Preparation and characterization of V-Ag-O catalysts for the selective oxidation of toluene

V-Ag-O complex oxide catalysts with relatively high surface areas of 13-21 m(2)/g could be prepared by the heterogeneous azeotropic distillation (HAD) method. Specifically, V2O5 and AgNO3 were dissolved in aqueous solution of H2O2, followed by evaporation and drying in n-butanol at 353K. Silver vanadates with highly dispersed nano silver particles in the layered structures of VOx might be formed during the preparation process, which were then turned into Ag0.68V2O5 and metallic silver during the reaction of selective oxidation of toluene at 573 K. Characterizations with microcalorimetric adsorption of NH3, temperature programmed reduction and isopropanol probe reactions showed that the V-Ag-O catalysts exhibited weaker surface acidity but stronger redox ability than the VOx, and therefore the better performance for the selective oxidation of toluene to benzaldehyde and benzoic acid. In addition, the V-Ag-O catalysts prepared by the HAD method exhibited much higher activity than its counterpart prepared by the co-precipitation for the conversion of isopropanol and the selective oxidation of toluene to benzaldehyde and benzoic acid in air. (C) 2010 Elsevier B.V. All rights reserved.