Acylation of aromatic compounds on H-Beta zeolites

Friedel-Crafts acylation of anisole by acetic anhydride and the Fries rearr angement of phenyl acetate were investigated in the liquid phase using the H-form of various zeolites. Zeolite Beta was found to be the most active ca talyst for acylation reactions compared to Y- and ZSM-5 zeolites. The react ions were found to be controlled by mass transfer limitations caused by cok e deposition. Two types of coke (extractable and non-extractable) were iden tified. Combining liquid phase reaction with continuous extraction of the c atalyst with refluxing reaction mixture in a Soxhlet-like reactor led to a higher conversion of phenyl acetate in the Fries rearrangement. The ratio o f protonated to acylated surface centres strongly determines the selectivit y. The formation of o-hydroxyacetophenone proceeds both via intramolecular rearrangement and intermolecular acylation. On the other hand, p-hydroxyace tophenone is formed entirely by intermolecular acylation. (C) 1999 Elsevier Science B.V. All rights reserved.