Continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride

Abstract

The invention discloses a continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride, which comprises the following steps: (1) a mixed gas containing phosphorus pentafluoride and solid aluminum fluoride react to prepare an aluminum hexafluorophosphate solid, and the mixed gas contains phosphorus pentafluoride, hydrogen fluoride and hydrogen chloride; and (2) heating the prepared aluminum hexafluorophosphate solid to 250-450 DEG C, carrying out thermal decomposition, and collecting to obtain the high-purity phosphorus pentafluoride gas. The method has the advantages of no need of high-pressure and low-temperature physical separation in the technological process, safe and controllable reaction, high product purity, suitability for industrial production and the like.

Description

Technical Field

[0001] The invention relates to the field of new energy materials and is a raw material for preparing lithium hexafluorophosphate, an electrolyte for lithium-ion batteries, and in particular to a continuous preparation method for high-purity phosphorus pentafluoride. Background Art

[0002] In recent years, lithium-ion batteries have become a research hotspot in the field of new energy, and the preparation of lithium hexafluorophosphate, an electrolyte in its electrolyte, has received widespread attention and in-depth research. Generally, the preparation process of lithium hexafluorophosphate includes: 1) using phosphorus pentachloride and hydrogen fluoride as raw materials to prepare a mixed gas of phosphorus pentafluoride and hydrogen chloride; 2) the mixed gas is reacted with a hydrogen fluoride solution containing lithium fluoride to prepare a hydrogen fluoride solution of lithium hexafluorophosphate; 3) low-temperature freezing of the hydrogen fluoride solution containing lithium hexafluorophosphate, crystallization of lithium hexafluorophosphate, and filtering and drying to obtain a solid lithium hexafluorophosphate product. Among them, crystallization includes static crystallization process and dynamic crystallization process. The lithium hexafluorophosphate product obtained by the dynamic crystallization process has a low insoluble content and low acidity, which is better than the product quality obtained by static crystallization.

[0003] In order to meet the demand for higher quality lithium-ion battery electrolytes, in addition to adjusting the crystallization process of electrolyte salts, people have begun to study high-purity phosphorus pentafluoride to obtain high-quality lithium hexafluorophosphate to further improve the quality of the electrolyte.

[0004] Patent CN112850670A discloses a method for purifying a phosphorus pentafluoride mixed gas prepared from phosphorus trichloride, chlorine and hydrogen fluoride as raw materials using a distillation tower. This method can improve the purity of phosphorus pentafluoride, but the distillation of phosphorus pentafluoride requires low temperature and high pressure conditions, which consumes a lot of energy. In addition, phosphorus pentafluoride and hydrogen chloride have similar boiling points, making it difficult to completely separate them, and high-purity phosphorus pentafluoride cannot be obtained.

[0005] Patent CN113955729A discloses a method of using polyphosphoric acid and hydrogen fluoride as raw materials, using fuming sulfuric acid or sulfur trioxide to remove water produced during the reaction, and heating the reaction product hexafluorophosphoric acid to obtain phosphorus pentafluoride. However, this method also produces a by-product, phosphorus oxyfluoride, which needs to be separated to obtain phosphorus pentafluoride; at the same time, the amount of mixed acid produced by this method is large, which brings difficulties to the treatment of three wastes. Patent CN104261369A also discloses a method of using polyphosphoric acid as a raw material, and obtaining high-purity phosphorus pentafluoride through fluorination, dehydration, high-temperature distillation, and refining. Similarly, this patent has complex procedures, and multiple distillations are required to obtain high-purity phosphorus pentafluoride gas, and there are by-products such as phosphorus oxyfluoride, and there are problems in the treatment of fluorine-containing waste sulfuric acid. Patent CN104261369A further discloses a method for preparing high-purity phosphorus pentafluoride, including: 1) preparing a hexafluorophosphoric acid aqueous solution from polyphosphoric acid and anhydrous hydrogen fluoride; 2) reacting the hexafluorophosphoric acid aqueous solution with sulfur trioxide to obtain a mixture of hexafluorophosphoric acid and sulfuric acid; 3) heating the mixture to obtain a crude phosphorus pentafluoride; 4) condensing and liquefying the crude product with liquid nitrogen and pressurizing and rectifying it in a distillation tower to obtain a high-purity phosphorus pentafluoride gas. However, this method also produces a large amount of waste acid, and it is difficult to treat the three wastes.

