CN110642750A - Preparation method of perfluoroalkyl nitrile - Google Patents
Preparation method of perfluoroalkyl nitrile Download PDFInfo
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- CN110642750A CN110642750A CN201910980896.7A CN201910980896A CN110642750A CN 110642750 A CN110642750 A CN 110642750A CN 201910980896 A CN201910980896 A CN 201910980896A CN 110642750 A CN110642750 A CN 110642750A
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Abstract
The invention provides a preparation method of perfluoroalkyl nitrile, which comprises the following steps: s1, reacting perfluoroalkyl acyl fluoride with methanol to generate perfluoroalkyl carboxylic acid methyl ester; s2, reacting perfluoroalkyl carboxylic acid methyl ester with ammonia gas to generate perfluoroalkyl amide; s3, under the action of a dehydrating agent composition containing fluorinated carboxylic anhydride and N, N-dimethylformamide, alkali catalyst is not needed, and the perfluoroalkyl nitrile is obtained by dehydrating with high yield. The invention reduces the by-products and facilitates the recovery of the dehydrating agent by optimizing the reaction conditions and not adding an alkali catalyst. Moreover, the low-temperature rectification method is utilized to effectively recover the dehydrating agent fluorinated carboxylic anhydride, reduce the production cost and prepare the perfluoroalkyl nitrile in a green and high-efficiency manner.
Description
Technical Field
The invention relates to the technical field of chemical synthesis, in particular to a preparation method of perfluoroalkyl nitrile.
Background
Perfluoroisobutyronitrile, 2,3,3, 3-tetrafluoro-2-trifluoromethylpropionitrile, is a perfluoronitrile compound with a boiling point of-4.7 ℃. Colorless gas at normal temperature and normal pressure. The dielectric composition has the characteristics of low boiling point, high volatility, excellent electrical insulation property, good environmental protection performance and the like, and can be used as a gas dielectric material and used as a dielectric composition of an insulator in an electrical device. Perfluoroisobutyronitrile has a Global Warming Potential (GWP) of only 2210, which is much lower than that of sulfur hexafluoride (GWP 23500), and can be used for replacing the traditional sulfur hexafluoride insulating gas, thereby greatly reducing the problem of atmospheric greenhouse effect. Perfluoroisobutyronitrile has received much attention from the global electrical industry and is beginning to find application.
U.S. Pat. No. 4, 20150083979 discloses a process for producing perfluoroisobutyronitrile in multiple steps from methyl perfluoroisobutyrate as a raw material, which is a perfluoronitrile compound used as an electrically insulating gas. The method has the advantages that the yield of the heptafluoroisobutyramide prepared by the method is 81 percent, the yield of the perfluoroisobutyronitrile prepared by the method is 74.9 percent, and the total yield is only 60.6 percent. The main problem of the method is that the waste liquid generated by the preparation method contains a mixture of trifluoroacetic anhydride, DMF, pyridine and some complex byproducts, such as trifluoroacetic pyridine salt, N, N-dimethyl trifluoroacetamide and the like, and the three wastes are difficult to treat and difficult to industrially apply. The expensive trifluoroacetic anhydride in the mixture is difficult to recycle, resulting in increased manufacturing cost of perfluoroisobutyronitrile.
Trifluoroacetic anhydride and DMF readily form N, N-dimethyltrifluoroacetamide at room temperature, which is substantially converted to N, N-dimethyltrifluoroacetamide at 60 ℃. N, N-dimethyl trifluoroacetamide consumes a large amount of trifluoroacetic anhydride as a by-product, and the reaction equation is shown in figure 1.
