Effects of Dehydration Rate on the Yield of Ethyl Lactate in a Pervaporation-Assisted Esterification Process

Esterification of lactic acid and ethanol is typically a reversible reaction. The yield of ethyl lactate is low due to the limitation of chemical equilibrium. In this study, pervaporation composite membranes (glutaral crosslinked chitosan (GCCS)/carbomer (CP)/polyacrylonitrile (PAN), glutaral crosslinked gelatin (GCGE)/PAN, and glutaral crosslinked hyaluronic acid (GCHA)/hydrolysis modification (HM-PAN) inspired by the bioadhesion phenomena were fabricated and used for the synthesis of ethyl lactate, which could promote the reaction by removing the water perferentially. The influence of dehydration rate on chemical equilibrium shift in different operating conditions was investigated. Pervaporation-assisted esterification results suggested that the yield of ethyl lactate was determined by the match between reaction rate and dehydration rate. The process is controlled by the reaction rate initially and the dehydration rate as time goes by. The incorporation of the pervaporation process could break the limit of initial chemical balance, and the yield of ethyl lactate was substantially enhanced by 28.2%. Furthermore, the optimum technological parameter for the coupling process was confirmed, and the yield of ethyl lactate reached 94.9% after 8 h.