[0006] Patent CN112320824A discloses a method for producing lithium hexafluorophosphate, which includes: adding a fluorine-binding agent and a chlorine-binding agent to a mixed gas of phosphorus pentafluoride, hydrogen fluoride and hydrogen chloride obtained by the reaction of phosphorus pentachloride and hydrogen fluoride to remove hydrogen fluoride and hydrogen chloride respectively. However, the fluorine-binding agent and chlorine-binding agent used are sulfur trioxide, and the amount of waste acid generated is large and difficult to handle.

[0007] Patent CN114014283A discloses a method for obtaining phosphorus pentafluoride by catalytic reaction of hexafluorophosphate and catalyst solution, followed by condensation, pressurized liquefaction and adsorption of impurities. However, the method is complicated in operation and has high equipment cost.

[0008] Patent CN102372264A discloses a method for purifying phosphorus pentafluoride, which first obtains crude phosphorus pentafluoride gas with a purity of ≥95% by reacting fluorine gas and red phosphorus, then obtains liquid phosphorus pentafluoride gas by freezing and liquefaction, and then introduces high-purity inert gas into the phosphorus pentafluoride liquid to obtain high-purity phosphorus pentafluoride by bubbling and stripping. Although this method can obtain a product with a purity better than 99.9%, the fluorine gas cost is too high, the reaction conditions are harsh, and the equipment requirements are high, which is not conducive to industrial production.

[0009] Based on this, a reaction process is proposed on the basis of the existing process. The process does not require high-pressure and low-temperature physical separation process, the equipment structure is easy to manufacture, the product purity is high, the production process is safe and controllable, environmentally friendly, and suitable for industrial production. The high-purity phosphorus pentafluoride preparation process is of great research value and practical value. Summary of the invention

[0010] In order to solve the above technical problems, the present invention proposes a continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride using aluminum fluoride as a carrier and phosphorus pentafluoride mixed gas as a raw material, which does not require high-pressure and low-temperature physical separation of the mixed gas, has high efficiency, high product purity, a safe and controllable reaction process, is environmentally friendly, and has industrial feasibility and practicality.

[0011] The objective of the present invention is achieved through the following technical solutions:

[0012] A continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride, the preparation method comprising:

[0013] (1) reacting a mixed gas containing phosphorus pentafluoride with solid aluminum fluoride to prepare solid aluminum hexafluorophosphate, wherein the mixed gas contains phosphorus pentafluoride, hydrogen fluoride and hydrogen chloride;

[0014] (2) The aluminum hexafluorophosphate solid is decomposed by heating at 250-450° C., and high-purity phosphorus pentafluoride gas is obtained by collection.

[0015] Preferably, the aluminum hexafluorophosphate solid is thermally decomposed at 250-350°C, more preferably at 250-300°C.

[0016] The solid aluminum fluoride of the present invention is not arbitrary, but must be a porous aluminum fluoride obtained by dry method, free of crystal water, and having a pore size of ≤100nm and a specific surface area of ​​≥1.0m 2 / g;

[0017] The preferred pore size is ≤50nm and the specific surface area is ≥20m 2 / g;

[0018] More preferably, the pore size is ≤20nm and the specific surface area is ≥30m 2 / g.

[0019] The solid aluminum fluoride is a microcrystalline material with a developed internal void structure, a large specific surface area, and a strong adsorption capacity, and the particle size and pore size are evenly distributed. The aluminum fluoride of the present invention only reacts with phosphorus pentafluoride in the mixed gas.

[0020] In one embodiment, the mixed gas containing phosphorus pentafluoride is obtained by reacting phosphorus pentachloride and hydrogen fluoride. During preparation, solid phosphorus pentachloride is added to liquid hydrogen fluoride, or liquid hydrogen fluoride is added to solid phosphorus pentachloride, the molar ratio of phosphorus pentachloride to hydrogen fluoride is 1:(1-10), the reaction temperature is controlled at -20-100°C, and the reaction pressure is controlled at 0.01-0.5MPa;

[0021] The preferred reaction temperature is 50 to 80° C., and the preferred reaction pressure is 0.1 to 0.3 MPa.

[0022] The reaction may be a batch reaction or a continuous reaction, but a continuous reaction is preferred.

[0023] Phosphorus pentachloride and hydrogen fluoride react to generate phosphorus pentafluoride and by-product hydrogen chloride gas, and the reaction releases heat so that phosphorus pentafluoride and hydrogen chloride carry out part of the unreacted hydrogen fluoride when overflowing, forming a mixed gas containing phosphorus pentafluoride, hydrogen chloride and hydrogen fluoride. The mixed gas is introduced into a reactor containing solid aluminum fluoride, and the phosphorus pentafluoride and aluminum fluoride in the mixed gas react to generate aluminum hexafluorophosphate.

