Ind. Eng. Chem. Res. 1993, 32, 222G-2225
2220
Investigations in a Catalytic Distillation Pilot Plant: Vapor/Liquid Equilibrium, Kinetics, and Mass-Transfer Issues Jose L. Bravo? and Antti Pyhalahti Department of Chemical Engineering, Helsinki University of Technology, Kerninstintie 1, Espoo, Finland 02150
Harri Jarvelin' Neste Engineering, P.O. Box 310, Porvoo, Finland 06101
This paper describes a research project currently under way to establish the necessary parameters for the design of a catalytic distillation unit t o produce oxygenates. Experimental data regarding production of tert-amyl methyl ether (TAME) from a catalytic distillation pilot plant will be presented and discussed. Some preliminary attempts at modeling these results will also be described. Work in the areas of chemical equilibrium, kinetics, mass transfer, and hydraulics as they apply to catalytic distillation will be described. This work includes fundamental laboratory research as well as experiences in a pilot plant. TAME was selected as the subject of this study since there is a great deal of commercial interest in the production of oxygenates from heavier feedstocks. Methyl tertbutyl ether (MTBE) production is commonly practiced via catalytic distillation, but the application of this technology to the production of TAME is in its developmental stage. General Catalytic distillation is a unit operation that combines a catalyzed chemical reaction step with a distillation of the reaction materials in the same vessel. It offers some very attractive potential advantages in energy efficiency and capital cost over some conventional process schemes that utilize chemical reaction followed by distillation. Reactive distillation has been amply described in the literature, and catalytic distillation in particular is receiving much attention since it appears to be a viable way to produce oxygenated compounds from hydrocarbon streams. All the general thermodynamic, chemical engineering, and unit operations concepts applicable to reactor and distillation technology are also relevant in catalytic distillation. The technical challenge and research opportunities can be found mainly in the combination of conventional unit operation modeling with applications to catalytic distillation. The development of comprehensive models to describe catalytic distillation can open many research opportunities and lead to important basic developments in the field. Furthermore, little experimental data on catalytic distillation are available in the open literature. Any research and development project in this area has to be equally weighted in modeling and experimental efforts. Previous university work in the area has been almost exclusively devoted to modeling without formal validation of the models by experiments. Very little experimental data and analysis are available in the literature concerning catalytic distillation. This project will go a long way in filling such voids. A research project in the area of reactive distillation has been undertaken by the Chemical Engineering Department of TKK (Helsinki University of Technology) in Helsinki, Finland, in cooperation with Neste Oy, TEKES (Technology Development Centre), and the Nordic Research Ministry. The purpose of the research project is to investigate various mass-transfer, kinetics, hydraulics,
* To whom correspondence should be addressed. + Present address: Jaeger Products, Inc., 1611 Peach Leaf,
Houston, TX 77039.
and control aspects of a reactive distillation column that employs a fixed catalyst. The project has three distinct parts to it: steady-state modeling, dynamic modeling and control, and the generation of experimental data on reactive distillation for model validation purposes. These data will be among the first of their kind since most of the data in catalytic distillation is sequestered in proprietary developments. This project presents a unique opportunity for academic research. Recent work by Yuxiang and Xien (1992) addresses simulation of catalytic distillation using a ratebased modeling approach. This appears to be the proper way to tackle the simulation problem of reactive distillation since it is, even more so than conventional distillation, a rate-controlled process. Our simulation work so far has been based on equilibrium stage modeling approaches because of the availability of the tools. The experimental work described here was conducted in a pilot plant provided to the project by Neste. This is a very unique opportunity for graduate researchers to work on an industrial scale development unit using real feedstocks and confronting very practical research and development problems. With respect to steady-state modeling, the principal goal is to have a working model that not only incorporates the stage calculations and kinetics, but also the masstransfer efficiency and holdup effects. Several tasks toward this end are well under way: 1. A reliable reaction kinetics model for the reactions occurring in the pilot plant has been developed from extensive laboratory data with the cooperation of Neste and Yarsintez (Research Institute in Yaroslav, Russia) and is being tested by the research group of TKK. 2. Selection of consistent vapodliquid equilibrium (VLE) data has been accomplished. 3. A steady-state simulation program for reactive distillation (FLOWBAT) is in place and is being used to model the pilot plant column. FLOWBAT was first developed by Aittamaa (1982a,b), and later Ketunnen (1988) added the catalytic distillation section. 4. Experiments in a small-scale apparatus are planned to determine holdup in regimes where boiling liquids are flowing over the catalyst. The next step will be the
0888-5885/93/2632-2220$04.QQ/00 1993 American Chemical Society
Ind. Eng. Chem. Res., Vol. 32, No. 10, 1993 2221 investigation of external mass transfer coefficients at the gaslliquid, gaslsolid, and liquidlsolid interfaces at the conditions occurring in a catalyst pellet in a distillation environment.
