Binary Distillation
University of Illinois at Chicago
(Image from "Fractional Distillation.")
Binary Batch Distillation
Final Lab Report
Unit Operations Lab 2
19 February, 2011
Group 4
Tien Diep
Kevin Estacio
Sebastian Iskra
Zack Labaschin
Kevin Thompson
Felix Velazquez
Unit Operations ChE-382 Group No. 4
p. 1
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
1. Summary
The purpose of this lab is to run a batch binary distillation in order to separate methanol
and water. By heating the mixture to near its boiling point, the more volatile component will
vaporize first and travel up the distillation column. Data will be collected from the column at
various trays and compared with a calibration curve in order to determine weight fraction. Once
the weight fractions are determined, the tray efficiency can then be calculated. This was tested
with a 10 wt% methanol solution.
For this experiment the distillation column featured six bubble cap type trays and was set
up to operate at total reflux. At each stage there were two sample ports, one for collecting vapor
product and the other for liquid, with a single liquid sample port at the top just below the
condenser for drawing off a sample of reflux. Temperature probes were placed all over the
apparatus and connected to a digital thermometer unit used to monitor the temperature at each
tray, in the condenser, where the reflux was collecting, and the reboiler. The water pipes feeding
the condenser featured mechanical temperature gauges for monitoring the change in temperature
of the cooling water as it flowed through the condenser. Each sample taken from the column was
then put into a refractometer and analyzed against a calibration curve to determine its
composition.
The methanol concentration increased moving up the column, which makes sense as the
concentration should be increasing moving up the column as the methanol boils sooner than the
water; it is thus the lighter component and should be recovered in the distillate. The liquid
concentration consequently decreased up the column due to a high relative volatility (McCabe,
578). The vapor and liquid fractions of methanol per stage do not add up to 1 which means that
the species mass balance is not satisfied. This indicates a problem in the experiment, possibly
Unit Operations ChE-382 Group No. 4
p. 2
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
with the design of the apparatus. The diameter of the column is most likely too small causing
entrainment of the liquid. Another source of this error is that the methanol may have escaped the
system through the top of the column thus creating false results.
Unit Operations ChE-382 Group No. 4
p. 3
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
2. Results
The distillation module required that operators set up a calibration curve in order to
determine weight fractions at each tray via index of refraction (Figure 2.2). Different wt%
methanol/water solutions were placed on the cooled refractometer at intervals of 10 wt%
methanol. The purpose of this calibration curve is to compare it to the provided index of
refraction curve of the system (Figure 2.1) and to find out how to analyze the data collected from
the different stages of the distillation column after it has reached steady state.
A 32 Liter sample of 10wt% methanol was prepared in a side tank and then added to the
boiler pot of the column. The column was then heated to steady state (approx. 2 hours). Steady
state was distinguished by a lack of increase in temperature. Once reached, the compositions of
the system at each stage of the column along with the reflux was collected and analyzed in the
refractometer. The results for the gas composition at each stage showed that the methanol weight
fraction increases as gas at each stage of the column moving upward. At the same time, the
weight fraction of methanol in liquid decreased at each stage moving up the column (Bird, 698702). The total weight fraction of methanol did not add to one though, often being over or less
than 1. The final vapor weight percent exiting the column was found to be 79.51 wt% methanol.
For the liquid portion, there was a general trend for the weight fraction of the methanol to
decrease going from the top to the bottom of the column, but this was not the case for the liquid
reflux stage (Figure 2.4). The weight percent of the liquid leaving the column above the reflux
stage was found to be 1 wt% methanol, but the reflux stage was found to be 28.64 wt%.
