Hydrogen fluoride and preparation method therefor, and battery material

Abstract

Provided in the present disclosure are hydrogen fluoride and a preparation method therefor, and a battery material. The preparation method for hydrogen fluoride comprises: reacting fluosilicic acid with first sulfuric acid, so as to generate mixed gas and first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution comprising hydrogen fluoride, and the mixed gas comprises silicon tetrafluoride gas and hydrogen fluoride gas; washing the mixed gas with second sulfuric acid, so as to obtain second mixed sulfuric acid and washed silicon tetrafluoride gas, wherein the second mixed sulfuric acid is obtained by absorbing the hydrogen fluoride gas by the second sulfuric acid; washing water-containing hydrogen fluoride with the second mixed sulfuric acid, so as to obtain crude hydrogen fluoride gas; and purifying the crude hydrogen fluoride gas, so as to obtain anhydrous hydrogen fluoride.

Description

Hydrogen fluoride, its preparation method, and battery materials

[0001] Technical Field

[0002] This disclosure relates to the field of fluorochemical technology, specifically to a hydrogen fluoride, its preparation method, and battery materials. Background Technology

[0003] Currently, the main processes for producing anhydrous hydrogen fluoride are the fluorite method and the fluorosilicic acid method. The fluorite method uses the reaction of fluorite with sulfuric acid to produce anhydrous hydrogen fluoride. It is currently the mainstream process in the market, with mature technology, low investment, and high total output, but high production costs and significant environmental pressure. The fluorosilicic acid method is relatively mature and economically efficient, but it has high investment costs, a complex process flow, and requires a large amount of fluorinated dilute sulfuric acid to be nitrated in a phosphate chemical plant, which has certain limitations. Furthermore, the silica produced during the process can easily clog pipelines.

[0004] Currently, the method for preparing anhydrous hydrogen fluoride using fluorosilicic acid involves reacting 98% sulfuric acid with 40% fluorosilicic acid. However, the overall yield of hydrogen fluoride is only around 75%, and the yield needs to be further improved.

[0005] Application content

[0006] This application aims to at least partially address one of the technical problems in the related art. To this end, one objective of this application is to provide a hydrogen fluoride, a method for its preparation, and a battery material thereof. The method for preparing hydrogen fluoride is beneficial for improving the yield of hydrogen fluoride.

[0007] The first aspect of this application discloses a method for preparing hydrogen fluoride. According to the embodiments of this application, the preparation method includes:

[0008] Fluorosilicic acid is reacted with a first sulfuric acid to produce a mixed gas and a first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas.

[0009] The mixed gas was washed with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid was obtained by absorbing hydrogen fluoride gas with the second sulfuric acid.

[0010] The aqueous hydrogen fluoride was washed with a second mixed sulfuric acid to obtain crude hydrogen fluoride gas;

[0011] The crude hydrogen fluoride gas was purified to obtain anhydrous hydrogen fluoride.

[0012] This application involves reacting fluorosilicic acid with sulfuric acid, using sulfuric acid solution as a catalyst to promote the decomposition of fluorosilicic acid to produce silicon tetrafluoride and hydrogen fluoride. The decomposition principle of fluorosilicic acid is: H2SiF6 = HF + SiF4.

[0013] In this application, the mixed gas is washed with a second sulfuric acid (such as concentrated sulfuric acid), and some of the hydrogen fluoride gas in the mixed gas dissolves in the second sulfuric acid; another part of the hydrogen fluoride gas reacts with the second sulfuric acid to generate fluorosulfonic acid, and the resulting second mixed sulfuric acid includes sulfuric acid, water, hydrogen fluoride and fluorosulfonic acid.

[0014] The second mixed sulfuric acid washes the aqueous hydrogen fluoride. The second mixed sulfuric acid comes into contact with water and hydrogen fluoride gas. On one hand, the fluorosulfonic acid in the second mixed sulfuric acid hydrolyzes into hydrogen fluoride and sulfuric acid, releasing hydrogen fluoride gas. On the other hand, the dilution of the second mixed sulfuric acid with water releases heat, releasing the dissolved hydrogen fluoride. Finally, the mixture of hydrogen fluoride from the aqueous hydrogen fluoride, the hydrogen fluoride gas released from the hydrolysis of the second mixed sulfuric acid, and the dissolved hydrogen fluoride gas serves as crude hydrogen fluoride gas, which can be further purified to obtain anhydrous hydrogen fluoride. The preparation method provided in this application improves the yield of hydrogen fluoride in the mixed gas obtained from the main reaction, thereby improving the overall yield of hydrogen fluoride, reaching over 80%, more preferably over 90%.

[0015] The second aspect of this application discloses a hydrogen fluoride obtained by the preparation method described above.

[0016] This application uses the above preparation method to obtain hydrogen fluoride in high yield and with high purity.

[0017] The third aspect of this application discloses a battery material, the raw materials for which the battery material is prepared include hydrogen fluoride obtained by the above-described preparation method, or the above-described hydrogen fluoride.

[0018] The hydrogen fluoride obtained by the above preparation method can be used as a raw material for some battery materials, such as lithium hexafluorophosphate.

[0019] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0020] Figure 1 is a flowchart of the preparation method of hydrogen fluoride provided in the embodiments of this application.

[0021] Figure 2 is a flowchart illustrating the steps of the hydrogen fluoride preparation method provided in the embodiments of this application.

[0022] Figure 3 is a flowchart of the preparation method of hydrogen fluoride provided in the specific embodiments of this application.

[0023] Figure 4 is a schematic diagram of the system structure used in the hydrogen fluoride preparation method provided in the specific embodiments of this application. Embodiments of the present invention

[0024] The embodiments of this application are described in detail below and are intended to explain this application, but should not be construed as limiting this application.

