WO2021049680A1

WO2021049680A1 - Method for mass synthesis of carbon nanotubes using alkali metal catalyst and carbon nanotubes synthesized thereby

Info

Publication number: WO2021049680A1
Application number: PCT/KR2019/011746
Authority: WO
Inventors: 강준; 김대영
Original assignee: 한국해양대학교 산학협력단
Priority date: 2019-09-09
Filing date: 2019-09-10
Publication date: 2021-03-18
Also published as: KR102375946B1; KR20210029985A

Abstract

The present invention relates to a method for mass synthesis of carbon nanotubes using an alkali metal catalyst and carbon nanotubes synthesized thereby and, more specifically, to the synthesis of pure carbon nanotubes using an alkali metal catalyst based on a Group 1 element other than hydrogen, not using non-alkali metal catalysts such as iron, cobalt, and nickel. The subject matters of the present invention are a method for mass synthesis of carbon nanotubes using an alkali metal catalyst, and carbon nanotubes synthesized thereby, the method comprising the steps of: preparing a carbon source; forming an alkali metal catalyst precursor solution by dissolving, in a solvent, an alkali-metal-containing compound, which is based on an alkali metal; and spraying and heat-treating the alkali metal catalyst precursor solution while the carbon source is supplied, so that the alkali metal of the alkali metal catalyst precursor solution being sprayed agglomerates as a nanocatalyst, and the carbon source is dissolved by the nanocatalyst and crystallized to grow into carbon nanotubes and at the same time, the nanocatalyst is removed as the nanocatalyst vaporizes.

Description

Mass synthesis method of carbon nanotubes using alkali metal catalyst and carbon nanotubes synthesized therefrom

The present invention relates to a method for mass synthesis of carbon nanotubes using an alkali metal catalyst and to carbon nanotubes synthesized therefrom, and more particularly, without using a non-alkali metal catalyst such as iron, cobalt, nickel, and excluding hydrogen. It relates to the synthesis of pure carbon nanotubes using an alkali metal catalyst based on a group 1 element.

The carbon nanotubes discovered by Sumio Iijima in 1991 form a honeycomb-shaped hexagon by combining three neighboring carbon atoms with one carbon atom. This hexagonal structure is repeated to form a cylindrical shape or a tube shape. Say that.

Since the discovery of carbon nanotubes, many theoretical studies and industrial applications have been attempted to date.In particular, carbon nanotubes have excellent mechanical properties, electrical selectivity, excellent field emission characteristics, and high-efficiency hydrogen storage media characteristics. Therefore, it is known as a new material with few defects among existing materials.

However, since carbon nanotubes are expensive, it is required to synthesize carbon nanotubes in large quantities at low cost in order to be useful in various fields. Research is actively underway, such as arc discharge method, laser deposition method, CVD method, and HiPco method.

Among them, in the CVD method, carbon nanotubes are synthesized by dispersing and reacting a metal catalyst particle and a hydrocarbon-based raw material gas in a high-temperature fluidized bed reactor. In other words, the metal catalyst particles are suspended in the fluidized bed reactor by the raw material gas and react with the raw material gas to grow the carbon nanotubes.

For example, in the'method of manufacturing carbon nanotubes in a fluidized bed reactor (Publication No.: 10-2018-0134241)', iron (Fe) and cobalt (Co) in a fluidized bed reactor with an internal pressure of 0.5 to 12 barg (gauge pressure). , The content of synthesizing carbon nanotubes by supplying a metal catalyst such as nickel (Ni) or a metal alloy catalyst and a carbon source is mentioned.

As such, in the case of synthesizing carbon nanotubes in large quantities, the method of growing carbon nanotubes from these carriers by making metal catalysts necessary for carbon nanotube growth, such as iron, cobalt, nickel, etc., in the form of nanoparticles and supporting them on the carrier has been mainly made In order to remove metals, heat treatment at a very high temperature or acid treatment must be performed indispensably.

Therefore, the development of technology that can mass synthesize carbon nanotubes from a new perspective without depending on the combination of metals or alloys used as catalysts, the carrier used, the interaction between the catalyst and the carrier, the reaction temperature, residence time, and the reactor used. This is the time when research is desperately required.

