JPH1087310A - Production of fullerene and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method by which continuous synthesis of a fullerene and a metallic atom-contg. fullerene is easily carried out and the rates of recovery of fullerene and metallic atom-contg. fullerene and this reac tion yields can be enhanced as compared with the conventional techniques. SOLUTION: A gaseous medium for discharge is introduced into a discharge tube 2 disposed in a cavity resonator 1 causing microwave discharge, discharge is caused under atmospheric pressure to generate hot plasma and a hydrocarbon compd. or this compd. and a metal as starting materials are fed into the plasma, decomposed and brought into reaction to produce the objective fullerene and metallic atom-contg. fullerene.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for producing fullerene and metal having a high utility value in a catalyst carrier, an electronic material and the like.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional apparatus for producing fullerenes containing metal atoms or fullerenes. The outline of the method for producing fullerenes and the like by the apparatus of FIG. 4 is as follows. That is, in a vacuum vessel 15 in an atmosphere of helium gas 17 of about 50 Torr, an arc discharge of 50 V and 100 A is caused between the graphite electrodes 14 by the DC power supply 16 to evaporate the graphite and turn it into plasma. After discharging for about 1 hour, soot containing fullerene attached to the inner wall of the vacuum vessel 15 and the water-cooled copper pipe 13 is collected. If the graphite electrode 14 is made of graphite mixed with an alkali metal such as Rb or a metal oxide such as lanthanum oxide, the metal atoms are vaporized together with the graphite when the graphite is evaporated and turned into plasma, and the graphite becomes fullerene in the plasma. When a dissociation and bonding reaction occurs, a metal atom is incorporated into the spherical fullerene molecule, and soot containing fullerene containing the metal atom is recovered.

[0003] In such a conventional method, fullerene generated by arc discharge is scattered throughout the vacuum vessel, so that the recovery rate is reduced, impurities are likely to be mixed, and the discharge current is reduced due to the heating method by arc discharge. There is a drawback that the graphite is localized in a part of the graphite surface and the surface temperature of the graphite is only high in a part of the region, but the sublimation amount of the graphite is small and not constant, so that the reaction efficiency is lowered. In addition, in the case of graphite containing metal atoms, the evaporation amount of metal atoms cannot be controlled well, and the sublimation amount of graphite by local heating is small and not constant, so that the reaction efficiency for taking in metal atoms inside is low. Furthermore, since the graphite rod, which is a raw material, also serves as an electrode for arc discharge, there is a disadvantage in that the electrode shape is largely fluctuated with time due to evaporation of graphite, and stable reaction conditions cannot be obtained.

As a method for improving the disadvantages of the method using the arc discharge, a method for producing fullerenes and fullerenes containing metal atoms by using microwave induction plasma by using an apparatus having a configuration shown in FIGS. It has been proposed (Japanese Patent Application No. 4-51255, Japanese Patent Application No. 4-130535). One example of fullerene production using the apparatus of FIG. 5 is as follows. A graphite powder 23 is introduced into a quartz discharge tube 22 from a graphite powder supply unit 24 using a helium gas 29 at a pressure of 20 Torr as a carrier. Discharge is performed in 22. The microwave generated by the microwave oscillator 25 is guided to the cylindrical cavity 21 using the waveguide 26, and the deviation of the resonance frequency due to the evaporation of graphite during discharge is reduced by the end of the cylindrical cavity 21. The adjustment is made by the tuner 27 attached to the plate so as to be always uniform. After discharging for a predetermined time, soot containing fullerene collected by the cyclone 28 is collected.

