Preparation method of high-multiplying carbon nanotube and catalyst based on sol-gel method

Abstract

The application provides a high-multiplying carbon nanotube based on a sol-gel method, and the high-multiplying nanotube is prepared by the sol-gel method and comprises the following operation steps: S1-1: when a vapor deposition reaction is started, a tubular furnace is heated to 660-680 DEG C at a rate of 10 DEG C / min, and nitrogen is continuously introduced at a gas flow rate of 200 ml / min; S1-2: after the tubular furnace is heated to a set highest reaction temperature and kept constant, catalyst powder is evenly laid in a boat. The application provides a high-multiplying carbon nanotube based on a sol-gel method and a catalyst preparation method, catalyst is prepared by adopting a sol-gel method combined with a high-molecular dispersant such as polyethylene glycol, agglomeration and growth of transition metal nanoparticles such as Fe and Co in a calcination process are effectively inhibited by using a steric hindrance effect of the dispersant, and a catalytic active center with uniform particle size and excellent dispersity is successfully constructed, which ensures that the catalyst active center has uniform particle size and excellent dispersity.

Description

Technical Field

[0001] This invention relates to the field of high-ratio carbon nanotube production, and more particularly to a method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method. Background Technology

[0002] Carbon nanotubes, as a typical one-dimensional carbon allotrope, have a framework composed of sp... 2 Composed of a hybrid carbon lattice, it possesses excellent mechanical strength, electrical and thermal conductivity, and high specific surface area, showing broad application prospects in fields such as composite material reinforcement phases, catalyst supports, and electronic device components.

[0003] The efficient synthesis of high-ratio carbon nanotubes is key to promoting their large-scale application, which can significantly reduce production costs and improve product purity, while reducing the burden on subsequent purification processes.

[0004] Catalysts are the core element in the synthesis of carbon nanotubes by chemical vapor deposition. They not only serve as active centers for carbon source cracking and graphitic carbon deposition, but also directly regulate the nucleation efficiency, growth rate, morphology, and final growth rate of carbon nanotubes.

[0005] Transition metals iron, cobalt, and nickel are the mainstream active components for catalytic carbon nanotube growth, but their nanoparticles are prone to agglomeration and growth during calcination and reduction, leading to catalytic activity decay and poor product quality stability.

[0006] Therefore, it is necessary to provide a method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method to solve the above-mentioned technical problems. Summary of the Invention

[0007] This invention provides a method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method, which solves the problem that transition metals such as iron, cobalt, and nickel are prone to agglomeration and growth of nanoparticles during calcination and reduction, leading to catalytic activity decay and poor product quality stability.

[0008] To address the aforementioned technical problems, this invention provides a high-ratio carbon nanotube based on the sol-gel method. The high-ratio nanotube is prepared via the sol-gel method, comprising the following steps: S1-1: When the vapor deposition reaction is started, the temperature of the tube furnace is increased to 660-680℃ at 10℃ / min, and nitrogen is continuously introduced at a gas flow rate of 200 ml / min. S1-2: After the tube furnace is heated to the set maximum reaction temperature and kept constant, the catalyst powder is evenly spread in the material boat, and then the material boat is placed in the constant temperature reaction zone in the middle of the quartz reaction tube. S1-3: Preheat the catalyst at the highest reaction temperature for 10 minutes, with the highest temperature range being 580-700℃. First, introduce reducing gas to reduce the catalyst for 10 minutes, then turn off the reducing gas and introduce a mixed gas of carbon source and carrier gas with a gas volume ratio between 1:1 and 1:3. S1-4: The tube furnace maintains the highest reaction temperature and continuously introduces the above mixed gas to carry out the vapor phase deposition reaction, thereby achieving the growth and preparation of carbon nanotubes. S1-5: After the deposition reaction is completed, the carrier gas atmosphere is continuously introduced, the tube furnace is cooled to room temperature, and then the carbon nanotube products in the quartz reaction tube are collected.

