Preparation method of heptafluoroisobutyronitrile

Abstract

The invention relates to the field of fluorine-containing compounds, in particular to a preparation method of heptafluoroisobutyronitrile. The preparation method comprises the following steps: S1, by taking hexafluoropropylene, fluoride salt and bis (trichloromethyl) carbonate as raw materials, preparing bis (heptafluoroisopropyl) ketone by adopting a'one-pot method 'reaction; s2, carrying out ammonolysis on the bis (heptafluoroisopropyl) ketone to obtain heptafluoroisobutyramide; and S3, dehydrating the heptafluoroisobutyramide to prepare the heptafluoroisobutyronitrile. The method has the advantages of cheap and easily available raw materials, low toxicity, mild reaction conditions, easy implementation, strong controllability, high safety and easy industrial production.

Description

Technical Field

[0001] This invention relates to the field of fluorinated compounds, and more specifically, to a method for preparing heptafluoroisobutyronitrile. Background Technology

[0002] With the development and innovation of ultra-high voltage technology and energy internet technology, high-voltage electrical equipment using gas as the insulating medium is being used more and more widely in power grid systems. Heptafluoroisobutyronitrile (HFC) is a chemically stable, non-flammable, and non-explosive low-toxicity gas with an atmospheric lifetime of approximately 22 years and a gas volatile organic compound (GWP) value of 2400, about one-tenth that of SF6 gas. Its insulating strength is about 2.2 times that of SF6 gas. It has received widespread attention and research in the electrical industry and is considered one of the best alternatives to SF6 as an insulating gas.

[0003] In patent US10573462, 3M Company uses a reaction of heptafluoroisobutyryl fluoride and methanol to prepare methyl heptafluoroisobutyrate, which is then converted into heptafluoroisobutyramide, followed by dehydration to obtain heptafluoroisobutyronitrile. The heptafluoroisobutyryl fluoride used is prepared by electrolytic fluorination of isobutyric anhydride. However, the electrolytic fluorination process is complex, requiring specialized equipment and using highly corrosive hydrogen fluoride as the fluorine source, posing a significant risk. Furthermore, the efficiency of electrolytic fluorination itself is low, and the product contains many isomers, resulting in low overall production efficiency. Patent CN108395382 reports a method for synthesizing heptafluoroisobutyronitrile, using chloroformate as a raw material to prepare heptafluoroisobutyrate, followed by ammonolysis to obtain heptafluoroisobutyramide, and then dehydration to prepare heptafluoroisobutyronitrile. However, chloroformate, especially methyl chloroformate and ethyl chloroformate used in the examples, are highly toxic chemicals subject to extremely strict control, making them difficult to purchase and transport. Patents CN107935884, CN108424375, and CN118056812 report a method for preparing acyl fluoride from carbonyl fluoride and perfluoroolefin, and then preparing perfluoronitrile through esterification, ammonolysis, and dehydration. However, carbonyl fluoride is extremely toxic, has no large-scale industrial production, and poses a very high transportation risk. Summary of the Invention

[0004] In view of this, the present invention aims to provide a safe and efficient method for synthesizing heptafluoroisobutyronitrile. First, bis(trichloromethyl) carbonate, fluoride salt, and hexafluoropropylene are used as raw materials to prepare bis(heptafluoroisopropyl) ketone using a one-pot method. Then, bis(heptafluoroisopropyl) ketone is ammonolyzed to obtain heptafluoroisobutyramide, and the heptafluoroisobutyramide is dehydrated to obtain heptafluoroisobutyronitrile. Bis(trichloromethyl) carbonate, fluoride salt, and hexafluoropropylene are all mature industrial products, inexpensive, and widely available, which can significantly reduce the manufacturing cost of the product.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows:

[0006] This invention provides a method for preparing heptafluoroisobutyronitrile, comprising the following steps:

[0007] S1. Mix bis(trichloromethyl) carbonate, fluoride salt, hexafluoropropylene and solvent and react to obtain bis(heptafluoroisopropyl) ketone;

[0008] S2. Reaction of bis(heptafluoroisopropyl) ketone with ammonia yields heptafluoroisobutyramide;

[0009] S3. Heptafluoroisobutyramide is dehydrated to obtain heptafluoroisobutyronitrile.

