Method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride

Abstract

The invention belongs to the technical field of phosphorus pentafluoride preparation, and particularly relates to a method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride. The synthesis method comprises the following steps: adding phosphoric acid and anhydrous hydrogen fluoride into a reactor at the temperature of-20 DEG C to 10 DEG C, uniformly mixing, then introducing SF4, carrying out mixing reaction, introducing the reaction mixture into a heating decomposition kettle, carrying out heating decomposition, and carrying out rectification separation on a gas-phase product obtained by decomposition to obtain high-purity phosphorus pentafluoride, wherein the molar ratio of the phosphoric acid to the anhydrous hydrogen fluoride is 1: (1-2); the molar ratio of the SF4 to the phosphoric acid is (2-2.5): 1. According to the method, phosphoric acid and anhydrous hydrogen fluoride are adopted as raw materials, and SF4 is added as a dehydrating agent and an auxiliary fluorinating agent, so that the fluorination reaction efficiency can be remarkably improved, and the product quality and yield are improved. The synthesis method disclosed by the invention has the advantages of mild conditions, simple process, low equipment requirement, environment friendliness and high efficiency.

Description

Technical Field

[0001] The present invention belongs to the technical field of phosphorus pentafluoride preparation, and particularly relates to a method for efficiently synthesizing phosphorus pentafluoride by using phosphoric acid and hydrogen fluoride. Background Art

[0002] Phosphorus pentafluoride (PF5) is a colorless and odorless gas under normal conditions. It emits thick smoke violently in humid air. Its melting point is -93.78°C and its boiling point is -84.6°C under normal pressure. As a fluorinating agent, phosphorus pentafluoride can carry out ion transfer and is widely used in the fields of electronics industry, battery manufacturing, polymer materials, and catalysts, etc.

[0003] In semiconductor manufacturing, phosphorus pentafluoride becomes a plasma gas under microwave action for doping, which can significantly improve the performance of semiconductors. In the fields of polymer materials and chemical engineering, phosphorus pentafluoride can be used as a reactant to synthesize fluorinated organic dithiophosphates for preparing polymer materials with good anti-corrosion performance. Phosphorus pentafluoride can also be directly used as a catalyst for many copolymerization reactions, such as the copolymerization reaction of glucan and dehydrated mannose. In addition, phosphorus pentafluoride amine copolymer can be synthesized using phosphorus pentafluoride as a raw material as a herbicide. In addition, lithium hexafluorophosphate with excellent performance can be prepared using high-purity phosphorus pentafluoride as a raw material as an electrolyte for lithium batteries, thus significantly improving the performance of lithium batteries.

[0004] Currently, the preparation methods of phosphorus pentafluoride can be roughly divided into direct methods and indirect methods. The direct method generally uses hydrogen fluoride and fluorine gas, etc. as raw materials to prepare phosphorus pentafluoride through a one-step reaction. For example: synthesizing phosphorus pentafluoride by reacting fluorine gas and elemental phosphorus, and the reaction equation is 2P + 5F2 = 2PF5; preparing phosphorus pentafluoride by reacting phosphorus pentachloride and anhydrous hydrogen fluoride, which is also the most mature and common process in the lithium hexafluorophosphate industry, and the reaction equation is PCl5 + 5HF = PF5 + 5HCl; preparing phosphorus pentafluoride by reacting phosphorus trifluoride, and the reaction equation is 5PF3 + 3X2 → 3PF5 + 2PX5 (where X is a halogen).

[0005] The above reactions use fluorine gas and hydrogen fluoride, which are raw materials with strong corrosiveness and toxicity. They have high requirements for the reactor, and the reactions are highly exothermic and difficult to control, and easily produce by-products such as phosphorus trifluoride, affecting the product purity. The method of preparing phosphorus pentafluoride by reacting phosphorus pentachloride and anhydrous hydrogen fluoride produces a large amount of hydrogen chloride gas (the boiling point is close to that of phosphorus pentafluoride) that is difficult to separate, and the purification is very difficult.

[0006] The indirect production method is to first make appropriate reactants generate intermediate products (mainly POF3 and HPF6), and then process the intermediate products to generate phosphorus pentafluoride. However, the existing indirect production methods generally have the problems of many reaction steps and relatively complex process steps.

