Low Temperature Hydrogenation Of Sililcon Tetrachloride And Its Catalysts

Silicon tetrachloride is one of the byproducts in the production of polysilicon,which can cause serious environmental pollution without proper handling.Trichlorosilane,nano-silica,silicone products,silicon fiber were produced by hydrogenation process of silicon tetrachloride.The most convenient and economical process is for the product o f trichlorosilane.As we all know,the cold hydrogenation process is widely used in the world.The conversion efficiency was influenced by pressures,temperature and other factors,as well as the type and amount of catalyst.There are many researches about the cold hydrogenation process,but a few of literatures researched the catalyst.This paper studied the catalyst used in the hydrogenation process,we hope that it can treat silicon tetrachloride in the production of polysilicon,and reduce the costs.The main results were shown as follows:(1)The operating temperature,pressure and the thickness of the silicon powder were studied in the cold hydrogenation technology.The results shown that the best experimental conditions are: temperature fro m 430 to 520?,reaction pressure from 1.25 to 1.45 MPa,the ratio between hydrogen and silicon tetrachloride from 3 to 5,mixed gas flow rate from 0.04 to 0.07m/s,the silicon thickness from 0.4 to 1.2m,the weight ratio of silicon and catalyst from 85 to 100.(2)The effect of the quality of products and the conversion ratio of silicon tetrachloride were studied by different catalysts,such as nickel catalyst,copper catalyst,nickel copper alloy catalyst.The results shown that silicon tetrachloride molar conversion is from 17% to 30%,the highest conversion ratio is from nickel copper alloy;the lowest impurity content is also from nickel copper alloy for the cold hydrogenation product quality,in which B,P impurity was 70% lower than that of Al.The iron impurities are reduced by more than 90%.