Phosphorus pentafluoride purification method

Abstract

The present invention provides a phosphorus pentafluoride purification method, which comprises: introducing a first mixed gas containing phosphorus pentafluoride and impurities into liquid hydrogen fluoride at a flow rate v, and washing at a normal pressure and a temperature T to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride, wherein the impurities comprise phosphorus oxyfluoride, T is less than or equal to 15 DEG C, and v is more than or equal to 2mL / min and less than or equal to 10mL / min; and separating the second mixed gas to obtain phosphorus pentafluoride. According to the method, impurities in the phosphorus pentafluoride gas can be effectively removed, and the purity and the yield of phosphorus pentafluoride are improved.

Description

Technical Field

[0001] This invention relates to the field of phosphorus pentafluoride purification, and specifically to a method for purifying phosphorus pentafluoride. Background Technology

[0002] Phosphorus pentafluoride is a phosphorus halide compound with the chemical formula PF5. The phosphorus atom has an oxidation number of +5 and contains a three-center four-electron bond. It is a colorless gas with a pungent and irritating odor at room temperature and pressure. Its melting point at room pressure is -93.8℃ and its boiling point is -84.6℃. It can be used as a raw material for the synthesis of compounds such as hexafluorophosphate.

[0003] Currently, there are two main methods for the industrial production of phosphorus pentafluoride: one is to use fuming sulfuric acid or sulfur trioxide as a dehydrating agent to decompose hexafluorophosphate at high temperature to obtain phosphorus pentafluoride gas, as disclosed in patent documents CN104261369B and CN101570328B; the other is to react phosphorus pentachloride with hydrogen fluoride to obtain phosphorus pentafluoride, as disclosed in patent documents CN115583661A and CN114538406A. The phosphorus pentafluoride gas produced by existing processes contains various impurities such as phosphorus trifluoride oxyfluoride, which affects the quality of compounds such as hexafluorophosphate synthesized using this phosphorus pentafluoride gas.

[0004] Washing phosphorus pentafluoride gas with hydrogen fluoride can improve its purity to some extent. However, during the washing process, phosphorus trifluoride oxyfluoride and hydrogen fluoride usually react to form hexafluorophosphoric acid, and phosphorus pentafluoride also reacts with hydrogen fluoride to form hexafluorophosphoric acid. This not only affects the washing effect of hydrogen fluoride on phosphorus pentafluoride gas, but also significantly reduces the yield of phosphorus pentafluoride due to the reaction between phosphorus pentafluoride and hydrogen fluoride. Therefore, how to purify phosphorus pentafluoride from phosphorus pentafluoride gas containing impurities while improving both its purity and yield is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This invention provides a method for purifying phosphorus pentafluoride, which can purify phosphorus pentafluoride from phosphorus pentafluoride gas containing impurities, thereby improving both the purity and yield of phosphorus pentafluoride and effectively overcoming the defects of the prior art.

[0006] This invention provides a method for purifying phosphorus pentafluoride, comprising the following steps: passing a first mixed gas containing phosphorus pentafluoride and impurities into liquid hydrogen fluoride at a flow rate v, and washing it under normal pressure and temperature T to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride; wherein the impurities include phosphorus trifluoride, T≤15℃, 2mL / min≤v≤10mL / min; and separating the phosphorus pentafluoride from the second mixed gas.

[0007] According to one embodiment of the present invention, -50℃≤T≤15℃.

[0008] According to one embodiment of the present invention, -20℃≤T≤10℃.

[0009] According to one embodiment of the present invention, the mass ratio of the first mixed gas to the liquid hydrogen fluoride is 1:(1 to 10).

[0010] According to one embodiment of the present invention, the impurity includes a first impurity and / or a second impurity; the first impurity includes one or more of sulfur trioxide, fluorosulfonic acid, sulfuric acid, phosphorus oxyfluoride, and hydrogen fluoride; the second impurity includes hydrogen halide and / or phosphorus fluorohalides.

[0011] According to one embodiment of the present invention, the hydrogen halide includes hydrogen chloride; and / or, the phosphorus fluorohalide includes phosphorus fluorochloride, preferably the phosphorus fluorochloride includes one or more of phosphorus tetrafluoromonochloride, phosphorus trifluorodichloride, phosphorus difluorotrichloride, and phosphorus monofluorotetrachloride.

[0012] According to one embodiment of the present invention, the process of separating the phosphorus pentafluoride from the second mixed gas includes: distilling the second mixed gas to obtain the phosphorus pentafluoride and a liquid phase containing hydrogen fluoride; and returning the liquid phase containing hydrogen fluoride to the liquid hydrogen fluoride.

[0013] According to one embodiment of the present invention, the impurity includes a second impurity, and the second mixed gas includes hydrogen halide; the process of separating the phosphorus pentafluoride from the second mixed gas includes: washing the second mixed gas with a detergent and then distilling it to obtain the phosphorus pentafluoride and a liquid phase containing hydrogen fluoride; wherein, the hydrogen halide in the second mixed gas is removed during the washing process with the detergent; and the liquid phase containing hydrogen fluoride is returned to the liquid hydrogen fluoride.

[0014] According to one embodiment of the present invention, the detergent comprises fuming sulfuric acid, and the temperature of the second mixed gas being washed by the detergent is 5-15°C.

