Method for preparing high-quality single-walled carbon nanotubes and apparatus therefor

Abstract

The application discloses a high-quality single-walled carbon nanotube preparation method and a preparation device thereof, relates to the technical field of single-walled carbon nanotube material preparation, and comprises the following steps: after system vacuumization, arc starting gas is introduced to form stable high-temperature plasma torch; composite catalyst carrier gas and carbon source carrier gas are separately introduced in a branched manner; the composite catalyst and the carbon source are respectively transported to the high-temperature plasma zone to realize atomic-level uniform mixing and rapid melting and gasification; then, nucleation and growth are carried out in a temperature-controllable growth temperature zone; and single-walled carbon nanotubes are obtained through rapid quenching and gas-solid separation. The application breaks through the use limitation of catalysts in the existing preparation technology, is compatible with various catalyst forms, has strong carbon source adaptability, controllable process and high preparation efficiency, and the obtained product has low defect density, high graphitization degree and high length-diameter ratio, and can realize continuous and large-scale production and is suitable for high-end application fields such as new energy and electronic devices.

Description

Technical Field

[0001] This invention relates to the field of single-walled carbon nanotube material preparation technology, specifically to a method and apparatus for preparing high-quality single-walled carbon nanotubes. Background Technology

[0002] Compared with multi-walled carbon nanotubes, single-walled carbon nanotubes have higher aspect ratio, conductivity, flexibility and adhesion, and have broad application prospects in high-energy-density lithium batteries, all-solid-state batteries, antistatic plastics / rubber, lightweight and high-strength composite materials, optical films, electromagnetic shielding materials, functional coatings and other fields.

[0003] Currently, commonly used methods for mass production of single-walled carbon nanotubes include floating catalyst chemical vapor deposition (FCCVD), thermal plasma chemical vapor deposition (TPCVD), and direct current arc discharge (DCA). Among these, the low-temperature preparation method of single-walled carbon nanotubes, represented by chemical vapor deposition (CVD), has the advantages of high preparation efficiency, high purity of coarse single-walled carbon nanotube powder, long length, and relatively simple purification, and has been widely used in the industrial mass production of single-walled carbon nanotubes. However, the single-walled carbon nanotubes prepared by this method have high defect density and low Raman IG / ID ratios, making it difficult to meet the stringent requirements for high conductivity in high-end applications after purification and scissoring.

[0004] A plasma torch, also known as a plasma arc torch, is a device that uses electrical energy to heat and ionize gas into high-temperature plasma, which is then ejected through nozzles to form a high-temperature, high-energy jet. Its core temperature is extremely high, typically reaching thousands to tens of thousands of Kelvin; simultaneously, the high plasma density ensures high energy density and thermal conductivity, and it exhibits extremely high chemical reactivity, making it widely used in fields such as nanomaterial synthesis and carbon black preparation.

[0005] Traditional plasma torch processes for preparing carbon materials typically use hydrocarbon gases (such as methane, acetylene, and coalbed methane) or liquid hydrocarbons as carbon sources, which are then cracked in a plasma formed by inert gases such as nitrogen to generate carbon particles. For example, Chinese invention patent CN114180519B discloses an apparatus and method for producing hydrogen and nano-carbon materials through plasma decomposition of coalbed methane; Chinese invention patent CN118515238B discloses a process and system for producing conductive carbon nanomaterials and hydrogen through plasma cracking of methane. However, traditional plasma torch processes for preparing carbon materials have significant limitations: First, its products are mostly amorphous carbon black, lacking the ability to precisely control the microstructure of the products, and thus unable to prepare high-purity single-walled carbon nanotubes. Secondly, existing technologies often use nitrogen as a carrier gas, which may react with carbon and hydrogen at high temperatures to form cyanide groups, which has an adverse effect on the activity of the catalyst and introduces nitrogen-containing impurities. Furthermore, existing devices lack a systematic design for catalyst introduction methods, catalyst-carbon source mixing processes, and single-walled carbon nanotube growth environments, making it difficult to meet the requirements for single-walled carbon nanotube preparation.

