Method of industrial production of fullerenes

The invention relates to a process for the industrial synthesis, separation and purification of fullerenes.

Fullerene synthesis was first described as a process of evaporation of graphite electrodes in the resistive heating or arc under inert gas (Kraetsmer, et. Al. "Solid C60: A new form of carbon", Nature, Vol.247, p. 354-357, on Sep. 27, 1990; "Production, characterization, and deposition of carbon clusters", YK Bae, et. al. Clasters claster- assem.mater. 1991, p. 733-741 (Mater.res.soc.symp.proc . Vol. 206). This method allows to produce a mixture of about 1 g fullerene per hour when the content of the fullerenes in the soot and 15% are other known methods for synthesizing fullerene-containing soot: laser ablation ("The formation of hydrogenated carbon clasters by laser ablation", N. Zhang, et. al. Chem. Phys.Letters, 1993, Vol. 205, N 2/3, p.178-182; "Laser ablation of carbonaceous materials: a method to produce fullerens", E. Millon, et. al . CR Acad. Sci. 11, 1992, Vol. 315, N 8, p.947-953; "Production of fullerenes by near-infrared laser", L.Laska, Czech, J. Phys. 1993, Vol.43, of N 2, p.193-195), pyrolysis and combustion of aromatic hydrocarbons ("Calculated equilibrum yields of C60 from hidrocarbon pyrolysis and combustion", JTMcKinnon, J. Phys. Chem. 1991, Vol. 95, N 22, p. 8941-8944; "Formation of C60 by pyrolysis of naphthalene", R.Taylor, et. al. Nature, 1993, Vol. 366, N 6457, p. 728-731; "Production of C60 and C70 fullerenes in benzene / oxigen flames", JBHoward, et. al. J.Phys. Chem. 1992, Vol.96, N 16, p.6657-6662; "Pyrolysis of KH carbon residues: a method of further production of fullerenes and specific formstion of C", JVWeber, et. al. J.Anal. Appl. Pyrolysis, 1994, Vol. 29, N 1, p.1-14), electric discharge ("A simple technique of producing fullerenes from electrically discharged benzene and toluene", DKModak, et. Al. Indian J. Phys. A. 1993, Vol. 67, N 4, p.307-310), plasma ("Formation of fullerenes in MeV ion track plasmas", G.Brinkmalm, et. al. Chem. Phys. Letters, 1992, Vol. 191, N 3/4, p. 345-350; "Novel method for C60 synthesis: a thermal plasma at atmospheric pressure", K. Yoshie, et. al. Appl. Phys. Letters, 1992, Vol. 61, N 23, p. 2782-2783), in including a laser ("Fullerenes from laser production plasma", PSR Prasad, et. al. Phys. Stat. Sol. A. 1993, Vol. 139, N 1, p.K1-K5), concentrated sunlight ("Solar generation of fullerenes ", LPFChibante, et. al. J.Phys. Chem. 1993, Vol. 97, N 34, p.8696-8700).

Common to all these methods is the presence of an inert atmosphere.

In addition, a method based on electron beam evaporation of graphite in a vacuum ("Electronic sputtering of fullerenes and the influence of primary ion charge state", G.Brincmalm, et. Al. Nucl. Instrum. Methods Phys. Res. B. 1994 , Vol. 84, N 1, p.37-42; "Fullerene formation in sputtering and electron beam evaporation processes", RFBunshah, et. al. J.Phys. Chem. 1992, Vol. 96, N 17, p.6866 -6869).

The resulting carbon black in all these ways, or is scraped from the walls of the evaporation chamber, and fullerenes are extracted from her organic solvents ("Supercritical fluid extraction of fullerenes C and C from carbon soot", S. Saim, et. Al. Sep.Sci.Technol. 1993 , Vol.28, N 8, p.1509-1525) and separated by chromatography ("Purification of gram quantities of CA new inexpensive and facile method", WAScrivens, et. al. J.Amer. Chem. Soc. 1992, Vol. 114, V 20, p. 7914-7919) or by other methods ("Separation of C60 and C70 with activated carbon", T.Rong, et. al. Yingyong Huaxue, 1994, Vol. 11, N 3, p.112- 114.

