Surface acidic and redox properties of V-Zr-O catalysts for the selective oxidation of toluene to benzaldehyde

A series of V-Zr-O (V2O5-ZrO2) complex oxides were prepared by the sol-gel method. The phases of the samples as detected by the X-ray diffraction depended on the content of V2O5 in the complex oxides. ZrV2O7 was found to be the main phase in the 50% V2O5-ZrO2, The results of temperature programmed reduction showed that the complex oxides V-Zr-O were easier reduced than the single oxides ZrO2 and V2O5, indicating the increased redox ability of the complex oxides. On the other hand, the complex oxides with surface ZrV2O7 exhibited the significantly lower surface acidity and relatively stronger redox ability, and thus, the better reactivity for the selective oxidation of toluene to benzaldehyde and benzoic acid. (c) 2007 Elsevier B.V. All rights reserved.