Acylation of p-xylene over zeolites

Zeolites differing in structure and acidity were tested in liquid phase acylation of p-xylene. Hexanoyl chloride, propionic anhydride and isobutyric anhydride were used as acylating agents. The highest conversions of acylating agent were achieved over large pore zeolites USY (66.3%) and Beta (58.2%). It was found that acylation of p-xylene proceeds only over large pore zeolites Beta and USY. Selectivities to monoacylated p-xylene obtained over USY zeolite decreased in the order: propionic anhydride 78.0% > hexanoyl chloride 67.2% > isobutyric anhydride 33.1%. Diacylated product was formed over zeolite USY with all acylating agents tested but only with hexanoyl chloride over zeolite Beta. It was found that the optimum Si/Al ratio of zeolite Beta for p-xylene acylation with propionic anhydride is 25, while for isobutyric anhydride is 19. Conversion of isobutyric anhydride decreased with increasing isobutyric anhydride concentration and increased with increasing amount of catalyst.

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► The acylation of p-xylene with acid anhydrides and acyl chlorides over different structural types of zeolites was studied.
► The effect of the catalyst structure, its acidity and type of acylating agent on the conversion and selectivity in p-xylene acylation was tested.
► The effect of amount of the catalyst, the molar ratio acylating agent/substrate on the course of the reaction were investigated.