JP2022091360A - Method for isolating fullerene c70 - Google Patents

Abstract

To provide a method for efficiently isolating a high-purity fullerene C70 from a mixed fullerene.SOLUTION: Fullerene C70 is isolated by a method for isolating fullerene C70 including an adsorption step of adsorbing a mixed fullerene containing fullerene C60 and fullerene C70 on activated carbon, a fullerene C60 elution step of eluting the fullerene C60 from the activated carbon with an eluting solvent, and a sublimation step of sublimating the fullerene C70 by heating the activated carbon having adsorbed the fullerene C70.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for isolating fullerene C ₇₀ (hereinafter, also referred to as “C ₇₀ ”).

As a method for producing fullerenes, (1) an electrode made of a carbonaceous material such as graphite is used as a raw material, and the raw material is evaporated by arc discharge between the electrodes (arc discharge method), and (2) a high current is passed through the carbonic material. A method of evaporating a raw material (resistance heating method), a method of (3) incomplete combustion of a hydrocarbon (combustion method), and the like are known. However, it is not possible to produce only the desired single type of fullerene by any of the current production methods, and it is possible to produce fullerene C ₆₀ (hereinafter, also referred to as “C ₆₀ ”) and mixed fullerene mainly composed of C ₇₀ and polycyclic. A mixture containing formula aromatic hydrocarbons and carbon-based polymer components (hereinafter, also referred to as “soot-like substance”) is produced.

For example, in the soot-like substance produced by the combustion method described in Patent Document 1, the mixed fullerene usually contains 10 to 30% by mass. It is possible to extract mixed fullerenes from soot-like substances by utilizing the properties of fullerenes and polycyclic aromatic hydrocarbons, carbon-based polymer components, etc., which have different solubilities in organic solvents such as benzene, toluene, and carbon disulfide. ..

Since several types of fullerenes having different carbon atoms are mixed in the mixed fullerenes, it is desired to provide a single type of fullerenes with high purity. For example, as disclosed in Patent Documents 2 and 3, a method for isolating fullerenes using activated carbon is known. Further, C ₇₀ has a stronger adsorption force to activated carbon than C ₆₀ , and a large amount of C ₇₀ is adsorbed to the activated carbon after elution of C ₆₀ . In Patent Document 4, C ₇₀ is eluted from activated carbon using an eluent containing an aromatic compound having a naphthalene skeleton or an aromatic compound having a skeleton in which one or two carbon atoms forming the naphthalene skeleton are replaced with nitrogen atoms. A method for isolating ₇₀ is disclosed.

US Pat. No. 5,273,729 Japanese Unexamined Patent Publication No. 2005-187252 Japanese Unexamined Patent Publication No. 2004-99380 Japanese Patent No. 3974049

However, the purity of C ₇₀ obtained by the method for isolating C ₇₀ described in Patent Document 4 is insufficient. Further, since the yield of C ₇₀ in the method for isolating C ₇₀ described in Patent Document 4 is low, there is room for further improvement in recovery efficiency.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for efficiently isolating high-purity C ₇₀ from mixed fullerenes.

(1) A method for isolating C ₇₀ from a mixed fullerene containing C ₆₀ and C ₇₀ , in which an adsorption step of adsorbing the mixed fullerene on activated carbon and C in which the C ₆₀ is eluted from the activated carbon with an elution solvent. A method for isolating C ₇₀ , comprising ₆₀ elution steps and a sublimation step of heating the activated carbon adsorbing the C ₇₀ to sublimate the C ₇₀ .
(2) The method for isolating _C70 according to (1), wherein a column using the activated carbon as a filler is used to adsorb the mixed fullerene on the activated carbon.
(3) The method for isolating _C70 according to (1) or (2), wherein the heating temperature of the sublimation step is 400 ° C to 1000 ° C.
(4) The method for isolating _C70 according to any one of (1) to (3), wherein the sublimation step is carried out in an inert gas atmosphere.
(5) The method for isolating _C70 according to any one of (1) to (4), wherein the activated carbon has a specific surface area of 1600 m ² / g or more by the BET method.
(6) The elution solvent is at least one selected from aromatic hydrocarbons having 6 to 20 carbon atoms, halogen-containing aromatic hydrocarbons, polycyclic aromatic hydrocarbons, and carbon disulfide (1) to (1). 5) The method for isolating _C70 according to any one of 5).