The present invention was invented to solve the above problems, and a mass synthesis method of carbon nanotubes using an alkali metal catalyst based on a group 1 element excluding hydrogen without using a non-alkali metal catalyst such as iron, cobalt, nickel And it is an object to provide a carbon nanotube synthesized therefrom.

The present invention for achieving the above object, the step of preparing a carbon source (carbon source); Dissolving an alkali metal-based alkali metal-containing compound in a solvent to form an alkali metal catalyst precursor solution; And heat treatment while spraying the alkali metal catalyst precursor solution while supplying the carbon source, whereby the alkali metal of the sprayed alkali metal catalyst precursor solution is aggregated into a nano catalyst, and the carbon source is dissolved and crystallized in the nano catalyst. At the same time as the tube is grown, the nanocatalyst is removed while evaporating, and a method for mass-synthesizing carbon nanotubes using an alkali metal catalyst is a technical gist of the present invention.

Preferably, the alkali metal catalyst precursor solution is characterized in that it is formed by dissolving 0.1 to 0.5 g of the alkali metal-containing compound per 100 ml of the solvent.

Preferably, in the step of forming the alkali metal catalyst precursor solution, when the solvent is a non-polar solvent, crown ether is added so that the alkali metal cation of the alkali metal-containing compound is the cavity of the crown ether. By forming a complex by coordinating to, the alkali metal cation is solvated to prepare an alkali metal catalyst precursor solution.

Preferably, the alkali metal-containing compound is selected from the group consisting of a lithium precursor, a sodium precursor, a potassium precursor, and a mixture thereof.

Preferably, the carbon source is composed of any one or more of a liquid CNT growth material, a gaseous CNT growth material, and a solid CNT growth material, but the liquid CNT growth material is ethanol (C ₂ H ₆ O), benzene (C ₆ H ₆ ), xylene (xylene), toluene (C ₇ H ₈ ) and a mixture thereof, and the gaseous CNT growth material is methane (CH ₄ ), propylene (C ₃ H ₆ ), propene (C ₃ Group consisting of H ₄ ), propane (C ₃ H ₈ ), butane (C ₄ H ₁₀ ), butylene (C ₄ H ₈ ), butadiene (C ₄ H ₆ ), ethylene (C ₂ H ₂ ), and mixtures thereof It is selected from, and the solid CNT growth material is characterized in that the _{camphor (C 10} H _{16 O).}

Preferably, the carbon nanotubes are synthesized through heat treatment in a temperature range of 500 to 1,200°C.

The present invention for achieving the above object is, in the presence of a carbon source, in a carbon nanotube, an alkali metal catalyst precursor solution in a state in which an alkali metal-based alkali metal-containing compound is dissolved in a solvent is sprayed while heat treatment The alkali metal of the alkali metal catalyst precursor solution is agglomerated into a nano catalyst, and the carbon source is dissolved in the nano catalyst to crystallize and synthesized in the form of a powder. The technical gist of carbon nanotubes synthesized by mass synthesis method.

The method for mass synthesis of carbon nanotubes using an alkali metal catalyst according to the present invention, and the carbon nanotubes synthesized therefrom, according to the present invention by means of solving the above problems, have the following effects.

First, the existing catalysts based on non-alkali metals of groups 8, 9, and 10 such as iron (Fe), cobalt (Co), and nickel (Ni) were used to synthesize carbon nanotubes, excluding hydrogen. Among the elements of Group 1, alkali metal-based catalysts such as lithium (Li), sodium (Na), and potassium (K) have the effect of synthesizing carbon nanotubes.

Second, unlike the existing carbon nanotubes were synthesized only through heat treatment at a high temperature such as 800℃ by using a non-alkali metal catalyst, the alkali metal aggregated in the alkali metal catalyst precursor solution is much lower than that of the carbon nanotubes at 500℃. There is an effect that the synthesis is sufficiently performed.

Third, the alkali metal of the sprayed alkali metal catalyst precursor solution is agglomerated into a nano-catalyst through heat treatment, and the carbon source is dissolved in the agglomerated nano-catalyst and grown into carbon nanotubes, synthesized, and vaporized and removed. After synthesis, there is no need for additional heat treatment or acid treatment to remove the nanocatalyst attached to the carbon nanotubes, thereby enabling continuous mass synthesis of carbon nanotubes.