[0009] A method for preparing a catalyst using high-ratio carbon nanotubes, comprising the aforementioned high-ratio carbon nanotubes based on the sol-gel method, wherein the method for preparing the catalyst using the high-ratio carbon nanotubes based on the sol-gel method includes the following steps: S2-1: Dissolve 0.003-0.005 mol ferric nitrate, 0.001-0.002 mol cobalt nitrate, 0.001-0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.002-0.007 mol aluminum nitrate in the above solution and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.01-0.20 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. S2-3: Place solution A in a water bath and stir continuously. Add solution B to it at a constant speed using a peristaltic pump, and keep stirring until the mixture is clear and transparent. Record this as solution C. S2-4: Stir solution C in an oil bath until the system shows no obvious liquid flow and has a gel-like texture to obtain the catalyst precursor; S2-5: The catalyst precursor is calcined in a muffle furnace at 400-700℃ for 30-60 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst.

[0010] Preferably, in steps S2-5, the catalyst precursor is sieved through a sieve with a mesh size of 10-80.

[0011] Preferably, the complexing agent in step S2-2 is EDTA, urea, and citric acid.

[0012] Preferably, the auxiliary metal salt in step S2-2 is ammonium molybdate, ammonium metatungstate, or ammonium metavanadate.

[0013] Preferably, in step S2-1, 0.003 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.003 mol aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A; In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.2 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 600°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 660 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 4:3.

[0014] Preferably, in step S2-1, 0.005 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.002 mol nickel nitrate, and 0.007 mol aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A; In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.15 and place it in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 680 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 1:1.

[0015] Preferably, in step S2-1, 0.004 mol ferric nitrate, 0.002 mol cobalt nitrate, 0.001 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.002 mol aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A; In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.1 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 680 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 3:2.

[0016] Preferably, in steps S2-4, the gel is formed by a two-stage gradient oil bath temperature control, and then statically aged at 60°C for 10 hours in a sealed environment.

[0017] Preferably, in steps S2-5, a three-stage temperature-increasing air calcination process is used, followed by cooling and uniform 20-mesh standard sieving. Finally, the catalyst is placed in a nitrogen atmosphere drying oven to isolate it from air and thus obtain a high-performance composite catalyst suitable for high-ratio carbon nanotube growth.

[0018] Compared with related technologies, the method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method provided by this invention has the following beneficial effects: This invention provides a method for preparing high-rate carbon nanotubes and catalysts based on the sol-gel method. The catalyst is prepared by combining the sol-gel method with polymeric dispersants such as polyethylene glycol. The steric hindrance effect of the dispersant effectively inhibits the agglomeration and growth of transition metal nanoparticles such as Fe and Co during calcination, successfully constructing catalytic active centers with uniform particle size and excellent dispersibility. This ensures the uniform particle size and excellent dispersibility of the catalyst active centers, thereby improving the catalyst's stability and lifespan. This lays a solid foundation for the controllable synthesis of carbon nanotubes, enabling efficient and continuous preparation of carbon nanotubes. The product exhibits high crystallinity and excellent thermal stability, demonstrating excellent catalytic stability and high-rate growth characteristics in carbon nanotube synthesis. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a preferred embodiment of a high-ratio carbon nanotube based on the sol-gel method provided by the present invention. Figure 2 A schematic diagram of the structure of a first embodiment of a method for preparing a high-rate carbon nanotube catalyst provided by the present invention; Figure 3 This is a schematic diagram of the fifth embodiment of a method for preparing a high-rate carbon nanotube catalyst provided by the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Please refer to the following: Figure 1 and Figure 2 ,in, Figure 1 This is a schematic diagram of a preferred embodiment of a high-ratio carbon nanotube based on the sol-gel method provided by the present invention. Figure 2 This is a schematic diagram of the structure of a first embodiment of a method for preparing a high-ratio carbon nanotube catalyst provided by the present invention. A high-ratio carbon nanotube based on the sol-gel method is prepared by the following steps:

[0022] S1-1: When the vapor deposition reaction is started, the temperature of the tube furnace is increased to 660-680℃ at 10℃ / min, and nitrogen is continuously introduced at a gas flow rate of 200 ml / min. S1-2: After the tube furnace is heated to the set maximum reaction temperature and kept constant, the catalyst powder is evenly spread in the material boat, and then the material boat is placed in the constant temperature reaction zone in the middle of the quartz reaction tube. S1-3: Preheat the catalyst at the highest reaction temperature for 10 minutes, with the highest temperature range being 580-700℃. First, introduce reducing gas to reduce the catalyst for 10 minutes, then turn off the reducing gas and introduce a mixed gas of carbon source and carrier gas with a gas volume ratio between 1:1 and 1:3. S1-4: The tube furnace maintains the highest reaction temperature and continuously introduces the above mixed gas to carry out the vapor phase deposition reaction, thereby achieving the growth and preparation of carbon nanotubes. S1-5: After the deposition reaction is completed, the carrier gas atmosphere is continuously introduced, the tube furnace is cooled to room temperature, and then the carbon nanotube products in the quartz reaction tube are collected.

[0023] In step S1-3, the reducing gas is hydrogen, with a flow rate between 100 and 300 mL / min, and the reduction lasts for 10 minutes.

[0024] The carbon source gas is selected from one or more of methane, ethylene, and propylene, and the carbon source flow rate is 100-300 mL / min.

[0025] During the vapor deposition reaction, the tubular furnace is heated to 600-720℃ at a heating rate of 10℃ / min.

[0026] Highly efficient catalytic growth of high-rate carbon nanotubes: This catalyst, using metal salts such as iron, cobalt, and nickel as the main active components and combined with a uniformly dispersed system formed by the sol-gel method, can efficiently catalyze the cracking of carbon sources and the ordered deposition of graphitic carbon. Experimental results show that this catalyst exhibits excellent catalytic activity and high-rate growth characteristics during chemical vapor deposition (CVD), promoting the synthesis of multi-walled carbon nanotubes at high rates (i.e., high growth rate and high yield), significantly improving the crystallinity and thermal stability of the product, while reducing the load on subsequent purification processes.

[0027] The synthesized carbon nanotubes exhibit excellent overall physicochemical properties. The high-rate multi-walled carbon nanotubes synthesized using this catalyst not only possess excellent high-rate growth characteristics, but also have high crystallinity and excellent thermal stability. The product has good quality uniformity and takes into account the conductivity and structural characteristics of the carbon nanotube core as well as the stability required for practical applications. This provides a reliable technical path for the large-scale industrial application of carbon nanotubes and has the potential to promote industrialization.

[0028] First Embodiment A method for preparing a catalyst using high-ratio carbon nanotubes, comprising the aforementioned high-ratio carbon nanotubes based on the sol-gel method, wherein the method for preparing the catalyst using the high-ratio carbon nanotubes based on the sol-gel method includes the following steps: S2-1: Dissolve 0.003-0.005 mol ferric nitrate, 0.001-0.002 mol cobalt nitrate, 0.001-0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.002-0.007 mol aluminum nitrate in the above solution and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.01-0.20 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. S2-3: Place solution A in a water bath and stir continuously. Add solution B to it at a constant speed using a peristaltic pump, and keep stirring until the mixture is clear and transparent. Record this as solution C. The water bath temperature required for solution mixing is 40-60℃.

[0029] S2-4: Stir solution C in an oil bath until the system shows no obvious liquid flow and has a gel-like texture to obtain the catalyst precursor; The gelation time of solution C depends on the condition of the solution, with a stirring time range of 5-10 hours and an oil bath temperature of 100-130℃.

[0030] S2-5: The catalyst precursor is calcined in a muffle furnace at 400-700℃ for 30-60 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst.

[0031] In step S2-1, an appropriate amount of soluble metal salt can be weighed and placed in deionized water, and stirred continuously until the solution is clear and transparent to form solution A.

