A highly efficient continuous production process of sodium hexafluorophosphate

Abstract

The application relates to a high-efficiency continuous production process of sodium hexafluorophosphate and relates to the technical field of sodium hexafluorophosphate synthesis. Phosphorus pentachloride is reacted with anhydrous hydrogen fluoride to generate phosphorus pentafluoride, the phosphorus pentafluoride is introduced into an anhydrous hydrogen fluoride solution of sodium fluoride to obtain a sodium hexafluorophosphate solution, the solution is filtered through a continuous filter, the filter cake is dried and broken, the filtrate is introduced into a closed adsorption column filled with low-temperature plasma modified chelating resin to remove impurities, double-effect evaporation crystallization is carried out, and after forced circulation evaporation crystallization, thickening and filtration, the solid is dried and broken to obtain sodium hexafluorophosphate; unqualified products are dissolved in anhydrous hydrogen fluoride and returned to the S2 process to be purified again; the product prepared by the application has high purity, low moisture content and low free acid content, and meets high-end electronic grade indexes.

Description

Technical Field

[0001] This invention relates to the technical field of sodium hexafluorophosphate synthesis, and in particular to a highly efficient continuous production process for sodium hexafluorophosphate. Background Technology

[0002] Electrolyte is the core component of sodium-ion batteries, responsible for sodium ion conduction and directly determining the battery's cycle life, rate performance, electrochemical window, and safety. Sodium hexafluorophosphate is currently the most commercially viable sodium salt: it has high solubility in carbonate solvents, excellent ionic conductivity, and a wide electrochemical stability window. The decomposition of hexafluorophosphate ions can form a stable SEI film containing sodium fluoride on the electrode surface, effectively passivating aluminum current collectors. It also has good compatibility with mainstream hard carbon anodes and oxide / Prussian blue cathodes, making it the preferred conductive salt for sodium-ion battery electrolytes.

[0003] Chinese Patent CN120829177A relates to the field of compound preparation and discloses a continuous preparation method for hexafluorophosphate, comprising the following steps: continuously introducing a lithium source or sodium source and phosphorus pentafluoride raw material into a primary reactor; the gas discharged from the primary reactor enters a secondary reactor, while a lithium source or sodium source is continuously introduced into the secondary reactor, and an excess of lithium source or sodium source is maintained to ensure that the phosphorus pentafluoride gas in the secondary reactor reacts fully, and the tail gas is discharged from the secondary reactor.

[0004] Chinese Patent CN119706881A: A continuous cyclic preparation method for sodium hexafluorophosphate, comprising the following steps: S1, preparation of anhydrous hydrogen fluoride solution of metallic sodium: anhydrous hydrogen fluoride and metallic sodium halide are added to a reaction vessel and mixed evenly to dissolve the metallic sodium halide in the anhydrous hydrogen fluoride to obtain anhydrous hydrogen fluoride solution of metallic sodium; S2, preparation of anhydrous hydrogen fluoride solution of sodium hexafluorophosphate: under temperature control, phosphorus pentachloride is added to the reaction vessel to react, obtaining anhydrous hydrogen fluoride solution of sodium hexafluorophosphate; S3, filtration of sodium hexafluorophosphate: the anhydrous hydrogen fluoride solution of sodium hexafluorophosphate is transferred to a drying tower for drying. The anhydrous hydrogen fluoride vaporized at the top of the drying tower is condensed into liquid anhydrous hydrogen fluoride by a condenser and returned to the reaction vessel of step S1. The sodium hexafluorophosphate product is collected at the bottom of the drying tower, and the uncondensed gas is fed into a recovery system for recovery.

[0005] Existing technologies only achieve continuous single-stage synthesis, resulting in defects such as low product purity, high moisture content, and high free hydrogen fluoride content in sodium hexafluorophosphate, which cannot meet the production requirements of high-end electronic-grade and power battery-grade high-purity sodium hexafluorophosphate. Summary of the Invention

[0006] To address the above problems, this invention provides a highly efficient continuous production process for sodium hexafluorophosphate, the operation steps of which are as follows: (all figures are parts by weight) 1. A highly efficient continuous production process for sodium hexafluorophosphate, characterized by comprising the following steps: [The process involves] distributing sodium hexafluorophosphate in parts by weight... S1. Phosphorus pentafluoride gasification: 100-200 parts of solid phosphorus pentachloride are quantitatively transported from the warehouse to the silo, and then anhydrous hydrogen fluoride liquid is quantitatively transported from the storage tank to the intermediate tank. The two materials are continuously fed into the reactor in a certain ratio to continuously react and generate phosphorus pentafluoride gas; wherein, the molar ratio of phosphorus pentachloride to anhydrous hydrogen fluoride is 1:5 to 1:10, the reaction time is 90-120 min, and the reaction temperature is 100-120℃; S2. Preparation of sodium fluoride preparation solution: Add 10-20 parts of sodium fluoride solid to the mixing tank, pass in 70-90 parts of anhydrous hydrogen fluoride liquid, then add sodium hexafluorophosphate mother liquor, and stir continuously until the mixture is homogeneous to prepare sodium fluoride preparation solution. S3. Sodium hexafluorophosphate synthesis: The sodium fluoride solution prepared in step S2 is put into the synthesis tank, and the phosphorus pentafluoride gas generated in step S1 is continuously introduced to react and generate sodium hexafluorophosphate and supersaturated crystals are precipitated. S4. Phosphorus pentafluoride recovery: Unreacted gas is sent to a phosphorus recovery spray tower, where an anhydrous hydrogen fluoride solution of sodium fluoride is used to spray and absorb excess unreacted phosphorus pentafluoride gas. S5. Solid-liquid filtration: The reaction solution after the synthesis reaction is sent to a continuous filter for filtration. The resulting filter cake is dried and crushed for later use, and the filtrate is collected for later use. S6. Resin adsorption purification and impurity removal: The filtered filtrate is passed into a closed adsorption column filled with low-temperature plasma modified chelating resin to continuously remove trace impurities from the solution. S7. Double-effect evaporation crystallization: The filtrate after resin refining enters the double-effect evaporation crystallization process. After forced circulation evaporation crystallization, thickening, and precision filtration, the solid material is dried and crushed to obtain sodium hexafluorophosphate product. All crystallization mother liquor is returned to step S2 for recycling. S8. Reuse of unqualified products: Sodium hexafluorophosphate products that fail the test are completely dissolved in anhydrous hydrogen fluoride and returned to step S2 for re-blending and purification.

