A method and apparatus for simultaneously producing a plurality of perfluoroalkanes

Abstract

This invention relates to the field of haloalkanes preparation, specifically to a method and apparatus for simultaneously preparing multiple perfluoroalkanes. The method includes the following steps: (1) thermally cracking polytetrafluoroethylene to form a pyrolysis gas containing fluoroolefins; (2) reacting the pyrolysis gas with fluorine gas to form crude perfluoroalkanes gas; (3) subjecting the crude perfluoroalkanes gas to deep catalytic fluorination under the action of a catalyst to remove fluoroolefins, followed by distillation to obtain hexafluoroethane, octafluoropropane, or hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane, respectively. This invention achieves the preparation of high-purity perfluoroalkanes such as hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane through pyrolysis, fluorine addition, catalytic fluorination, and distillation processes, featuring low cost, high efficiency, and suitability for industrial production.

Description

Technical Field

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

[0002] Perfluoroalkane such as hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane have wide applications in ultrasound contrast agents, IC integrated circuits, and other fields.

[0003] In the field of ultrasound contrast agents, high-purity hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane can all be used to prepare ultrasound contrast agents. Ultrasound contrast agents, after intravenous injection, can dynamically display organ blood perfusion in real time. The microspheres of ultrasound contrast agents have a diameter range of 2-5 micrometers and can enter the systemic circulation via peripheral intravenous injection. They do not penetrate the vascular endothelium and are not metabolized by the liver or kidneys, ultimately being excreted through respiration. Their imaging mechanism is based on the scattering and enhancement effect of ultrasound waves by microbubbles in the blood, and can clearly display tiny lesions with a diameter of 1-2 millimeters. Compared with similar imaging technologies, its advantages are: no ionizing radiation during the examination process, repeated acquisition of dynamic images in a single examination, examination intervals not limited by iodine metabolism, and real-time observation of tissue blood perfusion.

[0004] Since the birth of integrated circuits, etching has been a crucial technical step in their manufacturing process, with dry etching being the mainstream method. Fluorocarbon compounds are commonly used as etching or passivation gases in dry etching. Furthermore, CVD (chemical vapor deposition) equipment, used for depositing high-purity, high-performance thin film materials, also requires significant amounts of fluorocarbon compounds to clean the internal surfaces of the equipment, ensuring highly purified deposition conditions within the chamber. Therefore, perfluoroalkanes have wide applications in the etching and cleaning processes of integrated circuit manufacturing.

[0005] Chinese invention patent CN 117024245 B, published on June 18, 2024, discloses a method for producing tetrafluoromethane from waste polytetrafluoroethylene (PTFE) via thermal plasma pyrolysis. The method involves subjecting waste PTFE to plasma pyrolysis at 1800-5000K, followed by quenching and gas-solid separation of the pyrolysis products to obtain pyrolysis gas containing tetrafluoromethane. This method utilizes thermal plasma pyrolysis technology, which places high demands on equipment and increases the production cost of tetrafluoromethane.

[0006] Currently, other methods for preparing perfluoroalkanes include: polymerization / fluorination using tetrafluoroethylene as a raw material, electrochemical fluorination, fluorination of haloalkanes, and byproduct recovery. These methods introduce or generate many impurities during the preparation process, and the separation and purification process to remove these impurities is quite complex, often resulting in unsatisfactory separation and purification effects. This makes it difficult to obtain high-purity perfluoroalkanes and is also very costly. Summary of the Invention

[0007] The purpose of this invention is to provide a method for simultaneously preparing multiple perfluoroalkanes, thereby solving the problem that existing methods cannot prepare multiple perfluoroalkanes at low cost.

[0008] A second objective of this invention is to provide an apparatus capable of simultaneously preparing multiple perfluoroalkanes to address the aforementioned problems.

[0009] To achieve the above objectives, the technical solution of the present invention for the simultaneous preparation of multiple perfluoroalkanes is as follows: A method for simultaneously preparing multiple perfluoroalkanes includes the following steps: (1) Polytetrafluoroethylene is thermally decomposed to form pyrolysis gas containing fluoroolefins; (2) The pyrolysis gas and fluorine gas are subjected to an addition reaction to form crude perfluoroalkane gas, wherein the crude perfluoroalkane gas contains hexafluoroethane and octafluoropropane, or contains hexafluoroethane, octafluoropropane, octafluorocyclobutane and decafluorobutane. (3) The crude perfluoroalkane gas is subjected to deep catalytic fluorination under the action of a catalyst to remove fluoroolefins, and then distilled to obtain hexafluoroethane, octafluoropropane, or hexafluoroethane, octafluoropropane, octafluorocyclobutane and decafluorobutane respectively.

[0010] This invention is a pioneering invention. It uses polytetrafluoroethylene as raw material and achieves the preparation of high-purity perfluoroalkanes such as hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane through pyrolysis, fluorine addition, catalytic fluorination, and distillation processes. It has the characteristics of low cost, high efficiency, and suitability for industrial production.

[0011] Preferably, in step (1), the pyrolysis is carried out under a protective atmosphere at a temperature of 300-800℃ or 400-800℃, and the pressure of the protective atmosphere is 10Pa-150kPa. For example, a pyrolysis temperature of 30kPa-60kPa and a temperature of 600-650℃ can be selected, with a molar ratio of fluoroolefins to fluorine of 1:(2-3), resulting in a ratio of hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane of (6-8):(3-4):(3-4):1. Alternatively, a pyrolysis temperature of 10kPa-60kPa and a temperature of 600-800℃ can be selected, with a molar ratio of fluoroolefins to fluorine of 1:(1-3), resulting in a ratio of hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane of (1.6-8):(2.3-4):(1.3-4):1. The thermal decomposition temperature can be selected as 140kPa-150kPa, the temperature is 400±40℃, and the molar ratio of fluoroolefins to fluorine is 1:(4-5), which can produce perfluoroalkanes with a molar ratio of hexafluoroethane and octafluoropropane of 1:0.8-1.2.

[0012] Preferably, in step (2), the addition reaction is a packed fixed-bed reaction, and the packing material used in the packed fixed-bed reaction is nickel particles, cobalt particles, nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles; the molar ratio of fluoroolefins to fluorine in the pyrolysis gas is 1:(1-5). It is preferable that the theoretical amount or a relative excess of the theoretical amount of fluorine is used. Under the set pyrolysis temperature and pyrolysis pressure, the amount of fluoroolefins generated remains basically stable. The amount of fluoroolefins generated can be determined through pyrolysis experiments, and therefore can be used as a benchmark for the amount of fluorine added. For example, the molar ratio of fluoroolefins to fluorine can be 1:(2-3).

[0013] Preferably, in step (3), the catalyst is a transition metal or a transition metal fluoride, and the temperature for catalytic fluorination is 80-250°C.

[0014] More preferably, the transition metal is nickel, cobalt, or silver; and the transition metal fluoride is nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles.

[0015] Preferably, in step (3), the perfluoroalkane crude gas is subjected to deep catalytic fluorination after being washed with water to remove fluorine and dehydrated and dried.

[0016] The technical solution of the apparatus of the present invention capable of simultaneously preparing multiple perfluoroalkanes is as follows: An apparatus capable of simultaneously producing multiple perfluoroalkanes includes a polytetrafluoroethylene (PTFE) pyrolysis unit and a fluorine addition unit connected to the PTFE pyrolysis unit, the fluorine addition unit having a crude perfluoroalkane gas outlet; it also includes a deep catalytic fluorination unit and a distillation unit, the deep catalytic fluorination unit having a crude perfluoroalkane gas inlet and a fluorine gas outlet, and the distillation unit having a liquid fluorine gas inlet and a high-purity perfluoroalkane gas outlet.

[0017] The device of the present invention can simultaneously prepare multiple perfluoroalkanes, and can achieve efficient and low-cost preparation of single-component high-purity perfluoroalkanes such as hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane. It does not require complex equipment such as thermal plasma, which can reduce fixed asset investment and improve the economics of large-scale industrial production.

