P-methyl acetephenone synthesis from toluene and acetic anhydride over HPW(H3PW12O40)/TiO2 was carefully studied, and catalysts were characterized by BET, XRD and NH3-TPD. The characterized results displayed that the interaction between HPW and TiO2 prevented the loss of acidic protons from HPW to form the weak Lewis acid sites over HPW/TiO2. The weak acid sites over HPW/TiO2 came into being in case of much more HPW being loaded onto TiO2 or HPW/TiO2 being calcined at high temperature. The reaction results suggest that p-methyl acetephenone yield and selectivity depended on the acidity of catalysts, and the appearance of weak Lewis acid sites over HPW/TiO2 resulted in p-methyl acetephenone yield decline. (C) 2011 Elsevier B.V. All rights reserved.