A catalyst and a method for preparing the same, and an array-type carbon nanotube and a method for preparing the same

Abstract

The application relates to the field of carbon nanotube catalyst materials, and specifically discloses a catalyst and a preparation method thereof, an array type carbon nanotube and a preparation method thereof. A catalyst is formed into a sheet-shaped nanocrystalline grain, and the sheet-shaped nanocrystalline grain comprises at least one kind of microwave active metal ion. The preparation method of the catalyst comprises the following steps: S1, microwave-assisted reaction; S2, standing and aging; and S3, calcination treatment. An array type carbon nanotube is prepared by catalysis of the catalyst, the array type carbon nanotube has a plurality of unit carbon nanotube bundles, the unit carbon nanotube bundle comprises a plurality of carbon nanotubes which are intertwined and have a tube length greater than 1 mu m, and the tube diameter of the unit carbon nanotube bundle is 0.2-2 mu m. The carbon nanotube prepared by catalysis of the catalyst has a consistent length-diameter ratio, good orientation and high purity, so that the excellent performance of the carbon nanotube can be brought into play.

Description

Technical Field

[0001] This application relates to the field of carbon nanotube catalyst materials, and in particular to a catalyst and its preparation method, and an array-type carbon nanotube and its preparation method. Background Technology

[0002] As a novel nanomaterial, carbon nanotubes have attracted widespread attention due to their unique nanostructure and excellent physicochemical properties. Carbon nanotubes exhibit special properties in many aspects, including mechanics, electricity, heat, and optics, thus revealing potential new applications in numerous fields.

[0003] Generally, based on their microscopic aggregation state, carbon nanotubes can be classified into array-type carbon nanotubes and aggregated carbon nanotubes. Because carbon nanotubes grown on randomly stacked catalysts exhibit a certain degree of aggregation, severe entanglement, and disordered arrangement, subsequent dispersion and other processing become difficult. Therefore, under certain conditions, carbon nanotubes can be made to exhibit significant orientation, achieving parallel alignment, thus forming a carbon nanotube array. Compared to aggregated carbon nanotubes, array-type carbon nanotubes possess a consistent aspect ratio, good orientation, and higher purity, thus contributing to their superior performance.

[0004] Chinese invention patent CN112871181A discloses a carbon nanotube catalyst and its preparation method, which can improve the yield of carbon nanotubes and reduce the production cost of carbon nanotubes. The preparation method of the carbon nanotube catalyst includes: mixing an active component solution, an inactive component solution, and a carbon support to obtain a precursor solution; removing the solvent from the precursor solution to obtain a precursor; calcining the precursor under anaerobic conditions to obtain the carbon nanotube catalyst; and using the catalyst to prepare carbon nanotubes. However, the carbon nanotubes prepared using the catalyst in the above patent have an uneven structure and cannot effectively produce array-type carbon nanotubes. Furthermore, traditional preparation methods for nanocatalysts suffer from slow reaction rates, long aging times, and large crystal particle sizes, which are detrimental to the growth of high-quality, high-yield carbon nanotubes. Summary of the Invention

[0005] To address the issues of poor production efficiency and defective quality of carbon nanotube materials produced by existing arrayed carbon nanotube catalysts, this application provides a catalyst and its preparation method, as well as arrayed carbon nanotubes and their preparation method.

[0006] In a first aspect, this application provides a catalyst, which adopts the following technical solution:

[0007] A catalyst is a sheet-like nanocrystal that includes n kinds of microwave-active metal ions, wherein the number of microwave-active metal ions n≥1.

[0008] By adopting the above technical solution, this application optimizes the structure of the catalyst material by preparing the catalyst into sheet-like nanocrystals. Since the catalyst can significantly affect the structural properties of carbon nanotubes during their actual growth and preparation, the optimized sheet-like nanocrystals of this application exhibit higher activity and are more suitable for mass production of array-type carbon nanotubes with superior rate capability and conductivity.

[0009] The technical solution of this application uses microwave-active metal ions to prepare the sheet-like nanocrystals, so that in the actual production process, the catalyst generates a thermal effect by exciting the dipole orientation polarization and interface polarization of polar microparticles, thereby giving the prepared catalyst material a good sheet-like morphology.

