In this study, the esterification of isopropanol and propionic acid, in a system coupled with the vapor permeation process was investigated. For this purpose, two different commercial membranes, a tubular NaA zeolite membrane and a flat polymeric membrane (PERVAP ® 2201), were used in the vapor permeation module to remove water from the reaction atmosphere during the synthesis of isopropyl propionate. The reaction was carried out in a batch reactor using 3 wt.% (relative to propionic acid) of para toluene sulfonic acid (PTSA) and 3, 4, 10 and 12 wt.% of Amberlyst 15 as catalyst. Adding the membrane process with both the zeolite and polymeric membranes significantly increased acid conversion during the reaction. For example, for the reaction with PTSA as catalyst, the equilibrium conversion without using membrane process, reached about 72% at the alcohol/acid molar ratio of 1.5:1. But, adding the membranes process to the system for simultaneous selective water removal form reaction media gave complete acid conversion in a reasonable shorter time. Study on the effect of alcohol/acid molar ratio with three different values of 1:1, 1.5:1 and 3:1 showed that this ratio had considerable effect on the acid conversion and on the amount of remained water in the reaction mixture during the process. The highest reaction rate was seen for alcohol/acid molar ratio of 1.5:1 for all configurations of the membranes and catalysts. However, increasing this ratio from 1.5:1 to 3:1 did not make a positive effect on the reaction conversion, but rather decreased it. The effect of catalyst loading was investigated by varying the catalyst weight of Amberlyst 15 from 3 to 12 wt.%. It was found that increasing catalyst loading had a significant positive effect on the acid conversion, which was in agreement with the findings of other researchers. In general, in the hybrid process with high acid conversion, the zeolite membrane showed superior results, due to the swelling effects for the polymeric membrane at aqueous mixture. Moreover, based on the mechanism of the esterification reaction, extra acid conversions were obtained by using PTSA as the catalyst. For example, at the same experimental conditions, using 3 wt.% of Amberlyst 15 and PTSA as catalysts, gave 50% and nearly 100% of acid conversions after 180 and 140 minutes from beginning of the process, respectively. No specific trend was observed in the results obtained for the separation factors. This was due to the fact that separation factor in the coupled process was affected by two phenomena of reaction and separation. These two processes are influenced by some parameters such as the rate Keywords : Esterification, Membrane Reactor, Zeolite Membrane, PERVAP ® 2201, Isopropyl propionate.
