Pd/ZSM-5催化剂加氢裂化性能研究

采用N2吸附-脱附和NH3-TPD分析手段，考察了ZSM-5分子筛硅铝比和晶粒粒径对载体孔结构和酸性的影响，并以正庚烷和环己烷为原料，考察了硅铝比和晶粒粒径对催化剂加氢裂化性能的影响以及Pd负载量对双功能催化剂加氢裂化性能的影响。结果表明：随着硅铝比增大，催化剂的酸性中心数量减少，加氢活性中心数量相对提高，在抑制二次裂化的同时，可提高异构化选择性；而分子筛晶粒粒径的变化对载体外比表面积的影响不大，分子筛晶粒粒径的降低，使催化剂的酸度略有减小，但对催化剂的活性改进有限；分子筛载体负载Pd后，改变了反应路径，使催化剂的加氢裂化性能明显提高，当负载量大于0.4%时，催化剂的加氢转化活性趋于稳定，成为平衡双功能催化剂。

STUDY ON PD/ZSM-5 HYDROCRACKING CATALYST

In this paper, the effect of silicon/aluminum ratio and grain size on pore structure and acidity of ZSM-5 molecular sieve was investigated by N2 adsorption-desorption and NH3-TPD methods, and the hydrogenation performance of modified ZSM-5 molecular sieves and Pd/ZSM-5 catalysts were evaluated using heptane and cyclohexane as feeds. Results indicate that increasing the ratio of silicon and aluminum will reduce the acid sites of the catalyst and relatively increase the amount of hydrogenation active center. Due to reduction of secondary cracking, the selectivity of isomerization is improved; the nano-size ZSM-5 greatly improves the activity of the catalyst. The Pd loading changes the reaction pathway and lowers dawn the alkanes activation energy, resulting in improvement of hydrogenation activity. When the Pd loading is larger than 0.4%, the hydrogenation activity of the catalyst will level off.