Method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas

Abstract

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, which comprises the following steps: dissolving yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution, then introducing the yellow phosphorus solution and fluorine gas into a micro-channel reactor for mixed reaction, and separating and purifying the generated gas product through a pressurized condensation system to obtain phosphorus pentafluoride. According to the synthesis method disclosed by the invention, yellow phosphorus with high reaction activity is dissolved by selecting the specific inert solvent, and then phosphorus pentafluoride is continuously synthesized by the yellow phosphorus and fluorine in the micro-channel reactor in a gas-liquid phase reaction manner, so that the synthesis method has the advantages of low reaction temperature, high reaction efficiency, few reaction byproducts and high product yield.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of phosphorus pentafluoride, 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 halide compound. It is a colorless and stinking gas under normal temperature and pressure. It has strong irritation to skin, eyes and mucous membranes, and is a highly active compound, which is widely used in industry. Lithium-ion secondary batteries with lithium hexafluorophosphate as the electrolyte have been widely used due to their many advantages. Phosphorus pentafluoride gas has found new applications as a raw material for the synthesis of lithium hexafluorophosphate. At present, in industry, PF5 and LiF are mostly used as raw materials, and HF is used as a solvent to synthesize LiPF6. Therefore, the synthesis of high-purity phosphorus pentafluoride is of great significance for the synthesis of lithium hexafluorophosphate.

[0003] At present, the 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 by-product hydrochloric acid, and hydrofluoric acid has strong corrosion to equipment, low raw material utilization rate and high requirements for the reaction device.

[0004] The direct reaction of fluorine gas and elemental phosphorus to synthesize PF5 has the advantage of high raw material utilization rate. However, the currently disclosed direct synthesis methods mainly use the gas-solid phase reaction of gaseous elemental fluorine and solid elemental phosphorus, which have problems such as high reaction temperature (for red phosphorus), difficult control of reaction heat release (for yellow phosphorus), low reaction efficiency and poor reaction continuity. The invention patent with the publication number CN107619028A records a high-efficiency continuous synthesis device and process for phosphorus pentafluoride. By installing a fluorine gas injection nozzle directly below the outlet of the discharge bin of the screw feeder, the nozzle sprays a high-speed fluorine gas stream at a specific downward inclination angle, entraining the powdered red phosphorus quantitatively conveyed by the screw feeder. The two form a gas / solid turbulent cluster and rotate downward for continuous and efficient reaction to generate phosphorus pentafluoride gas. Although this device and process achieve continuous reaction, they still use the gas-solid phase reaction method, and still have problems such as high reaction temperature and low reaction efficiency. In addition, there are also problems such as low product purity and low yield caused by many side reactions during the reaction at high temperature. The existing gas-liquid phase reaction of fluorine gas and liquid elemental phosphorus is carried out above the melting point temperature of elemental phosphorus, which has problems such as high danger (yellow phosphorus is easy to self-ignite above the melting point temperature), low reaction efficiency (the compatibility of liquid phosphorus element and fluorine gas is relatively low) and low product purity and low yield caused by many side reactions. Summary of the Invention

[0005] Aiming at the disadvantages and deficiencies of the above-mentioned existing technologies, the primary object of the present invention is to provide a method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. The synthesis method of the present invention dissolves highly reactive yellow phosphorus in a specific inert solvent, and then continuously synthesizes phosphorus pentafluoride with fluorine gas in a microchannel reactor through a gas-liquid phase reaction, having the advantages of low reaction temperature, high reaction efficiency, few reaction by-products, and high product yield.

[0006] The object of the present invention is achieved by the following technical solutions: A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Dissolve yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution, then introduce it and fluorine gas into a microchannel reactor for mixing reaction, and separate and purify the generated gas product through a pressurized condensation system to obtain phosphorus pentafluoride.

[0007] The chemical reaction involved in the present invention is as follows: Yellow phosphorus (P4) reacts with fluorine gas (F2) to form phosphorus pentafluoride (PF5): P4 + 10F2 → 4PF5.

[0008] Further, 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 products and water can be effectively reduced.

