Preparation and Catalytic Performance of Al2O3, TiO2 and SiO2 Supported Vanadium Based-Catalysts for C-H Activation

A series of Al2O3, SiO2 and TiO2-supported vanadium oxide catalysts with different vanadium loadings has been prepared by two different methods: wet impregnation using ammonium metavanadate as a vanadium precursor and grafting using VOCl3. Characterization of these catalysts by XRD, FTIR, TEM, SEM, EDX, DR and TGA techniques revealed that the structure of vanadium oxide VO (x) species depends on the preparation method, the type of the support and loadings of vanadium on the oxides surfaces. Monomeric vanadium oxide species are predominant at low vanadium loadings while polymeric vanadium oxide species increase with higher loadings. The catalytic activity of the prepared catalysts was evaluated for the liquid-phase oxidation of cyclohexane as a model reaction to obtain cyclohexylhydroperoxide, cyclohexanol and cyclohexanone with PCA as co-catalyst. The results show that the catalysts exhibit good cyclohexane conversion and remarkable selectivity to the target products and high turnover numbers (TON).