[0025] Currently, the preparation of anhydrous hydrogen fluoride from fluorosilicic acid involves a main decomposition reaction of 98% sulfuric acid and 40% fluorosilicic acid to produce fluorinated sulfuric acid. The fluorinated sulfuric acid is then distilled to obtain anhydrous hydrogen fluoride. After washing, cooling, rectification, and degassing, anhydrous hydrogen fluoride is obtained. However, the overall yield of hydrogen fluoride is only around 75%, especially the recovery of hydrogen fluoride from the gas phase obtained from the main decomposition reaction is poor, which means that the overall yield of hydrogen fluoride needs to be further improved.

[0026] Therefore, the first aspect of this application provides a method for preparing hydrogen fluoride. According to the embodiments of this application, the preparation method includes:

[0027] Fluorosilicic acid is reacted with a first sulfuric acid to produce a mixed gas and a first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas.

[0028] The mixed gas was washed with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid was obtained by absorbing hydrogen fluoride gas with the second sulfuric acid.

[0029] The aqueous hydrogen fluoride was washed with a second mixed sulfuric acid to obtain crude hydrogen fluoride gas;

[0030] The crude hydrogen fluoride gas was purified to obtain anhydrous hydrogen fluoride.

[0031] In this embodiment, fluorosilicic acid is reacted with first sulfuric acid, and the first sulfuric acid, i.e., sulfuric acid solution, is used as a catalyst to promote the decomposition of fluorosilicic acid to produce silicon tetrafluoride and hydrogen fluoride. The decomposition principle of fluorosilicic acid is: H2SiF6 = HF + SiF4.

[0032] In this embodiment, the mixed gas is washed with a second sulfuric acid (such as concentrated sulfuric acid), and some of the hydrogen fluoride gas in the mixed gas dissolves in the second sulfuric acid; another part of the hydrogen fluoride gas reacts with the second sulfuric acid to generate fluorosulfonic acid, and the resulting second mixed sulfuric acid includes sulfuric acid, water, hydrogen fluoride and fluorosulfonic acid.

[0033] The second mixed sulfuric acid washes the aqueous hydrogen fluoride. The second mixed sulfuric acid comes into contact with water and hydrogen fluoride gas. On one hand, the fluorosulfonic acid in the second mixed sulfuric acid hydrolyzes into hydrogen fluoride and sulfuric acid, releasing hydrogen fluoride gas. On the other hand, the dilution of the second mixed sulfuric acid with water releases heat, releasing the dissolved hydrogen fluoride. Finally, the mixture of hydrogen fluoride from the aqueous hydrogen fluoride, the hydrogen fluoride gas released from the hydrolysis of the second mixed sulfuric acid, and the dissolved hydrogen fluoride gas serves as crude hydrogen fluoride gas, which can be further purified to obtain anhydrous hydrogen fluoride. The preparation method provided in this application improves the yield of hydrogen fluoride in the mixed gas obtained from the main reaction, thereby improving the overall yield of hydrogen fluoride, reaching over 80%, more preferably over 90%.

[0034] In the second mixed washing process, the hydrolysis reaction mechanism of fluorosulfonic acid is: HSO3F + H2O = H2SO4 + HF.

[0035] In addition, as an example, concentrated sulfuric acid includes sulfuric acid with a mass concentration of 98%.

[0036] Furthermore, the preparation process of hydrogen fluoride is shown in Figure 1:

[0037] Step a. React fluorosilicic acid with the first sulfuric acid to produce a mixed gas and a first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas;

[0038] Step b. Wash the mixed gas with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing hydrogen fluoride gas with the second sulfuric acid;

[0039] Step c. Wash the aqueous hydrogen fluoride with a second mixed sulfuric acid to obtain crude hydrogen fluoride gas;

[0040] Step d. Purify the crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride.

[0041] In some embodiments of this application, the preparation method satisfies at least one of the following:

[0042] (A) The mass ratio of water to hydrogen fluoride in aqueous hydrogen fluoride is 1:5 to 1:19;

[0043] (B) Hydrogen fluoride containing water includes at least one of the following: hydrofluoric acid from the tail gas absorption tower of the fluorite process, hydrofluoric acid from the tail gas absorption tower of electronic grade hydrofluoric acid, and hydrofluoric acid from the tail gas absorption tower of phosphorus chemical industry.

[0044] In this embodiment, the mass ratio of water to hydrogen fluoride in the aqueous hydrogen fluoride meets the above conditions. This stabilizes the sulfuric acid composition in the washing tower while a small amount of water promotes the release of hydrogen fluoride from the washing tower, which is beneficial for promoting the release of hydrogen fluoride gas from the second mixed sulfuric acid and increasing the yield of hydrogen fluoride.

[0045] If the mass ratio of water to hydrogen fluoride is higher than 1:5, a large amount of water will enter the washing tower, resulting in an excessively low sulfuric acid concentration in the washing tower, which will affect the subsequent decomposition reaction. If the mass ratio of water to hydrogen fluoride is lower than 1:19, it can directly enter the distillation tower, and the entire process will change.

[0046] In specific examples, the mass ratio of water to hydrogen fluoride in aqueous hydrogen fluoride is 1:5, 1.6, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, and 1:19.

[0047] Furthermore, the mass ratio of water to hydrogen fluoride in aqueous hydrogen fluoride is 1:8 to 1:12.

[0048] In this embodiment, the mass ratio of water to hydrogen fluoride is controlled to be between 1:8 and 1:12, the hydrogen fluoride yield is between 80% and 85%, and the amount of water introduced is moderate, which can effectively release the hydrogen fluoride in the second mixed sulfuric acid.

[0049] In some embodiments of this application, the first mixed sulfuric acid is subjected to falling film evaporation to obtain liquid dilute sulfuric acid and gaseous hydrogen fluoride, with the gaseous hydrogen fluoride serving as the source of aqueous hydrogen fluoride.

