A method for synthesizing a hydrofluoroether

Abstract

The application provides a method for preparing a hydrofluoroether by a continuous gas phase method, and the synthesis method comprises the following steps: 1) using a fluoride or an oxide and a carrier to obtain a fluorination agent through granulation, drying and activation, 2) loading the fluorination agent in a fixed bed reactor, carrying out vaporization pretreatment on a raw material alkene ether, simultaneously introducing fluorine gas into the fixed bed reactor to carry out a gas phase addition reaction, and after the reaction is completed, carrying out liquefaction and rectification to obtain the hydrofluoroether. The fluorination agent has a long service life and is not easy to be pulverized, the synthesis of the hydrofluoroether is carried out by using the fluorination agent, the fluorination addition is efficiently carried out through the continuous gas phase method, the yield reaches 81%, and the purity reaches 98%.

Description

Technical Field

[0001] This invention relates to the field of fine fluorine chemical technology, and specifically to a method for preparing hydrofluoroethers via a continuous gas-phase process. Background Technology

[0002] Currently, the massive release of chlorofluorocarbons (CFCs) is causing increasingly severe damage to the ozone layer. In 1987, the international community adopted the Montreal Protocol, requiring a phase-out of the use of ozone-depleting chemicals such as CFCs. The phase-out deadlines for refrigerants, foaming agents, and cleaning agents such as chloroform (R-11), dichlorofluoromethane (R-11), and dichlorofluoromethane (R-22) are approaching, making environmentally friendly refrigerants, foaming agents, and electronic cleaning agents that do not deplete the ozone layer urgently needed.

[0003] Fluorinated ethers, especially hydrofluoroethers, have zero ozone depletion potential (ODP), low global warming potential (GWP), and short atmospheric residence time. They are non-toxic, non-corrosive, non-flammable, do not produce smoke or dust, and have good material compatibility. They have both moderate solubility and good material compatibility, making them an ideal substitute for ODS (ozone-depleting substances). They can be used in cleaning agents, deposition solvents, battery electrolyte solvents, heat transfer media, and other fields.

[0004] Currently, the main methods for synthesizing hydrofluoroether compounds are as follows: (1) fluorination of ether compounds by fluorine gas or metal fluorides; (2) electrochemical fluorination of ether compounds; (3) reaction of fluorinated alcohols with haloalkanes in the presence of alkali metal hydroxides to obtain fluorinated ethers; (4) addition reaction of fluorinated alcohols with fluorinated alkenes; (5) alkylation reaction of fluorinated acyl fluorides or fluorinated ketones, etc.

[0005] All of the above methods have shortcomings: Method (1) has poor reaction selectivity, produces many by-products, and generates highly corrosive hydrogen fluoride during the reaction, which places stringent requirements on production equipment; Method (2) consumes a lot of electricity, has a low yield, and produces many by-products; Method (3) can be used, but most of the reactions are long and the reaction temperature is high, with a yield of only 40-60%; and the target product, hydrofluoroether, will undergo dehydrohalogenation under strong alkaline conditions to generate double bond by-products. These by-products have boiling points close to the target product and are difficult to separate effectively by distillation; Method (4) is relatively simple and has a high yield, and is currently the main method for preparing hydrofluoroether. This method is generally divided into two types. One type uses strong polar substances such as DMF or DMSO as solvents and alkali metal hydroxides as catalysts. The disadvantage is that it will generate a large amount of solid waste and liquid waste. The other type does not add solvents and reacts alcohols with fluorinated olefins in the presence of strong base catalysts. This reaction has a lower cost but a very slow reaction rate. Both of these methods are the same as method (3). Due to the presence of strong base compounds in the reaction system, dehydrohalogenation reaction will occur, resulting in the presence of alkene compounds in the product. In method (5), electro-fluorination is usually used to prepare fluorinated acyl fluoride and further prepare hydrofluoroether. However, the electro-fluorination method not only consumes a lot of electricity, has a low yield and many by-products in the production process, but also usually produces a large number of isomers rather than a specific perfluorinated acyl fluoride.

[0006] Therefore, in general, although method (1) still has shortcomings, it still has its unique advantages.

[0007] Hydrofluoroethers are prepared by fluorination of ether compounds, mainly using metal fluorides such as SbF5, CoF3, and MnF3, but also using fluorinating agents such as F2 and HF.

