PMMA (polymethyl methacrylate)-regulated layered hydroxide, preparation method thereof and application of PMMA-regulated layered hydroxide in preparation of single-walled carbon nanotubes by catalytic cracking of methane

Abstract

The invention discloses a PMMA (polymethyl methacrylate)-regulated layered hydroxide, a preparation method thereof and application of the PMMA-regulated layered hydroxide in preparation of a single-walled carbon nanotube by catalytic cracking of methane. The layered hydroxide is FeMgAl layered hydroxide, PMMA (polymethyl methacrylate) is introduced in the preparation process of the FeMgAl layered hydroxide inorganic functional material for the first time, and the sheet structure prepared under the regulation and control of PMMA is uniform, has excellent catalytic activity, is low in raw material cost and is beneficial to regulation and control; and the obtained catalyst does not need to be reduced by hydrogen before the single-walled carbon nanotube is prepared, and meanwhile, Ar does not need to be introduced as a protective gas in the heating process, so that the catalyst has high selectivity on the single-walled carbon nanotube, the production cost is saved, and the large-scale industrial application of the single-walled carbon nanotube prepared by methane cracking is favorably popularized.

Description

Technical Field

[0001] The present invention relates to the field of catalyst technology, and more specifically, to a novel inorganic functional material with a layered structure and its application in preparing single-walled carbon nanotubes by cracking methane. Background Art

[0002] Single-walled carbon nanotubes have excellent optoelectronic properties, mechanical properties, and mechanical properties, and have broad application prospects in the fields of electronics, biology, energy, and environment. The methods for preparing single-walled carbon nanotubes are usually arc discharge, laser ablation, and chemical vapor deposition (CVD). Although arc discharge and laser ablation methods can effectively produce single-walled carbon nanotubes with perfect structure and high degree of graphitization, due to the high temperature evaporation used in these two methods, this will lead to the formation of amorphous carbon, carbon-encapsulated metal nanoparticles, and multi-walled carbon nanotubes. At the same time, these two methods are difficult to scale up. In contrast, the CVD method has relatively mild growth conditions for carbon nanotubes, and is widely used in the large-scale synthesis of single-walled carbon nanotubes due to its low cost and good controllability.

[0003] Since transition metals Fe, Ni, Co and Mo have high carbon solubility, they are often used as active components for the preparation of single-walled carbon nanotubes. The growth of single-walled carbon nanotubes requires not only good dispersion of active metal components on the catalyst support and a suitably large BET surface area, but also layered double hydroxides (LDHs), also known as hydrotalcite-like materials, are a kind of magnesite (Mg(OH) 2 ) Layered two-dimensional nanostructured materials with a BET surface area of ​​up to 1289 m 2 / g can be used as a new catalyst for the growth of single-walled carbon nanotubes. The cost of Fe is relatively cheap, and during the calcination process, Fe easily forms a strong interaction with the carrier, which can effectively prevent the catalyst from sintering during the reaction, resulting in a larger diameter of the generated single-walled carbon nanotubes, and may even generate multi-walled carbon nanotubes.

[0004] In the currently reported method for preparing hydrotalcite, its layered structure is prone to stacking during the preparation process, and some active sites are wrapped and cannot be fully utilized, resulting in a decrease in the yield of single-walled carbon nanotubes. PMMA (polymethyl methacrylate) is usually used as a pore-forming agent for 3D macropores. The present invention adds PMMA during the preparation of hydrotalcite, and grows with PMMA as the substrate during the growth of hydrotalcite, and finally coats PMMA. In the subsequent high-temperature calcination process, the decomposition of PMMA will cause the agglomerated petal-shaped hydrotalcite to disperse, thereby exposing more active sites to improve the yield of single-walled carbon nanotubes. Due to the unique layered structure of hydrotalcite, the layered structure will not be destroyed even after high-temperature calcination. Summary of the invention

[0005] The purpose of the present invention is to provide a new inorganic functional material with a layered structure, a preparation method thereof, and an application in preparing single-walled carbon nanotubes by cracking methane, in view of the fact that in the prior art, the diameter of single-walled carbon nanotubes becomes larger and the yield decreases due to catalyst sintering during high-temperature reactions.

