BACHELOR OF ENGINEERING (HONS) CHEMICAL CHE 465 CHEMICAL ENGINEERING LABORATORY I
VAPOR-LIQUID EQUILIBRIUM UNIT
PREPARED BY EH2202B HAFIZAH BINTI OSMAN (20!6"6#!6) ILI NADIA ISMAIL (20!220"4) $AILANI BIN ZUL%IFLI ZUL%IFLI (20!450!2") (20!450!2") $EALONOVIER $EALONOVIER SAY SAYAS ANA% $EMON (20!""6&6 (20!""6&66) 6) MARLISSA BINTI AZEMI (20!"56")
PREPARED PREPARED FOR MISS SITINOOR ADEIB BINTI IDRIS VAPOR-LIQUID EQUILIBRIUM UNIT CHE 465-MISS SITINOOR ADEIB IDRISP'
ABSTRACT Experiment of liquid vapour equilibrium (VLE) unit is used to study about the binary system. The mixture used is methanol-water mixture. The first objetive of this experiment is to onstrut the equilibrium urve for the methanol-water system at atmospheri pressure. !eondly" the objetive is to investi#ate the relationship between vapour and liquid at equilibrium and thirdly" to determine the omposition of methanol at liquid and vapour phase. The quantity of methanol is added for a few times until the quantity of methanol is $liters and water is %litres. The mixture is heated until it boiled. The onstant temperature is ta&en and at onstant temperature" the liquid vapour sample is drain and the refrative index is read by usin# the refratometer.
INTRODUCTION 'n industry" the most of the separation proess used the vapour liquid equilibrium onept that appliable for the binary s ystem. 't used the onept based on the differenes of the boilin# point. 'n the experiment of liquid vapour equilibrium (VLE) unit the pressure used may be onstant (at atmospheri pressure) or at differenes pressure. 'n this experiment" the pressure used is atmospheri pressure and it means that the pressure is onstant. The mixture used is methanol-water mixture. or the separation proess between methanol and water" the substane with low boilin# point will vaporised first. 'n this mixture" water has hi#h boilin# point ompare to methanol. This is beause water has the moleule that attrat with the stron#est hydro#en bond. Thus" methanol will vaporise first. There are a few laws that an be used to relate with this experiment. aoult*s Law state that the vapour pressure of a solution depends on the mole fration of a solute added to the solution. This law only used for the ideal mixture and for the ideal solution. Then" +alton*s Law state that the total pressure exerted by the mixture of non-reative #as is equal to the sum of the partial pressure of the partial pressure of #ases itself. or this experiment" ,ntoine equation is used to desribe the relation between vapour pressure and temperature for pure omponents.
CHE 465-MISS SITINOOR ADEIB IDRISP' 2
The vapour liquid equilibrium unit is used for any binary system and used the onept of boilin# point. 'n this experiment" the mixture of methanol-water of un&nown omposition is fed into the evaporator. hen the heater is swith on" the mixture started to boil until it vaporised. The ondenser is plaed at the top of the evaporator. 't is used to ooled down the vaporised mixture and prevent the mixture from further vaporised. ,s the vapour start to ondensed" the liquid will fall ba& into the evaporator. ,t onstant temperature reahes" the system will stabilied and reahed equilibrium. ,t this point" the sample is ta&en to determine the refrative index by usin# the refratometer. The omposition is obtained by usin# the refrative index.
OBJECTIVES The objetives of this experiment are/ to investi#ate the relationship between vapor and liquid at equilibrium/ to onstrut an equilibrium urve for the methanol and water system at atmospheri pressure/ and to study the effet of initial mixture omposition upon boilin# temperature and vapor-liquid phase ompositions.
