Preparation method of heptafluoroisobutyronitrile

Abstract

The invention discloses a preparation method of heptafluoroisobutyronitrile, and belongs to the technical field of fluorine chemical industry. The method comprises the following steps: ball-milling and mixing fluorite and phosphate to prepare a phosphorylated fluorination reagent; mixing the phosphorylated fluorination reagent with a C4 nitrile compound, a crown ether phase transfer catalyst and a polar organic solvent, carrying out fluorination reaction in an inert atmosphere to obtain a heptafluoroisobutyronitrile suspension, and purifying the suspension to obtain heptafluoroisobutyronitrile. According to the method, the phosphorylated fluorination reagent is prepared through ball milling, direct use of hydrogen fluoride is avoided, and heptafluoroisobutyronitrile can be generated through reaction under mild reaction conditions. The method is simple, safe and rapid to operate, low in production energy consumption and high in product heptafluoroisobutyronitrile yield.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and particularly relates to a method for preparing heptafluoroisobutyronitrile. Background Art

[0002] Heptafluoroisobutyronitrile is a new type of environmentally friendly insulating gas with low toxicity and excellent chemical stability. It is the best substitute for sulfur hexafluoride. The commonly used preparation methods include: (1) gas phase catalytic addition method using carbonyl fluoride as raw material; (2) gas phase catalytic cracking method using perfluoroolefin as raw material.

[0003] The Chinese invention patent document with publication number CN108424375A discloses a method for preparing perfluoronitrile: a. Perfluoroolefin R 1 R 2 C=CR 3 R 4 Gas phase addition reaction with carbonyl fluoride gives acyl fluoride R 1 R 2 (COF)C-CFR 3 R 4 (R 1 , R 2 , R 3 and R 4 The general formula is -C n F 2n+1 Group); b. acyl fluoride R 1 R 2 (COF)C-CFR 3 R 4 With acyl fluoride and alkali metal amide or amino compound R-NH 2 (R is lithium, sodium, potassium, rubidium, cesium or -C m H 2m+1 The yield of heptafluoroisobutyronitrile is only 84.0%. The reaction temperature is 0-300°C and the reaction time is 2-30 hours. It can be seen that the yield of heptafluoroisobutyronitrile is low, the reaction route is long, and the acyl fluoride raw materials are highly toxic, and the production, storage, use and discharge are strictly controlled; the dehydration reaction produces a large amount of fluorine-containing acidic waste liquid, the production and operation conditions are harsh, and the operation cost is high.

[0004] The Chinese invention patent document with publication number CN113683530A discloses a method for preparing heptafluoroisobutyronitrile by gas phase fluorination: hexafluoropropylene is used as a raw material, and in the presence of a fluorination catalyst, a gas phase catalytic reaction is carried out with hydrogen fluoride and X-CN to obtain heptafluoroisobutyronitrile. Although the hexafluoropropylene conversion rate is 98.7% and the heptafluoroisobutyronitrile selectivity is 97.4%, the reaction conditions of the heptafluoroisobutyronitrile production route are: reaction pressure 0.1-1.5MPa, reaction temperature 100-500°C, high energy consumption and high cost; at the same time, the reaction process uses highly dangerous reagent hydrogen fluoride as a fluorination agent, and highly corrosion-resistant equipment is required, which increases equipment investment.

