Sodium hexafluorophosphate concentrated solution, its preparation method and application

Abstract

The application provides a preparation method and application of a sodium hexafluorophosphate concentrated solution and belongs to the field of batteries. Sodium halide and phosphorus pentachloride are reacted in a solvent (first reaction), a precursor solution generated in the reaction is reacted with hydrogen fluoride (second reaction), a sodium hexafluorophosphate solution is generated, and then degassing, filtration, concentration, dilution and resin deacidification are sequentially performed to obtain the sodium hexafluorophosphate concentrated solution. Then, impurities are removed by degassing, filtration, concentration, dilution and deacidification resin to obtain a final product. The sodium hexafluorophosphate concentrated solution product obtained by the application can be used as an electrolyte salt for a sodium ion battery electrolyte, and has the same or higher battery performance as that of a common sodium hexafluorophosphate crystal.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of batteries and relates to a sodium hexafluorophosphate concentrated solution and a preparation method and application thereof. BACKGROUND

[0002] Sodium hexafluorophosphate is an important electrolyte salt and is mainly used in the non-aqueous electrolyte of sodium ion batteries, so it is required to have a very high purity (usually not less than 99.5%), and the contents of impurities such as water, alkali metals, heavy metals, chloride ions, sulfate radicals or free acid must be strictly controlled, otherwise it will cause the problems of increased internal resistance of the battery, fast capacity attenuation of the battery and shortened cycle life. Therefore, it has important practical significance to obtain a sodium hexafluorophosphate product with high purity and low cost.

[0003] The existing mainstream sodium hexafluorophosphate production process mainly generates phosphorus pentafluoride, reacts with sodium fluoride to generate a sodium hexafluorophosphate solution, and obtains crystalline sodium hexafluorophosphate through crystallization. Since the above schemes all need crystallization purification, considering that sodium hexafluorophosphate needs to return to the dissolved state when it is applied in the electrolyte, if the crystallization purification step can be omitted while the purity of sodium hexafluorophosphate in the solution is ensured, a large number of process procedures can be saved, thereby reducing equipment investment and land occupation, and reducing time and price costs.

[0004] Therefore, it is still necessary to develop a new process to directly obtain a sodium hexafluorophosphate solution product with high purity and low cost, so as to omit subsequent crystallization purification and other process steps and realize its wide application in sodium ion batteries.

[0005] PRIOR ART DOCUMENTS

[0006] [Patent Document 1] CN116534874A

[0007] [Patent Document 2] CN116462167A SUMMARY

[0008] In view of the problems in the prior art, the purpose of the present application is to provide a sodium hexafluorophosphate concentrated solution and a preparation method and application thereof. The preparation method makes sodium halide react with phosphorus pentachloride in a solvent, then reacts with hydrogen fluoride to generate a sodium hexafluorophosphate solution, and then sequentially performs degassing, filtration, concentration, dilution and resin deacidification to obtain a sodium hexafluorophosphate concentrated solution. The present application uses a continuous reaction scheme to inhibit the risk of using hydrogen fluoride and improve the yield, uses degassing, filtration, concentration, dilution and deacidification resin to remove impurities, and further collects by-products to obtain high-purity hydrogen chloride for external sale and high-purity hydrogen fluoride for reuse.

[0009] To achieve this purpose, the present application adopts the following technical scheme:

[0010] In a first aspect, the present application provides a method for preparing a sodium hexafluorophosphate concentrate, the method comprising:

[0011] reacting sodium halide with phosphorus pentachloride in a solvent to form a precursor solution;

[0012] reacting the precursor solution with hydrogen fluoride to form a sodium hexafluorophosphate solution;

[0013] sequentially degassing, filtering, concentrating, diluting, and resin deacidification of the sodium hexafluorophosphate solution to obtain the sodium hexafluorophosphate concentrate.

[0014] In view of the problems in the prior art, such as complex preparation method, large occupied area, difficulty in impurity removal, large influence of insoluble substances, long process route, and high safety risk, the present application provides a method for preparing a sodium hexafluorophosphate concentrate, wherein the second reaction uses a continuous process to inhibit the safety risk of using hydrogen fluoride and improve the yield; the methods of degassing, filtering, concentrating, diluting, and resin deacidification are beneficial to the removal of impurities, and further, the by-products can be collected to obtain high-purity hydrogen chloride for external sale and high-purity hydrogen fluoride for reuse, which is beneficial to reducing the comprehensive cost.

