阅读说明：本技术 一种碳纳米管催化剂及其制备方法、碳纳米管的制备方法 (Carbon nanotube catalyst, preparation method thereof and preparation method of carbon nanotube ) 是由 曹雅琴 张建祥 李阳 于建涛 宋新朝 李金来 于 2019-11-29 设计创作，主要内容包括：本发明公开一种碳纳米管催化剂及其制备方法、碳纳米管的制备方法,涉及碳纳米技术领域,以提高碳纳米管的产率,并降低碳纳米管的生产成本。所述碳纳米管催化剂的制备方法包括：将活性组分溶液、非活性组分溶液与碳载体进行混合,获得前驱体溶液；去除前驱体溶液含有的溶剂,获得前驱体；将前驱体在无氧条件下进行焙烧,获得碳纳米管催化剂。所述碳纳米管催化剂的制备方法应用上述方法制备的碳纳米催化剂。本发明提供的碳纳米管催化剂用于碳纳米管催化中。(The invention discloses a carbon nanotube catalyst, a preparation method thereof and a preparation method of a carbon nanotube, and relates to the technical field of carbon nanotubes, so as to improve the yield of the carbon nanotube and reduce the production cost of the carbon nanotube. The preparation method of the carbon nanotube catalyst comprises the following steps: mixing the active component solution, the inactive component solution and the carbon carrier to obtain a precursor solution; removing the solvent contained in the precursor solution to obtain a precursor; and roasting the precursor under an anaerobic condition to obtain the carbon nano tube catalyst. The preparation method of the carbon nano tube catalyst applies the carbon nano catalyst prepared by the method. The carbon nanotube catalyst provided by the invention is used for carbon nanotube catalysis.)

1. A method for preparing a carbon nanotube catalyst, comprising:

mixing the active component solution, the inactive component solution and the carbon carrier to obtain a precursor solution;

removing the solvent contained in the precursor solution to obtain a precursor;

and roasting the precursor under an anaerobic condition to obtain the carbon nano tube catalyst.

2. The method for preparing a carbon nanotube catalyst according to claim 1, wherein the active component contained in the active component solution is an active metal salt; and/or the presence of a gas in the gas,

the inactive component contained in the inactive component solution is an inactive metal salt; and/or the presence of a gas in the gas,

the carbon carrier comprises one or more of graphene, graphite and carbon nanotubes.

3. The method of preparing a carbon nanotube catalyst according to claim 1, wherein the mixing the active component solution, the inactive component solution, and the carbon support to obtain the precursor solution comprises:

uniformly mixing the active component solution, the inactive component solution and the complexing agent solution to obtain a premixed solution;

and adding the premixed solution into a carbon carrier to obtain a precursor solution.

4. The method for producing a carbon nanotube catalyst according to claim 3, wherein the complexing agent contained in the complexing agent solution includes ammonium carbonate and/or ethylene glycol; and/or the presence of a gas in the gas,

the active component solution contains active components with the concentration of 0.1-2 mol/L, the inactive components with the concentration of 0.01-0.5 mol/L, and the complexing agent with the concentration of 1-5 mol/L; and/or the presence of a gas in the gas,

the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is (80-150): (15-30): 1.

5. The method for preparing a carbon nanotube catalyst according to any one of claims 1 to 4, wherein the removing the solvent contained in the precursor solution to obtain the precursor comprises: removing the solvent contained in the precursor solution by using a rotary evaporator; and/or the presence of a gas in the gas,

the roasting temperature is 400-600 ℃; and/or the presence of a gas in the gas,

the total volume of the active component solution and the inactive component solution contained in the precursor solution is 1.1-1.5 times of the minimum impregnation volume of the carbon carrier.

6. A carbon nanotube catalyst comprising a carbon support and a metal oxide distributed in the carbon support.

7. The carbon nanotube catalyst according to claim 6, wherein the carbon nanotube catalyst is prepared by the method of any one of claims 1 to 5.

8. A method for producing a carbon nanotube, comprising: preparing carbon nanotubes by a vapor deposition method using a carbon nanotube catalyst as a catalyst, wherein the carbon nanotube catalyst is the carbon nanotube catalyst according to claim 6 or 7.

9. The method of claim 8, wherein the step of preparing carbon nanotubes by vapor deposition using the carbon nanotube catalyst as a catalyst comprises:

placing the carbon nanotube catalyst of claim 6 or 7 in a reaction chamber;

introducing a reaction gas flow at least containing a carbon source into the reaction cavity in a heating state;

the reaction gas flow at least containing the carbon source is contacted with the carbon nanotube catalyst in a suspension state, so that the carbon source contained in the reaction gas flow at least containing the carbon source is decomposed, and the carbon nanotubes grow on the active sites of the carbon nanotube catalyst.

10. The method of claim 9, wherein before the step of introducing the gas flow containing at least the carbon source into the reaction chamber, the method further comprises: introducing protective gas flow into the reaction cavity; and/or the presence of a gas in the gas,

the flow rate of the reaction gas flow is 3L/min-5L/min; and/or the presence of a gas in the gas,

the reaction gas flow also contains protective gas, and the volume ratio of the protective gas to the carbon source contained in each liter of the reaction gas flow is (0.5-2): 1; the decomposition temperature of the carbon source is 600-700 ℃, and the time for growing the carbon nano tube on the active site of the carbon nano tube catalyst is 20-40 min.

