Method for synthesizing heptafluoro-n-propyl ether by taking hexafluoropropylene oxide as raw material

Abstract

The invention discloses a method for synthesizing heptafluoro-n-propyl ether by taking hexafluoropropylene oxide as a raw material. The method comprises the following steps: with hexafluoropropylene oxide as a raw material, carrying out a ring-opening reaction under the action of a supported metal catalyst to obtain perfluoropropionyl fluoride; and mixing the perfluoropropionyl fluoride with inorganic fluoride, and then adding an aprotic polar solvent and an alkylating reagent to carry out alkylation reaction, thereby obtaining the perfluoropropionyl fluoride. The active metal of the supported metal catalyst comprises at least one of Ni, Fe, Co and Cu; a carrier of the supported metal catalyst is modified lignocellulose biochar. The supported metal catalyst is adopted to synthesize the perfluoropropionyl fluoride intermediate product, the reaction efficiency is improved, the reaction conditions are milder, the yield and purity of the obtained intermediate product are high, and the heptafluoro-n-propyl ether product continuously synthesized by adopting the intermediate product is high in yield and good in quality. The method greatly reduces the production cost of hydrofluoroether, and is simple in process and suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing hydrofluoroether, in particular to a method for synthesizing heptafluoro n-propyl ether by taking hexafluoropropylene oxide as a raw material, and belongs to the technical field of fluorine fine chemical industry. Background Art

[0002] Traditional compounds such as chlorofluorocarbons (CFCs) have good chemical stability and have been widely used in refrigeration, foaming and cleaning. However, these compounds will deplete the ozone layer and have a high ozone depletion potential (ODP). With the development and progress of human society, the requirements for environmental protection are gradually increasing, and the protection of the atmospheric ozone layer is also increasing. Therefore, strict restrictions are imposed on the production and use of these compounds. Hydrofluoroether compounds refer to the general name of ether compounds containing hydrogen atoms and fluorine atoms. So far, a large number of literature and patents have shown that hydrofluoroethers (HFE) can be used as a substitute for chlorofluorocarbons in industrial production and other fields, and there are also a lot of practices that prove that hydrofluoroethers have good thermal stability and chemical stability. They do not react with most common chemicals at room temperature. They can be used as solvents, cleaning agents, refrigerants and surfactants. They can be used in the field of organic synthesis and have certain application value. Hydrofluoroether compounds do not contain halogens other than fluorine and basically do not affect the earth's ozone layer. In addition, hydrofluoroether compounds are more easily degraded in the Earth's atmosphere and have a lower global warming potential (GWP), making them an ideal substitute for chlorofluorocarbons.

[0003] At present, the preparation methods of hydrofluoroethers mainly include the following: (1) Fluorination of ether compounds by fluorine gas or metal fluoride compounds; (2) Electrochemical fluorination of ether compounds; (3) Addition reaction of fluorinated olefins and alcohols; (4) Alkylation reaction of perfluoroacyl fluoride or perfluoroketone.

