers and su##liers o& associated ra' materials and &inished #ackaging, Rati"nale) One o& the article in this 'ebsite is on the manu&acturing #rocesses
&or soa#s and detergents, It includes the history o& soa#4 soa# making4 chemistry4 ingredients and manu&acturing #rocesses, %he ex#lanations 'hich are in laymans language are su##lemented 'ith interesting gra#hic illustrations, %his 'ill greatly aid you in the study o& this to#ic in Unit 6,
=I&. LEARNIN9 ACTI&ITIES ACTI&ITY 1 INTR(DUCTI(N T( INDUSTRIAL CHEMISTRY AND THE CHEMICAL INDUSTRY
At the end o& this learning actiity4 you should be able to9 a, 7istinguish bet'een classical and industrial chemistry b, Classi&y the chemical industry in terms o& scale4 ra' materials4 end use and alue addition c, 7istinguish bet'een unit o#erations and unit #rocesses d, 7escribe chemical #rocesses by means o& &lo' diagrams e, Carry out material balances &or a sim#le #rocess
ummary o& the learning actiity %his learning actiity introduces you to industrial chemistry and the chemical industry and enables you to study subse(uent units more easily, It includes the &ollo'ing to#ics9 Introduction to industrial chemistry4 classi&ication o& the chemical industry4 ra' materials &or the chemical industry4 unit o#erations and unit
19
#rocesses4 &lo' diagrams4 material and energy balances, %he arious readings gien su##lement the material #resented in this module, At the end o& the unit4 there are exercises you are re(uired to do to test your understanding o& the unit,
List "< rele2ant readin%s
), Chang :, -)$$)., Chemistry4 2 th 1dition4 Mc?ra'3Hill Inc, Ee' 8ork, *, Chang :, and %ikkanen <, -)$FF., %he %o# i&ty Industrial Chemicals, 0, /rice :,, and :egester M,M, -*+++.4 <1A Industrial Monitor4 *+++3 *++)4 @ohn
List "< rele2ant res"ur*es •
Com#uter 'ith internet &acility to access links and releant co#y'rite &ree resources
•
C73:om accom#anying this module &or com#ulsory reading and demonstrations
•
Multimedia resources like ideo4VC74and C7 #layers
List "< rele2ant use
htt#9;;commons,'ikimedia,org;'iki;Category9/rocess&lo'diagrams htt/)$$$.i*is.*"mintelli%en*e.as/
The
20
1.1. The di<
Be&ore 'e de&ine industrial chemistry4 it may be hel#&ul to kno' that the deelo#ment o& industrial chemistry started 'hen a need to kno' ho' arious chemicals are #roduced in much more than the laboratory scale4 arose, Chemistry kno'ledge 'as a##lied to &urnish the ra#idly ex#anding chemical industries 'ith SSreci#esSS 'hich 'e no' call *hemi*al /r"*esses, Industrial chemistry kee#s u# 'ith the #rogress in science and technology, It incor#orates other
emerging
disci#lines
such
as
biotechnology4
microelectronics4
#harmacology and material science, %he disci#line is also concerned 'ith economics and the need to #rotect the enironment,
Classical chemistry -organic4 inorganic and #hysical chemistry. is ery essential &or adancing the science o& chemistry by discoering and re#orting ne' #roducts4 routes and techni(ues, On the other hand industrial chemistry hel#s us to close the ga# bet'een classical chemistry as it is taught in colleges and uniersities4 and chemistry as it is #racticed commercially, %he sco#e o& industrial chemistry there&ore includes9 •
•
%he ex#loitation o& materials and energy in a##ro#riate scale A##lication o& science and technology to enable humanity ex#erience the bene&its o& chemistry in areas such as <""d /r"du*ti"n4 health and hy%iene6 shelter6 /r"te*ti"n6 de*"rati"n6 re*reati"n and entertainment.
1.. Classi
Industry is a general term that re&ers to all economic actiities that deal 'ith #roduction o& goods and serices, ?oods and serices are key 'ords 'hen you talk o& industry,
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•
•
Manu
Agriculture
•
1nergy
•
%rans#ort
•
Communication
•
1ducation
•
%ourism
•
Building and construction
•
%rade
•
inance
•
etc
1..1. Classi
%he manu&acturing industry is the area o& &ocus in the study o& this module, Manu&acturing #roduces manu&actured goods, %his makes it distinct &rom other sectors like agriculture 'hich also #roduce goods, In manu&acturing4 materials are trans&ormed into other more aluable materials,
Manu&acturing industry can be classi&ied into t'o ma=or categories namely4 hea2y and li%ht industry ,
Ca#ital3intensie industries are classi&ied as heay 'hile labour intensie industries are classi&ied as light industries,
>ight industries are easier to relocate than heay industries and re(uire less ca#ital inestment to build,
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Using the aboe classi&ication criteria4 exam#les o& heay industries include those that #roduce industrial machinery4 ehicles and basic chemicals, Other measures used to classi&y industries include the 'eight or olume o& #roducts handled and 'eight #er cost o& #roduction, or exam#le the 'eight o& steel #roduced #er dollar is more than the 'eight #er dollar o& a drug, In this case4 steel industry is a heay industry 'hereas drug manu&acture is a light industry, ometimes goernments de&ine heay industry in terms o& its im#act on the enironment, Many #ollution control la's target heay industries 'hich in most cases #ollute more than light industries, %here&ore4 #ul# and #a#er industry is a heay industry since its contribution to #ollution is enormous, Both inorganic and organic chemical industry can be either heay or light industry, or exam#le the #harmaceutical industry 'hich is basically organic is light industry, /etroleum re&ining is organic but heay industry, Iron and steel industry is inorganic and heay industry, 1... Manu
Because the ra' materials and the actual #roducts manu&actured are so aried4 di&&erent skills and technologies are needed in manu&acturing, Manu&acturing is there&ore diided into su:4se*t"rs 'hich ty#ically deal 'ith category o& goods such as the &ollo'ing9 •
ood4 beerages and tobacco
•
%extiles4 'earing a##arel4 leather goods
•
/a#er #roducts4 #rinting and #ublishing
•
Chemi*al6 /etr"leum6 ru::er and /lasti* /r"du*ts
•
Eon3metallic mineral #roducts other than #etroleum #roducts
•
Basic metal #roducts4 machines and e(ui#ment,
>et us no' &ocus on the *hemi*al6 /etr"leum6 ru::er and /lasti* /r"du*ts su:4se*t"r.
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1.3. The Chemi*al Industry
%he chemical industry can also be classi&ied according to the ty#e o& main ra' materials used and;or ty#e o& #rinci#al #roducts made,
substances4 make com#osites o& the same and also synthesi"e inorganic chemicals, Heay industrial organic chemical industries #roduce #etroleum &uels4 #olymers4 #etrochemicals and other synthetic materials4 mostly &rom #etroleum, >ight
organic
industries
#roduce
s#ecialty
chemicals
'hich
include
#harmaceuticals4 dyes4 #igments and #aints4 #esticides4 soa#s and detergents4 cosmetic #roducts and miscellaneous #roducts, 1.3.1. The Stru*ture "< the 9l":al Chemi*al Industry
%he global chemical industry is &ounded on basic inorganic chemicals -BIC. and basic organic chemicals -BOC. and their intermediates, Because they are #roduced directly &rom natural resources or immediate deriaties o& natural resources4 they are #roduced in large (uantities, In the to# ten BIC 6 almost all the time4 sul#huric acid4 nitrogen4 oxygen4 ammonia4 lime4 sodium hydroxide4 #hos#horic acid and chlorine dominate, %he reason sul#huric acid is al'ays number one is because it is used in the manu&acture o& &ertili"ers4 #olymers4 drugs4 #aints4 detergents and #a#er, It is also used in
24
#etroleum re&ining4 metallurgy and in many other #rocesses, %he to# ranking o& oxygen is to do 'ith its use in the steel industry, 1thylene and #ro#ylene are usually among the to# ten BOC, %hey are used in the #roduction o& many organic chemicals including #olymers, BIC and BOC are re&erred to as commodity or industrial chemicals, Commodity chemicals are there&ore de
High3alue adding inoles the #roduction o& small (uantities o& chemical #roducts &or s#eci&ic end uses, uch #roducts are called s#ecialty chemicals, %hese are high alue3added #roducts #roduced in lo' olumes and sold on the basis o& a s#eci&ic &unction, In this category are the so3called /er<"rman*e *hemi*als 'hich are high alue #roducts #roduced in lo' olumes and used in extremely lo' (uantities, %hey are =udged by #er&ormance and e&&iciency, 1n"ymes and dyes are #er&ormance chemicals, Other exam#les o& s#ecialty chemicals include medi*inal *hemi*als6 a%r"*hemi*als6 /i%ments6
#ecialty chemicals are mainly used in the &orm o& &ormulations, /urity is o& ital im#ortance in their &ormulation, %his calls &or organic synthesis o& highly alued #ure chemicals kno'n as
1.3.1.3.7ine Chemi*als)
At times you 'ill &ind that the ra' materials &or your #roduct need to be ery #ure &or the #roduct to &unction as desired, :esearch chemicals are in this category as also are #harmaceutical ingredients, uch #uri&ied or re&ined chemicals are called &ine chemicals, By de
C"mm"dities
B0
S/e*ialties
1B
7ine
1.. Ra$ material <"r the Chemi*al Industry
%he atmos#here is the &ield aboe ground leel, It is the source o& air &rom 'hich six industrial gases namely E *4 O*4 Ee4 Ar4 r and Te are manu&actured, %he mass o& the earths atmos#here is a##roximately 5x )+ )5 tons and there&ore the su##ly o& the gases is irtually unlimited, aw materials from the hydrosphere
Ocean 'ater 'hich amounts to about ),5x )+ *) litres contains about 0,5 #ercent by mass dissoled material, ea'ater is a good source o& sodium chloride4 magnesium and bromine, aw materials from the lithosphere
%he ast ma=ority o& elements are obtained &rom the earths crust in the &orm o& mineral ores4 carbon and hydrocarbons, Coal4 natural gas and crude #etroleum besides being energy sources are also conerted to thousands o& chemicals, aw materials from the biosphere
Vegetation and animals contribute ra' materials to the so3called agro3based industries, Oils4 &ats4 'axes4 resins4 sugar4 natural &ibres and leather are exam#les o& thousands o& natural #roducts, 1.. Chemi*al r"*esses
26
1ery industrial #rocess is designed to #roduce a desired #roduct &rom a ariety o& starting ra' materials using energy through a succession o& treatment ste#s integrated in a rational &ashion, %he treatments ste#s are either #hysical or chemical in nature,
1nergy is an in#ut to or out#ut in chemical #rocesses, %he layout o& a chemical #rocess indicates areas 'here9 •
ra' materials are #re3treated
•
conersion takes #lace
•
se#aration o& #roducts &rom by3#roducts is carried out
•
re&ining;#uri&ication o& #roducts takes #lace
•
entry and exit #oints o& serices such as cooling 'ater and steam
1..1. Units that ma5e u/ a *hemi*al /r"*ess
A chemical #rocess consists o& a combination o& chemical reactions such as synthesis4 calcination4 ion exchange4 electrolysis4 oxidation4 hydration and o#erations based on #hysical #henomena such as ea#oration4 crystalli"ation4 distillation and extraction A chemical #rocess is there&ore any single #rocessing unit or a combination o& #rocessing units used &or the conersion o& ra' materials through any combination o& chemical and #hysical treatment changes into &inished #roducts, 1..1.1. Unit /r"*esses
27
Unit #rocesses are the chemical trans&ormations or conersions that are #er&ormed in a #rocess, In %able ),)4 exam#les o& some unit #rocesses are gien,
Ta:le 1.1
Eam/les "< unit /r"*esses
Acylation Alcoholysis Alkylation Amination Ammonolysis Aromati"ation
Calcinations Carboxylation Causiti"ation Combustion Condensation 7ehydration
7ehydrogenation 7ecom#osition 1lectrolysis 1steri&ication ermentation Hydrogenation
Hydrolysis Ion 1xchange Isomeri"ation Eeutrali"ation Oxidation /yrolysis
1..1.. Unit (/erati"ns %here are many ty#es o& chemical #rocesses that make u# the global chemical
industry, Ho'eer4 each may be broken do'n into a series o& ste#s called unit "/erati"ns. %hese are the #hysical treatment ste#s4 'hich are re(uired to9 •
#ut the ra' materials in a &orm in 'hich they can be reacted chemically
•
#ut the #roduct in a &orm 'hich is suitable &or the market
In %able),*4 some common unit o#erations are gien,
Ta:le 1. Eam/les "< unit "/erati"ns
Agitation Atomi"ation Centri&uging Classi&ication Crushing 7ecanting
7is#ersion 7istillation 1a#oration iltration lotation ?as absor#tion
Heat trans&er Humidi&ication Mixing /um#ing ettling i"e reduction
It is the arrangement or se(uencing o& arious unit o#erations cou#led 'ith unit #rocesses and together 'ith material in#uts4 'hich gie each #rocess its indiidual character, %he indiidual o#erations hae common techni(ues and are based on the same scienti&ic #rinci#les, or exam#le4 in many #rocesses4 solids and &luids must be moedQ heat or other &orms o& energy may be trans&erred &rom
28
one substance to anotherQ drying4 si"e reduction4 distillation and ea#oration are #er&ormed, By studying systematically these unit "/erati"ns 4 'hich cut across industry and #rocess lines4 the treatment o& all #rocesses is uni&ied and sim#li&ied,
1.,. 7l"$ Dia%rams ! picture says more than a thousand words
ome chemical #rocesses are (uite sim#leQ others such as oil re&ineries and #etrochemical #lants can be ery com#lex, %he #rocess descri#tion o& some #rocesses could take a lot o& text and time to read and still not yield )++ com#rehension, 1rrors resulting &rom misunderstanding #rocesses can be extremely costly, %o sim#li&y #rocess descri#tion4 &lo' diagrams also kno'n as &lo' sheets are used. A
se(uence o& e(ui#ment and unit o#erations in the oerall #rocess to sim#li&y the isuali"ation o& the manu&acturing #rocedures and to indicate the (uantities o& material and energy trans&erred, A &lo' diagram is not a scale dra'ing but it9 •
#ictorially identi&ies the chemical #rocess ste#s in their #ro#er;logical se(uence
•
includes su&&icient details in order that a #ro#er mechanical inter#retation may be made
%'o ty#es o& &lo' diagrams are in common use4 namely4 the block diagrams and the #rocess &lo' diagrams, 1.,.1. l"*5 Dia%rams
%his is a schematic diagram4 'hich sho's9 •
'hat is to be done rather than ho' it is to be done, 7etails o& unit o#erations;#rocesses are not gien
•
&lo' by means o& lines and arro's
29
•
unit o#erations and #rocesses by &igures such as rectangles and circles
•
ra' materials4 intermediate and &inal #roducts
ig, ),) is an exam#le o& a block diagram,
7i% 1.1 A :l"*5 dia%ram <"r a sul/huri* a*id /lant
1.,.. r"*ess
Chemical #lants are built &rom #rocess &lo' dra'ings or &lo' sheets dra'n by chemical engineers to communicate conce#ts and designs, Communication is im#aired i& the reader is not gien clear and unmistakable #icture o& the design, %ime is also 'asted as reader (uestions or #u""les out the &lo' diagram, %he reader may make serious mistakes based on erroneous inter#retation o& the &lo' diagram,
30
Communication is im#roed i& acce#ted symbols are used, %he adantages o& correct use o& symbols include9 •
the &unction being #er&ormed is em#hasi"ed by eliminating distractions caused by detail
•
#ossibility o& error that is likely to occur 'hen detail is re#eated many times is irtually done a'ay 'ith
•
e(ui#ment symbols should neither dominate the dra'ing nor be too small &or clear understanding,
lo' sheet symbols are #ictorial (uick3to3dra'4 easy3to3understand symbols that transcend language barriers, ome hae already been acce#ted as national standards 'hile others are symbols commonly used in chemical #rocess industries4 'hich hae been #roen to be e&&ectie, 1ngineers are constantly deising their o'n symbols 'here standards do not exist, %here&ore4 symbols and #resentation may ary &rom one designer or com#any to another, Belo' is a cement #rocess &lo' diagram illustrating the use o& e(ui#ment symbols,
31
7i% 1. ) A /r"*ess
1.'. Material alan*es
rom the la' o& conseration o& mass4 'e kno' that mass can neither be created nor destroyed, Ho'eer4 in nuclear reactions4 mass and energy can be conerted into each other res#ectiely, Because o& this4 'e can 'rite e(uations called mass balances or material balances, Any #rocess being studied must satis&y balances on the total amount o& material4 on each chemical com#onent4 and on indiidual atomic s#ecies, As 'e hae seen in the study o& #rocess diagrams4 a #rocess can hae &e' or many streams de#ending on its com#lexity,
1.'.1. The /ur/"se "< mass :alan*e *al*ulati"ns
Mass balance calculations sere the &ollo'ing #ur#oses9 ), %hey hel# us kno' the amount and com#osition o& each stream in the #rocess,
32
*, %he calculations obtained in ) &orm the basis &or energy balances through the a##lication o& the la' o& conseration o& energy, 0,
%here is no trans&er o& mass to energy
•
Mass is consered &or each element or com#ound on either molar or 'eight basis
It is im#ortant to note the &ollo'ing9 •
Mass and atoms are consered
•
Moles are consered only 'hen there is no reaction
•
Volume is not consered,
8ou may 'rite balances on total mass4 total moles4 mass o& a com#ound4 moles o& an atomic s#ecies4 moles o& a com#ound4 mass o& a s#ecies4 etc,
1.'.. Material alan*e E!uati"ns
In #ractice4 some material may accumulate in the #rocess or in some #articular #rocess units, or exam#le4 in a batch #rocess4 some material may remain adhered to the 'alls o& containers, In the dehydration o& ethane to ethylene4 #ossible chemical reactions are as &ollo's9 C*H6 -g.
C*H2-g.
C*H6 -g.
*C-s. D0H*-g.
C*H2-g.
*C-s. D*H*-g.
%he carbon &ormed accumulates in the reactor, Because #rocesses may be batch 'ith no in&lo' and out&lo' or continuous 'ith in&lo' and out&lo'4 and that there may be conersion o& chemical s#ecies4 a good
33
mass balance e(uation takes care o& all these as#ects, %he &ollo'ing is a general mass balance e(uation,
A**umulati"n $ithin the system F 7l"$ In thr"u%h the system :"undaries 4 7l"$ (ut thr"u%h the system :"undaries G %enerati"n $ithin the system 4 C"nsum/ti"n $ithin the system
im#ly #ut9 A**umulati"n F7l"$ in 7l"$ "ut G r"du*ti"n C"nsum/ti"n
%he system is any #rocess or #ortion o& a #rocess chosen &or analysis, A system is said to be o#en i& material &lo's across the system boundary during the interal o& time being studiedQ closed i& there are no &lo's in or out, Accumulation is usually the rate o& change o& holdu# o& material 'ithin the
system, I& material is increasing4 accumulation is #ositieQ i& it is decreasing4 it is negatie, I& the system does not change 'ith time4 it is said to be at steady state4 and the net accumulation 'ill be "ero, %he generation and consum#tion o& material are the conse(uences o& chemical reactions, I& there is no chemical reaction4 the #roduction and consum#tion terms are ty#ically "ero,
1.'.3. Mass :alan*e *al*ulati"n /r"*edure
%he general #rocedure &or carrying out mass balance calculations is as &ollo's9 ), Make a block diagram -&lo' sheet. oer the #rocess *, /ut numbers on all the streams 0, >ist do'n all the com#onents that #artici#ate in the #rocess, 2, ind the com#onents that are in each stream and list them ad=acent to the stream in the block diagram 5, 7ecide on an a##ro#riate basis &or the calculations e,g, )++kg ra' material A4 )++kg;hr A4 ) ton o& #roduct4 )++ moles reactant B etc,
34
6, ind out the total number o& inde#endent relations, %his is e(uialent to the total number o& stream com#onents, !, /ut u# di&&erent relations bet'een stream com#onents and inde#endent relations to calculate concentrations F, %abulate results, 1.'.. Eam/le)
%hree ra' materials are mixed in a tank to make a &inal #roduct in the ratio o& )9+,29),5 res#ectiely, %he &irst ra' material contain A and B 'ith 5+ A, %he second ra' material contain C 'hile the third ra' material contain A and C 'ith !5 A, Assuming a continuous #rocess at steady state4 &ind the &lo' and com#osition o& the #roduct, S"luti"n)
), Make a block diagram -&lo' sheet. oer the #rocess
*, /ut numbers on all the streams *
)
0 2
0, >ist do'n all the com#onents that #artici#ate in the #rocess, %he com#onents are A4 B and C, 2, ind the com#onents that are in each stream and list them ad=acent to the stream in the block diagram, >et < re#resent com#osition by 'eight,
35
*
< A)4
)
0 < A04
5, 7ecide on an a##ro#riate basis &or the calculations, >et us use as basis )++ kg;hr o& the &irst ra' material 6, ind out the total number o& inde#endent relations, %his is e(uialent to the total number o& stream com#onents, %he total number o& inde#endent relations the total number o& stream com#onents tream com#onents are < A)4
Basis9 tream ) is )++kg
%he ratio o& the three ra' materials
< A) is 5+
Material balance &or A
Material balance &or B
Material balance &or C
36
or a mixing reaction4 #roduction and consum#tion are "ero, %here&ore9 A**umulati"n
F
+71 G 7 G 73- 7
'here the &lo' rates are in kg #er hour, Because the system is at steady state4 accumulation is "ero4 and9 7
F
71 G 7 G 73
rom the ratio o& in#ut &lo's4
* +,2T-)++;). 2+kg 0 ),5T-)++;). )5+kg
%here&ore 2
)++ D 2+ D )5+ *$+kg
%he next ste# is to &ind the (uantities o& A4 B and C in 2, %o do this4 'e shall 'rite the mass balance e(uation &or each o& these three com#onents assuming no accumulation, or A9 Accumulation A lo' in A J lo' out A D /roduction A J Consum#tion A Accumulation A
+
-) < A) D * < A* D 0 < A0. J 2 < A2
+
)++-+,5. D 2+-+. D )5+-+,!5. J *$+< A2
)6*,5 J *$+< A2
)6*,5;*$+
+,56
< A2
imilar balances are done &or B and C9 AccumulationB
+
-)
+
)++-+,5. D 2+-+. D )5+-+. J *$+< B2
5+ J *$+< B2
5+;*$+
+,)!
+
-)
+
)++-+. D 2+-). D )5+-+,*5. J *$+< C2
!!,5 J *$+< C2
!!,5;*$+
+,*!
AccumulationC
37
It is al'ays good to check ans'ers &or consistency,
F, Ta:ulate results, tream
Com#onent
g;hr
g
)
s A
5+
* 0
B C A
5+ 2+ ))*,5
)++ )++
5+ )++ !5
)++ )++
0!,5 )6*,5
)5+
*5 56
)++
2
C A B
5+
C
!!,5
5+
)! *$+
*!
)++
7"rmati2e E2aluati"n
), 7istinguish bet'een industrial and classical chemistry *,
38
CO CO
*F,+
),*5+)
CO*
0, 0,5
),$!6F
O*
+,5
),2*F$
E*
6F,+
),*5+!
%he gas is burned 'ith oxygen according to the &ollo'ing e(uation9 *CO D O*
*CO*
%he oxygen is &rom the air 'hose olumetric com#osition is assumed to be F+ E* and *+ O *, %he oxygen &ed &rom the air and the #roducer gas is *+ in excess o& the amount re(uired &or com#lete combustion, combustion, %he combustion is $F com#lete, Carry out total material balance &or this #rocess based on )++kg o& gas burned,
39
LEAR ARNI NING NG ACTI CTIIT IT! !" 11. LE
#NIT #NIT O$E O$ERA RAT TION% ION% AND #NI #NIT T $RO $ROCE CE%% %%E% E%
At the end end o& this unit you you should be able to9 to9 a, >ist the the arious arious reasons reasons &or undertak undertaking ing si"e reduction reduction and enlargeme enlargement nt in the chemical industry b, 7escrib 7escribe e the o#eration o#eration #rinci#le #rinci#les s o& some si"e si"e reduction reduction e(ui#men e(ui#mentt and si"e enlargement e(ui#ment c, 1x#la 1x#lain in ho' ho' indust industria riall mater material ials s can can be se#ara se#arate ted d on the basis basis o& their their magnetic4 electrostatic4 hydro#hobic and olatility di&&erences res#ectiely d, 7isc 7iscus uss s
ari ariou ous s
orga organi nic c
unit unit
#roc #roces esse ses s
incl includ udin ing g
#oly #olyme meri ri"a "ati tion on44
alkylation4 and hydrolysis and their a##lication in the #roduction o& organic chemicals Summary "< the Learnin% A*ti2ity
In >earning Actiity ) 'e learnt that chemical #rocesses can be broken do'n into unit unit
o#er o#erat atio ions ns
and and
unit unit
#roc #roces esse ses, s,
Unit Unit
o#er o#erat atio ions ns
ino inol le e
#hy #hysica sicall
trans&ormations 'hile unit #rocesses consist o& chemical conersions, In this unit4 'e 'ant 'ant to stud study y the the #ur# #ur#os oses es and and o#er o#erat atin ing g #rin #rinci ci#l #les es o& comm common on unit unit o#erations and unit #rocesses4 es#ecially those 'e shall encounter later in the study study o& industri industrial al inorganic inorganic and organic organic chemical chemical #rocess #rocesses, es, Actiity includes9 includes9
i"e reduction reduction
%he >earning >earning
and si"e enlargement4 enlargement4 magnetic and
electrostatic se#aration4 &roth &lotation4 &ractional distillation4 other unit o#erations4 #olymeria"ation4 alkylation4 hydrolysis and other uni #rocesses,
List "< rele2ant readin%s
), hukla , 7 and /andey ?, E4 -)$!F., F., A %extbook ook o& Chemic mical %echnology, Vol,) -Inorganic;Organic., Vikas #ublishing House /V% >td, Ee' 7elhi, *, ?erhar ?erhart" t"44 <, -1dit -1ditor or.4 .4 -)$F! -)$F!., ., Ullma Ullmann nns s 1ncy 1ncyclo clo#ae #aedia dia o& Indus Industri trial al Chemistry4 5 th 1dition4 VCH Verlagsgesellscha&t mbH4
40
2, ?roggins ?roggins /, /,H, -)$5F., -)$5F., Unit /rocesse /rocesses s in Organic Organic ynthes ynthesis4 is4 5 th 1dition4 Mc?ra'3Hill Book Com#any4 Ee' 7elhi,
List "< rele2ant use
htt#9;;''',mine3engineer,com; %his link has use&ul in&ormation on arious unit o#erations used in the chemical industry, /hotogra#hs and other illustrations are gien,
.1. Unit (/erati"ns
In Unit )4 'e de&ined unit o#erations as #hysical trans&ormations, %hey are ery many and include si"e reduction4 si"e enlargement and se#aration o& mixtures, In this this unit unit44 'e shal shalll look look at o#er o#erat atio ion n #rin #rinci ci#l #les es o& e(ui e(ui#m #men entt in thes these e unit unit o#erations and their a##lication in the chemical industry, .1.1. Si8e Redu*ti"n
i"e reduction re&ers to all the 'ays in 'hich #articles are cut or broken into smaller #ieces, #ieces, %he ob=ectie ob=ectie is to #roduce small small #articles &rom big ones ones &or any o& the &ollo'ing reasons9 ),
%o red reduc uce e chun chunks ks o& o& ra' ra' mate materi rial als s to 'or 'orka kabl ble e si"e si"es s e,g, e,g, cru crush shin ing g o& mineral ore,
*,
%o incre increas ase e the the react reactii iity ty o& o& mater material ials s by incre increasi asing ng the the sur& sur&ac ace e area area,,
0,
%o rele releas ase e alua aluabl ble e subst substan ance ces s so that that they they can can be se#ar se#arat ated ed &rom &rom un'anted material,
2,
%o redu reduce ce the the bul bulk k o& o& &ib &ibro rous us mate materi rial als s &or &or easi easier er hand handli ling ng,,
5,
%o meet meet stan standa dard rd s#ec s#eci& i&ic icat atio ions ns on si"e si"e and and sha sha#e #e,,
6,
%o incr increa ease se #art #artic icle les s in numb number er &or &or the the #ur #ur#o #ose se o& sell sellin ing, g,
!,
%o im# im#roe blen lending ing e&&icie icien ncy o& &ormul rmula ations ions44 com#os m#osit ite es e,g, insecticides4 dyes4 #aints
.1.1.1. rin*i/les "< si8e redu*ti"n
Most si"e reduction machines are based on mechanical com#ression or im#act,
41
&ragments &ormed are o& di&&erent si"es, An exam#le o& an industrial e(ui#ment that is based on com#ression is a =a' crusher, Im#act is the breaking u# o& material 'hen it is hit by an ob=ect moing at high s#eed, %he #roduct contain coarse and &ine #articles, A ball mill is based on im#act, .1.1.. a$ Crusher
ig,*,) is a schematic diagram o& a =a' crusher,
7i% .1. a$ *rusher
A =a' crusher consists o& a ertical &ixed =a' and another s'inging =a' that moes in the hori"ontal #lane, In the diagram aboe4 the =a's are coloured red, %he t'o =a's make *+30+ o angle bet'een them, %he s'inging =a' closes about *5+ to 2++ times;min, eed is admitted bet'een the =a's, It is crushed seeral times bet'een the =a's be&ore it is discharged at the bottom o#ening, A =a' crusher #roduces a coarse #roduct,
.1.1.3. all Mill
A ball mill is a tumbling mill generally used &or #reiously crushed materials, It is
42
generally used to grind material 6mm and &iner4 do'n to a #article si"e o& *+ to !5 microns,
7i%. . all mill
%he o#eration o& a ball mill is illustrated in ig *,*, %he mill consists o& a cylinder containing a mixture o& large and small steel grinding balls and the &eed,
43
7i% .3 h"t"%ra/h "< a :all mill in a Cement lant.
