Mechanism of Phenylacetate Transformation on Zeolites

Summary The transformation of phenylacetate was carried out over two zeolites: HY (Si/Al = 20) and HZSM5 (Si/Al = 40) at 400°C under atmospheric pressure. The reactivities of the products and intermediates were also studied under the same conditions. On both catalysts the main product was phenol which means that ketene was also formed. HY led mainly to ortho-hydroxyacetophenone while HZSM5 gave both ortho- and para-hydroxyacetophenones in equal amounts. 2-Methylchromone and 4-methylcoumarine were formed on HY only and supposedly resulted from an intramolecular condensation of ortho-acetoxyacetophenone which was not observed among the products. On HZSM5 dehydroacetic acid and 4-acetoxy 6-methyl 2-pyrone were formed presumably through autocondensation of ketene. Para-acetoxyacetophenone was observed on both catalysts. Water had practically no effect on the activity and selectivity of HY while it increased the stability of HZSM5 markedly.