CN116239496A

CN116239496A - Method for continuously preparing heptafluoroisobutyronitrile

Info

Publication number: CN116239496A
Application number: CN202111487262.1A
Authority: CN
Inventors: 陈伟; 倪航; 蒋强; 杨汪松
Original assignee: Zhejiang Chemical Industry Research Institute Co Ltd; Sinochem Lantian Co Ltd
Current assignee: Zhejiang Chemical Industry Research Institute Co Ltd; Sinochem Lantian Co Ltd
Priority date: 2021-12-08
Filing date: 2021-12-08
Publication date: 2023-06-09

Abstract

The invention discloses a method for continuously preparing heptafluoroisobutyronitrile, which comprises the following steps: firstly, preparing the heptafluoroisobutyramide, organic base and solvent into mixed solution, then continuously introducing the mixed solution and a dehydrating agent into a continuous reactor respectively for dehydration reaction, and collecting at the outlet of the continuous reactor to obtain the heptafluoroisobutyronitrile gas. The preparation method provided by the invention has the advantages of high selectivity, high reaction efficiency, less byproducts, suitability for industrial production and the like.

Description

Method for continuously preparing heptafluoroisobutyronitrile

Technical Field

The invention relates to a preparation method of heptafluoroisobutyronitrile, in particular to a method for continuously preparing heptafluoroisobutyronitrile.

Background

Heptafluoroisobutyronitrile is a novel environment-friendly insulating gas, has a Global Warming Potential (GWP) of 2100 and an atmospheric lifetime of 30 years, and is the most potential environment-friendly gas for replacing sulfur hexafluoride at present.

At present, the preparation of the heptafluoroisobutyronitrile mainly takes the heptafluoroisobutyryl fluoride as a raw material, firstly prepares the heptafluoroisobutyramide, and then generates the heptafluoroisobutyronitrile under the action of a dehydrating agent and alkali.

PCT patent WO2013151741A1 discloses a method for obtaining sevoflurane by adding hexafluoropropylene and carbonyl fluoride to obtain perfluoro isobutyryl fluoride, reacting perfluoro isobutyryl fluoride with ammonia gas to obtain perfluoro isobutyramide, and finally dehydrating perfluoro isobutyramide under the action of trifluoroacetic anhydride. The method has the advantages of large dosage of the dehydrating agent, more three wastes, incomplete conversion of raw materials, high content of byproducts of trifluoroacetonitrile and heptafluoropropane and high purification difficulty.

Chinese patent CN109320436a discloses a method for preparing perfluoronitrile by dehydrating heptafluoroisobutyramide under the catalysis of metal oxide, the purity of the product is 99.5%, and the yield is 99.2%. However, the method uses catalysts such as cobalt, niobium and the like with higher price, the catalysts are easy to deactivate, the components are complex and difficult to recycle, and the heavy metal compounds are harmful to the environment.

Chinese patent CN109748814a discloses a method for preparing perfluoroisobutyronitrile by dehydrating heptafluoroisobutyramide with a dehydrating agent, wherein the dehydrating agent is a phosphorus pentoxide/sulfuric acid system, a trifluoroacetic anhydride/triethylamine/N, N-dimethylformamide system or a cyanuric chloride/N, N-dimethylformamide system, but the reaction yield is only 65% -70%, and the raw materials cannot be completely converted.

The dehydrating agent/catalyst disclosed in the prior art is mostly a dehydrating agent such as trifluoroacetic anhydride or a mixed dehydrating system such as trifluoroacetic anhydride/triethylamine/N, N-dimethylformamide system or a metal oxidant such as cobalt oxide, or the reaction yield is low, or the catalyst is easy to deactivate, the cost is high, or byproducts are more and the purification is difficult. In order to realize the replacement of sulfur hexafluoride, a method which is feasible in technology, low in cost, simple in process and suitable for industrial production must be found, and the method directly relates to whether the heptafluoroisobutyronitrile can realize the large-scale replacement of sulfur hexafluoride.

Disclosure of Invention

In order to solve the technical problems, the invention provides a method for continuously preparing the heptafluoroisobutyronitrile, which has the advantages of mild conditions, simple process, high conversion rate and yield of products, environmental protection and few byproducts and is suitable for industrial production.

According to the invention, in the kettle-type reactor, acid formed by dehydration cannot be discharged as soon as possible, so that a reaction system presents obvious acidity, and therefore, the occurrence of tautomerism is inhibited by the heptafluoroisobutyramide, the raw materials cannot be completely converted, and the smooth reaction is not facilitated; in a parallel propulsion system, the heptafluoroisobutyramide is easy to form tautomerism, which is favorable for smooth dehydration and complete conversion of raw materials.

