A method and apparatus for the production of perfluoroalkanes

Abstract

This invention belongs to the field of haloalkanes preparation, specifically relating to a method and apparatus for preparing perfluoroalkanes. The method for preparing perfluoroalkanes includes the following steps: [The text abruptly ends here, so the translation stops.] 2‑4 Alkanes and fluorine undergo a substitution reaction in the presence of a catalyst, wherein the catalyst is a transition metal or its fluoride. The reacted gas is then washed with water to remove impurities, dried to remove water, and purified by distillation to obtain perfluoroalkanes. This invention utilizes a high-temperature catalytic fluorine substitution process, followed by water washing to remove fluorine impurities. The catalyst used is transition metal particles or transition metal fluoride particles, which have a simple structure and low cost. The separation and purification process is simplified and effective, effectively reducing the industrial production cost of perfluorobutane and other perfluoroalkanes.

Description

Technical Field

[0001] This invention belongs to the field of preparation of haloalkanes, and specifically relates to a method and apparatus for preparing perfluoroalkanes. Background Technology

[0002] Perfluorobutane microspheres for injection are a commonly used clinical ultrasound contrast agent that, after intravenous injection, allows for real-time dynamic visualization of organ blood perfusion. Perfluorobutane microspheres for injection are suitable for: qualitative diagnosis of focal liver lesions, differentiation of benign and malignant thyroid nodules, analysis of blood flow characteristics in breast tumors, and real-time navigation in interventional therapy. The diameter of the perfluorobutane microspheres ranges from 2 to 5 micrometers. They can enter the systemic circulation via peripheral intravenous injection, do not penetrate vascular endothelium, and are not metabolized by the liver or kidneys, ultimately being excreted through respiration. The imaging mechanism is based on the scattering and enhancement effect of ultrasound waves by microbubbles in the blood, clearly displaying tiny lesions with a diameter of 1-2 millimeters. Compared with similar imaging technologies, its advantages include: no ionizing radiation during the examination, repeated acquisition of dynamic images in a single examination, no examination interval limitations due to iodine metabolism, and real-time observation of tissue blood perfusion.

[0003] High-purity perfluorobutane is the core raw material for manufacturing injectable perfluorobutane microspheres. It is a chemical substance among perfluorinated compounds (PFAS), a colorless, non-toxic, and non-flammable gas at room temperature and pressure, easily liquefied, with a boiling point of -2.0℃. Perfluorobutane is chemically stable, but may decompose to produce toxic substances when mixed with flammable gases. Toxicological studies have shown that it poses no direct harm to the human body and has good compatibility with common metals and plastics; polytetrafluoroethylene (PTFE) and nitrile rubber (NBR) are recommended sealing materials.

[0004] The low-cost industrial production of high-purity perfluorobutane and other perfluoroalkanes is one of the key conditions for the large-scale commercialization of such materials. Chinese invention patent application CN 110590493 A, published on December 20, 2019, discloses a method for preparing high-purity hexafluoroethane. This method uses a Co2O3-NiO-Cr2O3 catalyst, which, after activation, is used to react with a feed gas (a mixture of pentafluorochloroethane and pentafluoroethane) and hydrogen fluoride to produce hexafluoroethane gas. This gas is then purified by distillation and a purifier to obtain high-purity hexafluoroethane gas. This method uses a specially structured Co2O3-NiO-Cr2O3 catalyst, and the separation and purification process is relatively complex, resulting in high actual industrialization costs.

[0005] Chinese invention patent application CN 116283479 A, ​​published on June 23, 2023, discloses a method for preparing electronic-grade octafluoropropane. This method utilizes a transparent tubular reaction vessel containing a CTN catalyst, using a gas containing propane and an electrophilic fluorinating agent (e.g., a fluorine-nitrogen mixture) as the reaction gas. The reaction vessel is subjected to light irradiation while the CTN catalyst is simultaneously electrolyzed for dual excitation. The reaction gas then reacts to obtain electronic-grade octafluoropropane. The CTN catalyst is a C-Ti-Ni-O catalyst, containing elemental carbon as a framework and doped with Ni(II) oxide, Ti(IV) oxide, and Ni(III) oxide. The C-Ti-Ni-O catalyst consists of several single-layer porous membrane structures, which exhibit a honeycomb-like two-dimensional structure. This method also requires expensive catalysts and dual activation by light and electricity, placing high demands on production equipment and hindering the reduction of industrial-scale costs for octafluoropropane. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing perfluoroalkanes, so as to solve the problems of existing perfluoroalkane production methods, such as the need for expensive catalysts, complex purification processes, and high costs.

[0007] A second objective of this invention is to provide an apparatus for preparing perfluoroalkanes to solve the aforementioned problems.

[0008] To achieve the above objectives, the technical solution of the method for preparing perfluoroalkane of the present invention is as follows: A method for preparing perfluoroalkane includes the following steps: C 2-4 Alkanes and fluorine undergo a substitution reaction in the presence of a catalyst, wherein the catalyst is a transition metal or its fluoride; the gas after the reaction is washed with water to remove impurities, dried to remove water, and purified by distillation to obtain perfluoroalkanes.