Technical Field

The invention relates to the technical field of carbon nano-tubes, in particular to a carbon nano-tube catalyst and a preparation method thereof, and a preparation method of a carbon nano-tube.

Background

Carbon nanotubes (abbreviated as CNTs) are a one-dimensional nanomaterial, and have the characteristics of light weight, perfect connection of hexagonal structures, excellent electrical conductivity, ultrahigh mechanical strength, extremely high chemical stability and thermal stability, and the like, and can be widely applied to the fields of high-performance composite materials, capacitors, hydrogen storage, electromagnetic wave-absorbing materials, and the like.

At present, carbon nanotubes can be produced by using a nano metal catalyst as a carrier and a Chemical Vapor Deposition (CVD) method. However, the reaction time for producing carbon nanotubes using the nano metal catalyst as a carrier is long, and the yield of the obtained carbon nanotubes is low. And when the nano metal catalyst is an ore catalyst, hydrofluoric acid is needed to remove silicon element contained in the carbon nano tube in the purification process, so that the environmental pollution is caused.

Disclosure of Invention

The invention aims to provide a carbon nanotube catalyst, a preparation method thereof and a preparation method of a carbon nanotube, so as to improve the yield of the carbon nanotube and reduce the production cost of the carbon nanotube.

In order to achieve the above object, the present invention provides a method for preparing a carbon nanotube catalyst. The preparation method of the carbon nano tube catalyst comprises the following steps:

mixing the active component solution, the inactive component solution and the carbon carrier to obtain a precursor solution;

removing the solvent contained in the precursor solution to obtain a precursor;

and roasting the precursor under an anaerobic condition to obtain the carbon nano tube catalyst.

Compared with the prior art, in the preparation method of the carbon nanotube catalyst, the active component solution, the inactive component solution and the carbon carrier are uniformly mixed to form the precursor solution, so that the precursor contained in the precursor solution is the carbon carrier which is substantially and uniformly loaded with the active component and the inactive component. After removing the solvent contained in the precursor solution, roasting the precursor under the oxygen-free condition. Therefore, the preparation time of the carbon nanotube catalyst provided by the invention is relatively short, and the obtained carbon nanotube catalyst comprises a carbon carrier, and an active component oxide and an inactive component oxide which are uniformly distributed on the carbon carrier, and the carbon nanotube is also a carbon material, so that impurities introduced into the carbon nanotube are reduced, and the purification complexity and difficulty of the carbon nanotube are reduced. And because the carbon nanotube catalyst comprises the carbon carrier, and the active substances and the inactive substances which are uniformly distributed on the carbon carrier, the inactive substances can avoid the agglomeration of the active substances on the carbon carrier, so that when the carbon nanotube catalyst is used as the catalyst to grow the carbon nanotube, the problems of thicker tube diameter of the carbon nanotube and quicker inactivation of the catalyst caused by larger catalyst particles are solved, the speed of generating the carbon nanotube by using the active metal oxide loaded on the carbon carrier as an active center is ensured to be higher, and the yield of the carbon nanotube is further improved.

The invention also provides a carbon nano tube catalyst. The carbon nanotube catalyst includes a carbon support and a metal oxide distributed in the carbon support.

Compared with the prior art, the carbon nanotube provided by the invention has the same beneficial effect as the preparation method of the carbon nanotube, and the detailed description is omitted here.

The invention also provides a preparation method of the carbon nano tube. The preparation method of the carbon nano tube comprises the following steps: the carbon nanotube catalyst is used as a catalyst, and is prepared by adopting a vapor deposition method, wherein the carbon nanotube catalyst is the carbon nanotube catalyst in the technical scheme.

Drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 is a first schematic flow chart illustrating a process for preparing a carbon nanotube catalyst according to a first embodiment of the present invention;

fig. 2 is a schematic view of a second process for preparing a carbon nanotube catalyst according to a first embodiment of the present invention;

fig. 3 is a schematic flow chart of a process for preparing carbon nanotubes according to a third embodiment of the present invention;

FIG. 4 is a scanning electron microscope image of a carbon nanotube prepared according to a fourth embodiment of the present invention;

FIG. 5 is a scanning electron microscope image of a carbon nanotube prepared in example V of the present invention;

fig. 6 is a scanning electron microscope image of the carbon nanotube prepared in the sixth embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

At present, the methods for preparing carbon nanotubes mainly include arc discharge, laser evaporation, and Chemical Vapor Deposition (CVD). CVD is the main technique used in the industrial production of multi-walled carbon tubes. The following is an example of the CVD method for producing carbon nanotubes, and the principle of the production of carbon nanotubes will be described.

In the CVD process of preparing carbon nanotubes, it is necessary to catalyze a carbon source gas using a nano metal catalyst as a carbon nanotube catalyst, and the nano metal catalyst may be in a liquid state or a quasi-liquid state. The carbon source gas entering the CVD reaction chamber is diffused to the surface of the nano metal catalyst, and carbon is dissolved in metal or diffused on the surface of the metal and is separated out in the form of a tubular graphite layer, so that the carbon nano tube is obtained. Specifically, after the carbon source gas is adsorbed on the metal catalyst, the carbon source gas is reacted and cracked to produce metal carbide, and when the concentration of carbon reaches a certain degree, the metal carbide is supersaturated and precipitated to form a graphite layer which is regularly arranged. Meanwhile, the diameter of the carbon nanotube is related to the diameter of the metal particle, the continuous growth of the carbon nanotube is driven by the diffusion of carbon through the metal catalyst particle, and when the rate of carbon diffusion does not match the deposition rate, excessive carbon deposition may wrap the entire catalyst surface, thereby causing growth to stop. Therefore, the nano metal catalyst plays a crucial role in the form and structure of the decomposition product as a carbon source decomposition active center and a graphitic carbon deposition center, is the key for synthesizing the carbon nanotube by the CVD method, can reduce the decomposition temperature of the carbon source, can be used as a nucleation point and an energy transporter for the growth of the carbon nanotube, has important influence on the nucleation, growth, density, separation, purification and the like of the carbon nanotube, and determines the form and structure of the carbon nanotube.

