A method and apparatus for preparing perfluorohexane

Abstract

This application relates to a process for preparing fluorinated liquids, specifically a method and apparatus for preparing perfluorohexane. The method involves first reacting hexafluoropropylene with a fluorine-containing gas to obtain crude perfluorohexane; then subjecting the crude perfluorohexane to primary and secondary alkaline washing, followed by water removal; and finally, primary and secondary condensation. The primary condensation yields the product perfluorohexane, while the secondary condensation recovers hexafluoropropylene for recycling. The apparatus comprises a reaction tower, a buffer tank, a primary alkaline washing tower, a secondary alkaline washing tower, a drying tower, a first cold trap, and a second cold trap, connected in sequence. This application features a simple production process, high hexafluoropropylene conversion rate, high product purity, and low overall cost, demonstrating good economic benefits and application prospects.

Description

Technical Field

[0001] This application relates to a process for preparing fluorinated liquids, specifically, a method and apparatus for preparing perfluorohexane. Background Technology

[0002] Perfluorohexane has the chemical formula C6F. 14 Perfluorohexane is a colorless, odorless, and non-flammable liquid with excellent chemical and thermal stability, making it widely used in many fields. Below are some of the main applications of perfluorohexane:

[0003] ① Industrial solvent and cleaning agent: Perfluorohexane, as a high-performance industrial solvent, is commonly used in the cleaning and degreasing processes of precision equipment. ② Coolant for electronic products: Due to its good thermal stability and chemical inertness, perfluorohexane can be used as a coolant for electronic products, especially in high-temperature or high-pressure environments. ③ Alternative substance: Perfluorohexane can also be used as a safe alternative to certain hazardous substances, such as replacing traditional hydrocarbon solvents in some industrial processes. ④ Lubricant or plastic additive: In the automotive and aerospace industries, perfluorohexane can be used as a lubricant and plastic additive to improve product performance and durability. ⑤ Medical applications: The bioinertness and chemical stability of perfluorohexane have attracted attention in the medical field. It can dissolve gases (including oxygen in the air) to higher concentrations than common organic solvents, making it a potential oxygen delivery medium.

[0004] Due to its wide range of applications, the synthesis of perfluorohexane has attracted increasing attention. Currently, there are two main methods for preparing perfluorohexane. One is the electrolytic method. Chinese patent CN109652819B discloses a method for preparing branched perfluorohexane, which uses hexafluoropropylene dimer as a raw material and catalytically hydrogenates it to synthesize dodecafluorodihydrohexane. Then, dodecafluorodihydrohexane, anhydrous hydrogen fluoride, and the conductive additive dimethyl disulfide are electrochemically fluorinated in an electrolytic cell to obtain perfluorohexane. However, the electrolytic method for preparing perfluorohexane is complex, the raw material hexafluoropropylene dimer is expensive, there are many side reactions, and the product has many impurities that are difficult to purify. The other method is to directly fluorinate hexane using fluorine gas at high temperature. However, this reaction is carried out at high temperature, which not only results in harsh reaction conditions and many side reactions, but also makes the product difficult to purify and has a low yield.

[0005] In summary, existing methods for preparing perfluorohexane suffer from problems such as harsh reaction conditions, difficulty in controlling the reaction process, difficulty in purifying the product, and low product yield. Therefore, there is an urgent need to propose a method for preparing perfluorohexane with mild reaction conditions, fewer reaction byproducts, and simpler product purification to solve the current problems. Summary of the Invention

[0006] To address the problems of harsh reaction conditions, difficulty in controlling the reaction process, difficulty in purifying the product, and low product yield in existing methods for preparing perfluorohexane, this application proposes a method and apparatus for preparing perfluorohexane.

[0007] The technical solution of this application:

[0008] On the one hand, this application provides a method for preparing perfluorohexane, comprising the following steps:

[0009] Step S1. Mix hexafluoropropylene and fluorine-containing gas to react and obtain crude perfluorohexane;

[0010] Step S2. The crude perfluorohexane is subjected to primary and secondary alkaline washing, followed by removal of water. Finally, it is subjected to primary and secondary condensation. The primary condensation yields the product perfluorohexane, while the secondary condensation recovers hexafluoropropylene for recycling.

[0011] Preferably, in step S1, the molar ratio of hexafluoropropylene to fluorine in the fluorine-containing gas is (2-6):1, and the fluorine-containing gas is a mixture of fluorine and an inert gas, wherein the inert gas accounts for 40-70 vol% of the total amount of hexafluoropropylene and the fluorine-containing gas.

[0012] Preferably, the temperature of the mixing reaction in step S1 is 10 to 200°C and the pressure is -0.05 to 0.3 MPa.

