A method for preparing phosphorus pentafluoride from calcium fluoride sludge solid phase

Abstract

The present invention discloses a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase, belonging to the fields of inorganic, chemical, and environmental technologies. The method comprises: subjecting dried CaF2 sludge and P2O5 to alternating high- and low-speed ball milling and oscillation at a certain mass ratio under dry conditions; then subjecting the high-speed, low-speed, and high-speed / low-speed alternating mixture of CaF2 sludge and P2O5 to a solid-phase reaction at a predetermined reaction temperature and vacuum drying conditions, while simultaneously applying oscillations including high-frequency, low-frequency, and alternating high- and low-frequency oscillations; the predetermined reaction temperature may include programmed temperature rise or rapid temperature rise; the CaF2 sludge and P2O5 mixture undergo a solid-phase reaction to generate PF5 gas; the resulting PF5 reaction product is withdrawn from a closed reactor, compressed, condensed, and distilled to obtain a PF5 product. The method utilizes inexpensive calcium fluoride sludge solid waste to produce a high-value-added phosphorus pentafluoride product, achieving both environmental and economic benefits.

Description

Technical Field

[0001] The invention discloses a method for recycling calcium fluoride sludge resources, belonging to the technical fields of inorganic, chemical and environmental technology. Background Art

[0002] Phosphorus pentafluoride is an important inorganic fluoride widely used in industry. It can effectively improve semiconductor performance, is a raw material for synthesizing organic polymers such as phthalates, and can also act as a catalyst to improve metal selectivity.

[0003] With the development of the times, the demand for lithium batteries continues to increase. Using phosphorus pentafluoride as a raw material, excellent lithium hexafluorophosphate electrolytes can be prepared, significantly improving the performance of lithium batteries. However, research on the preparation of phosphorus pentafluoride in China is very limited, and overseas research on phosphorus pentafluoride began in the 1950s.

[0004] Current research on phosphorus pentafluoride preparation, both domestically and internationally, can be broadly categorized into indirect and direct methods. The indirect method involves reactants first generating intermediates, which are then processed to produce phosphorus pentafluoride. The intermediates primarily consist of phosphorus trioxide and hexafluorophosphoric acid. The direct method involves reactants generating phosphorus pentafluoride in a single step.

[0005] The indirect method for preparing phosphorus pentafluoride is complicated and easily produces more impurities.

[0006] The direct method has the disadvantages of violent reaction of reactants, difficult to control the reaction process, expensive raw materials, safety and economic benefits of the preparation process, making it difficult to apply to industrial production.

[0007] Patent publication number CN101417791 discloses a method for preparing crude phosphorus pentafluoride by reacting elemental phosphorus with fluorine gas. The crude product is then condensed and distilled to produce a high-purity phosphorus pentafluoride product. However, the reaction between fluorine gas and elemental phosphorus is very violent, releasing a large amount of heat and making the reaction difficult to control.

[0008] Patent document publication number CN101353161A discloses a method in which a phosphorus pentachloride solution obtained by mixing under low temperature conditions is introduced into anhydrous hydrogen fluoride gas under an inert gas atmosphere to react with the phosphorus pentachloride solution to produce phosphorus pentafluoride. This method also has a violent reaction and the resulting product contains a large amount of impurities and is low in purity. In addition, phosphorus pentachloride is a solid at room temperature and difficult to handle. Phosphorus trichloride is a liquid at room temperature and is easier to handle than phosphorus pentafluoride.

[0009] Patent publication number CN110072807A discloses a method for producing phosphorus pentafluoride gas by reacting phosphorus trichloride, chlorine, and excess anhydrous hydrogen fluoride. The heat of reaction generated by the formation of phosphorus pentafluoride is removed by utilizing the latent heat of vaporization of hydrogen fluoride. While this method is low-cost and relatively safe, the reaction apparatus is relatively complex.

[0010] In summary, most existing phosphorus pentafluoride preparation methods have the characteristics of high cost, complicated steps, low safety, etc. Therefore, seeking a simple, safe and feasible preparation method for phosphorus pentafluoride is an urgent problem to be solved in the field.