[0015] According to one embodiment of the present invention, the distillation conditions are: pressure of 0.6 MPa to 1 MPa and temperature of -70°C to -50°C.

[0016] The method for purifying phosphorus pentafluoride provided by this invention involves passing a first mixed gas containing phosphorus pentafluoride and impurities into liquid hydrogen fluoride at a flow rate v, and washing it at atmospheric pressure and temperature T. This method not only efficiently removes impurities and improves the purity of phosphorus pentafluoride, but also inhibits the reaction between phosphorus pentafluoride and hydrogen fluoride, and converts phosphorus trifluoride oxyfluoride in the first mixed gas into phosphorus pentafluoride. Therefore, it significantly improves both the purity and yield of phosphorus pentafluoride. Thus, this invention can purify phosphorus pentafluoride from phosphorus pentafluoride gas containing impurities, simultaneously improving both the purity and yield. The purified phosphorus pentafluoride can be used as a raw material for synthesizing compounds such as hexafluorophosphate, improving the quality of the synthesized compounds. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] According to the inventors' research, in conventional processes for removing impurities such as POF3 from phosphorus pentafluoride (PF5) gas using a reaction between POF3 and hydrogen fluoride (HF), POF3 and other impurities can react with HF (for example, the reaction formula between POF3 and HF is shown in reaction formula 1 below). PF5, as the main component, also reacts with HF to generate hexafluorophosphoric acid (HPF6), resulting in a significant reduction in the yield of purified PF5 (the reactions involved are shown in reaction formula 2). Simultaneously, the generated HPF6 exists throughout the reaction system, which also affects the washing effect of hydrogen fluoride on the phosphorus pentafluoride gas, thus affecting the purity of the washed phosphorus pentafluoride.

[0019] POF3 + 3HF = HPF6 + H2O (Reaction 1)

[0020] PF5 + HF = HPF6 (Reaction 2)

[0021] According to the inventors' further research, although increasing the temperature can inhibit the reaction between PF5 and HF to some extent, it will also be detrimental to the reaction between POF3 and HF, and thus hinder the removal of POF3. For example, when the temperature is higher than the boiling point of HF, it is not conducive to using hydrogen fluoride in liquid form to wash the impurity-containing phosphorus pentafluoride gas. Moreover, the heating and pressurizing process is not conducive to actual industrial production. More importantly, the reaction between POF3 and HF is an exothermic reaction, and excessively high temperatures are not conducive to the reaction proceeding to the right (i.e., forward), affecting the removal effect of POF3 and thus the purity of phosphorus pentafluoride.

[0022] In view of this, embodiments of the present invention provide a method for purifying phosphorus pentafluoride, comprising the following steps: passing a first mixed gas containing phosphorus pentafluoride and impurities into liquid hydrogen fluoride at a flow rate v, and washing it under normal pressure and temperature T to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride; wherein, the impurities (or impurity gases) include phosphorus trifluoride, T≤15℃, 2mL / min≤v≤10mL / min; and separating phosphorus pentafluoride (i.e., purified phosphorus pentafluoride (high-purity phosphorus pentafluoride gas)) from the second mixed gas.

[0023] According to the inventors' research, in the above-mentioned PF5 purification process, a first mixed gas is continuously passed into liquid hydrogen fluoride, allowing the first mixed gas to be washed as it flows through the liquid hydrogen fluoride. Under this washing state, the first mixed gas is continuously passed into the liquid hydrogen fluoride at a flow rate of 2 mL / min ≤ v ≤ 10 mL / min, allowing the entire reaction system to contact under a disturbed state of the first mixed gas (whereby impurity molecules in the first mixed gas collide with HF in the liquid hydrogen fluoride, and then react). Simultaneously, by coordinating atmospheric pressure and temperature T (T ≤ 15℃), the contact state and thermodynamic reaction behavior between gas molecules from the first mixed gas and HF in the liquid hydrogen fluoride are controlled, inhibiting the reaction between PF5 and HF, and simultaneously directing POF3 and HF towards the forward reaction direction for the formation of PF5. The process involves converting POF3 into PF5 (the reaction formula for the formation of PF5 from POF3 and HF is shown in reaction formula 3 below). This significantly increases the yield of PF5 while removing POF3 from the gas. The reason for this is that the enthalpy and Gibbs free energy, among other thermodynamic functions, of the reactions of POF3 and HF to form HPF6 (as shown in reaction formula 1) and POF3 and HF to form PF5 (as shown in reaction formula 3) are different. Under the above reaction conditions, at a temperature T≤15℃ and a pressure of atmospheric pressure, the thermodynamic reaction behavior of POF3 and HF is controlled to favor the forward reaction of POF3 and HF towards the formation of PF5, thus converting POF3 into PF5. The generated PF5 is a gas and enters the second mixed gas. Phosphorus pentafluoride (phosphorus pentafluoride gas) is obtained by separating it from the second mixed gas, thereby increasing the yield of phosphorus pentafluoride.

