A method for preparing carbon nanotubes

Abstract

The present invention relates to the technical field of carbon nanotube preparation, and in particular to a method for preparing carbon nanotubes. The method comprises: weighing a quantitative amount of active substances and auxiliary agents, wherein the mass ratio between the active substances and the auxiliary agents is 1: (0.1-50); dispersing the active substances and auxiliary agents in water, wherein the ratio of the active substances to water is 1: (10-600), and stirring evenly to obtain a first solution; weighing a pH regulator, and dissolving it in water to obtain a second solution; weighing a quantitative carrier, and dispersing the carrier in water to obtain a third solution; adding the third solution to the first solution under stirring, and then slowly dropping the second solution into the first solution until no precipitation is generated, stopping stirring, and then filtering and washing to obtain a precipitate; freeze-drying the precipitate to obtain a powder; calcining the powder to obtain a carbon nanotube catalyst; placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes.

Description

Technical Field

[0001] The invention relates to the technical field of carbon nanotube preparation, and in particular to a method for preparing carbon nanotubes. Background Art

[0002] Carbon nanotubes are a type of coaxial circular tubes composed of several to dozens of layers of carbon atoms arranged in a hexagonal shape. The structure can be a winding type, with a fixed distance of about 0.34nm between layers, and the diameter is generally 2-20nm. According to the different orientations of the carbon hexagons along the axial direction, they can be divided into three types: zigzag, armchair and spiral. Among them, spiral carbon nanotubes have chirality, while zigzag and armchair carbon nanotubes have no chirality. Carbon nanotubes have excellent mechanical properties, electrical conductivity, thermal conductivity and hydrogen storage capacity, and are considered to be an ideal additive phase for composite materials. As a reinforcing phase and conductive phase, they have great application potential in the field of nanocomposites. At present, the catalysts for preparing carbon nanotubes are mostly transition metal elements or their compounds, which have the problems of low catalyst yield and poor performance of carbon nanotubes. In order to solve this technical problem, a method for preparing carbon nanotubes is proposed. Summary of the invention

[0003] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a method for preparing carbon nanotubes.

[0004] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions: In a first aspect, in one embodiment provided by the present invention, a method for preparing carbon nanotubes is provided, the method comprising the following steps: Weigh a certain amount of active substance and auxiliary agent, the mass ratio between the active substance and the auxiliary agent is 1: (0.1-50); Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:(10-600), and stirring evenly to obtain a first solution; Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:(10-300) to obtain a second solution; Weigh a quantitative carrier, the ratio of active substance to carrier is 1: (0.1-100), disperse the carrier in water, the ratio of carrier to water is 1: (20-500), to obtain a third solution; The third solution is added to the first solution under stirring, and then the second solution is slowly added dropwise to the first solution until no precipitation is generated, stirring is stopped, and then filtering and washing are performed to obtain a precipitate; The precipitate is freeze-dried to obtain a powder; The powder is calcined to obtain a carbon nanotube catalyst; The obtained catalyst sample is placed in a fluidized bed to prepare carbon nanotubes.

[0005] As a further embodiment of the present invention, the active substance is one or more of ferric chloride, ferric nitrate, ferric oxide, ferrocene, ferric sulfate and other iron salts, cobalt nitrate, cobalt chloride and cobalt tetroxide.

[0006] As a further embodiment of the present invention, the active substance is one or more of nickel sulfate, nickel chloride, nickel nitrate, chloroplatinic acid, sodium chloroplatinate, ruthenium chloride, and palladium oxide compounds.

[0007] As a further embodiment of the present invention, the active material is a transition metal element and a compound thereof.

[0008] As a further embodiment of the present invention, the auxiliary agent is one or more of carboxymethyl cellulose, carboxyethyl cellulose, ethyl cellulose, carboxymethyl ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, styrene maleimide resin, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyvinylidene fluoride, polyethylene glycol, polyacrylamide, polyacrylic acid, polyvinyl pyrrolidone and polyvinyl alcohol.

