1 INTRODUCTION. 2 CHEMICAL KINETICS AND VAPOR LIQUID EQUILIBRIUM 2.1 Chemical kinetics

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1 Chinese Journal of Chemical Engineering, 19(5) (2011) Simulation for Transesterification of Methyl Acetate and n-butanol in a Reactive and Extractive Distillation Column Using Ionic Liquids as Entrainer and Catalyst * CAI Jialin ( 蔡贾林 ), CUI Xianbao ( 崔现宝 ) ** and YANG Zhicai ( 杨志才 ) State Key Laboratory of Chemical Engineering (Tianjin University), School of Chemical Engineering and Technology, Tianjin University, Tianjin , China Abstract A new reactive and extractive distillation process with ionic liquids as entrainer and catalyst (RED-IL) was proposed to produce methanol and n-butyl acetate by transesterification reaction of methyl acetate with n-butanol. The RED-IL process was simulated via a rigorous model, and high purity products of methanol and n-butyl acetate can be obtained in such a process. The effects of reflux ratio, feed mode, holdup, feed location, entrainer ratio and catalyst concentration on RED-IL process were investigated. The conversion of methyl acetate and purities of products increase with the holdup in column, entrainer ratio and catalyst content. An optimal reflux ratio exists in RED-IL process. Comparing to the mixed-feed mode, the segregated-feed mode is more effective, in which the optimal feed locations of reactants exist. Keywords ionic liquid, reactive and extractive distillation, transesterification reaction, azeotropic mixture 1 INTRODUCTION Reactive and extractive distillation (RED) is a process that integrates reactive distillation and extractive distillation into one column to take the advantages of reactive distillation and extractive distillation, so that the conversion of an equilibrium reaction can be enhanced and the energy consumed can also be saved. RED is more flexible than reactive distillation, since the relative volatilities of the reactants and products can be adjusted by the entrainer to make the products be the lightest and (or) the heaviest components in a RED process. RED can be used in many kinds of reactions, for example, esterification, transesterification, etherification, hydrogenation, dehydrogenation and alkylation, etc [1-5]. Methyl acetate is a byproduct in the industrial manufacturing process of poly(vinyl alcohol) (PVA). For one ton of PVA, 1.68 tons of methyl acetate is produced. Because the industrial application of methyl acetate is limited, Jimenze et al. proposed a RED process to convert methyl acetate with n-butanol to methanol and n-butyl acetate, using ion-exchange resin as catalyst and o-xylene as entrainer [2, 3]. Methanol is a feed stock of PVA production, and n-butyl acetate is an important solvent and intermediate in organic synthesis and in the photographic industry [6, 7]. Luyben et al., Wang et al. and He et al. developed a number of reactive distillation processes to convert methyl acetate with n-butanol to n-butyl acetate and methanol, and they all used ion-exchange resin as catalyst [8-11]. However, as stated by Jimenez et al. [2], the main drawbacks of ion-exchange resin catalyst were the low thermal stability, need for catalyst containers to improve mechanical properties, and possible diffusion problems. Moreover, resins are also susceptible to both short-term poisoning and long-term deactivation. Ionic liquids (ILs) are chemicals composed of organic cations and organic or inorganic anions with low melting points and neglected vapor pressures. As green solvents, they can be utilized to replace the conventional volatile entrainers. Because of its negligible vapor pressure, ionic liquid is easily separated from volatile chemicals by simple