1 is a block diagram of an apparatus according to a preferred embodiment of the present invention.

Figure 2 is a crown ether coordinated with an alkali metal cation according to a preferred embodiment of the present invention.

3 is a SEM photograph of a carbon nanotube synthesized using a Li precursor according to a preferred embodiment of the present invention.

4 is a SEM photograph of carbon nanotubes synthesized using Na precursors according to a preferred embodiment of the present invention.

5 is a SEM photograph of a carbon nanotube synthesized using a K precursor according to a preferred embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention uses alkali metals such as lithium (Li), sodium (Na), and potassium (K) rather than non-alkali metals such as iron (Fe), cobalt (Co), and nickel (Ni) to form carbon nanotubes. There is a technical gist of what can be synthesized in large quantities.

That is, in the present invention, in the presence of a carbon source, an alkali metal catalyst precursor solution in which an alkali metal-containing compound based on a group 1 element other than hydrogen is dissolved in a solvent is sprayed. In the metal catalyst precursor solution, alkali metals are aggregated into nano-catalysts, and carbon sources are dissolved and crystallized in these nano-catalysts, growing and synthesizing carbon nanotubes, and simultaneously evaporating and removing carbon nanoparticles in the form of pure powder. It is characterized by being able to produce tubes. However,'catalyst' referred to in the present invention will be interpreted as the same meaning as'nano catalyst' and'alkali metal catalyst'.

1 is a block diagram of an apparatus according to a preferred embodiment of the present invention. Referring to FIG. 1, a carbon source supply unit 100, a chamber unit 200, and an injection unit ( 300), a CNT synthesis unit 400 and a collector unit 500 can be seen in a mass synthesis apparatus for carbon nanotubes.

First, the carbon source supply unit 100 is a tank 110 in which a carbon source in a liquid phase, a gas phase, or a solid phase is accommodated, and a predetermined space in which the tank 110 can be seated. On the hot plate 120 to apply heat to the carbon source and the carbon source accommodated in the tank 110 to be transferred to the CNT synthesis unit 400 for the furnace heat treatment process. It may be made of a gas supplier 130 connected by a second flow path (L2) to supply a carrier gas (carrier gas).

In the case of a carrier gas, it is to export unnecessary elements such as hydrogen and oxygen separated from the carbon precursor contained in the carbon source contained in the carbon source supply unit 100 to the outside, argon (Ar), nitrogen (N ₂ ), hydrogen ( It may be one or more selected from the group consisting of _{H 2} ), ammonia (NH ₃ _{) and mixed gases thereof, but in the case of hydrogen (H 2} ), there is a risk of explosion and may not be stable in use, so nitrogen (N ₂ ) It is preferable to use or a mixed gas of hydrogen and nitrogen.

Second, the chamber unit 200 can be installed at a relatively higher position than the carbon source supply unit 100, and is an alkali metal catalyst precursor formed by dissolving an alkali metal-containing compound based on a Group 1 alkali metal element excluding hydrogen in a solvent. Provide a space in which the solution can be accommodated. However, the difference in height at which the carbon source supply unit 100 and the chamber unit 200 can be installed is not limited.

Third, the injection unit 300 is installed between the chamber unit 200 and the CNT synthesis unit 400 to connect the alkali metal catalyst precursor solution accommodated and stored in the chamber unit 200 to the injection unit 300. ) To the CNT synthesis unit 400 through the spray in a droplet state.

Fourth, the CNT synthesis unit 400 is a furnace constituting a reactor for heat treatment, and is supplied while being sprayed in the state of particles or droplets through the atomizer (A) of the injection unit 300 installed under the chamber unit 200 As the received alkali metal catalyst precursor solution and the carbon source supplied from the carbon source supply unit 100 along the first flow path (L1) are reacted through heat treatment, the alkali metal in the alkali metal catalyst precursor solution is agglomerated into the nano catalyst. As the carbon source is dissolved and crystallized, the carbon source is eventually grown to produce carbon nanotubes in a manner that can be continuously mass-synthesized.

