Hydrodesulfurization of dibenzothiophene derivatives over TiO2-Al2O3 supported sulfided molybdenum catalyst

omposite TiO2-Al2O3 supports with different loadings of TiO2 have been prepared by chemical vapor deposition (CVD), using TiCl4 as the precursor. The supports have been characterized by N-2 adsorption measurements, X-ray photoelectron spectroscopy (XPS), X-ray fluorescence analysis (XRF) and IR spectroscopy. The specific surface area of each TiO2-Al2O3 support is comparable to that of gamma-Al2O3. High dispersion of TiO2 on the Al2O3 surface has been obtained, and no cluster formation has been detected. Mo/TiO2-Al2O3 and Ni-Mo/TiO2-Al2O3 catalysts have been synthesized by impregnation and co-impregnation method. We studied the conversion of Mo and Ni from the oxidic to the sulfidic state by XPS. Furthermore, the catalytic behavior of Mo and Ni-Mo supported on Al2O3, TiO2 and TiO2-Al2O3 has been investigated for the deep hydrodesulfurization (I-IDS) of dibenzothiophene (DBT) and methyl substituted DBT derivatives. The conversion over the TiO2-Al2O3 supported catalysts, in particular for the HDS of 4-methyl-DBT (4-MDBT) and 4,6-dimethyl-DBT (4,6-DMDBT), is much higher than the conversion obtained over Al2O3 supported materials. In particular with regard to the Ni-Mo catalysts, the ratio of the corresponding cyclohexylbenzene (CHB)/biphenyl (BP) derivatives is increased over the composite support, indicating that the prehydrogenation of an aromatic ring is important for the HDS of DBT derivatives over TiO2-Al2O3 supported catalysts. (C) 1997 Elsevier Science B.V.