Preparation method and continuous production system for single-walled carbon nanotubes

Abstract

Provided are a preparation method and continuous production system for single-walled carbon nanotubes. The preparation method for single-walled carbon nanotubes comprises the following steps: catalyst pretreatment: using a microwave plasma generator (4) to excite a catalyst to form nanoscale particles, then sequentially using gases having decreasing densities to perform gradient screening on the nanoscale catalyst particles, and forming a catalyst dispersion from the screened nanoscale catalyst particles together with a liquid carbon source and a promoter; and catalytic growth: atomizing the catalyst dispersion by means of an atomizer (5), then bringing the atomized catalyst dispersion into a reactor (6) by means of a carrier gas, and heating the reactor (6) to 1000-1500°C to grow single-walled carbon nanotubes. In the provided preparation method for single-walled carbon nanotubes, the microwave plasma generator (4) is used to excite the catalyst, so that the catalyst forms nanoscale particles, and gas screening is then performed on the nanoscale particles to obtain a catalyst having a smaller size and a narrower particle size, so that the purity of the finally obtained single-walled carbon nanotubes is high.

Description

Preparation method of single-walled carbon nanotubes and continuous production system TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon nanotube growth, in particular to a preparation method of single-walled carbon nanotubes and a continuous production system. BACKGROUND

[0002] Carbon nanotubes are tubular structures curled from graphene, and can be divided into single-walled carbon nanotubes and multi-walled carbon nanotubes according to the number of layers of the carbon nanotube wall. Single-walled carbon nanotubes have excellent lightweight, mechanical, electrical, thermal, optical and other properties. These special properties make single-walled carbon nanotubes have great application potential in aerospace equipment, energy storage, flexible transparent microelectronics, multifunctional composites and other applications. However, how to mass-produce single-walled carbon nanotubes has been restricting their application in various fields, so it is necessary to study the mass production technology of single-walled carbon nanotubes.

[0003] The preparation method of carbon nanotubes includes arc discharge method, laser evaporation method and chemical vapor deposition method, etc. The arc discharge method and the laser evaporation method have low yield and high energy consumption, and are difficult to realize large-scale production. The floating catalyst chemical vapor deposition method for preparing carbon nanotubes has the advantages of high purity, strong continuity and easy scaling, and is the main scheme for preparing carbon nanotubes at present. However, in the floating catalyst chemical vapor deposition method, the size of the catalyst cannot be controlled, and a large amount of multi-walled carbon nanotubes are contained in the prepared product.

[0004] Therefore, how to control the size of the metal catalyst and realize continuous and stable preparation of single-walled carbon nanotubes is a problem to be solved. SUMMARY

[0005] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0006] The purpose of the present application is to provide a preparation method of single-walled carbon nanotubes and a continuous production system. The preparation method of single-walled carbon nanotubes excites the catalyst by a microwave plasma generator to form nanoscale catalyst particles, and then gradually screens the nanoscale catalyst particles by gas to obtain a nanoscale catalyst dispersion liquid, thereby solving the problem that the size of the catalyst cannot be controlled in the prior art, resulting in a large amount of multi-walled carbon nanotubes in the product.

[0007] In order to achieve one of the above purposes, an embodiment of the present application provides a preparation method of single-walled carbon nanotubes and a continuous production system. The catalyst is pretreated by using a microwave plasma generator to excite the catalyst to form nanoscale particles, and then using gas with decreasing density to gradiently screen the nanoscale catalyst particles. The screened nanoscale catalyst particles form a catalyst dispersion liquid with a liquid carbon source and a promoter.

[0008] Catalytic growth: the catalyst dispersion liquid is atomized by an atomizer and then carried into the reactor by a carrier gas. The reactor is heated to 1000-1500°C to grow single-walled carbon nanotubes.

[0009] As a further improvement of the embodiment of the present application, a graphite tube is used as the reactor.

[0010] As a further improvement of the embodiment of the present application, the surface of the graphite tube is coated with a metal coating.

[0011] As a further improvement of the embodiment of the present application, the metal coating is a titanium-based, nickel-based or zirconium-based coating.

