Highly selective vapor phase Fries rearrangement of phenyl acetate to 2-hydroxyacetophenone using H3PO4/ZrO2–TiO2

ZrO₂–TiO₂ mixed oxides with a Ti and Zr molar ratio of 1/1 were prepared with and without surfactant by the sol–gel method. Catalysts containing 5–35% H₃PO₄ were prepared using these mixed oxides and the catalytic performance of each material for vapor phase Fries rearrangement of phenyl acetate (PA) to 2-hydroxyacetophenone (2-HAP) was determined. At optimized conditions, the conversion of PA over 15 wt.% H₃PO₄/TiO₂–ZrO₂-surf and 15 wt.% H₃PO₄/TiO₂–ZrO₂varied between 91% and 85.2% and selectivity to 2-HAP was between 81.9% and 48.3%, respectively. In all cases, the formation of 2-HAP was clearly favored in comparison to that of para isomer. The 4-HAP in the improved conditions was about 1.1%. In comparison with other catalysts, the percentage of phenol in the optimized condition was lower than 16%. The solvent effect on Fries rearrangement was investigated and dichloromethane showed better results. The Fries rearrangement was carried out in the temperature range of 473–673 K.