[0008] In patent WO9730961, Toshikazu et al. used HF as a fluorinating agent and H2SO4 as a catalyst to prepare a diether (CF3)2CHOCH2OCH(CF3)2 with a purity of 95% and a yield of 84%. In patent US5382704, Krespan Carl G et al. used HF as a fluorinating agent and BF3 as an auxiliary agent to synthesize CF3CH2OCF3 from trifluoroethanol and carbon tetrachloride with a yield of 93%. In patent US5705710, BakerMax T et al. used BrF3 to fluorinate 2-methoxy-1,3-propanedicyandiamide to prepare hexafluoroisopropyl methyl ether and hexafluoroisopropyl fluoromethyl ether. Further fluorination of hexafluoroisopropyl methyl ether with BF3 yields a single product, hexafluoroisopropyl fluoromethyl ether.

[0009] Fluorination of metal fluorides offers high fluorination yields and allows for renewable reuse, but its high cost limits its widespread use. In comparison, F2 fluorination exhibits higher reactivity but poor selectivity. Traditional fluorination addition synthesis processes require stringent temperature requirements for the direct addition of fluorine gas, resulting in low selectivity and the formation of significant amounts of overfluorinated products.

[0010] Patent US5741950 uses (CF3)2C=CFOCH3 as a raw material, which is fluorinated with fluorine gas to obtain the product (CF3)2CFCF2OCH3. Due to the strong oxidizing properties of fluorine gas, a large number of byproducts are generated, resulting in a selectivity of less than 70%. Patent CN108101754 uses a composite fluorinating agent composed of multiple fluorinating metals as a catalyst and trifluorotrichloroethane, perfluorocyclic ethers, perfluorotriethylamine, hexafluoropropylene trimer, etc. as solvents to achieve the fluorination of alkenyl ethers to prepare hydrofluoroethers with a yield greater than 90%. However, this patent does not report selectivity, and fluorides are expensive, making recycling a problem. Furthermore, the intermittent reaction limits its industrial application. Summary of the Invention

[0011] The purpose of this invention is to solve the aforementioned technical problems existing in the prior art and to provide a continuous gas-phase method for preparing hydrofluoroethers. This invention uses a self-made fluorinating agent for the synthesis of hydrofluoroethers, enabling continuous and efficient fluorination addition with a yield of 81% and a purity of 98%, effectively overcoming the shortcomings of previous synthesis processes.

[0012] To achieve the above objectives, the present invention adopts the following technical solution:

[0013] One objective of this invention is to provide a method for synthesizing hydrofluoroethers, comprising the following steps:

[0014] 1) The fluoride or oxide and the carrier are crushed, granulated, sieved, mixed evenly and pressed into shape to obtain the fluorinating agent precursor. The precursor is dehydrated and dried, and calcined in an atmosphere of hydrogen fluoride and nitrogen. After the fluoride or oxide on the fluorinating agent precursor is completely fluorinated, the fluorinating agent is obtained.

[0015] 2) The fluorinating agent is packed into a fixed-bed reactor, and the raw material alkenyl ether is pretreated by vaporization. It is then introduced into the fixed-bed reactor at the same time as fluorine gas to undergo a gas-phase addition reaction. After the reaction is completed, hydrofluoroether is obtained by liquefaction and distillation.

[0016] In the hydrofluoroether synthesis method of the present invention, preferably, step 1) includes:

[0017] The fluoride or oxide is at least one of nickel fluoride, chromium fluoride, cobalt fluoride, manganese fluoride, arsenic fluoride, nickel oxide, chromium oxide, cobalt oxide, manganese oxide, and arsenic oxide.

[0018] The carrier is at least one of alumina, aluminum fluoride, hydroxymethyl cellulose, pumice, magnesium stearate, diatomaceous earth, and graphite.

[0019] The mass ratio of the fluoride or oxide to the carrier is 1:0.5 to 5;

[0020] The fluoride or oxide and the carrier are pulverized and granulated, then passed through a 50-200 mesh sieve.

[0021] The calcination temperature of the fluorinating agent precursor is 300–500°C;

[0022] The calcination time of the fluorinating agent precursor is 3 to 20 hours.

[0023] In the hydrofluoroether synthesis method of the present invention, preferably, step 2) includes:

[0024] The reaction temperature is 50–350°C;

[0025] The reaction residence time is 5–20 s;

[0026] The alkenyl ether is one of (CF3)2C=CFOCH3, (CF3)2C=CFOC2H5, CHF2CF=CHOCF2CF2H, CF2=CFCH2OCF2CF2H, CF2=CHOCF2CF2H, CF3CF=CFOCH3, (E)-1,2-dimethoxyethylene, 3,4-dihydro-2H-pyran, 2,3-dihydrofuran, and 1,4-dioxane;

[0027] The molar ratio of the alkenyl ether to fluorine gas is 1:0.5 to 2;

[0028] After the reaction was completed, the mixture was distilled, and the fraction was collected to obtain purified hydrofluoroether.