[0012] As a further improvement of the embodiment of the present application, in the catalyst pretreatment, Kr and N2 are used in sequence to screen the catalyst particles.

[0013] As a further improvement of the embodiment of the present application, the catalyst is a metal catalyst, and the metal catalyst is at least one of Fe, Co, Ni, Pd, Pt, Cu, Mn, Cr, Mo and Ge.

[0014] As a further improvement of the embodiment of the present application, the liquid carbon source is an organic hydrocarbon liquid carbon source or an organic alcohol liquid carbon source.

[0015] As a further improvement of the embodiment of the present application, the liquid carbon source is at least one of methanol, ethanol, acetone, butanol, benzyl alcohol, benzene, ethylene glycol, diethyl ether or n-hexane.

[0016] As a further improvement of the embodiment of the present application, in the catalytic growth step, a gaseous carbon source is filled into the reactor.

[0017] As a further improvement of the embodiment of the present application, the gaseous carbon source is one or more of carbon monoxide, methane, ethylene and acetylene.

[0018] As a further improvement of the embodiment of the present application, the promoter is one or more of water, thiophene and molybdenum acetate.

[0019] The embodiment of the present application also provides a continuous production system of single-walled carbon nanotubes, comprising:

[0020] The catalyst pretreatment device comprises a reaction tank, a screening tank and a collection tank connected in sequence, the reaction tank is connected with a microwave plasma generator, and the reaction tank and the screening tank are sequentially filled with gases with decreasing densities;

[0021] The reaction device comprises an atomizer connected with the collection tank, a reactor connected with the atomizer and a heater for heating the reactor, and a gas supply tank is connected between the atomizer and the reactor.

[0022] A collecting device is connected to the output end of the reactor.

[0023] As a further improvement of the embodiment of the present application, the reactor is connected to a carbon source supplementing unit, which is connected to the middle part of the reactor.

[0024] As a further improvement of the embodiment of the present application, the gas supplied in the gas supply tank is H2, N2 or Ar.

[0025] As a further improvement of the embodiment of the present application, the collecting device comprises a collecting tank, an exhaust gas discharge pipeline connected to the collecting tank, and a switch valve group for cutting off or connecting the collecting tank and the reactor.

[0026] The one or more technical solutions provided by the present application have at least the following technical effects or advantages:

[0027] The preparation method of the single-walled carbon nanotube provided by the present application first excites the catalyst by a microwave plasma generator, so that the catalyst forms nanoscale catalyst particles; then the catalyst particles with smaller sizes are screened out by using gases with decreasing densities in a step-by-step manner, and the catalyst particles are mixed with a liquid carbon source to obtain a catalyst dispersion liquid; then the catalyst dispersion liquid is atomized by an atomizer and is carried into a reactor by a carrier gas; after being heated, carbon atoms grow on the surface of the catalyst, and the produced single-walled carbon nanotube has a purity of I G / I D >80.

[0028] Other aspects can become apparent after reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0029] The accompanying drawings are included to provide a further understanding of the technical solutions of the present application, and constitute a part of the specification, and are used together with the embodiments of the present application to explain the technical solutions of the present application, and do not constitute a limitation on the technical solutions of the present application.

[0030] FIG. 1 is a structural schematic diagram of a catalyst pretreatment device in an embodiment of the present application.

[0031] FIG. 2 is a structural schematic diagram of a reaction device in an embodiment of the present application.

[0032] FIG. 3 is a scanning electron microscope photo of single-walled carbon nanotubes produced in Example 1.

[0033] FIG. 4 is a scanning electron microscope photo of single-walled carbon nanotubes produced in Example 2.

[0034] FIG. 5 is a scanning electron microscope photo of single-walled carbon nanotubes produced in Example 3.

[0035] Figure 6 is a scanning electron micrograph of single-walled carbon nanotubes produced in Example 4.

[0036] Figure 7 is a Raman spectrum of single-walled carbon nanotubes produced in Example 4.

[0037] Figure 8 is a Raman spectrum of the single-walled feature of single-walled carbon nanotubes produced in Example 4.