[0050] In this embodiment, a falling film evaporation method is used to evaporate the first mixed sulfuric acid. Under negative pressure, hydrogen fluoride is more easily volatilized, which can significantly improve the evaporation and extraction efficiency of hydrogen fluoride and reduce the consumption of sulfuric acid. Moreover, the overall temperature of falling film evaporation is relatively low, which helps to reduce steam loss.

[0051] In this embodiment, the gaseous hydrogen fluoride evaporated from the falling film can be directly washed with a second mixed sulfuric acid. This gaseous phase usually carries water vapor, which promotes the release of hydrogen fluoride from the second mixed sulfuric acid. This facilitates the effective recovery of hydrogen fluoride produced by the main reaction (i.e., the reaction of fluorosilicic acid with the first sulfuric acid), increases the yield of hydrogen fluoride, and also helps to reduce the consumption of sulfuric acid.

[0052] In some embodiments of this application, the mass percentage of hydrogen fluoride in the aqueous hydrogen fluoride is 40% to 95%, based on the total mass of the aqueous hydrogen fluoride.

[0053] As an example, based on the total mass of aqueous hydrogen fluoride, the mass percentage of hydrogen fluoride in aqueous hydrogen fluoride is 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

[0054] In some embodiments of this application, a second mixed sulfuric acid is used to wash the aqueous hydrogen fluoride gas to obtain a third mixed sulfuric acid; the third mixed sulfuric acid serves as the source of the first sulfuric acid and reacts with fluorosilicic acid.

[0055] In this embodiment, the third mixed sulfuric acid still contains some hydrogen fluoride. Returning the third mixed sulfuric acid, which contains residual hydrogen fluoride, as a raw material for the reaction with fluorosilicic acid and continuing the recycling operation can further improve the yield of hydrogen fluoride and reduce the loss of hydrogen fluoride.

[0056] In some embodiments of this application, the preparation method further includes: treating the washed silicon tetrafluoride gas, including the step of:

[0057] The silicon tetrafluoride gas after washing was absorbed by the first fluorosilicic acid solution to obtain a mixed fluorosilicic acid solution containing silicon dioxide precipitate. Solid-liquid separation was performed to obtain a second fluorosilicic acid solution and silicon dioxide precipitate.

[0058] The silica precipitate was washed to obtain a trifluorosilicic acid solution and silica solid.

[0059] In this embodiment, a first fluorosilicic acid solution is used to absorb the washed silicon tetrafluoride gas. The first fluorosilicic acid provides an acidic environment, promoting the hydrolysis reaction of silicon tetrafluoride as follows: SiF4 + H2O = H2SiF6 + SiO2, thereby obtaining a mixed solution of fluorosilicic acid containing silica precipitate. Compared to the first fluorosilicic acid solution, the mass concentration of fluorosilicic acid in the mixed solution containing silica precipitate is increased. Therefore, this absorption process serves two purposes: firstly, to obtain silica as a byproduct, and secondly, to concentrate the fluorosilicic acid.

[0060] In this embodiment, a fluorosilicic acid mixed solution containing silica precipitate is subjected to solid-liquid separation (such as filtration) to obtain a second fluorosilicic acid solution and silica precipitate. Through solid-liquid separation, silica is further extracted, and a concentrated second fluorosilicic acid solution is obtained. The mass concentration of the second fluorosilicic acid solution is greater than that of the first fluorosilicic acid solution.

[0061] In this embodiment of the application, impurities in the silica precipitate are further removed by washing to obtain silica byproducts with high purity, while a trifluorosilicic acid solution with low mass concentration is also obtained.

[0062] In some embodiments of this application, the treated silicon tetrafluoride gas after washing satisfies at least one of the following:

[0063] (i) The mass concentration of the first fluorosilicic acid solution is 25%~30%;

[0064] (ii) The mass concentration of the second fluorosilicic acid solution is 40%~55%;

[0065] (iii) The mass concentration of the trifluorosilicic acid solution is 11%~18%;

[0066] (iv) The third fluorosilicic acid solution is concentrated to produce the first fluorosilicic acid solution;

[0067] (v) The second fluorosilicic acid solution, as a source of fluorosilicic acid, reacts with the first sulfuric acid.

[0068] In the embodiments of this application, the mass concentration of the first fluorosilicic acid solution is 25%~30%, and in specific examples, the mass concentration is 25%, 25.5%, 26%, 26.5%, 27%, 27.5%, 28%, 28.5%, 29%, 29.5%, 30%, etc.

[0069] In this embodiment of the application, the mass concentration of the second fluorosilicic acid solution is 40%~50%. In specific examples, the mass concentration is 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, 44%, 44.5%, 45%, 45.5%, 46%, 46.5%, 47%, 47.5%, 48%, 48.5%, 49%, 49.5%, 50%, etc.

[0070] In the embodiments of this application, the mass concentration of the third fluorosilicic acid solution is 11%~18%, and in specific examples, the mass concentration is 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, etc.

[0071] In this embodiment, the third fluorosilicic acid solution is concentrated to produce the first fluorosilicic acid solution. Vacuum concentration can be used to increase the concentration of the third fluorosilicic acid solution.

[0072] In this embodiment, a high-concentration second fluorosilicic acid solution can be used as the source of fluorosilicic acid in the main reaction, reacting with the first sulfuric acid. The fluorosilicic acid has a high mass concentration, specifically 40%~50% in this example, which helps reduce the amount of first sulfuric acid used and lowers sulfuric acid consumption. Furthermore, it enables the recycling of fluorosilicic acid, improving resource utilization.

[0073] According to an embodiment of this application, after absorbing and washing silicon tetrafluoride gas with a first fluorosilicic acid solution of 25% to 30% by mass, the silicon tetrafluoride decomposes to produce fluorosilicic acid, which increases the concentration of the silicic acid solution. After filtration, a second fluorosilicic acid solution with a mass concentration of 40% to 50% is obtained, which is used for a decomposition reaction with the first sulfuric acid solution. Furthermore, after washing the precipitated silica, byproduct silica and a third fluorosilicic acid solution with a mass concentration of 11% to 18% are obtained. The third fluorosilicic acid solution is then concentrated under vacuum to obtain a first fluorosilicic acid solution with a mass concentration of 25% to 30%, thus achieving the recycling of the byproduct fluorosilicic acid.

