A preparation method of heptafluoroisobutyronitrile

Abstract

The present invention discloses a method for preparing heptafluoroisobutyronitrile, belonging to the technical field of fluorine chemical industry. Fluorite and phosphate are first ball-milled to prepare a phosphorylation fluorination reagent; the phosphorylation fluorination reagent is then 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. The suspension is purified to obtain heptafluoroisobutyronitrile. This method utilizes ball milling to prepare the phosphorylation fluorination reagent, avoiding the direct use of hydrogen fluoride, and can react to produce heptafluoroisobutyronitrile under mild reaction conditions. This method is simple, safe, and rapid to operate, has low production energy consumption, and has a high yield of the product heptafluoroisobutyronitrile.

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. a perfluoroolefin R1R2C=CR3R4 undergoes a gas phase addition reaction with carbonyl fluoride to obtain an acyl fluoride R1R2(COF)C-CFR3R4 (the general formula of R1, R2, R3 and R4 are all -C n F 2n+1 Group); b. Acyl fluoride R1R2(COF)C-CFR3R4 and acyl fluoride and alkali metal amide or amino compound R-NH2 (R is lithium, sodium, potassium, rubidium, cesium or -C m H 2m+1 The yield of heptafluoroisobutyronitrile (FIP) is only 84.0%. The reaction temperature is 0-300°C, and the reaction time is 2-30 hours. This method has a low yield of heptafluoroisobutyronitrile, a long reaction route, and the acyl fluoride raw materials are highly toxic, requiring strict regulations on their production, storage, use, and discharge. The dehydration reaction also produces a large amount of fluorine-containing acidic wastewater, resulting in demanding production and operating conditions and high operating costs.

[0004] Chinese invention patent publication number CN113683530A discloses a method for preparing heptafluoroisobutyronitrile by gas-phase fluorination. Hexafluoropropylene is reacted with hydrogen fluoride and X-CN in the presence of a fluorination catalyst to produce heptafluoroisobutyronitrile. While the hexafluoropropylene conversion rate is 98.7% and the heptafluoroisobutyronitrile selectivity is 97.4%, the production process requires high energy consumption and costs due to the reaction conditions of a reaction pressure of 0.1 to 1.5 MPa and a reaction temperature of 100 to 500°C. Furthermore, the reaction uses the highly hazardous reagent hydrogen fluoride as a fluorinating agent, requiring the use of highly corrosion-resistant equipment, which increases equipment investment.

[0005] Chinese invention patent publication number CN 116693420 A discloses a liquid-phase method for preparing heptafluoroisobutyronitrile: S1. Catalyst preparation: Antimony blocks are crushed and loaded into a reactor; chlorine gas is introduced into the reactor to react and produce the catalyst, antimony pentachloride; S2. Catalyst prefluorination: Anhydrous hydrogen fluoride is introduced into the antimony pentachloride and the temperature is raised to 50-100°C while stirring; S3. Anhydrous hydrogen fluoride and a nitrile compound are continuously introduced into the reactor, the temperature is controlled at 50-100°C, and the reaction pressure is maintained at 0.4-0.7 MPa to produce heptafluoroisobutyronitrile. Although this method achieves a nitrile compound conversion rate of 99.6% and a heptafluoroisobutyronitrile selectivity of 99.7%, it also uses the highly hazardous reagent hydrogen fluoride as the fluorinating agent and the reaction process is complex. 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:

[0008] A preparation method of heptafluoroisobutyronitrile comprises the following steps: mixing fluorite and phosphate by ball milling to obtain a phosphorylation-fluorination reagent; mixing the phosphorylation-fluorination reagent with a C4 nitrile compound, a crown ether phase transfer catalyst, and a polar organic solvent, carrying out a fluorination reaction under an inert atmosphere to obtain a heptafluoroisobutyronitrile suspension; and purifying the suspension to obtain heptafluoroisobutyronitrile.