.1.. Si8e Enlar%ement +A%%l"merati"ni"e enlargement4 also re&erred to as agglomeration4 is carried out 'hen #articles are too small &or use in a later stage o& the #rocess, or exam#le in metal extraction4 some #articles may be too &ine to be &ed into a blast &urnace, .1..1. ur/"ses "< si8e enlar%ement
%he &ollo'ing are some o& the #ur#oses o& si"e enlargement in arious industries9 ), :educe dusting losses *, :educe handling ha"ards #articularly 'ith res#ect to irritating and obnoxious #o'ders, 0, :ender #articles &ree &lo'ing, 2, 7ensi&y materials, 5, /reent caking and lum# &ormation 6, /roide de&inite (uantity o& units suitable &or metering4 dis#ensing and administering !, /roduce use&ul structural &orms F, Create uni&orm blends o& solids 'hich do not segregate $, Im#roe a##earance o& #roducts )+,/ermit control oer #ro#erties o& &inely diided solids e,g, solubility4 #orosity4 sur&ace olume ratio4 heat trans&er
44
)), e#arate multicom#onent #article si"e mixtures by selectie 'etting and agglomeration )*,:emoe #articles &rom li(uids In si"e enlargement4 small #articles are gathered into larger4 relatiely #ermanent masses in 'hich the original #articles can still be identi&ied, %he #roducts o& si"e enlargement are either regular sha#es e,g, bricks4 tiles4 tablets4 #ellets or irregular sha#es such as sintered ore, Agglomerators are used to increase the #article si"e o& #o'ders, %here are t'o basic ty#es o& agglomeratorsQ com#action and non3com#action agglomerators, %he com#action ty#e uses mechanical #ressure -and o&ten ery high #ressures. to #ress the #o'ders together, or these4 binders are sometimes not needed to make the #article, /ellet mills are com#action agglomerators,
.1... ellet mills
Moist &eed in #lastic state is #assed through a die containing holes, %he die is su##lied 'ith #o'er to rotate around a &reely rotating roller, %he &riction o& material in the die holes su##lies resistance necessary &or com#action, A kni&e cuts the exudates into #ellets, %his is sho'n in ig, *, 2, Bonding agents such as glue or starch may be mixed 'ith the &eed, /ellet (uality and ca#acity de#ends on9 •
eed #ro#erties e,g, moisture
•
>ubricating characteristics
•
/article si"e
•
•
Abrasieness 7ie characteristics and s#eed
45
7i% .. The /ellet mill
A #icture o& a #ellet mill conerting 'ood #lanings and sa'dust into &uel #ellets is sho'n in ig *,5, %hese ra' materials are com#ressed under high #ressure into small4 cylindrical rolls, /ellets gain their &irmness solely &rom the #ressing #rocess 'ithout addition o& any chemical or synthetic adhesie agent,
46
7i%. .,) h"t"%ra/h "< a /elleti8er in "/erati"n that *"n2erts /lanin%s int"
%he common action o& most non3com#action agglomerators is to kee# the #o'ders in motion by tumbling4 ibrating or shaking4 'hile s#raying a correct amount o& li(uid binder, %he binder is s#ecially selected to hold the smaller #articles together4 creating a larger #article, A&ter the #articles stick together to &orm a nucleus or germ4 then &ollo's the layering or de#osition o& layers o& the ra' materials into #reiously &ormed nucleus, %his re(uires high recycle ratio 'hose increase leads to larger and denser agglomerates o& high 'et strength, It also re(uires lo' moisture content in s#ite o& the &act that increase in li(uid content leads to increase in agglomerate si"e, %he layering #rocess is sho'n in ig, *,6
7i%. .') Illustrati"n "< the /"$der layerin% /r"*ess.
%he &ormed agglomerates are sub=ect to the &ollo'ing &orces9 a. 7estructie &orces 'ithin the &eed as #articles im#act on each other during the rolling action b. Cohesie &orces holding #ellets together
47
O#timum agglomeration is obtained 'hen correct tumbling and cascading motion occurs in the charge, Motion is caused by centri&ugal &orces, %he deices may be o#erated at an angle, %'o ty#es o& tumbling agglomerators are used9 inclined #an agglomerator and a drum agglomerator, .1..3.1 In*lined /an a%%l"merat"r
%his is sho'n in ig *,!, It consists o& #an rotating at an incline, It is &ed 'ith the #o'dery ra' material, Material layers oer a nucleus #article to &orm balls, 1nlarged balls roll o&& the #an, ine materials silts do'n through the large balls and remain in the #an,
7i% .. In*lined /an a%%l"merat"r
%he &ollo'ing are the adantages o& an inclined #an9 ). Uni&orm #roduct 'ithout need &or a screen
48
*. >o' e(ui#ment cost 'hich is sim#le to control 0. 1asy obseration o& the balling action Ho'eer4 an inclined #an has one disadantage9 it #roduces dust, .1..3.. Drum a%%l"merat"r
ig *,F is an illustration o& the o#eration o& a drum agglomerator,
7i% .B) Cr"ss se*ti"nal 2ie$ "< an a%%l"merat"r
As the drum rotates clock'ise4 the bars -labeled :od Cage. li&t the &iner #o'ders and create a &alling3curtain o& the smaller and dry #articles, %he li(uid binder is s#rayed -#ray 7ro#lets. onto this curtain4 'hich #re&erentially agglomerate only the small #articles li&ted by the :od Cage, A drum agglomerator has the &ollo'ing adantages oer a #an agglomerator9 ). >arge ca#acity *. >arge retention time i& re(uired 0. >ess sensitiity to u#sets in the system due to the dum#ing e&&ect o& large recirculating load
49
%he drum agglomerator has one disadantage, Because #articles o& arious si"es are #roduced4 a screen is re(uired to se#arate enlarged #articles &rom the smaller #articles,
.1.3. Se/arati"n (< Materials
In this section4 'e 'ill learn ho' di&&erences in the #hysical #ro#erties o& materials are used to se#arate mixtures in the chemical industries, .1.3.1. Ma%neti* Se/arati"n
I& a mixture containing magnetic materials and non3magnetic materials is sub=ected to a magnetic &ield4 there is com#etition &or the #articles bet'een seeral &orces namely4 magnetic4 inertia4 graitational and inter#article &orces, %hree #roducts can be obtained during magnetic se#aration, %hese are9
A strongly magnetic #roduct
A 'eakly magnetic -middlings. #roduct
A non3magnetic -tailings. #roduct
e#aration is carried out either dry using belt li&ting magnets or 'et using drum magnetic se#arators, %his technology is a##lied in mineral ore #rocessing4 as 'e shall see in Unit 2, %he method used &or dry #articles is illustrated schematically in ig *,$,
50
7i% .>. Illustrati"n "< the /rin*i/le "< dry ma%neti* se/arati"n
Material to be se#arated is &ed into the &irst coneyor, Aboe this coneyor is another coneyor 'ith an electromagnet inside, %he electromagnetic &ield decreases to'ards the right, trongly and 'eakly magnetic materials are attracted and #icked by the magnet, %he non3magnetic materials continue to be coneyed by the bottom coneyor and dro# in the &irst bin, As the strength o& the electromagnet 'eakens to'ards the right4 the middlings i,e, the 'eakly magnetic materials lose attachment and dro# in the middle bin, %he strongly magnetic materials dro# o&& at the end o& the electromagnet into the third bin,
.1.3.. 7r"th 7l"tati"n
%his is a #rocess in solids3li(uids se#aration technology that uses di&&erences in 'ettability o& arious materials such as mineral ores, Although these materials are generally hydro#hilic4 the sur&ace #ro#erties o& com#onents they contain may ary 'ithin a ery narro' range, %hese small di&&erences can be am#li&ied by
51
selectie adsor#tion that makes some o& the #articles hydro#hobic, uch hydro#hobic #articles in a 'ater sus#ension are &loated by attaching them to air bubbles, .1.3..1. Ma5in% /arti*les hydr"/h":i* and
A s#ecial sur&ace3actie agent -sur&actant. called *"lle*t"r or /r"m"ter is added to the sus#ension, Collectors are usually C * to C6 com#ounds containing #olar grou#s, %hey include &atty acids4 &atty acid amines and sul#honates among others, Collector selection de#ends on the material being se#arated,
%he
collector molecule adsorbs on to the solid sur&ace ia the #olar -charged. grou#, %his reaction is kno'n as chemisor#tion, %he hydrocarbon chain is &acing the a(ueous #hase, %his is sho'n in ig,*,)+,
7i% .10) h"$ a *"lle*t"r renders a /arti*le hydr"/h":i*
A layer #robably4 a monolayer o& the collector molecules become attached to the sur&ace o& the #article,
Because the hydrocarbon chain and the 'ater do not
mix4 the coated #article sur&ace becomes hydro#hobic, By being hydro#hobic4 a #article re#els 'ater, %his results in the 'eakening o& the &orces acting bet'een the #article sur&ace and 'ater and hence the diminishing o& sur&ace3'ater interactions at solid3sur&ace inter&ace, %his causes the dis#lacement o& 'ater &ilm
52
&rom the 'etted solid sur&ace by air, In addition to the use o& collectors to change the sur&ace #ro#erty o& the #articles4 other chemicals may be added to &urther modi&y either the #articles to be &loated4 or the #articles that are to remain in the sus#ension, uch chemical substances are called modi&iers, .1.3.. 7l"tati"n *ell
%he &lotation cell is sho'n in ig, *,)), %he material is ground in 'ater to a maximum *5+Wm, It is introduced into the &lotation cell, A &rothing agent is added to create a generous su##ly o& &ine bubbles 'hen air is s#arged, 1xam#les o& &rothers include #ine oil and methyl amyl alcohol, %he collector and other addities are added, Hydro#hobic #articles are collected at the air3bubble inter&ace, %he bubbles 'ith attached mineral #articles rise to the sur&ace 'here the material is remoed, /articles that are readily 'etted by 'ater -hydro#hilic. tend to remain in the 'ater sus#ension,
7i% .11 a
53
.1.3.3. 7ra*ti"nal Distillati"n
7istillation is used to se#arate a mixture o& miscible li(uids 'hich hae di&&erent olatilities, u##ose a mixture 'ith lo' concentration o& the more olatile com#onent is distilled and the a#our condensed, %he condensate 'hich 'e re&er to as distillate 'ill be more concentrated 'ith this com#onent than the &eed, I& 'e return the distillate to the distillation a##aratus and distill it to a second distillate4 this distillate 'ill be more richer in the more olatile com#onent than the &irst distillate, I& 'e continue this #rocess4 'e 'ill a##roach a #ure distillate o& the more olatile com#onent, %he greater the relatie olatility bet'een the t'o com#onents4 the &e'er the needed distillation stages, %his is the conce#t o& &ractional distillation, It is used 'hen9 •
Boiling #oints o& mixture com#onents are close
•
Volatilities o& the com#onents are close
%his is the case in #etroleum re&ining, Industrially4 &ractional distillation is carried out in distillation columns also kno'n as distillation to'ers, %hey are like many distillation stills stack together ertically, %he &ractionation columns can be batch or continuous and they can be many in series, ig, *,)0 is a #icture o& an industrial distlillation #lant
54
7i% .13. An industrial
or distillation to take #lace in a distillation column4 both a#our and li(uid &lo'ing u# and do'n res#ectiely must be brought into intimate contact, %his is done by #acking the column 'ith inert solids4 or installing #lates at regular interals throughout the column height, mall distillation columns are normally #acked 'hile large distillation columns are #lated, In #lated columns4 'e need to #roide &or both a#our #ath and li(uid #aths at each #late, %he #lates are #er&orated and the a#our #asses through the #er&orations, %he li(uid &lo's through #i#es kno'n as do'ncomers next to the colum 'all, In ig *,)04 the com#onents o& a continuous distillation column are sho'n,
55
7i% .13 A *"ntinu"us distillati"n *"lumn
.1.3.3.1. Re*ti
>et us look at 'hat ha##ens inside a distillation column 'hen it is running, u##ose there are t'o com#onents A and B being se#arated 'ith A being more olatile than B, Com#onent A leaes at the to#, At each distillation #late4 the li(uid mixture is at boiling #oint, %he boiling #oint o& A4 % A is lo' com#ared to % B4 the boiling #oint o& B coming out at the bottom,
56
kno'n as re*ti
.1.3. (ther Unit (/erati"ns
%here are many unit o#erations that are em#loyed in the chemical industry, It is im#ossible to coer all o& them in this unit, In %able *,) a summary o& some other unit o#erations is gien,
Ta:le .1 (ther unit "/erati"ns Unit (/erati"n 1lectrostatic se#aration
ur/"se e#aration o& solids on the basis
o& the di&&erence
electrical
conductiity
com#onents e#aration o&
edimentation
solids
A//li*ati"n Mineral ore dressing
in o&
&rom
li(uids mostly by graitational &orces e#aration o& solid #articles
Crystalli"ation olidJli(uid
extraction
&rom their saturated solutions or 1xtraction o& a soluble solid
leaching
ugar manu&acture Mineral ore #rocessing
&rom its mixture 'ith an inert solid4 by use o& li(uid solent
#ray drying
>i(uid
J
li(uid
or solent
extration
in 'hich it is soluble, A li(uid containing a dissoled
/roduction
solid is s#rayed and contacted
detergent #o'der4 #o'dered
'ith hot air 'hich ea#orates
milk4
the
inorganic salts
solent
yielding
a
#o'dered #roduct e#aration o& a li(uid solute
o&
synthetic
#igments4
resins
and
olent recoery4 remoal o&
&rom its mixture 'ith another na#hthenic
and
aromatic
Ninert li(uid by means o& com#ounds &rom lubricating oil another li(uid in 'hich it is Absor#tion
soluble :emoal o& a com#onent &rom
remoal o& hydrogen sul#hide
a gas mixture by dissoling it
-H*. &rom hydrocarbon gases
in a li(uid
using alkaline solutions,
.. UNIT R(CESSES 57
In Unit )4 'e de&ined unit #rocesses as chemical trans&ormations or conersions, Unit #rocesses are the core o& industrial synthetic chemistry and are dominant in organic #rocesses,
..1. (LYMERISATI(N
%he term #olymer comes &rom t'o ?reek 'ords9 X#olysY 'hich means XmanyY and XmerosY 'hich means X#arts,Y A #olymer is there&ore a substance haing hundreds or thousands o& many smal identical #arts kno'n as monomers4 'hich are bonded together coalently in a chemical #rocess kno'n as #olymeri"ation, ..1.1."lymeri8ati"n rea*ti"ns
or #olymerisation to yield #olymers 'ith long chain -high #olymers.4 the monomers must9
Be #oly&unctional i,e, contain at least t'o reactie grou#s
Eot gie cyclic #roducts by intramolecular ring closure because this 'ill terminate #olymerisation,
/olymeri"ation reactions &all into t'o general classes9 ),
Addition or chain #olymeri"ation inoling successie stages o& reaction
initiati"n6 /r"/a%ati"n and terminati"n. 1xam#les o& addition #olymers include
#olyethylene4 #oly#ro#ylene4 #olyinyl chloride and #olystyrene, *, Condensation or ste#3reaction #olymeri"ation, %his inoles condensation reaction bet'een t'o #oly&unctional molecules4 sometimes 'ith the elimination o& a small molecule such as 'ater, Eylon is a condensation #olymer o& hexamethylene diamine and adi#ic acid as sho'n in the e(uation belo'9
HN4+CH-'4NH G H((C4+CH -4C((H
H( G 4+NH4+CH -'4NH4C(4+CH--4
I& one o& the reactants in a ste#3reaction #olymeri"ation contain more than t'o &unctional grou#s4 a cross3linked #olymer is obtained,
58
..1. 7ree radi*al /"lymeri8ati"n
One o& the most common and use&ul reactions &or making #olymers is &ree radical #olymeri"ation, It is used to make #olymers &rom inyl monomers4 that is4 &rom small molecules containing carbon3carbon double bonds, /olymers made by &ree radical #olymeri"ation include #olystyrene4 #olymethylmethacrylate4 #olyinyl acetate and branched #olyethylene Initiati"n) %he 'hole #rocess starts o&& 'ith a molecule called an initiator, %his is
a molecule like ben"oyl #eroxide or *4*S3a"o3 bis3isobutyrylnitrile -AIBE., %he s#ecial characteristic o& these molecules is that they hae an ability to s#lit in unusual 'ay,
exact same 'ay as the initiator &ragment did, A &ree radical is &ormed 'hen this reaction takes #lace oer and oer again and the chain gro's, %he adding o& more and more monomer molecules to the gro'ing chain is called propagation, Because 'e kee# remaking the radical4 'e can kee# adding more and more ethylene molecules4 and build a long chain, el&3#er#etuating reactions like this are called chain reactions, Terminati"n) %ermination is the third and &inal ste# o& a chain3gro'th
#olymeri"ation, ree radicals are unstable4 and eentually they &ind a 'ay to become #aired 'ithout generating a ne' radical, %hen the chain reaction 'ill grind to a halt, %his ha##ens in seeral 'ays, %he sim#lest 'ay is &or t'o
59
gro'ing chain ends to &ind each other, %he t'o un#aired electrons then =oin to &orm a #air4 and a ne' chemical bond =oining their res#ectie chains, %his is called coupling , Cou#ling is one o& t'o main ty#es o& termination reaction, Another 'ay in 'hich the un#aired electrons can shut do'n #olymeri"ation is called disproportionation, In dis#ro#ortionation4 the un#aired electron o& one chain &inds an electron in the carbon3hydrogen bond o& the next carbon atom &orming a double bond at the end o& the #olymer chain, ometimes4 the un#aired electron at the end o& a gro'ing chain #airs 'ith an electron &rom a carbon3hydrogen bond along the backbone o& another #olymer chain, %his starts a ne' chain gro'ing out o& the middle o& the main chain, %his is called chain transfer to polymer 4 and the result is a branched polymer , It is es#ecially a #roblem 'ith #olyethylene4 so much that linear non3branched #olyethylene cannot be made by &ree radical #olymeri"ation, /olymerisation #roducts are numerous 'ith many uses and include #henolic resins4 alkyl resins4 #olyamides4 #olyesters4 elastic &oams4 silicon #olymers4 isocyanate #olymers4 e#oxy resins4 adhesies4 coatings4 #olyethylene4 inyl #olymers and acrylic #olymers -&or #aint industry. to mention but a &e', ..1.3. Emulsi"n /"lymeri8ati"n 1mulsion #olymeri"ation is a ty#e o& &ree radical #olymeri"ation that usually starts
'ith an emulsion consisting o& 'ater4 monomer and sur&actant, %he most common ty#e o& emulsion #olymeri"ation is an oil3in3'ater emulsion4 in 'hich dro#lets o& monomer -the oil. are emulsi&ied -'ith sur&actants. in a continuous 'ater #hase,
60
#aints4 #a#er and textile coatings, Because they are not solent3based4 they are eco3&riendly, Adantages o& emulsion #olymeri"ation include9 •
High molecular 'eight #olymers can be made at &ast #olymeri"ation rates
•
%he continuous 'ater #hase is an excellent conductor o& heat and allo's the heat to be remoed &rom the system4 allo'ing many reaction methods to increase their rate,
•
ince #olymer molecules are contained 'ithin the #articles4 iscosity remains close to that o& 'ater and is not de#endent on molecular 'eight
•
%he &inal #roduct can be used as is and does not generally need to be altered or #rocessed,
7isadantages o& emulsion #olymeri"ation include9 •
ur&actants and other #olymeri"ation ad=uants remain in the #olymer or are di&&icult to remoe
•
or dry -isolated. #olymers4 'ater remoal is an energy3intensie #rocess
1mulsion #olymeri"ations are usually designed to o#erate at high conersion o& monomer to #olymer, %his can result in signi&icant chain trans&er to #olymer %he mith31'art3Harkins theory &or the mechanism o& &ree3radical emulsion #olymeri"ation is summari"ed by the &ollo'ing ste#s9 •
A monomer is dis#ersed or emulsi&ied in a solution o& sur&actant and 'ater &orming relatiely large dro#lets o& monomer in 'ater,
•
1xcess sur&actant creates micelles in the 'ater,
•
mall amounts o& monomer di&&use through the 'ater to the micelle,
•
A 'ater3soluble initiator is introduced into the 'ater #hase 'here it reacts 'ith monomer in the micelles, %his is considered mith31'art Interal ),
•
%he total sur&ace area o& the micelles is much greater than the total sur&ace area o& the &e'er4 larger monomer dro#letsQ there&ore the initiator ty#ically reacts in the micelle and not the monomer dro#let,
61
•
Monomer in the micelle (uickly #olymeri"es and the gro'ing chain terminates, At this #oint the monomer3s'ollen micelle has turned into a #olymer #article,
•
More monomer &rom the dro#lets di&&uses to the gro'ing #article4 'here more initiators 'ill eentually react,
•
1entually the &ree monomer dro#lets disa##ear and all remaining monomer is located in the #articles, %his is considered mith31'art Interal 0,
•
7e#ending on the #articular #roduct and monomer4 additional monomer and initiator may be continuously and slo'ly added to maintain their leels in the system as the #articles gro',
•
%he &inal #roduct is a dis#ersion o& #olymer #articles in 'ater, It can also be kno'n as a #olymer colloid4 a latex4 or commonly and inaccurately as an SemulsionS,
1mulsion #olymeri"ations hae been used in batch4 semi3batch4 and continuous #rocesses, %he choice de#ends on the #ro#erties desired in the &inal #olymer or dis#ersion and on the economics o& the #roduct, ... AL#YLATI(N
Alkylation is the introduction o& an alkyl radical by substitution or addition into an organic com#ound, or exam#le4 the combining o& an ole&in to a hydrocarbon is an alkylation reaction, In the #resence o& an acid catalyst such as hydrogen &luoride or sul#huric acid4 this reaction is used &or the conersion o& gaseous hydrocarbons to gasoline, %he #rocesses are usually exothermic and similar to #olymerisation, Another exam#le is the &ormation o& *4*37imethylbutane &rom ethylene and isobutane9
62
Alkylation reactions include the binding o& an alkyl grou# to9 ).
Carbon -to make #roducts such as gasoline alkylates4 ethylben"ene etc.
*.
Oxygen o& a hydroxyl grou# o& an alcohol or #henol -ethers4 alkaloids.
0.
%rialent nitrogen -amines.
2.
A tertiary nitrogen com#ound -(uaternary ammonium com#ounds.
5.
Metals
6.
Miscellaneous elements such as sul#hur or silicon
In 6.4 the alkyl is in the &orm o& alkyl halide or ester, A#art &rom gasoline4 other classes o& #roducts &rom alkylation reactions include #harmaceuticals4 detergents4 disin&ectants4 dyes and #lastics, Alkylates o& actie methylenes are easily #re#ared using a base such as ethoxide4 1tO 3,
Methyl and #rimary halides are most suitable &or alkylation reactions, In #rinci#le both o& the hydrogens can be re#laced 'ith alkyl grou#s9
%his can be utili"ed to &orm a cyclic system by using a dihalide as sho'n belo'9
63
..3. HYDR(LYSIS
In the hydrolysis o& either organic or inorganic com#ounds4 'ater and another com#ound undergo double decom#osition to &orm t'o #roducts, %he hydrogen &rom the 'ater goes to one #roduct 'hile the hydroxyl goes to the other #roduct as illustrated in the &ollo'ing e(uation9 T8 DH*O
H8 D TOH
I& T8 'ere an inorganic com#ound4 this 'ould be the reerse o& neutrali"ation, But in organic chemistry4 hydrolysis has a 'ider sco#e4 'hich includes9 •
Inersion o& sugar
•
Breaking do'n o& #roteins
•
a#oni&ication o& &ats and oils
%hese reactions can be carried out 'ith 'ater alone, Ho'eer4 there are agents that accelerate or catalyse the hydrolysis, %hese include9 •
Alkalis
•
Acids
•
1n"ymes
..3.1. Hydr"lysis "< esters
%his hydrolysis is re&erred to as sa#oni&ication, A good exam#le is the sa#oni&ication o& &ats and oils to glycerol and either soa# or &atty acids, 1ster hydrolysis is reersible and is catalysed by both the oxonium ion -H 0OD.4 and hydroxyl ion -OH 3., %hat is4 it can be either acid or alkali catalysed, Addition o& acid s#eeds u# reaction 'ithout shi&ting the e(uilibrium signi&icantly, On the other hand4 alkali addition accelerates reaction and shi&ts the reaction to the right so that it goes to com#letion, In Unit 64 'e shall study the a##lication o& ester hydrolysis in soa# making,
... (THER UNIT R(CESSES
In table *,*4 you 'ill &ind other unit #rocesses 'ith their de&inition and industrial a##lication,
64
Ta:le .. (ther unit /r"*esses $ith their industrial a//li*ati"ns , Unit /r"*ess Sul/h"nati"n
rie< des*ri/ti"n A chemical #rocess inoles
that
introduction
Industrial a//li*ati"ns Intermediates in manu&acture o& #henol4
o& xylene4 dodecyl ben"ene sul#honic acid
sul#honic acid grou# -O*OH.
detergent4
#olystyrene4
na#hthalene
or its corres#onding salt or deriaties and ali#hatic sul#honated sul#honyl halide -O*Cl. into an
organic
molecule,
sul#honating
agents
com#ounds,
%he
include
sul#huric acid -$F.4 sul#hur trioxide in 'ater -oleum. and Esteri
Hydr"%enati"n
&uming sul#huric acid, A chemical #rocess in 'hich an
/roduction
ester and 'ater are &ormed
#olyethylene tere#hthalate4 manu&acture
'hen an organic radical is
o& alkyl resins and #olyinyl acetate4
substituted &or in a molecule by
#re#aration o& ter#ene and cellulose
an ionisable hydrogen o& an
esters
acid, A chemical molecular another
reaction
hydrogen substance
o&
synthetic
&ibres
like
o& Manu&acture ammonia -see details in 'ith
learning actiity t'o.4 manu&acture o&
the
li(uid &uels4 hydrogenated egetable &ats4
in
#resence o& a catalyst,
hydrogenation
o&
carbohydrates
to
#ro#ylene4 glycol and sorbitol and many Hal"%enati"n
others, Inoles addition o& one or Chlorinated com#ounds are used in the
+*hl"rinati"n6
more halogen atoms to an
chlorohydrocarbons such as chloro&orm4
:r"minati"n and
organic com#ound
ethylene
i"dinati"n-
Nitrati"n
chlorohydrin
-&reon.4
77%4
carbon tetrachloride4 ole&inic acids4 acid %his is the introduction o& one
chlorides4 etc, Industrial solents4 dyestu&&s4 ex#losies4
or more nitro grou#s -3EO *. into
#harmaceuticals and as intermediates in
an
the #roduction o& amines
organic
com#ound,
Monoalent atoms or grou#s o& atoms are re#laced by the nitro grou#
7"rmati2e E2aluati"n
65
), >ist do'n the arious #ur#oses &or si"e reduction, *, 1x#lain ho' a ball mill 'orks, 0, ist do'n the arious ty#es o& alkylation reactions )+,
alkylation
-ii.
hydrolysis
-iii.
sul#honation
-i.
nitration
66
LEARNIN9 ACTI&ITY 3) IN(R9ANIC CHEMICAL INDUSTRIES ART 1) E=TRACTI&E METALLUR9Y Unit (:;e*ti2es
At the end o& this unit you should be able to9 a, 7escribe the arious stages mineral ores go through in a ty#ical ore dressing #rocess, b,
In this unit4 'e shall study ho' metals are extracted &rom mineral ores in 'hich they exist 'ith other materials o& less alue, ?enerally4 ores are &irst taken through si"e reduction4 sorting and agglomeration to trans&orm them into a &orm that can be taken through extraction #rocesses including calcining4 roasting4 smelting and re&ining, 1xtractie metallurgy o& iron4 aluminium and co##er res#ectiely are then #resented,
List "< rele2ant readin%s
7as :,, -)$FF. Industrial Chemistry9 Metallurgy4 alyani /ublishers4 Ee' 7elhi,
List "< rele2ant res"ur*es •
Com#uter 'ith internet &acility to access links and releant co#y'rite &ree resources
•
C73:om accom#anying this module &or com#ulsory reading and demonstrations
•
Multimedia resources like ideo4VC74and C7 #layers
List "< rele2ant use
67
htt#9;;''',mine3engineer,com htt#9;;electrochem,c'ru,ed;encycl %he &irst site has use&ul in&ormationon on arious unit o#erations used in the chemical industry, /hotogra#hs and other illustrations are gien, %he second site has in&ormation on aluminium #roduction, 3.1. Mineral "res
An ore is a mineral de#osit 'hich can be #ro&itably ex#loited, It may contain three grou#s o& minerals namely9 a. aluable minerals o& the metal 'hich is being sought b. com#ounds o& associated metals 'hich may be o& secondary alue c. gangue minerals o& minimum alue, Almost all metals are deried &rom mineral ores, %here are also ores that contain non3metals such as sul#hur . ?enerally4 the aluable mineral in an ore may be &ound in the &orm o& natie metal4 oxides4 oxy3salts4 sul#hides or arsenides, 7uring mining4 large o#en #its are excaated by breaking the ore using ex#losies, Ores as mined may be in large lum#s and there&ore4 some si"e reduction is done at the mine, %he ore is shoeled into trucks and trans#orted to the &actory, I& the mineral ore is &ound in 'aterbeds4 mining is carried out by dredging, or exam#le4 sand is dredged &rom rier beds,
3.. (re dressin%
Be&ore the ores are sub=ected to the main chemical treatment ste#s4 they are #re3 treated by a series o& relatiely chea# #rocesses4 mainly #hysical rather than chemical in nature, %hese #rocesses constitute 'hat is kno'n as "re dressin%. %hey are meant to e&&ect the concentration o& the aluable minerals and to render the enriched material into the most suitable #hysical condition &or subse(uent o#erations, Ore dressing may include9
Si8e Redu*ti"n to such a si"e as 'ill release or ex#ose all aluable
minerals
68
S"rtin% to se#arate #articles o& ore minerals &rom gangue -non3aluable.