[0006] Chinese invention patent CN109970046B discloses a method for preparing fine-diameter carbon nanotubes using a plasma torch. This method employs an organic carbon source and a porous carbon-supported catalyst to prepare oligowalled carbon nanotubes (a mixture containing multiwalled, double-walled, and single-walled carbon nanotubes) through a high-temperature pyrolysis reaction. However, it cannot produce pure single-walled carbon nanotubes. Chinese invention patent CN116622416B discloses a method for generating high-temperature coal gas based on an electric arc plasma torch. Chinese invention patent CN117619302A discloses a method for preparing acetylene and an electric arc plasma reaction device. Both utilize electric arc plasma to gasify carbon powder, which is then mixed with a reaction gas to obtain high-temperature coal gas or acetylene gas. These technologies also lack a systematic design for the catalyst introduction method and the growth environment of single-walled carbon nanotubes. Furthermore, the low gasification rate of solid carbon within a limited time leads to the formation of graphitic particles from ungasified carbon, reducing product purity. This makes it impossible to apply these methods to the preparation of single-walled carbon nanotube materials through simple equipment optimization.

[0007] Therefore, developing a method and apparatus for preparing single-walled carbon nanotubes that has strong carbon source compatibility, high preparation efficiency, controllable cost, low material defect density, and is easy to scale up industrially is of great technical significance and economic value. Summary of the Invention

[0008] Therefore, the purpose of this invention is to provide a method and apparatus for preparing high-quality single-walled carbon nanotubes.

[0009] The objective of this invention is achieved through the following technical solution: <First Aspect> A method for preparing single-walled carbon nanotubes based on an electric arc plasma torch includes the following steps: S1. The carrier gas carries the carbon source and composite catalyst from different feed channels into the electric arc plasma torch, where they are uniformly mixed and melted and vaporized to form an atomic-scale catalyst / carbon mixture system. S2. The catalyst / carbon mixture is transported to the growth temperature zone by an electric arc plasma torch jet to nucleate and grow single-walled carbon nanotubes, forming a gas-solid mixture. S3. The gas-solid mixture formed is carried by the airflow into the growth quenching zone connected at the end of the growth temperature zone for rapid quenching. S4. After cooling, the gas-solid mixture is subjected to gas-solid separation, and the solid product is collected to obtain single-walled carbon nanotubes.

[0010] As one implementation, the carbon source and the composite catalyst are respectively transported along with the carrier gas into the plasma discharge chamber of the arc plasma torch.

[0011] As one implementation scheme, the vacuum level in step S1 is no greater than 10 Pa.

[0012] As one implementation, the arc-initiating gas is argon and / or helium, with a flow rate ranging from 1 to 20 SLM.

[0013] As one implementation, the plasma torch power is 10~200 kW.

[0014] As one implementation, the carrier gas is helium and / or argon, and hydrogen may be selectively added as an auxiliary component. The volume percentage of hydrogen in the carrier gas does not exceed 60%, and the flow rate ranges from 2 to 150 SLM.

[0015] In some embodiments, the flow rate of the carrier gas ranges from 2 to 80 SLM.

[0016] As one implementation, the carbon source is a gaseous carbon source and / or a liquid carbon source.

[0017] In some embodiments, the gaseous carbon source is any one of methane, high-purity coalbed methane, high-purity natural gas, and ethane.

[0018] In some embodiments, the flow rate of the gaseous carbon source is in the range of 10 to 150 SLM.

[0019] In some embodiments, the liquid carbon source is benzene and / or ethanol.

[0020] In some embodiments, the feed rate of the liquid carbon source is 10~150 mL / min.

[0021] As one implementation, the composite catalyst consists of a main catalyst, a co-catalyst, and a growth promoter.

[0022] In some embodiments, the main catalyst is one or more of an iron-based metal, its oxide, or its organometallic complex.

[0023] In some embodiments, the main catalyst is one or more of the following metallic elements: iron, cobalt, and nickel.

[0024] In some embodiments, the main catalyst is in the form of an oxide, such as one or more of iron oxide, nickel oxide, and cobalt oxide.

[0025] In some embodiments, the main catalyst is an organometallic complex, such as one or more of ferrocene, cobalt dicene, and nickel dicene.

[0026] In some embodiments, the co-catalyst is one or more of yttrium oxide, cerium oxide, and lanthanum oxide.

[0027] In some embodiments, the growth promoter is one or more of sulfur, thiophene, and thiourea.

[0028] As one implementation, the composite catalyst has a particle size of 200-1000 mesh.