[0009] 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.

[0010] 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.

[0011] Preferably, 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.

[0012] Preferably, the crown ether phase transfer catalyst is any one of 18-crown-6, 15-crown-5, 24-crown-8, and 12-crown-4.

[0013] Preferably, the polar organic solvent is one of dichloromethane, acetonitrile, dimethyl sulfoxide and dichloroethane.

[0014] Preferably, the inert gas is nitrogen or argon; the mass ratio of the polar organic solvent, C4 nitrile compound, phosphorylation fluorination reagent and 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.

[0015] Compared with the existing technology, it has the following beneficial effects:

[0016] (1) The existing technology cannot do without the participation of HF in the preparation process of heptafluoroisobutyronitrile. However, the method of the present invention adopts the ball milling method to fully mix fluorite and phosphate, and converts fluorite into a phosphorylation fluorination reagent under the mechanochemical action of high temperature and high pressure. That is, the fluorination reagent is directly generated from the Ca-F of fluorite, 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.

[0017] (2) The present invention prepares a phosphorylation fluorination reagent, which shows excellent performance in the process of preparing heptafluoroisobutyronitrile using C4 nitrile compounds as raw materials. 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 production of heptafluoroisobutyronitrile is improved to 97.4-99.3%, and the yield reaches 95.5-97.7%. The reaction conditions are mild and the yield of heptafluoroisobutyronitrile is high. This is mainly because the phosphate group in the phosphorylation fluorination reagent used has a high electron-attracting ability, which weakens the electron-attracting ability of fluorine atoms. During the fluorination reaction, the fluorine atoms in the phosphorylation 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 atoms, so that the phosphorylation fluorination reagent has excellent fluorine supply performance, thereby achieving high selectivity and high yield of heptafluoroisobutyronitrile.

[0018] (3) In the method of the present invention, the phosphorylation fluorination reagent prepared 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

[0019] In a 500 mL stainless steel grinding jar, 60 g of stainless steel balls, 10 g of fluorite, and 20 g of K2HPO4 were added. The jar was then closed and securely mounted in a ball mill, and ground at 1000 rpm for 0.5 h to obtain phosphorylation-fluorination reagent A.

[0020] Under nitrogen purge protection, 10 g of isobutyronitrile, 10 g of phosphorylation-fluorination reagent A, 10 g of 18-crown ether-6, and 30 g of acetonitrile were added to a 500 mL dry autoclave and reacted at 100°C under 0.1 MPa for 5 hours. After completion of the reaction, the mixture was cooled to room temperature to obtain crude heptafluoroisobutyronitrile. Chromatographic analysis of the crude heptafluoroisobutyronitrile revealed a conversion of 98.4% for C4 nitrile compounds and a selectivity of 99.3% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile. Example 2

[0021] In a 500 mL stainless steel grinding jar, 50 g of stainless steel balls, 20 g of fluorite, and 20 g of K 3 PO 4 were added. The jar was then closed and securely mounted in a ball mill, and the mixture was ground at 1050 rpm for 0.6 h to obtain phosphorylation-fluorination reagent B.

[0022] Under argon replacement, a 500 mL dry autoclave was charged with 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. The reaction was allowed to proceed at 90°C under 0.2 MPa for 6 hours. After completion, the reaction was cooled to room temperature to obtain crude heptafluoroisobutyronitrile. Chromatographic analysis of the crude heptafluoroisobutyronitrile revealed a conversion of 99.1% for C4 nitrile compounds and a selectivity of 98.5% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile. Example 3

[0023] In a 500 mL stainless steel grinding jar, 180 g of stainless steel balls, 20 g of fluorite, and 40 g of Na2HPO4 were added. The jar was then closed and securely mounted in a ball mill, and the mixture was ground at 1100 rpm for 0.7 hours to obtain phosphorylation-fluorination reagent C.

