Method for preparing phosphorus pentafluoride

Abstract

Provided in the present application is a method for preparing phosphorus pentafluoride, comprising: mixing a hexafluorophosphoric acid solution and a dehydrating agent, and then performing a dehydration reaction, the dehydration reaction being performed at 30-160°C under a pressure of 0.1-3 MPa, and the hexafluorophosphoric acid solution containing water and hydrogen fluoride; after the dehydration reaction is completed, performing quick pressure relief on the reaction system to obtain a mixed gas containing phosphorus pentafluoride, the pressure relief rate of the quick pressure relief being greater than or equal to 0.1 MPa / min; and purifying the mixed gas containing phosphorus pentafluoride to prepare phosphorus pentafluoride gas.

Description

Preparation method of phosphorus pentafluoride

[0001] The present application claims priority to the Chinese patent application No. 202411363234.2, filed on September 27, 2024, and entitled "Preparation method of phosphorus pentafluoride", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the field of phosphorus pentafluoride preparation, in particular to a preparation method of phosphorus pentafluoride. BACKGROUND

[0003] Phosphorus pentafluoride (PF5) is a colorless gas, with a melting point of -93.8℃ and a boiling point of -84.6℃ at normal pressure. It will hydrolyze violently in moist air to produce toxic and corrosive hydrogen fluoride white smoke. It has a relatively wide range of applications, such as being used as a fluorination reagent in the electronic industry and polymer material manufacturing field, and being used as a catalytic fluorination agent in the field of organic synthesis.

[0004] In recent years, with the increasing popularity and promotion of new energy vehicles, lithium ion batteries with lithium hexafluorophosphate as electrolyte have received widespread attention and use. Lithium hexafluorophosphate is mainly used as an electrolyte in the electrolyte of lithium ion batteries. In order to meet the requirements of high electrolyte conductivity, high chemical and electrochemical stability, wide use range, good safety performance, low price and the like, higher requirements are put forward for the purity of lithium hexafluorophosphate (usually the purity of lithium hexafluorophosphate is required to be more than 99.9%), and accordingly higher requirements are also put forward for the purity and other properties of phosphorus pentafluoride as a raw material for preparing lithium hexafluorophosphate.

[0005] The preparation processes of phosphorus pentafluoride gas mainly include phosphorus pentachloride method, fuming sulfuric acid method and fluorine gas method. The existing preparation methods use many raw materials, which can easily introduce impurities and produce by-products, so that the purity of the prepared phosphorus pentafluoride is low. At the same time, the existing preparation processes of phosphorus pentafluoride also have problems such as complex process, high energy consumption, complex structure of equipment used, etc., which limit the actual production and application.

[0006] For example, in the prior art, phosphorus pentafluoride is usually prepared by using polyphosphoric acid, which needs to go through multiple condensation, multi-stage pressurization and rectification processes to realize the preparation and purification of phosphorus pentafluoride gas, and the process is complex.

[0007] For another example, the gas evolution reaction of the fuming sulfuric acid method for preparing phosphorus pentafluoride is mixed with fuming sulfuric acid at low temperature, and the hexafluorophosphoric acid usually contains hydrofluoric acid, which is easy to react with fuming sulfuric acid to generate by-products such as fluorosulfonic acid, thereby affecting the decomposition efficiency of hexafluorophosphoric acid and the purity of phosphorus pentafluoride. SUMMARY

[0008] The application provides a phosphorus pentafluoride preparation method, which can improve the purity of phosphorus pentafluoride, simplify the preparation process, reduce energy consumption and effectively overcome the defects in the prior art.

[0009] The application provides a phosphorus pentafluoride preparation method, which comprises the following steps: mixing a hexafluorophosphoric acid solution and a dehydrating agent to perform a dehydration reaction, wherein the dehydration reaction is performed at a temperature of 30-160 DEG C and a pressure of 0.1-3 MPa; the hexafluorophosphoric acid solution contains water and hydrogen fluoride; after the dehydration reaction is completed, the reaction system is rapidly depressurized to obtain a mixed gas containing phosphorus pentafluoride; the depressurization rate of the rapid depressurization is greater than or equal to 0.1 MPa / min; and the mixed gas containing phosphorus pentafluoride is purified to obtain phosphorus pentafluoride gas.

