A method for the production of hydrogen fluoride

Abstract

The application relates to the fluorine chemical technology field, in particular to a hydrogen fluoride preparation method. The hydrogen fluoride preparation method comprises the following steps: firstly, mixing ammonium hydrogen fluoride solid, a breaking azeotrope agent and water, and then distilling to obtain a hydrofluoric acid condensate; secondly, adding a water removing agent into the hydrofluoric acid condensate, and then distilling to obtain anhydrous hydrogen fluoride; wherein the breaking azeotrope agent is a fluoride, an oxide and / or a hydroxide of a covalent metal element; the covalent metal element is selected from antimony or beryllium. The prepared anhydrous hydrogen fluoride product does not introduce impurities, has high product quality and high yield, the whole process does not have very high temperature, the energy consumption is relatively low, the fluorine element is fully utilized, the economic benefit is relatively good, and the method is suitable for large-scale production.

Description

Technical Field

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

[0002] Fluorite is the preferred resource for producing hydrogen fluoride due to its simple process and low cost. However, fluorite reserves are limited, and mining has been restricted by the state. In recent years, the production of hydrogen fluoride using fluorosilicic acid has gradually become a research hotspot. Fluorosilicic acid is a byproduct of the wet-process phosphate fertilizer industry, with large output and low price. The production of hydrogen fluoride using fluorosilicic acid is generally divided into wet and dry methods. The wet method involves reacting concentrated sulfuric acid with fluorosilicic acid to produce hydrogen fluoride and silicon tetrafluoride, which is relatively simple. However, its disadvantage is the low utilization rate of fluorine, with only 1 / 3 of the fluorine being utilized. Another method involves converting fluorosilicic acid into fluorosilicates, then pyrolyzing them to obtain fluoride salts and silicon tetrafluoride. The fluoride salts then react with acid to produce hydrogen fluoride. This method also suffers from the problem of low fluorine utilization, and the pyrolysis temperature of fluorosilicates is high, resulting in high energy consumption and demanding equipment requirements.

[0003] Currently, the preparation of hydrogen fluoride using dilute hydrofluoric acid concentration or waste hydrofluoric acid purification is mentioned in Chinese invention patent application CN115738340A, published on March 7, 2023. This invention discloses a method for preparing high-concentration or anhydrous hydrofluoric acid using an extractant. The method uses one of phosphoric acid, sulfuric acid, or fluoride salt as the extractant, mixes dilute hydrofluoric acid with the extractant, and distills it to break the azeotropic point of hydrofluoric acid and water. After distillation, high-concentration or anhydrous hydrofluoric acid is obtained.

[0004] Chinese invention patent application CN104261349A, published on March 7, 2023, discloses a process for separating hydrofluoric acid and nitric acid from electronic waste. Under normal pressure, the electronic waste liquid is placed in the bottom of a distillation column. A certain amount of cesium nitrate and one or two of its homologues are added according to the feed amount of the electronic waste liquid. The bottom and top temperatures are controlled, and the top products are collected separately to obtain hydrofluoric acid and nitric acid. This method effectively solves the problem that hydrofluoric acid and nitric acid are prone to azeotropic reaction with water, making them difficult to separate using conventional distillation, thus achieving the goal of separating the two.

[0005] Chinese invention patent application CN116081575A, published on May 9, 2023, discloses a method for preparing electronic-grade inorganic acid using waste hydrofluoric acid solution as raw material. First, an alkali metal salt containing alkali metal fluoride and alkali metal nitrate is added to the waste hydrofluoric acid solution containing hydrofluoric acid, nitric acid, and water to disrupt the azeotropic phenomenon between hydrofluoric acid and water, thereby separating hydrogen fluoride vapor. The distillate residue is a mixed solution of nitric acid, water, alkali metal nitrate, and alkali metal fluoride. Next, impurity droplets entrained in the hydrogen fluoride vapor are removed to obtain pure hydrogen fluoride vapor. Then, the pure hydrogen fluoride vapor is condensed and its concentration is adjusted with ultrapure water to obtain electronic-grade hydrofluoric acid. The alkali metal fluoride is selected from one or more of lithium fluoride, potassium fluoride, and cesium fluoride.

[0006] In summary, the aforementioned Chinese invention patents use dilute hydrofluoric acid or waste hydrofluoric acid as raw materials to obtain anhydrous hydrofluoric acid and electronically grade hydrofluoric acid. However, the resources of these raw materials are limited, making them suitable for internal recycling within enterprises but not for large-scale production. Furthermore, the azeotropic breakers sodium fluoride and cesium fluoride have weak azeotropic breaking effects, resulting in low hydrogen fluoride yields. The use of phosphoric acid and sulfuric acid as azeotropic breakers introduces new impurities, leading to low product purity and quality. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing hydrogen fluoride, which solves the problems of low yield and low quality of hydrogen fluoride products obtained by existing methods.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing hydrogen fluoride includes the following steps:

[0010] (1) After mixing solid ammonium bifluoride, an azeotropic depressant and water, distillation is used to obtain hydrofluoric acid condensate;

[0011] (2) Add a dehydrating agent to the hydrofluoric acid condensate and distill to obtain anhydrous hydrogen fluoride;

[0012] The azeotropic detonator is a fluoride, oxide, and / or hydroxide of a covalent metal element; the covalent metal element is selected from antimony or beryllium.

