Preparation and characterization of In 2O 3-TiO 2 and V 2O 5/In 2O 3-TiO 2 composite oxides for catalytic applications

Abstract

In 2O 3-TiO 2 (1:13 mole ratio) mixed oxide was prepared by a co-precipitation method with in situ generated ammonium hydroxide and was impregnated with various amounts of V 2O 5 (4–12 wt.%). The In 2O 3-TiO 2 and V 2O 5/In 2O 3-TiO 2 samples were subjected to thermal treatments from 773 to 1073 K and were investigated by X-ray diffraction, FT-infrared, and BET surface area methods to establish the effects of vanadia loading and thermal treatments on the surface structure of the dispersed vanadium oxide species and temperature stability of these catalysts. Characterization results suggest that the co-precipitated In 2O 3-TiO 2 is in X-ray amorphous state and exhibits reasonably high specific surface area. The In 2O 3-TiO 2 also accommodates a monolayer equivalent of V 2O 5 (12 wt.%) in a highly dispersed state. The V 2O 5/In 2O 3-TiO 2 catalyst is thermally stable up to 873 K calcination temperature. When subjected to thermal treatments beyond 873 K, the dispersed vanadium oxide selectively interacts with In 2O 3 portion of the mixed oxide and forms InVO 4 compound. The remaining TiO 2 appears in the form of anatase or rutile phase. These samples were evaluated for one step synthesis of 2,6-dimethylphenol from cyclohexanone and methanol mixtures in the vapour phase at normal atmospheric pressure. The 12% V 2O 5/In 2O 3-TiO 2 catalyst exhibits good conversion and product selectivity among various samples investigated.