Preparation method of fluorinated alkene ether

Abstract

The invention discloses a preparation method of fluorinated alkene ether, which comprises the following steps: replacing alkene CFCl = CFCl in a 1, 2-difluorodichloroethylene method with hydrogen-containing fluorinated alkene CFH = CFX, carrying out fluorination reaction on the fluorinated alkene CFH = CFX, fluorine gas and fluorinated acyl fluoride (RCOF) under the action of a catalyst, and directly generating an intermediate (namely a fluorinated ether isomer mixture comprising RCF2OCFHCF2X and an isomer thereof RCF2OCFXCF2H) in one step, the intermediate continues to be subjected to a dehydrohalogenation reaction with alkali, and the product fluorinated alkene ether (RCF2OCF = CF2) is obtained. According to the method, synthesis, use and storage of an unstable intermediate, namely, hypofluoro acid ester RCF2OF with strong oxidation and high explosion risk can be effectively avoided, meanwhile, decomposition caused in the reaction process of special unstable raw material acyl fluoride such as ROCOF and fluorine gas can be reduced, and the safety is effectively improved; the problems of heavy metal use and pollution caused by a zinc powder dehalogenation process in a 1, 2-difluorodichloroethylene method are solved; the method has the advantages of short process flow, mild reaction conditions, environmental protection, high product purity and the like.

Description

Technical Field

[0001] This invention relates to the field of fluorinated chemical technology, specifically to a method for preparing fluorinated alkenyl ethers. Background Technology

[0002] Fluorinated alkenyl ethers, especially perfluoroalkenyl ethers (general formula ROCF=CF2, where R is a perfluoroalkyl group or a fluoroalkyl or perfluoroalkyl group containing heteroatoms such as O, N, and S), are important functional monomers for fluororubber. They can reduce the crystallinity of fluororubber, and the synthesized fluororubber exhibits excellent thermoplastic processing properties and low-temperature resistance. The main synthetic methods for fluoroalkenyl ethers are the hexafluoropropane oxide method and the 1,2-difluorodichloroethylene method.

[0003] The hexafluoropropane process involves the addition and decarboxylation of fluoroacyl fluoride with hexafluoropropane to obtain fluoroolefin ethers. Chinese patent document CN101817728A discloses a method for producing hexafluoropropane and co-producing perfluorovinyl ethers, including a reaction of hexafluoropropylene oxidation to synthesize hexafluoropropane. The resulting mixed gas is sent to a crude separator, and the separated heavy components are purified by distillation to obtain hexafluoropropane. The separated light components enter a distillation column to remove non-condensable gases, yielding a mixed gas of carbonyl fluoride and perfluoroacetyl fluoride. This gas is then passed through hexafluoropropane for polymerization to obtain a corresponding perfluoropolyether mixture. After cracking in the presence of sodium carbonate at 150-300 °C, a mixture of perfluorovinyl ethers is obtained, which is then separated by a distillation column to obtain PMVE, PEVE, and PPVE. Patent document US3291843A discloses a method for preparing R by pyrolysis of perfluorocarboxylic acid metal salts. f The OCF=CF2 method: In a polar solvent, the addition product R of fluoroacyl fluoride and epoxy hexafluoropropane. f OCF(CF3)COF reacts with alkali metal salts of Group IA and IIA elements to form metal salts R. f OCF(CF3)COOM, this metal salt is further heated to remove the acyl fluoride group to generate fluorinated vinyl ether R. f OCF=CF2.

[0004] The 1,2-difluorodichloroethylene process involves the reaction of acyl fluoride with fluorine gas and 1,2-difluorodichloroethylene to generate the addition product R. f OCFClCF2Cl, addition product R f OCFCl and CF2Cl react with zinc powder in a polar solvent to produce fluoroalkenyl ether R. fOCF=CF2. Chinese patent document CN114656338A describes the reaction of pentafluoropropionyl fluoride with a fluorine-nitrogen mixture under alkali metal fluoride catalysis to obtain hypofluoroester CF3CF2CF2OF. CF3CF2CF2OF then undergoes addition with 1,2-difluorodichloroethylene to yield a haloether CF3CF2CF2OCFClCF2Cl. The haloether CF3CF2CF2OCFClCF2Cl is then dechlorinated with zinc powder in an organic solvent to generate a fluoroalkenyl ether CF3CF2CF2OCF=CF2.

