A highly efficient and energy-saving process for preparing sodium difluorophosphate

Abstract

This invention relates to a highly efficient and energy-saving process for preparing sodium difluorophosphate, comprising the following steps: 1) dissolving sodium hexafluorophosphate in diethyl carbonate solvent, adding a catalyst for activation to obtain an activated reaction solution; 2) adjusting the temperature of the activated reaction solution to below 50°C, adding sodium carbonate, gradually raising the temperature to 90-100°C and maintaining the temperature for reaction; 3) after the reaction is completed, cooling to room temperature, separating the solid and liquid, washing, and drying to obtain the final product. This method offers controllable process, stable yield, safety, and environmental friendliness, solving the problems of low reaction efficiency, high energy consumption, difficult separation of byproducts, and high safety risks in existing technologies, and meeting the demand for high-purity sodium difluorophosphate in the sodium-ion battery field.

Description

Technical Field

[0001] This invention belongs to the field of fluorochemical fine chemical preparation technology, specifically relating to a method for preparing sodium difluorophosphate efficiently and energy-savingly using DEC (diethyl carbonate) as a solvent and a segmented heating process. Background Technology

[0002] Sodium difluorophosphate (NaPO2F2), as a key additive in sodium-ion battery electrolytes, can significantly improve battery cycle stability and low-temperature performance, showing broad application prospects. Existing preparation processes mostly employ solid-phase methods or traditional organic solvent systems, which suffer from low yields (10%-20%), stringent reaction conditions, high energy consumption, and difficulties in separating byproducts. Some processes require the use of toxic gases such as HF, posing safety risks and exhibiting poor environmental friendliness. For example, CN116924381A discloses a method for preparing sodium difluorophosphate, comprising the following steps: reacting sodium oxalate and sodium hexafluorophosphate in a polar solvent, wherein the molar ratio of sodium oxalate to sodium hexafluorophosphate is 1.9-2.2:1, the reaction temperature is 90-120℃, and the reaction time is 90-150 min; after the reaction is complete, filtering the reaction solution yields a mixture containing sodium difluorophosphate and sodium fluoride; and obtaining sodium difluorophosphate through separation and purification. The polar solvent is one of dimethyl sulfoxide, anhydrous acetonitrile, dimethylformamide, acetone, ethylene glycol, and ethanol.

[0003] Therefore, the present invention aims to provide a process-controllable, yield-stable, safe and environmentally friendly method for preparing sodium difluorophosphate, solving the problems of low reaction efficiency, high energy consumption, difficult separation of by-products and high safety risks in the prior art, and meeting the demand for high-purity sodium difluorophosphate in the sodium-ion battery field. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a highly efficient and energy-saving process for preparing sodium difluorophosphate. This method offers controllable process, stable yield, safety, and environmental friendliness, solving the problems of low reaction efficiency, high energy consumption, difficulty in separating byproducts, and high safety risks in existing technologies, thus meeting the demand for high-purity sodium difluorophosphate in the sodium-ion battery field.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A highly efficient and energy-saving process for preparing sodium difluorophosphate includes the following steps: 1) Raw material dissolution and activation: Sodium hexafluorophosphate (NaPF6) is dissolved in diethyl carbonate (DEC) solvent, and a catalyst is added for activation to obtain an activated reaction solution; 2) Segmented heating reaction: Adjust the temperature of the activation reaction solution to below 50℃, add sodium carbonate (Na2CO3), gradually raise it to 90-100℃ and keep it at the temperature to produce sodium difluorophosphate, sodium fluoride (NaF) and carbon dioxide (CO2). 3) Post-processing and purification: After the reaction is completed, the mixture is cooled to room temperature and separated into solid and liquid phases. After washing and drying, high-purity sodium difluorophosphate is obtained.

[0006] Specifically, in step 1), the catalyst is triphenyl phosphite, and the amount of catalyst used is 2%-5% of the mass of sodium hexafluorophosphate.

[0007] Furthermore, in step 1), activation is carried out at 60-85℃ for 2-4 hours.

[0008] Furthermore, in step 1), the ratio of sodium hexafluorophosphate to the solvent diethyl carbonate is 1g:8-15mL.

[0009] Specifically, in step 2), the molar ratio of sodium carbonate to sodium hexafluorophosphate is 1-2.5:1.

[0010] Furthermore, in step 2), during the segmented heating process, the temperature is increased by 8-15°C every half hour, and the holding time for each segment is 20-45 minutes, gradually increasing to 100°C and holding for reaction, with the final holding time at 100°C being 2-4 hours. Preferably, the temperature is increased by 10°C every half hour, and the holding time for each segment is 30 minutes.