[0024] POF3 + 2HF = PF5 + H2O (Reaction Equation 3)

[0025] Therefore, in this embodiment of the invention, by passing a first mixed gas containing phosphorus pentafluoride and impurities into liquid hydrogen fluoride for washing, and by coordinating and controlling the flow rate v, temperature T, and pressure (atmospheric pressure) to satisfy the above-mentioned ranges (i.e., 2 mL / min ≤ v ≤ 10 mL / min, T ≤ 15℃, and pressure at atmospheric pressure), not only can impurities in the first mixed gas be effectively removed, improving the purity of the obtained phosphorus pentafluoride, but the reaction between phosphorus pentafluoride and hydrogen fluoride can also be inhibited. At the same time, phosphorus trifluoride oxyfluoride can react with hydrogen fluoride to generate phosphorus pentafluoride, thereby significantly improving the yield of phosphorus pentafluoride. Meanwhile, the washing effect of phosphorus pentafluoride caused by the reaction of phosphorus trifluoride oxyfluoride with hydrogen fluoride to generate other impurity molecules can be avoided, further ensuring the purity of phosphorus pentafluoride.

[0026] Furthermore, by synergistically controlling the flow rate v, temperature T, and pressure to meet the aforementioned ranges (i.e., 2 mL / min ≤ v ≤ 10 mL / min, T ≤ 15℃, and pressure at atmospheric pressure), hydrogen fluoride can be ensured to exist in liquid form without pressurization, thus guaranteeing the purification effect. This purification process also has advantages such as no need for heating or pressurization, mild reaction conditions, and ease of operation, which are beneficial for practical industrial applications.

[0027] Under normal circumstances, the first mixed gas contains a variety of impurities. The above-mentioned phosphorus pentafluoride purification process can improve the removal rate of these impurities, thereby improving the purity of the obtained phosphorus pentafluoride.

[0028] Specifically, the impurities may include a first impurity, which may include one or more of sulfur trioxide (SO3), fluorosulfonic acid (FSO3H), sulfuric acid (H2SO4), phosphorus trifluoride, and hydrogen fluoride.

[0029] In addition, impurities may include second impurities, which mainly include impurities containing halogens. Halogens may include chlorine. In other words, second impurities may specifically include impurities containing chlorine.

[0030] Specifically, halogen-containing impurities may include hydrogen halides (HX) and / or phosphorus fluorohalides (PFH). a X b In this context, X represents a halogen, such as chlorine (Cl). Hydrogen halides can include hydrogen chloride (HCl), and phosphorus fluorohalides can include phosphorus fluorochlorides (PFH). a Cl b ).

[0031] In addition, PF a X b In this case, 1≤a≤4, 1≤b≤4, where a and b are integers. For example, a can be 1, 2, 3 or 4, and b can be 1, 2, 3 or 4.

[0032] In some embodiments, the second impurity may include hydrogen chloride and / or PF.a Cl b PF a Cl b In the expression, 1≤a≤4, 1≤b≤4, where a and b are integers.

[0033] Specifically, phosphorus fluorides may include one or more of phosphorus tetrafluoromonochloride (PF4Cl), phosphorus trifluorodichloride (PF3Cl2), phosphorus difluorotrichloride (PF2Cl3), and phosphorus monofluorotetrachloride (PFCl4).

[0034] According to the inventor's further research, for the first mixed gas containing phosphorus fluoride, by passing the first mixed gas into liquid hydrogen fluoride at a flow rate v and washing it under normal pressure and temperature T, the phosphorus fluoride can react with hydrogen fluoride to generate phosphorus pentafluoride during the washing process (the reactions involved are shown in reaction formula 4 and reaction formula 4-1), thus improving both the purity and yield of phosphorus pentafluoride.

[0035] PF a X b +bHF=PF5+bHX Reaction 4

[0036] PF a Cl b +b HF=PF5+b HCl Reaction Equation 4-1

[0037] In addition, during the washing process described above, other impurities in the first mixed gas can be removed by dissolving in liquid hydrogen fluoride, or by reacting with hydrogen fluoride to generate high-boiling-point compounds, which are then dissolved in liquid hydrogen fluoride. For example, sulfur trioxide can react with hydrogen fluoride to generate high-boiling-point fluorosulfonic acid (the reaction involved is shown in reaction formula 5). The generated high-boiling-point compounds, as well as the high-boiling-point compounds such as fluorosulfonic acid and sulfuric acid originally present in the first mixed gas, dissolve in liquid hydrogen fluoride. That is, the high-boiling-point compounds remain in liquid hydrogen fluoride, thereby achieving the effect of removing impurities.

[0038] SO3 + HF = FSO3H (Reaction equation 5)

[0039] Specifically, the first mixed gas is phosphorus pentafluoride gas containing impurities, which can be derived from conventional phosphorus pentafluoride preparation processes in the art. Specifically, the phosphorus pentafluoride gas obtained by the phosphorus pentafluoride preparation process contains impurities. This phosphorus pentafluoride gas containing impurities is used as the first mixed gas. Through the above-mentioned phosphorus pentafluoride purification process, the impurities can be effectively removed, the purity of the obtained phosphorus pentafluoride can be improved, and the yield of phosphorus pentafluoride can be increased.

[0040] For example, the first mixed gas may include phosphorus pentafluoride gas (phosphorus pentafluoride mixture) prepared according to the following phosphorus pentafluoride preparation process: phosphorus pentafluoride gas is obtained by decomposing hexafluorophosphoric acid at high temperature (e.g., 140°C–160°C) using fuming sulfuric acid or sulfur trioxide as a dehydrating agent. This phosphorus pentafluoride preparation process may, for example, be the process described in patent documents CN104261369B or CN101570328B. The phosphorus pentafluoride gas prepared by this type of phosphorus pentafluoride preparation process typically contains primarily a first impurity.