[0005] The Chinese invention patent document with the publication number CN 116693420 A discloses a method for preparing heptafluoroisobutyronitrile in liquid phase: S1 Preparation of catalyst: crush antimony block and load into reactor: introduce chlorine into reactor to react and obtain catalyst antimony pentachloride; S2 Pre-fluorination of catalyst: introduce anhydrous hydrogen fluoride into antimony pentachloride and heat to 50-100°C under stirring; S3 Continue to introduce anhydrous hydrogen fluoride and nitrile compound into reactor, control the temperature to 50-100°C, the reaction pressure to 0.4-0.7MPa, react and obtain heptafluoroisobutyronitrile. Although the conversion rate of nitrile compound obtained by this method is 99.6% and the selectivity of heptafluoroisobutyronitrile is 99.7%, this method also uses highly dangerous reagent hydrogen fluoride as fluorinating agent, and the reaction process is complicated. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing heptafluoroisobutyronitrile with safety, low pollution, low energy consumption and high yield.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions: A method for preparing heptafluoroisobutyronitrile comprises the following steps: mixing fluorite and phosphate by ball milling to obtain a phosphorylation fluorination reagent; 4 A nitrile compound, a crown ether phase transfer catalyst and a polar organic solvent are mixed, and a fluorination reaction is carried out under an inert atmosphere to obtain a heptafluoroisobutyronitrile suspension, and the suspension is purified to obtain heptafluoroisobutyronitrile.

[0008] Preferably, the phosphate is one or more of potassium phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate or sodium phosphate; and the mass ratio of fluorite to phosphate is 1:1-2.

[0009] Preferably, the ball milling conditions are: a rotation speed of 1000-1200 r / min, a time of 0.5-1 h, and a ball-to-material ratio of 1-3:1.

[0010] Preferably, the C 4The nitrile compound is isobutyronitrile and / or 2-x-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, wherein x is H or Cl or Br.

[0011] Preferably, the crown ether phase transfer catalyst is any one of 18-crown ether-6, 15-crown ether-5, 24-crown ether-8, and 12-crown ether-4.

[0012] Preferably, the polar organic solvent is one of dichloromethane, acetonitrile, dimethyl sulfoxide and dichloroethane.

[0013] Preferably, the inert gas is nitrogen or argon; polar organic solvent, C 4 The mass ratio of the nitrile compound, the phosphorylation fluorination reagent and the crown ether phase transfer catalyst is 3-15:1:1-3:1-3; the reaction temperature is 80-120°C; the fluorination reaction pressure is 0.1-0.3Mpa, and the fluorination reaction time is 5-10h.

[0014] Compared with the prior art, it has the following beneficial effects: (1) The prior art cannot do without the participation of HF in the preparation of heptafluoroisobutyronitrile, while the method of the present invention uses a ball milling method to fully mix fluorite and phosphate, and converts fluorite into a phosphorylation fluorination agent under the mechanochemical action of high temperature and high pressure, that is, directly generating a fluorination agent from the Ca-F of fluorite, thereby avoiding the direct participation of the highly dangerous and highly corrosive fluorination agent HF, thereby reducing environmental pollution, simplifying the production process, reducing equipment investment costs and energy loss, and reducing operating costs.

[0015] (2) The phosphorylation fluorination reagent prepared by the present invention is prepared by using C 4 The process of preparing heptafluoroisobutyronitrile using nitrile compounds as raw materials shows excellent performance. When the reaction temperature is 80-120°C, the pressure is 0.1-0.3Mpa, and the time is 5-10h, the selectivity of the obtained phosphorylated fluorination reagent for the generation of heptafluoroisobutyronitrile is increased to 97.4-99.3%, and the yield is 95.5-97.7%. The reaction conditions are mild and the yield of heptafluoroisobutyronitrile is high. This is mainly because the phosphate in the phosphorylated fluorination reagent used has a high ability to attract electrons, which weakens the ability of fluorine atoms to attract electrons. In the fluorination reaction process, the fluorine atoms in the phosphorylated fluorination reagent are more likely to form fluorine free radicals. In the fluorination reaction process, the fluorine atoms in the phosphorylated fluorination reagent are more likely to form fluorine free radicals. 4 After the nitrile compound reactants come into contact, the fluorine free radicals efficiently and directionally replace other atoms or atomic groups on the carbon atoms, so that the phosphorylation fluorination reagent has excellent fluorine supply performance, thereby achieving high selectivity and high yield of heptafluoroisobutyronitrile; (3) In the method of the present invention, the prepared phosphorylation fluorination reagent is a nucleophilic fluorination reagent. Compared with the electrophilic fluorination reagent of hydrogen fluoride, it can generate fluorine free radicals at a lower temperature under the strong electron attraction of phosphate, thereby showing a lower fluorination reaction temperature. DETAILED DESCRIPTION Example 1

[0016] Add 60 g of stainless steel balls, 10 g of fluorite and K into a 500 mL stainless steel grinding jar. 2 HPO 4 The jar was then closed and securely mounted in a ball mill and ground at 1000 rpm for 0.5 hours to obtain phosphorylation fluorination reagent A.

