Method for preparing silicon tetrafluoride and anhydrous hydrogen fluoride by taking sodium fluorosilicate as raw material

Abstract

The invention discloses a method for preparing silicon tetrafluoride and anhydrous hydrogen fluoride by taking sodium fluorosilicate as a raw material. The method is characterized by comprising the following steps of: (1) drying sodium fluorosilicate for removing water; (2) adding the dried sodium fluorosilicate and sulfuric acid into a rotary kiln reactor in the molar ratio of 1:1, and reacting at the temperature of 160-220 DEG C for 30-180 minutes to generate a sodium sulfate solid and a mixed gas of silicon tetrafluoride and hydrogen fluoride; (3) dedusting, pressurizing and precooling to between 20 DEG C below zero and 30 DEG C below zero; (4) feeding the precooled mixed gas into a rectifying tower for separating, controlling the pressure of the rectifying tower at 0.6-0.75 MPaG and the temperature of tower top condenser between 70 DEG C below zero and 80 DEG C below zero, and discharging anhydrous hydrogen fluoride from the tower bottom; and (5) discharging silicon tetrafluoride from the tower top in the form of a liquid phase, decompressing, gasifying, dedusting and feeding into a silicon tetrafluoride washing tower to obtain silicon tetrafluoride gas. The method has the advantages that: corrosion to equipment can be reduced greatly, the obtained silicon tetrafluoride and hydrogen fluoride products have high purity, and the production process has low energy consumption and is environmentally-friendly.

Description

technical field [0001] The invention relates to the technical field of fluorine chemical industry, in particular to a method for preparing silicon tetrafluoride and anhydrous hydrogen fluoride by using sodium fluorosilicate as raw material. Background technique [0002] Silicon tetrafluoride is an electronic specialty gas used in semiconductor and optical fiber processing applications, and is an important component in the ion implantation method used in the manufacture of silicon-based semiconductor devices. Silicon tetrafluoride will have broad application prospects in the microelectronics industry. Anhydrous hydrogen fluoride (AHF) is widely used in atomic energy, chemical industry, petroleum and other industries. It is a strong oxidant and a basic raw material for the production of elemental fluorine, various fluorine refrigerants, inorganic fluorides and organic fluorides. [0003] The Chinese patent name is the method for preparing silicon tetrafluoride and anhydrous h...

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Problems solved by technology

[0003] The Chinese patent name is the method of preparing silicon tetrafluoride and anhydrous hydrogen fluoride by acidifying sodium fluorosilicate with sulfuric acid (application number is 201010504248.3) which discloses a A method for preparing silicon tetrafluoride and anhydrous hydrogen fluoride by reacting sodium with sulfuric acid, the process steps are: a. Sodium fluorosilicate and excess sulfuric acid are stirred and reacted below 150°C to obtain silicon tetrafluoride gas and hydrogen fluoride remaining in the solid residue; b. The silicon tetrafluoride gas produced in step a is dedusted, cooled, dried, refined, and compressed to obtain high-purity silicon tetrafluoride gas; c. continue to heat up to 200 ° C, hydrogen fluoride gas escapes; d. hydrogen fluoride gas escapes in step c After dedusting, cooling, drying, refining, and compression, anhydrous hydrogen fluoride gas sodium fluorosilicate is obtained, which has low added value as a by-product of the phosphate fertilizer industry. The sodium fluorosilicate produced for waste treatment has been comprehensively utilized to make fluorine, silicon Elements are converted into silicon tetrafluoride and anhydrous hydrogen fluoride with high added value and wide application, but the above process has the following disadvantages:

[0004] (1) The excess sulfuric acid after the reaction in step a is easy to cause corrosion to the equipment; (2) Silicon tetrafluoride gas and hydrogen fluoride gas are separated by controlling the reaction temperature Escape to achieve separation, because there is a complex endothermic and exothermic process in the reaction process, it is very difficult to accurately control the temperature, so the separation is achieved only by controlling the reaction temperature, and the purity is not high; (3) The reaction between sodium fluorosilicate and excess sulfuric acid is theoretical SiHF5 is generated, and then SiHF5 is easily thermally decomposed into SiF4 and HF. Therefore, it is difficult to achieve separation only by controlling the reaction temperature. (4) The above process does not disclose in detail the specific process of dust removal, cooling, drying, refining and compression of silicon tetrafluoride and hydrogen fluoride

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