A method for selectively synthesizing highly active hexafluoropropylene dimer

Abstract

The present invention proposes a method for preparing a selectively synthesized highly active hexafluoropropylene dimer, characterized in that the steps are followed, a catalyst is dispersed in an organic solvent to form a saturated catalyst-solvent mixed solution, 50 to 100 parts of the catalyst-solvent mixed solution are taken into an autoclave, and 0.5 to 2 parts of the composite catalyst and 0.25 to 1 parts of the co-catalyst are simultaneously taken into the autoclave; 20°C cooling, then vacuuming, and after replacing with high-purity nitrogen 2 to 3 times, stirring and mixing uniformly, the temperature is controlled at 80 to 150°C, and then hexafluoropropylene gas is slowly and continuously introduced, the stirring reaction is 2 to 4 hours, cooled to room temperature, the excess hexafluoropropylene gas is discharged, the lower layer solution is obtained by liquid separation, washed with water and an organic alcohol reagent, and the highly active hexafluoropropylene dimer is obtained by distillation. The present application has a higher yield and a higher product purity.

Description

Technical Field

[0001] The invention relates to a preparation method for selectively synthesizing a high-activity hexafluoropropylene dimer. Background Art

[0002] Hexafluoropropylene dimer is an important fluorine-containing fine chemical product. It has two structures, D1 cis-trans isomers and D2. D1 is stable and has low toxicity, and can be directly used as a solvent, cleaning agent, and foaming agent; D2 has certain toxicity, but the double bond is more active, and can be used for further reactions to obtain fluorine-containing surfactants, foaming agents, and demolding agents.

[0003] Hexafluoropropylene dimer is obtained by polymerization of hexafluoropropylene (HFP), and the synthesis method includes gas phase and liquid phase. As the name implies, the gas phase method for synthesizing hexafluoropropylene dimer is a gas-solid reaction, and there is no solvent involved in the whole process. Its characteristics are: high reaction temperature (250℃~600℃) (Geula D et al., J Phys Chem. 49(1993), simple post-treatment, and no problem of catalyst recovery and reuse; the liquid phase polymerization hexafluoropropylene dimer process refers to polymerization under the action of polar aprotic solute neutralizing catalyst metal fluoride, auxiliary organic amine, etc. (John Brehm et al., US: 2918501). Compared with the gas phase method, the liquid phase method has high yield and single conversion rate, low reaction control requirements, low reaction temperature (30~150℃), and low equipment cost. Therefore, the present invention studies the liquid phase polymerization process.

[0004] Patent A highly reactive D2 structure hexafluoropropylene dimer Patent No. CN 111056914A discloses that according to the mass fraction, 0.01-0.15 parts of polymerization catalyst, 0.01-0.1 parts of structural isomerization aid and 50-70 parts of organic solvent are added to the reactor, stirred and mixed evenly, and then argon is bubbled for 5-10 minutes, and then vacuumed, argon is filled and circulated for 3 times, and 15-28 parts of hexafluoropropylene are filled under vacuum conditions, the temperature is controlled at 30-45°C, and the reaction is stirred for 2-8 hours. After the reaction is completed, the temperature is lowered to 5-10°C, and then the residual hexafluoropropylene gas is discharged, and the lower layer of liquid is obtained by separation and added to the high-pressure reactor, and 0.02-0.12 parts of metal fluoride and 0.05-0 .5 parts of structural isomerization aid, heated to 60-80°C under nitrogen protection, reacted for 40-60 minutes, cooled to room temperature after the reaction was completed, and the catalyst was separated to obtain the highly reactive D2 structure hexafluoropropylene dimer. It is a two-step process, the first step is a polymerization reaction, and the second step is an isomerization reaction, which results in a long reaction time, and both steps require manual operation, which increases the waste of manpower and material resources.