[0009] The key of the present invention is to dissolve yellow phosphorus with an inert solvent and then carry out the reaction. Through the gas-liquid phase reaction of the yellow phosphorus solution and fluorine gas, it can be applied to the mixing reaction in a microchannel reactor. The inert solvent used needs to be able to dissolve yellow phosphorus well, and have a certain solubility for fluorine gas, so that it can be well mixed and contacted in the microchannel reactor, and be inert to both yellow phosphorus and fluorine gas under the reaction conditions controlled in the microchannel reactor. The inert solvent selected under the above requirements can ensure the gas-liquid phase reaction efficiency of yellow phosphorus and fluorine gas and reduce the occurrence of side reactions, thereby improving the product yield and purity.

[0010] Further, the method for dissolving yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution is: grind yellow phosphorus into powder under an inert atmosphere, and then add it to the inert solvent and stir to dissolve at a temperature of 30 - 45 °C. Grinding into powder can accelerate the dissolution of yellow phosphorus, and the dissolution of yellow phosphorus can be accelerated at the above dissolution temperature, while ensuring good operation safety (reducing the risk of spontaneous combustion).

[0011] Furthermore, the mass concentration of the yellow phosphorus solution is 30-50%. If the concentration is too low, the production efficiency per batch is low and the production cost increases; if the concentration is too high, solid yellow phosphorus may precipitate supersaturated under the reaction conditions controlled in the microchannel reactor, affecting the reaction efficiency.

[0012] Furthermore, the purity of the fluorine gas is greater than 99.9%. Under the above purity requirements of the fluorine gas, the risk of introducing difficult-to-separate impurities through raw materials can be reduced.

[0013] Furthermore, the molar ratio of yellow phosphorus (P4) to fluorine gas (F2) is 1:10-12. The theoretical molar ratio of the reaction between P4 and F2 is 1:10. Using a slightly excessive amount of fluorine gas is beneficial to improving the conversion rate of yellow phosphorus, but too much excess will increase the load of the reaction device and the energy consumption for subsequent product separation.

[0014] Furthermore, the microchannel reactor is made of polytetrafluoroethylene material. By using the corrosion-resistant polytetrafluoroethylene material, corrosion of the reaction device and introduction of impurities can be avoided.

[0015] 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, with the aim of achieving good mixing of the yellow phosphorus solution and fluorine gas.

[0016] Furthermore, the temperature of the mixing reaction in the microchannel reactor is -10°C to 0°C, and the pressure is 1.0 to 2.0 MPa. Under the above temperature and pressure conditions of the microchannel reactor, good yields and purities of the target products can be achieved simultaneously. If the temperature and pressure are too low, the reaction efficiency is low and the yield of the target product decreases; if the temperature and pressure are too high, uncontrollable side reactions increase, and the content of by-product impurities in the product increases, resulting in a decrease in product purity.

[0017] Furthermore, the reaction time of the mixing reaction in the microchannel reactor is 1-10 min. Under the above reaction time, good conversion rates can be ensured while taking into account production efficiency.

[0018] Under the above parameter conditions of the microchannel reactor, the mixing of fluorine gas and yellow phosphorus solution and the gas-liquid phase contact reaction can be better realized, so as to achieve good product yields and purities, and have a high production efficiency.

[0019] Furthermore, the separation and purification by the pressurized condensation system refers to separation by pressurized condensation, collecting the condensate components at a temperature of 5 - 15 °C and a pressure of 3 - 4 MPa to obtain phosphorus pentafluoride with a purity > 99%. Pressurized condensation separation is a conventional method for the separation and purification of gas-phase components. Its principle is to utilize the differences in critical temperature and critical pressure of different gas-phase components to achieve separation. By maintaining within a certain temperature and pressure range, the components with a critical temperature higher than this temperature and / or a critical pressure lower than this pressure will condense into liquid, while the components with a critical temperature lower than this temperature and / or a critical pressure higher than this pressure will remain in the gaseous state, thus achieving separation. The critical temperature of the target product phosphorus pentafluoride in the present invention is 18.95 °C, and the critical pressure is 3.39 MPa. Under the conditions of a temperature of 5 - 15 °C and a pressure of 3 - 4 MPa, it can ensure that phosphorus pentafluoride condenses into liquid, and at the same time, it can ensure that most of the impurity components (such as unreacted F2 (critical temperature -128.8 °C), the possible main by-product PF3 (critical temperature -2.0 °C), etc.) remain in the gaseous state, thereby achieving the separation and purification of phosphorus pentafluoride.