[0009] As a further embodiment of the present invention, the pH regulator may be one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonium carbonate, sodium carbonate, and ammonia water.

[0010] As a further embodiment of the present invention, the selected carrier is one or more of aluminum nitrate, aluminum chloride, magnesium nitrate, magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, zinc sulfate, fumed silica, talcum powder, medical stone powder, feldspar powder, and titanium dioxide.

[0011] As a further solution of the present invention, the filtration and washing is performed by using deionized water or ethanol for washing and purification through suction filtration, centrifugal filtration or pressure filtration.

[0012] As a further solution of the present invention, the calcination temperature is 150-800°C, the heating rate is 0.5-10°C / min, and the holding time is 0.5-12h.

[0013] As a further embodiment of the present invention, the step of placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes comprises: Nitrogen is introduced at a rate of 400-500m1 / min, and the temperature is raised to 600-750°C at a rate of 5-10°C / min. Propylene is introduced at a rate of 100-200m1 / min, and maintained for 1-2h. The ethylene gas is turned off, and the mixture is naturally cooled to room temperature. The nitrogen is turned off to obtain carbon nanotubes.

[0014] The technical solution provided by the present invention has the following beneficial effects: The raw materials used in the present invention mainly include active materials, auxiliary agents, pH regulators, and carriers; the active materials are the main components that play a catalytic role, the auxiliary agents are used to adjust the reaction rate and reaction uniformity of the reaction system, and the carriers are used as dispersions of the active components. The catalyst of the present invention has a high yield and good carbon nanotube performance.

[0015] These and other aspects of the present invention will be more clearly understood in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory and cannot limit the present invention. DETAILED DESCRIPTION

[0016] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] The present invention provides a method for preparing carbon nanotubes, which comprises the following steps: S1. Weigh a certain amount of active substance and auxiliary agent, the mass ratio between the active substance and the auxiliary agent is 1: (0.1-50).

[0018] The active material can be a transition metal element such as iron, cobalt, nickel, platinum, palladium, ruthenium and the like and its compounds, such as iron salts such as ferric chloride, ferric nitrate, ferric oxide, ferrocene, ferric sulfate, cobalt nitrate, cobalt chloride, cobalt tetroxide, etc.; nickel sulfate, nickel chloride, nickel nitrate, etc., and one or more of other precious metal compounds such as chloroplatinic acid, sodium chloroplatinate, ruthenium chloride, palladium oxide and the like.

[0019] The auxiliary agent is one or more of carboxymethyl cellulose, carboxyethyl cellulose, ethyl cellulose, carboxymethyl ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, styrene maleimide resin, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyvinylidene fluoride, polyethylene glycol, polyacrylamide, polyacrylic acid, polyvinyl pyrrolidone, polyvinyl alcohol, etc.

[0020] S2. Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:(10-600), and stirring evenly to obtain a first solution.

[0021] S3. Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:(10-300) to obtain a second solution.

[0022] The pH regulator can be one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonium carbonate, sodium carbonate, ammonia water, etc.

[0023] S4. Weigh a quantitative carrier, the ratio of active substance to carrier is 1: (0.1-100), disperse the carrier in water, the ratio of carrier to water is 1: (20-500), to obtain a third solution.

[0024] The selected carrier is one or more of aluminum nitrate, aluminum chloride, magnesium nitrate, magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, zinc sulfate, fumed silica, talcum powder, medical stone powder, feldspar powder, titanium dioxide, etc.

[0025] S5. Add the third solution to the first solution under stirring, and then slowly drop the second solution into the first solution until no more precipitation is generated, stop stirring, and then filter and wash to obtain a precipitate.

[0026] Filtration and cleaning can be performed by using deionized water, ethanol, suction filtration, centrifugal filtration, or filter press for washing and purification.

[0027] S6. Freeze-drying the precipitate to obtain powder.

[0028] S7, calcining the powder to obtain a carbon nanotube catalyst.