Disclosure of Invention
The invention provides a preparation method of perfluoroalkyl nitrile, which comprises the following steps:
s1 perfluoroalkyl acyl fluoride Rf 1Reaction of COF with methanol to form perfluoroalkyl carboxylate Rf 1COOCH3；
S2, perfluoroalkyl carboxylic acid methyl ester Rf 1COOCH3With ammonia NH3Reaction to form perfluoroalkyl amide Rf 1CONH2；
S3, perfluoroalkyl amide Rf 1CONH2In the presence of fluorinated carboxylic acid anhydride (R)f 2CO)2Under the action of a dehydrating agent composition of O and N, N-dimethylformamide, a base catalyst is not added, and the perfluoroalkyl nitrile R is obtained by dehydrationf 1CN；
Wherein R isf 1Is composed of
R1、R2Each independently is-F or-CF3M is 0, 1 or 2; n is 0 or 1; i is 0 or 1; rf 2is-CF3，-CF2CF3or-CF2CF2CF3。
Preferably, Rf 1Is selected from-CF3，-CF2CF3，-CF2CF2CF3，-CF(CF3)2，-CF2CF2CF2CF3，-CF(CF3)OCF3，-CF(CF3)OCF2CF3，-CF(CF3)OCF2CF3，-CF(CF3)OCF2CF2CF3。
In step S1, the molar ratio of the reactant methanol to the perfluoroalkanoyl fluoride is 1:1 to 5:1, preferably 2:1 to 3: 1.
Step S1, adding the alkali metal fluoride and the aprotic solvent into a reactor with a stirrer and a temperature control device, adding the raw material methanol, cooling the reaction mixture to a set temperature under stirring, introducing the perfluoroalkyl acyl fluoride gas under stirring, and adjusting according to the temperature of the reactant to keep the temperature of the reactant within +/-5 ℃ of the set temperature; after the complete fluoroalkylcarbonyl fluoride was introduced, the temperature of the reaction was maintained and stirring was continued for 2 hours, after which the stirring was stopped and the solid was removed by filtration. Then pressing the material into a rectifying device, heating and raising the temperature, and rectifying to obtain perfluoroalkyl carboxylic methyl ester Rf 1COOCH3。
In step S2, the aprotic solvent refers to ethylene glycol dimethyl ether, diethylene glycol diethyl ether, n-hexane, petroleum ether, toluene, ethylbenzene, dichloromethane, dichloroethane, hydrofluoroether solvent, etc., preferably dichloroethane, toluene, or a mixture of the two, and the molar ratio of the aprotic solvent to the perfluoroalkyl carboxylate is 1:1-5:1, preferably 2:1-3: 1;
in step S2, the perfluoroalkyl carboxylic acid methyl ester R is added into a reactor with a stirrer and a temperature control devicef 1COOCH3And an aprotic solvent; then introducing ammonia gas into the reactor, wherein the reaction is carried out and certain heat is released; after the addition of ammonia gas, stirring was continued for 1 hour, and the reaction was analyzed by gas chromatography GC to confirm completion of the reaction of the methyl ester. Then raising the temperature, distilling and extracting part of the solvent until all the methanol is extracted. The rest materials can be directly used for the next reaction.
In step S3, the perfluoroalkyl carboxylic acid anhydride refers to trifluoroacetic anhydride, pentafluoropropionic anhydride, difluoroacetic anhydride, heptafluorobutyric anhydride, perfluoro-3 oxobutyric anhydride, and the like; trifluoroacetic anhydride is preferred. And (3) adding N, N-dimethylformamide into the reaction kettle in the step S2, then slowly dropwise adding perfluoroalkyl carboxylic anhydride, and performing dehydration reaction to obtain perfluoroalkyl nitrile.
The preparation equation for perfluoroalkylnitriles is shown below, where the parameters are defined as previously:
1)Rf 1COF+CH3OH＝Rf 1COOCH3
2)Rf 1COOCH3+NH3＝Rf 1CONH2+CH3OH
3)Rf 1CONH2+(Rf 2CO)2O＝Rf 1CN+2Rf 2COOH
as a further improvement of the present invention, the perfluoroalkyl acyl fluoride is one selected from trifluoroacetyl fluoride, pentafluoropropionyl fluoride, heptafluorobutyryl fluoride and perfluoroisobutyryl fluoride, perfluoro-2-methoxypropionyl fluoride, perfluoro-2-ethoxypropionyl fluoride and perfluoro-2-propoxypropionyl fluoride.