The closest to the invention is a method for producing fullerenes described in the article Kraetsmer etal. currently used for the production of fullerenes. This method, like other prior art methods have the following disadvantages.

All of the above technologies provide only small amounts of fullerenes that may be used only for experimental purposes. Production of significant quantities of fullerenes satisfying the industry needs, this method is not possible. Furthermore, in the process of evaporation of graphite on the workpiece can be formed of graphite isothermal layer preventing further evaporation, increase the pressure of the gases inside the billet, leading to its destruction, whereby the heating process is terminated.

An object of the invention is to enable production of fullerenes in amounts satisfying the needs of the industry by increasing the productivity of synthesis of fullerenes, as well as reducing waste in the production of fullerenes. An object of the invention is to ensure the separation and purification of fullerenes in the process of their synthesis.

The invention is based on the observation that the diamond directly from fullerenes do not form under any circumstances, and on the contrary, the more a substance is contained in the original crystalline fragments "graphite" type, that is flat hexagons C6, the higher the yield of fullerenes. Consequently, the primary building material for fullerenes are not single atoms or clusters maloatomnyh atoms less than six, and flat pieces of crystalline structure of graphite. Such fragments are formed at much lower energy impact on substance than is required for atomization. From this point of view the known methods for synthesis of fullerenes essentially ineffective as a significant portion of them externally applied or formed during the reaction heat energy is consumed for atomizing carbon.

At the same time, as shown by experiments on time-of-flight mass spectrometer, the lifetime of large clusters of carbon atoms n> 18 is less than 10 ms (in vacuo). Therefore, the density of clusters should be such that they could in less than 10 ms react and form a stable closed structure of fullerene.

Necessary conditions for synthesis are achieved in vacuum or an inert gas if the counter flows organized clusters of low-energy emitted from the surface of the heated graphite solid with simultaneous removal of the surface layer with isothermal graphite.

Thus, the problem is solved by a method for producing fullerenes comprising the formation of carbon clusters with planar hexagonal structure by heating the solid carbonaceous preform to a temperature of the emitting surface of 4300 ± 100 ° C and subsequent synthesis of these fullerene molecules, synthesis of fullerenes produced in the opposite direction, and / or intersecting flows of carbon clusters, while simultaneously heating the preform produce localized heating surface of the workpiece by arc electric discharge, the stain local heating is moved over the surface of the workpiece, and the temperature of the local heating and the velocity of the spot local heating is selected from the condition of destruction layer insulated graphite.

In the particular case of heating the workpiece and produce a synthesis of the fullerene molecules in a vacuum, the solid carbonaceous preform is shaped, oppositely directed to ensure the education and intersecting streams of carbon clusters when it is heated, and the displacement of local heating spots by rotating the workpiece. In this parallel or under small angles mutually workpiece surface heat emission, and their temperature significantly exceeds the temperature on the external surfaces and in the case of surface heating and temperature inside the volume.

In another particular case of heating the workpiece and the synthesis of fullerenes produced in argon, opposite direction and / or cross flow of carbon clusters provide a magnetic field formed by the electric arc and the coil annular magnetron, installed coaxially with the workpiece and moving the spot of the local heating is carried out by annular magnetron, while providing additional heat emitting surface by exposure to the argon ions generated in the plasma electric arc.

At the same time heating the solid carbonaceous preform produce resistive, inductive, magnetron, laser or other method.

To increase the yield of fullerenes preform brought into oscillation by sound or supersonic speed, wherein an optimum range of frequencies when the heating is from 8 to 40 kHz. Apparently, this phenomenon is caused by the formation of standing waves in a vapor atmosphere of carbon that improves cluster interaction with each other.

In addition, simultaneously with the synthesis of fullerene molecules produce their separation from soot.

