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CN-121971956-A - Separation SiF4Method for preparing HCl in gas

CN121971956ACN 121971956 ACN121971956 ACN 121971956ACN-121971956-A

Abstract

The invention provides a method for separating HCl in SiF 4 gas, which comprises the steps of S1, introducing silicon tetrafluoride gas containing hydrogen chloride into glycerin for gas absorption to obtain a mixture containing hydrogen chloride, silicon tetrafluoride and glycerin and absorbed silicon tetrafluoride gas, S2, desorbing the hydrogen chloride and the silicon tetrafluoride in the mixture, and carrying out at least two-stage desorption under the negative pressure condition, wherein the desorption temperature is gradually increased. The process of the present invention uses glycerol as an absorbent to achieve a highly selective absorption of HCl in SiF 4 .

Inventors

  • YANG FAN
  • LIU CHENJUN
  • YANG XIAOJIAN
  • Su Wenjiao
  • WAN SHAOLONG
  • SHI JINPENG
  • CHEN GUANGPENG
  • He Wangzhiyuan
  • LIU FEI
  • FAN LITING

Assignees

  • 瓮福（集团）有限责任公司
  • 厦门大学

Dates

Publication Date
20260505
Application Date
20260203

Claims (10)

  1. 1. A method for separating HCl in SiF 4 gas, comprising the steps of: S1, introducing silicon tetrafluoride gas containing hydrogen chloride into glycerol for gas absorption to obtain a mixture containing hydrogen chloride, silicon tetrafluoride and glycerol and absorbed silicon tetrafluoride gas; S2, desorbing hydrogen chloride and silicon tetrafluoride in the mixture, and carrying out at least two sections of desorption under the negative pressure condition, wherein the desorption temperature is raised section by section.
  2. 2. The method of claim 1, wherein the desorption in step S2 comprises the steps of performing a first-stage desorption at 60-72 ℃ and performing a last-stage desorption at 85-92 ℃.
  3. 3. The method according to claim 1, wherein the desorption in the step S2 comprises the steps of performing initial desorption at 60-72 ℃, performing middle desorption at 75-82 ℃ and performing tail desorption at 85-92 ℃.
  4. 4. The method according to claim 1, wherein the desorption in the step S2 comprises the steps of performing initial desorption at 60-62 ℃, middle desorption at 70-82 ℃ and tail desorption at 85-92 ℃.
  5. 5. The method according to any one of claims 1 to 4, wherein in step S2, the negative pressure condition is 2 to 30kpa.
  6. 6. The method according to any one of claims 1 to 4, wherein glycerin obtained after completion of the desorption in step S2 is used for the gas absorption in step S1.
  7. 7. An apparatus for use in the method of any one of claims 1 to 6, comprising: The absorption tower and the desorption system are used for introducing glycerol and silicon tetrafluoride gas containing hydrogen chloride into the absorption tower for gas absorption, a liquid phase generated by the absorption tower is fed into the desorption system for desorption, the desorption system comprises at least two desorption towers which are arranged in a cascade connection, the liquid phase generated by the former desorption tower is fed into the next desorption tower for continuous desorption, negative pressure conditions are adopted in all the desorption towers, and the temperature in the desorption towers is gradually increased.
  8. 8. The apparatus of claim 7, wherein the desorption system comprises a primary desorption tower and a tail desorption tower, the temperature of the primary desorption tower is 60-72 ℃, and the temperature of the tail desorption tower is 85-92 ℃.
  9. 9. The apparatus of claim 7, wherein the desorption system comprises a preliminary section desorber, a final section desorber, and a middle section desorber disposed between the preliminary section desorber and the final section desorber.
  10. 10. The apparatus according to claim 9, wherein the temperature of the primary desorber is 60 to 72 ℃, the temperature of the middle desorber is 75 to 82 ℃, and the temperature of the tail desorber is 85 to 92 ℃, or The temperature of the primary section desorption tower is 60-62 ℃, the temperature of the middle section desorption tower is 70-82 ℃, and the temperature of the tail section desorption tower is 85-92 ℃.