Some methods for synthesizing carbon nanotubes are disclosed in the prior art, but the preparation of the carbon nanotube catalyst used in the carbon nanotubes is complicated and takes a long time. The carbon nanotube catalyst used in the prior art is generally a non-carbon carrier, which leads to the introduction of impurities in the preparation of the existing carbon nanotube catalyst and increases the difficulty in purifying the carbon nanotube.

Example one

As shown in fig. 1, an embodiment of the present invention provides a method for preparing a carbon nanotube catalyst. The preparation method of the carbon nano tube catalyst comprises the following steps:

step 101: and mixing the active component solution, the inactive component solution and the carbon carrier to obtain a precursor solution. Wherein, when the active component solution and the inactive component solution are mixed with the carbon support, the active component and the inactive component may be supported on the carbon support. It should be understood that the active component solution herein means that the active component solution contains an oxide formed by the active component that can catalyze the growth of the carbon nanotube. The oxide formed by the inactive components contained in the inactive component solution cannot catalyze the growth of the carbon nano tube.

Step 102: and removing the solvent contained in the precursor solution to obtain the precursor. In this case, the precursor is substantially the carbon support loaded with the active component solution and the inactive component solution described above.

Step 103: and roasting the precursor under an anaerobic condition to obtain the carbon nano tube catalyst. The calcination temperature can be 400-600 ℃, as long as the inorganic metal salt and the metal oxometallate contained in the precursor can be decomposed. Both the active and inactive components are oxidized during firing to form active and inactive component oxides. At this time, the obtained carbon nanotube catalyst includes a carbon support and an active component oxide and an inactive component oxide uniformly dispersed on the carbon support.

Compared with the existing method for preparing the carbon nanotube catalyst by adopting a hydrothermal method, the preparation method of the carbon nanotube catalyst provided by the embodiment of the invention is simple to operate and short in time consumption. Compared with the mineral carbon nanotube catalyst, the carbon nanotube catalyst obtained by the preparation method of the carbon nanotube catalyst provided by the embodiment of the invention comprises the carbon carrier, and the active component oxide and the inactive component oxide which are uniformly distributed on the carbon carrier, and the carbon nanotube is also a carbon material, so that the impurities introduced into the carbon nanotube are reduced, and the purification complexity and difficulty of the carbon nanotube are reduced.

In the preparation method of the carbon nanotube catalyst provided by the embodiment of the invention, the carbon nanotube catalyst comprises the carbon carrier, and the active substances and the inactive substances which are uniformly distributed on the carbon carrier, and the inactive substances can avoid the concentrated distribution of the active substances on the carbon carrier, so that when the carbon nanotube catalyst grows the carbon nanotube, the problem of the catalytic performance failure or reduction of the active substances caused by the local over-concentration of the carbon source gas on the carbon carrier is avoided, and the high speed of generating the carbon nanotube by taking the active metal oxide loaded by the carbon carrier as an active center is ensured. At the same time, compared with Al₂O₃、SiO₂The conventional catalyst carrier has the advantages that the carbon nano tube/graphene has large specific surface area and strong surface adsorption force, can provide larger space, and can be used as the carrier to increaseThe dispersion degree of the active components improves the reaction activity and the anti-sintering performance of the catalyst. Therefore, the carbon nanotube catalyst prepared by the preparation method of the carbon nanotube catalyst provided by the embodiment of the invention has a relatively high reaction speed and a relatively high yield. Experiments prove that the yield of the carbon nano tube prepared by using the prepared carbon nano tube catalyst as a catalyst and adopting a vapor deposition method within 20-50 min reaches 20 times or even more than 20 times.

In order to reduce the difficulty of impurity removal of the carbon nano tube, the active component contained in the active component solution is active metal salt. The inactive components contained in the inactive component solution are inactive metal salts, active metal oxides formed by the active metal salts are dissolved in conventional low-pollution acidic liquid, and the acidic solution with high pollution such as hydrofluoric acid is not needed, so that the pollution of the preparation process of the carbon nano tube to the environment is effectively reduced. The low-pollution acidic liquid is generally hydrochloric acid, sulfuric acid, nitric acid and the like. The inactive metal oxide formed with respect to the inactive metal salt remains in the carbon nanotube as a trace amount of ash.

Illustratively, when the active metal salt and the inactive oxometallate are water-soluble inactive oxometallate salts, the solvent of the active component solution and the inactive component solution may be selected to be water.