[0004] The invention patent with publication number US5741950 discloses a method for preparing non-fluorinated isobutyl methyl ether, which uses (CF3)2C=CFOCH3 as a raw material and prepares (CF3)2CFCF2OCH3 through fluorine gas fluorination. Due to the strong oxidizing property of fluorine gas, a large amount of by-products (CF3)2CFCF2OCH2F, (CF3)2CFCF2OCHF2, and (CF3)2C=CFOCH2F are generated, and the selectivity is less than 70%. The invention patent with publication number CN108441883A discloses a method for preparing methyl perfluoroisobutyrate by electrochemical fluorination, which uses methacrylic acid and its derivatives as starting materials, and carries out electrochemical fluorination reaction with hydrogen fluoride in an electrochemical reactor, and the obtained gas phase product is passed into a methanol solution for full reaction and esterification, and the reaction liquid is distilled to collect the product. This invention patent cannot selectively synthesize the target product and needs to be reprocessed. The invention patent with publication number CN102115428A discloses a method for synthesizing hydrofluoroethers. According to the weight ratio, 20 to 100 parts of alcohol are used as raw materials. In the presence of 1 to 6 parts of a strong base catalyst, 34 to 108 parts of fluorinated olefins are continuously added, and the reaction is carried out at 110 to 180°C. The reaction pressure is 0.6 to 1.2 MPa, and the reaction time is 1 to 5 hours. The target product is obtained after distillation separation. This invention patent has problems such as large amount of catalyst solid residue and high processing cost, and continuous production cannot be achieved. The patent with publication number CN110002968A discloses a method for preparing fluorinated ethers. The corresponding perfluoroalcohol anion intermediate is prepared by the reaction of heptafluorobutyryl fluoride and silver fluoride. At 20°C, with valeronitrile as a solvent, perfluoroalcohol anions are used as nucleophiles to attack the alkylating agent dimethyl ether to obtain hydrofluoroether compounds. This invention patent uses a low-toxic reagent as an alkylation reagent. The process is safe and reliable, the reaction conditions are mild, the yield of fluorinated ether is high, and the product can be effectively separated by distillation and other methods.

[0005] Among them, route (1) uses toxic fluorine gas, which poses a great safety hazard, and the production process will produce HF, which is highly corrosive and has high requirements for reaction equipment. Route (2) fluorinates ether compounds by electrochemical fluorination. Since selective fluorination is difficult, the yield of hydrofluoroether is low. Route (3) generates hydrofluoroether by allowing fluorine-containing alcohols and fluorine-containing olefins to undergo addition reaction. Although the yield is high, the reaction requires the addition of a strong base catalyst, and there are certain problems in the subsequent treatment of waste liquid. In addition, under alkaline conditions, a certain amount of olefinic ether compounds often exist in the product. The boiling point of olefinic ether compounds is not much different from that of hydrofluoroethers, so it is not conducive to subsequent separation and purification. Route (4) uses perfluoroacyl fluoride or perfluoroketone as raw material to prepare hydrofluoroether through alkylation reaction. Fluorine gas, strong base and other reagents are not used in the reaction process. The reaction conditions are relatively mild, and hydrofluoroethers with different branches can be synthesized by selecting different alkylating agents. However, compared with the previous three routes, although route (4) has milder conditions and higher yield of hydrofluoroether, the existing technologies all directly purchase perfluoroacyl fluoride or perfluoroketone products as raw materials, which has the problems of expensive raw material prices and high synthesis costs. Therefore, it is of great significance to develop a low-cost, simple process and high-purity hydrofluoroether synthesis route. Summary of the invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for synthesizing heptafluoro n-propyl ether using hexafluoropropylene oxide as a raw material. The product obtained by the method has high purity, high yield, simple process, easy-to-obtain raw materials, low cost, and is suitable for industrial-scale application.

[0007] In order to achieve the above technical purpose, the present invention provides a method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material. The method uses hexafluoropropylene oxide as a raw material, performs a ring-opening reaction under the action of a supported metal catalyst to obtain perfluoropropionyl fluoride; the perfluoropropionyl fluoride is mixed with an inorganic fluoride, and then a non-protonic polar solvent and an alkylating agent are added to carry out an alkylation reaction to obtain heptafluoro-n-propyl ether; the active metal of the supported metal catalyst includes at least one of Ni, Fe, Co, and Cu; and the carrier of the supported metal catalyst is modified lignocellulose biochar.

[0008] The present invention uses hexafluoropropylene oxide as an initial raw material, first synthesizes a perfluoropropionyl fluoride intermediate product, and then uses the perfluoropropionyl fluoride intermediate product to prepare heptafluoro n-propyl ether. Among them, the present invention uses at least one metal among Ni, Fe, Co, and Cu as a catalyst active component for synthesizing perfluoropropionyl fluoride, and uses modified lignocellulose biochar as a carrier of the catalyst for synthesizing perfluoropropionyl fluoride, which has the characteristics of high specific surface area and developed porosity, so that the active metal component load is more uniform and stable, the activity of the active metal is guaranteed, and the catalytic efficiency of the catalyst is greatly improved, thereby making the synthesis conditions of perfluoropropionyl fluoride milder, and the catalyst is easy to separate and recover, greatly reducing the preparation cost, and the synthesized perfluoropropionyl fluoride intermediate product has high yield and high purity. At the same time, the heptafluoro n-propyl ether product prepared by using the perfluoropropionyl fluoride intermediate product also has high purity and yield.

