METHOD FOR PRODUCTION OF GRANULES OF ESPECIALLY PURE SILICON DIOXIDE Russian patent published in 2022 - IPC C01B33/12 C01B33/193 

FIELD: chemistry.

SUBSTANCE: invention relates to methods for the production of quartz glass of high purity by sol-gel process; it can be used for the production of products of electronic and optical, in particular laser industry. A method is proposed for the production of granules of especially pure silicon dioxide by hydrolysis of tetraethoxysilane (hereinafter – TEOS) with an especially pure aqueous solution of nitric acid. At the same time, ethanol is first pre-added to the nitric acid solution. Then, with mixing for 10-25 min, the hydrolysis of TEOS is carried out in the ratio of TEOS:aqueous solution of nitric acid with ethanol of 1:(2-2.5) with pH from 3.5 to 6. Then a dilute ammonia solution is added to bring pH to 9-10, and mixing is continued for 8-15 min at a temperature of 20-60°C. After that, silicon hydroxide obtained in the form of gel is dried with mixing with simultaneous distillation of an aqueous-alcohol mixture with the formation of solid particles of orthosilic acid. After that, remains of organic substances and the bulk of hydroxyl groups of substances are removed by heat treatment of orthosilic acid at a temperature from 200 to 250°C for 50-80 min. Then, solid particles of orthosilicic acid with a size less than 0.05 mm are separated, and remaining solid particles are calcined at a temperature from 1100 to 1300°C for 3 to 5 h to obtain granules of especially pure silicon dioxide with a size from 0.05 to 0.50 mm.

EFFECT: production of granules of especially pure silicon dioxide with a yield of at least 93% by wt.

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