[0010] Preferably, the microwave-active metal ions include one or more of Fe ions, Co ions, Ni ions, Zn ions, Mg ions, Al ions, Mo ions, and La ions.

[0011] By adopting the above technical solution, this application further optimizes the microwave-active metal ions. The catalyst material prepared by the above microwave-active metal ions can continuously vibrate and move under the assistance of microwave heating, thereby reducing the number of defective lattices and making the structure of the prepared catalyst material more regular, thus further optimizing the structure of the prepared catalyst.

[0012] Secondly, this application provides a method for preparing a catalyst, comprising the following preparation steps:

[0013] S1. Microwave-assisted reaction: Place a microwave-active metal ion salt solution in a microwave reaction apparatus, microwave heat it and add an alkaline salt solution, keep it warm and stir the reaction.

[0014] S2. Static aging: After stopping stirring, continue the microwave reaction, allow to stand and age, filter and collect the filter cake, wash and dry, and collect the reactants;

[0015] S3. Calcination treatment: Take the reactants and calcine them. After cooling and standing, grind and sieve them to prepare the array-type carbon nanotube catalyst.

[0016] By adopting the above technical solution, this application prepares array-type carbon nanotube catalyst materials using microwave assistance. Because microwave radiation generated during microwave assistance has the characteristic of rapid heating, polar molecules quickly gain energy, intensify their movement, and significantly shorten the crystallization time, thereby saving catalyst production and reaction time and improving production efficiency. Secondly, this application uses microwave assistance to promote the good growth of catalyst crystal nanosheet structures, thereby producing array-type carbon nanotube products with high scaling factor and good conductivity.

[0017] Preferably, the microwave-active metal ion salt described in step S1 includes a metal ion salt capable of generating layered dihydroxy hydroxides.

[0018] By adopting the above technical solution, this application optimizes the type of metal ion salt and selects a metal ion salt that can produce layered dihydroxy hydroxides. Since the layered hydroxides are formed by octahedra formed by six hydroxide ions coordinated with metal ions sharing six edges and extending infinitely on the crystallographic ab plane, this layered structure is very suitable as a matrix for the longitudinal growth of arrayed carbon nanotubes. Therefore, using it as a catalyst to prepare carbon nanotubes can produce arrayed carbon nanotube products with high magnification and good conductivity.

[0019] Preferably, the alkaline salt solution includes one or two of sodium carbonate solution, sodium bicarbonate solution, ammonium carbonate solution, ammonium bicarbonate solution, or urea solution.

[0020] By adopting the above technical solution, this application optimizes the types of alkaline salt solutions. By co-precipitating alkaline salt solutions with microwave-active metal ion salts under microwave conditions, catalyst materials with excellent structures can be prepared, thereby enabling the production of array-type carbon nanotube products with high rate of change and good conductivity.

[0021] Preferably, the microwave heating in step S2 includes: adjusting the microwave power to 500-4000W, controlling the microwave heating reaction temperature to 50℃-100℃, and the microwave reaction time to 0.5-6h.

[0022] By adopting the above technical solution, this application further optimizes the microwave-assisted process by adjusting the microwave power, temperature, and time. Prolonged high-power operation intensifies the movement of polar molecules, enhancing their interaction with interlayer structures while weakening van der Waals interactions between layers, thus reducing the orderliness along the stacking direction. Therefore, precise control of microwave power, temperature, and time is necessary. Extending the crystallization time or increasing the crystallization power leads to incomplete material structures in the crystallized product. Therefore, it is necessary to adjust the microwave-assisted conditions to effectively improve the regularity of the prepared catalyst, thereby enabling the production of array-type carbon nanotube products with high rate of change and good conductivity.

[0023] Preferably, the temperature for static aging in step S2 is 50–100°C, and the static aging time is 1–12 hours.

[0024] By adopting the above technical solution, this application further optimizes the temperature of static aging. By adjusting the temperature of static aging, the OH groups generated by ionization or hydrolysis in the alkaline salt solution are reduced. -It reacts with microwave-active metal ions for co-precipitation. Under alkaline conditions, through continuous precipitation and growth, and with microwave assistance, it forms catalyst particles with a sheet-like nanocrystalline structure, thereby enabling the production of array-type carbon nanotube products with high yield and good conductivity.

