Investigation On The Preparation And Properties Of Three-dimensionally Porous CoMo Supported Catalysts For Thiophene Hydrodesulfurization

The sulfur-containing compounds in the fuels contribute to global environmental degradation,therefore,countries around the world limited the sulfur content in the fuels by legislation to achieve the goal of a“sulfur-free”society.Compared with other desulfurization technologies,hydrodesulfurization（HDS）technology still is the most effective process to reduce the sulfur-containing compounds in fuel to the ultra-low level.Although the traditional supported HDS catalysts have been widely used in refineries,the disadvantages,such as the lower content of active metals,the low removal efficiency of sulfur-containing compounds with large steric hindrance effect,etc.have limited the further development of these supported catalysts.In this thesis,we successfully synthesized the CoMosupported catalysts with a three-dimensionally porous（3DP）structure to solve the problems of traditional supported catalysts,and to reduce the catalyst preparation cost.（1）Firstly,the preliminary study on the preparation of catalysts was conducted.The SEM,TG/DTG,and high-resolution optic microscope were employed to analyze the microstructure and the thermal decomposition characteristic of the compressed and uncompressed melamine foam（MF）.The fire resistance ability and the degree of carbonization of the MF were evaluated to choose the appropriate calcination process.Finally,the compressed MF was used as the catalyst support after the evaluation of the results of the solvent absorption capacity test,and the impregnation time test.（2）The influence of impregnation times and the concentration of the precursor solution on the catalysts were investigated based on the MF support.Firstly,a serious of the 3DP CoMosupported catalysts had been prepared with different CoMomolar ratios by the excessive impregnation method.And the prepared catalysts were characterized by XRD,SEM,low-temperature N₂ adsorption-desorption,and HRTEM.The HDS activities of thiophene over these catalysts were evaluated by a fixed-bed microreactor.The results revealed that the catalysts with a macroporous-mesoporous structure could decrease the mass transfer resistance of the reactants or products and exhibit abundant activity sites.The highest conversion of thiophene was 97.0%for the Co_2.0Mo/MF catalyst under the reaction condition of the temperature of 360℃and the H₂ pressure of 1 MPa.（3）Using thiourea as the source of sulfur,the 3DP pre-sulfurized supported catalysts were prepared by the hydrothermal method with the calcined MF as support.The prepared catalysts were also characterized and evaluated their HDS performance.The results showed that all catalysts have 3DP structures to enhance the accessibility of the reactants.And the metal species were attached to the skeleton of the carbon sponge to form the accumulated spheres with more exposed active sites,which would increase the utilization efficiency of the metals.The thiophene conversion of the Co_2.0MoS/CMF reached 99.2%under the same reaction condition as the above-mentioned catalyst.