CN113148982B - Preparation method of high-purity double-wall carbon nano tube - Google Patents
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Abstract
The invention belongs to the technical field of carbon nano-material preparation, and particularly relates to a preparation method of a high-purity double-wall carbon nano-tube. The beneficial effects of the invention are: the high-quality double-wall carbon nano tube with the diameter of 2-4 nm is prepared by the method, the purity is higher than 93%, and the Raman G/D peak value ratio is higher than 10. The preparation process is simple and easy to implement, the raw materials are low in cost, and the method has a promoting significance for basic research and pilot-scale production of the high-quality double-wall carbon nano tube.
Description
The technical field is as follows:
the invention belongs to the technical field of preparation processes and application of carbon nano materials, and particularly relates to a preparation method of a high-purity double-wall carbon nano tube.
The background art comprises the following steps:
in 1991, carbon nanotubes were discovered by the japanese scholars in the rice island, and under a transmission electron microscope, the carbon nanotubes have a hollow tubular structure, a diameter of a tube is nanometer scale, a length of the tube is usually more than micrometer, and the carbon nanotubes are a typical one-dimensional nanomaterial, and then have received extensive attention and intensive research. Carbon nanotubes can be regarded as seamless tube structures formed by curling graphite, and can be classified into single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes according to the number of layers of a curled graphite layer. The single-walled carbon nanotube has extremely high specific surface area, and the specific surface area is easily annihilated by forming a single-walled carbon nanotube bundle with the tubes, so that the surface energy is reduced and stably exists, and the single-walled carbon nanotube is difficult to disperse and easy to break and destroy in practical application, thereby greatly reducing the monodispersity and the conductivity of the single-walled carbon nanotube. Double-walled and multi-walled carbon nanotubes are relatively easy to disperse and exist freely due to the van der waals force between layers. The graphitization degree of the single-wall carbon nano tube and the double-wall carbon nano tube is usually one to two orders of magnitude higher than that of the multi-wall carbon nano tube, so that the carbon nano tube has better conductivity. In conclusion, the double-walled carbon nanotube with easy dispersion and freeness has more obvious conductive advantages in practical application.
The layered multi-metal hydroxide is of a hydrotalcite-like structure, and active metals of iron, cobalt and nickel are introduced into a traditional magnesium aluminum hydrotalcite sheet layer and can be used for growing carbon nano materials. The active metal is uniformly distributed in the crystal lattice of the hydrotalcite, so that the hydrotalcite has high-temperature thermal stability. When the layered multi-metal hydroxide is reduced at high temperature, active metal nano-particles are formed, the particle size of the active metal nano-particles can be controlled by regulating the distribution density of the active metal, and the strong interaction of the active metal nano-particles and a hydrotalcite lamellar matrix can inhibit sintering by preventing the austenite aging effect of the active metal nano-particles. When the layered multi-metal hydroxide is used as a catalyst to grow the carbon nano tube, the contact surface between an active site in the catalyst and a carbon source gas can be effectively improved, and the graphitization degree of the grown carbon nano tube is favorably improved. On the other hand, the wall number of the carbon nano tube can be selectively regulated and controlled by regulating and controlling the distribution density of the active metal in the lamellar crystal lattice. The carbon nanotubes grown at lower temperature usually have multi-wall, high yield but serious defects, and the like (patent publication No. CN 1718278) are synthesized into the multi-wall carbon nanotubes with the diameter of 20-50nm by using a double-metal hydroxide catalyst. When the temperature is increased to 800 ℃, although the yield of the carbon nano tube is reduced, the appearance of the carbon nano tube is changed into a single-wall carbon nano tube, a double-wall carbon nano tube and a carbon nano tube with few walls, and the graphitization degree and the conductivity of the carbon nano tube are greatly increased. Weifei et al (patent publication No. CN 101665248B) adopt double metal hydroxide catalyst to prepare high quality single and double walled carbon nanotubes. However, the yield is greatly reduced due to the fact that the temperature is increased and the catalyst is deactivated quickly, the sheet layer of the bimetal hydroxide matrix after reaction is obviously visible under a scanning electron microscope, and an effective purification method is not provided in the patent. Therefore, according to the method, firstly, the layered multi-metal hydroxide catalyst is adopted to prepare the high-quality double-wall carbon nano tube, and then, the magnesium oxide, the aluminum oxide and the active metal particles remained in the lamellar matrix of the layered multi-metal hydroxide catalyst are soaked and washed by hydrofluoric acid solution, sodium hydroxide solution and concentrated hydrochloric acid.