[0006] The present invention effectively avoids the agglomeration phenomenon of the hydrotalcite sheet structure, and the active component distribution of the catalyst prepared by the present invention is more uniform. Based on the special layered structure, Fe in the metal oxide obtained after calcination can form a strong interaction with the carrier; at the same time, due to the high dispersion of the active component Fe, Fe is prevented from sintering into larger particles, the diameter of the single-walled carbon nanotube is reduced, and the diameter distribution is more concentrated.

[0007] The technical purpose of the present invention is achieved through the following technical solutions.

[0008] PMMA-regulated layered hydroxide and its preparation method, i.e., a new inorganic functional material with a layered structure and its preparation method, wherein:

[0009] PMMA regulates the layered hydroxide to be FeMgAl layered hydroxide, which has a uniform petal-like flaky structure under the regulation of PMMA. The particles of the prepared layered hydroxide inorganic functional material are smaller and more uniform, the specific surface area is improved, and the pore volume and average pore size distribution are maintained.

[0010] The molar ratio of the three elements is Fe:Mg:Al=x:2:1, where x is between 0.025-0.5, preferably 0.025-0.2.

[0011] Specific surface area is 220-260m 2 / g, preferably 240-260m 2 / g.

[0012] Pore ​​volume is 0.6-1cm 3 / g, preferably 0.8-0.9cm 3 / g.

[0013] The average pore diameter is 3-6 nm, preferably 3-5 nm.

[0014] The preparation method of PMMA-regulated layered hydroxide is carried out according to the following steps:

[0015] Step 1, stirring the PMMA dispersion at 60-80 degrees Celsius, and when the temperature is stabilized at 60-80 degrees Celsius, adjusting the pH of the PMMA dispersion to 8.0-11.0 using an alkali solution;

[0016] In step 1, the alkali solution is an aqueous solution of sodium hydroxide and sodium carbonate, such as weighing a predetermined amount of sodium hydroxide and sodium carbonate, adding deionized water to dissolve; the concentration of sodium hydroxide is controlled at 0.10-0.30 mol / L, and the concentration of sodium carbonate is controlled at 0.6-1.0 mol / L.

[0017] In step 1, PMMA powder is weighed, and then 10-50 mL of deionized water and 10-30 mL of anhydrous ethanol are added for dispersion to obtain a PMMA dispersion.

[0018] In step 1, the stirring speed is 100-500 revolutions per minute.

[0019] In step 1, the pH is adjusted to 9.0-10.0.

[0020] Step 2, adding the nitrate solution and the alkali solution to the mixed solution obtained in step 1 simultaneously while stirring, maintaining the temperature at 60-80 degrees Celsius, and controlling the pH at 8.0-11.0;

[0021] In step 2, corresponding iron nitrate, magnesium nitrate and aluminum nitrate are weighed according to the ratio of the three metal elements, and deionized water is added to dissolve to form a nitrate solution, and the total metal ion concentration is controlled at 0.20-0.50 mol / L.

[0022] In step 2, the alkali solution is an aqueous solution of sodium hydroxide and sodium carbonate, such as weighing a predetermined amount of sodium hydroxide and sodium carbonate, adding deionized water to dissolve; the concentration of sodium hydroxide is controlled at 0.10-0.30 mol / L, and the concentration of sodium carbonate is controlled at 0.6-1.0 mol / L.

[0023] In step 2, the dropping speed of the nitrate solution should be controlled within a range of 1 drop per 2 seconds to 2 drops per 1 second; the dropping speed of the alkali solution should be controlled according to the pH change of the reaction system during the entire reaction process.

[0024] In step 2, the pH is controlled to 9.0-10.0.

[0025] In step 2, the stirring speed is 100-500 revolutions per minute.

[0026] Step 3, after the addition is completed, stop stirring, age the obtained precipitate in a 40-80°C water bath for 2-10 hours, filter, wash and dry the precipitate to obtain a precursor

[0027] In step 3, the aging temperature is 60-80 degrees Celsius, and the aging time is 4-6 hours.

[0028] In step 3, the drying temperature is 60-120° C., and the drying time is 8-24 hours.

[0029] Step 4, grinding the precursor obtained in step 3 and calcining it, starting from room temperature of 20-25 degrees Celsius in an air atmosphere, heating at a rate of 1-5°C / min to 300-450°C, and keeping it warm for 1-5 hours; then heating at a rate of 1-5°C / min to 450-900°C, keeping it warm for 1-5 hours, and finally cooling it to room temperature of 20-25 degrees Celsius with the furnace to obtain PMMA-regulated layered hydroxide (i.e., FeMgAl layered hydroxide, or FeMgAl layered metal oxide inorganic functional material).

