Ethyl lactate production via esterification of lactic acid with ethanol combined with pervaporation

Abstract

The synthesis of ethyl lactate from ethanol and lactic acid has been studied in a batch reactor combined with a pervaporation unit. The commercial acid resin Amberlyst 15 and the hydrophilic membrane PERVAP ® 2201 were used in the experiments. First esterification–pervaporation experiments were performed for dilute lactic acid aqueous solutions. Results show that the yield of ethyl lactate exceeds the corresponding thermodynamic equilibrium via selective removal of water from the reaction mixture through the membrane. If the process is performed sufficiently long, near total use of lactic acid could be reached. The water production and removal rates obtained from independent reaction and pervaporation experiments were used to simulate the behavior of the coupled system. The simulation results reveal the same trend observed in the experiments. The influence of different kinetic and pervaporation parameters such as initial reactant molar ratio, amount of catalyst, temperature and the ratio of membrane area/initial volume of reaction was analyzed in terms of ethyl lactate yield. For dilute lactic acid aqueous solutions the effect of catalyst loading has been found not to have a great influence, unlike the other parameters. Additionally the effect of the initial concentration of lactic acid aqueous solution was evaluated by performing experiments with different lactic acid aqueous solutions concentrations (20, 50 and 79–81 wt%). Initial water content has a great influence since total permeation is proportional to water concentration in the reactor.