Faculty of
Chemical
Engineering
FINAL REPORT SKF 3751
CHEMICAL REACTION ENGINEERING
LABORATORY
2011/2012-SEM 02
EXPERIMENT 3
Saponification of Ethyl Acetate And Sodium Hydroxide in CSTR
DATE OF EXPERIMENT
16 March 2012
DATE OF REPORT SUBMISSION
23 March 2012
LECTURER
Dr. Dayang Nurul Fairuz Bt Abang Zaidel
TECHNICIAN
Mr. Zainor Abidin
SECTION 02
GROUP
NO
TEAM MEMBERS
MATRICS NUM.
NRIC
1
2
3
4
Mohd Syamsul Fitri Bin Saad
Wan Nur'ain Nabila Binti Wan Nain
Nur Mizatul Hidayah Binti Ismail
Sarah Eleena Binti Mohd Usli
AK090144
AK090369
AK090224
AK090255
890428-03-5843
911231-03-5284
900110-01-5814
900707-14-6462
EXPERIMENT: 1| (SECTION 02)
1
TABLE OF CONTENT
NUM CONTENTS
1.0
Abstract
2.0
Introduction
1.1 Experimental background
1.2 Objective
1.3 Experimental scope
Theory/Literature Study
3.0
PAGE
4.0
Methodology
3.1 Equipment and Materials
3.2 Experimental procedure/methodology
5.0
6.0
Result and Discussion
4.1Experimental data
4.2 Data analysis and discussion
4.3 Answer to the question in the experimental module
Conclusion
7.0
References
8.0
Appendices
EXPERIMENT: 1| (SECTION 02)
2
1.0 ABSTARCT
This experiment is carried out to understand the CSTR system, study the use of a CSTR and
the effects of flow changes. Other significance of doing this experiment is to determine rate
constant from data and also to study the temperature effects for reaction. The real objective of
conducting the experiment is to study the reaction process of saponification reaction between
sodium hydroxide and ethyl acetate in CSTR.
The first things before all the apparatus is set-up, the conductivity calibration curve is
prepared using different molar concentration of sodium hydroxide and sodium acetate. This
calibration curve can be used to determine the reaction kinetics and the rate law of the process.
Then, both sodium hydroxide and ethyl acetate is prepared according to the given volume and
molar concentration before it is transferred into the tank. When the process started, the
conductivity and temperature of the reaction is recorded for every two minutes for over 30
minutes. The space time as well as the conductivity and the temperature of the reaction
medium are recorded when the liquid level in the CSTR reach two litres. After flow the
reaction into the buffer tank, the readings are recorded for another ten minutes. The process
are repeated for different amount of feed flow rates.
Based on methodology section in the report, it tells about the steps involved while conducting
the experiment while the results section shows the recorded value of conductivity and
medium reaction temperature. In addition, it also shows the calculated concentrations of the
input and output chemicals, rate of reaction and theoretical space time of the CSTR. Instead
of that, the discussion section shows the graph plotted using the result obtained and discussed
it more detail based on chemical reaction engineering theory. The error and recommendation
to avoid mistakes while doing the experiment is also shared in the discussion. The conclusion
section concludes all the objectives and calculations of this experiment.
EXPERIMENT: 1| (SECTION 02)
3
2.0 INTRODUCTION
A common type of reactor used in industrial processing is the continuous-stirred tank reactor
(CSTR) which is used primarily for liquid phase reaction. It is normally operated at steady
state and assumed to be perfectly mixed. Usually there is no time dependence or position
dependence of the temperature, the concentration or the reaction rate inside the tank. This
means that every variable is the same inside the reactor. Because the compositions of
mixtures leaving a CSTR are those within the reactor, the reaction driving forces, usually the
reactant concentrations, are necessarily low. Therefore, except for reaction orders zero- and
negative, a CSTR requires the largest volume of the reactor types to obtain desired
conversions. However, the low driving force makes possible better control of rapid
exothermic and endothermic reactions. When high conversions of reactants are needed,
several CSTRs in series can be used. Equally good results can be obtained by dividing a
single vessel into compartments while minimizing back-mixing and short-circuiting. The
larger the number of CSTR stages, the closer the performance approaches that of a tubular
plug-flow reactor.
Figure shows Continuous stirred tank reactors, (a) With agitator and internal heat
transfer surface, (b) With pump around mixing and external heat transfer surface.
