Preparation method of nonafluoroisobutyl ether

Abstract

The invention discloses a preparation method of nonafluoroisobutyl ether. The preparation method comprises the following steps: S1, adding a polar aprotic solvent, crown ether, a fluorine-containing phase transfer catalyst, metal fluoride and an alkylation reagent into a reaction device; s2, perfluoroisobutyryl fluoride is added into the reaction device at the speed of 1.5 g / min to 2.5 g / min, and the temperature of the reaction device ranges from-20 DEG C to 10 DEG C; s3, after ventilation is finished, the temperature of the reaction device is increased to 20-50 DEG C, the temperature is kept for 0.5-5 h, and then the reaction is stopped. According to the method, the perfluoroisobutyryl fluoride and the metal fluoride are fully reacted at a low temperature and then are heated, and the intermediate product is reacted with the alkylation reagent, so that the reaction conditions are mild, the reaction time is short, and the reaction selectivity is improved.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, and in particular to a method for preparing nonafluoroisobutyl ether. Background Technology

[0002] Nonafluoroisobutyl ether (NCOBE) is a class of chemically inert hydrofluoroether compounds. In these compounds, the vast majority of hydrogen atoms are replaced by fluorine atoms, resulting in a significant change in the electron cloud distribution of the entire molecule. This alters the dipole moment and intermolecular forces, leading to good insulation properties and low surface tension. Due to its special properties, this type of compound is currently a widely used cleaning agent in the wafer cleaning and drying process of semiconductor fabrication. Its low surface tension helps protect the fine structure after etching from damage during the drying process. Furthermore, this type of compound is non-flammable and chemically stable, possessing advantages that other types of cleaning agents, such as isopropanol, cannot replace.

[0003] Meanwhile, chlorinated compounds such as CFC-113, HCFC-141b, and HCFC-225, commonly used in the electronics industry, cause ozone layer depletion and contribute to the greenhouse effect, and have been banned or restricted. Hydrofluoroethers (HFEs), as alternatives to these compounds, have the characteristics of zero ozone layer depletion potential, low global warming potential, short atmospheric lifetime, and near-non-toxicity. Furthermore, they are not classified as volatile organic compounds, thus meeting environmental regulations. This alternative has also been recognized by the U.S. Environmental Protection Agency.

[0004] Currently, the reported methods for synthesizing nonafluorobutyl ether are relatively limited, mainly relying on the electrolytic fluorination synthesis process developed by 3M Corporation. For example, patent US8193397 uses an electrolytic fluorination method to prepare perfluoro-n- / isobutyryl fluoride by electrolyzing n-butyryl chloride, followed by a methyl etherification reaction of the two isomers with dimethyl sulfate to obtain the product. The reaction formula is as follows:

[0005]

[0006] The reaction inevitably produces two isomers, perfluorobutyryl fluoride and perfluoroisobutyryl fluoride, in a ratio of approximately 60:40. At the same time, the electrolytic fluorination process requires a large amount of hydrogen fluoride, which poses a high risk and is difficult to implement. Moreover, the yield is only 35%, and the byproducts are various small-molecule perfluoroalkanes such as hexafluoroethane and octafluoropropane, resulting in poor atom economy.

[0007] Meanwhile, since the boiling point of perfluoroisobutyryl fluoride is around 0℃ under normal pressure, the system contains two phases of gas and liquid under the conditions required for its methyl etherification reaction. The contact between the two phases is poor. Therefore, even though perfluoroisobutyryl fluoride has high reactivity, it is difficult to generate intermediates that are soluble in the liquid phase, which leads to a longer reaction time, lower yield, and more side reactions. For example, the literature "Journal of Industrial and Engineering Chemistry, 2007, 13(4), 537-544" reported the process of preparing nonafluoroisobutyl ether by reacting perfluoroisobutyryl fluoride directly with potassium fluoride and dimethyl sulfate. Due to the poor contact between the gas and liquid phases, the highest yield of the reaction was only 64%, and the selectivity of nonafluoroisobutyl ether was only 85%. Patent CN110002968A discloses a method for preparing nonafluoroisobutyl ether by reacting perfluorobutyryl fluoride with alkylating agents such as silver fluoride and dimethyl carbonate. The highest yield of this method is 83%, but the reaction time is 24 hours and it requires the use of relatively expensive silver fluoride as a fluoride ion source, making it difficult to carry out large-scale production. Summary of the Invention

[0008] To address the issues of long reaction times and low product yields, the inventors of this invention discovered that under low-temperature conditions, after the liquid-phase perfluoroisobutyryl fluoride fully reacts with the metal fluoride, the reaction is then heated to react with the alkylating agent, which not only shortens the reaction time but also significantly improves the yield.