minerals or di&&erent ores &rom one another
A%%l"merati"n may be carried out sometimes be&ore a roasting o#eration
I& the ores are rich in the aluable mineral4 aboe #rocesses may not add alue, uch ores can be ground4 si"ed and blended 'ith other ores in order to #roide a homogeneous &eed to say4 a blast &urnace or reaction bed,
3..1. Si8e Redu*ti"n
i"e reduction may be carried out by &irst crushing the ore do'n to !mm maximum &ollo'ed by grinding to smaller si"es, @a' crushers can be used dee# in the mine to #re#are the ore &or trans#ortation to the sur&ace e,g, using bucket eleators, 3... Si8in%
creens are used to se#arate #articles according to si"e and may not a&&ect the concentrations o& the ore minerals, /articles are se#arated into oersi"e and undersi"e, 3..3. S"rtin%
%he #articles may be sorted by classi&ication4 &lotation or magnetic methods, "lassifiers
%hese are deices that se#arate #articles according to their di&&erent rates o& trael under graity through a &luid medium such as 'ater, /articles o& di&&erent densities4 si"es and sha#es hae di&&erent &alling elocities, Classi&iers include rake classi&iers and =igs, 3... 7l"tati"n
lotation uses di&&erence in sur&ace #ro#erties o& the indiidual minerals, It is readily a##lied to ery &ine concentrates and can distinguish ore mineral &rom gangue4 and also4 one ore mineral &rom another, 3..,. Ma%neti* Se/arati"n
erromagnetic magnetite or iron minerals 'hich can be chemically altered to #roduce magnetite may be sorted out using a magnetic se#arator as described in Unit *,
69
3..'. Ele*tr"stati* Se/arati"n
Minerals hae a 'ide range o& electrical conductiity and can be distinguished by this #ro#erty, I& seeral kinds o& #articles are gien an electrostatic charge and are then brought into contact 'ith an electrical conductor at earth #otential4 the charge 'ill leak a'ay &rom good conductors much more ra#idly than &rom #oor conductors,
7i% 3.1. Ele*tr"stati* se/arati"n 3... De$aterin% and
70
A&ter sorting and leaching4 it is necessary to se#arate the solid and li(uid #hases, Coarse solids may be &reed &rom most o& their moisture by draining, lurries 'ith #articles 'hich can settle may be se#arated &rom the bulk o& the li(uid by settling and subse(uent decantation, %hese de'atering methods may reduce moisture content to 5+, %he moisture content may be reduced &urther by &iltration and drying, I& the aluable ore is in the &iltrate4 it can be recoered by ea#oration &ollo'ed by drying, 3..B. A%%l"merati"n
#elleti"ing
bri(ueting
sintering
Bri#ueting
%his is a mechanical #rocess o& agglomeration in 'hich the materials4 a&ter mixing 'ith 'ater and necessary bonding agents are #ressed or extruded into brick or block &orm, %hese blocks are then dried and hardened by heating, Use o& hydraulic cement allo's hardening to be carried out cold, Bri(ueting is not #o#ular in mineral ore agglomeration, $intering
intering inoles di&&usion o& material bet'een #articles, It is a##lied to the consolidation o& metallic and ceramic #o'der com#acts 'hich are heated to tem#eratures a##roaching their melting #oints to allo' di&&usion to take #lace at the #oints o& contact o& #articles so that they gro' together to &orm a rigid entity, %he #rocess can be enisaged as a net migration o& acancies into the solid at the highly cured energy sur&aces near #oints o& contact and again at lo' energy areas a'ay &rom contact #oints intering may be accom#anied by a chemical reaction,
3.3. Etra*ti"n r"*esses
71
o &ar 'e hae been dealing 'ith unit o#erations that #re#are the ore &or chemical reactions used to extract the aluable metal &rom the ore, Eo' 'e 'ant to look at extraction and re&ining o& the metal,
3.3.1. Cal*inati"n
%his is the thermal treatment o& an ore to e&&ect its decom#osition and the elimination o& a olatile #roduct4 usually carbon dioxide or 'ater, %he &ollo'ing are calcinations reactions CaC(3
Ca(
G
C(
T F 10000C
M%C(3
M%( G
C(
T F 1 0C
MnC(3
Mn( G
C(
T F 3 0C
7eC(3
7e(
C(
T F 00 0C
G
Calcination may be carried out in rotating kilns using countercurrent &lo' &or e&&icient heat trans&er,
3.3.. R"astin%
:oasting inoles chemical changes other than decom#osition4 usually 'ith &urnace atmos#here, A roast may e&&ect calcinations and drying as sho'n belo', CuS G
(
CuS G
S( +*al*inati"n-
CuS G
(
Cu
S(
G
+r"astin%-
3.3.3. Smeltin%
%his is essentially a smelting #rocess in 'hich the com#onents o& the charge in the molten state se#arate into t'o or more layers 'hich may be slag4 matte4 s#eiss or metal
matte9 heay sul#hide material
slag9 light oxide material
s#eiss9
iron oxide4 insoluble in matte4 slag or metalQ it may contain
elements
72
melting o& metal inoles reduction4 usually by carbon or coal or coke and may be #er&ormed in a blast &urnace or an electric &urnace, In the blast &urnace4 coke is burned into CO * 'hich reacts &urther 'ith the carbon to &orm CO, %he ascending gases #re3heat the solid charge descending the stack and reduce metal oxides to metal, %his then is a #rocess o& drying &ollo'ed by calcination and roasting, %he metal melts and the slag &orms gangue and &lux,
3.3.. Re
1lectrolysis may be used &or metal extraction and metal re&ining, In &ire re&ining4 extracted metals are brought into li(uid state and their com#osition &inally ad=usted, In some case4 this may be sim#le smelting to allo' cathodically entrained hydrogen to esca#e by di&&usion, In other cases4 im#urities may react to &orm com#ounds 'hich are insoluble in the molten state, Conerters are used &or oxidi"ing im#urities out o& blast &urnace iron in steel3 making and &or oxidation o& sul#hur &rom co##er and nickel matte, 7istillation may also be a##lied in metal #uri&ication,
3.. Etra*ti2e Metallur%y (< Ir"n 3..1. Uses "< ir"n
Iron is used in the &orms sho'n belo' as material o& construction &or machines4 #lants4 buildings4 locomoties4 shi#s4 automobiles4 rail'ay lines and &or many other things, All these &orms are obtained &rom #ig iron 'hich is &irst obtained &rom the iron ore, a,
73
e, Alloy or s#ecial steels 'hich besides carbon contain one or more metals such as Ei4 Cr4 <4 V4 Mo4 Mn, 3... Ra$ materials
%he main ra' materials &or the manu&acture o& iron and steel are iron ore and limestone or dolomite as &lux, Coking coal is used as &uel, %he &uel seres t'o #ur#oses9 to heat the &urnace and to #roduce CO 'hich acts as the reducing agent, %o make s#ecial steels other materials such as nickel4 chromium4 cobalt are added, Iron ore de#osits are &ound in India4 China4 Bra"il4 Canada4 ?ermany and United tates o& America, %he ores include red haematite -e *O0.4 the less in&erior bro'n hydrated haematite also kno'n as limonite -*e *O0,0H*O.4 the magnetic magnetite -e 0O2. 'hich is black in colour and #yrites -e *., %he haematite is easily reduced, Magnetite contains about !* #ure metal and it is reduced 'ith some di&&iculty, 3..3. Rem"2al "< im/urities in ir"n "re
%he #resence o& im#urities in the iron ore not only reduce the iron content in the ore but also increase #roduction costs es#ecially 'ith regard to consum#tion o& &lux and &uel, I& limonite is used4 it is &irst dried be&ore use,
74
the #ig iron 'here it is combined 'ith steel in the conertor, As a result4 the ores are sometimes classi&ied as acid or basic ores according to the amount o& #hos#horus #resent, Acid ores contain less than +,+5 #hos#horus 'hile basic ores has more than +,+5, A small amount o& manganese is generally #resent in iron ores, Manganese is adantageous &or steel #roduction because it reduces the e&&ect o& sul#hur by &orming manganese sul#hide -Mn., ometimes4 i& manganese is absent &rom the ores4 it is added, 3... 7uel
Coke is the &uel used to melt the ore and also to reduce the iron ore to metallic iron, Coke is #roduced at the bottom o& the blast &urnace by carboni"ation o& coal i,e, burning o& coal in the absence o& oxygen to remoe olatile matter, ?ood (uality coke has about F+ carbon and *+ ash, It is hard to #reent the &ormation o& CO and its high #orosity #roides large sur&ace area &or the chemical reactions, It is consumed at the rate o& one ton #er ton o& #ig iron,
3..,. Manu
/ig iron is a direct #roduct o& smelting iron ore 'ith &luxes and &uel in a tall blast &urnace, %he oxygen is introduced at the to# o& the &urnace4 blo'n or blasted through bron"e or co##er no""les oer the &urnace materials in a number o& symmetrically #laced tubes4 called tuyeres, %he air blast is #reheated to a tem#erature o& about !++ +C and #ressure o& *,5kg;cm * using the hot exhaust gases leaing the &urnace at the to#, /reheating greatly increases the economy o& steel #roduction, %he molten iron and slag collect at the bottom o& the &urnace 'hile the gases esca#e &rom the to#, %he slag layer &loats oer the heaier iron and is #eriodically collected as dross and stored as 'aste material that can be used &or cement manu&acture or &or making &loor tiles %he #ig iron is ta##ed and is either used to #roduce cast iron4 stored in #igs o& sand bags or is taken &or steel #roduction, %o make cast iron4 the molten metal is
75
#oured into moulds o& desired si"e and sha#e, %he metal gets cooled and solidi&ies taking the desired sha#e,
7i% 3.. S*hemati* dia%ram "< a :last
3..'. Rea*ti"ns "< the :last
%he tem#erature o& the blast &urnace #rogressiely rises u# &rom to# to bottom, %he &ollo'ing reactions take #lace at di&&erent "ones9 Iron ore reduction9 7e(3 G C(
C( G 7e 3(
7e3( G C(
37e( G C(
37e( G 3C(
37e G 3C(
uel reactions C G (
C(
C( G C
C(
lag &ormation reactions CaC(3 Ca( G Si(
Ca( G C( CaSi(3
76
7e G Si(
7e( G Si
Mn G Si(
Mn( G Si
Mn( G C
Mn G C(
7eS G Ca( G C
CaS G 7e G C(
7eS G Mn
7e G MnS
Ca3+(- G 3Si( G ,C
3CaSi( 3 G G C(.
Most o& the sul#hur #asses into the slag as Ca and Mn and only a small #ortion remains in the metal as e and Mn,
3.,. Etra*ti2e Metallur%y (< Aluminium Aluminium is the most abundant metal in earth and is commercially extracted &rom bauxite ores in 'hich it occurs as hydrated aluminium oxide, 1xtraction o& aluminium &rom bauxite is carried out in three stages9
(re dressin%9 cleaning ore by means o& se#aration o& the metal
containing mineral &rom the 'aste -gangue.,
Chemi*al treatment "< :auite &or conerting the hydrated aluminium
oxide to #ure aluminum oxide,
Redu*ti"n "< aluminium
#rocess, Ore dressing may inole 'ashing the ore4 si"e classi&ication and leaching,
3.,.1. Chemi*al treatment "< :auite
At this stage bauxite is crushed and ground to the correct #article si"e &or e&&icient extraction o& the alumina through digestion 'ith hot sodium hydroxide solution 'hich dissoles the aluminium hydroxide4 &orming a solution o& sodium aluminate, Na(H G Al (3
NaAl(3 G H(
%he residual im#urities -oxides o& silicon4 iron4 titanium and aluminium i,e, iO *4 e*O04 %iO*4 Al*O0., %hese insoluble im#urities are called Xred mudY 'hich together 'ith &ine solid im#urities4 are se#arated &rom the sodium aluminate solution by 'ashing and thickening, %he solution is then seeded 'ith aluminium
77
hydroxide &rom a #reious batch in #reci#itator tanks4 'here aluminium hydroxide #reci#itates &rom the solution,
NaAl(3 G H(
Al+(H- 3 G Na(H
%he aluminium hydroxide a&ter se#aration &rom the sodium hydroxide is conerted into #ure aluminium oxide by heating to )F++ -)+++ZC. in rotary kilns or &luidi"ed bed calciners, Al+(H-3
Al(3 G 3H(
3.,.. Redu*ti"n "< aluminum
/rimary aluminium is #roduced by the electrolytic reduction o& the aluminium oxide, As aluminium oxide is a ery #oor electricity conductor4 its electrolysis is carried out in a bath o& molten cryolite -mineral4 containing sodium aluminium &luoride J Ea 0 Al6. as sho'n in the schematic diagram belo',
7i% 3.3. Ele*tr"lyti* /r"*ess <"r aluminium manu
%his technology is called Hall4Her"ult /r"*ess. %he electrolytic cell &or aluminum #roduction consists o& a #ot 'ith carbon lining %he carbon lining is
78
contained contained in a steel shell 'ith a thermal insulation insulation o& alumina or insulating brick, brick, , %his carbon lining seres as the negatie electrode -cathode., /rebaked carbon anodes are connected and sus#ended &rom the current conductor -bus bar., %he anode anodes s are are immer immerse sed d into into the bath o& molte molten n cryoli cryolite te at $)5 to $5+ $5+
o
C, %he
aluminum oxide is added to the cryolite and dissoled in it,
79
%he anode butts are sent back to the anode #lant to be ground and mixed into ne' anode #aste to be #ressed and baked, %he molten aluminium is #eriodically ta##ed under acuum &rom the &urnace into a crucible and cast into ingots,
3.'. E=TRACTI&E M META ETALLUR9Y LLUR9Y (7 C(ER
Co##er is mostly extracted &rom ores containing co##er sul#hides4 co##er oxides or co##er carbonates, Co##er ores are generally #oor and contain bet'een ),5 and 5 co##er co##er,, %here& %here&ore4 ore4 commerci commercial al extract extraction ion o& co##er co##er inole inoles s seeral seeral dressing o#erations be&ore the smelting stage, %he %he extr extract action ion o& co## co##er er &rom &rom its sul#h sul#hide ide ores ores is done done by elimin eliminat ating ing the the gangue4 iron4 sul#hur and minor im#urities by the &ollo'ing ste#s yielding the sho'n co##er a&ter each ste#9 co##er
C"n*entrati"n
)53*5
R"astin%
0+325
Smeltin%
3
Matte *"n2ersi"n
$F
7ire re
$$,5
Ele*tr"lyti* *"n2ersi"n
$$,$
0,6,), Concentrating %he #ur#ose o& concentration ste# is to se#arate the co##er mineral &rom the gangue, %he ore is &irst crushed and &inely ground, It is made into a slurry 'ith 'ater and then &ed into a &roth &lotation cell, %he ore #articles are li&ted u# by air bubbles 'hile the gangue remain in the cell, %he &roth containing the ore is thickened and &iltered,%he #ul# is dried to about 6 moisture,
80
3.'.. R"astin%
%he ob=ectie o& roasting is to remoe excess sul#hur, %hus4 i& the ore does not contain excess sul#hur4 roasting may be omitted and the ore directly smelted, :oasting is carried out in a multi#le hearth &urnace or in a &luidi"ed bed, %he dry #ul# is &ed into the roaster at 6++ to !++ oC, %he burning o& the sul#hide ores su##lies the heat to maintain the tem#erature at 'hich roasting takes #lace, %he reactions at the roaster are as &ollo's,
AsS3 G >(
As(3 G 'S(
S:S3 G >(
S:(3 G 'S(
7eS3
7eS G S
S G (
S(
7eS G 3(
S( G 7e(
7e( G (
7e(3
%he arsenic and antimony are olatiles and and leae 'ith sul#hur dioxide,
3.'.3. Matte smeltin%
At this stage the concentrate concentrate is smelted in a &urnace to #roduce #roduce a mixture o& co##er and iron4 called matte, melting is carried out at about )05+ oC, %he rasted ore is in #o'der &orm and cannot there&ore be smelted coneniently in a blast &urnace, It is done in a long reerberatory &urnace heated by coal dust, %he &ollo'ing are the reactions that take #lace in the &urnace9
7eS G 3(
7e( G S(
7e( G Si(
7eSi(3
Cu( G 7eS
CuS G 7e(
Cu( G 7eS
CuS G 7e(
CuS 37e(3 G 7eS
CuS G S 7e( G S(
81
Cu* and #art o& the e &orm the matte, %he silicates and oxides o& iron are slagged, %he gangue is absorbed by the slag and remoed,
3.'.. lister *"//er /r"du*ti"n
%he ob=ect o& the conerter o#eration is to conert matte into molten blister co##er containing $6 to $F co##er and remoe the iron rich slag %he o#eration is carried out in t'o stages each o& 'hich has a distinctie &lame colour, In the &irst stage4 air is blo'n through the matte untill all the slag is &ormed i,e, the total elimination o& the e, ilica is used to react 'ith the oxide, %he slag is remoed by tilting the conerter, Air is again blo'n through the matte and the Cu* is conerted to Cu, %he &ollo'ing are the reactions in the conerter9 lag &ormation stage9
Blister co##er &ormation
7eS G 3(
7e( G S(
7e( G Si(
7eSi(3
CuS G 3(
Cu( G S(
Cu( G CuS
'Cu G S(
3.'.,. 7ire Re
%he blister co##er is &ed into a &urnace 'here some o& the Cu is oxidixed into Cu*O 'hich dissoles in the molten co##er, %he oxide ra#idly oxidi"es the im#urities, O * #asses out 'hile other im#urities &orm dross on the sur&ace, %he dross is &re(uently skimmed o&& to ex#ose &resh sur&ace &or oxidation, A #ole o& green 'ood is then thrust in and hydrogen &rom the 'ood reduces the excess oxygen, /oling is continued until #ro#er sur&ace characteristics o& the cooled sam#les are obtained, %he #roduct is called tough #itch, It has good electrical conductiity, It is cast into slabs, 3.'.'. Ele*tr"lyti* re
%ough #itch co##er is not &it &or gas3'elding until it is deoxidi"ed &urther, It is made into im#ure co##er anodes 'hich are immersed in a 5 to )+ sul&uric acid bath contaning co##er sul#hate, /ure co##er &oil seres as the cathode 'here co##er de#osits, Cathodes #roduced as a result o& the electrolytic re&ining #rocess contain $$,$ o& co##er 'hich is used &or manu&acturing co##er and co##er alloys #roducts,
82
7"rmati2e E2aluati"n
),
83
LEARNIN9 ACTI&ITY ) IN(R9ANIC CHEMICAL INDUSTRIES ART II) CHL(R4AL#ALI6 AMM(NIA6 SULHURIC ACID6 7ERTILIJER AND CEMENT
Unit ":;e*ti2es
At the end o& this unit you should be able to9 a, 7escribe using e(uations and diagrams4 the electrolytic #roduction o& sodium hydroxide and chlorine using mercury4 dia#hram and membrane cells b, 1x#lain ho' ammonia is manu&actured &rom methane and air by the Haber #rocess c, 7escribe the Contact #rocess &or the manu&acture o& sul#huric acid d, 7iscuss the arious ty#es o& &ertli"ers and the manu&acture o& #hos#hate &ertili"er e, 7escribe using diagrams4 e(uations and unit o#erations4 the #rocess &or the manu&acture o& /ortland cement, Summary "< the learnin% a*ti2ity
In this Unit4 'e 'ill look at industrial manu&acture o& some o& the common basic chemicals, 8ou 'ill learn about the #rocesses and the chemistry inoled in the manu&acture o&4 sodium hydroxide and chlorine4 ammonia4 sul#huric acid4 &ertili"er and #ortland cement,
), Chang :, and %ikkanen <, -)$FF., %he %o# &&ty Industrial Chemicals, *, ?eorge %, A, -)$!!., Shreve’s Chemical Process Industries. 5 th edn. Mc?:A<3HI>> IE%1:EA%IOEA> 17I%IOE, Chemical 1ngineering eries, inga#ore, 0, hukla , 7 and /andey ?, E4 -)$!F., A %extbook o& Chemical %echnology, Vol,) -Inorganic;Organic., Vikas #ublishing House /V% >td, Ee' 7elhi 2, te#henson :,M, -)$66., Introduction to the Chemical /rocess Industries4 :einhold /ublishing Cor#oration4 Ee' 8ork,
84
5, ?erhart"4 <, -1ditor.4 -)$F!., Ullmanns 1ncyclo#aedia o& Industrial Chemistry4 5 th 1dition4 VCH Verlagsgesellscha&t mbH4
List "< rele2ant res"ur*es •
Com#uter 'ith internet &acility to access links and releant co#y'rite &ree resources
•
C73:om accom#anying this module &or com#ulsory reading and demonstrations
•
Multimedia resources like ideo4VC7 and C7#layers
List "< rele2ant use
htt#9;;cheresources,com htt#9;uk,encarta,msn,com;media!6)566$06;ul#huric Acid,html htt#;''',icis,com;chemical;intelligence %hese sites hae in&ormation and other links on manu&acturing technologies o& arious chemical #roducts,
.1. Manu
Be&ore the electrolytic method o& making sodium hydroxide and chlorine -chlor3 alkali #rocess. became 'idely used4 sodium hydroxide 'as made &rom soda ash by the lime4s"da #rocess, %he soda ash as a(ueous Ea *CO0 is reacted 'ith slaked lime -Ca-OH. *. according to the &ollo'ing e(uation9 Ea*CO0-a(. D Ca-OH. *-s. *EaOH-a(. D CaCO 0-s. %he chlor3alkali #rocess has gradually re#laced the lime3soda #rocess, .1.. Ra$ Materials
%he chlor3alkali industry uses rock salt4 a natural de#osit o& sodium chloride, %he a(ueous sodium chloride solution4 re&erred to as brine contains Ea D4 Cl34 HD and
85
OH3 ions, 1lectrolysis o& this solution #roduces simultaneously chlorine4 sodium hydroxide and hydrogen in the ratio o& )9),)09+,+*F
.1.3. Chl"r4al5ali /r"*ess
%he term chlor3alkali re&ers to the t'o chemicals -chlorine and an alkali. 'hich are simultaneously #roduced as a result o& the electrolysis o& brine, %he most common chlor3alkali chemicals are chlorine and sodium hydroxide -caustic soda. but can include #otassium hydroxide 'hen a #otassium brine is used, Brine electrolysis #roduces chlorine at the anode and hydrogen along 'ith the alkali hydroxide at the cathode, %he t'o #roducts are remoed in se#arate streams, %he oerall chemical reaction o& electrolysis o& sodium chloride is9 *EaCl-a(. D *H *O-l. *EaOH-a(. D Cl *-g. D H*-g. I& chlorine is not se#arated &rom the sodium hydroxide4 side reactions such as the &ollo'ing 'ould occur9 *EaOH-a(. D Cl *-g. EaOCl-a(. D EaCl-a(. D H *O-l. H*-g. D Cl-g. *HCl-g.
%hree #rocesses are in use9 the dia#hragm3cell #rocess4 the membrane3cell #rocess4 and the mercury3cell #rocess, %hese are sho'n in the &igures belo',
86
7i% .1. Chl"r4al5ali *ells
.1.. Mer*ury Cells
In the mercury3cell #rocess4 a &lo'ing #ool o& mercury at the bottom o& the electrolytic cell seres as the cathode, %he anodes are gra#hite or modi&ied titanium,
Cell rea*ti"ns
At the anode −
2Cl ( aq )
→
Cl 2( g ) + 2e
−
At cathode
2 Na
+
( aq ) +
2e
−
Hg
→
Oerall9 2 NaCl ( aq )
2 Na / Hg →
2 NaHg + Cl 2 ( g )
%he amalgam -a mercury3sodium alloy. is taken to a di&&erent essel &or decom#osition according to the e(uation9
87
*Ea ,Hg D *H *O *EaOH D H* D Hg
Initially mercury cells seemed to dominate the &ield because it #roduced high (uality #roducts,
.1.,. Dia/hra%m Cells
%hese cells contain a dia#hragm4 usually made o& asbestos &ibres that se#arate the anode &rom the cathode, %he dia#hragm also allo's ions to #ass by electrical migration but limit the di&&usion o& #roducts, %he anodes are made o& gra#hite and the cathodes o& cast iron ,
i,
%he electrodes can be #laced close together and this #ermits com#actness o& dia#hragm cells o& lo' electrical resistance,
ii,
%hey easily become congested 'ith use -sho'n by high oltage dro#. and there&ore must be re#laced regularly,
iii,
7ia#hragms #ermit &lo' o& brine &rom anode to cathode and this reduces greatly on side reactions like &ormation o& sodium hy#ochlorite,
i,
7ia#hragm cells 'ith metal cathodes like titanium coated 'ith rare earth oxides4 rarely deelo# congested dia#hragms and do not re(uire regular re#lacement, %his reduces on o#erating costs,
88
,
%he release o& asbestos to the enironment is a ma=or antici#ated #roblem o& dia#hragm cells, 7ia#hragms made o& corrosion resistant #lastics are a #ro#osed solution to asbestos #ollution,
i,
A ma=or adantage is that dia#hragm cells can o#erate on dilute *+ reasonably im#ure brine, uch brines #roduce dilute sodium hydroxide -about )5. contaminated 'ith sodium chloride, Concentrations to about 5+ are achieed by use o& multi3e&&ect ea#orators, tudies hae sho'n that nearly *46++kg o& 'ater must be ea#orated to obtain ) ton o& 5+ caustic soda,
7ia#hragm cell technology is still in use4 but the use o& asbestos in the cells is causing ne' #lants to turn to the ne'er ion3exchange or membrane technology,
.1.'. Mem:rane Cells
Im#roed designs o& membrane cells and chea#er #uri&ication hae increased the economics o& the ne' membrane #rocess, ig 2,* re#resents a condensed oerie' o& a membrane cell #rocess,
7i% . Mem:rane *hl"r4al5ali /r"*ess
In this #rocess4 rather than using a dia#hragm4 semi #ermeable membrane made o& #lastic sheets is used to se#arate the anode and cathode com#artments, %he
89
#lastic sheets are #orous and chemically actie to allo' sodium ions to #ass through but re=ect hydroxyl ions, An exam#le o& membrane material is #er&luorosul#honic acid #olymer, %he membranes exclude OH 3 and Cl 3 ions &rom the anode chamber thereby making the #roduct &ree &rom the salt contamination ex#erienced in the dia#hragm cell, %he membrane cells use more concentrated brine solutions and #roduce #urer and more concentrated sodium hydroxide4 'hich re(uire less ea#oration during concentration,
7i% .3. Chl"r4al5ali mem:rane *ell
Brine is #um#ed into the anode com#artment4 and only sodium ions #ass into the cathode com#artment4 'hich contains #ure 'ater, %hus4 the caustic soda #roduced has ery little salt contamination,
.. Manu
..1. Intr"du*ti"n.
90
Ammonia is one o& the most highly #roduced inorganic chemicals in the 'orld because o& its 'ides#read a##lication, ynthetic ammonia is #roduced &rom the reaction bet'een nitrogen and hydrogen, Be&ore synthetic nitrogen &ixation 'as discoered4 manures4 ammonium sul&ate -a by3#roduct &rom the coking o& coal.4 Chilean salt#etre4 and later4 ammonia recoered &rom coke manu&acture 'ere some o& the im#ortant sources o& &ixed nitrogen, 7uring the &irst decade o& the t'entieth century4 the 'orld'ide demand &or nitrogen3based &ertili"ers &ar exceeded the existent su##ly,
... Uses "< amm"nia
Ammonia is the basis &rom 'hich irtually all nitrogen3containing #roducts are deried, %he main uses o& ammonia include the manu&acture o&9 •
ertili"ers --ammonium sul&ate4 diammonium #hos#hate4 urea.
•
Eitric acid
•
1x#losies
•
ibres4 synthetic rubber4 #lastics such as nylon and other #olyamides
•
:e&rigeration &or making ice4 large scale re&rigeration #lants4 air3 conditioning units in buildings and #lants
•
/harmaceuticals -sul&onamide4 itamins4 etc,.
•
/ul# and #a#er
•
1xtractie metallurgy
•
Cleaning solutions
.1.3. Ra$ Materials
%he ra' materials used to manu&acture ammonia are air4 'ater and4 hydrocarbons, Coal can also be used in #lace o& hydrocarbons but the #rocess is com#lex and ex#ensie,
... Nitr"%en
91
or a long time4 commercial deelo#ment o& nitrogen &ixation ammonia #rocess had #roed elusie, Old methods used to #roduce ammonia included dry distillation o& nitrogenous egetable and animal 'aste #roducts, Here4 nitrous acid and nitrites 'ere reduced 'ith hydrogen according to the &ollo'ing e(uation9 E*O D 2H* *EH0 D H*O Ammonia 'as also #roduced by the decom#osition o& ammonium salts using alkaline hydroxides such as (uicklime as sho'n in the &ollo'ing e(uation, *EH2Cl D *CaCl * CaCl* D Ca-OH. * D *EH0
Haber inented a large3scale catalytic synthesis o& ammonia &rom elemental hydrogen and nitrogen gas4 reactants 'hich are abundant and inex#ensie, By using high tem#erature -around 5++ oC.4 high #ressure -a##roximately )5+3*++ atm.4 and an iron catalyst4 Haber could &orce relatiely unreactie gaseous nitrogen and hydrogen to combine into ammonia, %he collaboratie e&&orts o& Haber and Carl Bosch made the commercial high3 #ressure synthesis o& ammonia #ossible by )$)0, %his energy3intensie #rocess has undergone considerable modi&ication in recent years , ..,. Chemi*al Rea*ti"n and E!uili:rium
Ammonia synthesis &rom nitrogen and hydrogen is an exothermic reersible reaction and can be described by the &ollo'ing oerall reaction, &'"N" ( )'"*"
+,, o
C- e
Δ
N* )
* / 0+.123'mol
%he reaction is accom#anied by decrease in olume and by >e Chateliers #rinci#le4 increasing the #ressure causes the e(uilibrium to shi&t to the right resulting in a higher yield o& ammonia, ince the reaction is exothermic4 decreasing the tem#erature also causes the e(uilibrium #osition to moe to the right again resulting in a higher yield o& ammonia,
92
nitrogen re(uires a lot o& energy to dissociate, In the gas #hase this dissociation occurs only at around 0+++[C, 1en the hydrogen molecule4 'hich has a 'eaker molecular bond4 only dissociates markedly at tem#eratures aboe )+++[C, ..'. Catalyst
ince the ammonia synthesis reaction cannot be moed to the right at lo' tem#erature4 this calls &or tem#erature increase4 'hich un&ortunately dries the reerse reaction, %his is 'here the role o& the iron catalyst comes in, %he reaction 'hen carried out at high #ressures and tem#eratures occurs 'ith large yields 'hen iron catalysts are #resent, %he hydrogen and nitrogen molecules lose their translational degrees o& &reedom 'hen bound to the catalyst sur&ace,
%his
reduces the actiation energy &or the release o& atomic nitrogen dramatically4 and thus makes the &or'ard reaction go &aster at lo'er tem#eratures, %he use o& lo'er tem#erature reaction conditions means there is limited reerse reaction, But 'e still need reasonably high tem#eratures -*5+32++[C. een 'ith the use o& a catalyst 'hich essentially accelerates the reaction su&&iciently so that 'e can obtain ammonia at conditions 'here the e(uilibrium conersion is large enough to be use&ul, %ron catalyst
%he real #roblem has been to &ind a suitable catalyst so that the maximum amount o& #roduct is obtained 'ith minimum olume o& the catalyst in the shortest time #ossible, %he catalysts4 'hich Haber initially em#loyed4 'ere catalytically actie #ure metals4 'hich 'ere too ex#ensie, %hey also lost catalytic actiity a&ter a short time due to #oisoning, Iron 'as one o& the metals that sho'ed high actiity, Ho'eer4 #ure iron has a regular sha#e 'ith lo' #orosity 'hich is a disadantage &or a catalyst, %he iron can be made irregular by mixing and &using iron oxide 'ith other oxides combinations, %his is re&erred to as stru*tural /r"m"ti"n, A common iron catalyst #romoter is a mixture o& Al *O0 and *O, Its o#timal #er&ormance re(uires reaction tem#eratures around 2++ZC and #ressures &rom )5+30++ atmos#heres, Ammonia synthesis reaction is carried out commercially at *++35++ atm and 25+ to 6++ oC,
93
..B. M"dern Meth"d "< Manu
%he manu&acturing #rocess consists o& six stages namely9 manu&acture o& reactant gases4 #uri&ication4 com#ression4 catalytic reaction4 recoery o& ammonia &ormed and recirculation and ammonia remoal as sho'n in the &lo' diagram ig, 2,2,
7i%. .. l"*5 dia%ram "< an amm"nia /lant
Hydrogen is obtained by conersion o& hydrocarbons such as methane4 #ro#ane4 butane or na#htha into gaseous hydrogen, ..B.1. Desul/huri8ati"n
Hydrocarbon &eedstocks contain sul#hur in the &orm o& H *4 CO4 C * and merca#tans, %he catalyst used in the re&orming reaction is deactiated -#oisoned. by sul#hur, %he #roblem is soled by catalytic hydrogenation o& the sul#hur com#ounds as sho'n in the &ollo'ing e(uation9 HGRSH F RH G H S+%-
94
%he gaseous hydrogen sul#hide is then remoed by #assing it through a bed o& "inc oxide 'here it is conerted to solid "inc sul#hide9 HSGJn( F JnSGH (
..B.. rimary +Steam- Re<"rmin%.