[0013] The beneficial effects of this invention are as follows: This invention improves upon existing technology. In this invention, ammonium bifluoride is prepared into a saturated solution containing hydrogen fluoride, and then an azeotropic depressant is used to break the azeotropic phenomenon between hydrogen fluoride and water. High-concentration hydrofluoric acid condensate is obtained by distillation, and further dehydration yields anhydrous hydrogen fluoride. The azeotropic depressant is a fluoride, oxide, and / or hydroxide of a covalent metal element, selected from antimony or beryllium. It dissolves in the acidic ammonium bifluoride solution, resulting in a large number of covalent bonds FM (M representing the covalent metal) distributed in the water. This displaces the opportunity for FH to combine with water molecules to form hydrogen bonds, preventing some HF from being bound by hydrogen bonds, thereby disrupting the azeotropic phenomenon. The advantages of the azeotropic detonator used in this invention are: ① The azeotropic detonator can play a good role in breaking the azeotropic effect, resulting in hydrofluoric acid condensate with high concentration and high yield; ② While preparing hydrofluoric acid condensate, there is also a bottom liquid. The bottom liquid is separated into ammonium fluoride and mother liquor A. The azeotropic detonator can be effectively separated from mother liquor A, which is convenient for reuse; ③ Using the above-mentioned azeotropic detonator does not introduce impurities into the system.

[0014] The anhydrous hydrogen fluoride product prepared by the above method does not introduce impurities during the preparation process. The concentration of the hydrofluoric acid condensate obtained after using the above-mentioned azeotropic de-oxidizer is high, above 98.6 wt%, with a high yield. The final anhydrous hydrofluoric acid has a purity of above 99.8 wt%, low water content, and high product quality. At the same time, the yield of anhydrous hydrofluoric acid is high. Moreover, the azeotropic de-oxidizer does not volatilize when heated in the mixture of ammonium hydrogen fluoride solid and water, and remains in the solution, which can be recycled along with the liquid. In addition, there is still bottom liquid after distillation in step (1), and the ammonium fluoride in the bottom liquid can also be recycled. The above preparation method does not involve very high temperatures throughout the process, has low energy consumption, makes full use of fluorine, has good economic benefits, and is suitable for large-scale production.

[0015] To better achieve the disruption of the azeotropic phenomenon without introducing impurities, the azeotropic disruptor is preferably at least one of antimony trifluoride, beryllium difluoride, antimony trioxide, beryllium oxide, antimony hydroxide, and beryllium hydroxide.

[0016] To ensure complete dissolution of the azeotropic depressant while considering cost factors, preferably, the weight of the azeotropic depressant is 10-30% of the weight of water.

[0017] To improve the recycling of the bottom liquid, preferably, the bottom liquid is obtained after distillation in step (1), and the bottom liquid is separated into ammonium fluoride and mother liquor A; when the concentration of phosphate and / or sulfate in mother liquor A is ≤0.4wt%, mother liquor A is reused in step (1); when the concentration is >0.4wt%, mother liquor A is purified, and after purification, it is mixed into fluorosilicic acid solution to prepare solid ammonium hydrogen fluoride.

[0018] After the mother liquor A separated from the distillation bottom liquid in step (1) is recycled multiple times, the impurities phosphate and sulfate from the fluorosilicic acid solution will gradually accumulate to a high concentration, which will affect the quality of subsequent products. Therefore, it is necessary to remove impurities from mother liquor A. Preferably, the impurity removal includes the following steps:

[0019] a. Ammonia gas is introduced into mother liquor A to carry out precipitation reaction, and antimony or beryllium hydroxide and mother liquor B are obtained by solid-liquid separation. Antimony or beryllium hydroxide is used as an azeotropic de-oxidant and recycled in step (1).

[0020] b. The mother liquor B is mixed with the fluorosilicic acid solution to obtain a mixed solution with a pH of 2-3. Then, a lead compound is added to carry out a mixing reaction. The lead ions in the system after the mixing reaction are removed with a lead adsorbent to obtain a purified solution. The purified solution is mixed with the fluorosilicic acid solution to prepare ammonium bifluoride solid.

[0021] In step a, antimony or beryllium hydroxides are amphoteric compounds, soluble in acids and strong bases but insoluble in weak bases. Precipitation occurs when the solution is weakly alkaline. In step b, lead compounds dissolve in the acidic mixture to produce lead ions. These lead ions then react with phosphate and sulfate ions in the mixture to form a precipitation solution. Excess lead ions are removed using a lead adsorbent, and finally, solid-liquid separation is performed to obtain the purified solution. This purification method is simple to operate and can efficiently remove phosphate and sulfate ions from the mother liquor B without introducing other impurity ions.

[0022] To ensure the precipitation reaction proceeds fully, preferably, the pH value of the precipitation reaction in step a is 8 to 10.

[0023] Preferably, in step (1), the heating temperature during distillation is 60–80°C, and the condensation temperature is 10–18°C. The ammonium bifluoride solution containing the azeotropic detonator is heated in the distiller, and the hydrogen fluoride gas volatilizes and condenses into a liquid. At the same time, a small amount of water vapor is mixed with the hydrogen fluoride gas and condenses together. The resulting hydrofluoric acid condensate contains 0.2–2% water.

[0024] Preferably, the dehydrating agent in step (2) is one of fluorine, carbonyl fluoride, and sulfur trioxide, and the weight of the dehydrating agent is 4-8% of the weight of the hydrofluoric acid condensate. The dehydrating agent reacts with a small amount of water in the hydrofluoric acid condensate to generate hydrogen fluoride and other easily separable substances, such as oxygen, carbon dioxide, and sulfuric acid. After distillation, the hydrogen fluoride is distilled off separately to obtain anhydrous hydrogen fluoride.

[0025] More preferably, the weight of the dehydrating agent is 4-5% of the weight of hydrofluoric acid.

[0026] In order to ensure that hydrogen fluoride is distilled out separately, preferably, the heating temperature in step (2) is 25-40°C and the condensation temperature is 5-18°C.

[0027] More preferably, the heating temperature during distillation in step (2) is 25–40°C, and the condensation temperature is 5–15°C.