..... h l b m e W
2
2m82bulene
0
o
Reaction Model The reaction scheme for the production of TAME from a C5 stream is given below. The foIlowing nine reactions are the most important to be considered in TAME production from a C5 olefin mixture: 2-Me-1-butene + methanol (MeOH)
+ MeOH
2-Me-2-butene
2-Me-1-butene 2-Me-1-butene
-
2 2-Me-2-butene 2 MeOH
-
-
-
0.26
0.9
o s
a4
Mole hadlon ol2-nwlh~l-l-bulone
Figure 1. Activity coefficients of MeOH, TAME, and the reactive olefins as a function of composition showing the highly nonideal behavior of MeOH.
(2)
- - - ZMzB+MeOHUAZB
(3)
C,,H,,
-
0.2
.....
CH,OCH,+H,O
2-Me-1-butene + H,O
0.15
140
TAME
+ 2-Me-2-butene
0.1
TAME (1)
2-Me-2-butene
2 2-Me-1-butene
2-Me-1-butene + H,O
-
-
0.05
(9)
Reactions 1,2,3,8,and 9 are equilibrium reactions; the rest are irreversible and go only toward the right. The desired reactions in terms of TAME production are reactions 1and 2. Reaction 3 is harmful, because the fastreacting 2-methyl-1-buteneis replaced with slow-reacting 2-methyl-2-butene. Reactions 4-6 describe the formation dimers, which are unwanted side products. Formation of many different isomers took place in our pilot column when conditions were suitable, i.e., alcohol concentration in the reaction zone was low. Trimers were also encountered as were combinations of other multi-olefins . In any event, the dimers of the two reactive olefins were probably the most important side products in terms of their effect in the production of ethers. Some of the dimers even suffered etherification themselves, which opens the possibility of oxygenate streams that would have a variety of ethers in them. Reaction 7 describes the dimerization of MeOH. This ether has a high octane number, but its vapor pressure is also quite high so it is considered less useful. Another problem associated with that reaction is the formation of water. In a gasoline additive that is of course a very undesirable situation. Moreover,we did notice that if there is a considerable amount of MeOH in the liquid at any point in the column, it is easily separated into two liquid phases upon cooling. One phase contains mostly MeOH; another is rich in hydrocarbons. Water strongly promotes this behavior of the liquid phases, so ita formation should be prevented if possible. Reactions 8 and 9 describe the formation of TAOH, which is actually a useful product but not as good an octane enhancer as TAME. One positive property of this reaction is that it consumes some of the water produced by dimerization of MeOH. These two reactions are also equilibrium reactions.
T e m p m u n (K)
Figure 2. Chemical equilibrium constants as a function of ternperatuxefor the TAME-producingreactions.The reactions markedly favor the product side.
Reaction rates and equilibria depend on the activities of the components in the liquid. Liquid activity coefficients have been calculated by the UNIQUAC model. An example of these is given in Figure 1. It may be seen that the activity coefficient of methanol differs greatly from 1 whereas the others are relatively close to 1. Having one component largely nonideal can cause very peculiar behavior of concentration profiles in a reactive distillation column as will be illustrated later. Typical values for the equilibrium constants for some of the most important reaction are given in Figure 2. These data clearly indicate that, under normal operating conditions, the reactions are strongly favored toward the products side. As discussed later in the paper, this feature of the system allows process schemes that do not combine reaction and distillation in a singleoperation to be seriously considered.