The invention content is as follows:
the present invention is directed to a method for preparing high purity double-walled carbon nanotubes that solves any of the above-mentioned and other potential problems of the prior art.
The invention is realized by adopting the following technical scheme: a preparation method of high-purity double-wall carbon nano tubes is characterized in that layered multi-metal hydroxide is used as a catalyst, double-wall carbon nano tubes are prepared through chemical vapor deposition, and then residual catalyst is removed through solvent immersion cleaning in sequence, so that the high-purity double-wall carbon nano tubes with high graphitization degree are prepared.
Further, the method specifically comprises the following steps:
s1) preparing a layered multi-metal hydroxide catalyst, drying the prepared layered multi-metal hydroxide catalyst, fully grinding the dried layered multi-metal hydroxide catalyst into powder, and placing the powder into a container;
s2) placing a container filled with layered multi-metal hydroxide catalyst powder in a horizontal tube furnace, continuously introducing inert protection at a certain flow rate after evacuation, heating at a certain heating rate, introducing carbon-containing gas at a certain flow rate after heating to a reaction temperature for reaction, cooling and collecting a sample to obtain a double-wall carbon nano tube crude product;
and S3) carrying out hydrothermal reaction and ultrasonic treatment on the crude product of the double-wall carbon nano tube obtained in the step S2) by using a solvent to remove residual catalyst, thus obtaining the purified double-wall carbon nano tube with the diameter of 2-4 nm, the purity of more than 93 percent and the Raman G/D peak value ratio of more than 10.
Further, the step S2 further includes the steps of: introducing hydrogen into the horizontal tubular furnace to pre-reduce the layered multi-metal hydroxide catalyst if the carbon-containing gas mainly comprises CH4Then pre-reduction of the layered multimetal hydroxide catalyst is not required.
Further, the layered multi-metal hydroxide catalyst comprises a carrier metal compound, an active metal compound and a rare earth element;
wherein the total molar ratio of all divalent metal elements to all trivalent metal elements in the layered multimetallic hydroxide catalyst is from 1.2 to 2.5:1, the molar ratio of the rare earth element to the aluminum element in the carrier metal compound is 1:9.
further, the carrier metal compound is a compound containing aluminum element;
the active metal compound is a metal compound containing one or more of active metal elements of iron, cobalt and nickel;
the rare earth element is one of lanthanum, cerium, praseodymium or dysprosium.
Further, the layered multi-metal hydroxide catalyst is prepared by adopting a coprecipitation method.
Further, in the step S2), the volume ratio of the flow rates of the carbon-containing gas and the inert gas is 1:1 to 5;
the heating rate is 10 ℃/min, and the reaction temperature is 800-1000 ℃.
Further, the carbonaceous gas comprises methane, natural gas, coal bed gas or biogas;
the inert gas comprises argon or nitrogen.
Further, the specific process of S3) is as follows:
s3.1) adding the crude product of the double-wall carbon nano tube into a first solvent for hydrothermal treatment for 4 hours, cooling and centrifuging,
and S3.2) carrying out hydrothermal treatment for 4h by using a second solvent, cooling, centrifuging, adding into a third solvent, carrying out ultrasonic treatment for 8-15min, stirring for 8h, carrying out suction filtration, repeatedly washing with water, and collecting to obtain the purified double-wall carbon nanotube.
Further, the first solvent is HF aqueous solution with the mass fraction of 25-40 wt%;
the second solvent is sodium hydroxide aqueous solution with the concentration of 5-10 mol/L;
the third solvent is concentrated hydrochloric acid;
the hydrothermal temperature is 120-300 ℃.
