无粘结剂ZSM-5催化剂改性及其甲苯与乙烯择形烷基化反应的催化性能

Modified Binder-free ZSM-5 and Its Catalytic Performance in Shape Selective Alkylation of Toluene with Ethylene

利用甲苯与乙烯的烷基化反应制备对甲乙苯,是一条具有技术经济性的合成工艺路线。本工作对无粘结剂ZSM-5分子筛催化剂颗粒进行了聚苯甲基硅氧烷(PPMS)修饰剂化学液相沉积(CLD)改性处理研究,考察了其对催化剂物化性质与择形烷基化反应性能的影响。在CLD改性过程中形成的SiO_(2)使ZSM-5孔口收窄、外表面酸性位点钝化,这可以有效阻止对甲乙苯异构化为间甲乙苯或邻甲乙苯。经过重复3次改性的无粘结剂ZSM-5可将对甲乙苯的择形选择性提高至97%以上,与改性的常规含粘结剂ZSM-5催化剂颗粒相比,CLD改性的无粘结剂ZSM-5催化剂颗粒具有更好的烷基化活性和反应稳定性。

Production of Para-ethyltoluene(p-ET)via alkylation of toluene and ethylene is considered to be an economical pathway.In this work,binder-free ZSM-5 catalysts modified by chemical liquid deposition(CLD)of polyphenylmethylsiloxane(PPMS)were studied on the physicochemical properties and the shape selective catalytic performance.Through CLD modification,the open mouth of zeolitic channel was narrowed down by SiO_(2) formed,and the acid sites on external surface was passivated.As a result,the non-shape-selective isomerization of p-ET to m-ET or o-ET was suppressed.And the shape selectivity of p-ET was enhanced to more than 97%over binder-free ZSM-5 with three cycles of CLD modification.Compared with modified conventionally shaped ZSM-5 with alumina,CLD modified binder-free ZSM-5 catalysts showed better alkylation activity and stability.