[0010] According to an embodiment of the application, the mass percentage of water in the hexafluorophosphoric acid solution is 10-30%, and / or the mass percentage of hydrogen fluoride in the hexafluorophosphoric acid solution is 10-50%.

[0011] According to an embodiment of the application, the dehydrating agent comprises fuming sulfuric acid and / or sulfur trioxide; and the molar ratio of the dehydrating agent to water in the hexafluorophosphoric acid solution is (1.5-2):1, calculated based on sulfur trioxide.

[0012] According to an embodiment of the application, the dehydration reaction is performed under stirring at a stirring speed of 100-500 rpm.

[0013] According to an embodiment of the application, the process of mixing the hexafluorophosphoric acid solution and the dehydrating agent to perform the dehydration reaction comprises: adding the hexafluorophosphoric acid solution into a reactor, then adding the dehydrating agent into the reactor, and starting stirring to perform the dehydration reaction.

[0014] According to an embodiment of the application, the dehydration reaction is performed for 3-10 h.

[0015] According to an embodiment of the application, the depressurization rate of the rapid depressurization is 0.1-1 MPa / min.

[0016] According to an embodiment of the application, the depressurization rate of the rapid depressurization is 0.5-1 MPa / min.

[0017] According to an embodiment of the present application, the dehydration reaction is carried out in a reactor, the purification treatment is carried out in a purification unit, the reactor is in communication with the purification unit through a pipeline, the pipeline is provided with a valve; when the dehydration reaction is carried out, the valve is kept closed; after the dehydration reaction is completed, the valve is opened to make the mixed gas in the reactor enter the purification unit, so as to realize the rapid pressure relief.

[0018] According to an embodiment of the present application, the purification treatment comprises: condensing the mixed gas containing phosphorus pentafluoride to obtain the phosphorus pentafluoride gas.

[0019] The present application has at least the following beneficial effects: the temperature in the dehydration reaction process is controlled to be 30-160℃, and the pressure is controlled to be 0.1-3 MPa, so that most of the water in the hexafluorophosphoric acid solution exists in a liquid state, and most of the hydrogen fluoride (HF) exists in a gaseous state, which can make the SO3 from the dehydration agent preferentially react with water to generate sulfuric acid (sulfuric acid is in a liquid phase, and basically will not be doped in the finally prepared phosphorus pentafluoride gas), and reduce the reaction of HF and SO3 and the by-products such as fluorosulfonic acid generated by the reaction, thereby reducing the amount of the dehydration agent, and improving the purity and yield of the prepared phosphorus pentafluoride gas.

[0020] In addition, in the present application, in the dehydration reaction process, the SO3 from the dehydration agent preferentially reacts with water, the reaction of SO3 and water is an exothermic reaction, which can supplement the heat required in the dehydration process, improve the dehydration efficiency, and reduce external heating, thereby reducing energy consumption.

[0021] In addition, in the present application, in the dehydration reaction process, the hexafluorophosphoric acid is decomposed into HF and phosphorus pentafluoride (PF5), but the decomposition is not complete, and after the dehydration reaction is completed, the rapid pressure relief can produce a flash effect, which is beneficial to the rapid and complete decomposition of the hexafluorophosphoric acid, and improves the conversion rate of the hexafluorophosphoric acid.

[0022] In addition, in the present application, the dehydration reaction of the hexafluorophosphoric acid solution and the reaction of the decomposition of the hexafluorophosphoric acid into phosphorus pentafluoride are carried out in the same reactor, which simplifies the structure of the equipment for preparing phosphorus pentafluoride.

[0023] Therefore, the method for preparing phosphorus pentafluoride provided by the present application has the advantages of fast reaction gas production rate, high conversion rate of hexafluorophosphoric acid, high yield of phosphorus pentafluoride, and reduced generation of by-products, and can reduce energy consumption and the amount of the dehydration agent by utilizing the heat released by the mixed acid (hexafluorophosphoric acid solution and dehydration agent) reaction, which is beneficial to the actual industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0024] FIG. 1 is a preparation flow diagram for preparing phosphorus pentafluoride according to an embodiment of the present application. DETAILED DESCRIPTION

[0025] In order to make the technical personnel in the art better understand the scheme of the present application, the present application is further described in detail below. The following specific embodiments are only to describe the principles and characteristics of the present application, and the examples are only used to explain the present application, but not to limit the scope of the present application. Based on the embodiments of the present application, all other embodiments obtained by the ordinary skilled in the art belong to the scope of protection of the present application.

