Device and method for preparing single-walled carbon nanotubes by reverse-flow floating catalysis

Abstract

An apparatus and method for preparing single-walled carbon nanotubes by reverse-flow floating catalysis. The apparatus includes a gas-liquid supply device, a floating catalytic cracking device, and a product collection device. The gas-liquid supply device is arranged at the tail end of the floating catalytic cracking device and is interconnected with the floating catalytic cracking device for supplying reaction materials. The head end of the floating catalytic cracking device is interconnected with the product collection device through a pipeline. An inverse gas flow device is further arranged in the floating catalytic cracking device. The inverse gas flow device is located at a position near the discharge end in the floating catalytic cracking device, and the inverse gas flow device is used to form an axial or radial gas flow. The solution of this application introduces an inverse gas flow into the floating catalytic cracking reaction chamber, thereby forming a vortex in the high-temperature zone, greatly increasing the contact time between carbon-containing free radicals and the catalyst, and thus improving the yield of single-walled carbon nanotubes.

Description

Technical Field

[0001] This application relates to the technical field of single-walled carbon nanotubes, and particularly to an apparatus and method for preparing single-walled carbon nanotubes by reverse-flow floating catalysis. Background Art

[0002] As a new type of one-dimensional nanomaterial, single-walled carbon nanotubes (SWCNTs) have been widely used in new energy, transparent display, anti-static, semiconductor, engineering plastics and other fields due to their excellent electrical conductivity, thermal conductivity, heat resistance, chemical resistance and mechanical properties. However, the batch preparation technology of SWCNTs has always restricted their applications in various fields. Therefore, how to achieve low-cost and scalable preparation is an urgent problem to be solved.

[0003] At present, there are mainly three methods for preparing single-walled carbon nanotubes: arc method, laser ablation method, and chemical vapor deposition method. The existing arc method and laser ablation method have low yields and high energy consumption, making it difficult to achieve large-scale production. The floating catalyst chemical vapor deposition method (FCCVD) is the most batchable technical solution at present due to the continuity of raw material supply and product collection (Synthesis of Carbon Nanotubes by Floating Catalyst Chemical Vapor Depositionand TheirApplications. Adv. Funct. Mater. DOI: 10.1002 / adfm.202108541); The main ways to improve the SWCNT synthesis yield based on the FCCVD method are: 1. Optimize the formulation system; 2. Optimize the reactor; 3. Optimize the reaction conditions. By optimizing the C / H / O atomic ratio, adjusting the catalyst and type, and optimizing the process parameters, the yield of carbon nanotubes can be increased to a certain extent, but at the same time, their quality and purity will be reduced. Optimizing the reactor structure is also a way to increase production capacity. However, due to the harsh reaction conditions of single-walled carbon nanotubes, after the cavity structure changes, the temperature field distribution of the furnace body also changes, and the gas flow forms eddies in the cavity. Moreover, the heat capacity of the carrier gas is small, and after introducing cold gas flow, the temperature is uneven at the middle and the tube wall. Carbon nanotubes are more likely to grow along the tube wall, so the yield and purity are relatively low. Recently, the Zhang Rufan research group proposed a substrate interception and guiding strategy to achieve the ultra-high-yield preparation of ultra-long carbon nanotubes. This strategy vaporizes the catalyst solution and introduces it into the front end of the carbon nanotube growth device. At the same time, a high-temperature resistant flat substrate is placed in the middle of the growth device to divide the flow field and intercept floating short carbon nanotubes, enabling a large number of floating short carbon nanotubes to transform into the growth mode of ultra-long carbon nanotubes and improving the utilization rate of the catalyst (Synthesis ofUltralong Carbon Nanotubes with Ultrahigh Yields, Nano Letters, 2023, 23(2), 523-532).

[0004] Therefore, for the preparation of single-walled carbon nanotubes by the existing floating catalytic cracking method, how to optimize the synthesis method from the perspective of the growth mechanism of single-walled carbon nanotubes, fully realize the dynamic process of gasification-cracking-molten carbon-precipitation of organic precursors, improve the utilization efficiency of the catalyst as much as possible, reduce the "wall growth" phenomenon of carbon nanotubes in the traditional floating catalytic cracking method, and achieve "volume growth", so as to improve the yield of single-walled carbon nanotubes, is an urgent problem to be solved. Summary of the Invention

[0005] In view of the above deficiencies of the prior art, the present application provides an apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis, which introduces a reverse air flow into a floating catalytic cracking reaction chamber to form a vortex in a high-temperature zone, greatly increasing the contact time between carbon-containing free radicals and a catalyst, thereby improving the yield of single-walled carbon nanotubes.

[0006] To solve the above technical problems, the technical solution adopted in the present application is as follows: An apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis, which includes a gas-liquid supply device, a floating catalytic cracking device, and a product collection device; the gas-liquid supply device is arranged at the tail end of the floating catalytic cracking device and is in communication with the floating catalytic cracking device to supply reaction materials; the head end of the floating catalytic cracking device is in communication with the product collection device through a pipeline; a reverse air flow device is further arranged in the floating catalytic cracking device, the reverse air flow device is located at a position near the discharge end in the floating catalytic cracking device, and the reverse air flow device is used to form an axial or radial air flow.

[0007] With the above structure, the present application for the first time arranges a reverse air flow device at a position near the discharge end in the floating catalytic cracking device. By introducing gas through this reverse air flow device, an air flow extending axially or radially is formed in the cracking device. This air flow can interact with the rising reaction air flow to generate a vortex or turbulence, greatly increasing the contact time between carbon-containing free radicals and the catalyst in the floating catalytic cracking device, thereby improving the utilization rate of the catalyst and further improving the yield of single-walled carbon nanotubes.

[0008] Further, the end face of the reverse air flow device near the gas-liquid supply device is located at the critical point between the heating zone and the heat preservation zone near the discharge end in the floating catalytic cracking device; this critical point here is a position in the floating catalytic cracking device near the discharge end that is lower than the defined temperature of the high-temperature zone. For example, if the defined temperature of the high-temperature zone is 1400 °C, then the position lower than 1400 °C is the critical point. Starting from this point is the heat preservation zone, and this critical point is the critical position; with this structure, a vortex or turbulence can be formed at this critical point position to improve the yield of the target product, and the gasification of materials in the low-temperature zone will not be affected at this position.

[0009] Further, the reverse air flow device includes a gas guide pipe and an air flow dispersion disk. The air flow dispersion disk is placed inside the floating catalytic cracking device and is in communication with the gas guide pipe. The other end of the gas guide pipe extends out of the floating catalytic cracking device and is used for gas transmission; with this structure, the air flow can be conveniently introduced into the air flow dispersion disk, and then output to the floating catalytic cracking device through the air flow dispersion disk to interact with the reaction air flow and form a vortex.

[0010] Further, the air duct is connected to the axial side wall or one end face of the air flow dispersion disk, and the outer wall of the air duct is closely attached to the inner wall of the floating catalytic cracking device; with the above structure, the area of the air duct exposed to the inner cavity of the floating catalytic cracking device can be minimized, thereby preventing the product from adhering to the air duct and causing loss of yield.

[0011] Furthermore, the air duct is made of a high-temperature resistant inorganic material such as 310S stainless steel pipe, corundum pipe, quartz pipe or graphite pipe, preferably 310S stainless steel pipe; with the above structure, the air duct can withstand the high temperature in the inner cavity of the floating catalytic cracking device, avoiding deformation of the air duct and affecting the gas transportation.

[0012] Furthermore, the inner diameter of the air duct is 6 - 12 mm, and the wall thickness is 0.5 - 2 mm. With this structure, not only can the air duct be effectively and fixedly connected to the dispersion disk, but also a sufficient and appropriate amount of gas can be transported to meet the formation of vortices at the critical point.

[0013] Further, the air flow dispersion disk is a convection air flow dispersion disk (used to form an air flow opposite to the axial direction of the reaction air flow), or a vertical air flow dispersion disk (forming a radial air flow perpendicular to the reaction air flow); with the above structure, different-direction air flows can be formed through these two methods, and the vortex effect at the critical points of the low-temperature zone and the high-temperature zone can be achieved.

[0014] Furthermore, the diameter of the convection air flow dispersion disk is 1 / 2 - 2 / 3 of the inner diameter of the inner cavity of the floating catalytic cracking device, and the placement position is set at the critical point between the heating zone (high-temperature zone) and the heat preservation zone and is centered; the axial length of the convection dispersion disk is 12 - 50 mm; with this structure, the formation of a vortex air flow with a sufficient area can be ensured, and it is located at the critical point between the high-temperature zone and the heat preservation zone, thereby achieving the effect of prolonging the contact time between carbon-containing free radicals and the catalyst. Moreover, this size of the convection air flow dispersion disk has a certain gap from the inside of the floating catalytic cracking device and will not block the reaction materials, ensuring the continuous operation of the reaction materials towards the next process; setting its axial length can also prevent the deposition of carbon nanotube products in the heat preservation zone and prevent the deposited products from hindering the discharge of the products with the carrier gas.

[0015] Furthermore, the vertical flow type air flow dispersion disc is of a hollow cylindrical type, and the outer diameter of the hollow cylindrical vertical flow type air flow dispersion disc is equivalent to the inner diameter of the inner cavity of the floating catalytic cracking device; the wall thickness of the hollow cylindrical vertical flow type air flow dispersion disc is 10 - 20 mm, the inner wall is a microporous titanium plate, a microporous stainless steel plate, a microporous nickel plate, a microporous corundum plate or a microporous graphite plate, and the micropore direction extends along the radial direction; with this structure, air flow can be blown inward in the radial direction, and mixed and collided with the rising process gas to form a vortex, and then they run upward together.

[0016] Further, the convective air flow dispersion disc is composed of integrally formed high-temperature resistant alumina ceramics, and a gas guide pipe is connected to one end or the side wall in the axial direction, and the other end is an air outlet end face and is provided with a microporous structure, and the air outlet end face is close to the side of the gas-liquid supply device; with this structure, it can adapt to the high temperature in the inner cavity of the floating catalytic cracking device, and at the same time, through the setting of the microporous structure, the introduced air flow is dispersed and ejected, and the direction is opposite to the process air flow, so as to form a larger contact area with the rising material and extend the contact time between the carbon-containing free radicals and the catalyst.

[0017] Furthermore, the axial extension length of the vertical flow type air flow dispersion disc is 50 - 100 mm, and its position is set at the critical point between the heating zone and the heat preservation zone in the upper part of the inner cavity of the floating catalytic cracking device; with this structure, the length of the vertical flow type air flow dispersion disc can cover the length range at the critical point between the heating zone and the heat preservation zone, achieve a sufficient vortex effect, and increase the yield of the target product.

[0018] Further, the convective air flow dispersion disc can also be composed of a stainless steel cavity body and a microporous metal plate sealed by a sealing member, and a gas guide pipe is connected to one end or the side wall in the axial direction, and the other end is an air outlet end face which is composed of one of a microporous titanium plate, a microporous stainless steel plate, a microporous nickel plate, a microporous corundum plate or a microporous graphite plate; this structure is convenient for disassembly to replace the microporous plate.

[0019] Furthermore, the aperture of each micropore (the micropore on the air flow dispersion disc for forming axial and radial air flows) is 5 - 30 μm, and the porosity is 50% - 90%; with this structure, a uniform reverse vortex gas can be formed to have a larger contact area with the rising reaction air flow, so as to extend the contact time between the carbon-containing free radicals and the catalyst.

[0020] Furthermore, the gas-liquid supply device includes a gas pipeline, a stainless steel capillary liquid pipeline, and a sealing flange; the gas pipeline and the stainless steel capillary liquid pipeline are hermetically connected to the flange, and the sealing flange is connected to the feed end of the fluid catalytic cracking device through a high-temperature sealing ring; with the above structure, the effective transportation of gas-liquid materials can be achieved, and the sealing effect with the outside world can be realized, ensuring that the materials in the furnace tube of the fluid catalytic cracking device react sufficiently.

[0021] Furthermore, the gas pipeline surrounds and covers the outer periphery of the stainless steel capillary liquid pipeline. Axially, the outlet end of the stainless steel capillary liquid pipeline extends out of the outlet end of the gas pipeline, and the distance between their outlet ends is 5 - 20 mm; with this structure, the liquid material transported from the stainless steel capillary liquid pipeline is at a higher position compared to the gas coming out of the gas pipeline, thus facilitating the gas to drive the liquid to move upward together; moreover, the structure of the gas pipeline surrounding and covering the capillary liquid pipeline is adopted because if the gas pipeline and the capillary liquid pipeline are separately and independently arranged, the liquid coming out of the capillary is likely not to move upward sufficiently. By surrounding and covering and setting a specific outlet height difference, the liquid can be fully carried by the carrier gas of the gas pipeline to the high-temperature zone for reaction, improving the reaction efficiency.

[0022] Furthermore, the inner diameter of the stainless steel capillary liquid pipeline is 0.3 - 1.5 mm; a gas distributor is arranged at the tail end (upper part near the outlet end) of the gas pipeline. The outlet ends of the gas pipeline and the stainless steel capillary are both located inside the gas distributor and are hermetically connected to the gas distributor (the seal refers to the seal at the connection, and the material outlets on the gas distributor are in normal use); the purpose and effect of setting the gas distributor here are to enable the reaction materials to move upward in a more dispersed manner and distribute as much as possible over the inner diameter area of the furnace tube, so as to obtain sufficient heating and mixing and react more thoroughly.

[0023] Furthermore, the gas distributor is arranged inside the fluid catalytic cracking device, and the temperature inside the gas distributor is controlled at 300°C - 500°C; this temperature is the temperature inside the gas distributor. The setting of this temperature can make the materials inside the gas distributor gasify and mix more evenly and then be blown into the reaction zone, making the reaction more thorough.

[0024] Furthermore, the gas distributor is composed of a porous nickel mesh, a copper mesh, a titanium mesh, or a microporous ceramic; this structure can make the material flow disperse more evenly and the reaction more sufficient.

[0025] Further, the floating catalytic cracking device includes a heating furnace body and an internal furnace tube (the heating furnace body is wrapped around the outer periphery of the furnace tube). The heating furnace body is composed of silicon molybdenum rod or silicon carbide rod heating elements and polycrystalline alumina fiber thermal insulation materials. The heating temperature of the heating furnace body is 1100 - 1400 °C, and the heating zone length is 300 - 1000 mm. The furnace tube of the floating catalytic cracking device is composed of corundum tube or silicon carbide tube. The diameter of the furnace tube is 60 - 500 mm, and the length is 1000 - 3000 mm. With this structure, a low-temperature zone near both ends and a high-temperature zone in the middle are formed within the axial length of the furnace tube. The high-temperature zone is wrapped by the heating furnace body to achieve high temperature, and the two ends can be made into a low-temperature zone compared with the high-temperature zone through heat preservation and temperature control. And the gas flow dispersion plate of the present application is arranged in the critical zone between the high-temperature zone and the low-temperature zone above the furnace tube. In this area, the materials transported from the gas-liquid supply device below have been fully reacted and will not interfere with the reaction. At the same time, in this critical zone, the final single-walled carbon nanotubes have not been formed yet, but vortices are formed here (the end of the high-temperature zone disorderly disperses the process gas flow to form continuous and stable turbulence). This is essentially different from the reported floating catalytic method. This method enables the catalyst and carbon-containing free radicals to contact more fully in the high-temperature zone, improves the defect that carbon nanotubes grow along the tube wall in the traditional floating catalytic cracking method, greatly improves the catalyst utilization rate and the carbon source conversion rate, and is more likely to achieve volume growth.

[0026] Further, the product collection device includes a collection tank, a back-blowing chamber, a microporous filter plate, and an air extraction device. The back-blowing chamber is interconnected with the discharge pipeline of the floating catalytic cracking device. The microporous filter plate is located above the discharge pipeline, and the air outlet of the air extraction device is located above the microporous filter plate. The collection tank is located below the back-blowing chamber. With the above connection method, air can be extracted through the air extraction device and the air outlet, so that the air flow drives the product to adhere to the bottom surface of the microporous filter plate, thereby realizing the collection of the product. And when there is too much product adhering to the bottom surface of the microporous filter plate, the product can also be blown off into the collection tank by blowing air from the outlet gas towards the microporous filter plate in the reverse direction.

[0027] Furthermore, the microporous filter plate can be a microporous titanium plate or a microporous copper plate made of metal, etc., or a sand core filter plate made of ceramic material.

[0028] The present application also provides a method for preparing single-walled carbon nanotubes using the device for preparing single-walled carbon nanotubes by reverse flow floating catalysis as described above. Specifically, this method includes:

[0029] (1) Connect the gas-liquid pipelines, and install the reverse gas flow device at a set position (the critical point between the high-temperature zone and the heat preservation zone) inside the furnace tube of the floating catalytic cracking device;

[0030] (2) Vent the process gas and set the process temperature according to the process requirements.

[0031] (3) Keep the temperature for 25 - 40 minutes after the set temperature is reached.

[0032] (4) Open the gas - liquid supply device, feed materials according to the set gas flow rate and liquid supply rate, and set the gas flow rate of the reverse gas flow device to start synthesizing single - wall carbon nanotubes.

[0033] (5) Collect the product into the product collection device.

[0034] Further, the gas flow rate of the reverse gas flow device is 50% - 120% of the gas flow rate of the gas - liquid supply device; if the reverse gas flow rate is too low, the contact between the catalyst and carbon - containing free radicals in the high - temperature zone is insufficient, and the result is not much different from traditional floating - catalyst cracking; if the reverse gas flow rate is too high, the gas flow rate in the high - temperature zone is too fast, the growth time of carbon nanotubes is short, and the yield decreases.

[0035] Further, the process gas or the gas in the gas - flow dispersion plate is one or a mixture of nitrogen, argon, helium, and hydrogen, and argon is preferred.

[0036] Further, the process temperature in step (2) is: 1100 - 1500 °C for the high - temperature cavity.

[0037] Further, the liquid supplied in step (4) is an organic liquid precursor, which can be a formulation for synthesizing single - wall carbon nanotubes reported in the literature and known patents, generally including a carbon source, a catalyst, a promoter, an etchant, etc. The carbon source is a liquid carbon source such as ethanol, methanol, toluene, xylene, tetrahydrofuran, benzene, n - hexane, cyclohexane, etc., or a gaseous carbon source such as methane, acetylene, etc.; the catalyst is generally ferrocene, nickelocene, cobaltocene, ferric chloride, iron carbonyl, iron lactate, etc. (the solid catalyst can be placed in a specific position in the furnace tube in advance, and if it is a gas, it is transported into the furnace tube through a gas pipeline); the promoter is generally a sulfur - containing compound such as thiophene.

[0038] Further, the gas and liquid flow rates of the gas - liquid supply device are consistent with the process parameters for synthesizing single - wall carbon nanotubes reported in the literature and known patents, and these parameters vary depending on the formulation and the diameter of the furnace tube.

[0039] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0040] (1) The technical solution of this application first introduces an air flow dispersion disk into the floating catalytic cracking device, and the position of this air flow dispersion disk is crucial because its main function is to form vortex (turbulent) disturbances in the critical area between the high-temperature zone and the heat preservation zone, improving the contact efficiency between the catalyst and carbon-containing free radicals; when the air flow dispersion disk is completely placed in the high-temperature zone, the generated turbulence destroys the environment for carbon source and catalyst cracking, having a negative impact on it, resulting in too large catalyst size and reduced activity; when the air flow dispersion disk is completely placed in the heat preservation zone after the high-temperature zone, the carbon source completes the cracking-melting process under the action of the catalyst, and forms carbon nanotube products by supersaturated precipitation in the heat preservation zone (low-temperature zone). The reverse air flow has an insignificant effect on improving the synthesis yield of single-walled carbon nanotubes, but instead causes network-shaped carbon nanotube fibers to block here, resulting in inconvenient collection; therefore, the reverse air flow device in this application is set at the end of the high-temperature zone (i.e., the critical point between the high-temperature zone and the heat preservation zone), opposite or perpendicular to the process air flow direction (the air flow conveyed by the gas-liquid supply device), and disorderly disperses the process air flow at the end of the high-temperature zone to form continuous and stable turbulence, which is essentially different from the reported floating catalytic method. This solution of this application can make the catalyst and carbon-containing free radicals contact each other more fully in the high-temperature zone, improving the defect that carbon nanotubes grow along the tube wall in the traditional floating catalytic cracking method, greatly enhancing the catalyst utilization rate and carbon source conversion rate, and making it easier to achieve volume growth.

[0041] (2) The reverse air flow in this application does not interfere with the behavior of the process gas in the low-temperature zone and does not affect the gasification of the catalyst and carbon source. At the same time, the introduction of the reverse air flow increases the air flow velocity in the reaction chamber at the rear end of the high-temperature zone (because after the air flow of the air flow dispersion disk is mixed with the process air flow, the two flow out simultaneously from the gap between the vertical air flow dispersion disk or the convective air flow dispersion disk and the inner wall of the furnace tube. At this time, the gas volume is the sum of the two gas volumes, so the gas volume increases, and the air outlet area decreases, so the gas flow velocity increases). Therefore, carbon nanotubes are not easily lapped into a network fiber structure and do not block the pipe orifice, making it easier to collect single-walled carbon nanotube powder and easier to achieve large-scale preparation.

[0042] (3) Compared with the traditional floating catalytic cracking method, the yield of single-walled carbon nanotubes in this application is increased by 3 to 5 times, the carbon source conversion rate is 3 to 7%, the purity analyzed by TGA is 60% to 85%, and the Raman I D / I G is 0.1 to 0.4, and the diameter of single-walled carbon nanotubes is about 1.8 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic structural diagram of a reverse flow floating catalytic cracking device according to an embodiment of this application.

[0044] Figure 2Schematic structural diagram of the reverse flow floating catalytic cracking device according to another embodiment of the present application.

[0045] Figure 3 Schematic structural diagram of the convection airflow dispersion plate according to the present application.

[0046] Figure 4 Schematic structural diagram of the vertical flow airflow dispersion plate according to the present application.

[0047] Figure 5 Schematic structural diagram of the gas-liquid supply device according to the present application.

[0048] Figure 6 Schematic structural diagram of the reverse airflow device according to the present application.

[0049] Figure 7 Schematic structural diagram of the reverse flow floating catalytic cracking device (vertical flow type) according to the third embodiment of the present application.

[0050] Figure 8 Schematic structural diagram of the vertical flow reverse airflow device according to the present application.

[0051] Figure 9 Photo of the carbon nanotube product in a preferred embodiment of the present application.

[0052] Figure 10 Raman spectrum of single-walled carbon nanotubes in a preferred embodiment of the present application.

[0053] As shown in the attached drawings: As shown in the attached drawings: 1 - gas-liquid supply device; 11 - gas pipeline; 12 - stainless steel capillary liquid pipeline; 13 - sealing flange; 14 - gas distributor; 15 - perforated plate of the gas distributor; 2 - floating catalytic cracking device; 21 - heating furnace body; 22 - furnace tube; 23 - heating element; 3 - product collection device; 31 - collection tank; 32 - product back-blowing chamber; 33 - microporous filter plate; 34 - air outlet (exhaust port); 4 - reverse airflow device; 41 - air guide pipe; 42 - airflow dispersion plate; 43 - air outlet end face. Detailed implementation manners

[0054] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the embodiments and the attached drawings. Obviously, the described embodiments are only preferred embodiments, rather than all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application;

[0055] In addition, it should be noted that when a component is referred to as "fixed to" another component, it can be directly on the other component or there may be another intermediate component through which it is fixed. When a component is considered to be "connected" to another component, it can be directly connected to the other component or there may be another intermediate component at the same time. When a component is considered to be "disposed on" another component, it can be directly disposed on the other component or there may be another intermediate component at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used in this article are only for the purpose of illustration. Unless otherwise defined, all technical and scientific terms used in this article have the same meaning as commonly understood by those skilled in the technical field to which this application belongs. The terms used in the specification of this application in this article are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this article includes any and all combinations of one or more of the related listed items.

[0056] As shown in the attached Figure 1-8 figure, a device for preparing single-walled carbon nanotubes by reverse flow floating catalysis according to the present application, the device includes a gas-liquid supply device 1, a floating catalytic cracking device 2 and a product collection device 3; the gas-liquid supply device 1 is disposed at the tail end of the floating catalytic cracking device 2 (the lower end when in a vertical structure, the left end when in a horizontal structure as shown Figure 1 in the vertical structure, and the left end when in a horizontal structure as shown Figure 2 in the figure) and is in communication with the floating catalytic cracking device 2 to supply reaction materials; the head end of the floating catalytic cracking device 2 (the upper end when in a vertical structure, the right end when in a horizontal structure as shown Figure 1 in the vertical structure, and the right end when in a horizontal structure as shown Figure 2 in the figure) is in communication with the product collection device 3 through a pipeline; a reverse air flow device 4 is further disposed in the floating catalytic cracking device 2, and the reverse air flow device 4 is located at a position close to the discharge end in the floating catalytic cracking device 2 (the position close to the upper end when in a vertical structure, as shown Figure 1 in the vertical structure, and the position close to the upper end when in a vertical structure, as shown Figure 2The horizontal structure shown is at a position near the right end. The reverse air flow device 4 is used to form an axial or radial air flow (that is, the reverse air flow device will eject an air flow, and this air flow is axially opposite or vertically in contact with the reaction material air flow coming from the direction of the gas-liquid supply device, thereby forming a turbulent flow or a so-called eddy current). More preferably, the reverse air flow device 4 is arranged at the critical point between the heating zone and the heat preservation zone near the discharge end in the fluid catalytic cracking device. Specifically, the end face of the reverse air flow device 4 close to the gas-liquid supply device 1 side is placed at the critical point between the heating zone and the heat preservation zone in the upper part of the fluid catalytic cracking device 2. This critical point is the critical point between the high-temperature zone and the heat preservation zone in the fluid catalytic cracking device. For example, if the defined temperature in the high-temperature zone is 1400 °C, then the point below 1400 °C is the critical point, and from this point on is the heat preservation zone. This critical point can also be called the rear end position of the high-temperature zone.

[0057] With the above structure, the present application first sets a reverse air flow device in the fluid catalytic cracking device. By introducing gas through this reverse air flow device, an eddy current is formed at the critical point between the heat preservation zone (low-temperature zone) and the high-temperature zone of the fluid catalytic cracking device, greatly increasing the contact time between the carbon-containing free radicals and the catalyst in the fluid catalytic cracking device, thereby improving the utilization rate of the catalyst and further increasing the yield of single-walled carbon nanotubes.

[0058] As shown in Figure 1-4 Figures 7-8, the reverse air flow device 4 described in the present application includes a gas guide pipe 41 and an air flow dispersion disk 42. The air flow dispersion disk 42 is placed inside the fluid catalytic cracking device 2 and is connected to the gas guide pipe 41. The other end of the gas guide pipe 41 (the end not connected to the air flow dispersion disk) extends out of the fluid catalytic cracking device 2 and is used for gas transmission. With this structure, the air flow can be conveniently introduced into the air flow dispersion disk through the gas guide pipe, and then output to the fluid catalytic cracking device through the air flow dispersion disk to interact with the above-mentioned air flow of the gas-liquid supply device to form a continuous and stable eddy current, prolonging the contact between the catalyst and the carbon-containing free radicals in the high-temperature region more fully, improving the defect that carbon nanotubes grow along the tube wall in the traditional fluid catalytic cracking method, greatly enhancing the utilization rate of the catalyst and the conversion rate of the carbon source, and making it easier to achieve volume growth.

[0059] As shown in Figure 1-4 Figures 7-8, the gas guide pipe 41 described in the present application is connected to the axial side wall or one end face of the air flow dispersion disk 42, and the outer wall of the gas guide pipe 41 is closely attached to the inner wall of the fluid catalytic cracking device. With the above structure, the area of the gas guide pipe exposed to the inner cavity of the fluid catalytic cracking device can be minimized, thereby preventing the product from adhering to the gas guide pipe and causing a loss in yield.

[0060] As an example, the gas guide pipe 41 described in the present application is composed of high-temperature resistant inorganic materials such as 310S stainless steel pipe, corundum pipe, quartz pipe or graphite pipe, and 310S stainless steel pipe is preferred; with the above structure, the gas guide pipe can withstand the high temperature in the inner cavity of the floating catalytic cracking device, avoiding deformation of the gas guide pipe and affecting the gas transportation.

[0061] As an example, the inner diameter of the gas guide pipe 41 described in the present application is 6-12 mm, and the wall thickness is 0.5-2 mm. With this structure setting, it can not only effectively fix and connect the gas guide pipe with the dispersion plate, but also transport a sufficient and appropriate amount of gas to meet the formation of eddy currents in the high-temperature area.

[0062] As shown in the appendix Figure 2 、 4 and 8, the gas flow dispersion plate 42 described in the present application is a convective gas flow dispersion plate ( Figure 2 shown), or a vertical gas flow dispersion plate ( Figure 4 、 8 shown); both gas flow dispersion plates are cylindrical structures; specifically, the body of the convective gas flow dispersion plate is provided with a cavity, and the end face close to the gas-liquid supply device is an end face with evenly distributed micropores. The gas flow of the gas guide pipe is introduced into the cavity and then ejected from the micropores of the micropore end face, just aligning with the gas flow provided by the gas-liquid supply device, and the two interact to form a stable eddy current or turbulence at this place; for the vertical gas flow dispersion plate, the body of the dispersion plate is a hollow cylindrical structure that penetrates up and down, and it has double-layered side walls with a sandwich. A plurality of evenly distributed micropores are radially arranged on the inner side wall close to it. The gas guide pipe introduces the gas flow into the sandwich and then ejects it radially from the micropores, just perpendicular to the gas flow provided by the gas-liquid supply device, and the two gas flows interact to form turbulence; with the above structure, different directions of gas flows can be formed through the above two methods, and the eddy current effect at the critical point between the low-temperature area and the high-temperature area can be achieved.

[0063] As an example, the diameter of the convective gas flow dispersion disk 42 described in the present application is 1 / 2 to 2 / 3 of the inner diameter of the inner cavity of the floating catalytic cracking device 2. The placement position (being set at the critical point between the heating zone (high-temperature zone) and the heat preservation zone specifically means that the end face of the convective gas flow dispersion disk close to the gas-liquid supply device is set at the critical point) and is centered (that is, the gas flow dispersion disk is cylindrical, and its outer edge is equidistant from the inner wall of the floating catalytic cracking device, that is, the two are coaxially arranged); the axial length of the convective dispersion disk is 12 - 50 mm; adopting this structure can ensure the formation of a vortex gas flow with sufficient area, and make it located at the critical point between the high-temperature zone and the heat preservation zone, thereby achieving the effect of prolonging the contact time between the carbon-containing free radicals and the catalyst. Moreover, the convective gas flow dispersion disk of this size has a certain gap from the inside of the floating catalytic cracking device and will not block the reaction materials, ensuring the continuous operation of the reaction materials towards the next process; setting its axial length can avoid the deposition of carbon nanotube products in the heat preservation zone and prevent the deposited products from hindering the discharge of the products with the carrier gas.

[0064] As an example, as shown in the appendix Figure 7-8 The vertical gas flow dispersion disk 42 described in the present application is of a hollow cylindrical type. The outer diameter of the hollow cylindrical vertical gas flow dispersion disk is equivalent to the inner diameter of the inner cavity of the floating catalytic cracking device (that is, the inner and outer diameters of the two are mutually adapted, and the gas flow runs through the hollow cavity that runs through the vertical gas flow dispersion disk up and down); the wall thickness of the hollow cylindrical vertical gas flow dispersion disk is 10 - 20 mm (the difference between the outermost circumference and the inner side wall), and the inner wall is provided with an air outlet end face 43. The air outlet end face can specifically be a microporous titanium plate, a microporous stainless steel plate, a microporous nickel plate, a microporous corundum plate or a microporous graphite plate, etc., and the micropore direction extends along the radial direction; adopting this structure can realize the inward blowing of the gas flow in the radial direction, and form a vortex after mixing and colliding with the rising process gas, and then run upward together.

[0065] As an example, the convective gas flow dispersion disk 42 described in the present application is composed of integrally formed high-temperature resistant alumina ceramics, and one end or side wall of its axis ( Figure 3 as shown) is connected with a gas guide pipe 41, and the other end is an air outlet end face 43 and is set into a microporous structure. The air outlet end face 43 is close to the side of the gas-liquid supply device; adopting this structure can adapt to the high temperature of the inner cavity of the floating catalytic cracking device, and at the same time, through the setting of the microporous structure, the introduced gas flow is dispersed and ejected, and the direction is opposite to the process gas flow, so as to form a larger area of contact with the rising material gas flow and prolong the contact time between the carbon-containing free radicals and the catalyst.

[0066] As an example, the axial extension length of the vertical flow type gas flow dispersion disk described in the present application is 50 to 100 mm, and its position is set at the critical point between the heating zone and the heat preservation zone in the upper part of the inner cavity of the floating catalytic cracking device (that is, the end face of the vertical flow type gas flow dispersion disk close to the gas-liquid supply device side is located at this critical point, so as to form a turbulent gas flow at this critical point); adopting this structure, the length of the vertical flow type gas flow dispersion disk can cover the length range of the critical point between the heating zone and the heat preservation zone, achieve sufficient eddy current effect, and increase the yield of the target product.

[0067] As an example, the convective gas flow dispersion disk 42 described in the present application can also be composed of a stainless steel cavity (that is, a cylinder with one end open, and the open end and the microporous metal plate are sealed with each other through a seal) and the microporous metal plate sealed by a seal. One end or the side wall of its axis is connected with a gas guide pipe 41 (the gas guide pipe is connected to the sealed end of the microporous metal plate at the opposite end of the axis and communicates with the inside of the stainless steel cavity, introduces the gas flow and sprays it out from the micropores of the microporous metal plate, and contacts the process gas flow reversely to form a turbulent flow), and the other end is the gas outlet end face 43 which is composed of one of a microporous titanium plate, a microporous stainless steel plate, a microporous nickel plate, a microporous corundum plate or a microporous graphite plate; this structure is convenient for disassembly to replace the microporous plate.

[0068] As an example, the aperture of each micropore described in the present application is 5 to 30 μm, and the porosity is 50% to 90% (that is, the distribution rate of these micropores on the opposite inner wall or end face); adopting this structure can form a uniform reverse eddy current gas to contact with the rising material over a larger area, thereby prolonging the contact time between the carbon-containing free radicals and the catalyst.

[0069] As shown in Figure 1-2 Figures 5 and 7, the gas-liquid supply device 1 described in the present application includes a gas pipeline 11, a stainless steel capillary liquid pipeline 12 and a sealing flange 13; the gas pipeline 11 and the stainless steel capillary liquid pipeline 12 are hermetically connected to the flange 13, and the sealing flange 13 is connected to the furnace tube 22 of the floating catalytic cracking device 2 through a high-temperature sealing ring; adopting the above structure, the effective transportation of gas-liquid materials can be realized, and the sealing effect with the outside can be realized, ensuring the full reaction of the materials in the furnace tube of the floating catalytic cracking device.

[0070] As shown in Figure 1-2, as shown in Figures 5 and 7, the gas pipeline 11 described in this application is wrapped around the outer periphery of the stainless steel capillary liquid pipeline 12. Axially, the upper end outlet of the stainless steel capillary liquid pipeline 12 extends out of the upper end outlet of the gas pipeline 11, and the outlet spacing between the two is 5 - 20 mm (that is, the upper ports of both the stainless steel capillary liquid pipeline and the gas pipeline extend into the furnace tube, and the upper port of the stainless steel capillary liquid pipeline extends out of the upper port of the gas pipeline body, forming a drop between the two); an intake branch pipe extends from the side wall of the gas pipeline in this application, and gas enters the gas pipeline from this side branch pipe. The lower end face of the gas pipeline is sealed with the capillary; with this structure, the liquid material transported from the stainless steel capillary liquid pipeline is at a higher position than the gas coming out of the gas pipeline, thus facilitating the gas to drive the liquid to move upward together; moreover, the structure of using the gas pipeline to wrap around the capillary liquid pipeline is because if the gas pipeline and the capillary liquid pipeline are set independently, the liquid coming out of the capillary is likely not to fully move upward. By wrapping around and setting a specific outlet drop, the liquid can be fully carried by the carrier gas of the gas pipeline to the high-temperature zone for reaction, improving the reaction efficiency.

[0071] As an example, the inner diameter of the stainless steel capillary liquid pipeline 12 described in this application is 0.3 - 1.5 mm; a gas distributor 14 is provided at the tail end (near the outlet end in the upper part) of the gas pipeline 11. The outlet ends of the gas pipeline 11 and the stainless steel capillary pipeline 12 are both located inside the gas distributor 14 and are hermetically connected to the gas distributor 14 (only discharging through the micropores of the gas distributor); the purpose and effect of setting the gas distributor here is to enable the reaction materials to move upward in a more dispersed manner and distribute as much as possible over the inner diameter area of the furnace tube, so as to obtain sufficient heating and mixing and make the reaction more thorough.

[0072] As an example, the gas distributor 14 described in this application is arranged inside the furnace tube 22 for catalytic cracking, and the temperature inside the gas distributor 14 is controlled at 300°C - 500°C; this temperature is the temperature inside the gas distributor. The setting of this temperature can make the materials inside the gas distributor gasify and mix more evenly and then be blown into the reaction zone, making the reaction more thorough. As an example, the gas distributor 14 described in this application is composed of porous nickel mesh, copper mesh, titanium mesh or microporous ceramic; this structure can make the dispersion more uniform and the reaction more sufficient.

[0073] As an example, the floating catalytic cracking device 2 described in the present application includes a heating furnace body 21 and an internally disposed furnace tube 22. The heating furnace body 21 is composed of heating elements 23 such as silicon molybdenum rods or silicon carbide rods (the heating unit is used for heating the furnace body) and polycrystalline alumina fiber thermal insulation materials. The heating temperature of the heating furnace body 21 is 1100 - 1400 °C, and the length of the heating zone is 300 - 1000 mm (the heating furnace body is wrapped outside the furnace tube and is centered along the axial direction of the furnace tube, covering a part of the length of the furnace tube); the furnace tube 22 of the floating catalytic cracking device 2 is made of materials such as corundum tubes or silicon carbide tubes. The diameter (inner diameter) of the furnace tube 22 is 60 - 500 mm, and the length is 1000 - 3000 mm; with this structure, a low-temperature zone (or insulation zone) near both ends and a high-temperature zone or heating zone in the middle are formed within the axial length of the furnace tube. The high-temperature zone is wrapped with the heating furnace body to achieve the high-temperature heating function. There is no heating furnace body wrapping at both ends, and a low-temperature zone or insulation zone compared to the high-temperature zone can be achieved through heat insulation measures and temperature control measures; and the gas flow dispersion plate of the present application is arranged in the critical zone between the high-temperature zone and the insulation zone (low-temperature zone) above the furnace tube. In this area, the materials transported from the gas-liquid supply device below have fully reacted and will not interfere with the reaction. At the same time, in this critical zone, the final single-walled carbon nanotubes have not been formed yet. Instead, the process gas flow is disorderly dispersed through the gas flow dispersion plate at the end of the high-temperature zone to form a continuous and stable turbulent flow or eddy current; therefore, the above-mentioned solution of the present application is essentially different from the reported floating catalytic method. This method enables the catalyst and carbon-containing free radicals to contact more fully in the high-temperature region, improves the defect of carbon nanotube growth along the tube wall in the traditional floating catalytic cracking method, greatly improves the catalyst utilization rate and carbon source conversion rate, and is more likely to achieve volume growth.

[0074] As shown in the appendix Figure 1-2 and 7, the product collection device 3 described in the present application includes a collection tank 31, a backflush chamber 32, a microporous filter plate 33, and an air extraction device (conventional devices such as an air extraction pump for realizing air flow extraction can be omitted here); the backflush chamber 32 is interconnected with the discharge pipeline of the floating catalytic cracking device 2. The microporous filter plate 33 is located above the discharge pipeline, and the air outlet (exhaust port) 34 of the air extraction device is located above the microporous filter plate 33; the collection tank 21 is located below the backflush chamber 32; there is a narrowed channel between the collection tank and the backflush chamber to prevent the material from being back-extracted into the collection tank; with the above connection method, air can be extracted through the air extraction device and the air outlet, so that the air flow drives the product to adhere to the bottom surface of the microporous filter plate, thereby realizing the collection of the product; and when too much product adheres to the bottom surface of the microporous filter plate, the product can also be blown onto the microporous filter plate in the reverse direction by the outlet gas, so that the product falls into the collection tank.

[0075] As an example, the microporous filter plate 33 described in the present application can be a microporous titanium plate or a microporous copper plate made of metal, or a sand core filter plate made of ceramic material.

[0076] The present application also provides a method for preparing single-walled carbon nanotubes by using the device for preparing single-walled carbon nanotubes through reverse flow floating catalysis as described above. Specifically, the method includes:

[0077] (1) Connect the gas-liquid pipeline, and install the reverse gas flow device at a set position inside the furnace tube of the floating catalytic cracking device;

[0078] (2) Pass in process gas to evacuate, and set the process temperature according to process requirements;

[0079] (3) Keep the temperature constant for 25 - 40 min after the set temperature is reached;

[0080] (4) Open the gas-liquid supply device, feed materials at a certain gas flow rate and liquid supply rate, and set the gas flow rate of the reverse gas flow device to start synthesizing single-walled carbon nanotubes;

[0081] (5) Collect the product into a collection tank to obtain the target product of single-walled carbon nanotubes.

[0082] As an example, the gas flow rate of the reverse gas flow device described in the present application is 50% - 120% of the gas flow rate of the gas-liquid supply device; because if the flow rate of the reverse gas is too low, the contact between the catalyst and carbon-containing free radicals in the high-temperature zone will be insufficient, and the result will be not much different from that of traditional floating catalytic cracking; while if the flow rate of the reverse gas flow is too high, the gas flow rate in the high-temperature zone will be too fast, the growth time of carbon nanotubes will be short, and the yield will decrease.

[0083] As an example, the process gas or the gas in the gas flow dispersion plate described in the present application is a mixed gas of one or more of nitrogen, argon, helium, and hydrogen, and argon is preferred.

[0084] As an example, the process temperature described in step (2) of the present application is: the temperature in the high-temperature cavity is 1100 - 1500 °C (i.e., the set temperature range in the high-temperature zone inside the furnace tube of the floating catalytic cracking device).

[0085] In this application, the organic liquid precursor supplied in step (4) can be the formulations for synthesizing single-walled carbon nanotubes reported in the literature and known patents, generally including a carbon source, a catalyst, a promoter, an etchant, etc. The carbon source is a liquid carbon source such as ethanol, methanol, toluene, xylene, tetrahydrofuran, benzene, n-hexane, cyclohexane, etc., or a gaseous carbon source such as methane, acetylene, etc.; the catalyst is generally ferrocene, nickelocene, cobaltocene, ferric trichloride, iron carbonyl, iron lactate, etc. (The solid catalyst can be placed in a specific position inside the furnace tube in advance. If it is a gas, it is transported into the furnace tube through a gas pipeline); the promoter is generally a sulfur-containing compound such as thiophene.

[0086] In this application, the gas and liquid flow rates of the gas-liquid supply device are consistent with the process parameters for synthesizing single-walled carbon nanotubes reported in the literature and known patents, and these parameters vary depending on the formulation and the diameter of the furnace tube.

[0087] If the catalyst in this application is solid, it can be placed in the furnace tube first, and then the gaseous material is introduced into the furnace tube through the gas pipeline, and the liquid material is introduced into the furnace tube through the stainless steel capillary liquid pipeline; the main innovation point of this application lies in the setting of the reverse gas flow device and the control of the ratio relationship between its intake speed and the process gas flow; all the materials for preparing single-walled carbon nanotubes in this application can be the existing preparation materials.

[0088] The following is the preparation of single-walled carbon nanotubes through specific examples and the above device:

[0089] Organic precursor formulation (mass ratio): methanol / benzene / ferrocene / thiophene = 90 / 10 / 2.5 / 1;

[0090] The floating catalyst cracking device is as follows: a silicon molybdenum rod heating furnace with a heating zone length of 300 mm; the furnace tube is a 99 alumina tube (temperature resistant to 1650 °C, outer diameter 80 mm, inner diameter 70 mm), with a length of 1 meter (1000 mm); the gas distributor is a porous copper mesh, and the reverse gas flow device is fixed by penetrating from the product outlet end to the edge of the high-temperature zone (the starting end face is located at the critical point between the high-temperature zone and the heat preservation zone). The inner diameter of the gas guide pipe of the reverse gas flow device is 8 mm, and the material is 310S. The gas guide pipe is closely attached to the inner wall of the heating furnace tube; in some embodiments, the gas flow dispersion disc of the reverse gas flow device is a convective gas flow dispersion disc ( Figure 1-3 shown), the outer diameter of the convective gas flow dispersion disc is 40 mm, and the side with the air outlet is a microporous titanium plate with a pore diameter of 10 μm; in some embodiments, the gas flow dispersion disc of the reverse gas flow device is a vertical gas flow dispersion disc ( Figure 4 、 7 -8 shown), with a length of 60 mm, an outer diameter of 68 mm, and the wall thickness of the cylinder is 10 mm (the difference between the overall outer diameter and the inner diameter), the inner diameter of the gas guide pipe is 10 mm, and the inner wall is provided with a microporous titanium plate with a micropore diameter of 10 μm.

[0091] The Raman test uses a confocal Raman spectroscopy system with a 532 nm single-mode laser, wavelength range: 531 - 632 nm, wavenumber range: -20 - 2800 cm -1 , and by comparing the intensity ratios of the wavenumbers near 1350 and 1580, the intensity ratio of the D peak and the G peak is obtained to evaluate the degree of disorder and the density of defects of the carbon nanotubes; by observing the Raman signal between 100 - 300 wavenumbers, the radial breathing mode (RBM) of the single-walled carbon nanotubes is evaluated to obtain the diameter information.

[0092] Example 1

[0093] Use the vertical floating catalytic cracking furnace as shown in the appendix Figure 1 and the reverse gas flow device as shown in the appendix. Figure 3 shown in the appendix.

[0094] Step 1: Connect the gas-liquid pipeline and install the reverse gas flow device at the set position inside the furnace tube;

[0095] Step 2: Purge with argon and set the temperature of the heating furnace to 1450 °C;

[0096] Step 3: Keep the temperature constant for 30 min after reaching the set temperature;

[0097] Step 4: Open the gas-liquid supply device, set the liquid feeding speed to 1.0 g / min, the flow rate of the gas, i.e., argon, to 1.5 L / min; and set the argon flow rate of the reverse gas flow device to 1.0 L / min, and start synthesizing single-walled carbon nanotubes;

[0098] Step 5: Collect the product into the collection tank;

[0099] After preparation, it is detected that: the yield of single-walled carbon nanotubes in this example is 4.1 g / h, the carbon source conversion rate is 6.83%, and the purity analyzed by TGA is 84%; Figure 9 This is a specific product photo of the single-walled carbon nanotubes prepared in this example. From the Raman spectrum analysis shown in the appendix Figure 10 , it can be seen that the Raman I D / I G is 0.13, and the position of the RBM peak is 138 cm -1 . Calculated by d = 248 / ω, the diameter of the single-walled carbon nanotubes is about 1.8 nm.

[0100] Example 2

[0101] Use the vertical floating catalytic cracking furnace as shown in the appendix Figure 7 and the reverse gas flow device as shown in the appendix Figure 4 , 8 shown in the appendix.

[0102] Step 1: Connect the gas-liquid pipeline and install the reverse gas flow device at the set position inside the furnace tube;

[0103] Step 2: Purge with argon and set the temperature of the heating furnace to 1450 °C;

[0104] Step 3: Keep the temperature constant for 30 min after reaching the set temperature;

[0105] Step 4: Turn on the gas-liquid supply device, set the liquid feed rate to 1.0 g / min and the argon flow rate to 1.5 L / min; and set the argon flow rate of the reverse gas flow device to 1.0 L / min, and start synthesizing single-walled carbon nanotubes;

[0106] Step 5: Collect the product into the collection tank;

[0107] The yield of single-walled carbon nanotubes in this example is 3.7 g / h, the carbon source conversion rate is 6.17%, the purity analyzed by TGA is 82%, and I D / I G is 0.15.

[0108] Example 3

[0109] Use the horizontal floating catalytic cracking furnace as shown in the appendix Figure 2 and the reverse gas flow device as shown Figure 3 in the figure.

[0110] Step 1: Connect the gas-liquid pipeline and install the reverse gas flow device at the set position inside the furnace tube;

[0111] Step 2: Purge with argon and set the temperature of the heating furnace to 1450 °C;

[0112] Step 3: Keep the temperature constant for 30 min after reaching the set temperature;

[0113] Step 4: Turn on the gas-liquid supply device, set the liquid feed rate to 1.0 g / min and the argon flow rate to 1.5 L / min; and set the argon flow rate of the reverse gas flow device to 1.0 L / min, and start synthesizing single-walled carbon nanotubes;

[0114] Step 5: Collect the product into the collection tank;

[0115] The yield of single-walled carbon nanotubes in this example is 3.9 g / h, the carbon source conversion rate is 6.5%, the purity analyzed by TGA is 83%, and I D / I G is 0.14.

[0116] Example 4

[0117] Use the horizontal floating catalytic cracking furnace as shown in the appendix Figure 2 and the reverse gas flow device as shown Figure 4 in the figure.

[0118] Step 1: Connect the gas-liquid pipeline, and install the reverse gas flow device at the set position inside the furnace tube;

[0119] Step 2: Introduce argon to evacuate, and set the temperature of the heating furnace to 1450 °C;

[0120] Step 3: Keep the temperature for 30 min after it reaches the set value;

[0121] Step 4: Turn on the gas-liquid supply device, set the liquid feeding rate to 1.0 g / min and the argon flow rate to 1.5 L / min; and set the argon flow rate of the reverse gas flow device to 1.0 L / min, and start synthesizing single-walled carbon nanotubes;

[0122] Step 5: Collect the product into the collection tank;

[0123] The yield of single-walled carbon nanotubes in this example is 3.6 g / h, the carbon source conversion rate is 6%, the purity analyzed by TGA is 79%, and I D / I G is 0.17.

[0124] Example 5

[0125] Use the vertical floating catalytic cracking furnace as shown in the attached Figure 1 figure, Figure 3 and the reverse gas flow device as shown.

[0126] Step 1: Connect the gas-liquid pipeline, and install the reverse gas flow device at the set position inside the furnace tube;

[0127] Step 2: Introduce argon to evacuate, and set the temperature of the heating furnace to 1450 °C;

[0128] Step 3: Keep the temperature for 30 min after it reaches the set value;

[0129] Step 4: Turn on the gas-liquid supply device, set the liquid feeding rate to 1.0 g / min and the argon flow rate to 1.5 L / min; and set the argon flow rate of the reverse gas flow device to 0.75 L / min, and start synthesizing single-walled carbon nanotubes;

[0130] Step 5: Collect the product into the collection tank;

[0131] The yield of single-walled carbon nanotubes in this example is 1.9 g / h, the carbon source conversion rate is 3.17%, the purity analyzed by TGA is 76%, and the Raman I D / I G is 0.31.

[0132] Example 6

[0133] Use the as-attached Figure 1The vertical floating catalytic cracking furnace shown Figure 3 The reverse gas flow device shown

[0134] Step 1: Connect the gas-liquid pipeline and install the reverse gas flow device at the set position in the furnace tube;

[0135] Step 2: Purge with argon and set the heating furnace temperature to 1450 °C;

[0136] Step 3: Keep the temperature constant for 30 min after the set temperature is reached;

[0137] Step 4: Open the gas-liquid supply device, set the liquid inlet rate to 1.0 g / min and the argon flow rate to 1.5 L / min; and set the argon flow rate of the reverse gas flow device to 1.8 L / min, and start synthesizing single-walled carbon nanotubes;

[0138] Step 5: Collect the product into the collection tank;

[0139] The yield of single-walled carbon nanotubes in this example is 2.1 g / h, the carbon source conversion rate is 3.5%, the purity analyzed by TGA is 75%, and the Raman I D / I G is 0.39.

[0140] Comparative Example 1

[0141] Comparative Example 1 is the same as Example 1 in steps, except that the reverse gas flow device is not installed;

[0142] The yield of the single-walled carbon nanotube powder prepared in this comparative example is 0.6 g / h, the carbon source conversion rate is 1%, the purity is 70%, and I D / I G is 0.45.

[0143] Comparative Example 2

[0144] Comparative Example 2 is the same as Example 1 in steps, except that the reverse gas flow device is completely installed in the high-temperature zone (i.e., within the length range of the furnace tube covered by the highest temperature of the heating rod of the heating furnace);

[0145] The yield of the single-walled carbon nanotube powder prepared in this comparative example is 0.3 g / h, the carbon source conversion rate is 0.5%, the purity is 53%, and ID / IG is 0.78.

[0146] Comparative Example 3

[0147] Comparative Example 3 is the same as Example 1 in steps, except that the argon flow rate of the reverse gas flow device is 0.2 L / min;

[0148] The yield of the single-walled carbon nanotube powder prepared in this comparative example is 0.7 g / h, the carbon source conversion rate is 1.16%, the purity is 64%, and ID / I G is 0.51.

[0149] Comparative Example 4

[0150] Comparative Example 4 is the same as Example 1 in steps, except that the argon flow rate of the reverse air flow device is 3 L / min;

[0151] The yield of the single-walled carbon nanotube powder prepared in this comparative example is 0.9 g / h, the carbon source conversion rate is 1.5%, the purity is 68%, I D / I G is 0.47.

[0152] Comparative Example 5

[0153] Comparative Example 5 is the same as Example 1 in steps, except that the air flow dispersion disk of the reverse air flow device is a convection air flow dispersion disk, and the outer diameter of the dispersion disk is 20 mm (much smaller than the inner diameter of the furnace tube);

[0154] The yield of the single-walled carbon nanotube powder prepared in this comparative example is 1.4 g / h, the carbon source conversion rate is 2.3%, the purity is 72%, I D / I G is 0.41.

[0155] Comparative Example 6

[0156] Comparative Example 6 is the same as Example 1 in steps, except that the air flow dispersion disk of the reverse air flow device is a convection air flow dispersion disk, the pore diameter of the dispersion disk is 1 μm, and the porosity is 30%;

[0157] The yield of the single-walled carbon nanotube powder prepared in this comparative example is 1.7 g / h, the carbon source conversion rate is 2.8%, the purity is 74%, I D / I G is 0.39.

[0158] Comparative Example 7

[0159] Comparative Example 7 is the same as Example 1 in steps, except that the microporous dispersion disk is not used in the reverse air flow device, and the gas supply pipe directly supplies gas;

[0160] The yield of the single-walled carbon nanotube powder prepared in this comparative example is 0.7 g / h, the carbon source conversion rate is 1.16%, the purity is 59%, I D / I G is 0.59.

[0161] Results: As can be seen from the results of Examples 1 to 6, within the set parameter range of this application, the reverse air flow device used can synthesize single-walled carbon nanotubes with high yield and purity. From Examples 1 and 2, it can be seen that the result of the convective air flow dispersion disk is slightly better than that of the vertical air flow dispersion disk. This is because the catalyst and carbon-containing free radicals are more fully mixed in the convective structure, so the yield is slightly higher. From the comparison results of Examples 1 and 3 and Examples 2 and 4, it can be seen that introducing a reverse air flow device into the horizontal floating catalytic cracking device and the vertical floating catalytic cracking device can both synthesize single-walled carbon nanotubes with high yield. Adjusting the gas flow rate in the reverse air flow device in Examples 5 and 6 has an obvious impact on the yield of single-walled carbon nanotubes. Combining the results of Comparative Example 3 and Comparative Example 4, it can be analyzed that too low reverse air flow rate will lead to insufficient contact between the catalyst and carbon-containing free radicals in the high-temperature zone, resulting in a significant reduction in yield; too high reverse air flow rate will lead to too fast air flow velocity in the high-temperature zone, and the growth time of carbon nanotubes is short, and the yield will also decrease.

[0162] In Comparative Example 1, the reverse air flow device was not used, and the yield of single-walled carbon nanotubes was only 0.7 g / h, and the carbon source conversion rate was 1.16%. There was a large difference compared with Example 1 (yield 4.1 g / h, carbon source conversion rate 6.83%). In Comparative Example 2, the reverse air flow device was completely placed in the high-temperature zone, and the yield decreased and the product quality deteriorated (the yield of single-walled carbon nanotube powder was 0.3 g / h, the carbon source conversion rate was 0.5%, and the purity was 53%, I D / I G was 0.78). This is because the main function of the reverse air flow device is to form turbulent disturbances and improve the contact efficiency between the catalyst and carbon-containing free radicals. When the air flow dispersion disk is completely placed in the high-temperature zone, the turbulence destroys the environment of carbon source and catalyst cracking, has a negative impact on it, causes the catalyst size to be too large and the activity to decrease, and then the output decreases. In Comparative Examples 5 to 7, changing the structure of the reverse air flow device results in too fast or too slow reverse air flow velocity, which is not conducive to air flow disturbance in the high-temperature zone and causes the output to decrease.

[0163] The above are only the preferred embodiments of this application and are not used to limit this application. Any modifications, equivalent replacements, and improvements made within the principle and spirit of this application shall be included within the protection scope of this application.

Claims

1. An apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis, characterized in that: The device includes a gas-liquid supply device, a floating catalytic cracking device, and a product collection device; the gas-liquid supply device is arranged at the tail end of the floating catalytic cracking device and is interconnected with the floating catalytic cracking device for supplying reaction materials; the head end of the floating catalytic cracking device is interconnected with the product collection device through a pipeline; a reverse air flow device is also arranged in the floating catalytic cracking device, the reverse air flow device is located at a position near the discharge end in the floating catalytic cracking device, and the reverse air flow device is used to form an axial or radial air flow; the end face of the reverse air flow device near the gas-liquid supply device side is located at the critical point between the heating zone and the heat preservation zone near the discharge end in the floating catalytic cracking device; the reverse air flow device includes a gas guide pipe and an air flow dispersion disc, the air flow dispersion disc is placed inside the floating catalytic cracking device and is connected with the gas guide pipe, and the other end of the gas guide pipe extends out of the floating catalytic cracking device and is used for gas transmission; the gas guide pipe is connected to the axial side wall or one end face of the air flow dispersion disc, and the outer wall of the gas guide pipe is closely attached to the inner wall of the floating catalytic cracking device.

2. The apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis according to claim 1, wherein: The gas guide pipe is a 310S stainless steel pipe, a corundum pipe, a quartz pipe, or a graphite pipe; the inner diameter of the gas guide pipe is 6 - 12 mm, and the wall thickness is 0.5 - 2 mm.

3. The apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis according to claim 1, wherein: The air flow dispersion disc is a convective air flow dispersion disc or a vertical air flow dispersion disc.

4. The apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis according to claim 3, wherein: The diameter of the convective air flow dispersion disc is 1 / 2 - 2 / 3 of the inner diameter of the inner cavity of the floating catalytic cracking device, and the placement position is set at the critical point between the heating zone and the heat preservation zone and is centered. The axial length of the convective dispersion disc is 12 - 50 mm; the vertical air flow dispersion disc is a hollow cylindrical type, and the outer diameter of the hollow cylindrical vertical air flow dispersion disc is equivalent to the inner diameter of the inner cavity of the floating catalytic cracking device; the wall thickness of the hollow cylindrical vertical air flow dispersion disc is 10 - 20 mm, its inner wall is a microporous titanium plate, a microporous stainless steel plate, a microporous nickel plate, a microporous corundum plate, or a microporous graphite plate, and the micropore direction extends along the radial direction.

5. The apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis according to claim 4, wherein: The convective air flow dispersion disc is composed of integrally formed high-temperature resistant alumina ceramics. One end or side wall in the axial direction is connected with a gas guide pipe, and the other end is an air outlet end face and is provided with a microporous structure. The air outlet end face is close to the gas-liquid supply device side; the axial extension length of the vertical air flow dispersion disc is 50 - 100 mm, and its position is set at the critical point between the heating zone and the heat preservation zone in the upper part of the inner cavity of the floating catalytic cracking device.

6. The apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis according to claim 4, characterized in that: The convective air flow dispersion disc is composed of a stainless steel cavity body and a microporous metal plate sealed by a seal. One end or side wall in the axial direction is connected with a gas guide pipe, and the other end is an air outlet end face which is composed of one of a microporous titanium plate, a microporous stainless steel plate, a microporous nickel plate, a microporous corundum plate, or a microporous graphite plate.

7. The apparatus for preparing single-walled carbon nanotubes by reverse flow floating catalysis according to claim 5, wherein: The aperture of each micropore is 5 - 30 um, and the porosity is 50% - 90%.

8. The apparatus for preparing single-walled carbon nanotubes by reverse flow floating catalysis according to claim 1, wherein: The described gas-liquid supply device includes a gas pipeline, a stainless steel capillary liquid pipeline, and a sealing flange; the gas pipeline and the stainless steel capillary liquid pipeline are hermetically connected to the flange, and the sealing flange is connected to the feed end of the fluid catalytic cracking device through a high-temperature sealing ring.

9. The apparatus for preparing single-walled carbon nanotubes by reverse flow floating catalysis according to claim 8, characterized in that: The described gas pipeline surrounds and covers the outer periphery of the stainless steel capillary liquid pipeline. Axially, the outlet end of the stainless steel capillary liquid pipeline extends out of the outlet end of the gas pipeline, and the distance between their outlet ends is 5 - 20 mm; the inner diameter of the stainless steel capillary liquid pipeline is 0.3 - 1.5 mm; a gas distributor is provided at the outlet end of the gas pipeline, and the outlet ends of the gas pipeline and the stainless steel capillary are both located inside the gas distributor and are hermetically connected to the gas distributor.

10. The apparatus for preparing single-walled carbon nanotubes by reverse-flow floating catalysis according to claim 9, wherein: The described gas distributor is arranged inside the fluid catalytic cracking device, and the temperature inside the gas distributor is controlled at 300°C - 500°C; the gas distributor is composed of porous nickel mesh, copper mesh, titanium mesh, or microporous ceramics.

11. The apparatus for preparing single-walled carbon nanotubes by reverse flow floating catalysis according to claim 1, wherein: The described fluid catalytic cracking device includes a heating furnace body and an internal furnace tube. The heating furnace body is composed of silicon molybdenum rod or silicon carbide rod heating elements and polycrystalline alumina fiber thermal insulation materials. The heating temperature of the heating furnace body is 1100 - 1400°C, and the length of the heating zone is 300 - 1000 mm; the furnace tube is composed of corundum tube or silicon carbide tube, and the diameter of the furnace tube is 60 - 500 mm and the length is 1000 - 3000 mm.

12. The apparatus for preparing single-walled carbon nanotubes by reverse flow floating catalysis according to claim 1, wherein: The described product collection device includes a collection tank, a back-blowing chamber, a microporous filter plate, and an air extraction device; the back-blowing chamber is in communication with the discharge pipeline of the fluid catalytic cracking device, the microporous filter plate is located above the discharge pipeline, and the air outlet of the air extraction device is located above the microporous filter plate; the collection tank is located below the back-blowing chamber.

13. The apparatus for preparing single-walled carbon nanotubes by reverse flow floating catalysis according to claim 12, characterized in that: The described microporous filter plate is one of microporous titanium plates or microporous copper plates made of metal materials.

14. A method for preparing single-walled carbon nanotubes by using the apparatus for preparing single-walled carbon nanotubes through reverse-flow floating catalysis according to any one of claims 1 to 13, characterized in that: Specifically, the method includes: (1) Connect the gas-liquid pipeline, and install the reverse gas flow device at a set position inside the furnace tube of the fluid catalytic cracking device; (2) Pass in process gas to evacuate, and set the process temperature according to process requirements; (3) Keep the temperature constant for 25 - 40 min after the set temperature is reached; (4) Open the gas-liquid supply device, feed according to the set gas flow rate and liquid supply rate, and set the gas flow rate of the reverse gas flow device to start synthesizing single-walled carbon nanotubes; (5) Collect the product into the product collection device.

15. The method for preparing single-walled carbon nanotubes according to claim 14, wherein: The gas flow rate of the described reverse gas flow device is 50% - 120% of the gas flow rate of the gas-liquid supply device; the process gas or the gas in the gas flow dispersion plate is one or a mixture of several of nitrogen, argon, helium, and hydrogen; the process temperature described in step (2) is: the temperature inside the high-temperature cavity is 1100 - 1500°C.

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