Catalyst for preparing carbon nanofibers as well as preparation method and use method of catalyst

Abstract

The invention discloses a catalyst for preparing carbon nanofibers as well as a preparation method and a use method of the catalyst, and belongs to the technical field of catalysts. The invention discloses a carbon nanofiber catalyst which is obtained by stirring, heating and dissolving nitrates of nickel, lanthanum, cobalt, copper, aluminum and molybdenum in deionized water, adding a carrier, adding sodium carbonate, stirring and separating out under an ultrasonic condition, fishing out the carrier, and sintering in a vacuum sintering furnace, wherein the carrier is porous anodic aluminum oxide obtained through multiple times of anodic oxidation, and the yield of the carbon nanofibers prepared by using the catalyst of the carbon nanofibers is higher.

Description

Technical Field

[0001] The present invention relates to a catalyst for preparing nanocarbon fibers, a preparation method thereof, and a usage method thereof. Background Art

[0002] Nanocarbon fiber (NCF) is a material with high performance and high strength. Due to its excellent electrical conductivity, thermal conductivity, and mechanical properties, it shows broad application prospects in the fields of aerospace, electronic devices, energy storage devices, and composite materials. However, in the current preparation process of nanocarbon fibers, there is a problem of low yield, which has become a key bottleneck restricting its large-scale industrial application.

[0003] Common preparation methods of nanocarbon fibers:

[0004] (1) Preparation of nanocarbon fibers by electrospray method

[0005] The electrospray method realizes liquid spraying and rapid drying through a high-voltage electric field, thereby forming nanoparticles or fibers. This method can precisely control the diameter and length of the fibers and is suitable for preparing uniform nanocarbon fibers. In actual operation, it is necessary to select appropriate carbon sources and solvents and optimize the fiber morphology by adjusting voltage parameters. However, the electrospray method has high requirements for equipment and low production efficiency, making it difficult to meet industrial demands.

[0006] (2) Chemical vapor deposition (CVD)

[0007] The chemical vapor deposition method is one of the main methods for preparing nanocarbon fibers at present. This method introduces a carbon source gas into a high-temperature reaction environment and makes it chemically react with the surface of a metal catalyst to generate carbon fibers. The advantage of the CVD method is that it can achieve large-scale production of high-quality nanocarbon fibers, but its disadvantage is that the selection and activity of the catalyst directly affect the quality and yield of the fibers. Existing catalysts usually have problems such as low catalytic efficiency and poor stability, resulting in limited yields of nanocarbon fibers.

[0008] (3) Preparation of nanocarbon fibers by sol-gel method

[0009] The sol-gel method uses organic or inorganic substances as raw materials to prepare nanocarbon fibers through dissolution, gelation, and high-temperature carbonization processes. This method is simple to operate and suitable for laboratory research, but its process complexity is relatively high, and it is difficult to control the temperature and pressure during the carbonization process, which easily leads to uneven fiber morphology and further affects the yield.

[0010] (4) Preparation of nanocarbon fibers by template method

[0011] The template method involves depositing a carbon source using a specific template and then performing a heat treatment. Finally, nanofibers are obtained by ablating the template. This method can produce fibers with consistent diameters and lengths, exhibiting high uniformity. However, the selection and preparation cost of the template are relatively high, and the process of removing the template may cause damage to the fibers, reducing the product quality.

[0012] (5) Preparation of nanofibers by electrospinning

[0013] The electrospinning method involves stretching a polymer material or other organic compound into fibers and then converting them into nanofibers through carbonization treatment. For example, the patent document with the application number 02115886.X proposed a method for preparing nanofibers based on the combustion of a metal substrate. Although this method is easy to operate, in practical applications, due to the poor catalytic effect, the fiber yield is still relatively low.

[0014] Although the above methods have their respective advantages, in actual production, there is a common problem that the carbon source conversion rate of the catalyst used for preparing nanofibers is low, and it is difficult to improve the yield of nanofibers.