[0025] Thirdly, this application also provides an array-type carbon nanotube prepared by catalysis using the above-mentioned catalyst, wherein the array-type carbon nanotube has a plurality of unit carbon nanotube bundles;

[0026] The unit carbon nanotube bundle comprises a plurality of intertwined carbon nanotubes with a tube length greater than 1 μm;

[0027] The diameter of the unit carbon nanotube bundle is 0.2-2 μm.

[0028] By employing the above-described technical solution, this application achieves the catalytic preparation of array-type carbon nanotubes exhibiting significant orientation and parallel alignment. Compared to aggregated carbon nanotubes, in the array, all carbon nanotubes possess a more consistent aspect ratio, better orientation, and higher purity, thus contributing to their superior performance.

[0029] Preferably, the arrayed carbon nanotubes have a specific surface area greater than 400 m² / g and a powder resistivity less than 30 mΩ•cm.

[0030] Fourthly, this application also provides a method for preparing arrayed carbon nanotubes, comprising the following preparation steps:

[0031] The catalyst was placed in a reactor and heated to 700–750°C under a protective gas. Then, the protective gas was stopped and replaced with a carbon source gas. The catalytic reaction was carried out at 700–750°C for 20–50 minutes to obtain the array-type carbon nanotubes.

[0032] By adopting the above technical solution, this application optimizes the preparation method of arrayed carbon nanotubes. By selecting a catalyst for the preparation of arrayed carbon nanotubes, the prepared arrayed carbon nanotubes have higher rate capability and better conductivity.

[0033] In summary, this application has the following beneficial effects:

[0034] First, this application optimizes the structure of the catalyst material by preparing the catalyst into sheet-like nanocrystals. Since the catalyst can significantly affect the structural properties of carbon nanotubes during the actual growth and preparation process, the optimized sheet-like nanocrystals of this application have higher activity and are more suitable for mass production of array-type carbon nanotubes with better rate capability and conductivity.

[0035] The technical solution of this application uses microwave-active metal ions to prepare the sheet-like nanocrystals, so that in the actual production process, the catalyst generates a thermal effect by exciting the dipole orientation polarization and interface polarization of polar microparticles, thereby giving the prepared catalyst material a good sheet-like morphology.

[0036] Secondly, this application utilizes microwave-assisted preparation of array-type carbon nanotube catalyst materials. Because microwave radiation generates rapid heating during microwave assistance, polar molecules quickly gain energy, intensifying their movement and significantly shortening the crystallization time. This saves time in catalyst production and reaction, improving production efficiency. Furthermore, microwave assistance in this application promotes the healthy growth of catalyst crystal nanosheet structures, resulting in array-type carbon nanotube products with high growth rate and good conductivity.

[0037] Third, this application demonstrates significant orientation in the catalytically prepared array-type carbon nanotubes. Compared to aggregated carbon nanotubes, the array-type carbon nanotubes exhibit a more consistent aspect ratio, better orientation, and higher purity, which is beneficial for realizing their superior performance. Attached Figure Description

[0038] Figure 1 This is a SEM image of the catalyst prepared in Example 1 of this application;

[0039] Figure 2 This is a SEM image of the carbon nanotubes prepared in Example 1 of this application;

[0040] Figure 3 This is a SEM image of the catalyst prepared in Example 4 of this application;

[0041] Figure 4 This is a SEM image of the carbon nanotubes prepared in Example 4 of this application;

[0042] Figure 5 This is a SEM image of the catalyst prepared in Comparative Example 1 of this application;

[0043] Figure 6 This is a SEM image of the carbon nanotubes prepared in Comparative Example 1 of this application. Detailed Implementation

[0044] The present application will be further described in detail below with reference to the embodiments. Example

[0045] Example 1

[0046] The raw materials used in an array-type carbon nanotube catalyst are: aluminum nitrate nonahydrate, magnesium nitrate hexahydrate, cobalt nitrate hexahydrate, ferric nitrate nonahydrate, and sodium carbonate.

