Method and system for preparing single-walled carbon nanotubes based on a molten metal reaction bed

Abstract

The present invention discloses a method and system for preparing single-walled carbon nanotubes based on a molten metal reaction bed. The preparation method includes: forming a molten metal reaction bed, and bringing a catalyst and a promoter into contact with the molten metal reaction bed, and being excited under the thermal action of the molten metal reaction bed to form nano-catalyst particles; the nano-catalyst particles are combined with a carbon source to form single-walled carbon nanotubes. The technical solution provided by the present invention realizes the formation of nano-catalysts through a molten metal reaction bed, can provide high-temperature conditions for the growth of single-walled carbon nanotubes, is beneficial to obtaining high-quality single-walled carbon nanotubes, and the molten liquid metal reaction bed can dissolve and absorb excess catalyst particles, which is beneficial to improving the purity of single-walled carbon nanotubes.

Description

Technical Field

[0001] The present invention relates to the technical field of nanomaterials, and in particular to a method and system for preparing single-walled carbon nanotubes based on a molten metal reaction bed. Background Art

[0002] Single-walled carbon nanotubes are one of the most representative one-dimensional nanomaterials and can be regarded as a hollow tubular structure formed by curling a single layer of graphene. Due to their unique structure, they possess super-strong mechanical properties, extremely high carrier mobility, adjustable band gaps, excellent thermal properties, optoelectronic properties, stable chemical properties, etc. Carbon nanotubes combine various excellent properties, enabling them to have broad prospects in the fields of composite materials, functional coatings, electronic devices, electrochemical energy storage, etc.

[0003] Currently, methods for preparing single-walled carbon nanotubes include arc discharge method, laser evaporation method, plasma method, high-pressure carbon monoxide method, chemical vapor deposition method, etc. The diameter of single-walled carbon nanotubes is small and the curvature is large. When growing, a huge reaction barrier needs to be overcome, which poses high requirements for growth conditions and requires high-temperature reaction conditions. However, under high-temperature conditions, the catalyst is extremely prone to agglomeration and deactivation. The arc discharge method, laser evaporation method, and plasma method belong to transient high-temperature methods. There is a huge temperature gradient during the reaction of these methods, making it difficult to control the size of the catalyst. Therefore, a large amount of impurities are contained in the prepared single-walled carbon nanotubes. The chemical vapor deposition method, especially the floating chemical vapor deposition method, has a stable temperature, so high-quality and high-purity single-walled carbon nanotubes can be obtained. However, since it is difficult to increase the catalyst concentration in the floating chemical vapor deposition method, the improvement of the yield of single-walled carbon nanotubes is limited. Improving the catalyst concentration through various existing technical means brings the problem of a decrease in the quality of the grown carbon nanotubes.

[0004] Developing a method for preparing single-walled carbon nanotubes with both high quality and high yield is the key to breaking through the mass production technology of single-walled carbon nanotubes. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method and system for preparing single-walled carbon nanotubes based on a molten metal reaction bed.

[0006] To achieve the foregoing invention purpose, the technical solutions adopted by the present invention include:

[0007] In a first aspect, the present invention provides a method for preparing single-walled carbon nanotubes, which includes:

[0008] Forming a molten metal reaction bed, and bringing a catalyst and a cocatalyst into contact with the molten metal reaction bed, and being excited by the heat of the molten metal reaction bed to form nano-catalyst particles;

[0009] The nano-catalyst particles are combined with a carbon source to form single-walled carbon nanotubes.

[0010] In a second aspect, the present invention also provides a preparation system for carbon nanotubes to implement the above preparation method, which includes: a reaction chamber, a feeding device, and a melting device;

[0011] The reaction chamber is used to accommodate the molten metal reaction bed, and there is a reaction space above the molten metal reaction bed; the melting device is used to provide energy to the area where the molten metal reaction bed is located to form and maintain the molten metal reaction bed; the feeding device is used to provide reaction materials to the molten metal reaction bed and the reaction space, and the reaction materials include a catalyst, a promoter, a carbon source, and a carrier gas.

[0012] Based on the above technical solutions, compared with the prior art, the beneficial effects of the present invention at least include:

[0013] In the technical solution provided by the present invention, the formation of nano-catalysts is achieved through a molten metal reaction bed, which can provide high-temperature conditions for the growth of single-walled carbon nanotubes, is conducive to obtaining high-quality single-walled carbon nanotubes, and the molten liquid metal reaction bed can dissolve and absorb excess catalyst particles, which is conducive to improving the purity of single-walled carbon nanotubes.