[0029] As one embodiment, the carrier gas of the composite catalyst is helium and / or argon, and hydrogen may be selectively added as an auxiliary component; the volume percentage of hydrogen in the carrier gas of the composite catalyst does not exceed 40%, and the flow rate ranges from 2 to 40 SLM.

[0030] As one implementation, the feed rate of the composite catalyst is 1~100 g / min.

[0031] In some embodiments, the feed rate of the composite catalyst is 1~35 g / min.

[0032] In some embodiments, when the carbon source is gaseous, the flow rate is 10~100 SLM; when the carbon source is liquid, the flow rate is 120~150 mL / min.

[0033] As one implementation, the carbon source carrier gas is helium and / or argon, and hydrogen may be selectively added as an auxiliary component; the volume percentage of hydrogen in the carbon source carrier gas does not exceed 60%, and the flow rate ranges from 10 to 80 SLM.

[0034] In some embodiments, when the carbon source is gaseous, the carbon source carrier gas flow rate ranges from 10 to 50 SLM; when the carbon source is liquid, the carbon source carrier gas flow rate ranges from 30 to 80 SLM.

[0035] As one implementation, the temperature of the growth zone is 900~1200 ℃.

[0036] As one implementation, the mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:0~6:0.5~6.

[0037] In some embodiments, the mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:0.1~5:2~6.

[0038] <Second aspect> The electric arc plasma torch device includes a feeding system, a plasma torch generation system, a growth temperature zone, a growth quenching zone, and a gas-solid separation device.

[0039] As one implementation, the plasma torch generation system includes a cathode and an anode, with a discharge chamber formed between the cathode and the anode. The front end of the cathode is a discharge tip, and the anode has an annular nozzle structure, with the nozzle positioned directly below the discharge tip of the cathode.

[0040] As one implementation, the cathode is provided with an axial gas channel on its outer periphery for conveying working gas axially into the discharge cavity.

[0041] As one implementation, several inclined through-feed channels are arranged circumferentially on the side wall of the discharge chamber, with the outlet end of the feed channel facing the inside of the discharge chamber, for conveying the reactants to the discharge chamber.

[0042] As one implementation, the feed channel is inclined with the outer side higher than the inner side.

[0043] As one implementation, the growth temperature zone is located downstream of the plasma torch generation system, forming a direct current channel along the plasma torch jet propagation direction.

[0044] As one implementation, the cavity of the growth temperature zone is provided with a heating system and an insulation structure covering the heating system.

[0045] As one implementation, the flow channel of the growth quenching zone is connected to the DC channel of the growth temperature zone.

[0046] As one implementation, the growth quenching zone is laterally connected to the end of the DC channel of the growth temperature zone.

[0047] In some embodiments, the flow channels at both ends of the growth temperature zone and the growth quenching zone form an L-shaped bend flow channel.

[0048] As one implementation, the growth quenching zone is a cooling zone.

[0049] In some embodiments, the cooling method of the growth quenching zone is to spray atomized water into the cavity.

[0050] As one implementation, the gas-solid separation device is connected to the cavity outlet of the growth quenching zone.

[0051] In some embodiments, the gas-solid separation device includes a vertical cyclone separator and a bag filter.

[0052] As one implementation, the feeding system also includes a loss-in-weight feeding system, which is connected to each feed channel and is used to continuously and quantitatively feed the reactants.

[0053] Compared with the prior art, the present invention has the following beneficial effects: (1) The catalyst system has strong compatibility and the formulation ratio can be selected more flexibly. In this invention, the main catalyst can be introduced in one or more combinations of elemental metals, inorganic metal compounds, or metal cadmiums, effectively improving the flexibility of catalyst introduction. This overcomes the technical limitations of FCCVD (floating catalyst chemical vapor deposition) which relies solely on ferrocene-based metal-organic precursors, and traditional thermal plasma CVD which is largely limited to elemental metal powder feedstocks. By flexibly selecting different types of catalyst precursors and their proportions, more technical approaches are provided for the diameter / chirality-selective growth of single-walled carbon nanotubes.

