The Preparation Of Mo-base Catalysts And Its Application In Oxidative Desulfurization

Ultra-deep desulfurization of diesel fuel has become an important research subject due to the upcoming legislative regulations to limit sulfur content more and more drastically.In industry,conventional hydrodesulfurization(HDS) process can remove organic sulfur compounds from fuels effectively.However,to produce ultra-clean fuels,both capital investment and operational costs would be rather high due to more severe operating conditions.Consequently,people have begun to look for alternative approaches.Among them, oxidative desulfurization as an effective and promising approach in ultra-deep desulfurization of diesel fuels can be operated at atmospheric pressure and moderate conditions.In the present paper,MoO₃-SiO₂ mixed oxides were prepared by sol-gel method,and Ce was introduced into mixed oxides to improve catalytic performance.The catalysts were characterized by X-ray diffraction,Fourier-transform infrared and diffuse reflection spectroscopy.It was suggested that for MoO3-SiO2 mixed oxides,when the molar ratio of Mo/Si＜0.1,molybdenum oxide species exist in a highly dispersed amorphous state,and when Mo/Si≥0.1,MoO₃ crystal grains formed,and a certain amount of Ce incorporation into the structure of mixed oxides can inhibit the formation of MoO₃ crystal grains,promote the dispersion of molybdenum oxide species in mixed oxides.The FTIR spectra of MoO₃-SiO₂ mixed oxides present a band at 916 cm^-1(Mo-O-Si vibration) indicated that molybdenum oxide species were incorporated into silica matrix.The DRS spectra indicated that tetrahedral molybdenum oxide species formed at low Mo content whereas at high Mo content molybdenum oxide species aggregated into octahedral species.The oxidation of model sulfur-containing compound DBT was performed with oil-soluble CHP as oxidant in the presence of MoO3-SiO2 mixed oxides prepared by sol-gel method.In the case of MoO3-SiO2 mixed oxides,when molar ratio of Mo/Si was 0.1,the catalyst had best performance.The effect of the preparation parameters of catalysts,reaction temperature and molar ratios of oxidant to DBT were investigated.Experimental results show that the conversion of DBT become larger with the increase of reaction temperature and O/S molar ratio,and a certain addition of Ce into Mo_0.1Si catalysts improved catalytic performance of mixed oxides in the oxidation of DBT.When molar ratio of Ce/Mo was 0.2, the conversion of DBT could be improved at least 5%compared to the catalyst without Ce in the same reaction conditions.