[0028] Preferably, in step (1), the weight ratio of ammonium bifluoride solid to water is (2-10):1. A slurry is prepared by mixing ammonium bifluoride and water, during which some of the ammonium bifluoride dissolves and dissociates into F. + NH 4+ H + HF and HF escape under the action of the azeotropic depressant and heating. As the amount of HF in the liquid decreases, undissolved ammonium bifluoride continues to dissolve to replenish HF until all the ammonium bifluoride dissolves. When no more hydrogen fluoride gas is produced, the bottom liquid mainly contains solid ammonium fluoride and liquid containing the azeotropic depressant, ammonium fluoride and a small amount of ammonium bifluoride. After distillation in step (1), a bottom liquid is obtained. The bottom liquid is separated into solid and liquid components to obtain ammonium fluoride and mother liquor A. The obtained mother liquor A is reused in step (1), that is, ammonium bifluoride is added for continued use.

[0029] More preferably, in step (1), the weight ratio of ammonium bifluoride solid to water is (3-9):1.

[0030] To obtain high-quality ammonium bifluoride solid using inexpensive fluorosilicic acid solution, preferably, the preparation method of the ammonium bifluoride solid includes the following steps: ammonifying fluorosilicic acid solution with ammonia water, separating the solid and liquid to obtain ammonium bifluoride solution and silica ointment; evaporating and concentrating the ammonium bifluoride solution and thermally decomposing it to obtain molten ammonium bifluoride liquid, and cooling it to obtain solid ammonium bifluoride.

[0031] Preferably, the evaporation and concentration temperature is 90–130°C, and the thermal decomposition temperature is 140–180°C. The ammonium fluoride solution is evaporated, concentrated, and thermally decomposed to obtain liquid ammonium bifluoride and ammonia. The evaporation and concentration process involves evaporating and concentrating the ammonium fluoride content in the solution to above 300 g / L. After decomposition, the percentage of ammonium bifluoride in the molten ammonium bifluoride liquid is not less than 90%. The ammonia is absorbed by water to obtain ammonia water, which is then reused in the ammoniation reaction between the fluorosilicic acid solution and the ammonia water.

[0032] More preferably, the evaporation and concentration temperature is 105–130°C, and the thermal decomposition temperature is 140–180°C.

[0033] To ensure that the fluorosilicic acid solution undergoes a complete ammoniation reaction, preferably, the concentration of the fluorosilicic acid solution is 15-22 wt%, and the concentration of the ammonia solution is 15-17 wt%. Attached Figure Description

[0034] Figure 1 This is a process flow diagram of the preparation method of hydrogen fluoride in Example 1 of the present invention;

[0035] Figure 2This is a flow chart of the mother liquor A impurity removal process in Example 5 of this invention. Detailed Implementation

[0036] Existing methods for preparing hydrogen fluoride result in low yields and low quality products. This invention provides a method for preparing hydrogen fluoride, comprising the following steps:

[0037] (1) After mixing solid ammonium bifluoride, an azeotropic depressant and water, distillation is used to obtain hydrofluoric acid condensate;

[0038] (2) Add a dehydrating agent to the hydrofluoric acid condensate and distill to obtain anhydrous hydrogen fluoride;

[0039] The azeotropic detonator is a fluoride, oxide, and / or hydroxide of a covalent metal element; the covalent metal element is selected from antimony or beryllium.

[0040] The technical concept of this invention is as follows: After preparing a saturated solution of hydrogen fluoride containing ammonium bifluoride, an azeotropic depressant is used to break the azeotropic phenomenon between hydrogen fluoride and water. High-concentration hydrofluoric acid condensate is obtained by distillation, and further dehydration yields anhydrous hydrogen fluoride. The azeotropic depressant is a fluoride, oxide, and / or hydroxide of a covalent metal element, selected from antimony or beryllium. It dissolves in the acidic ammonium bifluoride solution, resulting in a large number of covalent bonds FM (M representing the covalent metal) distributed in the water. This displaces the opportunity for FH to combine with water molecules to form hydrogen bonds, preventing some HF from being bound by hydrogen bonds and thus disrupting the azeotropic phenomenon.

[0041] The anhydrous hydrogen fluoride product obtained by the above method does not introduce impurities. The concentration of the hydrofluoric acid condensate obtained after using the above azeotropic detonator is high, above 98.6 wt%, with a high yield. The final anhydrous hydrofluoric acid has a purity of above 99.8 wt%, low water content, and high product quality. At the same time, the yield of anhydrous hydrofluoric acid is high, and the azeotropic detonator does not volatilize when heated in the mixture of ammonium hydrogen fluoride solid and water, and remains in the solution, which can be recycled with the liquid. In addition, there is still bottom liquid after distillation in step (1), and the ammonium fluoride in the bottom liquid can also be recycled. When the bottom liquid needs to be cleaned, the bottom liquid is separated into solid and liquid to obtain ammonium fluoride and mother liquor A. The azeotropic detonator can be effectively separated from mother liquor A, which is convenient for reuse. The above preparation method does not involve high temperature throughout the process, has low energy consumption, makes full use of fluorine, has good economic benefits, and is suitable for large-scale production.

[0042] Specifically, a method for preparing hydrogen fluoride includes the following steps:

[0043] (1) Mix a fluorosilicic acid solution with ...

[0044] (2) The ammonium fluoride solution is evaporated and concentrated at a temperature of 105-130℃, so that the ammonium fluoride content in the ammonium fluoride solution is evaporated and concentrated to more than 300g / L. Then the temperature is raised to 140-180℃, and ammonia and water vapor are volatilized together. A molten liquid mainly composed of ammonium bifluoride is obtained in the container. The percentage content of ammonium bifluoride in the molten liquid of ammonium bifluoride is not less than 90%. Then the temperature is lowered to obtain solid ammonium bifluoride.

