Synthesis And Catalytic Performance Of Hydrodesulfurazation Catalysts Supported On Meso-microporous Molecular Sieve ZK-1

In recent years, air pollution caused by exhaust gas from diesel engine has become a serious problem. Environmental legislation places increasingly severe restrictions on sulfur content of fuels. Therefore, the research on efficient deep hytrodesulfurization catalyst becomes a hot topic. As a support, meso-microporous molecular sieve has been successfully applied to the catalytic reactions because of its unique pore structure and excellent hydrothermal stability. So far, some meso-microporous molecular sieves such as MCM-41/Y and SBA-15/Beta have been widely used as the supports of deep hytrodesulfurization catalysts. Although the experimental results presented high desulfurization activity, the synthesis processes of the supports were complicated. Micro-mesoporous molecular sieve ZSM-5/KIT-l(ZK-l) was synthesized by a one-step crystallization method with dual templates. The supported CoMo catalysts were also prepared by impregnation method and the catalytic performances of hydrodesulfurazation were investigated. The structures of the catalysts were characterized by XRD, N2physical absorption, NH3-TPD, Raman and UV-vis techniques.Firstly, the synthesis methods of the supported catalysts were optimized and the reaction conditions (temperature, pressure and H2/oil ratios) were investigated. The desulfurization rate increases significantly with increasing the loading. The catalytic activity is the highest, when the loading reaches20%MoOx7%CoOx,. As the loading further increases, the activity decreases. Deactivation is due to the formation of crystalline MoO3.The catalysts with different Si/Al ratios were synthesized. The effects of the acidic property and structural stability of the supports on the catalytic performance were investigated. The reaction results demonstrate that when the Si/Al ratio is30or40, the structure of the support is more stable. The catalysts contain weak acid sites together with less medium acid. Hence they show the best catalytic performances.The catalytic performances of the catalysts on different supports were investigated. Under the mild reaction conditions, the catalysts supported on ZK-1(Si/Al=30) and ZK-1(Si/Al=40) show the highest activity, and the desulfurization rate are93.5%and94.8%respectively. This is due to its better diffusion with large surface area and pore size and the modulated acidic property with zeolite structure unit in the supports.