GB609507A - Improved process for the production of alkyl silicon halides - Google Patents

Abstract

Alkyl silicon halides are prepared by bringing a vapour mixture of an alkyl halide, e.g. one which contains less than four carbon atoms in the molecule such as methyl or ethyl chloride, and a hydrogen halide, or a vapour mixture of an olefine and more than its molecular equivalent of a hydrogen halide, into contact with silicon at a reaction temperature between 250 DEG and 550 DEG C., but preferably between 300 DEG and 450 DEG C. The vapour mixture may comprise one part by volume of an alkyl halide and from 0.5 to 20 parts of a hydrogen halide. The silicon may be employed in the form of an alloy, e.g. ferrosilicon or calcium-manganese-silicon, manganese-zirconium-silicon, titanium-silicon, zirconium-silicon, or calcium-titanium-aluminium-zirconium-boron-iron-silicon alloys may be used. A substantial portion of the reaction products, e.g. from 0.5 to 0.8 of the reaction products, may be recirculated into contact with the silicon or an alloy thereof, and the remainder of the reaction products withdrawn from the system. The reaction is usually carried out at atmospheric pressure, but lower or higher pressures may be employed, and a diluent may be employed, e.g. carbon dioxide, carbon monoxide, silicon tetrachloride or trichlorosilane. The reaction may be effected in an intermittent or continuous way, or in a batchwise manner, e.g. in a bomb or autoclave. The preparation of methyl silicon trichloride is given by contacting methyl chloride vapours with heated ferrosilicon. In examples (1) to (4), methyl silicon trichloride, methyl-dichlorosilane, silicochloroform and silicon tetrachloride are obtained by contacting methyl chloride and hydrogen chloride vapours with heated ferrosilicon and ethyl silicon trichloride, silicon tetrachloride and silicochloroform by contacting ethyl chloride and hydrogen chloride with heated ferrosilicon. In example (5), ethyl silicon trichloride, silicon tetrachloride and silicochloroform are obtained by passing hydrogen chloride and ethylene over heated ferrosilicon. Specifications 575,667, 575,668, 575,673 and 575,674 are referred to. The Specification as open to inspection under Sect. 91 refers to the preparation of alkyl silicon halides by reacting alkyl halides, or components of alkyl halides which react readily to form alkyl halides, with silicon or an alloy thereof at an elevated temperature. In examples, methyl bromide is reacted with ferrosilicon to yield methyl silicon tribromide, silicon tetrabromide, dibromo- and tribromosilane and methyldibromosilane, ethyl chloride is reacted with heated ferrosilicon to yield ethyl silicon trichloride, silicon tetrachloride, silicochloroform and ethyldichlorosilane, isopropyl chloride is reacted with heated ferrosilicon to yield isopropyl-dichlorosilone, and methyl silicon trichloride is prepared by passing methyl chloride vapour over calcium silicon, calcium-manganese - silicon, manganese - zirconium - silicon, iron - silicon, zirconium - calcium - titanium-aluminium-boron-iron-silicon, zirconium-silicon, or titanium-aluminium-silicon alloy. This subject-matter does not p appear in the Specification as accepted.