JPH0826710A - Method for refining fullerene - Google Patents

Abstract

PURPOSE:To produce high purity fullerene in large quantities at a low cost by simple chromatographic operation from soot or other starting material contg. Fullerene. CONSTITUTION:When crude fullerene is refined by chromatography for separating a component in large quantities, activated carbon coated silica or activated carbon is used as a filler in a column and the volume ratio of the filler to the crude fullerene is set in accordance with the adsorption capacity of the filler.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a purification method for obtaining high-purity fullerene from a fullerene-containing raw material. The obtained high-purity fullerene is expected to be applied to a wide range of fields such as superconducting materials, medical materials and the like.

[0002]

2. Description of the Related Art A few methods have already been announced for the purification of fullerenes by an activated carbon column, but they are not always satisfactory. For example, J. M. Tour et al. Mixed activated carbon from Norit Co., USA with silica for chromatography to form a column packing material, and purified crude fullerenes by this column, but the purity could not be increased to 99% or more by one purification. This is because the loading of crude fullerenes corresponding to the fullerene adsorption capacity of activated carbon pointed out by the present invention is not appropriate [J. Am. C
hem. Soc. , 114 , 7917 (1992)].

In addition, A. D. Darwish et al. Also studied the purification of crude fullerenes by mixing the same activated carbon and alumina for chromatography as a column packing material. As a result, it is said that the quality of separation and purification and the yield vary greatly depending on the mixing ratio of activated carbon and alumina [J. Chem. Soc. ，
Chem. Commun. , 1994 , 15]. Thus, the chromatographic purification method using activated carbon as a filler has many unsolved problems.

[0004]

Therefore, in the present invention, it is considered that in the purification by the activated carbon column, the adsorption capacity of the fullerene of the activated carbon determines the quality of the purification, and this is measured to set the loading amount of the crude fullerene in the universal purification. We have developed a method and improved it so that high purity and high yield can always be obtained. We also modified the activated carbon used and developed a new silica coated with activated carbon.

[0005]

[Means for Solving the Problems] In the fullerene purification by an activated carbon column, the above-mentioned A. D. Darwish
As mentioned above, we examined how to solve the problem that the quality of refining changes sensitively depending on the type of activated carbon. In other words, it is thought that this can be solved if the fullerene adsorption capacity of the activated carbon is known, and we have measured a wide range of activated carbon and devised a universal refining method that takes this into consideration.

At the same time, the inventors have reached the development of a new activated carbon-coated silica capable of controlling the adsorption capacity of activated carbon. These means will be described in detail below.

Up to now, since there is no example of measuring the fullerene adsorption amount of activated carbon, it was measured for a wide range of activated carbon. As a result, the adsorption of fullerenes by the activated carbon in the toluene solution substantially follows the Freundlich isotherm adsorption equation. For example, the adsorption capacity at an equilibrium concentration of 0.1 mg / ml ranges from a small amount of about 1 mg per 1 g of activated carbon to 100 mg or more.

On the other hand, as a result of examining the purification of crude fullerenes (mixture of C ₆₀ and C ₇₀ ) with these activated carbons under the same conditions, it was found that high-purity fullerene was obtained because activated carbons with a small adsorption capacity were not sufficiently separated. On the contrary, a large amount of activated carbon was easy to obtain a pure product of C ₆₀ , but the expected result was that the yield was extremely low. Therefore, in the case of activated carbon with a small adsorption capacity, we tried to reduce the load of crude fullerene, and conversely, in the case of large activated carbon, we tried to increase the load.
As a result, it was found that the purification with activated carbon, which has a small adsorption capacity, can sufficiently satisfy the purity and yield of the purified product by reducing the loading amount. However, the adsorption capacity is 100 mg
With the above large activated carbon, separation and purification is limited even if the crude fullerene loading is increased, and especially the yield of toluene elution is low, and it is necessary to switch to monochlorobenzene, dichlorobenzene, or trichlorobenzene with higher solubility. It was Moreover, in consideration of the fact that all the purification experiments can flow the elution solvent at a low pressure as much as possible, instead of using activated carbon alone
Although it was used as a mixture with silica or alumina, in the purification by elution with toluene, only the ratio of the column filling amount of activated carbon and the loading amount of crude fullerene was set, and the filling amount of silica or alumina did not affect the quality of purification. It was also accepted. That is, if the adsorption capacity of activated carbon in a toluene solution of fullerene is A (mg / g), the packed amount of activated carbon in a column is B (kg), and the loading amount of crude fullerene in a column is C (kg). It was concluded that high-purity fullerenes can be obtained in a high yield in a single chromatographic operation if the charging amount of activated carbon or the loading amount of crude fullerenes is set so as to satisfy the relationship shown in Table 1 or FIG.

As a result of further expanding the research and studying the trial production of a new activated carbon-coated silica, a method has been developed in which the fullerene adsorption capacity can be controlled by changing the production conditions.
For example, silica for chromatography is reacted or impregnated with a monosaccharide, a polysaccharide, a polycyclic aromatic compound, and various other polymer compounds, and activated by carbonization in an inert or oxidizing gas atmosphere at a temperature of 300 ° C. or higher by a conventional method. By the method, activated carbon coated silica with wide adsorption capacity of fullerenes was obtained.