[0015] Therefore, developing a catalyst for efficiently preparing nanofibers and its preparation method is of great significance for improving the yield of nanofibers. Summary of the Invention

[0016] The purpose of the present invention is to provide a catalyst for preparing nanofibers, its preparation method, and its usage method to solve the technical problems mentioned in the above background technology.

[0017] The technical solution to achieve the purpose of the present invention is as follows:

[0018] In the first aspect of the present invention, a catalyst for preparing nanofibers is provided. The catalyst is obtained by stirring and heating nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate in deionized water to dissolve them, adding a carrier, then adding sodium carbonate and stirring to precipitate under ultrasonic conditions, and finally fishing out the carrier and sintering it in a vacuum sintering furnace.

[0019] Furthermore, the carrier is porous anodic aluminum oxide obtained by multiple anodic oxidations.

[0020] In the second aspect of the present invention, a preparation method of the catalyst for preparing nanofibers as described in the first aspect is provided, including the following preparation steps:

[0021] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly by mass ratio, then add deionized water, and heat to 130 - 190 °C and keep stirring until completely dissolved; at this time, nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate react with each other, and the stirred material is in a liquid state

[0022] (2) Add a carrier to the material obtained in step (1), then add sodium carbonate and stir. When solids start to precipitate, continue stirring under ultrasonic conditions until precipitation is complete. After stirring, let it stand overnight, then fish it out and put it into a vacuum sintering furnace for sintering to obtain the catalyst.

[0023] Further, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:205 - 215:9.5 - 10.5.

[0024] Further, the stirring and precipitation time in step (2) is not less than 4 h.

[0025] Further, the sintering temperature in step (2) is 400 - 500 °C, and the sintering time is not less than 4 h.

[0026] Further, the preparation method of the carrier is as follows:

[0027] S1. Anneal industrial pure aluminum sheets in a tube furnace under a nitrogen atmosphere at 450 - 550 °C for 1.5 - 2.5 h, and then cool with the furnace temperature.

[0028] S2. Place the aluminum specimens obtained in step S1 in absolute ethanol, and clean them with an ultrasonic cleaner for 4 - 6 min to remove grease, and then wash them with deionized water to remove residual ethanol.

[0029] S3. Place the aluminum specimens obtained in step S2 into 10 wt% sodium hydroxide solution and 10 wt% nitric acid solution in turn for ultrasonic cleaning to remove the oxide film.

[0030] S4. Use the aluminum specimens obtained in step S3 as the anode and a graphite rod as the cathode. Under the stirring condition where the polishing solution is a mixture of absolute ethanol / perchloric acid with a volume ratio of 4:1, the distance between the anode and cathode is 4 cm, the reaction temperature is 20 - 30 °C, and the rotation speed is 1000 - 3000 rpm, apply a constant voltage direct current of 20 V for 4 - 6 min until the aluminum specimens are as bright as a mirror.

[0031] S5. Seal the aluminum specimens obtained in step S4 with electrical tape, divide the aluminum specimens into a sealed area, and a conductive area and a reaction area on both sides of the sealed area. Insert the reaction area into the electrolyte. Use the aluminum specimens as the anode and a graphite rod as the cathode, with the distance between the anode and cathode being 4 cm. The electrolyte is 0.2 - 0.4 mol / L sulfuric acid solution, the reaction temperature is 10 - 20 °C, and under the stirring rate of 500 - 700 rpm, apply a constant voltage direct current of 25 V for 3 - 5 h.

[0032] S6. Put the aluminum test piece obtained in step S5 into deionized water at 90 - 100 °C for hydrothermal treatment for 1 - 2 h. Then take it out, dry it, and put it into a tube furnace for constant temperature roasting at 550 °C for 4 h, and cool it naturally for standby.

[0033] Further, the preparation method of the carrier further includes repeating the treatment of steps S5 - S6 on the aluminum test piece obtained in step S6 for 1 - 3 times.