[0024] In another embodiment, the mixed gas containing phosphorus pentafluoride is prepared by reacting phosphorus trichloride, hydrogen fluoride and liquid chlorine, the molar ratio of phosphorus trichloride, hydrogen fluoride and liquid chlorine is 1:(1-10):(1-1.1), the reaction temperature is controlled at -10-50°C, and the reaction pressure is controlled at 0.5-3.0MPa;

[0025] The reaction temperature is preferably 5-20°C and the reaction pressure is 1.0-2.5 MPa to ensure that phosphorus trichloride is completely converted into phosphorus pentafluoride. Similarly, the reaction can be a batch reaction or a continuous reaction, preferably a continuous reaction.

[0026] Phosphorus pentafluoride in the mixed gas obtained in the above two embodiments reacts with solid aluminum fluoride, phosphorus pentafluoride reacts completely, unreacted hydrogen fluoride and hydrogen chloride enter the separation system, and are separated by pressurization and low temperature to obtain hydrogen fluoride and hydrogen chloride respectively. Hydrogen fluoride can be recycled, and hydrogen chloride enters the absorption system to prepare industrial hydrochloric acid.

[0027] In step (1), the reaction of the mixed gas containing phosphorus pentafluoride and solid aluminum fluoride is continuously carried out in a double-layer fluidized bed. During the double-layer fluidized bed reaction, the mixed gas containing phosphorus pentafluoride and aluminum fluoride are transported in reverse, specifically: solid aluminum fluoride enters the reactor from the upper feeding port, and the mixed gas containing phosphorus pentafluoride enters from the bottom reaction bed. After the reaction in the lower reaction bed, the unreacted gas enters the upper reaction bed to react with the solid aluminum fluoride. The residence time of phosphorus pentafluoride and aluminum fluoride is 10 to 600 seconds, preferably 30 to 480 seconds, and more preferably 60 to 300 seconds, so that phosphorus pentafluoride is completely converted.

[0028] In step (1), the mixed gas containing phosphorus pentafluoride and aluminum fluoride can also be carried out in a double-layer gas-solid phase reactor or a gas-solid phase reaction tower. The residence time of the mixed gas containing phosphorus pentafluoride and aluminum fluoride is 10 to 600 seconds to ensure that the reaction materials are completely reacted, preferably 60 to 480 seconds, more preferably 120 to 300 seconds, so that phosphorus pentafluoride is completely converted.

[0029] Since the reaction of phosphorus pentafluoride and aluminum fluoride is an exothermic reaction, the reactor (double-layer fluidized bed, double-layer gas-solid phase reactor or gas-solid phase reaction tower) is equipped with a heat transfer jacket to control the reaction temperature.

[0030] In addition, the present invention also controls the reaction speed and heat release rate of phosphorus pentafluoride and aluminum fluoride by controlling the mixed gas flow rate and flow rate to ensure the safety of the reaction process. Specifically,

[0031] In step (1), in the mixed gas containing phosphorus pentafluoride, the molar ratio of phosphorus pentafluoride to aluminum fluoride is 1:(1.0-100), preferably 1:(5-50), and more preferably 1:(5-10), based on the amount of phosphorus pentafluoride.

[0032] In step (1), the reaction temperature of the mixed gas containing phosphorus pentafluoride and aluminum fluoride is 0 to 150°C, preferably 50 to 150°C; more preferably 50 to 100°C.

[0033] In step (1), the reaction pressure of the mixed gas containing phosphorus pentafluoride and aluminum fluoride is 0.1 to 2.0 MPa, and preferably the reaction pressure is controlled between 0.2 and 1.0 MPa.

[0034] In step (2), the thermal decomposition reaction of solid aluminum hexafluorophosphate is carried out in a temperature-controllable thermal decomposition reactor. The thermal decomposition time of aluminum hexafluorophosphate is 0.1 to 10 hours, preferably 0.3 to 6 hours.

[0035] According to any of the above-mentioned continuous or semi-continuous preparation methods of high-purity phosphorus pentafluoride, the continuous preparation method specifically comprises:

[0036] A1. Phosphorus pentafluoride and aluminum fluoride in the mixed gas react continuously in a double-layer fluidized bed to generate aluminum hexafluorophosphate. Other gases in the mixed gas that do not react with aluminum fluoride are pressurized and then separated in a gas separation section. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, and the separated hydrogen fluoride and / or chlorine are recycled;

[0037] A2. The aluminum hexafluorophosphate generated by the reaction continuously enters the thermal decomposition reactor for decomposition, and the generated phosphorus pentafluoride gas is collected through the gas outlet to obtain high-purity phosphorus pentafluoride gas or directly enters the next reaction section through a pipeline.