[0018] Preferably, the fluorine addition device is connected to the top of the polytetrafluoroethylene pyrolysis device to receive the pyrolysis gas generated by the polytetrafluoroethylene pyrolysis device. The lower part of the fluorine addition device is connected to a fluorine inlet pipe for introducing fluorine gas. The fluorine addition device also has a reaction chamber for supplying the pyrolysis gas to carry out the addition reaction. The reaction chamber is filled with packing material, and the top of the reaction chamber is provided with the crude gas outlet of the perfluoroalkane.

[0019] Preferably, a water washing and defluorination drying device is provided downstream of the fluorine addition device and upstream of the deep catalytic fluorination device, wherein the water washing and defluorination drying device performs water washing, defluorination and dehydration drying on the perfluoroalkane crude gas generated by the fluorine addition device.

[0020] More preferably, the above-mentioned equipment capable of simultaneously producing multiple perfluoroalkanes further includes a collection tank for collecting liquid perfluoroalkanes, wherein a cold energy storage packing layer is provided in the upper middle part of the collection tank. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the perfluoroalkane synthesis apparatus in Embodiment 1 of the present invention; Among them, 1-polytetrafluoroethylene (PTFE) cracking furnace; 2-cracking furnace inlet pipe; 3-PTFE feeding tank; 4-feeding tank inlet pipe; 5-PTFE feeding hopper; 6-feeding hopper control valve; 7-feeding tank vacuum pipe; 8-fluorine addition reaction tower outlet pipe; 9-fluorine addition reaction tower; 10-fluorine addition reaction tower inlet pipe; 11-fluorine addition reaction tower material valve; 12-cracking furnace outlet pipe; 13-feeding pipe control valve; 14-cracking furnace flange cover; 15-cracking furnace electric heating jacket; 16-... 17- First collecting tank inlet pipeline; 18- First collecting tank vacuum pipeline; 19- First perfluoroalkane liquefaction collecting tank; 201- Crack furnace inlet pipeline valve; 202- Feed tank inlet pipeline valve; 203- Feed tank vacuum pipeline valve; 204- Fluorine addition reaction tower outlet pipeline valve; 205- Fluorine addition reaction tower inlet pipeline valve; 206- Crack furnace outlet pipeline valve; 207- Collecting tank inlet pipeline valve; 208- Collecting tank vacuum pipeline valve; Figure 2 This is a schematic diagram of the water washing defluorination and dehydration drying device in Embodiment 1 of the present invention; Among them, 21-perfluoroalkane raw material tank; 22-water washing tower; 23-water-gas separator; 24-drying tower; 25-second perfluoroalkane liquefaction collection tank; 26-air inlet pipeline of the first raw material tank; 27-air outlet pipeline of the first raw material tank; 28-air inlet pipeline of the water washing tower; 29-inlet and outlet pipelines of the water washing tower cleaning water; 30-pipeline before the water washing tower circulating water pump; 31-water washing tower circulating water pump; 32-water washing tower circulating water spray pipeline; 33-air outlet pipeline of the water washing tower; 34-air inlet pipeline of the water-gas separator; 35-air outlet pipeline of the water-gas separator; 36-wastewater discharge pipeline of the water-gas separator; 37-air inlet pipeline of the drying tower; 38-air outlet pipeline of the drying tower; 39-air inlet pipeline of the second collection tank; 40-air outlet pipeline of the second collection tank. Empty pipeline; 4101 - First raw material tank inlet pipeline valve; 4102 - First raw material tank outlet pipeline valve; 4103 - Water washing tower inlet pipeline valve; 4104 - Water washing tower cleaning water inlet and outlet pipeline valve; 4105 - Water washing tower circulating water pump front pipeline valve; 4106 - Water washing tower circulating water spray pipeline valve; 4107 - Water washing tower outlet pipeline valve; 4108 - Water-gas separator inlet pipeline valve; 4109 - Water-gas separator wastewater discharge pipeline valve; 4110 - Water-gas separator outlet pipeline valve; 4111 - Drying tower inlet pipeline valve; 4112 - Drying tower outlet pipeline valve; 4113 - Second collection tank inlet pipeline valve; 4114 - Second collection tank vacuum pipeline valve; Figure 3 This is a schematic diagram of the catalytic reaction device in Embodiment 1 of the present invention; Among them, 42-perfluoroalkane fluorination feedstock tank; 43-catalytic fluorination reactor; 44-third perfluoroalkane liquefaction collection tank; 45-second feedstock tank inlet pipeline; 46-second feedstock tank outlet pipeline; 47-catalytic fluorination reactor inlet pipeline; 48-catalytic fluorination reactor outlet pipeline; 49-third collection tank inlet pipeline; 50-third collection tank vacuum pipeline; 511-second feedstock tank inlet pipeline valve; 512-second feedstock tank outlet pipeline valve; 513-catalytic fluorination reactor inlet pipeline valve; 514-catalytic fluorination reactor outlet pipeline valve; 515-third collection tank inlet pipeline valve; 516-third collection tank vacuum pipeline valve; Figure 4 This is a schematic diagram of the distillation apparatus in Embodiment 1 of the present invention; 52-Perfluoroalkane distillation feed tank; 53-Perfluoroalkane distillation column; 54-Single-component high-purity perfluoroalkane liquefaction collection tank; 55-Inlet pipe of distillation feed tank; 56-Liquid gas outlet pipe of feed tank; 57-Liquid gas inlet pipe of perfluoroalkane distillation column; 58-Thermostatic jacket of distillation column evaporator; 59-Gas outlet pipe of distillation column; 60-Inlet pipe of fourth collection tank; 61-Vacuum pipe of collection tank; 621-Valve of inlet pipe of distillation feed tank; 622-Valve of liquid gas outlet pipe of feed tank; 623-Valve of liquid gas inlet pipe of perfluoroalkane distillation column; 624-Valve of gas outlet pipe of distillation column; 625-Valve of inlet pipe of fourth collection tank; 626-Valve of vacuum pipe of fourth collection tank. Detailed Implementation

[0022] (a) Preferred embodiment of the apparatus of the present invention capable of simultaneously preparing multiple perfluoroalkanes The technical concept of this invention is to use polytetrafluoroethylene (PTFE) particles as raw material, obtain pyrolysis gas containing fluorinated olefins through pyrolysis, and then perform fluorination, water washing to remove impurities, and catalytic fluorination to form a high-purity perfluoroalkane mixture. This mixture is then washed again to remove impurities, and finally distilled to obtain single-component perfluoroalkanes. By adjusting the pyrolysis process, different proportions of perfluoroalkane combinations can be obtained, thereby achieving efficient and low-cost preparation of perfluoroalkanes such as hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane.

[0023] Water washing for impurity removal includes water washing for defluorination and drying.

[0024] The equipment of the present invention, which can simultaneously prepare multiple perfluoroalkanes, is compatible with the above-mentioned process and needs to realize functions such as polytetrafluoroethylene thermal cracking, fluorination of fluoroolefins, water washing to remove impurities, catalytic fluorination, and distillation, so as to ensure the preparation of perfluoroalkanes.

[0025] The preferred embodiments described above will be illustrated below with specific examples.

[0026] Example 1 The apparatus in this embodiment, capable of simultaneously preparing multiple perfluoroalkanes, includes a perfluoroalkane synthesis unit, a water washing and defluorination / drying unit, a catalytic reaction unit, and a distillation unit, which are described below: 1. Structure and Operating Instructions of the Perfluoroalkane Synthesis Unit The perfluoroalkane synthesis unit is based on the thermal cracking of polytetrafluoroethylene and the fluorination reaction of fluoroolefins. Its structural schematic diagram is shown below. Figure 1 As shown, it includes a polytetrafluoroethylene cracking furnace 1, a polytetrafluoroethylene feeding tank 3, a fluorination reaction tower 9, and a first perfluoroalkane liquefaction collection tank 18.

[0027] The PTFE pyrolysis furnace 1 is equipped with a pyrolysis furnace inlet pipe 2 and a pyrolysis furnace outlet pipe 12. During the pyrolysis process under anaerobic conditions, high-purity nitrogen, high-purity argon, or high-purity helium, or other balancing gases, can be introduced into the pyrolysis furnace through the pyrolysis furnace inlet pipe 2. The pyrolysis furnace outlet pipe 12 is connected to a vacuum exhaust system. The pyrolysis furnace inlet pipe 2, in conjunction with the pyrolysis furnace outlet pipe 12, can regulate the gas pressure inside the pyrolysis furnace. The main body of the PTFE pyrolysis furnace 1 is a cylindrical furnace tube with a U-shaped structure. The cylindrical furnace tube is equipped with a pyrolysis furnace electric heating jacket 15. The PTFE pyrolysis furnace 1 and its auxiliary pipes are made of 310 stainless steel.

