A method for preparing high-purity phosphorus pentafluoride gas from non-aqueous hexafluorophosphate ionic liquid

Abstract

The present invention provides a method for preparing high-purity phosphorus pentafluoride gas from a non-aqueous hexafluorophosphate ionic liquid. The method comprises the following steps: (1) reacting an oxygen-containing phosphorus compound with anhydrous hydrogen fluoride to obtain an aqueous hexafluorophosphate solution; (2) reacting the reaction liquid of the hexafluorophosphate aqueous solution obtained in step (1) with an organic amine to prepare an anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid; and (3) reacting the anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid obtained in step (2) with a strong protonic acid or anhydride to prepare high-purity phosphorus pentafluoride. The preparation process has few by-products, simple equipment, low corrosiveness, and can be continuously produced. The purity of the final product can reach above 99.99%, with HF ≤ 30 ppm and H2O ≤ 20 ppm, and no impurities such as phosphorus oxytrifluoride and phosphorus trifluoride are generated.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical material preparation, and relates to a method for preparing high-purity phosphorus pentafluoride gas from non-aqueous hexafluorophosphate ionic liquid. Background Art

[0002] Phosphorus pentafluoride (PF5) is a colorless and odorless gas under normal conditions. It reacts with moisture in humid air to produce fumes. It has extensive applications in chemical catalysis, the semiconductor industry, and the new energy sector. In the electronics industry, PF5 is a source of N-type dopants for silicon epitaxy, diffusion, and ion implantation, effectively improving semiconductor performance. In the field of polymer materials, PF5 is a raw material for synthesizing fluorinated organic dithiophosphates, terephthalate esters, and other polymer materials. In the field of catalysis, PF5 is a catalyst for polymerization, hydrocarbonation, dehydrogenation, and hydrocarbon cracking reactions. Using metal oxides such as titanium, nickel, and beryllium treated with PF5 as catalysts can improve reaction selectivity. In the new energy industry, PF5 is a core raw material for synthesizing lithium hexafluorophosphate electrolytes. Therefore, research on the preparation technology of high-purity PF5 is of great significance.

[0003] In the prior art, the commonly used preparation techniques for phosphorus pentafluoride are as follows:

[0004] 1. Using elemental phosphorus as a raw material, phosphorus pentafluoride is reacted with fluorine gas (a highly dangerous and toxic substance) to produce phosphorus pentafluoride. CN101417791A discloses that elemental phosphorus is first added to a fixed-bed reactor, and then fluorine gas is introduced to react to produce a mixture of phosphorus pentafluoride and excess fluorine gas. Finally, high-purity phosphorus pentafluoride is obtained by compression, liquefaction, and cryogenic distillation. Disadvantages: The reaction between fluorine gas and elemental phosphorus is very violent, releasing a large amount of heat. The reaction process is difficult to control, resulting in a relatively difficult process control. Similar patent applications include CN109052350A, CN107619028A, CN203513282U, and CN102674275A.

[0005] 2. A preparation method using phosphorus halides as raw materials involves reacting phosphorus pentachloride and phosphorus trichloride with hydrofluoric acid, fluorine gas, chlorine gas, and the like to produce phosphorus pentafluoride. CN102951620A discloses a method for preparing phosphorus pentafluoride and lithium hexafluorophosphate, which can be synthesized in a two-step process. First, hydrogen fluoride and phosphorus pentachloride react in a reactor at -50 to -26°C to produce hexafluorophosphoric acid, and then the hexafluorophosphoric acid is decomposed at -20 to 30°C to produce phosphorus pentafluoride gas. This method can control the reaction rate by controlling the hydrogen fluoride addition rate. The production of hexafluorophosphoric acid and phosphorus pentafluoride is carried out in two stages, improving product purity. Similarly, CN102320584A discloses a method for preparing phosphorus pentafluoride, using calcium fluoride instead of hydrogen fluoride. Under an inert gas atmosphere and a reaction pressure of -0.1 to 0.15 MPa and a reaction temperature of 100 to 300°C, phosphorus pentachloride and calcium fluoride solid powders are added to a reactor to generate phosphorus pentafluoride gas. The byproduct, calcium chloride, is a non-toxic and harmless solid residue. Disadvantages: The phosphorus pentachloride raw material itself contains a certain amount of water and metal ions, making it difficult to obtain high-purity phosphorus pentafluoride using this method. Furthermore, the hydrogen chloride generated during the phosphorus pentafluoride production process can corrode equipment, making it unsuitable for industrial synthesis. Similar patent applications include CN110072807A and CN103153847A.

[0006] 3. The preparation method using oxygen-containing phosphorus compounds as raw materials involves first preparing an aqueous hexafluorophosphoric acid solution by reacting phosphorus pentoxide, polyphosphoric acid, phosphoric acid, etc. with anhydrous hydrogen fluoride. The synthesized aqueous hexafluorophosphoric acid solution is then directly reacted with sulfur trioxide or fuming sulfuric acid to produce a mixture of hexafluorophosphoric acid and sulfuric acid. Finally, crude phosphorus pentafluoride is obtained after heating and condensation. Disadvantages: Due to the presence of a large amount of water (25-35 wt%) in the aqueous hexafluorophosphoric acid solution, the acidification process produces a large number of byproducts, such as phosphorus oxytrifluoride, water, and phosphorus trifluoride. Phosphorus trifluoride has a boiling point close to that of phosphorus pentafluoride, requiring multiple purification steps using pressurized distillation to meet usage standards. The purification conditions are very demanding, requiring large equipment investment and energy consumption, and byproduct disposal is difficult. Similar patent applications include CN104261369A, CN101391760A, CN102502544A, and CN104310327A. Summary of the Invention