[0038] In step A2, a screw conveyor is provided in the thermal decomposition reactor to achieve continuous thermal decomposition of aluminum hexafluorophosphate. The screw conveyor is a single screw conveyor or a twin screw conveyor, preferably a twin screw conveyor.

[0039] In step A2, the aluminum fluoride obtained by heating and decomposition is returned to step A1 to continue the reaction.

[0040] In another specific embodiment, the preparation of high-purity phosphorus pentafluoride can also adopt a semi-continuous preparation method, and the semi-continuous preparation method specifically includes:

[0041] B1. The mixed gas containing phosphorus pentafluoride continuously enters a double-layer gas-solid phase reactor or a gas-solid phase reaction tower filled with aluminum fluoride to react and generate aluminum hexafluorophosphate. Other gases in the mixed gas that do not react with aluminum fluoride are discharged through the reactor outlet and pressurized before entering the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, and the separated hydrogen fluoride and / or chlorine are recycled;

[0042] B2. After a controlled amount of mixed gas containing phosphorus pentafluoride is introduced, the feeding is suspended, and the aluminum hexafluorophosphate generated by the reaction is transported to the thermal decomposition reactor for decomposition. The generated phosphorus pentafluoride gas is collected through the gas outlet to obtain high-purity phosphorus pentafluoride gas or directly enters the next reaction section through a pipeline, and the generated aluminum fluoride is collected uniformly; after the decomposition reaction is completed, a fixed amount of aluminum fluoride is loaded into the double-layer gas-solid reactor or the gas-solid reaction tower, and then reacts with the phosphorus pentafluoride mixed gas, and the cycle is repeated in sequence.

[0043] Optionally, the thermal decomposition reactor in step B2 is a thermal decomposition reactor; the aluminum fluoride obtained by thermal decomposition is returned to step B1 to continue the reaction.

[0044] Of course, when designing the device, continuous preparation can also be achieved by setting up double-layer gas-solid reactors, gas-solid reaction towers, thermal decomposition reactors and other equipment in parallel and switching the equipment.

[0045] The method for obtaining phosphorus pentafluoride by thermally decomposing aluminum hexafluorophosphate of the present invention has no other by-products and can obtain high-purity phosphorus pentafluoride gas with a purity of ≥99.95% and a chloride ion content of ≤2ppm without separation or distillation.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] 1. The present invention uses aluminum fluoride as a carrier, first prepares aluminum hexafluorophosphate solid with phosphorus pentafluoride mixed gas and aluminum fluoride, and then obtains high-purity phosphorus pentafluoride gas through thermal decomposition, which can not only effectively remove by-product hydrogen chloride and unreacted raw material chlorine, but also solve the problem that phosphorus pentafluoride and unreacted raw materials hydrogen fluoride and hydrogen chloride are difficult to separate, and has the advantages of no need for high-pressure and low-temperature physical separation, environmental friendliness, high reaction efficiency, high product purity, and aluminum fluoride can be reused and suitable for industrial application.

[0048] 2. The aluminum fluoride carrier of the present invention has good stability. The operation is convenient, safe and controllable in the process of synthesizing aluminum hexafluorophosphate and then thermally decomposing to obtain high-purity phosphorus pentafluoride gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Attached Figure 1 This is a simplified process flow diagram of the continuous preparation of high-purity phosphorus pentafluoride in Example 1 of the present invention;

[0050] Attached Figure 2 This is a simplified process flow diagram of semi-continuous preparation of high-purity phosphorus pentafluoride according to Example 2 of the present invention;

[0051] Attached Figure 3 This is a simplified process flow chart of semi-continuous preparation of high-purity phosphorus pentafluoride according to Example 3 of the present invention. DETAILED DESCRIPTION

[0052] The present invention is further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all possible alternatives, improvements and equivalents within the scope of the claims.

[0053] In the embodiments and comparative examples of the present invention, the analysis and detection methods involved are as follows:

[0054] The molar content of aluminum hexafluorophosphate was determined by the nuclear magnetic resonance internal standard method, specifically: 1,3-di(trifluoromethyl)benzene was used as the internal standard, and the nuclear magnetic resonance fluorine spectrum ( 19 F NMR) analysis.

[0055] The purity of phosphorus pentafluoride is analyzed by a derivatization method, specifically: phosphorus pentafluoride gas is passed into a 5% alkaline solution for absorption, and the phosphate and chloride ion contents in the alkaline solution are analyzed by ion chromatography.

[0056] The fluoride ion content in the separated hydrogen chloride is analyzed by potentiometric titration, which is a prior art in the art and will not be described in detail here.