For example, the active metal salt may be a main group metal salt and/or a transition metal salt, depending on the kind of metal contained in the metal salt. The main group metal salts include: magnesium metal salt and/or aluminium metal salt. The transition metal salt comprises one or more of iron metal salt, manganese metal salt, cobalt metal salt and nickel metal salt. The active metal salt may be classified into a metal sulfate, a metal nitrate, and a metal chloride, depending on the anion contained in the metal salt. For example: the active component solution comprises one or more of ferric nitrate, ferric chloride, ferric sulfate, magnesium chloride, magnesium nitrate, magnesium acetate, aluminum nitrate, aluminum chloride, aluminum sulfate, cobalt nitrate, cobalt chloride, cobalt sulfate, manganese chloride, manganese nitrate, manganese sulfate, nickel nitrate, nickel chloride or nickel sulfate.

It is verified that the carbon nanotube catalyst has a good catalytic effect when the metal oxide species contained in the carbon nanotube catalyst are various. For example: when the carbon nanotube catalyst contains iron oxide and cobalt oxide, or contains iron oxide and nickel oxide, the catalytic effect of the carbon nanotube catalyst is good. Based on the above, in the embodiment of the present invention, the active component solution may be selected from a combination of iron salt and cobalt salt, or a combination of iron salt and nickel salt.

The inactive component solution may be an inactive oxometalate, such as an inactive oxometalate ammonium salt. The non-reactive metal oxo acid ammonium salt may be a molybdenum metal salt and/or a chromate salt, although other non-reactive metal oxo acid salts may be selected. For example: the molybdenum metal salt may be one or more of ammonium tetramolybdate, ammonium molybdate tetrahydrate, ammonium dimolybdate, ammonium heptamolybdate, and ammonium octamolybdate. During the calcination, the ammonium groups contained in the ammonium oxometallate are released as ammonia gas, and the ammonium oxometallate is converted into a metal oxide. It will be appreciated that where the non-reactive oxometalate is one which is soluble in water, the solvent of the non-reactive solution may be selected to be water.

The carbon carriers are of various types, for example: the carbon carrier comprises one or more of graphene, expanded graphite and carbon nanotubes, and can be selected according to actual conditions.

If the valence states of some metal ions contained in the active component solution and the inactive component solution are easily changed, in order to stabilize the valence states of such metal ions, as shown in fig. 2, the active component solution, the inactive component solution and the carbon support are mixed to obtain a precursor solution including:

step 1011: and uniformly mixing the active component solution, the inactive component solution and the complexing agent solution to obtain a premixed solution. In the process of uniform mixing, the three solutions can be ensured to be uniformly mixed in a mechanical stirring mode and/or an ultrasonic oscillation mode. It is understood that the complexing agent solution can be added dropwise to the active component solution in advance, so that the complexing agent contained in the complexing agent solution can be combined with the active component contained in a part of the active component solution to form an active metal ion complex, and the active component contained in the active component solution can be protected from being uniformly dispersed. Meanwhile, after the inactive component solution is added, the complexing agent can be combined with the inactive component to form an inactive metal ion complex, so that the inactive component is fully dispersed. At this time, when the precursor is roasted under an oxygen-free condition, the agglomeration phenomenon generated in the roasting process can be reduced, and the carbon nanotube catalyst formed by roasting has a porous structure, so that the active metal oxide in the obtained carbon nanotube catalyst can be uniformly dispersed. When the carbon nanotube catalyst is used for preparing the carbon nanotube, the generated carbon nanotube is more loose and dispersed, and the problem of local agglomeration of the carbon nanotube can not occur.

Step 1012: and adding the premixed solution into a carbon carrier to obtain a precursor solution. The premixed solution may be added to the carbon carrier in a dropwise manner, or may be added to the carbon carrier in a pouring manner, which may be selected according to the actual situation.

Specifically, the complexing agent contained in the complexing agent solution includes citric acid and/or ethylene glycol. The citric acid and/or the glycol can form a complex with the active component contained in the active component solution and the inactive component contained in the inactive component solution, so that the obtained carbon nano tube has good dispersibility and uniformity.

When the concentration of the active component contained in the active component solution is 0.1-2 mol/L, the concentration of the inactive component contained in the inactive component solution is 0.01-0.5 mol/L, and the concentration of the complexing agent contained in the complexing agent solution is 1-5 mol/L; the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is (80-150): (15-30): 1. For example: the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is 100:20: 1.

The total volume of the active component solution and the inactive component solution contained in the precursor solution is 1.1-1.5 times of the minimum impregnation volume of the carbon carrier, so that the active component and the inactive component can be fully contacted with the carbon carrier, and the problem of low effective load rate of the carbon carrier caused by over-dilution of the solution is avoided. The payload rate refers to the percentage of the species (e.g., inorganic metal salt) actually adsorbed on the carbon support to the species contained in the precursor solution.

In order to ensure that the inorganic metal salt and the metal oxolate supported by the carbon carrier are relatively uniform, the removing the solvent contained in the precursor solution to obtain the precursor comprises the following steps:

and removing the solvent contained in the precursor solution by using a rotary evaporator. In the process of removing the solvent contained in the precursor solution by using the rotary evaporator, the reaction bottle in which the precursor solution is positioned is in continuous rotation, and the active component and the inactive component can be uniformly loaded on the carbon carrier at the moment, but cannot be enriched on the surface of the carbon carrier due to the evaporation of the solvent. For example: the solvent contained in the precursor solution can be evaporated at 90-110 ℃. Of course, the temperature for removing the solvent contained in the precursor solution can also be reduced by adopting a vacuumizing mode in the process of removing the solvent contained in the precursor solution by using a rotary evaporator.

