A method for producing hydrogen fluoride using ammonium fluoride

Abstract

This invention discloses a method for preparing hydrogen fluoride using ammonium fluoride. Specifically, ammonium fluoride and potassium fluoride are dissolved in water to obtain a mixed solution. After the mixed solution reacts at 100℃~200℃, solid-liquid separation is performed. The solid is dried to obtain potassium fluoride solid, while the liquid is returned to the initial ammonium fluoride and potassium fluoride reaction system for recycling. Potassium fluoride and sodium fluoride are mixed and hydrogen fluoride gas is prepared under molten conditions. After the reaction, the residual solid is dissolved in water, filtered, and the filtrate is returned to the ammonium fluoride and potassium fluoride reaction system for recycling. The filter cake is dried and returned to the potassium fluoride and sodium fluoride reaction system for recycling. This method can realize material recycling and solves the problems of low raw material utilization and serious material waste in existing hydrogen fluoride preparation processes.

Description

Technical Field

[0001] This invention belongs to the field of fluorochemical technology, specifically relating to a method for preparing hydrogen fluoride using ammonium fluoride, and more particularly to a hydrogen fluoride preparation process that achieves material recycling and is environmentally friendly. Background Technology

[0002] Hydrogen fluoride (HF) is a fundamental raw material for the fluorochemical industry, widely used in the production of refrigerants, fluoropolymers, fluorinated salts, fluororubber, and fluorinated intermediates, with strong market demand. Currently, traditional industrial processes for producing hydrogen fluoride mostly use fluorite as a raw material, which suffers from high resource dependence, high energy consumption, and difficulty in recycling byproducts. Furthermore, fluorite is a non-renewable resource, and long-term over-exploitation has led to a gradual decrease in reserves, which is inconsistent with the industrial orientation of green chemistry and sustainable development.

[0003] To address the aforementioned issues, a process for preparing hydrogen fluoride using fluorine-containing byproducts from industrial production is being gradually explored. During the wet-process phosphoric acid production, a large amount of fluorosilicic acid is generated during the washing of the silicon tetrafluoride-containing tail gas. This fluorosilicic acid can be used to produce silica via ammonolysis, with ammonium fluoride as a byproduct. Ammonium fluoride is a highly promising carrier of fluorine resources, and its recycling is crucial for recovering fluorine resources and reducing the production cost of wet-process phosphoric acid. Patent US4089936A provides a method for preparing hydrogen fluoride: heating ammonium fluoride in an aqueous solution and reacting it in the presence of excess soluble potassium fluoride to form an aqueous solution of potassium hydrofluoride; filtering to obtain a solid product containing potassium hydrofluoride; reacting potassium hydrofluoride with a sodium fluoride solution to generate a sodium hydrofluoride solution; and then decomposing the sodium hydrofluoride by heating to above 180°C to release hydrogen fluoride, forming a solid product containing sodium fluoride. However, the liquid obtained from the sodium hydrofluoride solution in the process described in this patent is difficult to recycle into the reaction process between potassium hydrofluoride and sodium fluoride.

[0004] In view of this, this invention discloses a method for preparing hydrogen fluoride using ammonium fluoride. It creatively proposes a method for directly reacting potassium hydrofluoride and sodium fluoride at high temperature to prepare hydrogen fluoride. The remaining solids are dissolved and filtered to obtain a filtrate containing a mixture of potassium hydrofluoride and potassium fluoride, which is then recycled back into the potassium fluoride and ammonium fluoride reaction system. The filter cake obtained from the dissolution and filtration process contains sodium hydrofluoride and sodium fluoride, which is also recycled back into the potassium hydrofluoride and sodium fluoride reaction system. This invention is a green, environmentally friendly, and recyclable process that not only solves the problems of fluorine resource waste and environmental pollution but also reduces production costs and improves process economics. It aligns with the current development trend of greening, recycling, and refinement in the fluorochemical industry and has significant practical significance and application value for promoting the high-quality development of the fluorochemical industry. Summary of the Invention

[0005] To address the problem of low fluorine resource utilization in existing hydrogen fluoride preparation processes, this invention provides a method for preparing hydrogen fluoride using ammonium fluoride. By combining a stepwise reaction with a recycling system, the method achieves efficient preparation of hydrogen fluoride while reducing raw material consumption and environmental pollution, thus improving the economic efficiency and environmental friendliness of the process.

