A method for preparing high-purity phosphorus pentafluoride based on synergistic regulation of water activity and fluorine chemical potential
By synergistically regulating water activity and fluorine chemical potential, and employing low-temperature reaction and multi-stage condensation distillation techniques, the purity and stability issues in the preparation of phosphorus pentafluoride were resolved, achieving the generation of high-purity phosphorus pentafluoride and meeting the application requirements of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- GUIZHOU JURUI NEW MATERIAL TECH CO LTD
- Filing Date
- 2026-02-12
- Publication Date
- 2026-06-09
AI Technical Summary
In existing methods for preparing phosphorus pentafluoride, the lack of synergistic regulation between water activity and fluorine chemical potential leads to unstable intermediates, high HF residue, uneven mixing of the reaction system, easy generation of local high-temperature zones, frequent side reactions, and difficulty in obtaining high-purity phosphorus pentafluoride.
By controlling the synergistic regulation of water activity and fluorine chemical potential, a stable hexafluorophosphate intermediate is generated through low-temperature reaction, controlled dehydration, and multi-stage condensation distillation. The intermediate is then decomposed at low temperature to generate high-purity phosphorus pentafluoride. The specific steps include the system design of raw material mixing, low-temperature reaction, dehydration, and decomposition pathway.
High purity (≥99.95%) and high yield (96.2%~97.1%) of phosphorus pentafluoride were achieved, meeting the purity and stability requirements of phosphorus pentafluoride for lithium-ion batteries and reducing the probability of HF residue and side reactions.
Smart Images
Figure CN122166731A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of fluoride chemical synthesis and preparation technology of key materials for lithium-ion batteries, specifically to a method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential. Background Technology
[0002] Currently, phosphorus pentafluoride is a key precursor for lithium hexafluorophosphate in lithium-ion battery electrolytes, and its purity directly affects the electrochemical stability, water sensitivity, and cycle life of the electrolyte. Existing methods for preparing phosphorus pentafluoride mainly include the P2O5–HF method, the PCl5–HF method, the direct fluorination of yellow phosphorus, and the polyphosphoric acid (PPA)–HF method. However, these existing technologies generally suffer from the following common problems: 1. The lack of synergistic regulation between water activity and fluorine chemical potential during the reaction process leads to instability of the intermediate and high residual HF content; 2. Uneven mixing of the reaction system can easily lead to localized high-temperature zones, triggering side reactions and reducing product purity; 3. The dehydration process is uncontrollable or incomplete, causing PF5 to undergo secondary reactions or carry impurities during the decomposition stage; 4. Existing methods are insufficient to stably obtain battery-grade PF5 with a purity ≥99.95% under industrial conditions.
[0003] Therefore, there is an urgent need for a method that can precisely control the water activity and fluorine chemical potential distribution of the reaction system on an industrial scale to achieve PF5 A method for preparing high-purity, high-yield, safe and stable materials. Summary of the Invention
[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential. By systematically designing the raw material mixing, low-temperature reaction, dehydration process and decomposition path, the intermediate structure of hexafluorophosphate is stabilized, significantly reducing HF residue and the probability of side reactions, and achieving one-time high-purity generation of PF5, which meets the strict requirements of purity and stability for PF5 used in lithium-ion batteries.
[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential, characterized by comprising the following steps: Step 1 Polyphosphoric acid and anhydrous hydrogen fluoride are mixed in a mass ratio of 1:1.8 to 2.2 through a pipeline mixer and then fed into a reaction vessel. The reaction temperature is controlled at 0 to 10°C and the reaction time is 2 to 5 hours to generate hexafluorophosphate intermediate. Step Two The water activity of the reaction system is reduced through controlled dehydration, thus stabilizing the intermediate. Step 3 The intermediate is thermally decomposed at 150–250 °C to generate phosphorus pentafluoride gas. Step Four The phosphorus pentafluoride gas obtained in step three is subjected to low-temperature distillation to obtain phosphorus pentafluoride with a purity of not less than 99.95%.
