Method for purifying hydrofluoroether

Abstract

The invention provides a method for purifying hydrofluoroether. The method comprises the following steps: providing crude hydrofluoroether; carrying out reduced pressure distillation on the crude hydrofluoroether to obtain a light component and a heavy component; performing two or more adsorption sub-steps on the light component; and carrying out normal-pressure rectification on the adsorbed light components to obtain a hydrofluoroether product. According to the method disclosed by the invention, very high-purity hydrofluoroether suitable for being used in the electronic field can be efficiently obtained by a simple process.

Description

Technical Field

[0001] The present application relates to the field of chemical industry, and more specifically to a method for purifying hydrofluoroether to prepare ultra-high purity electronic grade hydrofluoroether. Background Art

[0002] Hydrofluoroether is a compound containing ether groups, carbon-fluorine bonds and carbon-hydrogen bonds. It has the advantages of high insulation and thermal conductivity, no flash point, non-flammable and non-explosive, high melting point and environmental protection. It is widely used as coolant, solvent, cleaning agent, desiccant (water removal agent) and anti-fingerprint agent in many precision equipment (especially precision electronic equipment) fields. In recent years, with the rapid development of precision electronic equipment, the demand for hydrofluoroether has also increased significantly.

[0003] However, the existing hydrofluoroether synthesis, refining and purification processes have obvious defects, which seriously restrict the large-scale marketization of hydrofluoroether in the field of precision electronic equipment, thereby restricting the rapid development of precision electronic equipment. Specifically, the existing hydrofluoroether synthesis methods (whether direct fluorination, electrochemical fluorination, or the process of synthesizing hydrofluoroether by various addition reactions, alkylation reactions or elimination reactions) will inevitably generate some organic byproducts (such as unsaturated byproducts, most typically fluorinated olefin ethers) very close to the boiling point of hydrofluoroether while synthesizing the target product hydrofluoroether. These organic byproducts remain in the hydrofluoroether, which will cause the various properties of the hydrofluoroether to be seriously reduced, and are not suitable for use in high-end precision electronic equipment.

[0004] In the prior art, the method of removing such organic byproducts from hydrofluoroethers is usually to combine complex and costly chemical reactions or physical and distillation processes, such as adding catalysts / oxidants / co-oxidants to hydrofluoroether products, or adding a large amount of sulfuric acid or salts, liquid bromine thereto, and converting the fluorinated ether impurities therein into substances with a large difference in boiling points after the chemical reaction, so as to remove them by physical purification methods. However, these impurity removal and purification processes are without exception unable to obtain ultra-high purity hydrofluoroethers (≥99.99%, also known as "electronic grade hydrofluoroethers") required for advanced precision electronic equipment, the target product hydrofluoroethers are insufficient in purity, have a high water content (e.g., about 500ppm), and have a low yield. In addition, the additional chemical reagents added in these prior art processes increase the production cost, resulting in the generation of three wastes and related treatment costs, the operation steps are cumbersome, and the corrosiveness of the chemical reagents also places higher requirements on equipment materials.

[0005] Therefore, the art particularly hopes to develop a new hydrofluoroether purification method, which preferably can avoid the use of the additional chemical reagents mentioned above, purify in a simple and low-cost method, and achieve the purpose of obtaining extremely high purity and low water content to meet the requirements of electronic grade hydrofluoroether.

[0006] In view of the problems existing in the above-mentioned prior art, the inventors of the present application have developed a technology for purifying hydrofluoroether to prepare electronic-grade hydrofluoroether through extensive and in-depth research, which unexpectedly solves the long-standing problem in the prior art that needs to be solved. Summary of the invention

[0007] The present application provides a method for purifying hydrofluoroether, the method comprising the following steps:

[0008] Step I: providing a crude hydrofluoroether;

[0009] Step II: performing reduced pressure distillation on the crude hydrofluoroether to obtain a light component and a heavy component;

[0010] Step III: performing two or more adsorption operations on the light component;

[0011] Step IV: distilling the adsorbed light components at atmospheric pressure to obtain a hydrofluoroether product.

[0012] According to one embodiment of the present application, the method further includes step V: after step IV, the purity of the hydrofluoroether product is monitored in an intermittent or continuous manner; if the purity of the hydrofluoroether product is lower than the target value, its purity is unqualified, and the hydrofluoroether product with unqualified purity is transported back to step II; if the purity of the hydrofluoroether product is equal to or higher than the target value, the purity is qualified.

[0013] According to another embodiment of the present application, the hydrofluoroether has a structure shown in Formula I:

[0014] R1-O-R2 formula I

[0015] Wherein R1 is selected from: C1-C6 alkyl, partially fluorinated C1-C6 alkyl, C1-C6 perfluoroalkyl; R2 is selected from: partially fluorinated C2-C8 alkyl, C2-C8 perfluoroalkyl, fluoro-chloro C2-C8 alkyl.