[0024] Under nitrogen purge protection, a 500 mL dry autoclave was charged with 10 g of 2-bromo-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 30 g of phosphorylation-fluorination reagent C, 20 g of 2,4-crown ether-8, and 120 g of dichloroethane. The mixture was sealed and reacted at 80°C under 0.3 MPa for 7 hours. After completion, the reaction was cooled to room temperature to obtain crude heptafluoroisobutyronitrile. Chromatographic analysis of the crude heptafluoroisobutyronitrile revealed a conversion of 98.6% for C4 nitrile compounds and a selectivity of 99.1% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile. Example 4

[0025] In a 500 mL stainless steel grinding jar, 50 g of stainless steel balls, 10 g of fluorite, and 10 g of Na 3 PO 4 were added. The jar was then closed and securely mounted in a ball mill, and ground at 1150 rpm for 0.8 h to obtain phosphorylation-fluorination reagent D.

[0026] Under argon replacement, a 500 mL dry autoclave was charged with 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. The mixture was allowed to react at 110°C and 0.2 MPa for 8 hours. After completion, the reaction was cooled to room temperature to obtain crude heptafluoroisobutyronitrile. Chromatographic analysis of the crude heptafluoroisobutyronitrile revealed a conversion of 98.3% for C4 nitrile compounds and a selectivity of 97.5% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile. Example 5

[0027] A 500 mL stainless steel grinding jar was charged with 90 g of stainless steel balls, 20 g of fluorite, 20 g of Na₃PO₄, and 10 g of K₃PO₄. The jar was then closed and securely mounted in a ball mill. The mixture was ground at 1100 rpm for 0.9 hours to obtain phosphorylation-fluorination reagent E.

[0028] Under nitrogen purge protection, a 500 mL dry autoclave was charged with 5 g of isobutyronitrile, 5 g of 3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 20 g of phosphorylation fluorination reagent E, 10 g of 12-crown ether-4, and 80 g of acetonitrile. The mixture was reacted in a sealed container at 120°C and 0.1 MPa for 9 hours. After completion, the reaction was cooled to room temperature to obtain crude heptafluoroisobutyronitrile. Chromatographic analysis of the crude heptafluoroisobutyronitrile revealed a conversion of 96.5% for C4 nitrile compounds and a selectivity of 99.0% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile. Example 6

[0029] In a 500 mL stainless steel grinding jar, 90 g of stainless steel balls, 30 g of fluorite, 20 g of K2HPO4, and 20 g of K3PO4 were added. The jar was then closed and securely mounted in a ball mill, and ground at 1100 rpm for 1 hour to obtain the phosphorylation-fluorination reagent F.

[0030] Under nitrogen purge protection, a 500 mL dry autoclave was charged with 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. The reaction was allowed to proceed at 120°C under 0.1 MPa for 9 hours in a sealed container. After completion, the reaction was cooled to room temperature to obtain crude heptafluoroisobutyronitrile. Chromatographic analysis of the crude heptafluoroisobutyronitrile revealed a conversion of 97.7% for C4 nitrile compounds and a selectivity of 98.6% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile. Example 7

[0031] In a 500 mL stainless steel grinding jar, 60 g of stainless steel balls, 20 g of fluorite, 20 g of Na2HPO4, and 20 g of K3PO4 were added. The jar was then closed and securely mounted in a ball mill. The mixture was ground at 1200 rpm for 0.7 hours to obtain phosphorylation-fluorination reagent G.