[0038] Figure 9 is a transmission electron micrograph of single-walled carbon nanotubes produced in Example 5.

[0039] Figure 10 is a Raman spectrum of single-walled carbon nanotubes produced in Example 5.

[0040] Figure 11 is a Raman spectrum of the single-walled feature of single-walled carbon nanotubes produced in Example 5.

[0041] 1. reaction tank; 2. screening tank; 3. collection tank; 4. microwave plasma generator; 5. atomizer; 6. reactor; 7. heater; 8. collection device; 9. gas supply tank; 10. carbon source supplement unit. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0043] The terms such as "central", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like used herein to indicate spatial relative positions are for the purpose of convenient description to describe the relationship of one unit or feature relative to another unit or feature as shown in the drawings. The spatial relative position terms can be intended to include different orientations of the device in use or work other than the orientation shown in the drawings.

[0044] For example, if the device in the drawing is turned over, the unit described as being "below" or "under" the other unit or feature will be "above" the other unit or feature. Therefore, the exemplary term "below" can encompass both upward and downward orientations. The device can be oriented in other ways (rotated 90 degrees or other orientations), and the spatially-related descriptions used herein are interpreted accordingly.

[0045] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connecting" should be understood in a broad sense, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0046] The embodiment of the present application provides a preparation method of single-walled carbon nanotubes, comprising the following steps:

[0047] The catalyst is excited to form nanoscale particles by using a microwave plasma generator 4, and then the nanoscale catalyst particles are screened by using gases with gradually decreasing densities in sequence. The screened nanoscale catalyst particles form a catalyst dispersion liquid together with a liquid carbon source and a promoter.

[0048] The catalyst dispersion liquid is atomized by an atomizer 5 and then carried into a reactor 6 by a carrier gas. The reactor 6 is heated to 1000-1500 DEG C to grow single-walled carbon nanotubes.

[0049] In the catalyst pretreatment, the catalyst is rapidly excited to form nanoscale particles by using a microwave plasma generator 4. Since the lower the gas density, the lower the lifting capacity of the catalyst particles, that is, the particles with smaller particle size and narrower particle size distribution are screened by using gases with gradually decreasing densities in sequence, so that the size of the catalyst is more uniform, and the purity of the single-walled carbon nanotubes produced by the catalyst is higher.

[0050] After the smaller nanoscale catalyst particles screened are added into the liquid carbon source and the promoter, the catalyst is dispersed in the liquid carbon source to form a catalyst dispersion liquid. The catalyst dispersion liquid is atomized by an atomizer 5 and then carried into a reactor 6 by a carrier gas. The liquid carbon source is cracked into carbon atoms at high temperature to grow single-walled carbon nanotubes on the surface of the catalyst.

[0051] In some embodiments, the carrier gas can be H2, N2 or Ar.

[0052] The promoter can maintain the activity of the catalyst and prevent the catalyst from being deactivated by agglomeration. In some embodiments, the promoter is one or more of water, thiophene and molybdenum acetate.

[0053] In some embodiments, a graphite tube is used as the reactor 6. Graphite has excellent thermal conductivity, which is better than that of mullite, quartz, corundum and silicon carbide, which can be used as the material of the reactor 6. The graphite tube as the reactor 6 has more uniform temperature field distribution, smaller gas flow dynamics and stable carbon source pyrolysis, which is beneficial to improve the growth efficiency of single-walled carbon nanotubes.

[0054] In some embodiments, the graphite tube surface is coated with a metal coating layer, which can effectively absorb the deposited catalyst particles and reduce the interference of the excess catalyst on the growth, thereby greatly improving the continuity of the single-walled carbon nanotube growth.

[0055] In some embodiments, the metal coating layer is a titanium-based, nickel-based or zirconium-based coating layer.

[0056] In some embodiments, Kr and N2 are used in sequence to screen the catalyst particles in the catalyst pretreatment. Kr is a rare gas with relatively high atomic mass, high density and strong lifting force, which can screen out nanoscale catalyst particles. N2 has a lower density and can only screen out smaller catalyst particles.

