A method for purifying phosphorus pentafluoride

Abstract

The present invention provides a method for purifying phosphorus pentafluoride, which comprises the following steps: subjecting an adsorbent to a first nitrogen purge treatment to obtain a primary treatment adsorbent; contacting the primary treatment adsorbent with chlorine gas to subject the primary treatment adsorbent to a chlorination treatment to obtain a secondary treatment adsorbent; contacting the secondary treatment adsorbent with hydrogen fluoride to subject the secondary treatment adsorbent to a fluorination treatment to obtain a tertiary treatment adsorbent; subjecting the tertiary treatment adsorbent to a second nitrogen purge treatment to obtain a purified adsorbent; contacting the purified adsorbent with a mixture comprising chlorine gas and phosphorus pentafluoride to obtain refined phosphorus pentafluoride; the adsorbent is activated carbon. The method for purifying phosphorus pentafluoride provided by the present invention has the characteristics of low cost and safety, and can produce high-purity phosphorus pentafluoride.

Description

Technical Field

[0001] The invention relates to the field of chemical industry, and in particular to a method for purifying phosphorus pentafluoride. Background Art

[0002] Lithium hexafluorophosphate is used as the electrolyte of lithium-ion batteries. The existing product forms are mainly solid salt and liquid salt. The solid salt is mostly prepared by the reaction of chlorine with phosphorus trichloride and HF to produce phosphorus pentafluoride. The purity of phosphorus pentafluoride is about 40%, the hydrogen chloride content is about 60%, and it also contains <0.1% of the key impurity of chlorine. The liquid salt adopts the polyphosphoric acid method to produce phosphorus pentafluoride, and the purity of phosphorus pentafluoride is >99.9%.

[0003] The polyphosphoric acid method uses polyphosphoric acid and hydrogen fluoride and nicotinic acid through multi-step reactions and separations. Although the purity is high, the process involves multiple corrosive acids such as hydrogen fluoride, nicotinic acid, sulfuric acid, hexafluorophosphoric acid, sulfonic acid, etc., and has high requirements on the material and form of the equipment, and the production cost of phosphorus pentafluoride is relatively high. The chlorine method uses chlorine to react with phosphorus trichloride and HF to prepare phosphorus pentafluoride. The production process is relatively short and the cost is relatively high. The polyphosphoric acid method has significant advantages. Among them, hydrogen chloride has been shown to be inert in the salt-forming reaction of liquid lithium hexafluorophosphate. The key impurity chlorine will cause the liquid lithium hexafluorophosphate product to have defects such as high residual chlorine and high color number.

[0004] At present, there are few literatures on the purification and separation of phosphorus pentafluoride by chlorine gas. Among them, CN217780758U reported the use of distillation to solve the problem that the intermediate components synthesized in the phosphorus pentafluoride synthesis reactor are complex and cannot be directly used for lithium hexafluorophosphate synthesis. However, this method has high requirements for the condensation process, so the cost is high, and the acidic corrosive gas needs to be compressed to high pressure, which has certain safety hazards.

[0005] Therefore, developing a low-cost and safe method for purifying phosphorus pentafluoride that can produce high-purity phosphorus pentafluoride has become a research direction in this field. Summary of the invention

[0006] The invention provides a method for purifying phosphorus pentafluoride. The method has the characteristics of low cost and safety, and can prepare high-purity phosphorus pentafluoride.

[0007] The present invention provides a method for purifying phosphorus pentafluoride, which comprises the following steps:

[0008] Performing a first nitrogen purge treatment on the adsorbent to obtain a primary treated adsorbent;

[0009] Using chlorine gas to contact the primary treatment adsorbent, chlorinating the primary treatment adsorbent to obtain a secondary treatment adsorbent;

[0010] contacting the secondary treatment adsorbent with hydrogen fluoride to perform fluorination treatment on the secondary treatment adsorbent to obtain a tertiary treatment adsorbent;

[0011] performing a second nitrogen purge treatment on the tertiary treated adsorbent to obtain a purified adsorbent;

[0012] contacting the purification adsorbent with a mixture comprising chlorine gas and phosphorus pentafluoride to obtain purified phosphorus pentafluoride;

[0013] The adsorbent is activated carbon.

[0014] The method for purifying phosphorus pentafluoride as described above, wherein the treatment temperature of the first nitrogen purge treatment is 80-200°C, the treatment pressure is 0-0.3MPa, and the treatment space velocity is 10-30h -1 , the processing time is 300-700min.