Unit Operations ChE-382 Group No. 4
p. 4
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
Known Index of Refractions for the Methanol/Water System at 22C
y = -5E-06x2 + 0.0005x + 1.3317
R² = 0.9776
1.344
Index of Refraction
1.342
1.34
1.338
1.336
n
1.334
Poly. (n)
1.332
1.33
1.328
0
20
40
60
80
100
120
Weight Percent of Methanol
Figure 2.1: Index of Refractions for the Methanol/Water System at 22 °C
Calibration Index of Refraction for Gas Phase Methanol/Water System at 34F
1.355
y = -5E-06x2 + 0.0006x + 1.3308
R² = 0.9466
Index of Refraction
1.35
1.345
1.34
n
1.335
1.33
1.325
-20
0
20
40
60
80
100
120
Weight Percent of Methanol
Figure 2.2: Calibration Index of Refraction for Methanol/Water System at 34 ˚F
Unit Operations ChE-382 Group No. 4
p. 5
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
Index of Refraction for Gas Comp. vs. Stage
1.346
1.344
1.342
1.34
1.338
1.336
1.334
1.332
1.33
1.328
-2
-1
0
1
2
3
4
5
6
7
Figure 2.3: Index of Refraction vs Vapor Stage of Distillation
Index of Refraction for Liquid Comp. vs. Stage
1.346
1.344
1.342
1.34
1.338
1.336
1.334
1.332
1.33
1.328
1.326
0
1
2
3
4
5
6
7
8
9
Figure 2.4: Index of Refraction vs Liquid Stage of Distillation
Unit Operations ChE-382 Group No. 4
p. 6
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
3. Discussion
In this experiment, a 10 wt% methanol water solution was prepared to gather the VLE
data of the distillation system to determine the batch column efficiency for the system at total
reflux. The 10% wt. methanol solution took about 2.5 hours to reach an equilibrium temperature
across the 6-stages in the distillation column. The compositions of vapor and liquid samples
collected at various stages of the column were determined using the calibration curve. The
calibration curve was plotted by measuring the refractive indices of methanol and water solutions
of known compositions (0-100 wt% methanol in increments of ten). The feed was assumed to be
saturated vapor. The liquid that gathers on the trays was then reheated via convection of upward
flowing vapor to allow for more of the volatile component to become a vapor and for water to
flow downward as liquid. This allowed for a high purity in both the top and bottom of the
distillation column and the component with the higher volatility was easier to vaporize.
The data indicates that the higher stages contained more methanol vapor, which is
expected as methanol is the more volatile component of the methanol-water system. The index of
refractions of the liquid and vapor compositions were analyzed at each stage of the distillation
system in the refractometer and a corresponding index of refraction was recorded. In Figure 2.3,
stage 0 in the index of refraction was 1.3431 and 1.3321 at stage 6. Since the calibration curve is
a parabola, the higher the index of refraction, the closer to 50% wt for each component. As the
stage height increases, the lower index of refraction is expected to increase the weight fraction of
methanol in gas and decrease in liquid. Therefore the index of refraction is much higher at stage
0, where there is a higher concentration of both methanol and water, than is at stage 6, which is
at the top of column.
Unit Operations ChE-382 Group No. 4
p. 7
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
As a result, to achieve a higher percentage of separation, more stages are needed or the
vapor collected should be fed to another column for purification. The experimental errors were
due to the fact that the concentration of the binary mixture was taken as an approximation. The
temperature kept fluctuating from time to time, so the steady-state temperature might not have
been at steady-state when taking stage readings for both liquid and gas.
4. Conclusions
A 10 wt% methanol solution was to be distilled from water and analyzed for purity.
Solutions of differing concentrations of methanol were analyzed with a refractometer and a
calibration curve, shown in Figure 2.2, was generated. This calibration curve was used to classify
the composition of methanol in the samples analyzed. Once the column reached steady state
samples were drawn from each stage of the column in the vapor and liquid phases. Each sample
was then analyzed using the refractometer and compared against the calibration curve.
The final vapor weight percent exiting the column was found to be 79.51 wt% methanol.
For the liquid portion, there was a general trend for the weight fraction of the methanol to
decrease going from the top to the bottom of the column. The weight percent of the liquid
leaving the column above the reflux stage was found to be 1 wt% methanol, but the reflux stage
was found to be 28.64 wt%. The methanol concentration increased moving up the column in the
gaseous state as it is the lighter component (Wankat, 26).
The composition of the product was not equal to 100% methanol. Methanol present in
the column from previous experiments could be a source of impurity that may have oxidized to
formaldehyde. Even though there were impurities present while conducting the experiment, the
separation of two components was observed applying the concept of binary distillation.
Unit Operations ChE-382 Group No. 4
p. 8
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
5. References
"Binary Batch Distillation." University of Illinois at Chicago - UIC. Web. 14 Feb. 2011.
<http://www.uic.edu/depts/chme/UnitOps/che382-2005f-frame.html>.
Bird, R. Byron, Warren E. Stewart, and Edwin N. Lightfoot. Transport Phenomena. New York:
J. Wiley, 2007. Print.
"Fractional Distillation." Engineering. Web. 14 Feb. 2011.
<http://engineering.wikia.com/wiki/Fractional_distillation>
.
McCabe, Warren L., Julian C. Smith, and Peter Harriott. Unit Operations of Chemical
Engineering. Boston: McGraw-Hill, 2005. 576-78. Print.