[0010]

[Examples] The above will be described in more detail with reference to Examples. The present invention is not limited to these examples.

Example 1 Of the wide range of commercially available activated carbons tested, as typical ones, three fullerene adsorption capacities A of 4.0, 40.0, and 150 mg / g were selected, and the column packing amount was selected. B
kg and crude fullerenes (C ₆₀ about 80%, C ₇₀ about 20%
Chromatographic purification was carried out by changing the ratio B / C of the loading amount Ckg of the mixture) of 4 points for each activated carbon. When B / C was changed, silica for chromatography unrelated to purification was mixed and only B was changed, and C was determined. Further, as the solvent, first, toluene, then chlorobenzene, and finally o-dichlorobenzene were used in this order, and C ₆₀ and C ₇₀ were used under the same conditions.
Was purified by elution. The result is as shown in Figure 1,
The circles indicate that 99% or more of high-purity purified product was obtained in a high yield of 90% or more, and the X indicates that the purity or yield of the purified product was low. As you can see in the figure, the range where the best results are obtained is the area within the two diagonal lines,
It corresponds to the condition where a high-purity product cannot be obtained or a high yield cannot be obtained due to insufficient separation in the part outside the diagonal line (arrow 1 in FIG. 1).

Example 2 Chromatographic silica and phenyldimethylchlorosilane were reacted in a conventional manner to produce phenyldimethylsilica, which was impregnated with toluene solutions of polystyrene of various concentrations (1.0, 5.0, and 10%). And remove toluene under reduced pressure,
Dried. The impregnation rate for each concentration is 5.0, 2
1.5 and 54.0%. These impregnated silicas were placed in a ring furnace and the temperature was adjusted to 30
Carbonization was activated at 0 to 900 ° C. The fullerene adsorption capacities of the obtained activated carbon-coated silica were 7.8, 35.0, and 95.0 mg / g corresponding to the respective impregnation rates. Crude fullerenes were purified from these activated carbon-coated silicas in the same manner as in Example 1 and the same results as in FIG. 1 were obtained (arrow 2 in FIG. 1).

Example 3 Commercially available activated carbon having a fullerene adsorption capacity of about 100 mg / g was impregnated with a 10% sucrose solution, and the solvent was removed under reduced pressure.
It was dried to obtain sucrose-impregnated activated carbon having an impregnation rate of 30%. In the same manner, activated carbon impregnated with dextran, ethyl cellulose, polyvinyl alcohol, and polystyrene was obtained. These impregnated activated carbons were activated under the same conditions as in Example 2 to obtain modified activated carbons having a fullerene adsorption capacity of about 25 to 80 mg / g. Crude fullerenes were purified from these modified activated carbons in the same manner as in Example 1, and the same results as in FIG. 1 were obtained (arrow 3 in FIG. 1).

[0014]

EFFECTS OF THE INVENTION When crude fullerenes are purified by a simple chromatographic operation using activated carbon as a column packing, the quantitative relationship between the fullerene adsorption capacity of the activated carbon to be used, the filling amount in the column, and the loading amount of crude fullerenes is determined. High purity products can always be obtained in high yields by setting the ratio to.

As the activated carbon used for this purpose, commercially available silica may be simply mixed and used, but the activated carbon-coated silica of the present invention in which the adsorption capacity can be freely controlled is more convenient.

[Brief description of drawings]

FIG. 1 shows the range of conditions for purifying crude fullerenes by column chromatography. The vertical axis represents the amount B of activated carbon-coated silica (or activated carbon) packed in the column and the loading C of the fullerenes. Ratio B / C, and the horizontal axis represents the fullerene adsorption capacity A of activated carbon-coated silica (or activated carbon), and thus B / C vs A. The circles show the results that high-purity products were obtained in high yield when purified under these conditions, and the x marks show the results that either purity or yield was low. That is, the inside of the two shaded lines corresponds to the suitable range, and the outside of the shaded lines represents the unsuitable range. The arrows and numbers correspond to those in Examples 1 to 3.

Claims (4)

[Claims] 1. When obtaining high-purity fullerene from a fullerene-containing raw material by column chromatography, activated carbon-coated silica (or activated carbon) is used as a column packing, and the fullerene loading amount is adjusted according to the fullerene adsorption capacity. A characteristic method for purifying fullerenes. 2. In toluene, when the adsorption equilibrium concentration of fullerene is 0.1 mg / ml, the adsorption amount of fullerene on activated carbon-coated silica (or activated carbon) is Amg / g, the loading amount on the column is Bkg, and the crude fullerene is The method for purifying fullerenes according to claim 1, wherein the relationship of Table 1 is satisfied, where Ckg is the load amount of. [Table 1] 3. The activated carbon coating according to claim 1, which is obtained by reacting or impregnating silica with an organic compound to coat the surface, and carbonizing and activating in an inert gas or oxidizing gas atmosphere at a temperature of 300 ° C. or higher. Fullerene purification method using silica. 4. The activated carbon according to claim 1, which is obtained by fixing existing activated carbon as it is or impregnated with various inorganic or organic compounds and then fixing it at a temperature of 300 ° C. or higher in an inert gas or oxidizing gas atmosphere. Fullerene purification method.