[0030] In step 4, starting from room temperature of 20-25 degrees Celsius, the temperature is raised at a rate of 1-2 degrees Celsius / min to 300-450 degrees Celsius under air atmosphere, and kept at this temperature for 3-4 hours; then the temperature is raised at a rate of 1-2 degrees Celsius / min to 600-700 degrees Celsius, and kept at this temperature for 2-3 hours, and finally cooled to room temperature of 20-25 degrees Celsius with the furnace.

[0031] In step 4, a muffle furnace is selected for calcination.

[0032] The PMMA-controlled layered hydroxide of the present invention is used in the preparation of single-walled carbon nanotubes by catalytic cracking of methane. In the whole process, it is not necessary to reduce the PMMA-controlled layered hydroxide with hydrogen, and it is not necessary to introduce an inert protective gas as a protective atmosphere during the heating process, thereby saving the cost of raw materials. The inert protective gas is nitrogen, argon or helium.

[0033] The specific steps are as follows:

[0034] Step 1, weighing a predetermined amount of PMMA-regulated layered hydroxide and placing it in an ark, and heating it to a reaction temperature in an air atmosphere in a tube furnace;

[0035] Step 2, introducing an inert protective gas to exhaust the air, such as for 30-60 minutes, with a flow rate of the inert protective gas of 50-80 mL / min;

[0036] Step 3, passing methane to react, the reaction time is 30-60min, and the methane flow rate is 10-30mL / min;

[0037] Step 4, turning off the methane, cooling with the furnace in an inert protective gas atmosphere, and obtaining single-walled carbon nanotubes.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. The FeMgAl layered hydroxide inorganic functional material of the present invention has a uniform sheet structure under the regulation of PMMA, has excellent catalytic activity, and has high selectivity for single-walled carbon nanotubes. The preparation method of the FeMgAl layered hydroxide inorganic functional material has a simple process flow, the obtained metal oxide catalyst is very innovative, the raw material cost is low and is easy to regulate, which is conducive to promoting the large-scale industrial application of methane cracking to prepare single-walled carbon nanotubes.

[0040] 2. In the present invention, metal oxides are the main active components for promoting methane cracking. No hydrogen reduction is required before preparing single-walled carbon nanotubes. At the same time, no Ar is required as a protective gas during the heating process, which saves production costs.

[0041] 3. The FeMgAl layered metal oxide of the present invention is used as a catalyst, and the selectivity of single-walled carbon nanotubes is greatly improved compared with general metal oxide catalysts; the performance of the catalyst can be further improved by changing the Fe ratio and calcination temperature. Compared with other types of catalysts, it has the advantages of low cost, simple preparation method, high selectivity and high activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a SEM photograph of the comparative example in the embodiment of the present invention.

[0043] Figure 2 This is a SEM photograph of Example 1 in the examples of the present invention.

[0044] Figure 3 This is the XRD spectrum of Example 1 in the examples of the present invention.

[0045] Figure 4 This is a BET test result curve diagram of Example 1 in the embodiments of the present invention.

[0046] Figure 5 This is a graph showing the thermogravimetric test results of Example 1 in the embodiments of the present invention.

[0047] Figure 6 TEM photos of single-walled carbon nanotubes prepared in Example 1 and Comparative Example of the present invention.

[0048] Figure 7 This is a Raman test image of single-walled carbon nanotubes prepared by adding PMMA to FeMgAl layered metal oxide at 900°C in Example 1 of the present invention. DETAILED DESCRIPTION

[0049] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] Example 1

[0051] A FeMgAl layered metal oxide inorganic functional material is prepared by the following steps:

[0052] Step 1, weigh 0.4040gFe(NO 3 ) 3 、5.1282gMg(NO 3 ) 2 、3.7513gAl(NO 3 ) 3 Dissolve in 80 mL of deionized water.

[0053] Step 2: weigh 1.0 g NaOH, 8.7492 g Na 2 CO 3 Dissolve in 100 mL of deionized water.

[0054] Step 3, weighing 1.0 g of PMMA, and then adding 25 mL of deionized water and 15 mL of anhydrous ethanol to disperse to obtain a dispersion;

[0055] Step 4, the dispersion is placed in a 60° C. water bath for stirring. When the dispersion is stabilized at 60° C., the pH of the dispersion is adjusted to 9.0±0.05 with the alkaline solution obtained in step 2.

