JP2003292314A - Production of carbon nanotube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily produce a large amount thin carbon nanotubes, each having a small number of layers, in high yield as well as in high selectivity. <P>SOLUTION: The production method of the carbon nanotubes is characterized by contacting gaseous fullerene molecule with a metal atom or an alloy containing the metal atom at the temperature range of 400-1,200°C. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing carbon nanotubes, and more particularly to a method for producing carbon nanotubes which enables a large amount of thin carbon nanotubes having a small number of layers to be easily produced in high yield and high selectivity. Regarding the method.

[0002]

2. Description of the Related Art Carbon nanotubes are cylindrical allotropes of graphene, which is an allotrope of carbon and are single-layer graphite, and are not limited in diameter and length, but for example, diameters of about 0.4 nm to It has a fine structure of 50 nm and a length of about several μm. These carbon nanotubes have already been put to practical use as cold cathodes, and are being studied for applications in various fields such as semiconductor super integrated circuits, fiber materials, and hydrogen storage materials, and are expected as potential materials. There is. However, since mass production is still difficult and expensive, it has been desired to develop a method capable of mass-producing a large amount of carbon nanotubes with high yield and high selectivity.

Conventionally, as a method for producing carbon nanotubes, generally, in an inert gas atmosphere under reduced pressure, a mixture of carbon and a catalytic metal such as cobalt is irradiated with laser to evaporate and cool the carbon. A method of growing carbon nanotubes on a needle-shaped object (laser method), using a carbon rod as an electrode, performing arc discharge in an inert gas atmosphere under reduced pressure, and carbon on the carbon rod or / and the chamber inner wall. A method of growing nanotubes (arc discharge method), a method of contacting a catalytic metal and a gaseous hydrocarbon at high temperature (600 to 1200 ° C.) (chemical vapor deposition method (CVD method)), etc. are known.

[0004]

However, the laser method and the arc discharge method require a laser light source and an arc discharge device, and the size of the device is large, and the yield is low, and a large amount can be obtained by one growth. There is a problem that carbon nanotubes cannot be manufactured. Also, CVD
Although the method is inexpensive and suitable for mass production, it has a drawback that thin single-walled carbon nanotubes cannot be synthesized with high yield and high selectivity.

An object of the present invention is to provide a carbon nanotube which is thin and has a small number of layers, preferably 5 or less, and particularly preferably 3 or less, in a large amount and easily in high yield and with high selectivity. It is to provide a method of manufacturing a nanotube.

[0006]

The method for producing carbon nanotubes of the present invention which achieves the above object comprises contacting gaseous fullerene molecules with a metal element or an alloy containing a metal element at a temperature of 400 to 1200 ° C. It is what

According to the present invention, a large amount of thin carbon nanotubes can be prepared simply by bringing the fullerene molecule in the gaseous state as described above into contact with the metal element or the alloy containing the metal element at a temperature of 400 to 1200 ° C. It enables to manufacture with high yield and high selectivity.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a fullerene molecule has a carbon number of C36, C60, C70, C76, C7.
It refers to spherical carbon cluster molecules such as 8, C80, C82 and C84. The carbon number is preferably 60 or more, and higher-order fullerene molecules are more preferable. These may be used alone or may be a mixture of plural kinds. A large amount of these fullerene molecules can be synthesized by a known arc discharge method using a carbon electrode or a combustion method.

Fullerenes are usually solid at room temperature and atmospheric pressure, but start to sublime when heated. The fullerene thus heated and sublimated is a gaseous fullerene molecule, and in the present invention, a metal element or an alloy containing a metal element and a temperature of 400 to 1200 ° C. are used in the present invention.
It is characterized by making contact with. The temperature for heating the fullerene to make the fullerene molecule gaseous is
The temperature is not particularly limited as long as it is a temperature at which the fullerene sublimes, but preferably 400 ° C or higher, particularly preferably 500 ° C.
The above is better. In particular, it is preferable that the temperature is higher than the temperature at which the gaseous fullerene molecule is brought into contact with the metal element or the alloy containing the metal element.

