Method for producing hydrofluoroether

Abstract

A process for producing a hydrofluoroether, comprising: ·A) providing a mixture comprising one or more polar aprotic organic solvents having a boiling point measured at 1 atm (1.01 bar) in the range of 60 °C to 170 °C, and one or more compounds carrying at least one -OH group which is part of an alcohol or phenol group; ·B) reacting the one or more compounds carrying at least one -OH group with one or more fluorinated olefins in the presence of a basic catalyst, thereby providing a reaction mixture comprising one or more hydrofluoroethers.

Description

Technical Field

[0001] This application claims priority from European Patent Application Publication No. 22181821.4 filed on June 29, 2022, the entire content of which is incorporated herein by reference for all purposes.

[0002] The present invention relates to a process for preparing hydrofluoroethers starting from monofunctional or polyfunctional alcohols or phenols and fluorinated olefins.

Background Art

[0003] Various processes for producing hydrofluoroethers are known in the art. US Patent No. 4208081 (Du Pont) describes the preparation of hydrofluoroethers using ethylene glycol and tetrafluoroethylene (TFE) in a diethyl ether solution. However, the reaction does not go to completion because two reaction products are formed in approximately equal amounts: one in which both -OH groups of ethylene glycol are converted to ether groups, and another in which only one of the -OH groups of ethylene glycol is converted to an ether and the other remains as a free hydroxyl group.

[0004] Russian Federation Patent No. 1810324 granted to Natalya Guseva reports the preparation of hydrofluoroethers from the reaction between ethylene glycol and TFE in a diglyme solvent in an anhydrous process with a yield of 78%.

[0005] Processes for manufacturing hydrofluoroethers are known, but there is still a need for a process with a high yield, i.e., a better yield than prior art processes.

Summary of the Invention

[0006] The present invention is a process for producing hydrofluoroethers, comprising A) providing a mixture comprising one or more polar aprotic organic solvents having a boiling point measured at 1 atm in the range of 60°C to 170°C and one or more compounds carrying at least one -OH group which is part of an alcohol or phenol group; B) reacting the one or more compounds carrying at least one -OH group in the presence of a basic catalyst with one or more fluorinated olefins, thereby providing a reaction mixture comprising one or more hydrofluoroethers; and a method comprising the same.

DETAILED DESCRIPTION OF THE INVENTION

[0007] Accordingly, it is an object of the present invention to provide a process for preparing hydrofluoroethers derived from the reaction of a compound carrying at least one -OH group which is part of an alcohol or phenol group with a fluorinated olefin (including partially and fully fluorinated olefins), which advantageously provides high yields and can be easily carried out under mild conditions and without the need for environmentally harmful starting materials.

[0008] In connection with the present invention, "hydrofluoroether" is defined as a compound having the general formula R-O-R', wherein at least one of R and R' contains at least one C-F bond and at least one C-H bond.

[0009] One way to form hydrofluoroethers is to react a compound carrying at least one -OH group which is part of an alcohol or phenol group with a fluorinated olefin which can be partially or fully fluorinated. The reaction between the -OH group and the C=C double bond of the olefin can be explained as an addition to the C=C double bond in which one of the carbon atoms forms a C-O bond and the other forms a C-H bond.

[0010] In a first step (A) of the process of the present invention, a mixture is provided comprising one or more polar aprotic organic solvents and one or more compounds carrying at least one -OH group which is part of an alcohol or phenol group.

[0011] Suitable polar aprotic organic solvents for use in the method of the present invention are polar aprotic organic solvents having a boiling point measured at atmospheric pressure (1 atm) of 60 to 170°C, preferably 70°C to 90°C. Particularly suitable polar aprotic solvents for use herein are those carrying a nitrile group, and a particularly preferred solvent is acetonitrile.

[0012] Another essential component of the mixture provided in step A of the method of the present invention is one or more compounds carrying at least one -OH group which is part of an alcohol or phenol group. In the present invention, the -OH group is part of an alcohol group when it is covalently bonded to an aliphatic carbon atom that is not part of a carbonyl group (C=O), and the -OH group is intended to be part of a phenol group when it is covalently bonded to an aromatic carbon (i.e., a carbon that is part of an aromatic ring).

