A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas

Abstract

The present invention belongs to the technical field of phosphorus pentafluoride preparation, and specifically relates to a method for synthesizing phosphorus pentafluoride by using yellow phosphorus and fluorine gas. The synthesis method comprises the steps of dissolving yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution, then passing the yellow phosphorus solution and fluorine gas into a microchannel reactor for mixed reaction, and separating and purifying the generated gaseous product through a pressurized condensation system to obtain phosphorus pentafluoride. The synthesis method of the present invention utilizes a specific inert solvent to dissolve highly reactive yellow phosphorus, and then continuously synthesizes phosphorus pentafluoride by reacting the yellow phosphorus solution with fluorine gas in a microchannel reactor through a gas-liquid phase reaction. The method has the advantages of low reaction temperature, high reaction efficiency, few reaction by-products, and high product yield.

Description

Technical Field

[0001] The invention belongs to the technical field of phosphorus pentafluoride preparation, and particularly relates to a method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Background Art

[0002] Phosphorus pentafluoride (PF5) is an important phosphorus-halogen compound. It is a colorless, foul-smelling gas at room temperature and pressure. It is highly irritating to the skin, eyes, and mucous membranes. It is a highly reactive compound and widely used in industry. Lithium-ion secondary batteries using lithium hexafluorophosphate as an electrolyte have gained widespread use due to their numerous advantages. Phosphorus pentafluoride gas has found new applications as a raw material for the synthesis of lithium hexafluorophosphate. Currently, the industry primarily uses PF5 and LiF as raw materials, using HF as a solvent, to synthesize LiPF6. Therefore, the synthesis of high-purity phosphorus pentafluoride is crucial for the synthesis of lithium hexafluorophosphate.

[0003] The current process for synthesizing phosphorus pentafluoride mainly uses the reaction of hydrofluoric acid and phosphorus pentachloride to synthesize phosphorus pentafluoride. However, this method will produce a large amount of hydrochloric acid as a by-product, and hydrofluoric acid is highly corrosive to equipment, the raw material utilization rate is not high, and the requirements for the reaction device are high.

[0004] Synthesizing PF5 through the direct reaction of fluorine gas and elemental phosphorus offers the advantage of high raw material utilization. However, currently disclosed direct synthesis methods primarily utilize a gas-solid phase reaction between gaseous elemental fluorine gas and solid elemental phosphorus. This method suffers from high reaction temperatures (for red phosphorus), difficult-to-control exothermic reaction (for yellow phosphorus), low reaction efficiency, and poor reaction continuity. Patent publication number CN107619028A describes a highly efficient and continuous phosphorus pentafluoride synthesis device and process. This device utilizes a fluorine gas injection nozzle installed directly below the outlet of a screw feeder. The nozzle injects a high-speed fluorine gas stream at a specific downward angle, entraining powdered red phosphorus delivered in a fixed quantity by the screw feeder. The two streams form a turbulent gas / solid flow that rotates downward, resulting in a continuous and efficient reaction to produce phosphorus pentafluoride gas. While this device and process achieve a continuous reaction, it still utilizes a gas-solid phase reaction, which still presents challenges such as high reaction temperatures and low reaction efficiency. Furthermore, the high-temperature reaction also presents challenges such as low product purity and yield due to numerous side reactions. The existing gas-liquid phase reaction using fluorine gas and liquid elemental phosphorus is carried out above the melting point of elemental phosphorus. This has the following problems: high risk (yellow phosphorus is prone to spontaneous combustion above the melting point), low reaction efficiency (liquid elemental phosphorus has low compatibility with fluorine gas), and low product purity and yield due to many side reactions. Summary of the Invention

[0005] In response to the shortcomings and deficiencies of the above-mentioned prior art, the primary objective of the present invention is to provide a method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. This method utilizes a specific inert solvent to dissolve highly reactive yellow phosphorus, which is then reacted with fluorine gas in a microchannel reactor via a gas-liquid phase reaction to continuously synthesize phosphorus pentafluoride. This method offers the advantages of low reaction temperature, high reaction efficiency, minimal reaction byproducts, and high product yield.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0008] Yellow phosphorus is dissolved in an inert solvent to prepare a yellow phosphorus solution, which is then introduced into a microchannel reactor with fluorine gas for mixed reaction, and the generated gas product is separated and purified through a pressurized condensation system to obtain phosphorus pentafluoride.

