Stoichiometric Ester Condensation Reaction Processes by Pervaporative Water Removal via Acid-Tolerant Zeolite Membranes

Abstract

We successfully developed a pervaporation-aided (PV-aided) dehydration reaction process that enabled ester condensation reactions stoichiometrically at nearly room temperature. The reactions were conducted at nearly room temperature, lower than 323 K, by the help of effective water removal by PV at that temperature. Zeolite membranes we developed consist of acid-tolerant hydrophilic zeolites, which have excellent permselectivity of water, even with coexistence of methanol. The acid-tolerant nature of membranes enabled stable and continuous dehydration via PV during the reaction. The advantage of the PV-aided dehydration reaction became apparent in ester condensation reactions with alcohols, in which the ester yields exceeded by >20% from equilibrium conversion without distillation. Also, compared with the conventional reactive distillation process (Eastman Process), our reaction process does not alter the volatility of the product, because water is removed from the reaction system in any combination of substrates. We regard that the reaction process will show advantages for the dehydration reaction dealing with lower alcohols (methanol, ethanol, etc.), such as free acid treatment in biodiesel fuel (BDF) production processes or perfume synthesis.