Kettle type system reaction formula:

parallel system reaction formula:

the invention aims at realizing the following technical scheme:

a process for the continuous preparation of heptafluoroisobutyronitrile, said process comprising: firstly, preparing the heptafluoroisobutyramide, organic base and solvent into mixed solution, then continuously introducing the mixed solution and a dehydrating agent into a continuous reactor respectively for dehydration reaction, and collecting at the outlet of the continuous reactor to obtain the heptafluoroisobutyronitrile gas.

The organic base is selected from at least one of pyridine, triethylamine, 1, 8-diazabicyclo [5.4.0] undec-7-ene and picoline; preferably, the organic base is pyridine or triethylamine.

The solvent is at least one selected from N, N-dimethylformamide, N-dimethylacetamide, hexamethylphosphoramide and formamide; preferably, the solvent is selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide. In the mixed solution, the molar ratio of the heptafluoroisobutyramide to the organic base is 1 (1-5); preferably 1 (1) to (2).

The dehydrating agent is at least one selected from phosphorus pentoxide, phosphorus oxychloride, trifluoro anhydride, acetic anhydride and oxalyl chloride; preferably, the dehydrating agent is at least one selected from phosphorus pentoxide, phosphorus oxychloride and trifluoro anhydride.

The molar ratio of the heptafluoroisobutyramide to the dehydrating agent is 1 (1-3); preferably 1 (1) to (2). The reaction temperature of the dehydration reaction is between-20 and 80 ℃, and the residence time is between 10 and 200 seconds. Preferably, the reaction temperature of the dehydration reaction is-10 ℃ to 30 ℃ and the residence time is 20S to 120S.

The continuous reactor is a tubular reactor, a coil reactor or a microchannel reactor.

The method for continuously preparing the heptafluoroisobutyronitrile can realize single impurity control, effectively reduce the contents of byproduct trifluoroacetonitrile and heptafluoropropane, and solve the problem of difficult rectification and purification of the heptafluoroisobutyronitrile, thereby improving the purity and yield of the product heptafluoroisobutyronitrile.

Compared with the prior art, the invention has the following beneficial effects:

1. the invention has mild condition, easy industrialized production, high conversion rate of the heptafluoroisobutyramide, high reaction yield and high purity of the heptafluoroisobutyronitrile product;

2. the preparation process is simple, green and environment-friendly, and three wastes are not generated.

Detailed Description

The invention will be further illustrated with reference to the following specific examples, without limiting the invention to these specific embodiments. It will be appreciated by those skilled in the art that the invention encompasses all alternatives, modifications and equivalents as may be included within the scope of the claims.

Example 1

Dissolving heptafluoroisobutyramide into a mixed solution of triethylamine and N, N-dimethylformamide, and continuously introducing the mixed solution and trifluoroacetic anhydride into a microreactor by using a feed pump, wherein the molar ratio of the heptafluoroisobutyramide to the triethylamine is 1:2.2, molar ratio of heptafluoroisobutyramide/trifluoroacetic anhydride of 1:1.1, controlling the reaction temperature to be 10 ℃; the residence time is 40S, and the heptafluoroisobutyronitrile is collected after being separated by a gas-liquid separator at an outlet.

And (3) detecting: the conversion rate of the heptafluoroisobutyramide is 92.3%, the content of the heptafluoroisobutyronitrile is 99.1%, the content of the trifluoroacetonitrile is 0.33%, the content of the heptafluoropropane is 0.1%, and the yield is 90.2%.

Example 2

Dissolving heptafluoroisobutyramide into a mixed solution of pyridine and N, N-dimethylacetamide, and continuously introducing the mixed solution and phosphorus oxychloride into a coil reactor by using a feed pump, wherein the molar ratio of the heptafluoroisobutyramide to the pyridine is 1:2.1, molar ratio of heptafluoroisobutyramide/phosphorus oxychloride is 1:1.05, controlling the reaction temperature to be 30 ℃; the retention time is 100S, and the heptafluoroisobutyronitrile is collected after being separated by a gas-liquid separator at an outlet.

And (3) detecting: the conversion rate of the heptafluoroisobutyramide is 91.0%, the content of the heptafluoroisobutyronitrile is 99.3%, the content of the trifluoroacetonitrile is 0.42%, the content of the heptafluoropropane is 0.2%, and the yield is 92.8%.