[0009] The present invention relates to the following chemical reaction:

[0010] Yellow phosphorus (P4) reacts with fluorine gas (F2) to form phosphorus pentafluoride (PF5):

[0011] P4 + 10F2 → 4PF5.

[0012] Furthermore, the inert solvent is dichloromethane or carbon tetrachloride, and the water content of the inert solvent is ≤20 ppm. By controlling the water content of the inert solvent, the risk of side reactions between the reaction raw materials and reaction products and water can be effectively reduced.

[0013] The key to the present invention is that an inert solvent is used to dissolve yellow phosphorus before the reaction. The gas-liquid phase reaction between the yellow phosphorus solution and fluorine gas makes it suitable for the mixed reaction in a microchannel reactor. The inert solvent used must be able to dissolve yellow phosphorus well and have a certain solubility for fluorine gas, allowing for good mixed contact in the microchannel reactor. It must also be reactive towards both yellow phosphorus and fluorine gas under the reaction conditions controlled in the microchannel reactor. The inert solvent selected under these requirements can ensure the gas-liquid phase reaction efficiency of yellow phosphorus and fluorine gas and reduce the occurrence of side reactions, thereby improving product yield and purity.

[0014] Furthermore, the method for dissolving yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution comprises grinding the yellow phosphorus into a powder under an inert atmosphere, then adding the powder to the inert solvent and stirring to dissolve the solution at a temperature of 30 to 45°C. Grinding the yellow phosphorus into a powder can accelerate the dissolution of the yellow phosphorus, and the yellow phosphorus can dissolve more quickly at the above dissolution temperature while ensuring good operational safety (reducing the risk of spontaneous combustion).

[0015] Furthermore, the mass concentration of the yellow phosphorus solution is 30-50%. If the concentration is too low, the single batch production efficiency is low and the production cost increases; if the concentration is too high, solid yellow phosphorus may be precipitated from supersaturation under the reaction conditions controlled in the microchannel reactor, affecting the reaction efficiency.

[0016] Furthermore, the purity of the fluorine gas is greater than 99.9%. Under the above fluorine gas purity requirements, the risk of introducing difficult-to-separate impurities through the raw materials can be reduced.

[0017] Furthermore, the molar ratio of yellow phosphorus (P4) to fluorine gas (F2) is 1:10 to 12. The theoretical reaction molar ratio of P4 to F2 is 1:10. While using a slightly excess amount of fluorine gas can help improve the yellow phosphorus conversion rate, a large excess can increase the load on the reaction unit and the energy consumption for subsequent product separation.

[0018] Furthermore, the microchannel reactor is made of polytetrafluoroethylene material. By adopting the corrosion-resistant polytetrafluoroethylene material, corrosion of the reaction device and introduction of impurities can be avoided.

[0019] Furthermore, the channel diameter of the microchannel reactor is 1-2 mm. The channel diameter of the microchannel reactor can be appropriately adjusted according to the production scale, the purpose of which is to achieve good mixing of the yellow phosphorus solution and the fluorine gas.

[0020] Furthermore, the temperature of the mixing reaction in the microchannel reactor is between -10°C and 0°C, and the pressure is between 1.0 and 2.0 MPa. Under the above temperature and pressure conditions of the microchannel reactor, a good yield and purity of the target product can be simultaneously achieved. Excessively low temperature and pressure lead to low reaction efficiency and reduced target product yield; excessively high temperature and pressure lead to an increase in uncontrollable side reactions, an increase in the content of by-product impurities in the product, and a decrease in product purity.