[0009] In addition, in the alkylation reaction of perfluoropropionyl fluoride, the fluorinating agent is first mixed with perfluoropropionyl fluoride to react so that the perfluoropropionyl fluoride becomes a perfluoroalcohol anion, and then reacts with the alkylating agent. This can make the perfluoropropionyl fluoride less likely to be hydrolyzed during the reaction process, and the yield and purity of the obtained hydrofluoroether are higher.

[0010] As a preferred solution, the mass ratio of the active metal to the carrier of the supported metal catalyst is 1:5-10.

[0011] As a preferred solution, the modified lignocellulosic biochar includes at least one of modified coconut shell biochar, modified corn straw biochar, and modified bamboo charcoal.

[0012] As a preferred scheme, the preparation process of the supported metal catalyst is: dispersing the metal salt and the modified lignocellulosic biochar in a solvent for a loading reaction to obtain a composite solid product, and then calcining the composite solid product to obtain the supported metal catalyst.

[0013] As a preferred solution, the mass ratio of the metal salt to the modified lignocellulosic biochar is 3-7:5-10.

[0014] The metal salts include nickel salts, iron salts, copper salts, and cobalt salts. Nickel salts include nickel nitrate, nickel chloride, etc. Iron salts include iron nitrate, iron chloride, etc. Copper salts include copper nitrate, copper chloride, etc. Cobalt salts include cobalt nitrate, cobalt chloride, etc.

[0015] As a preferred solution, the loading reaction process is: stirring at 20-50° C. for 6-12 hours.

[0016] As a preferred solution, the composite solid product obtained after the loading reaction is dried and ground in sequence.

[0017] As a preferred solution, the calcination process is: firstly heating to 600-800°C in a protective atmosphere for reaction for 1-2 hours, and then continuing the reaction at 700-900°C in a reducing atmosphere for 2-4 hours.

[0018] As a preferred solution, the protective atmosphere is nitrogen.

[0019] As a preferred solution, the reducing atmosphere is a mixed atmosphere of hydrogen and nitrogen.

[0020] As a preferred solution, the volume percentage of the hydrogen in the mixed atmosphere is 10-30%.

[0021] As a preferred scheme, the preparation process of the modified lignocellulosic biochar is as follows: the biochar raw material is subjected to heat treatment I to obtain pyrolyzed biochar, the pyrolyzed biochar is sequentially immersed in an acid solution and a metal chloride solution, and then subjected to heat treatment II to obtain modified lignocellulosic biochar.

[0022] As a preferred solution, the conditions of the heat treatment I are: temperature of 400-600°C, time of 1-2h, and heating rate of 5-10°C / min.

[0023] As a preferred solution, the solid-liquid mass ratio during the soaking process is 1:5-10.

[0024] As a preferred solution, the acid solution is hydrochloric acid.

[0025] As a preferred solution, the mass concentration of the hydrochloric acid does not exceed 10%.

[0026] As a preferred embodiment, the metal chloride salt includes ZnCl2 and / or FeCl3.

[0027] As a preferred solution, the molar concentration of the metal chloride solution is 0.1-1.0 mol / L.

[0028] As a preferred solution, the conditions of the heat treatment II are: temperature of 300-500°C and time of 1-2h.

[0029] As a preferred solution, the mass ratio of hexafluoropropylene oxide to the supported metal catalyst is 5-10:1-2.

[0030] As a preferred solution, the conditions of the ring-opening reaction are: temperature of 20-60° C., pressure of 0.15-0.2 MPa, and time of 6-12 h.

