Silica-Supported Heteropoly Acid Catalyst for Liquid-Phase Friedel-Crafts Reactions

Article abstract of DOI:10.1246/bcsj.62.2159

Silica-supported Keggin-type heteropoly acids such as 12-tungstophosphoric, molybdophosphoric, and tungstosilicic acids efficiently catalyzed Friedel-Crafts alkylation and acylation reactions of aromatic hydrocarbons with 1-octene, benzyl chloride and benzoyl chloride in the liquid phase.The catalytic activity of heteropoly acid was generally enhanced when supported on silica.Silica-supported tungstosilicic acid worked as an insoluble heterogenous catalyst even to the acylation of p-xylene with benzoyl chloride or benzoic anhydride, though deactivation was observed during repeated use.Considering that supported p-toluenesulfonic acid, an ordinarily used typical strong protonic acid, was far less active than the supported heteropoly acid, the high catalytic efficiency revealed by heteropoly acid appears to be due to a unique property of heteropoly anion which can stabilize alkyl and acyl cations as the reaction intermediates.