Single-walled carbon nanotube preparation method and system based on molten metal reaction bed

Abstract

The invention discloses a single-walled carbon nanotube preparation method and system based on a molten metal reaction bed. The preparation method comprises the following steps: forming a molten metal reaction bed, contacting a catalyst and a promoter with the molten metal reaction bed, and exciting 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 a single-walled carbon nanotube. According to the technical scheme provided by the invention, the formation of the nano-catalyst is realized through the molten metal reaction bed, a high-temperature condition can be provided for the growth of the single-walled carbon nanotubes, the high-quality single-walled carbon nanotubes can be obtained, and the molten liquid metal reaction bed can dissolve and absorb redundant catalyst particles, so that the yield of the single-walled carbon nanotubes is improved. And the purity of the single-walled carbon nanotube can be improved.

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 seen as a hollow tubular structure formed by curling up a single layer of graphene. Its unique structure gives it superb mechanical properties, extremely high carrier mobility, adjustable band gap, excellent thermal properties, optoelectronic properties, stable chemical properties, etc. Carbon nanotubes combine various excellent properties, giving them broad prospects in the fields of composite materials, functional coatings, electronic devices, and electrochemical energy storage.

[0003] At present, the preparation methods of single-walled carbon nanotubes include arc discharge method, laser evaporation method, plasma method, high-pressure carbon monoxide method, chemical vapor deposition method, etc. Single-walled carbon nanotubes have a small diameter and a large curvature. When growing, they need to overcome a huge reaction barrier, which places high demands on the growth conditions and requires high-temperature reaction conditions. However, the catalyst is very easy to agglomerate and deactivate under high-temperature conditions. Arc discharge method, laser evaporation method, and plasma method belong to transient high-temperature methods. Such methods have a huge temperature gradient during the reaction, which makes it difficult to control the size of the catalyst. Therefore, the prepared single-walled carbon nanotubes contain a large amount of impurities. 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 the catalyst concentration of the floating chemical vapor deposition method is difficult to increase, the increase in the yield of single-walled carbon nanotubes is limited. Increasing the concentration of the catalyst through the existing various technical means has brought about the problem of quality degradation of the carbon nanotubes formed by the growth.

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

[0005] In view of the deficiencies in the prior art, the object 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] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes: In a first aspect, the present invention provides a method for preparing single-walled carbon nanotubes, comprising: Forming a molten metal reaction bed, and making the catalyst and the promoter contact the molten metal reaction bed, and being excited by the heat 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.

[0007] In a second aspect, the present invention further provides a carbon nanotube preparation system for implementing the above preparation method, which 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, promoters, carbon sources and carrier gases.

[0008] Based on the above technical solution, compared with the prior art, the beneficial effects of the present invention at least include: In the technical solution provided by the present invention, the formation of nanocatalysts is achieved through a molten molten metal reaction bed, which can provide high-temperature conditions for the growth of single-walled carbon nanotubes, which is beneficial to obtaining high-quality single-walled carbon nanotubes. The molten liquid metal reaction bed can dissolve and absorb excess catalyst particles, which is beneficial to improving the purity of the single-walled carbon nanotubes.

[0009] 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 them according to the contents of the specification, the following is a description of the preferred embodiments of the present invention in conjunction with detailed drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a structural schematic diagram of a preparation system provided by a typical implementation case of the present invention; Figure 2 is a structural schematic diagram of a preparation system provided by another typical implementation case of the present invention; Figure 3 is a Raman spectrum of a single-walled carbon nanotube prepared in a typical implementation case of the present invention; Figure 4 is a thermogravimetric analysis curve of single-walled carbon nanotubes prepared in a typical embodiment of the present invention; Figure 5 is a scanning electron microscope photograph of a single-walled carbon nanotube prepared in a typical embodiment of the present invention; Figure 6 The figure is a transmission electron microscope photograph of a single-walled carbon nanotube prepared in a typical implementation case of the present invention.

[0011] Description of reference numerals: 11. Reaction chamber; 12. Molten metal reaction bed; 13. Discharge port; 21. First feed channel; 22. Second feed channel; 31-1 is induction heating coil; 31-2. Arc generator; 32. Arc. DETAILED DESCRIPTION

[0012] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0013] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0014] Moreover, relational terms such as “first” and “second” are merely used to distinguish one component or method step from another with the same name, but do not necessarily require or imply any such actual relationship or order between these components or method steps.