[0007] To address the shortcomings of the existing technology, the present invention provides a method for preparing high-purity phosphorus pentafluoride gas from a non-aqueous hexafluorophosphate ionic liquid. This method produces few byproducts, requires simple equipment, is less corrosive, and can be used in continuous production. The final product achieves a purity exceeding 99.99%, with low impurity content. Impurities such as phosphorus oxytrifluoride and phosphorus trifluoride are absent, with HF ≤ 30 ppm and H₂O ≤ 20 ppm, meeting the needs of the semiconductor and lithium battery industries.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In one aspect, the present invention provides a method for preparing high-purity phosphorus pentafluoride gas from a non-aqueous hexafluorophosphate ionic liquid, the method comprising the following steps:

[0010] (1) reacting an oxygen-containing phosphorus compound with anhydrous hydrogen fluoride to obtain an aqueous solution of hexafluorophosphoric acid;

[0011] (2) reacting the hexafluorophosphoric acid aqueous solution obtained in step (1) with an organic amine to prepare an anhydrous high-purity non-aqueous hexafluorophosphoric acid ionic liquid;

[0012] (3) The anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid obtained in step (2) is reacted with a strong proton acid or anhydride to prepare high-purity phosphorus pentafluoride.

[0013] In the present invention, an ionic liquid of hexafluorophosphoric acid is first prepared, and then reacted with an organic amine and a strong protonic acid to obtain high-purity phosphorus pentafluoride. The preparation process has few by-products, a simple device, low corrosiveness, and can be continuously produced. The purity of the final product can reach above 99.99%, and the impurities HF ≤ 30 ppm and H2O ≤ 20 ppm.

[0014] Preferably, the oxygen-containing phosphorus compound in step (1) is selected from any one or a combination of at least two of phosphorus pentoxide, refined phosphoric acid, polyphosphoric acid, hypophosphoric acid, pyrophosphoric acid, pyrophosphorous acid or metaphosphoric acid.

[0015] Preferably, the ratio of the total molar amount of phosphorus in the oxygen-containing phosphorus compound in step (1) to the total molar amount of fluorine in anhydrous hydrogen fluoride is 1:8 to 1:16, for example, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15 or 1:16, preferably 1:10.

[0016] Preferably, the reaction temperature in step (1) is less than or equal to 60°C, such as 60°C, 55°C, 50°C, 45°C, 40°C, 35°C, 30°C, 25°C or 20°C, preferably 30-40°C.

[0017] Preferably, the reaction in step (1) is carried out at a pressure of ≤0.35 MPa, for example, the pressure can be 0.35 MPa, 0.30 MPa, 0.25 MPa, 0.20 MPa, 0.15 MPa, 0.10 MPa, 0.05 MPa, 0.03 MPa, 0.01 MPa, etc., preferably 0.05 MPa-0.35 MPa, and more preferably 0.05 to 0.098 MPa.

[0018] Preferably, the reaction time of step (1) is 1-3 h, such as 1 h, 1.5 h, 1.8 h, 2 h, 2.5 h, 2.8 h or 3 h, preferably 2 h.

[0019] Preferably, after the reaction in step (1) is completed, the temperature is lowered to 20-25°C, such as 20°C, 22°C, 24°C or 25°C.

[0020] Preferably, the specific operation of the reaction in step (1) is:

[0021] Anhydrous hydrogen fluoride is added to the reactor at a temperature below 5°C, an oxygen-containing phosphorus compound is added to the reactor at a temperature below 8°C, the reaction temperature is controlled within 60°C, the reaction is carried out, and the temperature is lowered to 20-25°C to obtain an aqueous solution of hexafluorophosphoric acid.

[0022] Preferably, the feed ratio of the hexafluorophosphoric acid aqueous solution to the organic amine in step (2) is controlled to a pH value of the reaction solution of 6.5 to 7.5, for example, 6.5, 6.8, 7.0, 7.3 or 7.5.

[0023] Preferably, the organic amine in step (2) is added dropwise to the reaction solution containing the hexafluorophosphoric acid aqueous solution.

[0024] Preferably, the organic amine in step (2) is selected from tertiary organic amines.

[0025] Preferably, the organic amine is selected from any one or a combination of at least two of triethylamine, tri-n-propylamine, tri-n-butylamine, pyridine, pyrrolidine, methylimidazole, piperidine or morpholine.

[0026] Preferably, the dropping is carried out at a temperature of ≤30°C, for example, the dropping temperature is 30°C, 25°C, 20°C, 18°C, 15°C, 10°C, 8°C, 5°C, 3°C, 1°C, etc.

[0027] Preferably, the reaction in step (2) is carried out under normal pressure.

[0028] Preferably, the reaction temperature in step (2) is ≤30°C, such as 30°C, 25°C, 20°C, 18°C, 15°C, 10°C, 8°C, 5°C, 3°C, 1°C, etc., preferably 5-10°C.

[0029] Preferably, the reaction time in step (2) is 2-3 hours, such as 2 hours, 2.5 hours, 2.8 hours or 3 hours, preferably 3 hours.

[0030] Preferably, the endpoint pH value of the reaction in step (2) is 6.5 to 7.5, for example, 6.5, 6.8, 7.0, 7.3 or 7.5.

[0031] Preferably, after the reaction in step (2) is completed, the reaction solution is allowed to stand for phase separation for 2 to 4 hours, and the separated lower layer ionic liquid is washed with an equal mass of high-purity water for multiple phase separations to remove impurities, until the total integrated area of ​​the impurity anions other than hexafluorophosphate in the ionic liquid after the last washing water and the final washing is ≤0.001% by ion chromatography, and the washed ionic liquid is vacuum dehydrated and dried to obtain the anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid.