One example of a method for producing fullerene containing metal atoms will be described with reference to FIG. 6. A graphite rod 34 containing 5% copper oxide is installed in a discharge tube 32, and a helium gas 39 at a pressure of 20 Torr is provided. To discharge in the discharge tube 32. When the microwave generated by the microwave oscillator 35 is guided to the cylindrical cavity resonators 31 and 32 using the waveguide 36, the heating / evaporation cavity resonator 31 is formed.
Then, high-temperature plasma is generated, and graphite and copper atoms evaporate. The evaporated graphite and copper atoms are guided into the low-temperature plasma of the reaction control cavity resonator 32 on the downstream side, and the copper atoms are taken in with the production of fullerene. The deviation of the resonance frequency in each cavity resonator is adjusted by the tuner 37 attached to the end plate of the cavity resonator so as to be always uniform. After discharging for a predetermined time, the discharge tube wall and the filter 38
The soot adhering to is recovered, and fullerene containing copper atoms is recovered by solvent extraction.

[0006] In such a method using microwave induced plasma, graphite is used as a raw material.
The temperature must be at least 00 ° C. However, depending on the gas conditions, the plasma diffuses throughout the discharge tube and the graphite cannot be heated sufficiently, and the electrical conductivity of the graphite is relatively high. And Q value). Therefore, graphite powder using microwave discharge,
Alternatively, it is very difficult to stably maintain the entire bar at 3000 ° C. or higher. In addition, when discharge plasma is generated in such a state, the sublimation amount of graphite is not constant because the sublimation amount of graphite is small only at a high temperature in a partial area of the graphite particles and rods, and the reaction efficiency is reduced by a slight difference in conditions. There are issues such as things. In such a situation, only a part of the raw graphite (powder, rod) undergoes sublimation and reaction, but most of it is collected as unreacted substances, so the yield of fullerene and fullerene containing metal atoms is remarkable. It is low.

[0007]

SUMMARY OF THE INVENTION In view of the state of the art, the present invention facilitates continuous synthesis of fullerenes containing fullerenes and metal atoms, and has a higher recovery rate of fullerenes containing fullerenes and metal atoms than the prior art. And a production method and apparatus capable of improving the reaction yield.

The present invention adopts the following constitutions (1) to (6). (1) A discharge medium gas is introduced into a discharge tube installed in a cavity that generates a microwave discharge, a discharge is generated under atmospheric pressure, and a hydrocarbon compound raw material is supplied into the obtained high-temperature plasma. And producing a fullerene by decomposing and reacting.

(2) A discharge medium gas is introduced into a discharge tube installed in a cavity resonator for generating microwave discharge,
In the process of generating discharge under atmospheric pressure, supplying the hydrocarbon compound raw material into the obtained high temperature plasma, decomposing and reacting, and synthesizing fullerene, the high temperature plasma part where the hydrocarbon compound raw material is added or downstream of the high temperature plasma part. A method for producing fullerene containing metal atoms, characterized in that a metal material is added to a low-temperature reaction region to cause a reaction.

(3) The method for producing fullerene containing a metal atom according to (2), wherein the metal raw material is an organometallic compound. (4) The method for producing fullerenes according to any one of (1) to (3), wherein the carbon compound raw material is an aromatic hydrocarbon compound.

(5) A microwave oscillator, a waveguide for propagating microwaves oscillated by the oscillator, a cavity connected to the waveguide, and a cavity inserted into the cavity. An apparatus for producing fullerene, comprising: a discharge tube; gas supply means for introducing a discharge medium into the discharge tube; and a vaporization chamber for a hydrocarbon compound raw material connected to the discharge tube.

(6) A microwave oscillator, a waveguide for propagating microwaves oscillated by the oscillator, a cavity resonator connected to the waveguide, and a resonator inserted into the cavity resonator. A discharge tube, gas supply means for introducing a discharge medium into the discharge tube, and a vaporization chamber for a hydrocarbon compound raw material and a vaporization chamber for a metal raw material connected to the discharge tube; Fullerene manufacturing equipment.