[0074] In some embodiments of this application, the purification of crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride includes:

[0075] Crude hydrogen fluoride gas is condensed to obtain crude anhydrous hydrogen fluoride; the crude anhydrous hydrogen fluoride is then subjected to distillation and degassing treatments to obtain anhydrous hydrogen fluoride.

[0076] In this embodiment, crude hydrogen fluoride gas is condensed to obtain anhydrous hydrogen fluoride crude product; the anhydrous hydrogen fluoride crude product is then subjected to distillation and degassing treatment to obtain anhydrous hydrogen fluoride finished product, namely the target product, anhydrous hydrogen fluoride.

[0077] In some embodiments of this application, liquid dilute sulfuric acid is stripped by air to obtain a mixture of dilute sulfuric acid and stripping gas, the stripping mixture including air and stripped hydrogen fluoride; the stripping mixture is then treated by water absorption to obtain hydrofluoric acid.

[0078] In this embodiment, hot air is used to strip the liquid-phase dilute sulfuric acid, which reduces steam loss and the generation of byproduct sulfuric acid. Stripping yields byproduct dilute sulfuric acid and a stripping mixture; hot air and hydrogen fluoride are absorbed by water to produce byproduct hydrofluoric acid, thus yielding two byproducts; moreover, the stripping mixture contains hot air, which carries a high amount of heat into the water absorption device, thereby reducing the heating energy consumption of the water absorption device and improving resource utilization.

[0079] In some embodiments of this application, the falling film evaporation treatment of the first mixed sulfuric acid includes at least one of the following:

[0080] (a) Control the falling film evaporation temperature to 130 ℃~160 ℃;

[0081] (b) Control the falling film evaporation pressure to -30 kPa to 0 kPa;

[0082] (c) The content of hydrogen fluoride in the liquid phase dilute sulfuric acid is less than 5‰.

[0083] In this embodiment, during the falling film evaporation treatment of the first mixed sulfuric acid, controlling the temperature and / or pressure parameters to meet the above conditions is beneficial for improving the evaporation effect, increasing the recovery rate of hydrogen fluoride, and avoiding excessive moisture and sulfuric acid entrainment in the hydrogen fluoride gas, thereby reducing sulfuric acid consumption. In specific examples, the temperature is 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃, or 160 ℃, etc. In specific examples, the pressure is -30 kPa, -25 kPa, -20 kPa, -15 kPa, -10 kPa, -5 kPa, -1 kPa, etc.

[0084] Furthermore, the falling film evaporation temperature is 135 ℃~145 ℃. In specific examples, the falling film evaporation temperatures are 135 ℃, 136 ℃, 137 ℃, 138 ℃, 139 ℃, 140 ℃, 141 ℃, 142 ℃, 143 ℃, 144 ℃, 145 ℃, etc.

[0085] Furthermore, the falling film evaporation pressure is -15 kPa to -5 kPa. In specific examples, the falling film evaporation pressures are -15 kPa, -14 kPa, -13 kPa, -12 kPa, -11 kPa, -10 kPa, -9 kPa, -8 kPa, -7 kPa, -6 kPa, -5 kPa, etc.

[0086] In this embodiment, sulfuric acid containing hydrogen fluoride is treated by falling film evaporation to control the hydrogen fluoride content in the raw liquid dilute sulfuric acid to be less than 5‰, ensuring that most of the hydrogen fluoride is separated from the sulfuric acid, which is beneficial to improving the recovery rate of hydrogen fluoride. Specific examples include hydrogen fluoride contents of less than 5‰, less than 4.5‰, less than 4‰, less than 3.5‰, less than 3‰, less than 2.5‰, less than 2‰, less than 1.5‰, and less than 1‰.

[0087] In some embodiments of this application, the reaction of fluorosilicic acid with the first sulfuric acid satisfies at least one of the following:

[0088] (α) Control the reaction temperature to 60 ℃~140 ℃;

[0089] (β) Fluorosilicic acid is used with a mass concentration of 40%~50%;

[0090] (γ) The composition of the first sulfuric acid includes: 91%~95% sulfuric acid and 1%~5% hydrogen fluoride.

[0091] In this embodiment of the application, the reaction temperature in the step of decomposing fluorosilicic acid with sulfuric acid is 60℃~140℃. Specifically, the reaction temperatures are 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 92℃, 94℃, 96℃, 98℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, and 140℃. Further, the reaction temperature is 90℃~100℃, specifically, the reaction temperatures are 90℃, 91℃, 92℃, 93℃, 94℃, 95℃, 96℃, 97℃, 98℃, 99℃, and 100℃.

[0092] In this embodiment of the application, fluorosilicic acid is used as a raw material, decomposing to produce hydrogen fluoride and silicon tetrafluoride. The mass concentration of fluorosilicic acid meets the above conditions, which is beneficial for improving reaction efficiency, reducing the amount of first sulfuric acid used, increasing the yield of hydrogen fluoride, and further reducing sulfuric acid consumption. In specific examples, the mass concentration of fluorosilicic acid is 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, or 50%, etc.

[0093] In the embodiments of this application, the composition of the first sulfuric acid is as described above, and a by-product sulfuric acid solution can be used, such as a third mixed sulfuric acid. In specific examples, the sulfuric acid content in the first sulfuric acid can be 91%, 92%, 93%, 94%, or 95%, etc.; the hydrogen fluoride content can be 1%, 2%, 3%, 4%, 5%, etc.