[0020] Compared with the prior art, the beneficial effects of the present invention are: (1) The method of directly reacting fluorine gas with elemental phosphorus to synthesize PF5 in the present invention is improved from the traditional gas-solid reaction mode to a gas-liquid 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 generated by incomplete fluorination, and HF and POF3 generated by the reaction of raw material F2 and product PF5 with trace water in the system), thereby improving the product yield and purity.

[0021] (2) The present invention further adopts a microchannel reactor to improve the heat transfer efficiency and mass transfer efficiency of the gas-liquid reaction. The reaction heat can be quickly exported, reducing side reactions and safety risks caused by heat accumulation, and at the same time improving the reaction conversion rate.

[0022] (3) The synthesis method of the present invention has low requirements for equipment, is suitable for continuous production, and can significantly improve production efficiency and reduce production costs. Specific Embodiments

[0023] The present invention will be further described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto.

[0024] Example 1 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas includes the following steps: Yellow phosphorus is ground into powder under nitrogen protection, and then added to dichloromethane solvent (which is dried and dehydrated before use to make the water content ≤ 20 ppm) and stirred and dissolved at a temperature of 35 - 40 °C to prepare a yellow phosphorus solution with a mass concentration of 30%. Then, it is mixed and reacted with fluorine gas (purity > 99.9%) in a polytetrafluoroethylene microchannel reactor with a channel diameter of 1 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:10. The reaction temperature in the microchannel reactor is controlled at -10 °C, the reaction pressure is 1.0 MPa, and the reaction time is 3 min. The gas generated by the reaction is introduced into a pressurized condensation system for pressurized condensation separation, and the condensation component at a temperature of 5 °C and a pressure of 3 MPa is collected to obtain phosphorus pentafluoride.

[0025] The phosphorus pentafluoride obtained in this example is detected to have a purity of 99.5% (by infrared detection), and the product yield is calculated to be 80% (the mass of the actually obtained phosphorus pentafluoride / the theoretical mass of phosphorus pentafluoride formed by the complete reaction of yellow phosphorus).

[0026] Example 2 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Yellow phosphorus is ground into powder under nitrogen protection, and then added to carbon tetrachloride solvent (which is dried and dehydrated before use to make the water content ≤ 20 ppm) and stirred and dissolved at a temperature of 35 - 40 °C to prepare a yellow phosphorus solution with a mass concentration of 30%. Then, it is mixed and reacted with fluorine gas according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:12 in a polytetrafluoroethylene microchannel reactor with a channel diameter of 2 mm. The reaction temperature in the microchannel reactor is controlled at 0 °C, the reaction pressure is 1.5 MPa, and the reaction time is 5 min. The gas generated by the reaction is introduced into a pressurized condensation system for pressurized condensation separation, and the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0027] The phosphorus pentafluoride obtained in this example is detected to have a purity of 99.3%, and the product yield is calculated to be 85%.

[0028] Example 3 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to dichloromethane solvent (which has been dried to remove water before use so that the water content is ≤ 20 ppm), stir and dissolve it at a temperature of 40 - 45 °C to prepare a yellow phosphorus solution with a mass concentration of 30%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1.5 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:11 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be -5 °C, the reaction pressure to be 1.5 MPa, and the reaction time to be 8 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0029] The phosphorus pentafluoride obtained in this example was detected to have a purity of 99.4%, and the product yield was calculated to be 87%.

[0030] Example 4 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas includes the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to carbon tetrachloride solvent (which has been dried to remove water before use so that the water content is ≤ 20 ppm), stir and dissolve it at a temperature of 35 - 40 °C to prepare a yellow phosphorus solution with a mass concentration of 40%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:10 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be -10 °C, the reaction pressure to be 1.2 MPa, and the reaction time to be 2 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 5 °C and a pressure of 3 MPa to obtain phosphorus pentafluoride.

[0031] The phosphorus pentafluoride obtained in this example was detected to have a purity of 99.6%, and the product yield was calculated to be 75%.

[0032] Example 5 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas includes the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to dichloromethane solvent (which has been dried to remove water before use so that the water content is ≤ 20 ppm), stir and dissolve it at a temperature of 35 - 40 °C to prepare a yellow phosphorus solution with a mass concentration of 40%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 2 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:10 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be 0 °C, the reaction pressure to be 1.8 MPa, and the reaction time to be 10 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0033] The phosphorus pentafluoride obtained in this example was detected to have a purity of 99.2%, and the product yield was calculated to be 92%.