[0009] This invention is an improved invention. It uses a high-temperature catalytic fluorine substitution process followed by a water washing process to remove fluorine impurities. The catalyst used is a transition metal particle or a transition metal fluoride particle. The catalyst has a simple structure and low cost. The separation and purification process is simplified and effective, which can effectively reduce the industrial production cost of perfluoroalkanes such as perfluorobutane.

[0010] Preferably, the substitution reaction is carried out at a pressure of 100-500 kPa and a temperature of 300-800 °C. More preferably, the substitution reaction conditions are a pressure of 250-500 kPa and a temperature of 450-800 °C, under which it is expected to obtain a gas with high purity and yield.

[0011] More preferably, the substitution reaction takes 2-24 hours.

[0012] Preferably, the C 2-4 The molar ratio of alkanes to fluorine is 1:(10-30). A more preferred molar ratio is 1:(15-30). Under these preferred conditions, the C content can be further increased. 2-4 Conversion efficiency of alkanes.

[0013] Preferably, the substitution reaction is carried out in a reactor rotating about a horizontal axis, during which alkanes, fluorine gas, and catalyst particles are mixed; the catalyst particles are nickel particles, cobalt particles, silver particles, nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles. This rotating reaction method allows for high throughput and ensures thorough mixing and mass transfer between the catalyst particles and the reactant gases. Furthermore, the catalyst particles are all simple elements or compounds, significantly reducing the manufacturing and usage costs of the catalyst, thus making it suitable for industrial production.

[0014] Preferably, the C 2-4 The alkane is ethane, propane, or butane, and the corresponding perfluoroalkane is perfluoroethane, perfluoropropane, or perfluorobutane.

[0015] Preferably, the process further includes a repeated substitution reaction step: the perfluoroalkane obtained by drying and removing water and fluorine gas are subjected to the substitution reaction in the presence of a catalyst, and the gas after the reaction is washed with water to remove impurities and dried to remove water; the substitution reaction is carried out 2-11 times in total to obtain high-purity perfluoroalkane.

[0016] More preferably, in the repeated substitution reaction step, the molar ratio of perfluoroalkane to fluorine is 1:(1-10). The molar ratio of perfluoroalkane to fluorine is further preferably 1:(5-10).

[0017] The technical solution of the apparatus for preparing perfluoroalkanes of the present invention is as follows: An apparatus for preparing perfluoroalkanes includes a fluorine substitution reactor, a defluorination drying device for washing and drying the gas produced by the fluorine substitution reactor, and a distillation purification device located downstream of the defluorination drying device; the fluorine substitution reactor has a reaction chamber for accommodating catalyst particles, and is also provided with a method for adding C 2-4 Import of gaseous materials such as alkanes and fluorine.

[0018] The equipment for preparing perfluoroalkane provided by this invention is a production device specifically designed for the industrial production of perfluoroalkane. It features high reaction efficiency, easy maintenance, and stable post-processing, and can conveniently and efficiently produce high-purity perfluoroalkanes such as perfluorobutane.

[0019] Preferably, the central axis of the fluorine substitution reactor extends in the front-to-back direction, and the device further includes a drive unit for driving the fluorine substitution reactor to rotate around its central axis; the defluorination drying device includes a water washing tower, a water vapor separator and a drying tower arranged in sequence. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the fluorine substitution reaction apparatus in Embodiment 1 of the present invention; Among them, 1-catalytic fluorine substitution reactor; 2-reactor heating jacket; 3-reactor rotating shaft; 4-rotating motor; 5-reactor rotating shaft support; 6-reactor material pipe; 7-reactor gas pipeline; 8-reactor material pipe support; 9-reactor gas pipeline valve; Figure 2 This is a schematic diagram of the water washing defluorination device in Embodiment 1 of the present invention; Among them, 10-washing tower; 11-water-gas separator; 12-drying tower; 13-perfluorobutane liquefaction collection tank; 14-washing tower outlet pipeline; 15-washing tower inlet pipeline; 16-washing tower cleaning water inlet and outlet pipeline; 17-washing tower circulating water pump front pipeline; 18-washing tower circulating water pump; 19-washing tower circulating water spray pipeline; 20-water-gas separator inlet pipeline; 21-water-gas separator outlet pipeline; 22-water-gas separator wastewater discharge pipeline; 23-drying tower inlet pipeline; 24-drying tower outlet pipeline; 25-collection tank inlet pipeline; 26-collection tank vacuum pipeline; 27- Collection tank cold trap; 2801-Water washing tower inlet pipeline valve; 2802-Water washing tower cleaning water inlet and outlet pipeline valve; 2803-Water washing tower circulating water pump front pipeline valve; 2804-Water washing tower circulating water spray pipeline valve; 2805-Water washing tower outlet pipeline valve; 2806-Water-gas separator inlet pipeline valve; 2807-Water-gas separator wastewater discharge pipeline valve; 2808-Water-gas separator outlet pipeline valve; 2809-Drying tower inlet pipeline valve; 2810-Drying tower outlet pipeline valve; 2811-Collection tank inlet pipeline valve; 2812-Collection tank vacuum pipeline valve; Figure 3 This is a schematic diagram of the distillation and purification apparatus in Embodiment 1 of the present invention; 29-Perfluorobutane distillation feed tank; 30-Perfluorobutane distillation column; 31-High-purity perfluorobutane liquefaction collection tank; 32-Inlet pipe of distillation feed tank; 33-Liquid gas outlet pipe of feed tank; 34-Liquid gas inlet pipe of perfluorobutane distillation column; 35-Thermostatic jacket of distillation column evaporator; 36-Gas outlet pipe of distillation column; 37-Inlet pipe of high-purity perfluorobutane liquefaction collection tank; 38-Vacuum pipe of collection tank; 391-Valve of inlet pipe of distillation feed tank; 392-Valve of liquid gas outlet pipe of feed tank; 393-Valve of liquid gas inlet pipe of perfluoroalkane distillation column; 394-Valve of gas outlet pipe of distillation column; 395-Valve of inlet pipe of high-purity perfluorobutane liquefaction collection tank; 396-Valve of vacuum pipe of high-purity perfluorobutane liquefaction collection tank. Detailed Implementation