[0007] Therefore, there is an urgent need for an economical, efficient and simple-process method for synthesizing phosphorus pentafluoride. Summary of the Invention

[0008] Aiming at the disadvantages and deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide a method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride. The synthesis method of the present invention uses phosphoric acid and hydrogen fluoride as reaction raw materials, and sulfur tetrafluoride as a dehydrating agent and auxiliary fluorinating agent for fluorination reaction, which has the advantages of mild conditions, simple process, low equipment requirements, environmental protection and high efficiency. It can significantly reduce the occurrence of side reactions and the generation of by-products, and improve the yield and quality of phosphorus pentafluoride.

[0009] The purpose of the present invention is achieved through the following technical solutions: A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride, comprising the following steps: At a temperature of -20°C to 10°C, phosphoric acid and anhydrous hydrogen fluoride are added to a reactor and mixed evenly, then sulfur tetrafluoride (SF4) is introduced for mixing reaction, and the reaction mixture is introduced into a heating decomposition kettle for heating decomposition, and the gaseous products obtained by decomposition are subjected to rectification separation to obtain high-purity phosphorus pentafluoride; Among them, the molar ratio of the added phosphoric acid and anhydrous hydrogen fluoride is 1:1 to 2; the molar ratio of SF4 to phosphoric acid is 2 to 2.5:1.

[0010] Further, in the above synthesis method, the high-purity phosphorus pentafluoride refers to phosphorus pentafluoride with a purity of not less than 99.5%.

[0011] Further, in the above synthesis method, the time of the mixing reaction is 1 to 3 h.

[0012] Further, in the above synthesis method, the temperature of the heating decomposition is 138°C to 168°C.

[0013] Further, in the above synthesis method, the rectification separation respectively obtains phosphorus pentafluoride, sulfur dioxide and hydrogen fluoride.

[0014] Further preferably, the temperature of the rectification separation of phosphorus pentafluoride is below -85°C, and the pressure is 0.1 to 0.5 MPa.

[0015] Further preferably, the temperature of the rectification separation of sulfur dioxide is -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa.

[0016] Further preferably, the temperature of the rectification separation of hydrogen fluoride is 20°C to 50°C, and the pressure is 0.5 to 2.0 MPa.

[0017] Further, in the above synthesis method, the yield of the high-purity phosphorus pentafluoride ≥ 88.5%.

[0018] The principle of the present invention is as follows: In the process of producing phosphorus pentafluoride by the indirect method using phosphoric acid and anhydrous hydrogen fluoride as raw materials, the fluorination ability of HF is weak, resulting in low reaction efficiency and product yield. In addition, the water generated by the reaction will react with phosphorus pentafluoride, leading to reverse reaction or hydrolysis: PF5 + H2O → POF3 + 2HF, which affects the product quality and yield. Usually, multiple fluorination reactions and dehydration steps are required to improve the conversion rate of the target product. By adding SF4 as a dehydrating agent and auxiliary fluorinating agent during the reaction process, the present invention can significantly improve the fluorination reaction efficiency, product quality and yield. The chemical reactions involved in using SF4 as a dehydrating agent and auxiliary fluorinating agent in the present invention are as follows: H3PO4 + 6HF → HPF6 + 4H2O; HPF6 → PF5 + HF; H3PO4 + HF + SF4 → PF5 + SO2 + 2H2O; SF4 + 2H2O → SO2 + 4HF.

[0019] It can be seen from the above reaction formulas that SF4 can react with the water generated by the main reaction to generate HF, further increasing the concentration of the fluorinating agent while effectively reducing the reverse reaction or hydrolysis of phosphorus pentafluoride, thereby promoting the forward progress of the main reaction (the process of H3PO4 reacting with HF to generate HPF6); at the same time, SF4 can assist HF in the fluorination reaction to directly generate PF5, reducing the amount of water generated while improving the reaction efficiency, thereby achieving the effect of significantly improving the fluorination reaction efficiency, product quality and yield.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) By using phosphoric acid and anhydrous hydrogen fluoride as raw materials and adding SF4 as a dehydrating agent and auxiliary fluorinating agent, the present invention can significantly improve the fluorination reaction efficiency, product quality and yield.