As a further improvement of the invention, the fluorinated carboxylic anhydride is selected from one of trifluoroacetic anhydride, pentafluoropropionic anhydride, heptafluorobutyric anhydride, and heptafluoroisobutyric anhydride.
In a further improvement of the present invention, the ratio of the amount of the substance of the perfluoroalkylamide to the amount of the fluorinated carboxylic acid anhydride is 1.2 to 2.
As a further improvement of the invention, the reaction temperature in the step S3 is-40 to 30 ℃. Preferably, the reaction temperature of step S1 is 0-20 ℃.
As a further development of the invention, the step S2 is carried out in an aprotic inert solvent and the step S3 is carried out in an aprotic polar solvent.
The aprotic solvent includes dichloroethane, dimethyl sulfoxide, hexamethylphosphoric triamide, acetonitrile, acetone, and the like.
The aprotic polar solvent includes N, N-dimethylformamide, N-dimethylacetamide.
Preferably, a dehydrating agent composition comprising a fluorinated carboxylic acid anhydride (R)f 2CO)2O and N, N-dimethylformamide.
Preferably, the composite dehydrating agent is prepared by the following method:
adding DMF (dimethyl formamide) under the protection of nitrogen, cooling for a plurality of minutes in an ice-water bath, dropwise adding oxalyl chloride by using a constant-pressure dropping funnel, immediately enabling a large amount of white solids to appear in a reaction system and generating a large amount of gas, after the oxalyl chloride is dropwise added and no bubbles are generated, adding aniline (DMF) into the constant-pressure dropping funnel for dissolving, slightly raising the temperature of the system, stopping the temperature from changing when the temperature is reduced to 0 ℃ and no change is caused by silica gel thin-layer chromatography tracing, finishing the reaction and filtering impurities to obtain a yellow solution, performing reduced pressure distillation to remove excessive DMF, crystallizing yellow granular crystals by using diethyl ether, and performing vacuum drying to obtain a product with a melting point of 120.
The invention also protects perfluoroalkyl nitrile Rf 1CN，
Rf 1Is composed of
R1、R2Each independently being F or-CF3M is 0, 1 or 2; n is 0 or 1; i is 0 or 1;
preferably, Rf 1Is selected from-CF3,-CF2CF3,-CF2CF2CF3,-CF(CF3)2,-CF2CF2CF2CF3,-CF(CF3)OCF3,-CF(CF3)OCF2CF3，-CF(CF3)OCF2CF3，-CF(CF3)OCF2CF2CF3。
The invention further provides a recycling method of perfluoroalkyl carboxylic anhydride, which comprises the following steps:
a method for recycling fluorinated carboxylic anhydride comprises the following steps:
s1, heating and rectifying the system after the reaction of the perfluoroalkyl nitrile under a reduced pressure condition to obtain a mixture of perfluorocarboxylic acid and perfluorocarboxylic anhydride;
s2, adding phosphorus pentoxide into a mixture of perfluorocarboxylic acid and perfluorocarboxylic anhydride for dehydration, and simply distilling to obtain perfluorocarboxylic anhydride (R)f 2CO)2O。
As a further improvement of the invention, the rectification pressure is 0mmHg to 100 mmHg.
Preferably 10-30 mmHg.
As a further improvement of the invention, the internal temperature of the heating for recovering the trifluoroacetic anhydride is 0-30 ℃.
Preferably 15-25 deg.c.
The invention has the following beneficial effects: according to the preparation method, the preparation process of the perfluoroalkyl nitrile is further researched by using fluorinated carboxylic anhydride and perfluoroalkyl carboxamide without using an alkali catalyst such as pyridine, and a more environment-friendly and economic synthesis process condition is found, so that the perfluoroalkyl nitrile can be synthesized in a large amount at low cost, and the important environment-friendly insulating gas is provided for the power industry.
