Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Patent
1995-05-31
1997-12-16
Bos, Steven
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
210656, C01B 3100
Patent
active
056981740
DESCRIPTION:
BRIEF SUMMARY
Starting out from fullerene black, for example from electric arc plants, the fullerenes C.sub.60 /C.sub.70 and traces higher fullerenes can be isolated by extraction, preferably using toluene (R. Haufler J. Phys. Chem. 94, 8634 (1990)). Liquid chromatography (LC) in particular is then employed for separating fullerenes on a preparative scale. The stationary phase used here is silica gel, modified silica gels such as Pirkle phase or reversed-phase silica gels, aluminum oxide or graphite columns (A. Vassallo et al. J. Chem. Soc. Chem. Commun. 1992, 60). However, a satisfactory separation can only be achieved on these columns using solvent mixtures. Thus, for example, the aluminum oxide and also the graphite column are operated using a mixture of hexane (about 90%) and toluene (about 10%), but in contrast a reversed-phase silica column has to be eluted using toluene/alcohol or toluene/acetonitrile.
For an economical total process for isolating pure C.sub.60 or C.sub.70, it would be advantageous if extraction and chromatographic separation could be carried out using the same solvent. This should preferably be done using a solvent in which fullerenes are readily soluble, e.g. toluene.
The use of eluants having a low toluene content (e.g. toluene:hexane=10:90) is frequently problematical, since the extracts may crystallize on the column shortly after application and can hardly be redissolved during the course of chromatography, since the solubility of fullerenes in toluene mixtures, for example hexane:toluene=9:1, is significantly less than in pure toluene. For this reason, only a relatively small amount of fullerene can be applied to the column.
The use of pure toluene as eluant would significantly increase the loading of the separation column with crude fullerenes. Crystallization on the column would thus be able to be effectively prevented. In addition, the loading of the separation column would be able to be further increased if it were possible to carry out chromatography using toluene as eluant at elevated temperature.
M. Meier (JOC 1992, 57, 1924) was able to carry out the C.sub.60 /C.sub.70 separation using the system: Ultrastyragel (gel permeation material)/100% toluene. However, this process requires a very expensive column material which is normally used only for analytical purposes. Furthermore, the elution curve has no baseline separation.
It has now surprisingly been found that the chromatographic separation of fullerenes using nonpolar solvents as eluant in which the fullerene is readily soluble can be carried out using coke, anthracite and/or graphite as support material.
The invention accordingly provides a process for the chromatographic separation of fullerenes using a nonpolar aromatic solvent as eluant, wherein the support material used is coke, anthracite and/or graphite and the nonpolar aromatic solvent is the main constituent of the eluant.
Using the process, it is possible to separate, in particular, C.sub.60 from C.sub.70 fullerenes or C.sub.60 and/or C.sub.70 from other, preferably higher fullerene fractions. The fullerene material to be separated is obtained by preparation of fullerene black in an electric arc process and subsequent extraction with a nonpolar organic solvent (crude fullerene) as described, for example, in WO 92/04279. The crude fullerene can advantageously be separated off continuously by means of a decanter or in a batch process.
The support material coke, anthracite and graphite is, owing to its microstructure, crystal modification and porosity, particularly suitable for the described separation of fullerenes.
The following carbon materials are suitable for this purpose:
The ash content of the support materials should, owing to possible interactions, be limited, for example to <1-0.1%, with it being possible for higher values to still be tolerable. Which values are tolerable can be determined in simple experiments without inventive effort.
The carbon materials have to he introduced in milled form; the milling should not be too coarse (separation insufficiently sh
REFERENCES:
patent: 5098784 (1992-03-01), Ichikawa et al.
patent: 5227038 (1993-07-01), Smalley et al.
patent: 5310532 (1994-05-01), Tour et al.
Kremenskaya, I.N., et al., "Isolation of Individual Fullerenes . . . " Mendeleev Communications, vol.1, (1993), p.9. (May 3, 1993).
Pang, L.S.K. et al., "Fullerenes from Coal: A Self-Consistent Preparation and Purification Process" Energy & Fuels, 1992, 6, pp. 176-179 (Mar., 1992).
Meier, M.S. et al., "Efficient Preparative Separation of c.sub.60 . . ." J. Org. Chem. 1992, 57, pp. 1924-1926.
Vassallo, A.M. et al., "Improved Separation of Fullerene-60 and 70" J. Chem. Soc. Commun. 1992, No. 1, pp. 60-61 (Jan. 1992).
Broll Richard
Daimer Johann
Muller Roland
Muller Wolfgang
Weber Eckhard
Bos Steven
DiMauro Peter T.
Hoechst Aktiengesellschaft
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