[0015] In the above-mentioned method for purifying phosphorus pentafluoride, when the dew point of the gas obtained by the first nitrogen purge treatment is lower than -20°C, the first nitrogen purge treatment is stopped.

[0016] In the above-mentioned method for purifying phosphorus pentafluoride, the treatment temperature of the chlorination treatment is 100-160° C., the treatment pressure is 0.1-0.5 MPa, and the treatment time is 150-300 min.

[0017] In the above-mentioned method for purifying phosphorus pentafluoride, when the CO content in the gas obtained by the chlorination treatment is less than 1 ppm, the chlorination treatment is stopped.

[0018] In the above-mentioned method for purifying phosphorus pentafluoride, the treatment temperature of the fluorination treatment is 30-70° C., the treatment pressure is 0.1-0.4 MPa, and the treatment time is 80-300 min.

[0019] The method for purifying phosphorus pentafluoride as described above, wherein the treatment temperature of the second nitrogen purge treatment is 30-70°C, the treatment pressure is 0.1-0.4MPa, and the treatment space velocity is 10-30h -1 , the processing time is 100-500min.

[0020] In the above-mentioned method for purifying phosphorus pentafluoride, when the HF content in the gas obtained by the second nitrogen purge treatment is less than 0.1 ppm, the second nitrogen purge treatment is stopped.

[0021] The method for purifying phosphorus pentafluoride as described above, wherein during the contacting process of the purification adsorbent with the mixture comprising chlorine and phosphorus pentafluoride, the pressure is 0.6-1.2 MPa, the temperature is -45 to -30°C, and the space velocity is 0.5-1.5 h -1, the chlorine content after removal is <0.1ppm.

[0022] In the above-mentioned method for purifying phosphorus pentafluoride, phosphorus trichloride, chlorine gas and hydrogen fluoride are reacted to obtain the mixture including chlorine gas and phosphorus pentafluoride.

[0023] The phosphorus pentafluoride purification method provided by the present invention uses hot nitrogen, chlorine and hydrogen fluoride to remove trace moisture and unstable carbon source in an adsorbent respectively to obtain a purified adsorbent; then the purified adsorbent is used to contact phosphorus pentafluoride containing chlorine to remove the trace chlorine contained therein, thereby obtaining phosphorus pentafluoride with high purity, low cost and relatively safe. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme in the embodiment of the present application will be described in more detail below. The same or similar reference numerals throughout represent the same or similar parts or parts with the same or similar functions. The described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The embodiments described below are exemplary and are intended to be used to explain the present application, and should not be construed as limitations on the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present application. The embodiments of the present application are described in detail below.

[0025] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, or it can be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0026] In the description of the present application, it should be understood that the terms "upper", "lower", "front", "back", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating directions or positional relationships, are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present application.

[0027] The description and claims of the present application and the terms "first", "second" and "third" (if any) are used to distinguish similar objects and are not necessarily used to describe a particular sequence or order.

[0028] In addition, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, for example, a process, method, system, product, or display comprising a series of steps or elements is not necessarily limited to those steps or elements explicitly listed, but may include other steps or elements not explicitly listed or inherent to such process, method, product, or display.

[0029] In addition, the pressures mentioned in the present invention are all gauge pressures.

[0030] In the prior art, when adsorbents are used to adsorb chlorine from phosphorus pentafluoride containing chlorine, new impurities such as phosphorus oxyfluoride and low-boiling chlorinated alkane are often introduced into the phosphorus pentafluoride. The inventors speculate that the reason may be that the adsorbent contains trace amounts of water and unstable substances, which react with chlorine to produce impurities. Therefore, if the purity of the adsorbent can be improved, the above defects can be solved.

[0031] Based on this, the first aspect of the present invention provides a method for purifying phosphorus pentafluoride, the method comprising the following steps:

[0032] Performing a first nitrogen purge treatment on the adsorbent to obtain a primary treated adsorbent;

[0033] Using chlorine gas to contact the primary treatment adsorbent, chlorinating the primary treatment adsorbent to obtain a secondary treatment adsorbent;

[0034] contacting the secondary treatment adsorbent with hydrogen fluoride to fluorinate the secondary treatment adsorbent to obtain a tertiary treatment adsorbent;

[0035] performing a second nitrogen purge treatment on the tertiary treated adsorbent to obtain a purified adsorbent;

[0036] contacting a purification adsorbent with a mixture comprising chlorine gas and phosphorus pentafluoride to obtain purified phosphorus pentafluoride;

[0037] The adsorbent is activated carbon.