[0021] Furthermore, the reaction time of the mixing reaction in the microchannel reactor is 1 to 10 minutes. Under the above reaction time, a good conversion rate can be ensured while taking into account production efficiency.

[0022] Under the above microchannel reactor parameter conditions, the mixing of fluorine gas and yellow phosphorus solution and the gas-liquid contact reaction can be well achieved, thereby achieving good product yield and purity and having high production efficiency.

[0023] Furthermore, the separation and purification by a pressurized condensation system refers to separation by pressurized condensation, collecting condensed components at a temperature of 5-15°C and a pressure of 3-4 MPa to obtain phosphorus pentafluoride with a purity of >99%. Pressurized condensation separation is a conventional method for separating and purifying gaseous components. Its principle is to achieve separation by utilizing the differences in critical temperature and critical pressure of different gaseous components. Within a certain temperature and pressure range, components with a critical temperature higher than the temperature and / or a critical pressure lower than the pressure are condensed into liquids, while components with a critical temperature lower than the temperature and / or a critical pressure higher than the pressure remain in a gaseous state, thereby achieving separation. The target product, phosphorus pentafluoride, has a critical temperature of 18.95° C. and a critical pressure of 3.39 MPa. Under the conditions of a temperature of 5-15° C. and a pressure of 3-4 MPa, phosphorus pentafluoride can be condensed into a liquid state while most impurity components (such as unreacted F2 (critical temperature -128.8° C.) and possible main by-product PF3 (critical temperature -2.0° C.)) can be kept in a gaseous state, thereby achieving separation and purification of phosphorus pentafluoride.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention improves the method of synthesizing PF5 by directly reacting fluorine gas with elemental phosphorus from the traditional gas-solid phase reaction mode to a gas-liquid phase reaction mode. By selecting a suitable inert solvent, PF5 can be efficiently synthesized at a lower reaction temperature, while reducing the occurrence of side reactions (mainly PF3 produced by incomplete fluorination, and HF and POF3 produced by the reaction of raw material F2 and product PF5 with trace water in the system), thereby improving the product yield and purity.

[0026] (2) The present invention further uses a microchannel reactor to improve the heat transfer efficiency and mass transfer efficiency of the gas-liquid phase reaction. The reaction heat can be quickly discharged, reducing the side reactions and safety risks caused by heat accumulation, while improving the reaction conversion rate.

[0027] (3) The synthesis method of the present invention has low requirements on equipment, is suitable for continuous production, and can significantly improve production efficiency and reduce production costs. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

[0029] Example 1

[0030] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0031] Yellow phosphorus was ground into a powder under nitrogen protection and then added to a dichloromethane solvent (dried and dehydrated to a water content of ≤20 ppm before use) with stirring and dissolving at 35-40°C to prepare a 30% yellow phosphorus solution. This solution was then mixed with fluorine gas (purity >99.9%) at a molar ratio of 1:10 (phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 1 mm channel diameter. The reaction temperature in the microchannel reactor was controlled at -10°C, the pressure at 1.0 MPa, and the reaction time for 3 minutes. The generated gas was passed into a pressurized condensation system for pressurized condensation separation. The condensed fraction at 5°C and 3 MPa was collected to obtain phosphorus pentafluoride.

[0032] The purity of the phosphorus pentafluoride obtained in this example was 99.5% (infrared detection), and the calculated product yield was 80% (actual mass of phosphorus pentafluoride obtained / theoretical mass of phosphorus pentafluoride generated after complete reaction of yellow phosphorus).

[0033] Example 2

[0034] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0035] Yellow phosphorus is ground into a powder under nitrogen protection. The powder is then added to a carbon tetrachloride solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and dissolved with stirring at 35-40°C to prepare a 30% yellow phosphorus solution. This solution is then mixed with fluorine gas at a molar ratio of 1:12 (phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 2 mm diameter channel. The reaction temperature, pressure, and time in the microchannel reactor are controlled at 0°C, 1.5 MPa, and 5 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 10°C and 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0036] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.3%, and the calculated product yield was 85%.