[0031] As a preferred embodiment, the molar ratio of the inorganic fluoride to perfluoropropionyl fluoride is 1:2-5.

[0032] As a preferred embodiment, the mass ratio of the aprotic polar solvent to perfluoropropionyl fluoride is 1:1-5.

[0033] As a preferred embodiment, the molar ratio of the alkylating agent to perfluoropropionyl fluoride is 1-2:1.

[0034] As a preferred embodiment, the inorganic fluoride includes at least one of sodium fluoride, potassium fluoride and aluminum fluoride.

[0035] As a preferred solution, the aprotic polar solvent includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, and 1,3-dimethyl-2-imidazolidinone.

[0036] As a preferred solution, the alkylating agent includes at least one of dimethyl sulfate and diethyl sulfate.

[0037] As a preferred solution, the conditions for mixing the perfluoropropionyl fluoride and the inorganic fluoride are: temperature of -25 to 50° C. and time of 1 to 24 hours.

[0038] As a preferred solution, the conditions of the alkylation reaction are: temperature of 20-80° C. and time of 2-10 h.

[0039] As a preferred solution, after the alkylation reaction is completed, solid-liquid separation and distillation purification are performed to obtain heptafluoro-n-propyl ether product.

[0040] Compared with the prior art, the present invention has the following beneficial effects: (1) Heptafluoro-n-propyl ether is synthesized using hexafluoropropylene oxide as a raw material, which reduces the production cost and obtains heptafluoro-n-propyl ether with high yield, high purity and good quality; (2) Using a supported metal catalyst containing at least one of Ni, Fe, Co, and Cu as a catalyst for synthesizing perfluoropropionyl fluoride intermediates from hexafluoropropylene oxide greatly improves the catalytic efficiency, making the synthesis conditions of perfluoropropionyl fluoride milder, and the catalyst is easy to separate and recover, reducing the preparation cost. The synthesized perfluoropropionyl fluoride intermediate has a high yield and high purity; (3) Modified lignocellulosic biochar is used as a carrier for the catalyst for synthesizing perfluoropropionyl fluoride. It has the characteristics of high specific surface area and developed porosity, which makes the active metal component loading more uniform and stable, ensures the activity of the active metal, and greatly improves the catalytic efficiency of the catalyst; (4) The synthesis method is simple, low-cost, and suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the carbon NMR spectrum of the perfluoropropionyl fluoride intermediate product.

[0042] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of heptafluoro-n-propyl ethyl ether prepared in Example 1.

[0043] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of heptafluoro-n-propyl methyl ether prepared in Example 2. DETAILED DESCRIPTION

[0044] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the content of the present invention still fall within the scope of protection of the present invention.

[0045] Unless otherwise specified, the materials, reagents, etc. used in the examples of this application can be obtained from commercial sources.

[0046] Several methods for preparing supported metal catalysts are provided below.

[0047] The preparation process of the catalyst using modified coconut shell biochar as a carrier of the supported metal catalyst is as follows: (1) Weigh 1 kg of coconut shell, crush and sieve it with a pulverizer, and then perform oxygen-limited pyrolysis in a tube furnace at a temperature of 500°C at a heating rate of 10°C / min. After reacting for 2 hours, the original biochar material (pyrolysis biochar material) was obtained, named CBC. The original biochar was modified by weighing 100 g of CBC and mixing it with 5% hydrochloric acid at a solid-liquid ratio of 1:5, then washing it with deionized water until it was neutral and drying it in an oven. Next, the dried CBC biochar was added to a ZnCl2 solution (concentration of 0.5 mol / L) at a solid-liquid ratio of 1:5, stirring and drying it, and then performing secondary pyrolysis. The temperature of the secondary pyrolysis was set to 400°C. After reacting for 2 hours, the modified coconut shell biochar MCBC was obtained.