The atmosphere for contacting the heated and sublimated gaseous fullerene molecule with the metal element or the alloy containing the metal element may be atmospheric pressure, reduced pressure, or increased pressure. Is also good. Further, it is preferable that the fullerene is heated in the presence of a carrier gas to be a gas. The reason is that fullerenes are easily sublimated, and the sublimated gaseous fullerene molecules can be efficiently brought into contact with a metal element or an alloy containing a metal element.
It is not clear why good-quality carbon nanotubes can be obtained by using gaseous fullerenes, but gaseous fullerenes have fullerene in a monomolecular state, and the fullerene in the monomolecular state serves as a nucleus to form carbon nanotubes. It can be presumed to be generated. When the solid fullerene is brought into contact with a metal, thick carbon nanotubes are produced because the polymer is in contact with the fullerene.

The carrier gas is not particularly limited, but is preferably argon, helium, nitrogen, hydrogen,
Sulfur hexafluoride, carbon monoxide, carbon dioxide are used,
Particularly preferably, argon, helium, nitrogen and hydrogen are used.

In the present invention, the metal element is preferably a metal of Group 3 to Group 12, and particularly preferably a metal of Group 5 to 11. Among them, especially V, Mo, Fe, C
O, Ni, Pd, Pt, Rh and the like are preferably used.

The metal may be a single metal or an alloy. In the case of an alloy, a combination of Co, Ni, Pd, Pt, Rh and another metal is preferable. Especially Co and Fe,
The combination of at least one of Ni, V, Mo and Pd is most preferable. The combination is not limited to two kinds, and may be an alloy in which three or more kinds of metals are combined.

In the present invention, the metal element or the alloy containing the metal element is not limited to the metal state because there is no means for investigating what kind of state it is in during the reaction, and it is widely used as a compound containing the metal element. Interpret. For example, it may be brought into contact with the fullerene molecule in a gaseous state in the form of an organometallic complex, or may be a solid metal element or an alloy containing the metal element. Preferably, the carrier is made to carry a metal element or an alloy containing a metal element. The reason is that the metal is supported as fine particles even at high temperature, and the contact efficiency with gaseous fullerene molecules is improved.

The method of supporting the metal element or the alloy containing the metal element on the carrier is not particularly limited. For example, a carrier is impregnated in a non-aqueous solution in which a salt of a metal to be supported is dissolved (for example, a methanol solution, an ethanol solution) or an aqueous solution, sufficiently dispersed and mixed, and then dried, and then heated at a high temperature in nitrogen or an inert gas ( By heating at, for example, 300 ° C. or higher, a metal species (a metal element or an alloy containing a metal element in the present invention) can be supported on a carrier (impregnation method).

The metal salt is not limited, but, for example, acetate, nitrate, chloride and the like can be used. The carrier may be any solid. Those having heat resistance are particularly preferable. Examples thereof include oxides such as silica, alumina and magnesia, composite oxides such as aluminosilicate, and crystalline porous oxides such as zeolite. Of these, zeolite is particularly preferable as the carrier. The shape of the carrier is not particularly limited,
Preferably, it is in the form of powder, granules, or film.

In the present invention, the temperature at which the gaseous fullerene molecule is brought into contact with the metal element or the alloy containing the metal element is 400 to 1200 ° C., preferably 40.
It is better to set it to 0 to 1000 ° C. The contact time is not particularly limited.

Gaseous fullerene molecules are contacted with a metal element or an alloy containing a metal element at the above temperature,
Carbon nanotubes are deposited on the metal element or an alloy containing the metal element. At this time, when the fullerene is heated and sublimated to a gaseous fullerene molecule as a heating temperature, the gaseous fullerene molecule is vaporized at a temperature equal to or higher than a temperature at which the gaseous fullerene molecule is brought into contact with a metal element or an alloy containing the metal element. Can be improved.