[0034] The third aspect of the present invention provides a method for using the catalyst for preparing nano - carbon fibers as described in the first aspect. The using steps are as follows: Put the catalyst into a small porcelain boat, place the small porcelain boat in the middle part of the tube furnace, then evacuate the tube furnace, introduce a carbon source gas, and then heat up to 750 - 850 °C at a heating rate of 10 °C / min, and keep the temperature for reaction for 90 - 180 min. After that, stop introducing the carbon source gas, cool it under nitrogen protection, and collect the product nano - carbon fibers.

[0035] Further, the carbon source gas includes methane, and the flow rate of methane is 3 - 5 L / (min·g catalyst).

[0036] With the above - mentioned technical solutions, the present invention has the following beneficial effects:

[0037] (1) The catalyst for preparing nano - carbon fibers of the present invention is obtained by stirring and heating nickel, lanthanum, cobalt, copper, aluminum, and molybdenum nitrates to dissolve in deionized water, adding a carrier, then adding sodium carbonate and stirring to precipitate under ultrasonic conditions. Then, the carrier is fished out and sintered in a vacuum sintering furnace. Among them, the carrier is porous anodic alumina obtained by multiple anodic oxidations. When the prepared catalyst for nano - carbon fibers is used to prepare nano - carbon fibers, the yield of nano - carbon fibers is relatively high.

[0038] (2) The carrier of the present invention is porous anodic alumina obtained by multiple anodic oxidations, which can effectively avoid defects such as too large pressure drop in the traditional catalyst bed, uneven temperature distribution at each point, and insufficient contact between the catalyst and the reactants. Moreover, it can also strengthen the chemical process, make the catalyst more compact and stable. And the surface pores of the porous anodic alumina after multiple anodic oxidations are more orderly, and the specific surface area is larger, which can quickly adsorb the solids precipitated during the catalyst preparation process, increase the adhesion amount of the catalyst on the carrier, and further provide more catalytic active sites, thereby increasing the yield of nano - carbon fibers.

[0039] (3) The catalyst for nano - carbon fibers of the present invention is mixed with nickel, lanthanum, cobalt, copper, aluminum, and molybdenum nitrates according to a mass ratio of 8.4:0.8:5.7:1.2:1.7:0.2. The prepared catalyst has high catalytic efficiency, and the yield of nano - carbon fibers obtained by using the catalyst is relatively high.

[0040] (4) During the preparation of the catalyst for the nanofibrous carbon of the present invention, precipitation occurs under stirring conditions with ultrasonic waves, which can effectively refine the particle size of the precipitated solid, thereby increasing the specific surface area of the catalyst, providing more catalytic active sites, and synergistically acting with the carrier to increase the yield of nanofibrous carbon. Detailed Embodiments

[0041] To better understand the above technical solutions, the following will describe the above technical solutions in detail in conjunction with specific embodiments.

[0042] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and should not be used to limit the protection scope of the present invention.

[0044] (Example 1)

[0045] A preparation method for a catalyst for preparing nanofibrous carbon, comprising the following preparation steps:

[0046] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly by mass ratio, then add deionized water, and raise the temperature to 190 °C for heat preservation and stirring until completely dissolved;

[0047] (2) Add a carrier to the material obtained in step (1), then add sodium carbonate and stir until solid begins to precipitate, and continue stirring and precipitating for 4 h under ultrasonic conditions of 25 kHz. After stirring, let it stand overnight, then fish it out and put it into a vacuum sintering furnace for sintering at 500 °C for 4 h to obtain the catalyst.

[0048] Among them, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:215:10.5.

[0049] The preparation method of the carrier is as follows:

[0050] S1. Anneal industrial pure aluminum sheets at a high temperature of 550 °C for 2.5 h in a tube furnace under a nitrogen atmosphere, and then cool with the furnace temperature;

[0051] S2. Place the aluminum test pieces obtained in step S1 in absolute ethanol, clean them with an ultrasonic cleaner for 6 min to remove grease, and then wash them with deionized water to remove residual ethanol;

[0052] S3. Place the aluminum test pieces obtained in step S2 in a 10 wt% sodium hydroxide solution and a 10 wt% nitric acid solution in turn for ultrasonic cleaning to remove the oxide film;