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for efficiently isolating high-purity C ₇₀ from mixed fullerenes.

It is a figure which shows the structure of the sublimation apparatus used in an Example.

Hereinafter, the method for isolating _C70 according to the present invention will be described in more detail. The present invention is not limited to the following methods, and various modifications can be made without changing the gist of the present invention.

The mixed fullerene applied to the isolation method of the present embodiment may be obtained by any method. For example, a soot-like substance produced by a combustion method from which polycyclic aromatic hydrocarbons and carbon-based polymer components have been removed in advance can be mentioned. Examples of the method for removing polycyclic aromatic hydrocarbons from soot-like substances include a method for extracting and removing polycyclic aromatic hydrocarbons using a solvent having a low solubility of fullerenes. Examples of the method for removing the carbon-based polymer component from the soot-like substance include a method of extracting the fullerene using a solvent having a high solubility of the fullerene and filtering the insoluble carbon-based polymer component.

In the mixed fullerene, the total ratio of C ₆₀ and C ₇₀ is preferably 50% by mass or more, more preferably 70% by mass or more, and particularly preferably 90% by mass or more. Further, the ratio of C ₇₀ is preferably 10% by mass or more. The mixed fullerene may contain impurities other than fullerene (for example, polycyclic aromatic hydrocarbons, carbon-based polymers, etc.). The content of impurities is preferably 10% by mass or less, more preferably 5% by mass or less.

Hereinafter, the adsorption step, the C ₆₀ elution step, and the sublimation step of the method for isolating C ₇₀ according to the present embodiment will be described.

(Adsorption step)
The adsorption step is a step of adsorbing mixed fullerene on activated carbon. Specific examples of the method for adsorbing mixed fullerene on activated carbon include (a) a method of adsorbing mixed fullerene on activated carbon by mixing and stirring the activated carbon, mixed fullerene, and an elution solvent, or (b) column. There is a method of adsorbing mixed carbon to activated carbon by filling the mixture with activated carbon as a filler and flowing a mixed solution containing mixed fullerene and an elution solvent from the upper part of the column.

Examples of the activated carbon include activated carbon having an integrated pore volume of 0.3 cm ³ / g or more in pores having a diameter of 2 nm or less. Since this activated carbon has a relatively small adsorption force for C ₆₀ and a relatively high adsorption force for higher-order fullerenes of C ₇₀ or higher, it has an excellent ability to separate C ₆₀ and higher-order fullerenes of C ₇₀ or higher. That is, the concentration of C ₇₀ adsorbed on the activated carbon can be increased in advance before the next C ₆₀ elution step.
The integrated pore volume of the pores having a diameter of 2 nm or less is preferably 0.4 cm ³ / g or more, and more preferably 0.5 cm ³ / g or more. The upper limit is not particularly specified, but is usually 10 cm ³ / g or less.
The specific surface area of the activated carbon by the BET method is preferably 1600 m ² / g or more, more preferably 2000 m ² / g or more, and particularly preferably 2500 m ² / g or more. If the specific surface area is in the above range, the processing capacity of the mixed fullerene at one time is increased.
The activated carbon preferably has a particle size of 30 μm or less in an amount of 40% or less, more preferably 30% or less, and particularly preferably 25% or less. When the ratio of activated carbon having a small particle size of 30 μm or less is within the above range, the operation of the _C60 elution step described later becomes easy.

(C ₆₀ elution step)
Of the mixed fullerenes adsorbed on the activated carbon, C ₆₀ elutes preferentially over C ₇₀ , and this property is utilized to elute C ₆₀ from the activated carbon.
Specifically, the above-mentioned adsorption step (a) may include filtering a mixture of activated carbon, mixed fullerene, and an elution solvent. Further, the solid obtained by filtration may be further mixed with a new elution solvent, stirred, and then filtered again, or this operation may be repeated a plurality of times. In this way, the C ₆₀ adsorbed on the activated carbon is dissolved in the elution solvent, and the C ₆₀ can be separated from the activated carbon.
Alternatively, for ₍ b) of the adsorption step described above, C60 can be eluted from the activated carbon by flowing a mixed solution containing mixed fullerenes and an elution solvent from the upper part of the column and then flowing the elution solvent from the upper part of the column. can.
By the C ₆₀ elution step, activated carbon having almost no C ₆₀ and adsorbing a large amount of C ₇₀ can be obtained.