[0032] Preferably, the drying temperature of the vacuum dehydration drying is 80-110°C (for example, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C or 110°C), the absolute vacuum degree is ≤200Pa (for example, 200Pa, 150Pa, 100Pa, 80Pa, 50Pa, 30Pa, 10Pa, etc.), and the vacuum drying time is 8-12 hours (for example, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours).

[0033] Preferably, the water content in the anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid in step (2) is ≤20 ppm, for example, it can be 20 ppm, 15 ppm, 10 ppm, 5 ppm, 3 ppm, 1 ppm, etc.

[0034] In the present invention, the PF6 - The content reaches more than 99.99%, and the cationic content reaches more than 99.99%.

[0035] Preferably, the molar ratio of the anhydrous high-purity nonaqueous hexafluorophosphate ionic liquid to the strong protonic acid or anhydride in step (3) is 1:1.05 to 1:1.2, for example, 1:1.05, 1:1.1, 1:1.15, 1:1.18 or 1:1.2.

[0036] Preferably, the strong protonic acid or anhydride in step (3) is selected from any one of fuming sulfuric acid, sulfur trioxide, fluorosulfonic acid or trifluoromethanesulfonic acid, or a combination of at least two thereof.

[0037] Preferably, the reaction temperature in step (3) is 80-160°C, such as 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C or 160°C, preferably 100-120°C.

[0038] Preferably, the reaction in step (3) is carried out at a pressure of 1.0 to 1.5 MPa, such as 1.0 MPa, 1.1 MPa, 1.2 MPa, 1.3 MPa, 1.4 MPa or 1.5 MPa, preferably 1.2 MPa.

[0039] Preferably, the specific operation of the reaction in step (3) is: adding a strong protonic acid or anhydride to the reactor, maintaining the temperature within 25°C, then slowly adding anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid for mixing, maintaining the system temperature not exceeding 50°C, to form a relatively stable mixture system; heating the above mixture system, when the temperature reaches 80°C, the system begins to generate phosphorus pentafluoride gas, controlling the heating temperature at 80-160°C, controlling the reaction system pressure at 1.0-1.5MPa, and continuously producing a mixed gas of phosphorus pentafluoride and hydrogen fluoride.

[0040] Preferably, after the reaction in step (3) is completed, the crude phosphorus pentafluoride gas is passed through a hydrogen fluoride deacidification device to remove hydrogen fluoride to obtain high-purity phosphorus pentafluoride.

[0041] Preferably, the hydrogen fluoride deacidification device is a three-stage combined low-temperature cryogenic condenser with a condensation temperature of -70 to -30°C, such as -70°C, -60°C, -50°C, -40°C or -30°C.

[0042] The phosphorus pentafluoride gas prepared by the preparation method of the present invention has a purity of more than 99.99% after testing, wherein the HF content is ≤30ppm and the H2O content is ≤20ppm.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The method of the present invention has few by-products in the preparation process, simple equipment, low corrosivity, and can be produced continuously. The purity of the final product can reach more than 99.99%, the impurity content is low, no impurities such as phosphorus oxyfluoride and phosphorus trifluoride are generated, HF≤30ppm, H2O≤20ppm, and can meet the needs of the semiconductor industry and the lithium battery industry. DETAILED DESCRIPTION

[0045] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0046] Example 1

[0047] Preparation of hexafluorophosphoric acid aqueous solution

[0048] First, the chilled water valve of the 5L fluorine-lined jacketed reactor with a reflux condenser was opened to cool the reactor down by 5°C. Second, 1667.0g (HF, 83.31mol) of anhydrous hydrogen fluoride was added to the reactor and stirred to maintain the system temperature at 8°C. Then, 1173.0g (H6P4O 133.47 mol of polyphosphoric acid (117% content as phosphorus pentoxide) was added dropwise to the reaction kettle (the polyphosphoric acid temperature was approximately 60°C). During the addition, the temperature in the reactor increased significantly. The addition rate was controlled to maintain the reaction temperature between 20-25°C. The reaction pressure was 0.098 MPa. After the addition was complete, the reaction was incubated for 2 hours. Finally, the temperature was lowered to 20°C via the jacket, yielding 2838.1 g of a hexafluorophosphoric acid aqueous solution. Ion chromatography (Dionex ICS-2000 anion chromatograph, USA) determined that it contained 65.70% wt hexafluorophosphoric acid (HPF6, 1864.6 g), 1.29% wt monofluorophosphoric acid (HPO3F, 36.65 g), 1.08% wt monofluorophosphorous acid (HPO2F, 30.72 g), 1.28% wt phosphoric acid (H3PO4, 36.29 g), 4.17% wt anhydrous hydrogen fluoride (HF, 118.48 g), and the rest was 26.47% wt water (H2O, 751.36 g).

