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本文用CaO对ZSM-5沸石进行改性,在丙烯的芳构化反应和甲苯的甲基化反应中,其对二甲苯选择性与未改性前相比,可得到很大的提高,同时应用分子筛窗口模型,计算了用CaO改性前后的ZSM-5沸石:对于甲苯分子中各碳原子的电荷密度的影响,从而解释氧化物改性使ZSM-5沸石对二甲苯选择性提高的原因。我们认为其原因主要不是沸石孔径的变化,而是由于改性后对反应物分子电荷分布产生的影响,也即改变了沸石表面酸性的结果。
In this paper, ZSM-5 zeolite modified with CaO, in the aromatization of propylene and toluene methylation reaction, the p-xylene selectivity compared with before unmodified, can be greatly improved, at the same time The molecular sieve window model was used to calculate the influence of the ZSM-5 zeolites before and after CaO modification on the charge density of each carbon atom in the toluene molecule to explain the reasons for the improved selectivity of ZSM-5 zeolite to xylene by oxide modification . We think that the main reason is not the zeolite pore size change, but because of the modification of the reactant molecular charge distribution, which changes the result of zeolite surface acidity.