It should be noted that the solvent, such as water, contained in the precursor solution can also be removed by using a rotary evaporator in combination with a conventional oven.

Example two

The embodiment of the invention also provides a carbon nano tube catalyst. The carbon nanotube catalyst comprises a carbon carrier, and an active component oxide and an inactive component oxide distributed in the carbon carrier, and the beneficial effects of the carbon nanotube catalyst are as described in the preparation method of the carbon nanotube.

Specifically, the carbon nanotube catalyst provided in the embodiment of the present invention may also be prepared by the method for preparing a carbon nanotube catalyst provided in the first embodiment, and the prepared carbon nanotube catalyst also includes a carbon support and a metal oxide distributed in the carbon support.

EXAMPLE III

The embodiment of the invention provides a preparation method of a carbon nano tube. The preparation method of the carbon nano tube comprises the following steps: the carbon nanotube catalyst is used as a catalyst, and the carbon nanotube is prepared by a vapor deposition method, wherein the carbon nanotube catalyst is the carbon nanotube catalyst provided in the second embodiment, and the beneficial effects refer to the beneficial effects of the carbon nanotube catalyst, which are not described in detail herein.

Specifically, as shown in fig. 3, the preparation of the carbon nanotube by using the carbon nanotube catalyst as a catalyst and using a vapor deposition method includes:

step 201: the carbon nanotube catalyst is placed in the reaction chamber. In specific implementation, the reaction cavity may be heated in advance, and then the carbon nanotube catalyst may be placed in the reaction cavity, or the carbon nanotube catalyst may be placed in the reaction cavity and then heated.

Step 202: and introducing reaction gas flow at least containing carbon sources into the reaction cavity in the heating state. It should be understood that, before the reaction gas flow is introduced, the reaction chamber may be heated, so that the reaction chamber is in a heating state, and thus, when the carbon source contained in the reaction gas flow contacts with the carbon nanotube catalyst, the carbon nanotube catalyst is heated sufficiently, and thus, the carbon source can be rapidly decomposed into graphitic carbon under the catalysis of the carbon nanotube catalyst and grow into the carbon nanotube.

The flow rate of the reaction gas stream containing the carbon source may be set according to the actual conditions, for example: 0.1m/s-1.5m/s, and under the flow velocity, the carbon source can be contacted with the carbon nanotube catalyst at a relatively proper concentration, so that the carbon nanotube catalyst is prevented from being deactivated due to overhigh concentration. The carbon source can be one or more of acetone, alcohols, hydrocarbons and ethers. The alcohol can be methanol, ethanol, etc. The hydrocarbon can be acetylene, ethylene, propylene, butylene, methane, propylene, butane, n-pentane, etc. The ether may be dimethyl ether.

Step 203: and (2) contacting the reaction gas flow at least containing the carbon source with the carbon nanotube catalyst in a suspension state, so that the carbon source contained in the reaction gas flow at least containing the carbon source is decomposed, and growing the carbon nanotubes on the active sites of the carbon nanotube catalyst, wherein the prepared carbon nanotubes are array-type carbon tubes. It is understood that the catalytic nature of the carbon nanotube catalyst used to catalyze the carbon nanotube preparation process is: hydrogen is generated during the decomposition of the carbon source, and the hydrogen reduces the active metal oxide, so that the active metal oxide is reduced to an active metal simple substance (certainly, the inactive metal oxide may also be reduced, or may not be reduced, and is not limited here). Under the catalysis of the active metal simple substance, the graphite carbon generated by the decomposition of the carbon source can generate the carbon nano tube. And after the reaction is sufficient, stopping the reaction and continuously cooling in a protective gas atmosphere to avoid the carbon nano tube from being oxidized, and finally obtaining the black fluffy carbon nano tube. It should be understood that the carbon nanotube catalyst is in a suspended state and contacts with a carbon source, the fluidization effect of the carbon nanotube catalyst is good, the carbon source can be effectively ensured to be in full contact with the carbon nanotube catalyst, the reaction speed and the yield of the carbon nanotube are improved, and the carbon nanotube can uniformly grow on the active site of the carbon nanotube catalyst. For example: the existing array type carbon tube has low production efficiency, the reaction time is basically 50-80 min, and the yield is 10-15 times, but in the embodiment of the invention, the reaction temperature is 600-700 ℃, and the reaction time is 20-40 min, and the yield of the carbon nano tube is 20 times or even more than 20 times.

And when the contact area of the carbon source and the carbon nanotube catalyst is large, the amount of the single active site of the carbon nanotube catalyst contacting the carbon source can be reduced, and the problem of inactivation of the single active site of the nanotube catalyst caused by too fast decomposition of the carbon source when the amount of the single active site of the nanotube catalyst contacting the carbon source is large is avoided.

In order to ensure that the reaction gas flow at least containing the carbon source can contact with the carbon nanotube catalyst in a suspension state, before introducing the gas flow at least containing the carbon source into the reaction cavity, the preparation method of the carbon nanotube further comprises the following steps: and introducing protective gas into the reaction cavity. The protective gas is generally inert gas such as nitrogen, argon and the like. The flow velocity of the protective gas flow is higher, so that the carbon nanotube catalyst can be suspended in the reaction cavity and fully dispersed, the carbon nanotube catalyst can be heated, and the effective contact area of the carbon nanotube catalyst and a carbon source is increased. Illustratively, the flow rate of the shielding gas stream is from 3L/min to 5L/min.