[0026] The embodiment of the present application provides a preparation method of phosphorus pentafluoride, comprising the following steps: mixing a hexafluorophosphoric acid solution and a dehydrating agent to perform a dehydration reaction, the temperature of the dehydration reaction is 30-160℃, and the pressure of the dehydration reaction is 0.1-3 MPa; wherein the hexafluorophosphoric acid solution contains water and hydrogen fluoride; after the dehydration reaction is completed, the reaction system is rapidly depressurized to obtain a mixed gas containing phosphorus pentafluoride; wherein the depressurization rate of the rapid depressurization is greater than or equal to 0.1 MPa / min; and the mixed gas containing phosphorus pentafluoride is subjected to a purification treatment to obtain phosphorus pentafluoride gas.

[0027] Specifically, the dehydrating agent comprises fuming sulfuric acid and / or sulfur trioxide.

[0028] According to the research of the inventor, SO3 is easy to react with HF and generate by-products such as fluorosulfonic acid, and the boiling point of fluorosulfonic acid is lower than that of sulfuric acid, which is easy to be gasified and doped in the prepared phosphorus pentafluoride gas, and fluorosulfonic acid has poor stability and is easy to decompose into by-products such as HF and sulfuric acid, thereby affecting the purity of the prepared phosphorus pentafluoride gas. However, in the above preparation system of the embodiment of the present application, by controlling the temperature and pressure in the dehydration reaction process within the above range, most of the water in the hexafluorophosphoric acid solution exists in the form of liquid, and most of the HF exists in the form of gas, so that SO3 from the dehydrating agent can preferentially react with water (H2O) to generate sulfuric acid (sulfuric acid is in liquid phase and basically will not be doped in the finally prepared phosphorus pentafluoride gas), thereby reducing the reaction of HF with SO3 and the by-products such as fluorosulfonic acid generated by the reaction, reducing the amount of dehydrating agent, and improving the purity and yield of the prepared phosphorus pentafluoride. In addition, in the above preparation system, even if a small amount of SO3 and HF react to generate fluorosulfonic acid, it will be quickly decomposed into sulfuric acid and HF, and finally the amount of by-products is reduced.

[0029] In addition, in the dehydration reaction process, SO3 from the dehydrating agent preferentially reacts with water, and the reaction of SO3 and water is an exothermic reaction, which can supplement the heat required in the dehydration process, improve the dehydration efficiency, and at the same time reduce external heating, thereby reducing energy consumption.

[0030] In addition, during the dehydration reaction, hexafluorophosphoric acid will decompose into HF and PF5, but the decomposition is not complete. After the dehydration reaction is completed, a flash effect can be generated by rapid pressure relief, which is conducive to the rapid and complete decomposition of hexafluorophosphoric acid towards the generation of phosphorus pentafluoride, thereby improving the conversion rate of hexafluorophosphoric acid (i.e., the phosphorus pentafluoride gas generation efficiency).

[0031] The reaction equation of the partial reaction involved is as follows:

[0032] Main reaction equation: H2O + SO3→ H2SO4 HPF6→ HF + PF5

[0033] Side reaction equation: HF + SO3→ FSO3H

[0034] Specifically, the dehydrating agent can be oleum or sulfur trioxide, or both oleum and sulfur trioxide are used as the dehydrating agent.

[0035] Exemplarily, the temperature of the dehydration reaction described above can be 30°C, 33°C, 35°C, 38°C, 40°C, 43°C, 45°C, 48°C, 50°C, 53°C, 55°C, 58°C, 60°C, 63°C, 65°C, 68°C, 70°C, 73°C, 75°C, 78°C, 80°C, 83°C, 85°C, 88°C, 90°C, 93°C, 95°C, 98°C, 100°C, 103°C, 105°C, 108°C, 110°C, 113°C, 115°C, 118°C, 120°C, 123°C, 125°C, 128°C, 130°C, 133°C, 135°C, 138°C, 140°C, 143°C, 145°C, 148°C, 150°C, 153°C, 155°C, 158°C, 160°C, or a range consisting of any two of them.

