JP2005187252A - Separation method of fullerene c60 - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently separating a large amount of high-purity C60 from a fullerene mixture. <P>SOLUTION: The method for separating fullerene C60 is characterized by the following: a fullerene mixture at least containing fullerene C60 is mixed with a first solvent and active carbon and then filtered to yield a first liquid with a raised percentage of fullerene C60; then the active carbon is washed with a second solvent to yield a second liquid; and the operation of filtrating the first liquid and the second liquid by bringing them into contact with new active carbon is carried out at least one time to collect the filtrate to separate fullerene C60. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for separating fullerene C60 from a fullerene mixture.

  In 1990, a new type of molecular carbon material called a closed-shell carbon cluster (spherical macromolecule) having 60, 70, 84 carbon atoms was synthesized and attracted attention. Carbon clusters having this special molecular structure are called fullerenes, and fullerenes are “molecules having a spherical or oblate spherical structure in which 20 or more carbon atoms are bonded to adjacent three atoms and closed. The number of members of the ring is not required). Fullerenes are called fullerene C60, fullerene C70, fullerene C84, etc. (hereinafter referred to as C60, C70, C84, etc. in this specification) depending on the number of carbon atoms constituting the molecular skeleton. Since these fullerenes are new carbon materials and have a special molecular structure, they are expected to exhibit unique physical properties. Therefore, it is expected to be used in a wide range of fields such as diamond coating, battery materials, paints, heat insulating materials, lubricants, cosmetics, and cancer therapeutics. Therefore, research on the properties and application development of fullerenes has been actively promoted.

  Known methods for producing fullerenes include an arc discharge method, a resistance heating method, a laser evaporation method, and a combustion method. However, it is not possible to produce only a single fullerene by any of the production methods, and a mixture of a plurality of fullerenes such as C60, C70, C76, C78, C84 and many other carbon compounds (this combustion product is It is sometimes called “煤”.

  As a method for separating fullerenes from “soot” as a combustion product, a method for extracting fullerenes from soot using an organic solvent (solvent extraction method) is well known. Fullerenes are dissolved in organic solvents such as benzene, toluene, carbon disulfide and the like, and other impurity components are difficult to dissolve. Therefore, extraction using these organic solvents is performed.

  The fullerenes thus obtained are a mixture of several types of molecules having different carbon numbers, but each fullerene has different properties depending on the number of carbons. For example, the absorption spectrum shows different shapes depending on the difference in the number of carbon atoms. Therefore, considering the application to cancer treatment using photosensitization, there will be a difference in sensitivity to the irradiated light, resulting in higher sensitivity. It is better to use carbon fullerene alone. However, it has been difficult to produce a fullerene species having a specific number of carbon atoms in a large amount with a high purity by the conventional production method.

  Conventionally, methods such as column chromatography, fractional recrystallization, and inclusion of fullerene have been used to separate a single fullerene from a solution containing fullerenes obtained by extraction.

  In 1994, Tour et al. Proposed a method for isolating fullerene having a specific carbon number using activated carbon as a separation agent for column chromatography (see Patent Document 1). This method is an excellent method for performing an operation of processing a small amount at a laboratory level only once, but has a drawback that it is not suitable for a large amount of processing. For this reason, there is a problem that it cannot be applied as an industrial process in view of cost and work load.

  In addition to this, a method for separating fullerene using activated carbon has been conventionally known (see, for example, Patent Documents 2 and 3), but the separation efficiency of C60 was not always good. Various points have also been pointed out that are not suitable for mass processing as industrial processes. For this reason, it has been required to develop a method for efficiently separating C60 in large quantities.

US Pat. No. 5,273,729 US Pat. No. 5,310,532 US Pat. No. 5,662,876

  This invention is made | formed in view of said situation, and it aims at providing the method of isolate | separating high purity C60 efficiently in large quantities from a fullerene mixture.

  As a result of intensive studies, the inventors mixed and stirred the fullerene mixture, solvent, and activated carbon, filtered to obtain a solution having a high C60 ratio, and further contacted / filtered with activated carbon one or more times. Thus, it was found that C60 having high purity can be efficiently separated from the fullerene mixture. Further, the present inventors have found that the recovery rate can be increased by recovering the cleaning liquid obtained by cleaning the activated carbon with a solvent, and the present invention has been provided.