The beneficial effects of the invention are: the invention can effectively control the generated carbon nano tube to be mainly double-wall by regulating and controlling the components and density distribution of active metal and rare earth metal in the layered multi-metal hydroxide, activates the amphoteric metal oxide in the residual catalyst by hydrofluoric acid, completely removes the amphoteric metal oxide by sodium hydroxide, removes the active metal and other residual metal oxides by concentrated hydrochloric acid, and finally prepares the double-wall carbon nano tube with high purity and high graphitization degree. By adopting the scheme, the high-quality double-wall carbon nano tube with the diameter of 2-4 nm is prepared, the purity is higher than 93%, and the Raman G/D peak value ratio is higher than 10. The preparation process is simple and easy to implement, the raw materials are low in cost, and the method has a promoting significance for basic research and pilot-scale production of the high-quality double-wall carbon nano tube.
Description of the drawings:
FIG. 1 shows Fe in example 10.4Mg2Al, fe in example 20.1Co0.2Mg2Al, fe in example 30.25Mg2Al, co in example 42Pr0.1Al, co in example 52Dy0.1XRD pattern of Al layered multimetal hydroxide catalyst.
FIG. 2 shows Fe synthesized in example 30.25Mg2Scanning pictures of Al layered multimetal hydroxide catalysts.
FIG. 3 shows the synthesis of Co in example 52Dy0.1Thermogravimetric decomposition profile of Al layered multimetallic hydroxide catalyst in nitrogen.
FIG. 4 shows Fe synthesized in example 60.01Mg2Double-walled carbon nanotubes grown with Al layered multimetallic hydroxide catalysts.
FIG. 5 shows Fe synthesized in example 70.01Co0.02La0.01Mg2Double-walled carbon nanotubes grown with Al layered multi-metal hydroxide catalysts.
FIG. 6 shows Fe synthesized in example 80.02Ce0.01Mg2Raman spectrum (excitation wavelength is 633 nm) of double-wall carbon nano-tube grown by Al layered multi-metal hydroxide catalyst.
FIG. 7 shows Fe synthesized in example 90.01Co0.01Ni0.01Pr0.01Mg2Thermogravimetric curve of double-wall carbon nano-tube grown by Al layered multi-metal hydroxide catalyst.
Fig. 8 is a scan (8 a), thermogravimetric curve (8 b) and transmission picture (8 c) of the purified double-walled carbon nanotube prepared in example 10.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art based on the embodiments of the present invention without any creative effort, fall within the protection scope of the present invention.
The invention relates to a preparation method of a high-purity double-wall carbon nano tube, which takes layered multi-metal hydroxide as a catalyst, prepares the double-wall carbon nano tube by chemical vapor deposition, and then sequentially removes the residual catalyst by solvent immersion, thus preparing the high-purity double-wall carbon nano tube with high graphitization degree.
The method specifically comprises the following steps:
s1) preparing a layered multi-metal hydroxide catalyst, drying the prepared layered multi-metal hydroxide catalyst, fully grinding the dried layered multi-metal hydroxide catalyst into powder, and placing the powder into a container;
s2) placing a container filled with layered multi-metal hydroxide catalyst powder in a horizontal tube furnace, continuously introducing inert protection at a certain flow rate after evacuation, heating at a certain heating rate, introducing carbon-containing gas at a certain flow rate after heating to a reaction temperature for reaction, cooling and collecting a sample to obtain a double-wall carbon nano tube crude product;
and S3) carrying out hydrothermal reaction and ultrasonic treatment on the crude product of the double-wall carbon nano tube obtained in the step S2) by using a solvent to remove residual catalyst, thus obtaining the purified double-wall carbon nano tube with the diameter of 2-4 nm, the purity of more than 93 percent and the Raman G/D peak value ratio of more than 10.
The S2 further comprises the following steps: introducing hydrogen into the horizontal tube furnace to pre-reduce the layered multi-metal hydroxide catalyst if the main component of the carbon-containing gas is CH4Then pre-reduction of the layered multimetal hydroxide catalyst is not required.
