A new method for the synthesis of molybdovanadophosphoric heteropoly acids and their catalytic activities

Abstract

An environmentally benign method for the synthesis of heteropoly acids H_3+nPMo_{12 n}V_nO₄₀·xH₂O (PMoV_n, n = 1−3) was developed by the reaction of an aqueous slurry which contained stoichiometric amounts of MoO₃, V₂O₅ and H₃PO₄. Characterization of the as-synthesized catalysts with inductively coupled plasma (ICP) elemental analysis, thermogravimetry (TG), X-ray diffraction (XRD) and infrared (IR) spectroscopy indicated that V ions substituted for Mo ions in Keggin-type phosphomolybdic acid. The as-synthesized samples were found to be an efficient catalyst for the hydroxylation of benzene which was carried out in a mixed solvent of acetonitrile and acetic acid with aqueous hydrogen peroxide as oxidant. PMoV₂ exhibi ted the highest benzene conversion of 34.5% with phenol selectivity of 100%.