A nickel-based catalyst, its preparation method and use

Abstract

The application provides a nickel-based catalyst and a preparation method and application thereof, and relates to the technical field of catalyst preparation.A special acting force is formed between metal Ni and a NiFe alloy in the catalyst prepared by the application, an alloy structure of Ni-NiFe is formed, a balance between carbon atom generation, diffusion and precipitation rates is maintained, and the morphology of carbon nanotubes is improved and the service life of the catalyst is prolonged.

Description

Technical Field

[0001] This invention relates to the field of methane cracking catalysis technology, and in particular to a nickel-based catalyst for the cracking of methane to produce carbon nanotubes, its preparation method, and its application. Background Technology

[0002] Methane cracking is a crucial pathway for carbon nanotube production, and catalysts are the core technology in this process. Nickel-based catalysts are the primary catalysts for carbon nanotube production from methane cracking. Nima Bayat, Gaowei Wang, and others prepared Ni-Fe-Al catalysts using impregnation and co-precipitation methods, respectively, forming Ni-Fe alloys. Their results showed that the addition of appropriate amounts of Fe can increase the carbon diffusion rate and decrease the carbon formation rate, thus maintaining a balance between carbon atom formation, diffusion, and precipitation rates and enhancing catalyst stability. However, the catalysts still suffer from problems such as short lifetime due to graphitic carbon covering the active sites and deactivation due to nickel grain aggregation at high temperatures. Summary of the Invention

[0003] This invention creatively prepares a catalyst for the reaction of methane cracking to produce carbon nanotubes. In this catalyst, a special force is formed between metallic Ni and NiFe alloy, forming a Ni-NiFe alloy structure, which maintains the balance between the generation, diffusion and precipitation rates of carbon atoms, improves the morphology of carbon nanotubes, effectively restricts the agglomeration between Ni grains, and improves the high-temperature activity and lifetime of nickel-based catalysts.

[0004] One of the objectives of this invention is to provide a method for preparing a nickel-based catalyst.

[0005] The second objective of this invention is to provide a nickel-based catalyst prepared by this method.

[0006] A third objective of this invention is to provide an application of this nickel-based catalyst.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] In a first aspect, the present invention provides a method for preparing a nickel-based catalyst, comprising the following steps:

[0009] S1. Heating ammonia water yields solution a;

[0010] S2. Mix nickel salt, iron salt, water and citric acid and heat to prepare solution b (i.e., a complex aqueous solution of nickel salt and iron salt), wherein the molar ratio of Ni to Fe is 5:1 to 5:3, and the molar ratio of citric acid to metal salt (i.e., the sum of nickel salt and iron salt) is 1:10 to 3:10.

[0011] S3. Mix tetraethyl orthosilicate and anhydrous ethanol and heat to prepare solution c;

[0012] S4. Add solution c to solution b, mix and heat, then add solution a, mix and heat until the mixed solution becomes viscous, dry, and calcine under a mixed atmosphere of N2 and H2 to obtain a nickel-based catalyst.

[0013] Step S1:

[0014] Industrial ammonia water is an aqueous solution containing 25% to 28% ammonia;

[0015] In some embodiments, the heating temperature in step S1 is 60°C to 80°C.

[0016] Step S2:

[0017] In some embodiments, in step S2, the nickel salt includes one or more of nickel nitrate, nickel sulfate, and nickel acetate; the iron salt includes one or more of iron nitrate, iron sulfate, and iron acetate.

[0018] In some embodiments, in step S2, the mass ratio of metal salt to water is 0.2 to 0.4;

[0019] In some embodiments, the heating temperature in step S2 is 60°C to 80°C.

[0020] Step S3:

[0021] In some embodiments, in step S3, the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is 1 to 3.

[0022] In some embodiments, the heating temperature in step S3 is 60°C to 80°C.

[0023] Step S4:

[0024] In some embodiments, in step S4, the ratio of tetraethyl orthosilicate, metal salt and ammonia in the mixed solution is 90-140g: 180-260g: 16-36mL;

[0025] In some embodiments, in step S4, the heating temperature after adding solution c to solution b is 60°C to 80°C.

[0026] In some embodiments, in step S4, the heating temperature after adding solution a is 60°C to 800°C;

[0027] In some embodiments, in step S4, the drying temperature is 100-120°C and the drying time is 12-24 hours;

[0028] In some embodiments, in step S4, the volume ratio of N2 to H2 is 4:1 to 10:1;

[0029] In some embodiments, in step S4, the calcination temperature is 650–850°C and the calcination time is 4–6 hours.