[0011] Patent publication number CN103253641A discloses a method for producing high-purity phosphorus pentafluoride gas using a solid-phase process. Phosphorus pentoxide and calcium fluoride are mixed in a solid phase and heated in the presence of an excess of phosphorus pentoxide to produce phosphorus pentafluoride gas. This method does not involve a solution, eliminating moisture interference throughout the reaction process, which is beneficial for the production process and the final product. The reaction is simple and easily commercializable.

[0012] Calcium fluoride is the primary component of fluorspar, a non-renewable resource. Besides fluorspar, calcium fluoride is also generated by fluorine-containing waste gas, wastewater, and sludge from fluorine-containing industries such as metallurgy, fluorine-organic chemicals, photovoltaics, display screens, and the integrated circuit industry. Table 1 below shows the calcium fluoride sludge generated by various industries.

[0013] Table 1 Main components and contents of fluorine-containing sludge on dry basis from four enterprises (wt%)

[0014]

[0015] Note: LOI in Table 1 is loss on ignition, i.e. the loss of organic matter including organic flocculant PAM.

[0016] [Al2(OH) n Cl 6-n ] m It is a polyaluminium chloride flocculant.

[0017] China's integrated circuit (IC) industry has grown rapidly in recent years. Calcium fluoride sludge generated by this industry, primarily focused on chip manufacturing, has become a new source of fluoride pollution in my country over the past decade. The IC industry uses large amounts of hydrofluoric acid to etch single-crystalline silicon wafers, which discharges fluoride-containing wastewater. This wastewater treatment process, known as chemical coagulation and sedimentation, is currently the mainstream treatment method for fluoride-containing wastewater. This process first adjusts the wastewater's pH, then adds CaCl2 or CaO to a sedimentation tank to form a CaF2 precipitate. Polyacrylamide (PAM) or polyaluminum chloride (PAC) is then added for precipitation and flocculation. The resulting sludge is primarily composed of CaF2 and SiO2, hence its common name, calcium fluoride sludge.

[0018] Currently, the main method of disposing of calcium fluoride sludge is landfill. This method is simple and convenient, but it also occupies land and causes waste of resources. Moreover, if it is not handled properly, the fluoride ions contained in it will contaminate the surrounding soil, and then contaminate groundwater and human drinking water, affecting human health. Although calcium fluoride has extremely low solubility in water, only 0.0016g is dissolved in 100g of water at 18°C, or 16mg / L, which is 7.9mg / L based on fluoride ions. However, this value far exceeds the limit of 1.0mg / L of fluoride in drinking water specified in the "Sanitary Standard for Drinking Water" (GB5749-2006). Therefore, how to recycle calcium fluoride sludge as a resource has become a focus of current attention.

[0019] Currently, the resource utilization of calcium fluoride sludge primarily involves purification technologies such as flotation enrichment, atmospheric distillation, acid washing, and purification of fluoride-containing wastewater. Calcium fluoride sludge, as a fluorspar substitute, is being reused in industries such as fine aggregate in the concrete industry, brick making in the construction industry, and adsorption materials.

[0020] These calcium fluoride sludge recycling technologies have the disadvantages of low added value, high cost, and difficulty in industrial promotion. How to efficiently reuse calcium fluoride sludge is currently an urgent problem to be solved. Summary of the Invention

[0021] In order to solve the problems of the prior art, the purpose of the present invention is to overcome the shortcomings of the existing technology and provide a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase, thereby reducing the preparation cost of phosphorus pentafluoride and achieving efficient reuse of calcium fluoride sludge. The method of the present invention solves the problem of efficient utilization of calcium fluoride sludge and avoids environmental pollution caused by calcium fluoride sludge; the use of solid waste to prepare phosphorus pentafluoride reduces its preparation cost and provides a new approach for the production of lithium batteries.