[0005] The hexafluoropropane oxide process requires a high-temperature decarboxylation step, which easily generates the hydrogen fluoride addition byproduct R of fluoroolefin ethers. f OCFHCF3, hydrogen-containing byproduct R f OCFHCF3 is prone to chain transfer reactions during polymerization, affecting polymer properties. Furthermore, during the oxidation of hexafluoropropylene to prepare the raw material hexafluoropropane oxide, unreacted hexafluoropropylene, byproduct trifluoroacetyl fluoride, hexafluoroacetone, and other impurities also affect the purity of fluoroolefin ethers, making it difficult to obtain high-purity fluoroolefin ether monomers that meet polymerization requirements. The 1,2-difluorodichloroethylene method uses heavy metal zinc for dechlorination, and the resulting byproduct zinc chloride readily forms complexes with solvents such as N,N-dimethylformamide, making treatment difficult and causing environmental pollution.

[0006] In addition, Chinese patent document CN115246766A discloses a method for treating fluorinated tail gas in a perfluoropolyether synthesis process, mainly including: reacting the fluorinated tail gas with fluorine gas to obtain intermediate B, reacting intermediate B with 1,2-difluoro-1,2-dichloroethylene to obtain intermediate C, and reacting intermediate C with zinc to obtain the product, as shown in the following reaction formula: .

[0007] Chinese patent document CN114174250A discloses a process for producing perfluoromethyl vinyl ethers by using addition and elimination reactions of CF3OF with trifluoroethylene or trichloroethylene in a liquid phase reaction in a microreactor, followed by fluorination with anhydrous hydrogen fluoride under Lewis acid catalysis. This process involves the initial addition reaction of CF3OF with trifluoroethylene or trichloroethylene to generate fluoroethers CF3OCFHCF3F and CF3OCF2CF2H. The defluorination reaction of these fluoroethers requires harsh conditions and has a low yield. Using trichloroethylene requires further fluorination to generate CF3OCF2=CF2, resulting in a lengthy process. Furthermore, the process involves the prior preparation of highly oxidizing and explosive unstable hypofluoroester CF3OF using carbonyl fluoride and fluorine gas. Hypofluoroester CF3OF poses significant safety risks in its production, use, and storage. Therefore, this process is lengthy and carries high safety risks. Additionally, the process involves easily decomposable fluorocarbonate raw material R... f OCOF is especially unsuitable for this purpose.

[0008] Therefore, in order to solve the problems of difficult separation of high-temperature decarboxylation side reactions, heavy metal use and pollution in the existing fluoroolefin synthesis methods such as the hexafluoropropane oxide method and the 1,2-difluorodichloroethylene method, it is urgent to find a new method for the preparation of fluoroolefins. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention provides a method for preparing fluoroolefin ethers, which employs halogen and metal halide catalysts and alkalis to carry out fluorination and dehydrohalogenation reactions, respectively, thereby improving reaction yield and reducing the formation of byproducts.

[0010] A method for preparing a fluoroalkenyl ether includes the following steps: (1) Add RCOF, catalyst, and CFH=CFX to the reactor, and introduce fluorine gas to carry out the fluorination reaction. After the reaction is completed, wash and distill the reaction solution to obtain a mixture of fluorinated ether isomers. (2) The mixture of fluorinated ether isomers obtained in step (1) is subjected to dehydrohalogenation reaction with alkali. After the reaction is completed, it is purified by distillation to obtain fluorinated alkenyl ether.

[0011] In this invention, a hydrogen-containing fluoroolefin CFH=CFX is used to replace the olefin CFCl=CFCl in the 1,2-difluorodichloroethylene method. Under the action of a catalyst, the fluoroolefin (CFH=CFX) undergoes a fluorination reaction with fluorine gas and fluoroacyl fluoride (RCOF) to directly generate an intermediate (i.e., a mixture of fluoroether isomers, including RCF2OCFHCF2X and its isomer RCF2OCFXCF2H). The intermediate is then further reacted with a base to undergo dehydrohalogenation to obtain the product fluoroolefin ether (RCF2OCF=CF2).