[0007] Furthermore, in S1, phosphorus pentachloride and anhydrous hydrogen fluoride are reacted in a continuous quantitative feeding mode in a completely closed reaction, which is used to stably prepare high-purity phosphorus pentafluoride gas.

[0008] Furthermore, in step S2, the mass concentration of sodium fluoride in the preparation solution is controlled to be 8-18 wt%, the stirring time is 60-90 min, the stirring rate is 200-300 r / min, and the system temperature is 30-40℃.

[0009] Furthermore, in step S3, phosphorus pentafluoride gas generated in step S1 is introduced to carry out the reaction. The reaction temperature is 10-25℃, the reaction time is 150-200 min, and the stirring rate of the synthesis tank is 200-300 r / min.

[0010] Furthermore, in step S4, the phosphorus pentafluoride-containing absorbent solution after spray absorption can be recycled and reused, realizing closed-loop utilization of raw materials and reducing material loss.

[0011] Furthermore, in S5, the rotation speed of the continuous filter is controlled at 1500-3000 r / min to achieve efficient and thorough solid-liquid separation of the reaction liquid.

[0012] Furthermore, in the S6 resin adsorption and purification process, the resin activation conditions are: immersion in anhydrous hydrogen fluoride dilute solution for 4-6 hours, activation temperature 25-35℃; the adsorption conditions are: adsorption temperature 20-35℃, feed flow rate 5-15 BV / h, system pressure 0.1-0.3 MPa, and a dual-column series continuous adsorption mode is adopted.

[0013] Furthermore, the preparation method of the low-temperature plasma-modified chelating resin in S6 includes the following steps: A1. Resin pretreatment: Select a single aminophosphonic acid chelating resin with a polystyrene cross-linked backbone; ultrasonically clean the resin with ultrapure water for 10-25 min, and dry it at 45-55℃ to constant weight; then immerse the dried resin in an anhydrous hydrogen fluoride solution of 2-5wt% sodium fluoride for 30-60 min at 20-30℃, and dry it at low temperature before placing it into the plasma equipment cavity; A2. Plasma modification gas supply: Hydroxyethyl methacrylate (GMA) monomer and N-vinylcaprolactam are used as the modification gas source in a time-division manner, with high-purity argon as the carrier gas. The two-stage steam volume ratio is 1:0.5-0.9, and the single-stage steam volume concentration is 8-12%. The cavity vacuum degree is 11-14 Pa, and the staged discharge power is 55W and 60-70W respectively. The resin temperature is controlled to be ≤37℃ throughout the process. A3. Segmented activation: After vacuuming the sealed cavity, segmented activation is performed: hydroxyethyl methacrylate (GMA) monomer is activated by vapor for 15-30 min, and N-vinylcaprolactam is activated by vapor for 20-35 min. A4. Post-treatment molding: After activation, the cavity is left to stand for 15-30 minutes, the resin is thoroughly rinsed with ultrapure water, and then vacuum dried at 50-60℃ and a vacuum degree of -0.07 to -0.09 MPa to obtain low-temperature plasma modified chelating resin.

[0014] Furthermore, in the S7 double-effect evaporation crystallization, 60-80℃ hot water is used as the heating medium, the first-stage evaporator operates at atmospheric pressure, and the vacuum degree of the second-stage evaporator is controlled at -0.06 to -0.07 MPa to achieve gradient evaporation crystallization.

[0015] Furthermore, the entire production process adopts an anhydrous closed nitrogen protection system to isolate air and water vapor impurities from interference. Combined with the mother liquor circulation and unqualified product recycling system, it realizes continuous closed-loop production throughout the entire process.

[0016] Reaction mechanism: The fluorination displacement gasification mechanism of phosphorus pentafluoride: In a high-temperature reactor system under anhydrous, closed-loop nitrogen protection, phosphorus pentachloride undergoes a highly efficient halogen displacement reaction with anhydrous hydrogen fluoride. Fluoride ions gradually replace chloride ions in phosphorus pentachloride, continuously removing hydrogen chloride byproducts and stably generating high-purity phosphorus pentafluoride gas. The completely closed anhydrous environment effectively prevents the hydrolysis and failure of phosphorus pentafluoride, providing qualified gaseous feedstock for subsequent synthesis processes.

