Hydrodesulfurization of dibenzothiophene derivatives over TiO 2Al 2O 3 supported sulfided molybdenum catalyst

Abstract

Composite TiO 2Al 2O 3 supports with different loadings of TiO 2 have been prepared by chemical vapor deposition (CVD), using TiCl 4 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 TiO 2Al 2O 3 support is comparable to that of γ-Al 2O 3. High dispersion of TiO 2 on the Al 2O 3 surface has been obtained, and no cluster formation has been detected. Mo TiO 2  Al 2O 3 and Ni Mo TiO 2  Al 2O 3 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 Al 2O 3, TiO 2 and TiO 2-Al 2O 3 has been investigated for the deep hydrodesulfurization (HDS) of dibenzothiophene (DBT) and methyl substituted DBT derivatives. The conversion over the TiO 2Al 2O 3 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 Al 2O 3 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 TiO 2Al 2O 3 supported catalysts.