Yang Jing
School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, China.
Chemphyschem. 2009 Apr 14;10(6):946-53. doi: 10.1002/cphc.200800785.
Two different mechanisms: Shift 1,2-isomerization and isomerization via the disproportionation reaction are investigated for aromatic hydrocarbons over acidic mordenite zeolite by using our own n-layered integrated molecular orbital and molecular mechanics (ONIOM) scheme. The picture shows a schematic energy profile for the isomerization of toluene catalyzed by acidic mordenite.The geometrical structures and energies of isomerization reactions of aromatic hydrocarbons catalyzed by the 128T cluster model of acidic mordenite zeolite are studied by using our own n-layered integrated molecular orbital and molecular mechanics (ONIOM) scheme. The aromatic hydrocarbons investigated are toluene, xylenes, and trimethylbenzenes. Two proposed intramolecular reaction mechanisms, that is, shift 1,2-isomerization and isomerization via the disproportionation reaction, are studied and discussed in detail. Both of the mechanisms firstly proceed by protonation of aromatic hydrocarbons to form the aromatic-based carbenium ions. Attempts to determine the prevailing reaction mechanism of the isomerization are evaluated. In most cases, the isomerization reactivity sequence is: trimethylbenzenes>xylenes>toluene. The conclusions obtained using the ONIOM scheme agree with the available periodic DFT and experimental results on acidic mordenite zeolite.
利用我们自己的n层集成分子轨道和分子力学（ONIOM）方法，研究了酸性丝光沸石上芳烃的两种不同机理：1,2-异构化和通过歧化反应的异构化。图中展示了酸性丝光沸石催化甲苯异构化的示意能量剖面图。利用我们自己的n层集成分子轨道和分子力学（ONIOM）方法，研究了酸性丝光沸石的128T簇模型催化芳烃异构化反应的几何结构和能量。所研究的芳烃为甲苯、二甲苯和三甲苯。详细研究和讨论了两种提出的分子内反应机理，即1,2-异构化和通过歧化反应的异构化。两种机理均首先通过芳烃质子化形成芳基碳正离子来进行。对确定异构化主要反应机理的尝试进行了评估。在大多数情况下，异构化反应活性顺序为：三甲苯>二甲苯>甲苯。使用ONIOM方法得到的结论与酸性丝光沸石上现有的周期性密度泛函理论（DFT）和实验结果一致。
