Process for the preparation of anhydrous synthetic silicon dioxide

摘要

The invention relates to a process for the preparation of anhydrous synthetic silicon dioxide by thermal oxidation of a silicon compound using oxygen in the gas phase, which process enables the economic production of OH-free high-purity, specifically doped quartz glass. It is proposed to heat at least the oxygen to the reaction temperature by the external action of heat, to carry out the oxidation of the silicon compound in a reaction space isolated from the external atmosphere and to cool amorphous silicon dioxide formed during the oxidation and to deposit it in wet form outside the reaction space. The amorphous silicon dioxide is shaped in the moist state, subsequently dried, sintered and melted in a conventional manner to give quartz glass. The silicon compound employed is a rectifiable silicon halide comprising silicon and chlorine and optionally oxygen. The liquid used for the wet deposition is one of the reactants. Oxygen is passed in countercurrent to the silicon dioxide. Chlorine is recovered quantitatively in elemental form.