[0021] (I) Preferred embodiments of the method and equipment for preparing perfluoroalkane of the present invention The equipment for preparing perfluoroalkanes of this invention is designed based on a novel process for preparing perfluoroalkanes. This process involves a high-temperature mixed fluorine substitution reaction of high-purity n-alkanes, high-purity fluorine gas, and catalyst particles. The gas after the reaction is then washed with water to remove fluorine and dried to remove water, achieving purification. To further improve the purity of the perfluoroalkanes, the purified perfluoroalkanes can be further subjected to a high-temperature mixed fluorine substitution reaction with high-purity fluorine gas and catalyst particles. The gas after the reaction is then washed with water to remove fluorine and dried to remove water again. This process is repeated until the gas is purified by distillation, ultimately yielding high-purity perfluoroalkanes.

[0022] The catalyst particles used in the aforementioned new process are nickel particles, cobalt particles, silver particles, nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles. The particle size of the catalyst can be 10 μm-2 mm; preferably 100 μm-1000 μm, and more preferably 200 μm-800 μm. These types of catalyst particles are readily available, have low operating costs, and can effectively reduce the manufacturing and maintenance costs of the catalyst.

[0023] When high-purity n-alkanes, high-purity fluorine gas, and catalyst particles undergo a high-temperature fluorine substitution reaction, the molar ratio of high-purity n-alkanes to high-purity fluorine gas is 1:(10-30). Preferably, the molar ratio of high-purity n-alkanes to high-purity fluorine gas is 1:(15-25).

[0024] The high-temperature mixed fluorine substitution reaction is carried out in a closed reactor, and the amount of catalyst particles added can be 10-50% of the reactor volume. For example, it can be 33-50% of the reactor volume. The above high-temperature mixed substitution reaction is preferably carried out under conditions of 100-500 kPa pressure and 300-800°C temperature. The reaction time can be 2-24 h. More preferably, the high-temperature mixed fluorine substitution reaction is carried out at a pressure of 250-500 kPa, a temperature of 450-800°C, and a time of 12-24 h.

[0025] To achieve efficient mixing of high-purity n-alkanes, high-purity fluorine gas, and catalyst particles, a reactor extending along its longitudinal direction can be designed. This reactor is driven to rotate around its central axis, thus achieving efficient mixing of the catalyst particles and gaseous materials. The reactor rotation speed can be controlled between 5-100 rpm. This high-temperature fluorine substitution reaction occurs under high pressure conditions; therefore, the reactor must possess high-temperature and high-pressure resistance. Furthermore, the reactor should be well-matched with vacuum equipment and gas conveying equipment to facilitate vacuuming, gas conveying, and ensure airtightness.

[0026] In subsequent repeated high-temperature mixed fluorination substitution reactions of perfluoroalkanes with high-purity fluorine gas and catalyst particles, the amount of fluorine gas used can be reduced accordingly, and the molar ratio of high-purity fluorine gas to perfluoroalkanes can be (1-10):1. The high-temperature mixed fluorination substitution reaction can be repeated more than 5 times, for example, 5-10 times. After each high-temperature mixed fluorination substitution reaction, water washing and drying are performed to remove fluorine and water. Finally, through distillation purification, high-purity perfluoroalkanes with a purity of over 99.9% can be obtained.

[0027] During distillation purification, the pressure can be controlled at 80~120kPa. First, the component from -10 to -5℃ is distilled off, then the component from -4 to -2℃ is distilled off and liquefied to obtain perfluorobutane. Finally, the component from -2 to 0℃ is distilled off and liquefied to be used as the raw material for the next distillation.