THEORY 'n vapor liquid equilibrium" there are two laws related to the experiment whih is aoult*s law and +alton*s law. 0esides" ,ntoine equation is also used in findin# the vapor pressure. ,fter #ettin# the vapor pressure from ,ntoine equation" used the equation from aoult*s law to find the mole fration. aoult*s law is usually used for preditin# the vapor liquid equilibrium for an ideal solution in equilibrium with an ideal #as mixture from the pure omponent vapor pressure. 't states that the vapor pressure of a solvent above a solution is equal to the vapor pressure of the pure solvent at the same temperature saled by the mole fration of the solvent. 1solution 23solvent1osolvent
CHE 465-MISS SITINOOR ADEIB IDRISP' !
here
1solution 2 equilibrium partial pressure 1osolvent 2 vapor pressure of solvent in pure state 3solvent 2 mole fration
4eanwhile" +alton*s law states that the total pressure of a #as or vapor mixture in a ontainer is the sum of the partial pressures of the individual #ases or vapor mixture in the ontainer. 't an be stated as 1total 2 1% 5 16 5 17 5 ... 1 n ,ntoine equation is a vapor pressure equation and desribes the relation between the vapor pressure and temperature for pure omponents. The basi form of the equation is8
here
1 2 the absolute vapor pressure of a substane T 2 the temperature of the substane ," 0" 9 2 substane speifi oeffiient (i.e. onstants or parameters)
Temperature versus x and y dia#ram (Txy) and x versus y dia#ram are the VLE dia#rams used to represent the data for binary systems. 3 represents the liquid omposition and : represents the vapor omposition where both are in mole fration.
CHE 465-MISS SITINOOR ADEIB IDRISP' 4
i#ure %8 0oilin# 1oint +ia#ram for 4ethanol;ater
i#ure 6 8 Equilibrium +ia#ram The urved line is alled the equilibrium line and desribes the ompositions of the liquid and vapor in equilibrium at some fixed pressure.
MATERIALS CHE 465-MISS SITINOOR ADEIB IDRISP' 5
D*+,*. /', '1. ,3'1
APPARATUS efratometer/ !
)/ !ample olletor/ +ropper/ %??? mL and 6??? mL bea&er/ $?? mL and $? mL measurin# ylinder
EXPERIMENTAL PROCEDURE % 6 7 A
The #eneral start-up proedures were performed. ,bout %6 L of pure methanol and $ L deionied water were prepared. Valve V@ was opened. ?.% L methanol and 7 L water were poured into the evaporator throu#h valve V% and
$
Valve V% was losed. Valve V%7 and V%A were opened at the level si#ht tube. The liquid level was ensured
>
above the safety line on the level si#ht tube. Valve V%7 and V%A were then losed ba&. Valve V%? was opened and adjusted to allow $ L;min of oolin# water to flow throu#h
B
the ondenser. The temperature ontroller T'9-?% was set to about %??C9 and the heater was swithed
@
on. Temperature rise in T'9-?% was observed. The liquid in the evaporator be#ins to boil when the temperature at T'-?6 starts to inrease sharply. The pressure at 1'-?% was
observed. ,ll temperature and pressure were left to stabilie to a steady state value. D The evaporator pressure and the liquid and vapour temperatures were reorded. %? , liquid and vapour samples from the unit were olleted usin# the standard olletion proedure. The samples were analysed to determine their omposition. %% The heater was swithed off and valve V%% was opened to allow oolin# water to flow throu#h the oolin# oil in the evaporator. %6 The temperature at T'-?6 was observed until it drops si#nifiantly to si#nify that boilin# has stopped. Valve V%% was losed. %7 ,n additional ?.6 L methanol was poured into the evaporator throu#h valve V%. Valve V% was losed. There was now about ?.7 L methanol and 7 L water in the evaporator. !teps $ to %6 above were repeated. %A ,n additional ?.6 L methanol was poured into the evaporator throu#h valve V%. Valve V% was losed. There was now about ?.$ L methanol and 7 L water in the evaporator. !teps $ to %6 above were repeated.