[0028] The top of the polytetrafluoroethylene (PTFE) cracking furnace 1 is connected to a PTFE feeding tank 3 and a fluorine addition reaction tower 9. The upper part of the cylindrical furnace tube of the PTFE cracking furnace 1 is a detachable cracking furnace flange cover 14. One side of the cracking furnace flange cover 14 is connected to the PTFE feeding tank 3, and the other side is connected to the fluorine addition reaction tower 9.

[0029] The upper part of the PTFE feeding tank 3 is connected to the PTFE feeding hopper 5 via a feed pipe, and a feeding hopper control valve 6 is installed in the middle of the feed pipe. The lower part of the PTFE feeding tank 3 is connected to the PTFE cracking furnace 1 via a discharge pipe, and a feeding pipe control valve 13 is installed on the discharge pipe. The PTFE feeding tank 3 is connected to a feeding tank inlet gas pipe 4 and a feeding tank vacuum pipe 7. The feeding tank inlet gas pipe 4 is used to introduce balancing gas into the feeding tank, and the feeding tank vacuum pipe 7 can be used for evacuation. The PTFE feeding tank 3 has a cylindrical structure. The PTFE feeding tank 3 and its auxiliary pipes and valves are made of 316 stainless steel. The PTFE feeding tank 3 is also equipped with a cooling jacket, which is used during the operation of the PTFE cracking furnace 1 to ensure that the temperature of the PTFE feeding tank 3 does not exceed 200℃.

[0030] The lower end of the fluorination reaction tower 9 is connected to the cracking furnace flange cover 14 via a flange, and a fluorination reaction tower material valve 11 is installed on the pipe connected to the cracking furnace flange cover 14. A fluorination reaction tower inlet pipe 10 is installed at the bottom of the fluorination reaction tower 9 for introducing high-purity fluorine gas or a fluorine-containing mixture of high-purity fluorine gas and balance gas. A fluorination reaction tower outlet pipe 8 is installed at the top of the fluorination reaction tower 9. To further optimize the fluorine addition effect, a packed fixed bed is installed inside the fluorination reaction tower 9, forming a packed fixed bed reaction tower. The packing material can be nickel particles, cobalt particles, nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles. The fluorination reaction tower 9 and its auxiliary pipes and valves are made of 316 stainless steel and are equipped with a temperature control jacket to control the temperature of the addition reaction.

[0031] The top of the first perfluoroalkane liquefaction collection tank 18 is connected to both a first collection tank inlet pipe 16 and a first collection tank vacuum pipe 17. The upper end of the first collection tank inlet pipe 16 is connected to the outlet pipe 8 of the fluorination reaction tower, and the lower end is inserted into the bottom of the first perfluoroalkane liquefaction collection tank 18. The upper part of the first perfluoroalkane liquefaction collection tank 18 has a cold energy storage packing layer. The first perfluoroalkane liquefaction collection tank 18 is immersed in a collection tank cold trap 19, which is filled with a cryogenic medium. The packing material in the cold energy storage packing layer can be nickel particles or cobalt particles. The cryogenic medium can be ethanol or liquid argon, and the temperature of the cryogenic medium is controlled from -150℃ to -100℃. The first perfluoroalkane liquefaction collection tank 18 is an aluminum alloy tank.

[0032] The following gas lines are respectively equipped with valves for controlling the opening and closing of the corresponding gas lines: 201 for the pyrolysis furnace inlet pipeline, 202 for the feed tank inlet pipeline, 203 for the feed tank vacuum pipeline, 204 for the fluorination reaction tower outlet pipeline, 205 for the fluorination reaction tower inlet pipeline, 206 for the pyrolysis furnace outlet pipeline, 207 for the collection tank inlet pipeline, and 208 for the collection tank vacuum pipeline.

[0033] The use of the aforementioned perfluoroalkane synthesis unit includes granular polytetrafluoroethylene feeding, polytetrafluoroethylene cracking, fluorination reaction of cracked gas, and liquefaction and collection of crude perfluoroalkane gas.

[0034] The granular polytetrafluoroethylene (PTFE) feeding process is as follows: Close the following valves: hopper control valve 6, pyrolysis furnace inlet valve 201, feed tank inlet valve 202, feed tank vacuum valve 203, fluorine reaction tower inlet valve 205, and pyrolysis furnace outlet valve 206. Open all other valves. Vacuum the entire PTFE pyrolysis unit through the first collection tank vacuum pipeline 17. When the vacuum is below 10 Pa, close the collection tank vacuum pipeline valve 208 and open the pyrolysis furnace inlet valve 201 to allow the equilibrium gas (high-purity nitrogen, high-purity argon, or high-purity helium) to flow into the PTFE pyrolysis unit. When the pressure reaches 50-250 kPa, close the pyrolysis furnace inlet valve 201 and open the collection tank vacuum pipeline valve 208. Repeat this process 3-10 times until the pressure in the PTFE pyrolysis unit is maintained below 10 Pa. Then, close all valves in the PTFE pyrolysis unit.

[0035] Next, open valve 202 on the inlet pipe of the feeding tank to allow the balancing gas (high-purity nitrogen, high-purity argon, or high-purity helium) to flow into the PTFE feeding tank 3, reaching a pressure of 150-250 kPa. Then, close the inlet pipe 4 of the feeding tank, open the control valve 6 of the feeding hopper to allow the granular PTFE in the feeding hopper to flow into the PTFE feeding tank 3, close the control valve 6 of the feeding hopper, and open the vacuum pipe valve 203 of the feeding tank to perform vacuuming. When the vacuum in the PTFE feeding tank 3 is lower than 10 Pa, close the vacuum pipe valve 203 of the feeding tank, open the inlet pipe valve 202 of the feeding tank to allow the balancing gas (high-purity nitrogen, high-purity argon, or high-purity helium) to flow into the PTFE feeding tank 3, reaching a pressure of 50-250 kPa. At kPa, close the inlet valve 202 of the feeding tank and open the vacuum valve 203 of the feeding tank to perform vacuuming. Repeat this process 3 to 10 times until the pressure in the PTFE feeding tank 3 is maintained below 10Pa. Then, close the vacuum valve 203 and the inlet valve 202 of the feeding tank. Open the control valve 13 of the feeding tank, and the granular PTFE flows into the PTFE cracking furnace 1 by gravity. Then, close the control valve 13 of the feeding tank.

[0036] Polytetrafluoroethylene (PTFE) pyrolysis process: The amount of balance gas (high-purity nitrogen, high-purity argon, or high-purity helium) added is controlled by valve 201 in the pyrolysis furnace inlet pipeline. Before the PTFE pyrolysis furnace 1 is heated and started, the pressure inside the pyrolysis furnace is controlled by valve 206 in the pyrolysis furnace outlet pipeline. After the PTFE pyrolysis furnace 1 is heated and started, the vacuum gas flow rate is controlled by valve 208 in the vacuum pipeline of the collection tank. The pressure inside the PTFE pyrolysis furnace is controlled at 10 Pa to 150 kPa. The temperature of the PTFE pyrolysis furnace is controlled at 300 to 800℃ by the electric heating jacket of the pyrolysis furnace.

[0037] The fluorination reaction process for cracked gas: The fluorination reaction tower 9 operates together with the polytetrafluoroethylene (PTFE) cracking furnace 1. After the PTFE cracking furnace 1 starts operating, the material valve 11 and the inlet valve 205 of the fluorination reaction tower are opened, allowing PTFE cracked gas to flow into the fluorination reaction tower 9. High-purity fluorine gas or a high-purity fluorine mixture (with high-purity nitrogen, high-purity argon, or high-purity helium as the balance gas, and a high-purity fluorine content of 0.1%~80%) enters the fluorination reaction tower 9 through the inlet pipe 10 and mixes with the PTFE cracked gas. The molar ratio of cracked gas generation to fluorine addition is controlled at 1:(1~5). The outlet valve 204 and the material valve 11 of the fluorination reaction tower are opened together. The temperature of the fluorination reaction can be controlled within the range of 50~300℃, preferably within the range of 80~250℃.

