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 using sodium fluorosilicate as raw material, which is characterized in that it comprises the following steps: 1) drying sodium fluorosilicate to remove water; Add sodium sulfate and sulfuric acid into the rotary kiln reactor at a molar ratio of 1:1, and react for 30-180 minutes at 160-220°C to generate sodium sulfate solid and mixed gas of silicon tetrafluoride and hydrogen fluoride; 3) Then dedust and pressurize Cool to -20~-30℃; 4) Send the pre-cooled mixed gas to the rectification tower for separation, control the pressure of the rectification tower to 0.6~0.75MPaG, the temperature of the condenser at the top of the tower is -70~-80℃, the bottom of the tower Extract anhydrous hydrogen fluoride; 5) Silicon tetrafluoride is extracted from the top of the tower in the form of liquid phase, and then sent to the silicon tetrafluoride washing tower to obtain silicon tetrafluoride gas after decompression gasification and dust removal. Corrosion of equipment, the obtained silicon tetrafluoride and hydrogen fluoride products have high purity and the production process is energy-saving and 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. stirring and reacting sodium fluorosilicate and excess sulfuric acid 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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