[0005] Currently, there is no one-step method for preparing D2 structure hexafluoropropylene dimer, and this method will not affect the yield and purity of D2 structure hexafluoropropylene dimer and reduce the content of hexafluoropropylene trimer. Summary of the invention

[0006] The invention provides a preparation method for selectively synthesizing a high-activity hexafluoropropylene dimer, and solves the technical problem of improving the yield and purity of the hexafluoropropylene dimer and reducing the content of the hexafluoropropylene trimer.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for selectively synthesizing a highly active hexafluoropropylene dimer is carried out according to the following steps:

[0009] dispersing the catalyst in an organic solvent to obtain a saturated catalyst-solvent mixed solution;

[0010] Take 50-100 parts of a saturated catalyst-solvent mixed solution into a high-pressure reactor, add 0.25-1 parts of an isomerization aid and 0.25-1 parts of a co-catalyst, cool to -20°C, evacuate to a pressure of -0.1Mpa, introduce nitrogen, replace 3 times, start stirring, introduce hexafluoropropylene gas at a temperature of 70-90°C, maintain the pressure between 0.35 and 0.54Mpa, stir and react at a temperature of 70-120°C for 4-8h, cool to room temperature, discharge excess hexafluoropropylene gas, separate to obtain a lower layer solution, wash with water to remove residual catalyst and salts, wash with an organic alcohol to remove residual organic solvent, and distill to obtain a highly active hexafluoropropylene dimer;

[0011] The catalyst is an alkali metal fluoride;

[0012] The organic solvent is one or more of N-methylpyrrolidone, tetrahydrofuran, ethylene glycol dimethyl ether, cyclopentane, dimethyl sulfoxide, acetonitrile and N,N-dimethylacetamide;

[0013] The isomerization aid is one or more of halogen, halide, metal and acid oxide;

[0014] The co-catalyst is one or more of ammonium salt, alkylamine, thiocyanate, crown ether and polyethylene glycol;

[0015] The organic alcohol is one or more of methanol, propanol, cyclohexanol and isopropanol;

[0016] The distillation temperature is 85-120°C;

[0017] The isomerization aid is prepared according to the following steps:

[0018] Adding catalyst 1 to a carrier, adding solvent 1, loading catalyst 1 on the carrier, and drying to obtain an isomerization catalyst;

[0019] The isomerization catalyst is evenly distributed in the solvent 2 to obtain an isomerization aid;

[0020] The carrier is one or more of molecular sieve, alumina and graphene;

[0021] The catalyst 1 is one or more of halogen, halide, metal and acid oxide;

[0022] The solvent 1 is one or more of methanol, ethanol, deionized water, DMF and ethylene glycol diethyl ether;

[0023] The solvent 2 is one or more of ethanol, naphthol solution and ether;

[0024] The volume ratio of the ethanol to the naphthol solution=36:1.

[0025] The alkali metal fluoride includes one or more of potassium fluoride, rubidium fluoride, cesium fluoride and sodium fluoride;

[0026] The halogen is one or both of Br- and Cl-;

[0027] The halide is one or both of carbon tetrachloride and sulfur hexafluoride;

[0028] The metal is one or more of Fe, Ni, Pt and Co;

[0029] The co-catalyst is polyethylene glycol.

[0030] The loading method is one or more of hydrothermal, ball milling and electrodeposition.

[0031] The invention has the following beneficial technical effects:

[0032] 1. The one-step synthesis method is adopted to simplify the process, making the reaction more operable and suitable for further expansion of scale production.

[0033] 2. The composite multifunctional isomerization reagent is added together with the catalyst to participate in the polymerization reaction; the composite multifunctional isomerization reagent has strong stability and can be reused, and can selectively synthesize hexafluoropropylene dimer (D2) while inhibiting over-polymerization. The yield is higher and the product purity is higher.

[0034] 3. The dosage of the catalyst is to disperse the metal fluoride in the solvent to form a saturated solution. Since metal fluorides are difficult to dissolve in low-polarity aprotic solvents (for example, at room temperature, 100 ml of acetonitrile only dissolves 0.0036 g of potassium fluoride (see Solubility, Fourth Edition, Volume II, Pages 79 and 209, American Chemical Society, Washington, DC (1965)), this method saves process steps, saves catalysts, and reduces costs.