Experimental System and Test Conditions We chose to use the TAME reaction as produced by the reaction of C5 olefins with methanol as the model for this research project. This process has a great deal of commercial interest as C5 olefins in refineries are typically blended into the gasoline pool. The concentration of C5 olefinswould increase the vapor pressure with the resulting negative environmental impact. By convertingthe reactive isoamylenes to TAME, the high vapor pressure is reduced and a high-octane oxygenate is added in place. The feedstocks used for TAME production are heavier and hence are presumed to have a lower raw material cost than those used for MTBE. The pilot plant consists mainly of a fully instrumented distillation column that has been fitted with reaction zones. The column is depicted in Figure 3. On-line instrumentation allowed us to obtain real-time temperature and composition profiles in the column. The system is run under steady-state conditions, and the materialand energy balances are continuously verified by the computer data system. The feedstock employed was directly obtained from a refinery stream and used for the experiments. Typical feed compositions are illustrated in Table I. Chemical
2222 Ind. Eng. Chem. Res., Vol. 32, No. 10,1993
-t
MeOH. EXP
--O-
TAME. EXP
-
2M1B. EXP
2Mm. EXP
,IM.
10
0 1
2 3 1 5 8 7 8 9 Mm~nmMtpain( numbor (numbor 1 Is column lop, 10 m o m )
10
Figure 4. Concentration profides for reagents and products under high reflux and methanol conditions (run 12.9.91). W T
Feed points
>
Reaotlon
-
sectlon
MeOH, EXP
-t
TAME, EXP 2MlB. EXP
-0- 2M2B. EXP
Column helght 11 m DheW 0.15m
1
2
3
4 5 6 7 8 Measurementpoint number
9
10
Figure 5. Concentration profiles for reagents and products under high methanol and moderate reflux conditions (run 13.9.91). €0
---C
-
MsOH, EXP
TAME, EXP
2MlB. EXP -0-
Figure 3. Schematic of the pilot plant reactive distillation column used in the experiments. Table I. Typical Feed Compositions for TAME Production Experiments compd isobutane butane cis-2-butene isopentane 2-Me-1-butene 2-Me-1,3-butadiene cis-2-pentene cyclopentadiene cyclopentene cyclopentane 3-Me-pentane 2-Me-2-pentene
wt%
0.41 1.13 3.27 23.61 7.99 0.25 5.65 0.14 1.68 0.41 1.98 1.10
compd iso-1-butene tram-2-butene 3-Me-1-butene 1-pentene pentane trans-8pentene 2-Me-2-butene 2,a-Mea-butane 4-Me-1-pentene 2-Me-pentane 2-Me-1-pentene other C6's
wt%
1.58 3.11 1.45 4.12 3.57 10.32 14.08 0.2 0.36 4.15 0.97 balance
grade methanol constituted the alcoholfeed to the column. The column was operated a t an absolute pressure of 300 kPa. The catalyst was conventional ion exchange resin Amberlite XAD. It is the same catalyst commonly used in MTBE production. Several experimental runs were conducted, and the conditions for the ones discussed in this paper are summarized in Table 11.
Experimental Results Figures 4-9 are actual experimental concentration profiles found in the pilot column for the runs described in Table 11. The compositions are measured a t various sampling points. Sample point 1is the distillate, sample point 10 is the bottoms, and the rest are located in the column itself with points 4-8 located within the reaction zone.
2Mm, EXP
0 1
2
3
4
5
6
7
8
9
10
M.arurment points
Figure 6. Concentration profies for reagents and products under medium methanol and moderate reflux conditions (run 17.9.91). 25
T
A
-
MeOH. EXP TAME, EXP
1 -
2M1B, EXP
ZMZB, EXP
1
2
3
4 5 6 7 8 Measurement point number
9
10
Figure 7. Concentration profies for reagents and products under low methanol and moderate reflux conditions (run 18.9.91).
Discussion of Observations Three very distinct regions are evident from the data in Figures 4-9. Figures 4 and 5 indicate runs at high methanol levels, and the composition profiles are almost flat in the column. This behavior is undoubtedly caused by irregularities in the phase equilibria. Figures 7 and 8 are run under deficient methanol conditions, and the profiles show more variation indicating a more conventional VLE behavior. Figures 6 and 9 fall in between. The system then exhibits notably different behavior under high, medium, and low methanol conditions. This fact is not only important in steady-state conditions but it becomes of fundamental concern in dynamic simulations and control model development. The methanol concen-
Ind. Eng. Chem. Res., Vol. 32,No. 10, 1993 2223
-
MeOH. CALC
MsOH, W P
--
TAME, EXP
TAME, CALC
2M18, WP 2M28, EXP
-
0 1
I
2
3
4
5
6
7
8
9
2
3
4
5
t
f
6
7
-: . - 4
8
9
\ -
7
10
1.
2h416, EXP
-2M18, CALC 0..