[0028] The preferred embodiments of the method and apparatus for preparing perfluoroalkanes are illustrated below with specific examples. In the following examples, the purity of each gas refers to a volume percentage.

[0029] In the following examples, the specific production of high-purity perfluorobutane is used as an example for illustration. The purity of high-purity butane is 99.999%, and the purity of high-purity fluorine gas is 99.999%.

[0030] Example 1 The equipment for preparing perfluoroalkanes in this embodiment includes a fluorine substitution reaction apparatus, a water washing and defluorination apparatus, and a distillation and purification apparatus. The structure and usage of the fluorine substitution reaction apparatus, the water washing and defluorination apparatus, and the distillation and purification apparatus are described in detail below: 1. Fluorine substitution reaction apparatus The fluorine substitution reaction apparatus mainly realizes the high-temperature catalytic fluorine substitution reaction of high-purity butane, fluorine gas, and catalyst particles. Its structural schematic diagram is shown below. Figure 1 As shown, it includes a catalytic fluorine substitution reactor 1, which is an elongated cylindrical container with one open end and a diameter-to-height ratio of 1:(2-15). A reactor heating jacket 2 is installed outside the elongated cylindrical container to adjust the temperature of the high-temperature catalytic fluorine substitution reactor.

[0031] A reactor rotation shaft 3 is installed at one end along the length of the catalytic fluorine substitution reactor 1. The reactor rotation shaft 3 is connected to a rotary motor 4, which drives the elongated cylindrical container to rotate around its central axis (extending along the length or front-back direction). The rotation speed is adjustable. A reactor rotation shaft support 5 is connected to the lower part of the reactor rotation shaft 3. The other end of the catalytic fluorine substitution reactor 1 is connected to a reactor material pipe 6. The reactor material pipe 6 has an open structure to allow the addition of catalyst particles into the reactor, or to connect to a reactor gas pipeline 7 to introduce high-purity butane, high-purity fluorine, or other gaseous materials into the reactor. A reactor material pipe support 8 is connected to the lower part of the reactor material pipe 6. The reactor material pipe 6 is equipped with a flange connecting to the reactor gas pipeline 7, and a reactor gas pipeline valve 9 is installed on the reactor gas pipeline 7.

[0032] The operation of this fluorine substitution reaction device is as follows: Nickel particles, cobalt particles, silver particles, nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles are added to the reactor through the reactor material pipe 6, with the amount added being one-tenth to one-half of the reactor volume. This is then connected to the reactor gas pipeline 7 via a flange. The reactor gas pipeline 7 is connected to the gas material feeding pipeline, which has functions such as vacuuming, balance gas replacement, and gas material addition. The balance gas can be high-purity nitrogen, high-purity argon, or high-purity helium. First, a vacuum is drawn until the pressure inside the reactor is below 10 Pa. Then, balance gas is added to the reactor, and the pressure is increased to 50-200 kPa. Vacuuming is then repeated 3-10 times until the reactor pressure is maintained below 10 Pa. Then, high-purity butane and high-purity fluorine gas are added to the reactor. After the reactants are added, the pressure inside the reactor is 100-500 kPa, and the molar ratio of butane to fluorine gas in the reactor is 1:(10-30). After the reactants are added, the connection between the reactor gas pipeline 7 and the gas feed pipeline is disconnected. The reactor is placed inside the reactor heating jacket 2, and the rotating motor 4 is turned on. The reactor rotation speed is controlled at 5-100 rpm, the reactor temperature is controlled at 300-800℃, and the reaction time is 2-24 hours.

[0033] 2. Water washing defluorination device The water-washing defluorination unit is mainly used to wash, defluorinate, and dry the gas produced by the fluorine substitution reaction unit. A schematic diagram is shown below. Figure 2As shown, it includes a water washing tower 10, a water-gas separator 11, a drying tower 12, and a perfluorobutane liquefaction collection tank 13 connected in sequence.

[0034] The washing tower 10 is a spray-type washing device with a packing layer in the middle, a circulating water tank at the bottom, and a washing tower outlet pipe 14 connected to the top. Below the packing layer of the washing tower 10, there is a washing tower inlet pipe 15. After the washing tower inlet pipe 15 is connected to the reactor gas pipeline 7 of the fluorine substitution reaction device, the gas produced by the fluorine substitution reaction device can be introduced into the washing tower 10. On one side of the circulating water tank is the washing tower cleaning water inlet and outlet pipe 16, and on the other side is the washing tower circulating water pump inlet pipe 17. The washing tower circulating water pump inlet pipe 17 is connected to the washing tower circulating water pump 18. The outlet of the washing tower circulating water pump 18 is connected to the washing tower circulating water spray pipe 19. The washing tower circulating water spray pipe 19 extends vertically upwards and extends into the washing tower 10 above the packing layer. Circulating water sprayers are installed on the washing tower circulating water spray pipe 19 at positions corresponding to the packing layer. After the circulating water flows out of the sprayer, it flows from top to bottom, while the perfluorobutane gas flows from bottom to top. The circulating water and the perfluorobutane gas come into full contact in the packing layer in the middle of the water washing tower. The circulating water eventually flows into the circulating water pool at the bottom of the water washing tower 10. After cleaning, the perfluorobutane gas flows out of the water washing tower 10 through the water washing tower outlet pipe 14 at the top of the water washing tower 10.