[0054] (2) Atomic-level homogeneous mixing reaction and higher graphitization degree with lower defect density This invention employs a carrier gas-carried composite catalyst powder, directly injected into the core region of a high-temperature plasma torch through a feed channel. The catalyst is rapidly vaporized, forming a uniformly dispersed, highly active atomic-level catalyst. Simultaneously, the carbon source is fully decomposed into high-density active carbon atoms in the same region. The two are atomically homogeneously mixed in the high-temperature region of the plasma torch, providing a foundation for the high-density nucleation and growth of single-walled carbon nanotubes. This process achieves the same high-graphitization, low-defect-density preparation of single-walled carbon nanotubes as traditional arc discharge methods, while avoiding the problem of excessive graphite impurities. This results in single-walled carbon nanotubes with high graphitization, low defect density, and high purity.

[0055] (3) Hydrogen in-situ etching and controlled growth This invention employs a gaseous or liquid carbon source and uses hydrogen as an auxiliary gas. Hydrogen not only increases the content of single-walled carbon nanotubes in the initial product but also etches amorphous carbon and other byproducts in situ during growth, improving product purity. Simultaneously, by utilizing the high-temperature characteristics of the plasma torch and the independently controlled growth temperature zone, the growth time window for single-walled carbon nanotubes can be effectively extended, resulting in high-quality single-walled carbon nanotubes with higher aspect ratios and better crystallinity.

[0056] (4) Strong process controllability This invention effectively controls the diameter, length, and yield of single-walled carbon nanotubes by independently adjusting parameters such as the gas components and their flow rates, the composite catalyst formulation and feeding rate, the plasma torch power, and the growth zone temperature, offering high process flexibility. Furthermore, this invention employs a crucible-free continuous feeding design, leveraging the high jet velocity of the plasma torch to achieve continuous production of reaction products. The process exhibits excellent scalability; yield can be increased by adjusting the plasma torch power and feed rate, making it suitable for applications ranging from laboratory research to industrial-scale continuous production. Attached Figure Description

[0057] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 The electric arc plasma torch device provided by the present invention; Figure 2 This is a schematic diagram showing the distribution of the feed channels in an electric arc plasma torch device. Figure 3 This is a flowchart of the preparation of single-walled carbon nanotubes based on an electric arc plasma torch; Figure 4 The Raman spectrum of the single-walled carbon nanotubes prepared in Example 2; Figure 5 This is a scanning electron microscope image of the single-walled carbon nanotubes prepared in Example 2. Detailed Implementation

[0058] The present invention will be described in detail below with reference to embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several adjustments and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0059] Example 1 See Figure 1 An electric arc plasma torch device includes a shell, a feeding system, a plasma torch generation system, a growth temperature zone 7, a growth quenching zone 10, and a gas-solid separation device.

[0060] It should be noted that the shell does not simply refer to the external protective outer shell, but also includes related supporting structures such as electrode insulation and isolation structures, which will not be elaborated here.

[0061] The plasma torch generation system is located at the top of the device and includes a cathode 1 and an anode 5. The front end of the cathode 1 is a discharge tip, and the anode 5 has an annular nozzle structure, which is coaxially arranged with the cathode 1. The nozzle of the anode 5 is located below the discharge tip of the cathode 1, forming a discharge cavity between the anode 5 and the cathode 1.

[0062] In this embodiment, both cathode 1 and anode 5 are graphite electrodes.

[0063] The cathode 1 is surrounded by a shell, and an axial gas channel 2 is formed between the outer periphery of the cathode 1 and the inner wall of the shell. The axial gas channel 2 can be configured as a continuous annular channel along the circumference; or it can be configured as a combination of gas channels arranged uniformly and symmetrically along the circumference.

[0064] When the axial gas channel 2 is a continuous annular channel, an insulating support structure is installed at the rear end of the cathode 1 and fixedly mounted on the housing to achieve positioning and insulation isolation.

[0065] When the axial gas channel 2 is a combination of gas channels, radial support ribs are provided between adjacent gas channels. The inner end is connected to the outer wall of the cathode 1 and the outer end is connected to the inner wall of the shell. This not only provides radial positioning and fixation for the cathode 1, but also divides the circumferential space into gas channels that are independent and symmetrically arranged.

[0066] The outlet end of the axial gas channel 2 extends to the discharge cavity between the discharge tip of the cathode 1 and the anode 5, and is used to deliver working gas axially into the discharge cavity.

[0067] The working gas is used as the arc-initiating gas. A voltage is applied between the cathode 1 and the anode 5 to break down the working gas, ionize it in the discharge cavity to form an electric arc and generate plasma. The plasma is then concentrated and ejected through the annular nozzle of the anode 5 to form a directional plasma torch jet 6.

[0068] On the side wall of the shell corresponding to the discharge chamber, several inclined through-feed channels are symmetrically arranged in the circumferential direction. Each feed channel extends from the outside of the shell to the inside and is inclined with the outside higher and the inside lower. The outlet end of the feed channel faces the inside of the discharge chamber and is aligned with the discharge area between the cathode 1 and the anode 5. It is used to feed the reactant into the discharge chamber, so that the material is mixed with the working gas and sprayed into the downstream growth temperature zone 7 through the nozzle of the anode 5 along with the plasma torch jet 6.

[0069] As one implementation scheme, the feeding channels are divided into two groups: the first feeding channel group 3 and the second feeding channel group 4. The two groups of feeding channels are arranged circumferentially at intervals, respectively conveying different reactive materials to achieve axially staggered and uniform feeding.

[0070] In this embodiment, as Figure 2 As shown, six feeding channels are evenly distributed, with the first feeding channel group 3 and the second feeding channel group 4 alternating and arranged symmetrically.

[0071] The feeding system adopts a loss-in-weight feeding system, which is connected to each feed channel to achieve continuous and precise quantitative feeding of the reactants.

[0072] The growth temperature zone 7 is located downstream of the plasma torch generation system, forming a direct current channel along the direction of the plasma torch jet 6.

[0073] The growth temperature zone 7 is equipped with a heating system 8 and a heat insulation structure 9 covering the outside of the cavity. These are used to maintain the temperature stability inside the cavity and provide a suitable temperature environment for the nucleation, phase transformation and grain growth of the reactants as they travel with the plasma torch jet 6.

[0074] The growth quenching zone 10 is laterally connected to the end of the growth temperature zone 7, and the DC channel of the growth temperature zone 7 is bent and connected to the flow channel of the growth quenching zone 10.

[0075] The growth quenching zone 10 is a cooling zone that terminates grain growth by lowering the temperature of the gas-solid mixture.

[0076] In this embodiment, the cooling method for the growth quenching zone 10 is to spray atomized water into the cavity.

[0077] In actual implementation, the cooling method for the growth quenching zone 10 can also be the injection of cooling gas into the cavity.

[0078] In this embodiment, the growth temperature zone 7 and the growth quenching zone 10 are connected one after the other, and the two flow channels together form an L-shaped bent flow channel.

[0079] The gas-solid separation device is connected to the outlet of chamber 10 in the growth and quenching zone. It consists of a vertical cyclone separator and a bag filter, allowing the gas-solid mixture to enter the gas-solid separation process with the airflow.

[0080] In this embodiment, the gas-solid separation device is arranged perpendicularly to the growth and quenching zone 10.

[0081] It should be noted that the gas-solid separation device is equipped with an induced draft fan and an exhaust gas treatment device. The induced draft fan is located at the rear end of the bag filter, and the exhaust gas treatment device is used to treat the exhaust gas after gas-solid separation.

[0082] This specific embodiment also provides a method for using the above-described arc plasma torch device to prepare single-walled carbon nanotubes, such as... Figure 3 As shown, it includes the following steps: S1. After the system is evacuated, an arc-initiating gas is introduced and a direct current is applied to initiate an electric arc to form a stable high-temperature plasma torch. The carrier gas carries the carbon source and composite catalyst from different feed channels to the electric arc plasma torch, so that they are uniformly mixed and rapidly melted and vaporized to form an atomic-scale catalyst / carbon mixture system. S2. The catalyst / carbon mixture is transported to the growth temperature zone by an electric arc plasma torch jet to nucleate and grow single-walled carbon nanotubes, forming a gas-solid mixture. S3. The gas-solid mixture formed is carried by the airflow into the growth quenching zone connected at the end of the growth temperature zone for rapid quenching. S4. The cooled gas-solid mixture enters the gas-solid separation device with the airflow for gas-solid separation, and the generated single-walled carbon nanotube powder is collected. The separated gas enters the tail gas treatment device for treatment.

[0083] Based on the above preparation method, several examples and comparative examples were prepared by adjusting key process parameters, as detailed below.