Wankat, Phillip C. Separation Process Engineering. Upper Saddle River, NJ: Prentice Hall,
2007. Print.
Unit Operations ChE-382 Group No. 4
p. 9
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
6. Appendix I: Data Tabulation/Graphs
Stage
0
1
2
3
4
5
Gas Weight Fraction
Index of Refraction
Weight Fraction
1.3431
0.51859
1.3405
0.54175
1.3391
0.573386
1.3379
0.602508
1.3345
0.7
1.3321
0.7951
Efficiency
-0.059913762
-0.116102287
-0.205783243
2.42089838
0.259461356
3.085329478
Table I.1
Stage
1
2
3
4
5
6
Reflux
Liquid Weight Fraction
Index of Refraction
Weight Fraction
1.3419
0.45825
1.3432
0.5138
1.3404
0.45607
1.3375
0.387298
1.3331
0.248897
1.3305
0.1
1.3341
0.286356
Efficiency
0.15444719
-0.112569933
-0.304611073
1.163148916
0.261854623
-0.309287681
0.478263469
Table I.2
Unit Operations ChE-382 Group No. 4
p. 10
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
7. Appendix II: Error Analysis
Component
Uncertainty
Expected
100 mL Graduated
Cylinder
± 0.5mL
Digital Temperature
Monitor
± 0.1 oC
Refractometer
±0.0001
Description
The 100mL graduated cylinder measures liquid in
increments of 1mL. The lines can be accurately
read to within ± 0.5mL
The temperature monitor measures in increments
of 0.1 oC and is accurate to ± 0.1 oC.
The refractometer measures the refractive index of
a mixture in increments of 0.0001 and values can
be read accurately to the nearest 0.0001.
Table II.1
Error existed all throughout this lab. The preceding table shows the uncertainties of
equipment used in the experiment. This uncertainty comes from the approximated error that
comes from the reading of the instrumentation as these readings are fairly objective.
There was also error in the running of the operation of the experiment. The calibration
curve itself was an error as it is a polynomial regression of data points. This regression was done
over as many data points as possible in order to minimize this error, but this regression is only an
estimate and not exact. Also, when mixing the solutions due to the uncertainty of the equipment
more error was added into the polynomial regression. A polynomial regression was chosen due
to the shape of the graph being a parabola as well as the polynomial regression being the best fit
with a correlation factor of 0.94.
During column operation, when taking samples of low stage liquid or gas, the column
sputtered and leaked, making contact with the operator. Not only is contamination of stage
composition possible, but also the operator is put at risk by making undesired contact with
methanol.
One improvement that can be made would be to obtain a different refractometer or
different cooling system for the current refractometer, as the constant fluctuating coolant
Unit Operations ChE-382 Group No. 4
p. 11
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
temperature of the system may have contributed to error in this lab’s results. Potential error in
results may have occurred at the refractor station, as the refractor surface must be cleaned after
every test, and the potential for accidental spills or contamination is high. Also, it would be more
accurate to use fresh methanol as opposed to methanol that has been sitting in a drum for a long
time since it’s possible that the old methanol oxidized over time.
Unit Operations ChE-382 Group No. 4
p. 12
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
8. Appendix III: Sample Calculations
The quadratic equation is obtained from plotting the index of refraction versus the weight percent
of methanol:
-5*10-06x2 + 0.0001x + 1.331
For vapor composition:
-5*10-06x2 + 0.0001x + 1.331= 1.3431 (stage 1)
x = 51.85wt% vapor
𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑀𝑒𝑡ℎ𝑎𝑛𝑜𝑙
mol% ratio: 𝑀𝑜𝑙𝑒𝑐𝑢𝑙𝑎𝑟 𝑤𝑒𝑖𝑔ℎ𝑡 𝑜𝑓 𝑀𝑒𝑡ℎ𝑎𝑛𝑜𝑙 𝑎𝑛𝑑 𝑤𝑎𝑡𝑒𝑟 =
= 0.6403
mol% methanol = 0.6403 * 0.5185 = 0.3319 mol% methanol
For liquid composition:
-5*10-06x2 + 0.0001x + 1.331= 1.3419 (stage 1)
x = 45.82 wt% liquid
mol% ratio = 0.6403
mol% methanol =0.6403 * 0.4582 = 0.2933 mol% methanol
For Murphee efficiency:
0.5189−0.5417
= 1−0.5185
0.5185
= - 0.05991
−0.5417
Unit Operations ChE-382 Group No. 4
p. 13
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
