Effect of Titania Loading on Properties and Catalytic Activity of Nanostructured Phosphate–Vanadia-Impregnated Silica–Titania Oxidative–Acidic Bifunctional Catalyst

Effect of titania loading on physical–chemical properties and bifunctional catalytic activity of phosphate–vanadia-impregnated silica–titania was investigated. Different concentrations of titanium were impregnated into fumed silica, followed by impregnation of vanadium and phosphoric acid simultaneously onto the prepared silica–titania. Results revealed that Ti amount did not have significant effect on crystallinity, surface area and particle size of the resulted materials. However, quantity of tetrahedrally coordinated Ti species increased with increasing Ti content in the sample. Pyridine adsorption study showed the presence of both Brønsted and Lewis acid sites in all the samples even in the titanium-free phosphate–vanadia-impregnated silica sample. The catalytic testing showed that phosphate–vanadia-impregnated silica–titania with the molar ratio of Si:Ti=33:1 was the best bifunctional catalyst in the transformation of 1-octene to 1,2-octanediol using aqueous hydrogen peroxide as oxidant.