[0017] The low-temperature plasma-modified chelating resin prepared by this process achieves precise impurity removal through the synergistic coupling of physical sieving and chemical chelation. After time-sequential grafting modification by low-temperature plasma, the resin's surface and pore inner walls are constructed with hydroxyl and lactam nitrogen composite functional groups. Simultaneously, plasma etching regulates the resin's pore structure, forming sieving channels of suitable size. The monovalent sodium ions in the sodium hexafluorophosphate solution have small hydrated particle sizes and can freely pass through the resin pores, while the polyvalent impurity metal ions such as calcium, magnesium, and iron in the system have larger hydrated sizes and are physically trapped and enriched by the resin surface pores, achieving preliminary physical sieving and separation of target ions and impurity ions.

[0018] Based on physical sieving, the modified resin achieves deep impurity removal through selective chelation at multiple coordination sites. The aminophosphonic acid groups in the resin bulk, along with the hydroxyl and nitrogen-containing lactam groups grafted onto the surface, form a multi-electron donor coordination system. This system can form stable chelate ring structures with multivalent impurity metal ions, exhibiting strong and highly specific binding forces. Monovalent sodium ions, however, have poor acid-base compatibility and cannot form stable coordination structures. In the ion-competitive environment of high-sodium salt solutions, they are almost not adsorbed or retained. Therefore, efficient separation of impurity metal ions from target sodium ions is achieved through coordination selectivity. Technical Effects: The present invention provides a highly efficient continuous production process for sodium hexafluorophosphate. Compared with the prior art, the present invention has the following significant advantages: 1. Construct a fully closed-loop continuous production system: The first continuous closed-loop process for the entire process of gasification, blending, synthesis, filtration, resin refining, evaporation and crystallization, mother liquor reuse, and regeneration of defective products, with no interruption waiting process, greatly improves production capacity and is suitable for mass production of tens of thousands of tons.

[0019] 2. This modified resin, through a sieving-chelation coupling mechanism, thoroughly overcomes the shortcomings of traditional unmodified resins, such as poor selectivity and susceptibility to interference from high-salt systems. Relying on the surface functionalized modified structure, it significantly reduces ion diffusion resistance and accelerates the adsorption response speed of impurity ions, making it suitable for continuous material flow processing and meeting the operational requirements of continuous industrial production of sodium hexafluorophosphate.

[0020] Modified resin concentrates chelating functional sites on the resin surface and pore walls, effectively preventing impurity ions from penetrating and accumulating inside the resin, thus eliminating the problem of rapid saturation and failure of internal resin sites. This significantly extends the continuous operating time of the resin, reduces the frequency of resin regeneration operations, simplifies production processes, lowers production and maintenance costs, and simultaneously ensures the stability and consistency of impurity removal from the feed solution.

[0021] 3. Stable and excellent product performance: The entire process is waterless and sealed, with automated and precise temperature, pressure, and flow rate control, eliminating the introduction of external impurities and human operation errors. The prepared sodium hexafluorophosphate product has high purity and extremely low moisture and free hydrogen fluoride content, fully meeting the standards for high-end electronic and power battery applications. Detailed Implementation

[0022] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples: 1. Product purity: The purity is tested using the difference subtraction method in the group standard T / CAAMTB 188-2024.

[0023] 2. Moisture content: Detected using Karl Fischer microtiter method.

[0024] 3. Free acid (calculated as HF) content: The free acid detection method in the group standard T / CAAMTB 188-2024, namely acid-base titration method, is adopted for detection.

[0025] Example 1: A highly efficient continuous production process for sodium hexafluorophosphate, comprising the following steps: S1. Phosphorus pentafluoride gasification: 100 kg of phosphorus pentachloride solid is quantitatively transported from the warehouse to the silo, and then anhydrous hydrogen fluoride liquid is quantitatively transported from the storage tank to the intermediate tank. The two materials are continuously fed into the reactor in a certain ratio to continuously react and generate phosphorus pentafluoride gas; wherein, the molar ratio of phosphorus pentachloride to anhydrous hydrogen fluoride is 1:5, the reaction time is 90 min, and the reaction temperature is 100℃. S2. Preparation of sodium fluoride preparation solution: 10 kg of sodium fluoride solid was added to a mixing tank, 70 kg of anhydrous hydrogen fluoride liquid was introduced, and then sodium hexafluorophosphate mother liquor was added. The mixture was stirred continuously and mixed evenly to obtain sodium fluoride preparation solution. The mass concentration of sodium fluoride in the preparation solution was controlled at 8 wt%, the stirring time was 60 min, the stirring rate was 200 r / min, and the system temperature was 30℃. S3. Sodium hexafluorophosphate synthesis: The sodium fluoride solution prepared in step S2 is put into the synthesis tank, and the phosphorus pentafluoride gas generated in step S1 is continuously introduced to react and generate sodium hexafluorophosphate and supersaturated crystals are precipitated; the reaction temperature is 10℃, the reaction time is 150min, and the stirring rate of the synthesis tank is 200r / min. S4. Phosphorus pentafluoride recovery: Unreacted gas is sent to a phosphorus recovery spray tower, where an anhydrous hydrogen fluoride solution of sodium fluoride is used to spray and absorb excess unreacted phosphorus pentafluoride gas, thereby realizing the recovery and reuse of raw materials and avoiding material waste and exhaust gas pollution. S5. Solid-liquid filtration: The reaction liquid after the synthesis reaction is sent to a continuous filter for filtration. The resulting filter cake is dried and crushed for later use, and the filtrate is collected for later use, so as to achieve precise solid-liquid separation. S6. Resin adsorption purification and impurity removal: The filtered filtrate is passed into a closed adsorption column filled with low-temperature plasma modified chelating resin to continuously remove trace metal impurities, organic impurities and residual acidic impurities from the solution. S7. Double-effect evaporation crystallization: The filtrate after resin refining enters the double-effect evaporation crystallization process. After forced circulation evaporation crystallization, thickening, and precision filtration, the solid material is dried and crushed to obtain sodium hexafluorophosphate product. All crystallization mother liquor is returned to step S2 for recycling. S8. Reuse of unqualified products: Sodium hexafluorophosphate products that fail the test are completely dissolved with anhydrous hydrogen fluoride and returned to step S2 for re-blending and purification, achieving zero waste of materials.

