A method for producing hydrogen fluoride

Abstract

This invention relates to the field of hydrogen fluoride preparation technology, specifically to a method for preparing hydrogen fluoride. The method includes the following steps: a decomposition reaction is carried out between concentrated fluorosilicic acid and concentrated sulfuric acid to remove silicon tetrafluoride gas, resulting in fluorinated sulfuric acid. One to two trifluoromethyl-substituted phenyl compounds are added to the fluorinated sulfuric acid, followed by distillation. By distilling the fluorinated sulfuric acid under the influence of the one to two trifluoromethyl-substituted phenyl compounds, the phenyl compounds form numerous fine droplets that are uniformly dispersed in the mixture. These droplets then insert into the spaces between fluorosulfonic acid molecules, disrupting the molecular cluster structure and allowing fluorosulfonic acid to exist as individual molecules. This makes the S-F bonds in the fluorosulfonic acid molecules more readily accept external energy and break, significantly reducing the energy required to decompose fluorosulfonic acid and significantly lowering the distillation temperature while increasing the yield of hydrogen fluoride products.

Description

Technical Field

[0001] This invention relates to the field of hydrogen fluoride preparation technology, and specifically to a method for preparing hydrogen fluoride. Background Technology

[0002] Hydrogen fluoride is a crucial raw material in the fluorochemical industry, widely used in new energy, electronics, refrigerants, pharmaceuticals, and rubber. Its primary raw material is fluorite. However, with the rapid development of the fluorochemical market, my country's fluorite resources are scarce, making the search for a new source of fluorine crucial. Phosphate rock contains 3-4% fluorine by mass, which exists as a byproduct of wet-process phosphoric acid production: fluorosilicic acid. Previously, the main method for recovering fluorosilicic acid was to convert it into fluorosilicates, cryolite, and aluminum fluoride, but this resulted in poor product quality and low added value. Currently, converting fluorosilicic acid into anhydrous hydrogen fluoride, which has higher added value, has become a hot topic in the industry. This can improve the economic benefits of enterprises and help solve the problem of my country's fluorite resource shortage.

[0003] There are several methods for preparing hydrogen fluoride from fluorosilicic acid. One of the most mature methods is the sulfuric acid method, which involves first concentrating dilute fluorosilicic acid, then mixing it with concentrated sulfuric acid and heating it to decompose the concentrated fluorosilicic acid into a mixed gas of HF and SiF4. The reaction formula is: concentrated H2SiF6 + concentrated H2SO4 → HF + SiF4. In the concentrated sulfuric acid, the HF and SiF4 mixed gas is absorbed by the concentrated sulfuric acid, while SiF4 is released as a gas. After removing the silicon tetrafluoride gas, a mixture of hydrogen fluoride and concentrated sulfuric acid is obtained. Distillation then yields crude hydrogen fluoride, and further purification can produce relatively pure anhydrous hydrogen fluoride.

[0004] When hydrogen fluoride coexists with concentrated sulfuric acid, a large amount of fluorosulfonic acid (HSO3F) is generated. During distillation, fluorosulfonic acid must be decomposed under heating conditions before hydrogen fluoride can escape in gaseous form. Therefore, decomposing fluorosulfonic acid is the key to separating hydrogen fluoride. The heating temperature generally needs to reach 100-160℃. Too low a temperature will result in incomplete decomposition of fluorosulfonic acid, causing excessive hydrogen fluoride to remain in the sulfuric acid. Industrially, the reaction of concentrated fluorosilicic acid with concentrated sulfuric acid involves a large volume and a high specific heat capacity of the solution. Heating it above 100℃ consumes a large amount of heat energy, which is a significant component of manufacturing costs.

[0005] For example, Chinese Patent CN116332133B, authorized on May 30, 2025, provides a method for separating a mixed solution containing hydrogen fluoride and sulfuric acid. Concentrated fluorosilicic acid and concentrated sulfuric acid react to generate silicon tetrafluoride gas and a sulfuric acid solution containing hydrogen fluoride. The first part of the sulfuric acid solution containing hydrogen fluoride is subjected to primary distillation at 100~160℃, and the solution after primary distillation is subjected to secondary distillation at 130~180℃ to obtain hydrogen fluoride gas. The second part of the sulfuric acid solution containing hydrogen fluoride is heated and recycled to the reaction device. Compared with the traditional one-step separation, this two-stage separation method improves heat exchange efficiency, has a compact device layout, and can improve system operating energy consumption and product yield.

