Method of obtaining soot, which contains fullerenes and nanotubes, from gaseous hydrocarbon raw material

FIELD: chemistry.

SUBSTANCE: invention relates to the field of plasmochemistry and can be applied for production of fullerenes and nanotubes. A carbon-containing raw material is decomposed in a gas discharge. For this purpose, first, inflamed is a volume glow discharge in a mixture of gaseous hydrocarbons and inert gas under pressure of 20-80 Torr. Then, under visual observation burning of the glow discharge with a constricted cathode area and diffuse positive column is obtained. Products of decomposition are precipitated in the form of soot.

EFFECT: carrying out process in a strongly non-equilibrium electric discharge makes it possible to increase the speed of soot obtaining and 9,6 times increase the output of nanotubes and fullerenes per unit of put in energy.

1 dwg

 

The invention relates to the field of plasma chemistry, plasma processing and decomposition of materials, production of fullerenes and nanotubes.

A method of obtaining soot containing fullerenes, which involves the burning of hydrocarbons (A.V. Eletskii, BM Smirnov "Fullerenes and structure of carbon," Phys, t, No. 9, 1995, s). A negative feature of the fullerenes is that they form bonds with oxygen, which greatly affects their properties.

A method of obtaining soot containing fullerenes and nanotubes, which consists in evaporation of graphite with a laser (H.W.Kroto, J.R.Heath, S.C.O''brien, R.F.Curi & R.E.Smolley // Nature, 1985. V.318. P.162). Evaporation of graphite is carried out in a helium environment. Helium served pulses at the time of the order of 10-3C. the Laser is switched on in the middle of the time source of helium. The evaporating material is captured by the flow of helium, mixed, cooled and then condensed.

The disadvantage of this method is the small amount of evaporated graphite and, accordingly, a small amount fullerenelike soot.

A method of obtaining soot containing fullerenes and nanotubes, which is to supply the powder of graphite in the area of microwave gas discharge, in which graphite is evaporated, and the vapor of carbon fullerenes are formed (No. 05-238717, MKI SW 31/02, publ. 17.09.93). When implementing this method, there is low productivity of the process, a low content of fullerenes in soot and large energy consumption for production of one gram of carbon black. In addition, you must provide protection from the used microwave radiation.

Also known is a method of obtaining soot containing fullerenes and nanotubes, which includes the operation of evaporation of graphite in the arc discharge. The discharge is ignited in an atmosphere of helium at a pressure of 100 Torr. To obtain the arc discharge is used alternating current I=100 - 200 a, frequency f=60 Hz and voltage U=20-30 (Electric arc process for making fallerenes. United States Patent. US 5227038. Jul. 13, 1993).

A method of obtaining soot containing fullerenes, which includes evaporation of graphite in an electric arc DC coaxially between graphite electrodes placed in an atmosphere of inert gas, a movement formed in the electric arc products with an inert gas and subsequent precipitation in the form of soot containing fullerenes (patent RU 2234457 C2, IPC SW 31/02, publ. 20.08.2004, prototype). The disadvantages of these methods include low capacity and high consumption.

The technical result of the claimed invention to provide a soot containing fullerenes and nanotubes, strongly nonequilibhum high voltage electricity is practical discharge by decomposition of hydrocarbons, the increase of the speed of soot containing fullerenes and nanotubes.

The technical result is solved by the described method to obtain soot containing fullerenes and nanotubes, which consists in the decomposition of carbon-containing raw material gas discharge and deposition of decomposition products in the form of soot.

What's new is that first light volume glow discharge in a mixture of gaseous hydrocarbons and inert gas at a pressure of 20-80 Torr, then by visual observation achieve burning glow discharge with the constricted cathode region, which for a short time increase the electric current until the lacing just discharge, and then reduce it to the optimal value, which is characterized by diffuse positive pole of the constricted cathode region of a glow discharge.

