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, which exhibited much higher activity and selectivity than the counterparts prepared by the co-precipitation (CP) method for the selective oxidation of toluene to benzaldehyde and benzoic acid. 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, V 2O 5 and AgNO 3 were dissolved in aqueous solution of H 2O 2, followed by evaporation and drying in n-butanol at 353 K. Silver vanadates with highly dispersed nano silver particles in the layered structures of VO x might be formed during the preparation process, which were then turned into Ag 0.68V 2O 5 and metallic silver during the reaction of selective oxidation of toluene at 573 K. Characterizations with microcalorimetric adsorption of NH 3, temperature programmed reduction and isopropanol probe reactions showed that the V-Ag-O catalysts exhibited weaker surface acidity but stronger redox ability than the VO x , 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.