[0026] In the S6 resin adsorption purification process, the resin activation conditions are: 4 hours of immersion in anhydrous hydrogen fluoride dilute solution and activation temperature of 25°C; the adsorption conditions are: adsorption temperature of 20°C, feed flow rate of 5 BV / h, system pressure of 0.1 MPa, and a dual-column series continuous adsorption mode is adopted to ensure the continuity and stability of impurity removal.

[0027] The preparation method of the low-temperature plasma-modified chelating resin in S6 includes the following steps: A1. Resin pretreatment: D418 aminophosphonic acid chelating resin was selected, with a polystyrene cross-linked skeleton. The resin was ultrasonically cleaned with ultrapure water for 10 min and dried at 45℃ to constant weight. Then, the dried resin was immersed in an anhydrous hydrogen fluoride solution of 2wt% sodium fluoride for 30 min at 20℃. After low-temperature drying, it was placed in the plasma equipment cavity. A2. Plasma modification gas supply: Hydroxyethyl methacrylate (GMA) monomer and N-vinylcaprolactam are used as the modification gas source in a time-division manner, with high-purity argon as the carrier gas. The two-stage steam volume ratio is 1:0.5, and the single-stage steam volume concentration is 8%. The cavity vacuum degree is 11Pa, and the staged discharge power is 55W and 60W respectively. The resin temperature is controlled to be ≤37℃ throughout the process. A3. Segmented activation: After evacuating the sealed cavity, segmented activation is performed: hydroxyethyl methacrylate (GMA) monomer is activated by vapor for 15 min, and N-vinylcaprolactam is activated by vapor for 20 min. A4. Post-treatment molding: After activation, the cavity is left to stand for 15 minutes, the resin is thoroughly rinsed with ultrapure water, and then vacuum dried at 50℃ and a vacuum degree of -0.07MPa to obtain low-temperature plasma modified chelating resin.

[0028] The S7 double-effect evaporation crystallization uses 60℃ hot water as the heating medium. The first-stage evaporator operates at atmospheric pressure, and the vacuum degree of the second-stage evaporator is controlled at -0.06MPa. Gradient evaporation ensures crystallization uniformity and improves the purity of the finished product.

[0029] The rotation speed of the continuous filter in S5 is controlled at 1500 r / min to ensure thorough solid-liquid separation.

[0030] The entire production process employs a waterless, closed nitrogen protection system to isolate the product from air and moisture impurities, prevent product hydrolysis and oxidation, and ensure stable product quality.

[0031] Example 2: A highly efficient continuous production process for sodium hexafluorophosphate, comprising the following steps: S1. Phosphorus pentafluoride gasification: 135 kg of phosphorus pentachloride solid is quantitatively transported from the warehouse to the silo, and then anhydrous hydrogen fluoride liquid is quantitatively transported from the storage tank to the intermediate tank. The two materials are continuously fed into the reactor in a certain ratio to continuously react and generate phosphorus pentafluoride gas; wherein, the molar ratio of phosphorus pentachloride to anhydrous hydrogen fluoride is 1:6, the reaction time is 100 min, and the reaction temperature is 105℃. S2. Preparation of sodium fluoride preparation solution: 13 kg of sodium fluoride solid was added to a mixing tank, 80 kg of anhydrous hydrogen fluoride liquid was introduced, and then sodium hexafluorophosphate mother liquor was added. The mixture was stirred continuously and mixed evenly to obtain sodium fluoride preparation solution. The mass concentration of sodium fluoride in the preparation solution was controlled at 12 wt%, the stirring time was 70 min, the stirring rate was 230 r / min, and the system temperature was 34 ℃. S3. Sodium hexafluorophosphate synthesis: The sodium fluoride solution prepared in step S2 is put into the synthesis tank, and the phosphorus pentafluoride gas generated in step S1 is continuously introduced to react and generate sodium hexafluorophosphate and supersaturated crystals are precipitated; the reaction temperature is 15℃, the reaction time is 160min, and the stirring rate of the synthesis tank is 220r / min. S4. Phosphorus pentafluoride recovery: Unreacted gas is sent to a phosphorus recovery spray tower, where an anhydrous hydrogen fluoride solution of sodium fluoride is used to spray and absorb excess unreacted phosphorus pentafluoride gas, thereby realizing the recovery and reuse of raw materials and avoiding material waste and exhaust gas pollution. S5. Solid-liquid filtration: The reaction liquid after the synthesis reaction is sent to a continuous filter for filtration. The resulting filter cake is dried and crushed for later use, and the filtrate is collected for later use, so as to achieve precise solid-liquid separation. S6. Resin adsorption purification and impurity removal: The filtered filtrate is passed into a closed adsorption column filled with low-temperature plasma modified chelating resin to continuously remove trace metal impurities, organic impurities and residual acidic impurities from the solution. S7. Double-effect evaporation crystallization: The filtrate after resin refining enters the double-effect evaporation crystallization process. After forced circulation evaporation crystallization, thickening, and precision filtration, the solid material is dried and crushed to obtain sodium hexafluorophosphate product. All crystallization mother liquor is returned to step S2 for recycling. S8. Reuse of unqualified products: Sodium hexafluorophosphate products that fail the test are completely dissolved with anhydrous hydrogen fluoride and returned to step S2 for re-blending and purification, achieving zero waste of materials.