[0014] The above description is only an overview of the technical solution of the present invention. In order to enable those skilled in the art to more clearly understand the technical means of the present application and implement it in accordance with the content of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of a preparation system provided by a typical embodiment of the present invention;

[0016] Figure 2 is a schematic structural diagram of a preparation system provided by another typical embodiment of the present invention;

[0017] Figure 3 is a Raman spectrum diagram of single-walled carbon nanotubes prepared by a typical embodiment of the present invention;

[0018] Figure 4 is a thermogravimetric analysis curve diagram of single-walled carbon nanotubes prepared by a typical embodiment of the present invention;

[0019] Figure 5 is a scanning electron microscope photograph of single-walled carbon nanotubes prepared by a typical embodiment of the present invention;

[0020] Figure 6 is a transmission electron microscope photograph of single-walled carbon nanotubes prepared by a typical embodiment of the present invention.

[0021] Description of the reference numerals:

[0022] 11. Reaction chamber; 12. Molten metal reaction bed; 13. Discharge port; 21. First feed channel; 22. Second feed channel; 31-1 is an induction heating coil; 31-2. Arc generator; 32. Arc. Detailed implementation manners

[0023] In view of the deficiencies in the prior art, the inventors of this case have proposed the technical solution of the present invention through long-term research and a large number of practices. The following will further explain the technical solution, its implementation process, principles, etc.

[0024] Many specific details are set forth in the following description in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0025] Moreover, relational terms such as "first" and "second" are only used to distinguish one component or method step with the same name from another, and do not necessarily require or imply any actual relationship or order between these components or method steps.

[0026] The embodiment of the present invention first provides a method for preparing single-walled carbon nanotubes, which includes the following steps:

[0027] Form a molten metal reaction bed, and bring a catalyst and a cocatalyst into contact with the molten metal reaction bed, and be excited to form nano-catalyst particles under the thermal action of the molten metal reaction bed;

[0028] The nano-catalyst particles are combined with a carbon source to form single-walled carbon nanotubes.

[0029] In some embodiments, the temperature of the molten metal reaction bed is 1000°C - 3000°C and is soluble in the nano-catalyst particles.

[0030] In order to solve the problems mentioned in the above background art, the technical solution proposed by the embodiment of the present invention is: a method for preparing single-walled carbon nanotubes using a molten metal reaction bed. This method uses the molten metal reaction bed as a heat source to evaporate and / or crack the introduced catalyst to form nano-catalyst particles, and at the same time combines with a carbon source to catalytically grow single-walled carbon nanotubes. In the solution of the present invention, the molten metal can provide high-temperature conditions for the growth of single-walled carbon nanotubes, which is beneficial to obtaining high-quality single-walled carbon nanotubes, and the molten liquid metal reaction bed can dissolve and absorb excess catalyst particles, which is beneficial to improving the purity of single-walled carbon nanotubes.

[0031] Some prior arts have mentioned technical solutions that use molten metal to participate in the preparation of single-walled carbon nanotubes. For example, a technical solution that uses molten metal as a floating medium, floats the catalyst precursor on the surface of this medium, and then applies an electric arc to the catalyst precursor to cause reactions such as evaporation or cracking to form catalyst particles. However, although this technical solution uses molten metal, and even the structures of some devices have certain similarities with some embodiments of the present invention, their operating principles are completely different.

[0032] Specifically, the first difference between the two lies in the heat source. In these prior arts, plasma is used as the heat source, and its area is small, the temperature gradient is large, and it is not easy to control, resulting in difficulty in controlling the uniformity of the product. In contrast, the area of the molten liquid surface in the present invention is larger, the temperature is more uniform, and the molten metal can provide a large reaction area and a uniform temperature field, taking into account both the yield and the uniformity of the product. In addition, another innovation point of the present invention is that the molten liquid metal reaction bed can dissolve and absorb excess catalyst particles, which is beneficial to improving the purity of single-walled carbon nanotubes.