The invention reduces the by-products and facilitates the recovery of the dehydrating agent by optimizing the reaction conditions and not adding an alkali catalyst. Moreover, the low-temperature rectification method is utilized to effectively recover the dehydrating agent fluorinated carboxylic anhydride, reduce the production cost and prepare the perfluoroalkyl nitrile in a green and high-efficiency manner.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a reaction scheme of trifluoroacetic anhydride and DMF in the prior art;
FIG. 2 is an IR spectrum of perfluoroisobutyronitrile according to example 1 of the present invention;
FIG. 3 is a GC-MS spectrum of perfluoroisobutyronitrile according to example 1 of the present invention;
FIG. 4 is a gas chromatogram of perfluoroisobutyronitrile according to example 1 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The preparation method of perfluoro-2-methoxypropionyl fluoride, perfluoro-2-ethoxypropionyl fluoride and perfluoro-2-propoxypropionyl fluoride can refer to the Chinese patent CN 101817728B.
Perfluoro isobutyryl fluoride, CAS number: 335-42-0;
heptafluoroisobutyramide obtained by reacting methyl heptafluoroisobutyrate with ammonia gas at a yield of 81.1% (see chinese patent CN 104662617A).
Trifluoroacetamide, CAS number: 354-38-1;
trifluoroacetic anhydride, CAS No.: 407-25-0;
perfluoroisobutyronitrile, CAS No.: 42532-60-5;
heptafluoroisobutyric anhydride, CAS No.: 336-59-4;
the reagents of the invention were purchased from Schensz reagent Inc.
Example 1
A dry 2-liter stainless steel autoclave with stirring and temperature control devices was charged with 192g (6.0mol) of anhydrous methanol, respectively, subjected to ice-water bath treatment in the autoclave, and then maximum negative pressure was applied. Then 864g perfluoroisobutyryl fluoride (4.0mol) was slowly charged, the process internal temperature was controlled to be less than 20 ℃, and after the completion of charging, stirring was carried out for another 1 hour. Then, the contents of the autoclave were slowly dropped into 1000g of ice water through a liquid phase tube, and stirred and washed, with the temperature of the ice water being controlled to be less than 10 ℃. After washing with ice water for 2 times, the crude methyl perfluoroisobutyrate was neutralized to neutrality with 200mL of a 10% aqueous solution of sodium hydrogencarbonate, and dried over anhydrous magnesium sulfate. After drying, the crude perfluoromethyl isobutyrate was subjected to column distillation using a glass packing to obtain 866g (3.8mol) of perfluoromethyl isobutyrate in a reaction yield of 95%.
A2-liter autoclave was charged with 866g (3.8mol) of methyl perfluoroisobutyrate and 400mL of methylene chloride, followed by introduction of 77.52g (4.56mol) of ammonia gas, with a process control internal temperature of less than 40 ℃ and stirring at 30 to 40 ℃ for 1 hour with dropping of the internal temperature controlled. After completion of the reaction, a mixture of by-produced methanol and methylene chloride was distilled off, and no methanol remained by GC analysis, whereby heptafluoroisobutyramide (3.72mol, yield 98%) was obtained.
720g of N, N-dimethylformamide was added to the autoclave, and the mixture was cooled to-5 ℃ or lower, and then, 958g (4.56mol) of trifluoroacetic anhydride was added dropwise thereto slowly via a dropping funnel while controlling the internal temperature at <0 ℃ in the dropping process. In the dropping process, a production valve is opened to collect the perfluoroisobutyronitrile, the temperature is slowly raised to 10 ℃ in the later period, the perfluoroisobutyronitrile is produced by a gas diaphragm pump, 683g (3.5mol) of the perfluoroisobutyronitrile is produced in total, the GC purity is 98 percent, and the overall yield is 92 percent.
