Friedel-Crafts acylation of benzene (BEN) with benzoic anhydride (BAN) to produce benzophenone (BPH) was studied over various ion-exchanged heteropoly acids (HPA). No metal chloride such as AlCl3 was used as a catalyst. No acid chloride was used as an acylating agent. Therefore, this reaction could be a model of chlorine-free fine chemical synthesis process. As the activity of benzene was lower than that of toluene, a higher reaction temperature, above boiling point of benzene, was required. Effects of partial ion exchange with Na, K, Cs, and Mg on HPA were tested with an autoclave reactor. Among tested catalysts, the insoluble H0.5SCs2.5PW12O40 catalyst showed the highest activity. The catalyst was active for the second run, but the activity gradually decreased at the third run. Adsorption of produced ketone and benzoic acid (BAC) on the catalyst was proposed as the reason for the deactivation. (C) 2003 Elsevier B.V. All rights reserved.