[0032] In the S6 resin adsorption purification process, the resin activation conditions are as follows: 4.5 hours of immersion in anhydrous hydrogen fluoride dilute solution and activation temperature of 28°C; the adsorption conditions are as follows: adsorption temperature of 25°C, feed flow rate of 7 BV / h, system pressure of 0.15 MPa, and a dual-column series continuous adsorption mode is adopted to ensure the continuity and stability of impurity removal.

[0033] The preparation method of the low-temperature plasma-modified chelating resin in S6 includes the following steps: A1. Resin pretreatment: D402 aminophosphonic acid chelating resin was selected, with a polystyrene cross-linked skeleton. The resin was ultrasonically cleaned with ultrapure water for 15 min and dried at 47℃ to constant weight. Then, the dried resin was immersed in an anhydrous hydrogen fluoride solution of 3wt% sodium fluoride for 35 min at 24℃. After low-temperature drying, it was placed in the plasma equipment cavity. A2. Plasma modification gas supply: Hydroxyethyl methacrylate (GMA) monomer and N-vinylcaprolactam are used as the modification gas source in a time-division manner, with high-purity argon as the carrier gas. The two-stage steam volume ratio is 1:0.6, and the single-stage steam volume concentration is 9%. The cavity vacuum degree is 12Pa, and the staged discharge power is 55W and 65W respectively. The resin temperature is controlled to be ≤37℃ throughout the process. A3. Segmented activation: After evacuating the sealed cavity, segmented activation is performed: hydroxyethyl methacrylate (GMA) monomer is activated by vapor for 17 min, and N-vinylcaprolactam is activated by vapor for 25 min. A4. Post-treatment molding: After activation, the cavity is left to stand for 18 minutes, the resin is thoroughly rinsed with ultrapure water, and then vacuum dried at 55℃ and a vacuum degree of -0.08MPa to obtain low-temperature plasma modified chelating resin.

[0034] The S7 double-effect evaporation crystallization uses 65℃ hot water as the heating medium. The first-stage evaporator operates at atmospheric pressure, and the vacuum degree of the second-stage evaporator is controlled at -0.085MPa. Gradient evaporation ensures crystallization uniformity and improves the purity of the finished product.

[0035] The rotation speed of the continuous filter in S5 is controlled at 2100 r / min to ensure thorough solid-liquid separation.

[0036] The entire production process employs a waterless, closed nitrogen protection system to isolate the product from air and moisture impurities, prevent product hydrolysis and oxidation, and ensure stable product quality.

[0037] Example 3: A highly efficient continuous production process for sodium hexafluorophosphate, comprising the following steps: S1. Phosphorus pentafluoride gasification: 160 kg of solid phosphorus pentachloride is quantitatively transported from the warehouse to the silo, and then anhydrous hydrogen fluoride liquid is quantitatively transported from the storage tank to the intermediate tank. The two materials are continuously fed into the reactor in a certain ratio to continuously react and generate phosphorus pentafluoride gas. The molar ratio of phosphorus pentachloride to anhydrous hydrogen fluoride is 1:7, the reaction time is 105 min, and the reaction temperature is 108℃. S2. Preparation of sodium fluoride preparation solution: 15 kg of sodium fluoride solid was added to a mixing tank, 85 kg of anhydrous hydrogen fluoride liquid was introduced, and then sodium hexafluorophosphate mother liquor was added. The mixture was stirred continuously and mixed evenly to obtain sodium fluoride preparation solution. The mass concentration of sodium fluoride in the preparation solution was controlled at 15 wt%, the stirring time was 80 min, the stirring rate was 270 r / min, and the system temperature was 37℃. S3. Sodium hexafluorophosphate synthesis: The sodium fluoride solution prepared in step S2 is put into the synthesis tank, and the phosphorus pentafluoride gas generated in step S1 is continuously introduced to react and generate sodium hexafluorophosphate and supersaturated crystals are precipitated; the reaction temperature is 22℃, the reaction time is 180min, and the stirring rate of the synthesis tank is 270r / min. S4. Phosphorus pentafluoride recovery: Unreacted gas is sent to a phosphorus recovery spray tower, where an anhydrous hydrogen fluoride solution of sodium fluoride is used to spray and absorb excess unreacted phosphorus pentafluoride gas, thereby realizing the recovery and reuse of raw materials and avoiding material waste and exhaust gas pollution. S5. Solid-liquid filtration: The reaction liquid after the synthesis reaction is sent to a continuous filter for filtration. The resulting filter cake is dried and crushed for later use, and the filtrate is collected for later use, so as to achieve precise solid-liquid separation. S6. Resin adsorption purification and impurity removal: The filtered filtrate is passed into a closed adsorption column filled with low-temperature plasma modified chelating resin to continuously remove trace metal impurities, organic impurities and residual acidic impurities from the solution. S7. Double-effect evaporation crystallization: The filtrate after resin refining enters the double-effect evaporation crystallization process. After forced circulation evaporation crystallization, thickening, and precision filtration, the solid material is dried and crushed to obtain sodium hexafluorophosphate product. All crystallization mother liquor is returned to step S2 for recycling. S8. Reuse of unqualified products: Sodium hexafluorophosphate products that fail the test are completely dissolved with anhydrous hydrogen fluoride and returned to step S2 for re-blending and purification, achieving zero waste of materials.

