A process for the preparation of heptafluoropropane

Abstract

The application discloses a preparation method of heptafluoropropane, which comprises the following steps: adding a certain amount of an aprotic polar solvent, an alkali metal hydrogen fluoride and an alkali earth metal fluoride into a reaction container, introducing hexafluoropropene, and performing a fluorination addition reaction at a temperature of 50-250 DEG C; and after the reaction is completed, the material is distilled into a condensation separation tower to separate heptafluoropropane products. The method solves the problems of hydrogen fluoride transportation and storage, and the safety hidden danger and environmental protection pressure of hydrogen fluoride in the production process, and is an energy-saving, emission-reducing, sustainable development, circular economy and environment-friendly production technology.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for preparing heptafluoropropane, in particular a method for preparing heptafluoropropane using hexafluoropropene as raw material. BACKGROUND

[0002] Heptafluoropropane is a colorless and odorless gas at room temperature, non-conductive, non-corrosive, no environmental restrictions, and has a short atmospheric residence period. As a substitute for Halon 1301, heptafluoropropane has gradually become the main variety of indoor fire extinguishing agent. Although heptafluoropropane is relatively stable at room temperature, it does not contain chlorine or bromine and does not damage the atmospheric ozone layer, so it is used to replace the environmentally hazardous Halon 1301 and Halon 1211 as a raw material for fire extinguishing agents. Therefore, from the purpose of reducing costs and process improvement, the development of new preparation technology of heptafluoropropane and its application in production is of great significance to the sustainable development of enterprises.

[0003] Currently, the preparation methods of heptafluoropropane mainly include perfluoropropene fluorination method, propane (propylene or its derivative) bioelectrolysis method, heptafluoro-chloropropane catalytic hydrogenation method, and catalytic chlorofluorination of propylene and propane. Among them, the direct use of propane (propylene or its derivative) bioelectrolysis technology is difficult, and the side reaction is complex with low yield; the catalytic hydrogenation of heptafluoro-chloropropane is a new method developed in the 1990s, which breaks the limitation of using perfluoropropene as raw material and is more advanced in process, but there is a problem of raw material matching, which is difficult to realize industrial production. The catalytic chlorofluorination method uses propylene and propane as raw materials and simultaneously catalyzes chlorofluorination with hydrogen fluoride and chlorine, but the process of catalytic chlorofluorination in this method is relatively complex, and the recovery and utilization of raw materials are also difficult to industrialize, which has a high technical difficulty. Chinese patent CN102731245A, a production method of heptafluoropropane, uses perfluoropropene and hydrogen fluoride to directly add, and uses an ionic liquid catalytic system composed of alkali metal fluoride and amide ionic liquid, which has a short process route, sufficient raw material source, high conversion rate, and high selectivity. However, it is found through long-time production that part of the hexafluoropropylene polymer has a great influence on the ionic liquid catalytic system during the reaction process, and the catalyst often fails and agglomerates. The replacement of the catalyst not only affects the environment but also is difficult to operate. Therefore, in the preparation of heptafluoropropane from hexafluoropropylene, the development of a new fluorination catalytic system is a development direction for the preparation of heptafluoropropane. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a method for preparing heptafluoropropane by directly fluorinating and adding hexafluoropropylene with alkali metal fluorohydride and alkaline earth metal fluoride in an aprotic polar solvent, which avoids the transportation and storage problems of hydrogen fluoride and the safety hazards of hydrogen fluoride in the production process.

[0005] To solve the above technical problems, the application discloses a preparation method of heptafluoropropane, which comprises the following steps: adding a certain amount of an aprotic polar solvent, an alkali metal fluorohydride and an alkaline earth metal fluoride into a reaction container, introducing hexafluoropropene, and performing a fluorination addition reaction at a temperature of 50-250 DEG C; tracking and detecting the reaction end point by gas chromatography; and after the reaction is completed, distilling the material into a condensation separation tower to separate heptafluoropropane product.

[0006] Further, the fluorination addition reaction is performed at a temperature of 100-200 DEG C.

[0007] Further, the aprotic polar solvent is one or more than two of acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methyl pyrrolidone, ethyl acetate, butyl acetate, acetone, butanone, cyclohexanone, cyclohexane, dimethyl carbonate, diethyl carbonate and dichloromethane.