[0006] The separation method described above increases the complexity of the production system, and the distillation temperatures of both stages are relatively high, resulting in limited reduction of energy consumption in the production system, while also yielding a low amount of hydrogen fluoride. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing hydrogen fluoride, which solves the problems of high distillation temperature and low hydrogen fluoride yield in existing separation methods.

[0008] To solve the above-mentioned technical problems, the technical solution of the hydrogen fluoride preparation method of the present invention is as follows: A method for preparing hydrogen fluoride includes the following steps: decomposing concentrated fluorosilicic acid and concentrated sulfuric acid to remove silicon tetrafluoride gas, obtaining fluorinated sulfuric acid, adding 1-2 trifluoromethyl-substituted phenyl compounds to the fluorinated sulfuric acid, and then distilling.

[0009] This invention improves upon existing technology by providing a method for preparing hydrogen fluoride. It involves distilling fluorinated sulfuric acid in the presence of phenyl compounds substituted with 1-2 trifluoromethyl groups. These trifluoromethyl-substituted phenyl compounds insert into the spaces between fluorosulfonic acid molecules, disrupting the molecular cluster structure and allowing fluorosulfonic acid to exist as individual molecules. This makes the SF bonds in the fluorosulfonic acid molecules more readily accept external energy and break, significantly reducing the energy required to decompose fluorosulfonic acid. Consequently, the energy consumption for distilling and separating hydrogen fluoride is drastically reduced, and the distillation temperature is significantly lowered from 100-160°C to 80-100°C, while simultaneously increasing product yield. Furthermore, the lower temperature significantly reduces equipment corrosion and wear, reducing production and maintenance costs, and indirectly lowering overall costs.

[0010] Preferably, after adding 1 to 2 trifluoromethyl-substituted phenyl compounds to fluorinated sulfuric acid, the mixture is continuously stirred to ensure homogeneity, and the distillation is carried out under continuous stirring.

[0011] Preferably, the amount of the 1-2 trifluoromethyl-substituted phenyl compounds added is 1-5% of the mass of fluorinated sulfuric acid.

[0012] Preferably, the 1-2 trifluoromethyl-substituted phenyl compounds are selected from one or more of trifluorotoluene, 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, and 1,4-bis(trifluoromethyl)benzene.

[0013] Understandably, the decomposition of fluorosulfonic acid is key to the separation of hydrogen fluoride. In fluorinated sulfuric acid, fluorosulfonic acid forms molecular clusters through hydrogen bonding and dipole-dipole interactions. This aggregation enhances the stability of the SF bond, leading to the need for higher temperatures for fluorosulfonic acid decomposition. Phenyl compounds with one or two trifluoromethyl substituted molecules are weakly polar solvents. Their addition inserts between fluorosulfonic acid molecules, disrupting the molecular cluster structure and allowing fluorosulfonic acid to exist as individual molecules. This makes the SF bond more susceptible to breakage due to external energy. Although phenyl compounds with 1-2 trifluoromethyl substituted molecules are poorly soluble in sulfuric acid, when mixed thoroughly, they form numerous tiny droplets that are evenly dispersed in the mixture. The weakly polar solvent molecules are adsorbed onto the surface of the fluorosulfonic acid molecular clusters through van der Waals forces, and then squeeze into the gaps between the fluorosulfonic acid molecular clusters, disrupting the hydrogen bonds and dipole-dipole interactions between molecules. This causes the fluorosulfonic acid molecules aggregated on the surface of the molecular clusters to dissociate into individual molecules. As the surface fluorosulfonic acid decomposes, the lower molecular clusters continuously replenish the interface and continue to interact with the solvent of the phenyl compounds with 1-2 trifluoromethyl substituted molecules.

[0014] Furthermore, these solvent molecules are very stable and can remain stable in strong dehydrating and oxidizing fluorinated sulfuric acid; and their boiling points are between 110-120℃. They do not volatilize during distillation and remain in the remaining bottom liquid. Because they are insoluble in sulfuric acid, further separation of the bottom liquid by standing allows these 1-2 trifluoromethyl-substituted phenyl compounds to be easily separated and reused as auxiliaries after aggregation.