[0041] For example, the first mixed gas may include phosphorus pentafluoride gas obtained by reacting phosphorus pentachloride and hydrogen fluoride. That is, the phosphorus pentafluoride gas may be phosphorus pentafluoride gas prepared by a phosphorus pentafluoride preparation process based on the reaction of phosphorus pentachloride and hydrogen fluoride to produce phosphorus pentafluoride. The phosphorus pentafluoride preparation process may be, for example, the phosphorus pentafluoride gas prepared by the relevant process described in patent documents CN115583661A or CN114538406A. In addition to phosphorus trifluoride oxyfluoride, the phosphorus pentafluoride gas prepared by such a phosphorus pentafluoride preparation process also contains a second impurity.

[0042] The phosphorus pentafluoride purification method of this invention is applicable to the purification of phosphorus pentafluoride gas obtained by various phosphorus pentafluoride preparation processes. For example, it is applicable to the purification of phosphorus pentafluoride gas produced by the process route of using fuming sulfuric acid or sulfur trioxide as a dehydrating agent to decompose hexafluorophosphoric acid at high temperature to obtain phosphorus pentafluoride gas, and the purification of phosphorus pentafluoride gas produced by the process route based on the reaction of phosphorus pentachloride and hydrogen fluoride. It can efficiently remove impurities such as phosphorus trifluoride oxyfluoride, sulfur-containing compounds (such as SO3, FSO3H, H2SO4), and halogen-containing compounds (such as hydrogen halides and / or phosphorus fluorohalides) from these phosphorus pentafluoride gases. At the same time, it can convert at least some of the impurities into phosphorus pentafluoride (for example, it can convert phosphorus trifluoride oxyfluoride and phosphorus fluorohalides into phosphorus pentafluoride), and can inhibit the reaction between phosphorus pentafluoride and hydrogen fluoride, thereby efficiently removing impurities from phosphorus pentafluoride gas while improving the yield of phosphorus pentafluoride.

[0043] Specifically, the temperature T used for washing the first mixed gas with liquid hydrogen fluoride can be -50℃ to 15℃ (i.e., -50℃ ≤ T ≤ 15℃), for example, a range of -50℃, -45℃, -40℃, -35℃, -30℃, -25℃, -20℃, -18℃, -15℃, -12℃, -10℃, -8℃, -5℃, -3℃, 0℃, 1℃, 3℃, 5℃, 8℃, 10℃, 13℃, 15℃, or any combination thereof, preferably -20℃ ≤ T. A temperature range of ≤10℃ is advantageous for further improving the purity and yield of phosphorus pentafluoride. The reason for this is that within this temperature range, it is easier to adapt to conditions such as atmospheric pressure and the flow rate (v) of liquid hydrogen fluoride in the first mixed gas. This allows for the regulation of the contact state and thermodynamic reaction behavior between phosphorus trifluoride and other gas molecules and hydrogen fluoride, inhibiting the reaction between phosphorus pentafluoride and hydrogen fluoride, and promoting the forward reaction of impurity molecules such as phosphorus trifluoride with hydrogen fluoride towards the formation of phosphorus pentafluoride, thereby improving the purity and yield of phosphorus pentafluoride. Furthermore, compared to a temperature condition of T < -20℃, controlling the temperature T within the range of -20℃ to 10℃ requires less energy and is easier to operate. Therefore, by further controlling -20℃ ≤ T ≤ 10℃, it is beneficial to further improve the purity and yield of phosphorus pentafluoride while making the purification process more energy-efficient and simpler to operate.

[0044] Specifically, the flow rate (ventilation rate) v of the first mixed gas can be, for example, a range of 2 mL / min, 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, or any combination thereof.

[0045] Furthermore, the mass ratio of the first mixed gas to liquid hydrogen fluoride can be 1:(1-10), for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, or any combination thereof. This is beneficial for further improving the purity and yield of phosphorus pentafluoride. The reason for this is that during the washing of the first mixed gas with liquid hydrogen fluoride, high-boiling-point compounds in the first mixed gas, as well as high-boiling-point compounds generated by the reaction of impurities in the first mixed gas with hydrogen fluoride, continuously dissolve in the liquid hydrogen fluoride. Maintaining a relatively high amount of liquid hydrogen fluoride (the mass ratio of the first mixed gas to liquid hydrogen fluoride should not exceed 1:10) can further weaken the influence of these high-boiling-point compounds on the washing effect of the first mixed gas. For example, it is beneficial for the liquid hydrogen fluoride to be absorbed during the washing process. The process maintains high purity and dilutes the concentration of high-boiling-point compounds in the liquid hydrogen fluoride, reducing their interference with the reaction between impurity molecules in the first mixed gas and hydrogen fluoride. This further improves the washing effect on the first mixed gas, increasing the purity and yield of phosphorus pentafluoride. Simultaneously, with a mass ratio of the first mixed gas to liquid hydrogen fluoride of not less than 1:1, and by introducing the first mixed gas into the liquid hydrogen fluoride at a flow rate v and washing at atmospheric pressure and temperature T, a good washing effect can be achieved with a small amount of liquid hydrogen fluoride, improving the yield and purity of phosphorus pentafluoride. The reduced amount of liquid hydrogen fluoride helps lower costs and reduces the need for post-processing of the washed liquid hydrogen fluoride, resulting in a lower cost and simpler process for the entire phosphorus pentafluoride supply.