[0016] According to another embodiment of the present application, in step I, the crude hydrofluoroether is prepared by allowing the fluorinated olefin to undergo an addition reaction with an alkyl alcohol in the presence of a base catalyst and an organic solvent. According to another embodiment of the present application, the fluorinated olefin is selected from one or more of the following: partially fluorinated C2-C8 olefins, perfluorinated C2-C8 olefins, fluorinated-chloro C2-C8 olefins. According to another embodiment of the present application, the alkyl alcohol is selected from one or more of the following: C1-C6 alkyl alcohol, partially fluorinated C1-C6 alkyl alcohol, C1-C6 perfluoroalkyl alcohol; provided that the fluorinated olefin and the alkyl alcohol are not perfluorinated at the same time. According to another embodiment of the present application, the molar ratio of the alkyl alcohol, the fluorinated olefin and the organic solvent in the addition reaction is 1:(1-2):(1-5). According to another embodiment of the present application, the reaction temperature of the addition reaction is 30-100°C and the pressure is 0.1-0.5MPa.

[0017] According to another embodiment of the present application, the fluorinated olefin is selected from one or more of the following: hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, trifluorochloroethylene, tetrafluoropropylene, vinyl fluoride, and vinylidene fluoride. According to another embodiment of the present application, the alkyl alcohol is selected from one or more of the following: methanol, ethanol, n-propanol, isopropanol, trifluoromethanol, trifluoroethanol, pentafluoropropanol, hexafluoroisopropanol, heptafluorobutanol, and tetrafluorobutanol. According to another embodiment of the present application, the organic solvent is selected from one or more of the following: tetrahydrofuran, acetonitrile, butyronitrile, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dimethyl sulfoxide, N,N-dimethylformamide, and glycerol.

[0018] According to another embodiment of the present application, the content of hydrofluoroether in the crude hydrofluoroether is 30-60%, and the target purity of the hydrofluoroether product is ≥99.99%.

[0019] According to another embodiment of the present application, the vacuum distillation in step II is carried out in a vacuum distillation kettle, the bottom temperature of the vacuum distillation kettle is 70-110°C, the pressure is -0.001Mpa to -0.050MPa, the top temperature is 25-65°C, and the heavy component is transported to the addition reaction for preparing crude hydrofluoroether in step I.

[0020] According to another embodiment of the present application, in step III, the light component is passed through a primary adsorption tower and a secondary adsorption tower in sequence, at least a portion of organic impurities in the light component is removed in the primary adsorption tower, and at least a portion of water in the light component is removed in the secondary adsorption tower. According to another embodiment of the present application, the primary adsorption tower is filled with a molecular sieve adsorbent loaded with silver salt. According to another embodiment of the present application, the secondary adsorption tower is filled with a water absorbent.

[0021] According to another embodiment of the present application, the atmospheric distillation of step IV is carried out in an atmospheric distillation tower, the theoretical plate number of the atmospheric distillation tower is 15-60, the bottom temperature is 30-70°C, the top temperature is 25-65°C, the pressure difference is 5-10kPa, and the reflux ratio is 5:1-15:1.

[0022] According to another embodiment of the present application, the purity of the hydrofluoroether product is ≥99.99%, the water content thereof is ≤50 ppm, and the product yield is >80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic flow chart of the method of the present application is shown;

[0024] Figure 2 A schematic diagram of synthesizing hydrofluoroether according to an exemplary embodiment of the present application is shown. DETAILED DESCRIPTION

[0025] "Range" disclosed herein is in the form of lower limit and upper limit. It can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges that can be defined in this way are inclusive and combinable, i.e. any lower limit can be combined with any upper limit to form a range. For example, a range of 60-120 and 80-110 is listed for a particular parameter, and it is understood that a range of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.

[0026] In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.

[0027] In this application, unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined with each other to form a new technical solution.

[0028] In this application, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0029] In this application, unless otherwise specified, the term "comprising" as used herein may be open-ended or closed-ended. For example, the term "comprising" may mean that other components not listed may also be included, or may only include the listed components.

[0030] In the present invention, "hydrofluoroether" refers to a compound containing an "ether group", a "carbon-fluorine bond" and a "carbon-hydrogen bond" in one molecule. According to one embodiment of the present application, the hydrofluoroether has a structure shown in Formula I:

[0031] R1-O-R2 formula I

[0032] According to one embodiment of the present application, in Formula I, R1 is selected from: C1-C6 alkyl, partially fluorinated C1-C6 alkyl, C1-C6 perfluoroalkyl; preferably R1 is selected from: C1-C4 alkyl, partially fluorinated C1-C4 alkyl, C1-C4 perfluoroalkyl; more preferably R1 is selected from: methyl, ethyl, n-propyl, isopropyl, trifluoromethyl, trifluoroethyl (e.g. 2,2,2-trifluoroethyl), pentafluoropropyl (e.g. 2,2,3,3,3-pentafluoropropyl), hexafluoropropyl (e.g. hexafluoroisopropyl), heptafluorobutyl (e.g. 2,2,3,3,4,4,4-heptafluorobutyl, 2,3,3,3,3',3',3'-heptafluorobutyl), tetrafluorobutyl (e.g. 2,2,3,3-tetrafluorobutyl).

