Deutsche Gold- Und Silber-scheideanstalt Vormals Roessler

Axel Volling

Hans Klebe

Ludwig Lange

Jean Diether

Process for the production of finely divided silicon dioxide having a surface of more than about 380 m.sup.2 /g BET which comprises converting a volatile silicon halide in an inert gas vehicle with a gas forming water upon combustion and oxygen gas or air in a flame, the quantity of oxygen being sufficient for the practically complete combustion of the combustible gas, and the quantities of oxygen or air and combustible gas being sufficient to produce a quantity of water which will at least suffice for the hydrolysis of the volatile silicon halide, said volatile silicon halide consisting essentially of trichlorosilane and said inert gas vehicle consisting for instance of nitrogen, carbon dioxide, noble gases or others the amount of trichlorosilane vapor being about 410-565 g trichlorosilane vapor per Nm.sup.3 /h total gas, the molar ratio of trichlorosilane vapor to nitrogen being about 0.5:1 - 5:1, the molar ratio of hydrogen in the combustible gas to oxygen being about 0.5:1 - 1.3:1, and separating the resulting silicon dioxide from other reaction products. Finely divided silicon dioxide prepared according to this process is also provided. The finely divided silicon dioxide is useful as a thickening agent in liquid systems.

Process for the production of finely divided silicon dioxide having a

Process for the production of a finely divided oxide of a metal or silicon by the hydrolytic conversion of a volatile corresponding metal halide or silicon halide in a flame, said process comprising feeding the volatile halide in a mixture with a combustible hydrogen-containing gas and air or oxygen to a burner provided with a mouth emitting a flame, burning the mixture in a fire tube to form a first portion of water vapor, said burner surrounded by an annular chamber forming a nozzle through which hydrogen is passed to keep the mouth of the burner free of attachments of solid substances, the quantity of oxygen or air being sufficient for the practically complete combustion of the combustible gas, and the quantities of oxygen or air and combustible gas being sufficient to produce the first portion of water vapor which will at least suffice for the hydrolysis of the volatile halides, and further wherein said flame is allowed to burn in an atmosphere consisting of gases containing a second portion of water vapor, to avoid the formation of halogen gas in waste gases and separating the resulting oxide from other reaction products. The finely divided oxides are useful as additives and fillers in the manufacture of coatings, adhesives and elastomers.

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Rheinfelden, Germany

Axel Volling