2M2B.EXP
1
2M28. CALC
M.aclument point number
10
wlruunmom point number
Figure 8. Concentration profiles for reagents and products under low methanol and moderate reflux conditions. Methanol mixed with the feed prior to entering the column (run 19.9.91).
MeOH. EXP
---=--
-.-
TAME, EXP 2M16, EXP
Figure 10. Comparison between simulation results and the concentration profiles obtained under experimental conditions at moderate methanol concentration~.
a trade-off between TAME conversion and MeOH recovery. All in all, the optimum running conditions are very tight and the range is narrow: not necessarily very efficient in terms of pure separation. The separation column in a conventional reactor/distillation train would run under much less stringent conditions.
+2M2B. EXP
Comparison of Calculated and Experimental Results 1
2
3
4 5 6 7 8 Measurement point number
9
10
Figure 9. Concentration profiles for reagents and products under medium methanol and moderate reflux Conditions. Methanol mixed with the feed prior to entering the column (run 20.9.91). Table 11. Experimental Conditions for TAME Runs. methanol feed MeOH/feed runno. mition ratio refluxlfeed eteamlfeed 0.21 3.27 1.18 12.9.91 between beds 0.21 3.00 0.80 13.9.91 between beds 0.126 2.51 0.85 17.9.91 between bede 0.080 2.59 0.91 18.9.91 between bede 0.080 3.33 1.01 19.9.91 mixed with feed 0.113 4.88 1.50 20.9.91 mixed with feed 0 All ration are maas ratios. Stoichiometric ratios of methanol to the a- and fl-2-Me-butenesvaried from 0.7 to 2. ~
~~
~~~
tration of the distillate in the high and medium methanol runs is virtually constant by virtue of the VLE, and the methanol concentration of bottoms product depends obviously on methanol feed rate. This indicates an azeotrope-like behavior predicted only when the conventional VLE model is used in conjunction with the reactive distillation model. The presence of these peculiar azeotropes could also explain the flat concentration profiles encountered in Figures 4 and 5. This situation changes abruptly when methanol feed rate is lowered. Then relatively small decreases of methanol feed rate make the concentration profiles of methanol go down through the whole column. It is important to note that the methanol concentration profiles in the column are relatively stable when there is some excess of methanol in the feed. Then the concentrations in the middle part of the column are conducive to good reaction conversion. The VLE in the presence of reaction is thus favorable to the production of TAME. The column has to be run very stringently to maintain the methanol in the reaction zone. This requires high reflux rates and higher energy consumption. The most desirable situation is when no methanol exists in the bottoms but high methanol exists in the reaction zone. Thus the stripping section of the column has to be run at high vapor rates. Also, one would try to minimize the amount of methanol in the distillate to reduce recovery costs. This is all constrained by the VLE and represents
We have simulated the behavior of the pilot column with the FLOWBAT process simulation program using the reactions, kinetics models, and VLE models outlined above. Figure 10(lower methanol feed rate) shows the predicted composition profiles using FLOWBAT. The results in terms of the profile are encouraging, and the results with respect to conversion and yield were excellent. More work is required in the kinetic model to make the simulation more accurate, but we appear to have a very viable model at this point.