[0036] Exemplarily, the pressure of the dehydration reaction described above can be 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa, 0.9 MPa, 1 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa, 1.5 MPa, 1.6 MPa, 1.7 MPa, 1.8 MPa, 1.9 MPa, 2 MPa, 2.1 MPa, 2.2 MPa, 2.3 MPa, 2.4 MPa, 2.5 MPa, 2.6 MPa, 2.7 MPa, 2.8 MPa, 3 MPa, or a range consisting of any two of them.

[0037] Specifically, as shown in Fig. 1, the dehydration reaction is carried out in a reactor, and the purification treatment is carried out in a purification unit, the reactor and the purification unit are connected by a pipeline, and the pipeline is provided with a valve; during the dehydration reaction, the valve is kept closed to maintain a closed environment in the reactor and avoid the gas in the reactor entering the purification unit; after the dehydration reaction is completed, the valve is opened to allow the mixed gas in the reactor to enter the purification unit, thereby achieving rapid pressure relief.

[0038] In the embodiments of the present application, a conventional valve capable of adjusting the pressure relief rate can be used, for example, a control valve with an automatic interlocking device is used, and after the dehydration reaction, the valve is opened to automatically relieve pressure according to the set pressure value and the pressure relief rate, which is not particularly limited. For example, the valve used is a Q41F-16P valve.

[0039] In the embodiments of the present application, the temperature of the dehydration reaction can be the temperature inside the reactor (also the temperature of the reaction system after the hexafluorophosphoric acid solution and the dehydrating agent are mixed to carry out the dehydration reaction), which can be controlled by a conventional temperature control device arranged in the reactor, which is not particularly limited.

[0040] In addition, the temperature of the dehydration reaction can be regulated by external heating or cooling, for example, the reaction of SO3 and water produced by the dehydrating agent is an exothermic reaction, if the heat generated by the exothermic reaction in the reactor is insufficient to reach the preset dehydration reaction temperature, additional heat can be supplied by external heating to make the temperature in the reactor reach the preset dehydration reaction temperature; if the heat generated by the exothermic reaction in the reactor is too high, the temperature in the reactor can be lowered by external cooling to make the temperature in the reactor reach the preset dehydration reaction temperature.

[0041] In the embodiments of the present application, the pressure of the dehydration reaction refers to the pressure in the reactor, which can be controlled and monitored by conventional methods, for example, the reactor used can be a reaction kettle (such as a stainless steel reaction kettle, a high-pressure reaction kettle, etc.) connected with a control pressure valve.

[0042] In the embodiments of the present application, the pressure relief rate of the rapid pressure relief is greater than or equal to 0.1 MPa / min, that is, during the rapid pressure relief, the pressure in the reactor decreases at a rate of at least 0.1 MPa per minute until the pressure balance is reached.

[0043] In some embodiments, the pressure relief rate of the rapid pressure relief is 0.1 MPa / min to 1 MPa / min, for example, 0.1 MPa / min, 0.2 MPa / min, 0.3 MPa / min, 0.4 MPa / min, 0.5 MPa / min, 0.6 MPa / min, 0.7 MPa / min, 0.8 MPa / min, 0.9 MPa / min, 1 MPa / min, or a range defined by any two of them. By further controlling the pressure relief rate in this range, the purity and yield of phosphorus pentafluoride gas can be further improved. The reason is that such a pressure relief rate range is more suitable for the conditions such as temperature and pressure of the above dehydration reaction. In the pressure relief process after the dehydration reaction, the pressure relief state based on the similar flash effect makes the hexafluorophosphoric acid quickly and completely decompose towards the direction of generating phosphorus pentafluoride gas, thereby improving the purity and yield of phosphorus pentafluoride gas.

[0044] Further research shows that the pressure relief rate of the rapid pressure relief can be further 0.5 MPa / min to 1 MPa / min, which is more suitable for the conditions such as temperature and pressure of the above dehydration reaction, and more significantly improves the purity and yield of phosphorus pentafluoride.