[0011] Specifically, in step 3), dimethyl carbonate is used for washing.

[0012] Furthermore, in step 3), the drying conditions are: vacuum drying at 50-60℃ for 12-20 hours, preferably vacuum drying at 55℃ for 15 hours.

[0013] Compared with the prior art, the method of the present invention has the following advantages and beneficial effects: In the method of this invention, DEC with a boiling point of 117°C is used as a solvent, and sodium hexafluorophosphate is added in proportion to completely dissolve it. Triphenyl phosphite is added as a catalyst to carry out an activation reaction to obtain an activated reaction solution. Then, sodium carbonate is added at a lower temperature to carry out a staged heating reaction. After the reaction is completed, high-purity sodium difluorophosphate is obtained by solid-liquid separation, washing, and drying.

[0014] The method of this invention is controllable, has stable yield, and is safe and environmentally friendly. It solves the problems of low reaction efficiency, high energy consumption, difficulty in separating by-products, and high safety risks in the prior art, and meets the demand for high-purity sodium difluorophosphate in the sodium-ion battery field. Detailed Implementation

[0015] The technical solution of the present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the present invention is not limited thereto.

[0016] In the following examples, all raw materials used are common commercially available products that can be purchased directly, or can be prepared using conventional techniques in the art. Example 1

[0017] A highly efficient and energy-saving process for preparing sodium difluorophosphate includes the following steps: 1. Raw material dissolution and activation: At room temperature, add 200 mL of DEC solvent to a 500 mL three-necked flask, add 20 g (0.12 mol) of sodium hexafluorophosphate, stir until completely dissolved, add 0.4 g of triphenyl phosphite, heat to 70 °C, and activate at a constant temperature for 2 hours to obtain the activated reaction solution; 2. Segmented heating reaction: The activated reaction solution was naturally cooled to 50℃, and 25.2g of sodium carbonate (0.24mol, molar ratio 2:1) was added. The mixture was stirred evenly and the segmented heating was started: 50℃ for 30 minutes → 60℃ for 30 minutes → 70℃ for 30 minutes → 80℃ for 30 minutes → 90℃ for 30 minutes → 100℃ for 3 hours. The CO2 generated during the reaction was absorbed and treated by alkaline solution. 3. Post-processing and purification: After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain a solid mixture. It was washed three times with 80 mL of dimethyl carbonate to remove unreacted raw materials and byproduct sodium fluoride. The washed solid was placed in a vacuum drying oven and dried under vacuum at 55°C for 15 hours to obtain 12.8 g of white powdered sodium difluorophosphate. The purity was tested to be 99.2% and the yield was 91.4%. Example 2

[0018] A highly efficient and energy-saving process for preparing sodium difluorophosphate includes the following steps: 1. Raw material dissolution and activation: At room temperature, add 200 mL of DEC solvent and 20 g of sodium hexafluorophosphate to a 500 mL three-necked flask, stir until completely dissolved, add 0.8 g of triphenyl phosphite, heat to 70 °C, and activate at a constant temperature for 2 hours to obtain the activated reaction solution; 2. Segmented heating reaction: Cool the activated reaction solution naturally to 50℃, add 25.2g of sodium carbonate (molar ratio 2:1), stir evenly, and start segmented heating: 50℃ for 30 minutes → 60℃ for 30 minutes → 70℃ for 30 minutes → 80℃ for 30 minutes → 90℃ for 30 minutes → 100℃ for 2.5 hours. The CO2 generated during the reaction is absorbed and treated by alkaline solution. 3. Post-processing and purification: After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain a solid mixture. It was washed three times with 80 mL of dimethyl carbonate. The washed solid was placed in a vacuum drying oven and dried under vacuum at 55 °C for 15 hours to obtain 12.6 g of white powdered sodium difluorophosphate. The purity was tested to be 99% and the yield was 90.1%. Example 3