[0033] Therefore, in terms of the requirements for the physical properties of the molten metal reaction bed, there are some obvious differences between the present invention and the above-mentioned prior arts. The above-mentioned prior arts require the catalyst precursor to float on the surface of the molten metal, so there are requirements for their densities, otherwise floating cannot be achieved; in addition, the molten metal cannot dissolve the catalyst, otherwise it is also difficult to achieve the purpose. However, the present invention is different. Since evaporation / cracking can occur when the catalyst and the promoter come into contact, there is no requirement to form a floating state, and there are basically no such requirements for their densities. Moreover, in order to improve the product purity, it is encouraged that the molten metal reaction bed can dissolve some excess catalyst particles, so there are also differences in solubility from the above-mentioned prior arts.

[0034] In the above-mentioned prior arts, through arc evaporation, the temperature in the arc region is very high, but the temperature is not uniform. The temperature provided by the present invention is more uniform, and compared with other methods, such as floating chemical vapor deposition, the molten metal can provide a higher temperature. Therefore, although there are some overlaps in some specific details between the present invention and the above-mentioned prior arts, there are still essential differences in the basic technical ideas and specific functions, etc.

[0035] Thus, in some embodiments, the metal in the molten metal reaction bed may specifically include transition metal elements from the 4th to 6th periods and / or alloys of the transition metal elements.

[0036] Specifically, in some embodiments, the metal element includes any one or a combination of two or more of vanadium, chromium, manganese, iron, cobalt, nickel, niobium, molybdenum, tantalum, and tungsten.

[0037] Regarding the specific input methods of the carbon source, catalyst, and cocatalyst, in some embodiments, the carbon source includes a liquid carbon source and / or a gaseous carbon source; the catalyst and / or cocatalyst are dissolved in the liquid carbon source and carried to the molten metal reaction bed; and / or, the catalyst and / or cocatalyst are in the form of solid powders and fall into the molten metal reaction bed.

[0038] In the above solutions, the catalyst and cocatalyst can be input in different situations. One is to simply input a liquid carbon source in which the above catalyst and cocatalyst are dissolved; one is to input a liquid carbon source in which the above catalyst and cocatalyst are dissolved, and input a gaseous carbon source in another passage, so that the carbon source simultaneously uses liquid and gaseous multi-carbon sources; and there is also one in which a solid powder catalyst and cocatalyst are input, and a gaseous carbon source is input in another passage.

[0039] The above three situations are representative ways, but are not limited thereto, and their combinations / variations still fall within the scope of implementation of the present invention. For example, the catalyst and cocatalyst are respectively input via different passages, etc.

[0040] Regarding the specific material selection range, in some embodiments, the catalyst includes any one or a combination of two or more of iron powder, iron(III) oxide, iron(II,III) oxide, ferrocene, iron carbonyl, nickel powder, nickel oxide, nickelocene, cobalt powder, cobalt(II,III) oxide, cobaltocene, and is not limited thereto.

[0041] In some embodiments, the cocatalyst includes any one or a combination of two or more of thiophene, carbon disulfide, dimethyl sulfoxide, sulfur powder, selenium powder, and is not limited thereto.

[0042] In some embodiments, the carbon source includes any one or a combination of two or more of toluene, ethanol, methane, ethane, ethylene, acetylene, propylene, and is likewise not limited thereto.

[0043] The specific selections of the above carbon source, catalyst, and cocatalyst are exemplary and do not mean that they are limited to the exemplified scope. Those skilled in the art refer to multiple existing technologies or find new similar various reactants by themselves. As long as they can play the same role, they still belong to equivalent replacements. In addition, regarding the specific proportions of the carbon source, catalyst, and cocatalyst, they can be appropriately determined with reference to many existing technologies or the following implementation cases or adjusted through condition tests, which are not the key control conditions of the present invention.

[0044] Regarding other implementation details, in some embodiments, the molten metal reaction bed can be formed by induction melting and / or arc melting, but is not limited thereto.

[0045] In some embodiments, the preparation method may further include the following steps:

[0046] The carrier gas is continuously circulated around the molten metal reaction bed to carry the single-walled carbon nanotubes away from the location of the molten metal reaction bed.

[0047] In some embodiments, the carrier gas may include any one of nitrogen, argon, and hydrogen, or a combination of two or more thereof. In these carrier gases, the addition of hydrogen will improve the quality of single-walled carbon nanotubes, but single-walled carbon nanotubes can also be prepared without hydrogen, depending on the catalyst. Because hydrogen can also reduce the catalyst, in the present application, the catalyst precursor in some embodiments is an oxide, and hydrogen can reduce the oxide to a metal element, but this does not mean that hydrogen is necessary in all implementation cases.

