A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride

Abstract

The present invention belongs to the technical field of phosphorus pentafluoride preparation, and in particular to a method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride. The synthesis method comprises the following steps: adding phosphoric acid and anhydrous hydrogen fluoride into a reactor at a temperature of 20°C to 10°C and mixing them uniformly, then passing SF4 into a mixed reaction, introducing the reaction mixture into a thermal decomposition kettle for thermal decomposition, and performing rectification and separation on the gas phase product obtained by decomposition to obtain high-purity phosphorus pentafluoride; wherein the molar ratio of the phosphoric acid and anhydrous hydrogen fluoride added is 1:1~2; the molar ratio of the SF4 to phosphoric acid is 2~2.5:1. The present invention uses phosphoric acid and anhydrous hydrogen fluoride as raw materials, and by adding SF4 as a dehydrating agent and an auxiliary fluorinating agent, the efficiency of the fluorination reaction can be significantly improved, and the product quality and yield can be improved. The synthesis method of the present invention has the advantages of mild conditions, simple process, low equipment requirements, and environmental protection and high efficiency.

Description

Technical Field

[0001] The 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 violent fumes in moist air. Its melting point at normal pressure is -93.78°C and its boiling point is -84.6°C. As a fluorinating agent, phosphorus pentafluoride can undergo ion transfer and is widely used in the electronics industry, battery manufacturing, polymer materials, and catalysts.

[0003] In semiconductor manufacturing, phosphorus pentafluoride, when transformed into a plasma gas under microwaves, can significantly improve semiconductor performance for doping. In the fields of polymer materials and chemical engineering, phosphorus pentafluoride can be used as a reactant to synthesize fluorinated organodithiophosphates, which are used to prepare polymer materials with excellent corrosion resistance. Phosphorus pentafluoride can also be used directly as a catalyst in many copolymerization reactions, such as the copolymerization of anhydroglucose and dehydromannose. Furthermore, phosphorus pentafluoride can be used as a raw material to synthesize phosphorus pentafluoride-amine copolymers for use as herbicides. Furthermore, high-purity phosphorus pentafluoride can be used to prepare high-performance lithium hexafluorophosphate, which can be used as an electrolyte in lithium batteries, significantly improving their performance.

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

[0005] The fluorine gas and hydrogen fluoride used in the above reaction are highly corrosive and toxic raw materials, placing high demands on the reactor. Furthermore, the reaction is highly exothermic and difficult to control, and easily produces byproducts such as phosphorus trifluoride, which affects product purity. The method for preparing phosphorus pentafluoride by reacting phosphorus pentachloride with anhydrous hydrogen fluoride produces large amounts of difficult-to-separate hydrogen chloride gas (with a boiling point close to that of phosphorus pentafluoride), making purification extremely challenging.

[0006] Indirect production methods involve first generating intermediate products (primarily POF3 and HPF6) from appropriate reactants, which are then processed to produce phosphorus pentafluoride. However, existing indirect production methods generally suffer from multiple reaction steps and relatively complex process steps.

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

[0008] In response to the shortcomings and deficiencies of the above-mentioned prior art, the present invention aims to provide a method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride. The present method utilizes phosphoric acid and hydrogen fluoride as the raw materials, and sulfur tetrafluoride as a dehydrating agent and auxiliary fluorinating agent for the fluorination reaction. The method has the advantages of mild conditions, simple process, low equipment requirements, and environmental and high efficiency. It can significantly reduce the occurrence of side reactions and the formation of by-products, thereby improving the yield and quality of phosphorus pentafluoride.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0011] Phosphoric acid and anhydrous hydrogen fluoride are added to a reactor at a temperature of -20°C to 10°C and mixed evenly. Then, sulfur tetrafluoride (SF4) is introduced into the mixed reaction. The reaction mixture is introduced into a thermal decomposition kettle for thermal decomposition. The gas phase product obtained by decomposition is subjected to rectification and separation to obtain high-purity phosphorus pentafluoride.

[0012] The molar ratio of phosphoric acid to anhydrous hydrogen fluoride is 1:1-2; the molar ratio of SF4 to phosphoric acid is 2-2.5:1.

[0013] Furthermore, in the above synthesis method, the high-purity phosphorus pentafluoride refers to phosphorus pentafluoride with a purity of not less than 99.5%.

[0014] Furthermore, in the above synthesis method, the mixing reaction time is 1 to 3 hours.

[0015] Furthermore, in the above synthesis method, the temperature of the thermal decomposition is 138°C to 168°C.

[0016] Furthermore, in the above synthesis method, the distillation separation obtains phosphorus pentafluoride, sulfur dioxide and hydrogen fluoride respectively.

[0017] More preferably, the temperature for the distillation separation of phosphorus pentafluoride is below -85°C and the pressure is 0.1-0.5 MPa.

[0018] Further preferably, the temperature of the sulfur dioxide distillation separation is -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa.

[0019] More preferably, the temperature of the hydrogen fluoride distillation separation is 20° C. to 50° C., and the pressure is 0.5 to 2.0 MPa.

