Closed loop process for producing polycrystalline silicon and fumed silica

摘要

A closed loop process for producing electronic grade polycrystalline silicon from silane and fume silica from silicon tetrachloride comprises the steps of: (a) subjecting impure silicon to hydrochlorination with hydrogen chloride to produce trichlorosilane and silicon tetrachloride together with minor amounts of dichlorosilane and monochlorosilane; (b) converting the trichlorosilane to silicon tetrachloride and silane; (c) converting the silane to polycrystalline silicon and hydrogen; (d) reacting the silicon tetrachloride from steps (a) and (b) with hydrogen and oxygen to produce fume silica and hydrogen chloride, and (e) recycling the hydrogen chloride from step (d) for use in step (a).