:e&orming is the #rocess o& conerting natural gas or na#tha -C nH*nD*. into hydrogen4 carbon monoxide and carbon dioxide, team and natural gas are combined at a three3to3one ratio, %his mixture is #reheated and #assed through catalyst3&illed tubes in the #rimary re&ormer, Catalytic steam re&orming o& the sul#hur3&ree &eedstock #roduces synthesis gas -hydrogen and carbon monoxide., Using methane as an exam#le9 CH Ni6 1,40 atm6 100041100 "C C( G 3H
%he reaction is endothermic, It is o#erated at )+++3))++ oC, It is not &aoured by high #ressures4 but to reduce olumetric &lo' rate at high tem#erature4 the steam re&orming reaction is carried out at high #ressures o& )5 to *+ atm, ..B.3. Se*"ndary re<"rmer
rom the #rimary re&ormer4 the mixture &lo's to the secondary re&ormer, Air is &ed into the re&ormer to com#letely conert methane to CO in the &ollo'ing endothermic reaction, CH G Air
Ni6 1,40 atm6 100041100 "
* C( G H ( G N
%he nitrogen and hydrogen coming out o& the secondary re&ormer are in the ratio o& 09), %his mixture is kno'n as the synthesis gas, ..B.. Shi
%he carbon monoxide is conerted to carbon dioxide 'ith the assistance o& catalyst beds at di&&erent tem#eratures, C(GH( F C(GH
%his 'ater3gas shi&t reaction is &aorable &or #roducing carbon dioxide 'hich is used as a ra' material &or urea #roduction, At the same time more hydrogen is #roduced,
..B.,. uri
95
%he carbon dioxide is remoed either by scrubbing 'ith 'ater4 a(ueous monoethanolamine solution or hot #otassium carbonate solution, CO is an irreersible #oison &or the catalyst used in the synthesis reaction4 hence the need &or its remoal %he synthesis gas is #assed oer another catalyst bed in the methanator4 'here remaining trace amounts o& carbon monoxide and dioxide are conerted back to methane using hydrogen, CO()*" / C*0(*"O
C(GH F CHGH( ( G H
H(
Eote that the &irst e(uation is the o##osite o& the re&ormer reaction, ..B.'. Amm"nia C"n2erter.
A&ter leaing the com#ressor4 the gaseous mixture goes through catalyst beds in the synthesis conerter 'here ammonia is #roduced 'ith a three3to3one hydrogen3to3nitrogen stoichiometric ratio, Ho'eer4 not all the hydrogen and nitrogen are conerted to ammonia, %he unconerted hydrogen and nitrogen are se#arated &rom the ammonia in the se#arator and re3cycled back to the synthesis gas com#ressor and to the conerter 'ith &resh &eed, Because the air contains argon 'hich does not #artici#ate in the main reactions4 #urging it minimi"es its build u# in the recycle loo#, ..B.. Amm"nia Se/arati"n
%he remoal o& #roduct ammonia is accom#lished ia mechanical re&rigeration or absor#tion;distillation, %he choice is made by examining the &ixed and o#erating costs, %y#ically4 re&rigeration is more economical at synthesis #ressures o& )++ atm or greater, At lo'er #ressures4 absor#tion;distillation is usually &aoured, ..B.B. Amm"nia St"ra%e
Ammonia is stored in tanks as a re&rigerated li(uid, ome ammonia is used directly as a &ertili"er, Most ammonia is conerted in do'nstream #rocesses to urea -26 nitrogen. or ammonium nitrate -02 nitrogen. &or use as &ertili"er,
..>. S"me en2ir"nmental im/a*ts "< amm"nia /r"du*ti"n
96
Ammonia is toxic4 irritant and corrosie to metal alloys -e,g, co##er alloys., In re&rigeration4 its re#lacement by the non3toxic chloro&luorocarbon -CCs. has contributed to global 'arming, In large industrial #rocesses such as bulk ice making4 and &ood #rocessing and #reseration4 ammonia is still being used as a re&rigerant, %he toxicity o& ammonia solution is usually not harm&ul to human beings because it is easily excreted in urine, Ho'eer4 ammonia een in dilute concentrations is toxic to a(uatic animals because they do not hae the mechanisms to eliminate it &rom their bodies by excretion,
.3. Sul/huri* A*id Manu
7uring the )$th century4 the ?erman chemist Baron @ustus on >iebig discoered that sul#huric acid4 'hen added to the soil4 increased the amount o& soil #hos#horus aailable to #lants, %his discoery gae rise to an increase in the commercial #roduction o& sul#huric acid and led to im#roed methods o& manu&acture, .3.. Uses "< sul/huri* a*id
ul#huric acid is the most 'idely used chemical .%he largest single use o& sul#huric acid is &or making #hos#hate and ammonium sul#hate &ertili"ers, Other uses include #roduction o& #hos#horic acid4 trisodium #hos#hates &or detergent making, ul#huric acid is also used in large (uantities in iron and steel making as a #ickling agent to remoe oxidation4 rust and scale &rom &rom the metals, It is an oxidi"ing and dehydrating agent, Its dehydrating action is ital in absorbing 'ater &ormed
in
chemical
conersions
such
as
nitration4
sul#honation4
and
esteri&ication, It igorously remoes 'ater &rom4 and there&ore chars4 'ood4 cotton4 sugar4 and #a#er, As a strong oxidi"ing agent it is ca#able o& dissoling such relatiely unreactie metals as co##er4 mercury4 and lead to make com#ounds o& these metals,
97
It is used in the manu&acture o& aluminium sul#hate &or a##lication in #a#er #ul# #roduction and in 'ater treatment, It is also used as an electrolyte in lead acid batteries &ound in cars, Various concentrations o& sul#huric acid are aailable de#ending on the a##lication #ur#ose, %hese include9 •
)+ dilute acid &or laboratory use4 #H )
•
00,0 &or lead acid batteries4 #H +,5
•
6*,* &or chamber and &ertili"er manu&acture4 #H +,2
•
!!,! to'er or ?loer acid #H +,*5
•
$0,* Oil o& Vitriol
•
$F conc acid4 #H +,)
•
)++ H*O2
•
*+ oleum -)+2,5 H *O2.
.3.3. Ra$ Materials
:a' materials &or sul#huric acid are those that #roduce sul#hur dioxide 'hen reacted 'ith oxygen, %he commonly used ra' materialds are9
1lemental sul#hur
ul#hides such as #yrites
Hydrogen sul#hide &rom #etroleum re&ineries
.3.. Manu
%'o #rocesses4 the lead3chamber and contact #rocesses4 are used &or the #roduction o& sul#huric acid, In their initial ste#s4 both #rocesses re(uire the use o& sul#hur dioxide, .3..1. The Lead4*ham:er /r"*ess
%his #rocess em#loys as reaction essels large lead3sheathed brick to'ers, In these to'ers4 sul#hur3dioxide gas4 air4 steam4 and oxides o& nitrogen react to yield sul#huric acid as &ine dro#lets that &all to the bottom o& the chamber, Almost all the nitrogen oxides are recoered &rom the out&lo'ing gas and are brought
98
back to the chamber to be used again, ul#huric acid #roduced in this 'ay is only about 6* to !+ #er cent H *O2, %he rest is 'ater, %he chamber #rocess has become obsolete and has been re#alced by the *"nta*t #rocess due to the &ollo'ing reasons9 i, An increased demand &or strong4 #ure acid and oleum ii, Contact #rocess #lants are chea#er and more com#act .3... The C"nta*t r"*ess
%he second method o& manu&acturing sul#huric acid4 the contact #rocess4 'hich came into commercial use about )$++4 de#ends on oxidation o& sul#hur dioxide to sul#hur trioxide4 O 04 under the accelerating in&luence o& a catalyst , %he &irst contact #lants -be&ore )$*+. 'ere built using #latinum catalysts, inely diided #latinum4 the most e&&ectie catalyst4 has t'o disadantages9 it is ery ex#ensie4 and it is deactiated by certain im#urities in ordinary sul#hur dioxide, %hey include com#unds o& arsenic4 antimony and lead, In the middle o& )$*+s4 anadium catalysts started being used and hae since then re#laced #latinum, By )$0+4 the contact #rocess could com#ete 'ith the chamber #rocess and because it #roduces high strength acid4 it has almost re#laced the chamber #rocess, ince the oxidation o& sul#hur and sul#hur dioxide releases large amounts o& energy4 ma=or changes in the manu&acturing #lant design 'ere introduced to utilise this heat energy in the #roduction o& steam &or generating electrical #o'er, %his combination o& a chemical #lant and electrical generation is kno'n as co3 generation, %he &lo' diagram &or sul#huric acid manu&acture by the contact #rocess is sho'n in ig, 2,5
99
7i%. .,. l"*5 dia%ram <"r the manu
%he main ste#s in the contact #lant are9 •
#roduction o& sul#hur dioxide gas
•
#uri&ying and cooling the gas
•
the gas conersion o& O * into sul#hur trioxide -O 0. by #assing it through a conerter containing the catalyst
•
absorbing the sul#hur trioxide in sul#huric acid
.3..3. r"du*ti"n "< S(3
ul#hur is burned in the sul#hur burner to #roduce sul#hur dioxide9 S+s-G(+%- F S(+%-6 KH F 4>B.3 5at , 0C
Be&ore combustion4 sul#hur4 is &irst melted by heating it to )05[C, Combustion is carried out at bet'een $++ and )F++[C, %he combustion unit has a #rocess gas cooler, %he O * content o& the combustion gases is generally around )F by
100
olume and the O * content is lo' but higher than 0, %he gases are generally diluted to $3)* O * be&ore entering the conersion #rocess, "onversion of $& ' into $& (
%he design and o#eration o& sul#huric acid #lants are &ocused on the &ollo'ing gas #hase chemical reaction in the #resence o& a catalyst9 *O*DO*-g. *O0-g.4 \H 3$F,0k@ at *5 +C rom thermodynamic and stoichiometric considerations4 the &ollo'ing methods are aailable to maximise the &ormation o& O 0 &or the O *;O*;O0 system, •
heat remoal9 the &ormation o& O 0 is exothermic4 so a decrease o& tem#erature 'ill be &aourable
•
increased oxygen concentration
•
remoal o& O 0
•
raising the system #ressure
•
catalyst selection to reduce the 'orking tem#erature
•
longer reaction time
%his reaction is a reersible reaction and the conditions used are a com#romise bet'een e(uilibrium and rate considerations, It is necessary to shi&t the #osition o& the e(uilibrium as &ar as #ossible to the right in order to #roduce the maximum #ossible amount o& sul#hur trioxide in the e(uilibrium mixture, 1en though excess O * 'ould moe the O * &ormation to the right4 the )9) mixture gies the best #ossible oerall yield o& sul#hur trioxide, %he &or'ard reaction is exothermic and is &aoured by lo' tem#erature, Ho'eer4 too lo' a tem#erature slo's the reaction, %o get the gases to reach e(uilibrium 'ithin a ery short time4 a com#romise tem#erature o& 2++J25+
o
C is used,
According to >e Chateliers #rinci#le high #ressures &aour the &or'ard reaction, Ho'eer4 een at relatiely lo' #ressures o& ) to * atmos#heres4 there is a $$,5 conersion o& sul#hur dioxide into sul#hur trioxide, In the absence o& a catalyst the reaction is (uite slo' and is there&ore carried out in the #resence o& a anadium oxide catalyst 'hich has a long li&e because it is not easily #oisoned, urther more4 anadium catalyst has high conersion e&&iciency, Its only
101
disadantage is that it re(uires use o& lo' sul#hur dioxide concentration 'hich makes #lant ca#ital cost to be high, In summary4 o#timum conditions &or sul#huric acid #roduction in the contact #rocess are9 •
A tem#erature o& about 20+ +C
•
A #ressure o& * atmos#heres
•
Vanadium #entoxide catalyst,
A diagram o& the conerter is sho'n in ig, 2,6
7i% .'. C"n2erter <"r S( int" S( 3
102
.3... A:s"r/ti"n "< S( 3
ul#huric acid -H *O2. is obtained &rom the absor#tion o& O 0 into sul#huric acid 'ith a concentration o& at least $F4 &ollo'ed by the ad=ustment o& the strength by the controlled addition o& 'ater, O04 'ill react 'ith 'ater to &orm sul#huric acid, Ho'eer4 conerting the sul#hur trioxide into sul#huric acid cannot be done by sim#ly adding 'ater to the sul#hur trioxide, 7irect mixing o& sul#hur trioxide 'ith 'ater by the &ollo'ing reaction is uncontrollable, %he exothermic nature o& the reaction means it generates a &og or mist o& sul#huric acid4 'hich is more di&&icult to 'ork 'ith than a li(uid, S(3+%-GH(+l- F H S(+l-6 KH F 4130.5 at , 0C
Instead4 the sul#hur trioxide is &irst dissoled in concentrated -$F. sul#huric acid to &orm a #roduct kno'n as &uming sul#huric acid or oleum, S(3GHS(+l-G F H S(+l-
%he oleum can then be reacted sa&ely 'ith 'ater to #roduce concentrated sul#huric acid, HS(+l-GH(+l- F H S(+l-
.3..,. En2ir"nmental Issues
ul#huric acid is a constituent o& acid rain4 &ormed by atmos#heric oxidation o& sul#hur dioxide in the #resence o& 'ater, ul#hur dioxide is released 'hen &uels containing sul#hur such as oil and coal are burned, %he gas esca#es into the atmos#here &orming sul#huric acid, ul#huric acid is also &ormed naturally by oxidation o& sul#hide ores,
103
.. Manu
..1. Intr"du*ti"n
ertili"er is a substance added to soil to im#roe the gro'th and yield o& #lants, Modern synthetic &ertili"ers are com#osed mainly o& nitrogen4 #hos#horus4 and #otassium com#ounds 'ith secondary nutrients added, %he #rocess o& adding substances to soil to im#roe its gro'ing ca#acity 'as deelo#ed in the early days o& agriculture, Ancient &armers kne' that the &irst yields on a #lot o& land 'ere much better than those o& subse(uent years, %his caused them to moe to ne'4 uncultiated areas4 'hich again sho'ed the same #attern o& reduced yields oer time, 1entually it 'as discoered that #lant gro'th on a #lot o& land could be im#roed by s#reading animal manure throughout the soil, Oer time4 &ertili"er technology became more re&ined, Ee' substances that im#roed the gro'th o& #lants 'ere discoered,
... Uses "<
%he use o& synthetic &ertili"ers has signi&icantly im#roed the (uality and (uantity o& the &ood aailable today4 although their long3term use is an enironmental sub=ect o& debate, As has been mentioned4 &ertili"ers are ty#ically com#osed o& nitrogen4 #hos#horus4 and #otassium as micronutrients, Eitrogen hel#s make #lants green and #lays a ma=or role in boosting cro# yields, It #lays a critical role in #rotein &ormation and is a key com#onent o& chloro#hyll, /lants 'ith ade(uate nitrogen sho' healthy igorous gro'th4 strong root deelo#ment4 dark green &oliage4 increased seed and &ruit &ormation and higher yields, /lants also need #hos#horus4 a com#onent o& nucleic acids4 #hos#holi#ids4 and seeral #roteins, /hos#horus is also needed to #roide the energy to drie metabolic chemical reactions,
104
#rocesses, 8ello'ing4 s#ots o& dead tissue4 and 'eak stems and roots are all indicatie o& #lants that lack enough #otassium, Besides the aboe three macronutrients4 &ertili"ers also contain trace elements that im#roe the gro'th o& #lants, Calcium4 magnesium4 and sul&ur are also im#ortant materials in #lant gro'th, %hey are only included in &ertili"ers in small amounts4 ho'eer4 since most soils naturally contain enough o& these com#onents, Other micronutrients include iron4 chlorine4 co##er4 manganese4 "inc4 molybdenum4 and boron4 'hich #rimarily &unction as co&actors in en"ymatic reactions,
..3. Ra$ materials
/rimary &ertili"ers include substances deried &rom nitrogen4 #hos#horus4 and #otassium, Eitrogen is deried &rom ammonia4 #hos#horus &rom #hos#hate rock and #otassium &rom #otassium chloride4 a #rimary com#onent o& #otash,
... The Manu
ully integrated &actories hae been designed to #roduce com#ound &ertili"ers &rom #rimary &ertili"ers, 7e#ending on the actual com#osition o& the end #roduct4 the #roduction #rocess 'ill di&&er &rom manu&acturer to manu&acturer, Multicom#onent &ertili"ers are com#ound &ertili"ers com#osed o& #rimary nitrogen4 #hos#horus4 and #otassium -E/. &ertili"ers and secondary nutrients, ?enerally4 each granule o& the com#ound &ertili"er contains a uni&orm ratio o& nutrients4 or blends, %he three numbers on a bag o& such a &ertili"er are re&erred to as the analysis, It is the #ercentage o& nitrogen4 #hos#hate and #otash that is aailable to #lants &rom that bag o& &ertili"er, E353/3)+335 or sim#ly 53)+35 means 5 #ercent nitrogen4 )+ #ercent #hos#hate and 5 #ercent #otash, %he analysis &ound on a bag or bulk shi#ment o& &ertili"er tells the &armer or consumer the amount o& nutrients being su##lied,
105
%he balance F+ #ercent 'ill contain some micronutrients and &iller material4 'hich allo's &or een a##lication o& the nutrients across the &ertili"ed area,
7i% .. A :a% "<
or re&rigerated4 it becomes a gas 'hen ex#osed to air and is in=ected into the soil It is also used as a building block to make other easy to handle nitrogen &ertili"er #roducts4 including urea4 ammonium nitrate4 ammonium sul&ate and 'ater3based li(uid nitrogen &ertili"ers, Eitric acid and ammonia are used to make ammonium nitrate -023+3+.4 a solid granular &ertili"er 'ith a high concentration o& nitrogen, %he t'o materials are mixed together in a tank and a neutrali"ation reaction occurs4 #roducing ammonium nitrate, %his material can then be stored until it is ready to be granulated and blended 'ith the other &ertili"er com#onents, Urea )/++- is a solid nitrogen #roduct ty#ically a##lied in granular &orm, It can
be combined 'ith ammonium nitrate and dissoled in 'ater to make a highly soluble li(uid nitrogen &ertili"er kno'n as urea ammonium nitrate -UAE. solution ty#ically containing *F to 0* nitrogen, !mmonium sulfate )'0++- is another solid nitrogen &ertili"er, .... h"s/hate
/hos#hate rock4 Ca 5-/O2.0 'hich contains *! to 0F #hos#horus #entoxide -/*O5.4 is the main ra' material source &rom 'hich most ty#es o& #hos#hate &ertili"ers are #roduced,
106
In its un#rocessed state4 #hos#hate rock is not suitable &or direct agricultural a##lication4 since the #hos#horus it contains is insoluble, %o trans&orm the #hos#horus into a #lant3aailable &orm -CaH 2-/O2.,H*O. and to obtain a more concentrated #roduct4 #hos#hate rock is #rocessed using sul#huric acid4 #hos#horic acid and;or nitric acid, Acidulation by means o& sul#huric acid conerts the rock to monocalcium #hos#hate #o#ularly kno'n as normal or single su#er#hos#hate -/. haing a #hos#horus content o& )53*+ / *O5, ?round #hos#hate rock is thoroughly mixed 'ith metered (uantities o& 6+3!+ sul#huric acid in the ratio o& +,F* to +,$5 acid to #hos#hate rock, %he heat o& dilution seres to heat the acid to #ro#er reaction tem#erature, 1xcess heat is dissi#ated by ea#oration o& extra 'ater added, %he rate o& 'ater and acid addition is aried to control moisture leel, %he &resh su#er#hos#hate dro#s to a slo' moing coneyor in a den 'here it takes I hour in order to solidi&y, A disintegrator slices the solid mass o& crude #roduct be&ore it is taken to #ile storage, %he chemical reaction continues &or 236 'eeks to )53*+ / *O5, A&ter curing4 the #roduct is bagged and shi##ed,
Ca,+(-37 G HS( G 3H(
3CaH+(-.H( G CaS( G H7
ul#huric acid is also used to manu&acture #hos#horic acid4 an intermediate #roduct in the #roduction o& tri#le su#er#hos#hate -%/., Acidulation o& the #hos#hate rock using #hos#horic acid #roduces tri#le su#er#hos#hate by the &ollo'ing reaction9
Ca,+(-37 G H3( G ,H(
,CaH+(-.H( GH7
ince no CaO 2 is &ormed4 the #hos#horus content is not diluted, %here&ore4 %/ -+3263+. has a #hos#horus content o& 2032F #ercent as / *O5, %'o #rocesses are used to #roduce %/ &ertili"ers9 run3o&3#ile and granular, %he run3o&3#ile #rocess is similar to the / #rocess, ?ranular %/ uses lo'er
107
strength #hos#horic acid -2+ #ercent com#ared to 5+ #ercent &or run3o& 3#ile., /uleri"ed ground #hos#hate rock is mixed 'ith #hos#horic acid in the reactor, %he resultant slurry is s#rayed into the granulator, %he #roduct is dried4 screened and cooled, It is stored &or 236 'eeks to cure, 1onoammonium 2hosphate )1!2- )00+3'+- and Diammonium 2hosphate )D!2- )0*+/+- are called ammoniated #hos#hates because #hos#horic acid is
treated 'ith ammonia to &orm these basic #hos#hate #roducts that also contain nitrogen, %hey are 'idely #roduced in the granular &orm &or blending 'ith other ty#es o& &ertili"ers4 and are also #roduced in non3granular &orms &or use in li(uid &ertili"ers, Acidulation o& #hos#hate rock using nitric acid #roduces E/ slurries &or use in the manu&acture o& com#ound &ertili"ers,
...3. "tassium
Most #otassium -. is obtained &rom naturally occurring ore de#osits, Although the lo'3grade unre&ined mineral ores can be directly a##lied4 it is normally #uri&ied, /otassium in the &orm o& #otassium chloride and #otassium magnesium sul#hate are used in the manu&acture o& multi3nutrient &ertili"ers, /otassium chloride is ty#ically su##lied to &ertili"er manu&acturers in bulk, %he manu&acturer conerts it into a more usable &orm by granulating it, %his makes it easier to mix 'ith other &ertili"er com#onents,
.... Manu
%he ra' materials4 in solid &orm4 can be su##lied to &ertili"er manu&acturers in bulk (uantities o& thousands o& tons4 drum (uantities4 or in metal drums and bag containers, econdary nutrients are added to some &ertili"ers to hel# make them more e&&ectie, %he di&&erent ty#es o& #articles are blended together in a##ro#riate #ro#ortions to #roduce a com#osite &ertili"er, %y#ically4 com#lex E/ &ertili"ers are manu&actured by #roducing slurries o& ammonium #hos#hates4 to 'hich #otassium salts are added #rior to being made into granules, / &ertili"ers4 on
108
the other hand4 are generally #roduced by granulation o& su#er#hos#hates -/ or %/. 'ith #otassium salts, One method o& granulation inoles #utting the solid materials into a rotating drum 'hich has an inclined axis, -:e&er to drum agglomerator in Unit *., As the drum rotates4 #ieces o& the solid &ertili"er take on small s#herical sha#es, %hey are #assed through a screen that se#arates out ade(uately si"ed #articles, A coating o& inert dust is then a##lied to the #articles to make them remain discreet and to inhibit moisture retention, inally4 the #articles are dried4 thus com#leting the granulation #rocess, %he &ertili"er is em#tied onto a coneyor belt4 'hich trans#orts it to the bagging machine,
..,. ?uality C"ntr"l
%o ensure the (uality o& the &ertili"er that is #roduced4 manu&acturers monitor the #roduct at each stage o& #roduction, %he ra' materials and the &inished #roducts are all sub=ected to a battery o& #hysical and chemical tests to sho' that they meet the s#eci&ications #reiously deelo#ed, ome o& the characteristics that are tested include #H4 a##earance4 density4 and melting #oint, ince &ertili"er #roduction is goernment3regulated4 tests are run on sam#les to determine total content o& nitrogen4 #hos#hate4 and other elements in the s#eci&ications,
.,. Manu
.,.1. Intr"du*ti"n
Historically4 cement can be traced back to the early :oman 1m#ire, It contributed to the building o& the great structures o& the :oman 1m#ire, /ortland cement is a &ine #o'der4 generally gray in colour, It is com#osed #rimarily o& calcium silicates4 calcium aluminates4 and calcium &errites,
109
ingredients4 cement 'ith arious #ro#erties may be obtained, Concrete is a mixture o& grael4 sand and cement,
.,.. Ra$ materials
%he ma=or com#onents o& cement in terms o& metal oxides are CaO4 iO *4 Al*O04 and e*O0, %y#ically4 Ca is #roided &rom limestone4 i &rom sand or &lyash4 Al &rom &lyash or clay4 and e &rom iron ore or slag,
.,.3. Manu
ig 2,F is a #rocess &lo' diagram &or a ty#ical cement manu&acturing #lant,
7i% .B. A *ement manu
.,.3.1. 9rindin%
%he &eed to the grinding #rocess is #ro#ortioned to meet a desired chemical com#osition, %y#ically4 it consists o& F+ limestone4 $ silica4 $ &lyash4 and * iron ore, %hese materials are ground to !5 micron in a ball mill, ?rinding can be either 'et or dry, %he Xra' mealY &rom dry milling is stored in a homogeni"ing silo
110
in 'hich the chemical ariation is reduced, In the 'et #rocess4 each ra' material is &ed 'ith 'ater to the ball mill, %his slurry is #um#ed to blending tanks and homogeni"ed to correct chemical com#osition, %he slurry is stored in tanks until re(uired,
.,.3.. yr"/r"*essin%
In the #reheater4 the ra' meal &rom the mill is heated 'ith the hot exhaust gas &rom the kiln be&ore being &ed into the rotary kiln to &orm a semi3#roduct kno'n as clinker, %he ash &rom &uel used is also absorbed into the clinker, %he #article si"e range &or clinker is &rom about * inches to about )+ mesh,
7i% .>. A *ement 5iln .,.3.3. Rea*ti"ns in the 5iln
Basic chemical reactions are9 ea#orating all moisture4 calcining the limestone to #roduce &ree calcium oxide4 and reacting the calcium oxide 'ith the minor materials -sand4 shale4 clay4 and iron., %his results in a &inal black4 nodular #roduct kno'n as clinker 'hich has the desired hydraulic #ro#erties, A summary o& the #hysical and chemical reactions that take #lace in the kiln are sho'n in %able 2,),
111
Ta:le .1. Rea*ti"ns in a *ement 5iln
% oC )++
:eaction 1a#oration o& 'ater
:emarks olid #hase reactions4
]5++
1olution o& combined 'ater
endothermic olid #hase reactions4
$++
&rom the clay Crystalli"ation o& amor#hous
endothermic olid #hase reactions4
dehydration #roducts
endothermic
Carbon dioxide eolution &rom $++ 3)*++
CaCO0 Main reactions bet'een lime
usion reactions4 exothermic
)*5+ 3 )*F+ )*F+ 3)55+
and clay to &orm clinker Beginning o& li(uid &ormation urther li(uid &ormation and
usion reactions4 endothermic usion reaction4 endothermic
&inal cement &ormation %he main reactions 'hich gie the real strength o& cement are as &ollo's9
Ca( G Ca(.Si( >004100 Ca( G Ca(.Si( 10041,00 3Ca(.Si(
%he main constituents o& clinker are sho'n in %able 2,*,
Ta:le .. Main *"nstituents "< *lin5er
*CaO,iO *
Abbreiation Common name C* 7icalcium silicate
unction %ogether 'ith 0CaO,iO *4 res#onsible &or &inal strength
0CaO,iO * 0CaO,Al *O0
C0 C0 A
%ricalcium silicate
-I year. :es#onsible &or early
%ricalcium
strength i,e, !3F days Causes &ast hardeningQ
aluminate
needs retardation by gy#sum by &orming
0CaO,
C2 A
%etracalcium
112
0CaO,Al *O0Cao2,0H*O Im#roes chemical
Al*O0,e*O0
alumino3&errate
resistance
%he rotary kiln discharges the red3hot clinker under the intense &lame into a clinker cooler, %he clinker cooler recoers heat &rom the clinker and returns the heat to the #yro#rocessing system thus reducing &uel demand and cooling the clinker to a tem#erature conducie &or handling in subse(uent ste#s, .,.3.. 7inish 9rindin%
%he &inal #rocess o& cement making is called &inish grinding, %he clinker is dosed 'ith a controlled amount o& gy#sum and &ed into a &inish mill, Other addities may be added during the &inish grinding #rocess to #roduce &ormulated cements such as 'ater#roo&ing and corrosion resistant cements, %he cement is stored in a bulk silo &or #ackaging and;or bulk distribution, 7"rmati2e E2aluati"n
),
*O0-g. \H 3$F,0 k@;mol at *5 oC
1x#lain the reason behind setting the conditions as &ollo's9 •
%em#erature9 2++325+ oC
•
/ressure9 * atmos#heres
•
O*9O* ratios9 )9)
!,
113
-iii. 53)+35 $,
114
LEARNIN9 ACTI&ITY ,) (R9ANIC CHEMICAL INDUSTRIES ART I) ETR(LEUM6 ETR(CHEMICALS AND (LYMERS Unit ":;e*ti2es
At the end o& this unit you should be able to9 a, 7iscuss the occurrence and extraction o& #etroleum b, 1x#lain the #ur#oses and a##lication o& &ractional distillation4 catalytic cracking and catalytic re&orming during #etroleum #rocessing c, 7escribe using e(uations and &lo' diagrams4 the manu&acture o& some #etrochemicals4 namely4 #hthalic anhydride and adi#ic acid d, Categori"e #olymeri"ation reactions4 #olymers and #olymer #roducts e, 7escribe the uses o& arious #lastics &, 1x#lain ho' #olyethylene and styrene butadiene rubber are manu&actured Summary "< learnin% a*ti2ity
%his is the &irst o& t'o units dealing 'ith organic chemical industries,
List "< rele2ant readin%s
), ?eorge %, A, -)$!!., Shreve’s Chemical Process Industries. 5 th edn. Mc?:A<3HI>> IE%1:EA%IOEA> 17I%IOE, Chemical 1ngineering eries, inga#ore, *, te#henson :,M, -)$66., Introduction to the Chemical /rocess Industries4 :einhold /ublishing Cor#oration4 Ee' 8ork 0, ?roggins /,H, -)$5F., Unit /rocesses in Organic ynthesis4 5 th 1dition4 Mc?ra'3Hill Book Com#any4 Ee' 7elhi, 2, ?erhart"4 <, -1ditor.4 -)$F!., Ullmanns 1ncyclo#aedia o& Industrial Chemistry4 5 th 1dition4 VCH Verlagsgesellscha&t mbH4
115
List "< rele2ant res"ur*es •
Com#uter 'ith internet &acility to access links and releant co#y'rite &ree resources
•
C73:om accom#anying this module &or com#ulsory reading and demonstrations
•
Multimedia resources like ideo4 VC7 and C7 #layers
List "< rele2ant use
htt#9;;''',setlaboratories,com htt#9;''',lloyadministerheayoil,co htt#9;;chem,ucalgary,ca;course;05);carey;Ch+F;ch32,html htt#9;;chemguide,co,uk htt#9;;#slc,'s; htt#9;;''','isegeek,com htt#9;;&aculty,'ashington,edu;&inlayso;/olyeth;?rou#B;themer,html rom these sites4 you 'ill &ind a 'ealth o& in&ormation on the technology o& #etrolem re&ining 'ith associated #rocess &lo' diagrams, %he chemistry including reaction mechanisms o& most o& the #rocesses are gien, 8ou 'ill also &ind a 'ide ariety o& chemical #roducts and their #roduction methods,
,.1 ETR(LEUM R(CESSIN9 ,.1.1. Intr"du*ti"n
%he term petroleum comes &rom the >atin stems petra4 rock4 and oleum4 oil, It is used to describe a broad range o& hydrocarbons that are &ound as gases4 li(uids4 or solids beneath the sur&ace o& the earth, %he t'o most common &orms are natural gas and crude oil, Natural gas4 Eatural gas 'hich is a mixture o& light'eight alkanes4 accumulates
in #orous rocks, A ty#ical sam#le o& natural gas 'hen it is collected at its source contains about F+ methane -CH 2.4 ! ethane -C *H6.4 6 #ro#ane -C 0HF.4 2 butane and isobutane -C 2H)+.4 and 0 #entanes -C 5H)*., %he C 04 C24 and C5 hydrocarbons are remoed be&ore the gas is sold, %he commercial natural gas
116
deliered to the customer is there&ore #rimarily a mixture o& methane and ethane, %he #ro#ane and butanes remoed &rom natural gas are usually li(ue&ied under #ressure and sold as li(ue&ied #etroleum gases - LP., "rude oil is a com#osite mixture o& hydrocarbons -5+3$5 by 'eight. occurring
naturally, %he &irst ste# in re&ining crude oil inoles se#arating the oil into di&&erent hydrocarbon &ractions by distillation, 1ach &raction is a com#lex mixture, or exam#le4 more than 5++ di&&erent hydrocarbons can be &ound in the gasoline &raction, /etroleum is &ound in many #arts o& the 'orld 'hich include the Middle 1ast4 southern United tates4 Mexico4 Eigeria and the &ormer oiet Union,
,.1.. Uses "< /etr"leum
Most o& the crude oil is used in the #roduction o& &uels such as gasoline4 kerosene4 and &uel oil, Eon3&uel uses include #etroleum solents4 industrial greases and 'axes4 or as ra' materials &or the synthesis o& #etrochemicals, /etroleum #roducts are used to #roduce synthetic &ibres such as nylon and other #olymers such as #olystyrene4 #olyethylene and synthetic rubber, %hey also sere as ra' materials in the #roduction o& re&rigerants4 aerosols4 anti&ree"e4 detergents4 dyes4 adhesies4 alcohols4 ex#losies and #esticides, %he H * gien o&& in re&inery o#erations can be used to #roduce a number o& inorganic #etrochemicals4 such as ammonia4 ammonium nitrate4 and nitric acid &rom 'hich most &ertili"ers as 'ell as other agricultural chemicals are made,
,.1.3. (il Etra*ti"n
%he ast ma=ority o& #etroleum is &ound in oil&ields or reseroirs belo' the earths sur&ace as sho'n in ig 5,),
117
7i% ,.1. S*hemati* dia%ram "< a *rude "il reser2"ir
%he oil is sometimes under high #ressure and can &lo' to the sur&ace on its o'n 'ithout #um#ing, Ho'eer4 most 'ells re(uire induced #ressure using 'ater4 carbon dioxide4 natural gas or steam in order to bring the oil to the sur&ace, /etroleum re&ining has eoled continuously in res#onse to changing consumer demand &or better and di&&erent #roducts, %he original re(uirement 'as to #roduce kerosene as a chea#er and better source o& light than 'hale oil, %he deelo#ment o& the internal combustion engine led to the #roduction o& gasoline and diesel &uels, %he eolution o& the air#lane created an initial need &or high3 octane aiation gasoline and then &or =et &uel4 a so#histicated &orm o& the original #roduct4 kerosene, /resent3day re&ineries #roduce a ariety o& #roducts including many re(uired as &eedstock &or the #etrochemical industry, Common #etroleum #roducts include gasoline4 li(ue&ied re&inery gas4 still gases4 kerosene4 aiation &uel4 distillate &uel oil4 residual &uel oil4 lubricating oils4 as#halt4 coke and #etrochemical &eedstocks,
%he history o& #etroleum re&ining is gien in %able 5,),
Ta:le ,.1. Hist"ry "< etr"leum re
/rocess Atmos#heric
/ur#ose /roduce kerosene
By3/roducts4 etc, Ea#htha4 tar4 etc,
)F!+
distillation Vacuum distillation
>ubricants originally4 then cracking
As#halt4 residual4 Coker
118
)$)0 )$)6 )$0+ )$0* )$0* )$00 )$05 )$05
%hermal cracking 'eetening %hermal re&orming Hydrogenation Coking olent extraction olent de'axing Cat, #olymeri"ation
&eedstocks -)$0+Ss. Increase gasoline yield :educe sul&ur R odor Im#roe octane number :emoe sul&ur /roduce gasoline basestock Im#roe lubricant iscosity index Im#roe #our #oint Im#roe gasoline yield and octane
)$0!