[0038] In the S6 resin adsorption purification process, the resin activation conditions are: 5.5 h of immersion in anhydrous hydrogen fluoride dilute solution and activation temperature of 30℃; the adsorption conditions are: adsorption temperature of 30℃, feed flow rate of 14 BV / h, system pressure of 0.25 MPa, and a dual-column series continuous adsorption mode is adopted to ensure the continuity and stability of impurity removal.

[0039] The preparation method of the low-temperature plasma-modified chelating resin in S6 includes the following steps: A1. Resin pretreatment: LSC-500 aminophosphonic acid chelating resin was selected, with a polystyrene cross-linked skeleton. The resin was ultrasonically cleaned with ultrapure water for 20 min and dried at 50℃ to constant weight. Then, the dried resin was immersed in an anhydrous hydrogen fluoride solution of 4wt% sodium fluoride for 50 min at 28℃. After low-temperature drying, it was placed in the plasma equipment cavity. A2. Plasma modification gas supply: Hydroxyethyl methacrylate (GMA) monomer and N-vinylcaprolactam are used as the modification gas source in a time-division manner, with high-purity argon as the carrier gas. The two-stage vapor volume ratio is 1:0.8, and the single-stage vapor volume concentration is 11%. The cavity vacuum degree is 13Pa, and the staged discharge power is 55W and 67W respectively. The resin temperature is controlled to be ≤37℃ throughout the process. A3. Segmented activation: After evacuating the sealed cavity, segmented activation is performed: hydroxyethyl methacrylate (GMA) monomer is activated by vapor for 25 min, and N-vinylcaprolactam is activated by vapor for 30 min. A4. Post-treatment molding: After activation, the cavity is left to stand for 27 minutes, the resin is thoroughly rinsed with ultrapure water, and then vacuum dried at 58℃ and -0.08MPa to obtain low-temperature plasma modified chelating resin.

[0040] The S7 double-effect evaporation crystallization uses 70℃ hot water as the heating medium. The first-stage evaporator operates at atmospheric pressure, and the vacuum degree of the second-stage evaporator is controlled at -0.065MPa. Gradient evaporation ensures crystallization uniformity and improves the purity of the finished product.

[0041] The rotation speed of the continuous filter in S5 is controlled at 2800 r / min to ensure thorough solid-liquid separation.

[0042] The entire production process employs a waterless, closed nitrogen protection system to isolate the product from air and moisture impurities, prevent product hydrolysis and oxidation, and ensure stable product quality.

[0043] Example 4: A highly efficient continuous production process for sodium hexafluorophosphate, comprising the following steps: S1. Phosphorus pentafluoride gasification: 200 kg of solid phosphorus pentachloride is quantitatively transported from the warehouse to the silo, and then anhydrous hydrogen fluoride liquid is quantitatively transported from the storage tank to the intermediate tank. The two materials are continuously fed into the reactor in a certain ratio to continuously react and generate phosphorus pentafluoride gas; wherein, the molar ratio of phosphorus pentachloride to anhydrous hydrogen fluoride is 1:10, the reaction time is 120 min, and the reaction temperature is 120℃. S2. Preparation of sodium fluoride preparation solution: 20 kg of sodium fluoride solid was added to a mixing tank, 90 kg of anhydrous hydrogen fluoride liquid was introduced, and then sodium hexafluorophosphate mother liquor was added. The mixture was stirred continuously and mixed evenly to obtain sodium fluoride preparation solution. The mass concentration of sodium fluoride in the preparation solution was controlled at 18 wt%, the stirring time was 90 min, the stirring rate was 300 r / min, and the system temperature was 40℃. S3. Sodium hexafluorophosphate synthesis: The sodium fluoride solution prepared in step S2 is put into the synthesis tank, and the phosphorus pentafluoride gas generated in step S1 is continuously introduced to react and generate sodium hexafluorophosphate and supersaturated crystals are precipitated; the reaction temperature is 25℃, the reaction time is 200min, and the stirring rate of the synthesis tank is 300r / min. S4. Phosphorus pentafluoride recovery: Unreacted gas is sent to a phosphorus recovery spray tower, where an anhydrous hydrogen fluoride solution of sodium fluoride is used to spray and absorb excess unreacted phosphorus pentafluoride gas, thereby realizing the recovery and reuse of raw materials and avoiding material waste and exhaust gas pollution. S5. Solid-liquid filtration: The reaction liquid after the synthesis reaction is sent to a continuous filter for filtration. The resulting filter cake is dried and crushed for later use, and the filtrate is collected for later use, so as to achieve precise solid-liquid separation. S6. Resin adsorption purification and impurity removal: The filtered filtrate is passed into a closed adsorption column filled with low-temperature plasma modified chelating resin to continuously remove trace metal impurities, organic impurities and residual acidic impurities from the solution. S7. Double-effect evaporation crystallization: The filtrate after resin refining enters the double-effect evaporation crystallization process. After forced circulation evaporation crystallization, thickening, and precision filtration, the solid material is dried and crushed to obtain sodium hexafluorophosphate product. All crystallization mother liquor is returned to step S2 for recycling. S8. Reuse of unqualified products: Sodium hexafluorophosphate products that fail the test are completely dissolved with anhydrous hydrogen fluoride and returned to step S2 for re-blending and purification, achieving zero waste of materials.

