The Study Of Precipitated Silica Preparation Using Silicon Tetrachloride,the Byproduct Of Polysilicon

This article respectively studies two methods of preparing precipitated silica utilizing the main by-product of polycrystalline silicon industry—silicon tetrachloride as a major raw material.The preparing conditions were optimized and the basic performance of silica powders produced has been characterized by means of SEM,TEM,XRD,FTTR, TG,etc.Firstly, the method was studied of preparing precipitated silica using silicon tetrachloride and soluble glass as major raw material,polyethylene glycol(PEG) as the surface active agent,alcohol as dispersant. Influences of factors such as reaction temperature, pH value, the amount of surface active agent and dispersing agent,soluble glass concentration on the size and appearance of precipitated silica particles was studied. Products were analyzed by a series of modern characterizing techniques and results indicated that the average particle size is about 280nm with unregular appearance and poor dispersion.Secondly, the method of preparing precipitated silica by the hydrolysis of silicon tetrachloride in ammonia solution was studyed, in which silicon tetrachloride was used as major raw material,ammonia as the precipitant,cetyltrimethylammonium bromide as the surface active agent and alcohol as dispersant.Similarly, the Influences of factors as the amount of ammonia and surface active agent,stirring speed,calcination temperature on the size and appearance of precipitated silica particles was studied. The characterizing results indicated that the precipitated silica is amorphous and has the average particle size of about 200nm with unregular appearance and poor dispersion due to agglomeration.Our work included in this thesis provides a new way to dispose the silicon tetrachloride (SiCl₄),the by-product generated in the polycrystalline silicon industry harmlessly and utilize it resourcefully. It has important environmental significance and some economic value.