[0032] Soluble metal salts include: active substance soluble metal salts and carrier soluble metal salts.

[0033] The soluble metal salts of active substances include soluble iron salts, soluble cobalt salts, and soluble nickel salts; The carrier soluble metal salt includes soluble aluminum salt, soluble copper salt, soluble magnesium salt, etc. When preparing the carrier soluble metal salt, one or more of the other carrier soluble metal salts can be used in combination.

[0034] In step S2-5, the catalyst precursor is sieved through a sieve with a mesh size of 10-80.

[0035] The complexing agent mentioned in step S2-2 is at least one or any combination of EDTA (ethylenediaminetetraacetic acid), urea, and citric acid.

[0036] Citric acid 2-10 parts, ammonium molybdate 0.01-0.05 parts, the mass ratio of dispersant to active substance and carrier metal salt is 0.01-0.20; the molar ratio of organic complexing agent to metal salt is between 0.1 and 0.7.

[0037] The auxiliary metal salt mentioned in step S2-2 is at least one or any combination of ammonium molybdate, ammonium metatungstate, and ammonium metavanadate.

[0038] Dispersants include one or any combination of PEG (polyethylene glycol), PVA (polyvinyl alcohol), and PVP (polyvinylpyrrolidone).

[0039] Second Embodiment The second embodiment of this application provides a method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method, which differs in that, in step S2-1, 0.003 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.003 mol aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A; In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.2 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 600°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 660 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 4:3.

[0040] The specific steps are as follows: S2: Catalyst Synthesis S2-1: Dissolve 0.003 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.003 mol aluminum nitrate in the above solution and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh out an appropriate amount of ammonium molybdate 0.00002 mol, the mass ratio of PEG to active material and carrier metal salt is 0.2; the molar ratio of the organic complexing agent to the metal salt is 0.1, and mix them uniformly to form solution B; S2-3: Place solution A in a water bath and stir continuously. Use a peristaltic pump to add solution B to solution A at a constant speed. Keep stirring until the mixture is clear and transparent. Record this as solution C. S2-4: Stir solution C at 120℃ until the system shows no obvious liquid flow and has a gel-like texture to obtain the catalyst precursor; S2-5: The catalyst precursor is calcined in a muffle furnace at 600°C for 40 minutes, then naturally cooled to room temperature, and sieved through a 20-mesh sieve to obtain the target catalyst.

[0041] Preparation methods of carbon nanotubes: S1: Synthesis of High Specific Surface Area Carbon Nanotubes S1-1: In the vapor deposition experiment, the tube furnace was heated to 660℃ at a rate of 10℃ / min, and nitrogen was continuously introduced at a flow rate of 200ml / min. S1-2: After the tube furnace reaches its maximum temperature, spread the catalyst powder evenly on the material boat and place the material boat in the constant temperature zone in the middle of the quartz reaction tube. S1-3: Preheat the catalyst at the highest reaction temperature for 10 minutes, then reduce it with hydrogen gas for 10 minutes. After that, turn off the reducing gas and introduce a mixture of carrier gas and carbon source at a volume ratio of 4:3.

[0042] S1-4: The above mixed gas is continuously introduced for 60 minutes to carry out the vapor phase deposition reaction and achieve the growth and preparation of carbon nanotubes.

[0043] Third Embodiment The difference in the third embodiment of this application regarding the preparation method of high-ratio carbon nanotubes and catalysts based on the sol-gel method is that, in step S2-1, 0.005 mol of ferric nitrate, 0.001 mol of cobalt nitrate, 0.002 mol of nickel nitrate, and 0.007 mol of aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent, forming solution A; In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.15 and place it in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 680 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 1:1.