[0015] The preparation method has mild reaction conditions, and the obtained sodium hexafluorophosphate product has high purity (99.5% to 99.8%) and low impurity content (chloride ion less than 20 ppm, hydrofluoric acid (calculated as HF) less than 50 ppm, moisture (Karl Fischer method) less than 20 ppm, Hazen color less than 150, each metal ion (Fe, Pb, Na, K, Ca) less than 3 ppm, and insoluble substance less than 10 ppm). The product can be directly used as an electrolyte for sodium ion batteries and has battery performance equivalent to or higher than that of a product obtained by a common sodium hexafluorophosphate crystallization impurity removal process. The preparation method has cheap and readily available raw materials, high yield, simple operation, high safety, and all by-products can be recycled and utilized, and the comprehensive cost is much lower than that of a common sodium hexafluorophosphate crystallization process, so that the product can be applied in the fields of 3C, electric vehicles, and energy storage.

[0016] The continuous reaction refers to that the precursor solution and hydrogen fluoride, especially pressurized hydrogen fluoride (liquid), are continuously fed into a continuous reactor, such as a tubular reactor, mixed, and reacted to form a sodium hexafluorophosphate solution, and the whole process of the sodium hexafluorophosphate solution through degassing, filtering, concentrating, diluting, and resin deacidification to obtain the final product. Compared with the traditional batch reaction process of the sodium hexafluorophosphate crystallization process, the continuous reaction for producing the sodium hexafluorophosphate concentrate product provided by the present application can effectively improve the production capacity and safety, has the innovative characteristics of less equipment investment, high safety, increased performance, simple operation, low cost, and all by-products can be recycled and utilized, and is more suitable for industrial large-scale production.

[0017] The following are preferred technical solutions of the present application, but not as the technical solutions provided by the present application, through the following technical solutions, the technical purpose and beneficial effect of the present application can be better achieved and realized.

[0018] As a preferred technical solution of the present application, the sodium halide includes sodium chloride and / or sodium fluoride.

[0019] Preferably, the water content of the sodium halide is <50 ppm, for example, it can be 48 ppm, 45 ppm, 40 ppm, 35 ppm, 30 ppm, 25 ppm, 20 ppm, 15 ppm, 10 ppm, 5 ppm or 0 ppm, etc., but not limited to the listed values, other values not listed in the above value range are also used.

[0020] Preferably, the molar ratio of the sodium halide to phosphorus pentachloride is 1:(1-1.5), for example, 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45 or 1:1.5, etc., but not limited to the listed values, other values not listed in the above value range are also used.

[0021] Preferably, the phosphorus pentachloride is a solid.

[0022] Preferably, the hydrogen fluoride is a pressurized hydrogen fluoride liquid.

[0023] As a preferred technical solution of the present application, when the sodium halide includes sodium chloride, the molar ratio of hydrogen fluoride to sodium chloride is (6-6.6):1, for example, 6:1, 6.05:1, 6.1:1, 6.15:1, 6.2:1, 6.25:1, 6.3:1, 6.35:1, 6.4:1, 6.45:1, 6.5:1, 6.55:1 or 6.6:1, etc., but not limited to the listed values, other values not listed in the above value range are also applicable.

[0024] Preferably, when the sodium halide includes sodium fluoride, the molar ratio of sodium fluoride to hydrogen fluoride is (5-5.5):1, for example, 5:1, 5.05:1, 5.1:1, 5.15:1, 5.2:1, 5.25:1, 5.3:1, 5.35:1, 5.4:1, 5.45:1 or 5.5:1, etc., but not limited to the listed values, other values not listed in the above value range are also used.

[0025] As a preferred technical solution of the present application, the solvent is a non-aqueous solvent.

[0026] Preferably, the non-aqueous solvent has a water content of < 20 ppm, such as 18 ppm, 15 ppm, 12 ppm, 9 ppm, 7 ppm, 5 ppm, 3 ppm, 1 ppm, or 0 ppm, etc. 0 ppm and no water, but not limited to the listed values, other values not listed in the above range are also used.