[0015] The present invention first provides a method for preparing single-walled carbon nanotubes, which comprises the following steps: Forming a molten metal reaction bed, and making the catalyst and the promoter contact the molten metal reaction bed, and being excited by the heat 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.

[0016] In some embodiments, the temperature of the molten metal reaction bed is 1000° C. to 3000° C. and is soluble in the nano-catalyst particles.

[0017] In order to solve the problems mentioned in the above background technology, the technical solution proposed in the embodiment of the present invention is: a method for preparing single-walled carbon nanotubes using a molten metal reaction bed, which 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 the carbon source to catalyze the growth to form single-walled carbon nanotubes. In the scheme of the present invention, the molten metal can provide high temperature conditions for the growth of single-walled carbon nanotubes, which 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.

[0018] Some prior arts mention the technical solution of using molten metal to participate in the preparation of single-walled carbon nanotubes, for example, using molten metal as a floating medium, floating a catalyst precursor on the surface of the medium, and then applying an electric arc to the catalyst precursor to cause it to evaporate or crack to form catalyst particles. However, although this technical solution uses molten metal, and even the structure of some equipment has certain similarities with some embodiments of the present invention, its working principle is completely different.

[0019] Specifically, the difference between the two lies first in the different heat sources. In these prior arts, plasma is used as a 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 the present invention, the area of ​​the molten liquid surface 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 uniformity of the product. In addition, another innovative point of the present invention is that the molten liquid metal reaction bed can dissolve and absorb excess catalyst particles, which is beneficial to improve the purity of single-walled carbon nanotubes.

[0020] 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 art. The above-mentioned prior art requires the catalyst precursor to float on the surface of the molten metal, so there are certain requirements on the density of the two, otherwise floating cannot be achieved; in addition, the molten metal cannot dissolve the catalyst, otherwise it is difficult to achieve the purpose. The present invention is different from this. Since the catalyst and the co-catalyst can evaporate / crackle when they come into contact, there is no need to form a floating state, and there is basically no such requirement for the density of the two. In order to improve the purity of the product, it is also encouraged that the molten metal reaction bed can dissolve some excess catalyst particles. Therefore, the solubility is also different from the above-mentioned prior art.

[0021] The above-mentioned prior art uses arc evaporation, and the temperature of the arc area 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 the present invention and the above-mentioned prior art overlap in some specific details, there are still essential differences in basic technical ideas and specific functions.

[0022] 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.

[0023] 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.

[0024] As for the specific input method of the carbon source, catalyst and co-catalyst, in some embodiments, the carbon source includes a liquid carbon source and / or a gaseous carbon source; the catalyst and / or co-catalyst are dissolved in the liquid carbon source and carried to the molten metal reaction bed; and / or the catalyst and / or co-catalyst are in the form of solid powder and fall into the molten metal reaction bed.

[0025] In the above scheme, the catalyst and the co-catalyst can be input in different situations. One is to simply input a liquid carbon source and dissolve the above-mentioned catalyst and co-catalyst; one is to input a liquid carbon source and dissolve the above-mentioned catalyst and co-catalyst, and input a gaseous carbon source in another passage, so that the carbon source uses both liquid and gaseous carbon sources at the same time; and another is to input solid powder catalysts and co-catalysts, and input a gaseous carbon source in another passage.

[0026] The above three situations are representative, but not limited thereto, and their combinations / variations still fall within the applicable scope of the present invention, such as the catalyst and the co-catalyst being inputted via different pathways respectively.

[0027] As for the specific range of material selection, in some embodiments, the catalyst includes any one or a combination of two or more of iron powder, ferric oxide, ferrocene, carbonyl iron, nickel powder, nickel oxide, nickelocene, cobalt powder, cobalt tetroxide, and cobaltocene, and is not limited thereto.

[0028] In some embodiments, the co-catalyst includes any one or a combination of two or more of thiophene, carbon disulfide, dimethyl sulfoxide, sulfur powder, and selenium powder, but is not limited thereto.

[0029] In some embodiments, the carbon source includes any one or a combination of two or more of toluene, ethanol, methane, ethane, ethylene, acetylene, and propylene, and is also not limited thereto.