[0045] (3) A slurry is prepared by mixing solid ammonium bifluoride with water in a weight ratio of (2-10):1. Then, an azeotropic de-oxidant is added, the weight of which is 10-30% of the weight of water. The mixture is stirred and dissolved, then transferred to a distiller and heated to 60-80°C. The hydrogen fluoride evaporates and is then condensed to 10-18°C to obtain a certain concentration of hydrofluoric acid condensate and bottom liquid.

[0046] (4) Add a dehydrating agent to the hydrofluoric acid condensate. The weight of the dehydrating agent is 4-5% of the weight of the hydrofluoric acid condensate. Then transfer it to a distiller and heat it to 25-40°C. The hydrogen fluoride will evaporate. Then condense it to 5-18°C to obtain anhydrous hydrogen fluoride.

[0047] The chemical reactions involved in step (1) include:

[0048] H2SiF6+2NH4OH→(NH4)2SiF6+2H2O;

[0049] (NH4)2SiF6+4NH4OH+nH2O→6NH4F+SiO2·nH2O↓+2H2O.

[0050] It should be noted that the resulting ammonium fluoride solution will contain a small amount of unreacted ammonium fluorosilicate. Ammonium fluorosilicate does not participate in chemical reactions or undergo any changes during subsequent concentration, pyrolysis, and distillation, and does not affect the quality of subsequent products.

[0051] The chemical reactions involved in step (2) include:

[0052] 2NH4F→NH4HF2+NH3↑.

[0053] Preferably, during distillation in step (3), the vacuum degree in the distiller is 0 to -70 kPa.

[0054] Preferably, the azeotropic detonator in step (3) is at least one of antimony trifluoride, beryllium difluoride, antimony trioxide, beryllium oxide, antimony hydroxide, and beryllium hydroxide.

[0055] Specifically, in step (3), the bottom liquid is separated into solid and liquid phases to obtain ammonium fluoride and mother liquor A. The impurity removal of mother liquor A includes the following steps:

[0056] a. First, ammonia gas is introduced into mother liquor A to make the pH value of the solution 8-10. At this time, antimony or beryllium will precipitate out in the form of hydroxide. Solid-liquid separation is performed to obtain antimony or beryllium hydroxide and mother liquor B. Antimony or beryllium hydroxide is used as an azeotropic de-oxidant and recycled in step (3).

[0057] b. Mix 1000g of mother liquor B with fluorosilicic acid solution to obtain a mixed solution with pH 2-3. Then add lead compound to the mixed solution for mixing reaction. Then add lead adsorbent to the mixed reaction system for lead removal reaction. The filtered liquid is the impurity removal liquid. This impurity removal liquid can be mixed with the raw material fluorosilicic acid solution for reuse.

[0058] The implementation process of the present invention will be described in detail below with reference to specific embodiments.

[0059] In the following examples, Examples 1-4 are for the preparation of hydrogen fluoride, and Examples 5-7 are for the purification of mother liquor A from Examples 1-3. The fluorosilicic acid solution used was purchased from a domestic wet-process phosphate fertilizer plant. The mass fraction of fluorosilicic acid in the fluorosilicic acid solution was 5-22%, the mass fraction of phosphate was 0.03-0.1%, the mass fraction of sulfate was 0.04-0.15%, and the mass fraction of lead ions was 1-4 ppm. All other raw materials were commercially available conventional raw materials. Where specific techniques or conditions are not specified in the examples, they should be carried out in accordance with the techniques or conditions described in the relevant literature or the product instructions.

[0060] I. Specific Embodiments of the Method for Preparing Hydrogen Fluoride of the Present Invention

[0061] Example 1

[0062] The method for preparing hydrogen fluoride in this embodiment includes the following steps:

[0063] (1) A 15wt% fluorosilicic acid solution was mixed with a 17wt% ammonia solution for ammoniation. The endpoint pH was controlled at 6, the temperature at 48℃, and the reaction time at 20 min. Ammonia solution was then added, and the endpoint pH was controlled at 9, the temperature at 40℃, and the reaction time at 30 min. A mixture containing silica gel was obtained. Solid-liquid separation yielded an ammonium fluoride solution and silica ointment, as follows: Figure 1 As shown;

[0064] (2) The ammonium fluoride solution is evaporated and concentrated at 130°C, so that the ammonium fluoride content in the ammonium fluoride solution is evaporated and concentrated to 360g / L. Then the temperature is raised to 180°C, and ammonia and water vapor are volatilized together until no more ammonia is volatilized. At this time, a molten liquid mainly composed of ammonium bifluoride is obtained in the container. The percentage content of ammonium bifluoride in the molten liquid of ammonium bifluoride is 94wt%. Then the temperature is lowered to obtain solid ammonium bifluoride.

[0065] (3) A slurry was prepared by mixing solid ammonium bifluoride with water in a weight ratio of 9:1. Then, antimony trioxide was added, with the weight of antimony trioxide being 30% of the weight of water. The mixture was stirred and dissolved, then transferred to a distiller and heated to 60°C. The hydrogen fluoride was volatilized and then condensed to 10°C to obtain a hydrofluoric acid condensate and bottom liquid with a concentration of 99.5 wt%.

[0066] (4) Sulfur trioxide was added to the hydrofluoric acid condensate, the weight of which was 8% of the weight of the hydrofluoric acid condensate. The mixture was then transferred to a distiller and heated to 40°C. The hydrogen fluoride evaporated and was then condensed to 5°C to obtain anhydrous hydrogen fluoride. The purity of the hydrogen fluoride was found to be 99.99 wt%, the water content of the hydrogen fluoride was 0.003%, and the yield was 98.8%.