[0027] Preferably, the solvent includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, a combination of dimethyl carbonate and diethyl carbonate, a combination of ethyl methyl carbonate and dimethyl carbonate, and a combination of diethyl carbonate and ethyl methyl carbonate.

[0028] As a preferred technical solution of the present application, the temperature for the reaction of sodium halide and phosphorus pentachloride in the solvent is 0-60°C, such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, etc. The time is 4-8h, such as 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, or 8h, etc. but not limited to the listed values, other values not listed in the above range are also applicable.

[0029] Preferably, the temperature for the reaction of the precursor solution and hydrogen fluoride is 0-60°C, such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, etc. The time is 5-10h, such as 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, or 10h, etc. but not limited to the listed values, other values not listed in the above range are also used.

[0030] Preferably, the preparation method is carried out in the presence of an inert atmosphere.

[0031] Preferably, the inert atmosphere includes at least one of nitrogen, argon, or helium, such as a combination of nitrogen and argon, a combination of nitrogen and helium, or a combination of argon and helium.

[0032] As a preferred technical solution of the present application, the second reaction is carried out in a tubular reactor.

[0033] Preferably, the method further includes collecting hydrogen chloride and / or hydrogen fluoride gas generated by the second reaction.

[0034] The second reaction produces by-products, namely a mixture of hydrogen chloride and hydrogen fluoride. The mixture is subjected to rectification to obtain high-purity hydrogen fluoride and hydrogen chloride products. The hydrogen fluoride product can be reused for reaction with the precursor solution, and the hydrogen chloride product can be sold.

[0035] Preferably, the collection method comprises using a pressurized rectification tower for pressurized rectification.

[0036] Preferably, the rectification tower has 12 to 30 plates, a reflux ratio of 0.5 to 2, a top temperature of -65 to 20°C, a top pressure of 0.8 to 3 MPa, hydrogen fluoride product taken from the tower bottom, and hydrogen chloride product taken from the tower top. However, other values not listed within the above ranges can also be used.

[0037] Preferably, the purity of the hydrogen fluoride product and the hydrogen chloride product is greater than 99.99%. However, other values not listed within the above ranges can also be used.

[0038] Preferably, the obtained hydrogen fluoride product is used for reaction with the precursor solution.

[0039] As a preferred technical solution of the present application, the degassing is used to remove residual hydrogen fluoride and hydrogen chloride, and the degassing method comprises reduced-pressure degassing.

[0040] Preferably, the reduced-pressure degassing has a pressure of 0.5 to 10 kPa, such as 0.5 kPa, 1 kPa, 1.5 kPa, 2 kPa, 2.5 kPa, 3 kPa, 3.5 kPa, 4 kPa, 4.5 kPa, 5 kPa, 5.5 kPa, 6 kPa, 6.5 kPa, 7 kPa, 7.5 kPa, 8 kPa, 8.5 kPa, 9 kPa, 9.5 kPa, or 10 kPa, etc. However, other values not listed within the above ranges can also be used.

[0041] Preferably, the reduced-pressure degassing has a temperature of 0 to 60°C, such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, etc. However, other values not listed within the above ranges can also be used.

[0042] Preferably, the reduced-pressure degassing has a time of 5 to 10 h, such as 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, or 10 h, etc. However, other values not listed within the above ranges can also be used.

[0043] As a preferred technical solution of the present application, the filter uses a fluorine-containing resin filter core with a pore size of 0.2-2.0 microns, such as 0.2 microns, 0.4 microns, 0.6 microns, 0.8 microns, 1 micron, 1.2 microns, 1.4 microns, 1.6 microns, 1.8 microns or 2 microns, etc., but not limited to the listed values, other values not listed within the above value range are also used.