Catalytic cracking
number Higher octane gasoline
&eedstocks /etrochemical4
)$0$ )$2+
Visbreaking Alkylation
:educe iscosity Increase gasoline octane R yield
&eedstocks Increased distillate4 tar High3octane aiation
)$2+ )$2*
Isomeri"ation luid catalytic
/roduce alkylation &eedstock Increase gasoline yield R octane
)$5+ )$5* )$52 )$56 )$5!
cracking 7eas#halting Catalytic re&orming Hydrodesul&uri"ation Inhibitor s'eetening Catalytic
/etrochemical &eedstocks Increase cracking &eedstock Conert lo'3(uality na#htha :emoe sul&ur :emoe merca#tan Conert to molecules 'ith
)$6+ )$!2 )$!5
isomeri"ation Hydrocracking Catalytic de'axing :esidual
octane number Im#roe (uality and reduce sul&ur Im#roe #our #oint Increase gasoline yield &rom residual
&eedstocks :esidual4 bunker &uel ul&ur :esidual ul&ur Coke Aromatics
gasoline Ea#htha
As#halt Aromatics ul&ur 7isul&ides high Alkylation &eedstocks Alkylation &eedstocks
hydrocracking
S"ur*e) 4ttp5''666.setla7oratories.com
,.1.. Chara*teristi*s and *lassi
As has been mentioned4 crude oils are com#lex mixtures containing many di&&erent hydrocarbon com#ounds that ary in a##earance and com#osition &rom one oil &ield to another, Crude oils range in consistency &rom 'ater to tar3like solids4 and in color &rom clear to black, An aerage crude oil contains about F2 carbon4 )2 hydrogen4 )30 sul&ur4 and less than ) each o& nitrogen4 oxygen4 metals4 and salts, Crude oils are generally classi&ied as #ara&&inic4 na#hthenic4 or aromatic4 based on the #redominant #ro#ortion o& similar hydrocarbon molecules, Oils 'ith lo' carbon4 high hydrogen4 and high A/I -American /etroleum Institute. graity are usually rich in #ara&&ins and tend to yield greater #ro#ortions o& gasoline and light
119
#etroleum #roductsQ those 'ith high carbon4 lo' hydrogen4 and lo' A/I graities are usually rich in aromatics, %he &ormer category is kno'n as light crudes and the latter as heay crudes, Crude oils that contain a##reciable (uantities o& hydrogen sul&ide or other reactie sul&ur com#ounds are generally called sour, 'hile those 'ith lo'er sul&ur are called s'eet, ,.1.. C"m/"siti"n "< /etr"leum
Crude #etroleum contain hydrocarbon and non3hydrocarbon com#ounds, Hyr"*ar:"n *"m/"unds 2araffins 4 %he #ara&&inic crude oil hydrocarbon com#ounds &ound in crude oil
hae the general &ormula C nH*nD* and can be either straight chains -normal. or branched chains -isomers. o& carbon atoms, %he lighter4 straight chain #ara&&in molecules are &ound in gases and #ara&&in 'axes, %he branched3chain -isomer. #ara&&ins such as isobutene are usually &ound in heaier &ractions o& crude oil and hae higher octane numbers than normal #ara&&ins, !romatics) %he aromatic series include sim#le aromatic com#ounds such as
ben"ene4 na#hthalenes and the most com#lex aromatics4 the #olynuclears 'hich hae three or more &used aromatic rings, %hey hae high anti3knock alue and good storage stability, Naphthenes )Naphtha-4 %hese are saturated hydrocarbon grou#ings 'ith the
general &ormula C nH*n4 arranged in the &orm o& closed rings -cyclic. and &ound in all &ractions o& crude oil exce#t the ery lightest, ingle3ring na#hthenes -monocyclo#ara&&ins. 'ith &ie and six carbon atoms such as cyclohexane #redominate, %'o3ring na#hthenes -dicyclo#ara&&ins. are &ound in the heaier ends o& na#htha, !l5enes )&lefins-4 Ole&ins such as ethylene4 butene4 isobutene are usually
&ormed by thermal and catalytic cracking and rarely occur naturally in un#rocessed crude oil, %hey are unstable and also im#roe the anti3knock tendencies o& gasoline but not as much as the iso3alkanes,
120
Dienes and !l5ynes! 1xam#les o& dienes or diole&ins4 are )4*3butadiene and
)403butadiene, Acetylene is a ty#ical alkyne, %his category o& hydrocarbons is obtained &rom lighter &ractions through cracking, N"n4hydr"*ar:"ns $ulfur "ompounds) ul&ur may be #resent in crude oil as hydrogen sul&ide
-H*.4 as merca#tans4 sul&ides4 disul&ides4 thio#henes4 etc, or as elemental sul&ur, 1ach crude oil has di&&erent amounts and ty#es o& sul&ur com#ounds4 but as a rule the #ro#ortion4 stability4 and com#lexity o& the com#ounds are greater in heaier crude3oil &ractions, ul#hur is an undesirable com#onent because o& its strong o&&ensie odour4 corrosion4 air #ollution by some o& its com#ounds and its e&&ect o& reducing tetraethyl lead -anti3knock agent., Hydrogen sul&ide is a #rimary contributor to corrosion in re&inery #rocessing units, Other corrosie substances are elemental sul&ur and merca#tans, %he corrosie sul&ur com#ounds also hae an obnoxious odor, %he combustion o& #etroleum #roducts containing sul&ur com#ounds #roduces undesirables such as sul&uric acid and sul&ur dioxide, Catalytic hydrotreating #rocesses such as hydrodesul&uri"ation remoe sul&ur com#ounds &rom re&inery #roduct streams, 'eetening #rocesses either remoe the obnoxious sul&ur com#ounds or conert them to odorless disul&ides4 as in the case o& merca#tans, &6ygen "ompounds) Oxygen com#ounds such as #henols4 ketones4 and
carboxylic acids occur in crude oils in arying amounts, Nitrogen "ompounds) Eitrogen is &ound in lighter &ractions o& crude oil as basic
com#ounds4 and more o&ten in heaier &ractions o& crude oil as nonbasic com#ounds, Eitrogen oxides can &orm in #rocess &urnaces, %he decom#osition o& nitrogen com#ounds in catalytic cracking and hydrocracking #rocesses &orms ammonia and cyanides that can cause corrosion, 7race 1etals) Metals4 including nickel4 iron4 and anadium are o&ten &ound in
crude oils in small (uantities and are remoed during the re&ining #rocess, Burning heay &uel oils in re&inery &urnaces and boilers can leae de#osits o& anadium oxide and nickel oxide in &urnace boxes4 ducts4 and tubes, It is also
121
desirable to remoe trace amounts o& arsenic4 anadium4 and nickel #rior to #rocessing as they can #oison certain catalysts, $alts4 Crude oils o&ten contain inorganic salts such as sodium chloride4
magnesium chloride4 and calcium chloride in sus#ension or dissoled in entrained 'ater -brine. in the &orm o& an emulsion, %hese salts must be remoed or neutrali"ed be&ore #rocessing to #reent catalyst #oisoning4 e(ui#ment corrosion4 and &ouling, alt corrosion is caused by the hydrolysis o& some metal chlorides to hydrogen chloride -HCl. and the subse(uent &ormation o& hydrochloric acid 'hen crude oil is heated, Hydrogen chloride may also combine 'ith ammonia to &orm ammonium chloride -EH 2Cl.4 'hich causes &ouling and corrosion, alt is remoed mainly by mechanical or electrical desalting "arbon Dio6ide) Carbon dioxide may result &rom the decom#osition o&
bicarbonates #resent in or added to crude4 or &rom steam used in the distillation #rocess, Naphthenic !cids) ome crude oils contain na#hthenic -organic. acids4 'hich
may become corrosie at tem#eratures aboe *0+[C 'hen the acid alue o& the crude is aboe certain leel,
,.1. ,. etr"leum Re
%he #etroleum industry began 'ith the success&ul drilling o& the &irst commercial oil 'ell in )F5$4 and the o#ening o& the &irst re&inery t'o years later to #rocess the crude into kerosene, %oday4 #etroleum re&inery #roducts obtained include gasoline4 kerosene4 #ro#ane4 &uel oil4 lubricating oil4 'ax4 and as#halt, :e&ining crude oil inoles t'o kinds o& #rocesses9 irst4 there are #hysical #rocesses 'hich sim#ly re&ine the crude oil -'ithout altering its molecular structure. into use&ul #roducts such as lubricating oil or &uel oil, /etroleum re&ining begins 'ith distillati"n4 or &ractionation4 'hich se#arates crude oil in atmos#heric and acuum distillation to'ers into grou#s o& hydrocarbon com#ounds o& di&&ering boiling3#oint ranges called &ractions or cuts, econd4 there are *hemi*al *"n2ersi"n /r"*esses 'hich alter the si"e and;or molecular structure o& hydrocarbon molecules to #roduce a 'ide range o&
122
#roducts4 some o& them kno'n by the general term #etrochemicals, Conersion #rocesses include9 •
De*"m/"siti"n -diiding. by thermal and catalytic crackingQ
•
Uni
•
Alterati"n -rearranging. 'ith isomeri"ation and catalytic re&orming,
As seen aboe4 the ma=or chemical conersions include cracking4 alkylation4 #olymerisation4 isomerisation and re&orming, %he conerted #roducts are then sub=ected to arious treatment and se#aration #rocesses, Treatment r"*esses are intended to #re#are hydrocarbon streams &or
additional #rocessing and to #re#are &inished #roducts, %reatment may include the remoal or se#aration o& aromatics and na#hthenes as 'ell as im#urities and undesirable contaminants, %reatment may inole chemical or #hysical se#aration such as dissoling4 absor#tion4 or #reci#itation using a ariety and combination o& #rocesses including hydrodesul&uri"ing and s'eetening
.
7"rmulatin% and lendin% is the #rocess o& mixing and combining hydrocarbon
&ractions4 addities4 and other com#onents to #roduce &inished #roducts 'ith s#eci&ic #er&ormance #ro#erties, Integrated re&ineries incor#orate &ractionation4 conersion4 treatment4 and blending o#erations and may also include #etrochemical #rocessing,
,.1.'. (*tane num:er and the de2el"/ment "< *ra*5in% and re<"rmin% /r"*esses
About )+ o& the #roduct o& the distillation o& crude oil is a &raction kno'n as strai%ht4run %as"line4 'hich sered as a satis&actory &uel during the early days
o& the internal combustion engine, As the automobile engine deelo#ed4 it 'as made more #o'er&ul by increasing the com#ression ratio, Modern cars run at com#ression ratios o& about $9)4 'hich means the gasoline3air mixture in the cylinder is com#ressed by a &actor o& nine be&ore it is ignited, traight3run gasoline burns uneenly in high3com#ression engines4 #roducing a shock 'ae that causes the engine to knock4 %he challenge &or the #etroleum industry 'as
123
to increase the yield o& gasoline &rom each barrel o& crude oil and to decrease the tendency o& gasoline to knock 'hen it burned, It 'as &ound that9 •
Branched alkanes and cycloalkanes burn more eenly than straight3chain alkanes,
•
hort alkanes -C 2H)+. burn more eenly than long alkanes -C !H)6.,
•
Alkenes burn more eenly than alkanes,
•
Aromatic hydrocarbons burn more eenly than cycloalkanes,
%he most commonly used measure o& a gasolineSs ability to burn 'ithout knocking is its "*tane num:er , Octane numbers com#are a gasolineSs tendency to knock against the tendency to knock o& a blend o& t'o hydrocarbons he#tane and *4*423trimethyl#entane4 -isooctane., He#tane #roduces a great deal o& knocking 'hile isooctane is more resistant to knocking, ?asolines that match a blend o& F! isooctane and )0 he#tane are gien an octane number o& F!, %here are three 'ays o& re#orting octane numbers, Measurements made at high s#eed and high tem#erature are re#orted as motor octane numbers 'hile measurements taken under relatiely mild engine conditions are kno'n as research octane numbers, %he road"inde# octane numbers re#orted on gasoline
#um#s are an aerage o& these t'o, :oad3index octane numbers &or a &e' #ure hydrocarbons are gien in the %able 5,*,belo',
Ta:le ,.. Hydr"*ar:"n R"ad (*tane Num:ers $ydrocarbon
%oad Inde# &ctane
He#tane *3Methylhe#tane Hexane *3Methylhexane )3He#tene /entane )3/entene Butane
'umber + *0 *5 22 6+ 6* F2 $)
124
Cyclohexane *4*423%rimethyl#entane
$! )++
-isooctane. Ben"ene %oluene
)+) ))*
By )$** a number o& com#ounds had been discoered that could increase the octane number o& gasoline, Adding as little as 6 ml o& tetraethyllead to a gallon o& gasoline4 &or exam#le4 can increase the octane number by )5 to *+ units, %his discoery gae rise to the &irst ethyl gasoline4 and enabled the #etroleum industry to #roduce aiation gasolines 'ith octane numbers greater than )++, Another 'ay to increase the octane number is thermal re<"rmin%, At high tem#eratures -5++36++oC. and high #ressures -*535+ atm.4 straight3chain alkanes isomeri"e to &orm branched alkanes and cycloalkanes4 thereby increasing the octane number o& the gasoline, :unning this reaction in the #resence o& hydrogen and a catalyst such as a mixture o& silica -iO *. and alumina -Al *O0. results in *atalyti* re<"rmin%4 'hich can #roduce a gasoline 'ith een higher octane numbers, %he yield o& gasoline is increased by cracking the long chain hydrocarbons into smaller #ieces at high tem#eratures -5++ oC. and high #ressures -*5 atm., A saturated C )* hydrocarbon in kerosene4 &or exam#le4 might break into t'o C 6 &ragments, Because the total number o& carbon and hydrogen atoms remains constant4 one o& the #roducts o& this reaction must contain a CC double bond .
%he #resence o& alkenes in thermally cracked gasolines increases the octane number -!+. relatie to that o& straight3run gasoline -6+.4 but it also makes thermally3cracked gasoline less stable &or long3term storage, %hermal cracking has there&ore been re#laced by *atalyti* *ra*5in%4 'hich uses catalysts instead o& high tem#eratures and #ressures to crack long3chain hydrocarbons into smaller &ragments &or use in gasoline,
125
%he &lo' diagrams ig, 5,* and 5,0 sho' the arious #rocesses undertaken to im#roe the yields and (uality o& #etroleum #roducts, Among them are catalytic cracking and catalytic re&orming,
Fig. 5.2. Refining operations
126
ig +.) $etroleum re8ining
,.1.. Catalyti* Cra*5in% 1thylene and #ro#ylene are the most im#ortant organic chemical &eedstocks
accounting &or oer 5+36+ o& all organic chemicals, But because o& their relatiely high reactiities4 ery &e' ole&ins are &ound in natural gas or crude oil, %here&ore4 they must be manu&actured by cracking #rocesses, 127
%he #ur#ose o& cracking is to break com#lex hydrocarbons into sim#ler molecules in order to increase the (uality and (uantity o& lighter4 more desirable #roducts and decrease the amount o& residuals, %he heay hydrocarbon &eedstock is cracked into lighter &ractions such as kerosene4 gasoline4 >/?4 heating oil4 and #etrochemical &eedstock, >/? gases are &eedstock &or ole&ins such as ethylene and #ro#ylene, %he decom#osition takes #lace by catalytic action or heating in the absence o& oxygen -#yrolysis., %he catalysts used in re&inery cracking units are ty#ically "eolite4 aluminum hydrosilicate4 treated bentonite clay4 &ullerSs earth4 bauxite4 and silica3alumina -iO*3Al*O0. all o& 'hich come in the &orm o& #o'ders4 beads4 or #ellets, %he &ormation o& gasoline -'ith lo' molecular 'eight. &rom heay gas oil o& high molecular 'eight is sho'n in the &ollo'ing e(uation9
%here are three basic &unctions in the catalytic racking #rocess9 •
:eaction 3 eedstock reacts 'ith catalyst and cracks into di&&erent hydrocarbons
•
:egeneration 3 Catalyst is reactiated by burning o&& coke
•
ractionation 3 Cracked hydrocarbon stream is se#arated into arious #roducts,
,.1.B. Catalyti* Re<"rmin%
Catalytic re&orming is an im#ortant #rocess used to conert lo'3octane na#hthas into high3octane gasoline blending com#onents called re&ormates, 7e#ending on the #ro#erties o& the na#htha &eedstock -as measured by the #ara&&in4 ole&in4 na#hthene4 and aromatic content. and catalysts used4 re&ormates can be #roduced 'ith ery high concentrations o& toluene4 ben"ene4 xylene4 and other aromatics use&ul in gasoline blending and #etrochemical #rocessing, Hydrogen4 a signi&icant by3#roduct4 is se#arated &rom the re&ormate &or recycling and use in
128
other #rocesses, Most #rocesses use #latinum as the actie catalyst, ometimes #latinum is combined 'ith a second catalyst -bimetallic catalyst. such as rhenium or another noble metal, %he conersion is illustrated by the &ollo'ing reaction in 'hich a cycloalkane is conerted to an aromatic com#ound4 usually o& higher octane number,
%he na#htha &eed is mixed 'ith recycled hydrogen and introduced to the &eed #reheater to raise the tem#erature, %he hot mixture o& hydrogen and na#htha a#ours is #assed through a series o& &our reactors containing the catalyst, %he 'orking tem#eratures and #ressures are usually bet'een )5+ oC to 5)+oC and )5++k/a to !+++k/a res#ectiely, %he #roducts are cooled and about $+ o& the hydrogen is com#ressed and recycled, %he main #roduct is &ractionated, %he oerhead #roduct can be used as a &uel, ome catalytic re&orming systems continuously regenerate the catalyst 'hile in other systems one reactor at a time is taken o&&3stream &or catalyst regeneration4 ome &acilities regenerate catalysts &rom all o& the reactors during shutdo'n,
,.1.>. "lymeri8ati"n
%his is the =oining u# o& lo' molecular 'eight &ractions to &orm high molecular 'eight com#onents, %his #rocess conerts by3#roducts hydrocarbon gases into li(uid hydrocarbons that are suitable &or use as high octane number &uels and &or #etrochemical industry, %he combining molecules are usually unsaturated, /ro#ylene and iso3butylene are common ole&ins #olymerised in the a#our #hase in reactions such as sho'n here9
129
,.1.10. Al5ylati"n
Akylation 'as discussed in Unit * under unit #rocesses, In the context o& #etroleum #rocessing4 it is the combining o& an ole&in 'ith an aromatic hydrocarbon, %he #rocess is o& relatiely minor im#ortance com#ared to the catalytic cracking and catalytic re&orming #rocesses, It is used mainly &or conerting gaseous hydrocarbons to gasoline in the #resence o& an acid catalyst such as hydrogen &luoride or sul#huric acid, %he #rocesses are usually exothermic and similar to #olymerisation, An exam#le is the &ormation o& *4*3 7imethylbutane &rom ethylene and isobutane9
,.1.11. Treatin%S$eetenin% dryin% %reating is a means by 'hich contaminants such as organic com#ounds
containing sul&ur4 nitrogen4 and oxygenQ dissoled metals and inorganic saltsQ and soluble salts dissoled in emulsi&ied 'ater are remoed &rom #etroleum &ractions or streams, 'eetening4 a ma=or re&inery treatment o& gasoline4 treats sul&ur com#ounds -hydrogen sul&ide4 thio#hene and merca#tan. to im#roe colour4 odour4 and oxidation stability, 'eetening also reduces concentrations o& carbon dioxide, %reating can be accom#lished at an intermediate stage in the re&ining #rocess4 or =ust be&ore sending the &inished #roduct to storage, Choices o& a treating method de#end on the nature o& the #etroleum &ractions4 amount and ty#e o& im#urities in the &ractions to be treated4 the extent to 'hich the #rocess remoes the im#urities4 and end3#roduct s#eci&ications, %reating materials include acids4 solents4 alkalis4 oxidi"ing4 and adsor#tion agents, ul&uric acid is the most commonly used acid treating #rocess, ul&uric acid treating results in #artial or com#lete remoal o& unsaturated hydrocarbons4 sul&ur4 nitrogen4 oxygen com#ounds4 resinous and as#haltic com#ounds, It is used to im#roe the odour4 colour4 stability4 carbon residue4 and other #ro#erties
130
o& the oil, Clay;lime treatment o& acid3re&ined oil remoes traces o& as#haltic materials and other com#ounds to im#roe #roduct colour4 odour4 and stability, Caustic treating 'ith sodium -or #otassium. hydroxide is used to im#roe odour and colour by remoing organic acids -na#hthenic acids4 #henols. and sul&ur com#ounds -merca#tans4 H *. by a caustic 'ash, By combining caustic soda solution 'ith arious solubility #romoters -e,g,4 methyl alcohol and cresols.4 u# to $$ o& all merca#tans as 'ell as oxygen and nitrogen com#ounds can be dissoled &rom #etroleum &ractions, Drying is accom#lished by the use o& 'ater absor#tion or adsor#tion agents to
remoe 'ater &rom the #roducts, ome #rocesses simultaneously dry and s'eeten by adsor#tion on molecular siees, $ulfur ecovery
ul&ur recoery conerts hydrogen sul&ide in sour gases and hydrocarbon streams to elemental sul&ur, A ty#ical #rocess #roduces elemental sul&ur by burning hydrogen sul&ide under controlled conditions, %he gases are then ex#osed to a catalyst to recoer additional sul&ur, ul&ur a#or &rom burning and conersion is condensed and recoered, Hydrogen $ulfide $crubbing
Hydrogen sul&ide scrubbing is a common treating #rocess in 'hich the hydrocarbon &eedstock is &irst scrubbed to #reent catalyst #oisoning, Hydrotreating &or sul&ur remoal is called hydr"desul
131
o& H* and other undesirable com#onents, In cases 'here steam is used &or stri##ing4 the #roduct is sent to a acuum drier &or remoal o& 'ater, Hydrodesul&uri"ed #roducts are blended or used as catalytic re&orming &eedstock,
+.". $etroc4emical Industry /etrochemicals are chemicals4 other than &uels4 deried &rom #etroleum, %hese chemicals include a large number o& ali#hatic and aromatic organic com#ounds o& arious &unctional grou#s, 1xam#les include ben"ene and it deriaties4 methane4 ethylene4 #ro#ylene4 butene4 toluene4 and xylene and their deriaties,
,..1. hthali* Anhydride
,..1.1 Intr"du*ti"n
/hthalic anhydride -C 6H2-CO.*O. is a colourless solid 'hich 'as &irst re#orted in )F06, It is a #recursor to a ariety o& industrial organic chemicals,
,..1.. Uses
/hthalic anhydride is a ersatile intermediate in organic chemistry #artly because it is bi&unctional and chea#ly aailable, Most characteristically4 it undergoes hydrolysis and alcoholysis, Hydrolysis by hot 'ater4 &orms ortho3#hthalic acid, %his #rocess is reersible 'ith #hthalic anhydride re3&orming u#on heating the acid aboe )F+ [C, %he alcoholysis reaction is the basis o& the manu&acture o& #hthalate esters 'hich are 'idely used #lastici"ers, %hese are addities that gie #olymers more &lexibility, :eaction o& #hthalic anhydride 'ith alcohols gies diesters as &ollo's9 C'H+C(-( G R(H
C 'H+C(H-C(R
%he second esteri&ication is more di&&icult and re(uires remoal o& 'ater9 C'H+C(H-C(R G R(H
C 'H+C(R- G H(
132
%'o o& the most im#ortant diesters bis-*3ethylhexyl. #hthalate -71H. and dioctyl #hthalate -7O/. are used as #lasticisers in the manu&acture o& #olyinyl chloride, Other ma=or uses o& #hthalic anhydride are in #olyester resins and -decreasingly. in alkyd resins, Alkyd resins containing /A are used in solent3borne #rotectie coatings, As #aint technology increasingly utilises 'ater3borne technologies4 many /A3based alkyds hae lost out to alternatie ra' materials, /hthalic anhydride is 'idely used in industry &or the #roduction o& certain dyes such as the 'ell3kno'n anthro(uinone dye,
,..1.3. r"du*ti"n r"*ess
/hthalic anhydride 'as &irst #roduced by the oxidation o& na#hthalene &rom coal in concentrated sul#huric acid in the #resence o& mercury sul#hate, %his route 'as later re#laced by the catalytic a#our #hase oxidation o& na#hthalene in air in the #resence o& a anadium oxide catalyst, %oday4 na#hthalene &eedstock has been generally su#erseded by the use o& orthoxylene obtained &rom re&ineries and crackers, %he commonly used catalyst is anadium #entoxide 'ith titanium dioxide3antimony trioxide, Alternatie catalysts include molybdenum trioxide and calcium oxide4 or manganese oxides, %he res#ectie reactions &or the t'o &eedstocks are as &ollo's9 C10HB G ., (
C'H+CH3- G 3 (
C'H+C(-( G H ( G C(
C'H+C(-( G 3 H ( H>B F4161 5m"l
%he #rocess technology has changed little although yields hae im#roed and catalysts in current use hae a longer li&e o& three years, Another deelo#ment has been the lo'ering o& the air to orthoxylene 'eight ratio to $,59)4 do'n &rom about *+9)4 thus allo'ing a reduction in ca#ital costs and energy saings, In the orthoxylene3based #rocess sho'n in ig 5,24 the &eedstock is a#ouri"ed and mixed 'ith air, %he air3orthoxylene mixture is &ed to a reactor 'ith ertical tubes &illed 'ith catalyst, %he reaction takes #lace at 0!532*5 #ressure,
133
o
C and belo' ) bar
%alt cooler Reactor
%6itc4 Condensers' Desu7limation' Melting
%team generator
apouri9er acuum Distillation
7i% ,. r"*ess
%em#erature control is im#ortant because the main reaction and the side reactions are exothermic, %he reactor is cooled by recirculating a molten salt on the outside o& the tubes, About !+ o& xylene is conerted to /A4 )5 is unconerted4 )5 is oxidi"ed into maleic anhydride 'hile the ) balance &orms a heay im#urity, %he maleic anhydride is &ormed by the &ollo'ing reaction9
C'H+CH3- G ., (
CH(3 G H( G C(
%he gases &rom the reactor are cooled be&ore entering a series o& three s'itch condensers 'hich se#arates #hthalic anhydride &rom the by#roducts, Because o& the lo' #artial #ressure o& #hthalic anhydride in the stream4 it desublimates rather than condenses, /hthalic anhydride collects on the 'alls o& the condensers as a solid,
