Method for collecting crude perfluorobutyryl fluoride electrolysis gas

Abstract

The invention relates to the technical field of fluorine-containing fine chemical engineering, in particular to a method for collecting a perfluorobutyryl fluoride electrolytic gas crude product. Comprising the following steps: S1, cooling an electrolytic bath; s2, adding anhydrous hydrogen fluoride, raw materials and electrolyte into an electrolytic cell, uniformly stirring, and controlling the temperature and voltage of the electrolytic cell for electrolysis; s3, electrolytic gas is introduced into a low-temperature crude product tank containing an extraction agent in the electrolysis process; and S4, rectifying the crude product in the crude product tank to obtain refined perfluorobutyryl fluoride, and recovering the extracting agent. According to the method for collecting the crude perfluorobutyryl fluoride electrolytic gas, an ultralow-temperature cooling method is not needed for collecting the crude perfluorobutyryl fluoride, the process is simple, the extraction agent is easily separated from the product and can be recycled, in addition, due to the fact that the extraction agent and hydrogen fluoride are immiscible, the effect of separating the hydrogen fluoride and the perfluorobutyryl fluoride can be achieved, and the method is suitable for industrial production. The purity of the crude product is more than 95%.

Description

Technical Field

[0001] This application relates to the field of fluorine-containing fine chemical technology, and in particular to a method for collecting crude perfluorobutyryl fluoride electrolysis gas. Background Technology

[0002] Perfluorobutyryl fluoride (C4F8O), an important fluorinated fine chemical, possesses both carbonyl fluoride active groups and perfluorocarbon chains in its molecular structure. It can serve as a key monomer or modifier in the synthesis of various fluorinated polymers, such as fluorinated polyimides, fluorinated polyesters, and fluorinated polyethers. These fluorinated polymers, with their excellent chemical stability, high thermal stability, corrosion resistance, and outstanding tensile strength and abrasion resistance, show broad application prospects in aerospace, electronics, petrochemicals, and high-end medical devices. Furthermore, perfluorobutyryl fluoride is an important intermediate in the synthesis of various high-performance fluorinated organic compounds, such as the electronic component cleaning agents Novec 7100 and Novec 7200, as well as downstream products like the environmentally friendly insulating gas perfluoroisobutyronitrile and the novel fire extinguishing agent perfluorohexanone. Its development has attracted significant attention from the industry.

[0003] Currently, the industrial production of perfluorobutyryl fluoride mainly relies on chemical synthesis and electrolysis. Chemical synthesis typically uses hexafluoropropylene as a raw material, reacting it with carbonyl fluoride in a one-step reaction under alkali metal fluoride catalysis to produce perfluoroisobutyryl fluoride. Electrolysis often uses butyryl chloride, butyryl fluoride, or butyric anhydride as raw materials, with hydrogen fluoride (HF) as the fluorine source, applying voltage at low temperatures to directly produce perfluorobutyryl fluoride. However, existing technologies, especially the electrolysis method considered more direct, face significant challenges in practical industrial applications. A key difficulty lies in the low boiling point of perfluorobutyryl fluoride, which presents complex technical challenges for the collection of crude products and subsequent purification. For example, in the technical solution of a method and equipment for purifying perfluorobutyryl fluoride electrolytic gas (Announcement No. CN117224989A), the crude gas generated by electrolysis needs to be first passed into a tubular absorption tower to remove hydrogen fluoride, and then the gas exiting the tower is distilled to obtain perfluorobutyryl fluoride product with a purity of about 95%. However, this process is costly and the product collection stability is insufficient. In the technical solution of a method for preparing heptafluorobutyryl fluoride by electrochemical means (Announcement No. CN118543309A), a more complex purification route is attempted. The gas containing heptafluorobutyryl fluoride is first cooled and collected in a low-temperature cold trap, and then it is sequentially passed through a membrane separator equipped with modified carbon nanotube membranes and a packed tower for distillation. This method is cumbersome, requires large equipment investment, and is difficult to implement economically and efficiently in large-scale production.

[0004] Existing electrochemical methods for preparing heptafluorobutyryl fluoride generally suffer from low yields, directly increasing production costs and posing a significant obstacle to industrial-scale production. The crude product typically contains various impurities such as HF, CF4, Cl2, and HCl, which are often difficult to completely remove using conventional distillation techniques alone, affecting the purity and performance consistency of the final product.