When the gaseous fullerene molecule is brought into contact with the metal element or the alloy containing the metal element, the yield can be further improved by bringing it into contact with the gaseous carbon-containing compound as a mixed gas. When the gaseous fullerene molecule is supplied as a mixed gas with the gaseous carbon-containing compound in this manner, carbon is supplied from the gaseous carbon-containing compound with the fullerene deposited on the metal element or the alloy containing the metal element as a nucleus, Carbon nanotubes can be obtained in high yield, and are particularly thin (the number of layers is small and the inner diameter is small).
Carbon nanotubes can be obtained in high yield.
It is possible to obtain carbon nanotubes having 5 or less layers, particularly 3 or less layers.

The carbon-containing compound used as the mixed gas here is not particularly limited, and examples thereof include carbon monoxide, carbon dioxide, aromatic and non-aromatic hydrocarbons. Of these, aromatic hydrocarbons are not particularly limited, and examples thereof include benzene, toluene, xylene, cumene, ethylbenzene, diethylbenzene, trimethylbenzene, naphthalene, phenanthrene, anthracene, and the like, or a mixture thereof. it can. Further, the non-aromatic hydrocarbon is not particularly limited, but for example, methane, ethane, propane,
Examples thereof include butane, pentane, hexane, heptane, ethylene, propylene, acetylene, and the like, or a mixture thereof. Hydrocarbons include those containing oxygen, for example, alcohols such as methanol, ethanol, propanol and butanol, ketones such as acetone, and aldehydes such as formaldehyde or acetaldehyde, ethers such as diethyl ether and dioxane, or a mixture thereof. It can be used, but is not limited to. These various carbon-containing compounds may be used alone or in a mixture.

As described above, in the production method in which gaseous fullerene molecules are supplied as a mixed gas with a gaseous carbon-containing compound, expensive fullerenes can be produced in a small amount, and thus carbon nanotubes can be produced at low cost. be able to.

In the present invention, the most preferable production method is to place a heated fullerene under the flow of a carrier gas containing a gas of a carbon-containing compound, and to disperse gaseous fullerene molecules sublimated from the fullerene together with the above-mentioned carrier gas into a metal element or a metal. The catalyst is supplied on a catalyst containing an alloy containing an element and brought into contact at a temperature of 400 to 1200 ° C. Also in this production method, it is needless to say that the catalyst containing the metal element or the alloy containing the metal element is preferably used by being supported on a carrier, and the sublimation temperature of fullerene is preferably the reaction temperature or higher. .

[0023]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples, and various modifications can be made within the scope of the claims. Needless to say.

Example 1 0.08 g of ferrous acetate (manufactured by Aldrich) and 0.11 g of cobalt acetate tetrahydrate (manufactured by Nacalai Tesque) were added to 7 ml of ethanol (manufactured by Nacalai Tesque) and ultrasonicated. Suspension was carried out for 10 minutes with a washing machine. To this suspension, 1.0 g of zeolite HSZ-390HUA (manufactured by Tosoh Corporation) was added, treated with an ultrasonic cleaner for 10 minutes, and ethanol was removed at a constant temperature of 120 ° C. to obtain a metal-supported catalyst. .

Next, using the reactor shown in FIG. 1, 30 mg of fullerene C60 as shown by reference numeral 1 was placed on the bottom of the container 4 made of quartz tube. Furthermore, this fullerene C6
10 mg of the metal-supported catalyst 3 prepared above was placed above 0 through the quartz wool 2.

Next, the cock 5 provided in the communication pipe 6 at the upper end of the quartz tube container 4 is opened, the interior of the container 4 is evacuated by a rotary pump (not shown), the cock 5 is closed, and the communication pipe 6 is heated by a gas burner. And sealed the tube. Quartz tube container 4 after sealing
Was placed in a box-shaped electric furnace heated to 800 ° C. and heated for 30 minutes. During this heating, fullerene C60 at the bottom of the container 4
Was sublimed into gaseous fullerene molecules, and contact-reacted with the metal-supported catalyst 3 on the quartz wool 2 above.