In particular, the separation of fullerenes from soot produced by evaporating fullerenes from soot collections by heating them to 700-900oS.

Additionally, after separation of fullerenes collect soot, carbon black is mixed with graphite powder and pressed from this mixture a new workpiece and dried in vacuo.

In particular, the drying of the preform is performed by heating it in a vacuum chamber for the synthesis of fullerenes.

In addition to the separation of fullerenes from soot simultaneously with the synthesis of fullerene molecules produce their separation into fractions by molecular weight.

In particular, the separation into fractions of fullerenes produced on the collectors heated to form a temperature gradient from 400 to 480oS.

FIG. 1 shows a diagram of the process of production of fullerenes; FIG. 2 - scheme of molecular flows during the formation of fullerenes in vacuo using a special form of the workpiece; FIG. 3 illustrates exemplary embodiments of the carbon emitters and methods of excitation: a) the resistive and b) induction heating; FIG. 4 shows the dependence of the yield of fullerenes frequency alternating current at a) the resistive and b) induction heating.

The process scheme of production of fullerenes is shown in Figure 1.

Preparation includes homogenizing the mixture in the mixer the mixture of graphite powder, soot and residue preceding the preform.

Extrusion billets as washers carried on a press.

Drying first blanks produced in an electric furnace in air at a temperature of 400C, and then directly into the working chamber at a temperature of 1000C installation with evacuation of gases evolved vacuum pump.

Synthesis of fullerenes in vacuo occur between parallel or angled surfaces located heated preforms. Effective emittirovanie metastable clusters C n, where n 2.18 Tkrit begins at 4300 ± 100 ° C, which is close to the melting point of graphite. Emitting surface of mutually heat radiation (2) to a temperature T1, T2> Tkrit 4300oS. The temperature at which the temperature is superior to both the outer surface of the workpiece (T1), which lose heat by radiation and within the scope of the workpiece (T0), which does not penetrate the heating energy. To prevent the complete destruction of the emitter the process of synthesis of fullerenes should be carried out quickly enough that the average temperature of the emitter did not have time due to the thermal conductivity of the temperature on the emitting surface. This requirement is achieved under the conditions of a fully developed surface of the emitter, and a sufficiently large capacity power supply is available. As a result, only the fusion emitting surfaces and their conversion into fullerene, and at least part of the heated emitter retained in solid form and can be used as raw materials for re-synthesis. Particular values ​​of input power and time determined by the shape of the emitter synthesis and method for supplying energy, and may vary in the range of 100 kW or more and 10 to 60. Thus 10-70% of the mass of the emitter can turn in fullerene soot containing useful product of 5-20% and above.

Opposite directions and intersecting streams of carbon clusters can be arranged in an argon atmosphere by overlapping magnetic fields. The ionized argon atoms striking the surface of the workpiece is selected metastable carbon clusters.

When the temperature of the preform 3500-4500oS on its surface, a layer of graphite isothermal. To remove this layer from the surface of the workpiece between the workpiece (cathode) and the housing chamber (anode) electrical arc is ignited. Furthermore, in the case of filling the chamber with argon, argon ions formed in the plasma arc impinges on the workpiece surface and further heats it, knocking carbon clusters. When using special blank forms the cathode spot is moved across the emitting surface of the workpiece by rotating the workpiece. In another case, the cathode spot is rotated uniformly at the cylindrical end surface of the workpiece forms with the annular magnetron. In place of the cathode spot occurs 6000oS temperature and higher evaporating thus isothermal layer of graphite in the area of ​​local heating and opening the possibility of further emittirovaniya carbon clusters. Modes (rotational speed of the cathode spot, the velocity of vertical movement preform temperature at a spot of local heating) is selected so that the smallest hexes graphite subjected to evaporation.

In practice, the synthesis can be carried out in a device main part of which is water cooled or filled with argon Evacuated chamber made of stainless steel, which is located in the center of the heating element, for example, circular water-cooled copper induction coil. The axis of the heating element is an inductor emitter is a rod composed of washers workpieces or workpiece cylindrical shape.