[0022] In order to achieve the above invention purpose, the present invention adopts the following technical solutions:

[0023] A method for preparing phosphorus pentafluoride from calcium fluoride sludge solid phase, comprising the following preparation steps:

[0024] (1) The CaF2 sludge is subjected to drying pretreatment to remove moisture. Under dry conditions, the dried CaF2 sludge is mixed with P2O5 and subjected to ball milling and shaking at room temperature;

[0025] or under dry conditions, the dried CaF2 sludge is mixed with P2O5 and ball-milled while being heated;

[0026] A mixture of CaF2 sludge and P2O5 is obtained;

[0027] (2) performing a solid phase reaction on the mixture of CaF2 sludge and P2O5 obtained by ball milling while shaking at a predetermined reaction temperature of not less than 200° C. and under vacuum drying conditions;

[0028] (3) The CaF2 sludge and P2O5 mixture react in a solid phase to generate PF5 gas. The resulting PF5 reaction product is discharged from a closed reactor, compressed, condensed, and distilled to obtain a PF5 product.

[0029] Preferably, the ball milling is performed at any one of high speed, low speed, and high speed / low speed alternation; and the oscillation is performed at any one of high frequency, low frequency, and high frequency and low frequency alternation.

[0030] Preferably, in step (1), the calcium fluoride sludge is calcium fluoride sludge produced by the microelectronics industry, photovoltaic industry and fluorine chemical industry, or calcium fluoride sludge produced by fluorine-containing wastewater through CaO, CaCl2 or Ca(OH)2 precipitation.

[0031] Preferably, in step (1), the ball milling mixing time of P2O5 and CaF2 sludge is 10 minutes to 5 hours, and the mass ratio of P2O5 to CaF2 is 0.5:1-5:1.

[0032] Preferably, in step (1), the dried CaF2 sludge and P2O5 are ball-milled and heated according to a certain mass ratio, and the heating temperature is lower than the temperature at which the CaF2 sludge and P2O5 undergo solid-phase reaction or the temperature at which the CaF2 sludge and P2O5 undergo solid-phase reaction.

[0033] Preferably, the ball milling speed is 100-2000 rpm, and the oscillation frequency is 50-200 rpm.

[0034] Preferably, in step (2), the predetermined reaction temperature is programmed or rapidly heated.

[0035] Preferably, in step (2), the solid phase reaction time of P2O5 and CaF2 sludge is 1 to 8 hours, and the predetermined reaction temperature is 200-500°C.

[0036] Preferably, in step (2), the gas pressure in the reactor is pumped to 0-0.5 MPa before the reaction, and is controlled below 0.1-1.5 MPa during the reaction.

[0037] Preferably, in step (3), when condensing, the cooling medium for condensation is industrial alcohol, and the industrial alcohol is frozen with liquid nitrogen.

[0038] Compared with the prior art, the present invention has the following obvious outstanding substantial features and significant advantages:

[0039] 1. The method of the present invention produces phosphorus pentafluoride gas by solid-phase reaction of calcium fluoride sludge with phosphorus pentoxide. This method utilizes inexpensive calcium fluoride sludge solid waste to produce a high-value-added phosphorus pentafluoride product, achieving both environmental and economic benefits.

[0040] 2. The method of the present invention solves the problem of efficient utilization of calcium fluoride sludge and avoids environmental pollution caused by calcium fluoride sludge; the preparation of phosphorus pentafluoride using solid waste reduces its preparation cost and provides a new approach for the production of lithium batteries. DETAILED DESCRIPTION

[0041] The above solution is further described below with reference to specific implementation examples. The preferred embodiments of the present invention are described in detail as follows:

[0042] Example 1

[0043] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0044] First, the calcium fluoride sludge is dried in a drying oven at 105°C for 24 hours. The dried calcium fluoride sludge is then placed in a closed ball mill reactor equipped with ceramic balls. At room temperature and under a blanket of dry nitrogen, phosphorus pentoxide is added to the mixture at a mass ratio of 2:1, followed by ball milling and oscillation. The milling process lasts for 1 hour, using a speed of 800-1000 rpm for 10 minutes, followed by 300-500 rpm for 20 minutes, alternating between high and low speeds. The oscillation frequency is 50 rpm for 10 minutes, followed by 100 rpm for 20 minutes, alternating between high and low speeds. Ball milling increases the contact surface area between the calcium fluoride sludge and phosphorus pentoxide, ensuring more thorough mixing. Alternating high and low speeds provides a buffer, facilitating better mill operation. Oscillation is used during ball milling because ball milling can cause agglomeration in the reactants. Oscillation redisperses and re-mixes these agglomerated materials, promoting a more complete reaction.