[0034] Example 6 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to carbon tetrachloride solvent (dried and dehydrated before use to make the water content ≤ 20 ppm), stir and dissolve at a temperature of 30 - 35 °C to prepare a yellow phosphorus solution with a mass concentration of 50%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1.5 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:12 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be -5 °C, the reaction pressure to be 1.5 MPa, and the reaction time to be 4 min. Pass the reaction-generated gas into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0035] The phosphorus pentafluoride obtained in this example was detected to have a purity of 99.5%, and the product yield was calculated to be 81%.

[0036] Example 7 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to dichloromethane solvent (dried and dehydrated before use to make the water content ≤ 20 ppm), stir and dissolve at a temperature of 30 - 35 °C to prepare a yellow phosphorus solution with a mass concentration of 50%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:11 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be -10 °C, the reaction pressure to be 1.0 MPa, and the reaction time to be 6 min. Pass the reaction-generated gas into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 5 °C and a pressure of 3 MPa to obtain phosphorus pentafluoride.

[0037] The phosphorus pentafluoride obtained in this example was detected to have a purity of 99.7%, and the product yield was calculated to be 86%.

[0038] Example 8 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to carbon tetrachloride solvent (which has been dried to remove water before use so that the water content is ≤20 ppm), stir and dissolve it at a temperature of 35 - 40 °C to prepare a yellow phosphorus solution with a mass concentration of 35%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 2 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:10 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be 0 °C, the reaction pressure to be 1.2 MPa, and the reaction time to be 7 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 15 °C and a pressure of 4 MPa to obtain phosphorus pentafluoride.

[0039] The phosphorus pentafluoride obtained in this example was detected to have a purity of 99.4%, and the product yield was calculated to be 88%.

[0040] Example 9 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to dichloromethane solvent (which has been dried to remove water before use so that the water content is ≤20 ppm), stir and dissolve it at a temperature of 35 - 40 °C to prepare a yellow phosphorus solution with a mass concentration of 35%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1.5 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:12 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be -5 °C, the reaction pressure to be 1.8 MPa, and the reaction time to be 9 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 15 °C and a pressure of 4 MPa to obtain phosphorus pentafluoride.

[0041] The phosphorus pentafluoride obtained in this example was detected to have a purity of 99.3%, and the product yield was calculated to be 86%.

[0042] Example 10 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, comprising the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to carbon tetrachloride solvent (which has been dried to remove water before use so that the water content is ≤20 ppm), stir and dissolve it at a temperature of 35 - 40 °C to prepare a yellow phosphorus solution with a mass concentration of 35%. Then, introduce it and fluorine gas into a polytetrafluoroethylene microchannel reactor with a channel diameter of 1 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:11 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be -10 °C, the reaction pressure to be 2.0 MPa, and the reaction time to be 1 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 5 °C and a pressure of 3 MPa to obtain phosphorus pentafluoride.

[0043] The purity of phosphorus pentafluoride obtained in this example was detected to be 99.6%, and the product yield was calculated to be 70%.

[0044] Example 11 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas includes the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to dichloromethane solvent (which has been dried and dewatered before use to make the water content ≤ 20 ppm), stir and dissolve it at a temperature of 35 - 40 °C, and prepare a yellow phosphorus solution with a mass concentration of 30%. Then, mix and react it with fluorine gas (purity > 99.9%) in a polytetrafluoroethylene microchannel reactor with a channel diameter of 1 mm according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:10. Control the reaction temperature in the microchannel reactor to be -15 °C, the reaction pressure to be 0.5 MPa, and the reaction time to be 3 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 5 °C and a pressure of 3 MPa to obtain phosphorus pentafluoride.

[0045] The purity of phosphorus pentafluoride obtained in this example was detected to be 99.6%, and the product yield was calculated to be 69%.

[0046] It can be seen from the comparison results with Example 1 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 decreases significantly, which is due to the decrease in reaction efficiency.

[0047] Example 12 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas includes the following steps: Grind yellow phosphorus into powder under nitrogen protection, then add it to carbon tetrachloride solvent (which has been dried and dewatered before use to make the water content ≤ 20 ppm), stir and dissolve it at a temperature of 35 - 40 °C, and prepare a yellow phosphorus solution with a mass concentration of 30%. Then, mix and react it with fluorine gas according to a molar ratio of yellow phosphorus (P4) to fluorine gas (F2) of 1:12 in a polytetrafluoroethylene microchannel reactor with a channel diameter of 2 mm. Control the reaction temperature in the microchannel reactor to be 5 °C, the reaction pressure to be 2.5 MPa, and the reaction time to be 5 min. Pass the gas generated by the reaction into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0048] The purity of phosphorus pentafluoride obtained in this example was detected to be 98.7%, and the product yield was calculated to be 87%.