[0047] A method for preparing a catalyst for arrayed carbon nanotubes:

[0048] S1. Microwave-assisted reaction: Dissolve 10g aluminum nitrate nonahydrate, 14g magnesium nitrate hexahydrate, 10g cobalt nitrate hexahydrate and 8g ferric nitrate nonahydrate in 500mL of deionized water to form solution A. Dissolve 50g anhydrous sodium carbonate in 500mL of deionized water to form solution B. Add solution A to a microwave reactor, turn on the stirring and microwave heat at 500W. After heating to 50℃, slowly add solution B dropwise into the reactor. Maintain the microwave heating temperature at 50℃ and the dropwise reaction time is 0.5h.

[0049] S2. Static Aging: After the reaction is complete, stop stirring, set the microwave reactor temperature to 50℃, and continue aging for 1 hour. Remove the reactants, cool to room temperature, then filter, wash until neutral, and dry.

[0050] S3. Calcination treatment: The dried precursor is placed in a high-temperature muffle furnace and calcined at 400°C for 0.5 h, then cooled to room temperature. The resulting solid is ground to 100 mesh to obtain the catalyst for array-type carbon nanotubes.

[0051] An array-type carbon nanotube is prepared by the following method: 0.5g of catalyst is added to a quartz boat, the quartz boat is placed in a fixed-bed reactor, and the temperature is increased to 720℃ at 20℃ / min under nitrogen protection. The nitrogen gas is then stopped and replaced with ethylene, a carbon source gas. The reaction is carried out at 720℃ for 30min to obtain the array-type carbon nanotube.

[0052] Example 2

[0053] The raw materials used in an array-type carbon nanotube catalyst are: aluminum nitrate nonahydrate, magnesium nitrate hexahydrate, cobalt nitrate hexahydrate, ferric nitrate nonahydrate, and sodium carbonate.

[0054] A method for preparing a catalyst for arrayed carbon nanotubes:

[0055] S1. Microwave-assisted reaction: Dissolve 10g aluminum nitrate nonahydrate, 14g magnesium nitrate hexahydrate, 10g cobalt nitrate hexahydrate and 8g ferric nitrate nonahydrate in 500mL of deionized water to form solution A. Dissolve 50g anhydrous sodium carbonate in 500mL of deionized water to form solution B. Add solution A to a microwave reactor, turn on the stirring and microwave heat at 2000W. After heating to 60℃, slowly add solution B dropwise into the reactor. Maintain the microwave heating temperature at 60℃ and the dropwise reaction time is 2h.

[0056] S2. Static Aging: After the reaction is complete, stop stirring, set the microwave reactor temperature to 75℃, and continue aging for 2 hours. Remove the reactants, cool to room temperature, then filter, wash until neutral, and dry.

[0057] S3. Calcination treatment: The dried precursor is placed in a high-temperature muffle furnace and calcined at 600°C for 1 hour, then cooled to room temperature. The resulting solid is ground to 100 mesh to obtain the array-type carbon nanotube catalyst.

[0058] An array-type carbon nanotube is prepared by the following method: 0.5g of catalyst is placed in a quartz boat, the quartz boat is placed in a fixed-bed reactor, and the temperature is increased to 700℃ at 20℃ / min under nitrogen protection. The nitrogen gas is then stopped and replaced with propylene as the carbon source gas. The reaction is carried out at 700℃ for 30min to obtain the array-type carbon nanotube.

[0059] Example 3

[0060] The raw materials used in an array-type carbon nanotube catalyst are: aluminum nitrate nonahydrate, magnesium nitrate hexahydrate, cobalt nitrate hexahydrate, ferric nitrate nonahydrate, and sodium carbonate.

[0061] A method for preparing a catalyst for arrayed carbon nanotubes:

[0062] S1. Microwave-assisted reaction: Dissolve 10g aluminum nitrate nonahydrate, 14g magnesium nitrate hexahydrate, 10g cobalt nitrate hexahydrate and 8g ferric nitrate nonahydrate in 500mL of deionized water to form solution A. Dissolve 50g anhydrous sodium carbonate in 500mL of deionized water to form solution B. Add solution A to a microwave reactor, turn on the stirring and microwave heat at 4000W. After heating to 100℃, slowly add solution B dropwise into the reactor. Maintain the microwave heating temperature at 100℃ and the dropwise reaction time is 6h.