[0038] Perfluoroalkane crude gas liquefaction and collection process: The first perfluoroalkane liquefaction and collection tank 18 operates together with the polytetrafluoroethylene cracking furnace 1. After the polytetrafluoroethylene cracking furnace 1 starts operating, the gas inlet valve 207 and the vacuum valve 208 of the collection tank are opened. The perfluoroalkane crude gas flowing out of the fluorination reaction tower 9 enters the first perfluoroalkane liquefaction and collection tank 18, where the perfluoroalkane is liquefied. The balance gas (high-purity nitrogen, high-purity argon, or high-purity helium) is vacuumed in gaseous form through the vacuum pipeline 17 of the first collection tank. The cold trap 19 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 at -150℃ to -100℃. The cold energy storage packing layer of the perfluoroalkane liquefaction and collection tank ensures the cooling conditions in the upper part of the first perfluoroalkane liquefaction and collection tank 18, preventing the liquefied perfluoroalkane from vaporizing.

[0039] 2. Structure and Operating Instructions of the Water Washing Defluorination and Dehydration Drying Equipment The water-washing defluorination and dehydration drying unit's core functions are water washing defluorination and dehydration drying. It removes fluorine and other water-soluble impurities from perfluoroalkane crude gas, which helps improve product purity and reduce equipment corrosion. Its structural diagram is shown below. Figure 2 As shown, it includes a perfluoroalkane feedstock tank 21, a water washing tower 22, a water-gas separator 23, a drying tower 24, and a second perfluoroalkane liquefaction collection tank 25.

[0040] The perfluoroalkane feedstock tank 21 is also known as the first perfluoroalkane liquefaction collection tank 18. The first perfluoroalkane liquefaction collection tank 18 is removed from the cold trap and placed at room temperature, maintained above 25°C, until all the perfluoroalkane has vaporized. It can then be used as the perfluoroalkane feedstock tank 21. The top of the perfluoroalkane feedstock tank 21 has one inlet pipe 26 and one outlet pipe 27 for the first feedstock tank.

[0041] A water washing tower 22 is connected downstream of the perfluoroalkane feedstock tank 21 to wash and remove impurities from the vaporized perfluoroalkane in the tank. The water washing tower 22 is a spray-type water scrubber. The lower part of the water washing tower 22 is equipped with a water washing tower inlet pipe 28 connected to the outlet pipe 27 of the first feedstock tank. The bottom of the water washing tower 22 is a circulating water pool. One side of the circulating water pool has a water washing tower cleaning water inlet / outlet pipe 29, and the other side has a water washing tower circulating water pump front pipe 30. The water washing tower circulating water pump front pipe 30 is connected to the water washing tower circulating water pump 31. The outlet of the water washing tower circulating water pump 31 is connected to the water washing tower circulating water spray pipe 32. A water washing tower circulating water sprayer is installed on the tower circulating water spray pipe 32. The water washing tower circulating water sprayer is installed on the upper part of the water washing tower 22. After the circulating water flows out from the sprayer, the circulating water flows from top to bottom, and the perfluoroalkane gas flows from bottom to top. The circulating water and the perfluoroalkane gas are fully in 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. After cleaning, the perfluoroalkane gas flows out of the water washing tower 22 through the water washing tower outlet pipe 33 at the top of the water washing tower 22.

[0042] A water-gas separator 23 is connected downstream of the water washing tower 22 to separate the perfluoroalkane gas after water washing. The water-gas separator 23 is a tank with a packing layer in the middle. Below the packing layer is a water-gas separator inlet pipe 34 connected to the water washing tower outlet pipe 33, and above the packing layer is a water-gas separator outlet pipe 35. The perfluoroalkane gas containing moisture passes upwards through the packing layer, where the moisture is trapped and flows downwards into the bottom of the water-gas separator 23. The bottom of the water-gas separator 23 is connected to a water-gas separator wastewater discharge pipe 36, and the perfluoroalkane gas, now free of moisture, flows out from the water-gas separator outlet pipe 35.

[0043] Drying tower 24 is connected downstream of water-vapor separator 23 to dry the perfluoroalkane gas after water-vapor separation. Drying tower 24 is a fixed-bed packed tower. The bottom of drying tower 24 is connected to drying tower inlet pipe 37, which is connected to water-vapor separator outlet pipe 35. Perfluoroalkane gas containing trace amounts of water passes from bottom to top through the desiccant packing layer of drying tower, and the dried perfluoroalkane gas flows out from drying tower outlet pipe 38 at the top of drying tower 24.

[0044] The second perfluoroalkane liquefaction collection tank 25 is an aluminum alloy tank. The top of the aluminum alloy tank is connected to one inlet pipe 39 and one vacuum pipe 40 of the second collection tank. The inlet pipe 39 of the second collection tank is connected to the outlet pipe 38 of the drying tower. The inlet pipe 39 of the second collection tank is inserted into the bottom of the second perfluoroalkane liquefaction collection tank 25. The upper part of the second perfluoroalkane liquefaction collection tank 25 has a cold energy storage packing layer. The perfluoroalkane liquefaction collection tank is immersed in the cold trap 19 of the collection tank, which is filled with a low temperature medium.

[0045] The following pipelines are installed: first raw material tank inlet pipe 26, first raw material tank outlet pipe 27, water washing tower inlet pipe 28, water washing tower cleaning water inlet / outlet pipe 29, water washing tower circulating water pump front pipe 30, water washing tower circulating water spray pipe 32, water washing tower outlet pipe 33, water-gas separator inlet pipe 34, water-gas separator wastewater discharge pipe 36, water-gas separator outlet pipe 35, drying tower inlet pipe 37, drying tower outlet pipe 38, second collection tank inlet pipe 39, and second collection tank vacuum pipe 40. A valve 4101 for the first raw material tank inlet pipe and a valve 4101 for the first raw material tank outlet pipe are respectively installed on these pipelines. Valve 4102, air inlet valve of water washing tower; valve 4103, cleaning water inlet / outlet valve of water washing tower; valve 4104, circulating water pump inlet valve of water washing tower; valve 4105, circulating water spray valve of water washing tower; valve 4106, air outlet valve of water washing tower; valve 4107, air inlet valve of water-gas separator; valve 4108, wastewater discharge valve of water-gas separator; valve 4109, air outlet valve of water-gas separator; valve 4110, air inlet valve of drying tower; valve 4111, air outlet valve of drying tower; valve 4112, air inlet valve of second collection tank; valve 4113, vacuum pipeline valve of second collection tank; valve 4114.

[0046] The use of water washing defluorination and dehydration drying equipment includes perfluoroalkane crude gas supply process, water washing defluorination process, drying and dehydration process, and perfluoroalkane liquefaction and collection process.

[0047] Perfluoroalkane crude gas supply process: The first perfluoroalkane liquefaction collection tank 18 in the perfluoroalkane synthesis unit is taken out from the collection tank cold trap 19. The temperature of the first perfluoroalkane liquefaction collection tank 18 is kept constant to room temperature (10~50℃), which is the perfluoroalkane raw material tank 21. The perfluoroalkane raw material tank 21 is full of gas. The raw material tank inlet valve 4101 and the raw material tank outlet valve 4102 are opened. The first raw material tank inlet pipeline 26 delivers the balance gas (high-purity nitrogen, high-purity argon or high-purity helium) into the perfluoroalkane raw material tank 21. The balance gas, together with the raw material gas in the perfluoroalkane raw material tank 21, flows into the water washing tower 22 through the first raw material tank outlet pipeline 27.

