MXPA99011325A - Method and device for producing fullerenes - Google Patents

Abstract

The invention relates to a method and a device for the continuous production of carbon black with a high fullerene content. The device essentially consists of a plasma reactor (1), a downstream heat separator (2) to separate the non-liquid constituents and a cold separator (3) attached thereto.

Description

METHOD AND DEVICE FOR PRODUCING FOLERENS DESCRIPTIVE MEMORY The invention relates to a method and a device for the continuous production of carbon black with high fullerene content. In the following, the term fullerene refers to molecular fullerenes, chemically homogeneous and stable. They are representatives of this group of fullerenes Cßo, C70 or Cs4- These fullerenes are generally soluble in aromatic solvents. A particularly preferred fullerene is fullerene CTO. For the production of carbon black containing fullerenes, several methods are known. However, the feasible concentration of fullerenes in the carbon black obtained is so low that a preparation of pure fullerenes is possible only with large outlays. Due to the high pressure resulting from pure fullerenes, interesting applications in different fields of technology are not conceivable a priori for economic reasons. The document of E.U.A. 5,227,038 discloses, for example, a laboratory apparatus that allows a few grams of fullerenes to be produced discontinuously by means of an electric arc between the carbon electrodes that serve as starting material. Apart from the fact that the quantities produced are small, the concentration of fullerenes C-60 in the carbon black deposited is very low and never exceeds 10% of the mass produced. In addition, the fullerene Cßo is present in this method in a mixture with higher fullerene compounds which require expensive fractional distillation for an isolation with sufficient purity. Document A 5,304,366 discloses a method that allows some concentration of the product, but using a system for filtering a high temperature gas flow that is difficult to perform practically. EP-B1 0 682 561 describes a general method for the production of carbon black with a nanostructure defined by the influence of a gaseous plasma on carbon at high temperatures. In series of products obtained in this way, fullerenes can be obtained at sufficient treatment temperatures in a continuous technical manner. However, the reaction products resulting from the method according to EP-B1 0 682 561 are very impure and contain, apart from carbon that has not been transformed into fullerenes, at most 10% C6o fullerenes as a mixture with fullerenos superiors. It was therefore the problem of the invention to develop a device and a method that would allow continuously producing carbon black with high fullerenes content. This problem was solved with the device according to the invention according to claim 1 and the method according to claim 12 based thereon.