[0063] S2. Static Aging: After the reaction is complete, stop stirring, set the microwave reactor temperature to 100℃, and continue aging for 12 hours. Remove the reactants, cool them to room temperature, then filter, wash until neutral, and dry.

[0064] S3. Calcination treatment: The dried precursor is placed in a high-temperature muffle furnace and calcined at 900℃ for 10 hours, then cooled to room temperature. The resulting solid is ground to 100 mesh to obtain the catalyst for array-type carbon nanotubes.

[0065] An array-type carbon nanotube is prepared by the following method: 0.5g of catalyst is placed in a quartz boat, the quartz boat is placed in a fixed-bed reactor, and the temperature is increased to 700℃ at 20℃ / min under nitrogen protection. The nitrogen gas is then stopped and replaced with propylene as the carbon source gas. The reaction is carried out at 700℃ for 30min to obtain the array-type carbon nanotube.

[0066] Example 4

[0067] The raw materials used in an array-type carbon nanotube catalyst are as follows: Solution A: 10g aluminum nitrate nonahydrate, 14g magnesium nitrate hexahydrate, 10g ferric nitrate nonahydrate and 1g ammonium molybdate heptahydrate are dissolved in 500mL of deionized water to form Solution A.

[0068] Solution B: Dissolve 20g of anhydrous sodium carbonate and 30g of sodium bicarbonate in 500mL of deionized water to form solution B.

[0069] Example 5

[0070] The raw materials used in a catalyst for array-type carbon nanotubes are as follows: Solution A: 10g zinc nitrate hexahydrate, 14g lanthanum nitrate hexahydrate, 10g nickel nitrate hexahydrate and 1g ammonium molybdate heptahydrate are dissolved in 500mL of deionized water to form Solution A.

[0071] Solution B: Dissolve 20g of ammonium carbonate and 30g of ammonium bicarbonate in 500mL of deionized water to form solution B.

[0072] It should be noted that the protective gas includes, but is not limited to, nitrogen or one or more combinations of inert gases.

[0073] The carbon source gas includes, but is not limited to, any one of methane, ethane, propane, ethylene, and propylene.

[0074] Comparative Example

[0075] Comparative Example 1

[0076] A catalyst for array-type carbon nanotubes, differing from Example 1 in that microwave-assisted heating was not used in Comparative Example 1, and this catalyst is used to produce carbon nanotubes. The specific preparation steps are as follows:

[0077] 0.5g of catalyst was placed in a quartz boat, which was then placed in a fixed-bed reactor. Under nitrogen protection, the temperature was increased to 720℃ at a rate of 20℃ / min. Nitrogen was then stopped, and ethylene was introduced instead. The reaction was carried out at 720℃ for 30min to prepare carbon nanotubes.

[0078] Performance testing

[0079] The carbon nanotubes prepared in Examples 1-5 and Comparative Example 1 were tested, specifically their resistivity and rate of change (the rate of change refers to the ratio of the mass of the prepared carbon nanotubes to the mass of the catalyst). The test results are shown in Table 1 below.

[0080] The catalysts and carbon nanotubes prepared in Examples 1, 4, and Comparative Example 1 were examined using scanning electron microscopy, specifically as follows: Figures 1-6 As shown.

[0081] Table 1 Performance Test Table

[0082]

[0083] By comparing Examples 1-5, Comparative Example 1, and Table 1 (performance test table), it can be found that:

[0084] Figure 1 , Figure 3 All of them showed that the catalysts have a good nanosheet structure in their microstructure.

[0085] Figure 2 and Figure 4 The microstructure of carbon nanotubes exhibits a unique array structure.

[0086] Figure 5 This shows that the catalyst in Comparative Example 1 has a particulate microstructure and does not have a nanosheet structure.

[0087] and Figure 6 This shows that the microstructure of the carbon nanotubes in Comparative Example 1 is an aggregate structure.