[0044] Preferably, the fluorine-containing resin filter core uses a modified polytetrafluoroethylene membrane microporous folded filter core, and its preparation method is as follows:

[0045] H1: by weight parts, the polytetrafluoroethylene membrane microporous folded filter core is put into a plasma device, and plasma modification is carried out in a tetrakis(dimethylsiloxy)silane steam atmosphere, a 500W radio frequency power source plasma device; the radio frequency power source is a frequency of 10-18MHz; the gas flow is 10-20ml / min, the processing time is 100-120min, and a polytetrafluoroethylene membrane microporous folded filter core with a silicon-hydrogen bond is obtained;

[0046] H2: by weight parts, 0.5-2 parts of 1,3,5-tris-acryloyl-s-triazine (959-52-4), 0.003-0.03 parts of 5,10,15,20-tetrakis(4-vinylphenyl)porphyrin, 2-5 parts of Karstedt catalyst, CAS number: 68478-92-2, and 100-140 parts of the polytetrafluoroethylene membrane microporous folded filter core with a silicon-hydrogen bond are uniformly dispersed in 500-1000 parts of toluene, and reacted at 60-70℃ for 100-150 minutes, filtered, and dried to obtain the modified polytetrafluoroethylene membrane microporous folded filter core.

[0047] As a preferred technical solution of the present application, the concentration method includes reduced pressure heating.

[0048] Preferably, the pressure of the reduced pressure heating is 0.5-10kPa, such as 0.5kPa, 1kPa, 2kPa, 3kPa, 4kPa, 5kPa, 6kPa, 7kPa, 8kPa, 9kPa or 10kPa, etc., but not limited to the listed values, other values not listed within the above value range are also used.

[0049] Preferably, the temperature range of the reduced pressure heating is 30-60℃, such as 30℃, 34℃, 38℃, 42℃, 46℃, 50℃, 53℃, 57℃ or 60℃, etc., but not limited to the listed values, other values not listed within the above value range are also used.

[0050] Residual impurity gases, especially hydrogen fluoride and hydrogen chloride, can be further removed by concentration.

[0051] As a preferred technical solution of the present application, the dilution method comprises adding a solvent to make the mass fraction of sodium hexafluorophosphate 20% to 30%, such as 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30%, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0052] As a preferred technical solution of the present application, the resin used for resin deacidification comprises a basic resin.

[0053] Preferably, the temperature for resin deacidification is 0 to 60°C, such as 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, etc., and the time is 5 to 10 hours, such as 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, or 10 hours, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0054] In a second aspect, the present application provides a sodium hexafluorophosphate concentrate obtained by the preparation method of the first aspect.

[0055] Preferably, the purity of sodium hexafluorophosphate in the sodium hexafluorophosphate concentrate is 99.5% to 99.8%, the content of chloride ions is <20 ppm, such as 18 ppm, 15 ppm, 12 ppm, 9 ppm, 7 ppm, 5 ppm, 3 ppm, 1 ppm, or 0 ppm, etc., the HF acid content tested by titration method is <50 ppm, such as 48 ppm, 40 ppm, 35 ppm, 30 ppm, 25 ppm, 20 ppm, 15 ppm, 10 ppm, 5 ppm, 3 ppm, 1 ppm, or 0 ppm, etc., the water content tested by Karl Fischer method is <20 ppm, such as 18 ppm, 15 ppm, 12 ppm, 9 ppm, 7 ppm, 5 ppm, 3 ppm, 1 ppm, or 0 ppm, etc., the content of other metal ions except sodium is <3 ppm, such as 3 ppm, 2 ppm, or 1 ppm, etc., the Hazen color is <150, such as 148, 140, 130, 120, 110, 700, 90, 80, 70, 60, 50, 40, 30, 20, 10, or 5, etc., and the insoluble content is <10 ppm, such as 10 ppm, 5 ppm, or 0 ppm, etc., but not limited to the listed values, and other values not listed in the above value range are also applicable.

[0056] The above index data are used as the qualified judgment standard for the sodium hexafluorophosphate concentrate product of the present application.

[0057] In a third aspect, the application provides a use of the sodium hexafluorophosphate concentrated solution of the second aspect in a sodium ion battery.

[0058] Compared with the prior art, the application has at least the following beneficial effects:

[0059] 1: In order to solve the problems of complex preparation method, large occupied area, difficult impurity removal, long process route and high safety risk of sodium hexafluorophosphate product in the prior art, the application provides a preparation method of sodium hexafluorophosphate concentrated solution, which uses continuous reaction to inhibit the risk of using hydrogen fluoride and improve the yield, uses degassing, filtration, concentration, dilution and acid-removing resin to remove impurities, and further collects by-products to obtain high-purity hydrogen chloride for external sale and high-purity hydrogen fluoride for reuse, thereby being beneficial to reducing the comprehensive cost.