[0035] The water-gas separator 11 is a tank with a packing layer in the middle. A water-gas separator inlet pipe 20 is provided below the packing layer, and a water-gas separator outlet pipe 21 is provided above the packing layer. The water-gas separator inlet pipe 20 is connected to the water washing tower outlet pipe 14. Perfluorobutane gas containing moisture passes through the packing layer from bottom to top. The moisture is intercepted and flows downward into the bottom of the water-gas separator 11. The bottom of the water-gas separator 11 is connected to the water-gas separator wastewater discharge pipe 22. The perfluorobutane gas with moisture removed flows out from the water-gas separator outlet pipe 21.

[0036] The drying tower 12 is a fixed-bed packed tower. The bottom of the drying tower 12 is connected to the drying tower inlet pipe 23, which is connected to the water-gas separator outlet pipe 21. Perfluorobutane gas containing trace amounts of water passes through the desiccant packing layer of the drying tower from bottom to top, and the dried perfluorobutane gas flows out from the drying tower outlet pipe 24 at the top of the drying tower 12.

[0037] The perfluorobutane liquefaction collection tank 13 collects liquefied perfluorobutane and includes a tank body. The top of the tank body is connected to a collection tank inlet pipe 25 and a collection tank vacuum pipe 26. The collection tank inlet pipe 25 is connected to the drying tower outlet pipe 24. The collection tank inlet pipe 25 is inserted into the bottom of the perfluorobutane liquefaction collection tank 13. The upper part of the perfluorobutane liquefaction collection tank 13 has a cold energy storage packing layer. The perfluorobutane liquefaction collection tank 13 is immersed in the collection tank cold trap 27, which is filled with an ultra-low temperature medium.

[0038] The following pipelines are equipped with valves: air inlet pipe 15, cleaning water inlet / outlet pipe 16, circulating water pump pre-pipeline 17, circulating water spray pipe 19, air outlet pipe 14, water-gas separator inlet pipe 20, wastewater discharge pipe 22, air outlet pipe 21, drying tower inlet pipe 23, drying tower outlet pipe 24, collection tank inlet pipe 25, and collection tank vacuum pipe 26. Each of these pipelines has a water inlet valve 2801 for the air inlet pipe and a cleaning water inlet pipe for the water washing tower. 2802, valve 2803, valve 2804, valve 2805, valve 2806, valve 2807, valve 2808, valve 2809, valve 2810, valve 2811, valve 2812, valve 2812, valve 2803, valve 2804, valve 2805, valve 2806, valve 2807, valve 2808, valve 2809, valve 2810, valve 2811, valve 2812, valve 2813, valve 2814, valve 2805, valve 2806, valve 2807, valve 2808, valve 2809, valve 2810, valve 2811, valve 2812, valve 2812, valve 2813, valve 2804, valve 2805, valve 2806, valve 2807, valve 2808, valve 2809, valve 2801 ...01, valve 2811, valve 2812, valve 2813, valve 2804, valve 2805, valve 2806, valve 2807, valve 2808, valve 2809, valve 2801, valve 2801, valve 2801, valve 2812, valve 2811, valve 2812, valve 2813, valve 2804, valve 2805, valve 2806, valve

[0039] The operation process of the water washing defluorination device is as follows: The gas pipeline 7 of the catalytic fluorine substitution reactor is connected to the gas inlet pipeline 15 of the water washing tower. The gas flows from bottom to top in the water washing tower 10, passing through the packing layer in the middle of the water washing tower 10. The packing layer is filled with polytetrafluoroethylene rings. Clean cleaning water (ultrapure water) can be introduced into the circulating water pool at the bottom of the water washing tower 10 through the cleaning water inlet and outlet pipeline 16. After the water washing tower 10 finishes working, the cleaning wastewater can also be discharged through the cleaning water inlet and outlet pipeline 16. The circulating water pool at the bottom of the water washing tower 10 is connected to the water washing tower circulating water pump 18. After the circulating water passes through the circulating water pump, the circulating water sprays the cleaning water from top to bottom through the spray pipe at the top of the water washing tower. The cleaning water and gas are fully mixed in the packing layer in the middle of the water washing tower. The cleaned gas flows out from the gas outlet pipeline 14 of the water washing tower.

[0040] Gas flowing from the outlet pipe 14 of the water washing tower flows into the inlet pipe 20 of the water-gas separator and enters the water-gas separator 11. The packing material of the water-gas separator is polytetrafluoroethylene rings. There is a wastewater discharge pipe at the bottom of the water-gas separator 11. After the water-gas separator 11 finishes working, the wastewater can be discharged. Gas containing trace amounts of water flows out from the outlet pipe 21 of the water-gas separator and enters the drying tower 12. The gas flows upward in the drying tower 12, passing through the packing layer in the middle of the drying tower. The packing material in the packing layer is 3A molecular sieve or 13X molecular sieve. The dried gas flows out from the outlet pipe 24 of the drying tower.