distillation, so the recovery of IL entrainer can save energy comparing to the conventional entrainer. Ionic liquids are thermally stable up to 200 C, and exhibit Bronsted, Lewis, and Franklin acidity as well as superacidity, so ionic liquids can also act as substitutes for ion-exchange resin catalysts to overcome their defects. Therefore, ionic liquids are environmental friendly functional chemicals, the promising catalysts and entrainers in reaction and separation processes [12-15]. In this paper, a new RED process to conduct the transesterification of methyl acetate with n-butanol to methanol and n-butyl acetate, using ionic liquids as entrainer and catalyst were proposed. The process was simulated by the commercial software ChemCAD. The effects of reflux ratio, feed mode, holdup, location of feed tray, entrainer ratio and catalyst concentration on the conversion of methyl acetate and purities of the products, were also investigated. 2 CHEMICAL KINETICS AND VAPOR LIQUID EQUILIBRIUM 2.1 Chemical kinetics The transesterification reaction of methyl acetate with n-butanol is as follows: Received , accepted * Supported by the Innovation Fund of Tianjin University. ** To whom correspondence should be addressed. cxb@tju.edu.cn

2 Chin. J. Chem. Eng., Vol. 19, No. 5, October CH 3 COOCH 3 + CH 3 (CH 2 ) 3 OH CH 3 COO(CH 2 ) 3 CH 3 + CH 3 OH Recent research shows that the Bronsted acidic ILs with two different acid sites on the imidazolium cations are more efficient than the conventional Bronsted acidic ILs in esterification reaction [16]. Since the esterification and transesterification reaction are semblable, we chose [HSO 3 -bhim]hso 4 (Fig. 1) as catalyst for the transesterification of methyl acetate with n-butanol to n-butyl acetate and methanol, and measured the kinetic data (the detail of kinetic experiments will be presented elsewhere). The transesterification reaction was known to be a reversible second-order reaction [17]. We found the initial reaction rate r 0 was proportional to c 0.5 cat, and used the following equation to correlate the reaction rate. 11dni r = Vvi dt = c ( k x x k x x ) (1) ρ cat + BuOH MeOAc MeOH BuOAc where r is the reaction rate, mol L 1 min 1 ; V is the volume of reaction mixture, L; v is the stoichiometric coefficient; ρ is the molar density of the reaction mixture, mol L 1 ; c cat is the concentration of IL in reaction mixture, mol L 1 ; x MeOAc, x BuOH, x BuOAc, x MeOH are mole fractions of methyl acetate, n-butanol, n-butyl acetate and methanol; k + and k are forward and backward reaction rate constants, which can be expressed by Arrhenius equation: k k E = RT 0 A+ + k+ exp 0 EA = k exp RT (2) (3) 0 0 where, k + and k are pre-exponential factors, equal to mol 1.5 L 1.5 min 1 and mol 1.5 L 1.5 min 1, respectively; E A+ and E A are activation energies, equal to kj mol 1 and kj mol 1, respectively. The mean square deviation between the experimental and calculated conversions of methyl acetate was Figure 1 The structure of [HSO 3 -bhim]hso Vapor-liquid equilibrium Two azeotropes (methanol/methyl acetate and n-butanol/n-butyl acetate) appear in the transesterification reaction system. Methanol/methyl acetate can form a minimum-boiling azeotrope with methanol 0.35 (mole fraction) at 53.7 C, and n-butanol/n-butyl acetate can form a minimum-boiling azeotrope with n-butanol 0.75 (mole fraction) at C. The T-x-y diagrams for methanol/methyl acetate and n-butanol/ n-butyl acetate at kpa were calculated by Chem- CAD and shown in Fig. 2. (a) Liquid/vapor mole fraction of methanol (b) Liquid/vapor mole fraction of n-butanol Figure 2 T-x-y diagrams for methanol/methyl acetate (a) and n-butanol/n-butyl acetate (b) at kpa vapor phase; liquid phase