[0013]

According to the method of the present invention, a nitrogen gas is discharged under atmospheric pressure conditions in a discharge tube installed in a cavity resonator for microwave discharge, and a discharge is generated in the obtained discharge plasma. Fullerene can be synthesized. Furthermore, continuous synthesis of fullerenes becomes possible by using a hydrocarbon compound as a carbon material of fullerenes supplied into the high-temperature plasma. At that time, by adding the metal raw material during the synthesis reaction of the fullerene at the same position as the carbon atoms or at a low temperature region downstream of the plasma, the metal atoms are efficiently incorporated into the fullerenes, thereby producing fullerenes including the metal atoms. Can be.

In the cavity resonator for microwave discharge used in the present invention, a microwave (electromagnetic wave) sent from a power supply through a waveguide is reflected there and returns to the power supply without returning to the power supply. This is a device that is stored as energy. As a result, power supplied from a power supply is applied to the inside of the resonator in the form of an electric field and a magnetic field.

As the gas for the discharge medium, an inert gas such as argon or helium can be used, but nitrogen gas is preferred. Nitrogen gas is also used as a carrier gas for hydrocarbon compound raw materials and metal raw materials.

The temperature of the high-temperature plasma generated in the discharge tube is 2000K or more, preferably in the range of 3500-5500K.

In the present invention, as the carbon raw material for fullerene, any hydrocarbon compound which can be mixed in a supply gas in a gaseous form by means such as evaporation or sublimation can be used without any problem. Examples of such hydrocarbon compounds include acetylene, methylacetylene, butyne, pentyne, hexine, heptin, octyne, nonin, non-aromatic hydrocarbons such as acetylene-based hydrocarbon compounds such as desine,
Indene, tetralin, anthracene, phenanthrene, benzene, toluene, xylene, hemimelitene, pseudocumene, mesitylene, prenitene, isodurene, durene, pentamethylbenzene, hexamethylbenzene, ethylbenzene, propylbenzene, cumene,
Aromatic hydrocarbon compounds such as styrene, biphenyl, terphenyl, diphenylmethane, triphenylmethane, bibenzyl, stilbene and the like can be mentioned.

Pure metal, metal oxides, organometallic compounds and the like can be used as a metal raw material for producing fullerene containing metal atoms, and these are supplied in the form of powder or liquid. Ferrocene, (C _{2
H 5) 2 Fe, C 2} H 5 Zn, (C 2 H 5) 3 B, (C
H ₃ ) ₂ Al, (CH ₃ ) ₄ Sn, (CH ₃ ) ₃ P,
(CH ₃ ) ₂ (C ₆ H ₅ ) P, (C ₆ H ₅ ) ₂ Se, F
_{e (CO) 5, BH 3} S (CH 3) organometallic compounds such as _2, particularly organometallic complex.

[0019]

The present invention will be described more specifically with reference to the following examples. (Embodiment 1) FIG. 1 is a front sectional view showing an example of a fullerene manufacturing apparatus according to the present invention. Hereinafter, one embodiment of a method for producing fullerene of the present invention using the apparatus having the above-described configuration will be described with reference to FIG. Here, a case where a cylindrical cavity resonator using a coaxial waveguide is used as the cavity resonator is illustrated.

As shown in FIG. 2, the inner diameter of the outer conductor a is 50 mm and the inner conductor b is
Outer diameter of 15 mm, length of gap c between outer conductor and inner conductor 5
The discharge tube 2 made of quartz having a diameter of 12 mm was mounted inside the coaxial waveguide by penetrating the inside of the inner conductor of the coaxial waveguide converter 3. Nitrogen gas 4 was supplied to the discharge tube 2 inside the coaxial cavity resonator 1 at atmospheric pressure and at a flow rate of 20 l / min. Microwaves were generated by an oscillator 5 of 2.45 GHz, guided to the coaxial cavity resonator 1 through the coaxial waveguide converter 3, and discharged by the microwave electric field formed there. In the atmospheric pressure nitrogen plasma generated by the discharge, the heater 7
Naphthalene vapor generated from the naphthalene powder 8 heated to 100 ° C. in an oil bath 6 provided with nitrogen was supplied as a carrier gas using nitrogen gas. A power monitor 9 and a matching unit 10 were attached to a waveguide for transmitting microwaves. In addition,
The power monitor 9 is a device for measuring the incident microwave power (W) entering the resonator from the power supply and the reflected microwave power (W) reflected from the resonator to the power supply.
Is a device for adjusting the electric field near the entrance of the resonator to minimize the reflected microwave power (W).