[0045] Specifically, the mass percentage of water in the hexafluorophosphoric acid solution (i.e., the proportion of the mass of water to the total mass of the hexafluorophosphoric acid solution) can be 10% to 30%, for example, 10%, 15%, 20%, 25%, 30%, or a range defined by any two of them. This is conducive to reducing the amount of dehydrating agent and reducing the energy consumption of the dehydration reaction process while improving the purity and yield of the prepared phosphorus pentafluoride gas.

[0046] In addition, the mass percentage of hydrogen fluoride in the hexafluorophosphoric acid solution (i.e., the proportion of the mass of HF to the total mass of the hexafluorophosphoric acid solution) can be 10% to 50%, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or a range defined by any two of them. This is conducive to improving the purity of the prepared phosphorus pentafluoride gas.

[0047] In the embodiments of the present application, the hexafluorophosphoric acid solution (aqueous hexafluorophosphoric acid solution) can be obtained according to conventional methods in the art, for example, the hexafluorophosphoric acid solution is obtained by reacting polyphosphoric acid with hydrogen fluoride.

[0048] Specifically, the amount of dehydrating agent can satisfy that the molar ratio of the dehydrating agent (calculated as SO3) to water in the hexafluorophosphoric acid solution is (1.5-2):1, i.e., the amount of substance of the dehydrating agent is 1.5-2 times the amount of substance of water in the hexafluorophosphoric acid solution. Through the above preparation process, the decomposition efficiency of hexafluorophosphoric acid and the yield and purity of phosphorus pentafluoride can be maintained at a relatively high level with a relatively low amount of dehydrating agent.

[0049] Exemplarily, the molar ratio of the dehydrating agent to water in the hexafluorophosphoric acid solution, calculated based on SO3, can be 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or a range between any two of them.

[0050] Generally, the above dehydration reaction can be carried out under stirring. Relatively speaking, if the stirring rate is too slow (<100 rpm), the dehydration rate is slow, which affects the preparation efficiency of phosphorus pentafluoride gas. If the stirring rate is too fast (>500 rpm), SO3 generated by the dehydrating agent is easy to react with HF to generate by-products such as fluorosulfonic acid, which affects the purity of phosphorus pentafluoride gas. Therefore, considering these factors comprehensively, the above dehydration reaction can generally be carried out under stirring at a stirring rate of 100 rpm to 500 rpm.

[0051] Exemplarily, the above stirring rate can be 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, or a range between any two of them.

[0052] Specifically, the process of mixing the hexafluorophosphoric acid solution and the dehydrating agent to carry out the dehydration reaction can include: adding the hexafluorophosphoric acid solution into the reactor, then adding the dehydrating agent into the reactor, and then starting stirring to carry out the dehydration reaction.

[0053] In the embodiment of the present application, during the dehydration reaction, the dehydration reaction promotes the decomposition of hexafluorophosphoric acid to generate gas. When the pressure inside the reactor is basically unchanged, it indicates that the dehydration reaction is completed, and then the valve can be opened for rapid pressure relief.

[0054] Specifically, the dehydration reaction time can be 3h to 10h, for example, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, or a range between any two of them, which is conducive to combining the subsequent rapid pressure relief process, improving the decomposition efficiency of hexafluorophosphoric acid, and at the same time, improving the purity and preparation efficiency of phosphorus pentafluoride.

[0055] Specifically, the above purification treatment can include: condensing the mixed gas containing phosphorus pentafluoride to obtain phosphorus pentafluoride gas. At this time, the purification unit in FIG. 1 can be a condenser.

[0056] Specifically, the mixed gas containing phosphorus pentafluoride contains impurity gas in addition to phosphorus pentafluoride, and the impurity gas mainly includes hydrogen fluoride. As shown in FIG. 1, by condensing the mixed gas containing phosphorus pentafluoride, phosphorus pentafluoride gas (gas phase) and liquid phase containing HF are obtained respectively, thereby recovering the impurity gas such as hydrogen fluoride in the mixed gas containing phosphorus pentafluoride, separating the impurity gas and the phosphorus pentafluoride gas, and obtaining the phosphorus pentafluoride gas.

[0057] The present application does not particularly limit the condenser used for condensing the mixed gas containing phosphorus pentafluoride gas to recover HF and separate phosphorus pentafluoride gas.

[0058] Embodiment

[0059] The following examples and comparative examples are given to more specifically explain the embodiments of the present application. Various tests and evaluations were performed according to the following methods. In addition, "parts" and "%" are mass-based unless otherwise specified.