To select suitable ionic liquids as entrainers to break the azeotropic points of the two systems, the infinite dilution activity coefficients of methanol/methyl acetate and n-butanol/n-butyl acetate in hundreds of ILs were calculated using COSMO-SAC model [18, 19]. We found 1-octyl-3-methylimidazolium hexafluorophosphate ([OMIM][PF 6 ]) was a promising entrainer to separate the two azeotropic mixtures. In our previous paper, the vapor-liquid equilibrium (VLE) for the ternary mixture methanol + methyl acetate + [OMIM][PF 6 ] was measured and correlated by the NRTL equation [20]. The binary parameters for n-butanol-n-butyl acetate in these NRTL equation can be obtained from the database in ChemCAD. In order to obtain binary parameters for n-butanol-[omim][pf 6 ] and n-butyl acetate-[omim][pf 6 ], VLE and liquid-liquid equilibrium (LLE) for the ternary mixture n-butanol + n-butyl acetate + [OMIM][PF 6 ] were measured. The VLE and LLE data of the ternary mixture were also correlated by a NRTL model:

3 756 Chin. J. Chem. Eng., Vol. 19, No. 5, October 2011 Table 1 Values of binary parameters in the NRTL model i component j component α ij B ij /K B ji /K methanol methyl acetate methanol n-butanol methanol n-butyl aectate methanol [OMIM][PF 6 ] methyl acetate n-butanol methyl acetate n-butyl acetate methyl acetate [OMIM][PF 6 ] n-butanol n-butyl acetate n-butanol [OMIM][PF 6 ] n-butyl acetate [OMIM][PF 6 ] τ G x τ G x j xg j ij k lnγi = + ij Gki x τ k j Gkj x k Gkj xk k k k ji ji j kj kj k G (4) τ = B / T (5) ji ji = exp( α τ ) (6) ji ji ji where B ij is binary interaction parameter, K; α ji is non-randomness parameter; T is temperature, K; x i is mole fraction of component i in liquid phase; γ i is activity coefficient of component i. The binary parameters correlated by the NRTL model are listed in Table 1. For the system of both methanol + methyl acetate + [OMIM][PF 6 ] and n-butanol + n-butyl acetate + [OMIM][PF 6 ], the maximum absolute deviation Δy, mean absolute deviation σ y and root mean square deviation δ y between the experimental and calculated values of vapor-phase mole fractions exp cal exp cal (Δy = max y y ; σ y = (1/ N) Σ y y ; exp cal 2 1/ 2 δ y = [(1/ N) Σ( y y ) ] ) are less than 0.015, 0.01 and 0.01, respectively. The maximum absolute deviation ΔT, mean absolute deviation σ T and root mean square deviation δ T between the experimental and calculated values of equilibrium temperatures exp cal exp cal (ΔT = max T T ; σ T = (1/N) Σ T T ; exp cal 2 1/ 2 δ T = [(1/ N) Σ( T T ) ] ) are less than 0.80 K, 0.20 K and 0.25 K, respectively. The vapor-liquid equilibrium diagrams calculated by the NRTL model for the mixtures of methanol + methyl acetate + [OMIM][PF 6 ] and n-butanol + n-butyl acetate + [OMIM][PF 6 ] are plotted in Figs. 3 and 4. In Fig. 3, x 1 is the mole fraction of methanol excluding entrainer [OMIM][PF 6 ]. In Fig. 4, x 1 is the mole fraction of n-butanol excluding entrainer [OMIM][PF 6 ]. Figs. 3 and 4 show that [OMIM][PF 6 ] Figure 3 Influence of [OMIM][PF 6 ] and o-xylene on the vapor-liquid equilibrium of the methanol + methyl acetate system at kpa with an entrainer mole fraction x 3 = 0.6 without entrainer; o-xylene, calculated by modified UNIFAC; [OMIM][PF 6 ], calculated by NRTL Figure 4 Influence of [OMIM][PF 6 ] and o-xylene on the vapor-liquid equilibrium of the n-butanol + n-butyl acetate system at kpa with an entrainer mole fraction x 3 = 0.3 without entrainer; o-xylene, calculated by modified UNIFAC; [OMIM][PF 6 ], calculated by NRTL is more effective than the conventional entrainer o-xylene. Therefore, [OMIM][PF 6 ] is an effective entrainer to separate the azeotropes of methanol/methyl acetate and n-butanol/n-butyl acetate.