[0084] Example 2 In step S1, argon is selected as the arc-starting gas, and the flow rate is 20 SLM. A 70 kW DC current is applied between cathode 1 and anode 5 to initiate an electric arc, forming a stable high-temperature plasma torch; The main catalyst is iron powder with a particle size of 200 mesh; the co-catalyst is lanthanum oxide powder with a particle size of 200 mesh; and the growth promoter is sulfur powder with a particle size of 200 mesh. The three are mixed in a mass ratio of 10:0.1:6 to form a composite catalyst. Argon gas with a flow rate of 10 SLM is used as the carrier gas to transport the composite catalyst from the second feed channel group 4 into the discharge chamber at a feed rate of 2 g / min. The carbon source is methane. A mixture of argon and hydrogen (50% hydrogen by volume) with a flow rate of 40 SLM is used as the carrier gas and mixed with methane with a flow rate of 50 SLM. The mixture is then transported to the discharge chamber through the first feed channel group 3. This allows the composite catalyst and methane to be uniformly mixed and rapidly melted and vaporized, forming an atomic-scale catalyst / carbon mixture system in the arc plasma torch jet.

[0085] In step S2, the catalyst / carbon mixture is transported to a growth zone with heating and insulation by an arc plasma torch jet, where the temperature is controlled at 1000°C for the nucleation and growth of single-walled carbon nanotubes.

[0086] In step S3, the gas-solid mixture enters the growth quenching zone 10 under the combined action of the plasma torch jet and the gas flow. The formed single-walled carbon nanotubes are then rapidly quenched by spraying atomized water, halting their growth. Atomized water cooling is a standard industrial procedure and will not be described in detail here.

[0087] The resulting products are mainly single-walled carbon nanotubes with diameters ranging from 0.8 to 1.5 nm, and a crystallinity of I. G / I D It has a value of 152 and a purity of 60%.

[0088] The Raman spectrum of the single-walled carbon nanotube sample prepared in this embodiment is as follows: Figure 4 As shown. Scanning electron microscope image as follows. Figure 5 As shown.

[0089] Example 3 The preparation method in this embodiment is basically the same as that in Example 2, except that: The flow rate of the arc-initiating gas is 10 SLM, and the power of the plasma torch is 80 kW; The main catalyst is iron(III) oxide with a particle size of 500 mesh; The mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:0.1:4; The carrier gas flow rate of the composite catalyst was 20 SLM, and the feed rate of the composite catalyst was 3 g / min. The carbon source is high-purity coalbed methane, with a flow rate of 50 SLM; The carrier gas for the carbon source is a mixture of argon and hydrogen, with hydrogen content of 60% by volume and a flow rate of 30 SLM. The temperature in the growth zone is 1200 ℃.

[0090] The prepared products are mainly single-walled carbon nanotubes with a diameter distribution of 0.9–1.5 nm and a crystallinity of I. G / I D The value is 164, and the purity is 62%.

[0091] Example 4 The preparation method in this embodiment is basically the same as that in Example 2, except that: The plasma torch has a power of 120 kW; The main catalyst is ferrocene with a particle size of 200 mesh; The mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:0.2:2; The carrier gas flow rate of the composite catalyst is 40 SLM, and the feed rate of the composite catalyst is 10 g / min. The carbon source is high-purity natural gas, with a flow rate of 100 SLM; The carrier gas for the carbon source is a mixture of argon and hydrogen, with a hydrogen volume content of 60% and a flow rate of 60 SLM. The temperature in the growth zone is 1100 ℃.

[0092] The prepared products are mainly single-walled carbon nanotubes with a diameter distribution of 0.7~1.8 nm and a crystallinity of I. G / I D The value is 146, and the purity is 74%.

[0093] Example 5 The preparation method in this embodiment is basically the same as that in Example 2, except that: The plasma torch power is 10 kW; The arc-initiating gas velocity is 1 SLM; The main catalyst is ferrocene with a particle size of 500 mesh; The mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:0.2:2; The carrier gas flow rate of the composite catalyst is 2 SLM, and the feed rate of the composite catalyst is 1 g / min. The carbon source is high-purity natural gas, with a flow rate of 10 SLM; The carrier gas for the carbon source is a mixture of argon and hydrogen, with a hydrogen volume content of 20% and a flow rate of 10 SLM. The temperature in the growth zone is 1200 ℃.