second is in the melting mode 'hile the third is on standby, /uri&ication o& the #roduct is by acuum distillation, A #uri&ied #roduct 'ith a #urity o& oer $$,5 #hthalic anhydride is obtained, %he #roduct is stored either in a molten state or bagged as &lakes, ,... Adi/i* A*id ,...1. Intr"du*ti"n Adi#ic acid4 COOH3-CH*.03COOH4 is one o& the most im#ortant commercially
aailable ali#hatic dicarboxylic acids, %he t'o 3COOH grou#s can yield t'o kinds o& salts, %y#ically4 it is a 'hite crystalline solid4slightly soluble in 'ater and soluble in alcohol and acetone, Its consum#tion and #roduction is dominated by the United tates, O& the *,0 million metric tons o& adi#ic acid #roduced 'orld'ide4 about 2* is #roduced in the United tates 'hich also consumes 6* o& total #roduction,
,.... Uses
Adi#ic acid consum#tion is linked almost $+ to nylon, Eylon is used &or eeryday a##lications such as electrical connectors4 cable tires4 &ishing lines4 &abrics4 car#eting4 and many other use&ul #roducts, %echnical grade adi#ic acid is used to make #lastici"ers4 unsaturated #olyesters &or #roduction o& rigid and &lexible resins and &oams4 'ire coatings4 elastomers4 adhesies and lubricants, ood grade adi#ic acid is used as a gelling aid4 acidulant4 leaening and bu&&ering agent,
,...3. r"du*ti"n r"*ess
Almost all o& the commercial adi#ic acid is #roduced &rom cyclohexane in a continuous #rocess as sho'n in ig, 5,5,
135
Cyclohexane is air3oxidi"e at a tem#erature o& )5+ 3 )6+ oC and about F to )+ atm in the #resence o& a cobalt catalyst,
C'H1 G (
C'H11(H G C'H11(
%he #roduct is a cyclohexanol3cyclohexanone -ketone3alcohol4 or A. mixture, %he mixture is distilled to recoer unconerted cyclohexane 'hich is recycled to the reactor &eed, %he resultant A mixture may then be distilled &or im#roed (uality be&ore being sent to the nitric acid oxidation stage, %his #rocess yields !5 to F+ mole #ercent A4 'ith a ketone to alcohol ratio o& )9*, %he second ste# is the nitric acid oxidation o& the cyclohexanol;cyclohexanone -A. mixture, %he reaction #roceeds as &ollo's9 C'H11(H G C 'H11(
G 8HN( 3
H((C+CH -C((H G N ( GyN(
5+ to 6+ nitric acid in the #resence o& a co##er3anadium catalyst is reacted 'ith the A mixture in a reactor at 6+ to F+ oC and +,) to +,2 M/a, Conersion yields o& $* to $6 #ercent are attainable 'hen using high3#urity A &eedstock, As the reaction is highly exothermic4 the heat o& reaction is usually dissi#ated by maintaining a high ratio -2+9). nitric acid to A mixture,
#ig$ %"ess&"e '("&!!e"
)o* %"ess&"e '("&!!e"
Oxidation
Distillation
Refining
K Oxidation
!so"!e"
136
,"-stalliation/ 'e%a"ation
D"-ing and ,ooling
,on(ent"ation
+lea($e"
ig +.+. lo6 diagram 8or adipic acid manu8acture
U#on reaction4 nitric acid is reduced to nitrogen oxides9 EO *4 EO4 E*O4 and E*, %he dissoled oxides are stri##ed &rom the reaction #roduct using air in a bleaching column and subse(uently recoered as nitric acid in an absor#tion to'er, %he E * and E*O are released to the atmos#here, Eitrogen oxides4 entering the lo'er #ortion o& the absorber4 &lo' countercurrent to a 'ater stream4 'hich enters near the to# o& the absorber, Unabsorbed EO is ented &rom the to# 'hile diluted nitric acid is 'ithdra'n &rom the bottom o& the absorber and recycled to the adi#ic acid #rocess, %he stri##ed adi#ic acid;nitric acid solution is chilled and sent to a crystalli"er4 'here crystals o& adi#ic acid are &ormed, %he crystals are se#arated &rom the mother li(uor using a centri&uge and trans#orted to the adi#ic acid drying and;or melting
&acilities,
%he mother li(uor is se#arated &rom the
remaining
uncrystalli"ed adi#ic acid in the #roduct still and recycled to the reactors,
,.3. The "lymer Industry
,.3.1. Intr"du*ti"n
Industrial use o& #olymers started 'hen ?oodyear discoered the ulcani"ation o& rubber in )F0$, /olymer research ra#idly s#read throughout the 'orld a&ter )$0+ and this led to the deelo#ment o& many synthetic #olymers including nylon4 #olyethylene and #olyinyl chloride, /olymers are high molecular 'eight com#ounds built u# by the re#etition o& small chemical units kno'n as monomers, %hey are either natural or synthetic, %he natural #olymers include rubber4 cellulose4 'ool4 starch and #roteins,
137
%he term #olymer comes &rom t'o ?reek 'ords9 X#olysY 'hich means XmanyY and XmerosY 'hich means X#arts,Y A #olymer is there&ore a high molecular 'eight com#ound made u# o& hundreds or thousands o& many identical small basic units -monomers. o& carbon4 hydrogen4 oxygen or silicon atoms, %he monomers are linked together coalently in a chemical #rocess kno'n as #olymeri"ation, %his is illustrated in ig 5,2,
ig +.0. A polymer c4ain
,.3.. Classi
/olymers can be classi&ied into three ty#es9 ), >inear #olymers in 'hich the re#eating units are similar to the links in a ery long chain %hey are kno'n as #olymer chains, An exam#le is #olyethylene *, Branched #olymers in 'hich some o& the molecules are attached as side chains to the linear chains, %he indiidual molecules are still discrete, 0, %hree3dimensional cross3linked #olymers in 'hich branched chains are =oined together by cross3linking in a #rocess kno'n as XcuringY, Vulcani"ation o& rubber is a curing #rocess,
,.3.3. "lymer /r"/erties
/olymers hae three main #ro#erties9 Molecular 'eight9 %he molecular 'eight o& #olymers is not &ixed because o& arying chain length, Crystallinity9 Because o& high molecular 'eight and arying chain length4 most #olymers are amor#hous and only semi3crystalline, %hose 'ith high crystallinity
138
are tougher4 more o#a(ue4 more resistant to solents4 higher density and shar#ly de&ined melting #oint, ?lass transition tem#erature9 At lo' tem#erature4 een amor#hous #olymers are hard and brittle -glass3like., As tem#erature is increased4 kinetic energy increases, Ho'eer4 motion is restricted to short3range ibrations and rotations as long as glass3like structure is retained, At a certain tem#erature called the glass transition temperature( a #olymer loses glass3like #ro#erties, It becomes
so&ter and more elastomeric but it does not melt, I& heating is continued &urther4 the #olymer 'ill lose elastomeric #ro#erties and melt to a &lo'able li(uid,
,.3.. Ty/es "< /"lymer /r"du*ts 2lastics
A #lastic is a material that contains as an essential ingredient4 an organic substance o& a large molecular 'eight4 is solid in its &inished state4 and4 at some stage in its manu&acture or in its #rocessing into &inished articles4 can be sha#ed by &lo', In #ractice4 a #lastic is usually considered to be an amor#hous or crystalline #olymer 'hich is hard and brittle at ordinary tem#eratures, I& crystalline regions are #resent4 they are randomly oriented, )hermoplastics
A thermo#lastic material is one 'hich can be so&tened and molded on heating, %hey are elastic and &lexible aboe a certain glass transition tem#erature, Eylon is a thermo#lastic and it 'as the &irst commercial #olymer to be made as a substitute &or silk &or making #arachutes4 ehicle tires4 garments and many other #roducts, Current uses include9 &abrics4 &oot'ear4 &ishnets and car#ets to mention but a &e', %he t'o s#ecial grades o& Eylon are Eylon 636 and Eylon 6, Other thermo#lastic materials and their uses are gien in %able 5,*
Ta:le ,.. Uses "< 2ari"us therm"/lasti* materials lasti* ty/e >o' density #olyethylene ->7/1
Uses /ackaging &ilms4 'ire and cable
139
insulation4 toys4 &lexible bottles4 High density #olyethylene -H7/1.
house'are Bottles4 drums4 #i#es4 &ilms4 sheets4
/oly#ro#ylene //
'ire and cable insulation Automobile and a##liances #arts4 &urniture4 cordage4 car#ets4 &ilm
/olyinyl chloride /VC
#ackaging Construction4 rigid #i#es4 &looring4 'ire
/olystyrene
and cable insulation4 &ilm and sheet /ackaging -&oam and &ilm.4 &oam4 insulation4 insulation4 a##liances4 house'are
)hermosetting plastics
A thermosetting material is one 'hich inoles considerable crosslinking4 so that the &inished #lastic cannot be made to &lo' or melt, %hermosetting #lastics -thermosets. are #olymer materials that cure or are made strong by addition o& elements -e,g, sul#hur. or addition o& energy in &orm o& heat -normally aboe *++oC. through some chemical reaction, Be&ore curing #rocess4 they are usually in li(uid &orm4 #o'der or malleable &orms that can be moulded to a &inal &orm or used as adhesies, %he curing #rocess trans&orms these materials into #lastic or rubber through a cross linking #rocess, %he cross links #roduce a three dimensional rigid structure o& the material 'ith large molecular 'eight and a high melting #oint, %he three dimensional net'ork o& bonds in thermosets generally makes them much stronger than thermo#lastics, %his makes them suitable &or high tem#erature a##lications u# to the decom#osition tem#erature o& the material, A thermoset material cannot be melted and resha#ed a&ter &orming and curing and there&ore cannot be recycled unlike thermo#lastics, 1xam#les o& thermosets include9 #olyester resin4 ulcani"ed rubber4 bakelite and e#oxy resin, %able 5,0, gies uses o& arious thermosetting #lastics, Ta:le ,.3. rin*i/al therm"settin% /lasti*s Therm"settin% /lasti* /henol3&ormaldehyde -/.
Uses 1lectrical and electronic e(ui#ment4
140
automobile #arts4 utensils4 handles4 #ly'ood adhesies4 #article board Urea3&ormaldehyde -U. Unsaturated #olyester -U/.
binder imilar to /4 textile treatment4 coating Construction4 automobile #arts4 marine
1#oxy
accessories /rotectie coating4 adhesies4 electrical and electronics4 industrial &looring4 material com#osites imilar to U4 decoratie #anels4
Melamine3&ormaldehyde -M.
counter and table to#s4 dinner'are In the &abrication o& #lastic ob=ects4 addities such as colourants4 &illers4 #lastici"ers4 lubricants and stabili"ers are commonly added to modi&y the #hysical and mechanical #ro#erties o& the material, 8lastomers
An elastomer -or rubber. is a 'ord haing its origin &rom t'o 'ords9 XelasticY 'hich means the ability to return to original sha#e 'hen a &orce or stress is remoed and XmeroY 'hich means X#artsX im#lying many #arts or monomers, %here&ore4 an essential re(uirement o& an elastomer is that it must be elastic i,e, it must stretch ra#idly under tension to seeral times its original length 'ith little loss o& energy as heat, Industrial elastomers hae high tensile strength and high modulus o& elasticity, %hey are amor#hous #olymers 'ith considerable cross3 linkages, %he coalent cross3linkages make the elastomer to return to its original structure or sha#e 'hen the stress is remoed,
Eitrile rubber
•
Butyl rubber
•
ilicone rubber
•
/olyurethane rubber
141
•
/olysul#hide rubber
•
/oly butadiene
•
tyrene3butadiene
•
/olyiso#rene
•
%etra&luoroethylene
•
%etra&luoro#ro#ylene
!dhesives
%he heated glue3#ot 'hich traditionally contained glues based on animal #roducts such as hoo&4 horn and &ish residues has been re#laced by adhesies based on synthetic #olymers, %here is no' a 'ide range o& adhesies and sealants suited to a ariety o& tasks &rom #olyinyl acetate -/VA. 'ood4 board and #a#er glues to t'o3#art e#oxide resins &or riet3less bonding o& metal #anels,
*ibres
Animal &ibres4 such as 'ool or silk4 and egetable &ibres4 such as cotton4 continue to be used although there is a 'ealth o& synthetic &ibres such as cellulose acetate and nylon4 acrylic and #olyester, Carbon &ibres &or making adanced com#osites are #roduced by heat treatment o& #olyacrylonitrile and other synthetic &ibres,
*ilms
Animal membranes 'ere the only non3metallic &ilm &orming materials used be&ore the aailability o& rubber and these &ound little a##lication, %he success&ul deelo#ment o& a drum &or casting &ilms &rom iscose led in the )$*+s to the #roduction o& SCello#haneS3 still a 'idely used material, In the )$0+s4 unsu##orted /VC &ilms 'ere manu&actured but it 'as not until #olyethylene 'as aailable in the )$2+s that the #roduction o& &ilms &or bagging materials became common#lace,
142
Surface finishes
%he #aint industry 'as traditionally based on naturally occurring SdryingS oils such as linseed but since the )$0+s these hae gradually been re#laced by synthetic #olymers, Because o& toxicity #roblems &rom using #aints based on solents4 many more &inishes are no' 'ater3based #olymer emulsions, ,.3.,. "lyethylene ,.3.,.1. Intr"du*ti"n
%here are three ma=or classes o& #olyethylene, %hese are lo' density #olyethylene ->7/1.4 high density #olyethylene -H7/1. and linear lo' density #olyethylene ->>7/1., /ellets o& these #lastics are extruded and blo'n to #roduce &ilm, %his &ilm is used &or #ackaging and making #lastic bags, 1thylene is deried &rom either modi&ying natural gas -a methane4 ethane4 #ro#ane mix. or &rom the catalytic cracking o& crude oil, In a highly #uri&ied &orm4 it is #i#ed directly &rom the re&inery to a se#arate #olymeri"ation #lant, Here4 under the right conditions o& tem#erature4 #ressure and catalysis4 the double bond o& the ethylene monomer o#ens u# and many monomers link u# to &orm #olyethylene, In commercial #olyethylene4 the number o& monomer re#eat units ranges &rom )+++ to )+ +++, Molecular 'eight ranges &rom *F4+++ to *F4++++,
,.3.,..The "lyethylene Manu
%oday4 #olyethylene manu&acturing #rocesses are usually categori"ed into high #ressure and lo' #ressure o#erations, %he &ormer is generally recogni"ed as #roducing conentional lo' density #olyethylene ->7/1. 'hile the latter makes high density -H7/1. and linear lo' density ->>7/1. #olyethylenes, %he di&&erence bet'een these #olyethylene #rocesses and ty#es is outlined belo', Hi%h /ressure
/olyethylene 'as &irst #roduced by the high #ressure #rocess by ICI4 Britain4 in the )$0+Ss, %hey discoered that ethylene gas could be conerted into a 'hite solid by heating it at ery high #ressures in the #resence o& minute (uantities o& oxygen9
143
Ethylene G 10 //m "y%en
1000 4 3000 :ar
/"lyethylene
B0 4 300 "C
%he #olymeri"ation reaction 'hich occurs is a random one4 #roducing a 'ide distribution o& molecule si"es, By controlling the reaction conditions4 it is #ossible to select the aerage molecule si"e -or molecule 'eight. and the distribution o& si"es around this aerage -molecular 'eight distribution., %he chains are highly branched -at interals o& *+ J 5+ carbons., ICI named their ne' #lastic #olythene and &ound that they 'ere able to #roduce it in a density range o& about +,$)5 to +,$0+g cm , It is kno'n today as >7/1 and 0
has its single biggest usage in blo'n &ilm,
Reactor
*ig4 pressure %eparator
Lo6 pressure %eparator
%econdary Compressor
E:truder ' $elleti9er
$rimary Compressor
7i%. ,., Hi%h /ressure /r"*ess <"r the manu
L"$ /ressure
%he initial discoery o& >7/1 'as an accident, o 'as the discoery o& H7/1 in )$5*, :esearchers in ?ermany and Italy had succeeded in making a ne' aluminium based catalyst 'hich #ermitted the #olymeri"ation o& ethylene at much lo'er #ressures than the ICI #rocess9 Ethylene
10 4 B0 :ar
/"lyethylene
0 4 300 "C6 Al *atalyst
%he #roduct &rom this #rocess 'as &ound to be much sti&&er than #reious #roducts and had a density range o& about +,$2+ 3 +,$!+g cm , %he increased 0
sti&&ness and density 'ere &ound to be due to a much lo'er leel o& chain
144
branching, %he ne' H7/1 'as &ound to be com#osed o& ery straight chains o& ethylene 'ith a much narro'er distribution o& molecular 'eights -or chain lengths. and a #otentially ery high aerage chain length, In the late )$5+Ss4 7u/ont Canada &irst a##lied the lo' #ressure #rocess to the #roduction o& >>7/1, >>7/1 is made by co#olymeri"ing o& ethylene 'ith a small amount o& another monomer4 ty#ically butene4 hexene or octene, %he most common method used in industry is to #olymeri"e ethylene by means o& a &luidi"ed reactor bed, A &luidi"ed reactor bed consists o& metallic catalyst #articles that are S&luidi"edS by the &lo' o& ethylene gas, %his means that the catalyst #articles are sus#ended in the ethylene &luid as ethylene gas is #um#ed &rom the bottom o& the reactor bed to the to#, Be&ore the late )$!+Ss an organic #eroxide catalyst 'as em#loyed to initiate #olymeri"ation, Ho'eer4 because the organic #eroxide catalyst is not as actie as the metallic catalyst4 #ressures in excess o& )++ times the #ressure re(uired 'ith metallic catalysts 'ere necessary, Be&ore ethylene is sent to the &luidi"ed bed4 it must &irst be com#ressed and heated, /ressures in the range o& )++30++ #ounds #er s(uare inch -#si. and a tem#erature o& )++ oC are necessary &or the reaction to #roceed at a reasonable rate, %he catalyst is also #um#ed 'ith the ethylene stream into the reactor, %his is because #olyethylene molecules remain stuck to the catalyst #article &rom 'hich they 'ere #roduced thus incor#orating the catalyst 'ithin the #olyethylene #roduct, Hence the need to re#lenish the Xconsumed X catalyst %he conersion o& ethylene is lo' &or a single #ass through the reactor and it is necessary to recycle the unreacted ethylene, Unreacted ethylene gas is remoed o&& the to# o& the reactor, A&ter #uri&ication4 ethylene gas is then recom#ressed and recycled back into the reactor, ?ranular #olyethylene is gradually remoed &rom the bottom o& the reactor as soon as reasonable conersions hae been achieed, %y#ically4 a residence time o& 0 to 5 hours results in a $! conersion o& ethylene, /olyethylene comes out o& the reactor as granular #o'der4 'hich is then melted and &lo's through a &ilm extruder,
145
Compressor
luid 7ed reactor
Compressor
%eparator
E:truder
7i% ,.'. L"$ /ressure /r"*ess <"r manu
7/1 is the #re&erred #ackaging material due to its lim# &eel4 trans#arency4 toughness4 and the ability to ra#idly take u# the sha#e o& the contents o& the bag, %he garbage bag is =ust one o& many 'idely #ractical uses o& #lastic bags, /olyethylene &ilm4 #roduced by blo'n &ilm extrusion4 is commonly used &or #ackaging o& &oodstu&&s and other #roducts, %he thickness o& the &ilm #roduced tends to be &rom *+ 3 *++ Wm,
,.3.'. Styrene utadiene Ru::er +SR,.3.'.1. Intr"du*ti"n
1mulsion #olymeri"ed styrene3butadiene rubber -13B:. is one o& the most 'idely used #olymers in the 'orld today, 1mulsion B: is em#loyed in many
146
demanding a##lications4 'hich enhance the (uality o& li&e and contribute signi&icantly to our economy and standards o& liing, In the )$0+s4 the &irst emulsion #olymeri"ed B: kno'n as Buna 'as #re#ared by I, ?, arbenindustrie in ?ermany, %he U, , ?oernment in )$2+ established the :ubber :esere Com#any to start a stock#ile o& natural rubber and a synthetic rubber #rogram, %hese #rograms 'ere ex#anded 'hen the United tates entered
5,0,6,*, Uses B: is 'idely used &or rubber belting4 hose4 &looring4 molded goods4 rubber soles4 coated &abrics etc, It is com#atible 'ith natural rubber and has e(ual #er&ormance &or automobile tyres, But it is in&erior to natural rubber &or heay duty truck tyres, ,.3.'.3. Manu
B: is #roduced by the co#olymeri"ation o& butadiene 'ith styrene in the a##roximate #ro#ortion o& 09) by 'eight, In the emulsion #rocess4 'hich #roduces general #ur#ose grades4 the &eedstocks are sus#ended in a large #ro#ortion o& 'ater in the #resence o& an initiator or a catalyst and a stabiliser, A continuous #rocess is em#loyed, In the solution #rocess4 the co#olymerisation #roceeds in a hydrocarbon solution in the #resence o& an organometallic com#lex, %his can be either a continuous or batch #rocess, %he emulsion #olymeri"ation #rocess has seeral adantages, It is normally used under mild reaction conditions that are tolerant to 'ater and re(uires only the absence o& oxygen,
147
%he #rocess is relatiely robust to im#urities and amenable to using a range o& monomers, Additional bene&its include the &act that emulsion #olymeri"ation gies high solids contents 'ith lo' reaction iscosity and is a cost3e&&ectie #rocess, %he #hysical state o& the emulsion -colloidal. system makes it easy to control the #rocess, %hermal and iscosity #roblems are much less signi&icant than in bulk #olymeri"ation, %able 5,2 sho's the ra' materials re(uired in the #olymeri"ation o& 13B:4 %hey include the monomers styrene and butadiene4 'ater4 emulsi&ier4 initiator system4 modi&ier4 shortsto# and a stabili"er system, %he original #olymeri"ation reactions 'ere charged out in batch reactors in 'hich all the ingredients 'ere loaded to the reactor and the reaction 'as shortsto##ed a&ter it had reached the desired conersion, Current commercial #roductions are run continuously by &eeding reactants and #olymeri"ing through a chain o& reactors be&ore shortsto##ing at the desired monomers conersion, %he monomers are continuously metered into the reactor chains and emulsi&ied 'ith the emulsi&iers and catalyst agents, In cold #olymeri"ation4 the most 'idely used initiator system is the redox reaction bet'een chelated iron and organic #eroxide using sodium &ormaldehyde sul&oxide -. as reducing agent as sho'n in the &ollo'ing reactions,
7e+II-EDTA G R((H
7e+III-EDTA G R(G (H.
7e+III-EDTA G S7S
7e+II-EDTA
In hot #olymeri"ation4 #otassium #eroxydisul&ate is used as an initiator, Merca#tan is added to &urnish &ree radicals and to control the molecular 'eight distribution by terminating existing gro'ing chains 'hile initiating a ne' chain, %he thiol grou# acts as a chain trans&er agent to #reent the molecular 'eight &rom attaining the excessiely high alues #ossible in emulsion systems, %he sul&ur3hydrogen bond in the thiol grou# is extremely susce#tible to attack by the gro'ing #olymer radical and thus loses a hydrogen atom by reacting 'ith #olymer radicals as sho'n belo', %he : &ormed 'ill continue to initiate the
148
gro'th o& a ne' chain,
%he thiol #reents gel &ormation and im#roes the
#rocessability o& the rubber, . G RSH
4H G RS .
RS. G M
RS4M .
Ta:le ,.. Ty/i*al Re*i/e <"r SR Emulsi"n "lymeri8ati"n C"m/"nent
arts :y ei%ht
Cold
HO%
tyrene
*5
*5
Butadiene
!5
!+
)F+
)F+
1mulsi&ier -A4:A4 MA.
5
5
7odecyl merca#tan
+,*
+,F
Cumene hydro#eroxide
+,)!
3
eO2
+,+)!
3
17%A
+,+6
3
Ea2/*O!,)+H*O
),5
3
/otassuim #ersul&ate
+,0
+,)
tabili"er
aries
7uring #olymeri"ation4 #arameters such as tem#erature4 &lo' rate and agitation are controlled to get the right conersion, /olymeri"ation is normally allo'ed to #roceed to about 6+ conersion in cold #olymeri"ation and !+ in hot #olymeri"ation be&ore it is sto##ed 'ith a shortsto# agent that reacts ra#idly 'ith the &ree radicals, ome o& the common shortsto##ing agents are sodium dimethyldithiocarbamate and diethyl hydroxylamine, Once the latex is #ro#erly shortsto##ed4 the unreacted monomers are stri##ed o&& the latex, Butadiene is stri##ed by degassing the latex by means o& &lash distillation and reduction o& system #ressure, yrene is remoed by steam 149
stri##ing the latex in a column, %he latex is then stabili"ed 'ith the a##ro#riate antioxidant and trans&erred to blend tanks, In the case o& oil3extended #olymers or carbon black masterbatches4 these materials are added as dis#ersions to the stri##ed latex, %he latex is then trans&erred to &inishing lines to be coagulated 'ith sul&uric acid4 sul&uric acid;sodium chloride4 glue;sul&uric acid4 aluminum sul&ate4 or amine coagulation aid, %he ty#e o& coagulation system is selected de#ending on the end3use o& the #roduct, ul&uric acid;sodium chloride is used &or general #ur#ose, ?lue;sul&uric acid is used &or electrical grade and lo' 'ater sensitiity B:, ul&uric acid is used &or coagulations 'here lo'3ash3#olymer is re(uired, Amine coagulating aids are used to im#roe coagulation e&&iciency and reduce #roduction #lant #ollution, %he coagulated crumb is then 'ashed4 de'atered4 dried4 baled and #ackaged,
7"rmati2e
E2aluati"n
), rom 'hat you hae read about crude oil and natural4 'hat is the com#osition o& -i.
Crude oil
-ii.
Commercial natural gas
-iii.
>/?
*, 1x#lain ho' #etroleum re&ining has eoled oer the years as #roduct s#eci&ications changed, 0,
cracking
-ii.
re&orming
5, rom internet search and ; or other resources9 -i.
150
-ii.