[0046] Specifically, the liquid hydrogen fluoride used can be anhydrous hydrogen fluoride (or anhydrous hydrogen fluoride solution), which can be obtained by conventional methods in the art, such as being commercially available or self-made by conventional methods in the art.

[0047] In practice, a first mixed gas containing phosphorus pentafluoride and impurities can be introduced into liquid hydrogen fluoride under low temperature (temperature T) conditions (the amount of the first mixed gas and the amount of liquid hydrogen fluoride used should meet the above mass ratio). The mixture is then washed under stirring. After stirring and washing, a second mixed gas is obtained. Then, phosphorus pentafluoride (high-purity phosphorus pentafluoride gas) is separated from the second mixed gas through distillation and other treatments.

[0048] Specifically, the second mixed gas is phosphorus pentafluoride gas containing hydrogen fluoride. In the process of separating phosphorus pentafluoride from the second mixed gas, the main process is to separate phosphorus pentafluoride and impurities such as hydrogen fluoride to obtain purified phosphorus pentafluoride.

[0049] In some embodiments, the process of separating phosphorus pentafluoride from the second mixed gas may include: distilling the second mixed gas to obtain phosphorus pentafluoride (gas phase) and a liquid phase containing hydrogen fluoride, and returning (refluxing) the liquid phase containing hydrogen fluoride to the liquid hydrogen fluoride to participate in the washing process of the first mixed gas, forming a cycle. This is beneficial to improve the utilization rate of hydrogen fluoride while simultaneously improving the yield and purity of phosphorus pentafluoride, further reducing costs, and reducing the post-processing of the washed liquid hydrogen fluoride. As a result, the entire phosphorus pentafluoride supply process has advantages such as lower cost and simpler process flow.

[0050] According to the inventors' research, the first mixed gas is passed into liquid hydrogen fluoride at a flow rate v for washing, and with appropriate temperature T and atmospheric pressure conditions, the reaction between phosphorus pentafluoride and hydrogen fluoride can be suppressed under these washing conditions. Furthermore, the reaction between phosphorus trifluoride oxyfluoride and hydrogen fluoride can be redirected towards the formation of phosphorus pentafluoride, thus converting phosphorus trifluoride oxyfluoride into phosphorus pentafluoride. (When the first mixed gas contains phosphorus fluorohalides, the reaction between phosphorus fluorohalides and hydrogen fluoride can also be redirected towards the formation of phosphorus pentafluoride, fluorinating the phosphorus fluorohalides into phosphorus pentafluoride.) This reduces the generation of new impurities during the entire washing process (for example, it prevents the reaction of phosphorus pentafluoride with hydrogen fluoride to form phosphorus hexafluoride). Phosphoric acid fluoride, phosphorus trifluoride oxyfluoride, and hydrogen fluoride react to produce hexafluorophosphoric acid. After distillation of the second mixed gas, the liquid phase containing hydrogen fluoride can be kept at a high purity (this liquid phase is essentially liquid hydrogen fluoride). This liquid phase is then refluxed into liquid hydrogen fluoride (equivalent to treating the liquid phase containing hydrogen fluoride as liquid hydrogen fluoride) for recycling. Under this circulating washing process, the yield and purity of phosphorus pentafluoride can be improved, and the recycling of hydrogen fluoride can be achieved, further reducing costs and reducing the post-processing of the washed liquid hydrogen fluoride. This makes the entire phosphorus pentafluoride supply process have advantages such as lower cost and simpler process flow.

[0051] Specifically, the process of distilling the second mixed gas may include: condensing the second mixed gas to liquefy the hydrogen fluoride in the second mixed gas, thereby obtaining a gas phase containing phosphorus pentafluoride and a liquid phase containing hydrogen fluoride, respectively.

[0052] In some embodiments, the conditions for distilling (condensing) the second mixed gas can be: a pressure of 0.6 MPa to 1 MPa, for example, a range of 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa or any combination thereof; and a temperature of -70°C to -50°C, for example, -70°C, -68°C, 65°C, -63°C, -60°C, -58°C, -55°C, -53°C, -50°C or any combination thereof. Under these conditions, hydrogen fluoride and phosphorus pentafluoride gases can be efficiently separated, which facilitates the condensation and liquefaction of hydrogen fluoride in the second mixed gas to form a liquid phase (condensate) containing hydrogen fluoride. At the same time, the formed liquid phase containing hydrogen fluoride has a low temperature, which is beneficial for its return to the liquid hydrogen fluoride for recycling. It can also participate in controlling the temperature of the liquid hydrogen fluoride used to wash the first mixed gas, so that the first mixed gas introduced into the liquid hydrogen fluoride is washed under low temperature (T≤15°C) conditions, saving energy consumption.