[0053] S4. Use the aluminum test piece obtained in step S3 as the anode and a graphite rod as the cathode. In a polishing solution which is a mixture of absolute ethanol / perchloric acid with a volume ratio of 4:1, with the anode-cathode distance being 4 cm, the reaction temperature being 30 °C, and under the stirring condition of a rotation speed of 3000 rpm, pass a direct current of constant voltage of 20 V for 6 min until the aluminum test piece is as bright as a mirror;

[0054] S5. Seal the aluminum test piece obtained in step S4 with electrical insulating tape, dividing the aluminum test piece into a sealed area, and conductive areas and reaction areas on both sides of the sealed area. Insert the reaction area into the electrolyte solution. Use the aluminum test piece as the anode and a graphite rod as the cathode, with the anode-cathode distance being 4 cm, the electrolyte solution being a 0.4 mol / L sulfuric acid solution, the reaction temperature being 20 °C, and under the condition of a stirring rate of 700 rpm, pass a direct current of constant voltage of 25 V for 5 h;

[0055] S6. Place the aluminum test piece obtained in step S5 in deionized water at 100 °C for hydrothermal treatment for 2 h. Then take it out, dry it, and put it into a tube furnace for constant-temperature roasting at 550 °C for 4 h, and then cool it naturally;

[0056] S7. Repeat the treatment of steps S5 - S6 for the aluminum test piece obtained in step S6 three times.

[0057] (Example 2)

[0058] A preparation method of a catalyst for preparing carbon nanofibers, comprising the following preparation steps:

[0059] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly according to the mass ratio, and then add deionized water, and raise the temperature to 150 °C, keep it warm and stir until completely dissolved;

[0060] (2) Add a carrier to the material obtained in step (1), and then add sodium carbonate and stir. When solid begins to precipitate, continue to stir and precipitate for 4 h under the ultrasonic condition of 25 kHz. After the stirring ends, let it stand overnight, and then fish it out and put it into a vacuum sintering furnace for sintering at 450 °C for 4 h to obtain the catalyst.

[0061] Among them, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:210:10.

[0062] The preparation method of the carrier is as follows:

[0063] S1. Anneal an industrially pure aluminum sheet in a tube furnace under a nitrogen atmosphere at 500 °C for 2 h, and then cool it with the furnace temperature;

[0064] S2. Place the aluminum test piece obtained in step S1 in absolute ethanol, and clean it with an ultrasonic cleaner for 5 min to remove grease, and then wash it with deionized water to remove the residual ethanol;

[0065] S3. Place the aluminum test piece obtained in step S2 successively in a 10 wt% sodium hydroxide solution and a 10 wt% nitric acid solution for ultrasonic cleaning to remove the oxide film;

[0066] S4. Use the aluminum test piece obtained in step S3 as the anode and a graphite rod as the cathode. Under the stirring condition that the polishing solution is a mixture of absolute ethanol / perchloric acid with a volume ratio of 4:1, the distance between the anode and the cathode is 4 cm, the reaction temperature is 25 °C, and the rotation speed is 2000 rpm, pass a direct current of 20 V constant voltage for 5 min until the aluminum test piece is as bright as a mirror;

[0067] S5. Seal the aluminum test piece obtained in step S4 with electrical insulating tape, divide the aluminum test piece into a sealed area, a conductive area and a reaction area on both sides of the sealed area, insert the reaction area into the electrolyte, use the aluminum test piece as the anode and a graphite rod as the cathode, the distance between the anode and the cathode is 4 cm, the electrolyte is a 0.3 mol / L sulfuric acid solution, the reaction temperature is 15 °C, and pass a direct current of 25 V constant voltage for 4 h under the condition of a stirring rate of 600 rpm;

[0068] S6. Place the aluminum test piece obtained in step S5 in deionized water at 95 °C for hydrothermal treatment for 1.5 h, then take it out, dry it, put it into a tubular heating furnace, bake it at a constant temperature of 550 °C for 4 h, and cool it naturally;

[0069] S7. Repeat steps S5 - S6 for the aluminum test piece obtained in step S6 twice.

