JPH05282938A - Manufacture of metal stored fullerene and the like - Google Patents

Abstract

(57) [Abstract] [Purpose] To produce with high productivity various metal-containing fullerenes, which are compounds containing various metals (metals of Group IIIA of the Periodic Table) inside the closed carbon shell structure of various fullerenes. The present invention provides a method for producing a metal-encapsulated fullerene which is capable of being produced and is extremely easy to mass produce. [Structure] A mixture of a Group IIIA metal-containing compound of the periodic table with graphite and a carbonaceous binder was added at 10 ^-4 to 10 ^-7.
Method for producing metal-containing fullerenes extracted from soot generated by arc discharge using a positive electrode made of a material fired for 1 hour or more at a temperature of 1100 to 1500 ° C. under a pressure of Torr and a negative electrode made of graphite ..

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 a metal-encapsulated fullerene, and more specifically, a metal-encapsulated fullerene which is a compound in which a group IIIA metal of the periodic table is included in the carbon closed shell structure of a fullerene. Can be efficiently obtained with fullerenes,
The present invention relates to a method for producing metal-encapsulated fullerenes which is extremely advantageous as an industrial-scale mass production method.

The metal-encapsulated fullerenes obtained by the method of the present invention may be, for example, a conductive material by itself, as a mixture with ordinary fullerenes, or as a composition with other substances. , Superconducting materials, magnetic materials, etc., are expected to be used in various fields including the electric / electronic materials field.

[0003]

2. Description of the Related Art Recently, a new type of macromolecular carbon material having a closed shell (spherical shell) carbon cluster structure having a large number of carbon atoms such as 60, 70, 84 has been synthesized and attracted attention. Carbon clusters having this special structure, also referred to as fullerene, by carbon number (n) constituting the molecular skeleton, fullerene C _60, the C _70, (in general, fullerene C _n) such as the C ₈₄ called Alternatively, they are simply called C ₆₀ , C ₇₀ , C _84, etc. (generally C _n ). Since these fullerenes are new carbon materials and are expected to show unique physical properties because they have a special molecular structure, studies on their properties and application development are being actively pursued.

As a method for producing these C _{60 and} other fullerenes, a laser evaporation method of graphite (Kroto et al., Na
Nature, 318, 162, 1985) and resistance heating method (Kletschmer et al., Nature, 347, 3).
54, 1990) or arc discharge method (howler
Et al., J. Phys. chem. Volume 94, pages 8634, 1
990) is known. Here, since the laser evaporation method is remarkably poor in productivity and is not suitable for mass production, the above-mentioned arc discharge method and resistance heating method have been developed, and ordinary fullerenes can be relatively mass-produced. It's worth noting that. It should be noted that what is generated by the arc discharge method or resistance heating method of graphite is a soot-like substance containing fullerenes of various carbon numbers such as C ₆₀ and C ₇₀ ,
A technique for separating (concentrating) and purifying fullerenes from this soot-like substance is also important. As the separation / purification method, a method of extracting and separating from a soot-like substance obtained by the arc discharge method or the resistance heating method described above with an organic solvent such as benzene or toluene, which is a relatively soluble fullerene, or an aromatic hydrocarbon such as toluene It is also known that the fullerenes thus separated can be further purified by chromatographic separation using a neutral alumina column or the like, if necessary, and isolated as C ₆₀ , C ₇₀ or the like. There is.

As described above, the normal fullerenes can be mass-produced, and the researches on their application development have been significantly accelerated.

By the way, fullerenes such as C ₆₀ are expected to be used in various fields. For example, fullerenes are expected to be used as lubricants at the molecular level such as spherical macromolecules, and because they are unsaturated macrocarbon molecules with a uniform carbon number, graphite There are great expectations as a high-performance conductive material that can replace the above. In addition, since fullerenes are unsaturated molecules having an aromatic C = C bond, they are known to form various compounds and complexes such as hydrides, halides and metal compounds thereof, On the other hand, since it has a spherical shell structure having a relatively large intramolecular space, it is also known that it is possible to form an inclusion type molecule including various metals and other atoms or atomic groups in the intramolecular space. Further, it is also known that doping with a metal or the like can improve various properties such as improvement of conductivity and development of superconductivity.

