Liquid-phase oxygenation of benzene over supported vanadium catalysts

Abstract

The liquid-phase oxygenation of benzene was studied using supported vanadium(V) catalysts. Molecular oxygen and ascorbic acid were used as the oxidant and reducing reagent, respectively. The reduced vanadium species is suggested to be the active catalytic species in this reaction system. The catalytic 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 phenol. The leaching of the catalytically active V species from the support during the liquid-phase oxidation was also inhibited by the addition of Cu ions to the supported V catalysts. The concentration of acetic acid in the aqueous solvent was found to have an optimum value for the phenol production. The formation of hydrogen peroxide was observed during the benzene oxidation catalyzed by the supported V catalyst, and the accumulated amount of the formed hydrogen peroxide was quantitatively detected by iodometry. The electronic absorption spectra of the reaction solution including the V species also indicated the formation of hydrogen peroxide during the benzene oxidation. The produced hydrogen peroxide was suggested to directly participate in the phenol formation from benzene.