[0013] These compounds typically correspond to the general formula R1-OH, where R1 can be any group, provided that the oxygen atom in the -OH group is covalently bonded to R1, which is either an aliphatic carbon atom or an aromatic carbon atom that is not part of a carbonyl group as described above.

[0014] In addition to this requirement, R1 is not particularly limited and can be selected, for example, from aliphatic carbon groups which may be linear, branched, and / or contain a cyclic moiety, aromatic carbon groups which may or may not have other substituents on the aromatic ring, and aliphatic carbon groups containing one or more aromatic rings along the chain (for aliphatic carbon groups, it means a group with the group center on an aliphatic carbon, and for aromatic carbon groups, it means a group with the group center on an aromatic carbon).

[0015] R1 may also contain other functional groups and heteroatoms. In particular, it may preferably contain an oxygen heteroatom as part of another alcohol or phenol group or involved in an ether bond. When the -OH-containing compound of the present invention is a polyfunctional alcohol or phenol, R1 contains an additional -OH group. Examples of compounds carrying at least one -OH group suitable for use in the present invention are methanol, ethanol, n-propanol, iso-propanol, cyclohexanemethanol, cyclohexanol, ethylene glycol, di-ethylene glycol, tri-ethylene glycol, propylene glycol, di-propylene glycol, tri-propylene glycol, 1,3-propanediol, pentaerythritol, cyclohexanediol, cyclohexanedimethanol, allyl alcohol, phenol, cresol, methoxyphenol, fluorophenol, substituted phenols such as chlorophenol, benzene diols (resorcinol, catechol, hydroquinone, etc.) and triols.

[0016] The one or more compounds carrying at least one -OH group for use in the present invention may be non-halogenated, partially halogenated or fully halogenated. When it is halogenated, the halogen may preferably be selected from Cl and F.

[0017] Essentially any compound bearing at least one -OH group that is part of an alcohol or phenol group as defined above can be used in the method of the present invention. However, the Applicant has surprisingly found that the method of the present invention is very effective when the compound bearing at least one -OH group is a polyfunctional alcohol, particularly a difunctional alcohol. In fact, when forming hydrofluoroethers from polyfunctional alcohols, especially after one or more of them have already reacted with a fluorinated olefin to form a first ether bond, the yields tend to decrease because the various -OH groups can have different reactivities. The method of the present invention enables excellent yields to be obtained even with polyfunctional alcohols. Preferred polyfunctional alcohols for the present invention are ethylene glycol, di-ethylene glycol, tri-ethylene glycol, propylene glycol, di-propylene glycol, tri-propylene glycol. A particularly preferred polyfunctional alcohol for the present invention is ethylene glycol.

[0018] The present invention is also very effective when the compound bearing at least one -OH group is selected from phenols and benzene diols and triols. The method of the present invention also provides very good yields with these types of -OH-containing molecules. Preferred phenols for use herein are phenol, cresol, methoxyphenol, fluorophenol and chlorophenol.

[0019] In step A of the method of the present invention, one or more compounds carrying at least one -OH group as defined above are provided in a mixture with one or more polar aprotic solvents selected as defined above. Such solvents are generally good solvents for -OH-bearing compounds, and as a result, preferably, the mixture provided is homogeneous. The relative amounts of the one or more polar aprotic organic solvents selected and the one or more compounds carrying at least one -OH group are preferably at least 1:1 by weight, preferably at least 2:1, more preferably at least 3:1, and most preferably at least 4:1. Other solvents may be present in the mixture, but preferably, the total amount of the one or more -OH-bearing compounds and the one or more selected polar aprotic solvents represents at least 70% of the weight of the mixture, more preferably at least 80%, even more preferably at least 90%, and most preferably at least 95%.