As described above, fullerenes, including their derivatives, have been used in a wide range of applications, and as will be described later, they are widely used in electric and electronic materials such as superconducting materials and magnetic materials. It is expected to expand into the field.

Therefore, it is extremely important to develop a method for producing a derivative of fullerenes and to study the properties and uses of the derivative, and recently, much research has been done in this direction.

For example, recently, fullerene C₆₀To alkali
It was found that when metal is doped, it exhibits superconductivity.
By adding an alkali metal such as bidium or cesium,
It has also been shown that high-temperature superconductors can be obtained,
Attracting attention (Hepard et al .; Nature, 350
Vol. 600, 1991) . However, these
The fullerene compound that was pumped is not stable in the atmosphere.
There is a drawback.

On the other hand, as a compound containing a metal in fullerenes, a compound containing La is known. This L
Laser evaporation method is known as a method for producing endohedral fullerenes (Chai et al., J. Phys. Che.
m. , 95, 7564, 1991). However, in this prior art, since the laser evaporation method is used, there is a serious problem that the productivity is remarkably poor as described above and it is unsuitable for mass production. That is, in this laser evaporation method, the production rate of the La-encapsulating fullerenes, which is the main object, is remarkably slow, and the fullerene itself produced together with it is also remarkably slow, and both the yield and the selectivity thereof are remarkably low. Moreover, due to the nature of the laser evaporation method itself, it is extremely difficult to develop it into a mass production method.

Therefore, as described above, if the metal-encapsulated fullerenes can be produced by arc discharge or a resistance heating method, it is expected that the productivity will be greatly improved, as in the case of producing the normal fullerenes. However,
Conventionally, it has been considered difficult to manufacture not only the La-encapsulated fullerenes but also general metal-encapsulated fullerenes by an arc discharge or resistance heating method. The technology for producing the endohedral fullerenes was not known.

By the way, the metal-encapsulated fullerenes can be expected to have relatively high stability even in air because the metal is contained inside the carbon closed shell structure of the fullerenes, and since they are metal compounds, the metal Various unique physical properties not found in fullerenes themselves can be expected depending on the type of metal and the number of included metals. For example, various electrical and electronic materials such as conductive materials, superconducting materials and magnetic materials can be expected. Can be expected to be used in the field of

Therefore, there has been a strong demand for the development of a method for producing metal-encapsulated fullerenes which can produce various metal-encapsulated fullerenes with high productivity and which can be easily mass-produced.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances.

An object of the present invention is to produce with high productivity various metal-containing fullerenes, which are compounds in which various metals (metals of Group IIIA of the periodic table) are included in the carbon closed shell structure of various fullerenes. It is intended to provide a method for producing metal-encapsulated fullerenes which is extremely useful in practice and has the advantages that it can be produced and is extremely easy to mass produce.

[0016]

In order to achieve the above-mentioned object, the present inventors used various metal-encapsulated fullerenes as raw materials for graphite and metal components, and produced them by the arc discharge method, which was conventionally difficult. We have earnestly conducted research on techniques to obtain well. As a result, certain groups (Periodic Table III
A composition obtained by mixing various metal compounds belonging to Group A) and graphite powder with an appropriate binder component (for example, pitch, graphite cement, etc.) at a pressure and temperature within a specific range for a specific time or longer. A material obtained by firing is used as a positive electrode material, while an electrode material made of graphite is used as a negative electrode, and arc discharge is performed between the positive electrode and the negative electrode. It can be efficiently obtained as a soot-containing substance, by extracting from the obtained soot-like substance with a suitable solvent such as aromatic hydrocarbon or carbon disulfide, the target metal-encapsulated fullerenes as fullerenes It was found that it can be obtained as a mixture with good productivity. It was also confirmed that various metal-encapsulated fullerenes can be concentrated by purifying the obtained mixture of metal-encapsulated fullerenes and fullerenes by a conventional method.

The present inventors have completed the present invention mainly based on the above findings.

