The synthesis of phenol through the direct oxygenation of benzene was attempted using supported vanadium catalysts in aqueous acetic acid solvent. Gaseous oxygen and ascorbic acid were used as an oxidant and a reducing reagent, respectively. The yield of phenol increased with the increase in the concentration of acetic acid in the aqueous solvent, and had a maximum value at the acetic acid concentration of a-round 80vol.%. The influences of the partial pressure of 0, and the amount of ascorbic acid on the yield of phenol were investigated using V/AlO3 catalyst in the aqueous solvent containing 80 vol.% acetic acid. The oxidation of benzene catalyzed by V/AlO3 using hydrogen peroxide as an oxidant instead of gaseous oxygen indicated that the yield of phenol increased with the increase in the concentration of acetic acid in the aqueous solvent. The supported vanadium catalyst with added zinc had a catalytic activity for phenol formation, though the yield was low, even in the absence of ascorbic acid. (C) 2002 Elsevier Science B.V. All rights reserved.