[0030] In some specific embodiments, the preparation method of the nickel-based catalyst includes the following steps:

[0031] (1) Take a certain amount of ammonia water and heat it in a water bath to 60℃~80℃, and record it as solution a;

[0032] (2) Take a certain amount of Ni and Fe salts respectively, add a certain amount of deionized water and citric acid, stir and heat in a water bath to 60℃~80℃ to dissolve and prepare Ni and Fe salt complex solution, which is called solution b; the molar ratio of Ni to Fe is 5:1~5:3, and the molar ratio of citric acid to metal salt is 1:10~3:10.

[0033] (3) Take a certain amount of carrier tetraethyl orthosilicate, add a certain amount of anhydrous ethanol, stir and heat in a water bath to 60℃~80℃ to disperse the tetraethyl orthosilicate, and record it as solution c.

[0034] (4) Slowly add solution c to solution b, stir and heat the mixture in a water bath at 60℃~80℃, then slowly add solution a to the mixture, stir and heat in a water bath at 90℃~100℃ until the mixture becomes viscous, dry at 100~120℃ for 12~24h, and calcine at 650~850℃ for 4~6h in an atmosphere of N2 and H2 to obtain a nickel-based catalyst, denoted as Ni-NiFe / SiO2.

[0035] Secondly, the present invention provides a nickel-based catalyst prepared by the above-described preparation method.

[0036] The obtained nickel-based catalyst includes a support of SiO2 and Ni nanoparticles and NiFe alloy nanoparticles supported thereon. A special force is formed between Ni and NiFe alloy, resulting in a Ni-NiFe alloy structure.

[0037] Thirdly, the present invention provides an application of the above-mentioned nickel-based catalyst in the preparation of carbon nanotubes by methane cracking.

[0038] Preferably, the application includes: placing the catalyst into a reactor, reducing it by introducing a mixture of N2 and H2 gas for 0.5-1.5 hours, then introducing a mixture of raw material gas CH4 and N2 gas to react and decompose it to generate carbon nanotubes, and after the reaction is completed, introducing nitrogen gas to purify the carbon nanotubes;

[0039] The reaction conditions were: a reaction temperature of 700–800℃, a reaction pressure of 0.1–0.2 MPa, and a volume hourly space velocity of 400–600 h⁻¹. -1 The volume ratio of N2 to CH4 is 4:1 to 1:1.

[0040] The catalyst of this invention can be used to generate carbon nanotubes with fewer branches, longer lengths, and stronger continuity.

[0041] Technical effects:

[0042] This invention creatively prepares a Ni-NiFe catalyst for the methane cracking reaction that primarily produces high-value-added carbon nanotubes. A unique force is formed between metallic Ni and the NiFe alloy in this catalyst, resulting in a Ni-NiFe alloy structure. This maintains a balance between the rates of carbon atom generation, diffusion, and precipitation, improves the morphology of the carbon nanotubes, effectively limits the aggregation of Ni grains, and enhances the high-temperature activity and lifetime of the nickel-based catalyst.

[0043] The present invention has been described in detail above; however, the above embodiments are merely illustrative in nature and are not intended to limit the invention. Furthermore, this document is not limited to the foregoing prior art or the invention itself, or to any theory described in the following embodiments. Attached Figure Description

[0044] Figure 1 The image shows the XRD pattern of the catalyst prepared in Example 1, where the right image is a partial magnified view of the left image;

[0045] Figure 2 TPR spectra of the catalysts in the examples and comparative examples;

[0046] Figure 3 TEM image of carbon nanotubes generated by reaction with the catalyst of Example 1;

[0047] Figure 4 TEM image of carbon nanotubes generated by reaction with catalyst of Comparative Example 1;

[0048] Figure 5 SEM image of carbon nanotubes generated by the NiFe / Al2O3 reaction using Nima Bayat catalyst (background technology).

[0049] Figure 6 This is a SEM image of the carbon nanotubes generated using the catalyst from Example 1. Detailed Implementation

[0050] The present invention will be further described below with reference to the embodiments. It should be noted that the following embodiments are provided for illustrative purposes only and do not constitute a limitation on the scope of protection of the present invention.

[0051] Unless otherwise specified, the raw materials, reagents, and methods used in the embodiments are all conventional raw materials, reagents, and methods in the art.