[0038] When the adsorbent is activated carbon, the present invention does not limit the specific type of activated carbon. In a preferred embodiment, the adsorbent is specifically coconut shell type granular activated carbon, the pH of the activated carbon is 6-7, and the particle size is 30-100 mesh. Using this adsorbent to purify phosphorus pentafluoride can obtain a better purification effect.

[0039] In addition, the mixture comprising chlorine and phosphorus pentafluoride means that the mixture contains chlorine and phosphorus pentafluoride at the same time. The present invention does not exclude the presence of other substances in the mixture. For example, in one embodiment, the mixture also includes hydrogen chloride. In a more specific embodiment, the mixture comprising chlorine and phosphorus pentafluoride is composed of a mass ratio of phosphorus pentafluoride:hydrogen chloride of (39-41):(59-61), and the content of chlorine in the mixture is 0.01-0.1wt%.

[0040] The first nitrogen purge treatment refers to purging the adsorbent with nitrogen. In this process, nitrogen can remove the moisture contained in the adsorbent, so that the moisture content in the primary treatment adsorbent is lower. The present invention does not limit the specific treatment conditions of the first nitrogen purge treatment, and it only needs to meet the requirement that nitrogen can be used to remove moisture from the adsorbent. The present invention also does not limit the treatment device for performing the first nitrogen purge treatment. In one embodiment, the adsorbent can be placed in a DN25 tubular fixed bed, and nitrogen is introduced from one end of the tubular fixed bed to purge the adsorbent, and leaves from the other end of the tubular fixed bed, thereby completing the first nitrogen purge treatment.

[0041] Subsequently, chlorine is used to contact the primary treatment adsorbent, and the primary treatment adsorbent is chlorinated to obtain a secondary treatment adsorbent. In this process, chlorine is in contact with the primary treatment adsorbent, and the chlorine reacts with the residual moisture in the primary treatment adsorbent and the carbon element contained in the adsorbent to further remove the moisture in the adsorbent. Specifically, in this process, chlorine reacts with water and carbon to generate carbon monoxide and hydrogen chloride. Both carbon monoxide and hydrogen chloride are gases that escape from the adsorbent, thereby removing the moisture in the adsorbent.

[0042] The present invention does not limit the specific reaction conditions of the chlorination treatment, and it only needs to meet the requirement that chlorine reacts with water and carbon to generate carbon monoxide and hydrogen chloride. In addition, the present invention also does not limit the treatment device for performing the chlorination treatment. In one embodiment, the DN25 tubular fixed bed can be used in the same manner as the first nitrogen purge treatment, and nitrogen is introduced from one end of the tubular fixed bed, contacts with the primary treatment adsorbent, and leaves from the other end of the tubular fixed bed, thereby completing the chlorination treatment.

[0043] Subsequently, hydrogen fluoride is used to contact the secondary treatment adsorbent, and the secondary treatment adsorbent is subjected to fluorination treatment to obtain a tertiary treatment adsorbent. During the chlorination treatment, chlorine can react with the unstable carbon source in the adsorbent to generate chlorinated carbon compounds such as carbon tetrachloride. The above chlorinated carbon compounds react with hydrogen fluoride during the fluorination treatment to generate chlorofluoroalkanes with lower boiling points. The chlorofluoroalkanes are easy to detach from the adsorbent, thereby completing the removal of the unstable carbon source in the adsorbent.

[0044] The present invention does not limit the specific reaction conditions of the fluorination treatment, and only needs to satisfy the requirement that hydrogen fluoride reacts with chlorinated carbon compounds to generate fluorochloroalkanes. In addition, the present invention also does not limit the treatment device for performing the fluorination treatment. In one embodiment, a DN25 tubular fixed bed can be used, and hydrogen fluoride is introduced from one end of the tubular fixed bed, contacts with the secondary treatment adsorbent, and leaves from the other end of the tubular fixed bed, thereby completing the fluorination treatment.

[0045] Subsequently, the tertiary treatment adsorbent is subjected to a second nitrogen purge treatment to obtain a purified adsorbent. During the second nitrogen purge treatment, nitrogen contacts the tertiary treatment adsorbent to purge and remove the fluorochloroalkanes generated during the fluorination treatment, further reducing the possibility of the removal of the unstable carbon source during the adsorption process to generate impurities, thereby further improving the purity of the adsorbent.

[0046] The present invention does not limit the specific treatment conditions of the second nitrogen purge treatment, and it only needs to meet the requirement that nitrogen can be used to remove moisture from the adsorbent. The present invention also does not limit the treatment device for performing the second nitrogen purge treatment. In one embodiment, the adsorbent can be placed in a DN25 tubular fixed bed, and nitrogen is introduced from one end of the tubular fixed bed to purge the tertiary treatment adsorbent and leave from the other end of the tubular fixed bed, thereby completing the second nitrogen purge treatment.