[0045] After ball milling, the reactor is evacuated to a pressure of 0.1 MPa, and the evacuation valve is closed. After leak testing, the reactor is heated and programmed at a rate of 5°C / min. The final temperature is controlled between 280°C and 300°C, and the gas pressure is controlled below 0.15 MPa. The solid-phase reaction is carried out while ball milling and oscillating. This programmed temperature ensures more uniform heating of the mixture.

[0046] The reaction time is 3 hours. The ball milling frequency is: 800-1000 rpm for 10 minutes, 300-500 rpm for 20 minutes, and so on, alternating high-speed / low-speed ball milling. The oscillation frequency is: 50 rpm for 10 minutes, 100 rpm for 20 minutes, and so on, alternating high-speed / low-speed oscillation. The use of alternating ball milling and oscillation ensures more uniform mixing of the reaction materials, a more thorough reaction, and also acts as a buffer for the equipment. The combination of high-frequency ball milling / low-frequency oscillation and low-frequency ball milling / high-frequency oscillation optimizes the solid-phase reaction state and the buffering effect of the equipment. The resulting phosphorus pentafluoride reaction product is discharged from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product with high yield and purity.

[0047] Example 2

[0048] This embodiment is basically the same as the first embodiment, except that:

[0049] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0050] First, the calcium fluoride sludge is dried in a drying oven at 105°C for 24 hours. The dried calcium fluoride sludge is then placed in a closed ball mill reactor equipped with ceramic balls. Phosphorus pentoxide is added at a mass ratio of 2:1 to calcium fluoride sludge. Under a blanket of dry nitrogen, the mixture is ball milled and shaken at 120°C. Heating the materials during mixing maintains a dry mixing environment and prevents deliquescence of the phosphorus pentoxide. Preheating before the solid-phase reaction also promotes more uniform mixing, removes volatile impurities, and preheats the solid-phase reaction. The milling process lasts for 1 hour, using a rotational speed of 800-1000 rpm for 10 minutes, followed by a rotational speed of 300-500 rpm for 20 minutes, and then a high- and low-speed alternation. The shaking frequency is 100 rpm.

[0051] After ball milling, the reactor was evacuated to a pressure of 0.1 MPa, and the evacuation valve was closed. After leak testing, the reactor was further heated and programmed to 280-300°C at a rate of 5°C / min. The gas pressure was controlled below 0.15 MPa, and the solid-phase reaction was carried out while ball milling and shaking.

[0052] The reaction time is 3 hours. The ball milling frequency is: 800-1000 rpm for 10 minutes, 300-500 rpm for 20 minutes, and alternating high and low speeds. The oscillation frequency is 100 rpm. The resulting phosphorus pentafluoride reaction product is removed from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product.

[0053] Example 3

[0054] This embodiment is basically the same as the above embodiment, with the following special features:

[0055] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0056] First, the calcium fluoride sludge is placed in a drying oven and dried at 105°C for 24 hours. Then, the dried calcium fluoride sludge is placed in a closed ball mill reactor equipped with ceramic balls. Phosphorus pentoxide is added at a mass ratio of 2:1 between phosphorus pentoxide and calcium fluoride sludge. Under the protection of dry nitrogen, the reactor is evacuated to a pressure of 0.1MPa, and the evacuation valve is closed. After the leak test is passed, the reactor is heated and programmed to rise at a rate of 5°C / min. The temperature is controlled between 280°C and 300°C, and the gas pressure is controlled below 0.15MPa. A solid-phase reaction is carried out while ball milling and shaking. After the two materials are mixed, the temperature is directly raised to the solid-phase reaction temperature, which simplifies the temperature control process, but the reaction time needs to be increased to ensure that the two materials are fully mixed, heated evenly, and the reaction is complete.