[0052] Example 1

[0053] Take 32 ml of ammonia water (an aqueous solution containing 25% ammonia), heat it in a water bath to 80°C, and denote it as solution a;

[0054] Take 145g of Ni(NO3)2·6H2O and 75g of Fe(NO3)3·9H2O respectively, add 630g of deionized water and 26g of citric acid (the molar ratio of Ni to Fe is 5:2, and the molar ratio of citric acid to metal salt is 2:10), stir, heat in a water bath to 80℃ to dissolve and prepare a Ni and Fe salt complex solution, denoted as solution b;

[0055] Take 115g of carrier tetraethyl orthosilicate, add 115g of anhydrous ethanol, stir, heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and denot it as solution c.

[0056] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Then, solution a was slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio 9:1) to obtain the Ni-NiFe / SiO2 catalyst. Its XRD pattern is shown below. Figure 1 As shown, it can be seen that the characteristic peak of metallic nickel is at 2θ = 44.0, and the characteristic peak of NiFe alloy structure is at 2θ = 44.6. No characteristic peak of metallic iron has been found. Therefore, the Ni-NiFe / SiO2 catalyst has been obtained.

[0057] Example 2

[0058] Take 28 ml of ammonia water (an aqueous solution containing 25% ammonia), heat it in a water bath to 80°C, and denote it as solution a;

[0059] Take 145g of Ni(NO3)2·6H2O and 37g of Fe(NO3)3·9H2O respectively, add 530g of deionized water and 23g of citric acid (the molar ratio of Ni to Fe is 5:1, and the molar ratio of citric acid to metal salt is 2:10), stir, heat in a water bath to 80℃ to dissolve and prepare a Ni and Fe salt complex solution, denoted as solution b;

[0060] Take 135g of carrier tetraethyl orthosilicate, add 135g of anhydrous ethanol, stir, heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and denot it as solution c.

[0061] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the Ni-NiFe / SiO2 catalyst.

[0062] Example 3

[0063] Take 36 ml of ammonia water (an aqueous solution containing 25% ammonia), heat it in a water bath to 80°C, and denote it as solution a;

[0064] Take 145g of Ni(NO3)2·6H2O and 111g of Fe(NO3)3·9H2O respectively, add 740g of deionized water and 30g of citric acid (the molar ratio of Ni to Fe is 5:3, and the molar ratio of citric acid to metal salt is 2:10), stir, heat in a water bath to 80℃ to dissolve and prepare a Ni and Fe salt complex solution, denoted as solution b;

[0065] Take 95g of carrier tetraethyl orthosilicate, add 95g of anhydrous ethanol, stir, heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and denot it as solution c;

[0066] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the Ni-NiFe / SiO2 catalyst.

[0067] Example 4

[0068] Take 56 ml of ammonia water (an aqueous solution containing 25% ammonia), heat it in a water bath to 80°C, and denote it as solution a;

[0069] Take 145g of Ni(NO3)2·6H2O and 75g of Fe(NO3)3·9H2O respectively, add 580g of deionized water and 14g of citric acid (the molar ratio of Ni to Fe is 5:2, and the molar ratio of citric acid to metal salt is 1:10), stir, heat in a water bath to 80℃ to dissolve and prepare a Ni and Fe salt complex solution, denoted as solution b;

[0070] Take 115g of carrier tetraethyl orthosilicate, add 115g of anhydrous ethanol, stir, and heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and record it as solution c.

[0071] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the Ni-NiFe / SiO2 catalyst.

[0072] Example 5

[0073] Take 16 ml of ammonia water (an aqueous solution containing 25% ammonia), heat it in a water bath to 80°C, and denote it as solution a;

[0074] Take 145g of Ni(NO3)2·6H2O and 75g of Fe(NO3)3·9H2O respectively, add 700g of deionized water and 40g of citric acid (the molar ratio of Ni to Fe is 5:2, and the molar ratio of citric acid to metal salt is 3:10), stir, heat in a water bath to 80℃ to dissolve and prepare a Ni and Fe salt complex solution, denoted as solution b;

[0075] Take 115g of carrier tetraethyl orthosilicate, add 115g of anhydrous ethanol, stir, and heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and record it as solution c.

[0076] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the Ni-NiFe / SiO2 catalyst.

[0077] Comparative Example 1

[0078] Take 145g of Ni(NO3)2·6H2O and 75g of Fe(NO3)3·9H2O respectively, add 630g of deionized water and 26g of citric acid, stir, heat in a water bath to 80℃ to dissolve and prepare a Ni and Fe salt complex solution, denoted as solution b.

[0079] Take 115g of tetraethyl orthosilicate, add 115g of anhydrous ethanol, stir, and heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate. This solution is denoted as c.