The layered multi-metal hydroxide catalyst comprises a carrier metal compound, an active metal compound and a rare earth element;
wherein the total molar ratio of all divalent metal elements to all trivalent metal elements in the layered multimetallic hydroxide catalyst is from 1.2 to 2.5:1, the molar ratio of the rare earth element to the aluminum element in the carrier metal compound is 1:9.
the carrier metal compound is a compound containing aluminum element;
the active metal compound is a metal compound containing one or more of active metal elements of iron, cobalt and nickel;
the rare earth element is one of lanthanum, cerium, praseodymium or dysprosium.
The preparation of the layered multi-metal hydroxide catalyst is prepared by adopting a coprecipitation method.
In the step S2), the volume ratio of the flow rates of the carbon-containing gas to the inert gas is 1:1 to 5;
the heating rate is 10 ℃/min, and the reaction temperature is 800-1000 ℃.
The carbon-containing gas comprises methane, natural gas, coal bed gas or methane;
the inert gas comprises argon or nitrogen.
The S3) specific process comprises the following steps:
s3.1) adding the double-wall carbon nano tube crude product into a first solvent for hydrothermal treatment for 4 hours, cooling and centrifuging,
and S3.2) carrying out hydrothermal treatment for 4h by using a second solvent, cooling, centrifuging, adding into a third solvent, carrying out ultrasonic treatment for 8-15min, stirring for 8h, carrying out suction filtration, repeatedly washing with water, and collecting to obtain the purified double-wall carbon nanotube.
The first solvent is HF aqueous solution with the mass fraction of 25-40 wt%;
the second solvent is sodium hydroxide aqueous solution with the concentration of 5-10 mol/L;
the third solvent is concentrated hydrochloric acid;
the hydrothermal temperature is 120-300 ℃.
Examples 1 to 5 are experiments for preparing different types of layered multi-metal hydroxide catalysts, and their XRD patterns are shown in fig. 1.
Example 1: fe0.4Mg2Preparation of Al
In a 500mL round bottom flask, the molar ratio 0.4:2:1 respectively weighing and adding ferric nitrate, magnesium nitrate and aluminum nitrate, then adding excessive sodium hydroxide and sodium carbonate mixed solution, dissolving in 250mL water, magnetically stirring in a constant-temperature water bath kettle at 105 ℃ for 8h, cooling to 90 ℃ and aging for 12h, cooling and vacuum-filtering, washing a filter cake with a large amount of water, and finally transferring to a blast drying oven to dry at 60 ℃ to obtain Fe0.4Mg2An Al catalyst.
Example 2: fe0.1Co0.2Mg2Preparation of Al
In a 500mL round bottom flask, the molar ratio of 0.1:0.2:2:1 respectively weighing and adding ferric nitrate, cobalt nitrate, magnesium nitrate and aluminum nitrate, then adding excessive urea, dissolving in 250mL water, magnetically stirring in a constant-temperature water bath kettle at 105 ℃ for 8h, cooling to 90 ℃ and aging for 12h, cooling and vacuum-filtering, washing a filter cake with a large amount of water, and finally transferring to a blast drying oven to dry at 60 ℃ to obtain Fe0.1Co0.2Mg2An Al catalyst.
Example 3: fe0.25Mg2Preparation of Al
In a 500mL round bottom flask, the molar ratio of 0.25:2:1 respectively weighing and adding ferric nitrate, magnesium nitrate and aluminum nitrate, then adding excessive sodium hydroxide and sodium carbonate mixed solution, dissolving in 250mL water, magnetically stirring in a constant-temperature water bath kettle at 105 ℃ for 8h, cooling to 90 ℃ and aging for 12h, cooling and vacuum-filtering, washing a filter cake with a large amount of water, and finally transferring to a blast drying oven to dry at 60 ℃ to obtain Fe0.25Mg2The scanning picture of the Al catalyst is shown in FIG. 2.
Example 4: co2Pr0.1Preparation of Al
In a 500mL round bottom flask, the molar ratio of 2:0.1:1 respectively weighing and adding cobalt nitrate, praseodymium nitrate and aluminum nitrate, then adding excessive urea, dissolving in 250mL of water, magnetically stirring at 105 ℃ in a constant-temperature water bath kettle for 8 hours, then cooling to 90 ℃ for aging for 12 hours, cooling and vacuum-filtering, washing a filter cake with a large amount of water, and finally rotatingTransferring the mixture into a blast drying oven to be dried at 60 ℃ to obtain Co2Pr0.1An Al catalyst.
Example 5: co2Dy0.1Preparation of Al
In a 500mL round bottom flask, the molar ratio of 2:0.1:1, respectively weighing and adding cobalt nitrate, dysprosium nitrate and aluminum nitrate, then adding excessive urea, dissolving in 250mL of water, magnetically stirring in a constant-temperature water bath kettle at 105 ℃ for 8h, then cooling to 90 ℃ for aging for 12h, cooling and carrying out vacuum filtration, washing a filter cake with a large amount of water, finally transferring to a forced air drying oven to dry at 60 ℃ to obtain Co2Dy0.1The thermogravimetric decomposition curve of the Al catalyst under the protection of nitrogen is shown in figure 3.
Examples 6 to 9 are experiments for growing carbon nanotubes with different types of layered multimetallic hydroxide catalysts
Example 6: fe was prepared according to the methods of examples 1 to 50.01Dy0.01Mg2Transferring Al catalyst contained in quartz boat to horizontal tube furnace, heating to 900 deg.C at 10 deg.C/min under the protection of argon (flow rate 300 sccm), and introducing 80sccm CH4Reacting for 30min, cooling, collecting black powder, and scanning and characterizing as shown in figure 4.
Example 7: fe was prepared according to the methods of examples 1 to 50.01Co0.02La0.01Mg2Transferring Al catalyst contained in a quartz boat into a horizontal tube furnace, heating to 850 ℃ at a heating rate of 10 ℃/min under the protection of argon (flow rate of 300 sccm), and introducing 60sccm CH4Reacting for 45min, cooling, collecting black powder, and scanning and characterizing as shown in figure 5.
Example 8: fe was prepared according to the methods of examples 1 to 50.02Ce0.01Mg2Transferring Al catalyst contained in quartz boat to horizontal tube furnace, heating to 850 deg.C at 10 deg.C/min under the protection of argon (flow rate 400 sccm), and introducing 100sccm CH4Reacting for 60min, cooling, collecting black powder, and obtaining Raman spectrum with 633nm excitation wavelength as shown in FIG. 6.
Example 9: fe was prepared according to the methods of examples 1 to 50.01Co0.01Ni0.01Pr0.01Mg2Transferring Al catalyst in quartz boat to horizontal tube furnace, heating to 850 deg.C at 10 deg.C/min under argon protection (flow rate 400 sccm), and introducing 100sccm CH4Reacting for 60min, cooling, and collecting black powder, wherein the thermogravimetric decomposition curve is shown in FIG. 7.
Example 10: preparation of Fe by the method of example 1 to 5 or 80.02Dy0.01Mg2Transferring Al catalyst contained in quartz boat to horizontal tube furnace, heating to 850 deg.C at 10 deg.C/min under the protection of argon (flow rate 400 sccm), and introducing 100sccm CH4Reacting for 60min, cooling and collecting black powder. Weighing 100mg of the black powder, firstly reacting with 100mL 25wt% of HF aqueous solution at 120 ℃ for 4h, cooling, centrifuging, reacting with 100mL 5mol/L of sodium hydroxide aqueous solution at 120 ℃ for 4h, cooling, centrifuging, finally adding into 100mL of concentrated hydrochloric acid, performing ultrasonic treatment for 10min, stirring for 8h, performing vacuum filtration and repeated water washing to obtain the purified double-wall carbon nanotube, wherein a scanning picture, a thermogravimetric curve and a transmission picture of the purified double-wall carbon nanotube are respectively shown in FIGS. 8a, 8b and 8 c.
Example characterization results analysis:
FIG. 1 is Fe0.4Mg2Al (example 1) and Fe0.1Co0.2Mg2Al (example 2) and Fe0.25Mg2Al (example 3) and Co2Pr0.1Al (example 4) and Co2Dy0.1XRD pattern of Al (example 5) layered multi-metal hydroxide catalyst. It can be seen from the figure that the synthesized layered multi-metal hydroxides all have the characteristic peaks (003), (006), (009) of hydrotalcite, which indicates that the synthesized layered multi-metal hydroxides all have hydrotalcite-like lamellar structures.
FIG. 2 shows Fe synthesized in example 30.25Mg2Scanning pictures of Al layered multimetal hydroxide catalysts. From the figure, fe can be seen0.25Mg2Al has a lamellar structure with a size less than 2 μm and a thickness less than 100nm. The distribution of lamellae is relatively irregular, probably due to manual grinding.
FIG. 3 shows the synthesis of Co in example 52Dy0.1Thermogravimetric decomposition profile of Al layered multimetallic hydroxide catalyst in nitrogen: when the temperature is lower than 200 ℃, the catalyst only loses interlayer moisture but does not affect the structure of the catalyst, and when the temperature is 250-450 ℃, the weight loss of the catalyst is accelerated, more moisture is lost in the process, and simultaneously CO exists2Generating carbonate radical which is completely decomposed into CO when the temperature reaches 450 DEG C2To produce the multi-metal composite oxide. Upon continued heating, the multi-metal composite oxide begins to sinter, reducing the surface area and pore volume.
FIG. 4 shows Fe synthesized in example 60.01Mg2Double-walled carbon nanotubes grown with Al layered multi-metal hydroxide catalysts; FIG. 5 shows Fe synthesized in example 70.01Co0.02La0.01Mg2Double-walled carbon nanotubes grown with Al layered multi-metal hydroxide catalysts. It can be seen from the figure that carbon nanotubes are grown and suspended on the surface of the lamellar multi-metal hydroxide catalyst. The increase in reaction temperature reduces the yield of carbon nanotubes, so that the catalyst lamellae are clearly visible.
FIG. 6 shows Fe synthesized in example 80.02Ce0.01Mg2Raman spectrum (excitation wavelength is 633 nm) of double-wall carbon nano-tube grown by Al layered multi-metal hydroxide catalyst. Three different positions are randomly selected in the testing process, and the measured Raman spectrogram contains an obvious RMB peak, which indicates that the sample has single-wall, double-wall or few-wall carbon nanotubes; the G/D peak ratio is higher than 10, indicating that the sample has a higher degree of graphitization.
FIG. 7 shows Fe synthesized in example 90.01Co0.01Ni0.01Pr0.01Mg2Thermogravimetric curve of double-walled carbon nanotube grown by Al layered multi-metal hydroxide catalyst. When the temperature is higher than 430 ℃, the carbon-coated active metal begins to decompose, the temperature is higher than 500 ℃, the double-wall carbon nano tube begins to decompose, and the final residual quantity is 85 percent, which shows that the prepared double-wall carbon nano tube has extremely low purity (the<15％)。
Fig. 8 is a scan (8 a), thermogravimetric curve (8 b) and transmission picture (8 c) of the purified double-walled carbon nanotube prepared in example 10. A large number of carbon nanotube clusters can be seen in the scanned picture, and other impurities are rarely found; the thermogravimetric curve reflects that the decomposition interval of the purified double-wall carbon nano tube is 450-650 ℃, and the final residual ash content is 3 percent, which indicates that the purity of the double-wall carbon nano tube is 93 percent; a transmission electron microscope shows that the purified sample is mainly a double-wall carbon nano tube and has higher crystallinity, and meanwhile, the sample also contains a small amount of carbon-coated spherical metal particles.
Although only the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of those skilled in the art, and all changes are encompassed in the scope of the present invention.