In order to ensure that the concentration of the carbon source in the reaction cavity is in a proper range and avoid the problem of deactivation of the carbon nanotube catalyst, the flow rate of the reaction gas flow is 3L/min-5L/min.

In addition, in order to dilute the reaction gas, the reaction gas flow also contains a protective gas, and the volume ratio of the protective gas to the carbon source contained in each liter of the reaction gas flow in unit time is (0.5-2): 1. By adding the protective gas in the reaction gas flow, the carbon source can be properly diluted, and the problem of carbon nanotube catalyst inactivation caused by overhigh carbon source concentration is avoided.

It should be noted that, when the reaction gas flow is introduced, the shielding gas and the carbon source may be mixed in the pipe through which the shielding gas was previously introduced to form the reaction gas flow, and then the reaction gas flow may be introduced into the reaction gas flow by using the pipe through which the shielding gas was previously introduced.

Example four

The embodiment of the invention provides a preparation method of a carbon nano tube, which comprises the following steps:

firstly, dissolving manganese nitrate, aluminum nitrate and ferric nitrate in 500mL of water to obtain an active component solution, wherein the active component solution contains 0.1mol/L of manganese nitrate, 0.3mol/L of aluminum nitrate and 1mol/L of ferric nitrate. Ammonium molybdate tetrahydrate was dissolved in 50mL of water to obtain an inactive ingredient solution such that the inactive ingredient solution contained ammonium molybdate tetrahydrate at a concentration of 0.2mol/L and at this time molybdenum at a content of 0.2 mol/L.

Dissolving citric acid in 50mL of water to obtain a complexing agent solution, wherein the concentration of the citric acid contained in the complexing agent solution is 2 mol/L.

Secondly, slowly dripping the inactive component solution and the complexing agent solution into the rapidly stirred active component solution, and continuously stirring for 30min after finishing dripping to obtain a premixed solution; the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is 100:20: 1.

And step three, pouring the premixed solution into 25g of graphene, and carrying out ultrasonic treatment for 30min to uniformly mix the premixed solution and the graphene to obtain a precursor solution. The precursor solution contained the total volume of the active component solution and the inactive component solution which was 1.3 times the minimum impregnation volume of the carbon support.

And fourthly, placing the precursor solution in a rotary evaporator to carry out rotary evaporation for 6 hours at the temperature of 110 ℃ to obtain the precursor.

And fifthly, calcining the precursor at 400 ℃ for 1h to obtain the carbon nano tube catalyst.

Sixthly, placing the carbon nano tube catalyst in a vertical tube furnace at 670 ℃, wherein nitrogen with the flow rate of 4L/min is introduced into the vertical tube furnace, so that the carbon nano tube catalyst is suspended in the vertical tube furnace. After the carbon nano tube catalyst is put in, reaction airflow of propylene and nitrogen is uniformly introduced, the flow rate is 5L/min, the volume ratio of nitrogen to propylene contained in each liter of reaction airflow in unit time is 3:2, and the reaction is carried out for 40 min. Then stopping introducing the reaction airflow, and cooling to room temperature under the protection of nitrogen with the flow rate of 2L/min to obtain the carbon nano tube. The yield of carbon nanotubes was 20 times.

Fig. 4 is a scanning electron microscope image of the carbon nanotube prepared in the fourth embodiment of the present invention. As can be seen from fig. 4, the carbon nanotube catalyst prepared by the embodiment of the present invention can be used as a catalyst to prepare carbon nanotubes with uniform shapes.

EXAMPLE five

The embodiment of the invention provides a preparation method of a carbon nano tube, which comprises the following steps:

firstly, dissolving nickel nitrate, aluminum nitrate and ferric nitrate in 500mL of water to obtain an active component solution, wherein the concentration of nickel nitrate contained in the active component solution is 0.1mol/L, the concentration of aluminum nitrate is 0.5mol/L, and the concentration of ferric nitrate is 1 mol/L; ammonium molybdate tetrahydrate was dissolved in 50mL of water to obtain an inactive ingredient solution such that the inactive ingredient solution contained ammonium molybdate tetrahydrate at a concentration of 0.3mol/L and at this time molybdenum at a content of 0.3 mol/L.

Dissolving diethanol in 50mL of water to obtain a complexing agent solution, wherein the concentration of citric acid contained in the complexing agent solution is 1 mol/L.

Secondly, slowly dripping the inactive component solution and the complexing agent solution into the rapidly stirred active component solution, and continuously stirring for 30min after finishing dripping to obtain a premixed solution; the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is 80:30: 1.

And step three, pouring the premixed solution into 15g of graphene, and carrying out ultrasonic treatment for 30min to uniformly mix the premixed solution and the graphene to obtain a precursor solution. The precursor solution contained the total volume of the active component solution and the inactive component solution which was 1.3 times the minimum impregnation volume of the carbon support.

And fourthly, placing the precursor solution in a rotary evaporator to carry out rotary evaporation for 4 hours at the temperature of 110 ℃ to obtain the precursor.

And fifthly, calcining the precursor at 500 ℃ for 1h to obtain the carbon nano tube catalyst.