[0060] 2: The preparation method has mild reaction conditions, and the obtained product has high purity (99.5% to 99.8%), low impurity content (chloride ions less than 20 ppm, hydrofluoric acid (calculated as HF) less than 50 ppm, moisture (Karl Fischer method) less than 20 ppm, Hazen color less than 150, and metal ions (Fe, Pb, Na, K, Ca) other than sodium ions less than 3 ppm, and insoluble substances less than 10 ppm). The product can be directly used in an electrolyte of a sodium ion battery, has the same or better battery performance as a product obtained by a common sodium hexafluorophosphate crystallization and impurity removal process. The preparation method has cheap and easily available raw materials, high yield, simple operation, high safety, and all by-products can be recycled and utilized, and the cost is lower than that of a product obtained by a common sodium hexafluorophosphate crystallization process, so that the product can be applied in the fields of 3C, electric vehicles and energy storage.

[0061] 3: The polytetrafluoroethylene membrane microporous folded filter element with a silicon-hydrogen bond is subjected to a silicon-hydrogen addition reaction with 1,3,5-tris-acryloyl-s-triazine and 5,10,15,20-tetrakis(4-vinylphenyl)porphyrin. This step is to successfully connect functional groups to the polytetrafluoroethylene membrane microporous folded filter element through Si-H bond insertion reaction. These functional groups such as porphyrin and s-triazine are subjected to coordination complexation reaction with metal ions. Stable complexes are formed with metal ions. Due to this complexation, metal ions other than sodium ions (such as Fe, Pb, Na, K, Ca, etc.) are intercepted in the polytetrafluoroethylene membrane microporous folded filter element, and sodium ions are not easily complexed with these functional groups due to their specific properties, and thus can smoothly pass through the filter element. This property makes the modified polytetrafluoroethylene membrane microporous folded filter element an effective tool for removing trace metal ions. BRIEF DESCRIPTION OF DRAWINGS

[0062] Figure 1 A process schematic diagram of the continuous reaction in the preparation method of Example 1. DETAILED DESCRIPTION

[0063] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0064] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0065] Example 1

[0066] This embodiment provides a method for preparing a concentrated sodium hexafluorophosphate solution, the preparation method comprising:

[0067] In a 1000 mL three-necked flask, under nitrogen protection, 600 mL of methyl ethyl carbonate as a solvent, along with sodium fluoride and phosphorus pentachloride, were added, ensuring that the molar ratio of sodium fluoride to phosphorus pentachloride was 1:1.2. The mixture was stirred and the temperature was slowly increased to 60 °C for 6 hours to produce a sodium monofluoropentachlorophosphate solution.

[0068] In this example, the fluorinated resin filter element uses a modified polytetrafluoroethylene membrane microporous pleated filter element, and its preparation method is as follows:

[0069] H1: The polytetrafluoroethylene (PTFE) membrane microporous pleated filter element was placed in a plasma device and plasma modified in a tetra(dimethylsiloxy)silane vapor atmosphere. The plasma device used a 500W radio frequency power source with a frequency of 16MHz, a gas flow rate of 16ml / min, and a processing time of 120min to obtain a PTFE membrane microporous pleated filter element with silane-hydrogen bonds.

[0070] H2: Add 2 kg of 1,3,5-triacryloyltriazine (959-52-4), 0.03 kg of 5,10,15,20-tetra(4-vinylphenyl)porphyrin, 5 kg of caster catalyst (CAS No.: 68478-92-2), and 140 kg of polytetrafluoroethylene (PTFE) membrane microporous pleated filter element with silane-hydrogen bonds to a stirred tank, and uniformly disperse them in 1000 kg of toluene. React at 65°C for 130 minutes, filter, and dry to obtain the modified PTFE membrane microporous pleated filter element.