[0010] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, in step S1, the fluoride salt includes potassium fluoride and / or cesium fluoride;

[0011] And / or, in step S1, the solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0012] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, in step S1, the molar ratio of the bis(trichloromethyl) carbonate, the fluoride salt and the hexafluoropropylene is 1:6 to 20:6 to 12, preferably 1:8 to 18:6 to 10.

[0013] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, in step S1, the reaction temperature is 60-150°C, preferably 80-120°C, and the reaction time is 3-20 hours, preferably 5-20 hours.

[0014] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, step S1 specifically involves: mixing bis(trichloromethyl) carbonate, solvent and fluoride salt, sealing and evacuating, then introducing hexafluoropropylene to carry out the reaction, cooling and filtering after the reaction is completed, and then distilling the filtrate to obtain bis(heptafluoroisopropyl) ketone.

[0015] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, in step S2, the molar ratio of ammonia to bis(heptafluoroisopropyl) ketone is 1 to 5:1, preferably 1.5 to 4:1.

[0016] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, in step S2, the reaction temperature is -10 to 20°C, preferably -5 to 15°C, and the reaction time is 1 to 10 hours, preferably 1 to 8 hours.

[0017] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, step S2 specifically involves: adding bis(heptafluoroisopropyl) ketone dropwise to a methanol solution of ammonia, reacting, and removing methanol and unreacted ammonia after the reaction to obtain heptafluoroisobutyramide.

[0018] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, step S3 specifically comprises:

[0019] Heptafluoroisobutyramide and N,N-dimethylformamide were mixed and cooled to -10°C. Then pyridine and trifluoroacetic anhydride were added, and the mixture was stirred and dispersed for 1 hour. The mixture was then heated to 15°C and reacted for 20 minutes.

[0020] Preferably, in the above-mentioned method for preparing heptafluoroisobutyronitrile, the mass ratio of heptafluoroisobutyramide to N,N-dimethylformamide is 50-70:120-140;

[0021] The mass ratio of heptafluoroisobutyramide to pyridine is 50-70:55-65;

[0022] The mass ratio of heptafluoroisobutyramide to trifluoroacetic anhydride is 50–70:70–90.

[0023] The beneficial technical effects of the present invention through the above technical solution are as follows:

[0024] 1. The method provided in this application uses mature industrial products such as bis(trichloromethyl) carbonate and hexafluoropropylene, which are inexpensive and less toxic, as raw materials to prepare heptafluoroisobutyronitrile. This avoids the use of chemicals such as heptafluoroisobutyryl fluoride and carbonyl fluoride, which are difficult to obtain, highly toxic, and risky, thereby reducing costs and improving safety.

[0025] 2. The preparation method provided in this application has a fast reaction rate, mild conditions, strong controllability and high safety, and is easy to industrialize.

[0026] 3. The heptafluorobutane byproduct generated in step 2 by the method provided in this application is a high-end fire extinguishing material with extremely high product added value.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0028] This invention discloses a method for preparing heptafluoroisobutyronitrile. Those skilled in the art can refer to this document and appropriately modify the process parameters to achieve the desired result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments. Those skilled in the art can clearly modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit, and scope of this invention to realize and apply the technology of this invention.

[0029] This invention provides a method for preparing heptafluoroisobutyronitrile, comprising the following steps:

[0030] S1. A mixture of bis(trichloromethyl) carbonate, a fluorinated salt, hexafluoropropylene, and a solvent is reacted to yield bis(heptafluoroisopropyl) ketone; the reaction formula is shown below:

[0031]

[0032] S2. Reaction of bis(heptafluoroisopropyl)one with ammonia yields heptafluoroisobutyramide; the reaction formula is shown below:

[0033]

[0034] S3. Dehydrate heptafluoroisobutyramide to obtain heptafluoroisobutyronitrile; the reaction formula is shown below:

[0035]

[0036] In this invention, in step S1, the fluoride salt includes potassium fluoride and / or cesium fluoride;

[0037] In this invention, in step S1, the solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

[0038] In this invention, in step S1, the molar ratio of the bis(trichloromethyl) carbonate, the fluoride salt, and the hexafluoropropylene is 1:6 to 20:6 to 12. As an example, in step S1, the molar ratio of the bis(trichloromethyl) carbonate, the fluoride salt, and the hexafluoropropylene can be 1:6:6, 1:8:9, 1:10:10, 1:15:10, or 1:20:12, etc.; preferably, the molar ratio of the bis(trichloromethyl) carbonate, the fluoride salt, and the hexafluoropropylene is 1:8 to 18:6 to 10.