[0048] Water washing defluorination process: The gas outlet pipe 27 of the first raw material tank is connected to the gas inlet pipe 28 of the water washing tower. The gas flows from bottom to top in the water washing tower 22, passing through the packing layer in the middle of the water washing tower 22. The packing layer contains polytetrafluoroethylene rings. Clean cleaning water (ultrapure water) can be introduced into the circulating water pool at the bottom of the water washing tower 22 through the water washing tower cleaning water inlet / outlet pipe 29. After the water washing tower 22 finishes working, the cleaning wastewater can also be discharged through the water washing tower cleaning water inlet / outlet pipe 29. The circulating water pool at the bottom of the water washing tower 22 is connected to the water washing tower circulating water pump 31. The circulating water passes through... After 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 pipe 33 of the water washing tower, and then flows into the gas inlet pipe 34 of the water-gas separator, and enters the water-gas separator 23. The packing of the water-gas separator 23 is polytetrafluoroethylene rings. There is a wastewater discharge pipe 36 at the bottom of the water-gas separator 23. After the water-gas separator 23 finishes working, the wastewater can be discharged, and the gas containing trace amounts of water flows out from the gas outlet pipe 35 of the water-gas separator.

[0049] Drying and dehydration process: The gas outlet pipe 35 of the water-gas separator is connected to the gas inlet pipe 37 of the drying tower. The gas flows from bottom to top in the drying tower 24 and passes through the packing layer in the middle of the drying tower 24. The packing layer is filled with 3A molecular sieve or 13X molecular sieve. The dried gas flows out from the gas outlet pipe 38 of the drying tower.

[0050] Perfluoroalkane liquefaction and collection process: The second perfluoroalkane liquefaction and collection tank 25 operates together with the drying tower 24. After the drying tower 24 starts operating, the inlet valve 4113 and the vacuum valve 4114 of the second collection tank are opened. The perfluoroalkane gas flowing out of the drying tower 24 enters the second perfluoroalkane liquefaction and collection tank 25, where the perfluoroalkane is liquefied. The balance gas (high-purity nitrogen, high-purity argon, or high-purity helium) is vacuumed in gaseous form through the vacuum pipeline 40 of the second collection tank. The cold trap 19 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 at -150℃ to -100℃. The filler in the cold energy storage packing layer of the second perfluoroalkane liquefaction and collection tank 25 is nickel particles and cobalt particles.

[0051] 3. Structure and Operating Instructions of the Catalytic Reactor The catalytic reaction unit uses catalytic fluorination as its core to achieve deep fluorination and removal of trace amounts of fluoroolefins. Its structural schematic diagram is shown below. Figure 3 As shown, it includes a perfluoroalkane fluorination feedstock tank 42, a catalytic fluorination reactor 43, and a third perfluoroalkane liquefaction collection tank 44.

[0052] The perfluoroalkane fluorination feedstock tank 42 is the second perfluoroalkane liquefaction collection tank 25, which collects perfluoroalkane in the water washing defluorination and dehydration drying device. The second perfluoroalkane liquefaction collection tank 25 is removed from the collection tank cold trap and placed at room temperature, maintained above 25°C, until all the perfluoroalkane is vaporized. It can then be used as the perfluoroalkane fluorination feedstock tank 42. The top of the perfluoroalkane fluorination feedstock tank 42 is connected to one inlet pipe 45 and one outlet pipe 46 from the second feedstock tank.

[0053] The catalytic fluorination reactor 43 is connected to the perfluoroalkane fluorination feedstock tank 42 and performs a catalytic fluorination reaction on the gas flowing out from it. The catalytic fluorination reactor 43 is a fixed-bed catalytic reactor, in which the catalyst particles used are transition metals or their fluorides, such as nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles. The catalytic fluorination reactor 43 is equipped with a temperature control jacket to regulate the temperature of the catalytic fluorination reaction.

[0054] The catalytic fluorination reactor 43 is connected to a catalytic fluorination reactor inlet pipe 47 and a catalytic fluorination reactor outlet pipe 48. The catalytic fluorination reactor inlet pipe 47 is connected to the second raw material tank outlet pipe 46, and the catalytic fluorination reactor outlet pipe 48 is connected to the third perfluoroalkane liquefaction collection tank 44.

[0055] The third perfluoroalkane liquefaction collection tank 44 is used to collect perfluoroalkane after deep fluorination. Deep fluorination further reduces the content of fluoroolefins and improves the purity and yield of the perfluoroalkane gas. The top of the third perfluoroalkane liquefaction collection tank 44 is connected to both a third collection tank inlet pipe 49 and a third collection tank vacuum pipe 50. The third collection tank inlet pipe 49 is inserted into the bottom of the third perfluoroalkane liquefaction collection tank 44 and is connected to the outlet pipe 48 of the catalytic fluorination reactor. The third collection tank vacuum pipe 50 is connected to a vacuum pump. The upper part of the third perfluoroalkane liquefaction collection tank 44 has a cold energy storage packing layer. The third perfluoroalkane liquefaction collection tank 44 is immersed in a collection tank cold trap 19, which is filled with a low-temperature medium.

[0056] The second raw material tank inlet pipe 45, the second raw material tank outlet pipe 46, the catalytic fluorination reactor inlet pipe 47, the catalytic fluorination reactor outlet pipe 48, the third collection tank inlet pipe 49, and the third collection tank vacuum pipe 50 are respectively equipped with valves 511, 512, 513, 514, 515, and 516 of the second raw material tank inlet pipe, valve 516, valve 514, valve 515, and valve 516 of the third collection tank vacuum pipe.

[0057] The use of catalytic reaction equipment includes processes for supplying feed gas for perfluoroalkane fluorination, catalytic fluorination processes, and perfluoroalkane liquefaction and collection processes, as detailed below: Perfluoroalkane fluorination feedstock gas supply process: After the perfluoroalkane in the perfluoroalkane fluorination feedstock tank 42 is completely vaporized at room temperature, the valve 511 of the second feedstock tank inlet pipeline and the valve 512 of the second feedstock tank outlet pipeline are opened. The balance gas (high-purity nitrogen, high-purity argon or high-purity helium) is transported into the perfluoroalkane fluorination feedstock tank 42 through the second feedstock tank inlet pipeline 45. The balance gas, together with the feedstock gas in the perfluoroalkane fluorination feedstock tank 42, flows into the catalytic fluorination reactor 43 through the second feedstock tank outlet pipeline 46.

[0058] Catalytic fluorination process: Open valve 513 of the inlet pipe of the catalytic fluorination reactor, and the raw gas flows into the catalytic fluorination reactor 43. It flows through the packing material of the catalytic fluorination reactor, which is nickel fluoride particles, cobalt fluoride particles or silver fluoride particles. The temperature of the catalytic fluorination reactor 43 is controlled at 80-250℃. The gas flowing out of the outlet pipe 48 of the catalytic fluorination reactor enters the third perfluoroalkane liquefaction collection tank 44.

[0059] Perfluoroalkane liquefaction and collection process: The third perfluoroalkane liquefaction and collection tank 44 operates together with the catalytic fluorination reactor 43. After the catalytic fluorination reactor 43 starts operating, the inlet valve 515 and the vacuum valve 516 of the third collection tank are opened. The perfluoroalkane gas flowing out of the catalytic fluorination reactor 43 enters the collection tank, and the perfluoroalkane is liquefied. The balance gas (high-purity nitrogen, high-purity argon, or high-purity helium) is vacuumed in gaseous form through the vacuum pipeline 50 of the third 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 at -150~-100℃. The filler in the cold energy storage packing layer of the perfluoroalkane liquefaction and collection tank is nickel particles and cobalt particles.

[0060] 4. Structure and Operating Instructions of the Distillation Apparatus The distillation unit obtains single-component high-purity perfluoroalkanes through distillation separation. Its structural schematic diagram is shown below. Figure 4 As shown, it includes a perfluoroalkane distillation feed tank 52, a perfluoroalkane distillation column 53, and a single-component high-purity perfluoroalkane liquefaction collection tank 54.

[0061] The perfluoroalkane distillation feedstock tank 52 is the third perfluoroalkane liquefaction collection tank 44 in the catalytic reaction unit. The perfluoroalkane distillation feedstock tank 52 is immersed in a feedstock tank cold trap. The top of the feedstock tank has a feedstock tank inlet pipe 55 and a feedstock tank liquid gas outlet pipe 56. The feedstock tank liquid gas outlet pipe 56 extends into the bottom of the feedstock tank.

[0062] The perfluoroalkane distillation column 53 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 57, which is connected to a liquid-gas outflow pipe 56 from the feed tank. The evaporator is equipped with a thermostatic jacket 58 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 59.