[0049] Example 2

[0050] Preparation of hexafluorophosphoric acid aqueous solution

[0051] First, the chilled water valve of a 5L fluorine-lined jacketed reactor equipped with a reflux condenser was opened simultaneously to cool the reactor by 5°C. Next, 1500.0g (HF, 74.63 mol) of anhydrous hydrogen fluoride was added to the reactor, with stirring maintained at 8°C. Then, 709.3g (P2O5, 4.99 mol) of phosphorus pentoxide was added to the reactor using a solid screw feeder. During the addition, the reactor temperature increased significantly. The addition rate was controlled to maintain the reaction temperature between 25-30°C and the reaction pressure at 0.098 MPa. After the addition was complete, the reaction was incubated for 2 hours. Finally, the reaction mixture was cooled to 20°C via the jacket, yielding 2207.3g of a hexafluorophosphoric acid aqueous solution. Ion chromatography determined that it contained 64.78% wt hexafluorophosphoric acid (HPF6, 1429.8 g), 0.3% wt monofluorophosphoric acid (HPO3F, 6.59 g), 0.25% wt monofluorophosphorous acid (HPO2F, 5.52 g), 0.3% wt phosphoric acid (H3PO4, 6.53 g), 14.56% wt anhydrous hydrogen fluoride (HF, 321.3 g), and the remainder was 19.82% wt water (H2O, 437.53 g);

[0052] Example 3

[0053] Preparation of hexafluorophosphoric acid aqueous solution

[0054] First, the chilled water valve of a 5L fluorine-lined jacketed reactor equipped with a reflux condenser was opened to cool the reactor by 5°C. Next, 2572.71g (HF, 128.57 mol) of anhydrous hydrogen fluoride was added to the reactor, and stirring was initiated to maintain the system temperature at 8°C. Then, 1764.71g (H3PO4-85%, 15.31 mol) of purified phosphoric acid (85%) was added dropwise to the reactor. During the addition, the reactor temperature increased significantly. The addition rate was controlled to maintain the reaction temperature between 20-25°C and the reaction pressure was 0.098 MPa. After the addition was complete, the reaction was incubated for 2 hours. Finally, the reaction mixture was cooled to 20°C via the jacket, yielding 4335.3g of a hexafluorophosphoric acid aqueous solution. Ion chromatography determined that it contained 50.48% wt hexafluorophosphoric acid (HPF6, 2189.55 g), 0.23% wt monofluorophosphoric acid (HPO3F, 10.1 g), 0.20% wt monofluorophosphorous acid (HPO2F, 8.47 g), 0.23% wt phosphoric acid (H3PO4, 10.00 g), 17.70% wt anhydrous hydrogen fluoride (HF, 767.73 g), and the rest was 31.16% wt water (H2O, 1351.57 g).

[0055] Example 4

[0056] Preparation of anhydrous high-purity nonaqueous hexafluorophosphate ionic liquid

[0057] First, the 2L fluorine-lined jacketed reactor was cooled to 17°C and 500.52g of hexafluorophosphoric acid aqueous solution (HPF6 main content 65.70%, from Example 1) was added; secondly, 384.50g of triethylamine was added dropwise to the reactor for neutralization. The reaction temperature during the addition process was controlled within ≤30°C, the reaction pressure was normal pressure, the reaction time after the addition was completed was 3 hours, and the pH value at the reaction end point was 7.2; then, the above reaction solution was transferred to a separatory funnel and allowed to stand for 3 hours. At this time, the upper layer was aqueous phase and the lower layer was ionic liquid. Phase; The lower layer ionic liquid 560.21g was separated and washed three times with high-purity water of equal mass to remove impurities, and 553.82g of ionic liquid was obtained. The total integrated area of ​​the impurity anions in the ionic liquid after the last washing water and the final washing was ≤0.001% by ion chromatography; Finally, the washed ionic liquid was added to a stainless steel reactor for high vacuum dehydration and drying, the drying temperature was 102°C, the absolute vacuum was 190Pa, and the vacuum drying time was 10 hours. After cooling to room temperature, 549.6g of anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid was obtained. The moisture content was determined to be 15.6ppm, and the IC anion test (Swiss Metrohm 831 Coulometric Karl Fischer Moisture Tester) PF6 -The purity reaches 99.99%, the purity of IC cation (Et)3NH+ is 99.99%, and the total metal ions (K, Na, Fe, Ca, Ni, Cr, Cu, Zn, Pb, etc.) determined by ICP are ≤5ppm.

[0058] Example 5

[0059] Preparation of anhydrous high-purity nonaqueous hexafluorophosphate ionic liquid

[0060] First, the 2L fluorine-lined jacketed reactor was cooled to 16°C and 506.3g of hexafluorophosphoric acid aqueous solution (HPF6 main content 64.78%, from Example 2) was added; secondly, 636.4g of triethylamine was added dropwise to the reactor for neutralization. The reaction temperature during the addition process was controlled within ≤30°C, the reaction pressure was normal pressure, the reaction time after the addition was completed was 3 hours, and the pH value at the reaction end point was 7.1; then, the above reaction solution was transferred to a separatory funnel and allowed to stand for 3 hours. At this time, the upper layer was aqueous phase and the lower layer was ionic liquid. The bulk phase; 559.6g of the separated lower layer of ionic liquid was washed three times with an equal mass of high-purity water to remove impurities, and 550.5g of ionic liquid was obtained. Ion chromatography was used to detect the total integrated area of ​​impurity anions in the ionic liquid after the last and final washes, except for hexafluorophosphate, of ≤0.001%. Finally, the washed ionic liquid was added to a stainless steel reactor and dehydrated under high vacuum at a drying temperature of 97°C, an absolute vacuum of 150Pa, and a vacuum drying time of 9 hours. After cooling to room temperature, 547.2g of anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid was obtained. The water content was determined to be 18.6ppm, the IC anion test PF6- purity reached 99.99%, the IC cation (Et)3NH+ purity reached 99.99%, and the ICP determination of total metal ions (K, Na, Fe, Ca, Ni, Cr, Cu, Zn, Pb, etc.) was ≤5ppm.