[0070] (Example 3)

[0071] A preparation method of a catalyst for preparing nanocarbon fibers, comprising the following preparation steps:

[0072] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly according to the mass ratio, then add deionized water, and heat up to 130 °C, keep stirring until completely dissolved;

[0073] (2) Add a carrier to the material obtained in step (1), then add sodium carbonate and stir until solid begins to precipitate, continue to stir and precipitate for 4 h under ultrasonic conditions of 25 kHz, let it stand overnight after stirring, then fish it out and put it into a vacuum sintering furnace for sintering at 400 °C for 4 h to obtain the catalyst.

[0074] Among them, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:205:9.5.

[0075] The preparation method of the carrier is as follows:

[0076] S1. Anneal industrial pure aluminum sheets in a tube furnace under a nitrogen atmosphere at a high temperature of 450 °C for 1.5 h, and then cool with the furnace temperature.

[0077] S2. Place the aluminum specimens obtained in step S1 in absolute ethanol, clean them with an ultrasonic cleaner for 4 min to remove grease, and then wash them with deionized water to remove residual ethanol.

[0078] S3. Place the aluminum specimens obtained in step S2 successively in a 10 wt% sodium hydroxide solution and a 10 wt% nitric acid solution for ultrasonic cleaning to remove the oxide film.

[0079] S4. Use the aluminum specimens obtained in step S3 as the anode and a graphite rod as the cathode. Under the stirring condition that the polishing solution is a mixed solution of absolute ethanol / perchloric acid with a volume ratio of 4:1, the distance between the anode and the cathode is 4 cm, the reaction temperature is 20 °C, and the rotation speed is 1000 rpm, pass a direct current of 20 V constant voltage for 4 min until the aluminum specimens are as bright as a mirror.

[0080] S5. Seal the aluminum specimens obtained in step S4 with electrical insulating tape, divide the aluminum specimens into a sealed area, a conductive area and a reaction area on both sides of the sealed area, insert the reaction area into the electrolyte, use the aluminum specimens as the anode and a graphite rod as the cathode, the distance between the anode and the cathode is 4 cm, the electrolyte is a 0.2 mol / L sulfuric acid solution, the reaction temperature is 10 °C, and pass a direct current of 25 V constant voltage for 3 h under the condition that the stirring rate is 500 rpm.

[0081] S6. Place the aluminum specimens obtained in step S5 in deionized water at 90 °C for hydrothermal treatment for 1 h, then take them out, dry them, and then place them in a tube furnace for constant temperature roasting at 550 °C for 4 h, and cool naturally.

[0082] S7. Repeat the treatment of steps S5 - S6 on the aluminum specimens obtained in step S6 once.

[0083] (Example 4)

[0084] A preparation method of a catalyst for preparing carbon nanofibers includes the following preparation steps:

[0085] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly according to the mass ratio, then add deionized water, and heat up to 150 °C for heat preservation and stirring until completely dissolved.

[0086] (2) Add a carrier to the material obtained in step (1), then add sodium carbonate and stir until solid begins to precipitate, continue stirring and precipitating for 4 h under the ultrasonic condition of 25 kHz, let it stand overnight after stirring, then fish it out and put it into a vacuum sintering furnace for sintering at 450 °C for 4 h to obtain the catalyst.

[0087] Among them, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:210:10.

[0088] The preparation method of the carrier is as follows:

[0089] S1. Anneal the industrial pure aluminum sheet in a tube furnace under a nitrogen atmosphere at a high temperature of 500 °C for 2 h, and then cool it with the furnace temperature.

[0090] S2. Place the aluminum specimen obtained in step S1 in absolute ethanol, and clean it with an ultrasonic cleaner for 5 min to remove grease, and then wash it with deionized water to remove the residual ethanol.

[0091] S3. Place the aluminum specimen obtained in step S2 in a 10 wt% sodium hydroxide solution and a 10 wt% nitric acid solution in sequence for ultrasonic cleaning to remove the oxide film.