[0094] The prepared products are mainly single-walled carbon nanotubes with a diameter distribution of 0.7~1.8 nm and a crystallinity of I. G / I D The value is 156, and the purity is 76%.

[0095] Example 6 The preparation method in this embodiment is basically the same as that in Example 2, except that: Helium was used as the arc-starting gas at a flow rate of 20 SLM, and the plasma torch power was 100 kW. The main catalyst is nickel powder with a particle size of 500 mesh; The catalyst is yttrium oxide with a particle size of 1000 mesh; The growth promoter is sulfur powder with a particle size of 200 mesh; The mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:5:2; The carrier gas for the composite catalyst is a mixture of helium and hydrogen, with a hydrogen volume content of 20% and a flow rate of 20 SLM. The feed rate of the composite catalyst is 20 g / min; The carbon source is ethane gas, with a flow rate of 50 SLM; The carbon source carrier gas is a mixture of helium and hydrogen, with a hydrogen volume content of 10% and a flow rate of 80 SLM.

[0096] The prepared products are mainly single-walled carbon nanotubes with a diameter distribution of 1.2~1.7 nm and a crystallinity of I. G / I D The value is 356, and the purity is 78%.

[0097] Example 7 The preparation method in this embodiment is basically the same as that in Example 2, except that: Helium was used as the arc-starting gas at a flow rate of 10 SLM, and the plasma torch power was 160 kW. The main catalyst is nickel oxide powder with a particle size of 5000 mesh; The catalyst is cerium oxide with a particle size of 500 mesh; The growth promoter is thiophene with a particle size of 200 mesh; The mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:3:3; The carrier gas for the composite catalyst is a mixture of helium and hydrogen, with a hydrogen volume content of 20% and a flow rate of 20 SLM. The feed rate of the composite catalyst is 25 g / min; The carbon source is ethanol, and the flow rate is 150 mL / min; The carbon source carrier gas is a mixture of helium and hydrogen, with hydrogen volume content of 50% and a flow rate of 70 SLM. The growth temperature range is 900 ℃.

[0098] The prepared products are mainly single-walled carbon nanotubes with a diameter distribution of 1.2~1.7 nm and a crystallinity of I. G / I D It has a value of 285 and a purity of 65%.

[0099] Example 8 The preparation method in this embodiment is basically the same as that in Example 2, except that: Helium was used as the arc-starting gas at a flow rate of 20 SLM, and the plasma torch power was 200 kW. The main catalyst is nickel oxide powder with a particle size of 500 mesh; The catalyst is lanthanum oxide with a particle size of 1000 mesh; The growth promoter is thiourea with a particle size of 200 mesh; The mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:5:3; The carrier gas for the composite catalyst is a mixture of helium and hydrogen, with a hydrogen volume content of 20% and a flow rate of 20 SLM. The feed rate of the composite catalyst is 35 g / min; The carbon source is benzene, and the flow rate is 120 mL / min; The carbon source carrier gas is a mixture of helium and hydrogen, with hydrogen volume content of 50% and a flow rate of 80 SLM. The growth temperature range is 900 ℃.

[0100] The prepared products are mainly single-walled carbon nanotubes with a diameter distribution of 1.2~1.7 nm and a crystallinity of I. G / I D It has a value of 225 and a purity of 64%.

[0101] Example 9 The preparation method in this embodiment is basically the same as that in Example 2, except that: Argon was used as the arc-starting gas with a flow rate of 20 SLM and the plasma torch power was 150 kW. The main catalyst is a mixture of iron and cobalt powder with a particle size of 1000 mesh; The catalyst is yttrium oxide with a particle size of 500 mesh; The growth promoter is sulfur powder with a particle size of 500 mesh; The mass ratio of the main catalyst, co-catalyst, and growth promoter is 10:5:2; The carrier gas for the composite catalyst is a mixture of argon and hydrogen, with a hydrogen volume content of 40% and a flow rate of 20 SLM. The feed rate of the composite catalyst is 20 g / min; The carbon source is high-purity natural gas, with a flow rate of 100 SLM; The carbon source carrier gas is a mixture of argon and hydrogen, with a hydrogen volume content of 60% and a flow rate of 80 SLM. The temperature in the growth zone is 1100 ℃.

