Gas Phase Catalytic Oxidation of Toluene to Benzaldehyde over V-Sn Oxide Catalysts

A series of V-Sn mixed oxide and V 2O 5-SnO 2/η-Al 2O 3 catalysts with various atomic ratios of V to Sn were prepared by a solution-mixing and dipping method. It has been found that the binary oxides V 2O 5-SnO 2 show a series of properties different from that of single oxides and supported V 2O 5-SnO 2/η-Al 2O 3 catalysts. V 2O 5-SnO 2/η-Al 2O 3 catalysts displayed high catalytic activities and good selectivity to benzaldehyde under the experimental conditions used. When SnO 2 content increases, the activity decreases, the selectivity to benzaldehyde also decreases. It therefore seems unsuitable for SnO 2 to be used as a catalyst constitution for the toluene oxidation reaction. The main role of SnO 2 in the above samples is to provide a host lattice for the dispersion of vanadium, as has been proved by XRD.