[0067] Example 2

[0068] The method for preparing hydrogen fluoride in this embodiment includes the following steps:

[0069] (1) A 22wt% fluorosilicic acid solution was mixed with a 15wt% ammonia solution for ammoniation reaction. The endpoint pH was controlled at 7, the temperature at 50℃, and the reaction time at 20min. Then, ammonia solution was added to control the endpoint pH at 10, the temperature at 42℃, and the reaction time at 30min. A mixture containing silica gel was obtained. The solid and liquid were separated to obtain ammonium fluoride solution and silica ointment.

[0070] (2) The ammonium fluoride solution is evaporated and concentrated at 110°C, so that the ammonium fluoride content in the ammonium fluoride solution is evaporated and concentrated to 310g / L. Then the temperature is raised to 150°C, and ammonia and water vapor are volatilized together until no more ammonia is volatilized. At this time, a molten liquid mainly composed of ammonium bifluoride is obtained in the container. The percentage content of ammonium bifluoride in the molten liquid of ammonium bifluoride is 92wt%. Then the temperature is lowered to obtain solid ammonium bifluoride.

[0071] (3) A slurry was prepared by mixing solid ammonium bifluoride with water in a weight ratio of 3:1. Then, antimony trifluoride was added, with the weight of antimony trifluoride being 10% of the weight of water. The mixture was stirred and dissolved, then transferred to a distiller and heated to 60°C. The vacuum degree in the distiller was set to -70 kPa, and the hydrogen fluoride was volatilized. The mixture was then condensed to 15°C to obtain a hydrofluoric acid condensate and bottom liquid with a concentration of 98.6 wt%.

[0072] (4) Add fluorine gas to the hydrofluoric acid condensate. The weight of the fluorine gas is 4% of the weight of the hydrofluoric acid condensate. Then transfer it to a distiller and heat it to 30°C. The hydrogen fluoride evaporates and is then condensed to 15°C to obtain anhydrous hydrogen fluoride. The purity of the hydrogen fluoride was found to be 99.98 wt%, the water content of the hydrogen fluoride was 0.005%, and the yield was 99.0%.

[0073] Example 3

[0074] The method for preparing hydrogen fluoride in this embodiment includes the following steps:

[0075] (1) A 20wt% fluorosilicic acid solution was mixed with a 16wt% ammonia solution for ammoniation reaction. The final pH was controlled at 6.5, the temperature at 45℃, and the reaction time was 20min. Then, ammonia solution was added to control the final pH at 9.5, the temperature at 38℃, and the reaction time for 30min. A mixture containing silica gel was obtained. The solid and liquid were separated to obtain ammonium fluoride solution and silica ointment.

[0076] (2) The ammonium fluoride solution is evaporated and concentrated at 105°C, so that the ammonium fluoride content in the ammonium fluoride solution is evaporated and concentrated to 300g / L. Then the temperature is raised to 140°C, and ammonia and water vapor are volatilized together until no more ammonia is volatilized. At this time, a molten liquid mainly composed of ammonium bifluoride is obtained in the container. The percentage content of ammonium bifluoride in the molten liquid of ammonium bifluoride is 90wt%. Then the temperature is lowered to obtain solid ammonium bifluoride.

[0077] (3) A slurry is prepared by mixing ammonium bifluoride solid with water in a weight ratio of 5:1. Then beryllium difluoride is added, with the weight of beryllium difluoride being 20% ​​of the weight of water. The mixture is stirred and dissolved, then transferred to a distiller and heated to 80°C. The hydrogen fluoride evaporates and is then condensed to 18°C ​​to obtain a hydrofluoric acid condensate and bottom liquid with a concentration of 99.2 wt%.

[0078] (4) Add carbonyl fluoride to the hydrofluoric acid condensate. The weight of carbonyl fluoride is 4% of the weight of the hydrofluoric acid condensate. Then transfer it to a distiller and heat it to 25°C. The hydrogen fluoride evaporates and is then condensed to 10°C to obtain anhydrous hydrogen fluoride. The purity of the hydrogen fluoride was found to be 99.99 wt%, the water content of the hydrogen fluoride was 0.002%, and the yield was 98.9%.

[0079] Example 4

[0080] The method for preparing hydrogen fluoride in this embodiment includes the following steps:

[0081] (1) A 20wt% fluorosilicic acid solution was mixed with a 16wt% ammonia solution for ammoniation reaction. The final pH was controlled at 6.4, the temperature at 45℃, and the reaction time at 20min. Then, ammonia solution was added to control the final pH at 9.6, the temperature at 38℃, and the reaction time at 30min. A mixture containing silica gel was obtained. The solid and liquid were separated to obtain ammonium fluoride solution and silica ointment.

[0082] (2) The ammonium fluoride solution is evaporated and concentrated at 105°C, so that the ammonium fluoride content in the ammonium fluoride solution is evaporated and concentrated to 302 g / L. Then the temperature is raised to 140°C, and ammonia and water vapor are volatilized together until no more ammonia is volatilized. At this time, a molten liquid mainly composed of ammonium bifluoride is obtained in the container. The percentage content of ammonium bifluoride in the molten liquid of ammonium bifluoride is 91 wt%. Then the temperature is lowered to obtain solid ammonium bifluoride.

[0083] (3) A slurry was prepared by mixing ammonium bifluoride solid with water in a weight ratio of 5:1. Then beryllium oxide was added, with the weight of beryllium oxide being 12% of the weight of water. The mixture was stirred and dissolved, then transferred to a distiller and heated to 80°C. The hydrogen fluoride was volatilized and then condensed to 18°C ​​to obtain a hydrofluoric acid condensate and bottom liquid with a concentration of 99.4 wt%.