[0102] The prepared products are mainly single-walled carbon nanotubes with a diameter distribution of 1.0~1.6 nm and a crystallinity of I. G / I D It has a value of 185 and a purity of 60%.

[0103] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing single-walled carbon nanotubes, characterized in that, Includes the following steps: S1. The carrier gas carries the carbon source and composite catalyst from different feed channels into the electric arc plasma torch, where they are uniformly mixed and melted and vaporized to form an atomic-scale catalyst / carbon mixture system. S2. The catalyst / carbon mixture is transported to the growth temperature zone by an electric arc plasma torch jet to nucleate and grow single-walled carbon nanotubes, forming a gas-solid mixture. S3. The gas-solid mixture formed is carried by the airflow into the growth quenching zone connected at the end of the growth temperature zone for rapid quenching. S4. After cooling, the gas-solid mixture is subjected to gas-solid separation, and the solid product is collected to obtain single-walled carbon nanotubes.

2. The preparation method according to claim 1, characterized in that, The carrier gas is helium and / or argon, and hydrogen may be selectively added as an auxiliary component. The volume percentage of hydrogen in the carrier gas does not exceed 60%, and the flow rate ranges from 2 to 150 SLM.

3. The preparation method according to claim 2, characterized in that, The carrier gas of the composite catalyst is helium and / or argon, and hydrogen may be selectively added as an auxiliary component; the volume percentage of hydrogen in the carrier gas of the composite catalyst does not exceed 40%, and the flow rate ranges from 2 to 40 SLM. The carbon source carrier gas is helium and / or argon, and hydrogen may be selectively added as an auxiliary component; the volume percentage of hydrogen in the carbon source carrier gas does not exceed 60%, and the flow rate ranges from 10 to 80 SLM.

4. The preparation method according to claim 1, characterized in that, The composite catalyst consists of a main catalyst, a co-catalyst, and a growth promoter.

5. The preparation method according to claim 4, characterized in that, The main catalyst is one or more of iron-based metals, their oxides, and their organometallic complexes; the co-catalyst is one or more of yttrium oxide, cerium oxide, and lanthanum oxide; and the growth promoter is one or more of sulfur, thiophene, and thiourea.

6. The preparation method according to claim 5, characterized in that, When the main catalyst is an iron-based metal, the main catalyst is one or more of elemental iron, cobalt, and nickel; When the main catalyst is an iron-based metal oxide, the main catalyst is one or more of iron oxide, nickel oxide, and cobalt oxide; When the main catalyst is an iron-based metal organic complex, the main catalyst is one or more of ferrocene, cobalt dicene, and nickel dicene.

7. The preparation method according to claim 1, characterized in that, The carbon source is a gaseous carbon source and / or a liquid carbon source.

8. The preparation method according to claim 7, characterized in that, When the carbon source is gaseous, the gaseous carbon source is one or more of methane, high-purity coalbed methane, high-purity natural gas, and ethane, and the carbon source carrier gas flow rate is 10~50 SLM; When the carbon source is liquid, the liquid carbon source is benzene and / or ethanol, and the carbon source carrier gas flow rate is 30~80 SLM.

9. An arc plasma torch apparatus for use in the preparation method according to any one of claims 1 to 8, characterized in that, include: A plasma torch generation system includes a cathode, an anode, and a discharge cavity between the cathode and the anode. The front end of the cathode is a discharge tip, and the anode has an annular nozzle structure. The nozzle is positioned directly below the discharge tip of the cathode. An axial gas channel is provided on the outer periphery of the cathode for supplying working gas to the discharge cavity axially. Several inclined through-feed channels are arranged circumferentially on the side wall of the discharge cavity, with the outlet end of the feed channel facing the interior of the discharge cavity for supplying reactants to the discharge cavity. The growth temperature zone is located downstream of the plasma torch generation system. It is a direct current channel with a heating system and a heat preservation system on the outside. The growth quenching zone is a cooling zone, and its flow channels are connected to the DC channels of the growth temperature zone. The gas-solid separation device is connected to the outlet of the growth and quenching zone.

10. The apparatus according to claim 9, characterized in that, It also includes at least one of the following technical features: A. The growth quenching zone is laterally connected to the end of the DC channel of the growth temperature zone; B. The cooling method for the growth quenching zone is to spray atomized water into the cavity.

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