[0020] Furthermore, in the above synthesis method, the yield of the high-purity phosphorus pentafluoride is ≥88.5%.

[0021] The principle of the present invention is: in the process of producing phosphorus pentafluoride by an indirect method using phosphoric acid and anhydrous hydrogen fluoride as raw materials, the fluorination ability of HF is relatively weak, resulting in low reaction efficiency and product yield; in addition, the water generated by the reaction will react with phosphorus pentafluoride, resulting in a reverse reaction or hydrolysis: PF5+H2O→POF3+2HF, affecting the product quality and yield. It is usually necessary to go through multiple steps of fluorination reaction and dehydration steps to improve the conversion rate of the target product. The present invention can significantly improve the efficiency of the fluorination reaction, improve product quality and yield by adding SF4 as a dehydrating agent and auxiliary fluorinating agent during the reaction process. The chemical reactions involved in the present invention using SF4 as a dehydrating agent and auxiliary fluorinating agent are as follows:

[0022] H3PO4+6HF→HPF6+4H2O; HPF6→PF5+HF;

[0023] H3PO4+HF+SF4→PF5+SO2+2H2O; SF4+2H2O→SO2+4HF.

[0024] It can be seen from the above reaction formula that SF4 can react with the water generated in 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 generate PF5 in one step, thereby improving the reaction efficiency while reducing the amount of water generated, thereby significantly improving the fluorination reaction efficiency, improving product quality and yield.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) The present invention uses phosphoric acid and anhydrous hydrogen fluoride as raw materials, and by adding SF4 as a dehydrating agent and auxiliary fluorinating agent, it can significantly improve the efficiency of the fluorination reaction, improve product quality and yield.

[0027] (2) The existing technology uses fuming sulfuric acid as a dehydrating agent to promote fluorination, but the effect is limited. The reason is that fuming sulfuric acid easily reacts with hydrogen fluoride to form fluorosulfonic acid, which competes with the synthesis reaction of hexafluorophosphoric acid, reducing the efficiency of the main reaction and the product yield. Multiple fluorination reactions and dehydration steps are required to improve the fluorination effect. The present invention uses SF4 as a dehydrating agent. On the one hand, it reacts with water to form hydrofluoric acid (HF), which can increase the concentration of reactants and promote the forward reaction. On the other hand, it can cooperate with hydrogen fluoride and phosphoric acid to react in one step to generate the target product of phosphorus pentafluoride. Compared with the fuming sulfuric acid dehydrating agent, it significantly improves the efficiency of the fluorination reaction while reducing the generation of by-products and improving the utilization rate of raw materials.

[0028] (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, which has a relatively high boiling point difference from the boiling point of the product phosphorus pentafluoride and is easy to separate. The purification cost of phosphorus pentafluoride is low. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below with reference to examples, but the embodiments of the present invention are not limited thereto.

[0030] Example 1

[0031] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0032] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.5 at -5°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.0:1 to H₃PO₄. The reaction temperature was maintained at -5°C for 2 hours. The resulting mixture was introduced into a thermal decomposition reactor and heated to 150°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0033] The purity of the phosphorus pentafluoride gas obtained in this example was 99.6%, and the yield was 90.4% (calculated based on the amount of phosphoric acid input, the same below).

[0034] Example 2

[0035] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0036] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.6 at -10°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.2:1 to H₃PO₄. The reaction temperature was maintained at -10°C for 2.5 hours. The resulting mixture was introduced into a thermal decomposition reactor and heated to 160°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0037] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 92.3%.

[0038] Example 3

[0039] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0040] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.7 at -15°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.5:1 to H₃PO₄. The reaction temperature was maintained at -15°C for 3 hours. The resulting mixture was introduced into a thermal decomposition reactor and heated to 168°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0041] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 95.1%.

[0042] Example 4

[0043] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0044] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.0 at -12°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.1:1 to H₃PO₄. The reaction temperature was maintained at -12°C for 1.5 hours. The resulting mixture was introduced into a thermal decomposition reactor and heated to 138°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0045] The purity of the phosphorus pentafluoride gas obtained in this example is 99.6%, and the yield is 88.5%.

[0046] Example 5

[0047] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0048] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.8 at -15°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.3:1 to H₃PO₄. The reaction temperature was maintained at -15°C for 2 hours. The resulting mixture was then introduced into a thermal decomposition reactor and heated to 156°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0049] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 93.8%.

[0050] Example 6

[0051] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0052] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:2.0 at -9°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.4:1 to H₃PO₄. The reaction temperature was maintained at -9°C for 3 hours. The resulting mixture was introduced into a thermal decomposition reactor and heated to 152°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0053] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 94.6%.

[0054] Example 7

[0055] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0056] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.3 at 5°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.0:1 to H₃PO₄. The reaction temperature was maintained at 5°C for 1 hour. The resulting mixture was introduced into a thermal decomposition reactor and heated to 140°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0057] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 89.2%.

[0058] Example 8

[0059] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0060] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.7 at -20°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.5:1. The reaction temperature was maintained at -20°C for 2.5 hours. The resulting mixture was then introduced into a thermal decomposition reactor and heated to 165°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0061] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 95.4%.