[0057] The reaction time is 4 hours. The ball milling frequency is: 800-1000 rpm for 10 minutes, 300-500 rpm for 20 minutes, and alternating high and low speeds. The oscillation frequency is 100 rpm. The resulting phosphorus pentafluoride reaction product is removed from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product.

[0058] Example 4

[0059] This embodiment is basically the same as the above embodiment, with the following special features:

[0060] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0061] First, the calcium fluoride sludge is dried in a drying oven at 105°C for 24 hours. The dried calcium fluoride sludge is then placed in a closed ball mill reactor equipped with ceramic balls. At room temperature and under a dry nitrogen atmosphere, phosphorus pentoxide is added and mixed with calcium fluoride sludge at a mass ratio of 2:1. The milling process lasts for 2 hours at a speed of 300-500 rpm. Low milling speeds may result in incomplete mixing of the two materials, which can be adjusted by increasing the milling time.

[0062] After ball milling, the reactor is evacuated to a pressure of 0.1 MPa, and the evacuation valve is closed. After leak testing, the reactor is heated rapidly to 280°C-300°C. The gas pressure is controlled below 0.15 MPa, and the solid-phase reaction is carried out while ball milling and shaking. Rapid heating can shorten the time required to achieve the desired solid-phase reaction, but it may result in uneven heating of the mixture, affecting the reaction quality.

[0063] The reaction time is 3 hours. The ball milling frequency is 300-500 rpm, and the oscillation frequency is 50 rpm for 20 minutes and 200 rpm for 10 minutes. The resulting phosphorus pentafluoride reaction product is removed from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product.

[0064] Example 5

[0065] This embodiment is basically the same as the above embodiment, with the following special features:

[0066] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0067] First, the calcium fluoride sludge is dried in a drying oven at 105°C for 24 hours. The dried calcium fluoride sludge is then placed in a closed ball mill reactor equipped with ceramic balls. At room temperature and under a blanket of dry nitrogen, phosphorus pentoxide is added and mixed with calcium fluoride sludge at a mass ratio of 2:1. The milling process lasts for one hour at a speed of 1000-1500 rpm. Continuous high-speed operation of the ball mill increases equipment wear.

[0068] After ball milling, the reactor is evacuated to a pressure of 0.1 MPa, and the evacuation valve is closed. After leak testing is passed, the reactor is heated and rapidly raised to the solid-phase reaction temperature of 280°C-300°C. The gas pressure is controlled below 0.15 MPa, and the solid-phase reaction is carried out while ball milling and shaking.

[0069] The reaction time is 3 hours. The ball milling frequency is 1000-1500 rpm, and the oscillation frequency is 100 rpm. The phosphorus pentafluoride reaction product obtained is discharged from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product.

[0070] Example 6

[0071] This embodiment is basically the same as the above embodiment, with the following special features:

[0072] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0073] First, the calcium fluoride sludge is dried in a drying oven at 105°C for 24 hours. The dried calcium fluoride sludge is then placed in a closed ball mill reactor equipped with ceramic balls. At room temperature and under a blanket of dry nitrogen, phosphorus pentoxide is added and ball milled at a mass ratio of 2:1. The milling process lasts for 1 hour, using a mixture of high and low speeds, followed by 800-1000 rpm for 10 minutes and 300-500 rpm for 20 minutes.

[0074] After ball milling, evacuate the reactor to a pressure of 0.1 MPa and close the evacuation valve. After leak testing, heat the reactor to a temperature of 280°C-300°C and a gas pressure below 0.15 MPa, then ball mill for solid-phase reaction. Without vibration, simple ball milling can cause material agglomeration, hindering the full progress of the reaction.

