Studies On The Catalysts And Kinetics For The Hydrodesulfurization Of Gasoline And Diesel Fractions

More and stricter environment legislations limited the content of sulfur in gasoline and diesel oil all over the world, from which attention were paid by both researchers and refiners. Hydrodesulfurization (HDS) is still the key to produce the high quality fuel with low sulfur content. Development of novel catalysts for HDS plays an important role in fuel hydrotreatment. Moreover, studies on kinetics of HDS are helpful to understand the mechanism of HDS, improve the design of HDS reactor, optimize the HDS process, and predict the sulfur content in fuel products.Nickel phosphide of chemical formula Ni₂P has recently been reported as a new class of high-activity HDS and HDN catalyst. The surface area of unsupported Ni₂P catalyst is rather low (< 1 m²/g). In order to increase the active surface area, Ni₂P is dispersed on a high-surface support. Titania is a new class of support for hydrotreating catalysts, it has attracted attention in view of the higher HDS activity displayed by molybdenum-based sulfide supported on this oxide than on traditional Al₂O₃ and SiO₂. Therefore, the focus of this work was the preparation of TiO₂ supported Ni₂P catalysts and their activities in HDS of thiophene. In this thesis, nickel phosphides were successfully prepared in dispersion form on TiO₂ and HZSM-5 supports by means of temperature-programmed reduction of the corresponding phosphate. The phase of the obtained catalysts were established by x-ray diffraction (XRD), and the specific surface areas were determined by N₂ BET method. The catalytic activities of the catalysts were tested in a fixed bed reactor for the hydrodesulfuration ( HDS ) by using of thiophene and dibenzothiophene as a model compounds.TiO₂-supported nickel phosphides were prepared by means of temperature-programmed reduction of the corresponding phosphate in flowing 10%H₂/N-2 mixture gases. The precursors with molar ratios of Ni/P = 1/2 and 1/3 yielded catalysts containing phase-pure Ni₂P, whereas the precursors with molar ratio of Ni/P = 1/1, yielded catalysts containing phase Ni₂P and Ni₁₂P₅ as impurities. With Ni and P contents in the precursors increasing, the specific surface areas of obtained catalysts were decreasing. Thiophene HDS activities over TiO₂-supported Nickel...