[0020] The mixture provided in step A is reacted with one or more fluorinated olefins in step B of the method of the present invention. Any fluorinated olefin can be used in the present invention, including fully fluorinated olefins and partially fluorinated olefins. Partially fluorinated olefins include olefins that are fully halogenated (i.e., all hydrogens are replaced by halogens, provided that at least one hydrogen is replaced by a fluorine atom, such as TFE: tetrafluoroethylene, HFP: hexafluoropropylene, CTFE: chlorotrifluoroethylene, PMVE: perfluoromethyl vinyl ether, PEVE: perfluoroethyl vinyl ether, or PPVE: perfluoropropyl vinyl ether) and those that are partially halogenated such that they contain at least one C-F bond and at least one C-H bond and may contain one or more bonds between carbon and a halogen different from F, such as Cl, Br, or I, typically Cl (e.g., vinylidene fluoride: VDF, trifluoroethylene: TrFE). Fully halogenated olefins are preferred, and fully fluorinated olefins are more preferred.

[0021] In one embodiment, the fluorinated olefin for use in the method of the present invention has the following formula:

Chemical formula

[0022] Preferably, R a , R b , R c and R d are each independently selected from the group consisting of F, Cl, C1-C4 perfluorocarbon groups, C1-C4 oxygen-containing perfluorocarbon groups, C1-C4 fluorochlorohydrocarbon groups, and C1-C4 oxygen-containing fluorochlorohydrocarbon groups. More preferably, at least three of R a , R b , R c and R d are selected from F, Cl, and mixtures thereof).

[0023] Examples of such fluorinated olefins include tetrafluoroethylene (TFE), hexafluoropropylene (HFP), octafluorobutene, perfluoropentene, perfluorohexene, perfluoroheptene, perfluorooctene, perfluorocyclobutene, perfluorocyclopentene, perfluorocyclohexene, chlorotrifluoroethylene, dichlorodifluoroethylene, chloropentafluoropropene, perfluorobutadiene, perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether; CF3OCCl=CClF, trichloroethylene, tetrachloroethylene, dichloroethylene isomers; and the formula: [Chemical formula] (wherein X1, X2, X3 and X4, which may be the same as or different from each other, are F, R f and OR f (where R f is a (per)fluorocarbon group) are independently selected, and at least one of X3 and X4 is fluorine) Fluorodioxoles of may be mentioned. Preferably, the fluorinated olefin is among the fully halogenated olefins, more preferably selected from the group consisting of perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether, tetrafluoroethylene (TFE), chlorotrifluoroethylene (CTFE), hexafluoropropylene (HFP), and even more preferably TFE.

[0024] The fluorinated olefin can be initially charged into the reaction vessel or, advantageously, continuously supplied in the amount required during the reaction.

[0025] In step B of the method of the present invention, the mixture provided in step A is reacted with a fluorinated olefin in the presence of a basic catalyst.

[0026] The reaction between the -OH supported compound and the fluorinated olefin can be schematized as follows. [Chemical]

[0027] Referring thereto, the radical R1 may still contain other -OH groups according to the definition provided above (for example, in the case of a polyfunctional alcohol). Even in that case, the resulting hydrofluoroether will still contain the same -OH groups so that all the -OH groups can react further with other molecules of the fluorinated olefin until all of their oxygen atoms are involved in ether-type bonds.

[0028] The reaction can typically be carried out in a stirred reactor, preferably sealed. The molar ratio between the -OH-bearing compound and the fluorinated olefin is in principle stoichiometric, i.e., there should be the same molar amount of double bonds from the olefin as the molar amount of OH groups for a complete reaction and no residual reagents. Of course, in the case of a polyfunctional alcohol, each molecule bearing two or more -OHs can react with a number of molecules of the fluorinated olefin (one for each -OH group), so that, for example, 1 mole of ethylene glycol reacts stoichiometrically with 2 moles of olefin. Although a molar ratio of 1:1 between the double bond and the OH group is ideal, the present invention is effectively implemented even when one of the components is in a molar excess of up to 50%, preferably up to 30%, more preferably up to 20%, and most preferably up to 10%. When one component is in excess, the excess component is preferably the fluorinated olefin.

