Abstract The conduction of this experiment is based on a few targets, namely to carry out saponi saponific ficati ation on reacti reaction on betwee between n Sodium Sodium Hydrox Hydroxide ide,, NaOH and Ethyl Ethyl Aceta Acetate, te, Et(A! Et(A!,, to determine the effect of residence time to the reaction"s extent of con#ersion and lastly to e#aluate the reaction rate constant of this particular saponification reaction$ To achie#e these targets, an experiment experiment is finely designed so much so that these targets targets can be finely met$ Such experiment experiment in#ol#es using a unit called SO%TE& 'lug low )eactor (*odel+ ' -.-!, commonly /nown as '), as well as some common laboratory apparatus for titration process$ To put it simply, the two solutions Sodium Hydroxide, NaOH and Ethyl Acetate, Et(Ac! were reacted in the ') and the product is then analysed by the method of titration to determine how well did the reaction go$ Hence, the experiment was conducted and the results shows that the amount of con#ersion of Sodium Hydroxide, NaOH is almost unchanged as residence time increases$ urther details can be obtained in the results and discussion sections$
0$. 1NT)O23T1O 1NT)O23T1ON N
)eactors are used in the chemical industry for millions of processes$ There are many different types of reactors due to the numerous different factors that can control the formation of product during the reaction$ 'lug flow reactors are an ideali4ed scenario where there is no mixing in#ol#ed in the reactor$ 1t is the opposite of the continuous5stirred tan/ reactor (ST)!, where the reaction mixture is perfectly mixed$ The plug flow reactor has an inlet flow composed of the reactants$ The reactant flows into the reactor and is then con#erted into the product by a certain chemical reaction$ The product flows out of the reactor through the outlet flow$ 1n many scenarios, a catalyst is in#ol#ed in the reaction$ A catalyst is a substance that is not in#ol#ed in the chemical reaction but helps the reaction proceed at a faster rate$ 1n biological reactions, an en4yme, which is a biological catalyst, coats the wall, and substrate is imported through the inlet flow$ The 'lug low )eactor (')! is an 6ideal7 flow reactor model in which 6plugs7 of fluid are assumed to mo#e from the inlet to the outlet with no mixing or diffusion along the flow path$ 1n an ideal '), a pulse of tracer in8ected at the inlet would not undergo any dispersion as it passed through the reactor and would appear as a pulse at the outlet$ The degree of dispersion that occurs in a real reactor can be assessed by following the concentration of tracer #ersus time at the exit$ This procedure is called the stimulus5response techni9ue$ The nature of the tracer pea/ gi#es an indication of the non5ideality that would be characteristic of the reactor under study$ This e9uipment is designed to allow the study of the study of reaction rate constant and the effect of residence time on the con#ersion in a ')$ )esidence time distributions are measured by introducing a non5reacti#e tracer into the system at the inlet$ The concentration of the solution is changed according to a /nown function and the response is found by measuring the concent concentrat ration ion of the soluti solution on at the outlet outlet$$ The reside residence nce time time distri distribut bution ion() ()T2 T2!! of a chemical chemical reactor is a probability probability distribution distribution function function that describes describes the amount of time a fluid fluid element could spend inside the reactor$
:$. O;ET1
:$- To carry out a saponification reaction between NaOH and Et(Ac! in a plug flow reactor$ :$0 To determine the reaction rate constant$ :$: To determine the effect of residence time on the con#ersion in a plug flow reactor$
=$. THEO)>
=$- )ate of )eaction and )ate %aw
Simply put, rate of reaction can be roughly defined as the rate of disappearance of reactants or the rate of formation of products$ ?hen a chemical reaction is said to occur, a reactant(or se#eral! diminishes and a product(or se#eral! produced$ This is what constitutes a chemical reaction$ or example +
where A and represent reactants while and 2 represent products$ 1n this reaction, A and is being diminished and and 2 is being produced$ )ate of reaction, concerns itself with how fast the reactants diminish or how fast the product is formed$ )ate of reaction of each species corresponds respecti#ely to their stoichiometric coefficient$ As such +
=
=
=
The negati#e sign indicates reactants$ A usual e9uation for r A is +
where / 5 rate constant A 5 concentration of A species 5 concentration of species @ 5 stoichiometric coefficient of A 5 stoichiometric coefficient of
=$0 on#ersion Ta/ing species A as the basis, the reaction expression can be di#ided through the stoichiometric coefficient of species A, hence the reaction expression can be arranged as followsB
A + B + C + D on#ersion is an impro#ed way of 9uantifying exactly how far has the reaction mo#ed, or how many moles of products are formed for e#ery mole of A has consumed$ on#ersion CA is the number of moles of A that ha#e reacted per mole of A fed to the system$ As seen belowB