[0037] Example 3

[0038] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0039] Yellow phosphorus was ground into a powder under nitrogen protection. The powder was then added to a dichloromethane solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and dissolved with stirring at 40-45°C to prepare a 30% yellow phosphorus solution. This solution was then mixed with fluorine gas at a molar ratio of 1:11 (yellow phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1.5 mm. The reaction temperature in the microchannel reactor was controlled at -5°C, the pressure at 1.5 MPa, and the reaction time for 8 minutes. The generated gas was passed into a pressurized condensation system for pressurized condensation separation. The condensed fraction at 10°C and 3.5 MPa was collected to obtain phosphorus pentafluoride.

[0040] The purity of the phosphorus pentafluoride obtained in this example was tested to be 99.4%, and the calculated product yield was 87%.

[0041] Example 4

[0042] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0043] Yellow phosphorus is ground into a powder under nitrogen protection. The powder is then added to a carbon tetrachloride solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and stirred and dissolved at 35-40°C to prepare a 40% yellow phosphorus solution. This solution is then mixed with fluorine gas at a molar ratio of 1:10 (phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 1 mm diameter channel. The reaction temperature in the microchannel reactor is controlled at -10°C, the pressure at 1.2 MPa, and the reaction time is 2 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 5°C and 3 MPa is collected to obtain phosphorus pentafluoride.

[0044] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.6%, and the calculated product yield was 75%.

[0045] Example 5

[0046] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0047] Yellow phosphorus is ground into a powder under nitrogen protection. The powder is then added to a dichloromethane solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and stirred and dissolved at 35-40°C to prepare a 40% yellow phosphorus solution. This solution is then mixed with fluorine gas at a molar ratio of 1:10 (yellow phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 2 mm diameter channel. The reaction temperature, pressure, and time in the microchannel reactor are controlled at 0°C, 1.8 MPa, and 10 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 10°C and 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0048] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.2%, and the calculated product yield was 92%.

[0049] Example 6

[0050] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0051] Yellow phosphorus is ground into a powder under nitrogen protection. The powder is then added to a carbon tetrachloride solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and dissolved with stirring at 30-35°C to prepare a 50% yellow phosphorus solution. This solution is then mixed with fluorine gas at a molar ratio of 1:12 (phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 1.5 mm diameter channel. The reaction temperature in the microchannel reactor is controlled at -5°C, the pressure at 1.5 MPa, and the reaction time is 4 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 10°C and 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0052] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.5%, and the calculated product yield was 81%.

[0053] Example 7

[0054] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0055] Yellow phosphorus was ground into a powder under nitrogen protection. The powder was then added to a dichloromethane solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and dissolved with stirring at 30-35°C to prepare a 50% yellow phosphorus solution. This solution was then mixed with fluorine gas at a molar ratio of 1:11 (yellow phosphorus (P4) to fluorine gas (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 1 mm diameter channel. The reaction temperature in the microchannel reactor was controlled at -10°C, the pressure at 1.0 MPa, and the reaction time for 6 minutes. The generated gas was passed into a pressurized condensation system for pressurized condensation separation. The condensed fraction at 5°C and 3 MPa was collected to obtain phosphorus pentafluoride.

[0056] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.7%, and the calculated product yield was 86%.

[0057] Example 8

[0058] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0059] Yellow phosphorus is ground into a powder under nitrogen protection. The powder is then added to a carbon tetrachloride solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and stirred at 35-40°C to dissolve. This results in a 35% yellow phosphorus solution. This solution is then mixed with fluorine gas at a molar ratio of 1:10 (phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 2 mm diameter channel. The reaction temperature, pressure, and time in the microchannel reactor are controlled at 0°C, 1.2 MPa, and 7 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 15°C and 4 MPa is collected to yield phosphorus pentafluoride.

[0060] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.4%, and the calculated product yield was 88%.

