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Modeling and Simulation of Methyl Tertiary Butyl Ether (MTBE) Reactive
Distillation column using ASPEN PLUS
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Asian Journal of Convergence in Technology
Issn No.:2350-1146, I.F-2.71
Volume II, Issue III
Modeling and Simulation of Methyl Tertiary
Butyl Ether (MTBE) Reactive Distillation column
using ASPEN PLUS
Nitin G. Kanse,
Assistant Professor, Department
of chemical engineering, FAMT,
Ratnagiri(MS )India
nitin_475@yahoo.co.in
Dr. S. D. Dawande,
Associate Professor,
Laxminarayan Institute of
Technology, Nagpur (MS) India
sddawande@gmail.com
Abstract:
Reactive Distillation (RD) is a combination of reaction
and distillation in a single vessel owing to which it
enjoys a number of specific advantages over
conventional sequential approach of reaction followed
by distillation or other separation techniques. Reactive
distillation processes couple chemical reactions and
physical separations into a single unit operation. In the
present work, a reactive distillation column for the
production of methyl tertiary butyl ether (MTBE) is
simulated using Aspen Plus. The mathematical
equilibrium model was developed for reactive
distillation column. The component compositions,
temperature and enthalpy at each stage of the column
are predicted by using different thermodynamic
models. The effects of thermodynamic model on the
simulation results were presented.
Keywords: Reactive Distillation, MTBE, Modeling,
Simulation, Aspen Plus
I. INTRODUCTION:
Reactive distillation process has been given special
attention in the past two decades because of its
potential for process intensification for certain types
of chemical reactions. The most important benefit of
reactive distillation technology is a reduction in
capital investment, because two process steps can be
carried out in the same device. Such integration leads
to lower costs in pumps, piping and instrumentation.
For exothermic reaction, the reaction heat can be
used for vaporization of liquid [1]. This leads to
savings of energy costs by the reduction of reboiler
duties. Reactive distillation process is also
advantageous when the reactor product is a mixture
of species that can form several azeotropes with each
other. Reactive distillation conditions can allow the
azeotropes to be “reacted away” through reaction.
Although the advantageous of reactive distillation
process was known since 1920, even until 1980, the
technology was only utilized for homogeneous
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Prashant Dhanke
Assistant Professor, Department
of chemical engineering,
PVPIET, Budgaon,(MS) India
dbpchem@gmail.com
esterification reaction and was underutilized in other
areas [2-6]. Developing reactive distillation column is
a challenging task because of the complexities in
column design, process synthesis and operability of
reactive distillation processes resulting from the
interaction of reaction and distillation [7]. A
distillation column can be used advantageously as a
reactor for systems in which chemical reactions occur
at temperatures and pressures suitable to the
distillation of components. Several organic reactions
are carried out in a liquid phase using a homogeneous
catalyst. These reactions can be easily carried out in a
boiling phase using an appropriate distillation
column. In equilibrium limited reaction the continual
removal of products from the reaction mixture via
distillation favorably alters the equilibrium and
minimizes undesirable chain and side reactions.
Conversely, difficult phase separations of closely
boiling mixtures or azeotropes become feasible if one
of the components can be transformed via a chemical
reaction [8-10].
II. COMMERCIAL APPLICATIONS OF
REACTIVE DISTILLATION
 The esterification of acetic acid with ethanol
to produce Ethyl acetate and water.
 The reaction of isobutene with methanol to
produce methyl-tert-butyl
ether(MTBE),using a solid, strong–acid ionexchange resin catalyst, as patented by
Smith and further developed by DeGarmo,
Parulekar, and Pinjala
 The reaction of formaldehyde and methanol
to produce methyl and water, using a solid
acid catalyst, as described by Masamoto and
Matasuzaki.
 The esterification of acetic acid with
methanol to produce methyl acetate and
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Asian Journal of Convergence in Technology
Issn No.:2350-1146, I.F-2.71
water, using sulfuric acid as catalyst, as
patented by Agreda and Partin ,and
described by Agreda , Partin and Heise
III. ADVANTAGES OF REACTIVE
DISTILLATION
 Lesser wastes and fewer by-products.
 Reaction conversions can be increased by
overcoming chemical equilibrium limitation
through the removal of reaction products
 An equilibrium reaction can be driven to
completion by separation of theproducts
from the reacting mixture.
 Lower costs, reduced equipment use, energy
use and handling.
 Increased speed and improved efficiency
 Improved product quality-reducing
opportunity for degradation, because of less
heat, heat duty can be reduced by utilizing
the heat of reaction (if present) in situ.
 Recycle costs for excess reactant, which is
necessary for a conventional reactor to
prevent side reactions and chemical
equilibrium limitation, can be reduced.
