Gas-Liquid-Solid Three-Phase Catalyzed S-Methylation of Thiophenol with Dimethyl Carbonate in a Fixed-Bed Reactor: Catalytic Performances of Activated Alumina Supported Alkali Metal Carbonate Catalysts

The catalytic performances of activated alumina and its supported alkali metal carbonate catalysts for the reaction of thiophenol with dimethyl carbonate to prepare thioanisole (PhSMe) were investigated on a fixed bed reactor under the condition of atmospheric pressure. The properties of activated alumina and its loading alkali metal carbonate catalysts were characterized via IR, BET and XRD. The effect of loading amount of alkali metal carbonate, calcination temperature, reaction temperature and liquid volume hourly space velocity (LVHSV) of reactants on the catalytic performances of the catalysts was also examined. The yield of PhSMe was 93.5% when activated alumina was used as catalyst alone at 120 °C, however, the catalytic activities of the catalysts after loading 5-15 wt% K2CO3 were greatly improved, and the yield of PhSMe was 99-100%. Compared to activated alumina, the catalytic performances of catalysts after loading different alkali metal carbonate are greatly improved. The improvement of catalytic performance can be attributed to that carbonate may occupy the Lewis acid sites of the activated alumina surface, making it easier for the catalyst to activate thiophenol, thus giving benzenethiolate a stronger nucleophilic attack ability. The results of FTIR analysis show that the characteristic peaks of carbonate are blue shifted, also indicating that carbonate reacted with the surface of activated alumina. The Lewis basic site on the surface of the activated alumina is believed to play a crucial role.

YUCHEN WU, FENGHUA ZHANG, FEI LI, HENG JIANG, RUI WANG, HONG GONG