[0061] Example 6

[0062] Preparation of anhydrous high-purity nonaqueous hexafluorophosphate ionic liquid

[0063] First, the 2L fluorine-lined jacketed reactor was cooled to 15°C and 550.4g of hexafluorophosphoric acid aqueous solution (HPF6 main content 50.4%, from Example 3) was added; secondly, 724.1g of triethylamine was added dropwise to the reactor for neutralization. The reaction temperature during the addition process was controlled within 30°C, the reaction pressure was normal pressure, the reaction time after the addition was completed was 2.5 hours, and the pH value at the reaction end point was 6.8; then, the above reaction solution was transferred to a separatory funnel and allowed to stand for 3 hours. At this time, the upper layer was aqueous phase and the lower layer was ionic liquid. The bulk phase; 470.3g of the separated lower layer of ionic liquid was washed three times with an equal mass of high-purity water to remove impurities, and 462.6g of ionic liquid was obtained. Ion chromatography was used to detect the total integrated area of ​​impurity anions in the ionic liquid after the last and final washes, except for hexafluorophosphate, was ≤0.001%. Finally, the washed ionic liquid was added to a stainless steel reactor and dehydrated under high vacuum at a drying temperature of 105°C, an absolute vacuum of 168Pa, and a vacuum drying time of 11 hours. After cooling to room temperature, 460.3g of anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid was obtained. The water content was determined to be 12.6ppm, the IC anion test PF6- purity reached 99.99%, the IC cation (Et)3NH+ purity was 99.99%, and the ICP determination of total metal ions (K, Na, Fe, Ca, Ni, Cr, Cu, Zn, Pb, etc.) was ≤5ppm.

[0064] Example 7

[0065] Preparation of anhydrous high-purity nonaqueous hexafluorophosphate ionic liquid

[0066] First, the 2L fluorine-lined jacketed reactor was cooled to less than 20°C, and 805.5g of hexafluorophosphoric acid aqueous solution (main content of HPF6 65.70%, from Example 1) was added; secondly, 300.56g of pyridine was added dropwise to the reactor for neutralization. The reaction temperature during the addition process was controlled within 20-26°C, the reaction pressure was normal pressure, the reaction time after the addition was completed was 2.5 hours, and the pH value at the end of the reaction was 7.1; then, the above reaction solution was transferred to a separating funnel and allowed to stand for 3 hours. At this time, the upper layer was the aqueous phase and the lower layer was the ion phase. The ionic liquid phase was separated; 516.3 g of the lower layer ionic liquid was washed three times with an equal mass of high-purity water to remove impurities, and 503.4 g of ionic liquid was obtained. The total integrated area of ​​the impurity anions in the ionic liquid after the last washing and the final washing was ≤0.001% by ion chromatography; finally, the washed ionic liquid was added to a stainless steel reactor and dehydrated under high vacuum at a drying temperature of 103° C., an absolute vacuum of 125 Pa, and a vacuum drying time of 11 hours. After cooling to room temperature, 498.6 g of anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid was obtained. The water content was determined to be 13.6 ppm, the purity of PF6- in IC anion test reached 99.99%, the purity of Py (pyridine) in IC cation test reached 99.99%, and the total metal ions (K, Na, Fe, Ca, Ni, Cr, Cu, Zn, Pb, etc.) in ICP test were ≤5 ppm.

[0067] Example 8

[0068] Preparation of anhydrous high-purity nonaqueous hexafluorophosphate ionic liquid

[0069] First, the 2L fluorine-lined jacketed reactor was cooled to 17°C and 812.6g of hexafluorophosphoric acid aqueous solution (HPF6 main content 64.78%, from Example 2) was added; secondly, 687.2g of pyridine was added dropwise to the reactor for neutralization. The reaction temperature during the addition process was controlled at 25-30°C, the reaction pressure was normal pressure, the reaction time after the addition was completed was 2.5 hours, and the pH value at the end of the reaction was 7.3; then, the above reaction solution was transferred to a separatory funnel and allowed to stand for 3 hours. At this time, the upper layer was the aqueous phase and the lower layer was the ionic liquid. The bulk phase was prepared by washing the separated lower layer ionic liquid (771.3 g) three times with an equal mass of high-purity water to remove impurities, yielding 769.2 g of ionic liquid. Ion chromatography determined that the total integrated area of ​​impurity anions, excluding hexafluorophosphate, in the ionic liquid after the last and final washes was ≤0.001%. Finally, the washed ionic liquid was placed in a stainless steel reactor and dried under high vacuum at 101°C, an absolute vacuum of 128 Pa, and a vacuum drying time of 10 hours. After cooling to room temperature, 759.6 g of anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid was obtained, which had a water content of 18.6 ppm, an anion purity of PF6- of 99.99% as determined by IC, a cation purity of 99.99% as determined by IC, and a total metal ion purity of ≤5 ppm as determined by ICP.

[0070] Example 9

[0071] Preparation of High-Purity Phosphorus Pentafluoride

[0072] First, 96.5 g of sulfur trioxide was added to a 2 L lead reactor with a thermal oil jacket, and the temperature was maintained at 25-26 ° C. Then, 247.2 g of Et3NHPF6 ionic liquid (from Example 4) was slowly added and mixed, and the system temperature was maintained between 30 and 40 ° C to form a relatively stable mixture system. Secondly, the mixture system was heated with thermal oil. When the temperature reached 80 ° C, the system began to produce phosphorus pentafluoride gas. The temperature was slowly increased in a gradient to control the final temperature at 155.2 ° C. The pressure of the reaction system was controlled to be 1.0-1.5 MPa for continuous gas production. The gas was condensed at -35 ° C in a three-stage condenser to remove excess sulfur trioxide to obtain high-purity phosphorus pentafluoride. The purity of the high-purity phosphorus pentafluoride was 99.99% as determined by online GC detection (Agilent 7890B gas chromatograph, USA). The gas was absorbed with anhydrous ether and the HF content was determined to be 10.6 ppm and the H2O content was 6.9 ppm. The total mass of phosphorus pentafluoride obtained by absorption with anhydrous ether was 121.6 g, and the yield was 96.51% wt.