[0019] A highly efficient and energy-saving process for preparing sodium difluorophosphate includes the following steps: 1. Raw material dissolution and activation: At room temperature, add 200 mL of DEC solvent and 20 g of sodium hexafluorophosphate to a 500 mL three-necked flask, stir until completely dissolved, add 0.6 g of triphenyl phosphite, heat to 70 °C, and activate at a constant temperature for 2 hours to obtain the activated reaction solution; 2. Segmented heating reaction: Cool the activated reaction solution naturally to 50℃, add 25.2g of sodium carbonate (molar ratio 2:1), stir evenly, and start segmented heating: 50℃ for 30 minutes → 60℃ for 30 minutes → 70℃ for 30 minutes → 80℃ for 30 minutes → 90℃ for 30 minutes → 100℃ for 3.5 hours. The CO2 generated during the reaction is absorbed and treated by alkaline solution. 3. Post-processing and purification: After the reaction was completed, the mixture was cooled to room temperature and filtered to obtain a solid mixture. It was washed three times with 80 mL of dimethyl carbonate. The washed solid was placed in a vacuum drying oven and dried under vacuum at 55 °C for 15 hours to obtain 12.9 g of white powdered sodium difluorophosphate. The purity was tested to be 99.3% and the yield was 92.0%.

[0020] Comparative Example 1 This comparative example does not involve segmented heating.

[0021] 1. Raw material dissolution and activation: Same as in Example 1; 2. Direct heating reaction: Cool the activated reaction solution to 50°C, add 25.2g of sodium carbonate, and directly heat to 100°C and keep at that temperature for 5 hours. Other conditions are the same as in Example 1. 3. Post-processing purification: Same as in Example 1, 10.2g of sodium difluorophosphate product was obtained with a purity of 97.5% and a yield of 72.8%.

[0022] Comparative Example 2

[0023] This comparative example did not contain a catalyst.

[0024] 1. Raw material dissolution: In a 500mL three-necked flask, add 200mL of DEC solvent and 20g of sodium hexafluorophosphate. Stir until completely dissolved. No catalyst is added. Heat to 70℃ and activate at this temperature for 2 hours to obtain the activated reaction solution. 2. Segmented heating reaction: The activated reaction solution was naturally cooled to 50°C, 25.2g of sodium carbonate was added, and the reaction was carried out according to the segmented heating process in Example 1, with other conditions the same as in Example 1; 3. Post-processing purification: Same as in Example 1, 9.5g of sodium difluorophosphate product was obtained with a purity of 96.8% and a yield of 67.8%.

[0025] Example Effect Verification The product yield and purity data for each embodiment and comparative example are shown in the table below.

[0026]

[0027] As shown in the table above, the segmented heating process of this invention, when used in conjunction with a catalyst, can significantly improve the yield and purity of sodium difluorophosphate, solve the core pain points of existing technologies, and has good prospects for industrial application.

Claims

1. A highly efficient and energy-saving process for preparing sodium difluorophosphate, characterized in that, Includes the following steps: 1) Dissolve sodium hexafluorophosphate in diethyl carbonate, add a catalyst to activate it, and obtain an activated reaction solution; 2) Adjust the temperature of the activation reaction solution to below 50℃, add sodium carbonate, gradually raise it to 90-100℃ and keep it at that temperature for the reaction; 3) After the reaction is complete, cool to room temperature, separate the solid and liquid, and wash and dry to obtain the product.

2. The high-efficiency and energy-saving sodium difluorophosphate preparation process as described in claim 1, characterized in that, In step 1), the catalyst is triphenyl phosphite, and the amount of catalyst used is 2%-5% of the mass of sodium hexafluorophosphate.

3. The high-efficiency and energy-saving sodium difluorophosphate preparation process as described in claim 1, characterized in that, In step 1), activate at 60-85℃ for 2-4 hours.

4. The high-efficiency and energy-saving sodium difluorophosphate preparation process as described in claim 1, characterized in that, In step 1), the ratio of sodium hexafluorophosphate to diethyl carbonate solvent is 1g:8-15mL.

5. The high-efficiency and energy-saving sodium difluorophosphate preparation process as described in claim 1, characterized in that, In step 2), the molar ratio of sodium carbonate to sodium hexafluorophosphate is 1-2.5:

1.

6. The high-efficiency and energy-saving sodium difluorophosphate preparation process as described in claim 1, characterized in that, In step 2), the temperature is increased by 8-15°C every half hour, and the holding time for each segment is 20-45 minutes. The temperature is gradually increased to 100°C and held for reaction. The final holding time at 100°C is 2-4 hours.

7. The high-efficiency and energy-saving sodium difluorophosphate preparation process as described in claim 1, characterized in that, In step 3), dimethyl carbonate is used for washing.

8. The high-efficiency and energy-saving sodium difluorophosphate preparation process as described in claim 1, characterized in that, In step 3), the drying conditions are: vacuum drying at 50-60℃ for 12-20 hours.

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