 Non-reactive azeotropes may disappear
under reactive distillation conditions
Volume II, Issue III
Two primary approaches available in the literature
for modeling reactive distillation columns will be
taken up.
 Equilibrium stage model.
 Non-equilibrium stage model
1.
The Equilibrium Model
The equilibrium stage model assumes that the vapor
and liquid stream leaving a given stage are in
thermodynamic
equilibrium
with
one
another
(Krishna and Taylor, 1985). A schematic diagram of
an equilibrium stage is shown in Figure 1. Vapor
from the stage below and liquid from the stage above
are brought in to contact on stage together with any
fresh or recycle feeds, the vapor and liquid streams
leaving the stage are assumed to be in equilibrium
with each other
IV. MODELING
OF
REACTIVE
DISTILLATION COLUMN
A reactive distillation problem can be studied using
different
approaches
including:
feasibility,
simulation, modeling, design and experimental
studies in the laboratory and the pilot plant. A
combination of all of these methods gives rise to the
most accurate solution to the problem. One very
important aspect of predicting the behavior in these
systems is the model used to design and simulate the
reactive distillation process. An effective way of
decomposing the modeling aspects of reactive
distillation involves the following classification of
the models existing for distillation with reaction
(Baur, 2000):
The Stage Models:
1. Steady-state equilibrium stage model.
2. Dynamic equilibrium stage model.
3. Steady-state non-equilibrium stage model;
4. Dynamic non-equilibrium stage model;
5. Steady-state non-equilibrium cell model,
that accounts for staging of the vapor and
liquid phases inside the column.
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Fig. 1 General Equilibrium Stage Model
(1)
(2)
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Asian Journal of Convergence in Technology
Issn No.:2350-1146, I.F-2.71
Volume II, Issue III
(5)
Equilibrium Relationship:
Enthalpy Balance:
(3)
Summation equations:
(6)
(4)
V. MODEL DESCRIPTION
The RD column consists of 17 theoretical stages,
(IB)
(MeOH)
(MTBE)
including a total condenser and a partial reboiler.
The liquid-phase reaction is catalyzed by a strong
Reactive stages are located in the middle of the
acidic macro reticular ion exchange resin, for
column, stage 4 down to and including stage 11. In
example Amberlyst 15, and n-butene does not take
Aspen terminology, the numbering of the stages is
part in the reaction (inert). The forward and backward
top downward, the condenser is stage 1 and reboiler
rate laws and mole fraction taken from Seader and
is last stage. MTBE is produced by reaction of IB and
Henley,1998;Rehfinger and Hoffmann ,1990.
Me OH.
RDCOLUMN
CV1
CV2
POUT
PUMP
DIS
P1
METHA NOL
FL
BUTENES
CONPRESS
CV3
P2
FV
Fig.2 Reactive Distillation column
The specifications of the RD column and the other parameters used for simulation study are given in Table 1.
Table I
Column specifications and other parameters used for simulations
Parameters
For Pure Methanol Feed
For Butenes Feed
Feed stage
10
11
Temperature ( K)
320
350
Pressure(atm)
1
1
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BOT
Asian Journal of Convergence in Technology
Issn No.:2350-1146, I.F-2.71
Flow rate(kmol/hr)
711.30
Volume II, Issue III
1965.18
Property method
UNIFAC, NRTL, WILSON & VANLAAR
Total Stages
17 (including a total condenser and a partial reboiler)
Forward rate
x represents the liquid phase mole fraction
Backward rate
x represents the liquid phase mole fraction
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Asian Journal of Convergence in Technology
Issn No.:2350-1146, I.F-2.71
Volume II, Issue III
simulations were done using a reflux ratio equal to 7
Figs. 3, 4, and 5 shows the results of component
concentration profiles, temperature and MTBE
generation rate at each stage. The results compare
well with the results reported in literature.