[0035] 4. The obtained product is insoluble in the solvent, and the hexafluoropropylene dimer (D2) is in the lower layer of the mixed solution. After simple separation, water washing and distillation, the hexafluoropropylene dimer (D2) with a purity greater than 99% can be obtained.

[0036] 5. This application does not contain hexafluoropropylene trimer after purification. If the product contains hexafluoropropylene trimer: In practical applications (such as as a drug intermediate to synthesize drugs), hexafluoropropylene trimer is prone to form competitive reactions, increase by-products, and reduce yields. In the field of liquid cooling, if hexafluoropropylene trimer is contained, it will be miscible with dimer, thereby affecting the boiling point, resulting in inaccurate thermal management calculations and reduced heat dissipation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The gas phase spectrum data of the hexafluoropropylene dimer of structure D2 in Example 2; DETAILED DESCRIPTION

[0038] The present invention is further described below with reference to specific examples.

[0039] Example 1

[0040] KF was added to the acetonitrile solution until saturated, 5L was taken and put into the reactor, 15g of isomerization aid and 10g of polyethylene glycol were added, and the solution was evacuated to -0.1Mpa after cooling, and replaced with N2 for 3 times to ensure an oxygen-free environment in the reactor. Then, the solution was stirred and heated to 85°C, and hexafluoropropylene gas was slowly introduced and the pressure was controlled to 0.38 MPa. After reacting for 6h, the solution was cooled to room temperature and the lower layer of light yellow solution was separated. The solution was washed with pure water to remove excess catalyst and salts. The solution was washed with ethanol for 3 times to remove residual organic reagents. Finally, the pure product was distilled at 85°C with a yield of 89.7% (mass after purification / total HFP input). The content of D2 configuration of hexafluoropropylene dimer and D1 configuration of hexafluoropropylene trimer was 99.2% and 0.8% respectively according to gas chromatography.

[0041] Add 50 ml of N,N-dimethylformamide, 0.8 g of aluminum oxide and 2.8 g of cobalt oxide into a beaker and disperse them by ultrasonic machine for 30 minutes; then transfer to a 250 ml tetrafluoroethylene-lined reactor, hydroheat at 120°C for 12 hours, wash the lower layer of solid product with water, centrifuge for 2 to 3 times; dry in a vacuum drying oven for 12 hours (60°C) to obtain an isomerization catalyst;

[0042] Before use, 1 g of the isomerization catalyst was dispersed in an ethanol and naphthol solution (ethanol and naphthol volume ratio = 36:1) to obtain an isomerization aid.

[0043] Example 2

[0044] NaF was added to the DMA solution until saturated, 5L was taken and put into the reactor, 18g of isomerization aid and 6g of tetramethylethylenediamine were added, and the solution was evacuated to -0.1Mpa after cooling, and replaced with N2 for 3 times to ensure an oxygen-free environment in the reactor. Then, the solution was stirred and heated to 70°C, and hexafluoropropylene gas was slowly introduced and the pressure was controlled to 0.35 MPa. After reacting for 5h, the solution was cooled to room temperature and the lower layer of light yellow solution was separated. The solution was washed with pure water to remove excess catalyst and salts. The solution was washed with ethanol for 3 times to remove residual organic reagents. The pure product was distilled to obtain a yield of 86.9% (mass after purification / total HFP input). The content of hexafluoropropylene dimer D2 and the content of D1 configuration were 99.3% and 0.7% respectively according to gas chromatography. There was no hexafluoropropylene trimer.

[0045] Add 50 ml of methanol into a beaker, add 0.5 g of graphene and 2.32 g of nickel nitrate, and disperse them in an ultrasonic machine for 30 minutes; then transfer to a 250 ml tetrafluoroethylene-lined reactor and seal it; then place the reactor in an oven and hydroheat it at 80°C for 16 hours, wash the lower layer of solid product with water, and centrifuge it 2 to 3 times; dry it in a vacuum drying oven for 12 hours (60°C) to obtain an isomerization catalyst;

[0046] Before use, disperse 1 g of the dried isomerization catalyst in 50 ml of ether to obtain an isomerization aid.