[0029] A basic catalyst can be any compound that can create a basic environment, i.e., remove protons from the reagents and thus promote ionic reactions. Preferred basic catalysts are selected from inorganic hydroxides (such as NaOH, KOH, LiOH, Ca(OH)2, Mg(OH)2, etc.), inorganic salts of weak acids (such as alkali metal phosphates or carbonates, etc.), and organic basic compounds (such as alcoholates, etc.). The most preferred basic catalysts are NaOH and KOH.

[0030] The amount of catalyst used is typically 5% to 100 mol%, preferably 10% to 70 mol%, more preferably 15% to 50 mol% relative to the total number of moles of -OH groups.

[0031] Typically, the basic catalyst is added to the reactor and added to the mixture provided in Step A under stirring. The reactor is then typically sealed, and the fluorinated olefin is pumped in gaseous form to a pressure of 1 to 50 bar, preferably 2 to 30 bar, more preferably 3 to 20 bar, most preferably 4 to 14 bar. If the fluorinated olefin is in liquid form, the olefin can be introduced as a liquid, and if it remains in a liquid state at the reaction temperature, the reaction can be carried out at a lower pressure or even at atmospheric pressure.

[0032] The reaction typically starts immediately. Preferably, during the reaction, the reactor is maintained at a temperature of 20°C to 90°C, preferably 30°C to 80°C, most preferably 40°C to 70°C. The reaction time can vary depending on the temperature, pressure, and reagents used. Typically, the reaction will take 1 to 20 hours to complete.

[0033] After the reaction is complete, the reactor is typically degassed to remove the excess fluorinated olefin. At this stage, the reactor contains a liquid reaction mixture containing one or more hydrofluoroethers and one or more organic solvents, together with residues of the basic catalyst and a small amount of reaction by-products.

[0034] Hydrofluoroethers can be directly extracted from the reaction mixture using known techniques such as distillation in optional step C of the present invention. However, the reaction mixture obtained in step B still contains dissolved or dispersed solids, typically inorganic solids derived from basic catalysts, and as a result, direct distillation of said reaction mixture causes the accumulation of undesirable solid deposits on the distillation apparatus, which may be acceptable on a laboratory scale, but is more problematic on an industrial scale as it may require frequent stoppages to clean / rehabilitate the equipment. Therefore, preferably, before extracting the hydrofluoroether via distillation, the reaction mixture is purified to remove catalyst residues and solid by-products.

[0035] In one embodiment, the reaction mixture is purified via extraction with water. In another embodiment, the reaction mixture is purified through evaporation and recondensation. These two embodiments are described in detail below.

[0036] Evaporation / Recondensation Method: In optional step D of the present invention, the liquid reaction mixture obtained directly from the reaction of step B is completely evaporated and recondensed in liquid form, thereby obtaining a purified reaction mixture. Any available technique can be used to evaporate the liquid reaction mixture, for example, heating and vacuum can be used individually or in combination to evaporate the mixture. Conventional evaporation apparatuses (e.g., rotary evaporators) can be used. Following the evaporation of the liquid reaction mixture, a solid residue containing the residual basic catalyst and salts obtained as by-products of the reaction is formed, and they can be discarded or recycled.

[0037] The purified reaction mixture obtained in step D, unlike the reaction mixture obtained in step B, is pure enough to be distilled in a conventional distillation apparatus. This is carried out in step E of the method of the present invention.

[0038] Water Extraction Method: In optional step F of the process of the present invention, the liquid reaction mixture obtained directly from the reaction of step B is mixed with water and subjected to mixing and / or stirring to extract water-soluble impurities such as residues of basic catalysts and other impurities and by-products into the aqueous phase. The relative amounts of water and reaction mixture for use in this step are from 1:15 to 15:1 by weight, preferably from 1:5 to 5:1, more preferably from 2:1 to 1:2. Stirring can be carried out using any suitable technique known to those skilled in the art for extraction, and the aqueous phase can be separated from the phase containing the aprotic polar solvent and hydrofluoroether using a separating funnel or similar device. The resulting phase containing the aprotic polar solvent and hydrofluoroether, when separated from the aqueous phase, constitutes a purified reaction mixture that is pure enough to be subjected to distillation in a conventional distillation apparatus in step G of the process of the present invention.