[0084] (4) Add carbonyl fluoride to the hydrofluoric acid condensate. The weight of carbonyl fluoride is 4% of the weight of the hydrofluoric acid condensate. Then transfer it to a distiller and heat it to 25°C. The hydrogen fluoride evaporates and is then condensed to 10°C to obtain anhydrous hydrogen fluoride. The purity of the hydrogen fluoride was found to be 99.99 wt%, the water content of the hydrogen fluoride was 0.002%, and the yield was 99.0%.

[0085] Example 5

[0086] In step (3) of Example 1, the bottom liquid after distillation is subjected to solid-liquid separation to obtain mother liquor A. After mother liquor A is recycled 10 times, the content of phosphorus and sulfur impurities is tested. The mass fraction of phosphate is 0.42%, the mass fraction of sulfate is 0.33%, and the pH is 4.0. At this time, mother liquor A is purified to remove impurities, such as... Figure 2 As shown, it includes the following steps:

[0087] a. First, ammonia gas is introduced into mother liquor A to make the solution pH 10. Before the ammonia gas is introduced, the azeotropic detonator in mother liquor A is antimony fluoride converted from antimony trioxide after dissolution. After the ammonia gas is introduced, the azeotropic detonator antimony fluoride in mother liquor A precipitates out in the form of antimony hydroxide. Solid-liquid separation yields antimony hydroxide and mother liquor B. Antimony hydroxide is reused as the azeotropic detonator in step (3). The mass fraction of phosphate in mother liquor B is 0.60%, the mass fraction of sulfate is 0.47%, and the mass fraction of lead ions is 3 ppm.

[0088] b. Take 1000g of mother liquor B and mix it with a 5wt% clear fluorosilicic acid solution to obtain a mixed solution with a pH of 3. The mass fractions of phosphate and sulfate in the fluorosilicic acid solution are 0.03% and 0.04%, respectively, and the mass fraction of lead ions is 1ppm. The amounts of phosphate ions and sulfate ions in the mixed solution are 0.065mol and 0.052mol, respectively.

[0089] c. Add 34.7g of lead trioxide (0.150mol of lead in lead trioxide) to the mixed solution and stir at 50℃ for 0.5h (during the stirring reaction, monitor the pH value of the reaction system; when the pH value of the reaction system is greater than 3, add fluorosilicic acid solution to control the pH value of the reaction system at 3). Then add 13.9g of activated carbon to the reaction system and stir at 50℃ for 2h (during the stirring reaction, monitor the pH value of the system; when the pH value of the system is greater than 3, add fluorosilicic acid solution to control the pH value of the system at 3). The resulting liquid after filtration is the impurity-removed liquid, which can be mixed with the raw material fluorosilicic acid solution for reuse.

[0090] Example 6

[0091] In step (3) of Example 2, the bottom liquid after distillation is subjected to solid-liquid separation to obtain mother liquor A. After mother liquor A is recycled 10 times, the content of phosphorus and sulfur impurities is tested. The mass fraction of phosphate is 0.31%, the mass fraction of sulfate is 0.53%, and the pH is 4.0. At this time, the impurities in mother liquor A are removed, including the following steps:

[0092] a. First, ammonia gas is introduced into mother liquor A to make the solution pH 9. At this time, the azeotropic detonator antimony trifluoride in mother liquor A precipitates out in the form of antimony hydroxide. Solid-liquid separation yields antimony hydroxide and mother liquor B. Antimony hydroxide is reused as an azeotropic detonator in step (3). The mass fraction of phosphate in mother liquor B is 0.44%, the mass fraction of sulfate is 0.75%, and the mass fraction of lead ions is 5 ppm.

[0093] b. Take 1000g of mother liquor B and mix it with a 15wt% clear fluorosilicic acid solution to obtain a mixed solution with a pH of 2.5. The mass fractions of phosphate and sulfate in the fluorosilicic acid solution are 0.08% and 0.12%, respectively, and the mass fraction of lead ions is 3ppm. The amounts of phosphate ions and sulfate ions in the mixed solution are 0.048mol and 0.081mol, respectively.

[0094] c. Add 34.2g of lead oxide (0.153mol of lead element in lead oxide) to the mixed solution and stir at 50℃ for 0.5h (during the stirring reaction, monitor the pH value of the reaction system; when the pH value of the reaction system is greater than 2.5, add fluorosilicic acid solution to control the pH value of the reaction system at 2.5). Then add 10.25g of activated carbon to the reaction system and stir at 50℃ for 2h (during the stirring reaction, monitor the pH value of the system; when the pH value of the system is greater than 2.5, add fluorosilicic acid solution to control the pH value of the system at 2.5). The resulting liquid after filtration is the impurity removal liquid, which can be mixed with the raw material fluorosilicic acid solution for reuse.

[0095] Example 7

[0096] In step (3) of Example 3, the bottom liquid after distillation is subjected to solid-liquid separation to obtain mother liquor A. After mother liquor A is recycled 10 times, the content of phosphorus and sulfur impurities is tested. The mass fraction of phosphate is 0.71%, the mass fraction of sulfate is 0.79%, and the pH is 4.5. At this time, the impurities in mother liquor A are removed, including the following steps:

[0097] a. First, ammonia gas is introduced into mother liquor A to make the solution pH 8. At this time, the azeotropic detonator beryllium difluoride in mother liquor A precipitates out in the form of beryllium hydroxide. Solid-liquid separation yields beryllium hydroxide and mother liquor B. Antimony hydroxide is used as an azeotropic detonator and recycled in step (3). The mass fraction of phosphate in mother liquor B is 0.87%, the mass fraction of sulfate is 0.99%, and the mass fraction of lead ions is 5 ppm.

