Hydrolysis of ethyl lactate coupled by vapor permeation using polydimethylsiloxane/ceramic composite membrane

As a reversible reaction, the hydrolysis conversion of ethyl lactate is controlled by thermodynamic equilibrium. In order to improve the yield and conversion rate of hydrolysis of ethyl lactate, ethanol in the products should be removed in time. Hydrolysis of ethyl lactate coupled by vapor permeation (VP) for removing ethanol in the products was proposed. Here, the vapor permeation was carried out with a new polydimethylsiloxane (PDMS)/ceramic composite membrane prepared by our team. The PDMS/ceramic composite membrane was first characterized by scanning electron microscopy (SEM) images, pervaporation, and vapor permeation of ethanol/water mixtures. The characterization results showed that the PDMS/ceramic composite membrane was dense and uniform and had good separation performances. The permeate flux of pervaporation of 5 wt % ethanol arrived at 2541 g·m^-2·h^-1, and the separation factor was 7.5 at 353 K. As for vapor permeation of 10 wt % ethanol, the permeate flux was above 400 g·m^-2·h^-1 and separation factor was around 11. Then, the VP aided hydrolysis of ethyl lactate was investigated with the prepared PDMS/ceramic composite membrane. By coupling with VP, the final conversion of the ethyl lactate increased from 77.1% to 98.2% with the initial molar ratio of water to ethyl lactate 10:1 at 358 K. The larger initial molar ratio of water to ethyl lactate was helpful to improve the conversion of VP aided hydrolysis of ethyl lactate. The VP aided hydrolysis of ethyl lactate with the prepared PDMS/ceramic composite membrane was significantly enhanced.