Origin of the Deactivation of HBEA Zeolites During the Acylation of Phenol with Phenylacetate

During the transformation of a phenol–phenylacetate mixture over a HBEA zeolite (Si/Al=10), carried out in a batch reactor at 160°C in sulfolane or in dodecane solvents, a rapid initial decrease in the formation of hydroxyacetophenones is observed. The compositions of the reaction mixture, of the organic material recovered in methylene chloride by a direct soxhlet treatment and of the compounds retained in the zeolite pores (`coke') were compared after 2 h and 24 h reaction. `Coke' is mainly constituted of phenol and hydroxyacetophenones and of a small amount of heavy secondary reaction products: bisphenol A and acylated derivatives, hydroxy or acetoxy phenylbenzoate, hydroxy or acetoxydypnone, 2 methyl coumarine and 4 methyl chromone, and of sulfolane but not of dodecane. Only a very small quantity of phenylacetate is found. The rate of hydroxyacetophenone formation depends on the order of introduction of the reactants. It is shown that the rapid initial deactivation is not due to the heavy reaction products but to the limitations by phenols (reactant and products) of the access of phenylacetate to the inner acid sites.