4 Chin. J. Chem. Eng., Vol. 19, No. 5, October SIMULATION OF REACTIVE AND EX- TRACTIVE DISTILLATION PROCESS 3.1 Problem specification A reactive and extractive distillation (RED) column was employed to carry out the transesterification of methyl acetate with n-butanol, using ionic liquids as entrainer and catalyst (RED-IL). In conventional RED, a rectification region is needed to separate the entrainer and light product. However, in a RED-IL column (see Fig. 5), the catalyst and entrainer are fed at the top of column (even directly mixed with reflux), so the rectification region is eliminated, thus the extraction region and the reaction region occupy the whole column. Since the vapor pressures of ILs can be neglected, it is not necessary to use another column for the recovery: ILs can be recovered only by flash (T-2 in Fig. 6). Energy is saved in the entrainer recovery process in RED-IL, comparing with the conventional RED. equilibria used in simulation were provided in Section 2. The RED-IL process used in this study is shown in Fig. 6, including a RED-IL column (T-1) and a flash drum (T-2). The transesterification reaction is conducted in the RED-IL column, the light product methanol is removed from the top of the RED-IL column, the heavy product n-butyl acetate and ionic liquids (entrainer and catalyst) are removed from the bottom of RED-IL column and separated in the flash drum, so n-butyl acetate is withdrawn from the flash drum as product and the ionic liquids are recycled to RED-IL column. The RED-IL column having 40 stages (counting from top to bottom) is operated at kpa, and the pressure drop across the column is assumed to be 10 kpa. High-boiling reactant n-butanol is fed at tray 25 at a flowrate of 5 kmol h 1. The low-boiling reactant methyl acetate is fed at tray 35 at a flowrate of 5 kmol h 1. The entrainer is [OMIM][PF 6 ], and its flowrate is 3 kmol h 1. The catalyst is [HSO 3 -bhim]hso 4, and its flowrate is 0.5 kmol h 1. The entrainer and catalyst are mixed and fed at tray 2. The withdrawal flowrate at the top of the RED-IL column is set as 5 kmol h 1. The holdup on each tray is 25 L, and the reflux ratio is 5. For convenience, the operation conditions mentioned above are set as the standard operation conditions. 3.2 Simulated composition profiles Figure 5 RED-IL column Figure 7 shows the composition profiles of RED-IL column at the standard operation conditions, including the composition of entrainer and catalyst. It can be seen from Fig. 7 that the top of RED-IL column is rich in methanol, while the bottom is rich in n-butyl acetate. The concentration of methyl acetate in the column is low and only changes a little along the column. The concentration of n-butanol decreases sharply, while the concentration of n-butyl acetate increases sharply in the column below the n-butanol feed tray. Methanol is obtained from the top of T-1 with purity of (mole fraction). The high-boiling product of T-1 (n-butyl acetate + ILs) is fed to a flash drum, and n-butyl acetate with purity of (mole Figure 6 Process for converting methyl acetate with n-butanol to methanol and n-butyl acetate via RED-IL The transesterification of methyl acetate with n-butanol in RED-IL process was simulated using the rigorous distillation model provided by the ChemCAD software. The chemical kinetics and vapor liquid Figure 7 Liquid composition profiles for RED-IL column (T-1) methanol; n-butyl acetate; n-butanol; methyl acetate; [OMIM][PF 6 ]; [HSO 3 -bhim]hso 4

5 758 Chin. J. Chem. Eng., Vol. 19, No. 5, October 2011 fraction) is obtained from flash drum vapor and ILs with purity of (mole fraction, entrainer + catalyst) is removed from the flash drum bottom and recycled to the RED-IL column. 4 EFFECTS OF OPERATIONAL AND GEO- METRIC PARAMETERS Because the RED is an integrated process, its performance is influenced by several parameters [3]. In this paper, the effects of reflux ratio, feed mode, holdup, feed tray location, entrainer ratio and catalyst concentration were investigated by simulation. The operational and structural parameters and simulation results are listed in the appendix. 