[0015] Preferably, when the phenyl compound with 1-2 trifluoromethyl substituted members includes 1,2-bis(trifluoromethyl)benzene and 1,3-bis(trifluoromethyl)benzene, the mass ratio of 1,2-bis(trifluoromethyl)benzene to 1,3-bis(trifluoromethyl)benzene is (1-2):(1-2).

[0016] Preferably, the stirring speed during continuous stirring is 800~2000 rpm. Under strong stirring, trifluoromethyl substituted benzene will form a large number of fine droplets that are uniformly dispersed in the mixture, which has a stronger destructive effect on the molecular cluster structure of fluorosulfonic acid and can further improve the yield.

[0017] Preferably, the distillation temperature is 80~100℃, the distillation time is 2~3h, and the condensate at 8~12℃ is collected after distillation.

[0018] Preferably, the remaining liquid after distillation is allowed to stand and separate into layers to obtain 1-2 trifluoromethyl-substituted phenyl compounds, which are then added to fluorinated sulfuric acid for recycling.

[0019] Preferably, crude hydrogen fluoride is obtained after distillation, and pure hydrogen fluoride is obtained by further rectification. The rectification temperature is 35~40℃, and the condensate at 8~12℃ is collected after rectification.

[0020] Preferably, the mass ratio of concentrated fluorosilicic acid to concentrated sulfuric acid during the decomposition reaction is (1~1.2):(1.4~1.5); the mass concentration of concentrated fluorosilicic acid is not less than 30%, and the mass concentration of concentrated sulfuric acid is not less than 93%; the temperature of the decomposition reaction is 100~130℃, and the time of the decomposition reaction is 1~2h. Detailed Implementation

[0021] The technical concept of the hydrogen fluoride preparation method provided by this invention is as follows: Existing technologies separate hydrogen fluoride from sulfuric acid solutions containing hydrogen fluoride through two-stage high-temperature distillation. The separation system is complex, and the high temperatures of both stages of distillation significantly increase the energy consumption of the separation system, resulting in a low yield of hydrogen fluoride products.

[0022] This invention involves distilling fluorinated sulfuric acid under the action of phenyl compounds substituted with 1-2 trifluoromethyl groups. This causes the phenyl compounds substituted with 1-2 trifluoromethyl groups to form a large number of fine droplets that are uniformly dispersed in the mixture. These droplets then insert into the spaces between fluorosulfonic acid molecules, disrupting the molecular cluster structure and allowing fluorosulfonic acid to exist as individual molecules. This makes the SF bonds in the fluorosulfonic acid molecules more susceptible to breaking due to external energy, significantly reducing the energy required to decompose fluorosulfonic acid and significantly lowering the distillation temperature while increasing the yield of hydrogen fluoride products.

[0023] The method for preparing hydrogen fluoride provided by this invention includes the following steps: 1) Concentrated fluorosilicic acid and concentrated sulfuric acid undergo a decomposition reaction at 100~130℃ for 1~2 hours, and fluorinated sulfuric acid is obtained after removing silicon tetrafluoride gas.

[0024] In step 1), the mass ratio of concentrated fluorosilicic acid to concentrated sulfuric acid is (1~1.2):(1.4~1.5); the mass concentration of concentrated fluorosilicic acid is not less than 30%, and the mass concentration of concentrated sulfuric acid is not less than 93%. Specifically, the mass concentration of concentrated fluorosilicic acid is 45~60%; and the mass concentration of concentrated sulfuric acid is 93~98%.

[0025] 2) After adding 1 to 2 trifluoromethyl-substituted phenyl compounds to fluorinated sulfuric acid, the mixture is stirred continuously to ensure homogeneity. The distillation is carried out under continuous stirring.

[0026] In step 2), the amount of 1-2 trifluoromethyl-substituted phenyl compounds added is 1-5% of the mass of fluorinated sulfuric acid.

[0027] In step 2), the phenyl compound with 1-2 trifluoromethyl substituted molecule is selected from one or more of trifluorotoluene, 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, and 1,4-bis(trifluoromethyl)benzene. When the phenyl compound with 1-2 trifluoromethyl substituted molecule includes 1,2-bis(trifluoromethyl)benzene and 1,3-bis(trifluoromethyl)benzene, the mass ratio of 1,2-bis(trifluoromethyl)benzene to 1,3-bis(trifluoromethyl)benzene is (1-2):(1-2). Specifically, the mass ratio of 1,2-bis(trifluoromethyl)benzene to 1,3-bis(trifluoromethyl)benzene is 1:1.