[0048] (2) Fe(NO3)3·9H2O (35.06 g) and Ni(NO3)2·6H2O (25.32 g) were weighed at a molar ratio of 1:1. In addition, 100 g of the above-mentioned modified coconut shell biochar MCBC was weighed as a catalyst carrier. The catalyst carrier and the metal salt were mixed in a beaker, and 100 ml of distilled water was added for thorough stirring. The mixed solution was placed on a magnetic stirrer, heated and stirred at 30°C for 12 h. After thorough stirring, the mixed solution was placed in an oven for drying until the water was almost completely evaporated. After cooling to room temperature, the mixture was ground into powder using a mortar. The powdered mixture was placed in a horizontal tube furnace for calcination. The nitrogen flow rate was controlled to be 100 ml / min and the reaction temperature was set to 800°C. After 1 h, the calcined mixture was further activated in the horizontal tube furnace and reduced with a mixture of hydrogen / nitrogen with a volume ratio of 1:9. The reaction temperature was set to 800°C. After 2 h of reaction, the Ni / Fe-MCBC catalyst was obtained.

[0049] The Cu / Co-MCBC catalyst can be obtained by replacing the metal salt raw material in step (2) with Cu(NO3)2 (15.28 g) and Co(NO3)2·6H2O (23.66 g) in a molar ratio of 1:1, while keeping other conditions unchanged.

[0050] The preparation process of the catalyst using modified corn straw biochar as a carrier of the supported metal catalyst is as follows: (1) Weigh 1 kg corn stalk, crush and sieve it with a pulverizer, and then perform oxygen-limited pyrolysis in a tube furnace at a heating rate of 10℃ / min and a temperature of 600℃. After reacting for 1 hour, the original biochar material, named CSBC, was obtained. The original biochar was modified by weighing 100 g CSBC and mixing it with 2% hydrochloric acid at a solid-liquid mass ratio of 1:8, then washing it with deionized water until it was neutral and drying it in an oven. Next, the dried CSBC biochar was added to a FeCl3 solution (concentration of 0.2 mol / L) at a solid-liquid mass ratio of 1:8, stirring and drying it, and then performing secondary pyrolysis. The temperature of the secondary pyrolysis was set to 500℃. After reacting for 1 hour, the modified corn stalk biochar MCSBC was obtained.

[0051] (2) Fe(NO3)3·9H2O (35.06 g) and Ni(NO3)2·6H2O (25.32 g) were weighed at a molar ratio of 1:1. In addition, 100 g of the modified corn straw biochar MCSBC was weighed as a catalyst carrier. The catalyst carrier and the metal salt were mixed in a beaker, and 100 ml of distilled water was added for thorough stirring. The mixed solution was placed on a magnetic stirrer and heated and stirred at 40 °C for 12 h. After thorough stirring, the mixed solution was placed in an oven for drying until the water was almost completely evaporated. After cooling to room temperature, the mixture was ground into powder using a mortar. The powdered mixture was placed in a horizontal tube furnace for calcination. The nitrogen flow rate was controlled to be 100 ml / min and the reaction temperature was set to 700 °C. After 2 h, the calcined mixture was further activated in the horizontal tube furnace and reduced with a mixture of hydrogen / nitrogen with a volume ratio of 2:8. The reaction temperature was set to 800 °C. After 2 h of reaction, the Ni / Fe-MCSBC catalyst was obtained.

[0052] The Cu / Co-MCSBC catalyst was obtained by replacing the metal salt raw material in step (2) with Cu(NO3)2 (15.28 g) and Co(NO3)2·6H2O (23.66 g) metal salts in a molar ratio of 1:1, while keeping other conditions unchanged.

