Patent ID: 8974761
Filing Date: 2015-03-10
Classification: C01B,C25B,C25C

Abstract:
1. A closed-loop process for producing polycrystalline silicon, the process comprising: contacting a halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetrahalide, trihalosilane, dihalosilane and monohalosilane with an alkali or alkaline earth metal hydride to produce silane and an alkali or alkaline earth-metal halide salt; thermally decomposing silane to produce polycrystalline silicon and hydrogen; electrolyzing the halide salt to produce metallic alkali or alkaline earth metal and halogen gas; and producing a halogenated silicon feed gas comprising at least one halosilane selected from the group consisting of silicon tetrahalide, trihalosilane, dihalosilane and monohalosilane by contacting the halogen gas produced by electrolyzing the alkali or alkaline earth metal halide with at least one of: contacting the metallic alkali or alkaline earth-metal with hydrogen produced from the thermal decompositions of silane to produce an alkali or alkaline earth metal hydride; contacting the halogenated silicon feed gas produced by contacting halogen gas or hydrogen halide with silicon with the alkali or alkaline earth-metal hydride produced by contacting the metallic alkali or alkaline earth metal with hydrogen to produce silane and an alkali or alkaline earth-metal halide salt.