[0030] The specific selection of the above-mentioned carbon source, catalyst, and co-catalyst is exemplary and does not mean that it is limited to the scope of examples. Those skilled in the art refer to multiple prior arts or find new similar reactants on their own. As long as they can play the same role, they are still equivalent replacements. In addition, the specific ratio of carbon source, catalyst, and co-catalyst can be appropriately determined with reference to many prior arts or the following implementation cases or adjusted through conditional tests, which is not a key control condition of the present invention.

[0031] 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.

[0032] In some embodiments, the preparation method may further include the following steps: 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.

[0033] 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.

[0034] 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.

[0035] In some embodiments, the smelting apparatus includes an induction heating coil and / or an arc generator.

[0036] 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.

[0037] 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: 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; 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; S3) The generated product is pushed by the carrier gas and discharged from the discharge port along with the reaction tail gas.

[0038] The technical solution of the present invention is further described in detail below through several embodiments and 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.

[0039] Example 1 This embodiment first illustrates a system of single-walled carbon nanotubes, such as Figure 1 As shown in FIG. 1 , a system for preparing single-walled carbon nanotubes by induction heating of molten metal is shown in FIG. Figure 1 As 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, 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.

[0040] The preparation process of single-walled carbon nanotubes is as follows: Use Figure 1 The system for preparing single-walled carbon nanotubes by induction heating of a molten metal reaction bed shown in the figure adopts induction heating to melt the metal, and 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 additive is thiophene, and the carrier gas is argon and hydrogen, in which the volume ratio of argon to hydrogen is 2:1.

[0041] The catalyst ferrocene and the catalyst promoter thiophene are dissolved in ethanol, wherein the mass ratio of ethanol to ferrocene is 100:1, and the volume ratio of ethanol to thiophene is 400:1, and the reaction solution is configured for standby. A certain amount of molybdenum-iron alloy is added into the reaction chamber, and the induction melting device is turned on. The power of the melting device is 50kw. The molybdenum-iron alloy in the reaction chamber is melted into a liquid state. After reaching a predetermined temperature of 2000°C, a mixed gas of argon and hydrogen is introduced into the reaction chamber from the first feed channel 21 as a carrier gas, and the carrier gas flow rate is 100L / min; a reaction solution containing a carbon source and a catalyst is introduced into the reaction chamber from the second feed channel 22, and the injection rate of the reaction solution is 10mL / min; the catalyst and the catalyst promoter are evaporated and cracked when encountering a high-temperature molten metal to form catalytic nanoparticles, and then combined with the ethanol carbon source to generate single-walled carbon nanotubes, and the generated product is discharged from the discharge port with the reaction carrier gas, and the hourly output is 20g.

[0042] Product characterization: The Raman spectrum of the obtained product is shown in Figure 3 As shown, the excitation wavelength is 532nm, the product has the characteristic RBM peak of single-walled carbon nanotubes, and has a higher ratio of G peak to D peak, IG / ID=52, indicating that the prepared single-walled carbon nanotubes have a higher crystallinity; the TG curve of the product is as shown Figure 4 As shown, the TG residue is 17.23%, indicating a high purity; Figure 5 and Figure 6 These are scanning electron microscope and transmission electron microscope images of the product, respectively. The product exhibits significant single-walled carbon nanotube characteristics.

[0043] Example 2 Use Figure 1 The system for preparing single-walled carbon nanotubes by induction heating of a molten metal reaction bed is the same as the system used in Example 1, and 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 first carbon source is ethanol, the catalyst is ferrocene, the catalyst additive is thiophene, the second carbon source is methane, and the carrier gas is argon and hydrogen, in which the volume ratio of argon to hydrogen is 2:1.

[0044] The catalyst ferrocene and the catalyst auxiliary thiophene are dissolved in ethanol, wherein the mass ratio of ethanol to ferrocene is 50:1, and the volume ratio of ethanol to thiophene is 200:1, to prepare a reaction solution for standby use. A certain amount of molybdenum-iron alloy is added into the reaction chamber, and the induction melting device is turned on with a power of 50kw. The molybdenum-iron alloy in the reaction chamber is melted into a liquid state. After reaching a predetermined temperature of 2000°C, a mixed gas of argon and hydrogen is introduced into the reaction chamber from the first feed channel 21 as a carrier gas, and the carrier gas flow rate is 100L / min; methane is added to the reaction chamber from the first feed channel 21 as a second carbon source, and the flow rate of methane is 2L / min; a reaction solution containing the first carbon source and a catalyst is introduced into the reaction chamber from the second feed channel 22, and the injection rate of the reaction solution is 10mL / min; the catalyst and the catalyst aid 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 form single-walled carbon nanotubes, and the generated product is discharged from the discharge port along with the reaction carrier gas, with an output of 25g per hour.