[0047] Comparative Example 1 (except that the reaction temperature was 100° C., other preparation conditions were consistent with Example 1), the final product yield was 85.7%; gas chromatography analysis showed that the dimer D2 configuration was 65%, the D1 configuration was 32%, and the trimer content was 3%.

[0048] Comparative Example 2 (except that the reaction temperature was 120° C., other preparation conditions were consistent with Example 1), the product yield was 89%, and gas chromatography analysis showed that the dimer D2 configuration was 63%, the D1 configuration was 25%; the trimer content was 12%.

[0049] The final product yield of Comparative Example 3 (except for the reaction temperature of 65° C., all other preparation conditions were consistent with Example 1) was 92%. Gas chromatography analysis showed that the D2 configuration of the dimer was 85.8%, and the D1 configuration was 14.2%.

[0050]

Claims

1. A method for selectively synthesizing a highly active hexafluoropropylene dimer, characterized in that: Follow the steps below, dispersing the catalyst in an organic solvent to obtain a saturated catalyst-solvent mixed solution; Take 50-100 parts of a saturated catalyst-solvent mixed solution into a high-pressure reactor, add 0.25-1 parts of an isomerization aid and 0.25-1 parts of a co-catalyst, cool to -20°C, evacuate to a pressure of -0.1Mpa, introduce nitrogen, replace 3 times, start stirring, introduce hexafluoropropylene gas at a temperature of 70-90°C, maintain the pressure between 0.35 and 0.54Mpa, stir and react at a temperature of 70-120°C for 4-8h, cool to room temperature, discharge excess hexafluoropropylene gas, separate to obtain a lower layer solution, wash with water to remove residual catalyst and salts, wash with an organic alcohol to remove residual organic solvent, and distill to obtain a highly active hexafluoropropylene dimer; The catalyst is an alkali metal fluoride; The organic solvent is one or more of N-methylpyrrolidone, tetrahydrofuran, ethylene glycol dimethyl ether, cyclopentane, dimethyl sulfoxide, acetonitrile and N,N-dimethylacetamide; The isomerization aid is one or more of halogen, halide, metal and acid oxide; The co-catalyst is one or more of ammonium salt, alkylamine, thiocyanate, crown ether and polyethylene glycol; The organic alcohol is one or more of methanol, propanol, cyclohexanol and isopropanol; The distillation temperature is 85-120°C; The isomerization aid is prepared according to the following steps: Adding catalyst 1 to a carrier, adding solvent 1, loading catalyst 1 on the carrier, and drying to obtain an isomerization catalyst; The isomerization catalyst is evenly distributed in the solvent 2 to obtain an isomerization aid; The carrier is one or more of molecular sieve, alumina and graphene; The catalyst 1 is one or more of halogen, halide, metal and acid oxide; The solvent 1 is one or more of methanol, ethanol, deionized water, DMF and ethylene glycol diethyl ether; The solvent 2 is one or more of ethanol, naphthol solution and ether; The volume ratio of the ethanol to the naphthol solution=36:

1.

2. A method for selectively synthesizing highly active hexafluoropropylene dimer as claimed in claim 1, characterized in that: The alkali metal fluoride includes one or more of potassium fluoride, rubidium fluoride, cesium fluoride and sodium fluoride; The halogen is one or both of Br- and Cl-; The halide is one or both of carbon tetrachloride and sulfur hexafluoride; The metal is one or more of Fe, Ni, Pt and Co; The co-catalyst is polyethylene glycol.

3. A method for selectively synthesizing highly active hexafluoropropylene dimer as claimed in claim 1, characterized in that: The loading method is one or more of hydrothermal, ball milling and electrodeposition.

Images