[0039] In all embodiments, distillation enables separation of the hydrofluoroether from the solvent and, if necessary, from themselves (when two or more hydrofluoroethers are obtained). Distillation can be carried out using conventional techniques and can be repeated if necessary to further purify the individual components. Generally, the solvent will be recovered by known methods for reuse.

[0040] The evaporation / rec condensation method described above is generally preferred over the water extraction method because the water extraction method produces a large amount of wastewater that is contaminated with system impurities and thus needs to be treated before disposal or reuse.

[0041] The process of the present invention can be carried out under mild conditions and a very high yield of hydrofluoroether is obtained.

[0042] Here, the present invention will be described in more detail in connection with the following examples, which are illustrative only and are not intended to limit the scope of the present invention. In case of conflict between the disclosure of any patent, patent application and publication incorporated herein by reference to the extent that it may obscure a term, the present description shall prevail.

Example

[0043] The identification of the product was carried out by NMR (F-NMR and H-NMR) and GC and GC-MS analysis (GC using CP-WAX52CB column and CP-Sil8CB column for GC-MS peak assignment).

[0044] Example 1 - Ethylene glycol + TFE + Evaporation 37 g of ethylene glycol, 211 g of acetonitrile and 9.4 g of sodium hydroxide were charged into a 600 ml stirred Hastelloy reactor. After purging with nitrogen and vacuum at 0.3 bar, the reactor was heated to 50 °C and pressurized to 11 bar with TFE (tetrafluoroethylene) while stirring. After 6 hours, stirring was stopped, the reactor was cooled, and the residue of TFE was purged with nitrogen. Then the reaction mixture was recovered, washed with 106 g of additional acetonitrile and drained. Next, the collected reaction mixture (480 g) was transferred to a glass flask and evaporated under a vacuum of 1 mbar in a rotary evaporator with the flask heated at 90 °C. The solid by-products (14.5 g) were discarded and a clear colorless purified reaction mixture (445 g) was collected. Then the purified reaction mixture was distilled in a glass distillation apparatus equipped with a flask, a packed column and a condenser with a vacuum pump. The distillation was carried out by raising the temperature from 100 °C to 155 °C and lowering the pressure from 950 mbar to 50 mbar. The distillation product contained 142 g of diether HCF2CF2-O-CH2CH2-O-CF2CF2H and 0.02 g of monomer ether HCF2CF2-O-CH2CH2-OH (0.01 wt% of the diether). The overall process yield based on the input amount of ethylene glycol was 90.3%.

[0045] Example 2 - Ethylene glycol + TFE + Water extraction 7231 g of acetonitrile, 2200 g of ethylene glycol and 1290 g of sodium hydroxide were charged into a 22 L stirred Hastelloy reactor. After purging four times with nitrogen and vacuum at 0.3 bar, the reactor was heated to 60 °C and pressurized with TFE (tetrafluoroethylene) to 3.5 bar under stirring, and TFE was continuously supplied to maintain the initial pressure. During the reaction, since the reaction was active and exothermic, the reactor was cooled. Approximately 1300 g / h of TFE was consumed. After 7.5 h, the reaction was stopped and the TFE supply was aborted. The reactor was kept at 60 °C with stirring, cooled to 25 °C, the excess TFE was purged with nitrogen, the reaction mixture was recovered and discharged. Then, the collected reaction mixture was transferred to a 200 L container, washed with 150 L of deionized water stirred at 25 °C for 6 h, and left to separate for 10 h. Then, the bottom organic layer was separated (9300 g) and batch distilled in a rectification column (2.70 m long, 40 mm inner diameter and 10 L bottom reboiler filled with 1 / 4 inch Teflon® cylinders).

[0046] The distillation of the hydrofluoroether was carried out under reduced pressure (80 mbar, 81 °C, head reflux ratio 10:1). The obtained hydrofluoroether mixture was 8060 g and was found to contain 8052 g of the diether HCF2CF2-O-CH2CH2-O-CF2CF2H and 8 g of the monoether HCF2CF2-O-CH2CH2-OH (0.1 wt% of the diether). The overall process yield based on the ethylene glycol charge was 86%.