After discharging by introducing a mixed gas of naphthalene and nitrogen for 60 minutes, black product (soot) adhering to the inner wall of the discharge tube 2, the collecting container 11 and the filter 12 is collected, and toluene is used as a solvent. Fullerene (C ₆₀ , C ₇₀ ) was recovered by Soxhlet extraction. Table 1 shows the results of obtaining the fullerene yield obtained by changing the microwave input power (W) (incident microwave power-reflected microwave power). In this embodiment, the temperature of the nitrogen plasma is about 400
Although the microwave power input into the coaxial cavity resonator 1 was adjusted to be 0K, the power was set to about 600 W. However, in order to increase the productivity of fullerene, the cross section of the discharge tube 2 was increased to increase the microwave power. This can be dealt with by increasing the power and increasing the supply amounts of the nitrogen and naphthalene raw materials.

Fullerene was recovered in the same manner as above except that benzene was used instead of naphthalene. Table 1 shows the results. Table 1 also shows the synthesis results of fullerene using graphite as a raw material by the apparatus having the configuration shown in FIG. When a raw material such as benzene that is liquid at room temperature is used, molecules atomized by a sprayer or the like can be directly added to the discharge plasma.

[0023]

[Table 1] 1) [(weight of recovered fullerene) / (weight of recovered soot)] x 100 (%)

Embodiment 2 FIG. 3 is a front sectional view showing an example of the apparatus for producing fullerene containing metal atoms of the present invention. Hereinafter, one embodiment of the method for producing fullerene containing metal atoms of the present invention using the apparatus having such a configuration will be described with reference to FIG. The apparatus of FIG. 3 is the same as the apparatus of FIG. 1 except that a function of supplying ferrocene 13 as a metal raw material is provided, and a duplicate description will be omitted. Naphthalene vapor generated from naphthalene powder 8 heated to 100 ° C. in an oil bath 6 equipped with a heater 7 was supplied as nitrogen carrier gas into atmospheric nitrogen plasma generated in the same manner as in Example 1. Ferrocene powder 13 was selected as a metal material to be included, and ferrocene evaporated at a temperature of 150 ° C. was supplied into a discharge plasma with nitrogen gas as a carrier gas.

After a mixed gas of naphthalene and nitrogen and a mixed gas of ferrocene and nitrogen are introduced for 60 minutes and discharged,
The black product (soot) attached to the inner wall of the discharge tube 2, the collection container 11 and the filter 12 was collected, and fullerene containing iron atoms was collected by Soxhlet extraction using toluene as a solvent. Table 2 shows the results of obtaining the fullerene yield obtained by changing the microwave input power (W) (incident microwave power-reflected microwave power). In the present embodiment, the microwave power input into the coaxial cavity resonator 1 was adjusted to about 600 W so that the temperature of the nitrogen plasma was about 4000 K. However, in order to increase the productivity of fullerenes, the discharge tube was increased. 2 can be dealt with by increasing the microwave power by enlarging the cross section and increasing the supply amount of the nitrogen or naphthalene raw material.

Except that benzene was used instead of naphthalene, the same operation as above was carried out to recover fullerene containing an iron atom. Table 2 shows the results. Table 2 also shows the results of synthesizing fullerene using graphite mixed with iron oxide by the apparatus having the configuration shown in FIG. In this embodiment, an example is shown in which ferrocene is supplied as nitrogen gas as a carrier.However, a solution in which a metal salt is dissolved in an aromatic hydrocarbon compound such as benzene is atomized by a sprayer or the like and directly into the discharge plasma. It is also possible to add metal or by heating and evaporating the metal itself.