  That is, the method for separating C60 of the present invention includes (1) a first step of obtaining a first liquid having an increased C60 ratio by mixing and filtering a fullerene mixture containing at least C60, a first solvent, and activated carbon; 2) The second step of obtaining the second liquid by washing the activated carbon with the second solvent, (3) The filtrate obtained by contacting the first liquid and the second liquid with fresh activated carbon and performing filtration one or more times. It is characterized by the third step of separating C60 by collecting

Preferred embodiments of the present invention include those described below. These aspects can be appropriately combined as long as there is no contradiction.
The first solvent and the second solvent used in the present invention may be the same solvent. As the first solvent and / or the second solvent, a solvent containing an aromatic hydrocarbon compound (for example, 1,2,4-trimethylbenzene or tetralin) can be suitably used. Since these compounds are structurally similar to fullerenes, a larger amount of C60 can be dissolved, whereby a large amount of C60 can be separated and recovered more efficiently.

The specific surface area of the activated carbon used in the present invention is preferably 1600 m ² / g or more. It is also preferable to use activated carbon in which the ratio of particles having a particle size of 10 μm or less, preferably 5 μm or less, more preferably 2 μm or less is 40% or less. By using these activated carbons, the processing efficiency can be further increased.

  In the first step of the present invention, a polycyclic aromatic hydrocarbon is sublimated by heating a rod-shaped material containing fullerenes, a polycyclic aromatic hydrocarbon, and a carbon-based polymer material under an inert gas. And then separating the fullerenes and the carbon-based polymer substance and the extraction solvent to obtain an extract solution in which the fullerene mixture is dissolved. The first liquid can be obtained by mixing with activated carbon and filtering. In this case, 1,2,4-trimethylbenzene or tetralin is preferably used as the extraction solvent. Moreover, as a soot-like substance containing fullerenes, polycyclic aromatic hydrocarbons and carbon-based polymer substances, those obtained by combustion and / or thermal decomposition of hydrocarbon compounds can be preferably used. For this reason, it is possible to carry out a large amount of processing using the present invention, and it can be sufficiently applied industrially.

A first liquid having an increased C60 ratio is obtained by mixing and filtering the fullerene mixture, the first solvent, and the activated carbon, and the activated carbon is washed with the second solvent to obtain the second liquid. According to the method of the present invention in which C60 is separated by collecting the filtrate by performing an operation of bringing the second liquid into contact with new activated carbon and filtering it one or more times, it is possible to efficiently separate a large amount of C60. it can.
In the C60 separation method of the present invention, the higher the contact / filtration frequency of the solution separated from the activated carbon and the new activated carbon, the higher the purity of C60 can be obtained. Also, the yield can be increased by washing the activated carbon with a solvent as appropriate and collecting the washing liquid. By appropriately combining these operations, a person skilled in the art can determine the number of times of contact / filtration and the number of washings necessary to meet the required purity level and target yield.

BEST MODE FOR CARRYING OUT THE INVENTION

  Hereinafter, the C60 separation method of the present invention will be described in detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

(1) First Step In the C60 separation method of the present invention, first, a first liquid having a higher C60 ratio is obtained by mixing and filtering a fullerene mixture containing at least C60, a first solvent, and activated carbon. Perform the process.

  In this step, first, an operation of mixing the three components of the fullerene mixture, the first solvent, and the activated carbon is performed. The order of mixing the three components is not particularly limited. Therefore, the fullerene mixture may be dissolved in the first solvent in advance to prepare a solution of the fullerene mixture, and then the solution may be mixed with activated carbon. The activated carbon and solvent mixture may be prepared in advance, A fullerene mixture may be added to and mixed. Alternatively, the first solvent may be divided and partly used to prepare a fullerene mixture solution, and partly added when mixed with activated carbon. Furthermore, you may mix a fullerene mixture, activated carbon, and a 1st solvent at once.

  Preferred is a case where a first solvent and fullerene mixture are mixed in advance to prepare a solution, and this solution is mixed with activated carbon. At this time, it is not always necessary that all the components contained in the fullerene mixture are dissolved in the first solvent. However, it is preferable that all or most of C60 contained in the fullerene mixture is dissolved in the first solvent. For this reason, by taking means such as pulverization and stirring as necessary, the entire amount or most of C60 contained in the fullerene mixture may be treated so as to be dissolved in the first solvent. Ingredients that do not dissolve in the first solvent are filtered off in a filtration step performed after mixing with activated carbon.

