Study On The Direct Synthesis Of Methylchlorosilanes Using The Fixed-bed Reactor

The direct synthesis of methylchlorosilanes(MCS) was studied by the use of Si powder and CH3CI catalyzed by copper together with some promoters in the fixed-bed reactor. The promoters included zinc powder, tin powder, nickel powder, aluminum powder, etc. The crude methylchlorosilane obtained was characterized by ¹H-NMR to determine the selectivity.Three types of copper catalysts were used to investigate their effects on the MCS reaction. The results revealed that different copper catalysts had different effects on the selectivity for methylchlorosilanes under different conditions, such as the addition of the promoters, the flow ratio of CH₃CI to H₂ and treatment of catalysts.In this paper, the addition of nickel powder made CH₃CI decompose to form HC1 properly and improved reaction of HC1 with Si and CH₃CI to form desired product CH₃SiHCl₂ efficiently. The addition of tin powder made the crude MCS quality very poor and showed deleterious effect on the whole reaction. The addition of zinc promoted the decomposition of CH₃CI and resulted in higher selectivity for Si-H compound and undesired CH₃SiCl₃. Decomposition of CH₃CI produced great amount of by-product as carbon. Then copper and promoters were accumulated on the surface of these carbon instead of silicon. Thus deactivation of the reactive site had negative effect on the reaction. The dosage of aluminum powder made great effect on the crude MCS quality.The effect of treatment of copper and promoters on the MCS reaction was discussed. It was found that the effect of the treatment of catalysts had close relation with the specification of silicon powder.