[0071] like Figure 1 As shown, after the reaction is complete, the sodium pentachlorophosphate solution and liquid hydrogen fluoride are introduced into a continuous reactor (tubular reactor) at the same temperature at a molar ratio of hydrogen fluoride to sodium fluoride of 5.2:1 until the reaction is complete. During the reaction, hydrogen chloride gas is generated and introduced into a pressurized distillation column for separation by pressurized distillation. The distillation column has 21 trays, a reflux ratio of 1.2, a top temperature of 5°C, and a top pressure of 1.8 MPa, yielding reusable hydrogen fluoride (mass ratio greater than 99.99%) and exportable hydrogen chloride (mass ratio greater than 99.99%).

[0072] After the reaction is completed, the same temperature condition is maintained, a vacuum pump is opened to slowly extract and degas the reaction bottle, and it takes about 6 hours to end at a pressure of 5 kPa; the degassed sodium hexafluorophosphate solution is filtered by using a fluorine-containing resin PTFE filter core with a pore size of 0.4-1 microns; the pressure is controlled in the range of 0.5-10 kPa, and the temperature is 60 DEG C, and the concentration is performed by heating under reduced pressure; the concentration is adjusted by using a solvent methyl ethyl carbonate; and then the acid is removed by using an alkaline resin at 60 DEG C, and the sodium hexafluorophosphate concentrated solution is obtained after precision filtration.

[0073] Example 2

[0074] The embodiment provides a preparation method of a sodium hexafluorophosphate concentrated solution, the preparation method keeps the molar ratio of sodium fluoride to phosphorus pentachloride at 1:1.2, adjusts the molar ratio of hydrogen fluoride to sodium fluoride from 5.2:1 to 5.1:1, and is completely same as example 1 except the above.

[0075] Example 3

[0076] The embodiment provides a preparation method of a sodium hexafluorophosphate concentrated solution, the preparation method adjusts the molar ratio of sodium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.05, and is completely same as example 1 except the above.

[0077] Example 4

[0078] The embodiment provides a preparation method of a sodium hexafluorophosphate concentrated solution, the preparation method adjusts the molar ratio of hydrogen fluoride to sodium fluoride from 5.2:1 to 5.6:1, and is completely same as example 1 except the above.

[0079] Example 5

[0080] The embodiment provides a preparation method of a sodium hexafluorophosphate concentrated solution, the preparation method adjusts the molar ratio of sodium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.6, and is completely same as example 1 except the above.

[0081] Example 6

[0082] The embodiment provides a preparation method of a sodium hexafluorophosphate concentrated solution, the preparation method comprises:

[0083] In a 1000 mL three-necked flask, 600 mL methyl ethyl carbonate is added as a solvent under nitrogen protection, and sodium chloride and phosphorus pentachloride are added to ensure that the molar ratio of sodium chloride to phosphorus pentachloride is 1:1.1, the reaction is slowly warmed under stirring, and a sodium hexachlorophosphate solution is generated at 60 DEG C for 6 hours.

[0084] After the reaction is completed, the sodium hexachlorophosphate solution and hydrogen fluoride liquid are introduced into the continuous reactor at the same temperature in a molar ratio of hydrogen fluoride to sodium fluoride of 6.2:1 until the reaction is completed; during the reaction, hydrogen chloride gas is generated and introduced into a rectification tower for separation by pressurized rectification, the rectification tower has 21 plates, the reflux ratio is 1.2, the tower top temperature is 5°C, the tower top pressure is 1.8 MPa, and reusable hydrogen fluoride (mass ratio greater than 99.99%) and saleable hydrogen chloride (mass ratio greater than 99.99%) are obtained.

[0085] After the reaction is completed, the sodium hexachlorophosphate solution and hydrogen fluoride liquid are introduced into the continuous reactor at the same temperature in a molar ratio of hydrogen fluoride to sodium fluoride of 6.2:1 until the reaction is completed; during the reaction, hydrogen chloride gas is generated and introduced into a rectification tower for separation by pressurized rectification, the rectification tower has 21 plates, the reflux ratio is 1.2, the tower top temperature is 5°C, the tower top pressure is 1.8 MPa, and reusable hydrogen fluoride (mass ratio greater than 99.99%) and saleable hydrogen chloride (mass ratio greater than 99.99%) are obtained.