[0053] The preparation process of the catalyst using modified bamboo charcoal as a carrier of a supported metal catalyst is as follows: (1) Weigh 1 kg of bamboo, crush and sieve it with a pulverizer, and then perform oxygen-limited pyrolysis in a tube furnace at a heating rate of 10 °C / min and a temperature of 400 °C. After reacting for 2 hours, the original biochar material was obtained, named BBC. The original biochar was modified by weighing 100 g of BBC and mixing it with 10% hydrochloric acid at a solid-liquid ratio of 1:5, then washing it with deionized water until it is neutral and drying it in an oven. Next, the dried BBC biochar was added to a ZnCl2 solution (concentration of 1 mol / L) at a solid-liquid ratio of 1:5, stirring and drying it, and then performing secondary pyrolysis. The temperature of the secondary pyrolysis was set to 300 °C. After reacting for 2 hours, the modified bamboo charcoal MBBC was obtained.

[0054] (2) Fe(NO3)3·9H2O (35.06 g) and Ni(NO3)2·6H2O (25.32 g) were weighed at a molar ratio of 1:1. 100 g of the modified bamboo charcoal MBBC was weighed as a catalyst carrier. The catalyst carrier and the metal salt were mixed in a beaker, and 100 ml of distilled water was added for thorough stirring. The mixed solution was placed on a magnetic stirrer, heated and stirred at 30°C for 12 h. After thorough stirring, the mixed solution was placed in an oven for drying until the water was almost completely evaporated. After cooling to room temperature, the mixture was ground into powder using a mortar. The powdered mixture was placed in a horizontal tube furnace for calcination. The nitrogen flow rate was controlled to be 100 ml / min and the reaction temperature was set to 800°C. After 1 h, the calcined mixture was further activated in the horizontal tube furnace and reduced with a mixture of hydrogen and nitrogen with a volume ratio of 3:7. The reaction temperature was set to 800°C. After 2 h of reaction, the Ni / Fe-MBBC catalyst was obtained.

[0055] The Cu / Co-MBBC catalyst can be obtained by replacing the metal salt raw material in step (2) with Cu(NO3)2 (15.28 g) and Co(NO3)2·6H2O (23.66 g) metal salts in a molar ratio of 1:1, while keeping other conditions unchanged. Example 1

[0056] A method for synthesizing heptafluoro n-propyl ether using hexafluoropropylene oxide as a raw material comprises the following steps: First, the Cu / Co-MCBC (10 g) catalyst prepared above was added to a stainless steel high-pressure reactor, and the reaction system was purged with high-purity nitrogen to remove oxygen. Then, hexafluoropropylene oxide (50 g) gas was introduced into the high-pressure reactor for reaction. The reaction temperature was controlled at 40°C and the reaction pressure was 0.15 MPa. After 12 hours of reaction, solid-liquid separation and distillation purification were performed to obtain perfluoropropionyl fluoride, which was analyzed by nuclear magnetic resonance and liquid chromatography-mass spectrometry.

[0057] The perfluoropropionyl fluoride obtained by distillation was added to a high-pressure reactor, circulated with nitrogen, and then aluminum fluoride (0.15 mol) was added. At this time, the reaction temperature was controlled to be 50°C. After reacting for 12 hours, dimethyl sulfoxide solvent (20 g) and diethyl sulfate (0.45 mol) were continued to be added to the high-pressure reactor for reaction. The reaction temperature was raised to 80°C. After reacting for 8 hours, the reaction mixture was extracted and fractionated with tetrafluorohexachlorobutane to purify the reaction mixture. The fraction at about 40°C was taken, and then the components and contents were analyzed by nuclear magnetic resonance and liquid phase mass spectrometry.

[0058] like Figure 1 and Figure 2As shown, after analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry, it was found that the yield of perfluoropropionyl fluoride obtained in the first step was 95%, the yield of heptafluoro-n-propyl ether in the recovered liquid was 85%, and the purity was 95%.