[0048] An embodiment of the present invention further provides a carbon nanotube preparation system, which is used to implement the preparation method provided by any of the above-mentioned embodiments, and comprises: a reaction chamber, a feeding device and a smelting device; the reaction chamber is used to accommodate the molten metal reaction bed, and there is a reaction space above the molten metal reaction bed; the smelting device is used to provide energy to the area where the molten metal reaction bed is located, so as to form and maintain the molten metal reaction bed; the feeding device is used to provide reaction materials to the molten metal reaction bed and the reaction space, and the reaction materials include catalysts, co-catalysts, carbon sources and carrier gases.

[0049] In some embodiments, the smelting apparatus includes an induction heating coil and / or an arc generator.

[0050] In some embodiments, the feeding device includes a first feeding channel for conveying gaseous reaction materials and a second feeding channel for conveying solid powder or liquid reaction materials, and the second feeding channel is arranged above the area where the molten metal reaction bed is located.

[0051] As some typical examples of the above technical solutions, the preparation method provided by the present invention adopts the above preparation system to prepare single-walled carbon nanotubes, and the specific process operation flow includes the following steps:

[0052] S1) turning on the smelting device to melt the metal in the reaction chamber into a liquid state, and adjusting the smelting power so that the metal in the reaction chamber is in a liquid state and the temperature remains stable;

[0053] S2) introducing a carrier gas, a catalyst, a catalyst promoter and a carbon source into the reaction chamber, wherein the catalyst and the catalyst promoter evaporate and crack when encountering a high temperature molten metal to form nanoparticles with catalytic effects, and then combine with the carbon source to form single-walled carbon nanotubes;

[0054] S3) The generated product is pushed by the carrier gas and discharged from the discharge port along with the reaction tail gas.

[0055] The technical solution of the present invention will be further described in detail below through several embodiments in conjunction with the accompanying drawings. However, the selected embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0056] Embodiment 1

[0057] This embodiment first exemplifies a single-walled carbon nanotube system, as Figure 1 shown, a system for preparing single-walled carbon nanotubes by induction heating molten metal is as Figure 1 shown. The system includes: a reaction chamber 11, a molten metal reaction bed 12, a discharge port 13, a first feed channel 21, a second feed channel 22, and an induction heating coil 31-1; wherein the molten metal reaction bed 12 is contained in the reaction chamber 11, and the induction heating coil 31-1 is used to melt the metal 12, and the feeding device is used to introduce a carrier gas, a carbon source, and a catalyst into the reaction chamber.

[0058] The preparation process of single-walled carbon nanotubes is as follows:

[0059] Using an induction heating molten metal reaction bed as shown in Figure 1 to prepare a single-walled carbon nanotube preparation system, the metal is melted by induction heating. The molten metal reaction bed 12 is a molybdenum-iron alloy, in which the mass fraction of molybdenum is 60% and the mass fraction of iron is 40%; the carbon source is ethanol, the catalyst is ferrocene, the catalyst assistant is thiophene, and the carrier gas is argon and hydrogen, and the volume ratio of argon to hydrogen is 2:1.

[0060] Dissolve the catalyst ferrocene and the catalyst assistant thiophene in ethanol, where the mass ratio of ethanol to ferrocene is 100:1 and the volume ratio of ethanol to thiophene is 400:1, and prepare a reaction solution for standby. Add a certain amount of molybdenum-iron alloy to the reaction chamber, turn on the induction melting device, and the power of the melting device is 50 kw. Melt the molybdenum-iron alloy in the reaction chamber into a liquid state. After reaching the predetermined temperature of 2000 °C, introduce a mixed gas of argon and hydrogen as the carrier gas into the reaction chamber through the first feed channel 21, and the carrier gas flow rate is 100 L / min; introduce the reaction solution containing the carbon source and the catalyst into the reaction chamber through the second feed channel 22, and the injection rate of the reaction solution is 10 mL / min; the catalyst and the catalyst assistant evaporate and crack in the presence of the high-temperature molten metal to form catalytic nanoparticles, and then combine with the ethanol carbon source to generate single-walled carbon nanotubes. The generated product is discharged from the discharge port with the reaction carrier gas, and the hourly output is 20 g.