[0053] Generally, when the second mixed gas contains virtually no hydrogen halides, the first mixed gas correspondingly contains virtually no hydrogen halides or impurities that can generate hydrogen halides during the washing process. In this case, the impurities in the first mixed gas include, for example, the first impurity but virtually no second impurity. Specifically, this type of first mixed gas can be phosphorus pentafluoride gas obtained by high-temperature decomposition of hexafluorophosphoric acid using fuming sulfuric acid or sulfur trioxide as a dehydrating agent. In this case, after distilling the second mixed gas, the resulting gas phase is purified phosphorus pentafluoride (i.e., high-purity phosphorus pentafluoride gas). That is, in the purification process of phosphorus pentafluoride, the obtained second mixed gas can be directly distilled to separate the purified phosphorus pentafluoride without further washing or other treatments before distillation.

[0054] When the second mixed gas contains hydrogen halides (such as hydrogen chloride), these hydrogen halides may include hydrogen halides (second impurities) present in the first mixed gas and / or hydrogen halides produced during the washing of the first mixed gas with liquid hydrogen fluoride (e.g., hydrogen halides produced by the reaction of phosphorus fluoride and hydrogen fluoride). In this case, the impurities in the first mixed gas may include the second impurities. Specifically, this type of first mixed gas may be phosphorus pentafluoride gas produced by a phosphorus pentafluoride preparation process based on the reaction of phosphorus pentachloride and hydrogen fluoride to produce phosphorus pentafluoride. In this case, the second mixed gas can be washed with a detergent to remove the hydrogen halides before distillation. That is, in the purification process of phosphorus pentafluoride, the second mixed gas can be washed with a detergent and then distilled to obtain phosphorus pentafluoride and a liquid phase containing hydrogen fluoride. During the washing process of the second mixed gas with the detergent, the hydrogen halides in the second mixed gas are removed, and the liquid phase containing hydrogen fluoride is returned to the liquid hydrogen fluoride, forming a cycle.

[0055] Specifically, the detergent may include fuming sulfuric acid, and the temperature during the washing process of the second mixed gas with the detergent may be 5-15°C (i.e., the second mixed gas may be washed at a temperature of 5-15°C), for example, a range of 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 11°C, 12°C, 13°C, 14°C, 15°C or any combination thereof. During this washing process, hydrogen halide reacts with sulfur trioxide in the detergent to generate halosulfonic acid (e.g., hydrogen chloride reacts with sulfur trioxide to generate chlorosulfonic acid), thereby removing hydrogen chloride.

[0056] In specific implementation, if the first mixed gas contains virtually no hydrogen halides, liquid hydrogen fluoride can be placed in the first reactor, and then the first mixed gas can be introduced into the liquid hydrogen fluoride in the first reactor. Under normal pressure and temperature T, the mixture is washed to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride. Then, the second mixed gas is fed into a distillation apparatus for distillation to obtain phosphorus pentafluoride and a liquid phase containing hydrogen fluoride, respectively. The liquid phase containing hydrogen fluoride is then returned to the first reactor to form a cycle.

[0057] Furthermore, if the second mixed gas contains hydrogen halides (such as hydrogen chloride), liquid hydrogen fluoride can be placed in the first reactor, and then the first mixed gas can be introduced into the liquid hydrogen fluoride in the first reactor for washing under normal pressure and temperature T to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride. Then, the second mixed gas is introduced into the second reactor and contacted with the detergent entering the second reactor to remove impurities such as hydrogen halides from the second mixed gas, resulting in a washed second mixed gas. Subsequently, the washed second mixed gas is introduced into a distillation unit for distillation to obtain phosphorus pentafluoride and a liquid phase containing hydrogen fluoride, respectively. The liquid phase containing hydrogen fluoride is then returned to the first reactor to form a cycle.

[0058] In this embodiment of the invention, the first reactor, the second reactor, and the distillation equipment used can be conventional equipment capable of performing the above-mentioned washing, distillation, and other processes. The operating conditions of each device, such as temperature and pressure, can be adjusted in a conventional manner, and there are no particular limitations on this.

[0059] The present invention will be further described below through examples.

[0060] Example 1

[0061] In this embodiment 1, the first mixed gas is phosphorus pentafluoride gas obtained by decomposing hexafluorophosphoric acid at a high temperature of about 150°C using fuming sulfuric acid as a dehydrating agent. The impurities in the mixture include sulfur trioxide, fluorosulfonic acid, sulfuric acid, phosphorus oxyfluoride, and hydrogen fluoride.

[0062] In this embodiment 1, the purification process of the first mixed gas includes:

[0063] S101. The first mixed gas is passed into liquid hydrogen fluoride at a flow rate v and washed under normal pressure and temperature T to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride.

[0064] S102. The second mixed gas is distilled to obtain purified phosphorus pentafluoride and a liquid phase containing hydrogen fluoride.

[0065] S103. The liquid phase containing hydrogen fluoride is refluxed into the liquid hydrogen fluoride in step S101 to form a cycle.

[0066] Examples 2 to 22, Comparative Examples 1 to 5: The difference from Example 1 is that the flow rate v and temperature T in step S101, the mass ratio of the first mixed gas to liquid hydrogen fluoride, and the distillation temperature and pressure in step S102 (distillation temperature and distillation pressure in Table 1) are different, as shown in Table 1. Except for the differences shown in Table 1, the other conditions are the same.

