Article pubs.acs.org/IECR
Reactive Distillation Using an Ion-Exchange Catalyst: Experimental and Simulation Studies for the Production of Methyl Acetate K. Sandesh, P. E. JagadeeshBabu,* Suhas Math, and M. B. Saidutta Department of Chemical Engineering, National Institute of Technology Karnataka, Surathkal, Mangalore, India ABSTRACT: In this study, the performance of a packed-bed reactive distillation (RD) column for the production of methyl acetate (MeOAc) using an ion-exchange catalyst and simulation of the same using CHEMCAD were analyzed. An ion-exchange catalyst, Indion 190, was used in this study. The performance of the RD column was evaluated based on the MeOAc concentration in the top product. Both steady- and unsteady-state behavior of the column was simulated using CHEMCAD, and the results were experimentally validated. The process parameters, viz., reboiler temperature, enriching temperature, reactor temperature, catalyst loading, molar ratio of the reactant, and flow rate of reactants, were studied, and the optimal values were found to be 73 °C, 56 °C, 72 °C, 100 g, 1:2, and 15 mL/min, respectively. Feed locations of acid and alcohol to the reactor that gave maximum MeOAc concentration in the top product were determined. A mathematical model based on the rigorous calculation using SCDS (used to calculate the nonideal K value) was used to simulate the RD in CHEMCAD. The simulated values were found to deviate from the experimental values within ±5−10%. phase esterification reaction.17,18 There are a few reports in the literature on the recovery of lactic acid, adipic acid, myristic acid, succinic acid, chloroacetic acid, glycolic acid, and trifluoroacetic acid from their dilute solutions using an ionexchange catalyst in a RD column.19−21 The kinetics of HOAc esterification reaction using an ion-exchange catalyst was studied by Xu and Chuang22 and JagadeeshBabu et al.23 A generalized methodology to model and simulate a RD column for the production of a particular compound and the reaction feasibility study in the RD column are limited.24−26 In the present work, the performance of a RD column to synthesize MeOAc by esterification of HOAc with MeOH in the presence of an ion-exchange acid catalyst (Indion 190) is investigated. The effect of various operating parameters such as the reboiler duty, reactor temperature, molar ratio of the reactants, feed flow rate, feed location, and catalyst loading on the purity of MeOAc was studied in a RD pilot plant. Simultaneously, the performance of a RD column for the production of MeOAc using an ion-exchange acid catalyst was simulated using CHEMCAD and the simulated results were validated using experimental results. On the basis of this comparison, an algorithm has been developed to analyze the performance of RD in CHEMCAD.
1. INTRODUCTION Reactive distillation (RD) is a combination of physical separation and chemical reaction in a single unit operation, which is basically a method of process intensification. Process intensification of reaction and separation as RD improves the process and leads to improvement in the selectivity, conversion, heat control, and effective utilization of reaction heat. RD can handle difficult separations and in many cases avoid the formation of azeotropes. RD has been successfully optimized for the production of certain bulk chemicals such as methyl tertbutyl ether (MTBE),1 ethyl tert-butyl ether (ETBE),2 Nylon 66,3 isopropyl palmitate,4 n-hexyl acetate,5 etc. As a result, RD is being explored as a potential source for many catalytic reversible reactions such as esterification,6,7 transesterification,8 and etherification. Methyl acetate (MeOAc), synthesized by esterification of acetic acid (HOAc) with methanol (MeOH) and catalyzed using a strong acid catalyst, finds wide application in the fine chemical industry. MeOAc is widely used as a solvent in the production of coating materials, nitrocellulose, cellulose acetate, cellulose ethers, and celluloid. It is also used with a wide variety of resins, plasticizers, lacquers, and certain fats.9 High-purity MeOAc is used as an intermediate in the production of a variety of polyesters.10 Esterification of HOAc with MeOH is an extremely slow reaction11 in the absence of catalyst because the rate of reaction depends on the autoprotolysis of carboxylic acid. To enhance the rate of reaction, an acid catalyst is generally used, which acts as a proton donor to carboxylic acid. In general, many have used a homogeneous acid catalyst for the production of MeOAc because of its high catalytic activity.11,13−15 The major disadvantages of a homogeneous acid catalyst are its high corrosive nature, the occurrence of side reactions, and the separation of the catalyst from the reaction medium.12,15−17 Heterogeneous acid catalysts can be used to catalyze the reaction to overcome the disadvantages of a homogeneous acid catalyst. Ion-exchange resins are the most commonly used heterogeneous catalysts especially for liquid© XXXX American Chemical Society
2. MATERIALS AND METHOD 2.1. Chemicals. Chemicals used in this study were purchased from different industries: acetic acid (HOAc, glacial, 99%) from Nice Chemical, Cochin; methanol (MeOH, 99%) and methyl acetate (MeOAc, 99.8%) from Merck Limited, Mumbai. Received: October 24, 2012 Revised: March 19, 2013 Accepted: April 17, 2013
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dx.doi.org/10.1021/ie3029174 | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX
Industrial & Engineering Chemistry Research
Article
2.2. Catalyst. In this work, a macroporous strong acidic cation-exchange resin (Indion 190) was used as the catalyst. Indion 190 was purchased from Ion Exchange India Ltd., Mumbai. Indion 190 is a cross-linked three-dimensional polymeric material obtained by sulfonation of polystyrene and divinylbenzene (DVB). These resins were dried in an oven at 90 °C to completely remove its moisture content before using it in the reactor. The detailed properties of the ionexchange resin are listed in Table 1. Table 1. Properties of the Ion-Exchange Resin Indion 190 parameter
specification
appearance resin type matrix functional group ionic form concentration of acid sites moisture content particle size >1.2 mm