That is, according to the present invention, a mixture of a Group IIIA metal-containing compound of the periodic table, graphite and a carbonaceous binder is added at a pressure of 10 ^-4 to 10 ^-7 Torr and 1100 to 100
A method for producing metal-encapsulated fullerenes, which comprises extracting from soot generated by arc discharge using a positive electrode made of a material fired at a temperature of 1500 ° C. for 1 hour or more and a negative electrode made of graphite Is.

In the method of the present invention, the material used as the positive electrode, that is, the positive electrode material, is prepared by firing at least a mixture of a Group IIIA metal-containing compound of the periodic table, graphite and a carbonaceous binder under the above specific conditions. To do.

Any metal belonging to Group IIIA of the periodic table may be used as the metal of Group IIIA of the periodic table. Specifically, various lanthanoids and actinides such as Sc, Y, La and Sm can be used. Can be mentioned.
Among these, as a particularly preferable metal, for example, L
a, Y, Sm, Sc, etc. can be mentioned. As the group IIIA metal-containing compound of the periodic table, inorganic compounds and complexes such as oxides, nitrides, borides, halides, carbides, hydroxides, hydrides, nitrates, cyanides and carbonates of these metals. Alternatively, various compounds such as a carbonyl complex, an arene complex, an allyl complex, an alkyl complex, an acetylacetonato complex, a carboxylate, an organic metal compound such as an alkoxide, or an organic compound can be used. Or two or more kinds of compounds may be used together as a mixture or a complex compound depending on the case. In that case, it can also be utilized as a compound or mixture containing two or more metals.

Specific examples of the oxide include La
_{2 O 3, Y 2 O 3} , Sm 2 O 3, Sc 2 O 3 or the like can be exemplified.

Specific examples of the boride include, for example, L
Examples include aB ₆ , YB _{6 and the} like.

Specific examples of the halide include LaCl ₃ , LaBr ₃ .7H ₂ O, YCl ₃ and Sm.
Examples thereof include Cl ₃ and ScCl ₃ .

Examples of the acetylacetonate complex include La (AcAc) ₃ and Y (AcAc) ₃ [AcAc represents an acetylacetate group].

As for other compounds, various known compounds can be appropriately selected and used.

Among these, particularly preferable examples of compounds include, for example, Y ₂ O ₃ , La ₂ O ₃ , Sm ₂ O ₃ and Sc.
₂ O _{3 and the} like can be exemplified.

As the graphite used as the raw material of the positive electrode material, those obtained by various manufacturing methods can be used.
This graphite is usually preferably used in the form of powder, but a method of pulverizing by kneading or the like at the time of mixing to make fine particles can also be suitably adopted. In any case, it is preferable that after mixing, if the particles are sufficiently finely mixed, the particles are uniformly mixed and the contact property with the Group IIIA metal-containing compound of the periodic table is improved. Also, in advance, for example, 10
A method in which fine particles having a size of μm or less are provided for mixing is also suitably used.

As the carbonaceous binder, various kinds can be used as long as they have a function as a binder and can be decomposed into carbon or carbonaceous matter by firing, but usually pitch and graphite are used. Cement or the like is preferably used. Other than this, for example, a liquid or grease-like hydrocarbon resin or the like can be appropriately used.

Of these, pitch is particularly preferable. Various pitches such as petroleum and coal can be used as the pitch.

These carbonaceous binders may be used alone or in combination of two or more as a mixture or composition.

The group IIIA metal-containing compound of the periodic table is
When mixed with the graphite and the carbonaceous binder, they can be used in various forms such as powder, solution, dispersion solution (slurry). When used in the form of a solution, for example, a mixing method in which graphite powder is preliminarily impregnated and supported on graphite fine particles can be suitably used. Needless to say, powdery materials such as fine particles may be provided for mixing, or fine particles may be formed by kneading during mixing. In any case, it is preferable to mix them uniformly so as to enhance the contact property with graphite.

The mixing ratio of the group IIIA metal-containing compound of the periodic table, graphite and the carbonaceous binder is as follows:
There is no particular limitation, but normally, the graphite is contained in an amount of 5 to 50 per 100 parts by weight of the Group IIIA metal-containing compound of the periodic table.
It is suitable to use a mixture in an amount of 0 parts by weight (more preferably 50 to 200 parts by weight) and 10 to 500 parts by weight (more preferably 50 to 200 parts by weight) of the carbonaceous binder. ..