[0047] Finally, the purified adsorbent obtained in the above steps is contacted with a mixture including chlorine and phosphorus pentafluoride to purify the chlorine in the adsorbed mixture, thereby improving the purity of phosphorus pentafluoride.

[0048] The present invention is not limited to the processing device used to perform the above process. In one embodiment, the purification adsorbent can be placed in a DN25 tubular fixed bed, and the mixture including chlorine and phosphorus pentafluoride is introduced from one end of the tubular fixed bed, contacts with the mixture including chlorine and phosphorus pentafluoride, and leaves from the other end of the tubular fixed bed, thereby completing the purification of phosphorus pentafluoride.

[0049] The method for purifying phosphorus pentafluoride provided by the present invention adopts an efficient and low-cost method to remove residual chlorine in a mixed gas of phosphorus pentafluoride and hydrogen chloride, and the chlorine content can be controlled to be below 1ppm. The method combines physical and chemical methods to deeply remove moisture in the adsorbent, and overcomes the problem of generating phosphorus oxytrifluoride impurities and heat generation due to the reaction of moisture with phosphorus pentafluoride during the dechlorination process. In addition, the method also removes unstable carbon sources in the adsorbent by chlorination and fluorination methods, avoids the generation of low-boiling fluorochloroalkanes during the dechlorination process and the impact on downstream applications. The process of the present invention is simple to operate, can avoid the risk of new substances generated during the absorption process, ensures safe and low-energy consumption removal of phosphorus pentafluoride impurities, and enables phosphorus pentafluoride by chlorine method to meet the production requirements of liquid lithium hexafluorophosphate.

[0050] The above process involves the following reactions:

[0051] C+Cl 2 →CCl 4

[0052] C+H 2 O+Cl 2 →CO+HCl

[0053] CC1 4 +HF→CCl 2 F 2 +CClF 3 +CF 4

[0054] In order to more efficiently remove free water and adsorbed water in the adsorbent, the treatment temperature of the first nitrogen purge treatment can be controlled to 80-200°C, the treatment pressure to 0-0.3MPa, and the treatment air velocity to 10-30h -1 , the treatment time is 300-700min. The above treatment conditions balance the relationship between efficient desorption and adsorbent stability through appropriate temperature and space velocity, which not only ensures the full removal of water, but also avoids the damage of high temperature to the adsorbent structure and activity. At the same time, the uniform purge under low pressure conditions further enhances the dehydration effect. The overall technical effect is to thoroughly dry the adsorbent, avoid the generation of side reaction impurities such as phosphorus oxyfluoride due to residual water during the subsequent chlorine and phosphorus pentafluoride treatment, thereby improving the process efficiency and product purity.

[0055] Furthermore, in order to further improve the efficiency of the first nitrogen purge treatment, the first nitrogen purge treatment can be stopped when the dew point of the gas obtained by the first nitrogen purge treatment is less than -20°C. The gas obtained by the first nitrogen purge treatment refers to a gas whose main component is nitrogen obtained after contact with the adsorbent.

[0056] Dew point is a key indicator for measuring the water vapor content in the gas. The lower the dew point, the less water content in the gas. When the dew point is below -20°C, the water vapor content in the gas is already very low, indicating that most of the residual water in the pores and on the surface of the adsorbent has been desorbed. In addition, this dew point range is already lower than the critical water content required for water to induce side reactions in many chemical reactions. Therefore, it can fundamentally avoid the formation of by-products caused by the presence of water in subsequent steps, such as the formation of trifluorophosphorus oxyfluoride or low-boiling point chlorinated compounds, further improving the reliability of the process and product purity. At the same time, by controlling the purge endpoint through dew point, not only can the completion status of water removal be accurately judged, but also unnecessary energy consumption and potential loss of adsorbents can be avoided, making the entire process more efficient and economical.

[0057] In one embodiment, the treatment temperature of the chlorination treatment can be controlled to be 100-160°C, the treatment pressure to be 0.1-0.5MPa, and the treatment time to be 150-300min. The above treatment conditions are more conducive to the reaction of chlorine with the residual moisture and unstable carbon source in the adsorbent to generate volatile products such as carbon monoxide and hydrogen chloride, thereby further removing deep moisture and unstable carbon source in the adsorbent. This process effectively improves the purity of the adsorbent and avoids side reactions caused by residual moisture and carbon source during the subsequent use of the adsorbent, such as the generation of phosphorus oxyfluoride or low-boiling chlorinated alkanes.

