Method for synthesizing high-boiling-point hydrofluoroether solvent by taking fluorochloroethylene as raw material

Abstract

The invention discloses a method for synthesizing a high-boiling-point hydrofluoroether solvent by taking fluorochloroethylene as a raw material, which comprises the following steps: under the action of a basic catalyst, carrying out addition reaction on the fluorochloroethylene and fluorine-containing alkyl polyol to obtain a chlorine-containing ether compound; and carrying out fluorination reaction on the chlorine-containing ether compound under the action of a metal fluorinating agent to obtain the hydrofluoroether. The high-boiling-point hydrofluoroether solvent is synthesized by taking fluorochloroethylene as a raw material, the raw material can reduce steric hindrance, prevents isomerism and is low in price, the reaction is easy to carry out in the reaction process, the boiling point of the product is high, the whole scheme is simple in reaction, the product is easy to separate, the yield is high, and the hydrofluoroether solvent has remarkable advantages in the aspects of cost, efficiency and product treatment.

Description

Technical Field

[0001] The invention relates to the technical field of fluorine fine chemicals, and in particular to a method for synthesizing a high-boiling-point hydrofluoroether solvent by using fluorochloroethylene as a raw material. Background Art

[0002] Traditional compounds such as chlorofluorocarbons (CFCs) have good chemical stability and have been widely used in refrigeration, foaming, cleaning and other fields. 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 (HFEs) can be used as substitutes for chlorofluorocarbons in industrial production and other fields, and a large number of practices have proved that hydrofluoroethers have good thermal stability and chemical stability. They do not react with most common chemicals at room temperature and 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 other halogens except 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] Hydrofluoroethers have acid and alkali resistance, high temperature resistance, corrosion resistance and low surface tension, which makes them widely developed and applied in the field of solvents. At present, the preparation methods of hydrofluoroether solvents mainly include the following: (1) fluorine gas fluorination, electrochemical fluorination or metal fluorination of ether compounds; (2) alkylation reaction of perfluoroacyl fluoride or perfluoroketone; (3) intermolecular elimination of fluorinated alcohols and halogenated hydrocarbons; (4) addition reaction of fluorinated olefins and alcohols. These synthetic routes all have some disadvantages. The electrochemical fluorination of ether compounds has high energy consumption and poor reaction selectivity, making it difficult to carry out large-scale production. The fluorine gas fluorination reaction process is relatively dangerous, and due to the high reactivity of fluorine gas, the reaction selectivity is poor. Although metal fluorination is efficient, the price of the fluorinating agent is relatively expensive. The alkylation reaction process of perfluorinated acyl fluoride or perfluoroketone is relatively simple, but this method is often accompanied by a large number of by-products and has poor atom economy. The use of fluorinated halogenated hydrocarbons and alcohol salts to undergo intermolecular elimination reactions is one of the early methods for preparing hydrofluoroethers. This process route needs to be carried out under high temperature and high pressure, with a long reaction time and low yield. Among them, the addition reaction process of fluorinated olefins is relatively simple, with a high raw material conversion rate. It is a green new synthetic route, but it also has some disadvantages. For example, when hydrofluoroether is synthesized using hexafluoropropylene as a raw material, isomers will be produced due to asymmetric addition, or when hydrofluoroether is synthesized using tetrafluoroethylene as a raw material, there are certain risks due to the strong reactivity of tetrafluoroethylene.

[0004] There are many issues that need to be considered during the actual synthesis and use of solvents. In addition to the generation of by-products such as isomers, the efficiency and cost of catalysts, and the purification of subsequent products, the physical properties of the solvent such as the boiling point also need to be considered. The boiling point largely determines its application field and scope. Low-boiling-point solvents often evaporate during transportation and use due to shock or high temperatures generated by the reaction, causing them to lose their function as solvents, indirectly affecting the efficiency of chemical reactions and product yields. Therefore, in the process of synthesizing hydrofluoroethers, it is necessary to select suitable raw materials to increase the boiling point of the product. Although the longer the carbon chain, the higher the boiling point, the difficulty of the reaction may be affected as the carbon chain grows.