[0027]

[Table 2] 2) [(recovered metal atom-containing fullerene weight) / (recovered soot weight)] x 100 (%)

[0028]

According to the method and apparatus for producing fullerene of the present invention, nitrogen gas can be used as a carrier gas for a discharge medium and a raw material, so that an expensive gas such as helium or argon is not used, and the reaction pressure is reduced. Atmospheric pressure has the advantage that there is no need to install a vacuum pump or the like in the reactor. Further, in the present invention, since a hydrocarbon compound which is easily vaporized is used as the carbon raw material, a simple heating device such as an oil bath can be used as the raw material supply means coupled to the cavity resonator. Furthermore, by installing a discharge tube inside the inner conductor of a coaxial waveguide that becomes a microwave transmission line, efficient raw material supply into the plasma can be performed, and continuous production of fullerene, which was difficult with the conventional technology, can be performed. It can be carried out.

According to the method and apparatus for producing fullerenes containing metal atoms of the present invention, in addition to the effects of the production of fullerenes, metal atoms can be reduced together with benzene or naphthalene as a raw material of fullerene, such as organometallic compounds. Direct addition of the compound in the form of a molecular compound into plasma serving as a reaction field increases the controllability of the reaction and improves the production efficiency. Further, it is possible to suppress a decrease in the recovery rate of soot containing metal-encapsulated fullerene, which is a drawback of the related art.

[Brief description of the drawings]

FIG. 1 is a front sectional view of a fullerene manufacturing apparatus according to a first embodiment.

FIG. 2 is an explanatory diagram of a main part configuration of the coaxial cavity resonator of FIG. 1;

FIG. 3 is a front sectional view of a fullerene manufacturing apparatus including metal atoms according to a second embodiment.

FIG. 4 is a front cross-sectional view showing one example of a conventional fullerene manufacturing apparatus using arc discharge.

FIG. 5 is a front sectional view showing an example of a conventional fullerene producing apparatus using microwave discharge.

FIG. 6 is a front cross-sectional view showing one example of a conventional fullerene producing apparatus containing metal atoms by microwave discharge.

Claims (6)

[Claims] 1. A gas for a discharge medium is introduced into a discharge tube installed in a cavity resonator for generating a microwave discharge, and a discharge is generated under atmospheric pressure. A method for producing fullerenes, wherein the fullerenes are supplied and decomposed and reacted to synthesize fullerenes. 2. A gas for a discharge medium is introduced into a discharge tube installed in a cavity resonator for generating a microwave discharge, and a discharge is generated under atmospheric pressure. In the step of supplying, decomposing and reacting, and synthesizing fullerene, a metal atom is characterized by adding a metal material to a high-temperature plasma part for adding a hydrocarbon compound material or a low-temperature reaction region downstream thereof and reacting the same. A method for producing fullerenes. 3. The method for producing fullerene containing metal atoms according to claim 2, wherein the metal raw material is an organometallic compound. 4. The method for producing fullerene according to claim 1, wherein the hydrocarbon compound raw material is an aromatic hydrocarbon compound. 5. A microwave oscillator, a waveguide for propagating microwaves oscillated by the oscillator, a cavity resonator connected to the waveguide, and a discharge inserted into the cavity resonator. Tube, gas supply means for introducing a discharge medium into the discharge tube,
An apparatus for producing fullerenes, comprising a vaporization chamber for a hydrocarbon compound raw material connected to the discharge tube. 6. A microwave oscillator, a waveguide for propagating microwaves oscillated by the oscillator, a cavity connected to the waveguide, and a discharge inserted into the cavity. Tube, gas supply means for introducing a discharge medium into the discharge tube,
An apparatus for producing fullerene containing metal atoms, comprising a vaporization chamber for a hydrocarbon compound raw material and a vaporization chamber for a metal raw material connected to the discharge tube.