[0058] In order to further improve the efficiency of chlorination treatment, chlorination treatment can be stopped when the CO content in the gas obtained by chlorination treatment is less than 1ppm. The reason is that the CO content can directly reflect the degree of removal of residual moisture and unstable carbon sources in the adsorbent. During the chlorination process, chlorine reacts with moisture and carbon to produce CO and HCl. When the CO content drops to less than 1ppm, it indicates that the deep moisture and carbon source in the adsorbent have been basically completely removed. Stopping the treatment at this time can avoid energy waste caused by excessive reaction and possible structural damage to the adsorbent, while ensuring that the adsorbent reaches the optimal purification state, providing higher selectivity and efficiency for the subsequent removal of trace chlorine in the phosphorus pentafluoride mixed gas, thereby improving the economy of the overall process and product purity.

[0059] Further, in one embodiment, the treatment temperature of the fluorination treatment can also be controlled to be 30-70°C, the treatment pressure to be 0.1-0.4MPa, and the treatment time to be 80-300min. Controlling the above conditions can make hydrogen fluoride more efficiently react with the chlorinated carbon compounds (such as carbon tetrachloride, etc.) generated by the oxidation of chlorine and unstable carbon in the adsorbent during the chlorine treatment process to generate volatile products such as fluorochloroalkanes with lower boiling points, thereby effectively removing unstable carbon sources in the adsorbent. This process can further improve the purity of the adsorbent, avoid the generation of by-products (such as low-boiling fluorochloroalkanes, specifically such as monofluorotrichloride, difluorocarbon dichloride, trifluorocarbon monochloride, etc.) due to the participation of unstable carbon sources in the reaction in subsequent dechlorination operations, thereby ensuring the high purity of the product and the safety of downstream applications.

[0060] In one embodiment, the second nitrogen purge treatment can also be controlled to have a treatment temperature of 30-70°C, a treatment pressure of 0.1-0.4 MPa, and a treatment air velocity of 10-30 h. -1 , the processing time is 100-

[0061] 500min. Controlling the above conditions can more efficiently remove low-boiling-point byproducts such as chlorofluorocarbons and other residual volatile substances generated during the fluorination process through nitrogen purging, thereby further improving the purity of the adsorbent. This treatment effectively avoids secondary pollution or adverse reactions that may be caused by residual byproducts in subsequent dechlorination operations, while ensuring the stability and high selectivity of the adsorbent during use.

[0062] In order to improve the efficiency of the second nitrogen purge treatment, the second nitrogen purge treatment is stopped when the HF content in the gas obtained by the second nitrogen purge treatment is less than 0.1ppm. When the HF content drops to less than 0.1ppm, it indicates that the chlorofluorocarbons and other volatile substances inside the adsorbent have been completely removed, and the adsorbent has reached a high purity state. Stopping the purge at this time not only avoids the energy waste caused by excessive treatment, but also protects the structure and activity of the adsorbent, ensuring that it has higher selectivity and adsorption efficiency in subsequent dechlorination operations, while greatly reducing the risk of potential side reactions or product contamination caused by residual HF, providing a reliable guarantee for the production of high-purity phosphorus pentafluoride.

[0063] Further, during the contacting of the purified adsorbent with the mixture comprising chlorine and phosphorus pentafluoride, the pressure of the contacting process can be controlled to be 0.6-1.2 MPa, the temperature to be -45 to -30°C, and the space velocity to be 0.5-1.5 h -1 , the chlorine content after removal is <0.1ppm. Controlling the above conditions can efficiently and selectively remove trace chlorine in phosphorus pentafluoride mixed gas, reducing the chlorine content after removal to <0.1ppm. This process condition ensures the efficient adsorption performance of the adsorbent for chlorine, while avoiding competition or interference with the adsorption sites of the adsorbent by other components (such as phosphorus pentafluoride and hydrogen chloride), ensuring the high purity of the product.

[0064] In one embodiment, the mixture comprising chlorine and phosphorus pentafluoride can be prepared by the following method: phosphorus trichloride, chlorine, and hydrogen fluoride are reacted to obtain a mixture comprising chlorine and phosphorus pentafluoride. The present invention does not limit the specific conditions of the above reaction, as long as phosphorus trichloride, chlorine, and hydrogen fluoride can be reacted to obtain a mixture comprising chlorine and phosphorus pentafluoride. In one embodiment, the reaction conditions of the above reaction are: operating temperature 10-30°C, operating pressure 0.9-1.8Mpa, and the molar ratio of phosphorus trichloride, chlorine, and hydrogen fluoride is 1: (1-1.02): (5-5.1).