4.1 Effects of reflux ratio To investigate the effects of reflux ratio, simulations were carried out at different reflux ratios, keeping the other parameters the same as the standard operation conditions mentioned in Section 3.1. The results of conversion of methyl acetate and purities of products at different reflux ratios are plotted in Figs. 8 and 9, which indicate that there exists an optimal reflux ratio. For conventional distillation, the purities of the products generally increase with reflux ratio. However, for the reactive and extractive distillation, the chemical reaction and separation process are coupled, so the effects of reflux ratio are more complicated. If the reflux ratio is very low, methanol and n-butyl acetate can only be separated from methyl acetate and n-butanol roughly, the concentrations of methanol at the top and n-butyl acetate at the bottom of the RED-IL column are relative low, some of the reactants (methyl acetate and n-butanol) are removed from the top and the bottom of the column, so the conversion is low. If the reflux ratio increases, the purities of methanol removed from the top and n-butyl acetate removed from the bottom of the RED-IL column will increase, and the amount of reactants removed from the top and bottom of the column will Figure 8 Effects of reflux ratio on conversion of methyl acetate Figure 9 Effects of reflux ratio on the purities of methanol and n-butyl acetate methanol; n-butyl acetate decrease, so the conversion will increase. However, if the reflux ratio is too large, the entrainer in the column is greatly diluted by the reflux, the relative volatilities of azeotropes will decrease, methanol and n-butyl acetate can not be separated to high purity and the conversion will decrease. 4.2 Effects of feed mode There are usually two feeding modes for a RED-IL process. One is the mixed-feed mode (mixing all the reactants in one stream), the other is segregated-feed mode (different reactants are fed to different trays). In the standard operation conditions, n-butanol is fed at tray 25 and methyl acetate is fed at tray 35 (segregated-feed mode), the purity of methanol and n-butyl acetate are and (mole fraction), respectively. The conversion of methyl acetate in the standard case is (see Table 2). Here we investigate mainly the mixed-feed mode in which methyl acetate and n-butanol are mixed and fed into the column at trays varied from 25 to 35 and compare it with the segregated-feed mode under the standard operation conditions. The comparison of mixed-feed mode and segregated- feed mode is given in Table 2. The simulation results of the mixed-feed mode show that when reactants are fed at tray 32, the purities of top product (methanol) and bottom product (n-butyl acetate), as well as the conversion of methyl acetate reach the maximum values, which are 0.937, (mole fraction) and 0.947, respectively. The maximum values of conversion and product purifications for the mixed-feed mode are lower than those of segregated-feed mode, so the segregated-feed mode is more effective than the mixed-feed mode for the RED-IL process. The composition profile of RED-IL column of mixed-feed mode fed at tray 32 is shown in Fig. 10. Comparing with Fig. 7, we find the average concentration of n-butanol along the column is lower, while n-butyl acetate is higher, so the conversion is lower.

6 Chin. J. Chem. Eng., Vol. 19, No. 5, October Table 2 Comparison of mixed-feed mode and segregated-feed mode Operation mode Feed tray Purity of methanol Purity of n-butyl acetate Conversion of n-butanol Methyl acetate (mole fraction) (mole fraction) methyl acetate segregated-feed mixed-feed Figure 10 Liquid composition profiles for the reactive and extractive distillation column (T-1) in a mixed-feed mode methanol; n-butyl acetate; n-butanol; methyl acetate; [OMIM][PF 6 ]; [HSO 3 -bhim]hso 4 Figure 12 Effect of holdup on conversion of methyl acetate 4.3 Effects of holdup Since in a RED-IL column, the reaction may occur in the whole column, the holdups in the column are the reaction volume. The effects of holdup on purities of methanol and n-butyl acetate and conversion of methyl acetate are shown in Figs. 11 and 12. The simulations were made with the holdup on each tray changed from 15 L to 30 L, while keeping the other parameters fixed. As shown in Figs. 11 and 12, the