The effects of wet impregnation and sol-gel methods and presence of competitive hydrocarbons on oxidation of dibenzothiophene over titanium-silica nanocatalyst

Oxidative desulfurization process using heterogeneous catalysts is considered as a complementary and promising method for hydrodesulfurization of liquid hydrocarbon fuels to remove their sulfur-resistant compounds. In this research, a titania-silica catalyst with a 10 wt.% loading of titania as the active phase was synthesized using two methods, i.e., sol-gel and wet impregnation, and the performance in the oxidative desulfurization of dibenzothiophene was investigated and compared. Oxidative desulfurization was carried out at a low temperature of 50°C, atmospheric pressure, an O/S molar ratio of 5, and a catalyst loading of 0.3 g per 3 g of fuel. To better identify the physico-chemical characteristics of the catalysts and find the structure-performance relationship, analytical techniques such as nitrogen adsorption-desorption, Fourier-transform infrared spectroscopy, X-ray fluorescence, and X-ray diffraction were employed. By comparing the performance of the catalyst samples, it was found that the conversion of dibenzothiophene in the presence of the catalyst prepared by the sol-gel method was higher, achieving 100% conversion within a short reaction time of 30 minutes. Furthermore, the effect of the presence of competitive nitrogen-containing compounds (indole and quinoline) and olefin (cyclohexene) on the oxidative desulfurization of dibenzothiophene with the optimized catalyst was evaluated. The highest and lowest negative effects were observed for cyclohexene and quinoline, respectively.