[0017] Under nitrogen replacement protection, add 10g of isobutyronitrile, 10g of phosphorylation fluorination reagent A, 10g of 18-crown ether-6, and 30g of acetonitrile into a 500mL dry autoclave, and react for 5 hours at 100°C and 0.1Mpa. After the reaction is completed, cool at room temperature to obtain a crude product of heptafluoroisobutyronitrile. Take the crude product of heptafluoroisobutyronitrile for chromatographic analysis, among which C 4 The conversion rate of nitrile compounds was 98.4%, and the selectivity of heptafluoroisobutyronitrile was 99.3%. The upper suspension was purified to obtain heptafluoroisobutyronitrile. Example 2

[0018] Add 50 g of stainless steel balls, 20 g of fluorite and K into a 500 mL stainless steel grinding jar. 3 PO 4 The jar was then closed and securely mounted in a ball mill and ground at 1050 rpm for 0.6 hours to obtain phosphorylation fluorination reagent B.

[0019] Under argon replacement protection, 10 g of 2-chloro-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 20 g of phosphorylation fluorination reagent B, 20 g of 15-crown ether-5, and 100 g of dimethyl sulfoxide were added to a 500 mL dry autoclave, and the mixture was sealed and reacted at 90°C and 0.2 MPa for 6 hours. After the reaction was completed, the mixture was cooled at room temperature to obtain a crude product of heptafluoroisobutyronitrile. The crude product of heptafluoroisobutyronitrile was subjected to chromatographic analysis, and C 4 The conversion rate of nitrile compounds was 99.1%, and the selectivity of heptafluoroisobutyronitrile was 98.5%. The upper suspension was purified to obtain heptafluoroisobutyronitrile. Example 3

[0020] Add 180 g of stainless steel balls, 20 g of fluorite and Na 2 HPO 4The jar was then closed and securely mounted in a ball mill and ground at 1100 rpm for 0.7 hours to obtain phosphorylation fluorination reagent C.

[0021] Under nitrogen replacement protection, 10 g of 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 30 g of phosphorylation fluorination reagent C, 20 g of 24-crown ether-8, and 120 g of dichloroethane were added to a 500 mL dry autoclave, and the mixture was sealed and reacted at 80°C and 0.3 MPa for 7 hours. After the reaction was completed, the mixture was cooled at room temperature to obtain a crude product of heptafluoroisobutyronitrile. The crude product of heptafluoroisobutyronitrile was subjected to chromatographic analysis, and C 4 The conversion rate of nitrile compounds was 98.6%, and the selectivity of heptafluoroisobutyronitrile was 99.1%. The upper suspension was purified to obtain heptafluoroisobutyronitrile. Example 4

[0022] Add 50 g of stainless steel balls, 10 g of fluorite and Na 3 PO 4 The jar was then closed and securely mounted in a ball mill and ground at 1150 rpm for 0.8 hours to obtain phosphorylation fluorination reagent D.

[0023] Under argon replacement protection, 10 g of 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 30 g of phosphorylation fluorination reagent D, 10 g of 12-crown ether-4, and 150 g of dichloromethane were added to a 500 mL dry autoclave, and the mixture was sealed and reacted for 8 hours at 110°C and 0.2 MPa. After the reaction was completed, the mixture was cooled at room temperature to obtain a crude product of heptafluoroisobutyronitrile. The crude product of heptafluoroisobutyronitrile was subjected to chromatographic analysis, and C 4 The conversion rate of nitrile compounds was 98.3%, and the selectivity of heptafluoroisobutyronitrile was 97.5%. The upper suspension was purified to obtain heptafluoroisobutyronitrile. Example 5

[0024] Add 90 g of stainless steel balls, 20 g of fluorite and Na 3 PO 4 20g, K 3 PO 4 The jar was then closed and securely mounted in a ball mill and ground at 1100 rpm for 0.9 hours to obtain phosphorylation fluorination reagent E.