[0039] In this invention, in step S1, the reaction temperature is 60–150°C, and the reaction time is 3–20 hours. As an example, in step S1, the reaction temperature can be 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150°C, and the reaction time can be 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, or 20 hours. Preferably, the reaction temperature is 80–120°C, and the reaction time is 5–20 hours.

[0040] In this invention, step S1 specifically involves mixing bis(trichloromethyl) carbonate, solvent, and fluoride salt, sealing and evacuating the mixture, then introducing hexafluoropropylene to carry out the reaction. After the reaction is completed, the mixture is cooled and filtered, and then the filtrate is distilled to obtain bis(heptafluoroisopropyl) ketone.

[0041] In this invention, in step S2, the molar ratio of ammonia to bis(heptafluoroisopropyl)ketone is 1 to 5:1. As an example, in step S2, the molar ratio of ammonia to bis(heptafluoroisopropyl)ketone can be 1:1, 2:1, 3:1, 4:1, or 5:1, etc. Preferably, the molar ratio of ammonia to bis(heptafluoroisopropyl)ketone is 1.5 to 4:1.

[0042] In this invention, in step S2, the reaction temperature is -10 to 20°C, and the reaction time is 1 to 10 hours. As an example, in step S2, the reaction temperature can be -10, -5, 0, 5, 10, 15, or 20°C, and the reaction time can be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours. Preferably, the reaction temperature is -5 to 15°C, and the reaction time is 1 to 8 hours.

[0043] In this invention, step S2 specifically involves: adding bis(heptafluoroisopropyl) ketone dropwise to a methanol solution of ammonia, reacting, and removing methanol and unreacted ammonia after the reaction to obtain heptafluoroisobutyramide.

[0044] In this invention, step S3 specifically includes:

[0045] Heptafluoroisobutyramide and N,N-dimethylformamide were mixed and cooled to -10°C. Then pyridine and trifluoroacetic anhydride were added, and the mixture was stirred and dispersed for 1 hour. The mixture was then heated to 15°C and reacted for 20 minutes.

[0046] In this invention, the mass ratio of heptafluoroisobutyramide to N,N-dimethylformamide is 50-70:120-140;

[0047] The mass ratio of heptafluoroisobutyramide to pyridine is 50-70:55-65;

[0048] The mass ratio of heptafluoroisobutyramide to trifluoroacetic anhydride is 50–70:70–90.

[0049] As an example, step S3 specifically involves: a jacketed flask equipped with a magnetic stirrer, a thermometer, a gas outlet pipe, and a dropping funnel. The gas outlet pipe is connected to a receiving bottle, which is placed in a low-temperature bath. The jacket of the jacketed flask is connected to a low-temperature constant-temperature bath. Heptafluoroisobutyramide and N,N-dimethylformamide are first added to the jacketed flask and stirred until dissolved. Cooling liquid is then passed through the jacket. After the material temperature is cooled to -10°C, pyridine is slowly added dropwise. After the pyridine is added, trifluoroacetic anhydride is slowly added dropwise. The material temperature is controlled below 0°C. The gas generated during the addition process is condensed and collected in the receiving bottle. After the addition is completed, stirring continues. After 1 hour, the temperature of the low-temperature constant-temperature bath is increased to heat the material to 15°C. Heptafluoroisobutyramide escapes into the receiving bottle and is condensed and collected.

[0050] The present invention will be further described in detail below through examples. All raw materials used in the examples are commercially available.