[0012] This invention can effectively avoid the synthesis, use, and storage of the unstable intermediate hypofluoroester RCF2OF, which has strong oxidizing and high explosion risks. At the same time, it can reduce the decomposition caused by the reaction of special unstable raw material acyl fluoride such as ROCOF with fluorine gas, thus effectively improving safety. It also solves the problems of zinc in the 1,2-difluorodichloroethylene method, and has the advantages of being green, environmentally friendly, and producing high-purity products.

[0013] Preferably, in step (1), in the RCOF, R is selected from F, halogen-substituted C1~C6 alkyl groups, and halogen-substituted C1~C6 heteroalkyl groups; the main chain of the heteroalkyl group has heteroatoms, wherein the heteroatoms are O, S or N.

[0014] More preferably, R is selected from CF3, CF2Cl, CF2Br, C2F5, C3F7, C4F9, and C5F. 11 C6F 13 One of CF3O, C2F5O, CF3OCF2, CF3OCF2O, (CF3)2N, (CF3)2N CF2, SF5, and perfluorocyclohexyl.

[0015] Preferably, in step (1), X in CFH=CFX is a halogen, specifically F, Cl or Br.

[0016] Preferably, in step (1), the catalyst is a halogen element or an alkali metal halide.

[0017] In this invention, the halogen element can be chlorine, bromine, or iodine, and the alkali metal halide can be cesium fluoride, potassium fluoride, sodium fluoride, cesium chloride, potassium chloride, sodium chloride, cesium bromide, potassium bromide, sodium bromide, cesium iodide, potassium iodide, or sodium iodide.

[0018] The fluorination reaction utilizes halogen elements and metal halide catalysts, which reduces the byproduct of the reaction between fluorine gas and fluorinated olefins (CFH=CFX) to form fluorinated alkanes (CF2HCF2X), thus improving the reaction yield. Halogen elements act as negative catalysts, slowing down the reaction rate. The highly reactive fluorine gas reacts with halogen elements to first form less reactive fluorohalides, which then proceed to the next reaction. This effectively reduces side reactions such as olefin addition, dimerization and polymerization, and hydrogen substitution caused by highly reactive fluorine gas, improving reaction selectivity and yield. Metal halides (MX) react with fluorine gas to form fluorohalides (MF). MF acts as a base, reacting with acyl fluoride (RCOF) to form RCF2OM. RCF2OM then reacts with fluorohalides to form RCF2OX, which is beneficial for the reaction.

[0019] Preferably, in step (1), the fluorine content in the introduced fluorine gas is 10~100 wt%.

[0020] Preferably, in step (1), the molar ratio of RCOF, fluorine gas, catalyst, and CFH=CFX is 0.5~2:0.5~3:0.05~0.2:1.

[0021] Preferably, in step (1), the fluorination reaction is carried out at a temperature of -120 to -40 °C, a pressure of 0 to 0.8 MPa, and a time of 2 to 8 h.

[0022] Preferably, in step (1), solvent I is added to the fluorination reaction, and solvent I is one of haloalkanes, hydrofluoroethers, perfluoropolyethers, perfluorocyclic ethers, and perfluoroamines.

[0023] In this invention, the fluorination reaction can be carried out under solvent-free conditions or in a solvent. Solvent I can be pentafluorochloroethane, HFE-254, HFE-347, HFE-6512, HFE-7100, HFE-7500, perfluorotripropylamine, perfluorotributylamine, perfluoropolyether, etc.

[0024] Preferably, in step (2), the alkali is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, triethylamine, tributylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]non-5-ene (DBN), and N,N,N,N-tetramethylethylenediamine.

[0025] In this invention, the alkali can be added in the form of an aqueous solution or in the form of a pure substance.

[0026] Preferably, in step (2), the molar ratio of the fluoroether isomer mixture to the base is 1:1~3.

[0027] Preferably, in step (2), the dehydrohalogenation reaction further includes solvent II, which is one or more of N,N-dimethylformamide (DMF), N,N-dimethylacetamide, dimethyl sulfoxide (DMSO), sulfolane, N-methylpyrrolidone, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether (DG), tetraethylene glycol dimethyl ether (TG), dioxane, propylene glycol dimethyl ether, methyltetrahydrofuran, and tetrahydrofuran.