As described above, at least the periodic table II
A Group IA metal-containing compound, graphite and a carbonaceous binder are mixed to obtain the mixture. This method of mixing (order,
There is no particular limitation on the method) and various methods including the method described above can be adopted. For example, a wet kneading method, a dry kneading method, a combination thereof, or the like can be appropriately adopted. In any case, it is preferable that this mixing be performed uniformly.

The mixture thus obtained is fired under the above-mentioned predetermined conditions and used as a positive electrode material. Before being subjected to this firing, the mixture is usually pressed, for example, into a desired shape such as a rod. It is usually molded into. Further, calcination may be performed prior to the calcination under the predetermined conditions, and calcination is usually preferable. In addition, it is preferable that this calcination is usually performed at a temperature of 800 to 1100 ° C. and a pressure of 10 ⁻² to 10 ⁻⁴ Torr for 1 hour or more.

It is preferable that the mixture is pre-baked in this manner, but in any case, 1100 to 15 under the predetermined conditions, that is, a pressure of 10 ^-4 to 10 ^-7 Torr.
It is important to perform firing (main firing) for 1 hour or more at a temperature of 00 ° C. If the system pressure in this firing (main firing) is higher than 10 ^-2 Torr, the decomposition gas may be insufficiently removed, or a dense firing material may not be obtained due to the presence of the gas. This causes troubles such as the oxidation of carbon components and metal components by air and the like. On the other hand, if the pressure is less than 10 ⁻⁷ Torr, it is difficult to achieve such a low pressure by the ordinary pressure reducing means, and thus a special pressure reducing device is required, resulting in high cost. In some cases, the pressure is too low, and problems such as evaporation of metal components easily occur. If the firing (main firing) temperature is lower than 1100 ° C, sufficient firing cannot be achieved, the carbonaceous binder is not sufficiently decomposed into carbon or carbonaceous matter, and the effect as a binder is also insufficient. And the interaction between the metal component and the carbonaceous material such as graphite becomes insufficient. As a result, the reaction due to preferable arc discharge hardly occurs, and the desired metal-containing fullerene is obtained. Insufficient production rate of the class. On the other hand, if the firing temperature exceeds 1500 ° C,
The reactor is damaged, the energy cost is high, and the firing temperature is too high, so that problems such as decomposition and evaporation of metal components and carbonaceous components are likely to occur. Further, if the firing time of the firing (main firing) is less than 1 hour, the firing becomes insufficient, and the reaction due to the preferable arc discharge is less likely to occur as described above, and the production rate of the desired metal-encapsulated fullerenes becomes insufficient. ..

The firing material obtained by firing (main firing) as described above is used as a positive electrode for arc discharge or its material.

In the method of the present invention, graphite or a material containing graphite as a main component is used as the material of the negative electrode for performing the arc discharge. Normally, graphite itself, that is, 100% graphite may be used, but the present invention is not necessarily limited to this.
The graphite may contain other components as long as the object of the present invention is not impaired.

In the method of the present invention, the positive electrode material made of the material obtained by the above firing (main firing) is used as the positive electrode, while
A negative electrode material made of graphite is used as a negative electrode, a voltage is applied between both electrodes to perform arc discharge, and soot is generated by sparks at that time. In addition,
This arc discharge method itself can be performed by a usual method.

The soot thus obtained contains the desired group IIIA metal-containing fullerenes of the periodic table and ordinary fullerenes (metal-free fullerenes). The metal-encapsulated fullerenes are usually
For example, fullerenes of various carbon numbers containing one metal such as YC ₈₂ , YC ₈₄ , and YC ₉₀ , or Y ₂ C ₈₂ ,
It is contained in a mixed state such as fullerenes of various carbon numbers containing two metals such as Y ₂ C ₈₄ and Y ₂ C ₉₀ .
The fullerenes are contained in a mixed state of fullerenes having various carbon numbers such as C ₆₀ , C ₇₀ and C ₈₄ .