Description

Method for separating HCl in SiF 4 gas Technical Field The invention relates to the technical field of fluorine chemical industry, in particular to a method for separating HCl in SiF 4 gas. Background In the semiconductor, photovoltaic and specialty gas industries, siF 4 is a critical electron specialty gas whose purity directly affects the performance of downstream products. The process for producing hydrofluoric acid by the fluosilicic acid method uses concentrated sulfuric acid or concentrated sulfuric acid containing hydrogen fluoride to purify silicon tetrafluoride gas, and removes moisture, hydrogen fluoride gas and oxyfluoride. In the main reaction of fluosilicic acid solution and sulfuric acid, fluorine element is released in the form of HF and SiF 4, and chlorine ion reacts with sulfuric acid to generate volatile hydrogen chloride (HCl), and finally, the mixed gas of silicon tetrafluoride and hydrogen chloride is formed. Due to the lack of an efficient separation process, hydrogen chloride may be gradually enriched in the system, with a concentration of even more than 15%. This severely reduces the capacity of the apparatus, increases the cost of subsequent separations, and causes significant corrosion to the apparatus. Therefore, the efficient separation of the hydrogen chloride by-product becomes a key step for realizing the stable preparation of the high-purity SiF 4 product, and is a core technical challenge for improving the production efficiency of hydrofluoric acid by a phosphorite method. However, no report of directly removing HCl gas in SiF 4 exists at present. The current separation methods of hydrogen chloride in industry mainly comprise an adsorption method and an absorption method. The adsorption method uses adsorbent as core, uses its large specific surface area and porous structure to adsorb acid gas, hydrocarbon, inert gas and metal and non-metal impurities, and uses the adsorbent as silica gel, alumina, molecular sieve and active carbon. In the prior art, basic adsorbents are basically utilized to chemically adsorb HCl gas through acid-base action. Higher temperatures are often required during the preparation, adsorption and desorption processes. Because of the occurrence of chemical reaction, the adsorbed hydrogen chloride gas is difficult to desorb, and the adsorbent is not recycled in most cases, so that the method is not suitable for removing a large amount of HCl gas with high concentration. On the other hand, silicon tetrafluoride is also a strong lewis acid, and a strong acid-base action with an alkaline adsorbent occurs, so that selective removal of HCl cannot be realized. The solvent absorption rule is to utilize the solubility difference of different gases in the solvent and achieve the purpose of high-efficiency removal by selectively dissolving hydrogen chloride (HCl) gas. The key point of the method is to select a proper solvent, however, most of research on the solvent in the industry is performed in mixed gas of hydrogen chloride and inert gas, and the solubility of the inert gas in a common solvent is extremely low, so that the problem of competitive absorption does not exist. Unlike inert gases, silicon tetrafluoride (SiF 4) acts as a strong lewis acid, which has similar chemical properties to hydrogen chloride and is also capable of reacting with basic solvents. The prior SiF 4 mainly has the following problems that 1) HCl and SiF 4 are acid gases, the HCl cannot be separated through an alkaline absorbent, the HCl cannot be effectively separated, 2) SiF 4 gas and HCl gas have similar boiling points, siF 4 gas cannot be purified through a compression freezing method, and 3) the existing solvent for separating the HCl has low selectivity, and cannot be efficiently and selectively absorbed. Disclosure of Invention The SiF 4 gas prepared by the fluosilicic acid method contains HCl gas, the concentration of the HCl gas is gradually increased due to continuous recycling of the SiF 4 gas in the actual production process of enterprises, the content of the HCl gas in the SiF 4 is sometimes even more than 20%, and the utilization of SiF 4 by enterprise production is influenced by the fact that the HCl gas cannot be discharged. In view of the above problems, the present invention provides a method for separating HCl in SiF 4 gas, which can realize high selective absorption of HCl in SiF 4 by using glycerol, thereby realizing separation of HCl in SiF 4 gas. In order to achieve the above object, the present invention provides the following technical solutions: In a first aspect the invention provides a method for separating HCl from SiF 4 gas, comprising the steps of: s1, introducing silicon tetrafluoride gas containing hydrogen chloride into glycerin for gas absorption to obtain a mixture containing hydrogen chloride, silicon tetrafluoride and glycerin and absorbed silicon tetrafluoride gas. S2, desorbing hydrogen chloride and silicon tetrafluoride in the mixture, and carryi