conversions of methyl acetate and purities of methanol and n-butyl acetate increase continuously with the tray holdup, and the reaction volume increases, more reactants will be converted in unit time, so that the products can be purified to higher purities. Figure 11 Effect of holdup on the purities of methanol and n-butyl acetate methanol; n-butyl acetate 4.4 Effects of feed location As described above, the segregated-feed mode is more suitable than mixed-feed mode for the RED-IL process, so we only discuss the effects of feed location for the segregated-feed mode with the other parameters kept the same as the standard operation conditions. Two cases were investigated: (1) both the feed locations and the trays between n-butanol and methyl acetate (feed tray interval) are changed; (2) only the feed locations changes, but the feed tray interval is kept constant. For the first case, different feed tray intervals were studied. In the standard operation conditions, n-butanol is fed at tray 25 and methyl acetate is fed at tray 35 and the feed tray interval is 10. We also investigated other four situations: (1) feed tray interval 5 with n-butanol fed at tray 25 and methyl acetate fed at tray 30; (2) feed tray interval 8 with n-butanol fed at tray 22 and methyl acetate fed at tray 31; (3) feed tray interval 15 with n-butanol fed at tray 17 and methyl acetate fed at tray 32. (4) feed tray interval 20 with n-butanol fed at tray 15 and methyl acetate fed at tray 35. The results are given in Figs. 13 and 14. It can be seen that the conversion and purities of the products increase with the feed tray intervals, but the conversion and purities of the products only change slightly when the feed tray interval is greater than10. For the second case, we used different feed locations for n-butanol and methyl acetate, keeping feed tray interval at 10. The results are shown in Figs. 15 and 16. In the figures, the feed locations of methyl

7 760 Chin. J. Chem. Eng., Vol. 19, No. 5, October 2011 acetate are 10 trays below the location of n-butanol. The figures show that when n-butanol is fed at around tray 25 the purities of methanol and n-butyl acetate and the conversion of methyl acetate reach the maximum values. 4.5 Effects of entrainer ratio Figure 13 Effect of feed tray interval on the purities of methanol and n-butyl acetate methanol; n-butyl acetate Figure 14 Effect of feed tray interval on conversion of methyl acetate In order to study the effects of entrainer ([OMIM][PF 6 ]), entrainer ratio is defined as the ratio of entrainer flowrate to the flowrate of methyl acetate. When the flowrate of [OMIM][PF 6 ] varies, entrainer ratio will also change, if the other operational parameters are the same as standard condition. The effects of entrainer ratio on the purities of the products and conversion are shown in Figs. 17 and 18. The figures indicate that the purities of methanol and n-butanol and the conversion of methyl acetate increase with entrainer ratio. The volatility of the azeotropic mixtures are greatly altered by the entrainer, if the entrainer ratio increase, the concentration of entrainer in the RED-IL column also increases, the relative volatilities of methanol to methyl acetate and n-butanol to n-butyl acetate will increase, so the purities of the products (methanol and n-butyl acetate) will also increase. When the purities of the product increase in the RED-IL column, the reactants contained in the products will decrease, so that the conversion will also increase. Figure 15 Effect of feed locations on the purities of methanol and n-butyl acetate methanol; n-butyl acetate Figure 17 Effect of entrainer ratio on the purities of methanol and n-butyl acetate methanol; n-butyl acetate Figure 16 Effect of feed locations on conversion of methyl acetate Figure 18 Effect of entrainer ratio on conversion of methyl acetate