X =
4.3
Plug Flow Reactor
This reactor is also /nown as tubular flow reactor which is usually used in industry complementary to ST)$ 1t consists of a cylindrical pipe and is usually operated at steady state$ or analytical purposes, the flow in the system is considered to be highly turbulent and may be modeled by that of a plug flow$ Therefore, there is no radial #ariation in concentration along the pipe$ 1n a plug flow reactor, the feed enters at one end of a cylindrical tube and the product stream lea#es at the other end$ The long tube and the lac/ of pro#ision for stirring pre#ent complete mixing of the fluid in the tube$ Hence the properties of the flowing stream will #ary from one point to another$ 1n an ideal tubular flow reactor, which is called plug flow reactor, specific assumptions are made regarding the extent of mixingB =$:$=$:$0 =$:$:
No mixing in the axial direction omplete mixing in the radial direction 3niform #elocity profile across the radius$
Tubular reactors are one type of flow reactors$ 1t has continuous inflow and outflow of materials$ 1n the tubular reactor, the feed enters at one end of a cylindrical tube and the product stream lea#es at the other end$ The long tube and the lac/ stirring pre#ent complete mixing of the fluid in the tube$
=$= )esidence Time 2istribution unction )esidence Time 2istribution is a characteristic of the mixing that occurs in the chemical reactor$ There is no axial mixing in a plug flow reactor, ') and this omission can be seen in the )esidence Time 2istribution, )T2 which is exhibited by this class of reactors$ The continuous
stirred tan/ reactor ST) is thoroughly mixed and its )T2 is hugely different as compared to the )T2 of ')$
D$. A''A)AT3S
The unit used in this experiment is SO%TE& 'lug low )eactor (*odel+ '-.-!
ig$ D$- + SO%TE& 'lug low )eactor (*odel+ '-.-!
'lug low )eactor (*odel+ '-.-! is used as it has been properly designed for students" experiment on chemical reactions in li9uid phase under isothermal and adiabatic conditions$
1ncluded in the unit is a 8ac/eted plug flow reactorB indi#idual reactant feed tan/s and pumps, temperature sensors and conducti#ity measuring sensor$ Apart from that, there were also some laboratory apparatus in#ol#ed such as + D$- urette D$0 onical flas/ D$: *easuring cylinder D$= ph indicator D$D ea/ers Among the chemicals used are + D$ .$- * Sodium Hydroxide, NaOH D$F .$- * Ethyl Acetate, Et(Ac! D$G .$- * Hydrochloric Acid, Hl D$ 2e5ionised water
$. ')OE23)ES
$- Ieneral Startup 'rocedures
$-$-
All the #al#es are ensured closed except <=,
$-$0
The following solutions are prepared+
i$
0. liter of NaOH (.$-*!
ii$
0. liter of Et(Ac! (.$-*!
iii$ $-$:
- liter of H% (.$0D*! for 9uenching
eed tan/ - was filled with NaOH while feed tan/ 0 was filled with the Et(Ac!$
$-$=
The water 8ac/et = was filled with water and pre5heater D was filled with clean water$
$-$D
The power for the control panel was turned on$
$-$
$-$F
oth pumps '- and '0 were switched on$ '- and '0 were ad8usted to obtained flow rate approximately :..m%Jmin at both flow meters l5 .- and l5.0$ oth flow rates were made sure to be e9ual$
$-$G
oth solutions then were allowed to flow through the reactor )- and o#erflow into waste tan/ :$
$-$
$0 Experiment 'rocedures $0$-
The general starts up procedures were performed$
$0$0
$0$:
oth the NaOH and Et(Ac! solutions were allowed to enter the plug reactor )- and empty into the waste tan/ :$
$0$=
'- and '0 were ad8usted to gi#e a constant flow rate of about :.. mlJmin at flow meters 15.- and 15.0$ oth flow rates were ensured same$ The flow rates were recorded$
$0$D
The inlet (&15.-! and outlet (&15.0! were started to monitor the conducti#ity #alues until they do not change o#er time$ This is to ensure that the reactor has reached steady state$
$0$
oth inlet and outlet steady state conducti#ity #alues were recorded$ The concentration of NaOH exiting the reactor and extent of con#ersion from the calibration cur#e$
$0$F
Optional$ Sampling was opened from #al#e <-D and D.ml of sample was collected$ A bac/ titration procedure was carried out manually to determine the concentration of NaOH in the reactor and extent of con#ersion$
$0$G
The experiment was repeated from step = to F for different residence times by reducing the feed flow rates of NaOH and Et(Ac! to about 0D.,0..,-D.,-.. and D. mlJmin$ oth flow rates were made sure to be e9ual$
$: ac/ Titration 'rocedures $:$-
The burette was filled up with .$- * NaOH solution$
$:$0
-. m% of .$0D * Hl was poured in a flas/$
$:$:
D. m% samples that were collected from the experiment at e#ery controlled flow rate (:.., 0D., 0.., -D., -.. and D. m%Jmin! were added into the -.m% Hl to 9uench the saponification reaction$
$:$=
: drops of phenolphthalein were dropped into the mixture of sample and Hl$
$:$D
The mixture then was titrated with NaOH until it turns light pin/$
$:$
The amount of NaOH titrated was recorded$
F$. )ES3%TS
on#ersion
Solution mixtures
oncentration onducti#ity of NaOH (*!