[0067] Example 23

[0068] In this embodiment 23, the first mixed gas is phosphorus pentafluoride gas obtained by reacting phosphorus pentachloride and hydrogen fluoride, and the impurities include phosphorus trifluoride, hydrogen fluoride, hydrogen chloride and phosphorus fluoride.

[0069] In this embodiment 23, the purification process of the first mixed gas includes:

[0070] S201. The first mixed gas is passed into liquid hydrogen fluoride at a flow rate v and washed under normal pressure and temperature T to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride.

[0071] S202. The second mixed gas is passed into fuming sulfuric acid and washed with fuming sulfuric acid to remove hydrogen chloride, thereby obtaining the washed second mixed gas.

[0072] S203. The second mixed gas after washing obtained in step S202 is subjected to distillation to obtain purified phosphorus pentafluoride and liquid phase containing hydrogen fluoride, respectively.

[0073] S204. The liquid phase containing hydrogen fluoride is refluxed into the liquid hydrogen fluoride in step S201 to form a cycle.

[0074] Examples 24 to 40, and Comparative Examples 6 to 10: The differences from Example 23 are as follows: the flow rate v and temperature T in step S201, the mass ratio of the first mixed gas to liquid hydrogen fluoride, the temperature of the process of washing the second mixed gas with fuming sulfuric acid in step S202 (fuming sulfuric acid washing temperature in Table 1), and the temperature and pressure of distillation in step S203 (distillation temperature and distillation pressure in Table 1) are different. See Table 1 for details. Except for the differences shown in Table 1, the other conditions are the same.

[0075] In addition, the purity of purified phosphorus pentafluoride in each embodiment and comparative example was measured by Fourier transform infrared spectroscopy, as shown in Table 1.

[0076] In addition, the yields of purified phosphorus pentafluoride in each embodiment and comparative example, measured by a mass flow meter, are shown in Table 1; wherein, the yield of purified phosphorus pentafluoride = mass of purified phosphorus pentafluoride / mass of the first mixed gas.

[0077] Table 1

[0078]

[0079] As shown in Table 1, compared to Comparative Examples 1 to 5, Examples 1 to 22, through synergistic control of the flow rate v (2 mL / min ≤ v ≤ 10 mL / min), washing temperature T (T ≤ 15 °C), and washing pressure (atmospheric pressure) of the first mixed gas, can efficiently purify phosphorus pentafluoride gas obtained by high-temperature decomposition of hexafluorophosphoric acid using fuming sulfuric acid as a dehydrating agent, while simultaneously improving the purity and yield of phosphorus pentafluoride. Specifically, the flow rate of the first mixed gas in Comparative Example 1 was too low (v < 2 mL / min), the flow rate in Comparative Example 2 was too high (v > 10 mL / min), and the washing temperature T in Comparative Example 3 was too high (T > 15 °C), resulting in lower phosphorus pentafluoride yield and purity. Even after increasing the washing temperature T and washing pressure in Comparative Example 4, and in Comparative Example 5, after increasing the flow rate v of the first mixed gas, the washing temperature T, and the washing pressure, it was still difficult to simultaneously improve the yield and purity of phosphorus pentafluoride.

[0080] Further, as can be seen from Examples 1, 5 to 11, by further controlling -50℃≤T≤15℃, Examples 1, 6 to 11 can improve the purity and yield of phosphorus pentafluoride with lower energy consumption. In particular, Examples 1 and 8 to 10, by further controlling -20℃≤T≤10℃, can further improve the purity and yield of phosphorus pentafluoride, and have the advantages of low energy consumption and simple operation.

[0081] Further, as can be seen from Examples 1, 12 to 17, Examples 1 and 13 to 16 can further improve the purity and yield of phosphorus pentafluoride by further controlling the mass ratio of the first mixed gas to liquid hydrogen fluoride within the range of 1:(1 to 10).

[0082] Furthermore, as can be seen from Examples 1, 18 to 20, Examples 1, 18 and 19 can further improve the purity and yield of phosphorus pentafluoride by further controlling the distillation temperature within the range of -70℃ to -50℃.

[0083] Furthermore, compared to Comparative Examples 6 to 10, Examples 23 to 40, by synergistically controlling the flow rate v (2 mL / min ≤ v ≤ 10 mL / min), washing temperature T (T ≤ 15°C), and washing pressure (atmospheric pressure) of the first mixed gas, can efficiently purify phosphorus pentafluoride gas obtained by the reaction of phosphorus pentachloride and hydrogen fluoride, while simultaneously improving the purity and yield of phosphorus pentafluoride. Specifically, in Comparative Example 6, the flow rate of the first mixed gas was too low (v < 2 mL / min), in Comparative Example 7, the flow rate was too high (v > 10 mL / min), and in Comparative Example 8, the washing temperature T was too high (T > 15°C), resulting in low yields and purity of phosphorus pentafluoride. In Comparative Example 9, even after increasing the washing temperature T and washing pressure, and in Comparative Example 10, after increasing the flow rate v of the first mixed gas, the washing temperature T, and the washing pressure, it was still difficult to simultaneously improve the yield and purity of phosphorus pentafluoride.

[0084] Further, as can be seen from Examples 24, 26 to 30, Examples 24, 27 to 30, by further controlling -50℃≤T≤15℃, can further improve the purity and yield of phosphorus pentafluoride with lower energy consumption. In particular, Examples 24, 28 and 29, by further controlling -20℃≤T≤10℃, can further improve the purity and yield of phosphorus pentafluoride, and have the advantages of low energy consumption and simple operation.