As the elution solvent, it is preferable to use an aromatic hydrocarbon having 6 to 20 carbon atoms, a halogen-containing aromatic hydrocarbon, a polycyclic aromatic hydrocarbon, and carbon disulfide. As an aromatic hydrocarbon compound having 6 to 20 carbon atoms, for example, it is a hydrocarbon compound having at least one benzene nucleus in the molecule, and specifically, benzene, toluene, xylene, ethylbenzene, n-propylbenzene, isopropylbenzene. , N-butylbenzene, sec-butylbenzene, tert-butylbenzene, 1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene, 1,2,3,4 -Alkylbenzenes such as tetramethylbenzene, 1,2,3,5-tetramethylbenzene, diethylbenzene and simen can be mentioned. Examples of the halogen-containing aromatic hydrocarbon include chlorobenzene, bromobenzene, 1,3-dichlorobenzene, 1,2-dichlorobenzene, 1,2-dibromobenzene, 1,3-dibrobenzene, 1,2,4-trichlorobenzene and the like. Can be mentioned. Examples of polycyclic aromatic hydrocarbons include quinoline, tetralin, 1-methylnaphthalene, dimethylnaphthalene, 1-phenylnaphthalene, 1-chloronaphthalene, 1-bromo-2-methylnaphthalene and the like. These may be used alone or in 2 or more at an arbitrary ratio. It is most preferable to use 1,2,4-trimethylbenzene and tetralin among them.

(Sublimation step)
Next, C ₇₀ is isolated from the activated carbon by heating the activated carbon obtained in the C ₆₀ elution step to sublimate C ₇₀ . As a pretreatment for the sublimation step, it is preferable to vacuum dry the activated carbon near the boiling point of the elution solvent to remove most of the elution solvent. If the elution solvent remains, the yield will decrease, which is not preferable. The residual amount of the elution solvent is preferably 0.5% by mass or less.

The sublimation step is carried out under normal pressure or reduced pressure of about 0.5 to 5 Pa. Normal pressure has the advantage of simplifying the device, and under reduced pressure has the advantage of lowering the sublimation temperature of fullerenes. Considering the economic efficiency, it should be carried out under the optimum conditions. In order to avoid the reaction of fullerene, it is preferable to replace the inside of the sublimation apparatus with an inert gas at the time of sublimation, and the oxygen content in the gas in the sublimation apparatus is preferably 10% by volume or less, preferably 5% by volume. It is preferably the following, and particularly preferably 1% by volume or less. When the oxygen content is high, an oxide of fullerene may be formed. Further, during heating, the inert gas is flowed at about 0.1 to 10 ml / min, preferably about 0.5 to 8 ml / min per 1 g of mixed fullerene, and the temperature is raised under the flow of the inert gas. Is preferable. The inert gas used for sublimation may or may not be preheated.
The temperature for sublimation is preferably 400 ° C. to 1000 ° C., more preferably 500 to 900 ° C., and even more preferably 600 ° C. to 800 ° C. When the sublimation temperature is 400 ° C. or higher, the sublimation efficiency of C ₇₀ is good, and when it is 1000 ° C. or lower, there is no possibility that C ₇₀ is denatured.

The apparatus used for sublimation is not particularly limited as long as it can withstand the above-mentioned temperature / pressure sublimation conditions, such as batch type, fixed bed type, fluidized bed type, and continuous type.
The C ₇₀ sublimated from the sublimation apparatus is carried to the inert gas, and the temperature is lowered to cause precipitation. The device for precipitation may be provided in the same device as the sublimation apparatus or may be provided separately. Further, it may be a batch type or a continuous type. To recover the precipitated C ₇₀ , it may be mechanically collected and recovered, or it may be dissolved in a solvent and recovered. The inert gas after depositing and recovering C ₇₀ is released to the atmosphere or recycled.

In the present embodiment, the inert gas means a gas that does not substantially react with C ₇₀ under sublimation temperature / pressure conditions. Types of the inert gas include helium, neon, argon, nitrogen gas and mixtures thereof.

