Preparation of silicon tetrafluoride

Abstract

The invention discloses a method for preparing silicon tetrafluoride, which takes hydrofluorosilicic acid and magnesia as raw materials, and comprises the following steps: (1) reacting hydrofluorosilicic acid solution with the magnesia for 10 and 60 minutes, filtering the mixture to obtain magnesium fluosilicate solution, and concentrating and crystallizing the mixture to obtain magnesium fluosilicate crystal hexahydrate; (2) pulsating the obtained magnesium fluosilicate crystal hexahydrate by air flow at a temperature of between 25 and 55 DEG C for 1 to 3 hours, and removing adhesive water and crystallization water; (3) sintering the magnesium fluosilicate removing the adhesive water and the crystallization water at a temperature of between 200 and 300 DEG C for 1 to 2 hours so as to obtain silicon tetrafluoride gas and magnesium flux; and (4) obtaining the high-purity silicon tetrafluoride gas after sublimating the silicon tetrafluoride gas. The invention has low production cost, the prepared silicon tetrafluoride has high quality, three wastes are not discharged; in addition, the co-produced magnesium flux can be taken as an additive in the aluminum electrolytic industry, the waste residue containing fluorine gas is not generated, and the invention has good social benefits and social benefits and is easily popularized and applied.

Description

technical field [0001] The invention relates to a method for preparing silicon tetrafluoride, in particular to a method for preparing silicon tetrafluoride by using fluorosilicic acid and magnesium oxide as raw materials. Background technique [0002] Silicon tetrafluoride is mainly used in the electronics and semiconductor industries as etchant for silicon nitride, tantalum silicide, etc., P-type dopant and epitaxial deposition diffusion silicon source, etc.; it can also be used to prepare electronic grade silane or silicon. Silicon tetrafluoride can also be used as a raw material for high-purity quartz glass for optical fibers. It can be hydrolyzed in a high-temperature flame to produce heat sink silicon dioxide with a high specific surface area; in addition, silicon tetrafluoride is also widely used in the preparation of solar cells. , Fluorosilicic acid and aluminum fluoride, fluorinating agents for chemical analysis, catalysts for oil well drilling, magnesium alloy cast...

AI Technical Summary

Problems solved by technology

The cost of the hydrofluoric acid method is high, the by-product recovery method is complicated, and it is not easy to realize industrialization; the fluosilicic acid method uses concentrated sulfuric acid, which is severely corroded, has high requirements on equipment, and by-products fluorine-containing waste liquid; the sulfuric acid method uses sulfuric acid, fluorite, di SiO 2 increases heat, causing serious corrosion and high energy consumption. Impurities such as siloxane are likely to be contained in the production of silicon tetrafluoride gas, which are not easy to remove during the process of refining silicon tetrafluoride, and fluorine-containing waste residue is also produced by-product; sodium fluorosilicate method Although it can reduce the production of siloxane and other impurities, it still has the disadvantages of high calcination temperature, serious corrosion of equipment, and high energy consumption.

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