[0056] Step 5, the nitrate solution and the alkali solution are simultaneously added dropwise into the dispersion liquid with adjusted pH under stirring in a 60°C water bath. During the addition process, the pH is controlled at 9.0±0.05, and the nitrate is added at a rate of 1 drop per second.

[0057] After the addition is completed, stirring is stopped, and the obtained precipitate is aged in a 60°C water bath for 4 hours. The precipitate is then filtered, washed, and dried to obtain a catalyst precursor. Deionized water is used for washing, the drying temperature is 60°C, and the drying time is 8-10 hours.

[0058] Step 6: The precursor is ground in a mortar and then placed in a muffle furnace for calcination. After cooling, FeMgAl layered hydroxide inorganic functional material is obtained.

[0059] In step 6, the calcination method is to place the ground precursor powder in an ark, and in an air atmosphere, heat it from room temperature at a rate of 1°C / min to 400°C, and keep it warm for 3 hours; then heat it at a rate of 2°C / min to 600°C, keep it warm for 2 hours, and finally cool it with the furnace to obtain FeMgAl layered metal oxide inorganic functional material.

[0060] like Figure 2As shown, (a) the FeMgAl layered hydroxide is obtained after adding PMMA and is not calcined. It can be found that the petal-shaped layered hydroxide has obvious agglomeration phenomenon; (b) the FeMgAl layered metal oxide is obtained after adding PMMA and calcining at 600°C for 2h. It can be seen that calcination does not change the petal-shaped layered hydroxide of the FeMgAl layered hydroxide. In the process of removing PMMA, the agglomerated petal-shaped layered hydroxide is dispersed, and water is lost to obtain the FeMgAl layered metal oxide inorganic functional material.

[0061] like Figure 3 As shown in FIG. 1 , (a) corresponds to the uncalcined XRD spectrum of FeMgAl layered hydroxide obtained by the method of the present invention without adding PMMA, indicating that the layered hydroxide Mg is successfully synthesized. 4 Al 2 (OH) 14 ·3H 2 O, and has good crystallinity; (b) XRD spectra of FeMgAl layered metal oxides obtained by the method of the present invention, with and without adding PMMA, calcined at 600°C for 2h, indicating that the addition of PMMA has no effect on the structure of the synthesized FeMgAl layered metal oxides.

[0062] like Figure 4 As shown in the table below, 600°C corresponds to the sample calcined at this temperature without PMMA, and PMMA-600°C corresponds to the FeMgAl layered hydroxide inorganic functional material prepared in Example 1. From the BET results, the starting and ending adsorption points after adding PMMA are significantly higher than those of the catalyst without PMMA, indicating that the adsorption amount in the low-pressure zone has increased; further analysis of the pore size distribution shows that the proportion of mesopores in the low-pressure zone is also significantly increased compared to the catalyst without PMMA. From the table data, after adding PMMA, the specific surface area of ​​the catalyst has been significantly improved, which further illustrates that after adding PMMA, the agglomerated petal-shaped hydrotalcite is dispersed due to the decomposition of PMMA during the high-temperature calcination process, thereby exposing more active sites. The pore volume and average pore size distribution did not change significantly, indicating that the addition of PMMA will not damage the layered structure during the high-temperature calcination process.

[0063]

[0064] like Figure 5As shown, pH=9 corresponds to the sample prepared at this pH and not regulated by PMMA (calcination temperature 600°C), and pH=9-PMMA corresponds to the FeMgAl layered hydroxide inorganic functional material prepared in Example 1. From the thermogravimetric graph, the content of single-walled carbon nanotubes is significantly increased after adding PMMA. This is because the decomposition of PMMA during the high-temperature calcination process disperses the agglomerated petal-shaped hydrotalcite, thereby exposing more active sites, thereby greatly improving the yield of single-walled carbon nanotubes, which is also consistent with the BET analysis results.

[0065] Example 2

[0066] The final calcination temperature of step 6 in Example 1 was changed, and the calcination temperature was controlled at 450° C., 500° C., and 550° C. during preparation to prepare different FeMgAl layered metal oxide inorganic functional materials. The remaining preparation steps were basically the same as in Example 1 to prepare FeMgAl layered metal oxide inorganic functional materials.