[0061] Product characterization: The Raman spectrum of the obtained product is as Figure 3As shown, the excitation wavelength is 532 nm. The product has the characteristic RBM peak of single-walled carbon nanotubes, and has a relatively high ratio of G peak to D peak, IG / ID = 52, indicating that the prepared single-walled carbon nanotubes have a high degree of crystallinity; the TG curve of the product is as Figure 4 shown, and the TG residue is 17.23%, indicating high purity; Figure 5 and Figure 6 are the scanning electron microscope and transmission electron microscope pictures of the product respectively, and the product shows significant single-walled carbon nanotube characteristics.

[0062] Example 2

[0063] Use the preparation system for single-walled carbon nanotubes with an induction heating molten metal reaction bed as shown in Figure 1 The system is the same as that used in Example 1. The metal is melted by induction heating. The molten metal reaction bed 12 is a ferromolybdenum alloy, in which the mass fraction of molybdenum is 60% and the mass fraction of iron is 40%; the first carbon source is ethanol, the catalyst is ferrocene, the catalyst promoter is thiophene, the second carbon source is methane, and the carrier gas is argon and hydrogen, where the volume ratio of argon to hydrogen is 2:1.

[0064] Dissolve the catalyst ferrocene and the catalyst promoter thiophene in ethanol. The mass ratio of ethanol to ferrocene is 50:1, and the volume ratio of ethanol to thiophene is 200:1. Prepare the reaction solution for standby. Add a certain amount of ferromolybdenum alloy to the reaction chamber, turn on the induction melting device, and the power of the melting device is 50 kw. Melt the ferromolybdenum alloy in the reaction chamber into a liquid state. After reaching the predetermined temperature of 2000 °C, pass a mixed gas of argon and hydrogen into the reaction chamber through the first feed channel 21 as the carrier gas, and the carrier gas flow rate is 100 L / min; supplement methane as the second carbon source to the reaction chamber through the first feed channel 21, and the methane flow rate is 2 L / min; pass the reaction solution containing the first carbon source and the catalyst into the reaction chamber through the second feed channel 22, and the injection rate of the reaction solution is 10 mL / min; the catalyst and the catalyst promoter evaporate and crack when encountering the high-temperature molten metal to form catalytic nanoparticles, and then combine with the first carbon source ethanol and the second carbon source methane to generate single-walled carbon nanotubes. The generated product is discharged from the discharge port with the reaction carrier gas, and the hourly output is 25 g.

[0065] Example 3

[0066] In this example, an arc generator is used as the melting device for the preparation of single-walled carbon nanotubes. The structure of this system is as shown in Figure 2 shown, and the specific process is as follows:

[0067] Use as shown in Figure 2The preparation system for single-walled carbon nanotubes using an arc-heated molten metal reaction bed as shown melts the metal by arc heating. The molten metal reaction bed 12 is tantalum-iron alloy, where the mass fraction of tantalum is 55% and the mass fraction of iron is 45%. The carbon source is methane, the catalyst is iron(III) oxide, the catalyst promoter is sulfur powder, and the catalyst and catalyst promoter are fed into the reaction chamber in powder form. The carrier gas is argon and hydrogen, and the volume ratio of argon to hydrogen is 2:1.

[0068] A certain amount of tantalum-iron alloy is added to the reaction chamber. 50 L / min of argon is introduced as the arc ignition gas through the arc generator 31-2, and the arc melting device is turned on. The power of the arc is 45 kw, and a direct current arc 32 is generated between the arc generator 31-2 and the molten metal reaction bed 12 to melt the tantalum-iron alloy in the reaction chamber into a liquid state. After reaching the predetermined temperature of 2100 °C, a mixed gas of argon and hydrogen is introduced into the reaction chamber as the carrier gas through the first feed channel 21 at a flow rate of 120 L / min, and methane is introduced as the carbon source at a flow rate of 10 L / min. Iron(III) oxide and sulfur powder are introduced into the reaction chamber as the catalyst through the second feed channel 22. The catalyst and catalyst promoter evaporate when encountering the high-temperature molten metal to form catalytic nanoparticles, and then combine with the carbon source to generate single-walled carbon nanotubes. The generated products are discharged from the discharge port with the reaction carrier gas, and the hourly output is 30 g.