Fifth, the collector unit 500 collects and accommodates only pure carbon nanotubes synthesized from the CNT synthesis unit 400. In particular, when the alkali metal in the alkali metal catalyst precursor solution is agglomerated into a nano-catalyst by heat treatment in the CNT synthesis unit 400, the carbon source is dissolved and crystallized in the nano-catalyst to grow and synthesize the carbon nanotubes and vaporize and remove them. , There is an advantage that there is no need to remove the catalyst by performing a post-treatment process such as a separate acid treatment on the carbon nanotubes collected by the collector unit 500.

In this way, a method of synthesizing carbon nanotubes in large quantities by simply spraying an alkali metal catalyst precursor solution is a carbon source supply unit 100, a chamber unit 200, an injection unit 300, and a CNT synthesis unit 400 shown in FIG. 1. And it can be achieved through a carbon nanotube mass synthesis apparatus consisting of the collector unit 500.

However, the carbon nanotubes using an alkali metal catalyst are synthesized through the step of preparing a carbon source (S10), the step of forming an alkali metal catalyst precursor solution (S20), and the step of synthesizing carbon nanotubes (S30). The description of the steps will be described in more detail below.

First, a carbon source is prepared (S10).

That is, in order to supply a material capable of growing and synthesizing carbon nanotubes to the CNT synthesis unit 400, a liquid type CNT growth material, a gas type gaseous CNT growth material, and a solid type Any one or more of solid CNT growth materials may be selected and used.

In the case of a liquid CNT growth material, any one or more of ethanol (C ₂ H ₆ O), benzene (C ₆ H ₆ ), xylene and toluene (C ₇ H ₈ ) may be selected. .

For gaseous CNT growth materials, methane (CH ₄ ), propylene (C ₃ H ₆ ), propene (C ₃ H ₄ ), propane (C ₃ H ₈ ), butane (C ₄ H ₁₀ ), It may be a hydrocarbon compound selected from the group consisting of butylene (C ₄ H ₈ ), butadiene (C ₄ H ₆ ), ethylene (C ₂ H _{2 ), and mixtures thereof.}

In the case of a solid CNT growth material, camphor (C ₁₀ H ₁₆ O), which is one of the monoterpene ketones, may be selected, and in the case of a solid type, it may be installed inside the CNT synthesis unit 400.

However, it is not limited to the above-described types, and can be used in various ways as long as it is a carbon source capable of growing into carbon nanotubes.

As described above, the gas supplier 130 in which a carrier gas is accommodated in the second flow path L2 connected to the first flow path L1 that allows the CNT growth material to be moved to the CNT synthesis unit 400. Can be connected and installed, such a carrier gas is to export unnecessary elements such as hydrogen and oxygen separated from the carbon precursor contained in the CNT growth material to the outside.

Next, an alkali metal-containing compound based on a Group 1 alkali metal element excluding hydrogen is dissolved in a solvent to form an alkali metal catalyst precursor solution (S20).

First, for the synthesis of carbon nanotubes, metal-based non-alkali metal catalysts such as iron (Fe), cobalt (Co), and nickel (Ni) have been mainly used. However, after the non-alkali metal catalyst is made in the form of nanoparticles and supported on a carrier, there is a problem that an additional process such as acid treatment is required to remove these metals again when the synthesis of carbon nanotubes is completed.

In order to solve this problem and easily mass-synthesize carbon nanotubes, in the present invention, an alkali metal-containing compound based on an element of Group 1 excluding hydrogen is used.

Here, the alkali metal-containing compound may be referred to as a term for generically referring to metallic salts and organometallic compounds. In preparing the alkali metal catalyst precursor solution using the alkali metal-containing compound as described above, it can be explained in the following two ways.

In the first method, an alkali metal catalyst is dissolved by dissolving 0.1 to 0.5 g of an alkali metal-containing compound selected from the group consisting of lithium precursor, sodium precursor, potassium precursor, and mixtures thereof per 100 ml of deionized water, that is, a solvent such as water. Prepare a precursor solution.

In the case of an alkali metal-containing compound, as mentioned above, it may be selected from alkali metal salts, organometallic compounds, and mixtures thereof, for example, any one of a lithium precursor, a sodium precursor, and a potassium precursor. It can be more than that.

