Apparatus and method for producing carbon nanotubes by microwave plasma combined with chemical vapor deposition
By combining microwave plasma with chemical vapor deposition, high-purity carbon nanotubes are generated at low temperatures, solving the problems of high temperature, high energy consumption, and limited large-scale production in existing technologies, and realizing low-energy continuous production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CHENGDU DAZHAN TIMES NANOTECHNOLOGY CO LTD
- Filing Date
- 2024-12-09
- Publication Date
- 2026-06-09
AI Technical Summary
Existing methods for preparing carbon nanotubes involve high temperatures and high energy consumption, and the growth of microwave plasma is limited under high pressure conditions, making it difficult to scale up production.
The method employs microwave plasma combined with chemical vapor deposition, which combines a microwave plasma generator with a heating furnace. The reaction temperature is below 800℃, requiring no substrate or high pressure. The carrier gas carries in highly active catalyst particles to mix with carbon nanoparticles for reaction, generating high-purity carbon nanotubes.
It achieves continuous production with low energy consumption and no electrode contamination, and produces carbon nanotubes with high purity, solving the problem of large-scale production.
Smart Images
Figure CN122179968A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanomaterial preparation technology, specifically to an apparatus and method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition. Background Technology
[0002] Carbon nanotubes (CNTs) are a class of nanomaterials composed of a two-dimensional hexagonal lattice of carbon atoms, which bend and bond together in one direction to form hollow cylinders. Carbon nanotubes possess high electrical conductivity, excellent current-carrying capacity, and good chemical and thermal stability. All of these indicate that carbon nanotubes have broad potential applications.
[0003] With the widespread application of carbon nanotubes in various fields, the technology for large-scale preparation of carbon nanotubes has developed rapidly. The main methods for preparing carbon nanotubes include: arc electrolysis, laser evaporation, and chemical vapor deposition (CVD). Among these, arc electrolysis and laser evaporation involve high temperatures, high energy consumption, and are difficult to control, resulting in large fluctuations in product quality and the ability to only produce carbon nanotube powders. Furthermore, arc electrolysis requires electrodes, leading to electrode consumption and contamination of the reaction chamber. CVD is significant for the preparation of carbon nanotube films, and its temperature is much lower than the previous two methods. However, the conventional CVD method (high-temperature pyrolysis method) still requires relatively high temperatures, generally exceeding 800℃, which surpasses the temperature tolerance of many substrate materials, limiting the choice of substrate materials. Moreover, carbon nanotubes produced by CVD have drawbacks such as high impurity levels and low purity, resulting in insufficient conductivity. When used in material composites, they cannot be effectively dispersed and composited, and their performance does not offer a significant advantage over traditional conductive carbon black.
[0004] In recent years, research has applied microwave plasma to the fabrication of carbon nanotubes. Microwave plasma, operating in a continuous flow at low pressure, is a unique type of plasma. Due to the non-equilibrium state between electrons and other heavy particles in the plasma space, these plasmas contain high-density electrons with energies exceeding 10 eV, leading to the non-thermal dissociation of gases to form active free radicals. This abundance of active substances provides opportunities for the synthesis of nanomaterials. However, applying microwave plasma to the fabrication of carbon nanotubes requires growth on a substrate under high pressure, limiting continuous growth. Therefore, providing a method for large-scale fabrication of carbon nanotubes is of practical significance for further promoting their applications. Summary of the Invention
[0005] To address the technical challenges of high temperatures and energy consumption in the preparation of carbon nanotubes using conventional methods such as arc evaporation, laser evaporation, and chemical vapor deposition, and the limitations of stringent production conditions and large-scale production when applying microwave plasma to carbon nanotube preparation, this invention provides an apparatus and method for preparing carbon nanotubes using a combination of microwave plasma and chemical vapor deposition. By combining microwave plasma with chemical vapor deposition, the reaction heating temperature is below 800°C, no substrate or high pressure is required, the reaction conditions are mild, and high-purity carbon nanotubes can be continuously produced.