[0028] More preferably, the mass ratio of solvent II to alkali is 2~10:1.

[0029] Preferably, in step (2), the temperature of the dehydrohalogenation reaction is 60~150 °C and the time is 2~10 h.

[0030] In this invention, the fluoroether isomer mixture can be added in a single step or by dripping.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Using halogen and metal halide catalysts can reduce the byproducts of the reaction between fluorine gas and fluorinated olefins CFH=CFX to generate fluorinated alkanes CF2HCF2X, thereby increasing the reaction yield. (2) The olefin CFH=CFX is directly reacted with fluorine gas and fluorinated acyl fluoride RCOF in a one-step process to generate intermediate fluorinated ether. This can effectively avoid the synthesis, use and storage of unstable intermediate hypofluoride ester RCF2OF with strong oxidation and high explosion risk. At the same time, it can reduce the decomposition caused by special unstable raw material acyl fluoride such as ROCOF during the reaction with fluorine gas, and effectively improve safety. (3) It solves the problem of heavy metal use and pollution caused by zinc powder dehalogenation process in the 1,2-difluorodichloroethylene method; it has the advantages of short process flow, mild reaction conditions, green and environmentally friendly, and high product purity. Attached Figure Description

[0032] Figure 1 The mass spectrum of the fluoroalkenyl ether CF3OCF=CF2 in Example 1 is shown.

[0033] Figure 2 The mass spectrum of fluoroalkenyl ether CF3OCF2OCF=CF2 is shown in Example 2.

[0034] Figure 3 The mass spectrum of fluoroalkenyl ether CF3CF2OCF=CF2 in Example 3 is shown. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the embodiments, but the implementation of the present invention is not limited to the following embodiments.

[0036] All raw materials used in this invention are commercially available.

[0037] Example 1 (1) Synthesis of a mixture of fluoroether isomers In a 1 L pressure reactor, 7.6 g (0.05 mol) of cesium fluoride and 400 g of pentafluoroethane were added and stirred. The mixture was then cooled to -100 °C using a liquid nitrogen ethanol bath. 49.3 g (0.5 mol) of 1,2-difluorochloroethylene (CFCl=CFH) and 49.5 g (0.75 mol) of carbonyl fluoride (COF2) were added. After the carbonyl fluoride was added, 142.5 g (0.75 mol) of a fluorine-nitrogen mixture with a fluorine concentration of 20% was introduced over 5 h (equivalent to 28.5 g of pure fluorine gas; subsequent examples will use the amount of pure fluorine gas). When the reactor pressure reached 0.6 MPa, the opening of the reactor tail gas outlet valve was adjusted to maintain the reactor pressure at 0.6 MPa. After the fluorine gas was added, the mixture was kept at -100 °C for 1 h. The reactor was then vented and the reaction liquid was distilled to obtain 77 g (0.38 mol) of a mixture of fluorinated ether isomers with a purity of 99.5%, yielding 76%.

[0038] (2) Synthesis of fluoroalkenyl ethers In a 1 L pressure reactor, 220 g DMSO, 110 g 48% (0.94 mol) potassium hydroxide, and 40.5 g (0.2 mol) of the fluoroether isomer mixture prepared in step (1) were added. The mixture was stirred and heated to 100 °C for reaction. After 4 h of reaction, the vent was opened, and the generated fluoroalkenyl ether CF3OCF=CF2 was distilled off and collected in a -50 °C cold trap. The collected crude CF3OCF=CF2 was purified by distillation to obtain 30.2 g (0.18 mol) of fluoroalkenyl ether CF3OCF=CF2 with a purity of 99.9%, yielding 90%. The mass spectra of the fluoroalkenyl ether are shown below. Figure 1 As shown, the vertical axis represents the relative percentage intensity of fragment ions, and the horizontal axis represents the mass-to-charge ratio (m / z) of fragment ions. Among them, m / z 147 is the CF2OCF=CF2 fragment peak after removing one F atom from CF3OCF=CF2, m / z 119 is the CF3CF2 fragment peak after rearrangement, m / z 81 is the CF=CF2 fragment peak, m / z 69 is the CF3 fragment peak, and m / z 50 is the CF2 fragment peak.