[0005] Therefore, developing a new process with high yield, simple and efficient purification process, and more suitable for large-scale continuous production of perfluorobutyryl fluoride, especially a technical solution that can effectively solve the problems of low-boiling-point product collection and deep removal of impurities, has become an urgent direction for breakthroughs in this field. Summary of the Invention

[0006] To address the issues of high impurity removal costs and complex processes in existing technologies, this application provides a method for collecting crude perfluorobutyryl fluoride electrolytic gas. This method eliminates the need for cryogenic cooling to collect crude perfluorobutyryl fluoride, is simple in process, and allows for easy separation and recycling of the extractant from the product. Furthermore, since the extractant is immiscible with hydrogen fluoride, it can also separate hydrogen fluoride from perfluorobutyryl fluoride.

[0007] The specific proposal of this application is as follows:

[0008] A method for collecting crude perfluorobutyryl fluoride electrolysis gas includes the following steps:

[0009] Step S1. Cool down the electrolytic cell;

[0010] Step S2. Add anhydrous hydrogen fluoride, raw materials and electrolyte to the electrolytic cell, stir evenly and then control the temperature and voltage of the electrolytic cell to carry out electrolysis;

[0011] Step S3. During the electrolysis process, the electrolytic gas is introduced into a low-temperature crude product tank containing the extractant;

[0012] Step S4. Distill the crude product in the crude product tank to obtain refined perfluorobutyryl fluoride and recover the extractant.

[0013] Preferably, in step S1, the temperature is lowered to 0-10°C. The purpose of lowering the temperature to a certain level is to facilitate the feeding of hydrogen fluoride.

[0014] Preferably, the raw material in step S2 is n-butyric anhydride, n-butyryl chloride, or n-butyryl fluoride.

[0015] Preferably, the electrolyte in step S2 is sodium fluoride, potassium fluoride, or lithium fluoride.

[0016] Preferably, the electrolysis temperature in step S2 is 0-10°C. The purpose of controlling the low temperature is to increase the absorption of perfluorobutyryl fluoride in the product and prevent the perfluorobutyryl fluoride from volatilizing and causing a decrease in yield.

[0017] Preferably, the electrolysis voltage in step S2 is 5.5 to 6.6V, in order to prevent the electrolysis of hydrogen fluoride from generating fluorine gas.

[0018] Preferably, the electrolysis time in step S2 is 72 hours.

[0019] Preferably, the mass ratio of anhydrous hydrogen fluoride, raw material and electrolyte in step S2 is 3:3:1 to 9:3:1.

[0020] Preferably, the temperature of the low-temperature crude product tank in step S3 is -10℃ to 0℃, and the low-temperature crude product tank is a polytetrafluoroethylene tank with a long inlet and a short outlet or a stainless steel tank.

[0021] Preferably, the extractant is perfluorohexane, and the purity of the extractant after recovery is ≥95%. If the purity is lower than 95%, it is purified again.

[0022] The beneficial effects of this application are:

[0023] This application provides a method for collecting crude perfluorobutyryl fluoride electrolytic gas. This method does not require the use of ultra-low temperature cooling to collect crude perfluorobutyryl fluoride. The process is simple, and the extractant is easy to separate from the product and can be recycled. In addition, since the extractant is immiscible with hydrogen fluoride, it can also separate hydrogen fluoride and perfluorobutyryl fluoride. The purity of the crude product is above 95%.

[0024] (1) This application does not require the use of a cold trap, nor does it require the collection of crude perfluorobutyryl fluoride under ultra-low temperature conditions, and the process is simple.

[0025] (2) The extractant used in this application is easy to separate from the product.

[0026] (3) The extractant used in this application is easy to recycle and reduce costs.

[0027] (4) The extractant used in this application can dissolve the product perfluorobutyryl fluoride well, but is immiscible with hydrogen fluoride, thus achieving the purpose of separating liquid hydrogen fluoride and facilitating subsequent distillation. Detailed Implementation

[0028] To further illustrate the technical means and effects adopted by this application in order to achieve the intended purpose of the invention, the following detailed description of the specific implementation methods, structures, features and effects of this application, in conjunction with preferred embodiments, is provided below.