[0009] The technical solution of the present invention is as follows:

[0010] This invention provides a method for preparing nonafluoroisobutyl ether, the method comprising:

[0011] S1: Add a polar aprotic solvent, crown ether, fluorine-containing phase transfer catalyst, metal fluoride, and alkylating agent to the reaction apparatus;

[0012] S2: Perfluoroisobutyryl fluoride is added to the reaction apparatus at a rate of 1.5 to 2.5 g / min, wherein the temperature of the reaction apparatus is -20 to 10°C;

[0013] S3: After the ventilation ends, raise the temperature of the reaction device to 20-50°C, maintain it for 0.5-5 hours, and then stop the reaction.

[0014] In step S2, the perfluoroisobutyryl fluoride is fed in the gas phase and liquefied after entering the reaction device.

[0015] In step S3, preferably, 30–120 minutes after the aeration ends, the temperature of the reaction apparatus is raised to 20–30°C and maintained for 0.5–5 hours before the reaction is stopped. More preferably, 60 minutes after the aeration ends, the temperature of the reaction apparatus is raised to 20–30°C and maintained for 0.5–5 hours before the reaction is stopped.

[0016] The polar aprotic solvent described in this invention is a commonly used solvent in the art. Preferably, the polar aprotic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, and acetonitrile; more preferably, the polar aprotic solvent is selected from at least one of N,N-dimethylformamide, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, and acetonitrile.

[0017] The crown ether is selected from at least one of benzo-15-crown ether-5, 15-crown ether-5, 18-crown ether-6, dibenzo-18-crown ether-6, and dicyclohexyl-18-crown ether-6, preferably, the crown ether is selected from 18-crown ether-6.

[0018] The fluorinated phase transfer catalyst is selected from at least one of tetrabutylammonium fluoride, hexafluorobisphenol A, tetra-n-butyldihydrotrifluoride, and tetramethylammonium fluoride. Preferably, the fluorinated phase transfer catalyst is selected from tetrabutylammonium fluoride.

[0019] The alkylating agent described in this invention is a commonly used alkylating agent in the art. Preferably, the alkylating agent is selected from at least one of dimethyl sulfate, dimethyl carbonate, diethyl sulfate, and diethyl carbonate. More preferably, the alkylating agent is selected from dimethyl sulfate, diethyl sulfate, and diethyl carbonate.

[0020] The metal fluoride is selected from at least one of potassium fluoride, cesium fluoride, and sodium fluoride.

[0021] The molar ratio of the perfluoroisobutyryl fluoride to the metal fluoride is 1:(1-5). From the perspective of product yield, preferably, the molar ratio of the perfluoroisobutyryl fluoride to the metal fluoride is 1:(1-2).

[0022] The molar ratio of the perfluoroisobutyryl fluoride to the alkylating agent is 1:(0.9-3). From the perspective of product yield, preferably, the molar ratio of the perfluoroisobutyryl fluoride to the alkylating agent is 1:(1-2).

[0023] The molar / volume ratio of the perfluoroisobutyryl fluoride to the polar aprotic solvent is 0.5–5 mol / L. From the perspective of product yield, preferably, the molar / volume ratio of the perfluoroisobutyryl fluoride to the polar aprotic solvent is 1–3 mol / L.

[0024] The molar ratio of the metal fluoride to the crown ether is (10-15):1, preferably, the molar ratio of the metal fluoride to the crown ether is 10:1.

[0025] The molar ratio of the perfluoroisobutyryl fluoride to the fluorinated phase transfer catalyst is (80-120):1, preferably, the molar ratio of the perfluoroisobutyryl fluoride to the fluorinated phase transfer catalyst is 100:1.