[0029] The calcination temperature is 150-800° C., the heating rate is 0.5-10° C. / min, and the insulation time is 0.5-12h.

[0030] S8. placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes.

[0031] The step S8, placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes, comprises: Nitrogen is introduced at a rate of 400-500m1 / min, and the temperature is raised to 600-750°C at a rate of 5-10°C / min. Propylene is introduced at a rate of 100-200m1 / min, and maintained for 1-2h. The ethylene gas is turned off, and the mixture is naturally cooled to room temperature. The nitrogen is turned off to obtain carbon nanotubes.

[0032] The raw materials used in the present invention mainly include active materials, auxiliary agents, pH regulators, and carriers; the active materials are the main components that play a catalytic role, the auxiliary agents are used to adjust the reaction rate and reaction uniformity of the reaction system, and the carriers are used as dispersions of the active components. The catalyst of the present invention has a high yield and good carbon nanotube performance.

[0033] Example 1 A method for preparing carbon nanotubes, comprising the following steps: S1. Weigh a certain amount of active substance and auxiliary agent, the mass ratio between the active substance and the auxiliary agent is 1: (0.1-50).

[0034] The active substances include ferric chloride, ferric nitrate, ferric oxide, ferrocene and ferric sulfate.

[0035] The auxiliary agent is carboxymethyl cellulose, carboxyethyl cellulose, ethyl cellulose, carboxymethyl ethyl cellulose, and hydroxymethyl cellulose.

[0036] S2. Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:600, and stirring evenly to obtain a first solution.

[0037] S3. Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:300, to obtain a second solution.

[0038] The pH regulator can be one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonium carbonate, sodium carbonate, ammonia water, etc.

[0039] S4. Weigh a quantitative carrier, with the ratio of active substance to carrier being 1:100, and disperse the carrier in water, with the ratio of carrier to water being 1:500, to obtain a third solution.

[0040] The selected supports are aluminum nitrate, aluminum chloride and magnesium nitrate.

[0041] S5. Add the third solution to the first solution under stirring, and then slowly drop the second solution into the first solution until no more precipitation is generated, stop stirring, and then filter and wash to obtain a precipitate.

[0042] Filtration and cleaning can be performed by using deionized water, ethanol, suction filtration, centrifugal filtration, or filter press for washing and purification.

[0043] S6. Freeze-drying the precipitate to obtain powder.

[0044] S7, calcining the powder to obtain a carbon nanotube catalyst.

[0045] The calcination temperature is 800° C., the heating rate is 10° C. / min, and the holding time is 0.5-12 h.

[0046] S8. placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes.

[0047] The step S8, placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes, comprises: Nitrogen was introduced at a rate of 500 ml / min, and the temperature was raised to 750°C at a rate of 10°C / min. Propylene was introduced at a rate of 200 ml / min and maintained for 2 hours. The ethylene gas was turned off, and the mixture was naturally cooled to room temperature. The nitrogen was turned off to obtain carbon nanotubes.

[0048] Example 2 A method for preparing carbon nanotubes, comprising the following steps: S1. Weigh a certain amount of active substance and auxiliary agent, the mass ratio between the active substance and the auxiliary agent is 1:0.1.

[0049] The active materials are nickel sulfate, nickel chloride and nickel nitrate.

[0050] The auxiliary agents are sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyvinylidene fluoride, polyethylene glycol, polyacrylamide, polyacrylic acid and polyvinyl pyrrolidone.

[0051] S2. Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:10, and stirring evenly to obtain a first solution.

[0052] S3. Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:10, to obtain a second solution.

[0053] The pH regulator can be one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonium carbonate, sodium carbonate, ammonia water, etc.

[0054] S4. Weigh a quantitative carrier, with the ratio of active substance to carrier being 1:0.1, and disperse the carrier in water, with the ratio of carrier to water being 1:20, to obtain a third solution.

[0055] The selected carriers are calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, zinc sulfate, fumed silica, talcum powder and medical stone powder.

[0056] S5. Add the third solution to the first solution under stirring, and then slowly drop the second solution into the first solution until no more precipitation is generated, stop stirring, and then filter and wash to obtain a precipitate.

[0057] Filtration and cleaning can be performed by using deionized water, ethanol, suction filtration, centrifugal filtration, or filter press for washing and purification.

[0058] S6. Freeze-drying the precipitate to obtain powder.

[0059] S7, calcining the powder to obtain a carbon nanotube catalyst.

[0060] The calcination temperature is 150° C., the heating rate is 0.5° C. / min, and the holding time is 0.5 h.

[0061] S8. placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes.

[0062] The step S8, placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes, comprises: Nitrogen was introduced at a rate of 400 ml / min, and the temperature was raised to 600°C at a rate of 5°C / min. Propylene was introduced at a rate of 100 ml / min and maintained for 1 hour. The ethylene gas was turned off, and the mixture was naturally cooled to room temperature. The nitrogen was turned off to obtain carbon nanotubes.

[0063] Example 3 A method for preparing carbon nanotubes, comprising the following steps: S1. Weigh a certain amount of active substance and auxiliary agent, the mass ratio between the active substance and the auxiliary agent is 1:40.

[0064] The active substances are cobalt nitrate, cobalt chloride and cobalt tetroxide.

[0065] The auxiliary agents are polyacrylamide, polyacrylic acid, polyvinyl pyrrolidone and polyvinyl alcohol.

[0066] S2. Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:500, and stirring evenly to obtain a first solution.

[0067] S3. Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:250, to obtain a second solution.

[0068] The pH regulator can be one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonium carbonate, sodium carbonate, ammonia water, etc.

[0069] S4. Weigh a quantitative carrier, the ratio of active substance to carrier is 1:80, and disperse the carrier in water, the ratio of carrier to water is 1:400, to obtain a third solution.

[0070] The selected carriers are aluminum nitrate, aluminum chloride, magnesium nitrate, magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, zinc sulfate, fumed silica and talc.

[0071] S5. Add the third solution to the first solution under stirring, and then slowly drop the second solution into the first solution until no more precipitation is generated, stop stirring, and then filter and wash to obtain a precipitate.

[0072] Filtration and cleaning can be performed by using deionized water, ethanol, suction filtration, centrifugal filtration, or filter press for washing and purification.

[0073] S6. Freeze-drying the precipitate to obtain powder.

[0074] S7, calcining the powder to obtain a carbon nanotube catalyst.

[0075] The calcination temperature is 600° C., the heating rate is 8° C. / min, and the holding time is 9 h.

[0076] S8. placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes.

[0077] The step S8, placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes, comprises: Nitrogen was introduced at a rate of 480 ml / min, and the temperature was raised to 720°C at a rate of 9°C / min. Propylene was introduced at a rate of 180 ml / min and maintained for 1.8 hours. The ethylene gas was turned off, and the mixture was naturally cooled to room temperature. The nitrogen was turned off to obtain carbon nanotubes.

[0078] Example 4 A method for preparing carbon nanotubes, comprising the following steps: S1. Weigh a certain amount of active substance and auxiliary agent, the mass ratio between the active substance and the auxiliary agent is 1:10.

[0079] The active substances are nickel sulfate, nickel chloride and nickel nitrate.

[0080] The auxiliary agent is carboxymethyl cellulose, carboxyethyl cellulose, ethyl cellulose, carboxymethyl ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate and styrene maleimide resin.

[0081] S2. Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:100, and stirring evenly to obtain a first solution.

[0082] S3. Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:100, to obtain a second solution.

[0083] The pH regulator can be sodium hydroxide.

[0084] S4. Weigh a quantitative carrier, with the ratio of active substance to carrier being 1:20, and disperse the carrier in water, with the ratio of carrier to water being 1:40, to obtain a third solution.

[0085] The selected carriers are calcium nitrate, zinc nitrate, zinc chloride, zinc sulfate, fumed silica, talcum powder, medical stone powder and feldspar powder.

