The Fries rearrangement of phenylacetate has been studied in the vapor-phase at 623 K over a series of surface modified and unmodified ZSM-5 (Si/Al = 60-170) loaded with H3PO4, differing in the external surface treatment of the zeolites. When the external surface of the zeolite is blocked with a surfactant before loading it with H3PO4, the selectivity to form the 4-hydroxyacetophenone was higher. This superior performance of the externally blocked catalysts, relative to the unmodified H3PO4/ZSM-5 catalyst, shows that by blocking the external surface area of the ZSM-5 support, it exhibits a superior catalytic selectivity than the unmodified catalyst. Catalysts containing 0-4.9 wt.% P were prepared using modified and unmodified ZSM-5 zeolites, and their catalytic performance for vapor-phase Fries rearrangement of phenylacetate to 2-hydroxyacetophenone (2-HAP), 4-hydroxyacetophenone (4-HAP) and 4-acetoxyacetophenone (4-AAP) was determined. The influence of the operating parameters on the performance of H3PO4/ZSM-5-surf catalysts was also investigated. (c) 2005 Elsevier B.V. All rights reserved.