[0013] Preferably, the alkaline solution used for the primary and secondary alkaline washing in step S2 is either sodium hydroxide or potassium hydroxide.

[0014] Preferably, the adsorbent used to remove moisture in step S2 is any one of 3A, 4A, 5A and Na-X zeolite.

[0015] On the other hand, this application provides an apparatus for preparing perfluorohexane, including a reaction tower, a buffer tank, a primary alkaline washing tower, a secondary alkaline washing tower, a drying tower, a first cold trap, and a second cold trap, wherein the reaction tower, buffer tank, primary alkaline washing tower, secondary alkaline washing tower, drying tower, first cold trap, and second cold trap are connected in sequence by pipelines.

[0016] Preferably, the reaction tower is filled with a packing material, which is a metal ring, and the metal ring is made of either nickel or Monel; the side of the reaction tower is provided with a hexafluoropropylene gas inlet and a fluorine-containing gas inlet.

[0017] Preferably, the first cold trap has a first cold trap column at the top and a first tower bottom at the bottom (the first cold trap column and the first tower bottom are connected); the second cold trap has a second cold trap column at the top and a second tower bottom at the bottom, the second cold trap column and the second tower bottom are connected, and the upper end of the second cold trap also has a gas outlet.

[0018] Preferably, the temperature of the first cold trap column is -25 to 20°C, and the temperature of the first reboiler is 0 to 40°C; the temperature of the second cold trap column is -90 to -40°C, and the temperature of the second reboiler is -50 to -30°C.

[0019] The beneficial effects of this application are:

[0020] The method for preparing perfluorohexane provided in this application has high conversion efficiency and low loss. By precisely controlling the molar ratio of hexafluoropropylene to fluorine (2-6):1 and optimizing the reaction temperature and pressure conditions, the efficient conversion of hexafluoropropylene to perfluorohexane is achieved. This not only improves the conversion rate but also significantly reduces the generation of by-products, greatly enhancing the overall economic efficiency of the process and reducing resource waste. The raw material for the preparation method of perfluorohexane provided in this application, hexafluoropropylene, is widely available, inexpensive, and easy to purchase, reducing production costs. The two-stage alkaline washing process (using sodium hydroxide or potassium hydroxide as the alkaline solution) used in the purification process effectively removes acidic gases and other impurities from the crude product. Subsequent drying further removes moisture, ensuring product purity and reducing the product's water content. After separation through primary and secondary condensation, perfluorohexane with a purity of up to 99.95% is obtained, meeting the stringent requirements of the high-end electronics industry for high-quality raw materials. Throughout the entire preparation process, unreacted hexafluoropropylene is recovered and recycled, reducing production costs and emissions of harmful substances. The raw materials used in this application are all environmentally friendly, with minimal environmental impact. The device described in this application constructs a closed-loop production system, achieving a balance between economic and environmental benefits. Attached Figure Description

[0021] Appendix Figure 1 This is a schematic diagram of the apparatus for preparing perfluorohexane in this application.

[0022] Reference numerals in the attached diagram: 1. Hexafluoropropylene gas inlet; 2. Fluorine-containing gas inlet; 3. Reaction tower; 4. Buffer tank; 5. First-stage alkaline scrubbing tower; 6. Second-stage alkaline scrubbing tower; 7. Drying tower; 8. Adsorbent plate; 9. First cold trap; 10. First cold trap column; 11. First tower bottom; 12. Second cold trap; 13. Second cold trap column; 14. Second tower bottom; 15. Gas outlet. Detailed Implementation

[0023] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0024] Example 1

[0025] This embodiment provides an apparatus for preparing perfluorohexane, such as... Figure 1As shown, the system includes a reaction tower 3, a buffer tank 4, a primary alkaline washing tower 5, a secondary alkaline washing tower 6, a drying tower 7, a first cold trap, and a first cold trap 12. The reaction tower 3, the buffer tank 4, the primary alkaline washing tower 5, the secondary alkaline washing tower 6, the drying tower 7, the first cold trap 9, and the first cold trap 12 are connected in sequence through pipelines.

[0026] The reaction tower 3 is filled with a packing material, which is a metal ring. The metal ring is made of either nickel or Monel. The side of the reaction tower 3 is provided with a hexafluoropropylene gas inlet 1 and a fluorine-containing gas inlet 2.

[0027] The first cold trap 9 has a first cold trap column 10 in the upper part and a first tower 11 in the lower part, and the first cold trap column 10 and the first tower 11 are connected; the second cold trap 12 has a second cold trap column 13 in the upper part and a second tower 14 in the lower part, and the second cold trap column 13 and the second tower 14 are connected; the second cold trap 12 also has a gas outlet 15 at the upper end.