[0026] The metal fluoride of the present invention is added to the reaction device in advance and dried at 120°C for 3 hours under nitrogen protection. Then the system is evacuated to -0.08 MPa and held for 5 minutes to remove moisture. After the evacuation is completed, nitrogen protection is introduced for standby.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows: the perfluoroisobutyryl fluoride of the present invention first undergoes a liquid-phase reaction to generate an intermediate, and then undergoes a gas-phase reaction. In addition, under the action of the crown ether and the fluorinated phase transfer catalyst, the perfluoroisobutyryl fluoride is rapidly converted into a more reactive intermediate after entering the reaction device, which accelerates the reaction, avoids the occurrence of a series of side reactions, shortens the reaction time, and improves the reaction yield. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0029] In the embodiments and comparative examples of this invention, gas chromatography was used to analyze the product content. The analytical instrument was a Shimadzu GC-2014; the chromatographic column was SH-1301 (inner diameter 0.25 mm, length 60 m); the GC analysis method was as follows: high-purity nitrogen and hydrogen were used as carrier gases, the detector temperature was 250 °C, the vaporization chamber temperature was 220 °C, the column temperature was 33 °C (10 min) - 10 °C / min - 200 °C (5 min); the carrier gas (nitrogen) flow rate was 30 mL / min, the air flow rate was 400 mL / min, the hydrogen flow rate was 40 mL / min, the injection port split ratio was 30.0, and the injection volume was 0.1 μL.

[0030] Example 1:

[0031] 50 mL of anhydrous N,N-dimethylformamide, dimethyl sulfate (15.13 g, 0.12 mol), 18-crown ether-6 (3.17 g, 0.012 mol), and 1 mL of tetrabutylammonium fluoride tetrahydrofuran solution (1 mol / L) were added to a dried round-bottom flask and mixed. Then, a reaction vessel containing dried potassium fluoride (6.97 g, 0.12 mol) was evacuated to -0.08 MPa and maintained for 5 minutes. The liquid from the round-bottom flask was then drawn into the reaction vessel through a tubing. The reactor was frozen to -20°C and evacuated. Then, the reactor was connected to the perfluoroisobutyryl fluoride gas line. Perfluoroisobutyryl fluoride (21.6 g, 0.1 mol) was introduced at a rate of 2 g / min. During the gas introduction process, the reactor was kept in a -20°C cold bath to maintain a low temperature. After the gas introduction was completed, the gas line was disconnected and the reactor was stirred at low temperature for 1 hour. Then, the reactor was slowly restored to 20°C and the reaction was carried out for 3 hours. After the reaction was completed, the pressure was released and the reactor was opened. The liquid in the reactor was collected by distillation, and the target product, nonafluoroisobutyl methyl ether, was obtained with a yield of 93% and a purity of 99%.

[0032] Example 2:

[0033] The operation was the same as in Example 1, except that anhydrous ethylene glycol dimethyl ether was used instead of anhydrous N,N-dimethylformamide. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was collected by distillation, and the target product, nonafluoroisobutyl methyl ether, was obtained with a yield of 92% and a purity of 99%.

[0034] Example 3:

[0035] The operation was the same as in Example 1, except that anhydrous diethylene glycol dimethyl ether was used instead of anhydrous N,N-dimethylformamide. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was collected by distillation, and the target product, nonafluoroisobutyl methyl ether, was obtained with a yield of 92% and a purity of 99%.

[0036] Example 4:

[0037] The procedure was the same as in Example 1, except that cesium fluoride (18.2 g, 0.12 mol) was used instead of potassium fluoride. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was collected by distillation, and the target product, nonafluoroisobutyl methyl ether, was obtained with a yield of 92% and a purity of 99%.

[0038] Example 5:

[0039] The procedure was the same as in Example 1, except that sodium fluoride (5.03 g, 0.12 mol) was used instead of potassium fluoride, and 15-crown ether-5 (2.64 g, 0.012 mol) was used instead of 18-crown ether-6. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was then distilled and the target product, nonafluoroisobutyl methyl ether, was collected. The yield was 90% and the purity was 99%.

[0040] Example 6:

[0041] The procedure was the same as in Example 1, except that dimethyl carbonate (10.8 g, 0.12 mol) was used instead of dimethyl sulfate. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was collected by distillation, and the target product, nonafluoroisobutyl methyl ether, was obtained with a yield of 91% and a purity of 99%.