[0057] Example 1

[0058] This embodiment provides a method for continuously preparing high-purity phosphorus pentafluoride gas. Figure 1 As shown, the specific steps include:

[0059] 1) Solid phosphorus pentachloride is added into a PF5 reactor made of 316L stainless steel with a condenser, which is sealed, and hydrogen fluoride is sprayed into the reactor in a spraying manner, wherein the molar ratio of the added phosphorus pentachloride to hydrogen fluoride is 1:1.5, and phosphorus pentafluoride and hydrogen chloride are reacted at about 60°C. Due to the exothermic reaction, a small portion of unreacted hydrogen fluoride forms a mixed gas with phosphorus pentafluoride and by-product hydrogen chloride;

[0060] 2) A mixed gas containing phosphorus pentafluoride, hydrogen chloride and a small amount of hydrogen fluoride is continuously introduced into the bottom of the double-layer fluidized bed, and aluminum fluoride is continuously introduced from the upper right corner of the double-layer fluidized bed. First, it gradually covers the entire upper layer of the upper aluminum fluoride bed under the rotation of the upper aluminum fluoride bed, and then covers the lower layer of the lower aluminum fluoride bed under the rotation of the lower aluminum fluoride bed. The mixed gas is introduced from the bottom of the lower aluminum fluoride bed and reacts with the aluminum fluoride on the lower aluminum fluoride bed. The unreacted phosphorus pentafluoride gas enters the upper aluminum fluoride bed to continue to react; based on the amount of phosphorus pentafluoride, the molar ratio of phosphorus pentafluoride to aluminum fluoride is 3:10, and the reaction residence time is 240 seconds. The reaction temperature is about 80°C, and the reaction pressure is controlled to be about 0.5MPa; the aluminum fluoride is a porous aluminum fluoride prepared by a dry method and does not contain crystal water, with a pore size of about 20nm and a specific surface area of ​​about 30m 2 / g;

[0061] A mixture of aluminum hexafluorophosphate and aluminum fluoride is obtained from the aluminum fluoride bed. Samples are taken for analysis. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 10%, indicating that phosphorus pentafluoride has been completely converted into aluminum hexafluorophosphate. The hydrogen chloride and a small amount of hydrogen fluoride in the mixed gas do not react with aluminum fluoride. After being discharged from the double-layer fluidized bed and pressurized, they enter the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 8ppm; the separated hydrogen fluoride is recycled.

[0062] 3) The aluminum hexafluorophosphate product is output from the double-layer fluidized bed and enters a thermal decomposition reactor with a set temperature of 300° C. A twin-screw conveyor is provided in the thermal decomposition reactor. The aluminum hexafluorophosphate is thermally decomposed and transported to the outlet for a residence time of 30 minutes. The generated phosphorus pentafluoride gas is discharged from the gas guide port.

[0063] The purity of phosphorus pentafluoride was analyzed by derivatization method, which was 99.99%, and the chloride ion content was 1.5ppm. The aluminum fluoride generated by the reaction was taken out from the thermal decomposition reactor and returned to the double-layer fluidized bed for recycling. The decomposition product was sampled and analyzed by nuclear magnetic internal standard method. The molar content of aluminum hexafluorophosphate was 1.5%, indicating that the decomposition rate of aluminum hexafluorophosphate was 85%.

[0064] Example 2

[0065] This embodiment provides a semi-continuous preparation method of high-purity phosphorus pentafluoride gas. Figure 2 As shown, the specific steps include:

[0066] 1) Using a delivery pump to deliver hydrogen fluoride liquid to a stainless steel autoclave, and then using a delivery pump with a metering device to add phosphorus trichloride and liquid chlorine, the molar ratio of the added phosphorus trichloride, hydrogen fluoride and liquid chlorine is 1:10:1.05, and react at 50°C to generate a mixed gas of phosphorus pentafluoride, hydrogen chloride, a small amount of hydrogen fluoride and chlorine;

[0067] 2) Introduce the mixed gas into a double-layer gas-solid phase reactor paved with aluminum fluoride, and introduce the mixed gas from the bottom of the reactor, control the gas flow rate and the pressure in the reactor, so that the mixed gas stays in the double-layer gas-solid phase reactor for 150 to 180 seconds, the reactor pressure is controlled to be about 0.5MPa, the reaction temperature is about 50°C, the reaction molar ratio of phosphorus pentafluoride to aluminum fluoride is 3:10, and stop ventilation. The aluminum fluoride is a porous aluminum fluoride prepared by a dry method and does not contain crystal water, with a pore size of about 20nm and a specific surface area of ​​about 30m 2 / g. After pressurization, the reaction tail gas enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 10ppm. The separated chlorine and hydrogen fluoride are recycled. The aluminum fluoride product containing aluminum hexafluorophosphate in the double-layer gas-solid phase reactor is sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 10%, indicating that phosphorus pentafluoride has been completely converted into aluminum hexafluorophosphate.