[0044] S2: Catalyst Synthesis S2-1: Dissolve 0.005 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.002 mol nickel nitrate, and 0.007 mol aluminum nitrate in the above solution and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh out an appropriate amount of ammonium molybdate 0.00002 mol, the mass ratio of PEG to active material and carrier metal salt is 0.15; the molar ratio of the organic complexing agent to the metal salt is 0.1, and mix them uniformly to form solution B; S2-3: Place solution A in a water bath and stir continuously. Use a peristaltic pump to add solution B to solution A at a constant speed. Keep stirring until the mixture is clear and transparent. Record this as solution C. S2-4: Stir solution C at 120℃ until the system shows no obvious liquid flow and has a gel-like texture to obtain the catalyst precursor; S2-5: The catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, and sieved through a 20-mesh sieve to obtain the target catalyst.

[0045] A method for preparing carbon nanotubes, characterized in that the carbon nanotubes are prepared by chemical vapor deposition, comprising the following steps: S1: Synthesis of High Specific Surface Area Carbon Nanotubes S1-1: In the vapor deposition experiment, the tube furnace was heated to 680℃ at a rate of 10℃ / min, and nitrogen was continuously introduced at a flow rate of 200ml / min. S1-2: After the tube furnace reaches its maximum temperature, spread the catalyst powder evenly on the material boat and place the material boat in the constant temperature zone in the middle of the quartz reaction tube. S1-3: Preheat the catalyst at the highest reaction temperature for 10 minutes, then reduce it with hydrogen gas for 10 minutes. After that, turn off the reducing gas and introduce a mixture of carrier gas and carbon source at a volume ratio of 1:1.

[0046] S1-4: The above mixed gas is continuously introduced for 60 minutes to carry out the vapor phase deposition reaction and achieve the growth and preparation of carbon nanotubes.

[0047] Fourth embodiment The fourth embodiment of this application provides a method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method, which differs in that, in step S2-1, 0.004 mol of ferric nitrate, 0.002 mol of cobalt nitrate, 0.001 mol of nickel nitrate, 0.005 mol of magnesium nitrate, and 0.002 mol of aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A; In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.1 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 680 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 3:2.

[0048] S2: Catalyst Synthesis S2-1: Dissolve 0.004 mol ferric nitrate, 0.002 mol cobalt nitrate, 0.001 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.002 mol aluminum nitrate in the above solution and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh out an appropriate amount of ammonium molybdate 0.00002 mol, the mass ratio of PEG to active material and carrier metal salt is 0.1; the molar ratio of the organic complexing agent to the metal salt is 0.2, and mix them uniformly to form solution B; S2-3: Place solution A in a water bath and stir continuously. Use a peristaltic pump to add solution B to solution A at a constant speed. Keep stirring until the mixture is clear and transparent. Record this as solution C. S2-4: Stir solution C at 120℃ until the system shows no obvious liquid flow and has a gel-like texture to obtain the catalyst precursor; S2-5: The catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, and sieved through a 20-mesh sieve to obtain the target catalyst.

[0049] A method for preparing carbon nanotubes, characterized in that the carbon nanotubes are prepared by chemical vapor deposition, comprising the following steps: S1: Synthesis of High Specific Surface Area Carbon Nanotubes S2-1: In the vapor deposition experiment, the tube furnace was heated to 680℃ at a rate of 10℃ / min, and nitrogen was continuously introduced at a flow rate of 200ml / min. S2-2: After the tube furnace reaches its maximum temperature, the catalyst powder is evenly spread on the material boat, and the material boat is placed in the constant temperature zone in the middle of the quartz reaction tube. S2-3: Preheat the catalyst at the highest reaction temperature for 10 minutes, then reduce it with hydrogen gas for 10 minutes. After that, turn off the reducing gas and introduce a mixture of carrier gas and carbon source at a volume ratio of 3:2.

[0050] S2-4: The above mixed gas is continuously introduced for 60 minutes to carry out the vapor phase deposition reaction, thereby achieving the growth and preparation of carbon nanotubes.