Example 3

Dissolving the heptafluoroisobutyramide into toluene, and continuously introducing the mixed solution and phosphorus pentoxide into a horizontal tubular reactor by using a feed pump, wherein the molar ratio of the heptafluoroisobutyramide to the phosphorus pentoxide is 1:1, controlling the reaction temperature to 20 ℃; the retention time is 80S, and the heptafluoroisobutyronitrile is collected after being separated by a gas-liquid separator at an outlet.

And (3) detecting: the conversion rate of the heptafluoroisobutyramide is 90.8%, the content of the heptafluoroisobutyronitrile is 99.5%, the content of the trifluoroacetonitrile is 0.36%, the content of the heptafluoropropane is 0.1%, and the yield is 91.8%.

Example 4

The heptafluoroisobutyramide is dissolved in methylene dichloride, and a feed pump is used for continuously introducing the mixed solution and trifluoroacetic anhydride into a microreactor respectively, wherein the molar ratio of the heptafluoroisobutyramide to the trifluoroacetic anhydride is 1:1.3, controlling the reaction temperature to be 0 ℃; the residence time is 50S, and the heptafluoroisobutyronitrile is collected after being separated by a gas-liquid separator at an outlet.

And (3) detecting: the conversion of heptafluoroisobutyramide is 89.2%, the content of heptafluoroisobutyronitrile is 99.1%, the content of trifluoroacetonitrile is 0.31%, the content of heptafluoropropane is 0.1%, and the yield is 90.7%.

Example 5

Dissolving heptafluoroisobutyramide into a mixed solution of triethylamine and N, N-dimethylformamide, and continuously introducing the mixed solution and trifluoroacetic anhydride into a microreactor by using a feed pump, wherein the molar ratio of the heptafluoroisobutyramide to the triethylamine is 1:2.0, molar ratio of heptafluoroisobutyramide/trifluoroacetic anhydride of 1:1, controlling the reaction temperature to be 0 ℃; the residence time is 30S, and the heptafluoroisobutyronitrile is collected after being separated by a gas-liquid separator at an outlet.

And (3) detecting: the conversion rate of the heptafluoroisobutyramide is 98.1%, the content of the heptafluoroisobutyronitrile is 99.5%, the content of the trifluoroacetonitrile is 0.11%, the content of the heptafluoropropane is 0.1%, and the yield is 95.3%.

Comparative example 1

Adding a mixed solution of heptafluoroisobutyramide, triethylamine and N, N-dimethylformamide into a three-neck flask, wherein the molar ratio of the heptafluoroisobutyramide to the triethylamine is 1:2.0, dropwise adding trifluoroacetic anhydride into the reaction bottle, wherein the molar ratio of the heptafluoroisobutyramide to the trifluoroacetic anhydride is 1:1, controlling the reaction temperature to be 0 ℃, and collecting the heptafluoroisobutyronitrile after the reaction is completed.

And (3) detecting: the conversion of heptafluoroisobutyramide is 64.8%, the content of heptafluoroisobutyronitrile is 89.1%, the content of trifluoroacetonitrile is 7.8%, the content of heptafluoropropane is 1.1%, and the yield is 53.2%.

Claims

1. A method for continuously preparing heptafluoroisobutyronitrile is characterized in that: the method comprises the following steps: firstly, preparing the heptafluoroisobutyramide, organic base and solvent into mixed solution, then continuously introducing the mixed solution and a dehydrating agent into a continuous reactor respectively for dehydration reaction, and collecting at the outlet of the continuous reactor to obtain the heptafluoroisobutyronitrile gas.

2. The method according to claim 1, wherein: the organic base is selected from at least one of pyridine, triethylamine, 1, 8-diazabicyclo [5.4.0] undec-7-ene and picoline.

3. The method according to claim 1, wherein: the solvent is at least one selected from N, N-dimethylformamide, N-dimethylacetamide, hexamethylphosphoramide and formamide.

4. The method according to claim 1, wherein: in the mixed solution, the molar ratio of the heptafluoroisobutyramide to the organic base is 1 (1-5).

5. The method according to claim 1, wherein: the dehydrating agent is at least one selected from phosphorus pentoxide, phosphorus oxychloride, trifluoro anhydride, acetic anhydride and oxalyl chloride.

6. The method according to claim 1, wherein: the molar ratio of the heptafluoroisobutyramide to the dehydrating agent is 1 (1-3).

7. The method according to claim 1, wherein: the reaction temperature of the dehydration reaction is between-20 and 80 ℃, and the residence time is between 10 and 200 seconds.

8. The method according to claim 7, wherein: the reaction temperature of the dehydration reaction is-10 ℃ to 30 ℃ and the residence time is 20S to 120S.

9. The method according to claim 1, wherein: the continuous reactor is a tubular reactor, a coil reactor or a microchannel reactor.