Research Of Mo-based Molecular Sieve Hydrodesulfurization Catalyst

The Mo-based molecular sieve HDS catalyst prepared by molybdenum sulfide as activecomponent and cobalt or nickel sulfide as cocatalyst component and MCM-41with higherspecific surface area, narrower pore size distribution and longer-range ordered pore assupporter possess high catalytic activity and provide the possibility for the production of cleanlight fuel. MCM-41with improvement of hydrothermal stability has been synthesized byusing ZSM-5as silica-alumina source. Ni-Mo/MCM-41and Co-Mo/MCM-41catalysts wereprepared by an isovolumetric impregnation method and their HDS activity was estimated.The HDS catalysts were characterized by XRD and N2adsorption instrument.The effects of synthesis factors were orthogonal investigated, such as molar ratio ofsodium hydroxide to silicon dioxide and template agent to silicon dioxide, pH value,crystallization time and crystallization temperature. The influence size of the synthetic factorson the relative orderly degree of molecular sieve was crystallization temperature＞molar ratioof sodium hydroxide to silicon dioxide＞pH value＞molar ratio of template agent to silicondioxide＞crystallization time. MCM-41with improvement of hydrothermal stability hadbeen synthesized at molar ratio of sodium hydroxide to silicon dioxide was0.8¹.1, molarratio of template agent to silicon dioxide was0.2⁰.3, pH value was9.7¹0.5, crystallizationtime was24⁴8h, crystallization temperature was80¹10℃.Ni-Mo/MCM-41（0⁰.8） and Co-Mo/MCM-41（0⁰.8） catalysts were prepared by anisovolumetric impregnation method. The HDS activities of the catalysts were investigated byusing decalin solution with1%DBT or0.5%4,6-DMDBT and FCC diesel on fixed bedmicro-reactor. The maximum HDS activity was observed at Ni（Co）/Mo atomic ratio of0.6.Ni-Mo/MCM-41（0.6） and Co-Mo/MCM-41（0.6） can remove of greater than99%of DBT,99%of4,6-DMDBT and98%of DBT,98%of4,6-DMDBT of the decalin solution at5.0MPa,320³80℃, hehydrogen-oil ratio=700⁸00, WHSV=30³8h-1. Ni-Mo/MCM-41andCo-Mo/MCM-41can remove of greater than96%and95%sulfide of the sulfur content of0.31%of FCC diesel at5.0MPa,320³80℃, hehydrogen-oil ratio=400⁴50,WHSV=2.5³.0h-1.When the Ni/Mo, Co/Mo less than0.6, The Ni or Co can priority to the formation ofNi（Co）-Mo interaction phase with Mo, promote Mo dispersion. When the Ni/Mo, Co/Mo more than0.6, excessive Ni or Co could generate Ni（Co）MoO₄with Mo or Co3O₄. The formation ofNi（Co）MoO₄or Co₃O₄reduce the number of Mo₇O₍240^6-, lower the activity ofhydrodesulfurization catalyst.