[0060] Test method and equipment

[0061] Test of phosphorus pentafluoride (PF5) gas purity ： 200 mL of phosphorus pentafluoride gas was sampled using a sampler, filled into a 200 mL infrared detector gas cell, and washed with phosphorus pentafluoride gas three times before being filled again. The gas cell was filled with phosphorus pentafluoride gas, and the gas cell was placed on the FT-IR. The spectrum was collected at 4000-400 cm - 1, 0.5 cm-1 resolution, 32 times of accumulated spectrum collection; the spectrum was collected at 3700 cm - 1 and 900 cm-1, respectively, to quantitatively determine HF and POF3, and the mass percentage content W HF % of HF and the mass percentage content w POF3 % of POF3, and then the PF5 purity was calculated by difference method = 100% - w HF % - w POF3 %.

[0062] Calculation of hexafluorophosphoric acid (HPF6) conversion rate: the molar amount n2 of HPF6 in the fed hexafluorophosphoric acid solution was tested, and the molar amount n1 of PF5 obtained after the reaction was tested, and the conversion rate of HPF6 was calculated = (n1 / n2) x 100%.

[0063] Embodiment 2

[0064] A hexafluorophosphoric acid solution with a water content of 20 wt% and an HF content of 30 wt% was added to a reaction kettle (reactor), and oleum (the amount of oleum used was such that the molar ratio of SO3 in the oleum to water in the hexafluorophosphoric acid solution was 1.8:1) was added thereto, stirring was started, the stirring rate was 300 rpm, and the dehydration reaction was carried out at 80°C and 1.5 MPa, the dehydration reaction time was 5 h, and a mixed gas containing phosphorus pentafluoride was obtained;

[0065] After the dehydration reaction was completed, the valve (valve model Q41F-16P) between the reactor and the condenser was opened, the mixed gas in the reactor entered the condenser, and rapid pressure relief was achieved during this process, the pressure relief rate of the rapid pressure relief was 0.5 MPa / min;

[0066] The mixed gas enters the condenser and is condensed in the condenser at a condensing pressure of 0.1 MPa and a temperature of -10°C, so that the hydrogen fluoride in the mixed gas is condensed into a liquid phase, thereby recovering the hydrogen fluoride from the mixed gas, and the gas phase output from the condenser is the phosphorus pentafluoride gas. The conversion rate of hexafluorophosphoric acid and the purity of the phosphorus pentafluoride gas are measured and shown in Table 1.

[0067] Examples 1, 3-32 and Comparative Examples 1-5 differ from Example 2 in that the water content (mass percentage of water) and the HF content (mass percentage of HF) of the hexafluorophosphoric acid solution, the molar ratio of oleum (calculated as SO3) to water in the hexafluorophosphoric acid solution (SO3:H2O molar ratio in Table 1), the temperature of the dehydration reaction, the pressure of the dehydration reaction, the stirring rate during the dehydration reaction, the dehydration reaction time, the pressure release rate after the dehydration reaction is completed, and the like are different, and the specific conditions are shown in Table 1. Except for the differences shown in Table 1, the other conditions are the same as those of Example 2. The conversion rate of hexafluorophosphoric acid and the purity of the phosphorus pentafluoride gas in each example and comparative example are measured and shown in Table 1.

[0068] Table 1: Preparation conditions of phosphorus pentafluoride and test results

[0069] As can be seen from Table 1, compared with Comparative Examples 1-5, in Examples 1-32, the dehydration reaction is carried out at a temperature of 30-160°C and a pressure of 0.1-3 MPa, and the reaction system after the dehydration reaction is completed is rapidly released at a pressure release rate of greater than or equal to 0.1 MPa / min, which can improve both the conversion rate of hexafluorophosphoric acid (HPF6) and the purity of the phosphorus pentafluoride (PF5) gas.