[0069] Example 4

[0070] Using the Figure 2 The preparation system for single-walled carbon nanotubes using an arc-heated molten metal reaction bed as shown melts the metal by arc heating. The molten metal reaction bed 12 is tantalum-iron alloy, where the mass fraction of tantalum is 55% and the mass fraction of iron is 45%. The carbon source is ethanol, the catalyst is ferrocene, the catalyst promoter is thiophene, and the carrier gas is argon and hydrogen, and the volume ratio of argon to hydrogen is 2:1.

[0071] Dissolve the catalyst ferrocene and the catalyst promoter thiophene in ethanol. The mass ratio of ethanol to ferrocene is 100:1, and the volume ratio of ethanol to thiophene is 400:1. Prepare a reaction solution for standby. Add a certain amount of tantalum-iron alloy into the reaction chamber. Pass 50 L / min of argon as the arc ignition gas through the arc generator 31-2. Turn on the arc melting device. The power of the melting device is 45 kw. Generate a DC arc 32 between the arc generator 31-2 and the molten metal reaction bed 12 to melt the tantalum-iron alloy in the reaction chamber into a liquid state. After reaching the predetermined temperature of 2100 °C, pass a mixed gas of argon and hydrogen into the reaction chamber as the carrier gas through the first feed channel 21. The flow rate of the carrier gas is 120 L / min. Pass the reaction solution containing the carbon source and the catalyst into the reaction chamber through the second feed channel 22. The injection rate of the reaction solution is 10 mL / min. The catalyst and the catalyst promoter evaporate and crack when encountering the high-temperature molten metal to form catalytic nanoparticles, and then combine with the ethanol carbon source to generate single-walled carbon nanotubes. The generated product is discharged from the outlet with the reaction carrier gas, and the hourly output is 20 g.

[0072] Comparative Example 1

[0073] This comparative example is generally the same as Example 1, and the main difference lies in:

[0074] Replace the molten metal reaction bed 12 with metal copper. Copper has a lower solubility for iron catalysts. Referring to relevant data, at 1094 °C, the solubility of iron in copper is 4.0%, and at 1477 °C, the solubility of iron in copper is 8%. The proportion of iron in common ferromolybdenum alloys can reach 40-50%.

[0075] The specific steps of this comparative example are as follows:

[0076] Adopt the Figure 1 A preparation system for single-walled carbon nanotubes using an induction-heated molten metal reaction bed as shown. Melt the metal by induction heating. The molten metal reaction bed 12 is made of metal copper. The carbon source is ethanol, the catalyst is ferrocene, the catalyst promoter is thiophene, and the carrier gas is argon and hydrogen. The volume ratio of argon to hydrogen is 2:1.

[0077] Dissolve the catalyst ferrocene and the catalyst promoter thiophene in ethanol. The mass ratio of ethanol to ferrocene is 100:1, and the volume ratio of ethanol to thiophene is 400:1. Prepare the reaction solution for later use. Add a certain amount of metallic copper into the reaction chamber, turn on the induction melting device with a power of 50 kw, melt the metallic copper in the reaction chamber into a liquid state. After reaching the predetermined temperature of 1250 °C, introduce a mixed gas of argon and hydrogen into the reaction chamber as the carrier gas through the first feed channel 21, with a carrier gas flow rate of 100 L / min; introduce the reaction solution containing the carbon source and the catalyst into the reaction chamber through the second feed channel 22, and the injection rate of the reaction solution is 10 mL / min; the catalyst and the catalyst promoter evaporate and crack when encountering the molten metallic copper to form catalytic nanoparticles, and then combine with the ethanol carbon source to generate single-walled carbon nanotubes. The generated product is discharged from the outlet with the reaction carrier gas.

[0078] Due to the relatively low melting temperature of copper, the evaporation efficiency of the catalyst and the reaction efficiency of the carbon source decrease, resulting in a decrease in the yield and crystallinity of the product. The hourly yield is 5 g, and the Raman IG / ID of the product is 24; due to the relatively low solubility of copper in iron, the iron catalyst generated by the decomposition of the excess ferrocene cannot be dissolved and absorbed by copper and is carried out with the product. The TG residue of the product is 65.72%, containing more residual catalyst compared to Example 1.