[0021] (2) In the prior art, using fuming sulfuric acid as a dehydrating agent to promote fluorination ability has limited effects. The reason is that fuming sulfuric acid is prone to side reactions with hydrogen fluoride to generate fluorosulfonic acid, competing with the synthesis reaction of hexafluorophosphoric acid, reducing the main reaction efficiency and product yield, and multiple fluorination reactions and dehydration steps are required to improve the fluorination effect. While the present invention uses SF4 as a dehydrating agent, on the one hand, it reacts with water to generate hydrofluoric acid (HF), which can increase the concentration of reactants and promote the forward progress of the reaction; on the other hand, it can cooperate with hydrogen fluoride to react with phosphoric acid to directly generate the target product of phosphorus pentafluoride. Compared with the fuming sulfuric acid dehydrating agent, it significantly improves the fluorination reaction efficiency while reducing the generation of by-products and improving the utilization rate of raw materials.

[0022] (3) In the reaction of the present invention, the hydrofluoric acid generated by the dehydration of SF4 can promote the forward progress of the main reaction. At the same time, the gaseous impurity component generated is sulfur dioxide, whose boiling point has a relatively high difference from the boiling point of the product phosphorus pentafluoride and is thus easy to separate, and the purification cost of phosphorus pentafluoride is low. Specific Embodiments

[0023] The present invention will be further described in detail below in conjunction with embodiments, but the embodiments of the present invention are not limited thereto.

[0024] Example 1 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: At a temperature of -5°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) are added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.5 and mixed evenly. Then, sulfur tetrafluoride (SF4) is introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 is 2.0:1. The reaction temperature is controlled at -5°C, and the reaction time is 2 h. The mixture after the reaction is completed is introduced into a heating decomposition kettle, heated to 150°C for decomposition, and the decomposed gaseous products are separated by rectification. The temperature at the lower section of the rectification column is controlled at 20°C to 50°C, and the pressure is 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column is controlled at -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column is controlled below -85°C, and the pressure is 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0025] The purity of the phosphorus pentafluoride gas obtained in this example is 99.6%, and the yield is 90.4% (calculated based on the input amount of phosphoric acid, the same below).

[0026] Example 2 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: At a temperature of -10°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) are added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.6 and mixed evenly. Then, sulfur tetrafluoride (SF4) is introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 is 2.2:1. The reaction temperature is controlled at -10°C, and the reaction time is 2.5 h. The mixture after the reaction is completed is introduced into a heating decomposition kettle, heated to 160°C for decomposition, and the decomposed gaseous products are separated by rectification. The temperature at the lower section of the rectification column is controlled at 20°C to 50°C, and the pressure is 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column is controlled at -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column is controlled below -85°C, and the pressure is 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0027] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 92.3%.

[0028] Example 3 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride includes the following steps: At -15°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) are added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.7 and mixed evenly. Then sulfur tetrafluoride (SF4) is introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 is 2.5:1. The reaction temperature is controlled at -15°C, and the reaction time is 3 h. The mixture after the reaction is introduced into a heating decomposition kettle, heated to 168°C for decomposition, and the decomposed gas-phase products are separated by rectification. The temperature at the lower section of the rectification column is controlled at 20°C to 50°C, and the pressure is 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column is controlled at -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column is controlled below -85°C, and the pressure is 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0029] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 95.1%.

[0030] Example 4 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride includes the following steps: At -12°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) are added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.0 and mixed evenly. Then sulfur tetrafluoride (SF4) is introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 is 2.1:1. The reaction temperature is controlled at -12°C, and the reaction time is 1.5 h. The mixture after the reaction is introduced into a heating decomposition kettle, heated to 138°C for decomposition, and the decomposed gas-phase products are separated by rectification. The temperature at the lower section of the rectification column is controlled at 20°C to 50°C, and the pressure is 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column is controlled at -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column is controlled below -85°C, and the pressure is 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0031] The purity of the phosphorus pentafluoride gas obtained in this example is 99.6%, and the yield is 88.5%.

[0032] Example 5 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride includes the following steps: At -15°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.8 and mixed evenly. Then, sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.3:1. The reaction temperature was controlled at -15°C, and the reaction time was 2 h. The mixture after the reaction was introduced into a heating decomposition kettle, heated to 156°C for decomposition, and the decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20°C - 50°C, and the pressure was 0.5 - 2.0 MPa to obtain the hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10°C - 10°C, and the pressure was 0.3 - 1.0 MPa to obtain the sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85°C, and the pressure was 0.1 - 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0033] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5%, and the yield was 93.8%.

