| Cyclohexene with active double bond, which is prone to oxidation, polymerization, coupling etc, is widely applied in the synthesis of a lot of chemical products. Especially, cyclohexanone and hexanedioic acid produced from cyclohexene are used as intermediates to the synthesis of polyamide fibre. Therefore study on the partial hydrogenation of benzene to cyclohexene is of great significance. Specific surface area, pore size, surface hydrophilicity and metal active center of Ru catalysts have effects on adsorption, desorption and mass transfer of benzene and cyclohexene in the reaction process. The catalytic performance can be modulated by modifying the above properties, and thus further hydrogenation of cyclohexene is avoided and the yield of cyclohexene is improved. In this thesis, three aspects are investigated in partial hydrogenation of benzene to cyclohexene, including influence of preparation method, support, and modification of Ru active center on the catalysis performance of the Ru catalysts.(1) The three catalysts, Ru/ZrO2-DP-1, Ru/ZrO2-DP-2and Ru/ZrO2-IP were prepared by deposition precipitation and impregnation methods by using ZrO2as support. Catalysts were characterized by XRD, TEM and N2adsorption-desorption, and the catalytic performance was evaluated with partial hydrogenation reaction of benzene. The effect of reaction temperature, hydrogen pressure and reaction time on the catalysis performance of Ru/ZrO2-DP-2were investigated. Based on the obtained results, the proper conditions have been established. Experimental results show that Ru/ZrO2-DP-2has the highest activity. After adding ZnSO4and NaOH, the increase in selectivity of cyclohexanone for Ru/ZrO2-DP-2is greater as compared to the Ru/ZrO2-DP-1and Ru/ZrO2-IP. The reason may be that the ruthenium is highly dispersed, and the number of Ru active sites is increased. The influence of ZnSO4and NaOH concentration on partial hydrogenation reaction of benzene was examined. With the increasing ZnSO4and NaOH concentration, the conversion of benzene decreased, whereas the selectivity and yield of cyclohexene increased significantly.(2) Using ZrO2with different specific surface and pore size as the support, ruthenium supported catalysts were prepared by deposition-precipitation methods. The result shows that the selectivity of and yield of cyclohexene from the catalyst prepared by using ZrO2-103support are higher compared with the catalyst supported by ZrO2-34and ZrO2-224. The result displays that the selectivity of cyclohexene has a certain relationship to specific surface area and pore size of catalyst support. At the same time, the catalytic performance of RuCo/ZrO2-DP-103modified by the promoter Co was studied. The impact of Ru/Co molar ratio on the benzene partial hydrogenation reaction was investigated. Selectivity of cyclohexene can be improved with Co promoter. In the reaction system with ZnSO4and NaOH, when the Ru/Co molar ratio is10:2, the highest yield of cyclohexene are15.8%and16.5%, respectively. The stability of Ru particle size and ruthenium electronic enrichment is caused by Co modification.π bond is formed by the combination between d orbit of Co and double bond of cyclohexene, which can inhibit further hydrogenation of cyclohexene and improve the yield.(3) The three ruthenium catalysts, RuB/BC, RuB/BC-IL and RuB/BC-IL-ZnCl2, were prepared from biomass char and functionalized ionic liquid biomass char. The result shows that biomass char functionized by ionic liquid and ZnCl2exhibits a good catalytic performance. The selectivity of cyclohexene is significantly higher as compared to general biomass char. The introduction of ionic liquid and ZnCl2improves the hydrophilicity of the catalyst. The imidazole in ionic liquid can coordinate with benzene, which can increase the concentration of benzene on the surface of the catalyst, occupy the active sites of the catalyst, make it easy for cyclohexene to be desorbed, and accordingly improve the selectivity of cyclohexene. |
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