RU2085484C1 - Method and apparatus for production of fullerenes - Google Patents

Abstract

FIELD: synthetic carbon materials. SUBSTANCE: invention relates to producing lubricating, accumulator, and composite materials for optical electronics, and drugs. Method consists in mixing carbon black, graphite, and wastes of stock, pressing resulting stock, and heat drying under vacuum in fullerene synthesis chamber. Heating of stock is effected to temperature of emitting surface 4300 ± 100 C using resistive, induction, magnetron, or another method. Stock is shaped in such a way as to provide countercurrent or crossing streams of carbon clusters. At the same time, produced fullerenes are separated from carbon black through evaporation from carbon black collectors by heating them to 700-900 C. Fullerenes are simultaneously separated according to their molecular weight on collectors heated to develop temperature gradient 400-480 C. Apparatus has water-cooled chamber 1 with heating element 2 in its center and, displaceable by mechanism 5, emitter 3 of carbon stock. Carbon black collectors 7,8 are made in the form of heat-resistant material containers. Fullerene collectors 11-16 are made as copper rings with vertical channels. Content of fullerenes is 5-20 wt % or higher. EFFECT: enhanced efficiency of process. 16 cl, 5 dwg, 1 tbl, 5 ex

Description

 The invention relates to the field of processes and apparatus for the synthesis, purification and separation of fullerenes.

For the first time, fullerene synthesis has been described as the process of evaporation of graphite electrodes by resistive heating or in an arc in an inert gas atmosphere (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 the production of about 1 g of a mixture of fullerenes in frequent with a content of fullerenes in soot up to 15%
Other methods for the synthesis of fullerene-containing soot are known: 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, No. 8, p. 947-953; "Production of fullerenes by near-infrared laser ", L. Laska, Czech, J. Phys. 1993, Vol. 43, No. 2, p. 193-195),
pyrolysis and combustion of aromatic hydrocarbons ("Calculated equilibrum yields of C60 from hidrocarbon pyrolysis and combustion", JT McKinnon, J.Phys. Chem. 1991, Vol. 95, No. 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 ", JB Howard, 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, No. 1, p. 1-14),
electric discharge ("A simple technique of producing fullerenes from electrically discharged benzene and toluene", DK Modak, et. al. Indian J. Phys. A. 1993, Vol. 67, No. 4, p.307-310),
in 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, No. 23, p. 2782-2783),
including laser ("Fullerenes from laser production plasma", PSR Prasad, et. al. Phys. Stat. Sol. A. 1993, Vol. 139, No. 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 gas atmosphere.

 In addition, a method is known based on the evaporation of graphite by an electron beam in 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", RF Bunshah, et. Al. J.Phys. Chem. 1992, Vol. 96, N 17, p. 6866-6869).

 The soot obtained in all of the above methods is either scraped off from the walls of the evaporation chamber, and the fullerenes are extracted from it with organic solvents (Supercritical fluid extraction of fullerenes C and C from carbon soot, S. Saim, et. Al. Sep.Sci.Technol. 1993 Vol. 28, No. 8, p. 1509-1525) and are separated by chromatographic ("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 other methods ("Separation of C60 and C70 with activated carbon", T. Rong, et. Al. Yingyong Huaxue, 1994, Vol. 11, No. 3, p. 112 -114; "High-purity vapor phase purification of C", RD Averitt, et. Al. Appl. Phys. Letters, 1944, Vol. 65, No. 3, p. 374-376). Or, the soot is transferred from the evaporation chamber of the arc reactor by an inert gas flow into the chamber with mechanical filters separating the fullerenes from the soot, and then the fullerenes are separated by a temperature gradient in the gas flow ("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).

 Closest to the proposed method and device are the method and device for the production of fullerenes described in the application WO 94/004461, cl. C 01 B 31/00, 1994.

 All the above technologies allow to obtain only small amounts of fullerenes, which can be used only for experimental purposes. Obtaining fullerenes in significant quantities that satisfy the needs of industry, these methods are impossible.

 An object of the invention is to provide the possibility of producing fullerenes in quantities that satisfy the needs of industry, by increasing the productivity of the synthesis of fullerenes, as well as reducing waste in the production of fullerenes. An object of the invention is also the provision of purification and separation of fullerenes in the process of their synthesis.

