Two different commercial (tubular NaA zeolite and flat polymeric (PERVAP (R) 2201)) membranes were used in a vapor permeation process 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 as the catalyst. Effects of membrane type and initial alcohol/acid molar ratio on the performance of the combined process were investigated. Experiments were carried out with three different levels of alcohol/acid molar ratio. It was found that the coupled process was generally capable of enhancing the conversion of reversible esterification reaction. However, complete acid conversion was achieved in a shorter period of time with zeolite membrane than with polymeric membrane. In addition, initial molar ratio of the reactants had a strong effect on both acid conversion and on water flux through the membranes. (C) 2010 Elsevier B.V. All rights reserved.