[0094] In some embodiments of this application, during the decomposition reaction of fluorosilicic acid with the first sulfuric acid, controlling the silicon content in the first mixed sulfuric acid to meet the above conditions can achieve complete decomposition of fluorosilicic acid. Specific examples include silicon contents of less than 2‰, less than 1.8‰, less than 1.6‰, less than 1.4‰, less than 1.2‰, less than 1.0‰, less than 0.8‰, less than 0.6‰, less than 0.4‰, less than 0.2‰, and less than 0.1‰.

[0095] In some embodiments of this application, after reacting fluorosilicic acid with a third mixed sulfuric acid, the resulting first mixed sulfuric acid has the following composition: sulfuric acid, 60%~70%; hydrogen fluoride, 3%~6%; and water, 25%~40%.

[0096] In some embodiments of this application, in the step of washing the mixed gas with a second sulfuric acid, the temperature of the sulfuric acid absorption tower is 20 ℃ to 80 ℃; and the temperature of the silicon tetrafluoride gas after washing is 20 ℃ to 60 ℃.

[0097] In some embodiments of this application, after washing the mixed gas with a second sulfuric acid, the composition of the second mixed sulfuric acid is: sulfuric acid, 94%~96%; hydrogen fluoride, 1%~3%; water: 2%~4%.

[0098] In some embodiments of this application, the first mixed sulfuric acid is subjected to falling film evaporation to produce a liquid dilute sulfuric acid with the following composition: sulfuric acid, 60%~70%; hydrogen fluoride, 0%~1%; and water, 30%~40%. Furthermore, the hydrogen fluoride content is less than 5‰.

[0099] In some embodiments of this application, in the step of washing aqueous hydrogen fluoride with a second mixed sulfuric acid, the temperature of the washing tower is 80 ℃~140 ℃ and the pressure is -3 kpa~0 kpa.

[0100] In some embodiments of this application, as shown in FIG2, the method for preparing hydrogen fluoride includes the following steps:

[0101] Step a. Decompose fluorosilicic acid with the first sulfuric acid to produce a mixed gas and a first mixed sulfuric acid; the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas.

[0102] Step b. Wash the mixed gas with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing hydrogen fluoride gas with the second sulfuric acid.

[0103] Step c. Absorb the silicon tetrafluoride gas after washing with a first fluorosilicic acid solution to obtain a mixed fluorosilicic acid solution containing silicon dioxide precipitate;

[0104] Step d. The fluorosilicic acid mixed solution containing silica precipitate is filtered to obtain a second fluorosilicic acid solution and silica precipitate. The filtered second fluorosilicic acid solution is recycled back to step a, either as fluorosilicic acid or as a raw material for fluorosilicic acid, to undergo a decomposition reaction with the first sulfuric acid. The silica precipitate is washed, and the resulting solid phase is dried to obtain byproduct silica. The liquid phase obtained from washing is the third fluorosilicic acid solution, which is used as a raw material for the first fluorosilicic acid solution.

[0105] Step e. The first mixed sulfuric acid is subjected to falling film evaporation to produce liquid dilute sulfuric acid and gaseous hydrogen fluoride;

[0106] Step f. Wash the gaseous hydrogen fluoride with a second mixed sulfuric acid to obtain crude hydrogen fluoride gas and a third mixed sulfuric acid. The third mixed sulfuric acid is recycled back to step a and used as the first sulfuric acid or as a raw material for the first sulfuric acid to decompose with fluorosilicic acid.

[0107] Step g. The crude hydrogen fluoride gas is condensed to obtain anhydrous crude hydrogen fluoride; the anhydrous crude hydrogen fluoride is then subjected to distillation and degassing to obtain the finished anhydrous hydrogen fluoride.

[0108] Step h. Liquid-phase dilute sulfuric acid is stripped with air to obtain byproduct dilute sulfuric acid and stripping mixed gas; the stripping mixed gas includes air and stripped hydrogen fluoride; the stripping mixed gas is treated with water absorption to obtain byproduct hydrofluoric acid.

[0109] In some embodiments of this application, as shown in FIG3, the method for preparing hydrogen fluoride includes the following steps:

[0110] Step a. 40%~50% fluorosilicic acid and the third mixed sulfuric acid enter the decomposition tower, where a reaction occurs, producing silicon tetrafluoride gas, hydrogen fluoride gas, and the first mixed sulfuric acid. The decomposition reaction occurring in the decomposition tower is shown below:

[0111] H2SiF6 = HF + SiF4.

[0112] Reaction temperature: 60 ℃~140 ℃, preferably 90 ℃~100 ℃.

[0113] The composition of the third mixed sulfuric acid is: sulfuric acid, 91%~95%; hydrogen fluoride, 1%~5%; and water, 2%~6%.

[0114] The first mixed sulfuric acid composition is: sulfuric acid, 60%~70%; hydrogen fluoride, 3%~6%; water, 25%~40%.

[0115] Step b. Pass the silicon tetrafluoride gas and hydrogen fluoride gas generated in step a through a sulfuric acid absorption tower. Use a second sulfuric acid, i.e., 98% sulfuric acid, to absorb the mixture of silicon tetrafluoride and hydrogen fluoride gas. The hydrogen fluoride gas is absorbed into the 98% sulfuric acid to obtain a second mixed sulfuric acid. At the same time, the 98% sulfuric acid cools the mixed gas.

[0116] The composition of the second mixed sulfuric acid is: sulfuric acid, 94%~96%; hydrogen fluoride, 1%~3%; water: 2%~4%.

[0117] Temperature of sulfuric acid absorption tower: 20 ℃~80 ℃; Temperature of silicon tetrafluoride gas: 20 ℃~60 ℃.

[0118] Step c. The silicon tetrafluoride gas absorbed in the absorption tower in step b is introduced into the silicon tetrafluoride absorption tower. A 25%–30% fluorosilicic acid solution is used to absorb the silicon tetrafluoride gas, forming a fluorosilicic acid solution containing silicon dioxide precipitate. The hydrolysis reaction carried out in the silicon tetrafluoride absorption tower is shown below:

[0119] SiF4 + H2O = H2SiF6 + SiO2.