  In the first step of the present invention, the first solvent can be separately prepared and mixed with the fullerene mixture or activated carbon as described above, but the first solvent is not necessarily prepared and added separately in the first step. It does not have to be. The fullerene mixture may be obtained in a solution state depending on the preparation method. In that case, you may use this solution for the 1st process of this invention as it is, and mix with activated carbon. As described above, the fullerene mixture may be obtained in the solution state without being obtained in the solid state, and used as it is in the first step of the present invention. In this case, the solvent contained in the solution of the fullerene mixture is required to be a solvent suitable as the first solvent. A solvent suitable as the first solvent will be described later.

  The weight ratio of the fullerene mixture and activated carbon to be mixed in the first step of the present invention is not particularly limited, but is usually within a range of 1:20 to 20: 1, preferably within a range of 1:15 to 10: 1. Yes, more preferably in the range of 1:10 to 2: 1. Moreover, 0.0125g-10g is normally mixed per 100ml of 1st solvents, Preferably it mixes 0.025g-2.5g, More preferably, 0.125g-1.25g is mixed.

  It is preferable to perform an operation such as stirring so that these three components are sufficiently mixed during or after the formation of the mixture containing the three components of the fullerene mixture, the first solvent, and the activated carbon. In order to perform adsorption with activated carbon quickly and efficiently, it is preferable to stir using a stirring blade, a stirring rod, or the like in the batch. The stirring is preferably performed to such an extent that the activated carbon is dispersed almost uniformly. The stirring time varies depending on the composition of the fullerene mixture, the amount ratio of the fullerene mixture and activated carbon, the temperature, etc., but is usually 0.5 to 180 minutes, preferably 1 to 120 minutes, more preferably 2 minutes to 60 minutes. Moreover, the temperature at the time of mixing and stirring three components is 0 degreeC-150 degreeC normally, Preferably it is 10 degreeC-60 degreeC, More preferably, it is 15 degreeC-40 degreeC.

The mixture comprising the three components of fullerene mixture, first solvent, and activated carbon is then filtered. The components insoluble in the activated carbon and the first solvent are removed by filtration. The pore diameter of the filter paper used at this time is not particularly limited as long as such a purpose can be achieved, but is usually 0.01 μm to 20 μm, preferably 0.05 μm to 10 μm, more preferably 0.1 μm. ~ 5 μm. During filtration, it is preferable to perform suction or pressurization in order to increase the yield of C60 and shorten the working time. Suction or pressurization may be performed continuously during the filtration operation or only at the final stage of the filtration operation.
By performing such a 1st process, the 1st liquid which is a filtrate can be obtained. The ratio of C60 contained in the first liquid (dry standard) is higher than the ratio of C60 contained in the fullerene mixture (dry standard).

(2) Second Step In the second step, the activated carbon filtered in the first step is washed with a second solvent. By washing with the second solvent, C60 adsorbed on the activated carbon can be recovered and the yield of C60 can be increased. The amount of the second solvent used for washing in the second step is usually 10 to 4000 ml, preferably 25 to 2000 ml, more preferably 50 to 1000 ml per 1 g of activated carbon. The washing is usually performed by passing the second solvent from above the filtered activated carbon, but if necessary, the activated carbon and the second solvent may be mixed and stirred for filtration. For example, the activated carbon may be transferred to a batch, and the second solvent may be added and stirred, followed by filtration.

Filtration may be performed while suctioning or pressurizing as in the first step. Moreover, the preferable range of the pore diameter of the filter paper is the same as the filter paper used in the first step.
In principle, the second step is performed at the same temperature as in the first step. However, the second solvent may be used for washing after heating or cooling, if necessary.

(3) Third Step In the third step, the filtrate is collected by performing the operation of bringing the first liquid and the second liquid into contact with new activated carbon and performing filtration one or more times.
It is preferable to mix the 1st liquid and the 2nd liquid before making it contact with a new activated carbon. However, the present invention includes a case where the first liquid and the second liquid are separately mixed with activated carbon and then both are mixed. When the first liquid and the second liquid are mixed, the second liquid obtained in the second step may not be mixed with the first liquid. The mixing amount of the second liquid can be appropriately determined in consideration of the intended purity and yield of C60. The second liquid that has not been used can be effectively used by mixing it with the first liquid obtained from another fullerene mixture or by using the second liquid as a fullerene mixture in the first step of the present invention. it can.