DESCRIPTION OF THE FIGURES Figure 1 shows an embodiment of the device according to the invention, consisting essentially of a plasma reactor (1) with a first reaction chamber (A) and a second reaction chamber (B), a downstream heat separator. and a connected cold separator (3). Figure 2 shows a detail of the part of the head of the plasma reactor (1) essentially comprising the first reaction chamber (A). Figure 3 shows a top view of the reactor (1) illustrating an embodiment of the invention with three electrodes (4) distributed at an angle of 120 °, a central supply device (5) for the material containing carbon and a coating heat resistant and heat insulator. Figure 4 shows a further embodiment of the device according to the invention consisting essentially of the same parts of figure 1, but in which the flow of the products in the plasma reactor (1) is directed opposite gravity. The device according to the invention consists in accordance with claim 1 in the following components: (a) the plasma reactor (1) consisting of a first reaction chamber (A) in which two or more electrodes are inserted ( 4), the first reaction chamber (A) further comprising a supply arrangement (5) for the plasma gas and the carbon-containing compounds that supply the plasma gas and the carbon-containing compounds centrally to the reaction zone; the plasma reactor (1) comprising a second reaction chamber (B) adjacent to the first reaction chamber (A) comprising suitable arrangements for cooling the reaction mixture leaving the first reaction chamber (A), b) a heat separator (2) connected to the plasma reactor, and c) a cold separator (3) connected to the heat separator (2). The plasma reactor (1) preferably consists of a cylinder-shaped metal cover that can be designed, if necessary, with a double wall. In this double wall, a suitable cooling medium can circulate. In the metal cover, an insulating material (6) which generally consists of graphite or additionally in a ceramic layer can also be provided. The first reaction chamber (A) is used only for the plasma reaction at very high temperatures. According to the invention, two or more, preferably three electrodes (4) are inserted into the head part of the first reaction chamber (A), the electrodes are preferably arranged at an angle with the axis, so that they form in the upper part of the first reaction chamber (A) an intersection and which can be adjusted individually and continuously by conduit collars (7). The inclination with respect to the vertical axis is preferably in the range of 15 ° to 90 °, however, in all cases the inclination is such that an easy start of the arc that produces the plasma is possible and that a maximum stability of the plasma is ensured. plasma. Preferably, the electrodes (4) are equally distributed, so that with three electrodes an angular distance of 120 ° results. Typically, plasma electrodes are used that are common in the field of experts. These electrodes typically consist of a graphite as pure as possible in the form of cylindrical rods generally having a diameter of a few centimeters. If necessary, the graphite may contain additional elements that have a stabilizing influence on the plasma. The electrodes are usually operated with an alternate voltage between 50 and 500 volts. The applied energy is typically in the range of 40 W to 150 kW. Proper control of the electrodes provides a constant and stable plasma zone. The electrodes are readjusted automatically corresponding to their consumption. The supply device (5) serves as a feeder unit for carbon-containing compounds as well as for the plasma gas. Devices that allow a constant supply, common for an expert, can be used for this purpose. The supply is preferably controlled centrally to the plasma by the electrodes. The second reaction chamber (B) comprises devices suitable for efficient and selective cooling of the reaction mixture leaving the first reaction chamber (A). In a preferred embodiment, a supply device (8) can be provided thereto, for example by allowing a suitable cyclone effect, for example, a plasma gas or, if necessary, another cooling medium. According to the invention, the reaction mixture leaving the second reaction chamber (B) is supplied to a heat separator (2). The heat separator (2) is preferably designed in the form of an insulated isothermally heated cyclone burner, containing at the bottom a shutter (9) for the separation of the non-volatile components a conduit (10) for the recovery of non-volatile components. The plasma reactor (1) is volatile and in the upper part a conduit (11) is used to conduct the volatile components to the cold separator (3). Isothermal heating of the cyclone burner can be effected by common resources. Alternatively, the heat separator can be replaced by a suitable heat resistant filter. Such a filter can consist, for example, of color-resistant materials and of a porous ceramic, a metal frit or graphite foam. As in the case of the heat separator, devices that are not shown can allow a recovery of the separate solid components and lines can be provided to drive gaseous compounds to the cold separator (3). A cold separator (3) is connected to the heat separator (2) preferably in the form of a cyclone burner that can be cooled and which comprises in the lower part a shutter (12) for the separation of the carbon black containing the fullerenes and in the upper part a conduit (10) for guiding the plasma gas back to the plasma reactor (1). The cooling of this cyclone burner can be carried out typically, for example by means of a cooling jacket supplied with a cooling fluid. In a further embodiment of the device according to the invention, a conduit (13) for supplying the cooling device of the second reaction chamber (B) may be branched from the conduit (10). In addition, an input device (14) for the carbon-containing material can also be present, allowing the supply of carbon-containing material through the plug (15) to the conduit (10). A further subject of the invention is a method for producing the carbon black with a high content of the fullerenes mentioned at the beginning, from carbon-containing compounds in a plasma by means of the device previously written according to the invention. The invention relates in particular to the production of the carbon black with a high content of C 1 - Preferably, the temperature of the plasma is adjusted so as to achieve the highest possible volatility of the inserted carbon-containing material. Generally, the minimum temperature in the first reaction chamber (A) is 4000 ° C. As the plasma gas, a noble gas or a mixture of different noble gases is preferably used. Helium is preferably used, if necessary in a mixture with a different noble gas. The noble gases used should be as pure as possible. As the carbon-containing material, a highly pure carbon is preferably used which is as free as possible from the interference and the quality of the fullerenes which negatively influence the impurities. Impurities, such as hydrogen, oxygen or sulfur, reduce the production yield of fullerenes and form unwanted byproducts. On the other hand, any gaseous impurity present in the circulation of the production cycle causes a decrease in the purity of the plasma gas and requires the supply of plasma gas in pure form to maintain the original composition. However, it is also possible to directly clean the plasma gas in the production cycle circulation. Preferably, highly pure, finely powdered carbon powders are used, for example acetylene black, graphite powders, carbon black, powdered pyrolytic graphite or highly calcined coke or mixtures of the mentioned coals. In order to obtain optimum evaporation in the plasma, the aforementioned carbon powders are preferably as fine as possible. Coarser carbon particles can pass the plasma zone without vaporizing. In this case, a device according to FIG. 4 can assist in which the carbon particles reach the plasma zone in the opposite direction with respect to gravity.