The invention is based on the observation that fullerenes do not form directly from diamond under any conditions, and vice versa, the more crystalline fragments of the “graphite” type, that is, flat C ₆ hexagons, are contained in the starting material, the higher the yield of fullerenes. Consequently, the primary building material for fullerenes are not single atoms or low-atomic clusters with less than six atoms, but flat fragments of the crystalline structure of graphite. Such fragments are formed with significantly lower energy impacts on the substance than is required for atomization. From this point of view, the known methods for the synthesis of fullerenes are fundamentally ineffective, since in them a significant part of the thermal energy applied from outside or generated during the reaction is spent specifically on carbon atomization.

 At the same time, as shown by experiments on a time-of-flight mass spectrometer, the lifetime of large carbon clusters with the number of atoms n> 18 is less than 10 ms (in vacuum). Consequently, the cluster density should be low enough so that they can interact in a time less than 10 ms and form a stable closed fullerene structure.

 The necessary synthesis conditions are achieved in vacuum if counter flows of low-energy clusters are emitted from the surface of a heated graphite-containing solid.

Thus, the problem is solved in that in the method for the production of fullerenes, which includes the formation of carbon clusters with a flat hexagonal structure by heating a solid carbon-containing preform to an emitting surface temperature of 4300 ± 100 ^o C, close to the melting point of graphite, and the subsequent synthesis of fullerene molecules from them , heating the preform and the synthesis of fullerene molecules is carried out in vacuum, while the synthesis is carried out in opposing or intersecting flows of carbon clusters.

 In this case, the heating of the solid carbon-containing preform is carried out by the resistive, induction, magnetron, laser or other method.

 To increase the yield of fullerenes, the workpiece is brought into oscillation with a sound or supersonic frequency, while the optimal frequency range during heating is from 8 to 40 kHz. Apparently, this phenomenon is due to the formation of standing waves in the atmosphere of carbon vapor, which improves the conditions for the interaction of clusters with each other.

 The problem is also solved by the fact that the formation of counter-directed or intersecting flows of carbon clusters during heating of the workpiece is achieved by giving the solid carbon-containing workpiece a special shape. In this case, the workpieces parallel or at small angles of the surface are mutually heated by radiation, and their temperature significantly exceeds the temperature on the external surfaces, and in the case of surface heating, the temperature inside the volume.

 In addition, simultaneously with the synthesis of fullerene molecules, they are separated from soot.

In particular, the separation of fullerenes from soot is carried out by evaporation of fullerenes from soot collectors by heating them to 700-900 ^o C.

 In addition, after separation of fullerenes, carbon black is collected, soot is mixed with graphite powder, a new preform is pressed from this mixture, and it is dried in vacuum.

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

 In addition to separating fullerenes from carbon black, simultaneously with the synthesis of fullerene molecules, they are divided into fractions by molecular weight.

In particular, the separation of fullerenes into fractions is carried out on collectors heated to form a temperature gradient from 400 to 480 ^o C.

 The problem is also solved by the fact that in the device for the synthesis of fullerenes, including an emitter made of a solid carbon-containing preform placed in the working chamber, and the means for heating the emitter with an energy source, the working chamber is made vacuum, the emitter has a shape that provides the formation of opposite intersecting flows of carbon clusters when it is heated, while the device is additionally equipped with a means for feeding and moving the workpiece and a control unit for heating Mitter.

 In addition, the device is additionally equipped with a soot collector installed in the working chamber.

 In addition, the device is additionally equipped with collectors of fullerenes, made with the possibility of separating fullerenes into fractions by molecular weight.

In particular, the soot collector is made in the form of two containers made in the form of rings of heat-resistant metal, mounted concentrically with respect to a vertically arranged emitter, and separated by a quartz ring, providing heating of the containers to 1200-2000 ^o С, while the upper ring of the collector is closed from above , and the bottom bottom with molybdenum filters with holes.

 In particular, the fullerene collectors are made in the form of two copper rings with vertical channels mounted directly on the upper and under the lower containers of the soot collector.

 To increase the output of fullerenes, the power supply is made in the form of an alternating current source with a frequency of 8 to 40 kHz.

 In FIG. 1 shows a diagram of a process for the production of fullerenes; in FIG. 2 is a diagram of molecular flows in the formation of fullerenes in vacuum; in FIG. 3 - possible options for carbon emitters and methods for their excitation: a) resistive and b) induction heating; in FIG. 4 the dependence of the output of fullerenes on the frequency of the alternating current with a) resistive and b) induction heating; in FIG. 5 shows a device for synthesis, separation from soot and separation of fullerenes.

 A diagram of the production process of fullerenes is shown in figure 1.

 Mixture preparation includes homogenization in a mixer of a mixture of graphite powder, soot and the remains of the previous workpiece.

 Pressing blanks in the form of washers is carried out on the press.

The preforms are dried first in an electric furnace in air at a temperature of 400 ^o С, and then directly in the working chamber of the installation at a temperature of 1000 ^o С with evacuation of evolved gases by a vacuum pump.

The synthesis of fullerenes in vacuum occurs between parallel or angled surfaces of heated preforms. Effective emitting of metastable clusters С _n , where n 2-18, begins at Т _crit 4300 ± 100 ^o С, which is close to the melting point of graphite. The emitting surfaces mutually heat radiation (Fig. 2) to temperatures T ₂ , T ₃ > T _crit 4300 ^o C. The temperature on them exceeds the temperature both on the outer surfaces of the workpiece (T), which lose heat due to radiation, and inside the volume of the workpiece (T), where the heating energy does not penetrate. In order to avoid complete destruction of the emitter, the process of synthesis of fullerenes should be carried out quickly enough so that the average temperature of the emitter does not have time to equalize due to thermal conductivity with the temperatures on the emitting surfaces. This requirement is achieved under conditions of a sufficiently developed emitter surface and a sufficiently large power source. As a result, only emitting surfaces are melted and converted into fullerenes, and the less heated parts of the emitter are stored in solid form and can be used as raw materials for re-synthesis. The specific values of the input power and the synthesis time are determined by the shape of the emitter and the method of supplying energy and can vary from 100 kW and above and from 10 to 60 s. In this case, 10-70 masses of the emitter can turn into fullerene-containing soot with a useful product content of 5-20% and higher.

Example 1. A blank of reactor graphite weighing 127.3 g, the shape of which is shown in FIG. 3b with a diameter of 60 mm, a height of 30 mm, was placed in a water-cooled inductor in a vacuum chamber. A vacuum of 10 ^-5 mm RT was reached in the chamber. Art. then a voltage of 700 V was applied to the inductor at a current of 300 A with a frequency of 10 kHz. After 10 seconds, the temperature on the outer surface of the workpiece reached 4000 ^° C, and on the inner surfaces of the annular grooves 4350 ^° C. After 10 seconds, the power source was turned off and the chamber was cooled, then evacuated and opened. The mass of the billet residue was 64.7 g, and 54.4 g of a dark brown powder of the following composition was collected by mechanical scraper from the chamber walls, g: solid impurities insoluble in toluene 43.2; C ₆₀ 10.8; C ₇₀ 0.13; the sum of higher fullerenes 0.27.

Example 2. Billet from reactor graphite weighing 17.4 g, the shape of which is shown in FIG. 3a, with a diameter of 4 mm and a height of 100 mm, after preliminary heating at 1000 ^° C, it was placed in a vacuum chamber at a pressure of 10 mm Hg. Art. A voltage of 50 V was applied to the workpiece through vacuum contacts at a current of 400 A with a frequency of 50 kHz. After 5 s, the temperature on the outer surface of the workpiece reached 4000 ^o С, and on the inner surfaces of the annular grooves 4300 ^o С. After 10 s, the power source was turned off and the chamber was cooled, then evacuated and opened. The mass of the workpiece residue was 15.3 g, and 1.5 g of the black powder of the following composition was collected from the walls of the chamber and current leads, g: solid impurities insoluble in toluene 1.3; C ₆₀ 0.16; C ₇₀ 0.11; the sum of higher fullerenes 0.02.

 In practice, the synthesis can be carried out in the device depicted in figure 5.

 The main part of the device is a water-cooled chamber 1 made of stainless steel, in the center of which a heating element 2 is placed, for example, a ring water-cooled inductor made of copper. On the axis of the heating element of the inductor moves the emitter 3, which is a rod made up of washer blanks and fixed from above and below by the holders 4. The movement is carried out using the mechanism 5 for feeding the blanks. The chamber is evacuated, and the movement of the workpieces occurs without violating the vacuum due to the use of bellows 6.

 When the heating element is turned on, for example, when the inductor is connected to a powerful high-frequency current source, the outer surfaces of the washers inside the heating element, such as the inductor, are heated. The movement mechanism 5 moves the workpieces at such a speed that the outer parts of the washer blanks almost completely evaporate, while the internal parts do not have time to melt. In the cavities formed by the protruding edges of the washers, the intense formation of fullerenes and soot occurs.