The reaction equation is as follows:
1)(CF3)2CFCOF+CH3OH＝(CF3)2CFCOOCH3
2)(CF3)2CFCOOCH3+NH3＝(CF3)2CFCONH2+CH3OH
3)(CF3)2CFCONH2+(CF3CO)2O＝(CF3)2CFCN+2CF3COOH
the infrared spectrum is shown in figure 2. Wherein 2272cm-1Being a functional group of a nitrile, C-F and CF3At an absorption position of 730--1In the meantime.
The GC-MS spectrum is shown in figure 3. The instruments and conditions used for the analysis were as follows:
an Agilent7980/5977E gas chromatography-mass spectrometer is adopted,
a chromatographic column: CS-GASPRO Quartz capillary chromatography column (30m 250 μm 0.25 μm, Agilent)
Column temperature: maintaining at 40 deg.C for 1min, then programming at 30 deg.C/min to 130 deg.C, then raising at 5 deg.C/min to 250 deg.C, then raising at 10 deg.C/min to 300 deg.C, and maintaining for 8 min;
carrier gas: helium, purity: 99.999%, flow rate of the split outlet: 1.2 mL/min;
sample inlet temperature: 280 deg.C
Ion source temperature: 230 deg.C
Quadrupole temperature: 150 ℃ C
Column carrier gas (flow rate): he (1.0mL/min, > 99.999%)
Sample introduction amount: 0.2mL
And (3) sample introduction mode: no shunt sampling;
a mass spectrum detector: EI source, 70eV.
Selective ion monitoring:
MS(EI)[m/e(species)]:
176((CF3)2C CN+)，
107(CF3 CCN+)，
100(CF 3CF 2+)，
76(CF 2CN+)，
the gas chromatogram is shown in figure 4, and the retention time of perfluoroisobutyronitrile is 5.47 min.
After the perfluoroisobutyronitrile is extracted, the remaining material is pressed into a condenser with chilled water of-20 ℃ and a rectifying still with a vacuum system, and is rectified to obtain a mixture of trifluoroacetic acid and trifluoroacetic anhydride with the total amount of 950g at the internal temperature of less than 20 ℃ and the vacuum degree of 40 mmHg.
After the collection, under the conditions that the internal temperature is lower than 60 ℃ and the vacuum degree is 25mmHg, the N, N-dimethylformamide is recovered by rectification, 620g is obtained, and the recovery rate is 86%.
To a mixture of 920g of trifluoroacetic acid and trifluoroacetic anhydride as described above, 300g of mesitylene was added, and 800g of phosphorus pentoxide was added for dehydration to give 820g of trifluoroacetic anhydride, the content was 99.3% by GC test, and the overall recovery was 85%.
Example 2
Following the procedure described in example 1, substituting "trifluoroacetic anhydride 958g (4.56 mol)" for "heptafluoroisobutyric anhydride 1686g (4.6 mol)" in step 2, followed by the procedure described in example 1, perfluoroisobutyronitrile 704.4g (3.6mol) was obtained in a yield of 95%.
Comparative example 1
1166.5g (5.96mol) of perfluoroisobutyronitrile as a dielectric gas was prepared in 74.5% yield according to the procedure of patent ZL 201810707330.2 for fluorinated nitriles as a dielectric gas.
Comparative example 2
According to the procedure described in example 1, heptafluoroisobutyramide: the mass ratio of trifluoroacetic anhydride is 1: the yield of perfluoroisobutyronitrile was 57.2% at a ratio of 1.
Example 3
A dry 2L stainless steel autoclave with stirring and temperature control devices was charged with 160g (5.0mol) of anhydrous methanol, respectively, and the autoclave was treated with an ice-water bath, and then maximum negative pressure was applied. 928g of perfluoro-2-methoxypropionyl fluoride (4.0mol) is slowly introduced, the internal temperature is controlled to be less than 10 ℃ in the process, and stirring is carried out for 2 hours after the introduction. And then, slowly dropwise adding the materials in the autoclave into ice water through a liquid phase pipe for washing, controlling the temperature of the ice water to be less than 5 ℃, and neutralizing the crude perfluoro-2-methoxypropionic acid methyl ester to be neutral by using a sodium bicarbonate aqueous solution after washing for 2 times by using the ice water. After neutralization, the crude perfluoro-2-methoxypropionic acid methyl ester is rectified by a glass packed column to obtain 917.4g (3.76mol) of perfluoro-2-methoxypropionic acid methyl ester, and the reaction yield is 94%.
A2 liter autoclave was charged with 917.4g (3.76mol) of methyl perfluoro-2-methoxypropionate, 800mL of a mixed solution of dichloroethane and toluene (volume ratio: 1), followed by introduction of 68g (4.0mol) of ammonia gas, with the internal temperature controlled to be less than 40 ℃ and stirring at 30 to 40 ℃ for 1 hour. After the reaction, the by-product methanol was distilled off, and no methanol remained by GC analysis, to obtain a dichloromethane/toluene solution of perfluoro-2-methoxypropionamide.
Transferring the dichloromethane/toluene solution of the perfluoro-2-methoxypropionamide into a 2L autoclave, cooling to below-2 ℃, slowly dropwise adding trifluoroacetic anhydride, controlling the internal temperature to be less than 0 ℃ in the dropwise adding process, and dropwise adding 957.6g (4.56mol) of the trifluoroacetic anhydride. The temperature was raised to 15 ℃ to collect 761.7g (3.61mol) of perfluoro-2-methoxypropionitrile, the yield was 96%.
Example 4
Preparation of a composite dehydrating agent:
adding 10 ml of DMF into a dry three-neck flask with nitrogen protection, placing the three-neck flask under an ice-water bath for cooling for a plurality of minutes until the temperature is reduced to 0 ℃, dropwise adding oxalyl chloride (1.3m L,0.015mol) by using an isopiestic dropping funnel, wherein a large amount of white solid appears in the reaction system immediately and a large amount of gas is generated until oxalyl chloride is generatedAfter the chlorine is dripped and no bubble is generated, aniline (1.40g,0.015mol) (DMF) is added by a constant pressure dropping funnel for dissolving, the system temperature is slightly increased (2-3 ℃), the temperature is not changed when the temperature is reduced to 0 ℃, and silica gel thin layer chromatography is used for tracing and no change, the reaction is ended, impurities are filtered to obtain yellow solution, the yellow granular crystal is crystallized by diethyl ether after the redundant DMF is distilled out under reduced pressure, the product is dried in vacuum to obtain 1.82g, the yield reaches 83%, the melting point reaches 120-,1HNMR(CDCl3):δ:0.87(3H,s,N-CH3),0.92(3H,s,N-CH3),4.02(1H，s，NH)，6.46-7.01(5H,m,ph),10.50(1H,s,＝N＝CH)。
the reaction equation is as follows:
example 5
A dry 2-liter stainless steel autoclave with stirring and temperature control devices was charged with 192g (6.0mol) of anhydrous methanol, respectively, subjected to ice-water bath treatment in the autoclave, and then maximum negative pressure was applied. Then 864g perfluoroisobutyryl fluoride (4.0mol) was slowly charged, the process internal temperature was controlled to be less than 20 ℃, and after the completion of charging, stirring was carried out for another 1 hour. Then, the contents of the autoclave were slowly dropped into 1000g of ice water through a liquid phase tube, and stirred and washed, with the temperature of the ice water being controlled to be less than 10 ℃. After washing with ice water for 2 times, the crude methyl perfluoroisobutyrate was neutralized to neutrality with 200mL of a 10% aqueous solution of sodium hydrogencarbonate, and dried over anhydrous magnesium sulfate. After drying, the crude perfluoromethyl isobutyrate was subjected to column distillation using a glass packing to obtain 866g (3.8mol) of perfluoromethyl isobutyrate in a reaction yield of 95%.
A2-liter autoclave was charged with 866g (3.8mol) of methyl perfluoroisobutyrate and 400mL of methylene chloride, followed by introduction of 77.52g (4.56mol) of ammonia gas, with a process control internal temperature of less than 40 ℃ and stirring at 30 to 40 ℃ for 1 hour with dropping of the internal temperature controlled. After the reaction, a mixture of by-products of methanol and dichloromethane was distilled off, and no methanol remained by GC analysis, thereby obtaining heptafluoroisobutyramide.
730g of the composite dehydrating agent prepared in example 4 was added to the autoclave, and the mixture was cooled to-5 ℃ or lower, and then slowly dropped using a dropping funnel with an internal temperature of 0 ℃ or lower during dropping. In the dropping process, a production valve is opened to collect the perfluoroisobutyronitrile, the temperature is slowly raised to 10 ℃ in the later period, the perfluoroisobutyronitrile is produced through a gas diaphragm pump, 728g (3.73mol) of the perfluoroisobutyronitrile is produced in total, the GC purity is more than 99%, and the overall yield is 98%.
The composite dehydrating agent prepared in the embodiment 4 of the invention is used for dehydration, and an alkali catalyst is not needed to be added, so that the obtained product has higher purity and higher yield.
Compared with the prior art, the preparation method further researches the preparation process of the perfluoroalkyl nitrile by using the fluorinated carboxylic anhydride and the perfluoroalkyl amide without using a base catalyst such as pyridine, finds more environment-friendly and economic synthesis process conditions, can synthesize a large amount of perfluoroalkyl nitrile at low cost, and provides the important environment-friendly insulating gas for the power industry.
According to the invention, by optimizing reaction conditions and adding no alkali catalyst, the generation of pyridine salt and other byproducts is avoided, the intermediate raw materials, the fluorinated carboxylic anhydride and the perfluoroamide which are products can be efficiently recovered, the reaction cost is reduced, and the perfluoroalkyl nitrile which is a product is obtained in a green and efficient manner.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (11)
1. Perfluoroalkyl nitrile Rf 1The preparation method of CN is characterized by comprising the following steps:
s1 perfluoroalkyl acyl fluoride Rf 1Reaction of COF with methanol to form perfluoroalkyl carboxylic acid methyl ester Rf 1COOCH3；
S2, perfluoroalkyl carboxylic acid methyl ester Rf 1COOCH3With ammonia NH3Reaction to form perfluoroalkyl amide Rf 1CONH2；
S3, perfluoroalkyl amide Rf 1CONH2With fluorinated carboxylic acid anhydride (R)f 2CO)2Under the action of a dehydrating agent composition of O and N, N-dimethylformamide, a base catalyst is not added, and the perfluoroalkyl nitrile R is obtained by dehydrationf 1CN；
Wherein R isf 1Is composed of
R1、R2Each independently is-F or-CF3M is 0, 1 or 2; n is 0 or 1; i is 0 or 1; rf 2is-CF3，-CF2CF3，-CF2CF2CF3Or (CF)3)2CFCF。
2. The process for producing a perfluoroalkylnitrile according to claim 1, wherein R isf 1Is selected from-CF3，-CF2CF3，-CF2CF2CF3，-CF(CF3)2，-CF2CF2CF2CF3，-CF(CF3)OCF3，-CF(CF3)OCF2CF3，-CF(CF3)OCF2CF2CF3。
3. The process for producing a perfluoroalkylcyanide according to claim 1, wherein the perfluoroalkylacyl fluoride is selected from the group consisting of trifluoroacetyl fluoride, pentafluoropropionyl fluoride, heptafluorobutyryl fluoride, perfluoroisobutyryl fluoride, perfluoro-2-methoxypropionyl fluoride, perfluoro-2-ethoxypropionyl fluoride, and perfluoro-2-propoxypropionyl fluoride.
4. The method for producing a perfluoroalkylnitrile as claimed in claim 1, wherein the fluorinated carboxylic acid anhydride is one selected from the group consisting of trifluoroacetic anhydride, pentafluoropropionic anhydride, heptafluorobutyric anhydride and heptafluoroisobutyric anhydride.
5. The process for preparing perfluoroalkyl nitriles as claimed in claim 1, characterized in that the mass ratio of perfluoroalkyl amides to fluorinated carboxylic anhydrides is from 1.1 to 1.5.
6. The method for preparing perfluoroalkylnitrile according to claim 1, wherein the reaction temperature in step S3 is-40 to 30 ℃, preferably 0 to 20 ℃.
7. The process for producing a perfluoroalkylnitrile as claimed in claim 1, wherein the step S2 is carried out in an aprotic inert solvent, and the step S3 is carried out in an aprotic polar solvent.
8. Perfluoroalkyl nitrile Rf 1CN, which is characterized in that,
Rf 1is composed of
R1、R2Each independently being F or-CF3M is 0, 1 or 2; n is 0 or 1; i is 0 or 1;
preferably, Rf 1Is selected from-CF3,-CF2CF3,-CF2CF2CF3,-CF(CF3)2,-CF2CF2CF2CF3,-CF(CF3)OCF3,-CF(CF3)OCF2CF3，-CF(CF3)OCF2CF2CF3。
9. A method for recycling fluorinated carboxylic anhydride is characterized by comprising the following steps:
s1, heating and rectifying a system obtained after the reaction of the perfluoroalkyl nitrile in the claim 1 under a reduced pressure condition to obtain a mixture of perfluorocarboxylic acid and perfluorocarboxylic anhydride;
s2, adding phosphorus pentoxide into a mixture of perfluorocarboxylic acid and perfluorocarboxylic anhydride for dehydration, and simply distilling to obtain perfluorocarboxylic anhydride (R)f 2CO)2O。
10. The method of claim 10, wherein the rectification pressure at step S1 is 0mmHg-100 mmHg.
11. The method of claim 10, wherein the internal temperature of the trifluoroacetic anhydride recovered by heating in step S1 is 0 to 30 ℃.
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| CN111825568A (en) * | 2020-08-14 | 2020-10-27 | 福建省漳平市九鼎氟化工有限公司 | Synthesis method of perfluoroisobutyronitrile |
| CN111825569A (en) * | 2020-08-14 | 2020-10-27 | 福建省漳平市九鼎氟化工有限公司 | Synthetic method of heptafluoroisobutyronitrile |
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| CN111995540A (en) * | 2020-07-30 | 2020-11-27 | 武汉轻工大学 | Preparation method of heptafluoroisobutyramide |
| CN113248404A (en) * | 2021-04-20 | 2021-08-13 | 三明市海斯福化工有限责任公司 | Preparation method of perfluoroalkyl nitrile |
| CN115819277A (en) * | 2022-12-22 | 2023-03-21 | 浙江诺亚氟化工有限公司 | Preparation method of perfluoroisobutyronitrile |
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| CN111995540A (en) * | 2020-07-30 | 2020-11-27 | 武汉轻工大学 | Preparation method of heptafluoroisobutyramide |
| CN111825568A (en) * | 2020-08-14 | 2020-10-27 | 福建省漳平市九鼎氟化工有限公司 | Synthesis method of perfluoroisobutyronitrile |
| CN111825569A (en) * | 2020-08-14 | 2020-10-27 | 福建省漳平市九鼎氟化工有限公司 | Synthetic method of heptafluoroisobutyronitrile |
| CN111848444A (en) * | 2020-08-14 | 2020-10-30 | 福建省漳平市九鼎氟化工有限公司 | Synthesis method of perfluoroisobutyronitrile |
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| CN113248404A (en) * | 2021-04-20 | 2021-08-13 | 三明市海斯福化工有限责任公司 | Preparation method of perfluoroalkyl nitrile |
| CN113248404B (en) * | 2021-04-20 | 2024-01-05 | 三明市海斯福化工有限责任公司 | Preparation method of perfluoroalkyl nitrile |
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