As an example of the sublimation apparatus, the one shown in FIG. 1 can be mentioned.
The sublimation apparatus 1 shown in FIG. 1 has a sublimation unit 2, a first precipitation unit 3, a second precipitation unit 4, a gas introduction pipe 5 connected to the sublimation unit 2, and a gas discharge unit connected to the second precipitation unit 4. A decompression unit 7 including a pipe 6 and a vacuum pump connected to the gas discharge pipe 6 is provided.

The sublimation section 2 has a sublimation tube 21, a heating section 22 arranged on the outer periphery of the sublimation tube 21 and heating at least a part of the sublimation tube 21, and a heat insulating section 23 holding the sublimation tube 21 and the heating section 22. .. Examples of the heating unit 22 include a resistance heating device, an infrared heating device, a high frequency induction heating device, and the like. Examples of the material of the heat insulating portion 23 include heat insulating materials such as alumina refractory bricks and alumina amorphous refractory materials. In the sublimation section 2, impurities having a lower sublimation temperature than C ₇₀ and C ₇₀ are sublimated.
The first precipitation section 3 has a first precipitation tube 31 and a heat dissipation section 32 arranged in a small part of the outer circumference of the first precipitation tube 31. Examples of the material of the heat radiating portion 32 include metals such as copper and aluminum having high thermal conductivity. In the first precipitation section 3, the sublimated C ₇₀ is precipitated.
The second precipitation section 4 has a second precipitation tube 41 and a cooling section 42 arranged on at least a part of the outer periphery of the second precipitation tube 41. Examples of the cooling unit 42 include a water-cooled jacket and a copper pipe through which a refrigerant flows. Sublimated impurities other than C ₇₀ are deposited in the second precipitation section 4.
Examples of the material of the sublimation tube 21, the first precipitation tube 31 and the second precipitation tube 41 include quartz glass, metals such as stainless steel, and ceramics. Further, the sublimation tube 21, the first precipitation tube 31, and the second precipitation tube 41 may be integrated, but it is preferable that the precipitated C ₇₀ can be separated from each other because of the ease of recovery.

The effects of this embodiment will be made clearer by the following examples and comparative examples. The present invention is not limited to the examples, and can be appropriately modified and implemented without changing the gist thereof.

[Example 1]
(Preparation of activated carbon column)
The powdered activated carbon MAXSORB MSC30 manufactured by Kansai Thermal Chemical Co., Ltd. (integrated pore volume of pores with a diameter of 2 nm or less; 0.55 cm ³ / g, specific surface area 3250 m ² / g; potassium hydroxide activated) was sieved by Yamato Scientific Co., Ltd. No. Weighed 95.1 g on 286 and sieved in air at the strength of scale 50 using a sieve shaking machine VSS-50 manufactured by Tsutsui Rikagaku Kikai Co., Ltd. and a sieve with an opening of 26 micrometers. , 49.5 g remained on the sieve and was transferred to a 1 L glass beaker. The same operation was repeated twice more while changing the amount to be weighed on the sieve, and a total of 177.6 g of MAXSORB MSC30 remaining on the sieve was obtained. When 0.2 g of MAXSORB MSC30 remaining on the sieve was weighed and dispersed in water and analyzed with a laser dispersion particle analyzer SALD-2000J manufactured by Shimadzu Corporation, the average particle size of the sieve residue was 94 μm. In addition, the proportion of particles having a particle size of 30 μm or less in the sieve residue was 13%.

The specific surface area of MAXSORB MSC30 remaining on the sieve was 2990 m ² / g calculated by the BET multipoint method in the range of relative pressure of 0.002 to 0.2. When the pore volume was calculated from the amount of nitrogen adsorbed at a relative pressure of 0.93, the sieve residue was 1.59 mL / g. Transfer 130 g of the sieve residue to another 1 L beaker, and stir 0.6 L of 1,2,4-trimethylbenzene (also known as pseudocumene) manufactured by Maruzen Petrochemical Co., Ltd. in a water bath at 22 ° C for 5 minutes. It was added slowly to prepare an activated carbon slurry.