[0067] Example 3

[0068] The ratio of Fe in step 1 of Example 1 was changed to 0.25:2:1 and 0.5:2:1 respectively. The corresponding mass of Fe(NO 3 ) 3 Mg(NO 3 ) 2 、Al(NO 3 ) 3 The remaining preparation steps are basically the same as those in Example 1.

[0069] Example 4

[0070] Following the preparation steps of Example 1, the pH value during preparation was changed to control the pH at 9.5±0.05, 10.0±0.05, and 10.5±0.05, and the PFeMgAl layered metal oxide inorganic functional material was prepared under the same preparation conditions.

[0071] Comparative Example

[0072] The preparation steps of Example 1 were followed, but PMMA was not added, and the PFeMgAl layered metal oxide inorganic functional material was prepared under the same preparation conditions.

[0073] like Figure 1As shown, (a) corresponds to the FeMgAl layered hydroxide obtained without adding PMMA and without calcination, and it is found that the petal-shaped layered hydroxide has obvious agglomeration phenomenon; (b) corresponds to the FeMgAl layered metal oxide obtained by calcining at 600°C for 2h without adding PMMA. It can be seen that calcination does not change the petal-shaped layered hydroxide of the FeMgAl layered hydroxide, and the petal-shaped layered hydroxide still has agglomeration phenomenon.

[0074] Example 5 - Application of the FeMgAl layered hydroxide inorganic functional material of the present invention to the preparation of single-walled carbon nanotubes by catalytic cracking of methane

[0075] The FeMgAl layered hydroxide inorganic functional material prepared in Example 1 and the inorganic functional material prepared in the comparative example were tested for catalytic performance, with reference to Hierarchical Composites of Single / Double-Walled Carbon Nanotubes Interlinked Flakes from Direct Carbon Deposition on Layered Double Hydroxides, Adv. Funct. Mater. 2010, 20, 677-685. The specific method is as follows:

[0076] 100 mg of the prepared inorganic functional materials of Example 1 and the comparative example were respectively taken, evenly spread in an ark and placed in a tubular furnace. Under an air atmosphere, the temperature was increased at a rate of 10°C / min from room temperature of 20-25°C to 900°C; then Ar was introduced to exhaust air for 30 minutes, and the Ar flow rate was 50 mL / min; finally, methane was introduced to react for 30 minutes to prepare single-walled carbon nanotubes.

[0077] exist Figure 6 In the figure, (a) corresponds to the single-walled carbon nanotubes prepared at 900°C in the corresponding comparative example, and (b) corresponds to the single-walled carbon nanotubes prepared at 900°C in Example 1. Figure 7 It can be seen that the FeMgAl layered hydroxide inorganic functional material of the present invention can be applied to the preparation of single-walled carbon nanotubes by catalytic cracking of methane, and the preparation of single-walled carbon nanotubes is successfully achieved. In this way, for the preparation of single-walled carbon nanotubes, there is no need to use hydrogen for reduction, and there is no need to introduce Ar as a protective gas during the heating process, which saves production costs.

[0078] According to the present invention, the process parameters in the embodiments are adjusted to achieve the preparation of layered metal oxides, and after testing, the performance is basically consistent with that of the present invention. The above is an exemplary description of the present invention. It should be noted that any simple deformation, modification or equivalent replacement that can be made by other technicians in this field without spending creative labor falls within the protection scope of the present invention without departing from the core of the present invention.

Claims

1. PMMA regulates layered hydroxide, characterized in that: PMMA regulates the layered hydroxide to be FeMgAl layered hydroxide, which has a uniform petal-like lamellar structure under the regulation of PMMA; The molar ratio of the three elements is Fe:Mg:Al=x:2:1, x is between 0.025-0.5, and the specific surface area is 220-260m 2 / g, pore volume is 0.6-1cm 3 / g, and the average pore size is 3-6nm.

2. The PMMA-controlled layered hydroxide according to claim 1, characterized in that: The molar ratio of the three elements is Fe:Mg:Al=x:2:1, x is 0.025-0.2, and the specific surface area is 240-260m 2 / g, pore volume is 0.8-0.9cm 3 / g, and the average pore size is 3-5nm.