[0061] Example 9

[0062] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0063] Yellow phosphorus was ground into a powder under nitrogen protection. The powder was then added to a dichloromethane solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and dissolved with stirring at 35-40°C to prepare a 35% yellow phosphorus solution. This solution was then mixed with fluorine gas at a molar ratio of 1:12 (yellow phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1.5 mm. The reaction temperature in the microchannel reactor was controlled at -5°C, the pressure at 1.8 MPa, and the reaction time for 9 minutes. The generated gas was passed into a pressurized condensation system for pressurized condensation separation. The condensed fraction at 15°C and 4 MPa was collected to obtain phosphorus pentafluoride.

[0064] The purity of the phosphorus pentafluoride obtained in this example was tested to be 99.3%, and the calculated product yield was 86%.

[0065] Example 10

[0066] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0067] Yellow phosphorus is ground into a powder under nitrogen protection. The powder is then added to a carbon tetrachloride solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and dissolved with stirring at 35-40°C to prepare a 35% yellow phosphorus solution. This solution is then mixed with fluorine gas at a molar ratio of 1:11 (phosphorus (P4) to fluorine (F2)) through a polytetrafluoroethylene microchannel reactor with a 1 mm diameter channel. The reaction temperature in the microchannel reactor is controlled at -10°C, the pressure at 2.0 MPa, and the reaction time at 1 minute. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 5°C and 3 MPa is collected to obtain phosphorus pentafluoride.

[0068] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.6%, and the calculated product yield was 70%.

[0069] Example 11

[0070] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0071] Yellow phosphorus was ground into a powder under nitrogen protection and then added to a dichloromethane solvent (dried and dehydrated to a water content of ≤20 ppm before use) with stirring and dissolving at 35-40°C to prepare a 30% yellow phosphorus solution. This solution was then mixed with fluorine gas (purity >99.9%) at a molar ratio of 1:10 (phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 1 mm diameter channel. The reaction temperature in the microchannel reactor was controlled at -15°C, the pressure at 0.5 MPa, and the reaction time for 3 minutes. The generated gas was passed into a pressurized condensation system for pressurized condensation separation. The condensed fraction at 5°C and 3 MPa was collected to obtain phosphorus pentafluoride.

[0072] The phosphorus pentafluoride obtained in this example was tested to have a purity of 99.6%, and the calculated product yield was 69%.

[0073] By comparing the results with those in Example 1, it can be seen that when the temperature of the mixed reaction in the microchannel reactor is lower than -10°C and the pressure is lower than 1.0 MPa, the yield of the obtained product is significantly reduced, which is due to the reduced reaction efficiency.

[0074] Example 12

[0075] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas comprises the following steps:

[0076] Yellow phosphorus is ground into a powder under nitrogen protection. The powder is then added to a carbon tetrachloride solvent (dried and dehydrated to a moisture content of ≤20 ppm before use) and stirred and dissolved at 35-40°C to prepare a 30% yellow phosphorus solution. This solution is then mixed with fluorine gas at a molar ratio of 1:12 (phosphorus (P4) to fluorine (F2)) and introduced into a polytetrafluoroethylene microchannel reactor with a 2 mm diameter channel. The reaction temperature, pressure, and time in the microchannel reactor are controlled at 5°C, 2.5 MPa, and 5 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 10°C and 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0077] The phosphorus pentafluoride obtained in this example was tested to have a purity of 98.7%, and the calculated product yield was 87%.

[0078] Comparison with the results of Example 2 shows that when the temperature of the mixed reaction in the microchannel reactor is above 0°C and the pressure is above 2.0 MPa, the purity of the obtained product is significantly reduced. Testing shows that the impurity components mainly include POF3 and HF. These impurity components condense together with the target product, phosphorus pentafluoride, under the above-mentioned condensation separation conditions. However, they can be separated by secondary pressurized condensation separation (e.g., pressurizing above the critical temperature of PF5 (18.95°C) and below the critical temperature of POF3 (73.3°C) and the critical temperature of HF (188.2°C) to condense POF3 and HF into liquids while maintaining PF5 in a gaseous state to achieve removal of the impurity components POF3 and HF). This shows that when the temperature of the mixed reaction in the microchannel reactor of the present invention is above 0°C and the pressure is above 2.0 MPa, the side reactions of HF and POF3 generated by the reaction of the raw material F2 and the product PF5 with trace amounts of water in the system are significantly increased.

