MIL⁃53(Al)催化甲基氯硅烷的歧化机理

利用B3LYP/6?311++G(3df,2pd)方法计算了MIL?53(Al)的3个位点催化甲基氯硅烷以制备二甲基二氯硅烷的活性差异,并对反应通道、能量、过渡态虚振模式、内禀反应坐标(IRC)、关键原子间距的变化等进行了分析和讨论,得出了一致的结论:1~3号活性位催化的主反应速控步的活化能分别为157.15、155.31和123.44 kJ·mol-1;副反应速控步的活化能分别为206.48、214.87和166.07 kJ·mol-1。MIL?53(Al)能顺利催化歧化反应的原因在于其催化中心Al—O—H上的Br?nsted酸H,活性的差异来源于其配位环境的不同。

Disproportionation Mechanism of Methylchlorosilanes Confinement Catalysis by MIL-53(Al)

Using B3LYP/6-311++G(3df, 2pd) method, the activity difference of three sites of MIL-53(Al) for the preparation of dimethyldichlorosilane was calculated. The change of reaction channels, energy, virtual modes of transition states, intrinsic response coordinates (IRC) and the distance between key atoms were discussed, and the same conclusion was drawn. The activation energy of the rate-determining-step in main reaction were 157.15, 155.31 and 123.44 kJ·mol^-1, and those in the side reaction were 206.48, 214.87 and 166.07 kJ·mol^-1, respectively. It can be seen that the order of catalytic activity of three sites was 3 > 1 > 2. The catalytic disproportionation activity of MIL-53(Al) is attributed to the Brønsted acid H on its catalytic center (Al-O-H). The difference in activity results from the difference in their coordination environment.