[0008] Further, the aprotic polar solvent is one or more than two of acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methyl pyrrolidone, ethyl acetate, acetone, butanone, cyclohexanone, diethyl carbonate.

[0009] Further, the alkali metal fluorohydride is one or more than two of potassium fluorohydride, sodium fluorohydride and cesium fluorohydride; and the alkaline earth metal fluoride is one or more than two of magnesium fluoride and calcium fluoride.

[0010] The mass ratio of the alkali metal fluorohydride to the alkaline earth metal fluoride is 1:1-10.

[0011] Further, the molar ratio of the hexafluoropropene to the alkali metal fluorohydride is 1:1-5.

[0012] Further, the molar ratio of the hexafluoropropene to the alkali metal fluorohydride is 1:2-3.

[0013] Further, the mass ratio of the hexafluoropropene to the aprotic polar solvent is 1:1-5.

[0014] Further, the mass ratio of the hexafluoropropene to the aprotic polar solvent is 1:3.

[0015] Further, the feeding speed of the hexafluoropropene is controlled to make the pressure in the reactor 1-10 kg / cm 2 .

[0016] The present application uses hexafluoropropylene as raw material, and reacts with alkali metal fluorohydride and alkaline earth metal fluoride in an aprotic polar solvent to directly fluorinate and add to prepare heptafluoropropane, the alkali metal fluorohydride can release hydrogen fluoride at the reaction temperature, avoiding a series of problems caused by directly using hydrogen fluoride gas, solving the problems of hydrogen fluoride transportation and storage, and the safety hazard and environmental pressure of hydrogen fluoride in the production process, being an energy-saving, emission-reducing, sustainable development, circular economy and environment-friendly production technology. The raw materials are easy to store and transport, the feeding operation is convenient, the industrial production is easy, the environment is not polluted, the alkali metal and alkaline earth metal fluoride can be regenerated and used, having the advantages of low cost and good product quality, and the yield is ≥96%. DETAILED DESCRIPTION

[0017] The present application will be further explained in combination with examples. The following examples are only used to illustrate the present application, but not used to limit the implementation range of the present application.

[0018] Example 1

[0019] In the reactor, acetonitrile 100 kg, dimethylformamide 50 kg, potassium fluorohydride 78 kg (1 k mol), magnesium fluoride 78 kg, hexafluoropropylene 150 kg (1 k mol) are added, the feeding speed of hexafluoropropylene is controlled, the reaction pressure in the reactor is 5 kg / cm 2 , and the reaction is carried out at 200 DEG C, the reaction end point is tracked by gas chromatography, after the reaction is completed, the material is distilled into a condensation separation tower to separate heptafluoropropane product 164 kg, the yield is 96.5%, and the purity is 99.98%.

[0020] Example 2

[0021] In the reactor, acetonitrile 400 kg, dimethylformamide 350 kg, potassium fluorohydride 78 kg (1 k mol), calcium fluoride 78 kg, hexafluoropropylene 150 kg (1 k mol) are added, the feeding speed of hexafluoropropylene is controlled, the reaction pressure in the reactor is 5 kg / cm 2 , and the reaction is carried out at 200 DEG C, the reaction end point is tracked by gas chromatography, after the reaction is completed, the material is distilled into a condensation separation tower to separate heptafluoropropane product 164.9 kg, the yield is 97.0%, and the purity is 99.97%.

[0022] Example 3

[0023] In the reactor, acetonitrile 400 kg, dimethylacetamide 50 kg, sodium fluorohydride 86 kg (1.4 k mol), magnesium fluoride 258 kg, hexafluoropropylene 150 kg (1 k mol) are added, the feeding speed of hexafluoropropylene is controlled, the reaction pressure in the reactor is 10 kg / cm 2, and the reaction was kept at 250°C. The reaction end point was tracked by gas chromatography. After the reaction was completed, the material was distilled into a condensation separation tower to separate the heptafluoropropane product 165.9 kg, with a yield of 97.6% and a purity of 99.94%.