[0033] According to another embodiment of the present application, in Formula I, R2 is selected from: partially fluorinated C2-C8 alkyl, C2-C8 perfluoroalkyl, fluoro-chloro C2-C8 alkyl; preferably, R2 is selected from: partially fluorinated C2-C4 alkyl, C2-C4 perfluoroalkyl, fluoro-chloro C2-C4 alkyl; preferably, R2 is selected from: monofluoroethyl, difluoroethyl, trifluoroethyl, trifluoromonochloroethyl, tetrafluoroethyl, hexafluoropropyl.

[0034] The method of the present invention is used to purify crude hydrofluoroether with relatively low purity to obtain electronic grade hydrofluoroether product with ultra-high purity (purity ≥ 99.99%). The crude hydrofluoroether purified by the method of the present invention has relatively low purity, and therefore does not meet the purity requirements of electronic grade hydrofluoroether product. For example, the purity of the crude hydrofluoroether may be lower than 95%, or lower than 90%, or lower than 80%, or lower than 60%. In the present invention, the purity of the hydrofluoroether is a percentage measured by gas chromatography.

[0035] The crude hydrofluoroether used as the purification target in the present invention can be a reaction mixture obtained by various hydrofluoroether synthesis techniques, or a crude product stream obtained after the reaction mixture is subjected to preliminary purification and / or preliminary separation treatment (such as filtration, decantation, etc.). According to an exemplary embodiment of the present application, the hydrofluoroether synthesis technique is selected from: direct fluorination, electrochemical fluorination, addition reaction of unsaturated hydrocarbons (such as olefins) and alcohols (one or both of the unsaturated hydrocarbons and alcohols are fluorinated or perfluorinated), alkylation reaction of fluorine-containing carbonyl compounds, and intermolecular elimination reaction of alkyl halides and alcohols, etc.

[0036] According to an exemplary embodiment of the present application, the crude hydrofluoroether as the purification target is prepared by an addition reaction of a fluorinated olefin and an alkyl alcohol in the presence of a base catalyst and an organic solvent.

[0037] In a more specific exemplary embodiment of the present application, the fluorinated olefin is selected from one or more of the following: partially fluorinated C2-C8 olefins, perfluorinated C2-C8 olefins, fluoro-chloro C2-C8 olefins; preferably, the fluorinated olefin is selected from one or more of the following: partially fluorinated C2-C6 olefins, perfluorinated C2-C6 olefins, fluoro-chloro C2-C6 olefins; more preferably, the fluorinated olefin is selected from one or more of the following: partially fluorinated C2-C4 olefins, perfluorinated C2-C4 olefins, fluoro-chloro C2-C4 olefins; most preferably, the fluorinated olefin is selected from one or more of the following: partially fluorinated C2-C3 olefins, perfluorinated C2-C3 olefins, fluoro-chloro C2-C3 olefins. According to a specific embodiment of the present application, the fluorinated olefin is selected from one or more of the following: hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, tetrafluoropropylene, vinyl fluoride, vinylidene fluoride.

[0038] In a more specific exemplary embodiment of the present application, the alkyl alcohol is selected from one or more of the following: C1-C6 alkyl alcohol, partially fluorinated C1-C6 alkyl alcohol, C1-C6 perfluoroalkyl alcohol; preferably, the alkyl alcohol is selected from one or more of the following: C1-C4 alkyl alcohol, partially fluorinated C1-C4 alkyl alcohol, C1-C4 perfluoroalkyl alcohol; more preferably, the alkyl alcohol is selected from one or more of the following: methanol, ethanol, n-propanol, isopropanol, trifluoromethanol, trifluoroethanol, pentafluoropropanol, hexafluoroisopropanol, heptafluorobutanol, tetrafluorobutanol.

[0039] However, the fluorinated olefins and alkyl alcohols mentioned above cannot be perfluorinated at the same time, that is, they contain at least one carbon-hydrogen bond (CH) in total.

[0040] According to one embodiment of the present application, the molar ratio of the alkyl alcohol to the fluorinated olefin used in the reaction is 1:1 to 1:2, preferably 1:1.1 to 1:1.8, and more preferably 1:1.2 to 1:1.5.

[0041] The organic solvent is selected from one or more of the following: tetrahydrofuran, acetonitrile, butyronitrile, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dimethyl sulfoxide, N,N-dimethylformamide, and glycerol.

[0042] According to one embodiment of the present application, the molar ratio of the alkyl alcohol to the organic solvent used in the reaction is 1:1 to 1:5, preferably 1:1.2 to 1:4, more preferably 1:1.3 to 1:3, and most preferably 1:1.4 to 1:2.

[0043] According to another embodiment of the present application, the base catalyst used in the reaction is an inorganic or organic base, preferably an inorganic base, such as potassium hydroxide, sodium hydroxide, lithium hydroxide, ammonia, etc. Based on the total weight of all raw materials used in the above reaction, the content of the base catalyst can be 0.1-5% by weight, preferably 0.5-3% by weight, and more preferably 1-2% by weight.