(mSJcm!
.$- m NaOH
.$- m Na(Ac!
H0O
.K
-.. m%
5
-.. m%
.$.D..
-.$F
0D K
FD m%
0D m%
-.. m%
.$.:FD
$F
D. K
D. m%
D. m%
-.. m%
.$.0D.
F$D
FD K
0D m%
FD m%
-.. m%
.$.-0D
D$
-.. K
5
-.. m%
-.. m%
.$....
=$.
Table F$-+ Table for 'reparation of alibration ur#e
Total
flow
me of
low
low
)ate
)ate
N
of
of
o$
NaOH
Et(Ac!
(mlJmi
(mlJmi
n!
n!
-
:.
:.=
-.
$F
.$:
$DDF=
D.$
-$D:D
0
0D=
0D
D-:
G$=
.$0
F$FF:
D.$=
-$:.:0
:
0.0
0.D
=.F
F$=
.$-
$G0G.
D.$0
-$.0DF
=
-D0
-D=
:.
$=
.$-
D.$0
.$FF--
D
-.-
-.=
0.D
D$D
.$0
D.$=
.$D0.G
D-
D:
-.=
=$F
.$0
D.$=
.$0=0
Outlet
rate of onducti# solutio
ity
ns,
NaO H titrate
&0
n!
d
)eaction )eside nce time, t (min!
on#ersi on, C (K!
-:$.F -$D-0 0 :G$=D
Table F$0 + 2ata and alculation from the Experiment
G$- )esidence Time or the data no$ - in the Table F$0
constant, M (%Jmol$ min!
(m%!
G$. SA*'%E A%3%AT1ONS
rate
)ate of reaction, 5r A (molJ%$ min!
:$F= C -.5: :$0.- C -.5: 0$D=:G C -.5: -$-0= C -.5: -$0G-: C -.5: $=F C -.5=
)esidence Time,
τ = Total flow rate
L
,v
Total flow rate,
)esidence Time,
τ =
L $DDF= min
G$0 on#ersion or the data no$- in the Table F$0+ i$
*oles of reacted NaOH, nn- L oncentration NaOH x
ii$
*oles of unreacted Hl, n0 *oles of unreacted Hl L *oles of reacted NaOH n0 L nn0 L .$....: mol
iii$
<- L
<- L
L .$...-0 % i#$
#$
*oles of reacted Hl, n: n:L oncentration Hl C <0 n:L .$0D C .$..GG n:L .$..0=F mol
#i$
*oles of unreacted NaOH, n= *oles of unreacted NaOH L *oles of unreacted Hl n= L n: n= L .$..0=F mol
#ii$
oncentration of unreacted NaOH
NaOH unreacted L
L
L .$.== * #iii$
Cunreacted
Cunreacted L
Cunreacted L
.
Cunreacted L .$==
ix$
Creacted Creacted L -5 Cunreacted
L - 5 .$== L .$D. x$
on#ersion for data No$ - in Table F$0 .$D. x -..K L D.$ K
G$: )eaction )ate onstant,/
k =
or data no$ - in Table F$0B <. L Total inlet flow rate <. L .$- %Jmin
k =
.
.