[0024] Example 4

[0025] In the reactor were added N-methylpyrrolidone 100 kg, ethyl acetate 50 kg, acetone 50 kg, potassium bifluoride 156 kg (2 kmol), magnesium fluoride 156 kg, hexafluoropropene 150 kg (1 kmol), and the feeding speed of the hexafluoropropene was controlled so that the reaction pressure in the reactor was 5 kg / cm 2 , and the reaction was kept at 50°C. The reaction end point was tracked by gas chromatography. After the reaction was completed, the material was distilled into a condensation separation tower to separate the heptafluoropropane product 164 kg, with a yield of 96.5% and a purity of 99.98%.

[0026] Example 5

[0027] In the reactor were added N-methylpyrrolidone 100 kg, ethyl acetate 50 kg, acetone 50 kg, potassium bifluoride 78 kg (1 kmol), magnesium fluoride 78 kg, hexafluoropropene 150 kg (1 kmol), and the feeding speed of the hexafluoropropene was controlled so that the reaction pressure in the reactor was 5 kg / cm 2 , and the reaction was kept at 50°C. The reaction end point was tracked by gas chromatography. After the reaction was completed, the material was distilled into a condensation separation tower to separate the heptafluoropropane product 164 kg, with a yield of 96.5% and a purity of 99.98%.

[0028] Example 6

[0029] In the reactor were added dimethyl sulfoxide 500 kg, ethyl acetate 100 kg, acetone 200 kg, potassium bifluoride 234 kg (3 kmol), magnesium fluoride 2340 kg, hexafluoropropene 150 kg (1 kmol), and the feeding speed of the hexafluoropropene was controlled so that the reaction pressure in the reactor was 1 kg / cm 2 , and the reaction was kept at 180°C. The reaction end point was tracked by gas chromatography. After the reaction was completed, the material was distilled into a condensation separation tower to separate the heptafluoropropane product 165.8 kg, with a yield of 97.5% and a purity of 99.98%.

[0030] Example 7

[0031] In the reactor were added dimethylacetamide 300 kg, acetone 200 kg, potassium bifluoride 156 kg (2 kmol), magnesium fluoride 780 kg, hexafluoropropene 150 kg (1 kmol), and the feeding speed of the hexafluoropropene was controlled so that the reaction pressure in the reactor was 3 kg / cm 2, and the reaction was kept at 100°C. The reaction end point was tracked by gas chromatography. After the reaction was completed, the material was distilled into a condensation separation tower to separate 164 kg of heptafluoropropane product, with a yield of 96.5% and a purity of 99.98%.

Claims

1. A method for preparing heptafluoropropane, characterized in that: A certain amount of aprotic polar solvent, alkali metal fluoride, and alkaline earth metal fluoride are added to a reaction vessel. Hexafluoropropylene is then introduced to carry out a fluorination addition reaction at a temperature of 100–200°C. After the reaction is completed, the material is distilled into a condenser to separate and obtain heptafluoropropane product. The alkali metal fluoride is one or both of potassium fluoride and sodium fluoride; the alkaline earth metal fluoride is one or both of magnesium fluoride and calcium fluoride, and the mass ratio of alkali metal fluoride to alkaline earth metal fluoride is 1:1 to 10. The molar ratio of hexafluoropropylene to alkali metal fluoride is 1:2-3. Controlling the feeding rate of hexafluoropropylene to maintain a reactor pressure of 1–10 kg / cm² 2 .

2. The method for preparing heptafluoropropane according to claim 1, characterized in that: The aprotic polar solvent is one or more of acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, ethyl acetate, butyl acetate, acetone, butanone, cyclohexanone, cyclohexane, dimethyl carbonate, diethyl carbonate, and dichloromethane.

3. The method for preparing heptafluoropropane according to claim 2, characterized in that: The aprotic polar solvent is one or more of acetonitrile, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, ethyl acetate, acetone, butanone, cyclohexanone, and diethyl carbonate.

4. The method for preparing heptafluoropropane according to claim 1, 2, or 3, characterized in that: The mass ratio of hexafluoropropylene to the aprotic polar solvent is 1:1 to 5.

5. The method for preparing heptafluoropropane according to claim 4, characterized in that: The mass ratio of hexafluoropropylene to the aprotic polar solvent is 1:3.