[0047] Example 3 - Phenol + TFE + Water Extraction 3000 g of phenol, 3956 g of acetonitrile and 420 g of sodium hydroxide were charged into a 22 L stirred Hastelloy reactor. After purging four times with nitrogen and vacuum at 0.3 bar, the reactor was heated to 60 °C and pressurized with TFE (tetrafluoroethylene) to 3.8 bar under stirring, and TFE was continuously supplied to maintain the initial pressure. When the reaction started and the temperature rose due to the exothermic reaction, the temperature of the reactor was controlled at 70 °C for 8.5 hours (the total TFE supplied was 3536 g). After cooling, the reactor was purged with nitrogen, the reaction mixture was recovered and discharged. The reaction mixture was then washed with an aqueous phase containing three times its volume of demineralized water and 4 wt% sodium chloride. The organic layer was then separated as the purified reaction mixture. The purified reaction mixture was then distilled in a 70 cm Rashig column with an inner diameter of 30 mm equipped with a reflux head condenser. The distillation product was a composition containing hydrofluoroether (5999 g) and vinyl ether C6H5-O-CF=CF2 (3.7 g, 0.06 wt% of hydrofluoroether). The overall yield was 96.4% based on phenol.

[0048] When comparing the purity and yield of the method of the present invention with those of the prior art, it is clear that the method of the present invention provides a higher yield and higher purity of the hydrofluoroether obtained.

[0049] Possible modifications and / or additional forms to the embodiments disclosed and illustrated above can be made by those skilled in the art while remaining within the scope of the following claims.

[0050] If the disclosure of any patent, patent application, and publication incorporated herein by reference conflicts with the description of this application to the extent that it may obscure a term, the description shall control.

Claims

1. A method for producing hydrofluoroethers, A) To provide a mixture comprising one or more polar aprotic organic solvents having a boiling point measured at 1 atmosphere between 60°C and 170°C, and one or more compounds supporting at least one -OH group which is part of an alcohol or phenol group. B) To provide a reaction mixture containing one or more hydrofluoroethers by reacting one or more compounds supporting at least one -OH group with one or more fluorinated olefins in the presence of a basic catalyst. A method that includes this.

2. The method according to claim 1, wherein the fluorinated olefin is a fully halogenated olefin.

3. The method according to claim 2, wherein the fluorinated olefin is selected from perfluoromethyl vinyl ether, perfluoroethyl vinyl ether, perfluoropropyl vinyl ether, tetrafluoroethylene, hexafluoropropylene, and chlorotrifluoroethylene.

4. The method according to claim 3, wherein the fluorinated olefin is tetrafluoroethylene.

5. The method according to claim 1, wherein the one or more compounds supporting at least one -OH group are selected from polyfunctional alcohols.

6. The method according to claim 5, wherein the one or more compounds supporting at least one -OH group are selected from ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, and mixtures thereof.

7. The method according to claim 5, wherein the one or more compounds supporting at least one -OH group are ethylene glycol.

8. The method according to claim 1, wherein the one or more compounds supporting at least one -OH group are selected from phenols.

9. The method according to claim 8, wherein the one or more compounds supporting at least one -OH group are selected from phenol, cresol, methoxyphenol, fluorophenol, and chlorophenol, and are preferably phenol.

10. The method according to claim 1, wherein the one or more polar aprotic organic solvents are acetonitrile.

11. The method according to claim 1, comprising an additional step C in which the hydrofluoroether is preferably extracted directly from the reaction mixture by distillation.

12. D) A step of completely evaporating the reaction mixture and then re-condensing it in liquid form to obtain a purified reaction mixture. E) A step of separating the purified hydrofluoroether from the purified reaction mixture by distillation. The method according to claim 1, further comprising:

13. F) A step of mixing the reaction mixture with water, stirring the mixture to extract water-soluble impurities from the reaction mixture, and separating the purified reaction mixture as a water-immiscible phase. G) A step of separating the purified hydrofluoroether from the purified reaction mixture by distillation. The method according to claim 1, further comprising: