A system and method for preparing a porous carbon material

Abstract

The application discloses a kind of porous carbon material preparation system and method, preparation system includes high-temperature reaction furnace body, high-temperature reaction furnace body includes horizontally placed quartz reaction tube, quartz reaction tube is externally provided with furnace body shell, one end of quartz reaction tube is provided with gas inlet, the other end is provided with gas outlet, quartz reaction tube is arranged with electric heating wire along the axis outside, electric heating wire is provided with heat preservation lining between furnace body shell, the upper end of quartz reaction tube is provided with feeding port;Gas inlet is connected atmosphere supply system, gas outlet is connected tail gas treatment system;Atmosphere supply system includes nitrogen supply system and hydrogen peroxide gas phase supply system.Preparation method includes steps S1-S5.The scheme uses integrated closed reaction system, can continuously complete coal pitch precursor nitrogen atmosphere pyrolysis crosslinking pore forming, in-situ hydrogen peroxide gas phase etching whole-process technology, without transferring material midway, completely avoid the problem that material contacts air oxidation, substantially improve product batch stability.

Description

Technical Field

[0001] This invention relates to the field of porous carbon material preparation, and more specifically to a porous carbon material preparation system and method. Background Technology

[0002] Porous carbon materials are widely used in supercapacitors, lithium-ion batteries, catalyst supports, water treatment, and gas adsorption due to their high specific surface area, well-developed pore structure, excellent chemical stability, and electrical conductivity. Coal tar pitch, as a major byproduct of the coal chemical industry, is characterized by its high carbon content, low cost, and ease of graphitization, making it an excellent precursor for the preparation of porous carbon materials.

[0003] In existing technologies, the preparation of coal tar pitch-based porous carbon typically employs a step-by-step process of pyrolysis carbonization followed by activation etching. The pyrolysis process is usually carried out in a tube furnace under a nitrogen atmosphere, where primary pores are formed through the pyrolysis and volatilization of polymeric pore-forming agents such as polyethylene, and benzaldehyde acts as a crosslinking agent to promote the formation of a stable carbon framework from the coal tar pitch. Subsequent etching often utilizes strong alkaline liquid-phase activation with KOH or liquid-phase immersion etching with hydrogen peroxide to regulate the pore structure and increase the specific surface area. However, existing preparation processes suffer from the following core defects: 1. Pyrolysis carbonization and etching activation are carried out in two steps in different equipment. During the transfer of materials, they are easily exposed to air and oxidized, which leads to damage to the carbon skeleton structure and poor product performance stability between batches. 2. Liquid phase etching process requires multiple steps such as immersion, drying, repeated washing, and secondary drying of materials. The process is long, generates a large amount of waste liquid, and has high environmental treatment costs. In addition, the etching reaction is concentrated on the surface of the material, the internal etching is uneven, and the pore structure control precision is low. 3. Existing preparation methods cannot achieve precise and continuous switching between inert pyrolysis atmosphere and oxidizing etching atmosphere, cannot complete pyrolysis crosslinking pore formation and in-situ vapor phase etching in the same closed reaction chamber, and are difficult to achieve precise gradient control of pore structure. Summary of the Invention

[0004] To address the aforementioned shortcomings of existing technologies, this invention provides a porous carbon material preparation system and method. To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows: A porous carbon material preparation system is provided, which includes a high-temperature reaction furnace body, a horizontally placed quartz reaction tube, a furnace shell is provided outside the quartz reaction tube, an air inlet is provided at one end of the quartz reaction tube and an air outlet is provided at the other end, an electric heating wire is arranged axially outside the quartz reaction tube, an insulating lining is provided between the electric heating wire and the furnace shell, and a feeding port is provided at the upper end of the quartz reaction tube. The air inlet is connected to the atmosphere supply system, and the air outlet is connected to the exhaust gas treatment system; the atmosphere supply system includes a nitrogen supply system and a hydrogen peroxide gas phase supply system. A gas distributor is installed on one side of the air inlet inside the quartz reaction tube. Several air vents are evenly distributed on the gas distributor. Anti-backflow valves are installed in the air vents. The anti-backflow valves open the air vents by the airflow flowing into the quartz reaction tube from the air inlet and close the air vents by the airflow flowing out of the quartz reaction tube from the air inlet.

[0005] Furthermore, the gas distributor includes a hemispherical cover and a gas distribution pipe connected to the hemispherical cover. The outer wall of the gas distribution pipe is provided with threads, and the gas distribution pipe is threadedly connected to the inner wall of the air inlet. Several vent holes are evenly distributed on the hemispherical cover.

[0006] Furthermore, the anti-backflow valve includes an outer piston and an inner piston disposed within a vent hole. The outer piston and the inner piston are rotatably connected to the inner wall of the vent hole in a sealing manner. An outer drive shaft and an inner drive shaft coaxial with the vent hole are respectively disposed on the outer piston and the inner piston. The outer drive shaft and the inner drive shaft are respectively installed in the vent hole through two layers of hollow brackets. The outer drive shaft and the inner drive shaft are connected to the two layers of hollow brackets through a bearing with a seat. Both the outer and inner drive shafts between the two hollowed-out supports are equipped with helical impellers, and the helical impellers on the outer and inner drive shafts rotate in opposite directions. An arc-shaped groove is formed on the upper surface of the inner piston that contacts the outer piston. The arc-shaped groove is concentric with the inner piston. An arc-shaped block extending downward is provided on the lower surface of the outer piston that contacts the inner piston. The arc-shaped block is inserted into the arc-shaped groove, and the length of the arc-shaped block is less than the length of the arc-shaped groove, so that the arc-shaped block can move within the arc-shaped groove during the relative rotation of the inner and outer pistons. An external through hole is formed on the arc-shaped block, penetrating the upper and lower ends of the outer piston. An internal through hole is formed in the arc-shaped groove, penetrating the lower end of the inner piston. The external through hole and the internal through hole have the same size. When the airflow enters the quartz reaction tube from the air inlet, it drives the outer piston and the inner piston to rotate relative to each other. The arc block moves to the inner and outer through holes of the arc groove, and the inner through hole is aligned with one side, so that the vent hole is opened. When the airflow flows out of the quartz reaction tube from the air inlet, it drives the outer piston and inner piston to rotate in opposite directions. The arc block moves to the side where the inner and outer through holes of the arc groove are misaligned, thus closing the vent hole.

[0007] Furthermore, the nitrogen supply system includes nitrogen cylinders connected in sequence to an air inlet via conduits. A nitrogen pressure reducing valve and a nitrogen mass flow controller are sequentially installed on the pipeline between the nitrogen cylinders and the air inlet.

[0008] Furthermore, the hydrogen peroxide gas phase supply system includes a hydrogen peroxide storage tank, which is connected to the vaporization chamber via a metering pump. The vaporization chamber is connected to the preheating buffer chamber via a heat tracing pipeline. The preheating buffer chamber is connected to the gas inlet via a first valve. A second valve is installed on the pipeline between the nitrogen mass flow controller and the gas inlet.

[0009] Furthermore, a hydrogen peroxide mass flow controller is installed between the vaporization chamber and the heat tracing pipeline, and a check valve is installed between the heat tracing pipeline and the preheating buffer chamber.

[0010] Furthermore, a third valve is provided between the metering pump and the vaporization chamber, and a bypass gas path is provided between the third valve and the vaporization chamber. The bypass gas path is connected between the second valve and the nitrogen mass flow controller, and a fourth valve is provided on the bypass gas path.

[0011] Furthermore, the exhaust gas treatment system includes a condenser trap, an acid-base scrubbing tower, and an activated carbon adsorption tower connected in sequence to the exhaust port, and a fifth valve is provided between the condenser trap and the exhaust port.

[0012] Furthermore, a pressure sensor is installed on the air outlet.

[0013] A method for preparing the above-mentioned porous carbon material preparation system is provided, which includes the following steps: S1: Mix coal tar pitch, polyethylene pore-forming agent and benzaldehyde crosslinking agent evenly according to a preset ratio to obtain a precursor mixture. Spread the precursor mixture evenly and put it into the quartz reaction tube through the feeding port. Close the gas outlet and gas inlet. S2: Open the second and fifth valves, close the first and fourth valves, and introduce nitrogen into the quartz reaction tube. Continue to introduce nitrogen for 30 minutes to completely replace the air in the quartz reaction tube and prevent the material from oxidizing during pyrolysis. S3: Turn on the electric heating wire to heat the quartz reaction tube and continuously introduce nitrogen gas to pyrolyze the precursor mixture. The pyrolysis temperature is maintained at 650℃. During the pyrolysis process, polyethylene decomposes and volatilizes to produce primary pores, and benzaldehyde promotes the cross-linking of coal tar pitch to form a stable carbon skeleton, thus completing carbonization and pore formation. S4: After pyrolysis, maintain the reaction temperature at 650℃, start the hydrogen peroxide gas phase supply system, and the metering pump sends the hydrogen peroxide solution in the hydrogen peroxide storage tank into the vaporization chamber. It is completely vaporized at 130℃. After passing through the heated pipeline and preheating buffer chamber, the hydrogen peroxide vapor is mixed with the nitrogen carrier gas and introduced into the quartz reaction tube for constant temperature etching for 1-3 hours. During this process, the oxygen free radicals generated by the decomposition of hydrogen peroxide uniformly etch the carbon skeleton, further regulate the pore structure, and form a porous carbon material with high specific surface area. S5: After etching, shut off the hydrogen peroxide gas phase supply system, open the fourth valve and close the third valve. Purge the hydrogen peroxide gas path with nitrogen for 10 minutes through the bypass gas path, while continuously introducing nitrogen into the reaction tube. Turn off the electric heating wire and cool the quartz reaction tube to room temperature at a cooling rate of 3℃ / min. Close all valves, open the feed port, and take out the prepared porous carbon material.

[0014] The beneficial effects of this invention are as follows: This solution adopts an integrated closed reaction system, which can continuously complete the entire process of nitrogen atmosphere pyrolysis crosslinking pore formation and in-situ hydrogen peroxide gas phase etching of coal tar pitch precursor. There is no need to transfer materials in the middle, which completely avoids the problem of material oxidation upon contact with air, greatly improves the batch stability of products, and significantly shortens the process flow.

[0015] This solution enables complete vaporization of liquid hydrogen peroxide and stable gas-phase delivery, precisely controlling the flow rate and concentration of hydrogen peroxide gas, avoiding premature decomposition of hydrogen peroxide and condensation in the pipeline, ensuring the stable progress of the gas-phase etching process, and achieving nanoscale precise control of the carbon framework pore structure.

[0016] This solution, in conjunction with a porous gas distributor at the air inlet, ensures that the reaction atmosphere and materials are in full and uniform contact, guaranteeing the internal and external consistency of the pyrolysis and etching processes and improving the uniformity of the product's pore structure. Attached Figure Description

[0017] Figure 1 A schematic diagram of a porous carbon material preparation system.

[0018] Figure 2 This is a structural diagram of a high-temperature reaction furnace.

[0019] Figure 3 This is a structural diagram of a gas distributor.

[0020] Figure 4 This is a diagram of the internal structure of the vent.

[0021] Figure 5 This is a structural diagram of the inner and outer pistons.

[0022] Figure 6 This is a top view of the inner piston.

[0023] The components include: 1. High-temperature reactor body; 2. Fifth valve; 3. Second valve; 4. Nitrogen mass flow controller; 5. Nitrogen pressure reducing valve; 6. Nitrogen cylinder; 7. First valve; 8. Check valve; 9. Preheating buffer chamber; 10. Heating pipeline; 11. Hydrogen peroxide mass flow controller; 12. Vaporization chamber; 13. Third valve; 14. Metering pump; 15. Hydrogen peroxide storage tank; 16. Condenser; 17. Acid-base washing tower; 18. Activated carbon adsorption tower; 19. Gas distributor; 20. Feed port; 21. Hollowed-out support; 22. Inner piston; 23. Outer piston; 24. Spiral impeller; 25. Arc groove; 26. Arc block; 27. Inner drive shaft; 28. Outer through hole; 29. ​​Outer drive shaft; 30. Inner through hole; 31. Hemispherical cover; 32. Gas distribution pipe. Detailed Implementation

[0024] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0025] like Figure 1 As shown, a porous carbon material preparation system includes a high-temperature reaction furnace body 1, such as... Figure 2 As shown, the high-temperature reactor body 1 includes a horizontally placed quartz reaction tube. A furnace shell surrounds the quartz reaction tube. One end of the quartz reaction tube has an inlet, and the other end has an outlet. An electric heating wire is axially arranged around the outer wall of the quartz reaction tube and is wound around its outer surface. The heating wire is connected to an external power source via a wire passing through the furnace shell. An insulating lining made of high-purity alumina ceramic fiber cotton is placed between the heating wire and the furnace shell to provide thermal insulation. A feed port 20 is located at the upper end of the quartz reaction tube. Inlet flanges and outlet flanges are installed at both ends of the quartz reaction tube to seal the connecting pipes.