Place a perforated plate in the bottom flange of a SUS304 column (inner diameter 68 mm, height 100 mm inside the column), place a PTFE membrane filter with a diameter of 68 mm and a hole diameter of 0.2 micron on the perforated plate, and attach it to the column body. It was fixed with screws. The upper flange portion was removed, 0.049 L of the activated carbon slurry was poured into the column body, and the activated carbon slurry was sucked under reduced pressure from the bottom extraction port to prepare an activated carbon bed while extracting 1,2,4-trimethylbenzene in the slurry. Remove trimethylbenzene until just before the upper part of the activated carbon bed rises above the liquid level, repeat the operation of adding slurry to make an activated carbon bed with a layer height of 98 mm, attach the upper flange containing the perforated plate and membrane filter, and screw. Fixed with. The volume of the activated carbon bed was 363 cm ³ . The entrance at the top of the column was connected to the liquid feed line. The bottom extraction port was connected to the filtrate collection tank.

₍ Adsorption step and C60 elution step)
20 g of mixed fullerene (mixing ratio: C ₆₀ / C ₇₀ / higher-order fullerene = 60/35/5% by mass (manufactured by Frontier Carbon Co., Ltd.)) and 180 g of elution solution 1,2,4-trimethylbenzene are mixed. , 60 min was stirred with a three-one motor to prepare a mixed solution.
The liquid feed pump was driven and the mixed liquid was fed to the column via the liquid feed line. The filtrate containing _C60 was collected from the extraction port. When the outflow rate of the filtrate flowing out from the extraction port was set to 40 ml / min, the display of the pressure gauge installed on the column was 0.1 MPa.
After the mixed solution was sent, the eluent solution 1,2,4-trimethylbenzene was sent to the 80.0 L column in the same manner. When the outflow rate of the solution flowing out from the extraction port was set to 160 ml / min, the display of the pressure gauge installed on the column was 0.5 MPa.
As a result of analyzing the eluate by high performance liquid chromatography, the total elution amounts of C ₆₀ and C ₇₀ eluted from the column were 11.70 g and 0.30 g, respectively.

(Sublimation step)
Subsequently, the upper flange of the column was removed, and all the activated carbon in the column was taken out. The removed activated carbon was placed in a tray and vacuum dried in a dryer at 120 ° C. for 10 hours. The dried activated carbon was pulverized in a mortar in two portions to obtain 137.8 g of activated carbon powder adsorbed with C ₇₀ .

The sublimation process was carried out using the sublimation apparatus 1 shown in FIG. The sublimation tube 21, the first precipitation tube 31, and the second precipitation tube 41 are quartz glass tubes having an inner diameter of 160 mm, and can be connected or separated from each other. The length of the sublimation tube 21 is 40 cm, the length of the first precipitation tube 31 is 50 cm, and the length of the second precipitation tube 41 is 60 cm.
The heating unit 22 is a carbon heater and is arranged so as to cover about 90% of the area of the outer peripheral surface of the sublimation tube 21. The heat insulating portion 23 is made of porous alumina.
The heat radiating portion 32 is a copper member that covers the entire outer peripheral surface of the first precipitation pipe 31. The cooling unit 42 is a water-cooled jacket that covers the entire outer peripheral surface of the second precipitation pipe 41 and allows water at room temperature to flow.
Further, in order to measure the temperatures of the sublimation tube 21, the first precipitation tube 31 and the second precipitation tube 41, thermocouples (not shown in the figure) were arranged in the intermediate portions thereof.

After connecting the sublimation pipe 21, the first precipitation pipe 31, and the second precipitation pipe 41 and charging 137.8 g of activated carbon powder adsorbing C ₇₀ into the sublimation pipe 21, the decompression unit 7 made of a vacuum pump is operated. Then, the pressure inside the sublimation tube 21, the first precipitation tube 31, and the second precipitation tube 41 was reduced. When the inside of the sublimation tube 21 was depressurized to 1.5 Pa, the vacuum pump was stopped and argon gas was flowed as an inert gas at a rate of 800.0 ml / min for 60 min to perform replacement. Next, the flow rate of the argon gas was set to 10.0 ml / min, and the suction force of the vacuum pump was adjusted so that the pressure inside the sublimation tube 21 was 3.4 Pa. Further, water at room temperature was flowed through the cooling unit 42 at a flow rate of 20 ml / min. Subsequently, the sublimation tube 21 was heated to 600 ° C. at a rate of 20 ° C./min, and kept warm at 600 ° C. for 24 hours. At the time of heat retention, the temperature of the sublimation tube 21 is 600 ° C., the temperature of the first precipitation tube 31 is 200 ° C., and the temperature of the second precipitation tube 41 is 100 ° C. Then, it was slowly cooled to room temperature, and 6.72 g of the precipitate was recovered from the first precipitation section 31.