[0049] It can be seen from the comparison results with Example 2 that when the temperature of the mixing reaction in the microchannel reactor is higher than 0 °C and the pressure is higher than 2.0 MPa, the purity of the obtained product is significantly reduced. After detection, the impurity components mainly include POF3 and HF. The above impurity components are condensed together with the target product phosphorus pentafluoride under the above condensation separation conditions, but can be separated by the method of secondary pressurized condensation separation (such as pressurizing above the critical temperature of PF5 (18.95 °C) and below the critical temperatures of POF3 (73.3 °C) and HF (188.2 °C) to condense POF3 and HF into liquid state while PF5 remains in gaseous state to remove the impurity components POF3 and HF). It can be seen from this that when the temperature of the mixing reaction in the microchannel reactor of the present invention is higher than 0 °C and the pressure is higher than 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 water in the system are significantly increased.

[0050] Comparative Example 1 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Example 1, a conventional gas-solid reaction is used to replace the gas-liquid reaction in the microchannel reactor, and the method includes the following steps: Place yellow phosphorus (P4) in a horizontal gas-solid reaction device. After vacuum degassing, introduce fluorine gas (F2) for reaction. The molar ratio of P4 to F2 is 1:10. Control the reaction temperature in the gas-solid reaction device to be -10 °C, the reaction pressure to be 1.0 MPa, and the reaction time to be 3 min. Pass the generated gas into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 5 °C and a pressure of 3 MPa to obtain phosphorus pentafluoride.

[0051] The purity of the phosphorus pentafluoride obtained in this comparative example is detected to be 99.6%, and the product yield is calculated to be 24%. After the reaction, the solid yellow phosphorus is not completely reacted, and at the same time, the content of the impurity component PF3 separated by pressurized condensation is relatively high. It shows that the efficiency of the conventional gas-solid reaction under the same temperature, pressure and reaction time is low, and the content of the incomplete fluorination by-product PF3 is relatively high, resulting in a decrease in the product yield.

[0052] Comparative Example 2 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Comparative Example 1, the yellow phosphorus is completely reacted by increasing the reaction temperature and reaction time, and the method includes the following steps: Place yellow phosphorus (P4) in a horizontal gas-solid reaction device. After vacuum degassing, introduce fluorine gas (F2) for reaction. The molar ratio of P4 to F2 is 1:10. Control the reaction temperature in the gas-solid reaction device to be 15 °C, the reaction pressure to be 1.0 MPa, and the reaction time to be 60 min to completely react the solid yellow phosphorus. Pass the generated gas into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 5 °C and a pressure of 3 MPa to obtain phosphorus pentafluoride.

[0053] The phosphorus pentafluoride obtained in this comparative example was detected to have a purity of 98.0%, and the product yield was calculated to be 80%. The detected impurity components mainly included POF3 and HF. It shows that the increase in reaction temperature and the extension of reaction time significantly increase the side reactions between the raw material F2 and the product PF5 and the trace residual moisture in the system.

[0054] Comparative Example 3 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Example 1, a gas-liquid phase reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions is used to replace the reaction of the yellow phosphorus solution under an inert solvent, and it includes the following steps: Yellow phosphorus (P4) was heated to 45-50 °C for liquefaction under nitrogen protection, and then it was mixed and reacted with fluorine gas (F2) in a polytetrafluoroethylene microchannel reactor with a channel diameter of 1 mm at a molar ratio of P4 to F2 of 1:10. The reaction temperature in the microchannel reactor was controlled at 45-50 °C, the reaction pressure was 1.0 MPa, and the reaction time was 3 min. The gas generated by the reaction was introduced into a pressurized condensation system for pressurized condensation separation, and the condensation component at a temperature of 5 °C and a pressure of 3 MPa was collected to obtain phosphorus pentafluoride.

[0055] The phosphorus pentafluoride obtained in this comparative example was detected to have a purity of 99.4%, and the product yield was calculated to be 51%. After the reaction, the yellow phosphorus was not completely reacted, and at the same time, the content of the impurity component PF3 separated by pressurized condensation was relatively high. It shows that the gas-liquid phase reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions at the same temperature, pressure and reaction time has a lower efficiency, and the content of the incomplete fluorination by-product PF3 is relatively high, resulting in a decrease in the product yield.