[0041] The perfluorobutane liquefaction collection tank 13 operates together with the drying tower 12. After the drying tower 12 starts operating, the inlet valve 2811 and the vacuum valve 2812 of the collection tank are opened. The perfluorobutane gas flowing out of the drying tower 12 enters the perfluorobutane liquefaction collection tank, where it is liquefied. The non-condensable gas is then extracted through the vacuum pipeline 26 of the collection tank. The cold trap 27 of the collection tank is filled with a cryogenic medium, which can be ethanol. The temperature of the cryogenic medium is controlled from -100 to 0°C. The packing material in the cold energy storage packing layer of the perfluorobutane liquefaction collection tank is nickel particles and cobalt particles.

[0042] 3. Structure and Operating Instructions of the Distillation and Purification Apparatus The distillation unit obtains single-component high-purity perfluorobutane through distillation separation. Its structural schematic diagram is shown below. Figure 3 As shown, it includes a perfluorobutane distillation feed tank 29, a perfluorobutane distillation column 30, and a high-purity perfluorobutane liquefaction collection tank 31.

[0043] The perfluorobutane distillation feedstock tank 29 is the perfluorobutane liquefaction collection tank in the water washing defluorination device. The perfluorobutane distillation feedstock tank 29 is immersed in the feedstock tank cold trap. The top of the feedstock tank has a distillation feedstock tank inlet pipe 32 and a feedstock tank liquid gas outlet pipe 33. The feedstock tank liquid gas outlet pipe 33 extends into the bottom of the feedstock tank.

[0044] The perfluorobutane distillation column 30 includes an evaporator at the bottom, a distillation unit in the middle, and a high-purity gas extractor at the top. The evaporator at the bottom is connected to a liquid-gas inflow pipe 34, which is connected to a liquid-gas outflow pipe 33 from the feed tank. The evaporator is equipped with a thermostatic jacket 35 to immerse it in a constant-temperature medium. Aluminum foil packing is placed in the distillation unit. The high-purity gas extractor at the top is connected to a gas outflow pipe 36.

[0045] The top of the high-purity perfluorobutane liquefaction collection tank 31 is connected to both an inlet pipe 37 and a vacuum pipe 38. One end of the inlet pipe 37 is connected to the gas outlet pipe 36 of the distillation column, and the other end is inserted into the bottom of the high-purity perfluorobutane liquefaction collection tank 31. A cold energy storage packing layer is provided in the upper part of the high-purity perfluorobutane liquefaction collection tank 31. The high-purity perfluorobutane liquefaction collection tank 31 is placed in a cold trap 27, which is filled with a low-temperature medium.

[0046] The following valves are respectively installed on the following pipelines: the inlet pipeline 32 of the distillation feed tank, the liquid gas outlet pipeline 33 of the feed tank, the liquid gas inlet pipeline 34 of the perfluorobutane distillation column, the gas outlet pipeline 36 of the distillation column, the inlet pipeline 37 of the high-purity perfluorobutane liquefaction collection tank, and the vacuum pipeline 38 of the collection tank. These valves control the opening and closing of the relevant pipelines: the inlet pipeline valve 391 of the distillation feed tank, the liquid gas outlet pipeline valve 392 of the feed tank, the liquid gas inlet pipeline valve 393 of the perfluorobutane distillation column, the gas outlet pipeline valve 394 of the distillation column, the inlet pipeline valve 395 of the high-purity perfluorobutane liquefaction collection tank, and the vacuum pipeline valve 396 of the high-purity perfluorobutane liquefaction collection tank.

[0047] The process of using the distillation and purification unit includes the perfluorobutane distillation feedstock supply process, the perfluorobutane distillation process, and the high-purity perfluorobutane liquefaction and collection process.

[0048] Perfluorobutane distillation feedstock supply process: The temperature of the perfluorobutane distillation feedstock tank 29 is kept constant at -20 to -10℃. The balance gas enters the feedstock tank through the feedstock tank inlet pipe 32, pressurizing the feedstock tank. The perfluorobutane liquid feedstock enters the perfluorobutane distillation column 30 through the feedstock tank liquid gas outlet pipe 33.

[0049] Perfluorobutane distillation process: The temperature of the evaporator is controlled by the constant temperature jacket 35 of the distillation column. The evaporator temperature is between -10 and -5℃, and the distillate is discarded. The evaporator temperature is between -4 and -2℃, and the distillate is liquefied to obtain high-purity perfluorobutane. The evaporator temperature is between -2 and 0℃, and the liquefied distillate is used as the raw material for the next distillation. During the distillation process, the pressure of the distillation column is controlled within the range of 80~120kPa.