 After evaporation of 50-70% of the material of the initial billet, the power source is turned off, and the chamber is cooled and evacuated. The final product in this case is fullerene-containing soot, which is removed mechanically from the chamber.

If it is necessary to obtain a pure mixture of fullerenes separately from the soot, the upper 7 and lower 8 soot collectors are installed in the chamber 1, which are containers of heat-resistant metal, for example tungsten, in the form of rings. In order to reduce losses of electromagnetic energy, the collectors do not have galvanic contact with each other, however, they are heated by a heating element 2, for example, an inductor, through a quartz ring 9. The thickness of the ring is selected so that during the synthesis the collectors are heated to 1200-2000 ^o C. Upper collector 7 closed at the top, and the bottom 8 at the bottom with molybdenum filters 10 with holes 10-100 microns.

During synthesis, about 90% of soot accumulates in the lower collection, the rest in the upper. At the indicated temperature, the fullerene sublimates and diffuses through the soot to less heated parts of the chamber. Thus, soot accumulates in the collectors, while fullerenes condense on the walls of the chamber, from where they can be removed mechanically. The final product here is a mixture of fullerenes C ₆₀ , C ₇₀ and higher, as well as carbon black, suitable for further use, including for the next synthesis cycle.

If necessary, the separation of fullerenes into fractions by molecular weights can be performed. For this purpose, upper 11, 12, 13 and lower 14, 15, 16 fullerene collectors, which are copper rings with vertical channels, are installed in chamber 1 on soot collectors 7 and 8. The collectors are heated due to thermal conductivity from soot collectors, and a gradient from 480 from 400 ^o C. is formed along their channels.

In the process of synthesis, pairs of fullerenes from soot collectors pass through the channels of the fullerene collectors and condense in them in accordance with their sublimation temperatures, which depend on molecular weight. A mixture of higher fullerenes C ₇₆ , C _82, and others on collectors 12 and 15 C ₇₀ , on collectors 11 and 16 C ₆₀ condenses on nearby collectors 13 and 14. The final products here are carbon black, which can be used in subsequent synthesis, and these fullerene fractions.

 The operation of the device for the production of fullerenes is illustrated by examples.

Example 3. For the synthesis, a mixture was prepared from 40% of the residues of the blanks from the previous synthesis, 40% of the carbon black obtained during the synthesis, and 20% of especially pure graphite powder. The mixture was homogenized in a mechanical mixer, and blanks were pressed from it in the form of washers with a diameter of 80 mm, a height of 30 mm, and a mass of 130 g each. The pressing was carried out on a mechanical press with a force of 30 tons. The washers were heated in an electric furnace at 400 ^o C.

A rod was composed of 16 washers with a total mass of 2080 g and placed in a chamber with an inductor with a diameter of 100 mm. The chamber was closed and evacuated to 10 ^-5 mm Hg.

10 s after connecting a power source of 100 kW, 10 kHz, a mechanism 5 was set in motion, which moved the workpiece from the bottom up through the heating element inductor at a speed of 500 mm / min. After the entire billet passed through the heating element-inductor, the power supply was turned off, the chamber was re-pumped to 10 ^-5 mm Hg. and a power of 250 kW was applied to the heating element-inductor. After 10 seconds using the movement mechanism, the workpiece was again drawn through the heating element-inductor in the direction from top to bottom at the same speed. After the entire workpiece passed through the heating element-inductor, the power supply was turned off, the chamber was cooled and evacuated.

The remains of the preform with a total weight of 810 g and fullerene-containing soot with small fragments of the preform with a total weight of 1260 were extracted from the chamber. The soot consisted of 79% of solid components insoluble in toluene: 20.2% C ₆₀ , 0.4% C ₇₀ and 0, 5% mixture of higher fullerenes.

 Example 4. The same blanks were used as in example 3, however, soot collectors 7 and 8 were installed in chamber 1. The synthesis was carried out in the same mode as in example 3.

After the chamber was opened, 805 g of the remainder of the billet were recovered, 980 g of soot containing no fullerenes from soot collectors, and 290 g of black-brown powder of the following composition were removed from the walls of the chamber and internal parts: 9.2% of solid components insoluble in toluene, 86, 4% C ₆₀ , 1.8% C ₇₀ and 2.6% of a mixture of higher fullerenes.

 Example 5. The same blanks were used as in example 3, however both soot collectors 7 and 8 and fullerene collectors 11-16 were installed in chamber 1. The synthesis was carried out in the same mode as in example 3.