[0092] S4. Use the aluminum specimen obtained in step S3 as the anode and a graphite rod as the cathode. Under the stirring condition that the polishing solution is a mixed solution of absolute ethanol / perchloric acid with a volume ratio of 4:1, the distance between the anode and the cathode is 4 cm, the reaction temperature is 25 °C, and the rotation speed is 2000 rpm, pass a constant voltage direct current of 20 V for 5 min until the aluminum specimen is as bright as a mirror.

[0093] S5. Seal the aluminum specimen obtained in step S4 with electrical insulating tape, divide the aluminum specimen into a sealed area, a conductive area on both sides of the sealed area, and a reaction area. Insert the reaction area into the electrolyte solution. Use the aluminum specimen as the anode and a graphite rod as the cathode. The distance between the anode and the cathode is 4 cm. The electrolyte solution is 0.3 mol / L sulfuric acid solution, the reaction temperature is 15 °C, and under the condition of a stirring rate of 600 rpm, pass a constant voltage direct current of 25 V for 4 h.

[0094] S6. Place the aluminum specimen obtained in step S5 in deionized water at 95 °C for hydrothermal treatment for 1.5 h, then take it out, dry it, put it into a tube furnace, and bake it at a constant temperature of 550 °C for 4 h, and cool it naturally for standby.

[0095] (Comparative Example 1)

[0096] A preparation method of a catalyst for preparing carbon nanofibers includes the following preparation steps:

[0097] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly by mass ratio, then add deionized water, and heat up to 150 °C for heat preservation and stirring until completely dissolved.

[0098] (2) Add a carrier to the material obtained in step (1), then add sodium carbonate and stir for precipitation for 4 h. After the stirring ends, let it stand overnight, then fish it out and put it into a vacuum sintering furnace for sintering at 450 °C for 4 h to obtain the catalyst.

[0099] Among them, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:210:10.

[0100] The preparation method of the carrier is as follows:

[0101] S1. Anneal industrial pure aluminum sheets in a tube furnace under a nitrogen atmosphere at a high temperature of 500 °C for 2 h, and then cool with the furnace temperature.

[0102] S2. Place the aluminum test pieces obtained in step S1 in absolute ethanol, and clean them with an ultrasonic cleaner for 5 min to remove grease, and then clean them with deionized water to remove residual ethanol.

[0103] S3. Place the aluminum test pieces obtained in step S2 into a 10 wt% sodium hydroxide solution and a 10 wt% nitric acid solution in turn for ultrasonic cleaning to remove the oxide film.

[0104] S4. Use the aluminum test pieces obtained in step S3 as the anode and a graphite rod as the cathode. Under the stirring conditions where the polishing liquid is a mixed solution of absolute ethanol / perchloric acid with a volume ratio of 4:1, the distance between the anode and the cathode is 4 cm, the reaction temperature is 25 °C, and the rotation speed is 2000 rpm, apply a constant voltage direct current of 20 V for 5 min until the aluminum test pieces are as bright as a mirror.

[0105] S5. Seal the aluminum test pieces obtained in step S4 with electrical tape, divide the aluminum test pieces into a sealed area, a conductive area and a reaction area on both sides of the sealed area, insert the reaction area into the electrolyte, use the aluminum test pieces as the anode and a graphite rod as the cathode, the distance between the anode and the cathode is 4 cm, the electrolyte is a 0.3 mol / L sulfuric acid solution, the reaction temperature is 15 °C, and apply a constant voltage direct current of 25 V for 4 h under the stirring rate of 600 rpm.

[0106] S6. Put the aluminum test pieces obtained in step S5 into deionized water at 95 °C for hydrothermal treatment for 1.5 h, then take them out, dry them, put them into a tube furnace for constant temperature roasting at 550 °C for 4 h, and cool naturally for standby.

[0107] S7. Repeat steps S5 - S6 for the aluminum test pieces obtained in step S6 twice.

