A method for preparing heptafluoroisobutyronitrile

Abstract

The present invention discloses a preparation method of heptafluoroisobutyronitrile. The preparation method includes: in an organic solvent, under the combined action of a catalyst, a ligand and a base, heptafluoro-2-halopropane reacts with a cyanation reagent to obtain heptafluoroisobutyronitrile; the catalyst is a copper salt and / or a cuprous salt, the ligand is an oxamide compound, and the base is an inorganic base and / or an organic base; the heptafluoro-2-halopropane is one of heptafluoro-2-chloropropane, heptafluoro-2-bromopropane or heptafluoro-2-iodopropane, and the cyanation reagent is selected from at least one of KCN, NaCN, CuCN or Zn(CN)2. The present invention has the advantages of fewer reaction steps, cheap and easily available catalyst, and simple reaction process, etc.

Description

Technical Field

[0001] The present invention relates to the field of insulating gases, and particularly to a method for preparing heptafluoroisobutyronitrile by a one-step cyanidation reaction. Background Art

[0002] Sulfur hexafluoride is a most widely used insulating gas and has been used for more than 70 years. However, its global warming potential (GWP) is 23,600 and its atmospheric lifetime is as high as 3,200 years, so it is a gas with a very serious greenhouse effect. While the global warming potential (GWP) of heptafluoroisobutyronitrile is 2,100 and its atmospheric lifetime is 30 years, so it is the most potential environmental-friendly gas to replace sulfur hexafluoride at present.

[0003] At present, the preparation of heptafluoroisobutyronitrile mainly uses heptafluoroisobutyryl fluoride as the raw material. First, heptafluoroisobutyramide is prepared, and then heptafluoroisobutyronitrile and by-product salts are generated under the action of a dehydrating agent and a base. For example, PCT patent application WO2013151741A1 discloses a method in which hexafluoropropene and carbonyl fluoride are added to obtain perfluoroisobutyryl fluoride, perfluoroisobutyryl fluoride reacts with ammonia to obtain perfluoroisobutyramide, and finally perfluoroisobutyramide is dehydrated to obtain heptafluoroisobutyronitrile. The reaction formula is as follows:

[0004]

[0005] This type of reaction route is long, the acyl fluoride gas is highly toxic, the raw material preparation cost is high, the recovery and utilization of the by-product salts obtained after the reaction is difficult, and the total reaction yield is lower than 70%, and the atom economy is poor.

[0006] In the prior art, the preparation of heptafluoroisobutyronitrile is mostly the dehydration method of heptafluoroisobutyramide. The research focus is on the dehydrating agent / catalyst, the route is relatively complex, and the preparation cost is high, making its selling price much higher than its substitute sulfur hexafluoride.

[0007] In order to achieve a large-scale replacement of sulfur hexafluoride, it is necessary to develop a preparation method of heptafluoroisobutyronitrile that is technically feasible, low in cost, simple in process and suitable for industrial production. Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a preparation method of heptafluoroisobutyronitrile with a short preparation route, inexpensive and easily available catalyst, less three wastes and suitable for industrial production.

[0009] The object of the present invention is achieved by the following technical solutions:

[0010] A preparation method of heptafluoroisobutyronitrile, the preparation method comprising: in an organic solvent, under the combined action of a catalyst, a ligand and a base, reacting heptafluoro-2-halopropane with a cyanation reagent to obtain heptafluoroisobutyronitrile, wherein the heptafluoro-2-halopropane is one of heptafluoro-2-chloropropane, heptafluoro-2-bromopropane or heptafluoro-2-iodopropane, and the cyanation reagent is selected from at least one of KCN, NaCN, CuCN, Zn(CN)₂.

[0011] The reaction formula is as follows:

[0012]

[0013] X = Cl, Br, I

[0014] The organic solvent is a polar aprotic solvent, preferably at least one of N,N-dimethylformamide, dimethyl sulfoxide, dioxane or N-methylpyrrolidone.

[0015] The catalyst is a copper salt and / or a cuprous salt. Preferably, the catalyst is selected from at least one of copper chloride, copper iodide, copper bromide, copper acetate, cuprous bromide, cuprous iodide.

[0016] The ligand is an oxamide compound. Preferably, the oxamide compound is selected from at least one of N,N'-bis(2,6-dimethylphenyl)oxamide, N,N'-bis(2-pyridyl)oxamide or N,N'-bis(2-hydroxyethyl)oxamide.

[0017] The base is an inorganic base or an organic base. Preferably, the base is selected from at least one of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, triethylamine.

[0018] According to the above preparation method of heptafluoroisobutyronitrile, the molar ratio of the catalyst to heptafluoro-2-halopropane is 0.001 - 0.06:1. Preferably, the molar ratio of the catalyst to heptafluoro-2-halopropane is 0.005 - 0.02:1.

[0019] Further, the molar ratio of the ligand to heptafluoro-2-halopropane is 0.001 - 0.01:1. Preferably, the molar ratio of the ligand to heptafluoro-2-halopropane is 0.002 - 0.005:1.