[0050] High-purity perfluorobutane liquefaction and collection process: The high-purity perfluorobutane liquefaction and collection tank 31 operates together with the perfluorobutane distillation column 30. After the perfluorobutane distillation starts, the inlet valve 395 and the vacuum valve 396 of the high-purity perfluorobutane liquefaction and collection tank are opened. The perfluorobutane gas flowing out of the perfluorobutane distillation column 30 enters the high-purity perfluorobutane liquefaction and collection tank 31, where the high-purity perfluorobutane is liquefied. The balance gas (high-purity nitrogen, high-purity argon, or high-purity helium) is vacuumed in gaseous form through the vacuum pipeline of the collection tank. The cold trap of the collection tank is filled with a cryogenic medium, which can be ethanol or liquid argon. The temperature of the cryogenic medium is controlled from -150°C to 0°C. The packing material in the cold energy storage packing layer of the perfluorobutane liquefaction and collection tank 31 is nickel particles and cobalt particles.

[0051] Example 2 The method for preparing perfluoroalkanes in this embodiment uses the equipment from Example 1 and specifically follows these steps: (1) High-purity butane, fluorine gas and catalyst particles are mixed in a rotating manner in a reactor and a high-temperature fluorine substitution reaction is carried out. The molar ratio of high-purity butane to fluorine gas is 1:30, the pressure in the reactor is 500 kPa, the temperature is controlled at 800℃, and the reaction time is 2h. The catalyst particles are silver fluoride with a particle size of 500 μm and the amount added is 1 / 10 of the reactor volume.

[0052] (2) The gas from the reaction in step (1) is passed into a water washing and defluorination device to remove hydrogen fluoride, fluorine gas and trace amounts of water-soluble impurities. After drying and dehydration, it is purified by distillation to obtain perfluorobutane.

[0053] The perfluorobutane obtained in this embodiment had a purity of 99.2% and a yield of 72.8%. The formation of perfluorobutane was characterized by infrared spectroscopy, and the purity of perfluorobutane was tested by gas chromatography.

[0054] Example 3 The method for preparing perfluoroalkane in this embodiment is based on Example 2, and involves repeated fluorine substitution reactions. The specific details are as follows: The perfluoroalkane gas obtained in step (2) is introduced into the fluorine substitution reactor as raw material, and an appropriate amount of high-purity fluorine gas is added. The molar ratio of perfluorobutane to high-purity fluorine gas is 1:5. The pressure inside the reactor is 100 kPa, the temperature is controlled at 480°C, and the reaction time is 24 h. The gas obtained from the reaction is passed into a water washing and defluorination device for water washing and defluorination, and then dried. This process is repeated 10 times, and then purified by distillation to obtain high-purity perfluorobutane.

[0055] The perfluorobutane obtained in this embodiment has a purity of 99.99% and a yield of 91.3%.

[0056] Example 4 The method for preparing perfluoroalkanes in this embodiment uses the equipment from Example 1 and specifically follows these steps: (1) High-purity butane, fluorine gas and catalyst particles are mixed in a rotating manner in a reactor and a high-temperature fluorine substitution reaction is carried out. The molar ratio of high-purity butane to fluorine gas is 1:10, the pressure in the reactor is 500 kPa, the temperature is controlled at 300℃, and the reaction time is 24 h. The catalyst particles are specifically cobalt metal with a particle size of 200 μm, and the amount added is 1 / 2 of the reactor volume.

[0057] (2) The gas from the reaction in step (1) is passed into a water washing and defluorination device for water washing and defluorination, drying and dehydration, and distillation purification to obtain perfluoroalkanes.

[0058] The purity of the perfluorobutane obtained in this embodiment is 98.7%, and the yield is 65.1%.

[0059] Example 5 The method for preparing perfluoroalkane in this embodiment is based on Example 4, and involves repeated fluorine substitution reactions. The specific details are as follows: The perfluoroalkane gas obtained in step (2) is introduced into the fluorine substitution reactor as raw material, and an appropriate amount of high-purity fluorine gas is added. The molar ratio of perfluorobutane to high-purity fluorine gas is 1:1. The pressure inside the reactor is 100 kPa, the temperature is controlled at 580°C, and the reaction time is 12 h. The gas obtained from the reaction is passed into a water washing and defluorination device for water washing and defluorination, and then dried. This process is repeated 10 times, and then purified by distillation to obtain high-purity perfluorobutane.

[0060] The perfluorobutane obtained in this embodiment has a purity of 99.9% and a yield of 90.7%.

[0061] Example 6 The method for preparing perfluoroalkanes in this embodiment uses the equipment from Example 1 and specifically follows these steps: (1) High-purity butane, fluorine gas and catalyst particles are mixed in a rotating manner in a reactor and a high-temperature fluorine substitution reaction is carried out. The molar ratio of high-purity butane to fluorine gas is 1:15, the pressure in the reactor is 250 kPa, the temperature is controlled at 450 °C, and the reaction time is 18 h. The catalyst particles are specifically metallic nickel with a particle size of 800 μm, and the amount added is 2 / 5 of the reactor volume.