[0006] In a first aspect, the present invention provides an apparatus for preparing carbon nanotubes by microwave plasma combined with chemical vapor deposition, comprising a microwave plasma generator, a heating furnace and a collecting device connected in sequence. A carrier gas channel runs through the microwave plasma generator, and a catalyst channel is nested inside the carrier gas channel. A quartz tube reaction channel runs through the furnace chamber of the heating furnace. The end of the quartz tube reaction channel near the microwave plasma generator is the inlet end, and the end near the collecting device is the outlet end. There is a ventilation jacket between the furnace chamber of the heating furnace and the quartz tube reaction channel. The outlet end of the carrier gas channel, the outlet end of the catalyst channel, and the ventilation jacket are respectively connected to the inlet end of the quartz tube reaction channel. A reaction gas feed channel extending into the ventilation jacket is provided at the end of the heating furnace near the collecting device.
[0007] Furthermore, the collection device is a particle trap.
[0008] Furthermore, the collection device is equipped with a discharge port at the bottom.
[0009] Furthermore, there are two reaction gas feed channels.
[0010] Secondly, the present invention provides a method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition, wherein the preparation of carbon nanotubes in the above-mentioned apparatus includes the following steps: (1) Set the power of the microwave plasma generator to 10-30kW. The inert gas catalyst is introduced into the microwave plasma generator through the catalyst channel for ionization to obtain highly active catalyst particles. The flow rate of the inert gas is 1-3slm. The catalyst is a mixture of catalyst metal and co-catalyst, and the amount of catalyst metal is 1-3g / min. (2) The reaction temperature of the heating furnace is set to 650-750℃. The mixed gas of methane and hydrogen enters the gas interlayer between the furnace chamber and the quartz tube reaction channel through the reaction gas feed channel. After heating, carbon nanoparticles are formed. They are then mixed with highly active catalyst particles at the outlet of the catalyst channel. Then, under the blowing force of inert gas in the carrier gas channel, they enter the quartz tube reaction channel and are heated to obtain carbon nanotubes. The flow rate of the mixed gas of methane and hydrogen is 2-4 slm, the methane concentration is 5 vol%-10 vol%, the hydrogen concentration is 10 vol%-30 vol%, and the remainder is inert gas.
[0011] Furthermore, the inert gas is argon.
[0012] Furthermore, the catalyst metal is ferrocene, and the co-catalyst is sulfur or sodium hydroxyethyl sulfonate.
[0013] Furthermore, the molar ratio of catalyst metal to co-catalyst is 10:1.
[0014] Furthermore, the total flow rate of the inert gas collected at the inlet end of the quartz tube reaction channel is 5-10 slm.
[0015] Furthermore, the carbon nanotubes obtained from the reaction are collected by a collecting device.
[0016] The beneficial effects of this invention are as follows: This invention provides an apparatus and method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition. The apparatus includes a microwave plasma generator, eliminating the need for electrodes and thus avoiding electrode consumption and reaction chamber contamination. The heating furnace operates at 650-750℃, lower than the temperature required for conventional chemical vapor deposition, resulting in energy savings. The catalyst is not in a conventional fixed-bed configuration, eliminating the need for catalyst replacement and reducing production efficiency. Furthermore, the catalyst is continuously fed into the microwave plasma generator via a carrier gas source, where it is ionized during the flow process. The resulting highly active catalyst particles mix with the carbon nanoparticles generated after heating in the furnace at the inlet of the quartz tube reaction channel, and then enter the quartz tube reaction channel together for further heating and reaction. The reaction requires no substrate or high pressure, and the generated carbon nanotubes are rapidly discharged and collected from the outlet of the quartz tube reaction channel by the gas flow, resulting in high efficiency, speed, and high purity carbon nanotubes. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a schematic diagram of an apparatus for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition.
[0019] Figure 2 This is a scanning electron microscope image of carbon nanotubes from Example 2.
[0020] Figure 3 This is a thermogravimetric diagram of carbon nanotubes from Example 2.
[0021] Figure 4 This is a scanning electron microscope image of carbon nanotubes in Comparative Example 1.
[0022] Figure 5 This is the thermogravimetric diagram of carbon nanotubes in Comparative Example 1.
