Method for preparing silicon tetrafluoride from calcium fluosilicate

Abstract

The invention discloses a method for preparing silicon tetrafluoride. In the method, hydrated calcium fluosilicate is used as a raw material. The method is characterized by comprising the following steps of: preheating the hydrated calcium fluosilicate to 60-100 DEG C and drying under pressure of 0.05-0.5 MPaG and at the temperature of 100-220 DEG C for 60-150 minutes to obtain solid powdery calcium fluosilicate with moisture content of less than 1.5 percent by weight; feeding the calcium fluosilicate into an intermediate storage tank, then feeding into a cracking reactor, and pyrolyzing under the pressure of 0.05-0.5 MPaG and at the temperature of 220-420 DEG C for 60-150 minutes to obtain a silicon tetrafluoride rough product; and feeding the silicon tetrafluoride rough product into a sulfuric acid washing tower for washing to remove moisture so as to obtain a silicon tetrafluoride product with purity of 99 percent. The method has the advantages of simple technical process, capability of relieving corrosion to equipment, energy conservation, environmental friendliness, low cost and capability of improving purity of the silicon tetrafluoride.

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 hydrated calcium fluorosilicate as a raw material. Background technique [0002] Silicon tetrafluoride, the molecular formula is SiF 4 , widely used in the electronics and semiconductor industries. It is mainly used as etchant for silicon nitride, molybdenum silicide, etc., P-type dopant, epitaxial deposition diffusion silicon source, etc. It can also be used for the preparation of electronic grade silane or silicon. Silicon tetrafluoride can also be used as a raw material for high-purity quartz glass for optical fibers, and its hydrolysis in a high-temperature flame can produce heat-sinking silica 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, oil we...

AI Technical Summary

Problems solved by technology

The sulfuric acid method uses sulfuric acid, fluorite, and silicon dioxide to react at high temperature, which has severe corrosion and high energy consumption. The silicon tetrafluoride gas produced is likely to contain impurities such as siloxane, which are difficult to remove during the refining of silicon tetrafluoride. Fluorine-containing waste residue is produced as a by-product; the fluosilicic acid method is obtained by the reaction of fluosilicic acid and concentrated sulfuric acid, the use of sulfuric acid severely corrodes the equipment, and fluorine-containing waste liquid is also produced as a by-product; the Chinese invention patent name is a preparation method of silicon tetrafluoride (The publication number is CN101481113), which discloses the reaction of fluorosilicic acid and magnesium oxide for 10-60 minutes, then gas agitation at 25-55°C for 1-3 hours, and finally calcining at 200-300°C for 1-2 hours to obtain four Silicon fluoride reduces the corrosion of equipment, but magnesium oxide is scarce and expensive in this method, and the cost of preparing silicon tetrafluoride with magnesium oxide is relatively high, and the yield of silicon tetrafluoride is relatively low

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