[0068] 3) The reaction product is sent to a thermal decomposition reactor and heated at 300°C for 2 hours. High-purity phosphorus pentafluoride gas is collected from the top of the thermal decomposition reactor. The purity of phosphorus pentafluoride is 99.99% and the chloride ion content is 1.2ppm by derivatization method. The aluminum fluoride generated by the reaction is taken out from the thermal decomposition reactor and can be returned to the double-layer gas-solid phase reactor for use. The decomposition product is sampled and analyzed by nuclear magnetic internal standard method. The molar content of aluminum hexafluorophosphate is 0.5%, indicating that the decomposition rate of aluminum hexafluorophosphate is 95%.

[0069] Of course, in this embodiment, two double-layer gas-solid phase reactors and thermal decomposition reactors can be arranged in parallel, and continuous production of phosphorus pentafluoride can also be achieved by switching.

[0070] Example 3

[0071] This embodiment proposes a semi-continuous preparation method of high-purity phosphorus pentafluoride gas. The specific operation is the same as that of Example 2, except that a gas-solid phase reaction tower is used instead of a double-layer gas-solid phase reactor, and the mixed gas is introduced into the gas-solid phase reaction tower from the bottom, and the pressurized gas blows up solid aluminum fluoride, so that the aluminum fluoride is suspended in the tower and reacts with phosphorus pentafluoride to obtain aluminum hexafluorophosphate; other operations remain unchanged.

[0072] The reaction tail gas is pressurized and then enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 11.8 ppm. The separated chlorine and hydrogen fluoride are recycled.

[0073] The products containing aluminum hexafluorophosphate and aluminum fluoride in the gas-solid phase reaction tower were sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate was 10%, indicating that phosphorus pentafluoride had been completely converted into aluminum hexafluorophosphate.

[0074] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 2.0 ppm.

[0075] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 0.8%, indicating that the decomposition rate of aluminum hexafluorophosphate was 92%.

[0076] Of course, in this embodiment, two gas-solid phase reaction towers and thermal decomposition reaction kettles can also be arranged in parallel, and continuous production of phosphorus pentafluoride can also be achieved by switching.

[0077] Example 4

[0078] This embodiment provides a method for preparing high-purity phosphorus pentafluoride gas. The specific operation is the same as that of Embodiment 1, except that in step 2), the residence time of the reaction of phosphorus pentafluoride and aluminum fluoride is reduced to 120 seconds, and other operations remain unchanged.

[0079] After the reaction tail gas is pressurized, it enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 25.0ppm. The separated hydrogen fluoride is recycled. The products containing aluminum hexafluorophosphate and aluminum fluoride in the gas-solid phase reaction tower are sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 10%, indicating that phosphorus pentafluoride has been completely converted into aluminum hexafluorophosphate.

[0080] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 3.8 ppm.

[0081] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 2.1%, indicating that the decomposition rate of aluminum hexafluorophosphate was 79%.

[0082] Example 5

[0083] This embodiment provides a method for preparing high-purity phosphorus pentafluoride gas. The specific operation is the same as that of embodiment 1, except that in step 2), the reaction temperature of phosphorus pentafluoride and aluminum fluoride is increased to about 100° C., and other operations remain unchanged.

[0084] After the reaction tail gas is pressurized, it enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 5.5ppm. The separated hydrogen fluoride is recycled. The aluminum fluoride product containing aluminum hexafluorophosphate in the gas-solid phase reaction tower is sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 10%, indicating that phosphorus pentafluoride has been completely converted into aluminum hexafluorophosphate.

[0085] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 0.8 ppm.

[0086] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 1.8%, indicating that the decomposition rate of aluminum hexafluorophosphate was 82%.

[0087] Example 6

[0088] This embodiment provides a method for preparing high-purity phosphorus pentafluoride gas. The specific operations are the same as those in Embodiment 1, except that in step 2), the reaction pressure is controlled to be about 0.8 MPa, and other operations remain unchanged.

[0089] After the reaction tail gas is pressurized, it enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 9.5ppm. The separated hydrogen fluoride is recycled. The aluminum fluoride product containing aluminum hexafluorophosphate in the gas-solid phase reaction tower is sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 10%, indicating that phosphorus pentafluoride has been completely converted into aluminum hexafluorophosphate.

[0090] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 2.0 ppm.