Applicability of Reactive Distillation to TAME and MTBE Production The advantages traditionally associated with reactive distillations are: the removal of reaction products from the reaction medium and the lower capital expense when compared to reactor/distillation column with recycle combinations. Let us address the first perceived advantage as it relates to TAME production. The reaction to form TAME is a condensationreaction where 1mol of methanol and 1mol of C5 olefin react to from 1mol of TAME. The product of this reaction is heavier and less volatile than either of the reagents. Interestingly, the TAME reaction takes place in the liquid phase so that, under distillation conditions, the reagents and not the products are removed from the reaction medium. This reduces the attractiveness of reactive distillation for this application but it does not totally eliminate it since presumably the "removed" reagents will be available for reaction at a higher point in the column. Furthermore, the reflux also makes some of the reagents available at lower parts in the column. The critical issue becomes then to operate the distillation in such a way that the reagents are forced to coexist at the same point in the column. (This can prove difficult when the volatilities of the reagents are very dissimilar.) It is important to note that this is the case also with MTBE production. The lack of definite and well-established advantages of the reactive distillation path are evidenced by how competitive traditional reactor/column arrangements are with the much publicized reactive/catalytic distillation approach. Reactive distillation would be much more attractive if the reaction took place in the vapor phase or if the desired
2224 Ind. Eng. Chem. Res., Vol. 32,No. 10, 1993
product were lighter than the reagents. Nevertheless, the unique VLE behavior of the reactive distillation system allows for good reaction rates to exist in the reaction zone of a column as evidenced by the data shown above. A further complication that reduces the attractiveness of reactive distillation for the production of TAME is the fact that the reagents, methanoland C5 olefins,have vastly different volatilities. This difference causes the concentration levels for methanol and C5 olefins to be very different from each other within a distillation column. What this means to the reaction is that it is difficult to have the best concentrations of reagents occur at the same point in the column, thus resulting in lower reaction rates. The only way to solve this problem is with excess methanol in the feed, high reflux, and stripping steam rates. These factors represent a significant load in the separation step that is probably higher than that required in a conventional reactorlseparator with recycle. Another consideration is the amount of catalyst required to achieve economic conversions. This is general large and necessitates the use of a prereactor upstream of the distillation column. All our data were taken with the feed directly into the column so that conversions were significantly lower than if we had a prereactor. The prereactor also acts as a guard bed against catalyst poisons that can affect the catalyst in the distillation column. The catalyst in the column is very difficult to replace and a guard bed reactor makes sense. But, if we are to have a guard bed reactor, why not have most of the reaction in that reactor since the equilibrium is favorable anyway? It is clear that, in an optimized process, the majority of the load will be on the prereactor and the reactive distillation column will act as an enhancer only. In any event, in spite of the factors outlined above that could indicate that a conventional reactor/distillation scheme would be just as effective and economical as a reactive distillation process for the production of oxygenates, the study of reactive distillation using the TAME and MTBE systems continues to be interesting since reactive distillation plants will continue to operate and be constructed for this purpose. One should consider catalytic distillation for MTBE production when the required conversions are very high and always with a prereactor. In the case of TAME the selection is not that clear.
Operational Difficulties in Reactive Distillation Systems Probably the most startling difficulty we found in the operation of the pilot column was the apparent existence of multiple steady state conditions. We were able to predict some of these with the simulations prior to the runs, but other factors appeared that we did not expect. An example of these is the fact that the catalyst behaved differently depending on how the column was started up. The catalyst exhibited a tendency to produce a much higher amount of dimers, even under steady-state conditions, when start-up did not go through a very high methanol concentration step. We also observed that traditional feedback proportional integral derivative control would land the column in different steady states when trying to correct small disturbances. The steady states were not radically different but enough to be of concern. Our observations indicate that a model-based control approach with a very strong dynamic simulation component is required for accurate control. A significant part of our research effort at the present stage of the project is directed toward the development of such a model.
Mass-Transfer and Hydraulic Issues The environment around the catalyst during reactive distillation conditionsis very complex to describe. Beyond the intraparticle mass-transfer issues and the kinetics of the reaction, one still has to deal with bulk mass transfer that is not equimolar counter diffusion and more significantly with an exothermic reaction where the liquid is at its boiling point. The generation of vapor around the particles in addition to the vapor normally present because of the distillation poses interesting modeling challenges in liquid holdup, in gas- and liquid-side mass-transfer coefficients,in effective interfacial area (vapodliquid), and even for capacity and pressure drop. Research is currently under way in equipment that simulates the catalyst bed aimed at measuring holdups, pressure drops, and mass-transfer parameters so that generalized models can be validated.
Pressure Drop and Holdup A catalytic distillation column contains parts which are very different from the internals of a traditional distillation column, and hydraulics of those parts need also consideration when a model of a catalytic distillation column is developed. It is obvious that data concerning maximum allowable liquid and gas flows and pressure drop is necessary for design of such a column. There are of course severalmodels for predicting pressure drops of traditional trays and packings, and they may be applied to such parts of catalytic distillation columns as well. However, the catalyst section of the column is very different. The same applies to the holdup. In a reactive system liquid holdup has a special significance, because it may have an effect on the reaction rates. Conclusions Catalytic distillation is obviously an attractive path for the production of TAME and MTBE and is a technology that offers exciting possibilities. New developments appear frequently, and as interests in oxygenatescontinues to grow so will the development of catalytic distillation. There is much to be learned, but unfortunately a great deal of knowledge has yet to appear in the public domain. Little unbiased and reliable experimental data concerning the production of oxygenates are available in the open literature and not tied up in proprietary packages. The amount of methanol in the feed to our experimental column was determined to be the most significantvariable with respect to operation, conversion, and recovery. Different methanol to hydrocarbon feed ratios produced vastly different operating regimes in the column. There appears to be some interaction between the reaction and the VLE that produces flat concentration profiles for large portions of the column under certain conditions. Efforts to model the behavior of the pilot column under steadystate conditions proved successful. The description of the operating regimes at different methanol levels via a steady-state simulator was achieved. The project described in this paper is producing information from laboratory research into kinetics and VLE, as well as mass transfer and hydraulics data, all coupled with actual pilot plant test data for the production of TAME. The data presented in this work are unique in that they come from actual experiments in a pilot plant and should prove useful to researchers involved in the modeling and simulation of catalytic distillation.