[0073] Example 10

[0074] Preparation of High-Purity Phosphorus Pentafluoride

[0075] First, 150.5 g of 65% fuming sulfuric acid was added to a 2 L lead reactor with a thermal oil jacket, and the temperature was maintained at 30-35 ° C. Then, 247.9 g of Et3NHPF6 ionic liquid (from Example 5) was slowly added and mixed, and the system temperature was maintained between 35 and 45 ° C to form a relatively stable mixture system. Secondly, the mixture system was heated with thermal oil. When the temperature reached 85 ° C, the system began to produce phosphorus pentafluoride gas. The temperature was slowly increased in a gradient to control the final temperature at 158.3 ° C. The pressure of the reaction system was controlled to be 1.0-1.5 MPa for continuous gas production. The gas was condensed at -35 ° C in a three-stage condenser to remove excess sulfur trioxide to obtain high-purity phosphorus pentafluoride. The purity of the high-purity phosphorus pentafluoride could reach 99.99% by online GC detection. The gas was absorbed with anhydrous ether and the HF content was determined to be 12.1 ppm and the H2O content was 10.6 ppm. The total mass of phosphorus pentafluoride obtained by absorption with anhydrous ether was 120.7 g, and the yield was 95.57% wt.

[0076] Example 11

[0077] Preparation of High-Purity Phosphorus Pentafluoride

[0078] At first, in the 2L lead reactor with thermal oil jacket, add the trifluoromethanesulfonic acid of 189.43g, maintain the temperature at 30~35 ℃, then slowly add the Et of 283.6g NHPF Ionic liquid (from embodiment 6) is mixed, keeps system temperature between 35~45 ℃, forms metastable mixture system; Secondly, above-mentioned mixture system is carried out thermal oil heating, when temperature reaches 75 ℃, system begins to produce phosphorus pentafluoride gas, gradient slowly heats up, and control final temperature at 152.1 ℃, and the control reaction system pressure is that 1.0~1.5MPa carries out continuous gas production, and gas removes excessive sulfur trioxide that condenses through triple condenser-35 ℃ and obtains high-purity phosphorus pentafluoride, and this high-purity phosphorus pentafluoride detects purity by online GC and can reach 99.99%; Gas uses anhydrous ether to absorb the back and measures that wherein HF is 14.6ppm, and H O is 12.4ppm. The total mass of phosphorus pentafluoride obtained by absorption with anhydrous ether was 138.9 g, and the yield was 96.13% wt.

[0079] Example 12

[0080] Preparation of High-Purity Phosphorus Pentafluoride

[0081] First, 395.74 g of fuming sulfuric acid (65%) was added to a 2 L lead reactor with a thermal oil jacket, and the temperature was maintained at 30-35 ° C. Then, 500.0 g of PyHPF6 ionic liquid (from Example 7) was slowly added and mixed, and the system temperature was maintained between 30 and 42 ° C. to form a relatively stable mixture system; secondly, the mixture system was heated with thermal oil. When the temperature reached 86 ° C, the system began to produce phosphorus pentafluoride gas. The temperature was slowly increased in a gradient, and the final temperature was controlled at 155.3 ° C. The pressure of the reaction system was controlled to be 1.0-1.5 MPa for continuous gas production. The gas was condensed at -35 ° C in a three-stage condenser to remove excess sulfur trioxide to obtain high-purity phosphorus pentafluoride. The purity of the high-purity phosphorus pentafluoride could reach 99.99% by online GC detection; the gas was absorbed by anhydrous ether and the HF content was determined to be 15.1 ppm and the H2O content was 12.2 ppm. The total mass of phosphorus pentafluoride obtained by absorption with anhydrous ether was 269.3 g, and the yield was 96.2% wt.

[0082] Example 13

[0083] Preparation of High-Purity Phosphorus Pentafluoride

[0084] First, 499.3 g of fuming sulfuric acid (65%) was added to a 2 L lead reactor with a thermal oil jacket, and the temperature was maintained at 30-35 ° C. Then, 600.0 g of IMI-PF6 ionic liquid (from Example 5) was slowly added and mixed, and the system temperature was maintained between 35 and 45 ° C. to form a relatively stable mixture system. Secondly, the mixture system was heated with thermal oil. When the temperature reached 82 ° C, the system began to produce phosphorus pentafluoride gas. The temperature was slowly increased in a gradient, and the final temperature was controlled at 152.3 ° C. The pressure of the reaction system was controlled to be 1.0-1.5 MPa for continuous gas production. The gas was condensed at -35 ° C in a three-stage condenser to remove excess sulfur trioxide to obtain high-purity phosphorus pentafluoride. The purity of the high-purity phosphorus pentafluoride could reach 99.99% by online GC detection. The gas was absorbed with anhydrous ether and the HF content was determined to be 16.1 ppm and the H2O content was 15.3 ppm. The total mass of phosphorus pentafluoride obtained by absorption with anhydrous ether was 348.6 g, and the yield was 98.72% wt.