[0063] The top of the single-component high-purity perfluoroalkane liquefaction collection tank 54 is connected to a fourth collection tank inlet pipe 60 and a collection tank vacuum pipe 61. One end of the fourth collection tank inlet pipe 60 is connected to the gas outlet pipe 59 of the distillation column, and the other end is inserted into the bottom of the single-component high-purity perfluoroalkane liquefaction collection tank 54. A cold energy storage packing layer is provided in the upper part of the single-component high-purity perfluoroalkane liquefaction collection tank 54. The single-component high-purity perfluoroalkane liquefaction collection tank 54 is placed in the collection tank cold trap 19, which is filled with a low-temperature medium.

[0064] The following valves are respectively installed on the following pipelines: the inlet pipeline 55 of the distillation feed tank, the liquid gas outlet pipeline 56 of the feed tank, the liquid gas inflow pipeline 57 of the perfluoroalkane distillation tower, the gas outlet pipeline 59 of the distillation tower, the inlet pipeline 60 of the fourth collection tank, and the vacuum pipeline 61 of the collection tank: the inlet pipeline valve 621 of the distillation feed tank, the liquid gas outlet pipeline valve 622 of the feed tank, the liquid gas inflow pipeline valve 623 of the perfluoroalkane distillation tower, the gas outlet pipeline valve 624 of the distillation tower, the inlet pipeline valve 625 of the fourth collection tank, and the vacuum pipeline valve 626 of the fourth collection tank.

[0065] The process of using the distillation unit includes the perfluoroalkane distillation feedstock supply process, the perfluoroalkane distillation process, and the single-component high-purity perfluoroalkane liquefaction and collection process.

[0066] Perfluoroalkane distillation feedstock supply process: The temperature of the perfluoroalkane distillation feedstock tank 52 is kept constant at -120 to -100℃. The balance gas enters the feedstock tank through the feedstock tank inlet pipe 55, pressurizes the feedstock tank, and the perfluoroalkane liquid feedstock enters the perfluoroalkane distillation tower 53 through the feedstock tank liquid gas outlet pipe 56.

[0067] Perfluoroalkane distillation process: The evaporator temperature is controlled by a constant-temperature jacket 58 in the distillation column. The evaporator temperature is between -100 and -80℃. The distillate component is liquefied and used as feedstock for the next distillation. The evaporator temperature is between -80 and -78℃. The distillate component is liquefied to obtain high-purity hexafluoroethane. The evaporator temperature is between -78 and -42℃. The distillate component is liquefied and used as feedstock for the next distillation. The evaporator temperature is between -42 and -39℃. The distillate component is liquefied to obtain high-purity octafluoropropane. The evaporator temperature is between -39℃. The distillate is liquefied at -8℃ and used as feedstock for the next distillation. The evaporator temperature is between -8℃ and -6℃, and the liquefied distillate is high-purity octafluorocyclobutane. The evaporator temperature is between -6℃ and -4℃, and the liquefied distillate is used as feedstock for the next distillation. The evaporator temperature is between -4℃ and -2℃, and the liquefied distillate is high-purity decafluorobutane. The evaporator temperature is between -4℃ and 0℃, and the liquefied distillate is used as feedstock for the next distillation. During the distillation process, the pressure of the distillation column is controlled within the range of 80~120 kPa.

[0068] Single-component high-purity perfluoroalkane liquefaction and collection process: The single-component high-purity perfluoroalkane liquefaction and collection tank 54 operates together with the perfluoroalkane distillation tower 53. After the perfluoroalkane distillation starts, the inlet valve 625 and the vacuum valve 626 of the fourth collection tank are opened. The perfluoroalkane gas flowing out of the perfluoroalkane distillation enters the single-component high-purity perfluoroalkane liquefaction and collection tank 54. The single-component high-purity perfluoroalkane 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 to 0°C. The packing material in the cold energy storage packing layer of the perfluoroalkane liquefaction and collection tank is nickel particles and cobalt particles. Different collection tanks are used to collect the distillate of the corresponding perfluoroalkane to obtain single-component perfluoroalkanes such as high-purity hexafluoroethane, high-purity octafluoropropane, high-purity octafluorocyclobutane, and high-purity decafluorobutane.

[0069] The above embodiments illustrate the preparation process of perfluoroalkanes using an intermittent operation mode. Its advantages include high process flexibility, allowing production to be arranged according to specific market demand for perfluoroalkanes. Based on these embodiments, a continuous production method can also be adopted. Specifically, between adjacent processes in the perfluoroalkan synthesis unit, water washing and defluorination / drying unit, catalytic reaction unit, and distillation unit, buffer containers can be used instead of the perfluoroalkanes liquefaction collection tanks used in the above embodiments, thereby achieving continuous production of perfluoroalkanes.

[0070] (II) Preferred embodiments of the method for simultaneously preparing multiple perfluoroalkanes according to the present invention This invention provides a method for simultaneously preparing multiple perfluoroalkanes. The method involves thermally cracking polytetrafluoroethylene (PTFE) particles, performing a fluorine addition reaction, washing with water to remove impurities, followed by catalytic fluorination, washing again, and finally distillation to obtain single-component high-purity perfluoroalkanes. The fluorine addition reaction during thermal cracking serves two purposes: 1. The products of thermal cracking react with each other at high temperatures; fluorine addition terminates these reactions, rapidly fixing the products. 2. Fluorine addition converts most fluoroolefins into fluoroalkanes. Washing the products after the fluorine addition reaction removes fluorine, hydrogen fluoride, and water-soluble impurities. The subsequent catalytic fluorination is an independent operation, eliminating the influence of other processes on the fluorination of small amounts of fluoroolefins. Under the action of the catalyst, all small amounts of fluoroolefins are converted into fluoroalkanes.

[0071] During pyrolysis, the process conditions such as temperature and pressure affect the proportion of fluoroolefins such as hexafluoropropylene and octafluorobutene in the pyrolysis gas, which in turn affects the proportion of hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane produced. In actual industrial production, the pyrolysis process can be adjusted according to the demand for each perfluoroalkane, thereby achieving high yield of specific perfluoroalkanes.

[0072] The method for simultaneously preparing multiple perfluoroalkanes is illustrated below with specific examples. The purity of each gas refers to its volume ratio.

[0073] Example 2 This embodiment of the method for simultaneously preparing multiple perfluoroalkanes uses the equipment of Example 1 and follows the steps below: (1) After adding polytetrafluoroethylene particles into the polytetrafluoroethylene cracking furnace, high-purity nitrogen gas is introduced into the polytetrafluoroethylene cracking furnace until the pressure inside the furnace is 30 kPa, and the temperature of the polytetrafluoroethylene cracking furnace is controlled at 600℃ to produce fluoroolefin pyrolysis gas.

[0074] (2) Fluoroolefin pyrolysis gas and fluorine gas enter the fluorination reaction tower for fluorination addition reaction. The molar ratio of fluoroolefin pyrolysis gas to fluorine gas is controlled at 1:2 to form crude perfluoroalkane gas containing hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane. The packing material used in the fluorination reaction tower is nickel fluoride, and the temperature is controlled at 200℃. The crude perfluoroalkane gas is then subjected to a water washing and defluorination drying device to complete the water washing and impurity removal, and the impurity-removed perfluoroalkane is obtained.

[0075] (3) The purified perfluoroalkane is subjected to deep catalytic fluorination in a catalytic fluorination reactor. The catalytically fluorinated gas is then cooled at -120 to -100°C to obtain liquefied perfluoroalkane gas. The catalytic fluorination reactor is a fixed-bed catalytic reactor, in which nickel fluoride particles are used as catalyst particles, and the catalytic fluorination temperature is 250°C.

[0076] (4) The perfluoroalkane liquefied gas obtained after catalytic fluorination is washed with water to remove fluorine and then dried to complete the water washing and impurity removal, and high-purity perfluoroalkane liquefied gas is obtained.

[0077] (5) The perfluoroalkane liquefied gas is distilled, the evaporator temperature is kept constant at -100℃, the equilibrium gas and low boiling point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, the single component of pure perfluoroalkane is prepared to be collected. The distillation pressure is kept stable at 100-120kPa, and the fractions at -80 to -78℃, -42 to -39℃, -8 to -6℃, and -4 to -2℃ are collected successively to obtain pure hexafluoroethane, pure octafluoropropane, pure octafluorocyclobutane and pure decafluorobutane respectively.