[0005] Chinese patent CN114605233 A discloses a method for synthesizing hydrofluoroether using fluorinated alcohol and fluorinated olefin as raw materials, wherein fluorinated alcohol and fluorinated olefin are used as raw materials, and a hydroalkoxylation reaction is carried out under the condition of using a main catalyst ionic liquid and a co-catalyst amine compound as a composite catalyst. The obtained mixture is distilled, and the crude product is washed, dried, and distilled to obtain hydrofluoroether. The method is simple to operate, has a mild preparation process, does not produce by-products, and the ionic liquid can be recycled and reused, no waste salt is produced, and the yield of hydrofluoroether is high. However, when asymmetric fluorinated olefins such as hexafluoropropylene are used as raw materials, the selectivity of the reaction product is often low, and it is necessary to change the type and amount of catalyst in a targeted manner to improve the selectivity and yield of the product, which indirectly increases the reaction cost. In addition, in the patent, the hydrofluoroether is prepared using a fluorinated alkyl unit alcohol as a raw material. As the alkyl chain increases, the reaction often becomes difficult, resulting in a decrease in the boiling point of the hydrofluoroether, which is not conducive to its practical application.

[0006] Therefore, it is necessary to develop a method for producing high-boiling-point hydrofluoroether with low cost, simple reaction process and mild reaction conditions. Summary of the invention

[0007] In view of the defects of low boiling point and difficult reaction of hydrofluoroether prepared in the prior art, the purpose of the present invention is to provide a method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material. The method uses fluorochloroethylene as a raw material to reduce the steric hindrance effect and prevent the generation of isomers. The chlorine-containing ether compound is first synthesized, and then the chlorine atom is removed to convert it into a high-boiling-point hydrofluoroether. The method has the characteristics of simple reaction, mild reaction conditions, easy separation of products and high selectivity.

[0008] In order to achieve the above technical purpose, the present invention provides a method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material, wherein fluorochloroethylene and a fluorine-containing alkyl polyol are subjected to an addition reaction under the action of an alkaline catalyst to obtain a chlorine-containing ether compound; the chlorine-containing ether compound is subjected to a fluorination reaction under the action of a metal fluorinating agent to obtain a hydrofluoroether.

[0009] The key technology of the present invention is to synthesize hydrofluoroether with fluorochloroethylene and fluorinated alkyl polyol as raw materials under the action of solvent, alkaline catalyst and metal fluoriding agent. The introduction of halogen element chloride ion into the fluorochloroethylene raw material of the present invention can reduce the steric hindrance effect of fluorinated polyol and make the reaction easier to carry out. At the same time, the symmetrical structure of ethylene can prevent the generation of isomers, greatly improving the selectivity of hydrofluoroether; and compared with other olefins, the olefin is cheap. In addition, by the addition reaction of fluorinated alkyl polyol and fluorochloroethylene, the difficulty of the reaction can be greatly reduced, the reaction can be promoted, and the product yield can be improved. At the same time, by introducing a fluorinated polyol with strong reaction activity for addition, the length of the alkyl chain can be increased, the boiling point of the hydrofluoroether product can be increased, and the obtained hydrofluoroether can be easier to preserve, and the fluorinated alcohol itself can be used as a solvent, which is conducive to the reaction.

[0010] The reaction synthesis equation of the present invention is as follows, taking fluorinated diol as an example:

[0011]

[0012] Where R f is a fluorinated alkyl group, and R1 and R2 are independently selected from Cl or F.

[0013] It can be seen from the above reaction synthesis equation that the present invention firstly performs an addition reaction between a fluorine-containing polyol and a plurality of carbon-carbon double bonds containing vinyl chloride, thereby increasing the alkyl chain length of the chlorine-containing ether compound, and thereby increasing the boiling point of the hydrofluoroether product, and the introduction of chlorine atoms reduces the reactivity of fluorine-containing olefins, which can effectively reduce the explosion risk of olefins during the reaction, while reducing the copolymerization activity of fluorine-containing olefins, and indirectly increasing the reaction yield; subsequently, the present invention can convert chlorine atoms into fluorine atoms under the action of a metal fluorinating agent with good selectivity, which not only reduces the generation of by-products but also ensures the smooth progress of the reaction.