[0085] Comparative Example 1

[0086] The aqueous solution of hexafluorophosphoric acid prepared in Example 1 was directly used to prepare phosphorus pentafluoride, specifically as follows:

[0087] First, 600.6 g of an aqueous solution of hexafluorophosphoric acid (mainly containing 65.70% HPF6, from Example 1) was added to a 2 L lead reactor with a thermal oil jacket, and the temperature was maintained at 25-26 ° C. Then, 246.7 g of sulfur trioxide was slowly added and mixed, and the system temperature was maintained between 30 and 40 ° C to form a mixture system; secondly, the above mixture system was heated with thermal oil. When the temperature reached 92.6 ° C, the system began to generate gas, and the temperature was slowly increased gradually to control the final temperature at 166.2 ° C. The pressure of the reaction system was controlled to 1.0 The gas was continuously produced at -1.5 MPa, and the gas was condensed at -35°C in a three-stage condenser to remove excess sulfur trioxide to obtain a product gas. The gas was detected by online GC (Agilent 7890B gas chromatograph, USA) and the purity of phosphorus pentafluoride was 91.8%, the impurity phosphorus oxyfluoride (POF3) content was 6.3%, and the impurity phosphorus oxyfluoride (POF2) content was 1.9%. The gas was absorbed by anhydrous ether and the HF content was 810.2 ppm and the H2O content was 214.6 ppm. The total mass obtained by absorption by anhydrous ether was 350.1 g.

[0088] The target gas phosphorus pentafluoride (PF5), impurity gases phosphorus oxytrifluoride (POF3) and phosphorus oxydifluoride (POF2) undergo the following reaction to produce:

[0089]

[0090]

[0091]

[0092]

[0093] Among them, reaction (1) is the main reaction to produce the target product, and the others (2)(3)(4) are side reactions.

[0094] Comparative Example 2

[0095] In this comparative example, phosphorus pentafluoride was prepared using the following method:

[0096] The 2L fluorine-lined jacketed reactor was cooled to 17°C and 455.9g of hexafluorophosphoric acid aqueous solution (mainly containing 65.70% HPF6, from Example 1) was added; then, 350.2g of triethylamine was added dropwise to the reactor for neutralization. The reaction temperature was controlled within 30°C during the addition process, and the reaction pressure was normal pressure. The reaction time after the addition was 3 hours, and the pH value at the reaction end point was 7.2; no water removal operation was performed, and the reaction was directly used in the next step:

[0097] 187.3 g of sulfur trioxide was added to a 2 L lead reactor with a thermal oil jacket, and the temperature was maintained at 25-26 ° C. Then, 247.2 g of Et3NHPF6 ionic liquid (from Example 4) was slowly added and mixed, and the system temperature was maintained between 30 and 40 ° C to form a relatively stable mixture system; secondly, the mixture system was heated with thermal oil. When the temperature reached 78 ° C, the system began to produce phosphorus pentafluoride gas. The temperature was slowly increased, and the final temperature was controlled at 149.9 ° C. The pressure of the reaction system was controlled. The gas was continuously produced at a pressure of 1.0 to 1.5 MPa, and the gas was condensed at -35°C in a three-stage condenser to remove excess sulfur trioxide to obtain a product gas. The purity of the gas was 92.6% for phosphorus pentafluoride, 5.5% for impurity phosphorus oxyfluoride (POF3), and 1.9% for impurity phosphorus oxyfluoride (POF2). The gas was absorbed by anhydrous ether and the HF content was 755.9 ppm and the H2O content was 305.3 ppm. The total mass of the gas was 265.6 g as determined by absorption by anhydrous ether.

[0098] The impurity gases phosphorus oxytrifluoride (POF3) and phosphorus oxydifluoride (POF2) undergo reactions as described above (2)(3)(4). The presence of a large amount of water seriously affects the preparation of high-purity phosphorus pentafluoride.

[0099] As can be seen from the above, in the present invention, impurities such as metaphosphoric acid and phosphorous acid that produce phosphorus oxyfluoride are washed away in advance (HPF6 aqueous solution is present in large quantities); 2. Ionic liquid dehydration technology is used to further reduce the water content to less than 50 ppm. Unlike the HPF6 aqueous solution that contains a large amount of water (approximately 300,000 ppm), a large amount of water is prone to local high temperature during the acidification process, resulting in the reaction of water and hexafluorophosphoric acid to produce oxygen-containing impurities such as phosphorus oxyfluoride, thereby greatly reducing the purity.

[0100] The applicant declares that while the above-described embodiments illustrate the preparation method of the present invention, the present invention is not limited to these embodiments, and does not necessarily rely on these embodiments for implementation. Those skilled in the art will appreciate that any improvements to the present invention, equivalent substitutions for raw materials in the product of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing high-purity phosphorus pentafluoride gas from non-aqueous hexafluorophosphate ionic liquid, characterized in that: The method comprises the following steps: (1) reacting an oxygen-containing phosphorus compound with anhydrous hydrogen fluoride to obtain an aqueous solution of hexafluorophosphoric acid; (2) reacting the hexafluorophosphoric acid aqueous solution obtained in step (1) with an organic amine to prepare an anhydrous high-purity non-aqueous hexafluorophosphoric acid ionic liquid; (3) reacting the anhydrous high-purity nonaqueous hexafluorophosphate ionic liquid obtained in step (2) with a strong proton acid or anhydride to prepare high-purity phosphorus pentafluoride; After the reaction in step (2) is completed, the reaction solution is allowed to stand for phase separation for 2 to 4 hours, and the separated lower layer ionic liquid is washed with high-purity water of equal mass for multiple phase separation to remove impurities, until the total integrated area of ​​the impurity anions other than hexafluorophosphate in the ionic liquid after the last washing and the final washing is ≤0.001% by ion chromatography, and the washed ionic liquid is vacuum dehydrated and dried to obtain the anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid; The molar ratio of the anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid to the strong proton acid or anhydride in step (3) is 1:1.05 to 1:1.

2.