Ind. Eng. Chem.Res., Vol. 32, No.10,1993 2226
Acknowledgment The authors wish to express their appreciation for the support of the Helsinki University of Technology (TKK), Neste Oy, Jaeger Products, TEKES, and NMR as well as for the enthusiastic participation of all the members of the Reactive Distillation Project Research Team. Literature Cited Aittamaa,J. Computing Multicomponent Distillation. Acta Polytech. S c a d . , Chem. Zncl. Metall. Ser. 1982a,No. 148. Aittamaa, J. Computational Methods for Distillation Design. Acta Polytech. Scad., Chem. Zncl. Metall. Ser. 1982b,No. 149. Kettunen, M. Modeling a Reactive Distillation. Master’s Thesis, Chemical Engineering, TKK, Espoo,Finland, 1988. Yuxiang, 2.;Xien, X.Study of Catalytic Distillation Processes. Part 11. Simulation of Catalytic Distillation Procesaes-Quasi-Homogeneoua and Rate-Based Model. Trans.Znst. Chem. Eng. 1992, 70,465-470.
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(8)Komatau, H.; Holland, C. D. A New Method of Convergence for SolvingReacting Distillation Problems. J . Chem.Eng. Jpn. 1977, 10,(4),292-297. (9)Lander, E.P.; Hubbard, J. N.; Smith, L. A. Rewing-up Profita With Catalytic Distillation. Chem. Eng. 1983,90,(4),36-39. (10)Nelson, P. A. Countercurrent Equilibrium Stage With Reaction. AZChE J . 1971,17,(5),1043-1049. (11) Reuter, E.;Wozny, G.;Jeromin, L. Modelling of Multicomponent Batch Distillation Processes With Chemical Reaction and Their Control Systems. Comp. Chem. Eng. 1989,13,(4/5), 499-510. (12)Saito, S.;Michiaita, T.; Maeda, S. Separation of Meta- and Para-xylene Mi.ture by Distillation Accompanied by Chemical Reaction. J. Chem. Eng. Jpn. 1971,4,(l),37-43. (13)Sawistowski,H. Distillation With Chemical Reaction. Nato ASZ Ser., Ser. E. 72,391-414. (14)Seader, J. D. The Rate-BasedApproach for ModellingStaged Separations. Chem. Eng. Prog. 1989,86,(lo),41-49. (15)Simandl, J.; Svrcek, Y. Process Simulation of Distillation Columns With Chemical Reactions. CHISA loth International Congressof Chemical Enpineering, Chemical Equipment Design and Automation, Praha, Czechoslovakia, Aug 26-31,1990. (16)Sivasubramanian, M. S.;Taylor, R.; Krishnamurthy, R. A Nonequilibrium Stage Model of Multicomponent Separation Processes Part Iv: A Novel Approach to Packed Column Design. AZChE J. 1987,33,(2),325-327. (17)Suzuki, I.; Yagi,H.; Komatau, H.; Hirata, J. Calculating of Multicomponent Distillation Accompanied by a Chemical Reaction. J. Chem. Eng. Jpn. 1971,4,(4),26-33. (18)Tierney, J. W.; Riquelme, G. D. Calculation Methods for Distillation Systems With Reaction. Chem. Eng Commun. 1982,16, 91-108. (19)Venkataram, 5.; Chan, W. K.; Boston, J. F. Reactive Distillation Using ASPEN PLUS. Chem. Eng. Prog. 1990,86,(8), 46-64. Received for review March 1, 1993 Revised manwcript received July 1, 1993 Accepted July 23, 1993. 9 Abstract published in Advance ACS Abstracts, September 15,1993.
