Pd/ZSM -22分子筛双功能催化剂的制备及其加氢异构化反应性能

摘要

ZSM -22 zeolite with different SiO2/Al2O3 were synthesized using 1 - ethylpyridinium bromide (EtPBr) as templates under static or dynamic conditions, the properties were characterized by X - ray diffraction(XRD), X Ray Fluorescence(XRF) , N2 adsorption, ammonia temperature -programmed desorption (NH3 -TPD)and FT-IR spectroscopy of adsorbed pyridine(Py -IR). The effects of crystallization methods on the structure and acidity were studied. The hydroisomerization of n - decane was investigated in the fixed reactor over 0. 5% Pd ( wt. ) supported on the ZSM - 22 zeolite synthesized by different crystallization methods. The results showed that ZSM - 22 zeolite synthesized by dynamic method has smaller crystallite size, larger micropore area, more acid sites and weaker acid strength. The higher isomerization selectivity of n - decalin has been obtained over the Pd/ZSM - 22 zeolite bi-functional catalysts synthesized under dynamic conditions.%以1-乙基溴化吡啶(EtPBr)为模板剂,分别采用动态和静态晶化的水热法合成了不同硅铝比的ZSM - 22分子筛,采用X射线衍射(XRD)、X射线荧光光谱(XRF)、N2物理吸附、氨程序升温脱附法(NH3 - TPD)和吡啶吸附的红外光谱(Py -IR)等手段对分子筛进行了表征.考察了晶化方式对分子筛的孔结构及酸性的影响.将两种晶化方式合成的分子筛用浸渍法制备了0.5％Pd/ZSM - 22双功能催化剂,并在连续微型固定床反应装置上考察了其对正癸烷加氢异构化反应的催化性能.结果表明,动态晶化法合成的ZSM - 22分子筛晶粒尺寸较小,具有较大的微孔表面积,酸性位数量较多,酸强度较弱,以该分子筛为酸性载体制备的Pd/ZSM - 22催化剂对正癸烷的加氢异构化反应具有更高的异构化选择性.