Device and method for preparing carbon nano tube by pull-type floating catalyst

Abstract

The invention relates to the technical field of carbon nanotube preparation, in particular to a device and a method for preparing a carbon nanotube by a pull-type floating catalyst. The carbon nanotube pushing and scraping device reciprocates in the furnace tube by utilizing the twisted rope, and the carbon nanotubes growing and deposited in the furnace tube are pushed, scraped and collected and then are returned to a set position; besides, the carrier gas with pressure uniformly injects the catalyst into the furnace tube, the catalyst can float in the furnace tube under the mixing action of a gas-phase mixture formed by the catalyst and the carrier gas and the carbon source gas, the catalyst and the carbon source gas are fully contacted with the carbon source gas, the carbon source gas is fully cracked to prepare the carbon nanotube, and the carbon source gas is fully utilized; the carbon nanotube pushing and scraping device moves to push, scrape and collect the carbon nanotubes growing and deposited in the furnace tube, and the industrial pain point that the carbon nanotubes are adhered to the wall and carbon is deposited during growth is solved. According to the invention, different catalysts and different carbon source gases are realized, various carbon nanotubes are prepared, and one device is universal.

Description

Technical Field

[0001] This invention relates to the preparation of carbon nanotubes, belonging to the field of carbon nanotube technology, and specifically to an apparatus and method for preparing carbon nanotubes using a traction-type floating catalyst. Background Technology

[0002] Carbon nanomaterials refer to materials in which the size of the dispersed phase is at least one dimension less than 100 nm. Currently reported carbon nanomaterials include carbon nanofibers, graphene, carbon nanospheres, etc., while carbon nanotubes are recognized as the finest fibers in the world. Due to their good electrical conductivity, high mechanical properties and high specific surface area, these materials play an important role in the fields of renewable energy conversion technologies such as electrochemical catalysis and energy storage.

[0003] Currently, the main method for the mass production of carbon nanotubes is chemical vapor deposition (CVD). This method utilizes a catalyst to crack hydrocarbons, with active metal atoms serving as catalyst nuclei. Carbon atoms are deposited around these nuclei to form carbon nanotubes. According to the principle of CVD, the more contact the active component of the catalyst has with the carbon source gas, the more carbon atoms generated by the cracking of carbon-hydrogen bonds will be deposited and grown on the surface of the active metal, resulting in more carbon nanotubes and better growth morphology. In engineering production, the main means of chemical vapor deposition are the moving method and the fluidized bed method. (1) The moving method uses a boat as a carrier. The catalyst is placed in the boat and moved within the tube of a tubular furnace. Carbon nanotubes are grown within the area where conditions are met. During the moving method, the catalyst is fixed in the boat and relies entirely on the carbon source gas to contact the catalyst by contacting the catalyst on the surface of the catalyst stack and by penetrating into it. In other words, the catalyst is passively in contact with the carbon source gas. Therefore, there are disadvantages such as insufficient contact between the catalyst and hydrocarbons, which affects the growth of carbon nanotubes. This means that it can only be used for the preparation of low-rate carbon nanotubes, and methane is usually used as the carbon source. (2) To overcome the aforementioned drawbacks of moving beds, the fluidized bed method (also known as the boiling method) for producing carbon nanotubes has emerged. The fluidized bed method uses nitrogen to suspend the catalyst in a well-type furnace filled with hydrocarbons, allowing for sufficient contact between the carbon source gas and the active metal catalyst, thus promoting better carbon nanotube growth. However, the fluidized bed method suffers from drawbacks such as unstable nitrogen pressure, making the growth process difficult to control. Furthermore, the large-scale introduction of nitrogen into the carbon source gas environment dilutes the gas, necessitating an excessive amount of gas to ensure carbon nanotube growth. This means the furnace pressure cannot be too high, requiring a large amount of gas to be discharged, resulting in un-decomposed carbon source gas, low conversion rate, and significant environmental pollution. Additionally, the use of stainless steel in the growth chamber, containing active metals like iron and nickel, causes carbon nanotubes to deposit on the surface, leading to adhesion and severely impacting the quality and efficiency of carbon nanotube production. Therefore, the fluidized bed method can only be used for small-diameter carbon nanotubes, typically using propylene as the carbon source. The moving method and the boiling method have their own specific requirements for catalyst preparation, and the catalysts cannot be used interchangeably.

[0004] To address the aforementioned technical problems, this invention discloses an apparatus and method for preparing carbon nanotubes using a traction-type floating catalyst. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an apparatus and method for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons. This invention solves the problems in the prior art, such as the inability to fully utilize carbon source gas (hydrocarbons), low carbon source gas conversion rate leading to environmental pollution, carbon nanotubes sticking to the inner wall of the equipment, and the inability of one device to produce multiple types of carbon nanotubes.

[0006] The objective of this invention is achieved through the following technical solution: In one aspect, a device for preparing carbon nanotubes by traction floating catalytic cracking of hydrocarbons is provided, including a horizontal furnace, a carbon nanotube pushing and scraping device, a catalyst feeding bin, and a catalyst injection device II. The horizontal furnace is equipped with horizontal furnace tubes, and the left and right ends of the furnace tubes are respectively equipped with a feeding sealing box and a discharging sealing box; in addition, the discharging sealing box is equipped with a collection box. The furnace tube is connected to a carbon source gas inlet pipe that can be opened and closed near the right end, and to a tail gas pipe that can be opened and closed near the left end. The catalyst feeding bin is located at the left end of the furnace tube. The catalyst feeding bin is connected to the catalyst buffer chamber via the screw feeder I. The catalyst buffer chamber is connected to the catalyst injection device II. The catalyst injection device II contains carrier gas, can preheat the carrier gas, and can spray pressurized carrier gas. The catalyst buffer chamber is connected to the catalyst injection pipe, which extends into the furnace tube along the inner wall of the furnace tube. When the preheated and pressurized carrier gas is introduced into the catalyst buffer chamber, the catalyst in the chamber can be injected into the furnace tube through the catalyst injection pipe. This allows the catalyst and the carrier gas to form a gas-solid mixture. When this gas-solid mixture encounters the carbon source gas, it can float, thereby allowing the catalyst and the carbon source gas to fully contact each other. The furnace tube is equipped with a carbon nanotube scraping device with a certain gap between it and the furnace tube. The left and right ends of the carbon nanotube scraping device are pulled by corresponding ropes, forming a structure in which the carbon nanotube scraping device can move back and forth in a suspended manner inside the furnace tube.

[0007] Furthermore, the end of the catalyst injection pipe that extends into the furnace tube extends to any axial position within the furnace tube; the end of the catalyst injection pipe that extends into the furnace tube is sealed, and multiple catalyst injection holes are opened on the side wall of the catalyst injection pipe; the diameter of the catalyst injection pipe is 10-100mm, and the diameter of the corresponding catalyst injection hole is adapted to be 1-50mm.

[0008] Furthermore, the number of catalyst injection pipes is 1 to 20, and each catalyst injection pipe is fixed at any position along the inner circumference of the furnace tube, including but not limited to the top and bottom of the furnace tube.

[0009] Furthermore, the shape of the carbon nanotube scraping device includes, but is not limited to, cylinders and various prismatic columns, so that the gap between the outer side of the carbon nanotube scraping device and the inner wall of the furnace tube is 1-50mm.

[0010] Furthermore, the sheath of the rope is covered with a flexible, high-temperature resistant rope tube; the corresponding rope and rope tube at the left end of the carbon nanotube scraping device are wound around the left winch, and the corresponding rope and rope tube at the right end of the carbon nanotube scraping device are wound around the right winch; the left and right winches are respectively installed in the feed sealing box and the discharge sealing box, both of which are connected to the corresponding traction motor drive, and the corresponding traction motor is electrically connected to the control panel.

[0011] Furthermore, the screw feeder I includes a horizontal pipe connected to the bottom of the catalyst feeding hopper. A feeding screw for conveying material is installed inside the horizontal pipe, and the feeding screw is driven and connected to a feeding motor. The screw feeding motor is connected to a control panel, which controls the rotation speed, number of rotations, and start / stop time of the feeding motor to ensure that the catalyst is delivered to the catalyst buffer chamber in a timely and quantitative manner. A catalyst feeding valve is also provided between the bottom of the catalyst feeding hopper and the screw feeder I.

[0012] Secondly, this solution also provides a method for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons, which uses the above-mentioned traction-type floating catalytic cracking of hydrocarbons to prepare carbon nanotubes. The specific steps are as follows: ① Catalyst metering: The catalyst is injected into the catalyst silo. By controlling the opening degree and opening time of the corresponding valve plate in the catalyst feeding valve, the catalyst is meteredly dropped into the catalyst buffer chamber, and then the catalyst feeding valve is closed. ②Pour carbon source gas: Move the carbon nanotube scraping device to the left to the appropriate position S1, so that all the catalyst injection holes are located on the right side of the carbon nanotube scraping device. Open the gas valve on the feeding sealing box, open the gas valve on the discharging sealing box, and open the valve on the tail gas pipe to allow nitrogen to fill the feeding sealing box, furnace tube, and discharging sealing box, thus replacing the oxygen content with less than 1%. Then close the gas valve on the feeding sealing box, close the gas valve on the discharging sealing box, and keep the valve on the tail gas pipe open; after heating the horizontal furnace to a suitable temperature, introduce carbon source gas. ③ Catalyst addition: Open the valve corresponding to the carrier gas source to allow the carrier gas to enter the catalyst buffer chamber and mix with the catalyst -- so that the catalyst and the carrier gas form a gas-solid mixture, and the gas-solid mixture is injected into the high-temperature reaction zone inside the furnace tube through the catalyst injection pipe. After the set time Ts is reached, close the switch on the carrier gas source, and the catalyst addition is completed. ④ Catalytic cracking: Carbon source gas is continuously introduced into the furnace tube, and at the same time, the carrier gas of the catalyst is injected through step ③. The gas-solid mixture in the furnace tube becomes a floating state under the action of the carbon source gas. This allows the catalyst in the gas-solid mixture to fully contact the carbon source gas. After the carbon-hydrogen bond is cracked, carbon atoms are deposited and grown into carbon nanotubes with the catalyst crystal nuclei as the nuclei. The generated carbon nanotubes are deposited inside the furnace tube. The waste gas generated during the pyrolysis process flows to the left through the gap between the carbon nanotube scraping device and the inner wall of the furnace tube, and is then discharged through the waste gas discharge pipe. ⑤ Carbon nanotube collection: When the carbon nanotube growth time reaches T1, the rope pulls the carbon nanotube pushing and scraping device to move to the right from position S1, pushing and scraping the carbon nanotubes grown in the furnace tube to the right and discharging them from the bottom outlet at the right end of the furnace tube. The discharged material falls into the collection box and quickly returns to position S1 after reaching the preset position S2. ⑥ Repeat step ③ to add the catalyst, and continue production through steps ④ and ⑤.

[0013] Furthermore, the horizontal furnace heating temperature is 600-900℃. The flow rate of the carbon source gas is 1-500 m³ / h. 3 / h. The carrier gas needs to be preheated to 100-500℃ and the carrier gas pressure is 50-1000KPa. The growth time T1 is 0.5-3.5h.

[0014] Furthermore, the carbon nanotube catalyst is at least one of nickel-based catalysts, iron-based catalysts, and cobalt-based catalysts. During catalyst injection, the catalyst is directly injected into the high-temperature section of the furnace tube by preheating the carrier gas, so as to grow carbon nanotubes by cracking the added high-temperature carbon source gas; the injection form of the catalyst includes, but is not limited to, single-tube injection, multi-tube injection, single-point or multi-point injection, axial or radial injection.

[0015] Furthermore, the carrier gas is hydrogen, argon, nitrogen, or a mixture of hydrogen and argon. The carbon source gas is at least one of methane, propylene or ethylene, or biogas.

[0016] The present invention has the following advantages: (1) The preparation method of the present invention uses a carbon nanotube pushing and scraping device to move to the right to push and scrape all the carbon nanotubes deposited and grown in the furnace tube into the right-side sealed box. The carbon nanotubes attached to the inner wall of the furnace tube are cleaned and collected in the sealed box in time under the pushing and scraping action of the pushing and scraping device, thus overcoming the problem of carbon nanotubes sticking to the wall and fundamentally solving the problem of wall sticking in the existing carbon nanotube preparation process. (2) The method disclosed in this invention utilizes the preheated carrier gas in the catalyst injection pipe that extends into the furnace tube to uniformly inject the catalyst in the catalyst buffer chamber into the high-temperature reaction zone inside the furnace tube. Under the interaction with the carrier gas and carbon source gas in the furnace tube, a floating state of boiling dust is formed, which achieves full contact with the carbon source gas and achieves full cleavage of carbon-hydrogen bonds. Carbon atoms are deposited and grown into high-quality carbon nanotubes with the catalyst crystal nuclei as nuclei. At the same time, the carbon source gas can be fully cleaved and grown into carbon nanotubes, so as to make full use of it. (3) The method disclosed in this invention is not only an integrated reaction device with a simple structure, but also allows for the preparation of various carbon nanotubes with different catalysts and carbon source gases by adjusting the carbon nanotube growth time, catalyst feeding motor frequency and pyrolysis temperature. One device can be used for all purposes. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the reaction apparatus according to an embodiment of the present invention; Figure 2 This is a diagram of the carbon nanotube scraping device in an embodiment of the present invention; Figure 3 This is a scanning electron microscope image of large-diameter carbon nanotubes prepared using methane as a carbon source in an embodiment of the present invention; Figure 4 This is a scanning electron microscope image of small-diameter carbon nanotubes prepared using propylene as a carbon source according to an embodiment of the present invention; in, Figure 1 , Figure 2 The component numbers are as follows: 1. Left winch, 2. Feeding sealing box, 3. Winch rope, 4. Furnace tube, 5. Carbon nanotube scraping device, 6. Left fixed winch rope screw hole, 7. Scraping device, 8. Right fixed winch rope screw hole, 9. Guide groove, 10. Winch rope tube, 11. Horizontal furnace, 12. Catalyst feeding chamber, 13. Catalyst feeding valve, 14. Catalyst buffer chamber, 15. Catalyst injection pipe, 16. Right winch, 17. Discharge sealing box. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0019] It should be noted that the orientation or positional relationship indicated by terms such as "left" and "right" is based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use, or the orientation or positional relationship in which those skilled in the art would conventionally understand it. Such terms are only for the convenience of describing the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention.

[0020] It should be noted that, unless otherwise specified, the embodiments and features and technical solutions in the present invention can be combined with each other.

[0021] like Figure 1 and Figure 2 As shown in the figure, this specific embodiment discloses an apparatus for preparing carbon nanotubes by traction floating catalytic cracking of hydrocarbons, including a horizontal furnace 11, a carbon nanotube pushing and scraping device 5, and a catalyst feeding bin 12. The horizontal furnace 11 is equipped with a horizontal furnace tube 4, and the left and right ends of the furnace tube 4 are respectively equipped with a feeding sealing box 2 and a discharging sealing box 17; in addition, a collection box is provided in the discharging sealing box 17, and the collection box is located below the right end of the furnace tube. Furthermore, a carbon source gas inlet pipe that can be opened and closed is connected to the right end of the furnace tube 4, and an exhaust gas pipe that can be opened and closed is connected to the left end of the furnace tube 4. A catalyst feeding chamber 12 is provided at the left end of the furnace tube 4. The catalyst feeding chamber 12 is connected to the catalyst buffer chamber 14 via a screw feeder I. The catalyst buffer chamber 14 is connected to the catalyst injection device II. The catalyst injection device II contains carrier gas, can preheat the carrier gas, and can spray pressurized carrier gas. At least one catalyst injection pipe 15 is connected to the catalyst buffer chamber 14. The catalyst injection pipe 15 extends into the furnace tube 4 and is attached to the inner wall of the furnace tube 4. The side wall of the catalyst injection pipe 15 has multiple catalyst injection ports. The preheated and pressurized carrier gas enters the catalyst buffer chamber 14, allowing the catalyst in the catalyst buffer chamber 14 to be injected into the furnace tube 4 through the catalyst injection pipe 15 from the catalyst injection ports. When the carrier gas and the catalyst flow in the catalyst injection pipe 15, they can form a gas-solid mixture together. When this gas-solid mixture encounters the carbon source gas in the furnace tube 4, it can exhibit a floating state, thus allowing the catalyst to fully contact the carbon source gas. Furthermore, a carbon nanotube scraping device 5 is installed inside the furnace tube 4. There is a certain gap between the carbon nanotube scraping device 5 and the furnace tube 4. The left and right ends of the carbon nanotube scraping device 5 are pulled by corresponding ropes 3, forming a structure in which the carbon nanotube scraping device can move left and right in a suspended manner inside the furnace tube. When the carbon nanotube scraping device 5 moves to the right, it can scrape away the carbon nanotubes that have grown inside the furnace tube 4 to the right, thus achieving material discharge.

[0022] The installation and structure of the catalyst injection pipe 15 will be further explained below.

[0023] Regarding the installation of the catalyst injection pipes 15: the number of catalyst injection pipes 15 is 1 to 20, and each catalyst injection pipe 15 extends into the furnace tube 4 along the inner wall of the furnace tube 4 (it can be fixed at any position along the inner circumference of the furnace tube, including but not limited to the top and bottom of the furnace tube, and preferably is evenly distributed). In addition, the end of the catalyst injection pipe 15 extending into the furnace tube can extend to any axial position inside the furnace tube.

[0024] Regarding the structure of the catalyst injection pipe 15: the end of the catalyst injection pipe 15 that extends into the furnace tube is sealed, and multiple catalyst injection holes are opened on the side wall of the catalyst injection pipe 15; and the diameter of the catalyst injection pipe 15 is 10-100mm, and the diameter of the corresponding catalyst injection hole is adapted to be 1-50mm (the diameter of the catalyst injection hole is appropriate according to the diameter of the catalyst injection pipe 15, so that the catalyst injection hole of the corresponding size can be opened in the catalyst injection pipe 15 of the corresponding size as the standard).

[0025] The installation and structure of the carbon nanotube scraping device 5 will be further explained below.

[0026] Regarding the structure of the carbon nanotube scraping device 5: the shape of the carbon nanotube scraping device 5 includes, but is not limited to, a cylinder or various prismatic columns, such that the gap between the outer side of the carbon nanotube scraping device and the inner wall of the furnace tube is 1-50mm. Furthermore, the materials of the carbon nanotube scraping device include, but are not limited to, various metals, carbon materials, ceramics, and other composite materials.

[0027] For the installation of the carbon nanotube scraping device 5, which can move left and right: the twisted rope 3 is covered with a flexible, high-temperature resistant twisted rope tube 10; the corresponding twisted rope 3 and twisted rope tube 10 at the left end of the carbon nanotube scraping device 5 are pulled and wound onto the left winch 1, and the corresponding twisted rope 3 and twisted rope tube 10 at the right end of the carbon nanotube scraping device 5 are pulled and wound onto the right winch 16; the left winch 1 and the right winch 16 are respectively installed in the feed sealing box 2 and the discharge sealing box 17, both of which are connected to the corresponding traction motor drive, and the corresponding traction motor is electrically connected to the control panel. The control panel can control the speed and limit position of the left and right movements of the left winch 1 and the right winch 16.

[0028] Furthermore, when the carbon nanotube scraping device 5 needs to move left and right during the scraping and collection of carbon nanotubes and the injection of catalyst through the catalyst injection pipe, it is pulled by the helical rope 3. The traction rope material includes, but is not limited to, metals, carbon fibers and their composites, ceramic fibers, high-silica fibers and their blends with basalt fibers, etc.

[0029] Furthermore, the outer cylindrical surface of the carbon nanotube scraping device 5 has multiple annular protrusions. A left fixing screw hole 6 for fixing the corresponding twisted rope 3 is opened at the center of the left end face of the carbon nanotube scraping device 5 (for example, the twisted rope 3 is fixed to a threaded pin, which is screwed into the left fixing screw hole 6). A right fixing screw hole 8 for fixing the corresponding twisted rope 3 is opened at the center of the right end face. Additionally, as... Figure 2 As shown, a guide groove 9 is opened on the outer cylindrical surface of the carbon nanotube scraping device 5. The guide groove 9 allows the catalyst injection pipe 15 to pass through the carbon nanotube scraping device 5 and extend into the corresponding position of the furnace tube 4.

[0030] Furthermore, when the carbon nanotube scraping device 5 moves left and right inside the furnace tube 4, there are left limit positions S1 and right limit positions S2. Positions S1 and S2 are located at the left and right ends of the furnace tube, respectively, and their setting methods include, but are not limited to, position switches, position sensor detection, and positioning methods obtained by setting displacement, time, and the rotation speed of the traction rope winch.

[0031] The following section provides a further explanation of the structure for adding catalyst at point 12 in the catalyst feeding chamber.

[0032] A screw feeder I is installed at the bottom of the catalyst feeding silo 12. The screw feeder I includes a horizontal pipe connected to the bottom of the catalyst feeding silo 12. A feeding screw is installed inside the horizontal pipe and is connected to a feeding motor. The feeding motor is connected to a control panel via a corresponding frequency converter. The control panel controls the rotation speed, number of rotations, and start / stop time of the feeding motor to ensure that the catalyst is delivered to the catalyst buffer chamber 14 in a timely and quantitative manner. In addition, a catalyst feeding valve 13 is installed between the bottom of the catalyst feeding silo 12 and the screw feeder I.

[0033] This specific embodiment also discloses a method for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons, which is implemented using the above-mentioned apparatus for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons. The specific steps are as follows: ① Catalyst metering: The catalyst is injected into the catalyst silo. By controlling the opening degree and opening time of the corresponding valve plate in the catalyst feeding valve 13, the catalyst is meteredly dropped into the catalyst buffer chamber 14, and then the catalyst feeding valve is closed. ②Pour carbon source gas: Move the carbon nanotube scraping device 5 to the left to a suitable position S1, so that all the catalyst injection holes are located on the right side of the carbon nanotube scraping device. Open the gas valve on the feeding sealing box 2, open the gas valve on the discharging sealing box 11, and open the valve on the tail gas pipe to allow nitrogen to fill the feeding sealing box, furnace tube, and discharging sealing box, thus replacing the oxygen content with less than 1%. Then close the gas valve on the feeding sealing box, close the gas valve on the discharging sealing box, and keep the valve on the tail gas pipe open; after heating the horizontal furnace 11 to the range of 600-900℃, introduce carbon source gas. ③ Catalyst addition: Preheat the carrier gas in the carrier gas source to 100-500℃, open the valve corresponding to the carrier gas source, and spray out the preheated carrier gas at a pressure of 50-1000KPa. Let the carrier gas enter the catalyst buffer chamber 12 and mix with the catalyst to form a gas-solid mixture. The gas-solid mixture is then injected into the high-temperature reaction zone inside the furnace tube 4 through the catalyst injection pipe 15. After the set time Ts is reached, turn off the switch on the carrier gas source. The catalyst addition is now complete. ④ Catalytic cracking: Carbon source gas is continuously introduced into the furnace tube, and the flow rate of the carbon source gas is 1-500 m³ / h. 3 / h, and at the same time, the catalyst carrier gas is injected through step ③, so that the gas-solid mixture becomes a floating state under the action of the carbon source gas in the furnace tube -- so that the catalyst in the gas-solid mixture is in full contact with the carbon source gas. After the carbon-hydrogen bond is broken, carbon atoms are deposited and grown into carbon nanotubes with the catalyst crystal nucleus as the nucleus. The generated carbon nanotubes are deposited inside the furnace tube 4. The waste gas generated during the pyrolysis process flows to the left through the gap between the carbon nanotube scraping device 5 and the inner wall of the furnace tube 4, and is then discharged through the waste gas discharge pipe. ⑤ Carbon nanotube collection: When the carbon nanotube growth time reaches T1, the growth time T1 is 0.5-3.5h. The rope 3 pulls the carbon nanotube pushing and scraping device 5 from position S1 to the right, pushing and scraping the carbon nanotubes grown in the furnace tube 4 to the right and discharging them from the bottom discharge port at the right end of the furnace tube 4. The discharged material falls into the collection box and quickly returns to position S1 after reaching the preset position S2. ⑥ Repeat step ③ to add the catalyst, and continue production through steps ④ and ⑤.

[0034] It should be noted that in this scheme, the carbon nanotube catalyst is at least one of nickel-based, iron-based, and cobalt-based catalysts. During catalyst injection, the catalyst is directly injected into the high-temperature section of the furnace tube by preheating the carrier gas, so as to grow carbon nanotubes by cracking the added high-temperature carbon source gas; the injection form of the catalyst includes, but is not limited to, single-tube injection, multi-tube injection, single-point or multi-point injection, axial or radial injection.

[0035] It should be noted that in this scheme, the carrier gas is hydrogen, argon, nitrogen, or a mixture of hydrogen and argon. The carbon source gas is at least one of methane, propylene or ethylene, or biogas.

[0036] It should be noted that in steps ① and ③, carbon nanotubes of different specifications can be prepared by adjusting the frequency of the motor of the feeding device, the carrier gas pressure and flow rate of the catalyst injection, and the carbon source gas pyrolysis temperature according to different catalysts or different carbon source gases.

[0037] The following detailed embodiments will provide a further understanding and explanation of this solution (it should be noted that although the endpoint values ​​of the corresponding parameters are not mentioned in the following embodiments, they are recorded in the specification and are still within the scope of protection of this solution).

[0038] (Example 1) The catalyst is fed into the catalyst feeding chamber. The nitrogen inlet valve is opened, and nitrogen is introduced to replace the oxygen in the feeding chamber. Once the oxygen content is less than 1%, the nitrogen is turned off. At the same time, the oxygen in the system is replaced to ensure that the oxygen content is ≤1%. The screw motor frequency is set to 3 Hz and the time is 30 minutes. 140 grams of nickel-based catalyst (SiO2 support, nickel oxide) with a loading of 6% is fed into the catalyst buffer chamber through the screw feeder. The catalyst feeding valve is closed, the horizontal furnace is heated to 790℃, the carbon source gas valve is opened, and methane is introduced. The methane flow rate is controlled at 2.5 m3 / h. The waste gas regulating valve is opened to ensure that the pressure difference in the system is about 200±50 Pa. The left winch 1 is started, and the carbon nanotube pushing and scraping device is pulled to the left to position S1 by the winch rope. The catalyst buffer chamber valve is opened, and preheated nitrogen gas at 300°C is introduced. The catalyst in the buffer chamber is then sprayed out through the injection port of the catalyst injection pipe and added to the high-temperature reaction zone inside the furnace tube. After the injection time Ts is 10 seconds, the nitrogen injection valve is closed, and the catalyst addition is complete. Initially, a small portion of the carbon-hydrogen bonds in the methane gas are broken down into carbon atoms and hydrogen at 790°C. The hydrogen reduces nickel oxide in the catalyst to elemental nickel. Using elemental nickel as a nucleus, it catalyzes the breakdown of more carbon-hydrogen bonds in hydrocarbons. Carbon atoms are deposited with nickel as a nucleus to form carbon nanotubes. Part of the hydrogen produced by the breakdown is used to reduce nickel oxide to elemental nickel and generate water, which is discharged as waste gas. The other part of the hydrogen is discharged through the waste gas pipe. In this process, carbon-hydrogen bonds in the furnace tube are broken down into carbon and hydrogen, and carbon atoms are continuously and uniformly loaded on the surface of the nickel-based catalyst to grow into carbon nanotubes. At the same time, part of the hydrogen produced is used as a carrier gas in the furnace tube, and part is discharged through the waste gas pipe. After a growth time T1 of 2.5 hours, the left winch 1 reverses direction, and the right winch 16 starts, pulling the carbon nanotube scraping device to the right by the winch rope. During the movement from left to right, the carbon nanotube scraping device scrapes the carbon nanotubes deposited and grown inside the furnace tube and discharges them through the bottom outlet at the right end of the furnace tube into the receiving sealed box. When it reaches position S2, the left winch 1 rotates forward and the right winch 16 reverses direction. The winch rope pulls the carbon nanotube scraping device to the left and moves it quickly to position S1. The left winch 1 and the right winch 16 then stop.

[0039] After the above reaction is complete, stop heating the horizontal furnace, close the carbon source gas valve, and open the system's nitrogen purging valve (located in the feed and discharge sealing boxes). Purge the waste gas and cool the system with nitrogen for 30 minutes, then close the nitrogen valve. After the reactor cools to room temperature, remove the material to obtain hollow fibrous carbon nanotubes, such as... Figure 3As shown, the carbon nanotubes have good morphology and relatively uniform diameter, with the diameter mainly distributed between 30 and 50 nm.

[0040] (Example 2) The catalyst is fed into the catalyst feeding chamber. The nitrogen inlet valve is opened, and nitrogen is introduced to replace the oxygen in the feeding chamber. Once the oxygen content is less than 1%, the nitrogen is turned off. At the same time, the oxygen in the system is replaced to ensure that the oxygen content is ≤1%. The screw motor frequency is set to 1.5 Hz and the time is 30 minutes. 70 grams of iron-based catalyst (SiO2 as the support and iron oxide as the iron oxide) with a loading of 6% is fed into the catalyst buffer chamber through the screw feeder. The catalyst feeding valve is closed, the horizontal furnace is heated to 660°C, the carbon source gas valve is opened, and propylene is introduced at a flow rate of 1.7 m3 / h. The waste gas regulating valve is opened to ensure that the pressure difference in the system is about +200 Pa. The winch 1 is started, and the carbon nanotube device is pulled to the left to position S1 by the winch rope. The nitrogen valve in the catalyst buffer chamber is opened, and preheated nitrogen at 300°C sprays the catalyst from the buffer chamber through the injection port of the catalyst injection pipe, adding it to the high-temperature reaction zone inside the furnace tube. After the injection time Ts is 10 seconds, the nitrogen injection valve is closed, and the catalyst addition is complete. Initially, a small portion of the carbon-hydrogen bonds in the propylene gas are broken down into carbon atoms and hydrogen at 660°C. The hydrogen reduces nickel oxide in the catalyst to elemental iron. Using elemental iron as a nucleus, it catalyzes the breakdown of more carbon-hydrogen bonds in hydrocarbons. Carbon atoms are deposited with iron as a nucleus to form carbon nanotubes. Part of the hydrogen produced by the breakdown is used to reduce iron oxide to elemental iron and generate water, which is discharged as waste gas. The other part of the hydrogen is discharged through the exhaust port. In this process, carbon-hydrogen bonds in the furnace tube are broken down into carbon and hydrogen, and carbon atoms are continuously and uniformly loaded on the surface of the iron-based catalyst to grow into carbon nanotubes. At the same time, part of the hydrogen produced is used as a carrier gas in the furnace tube, and part is discharged through the exhaust pipe. After a growth time T1 of 1.5 hours, winch 1 reverses direction, and winch 16 starts, pulling the carbon nanotube scraping device to the right by the winch rope. During the movement from left to right, the carbon nanotube scraping device scrapes the carbon nanotubes deposited and grown inside the furnace tube and discharges them through the bottom outlet at the right end of the furnace tube into the receiving sealed box. When it reaches position S2, winch 1 rotates forward and winch 16 reverses direction. The winch rope pulls the carbon nanotube scraping device to move quickly to the left to position S1, and winches 1 and 16 stop.

[0041] After the above reaction is complete, stop heating the horizontal furnace, close the carbon source gas valve, open the system purging nitrogen valve, and purge the system with nitrogen to purge the waste gas and cool the furnace. After purging with nitrogen for 30 minutes, close the nitrogen valve. After the reactor cools to room temperature, remove the material to obtain hollow fibrous carbon nanotubes, such as... Figure 4 As shown, the carbon nanotubes have good morphology and relatively uniform diameter, with the diameter mainly distributed between 10 and 15 nm.

[0042] In summary, the preparation method of the present invention is relatively simple to operate, and different carbon nanotubes can be prepared using all hydrocarbons as carbon source gases and different catalysts.

[0043] The above embodiments only illustrate preferred implementation methods, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this invention, and these all fall within the protection scope of this invention.

Claims

1. An apparatus for preparing carbon nanotubes using a traction-type floating catalyst, characterized in that: Includes a horizontal furnace (11), a carbon nanotube scraping device (5), a catalyst feeding bin (12), and a catalyst injection device II; The horizontal furnace (11) is equipped with a horizontal furnace tube (4), and the left and right ends of the furnace tube (4) are respectively equipped with a feeding sealing box (2) and a discharging sealing box (17); in addition, the discharging sealing box (17) is equipped with a collection box. The furnace tube (4) is connected to a carbon source gas inlet pipe that can be opened and closed near the right end, and the furnace tube (4) is connected to a tail gas pipe that can be opened and closed near the left end. The catalyst feeding bin (12) is located at the left end of the furnace tube (4). The catalyst feeding bin (12) is connected to the catalyst buffer bin (14) via the screw feeder I. The catalyst buffer bin (14) is connected to the catalyst injection device II. The catalyst injection device II is filled with carrier gas, can preheat the carrier gas, and can spray out pressurized carrier gas. The catalyst buffer bin (14) is connected to the catalyst injection pipe (15). The catalyst injection pipe (15) extends into the furnace tube (4) along the inner wall of the furnace tube. When the preheated and pressurized carrier gas is introduced into the catalyst buffer bin (14), the catalyst in the bin can be injected into the furnace tube (4) through the catalyst injection pipe (15) -- so that the catalyst and the carrier gas form a gas-solid mixed phase together, and the gas-solid mixed phase can float when it encounters the carbon source gas, so that the catalyst and the carbon source gas can be in full contact. The furnace tube (4) is equipped with a carbon nanotube scraping device (5). There is a certain gap between the carbon nanotube scraping device (5) and the furnace tube (4). The left and right ends of the carbon nanotube scraping device (5) are pulled by corresponding ropes (3) to form a structure in which the carbon nanotube scraping device can move back and forth in a suspended manner inside the furnace tube.

2. The apparatus for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to claim 1, characterized in that: The end of the catalyst injection pipe (15) that extends into the furnace tube can be inserted to any axial position inside the furnace tube; The end of the catalyst injection pipe (15) that extends into the furnace tube is sealed, and multiple catalyst injection holes are opened on the side wall of the catalyst injection pipe (15). The diameter of the catalyst injection pipe (15) is 10-100 mm, and the diameter of the corresponding catalyst injection hole is adapted to be 1-50 mm.

3. The apparatus for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to claim 2, characterized in that: The number of catalyst injection pipes (15) is 1 to 20, and each catalyst injection pipe (15) is fixed at any position along the inner wall of the furnace tube, including but not limited to the top and bottom of the furnace tube.

4. The apparatus for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to any one of claims 1 to 3, characterized in that: The shape of the carbon nanotube scraping device (5) includes, but is not limited to, a cylinder or various prismatic columns, which can make the gap between the outer side of the carbon nanotube scraping device and the inner wall of the furnace tube 1-50mm.

5. The apparatus for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to claim 1, characterized in that: The rope (3) is covered with a flexible, high-temperature resistant rope tube (10); the corresponding rope (3) and rope tube (10) at the left end of the carbon nanotube pushing and scraping device (5) are pulled and wound onto the left winch (1), and the corresponding rope (3) and rope tube (10) at the right end of the carbon nanotube pushing and scraping device (5) are pulled and wound onto the right winch (16); the left winch (1) and the right winch (16) are respectively installed in the feed sealing box (2) and the discharge sealing box (17), and both are connected to the corresponding traction motor drive, and the corresponding traction motor is electrically connected to the control panel.

6. The apparatus for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to claim 1, characterized in that: The screw feeding device I includes a horizontal pipe, which is connected to the bottom of the catalyst feeding bin (12). The horizontal pipe is equipped with a feeding screw for conveying materials. The feeding screw is connected to the feeding motor drive. The feeding motor is connected to the control panel. The control panel controls the rotation speed and number of rotations of the feeding motor, as well as the start and stop time, so that the catalyst is delivered to the catalyst buffer bin (14) in a timely and quantitative manner. A catalyst feeding valve (13) is also provided between the bottom of the catalyst feeding bin (12) and the screw feeding device I.

7. A method for preparing carbon nanotubes by traction-driven floating catalytic cracking of hydrocarbons, characterized in that: The apparatus for preparing carbon nanotubes using the traction-type floating catalytic cracking of hydrocarbons as described in any one of claims 1 to 6 comprises the following specific steps: ① Catalyst quantitative addition: The catalyst is injected into the catalyst silo. By controlling the opening degree and opening time of the corresponding valve plate in the catalyst feeding valve (13), the catalyst is quantitatively dropped into the catalyst buffer chamber (14), and then the catalyst feeding valve is closed. ② Pass carbon source gas: Move the carbon nanotube pushing and scraping device (5) to the left to a suitable position S1, so that the catalyst injection holes are all located on the right side of the carbon nanotube pushing and scraping device; Open the gas valve on the feeding sealing box (2), open the gas valve on the discharge sealing box (11), and open the valve on the tail gas pipe to allow nitrogen to fill the feeding sealing box, furnace tube, and discharge sealing box so that the oxygen content is less than 1%; Then close the gas valve on the feeding sealing box, close the gas valve on the discharging sealing box, and keep the valve on the tail gas pipe open; after heating the horizontal furnace (11) to a suitable temperature, introduce carbon source gas; ③ Catalyst addition: Open the valve corresponding to the carrier gas source to allow the carrier gas to enter the catalyst buffer chamber (12) and mix with the catalyst -- allowing the catalyst and carrier gas to form a gas-solid mixture, and the gas-solid mixture is injected into the high-temperature reaction zone inside the furnace tube (4) through the catalyst injection pipe (15). After the set time Ts is reached, close the switch on the carrier gas source and the catalyst addition is completed. ④ Catalytic cracking: Carbon source gas is continuously introduced into the furnace tube, and at the same time, the carrier gas of the catalyst is injected through step ③. The gas-solid mixture in the furnace tube becomes a floating state under the action of the carbon source gas. This allows the catalyst in the gas-solid mixture to fully contact the carbon source gas. After the carbon-hydrogen bond is cracked, carbon atoms are deposited and grown into carbon nanotubes with the catalyst crystal nuclei as the nuclei. The generated carbon nanotubes are deposited inside the furnace tube (4). The waste gas generated during the pyrolysis process flows to the left through the gap between the carbon nanotube scraping device (5) and the inner wall of the furnace tube (4), and is then discharged through the waste gas discharge pipe. ⑤ Carbon nanotube collection: When the carbon nanotube growth time reaches T1, the rope (3) pulls the carbon nanotube pushing and scraping device (5) to move to the right from position S1, pushing and scraping the carbon nanotubes grown in the furnace tube (4) to the right and discharging them from the bottom outlet at the right end of the furnace tube (4). The discharged material falls into the collection box and quickly returns to position S1 after reaching the preset position S2. ⑥ Repeat step ③ to add the catalyst, and continue production through steps ④ and ⑤.

8. The method for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to claim 7, characterized in that: The horizontal furnace described above has a heating temperature of 600-900℃; The flow rate of the carbon source gas is 1-500 m³ / h. 3 / h; The carrier gas needs to be preheated to 100-500℃ and the carrier gas pressure is 50-1000KPa; The growth time T1 is 0.5-3.5h.

9. The method for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to claim 7 or 8, characterized in that: The carbon nanotube catalyst is at least one of nickel-based catalysts, iron-based catalysts, and cobalt-based catalysts; During catalyst injection, the catalyst is directly injected into the high-temperature section of the furnace tube by preheating the carrier gas, so as to grow carbon nanotubes by cracking the added high-temperature carbon source gas. The injection form of catalyst injection includes, but is not limited to, single tube injection, multi-tube injection, single point or multi-point injection, axial or radial injection.

10. The method for preparing carbon nanotubes by traction-type floating catalytic cracking of hydrocarbons according to claim 7 or 8, characterized in that: The carrier gas is hydrogen, argon, nitrogen, or a mixture of hydrogen and argon. The carbon source gas is at least one of methane, propylene or ethylene, and biogas.

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