[0065] The following is a detailed explanation of the method for purifying phosphorus pentafluoride provided by the present invention through specific examples.

[0066] The following examples use Beijing Jianzhi online Raman infrared analyzer to test the substance content.

[0067] Example 1

[0068] The DN25 tubular fixed bed was filled with 200 mL of 100-mesh coconut shell activated carbon as the adsorbent, and the pH of the activated carbon was 6.7. The adsorbent was subjected to the first nitrogen purge treatment, and the specific process was as follows: the temperature was raised to 95°C, the operating pressure was 0.05 MPa, the bed purge medium was nitrogen, and the nitrogen space velocity was 30 h -1 The purge was continued for 630 min at this air velocity. The dew point at the outlet was tested by a dew point meter and was -26.3°C, thereby obtaining a primary treatment adsorbent.

[0069] The nitrogen in the fixed bed was vented, and the temperature was raised to 136°C. Chlorine was introduced into the fixed bed for chlorination treatment. The specific process was as follows: the pressure of the fixed bed was set to 0.45 MPa and maintained at this condition for 210 minutes. The chlorine in the fixed bed was then vented. The process of pressure relief and venting was continuously monitored by a gas detector. The CO content decreased from the initial 8.5 ppm to 0.27 ppm, and a secondary treatment adsorbent was obtained.

[0070] After the chlorine is emptied from the fixed bed, the operating temperature is reduced from 136°C to 58°C, and HF is introduced into the fixed bed for fluorination treatment. The specific process is: the pressure of the fixed bed is reduced to 0.34MPa, and after staying under this condition for 112 minutes, the tertiary treatment adsorbent is obtained. Nitrogen is introduced into the fixed bed for the second nitrogen purge treatment. The specific process is: the nitrogen space velocity is 13h -1 During the nitrogen replacement and purging process, the temperature was kept constant and the purging was continued for 320 minutes. The HF content detected at the outlet was 0.05ppm. After the above operation, the pretreatment of the adsorbent was completed to obtain a purified adsorbent.

[0071] The temperature of the fixed bed containing the purified adsorbent was reduced to -32 °C, the operating pressure was 1.14 MPa, and the space velocity was 1.3 h -1 The raw material composition of the mixed gas introduced was 40.56wt% phosphorus pentafluoride, 59.38wt% hydrogen chloride, and 0.06wt% chlorine. It was continuously monitored using an online Raman infrared analyzer. The composition of the outlet mixed gas was 40.58wt% phosphorus pentafluoride and 59.42wt% hydrogen chloride, with a chlorine content of 0.07ppm.

[0072] Example 2

[0073] The DN25 tubular fixed bed was filled with 200 mL of 100-mesh coconut shell activated carbon as the adsorbent. The pH of the activated carbon was 6.5. The adsorbent was subjected to the first nitrogen purge treatment. The specific process was as follows: the temperature was raised to 172°C, the operating pressure was 0.17 MPa, the bed purge medium was nitrogen, and the nitrogen space velocity was 18 h -1The purge was continued for 475 min at this air velocity. The dew point at the outlet was tested by a dew point meter and was -30.1°C, thereby obtaining a primary treatment adsorbent.

[0074] The nitrogen in the fixed bed was vented, and the temperature was raised to 107°C. Chlorine was introduced into the fixed bed to make the pressure of the fixed bed 0.29 MPa. This condition was maintained for 280 minutes. The chlorine in the fixed bed was then emptied. The process of pressure relief and emptying was continuously monitored by a gas detector. The CO content decreased from the initial 6.3 ppm to 0.35 ppm.

[0075] After the chlorine is emptied from the fixed bed, the operating temperature is reduced from 107°C to 42°C, and HF is introduced into the fixed bed for fluorination treatment. The specific process is: the pressure of the fixed bed is reduced to 0.22MPa, and after staying under this condition for 176 minutes, the tertiary treatment adsorbent is obtained. Nitrogen is introduced into the fixed bed for the second nitrogen purge treatment. The specific process is: the nitrogen space velocity is 27h -1 During the nitrogen replacement and purging process, the temperature was kept unchanged and the purging was continued for 190 minutes. The HF content detected at the outlet was 0.06ppm. After the above operation, the pretreatment of the adsorbent was completed to obtain a purified adsorbent.