[0051] Comparative Example S2-1: Dissolve 0.005 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.003 mol magnesium nitrate, and 0.003 mol aluminum nitrate in the above solution and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh out an appropriate amount of ammonium molybdate (0.00002 mol) and dissolve it in pure water; the molar ratio of the complexing agent citric acid to the sum of the metal salts is 0.1, and they are mixed uniformly to form solution B; S2-3: Place solution A in a water bath and stir continuously. Use a peristaltic pump to add solution B to solution A at a constant speed. Keep stirring until the mixture is clear and transparent. Record this as solution C. S2-4: The solution C is directly calcined in a muffle furnace at 600°C from room temperature for 60 min, then naturally cooled to room temperature, and sieved through a 20-mesh sieve to obtain the target catalyst.

[0052] A method for preparing carbon nanotubes, characterized in that the carbon nanotubes are prepared by chemical vapor deposition, comprising the following steps: S1: Synthesis of High Specific Surface Area Carbon Nanotubes S1-1: In the vapor deposition experiment, the tube furnace was heated to 660 °C at a rate of 10 °C / min, and nitrogen was continuously introduced at a flow rate of 200 ml / min. S1-2: After the tube furnace reaches its maximum temperature, spread the catalyst powder evenly on the material boat and place the material boat in the constant temperature zone in the middle of the quartz reaction tube. S1-3: Preheat the catalyst at the highest reaction temperature for 10 minutes, then reduce it with hydrogen gas for 10 minutes. After that, turn off the reducing gas and introduce a mixture of carrier gas and carbon source at a volume ratio of 4:3.

[0053] S1-4: The above mixed gas is continuously introduced for 60 minutes to carry out the vapor phase deposition reaction and achieve the growth and preparation of carbon nanotubes.

[0054] The preparation results of the above embodiments and comparative examples are shown in the table.

[0055] Table 1. Summary of carbon nanotube data for the examples and comparative examples: Table 2. Summary of thermogravimetric (TGA) data for carbon nanotube preparation examples and comparative examples: The working principle of the high-ratio carbon nanotube and catalyst preparation method based on the sol-gel method provided by this invention is as follows: When using, S2-1: Dissolve 0.003-0.005 mol ferric nitrate, 0.001-0.002 mol cobalt nitrate, 0.001-0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.002-0.007 mol aluminum nitrate in the above solution, and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.01-0.20 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. S2-3: Place solution A in a water bath and stir continuously. Add solution B to it at a constant speed using a peristaltic pump, and keep stirring until the mixture is clear and transparent. Record this as solution C. S2-4: Stir solution C in an oil bath until the system shows no obvious liquid flow and has a gel-like texture to obtain the catalyst precursor; S2-5: The catalyst precursor is calcined in a muffle furnace at 400-700℃ for 30-60 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst.

[0056] Compared with related technologies, the method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method provided by this invention has the following beneficial effects: This invention provides a method for preparing high-rate carbon nanotubes and catalysts based on the sol-gel method. The catalyst is prepared by combining the sol-gel method with polymeric dispersants such as polyethylene glycol. The steric hindrance effect of the dispersant effectively inhibits the agglomeration and growth of transition metal nanoparticles such as Fe and Co during calcination, successfully constructing catalytic active centers with uniform particle size and excellent dispersibility. This ensures the uniform particle size and excellent dispersibility of the catalyst active centers, thereby improving the catalyst's stability and lifespan. This lays a solid foundation for the controllable synthesis of carbon nanotubes, enabling efficient and continuous preparation of carbon nanotubes. The product exhibits high crystallinity and excellent thermal stability, demonstrating excellent catalytic stability and high-rate growth characteristics in carbon nanotube synthesis.

[0057] Fifth embodiment Please refer to the following: Figure 3 Based on the first embodiment of this application, which provides a method for preparing high-ratio carbon nanotubes and catalysts using a sol-gel method, the second embodiment of this application proposes another method for preparing high-ratio carbon nanotubes and catalysts using a sol-gel method. The fifth embodiment is merely a preferred embodiment of the first embodiment, and its implementation will not affect the individual implementation of the first embodiment.

