Carboxylic acid esters are important intermediates in chemical and pharmaceutical industries and mostly produced by esterification reaction. As a reversible reaction, it is beneficial to drive the reaction equilibrium forward by removing one of the products. In this paper, vapor permeation (VP) using NaA zeolite membrane was proposed to intensify the esterification reaction by removing the produced water in a timely manner. The prepared NaA zeolite membrane was characterized by scanning electron microscopy (SEM) images and VP of water/n-propanol mixtures. It showed that the used NaA zeolite membrane had a high selectivity for removing water from the water/n-propanol mixtures. The effects of the reaction temperature, initial molar ratio of reactants, and catalyst loading on the esterification coupled with VP were investigated. It was found that the reaction temperature, initial molar ratio of reactants, and catalyst loading had a significant effect on the conversion of the reaction and the permeate flux. As for the esterification coupled with VP, the final conversion of the reaction increased from 78.2% to 98.6% at alcohol/acid molar ratio 2:1 at 373 K in 420 min. The NaA zeolite membrane showed good VP performance after 400 h.

Sulfated zirconia catalysts are proposed for the reversible hydrolysis of ethyl lactate instead of liquid acids. Sulfated zirconia catalysts were prepared by precipitation-impregnation method. The zirconium hydroxide was produced from zirconium oxychloride by adding aqueous ammonia and then impregnated in sulfuric acid. The solid samples were obtained by filtration and evaporation of the mixtures, respectively. After the samples were calcined, the sulfated zirconia catalysts were prepared. The results showed that the catalyst prepared by evaporation has higher catalytic activity. The physicochemical characteristics of the sulfated zirconia catalysts were studied by thermal analysis, X-ray powder diffraction (XRD), temperature programmed desorption of ammonia (NH3-TPD) and N2 adsorption-desorption, respectively. By the precipitation-impregnation-evaporation method, the optimal sulfated zirconia catalyst of tetragonal phase was prepared under liquid-solid ratio of 5ml/g, 1 mol/L of H2SO4 and calcination at 650 °C for 3 h. The conversion of the ethyl lactate was 87.8% in 3 h at 85 °C with the catalyst loading 2 wt% and initial molar ratio of water to ethyl lactate 20: 1.