[0039] Example 2 (1) Synthesis of a mixture of fluoroether isomers In a 1 L pressure reactor, 16 g of elemental bromine and 200 g of HFE-7100 were added and stirred. The mixture was then cooled to -85 °C using a liquid nitrogen-ethanol bath. 33 g of CF3OCOF and 41 g of CFH=CF2 were added. After the addition of CF3OCOF, a fluorine-nitrogen mixture with a 20% fluorine concentration (equivalent to 19 g of pure fluorine) was introduced over 6 hours. When the reactor pressure reached 0.3 MPa, the opening of the tail gas outlet valve was adjusted to maintain the pressure at 0.3 MPa. After the fluorine addition was complete, the reactor was maintained at -85 °C for 1 hour. The reactor was then vented, and the reaction liquid was distilled to obtain 47.3 g of a mixture of fluorinated ether isomers with a purity of 99.5%, a yield of 75%.

[0040] (2) Synthesis of fluoroalkenyl ethers In a 1 L pressure reactor, 400 g DMF, 54.6 g tetramethylammonium hydroxide, and 50.4 g of the fluoroether isomer mixture prepared in step (1) were added, stirred, and heated to 120 °C for reaction. After 5 h of reaction, the vent was opened, and the generated fluoroalkenyl ether CF3OCF2OCF=CF2 was distilled off and collected in a -50 °C cold trap. The collected crude CF3OCF2OCF=CF2 was purified by distillation to obtain 39.4 g of fluoroalkenyl ether CF3OCF2OCF=CF2 with a purity of 99.9%, a yield of 85%. The mass spectra of the fluoroalkenyl ether are shown below. Figure 2 As shown, the vertical axis represents the relative percentage intensity of fragment ions, and the horizontal axis represents the mass-to-charge ratio (m / z) of fragment ions. Among them, m / z 232 is the peak of the CF3OCF2OCF=CF2 molecular ion; m / z 166 is the rearranged CF2OCFCF3 fragment peak; m / z 135 is the CF3OCF2 fragment peak; m / z 119 is the rearranged CF3CF2 fragment peak; m / z 81 is the CF=CF2 fragment peak; and m / z 69 is the CF3 fragment peak.

[0041] Example 3 (1) Synthesis of a mixture of fluoroether isomers In a 1 L pressure reactor, 6.4 g of cesium iodide and 400 g of perfluorotripropylamine were added and stirred. The mixture was then cooled to -80 °C using a liquid nitrogen-ethanol bath. 43.5 g of CF3COF and 49.5 g of CFH=CFCl were added. After the addition of CF3COF, a fluorine-nitrogen mixture with a 20% fluorine concentration (equivalent to 19 g of pure fluorine) was introduced over 4 h. When the reactor pressure reached 0.4 MPa, the opening of the tail gas outlet valve was adjusted to maintain the reactor pressure at 0.4 MPa. After the fluorine addition was complete, the reactor was maintained at -80 °C for another 1 h. The reactor was then vented, and the reaction liquid was distilled to obtain 64.4 g of a mixture of fluorinated ether isomers with a purity of 99.5%, a yield of 68%.

[0042] (2) Synthesis of fluoroalkenyl ethers In a 1 L pressure reactor, 250 g of dioxane, 40 g of DBU, and 50.5 g of the fluoroether isomer mixture prepared in step (1) were added, stirred, and heated to 50 °C for reaction. After 8 h of reaction, the vent was opened, and the generated fluoroalkenyl ether CF3CF2OCF=CF2 was distilled off and collected in a -50 °C cold trap. The collected crude CF3CF2OCF=CF2 was purified by distillation to obtain 40.6 g of fluoroalkenyl ether CF3CF2OCF=CF2 with a purity of 99.9%, a yield of 94%. The mass spectra of the fluoroalkenyl ether are shown below. Figure 3 As shown, the vertical axis represents the relative percentage intensity of fragment ions, and the horizontal axis represents the mass-to-charge ratio (m / z) of fragment ions. Among them, m / z 216 is the molecular ion peak of CF3CF2OCF=CF2, m / z 119 is the fragment peak of CF3CF2; m / z 100 is the fragment peak of CF2CF2; m / z 81 is the fragment peak of CF=CF2; m / z 69 is the fragment peak of CF3; and m / z 47 is the OCF fragment peak of CF3CF2OCF=CF2 after removing CF3CF2 and =CF2 respectively.