[0098] b. Take 1000g of mother liquor B and mix it with a 20wt% clear fluorosilicic acid solution to obtain a mixed solution with a pH of 2. The mass fractions of phosphate and sulfate in the fluorosilicic acid solution are 0.1% and 0.15%, respectively, and the mass fraction of lead ions is 4ppm. The amounts of phosphate ions and sulfate ions in the mixed solution are 0.093mol and 0.106mol, respectively.

[0099] c. Add 56.1g of lead tetroxide (0.245mol of lead in lead tetroxide) to the mixed solution and stir at 50℃ for 0.5h (during the stirring process, monitor the pH of the reaction system; when the pH is greater than 2, add fluorosilicic acid solution to control the pH at 2). Then add 19.6g of activated carbon to the reacted system and stir at 50℃ for 2h (during the stirring process, monitor the pH; when the pH is greater than 2, add fluorosilicic acid solution to control the pH at 2). The resulting liquid after filtration is the purified liquid, which can be mixed with the raw material fluorosilicic acid solution for reuse.

[0100] II. Comparative Example

[0101] Comparative Example 1

[0102] The method for preparing hydrogen fluoride in this comparative example differs from that in Example 1 in that: no azeotropic depressant is used in step (3), and hydrogen fluoride only volatilizes when heated to 112°C, along with water vapor. Condensation at 20°C yields hydrofluoric acid with a concentration of 37.6%. The method includes the following steps:

[0103] (1) Mix 15wt% fluorosilicic acid solution with 17wt% ammonia solution for ammoniation reaction, control the endpoint pH to 6, temperature to 48℃, reaction time to 20min, then continue to add ammonia solution, control the endpoint pH to 9, temperature to 40℃, reaction time to 30min, to obtain a mixture containing silica gel, solid-liquid separation, to obtain ammonium fluoride solution and silica ointment.

[0104] (2) The ammonium fluoride solution was evaporated and concentrated at 130°C to an ammonium fluoride content of 360 g / L. Then the temperature was raised to 180°C, and ammonia and water vapor were volatilized together until no more ammonia was volatilized. At this time, a molten liquid mainly composed of ammonium bifluoride was obtained in the container. The percentage content of ammonium bifluoride in the molten liquid was 94 wt%. The temperature was then lowered to obtain solid ammonium bifluoride.

[0105] (3) A slurry is prepared by mixing solid ammonium fluoride with water in a weight ratio of 9:1. The slurry is then transferred to a distiller and heated to 112°C. Hydrogen fluoride evaporates, along with water vapor. The slurry is then condensed to 20°C to obtain a hydrofluoric acid condensate with a concentration of 37.6 wt%.

[0106] Comparative Example 2

[0107] The method for preparing hydrogen fluoride in this comparative example differs from that in Example 1 in that the azeotropic detonator used in step (3) is cesium fluoride, which includes the following steps:

[0108] (1) Mix a 15wt% fluorosilicic acid solution with a 17wt% ammonia solution for ammoniation reaction, control the endpoint pH to 6, the temperature to 48℃, and the reaction time to 20min. Then add ammonia solution to control the endpoint pH to 9, the temperature to 40℃, and the reaction time to 30min to obtain a mixture containing silica gel. Separate the solid and liquid to obtain ammonium fluoride solution and silica ointment.

[0109] (2) The ammonium fluoride solution is evaporated and concentrated at 130°C, so that the ammonium fluoride content in the ammonium fluoride solution is evaporated and concentrated to 360g / L. Then the temperature is raised to 180°C, and ammonia and water vapor are volatilized together until no more ammonia is volatilized. At this time, a molten liquid mainly composed of ammonium bifluoride is obtained in the container. The percentage content of ammonium bifluoride in the molten liquid of ammonium bifluoride is 94wt%. Then the temperature is lowered to obtain solid ammonium bifluoride.

[0110] (3) A slurry is prepared by mixing ammonium bifluoride solid with water in a weight ratio of 9:1. Then, cesium fluoride is added, with the weight of cesium fluoride being 30% of the weight of water. The mixture is stirred and dissolved, then transferred to a distiller and heated to 60°C. The hydrogen fluoride evaporates and is then condensed to 10°C to obtain a hydrofluoric acid condensate and a bottom liquid with a concentration of 95.5%.

[0111] (4) Sulfur trioxide was added to the hydrofluoric acid condensate. The weight of sulfur trioxide was 8% of the weight of hydrofluoric acid. The mixture was then transferred to a distiller and heated to 40°C. Hydrogen fluoride evaporated and was then condensed to 5°C to obtain anhydrous hydrogen fluoride. The purity of the hydrogen fluoride was 97.24%, the water content of the hydrogen fluoride was 2.75%, and the yield was 92.3%.

[0112] Comparative Example 3

[0113] The method for preparing hydrogen fluoride in this comparative example differs from that in Example 1 in that the azeotropic detonator used in step (3) is sodium fluoride, and includes the following steps:

[0114] (1) Mix a 15wt% fluorosilicic acid solution with a 17wt% ammonia solution for ammoniation reaction, control the endpoint pH to 6, the temperature to 48℃, and the reaction time to 20min. Then add ammonia solution to control the endpoint pH to 9, the temperature to 40℃, and the reaction time to 30min to obtain a mixture containing silica gel. Separate the solid and liquid to obtain ammonium fluoride solution and silica ointment.

[0115] (2) The ammonium fluoride solution is evaporated and concentrated at 130°C, so that the ammonium fluoride content in the ammonium fluoride solution is evaporated and concentrated to 360g / L. Then the temperature is raised to 180°C, and ammonia and water vapor are volatilized together until no more ammonia is volatilized. At this time, a molten liquid mainly composed of ammonium bifluoride is obtained in the container. The percentage content of ammonium bifluoride in the molten liquid of ammonium bifluoride is 94wt%. Then the temperature is lowered to obtain solid ammonium bifluoride.