This experiment was conducted to study the saponification reaction between sodium
hydroxide and ethyl acetate in a continuous-stirred tank reactor (CSTR). The saponification
process is a process that produces soap, usually from fats and lye. In technical terms,
saponification involves base (usually caustic soda NaOH) hydrolysis of triglycerides, which
are esters of fatty acids, to form the sodium salt of a carboxylate.
EXPERIMENT: 1| (SECTION 02)
4
Instead of carry out the saponification process as the scope of the experiment, it also
conducted to identify the CSTR system and investigate its operational behavior of a reaction
in it, to calculate the reactant conversion based on the conductivity calibration curve and to
verify the reaction order obtained from the hypothesis of the experiment using graphical and
analytical techniques. The results from both techniques are compared. Besides that, the
significance of doing this experiment is to determine the rate constant of saponification
reaction by using both techniques again. In fact, the experiment is carry out to scale-up the
reactor for large scale production and to compare the kinetic reaction, rate law and
conversion in a CSTR to the one in a batch reactor system for the same reaction.
The reaction kinetics and rate law of saponification reaction in a CSTR can be determined
using conductivity calibration curve. Conductivity is a measure of how well a solution
conducts electricity. To carry a current a solution must contain charged particles, or ions.
Most conductivity measurements are made in aqueous solutions, and the ions responsible for
the conductivity come from electrolytes dissolved in the water. Salts like sodium chloride and
magnesium sulfate), acids (like hydrochloric acid and acetic acid), and bases (like sodium
hydroxide and ammonia) are all electrolytes. Although water itself is not an electrolyte, it
does have a very small conductivity, implying that at least some ions are present. The ions are
hydrogen and hydroxide, and they originate from the dissociation of molecular water.
There are two ways to calibrate conductivity sensors. The sensor can be calibrated against a
solution of known conductivity or it can be calibrated against a previously calibrated sensor
and analyser. Normally, the sensor should be calibrated at a point near the midpoint of the
operating range calibration changes the cell constant. In this experiment, the calibration curve
is prepared using different molar concentration of sodium hydroxide and sodium acetate.
EXPERIMENT: 1| (SECTION 02)
5
3.0 LITERATURE REVIEW
In the industrial, two type of the reactor that always used are continuous stirred-tank
reactor (CSTR) and packed bed reactor (PBR). The CSTR reactor will operate at the steady
state. The process of the reactants into the reactor bribes and spending is the product of the
reactor along the reactor operates continues. As a whole, the reactor was stirred continues
mixed perfect and there is no distinction in the overall density and temperature in the reactor.
This assumption may be made namely the concentration and temperature is identified in all
regions of the reactor is equal to the temperature and density at the reactor output. Another
advantage of this continuous stirred reactor is a reactor of this type has the ability to escort the
temperature and pressure.
EXPERIMENT: 1| (SECTION 02)
6
4.0 METHODOLOGY
A. Calibration graph plot
1. Conductivity calibration curve is prepared using three points:
i.
X = 0.0, use 10mL 0.1M NaOH
ii.
X = 0.5, use a mixture of 5 mL NaOH and 5 mL sodium acetate
iii.
X = 1.0, use 10 mL 0.1M sodium acetate
B. Operating procedure
1. 9L solution of 0.1M NaOH (8g per 2L H2O) and 9L solution of 0.1M EA (19.6mL
per 2L H2O) are prepared and these solutions were poured into T1 and T2
respectively.
2. Pumps P1 and P2, and stirrer S1 are switched on. The feed flow rates into the CSTR
are adjusted to be at 40 cm3/min using valves F1 and F2. The stopwatch was started
immediately as the pumps and stirrer were switched on. The conductivity and
temperature of the reaction medium in the CSTR were measured for every 2 minutes
for over 30 minutes.
3. When liquid level inside the CSTR reached 2000cm3 (2L), the space time,
conductivity and temperature of the reaction medium were recorded.
4. Then, the reaction is flowed into the buffer tank by opening valve V3. Measurements
were continued taken for 10 minutes.
5. When 30 minutes of reaction is over, valves F1 and F2 were closed, and pumps P1
and P2 were stopped. All liquids were discharged through valve V4.