After completion of the heat treatment, the quartz tube container 4 was cooled to room temperature, the metal-supported catalyst 3 was taken out from the inside, and the surface of the metal-supported catalyst 3 was observed with a high resolution transmission electron microscope. As a result, it was found that single-walled carbon nanotubes were generated on the surface of the metal-supported catalyst 3.

Comparative Example 1 The same reaction apparatus as in Example 1 shown in FIG.
An experiment was performed in the same manner as in Example 1 except that the same mixture of the metal-supported catalyst and fullerene C60 as in Example 1 was placed in the bottom of the lower container 4. During the heating, the fullerene C60 was allowed to directly react with the metal-supported catalyst.

Observation of the surface of the metal-supported catalyst 3 taken out from the quartz tube container 4 with a high resolution transmission electron microscope revealed that thin single-walled carbon nanotubes were not obtained.
A multi-walled carbon nanotube having a diameter of 10 nm or more, a carbon deposit, and a polymerized fullerene were produced.

Example 2 Using the reaction apparatus shown in FIG.
A quartz tube 4'of cm was inserted and arranged, and an argon gas was allowed to flow from one end of the quartz tube 4'as indicated by an arrow 8. Further, in the quartz tube 4 ', quartz plates 9 and 10 are sequentially arranged in the middle of the longitudinal direction of the tubular furnace 7 and slightly downstream thereof along the gas flow direction, and the fullerene C6 is placed in the plate 9.
0 was placed in an amount of 30 mg, and 10 mg of the same metal-supported catalyst prepared in Example 1 was placed in the dish 10.

Argon gas in the direction of arrow 8 is 30 ml /
The temperature was controlled so that the temperature was 900 ° C. at the position of the dish 9 while circulating for minutes. When the position of the dish 9 reached 900 ° C, the temperature of the position of the dish 10 was 800 ° C. That is, the fullerene C60 in the dish 9 was sublimated by heating at 900 ° C. to become a gaseous fullerene molecule, and was brought into contact with the metal-supported catalyst in the dish 10 at 800 ° C.

After 30 minutes of the above heat treatment, the material was cooled while flowing argon and further cooled to room temperature, the metal-supported catalyst was taken out from the dish 10, and the surface of the catalyst was observed with a high resolution transmission electron microscope. As a result, it was found that many single-walled carbon nanotubes were formed on the surface of the metal-supported catalyst.

Comparative Example 2 Using the same reactor shown in FIG. 2 as in Example 2, a mixture of 30 mg of fullerene C60 and 10 mg of the metal-supported catalyst prepared in Example 1 was placed in a quartz dish 9 and the dish was placed. The same experiment as in Example 2 was performed except that 10 was emptied.

When the metal-supported catalyst taken out from the dish 9 cooled after 30 minutes of heat treatment was observed with a high resolution transmission electron microscope, there was no single-walled carbon nanotube, and the diameter was 10
Only multi-walled carbon nanotubes of nm or more were produced.

Example 3 Using the reactor shown in FIG. 3, a tubular furnace 7 was inserted into a quartz tube 4 ′ inserted in the center of the tubular furnace 7 along the gas flow direction.
Fullerene C60, slightly upstream of the middle of the
A quartz dish 9 containing 5 mg of the above and a quartz dish 10 containing 10 mg of the same metal-supported catalyst prepared in Example 1 were placed in order. The temperature was controlled so that the temperature was 300 ° C. at the position of the dish 10 while flowing argon gas at a flow rate of 30 ml / min. After holding this temperature of 300 ° C. for 30 minutes, the temperature of the position of the dish 10 was raised to 800 ° C. When the position of the dish 10 reached 800 ° C, the temperature of the position of the dish 9 was 600 ° C.