[0085] Further, as can be seen from Examples 24, 31 to 34, Examples 24, 32 and 33 can further improve the purity and yield of phosphorus pentafluoride by further controlling the mass ratio of the first mixed gas to liquid hydrogen fluoride within the range of 1:(1 to 10).

[0086] Furthermore, as can be seen from Examples 24, 35 to 37, Examples 24, 35 and 36 can further improve the purity and yield of phosphorus pentafluoride by further controlling the distillation temperature within the range of -70℃ to -50℃.

[0087] Furthermore, as can be seen from Examples 24, 38 to 40, Examples 24, 38 and 39 can further improve the purity and yield of phosphorus pentafluoride by further controlling the temperature within the range of 5-15°C.

[0088] The results in Table 1 demonstrate that, in this embodiment of the invention, by passing a first mixed gas containing phosphorus pentafluoride and impurities into liquid hydrogen fluoride for washing, and by synergistically controlling the flow rate v, temperature T, and pressure (atmospheric pressure) to satisfy 2 mL / min ≤ v ≤ 10 mL / min, T ≤ 15 °C, and pressure at atmospheric pressure, impurities in the first mixed gas can be effectively removed, improving the purity of the obtained phosphorus pentafluoride. Simultaneously, the reaction between phosphorus pentafluoride and hydrogen fluoride can be inhibited, and impurities such as phosphorus trifluoride can be directed towards the reaction with hydrogen fluoride to generate phosphorus pentafluoride, thereby significantly improving the yield of phosphorus pentafluoride. Furthermore, it avoids the reaction of impurities such as phosphorus trifluoride with hydrogen fluoride to generate other impurity molecules, which would negatively impact the washing effect of phosphorus pentafluoride, thus further ensuring the purity of phosphorus pentafluoride. Based on this, by further adjusting the flow rate v of the first mixed gas, the washing temperature T, the mass ratio of the first mixed gas to liquid hydrogen fluoride, and the distillation temperature, the purification effect of phosphorus pentafluoride gas can be further optimized within the above-mentioned optimal range, thereby further improving the yield and purity of phosphorus pentafluoride.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying phosphorus pentafluoride, characterized in that, Includes the following steps: A first mixed gas containing phosphorus pentafluoride and impurities is passed into liquid hydrogen fluoride at a flow rate v and washed under normal pressure and temperature T to obtain a second mixed gas containing phosphorus pentafluoride and hydrogen fluoride; wherein the impurities include phosphorus trifluoride, T≤15℃, 2mL / min≤v≤10mL / min; The phosphorus pentafluoride was obtained by separating it from the second mixed gas.

2. The method for purifying phosphorus pentafluoride according to claim 1, characterized in that, -50℃≤T≤15℃。 3. The method for purifying phosphorus pentafluoride according to claim 2, characterized in that, -20℃≤T≤10℃。 4. The method for purifying phosphorus pentafluoride according to claim 1, characterized in that, The mass ratio of the first mixed gas to the liquid hydrogen fluoride is 1:(1-10).

5. The method for purifying phosphorus pentafluoride according to claim 1, characterized in that, The impurities include a first impurity and / or a second impurity; The first impurity includes one or more of sulfur trioxide, fluorosulfonic acid, sulfuric acid, phosphorus oxyfluoride, and hydrogen fluoride; The second impurity includes hydrogen halides and / or phosphorus fluorohalides.

6. The method for purifying phosphorus pentafluoride according to claim 5, characterized in that, The hydrogen halide includes hydrogen chloride; And / or, the phosphorus fluorohalides include phosphorus fluorochlorides, preferably the phosphorus fluorochlorides include one or more of phosphorus tetrafluoromonochloride, phosphorus trifluorodichloride, phosphorus difluorotrichloride, and phosphorus monofluorotetrachloride.

7. The method for purifying phosphorus pentafluoride according to any one of claims 1-6, characterized in that, The process of separating the phosphorus pentafluoride from the second mixed gas includes: distilling the second mixed gas to obtain the phosphorus pentafluoride and a liquid phase containing hydrogen fluoride; and returning the liquid phase containing hydrogen fluoride to the liquid hydrogen fluoride.

8. The method for purifying phosphorus pentafluoride according to claim 6, characterized in that, The impurity includes a second impurity, and the second mixed gas includes hydrogen halide; the process of separating the phosphorus pentafluoride from the second mixed gas includes: The second mixed gas is washed with a detergent and then distilled to obtain phosphorus pentafluoride and a liquid phase containing hydrogen fluoride; wherein, the hydrogen halide in the second mixed gas is removed during the washing process with the detergent. The liquid phase containing hydrogen fluoride is returned to the liquid hydrogen fluoride.

9. The method for purifying phosphorus pentafluoride according to claim 8, characterized in that, The detergent includes fuming sulfuric acid, and the temperature during the washing process of the second mixed gas with the detergent is 5-15°C.

10. The method for purifying phosphorus pentafluoride according to any one of claims 7-9, characterized in that, The distillation conditions are: pressure of 0.6 MPa to 1 MPa and temperature of -70℃ to -50℃.

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