Liquid Phase Hydrogenation Of Benzene On Supported Ru Catalysts

As a consequence of the stringent environmental regulations and the growing demand for cleaner fuel, the content of aromatics in fuel will be restricted more and more strictly. Moreover, the excessive aromatics content in the solvent oil limits its appliance field. The dearomatization of various petroleum products is playing an important role in modern refinery strategies. Therefore, there is considerable interest in developing new catalysts and processes for aromatics saturation with improved activity and stability at moderate temperature. So the research on following aspects was made:Firstly, Ruthenium nanoparticle catalysts supported on Betazeolite were prepared by alcohol reduction of RuCl3 solution in the presence of PVR Based on the results of characterization of TEM and CO-FTIR, it was found that mono-size, high dispersed and well controlled Ru nanoparticles could be formed and their size could be controlled by changing the amount of PVP at constant loading. The catalytic activity of this kind catalyst was tested in liquid phase hydrogenation of benzene for the characterization of the accessibility of the ruthenium particles and its catalytic performance. The reaction results exhibited that Ru-PVP/Beta was active for benzene hydrogenation reaction, this meant the metal atoms exposed to surface were able to coordinated benzene and activate hydrogen. It was interesting to observe that when water was added to the reaction system, the rate of benzene hydrogenation reaction increased significantly. This result could be contributed to the swellability of catalysts in water originating from the hydrophilicity of PVP. The property of catalysts increase the accessibility of ruthenium particles to reactant, so as to the rate of reaction. Moreover, the Ru-PVP/Beta catalysts kept intrinsic catalystic activity and could be easily recovered, giving the advantage of thegood stability of catalyst.Secondly, mesoporous molecular sieves MCM-41 were synthesized by hydrothermal method. The template in MCM-41 could be removed by calcining after extracting with various acid ethanol solutions. These synthesized MCM-41 and zeolites(HY, HBeta) were used as supports for Ru-supported catalysts via vacuumizing impregnation. N2 adsorption and XRD results of the supports and catalysts revealed that they had the characteristic of mesoporous molecular sieves, and the pore structure and surface area of MCM-41 was influenced by Si/Al ratio. Various catalysts was used in dearomatization model reaction of standard solution. It was concluded from results that the activity of the Ru-supported catalysts with the same Si/Al ratio MCM-41 supports increased with increasing the acidity of supports, the activity of the catalysts extracted with the same solvent increased with increasing Si/Al ratio of supports, and the catalyst based on the pure silica MCM-41 was more active than other samples, the higher surface area and better Ru dispersion obtained on Ru/Si-MCM-41 would be responsible for its higher hydrogenation activity. Compared withthe zeolite-based catalysts, Ru/H-MCM-41(N) had the superior hydrogenation activity of resulting from its mild acidic sites and high surface area.Finally, various catalysts was used in dearomatization reaction of 6# solvent oil, it was found that all catalysts could cut down the content of aromatics in solvent oil to below 30ppm, but their activity order changed owing to trace sulfur existing in 6 solvent oil. Compared with other catalysts, Al-constanting(Si/Al=15) support catalysts had the superior hydrogenation activity and sulfur tolerance owing to the high metal dispersion and the acidic nature of the support. The acid sites seemed to enhance the sulfur tolerance of supported ruthenium catalysts because of the election-deficient state of metal induced metal-support interaction. The result that the catalysts were used repeatedly indicated that they had good stability in dearomatization model reaction of standard solution, but their activity decreased rapidly in dearomatization of 6# solvent oil at the same reaction conditions owing to the presence of sulfur in solvent oil, and even the acidic support catalyst was unavoidable too. These results showed their poor stability in 6# solvent oil.