[0028] Example 2

[0029] Based on the perfluorohexane preparation apparatus provided in Example 1, this example provides a method for preparing perfluorohexane.

[0030] Hexafluoropropylene is introduced into reaction tower 3 through hexafluoropropylene gas inlet 1, while fluorine-containing gas is simultaneously introduced into reaction tower 3 through fluorine-containing gas inlet. A fluorination reaction takes place in reaction tower 3, with the reaction temperature controlled at 10℃ and the reaction pressure at -0.05MPa. The molar ratio of hexafluoropropylene to fluorine is 2, and helium accounts for 40 vol% of the total mixture of hexafluoropropylene and fluorine-containing gas. The packing material inside reaction tower 3 is nickel. The gas after the reaction enters buffer tank 4, then enters primary alkaline scrubbing tower 5, and after alkaline scrubbing, it enters secondary alkaline scrubbing tower 6 to remove acidic gases and other impurities from the gas after the reaction. The primary alkaline scrubbing tower 5 and the secondary alkaline scrubbing tower 6... The solution in washing tower 6 is NaOH solution, which then enters drying tower 7 to remove moisture from the gas. The adsorbent on the adsorbent plate 8 in drying tower 7 is 3A molecular sieve. Finally, the gas flows into the first cold trap 9, and the temperature of the first cold trap column 10 is controlled at -25℃, and the temperature of the first tower bottom 11 is 0℃. Perfluorohexane is collected in the first tower bottom 11. The remaining gas flows into the first cold trap 12, and the temperature of the second cold trap column 13 is controlled at -90℃, and the temperature of the second tower bottom 14 is -50℃. Hexafluoropropylene is collected in the second tower bottom 14 and can be recycled to participate in the reaction by reheating. Inert helium gas is discharged from gas outlet 15.

[0031] Example 3

[0032] Based on the perfluorohexane preparation apparatus provided in Example 1, this example provides a method for preparing perfluorohexane.

[0033] Hexafluoropropylene is introduced into reaction tower 3 through hexafluoropropylene gas inlet 1, while fluorine-containing gas is simultaneously introduced into reaction tower 3 through fluorine-containing gas inlet. The fluorination reaction takes place in reaction tower 3, with the reaction temperature controlled at 70℃ and the reaction pressure at -0.05MPa. The molar ratio of hexafluoropropylene to fluorine is 3, and helium accounts for 50 vol% of the total mixture of hexafluoropropylene and fluorine-containing gas. The packing material inside reaction tower 3 is Monel. The gas after the reaction enters buffer tank 4, then enters primary alkaline scrubbing tower 5, and after alkaline scrubbing, it enters secondary alkaline scrubbing tower 6 to remove acidic gases and other impurities from the gas after the reaction. The primary alkaline scrubbing tower 5 and the secondary alkaline scrubbing tower 6... The solution in alkaline washing tower 6 is KOH solution, which then enters drying tower 7 to remove moisture from the gas. The adsorbent on the adsorbent plate 8 in drying tower 7 is 4A molecular sieve. Finally, the gas flows into the first cold trap 9, and the temperature of the first cold trap column 10 is controlled at -10℃, and the temperature of the first tower bottom 11 is 15℃. Perfluorohexane is collected in the first tower bottom 11, and the remaining gas flows into the first cold trap 12, and the temperature of the second cold trap column 13 is controlled at -74℃, and the temperature of the second tower bottom 14 is -43℃. Hexafluoropropylene is collected in the second tower bottom 14 and can be recycled to participate in the reaction by reheating. Helium is discharged from gas outlet 15.

[0034] Example 4

[0035] Based on the perfluorohexane preparation apparatus provided in Example 1, this example provides a method for preparing perfluorohexane.

[0036] Hexafluoropropylene is introduced into reaction tower 3 through hexafluoropropylene gas inlet 1, while fluorine-containing gas is simultaneously introduced into reaction tower 3 through fluorine-containing gas inlet. The fluorination reaction takes place in reaction tower 3, with the reaction temperature controlled at 130℃ and the reaction pressure at 0.15 MPa. The molar ratio of hexafluoropropylene to fluorine is 4, and argon accounts for 60 vol% of the total mixture of hexafluoropropylene and fluorine-containing gas. The packing material inside reaction tower 3 is nickel. The gas after the reaction enters buffer tank 4, then enters primary alkaline scrubbing tower 5, and after alkaline scrubbing, it enters secondary alkaline scrubbing tower 6 to remove acidic gases and other impurities from the gas after the reaction. The primary alkaline scrubbing tower 5 and the secondary alkaline scrubbing tower 6... The solution in alkaline washing tower 6 is NaOH solution, which then enters drying tower 7 to remove moisture from the gas. The adsorbent on the adsorbent plate 8 in drying tower 7 is 5A molecular sieve. Finally, the gas flows into the first cold trap 9, and the temperature of the first cold trap column 10 is controlled at 5°C, and the temperature of the first tower bottom 11 is controlled at 30°C. Perfluorohexane is collected in the first tower bottom 11, and the remaining gas flows into the first cold trap 12, and the temperature of the second cold trap column 13 is controlled at -57°C, and the temperature of the second tower bottom 14 is controlled at -36°C. Hexafluoropropylene is collected in the second tower bottom 14 and can be recycled to participate in the reaction by reheating. Argon gas is discharged from gas outlet 15.