[0059] In this embodiment, Cu / Co-MCSBC catalyst or Cu / Co-MBBC catalyst can be used instead of Cu / Co-MCBC, and the quality and yield of the obtained perfluoropropionyl fluoride intermediate product and heptafluoro-n-propyl methyl ether product are almost the same. Example 2

[0060] A method for synthesizing heptafluoro n-propyl ether using hexafluoropropylene oxide as a raw material comprises the following steps: First, the Ni / Fe-MCBC (10 g) catalyst prepared above was added to a stainless steel high-pressure reactor, and the reaction system was purged with high-purity nitrogen to remove oxygen. Then, hexafluoropropylene oxide (50 g) gas was introduced into the high-pressure reactor for reaction. The reaction temperature was controlled at 40°C and the reaction pressure was 0.15 MPa. After 12 hours of reaction, solid-liquid separation and distillation purification were performed to obtain perfluoropropionyl fluoride, which was analyzed by nuclear magnetic resonance and liquid chromatography-mass spectrometry.

[0061] The perfluoropropionyl fluoride obtained by distillation was added to a high-pressure reactor, circulated with nitrogen, and then aluminum fluoride (0.15 mol) was added. At this time, the reaction temperature was controlled to be 50°C. After reacting for 12 hours, dimethyl sulfoxide solvent (20 g) and dimethyl sulfate (0.45 mol) were continued to be added to the high-pressure reactor for reaction. The reaction temperature was raised to 80°C. After reacting for 8 hours, the reaction mixture was extracted and fractionated with tetrafluorohexachlorobutane to purify the reaction mixture, and the fraction at about 40°C was taken. The components and contents were then analyzed by nuclear magnetic resonance and liquid phase mass spectrometry.

[0062] After analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry, it was found that the yield of perfluoropropionyl fluoride obtained in the first step was 90%, the yield of heptafluoro-n-propyl methyl ether in the recovered liquid was 90%, and the purity was 95%. The hydrogen spectrum of the heptafluoro-n-propyl methyl ether product showed Figure 3 .

[0063] In this embodiment, Ni / Fe-MCSBC catalyst or Ni / Fe-MBBC catalyst can be used instead of Ni / Fe-MCBC, and the quality and yield of the obtained perfluoropropionyl fluoride intermediate product and heptafluoro-n-propyl methyl ether product are almost the same. Comparative Example 1

[0064] The method of Example 1 was used to prepare the perfluoropropionyl fluoride intermediate product, except that: in this comparative example, triethylamine (10 g) was used as a catalyst to catalyze the ring-opening of hexafluoropropylene oxide. Analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry showed that the yield of perfluoropropionyl fluoride after distillation and purification was 75%, and the purity was 85%. Comparative Example 2

[0065] Cu(NO3)2 (15.28g) and Co(NO3)2·6H2O (23.66g) were weighed in a molar ratio of 1:1. In addition, 100g of purchased coconut shell activated carbon AC with an iodine value of 800 was weighed as a catalyst carrier. First, the mixture was ground and passed through a 100-mesh sieve, then mixed with the metal salt in a beaker, and 100ml of distilled water was added for thorough stirring. The mixed solution was placed on a magnetic stirrer, heated and stirred at 30°C for 12h, and after thorough stirring, the mixed solution was placed in an oven for drying until the water was almost completely evaporated. After cooling to room temperature, the mixture was ground into powder with a mortar. The powdered mixture was placed in a horizontal tube furnace for calcination, the nitrogen flow rate was controlled to be 100ml / min, and the reaction temperature was set to 800°C. After 1h, the calcined mixture was further activated in a horizontal tube furnace, and reduced with a mixture of hydrogen / nitrogen with a volume ratio of 1:9, and the reaction temperature was set to 800°C. After 2h of reaction, the Cu / Co-AC catalyst was obtained.

[0066] The method of Example 1 was used to prepare the perfluoropropionyl fluoride intermediate product, except that the catalyst was a Cu / Co-AC catalyst. Analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry showed that the yield of perfluoropropionyl fluoride after distillation and purification was 85%. Comparative Example 3

[0067] Heptafluoro-n-propyl ether was prepared by the method of Example 1, except that aluminum fluoride, dimethyl sulfoxide solvent and diethyl sulfate were directly mixed and added to a reactor for alkylation reaction. Analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry showed that the yield of heptafluoro-n-propyl ether after distillation and purification was 70% and the purity was 80%.