CHE 465-MISS SITINOOR ADEIB IDRISP' 6
%$ ,n additional ?.$ L methanol was poured into the evaporator throu#h valve V%. Valve V% was losed. There was now about % L methanol and 7 L water in the evaporator. !teps $ to %6 above were repeated. %> ,n additional %-L methanol was poured into the evaporator throu#h valve V%. Valve V% was losed. There was now about 6-L methanol and 7-L water in the evaporator. !teps $ to %6 above were repeated. %B ,n additional %-L methanol was poured into the evaporator throu#h valve V%. Valve V% was losed. There was now about 7-L methanol and 7-L water in the evaporator. !teps $ to %6 above were repeated. %@ Valve V6 and V7 were opened to drain all liquid from the evaporator. %D 6-L methanol and %-L water were poured into the evaporator throu#h valve V%. Valve V% was losed. !teps $ to %6 above were repeated. 6? ,n additional %-L methanol was poured into the evaporator throu#h valve V%. Valve V% was losed. There was now about 7-L methanol and %-L water in the evaporator. !teps $ to %6 above were repeated. 6% ,n additional 6-L methanol was poured into the evaporator throu#h valve V%. Valve V% was losed. There was now about $-L methanol and %-L water in the evaporator. !teps $ to %6 were repeated. 66 The #eneral shut-down proedures were performed.
RESULTS T' C'*',*1 T' 7 M,3'1-8',
CHE 465-MISS SITINOOR ADEIB IDRISP' &
ater (ml)
4ethanol (ml)
4ol ater
4ol 4ethanol
4ol Total
4ethanol 4ol ration
efrative 'ndex
%?
?
?.$$>
?
?.$$>
?
%.77?@
D
%
?.$??
?.?6$
?.$6$
?.?A@
%.77AD
@
6
?.AAA
?.?AD
?.AD7
?.%??
%.77@$
B
7
?.7@D
?.?BA
?.A>7
?.%>?
%.7A%?
>
A
?.777
?.?DD
?.A76
?.66D
%.7A%B
$
$
?.6B@
?.%67
?.A?%
?.7?B
%.7A6?
A
>
?.666
?.%A@
?.7B?
?.A??
%.7A%6
7
B
?.%>B
?.%B7
?.7A?
?.$?D
%.7A?%
6
@
?.%%%
?.%D@
?.7?D
?.>A%
%.77>%
%
D
?.?$>
?.666
?.6B@
?.BDD
%.77$?
?
%?
?
?.6AB
?.6AB
%.???
%.77A%
T' 2 V'9-L*:;*. E:;***; T' 9omponent
Temperature (9)
efrative 'ndex (n+)
ater
4ethanol
Vapor
Liquid
Vapor
Liquid
7.?
?.%
D$.7
DD.?
%.77AD
%.77A$
7.?
?.7
D?.%
D$.A
%.77D?
%.77$?
7.?
?.$
@B.>
D6.@
%.7A?$
%.77$A
7.?
%.?
@7.D
@>.7
%.7A%?
%.77B$
7.?
6.?
@?.%
@7.$
%.77BD
%.77D?
7.?
7.?
[email protected]
[email protected]
%.77>6
%.7A%?
%.?
6.?
B7.?
B7.$
%.77AD
%.7A%>
%.?
7.?
B%.@
B6.?
%.7777
%.7A?B
%.?
$.?
B?.%
B?.?
%.776?
%.77@6
F*; ! G'93 7 R7'<,*= I1.> V+;+ M F'<,*1
CHE 465-MISS SITINOOR ADEIB IDRISP' "
?!4 ?!4 ?!4 ?!4 ?!4 ?!! ?!! ?!! ?!! R!"racti#! I$!% ?!! ?!2
Mol Fractio
F*; 4 G'93 7 V'9-L*:;*. E:;***; 0?04 0?0! 0?0! 0?02 Va,or (ol "ractio )%+
0?02 0?0 0?0 0 0
0?0 0?0 0?02 0?02 0?0! 0?0! 0?04 0?04 Li&'i$ (ol "ractio )*+
CHE 465-MISS SITINOOR ADEIB IDRISP' #
F*; 5 T-@Y D*'' 7 M,3'1-8', S+, 20 00 "0 60 40 T!(, !rat'r! ).C+
20 0
Va,orLi&'i$ (ol "ractio
CHE 465-MISS SITINOOR ADEIB IDRISP' 0
V'9 L*:;*.
CALCULATIONS FGote that the vapor pressure of methanol is DB.>$@ mmH#.