[0051] Example 1

[0052] 40g of bis(trichloromethyl) carbonate, 120g of N,N-dimethylformamide, and 145g of anhydrous cesium fluoride were added to a 500mL dry stainless steel reactor. After the reactor was sealed and evacuated, 150g of hexafluoropropylene was introduced. The mixture was then stirred and heated to 80℃ for 12 hours. After cooling to room temperature, the material was filtered, and the filtrate was distilled to obtain 115g of bis(heptafluoroisopropyl) ketone product at 70-75℃.

[0053] The fluorine spectrum data of the bis(heptafluoroisopropyl)one product obtained in Example 1 are as follows: 19 FNMR (CDCl3, 376MHz) δ-73.26 (d, 12F), δ-189.12 (m, 1F).

[0054] Example 2

[0055] 40g of bis(trichloromethyl) carbonate, 120g of anhydrous acetonitrile, and 93g of anhydrous potassium fluoride were added to a 500mL dry stainless steel reactor. After the reactor was sealed and evacuated, 152g of hexafluoropropylene was introduced. The mixture was then stirred and heated to 90℃ for 16 hours. After cooling to room temperature, the material was filtered, and the filtrate was distilled to obtain 113g of bis(heptafluoroisopropyl) ketone product at 70-75℃.

[0056] The fluorine spectrum data of the bis(heptafluoroisopropyl)one product obtained in Example 2 are as follows: 19 FNMR (CDCl3, 376MHz) δ-73.20 (d, 12F), δ-189.18 (m, 1F).

[0057] Example 3

[0058] 40g of bis(trichloromethyl) carbonate, 120g of dried diethylene glycol dimethyl ether, and 90g of anhydrous potassium fluoride were added to a 500mL dry stainless steel reactor. After the reactor was sealed and evacuated, 150g of hexafluoropropylene was introduced. The mixture was then stirred and heated to 120℃ for 15 hours. After cooling to room temperature, the material was filtered, and the filtrate was distilled to obtain 107g of bis(heptafluoroisopropyl) ketone product at 70-75℃.

[0059] The fluorine spectrum data of the bis(heptafluoroisopropyl)one product obtained in Example 3 are as follows: 19 FNMR (CDCl3, 376MHz) δ-73.28 (d, 12F), δ-189.20 (m, 1F).

[0060] Example 4

[0061] 100 mL of methanol was added to a 500 mL jacketed flask equipped with a stirrer, thermometer, inlet (outlet) pipe, and dropping funnel. Coolant was circulated through the jacket at 0 °C. 11 g of ammonia was introduced while stirring. Then, 110 g of bis(heptafluoroisopropyl) ketone prepared in Example 1 was added dropwise to the flask. The dropping rate was controlled so that the reaction temperature did not exceed 10 °C. After the addition was completed, stirring was continued for 3 hours. The material was then transferred to a pear-shaped flask and rotary evaporated at 40 °C to remove methanol and unreacted ammonia, yielding 57.5 g of heptafluoroisobutyramide product.

[0062] The fluorine spectrum data of the heptafluoroisobutyramide prepared in Example 4 are as follows: 19 FNMR (CDCl3, 376MHz) δ-76.21~-76.37 (d, 6F), δ-181.20~-181.80 (m, 1F).

[0063] Example 5

[0064] 100 mL of methanol was added to a 500 mL jacketed flask equipped with a stirrer, thermometer, gas inlet, and dropping funnel. Coolant was circulated through the jacket at a temperature of -5 °C. 15 g of ammonia was introduced while stirring. Then, 110 g of bis(heptafluoroisopropyl) ketone prepared in Example 2 was added dropwise to the flask. The dropping rate was controlled to keep the reaction temperature below 5 °C. After the addition was complete, stirring was continued for 8 hours. Then, the mixture was rotary evaporated at 40 °C to remove methanol and unreacted ammonia, yielding 59.4 g of heptafluoroisobutyramide product.

[0065] The fluorine spectrum data of the heptafluoroisobutyramide prepared in Example 5 are as follows: 19 FNMR (CDCl3, 376MHz) δ-76.25~-76.35 (d, 6F), δ-181.25~-181.75 (m, 1F).