L -$D:D %$molJmin
G$= )ate of )eaction, 5r A
-rA = k (CA0)2 (1-X)2 For data no. 1 in a!le ".2 # -rA = 1.$3%$ (0.1)2 (1 - 0.$0%) 2 = 3."4&% ' 10 -3 ol.*in
$. 21S3SS1ONS
This experiment was conducted to determine the reaction rate constant and the effect of residence time on the con#ersion in a plug flow reactor$ The solutions used are NaOH and Et(Ac!$ These two solutions react together in the ') to complete saponification reaction$ 1n this experiment, residence times ha#e to be manipulated throughout the experiment and the effects of each one is studied$ )esidence time is #aried by the means of changing the flow rates of the feed solutions$ This is shown by the formulaB
)esidence Time,
τ = Total lowrate
L
,v
rom the e9uation abo#e, it can be seen that residence time is a function of total flow rates of the feed$ Hence, by #arying the flow rate of the feed solutions, se#eral residence times can be obtained and the effects of each one, studied$ After the experiment is conducted, raw data consisting inlet flow rates, conducti#ity #alue and #olume of NaOH used in the titration process are tabulated in Table F$- of the )esult Section$ rom the raw data obtained, a series of calculations were made, as seen in the Sample of alculation section, and the #alues of residence times, con#ersion of the reactions, reaction rate constants and rate of reactions were determined$ These #alues are tabulated in Table F$0 of the )esult section$ As the data of residence time and con#ersion from Table F$0 is plotted into a graph, the graph is shown in Iraph F$-$ The reason for plotting a graph with these two parameters is so that the effects of residence time can be studied$ on#ersion is a property that shows how much of the reaction has ta/en place$ Hence, by comparing this property with the residence time parameter, one can analy4e the effects of increasing residence time to the reaction itself$
y analy4ing Iraph F$-, it can be clearly seen that the con#ersion of the reaction remains fairly constant with the increasing residence time$ Therefore, one can postulate that residence time is not a factor for reaction con#ersion, as far as plug flow reactors are concerned$ One can also postulate that the reason for this phenomenon is that the ') lac/s a good mixing process$ Since the ') is designed not to stir the solution #igorously to maximi4e mixing process, the con#ersion of the reaction by using ') is fairly low$ Howe#er, since the experiment experienced some ma8or errors in the bac/ titration procedure, the output of the experiment was affected, and was not acceptable$ According to the laboratory technician, the error was mainly come from instrumental errors$ There might be contaminant in the e9uipments used and this may be caused by improper handling of the glassware$ They might not be cleaned properly after used pre#iously, and hence affect the outcomes of the experiments that come afterwards$ Therefore, for the sa/e of learning and understanding, the data used in this report was based on the data gi#en by the laboratory technician and from the pre#ious successful experiment$
-.$.
ON%3S1ON
Saponification process was completed$ Howe#er, the outcomes of the experiment were not accurate and discarded$ Then, in order to determine the rate constant and the reaction rate, the pre#ious data of a successful experiment was used$ This was for the sa/e of learning and understanding$
--$.
)EO**EN2AT1ONS
--$--$0
?ash the glassware properly after used for con#enience of the next users$ Time the sample well$ This is to reduce, or if possible, to a#oid time5wasting in ta/ing
samples$ *onitor the flow rates constantly in order to ma/e it remains constant throughout the --$: reaction, as re9uired$ efore conducting the experiment, locate all #al#es properly and familiari4e with their --$= locations$ Stop the titration immediately as soon as the indicator turned pin/$ --$D
)EE)ENES
ogler, H$S (0..!$ Elements of Chemical Reaction Engineering (:rd Edition!$ 'rentice Hall$
%e#enspiel, O$ (-!$ Chemical Reaction Engineering (:rd Edition!$ ;ohn ?iley$
Kinetic
Studies
of
the
Saponification
of
Ethyl
Acetate,
)etrie#ed
from
http+JJwww$researchgate$netJpublicationJ00:.FFPMineticPStudiesPonPSaponificationPofPEth ylPAcetateP3singPanP1nno#ati#ePonducti#ity5 *onitoringP1nstrumentPwithPaP'ulsatingPSensor at -.th OT 0.-D
Tracer Studies in a Plug Flow reactor , )etrie#ed from http+JJwww$egr$msu$eduJQhashshamJcoursesJeneG.JdocsJ'lugK0.lowK0.)eactor$pdf at -.th OT 0.-D
A''EN21ES
Conversion (%) VS Residence Time $0." $0.% $0.$ $0.4 $0.3 $0.2
Conversion (%)
$0.1 $0
Residence Time, t (min)
Iraph F$- + Iraph of on#ersion
con+er,ion (-)