[0023] In the diagram, 1-catalyst channel, 2-microwave plasma generator, 3-carrier gas channel, 4-heating furnace, 5-quartz tube reaction channel, 6-reaction gas feed channel, 7-particle collector, 8-discharge port. Detailed Implementation
[0024] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention. Wherein, the gas flow rate involved in this application refers to the flow rate at room temperature and pressure.
[0025] Example 1 like Figure 1 As shown, the apparatus for preparing carbon nanotubes by microwave plasma combined with chemical vapor deposition includes a microwave plasma generator 2, a heating furnace 4, and a particle trap 7 connected in sequence, and a discharge port 8 is provided at the bottom of the particle trap 7. A carrier gas channel 3 runs through the microwave plasma generator 2, and a catalyst channel 1 is nested inside the carrier gas channel 3. A quartz tube reaction channel 5 runs through the furnace chamber of the heating furnace 4. The end of the quartz tube reaction channel 5 near the microwave plasma generator 2 is the inlet end, and the end near the particle collector 7 is the outlet end. There is a ventilation jacket between the furnace chamber of the heating furnace 4 and the quartz tube reaction channel 5. The outlet end of the carrier gas channel 3, the outlet end of the catalyst channel 1, and the ventilation jacket are respectively connected to the inlet end of the quartz tube reaction channel 5. Two reaction gas feed channels 6 are provided on the heating furnace 4 near the particle collector 7, extending into the ventilation jacket.
[0026] Example 2 A method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition includes the following steps: (1) The power of the microwave plasma generator 2 is set to 30kW. The catalyst (a mixture of catalyst metal ferrocene and sodium hydroxyethyl sulfonate, with a molar ratio of ferrocene to sodium hydroxyethyl sulfonate of 10:1) is carried into the microwave plasma generator 2 by argon gas through catalyst channel 1 to ionize it and obtain highly active catalyst particles. The catalyst metal content is 1g / min and the carrier gas argon flow rate is 1slm. (2) The reaction temperature of the heating furnace 4 is set to 650℃. A mixture of methane and hydrogen gas (methane concentration is 10 vol%, hydrogen concentration is 20 vol%, and the remainder is carrier gas argon) is fed into the ventilation jacket between the furnace chamber of the heating furnace 4 and the quartz tube reaction channel 5 through the reaction gas feed channel 6. In the ventilation jacket, the methane is heated and decomposed into carbon nanoparticles, which are gathered at the inlet end of the quartz tube reaction channel 5 and mixed with the highly active catalyst particles at the outlet end of the catalyst channel 1. Then, under the blowing force of the argon gas flowing out of the carrier gas channel 3, it enters the quartz tube reaction channel 5 (at this time, the total flow rate of the argon gas gathered at the inlet end of the quartz tube reaction channel 5 is 5 slm). The carbon nanotubes are obtained by heating and reacting in the quartz tube reaction channel 5. (3) After the carbon nanotubes and a mixture of various gases (undecomposed methane, hydrogen, argon and other small molecule organic matter) come out of the outlet of the quartz tube reaction channel 5, they enter the particle collector 7 for electrostatic collection and bag collection, thereby achieving the collection of carbon nanotubes, and the carbon nanotubes are collected at the discharge port 8.
[0027] Example 3 A method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition includes the following steps: (1) The power of the microwave plasma generator 2 is set to 20kW. The catalyst (a mixture of catalyst metal ferrocene and co-catalyst sulfur, with a molar ratio of ferrocene to sulfur of 10:1) is carried into the microwave plasma generator 2 by argon gas through catalyst channel 1 to ionize it and obtain highly active catalyst particles. The catalyst metal content is 1g / min and the carrier gas argon flow rate is 2slm. (2) The reaction temperature of the heating furnace 4 is set to 700℃. A mixture of methane and hydrogen gas (methane concentration is 10 vol%, hydrogen concentration is 30 vol%, and the remainder is carrier gas argon) is fed into the ventilation interlayer between the heating furnace 4 and the quartz tube reaction channel 5 through the reaction gas feed channel 6. In the ventilation interlayer, the methane is heated and decomposed into carbon nanoparticles, which are gathered at the inlet end of the quartz tube reaction channel 5 and mixed with the highly active catalyst particles at the outlet end of the catalyst channel 1. Then, under the blowing force of the argon gas flowing out of the carrier gas channel 3, it enters the quartz tube reaction channel 5 (at this time, the total flow rate of the argon gas gathered at the inlet end of the quartz tube reaction channel 5 is 10 slm). The carbon nanotubes are obtained by heating and reacting in the quartz tube reaction channel 5. (3) After the carbon nanotubes and a mixture of various gases (undecomposed methane, hydrogen, argon and other small molecule organic matter) come out of the outlet of the quartz tube reaction channel 5, they enter the particle collector 7 for electrostatic collection and bag collection, thereby achieving the collection of carbon nanotubes, and the carbon nanotubes are collected at the discharge port 8.