[0080] Solution c was slowly added to solution b, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was then dried at 120°C for 24 hours and calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the NiFe / SiO2 catalyst.

[0081] Comparative Example 2

[0082] Take 16 ml of ammonia solution, heat it in a water bath to 80°C, and label it solution a.

[0083] Take 145g of Ni(NO3)2·6H2O and 75g of Fe(NO3)3·9H2O respectively, add 700ml of deionized water, stir, heat in a water bath to 80℃ to dissolve and prepare Ni and Fe salt aqueous solutions, which are denoted as solution b.

[0084] Take 115g of carrier tetraethyl orthosilicate, add 115g of anhydrous ethanol, stir, heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and denot it as solution c.

[0085] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the NiFe / SiO2 catalyst.

[0086] Comparative Example 3

[0087] Take 28 ml of ammonia solution, heat it in a water bath to 80°C, and label it solution a.

[0088] Take 145g of Ni(NO3)2·6H2O and 186g of Fe(NO3)3·9H2O respectively, add 820g of deionized water and 38g of citric acid (the molar ratio of Ni to Fe is 5:5, and the molar ratio of citric acid to metal salt is 2:10), stir, heat in a water bath to 80℃ to dissolve and prepare a Ni and Fe salt complex solution, denoted as solution b;

[0089] Take 55g of carrier tetraethyl orthosilicate, add 55g of anhydrous ethanol, stir, and heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and denote it as solution c;

[0090] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the NiFe / SiO2 catalyst.

[0091] Comparative Example 4

[0092] Take 20 ml of ammonia solution and heat it in a water bath to 80°C. This solution is labeled as solution a.

[0093] Take 145g of Ni(NO3)2·6H2O, add 450g of deionized water and 19g of citric acid (the molar ratio of Ni to Fe is 5:0, and the molar ratio of citric acid to metal salt is 2:10), stir, heat in a water bath to 80℃ to dissolve and prepare Ni salt complex solution, which is denoted as solution b.

[0094] Take 150g of carrier tetraethyl orthosilicate, add 150g of anhydrous ethanol, stir, and heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and denote it as solution c.

[0095] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the Ni / SiO2 catalyst.

[0096] Comparative Example 5

[0097] Take 20 ml of ammonia solution and heat it in a water bath to 80°C. This solution is labeled as solution a.

[0098] Take 75g of Fe(NO3)3·9H2O, add 210g of deionized water and 8g of citric acid (the molar ratio of Ni to Fe is 0:2, and the molar ratio of citric acid to metal salt is 2:10), stir, heat in a water bath to 80℃ to dissolve and prepare Fe salt complex solution, which is denoted as solution b.

[0099] Take 220g of carrier tetraethyl orthosilicate, add 220g of anhydrous ethanol, stir, and heat in a water bath to 80℃ to disperse the tetraethyl orthosilicate, and denote it as solution c;

[0100] Solution c was slowly added to solution b, stirred, and heated in a water bath at 80°C. Solution a was then slowly added to the mixture, stirred, and heated in a water bath at 100°C until the mixture became viscous. The mixture was dried at 120°C for 24 hours and then calcined at 750°C for 4 hours in an atmosphere of N2 and H2 (N2 to H2 volume ratio of 9:1) to obtain the Fe / SiO2 catalyst.

[0101] The TPR spectra of the catalysts in the examples and comparative examples are as follows: Figure 2 As shown. In the example, the reduction peak of Ni-NiFe is located at 340℃~700℃, showing a strong continuous "bun peak" shape, while in the comparative example, the reduction peak of Ni-NiFe is located at 300℃~600℃, showing a weak continuous "bun peak". This indicates that a special force is formed between Ni and NiFe in the example, and the force is stronger than that in the comparative example.

[0102] Catalyst performance testing:

[0103] The performance of the catalyst was evaluated in a quartz tube furnace. The catalyst was loaded into the reactor, and a mixture of N2 and H2 gas (N2 to H2 volume ratio of 9:1) was introduced for reduction for 1 hour. Then, a mixture of feed gas CH4 and N2 gas was introduced for reaction. Nitrogen was purified, and the methane content was analyzed by chromatography. The life of the catalyst was determined by detecting whether the methane content in the tail gas was close to that in the feed. The results are shown in Table 1.

[0104] Test conditions: catalyst loading 3g, temperature: 750℃, pressure: 0.1MPa, volume hourly space velocity 500h⁻¹ -1 The N2:CH4 volume ratio was 4:1, and nitrogen was purified for 1 hour.