[0088] Combined Figures 1-6 Examples 1-3, Examples 4-5, and Comparative Example 1 were used as a control group for comparison, as detailed below:

[0089] (1) First, the performance of Examples 1-3 was compared with that of Comparative Example 1. As can be seen from the data in Table 2, the data of Examples 1-3 are significantly better than those of Comparative Example 1, indicating that the technical solution of this application optimizes the structure of the catalyst material. By preparing the catalyst into sheet-like nanocrystals, since the catalyst can significantly affect the structural characteristics during the actual growth and preparation of carbon nanotubes, the optimized sheet-like nanocrystals of this application have higher activity in the process of catalytic production of carbon nanotube materials, and are more suitable for mass production of array-type carbon nanotubes with better rate and conductivity. At the same time, the technical solution of this application selects metal ions with microwave activity to prepare the sheet-like nanocrystals, so that this type of catalyst can generate a thermal effect by exciting the dipole orientation polarization and interface polarization of polar microparticles during the actual production process, thereby giving the prepared catalyst material a good sheet-like morphology.

[0090] (2) Comparing Examples 4-5, Example 1 and Comparative Example 1, the data of Examples 4-5 further reflect that the present application has optimized the microwave-active metal ions. The catalyst material prepared by the above-mentioned microwave-active metal ions can continuously vibrate and move under the auxiliary conditions of microwave heating, thereby reducing the number of defective lattices and making the structure of the prepared catalyst material more regular, thereby further optimizing the structure of the prepared catalyst.

[0091] This also explains why using metal ion salts that can produce layered dihydroxy hydroxides is possible. Since layered hydroxides are formed by octahedra with 6 hydroxide ions coordinated to metal ions sharing 6 edges and extending infinitely on the crystallographic ab plane, using them as catalysts to prepare carbon nanotubes can produce array-type carbon nanotube products with high magnification and good conductivity.

[0092] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing arrayed carbon nanotubes, characterized in that, The preparation steps include the following: The catalyst was placed in a reactor and heated to 700-750°C under a protective gas. Then the protective gas was stopped and replaced with a carbon source gas. The catalytic reaction was carried out at 700-750°C for 20-50 minutes to obtain the arrayed carbon nanotubes. The method for preparing the catalyst includes the following preparation steps: S1. Microwave-assisted reaction: Place a microwave-active metal ion salt solution in a microwave reaction apparatus, microwave heat it and add an alkaline salt solution, keep it warm and stir the reaction. S2. Static aging: After stopping stirring, continue the microwave reaction, allow to stand and age, filter and collect the filter cake, wash and dry, and collect the reactants; S3. Calcination treatment: Take the reactants and calcine them. After standing and cooling, grind and sieve them to prepare the array-type carbon nanotube catalyst. The catalyst is a sheet-like nanocrystal and includes n kinds of microwave-active metal ions, wherein the number of microwave-active metal ions n≥4; Microwave-active metal ions include multiple types of Fe ions, Co ions, Ni ions, Zn ions, Mg ions, Al ions, Mo ions, and La ions; The microwave-active metal ion salts mentioned in step S1 include metal ion salts capable of generating layered dihydroxy hydroxides; The microwave heating in step S1 includes: adjusting the microwave power to 500-4000W, controlling the microwave heating reaction temperature to 50℃-100℃, and the microwave reaction time to 0.5-6h; The alkaline salt solution includes one or two of sodium carbonate solution, sodium bicarbonate solution, ammonium carbonate solution, ammonium bicarbonate solution, or urea solution; The temperature for static aging in step S2 is 50-100℃, and the static aging time is 1-12 hours. The array-type carbon nanotubes have a plurality of unit carbon nanotube bundles; The unit carbon nanotube bundle comprises a plurality of intertwined carbon nanotubes with a tube length greater than 1 μm; The diameter of the unit carbon nanotube bundle is 0.2-2 μm, and the powder resistivity is less than 30 mΩ•cm.

2. The method for preparing arrayed carbon nanotubes according to claim 1, characterized in that, The specific surface area of ​​the arrayed carbon nanotubes is greater than 400 m² / g.

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