[0078] (6) The single-component pure perfluoroalkane collected in (5) is stored separately in liquid form, and then the liquid pure perfluoroalkane is used as raw material for further distillation: The distillation parameters for pure hexafluoroethane are as follows: the evaporator temperature is kept constant at -100℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -80 to -78℃.

[0079] The distillation parameters for pure octafluoropropane are as follows: the evaporator temperature is kept constant at -60℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -42 to -39℃.

[0080] The distillation parameters for pure octafluorocyclobutane and pure decafluorobutane are as follows: the evaporator temperature is kept constant at -20℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane and pure decafluorobutane are prepared for collection. The distillation pressure is stabilized at 100-120kPa, and the fractions from -8 to -6℃ and from -4 to -2℃ are collected successively to obtain high-purity octafluorocyclobutane and high-purity decafluorobutane, respectively.

[0081] The high-purity hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane obtained using the method of this embodiment all have a purity greater than 99.99%, with a molar ratio of 8:4:4:1 for each perfluoroalkane. The structures of hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane were characterized using infrared spectroscopy. The purity of each perfluoroalkane was tested using gas chromatography.

[0082] Example 3 The method for preparing perfluoroalkane in this embodiment is based on Example 2, and involves repeated re-distillation of liquid pure perfluoroalkane. The specific details are as follows: the high-purity perfluoroalkane obtained in step (6) is re-distilled, and the specific distillation parameters are the same as in step (6). This process is repeated 3 times to obtain hexafluoroethane, octafluoropropane, octafluorocyclobutane and decafluorobutane with higher purity.

[0083] The high-purity hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane obtained using the method of this embodiment all have a purity greater than 99.999%, and the molar ratio of each perfluoroalkane is approximately 8:4:4:1.

[0084] Example 4 This embodiment of the method for simultaneously preparing multiple perfluoroalkanes uses the equipment of Example 1 and follows the steps below: (1) After adding polytetrafluoroethylene particles into the polytetrafluoroethylene cracking furnace, high-purity nitrogen gas is introduced into the polytetrafluoroethylene cracking furnace until the pressure inside the furnace is 60 kPa, and the temperature of the polytetrafluoroethylene cracking furnace is controlled at 650℃ to produce fluoroolefin pyrolysis gas.

[0085] (2) Fluoroolefin pyrolysis gas and fluorine gas enter the fluorination reaction tower for fluorination addition reaction. The molar ratio of fluoroolefin pyrolysis gas to fluorine gas is controlled at 1:3 to form crude perfluoroalkane gas containing hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane. The packing material used in the fluorination reaction tower is silver fluoride, and the temperature is controlled at 120℃. The crude perfluoroalkane gas is then subjected to a water washing and defluorination drying device to complete the water washing and impurity removal, and the impurity-removed perfluoroalkane is obtained.

[0086] (3) The purified perfluoroalkane is subjected to deep catalytic fluorination in a catalytic fluorination reactor, and then the catalytically fluorinated gas is cooled at -120~-100℃ to obtain liquefied perfluoroalkane gas. The catalytic fluorination reactor is a fixed-bed catalytic reactor, in which silver fluoride particles are used as catalyst particles, and the catalytic fluorination temperature is 80℃.

[0087] (4) The perfluoroalkane liquefied gas obtained after catalytic fluorination is washed with water to remove fluorine and then dried to complete the water washing and impurity removal, and high-purity perfluoroalkane liquefied gas is obtained.

[0088] (5) The perfluoroalkane liquefied gas is distilled, the evaporator temperature is kept constant at -100℃, the equilibrium gas and low boiling point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, the single component of pure perfluoroalkane is prepared to be collected. The distillation pressure is kept stable at 100-120kPa, and the fractions at -80 to -78℃, -42 to -39℃, -8 to -6℃, and -4 to -2℃ are collected successively to obtain pure hexafluoroethane, pure octafluoropropane, pure octafluorocyclobutane and pure decafluorobutane respectively.

[0089] (6) The single-component pure perfluoroalkane collected in (5) is stored separately in liquid form, and then the liquid pure perfluoroalkane is used as raw material for further distillation: The distillation parameters for pure hexafluoroethane are as follows: the evaporator temperature is kept constant at -100℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -80 to -78℃.

[0090] The distillation parameters for pure octafluoropropane are as follows: the evaporator temperature is kept constant at -60℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -42 to -39℃.

[0091] The distillation parameters for pure octafluorocyclobutane and pure decafluorobutane are as follows: the evaporator temperature is kept constant at -20℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane and pure decafluorobutane are prepared for collection. The distillation pressure is stabilized at 100-120kPa, and the fractions from -8 to -6℃ and from -4 to -2℃ are collected successively to obtain high-purity octafluorocyclobutane and high-purity decafluorobutane, respectively.

[0092] The high-purity hexafluoroethane, high-purity octafluoropropane, high-purity octafluorocyclobutane, and high-purity decafluorobutane obtained using the method of this embodiment all have a purity greater than 99.99%, and the molar ratio of each perfluoroalkane is 6:3:3:1.

[0093] Example 5 The method for preparing perfluoroalkanes in this embodiment is based on Example 2, and involves repeated re-distillation of liquid pure perfluoroalkanes. The specific details are as follows: the high-purity perfluoroalkanes obtained in step (6) are re-distilled, and the specific distillation parameters are the same as in step (6). This process is repeated 10 times to obtain hexafluoroethane, octafluoropropane, octafluorocyclobutane and decafluorobutane with higher purity.

[0094] The high-purity hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane obtained using the method of this embodiment all have a purity greater than 99.999%, and the molar ratio of each perfluoroalkane is approximately 6:3:3:1.

[0095] Example 6 This embodiment of the method for simultaneously preparing multiple perfluoroalkanes uses the equipment of Example 1 and follows the steps below: (1) After adding polytetrafluoroethylene particles into the polytetrafluoroethylene cracking furnace, high-purity nitrogen gas is introduced into the polytetrafluoroethylene cracking furnace until the pressure inside the furnace is 150 kPa, and the temperature of the polytetrafluoroethylene cracking furnace is controlled at 400℃ to produce fluoroolefin pyrolysis gas.

[0096] (2) Fluoroolefin pyrolysis gas and fluorine gas enter the fluorination reaction tower for fluorine addition reaction. The molar ratio of fluoroolefin pyrolysis gas to fluorine gas is controlled at 1:5 to form crude perfluoroalkane gas containing hexafluoroethane and octafluoropropane. The packing material used in the fluorination reaction tower is cobalt metal, and the temperature is controlled at 80℃. The crude perfluoroalkane gas is then subjected to a water washing and defluorination and drying device to complete the water washing and impurity removal, and the impurity-removed perfluoroalkane is obtained.

[0097] (3) The purified perfluoroalkane is subjected to deep catalytic fluorination in a catalytic fluorination reactor. The catalytically fluorinated gas is then cooled at -120 to -100°C to obtain liquefied perfluoroalkane gas. The catalytic fluorination reactor is a fixed-bed catalytic reactor, in which cobalt particles are used as catalyst particles, and the catalytic fluorination temperature is 200°C.

[0098] (4) The perfluoroalkane liquefied gas obtained after catalytic fluorination is washed with water to remove fluorine and then dried to complete the water washing and impurity removal, and high-purity perfluoroalkane liquefied gas is obtained.

[0099] (5) The perfluoroalkane liquefied gas is distilled, the evaporator temperature is kept constant at -100℃, the equilibrium gas and low boiling point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, the single component of pure perfluoroalkane is prepared to be collected. The distillation pressure is kept stable at 100-120kPa, and the fractions from -80 to -78℃ and from -42 to -39℃ are collected successively to obtain pure hexafluoroethane and pure octafluoropropane, respectively.

[0100] (6) The single-component pure perfluoroalkane collected in (5) is stored separately in liquid form, and then the liquid pure perfluoroalkane is used as raw material for further distillation: The distillation parameters for pure hexafluoroethane are as follows: the evaporator temperature is kept constant at -100℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -80 to -78℃.

[0101] The distillation parameters for pure octafluoropropane are as follows: the evaporator temperature is kept constant at -60℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -42 to -39℃.