The weight ratio of the dry weight of the solids contained in the first liquid and the second liquid and the weight ratio of the activated carbon used in the third step is not particularly limited, but is usually in the range of 1:20 to 20: 1, preferably 1 : In the range of 15 to 10: 1, more preferably in the range of 1:10 to 2: 1. The operation of bringing the first liquid and the second liquid into contact with the activated carbon is preferably performed in a batch. It is preferable to stir at the time of mixing or after mixing as in the first step.
The third step is usually carried out at the same temperature as the first step, but can be carried out by setting a temperature different from the first step. The preferred conditions for the filtering conditions and the filter paper hole diameter are the same as in the first step. The filtration is preferably performed while suctioning.

You may perform the same operation as a 2nd process with respect to the activated carbon obtained after filtering at a 3rd process. That is, the activated carbon may be washed with the second solvent to recover the washing solution. Part or all of the recovered cleaning liquid can be mixed with the filtrate obtained in the third step.
The third step is performed at least once. When the third step is performed a plurality of times, each time may or may not include the second step. Moreover, there may be times including the second step and times not including the second step. Further, the amount of activated carbon used each time may be different each time. The number of times the third step is performed and the presence or absence of the second step can be appropriately determined according to the yield and purity of C60 to be separated.

  The filtrate obtained by performing the third step one or more times in this way contains C60 at a high concentration. By distilling off the solvent, a solid containing C60 with high purity can be obtained. The purity of C60 can be measured by a method such as liquid chromatography.

(4) Fullerene mixture The fullerene mixture applied to the C60 separation method of the present invention is not particularly limited as long as it contains at least C60 and other fullerenes. The fullerene mixture may be obtained by any method.

  Preferred as the fullerene mixture used in the present invention is a rod-like substance containing fullerenes, polycyclic aromatic hydrocarbons and carbon-based polymer components, and more preferably polycyclic aromatic hydrocarbons are converted from the rod-like substances. The removed soot-like substance or a mixture containing C60, C70 and higher fullerenes obtained by further removing the carbon-based polymer component from the soot-like substance. More specifically, a crude mixture before performing Step A or Step B described later, or an extract after performing Step A or Step B below (that is, higher-order fullerene (higher fullerene) in addition to C60 and C70). Etc.) can be used as the fullerene mixture.

  In order to produce fullerenes in large quantities, it is preferable to use a combustion method in which the hydrocarbon raw material is incompletely burned or a thermal decomposition method in which the hydrocarbon raw material is decomposed under high heat, and it is particularly preferable to use the combustion method. . The pressure for producing fullerenes by the combustion method is preferably 1330 to 13300 Pa (10 to 100 Torr), more preferably 3990 to 6650 Pa (30 to 50 Torr). The temperature is preferably 800 to 2500 ° C, more preferably 1000 to 2000 ° C.

  As raw materials for producing fullerenes, aromatic hydrocarbons having 6 to 15 carbon atoms such as benzene, toluene, xylene, naphthalene, methylnaphthalene, anthracene, and phenanthrene are preferably used. Moreover, you may use together aliphatic hydrocarbons, such as hexane, heptane, and octane, as a raw material with these aromatic hydrocarbons.

  In the combustion method, the raw material also acts as a heat source. That is, the raw material hydrocarbon reacts with oxygen to generate heat and raises the temperature to a temperature at which fullerene can be generated, and the raw material hydrocarbon is dehydrogenated to form a carbon unit for forming a fullerene skeleton. It is thought to generate. Carbon units aggregate under a certain pressure and temperature condition to form fullerenes.

The amount of oxygen used varies slightly depending on the type of raw material hydrocarbon, but when toluene is used as the raw material hydrocarbon, for example, it is preferably 0.5 to 9 times mol, more preferably 1 to 5 times mol relative to toluene. preferable.
In the reaction system in the combustion method, a gas inert to fullerene may be present in addition to oxygen. Examples of these inert gases include helium, neon, argon, nitrogen, carbon dioxide and the like.

  The soot-like substance obtained by the combustion method contains fullerenes and polycyclic aromatic hydrocarbons, and the other balance is usually a high molecular weight hydrocarbon having a carbon graphite structure and a few hydrogen atoms. It is a carbon polymer component such as carbon black. The soot-like substance preferably contains 5% by weight or more of fullerenes, more preferably 10% or more, and particularly preferably 15% or more. The fullerenes to be produced are not limited in the number of carbons as long as they meet the above definition, but are usually fullerenes having 60 to 84 carbon atoms, and among them, the ratio of C60 and C70 is preferably 50% in all fullerenes. Or more, more preferably 70% or more, and particularly preferably 80% or more.