[0044] In the S6 resin adsorption purification process, the resin activation conditions are: 6 hours of immersion in anhydrous hydrogen fluoride dilute solution and activation temperature of 35℃; the adsorption conditions are: adsorption temperature of 35℃, feed flow rate of 15 BV / h, system pressure of 0.3 MPa, and a dual-column series continuous adsorption mode is adopted to ensure the continuity and stability of impurity removal.

[0045] The preparation method of the low-temperature plasma-modified chelating resin in S6 includes the following steps: A1. Resin pretreatment: D860 aminophosphonic acid chelating resin was selected, with a polystyrene cross-linked skeleton. The resin was ultrasonically cleaned with ultrapure water for 25 min and dried at 55℃ to constant weight. Then the dried resin was immersed in an anhydrous hydrogen fluoride solution of 5wt% sodium fluoride for 60 min at 30℃. After low-temperature drying, it was placed in the plasma equipment cavity. A2. Plasma modification gas supply: Hydroxyethyl methacrylate (GMA) monomer and N-vinylcaprolactam are used as the modification gas source in a time-division manner, with high-purity argon as the carrier gas. The two-stage steam volume ratio is 1:0.9, and the single-stage steam volume concentration is 12%. The cavity vacuum degree is 14Pa, and the staged discharge power is 55W and 70W respectively. The resin temperature is controlled to be ≤37℃ throughout the process. A3. Segmented activation: After evacuating the sealed cavity, segmented activation is performed: hydroxyethyl methacrylate (GMA) monomer is activated by vapor for 30 min, and N-vinylcaprolactam is activated by vapor for 35 min. A4. Post-treatment molding: After activation, the cavity is left to stand for 30 minutes, the resin is thoroughly rinsed with ultrapure water, and then vacuum dried at 60℃ and a vacuum degree of -0.09MPa to obtain low-temperature plasma modified chelating resin.

[0046] The S7 double-effect evaporation crystallization uses 80℃ hot water as the heating medium. The first-stage evaporator operates at atmospheric pressure, and the vacuum degree of the second-stage evaporator is controlled at -0.07MPa. Gradient evaporation ensures crystallization uniformity and improves the purity of the finished product.

[0047] The rotation speed of the continuous filter in S5 is controlled at 3000 r / min to ensure thorough solid-liquid separation.

[0048] The entire production process employs a waterless, closed nitrogen protection system to isolate the product from air and moisture impurities, prevent product hydrolysis and oxidation, and ensure stable product quality.

[0049] Comparative Example 1 A highly efficient continuous production process for sodium hexafluorophosphate, comprising the following steps: The resin in S6 is D418 aminophosphonic acid chelating resin, without using modified resin, and otherwise the same as in Example 1.

[0050] Comparative Example 2 A highly efficient continuous production process for sodium hexafluorophosphate, comprising the following steps: A2: Only hydroxyethyl methacrylate (GMA) monomer is used as the modified gas source, and the rest is the same as in Example 1.

[0051] Comparative Example 3 A highly efficient continuous production process for sodium hexafluorophosphate, comprising the following steps: A2: Only N-vinylcaprolactam is used as the modified gas source, and everything else is the same as in Example 1.

[0052] Table 1. Detection results of product purity, moisture content, and free HF content in the specific implementation plan.

[0053] As shown in the table above, by adding a special modified resin adsorption and refining process, this invention can significantly reduce the moisture and free acid content of sodium hexafluorophosphate products, greatly improve product purity, and all indicators are far superior to traditional processes and ordinary resin impurity removal processes. The product quality meets the requirements for high-purity raw materials used in high-end electronic and power battery applications.