[0025] Under nitrogen replacement protection, add 5g of isobutyronitrile, 5g of 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 20g of phosphorylation fluorination reagent E, 10g of 12-crown ether-4, and 80g of acetonitrile into a 500mL dry autoclave, and react at 120°C and 0.1Mpa for 9 hours. After the reaction is completed, cool at room temperature to obtain a crude product of heptafluoroisobutyronitrile. Take the crude product of heptafluoroisobutyronitrile for chromatographic analysis, among which C 4 The conversion rate of nitrile compounds was 96.5%, and the selectivity of heptafluoroisobutyronitrile was 99.0%. The upper suspension was purified to obtain heptafluoroisobutyronitrile. Example 6

[0026] Add 90 g of stainless steel balls, 30 g of fluorite and K into a 500 mL stainless steel grinding jar. 2 HPO 4 20g, K 3 PO 4 The jar was then closed and securely mounted in a ball mill and ground at 1100 rpm for 1 hour to obtain phosphorylation fluorination reagent F.

[0027] Under nitrogen replacement protection, 5 g of 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 5 g of 2-chloro-3.3.3-trifluoro-2-(trifluoromethyl)propionitrile, 20 g of phosphorylation fluorination reagent F, 30 g of 18-crown ether-6, and 120 g of dichloroethane were added to a 500 mL dry autoclave, and the mixture was sealed and reacted at 120°C and 0.1 MPa for 9 hours. After the reaction was completed, the mixture was cooled at room temperature to obtain a crude product of heptafluoroisobutyronitrile. The crude product of heptafluoroisobutyronitrile was subjected to chromatographic analysis, and C 4 The conversion rate of nitrile compounds was 97.7%, and the selectivity of heptafluoroisobutyronitrile was 98.6%. The upper suspension was purified to obtain heptafluoroisobutyronitrile. Example 7

[0028] Add 60 g of stainless steel balls, 20 g of fluorite and Na 2 HPO 4 20g, K 3 PO 4 The jar was then closed and securely mounted in a ball mill and ground at 1200 rpm for 0.7 hours to obtain phosphorylation fluorination reagent G.

[0029] Under nitrogen replacement protection, add 5g of isobutyronitrile, 5g of 2-chloro-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 15g of phosphorylation fluorination reagent G, 10g of 15-crown ether-5, and 90g of acetonitrile into a 500mL dry autoclave, and react for 10 hours at 120°C and 0.1Mpa. After the reaction is completed, cool at room temperature to obtain a crude product of heptafluoroisobutyronitrile. Take the crude product of heptafluoroisobutyronitrile for chromatographic analysis, among which C 4 The conversion rate of nitrile compounds was 98.6%, and the selectivity of heptafluoroisobutyronitrile was 97.4%. The upper suspension was purified to obtain heptafluoroisobutyronitrile. Example 8

[0030] Under argon replacement protection, add 10g of isobutyronitrile, 10g of phosphorylation fluorination reagent A, 5g of phosphorylation fluorination reagent C, 10g of 24-crown ether-8, and 90g of dichloromethane in a 500mL dry autoclave, and react for 10 hours at 110°C and 0.2Mpa. After the reaction is completed, cool at room temperature to obtain a crude product of heptafluoroisobutyronitrile. Take the crude product of heptafluoroisobutyronitrile for chromatographic analysis, among which C 4 The conversion rate of nitrile compounds was 98.3%, and the selectivity of heptafluoroisobutyronitrile was 98.9%. The upper suspension was purified to obtain heptafluoroisobutyronitrile.

