Preparation method for preparing silica sol for catalyst high in purity and uniform in particle size

The present invention provides a preparation method for preparing a silica sol for a catalyst high in purity and uniform in particle size. According to the method, silicon tetrachloride, a by-product obtained during the production of polycrystalline silicon, is adopted as a main raw material. The silicon tetrachloride is subjected to reaction with mixed alcohol and organic amine with the presence of a catalyst. In this way, the problem that the hydrolysis of silicon tetrachloride is difficult to control is successfully solved through optimizing the process, adding an alleviator and the like. After that, the silica sol for the good-quality catalyst is prepared, wherein the catalyst is good in stability, high in purity and uniform in particle size. The particle size of the catalyst is 16-20 nm, and the pH value of the catalyst is 9.0-10. The viscosity of the catalyst is 3-4 mba.s, and the N+ of the catalyst is smaller than 0.01%. At the same time, the silica sol can be applied to the fields of precision casting