[0079] Comparative Example 1

[0080] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Example 1, uses a conventional gas-solid phase reaction instead of the gas-liquid phase reaction in the microchannel reactor, comprising the following steps:

[0081] Yellow phosphorus (P4) was placed in a horizontal gas-solid reactor. After vacuum degassing, fluorine gas (F2) was introduced for reaction. The molar ratio of P4 to F2 was 1:10. The reaction temperature in the gas-solid reactor was controlled at -10°C, the pressure at 1.0 MPa, and the reaction time was 3 minutes. The generated gas was passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at a temperature of 5°C and a pressure of 3 MPa was collected to obtain phosphorus pentafluoride.

[0082] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 99.6%, and the calculated product yield was 24%. After the reaction, the solid yellow phosphorus was not completely reacted, and the impurity component PF3 separated by pressurized condensation had a high content. This indicates that conventional gas-solid phase reactions under the same temperature, pressure, and reaction time are less efficient, and the incomplete fluorination byproduct PF3 has a high content, resulting in a reduced product yield.

[0083] Comparative Example 2

[0084] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Comparative Example 1, by increasing the reaction temperature and reaction time to allow the yellow phosphorus to react completely, comprises the following steps:

[0085] Yellow phosphorus (P4) was placed in a horizontal gas-solid reactor and, after vacuum degassing, introduced with fluorine gas (F2) for reaction. The molar ratio of P4 to F2 was 1:10. The reaction temperature in the gas-solid reactor was controlled at 15°C, the pressure at 1.0 MPa, and the reaction time was 60 minutes to ensure complete reaction of the solid-phase yellow phosphorus. The generated gas was passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at a temperature of 5°C and a pressure of 3 MPa was collected to obtain phosphorus pentafluoride.

[0086] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 98.0%, and the calculated product yield was 80%. The impurities tested mainly included POF3 and HF. This indicates that the increase in reaction temperature and the extension of reaction time significantly increase the side reactions of the raw material F2 and the product PF5 with trace amounts of residual water in the system.

[0087] Comparative Example 3

[0088] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Example 1, uses a gas-liquid phase reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions instead of the reaction of the yellow phosphorus solution in an inert solvent, comprising the following steps:

[0089] Yellow phosphorus (P4) is heated to 45-50°C under nitrogen protection to liquefy. It is then mixed with fluorine gas (F2) at a molar ratio of 1:10 and introduced into a polytetrafluoroethylene microchannel reactor with a 1mm channel diameter. The reaction temperature in the microchannel reactor is controlled at 45-50°C, the pressure at 1.0 MPa, and the reaction time is 3 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 5°C and 3 MPa is collected to obtain phosphorus pentafluoride.

[0090] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 99.4%, and the calculated product yield was 51%. After the reaction was completed, the yellow phosphorus was not completely reacted, and the impurity component PF3 separated by pressurized condensation had a high content. This indicates that under solvent-free conditions at the same temperature, pressure, and reaction time, the gas-liquid phase reaction efficiency above the liquefaction temperature of yellow phosphorus is low, and the content of the incomplete fluorination byproduct PF3 is high, resulting in a reduced product yield.

[0091] Comparative Example 4

[0092] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Example 2, uses a conventional gas-solid phase reaction instead of the gas-liquid phase reaction in the microchannel reactor, comprising the following steps:

[0093] Yellow phosphorus (P4) was placed in a horizontal gas-solid reactor. After vacuum degassing, fluorine gas (F2) was introduced for reaction. The molar ratio of P4 to F2 was 1:12. The reaction temperature in the gas-solid reactor was controlled at 0°C, the pressure at 1.5 MPa, and the reaction time at 5 minutes. The generated gas was passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at a temperature of 10°C and a pressure of 3.5 MPa was collected to obtain phosphorus pentafluoride.

