Improved conversion to ethyl acetate through removal of water of esterification by membrane pervaporation

Abstract

Crosslinked poly (vinyl alcohol) (PVA) membranes were prepared using maleic acid (MA) and citric acid (CA) as crosslinking agents. First the water separation ability of the crosslinked membranes from aqueous acetic acid (10-90% acetic acid) and ethanol (20-80% ethanol) solutions at 30 to 90ºC was tested by pervaporation. The effects of temperature, feed concentration, crosslinker type on pervaporation characteristics were investigated. The PVAMA membrane showed separation factors of 1.9-16.2 and fluxes of 4.26-38.48 kg/m² h and PVACA membrane showed separation factors of 3.8-33 and fluxes of 2.17-480.8 kg/m² h for acetic acid-water separation. In case of ethanol-water separation, the PVAMA membrane showed separation factors of 0.7-17.9 and fluxes of 2.5-36.2 kg/m² h and PVACA membrane showed separation factors of 1.4-41.9 and fluxes of 3.8-359.7 kg/m² h. PVACA membrane has shown high separation efficiency of water than that of PVAMA membrane. Having high selectivity and good permeating ability for water both the membranes were then used to remove water of esterification from reaction of acetic acid with ethanol by a batch pervaporation. Compared to around 60% conversion in conventional esterification, up to 98% conversion to ethyl acetate was achieved from ethanol and acetic acid when water by product was removed by pervaporation using the prepared membranes at same temperature.