Study on the Catalytic Conversion Mechanism of Methyldichlorosilane Based on Density Functional Theory

Improving the separation efficiency between methyldichlorosilane (CH3SiHCl2) and trichlorosilane (SiHCl3) is one of the key urgent problems to be solved for the quality improvement and consumption reduction in high-purity polysilicon. In this work, three types of porous supported catalysts were prepared via an in situ reaction method, taking aluminum chloride (AlCl3) as the active component and activated carbon, silica gel and activated alumina as support; the catalytic reaction mechanisms of CH3SiHCl2 and silicon tetrachloride (SiCl4) over the as-prepared porous supported catalysts were investigated, based on density functional theory (DFT). The results reveal that among the three supported catalysts, the activated carbon-supported aluminum chloride catalyst (C@AlCl3) possesses the maximum binding energy (−3.20 eV) between the active component and support. CH3SiHCl2 and SiCl4 possess the lowest co-adsorption energy (−1.8 eV) and the minimum reaction energy barrier (0.8 eV) on C@AlCl3, accompanied by the maximum charge transfer to the catalyst surface (−2.65 e and −2.80 e), thus exhibiting the highest catalytic activity, with the maximum single-pass conversion of CH3SiHCl2 exceeding 90%. This work provides material basis and theoretical guidance for constructing a reactive distillation strategy for high-efficiency and low-energy separation of CH3SiHCl2 from SiHCl3.