[0066] Example 6

[0067] A 500mL jacketed flask was equipped with a magnetic stirrer, a thermometer, a gas outlet tube, and a dropping funnel. The gas outlet tube was connected to a receiving bottle, which was immersed in a -20°C low-temperature bath. The jacket of the jacketed flask was connected to a low-temperature constant-temperature bath. First, 35g of heptafluoroisobutyramide prepared in Example 4, 30g of heptafluoroisobutyramide prepared in Example 5, and 130g of N,N-dimethylformamide were added to the jacketed flask. After stirring and dissolving, cooling liquid was passed through the jacket. After the material temperature was cooled to -10°C, 60g of pyridine was slowly added dropwise. After the pyridine was added, 80g of trifluoroacetic anhydride was slowly added dropwise. The material temperature was controlled below 0°C. The gas generated during the dropwise addition was condensed and collected in the receiving bottle. After the dropwise addition was completed, stirring was continued. After 1 hour, the temperature of the low-temperature constant-temperature bath was increased, and the material was heated to 15°C and maintained for 20 minutes. Heptafluoroisobutyrone escaped into the receiving bottle and was condensed and collected. A total of 44.6g of product was obtained.

[0068] The fluorine spectrum data of the heptafluoroisobutyramide prepared in Example 6 are as follows: 19 FNMR (CDCl3, 376MHz) δ-77.2~-77.6 (d, 6F), δ-177.5~-178.0 (m, 1F).

[0069] This application first prepares bis(heptafluoroisopropyl)ketone by reacting bis(trichloromethyl)carbonate, fluoride salt, and hexafluoropropylene in solvents such as acetonitrile. Then, bis(heptafluoroisopropyl)ketone and ammonia are reacted in methanol to prepare heptafluoroisobutyramide. Finally, heptafluoroisobutyramide is dehydrated to obtain heptafluoroisobutyronitrile. All three reaction steps are carried out under mild conditions, are highly controllable, and have high safety.

[0070] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing heptafluoroisobutyronitrile, characterized in that, Includes the following steps: S1. Mix bis(trichloromethyl) carbonate, fluoride salt, hexafluoropropylene and solvent, and react to obtain bis(heptafluoroisopropyl) ketone; S2. Reaction of bis(heptafluoroisopropyl) ketone with ammonia yields heptafluoroisobutyramide; S3. Heptafluoroisobutyramide is dehydrated to obtain heptafluoroisobutyronitrile.

2. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, In step S1, the fluoride salt includes potassium fluoride and / or cesium fluoride; And / or, in step S1, the solvent includes at least one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, and N-methylpyrrolidone.

3. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, In step S1, the molar ratio of the bis(trichloromethyl) carbonate, the fluoride salt, and the hexafluoropropylene is 1:6 to 20:6 to 12.

4. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, In step S1, the reaction temperature is 60–150°C, and the reaction time is 3–20 h.

5. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, Specifically, step S1 involves mixing bis(trichloromethyl) carbonate, solvent, and fluoride salt, sealing and evacuating the mixture, then introducing hexafluoropropylene to carry out the reaction. After the reaction is completed, the mixture is cooled and filtered, and the filtrate is then distilled to obtain bis(heptafluoroisopropyl) ketone.

6. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, In step S2, the molar ratio of the ammonia gas and the bis(heptafluoroisopropyl) ketone is 1 to 5:

1.

7. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, In step S2, the reaction temperature is -10 to 20°C, and the reaction time is 1 to 10 hours.

8. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, Step S2 specifically involves adding bis(heptafluoroisopropyl) ketone dropwise to a methanol solution of ammonia to carry out the reaction. After the reaction is complete, methanol and unreacted ammonia are removed to obtain heptafluoroisobutyramide.

9. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that, Step S3 specifically involves: Heptafluoroisobutyramide and N,N-dimethylformamide were mixed and cooled to -10°C. Then pyridine and trifluoroacetic anhydride were added, and the mixture was stirred and dispersed for 1 hour. The mixture was then heated to 15°C and reacted for 20 minutes.

10. The method for preparing heptafluoroisobutyronitrile according to claim 9, characterized in that, The mass ratio of heptafluoroisobutyramide to N,N-dimethylformamide is 50-70:120-140; The mass ratio of heptafluoroisobutyramide to pyridine is 50-70:55-65; The mass ratio of heptafluoroisobutyramide to trifluoroacetic anhydride is 50–70:70–90.

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