[0057] In some embodiments, the catalyst is a metal catalyst, and the metal catalyst is at least one of Fe, Co, Ni, Pd, Pt, Cu, Mn, Cr, Mo and Ge. Of course, the catalyst can also be a non-metal catalyst. Since the metal catalyst has higher efficiency, the metal catalyst is taken as an example in the present application.

[0058] In some embodiments, the liquid carbon source is an organic hydrocarbon liquid carbon source or an organic alcohol liquid carbon source. The organic hydrocarbon substance has a low possibility of producing other impurities because it only contains C and H elements in the molecule.

[0059] In some other embodiments, the liquid carbon source can also be at least one of methanol, ethanol, acetone, butanol, benzyl alcohol, benzene, ethylene glycol, diethyl ether or n-hexane.

[0060] In some embodiments, a gaseous carbon source is filled into the reactor 6 during the catalytic growth step. The gaseous carbon source is filled into the reactor 6 at the same time as the liquid carbon source is cracked and the single-walled carbon nanotubes are formed on the surface of the catalyst, thereby avoiding the insufficient carbon source from affecting the continuity of the single-walled carbon nanotube growth.

[0061] In some embodiments, the gaseous carbon source includes carbon monoxide, methane, ethylene or acetylene.

[0062] The present application also provides a continuous production system for single-walled carbon nanotubes, as shown in FIGS. 1-2, which includes a catalyst pretreatment device, a reaction device and a material collecting device 8. The catalyst pretreatment device includes a reaction tank 1, a screening tank 2 and a collecting tank 3 connected in sequence. The reaction tank 1 is connected to a microwave plasma generator 4. The reaction tank 1 and the screening tank 2 are filled with gases with decreasing densities in sequence. The reaction device includes an atomizer 5 connected to the collecting tank 3, a reactor 6 connected to the atomizer 5 and a heater for heating the reactor 6. A gas supply tank 9 is connected between the atomizer 5 and the reactor 6. The material collecting device 8 is connected to the output end of the reactor 6.

[0063] The catalyst is pretreated in a catalyst pretreatment device, specifically:

[0064] The catalyst is placed in the reaction tank 1, and is excited by the microwave plasma generator 4 to form nanoscale catalyst particles. As shown in FIG. 1, the pipelines connecting the reaction tank 1 and the screening tank 2, the screening tank 2 and the collection tank 3 are all communicated with the top of the reaction tank 1, the screening tank 2 and the collection tank 3, and the gas is filled from the bottom of the reaction tank 1 and the screening tank 2. The gas with slightly larger density, such as Kr, is filled into the reaction tank 1, and the nanoscale catalyst particles with smaller size are taken out from the top of the reaction tank 1 and into the screening tank 2; the gas with slightly smaller density, such as N2, is filled into the screening tank 2 to perform secondary screening on the catalyst particles, and the catalyst particles with smaller size are taken out from the screening tank 2 and into the collection tank 3 containing the liquid carbon source and the promoter to form a catalyst dispersion liquid.

[0065] The catalyst dispersion liquid in the collection tank 3 is ultrasonically atomized by the atomizer 5. In some embodiments, the catalyst dispersion liquid is pushed to the atomizer 5 by the injection pump, and then is supplied with gas by the gas supply tank 9 and is taken into the reactor 6 by the carrier gas. The heater heats the reactor 6 to a desired temperature, and the single-walled carbon nanotubes are formed on the surface of the catalyst after the carbon source is cracked.

[0066] In some embodiments, the reactor 6 is connected to the carbon source supplementing unit 10, and the carbon source supplementing unit 10 is communicated to the middle position of the reactor 6. The carbon source supplementing unit 10 is connected to the reactor 6 to supplement the carbon source in the reactor 6, so as to avoid the insufficient supply of the carbon source to interfere with the continuous casting growth of the single-walled carbon nanotubes.

[0067] In some embodiments, the gas supplied in the gas supply tank 9 is H2, N2 or Ar.

[0068] In some embodiments, the material collecting device 8 includes a material collecting box, an exhaust pipeline communicated with the material collecting box, and a switch valve group for cutting off or communicating the material collecting box and the reactor 6. The material collecting box collects the single-walled carbon nanotubes produced in the reactor 6, and the carrier gas filled in the gas supply tank 9 is discharged through the exhaust pipeline.