[0054] Compared to unmodified aminophosphonic acid chelating resin, this modified resin, relying on the sieving-chelation coupling mechanism, significantly optimizes the adsorption performance and anti-interference ability of calcium, magnesium, and iron impurities in high-sodium salt solution environments. It has higher ion mass transfer efficiency, stronger continuous impurity removal stability, and can be effectively adapted to the efficient and continuous production process of sodium hexafluorophosphate, possessing excellent advantages for industrial applications.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A highly efficient continuous production process for sodium hexafluorophosphate, characterized in that, Includes the following steps: By weight, S1. Phosphorus pentafluoride gasification: 100-200 parts of solid phosphorus pentachloride are quantitatively transported from the warehouse to the silo, and then anhydrous hydrogen fluoride liquid is quantitatively transported from the storage tank to the intermediate tank. The two materials are continuously fed into the reactor in a certain ratio to continuously react and generate phosphorus pentafluoride gas; wherein, the molar ratio of phosphorus pentachloride to anhydrous hydrogen fluoride is 1:5 to 1:10, the reaction time is 90-120 min, and the reaction temperature is 100-120℃; S2. Preparation of sodium fluoride preparation solution: Add 10-20 parts of sodium fluoride solid to the mixing tank, pass in 70-90 parts of anhydrous hydrogen fluoride liquid, then add sodium hexafluorophosphate mother liquor, and stir continuously until the mixture is homogeneous to prepare sodium fluoride preparation solution. S3. Sodium hexafluorophosphate synthesis: The sodium fluoride solution prepared in step S2 is put into the synthesis tank, and the phosphorus pentafluoride gas generated in step S1 is continuously introduced to react and generate sodium hexafluorophosphate and supersaturated crystals are precipitated. S4. Phosphorus pentafluoride recovery: Unreacted gas is sent to a phosphorus recovery spray tower, where an anhydrous hydrogen fluoride solution of sodium fluoride is used to spray and absorb excess unreacted phosphorus pentafluoride gas. S5. Solid-liquid filtration: The reaction solution after the synthesis reaction is sent to a continuous filter for filtration. The resulting filter cake is dried and crushed for later use, and the filtrate is collected for later use. S6. Resin adsorption purification and impurity removal: The filtered filtrate is passed into a closed adsorption column filled with low-temperature plasma modified chelating resin to continuously remove trace impurities from the solution. S7. Double-effect evaporation crystallization: The filtrate after resin refining enters the double-effect evaporation crystallization process. After forced circulation evaporation crystallization, thickening, and precision filtration, the solid material is dried and crushed to obtain sodium hexafluorophosphate product. All crystallization mother liquor is returned to step S2 for recycling. S8. Reuse of unqualified products: Sodium hexafluorophosphate products that fail the test are completely dissolved in anhydrous hydrogen fluoride and returned to step S2 for re-blending and purification.

2. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: In S1, phosphorus pentachloride and anhydrous hydrogen fluoride are reacted in a continuous quantitative feeding mode in a completely closed reaction, which is used to stably prepare high-purity phosphorus pentafluoride gas.

3. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: In step S2, the mass concentration of sodium fluoride in the preparation solution is controlled to be 8-18 wt%, the stirring time is 60-90 min, the stirring rate is 200-300 r / min, and the system temperature is 30-40℃.

4. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: In step S3, phosphorus pentafluoride gas generated in step S1 is introduced to carry out the reaction. The reaction temperature is 10-25℃, the reaction time is 150-200min, and the stirring rate of the synthesis tank is 200-300r / min.

5. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: In step S4, the phosphorus pentafluoride-containing absorbent solution after spray absorption can be recycled and reused.

6. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: In S5, the rotational speed of the continuous filter is controlled at 1500-3000 r / min.

7. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: In the S6 resin adsorption and refining process, the resin activation conditions are as follows: 4-6 hours of immersion in anhydrous hydrogen fluoride dilute solution and activation temperature of 25-35℃; the adsorption conditions are as follows: adsorption temperature of 20-35℃, feed flow rate of 5-15 BV / h, system pressure of 0.1-0.3 MPa, and a dual-column series continuous adsorption mode is adopted.

8. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: The preparation method of the low-temperature plasma-modified chelating resin in S6 includes the following steps: A1. Resin pretreatment: Select a single aminophosphonic acid chelating resin with a polystyrene cross-linked backbone; ultrasonically clean the resin with ultrapure water for 10-25 min, and dry it at 45-55℃ to constant weight; then immerse the dried resin in an anhydrous hydrogen fluoride solution of 2-5wt% sodium fluoride for 30-60 min at 20-30℃, and dry it at low temperature before placing it into the plasma equipment cavity; A2. Plasma modification gas supply: Hydroxyethyl methacrylate (GMA) monomer and N-vinylcaprolactam are used as the modification gas source in a time-division manner, with high-purity argon as the carrier gas. The two-stage steam volume ratio is 1:0.5-0.9, and the single-stage steam volume concentration is 8-12%. The cavity vacuum degree is 11-14 Pa, and the staged discharge power is 55W and 60-70W respectively. The resin temperature is controlled to be ≤37℃ throughout the process. A3. Segmented activation: After evacuating the sealed cavity, segmented activation is performed: hydroxyethyl methacrylate (GMA) monomer is activated by vapor for 15-30 min, and N-vinylcaprolactam is activated by vapor for 20-35 min. A4. Post-treatment molding: After activation, the cavity is left to stand for 15-30 minutes, the resin is thoroughly rinsed with ultrapure water, and then vacuum dried at 50-60℃ and a vacuum degree of -0.07 to -0.09 MPa to obtain low-temperature plasma modified chelating resin.

9. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: The S7 double-effect evaporation crystallization uses 60-80℃ hot water as the heating medium, the first-stage evaporator operates at atmospheric pressure, and the vacuum degree of the second-stage evaporator is controlled at -0.06 to -0.07 MPa.

10. The efficient continuous production process for sodium hexafluorophosphate according to claim 1, characterized in that: The entire production process adopts an anhydrous, closed nitrogen protection system to isolate air and water vapor impurities from interference, in conjunction with a mother liquor circulation and unqualified product recycling system.

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