9. Appendix IV: Individual Team Contributions
Name: Kevin Sean Thompson
Operator (Both Lab Days)
Pre- Lab Editing
Final-Lab Editing
Summary
Introduction
Literature Review/Theory
Apparatus
Materials and Supplies
Procedure
Anticipated Results
Results
Discussion
Conclusion
References
Data Tabulation/Graphs
Error Analysis
Sample Calculations
Job Safety Analysis
Power Point Presentation
Total
Time (HOURS)
8.00
0.50
1.00
1.00
0
0
0
0
0
1.50
0.50
0
0.50
0.50
0
1.00
0
0
2.00
16.50
Description
Time (HOURS)
8.00
0
0
0.50
0
4.00
0
0
0
0
0
1.00
0.50
0
3.00
0
0
0
0.50
17.50
Description
Operator both days
Final compilation
Final compilation
Wrote section
------------Reformatting
--Editing grammar and content
Found and formatter all references
--Wrote section
----Wrote powerpoint
Name: Zachary Daniel Labaschin
Operator (Both Lab Days)
Pre- Lab Editing
Final-Lab Editing
Summary
Introduction
Literature Review/Theory
Apparatus
Materials and Supplies
Procedure
Anticipated Results
Results
Discussion
Conclusion
References
Data Tabulation/Graphs
Error Analysis
Sample Calculations
Job Safety Analysis
Power Point Presentation
Total
Unit Operations ChE-382 Group No. 4
p. 14
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Operator both days
----Proof read
--Wrote section
----------Restyled emphasis
Proof read
--Did calculations
------Proof reading
Spring 2011
02/19/2011
Binary Distillation
University of Illinois at Chicago
Name: Kevin Manuel Estacio
Operator (Both Lab Days)
Time (HOURS)
8
Pre- Lab Editing
Final-Lab Editing
Summary
Introduction
Literature Review/Theory
Apparatus
Materials and Supplies
Procedure
Anticipated Results
Results
Discussion
Conclusion
References
Data Tabulation/Graphs
1
1.50
0
1
0
0
0
0
0
1
0
0
0
1
Error Analysis
Sample Calculations
Job Safety Analysis
Power Point Presentation
Total
0
0
0
0
13.50
Description
Day 1 – Operator
Day 2 – Lab writer
Grammar and content editing
Grammar and content editing
--Wrote entire section
----------Wrote first draft of section
------Compiled data into excel, composed index of
refraction curves
---------
Name: Felix Velazquez
Operator (Both Lab Days)
Time (HOURS)
8
Pre- Lab Editing
Final-Lab Editing
Summary
Introduction
Literature Review/Theory
Apparatus
0
0
0
0
0
2
Materials and Supplies
1.50
Procedure
Anticipated Results
Results
Discussion
Conclusion
References
Data Tabulation/Graphs
Error Analysis
Sample Calculations
0
0
0
2
0
0
0
0
0
Unit Operations ChE-382 Group No. 4
p. 15
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Description
Day 1 – Writer
Day 2 – Operator
----------Gathered information on each specific part
and label on picture
Provided a brief description of each
component and manufacturer if available
------Wrote discussion and edit
-----------
Spring 2011
02/19/2011
Binary Distillation
Job Safety Analysis
Power Point Presentation
Total
University of Illinois at Chicago
0
0
13.50
---
Name: Tien Diep
Operator (Both Lab Days)
Time (HOURS)
8
Pre- Lab Editing
Final-Lab Editing
Summary
Introduction
Literature Review/Theory
Apparatus
Materials and Supplies
Procedure
Anticipated Results
Results
Discussion
Conclusion
References
Data Tabulation/Graphs
Error Analysis
Sample Calculations
Job Safety Analysis
Power Point Presentation
Total
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1.50
1.50
0
11.00
Description
Day 1- Lab writer
Day 2 – operator
-------------------------------------
Name: Sebastian Tadeusz Iskra
Operator (Both Lab Days)
Pre- Lab Editing
Final-Lab Editing
Summary
Introduction
Literature Review/Theory
Apparatus
Materials and Supplies
Procedure
Anticipated Results
Results
Discussion
Conclusion
References
Time (HOURS)
8.00
0
0
0
0
0
0
0
0.50
0
0
0
0.50
0
Unit Operations ChE-382 Group No. 4
p. 16
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
Description
Operator both days
----------------------Wrote section
---
Spring 2011
02/19/2011
Binary Distillation
Data Tabulation/Graphs
Error Analysis
Sample Calculations
Job Safety Analysis
Power Point Presentation
Total
University of Illinois at Chicago
0
0
0
0
0
9.00
Unit Operations ChE-382 Group No. 4
p. 17
Diep, Estacio, Iskra, Labaschin, Thompson, Velazquez
-----------
Spring 2011
02/19/2011