[0058] Specifically, the fifth embodiment of this application provides a method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method, which differs in that in steps S2-4, the gel is prepared by temperature control in a two-stage gradient oil bath, and after gelation, it is statically aged at 60°C for 10 hours in a sealed environment.

[0059] The first stage involves stirring in an oil bath at 100℃ for 3 hours to remove free water from the system; the second stage involves stirring in an oil bath at 125℃ for 4 hours to slowly remove bound water, with the entire process conducted in a sealed oil bath environment; after gel formation, an innovative process of static aging at 60℃ for 10 hours is added to reconstruct the three-dimensional network framework of the gel, strengthen the metal-carrier interface interaction, significantly improve the catalyst's high-temperature anti-sintering performance, and adapt it to the high-temperature growth conditions of high-ratio carbon nanotubes.

[0060] In steps S2-5, a three-stage temperature-increasing air calcination process is used. After cooling, the catalyst is uniformly sieved through a 20-mesh standard sieve and finally placed in a nitrogen atmosphere drying oven to isolate it from air, thereby obtaining a high-performance composite catalyst suitable for high-ratio carbon nanotube growth.

[0061] The three-stage temperature-increasing air roasting process precisely decomposes impurities and regulates the active crystal phase: the first stage: the room temperature is raised to 220℃, the heating rate is 2℃ / min, and the temperature is held for 25min to steadily decompose nitrates and slowly release waste gas to avoid gas impact damaging the precursor structure. Second stage: Raise the temperature from 220℃ to the target calcination temperature of 400~700℃ at a rate of 4℃ / min, and hold for 30~60min to complete the formation of the active oxide crystal phase; The third step involves maintaining a constant temperature of 200℃ for 20 minutes after calcination to stabilize the catalyst's crystal structure and reduce lattice defects. After cooling, the catalyst is sieved through a 20-mesh standard sieve and then stored in a nitrogen-atmosphere drying oven to prevent oxidation and deactivation of the active metal, ultimately yielding a high-performance composite catalyst suitable for high-rate carbon nanotube growth.

[0062] Compared with related technologies, the method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method provided by this invention has the following beneficial effects: This invention provides a method for preparing high-ratio carbon nanotubes and catalysts based on the sol-gel method. The method involves two-stage gradient oil bath temperature-controlled gelation, followed by static aging at 60°C for 10 hours after gel formation. This aging process reconstructs the three-dimensional network framework inside the gel, effectively enhancing the interfacial bonding between the active metal components and the support, and significantly improving the catalyst's anti-sintering ability under high-temperature conditions. This adapts the method to the high-temperature growth process conditions in the large-scale preparation of high-ratio carbon nanotubes, effectively improving the rate performance and overall preparation stability of the carbon nanotube products.

[0063] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A high-ratio carbon nanotube based on the sol-gel method, characterized in that, The preparation of high-ratio nanotubes via the sol-gel method includes the following steps: S1-1: When the vapor deposition reaction is started, the temperature of the tube furnace is increased to 660-680℃ at 10℃ / min, and nitrogen is continuously introduced at a gas flow rate of 200 ml / min. S1-2: After the tube furnace is heated to the set maximum reaction temperature and kept constant, the catalyst powder is evenly spread in the material boat, and then the material boat is placed in the constant temperature reaction zone in the middle of the quartz reaction tube. S1-3: Preheat the catalyst at the highest reaction temperature for 10 minutes, with the highest temperature range being 580-700℃. First, introduce reducing gas to reduce the catalyst for 10 minutes, then turn off the reducing gas and introduce a mixed gas of carbon source and carrier gas with a gas volume ratio between 1:1 and 1:

3. S1-4: The tube furnace maintains the highest reaction temperature and continuously introduces the above mixed gas to carry out the vapor phase deposition reaction, thereby achieving the growth and preparation of carbon nanotubes. S1-5: After the deposition reaction is completed, the carrier gas atmosphere is continuously introduced, the tube furnace is cooled to room temperature, and then the carbon nanotube products in the quartz reaction tube are collected.

