RU2458006C2 - Method of producing high-purity synthetic silicon dioxide - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to chemical engineering of inorganic substances. The method of producing high-purity synthetic silicon dioxide involves reaction of the starting quartz-containing material with a fluoride, hydrofluoride of ammonium or mixture thereof to obtain ammonium silicofluoride and fluorides of impurity elements. The obtained ammonium silicofluoride is purified from metal impurities by sublimation. The ammonium silicofluoride solution in water is purified from non-metal impurities by extraction. Synthetic silicon dioxide is then precipitated from the ammonium silicofluoride solution using ammonia water.

EFFECT: obtaining high-purity synthetic silicon dioxide.

2 ex

Description

The invention relates to the field of chemical technology of inorganic substances and can be used in cases where it is necessary to obtain synthetic silicon dioxide of high purity.

A known method of purification of silicon dioxide, patent JP 62153111, the interaction of the source of silica with a mixture of hydrofluoric acid and sulfuric acid, precipitation from a solution of silica gel with ammonia water and separation of silica gel from the solution. The disadvantage of this method is the formation of a large amount of wastewater, which must be disposed of.

A known method for producing synthetic silicon dioxide is US Pat. No. 5,458,864, by reacting a quartz-containing feedstock with a solution of ammonium fluoride, ammonium hydrofluoride or a mixture thereof, separating ammonium silicofluoride from unreacted silica, and precipitating synthetic silicon dioxide and reacting a solution of ammonium silicofluoride with ammonia water. The disadvantage of this method is the incomplete processing of the original quartz-containing raw materials and, as a consequence, the formation of solid waste.

A known method of producing high-purity synthetic silicon dioxide, patent US 1859998, prototype, the interaction of quartz-containing raw materials with ammonium fluoride when heated, dissolving ammonium silicofluoride in water, treating the solution with ammonia water, followed by separation of synthetic silicon dioxide. The disadvantage of this method is the contamination of the final product with iron, titanium, boron, phosphorus and other elements.

An object of the present invention is to provide an industrial process for the preparation of high purity synthetic silicon dioxide.

The problem is solved in that the quartz-containing raw materials are mixed with fluoride, ammonium hydrodifluoride or a mixture thereof. Ammonium fluoride, hydrodifluoride, or a mixture thereof, is taken in excess of up to 20% of the stoichiometric amount necessary for the formation of ammonium silicofluoride:

SiO ₂ + 6NH ₄ F = (NH ₄ ) ₂ SiF ₆ + 4NH ₃ + 2H ₂ O

The process is conducted in the temperature range of 20-240 ° C.

Ammonium silicofluoride is sublimated in the temperature range 320-350 ° C in order to remove metals that remain in solid form from impurities, ammonium silicofluoride is captured and desublimated.

Ammonium silicofluoride purified from metal impurities is dissolved in water to obtain a saturated solution. The solution is purified from non-metallic impurities by extraction on brilliant green C ₂₉ H ₃₇ N ₂ O ₄ S and benzene C ₆ H ₆ . Non-metals pass into the organic phase, ammonium silicofluoride remains in the solution. The separation of organic and aqueous phases is carried out.

A solution containing ammonium silicofluoride purified from impurities is treated with a stoichiometric amount of ammonia water necessary for the formation of synthetic silicon dioxide:

(NH ₄ ) ₂ SiF ₆ + 4NH ₄ OH = SiO ₂ + 6NH ₄ F + 2H ₂ O

Solid silica is separated from the ammonium fluoride solution, dried and calcined.

The solution containing ammonium fluoride can be evaporated to obtain solid fluoride, ammonium hydrodifluoride or a mixture thereof, and used for processing the next batch of quartz-containing raw materials.

The technical result of the invention is the technology for producing synthetic silicon dioxide, purified from impurities of metals and non-metals.

Example 1. A sample of quartz (98.8% SiO ₂ purity) weighing 50 g is mixed with 156.75 g of ammonium hydrodifluoride and kept at 150 ° C until the evolution of gaseous reaction products ceases. The resulting product is heated to 340 ° C and maintained at this temperature until complete removal of ammonium silicofluoride in the form of gas. Gaseous ammonium silicofluoride is desublimated and dissolved in 690 ml of water. Non-metal impurities are removed from the solution of ammonium silicofluoride by extraction on diamond green C ₂₉ H ₃₇ N ₂ O ₄ S and benzene C ₆ H ₆ . The purified solution of ammonium cremofluoride is mixed with 240 g of 25% ammonia water. The solid reaction product is filtered off, washed with water and dried at 110 ° C. The mass of synthetic silicon dioxide obtained was 49.3996 g.

Example 2. It differs from Example 1 in that the quartz was mixed with 203.5 g of ammonium fluoride. The mass of synthetic silicon dioxide obtained was 49.3997 g.

Claims (1)

A method for producing high-purity synthetic silicon dioxide, including the interaction of quartz-containing raw materials with ammonium fluorides when heated, dissolving ammonium silicofluoride in water, treating a solution of ammonia water with subsequent separation of synthetic silicon dioxide, characterized in that the reaction of the initial quartz-containing raw material is carried out with fluoride, ammonium hydrodifluoride or with their mixture, the obtained ammonium silicofluoride is purified from metal impurities by sublimation distillation, a solution of ammonium silicofluoride in water, they remove impurities of non-metals by extraction.