[0045] Example 3 This embodiment uses an arc generator as a melting device to prepare single-walled carbon nanotubes. The structure of the system is as follows: Figure 2 As shown, the specific process is: Use Figure 2 The preparation system for preparing single-walled carbon nanotubes by arc heating a molten metal reaction bed is shown, wherein the metal is melted by arc heating, and the molten metal reaction bed 12 is a tantalum-iron alloy, wherein the mass fraction of tantalum is 55%, and the mass fraction of iron is 45%; the carbon source is methane, the catalyst is ferric oxide, and the catalyst additive is sulfur powder, and the catalyst and the catalyst additive are delivered into the reaction chamber in the form of powder; the carrier gas is argon and hydrogen, wherein the volume ratio of argon to hydrogen is 2:1.

[0046] A certain amount of tantalum-iron alloy is added into the reaction chamber, 50L / min of argon is introduced as arc-starting gas from the arc generator 31-2, the arc melting device is turned on, the arc power is 45kw, a DC arc 32 is generated between the arc generator 31-2 and the molten metal reaction bed 12, and the tantalum-iron alloy in the reaction chamber is melted into a liquid state; after reaching a predetermined temperature of 2100°C, a mixed gas of argon and hydrogen is introduced into the reaction chamber from the first feed channel 21 as a carrier gas, with a carrier gas flow rate of 120L / min, and methane is used as a carbon source, with a methane flow rate of 10L / min; ferric oxide and sulfur powder are introduced into the reaction chamber from the second feed channel 22 as catalysts; the catalyst and the catalyst additive evaporate when encountering the high-temperature molten metal to form catalytic nanoparticles, which are then combined with the carbon source to form single-walled carbon nanotubes, and the generated products are discharged from the discharge port along with the reaction carrier gas, with an output of 30g per hour.

[0047] Example 4 Use Figure 2 The arc-heated molten metal reaction bed preparation system for preparing single-walled carbon nanotubes adopts arc heating to melt the metal, and the molten metal reaction bed 12 is a tantalum-iron alloy, in which 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 additive is thiophene, and the carrier gas is argon and hydrogen, in which the volume ratio of argon to hydrogen is 2:1.

[0048] The catalyst ferrocene and the catalyst auxiliary thiophene are dissolved in ethanol, wherein the mass ratio of ethanol to ferrocene is 100:1, and the volume ratio of ethanol to thiophene is 400:1, to prepare a reaction solution for standby use. A certain amount of tantalum-iron alloy is added into the reaction chamber, 50L / min of argon is introduced as arc-starting gas from the arc generator 31-2, and the arc melting device is turned on. The power of the melting device is 45kw, and a DC 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 a predetermined temperature of 2100°C, a mixed gas of argon and hydrogen is introduced into the reaction chamber from the first feed channel 21 as a carrier gas, and the carrier gas flow rate is 120L / min; a reaction solution containing a carbon source and a catalyst is introduced into the reaction chamber from the second feed channel 22, and the injection rate of the reaction solution is 10mL / min; the catalyst and the catalyst additive evaporate and crack when encountering the high-temperature molten metal to form nanoparticles with catalytic effect, and then combine with the ethanol carbon source to form single-walled carbon nanotubes, and the generated product is discharged from the discharge port along with the reaction carrier gas, with an output of 20g per hour.

[0049] Comparative Example 1 This comparative example is substantially the same as Example 1, except that: The molten metal reaction bed 12 is replaced by molybdenum-iron alloy with metallic copper. The solubility of copper in the iron catalyst is low. According 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 molybdenum-iron alloy can reach 40-50%.

[0050] The specific steps of this comparative example are as follows: Use Figure 1 The system for preparing single-walled carbon nanotubes by induction heating of a molten metal reaction bed shown in the figure uses induction heating to melt the metal, and the molten metal reaction bed 12 is metallic copper; the carbon source is ethanol, the catalyst is ferrocene, the catalyst additive is thiophene, and the carrier gas is argon and hydrogen, wherein the volume ratio of argon to hydrogen is 2:1.

[0051] The catalyst ferrocene and the catalyst promoter thiophene are dissolved in ethanol, wherein the mass ratio of ethanol to ferrocene is 100:1, and the volume ratio of ethanol to thiophene is 400:1, and the reaction solution is prepared for standby. A certain amount of metallic copper is added into the reaction chamber, and the induction smelting device is turned on. The power of the smelting device is 50kw. The metallic copper in the reaction chamber is smelted into a liquid state. After reaching a predetermined temperature of 1250°C, a mixed gas of argon and hydrogen is introduced into the reaction chamber from the first feed channel 21 as a carrier gas, and the carrier gas flow rate is 100L / min; a reaction solution containing a carbon source and a catalyst is introduced into the reaction chamber from the second feed channel 22, and the injection rate of the reaction solution is 10mL / min; the catalyst and the catalyst promoter are evaporated and cracked when encountering the molten metallic copper to form nanoparticles with catalytic effect, and then combined with the ethanol carbon source to form single-walled carbon nanotubes, and the generated product is discharged from the discharge port along with the reaction carrier gas.

[0052] Due to the low melting point of copper, the evaporation efficiency of the catalyst and the reaction efficiency of the carbon source are reduced, resulting in reduced yield and crystallinity of the product. The output per hour is 5 g, and the Raman IG / ID of the product is 24. Due to the low solubility of copper in iron, the iron catalyst produced by the decomposition of excess ferrocene cannot be dissolved and absorbed by copper, and is taken out with the product. The TG residue of the product is 65.72%, which contains more residual catalyst than Example 1.

[0053] Example 5 This embodiment is substantially the same as Comparative Example 1, except that: The copper in the molten metal reaction bed 12 is replaced by metallic manganese, and the temperature in the reaction chamber is 1250° C., which is the same as Comparative Example 1.

[0054] The hourly output of this embodiment is 5.5g, the Raman IG / ID of the product is 26, and the TG residue of the product is 25.83%. It can be seen from the growth of the product that the output and Raman IG / ID ratio of the product are similar to those of Comparative Example 1, because the temperature of the molten metals of the two is the same, so 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 large solubility in iron, and can dissolve and absorb excess iron catalyst, reducing the content of residual iron catalyst in the product.

[0055] Based on the above embodiments, it can be clearly seen that in the technical solution provided by the present invention, the formation of nanocatalysts is achieved through a molten molten metal reaction bed, which 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.

[0056] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot 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 included in 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: include: Forming a molten metal reaction bed, and making the catalyst and the promoter contact the molten metal reaction bed, and being excited by the heat 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.

2. The preparation method according to claim 1, characterized in that: The temperature of the molten metal reaction bed is 1000° C.-3000° C. and has solubility for the nano catalyst particles.

3. The preparation method according to claim 1 or 2, characterized in that: The metal in the molten metal reaction bed includes transition metal elements from the 4th to 6th periods and / or alloys of the transition metal elements; Preferably, 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.

4. The preparation method according to claim 1, characterized in that: The carbon source includes a liquid carbon source and / or a gaseous carbon source; The catalyst and / or promoter are dissolved in the liquid carbon source and carried to the molten metal reaction bed; and / or the catalyst and / or promoter are in the form of solid powder and fall into the molten metal reaction bed.

5. The preparation method according to claim 1 or 4, characterized in that: The catalyst comprises any one of iron powder, ferric oxide, ferrocene, carbonyl iron, nickel powder, nickel oxide, nickelocene, cobalt powder, cobalt tetroxide, and cobaltocene, or a combination of two or more thereof; And / or, the co-catalyst includes any one or a combination of two or more of thiophene, carbon disulfide, dimethyl sulfoxide, sulfur powder, and selenium powder; And / or, the carbon source includes any one or a combination of two or more of toluene, ethanol, methane, ethane, ethylene, acetylene, and propylene.

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

7. The preparation method according to claim 1, characterized in that: Also includes: 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.

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

9. A system for preparing carbon nanotubes, used to implement the preparation method according to any one of claims 1 to 8, characterized in that: include: Reaction chamber, feeding device and 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 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, promoters, carbon sources and carrier gases.

10. The preparation system according to claim 9, characterized in that: The smelting device comprises an induction heating coil and / or an arc generator; And / or, 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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