Preparation of Cs–La–Sb/SiO2 catalyst and its performance for the synthesis of methyl acrylate by aldol condensation

Abstract

A variety of cesium supported catalysts with amorphous SiO₂ as a carrier were prepared by vacuum impregnation and ultrasonic impregnation methods, which were used for the synthesis of methyl acrylate by aldol condensation of methyl acetate and formaldehyde. The as-prepared catalysts were characterized by XRD, N₂ adsorption–desorption, NH₃-TPD, CO₂-TPD, XPS, ICP and TG. The results indicated that the bifunctional Cs–La–Sb/SiO₂ showed a high conversion of methyl acetate as well as a high yield of methyl acrylate, which was attributed to the weak acid–base sites and the formation of basic Cs–O–Si species with the addition of antimony and lanthanum, respectively. Furthermore, Cs–La–Sb/SiO₂-(V) prepared by vacuum impregnation showed a high initial catalytic activity, but its activity sharply decreased due to the loss of active species. Comparatively, Cs–La–Sb/SiO₂-(U) prepared by ultrasonic impregnation showed a good stability owing to the cavitation effect of ultrasonic waves. The conversion of methyl acetate and yield of methyl acrylate remained above 20% and 9.0% (based on methyl acetate) for 100 h without obvious deactivation. Moreover, carbon deposition was the main factor for the deactivation of Cs–La–Sb/SiO₂-(U), and the coked catalyst could be regenerated by calcination in air.