[0069] The technical solutions of the present application are further described below in combination with specific embodiments.

[0070] Embodiment 1

[0071] Embodiment 1 uses the continuous production system for single-walled carbon nanotubes provided by the present application to produce single-walled carbon nanotubes, wherein the reactor 6 uses a graphite tube coated with a 0.6 mm zirconia coating on the surface, and the preparation method of the single-walled carbon nanotubes includes the following steps:

[0072] Catalyst pretreatment: metal iron is placed in the reaction tank 1, and catalyst particles are formed by exciting the microwave plasma generator 4, Kr is filled at the bottom of the reaction tank 1, N2 is filled in the screening tank 2, and finally catalyst particles with a particle size of 0.2-2 nm are screened out, and the catalyst particles are blown into the collection tank 3 containing ethanol and a promoter to form a catalyst dispersion liquid, wherein the promoter is 95% thiophene + 5% water by mass fraction.

[0073] Catalytic growth: the catalyst dispersion liquid in the collection tank 3 is pushed into the atomizer 5 through the injection pump, and then enters the reactor 6 under the driving of the gas flow of H2 with a flow rate of 10 L / min and Ar with a flow rate of 10 L / min provided by the gas supply tank 9 after being atomized by the atomizer 5, and the heater is heated to 1400℃, while the carbon source supplementing unit 10 supplements CO into the reactor 6, and the carbon source forms single-walled carbon nanotubes on the surface of the catalyst after cracking, and the purity of the final product is I G / I D 82.

[0074] Example 2

[0075] Example 2 uses the single-walled carbon nanotube continuous production system provided in the present application to produce single-walled carbon nanotubes, wherein the reactor 6 uses a graphite tube coated with a 0.8mm zirconia coating on the surface, and the preparation method of the single-walled carbon nanotubes comprises the following steps:

[0076] Catalyst pretreatment: metal iron is placed in the reaction tank 1, and catalyst particles are formed by exciting the microwave plasma generator 4, Kr is filled at the bottom of the reaction tank 1, N2 is filled in the screening tank 2, and finally catalyst particles with a particle size of 0.2-2 nm are screened out, and the catalyst particles are blown into the collection tank 3 containing ethanol and a promoter to form a catalyst dispersion liquid, wherein the promoter is 95% thiophene + 5% water by mass fraction.

[0077] Catalytic growth: the catalyst dispersion liquid in the collection tank 3 is pushed into the atomizer 5 through the injection pump, and then enters the reactor 6 under the driving of the gas flow of H2 with a flow rate of 10 L / min and Ar with a flow rate of 10 L / min provided by the gas supply tank 9 after being atomized by the atomizer 5, and the heater is heated to 1400℃, while the carbon source supplementing unit 10 supplements CO into the reactor 6, and the carbon source forms single-walled carbon nanotubes on the surface of the catalyst after cracking, and the purity of the final product is I G / I D 85.

[0078] Example 3

[0079] Example 3 uses the single-walled carbon nanotube continuous production system provided by the present application to produce single-walled carbon nanotubes, wherein the reactor 6 uses a graphite tube coated with a 1.0 mm zirconium oxide coating on the surface, and the method for preparing single-walled carbon nanotubes includes the following steps:

[0080] Catalyst pretreatment: place the metal iron in the reaction tank 1, form catalyst particles by exciting with the microwave plasma generator 4, fill Kr at the bottom of the reaction tank 1, fill N2 in the screening tank 2, finally screen out catalyst particles with a particle size of 0.2-2 nm, and blow the catalyst particles into the collection tank 3 containing ethanol and a promoter to form a catalyst dispersion liquid, wherein the promoter is 95% thiophene + 5% water by mass fraction.