[0026] The air inlet is connected to the atmosphere supply system, and the air outlet is connected to the exhaust gas treatment system; the atmosphere supply system includes a nitrogen supply system and a hydrogen peroxide gas phase supply system.

[0027] A gas distributor 19 is installed on one side of the air inlet inside the quartz reaction tube. The gas distributor 19 has several evenly spaced vent holes, each equipped with an anti-backflow valve. The anti-backflow valve opens the vent hole using the airflow flowing into the quartz reaction tube from the air inlet and closes it using the airflow flowing out of the quartz reaction tube from the air inlet. By installing the gas distributor 19, the atmosphere entering the quartz reaction tube can be evenly dispersed, preventing the airflow from directly impacting the material and ensuring sufficient contact between the atmosphere and the material.

[0028] like Figure 3 As shown, the gas distributor 19 includes a hemispherical cover 31 and a gas distribution pipe 32 connected to the hemispherical cover 31. The outer wall of the gas distribution pipe 32 is provided with threads, and the gas distribution pipe 32 is threadedly connected to the inner wall of the air inlet. Several air vents are evenly distributed on the hemispherical cover 31.

[0029] like Figures 4-6 As shown, the anti-backflow valve includes an outer piston 23 and an inner piston 22 disposed in the vent hole. The outer piston 23 and the inner piston 22 are rotatably connected to the inner wall of the vent hole in a sealing manner. The outer piston 23 and the inner piston 22 are respectively provided with an outer drive shaft 29 and an inner drive shaft 27 coaxial with the vent hole. The outer drive shaft 29 and the inner drive shaft 27 are respectively installed in the vent hole through two layers of hollow brackets 21. The outer drive shaft 29 and the inner drive shaft 27 are connected to the two layers of hollow brackets 21 through a bearing with a seat. Spiral impellers 24 are provided on both the outer drive shaft 29 and the inner drive shaft 27 between the two hollow brackets 21, and the spiral impellers 24 on the outer drive shaft 29 and the inner drive shaft 27 rotate in opposite directions; An arc-shaped groove 25 is provided on the upper surface of the inner piston 22 that contacts the outer piston 23. The arc-shaped groove 25 is concentric with the inner piston 22. An arc-shaped block 26 extending downward is provided on the lower surface of the outer piston 23 that contacts the inner piston 22. The arc-shaped block 26 is inserted into the arc-shaped groove 25, and the length of the arc-shaped block 26 is less than the length of the arc-shaped groove 25, so that the arc-shaped block 26 can move within the arc-shaped groove 25 during the relative rotation of the inner piston 22 and the outer piston 23. An external through hole 28 is provided on the arc-shaped block 26 that penetrates the upper and lower ends of the outer piston 23. An internal through hole 30 is provided in the arc-shaped groove 25 that penetrates the lower end of the inner piston 22. The external through hole 28 and the internal through hole 30 have the same size. When the airflow enters the quartz reaction tube from the air inlet, it drives the outer piston 23 and the inner piston 22 to rotate relative to each other. The arc block 26 moves to the inner and outer through holes 28 and the inner through hole 30 of the arc groove 25 to align on one side, so that the vent hole is opened. When the airflow flows out of the quartz reaction tube from the air inlet, it drives the outer piston 23 and the inner piston 22 to rotate in opposite directions. The arc block 26 moves to the side where the inner and outer through holes 28 and the inner through hole 30 of the arc groove 25 are misaligned, thus closing the vent.

[0030] Since the quartz reaction tube is kept under high pressure for a long time, a special anti-backflow valve is installed on the vent hole to ensure that other backflows are avoided in the quartz reaction tube during the phase switching of nitrogen and hydrogen peroxide. This ensures that the gas pressure in the quartz reaction tube is stable enough in each preparation stage. Moreover, the anti-backflow valve does not require additional power. It is driven to open and close by the power of the airflow, realizing adaptive control of anti-backflow.

[0031] In this embodiment, the nitrogen supply system includes nitrogen cylinders 6 connected sequentially. Each nitrogen cylinder 6 is connected to an inlet via a conduit. A nitrogen pressure reducing valve 5 and a nitrogen mass flow controller 4 are sequentially installed on the pipe between the nitrogen cylinder 6 and the inlet. The nitrogen mass flow controller 4 has a range of 0-1000 sccm and a control accuracy of ±1% FS. It is used to precisely control the nitrogen flow rate, providing an inert protective atmosphere for the pyrolysis process and serving as the carrier gas for the etching process.