[0032] Under nitrogen purge protection, a 500 mL dry autoclave was charged with 5 g of isobutyronitrile, 5 g of 2-chloro-3,3,3-trifluoro-2-(trifluoromethyl)propionitrile, 15 g of phosphorylating fluorination reagent G, 10 g of 15-crown ether-5, and 90 g of acetonitrile. The mixture was allowed to react at 120°C under 0.1 MPa for 10 hours in a sealed container. After completion, the reaction was cooled to room temperature to obtain crude heptafluoroisobutyronitrile. Chromatographic analysis of the crude heptafluoroisobutyronitrile revealed a conversion of 98.6% for C4 nitrile compounds and a selectivity of 97.4% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile. Example 8

[0033] Under argon replacement protection, 10 g of isobutyronitrile, 10 g of phosphorylation-fluorination reagent A, 5 g of phosphorylation-fluorination reagent C, 10 g of 2,4-crown ether-8, and 90 g of dichloromethane were added to a 500 mL dry autoclave and reacted in a sealed chamber at 110°C and 0.2 MPa for 10 hours. After completion of the reaction, the mixture was cooled to room temperature to obtain a crude product of heptafluoroisobutyronitrile. Chromatographic analysis of the crude product revealed a conversion of 98.3% for C4 nitrile compounds and a selectivity of 98.9% for heptafluoroisobutyronitrile. The supernatant was purified to obtain heptafluoroisobutyronitrile.

[0034] The composition of heptafluoroisobutyronitrile prepared in Example was analyzed by gas chromatography

[0035] With reference to the calculation formula of CN117550950A, the conversion rate of C4 nitrile compounds and the selectivity of heptafluoroisobutyronitrile involved in each embodiment of the present invention are analyzed and calculated as follows:

[0036]

[0037] The analysis results are shown in Table 1

[0038]

[0039] 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. Fluorite reacts with phosphate and is 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, which can act as a nucleophilic reagent to attract other molecules or ions in the reaction, and then react with nitriles to produce heptafluoroisobutyronitrile by fluorination. The prepared phosphorylated fluorination reagent shows excellent performance in the process of preparing heptafluoroisobutyronitrile using C4 nitrile compounds as raw materials. When the reaction temperature is 80-120°C, the pressure is 0.1-0.3Mpa, and the reaction time is 5-10h, the selectivity of the obtained phosphorylated fluorination reagent for producing heptafluoroisobutyronitrile is improved to 97.4-99.3%, and the yield reaches The reaction temperature can reach 95.5-97.7%, the reaction conditions are mild, and the yield of heptafluoroisobutyronitrile is high. This is mainly because the phosphate group in the phosphorylation fluorination reagent used has a high electrophilic ability, which weakens the electrophilic ability of the fluorine atom. During the fluorination reaction, the fluorine atom in the phosphorylation fluorination reagent is more likely to form a fluorine free radical. During the fluorination reaction, after contacting with the C4 nitrile compound reactant, the fluorine free radical efficiently and directionally replaces other atoms or atomic groups on the carbon atom, so that the phosphorylation fluorination reagent has excellent fluorine supply performance, and the selectivity and yield of the obtained heptafluoroisobutyronitrile are high. At the same time, the phosphorylation fluorination reagent is a nucleophilic fluorination reagent. Compared with the hydrogen fluoride electrophilic fluorination reagent, the phosphorylation fluorination reagent can generate fluorine free radicals at a lower temperature under the strong electron attraction of the phosphate group, thereby showing a lower reaction temperature.

Claims

1. A method for preparing heptafluoroisobutyronitrile, characterized in that: The following steps are involved: ball-milling fluorite and phosphate to prepare a phosphorylation-fluorination reagent; mixing the phosphorylation-fluorination reagent with a C4 nitrile compound, a crown ether phase transfer catalyst, and a polar organic solvent, and conducting a fluorination reaction under an inert atmosphere to obtain a heptafluoroisobutyronitrile suspension; and purifying the suspension to obtain heptafluoroisobutyronitrile; 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; 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; 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; The inert gas is nitrogen or argon; the mass ratio of the polar organic solvent, C4 nitrile compound, phosphorylation fluorination reagent and 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.

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

3. The method for preparing heptafluoroisobutyronitrile according to claim 1, wherein The polar organic solvent is one of dichloromethane, acetonitrile, dimethyl sulfoxide and dichloroethane.

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