When the temperature of the plate 10 reaches 800 ° C., acetylene gas starts flowing at a flow rate of 1 ml / min.
After 0 minutes, the acetylene gas was stopped, and cooling was performed while flowing only argon gas. After the dish 10 was cooled to room temperature, the metal-supported catalyst was taken out and the surface of the metal-supported catalyst was observed with a high resolution transmission electron microscope. As a result, a bundle of single-walled carbon nanotubes as shown in the photograph of FIG. 4 was obtained. It was observed. The ratio of single-walled carbon nanotubes in all carbon nanotubes was about 60%.

Comparative Example 3 An experiment was conducted in the same manner as in Example 3 except that the dish 9 was emptied and 10 mg of the same metal-supported catalyst prepared in Example 1 was placed in the dish 10.

Although single-walled carbon nanotubes were formed on the surface of the metal-supported catalyst after the experiment, the ratio of single-walled carbon nanotubes in all carbon nanotubes was only 5%.
It was about%.

[0039]

As described above, according to the present invention, a large amount of thin carbon nanotubes can be obtained by contacting gaseous fullerene molecules with a metal element or an alloy containing a metal element at a temperature in the range of 400 to 1200 ° C. It can be easily produced with high yield and high selectivity.

[Brief description of drawings]

FIG. 1 is a schematic view illustrating a reaction apparatus used in the method for producing carbon nanotubes of the present invention.

FIG. 2 is a schematic view showing another example of a reaction device used in the method for producing carbon nanotubes of the present invention.

FIG. 3 is a schematic view showing still another example of the reaction apparatus used in the method for producing carbon nanotubes of the present invention.

FIG. 4 is a high resolution transmission electron micrograph of carbon nanotubes produced in an example of the present invention.

[Explanation of symbols]

1 fullerene 2 quartz wool 3 Metal supported catalyst 4,4 'quartz tube container 5 cooks 6 communication pipe 7 Tubular furnace 9,10 Quartz dish

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hisanori Shinohara             Furo-cho, Chikusa-ku, Nagoya City, Aichi Prefecture (No street number)               Nagoya University Graduate School of Science (72) Inventor Masato Yoshikawa             1 East of 9 Oemachi, Minato-ku, Nagoya City, Aichi Prefecture             Les Nagoya Office (72) Inventor Atsuto Okamoto             Aichi Prefecture Nagachite Town Aichi District             Ground 1 Toyota Central Research Institute Co., Ltd. (72) Inventor Atsushi Okamoto             1 East of 9 Oemachi, Minato-ku, Nagoya City, Aichi Prefecture             Les Nagoya Office (72) Inventor Masafumi Koseki             1 East of 9 Oemachi, Minato-ku, Nagoya City, Aichi Prefecture             Les Nagoya Office F-term (reference) 4G069 AA03 AA08 BA07B BA27B                       BC66B BC67B CB81 FB15                 4G146 AA11 BA04 BA12 BC08 BC32A                       BC32B BC33A BC33B BC34A                       BC34B BC44

Claims (5)

[Claims] 1. A method for producing carbon nanotubes, which comprises contacting gaseous fullerene molecules with a metal element or an alloy containing a metal element at a temperature of 400 to 1200 ° C. 2. The method for producing carbon nanotubes according to claim 1, wherein the gaseous fullerene molecule is mixed with a gaseous carbon-containing compound and brought into contact with the metal element or an alloy containing the metal element. 3. The method for producing a carbon nanotube according to claim 1, wherein the gaseous fullerene molecule is generated by heating fullerene. 4. The method for producing carbon nanotubes according to claim 3, wherein the heating temperature for making the fullerene in a gaseous state is equal to or higher than the temperature at which the gaseous fullerene is brought into contact with a metal element or an alloy containing a metal element. 5. The method for producing carbon nanotubes according to claim 1, wherein the metal element or an alloy containing the metal element is supported on a carrier.