[0094] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 99.2%, and the calculated product yield was 25%. After the reaction, the solid yellow phosphorus was not completely reacted, and the impurity component PF3 separated by pressurized condensation had a high content. This indicates that conventional gas-solid phase reactions under the same temperature, pressure, and reaction time are less efficient, and the incomplete fluorination byproduct PF3 has a high content, resulting in a reduced product yield.

[0095] Comparative Example 5

[0096] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Comparative Example 4, by increasing the reaction temperature and reaction time to allow the yellow phosphorus to react completely, comprises the following steps:

[0097] Yellow phosphorus (P4) was placed in a horizontal gas-solid reactor and, after vacuum degassing, introduced with fluorine gas (F2) for reaction. The molar ratio of P4 to F2 was 1:12. The reaction temperature in the gas-solid reactor was controlled at 15°C, the pressure at 1.5 MPa, and the reaction time for 60 minutes to ensure complete reaction of the solid-phase yellow phosphorus. The generated gas was passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at a temperature of 10°C and a pressure of 3.5 MPa was collected to obtain phosphorus pentafluoride.

[0098] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 98.1%, and the calculated product yield was 81%. The impurities tested mainly included POF3 and HF. This indicates that the increase in reaction temperature and the extension of reaction time significantly increase the side reactions of the raw material F2 and the product PF5 with trace amounts of residual water in the system.

[0099] Comparative Example 6

[0100] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Example 2, uses a gas-liquid phase reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions instead of the reaction of the yellow phosphorus solution in an inert solvent, comprising the following steps:

[0101] Yellow phosphorus (P4) is heated to 45-50°C under nitrogen protection to liquefy. It is then mixed with fluorine gas (F2) at a molar ratio of 1:12 and introduced into a 2mm diameter polytetrafluoroethylene microchannel reactor. The reaction temperature in the microchannel reactor is controlled at 45-50°C, the pressure at 1.5 MPa, and the reaction time is 5 minutes. The generated gas is passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at 10°C and 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0102] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 99.1%, and the calculated product yield was 58%. After the reaction was completed, the yellow phosphorus was not completely reacted, and the impurity component PF3 separated by pressurized condensation had a high content. This indicates that under solvent-free conditions at the same temperature, pressure, and reaction time, the gas-liquid phase reaction efficiency above the liquefaction temperature of yellow phosphorus is low, and the content of the incomplete fluorination byproduct PF3 is high, resulting in a reduced product yield.

[0103] Comparative Example 7

[0104] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Example 3, uses a conventional gas-solid phase reaction instead of the gas-liquid phase reaction in the microchannel reactor, comprising the following steps:

[0105] Yellow phosphorus (P4) was placed in a horizontal gas-solid reactor. After vacuum degassing, fluorine gas (F2) was introduced for reaction. The molar ratio of P4 to F2 was 1:11. The reaction temperature in the gas-solid reactor was controlled at -5°C, the pressure at 1.5 MPa, and the reaction time was 8 minutes. The generated gas was passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at a temperature of 10°C and a pressure of 3.5 MPa was collected to obtain phosphorus pentafluoride.

[0106] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 99.2%, and the calculated product yield was 26%. After the reaction, the solid yellow phosphorus was not completely reacted, and the impurity component PF3 separated by pressurized condensation had a high content. This indicates that conventional gas-solid phase reactions under the same temperature, pressure, and reaction time are less efficient, and the incomplete fluorination byproduct PF3 has a high content, resulting in a reduced product yield.

[0107] Comparative Example 8

[0108] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Comparative Example 7, by increasing the reaction temperature and reaction time to allow the yellow phosphorus to react completely, comprises the following steps:

[0109] Yellow phosphorus (P4) was placed in a horizontal gas-solid reactor and, after vacuum degassing, introduced with fluorine gas (F2) for reaction. The molar ratio of P4 to F2 was 1:11. The reaction temperature in the gas-solid reactor was controlled at 15°C, the pressure at 1.5 MPa, and the reaction time for 60 minutes to ensure complete reaction of the solid-phase yellow phosphorus. The generated gas was passed through a pressurized condensation system for pressurized condensation separation. The condensed fraction at a temperature of 10°C and a pressure of 3.5 MPa was collected to obtain phosphorus pentafluoride.