In the method of the present invention, the soot obtained by the arc discharge is subjected to an extraction treatment, and at least desired metal-encapsulated fullerenes are extracted and separated from the soot. For this extraction, a solvent that dissolves at least the desired metal-encapsulated fullerenes is used. Examples of the extraction solvent include:
Aromatic compounds such as alkylbenzenes such as benzene, toluene and xylene, aromatic hydrocarbons such as alkylnaphthalenes, or their halogenated compounds (halogenated benzenes such as chlorobenzene and chloronaphthalene and halogenated naphthalene), , Carbon disulfide, pyridine, quinoline, picoline and the like. These extraction solvents (compounds) may be used alone or in combination of two or more as a mixed solvent or the like. Among these various solvents, examples of a particularly preferable solvent include carbon disulfide or a mixed solvent containing it as a main component.

The extraction method itself is not particularly limited, and can be suitably performed by an ordinary method (for example, a solvent reflux method such as Soxhlet extraction method). After the extraction, the extract is removed from the solid content (insoluble content), but this removal method is not particularly limited, and a known method (for example,
Filtration, centrifugation, etc.) and various other methods. Usually, it can be suitably achieved by a filtration method. A method in which the solid content (insoluble content) separated and removed in this manner is washed with the solvent to collect the adhered content is also suitably adopted.

As described above, desired metal-encapsulated fullerenes can be efficiently extracted, separated, and recovered. In the extract thus extracted and separated, the desired metal-encapsulated fullerenes are dissolved, but usually, other than this, ordinary fullerenes (fullerenes containing no metal) are also dissolved. ing. The metal-encapsulated fullerenes are usually fullerenes of various carbon numbers containing one metal such as YC ₈₂ , YC ₈₄ , and YC ₉₀ , and
It is contained in a mixed state such as fullerenes of various carbon numbers containing two metals such as Y ₂ C ₈₂ , Y ₂ C ₈₄ and Y ₂ C ₉₀ . The fullerenes are, for example, C ₆₀ , C
It is contained in a mixed state of fullerenes of various carbon numbers such as ₇₀ and C ₈₄ . However, the ratio of the desired metal-encapsulated fullerenes to the normal fullerenes can be made higher than the ratio in the soot by selecting the solvent and the extraction conditions.

The extraction / separation and recovery liquid thus obtained can be directly used for various purposes, but if necessary, it can be used as a powder containing desired metal-encapsulated fullerenes by removing the solvent. You can also If necessary, the obtained powder may be dried before use.

Further, the metal-encapsulated fullerenes may be further purified and used by increasing the concentration thereof. That is, the Group IIIA metal-encapsulated fullerenes produced by the method of the present invention may be used as a mixture with a fullerene, as a mixed metal-encapsulated fullerene, or as a single metal-encapsulated fullerene. It may be used as a class, or may be used in the form of a solution, and can be obtained and used as products in various forms.

Thus, the metal-encapsulated fullerenes produced by the method of the present invention or the products containing the same are as they are, or are subjected to various physicochemical conversions such as doping, and as derivatives thereof in various states. It can be used in various fields, in particular, for example, conductive materials,
It can be expected to be suitably used in the electric / electronic material field as superconductivity, magnetic material and the like.

[0046]

EXAMPLES Examples of the present invention and comparative examples thereof will be shown below, and the present invention will be described in more detail with reference to these examples.
The invention is not limited to this example.

Example 1 A mixture of yttrium oxide (Y ₂ O ₃ ) 5.8 g, graphite powder (particle size 10 mμ) 2.9 g and pitch 5.2 g was pressed to form a rod of 8 mmφ. The rod was fired at 1000 ° C. for 5 hours under a vacuum of 10 ⁻³ Torr, and the degree of vacuum was further raised to 10 ⁻⁵ Torr.
It was baked at 00 ° C. for 5 hours. The material thus prepared was used as the positive electrode, while graphite (purity 10
Arc discharge was performed using a 0% rod (13 mmφ). At this time, 50 Torr of helium was added to the system as a buffer gas and discharged at a direct current of 200 to 250 A. The soot produced by this arc discharge was collected and extracted with carbon disulfide using a Soxhlet extractor.