Consider the implementation of the method of producing soot containing fullerenes and nanotubes, and the operation of the device to obtain a soot containing fullerenes and nanotubes. Bit device (1) mounted inside a vacuum enclosure 1 with a transparent window 2 (made, for example, made of thick plexiglass) to monitor the discharge. First, in a vacuum Cabinet 1 create a vacuum, and then through the valve inlet 3 serves a mixture of gaseous hydrocarbons and inert gas (such as helium or argon is). The inert gas may be up to 50% of the volume of the mixture. The pressure of the working gas in the vacuum Cabinet 1 set in the range of 20-80 Torr. After that, the conductive bus 4 through the ballast resistor serves the minimum voltage on the cathode 5 and the anode 6, which is sufficient for the breakdown of the interelectrode gap and the establishment of discharge, such as 4 kV. After the breakdown of the voltage drops on the ballast resistance (figure not shown), and the electrode gap is set to the burning voltage of a discharge. This approach implements a normal glow discharge with a volume form burning around the electrode gap, the cathode is observed cathode spot purple color, the area of which is proportional to the current discharge. Next, by visual observation through the window 2 of the vacuum enclosure 1 achieve burning glow discharge with the constricted cathode region, which increases the electric current until the lacing just discharge, and then reduce it to a value that is characterized by diffuse (volume) positive pole of the constricted cathode region of a glow discharge, the color of the discharge will change to orange-yellow. When this cathode spot is narrowed to bright luminous point, and the volume of the vacuum Cabinet begins the evolution of small soot particles in the form of smoke, the growth of a filament is the breaking of soot formation on the anode. When the interaction of the plasma discharge with a gaseous hydrocarbon feedstock occurs disconnection of hydrocarbon molecules and appears to atomic carbon ratio of the hydrocarbon and inert gas - argon 1:1). When the distance between the electrodes is 20 mm, the discharge voltage was 600 V at a current of 100 mA.

Upon reaching the discharge current of 100 mA discharge enters the combustion mode surround the positive pole of the constricted cathode part. In the volume of the vacuum Cabinet thus begins a selection of fine particles of soot in the form of smoke, filamentous growth of soot formation on the anode, which is periodically cleaned off with a scraper through the rotating anode disk. Soot accumulated in a special container. A certain amount of soot is carried away by convective gas flow occurring between the electrodes and deposited on the walls of the vacuum chamber.

We will evaluate the performance and economic efficiency of production of fullerene soot proposed method. When the current I=100 mA and a voltage of U=600 V for t=10 minutes, as the experiments have shown, is formed of m=0.3 g of fullerene soot. Then the amount of electricity required to produce 1 g of carbon black, as well

IUt/m=0,1 And 600 In 0,166 hour/0.3 g=33,2 W·h/g=0,0332 kWh/year

For comparison, we estimate the energy consumption in the proposed method in the patent RU 223457 C2, IPC SW 31/02, publ. 20.08.2004 (prototype). When the characteristic voltage U=30B, the arc current was I=80A, and the feed rate of a graphite electrode with a diameter d=6 mm was v=4 mm/min. Density graphite ρ=of 2.26 g/cm3. If we assume that in a single evaporation half Saramago graphite turns into soot (the second half is deposited on the cathode), the amount of graphite is equal to G=ρπd2v/8=2.26 3,14 0,36 0,4/8 g/min=0,1275 g/min Then the amount of electricity required to produce 1 g of carbon black as described in the prototype (EN 2234457 C2, IPC SW 31/02, publ. 20.08.2004), you will need electricity

IU/G=30V 80A min / 0,1275 g = 0,32 kW·h/year

Thus, the proposed method allows 9.6 times to increase the goods produced per unit of nested energy. Since the proposed method can be easily scaled, the result is a significant gain in performance.

The method of obtaining soot containing fullerenes and nanotubes, which consists in the decomposition of carbon-containing raw material using gas discharge and deposition of decomposition products in the form of soot, wherein the first volumetric light glow discharge in a mixture of gaseous hydrocarbons and inert gas at a pressure of 20-80 Torr, then by visual observation achieve burning glow discharge with the constricted cathode region and diffuse positive the post.



 

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