[0028] Example 4 A method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition includes the following steps: (1) The power of microwave plasma generator 2 is set to 10kW. The catalyst (a mixture of catalyst metal ferrocene and sodium hydroxyethyl sulfonate, with a molar ratio of ferrocene to sodium hydroxyethyl sulfonate of 10:1) is carried into microwave plasma generator 2 by argon gas through catalyst channel 1 to ionize it and obtain highly active catalyst particles. The catalyst metal content is 3g / min and the carrier gas argon flow rate is 3slm. (2) The reaction temperature of the heating furnace 4 is set to 750℃. A mixture of methane and hydrogen gas (methane concentration is 5 vol%, hydrogen concentration is 30 vol%, and the remainder is carrier gas argon) is fed into the ventilation interlayer between the heating furnace 4 and the quartz tube reaction channel 5 through the reaction gas feed channel 6. In the ventilation interlayer, the methane is heated and decomposed into carbon nanoparticles, which are gathered at the inlet end of the quartz tube reaction channel 5 and mixed with the highly active catalyst particles at the outlet end of the catalyst channel 1. Then, under the blowing force of the argon gas flowing out of the carrier gas channel 3, it enters the quartz tube reaction channel 5 (at this time, the total flow rate of the argon gas gathered at the inlet end of the quartz tube reaction channel 5 is 5 slm). The carbon nanotubes are obtained by heating and reacting in the quartz tube reaction channel 5. (3) After the carbon nanotubes and a mixture of various gases (undecomposed methane, hydrogen, argon and other small molecule organic matter) come out of the outlet of the quartz tube reaction channel 5, they enter the particle collector 7 for electrostatic collection and bag collection, thereby achieving the collection of carbon nanotubes, and the carbon nanotubes are collected at the discharge port 8.
[0029] Comparative Example 1 A method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition includes the following steps: (1) The power of the microwave plasma generator 2 is set to 5kW. The catalyst (a mixture of catalyst metal ferrocene and sodium hydroxyethyl sulfonate, with a molar ratio of ferrocene to sodium hydroxyethyl sulfonate of 10:1) is carried into the microwave plasma generator 2 by argon gas through catalyst channel 1 to ionize it and obtain highly active catalyst particles. The catalyst metal content is 2g / min and the carrier gas argon flow rate is 3.2slm. (2) The reaction temperature of the heating furnace 4 is set to 650℃. A mixture of methane and hydrogen gas (methane concentration is 5 vol%, hydrogen concentration is 10 vol%, and the remainder is carrier gas argon) is fed into the ventilation interlayer between the heating furnace 4 and the quartz tube reaction channel 5 through the reaction gas feed channel 6. In the ventilation interlayer, the methane is heated and decomposed into carbon nanoparticles, which are gathered at the inlet end of the quartz tube reaction channel 5 and mixed with the highly active catalyst particles at the outlet end of the catalyst channel 1. Then, under the blowing force of the argon gas flowing out of the carrier gas channel 3, it enters the quartz tube reaction channel 5 (at this time, the total flow rate of the argon gas gathered at the inlet end of the quartz tube reaction channel 5 is 5 slm). The carbon nanotubes are obtained by heating and reacting in the quartz tube reaction channel 5. (3) After the carbon nanotubes and a mixture of various gases (undecomposed methane, hydrogen, argon and other small molecule organic matter) come out of the outlet of the quartz tube reaction channel 5, they enter the particle collector 7 for electrostatic collection and bag collection, thereby achieving the collection of carbon nanotubes, and the carbon nanotubes are collected at the discharge port 8.
