中文摘要：

采用密度泛函（DFT）方法对于ZSm^-5分子筛上苯与乙烯的烷基化反应机理进行研究。选取了包含酸性质子的8T原子簇模型代表 ZSm^-5分子筛的部分结构。采用 B3LYP/6-31G（d）水平从生成能与反应活化能角度对于烷基化反应发生时可能存在的2种联合机理和一种分步机理进行了计算与比较。结果表明，联合反应机理中乙烯的质子化和C-C键的形成同时发生，而分步机理开始于乙醇盐中间体的生成，随后与苯反应生成反应产物。分步机理中乙醇盐中间体生成步骤的活化能（124.55 kJ/mol）低于联合机理的反应活化能（168.98 kJ/mol和156.06 kJ/mol），而烷基化步骤的活化能（209.35 kJ/mol）高于联合机理的反应活化能，由此可以推断ZSm^-5分子筛上苯与乙烯的烷基化反应时2种机理同时发生，存在竞争关系。

英文摘要：

The ZSm^-5 catalyzed alkylation of benzene with ethene is investigated based on DFT method.. A 8T cluster is selected to represent part of the ZSm^-5 zeolite. Two concerted mechanism and one stepwise reaction mechanisms have been analyzed at the B3LYP/6-31（d） level from the aspect of formation energy and reaction activation energy. The result showed that in the concerted schemes ethane protonation and C-C bond formation occur simultaneously while the stepwise scheme starts with the formation of a stable ethoxide intermediate which subsequently reacts with benzene to form the reaction product. The result showed that the activation energy for the ethoxide formation （124.55 kJ/mol） is smaller than the activation energy of the concerted mechanism （168.98 kJ/mol and 156.06 kJ/mol）, while the activation energy for the alkylation step（209.35 kJ/mol） is higher than that for the concerted mechanism, so we can conclude that both concerted and stepwise mechanism will occur in the reaction and they are competitive to each other.