[0081] Catalytic growth: push the catalyst dispersion liquid in the collection tank 3 to the atomizer 5 through the injection pump, then enter into the reactor 6 under the driving of the gas flow of H2 with a flow rate of 10 L / min and Ar with a flow rate of 10 L / min provided by the gas supply tank 9 after atomization by the atomizer 5, and the heater is heated to 1300°C, while the carbon source supplementing unit 10 supplements CO into the reactor 6, and single-walled carbon nanotubes are formed on the surface of the catalyst after the carbon source is cracked, and the purity of the final product is I G / I D 85.

[0082] Example 4

[0083] Example 4 uses the single-walled carbon nanotube continuous production system provided by the present application to produce single-walled carbon nanotubes, wherein the reactor 6 uses a graphite tube coated with a 1.0 mm zirconium oxide coating on the surface, and the method for preparing single-walled carbon nanotubes includes the following steps:

[0084] Catalyst pretreatment: place the metal iron in the reaction tank 1, form catalyst particles by exciting with the microwave plasma generator 4, fill Kr at the bottom of the reaction tank 1, fill N2 in the screening tank 2, finally screen out catalyst particles with a particle size of 0.2-2 nm, and blow the catalyst particles into the collection tank 3 containing ethanol and a promoter to form a catalyst dispersion liquid, wherein the promoter is 95% thiophene + 5% water by mass fraction.

[0085] Catalytic growth: push the catalyst dispersion liquid in the collection tank 3 to the atomizer 5 through the injection pump, then enter into the reactor 6 under the driving of the gas flow of H2 with a flow rate of 10 L / min and Ar with a flow rate of 10 L / min provided by the gas supply tank 9 after atomization by the atomizer 5, and the heater is heated to 1300°C, while the carbon source supplementing unit 10 supplements CO into the reactor 6, and single-walled carbon nanotubes are formed on the surface of the catalyst after the carbon source is cracked, and the purity of the final product is I G / I D 95.

[0086] Example 5

[0087] Example 5 uses the single-walled carbon nanotube continuous production system provided by the present application to produce single-walled carbon nanotubes, wherein the reactor 6 uses a graphite tube coated with a 1.0 mm zirconium oxide coating, and the method for preparing single-walled carbon nanotubes includes the following steps:

[0088] Catalyst pretreatment: Place the metal iron in the reaction tank 1, and form catalyst particles by exciting with the microwave plasma generator 4. Fill Kr into the bottom of the reaction tank 1 and N2 into the screening tank 2. Finally, screen out catalyst particles with a particle size of 0.2-2 nm, and blow the catalyst particles into the collection tank 3 containing acetone and a promoter, wherein the promoter is 95% thiophene + 5% water by mass ratio.

[0089] Catalytic growth: Push the catalyst dispersion liquid in the collection tank 3 to the atomizer 5 through the injection pump, and then enter the reactor 6 under the driving of the gas flow of H2 with a flow rate of 20 L / min and Ar with a flow rate of 20 L / min provided by the gas supply tank 9 after atomization by the atomizer 5. The heater is heated to 1500°C, and the carbon source supplement unit 10 supplements CO into the reactor 6. The carbon source forms single-walled carbon nanotubes on the surface of the catalyst after cracking, and the purity of the final product is I G / I D 100.

[0090] In combination with Examples 1-3, the influence of the thickness of the zirconium oxide metal coating and the reaction temperature on the I G / I D value measured by the Raman spectrometer is higher, indicating that the crystallinity of the carbon nanotube fiber bundle is better, and the amorphous carbon impurities are less. The I G / I D values of the carbon nanotubes prepared in Examples 1-3 are all greater than 80, indicating that the prepared carbon tubes have high purity and few defects; from the SEM images (Figures 3-5) of Examples 1-3, it can be seen that the metal coating can effectively absorb the excess catalyst. G / I D

[0091] The SEM image (Figure 6) of Example 4, compared with Example 3, has a decrease in amorphous carbon and catalyst content, and an increase in I G / I D value, indicating that after the carbon source is replaced by acetone, the carbon supply capacity is improved due to the rapid cracking of acetone into single-carbon and double-carbon radicals, and the conversion rate is significantly improved; in Example 5, the flow rate of the carrier gas is increased to speed up the gas mixing efficiency. From the Raman spectra of Examples 4 and 5, it can be seen that the RBM absorption peak in the 100-400 cm -1 region is higher in intensity in Example 5, further indicating that the single-walled tube has higher purity.​

[0092] In Example 4, the narrow peak distribution indicates that the carbon nanotubes have a good consistency in diameter.