[0044] According to one embodiment of the present application, the reaction temperature of the above reaction is 30-100°C, preferably 50-85°C; and the reaction pressure is 0.1-0.5MPa.

[0045] The reaction mixture obtained by the above reaction mainly contains solvent, target product hydrofluoroether, organic byproducts (such as unsaturated ether, more specifically fluorinated olefin ether), water and a small amount of unreacted raw material components, etc. According to another embodiment of the present application, the reaction mixture (the crude hydrofluoroether to be purified by the method of the present invention) contains 35-50% of the target product hydrofluoroether, 45-60% of the solvent, 0.5-2% of the organic byproducts, 10 ppm to 2000 ppm of water and 1-2% of other impurities.

[0046] Figure 2 An exemplary nucleophilic addition reaction for preparing a hydrofluoroether is shown, in which trifluoroethanol undergoes nucleophilic addition to the carbon-carbon double bond of tetrafluoroethylene in the presence of a KOH catalyst to generate the target product hydrofluoroether (tetrafluoroethyl trifluoroethyl ether).

[0047] According to one embodiment of the present application, the crude hydrofluoroether is then subjected to vacuum distillation, two or more adsorption operations, and atmospheric distillation in sequence to obtain an ultra-high purity hydrofluoroether product. Figure 1 A schematic diagram of the purification method of the present invention is shown.

[0048] like Figure 1As shown, in the second step of the method of the present invention, the crude hydrofluoroether is subjected to vacuum distillation in a vacuum distillation tower to separate the crude hydrofluoroether into a light component and a heavy component. The heavy component flows out from the bottom of the vacuum distillation tower, which mainly contains an organic solvent, and the heavy component can be transported back to the reactor for synthesizing hydrofluoroether for reuse (recycling). The heavy component can be directly returned to the reactor for reuse, or it can be further impurity-removed before reuse. The light component flowing out from the top of the vacuum distillation tower is a crude product flow with the organic solvent basically removed, which mainly contains the target product (hydrofluoroether), organic by-products, a small amount of residual organic solvent, moisture and other impurities, and the light component is transported to the downstream adsorption equipment for adsorption treatment.

[0049] According to another embodiment of the present application, during the process of the vacuum distillation, the bottom temperature of the vacuum distillation tower is 70-110°C, preferably 80-95°C; the pressure is -0.001MPa to -0.050MPa, preferably -0.010MPa to -0.020Mpa; and the top temperature is 25-65°C, preferably 30-50°C.

[0050] According to one embodiment of the present application, step III of the method of the present invention includes two sub-steps, namely, sub-step IIIa: removing at least a portion of organic impurities in the light component in a primary adsorption tower, and sub-step IIIb: removing at least a portion of water in the light component in a secondary adsorption tower.

[0051] According to one embodiment of the present application, the primary adsorption tower is filled with an adsorbent to remove at least a portion of the by-products and impurities (e.g., olefin ether by-products containing unsaturated bonds and other organic impurities) contained in the light component. The adsorbent can be formed by loading a silver salt on a molecular sieve, such as by treating the molecular sieve with a silver salt solution so that the silver salt is loaded thereon. Examples of the silver salt include silver nitrate, silver perchlorate, etc., preferably silver nitrate.

[0052] According to another embodiment of the present application, the secondary adsorption tower is filled with an adsorbent, examples of which are calcium hydride, calcium oxide, and the like.

[0053] In the fourth step of the method of the present invention, the light components subjected to the adsorption treatment are subjected to atmospheric distillation treatment to obtain electronic grade hydrofluoroether with the desired ultra-high purity. According to one embodiment of the present application, the atmospheric distillation treatment is carried out in an atmospheric distillation tower.

[0054] According to another embodiment of the present application, the number of theoretical plates of the atmospheric distillation tower is 50-120, preferably 80-100.

[0055] According to another embodiment of the present application, the bottom temperature of the atmospheric distillation tower is 30-70°C, the top temperature is 25-65°C, and the top temperature is 1-8°C lower than the bottom temperature, preferably the top temperature is 2-4°C lower than the bottom temperature. According to an exemplary embodiment of the present application, the bottom temperature of the atmospheric distillation tower is 55-60°C, the top temperature is 52-58°C, and the top temperature is 2-3°C lower than the bottom temperature. According to another exemplary embodiment of the present application, the bottom temperature of the atmospheric distillation tower is 38-42°C, the top temperature is 35-38°C, and the top temperature is 2-4°C lower than the bottom temperature.

[0056] According to another embodiment of the present application, the pressure difference in the atmospheric distillation tower (the pressure difference between the bottom of the tower and the top of the tower in the distillation tower) is 5-10 kPa, preferably 6-8 KPa.

[0057] According to another embodiment of the present application, the reflux ratio in the atmospheric distillation tower is 5: 1-15: 1, preferably 6: 1-10: 1, and more preferably 8: 1-10: 1. The reflux ratio described herein refers to the ratio of the reflux flow rate returned from the top of the distillation tower to the top product flow rate during the atmospheric distillation operation.