8 Chin. J. Chem. Eng., Vol. 19, No. 5, October Effects of catalyst concentration Catalyst is important for the RED-IL process, and the reaction rate in the column is greatly affected by the catalyst concentration. If other conditions are set the same as the standard conditions, the catalyst concentration in the column is determined by the flowrate of the catalyst. The catalyst we used is [HSO 3 -bhim]hso 4, and effects of catalyst flowrate are shown in Figs. 19 and 20. As shown in the figures, both the conversion of methyl acetate and the purities of methanol and n-butyl acetate increase sharply with the flowrate of the catalyst, if the flowrate of the catalyst is small ( 0.5 kmol h 1 ). However, the conversion of methyl acetate and the purities of methanol and n-butyl acetate increase smoothly with the flowrate of the catalyst, if the flowrate of the catalyst is large ( kmol h 1 ). the purities of products change only a little in such a case. 5 CONCLUSIONS A new process for transesterification of methyl acetate with n-butanol to methanol and n-butyl acetate by a reactive and extractive distillation process with ionic liquids as entrainer and catalyst (RED-IL) is proposed and investigated by numerical simulation. The simulation results indicate that: (1) RED-IL process is feasible to obtain high-purity methanol and n-butyl acetate; (2) The conversion of methyl acetate and purities of products increase with the increases of the holdup in column, the entrainer ratio and the catalyst concentration; (3) An optimal reflux ratio exists in RED-IL process; (4) The segregated-feed mode is more effective than mixed-feed mode for the RED-IL process, and there are optimal feed locations of reactants for the segregated-feed mode. REFERENCES Figure 19 Effect of catalyst flowrate on the purities of methanol and n-butyl acetate methanol; n-butyl acetate Figure 20 Effect of catalyst flowrate on conversion of methyl acetate The RED-IL process is a reaction and separation integrated process. When the flowrate of catalyst is small, the reaction rate in the column is low, so the RED-IL process is probably controlled by the reaction rate, and the conversion of the reactant and purities of the products would increase sharply with the flowrate of the catalyst. When the flowrate of the catalyst is large, the RED-IL process might be controlled by the separation process, so the conversion of reactant and 1 Beste, Y.A., Eggersmann, M., Schoenmakers, H., Method for chemically reacting and separating a mixture in a column, US Pat., Al (2006). 2 Jimenez, L., Garvin, A., Costa-Lopez, J., The production of butyl acetate and methanol via reactive and extractive distillation. I. Chemical equilibrium, kinetics, and mass-transfer issues, Ind. Eng. Chem. Res., 41, (2002). 3 Jimenez, L., Costa-Lopez, J., The Production of butyl acetate and methanol via reactive and extractive distillation. II. Process modeling, dynamic simulation, and control strategy, Ind. Eng. Chem. Res., 41, (2002). 4 Yang, B.L., Wu, J., Zhao, G.S., Wang, H.J., Lu, S.Q., Multiplicity analysis in reactive distillation column using ASPEN PLUS, Chin. J. Chem. Eng., 14, (2006). 5 Lei, Z.G., Li, C.Y., Chen, B.H., Behaviour of tributylamine as entrainer for the separation of water and acetic acid with reactive extractive distillation, Chin. J. Chem. Eng., 11, (2003). 6 Martin, M.C., Mato, R.B., Isobaric vapor-liquid equilibrium for methyl acetate + methanol + water at kpa, J. Chem. Eng. Data, 40, (1995). 7 Fuchigami, Y., Hydrolysis of methyl acetate in distillation column packed with reactive packing of ion-exchange resin, J. Chem. Eng. Jpn., 23, (1990). 8 Luyben, W.L., Pszalgowski, K.M., Schaefer, M.R., Siddons, C., Design and control of conventional and reactive distillation processes for the production of butyl acetate, Ind. Eng. Chem. Res., 43, (2004). 9 Wang, S.J., Wong, D.S.H., Yu, S.W., Design and control of transesterification reactive distillation with thermal coupling, Comput. Chem. Eng., 32, (2008). 10 Wang, S.J., Huang, H.P., Yu, C.C., Design and control of a heat-integrated reactive distillation process to produce methanol and n-butyl acetate, Ind. Eng. Chem. Res., 50, (2011). 11 He, J., Xu, B.Y., Zhang, W.J., Zhou, C.F., Chen, X.J., Experimental study and process simulation of n-butyl acetate produced by transesterification in a catalytic distillation column, Chem. Eng. Process., 49, (2010). 12 Han, X., Armstrong, D.W., Ionic liquids in separations, Acc. Chem. Res., 40, (2007). 13 Rogers, R.D., Voth, G.A., Ionic liquids, Acc. Chem. Res., 40,

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