When the fullerene mixture used in the present invention is produced by a combustion method or a pyrolysis method, a soot-like substance (fullerenes, polycyclic aromatic hydrocarbons and carbon-based polymers produced by the combustion method or the pyrolysis method) The component) is first heated under an inert gas to perform a step (Step A) to sublimate and separate the polycyclic aromatic hydrocarbon from the soot-like material, and then mix with the extraction solvent; It is preferable to carry out a step (step B) for obtaining an extract in which fullerenes are dissolved. If the separation method of the present invention is performed on those that have undergone such step A and step B, C60 can be separated more efficiently.
Below, these process A and process B are demonstrated in order.

(Process A)
The conditions for subliming polycyclic aromatic compound, the pressure is preferably from 100 to 2 × 10 ⁵ Pa, more preferably 1000~1.4 × 10 ⁵ Pa. When it is performed at normal pressure, there is a merit that the apparatus is simple, and when it is performed under reduced pressure, there is a merit that the sublimation temperature of the polycyclic aromatic hydrocarbon is lowered. In view of economic efficiency, the optimum conditions may be selected and implemented. The temperature is preferably 100 ° C to 800 ° C. Since the sublimation temperature varies depending on the pressure, it may be appropriately selected. In the case of normal pressure, 200 ° C. to 700 ° C. is preferable, and 300 ° C. to 600 ° C. is particularly preferable. If the temperature is too low, the sublimation of the polycyclic aromatic hydrocarbons becomes insufficient, and if the temperature is too high, the fullerenes also sublimate, and the recovery rate of fullerenes decreases.

  The apparatus used for sublimation is not particularly limited as long as it can withstand the above-mentioned sublimation conditions of temperature / pressure, such as a batch type, a fixed bed type, a fluidized bed type, and a continuous type. Examples of the material used for the sublimation apparatus include metals such as quartz glass and stainless steel, ceramics, and glass. Sublimation is performed in the presence of an inert gas. In the present invention, the inert gas means a gas that does not substantially react with fullerenes under the temperature / pressure conditions of sublimation.

  Examples of the inert gas include helium, neon, argon, nitrogen, and mixtures thereof. In order to avoid the reaction of fullerenes, it is preferable that the sublimation apparatus is substantially replaced with an inert gas during sublimation, and the oxygen content in the gas in the sublimation apparatus is preferably 10% by volume or less. % Or less is more preferable, and 1% by volume is particularly preferable. When the oxygen content is high, oxides of fullerenes may be generated.

  The sublimation of the polycyclic aromatic hydrocarbon is preferably performed under an inert gas flow. As a method performed under the flow of the inert gas, for example, an inert gas inlet and outlet are provided in the sublimation device, and the temperature is raised to a predetermined temperature while continuously flowing in and discharging the inert gas. A method can be mentioned. The inert gas may be preliminarily heated before flowing into the sublimation apparatus.

  The flow rate of the inert gas when sublimation is performed under the flow of the inert gas is preferably 1 to 10,000 ml / min, more preferably 5 to 5000 ml / min, with respect to 1 g of the soot-like substance. The flow of the inert gas may be continuous or intermittent.

  The polycyclic aromatic hydrocarbons sublimated from the sublimation apparatus are entrained by the inert gas and led to the precipitation apparatus, where they are deposited by lowering the temperature. The deposition apparatus may be provided in the same apparatus as the sublimation apparatus or may be provided separately. Moreover, any of a batch type and a continuous type may be sufficient. The precipitated polycyclic aromatic hydrocarbons may be collected by mechanical collection or may be recovered by dissolving in a solvent. The inert gas after depositing and collecting the polycyclic aromatic hydrocarbons is released into the atmosphere or recycled. The operation time varies depending on the temperature, pressure, and gas flow rate, but is usually about 10 minutes to 12 hours.

(Process B)
Next, the process of obtaining the extract which melt | dissolved fullerenes by mixing the fullerene from which the polycyclic aromatic hydrocarbon was isolate | separated, and the soot-like substance containing a carbon-type polymer component with an extraction solvent is implemented. As the extraction solvent, a solvent that does not substantially dissolve the carbon-based polymer component is selected. As the extraction solvent, a solvent containing an aromatic hydrocarbon is preferably used. As the aromatic hydrocarbon compound, those similar to those used in the first solvent and the second solvent described later are used.