[0120] Then, the fluorosilicic acid solution containing silica precipitate is filtered. The resulting second fluorosilicic acid solution enters a 40%–50% fluorosilicic acid storage tank and is returned to the decomposition tower for step a. The silica precipitate obtained from filtration is washed, and the resulting solid phase and washing liquid constitute the third fluorosilicic acid solution. The solid phase is dried to obtain byproduct silica, which is sold as a byproduct. The washing liquid enters an 11%–18% fluorosilicic acid solution storage tank. After vacuum concentration, the 11%–18% fluorosilicic acid solution is increased to a concentration of 25%–30% and then enters the silicon tetrafluoride absorption tower.

[0121] The concentration of fluorosilicic acid in the tertiary fluorosilicic acid solution is 3%~10%.

[0122] Temperature of the silicon tetrafluoride absorption tower: 20 ℃~50 ℃.

[0123] Step d. The first mixed sulfuric acid produced in step a enters a falling film evaporator for heating and evaporation, producing gaseous hydrogen fluoride and liquid dilute sulfuric acid.

[0124] Falling film evaporator temperature: 130 ℃~160 ℃; pressure: -3 kpa~0 kpa.

[0125] Composition of liquid dilute sulfuric acid: sulfuric acid, 60%~70%; hydrogen fluoride, 0%~1%; water, 30%~40%.

[0126] The gaseous hydrogen fluoride (containing sulfuric acid and water) generated in steps e and d enters the scrubbing tower and is scrubbed using the second mixed sulfuric acid from step b. The hydrogen fluoride in the second mixed sulfuric acid is released, resulting in crude hydrogen fluoride gas and the third mixed sulfuric acid.

[0127] The temperature of the scrubbing tower is 80 ℃~140 ℃, and the pressure is -3 kpa~0 kpa.

[0128] The composition of the third mixed sulfuric acid is: sulfuric acid, 91%~95%; hydrogen fluoride, 1%~5%; and water, 2%~6%.

[0129] Step f. The crude hydrogen fluoride gas obtained in step e is condensed in a condenser into anhydrous crude hydrogen fluoride (i.e., crude AHF).

[0130] Composition of crude anhydrous hydrogen fluoride: hydrogen fluoride, 97%~99%; sulfuric acid, 0%~1%; water, 0~1%.

[0131] Condenser temperature: 5 ℃~18 ℃.

[0132] Step g. The crude anhydrous hydrogen fluoride is fed into a distillation column for rectification, and then into a degassing column to obtain pure hydrogen fluoride, which is the finished anhydrous hydrogen fluoride product (i.e., finished product AHF). The liquid in the distillation column bottoms is returned to the washing column. After rectification, there is a small amount of sulfuric acid in the bottoms. As the distillation continues, the boiling point of the system increases, and the residue needs to be discharged to the sulfuric acid washing column for washing the mixed gas in a timely manner to control the temperature of the distillation column system.

[0133] Anhydrous hydrogen fluoride product purity: ≥99.97%, hydrogen fluoride yield: 80%~90%.

[0134] The composition of the liquid in the bottom of the distillation column is: hydrogen fluoride, 90%~95%; sulfuric acid, 1%~5%; and water, 0%~1%.

[0135] Distillation column bottom temperature: 21 ℃~28 ℃, distillation column top temperature: 17 ℃~19.5 ℃.

[0136] The temperature at the bottom of the degassing tower is 19.5 ℃~21 ℃, and the temperature at the top of the degassing tower is 17 ℃~19.5 ℃.

[0137] The liquid-phase dilute sulfuric acid produced in steps h and d enters a stripping tower, where hot air is used for stripping to remove hydrogen fluoride. The hydrogen fluoride and hot air then enter an absorption tower to obtain hydrofluoric acid as a byproduct. After stripping, the sulfuric acid is cooled to obtain 60%–70% dilute sulfuric acid.

[0138] Temperature of the stripping tower: 100 ℃~120 ℃.

[0139] Temperature of the absorption tower: 20 ℃~40 ℃.

[0140] The second aspect of this application provides a hydrogen fluoride, which is obtained by the preparation method described above.

[0141] The embodiments of this application use the above preparation method to obtain hydrogen fluoride with high yield and high purity.

[0142] The third aspect of this application provides a battery material, the raw materials for which include hydrogen fluoride obtained by the preparation method proposed in the first aspect, or hydrogen fluoride proposed in the second aspect.

[0143] The hydrogen fluoride obtained by the above preparation method in the embodiments of this application can be used as a raw material for some battery materials, such as lithium hexafluorophosphate, sodium hexafluorophosphate, potassium hexafluorophosphate, lithium difluorosulfonate, lithium fluorosulfonate, etc.

[0144] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way. The reagents used in the embodiments are all from Aladdin Biochemical Technology Co., Ltd.

[0145] Example 1

[0146] Step A: 50% fluorosilicic acid and the third mixed sulfuric acid enter the decomposition tower, where they react to produce silicon tetrafluoride gas, hydrogen fluoride gas, and the first mixed sulfuric acid. The decomposition reaction in the decomposition tower is shown below:

[0147] H2SiF6 = HF + SiF4.

[0148] Reaction temperature: 90 ℃.

[0149] The composition of the third mixed sulfuric acid is: sulfuric acid, 94%; hydrogen fluoride, 2%; water, 4%.

[0150] The first mixed sulfuric acid composition is: sulfuric acid, 67%; hydrogen fluoride, 3.5%; water, 29.5%.

[0151] Step B: The silicon tetrafluoride gas and hydrogen fluoride gas generated in Step A are passed through a sulfuric acid absorption tower. A second sulfuric acid, namely 98% sulfuric acid, is used to absorb the mixture of silicon tetrafluoride and hydrogen fluoride gases. The hydrogen fluoride gas is absorbed into the 98% sulfuric acid to obtain the second mixed sulfuric acid, while the 98% sulfuric acid also cools the mixed gas.