[0075] The reaction time is 3 hours. The ball milling frequency is: 800-1000 rpm for 10 minutes, 300-500 rpm for 20 minutes, and alternating high and low speed ball milling. The resulting phosphorus pentafluoride reaction product is removed from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product.

[0076] Example 7

[0077] This embodiment is basically the same as the above embodiment, with the following special features:

[0078] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0079] First, the calcium fluoride sludge is dried in a drying oven at 105°C for 24 hours. The dried calcium fluoride sludge is then placed in a closed ball mill reactor equipped with ceramic balls. Phosphorus pentoxide is added at a mass ratio of 2:1 between phosphorus pentoxide and calcium fluoride sludge. Under a blanket of dry nitrogen, the reactor is evacuated to a pressure of 0.1 MPa, and the evacuation valve is closed. After leak testing is completed, the reactor is heated to a temperature of 220°C-280°C and a gas pressure below 0.15 MPa. A solid-phase reaction is carried out while ball milling and shaking. The solid-phase reaction temperature directly affects the reaction. Low temperatures will result in an incomplete reaction, with only a portion of the mixture reacting to produce a small amount of phosphorus pentafluoride.

[0080] The reaction time is 3 hours. The ball milling frequency is: 800-1000 rpm for 10 minutes, 300-500 rpm for 20 minutes, and alternating high and low speeds. The oscillation frequency is 100 rpm. The resulting phosphorus pentafluoride reaction product is removed from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product.

[0081] Example 8

[0082] This embodiment is basically the same as the above embodiment, with the following special features:

[0083] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0084] First, the calcium fluoride sludge is dried in a drying oven at 105°C for 24 hours. The dried calcium fluoride sludge is then placed in a closed ball mill reactor equipped with ceramic balls. Phosphorus pentoxide is added at a mass ratio of 2:1 to calcium fluoride sludge. The mixture is ball milled at 150°C under a dry nitrogen atmosphere for one hour at a speed of 1500-2000 rpm.

[0085] After ball milling, the reactor is evacuated to a pressure of 0.1 MPa, and the evacuation valve is closed. After leak testing, the reactor is further heated to 280-400°C at a rate of 2°C / min. The gas pressure is controlled below 0.15 MPa, and the solid-phase reaction is carried out while ball milling and shaking. If the temperature is controlled too high, many side reactions will occur, significantly reducing the yield of phosphorus pentafluoride.

[0086] The reaction time is 2 hours. The ball milling frequency is 1500-2000 rpm, and the oscillation frequency is 100 rpm. The resulting phosphorus pentafluoride reaction product is removed from the closed reactor, compressed, condensed, and distilled to obtain the phosphorus pentafluoride product.

[0087] Example 9

[0088] This embodiment is basically the same as the above embodiment, with the following special features:

[0089] In this embodiment, a method for preparing phosphorus pentafluoride from calcium fluoride sludge in a solid phase comprises the following steps:

[0090] In the above embodiments, the ball milling frequency of calcium fluoride sludge, the ball milling frequency of mixing with phosphorus pentafluoride, reaction time, reaction temperature, reaction pressure, reaction oscillation frequency and other indicators can be adjusted and combined according to the indicator range of the technical solution, and are not limited to the above embodiments.

[0091] In summary, the present invention relates to a method for recycling calcium fluoride sludge resources. Dry CaF2 sludge and P2O5 are subjected to alternating high- and low-speed ball milling at a specific mass ratio under dry conditions. The high-speed, low-speed, and high-speed / low-speed alternating mixture of CaF2 sludge and P2O5 is then subjected to a solid-phase reaction at a predetermined reaction temperature and vacuum drying conditions, while simultaneously applying oscillations including high-frequency, low-frequency, and alternating high- and low-frequency oscillations. The predetermined reaction temperature may include programmed temperature rise or rapid temperature rise. The CaF2 sludge and P2O5 mixture undergo a solid-phase reaction to generate PF5 gas. The resulting PF5 reaction product is discharged from a closed reactor, compressed, condensed, and distilled to produce a PF5 product. The present method utilizes a solid-phase reaction between calcium fluoride sludge and phosphorus pentoxide to produce phosphorus pentafluoride gas. The goal is to utilize inexpensive calcium fluoride sludge solid waste to produce a high-value-added phosphorus pentafluoride product, achieving both environmental and economic benefits.