[0028] In step 2), the stirring speed is 800~2000 rpm. Under strong stirring, trifluoromethyl-substituted benzene will form a large number of fine droplets that are uniformly dispersed in the mixture. The weakly polar solvent molecules will be adsorbed onto the surface of the fluorosulfonic acid molecular clusters through van der Waals forces, and then squeezed into the gaps between the fluorosulfonic acid molecular clusters, breaking the hydrogen bonds and dipole-dipole interactions between molecules, causing the fluorosulfonic acid molecules aggregated on the surface of the molecular clusters to dissociate into individual molecules. As the surface fluorosulfonic acid decomposes, the lower molecular clusters will continuously replenish the interface and continue to interact with the solvent, which can further improve the yield.

[0029] It should be noted that continuous stirring during distillation can be achieved using distillation stirring systems commonly found in existing industrial systems. For example, a distillation tank with a built-in stirring system includes a distillation tank with a stirring motor located in the center of the top wall, connected to a stirring rod via an output shaft to achieve continuous stirring.

[0030] In step 2), the distillation temperature is 80~100℃, the distillation time is 2~3h, and the condensate at 8~12℃ is collected after distillation.

[0031] 3) After distillation, crude hydrogen fluoride is obtained. The crude hydrogen fluoride is further subjected to rectification to remove sulfur dioxide, hydrogen chloride (an impurity present in fluorosilicic acid itself), water, etc., to obtain pure hydrogen fluoride. The rectification temperature is 35~40℃, and the condensate at 8~12℃ is collected after rectification.

[0032] The remaining liquid after distillation was allowed to stand and separate into layers. After separation, 1-2 trifluoromethyl-substituted phenyl compounds were obtained and added to fluorinated sulfuric acid for recycling.

[0033] It should be noted that when the preparation method of the present invention is carried out in a continuous production mode system, fluorinated sulfuric acid is continuously generated and fed continuously, and phenyl compounds with 1 to 2 trifluoromethyl substituted compounds are also continuously fed. The feeding rate of the phenyl compounds with 1 to 2 trifluoromethyl substituted compounds is 1 to 5% of the feeding rate of fluorinated sulfuric acid.

[0034] The embodiments of the present invention will be further described below with reference to specific examples. Unless otherwise specified, the chemical reagents involved in the following examples are all commercially available conventional products. The method for calculating the yield of hydrogen fluoride is: actual mass of pure hydrogen fluoride obtained ÷ theoretical yield of hydrogen fluoride.

[0035] I. Specific Embodiments of the Hydrogen Fluoride Preparation Method of the Present Invention Example 1 The method for preparing hydrogen fluoride in this embodiment is as follows: 1000g of 55wt% fluorosilicic acid was mixed thoroughly with 1500g of 98wt% concentrated sulfuric acid and heated to 110℃ for 1 hour. Silicon tetrafluoride gas was then released, yielding 2099g of fluorinated sulfuric acid. 63g of 1,2-bis(trifluoromethyl)benzene (3% of the fluorinated sulfuric acid mass) was added to the fluorinated sulfuric acid, and the mixture was distilled at 90℃ for 2 hours with continuous stirring at 1200 rpm. The condensate was collected at 8℃ to obtain 154.6g of crude hydrogen fluoride. The crude hydrogen fluoride was further distilled at 35℃, and the condensate at 8℃ yielded 150.4g of anhydrous hydrogen fluoride, a yield of 98.5%. The remaining distillate was allowed to stand and separated to obtain 1,2-bis(trifluoromethyl)benzene, which can be reused as an auxiliary agent.