As the lithium precursor, it is preferable to use at least one of lithium benzoate and lithium chloride. As the sodium precursor, it is preferable to use at least one of sodium benzoate and sodium chloride. As the potassium precursor, it is preferable to use at least one of potassium benzoate, potassium hydroxide, and potassium chloride. However, it is not limited to the above-described types, and can be applied in various ways if it is an alkali metal-based material applicable as an alkali metal-containing compound.

The amount of alkali metal-containing compound is not particularly limited, but if it is mixed with less than 0.1 g per 100 ml of solvent, the amount of agglomeration by nano catalyst is not sufficient, and the reaction speed is increased until synthesis by growing into carbon nanotubes. It is not desirable in terms of production efficiency.

On the other hand, if the alkali metal-containing compound is mixed in excess of 0.5 g, the nano-catalyst aggregated from the alkali metal catalyst precursor solution during heat treatment in the furnace cannot be vaporized and remains partially attached to the carbon nanotubes. Since the purity of the collected carbon nanotubes may be lowered, it is not preferable.

For the reasons described above, the alkali metal-containing compound is preferably dissolved in the range of 0.1 to 0.5 g per 100 ml of the solvent, and more preferably 0.2 g is dissolved per 100 ml of the solvent.

In the case of a solvent, a polar solvent or a non-polar solvent may be selectively used, examples of which are as follows. That is, the solvent is preferably a polar solvent selected from water, a lower alcohol having 1 to 5 carbon atoms, and a mixture thereof, or a non-polar solvent selected from benzene, xylene, toluene, and a mixture thereof.

In addition, with the use of 0.2 g of an alkali metal-containing compound, approximately 2 g of carbon nanotube powder is synthesized later, so that the carbon nanotube is synthesized in an amount of 9 to 11 times (approximately 10 times) by weight of the alkali metal-containing compound. Able to know.

In the second method, the alkali metal cation of the alkali metal-containing compound is coordinated in the cavity of the crown ether by the addition of crown ether to form a complex, so that the alkali metal cation is solvated to form an alkali metal catalyst precursor solution. To manufacture.

That is, crown ether (x-Crown ether-y; x is the number of all atoms in the ring, y is the number of oxygen atoms) is an oligomer of ethylene oxide in which ethyleneoxy _{(-CH 2} CH _{2 O-) units are repeated.} (oligomer), by putting the alkali metal cation in the alkali metal catalyst precursor solution into the cavity at the center of the crown ether, forming a stable structure with the alkali metal cation, so that the alkali metal cation is solvated and dissolved, especially in non-polar solvents. It is a method of increasing the solubility of the alkali metal-containing compound as a solute.

In other words, crown ether makes a ^{stable complex with metal ions, that is, alkali metal cations such as Li +} , Na ⁺ , and K ⁺ , so that alkali metal-containing compounds such as benzene, xylene, and toluene are insoluble in non-polar solvents composed of hydrocarbons. It can be solvated to dissolve well.

When an alkali metal-containing compound is dissolved in a solvent through crown ether, it is converted into a transparent alkali metal catalyst precursor solution. In order to dissolve the alkali metal-containing compound as much as possible, it is recommended to adjust the ratio with crown ether (e.g., alkali metal). The weight ratio of the metal-containing compound and the crown ether may be 1:0.1 to 100.) It is also possible to control the solubility of the alkali metal catalyst precursor solution by adjusting the amount of crown ether. However, the amount in which the alkali metal-containing compound and the crown ether can be mixed is not limited.

In particular, since the solvent such as water suggested in the first method is polar, alkali metal-containing compounds are well dissolved, but since alkali metal-containing compounds do not dissolve in polar solvents and other non-polar solvents (eg, xylene), crown ether uses solutes. It can play an important role in increasing solubility by making plum.

In the case of crown ether, it can be used by selecting from the group consisting of 12-Crown-4, 15-Crown-5, 18-Crown-6, and a mixture thereof, which is coordinated with an alkali metal cation according to a preferred embodiment of the present invention. It can be confirmed through FIG. 2 showing an exemplary crown ether.

