HY催化C4烷基化中异丁烯质子化反应的分子模拟

采用MS QMERA中QM和MM（量子力学和分子力学）相结合的方法，选用84T HY分子筛簇模型，研究了HY分子筛催化C4烷基化反应中异丁烯质子化反应过程。结果表明，异丁烯首先吸附在分子筛上形成π-络合物，再通过正碳离子的过渡态生成表面烷氧基团；质子化反应的活化能能垒为98.74 kJ/mol，比单纯H⁺进攻异丁烯的能垒高。过渡态时烷基片段的正电荷数最高（0.675 e），且过渡态构象对应于势垒的最高点，极易向反应物或产物转化；同时，过渡态时Al-O1和 Al-O2的键长大致相等，而在反应物和生成物时的键长差异较大，表明处于过渡态的正碳离子不稳定。

Molecular Simulation of Isobutene Protonation in C4 Alkylation Catalyzed by HY

A cluster of 84T HY was chosen to study the protonation of isobutene in C4 alkylation on HY by using the QM/MM method in MS QMERA. The results showed that the transformation of the π-complex into a covalently bonded surface tert-butyl fragment occurred through a transition state of carbenium ion with an activation energy of 98.74 kJ/mol，which was much higher than the activation energy of isobutene addition reaction by proton directly. The transition state of carbenium ion located on the highest position of potential energy with a highest positive charge was not stable and could convert to reactant or product easily. Also，this was assisted by the fact that the bond lengths of Al-O1 and Al-O2 were almost equal in the transition state， but considerably differed from each other in the initial and final structures.