[0086] Example 7

[0087] The present example provides a preparation method of a sodium hexafluorophosphate concentrated solution, wherein the molar ratio of sodium chloride to phosphorus pentachloride is adjusted from 1:1.1 to 1:1.45, and other conditions are the same as those in Example 6.

[0088] Example 8

[0089] The present example provides a preparation method of a sodium hexafluorophosphate concentrated solution, wherein the molar ratio of sodium chloride to phosphorus pentachloride is adjusted from 1:1.1 to 1:1.3, the molar ratio of hydrogen fluoride to sodium chloride is adjusted from 6.2:1 to 6.0:1, and other conditions are the same as those in Example 6.

[0090] Example 9

[0091] The present example provides a preparation method of a sodium hexafluorophosphate concentrated solution, wherein the molar ratio of sodium chloride to phosphorus pentachloride is adjusted from 1:1.1 to 1:1.62, the molar ratio of hydrogen fluoride to sodium chloride is kept at 6.2:1, and other conditions are the same as those in Example 6.

[0092] Example 10

[0093] The present example provides a preparation method of a sodium hexafluorophosphate concentrated solution, wherein the molar ratio of sodium chloride to phosphorus pentachloride is adjusted from 1:1.1 to 1:1.3, the molar ratio of hydrogen fluoride to sodium chloride is adjusted from 6.2:1 to 5.8:1, and other conditions are the same as those in Example 6.

[0094] Example 11

[0095] This example provides a preparation method of a sodium hexafluorophosphate concentrated solution, which uses dimethyl carbonate to replace methyl ethyl carbonate, adjusts the molar ratio of sodium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.4, and keeps the molar ratio of hydrogen fluoride to sodium fluoride at 5.2:1, and other conditions are completely the same as those in Example 1.

[0096] Example 12

[0097] This example provides a preparation method of a sodium hexafluorophosphate concentrated solution, which uses dimethyl carbonate to replace methyl ethyl carbonate, adjusts the molar ratio of sodium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.3, adjusts the molar ratio of hydrogen fluoride to sodium fluoride from 5.2:1 to 5.3:1, and other conditions are completely the same as those in Example 11.

[0098] Example 13

[0099] This example provides a preparation method of a sodium hexafluorophosphate concentrated solution, which uses dimethyl carbonate to replace methyl ethyl carbonate, adjusts the molar ratio of sodium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.3, adjusts the molar ratio of hydrogen fluoride to sodium fluoride from 5.2:1 to 5.3:1, and other conditions are completely the same as those in Example 11.

[0100] Example 14

[0101] This example provides a preparation method of a sodium hexafluorophosphate concentrated solution, which keeps the molar ratio of sodium fluoride to phosphorus pentachloride at 1:1.2, keeps the molar ratio of hydrogen fluoride to sodium fluoride at 6.4:1, and other conditions are completely the same as those in Example 13.

[0102] Comparative Example 1

[0103] This comparative example provides a preparation method of a sodium hexafluorophosphate concentrated solution, which does not perform resin deacidification, and uses a common polytetrafluoroethylene filter core for filtration, and other conditions are completely the same as those in Example 1.

[0104] Comparative Example 2

[0105] This comparative example provides a preparation method of a sodium hexafluorophosphate concentrated solution, which does not perform reduced-pressure heating, i.e., does not perform concentration, and uses a common polytetrafluoroethylene filter core for filtration, and other conditions are completely the same as those in Example 1.

[0106] Comparative Example 3

[0107] The comparative example 1 provides a preparation method of sodium hexafluorophosphate concentrate solution, which does not perform vacuum degassing, uses a common polytetrafluoroethylene filter core for filtration, and is identical to the example 1 in other conditions.

[0108] The purity, hazen color, sodium hexafluorophosphate content, free acid, moisture, insoluble matter, and metal ion content of the sodium hexafluorophosphate concentrate solution products obtained in the examples 1-14 and the comparative examples 1-3 are determined, and whether the products are qualified is determined according to the product standards described above.

[0109] The above examples illustrate the detailed structural features of the present application, but the present application is not limited to the above detailed structural features, i.e., it does not mean that the present application must rely on the above detailed structural features to be implemented. It should be understood by those skilled in the art that any improvement on the present application, equivalent replacement of the components selected by the present application, addition of auxiliary components, selection of specific modes, etc., all fall within the protection scope and disclosure scope of the present application.