[0043] Example 4 (1) Synthesis of a mixture of fluoroether isomers In a 1 L pressure reactor, 5.6 g of cesium fluoride and 450 g of pentafluorochloroethane were added and stirred. The mixture was then cooled to -120 °C using a liquid nitrogen-ethanol bath. 166 g of C2F5COF and 71.5 g of CFH=CFBr were added. After the C2F5COF addition was complete, a fluorine-nitrogen mixture with a 95% fluorine concentration (equivalent to 38 g of pure fluorine) was introduced over 6 hours. When the reactor pressure reached 0.5 MPa, the opening of the tail gas outlet valve was adjusted to maintain the pressure at 0.5 MPa. After the fluorine addition was complete, the reactor was maintained at -120 °C for another 1 hour. The reactor was then vented, and the reaction liquid was distilled to obtain 121.2 g of a mixture of fluorinated ether isomers with a purity of 99.5%, a yield of 70%.

[0044] (2) Synthesis of fluoroalkenyl ethers In a 1 L pressure reactor, 300 g of sulfolane, 48.3 g of potassium carbonate, and 69.4 g of the fluoroether isomer mixture prepared in step (1) were added, stirred, and heated to 80 °C for reaction. After 2 h of reaction, the vent was opened, and the generated fluoroalkenyl ether C2F5CF2OCF=CF2 was distilled off and collected in a -50 °C cold trap. The collected crude C2F5CF2OCF=CF2 was purified by distillation to obtain 50.5 g of fluoroalkenyl ether C2F5CF2OCF=CF2 with a purity of 99.9%, a yield of 95%.

[0045] Example 5 (1) Synthesis of a mixture of fluoroether isomers In a 1 L pressure reactor, 19 g of elemental iodine and 100 g of Y-type perfluoropolyether (brand: Juhua, model: JHT-55H) with a boiling range of 55-65℃ were added and stirred. The mixture was then cooled to -60℃ using a liquid nitrogen-ethanol bath. 67 g of CF₂ClCOF and 49.5 g of CFH=CFCl were added. After the addition of CF₂ClCOF, a 10% fluorine-nitrogen mixture (equivalent to 57 g of pure fluorine) was introduced over 8 hours. When the reactor pressure reached 0.8 MPa, the opening of the tail gas outlet valve was adjusted to maintain the reactor pressure at 0.8 MPa. After the fluorine was completely added, the reactor was maintained at -60℃ for another 1 hour. The reactor was then vented, and the reaction liquid was distilled to obtain 86.6 g of a mixture of fluorinated ether isomers with a purity of 99.5%, a yield of 64%.

[0046] (2) Synthesis of fluoroalkenyl ethers In a 1 L pressure reactor, 400 g of DG, 80 g of 40% sodium hydroxide, and 54 g of the fluoroether isomer mixture prepared in step (1) were added. The mixture was stirred and heated to 70 °C for reaction. After 4 h of reaction, the vent was opened, and the generated fluoroalkenyl ether CF2ClCF2OCF=CF2 was distilled off and collected in a -50 °C cold trap. The collected crude CF2ClCF2OCF=CF2 was then distilled to obtain 43.4 g of fluoroalkenyl ether CF2ClCF2OCF=CF2 with a purity of 99.9%, a yield of 93%.

[0047] Example 6 (1) Synthesis of a mixture of fluoroether isomers In a 1 L pressure reactor, 19 g of potassium iodide and 200 g of Y-type perfluoropolyether (brand: Juhua, model: JHT-55) with a boiling range of 55-65 °C were added and stirred. The mixture was then cooled to -40 °C using a liquid nitrogen-ethanol bath. 124 g of (CF3)2NCF2COF and 143 g of CFH=CFBr were added. After the addition was complete, a fluorine-nitrogen mixture with a fluorine concentration of 30% (equivalent to 19 g of pure fluorine) was introduced over 2 hours. When the reactor pressure reached 0.1 MPa, the opening of the tail gas outlet valve was adjusted to maintain the reactor pressure at 0.1 MPa. After the fluorine addition was complete, the reactor was maintained at -40 °C for another 2 hours. The reactor was then vented, and the reaction liquid was distilled to obtain 133.4 g of a mixture of fluorinated ether isomers with a purity of 99.5%, a yield of 62%.