[0086] S5. Add the third solution to the first solution under stirring, and then slowly drop the second solution into the first solution until no more precipitation is generated, stop stirring, and then filter and wash to obtain a precipitate.

[0087] Filtration and cleaning can be performed by using deionized water, ethanol, suction filtration, centrifugal filtration, or filter press for washing and purification.

[0088] S6. Freeze-drying the precipitate to obtain powder.

[0089] S7, calcining the powder to obtain a carbon nanotube catalyst.

[0090] The calcination temperature is 250° C., the heating rate is 2° C. / min, and the holding time is 3 h.

[0091] S8. placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes.

[0092] The step S8, placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes, comprises: Nitrogen was introduced at a rate of 420 ml / min, and the temperature was raised to 630°C at a rate of 6°C / min. Propylene was introduced at a rate of 120 ml / min and maintained for 1.2 hours. The ethylene gas was turned off, and the mixture was naturally cooled to room temperature. The nitrogen was turned off to obtain carbon nanotubes.

[0093] Example 5 A method for preparing carbon nanotubes, comprising the following steps: S1. Weigh a certain amount of active substance and auxiliary agent, the mass ratio between the active substance and the auxiliary agent is 1:25.

[0094] The active materials are nickel sulfate, nickel chloride and nickel nitrate.

[0095] The auxiliary agent is one or more of polyethylene glycol, polyacrylamide, polyacrylic acid, polyvinyl pyrrolidone and polyvinyl alcohol.

[0096] S2. Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:300, and stirring evenly to obtain a first solution.

[0097] S3. Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:150, to obtain a second solution.

[0098] The pH regulator can be ammonium carbonate.

[0099] S4. Weigh a quantitative carrier, with the ratio of active substance to carrier being 1:50, and disperse the carrier in water, with the ratio of carrier to water being 1:250, to obtain a third solution.

[0100] The selected carriers are zinc chloride, zinc sulfate and fumed silica.

[0101] S5. Add the third solution to the first solution under stirring, and then slowly drop the second solution into the first solution until no more precipitation is generated, stop stirring, and then filter and wash to obtain a precipitate.

[0102] Filtration and cleaning can be performed by using deionized water, ethanol, suction filtration, centrifugal filtration, or filter press for washing and purification.

[0103] S6. Freeze-drying the precipitate to obtain powder.

[0104] S7, calcining the powder to obtain a carbon nanotube catalyst.

[0105] The calcination temperature is 400° C., the heating rate is 5° C. / min, and the holding time is 6 h.

[0106] S8. placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes.

[0107] The step S8, placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes, comprises: Nitrogen was introduced at a rate of 450 ml / min, and the temperature was raised to 680°C at a rate of 7°C / min. Propylene was introduced at a rate of 150 ml / min and maintained for 1.5 hours. The ethylene gas was turned off, and the mixture was naturally cooled to room temperature. The nitrogen was turned off to obtain carbon nanotubes.

[0108] Example 6 A method for preparing carbon nanotubes comprises the following steps: Weigh 10 g of active substances, ferric nitrate, 6 g of cobalt nitrate, 8 g of carboxymethyl cellulose, and 300 g of deionized water, and stir and disperse them thoroughly.

[0109] Weigh 16 g aluminum nitrate and 8 g magnesium nitrate, dissolve in 300 g water, add them to the solution in 1 after they are fully dissolved, and continue stirring at a stirring speed of 1000 r / min.

[0110] Weigh 80 g of potassium hydroxide (pH regulator), dissolve it in 1000 g of water, and slowly add it dropwise to the mixed solution in step 2 until no obvious precipitate is formed.

[0111] The precipitate was filtered and washed with deionized water to obtain a purified precipitate, which was freeze-dried at -40°C and 1 Pa to obtain a dry powder.

[0112] The powder obtained after freeze drying was heated to 500°C at 5°C / min and kept for 4 h to obtain catalyst powder.