[0092] The above describes the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made according to the spirit and principles of the technical solution of the present invention should be equivalent replacement methods. As long as they comply with the purpose of the invention and do not deviate from the technical principles and inventive concepts of the present invention, they belong to the scope of protection of the present invention.

Claims

1. A method for preparing phosphorus pentafluoride from calcium fluoride sludge solid phase, characterized in that: The method comprises the following preparation steps: (1) The CaF2 sludge is dried and pretreated to remove moisture. Under dry conditions, the dried CaF2 sludge is mixed with P2O5 and ball milled while shaking at room temperature; the ball milling time is 1 hour, the conditions are: ball milling at 800-1000 rpm for 10 minutes, ball milling at 300-500 rpm for 20 minutes, and high / low speed alternating ball milling; the shaking frequency is: 50 rpm for 10 minutes, 100 rpm for 20 minutes, and high / low speed alternating shaking; or under dry conditions, the dried CaF2 sludge is mixed with P2O5 and ball-milled while being heated; A mixture of CaF2 sludge and P2O5 is obtained; the ball milling mixing time of P2O5 and CaF2 sludge is 10 minutes to 5 hours, and the mass ratio is 0.5:1-5:1; the ball milling speed is 100-2000 rpm, and the oscillation frequency is 50-200 rpm; (2) at a predetermined reaction temperature of 200-500° C. and vacuum drying conditions, the mixture of CaF2 sludge and P2O5 obtained by ball milling is subjected to solid phase reaction by ball milling and shaking; the ball milling frequency is: 800-1000 rpm for 10 minutes, 300-500 rpm for 20 minutes, and high / low speed alternating ball milling; the shaking frequency is: 50 rpm for 10 minutes, 100 rpm for 20 minutes, and high / low speed alternating shaking; (3) The CaF2 sludge and P2O5 mixture react in a solid phase to generate PF5 gas. The resulting PF5 reaction product is discharged from the closed reactor and subjected to compression, condensation, and distillation to obtain the PF5 product.

2. The method for preparing phosphorus pentafluoride from calcium fluoride sludge in solid phase according to claim 1, characterized in that: In step (1), the calcium fluoride sludge is calcium fluoride sludge produced by the microelectronics industry, photovoltaic industry and fluorine chemical industry, or calcium fluoride sludge produced by fluorine-containing wastewater through CaO, CaCl2 or Ca(OH)2 precipitation.

3. The method for preparing phosphorus pentafluoride from calcium fluoride sludge in solid phase according to claim 1, characterized in that: In the step (1), the dried CaF2 sludge and P2O5 are heated and ball-milled according to a certain mass ratio, and the heating temperature is lower than the temperature at which the CaF2 sludge and P2O5 undergo solid-phase reaction.

4. The method for preparing phosphorus pentafluoride from calcium fluoride sludge in solid phase according to claim 1, characterized in that: In the step (2), the predetermined reaction temperature is programmed or rapidly heated.

5. The method for preparing phosphorus pentafluoride from calcium fluoride sludge in solid phase according to claim 1, characterized in that: In the step (2), the solid phase reaction time of P2O5 and CaF2 sludge is 1 to 8 hours.

6. The method for preparing phosphorus pentafluoride from calcium fluoride sludge in solid phase according to claim 1, characterized in that: In the step (2), the gas pressure in the reactor is pumped to 0-0.5 MPa before the reaction and is controlled below 0.1-1.5 MPa during the reaction.

7. The method for preparing phosphorus pentafluoride from calcium fluoride sludge in solid phase according to claim 1, characterized in that: In the step (4), when condensation is performed, the cooling medium for condensation is industrial alcohol, and the industrial alcohol is frozen with liquid nitrogen.

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