[0076] The temperature of the fixed bed containing the purified adsorbent was reduced to -37 °C, the operating pressure was 0.84 MPa, and the air velocity was 0.9 h -1 The raw material composition of the mixed gas introduced was 40.17wt% phosphorus pentafluoride, 59.80wt% hydrogen chloride, and 0.03wt% chlorine. It was continuously monitored using an online Raman infrared analyzer. The composition of the outlet mixed gas was 40.18wt% phosphorus pentafluoride and 59.82wt% hydrogen chloride, with a chlorine content of 0.06ppm.

[0077] Example 3

[0078] The DN25 tubular fixed bed was filled with 200 mL of 100-mesh coconut shell activated carbon as the adsorbent. The pH of the activated carbon was 6.8. The adsorbent was subjected to the first nitrogen purge treatment. The specific process was as follows: the temperature was raised to 143°C, the operating pressure was 0.26 MPa, the bed purge medium was nitrogen, and the nitrogen space velocity was 12 h -1 The purge was continued for 340 min at this air velocity. The dew point at the outlet was tested by a dew point meter and was -21.6°C, thereby obtaining a primary treatment adsorbent.

[0079] The nitrogen in the fixed bed was vented, and the temperature was raised to 154°C. Chlorine was introduced into the fixed bed for chlorination treatment. The specific process was as follows: the pressure of the fixed bed was set to 0.16 MPa and maintained at this condition for 160 minutes. The chlorine in the fixed bed was then vented. The process of pressure relief and venting was continuously monitored by a gas detector. The CO content dropped from the initial 10.7 ppm to 0.31 ppm, and a secondary treatment adsorbent was obtained.

[0080] After the chlorine is emptied from the fixed bed, the operating temperature is reduced from 154°C to 32°C, and HF is introduced into the fixed bed for fluorination treatment. The specific process is: the pressure of the fixed bed is adjusted to 0.15MPa, and after staying under this condition for 280 minutes, a tertiary treatment adsorbent is obtained. Nitrogen is introduced into the fixed bed for the second nitrogen purge treatment. The specific process is: the nitrogen space velocity is 21h -1 During the nitrogen replacement and purging process, the temperature was kept constant and the purging was continued for 470 minutes. The HF content detected at the outlet was 0.04 ppm. After the above operation, the pretreatment of the adsorbent was completed to obtain a purified adsorbent.

[0081] The temperature of the fixed bed containing the purified adsorbent was reduced to -45 °C, the operating pressure was 0.63 MPa, and the space velocity was 0.6 h -1 The raw material composition of the mixed gas introduced was 39.28wt% phosphorus pentafluoride, 60.63wt% hydrogen chloride, and 0.09wt% chlorine. It was continuously monitored using an online Raman infrared analyzer. The composition of the outlet mixed gas was 39.32wt% phosphorus pentafluoride and 60.68wt% hydrogen chloride, with a chlorine content of 0.03ppm.

[0082] Comparative Example 1

[0083] The DN25 tubular fixed bed was filled with 200 mL of 100-mesh coconut shell activated carbon. The pH of the activated carbon was 6.7. The temperature of the fixed bed was reduced to -28°C, the operating pressure was 1.14 MPa, and the air velocity was 1.3 h -1 The raw material composition of the mixed gas introduced was 40.56wt% of phosphorus pentafluoride, 59.38wt% of hydrogen chloride, and 0.06wt% of chlorine. It was continuously monitored using an online Raman infrared analyzer. The composition of the outlet mixed gas was 40.53wt% of phosphorus pentafluoride, 59.41wt% of hydrogen chloride, 0.05wt% of phosphorus oxytrifluoride, and 0.01% of low-fluorine chlorinated phosphide (monochlorophosphorus tetrafluoride and dichlorophosphorus trifluoride), of which the content of chlorine was 0.09ppm.

[0084] Comparative Example 2

[0085] The DN25 tubular fixed bed was filled with 200 mL of 100-mesh coconut shell activated carbon, the pH of the activated carbon was 6.7, the temperature was raised to 95°C, the operating pressure was 0.05 MPa, the bed purge medium was nitrogen, and the nitrogen space velocity was 30 h -1 The purge was continued at this airspeed for 630 minutes, and the dew point at the outlet was tested by a dew point meter and was -26.3℃.