[0020] Further, the molar ratio of the base to heptafluoro-2-halopropane is 1.0 - 2.5:1. Preferably, the molar ratio of the base to heptafluoro-2-bromopropane is 1.1 - 1.5:1.

[0021] Further, the molar ratio of the cyanation reagent to heptafluoro-2-halopropane is 3.0 - 1.0:1. Preferably, the molar ratio of the cyanation reagent to heptafluoro-2-halopropane is 2.0 - 1.0:1.

[0022] For the method for preparing heptafluoroisobutyronitrile in one step according to the present invention, the required reaction pressure is 0.2 - 2.0 MPa, the reaction temperature is 30 - 160 °C, and the reaction time is 2 - 15 h. Preferably, the reaction pressure is 0.3 - 1.3 MPa, the reaction temperature is 60 - 130 °C, and the reaction time is 6 - 10 h.

[0023] The method for preparing heptafluoroisobutyronitrile according to the present invention specifically comprises the following steps:

[0024] A1. Add an organic solvent, heptafluoro-2-halopropane, a cyanation reagent, a catalyst, a ligand, and a base into a reactor, and react at a reaction pressure of 0.2 - 2.0 MPa and a reaction temperature of 30 - 160 °C for 2 - 15 h;

[0025] A2. Cool down to 0 - 25 °C, and collect the heptafluoroisobutyronitrile gas.

[0026] The step A2 further comprises: cooling the reaction system to 0 - 25 °C, opening the gas phase valve on the reactor, and collecting the heptafluoroisobutyronitrile gas with a steel cylinder. More preferably, the steel cylinder is previously subjected to vacuum and freezing treatment.

[0027] The present invention also provides the application of heptafluoroisobutyronitrile prepared by any of the above-mentioned preparation methods. Specifically, the heptafluoroisobutyronitrile replaces sulfur hexafluoride as an insulating medium and is applied to the original sulfur hexafluoride application sites.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. The present invention uses heptafluoro-2-halopropane and a cyanation reagent as raw materials to prepare heptafluoroisobutyronitrile through a one-step reaction. The process is simple and the reaction conditions are mild, which is suitable for industrial production.

[0030] 2. The catalyst and the cyanation reagent are conventional reagents, which are easily available in the market and have a low price, thus having a cost advantage. Specific Embodiments

[0031] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternative solutions, improvement solutions, and equivalent solutions that may be included within the scope of the claims.

[0032] Example 1

[0033] The volume of the high-pressure reactor is 2 L, equipped with mechanical stirring, a temperature control system, and a gas-phase discharging system. Add N,N-dimethylformamide (400 mL), heptafluoro-2-chloropropane (204.5 g, 1.0 mol), KCN (65.0 g, 1.0 mol), copper chloride (0.7 g, 0.005 mol), N,N'-bis(2,6-dimethylphenyl)oxamide (0.6 g, 0.002 mol), and sodium carbonate (116.6 g, 1.1 mol) into the high-pressure reactor. After adding, heat up to 60 °C and react for 6.0 h. After the reaction is completed, cool down to 25 °C, connect the gas-phase discharging port to a steel cylinder, open the valve to collect the gas, and a total of 159.1 g of heptafluoroisobutyronitrile gas is obtained, with a purity of 99.5% and a yield of 81.2%.

[0034] Example 2

[0035] The volume of the high-pressure reactor is 2 L, equipped with mechanical stirring, a temperature control system, and a gas-phase discharging system. Add dimethyl sulfoxide (400 mL), heptafluoro-2-chloropropane (204.5 g, 1.0 mol), NaCN (58.8 g, 1.2 mol), copper bromide (2.2 g, 0.01 mol), N,N'-bis(2-pyridyl)oxamide (0.7 g, 0.003 mol), and potassium carbonate (165.6 g, 1.2 mol) into the high-pressure reactor. After adding, heat up to 80 °C and react for 7.0 h. After the reaction is completed, cool down to 25 °C, connect the gas-phase discharging port to a steel cylinder, open the valve to collect the gas, and a total of 164.9 g of heptafluoroisobutyronitrile gas is obtained, with a purity of 99.2% and a yield of 83.9%.

[0036] Example 3

[0037] The volume of the high-pressure reactor is 2 L, equipped with mechanical stirring, a temperature control system, and a gas-phase discharging system. Add dioxane (400 mL), heptafluoro-2-bromopropane (249.0 g, 1.0 mol), CuCN (125.4 g, 1.4 mol), copper acetate (3.0 g, 0.015 mol), N,N'-bis(2-hydroxyethyl)oxamide (0.7 g, 0.004 mol), and sodium hydroxide (52.0 g, 1.3 mol) into the high-pressure reactor. After adding, heat up to 100 °C and react for 8.0 h. After the reaction is completed, cool down to 25 °C, connect the gas-phase discharging port to a steel cylinder, open the valve to collect the gas, and a total of 170.6 g of heptafluoroisobutyronitrile gas is obtained, with a purity of 99.1% and a yield of 86.7%.