[0034] Example 6 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: At -9°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen in a molar ratio of 1:2.0 and mixed evenly. Then, sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.4:1. The reaction temperature was controlled at -9°C, and the reaction time was 3 h. The mixture after the reaction was introduced into a heating decomposition kettle, heated to 152°C for decomposition, and the decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20°C - 50°C, and the pressure was 0.5 - 2.0 MPa to obtain the hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10°C - 10°C, and the pressure was 0.3 - 1.0 MPa to obtain the sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85°C, and the pressure was 0.1 - 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0035] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5%, and the yield was 94.6%.

[0036] Example 7 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: At a temperature of 5 °C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.3 and mixed evenly. Then sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.0:1. The reaction temperature was controlled at 5 °C and the reaction time was 1 h. The mixture after the reaction was introduced into a heating decomposition kettle and heated to 140 °C for decomposition. The decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20 °C - 50 °C and the pressure was 0.5 - 2.0 MPa to obtain the hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10 °C - 10 °C and the pressure was 0.3 - 1.0 MPa to obtain the sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85 °C and the pressure was 0.1 - 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0037] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5% and the yield was 89.2%.

[0038] Example 8 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: At a temperature of -20 °C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.7 and mixed evenly. Then sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.5:1. The reaction temperature was controlled at -20 °C and the reaction time was 2.5 h. The mixture after the reaction was introduced into a heating decomposition kettle and heated to 165 °C for decomposition. The decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20 °C - 50 °C and the pressure was 0.5 - 2.0 MPa to obtain the hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10 °C - 10 °C and the pressure was 0.3 - 1.0 MPa to obtain the sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85 °C and the pressure was 0.1 - 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0039] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5% and the yield was 95.4%.

[0040] Example 9 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: At a temperature of -8°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.6 and mixed evenly. Then, sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.2:1. The reaction temperature was controlled at -8°C, and the reaction time was 3 h. The mixture after the reaction was introduced into a heating decomposition kettle, and the temperature was raised to 162°C for heating decomposition. The decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20°C to 50°C, and the pressure was 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10°C to 10°C, and the pressure was 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85°C, and the pressure was 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0041] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5%, and the yield was 92.6%.

[0042] Example 10 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: At a temperature of 8°C, phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen in a molar ratio of 1:1.5 and mixed evenly. Then, sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.1:1. The reaction temperature was controlled at 8°C, and the reaction time was 1.5 h. The mixture after the reaction was introduced into a heating decomposition kettle, and the temperature was raised to 150°C for heating decomposition. The decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20°C to 50°C, and the pressure was 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10°C to 10°C, and the pressure was 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85°C, and the pressure was 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0043] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5%, and the yield was 90.9%.

[0044] Example 11 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, comprising the following steps: Phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen at a molar ratio of 1:1.7 at a temperature of 10 °C and mixed evenly. Then sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.3:1. The reaction temperature was controlled at 10 °C and the reaction time was 1 h. The mixture after the reaction was introduced into a heating decomposition kettle and heated to 160 °C for decomposition. The decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20 °C to 50 °C and the pressure was 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10 °C to 10 °C and the pressure was 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85 °C and the pressure was 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0045] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5% and the yield was 93.0%.

[0046] Example 12 A method for efficiently synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride includes the following steps: Phosphoric acid (H3PO4) and anhydrous hydrogen fluoride (HF) were added to a reaction kettle purged with nitrogen at a molar ratio of 1:1.2 at a temperature of 0 °C and mixed evenly. Then sulfur tetrafluoride (SF4) was introduced for a mixed reaction. The molar ratio of SF4 to H3PO4 was 2.4:1. The reaction temperature was controlled at 0 °C and the reaction time was 2 h. The mixture after the reaction was introduced into a heating decomposition kettle and heated to 155 °C for decomposition. The decomposed gas-phase products were separated by rectification. The temperature at the lower section of the rectification column was controlled at 20 °C to 50 °C and the pressure was 0.5 to 2.0 MPa to obtain a hydrogen fluoride component; the temperature at the middle section of the rectification column was controlled at -10 °C to 10 °C and the pressure was 0.3 to 1.0 MPa to obtain a sulfur dioxide component; the temperature at the upper section of the rectification column was controlled below -85 °C and the pressure was 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0047] The purity of the phosphorus pentafluoride gas obtained in this example was 99.6% and the yield was 91.0%.