[0048] (2) Synthesis of fluoroalkenyl ethers In a 1 L pressure reactor, 600 g TG, 18 g DBU, 55 g potassium carbonate, and 102 g of the fluoroether isomer mixture prepared in step (1) were added, stirred, and heated to 60 °C for reaction. After 10 h of reaction, the vent was opened, and the generated fluoroolefin ether (CF3)2NCF2CF2OCF=CF2 was distilled off and collected in a -50 °C cold trap. The collected crude (CF3)2NCF2CF2OCF=CF2 was purified by distillation to obtain 82.2 g of fluoroolefin ether (CF3)2NCF2CF2OCF=CF2 with a purity of 99.9%, a yield of 96%.

[0049] Comparative Example 1: Synthesis of a mixture of fluoroether isomers Except for the reaction temperature of -20 °C, the other conditions were the same as in Example 1. After the reaction was completed, 34.4 g of fluoroether with a purity of 98.5% was obtained by distillation, with a yield of 34%.

[0050] Comparative Example 2: Synthesis of Fluoroalkenyl Ethers Except for the absence of the solvent DMSO, the conditions were the same as in Example 1. After the reaction was completed, the generated fluoroalkenyl ether was collected and distilled to obtain 15 g of fluoroalkenyl ether CF3OCF=CF2 with a purity of 98.8%, yielding 45.2%.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a fluoroalkenyl ether, characterized in that, Includes the following steps: (1) Add RCOF, catalyst, and CFH=CFX to the reactor, and introduce fluorine gas to carry out the fluorination reaction. After the reaction is completed, wash and distill the reaction solution to obtain a mixture of fluorinated ether isomers. (2) The mixture of fluorinated ether isomers obtained in step (1) is subjected to dehydrohalogenation reaction with an alkali. After the reaction is completed, it is purified by distillation to obtain fluorinated alkenyl ethers. In the RCOF, R is selected from F, halogen-substituted C1-C6 alkyl groups, and halogen-substituted C1-C6 heteroalkyl groups; the main chain of the heteroalkyl group has heteroatoms, wherein the heteroatoms are O, S or N.

2. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, The R is selected from CF3, CF2Cl, CF2Br, C2F5, C3F7, C4F9, and C5F. 11 C6F 13 One of CF3O, C2F5O, CF3OCF2, CF3OCF2O, (CF3)2N, (CF3)2NCF2, SF5, and perfluorocyclohexyl.

3. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (1), the catalyst is a halogen element or an alkali metal halide.

4. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (1), the molar ratio of RCOF, fluorine gas, catalyst, and CFH=CFX is 0.5~2:0.5~3:0.05~0.2:

1.

5. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (1), the fluorination reaction is carried out at a temperature of -120 to -40 °C, a pressure of 0 to 0.8 MPa, and a time of 2 to 8 h.

6. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (1), solvent I was added to the fluorination reaction. Solvent I is one of haloalkanes, hydrofluoroethers, perfluoropolyethers, perfluorocyclic ethers, and perfluoroamines.

7. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (2), the alkali is one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, calcium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide, triethylamine, tributylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, and N,N,N,N,N-tetramethylethylenediamine.

8. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (2), the molar ratio of the fluoroether isomer mixture to the base is 1:1~3.

9. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (2), solvent II is added to the dehydrohalogenation reaction. Solvent II is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, sulfolane, N-methylpyrrolidone, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dioxane, propylene glycol dimethyl ether, methyltetrahydrofuran, and tetrahydrofuran.

10. The method for preparing fluoroalkenyl ethers according to claim 1, characterized in that, In step (2), the temperature of the dehydrohalogenation reaction is 60~150 ℃ and the time is 2~10 h.

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