[0058] According to one embodiment of the present application, Figure 1 As shown in the process flow chart, the purity of the product stream flowing out of the top of the atmospheric distillation tower is monitored continuously or intermittently. When the purity of the product stream meets the purity requirement of electronic grade hydrofluoroether, the product stream is transported to the product collection tank; when the purity of the product stream does not meet the purity requirement of electronic grade hydrofluoroether, the unqualified product stream is recycled back to the upstream vacuum distillation tower, and the above steps II, III and IV are repeated until the purity of the product stream is monitored to be qualified.

[0059] The advantages of the present invention are:

[0060] 1. Through simple and low-cost equipment and steps, the purification of ultra-high purity electronic grade hydrofluoroether is efficiently achieved. The product purity can reach ≥99.99%, the yield is >80%, and the water content is ≤50ppm. It is expected to be used in high-end electronic fields such as big data immersion coolants, electronic cleaning agents, etc.

[0061] 2. Through the precise design of the equipment and steps of the present invention, the removal of byproducts, moisture and other impurities in the product is efficiently achieved. The inventor unexpectedly found that omitting any purification step of the method of the present invention, or replacing any purification step with other operations (other purification processes that are considered to have equivalent effects in the prior art), or reversing the order of any two or more purification steps, the beneficial effects of the present invention cannot be achieved.

[0062] The methods of the present application are specifically described in the following examples, the purpose of which is to better understand the content of the present application. It should be understood that these examples are merely illustrative and not restrictive. The reagents used in the examples are all purchased from the market and used directly without further purification.

[0063] Example

[0064] The following equipment was used in the following examples:

[0065] Vacuum distillation apparatus: The tower bottom is a 5L three-necked flask, which is connected to a thorn-shaped distillation column, a thermometer, a straight condenser, a tail pipe, a vacuum pump and a collecting bottle. The tower bottom is heated in a water bath, and all interfaces are wrapped with PTFE tape to prevent leakage.

[0066] Adsorption tower device: the first-stage adsorption tower is an adsorption column of 25 mm × 1000 mm, which is filled with molecular sieve loaded with silver nitrate; the second-stage adsorption tower is an adsorption column of 25 mm × 1000 mm, which is filled with calcium oxide.

[0067] Atmospheric distillation device: The tower kettle is a 3L three-necked flask, which is connected to the distillation tower body and thermometer respectively. The tower body vacuum interlayer is not silver-plated with an expansion ring fractionation column (25mm×1300mm), and stainless steel West Tower ring packing (6mm×6mm) is installed inside. The effective height is 120mm, using 5225 fractionation head, solenoid valve, reflux ratio controller, the tower kettle is heated by oil bath, the cooling of the tower top condenser is low-temperature coolant circulation pump, single-mouth collection bottle, all interfaces are wrapped with PTFE tape to prevent leakage. The theoretical number of plates is 80.

[0068] The sample composition in the embodiment is detected using an Agilent 8890 gas chromatograph equipped with a DB-624 chromatographic column with a column size of 60m×320μm×1.8μm. The gas chromatography detection conditions are as follows: detector temperature 250°C, injection port temperature 200°C, column flow 1.5mL / min, carrier gas speed: hydrogen 30mL / min, air 300mL / min, nitrogen 30mL / min, split ratio 60:1, injection volume 1μL. The program temperature is raised to 40°C for 10min, then raised to 120°C at a rate of 10°C / min and maintained for 2min; raised to 180°C at a rate of 20°C / min and maintained for 15min.

[0069] The moisture content of the samples in the examples was measured using a Karl Fischer titrator.

[0070] Example 1

[0071] In the present embodiment, firstly, the preparation of hydrofluoroether reaction solution is carried out by following steps: after checking that the air tightness of the reactor is qualified, potassium hydroxide 50g, trifluoroethanol 1000g, diethylene glycol dimethyl ether solvent 2000g are added into the reactor, the reactor is evacuated and replaced with nitrogen, and the process is repeated for many times, until the oxygen content <20ppm in the reactor is detected to be qualified. At this time, the reactor is evacuated again, and heating is started so that the temperature of the reactor rises to 50 ℃, and the temperature is maintained in the reaction process afterwards, and stirring is opened, tetrafluoroethylene 1200g is passed into the reactor, and the reaction is continuously carried out until the pressure in the reactor no longer has an obvious downward trend, and the reaction ends at this time, and the reactor is opened to discharge. The discharged material is filtered to obtain hydrofluoroether reaction solution 3800g.

[0072] The reaction liquid was tested by gas chromatography, and the content of tetrafluoroethyl trifluoroethyl ether, diethylene glycol dimethyl ether solvent content, 0.60% olefin ether impurity content, and other impurities content were 1.35%. The water content was 850 ppm by Karl Fischer titrator.