[0006] The process for preparing hydrogen fluoride using ammonium fluoride in this invention is as follows: 1. Preparation of potassium hydrofluoric acid: Ammonium fluoride and potassium fluoride are dissolved in water to prepare a mixed solution. The mixed solution is reacted at 100℃~200℃ for 1h~4h, then cooled to room temperature, the solid and liquid are separated, and the solid is dried to obtain potassium hydrofluoric acid solid. The molar ratio of ammonium fluoride to potassium fluoride is 1.5:1 to 1:1.5, and the mass concentration of ammonium fluoride and potassium fluoride in the mixed solution is 40% to 80%; drying is carried out at 100℃ to 150℃. 2. Preparation of hydrogen fluoride: Potassium hydrofluoride and sodium fluoride are mixed and hydrogen fluoride gas is prepared under molten conditions. After the reaction is completed, the mixture is cooled to room temperature. The residual solid is dissolved in water by stirring, filtered, and the filter cake is dried to obtain a mixed solid of sodium fluoride and sodium hydrofluoride. The filtrate is a mixed liquid of potassium hydrofluoride and potassium fluoride. The molar ratio of potassium hydrofluoric acid to sodium fluoride is 1.5:1 to 1:1.5, the melting reaction temperature is 180℃ to 300℃, and the reaction time is 1h to 4h; the residual solid is dissolved in water with a liquid-to-solid ratio of mL:g of 0.8 to 3.6, a stirring speed of 100rpm to 500rpm, and a stirring time of 0.5 to 1h. 3. Recycling process: After solid-liquid separation in step 1, the liquid is returned to the initial ammonium fluoride and potassium fluoride reaction system for recycling; in step 2, the filtrate is returned to the ammonium fluoride and potassium fluoride reaction system for recycling, and the filter cake is returned to the potassium hydrofluoride and sodium fluoride reaction system for recycling.

[0007] The beneficial effects of adopting the above technical solution are as follows: 1) The overall construction of a closed-loop process system for both liquid and solid phases improves raw material utilization, reduces material waste, and lowers production raw material costs; 2) No additional sodium hydrofluoric acid heating and decomposition process is required, reducing energy consumption; 3) Hydrogen fluoride gas is prepared in one step by reacting potassium fluoride with sodium fluoride in a molten reaction. Compared with the traditional segmented process of first crystallizing and purifying and then separately pyrolyzing at high temperature, this process has a shorter flow rate. Attached Figure Description

[0008] Figure 1 This is a process flow diagram of the method described in the embodiments of the present invention. Detailed Implementation

[0009] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the content described. Unless otherwise specified, the reagents and methods used in the embodiments are all conventional reagents and conventional methods.