[0014] As a preferred solution, the fluorochloroethylene is at least one of fluorotrichloroethylene, difluorodichloroethylene and trifluorochloroethylene; the fluorinated alkyl polyol is at least one of octafluoro-1,6-hexanediol, tetrafluorobutanediol and difluoropropylene glycol. The types of fluorochloroethylene used in the present invention can effectively reduce the steric hindrance effect and make the reaction easier when used in combination with the selected fluorinated alkyl polyol. A further preferred combination is fluorotrichloroethylene and tetrafluorobutanediol.

[0015] As a preferred solution, the metal fluoriding agent is one of silver fluoride, potassium fluoride and aluminum fluoride. The metal fluoride used in the present invention has good fluorination selectivity, simple reaction conditions and great development potential.

[0016] As a preferred solution, the alkaline catalyst is at least one of potassium hydroxide, sodium hydroxide, potassium bicarbonate and sodium bicarbonate. When the present invention uses an alkaline catalyst to carry out a catalytic addition reaction, the catalytic efficiency is high and the cost is low, so the overall selectivity is high.

[0017] As a preferred solution, the molar ratio of fluorochloroethylene to fluorinated alkyl polyol is (2-5):(1-2); the molar ratio of fluorinated alkyl polyol to alkaline catalyst is (5-10):(1-4). Within the preferred molar ratio range of the present invention, the yield and selectivity are relatively high. If the amount of fluorochloroethylene is too high, it may cause copolymerization of the product itself, thereby reducing the reaction yield.

[0018] As a preferred solution, an aprotic polar solvent may be added during the addition process. The aprotic polar solvent in the present invention can stabilize the transition state formed during the reaction, reduce the activation energy of the reaction, and thus promote the reaction.

[0019] As a preferred solution, the aprotic polar solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide and hexamethylphosphoric triamide.

[0020] As a preferred solution, the mass ratio of the aprotic polar solvent to the fluorinated alkyl polyol is (1-2):(1-5).

[0021] As a preferred solution, the conditions of the addition reaction are: temperature of 30-60° C., reaction time of 1-12 h, and reaction pressure of 0.1-0.15 MPa. The addition reaction conditions of the present invention are mild, which greatly improves the operability and safety of the reaction.

[0022] As a preferred solution, the molar ratio of the metal fluoriding agent to the chlorinated ether compound is (2-6):(1-2).

[0023] As a preferred solution, the fluorination reaction conditions are: temperature of 60-80° C., and reaction time of 1-24 h. Within the preferred fluorination reaction conditions and the amount of the metal fluoriding agent, a hydrofluoroether product with high yield and selectivity can be obtained.

[0024] Compared with the prior art, the technical solution of the present invention brings about the following innovative and beneficial technical effects:

[0025] 1) The present invention uses fluorochloroethylene as a raw material. In terms of steric hindrance, fluorochloroethylene can effectively reduce the steric hindrance effect. This characteristic makes it easier for molecular interactions to occur during the reaction, thereby significantly improving the reaction efficiency. From the perspective of the product structure, fluorochloroethylene can avoid the formation of isomers, thereby ensuring the purity and singleness of the product, which greatly reduces the difficulty of subsequent separation and purification processes. Furthermore, compared with other olefins, fluorochloroethylene has the significant advantage of low price. This characteristic makes it cost-competitive in large-scale industrial production, which helps to reduce production costs and improve economic benefits.

[0026] 2) The present invention introduces fluorinated polyols for addition reaction to increase the boiling point of hydrofluoroethers, which makes hydrofluoroethers more applicable in high temperature environments or scenarios where low volatility solvents are required. At the same time, fluorinated alcohols can act as solvents, which helps to fully mix the reactants, thereby increasing the reaction rate, and can simplify the reaction system, reduce the use of additional solvents, and thus reduce costs and subsequent separation steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the hydrofluoroether prepared in Example 1.

[0028] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the hydrofluoroether prepared in Example 2. DETAILED DESCRIPTION

[0029] The technical solution of the present invention will be further described below in conjunction with specific embodiments of the present invention. It should be noted that the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments; these embodiments are only for a better understanding of the present invention, rather than limiting the scope of protection of the present invention.