[0036] Example 2 The method for preparing hydrogen fluoride in this embodiment is as follows: 1000g of 45wt% fluorosilicic acid was mixed thoroughly with 1400g of 98wt% concentrated sulfuric acid and heated to 110℃ for 1 hour. The resulting gas was purged to obtain 2072g of fluorinated sulfuric acid. 21g of 1,2-bis(trifluoromethyl)benzene (1% of the mass of the fluorinated sulfuric acid) was added to the fluorinated sulfuric acid, and the mixture was distilled at 100℃ for 2 hours with continuous stirring at 2000 rpm. The condensate was collected at 12℃ to obtain 126.5g of crude hydrogen fluoride. The crude hydrogen fluoride was then distilled at 35℃, and the condensate at 8℃ was collected to obtain 123.3g of anhydrous hydrogen fluoride, with a yield of 98.7%.

[0037] Example 3 The method for preparing hydrogen fluoride in this embodiment is as follows: 1000g of 58wt% fluorosilicic acid was mixed thoroughly with 1500g of 93wt% concentrated sulfuric acid and heated to 110℃ for 1 hour. The resulting gas was purged to obtain 2080g of fluorinated sulfuric acid. 100g of 1,3-bis(trifluoromethyl)benzene (5% of the mass of the fluorinated sulfuric acid) was added to the fluorinated sulfuric acid. The mixture was distilled at 80℃ for 3 hours with continuous stirring at 800 rpm. The condensate was collected at 12℃ to obtain 163.0g of crude hydrogen fluoride. The crude hydrogen fluoride was then distilled at 35℃, and the condensate at 8℃ yielded 159.6g of anhydrous hydrogen fluoride, a yield of 99.1%.

[0038] Example 4 The method for preparing hydrogen fluoride in this embodiment is as follows: 1000g of 50wt% fluorosilicic acid was mixed thoroughly with 1500g of 96wt% concentrated sulfuric acid and heated to 110℃ for 1 hour. The resulting gas was purged to obtain 2137g of fluorinated sulfuric acid. 30g of 1,2-bis(trifluoromethyl)benzene and 30g of 1,3-bis(trifluoromethyl)benzene (the total amount of the two additives was 3% of the mass of the fluorinated sulfuric acid) were added to the fluorinated sulfuric acid. The mixture was distilled at 85℃ for 2.5 hours with continuous stirring at 1000 rpm. The condensate was collected at 12℃ to obtain 140.6g of crude hydrogen fluoride. The crude hydrogen fluoride was then distilled at 35℃, and the condensate at 8℃ was collected to obtain 136.7g of anhydrous hydrogen fluoride, with a yield of 98.4%.

[0039] II. Comparative Example Comparative Example 1 (without trifluoromethyl-substituted benzene) The method for preparing hydrogen fluoride in this comparative example is basically the same as that in Example 1, except that 1,2-bis(trifluoromethyl)benzene is not added during distillation. The specific method is as follows: 1000g of 55wt% fluorosilicic acid was mixed thoroughly with 1500g of 98wt% concentrated sulfuric acid and heated to 110℃ for 1 hour. Gas was released to obtain 2099g of fluorinated sulfuric acid. The mixture was then distilled at 90℃ for 2 hours with continuous stirring at 1200 rpm. The condensate was collected at 8℃ to obtain 114.3g of crude hydrogen fluoride. The crude hydrogen fluoride was then distilled at 35℃, and the condensate at 8℃ yielded 110.6g of anhydrous hydrogen fluoride, a yield of 72.4%.

[0040] Compared with Example 1, it can be seen that without adding trifluoromethyl-substituted benzene during distillation, distillation at low temperature will significantly reduce the yield of hydrogen fluoride products.

[0041] Based on the comparative example, even extending the distillation time at 90°C did not significantly improve the yield of hydrogen fluoride products.

[0042] Comparative Example 2 (without stirring during distillation) The method for preparing hydrogen fluoride in this comparative example is basically the same as that in Example 1, except that no stirring is performed during distillation. The specific method is as follows: 1000g of 55wt% fluorosilicic acid was mixed thoroughly with 1500g of 98wt% concentrated sulfuric acid and heated to 110℃ for 1 hour. The resulting gas was released to obtain 2099g of fluorinated sulfuric acid. 63g of 1,2-bis(trifluoromethyl)benzene was added to the fluorinated sulfuric acid, and the mixture was distilled at 90℃ for 2 hours. The condensate was collected at 8℃ to obtain 124.7g of crude hydrogen fluoride. The crude hydrogen fluoride was then distilled at 35℃, and the condensate at 8℃ was collected to obtain 123.5g of anhydrous hydrogen fluoride, with a yield of 80.9%.