[0010] Example 1: The process for preparing hydrogen fluoride using ammonium fluoride is as follows: 1. For example Figure 1 As shown, ammonium fluoride and potassium fluoride were added to the mixing reactor in a 1:1 molar ratio, along with deionized water. The mixture was stirred and dissolved to obtain a mixed solution with a mass concentration of 65% for ammonium fluoride and potassium fluoride. The mixed solution was reacted at 125°C for 2 hours. The reaction solution was then cooled to room temperature and subjected to solid-liquid separation by vacuum filtration (pressure -0.08 MPa) to obtain a filtrate (a mixed solution of ammonium fluoride, potassium fluoride, and potassium hydrofluoride) and a filter cake (crude potassium hydrofluoride solid). The filter cake was placed in a drying device and dried at a constant temperature of 150°C for 2 hours to obtain potassium hydrofluoride solid with a purity of 70 wt%. The filtrate is returned to the batching reactor through the first circulation pipeline, and ammonium fluoride and potassium fluoride are replenished. The reaction continues under the above conditions. After three cycles, the obtained potassium hydrofluoride has a purity of 69.5 wt%. 2. Add potassium hydrofluoric acid and sodium fluoride to the reactor in a 1:1 ratio for melting reaction. Adjust the reactor temperature to 210℃ and react for 3 hours. Cool the solid after melting reaction to room temperature. Add deionized water at a liquid-to-solid ratio of 2.4 mL:g and stir (200 rpm, 1 h) to dissolve. Filter using vacuum filtration (pressure -0.08 MPa) to obtain filtrate and filter cake. Return the filtrate to the ammonium fluoride and potassium fluoride batching reactor in step 1 through the second circulation pipeline. After replenishing the raw materials, continue the reaction. The filter cake was placed in a drying device and dried at a constant temperature of 120℃ for 2 hours to obtain a mixed solid. The mixed solid was returned to the melting reactor through a third circulation pipeline. After replenishing potassium hydrofluoric acid and sodium fluoride raw materials, the reaction was carried out. After three cycles, the purity of potassium hydrofluoric acid was 71.2 wt%; the filter cake yield was stable at 41.13%, and the Na content in the filter cake was 45.7 wt%. In this embodiment, the average yield of hydrogen fluoride was 30%, and the average purity of potassium fluoride was 70.2 wt%.

[0011] Example 2: The process for preparing hydrogen fluoride using ammonium fluoride is as follows: 1. Ammonium fluoride and potassium fluoride were added to a batching reactor at a molar ratio of 1:1.5, along with deionized water. The mixture was stirred and dissolved to obtain a mixed solution with a mass concentration of 65% for ammonium fluoride and potassium fluoride. The mixed solution was reacted at 135°C for 1.5 hours. The reaction solution was then cooled to room temperature and subjected to solid-liquid separation by vacuum filtration (pressure -0.08 MPa) to obtain a filtrate (a mixed solution of ammonium fluoride, potassium fluoride, and potassium hydrofluoride) and a filter cake (crude potassium hydrofluoride solid). The filter cake was placed in a drying device and dried at a constant temperature of 150°C for 2 hours to obtain potassium hydrofluoride solid with a purity of 90.26 wt%. The filtrate is returned to the batching reactor through the first circulation pipeline, and ammonium fluoride and potassium fluoride are replenished. The reaction continues under the above conditions. After three cycles, the obtained potassium hydrofluoride has a purity of 90.8 wt%. 2. Add potassium hydrofluoric acid and sodium fluoride to the reactor in a 1:1 ratio for melting reaction. Adjust the reactor temperature to 210℃ and react for 3 hours. Cool the solid after melting reaction to room temperature. Add deionized water at a liquid-to-solid ratio of 0.8 mL:g and stir (300 rpm, 0.5 h) to dissolve. Filter using vacuum filtration (pressure -0.08 MPa) to obtain filtrate and filter cake. Return the filtrate to the ammonium fluoride and potassium fluoride batching reactor in step 1 through the second circulation pipeline. After replenishing the raw materials, continue the reaction. The filter cake was placed in a drying device and dried at a constant temperature of 120℃ for 2 hours to obtain a mixed solid. The mixed solid was returned to the melting reactor through a third circulation pipeline. After replenishing potassium hydrofluoric acid and sodium fluoride raw materials, the reaction was carried out. After three cycles, the purity of potassium hydrofluoric acid was 91 wt%. The filter cake yield was stable at 65.37%, and the Na content in the filter cake was 46.56 wt%. In this embodiment, the average yield of hydrogen fluoride was 28.2%, and the average yield of potassium fluoride was 90.69 wt%.