6. The experiment was repeated for different feed flow rates: 60, 100 and 120 cm3/min.
7. Once the experiments were done, all residual NaOH and EA were discharged.
8. The pilot plant was cleaned up.
EXPERIMENT: 1| (SECTION 02)
7
5.0 RESULT AND DISCUSSION
Table 1 calibration data
Calibration data
0.1M NaOH
conversion
Conductivity
0.0
15.66
0.05M NaOH +
0.05M Sodium Acetate
0.5
9.80
0.1M Sodium
Acetate
1.0
6.05
Table 2 Experimental data: flow rate = 40cm3/min
Time, Conductivity
t (min)
0
6.11
2
6.25
4
7.21
6
7.88
8
9.32
10
11.2
12
10.06
14
11.92
16
9.60
18
9.80
20
9.91
22
8.02
24
8.11
26
8.22
28
8.89
30
8.47
Temp.
(oC)
26.0
26.1
26.2
26.1
26.1
26.2
26.3
26.2
26.3
26.3
26.2
26.1
26.1
26.2
26.1
26.2
Conversion
(mol)
0.950
0.936
0.837
0.769
0.621
0.427
0.546
0.353
0.594
0.573
0.562
0.758
0.749
0.738
0.668
0.712
CA
(mol/L)
0.0043
0.0057
0.0157
0.0227
0.0377
0.0573
0.0454
0.0647
0.0406
0.0427
0.0438
0.0242
0.0251
0.0262
0.0332
0.0288
CB
(mol/L)
0.0043
0.0057
0.0157
0.0227
0.0377
0.0573
0.0454
0.0647
0.0406
0.0427
0.0438
0.0242
0.0251
0.0262
0.0332
0.0288
CC
(mol/L)
0.0950
0.0936
0.0837
0.0769
0.0621
0.0427
0.0546
0.0353
0.0594
0.0573
0.0562
0.0758
0.0749
0.0738
0.0668
0.0712
CD
(mol/L)
0.0950
0.0936
0.0837
0.0769
0.0621
0.0427
0.0546
0.0353
0.0594
0.0573
0.0562
0.0758
0.0749
0.0738
0.0668
0.0712
CB
(mol/L)
0.0651
0.0542
0.0528
0.0432
0.0532
0.0331
0.0304
0.0265
0.0226
0.0203
0.0189
0.0169
0.0155
0.0111
0.0088
CC
(mol/L)
0.0349
0.0458
0.0472
0.0568
0.0648
0.0669
0.0696
0.0735
0.0774
0.0797
0.0811
0.0831
0.0845
0.0889
0.0912
CD
(mol/L)
0.0349
0.0458
0.0472
0.0568
0.0648
0.0669
0.0696
0.0735
0.0774
0.0797
0.0811
0.0831
0.0845
0.0889
0.0912
1/rA x10-5
11.9625
11.7875
10.5375
9.6625
7.7875
5.3375
6.8250
4.4125
7.4250
7.1625
7.0250
9.4750
9.3625
9.2250
8.3500
8.9000
Table 3 Experimental data: flow rate = 60cm3/min
Time,
t (min)
0
2
4
6
8
10
12
14
16
18
20
22
24
26
28
Conductivity Temp.
(oC)
11.95
26.5
10.91
26.6
10.78
26.9
9.85
27.0
9.08
27.0
8.87
27.1
8.62
26.6
8.24
27.1
7.87
27.1
7.65
27.1
7.51
27.0
7.32
26.6
7.19
25.6
6.76
27.0
6.54
27.0
Conversion
(mol)
0.349
0.458
0.472
0.568
0.648
0.669
0.696
0.735
0.774
0.797
0.811
0.831
0.845
0.889
0.912
CA
(mol/L)
0.0651
0.0542
0.0528
0.0432
0.0532
0.0331
0.0304
0.0265
0.0226
0.0203
0.0189
0.0169
0.0155
0.0111
0.0088
EXPERIMENT: 1| (SECTION 02)
1/rA x10-5
2.9083
3.8167
3.9333
4.7333
5.4000
5.5750
5.8000
6.1250
6.4500
6.6417
6.7583
6.9250
7.0417
7.4083
7.6000
8
Table 4 Experimental data: flow rate = 100cm3/min
Time,
t (min)
0
2
4
6
8
10
12
14
16
18
20
22
Conductivity Temp.