2. The method according to claim 1, characterized in that The oxygen-containing phosphorus compound in step (1) is selected from any one or a combination of at least two of phosphorus pentoxide, refined phosphoric acid, polyphosphoric acid, hypophosphoric acid, pyrophosphoric acid, pyrophosphorous acid or metaphosphoric acid.

3. The method according to claim 1, characterized in that The ratio of the total molar amount of phosphorus in the oxygen-containing phosphorus compound in step (1) to the total molar amount of fluorine in anhydrous hydrogen fluoride is 1:8 to 1:

16.

4. The method according to claim 3, characterized in that The ratio of the total molar amount of phosphorus in the oxygen-containing phosphorus compound in step (1) to the total molar amount of fluorine in anhydrous hydrogen fluoride is 1:

10.

5. The method according to claim 1, wherein The reaction temperature in step (1) is less than or equal to 60°C.

6. The method according to claim 5, characterized in that The reaction temperature in step (1) is 30-40°C.

7. The method according to claim 1, characterized in that The reaction in step (1) is carried out at a pressure of ≤0.35 MPa.

8. The method according to claim 7, characterized in that The reaction in step (1) is carried out under a pressure of 0.05Mpa-0.35Mpa.

9. The method according to claim 8, characterized in that The reaction in step (1) is carried out under a pressure of 0.05Mpa-0.098Mpa.

10. The method according to claim 1, characterized in that The reaction time of step (1) is 1-3h.

11. The method according to claim 10, characterized in that The reaction time of step (1) is 2h.

12. The method according to claim 1, characterized in that After the reaction in step (1) is completed, the temperature is lowered to 20-25°C.

13. The method according to claim 1, wherein The specific operation of the reaction in step (1) is as follows: adding anhydrous hydrogen fluoride to the reactor at a temperature below 5°C, adding an oxygen-containing phosphorus compound to the reactor at a temperature below 8°C, controlling the reaction temperature within 60°C, carrying out the reaction, and cooling to 20-25°C to obtain an aqueous solution of hexafluorophosphoric acid.

14. The method according to claim 1, wherein In step (2), the feed ratio of the hexafluorophosphoric acid aqueous solution to the organic amine is controlled so that the pH value of the reaction solution is 6.5 to 7.

5.

15. The method according to claim 1, wherein In step (2), the organic amine is added dropwise to the reaction solution containing the hexafluorophosphoric acid aqueous solution.

16. The method according to claim 1, wherein The organic amine in step (2) is selected from tertiary organic amines.

17. The method according to claim 1, wherein The organic amine is selected from any one or a combination of at least two of triethylamine, tri-n-propylamine, tri-n-butylamine, pyridine, pyrrolidine, methylimidazole, piperidine or morpholine.

18. The method according to claim 15, characterized in that The dropwise addition is carried out at a temperature of ≤30°C.

19. The method according to claim 1, wherein The reaction in step (2) is carried out under normal pressure.

20. The method according to claim 1, wherein The reaction temperature in step (2) is ≤30°C.

21. The method according to claim 20, characterized in that The reaction temperature in step (2) is 5-10°C.

22. The method according to claim 1, wherein The reaction time of step (2) is 2-3 hours.

23. The method according to claim 22, characterized in that The reaction time of step (2) is 3 hours.

24. The method according to claim 1, wherein The endpoint pH value of the reaction in step (2) is 6.5-7.

5.

25. The method according to claim 1, wherein The drying temperature of the vacuum dehydration drying is 80-110° C., the absolute vacuum degree is ≤200 Pa, and the vacuum drying time is 8-12 hours.

26. The method according to claim 1, wherein PF6 in the anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid of step (2) - The content is more than 99.99%, the cation content is more than 99.99%, and the moisture content is ≤50ppm.

27. The method according to claim 26, characterized in that The water content in the anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid in step (2) is ≤20ppm.

28. The method according to claim 1, wherein The strong protonic acid or anhydride in step (3) is selected from any one of fuming sulfuric acid, sulfur trioxide, fluorosulfonic acid or trifluoromethanesulfonic acid, or a combination of at least two thereof.

29. The method according to claim 1, wherein The reaction temperature in step (3) is 80-160°C.

30. The method according to claim 29, wherein The reaction temperature in step (3) is 100-120°C.

31. The method according to claim 1, wherein The reaction in step (3) is carried out under a pressure of 1.0 to 1.5 MPa.

32. The method according to claim 31, characterized in that The reaction in step (3) is carried out under a pressure of 1.2 MPa.

33. The method according to claim 1, wherein The specific operation of the reaction in step (3) is as follows: adding a strong protonic acid or anhydride to the reactor, maintaining the temperature within 25°C, then slowly adding anhydrous high-purity non-aqueous hexafluorophosphate ionic liquid for mixing, maintaining the system temperature not exceeding 50°C, to form a relatively stable mixture system; heating the above mixture system, when the temperature reaches 80°C, the system begins to generate phosphorus pentafluoride gas, controlling the heating temperature at 80-160°C, controlling the reaction system pressure at 1.0-1.5MPa, and continuously producing a mixed gas of phosphorus pentafluoride and hydrogen fluoride.

34. The method according to claim 1, wherein After the reaction in step (3) is completed, the crude phosphorus pentafluoride gas is passed through a hydrogen fluoride deacidification device to remove hydrogen fluoride to obtain high-purity phosphorus pentafluoride.

35. The method according to claim 34, wherein The hydrogen fluoride deacidification device is a three-stage combined low-temperature deep-cold condenser with a condensation temperature of -70 to -30°C.

36. The method according to claim 34, wherein The prepared phosphorus pentafluoride gas has a purity of more than 99.99%, wherein the HF content is ≤30ppm and the H2O content is ≤20ppm.

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