[0102] The high-purity hexafluoroethane and high-purity octafluoropropane obtained using the method of this embodiment have a purity greater than 99.99%, and the molar ratio of each perfluoroalkane is 1:1.

[0103] Example 7 This embodiment of the method for simultaneously preparing multiple perfluoroalkanes uses the equipment of Example 1 and follows the steps below: (1) After adding polytetrafluoroethylene particles into the polytetrafluoroethylene cracking furnace, high-purity nitrogen gas is introduced into the polytetrafluoroethylene cracking furnace until the pressure inside the furnace is 10 kPa, and the temperature of the polytetrafluoroethylene cracking furnace is controlled at 800℃ to produce fluoroolefin pyrolysis gas.

[0104] (2) Fluoroolefin pyrolysis gas and fluorine gas enter the fluorination reaction tower for fluorination addition reaction. The molar ratio of fluoroolefin pyrolysis gas to fluorine gas is controlled at 1:1 to form crude perfluoroalkane gas containing hexafluoroethane, octafluoropropane, octafluorocyclobutane, and decafluorobutane. The packing material used in the fluorination reaction tower is nickel fluoride, and the temperature is controlled at 250℃. The crude perfluoroalkane gas is then subjected to a water washing and defluorination drying device to complete the water washing and impurity removal, and the impurity-removed perfluoroalkane is obtained.

[0105] (3) The purified perfluoroalkane is subjected to deep catalytic fluorination in a catalytic fluorination reactor, and then the catalytically fluorinated gas is cooled at -120~-100℃ to obtain liquefied perfluoroalkane gas. The catalytic fluorination reactor is a fixed-bed catalytic reactor, in which nickel fluoride particles are used as catalyst particles, and the catalytic fluorination temperature is 120℃.

[0106] (4) The perfluoroalkane liquefied gas obtained after catalytic fluorination is washed with water to remove fluorine and then dried to complete the water washing and impurity removal, and high-purity perfluoroalkane liquefied gas is obtained.

[0107] (5) The perfluoroalkane liquefied gas is distilled, the evaporator temperature is kept constant at -100℃, the equilibrium gas and low boiling point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, the single component of pure perfluoroalkane is prepared to be collected. The distillation pressure is kept stable at 100-120kPa, and the fractions at -80 to -78℃, -42 to -39℃, -8 to -6℃, and -4 to -2℃ are collected successively to obtain pure hexafluoroethane, pure octafluoropropane, pure octafluorocyclobutane and pure decafluorobutane respectively.

[0108] (6) The single-component pure perfluoroalkane collected in (5) is stored separately in liquid form, and then the liquid pure perfluoroalkane is used as raw material for further distillation: The distillation parameters for pure hexafluoroethane are as follows: the evaporator temperature is kept constant at -100℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -80 to -78℃.

[0109] The distillation parameters for pure octafluoropropane are as follows: the evaporator temperature is kept constant at -60℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane is prepared for collection. The distillation pressure is kept stable at 100-120kPa, and the evaporator temperature is kept constant at -42 to -39℃.

[0110] The distillation parameters for pure octafluorocyclobutane and pure decafluorobutane are as follows: the evaporator temperature is kept constant at -20℃, the equilibrium gas and low-boiling-point impurities are distilled out from the distillation column, and when the pressure in the distillation column is lower than 100kPa, high-purity hexafluoroethane and pure decafluorobutane are prepared for collection. The distillation pressure is stabilized at 100-120kPa, and the fractions from -8 to -6℃ and from -4 to -2℃ are collected successively to obtain high-purity octafluorocyclobutane and high-purity decafluorobutane, respectively.

[0111] The high-purity hexafluoroethane, high-purity octafluoropropane, high-purity octafluorocyclobutane, and high-purity decafluorobutane obtained using the method of this embodiment all have a purity greater than 99.99%, and the molar ratio of each perfluoroalkane is 5:7:4:3.

[0112] As can be seen from the above embodiments, this method and equipment can efficiently and cost-effectively prepare a variety of perfluoroalkanes, with high purity of the obtained perfluoroalkanes and adjustable production ratios of different perfluoroalkanes, which can well meet the flexibility and economy requirements of industrial production of perfluoroalkanes.

[0113] 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 simultaneously preparing multiple perfluoroalkanes, characterized in that, Includes the following steps: (1) Polytetrafluoroethylene is thermally decomposed to form pyrolysis gas containing fluoroolefins; (2) The pyrolysis gas and fluorine gas are subjected to an addition reaction to form crude perfluoroalkane gas, wherein the crude perfluoroalkane gas contains hexafluoroethane and octafluoropropane, or contains hexafluoroethane, octafluoropropane, octafluorocyclobutane and decafluorobutane. (3) The crude perfluoroalkane gas is subjected to deep catalytic fluorination under the action of a catalyst to remove fluoroolefins, and then distilled to obtain hexafluoroethane, octafluoropropane, or hexafluoroethane, octafluoropropane, octafluorocyclobutane and decafluorobutane respectively.

2. The method for simultaneously preparing multiple perfluoroalkanes as described in claim 1, characterized in that, In step (1), the thermal decomposition is carried out under a protective atmosphere at a temperature of 300-800℃ or 400-800℃ and a pressure of 10Pa-150kPa.

3. The method for simultaneously preparing multiple perfluoroalkanes as described in claim 1, characterized in that, In step (2), the addition reaction is a packed fixed-bed reaction, and the packing material used in the packed fixed-bed reaction is nickel particles, cobalt particles, nickel fluoride particles, cobalt fluoride particles or silver fluoride particles; the molar ratio of fluoroolefins and fluorine in the pyrolysis gas is 1:(1-5).

4. The method for simultaneously preparing multiple perfluoroalkanes as described in claim 1, characterized in that, In step (3), the catalyst is a transition metal or a transition metal fluoride, and the temperature for catalytic fluorination is 80-250℃.

5. The method for simultaneously preparing multiple perfluoroalkanes as described in claim 4, characterized in that, The transition metal is nickel, cobalt, or silver; the transition metal fluoride is nickel fluoride particles, cobalt fluoride particles, or silver fluoride particles.

6. The method for simultaneously preparing multiple perfluoroalkanes as described in claim 1, 4, or 5, characterized in that, In step (3), the perfluoroalkane crude gas is subjected to deep catalytic fluorination after being washed with water to remove fluorine and dehydrated and dried.

7. An apparatus capable of simultaneously preparing multiple perfluoroalkanes, characterized in that, The device includes a polytetrafluoroethylene (PTFE) pyrolysis unit and a fluorine addition unit connected to the PTFE pyrolysis unit, the fluorine addition unit having a perfluoroalkane crude gas outlet; it also includes a deep catalytic fluorination unit and a distillation unit, the deep catalytic fluorination unit having a perfluoroalkane crude gas inlet and a fluorine addition gas outlet, and the distillation unit having a liquid fluorine addition gas inlet and a high-purity perfluoroalkane gas outlet.

8. The apparatus for simultaneously preparing multiple perfluoroalkanes as described in claim 7, characterized in that, The fluorine addition device is connected to the top of the polytetrafluoroethylene pyrolysis device to receive the pyrolysis gas generated by the polytetrafluoroethylene pyrolysis device. The lower part of the fluorine addition device is connected to a fluorine inlet pipe for introducing fluorine gas. The fluorine addition device also has a reaction chamber for supplying the pyrolysis gas to carry out the addition reaction. The reaction chamber is filled with packing material, and the top of the reaction chamber is provided with the crude gas outlet of the perfluoroalkane.

9. The apparatus for simultaneously preparing multiple perfluoroalkanes as described in claim 7, characterized in that, Downstream of the fluorine addition device and upstream of the deep catalytic fluorination device, a water washing defluorination and dehydration drying device is also provided. The water washing defluorination and dehydration drying device performs water washing defluorination and dehydration drying on the perfluoroalkane crude gas generated by the fluorine addition device.

10. The apparatus for simultaneously preparing multiple perfluoroalkanes as described in claim 7, 8, or 9, characterized in that, It also includes a collection tank for collecting liquid perfluoroalkane, wherein a cold energy storage packing layer is provided in the upper middle part of the collection tank.

Images