[0070] More specifically, as can be seen from Comparative Example 1 and Examples 1-4, the pressure release rate of the reaction system after the dehydration reaction affects the conversion rate of HPF6 and the purity of the PF5 gas. Compared with Comparative Example 1, Examples 1-4 can significantly improve the conversion rate of HPF6 (≥88%) and the purity of the PF5 gas (≥90%) by controlling the pressure release rate to be greater than or equal to 0.1 MPa / min. Among them, Examples 1-3 further control the pressure release rate to be in the range of 0.1-1 MPa / min, which is beneficial to further improving the purity of the PF5 gas while maintaining a high conversion rate of HPF6, and in particular, Examples 2 and 3 further control the pressure release rate to be in the range of 0.5-1 MPa / min, which can more significantly improve the purity of the PF5 gas.

[0071] In addition, it can be seen from Comparative Examples 2-5, Example 2, and Examples 5-12 that the dehydration reaction temperature and the reaction pressure affect the conversion rate of HPF6and the purity of PF5gas. Compared with Comparative Examples 2-5, Examples 2 and 5-12 can improve the conversion rate of HPF6(≥ 87%) and the purity of PF5gas (≥ 90%) by controlling the dehydration reaction temperature in the range of 30-160°C and the dehydration reaction pressure in the range of 0.1-3 MPa, while maintaining a lower dehydration reaction temperature and reaction pressure, the reaction conditions are more moderate, and energy consumption can be saved.

[0072] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not limited thereto. Although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions described in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents. The modification or replacement does not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A process for the preparation of phosphorus pentafluoride, characterized in that, The method comprises the following steps: The dehydrating reaction is carried out after mixing the hexafluorophosphoric acid solution and the dehydrating agent, the temperature of the dehydrating reaction is 30-160℃, and the pressure of the dehydrating reaction is 0.1-3 MPa; wherein the hexafluorophosphoric acid solution contains water and hydrogen fluoride; After the dehydrating reaction is completed, the reaction system is rapidly depressurized to obtain a mixed gas containing phosphorus pentafluoride; wherein the depressurization rate of the rapid depressurization is greater than or equal to 0.1 MPa / min; The mixed gas containing phosphorus pentafluoride is subjected to a purification treatment to obtain phosphorus pentafluoride gas.

2. The process for the preparation of phosphorus pentafluoride according to claim 1, characterized in that, The mass percentage of water in the hexafluorophosphoric acid solution is 10-30%; And / or, the mass percentage of hydrogen fluoride in the hexafluorophosphoric acid solution is 10-50%.

3. The process for the preparation of phosphorus pentafluoride according to claim 1, characterized in that, The dehydrating agent comprises oleum and / or sulfur trioxide; the molar ratio of the dehydrating agent to water in the hexafluorophosphoric acid solution is (1.5-2):1 in terms of sulfur trioxide.

4. The process for the preparation of phosphorus pentafluoride according to claim 1, characterized in that, The dehydrating reaction is carried out under stirring at a stirring rate of 100-500 rpm.

5. Process for the preparation of phosphorus pentafluoride according to any one of claims 1 to 4, characterized in that, The process of carrying out the dehydrating reaction after mixing the hexafluorophosphoric acid solution and the dehydrating agent comprises: adding the hexafluorophosphoric acid solution into a reactor, then adding the dehydrating agent into the reactor, and starting stirring to carry out the dehydrating reaction.

6. Process for the preparation of phosphorus pentafluoride according to any one of claims 1 to 4, characterized in that, The time of the dehydrating reaction is 3-10 h.

7. Process for the preparation of phosphorus pentafluoride according to any one of claims 1 to 4, characterized in that, The depressurization rate of the rapid depressurization is 0.1-1 MPa / min.

8. The process for the preparation of phosphorus pentafluoride according to claim 7, characterized in that, The depressurization rate of the rapid depressurization is 0.5-1 MPa / min.

9. The process for the preparation of phosphorus pentafluoride according to any one of claims 1 to 4, characterized in that, The dehydrating reaction is carried out in a reactor, the purification treatment is carried out in a purification unit, the reactor and the purification unit are connected through a pipeline, and the pipeline is provided with a valve; When the dehydrating reaction is carried out, the valve is kept closed; after the dehydrating reaction is completed, the valve is opened to make the mixed gas in the reactor enter the purification unit, thereby realizing the rapid depressurization.

10. The process for the preparation of phosphorus pentafluoride according to any one of claims 1 to 4, characterized in that, The purification treatment comprises condensing the mixed gas containing phosphorus pentafluoride to obtain the phosphorus pentafluoride gas.

Images