[0062] (2) The gas from the reaction in step (1) is passed into a water washing and defluorination device for water washing and defluorination, drying and dehydration, and distillation purification to obtain perfluorobutane.

[0063] The perfluorobutane obtained in this embodiment has a purity of 99.5% and a yield of 75.6%.

[0064] Example 7 The method for preparing perfluoroalkane in this embodiment is based on Example 6, and involves repeated fluorine substitution reactions. The specific details are as follows: The perfluoroalkane gas obtained in step (2) is introduced into the fluorine substitution reactor as raw material, and an appropriate amount of high-purity fluorine gas is added. The molar ratio of perfluorobutane to high-purity fluorine gas is 1:10. The pressure inside the reactor is 180 kPa, the temperature is controlled at 580°C, and the reaction time is 15 h. The gas obtained from the reaction is passed into a water washing and defluorination device for water washing and defluorination, and then dried. This process is repeated once, and then purified by distillation to obtain high-purity perfluorobutane.

[0065] The perfluorobutane obtained in this embodiment has a purity of 99.9% and a yield of 81.7%.

[0066] Example 8 The method for preparing perfluoroalkane in this embodiment is based on Example 6, and involves repeated fluorine substitution reactions. The specific details are as follows: The perfluoroalkane gas obtained in step (2) is introduced into the fluorine substitution reactor as raw material, and an appropriate amount of high-purity fluorine gas is added. The molar ratio of perfluorobutane to high-purity fluorine gas is 1:10. The pressure inside the reactor is 180 kPa, the temperature is controlled at 580°C, and the reaction time is 15 h. The gas obtained from the reaction is passed into a water washing and defluorination device for water washing and defluorination, and then dried. This process is repeated 8 times. After that, the gas is purified by distillation to obtain high-purity perfluorobutane.

[0067] The perfluorobutane obtained in this embodiment has a purity of 99.999% and a yield of 95.1%.

[0068] The above examples illustrate the preparation process of perfluorobutane in detail. Perfluoroethane and perfluoropropane have similar properties to perfluorobutane and can be prepared from high-purity ethane and propane using the same production method as perfluorobutane.

[0069] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing perfluoroalkanes, characterized in that, Includes the following steps: C 2-4 Alkanes and fluorine undergo a substitution reaction in the presence of a catalyst, wherein the catalyst is a transition metal or its fluoride; the gas after the reaction is washed with water to remove impurities, dried to remove water, and purified by distillation to obtain perfluoroalkanes.

2. The method for preparing perfluoroalkane according to claim 1, characterized in that, The substitution reaction was carried out under conditions of 100-500 kPa pressure and 300-800 °C temperature.

3. The method for preparing perfluoroalkane according to claim 2, characterized in that, The substitution reaction takes 2-24 hours.

4. The method for preparing perfluoroalkane as described in claim 1, 2, or 3, characterized in that, The C 2-4 The molar ratio of alkanes to fluorine is 1:(10-30).

5. The method for preparing perfluoroalkane as described in claim 1, 2, or 3, characterized in that, The substitution reaction is carried out in a reactor rotating about a horizontal axis, during which alkanes, fluorine gas and catalyst particles are mixed; the catalyst particles are nickel particles, cobalt particles, silver particles, nickel fluoride particles, cobalt fluoride particles or silver fluoride particles.

6. The method for preparing perfluoroalkane according to claim 1, 2, or 3, characterized in that, The C 2-4 The alkane is ethane, propane, or butane, and the corresponding perfluoroalkane is perfluoroethane, perfluoropropane, or perfluorobutane.

7. The method for preparing perfluoroalkane according to claim 1, 2, or 3, characterized in that, It also includes repeated substitution reaction steps: the perfluoroalkane obtained by drying and removing water and fluorine gas are subjected to the substitution reaction in the presence of a catalyst, and then the gas after the reaction is washed with water to remove impurities and dried to remove water; the substitution reaction is carried out 2-11 times in total to obtain high-purity perfluoroalkane.

8. The method for preparing perfluoroalkanes according to claim 7, characterized in that, In the repeated substitution reaction step, the molar ratio of perfluoroalkane to fluorine is 1:(1-10).

9. An apparatus for preparing perfluoroalkanes, characterized in that, The system includes a fluorine substitution reactor, a defluorination drying unit for washing and drying the gas produced by the fluorine substitution reactor, and a distillation purification unit located downstream of the defluorination drying unit; the fluorine substitution reactor has a reaction chamber for accommodating catalyst particles and is also equipped with a system for adding C 2-4 Import of gaseous materials such as alkanes and fluorine.

10. The apparatus for preparing perfluoroalkane as described in claim 9, characterized in that, The central axis of the fluorine substitution reactor extends in the front-to-back direction, and the device also includes a drive unit that drives the fluorine substitution reactor to rotate around its central axis; the defluorination drying device includes a water washing tower, a water vapor separator and a drying tower arranged in sequence.

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