[0068] It can be seen that in the process of producing the intermediate product of perfluoropropionyl fluoride, the supported metal catalyst used in the present invention has high catalytic efficiency, milder reaction conditions, fewer by-products, and easy purification of the product. In addition, in the alkylation reaction of perfluoropropionyl fluoride, a fluorinating agent is first used to convert it into a perfluoroalcohol anion, and then it reacts with an alkylating agent to obtain heptafluoro-n-propyl ether, which can make perfluoropropionyl fluoride less likely to be hydrolyzed during the reaction process, and the yield and purity of the obtained hydrofluoroether are higher.

[0069] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for synthesizing heptafluoro n-propyl ether using hexafluoropropylene oxide as a raw material, characterized in that: Hexafluoropropylene oxide is used as a raw material, and a ring-opening reaction is carried out under the action of a supported metal catalyst to obtain perfluoropropionyl fluoride; the perfluoropropionyl fluoride is mixed with an inorganic fluoride, and then a non-protonic polar solvent and an alkylating agent are added to carry out an alkylation reaction to obtain the product; the active metal of the supported metal catalyst includes at least one of Ni, Fe, Co, and Cu; and the carrier of the supported metal catalyst is modified lignocellulose biochar.

2. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1, characterized in that: The mass ratio of the active metal to the carrier of the supported metal catalyst is 1:5-10.

3. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1 or 2, characterized in that: The modified lignocellulosic biochar includes at least one of modified coconut shell biochar, modified corn straw biochar, and modified bamboo charcoal.

4. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1, characterized in that: The preparation process of the supported metal catalyst is as follows: dispersing the metal salt and the modified lignocellulose biochar in a solvent for a loading reaction to obtain a composite solid product, and then calcining the composite solid product to obtain the supported metal catalyst.

5. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 4, characterized in that: The mass ratio of the metal salt to the modified lignocellulosic biochar is 3-7:5-10; The metal salts include nickel salts, iron salts, copper salts, and cobalt salts; The preparation process of the modified lignocellulosic biochar is as follows: subjecting the biochar raw material to heat treatment I to obtain pyrolysis biochar, soaking the pyrolysis biochar in an acid solution and a metal chloride solution in sequence, and then subjecting the biochar to heat treatment II to obtain the modified lignocellulosic biochar; The calcination process is: firstly heating to 600-800°C in a protective atmosphere for reaction for 1-2 hours, and then continuing the reaction at 700-900°C in a reducing atmosphere for 2-4 hours.

6. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1, characterized in that: The mass ratio of the hexafluoropropylene oxide to the supported metal catalyst is 5-10:1-2.

7. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1 or 6, characterized in that: The conditions of the ring-opening reaction are: the atmosphere is a protective atmosphere, the temperature is 20-60° C., the pressure is 0.15-0.2 MPa, and the time is 6-12 hours.

8. The method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1, characterized in that: The molar ratio of the inorganic fluoride to perfluoropropionyl fluoride is 1:2-5; The mass ratio of the aprotic polar solvent to perfluoropropionyl fluoride is 1:1-5; The molar ratio of the alkylating agent to perfluoropropionyl fluoride is 1-2:

1.

9. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1 or 8, characterized in that: The inorganic fluoride includes at least one of sodium fluoride, potassium fluoride and aluminum fluoride; The aprotic polar solvent includes at least one of N,N-dimethylformamide, dimethyl sulfoxide, and 1,3-dimethyl-2-imidazolidinone; The alkylating agent includes at least one of dimethyl sulfate and diethyl sulfate.

10. A method for synthesizing heptafluoro-n-propyl ether using hexafluoropropylene oxide as a raw material according to claim 1 or 8, characterized in that: The conditions for mixing the perfluoropropionyl fluoride and the inorganic fluoride are: temperature of -25 to 50°C and time of 1 to 24 hours; The conditions of the alkylation reaction are: temperature of 20-80° C. and time of 2-10 h.

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