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用真空微量Cahn电天平法研究了中孔分子筛SAPO-11及HZSM-5分子筛样品上的二甲苯扩散性能,探讨了影响烷基化反应产物对位选择性的各种因素,并测定了样品上的二甲苯异构化反应性能。结果表明对-二甲苯选择性不仅与烷基化反应的扩散/反应动力学有关,还与产物在分子筛表面的二次异构化反应性能有关。中孔分子筛的对位选择性主要决定于酸性的强弱。未改性的SAPO-11分子筛正是由于它的特殊的中等孔径、一维直孔道结构和中等强酸性的协同效应而有较高的对位选择性。
The dispersive properties of xylene over mesoporous zeolites SAPO-11 and HZSM-5 zeolites were investigated by vacuum trace Cahn electronegativity method. Various factors influencing the para-selectivity of alkylated reaction products were discussed. Xylene isomerization reaction performance. The results show that the para-xylene selectivity is not only related to the diffusion / reaction kinetics of the alkylation reaction, but also to the secondary isomerization reaction of the product on the molecular sieve surface. The selectivity of mesoporous molecular sieves depends mainly on the strength of acidity. The unmodified SAPO-11 molecular sieve possesses high para-selectivity due to its special medium pore size, synergetic effect of one-dimensional straight tunnel structure and moderate strong acidity.