B
A
From Antoine’s Law8 P A
From Raoult’s Law 8 P A
¿ 10 −
¿ x
T + C
. P A
where x (vapor mol fraction) can be written as y (liquid mol fraction)
Therefore"
x
=
( A − B ) T + C 10
P°
Antoine’s Constant:
Temperature (9)
,
0
9
eferene
@?.$- 6D7.>7
$.%$@$7
%$>D.>%7
-7A.@A>
,mbrose" !pra&e" et al." %DB$
15.1-103.83
5.20409
1581.341
-33.50
Ambrose an !"ra#e$ 19%0
9alulation of 4ethanol 4ol ration in Vapor !tate. hen T 2 D$.7.?9 (7>@.7 I)
{ 10
5.20409 −
x =
1581.341
(
369.3+ − 33.50
)
} =¿
97.658
hen T 2 D?.%9 (7>7.% I)
CHE 465-MISS SITINOOR ADEIB IDRISP'
?.?76
{ 10
5.20409 −
x =
1581.341
(
)
363.1+ −33.50
} =¿
?.?6>
=¿
?.?6A
=¿
?.?6%
=¿
?.?%@
97.658
hen T 2 @B.> 9 (7>?.> I)
{ 10
5.20409 −
x =
1581.341
(
360.6 + − 33.50
)
}
97.658
hen T 2 @7.D9 (7$>.D I)
{ 10
5.20409 −
x =
1581.341
(
356.9+ − 33.50
)
}
97.658
hen T 2 @?.%9 (7$7.% I)
5.20409 −
x =
1581.341
(
)
353.1+ −33.50
10
}
97.658
hen T 2 [email protected]9 (7$%.7 I)
{ 10
5.20409 −
x =
1581.341
(
351.3+ − 33.50
)
} =¿
97.658
hen T 2 B7.?9 (7A>.? I)
CHE 465-MISS SITINOOR ADEIB IDRISP' 2
0?0&
5.20409 −
x =
10
1581.341
(
346.0+ − 33.50
)
} =¿
?.?%A
=¿
?.?%A
=¿
?.?%7
=¿
?.?7$
97.658
hen T 2 B%.@9 (7AA.@ I)
{ 10
5.20409 −
x =
1581.341
(
344.8+ − 33.50
)
}
97.658
hen T 2 B?.%9 (7A7.% I)
{ 10
5.20409 −
x =
1581.341
(
)
343.1+ −33.50
}
97.658
9alulation of 4ethanol 4ol ration in Liquid !tate. hen T 2 DD.?9 (7B6.? I)
5.20409 −
y =
10
1581.341
(
372.0+ −33.50
)
}
97.658
hen T 2 D$.A9 (7>@.A I)
CHE 465-MISS SITINOOR ADEIB IDRISP' !
{ 10
5.20409 −
y =
1581.341
(
368.4+ −33.50
)
} =¿
?.?7%
=¿
?.?6D
=¿
?.?67
=¿
?.?6%
=¿
?.?%@
97.658
hen T 2 D6.@9 (7>$.@ I)
5.20409 −
y =
10
1581.341
(
365.8+ −33.50
)
}
97.658
hen T 2 @>.79 (7$D.7 I)
{ 10
5.20409 −
y =
1581.341
(
359.3+ −33.50
)
}
97.658
hen T 2 @7.$9 (7$>.$ I)
5.20409 −
y =
10
1581.341
(
356.5+ −33.50
)
}
97.658
hen T 2 [email protected]9 (7$%.D I)
5.20409 −
y =
10
1581.341
(
351.9+ −33.50
)
}
97.658
hen T 2 B7.$9 (7A>.$ I)
CHE 465-MISS SITINOOR ADEIB IDRISP' 4
{ 10
5.20409 −
y =
1581.341
(
346.5+ −33.50
)
} =¿
?.?%$
=¿
?.?%A
=¿
?.?%7
97.658
hen T 2 B6.?9 (7A$.? I)
{ 10
5.20409 −
y =
1581.341
(
345.0+ −33.50
)
}
97.658
hen T 2 B?.?9 (7A7.? I)
{ 10
5.20409 −
y =
1581.341
(
343.0+ −33.50
)
}
97.658
!ample 9alulation of 4ethanol 4ol ration from 9alibration Table. ater
8 DmL
4ethanol 8 %mL
mole =
density x volume molecular mass
4ole of water8 1 18
× 1 ml =0.056 mol
4ole of methanol8
CHE 465-MISS SITINOOR ADEIB IDRISP' 5
0.79 32.04
× 9 ml= 0.222 mol
Therefore"
mol fractionof methanol =
moleof methanol mole of methanol + mole water
¿
0.222
0.056
+0.222