3. The method for preparing a PMMA-controlled layered hydroxide according to claim 1 or 2, wherein: Follow the steps below: Step 1, stirring the PMMA dispersion at 60-80 degrees Celsius, and when the temperature is stabilized at 60-80 degrees Celsius, adjusting the pH of the PMMA dispersion to 8.0-11.0 using an alkali solution; Step 2, adding the nitrate solution and the alkali solution to the mixed solution obtained in step 1 simultaneously while stirring, maintaining the temperature at 60-80 degrees Celsius, and controlling the pH at 8.0-11.0; Step 3, after the dropwise addition is completed, stirring is stopped, the obtained precipitate is aged in a water bath at 40-80° C. for 2-10 hours, and the precipitate is filtered, washed, and dried to obtain a precursor; Step 4, grinding the precursor obtained in step 3 and calcining it, starting from room temperature 20-25 degrees Celsius in an air atmosphere, heating at a rate of 1-5°C / min to 300-450°C, and keeping it warm for 1-5 hours; then heating at a rate of 1-5°C / min to 450-900°C, keeping it warm for 1-5 hours, and finally cooling it to room temperature 20-25 degrees Celsius with the furnace to obtain PMMA regulated layered hydroxide.

4. The method for preparing a PMMA-controlled layered hydroxide according to claim 3, characterized in that: In step 1, the alkali solution is an aqueous solution of sodium hydroxide and sodium carbonate, the concentration of sodium hydroxide is controlled at 0.10-0.30 mol / L, and the concentration of sodium carbonate is controlled at 0.6-1.0 mol / L; PMMA powder is weighed, and then 10-50 mL of deionized water and 10-30 mL of anhydrous ethanol are added for dispersion to obtain a PMMA dispersion; the stirring speed is 100-500 revolutions per minute; and the pH is adjusted to 9.0-10.

0.

5. The method for preparing a PMMA-controlled layered hydroxide according to claim 3, characterized in that: In step 2, corresponding iron nitrate, magnesium nitrate and aluminum nitrate are weighed according to the ratio of the three metal elements, and deionized water is added to dissolve them to form a nitrate solution, and the total metal ion concentration is controlled at 0.20-0.50 mol / L; the alkali solution is an aqueous solution of sodium hydroxide and sodium carbonate, and the concentration of sodium hydroxide is controlled at 0.10-0.30 mol / L, and the concentration of sodium carbonate is controlled at 0.6-1.0 mol / L.

6. The method for preparing a PMMA-controlled layered hydroxide according to claim 3, characterized in that: In step 2, the dripping speed of the nitrate solution should be controlled within a range of 1 drop per 2 seconds to 2 drops per 1 second; the dripping speed of the alkali solution should be controlled according to the pH change of the reaction system during the entire reaction process; The pH is controlled to 9.0-10.0 and the stirring speed is 100-500 revolutions per minute.

7. The method for preparing a PMMA-controlled layered hydroxide according to claim 3, characterized in that: In step 3, the aging temperature is 60-80 degrees Celsius, and the aging time is 4-6 hours; the drying temperature is 60-120°C, and the drying time is 8-24 hours.

8. The method for preparing a PMMA-controlled layered hydroxide according to claim 3, characterized in that: In step 4, starting from room temperature of 20-25 degrees Celsius, the temperature is raised at a rate of 1-2 degrees Celsius / min to 300-450 degrees Celsius under air atmosphere, and kept at this temperature for 3-4 hours; then the temperature is raised at a rate of 1-2 degrees Celsius / min to 600-700 degrees Celsius, and kept at this temperature for 2-3 hours, and finally cooled to room temperature of 20-25 degrees Celsius with the furnace.

9. The use of PMMA-controlled layered hydroxide in the preparation of single-walled carbon nanotubes by catalytic cracking of methane as claimed in claim 1 or 2, characterized in that: There is no need to use hydrogen to reduce the PMMA-controlled layered hydroxide, and no inert protective gas is introduced as a protective atmosphere during the heating process.

10. The use according to claim 9, characterized in that: Here are the steps: Step 1, weighing a predetermined amount of PMMA-regulated layered hydroxide and placing it in an ark, and heating it to a reaction temperature in an air atmosphere in a tube furnace; Step 2, introducing an inert protective gas to exhaust the air, such as for 30-60 minutes, with a flow rate of the inert protective gas of 50-80 mL / min; Step 3, passing methane to react, the reaction time is 30-60min, and the methane flow rate is 10-30mL / min; Step 4, turning off the methane, cooling with the furnace under an inert protective gas atmosphere, and obtaining single-walled carbon nanotubes.

Images