[0012] Example 3: The process for preparing hydrogen fluoride using ammonium fluoride is as follows: 1. Ammonium fluoride and potassium fluoride were added to a batching reactor at a molar ratio of 1.25:1, along with deionized water. The mixture was stirred and dissolved to obtain a mixed solution with a mass concentration of 65% for ammonium fluoride and potassium fluoride. The mixed solution was reacted at 135°C for 1.5 hours. The reaction solution was then cooled to room temperature and subjected to solid-liquid separation by vacuum filtration (pressure -0.08 MPa) to obtain a filtrate (a mixed solution of ammonium fluoride, potassium fluoride, and potassium hydrofluoride) and a filter cake (crude potassium hydrofluoride solid). The filter cake was placed in a drying device and dried at a constant temperature of 150°C for 2 hours to obtain potassium hydrofluoride solid with a purity of 94.5 wt%. The filtrate is returned to the batching reactor through the first circulation pipeline, and ammonium fluoride and potassium fluoride are replenished. The reaction continues under the above conditions. After three cycles, the obtained potassium hydrofluoride has a purity of 95.6 wt%. 2. Add potassium hydrofluoric acid and sodium fluoride to the reactor in a 1:1 ratio for melting reaction. Adjust the reactor temperature to 210℃ and react for 3 hours. Cool the solid after melting reaction to room temperature. Add deionized water at a liquid-to-solid ratio of 3.6 mL:g and stir (400 rpm, 0.5 h) to dissolve. Filter using vacuum filtration (pressure -0.08 MPa) to obtain filtrate and filter cake. Return the filtrate to the ammonium fluoride and potassium fluoride mixing reactor in step 1 through the second circulation pipeline. After replenishing the raw materials, continue the reaction. The filter cake was placed in a drying device and dried at a constant temperature of 120℃ for 2 hours to obtain a mixed solid. The mixed solid was returned to the melting reactor through a third circulation pipeline. After replenishing potassium hydrofluoric acid and sodium fluoride raw materials, the reaction was carried out. After three cycles, the purity of potassium hydrofluoric acid was 96.2 wt%. The filter cake yield was stable at 57.13%, and the Na content in the filter cake was 43.87 wt%. In this embodiment, the average yield of hydrogen fluoride was 29.1%, and the average yield of potassium fluoride was 95.4 wt%.

[0013] In summary, this invention can efficiently and recyclably produce hydrogen fluoride, realizing the recycling and utilization of fluorine resources.

Claims

1. A method for preparing hydrogen fluoride using ammonium fluoride, characterized in that, Includes the following steps: (1) Dissolve ammonium fluoride and potassium fluoride in water to prepare a mixed solution. After reacting the mixed solution at 100℃~200℃ for 1h~4h, cool to room temperature, separate the solid and liquid, dry the solid to obtain potassium hydrofluoride solid; return the liquid from the solid-liquid separation to the initial ammonium fluoride and potassium fluoride reaction system for recycling. (2) Potassium hydrofluoride and sodium fluoride are mixed and hydrogen fluoride gas is prepared under molten conditions. After the reaction is completed, the mixture is cooled to room temperature. The remaining solid is dissolved in water by stirring, filtered, and the filter cake is dried to obtain a mixed solid of sodium fluoride and sodium hydrofluoride. The filtrate is a mixed liquid of potassium hydrofluoride and potassium fluoride. The filtrate is returned to the reaction system of ammonium fluoride and potassium fluoride in step (1) for recycling, and the filter cake is returned to the reaction system of potassium hydrofluoride and sodium fluoride for recycling.

2. The method for preparing hydrogen fluoride using ammonium fluoride according to claim 1, characterized in that: The molar ratio of ammonium fluoride to potassium fluoride is 1.5:1 to 1:1.5, and the mass concentration of ammonium fluoride and potassium fluoride in the mixed solution is 40% to 80%.

3. The method for preparing hydrogen fluoride using ammonium fluoride according to claim 1, characterized in that: In step (1), the drying is carried out at 100℃~150℃.

4. The method for preparing hydrogen fluoride using ammonium fluoride according to claim 1, characterized in that: The molar ratio of potassium hydrofluoride to sodium fluoride is 1.5:1 to 1:1.5, the melting reaction temperature is 180℃ to 300℃, and the reaction time is 1h to 4h.

5. The method for preparing hydrogen fluoride using ammonium fluoride according to claim 1, characterized in that: In step (2), the residual solid is dissolved in water with a liquid-to-solid ratio of 0.8 to 3.6 mL:g, a stirring speed of 100 rpm to 500 rpm, and a stirring time of 0.5 to 1 h.

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