[0152] The composition of the second mixed sulfuric acid is: sulfuric acid, 96%; hydrogen fluoride, 2%; water, 2%.

[0153] Temperature of sulfuric acid absorption tower: 40 ℃; Temperature of silicon tetrafluoride gas: 80 ℃.

[0154] Step C: The silicon tetrafluoride gas absorbed in the absorption tower in Step B is introduced into the silicon tetrafluoride absorption tower. A first fluorosilicic acid solution, i.e., 30% fluorosilicic acid, is used to absorb the silicon tetrafluoride gas, forming a fluorosilicic acid solution containing silicon dioxide precipitate. The hydrolysis reaction carried out in the silicon tetrafluoride absorption tower is shown below:

[0155] SiF4 + H2O = H2SiF6 + SiO2.

[0156] Then, the fluorosilicic acid solution containing silica precipitate is filtered. The resulting second fluorosilicic acid solution enters a 50% fluorosilicic acid storage tank and returns to the decomposition tower for step A. The silica precipitate obtained from filtration is washed, and the resulting solid phase and washing liquid constitute the third fluorosilicic acid solution. The solid phase is dried to obtain byproduct silica, which is sold as a byproduct. The washing liquid enters an 18% fluorosilicic acid solution storage tank. After vacuum concentration, the 18% fluorosilicic acid is increased to a concentration of 30% fluorosilicic acid and then enters the silicon tetrafluoride absorption tower.

[0157] The concentration of fluorosilicic acid in the tertiary fluorosilicic acid solution is 10%.

[0158] Temperature of the silicon tetrafluoride absorption tower: 30 ℃.

[0159] Step D: The first mixed sulfuric acid produced in step A enters a falling film evaporator for heating and evaporation, producing gaseous hydrogen fluoride and liquid dilute sulfuric acid.

[0160] Falling film evaporator temperature: 150 ℃; pressure: -3 kPa.

[0161] Composition of liquid dilute sulfuric acid: sulfuric acid, 68%; hydrogen fluoride, 0.3%; water, 32%.

[0162] Step E: The gaseous hydrogen fluoride (containing sulfuric acid and water) generated in Step D enters the scrubbing tower and is scrubbed using the second mixed sulfuric acid from Step B. The hydrogen fluoride in the second mixed sulfuric acid is released, yielding crude hydrogen fluoride gas and the third mixed sulfuric acid.

[0163] The temperature of the scrubbing tower is 100 ℃, and the pressure is -3 kPa.

[0164] The composition of the third mixed sulfuric acid is: sulfuric acid, 94%; hydrogen fluoride, 2%; water, 4%.

[0165] Step F: The crude hydrogen fluoride gas obtained in step E is condensed in a condenser into anhydrous crude hydrogen fluoride (i.e., crude AHF).

[0166] Composition of crude anhydrous hydrogen fluoride: hydrogen fluoride, 99%; sulfuric acid, 0.6%; water, 0.4%.

[0167] Condenser temperature: 8 ℃.

[0168] Step G: The crude anhydrous hydrogen fluoride is fed into a distillation column for distillation, and then into a degassing column to obtain pure hydrogen fluoride, which is the finished anhydrous hydrogen fluoride product (i.e., finished product AHF). The liquid in the distillation column bottom is returned to a sulfuric acid scrubbing column used to wash the mixed gas.

[0169] Anhydrous hydrogen fluoride product purity: ≥99.97%, hydrogen fluoride yield: 85%.

[0170] The composition of the liquid in the distillation column bottoms: hydrogen fluoride, 96%; sulfuric acid, 2%; water, 2%.

[0171] Distillation column bottom temperature: 23 ℃, distillation column top temperature: 19 ℃.

[0172] The temperature at the bottom of the degassing tower is 21 ℃, and the temperature at the top of the degassing tower is 19 ℃.

[0173] Step H: The liquid-phase dilute sulfuric acid produced in step D enters a stripping tower and is stripped using hot air to remove hydrogen fluoride from the liquid-phase dilute sulfuric acid. The hydrogen fluoride and hot air then enter an absorption tower to obtain hydrofluoric acid as a byproduct. After stripping, the sulfuric acid is cooled to obtain 70% dilute sulfuric acid.

[0174] Temperature of the stripping tower: 120 ℃.

[0175] Temperature of the absorption tower: 30 ℃.

[0176] Example 2-Example 23

[0177] The specific preparation methods of hydrogen fluoride provided in Examples 2-23 are as shown in Example 1, and the specific parameter values ​​are shown in Table 1.

[0178] Table 1

[0179]

[0180] Performance testing

[0181] I. Testing Method:

[0182] 1. Yield of hydrogen fluoride: ,in:

[0183] m(AHF) represents the weight of the product's anhydrous hydrogen fluoride, in grams;

[0184] m(H2SiF6) represents the weight of fluorosilicic acid reacted with the first sulfuric acid, in grams;

[0185] w(H2SiF6) represents the mass fraction of fluorosilicic acid that reacts with the first sulfuric acid.

[0186] "2" represents the molar ratio of fluorosilicic acid to hydrogen fluoride; "20" represents the molar mass of HF; "144" represents the molar mass of H2SiF6.

[0187] 2. Purity of hydrogen fluoride: The purity of anhydrous hydrogen fluoride was tested according to the national standard GB / T 7746-2023.

[0188] 3. Sulfuric acid consumption: Consumption (H2SO4) = m(H2SO4) / m(anhydrous hydrogen fluoride), dimensionless; where:

[0189] m(H2SO4) represents the total weight of sulfuric acid added during the preparation process, in grams;

[0190] m (anhydrous hydrogen fluoride) indicates the weight of the product's anhydrous hydrogen fluoride, in grams.

[0191] II. Test Results:

[0192] The tests were conducted on Examples 1-23, and the results are shown in Table 2.