[0105] Table 1 Catalyst lifetimes of the Examples and Comparative Examples

[0106] catalyst Reaction temperature / °C Catalyst lifetime Comparative Example 1 750 10h Comparative Example 2 750 8h Comparative Example 3 750 10h Comparative Example 4 750 6h Comparative Example 5 750 7h Example 1 750 42h Example 2 750 38h Example 3 750 37h Example 4 750 40h Example 5 750 36h

[0107] As can be seen from Table 1, the Ni-NiFe / SiO2 catalyst prepared by the present invention through the method of complexing metal salt with citric acid, dispersing the precursor tetraethyl orthosilicate with ethanol, and coupling with ammonia water has a longer lifespan at 750°C, while the lifespan of the comparative catalyst is significantly shorter than that of the catalyst in the examples.

[0108] TEM images of the carbon nanotubes generated by the reactions in Example 1 and Comparative Example 1 are shown below. Figure 3 and Figure 4 As shown, the carbon nanotubes generated in Example 1 exhibit a high hollow ratio, few branches, strong continuity, and uniform diameter, while the carbon nanotubes in Comparative Example 1 have a lower hollow ratio, more branches, a bamboo-like shape, and lower diameter uniformity.

[0109] SEM images of carbon nanotubes generated using the Nima Bayat reaction and Example 1 are shown below. Figure 5 and Figure 6 As shown, the carbon nanotubes generated by the catalyst reaction using the background technology are sparsely distributed and short, while the carbon nanotubes generated by the reaction in Example 1 have fewer branches, stronger continuity, and are denser and longer, which significantly improves the morphology of the carbon nanotubes.

[0110] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and substance defined by the claims of the present invention; and such modifications or substitutions are still within the scope defined by the claims of the present invention.

Claims

1. A method for preparing a nickel-based catalyst, characterized in that, Includes the following steps: S1. Heating ammonia water yields solution a; S2. Mix nickel salt, iron salt, water and citric acid and heat to prepare solution b, wherein the molar ratio of Ni to Fe is 5:1 to 5:3 and the molar ratio of citric acid to metal salt is 1:10 to 3:

10. S3. Mix tetraethyl orthosilicate and anhydrous ethanol and heat to prepare solution c; S4. Add solution c to solution b, mix and heat, then add solution a, mix and heat until the mixed solution becomes viscous, dry, and calcine under a mixed atmosphere of N2 and H2 to obtain a nickel-based catalyst.

2. The preparation method according to claim 1, characterized in that, In step S1, the concentration of ammonia water is 25% to 28%; In step S1, the heating temperature is 60℃~80℃.

3. The preparation method according to claim 1, characterized in that, In step S2, the nickel salt includes one or more of nickel nitrate, nickel sulfate, and nickel acetate; the iron salt includes one or more of iron nitrate, iron sulfate, and iron acetate.

4. The preparation method according to claim 1, characterized in that, In step S2, the mass ratio of metal salt to water is 0.2 to 0.4; In step S2, the heating temperature is 60℃~80℃.

5. The preparation method according to claim 1, characterized in that, In step S3, the mass ratio of tetraethyl orthosilicate to anhydrous ethanol is 1 to 3; In step S3, the heating temperature is 60℃~80℃.

6. The preparation method according to claim 1, characterized in that, In step S4, the heating temperature after adding solution c to solution b is 60℃~80℃; In step S4, the heating temperature after adding solution a is 60℃~800℃.

7. The preparation method according to claim 1, characterized in that, In step S4, the ratio of tetraethyl orthosilicate, metal salt and ammonia in the mixed solution is 90-140g: 180-260g: 16-36mL; In step S4, the volume ratio of N2 to H2 is 4:1 to 10:1; In step S4, the roasting temperature is 650–850℃ and the roasting time is 4–6 hours.

8. A nickel-based catalyst, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.

9. The application of the nickel-based catalyst of claim 8 in the preparation of carbon nanotubes by methane cracking.

10. The application according to claim 9, characterized in that, The application includes: placing the nickel-based catalyst into a reactor, reducing it with a mixture of N2 and H2 gas for 0.5-1.5 hours, then introducing a mixture of raw material gas CH4 and N2 gas to react and decompose it to generate carbon nanotubes. After the reaction is completed, nitrogen gas is introduced to purify the carbon nanotubes. The reaction conditions were: a reaction temperature of 700–800℃, a reaction pressure of 0.1–0.2 MPa, and a volume hourly space velocity of 400–600 h⁻¹. -1 The volume ratio of N2 to CH4 is 4:1 to 1:1.

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