三氯化铝催化有机硅单体副产共沸物歧化反应密度泛函理论研究

摘要

The disproportionation reaction between (CH3)3SiCl and SiCl4 catalyzed by AlCl3 involves three reactions; the reaction between (CH3)3SiCl and SiCl4 to form (CH3)2SiCl2and CH3SiCl3(R1), the reaction between (CH3)2SiCl2and SiCl4to form CH3SiCl3(R2)and the reaction between (CH3)3SiCl and CH3SiCl3 to form (CH3)2SiCl2(R3). Density functional theory was used to study these reactions. The possible catalytic mechanisms of AlCl3 were stepwise reaction pathway of forming intermediate CH3AlCl2 and co-adsorption pathway of two reactants on AlCl3.The co-adsorption mechanism was more likely for these three reactions. The energy barrier ranking of these reactions was R2>R1>R3. By analyzing the thermodynamics data of these reactions, the effect of temperature on the Gibbs reaction energy of R2 was almost negligible within a temperature range of 543.15 K to 593.15 K. However, the Gibbs reaction energy of R1 and R3 significantly decreased at 593.15 K. These studies indicated that through appropriate temperature regulation, the reactions of R1 and R3 could be the dominant reactions while R2 would be effectively suppressed, influencing product distribution and facilitating formation of (CH3)2SiCl2.%AlCl3催化(CH3)3SiCl 和 SiCl4的歧化反应体系中可能存在(CH3)3SiCl 与 SiCl4生成(CH3)2SiCl2与 CH3SiCl3（反应1），(CH3)2SiCl2与SiCl4生成CH3SiCl3（反应2）和(CH3)3SiCl与CH3SiCl3生成(CH3)2SiCl2（反应3）等反应。本文采用密度泛函理论对这3种反应进行了研究。结果发现在AlCl3催化剂上，可能发生CH3AlCl2中间体生成的分步反应和反应物共吸附反应，对两种情况下3种反应的反应路径均进行了计算，发现3种反应均偏向于以双分子共吸附机理进行。3种反应的能垒排序是反应2＞反应1＞反应3。同时，热力学数据分析发现，在543.15～593.15 K之间，温度变化对反应2的摩尔Gibbs反应能变基本无影响，但在593.15 K时，反应1和反应3的Gibbs自由能变显著减小。这些计算结果显示，如果适当调控反应温度，就能够在保证反应1和3进行的同时，抑制反应2的进行，从而实现歧化产物组成的调控，有利于(CH3)2SiCl2的生成。