 After the chamber was opened, 807 g of the remainder of the billet were recovered; 978 g of carbon black containing no fullerenes were collected from soot collectors; preparations were collected from the fullerene collectors, the mass and composition of which are given in the table. In addition, 10.6 g of a mixture of 50% fullerenes, 45% carbon black, and 5% debris were collected from the internal parts and walls of the chamber.

 Fullerenes, whose existence was established in the mid-80s, and an efficient production technology was developed in 1990, are of great applied value.

 Interest in the study of fullerenes is associated, on the one hand, with a wide variety of new physicochemical phenomena that occur with the participation of fullerenes, and on the other hand with the diverse prospects for the application of this new class of substances.

 The results of studies carried out in recent years indicate significant prospects for the use of fullerenes and materials based on them in various fields of science and technology. So, the use of fullerenes as an additive to lubricating oil significantly (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 the basis for the production of batteries with higher efficiency, low weight, as well as environmental and sanitary safety compared to modern batteries.

 Other possibilities of commercial applications of fullerenes are also being actively developed, in particular, with the development of new composite materials, the creation of dyes for copiers, photodetectors, memory elements and optoelectronic devices, diamond and diamond-like films, drugs, superconducting materials, etc. Deserves special attention. the problem of using fullerenes in medicine and pharmacology, especially the idea of creating anti-cancer drugs based on water-soluble compounds ny fullerenes.

 Currently, the widespread adoption 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 does not have fundamental performance limitations and provides a waste-free and environmentally friendly process for the synthesis of fullerenes.

Claims (16)

1. A method for the production of fullerenes, including the formation of carbon clusters with a flat hexagonal structure by heating a solid carbon-containing preform and the subsequent synthesis of fullerene molecules from them, characterized in that the preform is heated to an emitting surface temperature (4300 ± 100) ^o C and fullerene molecules are synthesized in vacuum, while the synthesis is carried out in counter-directed or intersecting flows of carbon clusters.  2. The method according to claim 1, characterized in that the heating of the solid carbon-containing preform is produced by the resistive, or induction, or magnetron, or other method.  3. The method according to claim 1 or 2, characterized in that the heating is carried out using an alternating electric current with a frequency of 8 to 40 kHz.  4. The method according to claim 1 or 2, characterized in that the solid carbon-containing preform is shaped to ensure the formation of counter-directed or intersecting flows of carbon clusters when it is heated.  5. The method according to claim 1, characterized in that, simultaneously with the synthesis of fullerene molecules, they are separated from soot. 6. The method according to p. 5, characterized in that the separation of fullerenes from soot is produced by evaporation of fullerenes from soot collectors by heating them to 700 900 ^o C.  7. The method according to claim 5 or 6, characterized in that after separation of the fullerenes, soot is collected, soot is mixed with graphite powder, a new preform is pressed from this mixture and dried in vacuum.  8. The method according to claim 7, characterized in that the casing is dried by heating it in a vacuum chamber for the synthesis of fullerenes.  9. The method according to claim 1, characterized in that at the same time as the synthesis of fullerene molecules, they are divided into fractions by molecular weight. 10. The method according to p. 9, characterized in that the separation of fullerenes into fractions is carried out on collectors heated to form a temperature gradient of 400 480 ^o C.  11. A device for the synthesis of fullerenes, comprising an emitter made of a solid carbon-containing preform placed in the working chamber, and means for heating the emitter with a power source, characterized in that the working chamber is vacuum, the emitter has a shape that provides the formation of counter-directed or intersecting carbon flows clusters when it is heated, while the device is additionally equipped with a means for feeding and moving the workpiece and a control unit for controlling and controlling the heating of the emitter.  12. The device according to p. 11, characterized in that the power source is made in the form of an alternating current source with a frequency of 8 40 kHz.  13. The device according to PP.11 and 12, characterized in that it is additionally equipped with a soot collector installed in the working chamber. 14. The device according to item 13, wherein the soot collector is made in the form of containers made in the form of rings of heat-resistant metal, mounted concentrically relative to a vertically arranged emitter and separated by a quartz ring, which provides heating of containers to 1200 2000 ^o С, at In this case, the upper ring of the collector is closed at the top, and the lower - at the bottom with molybdenum filters with holes.  15. The device according to claim 11, characterized in that it is further provided with collectors of fullerenes, made with the possibility of separating fullerenes into fractions by molecular weight.  16. The device according to p. 15, characterized in that the fullerene collectors are made in the form of two copper rings with vertical channels mounted directly on the upper and under the lower containers of the soot collector.

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