Hydrodesulfurization of dibenzothiophene derivatives with TiO2-Al2O3 supported ulfided molybdenum catalyst

Abstract

TiO2-Al2O3 supports (TiO2 over-layers coated on Al2O3 supports) were prepared by chemical vapor deposition (CVD) of TiCl4 on the substrate. Mo catalyst supported on TiO2-Al2O3 showed significantly higher catalytic activity for hydrodesulfurization (HDS) of dibenzothiophene derivatives than catalysts supported on Al2O3. Especially, it showed higher activity for HDS of 4,6-DMDBT. From the analysis of liquid products, the authors found that rate of desulfurization after hydrogenation of the neighboring phenyl groups increased with the use of TiO2-Al2O3 supported catalysts. Attributed to reducing of steric hindrance by the methyl groups, therefore, TiO2-Al2O3 supported catalysts showed higher activity than that of the catalysts supported on Al2O3. IR, XPS, XRF, BET surface area, pore volume and pore size distribution analyses were conducted to characterize the TiO2-Al2O3 supports after deposition of TiO2. These results suggested that, applying the CVD method, TiCl4 first interacted with hydroxyl groups on Al2O3, after which TiO2 is deposited with Ti-O-Al bonding on the surface of Al2O3, after calcination. Further, the authors studied the catalysts after sulfidation by XPS. These results showed that the Mo species on TiO2-Al2O3 were more easily reduced from +6 to +4 with higher S/Mo ratio as compared with those on Al2O3. In conclusion, the authors suggest that the number of active sites had increased on the surface of TiO2-Al2O3 supports.