[0032] In this embodiment, the hydrogen peroxide gas phase supply system includes a hydrogen peroxide storage tank 15, which is connected to a vaporization chamber 12 via a metering pump 14. The vaporization chamber 12 is connected to a preheating buffer chamber 9 via a heat tracing pipeline 10. The preheating buffer chamber 9 is connected to an inlet via a first valve 7. A second valve 3 is installed on the pipeline between the nitrogen mass flow controller 4 and the inlet. Both the vaporization chamber 12 and the preheating buffer chamber 9 are equipped with electric heating modules to ensure the internal temperature, allowing the hydrogen peroxide solution to be completely vaporized into a gas phase. The outer wall of the heat tracing pipeline 10 is wrapped with an electric heating tape, and the heating temperature is consistent with the temperature control temperature of the vaporization chamber 12, preventing the hydrogen peroxide vapor from condensing during transportation. The preheating buffer chamber 9 is used to stabilize the pressure and concentration of the hydrogen peroxide gas phase, preventing violent decomposition after entering the reaction tube.

[0033] A hydrogen peroxide mass flow controller 11 is installed between the vaporization chamber 12 and the heat tracing pipeline 10, and a check valve 8 is installed between the heat tracing pipeline 10 and the preheating buffer chamber 9 to prevent the backflow of hydrogen peroxide gas in the preheating buffer chamber 9.

[0034] In this embodiment, a third valve 13 is provided between the metering pump 14 and the vaporization chamber 12, and a bypass gas path is provided between the third valve 13 and the vaporization chamber 12. The bypass gas path is connected between the second valve 3 and the nitrogen mass flow controller 4, and a fourth valve is provided on the bypass gas path. After the etching process is completed, the hydrogen peroxide gas phase supply gas path is purged with nitrogen to remove residual hydrogen peroxide vapor in the pipeline and avoid pipeline corrosion and blockage.

[0035] In this embodiment, the exhaust gas treatment system includes a condenser 16, an acid-base scrubbing tower 17, and an activated carbon adsorption tower 18, which are connected in sequence to the exhaust port. A fifth valve 2 is provided between the condenser 16 and the exhaust port. The condenser 16 is used to collect volatile organic compounds, tar, and unreacted hydrogen peroxide vapor generated during pyrolysis; the acid-base scrubbing tower 17 is used to neutralize acidic gases in the exhaust gas; and the activated carbon adsorption tower 18 is used to adsorb residual organic waste gas in the exhaust gas.

[0036] A pressure sensor is installed at the air outlet to monitor the pressure inside the quartz reaction tube in real time, ensuring that the reaction process is carried out under a slightly positive pressure of 0.01-0.05MPa, thus preventing outside air from seeping into the reaction tube.

[0037] A method for preparing the above-mentioned porous carbon material preparation system is provided, which includes the following steps: S1: Mix coal tar pitch, polyethylene pore-forming agent and benzaldehyde crosslinking agent evenly according to the preset ratio to obtain precursor mixture. Spread the precursor mixture evenly and put it into the quartz reaction tube through the feeding port 20. Close the gas outlet and the gas inlet. S2: Open the second valve 3 and the fifth valve 2, close the first valve 7 and the fourth valve, and introduce nitrogen into the quartz reaction tube. Continue to introduce nitrogen for 30 minutes to completely replace the air in the quartz reaction tube and avoid oxidation of the material during pyrolysis. S3: Turn on the electric heating wire to heat the quartz reaction tube and continuously introduce nitrogen gas to pyrolyze the precursor mixture. The pyrolysis temperature is maintained at 650℃. During the pyrolysis process, polyethylene decomposes and volatilizes to produce primary pores, and benzaldehyde promotes the cross-linking of coal tar pitch to form a stable carbon skeleton, thus completing carbonization and pore formation. S4: After pyrolysis, maintain the reaction temperature at 650℃ and start the hydrogen peroxide gas phase supply system. The metering pump 14 sends the hydrogen peroxide solution in the hydrogen peroxide storage tank 15 into the vaporization chamber 12, where it is completely vaporized at 130℃. The hydrogen peroxide vapor is mixed with nitrogen carrier gas after passing through the heating pipeline 10 and the preheating buffer chamber 9 and is introduced into the quartz reaction tube for constant temperature etching for 1-3 hours. During this process, the oxygen free radicals generated by the decomposition of hydrogen peroxide uniformly etch the carbon skeleton, further regulating the pore structure and forming a porous carbon material with a high specific surface area. S5: After etching, shut off the hydrogen peroxide gas phase supply system, open the fourth valve and close the third valve 13, purge the hydrogen peroxide gas path with nitrogen for 10 minutes through the bypass gas path, and continuously introduce nitrogen into the reaction tube at the same time, and turn off the electric heating wire to cool the quartz reaction tube to room temperature at a cooling rate of 3℃ / min, close all valves, open the feed port 20, and take out the prepared porous carbon material.