[0048] Comparative Example 1 In this comparative example, a method for synthesizing phosphorus pentafluoride from phosphoric acid and hydrogen fluoride, compared with Example 6, used an equimolar amount of fuming sulfuric acid instead of sulfur tetrafluoride as a dehydrating agent, and the rest was the same.

[0049] The purity of the phosphorus pentafluoride gas obtained in this comparative example was 99.5% and the yield was 25.2%.

[0050] By comparing with the results of Example 6, it can be concluded that after using fuming sulfuric acid to replace sulfur tetrafluoride as the dehydrating agent, the proportion of hydrogen fluoride in the fluorination reaction is insufficient and the yield of phosphorus pentafluoride is low.

[0051] Comparative Example 2 A method for synthesizing phosphorus pentafluoride by using phosphoric acid and hydrogen fluoride in this comparative example. Compared with Example 6, fuming sulfuric acid with an equimolar amount is used to replace sulfur tetrafluoride as the dehydrating agent, and the molar ratio of reaction HF to H3PO4 is increased to 11.6:1 (under the condition of the same F content ratio as in Example 6), and the rest is the same.

[0052] The purity of the phosphorus pentafluoride gas obtained in this comparative example is 99.5% and the yield is 74.6%.

[0053] By comparing with the results of Example 6, it can be concluded that after using fuming sulfuric acid to replace sulfur tetrafluoride as the dehydrating agent, even if an excessive amount of HF is used, the efficiency of the fluorination reaction is still low, resulting in a decrease in the yield of phosphorus pentafluoride. The reason is that the synergistic effect of fuming sulfuric acid in promoting fluorination ability is limited, and it is easy to carry out side reactions with hydrogen fluoride to form fluorosulfonic acid, competing with the reaction of H3PO4 and HF, affecting the efficiency of the fluorination reaction and resulting in a decrease in the product yield.

[0054] The above embodiments are the preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride, characterized in that, It includes the following steps: Add phosphoric acid and anhydrous hydrogen fluoride into a reactor at a temperature of -20°C to 10°C and mix evenly, then introduce SF4 for mixed reaction, introduce the reaction mixture into a heating decomposition kettle for heating decomposition, and carry out rectification separation on the gaseous products obtained by decomposition to obtain high-purity phosphorus pentafluoride; Among them, the molar ratio of the added phosphoric acid and anhydrous hydrogen fluoride is 1:1 to 2; the molar ratio of SF4 to phosphoric acid is 2 to 2.5:

1.

2. A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride according to claim 1, characterized in that, The high-purity phosphorus pentafluoride refers to phosphorus pentafluoride with a purity of not less than 99.5%.

3. A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride according to claim 1, characterized in that, The time of the mixed reaction is 1 to 3 h.

4. A method for efficiently synthesizing phosphorus pentafluoride by using phosphoric acid and hydrogen fluoride according to claim 1, characterized in that, The temperature of the heating decomposition is 138°C to 168°C.

5. A method for efficiently synthesizing phosphorus pentafluoride by using phosphoric acid and hydrogen fluoride according to claim 1, characterized in that, The rectification separation respectively obtains the high-purity phosphorus pentafluoride, sulfur dioxide and hydrogen fluoride.

6. The method for efficiently synthesizing phosphorus pentafluoride by using phosphoric acid and hydrogen fluoride according to claim 5, characterized in that, The temperature of the rectification separation of the phosphorus pentafluoride is below -85°C, and the pressure is 0.1 to 0.5 MPa.

7. A method for efficiently synthesizing phosphorus pentafluoride by using phosphoric acid and hydrogen fluoride according to claim 5, characterized in that, The temperature of the rectification separation of the sulfur dioxide is -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa.

8. A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride according to claim 5, characterized in that, The temperature of the rectification separation of the hydrogen fluoride is 20°C to 50°C, and the pressure is 0.5 to 2.0 MPa.

9. A method for efficiently synthesizing phosphorus pentafluoride by using phosphoric acid and hydrogen fluoride according to claim 1, characterized in that, The yield of the high-purity phosphorus pentafluoride ≥ 88.5%.