[0116] (3) A slurry is prepared by mixing solid ammonium bifluoride with water in a weight ratio of 9:1. Then sodium fluoride is added, with the weight of sodium fluoride being 30% of the weight of water. The mixture is stirred and dissolved, then transferred to a distiller and heated to 60°C. The hydrogen fluoride evaporates and is then condensed to 10°C to obtain a hydrofluoric acid condensate and a bottom liquid with a concentration of 90.6%.

[0117] (4) Sulfur trioxide was added to the hydrofluoric acid condensate. The weight of sulfur trioxide was 8% of the weight of hydrofluoric acid. The mixture was then transferred to a distiller and heated to 40°C. Hydrogen fluoride evaporated and was then condensed to 5°C to obtain anhydrous hydrogen fluoride. The purity of hydrogen fluoride was 92.26%, the water content of hydrogen fluoride was 7.74%, and the yield was 90.1%.

[0118] In summary, in the hydrogen fluoride preparation methods of Examples 1-4 of this invention, the addition of the aforementioned azeotropic de-oxidizing agent during the preparation process results in a high concentration of hydrofluoric acid condensate, exceeding 98.6 wt%, leading to a high yield of hydrofluoric acid. The anhydrous hydrogen fluoride obtained after dehydration distillation has a high purity, exceeding 99.98 wt%, with low water content, resulting in high product quality. Simultaneously, the yield of anhydrous hydrogen fluoride is also high. In contrast, in Comparative Example 1, since the aforementioned azeotropic de-oxidizing agent was not added during the preparation process, the concentration of the hydrofluoric acid condensate obtained was only 37.6 wt%, making it impossible to prepare subsequent anhydrous hydrogen fluoride. The azeotropic de-oxidizing agent, the impurity removal liquid, and the ammonium fluoride in the distillation bottom liquid obtained through the impurity removal method of this invention can be recycled. The entire process involves no high temperatures, low energy consumption, and full utilization of fluorine, resulting in good economic benefits and suitability for large-scale production.

[0119] The above is a detailed description of the embodiments, but it is not intended to limit the technical solutions of the present invention. Those skilled in the art should understand that any modifications, partial substitutions, and variations can be made to the above embodiments within the scope of the present invention, and all such modifications and variations should be covered within the scope of the present invention.

Claims

1. A method for preparing hydrogen fluoride, characterized in that, Includes the following steps: (1) After mixing ammonium bifluoride solid, an azeotropic depressant and water, hydrofluoric acid condensate is obtained by distillation; the weight of the azeotropic depressant is 10-30% of the weight of water; the weight ratio of ammonium bifluoride solid to water is (2-10):

1. (2) Add a dehydrating agent to the hydrofluoric acid condensate and distill to obtain anhydrous hydrogen fluoride; The azeotropic detonator is a fluoride, oxide, and / or hydroxide of a covalent metal element; the covalent metal element is selected from antimony or beryllium.

2. The method for preparing hydrogen fluoride according to claim 1, characterized in that, The azeotropic detonator is at least one of antimony trifluoride, beryllium difluoride, antimony trioxide, beryllium oxide, antimony hydroxide, and beryllium hydroxide.

3. The method for preparing hydrogen fluoride according to claim 2, characterized in that, The weight of the azeotropic de-oxidant is 12-20% of the weight of water.

4. The method for preparing hydrogen fluoride according to any one of claims 1-3, characterized in that, In step (1), a base liquid is obtained after distillation. The base liquid is separated into solid and liquid components to obtain ammonium fluoride and mother liquor A. When the concentration of phosphate and / or sulfate in mother liquor A is ≤0.4wt%, mother liquor A is reused in step (1). When the concentration is >0.4wt%, mother liquor A is purified and then mixed into a fluorosilicic acid solution to prepare solid ammonium hydrogen fluoride.

5. The method for preparing hydrogen fluoride according to claim 4, characterized in that, The impurity removal process includes the following steps: a. Ammonia gas is introduced into mother liquor A to carry out a precipitation reaction. The solid and liquid are separated to obtain antimony or beryllium hydroxide and mother liquor B. The antimony or beryllium hydroxide is used as an azeotropic de-escalator and recycled in step (1). b. The mother liquor B is mixed with the fluorosilicic acid solution to obtain a mixed solution with a pH of 2-3. Then, a lead compound is added to carry out a mixing reaction. The lead ions in the system after the mixing reaction are removed with a lead adsorbent to obtain a purified solution. The purified solution is mixed with the fluorosilicic acid solution to prepare ammonium bifluoride solid.

6. The method for preparing hydrogen fluoride according to claim 5, characterized in that, The pH value of the precipitation reaction in step a is 8 to 10.

7. The method for preparing hydrogen fluoride according to claim 1, characterized in that, In step (1), the heating temperature during distillation is 60-80℃, and the condensation temperature is 10-18℃.

8. The method for preparing hydrogen fluoride according to claim 1, characterized in that, In step (2), the dehydrating agent is one of fluorine, carbonyl fluoride, and sulfur trioxide, and the weight of the dehydrating agent is 4 to 8% of the weight of the hydrofluoric acid condensate.

9. The method for preparing hydrogen fluoride according to claim 1, characterized in that, In step (1), the weight ratio of ammonium bifluoride solid to water is (3-9):

1.

10. The method for preparing hydrogen fluoride according to claim 1 or 9, characterized in that, The preparation method of the ammonium bifluoride solid includes the following steps: ammonification reaction of fluorosilicic acid solution with ammonia water, solid-liquid separation, to obtain ammonium bifluoride solution and silica ointment; the ammonium bifluoride solution is evaporated, concentrated and thermally decomposed to obtain molten ammonium bifluoride liquid, and cooled to obtain ammonium bifluoride solid.

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