Figure 2-(a) exemplarily shows 12-Crown-4 forming a complex with ^{Li +,} and Figure 2-(b) exemplarily shows 15-Crown-5 forming a complex with ^{Na +} And FIG. 2-(c) exemplarily shows 18-Crown-6 forming a complex with ^{K +.}

Referring to FIG. 2, it can be seen that the oxygen atom constituting the crown helps coordinate alkali metal cations in the cavity within the crown, and the types of ions in which a stable complex is formed are different depending on the size of the crown. That is, Li ⁺ forms the most stable complex with 12-Crown-4, Na ⁺ forms the most stable complex with 15-Crown-5, and K ⁺ forms the most stable complex with 18-Crown-6. It is possible to check.

Finally, by heat treatment while spraying the alkali metal catalyst precursor solution while supplying the carbon source, the alkali metal of the sprayed alkali metal catalyst precursor solution is aggregated into the nano catalyst, and the carbon source is dissolved in the nano catalyst and crystallized to grow carbon nanotubes. Simultaneously, the nanocatalyst is removed while evaporating (S30).

First of all, the growth of the CVD method for the synthesis of carbon nanotubes has been studied for a long time, but so far, there has been no attempt to try a catalyst based on an alkali metal element.

This can be explained by a method in which carbon nanotubes are generally synthesized as follows. In other words, carbon nanotubes are grown in various materials through a method such as CVD (Chemical Vapor Deposition).For example, carbon fibers are coated on an iron-based non-alkali metal catalyst to contain carbon dioxide and other carbon. After being placed in a gas-passing furnace, carbon atoms began to dissolve in iron particles at a high temperature such as 800°C, eventually forming a vertical tube of carbon atoms around the carbon fibers.

Unlike the method in which carbon nanotubes are generally synthesized, in this step, a carbon source (e.g., liquid CNT growth material and The vapor phase CNT growth material) is transferred and charged in a vapor state through the first flow path (L1), and the alkali metal catalyst precursor solution stored in the chamber part 200 is connected to the spray part 300 and the installed atomizer (A) is sprayed. It is sprayed together into a furnace and is atomized and charged.

However, in order to have a sufficient reaction time inside the furnace, after placing a SUS pipe with a diameter of 5 cm and a length of about 20 cm that can serve as a screen, the carbon source and the alkali metal catalyst precursor solution are supplied to the inside of the SUS pipe. desirable.

When the alkali metal catalyst precursor solution is sprayed for 10 to 30 minutes in the presence of the carbon source supplied into the furnace, for example, the alkali metal in the atomized alkali metal catalyst precursor solution is aggregated in the form of a nano catalyst, and the carbon source is formed in the aggregated nano catalyst. As the carbon nanotubes are dissolved and synthesized, the alkali metal catalyst precursor solution that is atomized including the nano catalyst is simply vaporized or evaporated and removed due to the temperature in the furnace, so that only pure carbon nanotubes are collected into the collector unit 500. .

Therefore, without the need to separately prepare Group 1 elements as a catalyst in the form of particles, an alkali metal catalyst precursor solution in which an alkali metal-containing compound is dissolved through a solvent or crown ether in the presence of a carbon source that helps the growth of carbon nanotubes is used in the CNT synthesis unit. The synthesis of carbon nanotubes can be achieved just by spraying with 400.

Regarding the temperature conditions during heat treatment, in the conventional heat treatment through a non-alkali metal catalyst, carbon nanotubes were synthesized only when a high temperature of 800℃ or higher was applied. Synthesis is possible. Of course, it is possible to synthesize carbon nanotubes even at a high temperature of 1,200°C, but the use of an alkali metal catalyst precursor solution has an important meaning in that the synthesis of carbon nanotubes is possible even at a low temperature of 500°C.

Regarding the time conditions during the heat treatment, it can be made for 10 to 30 minutes, but when an alkali metal catalyst precursor solution in which 0.2 g of an alkali metal-containing compound is dissolved in 100 ml of a solvent is sprayed for about 20 minutes, 2 g of carbon nanotubes are synthesized. Therefore, the time can be varied in various ways depending on the amount of carbon nanotubes desired.