When the heating element, for example, by connecting the inductor to a powerful high-frequency heating of the source current is the emitting surface of the workpiece. The mechanism of movement is the movement of blanks at a rate such that the outer part of the washer blanks almost entirely disappeared, and the interior did not have time in this rasplavitsya.V cavities formed protruding edges of washers, there is an intensive formation of fullerenes and soot. Simultaneously, by applying a potential difference between the workpiece and the camera body is ignited arc. Movement of the cathode spot can also be achieved by rotating the workpiece.

In another embodiment, the intersecting flows carbon clusters emitted from the end surface of the workpiece, arranged by applying a magnetic field of a ring of the magnetron, a coil which is placed over the end surface of the workpiece. Rotation of the cathode spot, wherein a zone of local heating is performed by supplying current to the coil of the annular magnetron.

After evaporation of 50-70% of the original workpiece material source of power supply is turned off and the camera is cooled and razvakuumiruetsya. The end product in this case is a fullerene-containing soot, which is removed from the chamber by mechanical means.

If necessary, obtain a pure mixture of fullerenes from soot separately into the chamber is set upper and lower soot collections representing the heat-resistant metal containers, for example tungsten, in the form of rings. In the process of synthesis compilations heated to 1200-2000oS. Upper collection closed at the top and bottom of the lower molybdenum filters with openings of 10-100 microns.

In the synthesis of about 90% of the soot accumulated in the lower collection and the rest at the top. At this temperature, it is sublimated fullerene and carbon black to diffusion through the less heated parts of the chamber. Thus, there is an accumulation of soot in the collection, while the fullerenes condense on the walls of the chamber, from where they can be removed mechanically. The final product is a mixture of C60, C70 and higher, as well as carbon black, suitable for further use, including for the next round of synthesis.

If necessary, the separation can be performed on fullerene molecular weight fractions. To do this, the camera on the collections of black and set the upper and lower collectors of fullerenes, is a ring of copper with vertical channels. The collectors are heated by conduction from the collections of the carbon black and the channels formed along their gradient from 480 to 400 ° C.

During the synthesis of fullerenes pair collections soot pass through the channels and reservoirs fullerenes condense them in accordance with their respective sublimation temperatures, which depend on the molecular weight. In the Middle collectors condensed mixture of higher fullerenes C76, C82 and the other on the other C70, C60 on the rest. The final products here are carbon black, which can be used in the subsequent synthesis and said fraction of fullerenes.

Fullerenes, the existence of which was established in the mid-80s, and effective technology for producing developed in 1990 are of great practical importance.

Interest in the research of fullerene linked, on the one hand, a wide variety of new physico-chemical phenomena that occur involving fullerenes, and on the other hand diverse perspectives applied use of this new class of substances.

The results of research carried out in recent years indicate significant prospects for the use of fullerenes and related materials in various fields of science and technology. Thus, the use of fullerenes as an additive to a lubricating oil substantially, up to 10 times reduces the coefficient of friction of metal surfaces and accordingly increases the wear resistance of parts and assemblies. Fullerenes can also be used as a basis for the production of batteries having a high efficiency, low weight, as well as environmental and health safety over current batteries.

Developed other features of commercial applications of fullerenes, relating in particular to the development of new composite materials, creating dyes for copiers, photodetectors, memory elements and optoelectronic devices, diamond and diamond-like films, medicines, superconducting materials, and others. Particularly noteworthy are the problem the use of fullerenes in medicine and pharmacology, especially the idea of ​​the creation of anti-cancer drugs on the basis of water-soluble fullerene compounds.

Currently, the widespread introduction of technologies using fullerene-containing materials is difficult due to the relatively high cost of these materials.

The proposed method for the production of fullerenes has no fundamental limitations on the performance and provides waste-free and environmentally friendly process for synthesis of fullerenes.