VI. RESULTS AND DISCUSSION
The simulations are carried out using Aspen Plus
software. Reflux ratio of 7 was selected as optimum
as beyond this value the increased reflux had little
effect on MTBE purity in the distillate. All further
Table II
Aspen Plus Simulation Result with stage wise
PROPERTY
METHODS
U
N
I
F
A
C
W
I
L
S
O
N
N
R
T
L
V
A
N
L
A
R
NUMBER OF STAGES
PARAMETERS
1
2
3
9
10
11
16
17
Temperature
73.85
74.49
75.55
79.27
81.08
81.30
143.1
150.6
Pressure
Enthalpy (liquid)
Enthalpy (vapor)
Mol Fraction-X
Mol Fraction-Y
Density (liquid)
Density (Vapor)
11.15
-7.28
-4.18
0.0004
0.0001
528.7
25.88
11.18
-5.86
-3.12
0.001
0.0004
523.7
26.12
11.21
-5.11
-1.94
0.006
0.002
520.2
26.39
11.39
-10.9
-3.88
0.082
0.022
532.8
26.46
11.43
-14.9
-5.48
0.12
0.034
5442.7
23.81
11.46
-14.9
-5.43
0.13
0.035
542.2
26.83
11.62
-61.4
-47.4
0.89
0.74
570.2
34.92
11.65
-65.2
-56.2
0.96
0.88
566.1
34.92
Temperature
Pressure
Enthalpy (liquid)
Enthalpy (vapor)
Mol Fraction-X
Mol Fraction-Y
77.7
11.12
-6.19
-0.86
0.008
0.001
81.6
11.17
-11.6
-2.06
0.038
0.008
92.6
11.20
-25.1
-6.36
0.105
0.034
133.5
11.39
-50.4
-35.8
0.013
0.02
133.7
11.43
-50.5
35.90.013
0.021
139.6
11.46
-52.4
-42.8
0.002
0.004
142.7
11.62
-53.5
-46.6
0.00009
0.0001
142.8
11.65
-53.5
-46.6
0.00004
0.00009
Density (liquid)
517.7
529.5
558.7
622.4
622.4
630.2
634.3
634.1
Density (Vapor)
21.2
20.3
18.8
13.212.4
12.46
10.9
10.8
10.8
Temperature
Pressure
Enthalpy (liquid)
Enthalpy (vapor)
Mol Fraction-X
Mol Fraction-Y
Density (liquid)
Density (Vapor)
Temperature
Pressure
Enthalpy (liquid)
Enthalpy (vapor)
Mol Fraction-X
Mol Fraction-Y
78.2
11.5
-6.27
-0.20
0.02
0.004
519.3
21.2
88.1
11.2
-6.18
-0.25
0.01
0.002
84.1
11.2
-14.20
-2.09
0.09
0.02
536.2
20.8
94.3
11.2
-12.4
-1.77
0.04
0.01
97.5
11.2
-29.5
-8.45
0.26
0.08
566.3
20.9
107.3
11.3
-24.2
-6.68
0.11
0.04
125
11.4
-53.7
-35.9
0.45
0.31
611.2
19.7
137.6
11.4
-46.4
-31.23
0.14
0.09
125.5
11.4
-53.6
-36.3
0.43
0.31
612.2
18.32
138.1
11.4
-46.5
-31.6
0.13
0.08
129.32
11.5
-56.1
-42.2
0.38
0.32
622.7
18.6
141.7
11.5
-49.4
-37.2
0.12
-0.07
137.2
11.6
-60.5
-53.8
0.46
0.42
625.2
19.7
150.7
11.6
-57.5
-49.7
0.28
0.22
137.6
11.65
-61.4
-54.4
0.51
0.45
622.2
19.7
152.2
11.7
-58.7
-50.9
0.35
0.28
Density (liquid)
501.1
510.8
530.2
575.1
575.1
588.2
603.8
599.6
Density (Vapor)
20.4
19.5
18.4
15.2
14.5
13.3
15.8
15.8
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Asian Journal of Convergence in Technology
Issn No.:2350-1146, I.F-2.71
Volume II, Issue III
Fig 3. Stage wise composition profile of MTBE
Fig 4. Stage wise temperature profile
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Issn No.:2350-1146, I.F-2.71
Volume II, Issue III
Fig 5. Stage wise t Enthalpy of Liquid &Vapaor
VII. CONCLUSION
In this work, all the results are obtained from steadystate using ASPEN PLUS software for methyl
tertiary butyl ether (MTBE) reactive distillation
column. The result obtained from UNIFAC Property
method is compared with the other Property methods
like NRTL, WILSON & VANLAAR. The
compositions of MTBE from these property methods
were 0.51, 0.00004 & 0.35 respectively. The highest
composition of MTBE is 0.96 observed under
UNIFAC thermodynamic Property simulation result.
From the simulation results it’s noted that UNIFAC
thermodynamic Property method is the most suitable
property method for carrying out reactive distillation
process.
REFERENCES
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Rapmund P., Sundmacher, K., Hoffmann,
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distillation columns for the production of
fuel ethers MTBE and TAME: Theoretical
analysis and experimental verification”,
Chem. Eng. Sci., 54, 1029-1043, 1999.
[2] Hauan, S., Hertzberg, T., Lien, K.M.,
“Multiplicity in reactive distillation of
MTBE”, Comput. Chem. Eng., 21, 11171124,1997.
[3] J.D. Seader & Ernest J. Henley, ‚Separation
Process Principles‛, 2nd Edition, Wiley
India Pvt.Limited, 2010
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