The products in the obtained extract are shown in FIG.
As a result of the electron spin resonance spectrum analysis shown in, it was found that the metal-encapsulated fullerene was generated from the pattern. Further, when analyzed by using a laser desorption reflectron time-of-flight mass spectrometer (YAG laser triple wave: 355 nm), it is a mass spectrum shown in FIG. 2 and an enlarged spectrum diagram of its low mass number region. Got 3. As shown in FIGS. 2 and 3, as the above products, in addition to usual fullerenes containing no metal, C ₈₂
The Y is one containing a YC ₈₂ and two containing metal endohedral main component of Y ₂ C _82, other, C _84,
Metal-encapsulated fullerenes containing two Y's in each of C ₉₀ , C ₉₂ and C ₉₄ are also produced, and further, C _{96 to} C ₁₄₀
It was found that metal-encapsulated fullerenes containing two Ys in each fullerene of even carbon up to a certain degree were also formed.

COMPARATIVE EXAMPLE 1 Arc discharge and extraction with carbon disulfide were carried out in the same manner as in Example 1 except that ordinary graphite (purity 100%) was used as the positive electrode, and the product was analyzed. The mass spectrum of this product is shown in FIG. As shown in FIG. 4, in this case, ordinary fullerenes such as C ₆₀ , C ₇₀ , and C ₈₄ were obtained in the conventional manner, but it goes without saying that fullerenes containing Y, that is, metal-encapsulated fullerenes, were obtained. The kind has not been obtained.

[0050]

In the method of the present invention, the negative electrode is made of a graphite material which has been conventionally used.
As a positive electrode material, a composition obtained by mixing various metal compounds belonging to a specific group (Group IIIA of the periodic table) and graphite powder with an appropriate binder component (for example, pitch, graphite cement, etc.) can be used. Since arc discharge is performed using a specific material that is formed by firing at a pressure and temperature for a specific time or longer, various periodic tables IIIA such as Y can be produced by the arc discharge method, which has been conventionally difficult. Fullerenes encapsulating a group metal, that is, metal-encapsulated fullerenes, can be easily obtained as soot-like substances with metal-free fullerenes, i.e., normal fullerenes, with ease, and the metal-encapsulated fullerenes The substance is generally treated using an industrially advantageous solvent extraction method to separate the desired metal-encapsulated fullerenes together with the fullerenes. Because there can be efficiently obtained the endohedral with conventional fullerenes. Further, since the method of the present invention is based on the arc discharge method and the solvent extraction as described above, it has an advantage that mass production on an industrial level can be easily achieved.

That is, according to the present invention, various metal group-containing fullerenes of Group IIIA of the periodic table can be produced with good productivity by using a predetermined metal compound and inexpensive raw materials such as graphite, and mass production is extremely easy. It is possible to provide a method for producing a metal-encapsulated fullerene which is remarkably useful in practice and has advantages such as

[Brief description of drawings]

FIG. 1 is a spectral chart showing an electron spin resonance spectrum analysis result of a product obtained in the above-mentioned example which is an example of the method of the present invention.

FIG. 2 is a mass spectrum chart showing an example of mass spectrometry results of the product obtained in Example 1 which is an example of the method of the present invention.

3 is a mass spectrum chart showing an example of mass spectrometry results of the product obtained in Example 1 which is one example of the method of the present invention. This figure shows the low mass of the mass spectrum chart of FIG. It is an enlarged view of a number area.

FIG. 4 is a mass spectrum chart showing the results of mass spectrometry of the product obtained in Comparative Example 1 according to the conventional arc discharge method.

Claims (1)

[Claims] 1. A mixture of a Group IIIA metal-containing compound of the Periodic Table with graphite and a carbonaceous binder is added in an amount of 10 ^-4 -1.
It is characterized in that it is extracted from soot generated by arc discharge using a positive electrode made of a material fired for 1 hour or more at a temperature of 1100 to 1500 ° C. under a pressure of 0 ⁻⁷ Torr and a negative electrode made of graphite. A method for producing metal-encapsulated fullerenes.