The important point is that the alkali metal catalyst precursor solution sprayed through the atomizer (A) connected to the spray unit 300 is heat-treated in the CNT synthesis unit 400 to aggregate the alkali metal in the form of a nano catalyst, and the carbon source is formed in the nano catalyst. As the carbon nanotubes are grown and synthesized while being dissolved, they are vaporized and removed at the same time, so that the carbon nanotubes synthesized through the CNT synthesis unit 400 and collected by the collector unit 500 are not attached to the nanocatalyst in a bonded state. There is no need to remove the nanocatalyst by performing a separate additional heat treatment or post-treatment process such as acid treatment.

Even if some of the nanocatalysts remain in the carbon nanotubes, the advantages of the process can be maintained because the alkali ions have high reactivity with water, so that they can be removed by dissolving in water rather than acid treatment.

Hereinafter, a method for mass synthesis of carbon nanotubes using an alkali metal catalyst of the present invention and examples according to the carbon nanotubes synthesized therefrom will be described. In the following examples, an alkali metal in which an alkali metal-containing compound is dissolved in water The process of synthesizing carbon nanotubes by simply spraying the catalyst precursor solution has been described.

However, the following examples are merely illustrative to aid in understanding of the present invention, and the scope of the present invention is not limited thereby.

Lithium precursor solution was made into a catalyst material by dissolving 0.2 g of lithium benzoate in 100 ml of deionized water.

탄소나노튜브 합성온도Carbon nanotube synthesis temperature	700~1,000℃700~1,000℃
촉매 분사 매체Catalyst spraying medium	Atomizer(25psi)Atomizer(25psi)
Carrier gasCarrier gas	N₂(0.5L/min)N ₂ (0.5L/min)

After placing a SUS pipe (diameter 5cm, length 20cm) in the center of the furnace for heat treatment, the inside of the furnace is heated to a set temperature as in the spray conditions in Table 1, and when reached, the Li precursor solution is transferred to the SUS pipe through the atomizer. Sprayed. However, the heating rate inside the furnace did not affect the synthesis of carbon nanotubes. Ethanol vapor, a carbon source, was injected into the furnace for 20 minutes through _{N 2 bubbling along with the injection of the Li precursor solution to synthesize carbon nanotubes.} Then, it was finished by natural cooling to the ambient temperature.

0.2 g of sodium benzoate was dissolved in 100 ml of deionized water to make the Na precursor solution as a catalyst material. Carbon nanotubes were synthesized under the same spraying conditions as in Example 1, and then naturally cooled to ambient temperature to finish.

0.2 g of potassium hydroxide was dissolved in 100 ml of deionized water to make the K precursor solution as a catalyst material. Carbon nanotubes were synthesized under the same spraying conditions as in Example 1, and then naturally cooled to ambient temperature to finish.

3 is a SEM photograph of a carbon nanotube synthesized using a Li precursor according to a preferred embodiment of the present invention. 3-(a) and 3-(b) show SEM photographs of carbon nanotubes synthesized by spraying a Li precursor solution according to Example 1 at different positions.

4 is a SEM photograph of carbon nanotubes synthesized using Na precursors according to a preferred embodiment of the present invention. 4-(a) and 4-(b) show SEM photographs of carbon nanotubes synthesized by spraying the Na precursor solution according to Example 2 at different positions.

5 is a SEM photograph of a carbon nanotube synthesized using a K precursor according to a preferred embodiment of the present invention. 5-(a) and 5-(b) show SEM photographs of carbon nanotubes synthesized by spraying the K precursor solution according to Example 3 at different positions.

In summary, when the alkali metal catalyst precursor solution was sprayed for 20 minutes through an atomizer (25 psi) according to Examples 1, 2, and 3, about 2 g of carbon nanotube powder was produced. At this time, it was confirmed that 200 cc of ethanol was consumed.

In addition, as can be seen from the SEM photographs shown in FIGS. 3 to 5, the yield of the synthesized carbon nanotubes was confirmed to be about 80 to 90%, and the diameter of the carbon nanotubes was confirmed to be about 20 nm to 2 μm.