&ind a #aint &ormulation that contain an alkyd resin,
6,
7ield $"r5 +(/ti"nal-
%here are number o& industries engaged in the manu&acture o& #olymers such as #olyurethane4 #olyethylene4 #olyinyl chloride and #aint resins, 8our Centre 'ill assist you to isit some o& these industries, Once the isits hae been arranged4 read in adance about the #rocesses, 7uring the isit you 'ill identi&y the ra' materials used including their trade names, Obsere their #hysical a##earances ; #ro#erties and also the #roduction #rocesses, Ask (uestions that 'ill lead your &actory guide to gie you more releant in&ormation, >ater you 'ill describe the #roduction #rocesses as &ar as #ossible using &lo' diagrams and chemical e(uations,
151
LEARNIN9 ACTI&ITY ') (R9ANIC CHEMICAL INDUSTRIES ART II) 7ERMENTATI(N
INDUSTRIES6
HARMACEUTICALS6
S(AS
AND
DETER9ENTS
At the end o& this unit you should be able to9 a, 7iscuss &actors that a&&ect the iability o& the &ermentation route and those that a&&ect &ermentation yield b, 7escribe the #rocess o& manu&acuring &ermentation ethanol c, ?ie a brie& history o& the #harmaceutical industry and the role #layed by antibiotics d, 7escribe #roduction #rocesses o& t'o #harmaceuticals9 #enicilin and as#irin e, Outline the soa# manu&acturing #rocess &, 7iscuss the arious ty#es o& sur&actants g, 1x#lain ho' detergents are manu&actured
Summary "< Learnin% A*ti2ity
In this unit4 you 'ill learn ho' microorganisms under certain o#timum conditions are ex#loited commercially to #roduce chemical #roducts, 8ou 'ill learn about the #roduction o& ethanol and #encillin by &ermentation &ollo'ed by #uri&ication o& the #roducs by distillation and solent extraction res#ectiely, 8ou 'ill also learn ho' as#irin is #roduced synthetically, %he study o& soa#s and detergents is coered in the last section o& this unit,
List "< rele2ant readin%
), ?eorge %, A, -)$!!., hrees Chemical /rocess Industries, 5 th edn. Mc?ra'3Hill
International
1dition,
Chemical
1ngineering
eries,
inga#ore, *, te#henson :,M, -)$66., Introduction to the Chemical /rocess Industries4 :einhold /ublishing Cor#oration4 Ee' 8ork
152
0, ?roggins ?roggins /, /,H, -)$5F., -)$5F., Unit /rocesse /rocesses s in Organic Organic ynthes ynthesis4 is4 5 th 1dition4 Mc?ra'3Hill Book Com#any4 Ee' 7elhi, 2, Unde Underk rko& o&&e &err >,A4 >,A4 Hick Hickey ey :,@, :,@, -)$5 -)$52. 2. Indu Indust stri rial al erm ermen enta tati tion on Vol, I4 Chemical /ublishing Co, Inc, Ee' 8ork, 8ork, 5, ?erhar ?erhart" t"44 <, -1dit -1ditor or.4 .4 -)$F! -)$F!., ., Ullma Ullmann nns s 1ncy 1ncyclo clo#ae #aedia dia o& Indus Industri trial al Chemistry Vol AF4 5 th 1dition4 VCH Verlagsgesellscha&t mbH4
List "< rele2ant res"ur*es •
Com#uter 'ith internet &acility to access links and releant co#y'rite &ree resources
•
C73: C73:om om acco accom# m#an any ying ing this this modu module le &or &or com# com#ul ulso sory ry read readin ing g and and demonstrations
•
Multimedia resources like ideo4 VC7 and C7 #layers
List "< use
htt#9;;accessexcellence,org;>C;;&ermbiogra#hy,html htt#9;;''',madeho',com;Volume32;antibiotic,html htt#9;;bioto#ics,co,uk;microbes;#enici,html htt#9;;''',cleaning)+),com;cleaning;chemistry;soa#chem*,com
%hese sites #resent in&ormation on &ermentation4 antibiotics4 #enicillin #roduction soa# and detergents manu&acture res#ectiely in an interesting 'ay,
'.1. 7ERMENTATI(N '.1.1. Intr"du*ti"n
ermentation is a reaction 'herein a ra' material is conerted into a #roduct by the action o& micro3organisms or by means o& en"ymes,
153
1icrobial 1icrobial fermentations fermentations promoted promoted by micro+organi micro+organisms sms ,
Micro3organisms Micro3organisms
include bacteria4 iruses4 &ungi and #roto"oa, 7uring microbial &ermentation4 a ra' organic &eed is conerted into a #roduct by the action o& micro3organisms, At &irst the rate o& conersion o& ra' materials to #roducts is lo' because the micro3 organisms are &e' i,e, the catalytic agent is small, As more micro3organisms are &ormed4 the rate starts to rise, %he rate then reaches a maximum 'hen there is o#timum ratio o& unconerted material and the micro3organisms, %he rate then dro#s as the ra' material becomes de#leted, inally the rate sto#s 'hen the ra' material is &inished, It is im#ortant to note that micro3organisms are able to cataly"e many ty#es o& reactions, reactions, %here&ore %here&ore a microbial &ermentation &ermentation results results in more than one #roduct #roduct and this makes #uri&ication essential, 8n9ymatic fermentations cataly9ed by en9ymes , 1n"ymes are #roteins 'hich
occur in nature in micro3organisms4 animal organs and egetable extracts, %hey are biocatalysts 'hich bring about s#eci&ic biochemical reactions 'ithout their structure or (uantity (uantity being changed, %heir actiity de#ends de#ends on tem#erature4 tem#erature4 #H4 storage time and storage conditions, conditions, Because o& their s#eci&ity4 s#eci&ity4 only one #roduct is #roduced &rom a selected en"yme and there&ore4 there&ore4 #uri&ication is less ex#ensie ex#ensie than &or microbia microbiall &ermenta &ermentation tion,, Ho'eer Ho'eer44 en"ymes en"ymes are more ex#ens ex#ensie ie than than micro3organisms,
'.1.. E*"n"mi* *"nsiderati"ns
or microbial &ermentation route to be economically attractie &or a gien #roduct9 -a. %here must must be a microorganism microorganism that that 'ill &orm that that #roduct, -b. %he microorga microorganis nism m must be readily readily #ro#agated #ro#agated to gie consiste consistent nt yield yield and (uality -c. :a' materials materials must be aailable aailable chea#ly chea#ly in uni&orm uni&orm com#osition, com#osition, -d. %he yields yields must be be economically economically acce#table acce#table,, -e. /roduct recoery recoery and and #uri&ication #uri&ication should should be easy, easy, '.1.3. 7a*t"rs that a<
154
irst4 it is im#ortant to a##reciate that conditions that achiee maximum cell mass may not not neces necessa saril rily y be those those that that gie gie maximu maximum m yield yield o& some some #rodu #roduct ct o& metabolism, It may sometimes be necessary to semi3stare the micro3organisms to obtain o#timum yield yield o& #roducts, Ho'eer4 Ho'eer4 it is necessary necessary to gro' su&&icient su&&icient cell mass to cataly"e the &ermentation #rocess, In most &ermentations4 the &ollo'ing are the &actors that a&&ect #roduct yield, •
In"*ulum In"*ulum amount4 i,e,4 the initial amount o& cells &ed into the &ermenter4
'ill determine 'hether the cells are su&&icient or not to &uel #roduction, •
Initial le2el "< *"ntaminati"n brought in by the ra' materials or &ound in
e(ui#ment e(ui#ment and #i#elines, %he contaminating contaminating microorganism microorganism 'ill &eed &eed on the ra' materials materials and #roduce #roduce other #roducts, #roducts, 1(ui#ment 1(ui#ment and substrate substrate should there&ore there&ore be sterili"ed sterili"ed be&ore inoculation, It is im#ortant that sterile conditions conditions be maintained throughout the manu&acturing #rocess4 because contamination by &oreign microbes 'ill ruin the &ermentation, •
leel 'ill 'ill deter determin mine e 'heth 'hether er cont contami amina nant nts s 'ill 'ill multi multi#ly #ly or 'ill 'ill be /H leel re#ressed, /roducts o& microbial metabolism o&ten cause ma=or shi&ts in #H4 hence to maintain ra#id gro'th4 the #H must be ke#t close to the o#timum &or the #articular #articular organism, organism, or most micro3organisms4 micro3organisms4 o#timal o#timal #H is !, But some tolerate lo' #H, or exam#le4 yeast gro' best at 2 to 5 #H, It is im#ortant im#ortant to ex#loit ex#loit #H tolerance o& micro3organis micro3organisms, ms, Acid by3 #roducts may be neutrali"ed by adding ammonia4 calcium carbonate or calcium hydroxide taking into consideration the chemistry o& the #roduct being &ormed by the &ermentation #rocess,
•
a&&ect cts s the the acti actii ity ty o& the the micr micro3 o3or orga gani nism sms, s, %he %he best best Tem/erature a&&e tem#erat tem#erature ure &or culturin culturing g the micro3or micro3organi ganism sm aries aries 'ith 'ith the s#ecies, s#ecies, Micro3organisms naturally occurring in soil4 air or 'ater usually gro' best at *5 to 0+ oC 'hile those isolated &rom animals gro' best at 0! oC, Micro3 organisms 'hose gro'th is &aoured by lo' tem#eratures are re&erred to as
meso meso#h #hil ilic ic,,
%hos hose
that that
gro' gro'
bett better er
at
highe igherr
tem# tem#er erat atur ures es
-the -therm rmo# o#hi hili lic. c. o&&e o&&err a tech techni nica call ad adanta antage ge in that that the the gro' ro'th o& contaminants is inhibited, It is im#ortant to study tem#erature tolerance o&
155
micro3organisms, ince heat is #roduced during &ermentation4 tem#erature control is necessary to maintain o#timum actiity o& micro3organisms, •
r"du*t *"n*entrati"n may increase to a leel that inhibits the actiity o&
micro3organisms, •
The initial *"n*entrati"n "< the ra$ material -substrate.4 &or exam#le
sugar may be too high and there&ore adersely a&&ect the micro3 organisms, •
Micro3organisms ary in their need &or "y%en, ungi4 algae and a &e' bacteria are aerobic 'hile a &e' bacteria are anaerobic, or those 'hich are aerobic4 a too lo' oxygen leel leads to X#oisoningY o& &ermentation 'hile too high oxygen content causes excessie gro'th o& micro3 organisms at the ex#ense o& the #roduct, %he leel o& nutrients in the substrate may not be su&&icient to gie a &ast &ermentation rate, Eutrients include energy sources such as starch or sugar, %he cell mass is 5+ carbon4 there&ore4 carbon sources such as starch4 sugar and carbon dioxide are re(uired, %he cell mass also contains )+ nitrogen, Eitrogen sources include ammonia4 ammonium salts such as diammonium #hos#hate
-7A/.4 amino
acids
and
itamins,
Minerals including
#hos#horus4 #otassium4 sul#hur4 magnesium4 traces o& iron4 co##er4 cobalt4 manganese4 "inc and molybdenum are added as 'ater3soluble salts, '.1.. Media Sterili8ati"n
It is im#ortant to maintain sterile conditions during &ermentation in order to aoid lo' yield and loss o& culture, terili"ation may be carried out in either batch or continuous mode, %he &ollo'ing methods may be used in the case o& batch sterili"ation, ), /urging steam into the medium until the desired tem#erature is reached, *, Using an electric element to heat the medium
156
0, Using a =acketed =acketed essel, team can be #assed #assed through the =acket to raise the tem#erature during sterili"ation, Cooling 'ater through the =acket brings brings do'n do'n the tem#erature tem#erature to that o#timum o#timum &or &ermentation, &ermentation,
'.1.,. Air Sterili8ati"n
%here are ery many airborne micro3organ micro3organisms isms o& arious si"es, si"es, ome o& these are adsorbed in airbone dust and can be easily remoed &rom the air along 'ith larger #articles by using air &ilters, In the laboratory4 cotton #lugs are satis&actory, In #ilot #lant and small3scale &ermenters4 small &ibrous &ilters may be used, or large industrial industrial &ermenters4 heat heat may be used to sterili"e sterili"e air, An air com#ressor com#ressor can be used to raise tem#erature to a leel 'hich is lethal to microbes,
'.1.'. 7ermentati"n r"*ess "ulture 2reservation
A #resered #resered high yielding micro3organism micro3organism strain is a #rere(uisite #rere(uisite o& any good &ermentation #rocess, %he #resered culture is a aluable asset and as little as #ossible should be used to initiate the #rocess, ?enerally this #resered stock is in the &orm o& inert s#ores, $cale Up
cal cale e u# is an im#o im#ort rtan antt #art #art o& many many cell cell dri drien en #roc #roces esse ses, s, or or some some &ermentations4 it is essential to am#li&y the starting inoculum through a series o& eer increasing olumes until enough material exists to inoculate the #roduction system, In bacterial and yeast systems 'here igorous gro'th is antici#ated4 scale u# to an initial9&inal inoculum ratio o& )9*+ to )9)++ are common, %he seed tanks are steel tanks designed to #roide an ideal enironment &or gro' gro'in ing g micr microo oorg rgan anis isms ms,, %hey %hey are are &ill &illed ed 'ith 'ith all all the the thin things gs the the s#ec s#eci& i&ic ic microorg microorganis anism m 'ould 'ould need to surie surie and thrie4 thrie4 includi including ng 'arm 'arm 'ater 'ater and carbohy carbohydrat drate e &oods &oods like lactose lactose or glucose glucose sugars, sugars, Additi Additiona onally lly44 they contain contain other necessary carbon sources4 such as acetic acid4 alcohols4 or hydrocarbons4 and nitrogen sources like ammonium salts, ?ro'th &actors like itamins4 amino acids4 and minor nutrients com#lete the com#osition o& the seed tank contents,
157
%he %he seed seed tanks tanks are e(ui# e(ui##ed #ed 'ith 'ith mixer mixers4 s4 'hich 'hich kee# kee# the gro' gro'th th mediu medium m moing4 and a #um# to delier sterili"ed4 &iltered air, A&ter A&ter about *23*F hours4 the material in the seed tanks is trans&erred to the #rimary &ermentation tanks, :ermentation
%he &ermentation tank is essentially a larger ersion o& the steel4 seed tank, It is &illed 'ith the same gro'th media &ound in the seed tank and also #roides an enironment conducie to gro'th, Here the microorganisms are allo'ed to gro' and multi#ly, 7uring this #rocess4 they excrete large (uantities o& the desired #rod #roduc uct, t, %he tank tanks s are are cool cooled ed to main mainta tain in the the righ rightt tem# tem#er erat atur ure, e, %he &ermentation tank is constantly agitated4 and a continuous stream o& sterili"ed air is #um#ed into it, Anti3&oaming agents are #eriodically added to inhibit &oaming, Acids or bases are added to control #H to the leel 'hich is o#timal &or the gro'th o& the microorganism, %he %he &erm &ermen ente terr is the the hear heartt o& any any &erm &ermen enta tati tion on #roc #roces ess, s, %he %he desi design gn o& &ermenta &ermentation tion e(ui#me e(ui#ment nt and the o#erati o#eration on o& the &ermenta &ermentation tion #rocess #rocess must ensure the #rocess is contamination &ree4 and in the case o& #athogens4 they must be contained contained 'ith high degree degree o& sa&ety sa&ety,, Most #roduction #roduction &ermenters &ermenters are made o& stainless steel construction 'ith im#ellers &or good bulk li(uid mixing characteristics to ensure homogeneity 'ithin the essel, Air is s#arged into the essel belo' the bottom im#eller, ermenters #roduce heat through dis#ersion o& kinetic energy and metabolism4 there&ore the essel must hae a cooling system, Ase#tic o#eration o#eration at #rolonged #rolonged time #eriods demands that #i#elines trans#orting trans#orting sterile air4 seed and other materials re(uired &or the &ermentation be sterili"ed by ex#osure to steam4 usually at )*+ oC &or *+ to 0+ minutes, Belo' is a schematic diagram o& a ty#ical &ermenter,
158
7i% '.1. 7ermentati"n 2essel
'.1.. r"du*t Re*"2ery and uri
:ecoery and #uri&ication o& &ermentation #roducts can be more di&&icult and ex#ensi ex#ensie e than the &ermenta &ermentation tion ste# itsel&, itsel&,
Certain Certain #roducts #roducts are contained contained
inside the cells and are not released or are only #artially released to the medium, It may be #ossible or necessary to 'ash the cells to remoe im#urities be&ore breaking them them to get the #roduct, ome cells hae high high resistance to shear shear and re(uire s#eciali"ed s#eciali"ed e(ui#ment e(ui#ment to ru#ture them, Ultrasonic Ultrasonic ibrations4 grinding grinding in mills and high #ressure can be used to ru#ture cells, Centri&uges Centri&uges and rotary3drum &iltering are commonly used in the se#aration o& the cells &rom the broth, broth, /roducts /roducts in the broth may be recoered recoered by a ariety o& unit unit o#erations o#erations among them distillation4 extraction extraction 'ith salts and solents4 membrane ultra &iltration4 #reci#itation and chromatogra#hy,
159
'.. Manu
'..1 Intr"du*ti"n
/roduction o& ethanol by &ermentation &or beerage #ur#oses has been carried out &rom time immemorial, @ust be&ore
'... Ra$ Materials
Biomass ra' materials include those containing sugar4 starch and cellulose, %he sugar3containing ra' materials include sugar cane4 s'eet sorghum4 s'eet #otatoes4 sugar beet and molasses, %hese materials contain disaccharides 'hich are easily hydrolysed by 'ater to reducing sugar -glucose and &ructose. in e(uations similar to the &ollo'ing9
C1H(11 G H(
ucrose
C'H1(' G C'H1('
glucose
&ructose
Viable starch3containing materials include cassaa -ta#ioca.4 mai"e and #otatoes, /rior to &ermentation4 the starch is hydrolysed to #olysaccharides and then sacchari&ied to glucose, Cellulose contains com#lex carbohydrates that re(uire heat and en"ymatic treatment to extract &ermentable #olysaccharides, Cellulosic ra' materials include stra' and bagasse, %he micro3organisms mostly em#loyed in alcoholic &ermentation are yeasts, ?lucose is &ermented into alcohol according to the &ollo'ing e(uation9
C'H1('
yeast
CH,(H G C(
160
eeral iable yeast strains exist but the most commonly used strain is saccharomyces cerevesie,
%hese yeasts #roduce en"ymes that cataly"e the
reaction that conerts substrate into energy &or the yeast and ethanol, 7uring re#roduction4 the &ermentation yeast #roduces enough en"ymes needed &or the alcoholic &ermentation, %hese en"ymes 'ill continue &ermenting &ar beyond the yeasts need &or energy and een long a&ter re#roduction has sto##ed, %his is the &act that is ex#loited industrially,
'..3. r"du*ti"n r"*ess Usin% Star*h Ra$ Materials 8n9ymatic hydrolysis of carbohydrates
?round ra' material is heated to about 55 oC, tarch li(ue&ying en"ymes 'hich are either bacterial or &ungal ^3amylase4 are added, %he starch is then heated to about $5oC,
ermentation can be carried out either batch or continuously, Batch &ermentation is the sim#lest and most commonly used es#ecially &or small alcohol #lants,%he yeast inoculum is #re#ared in a )+3*+ solution in sterili"ed 'ater and added to the mixture o& substrate and nutrients in the &ermentation essel, A&ter addition o& the inoculum4 the yeast cells constitute about * to 2 by 'eight in the &ermentation mash, %he inoculum si"e greatly a&&ects &ermentation time,
&ermentation may go to com#letion 'ithin )+ hours using 2 yeast, At the end o& &ermentation4 about F+ o& the yeast may be recoered by centri&ugation or settling &or use in the next &ermentation batch, %he balance may be com#ressed into animal &eed,
161
:ermentation conditions
8east metabolism is inhibited by a concentration o& sugar higher than *+, %y#ical substrate concentrations are in the range o& )+3)2';, ome o& the ra' materials used4 namely barley4 'heat4 rye and molasses hae enough nutrients to gie e&&icient &ermentation, But small amounts o& nutrient sources such as ammonium #hos#hate4 ammonium sul#hate or urea are added such that nitrogen content is about +,6g;l o& the &ermentation mash, or most yeasts4 actiity is highest at *$30* oC,
Heat is released during
&ermentation and cooling coils and =ackets are installed in the most conentional &ermentation e(ui#ment, %he tem#erature range bet'een *$ and 0* oC is ideal &or yeast gro'th, %he #rinci#al microbial contaminants in a distillery are lactic acid &ormers 'hose deelo#ment is seerely su##ressed at #H alues belo' 5, %he #H is normally ad=usted at 2,F to 5 'ith sul#huric acid or the acidic media, I& starch ra' materials are used and dextrini"ation is not com#lete4 the
3amylase
α
may be inactiated at #H alues belo' 2, >ack o& enough oxygen reduces the iability o& the yeast,
%oo lo' oxygen
causes the #roduction o& an en"yme kno'n as diastase 'hich has aderse e&&ects on &ermentation, %oo high causes yeast gro'th, About )0 dissoled oxygen concentration increases the #ercentage o& cell surial and +,+!mm Hg oxygen tension is o#timum 'ith *+ glucose &eed, ermentation rate decreases 'ith increased alcohol concentration, It is there&ore im#ortant to dilute ra' materials -cane =uice4 sugar4 molasses. to a concentration that 'ill gie an o#timum concentration o& alcohol, Distillation
1thanol distillation #rocesses de#end on the (uantity o& beer handled4 the #urity o& the #roduct re(uired and the degree o& heat economy being exercised, Conentional #rocesses consist o& at least t'o distillation columns as sho'n in ig 6,*,
162
Recti8yi ng column
;eer column
7i%. '.. Ethan"l distillati"n
In the beer or stri##ing column4 the alcohol is stri##ed &rom the beer and concentrated to about 5+ to 6+ ;, %he beer may be #re3heated by the hot stillage coming &rom the bottom o& the column, In the recti&ying column4 the alcohol is concentrated to about $5 to $645 ;, It is 'ithdra'n near the to#, %he a#ours at the to# 'hich consist o& olatile com#onents such as aldehydes are condensed and some returned as re&lux, usel oil 'hich contains among others amyl alcohol4 is 'ithdra'n &rom the lo'er #art o& the column, '.3. harma*euti*al Industry '.3.1. Intr"du*ti"n
%he #harmaceutical industry manu&actures drugs, %he term drug re&ers to an article intended &or use in the diagnosis4 cure4 alleiation4 treatment or #reention o& diseases in humans and animals,
163
In the ancient times a large #art o& medicinal #roducts used 'ere natural #roducts mostly deried &rom #lants, In subse(uent centuries4 it 'as agreed that such #roducts must be #ure &or e&&ectie utili"ation as #harmaceutical #roducts, /harmaceuticals
are
#roduced
either
synthetically
or
biosynthetically,
ermentation has long been used to manu&acture most o& the im#ortant drug classes such as antibiotics4 itamins and hormones, Micro3organisms gro'ing under
controlled
&ermentation
conditions
#er&orm
com#lex
chemical
trans&ormations to #roduce #roducts more economically than by #urely chemical conersions, or exam#le the structural changes to make a deriatie o& natural steroid hormones are com#licated and 'ould be more costly i& #urely chemical conersions 'ere to be em#loyed, Modern research in #harmaceutical #roducts has resulted in #ure synthetic chemicals oertaking many o& the old drugs extracted &rom natural #roducts, Both biosynthesis and chemical synthesis are com#etitie in the #roduction o& #roducts such as ribo&lain and chloram#henicol, Ho'eer4 certain drugs such as mor#hine and codeine extracted &rom #lants still remain im#ortant since no synthetic substitutes hae been &ully acce#ted, %he modern #harmaceutical industry traces its origin in the )$ th century 'ith 'holesale #roduction o& drugs such as mor#hine and (uinine and the establishment o& research labs by dye and chemical com#anies 'ho discoered medical a##lications &or their #roducts, %his 'as &ollo'ed by the emergence o& #harmaceutical chemistry and #harmacology as scienti&ic &ields at the end o& the )$th century, %he com#lexity o& the chemical structure o& many medicines #erha#s has a direct relationshi# to the een greater com#lexity o& the sicknesses in humans and animal bodies, 1xtensie research #rocess and clinical tests on sa&ety and e&&icacy are &ollo'ed be&ore drugs are let into the market, %he drugs reach #atients through the #rescri#tions o& #hysicians,
164
'.3.. Anti:i"ti*s
Antibiotics are chemical substances that can inhibit the gro'th o&4 and een destroy4 harm&ul microorganisms, %hey are deried &rom s#ecial microorganisms or other liing systems4 and are #roduced on an industrial scale using a &ermentation #rocess, %he great medical adantage o& antibiotics in healing in&ections is that the #uri&ied &orms o& antibiotics are more or less harmless to most humans, %his means that they must act on some as#ect o& the gro'th o& micro3organisms 'hich di&&ers &rom ordinary mammalian cells, Antibiotics are either bactericidal or bacteriostatic, %hey kill bacteria or inhibit bacterial gro'th res#ectiely, Antibiotics 'ork by sto##ing bacterial en"ymes that control cell3'all creation and actiating other en"ymes that break a#art the bacteriumSs de&enses,
165
%he commercial deelo#ment o& an antibiotic is a long and costly #ro#osal, It begins 'ith basic research designed to identi&y organisms4 'hich #roduce antibiotic com#ounds, 7uring this #hase4 thousands o& s#ecies are screened &or any sign o& antibacterial action,
'.. eni*illin '..1. Intr"du*ti"n
/enicillin 'as discoered by bacteriologist Alexander leming in )$*F, He obsered that a #late culture o& ta#hylococcus had been contaminated by a blue3green mold and that colonies o& bacteria ad=acent to the mold 'ere being dissoled, %he mold -microorganism. is kno'n as Penicillium chrysogenum Curious4 Alexander leming gre' the mold in a #ure culture and &ound that it #roduced a substance 'hich he named #enicillin4 that killed a number o& disease3 causing bacteria, It has become the most outstanding drug eer discoered &or the treatment o& in&ections, Common bacteria that are susce#tible to #enicillin are9 those that cause throat in&ections4 i,e, stre#4 and other dangerous illnesses like9 #neumonia4 s#inal meningitis4 gas gangrene4 di#htheria4 sy#hilis4 and gonorrhea,
166
In addition to its high order o& actiity4 #enicillin is nontoxic, Its main bad &eature is that about 5 o& those receiing the drug su&&er &rom some degree o& allergic res#onse, All #enicillin ty#e antibiotics o#erate by inhibiting the #roduction o& cell 'alls by bacteria4 'hich there&ore #reents gro'th, It is no' kno'n that #enicillin has a :a*teri*idal rather than a bacteriostatic action4 i,e, it kills the bacteria4 rather
than merely inhibiting their gro'th4 as some antibiotics do, %he bacteria may die due to "sm"ti* dama%e because they are not #rotected by their outer 'all, Various other antibiotics hae also been deelo#ed 'ith di&&erent modes o& action4 e,g, inter&ering 'ith bacterial #rotein synthesis, /enicillin is a generic name re&erring to a class o& com#ounds 'ith the &ormula sho'n belo',
Although the molecular structure o& #enicillin is kno'n4 and it may be synthesised by chemical methods4 it is not economic to do so, %he #roduction #rocess still relies on &ungal &ermentation based on biological #rinci#les4 although modern strains are much more #roductie than the early strains, %his has been achieed through screening #rogrammes inoling isolates &rom di&&erent sources4 and treatment to encourage mutations, %here are t'o classes o& #enicillin, One is the biosynthetic or natural #enicillin 'hich is harested &rom the mold itsel& through &ermentation, A number o& #enicillins 'hich di&&er only in the com#osition o& the : grou# hae been isolated &rom natural #roducts, 7e#ending on the &ormula o& :4 the #enicillins are (uali&ied as 4 ?4 4 or T,
%he : grou# can be altered by introducing an a##ro#riate
#recursor in the &ermentation, or exam#le to #roduce ben"yl #enicillin4 the #recursor #henyacetic acid is used, %he mold &aourably inserts the #recursor into its #osition to #roduce the desired #enicillin, Ben"yl #enicillin4 or #enicillin ?