[0029] Example 1

[0030] Step S1. Cool the electrolytic cell to 0℃. Cooling to 0℃ is mainly due to the physical properties of anhydrous hydrogen fluoride. At room temperature, it easily volatilizes into a gaseous state, while the low temperature keeps it in a liquid state, which facilitates accurate measurement and stable addition to the electrolytic cell. At the same time, the low temperature environment can suppress side reactions in the initial stage of the electrolyte (such as premature decomposition of HF), creating a stable reaction matrix for subsequent electrolysis.

[0031] Step S2. Add 300 parts of anhydrous hydrogen fluoride, 300 parts of electrolytic raw material n-butyryl fluoride, and 100 parts of electrolyte sodium fluoride to the electrolytic cell. After stirring evenly, control the temperature of the electrolytic cell at 0°C. The purpose of controlling the low temperature is to increase the absorption of perfluorobutyryl fluoride and prevent the perfluorobutyryl fluoride from volatilizing and causing a decrease in yield. The low temperature slows down the thermal motion of perfluorobutyryl fluoride molecules, making them easier to be captured by the electrolyte rather than escape, thereby reducing volatilization loss. Electrolysis is carried out at a voltage of 5.5V to prevent the electrolysis of hydrogen fluoride from generating fluorine gas. Open the gas outlet valve of the electrolytic cell.

[0032] Step S3. During electrolysis, the electrolytic gas is introduced into the crude product tank containing perfluorohexane as the extractant. The temperature of the crude product tank is controlled at -10℃. Electrolysis is stopped after 72 hours, and the valves at the front and rear ends of the crude product tank are closed. The low-temperature crude product tank is a polytetrafluoroethylene tank with a long inlet and a short outlet.

[0033] Step S4. The crude product in the crude product tank is distilled to obtain high-quality perfluorobutyryl fluoride; the extractant is recovered and its purity is analyzed; the crude perfluorobutyryl fluoride gas is collected with a purity of 96% and a yield of 46%.

[0034] Example 2

[0035] Step S1. Cool the electrolytic cell to 5°C. Cooling to 5°C is mainly due to the physical properties of anhydrous hydrogen fluoride. At room temperature, it easily volatilizes into a gaseous state, while the low temperature keeps it in a liquid state, which facilitates accurate measurement and stable addition to the electrolytic cell. At the same time, the low temperature environment can suppress side reactions in the initial stage of the electrolyte (such as premature decomposition of HF), creating a stable reaction matrix for subsequent electrolysis.

[0036] Step S2. Add 600 parts of anhydrous hydrogen fluoride, 300 parts of electrolytic raw material n-butyryl chloride, and 100 parts of electrolyte potassium fluoride to the electrolytic cell. After stirring evenly, control the temperature of the electrolytic cell at 5°C. The purpose of controlling the low temperature is to increase the absorption of perfluorobutyryl fluoride and prevent the perfluorobutyryl fluoride from volatilizing and causing a decrease in yield. The low temperature slows down the thermal motion of perfluorobutyryl fluoride molecules, making them easier to be captured by the electrolyte rather than escape, thereby reducing volatilization loss. Electrolysis is carried out at 6V to prevent the electrolysis of hydrogen fluoride from generating fluorine gas. Open the gas outlet valve of the electrolytic cell.

[0037] Step S3. During electrolysis, the electrolytic gas is introduced into the crude product tank containing perfluorohexane as the extractant, and the temperature of the crude product tank is controlled at 0℃. Electrolysis is ended after 72 hours, and the valves at the front and rear ends of the crude product tank are closed. The low-temperature crude product tank is a polytetrafluoroethylene tank with a long inlet and a short outlet.

[0038] Step S4. The crude product in the crude product tank is distilled to obtain high-quality perfluorobutyryl fluoride; the extractant is recovered and its purity is analyzed; the crude perfluorobutyryl fluoride gas is collected with a purity of 98% and a yield of 41%.

[0039] Example 3

[0040] Step S1. Cool the electrolytic cell to 10°C. Cooling to 10°C is mainly due to the physical properties of anhydrous hydrogen fluoride. At room temperature, it easily volatilizes into a gaseous state, while the low temperature keeps it in a liquid state, which facilitates accurate measurement and stable addition to the electrolytic cell. At the same time, the low temperature environment can suppress side reactions in the initial stage of the electrolyte (such as premature decomposition of HF), creating a stable reaction matrix for subsequent electrolysis.