[0079] Example 5

[0080] This example is generally the same as Comparative Example 1, with the main differences being:

[0081] Replace the copper in the molten metal reaction bed 12 with metallic manganese. The temperature in the reaction chamber is 1250 °C, the same as in Comparative Example 1.

[0082] The hourly yield of this example is 5.5 g, the Raman IG / ID of the product is 26, and the TG residue of the product is 25.83%. From the growth situation of the product, it can be seen that the yield and the Raman IG / ID ratio of the product are similar to those of Comparative Example 1. This is because the temperatures of the molten metals in both are the same. Therefore, the reaction conversion efficiency and the crystallinity of the product are similar; however, the TG residue of the product is significantly lower than that of Comparative Example 1 because manganese has a relatively high solubility in iron, which can dissolve and absorb the excess iron catalyst, reducing the content of the residual iron catalyst in the product.

[0083] Based on the above examples, it can be clearly seen that in the technical solution provided by the present invention, the formation of the nano-catalyst is achieved through the molten metal reaction bed, which can provide high-temperature conditions for the growth of single-walled carbon nanotubes, is conducive to obtaining high-quality single-walled carbon nanotubes, and the molten liquid metal reaction bed can dissolve and absorb the excess catalyst particles, which is conducive to improving the purity of the single-walled carbon nanotubes.

[0084] It should be understood that the above embodiments are only used to illustrate the technical concept and features of the present invention. The purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and it should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing single-walled carbon nanotubes based on a molten metal reaction bed, characterized in that, Comprising: Forming a molten metal reaction bed, and bringing a catalyst and a promoter into contact with the molten metal reaction bed, and being excited by the heat of the molten metal reaction bed to form nano-catalyst particles, wherein the metal elements in the molten metal reaction bed include any one or a combination of two or more of vanadium, chromium, manganese, iron, cobalt, nickel, niobium, molybdenum, tantalum, and tungsten; Combining the nano-catalyst particles with a carbon source to form single-walled carbon nanotubes; Wherein, the temperature of the molten metal reaction bed is 1000°C - 3000°C and it has solubility for the nano-catalyst particles, and the carbon source includes a liquid carbon source and / or a gaseous carbon source; the catalyst and / or the promoter are dissolved in the liquid carbon source and carried to the molten metal reaction bed; and / or, the catalyst and / or the promoter fall into the molten metal reaction bed in the form of solid powders.

2. The preparation method according to claim 1, characterized in that, The catalyst includes any one or a combination of two or more of iron powder, iron(III) oxide, iron(II,III) oxide, ferrocene, iron carbonyl, nickel powder, nickel oxide, nickelocene, cobalt powder, cobalt(II,III) oxide, and cobaltocene.

3. The preparation method according to claim 1, characterized in that, The promoter includes any one or a combination of two or more of thiophene, carbon disulfide, dimethyl sulfoxide, sulfur powder, and selenium powder.

4. The preparation method according to claim 1, characterized in that, The carbon source includes any one or a combination of two or more of toluene, ethanol, methane, ethane, ethylene, acetylene, and propylene.

5. The preparation method according to claim 1, characterized in that, The molten metal reaction bed is formed by means of induction melting and / or arc melting.

6. The preparation method according to claim 1, characterized in that, Also comprising: Continuously circulating a carrier gas around the molten metal reaction bed to carry the single-walled carbon nanotubes away from the location where the molten metal reaction bed is located.

7. The preparation method according to claim 6, characterized in that, The carrier gas includes any one or a combination of two or more of nitrogen, argon, and hydrogen.

8. A preparation system for carbon nanotubes, which is used to implement the preparation method described in any one of claims 1-7, and is characterized in that, Comprising: A reaction chamber, a feeding device, and a melting device; The reaction chamber is used to accommodate the molten metal reaction bed, and there is a reaction space above the molten metal reaction bed; the melting device is used to provide energy to the area where the molten metal reaction bed is located for forming and maintaining the molten metal reaction bed; the feeding device is used to supply reaction materials to the molten metal reaction bed and the reaction space, and the reaction materials include a catalyst, a promoter, a carbon source, and a carrier gas.

9. The preparation system according to claim 8, characterized in that, The melting device includes an induction heating coil and / or an arc generator; The feeding device includes a first feeding channel for conveying gaseous reaction materials and a second feeding channel for conveying solid powder or liquid reaction materials, and the second feeding channel is arranged above the area where the molten metal reaction bed is located.

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