  When the solubility of fullerenes in the extraction solvent is too low, the extraction efficiency is lowered. Therefore, a solvent having a fullerene solubility of preferably 5 g / L or more, more preferably 10 g / L or more, and particularly preferably 15 g / L or more is used. Moreover, from an industrial viewpoint, among these extraction solvents, those which are liquid at normal temperature and have a boiling point of usually 100 to 300 ° C., particularly 120 to 250 ° C. are preferable.

  As the extraction solvent, it is necessary to use an amount sufficient to sufficiently extract fullerenes. Usually, it is preferable to use about 5 to 400 times the amount of the fullerenes in the rod-like substance, and about 40 to 200 times the amount considering the economy. In the extraction, a batch type, a semi-continuous type, a continuous type, or a combination thereof can be adopted, and details of the format and apparatus are not particularly limited.

  The soot-like substance usually contains 5 to 30% by weight of fullerenes. From the viewpoint of extraction efficiency, it is preferable that the amount of the extraction solvent used for the fullerenes is in the above range. Therefore, prior to the extraction operation, a part of the soot-like substance is analyzed to find the fullerene in the soot-like substance. It is preferable to measure the content. The extract thus obtained contains C60, C70 and higher fullerene having a carbon number larger than C70.

(5) First solvent and second solvent The first solvent mixed with the fullerene mixture and activated carbon in the first step, and the second solvent used when elution from the activated carbon in the second step dissolves the fullerene mixture of the present invention. The type is not particularly limited as long as it can carry out the C60 separation method. Preferable is a solvent containing an aromatic hydrocarbon compound. The aromatic hydrocarbon used as the extraction solvent is a hydrocarbon compound having at least one benzene nucleus in the molecule. 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-tetramethyl Examples thereof include alkylbenzenes such as benzene, 1,2,3,5-tetramethylbenzene, diethylbenzene, and cymene, alkylnaphthalenes such as 1-methylnaphthalene, and tetralin. Among these, it is preferable to use 1,2,4-trimethylbenzene (TMB) and tetralin.

As the extraction solvent, in addition to aromatic hydrocarbons, organic solvents such as aliphatic hydrocarbons and chlorinated hydrocarbons may be used alone or in admixture of two or more of them in an arbitrary ratio. .
As the aliphatic hydrocarbon, any aliphatic hydrocarbon such as cyclic or acyclic can be used. Examples of cycloaliphatic hydrocarbons include monocyclic aliphatic hydrocarbons such as cyclopentane, cyclohexane, cycloheptane, cyclooctane, and derivatives thereof such as methylcyclopentane, ethylcyclopentane, methylcyclohexane, ethylcyclohexane, 1 , 2-dimethylcyclohexane, 1,3-dimethylcyclohexane, 1,4-dimethylcyclohexane, isopropylcyclohexane, n-propylcyclohexane, t-butylcyclohexane, n-butylcyclohexane, isobutylcyclohexane, 1,2,4-trimethylcyclohexane, Examples include 1,3,5-trimethylcyclohexane and polycyclic decalin. Examples of acyclic aliphatic hydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, isooctane, n-nonane, n-decane, n-dodecane, n-tetradecane and the like.

  Examples of the chlorinated hydrocarbon include dichloromethane, chloroform, carbon tetrachloride, trichloroethylene, tetrachloroethylene, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, dichlorobenzene, 1-chloronaphthalene and the like. Other examples include ketones having 6 or more carbon atoms, esters having 6 or more carbon atoms, ethers having 6 or more carbon atoms, and carbon disulfide.

As the first solvent and the second solvent, in order to efficiently separate C60 in a large amount, it is preferable to use a solution having a high fullerene solubility and to treat a concentrated solution as much as possible. Specifically, it is preferable to use a fullerene having a solubility of 5 g / L or more, more preferably 10 g / L or more, and particularly preferably 15 g / L or more. Of these, 1,2,4-trimethylbenzene (TMB) and tetralin are preferable.
The first solvent and the second solvent may be the same or different. The case where a solvent miscible with each other is selected as the first solvent and the second solvent is preferable. This is because it is convenient when the first liquid and the second liquid are mixed and processed later. More preferably, the same solvent is used as the first solvent and the second solvent.

  Moreover, in order to perform the separation method of the present invention more efficiently, it is preferable that the extract and the first solvent used for obtaining the fullerene mixture are the same.