[0193] Table 2

[0194]

[0195] The anhydrous hydrogen fluoride preparation method provided in this application has a high yield and purity of hydrogen fluoride, and reduces the consumption of sulfuric acid. As shown in Examples 1-4, the yield of anhydrous hydrogen fluoride increases with the increase of hydrogen fluoride content in the gaseous hydrogen fluoride. As shown in Examples 5-8, the yield of anhydrous hydrogen fluoride increases with the increase of fluorosilicic acid concentration. In Examples 9-12, the lower the hydrogen fluoride content in the third mixed sulfuric acid, the higher the amount of hydrogen fluoride released by the washing tower, and the higher the yield of hydrogen fluoride. In Examples 13-18, the more hydrogen fluoride is distilled out with the increase of falling film evaporation temperature, the more beneficial it is to improving the yield of hydrogen fluoride. In Examples 19-23, the more hydrogen fluoride is evaporated with the decrease of falling film evaporation pressure, and the yield of hydrogen fluoride increases.

[0196] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0197] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A method for preparing hydrogen fluoride, wherein, include: Fluorosilicic acid is reacted with a first sulfuric acid to produce a mixed gas and a first mixed sulfuric acid, wherein the first mixed sulfuric acid is a sulfuric acid solution containing hydrogen fluoride, and the mixed gas includes silicon tetrafluoride gas and hydrogen fluoride gas; The mixed gas is washed with a second sulfuric acid to obtain a second mixed sulfuric acid and washed silicon tetrafluoride gas; the second mixed sulfuric acid is obtained by absorbing the hydrogen fluoride gas with the second sulfuric acid. The aqueous hydrogen fluoride was washed with the second mixed sulfuric acid to obtain crude hydrogen fluoride gas; The crude hydrogen fluoride gas was purified to obtain anhydrous hydrogen fluoride.

2. The preparation method according to claim 1, wherein, Meet at least one of the following: (A) The mass ratio of water to hydrogen fluoride in the aqueous hydrogen fluoride is 1:5 to 1:19; (B) The aqueous hydrogen fluoride includes at least one of the following: hydrofluoric acid from the tail gas absorption tower of the fluorite process, hydrofluoric acid from the tail gas absorption tower of electronic grade hydrofluoric acid, and hydrofluoric acid from the tail gas absorption tower of the phosphorus chemical industry.

3. The preparation method according to claim 1 or 2, wherein, The first mixed sulfuric acid is subjected to falling film evaporation to obtain liquid dilute sulfuric acid and gaseous hydrogen fluoride, wherein the gaseous hydrogen fluoride serves as the source of the aqueous hydrogen fluoride.

4. The preparation method according to claim 3, wherein, Based on the total mass of the aqueous hydrogen fluoride, the mass percentage of hydrogen fluoride in the aqueous hydrogen fluoride is 40% to 95%.

5. The preparation method according to claim 1, wherein, The washing of aqueous hydrogen fluoride with the second mixed sulfuric acid also yields a third mixed sulfuric acid. The third mixed sulfuric acid serves as the source of the first sulfuric acid and reacts with the fluorosilicic acid.

6. The preparation method according to claim 1, wherein, It also includes: treating the washed silicon tetrafluoride gas, including the following steps: The washed silicon tetrafluoride gas is absorbed by a first fluorosilicic acid solution to obtain a fluorosilicic acid mixed solution containing silicon dioxide precipitate. Solid-liquid separation is performed to obtain a second fluorosilicic acid solution and the silicon dioxide precipitate. The silica precipitate was washed to obtain a trifluorosilicic acid solution and silica solid.

7. The preparation method according to claim 6, wherein, The treatment of the washed silicon tetrafluoride gas satisfies at least one of the following: (i) The mass concentration of the first fluorosilicic acid solution is 25%~30%; (ii) The mass concentration of the second fluorosilicic acid solution is 40%~55%; (iii) The mass concentration of the third fluorosilicic acid solution is 11%~18%; (iv) The third fluorosilicic acid solution is concentrated to produce the first fluorosilicic acid solution; (v) The second fluorosilicic acid solution serves as the source of the fluorosilicic acid and reacts with the first sulfuric acid.

8. The preparation method according to claim 1, wherein, The purification of the crude hydrogen fluoride gas to obtain anhydrous hydrogen fluoride includes: The crude hydrogen fluoride gas is condensed to obtain crude anhydrous hydrogen fluoride; The crude anhydrous hydrogen fluoride was subjected to distillation and degassing processes in sequence to obtain anhydrous hydrogen fluoride.

9. The preparation method according to claim 3, wherein, The liquid-phase dilute sulfuric acid is stripped by air to obtain a mixture of dilute sulfuric acid and stripping gas, wherein the stripping mixture includes air and stripped hydrogen fluoride. The stripping mixture is treated with water absorption to obtain hydrofluoric acid.

10. The preparation method according to claim 3, wherein, The first mixed sulfuric acid is subjected to falling film evaporation treatment, which includes at least one of the following: (a) Control the falling film evaporation temperature to 130 ℃~160 ℃; (b) Control the falling film evaporation pressure to -30 kPa to 0 kPa; (c) The content of hydrogen fluoride in the liquid phase dilute sulfuric acid is less than 5‰.

11. The preparation method according to claim 1, wherein, The reaction of fluorosilicic acid with sulfuric acid shall satisfy at least one of the following conditions: (α) Control the reaction temperature to 60 ℃~140 ℃; (β) The fluorosilicic acid used is fluorosilicic acid with a mass concentration of 40%~50%; (γ) The first sulfuric acid consists of 91%~95% sulfuric acid and 1%~5% hydrogen fluoride.

12. A hydrogen fluoride, wherein, The hydrogen fluoride is obtained by the preparation method according to any one of claims 1 to 11.

13. A battery material, wherein, The raw materials for preparing the battery material include hydrogen fluoride obtained by the preparation method according to any one of claims 1 to 11, or include the hydrogen fluoride according to claim 12.

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