[0110] The above describes the preferred embodiments of the present application in detail, but the present application is not limited to the specific details in the above embodiments, and within the technical concept scope of the present application, various simple modifications can be made to the technical solutions of the present application, and these simple modifications all belong to the protection scope of the present application.

[0111] In addition, it should be noted that each specific technical feature described in the above specific embodiments can be combined in any appropriate manner without contradiction, and in order to avoid unnecessary repetition, the present application will not further describe various possible combination manners.

[0112] In addition, various different embodiments of the present application can also be combined in any manner, as long as it does not deviate from the idea of the present application, and it should be considered as the disclosed content of the present application.

Claims

1. A method for preparing a concentrated solution of sodium hexafluorophosphate, characterized in that, The preparation method comprises: carrying out a first reaction of sodium halide and phosphorus pentachloride in a solvent to generate a precursor solution; The solvent is a non-aqueous solvent; The sodium halide is sodium chloride or sodium fluoride; the molar ratio of the sodium halide to the phosphorus pentachloride is 1:(1-1.5); The precursor solution is subjected to a second reaction with liquid hydrogen fluoride to generate a sodium hexafluorophosphate solution, specifically, the precursor solution and the liquid hydrogen fluoride are continuously fed into a continuous reactor according to a certain ratio, mixed and reacted to generate the sodium hexafluorophosphate solution; When the sodium halide is sodium chloride, the molar ratio of the hydrogen fluoride to the sodium chloride is (6-6.6):1; when the sodium halide is sodium fluoride, the molar ratio of the hydrogen fluoride to the sodium fluoride is (5-5.5):1; The sodium hexafluorophosphate solution is sequentially subjected to vacuum degassing, filtration, concentration, dilution and resin deacidification to obtain a sodium hexafluorophosphate concentrate; The pressure range of the vacuum degassing is 0.5-10 kPa, and the temperature is 0-60 DEG C; The filtration uses a fluorine-containing resin filter core with a pore size of 0.2-2.0 microns; The fluorine-containing resin filter core adopts a modified polytetrafluoroethylene membrane microporous folded filter core, and the preparation method is as follows: H1: according to weight parts, the polytetrafluoroethylene membrane microporous folded filter core is put into a plasma device, and plasma modification is carried out in a tetrakis(dimethylsiloxy)silane steam atmosphere, a 500 W radio frequency power source plasma device; the radio frequency power source is a frequency of 10-18 MHz; the gas flow is 10-20 ml / min, the processing time is 100-120 min, and a polytetrafluoroethylene membrane microporous folded filter core with a silicon hydrogen bond is obtained; H2: according to weight parts, 0.5-2 parts of 1,3,5-tris-acryloyl-s-triazine, 0.003-0.03 parts of 5,10,15,20-tetrakis(4-vinylphenyl)porphyrin, 2-5 parts of Karstedt catalyst and 100-140 parts of the polytetrafluoroethylene membrane microporous folded filter core with a silicon hydrogen bond are uniformly dispersed in 500-1000 parts of toluene, and reaction is carried out at 60-70 DEG C for 100-150 min; after filtration and drying, a modified polytetrafluoroethylene membrane microporous folded filter core is obtained; The concentration method is vacuum heating, and the pressure range of the vacuum heating is 0.5-10 kPa, and the temperature range is 30-60 DEG C; The dilution method is to add the same solvent as the first reaction to make the mass fraction of sodium hexafluorophosphate be 20%-30%; The resin used for the resin deacidification includes an alkaline resin.

2. The production method according to claim 1, characterized by, The non-aqueous solvent is any one of methyl ethyl carbonate, dimethyl carbonate and diethyl carbonate or a mixed solvent formed by at least two of them.

3. The preparation method according to claim 1, characterized in that, The second reaction is carried out at 0-60 DEG C under an inert atmosphere.

4. The preparation method according to claim 1, characterized in that, The preparation method further comprises collecting hydrogen chloride and hydrogen fluoride gas generated in the second reaction; the collection method comprises using a pressurized rectifying column for pressurized rectification.

5. The preparation method according to claim 4, characterized in that, The collected hydrogen fluoride gas is recycled to the second reaction.

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