2 ?.BDD DISCUSSIONS Vapour-liquid equilibrium is ommonly used in distillation proess. This is involved of binary mixture whih is methanol and water for simpliity. 3 represented the mole fration of liquid and y represented the mole fration of #as. This information is tabulated in a #raft whih is equilibrium x-y dia#ram. Two-omponent (binary) system an be represented by T-xy +ia#ram. 0inary system is easier to analysis by T-xy dia#ram. There are two main fators that ma&e the vapour and liquid ompositions different at equilibrium whih are the pure omponent vapour pressures and the no ideal ties in the liquid phase. The refrative index for vapour and liquid is reorded. The omposition of methanol in the liquid and vaporise determined based on ,ntoine equation. or the first experiment" the volume of water is onstant" whih is 7L but the volume of methanol is inreased from ?.%L to 7L. 0ased on the experiment*s data" the temperature of liquid mixture derease from D$.79 to [email protected]9 and the temperature of vapour mixture dereased from DD9 to @7.$9. 0y omparin# the equilibrium line of experiment with the ideal equilibrium line" we only #ot the sli#htly line ompare to the literature line. This our maybe due to the error li&e puttin# the methanol in the bea&er without losin# and ause the methanol vaporise beause methanol is very volatile.
CHE 465-MISS SITINOOR ADEIB IDRISP' 6
The #raph of refrative index versus mol fration is the alibration urve of this experiment. The alibration urve is very important to determine the un&nown mole fration from the sample. T-xy dia#ram an be plot with help of the alibration urve. 0ut" we use the ,ntoine formula instead of this method.
CONCLUSION AND RECOMMENDATIONS or the onlusion" the experiment was onduted suessfully with some mista&e or error. The relationship of liquid and vapour at equilibrium is determined via the #raft of equilibrium. The omposition of methanol is hi#her in the vapour ompare to liquid and vie versa for the water. This is beause the methanol is volatile than the water" so methanol is easy to vaporised ompare to water. The experiment is onduted in a onstant pressure whih is atmosphere pressure (% atm). ater has hi#her boilin# point than the methanol due to lower vapour pressure. The objetives of the experiment are ahieved" it an be onluded that the experiment was suessfully done.
CHE 465-MISS SITINOOR ADEIB IDRISP' &
REFERENCES i) !&oo#" est" Holler J 9rouh" undamentals of ,nalytial 9hemistry" @th Ed" Thomson 0roo&s;9ole" 6??A. ii) aoult*s Law" http8;;hemwi&i.udavis.edu;1hysialK9hemistry;1hysialK1ropertiesKofK4atter;!oluti onsKandK4ixtures;'dealK!olutions;9han#esK'nKVaporK1ressure69KaoultsKLaw" aessed on %6th ,pril 6?%A. iii) +alton*s Law of 1artial 1ressures" http8;;hemistry.about.om;od;wor&edhemistryproblems;a;daltons-law-of-partial pressures.htm" aessed on %7th ,pril 6?%A. iv) Vapor-Liquid Equilibria" http8;;lorien.nl.a.u&;min#;distil;distilvle.htm" aessed on %6th ,pril 6?%A. v) ,ntoine Equation" http8;;www.tau.a.il;Mtsirel;dump;!tati;&nowino.or#;wi&i;,ntoineKequation.html" aessed on %7th ,pril 6?%A. =*) aoult*s Law" http8;;en.wi&ipedia.or#;wi&i;aoultsKlaw" aessed on %6th ,pril 6?%A.
CHE 465-MISS SITINOOR ADEIB IDRISP' "