Sixthly, placing the carbon nano tube catalyst in a vertical tubular furnace at 660 ℃, wherein nitrogen with the flow rate of 5L/min is introduced into the vertical tubular furnace, so that the carbon nano tube catalyst is suspended in the vertical tubular furnace. After the carbon nano tube catalyst is put in, reaction gas flow of propylene and nitrogen is uniformly introduced, the flow rate is 3L/min, the volume ratio of nitrogen to propylene contained in each liter of the reaction gas flow in unit time is 1:1, and the reaction is carried out for 30 min. Then stopping introducing the reaction gas flow, and cooling to room temperature under the protection of 2L/min of nitrogen to obtain the carbon nano tube. The yield of carbon nanotubes was 21 times.

Fig. 5 is a scanning electron microscope image of carbon nanotubes prepared in example five of the present invention. As can be seen from fig. 5, the carbon nanotube catalyst prepared by the embodiment of the present invention can be used as a catalyst to prepare carbon nanotubes with uniform shapes.

EXAMPLE six

The embodiment of the invention provides a preparation method of a carbon nano tube, which comprises the following steps:

firstly, dissolving cobalt nitrate, aluminum nitrate and ferric nitrate in 500mL of water to obtain an active component solution, wherein the concentration of cobalt nitrate contained in the active component solution is 0.5mol/L, the concentration of aluminum nitrate is 0.5mol/L, and the concentration of ferric nitrate is 1mol/L, and dissolving ammonium molybdate tetrahydrate in 40mL of water to obtain an inactive component solution, wherein the concentration of ammonium molybdate tetrahydrate contained in the inactive component solution is 0.5mol/L, and the content of molybdenum is 0.5 mol/L.

Dissolving citric acid in 50mL of water to obtain a complexing agent solution, wherein the concentration of citric acid contained in the complexing agent solution is 5 mol/L.

Secondly, slowly dripping the inactive component solution and the complexing agent solution into the rapidly stirred active component solution, and continuously stirring for 30min after finishing dripping to obtain a premixed solution; the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is 150:15: 1.

And step three, pouring the premixed solution into 15g of graphene, and carrying out ultrasonic treatment for 30min to uniformly mix the premixed solution and the graphene to obtain a precursor solution. The precursor solution contained the total volume of the active component solution and the inactive component solution 1.1 times the minimum impregnation volume of the carbon support.

And fourthly, placing the precursor solution in a rotary evaporator to carry out rotary evaporation for 3 hours at the temperature of 98 ℃ to obtain a precursor.

And fifthly, calcining the precursor at 500 ℃ for 1h to obtain the carbon nano tube catalyst.

Sixthly, placing the carbon nano tube catalyst in a vertical tubular furnace at 660 ℃, wherein nitrogen with the flow rate of 4L/min is introduced into the vertical tubular furnace, so that the carbon nano tube catalyst is suspended in the vertical tubular furnace. After the carbon nano tube catalyst is put in, reaction gas flow of propylene and nitrogen is uniformly introduced, the flow rate is 3L/min, the volume ratio of nitrogen to propylene contained in each liter of the reaction gas flow in unit time is 1:1, and the reaction is carried out for 30 min. Then stopping introducing the reaction gas flow, and cooling to room temperature under the protection of 2L/min of nitrogen to obtain the carbon nano tube. The yield of carbon nanotubes was 25 times.

Fig. 6 is a scanning electron microscope image of carbon nanotubes prepared in example five of the present invention. As can be seen from fig. 6, the carbon nanotube catalyst prepared by the embodiment of the present invention can be used as a catalyst to prepare carbon nanotubes with uniform shapes.

EXAMPLE seven

The embodiment of the invention provides a preparation method of a carbon nano tube, which comprises the following steps:

firstly, dissolving ferric chloride and cobalt sulfate in 500mL of water to obtain an active component solution, wherein the concentration of ferric chloride in the active component solution is 0.05mol/L, the concentration of cobalt sulfate in the active component solution is 0.05mol/L,

ammonium tetramolybdate was dissolved in 60mL of water to obtain an inactive ingredient solution such that the inactive ingredient solution contained ammonium tetramolybdate at a concentration of 0.01mol/L and at this time contained molybdenum at a concentration of 0.04 mol/L.

Dissolving citric acid in 50mL of water to obtain a complexing agent solution, wherein the concentration of citric acid contained in the complexing agent solution is 3 mol/L.

Secondly, slowly dripping the inactive component solution and the complexing agent solution into the rapidly stirred active component solution, and continuously stirring for 30min after finishing dripping to obtain a premixed solution; the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is 120:20: 1.

And step three, pouring the premixed solution into 10g of graphene, and carrying out ultrasonic treatment for 30min to uniformly mix the premixed solution and the graphene to obtain a precursor solution. The precursor solution contained the total volume of the active component solution and the inactive component solution which was 1.5 times the minimum impregnation volume of the carbon support.

And fourthly, placing the precursor solution in a rotary evaporator to carry out rotary evaporation for 4 hours at the temperature of 90 ℃ to obtain the precursor.

Fifthly, calcining the precursor at 600 ℃ for 0.5h to obtain the carbon nano tube catalyst.

Sixthly, placing the carbon nano tube catalyst in a vertical tube furnace at 700 ℃, wherein nitrogen with the flow rate of 5.2L/min is introduced into the vertical tube furnace, so that the carbon nano tube catalyst is suspended in the vertical tube furnace. After the carbon nano tube catalyst is put in, the flow rate of the reaction gas flow for uniformly introducing acetone and nitrogen is 4L/min, the volume ratio of nitrogen to acetone contained in each liter of the reaction gas flow in unit time is 0.5:1, and the reaction is carried out for 20 min. Then stopping introducing the reaction gas flow, and cooling to room temperature under the protection of nitrogen gas of 3L/min to obtain the carbon nano tube. The yield of carbon nanotubes was 15 times.