(6) Activated carbon The activated carbon used in the first step and the third step of the present invention is strongly adsorbent and mostly carbonaceous charcoal. The type and production method of the activated carbon are not particularly limited as long as the separation method of the present invention can be carried out. The activated carbon used in the first step and the activated carbon used in the third step may be the same or different.

Preferable examples of the activated carbon used in the present invention include activated carbon having a pore volume with a diameter of 2 nm or less and an integrated pore volume of 0.3 cm ³ / g or more. Since this activated carbon has a relatively low adsorption power for C60 and a relatively high adsorption power for higher-order fullerenes of C70 or higher, it has an excellent ability to separate C60 and higher-order fullerenes of C70 or higher. Can be isolated.
When the integrated pore volume of pores having a diameter of 2 nm or less is less than 0.3 cm ³ / g, the adsorption capacity for fullerenes is low, and the separability between C60 and C70 or higher order fullerenes may be lowered. The integrated pore volume of pores having a diameter of 20 mm or less is preferably 0.4 cm ³ / g or more, more preferably 0.5 cm ³ / g or more. The upper limit is not particularly defined, but is usually 10 cm ³ / g or less.

It is preferable that the specific surface area of the activated carbon is 1600 m ² / g or more, more preferably 2000 m ² / g or more, particularly preferably 2500 m ² / g or more. When the specific surface area is in the above range, the treatment capacity of fullerenes per one time is increased.
Furthermore, the activated carbon preferably has a ratio of particles having a particle size of 30 μm or less of 40% or less, more preferably 30% or less, and particularly preferably 25% or less. If the ratio of the activated carbon having a small particle diameter of 10 μm or less, preferably 5 μm or less, more preferably 2 μm or less is within the above range, the operation for treating the mixture of fullerenes becomes easy.

An example of the procedure of the mixed stirring treatment / filtration / solvent passage treatment operation in the C60 separation method of the present invention will be described below.
1. The fullerene mixture is dissolved in a solvent and used as a raw material liquid.
2. The raw material liquid and activated carbon are mixed and stirred.
3. Filter the mixture of 2 above.
4). The solvent is passed through the activated carbon layer on the filter of 3 above.
5). The filtrate obtained by the above operations 3 to 4 is used as a raw material liquid, and the operations of fresh activated carbon and the above-mentioned contact and filtration and liquid passing operations 2 to 4 are repeated.

  The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

<Example 1>
(Preparation of raw material liquid)
In addition to mixed fullerene (H60 fullerene) in addition to C60, C70 by Honjo Chemical Co., Ltd. 0.15 g of C60: 0.74, C70: 0.18) is 1,2,4- A uniform fullerene mixture solution was prepared by mixing with 25 ml of trimethylbenzene (TMB) and immersing in an ultrasonic cleaner at room temperature for 10 minutes, and this was used as a raw material liquid.
FIG. 1 shows a flowchart of the following steps.

(Batch contact of raw material liquid and activated carbon)
The total amount of the prepared raw material liquid and 0.12 g of activated carbon MSC30 manufactured by Kansai Thermal Chemical Co., Ltd. were brought into contact with each other in a 100 ml Erlenmeyer flask, a 1 cm long stirrer chip was placed in the flask, and the slurry was stirred with a magnetic stirrer at room temperature for 10 minutes. .

(Slurry filtration)
The slurry was suction filtered with a filter manufactured by Advantech Toyo Corporation over 4 minutes. At that time, an omnipore membrane having a pore diameter of 0.45 μm manufactured by Nippon Millipore Corporation was used as filter paper.

(Solvent passage through activated carbon layer)
50 ml of TMB was gently poured onto the activated carbon layer remaining in the filter, and suction filtration was performed for 5 minutes to allow TMB to flow. The liquid that passed through the activated carbon layer and the filtrate obtained in the above (slurry filtration) were mixed to obtain a product liquid.

(Repetition process 1)
Using the liquid obtained by the above operation as a raw material liquid, the operation from the above (batch contact between the raw material liquid and activated carbon) to (the passing of the solvent through the activated carbon layer) was repeated.

(Repetition process 2)
Using the liquid obtained by the above (repeating treatment 1) operation as a raw material liquid, the operation from the above (batch contact between the raw material liquid and activated carbon) to (solvent liquid passing through the activated carbon layer) was repeated.