[0108] (Comparative Example 2)

[0109] A preparation method of a catalyst for preparing carbon nanofibers, comprising the following preparation steps:

[0110] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly according to the mass ratio, then add deionized water, and heat up to 150 °C, keep warm and stir until completely dissolved;

[0111] (2) Add a carrier to the material obtained in step (1), then add sodium carbonate and stir. When solid begins to precipitate, continue stirring under ultrasonic conditions of 25 kHz for 4 h. After stirring ends, let it stand overnight, then take it out and put it into a vacuum sintering furnace for sintering at 450 °C for 4 h to obtain the catalyst.

[0112] Among them, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:210:10.

[0113] (Comparative Example 3)

[0114] A preparation method of a catalyst for preparing nanofibrous carbon, including the following preparation steps:

[0115] (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly according to the mass ratio, then add deionized water, and heat up to 150 °C, keep warm and stir until completely dissolved;

[0116] (2) Add a carrier to the material obtained in step (1), then add sodium carbonate and stir for 4 h until precipitation occurs. After stirring ends, let it stand overnight, then take it out and put it into a vacuum sintering furnace for sintering at 450 °C for 4 h to obtain the catalyst.

[0117] Among them, the mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:210:10.

[0118] Effect Example

[0119] Preparation of nanofibrous carbon: Put the catalysts prepared in the same volume of the examples and comparative examples into a small porcelain boat, place the small porcelain boat in the middle of a tubular furnace, then evacuate the tubular furnace, introduce the carbon source gas methane at a rate of 3 - 5 L / (min·g catalyst), then heat up to 800 °C at a heating rate of 10 °C / min, and keep the reaction for 90 min. After that, stop introducing the carbon source gas, cool under nitrogen protection, and collect the product nanofibrous carbon.

[0120] Yield: The ratio of the mass of the generated nanofibrous carbon to the total carbon mass in the carbon source gas during the reaction.

[0121] The following Table 1 shows the yields of nanofibrous carbon prepared by the catalysts prepared in Examples 1 - 4 and Comparative Examples 1 - 3:

[0122] Table 1

[0123] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Yield (%) 94 96 92 83 75 77 58

[0124] As can be seen from Table 1, when Examples 1 to 4 are compared with Comparative Examples 1 to 3, the yields of the nanofibrous carbon prepared by the catalysts prepared in Examples 1 to 3 are relatively high.

[0125] The difference between Example 4 and Example 2 is that the carrier in Example 4 was anodized only once. When Example 4 is compared with Example 2, the yield of the nanofibrous carbon prepared by the catalyst prepared in Example 2 is relatively high.

[0126] The difference between Comparative Example 1 and Example 2 is that ultrasonic treatment was not performed during the stirring and precipitation process in Comparative Example 1. When Comparative Example 1 is compared with Example 2, the yield of the nanofibrous carbon prepared by the catalyst prepared in Example 2 is relatively high.

[0127] The difference between Comparative Example 2 and Example 2 is that no carrier was used for the catalyst in Comparative Example 2. When Comparative Example 2 is compared with Example 2, the yield of the nanofibrous carbon prepared by the catalyst prepared in Example 2 is relatively high.

[0128] The difference between Comparative Example 3 and Example 2 is that no carrier was used for the catalyst in Comparative Example 2 and ultrasonic treatment was not performed during the stirring and precipitation process. When Comparative Example 3 is compared with Example 2, the yield of the nanofibrous carbon prepared by the catalyst prepared in Example 2 is relatively high.

[0129] In the above-mentioned specific embodiments, the purpose, technical solution and beneficial effects of the present invention have been further described in detail. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A catalyst for preparing carbon nanofibers, characterized in that, The catalyst is obtained by adding a carrier to a solution prepared by stirring and heating nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate in deionized water until dissolved, then adding sodium carbonate and stirring under ultrasonic conditions for precipitation, and finally fishing out the carrier and sintering it in a vacuum sintering furnace.

2. The catalyst for preparing carbon nanofibers according to claim 1, wherein The carrier is porous anodic aluminum oxide obtained by multiple anodic oxidations.

