Intensifying esterification reaction between lactic acid and ethanol by pervaporation dehydration using chitosan-TEOS hybrid membranes

摘要

Esterification assisted by pervaporation separation can enhance the yield of ester for thermodynamically or kinetically limited reaction via selective removal of water from the reaction mixture. In the present study, organic-inorganic hybrid membranes were prepared by in situ hydrolysis and condensation of tetraethoxysilane (TEOS) within chitosan (CS) aqueous solution for pervaporation-assisted esterification of lactic acid with ethanol, catalyzed by Amberlyst 15 ion-exchange resin. The composition and structural properties of CS-TEOS hybrid membranes were investigated by FT-1R, XRD, TGA and contact angle. The dehydration performances of hybrid membranes were evaluated by pervaporation of aqueous ethanol solution. Comparing with CS pristine membrane, CS-TEOS hybrid membranes exhibited remarkably enhancing pervaporation property. Pervaporation-assisted esterification results suggested that the incorporation of pervaporation process to preferentially remove water from the reaction mixture substantially enhanced the yield of ethyl lactate from 66wt.% to 80wt.%. The effects of membrane casting solution recipe, reaction temperature, initial molar ratio of ethanol to lactic acid and catalyst loading amount on the process performance have been examined in detail.