[0006] In this technical solution, the dehydration method is to pass fuming sulfuric acid through it for dehydration treatment, and the amount of fuming sulfuric acid added is 0.4 to 0.6 times the mass of polyphosphoric acid.
[0007] In this technical solution, the low temperature mentioned in step four is below -85℃.
[0008] In this technical solution, the concentration of polyphosphoric acid in step one is 85% to 95%, and the purity of anhydrous hydrogen fluoride is ≥99.9%.
[0009] In this technical solution, the mixing speed of the pipeline mixer in step one is 100-500 rpm.
[0010] In this technical solution, the fuming sulfuric acid is introduced at a rate of 0.1 to 0.5 L / min, and the dehydration time is 1 to 3 h.
[0011] In this technical solution, the distillation and purification in step four uses a multi-stage condenser to collect fractions below -85°C.
[0012] The advantages of this invention compared with the prior art are: by systematically designing the raw material mixing, low-temperature reaction, dehydration process and decomposition path, the structure of the hexafluorophosphate intermediate is stabilized, significantly reducing HF residue and the probability of side reactions, achieving one-time high-purity production of PF5, and meeting the strict requirements of purity and stability for PF5 used in lithium-ion batteries. Attached Figure Description
[0013] Figure 1 This is a flowchart of the present invention. Detailed Implementation
[0014] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0015] It is a method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential, including: Step 1 Polyphosphoric acid and anhydrous hydrogen fluoride are mixed in a mass ratio of 1:1.8 to 2.2 through a pipeline mixer and then introduced into a reactor. The reaction temperature is controlled at 0 to 10°C and the reaction time is 2 to 5 hours to keep the water activity in the system below the decomposition threshold of hexafluorophosphate intermediate, thereby generating a stable hexafluorophosphate intermediate, avoiding local overheating, inhibiting side reactions, and constructing a uniform fluorine chemical potential field.
[0016] Step Two The water activity of the reaction system is reduced through controlled dehydration, thus stabilizing the intermediate. Step 3 The intermediate is thermally decomposed at 150–250 °C to generate phosphorus pentafluoride gas. In a specific embodiment, the dehydrated reactants are fed into a heating decomposition tower and thermally decomposed at 150–250 °C to decompose the hexafluorophosphate intermediate along a preset reaction path to generate phosphorus pentafluoride gas. Step Four The phosphorus pentafluoride gas obtained in step three is subjected to low-temperature distillation to obtain phosphorus pentafluoride with a purity of not less than 99.95%. In a specific embodiment, the generated phosphorus pentafluoride gas is purified by distillation at a temperature below -85 °C through a multi-stage condenser, and the target fraction is collected to obtain a high-purity phosphorus pentafluoride product with a purity of not less than 99.95%.
[0017] In this embodiment, the dehydration method involves introducing fuming sulfuric acid. The amount of fuming sulfuric acid added is 0.4 to 0.6 times the mass of polyphosphoric acid, preferably 0.5 times. Fuming sulfuric acid is introduced into the reaction system at a controlled rate to further reduce the water activity of the system and effectively remove HF from the coordination environment of the intermediate. The dehydration time is 1 to 3 hours. This step is not simply dehydration, but rather a targeted regulation of the water activity of the intermediate and the chemical potential of HF to improve the selectivity of the subsequent thermal decomposition stage.
[0018] In this embodiment, the low temperature mentioned in step four is below -85°C.
[0019] In this embodiment, the concentration of polyphosphoric acid in step one is 85% to 95%, and the purity of anhydrous hydrogen fluoride is ≥99.9%.
[0020] In this embodiment, the mixing speed of the pipeline mixer in step one is 100–500 rpm to ensure a uniform distribution of the fluorine chemical potential in the reaction system. In this embodiment, the fuming sulfuric acid is introduced at a rate of 0.1–0.5 L / min, and the dehydration time is 1–3 h. After dehydration, the free HF content in the intermediate is below the threshold for side reactions occurring during the decomposition stage.
[0021] In this embodiment, the distillation purification in step four uses a multi-stage condenser to collect fractions below -85°C.