[0113] Weigh 50 g of the obtained catalyst sample and place it in a fluidized bed. Pass nitrogen at a rate of 400-500 ml / min. After heating to 600-750 °C at a rate of 5-10 °C / min, pass propylene at a rate of 100-200 ml / min and maintain for 1-2 hours. Turn off the ethylene gas, cool naturally to room temperature, turn off the nitrogen, and obtain carbon nanotubes.

[0114] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A method for preparing carbon nanotubes, characterized in that: The method comprises: weighing a certain amount of active substance and auxiliary agent, wherein the mass ratio between the active substance and the auxiliary agent is 1:(0.1-50); Dispersing the active substance and the auxiliary agent in water, with the ratio of the active substance to water being 1:(10-600), and stirring evenly to obtain a first solution; Weigh a pH regulator and dissolve it in water, wherein the ratio of the pH regulator to water is 1:(10-300) to obtain a second solution; Weigh a quantitative carrier, the ratio of active substance to carrier is 1: (0.1-100), disperse the carrier in water, the ratio of carrier to water is 1: (20-500), to obtain a third solution; The third solution is added to the first solution under stirring, and then the second solution is slowly added dropwise to the first solution until no precipitation is generated, stirring is stopped, and then filtering and washing are performed to obtain a precipitate; The precipitate is freeze-dried to obtain a powder; The powder is calcined to obtain a carbon nanotube catalyst; The obtained catalyst sample is placed in a fluidized bed to prepare carbon nanotubes.

2. The method for preparing carbon nanotubes according to claim 1, characterized in that: The active substance is one or more of ferric chloride, ferric nitrate, ferric oxide, ferrocene, ferric sulfate and other iron salts, cobalt nitrate, cobalt chloride and cobalt tetroxide.

3. The method for preparing carbon nanotubes according to claim 1, characterized in that: The active substance is one or more of nickel sulfate, nickel chloride, nickel nitrate, chloroplatinic acid, sodium chloroplatinate, ruthenium chloride, and palladium oxide compounds.

4. The method for preparing carbon nanotubes according to claim 1, characterized in that: The active material is a transition metal single substance and a compound thereof.

5. The method for preparing carbon nanotubes according to claim 4, characterized in that: The auxiliary agent is one or more of carboxymethyl cellulose, carboxyethyl cellulose, ethyl cellulose, carboxymethyl ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl cellulose, cellulose acetate, styrene maleimide resin, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, polyvinylidene fluoride, polyethylene glycol, polyacrylamide, polyacrylic acid, polyvinyl pyrrolidone and polyvinyl alcohol.

6. The method for preparing carbon nanotubes according to claim 1, characterized in that: The pH regulator can be one or more of sodium hydroxide, potassium hydroxide, sodium bicarbonate, ammonium carbonate, sodium carbonate, and ammonia water.

7. The method for preparing carbon nanotubes according to claim 1, characterized in that: The selected carrier is one or more of aluminum nitrate, aluminum chloride, magnesium nitrate, magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, zinc sulfate, fumed silica, talcum powder, medical stone powder, feldspar powder and titanium dioxide.

8. The method for preparing carbon nanotubes according to claim 1, characterized in that: The filtration and cleaning are performed by using deionized water or ethanol for washing and purification through suction filtration, centrifugal filtration or filter pressing.

9. The method for preparing carbon nanotubes according to claim 8, characterized in that: The calcination temperature is 150-800° C., the heating rate is 0.5-10° C. / min, and the insulation time is 0.5-12h.

10. The method for preparing carbon nanotubes according to claim 8, characterized in that: The step of placing the obtained catalyst sample in a fluidized bed to prepare carbon nanotubes comprises: Nitrogen is introduced at a rate of 400-500m1 / min, and the temperature is raised to 600-750°C at a rate of 5-10°C / min. Propylene is introduced at a rate of 100-200m1 / min, and maintained for 1-2h. The ethylene gas is turned off, and the mixture is naturally cooled to room temperature. The nitrogen is turned off to obtain carbon nanotubes.