3. A method for preparing a catalyst for preparing nano-carbon fibers as described in any one of claims 1 to 2, characterized in that, It includes the following preparation steps: (1) Mix nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, and molybdenum nitrate evenly according to the mass ratio, then add deionized water, and heat to 130 - 190 °C and keep stirring until completely dissolved; (2) Add the carrier to the material obtained in step (1), then add sodium carbonate and stir until solid begins to precipitate, and continue stirring for precipitation under ultrasonic conditions. After stirring, let it stand overnight, then fish out and sinter it in a vacuum sintering furnace to obtain the catalyst.

4. The preparation method of the catalyst for preparing carbon nanofibers according to claim 3, characterized in that, The mass ratio of nickel nitrate, lanthanum nitrate, cobalt nitrate, copper nitrate, aluminum nitrate, molybdenum nitrate, deionized water, and sodium carbonate is 8.4:0.8:5.7:1.2:1.7:0.2:205 - 215:9.5 - 10.

5.

5. The preparation method of the catalyst for preparing carbon nanofibers according to claim 3, characterized in that, The stirring and precipitation time in step (2) is not less than 4 h.

6. The preparation method of the catalyst for preparing carbon nanofibers according to claim 3, characterized in that, The sintering temperature in step (2) is 400 - 500 °C, and the sintering time is not less than 4 h.

7. The preparation method of the catalyst for preparing carbon nanofibers according to claim 3, characterized in that, The preparation method of the carrier is as follows: S1. Anneal industrial pure aluminum sheets in a tube furnace under a nitrogen atmosphere at 450 - 550 °C for 1.5 - 2.5 h, and then cool with the furnace temperature; S2. Place the aluminum test pieces obtained in step S1 in absolute ethanol, clean them with an ultrasonic cleaner for 4 - 6 min to remove grease, and then wash them with deionized water to remove residual ethanol; S3. Place the aluminum test pieces obtained in step S2 in a 10 wt% sodium hydroxide solution and a 10 wt% nitric acid solution in turn for ultrasonic cleaning to remove the oxide film; S4. Use the aluminum test pieces obtained in step S3 as the anode and a graphite rod as the cathode. Under the stirring conditions where the polishing solution is a mixture of absolute ethanol / perchloric acid with a volume ratio of 4:1, the distance between the anode and cathode is 4 cm, the reaction temperature is 20 - 30 °C, and the rotation speed is 1000 - 3000 rpm, pass a direct current of 20 V for 4 - 6 min until the aluminum test pieces are as bright as a mirror; S5. Seal the aluminum test pieces obtained in step S4 with electrical tape, divide the aluminum test pieces into a sealed area, and a conductive area and a reaction area on both sides of the sealed area. Insert the reaction area into the electrolyte. Use the aluminum test pieces as the anode and a graphite rod as the cathode, with a distance of 4 cm between the anode and cathode. The electrolyte is a 0.2 - 0.4 mol / L sulfuric acid solution, the reaction temperature is 10 - 20 °C, and the stirring rate is 500 - 700 rpm. Pass a direct current of 25 V for 3 - 5 h; S6. Place the aluminum test pieces obtained in step S5 in deionized water at 90 - 100 °C for hydrothermal treatment for 1 - 2 h, then take them out, dry them, and put them in a tube furnace for constant temperature roasting at 550 °C for 4 h, and then cool naturally for standby.

8. The preparation method of the catalyst for preparing carbon nanofibers according to claim 7, characterized in that, The preparation method of the carrier also includes repeating steps S5 - S6 for 1 - 3 times on the aluminum test pieces obtained in step S6.

9. A method for using a catalyst for preparing carbon nanofibers as described in any one of claims 1 to 2, characterized in that, The usage steps are as follows: Put the catalyst into a small porcelain boat, place the small porcelain boat in the middle part of the tube furnace, then evacuate the tube furnace, introduce the carbon source gas, and then heat up to 750 - 850 °C at a heating rate of 10 °C / min. After holding the temperature for reaction for 90 - 180 min, stop introducing the carbon source gas, cool under nitrogen protection, and collect the product, nanofibrous carbon.

10. The method for using the catalyst for preparing carbon nanofibers according to claim 9, characterized in that, The carbon source gas includes methane, and the flow rate of methane is 3 - 5 L / (min·g catalyst).