[0038] This solution adopts an integrated closed reaction system, which can continuously complete the entire process of nitrogen atmosphere pyrolysis crosslinking pore formation and in-situ hydrogen peroxide gas phase etching of coal tar pitch precursor. There is no need to transfer materials in the middle, which completely avoids the problem of material oxidation upon contact with air, greatly improves the batch stability of products, and significantly shortens the process flow.

[0039] This solution enables complete vaporization of liquid hydrogen peroxide and stable gas-phase delivery, precisely controlling the flow rate and concentration of hydrogen peroxide gas, avoiding premature decomposition of hydrogen peroxide and condensation in the pipeline, ensuring the stable progress of the gas-phase etching process, and achieving nanoscale precise control of the carbon framework pore structure.

[0040] This solution, in conjunction with the porous gas distributor 19 at the air inlet, ensures that the reaction atmosphere and materials are in full and uniform contact, guaranteeing the internal and external consistency of the pyrolysis and etching processes and improving the uniformity of the product's pore structure.

Claims

1. A porous carbon material preparation system, characterized in that, The device includes a high-temperature reactor body, which includes a horizontally placed quartz reaction tube. A furnace shell is provided outside the quartz reaction tube. One end of the quartz reaction tube is provided with an air inlet and the other end is provided with an air outlet. An electric heating wire is arranged axially around the outside of the quartz reaction tube. An insulation lining is provided between the electric heating wire and the furnace shell. A feeding port is provided at the upper end of the quartz reaction tube. The air inlet is connected to an atmosphere supply system, and the air outlet is connected to an exhaust gas treatment system; the atmosphere supply system includes a nitrogen supply system and a hydrogen peroxide gas phase supply system. A gas distributor is provided on one side of the air inlet in the quartz reaction tube. The gas distributor has several air vents evenly distributed on it. An anti-backflow valve is provided in each air vent. The anti-backflow valve opens the air vent by the airflow flowing into the quartz reaction tube from the air inlet and closes the air vent by the airflow flowing out of the quartz reaction tube from the air inlet.

2. The porous carbon material preparation system according to claim 1, characterized in that, The gas distributor includes a hemispherical cover and a gas distribution pipe connected to the hemispherical cover. The outer wall of the gas distribution pipe is provided with threads. The gas distribution pipe is threaded to the inner wall of the air inlet. A number of the air vents are evenly distributed on the hemispherical cover.

3. The porous carbon material preparation system according to claim 2, characterized in that, The anti-backflow valve includes an outer piston and an inner piston disposed in a vent hole. The outer piston and the inner piston are rotatably connected to the inner wall of the vent hole in a sealing manner. An outer drive shaft and an inner drive shaft coaxial with the vent hole are respectively disposed on the outer piston and the inner piston. The outer drive shaft and the inner drive shaft are respectively installed in the vent hole through two layers of hollow brackets. The outer drive shaft and the inner drive shaft are connected to the two layers of hollow brackets through a bearing with a seat. Both the outer drive shaft and the inner drive shaft between the two layers of hollow brackets are equipped with helical impellers, and the helical impellers on the outer drive shaft and the inner drive shaft rotate in opposite directions; An arc-shaped groove is formed on the upper surface of the inner piston that contacts the outer piston. The arc-shaped groove is concentric with the inner piston. An arc-shaped block extending downward is provided on the lower surface of the outer piston that contacts the inner piston. The arc-shaped block is inserted into the arc-shaped groove, and the length of the arc-shaped block is less than the length of the arc-shaped groove, so that the arc-shaped block can move within the arc-shaped groove during the relative rotation of the inner and outer pistons. An external through hole is formed on the arc-shaped block, penetrating the upper and lower ends of the outer piston. An internal through hole is formed in the arc-shaped groove, penetrating the lower end of the inner piston. The external through hole and the internal through hole have the same size. When the airflow enters the quartz reaction tube from the air inlet, it drives the outer piston and the inner piston to rotate relative to each other. The arc block moves to the inner and outer through holes of the arc groove, and the inner through hole is aligned with one side, so that the vent hole is opened. When the airflow flows out of the quartz reaction tube from the air inlet, it drives the outer piston and inner piston to rotate in opposite directions. The arc block moves to the side where the inner and outer through holes of the arc groove are misaligned, thus closing the vent hole.