[0030] Unless otherwise specified, all reagents and raw materials used in the present invention are commercially available products or products that can be prepared by known methods.

[0031] Example 1

[0032] Weigh tetrafluorobutanediol (80 g, 0.5 mol) and N,N-dimethylformamide solvent (40 g), add them into a 2L autoclave in turn for mixing, stir thoroughly, add NaOH (4 g, 0.1 mol), then introduce nitrogen at 100 ml / min for circulation to exhaust the air, introduce fluorotrichloroethylene (131 g, 1 mol) into the autoclave at a flow rate of 200 ml / min to react with tetrafluorobutanediol, control the reaction pressure to 0.1 MPa, and the reaction temperature to 50°C. After reacting for 10 hours, pour out the reaction mixture, extract and separate it with an aqueous solution, then distill and purify the product, and characterize and analyze it with instruments such as a nuclear magnetic resonance instrument and a liquid chromatography-mass spectrometer. The chloroether obtained by the first step of purification and KF (20 g, 0.35 mol) were added into a 2L high-pressure reactor at a molar ratio of 1:1, and 100 ml / min of nitrogen was introduced for circulation. The mixture was heated and stirred at 80°C. After 8 hours of reaction, KF was separated from the reaction mixture by cellulose filter paper, and then the remaining solution was distilled, separated and purified, and analyzed and characterized by instruments such as nuclear magnetic resonance and liquid chromatography-mass spectrometry.

[0033] like Figure 2 As shown, after analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry, it can be seen that the final hydrofluoroether structure is HCF2CF2OCH2CF2CF2CH2OCF2CF2H, with a yield of 90% and a selectivity of 98%.

[0034] Example 2

[0035] Weigh difluoropropylene glycol (112 g, 1 mol) and dimethyl sulfoxide solvent (40 g), add them into a 2L autoclave in sequence for mixing, stir thoroughly, add NaOH (4 g, 0.1 mol), then introduce nitrogen at 100 ml / min for circulation to exhaust the air, introduce trifluorochloroethylene (349 g, 3 mol) into the autoclave at a flow rate of 200 ml / min to react with difluoropropylene glycol, control the reaction pressure to 0.15 MPa, and the reaction temperature to 40°C. After reacting for 8 hours, pour out the reaction mixture, extract and separate with aqueous solution, then distill and purify the product, and characterize and analyze it with instruments such as nuclear magnetic resonance spectroscopy and liquid chromatography-mass spectrometry. The chloroether obtained by the first step of purification and KF (29 g, 0.5 mol) were added into a 2L high-pressure reactor at a molar ratio of 1:1, and 100 ml / min of nitrogen was introduced for circulation. The reaction was heated and stirred at 60°C. After the reaction was carried out for 12 hours, KF was separated from the reaction mixture through cellulose filter paper, and then the remaining solution was distilled, separated and purified, and analyzed and characterized by instruments such as nuclear magnetic resonance and liquid chromatography-mass spectrometry.

[0036] like Figure 2As shown, after analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry, it can be seen that the final hydrofluoroether structure is HCF2CF2OCH2CF2CH2OCF2CF2H, with a yield of 85% and a selectivity of 95%.

[0037] Example 3

[0038] The only difference between this embodiment and embodiment 1 is that no N,N-dimethylformamide solvent is added, and the final hydrofluoroether structure is HCF2CF2OCH2CF2CF2CH2OCF2CF2H, with a yield of 85% and a selectivity of 98%.

[0039] Comparative Example 1

[0040] The same as Example 1, except that the olefin used in the reaction is hexafluoropropylene and there is no second fluorination step. Analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry shows that the product structure is CF3CFHCF2OCH2CF2CF2CH2OCF2CFHCF3, the hydrofluoroether yield is 60%, and the selectivity is 75%.

[0041] Comparative Example 2

[0042] The same as Example 1, except that the alcohol used in the reaction is n-propanol, and analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry shows that the final hydrofluoroether structure is CH3CH2CH2OCF2CF2H, the yield is 75%, and the selectivity is 85%.