The carbon-containing material is preferably supplied together with the plasma gas through the supply arrangement (5) to the plasma reactor. The plasma gas contains the carbon-containing material preferably in an amount of 0.1 km / m3 to 5 kg / m3. The reaction mixture formed in the reaction chamber (A) is cooled, as already mentioned above, with sufficient efficiency in the second reaction chamber (B) to maintain it at a temperature preferably between 1000 ° C and 2700 ° C for a period of time. generally defined time of fractions of a second up to a second. In this phase, the gaseous carbon molecules leaving the first reaction chamber (A) recombine with the fullerenes mentioned at the beginning. The cooling is effected, as shown above, with suitable cooling devices, preferably by a homogeneous distribution of a defined amount of cold plasma gas in the second reaction chamber (B). This cold plasma gas is obtained from the recirculating plasma gas. At the outlet of the second reaction chamber (B), the mixture generally consists of the plasma gas, the desired fullerenes in the gaseous state, a fraction of the unconverted starting material and non-vaporizable fullerenes. In the heat separator (2), which is provided, as shown above, as a cyclone burner, the solid parts are separated from the gas parts by the cyclone effect. The desired fullerene, which is itself volatile, with a yield up to 90%, can be separated from the other non-volatile carbon compounds. The heat separator (2) is maintained isothermally by known means at a temperature preferably between 600 ° C and 1000 ° C to avoid any condensation of the desired fullerenes in any of its parts. A shutter (9) in the lower part of the heat separator (2) allows the heat that was not converted to the desired fullerene to be returned to the gas flow, for example by means of any blowing device. The filter mentioned above but not explained in detail can perform the same function as the heat separator (2) discussed above. A cold separator (3) follows the heat separator (2). The cold separator is cooled by any known means at a temperature sufficient for the condensation of the desired fullerene, preferably at a temperature ranging from room temperature to 200 ° C. At the outlet of the cold separator (3), a powder-like material containing black carbon or a reaction of the desired fullerenes is accumulated up to 40%. Thanks to the obturator (12), the carbon black can be taken from the process with the desired fullerenes accumulated and it can be subjected to further purification. Further purification can be carried out according to a known method, for example by extraction (Dresselhaus et al., Science of Fullerenes and Carbon Nanotubes, Academic Press, 1996, chapter 5, page 11, in particular chapters 5.2 and 5.3). . The plasma gas from the cold separator (3) can be returned, for example by means of a blowing machine, through the conduit (10) to the plasma reactor (1). A branch (13) of the conduit (10) allows a part of the cold flow to be guided back to the second reaction chamber (B) to cool the reaction mixture. The following examples illustrate the subject matter of the invention, however, without limiting it to the scope of the examples.

EXAMPLES EXAMPLE 1 The device consists of a cylindrical reactor with an internal diameter of 300 mm, a height of 150 cm and a double wall cooling jacket with water circulation. Between the graphite coating and the inner wall of the pressure chamber, an insulating layer of graphite foam is disposed. Three graphite electrodes with a diameter of 20 mm are placed with a device Sliding through the reactor shell by means of duct collars inserted into electrically insulating receptacles. A central duct with a diameter of 3 mm serves to introduce the suspension of graphite to the plasmagic gas. The plasma gas is pure helium kept in circulation. The electrodes are supplied with an alternating voltage in such a way that the power supplied is 10 kW. By means of a three-phase controller of the type used in an arc furnace, comparatively constant electrical properties are achieved at the plasma level. In this way, a plasma temperature of about 5000 ° C is maintained in the reaction chamber (A). The returned cold gas reaction chamber (B) is provided to maintain its temperature at a value of about 1600 ° C. The starting material is micronized graphite of the type TIMREX® KS 6 of Timcal AG, CH-Sins. With a gas quantity of 10 m3 / h at the height of the reactor inlet and an addition material of 10 kg / h, a permanent state is achieved after an operation time of 1 hour. In the heat separator (2), maintained at a temperature of 800 ° C, 8 kg / h of non-volatile carbon compounds were separated and recovered through the plug (9). It was found that about 10% of the carbon introduced under these conditions was converted to fullerene gas. With a heat separator efficiency of about 90%, the C-β fullerene was mixed in a small amount with non-volatile carbon compounds. helium. This aerosol was transmitted to the cold separator (3) maintained at a temperature of 150 ° C. The product that accumulated in the lower part of the cold separator (3) was removed during the constant operation of the obturator (12) in an amount of 2 kg / h and consisted of 30% of fullerene Cßo as a mixture with unconverted carbon . The product obtained in that state can be used, however it was further purified according to Dresselhaus et al., Science of Fuillions and Carbon Nanotubes, Academic Press, 1996, chapter 5, page 11, in particular chapters 5.2 and 5.3, by extraction with toluene. The exemplary production allows the production of 0.6 kg / h of pure C 1 pure fullerene.EXAMPLE 2 The method was repeated according to example 1, only that helium was replaced by argon. Under these conditions, pure C6o fullerene can be obtained after purification in the amount of 4.0 kg / h.

EXAMPLE 3 The method was repeated according to example 1, only that the heat separator (2) was replaced by a porous ceramic filter. The gas flow that came from the filter and entered the cold separator (3) consisted only of helium mixed with fullerene C gaseous gas. The efficiency of the filter was approximately 90%. According to this method, pure C6o fullerene can be obtained after purification in an amount of 0.6 kg / h.

EXAMPLE 4 The method was repeated according to example 1, except that the micronized graphite was replaced by a highly pure acetylene black from the company F-Berre l'Etang. With this method, pure C 1 pure fullerene can be obtained in an amount of 0.8 kg / h after purification.

