Friedel–Crafts benzoylation of diphenyl oxide over zirconia supported 12-tungstophosphoric acid

Abstract

Liquid phase benzoylation of diphenyl oxide (DPO) to 4-(benzoyl)-diphenyl oxide (p-isomer) with benzoyl chloride (BC) has been investigated with 12-tungstophosphoric acid supported on zirconia (TPA/ZrO2) as the catalyst. Among the catalysts, 15 wt.% TPA/ZrO2 calcined at 750 ◦C is found to be more active than others in the benzoylation reaction. The acid strengths of different TPA loaded catalysts are estimated by TPD of NH3 and among these 15 wt.%TPA/ZrO2 calcined at 750 ◦C has the highest acidity and hence more active in the reaction. The optimization of reaction conditions of benzoylation of DPO by BC is performed with 15 wt.%TPA/ZrO2 calcined at 750 ◦C (higher acidity) by varying catalyst concentration, 1–5 (wt.% of reaction mixture), temperature, 100–140 ◦C and DPO:BC molar ratio 1–15. Under the optimized reaction conditions, conversion of benzoyl chloride (39.3%) gave high selectivity to 4-(benzoyl) diphenyl oxide (97.4%) and remaining 2-(benzoyl) diphenyl oxide in 3 h. The reaction is found to be heterogeneously catalyzed and no contribution from homogeneous (leached) TPA into reaction medium.