[0043] Comparative Example 3

[0044] The same as Example 1, except that the alcohol used in the reaction is n-propanol and the olefin used is hexafluoropropylene and no fluorination reaction is performed. Analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry shows that the final hydrofluoroether structure is CH3CH2CH2OCF2CFHCF3, the yield is 65%, and the selectivity is 65%.

[0045] Comparative Example 4

[0046] The same as Example 1, except that the olefin used in the reaction is tetrafluoroethylene and does not undergo fluorination reaction. Analysis by nuclear magnetic resonance and liquid chromatography-mass spectrometry shows that the final hydrofluoroether structure is HCF2CF2OCH2CF2CF2CH2OCF2CF2H, with a yield of 75% and a selectivity of 90%.

[0047] From the test data of embodiment and comparative example: the raw materials used in the embodiment of the present invention are fluorinated alkyl polyols and fluorochloroethylene, chlorinated ether and hydrofluoroether productivity are higher, in comparative example 1, compared with trifluorochloroethylene, hexafluoropropylene causes the existence of part isomers in the product due to its asymmetric structure, which affects the productivity of the target product. And in comparative example 2, due to using propyl alcohol as raw material, relative to tetrafluorobutanediol, the alcohol anion formed under alkaline conditions is not so stable, so the hydrofluoroether productivity is relatively low. In comparative example 3, using hexafluoropropylene and propyl alcohol as raw materials, the hydrofluoroether hydrofluoroether productivity and selectivity obtained are lower. In comparative example 4, using tetrafluoroethylene as raw material, although selectivity is higher, due to the strong reactivity of tetrafluoroethylene, copolymers are easily produced in the reaction process, resulting in low productivity.

[0048] The above embodiments are only for better explanation of the principles and practical applications of the present invention, so that those skilled in the relevant technical field can better understand and utilize the present invention, but they are not intended to limit the patent scope of the present invention. All equivalent changes made using the contents of the present invention are within the patent protection scope of the present invention.

Claims

1. A method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material, characterized in that: Under the action of an alkaline catalyst, fluorochloroethylene and a fluorine-containing alkyl polyol undergo an addition reaction to obtain a chlorine-containing ether compound; the chlorine-containing ether compound undergoes a fluorination reaction under the action of a metal fluorinating agent to obtain a hydrofluoroether.

2. A method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to claim 1, characterized in that: The fluorochloroethylene is at least one of fluorotrichloroethylene, difluorodichloroethylene and trifluorochloroethylene; The fluorine-containing alkyl polyol is at least one of octafluoro-1,6-hexanediol, tetrafluorobutanediol and difluoropropylene glycol.

3. A method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to claim 2, characterized in that: The metal fluoriding agent is at least one of silver fluoride, potassium fluoride and aluminum fluoride; The alkaline catalyst is at least one of potassium hydroxide, sodium hydroxide, potassium bicarbonate and sodium bicarbonate.

4. A method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to claim 3, characterized in that: The molar ratio of fluorochloroethylene to fluorinated alkyl polyol is (2-5):(1-2); The molar ratio of the fluorine-containing alkyl polyol to the alkaline catalyst is (5-10):(1-4).

5. A method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to any one of claims 1 to 4, characterized in that: A non-protonic polar solvent may also be added during the addition reaction.

6. The method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to claim 5, characterized in that: The aprotic polar solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide and hexamethylphosphoric triamide.

7. A method for synthesizing a high-boiling-point hydrofluoroether solvent using chlorofluoroethylene as a raw material according to claim 6, characterized in that: The mass ratio of the aprotic polar solvent to the fluorinated alkyl polyol is (1-2):(1-5).

8. The method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to claim 1, characterized in that: The conditions of the addition reaction are: temperature of 30-60° C., reaction time of 1-12 h, and reaction pressure of 0.1-0.15 MPa.

9. A method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to claim 1 or 3, characterized in that: The molar ratio of the metal fluoriding agent to the chlorinated ether compound is (2-6):(1-2).

10. The method for synthesizing a high-boiling-point hydrofluoroether solvent using fluorochloroethylene as a raw material according to claim 9, characterized in that: The conditions of the fluorination reaction are: temperature of 60-80° C. and reaction time of 1-24 h.

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