The content (% by mass) of _C70 in the precipitate was measured using high performance liquid chromatography (HPLC) manufactured by Shimadzu Corporation. As a result, the content of C ₇₀ in the precipitate was 99.3% by mass. From this result, it was found that the content of C ₇₀ in the precipitate was 6.67 g.

(Example 2)
This is the same as in Example 1 except that the sublimation tube 21 is heated to 800 ° C.
6.75 g of the precipitate was recovered from the first precipitate 31. The content of C ₇₀ in the precipitate was 98.6% by mass. From this result, it was found that the content of C ₇₀ in the precipitate was 6.66 g.

(Comparative Example 1)
Since the adsorption step and the C ₆₀ elution step were the same as in Example 1, detailed description thereof will be omitted.
After the _C60 elution step, the liquid feed pump was stopped and the filtrate recovery tank connected to the bottom extraction port of the column was replaced with a tank for collecting _C70 eluate. Next, the liquid feed pump is started, 1-methylnaphthalene (manufactured by Tokyo Kasei) is fed to the column via the liquid feed line, and when the liquid feed volume of 1-methylnaphthalene reaches 80.0 L. The liquid feed pump was stopped. When the outflow rate of the _C70 eluent flowing out from the extraction port was set to 130 ml / min, the display of the pressure gauge installed on the column was 0.63 MPa. 79.9 L of C ₇₀ eluate was recovered.

By removing 1-methylnaphthalene from the C ₇₀ eluate using a rotary evaporator, the substance dissolved in the C ₇₀ eluent was precipitated as a precipitate. Next, the precipitate was taken out from the rotary evaporator, vacuum dried at 160 ° C. for 24 hours, and 7.40 g of the precipitate was recovered.
The content (% by mass) of _C70 in the precipitate was measured using high performance liquid chromatography (HPLC) manufactured by Shimadzu Corporation. As a result, the content of C ₇₀ in the precipitate was 85.0% by mass. From this result, it was found that the content of C ₇₀ in the precipitate was 6.29 g.

It was found that in Examples 1 and 2, the amount of C ₇₀ in the recovered precipitate was larger than that in Comparative Example 1, and the content of C ₇₀ was also high. That is, isolating C ₇₀ by the isolation method of the present invention can efficiently isolate C ₇₀ with higher purity than the prior art.

1: Sublimation apparatus 2: Sublimation part 21: Sublimation pipe 22: Heating part 23: Insulation part 3: First precipitation part 31: First precipitation pipe 32: Heat dissipation part 4: Second precipitation part 41: Second precipitation pipe 42: Cooling part 5: Gas introduction pipe 6: Gas discharge pipe 7: Decompression part

Claims (6)

A method for isolating fullerene C ₇₀ from a mixed fullerene containing fullerene C ₆₀ and fullerene C ₇₀ .
The adsorption step of adsorbing the mixed fullerene on activated carbon,
A fullerene C ₆₀ elution step in which the fullerene C ₆₀ is eluted from the activated carbon with an elution solvent, and
A method for isolating fullerene C ₇₀ , which comprises a sublimation step of heating the activated carbon adsorbed with the fullerene C ₇₀ to sublimate the fullerene C ₇₀ . The method for isolating fullerene C ₇₀ according to claim 1, wherein a column using the activated carbon as a filler is used to adsorb the mixed fullerene to the activated carbon. The method for isolating fullerene C ₇₀ according to claim 1 or 2, wherein the heating temperature of the sublimation step is 400 ° C to 1000 ° C. The method for isolating fullerene C ₇₀ according to any one of claims 1 to 3, wherein the sublimation step is carried out in an inert gas atmosphere. The method for isolating fullerene C ₇₀ according to any one of claims 1 to 4, wherein the activated carbon has a specific surface area of 1600 m ² / g or more by the BET method. The elution solvent is any one of claims 1 to 5, which is at least one selected from aromatic hydrocarbons having 6 to 20 carbon atoms, halogen-containing aromatic hydrocarbons, polycyclic aromatic hydrocarbons, and carbon disulfide. The method for isolating fullerene C ₇₀ according to the above.

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