4. The porous carbon material preparation system according to claim 1, characterized in that, The nitrogen supply system includes a nitrogen cylinder, which is connected to an inlet via a conduit. A nitrogen pressure reducing valve and a nitrogen mass flow controller are sequentially installed on the pipeline between the nitrogen cylinder and the inlet.

5. The porous carbon material preparation system according to claim 4, characterized in that, The hydrogen peroxide gas phase supply system includes a hydrogen peroxide storage tank, which is connected to a vaporization chamber via a metering pump. The vaporization chamber is connected to a preheating buffer chamber via a heat tracing pipeline. The preheating buffer chamber is connected to an inlet via a first valve. A second valve is installed on the pipeline between the nitrogen mass flow controller and the inlet.

6. The porous carbon material preparation system according to claim 5, characterized in that, A hydrogen peroxide mass flow controller is installed between the vaporization chamber and the heat tracing pipeline, and a check valve is installed between the heat tracing pipeline and the preheating buffer chamber.

7. The porous carbon material preparation system according to claim 6, characterized in that, A third valve is provided between the metering pump and the vaporization chamber. A bypass gas path is provided between the third valve and the vaporization chamber. The bypass gas path is connected between the second valve and the nitrogen mass flow controller. A fourth valve is provided on the bypass gas path.

8. The porous carbon material preparation system according to claim 1, characterized in that, The exhaust gas treatment system includes a condenser, an acid-base scrubbing tower, and an activated carbon adsorption tower connected in sequence to the exhaust port. A fifth valve is provided between the condenser and the exhaust port.

9. The porous carbon material preparation system according to claim 8, characterized in that, A pressure sensor is installed on the air outlet.

10. A method for preparing porous carbon materials using the porous carbon material preparation system according to any one of claims 1-9, characterized in that, Includes the following steps: S1: Mix coal tar pitch, polyethylene pore-forming agent and benzaldehyde crosslinking agent evenly according to a preset ratio to obtain a precursor mixture. Spread the precursor mixture evenly and put it into the quartz reaction tube through the feeding port. Close the gas outlet and gas inlet. S2: Open the second and fifth valves, close the first and fourth valves, and introduce nitrogen into the quartz reaction tube. Continue to introduce nitrogen for 30 minutes to completely replace the air in the quartz reaction tube and prevent the material from oxidizing during pyrolysis. S3: Turn on the electric heating wire to heat the quartz reaction tube and continuously introduce nitrogen gas to pyrolyze the precursor mixture. The pyrolysis temperature is maintained at 650℃. During the pyrolysis process, polyethylene decomposes and volatilizes to produce primary pores, and benzaldehyde promotes the cross-linking of coal tar pitch to form a stable carbon skeleton, thus completing carbonization and pore formation. S4: After pyrolysis, maintain the reaction temperature at 650℃, start the hydrogen peroxide gas phase supply system, and the metering pump sends the hydrogen peroxide solution in the hydrogen peroxide storage tank into the vaporization chamber. It is completely vaporized at 130℃. After passing through the heated pipeline and preheating buffer chamber, the hydrogen peroxide vapor is mixed with the nitrogen carrier gas and introduced into the quartz reaction tube for constant temperature etching for 1-3 hours. During this process, the oxygen free radicals generated by the decomposition of hydrogen peroxide uniformly etch the carbon skeleton, further regulate the pore structure, and form a porous carbon material with high specific surface area. S5: After etching, shut off the hydrogen peroxide gas phase supply system, open the fourth valve and close the third valve. Purge the hydrogen peroxide gas path with nitrogen for 10 minutes through the bypass gas path, while continuously introducing nitrogen into the reaction tube. Turn off the electric heating wire and cool the quartz reaction tube to room temperature at a cooling rate of 3℃ / min. Close all valves, open the feed port, and take out the prepared porous carbon material.

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