[0062] Example 9

[0063] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0064] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.6 at -8°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.2:1 to H₃PO₄. The reaction temperature was maintained at -8°C for 3 hours. The resulting mixture was then introduced into a thermal decomposition reactor and heated to 162°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0065] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 92.6%.

[0066] Example 10

[0067] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0068] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.5 at 8°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.1:1 to H₃PO₄. The reaction temperature was maintained at 8°C for 1.5 hours. The resulting mixture was introduced into a thermal decomposition reactor and heated to 150°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0069] The purity of the phosphorus pentafluoride gas obtained in this example is 99.5%, and the yield is 90.9%.

[0070] Example 11

[0071] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0072] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.7 at 10°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.3:1 to H₃PO₄. The reaction temperature was maintained at 10°C for 1 hour. The resulting mixture was introduced into a thermal decomposition reactor and heated to 160°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0073] The purity of the phosphorus pentafluoride gas obtained in this example was 99.5%, and the yield was 93.0%.

[0074] Example 12

[0075] A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride comprises the following steps:

[0076] Phosphoric acid (H₃PO₄) and anhydrous hydrogen fluoride (HF) were added to a nitrogen-purged reactor at a molar ratio of 1:1.2 at 0°C and mixed thoroughly. Sulfur tetrafluoride (SF₄) was then introduced for a reaction at a molar ratio of 2.4:1 to H₃PO₄. The reaction temperature was maintained at 0°C for 2 hours. The resulting mixture was introduced into a thermal decomposition reactor and heated to 155°C for decomposition. The decomposition gaseous products were separated by distillation. The lower section of the distillation tower was controlled at a temperature of 20°C to 50°C and a pressure of 0.5 to 2.0 MPa to obtain the hydrogen fluoride component; the middle section of the distillation tower was controlled at a temperature of -10°C to 10°C and a pressure of 0.3 to 1.0 MPa to obtain the sulfur dioxide component; and the upper section of the distillation tower was controlled at a temperature below -85°C and a pressure of 0.1 to 0.5 MPa to obtain high-purity phosphorus pentafluoride.

[0077] The purity of the phosphorus pentafluoride gas obtained in this example was 99.6%, and the yield was 91.0%.

[0078] Comparative Example 1

[0079] In a method of synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride in this comparative example, compared with Example 6, oleum in an equal molar amount is used instead of sulfur tetrafluoride as the dehydrating agent, and the rest of the method is the same.

[0080] The purity of the phosphorus pentafluoride gas obtained in this comparative example was 99.5%, and the yield was 25.2%.

[0081] By comparing the results with those of Example 6, it can be concluded that after using fuming sulfuric acid instead of 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.

[0082] Comparative Example 2

[0083] In this comparative example, a method for synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride is used. Compared with Example 6, an equal molar amount of fuming sulfuric acid is used instead of sulfur tetrafluoride as the dehydrating agent, and the molar ratio of HF to H3PO4 in the reaction is increased to 11.6:1 (the same F content ratio as in Example 6). All other conditions are the same.

[0084] The purity of the phosphorus pentafluoride gas obtained in this comparative example was 99.5%, and the yield was 74.6%.

[0085] Comparison with the results of Example 6 shows that even with excess HF, the fluorination reaction efficiency remains low when oleum is used instead of sulfur tetrafluoride as the dehydrating agent, resulting in a reduced yield of phosphorus pentafluoride. This is because oleum has limited synergistic effects on fluorination and readily reacts with hydrogen fluoride to form fluorosulfonic acid, which competes with the reaction between H₃PO₄ and HF, affecting the efficiency of the fluorination reaction and reducing the product yield.

[0086] The above embodiments are preferred implementations of the present invention, but the implementations of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride, characterized in that: The steps include: Phosphoric acid and anhydrous hydrogen fluoride are added to the reactor at a temperature of -20°C to 10°C and mixed evenly. SF4 is then introduced into the mixed reaction. The reaction mixture is introduced into a thermal decomposition kettle for thermal decomposition. The gaseous products obtained by decomposition are subjected to rectification and separation to obtain high-purity phosphorus pentafluoride. The molar ratio of phosphoric acid to anhydrous hydrogen fluoride is 1:1-2; the molar ratio of SF4 to phosphoric acid is 2-2.5:1; The mixing reaction time is 1 to 3 hours; the heating decomposition temperature is 138°C to 168°C; The high-purity phosphorus pentafluoride refers to phosphorus pentafluoride with a purity of not less than 99.5%.

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

3. The method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride according to claim 2, characterized in that: The temperature for the distillation separation of phosphorus pentafluoride is below -85°C and the pressure is 0.1-0.5 MPa.

4. The method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride according to claim 2, characterized in that: The temperature of the sulfur dioxide distillation separation is -10°C to 10°C, and the pressure is 0.3 to 1.0 MPa.

5. The method for efficiently synthesizing phosphorus pentafluoride using phosphoric acid and hydrogen fluoride according to claim 2, characterized in that: The temperature of the hydrogen fluoride distillation separation is 20° C. to 50° C., and the pressure is 0.5 to 2.0 MPa.

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