Liquid-phase oxygenation of benzene over supported vanadium catalysts

The liquid-phase oxygenation of benzene was studied using supported vanadiu m(v) catalysts. Molecular oxygen and ascorbic acid were used as the oxidant and reducing reagent, respectively. The reduced vanadium species is sugges ted to be the active catalytic species in this reaction system. The catalyt ic activity of the supported V catalysts for phenol formation was found to be somewhat higher than those of supported Cu counterparts. The addition of Cu ions to the supported V catalyst caused an increase in the yield of phe nol. The leaching of the catalytically active V species from the support du ring the liquid-phase oxidation was also inhibited by the addition of Cu io ns to the supported V catalysts. The concentration of acetic acid in the aq ueous solvent was found to have an optimum value for the phenol production. The formation of hydrogen peroxide was observed during the benzene oxidati on catalyzed by the supported V catalyst, and the accumulated amount of the formed hydrogen peroxide was quantitatively detected by iodometry. The ele ctronic absorption spectra of the reaction solution including the V species also indicated the formation of hydrogen peroxide during the benzene oxida tion. The produced hydrogen peroxide was suggested to directly participate in the phenol formation from benzene.