Oxidation of benzene to phenol with hydrogen peroxide catalyzed by heteropolymolybdovanadophosphoric acids

The oxidation of benzene to phenol with hydrogen peroxide was carried out by using Keggin-type H3+nPMo12-nVnO40 (n=0-4; abbreviated by PMo12-NVn) in a water-benzene biphase system. The hydroxylation reaction proceeded with the decomposition of hydrogen peroxide and a fairly good correlation was observed for the catalytic activity between them. The catalytic activity for the hydroxylation at 65 degrees C changed in the order of PMo10V2 approximate to PhMo9V3> PMosV4> PMo11V>>PMo12. The maximum yield of phenol for PMo9V3 on H2O2-basis was 36%. The slow addition of diluted aqueous hydrogen peroxide resulted in the great increase in the phenol yield and those for PMo10V2 and PMo9V3 were 91-93% on H2O2-basis with 100% selectivity to phenol (benzene basis). The yield of phenol reached the maxima around 45-65 degrees C. When the slow addition of hydrogen peroxide was repeated, the phenol yield increased significantly.