EXAMPLE 5 The method was repeated according to example 1, except that the micronized graphite was replaced by a degassed, highly pure pyrolytic graphite of the ENSACO Super P type from the company MMM-Carbon, B-Brussels. With this method, pure C 1 pure fullerene could be obtained in an amount of 0.7 kg / h after purification.

Claims (23)

NOVELTY OF THE INVENTION CLAIMS

1. Device for the continuous production of carbon black with a high content of fullerenes from compounds containing carbon in a plasma consisting of: (A) a plasma reactor (1) consisting of a first reaction chamber (A) wherein two or more electrodes (4) are inserted, wherein the first reaction chamber (A) further includes a supply arrangement (5) for the plasma gas and the carbon-containing compounds, for conducting the plasma gas and the carbon-containing compounds centrally to the reaction zone, wherein the plasma reactor (1) includes a second reaction chamber (B) adjacent to the first reaction chamber (A) having suitable devices for cooling the mixture of reaction coming out of the first reaction chamber (A); b) a heat separator (2) connected to the plasma reactor (1); and c) a cold separator (3) connected to the heat separator (2).

2. Device according to claim 1, further characterized in that the plasma reactor (1) is provided with a coating (6) heat resistant and heat insulator.

3. Device according to claim 2, further characterized in that the coating (6) consists of graphite.

4. - Device according to one of claims 1 to 3, further characterized in that the two or more electrodes (4) are arranged at an angle to the axis such that they form in the upper part of the first reaction chamber (A) an intersection and because they are individually adjustable in the direction of their axis by means of duct collars (7) inserted in the reaction chamber.

5. Device according to claim 4, further characterized in that three electrodes (4) are used, which are operated with an alternating voltage of three phases and consist of graphite.

6. Device according to one of claims 1 to 5, further characterized in that a supply arrangement (8) for plasma gas is provided as a device for cooling.

Device according to one of claims 1 to 6, further characterized in that the heat separator (2) is provided in the form of an isothermally heatable cyclone burner, comprising in the lower part a shutter (9) for the separation of the non-volatile compounds and a conduit (10) for guiding the non-volatile compounds back to the plasma reactor (1) and a conduit (1 1) on the top to guide the volatile compounds to the cold separator (3).

8. Device according to one of claims 1 to 7, further characterized in that the heat separator (2) is provided in the form of a heat-resistant filter.

9. - Device according to one of claims 1 to 8, further characterized in that the cold separator (3) is provided in the form of a cyclone burner that can be cooled, including in the lower part a shutter (12) for the separation of the carbon black containing the fullerenes and in the upper part a conduit (10) for guiding the plasma gas back the plasma reactor (1).

10. Device according to claim 9, further characterized in that a conduit (13) that is provided as a supply of the plasma gas to the second reaction chamber (B) branches off the conduit (10) provided to guide the gas of plasma back to the plasma reactor.

11. Device according to one of claims 1 to 10, further characterized in that an input device (14) is present for the material containing carbon, allowing the carbon-containing material through the obturator (15) to be fed to the conduit. (10)

12. Method for the continuous production of carbon black with high fullerenes content, further characterized in that the carbon-containing compounds are converted into the plasma by means of a device according to one of claims 1 to 11.

13.- Method according to claim 12, further characterized in that stable fullerenes chemically homogeneous are produced.

14. Method according to claim 12 or 13, further characterized in that the C 1, C 70 or C 84 fullerenes or mixtures of these fullerenes are produced.

15. Method according to one of claims 12 to 14, further characterized in that the temperature of the plasma has a minimum temperature of 4000 ° C in the first reaction chamber (A).

16. Method of compliance with one of claims 12 to 15, further characterized in that a noble gas or a mixture of different noble gases is used as a plasma gas.

17. Method of compliance with one of claims 12 to 16, further characterized in that helium is used as the plasma gas.

18. Method of compliance with one of claims 12 to 17, further characterized in that a highly pure carbon, for example acetylene black, graphite powder, carbon black, pulverized pyrolytic graphite or highly calcined coke or mixtures of the mentioned coals, is used as the carbon-containing material.

19. Method of compliance with one of claims 12 to 18, further characterized in that the temperature in the second reaction chamber (B) is maintained at a temperature between 1000 ° C and 2700 ° C.

20. Method according to claim 19, further characterized in that the temperature in the second reaction chamber (B) is regulated with the supply of cold plasma gas from the supply device (8).

21. - Method of compliance with one of claims 12 to 20, further characterized in that the heat separator (2) is maintained isothermally at a temperature of 600 ° C to 1000 ° C.

22. Method of compliance with one of claims 12 to 21, further characterized in that the cold separator (3) is operated at a temperature ranging from room temperature to 200 ° C.

23. Method of compliance with one of claims 12 to 22, further characterized in that a carbon black with a high content of C 14- fullerene is produced.