Study On Conversion Process Of Carbon Dichlorosilane Impurity Methyldichlorosilane In Chlorosilane

Polysilicon is one of the main materials used in chip manufacturing,and domestic polysilicon production has increased significantly in recent years.However,the electronic grade polysilicon that meets the chip manufacturing standards still relies heavily on imports,which seriously restricts the development of the domestic electronic chip field.Trichlorosilane is one of the important basic raw materials for the preparation of polysilicon,and its purity has an important impact on the quality of polysilicon.How to remove residual carbon-containing organic impurities in trichlorosilane is the bottlenecks in obtaining electronic grade polysilicon products.In this paper,the idea of using catalytic reaction to convert low-boiling substance methyldichlorosilane to high-boiling substance methyltrichlorosilane was proposed,and this thesis deeply studied the catalytic conversion process of methyldichlorosilane.This method provided a certain theoretical basis for the removal of carbon-containing organic impurities in the polysilicon industry and broke the technical blockade abroadThe main research contents and results of this round are as follows:（1）The effects of catalyst type,supported catalyst metal active components,Pd catalyst carrier type,Pd loading,calcination temperature,reduction temperature,and chlorine source species on the conversion rate of methyldichlorosilane were investigated through batch kettle catalytic reaction.After comprehensive consideration,when the catalyst was Pd/Al₂O₃,the loading was about 1‰,the calcination temperature was 450℃,and the reduction temperature was 150℃,the chlorine source material was CCl₄,and the conversion rate of methyldichlorosilane was 31.72%.After that,the optimized Pd/Al₂O₃ catalyst was characterized by nitrogen adsorption and desorption,XRD,SEM,XPS.（2）The effects of reaction temperature,reactant ratio,volumetric liquid hourly space velocity on the conversion rate of methyldichlorosilane were explored,and continuous catalytic reactions was carried out by using a gas-phase fixed bed.The best process conditions was obtained:the reaction temperature was about 140℃,the ratio of reactants was n（CH₃Cl₂SiH）:n（CCl₄）=3,the volume liquid hourly space velocity was 5h^-1.At this time,the instantaneous conversion rate of methyldichlorosilane was 69.76%.（3）The Pd/Al₂O₃ catalyst before and after the reaction was characterized by H₂ pulse-chemical adsorption and XRF.The reason for the decrease in catalyst activity was analyzed.It was concluded that the decrease in catalyst activity was related to the loss of palladium active components and poisoning,whic provided a basis for improving the catalyst performance.