2. A method for preparing a catalyst for high-ratio carbon nanotubes, comprising high-ratio carbon nanotubes based on the sol-gel method as described in claim 1, wherein the high-ratio carbon nanotube catalyst preparation method required in the preparation of the high-ratio carbon nanotubes based on the sol-gel method is characterized in that, Includes the following steps: S2-1: Dissolve 0.003-0.005 mol ferric nitrate, 0.001-0.002 mol cobalt nitrate, 0.001-0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.002-0.007 mol aluminum nitrate in the above solution and stir continuously until the solution is clear and transparent to form solution A; S2-2: Weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.01-0.20 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. S2-3: Place solution A in a water bath and stir continuously. Add solution B to it at a constant speed using a peristaltic pump, and keep stirring until the mixture is clear and transparent. Record this as solution C. S2-4: Stir solution C in an oil bath until the system shows no obvious liquid flow and has a gel-like texture to obtain the catalyst precursor; S2-5: The catalyst precursor is calcined in a muffle furnace at 400-700℃ for 30-60 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst.

3. The method for preparing a high-ratio carbon nanotube catalyst according to claim 2, characterized in that, In step S2-5, the catalyst precursor is sieved through a sieve with a mesh size of 10-80.

4. The method for preparing a high-ratio carbon nanotube catalyst according to claim 2, characterized in that, The complexing agent mentioned in step S2-2 is EDTA, urea, and citric acid.

5. The method for preparing a catalyst with high-ratio carbon nanotubes according to claim 2, characterized in that, The auxiliary metal salts mentioned in step S2-2 are ammonium molybdate, ammonium metatungstate, and ammonium metavanadate.

6. The method for preparing a catalyst with high-ratio carbon nanotubes according to claim 2, characterized in that, In step S2-1, 0.003 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.003 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.003 mol aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A. In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.2 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 600°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 660 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 4:

3.

7. The method for preparing a high-ratio carbon nanotube catalyst according to claim 6, characterized in that, In step S2-1, 0.005 mol ferric nitrate, 0.001 mol cobalt nitrate, 0.002 mol nickel nitrate, and 0.007 mol aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A. In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.15 and place it in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 680 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 1:

1.

8. The method for preparing a catalyst with high-ratio carbon nanotubes according to claim 7, characterized in that, In step S2-1, 0.004 mol ferric nitrate, 0.002 mol cobalt nitrate, 0.001 mol nickel nitrate, 0.005 mol magnesium nitrate, and 0.002 mol aluminum nitrate are dissolved in the above solution and stirred continuously until the solution is clear and transparent to form solution A. In step S2-2, weigh an appropriate amount of auxiliary metal salt, complexing agent and dispersant in a ratio of 0.1 and place them in deionized water. Stir continuously until the solution is clear and transparent to form solution B. In step S2-5, the catalyst precursor is calcined in a muffle furnace at 550°C for 40 minutes, then naturally cooled to room temperature, removed, sieved, and stored in a drying oven to obtain the target catalyst. In the vapor deposition experiment of step S1-1, the tube furnace is heated to 680 °C at 10 °C / min and nitrogen is continuously introduced at a flow rate of 200 ml / min. In steps S1-3, a mixture of carrier gas and carbon source is introduced, with a gas volume ratio of 3:

2.

9. The method for preparing a catalyst with high-ratio carbon nanotubes according to claim 2, characterized in that, In step S2-4, the gel is formed by temperature control in a two-stage gradient oil bath and then statically aged at 60°C for 10 hours in a sealed environment.

10. The method for preparing a catalyst with high-ratio carbon nanotubes according to claim 2, characterized in that, In steps S2-5, a three-stage temperature-increasing air calcination process is used. After cooling, the catalyst is uniformly sieved through a 20-mesh standard sieve and finally placed in a nitrogen atmosphere drying oven to isolate it from air, thereby obtaining a high-performance composite catalyst suitable for high-ratio carbon nanotube growth.

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