[0073] Subsequently, 3800 g of the reaction solution was transported to the vacuum distillation tower kettle for vacuum distillation. The conditions of the vacuum distillation tower were as follows: the kettle temperature was 90° C., the pressure was −0.020 MPa, and the tower top temperature was 48° C. The heavy components at the bottom of the tower were recycled back to the reactor for reuse, and the light components flowing out of the tower top were collected. The hydrofluoroether content was 99.09% as measured by gas chromatography.

[0074] The light component was passed through a primary adsorption tower and a secondary adsorption tower connected in series in sequence, and the hydrofluoroether content of the product stream after the secondary adsorption was measured by gas chromatography to be 99.65%.

[0075] The adsorbed material was transported to the atmospheric distillation tower. The conditions of the atmospheric distillation tower were as follows: tower bottom temperature 58°C, tower top 56°C, pressure difference 6kpa, reflux ratio 6:1, and the top fraction was collected. The content of hydrofluoroether in the top fraction was 99.993% and the content of other impurities was 0.007% as measured by gas chromatography. It took 20 hours and the yield of hydrofluoroether was 85%. The water content of the top fraction was 0.5ppm as measured by Karl Fischer titrator.

[0076] The composition of the reaction solution and the liquid stream after each purification step was detected by gas chromatography, and the results are summarized in the following Table 1.

[0077] Table 1 Composition of the reaction solution and the materials after each purification step

[0078]

[0079] Example 2

[0080] In the present embodiment, firstly, the preparation of hydrofluoroether reaction solution is carried out by following steps: after checking that the air tightness of the reactor is qualified, potassium hydroxide 50g, trifluoroethanol 1000g, diethylene glycol dimethyl ether solvent 2000g are added into the reactor, the reactor is evacuated and replaced with nitrogen, and the process is repeated for many times, until the oxygen content <20ppm in the reactor is detected to be qualified. At this time, the reactor is evacuated again, and heating is started so that the temperature of the reactor rises to 50 ℃, and the temperature is maintained in the reaction process afterwards, stirring is opened, hexafluoropropylene 1800g is passed into the reactor, and the reaction is continued until the pressure in the reactor no longer has an obvious downward trend, and the reaction ends at this time, and the reactor is opened for discharging. The discharged material is filtered to obtain hydrofluoroether reaction solution 4200g.

[0081] The reaction liquid was tested by gas chromatography, and the content of hexafluoropropyl trifluoroethyl ether in the reaction liquid was 55.20%, the content of diethylene glycol dimethyl ether solvent was 43.30%, the content of olefin ether impurities was 0.39%, and the content of other impurities was 1.11%. The water content was 780 ppm by Karl Fischer titrator.

[0082] Subsequently, 4200 g of the reaction solution was transported to the vacuum distillation tower kettle for vacuum distillation. The conditions of the vacuum distillation tower were as follows: the kettle temperature was 95° C., the pressure was −0.020 MPa, and the tower top temperature was 50° C. The heavy components at the bottom of the tower were recycled back to the reactor for reuse, and the light components flowing out of the tower top were collected. The hydrofluoroether content was measured by gas chromatography to be 99.10%.

[0083] The light component was passed through a primary adsorption tower and a secondary adsorption tower connected in series in sequence, and the hydrofluoroether content of the product stream after the secondary adsorption was measured by gas chromatography to be 99.70%.

[0084] The adsorbed material was transported to the atmospheric distillation tower. The conditions of the atmospheric distillation tower were as follows: tower bottom temperature 60°C, tower top 58°C, pressure difference 6kpa, reflux ratio 6:1, and the top fraction was collected. The content of hydrofluoroether in the top fraction was 99.991% and the content of other impurities was 0.009% as measured by gas chromatography. It took 25 hours and the yield of hydrofluoroether was 80%. The water content of the top fraction was 0.8ppm as measured by Karl Fischer titrator.

[0085] The composition of the reaction solution and the liquid stream after each purification step was detected by gas chromatography, and the results are summarized in Table 2 below.

[0086] Table 2 Composition of the reaction solution and the materials after each purification step

[0087]

[0088] Example 3

[0089] In the present embodiment, the preparation of hydrofluoroether reaction liquid is first carried out by the following steps: after checking that the air tightness of the reactor is qualified, potassium hydroxide 50g, methanol 320g, diethylene glycol dimethyl ether solvent 2000g are added into the reactor, the reactor is evacuated and replaced with nitrogen, and the process is repeated for many times until the oxygen content in the reactor is detected to be less than 20ppm, which is qualified. At this time, the reactor is evacuated again, and heating is started so that the temperature of the reactor rises to 30°C, and is maintained at this temperature during the subsequent reaction process, stirring is turned on, tetrafluoroethylene 1200g is passed into the reactor, and the reaction is continued until the pressure in the reactor no longer has an obvious downward trend, and the reaction ends at this time, and the reactor is opened for discharging. The discharged material is filtered to obtain 3000g of hydrofluoroether reaction liquid.

