Abstract:

TiO2-Al2O3 binary oxides were prepared by gas-phase deposition of TiCl4 on γ-Al2os support. It was found that TiO2 deposition is formed by the reaction of TiCl4 vapour with OH- group on A12O3 surface. The TiO2 loading increases with the number of gas phase deposition operations and the tetrahedral sites of Al2O3 surface was first covered by TiO2. S1ightly decrease of surface area) pore value and average of pore diameter of TiOz-AlzO3 compared with Al2O3 was observed. In Mo/TiO2-Al2O3 catalysts Mo exists mainly in the form of octahedral and polymer Mo7O2' species, while no tetrahedral Mo species has been observed. The model of Mo/TiO2-Al2O3 catalyst could be imagined as a sandwich of MoO2-TiO2-Al2O3. Due to the weaker interaction between Mo species and A1zoa support in this case more Mo6+ ions in Mo/TiO2-Al2O3 sample are reduced to low valence state comparing with that of Mo/Al2O3 at 5o(f C in H2. The experimental results demonstrate that the HDS and HYD activities of Mo/TiO2-Al2O3 catalysts increase with TiO2 content. It means that the full coverage of Al2O3 surface by TiO2 can improve effectively the catalyst activity of molybdenum catalyst in hydrotreating process.

Key words: Gas phase deposition, Surface phase structure, TiO2-Al2O3 carrier, Mo/TiO2-Al2O3, Hydrodesulfurization