(oC)
12.9
27.0
11.0
27.1
14.2
27.2
12.2
27.0
11.80
27.2
11.47
27.3
9.75
27.3
9.42
27.3
9.19
27.3
9.08
26.7
9.51
27.5
9.47
27.4
Conversion
(mol)
0.251
0.448
0.115
0.323
0.365
0.399
0.578
0.613
0.637
0.648
0.603
0.607
CA
(mol/L)
0.0749
0.0552
0.0885
0.0677
0.0635
0.0601
0.0422
0.0387
0.0363
0.0352
0.0392
0.0393
CB
(mol/L)
0.0749
0.0552
0.0885
0.0677
0.0635
0.0601
0.0422
0.0387
0.0363
0.0352
0.0392
0.0393
CC
(mol/L)
0.0251
0.0448
0.0115
0.0323
0.0365
0.0399
0.0578
0.0613
0.0637
0.0648
0.0603
0.0607
CD
(mol/L)
0.0251
0.0448
0.0115
0.0323
0.0365
0.0399
0.0578
0.0613
0.0637
0.0648
0.0603
0.0607
1/rA x10-5
CB
(mol/L)
0.0662
0.0374
0.0522
0.0596
0.0577
0.0507
0.0507
0.0493
0.0484
0.0498
0.0482
CC
(mol/L)
0.0338
0.0626
0.0478
0.0404
0.0423
0.0493
0.0493
0.0507
0.0516
0.0502
0.0518
CD
(mol/L)
0.0338
0.0626
0.0478
0.0404
0.0423
0.0493
0.0493
0.0507
0.0516
0.0502
0.0518
1/rA x10-5
1.2550
2.2400
0.0575
1.6150
1.8250
1.9950
2.8900
3.0650
3.1850
3.2400
3.0150
3.0350
Table 5 Experimental data: flow rate = 120cm3/min
Time,
t (min)
0
2
4
6
8
10
12
14
16
18
20
Conductivity Temp.
(oC)
12.06
27.1
9.29
27.3
10.71
27.4
11.43
27.3
11.24
27.4
10.57
27.3
10.57
27.1
10.44
27.1
10.35
27.1
10.48
26.8
10.33
27.6
Conversion
(mol)
0.338
0.626
0.478
0.404
0.423
0.493
0.493
0.507
0.516
0.502
0.518
CA
(mol/L)
0.0662
0.0374
0.0522
0.0596
0.0577
0.0507
0.0507
0.0493
0.0484
0.0498
0.0482
1.4083
2.6083
1.9917
1.6833
1.7625
2.0542
2.0542
2.1125
2.1500
2.0917
2.1583
Table 6 Experimental data: space time
Flowrate
vo
3
(cm /min)
40
60
100
120
Theoretical
Space time
Actual
Space time
(min)
50.00
33.33
25.00
16.67
(min)
20
18
12
10
Conductivity
Temp.
(oC)
Conversion
X
(mol)
9.91
7.65
9.75
10.57
26.2
27.1
27.3
27.3
0.562
0.797
0.578
0.493
EXPERIMENT: 1| (SECTION 02)
9
Calculation:
Conversion
From the calibration curve, straight line equation is Y = -0.1024X + 1.5757
Y - Conversion
X – Conductivity
For the flow rate of 40 cm3/min, conductivity at time t = 2 min is 6.25. Thus the value of
conversion is:
Y = -0.1024X + 1.5757
= -0.1024(6.25) + 1.5757
= 0.936
Concentration
CA=CAo(1-X)
CB = CA
CC = CAo. X
CD = CC
where CA = mol/L
where CC = mol/L
At, t= 2 min, (flowrate = 40cm3/min), X= 0.936, CAo= 0.1 mol/L
CA= CB = 0.1 mol/L x (1-0.936)
= 0.0064 mol/L
CC= CD = 0.1 mol/L x (0.936)
= 0.0936 mol/L
rate of reaction, -rA
Design equation of the CSTR was used to find the -rA. The equation is as below:
vC V
- rA  o AO
X
Example :
1/ rA = X / vo Cao V
= 0.930 / 40 (0.1)(2000)
= 11.962578 x 10-5
Theoretical space time,τ
Theoretical space time can be calculated by using the equation below:
τ
V
vo
For flow rate 40 cm3/min,
τ = 2000 cm3
40 cm3/min
= 50 min
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10