[0041] Step S2. Add 900 parts of anhydrous hydrogen fluoride, 300 parts of electrolytic raw material n-butyric anhydride, and 100 parts of electrolyte lithium fluoride to the electrolytic cell. After stirring evenly, control the temperature of the electrolytic cell at 10°C. The purpose of controlling the low temperature is to increase the absorption of perfluorobutyryl fluoride in the product and prevent the perfluorobutyryl fluoride from volatilizing and causing a decrease in yield. The low temperature slows down the thermal motion of perfluorobutyryl fluoride molecules, making them easier to be captured by the electrolyte rather than escape, thereby reducing volatilization loss. Electrolysis is carried out at a voltage of 6.5V to prevent the electrolysis of hydrogen fluoride from generating fluorine gas. Open the gas outlet valve of the electrolytic cell.

[0042] Step S3. During electrolysis, the electrolytic gas is introduced into the crude product tank containing perfluorohexane as the extractant. The temperature of the crude product tank is controlled at -5℃. Electrolysis is stopped after 72 hours, and the valves at the front and rear ends of the crude product tank are closed. The low-temperature crude product tank is a polytetrafluoroethylene tank with a long inlet and a short outlet.

[0043] Step S4. The crude product in the crude product tank is distilled to obtain high-quality perfluorobutyryl fluoride; the extractant is recovered and its purity is analyzed; the crude perfluorobutyryl fluoride gas is collected with a purity of 95% and a yield of 43%.

[0044] Comparative Example 1

[0045] The difference between this comparative example and Example 1 is that the voltage in this comparative example is 10V. Preliminary measurements showed that the purity of the crude perfluorobutyryl fluoride gas was 89%, and the yield was 29%. This may be because high pressure may trigger the decomposition of hydrogen fluoride or other side reactions, leading to an increase in impurities.

[0046] Comparative Example 2

[0047] The difference between this comparative example and Example 1 is that the electrolysis temperature in this comparative example is 20°C. Preliminary measurements showed that the purity of the crude perfluorobutyryl fluoride gas was 82%, and the yield was 24%. This may be because the high temperature intensifies the volatilization of perfluorobutyryl fluoride (boiling point -1°C), causing it to escape during electrolysis rather than be captured by the electrolyte.

[0048] Comparative Example 3

[0049] The difference between this comparative example and Example 1 is that the temperature of the crude product tank in this comparative example is controlled at 5°C. After preliminary measurement, the purity of the crude perfluorobutyryl fluoride gas is 76%, and the yield is 23%.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any way. Although this application has been disclosed above with reference to preferred embodiments, it is not intended to limit this application. 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 technical solution of this application. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of this application without departing from the scope of the technical solution of this application shall still fall within the scope of the technical solution of this application.

Claims

1. A method for collecting crude perfluorobutyryl fluoride electrolysis gas, characterized in that, Includes the following steps: Step S1. Cool down the electrolytic cell; Step S2. Add anhydrous hydrogen fluoride, raw materials and electrolyte to the electrolytic cell, stir evenly and then control the temperature and voltage of the electrolytic cell to carry out electrolysis; Step S3. During the electrolysis process, the electrolytic gas is introduced into a low-temperature crude product tank containing the extractant; Step S4. Distill the crude product in the crude product tank to obtain refined perfluorobutyryl fluoride and recover the extractant.

2. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, In step S1, the temperature is lowered to 0-10°C.

3. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, The raw material in step S2 is n-butyric anhydride, n-butyryl chloride, or n-butyryl fluoride.

4. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, The electrolyte in step S2 is sodium fluoride, potassium fluoride, or lithium fluoride.

5. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, The electrolysis temperature in step S2 is 0 to 10°C.

6. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, The electrolysis voltage in step S2 is 5.5 to 6.5V.

7. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, The electrolysis time in step S2 is 72 hours.

8. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, In step S2, the mass ratio of anhydrous hydrogen fluoride, raw materials, and electrolyte is 3:3:1 to 9:3:

1.

9. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, The temperature of the low-temperature crude product tank in step S3 is -10℃ to 0℃, and the low-temperature crude product tank is a polytetrafluoroethylene tank with a long inlet and a short outlet or a stainless steel tank.

10. The method for collecting crude perfluorobutyryl fluoride electrolysis gas according to claim 1, characterized in that, The extractant is perfluorohexane, and the purity of the recovered extractant is ≥95%.