[0029] The beneficial effects of this invention are as follows:

[0030] 1. This invention provides a method for preparing a fluorinating agent. The method combines a fluoride or oxide with a carrier. The fluoride generated by fluorination exerts its fluorination effect on a solid carrier. This fluorinating agent has a long service life and is not easily pulverized.

[0031] 2. The fluorinating agent described in this invention is suitable for use in combination with an alkenyl ether and a fixed-bed device to prepare hydrofluoroethers. This process has simple reaction equipment, is easy to operate, does not require the use of organic solvents, and is more environmentally friendly, convenient and efficient.

[0032] 3. It is synthesized efficiently through a continuous gas-phase method, which is convenient for industrialization. Detailed Implementation

[0033] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0034] The preparation of the fluorinating agent is carried out according to the following steps:

[0035] Example 1:

[0036] Weigh 100g of cobalt fluoride and 100g of alumina raw materials, crush, granulate, and pass through a 100-mesh sieve. Mix them evenly and press them into cylinders with a diameter-to-height ratio of 1:2. The bulk density after molding is 1.2kg / L. Then, dehydrate and dry at 80℃ for 10 hours. Then, continue to slowly heat to 450℃ and calcine in a mixed atmosphere of hydrogen fluoride and nitrogen for 8 hours to obtain the fluorinating agent.

[0037] Example 2:

[0038] Weigh 100g of chromium fluoride and 100g of alumina, crush, granulate, and pass through a 100-mesh sieve. Mix them evenly and press them into cylinders with a diameter-to-height ratio of 1:2. The bulk density after molding is 1.2kg / L. Then, dehydrate and dry at 80℃ for 10 hours. Then, continue to slowly heat to 450℃ and calcine for 8 hours in a mixed atmosphere of hydrogen fluoride and nitrogen to obtain the fluorinating agent.

[0039] Example 3:

[0040] Weigh 100g of chromium fluoride and 100g of magnesium stearate, crush, granulate, and pass through a 100-mesh sieve. Mix them evenly and press them into cylinders with a diameter-to-height ratio of 1:2. The bulk density after molding is 1.2kg / L. Then, dehydrate and dry at 80℃ for 10 hours. Then, continue to slowly heat to 450℃ and calcine for 8 hours in a mixed atmosphere of hydrogen fluoride and nitrogen to obtain the fluorinating agent.

[0041] Example 4:

[0042] Weigh 100g of chromium fluoride, 10g of magnesium stearate, and 90g of alumina, crush, granulate, and pass through a 100-mesh sieve. Mix them evenly and press them into cylinders with a diameter-to-height ratio of 5:6. The bulk density after molding is 1.2kg / L. Then, dehydrate and dry at 80℃ for 10 hours. Then, continue to slowly heat to 450℃ and calcine in a mixed atmosphere of hydrogen fluoride and nitrogen for 8 hours to obtain the fluorinating agent.

[0043] Example 5:

[0044] Weigh 100g of chromium oxide and 100g of aluminum oxide, crush, granulate, and pass through a 100-mesh sieve. Mix them evenly and press them into cylinders with a diameter-to-height ratio of 1:2. The bulk density after molding is 1.2kg / L. Then, dehydrate and dry at 80℃ for 10 hours. Then, continue to slowly heat to 450℃ and calcine for 8 hours in a mixed atmosphere of hydrogen fluoride and nitrogen to obtain the fluorinating agent.

[0045]

[0046] The synthesis of hydrofluoroethers is carried out according to the following steps:

[0047] Example 6:

[0048] The fluorinating agent obtained in Example 1 was filled into a reaction tube and then placed in a fixed-bed reactor. The gas inside the fixed-bed reactor was replaced with high-purity nitrogen. The vaporized ether (CF3)2C=CFOCH3 and fluorine gas were introduced in a molar ratio of 1:1 by pressurizing nitrogen. The reaction temperature was controlled to rise to 150°C and the residence time of the mixed gas was 8 seconds. The resulting mixed gas was cooled by a cold trap, and the resulting liquid was collected and distilled to obtain (CF3)2CFCF2OCH3 with a yield of 79% and a purity of 95%.

[0049] Example 7:

[0050] The fluorinating agent obtained in Example 1 was filled into a reaction tube and then placed in a fixed-bed reactor. The gas inside the fixed-bed reactor was replaced with high-purity nitrogen. The vaporized 2,3-dihydrofuran and fluorine were introduced by pressurizing nitrogen in a molar ratio of 1:1. The reaction temperature was controlled to rise to 60°C and the residence time of the mixed gas was 10 s. The resulting mixed gas was cooled by a cold trap, and the resulting liquid was collected and distilled to obtain (CF3)2CFCF2OCH3 with a yield of 81% and a purity of 98%.