[0042] Example 7:

[0043] The procedure was the same as in Example 1, except that diethyl sulfate (18.5 g, 0.12 mol) was used instead of dimethyl sulfate. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was collected by distillation, and the target product, nonafluoroisobutyl ether, was obtained with a yield of 92% and a purity of 99%.

[0044] Example 8:

[0045] The procedure was the same as in Example 1, except that diethyl carbonate (14.2 g, 0.12 mol) was used instead of dimethyl sulfate. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was collected by distillation, and the target product, nonafluoroisobutyl ether, was obtained with a yield of 90% and a purity of 99%.

[0046] Comparative Example 1:

[0047] The operation was the same as in Example 1, except that the reaction was not cooled; the feed was introduced at 20°C and the reaction was carried out. After the reaction was completed, the pressure was released and the vessel was opened. The liquid in the vessel was then collected by distillation, and the target product, nonafluoroisobutyl methyl ether, was obtained in a yield of 60%. GCMS analysis of the product revealed that 32% of C3F7COOCH3 was produced as a byproduct.

[0048] Comparative Example 2:

[0049] The procedure was the same as in Example 1, except that 18-crown ether-6 was not used. After the reaction was completed, the pressure was released and the vessel was opened. The target product, nonafluoroisobutyl methyl ether, was collected by distillation of the liquid in the vessel. The yield was 60%, and 32% of the perfluoroisobutyryl fluoride remained unreacted.

[0050] Comparative Example 3:

[0051] The procedure was the same as in Example 1, except that tetrabutylammonium fluoride was not used. After the reaction was completed, the pressure was released and the vessel was opened. The target product, nonafluoroisobutyl methyl ether, was collected by distillation of the liquid in the vessel. The yield was 69%, and 25% of perfluoroisobutyryl fluoride was unreacted.

Claims

1. A method for preparing nonafluoroisobutyl ether, characterized in that: The preparation method includes: S1: Add a polar aprotic solvent, crown ether, fluorine-containing phase transfer catalyst, metal fluoride, and alkylating agent to the reaction apparatus; S2: Perfluoroisobutyryl fluoride is added to the reaction apparatus at a rate of 1.5 to 2.5 g / min, wherein the temperature of the reaction apparatus is -20 to 10°C; S3: After the ventilation ends, raise the temperature of the reaction device to 20-50°C, maintain it for 0.5-5 hours, and then stop the reaction.

2. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The perfluoroisobutyryl fluoride enters the reaction apparatus in the gas phase.

3. The method for preparing nonafluoroisobutyl ether according to claim 1 or 2, characterized in that: S3. After the ventilation ends, raise the temperature of the reaction device to 20-50°C 30-120 minutes later, maintain this temperature for 0.5-5 hours, and then stop the reaction.

4. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The alkylating agent is selected from at least one of dimethyl sulfate, dimethyl carbonate, diethyl sulfate, and diethyl carbonate.

5. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The crown ether is selected from at least one of benzo-15-crown ether-5, 15-crown ether-5, 18-crown ether-6, dibenzo-18-crown ether-6, and dicyclohexyl-18-crown ether-6.

6. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The fluorinated phase transfer catalyst is selected from at least one of tetrabutylammonium fluoride, hexafluorobisphenol A, tetra-n-butyldihydrotrifluoride, and tetramethylammonium fluoride.

7. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The metal fluoride is selected from at least one of potassium fluoride, cesium fluoride, and sodium fluoride.

8. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The polar aprotic solvent is selected from at least one of N,N-dimethylformamide, N,N-dimethylacetamide, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, and acetonitrile.

9. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The molar ratio of the perfluoroisobutyryl fluoride to the metal fluoride is 1:(1-5), the molar ratio of the perfluoroisobutyryl fluoride to the alkylating agent is 1:(0.9-3), and the molar / volume ratio of the perfluoroisobutyryl fluoride to the polar aprotic solvent is 0.5-5 mol / L.

10. The method for preparing nonafluoroisobutyl ether according to claim 1, characterized in that: The molar ratio of the metal fluoride to the crown ether is (10-15):1, and the molar ratio of the perfluoroisobutyryl fluoride to the fluorinated phase transfer catalyst is (80-120):1.

Images