[0022] The following is an example of a production process: Example
[0023] 100 kg of 90% polyphosphoric acid and 200 kg of 99.9% anhydrous hydrogen fluoride were mixed in a pipeline mixer at a mixing speed of 300 rpm and then pumped into a reactor. The temperature was controlled at 5°C, and the reaction was carried out for 3 hours to generate hexafluorophosphate intermediate. Subsequently, 50 kg of fuming sulfuric acid was introduced at a rate of 0.3 L / min for dehydration for 2 hours. The dehydrated product was transferred to a heating decomposition tower and heated to 200°C to decompose, generating PF5 gas. The gas was purified by a -85°C distillation tower, and the fraction was collected to obtain PF5 product with a purity of 99.96% and a yield of 96.2%. Example
[0024] 80 kg of 85% polyphosphoric acid and 160 kg of 99.9% anhydrous hydrogen fluoride were mixed in a pipeline mixer at a mixing speed of 200 rpm and introduced into a reactor. The reaction was carried out at 0°C for 5 h. Subsequently, 40 kg of fuming sulfuric acid was introduced at a rate of 0.1 L / min for dehydration for 3 h. The dehydrated product was transferred to a heating decomposition tower at 150°C to decompose and generate PF5 gas. After distillation at -85°C, PF5 with a purity of 99.95% was obtained, with a yield of 95.5%. Example
[0025] 120 kg of 95% polyphosphoric acid and 240 kg of 99.9% anhydrous hydrogen fluoride were mixed at a rate of 500 rpm in a pipeline mixer at a reaction temperature of 10°C for 2 h. Then, 60 kg of fuming sulfuric acid was introduced at a rate of 0.5 L / min for dehydration for 1 h. The dehydrated product was transferred to a heating decomposition tower at 250°C to decompose and generate PF5 gas. After distillation at -85°C, PF5 with a purity of 99.97% and a yield of 97.1% was obtained.
[0026] Comparative example: Using the existing tubular reactor method (refer to CN113955729A), the purity is only 99.8% and the yield is 92%.
[0027] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations of these embodiments without departing from the principles and spirit of the present invention still fall within the protection scope of the present invention.
Claims
1. A method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential, characterized in that... Includes the following steps: Step 1 Polyphosphoric acid and anhydrous hydrogen fluoride are mixed in a mass ratio of 1:1.8 to 2.2 through a pipeline mixer and then fed into a reaction vessel. The reaction temperature is controlled at 0 to 10°C and the reaction time is 2 to 5 hours to generate hexafluorophosphate intermediate. Step Two The water activity of the reaction system is reduced through controlled dehydration, thus stabilizing the intermediate. Step 3 The intermediate is thermally decomposed at 150–250 °C to generate phosphorus pentafluoride gas. Step Four The phosphorus pentafluoride gas obtained in step three is subjected to low-temperature distillation to obtain phosphorus pentafluoride with a purity of not less than 99.95%.
2. The method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential according to claim 1, characterized in that... The dehydration method involves introducing fuming sulfuric acid for dehydration treatment, with the amount of fuming sulfuric acid added being 0.4 to 0.6 times the mass of polyphosphoric acid.
3. The method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential according to claim 1, characterized in that... The low temperature mentioned in step four is below -85℃.
4. The method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential according to claim 1, characterized in that... The concentration of polyphosphoric acid mentioned in step one is 85% to 95%, and the purity of anhydrous hydrogen fluoride is ≥99.9%.
5. The method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential according to claim 1, characterized in that... The mixing speed of the pipe mixer in step one is 100-500 rpm.
6. The method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential according to claim 2, characterized in that... The fuming sulfuric acid is introduced at a rate of 0.1–0.5 L / min, and the dehydration time is 1–3 h.
7. The method for preparing high-purity phosphorus pentafluoride based on the synergistic regulation of water activity and fluorine chemical potential according to claim 1, characterized in that... The distillation purification in step four uses a multi-stage condenser to collect fractions below -85°C.