[0056] Comparative Example 4 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Example 2, a conventional gas-solid phase reaction is used to replace the gas-liquid phase reaction in the microchannel reactor, and it includes the following steps: Yellow phosphorus (P4) was placed in a horizontal gas-solid reaction device, degassed under vacuum, and then fluorine gas (F2) was introduced for reaction. The molar ratio of P4 to F2 was 1:12. The reaction temperature in the gas-solid reaction device was controlled at 0 °C, the reaction pressure was 1.5 MPa, and the reaction time was 5 min. The gas generated by the reaction was introduced into a pressurized condensation system for pressurized condensation separation, and the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa was collected to obtain phosphorus pentafluoride.

[0057] The purity of the phosphorus pentafluoride obtained in this comparative example was detected to be 99.2%, and the product yield was calculated to be 25%. After the reaction, the solid yellow phosphorus was not completely reacted, and at the same time, the content of the impurity component PF3 separated by pressure condensation was relatively high. This shows that the efficiency of the conventional gas-solid reaction under the same temperature, pressure and reaction time is relatively low, and the content of the incomplete fluorination by-product PF3 is relatively high, resulting in a reduction in the product yield.

[0058] Comparative Example 5 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, the yellow phosphorus reacts completely, and the method includes the following steps: Place yellow phosphorus (P4) in a horizontal gas-solid reaction device. After vacuum degassing, introduce fluorine gas (F2) for reaction. The molar ratio of P4 to F2 is 1:12. Control the reaction temperature in the gas-solid reaction device to be 15 °C, the reaction pressure to be 1.5 MPa, and the reaction time to be 60 min to completely react the solid yellow phosphorus. Pass the gas generated by the reaction into a pressure condensation system for pressure condensation separation, and collect the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0059] The purity of the phosphorus pentafluoride obtained in this comparative example was detected to be 98.1%, and the product yield was calculated to be 81%. After detection, the impurity components mainly include POF3 and HF. This shows that the increase in the reaction temperature and the extension of the reaction time significantly increase the side reactions of the raw material F2 and the product PF5 with trace residual moisture in the system.

[0060] Comparative Example 6 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Example 2, a gas-liquid reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions is used to replace the reaction of a yellow phosphorus solution under an inert solvent, and the method includes the following steps: Heat yellow phosphorus (P4) to 45-50 °C for liquefaction under nitrogen protection, and then introduce it and fluorine gas (F2) into a microchannel reactor made of polytetrafluoroethylene with a channel diameter of 2 mm according to the molar ratio of P4 to F2 of 1:12 for mixing and reaction. Control the reaction temperature in the microchannel reactor to be 45-50 °C, the reaction pressure to be 1.5 MPa, and the reaction time to be 5 min. Pass the gas generated by the reaction into a pressure condensation system for pressure condensation separation, and collect the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0061] The purity of the phosphorus pentafluoride obtained in this comparative example was detected to be 99.1%, and the product yield was calculated to be 58%. After the reaction, the yellow phosphorus was not completely reacted, and at the same time, the content of the impurity component PF3 separated by pressure condensation was relatively high. This shows that the efficiency of the gas-liquid reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions is relatively low under the same temperature, pressure and reaction time, and the content of the incomplete fluorination by-product PF3 is relatively high, resulting in a reduction in the product yield.

[0062] Comparative Example 7 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Example 3, a conventional gas-solid reaction is used to replace the gas-liquid reaction in the microchannel reactor, and the method includes the following steps: Place yellow phosphorus (P4) in a horizontal gas-solid reaction device. After vacuum degassing, introduce fluorine gas (F2) for reaction. The molar ratio of P4 to F2 is 1:11. Control the reaction temperature in the gas-solid reaction device to be -5°C, the reaction pressure to be 1.5 MPa, and the reaction time to be 8 min. Pass the reaction-generated gas into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 10°C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0063] The phosphorus pentafluoride obtained in this comparative example is detected to have a purity of 99.2%, and the product yield is calculated to be 26%. After the reaction, the solid yellow phosphorus is not completely reacted, and at the same time, the content of the impurity component PF3 separated by pressurized condensation is relatively high. It shows that the efficiency of the conventional gas-solid reaction under the same temperature, pressure and reaction time is relatively low, and the content of the incomplete fluorination by-product PF3 is relatively high, resulting in a decrease in the product yield.