[0051] Example 8:

[0052] The fluorinating agent obtained in Example 1 was filled into a reaction tube and then placed in a fixed-bed reactor. The gas inside the fixed-bed reactor was replaced with high-purity nitrogen. The vaporized olefin ether 3,4-dihydro-2H-pyran and fluorine gas were introduced in a molar ratio of 1:1 by pressurizing nitrogen. The reaction temperature was controlled to rise to 90°C and the residence time of the mixed gas was 10 s. The resulting mixed gas was cooled by a cold trap, and the resulting liquid was collected and distilled to obtain (CF3)2CFCF2OCH3 with a yield of 75% and a purity of 93%.

[0053] Example 9:

[0054] The fluorinating agent obtained in Example 1 was filled into a reaction tube and then placed in a fixed-bed reactor. The gas inside the fixed-bed reactor was replaced with high-purity nitrogen. The vaporized 2,3-dihydrofuran ether and fluorine gas were introduced in a molar ratio of 1:1 by pressurizing nitrogen. The reaction temperature was controlled to rise to 60°C and the residence time of the mixed gas was 15s. The resulting mixed gas was cooled by a cold trap, and the resulting liquid was collected and distilled to obtain (CF3)2CFCF2OCH3 with a yield of 79% and a purity of 97%.

[0055] Example 10:

[0056] The fluorinating agent obtained in Example 1 was filled into a reaction tube and then placed in a fixed-bed reactor. The gas inside the fixed-bed reactor was replaced with high-purity nitrogen. The vaporized 2,3-dihydrofuran ether and fluorine gas were introduced in a molar ratio of 1:1 using nitrogen pressurization. The reaction temperature was controlled to rise to 90°C, and the residence time of the mixed gas was 10 s. The resulting mixed gas was cooled by a cold trap, and the resulting liquid was collected and distilled to obtain 2,3-difluorooxocyclohexane with a yield of 78% and a purity of 95%.

Claims

1. A method for preparing hydrofluoroethers via a continuous gas-phase process, characterized in that, Includes the following steps: 1) The fluoride or oxide and the carrier are crushed, granulated, sieved, mixed evenly, and pressed into shape to obtain a fluorinating agent precursor. The precursor is dehydrated and dried, and calcined in an atmosphere of hydrogen fluoride and nitrogen. After the fluoride or oxide on the fluorinating agent precursor is completely fluorinated, the fluorinating agent is obtained. The fluoride or oxide is at least one of nickel fluoride, chromium fluoride, cobalt fluoride, manganese fluoride, arsenic fluoride, nickel oxide, chromium oxide, cobalt oxide, manganese oxide, and arsenic oxide. 2) The fluorinating agent is packed into a fixed-bed reactor, and the raw material alkenyl ether is pretreated by vaporization. It is then introduced into the fixed-bed reactor simultaneously with fluorine gas to undergo a continuous gas-phase addition reaction. After the reaction is completed, hydrofluoroether is obtained by liquefaction and distillation.

2. The method for synthesizing hydrofluoroether according to claim 1, characterized in that: In step 1), The carrier is at least one of alumina, aluminum fluoride, hydroxymethyl cellulose, pumice, magnesium stearate, diatomaceous earth, and graphite. The mass ratio of the fluoride or oxide to the carrier is 1:0.5 to 5; The fluoride or oxide and the carrier are pulverized and granulated, then passed through a 50-200 mesh sieve. The calcination temperature of the fluorinating agent precursor is 300–500°C; The calcination time of the fluorinating agent precursor is 3 to 20 hours.

3. The method for synthesizing hydrofluoroether according to claim 1, characterized in that: In step 2), The reaction temperature is 50–350°C; The reaction residence time is 5–20 s; The alkenyl ether is one of (CF3)2C=CFOCH3, (CF3)2C=CFOC2H5, CHF2CF=CHOCF2CF2H, CF2=CFCH2OCF2CF2H, CF2=CHOCF2CF2H, CF3CF=CFOCH3, (E)-1,2-dimethoxyethylene, 3,4-dihydro-2H-pyran, 2,3-dihydrofuran, and 1,4-dioxane; The molar ratio of the alkenyl ether to fluorine gas is 1:0.5 to 2; After the reaction was completed, the mixture was distilled, and the fraction was collected to obtain purified hydrofluoroether.

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