[0038] Example 4

[0039] The volume of the high-pressure reactor is 2 L, equipped with mechanical stirring, a temperature control system, and a gas-phase discharging system. Add N-methylpyrrolidone (400 mL), heptafluoro-2-bromopropane (249.0 g, 1.0 mol), Zn(CN)₂ (117.4 g, 1.0 mol), cuprous bromide (2.9 g, 0.02 mol), N,N'-bis(2,6-dimethylphenyl)oxamide (1.5 g, 0.005 mol), and triethylamine (141.4 g, 1.4 mol) into the high-pressure reactor. After adding, heat up to 110 °C and react for 9.0 h. After the reaction is completed, cool down to 25 °C, connect the gas-phase discharging port to a steel cylinder, open the valve to collect the gas, and a total of 162.0 g of heptafluoroisobutyronitrile gas is obtained, with a purity of 99.3% and a yield of 82.5%.

[0040] Example 5

[0041] The volume of the high-pressure reactor is 2 L, equipped with mechanical stirring, a temperature control system, and a gas-phase discharging system. Add N,N-dimethylformamide (400 mL), heptafluoro-2-iodopropane (296.0 g, 1.0 mol), NaCN (78.4 g, 1.6 mol), copper chloride (1.1 g, 0.008 mol), N,N'-bis(2-pyridyl)oxamide (0.5 g, 0.002 mol), and sodium hydroxide (60.0 g, 1.5 mol) into the high-pressure reactor. After adding, heat up to 120 °C and react for 10.0 h. After the reaction is completed, cool down to 25 °C, connect the gas-phase discharging port to a steel cylinder, open the valve to collect the gas, and a total of 169.1 g of heptafluoroisobutyronitrile gas is obtained, with a purity of 99.5% and a yield of 86.3%.

[0042] Example 6

[0043] The volume of the high-pressure reactor is 2 L, equipped with mechanical stirring, a temperature control system, and a gas-phase discharging system. Add N-methylpyrrolidone (400 mL), heptafluoro-2-iodopropane (296.0 g, 1.0 mol), KCN (130.0 g, 2.0 mol), cuprous iodide (3.0 g, 0.016 mol), N,N'-bis(2-hydroxyethyl)oxamide (0.5 g, 0.003 mol), and potassium carbonate (151.8 g, 1.1 mol) into the high-pressure reactor. After adding, heat up to 130 °C and react for 7.0 h. After the reaction is completed, cool down to 25 °C, connect the gas-phase discharging port to a steel cylinder, open the valve to collect the gas, and a total of 161.8 g of heptafluoroisobutyronitrile gas is obtained, with a purity of 99.4% and a yield of 82.5%.

Claims

1. A method for preparing heptafluoroisobutyronitrile, characterized in that: In an organic solvent, in the co - action of a catalyst, a ligand and a base, heptafluoro - 2 - halopropane reacts with a cyanation reagent to obtain heptafluoroisobutyronitrile. The heptafluoro - 2 - halopropane is one of heptafluoro - 2 - chloropropane, heptafluoro - 2 - bromopropane or heptafluoro - 2 - iodopropane, and the cyanation reagent is selected from at least one of KCN, NaCN, CuCN, Zn(CN)₂; The catalyst is selected from at least one of copper chloride, copper iodide, copper bromide, copper acetate, cuprous bromide or cuprous iodide; the ligand is selected from at least one of N,N’ - bis(2,6 - dimethylphenyl)oxamide, N,N′ - bis(2 - pyridyl)oxamide or N,N′ - bis(2 - hydroxyethyl)oxamide; the base is an inorganic base and / or an organic base, selected from at least one of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or triethylamine.

2. The preparation method of heptafluoroisobutyronitrile according to claim 1, characterized in that: The organic solvent is selected from at least one of N,N - dimethylformamide, dimethyl sulfoxide, dioxane or N - methylpyrrolidone.

3. The preparation method of heptafluoroisobutyronitrile according to claim 1, characterized in that: The pressure of the cyanation reaction is 0.2 - 2.0 MPa, the reaction temperature is 30 - 160 °C, and the reaction time is 2 - 15 h.

4. The preparation method of heptafluoroisobutyronitrile according to claim 1, wherein: The molar ratio of the catalyst to heptafluoro - 2 - halopropane is 0.001 - 0.06:

1.

5. The preparation method of heptafluoroisobutyronitrile according to claim 1, wherein: The molar ratio of the ligand to heptafluoro - 2 - halopropane is 0.001 - 0.01:

1.

6. The preparation method of heptafluoroisobutyronitrile according to claim 1, characterized in that: The molar ratio of the base to heptafluoro - 2 - bromopropane is 1.0 - 2.5:

1.

7. The preparation method of heptafluoroisobutyronitrile according to claim 1, characterized in that: The preparation method comprises the following steps: A1. Add an organic solvent, heptafluoro - 2 - halopropane, a cyanation reagent, a catalyst, a ligand and a base into a reactor, and react at a reaction pressure of 0.2 - 2.0 MPa and a reaction temperature of 30 - 160 °C for 2 - 15 h; A2. Cool down to 0 - 25 °C and collect the heptafluoroisobutyronitrile gas.

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