Liquid phase acetylation of thioanisole with acetic anhydride to 4-(methylthio) acetophenone (4-MTAP) using H-beta catalyst

Abstract

Acetylation of thioanisole (TA) with acetic anhydride (AA) to give p-(methylthio) acetophenone (4-MTAP) has been investigated using different solid acid catalysts such as H-Y, H-ZSM-5, H-mordenite and H-beta in liquid phase conditions. The reaction is studied in the temperature range 80–180 °C in a pressure reactor under nitrogen atmosphere. Among the catalysts tested, H-beta is found to be more active and shape selective than other zeolite catalysts. The conversion of TA (32 mol%) with a turnover frequency, TOF, 30.6 (10 −4 s −1 mol −1 Al) gave exclusively 4-MTAP (99.9%) and the other o-(methylthio) acetophenone (2-MTAP) over H-beta at 150 °C after 2 h. Acidity and structural features of zeolites play an important role in the conversion and product distribution in acetylation of TA. The effect of AA/TA molar ratio, catalyst concentration and reaction temperature have been optimized to get higher conversion of TA and product selectivity. Efficient utility of AA has been established in the reaction. H-beta catalyst has been reused in few cycles after regeneration by washing with ethyl acetate followed by calcination at 500 °C for 4 h without loss in its activity.