In addition to the above-described embodiment, from the results of FIGS. 3 to 5, hydrogen was removed from the use of non-alkali metal-based catalysts such as iron (Fe), cobalt (Co), and nickel (Ni) for carbon nanotube synthesis. Among the remaining Group 1 elements, it can be seen that the continuous mass synthesis of carbon nanotubes is possible even with alkali metal-based catalysts such as lithium (Li), sodium (Na), and potassium (K).

In addition, since there is no need to perform a separate heat treatment or acid treatment to remove the catalyst attached to the carbon nanotubes after synthesis of the carbon nanotubes, not only the production time can be saved, but also the carbon nanotubes can be continuously synthesized through this. Can be seen.

In particular, it is expected that carbon nanotubes can be easily mass-synthesized by using various substances (eg, salt, seawater, etc.) containing sodium (Na) among the Group 1 elements as a catalyst.

The above description is merely illustrative of the technical idea of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention.

Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention, but to explain the technical idea, and the scope of the technical idea of the present invention is not limited by these embodiments.

The scope of protection of the present invention should be construed by the claims, and all technical thoughts within the scope equivalent thereto should be construed as being included in the scope of the present invention.

Claims

Preparing a carbon source;

Dissolving an alkali metal-based alkali metal-containing compound in a solvent to form an alkali metal catalyst precursor solution; And

By heat treatment while spraying the alkali metal catalyst precursor solution while supplying the carbon source, the alkali metal of the sprayed alkali metal catalyst precursor solution is aggregated into a nanocatalyst, and the carbon source is dissolved and crystallized in the nanocatalyst. The method of mass synthesis of carbon nanotubes using an alkali metal catalyst comprising; the step of removing the nanocatalyst while being evaporated while growing at the same time.
The method of claim 1,

The alkali metal catalyst precursor solution,

A method for mass synthesis of carbon nanotubes using an alkali metal catalyst, characterized in that the alkali metal-containing compound is formed by dissolving 0.1 to 0.5 g per 100 ml of the solvent.
The method of claim 1,

In the step of forming the alkali metal catalyst precursor solution,

When the solvent is a non-polar solvent, crown ether is added so that the alkali metal cation of the alkali metal-containing compound is coordinated in the cavity of the crown ether to form a complex, thereby dissolving the alkali metal cation. Mass synthesis method of carbon nanotubes using an alkali metal catalyst, characterized in that to prepare a precursor solution of an alkali metal catalyst by plumbing.
The method of claim 1,

The alkali metal-containing compound,

A method for mass synthesis of carbon nanotubes using an alkali metal catalyst, characterized in that it is selected from the group consisting of a lithium precursor, a sodium precursor, a potassium precursor, and a mixture thereof.
The method of claim 1,

The carbon source is,

Consisting of at least one of a liquid CNT growth material, a gaseous CNT growth material, and a solid CNT growth material,

The liquid CNT growth material is selected from the group consisting of ethanol (C 2 H 6 O), benzene (C 6 H 6 ), xylene, toluene (C 7 H 8 ), and a mixture thereof,

The gaseous CNT growth material is methane (CH 4 ), propylene (C 3 H 6 ), propene (C 3 H 4 ), propane (C 3 H 8 ), butane (C 4 H 10 ), butylene (C 4 H 8 ), butadiene (C 4 H 6 ), ethylene (C 2 H 2 ) and a mixture thereof,

The solid CNT growth material is a mass synthesis method of carbon nanotubes using an alkali metal catalyst, characterized in that the camphor (C 10 H 16 O).
The method of claim 1,

The carbon nanotubes,

A method for mass synthesis of carbon nanotubes using an alkali metal catalyst, characterized in that it is synthesized through heat treatment in a temperature range of 500 to 1,200°C.
In the carbon nanotube,

Synthesized by the synthesis method of any one of claims 1 to 6,

In the presence of a carbon source, the alkali metal catalyst precursor solution in which an alkali metal-based alkali metal-containing compound is dissolved in a solvent is sprayed, and the alkali metal of the alkali metal catalyst precursor solution is aggregated into the nano catalyst through heat treatment. , Carbon nanotubes synthesized from a mass synthesis method of carbon nanotubes using an alkali metal catalyst, characterized in that in the form of a powder synthesized while the carbon source is dissolved and crystallized in the nanocatalyst.