167
is the one in greatest demand by the medical #ro&ession, Its main &la' is that it tends to break do'n ery easily in acid, It there&ore must be administered by intramuscular in=ection, %he #otassium salt is the most commercially aailable &orm o& #enicillin ?, %he second &orm o& #enicillin is kno'n as semi synthetic #enicillin, Most &ungi that #roduce #enicillin can easily incor#orate a ariety o& com#ounds into the acyl #ortion o& the #enicillin molecule, %he synthesi"ed com#ounds must hae the initial bene&icial traits o& /enicillin ? along 'ith additional adantages such as acid stability -allo'ing &or oral ingestion.4 lo'ered allergenicity and greater resistance to #enicillinase, '... eni*illin r"du*ti"n r"*ess
#ores o& /, chrysogenum are used to inoculate )++ml o& gro'th medium in a 5++ml shake &lask, A&ter 2 days incubation4 the contents are trans&erred to gro'th medium in a 5++> reactor, A&ter three days incubation4 this culture is used to inoculate a )F+m 0 reactor, inal ermentation at about #H 6,5 and *03*F oC is com#leted in 536 days, , :iltration
%he broth contains *+305g;> o& #enicillin, It is #um#ed to a reseroir tank &rom 'here it is &ed to a continuous rotary acuum &ilter 'hich may use &ilter aids to &orm a #recoat, %he mycelium is se#arated &rom the li(uor and 'ashed on the &ilter, It is discharged &rom the &ilter as a thick blanket -cake. resembling #a#er #ul#, %he #enicillin3rich &iltrate is chilled to *32
o
C to minimi"e chemical and
en"yme degradation during solent extraction, %his o#eration is necessary since &iltration #rocess is not sterile, ?ro'th o& bacteria should not be allo'ed to build in the &iltration #rocess because this can result in seere destruction o& #enicillin by the action o& bacterial #enicillinases, %here&ore4 the &ilter is usually sterili"ed bet'een runs 'ith steam or germicidal solutions,
168
ecovery of 2enicillin by solvent e6traction
%his #rocess utili"es the &act that #enicillin is #re&erentially soluble in 'ater or organic solents de#ending on 'hether it is in the &ree acid or a salt, %he &iltered and chilled beer -broth. is #assed through another &ilter, Coagulation agents such as aluminium sul#hate or tannic acid may be added to #reci#itate #roteinous material, Eext4 #enicillin is extracted 'ith amyl acetate or butyl acetate in a continuous countercurrent #rocess at +,*3+,2 olumes solent #er olume o& beer, /enicillins are strong acids 'ith #a alues in the range o& *,530,), As the acid &orms are soluble in many organic solents4 they are extracted 'ith high e&&iciency into amyl acetate or butyl acetate at #H *,530,+ maintained by addition o& #hos#horic acid, A 'ater3solent emulsion is &ormed, A de3emulsi&ying agent may be added to break the emulsion, %he t'o #hases are se#arated in a continuous centri&uge, /enicillin is then back extracted into 'ater by the addition o& alkali -#otassium or sodium hydroxide. or bu&&er at #H 5,+3!,5 %he olume ratio o& 'ater to solent extract in this extractor is +,)3+,*, A&ter intimate mixing4 the t'o layers are se#arated, %he a(ueous #hase is chilled, It is then acidi&ied and extracted 'ith an organic solent such as anhydrous l3#ro#anol4 n3butanol or other olatile solent, /enicillin is once again extracted 'ith 'ater at #H 6,5 J!,*, An alkaline solution is added to #reci#itate a salt o& the selected base -Ea4 or . and the crystals &iltered out and &ree"e3dried,
'.,. (ther Anti:i"ti*s r"du*ed :y 7un%i
A&ter the discoery o& #enicillin4 other antibiotics 'ere sought, In )$0$4 'ork began on the isolation o& #otential antibiotic #roducts &rom the soil bacteria stre#tomyces 'hich is able to synthesi"e a ariety o& antibiotics, elman
169
solent extraction #rocedures, %he drug can be considered to be a cation and may be remoed &rom &iltered solution by ion3exchange, %his is because o& its strong basic character, Other antibiotics that hae been discoered since include bacitracin4 #olymyxin4 iomycin4 chloram#henicol and tetracyclines, ince the )$!+s4 most ne' antibiotics hae been synthetic modi&ications o& naturally occurring antibiotics,
'.'. Manu
Acetylsalicylic acid4 a #o#ular #ain3relieing drug -analgesic. 'as deelo#ed in the late )$th century as a household remedy &or aches and #ains, A rench chemist4 Charles rederic ?erhardt 'as the &irst to #re#are acetylsalicylic acid in )F50, By )F$$4 Bayer had dubbed this drug Aspirin and 'as selling it around the 'orld, %he name As#irin is deried &rom A Acetyl and #irs_ure an old -?erman. name &or salicylic acid, As#irin is the 'orldSs most 'idely used drug, It is one o& the most &re(uently used drugs in the treatment o& mild to moderate #ain4 including that o& migraines, It is o&ten combined 'ith other non3steroidal anti3in&lammatory drugs -EAI7s. in the treatment o& moderate to seere #ain, In high doses4 as#irin and other salicylates are used in the treatment o& rheumatic &eer4 rheumatic arthritis4 and other in&lammatory =oint conditions, As#irin 'orks by inter&ering 'ith t'o similar #rostaglandin3manu&acturing en"ymes4 /?H3) and /?H3*, %he inhibition o& /?H3* #roduces #ain relie&4 'hilst the inhibition o& /?H3) causes the side e&&ects, As#irin may cause stomach bleeding4 kidney damage4 and hearing de&ects, It is no longer considered suitable &or children under the age o& )* years because o& a sus#ected link 'ith a rare disease kno'n as :eyeSs syndrome, /aracetamol or other EAI7s4 such as ibu#ro&en4 are no' used instead
170
7i%. '.3. C"ated 3, m% as/irin ta:lets
As#irinSs #o#ularity declined a&ter the deelo#ment o& #aracetamol in )$56 and ibu#ro&en in )$6*, In the )$6+s and )$!+s4 @ohn Vane and others discoered the basic mechanism o& as#irinSs e&&ects4 'hile clinical trials and other studies &rom the )$6+s to the )$F+s established as#irinSs e&&icacy as an anti3clotting agent that reduces the risk o& clotting diseases, As#irin sales reied considerably in the last decades o& the t'entieth century4 and remain strong in the t'enty3&irst4 thanks to 'ides#read use as a #reentie treatment &or heart attacks and strokes
'.'.. r"/erties As#irin is an acetyl deriatie o& salicylic acid, It is a 'hite4 crystalline4 'eakly acidic substance4 'ith a melting #oint o& )05[C, Acetylsalicylic acid decom#oses ra#idly in solutions o& ammonium acetate or o& the acetates4 carbonates4 citrates or hydroxides o& the alkali metals, Acetylsalicylic acid is stable in dry air4 but gradually hydrolyses in contact 'ith moisture to acetic and salicylic acids, In solution 'ith alkalis4 the hydrolysis #roceeds ra#idly and the clear solutions &ormed may consist entirely o& acetate and salicylate, ormulations containing high concentrations o& as#irin o&ten smell like inegar, %his is because as#irin can decom#ose in moist conditions4 yielding salicylic acid and acetic acid, %he acid dissociation constant -# a. &or acetylsalicylic acid is 0,5 at *5 [C,
/./.(. 1anufacture %he synthesis o& as#irin is classi&ied as an esteri&ication reaction4 'here the alcohol grou# &rom the salicylic acid reacts 'ith an acid deriatie -acetic
171
anhydride.4 yielding methyl acetyl ester and acetic acid as a by#roduct, mall amounts o& sul&uric acid are o&ten used as a catalyst, %he manu&acture &ollo's carboxylation reaction by the chmitt modi&ication o& the olbe reaction as sho'n, %he salicylic acid is re&luxed 'ith acetic anhydride in toluene at about $+ +C &or *+ hours, %he reaction mixture is then cooled and the acetylsalicylic acid #reci#itates out as large crystals, %he crystals are se#arated either by &iltration or by centri&uging4 then 'ashed thoroughly and dried,
<. 1. %oaps and Detergents '..1. Intr"du*ti"n
172
oa# is integral to our society today, Ho'eer4 the current 'ides#read use o& soa# is only a ery recent occurrence4 des#ite the &act that it has been made &or more than *5++ years, oa#s and detergents contain a sur&actant ) as their actie ingredient, %his is a com#ound consisting o& a long4 linear4 non3#olar -hydro#hobic.tail 'ith a #olar -hydro#hilic. Nhead, %he tail is 'ater insoluble and the head is 'ater3soluble, %his di&&erence in solubility has t'o im#ortant im#lications, irstly4 this makes the sur&actant molecule a 'etting agent, %he tails migrate to align themseles 'ith the solid3'ater inter&ace4 thus lo'ering the sur&ace tension at that #oint so that the sur&actant #enetrates the &abric better, econdly4 it allo's the oily dirt #articles to &orm an emulsion 'ith the 'ater, %he tails o& many sur&actant molecules surround an oily dirt #article4 &orming a micelle 'ith the oil in the centre and the ionic heads o& the sur&actant molecules #ointing out'ards and hence kee#ing the micelle in the #olar solution, ur&actants #er&orm other im#ortant &unctions in cleaning4 such as loosening4 emulsi&ying -dis#ersing in 'ater. and holding soil in sus#ension until it can be rinsed a'ay, ur&actants can also #roide alkalinity4 'hich is use&ul in remoing acidic soils, Animal &ats and #lant oils contain com#ounds kno'n as &atty acids, %hese &atty acids are bound to glycerol to &orm triglycerides, In the #resence o& a strong base such as sodium hydroxide4 the triglycerides breakdo'n to &orm the metal salt o& the &atty acid, %his reaction 'hich is sho'n belo' is called sa/"ni
%he main sources o& &ats are bee& and mutton tallo'4 'hile #alm and coconut oils are the #rinci#al oils used in soa# making,
173
ur&actants are classi&ied by their ionic -electrical charge. #ro#erties in 'ater9 anionic -negatie charge.4 nonionic -no charge.4 cationic -#ositie charge. and am#hoteric -either #ositie or negatie charge., oa#s are anionic detergents because the actie #ortion -:CO *3. is negatiely charged, odium and #otassium soa#s are soluble in 'ater but Ca *D and Mg
*D
-alkaline earth metals. soa#s are
insoluble in 'ater,
%he mostly commonly used oils are tallo' and coconut oil, %hese are blended together and dried in a acuum chamber, Once the oils are dry4 bleaching earth is added to remoe any coloured im#urities, A&ter remoing the bleaching earth by &iltration4 the oils are stored ready &or sa#oni&ication, $tep ' + $aponification
%he mixture o& bleached oils is mixed 'ith recycled s#ent lye &rom the 'ashing stage do'nstream and &resh caustic soda solution, %he mixture is boiled &or seeral hours a&ter 'hich it settles into t'o layers 'ith the mixture o& soa# and unreacted oils at the to#, %he bottom layer i,e, the lye 'hich contains glycerine is #um#ed o&&, More caustic li(uor is added to this and the mixture reheated to sa#oni&y the remaining &ree oils,
174
$tep ( + Washing
%he crude soa# is 'ashed 'ith a mixture o& &resh caustic solution and nigre lye -see belo'., %he 'ashed soa# is sent to the &itting #ans4 'hile the lye is used in the next sa#onicaion, $tep + :itting
Here the remaining un'anted glycerine is remoed &rom the soa# by reboiling 'ith 'ater4 EaCl and a small amount o& EaOH solution, %he electrolyte concentration in the 'ater is such that the soa# and 'ater se#arates out into t'o layers, %he to# layer is neat 'et soa#4 'hich is #um#ed o&& to be dried, %he bottom layer is kno'n as the nigre layer4 and consists o& a solution o& soa#4 glycerine and EaCl, %his is le&t in the #an4 reboiled 'ith &urther salt and le&t to stand4 &orming a soa# crust oer a lo'er layer o& nigre lye -salt and glycerine., %his soa# is le&t in the #an and is mixed 'ith the next batch o& 'ashed soa#4 'hile the nigre lye is used to 'ash the next batch o& crude soa#, $tep / + Drying
inally4 the 'ater leel is reduced do'n to about )* by heating the soa# to about )*5 oC under #ressure and then s#raying it into a &lash tank at acuum #ressure o& about 2+ mm Hg -5,0 k/a., ome o& the li(uid a#ouri"es into a a#or 'hich is condensed in a barometric condenser, %he latent heat o& ea#oration lost as the 'ater boils o&& reduces the soa# tem#erature do'n to 25 o
C4 at 'hich tem#erature it solidi&es onto 'alls o& the &lash tank,
%he soa# chi#s are scra#ed o&& the 'alls and &ormed into soa# noodles in an e(ui#ment kno'n as #lodder, %he soa# is no' kno'n as base or neat soa#4 and can be conerted into a ariety o& di&&erent soa#s in the &inishing stages, In the &inal #rocessing ste#4 the dry soa# #ellets #ass through a bar soa# &inishing line, %he &irst unit in the line is a mixer4 called an amalgamator4 in 'hich the soa# #ellets are blended together 'ith &ragrance4 colorants and all other ingredients, %he mixture is then homogeni"ed and re&ined through rolling mills and re&ining #lodders to achiee thorough blending and a uni&orm texture, inally4 the mixture is continuously extruded &rom the #lodder4 cut into bar3si"e units and stam#ed into its &inal sha#e in a soa# #ress,
175
'..3. Laundry "r OhardO s"a/ manu
%he base soa# is mixed 'ith colour and #reseraties and milled, /er&ume is then added and the mixture #lodded or extruded into a continuous bar, %he bar is cut into billets and stam#ed out into tablets ready &or #ackaging,
'... T"ilet s"a/ manu
%oilet soa# is re(uired to hae less 'ater and more &atty material than laundry soa#, or this reason base soa# intended &or toilet soa# manu&acture usually has extra &atty acids added 'ith the #reseraties be&ore it is acuum dried, %hese ensure that there is no unreacted caustic le&t in the soa# by the time it reaches the consumer4 and also make the soa# so&ter, Ho'eer4 #ure soa# is hard and easily oxidised4 so arious addities are added to correct this and to make a more aesthetically #leasing #roduct, %he &irst such additie is glycerine4 'hich is #roduced in the sa#oni&ication reaction, ?lycerine makes the soa# smoother and so&ter than #ure soa#, Ho'eer4 it is also much more aluable than soa# itsel&4 so only a minimum o& glycerine is le&t in the soa# and the remainder is extracted4 #uri&ied and sold, /er&ume4 dye and o#aci&ier are then added to the dried soa# and the mixture milled to ensure een mixing, It is then #lodded and extruded out as a continuous bar4 cut into billets and stam#ed ready &or #ackaging and sale, '..,. 9ly*erine re*"2ery
:e&ined glycerine is an im#ortant industrial material used in &oods4 cosmetics4 drugs and many other #roducts, It is more aluable than the soa# :ecoery is done in a three3ste# #rocess, $tep 0 + $oap removal
irst4 excess caustic alkali is remoed using hydrochloric acid HCl G Na(H P NaCl G H(
%he &errous chloride is then added to remoe the dissoled soa#, %his reacts 'ith the soa# to &orm an insoluble &errous soa#9
176
7eCl G RC((Na P NaCl G +RC((- 7e
%his #reci#itate is &iltered out and then excess &errous chloride remoed 'ith caustic9 Na(H G 7eCl P 7e+(H- +s- G NaCl
%his is &iltered out4 leaing a soa#3&ree lye solution, $tep ' + $alt removal
$tep ( + ;lycerine purification
A small amount o& caustic soda is added to the crude glycerine and the solution then distilled under acuum in a heated still, %'o &ractions are taken o&& 3 one o& #ure glycerine and one o& glycerine and 'ater, %he glycerine thus extracted is bleached 'ith carbon black then trans&erred to drums &or sale4 'hile the 'ater;glycerine &raction is mixed 'ith the incoming s#ent lye, %his re#eats the treatment cycle, '..'. Disad2anta%es "< s"a/
Although soa# is an excellent detergents and )++ bidegradable4 it has t'o main disadantages9 ), oa# &orms an insoluble #reci#itate 'hen hard 'ater is used, Hard 'ater contains dissoled minerals such as calcium and magnesium 'hich react 'ith soa# to &orm insoluble calcium and magnesium soa#s, %his results in soa# 'astage as 'ell as the soiling o& laundry by the sticky #reci#itate, 2. oa# cannot be used in acidic solutions such as used during textile
#rocessing, trong acids 'ill react 'ith soa# to #reci#itate &atty acids
177
'hich adhere to the &abric and een #reent the a##lication o& dyestu&&s,
<.=. Detergents '.B.1. Hist"ri*al De2el"/ment "< Deter%ents
In the early )$0+s both the alcohol sul#hates and the alkyl aryl sul#honates 'ere the main cleaning materials, %he alkyl #ortion o& the sul#honate 'as &rom a kerosene &raction hence re&erred to as keryl ben"ene sul#honate, At the end o& the econd
'.B.. Deter%en*y im/r"2ement
178
success,
the #roteolytic en"ymes conert or Sbreak do'nS #roteins 'holly or #artially into amino acids, %hey 'ere initially added together 'ith a #ro#ortion o& amylase 'hich breaks do'n starches4 to S#re3soakS detergents, Better and better strains o& en"ymes 'ere deelo#ed4 'ith stability to a 'ider #H s#ectrum4 stability against #erborate and (uicker action, %oday en"ymatic #o'ders are no' holding a large #ro#ortion o& the household detergent, ome 'ashing3machine manu&acturers #roduce automatic 'ashing machines 'ith a SBioS #rogramme 'hich allo's the 'ashing to remain in contact 'ith the detergent solution &or an extended #eriod o& time at a relatiely lo' tem#erature be&ore beginning the 'ashing and heating cycle, a&ety and health concerns cause some en"ymes to be excluded in some detergent &ormulations, '.B.3. Deter%ent Ra$ materials
A detergent is a &ormulated #roduct 'hich is s#ecially designed to #romote the cleaning action, 1ach indiidual com#onent in the &ormulation has its o'n s#eci&ic &unctions in the 'ashing #rocess but it can also #roduce synergistic e&&ect 'ith other com#onents, ome com#onents are added to aid or im#roe e&&iciency o& the #roduction #rocess 'hile others are added to im#roe the a##earance and odour o& the #roduct, %he ma=or com#onents can be categori"ed into9
ur&actants
Builders
Bleaching agents
$urfactants
A sur&actant - sur< ace a*tie agent. is a com#ound 'ith a 'ater3soluble oil3 insoluble -hydro#hilic. #ortion on one side and an oil3soluble 'ater3insoluble -hydro#hobic. #ortion on the o##osite side, ?enerally4 the hydro#hobic #ortion is 179
a long alkyl chain 'hile the hydro#hilic #ortion is a solubility3enhancing #ortion, %he sur&actant exhibits sur&ace actiity by lo'ering the sur&ace tension o& li(uids, A sur&actant suited &or detergent manu&acture should hae the &ollo'ing characteristics9 ), s#eci&ic adsortion *, soil remoal 0, lo' sensitiity to 'ater hardness 2, dis#ersion #ro#erties 5, soil antirede#osition ca#ability 6, high solubility !, 'etting #o'er F, desirable &oam characteristics $, neutral odour )+,lo' intrinsic colour )), storage stability )*,&aourable handling characteristics )0,minimal toxicity to humans )2,no aderse enironmental im#acts )5,good ra' material su##ly )6,economy A sur&actant can be #laced in one o& &our classes9
anionic
cationic
nonionic
am#hoteric
!nionic surfactants
%hese include alkylben"ene su#honates4 &atty alcohol sul#hates -alkyl sul#hates. and alkyl ether sul#hates, Linear al,yl ben-ene sulphonate LAS/ is a leading detergent sur&actant, It has
good &oaming ability and its &oam can be readily stabili"ed, Its &oam can be
180
boosted or controlled by &oam inhibitors, >A is ho'eer sensitie to 'ater hardness, Its detergency #o'er decreases 'ith increasing 'ater hardness, *atty alcohol sulphates %&S& 0$/! %hese are the most im#ortant class o& &at3
deried sur&actants biodegradeable,
in terms
o& tonnage
#roduced,
%hey
are
readily
%hey are em#loyed in heay and light duty detergents as 'ell
as in toilet soa#s, %hey are chemically stable on the alkaline side and are easily hydrolysed on the acid side, %hey are incor#orated in s#ray3dried &ormulations, %hey can be conerted to the ammonium or sodium salts, Al,yl ether sulphates are obtained by ethoxylation o& natural and synthetic
alcohols, %he o#timal carbon chain length is C )*3C)2 'ith about * moles ethylene oxide, %hey are highly &oaming and hae lo' sensitiity to 'ater hardness, %hey also hae high solubility and good storage stability at lo' tem#eratures in li(uid &ormulations, %hey are #re&erred &or easy care and 'ool detergents as 'ell as dish'ashing li(uids4 hair sham#oos and &oam baths, Nonionics
%he most 'idely used nonionic detergents include9 Al,yl polyglycol ethers A1&/ 9 1thylene oxide reacts 'ith any com#ound haing
reactie hydrogen atoms, %his reaction is called ethoxylation, %he #olyglycol ethers o& straight chain alcohols i,e, :O-CH *CH*O.nH are #resently becoming the most im#ortant sur&actants because o& their im#roed biodegradability4 re#lacing the older #olyglycol ethers based on nonyl#henol #olyethylene glycol, Most o& these non3ionics are iscous li(uids or so&t #astes, A(ueous solutions exhibit an inerse solubility behaiour i,e, the solubility decreases 'ith increasing tem#erature, %he tem#erature at 'hich dilute a(ueous solutions clouds u# because o& insolubility o& the sur&actant is re&erred to as the *l"ud /"int , Al,ylolamides of fatty acids! %hese sur&actants hae the structure :COE-CH *
CHOH.*
-diethanolethamide. and
:COEHCH *CHOH
-monoethanolamide.,
Monoethanelamides are usually incor#orated into laundry detergents 'hile diethanolamides are used in light duty and dish'ashing detergents as 'ell as in sham#oos, %heir ma=or &unction is in &oam boosting and soil sus#ension,
181
"ationics
ince the sur&actant molecules bears a #ositie charge4 their adsor#tion reduces the negatie "eta3#otential o& solids #resent in a(ueous solutions, %hey there&ore reduce mutual re#ulsions including that bet'een soil and &ibres, 1xcess use causes charge reersal 'ith aderse e&&ect, %hey are not used &or the sole #ur#ose o& soil remoal because charge reersal in the direction o& negatie "eta3#otential occurs during rinsing causing #reiously remoe soil to be attracted to the &ibres, %hey are used &or s#ecial e&&ects &or exam#le as antistatic agents4 &abric so&tening and as microbicides, 2uaternary ammonium compounds 2AC/ ::YE-CH0.*Cl are among the most
'idely used cationic detergents, `AC :HE-CH 0.*Cl haing a single long ali#halic chain #ossess bacteriological #ro#erties, `uaternary ammonium com#ounds such as dialkyldimethyl ammonium chloride #ossessing t'o ali#hatic chains are used as textile so&teners &or both household and industrial use, ince cationics dis#lay behaiour o##osite to that o& anionics4 the t'o are incom#atible, %hey are incom#atible 'ith anionic antibacterial agents like hexachloro#hene but are com#atible 'ith cationic germicides such as mercurials, Eonionic sur&actants are more tolerant o& cationics than anionics, !mphoterics
%hese sur&actants #ossess both anionic and cationic grou#s in the same molecule, Am#hoterics sho' the #ro#erties o& anionics at high #H and those o& cationics at lo' #H, %hey are there&ore com#atible 'ith either cationic or anionic sur&actants, %hey are used to oercome #roblems associated 'ith high electrolyte leels and corrosion, %hey also hae other interesting #ro#erties such as9 ), excellent &oaming and lime soa# dis#ersing #ro#erties, *, antistatic #ro#erties 0, textile so&tening %hey include d icarbo#ylic acids such as :E-CH * COOH /. Alkyl amino#ro#ionic acids hae antistatic and hair so&tening #ro#erties,
182
" '"Al,ylbetains %' 3 C$ 0 /4 C$ 4C && . %hese are rarely used because they are
ex#ensie,
uilders
%hese are used to su##ort detergent action and to deal 'ith the #roblem o& 'ater hardness caused by the #resence o& calcium and magnesium ions, %hey include alkalis4 com#lexing agents and ion exchangers,
lea*hin% a%ents
Bleaches increase the re&lectance o& isible light at the ex#ense o& absor#tion, It inoles the remoal or change o& dyes and soil by mechanical and;or #hysical means, Hydrogen #eroxide is the main bleaching agent, odium #erborate EaBO0 is incor#orated in detergents as a source o& hydrogen #eroxide, '.B.. "$der Deter%ent Manu
combinations o& these methods, In the spray drying #rocess4 dry and li(uid ingredients are &irst combined into a slurry4 or thick sus#ension4 in a tank, %he slurry is heated and then #um#ed to the to# o& a to'er 'here it is s#rayed through no""les under high #ressure to #roduce small dro#lets, %he dro#lets &all through a current o& hot air4 &orming hollo' granules as they dry, %he dried granules are collected &rom the bottom o& the s#ray drier 'here they are screened to achiee a relatiely uni&orm si"e, A&ter the granules hae been cooled4 heat sensitie ingredients such as bleach4 en"ymes and &ragrance that cannot 'ithstand the high tem#eratures in the s#ray drier are added, %raditional s#ray drying #roduces relatiely lo' density #o'ders, Ee' technology has enabled the soa# and detergent industry to reduce the air inside the granules during s#ray drying to achiee higher densities, %he higher density #o'ders can be #acked in much smaller #ackages than 'ere needed #reiously, !gglomeration 4 'hich leads to higher density #o'ders4 consists o& blending dry
ra' materials 'ith li(uid ingredients, Hel#ed by the #resence o& a li(uid binder4
183
rolling or shear mixing causes the ingredients to collide and adhere to each other4 &orming larger #articles, Dry mi6ing or dry blending is used to blend dry ra' materials, mall (uantities o&
li(uids may also be added, '.B.. Deter%ent manu
%he solid and li(uid ra' ingredients are &ed into a large tank kno'n as a slurry mixer or clutcher, As the ingredients are added the mixture heats u# as a result o& t'o exothermic reactions9 the hydration o& sodium tri#oly#hos#hate and the reaction bet'een caustic soda and linear alkylben"enesul#honic acid, %he mixture is then &urther heated to about F5 oC and stirred until it &orms a homogeneous slurry, $tep ' + $pray drying
%he slurry is deaerated in a acuum chamber and then se#arated by an atomiser into &inely diided dro#lets, %hese are s#rayed into a column o& air at about 2*5oC4 'hich dries them instantaneously, %he resultant #o'der is kno'n as base #o'der &rom 'hich other #roducts are made, %he ingredients normally &ound in base #o'der and their &unctions are sho'n in %able 6,), $tep ( < 2ost dosing
Other ingredients are no' added4 and the air blo'n through the mixture in a &luidiser to mix them into a homogeneous #o'der,
184
7i% '. Deter%ent manu
Ta:le '.1
ase /"$der in%redients and their
In%redients odium tri#oly#hso#hate -%/.
7un*ti"n
odium sul#hate oa# noodles
alkalinity., Bulking and &ree3&lo'ing agent Causes ra#id &oam colla#se during
Geolite
rinsing
odium carboxymethyl cellulose
agent
detergents Increases the
&or
negatie
concentrated charge
on
cellulosic &ibres such as cotton and rayon4 causing them to re#el dirt #articles -'hich are #ositiely charged. <.=.+. LI>#ID DETERGENT MAN#ACT#RE
>aundry detergents may also be manu&actured in li(uid &orm, A ty#ical #rocess is as &ollo's9 $tep 0 + $oap manufacture. %he soa# is made by neutrali"ing &atty acids 'ith
either caustic soda or #otassium hydroxide, $tep ' + %ngredient mi6ing
All the other ingredients exce#t en"ymes are added and mixed, %em#erature is raised as may be re(uired to dissole the ingredients $tep ( + 8n9yme addition
%he mixture is cooled and milled4 and the en"ymes added in #o'der &orm,
Ta:le '. S"me Laundry li!uid deter%ents in%redients and their
>inear alkylben"ene sul#honic acid
ur&actant is the main actie ingredient
185
->A. Caustic soda solution Coconut diethanolamide or a &atty
Eeutrali"es the >A Eonionic detergent and &oam &ormer
alcohol ethoxylate9 Absorbs UV light and emits blue light4 luorescer
causing ageing cotton to a##ear 'hite
rather than yello', 7issoles the arious
oda ash -anhydrous Ea *CO0.
causing them to mix better, ee#s the #H at $,+3$,5, %his ensures
ingredients4
o#timum detergent &unction, Also &orms insoluble carbonates 'ith Ca and Mg4 Bleach
-usually
sodium
#erborate
EaBO0.
so acts as a 'ater so&tener, Bleaches and remoe stains 'ithout damaging colour3&ast dyes, odium #erborate
breaks
do'n
at
high
tem#eratures to release H *O*4 'hich &unctions this 'ay, Bleach
actiator
-e,g,
tetraacetylethylenediamine. 1n"ymes -e,g, alkaline #rotease.
Catalyses
sodium
#erborate
breakdo'n at lo' tem#eratures, Alkaline #rotease breaks do'n #roteins in the alkaline conditions created by soda ash4 hel#ing to remoe stains,
Colour and #er&ume
Create a more aesthetically #leasing
/reseraties4 e,g, &ormalin
#roduct, /rotects #roduct &rom microbial attack
'.B.'. a*5a%in%
7etergents4 including household cleaners4 are #ackaged in cartons4 bottles4 #ouches4 bags or cans, %he #ackaging materials and containers are selected on the basis o& #roduct com#atibility and stability4 cost4 #ackage sa&ety4 solid 'aste im#act4 shel& a##eal and ease o& use,
186
'.B.. R"le "< the La:"rat"ry
%he laboratory monitors the &ormulation and s#eci&ication o& #roducts &rom ra' material to &inished goods, Many soa#s are &ormulated locally4 and the laboratory tests a range o& &ormulations &or stability and manu&acturing #racticality, %he trial &ormulations are aged in a 'arm oen to simulate a cou#le o& years o& shel& li&e4 then checked &or #er&ume loss or alteration4 base odour4 colour stability and any general
rancidity,
ormulations
are
also
constantly
checked
&or
cost
e&&ectieness4 and soa#s are &re(uently re&ormulated &or cost and su##lier considerations,
%he incoming tallo' and coconut oil are tested &or colour -a&ter bleaching. and &ree &atty acid content, %he neat li(uid soa# is tested &or &ree alkali4 salt content and glycerol content4 'hile the soa# chi#s are tested &or moisture and &atty acid content,
187
Detergent powder
%he laboratory tests &or the concentrations o& actie detergent4 sodium tri#oly#hos#hate4 moisture4 soda ash4 en"ymes and bleach4 and monitors #hysical #ro#erties such as dynamic &lo' rate4 com#ressibility4 #article si"e4 colour and #er&ume, =i#uid detergent
%he #roduct is ty#ically tested &or iscosity4 #H4 cationic detergent -&abric conditioner. content4 en"yme content4 conductiity -a measure o& detergent stability.4 colour and #er&ume, En2ir"nmental Issues
/ro#ylene tetramer -/%. ben"ene sul#honate held almost undis#uted s'ay as the ma=or ingredient used in 'ashing o#erations till the early )$6+s, Around this time it 'as noted4 ho'eer4 that se'age treatment #roblems 'ere arising, %he amount o& &oam on riers 'as increasing and 'here 'ater 'as being dra'n &rom 'ells located close to household discharge #oints4 the 'ater tended to &oam 'hen coming out o& the ta#, %his 'as attributed to the &act that #ro#ylene3based alkyl ben"ene sul#honates are not com#letely degraded by the bacteria naturally #resent in e&&luents, It 'as &ound out that it 'as the branched3chain &ormation o& the alkyl ben"ene 'hich hinders the attack by the bacteria, It 'as #roed that linear alkyl ben"ene is biodegradable, eeral countries introduced legislation #rohibiting the discharge o& non3biologically degradable material into se'er systems, %his #romoted the change to linear alkyl ben"ene ->A. 'hich had )+ #er cent better detergency than /% ben"ene sul#honate in heay3duty &ormulations, olutions o& the neutrali"ed sul#honic acid had a lo'er iscosity4 an adantage 'hen the #roduct 'as s#ray3dried to a #o'der, Ho'eer4 #o'ders made &rom >A became sticky and lost their &ree3&lo'ing characteristics, Haing success&ully co#ed 'ith the #roblem o& biodegradation the industry &aced a ne' attack, It a##eared that in certain lakes and #onds algae started re#roducing at an un#recedented rate, %his 'as blamed on the extensie use o& #hos#hates in the &orm o& sodium tri#oly#hos#hate, %he term eutro#hication4
188
meaning nutrition by chemical means4 has been a##lied to this #henomenon, %his #roblem 'as com#ounded by concurrent increase in the use o& #hos#hate &ertili"ers4 'hich also &ind their 'ay into natural 'ater systems,
), 7istinguish bet'een microbial and en"ymatic &ermentation *,
189
a, 1thanol b, /enicillin 6, 1x#lain ho' antibiotics 'ork and the role they hae #layed in the im#roement o& human health, !, A., ra*ti*al 7ra' the block diagrams &or the &ollo'ing #rocesses9 ), /enicillin #roduction *, oa# manu&acture 0, ?lycerol #uri&ication =&. Synthesis "< the M"dule
%his is the only industrial chemistry module in the 'hole chemistry course, %here are six units in the module, %he &irst unit coers de&initions4 classi&ications4 in#uts and out#uts o& the manu&acturing industry and the chemical industry in #articular, %he use o& &lo' diagrams to su##lement descri#tion o& chemical #rocesses and as tools &or material balance calculations is #resented, %he second unit deals 'ith unit o#erations and unit #rocesses 'hich are the building blocks o& chemical #rocesses, Included in this Unit are si"e reduction4 unit o#erations dealing 'ith se#aration o& materials and im#ortant chemical reactions, %his kno'ledge #re#ares you &or the study o& industrial #rocesses, In unit 0 'e a##ly the kno'ledge in unit o#erations and unit #rocesses in the study o& extractie metallurgy and in #articular the manu&acture o& iron4 co##er and aluminium, %he &ourth unit is also on industrial inorganic chemistry and deals
190
'ith the manu&acture o& six basic chemicals namely4 sodium hydroxide and chlorine4 ammonia4 sul#huric acid4 &ertili"er and cement, %he &i&th unit is one o& t'o units dealing 'ith industrial organic #rocesses, /etroleum #rocessing4 manu&acture and uses o& some #etrochemicals and #olymers are #resented, %hese are #hthlic anydride and adi#c acid4 #olyethylene and styrene butadiene rubber res#ectiely, %he sixth and last unit in the module &ocuses on some organic #roducts some o& them the &ermentation #roducts, %hese are ethanol and #enicillin, As#irin is also coered under #harmaceuticals,
=&I. Summati2e E2aluati"n
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c, %ermination 2, ist do'n )+ reasons 'hy material si"e enlargement is carried out in industry, 6, e Chateliers #rinci#le,
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192
)F, 7escribe using e(uations4 the #rocess o& making as#irin )$,7escribe ho' sa#oni&ication is carried out during soa# manu&acture, Ho' is glycerol recoered &rom the lye *+,Ho' are #o'dered detergents made
=&II. Re
), ?eorge %, A, -)$!!., hrees Chemical /rocess Industries, 5 th edn, Mc?ra'3Hill
International
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inga#ore, *, Chang :, and %ikkanen <, -)$FF., %he %o# i&ty Industrial Chemicals, :andom House4 Ee' 8ork, 0, /rice :,, and :egester M,M, -*+++.4 <1A Industrial Monitor4 *+++3 *++)4 @ohn td, Ee' 7elhi, 6, te#henson :,M, -)$66., Introduction to the Chemical /rocess Industries4 :einhold /ublishing Cor#oration4 Ee' 8ork, !, ?roggins /,H, -)$5F., Unit /rocesses in Organic ynthesis4 5 th 1dition4 Mc?ra'3Hill Book Com#any4 Ee' 7elhi, F, 7as :,, -)$FF. Industrial Chemistry9 Metallurgy4 alyani /ublishers4 Ee' 7elhi, $, ?erhart"4 <, -1ditor.4 -)$F!., Ullmanns 1ncyclo#aedia o& Industrial Chemistry Vol AF4 5 th 1dition4 VCH Verlagsgesellscha&t mbH4 ,A4 Hickey :,@, -)$52. Industrial ermentation Vol, I4 Chemical /ublishing Co, Inc, Ee' 8ork,
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)*, /rice :,, and :egester M,M, -1ditors.4 -*+++., <1A Industrial Monitor *+++3*++)4 @ohn
=&III. Student Re*"rds
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