[0093] It should be understood that although the present specification is described in terms of embodiments, each of which contains only one independent technical solution, the specification is described in this way only for the sake of clarity, and the skilled person should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that the skilled person can understand.

[0094] The above series of detailed descriptions are only specific descriptions of the feasible embodiments of the present application, and are not intended to limit the protection scope of the present application. Any equivalent embodiments or changes made without departing from the spirit of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing single-walled carbon nanotubes, comprising the following steps: catalyst pretreatment: using a microwave plasma generator to excite the catalyst to form nanoscale particles, and then using gases with decreasing density to perform gradient screening on the nanoscale catalyst particles in sequence; the screened nanoscale catalyst particles form a catalyst dispersion liquid together with a liquid carbon source and a promoter; catalytic growth: the catalyst dispersion liquid is atomized by an atomizer and then carried into a reactor by a carrier gas, and the reactor is heated to 1000-1500°C to grow single-walled carbon nanotubes.

2. The method of claim 1, wherein the single-walled carbon nanotubes are produced by the method comprising: A graphite tube is used as the reactor.

3. The method of claim 2, wherein the single-walled carbon nanotubes are prepared by the method of claim 1. The surface of the graphite tube is coated with a metal coating.

4. The method of claim 3, wherein the single-walled carbon nanotubes are prepared by the method of claim 1 or 2. The metal coating is a titanium-based, nickel-based or zirconium-based coating.

5. The method of claim 1, wherein the single-walled carbon nanotubes are produced by the method comprising: In the catalyst pretreatment, Kr and N2 are used in sequence to screen the catalyst particles.

6. The method of claim 1, wherein the single-walled carbon nanotubes are produced by the method comprising: The catalyst is a metal catalyst, and the metal catalyst is at least one of Fe, Co, Ni, Pd, Pt, Cu, Mn, Cr, Mo and Ge.

7. The method of claim 1, wherein the single-walled carbon nanotubes are produced by the method comprising: The liquid carbon source is an organic hydrocarbon liquid carbon source or an organic alcohol liquid carbon source.

8. The method of claim 1, wherein the single-walled carbon nanotubes are produced by a method comprising: The liquid carbon source is at least one of methanol, ethanol, acetone, butanol, benzyl alcohol, benzene, ethylene glycol, diethyl ether or n-hexane.

9. The method of claim 1, wherein the single-walled carbon nanotubes are produced by a process comprising: In the catalytic growth step, a gaseous carbon source is filled into the reactor.

10. The method of claim 9, wherein the single-walled carbon nanotubes are prepared by a method comprising: The gaseous carbon source is one or more of carbon monoxide, methane, ethylene and acetylene.

11. The method of preparing single-walled carbon nanotubes according to claim 1, wherein, The promoter is one or more of water, thiophene and molybdenum acetate.

12. A continuous production system for single-walled carbon nanotubes, comprising: a catalyst pretreatment device: including a reaction tank, a screening tank and a collection tank connected in sequence, the reaction tank being connected to a microwave plasma generator, and the reaction tank and the screening tank being filled with gases with decreasing density in sequence; a reaction device: including an atomizer connected to the collection tank, a reactor connected to the atomizer, and a heater for heating the reactor, and a gas supply tank connected between the atomizer and the reactor; a material collection device connected to the output end of the reactor.

13. The continuous single-walled carbon nanotube production system of claim 12, wherein, The reactor is connected to a carbon source supplementing unit which communicates with the middle part of the reactor.

14. The continuous single-walled carbon nanotube production system of claim 12, wherein, The gas supplied in the gas supply tank is H2, N2 or Ar.

15. The continuous single-walled carbon nanotube production system of claim 12, wherein, The material collection device includes a material collection tank, an exhaust gas discharge pipeline communicating with the material collection tank, and a switch valve group for cutting off or communicating the material collection tank and the reactor.

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