Example eight

The embodiment of the invention provides a preparation method of a carbon nano tube, which comprises the following steps:

in the first step, nickel sulfate is dissolved in 500mL of water to obtain an active component solution such that the active component solution contains nickel sulfate at a concentration of 0.9 mol/L. Ammonium dimolybdate and ammonium heptamolybdate were dissolved in 30mL of water to obtain an inactive ingredient solution such that the inactive ingredient solution contained ammonium dimolybdate at a concentration of 0.2mol/L and ammonium heptamolybdate at a concentration of 0.3mol/L, at which time the molybdenum content was 2.5 mol/L. Dissolving citric acid in 50mL of water to obtain a complexing agent solution, wherein the concentration of the citric acid contained in the complexing agent solution is 2 mol/L.

Secondly, slowly dripping the inactive component solution and the complexing agent solution into the rapidly stirred active component solution, and continuously stirring for 30min after finishing dripping to obtain a premixed solution; the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is 90:15: 1.

And step three, pouring the premixed solution into 30g of graphene, and carrying out ultrasonic treatment for 30min to uniformly mix the premixed solution and the graphene to obtain a precursor solution. The precursor solution contained the total volume of the active component solution and the inactive component solution 1.4 times the minimum impregnation volume of the carbon support.

And fourthly, placing the precursor solution in a rotary evaporator to carry out rotary evaporation for 2 hours at the temperature of 100 ℃ to obtain the precursor.

Fifthly, calcining the precursor at 450 ℃ for 1.2h to obtain the carbon nano tube catalyst.

Sixthly, placing the carbon nano tube catalyst in a vertical tube furnace at 600 ℃, wherein nitrogen with the flow rate of 5L/min is introduced into the vertical tube furnace, so that the carbon nano tube catalyst is suspended in the vertical tube furnace. After the carbon nano tube catalyst is put in, a reaction gas flow containing nitrogen, ethylene and butane is uniformly introduced, the flow rate is 4L/min, the volume ratio of the nitrogen, the ethylene and the butane contained in each liter of the reaction gas flow in unit time is 1:0.5:0.5, and the reaction is carried out for 40 min. Then stopping introducing the reaction gas flow, and cooling to room temperature under the protection of 2L/min of nitrogen to obtain the carbon nano tube. The yield of carbon nanotubes was 23 times. It is to be understood that ammonium dimolybdate in this embodiment may also be replaced with ammonium heptamolybdate or ammonium octamolybdate.

Example nine

The embodiment of the invention provides a preparation method of a carbon nano tube, which comprises the following steps:

firstly, dissolving manganese sulfate and nickel chloride in 500mL of water to obtain an active component solution, wherein the concentration of nickel chloride contained in the active component solution is 1.2mol/L, and the concentration of manganese sulfate is 0.5 mol/L. Ammonium heptamolybdate was dissolved in 30mL of water to obtain an inactive ingredient solution such that the inactive ingredient solution contained ammonium heptamolybdate in a concentration of 0.2mol/L and at this time contained molybdenum in a concentration of 1.4 mol/L. Dissolving citric acid and diethanol in 50mL of water to obtain a complexing agent solution, wherein the concentration of the citric acid contained in the complexing agent solution is 1mol/L, and the concentration of the diethanol is 2 mol/L.

Secondly, slowly dripping the inactive component solution and the complexing agent solution into the rapidly stirred active component solution, and continuously stirring for 30min after finishing dripping to obtain a premixed solution; the volume ratio of the active component solution to the complexing agent solution to the inactive component solution is 100:30: 1.

And thirdly, pouring the premixed solution into 25g of expanded graphite and 5g of carbon nano tubes, and uniformly mixing by ultrasonic treatment for 40min to obtain a precursor solution. The precursor solution contained the total volume of the active component solution and the inactive component solution which was 1.2 times the minimum impregnation volume of the carbon support.

And fourthly, placing the precursor solution in a rotary evaporator to carry out rotary evaporation for 2 hours at the temperature of 100 ℃ to obtain the precursor.

And fifthly, calcining the precursor at 500 ℃ for 1h to obtain the carbon nano tube catalyst.

Sixthly, placing the carbon nano tube catalyst in a vertical tube furnace at 600 ℃, wherein nitrogen with the flow rate of 4.5L/min is introduced into the vertical tube furnace, so that the carbon nano tube catalyst is suspended in the vertical tube furnace. After the carbon nano tube catalyst is put in, reaction gas flow containing nitrogen, n-pentane, methanol and butylene is uniformly introduced, the flow rate is 3L/min, the volume ratio of the nitrogen, the n-pentane, the methanol and the butylene in each liter of the reaction gas flow in unit time is 2:1:0.5:0.5, and the reaction is carried out for 40 min. Then stopping introducing the reaction gas flow, and cooling to room temperature under the protection of 2L/min of nitrogen to obtain the carbon nano tube. The yield of carbon nanotubes was 28 times.

It should be noted that the carbon sources contained in the reaction gas streams of the fourth to ninth embodiments may be replaced by the carbon sources disclosed in the embodiments of the present application, and are not described one by one here.

In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.