[0043] Compared with Example 1, it can be seen that adding trifluoromethyl substituted benzene during distillation without stirring will prevent the trifluoromethyl substituted benzene from destroying the fluorosulfonic acid molecular cluster due to its low solubility in the mixed solution, and will also significantly reduce the yield of hydrogen fluoride product.

[0044] Comparative Example 3 (using existing high-temperature distillation technology) The method for preparing hydrogen fluoride in this comparative example is basically the same as that in Example 1, except that high-temperature distillation is used. The specific method is as follows: 1000g of 55wt% fluorosilicic acid was mixed thoroughly with 1500g of 98wt% concentrated sulfuric acid and heated to 110℃ for 1 hour. Gas was released to obtain 2099g of fluorinated sulfuric acid. The mixture was then distilled at 130℃ for 2 hours, and the condensate was collected at 8℃ to obtain 148.9g of crude hydrogen fluoride. The crude hydrogen fluoride was then distilled at 35℃, and the condensate at 8℃ was collected to obtain 145.7g of anhydrous hydrogen fluoride, yielding a yield of 95.4%.

[0045] Compared to Example 1, it can be seen that without the addition of trifluoromethyl-substituted benzene during distillation, the yield of hydrogen fluoride product is lower even when distilled at high temperatures.

[0046] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing hydrogen fluoride, characterized in that, Includes the following steps: The fluorinated sulfuric acid is obtained by decomposing concentrated fluorosilicic acid and concentrated sulfuric acid to remove silicon tetrafluoride gas. Then, 1-2 trifluoromethyl-substituted phenyl compounds are added to the fluorinated sulfuric acid and distilled.

2. The method for preparing hydrogen fluoride as described in claim 1, characterized in that, After adding 1-2 trifluoromethyl-substituted phenyl compounds to fluorinated sulfuric acid, the mixture is stirred continuously to ensure homogeneity, and the distillation is carried out under continuous stirring.

3. The method for preparing hydrogen fluoride as described in claim 2, characterized in that, The amount of the 1-2 trifluoromethyl-substituted phenyl compounds added is 1-5% of the mass of the fluorinated sulfuric acid.

4. The method for preparing hydrogen fluoride according to any one of claims 1-3, characterized in that, The 1-2 trifluoromethyl-substituted phenyl compounds are selected from one or more of trifluorotoluene, 1,2-bis(trifluoromethyl)benzene, 1,3-bis(trifluoromethyl)benzene, and 1,4-bis(trifluoromethyl)benzene.

5. The method for preparing hydrogen fluoride as described in claim 4, characterized in that, When the phenyl compound with 1 to 2 trifluoromethyl substituted members includes 1,2-bis(trifluoromethyl)benzene and 1,3-bis(trifluoromethyl)benzene, the mass ratio of 1,2-bis(trifluoromethyl)benzene to 1,3-bis(trifluoromethyl)benzene is (1 to 2): (1 to 2).

6. The method for preparing hydrogen fluoride as described in claim 2, characterized in that, The stirring speed is 800~2000 rpm during continuous stirring.

7. The method for preparing hydrogen fluoride according to claim 1, characterized in that, The distillation temperature is 80~100℃, the distillation time is 2~3h, and the condensate at 8~12℃ is collected after distillation.

8. The method for preparing hydrogen fluoride as described in claim 1 or 7, characterized in that, The remaining liquid after distillation was allowed to stand and separate into layers. After separation, 1-2 trifluoromethyl-substituted phenyl compounds were obtained and added to fluorinated sulfuric acid for recycling.

9. The method for preparing hydrogen fluoride according to claim 1, characterized in that, Crude hydrogen fluoride is obtained after distillation, and pure hydrogen fluoride is obtained by further rectification. The rectification temperature is 35~40℃, and the condensate at 8~12℃ is collected after rectification.

10. The method for preparing hydrogen fluoride according to claim 1, characterized in that, The mass ratio of concentrated fluorosilicic acid to concentrated sulfuric acid during the decomposition reaction is (1~1.2):(1.4~1.5); the mass concentration of concentrated fluorosilicic acid is not less than 30%, and the mass concentration of concentrated sulfuric acid is not less than 93%; the temperature of the decomposition reaction is 100~130℃, and the time of the decomposition reaction is 1~2h.