[0037] Example 5

[0038] Based on the perfluorohexane preparation apparatus provided in Example 1, this example provides a method for preparing perfluorohexane.

[0039] Hexafluoropropylene is introduced into reaction tower 3 through hexafluoropropylene gas inlet 1, while fluorine-containing gas is simultaneously introduced into reaction tower 3 through fluorine-containing gas inlet. A fluorination reaction takes place in reaction tower 3, with the reaction temperature controlled at 200℃ and the reaction pressure at 0.30 MPa. The molar ratio of hexafluoropropylene to fluorine is 6, and argon gas accounts for 70 vol% of the total mixture of hexafluoropropylene and fluorine-containing gas. The packing material inside reaction tower 3 is nickel. The gas after the reaction enters buffer tank 4, then enters primary alkaline scrubbing tower 5, and after alkaline scrubbing, it enters secondary alkaline scrubbing tower 6 to remove acidic gases and other impurities from the gas after the reaction. The primary alkaline scrubbing tower 5 and the secondary alkaline scrubbing tower 6... The solution in washing tower 6 is NaOH solution, which then enters drying tower 7 to remove moisture from the gas. The adsorbent on the adsorbent plate 8 in drying tower 7 is Na-X molecular sieve. Finally, the gas flows into the first cold trap 9, and the temperature of the first cold trap column 10 is controlled at 20°C, and the temperature of the first tower bottom 11 is controlled at 40°C. Perfluorohexane is collected in the first tower bottom 11, and the remaining gas flows into the first cold trap 12, and the temperature of the second cold trap column 13 is controlled at -40°C, and the temperature of the second tower bottom 14 is controlled at -30°C. Hexafluoropropylene is collected in the second tower bottom 14 and can be recycled to participate in the reaction by reheating. Argon gas is discharged from gas outlet 15.

[0040] Result detection

[0041] The purity of perfluorohexane in Examples 2-5 and the loss of hexafluoropropylene in the second cold trap were tested, and the results are shown in Table 1.

[0042] Table 1

[0043] sample Purity of perfluorohexane Loss of hexafluoropropylene Example 2 99.91％ 0.1％ Example 3 99.94％ 0.2％ Example 4 99.95％ 0.2％ Example 5 99.92％ 0.9％

[0044] Results Analysis

[0045] As can be seen from Comparative Examples 2-5 and Table 1, the perfluorohexane preparation method provided in this application has high conversion efficiency and low loss. By precisely controlling the molar ratio of hexafluoropropylene to fluorine (2-6):1 and optimizing the reaction temperature and pressure conditions, the efficient conversion of hexafluoropropylene to perfluorohexane is achieved, yielding perfluorohexane with a purity of up to 99.95%, which meets the stringent requirements of the high-end electronics industry for high-quality raw materials. Furthermore, the loss of hexafluoropropylene in the second cold trap is as low as 0.1%.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for the preparation of perfluorohexane, characterized in that, The method comprises the following steps: Step S1. Mixing and reacting hexafluoropropylene and fluorine-containing gas to obtain crude perfluorohexane; Step S2. Washing the crude perfluorohexane with primary alkali and secondary alkali, then removing water, and finally performing primary condensation and secondary condensation, wherein the primary condensation obtains product perfluorohexane, and the secondary condensation recycles hexafluoropropylene for recycling reaction; The molar ratio of hexafluoropropylene to fluorine in the fluorine-containing gas in the step S1 is (2-6):1, the fluorine-containing gas is a mixture of fluorine and inert gas, and the inert gas accounts for 40-70 vol% of the total amount of hexafluoropropylene and the fluorine-containing gas. The temperature of the mixing reaction in the step S1 is 10-200°C, and the pressure is -0.05-0.3 MPa.

2. The method for preparing perfluorohexane according to claim 1, characterized in that, The alkali solution for the primary alkali washing and the secondary alkali washing in the step S2 is any one of sodium hydroxide and potassium hydroxide.

3. The method for preparing perfluorohexane according to claim 1, characterized in that, The adsorbent for removing water in the step S2 is any one of 3A, 4A, 5A and Na-X zeolite.

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