[0090] The reaction liquid was tested by gas chromatography, and the content of tetrafluoroethyl methyl ether, diethylene glycol dimethyl ether solvent content, olefin ether impurity content, and other impurities content were measured to be 38.35%, 59.50%, 0.50%, and 1.65%, respectively. The water content was measured by Karl Fischer titrator to be 750 ppm.

[0091] Subsequently, 3000 g of the reaction solution was transported to the vacuum distillation tower kettle for vacuum distillation. The conditions of the vacuum distillation tower were as follows: the kettle temperature was 85° C., the pressure was −0.010 MPa, and the tower top temperature was 25° C. The heavy components at the bottom of the tower were recycled back to the reactor for reuse, and the light components flowing out of the tower top were collected. The hydrofluoroether content was measured by gas chromatography to be 98.85%.

[0092] The light component was passed through a primary adsorption tower and a secondary adsorption tower connected in series in sequence, and the hydrofluoroether content of the product stream after the secondary adsorption was measured by gas chromatography to be 99.33%.

[0093] The adsorbed material was transported to the atmospheric distillation tower. The conditions of the atmospheric distillation tower were as follows: tower bottom temperature 40°C, tower top 37°C, pressure difference 6kpa, reflux ratio 10:1, and the top fraction was collected. The content of hydrofluoroether in the top fraction was 99.994% and the content of other impurities was 0.006% by gas chromatography. It took 20 hours and the yield of hydrofluoroether was 80%. The water content of the top fraction was 0.6ppm by Karl Fischer titrator.

[0094] The composition of the reaction solution and the liquid stream after each purification step was detected by gas chromatography, and the results are summarized in Table 3 below.

[0095] Table 3 Composition of the reaction solution and the materials after each purification step

[0096]

[0097] Comparative Example 1

[0098] In this comparative example 1, a nucleophilic addition reaction was first carried out according to the same steps as in Example 1 to obtain 3800 g of a hydrofluoroether reaction solution.

[0099] Subsequently, 3800 g of the reaction solution was transported to the atmospheric distillation tower. The conditions of the atmospheric distillation tower were as follows: the tower temperature was 97°C, the tower top was 40°C, the reflux ratio was 10:1, and the tower top fraction was collected. The content of hydrofluoroether in the tower top fraction was 99.80% and the content of other impurities was 0.10% by gas chromatography. It took 60 hours and the yield of hydrofluoroether was 68%. The water content of the tower top fraction was 650 ppm by Karl Fischer titrator.

[0100] The compositions of the reaction liquid and the liquid stream after atmospheric distillation were detected by gas chromatography, and the results are summarized in Table 4 below.

[0101] Table 4 Composition of the reaction liquid and the material after atmospheric distillation

[0102]

[0103] Comparative Example 2

[0104] In this comparative example 2, a nucleophilic addition reaction was first carried out according to the same steps as in Example 1 to obtain 3800 g of a hydrofluoroether reaction solution.

[0105] Subsequently, 3800 g of the reaction solution was transported to the vacuum distillation tower kettle for vacuum distillation. The conditions of the vacuum distillation tower were as follows: the kettle temperature was 90° C., the pressure was −0.020 MPa, and the tower top temperature was 48° C. The heavy components at the bottom of the tower were recycled back to the reactor for reuse, and the light components flowing out of the tower top were collected. The hydrofluoroether content was 99.09% as measured by gas chromatography.

[0106] The light component was transported to the atmospheric distillation tower kettle. The conditions of the atmospheric distillation tower were as follows: the tower kettle temperature was 58°C, the tower top was 56°C, the pressure difference was 6kpa, the reflux ratio was 10:1, and the tower top fraction was collected. The gas chromatography measured that the content of hydrofluoroether in the tower top fraction was 99.92%, the olefin ether impurity content was 0.01%, and the content of other impurities was 0.07%. It took 40 hours and the yield of hydrofluoroether was 73%. The water content of the tower top fraction was 500ppm measured by Karl Fischer titrator.

[0107] The composition of the reaction solution and the liquid stream after each purification step was detected by gas chromatography, and the results are summarized in the following Table 5.

[0108] Table 5 Composition of the reaction solution and the materials after each purification step

[0109]

[0110] Comparative Example 3

[0111] In this comparative example 3, a nucleophilic addition reaction was first carried out according to the same steps as in Example 1 to obtain 3800 g of a hydrofluoroether reaction solution.

[0112] Subsequently, 3800 g of the reaction solution was transported to the vacuum distillation tower kettle for vacuum distillation. The conditions of the vacuum distillation tower were as follows: the kettle temperature was 90° C., the pressure was −0.020 MPa, and the tower top temperature was 48° C. The heavy components at the bottom of the tower were recycled back to the reactor for reuse, and the light components flowing out of the tower top were collected. The hydrofluoroether content was 99.09% as measured by gas chromatography.

[0113] The light component was transported to the bottom of the atmospheric distillation tower. The conditions of the atmospheric distillation tower were as follows: bottom temperature of 58°C, top of tower of 56°C, pressure difference of 6kpa, reflux ratio of 10:1, and the top fraction was collected. The content of hydrofluoroether in the top fraction was 99.85%, the content of olefin ether impurity was 0.09%, and the content of other impurities was 0.06% as measured by gas chromatography.