Claims (6)
1. A preparation method of high-purity double-wall carbon nanotubes is characterized by comprising the following steps of:
s1) preparing a layered multi-metal hydroxide catalyst, drying the prepared layered multi-metal hydroxide catalyst, fully grinding the dried layered multi-metal hydroxide catalyst into powder, and placing the powder into a container;
the layered multi-metal hydroxide catalyst comprises a carrier metal compound, an active metal compound and a rare earth element; wherein the total molar ratio of all divalent metal elements to all trivalent metal elements in the layered multimetallic hydroxide catalyst is from 1.2 to 2.5:1, the molar ratio of the rare earth element to the aluminum element in the carrier metal compound is 1:9;
the carrier metal compound is a compound containing aluminum element; the active metal compound is a metal compound containing one or more of active metal elements of iron, cobalt and nickel; the rare earth element is one of lanthanum, cerium, praseodymium or dysprosium;
s2) placing a container filled with layered multi-metal hydroxide catalyst powder in a horizontal tubular furnace, continuously introducing inert protective gas into the horizontal tubular furnace at a certain flow rate after emptying, heating at a certain heating rate, introducing carbon-containing gas at a certain flow rate after heating to a reaction temperature for reaction, cooling, and collecting to obtain a double-wall carbon nano tube crude product;
and S3) carrying out hydrothermal reaction and ultrasonic treatment on the crude product of the double-wall carbon nano tube obtained in the step S2) by using a solvent to remove residual catalyst, thus obtaining the purified double-wall carbon nano tube with the diameter of 2-4 nm, the purity of more than 93 percent and the Raman G/D peak value ratio of more than 10.
2. The preparation method according to claim 1, wherein the step of S2) further comprises the steps of: introducing hydrogen into the horizontal tube furnace to pre-reduce the layered multi-metal hydroxide catalyst if the main component of the carbon-containing gas is CH4Then pre-reduction of the layered multimetal hydroxide catalyst is not required.
3. The preparation method according to claim 1, wherein in S1) the layered multi-metal hydroxide catalyst is prepared by a coprecipitation method;
in the step S2), the volume ratio of the flow rates of the carbon-containing gas to the inert gas is 1:1 to 5; the heating rate is 10 ℃/min, and the reaction temperature is 800-1000 ℃.
4. The method of claim 3, wherein the carbonaceous gas comprises methane, natural gas, coal bed gas, or biogas; the inert gas comprises argon or nitrogen.
5. The preparation method according to claim 1, wherein the S3) specific process is: s3.1) firstly adding the double-wall carbon nano tube crude product into a first solvent for hydrothermal treatment for 4 hours, cooling and then centrifuging,
and S3.2) performing hydrothermal treatment for 4 hours by using a second solvent, cooling, centrifuging, adding into a third solvent, performing ultrasonic treatment for 8-15min, stirring for 8 hours, performing suction filtration, repeatedly washing with water, and collecting to obtain the purified double-walled carbon nanotube.
6. The production method according to claim 5, characterized in that the first solvent is an aqueous HF solution having a mass fraction of 25 to 40 wt%;
the second solvent is sodium hydroxide aqueous solution with the concentration of 5-10 mol/L; the third solvent is concentrated hydrochloric acid;
the hydrothermal temperature is 120-300 ℃.
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| CN100404130C (en) * | 2005-09-30 | 2008-07-23 | 清华大学 | Method for preparing supported catalyst with single wall or double wall carbon nano tube |
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| CN101665248B (en) * | 2009-09-11 | 2011-03-30 | 清华大学 | Method for preparing single-walled and double-walled carbon nanotubes based on layered dihydroxy metal hydroxide |
| CN102320593B (en) * | 2011-08-30 | 2013-02-27 | 中国科学院金属研究所 | Controllable preparation method of high-oxidation-resistance high-purity single/double-wall carbon nanotube |
| KR101303061B1 (en) * | 2012-09-25 | 2013-09-03 | 금호석유화학 주식회사 | A catalyst composition for the synthesis of multi-walled carbon nanotubes |
| CN111170309B (en) * | 2020-02-11 | 2023-01-06 | 江西铜业技术研究院有限公司 | Preparation method of ultra-long few-wall carbon nanotube array |
| CN111841561A (en) * | 2020-07-09 | 2020-10-30 | 江西铜业技术研究院有限公司 | High-efficiency catalyst for growing carbon nano tube and preparation and use methods thereof |
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| CN1663681A (en) * | 2004-03-02 | 2005-09-07 | 广东工业大学 | Catalyst for preparing carbon nanotube |
| CN1669652A (en) * | 2004-12-24 | 2005-09-21 | 宁波华实纳米材料有限公司 | Lanthanum doped monometallic catalyst for preparing carbon nano tube with uniform diameter and preparing process thereof |
| CN107601458A (en) * | 2017-09-12 | 2018-01-19 | 刘云芳 | A kind of preparation method of single-walled carbon nanotube |
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