SURFACE COMPLEXES IN ZEOLITE-CATALYZED ACYLATION REACTIONS DETECTED BY C-13 MAS NMR-SPECTROSCOPY

The state of the acylating agent acetyl chloride, adsorbed on a series of proton and metal ion exchanged zeolites X, Y (faujasite) and ZSM-5 , was investigated by C-13 MAS NMR spectroscopy. The observed carbonyl signals were assigned to two species: chemisorbed acetyl chloride bou nd to lattice oxygen (signals near 182 ppm), and acetyl chloride compl exed with counter cations in the lattice (signals near 172 ppm). In a few cases signals were observed which have been assigned to ''free'' a cylium cation stabilized on the surface of the solid (signal 160-165 p pm). Experiments in which toluene was adsorbed on to ZnY pretreated wi th acetyl chloride showed the participation of various adsorbed specie s in the acylation reaction of toluene.