The selective oxidations of toluene and ethylbenzene using hydrogen peroxide over vanadium-based catalysts such as VPO, VOPO₄, V₂O₅, VO(acac)₂ and NH₄VO₃ have been studied. These catalysts were found to be active for the oxidation of toluene and ethylbenzene to benzaldehyde and acetophenone as main products in acetonitrile solvent, respectively. The activity and selectivity, however, in a sequence of decrease order, was found to be followed as: VPOV₂O₅VOPO₄VO(acac)₂NH₄VO₃. The highest selectivities to benzaldehyde from toluene and acetophenone from ethylbenzene were 58.8% and 66.1% over VPO catalyst with P/V=1.1 (molar ratio) in acetonitrile solvent, resepectively. The catalytic performance of VPO with (VO)₂P₂O₇ phase was affected by the molar ratio of P/V, hydrogen peroxide amount, solvent property and temperature. The active center for the oxidation was believed to be (VO)₂P₂O₇ sites (V⁴⁺) in combination with dynamic V⁵⁺ sites involving a reversible redox cycle.

Key words: V2based catalyst, selective oxidation of toluene and ethylbenzene, hydrogen peroxide, benzaldehyde, acetophenone.