| With the growing worldwide oil depletion, but the social demand for clean fuel is increasing. In order to meet stringent environmental regulations, reducing the concentration of aromatics in the fuels have a very important significance. Aromatics in fuels, not only lower the cetane value of the diesel fuel, but also increaser the pollution of undesired exhaust emissions and particulate emissions. Therefore, interest in the development of novel catalysts for hydrodearomatic(HDA) has been spurred day by day.HDA is the main means to decreasing aromatic content in the fuels. The conventional catalysts for the HDA process are mainly alumina-supported Mo or W sulfides promoted by Ni or Co, but their HAD activities are generally quite low, and the drawbacks of these catalysts include severe operating conditions. Supported noble metal catalysts showed high catalytic activity for aromatic hydrogenation at low temperature. However, the presence of sulfur strongly influences their catalytic activity due to the poisoning of active sites. Transition metal phosphides have recently been the focus of research due to their higher activity compared to metal sulfides. Nevertheless, it is necessary to study on this class of new catalysts further in order to understand their structures and performances in hydrogenation(HYD). Nickel phosphide was chosen as the HDA catalyst in the present dissertation. For the supported nickel phosphide catalysts, SiO2 was used as the carrier. Moreover, the effect of the catalyst on the HYD of a-methylnaphthalene(1-MeNaph),β-methylnaphthalene(2-MeNaph), naphthalene(Naph)was investigated. The catalysts were characterized by XRD, N2 adsorption, TEM. The main contents are as follows:The SiO2-supported nickel phosphide catalysts with initial Ni/P atomic ratio of 0.5-2 in the oxidic precursors were prepared by an in-situ reduction method. The catalytic performances were evaluated in the HYD of 1-MeNaph,2-MeNaph. The results show that: The HYD increased drastically with the increase of reaction pressure, H2/liquor and space time, the optimum reaction temperature were 340℃. However, at the high volume ratios of H2/liquor the conversion was almost unaltered. Isomerization of methyl was also observed during the hydrogenation, methyl group suppressed hydrogenation of aromatics due to steric hindrance. By examining the space-time under different pressures, proving that under the conditions of high pressure help to creat full hydrogenation product and the the improvement of conversion rate. The catalytic performances were evaluated in the HYD of 1-MeNaph, the optimal initial Ni/P ratio is 1.25. It is indicated that the HYD of 1-MeNaph,2-MeNaph on the NiW/γ-Al2O3 and SiO2-Al2O3-supported Pd-Pt (4:1), the reaction process was same to Ni2P/ SiO2, It is also indicated that the HYD of Naph blend with 1-MeNaph or 2-MeNaph, the HYD of Naph was slower, the conversion of Naph and selectivity to decalin were reduced. The influence of 1-MeNaph,2-MeNaph to Naph was more than Naph to 1-MeNaph and 2-MeNaph. |