[0030] Experimental Example 1 Thermogravimetric analysis was performed on the products obtained in Examples 2-4 and Comparative Example 1. The results are shown in Table 1 and 2. Figure 3 , Figure 5 As shown.
[0031] Table 1 Thermogravimetric Analysis Results
[0032] From Table 1, Figure 3 and Figure 5 It can be seen that the residual amounts in Examples 2 to 4 are much smaller than those in Comparative Example 1, indicating that the products in Examples 2 to 4 are mostly carbon nanotubes with high purity. In contrast, the product in Comparative Example 1 is mostly unreacted metal catalyst, resulting in lower purity carbon nanotubes. This may be due to the microwave plasma generator in Comparative Example 1 having too low power and a high argon gas intake, leading to low catalyst ionization. Scanning electron microscopy (SEM) analysis also yielded similar conclusions, as seen in the SEM image of Example 2 (…). Figure 2 As can be seen from the SEM image of Comparative Example 1, the product is mostly composed of slender carbon nanotubes, with a small amount of carbon nanotube catalyst interspersed between them. Figure 4 The products in this process are mostly aggregated unreacted catalysts, with a relatively small amount of elongated carbon nanotubes generated.
[0033] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.
Claims
1. An apparatus for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition, comprising a microwave plasma generator (2), characterized in that, The microwave plasma generator (2), the heating furnace (4), and the collecting device are connected in sequence; A carrier gas channel (3) runs through the microwave plasma generator (2), and a catalyst channel (1) is installed inside the carrier gas channel (3); a quartz tube reaction channel (5) runs through the furnace chamber of the heating furnace (4), with the end of the quartz tube reaction channel (5) near the microwave plasma generator (2) being the inlet end and the end near the collecting device being the outlet end; there is a ventilation jacket between the furnace chamber of the heating furnace (4) and the quartz tube reaction channel (5), and the outlet end of the carrier gas channel (3), the outlet end of the catalyst channel (1), and the ventilation jacket are respectively connected to the inlet end of the quartz tube reaction channel (5); a reaction gas feed channel (6) extending into the ventilation jacket is provided on the end of the heating furnace (4) near the collecting device.
2. The apparatus for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 1, characterized in that, The collection device is a particle trap (7).
3. The apparatus for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 1, characterized in that, The bottom of the collecting device is equipped with a discharge port (8).
4. The apparatus for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 1, characterized in that, There are two reaction gas feed channels (6).
5. A method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition, characterized in that, The preparation of carbon nanotubes in the apparatus of claim 1 comprises the following steps: (1) Set the power of the microwave plasma generator to 10-30kW. The inert gas catalyst is introduced into the microwave plasma generator through the catalyst channel for ionization to obtain highly active catalyst particles. The flow rate of the inert gas is 1-3slm. The catalyst is a mixture of catalyst metal and co-catalyst, and the amount of catalyst metal is 1-3g / min. (2) The reaction temperature of the heating furnace is set to 650-750℃. The mixed gas of methane and hydrogen enters the gas interlayer between the furnace chamber and the quartz tube reaction channel through the reaction gas feed channel. After heating, carbon nanoparticles are formed. They are then mixed with highly active catalyst particles at the outlet of the catalyst channel. Then, under the blowing force of inert gas in the carrier gas channel, they enter the quartz tube reaction channel and are heated to obtain carbon nanotubes. The flow rate of the mixed gas of methane and hydrogen is 2-4 slm, the methane concentration is 5 vol%-10 vol%, the hydrogen concentration is 10 vol%-30 vol%, and the remainder is inert gas.
6. The method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 5, characterized in that, The inert gas is argon.
7. The method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 5, characterized in that, The catalyst metal is ferrocene, and the co-catalyst is sulfur or sodium hydroxyethyl sulfonate.
8. The method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 5, characterized in that, The molar ratio of catalyst metal to co-catalyst is 10:
1.
9. The method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 5, characterized in that, The total flow rate of the inert gas collected at the inlet end of the quartz tube reaction channel is 5-10 slm.
10. The method for preparing carbon nanotubes using microwave plasma combined with chemical vapor deposition as described in claim 5, characterized in that, The carbon nanotubes obtained from the reaction are collected by a collecting device.