[0091] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 1.8%, indicating that the decomposition rate of aluminum hexafluorophosphate was 82%.

[0092] Example 7

[0093] This embodiment provides a method for preparing high-purity phosphorus pentafluoride gas. The specific operation is the same as that of Embodiment 1, except that in step 3), the thermal decomposition reaction temperature of aluminum hexafluorophosphate is reduced to 250° C., and other operations remain unchanged.

[0094] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 2.0 ppm.

[0095] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 3.1%, indicating that the decomposition rate of aluminum hexafluorophosphate was 69%.

[0096] Example 8

[0097] This embodiment provides a method for preparing high-purity phosphorus pentafluoride gas. The specific operation is the same as that of Embodiment 1, except that in step 3), the residence time of the thermal decomposition reaction of aluminum hexafluorophosphate is increased to 60 minutes, and other operations remain unchanged.

[0098] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 2.0 ppm.

[0099] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 0.9%, indicating that the decomposition rate of aluminum hexafluorophosphate was 91%.

[0100] Example 9

[0101] This embodiment provides a method for preparing high-purity phosphorus pentafluoride gas. The specific operation is the same as that of Embodiment 2, except that in step 2), the reaction molar ratio of phosphorus pentafluoride to aluminum fluoride is 6:10, and other operations remain unchanged.

[0102] After the reaction tail gas is pressurized, it enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 7.5ppm. The separated hydrogen fluoride is recycled. The aluminum fluoride product containing aluminum hexafluorophosphate in the gas-solid phase reaction tower is sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 20%, indicating that phosphorus pentafluoride has been completely converted into aluminum hexafluorophosphate.

[0103] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 2.2 ppm.

[0104] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 2.8%, indicating that the decomposition rate of aluminum hexafluorophosphate was 86%.

[0105] Example 10

[0106] This embodiment provides a method for preparing high-purity phosphorus pentafluoride gas. The specific operation is the same as that of Example 2, except that in step 2), the reaction molar ratio of phosphorus pentafluoride to aluminum fluoride is 6:10, the residence time is 240 to 300 seconds, and other operations remain unchanged.

[0107] After the reaction tail gas is pressurized, it enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is 3.5ppm. The separated hydrogen fluoride is recycled. The aluminum fluoride product containing aluminum hexafluorophosphate in the gas-solid phase reaction tower is sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 20%, indicating that phosphorus pentafluoride has been completely converted into aluminum hexafluorophosphate.

[0108] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 1.0 ppm.

[0109] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 1.3%, indicating that the decomposition rate of aluminum hexafluorophosphate was 93.5%.

[0110] Comparative Example 1

[0111] This comparative example proposes a method for preparing high-purity phosphorus pentafluoride gas. The specific operation is the same as that of Example 1, except that ordinary powdered aluminum fluoride with a specific surface area of ​​0.1 m 2 / g, other operations remain unchanged.

[0112] After the reaction tail gas is pressurized, it enters the gas separation section for separation. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, in which the fluoride ion content is greater than 1%. The separated hydrogen fluoride is recycled. The products containing aluminum hexafluorophosphate and aluminum fluoride in the double-layer fluidized bed are sampled and analyzed. Using the nuclear magnetic internal standard method, the molar content of aluminum hexafluorophosphate is 2.3%, indicating that phosphorus pentafluoride has not been completely converted into aluminum hexafluorophosphate.

[0113] The collected high-purity phosphorus pentafluoride gas was analyzed by derivatization method and its purity was 99.99%, and the chloride ion content was 1.3 ppm.

[0114] The decomposition product was sampled and analyzed by nuclear magnetic resonance internal standard method. The molar content of aluminum hexafluorophosphate was 0.36%, indicating that the decomposition rate of aluminum hexafluorophosphate was 84%.

Claims

1. A continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride, characterized in that: The preparation method comprises the following steps: (1) reacting a mixed gas containing phosphorus pentafluoride with solid aluminum fluoride to prepare solid aluminum hexafluorophosphate, wherein the mixed gas contains phosphorus pentafluoride, hydrogen fluoride and hydrogen chloride; (2) The prepared aluminum hexafluorophosphate solid is heated to 250-450° C., decomposed by heat, and high-purity phosphorus pentafluoride gas is obtained by collection.

2. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 1, characterized in that: The solid aluminum fluoride is aluminum fluoride prepared by dry method and does not contain crystal water, and its pore size is ≤100nm and its specific surface area is ≥1.0m 2 / g.

3. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 1, characterized in that: The mixed gas containing phosphorus pentafluoride is obtained by reacting phosphorus pentachloride and hydrogen fluoride. The reaction temperature is controlled to be -20 to 100° C., and the reaction pressure is controlled to be 0.01 to 0.5 MPa.

4. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 1, characterized in that: The mixed gas containing phosphorus pentafluoride is prepared by reacting phosphorus trichloride, hydrogen fluoride and liquid chlorine. The reaction temperature is controlled at -10 to 50° C., and the reaction pressure is controlled at 0.5 to 3.0 MPa.

5. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 1, characterized in that: In the step (1), the mixed gas containing phosphorus pentafluoride has a molar ratio of phosphorus pentafluoride to aluminum fluoride of 1:(1.0-100) based on the amount of phosphorus pentafluoride.

6. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 1, characterized in that: In the step (1), the reaction temperature of the mixed gas containing phosphorus pentafluoride and aluminum fluoride is 0 to 150° C., and the reaction pressure is 0.1 to 2.0 MPa.

7. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 5 or 6, characterized in that: The reaction in step (1) is carried out continuously in a double-layer fluidized bed, wherein the mixed gas containing phosphorus pentafluoride and aluminum fluoride are transported in reverse order, and the residence time of phosphorus pentafluoride and aluminum fluoride is 10 to 600 seconds, so as to ensure that the reaction materials react completely. Alternatively, the reaction in step (1) is carried out semi-continuously in a double-layer gas-solid phase reactor or a gas-solid phase reaction tower, and the residence time of the mixed gas containing phosphorus pentafluoride and aluminum fluoride is 10 to 600 seconds to ensure complete reaction of the reaction materials.

8. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 1, characterized in that: In step (2), the thermal decomposition time of aluminum hexafluorophosphate is 0.1 to 10 hours.

9. The continuous preparation method of high-purity phosphorus pentafluoride according to claim 8, characterized in that: The reaction in step (2) is carried out in a temperature-controllable thermal decomposition reactor.

10. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to any one of claims 1 to 9, characterized in that: The continuous preparation method specifically comprises: A1. Phosphorus pentafluoride and aluminum fluoride in the mixed gas react continuously in a double-layer fluidized bed to generate aluminum hexafluorophosphate. Other gases in the mixed gas that do not react with aluminum fluoride are pressurized and then separated in a gas separation section. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, and the separated hydrogen fluoride and / or chlorine are recycled; A2. The aluminum hexafluorophosphate generated by the reaction continuously enters the thermal decomposition reactor for decomposition, and the generated phosphorus pentafluoride gas is collected through the gas outlet to obtain high-purity phosphorus pentafluoride gas or directly enters the next reaction section through a pipeline.

11. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to any one of claims 1 to 9, characterized in that: The semi-continuous preparation method specifically includes: B1. Phosphorus pentafluoride in the mixed gas continuously enters a double-layer gas-solid phase reactor or a gas-solid phase reaction tower filled with aluminum fluoride to react and generate aluminum hexafluorophosphate. Other gases in the mixed gas that do not react with aluminum fluoride are discharged through the reactor outlet, pressurized and separated in a gas separation section. The separated hydrogen chloride is used to prepare industrial hydrochloric acid, and the separated hydrogen fluoride and / or chlorine are recycled; B2. After a controlled amount of mixed gas containing phosphorus pentafluoride is introduced, the aluminum hexafluorophosphate generated by the reaction is taken out and transported to a thermal decomposition reactor for decomposition. The generated phosphorus pentafluoride gas is collected through a gas outlet to obtain high-purity phosphorus pentafluoride gas or directly enters the next reaction section through a pipeline. The generated aluminum fluoride is collected uniformly. After the decomposition reaction is completed, a fixed amount of aluminum fluoride is loaded into a double-layer gas-solid phase reactor or a gas-solid phase reaction tower, and then reacts with the mixed gas containing phosphorus pentafluoride, and the cycle is repeated in sequence.

12. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 10, characterized in that: In step A2, a screw conveyor is provided in the thermal decomposition reactor.

13. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 12, characterized in that: The screw conveyor is a single screw conveyor or a twin screw conveyor.

14. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 11, characterized in that: In step B2, the thermal decomposition reactor is a thermal decomposition reactor.

15. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to claim 10, characterized in that: In step A2, the aluminum fluoride obtained by heating and decomposition is returned to step A1 to continue the reaction; In step B2, the aluminum fluoride obtained by heating and decomposition is returned to step B1 to continue the reaction.

16. The continuous or semi-continuous preparation method of high-purity phosphorus pentafluoride according to any one of claims 1 to 15, characterized in that: The purity of the prepared high-purity phosphorus pentafluoride gas is ≥99.95%, and the chloride ion content is ≤2ppm.

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