[0064] Comparative Example 8 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Comparative Example 7, the yellow phosphorus is completely reacted by increasing the reaction temperature and reaction time, and the method includes the following steps: Place yellow phosphorus (P4) in a horizontal gas-solid reaction device. After vacuum degassing, introduce fluorine gas (F2) for reaction. The molar ratio of P4 to F2 is 1:11. Control the reaction temperature in the gas-solid reaction device to be 15°C, the reaction pressure to be 1.5 MPa, and the reaction time to be 60 min to completely react the solid-phase yellow phosphorus. Pass the reaction-generated gas into a pressurized condensation system for pressurized condensation separation, and collect the condensation component at a temperature of 10°C and a pressure of 3.5 MPa to obtain phosphorus pentafluoride.

[0065] The phosphorus pentafluoride obtained in this comparative example is detected to have a purity of 98.4%, and the product yield is calculated to be 80.5%. The detected impurity components mainly include POF3 and HF. It shows that the increase in the reaction temperature and the extension of the reaction time significantly increase the side reactions of the raw material F2 and the product PF5 with trace residual moisture in the system.

[0066] Comparative Example 9 A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas. Compared with Example 3, a gas-liquid reaction above the liquefaction temperature of yellow phosphorus under solvent-free conditions is used to replace the reaction of the yellow phosphorus solution under an inert solvent, and the method includes the following steps: Yellow phosphorus (P4) is heated to 45 - 50 °C for liquefaction under nitrogen protection, and then it is mixed and reacted with fluorine gas (F2) in a polytetrafluoroethylene microchannel reactor with a channel diameter of 1.5 mm at a molar ratio of P4 to F2 of 1:11. The reaction temperature in the microchannel reactor is controlled at 45 - 50 °C, the reaction pressure is 1.5 MPa, and the reaction time is 8 min. The gas generated by the reaction is introduced into a pressurized condensation system for pressurized condensation separation, and the condensation component at a temperature of 10 °C and a pressure of 3.5 MPa is collected to obtain phosphorus pentafluoride.

[0067] The purity of the phosphorus pentafluoride obtained in this comparative example is detected to be 97.6%, and the product yield is calculated to be 62%. After the reaction, yellow phosphorus is not completely reacted, and at the same time, the content of the impurity component PF3 separated by pressurized condensation is relatively high. This shows that under the same temperature, pressure and reaction time, the gas-liquid phase reaction efficiency above the liquefaction temperature of yellow phosphorus under the solvent-free condition is relatively low, and the content of the incompletely fluorinated by-product PF3 is relatively high, resulting in a decrease in the product yield.

[0068] From the comparison results of the above Comparative Examples 1 - 9 and Examples 1 - 3, it can be seen that the method of directly synthesizing phosphorus pentafluoride by the gas-liquid phase reaction of an inert solvent solution of yellow phosphorus and fluorine gas in a microchannel reactor in the present invention can significantly improve the reaction efficiency and reduce the occurrence of side reactions compared with the conventional gas-solid phase reaction method and the gas-liquid phase reaction method using fluorine gas and liquid elemental phosphorus above the melting point temperature in a microchannel reactor, thereby improving the product purity and yield at the same time.

[0069] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas, characterized in that, It includes the following steps: Dissolve yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution, then introduce it and fluorine gas into a microchannel reactor for mixing and reaction, and separate and purify the generated gas product through a pressurized condensation system to obtain phosphorus pentafluoride.

2. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that, The inert solvent used is dichloromethane or carbon tetrachloride, and the moisture content of the inert solvent is ≤ 20 ppm.

3. The method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that, The method of dissolving yellow phosphorus in an inert solvent to prepare a yellow phosphorus solution is as follows: grind yellow phosphorus into powder under an inert atmosphere, and then add it to the inert solvent and stir to dissolve at a temperature of 30 - 45 °C.

4. A 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. A 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. A 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. A 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 material, and the channel diameter of the microchannel reactor is 1 - 2 mm.

8. A method for synthesizing phosphorus pentafluoride from yellow phosphorus and fluorine gas according to claim 1, characterized in that, The temperature of the mixing reaction in the microchannel reactor is -10 °C to 0 °C, and the pressure 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 - 10 min.

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