[0110] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 98.4%, and the calculated product yield was 80.5%. The impurities tested mainly included POF3 and HF. This indicates that the increase in reaction temperature and the extension of reaction time significantly increase the side reactions of the raw material F2 and the product PF5 with trace amounts of residual water in the system.

[0111] Comparative Example 9

[0112] A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, compared with Example 3, uses a gas-liquid phase reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions instead of the reaction of the yellow phosphorus solution in an inert solvent, comprising the following steps:

[0113] Yellow phosphorus (P4) is heated to 45-50°C under nitrogen protection to liquefy. It is then mixed with fluorine gas (F2) at a molar ratio of 1:11 and introduced into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1.5 mm. The reaction temperature in the microchannel reactor is controlled at 45-50°C, the pressure at 1.5 MPa, and the reaction time is 8 minutes. The generated gas is passed into a pressurized condensation system for pressurized condensation separation. The condensed fraction at a temperature of 10°C and a pressure of 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0114] The phosphorus pentafluoride obtained in this comparative example was tested to have a purity of 97.6%, and the calculated product yield was 62%. After the reaction was completed, the yellow phosphorus was not completely reacted, and the impurity component PF3 separated by pressurized condensation had a high content. This indicates that under solvent-free conditions at the same temperature, pressure, and reaction time, the gas-liquid phase reaction efficiency above the liquefaction temperature of yellow phosphorus is low, and the content of the incomplete fluorination byproduct PF3 is high, resulting in a reduced product yield.

[0115] By comparing the results of the above comparative examples 1 to 9 with those of examples 1 to 3, it can be seen that the method of the present invention for directly synthesizing phosphorus pentafluoride by a gas-liquid phase reaction of an inert solvent solution of yellow phosphorus and fluorine gas in a microchannel reactor can significantly improve the reaction efficiency and reduce the occurrence of side reactions, thereby simultaneously improving the product purity and yield, compared with the conventional gas-solid phase reaction method and the gas-liquid phase reaction method using fluorine gas and liquid elemental phosphorus at a temperature above the melting point in a microchannel reactor.

[0116] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, characterized in that: The steps include: Yellow phosphorus is dissolved in an inert solvent to prepare a yellow phosphorus solution, which is then mixed with fluorine gas and introduced into a microchannel reactor for reaction, and the generated gas product is separated and purified through a pressurized condensation system to obtain phosphorus pentafluoride; The inert solvent is dichloromethane or carbon tetrachloride; The temperature of the mixing reaction in the microchannel reactor is -10°C to 0°C.

2. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The water content of the inert solvent is ≤20ppm.

3. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The method for dissolving yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution comprises the following steps: grinding the yellow phosphorus into powder under an inert atmosphere, then adding the powder into the inert solvent and stirring and dissolving the powder at a temperature of 30-45°C.

4. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The mass concentration of the yellow phosphorus solution is 30-50%.

5. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The purity of the fluorine gas is greater than 99.9%.

6. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The molar ratio of yellow phosphorus to fluorine gas is 1:(10-12).

7. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The microchannel reactor is made of polytetrafluoroethylene, and the channel diameter of the microchannel reactor is 1-2 mm.

8. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The pressure of the mixing reaction in the microchannel reactor is 1.0 to 2.0 MPa.

9. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The reaction time of the mixing reaction in the microchannel reactor is 1 to 10 minutes.

10. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that: The separation and purification by the pressurized condensation system includes separation by pressurized condensation, collecting condensed components at a temperature of 5-15° C. and a pressure of 3-4 MPa, and obtaining phosphorus pentafluoride with a purity greater than 99%.