[0114] The stream after atmospheric distillation was passed through a primary adsorption tower and a secondary adsorption tower connected in series in sequence. The hydrofluoroether content of the product stream after the secondary adsorption was measured by gas chromatography to be 0.85%.

[0115] The process took 45 hours and the yield of hydrofluoroether was 70%. The water content of the top fraction was measured by Karl Fischer titrator and was 56 ppm.

[0116] The composition of the reaction solution and the liquid stream after each purification step was detected by gas chromatography, and the results are summarized in the following Table 6.

[0117] Table 6 Composition of the reaction solution and the materials after each purification step

[0118]

Claims

1. A method for purifying a hydrofluoroether, the method comprising the following steps: Step I: providing a crude hydrofluoroether; Step II: performing reduced pressure distillation on the crude hydrofluoroether to obtain a light component and a heavy component; Step III: performing two or more adsorption operations on the light component; Step IV: distilling the adsorbed light components at atmospheric pressure to obtain a hydrofluoroether product.

2. The method according to claim 1, characterized in that The method further comprises step V: after step IV, monitoring the purity of the hydrofluoroether product in an intermittent or continuous manner; if the purity of the hydrofluoroether product is lower than the target value, the purity is unqualified, and the hydrofluoroether product with unqualified purity is transported back to step II; if the purity of the hydrofluoroether product is equal to or higher than the target value, the purity is qualified.

3. The method according to claim 1, characterized in that The hydrofluoroether has a structure shown in Formula I: R1-O-R2 formula I Wherein R1 is selected from: C1-C6 alkyl, partially fluorinated C1-C6 alkyl, C1-C6 perfluoroalkyl; R2 is selected from: partially fluorinated C2-C8 alkyl, C2-C8 perfluoroalkyl, fluoro-chloro C2-C8 alkyl.

4. The method according to claim 1, characterized in that In step I, the crude hydrofluoroether is prepared by subjecting a fluorinated olefin to an addition reaction with an alkyl alcohol in the presence of a base catalyst and an organic solvent; The fluorinated olefin is selected from one or more of the following: partially fluorinated C2-C8 olefins, perfluorinated C2-C8 olefins, fluorinated-chlorinated C2-C8 olefins; the alkyl alcohol is selected from one or more of the following: C1-C6 alkyl alcohol, partially fluorinated C1-C6 alkyl alcohol, C1-C6 perfluorinated alkyl alcohol; provided that the fluorinated olefin and the alkyl alcohol are not perfluorinated at the same time; The molar ratio of the alkyl alcohol, the fluorinated olefin and the organic solvent in the addition reaction is 1:(1-2):(1-5); The reaction temperature of the addition reaction is 30-100° C. and the pressure is 0.1-0.5 MPa.

5. The method according to claim 4, characterized in that The fluorinated olefin is selected from one or more of the following: hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, chlorotrifluoroethylene, tetrafluoropropylene, vinyl fluoride, and vinylidene fluoride; The alkyl alcohol is selected from one or more of the following: methanol, ethanol, n-propanol, isopropanol, trifluoromethanol, trifluoroethanol, pentafluoropropanol, hexafluoroisopropanol, heptafluorobutanol, tetrafluorobutanol; The organic solvent is selected from one or more of the following: tetrahydrofuran, acetonitrile, butyronitrile, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dimethyl sulfoxide, N,N-dimethylformamide, glycerol.

6. The method according to claim 4, characterized in that The content of hydrofluoroether in the crude hydrofluoroether is 30-60 mol %, and the target purity of the hydrofluoroether product is ≥99.99 mol %.

7. The method according to claim 1, characterized in that The vacuum distillation in step II is carried out in a vacuum distillation kettle, the kettle temperature of which is 70-110° C., the pressure is -0.001 MPa to -0.050 MPa, the tower top temperature is 25-65° C., and the heavy component is transported to the addition reaction in step I for preparing crude hydrofluoroether.

8. The method according to claim 1, characterized in that In step III, the light component is passed through a primary adsorption tower and a secondary adsorption tower in sequence, at least a portion of organic impurities in the light component is removed in the primary adsorption tower, and at least a portion of water in the light component is removed in the secondary adsorption tower; The primary adsorption tower is filled with a molecular sieve adsorbent loaded with silver salt; The secondary adsorption tower is filled with a water absorbent.

9. The method according to claim 1, characterized in that The atmospheric distillation of step IV is carried out in an atmospheric distillation tower having a theoretical plate number of 50-120, a bottom temperature of 30-70°C, a top temperature of 25-65°C, a pressure difference of 5-10 kPa, and a reflux ratio of 5:1-15:

1.

10. The method according to any one of claims 1 to 9, characterized in that The purity of the hydrofluoroether product is ≥99.99 mol %, the water content thereof is ≤50 ppm, and the product yield is >80%.

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