[0031] The composition of heptafluoroisobutyronitrile prepared in the embodiment was analyzed by gas chromatography With reference to the calculation formula of CN117550950A, the conversion rate of C4 nitrile compounds and the selectivity analysis and calculation method of heptafluoroisobutyronitrile involved in each embodiment of the present invention are as follows:

[0032] The analysis results are shown in Table 1

[0033] In summary, the present invention adopts a ball milling method. Under the high-speed rotation of the ball mill, fluorite and phosphate are subjected to mechanical energy and chemical energy, and the fluorite reacts with the phosphate to be converted into a phosphorylated fluorination reagent with a large lattice energy. The large lattice energy makes the fluoride ions in the fluorination reagent have a high nucleophilicity, and can act as a nucleophilic reagent in the reaction to attract other molecules or ions, and then react with nitriles to generate heptafluoroisobutyronitrile by fluorination. The phosphorylated fluorination reagent is prepared in C 4The process of preparing heptafluoroisobutyronitrile using nitrile compounds as raw materials shows excellent performance. When the reaction temperature is 80-120°C, the pressure is 0.1-0.3Mpa, and the time is 5-10h, the selectivity of the obtained phosphorylation fluorination reagent for the generation of heptafluoroisobutyronitrile is increased to 97.4-99.3%, and the yield is 95.5-97.7%. The reaction conditions are mild and the yield of heptafluoroisobutyronitrile is high. This is mainly because the phosphate in the phosphorylation fluorination reagent used has a high electrophilic ability, which weakens the electrophilic ability of the fluorine atom. In the process, the fluorine atoms in the phosphorylated fluorination reagent are more likely to form fluorine free radicals. During the fluorination reaction, after contacting with the C4 nitrile compound reactant, the fluorine free radicals efficiently and directionally replace other atoms or atomic groups on the carbon atom, so that the phosphorylated fluorination reagent has excellent fluorine supply performance, and the selectivity and yield of the obtained heptafluoroisobutyronitrile are high; at the same time, the phosphorylated fluorination reagent is a nucleophilic fluorination reagent. Compared with the hydrogen fluoride electrophilic fluorination reagent, it can generate fluorine free radicals at a lower temperature under the strong electron attraction of phosphate, thereby showing a lower reaction temperature.

Claims

1. A method for preparing heptafluoroisobutyronitrile, characterized in that: The following steps are involved: The fluorite and phosphate are ball-milled and mixed to obtain a phosphorylation fluorination reagent; the phosphorylation fluorination reagent is mixed with a C4 nitrile compound, a crown ether phase transfer catalyst, and a polar organic solvent, and a fluorination reaction is carried out under an inert atmosphere to obtain a heptafluoroisobutyronitrile suspension, and the suspension is purified to obtain heptafluoroisobutyronitrile.

2. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that: The phosphate is one or more of potassium phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate or sodium phosphate; the mass ratio of fluorite to phosphate is 1:1-2.

3. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that: The ball milling conditions are as follows: a rotation speed of 1000-1200 r / min, a time of 0.5-1 h, and a ball-to-material ratio of 1-3:

1.

4. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that: The C4 nitrile compound is isobutyronitrile and / or 2-x-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, wherein x is H or Cl or Br.

5. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that: The crown ether phase transfer catalyst is any one of 18-crown ether-6, 15-crown ether-5, 24-crown ether-8 and 12-crown ether-4.

6. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that: The polar organic solvent is one of dichloromethane, acetonitrile, dimethyl sulfoxide and dichloroethane.

7. The method for preparing heptafluoroisobutyronitrile according to claim 1, characterized in that: The inert gas is nitrogen or argon; the mass ratio of the polar organic solvent, the C4 nitrile compound, the phosphorylation fluorination reagent and the crown ether phase transfer catalyst is 3-15:1:1-3:1-3; the reaction temperature is 80-120°C; the fluorination reaction pressure is 0.1-0.3Mpa, and the fluorination reaction time is 5-10h.

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