(Repetition process 3)
Using the liquid obtained by the above (repeating treatment 2) operation as a raw material liquid, the operation from the above (batch contact of the raw material liquid and activated carbon) to (solvent flow through the activated carbon layer) was repeated.

(Repetition process 4)
Using the liquid obtained by the above (repeating treatment 3) operation as a raw material liquid, the operation from the above (batch contact between the raw material liquid and activated carbon) to (solvent liquid passing through the activated carbon layer) was repeated.

(analysis)
As a result of analyzing the solute concentration of the liquid obtained by the above (repeating treatment 4) operation by liquid chromatography, the mass concentration of C60 in the solute was 97.1%.

<Comparative Example 1>
(Preparation of raw material liquid)
A mixed fullerene mixture made by Honjo Chemical Co., Ltd. (0.15 g) was mixed with 25 ml of 1,2,4-trimethylbenzene (TMB) and immersed in an ultrasonic cleaner at room temperature for 10 minutes to prepare a uniform fullerene mixture solution. Was used as a raw material liquid.

(Batch contact of raw material liquid and activated carbon)
The total amount of the raw material liquid that was observed and 0.12 g of activated carbon MSC30 manufactured by Kansai Thermal Chemical Co., Ltd. were brought into contact with each other in a 100 ml Erlenmeyer flask. did.

(Slurry filtration)
The slurry was subjected to suction filtration with a filter KG-25 manufactured by Advantech Toyo Co., Ltd. over 4 minutes. At that time, an omnipore membrane having a pore diameter of 0.45 μm manufactured by Nippon Millipore Corporation was used as filter paper.

(Cleaning the activated carbon layer)
50 ml of TMB was gently poured onto the activated carbon layer remaining on the filter, and the activated carbon layer was washed for 5 minutes by suction filtration. The washing liquid that passed through the activated carbon layer and the filtrate obtained in the above (slurry filtration) were mixed to obtain a product liquid.

(analysis)
As a result of analyzing the solute concentration of the product solution obtained by the above operation by liquid chromatography, the mass concentration of C60 in the solute was 74.2%.

  The C60 separation method of the present invention makes it possible to separate C60 in large quantities and with high purity. Since the C60 separation method of the present invention is suitable for implementation on an industrial scale, its practicality is extremely high. C60 separated by the method of the present invention is expected to be used in a wide range of fields such as diamond coating, battery materials, paints, heat insulating materials, lubricants, cosmetics, and cancer therapeutic agents.

4 is a flowchart illustrating a method for separating C60 in the first embodiment.

Claims (8)

(1) A fullerene mixture containing at least fullerene C60, a first solvent, and activated carbon are mixed and filtered to obtain a first liquid in which the ratio of fullerene C60 is increased, and (2) the activated carbon is washed with the second solvent. To obtain the second liquid, and (3) separating the fullerene C60 by collecting the filtrate by performing the operation of bringing the first liquid and the second liquid into contact with new activated carbon and performing filtration once or more. A method for separating fullerene C60, which is characterized. The method for separating fullerene C60 according to claim 1, wherein the first solvent and the second solvent are the same solvent. The method for separating fullerene C60 according to claim 1 or 2, wherein a solvent containing an aromatic hydrocarbon compound is used as the first solvent and / or the second solvent. The method for separating fullerene C60 according to any one of claims 1 to 3, wherein 1,2,4-trimethylbenzene or tetralin is used as the first solvent and / or the second solvent. The method for separating fullerene C60 according to claim 1, wherein the activated carbon has a specific surface area of 1600 m ² / g or more. Heating the rod-like material containing fullerenes, polycyclic aromatic hydrocarbons, and carbon-based polymer material under an inert gas to sublimate and separate the polycyclic aromatic hydrocarbons from the rod-like material; Next, a soot-like substance containing fullerenes and a carbon-based polymer substance and an extraction solvent are mixed to obtain an extract in which the fullerene mixture is dissolved, and the extract is mixed with activated carbon in (1) and filtered. The method for separating fullerene C60 according to any one of claims 1 to 5, wherein the first liquid is obtained by: The method for separating fullerene C60 according to claim 6, wherein the extraction solvent contains 1,2,4-trimethylbenzene or tetralin. The fullerene C60 according to claim 6 or 7, wherein the rod-like substance containing fullerenes, polycyclic aromatic hydrocarbons and carbon-based polymer substances is obtained by combustion and / or thermal decomposition of a hydrocarbon compound. Separation method.