ZSM-5(8T)@γ-Al2O3 supported AlCl3 core-shell catalyst: Mechanism research on disproportionation reaction of methylchlorosilanes

Abstract

Organosilanes are important raw materials in today’s technology-intensive industries, and dichlorodimethylsilane is the most widely used and the largest consumed organosilicon monomer. In this article, B3LYP/6–311++G(3df, 2pd) basis set was used to calculate the disproportionating mechanism for the synthesis of the dichlorodimethylsilane by core-shell catalysts ZSM-5(8T)@γ-Al2O3 (active sites 1–5) and AlCl3/ZSM-5(8T)@γ-Al2O3 (active sites 6 and 7). The theory analysis of results showed that the activation energies of the main reactions’ rate determine steps in ZSM-5(8T)@γ-Al2O3 (active sites 1–5) were: 144.37, 145.40, 149.82, 152.98, 167.39 kJ·mol−1, respectively. ZSM-5(8T)@γ-Al2O3 is the catalyst with ZSM-5 as the core layer and γ-Al2O3 as the shell layer, which were catalyzed by Bronsted acids in essence. The activation energies (AlCl3/ZSM-5(8T)@γ-Al2O3′ active sites 6 and 7) of the rate determine steps in the main reactions were: 96.51 and 127.98 kJ·mol−1, respectively. It can be seen from the energy data that the catalysts exhibit strong Lewis acid activity after loading AlCl3, which was more conducive to the formation of target products. By comparing the calculation of energies, vibration frequency analysis, discussion of frontier molecular orbital theory with the Electron Localization Function (ELF) and the Localized Orbital Locator (LOL) figures, the results were quite consistent with the proposed mechanism.