[0086] The temperature of the fixed bed dropped to -28°C, the operating pressure was 1.14 MPa, and the air velocity was 1.3 h -1 The raw material composition of the mixed gas introduced is 40.56wt% of phosphorus pentafluoride, 59.38wt% of hydrogen chloride, and 0.06wt% of chlorine. It is continuously monitored using an online Raman infrared analyzer. The composition of the outlet mixed gas is 40.57wt% of phosphorus pentafluoride, 59.42wt% of hydrogen chloride, 0.008wt% of phosphorus trifluoride, and 0.002wt% of low-fluorine chlorinated phosphides (monochlorophosphorus tetrafluoride and dichlorophosphorus trifluoride), wherein the chlorine content is 0.08ppm.

[0087] It can be seen from the above that the outlet mixed gas obtained in Comparative Examples 1 and 2 has higher concentrations of chlorine, phosphorus oxytrifluoride and low-fluorine chlorophosphide than that in each embodiment. The reason may be that in Comparative Example 1, untreated adsorbent is directly contacted with a mixture including chlorine and phosphorus pentafluoride, and the trace moisture and unstable carbon source contained in the adsorbent react with chlorine and phosphorus pentafluoride to generate phosphorus oxytrifluoride and low-fluorine chlorophosphide impurities, and chlorine is difficult to be completely removed; Comparative Example 2 only performs a first nitrogen purge treatment on the adsorbent, and does not use chlorine and hydrogen fluoride to remove the unstable carbon source present in the adsorbent, so that the concentrations of chlorine, phosphorus oxytrifluoride and low-fluorine chlorophosphide in the obtained product are all high.

[0088] Finally, it should be noted that those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include common knowledge or customary technical means in the art not disclosed by the present invention, are not limited to the precise structure described above, and may be modified and changed in various ways without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for purifying phosphorus pentafluoride, characterized in that: The steps include: Performing a first nitrogen purge treatment on the adsorbent to obtain a primary treated adsorbent; Using chlorine gas to contact the primary treatment adsorbent, chlorinating the primary treatment adsorbent to obtain a secondary treatment adsorbent; contacting the secondary treatment adsorbent with hydrogen fluoride to perform fluorination treatment on the secondary treatment adsorbent to obtain a tertiary treatment adsorbent; performing a second nitrogen purge treatment on the tertiary treated adsorbent to obtain a purified adsorbent; contacting the purification adsorbent with a mixture comprising chlorine gas and phosphorus pentafluoride to obtain purified phosphorus pentafluoride; The adsorbent is activated carbon.

2. The method for purifying phosphorus pentafluoride according to claim 1, characterized in that: The treatment temperature of the first nitrogen purge treatment is 80-200°C, the treatment pressure is 0-0.3MPa, and the treatment air velocity is 10-30h -1 , the processing time is 300-700min.

3. The method for purifying phosphorus pentafluoride according to claim 2, characterized in that: When the dew point of the gas obtained by the first nitrogen purge process is lower than -20°C, the first nitrogen purge process is stopped.

4. The method for purifying phosphorus pentafluoride according to any one of claims 1 to 3, characterized in that: The treatment temperature of the chlorination treatment is 100-160° C., the treatment pressure is 0.1-0.5 MPa, and the treatment time is 150-300 min.

5. The method for purifying phosphorus pentafluoride according to claim 4, characterized in that: When the CO content in the gas obtained by the chlorination treatment is less than 1 ppm, the chlorination treatment is stopped.

6. The method for purifying phosphorus pentafluoride according to any one of claims 1 to 5, characterized in that: The fluorination treatment has a treatment temperature of 30-70° C., a treatment pressure of 0.1-0.4 MPa, and a treatment time of 80-300 min.

7. The method for purifying phosphorus pentafluoride according to any one of claims 1 to 6, characterized in that: The treatment temperature of the second nitrogen purge treatment is 30-70°C, the treatment pressure is 0.1-0.4MPa, and the treatment air velocity is 10-30h -1 , the processing time is 100-500min.

8. The method for purifying phosphorus pentafluoride according to claim 7, characterized in that: When the HF content in the gas obtained by the second nitrogen purge treatment is less than 0.1 ppm, the second nitrogen purge treatment is stopped.

9. The method for purifying phosphorus pentafluoride according to any one of claims 1 to 8, characterized in that: During the contacting of the purified adsorbent with a mixture comprising chlorine and phosphorus pentafluoride, the pressure is 0.6-1.2 MPa, the temperature is -45 to -30°C, and the space velocity is 0.5-1.5 h -1 , the chlorine content after removal is <0.1ppm.

10. The method for purifying phosphorus pentafluoride according to any one of claims 1 to 9, characterized in that: Phosphorus trichloride, chlorine gas and hydrogen fluoride are reacted to obtain the mixture including chlorine gas and phosphorus pentafluoride.