Chemistry of inorganic compounds – Carbon or compound thereof – Elemental carbon
Reexamination Certificate
1999-03-23
2001-07-17
Hendrickson, Stuart L. (Department: 1754)
Chemistry of inorganic compounds
Carbon or compound thereof
Elemental carbon
C423S44500R
Reexamination Certificate
active
06261532
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of producing high-functional carbon employed for a lithium ion battery, adsorbent, a liquid crystal material or the like.
2. Description of the Prior Art
Carbon nanotube, which is a kind of high-functional carbon, can be produced by sustaining stable arc discharge between carbon electrodes in helium gas under a high temperature and high pressure. Alternatively, carbon nanotube can be formed on the forward end of a cathode-side carbon electrode by causing dc discharge in an argon gas atmosphere.
In a known method of obtaining desired carbon having a controlled fine structure, amorphous carbon is irradiated with an electron beam in a vacuum atmosphere under the presence of an active metal or a carbon material is irradiated with an electron beam accelerated at a voltage exceeding a prescribed level.
In a conventional method of producing carbon nanotube, an important parameter influencing the yield thereof is the pressure of inert gas, and the internal pressure of a reactor must be kept at least 90 atm. Thus, a specific reactor is required.
The method of controlling the fine structure of carbon by irradiating the carbon material with an electron beam is unsuitable for mass production.
SUMMARY OF THE INVENTION
The objective of the present invention is to enable production of high-functional carbon such as carbon nanotube or production of carbon by controlling a fine structure under a lower temperature and ordinary pressure.
In order to produce high-functional carbon such as carbon nanotube under a lower temperature and ordinary pressure according to the present invention, reaction gas containing at least carbon dioxide and reducing gas is brought into contact with a transition metal catalyst at a reaction temperature of 400 to 900° C. for reducing the carbon dioxide contained in the reaction gas with hydrogen, thereby precipitating carbon such as carbon nanotube on the surface of the catalyst. Hydrogen or methane can be employed as the reducing gas.
When heating the transition metal catalyst to 400 to 900° C. and bringing the reaction gas containing carbon dioxide and reducing gas into contact with the catalyst, the carbon dioxide contained in the reaction gas is reduced with the reducing gas to precipitate carbon such as carbon nanotube on the surface of the catalyst.
In order to produce carbon by controlling a fine structure under a lower temperature and ordinary pressure according to the present invention, reaction gas containing a carbon compound is brought into contact with a transition metal catalyst at a reaction temperature of 400 to 900° C. for producing carbon having a different fine structure by changing the type of the catalyst or the reaction condition when precipitating carbon on the surface of the catalyst.
When heating the catalyst at 400 to 900° C. and bringing the reaction gas into contact with the transition metal catalyst for reducing the carbon compound contained in the reaction gas and precipitating carbon on the surface of the catalyst, the fine structure of the precipitated carbon is varied with the type of the catalyst or the reaction condition.
Examples of high-functional carbon are carbon nanotube, superfine carbon, nanocapsule, onion graphite, nanopolyhedron and the like.
The transition metal catalyst employed in the present invention is prepared from a transition metal (including an oxide) such as nickel (Ni) or cobalt (Co), preferably carried by a carrier such as silica or alumina. A reactor to which the present invention is applied is a fixed or fluidized bed reactor for circulating the reaction gas in contact with the catalyst. The fixed bed reactor is charged with the catalyst in a fixed state, while the fluidized bed reactor stores the catalyst in a flowable state.
According to the present invention, carbon such as carbon nanotube can be precipitated on the surface of the catalyst by bringing the reaction gas containing at least carbon dioxide and reducing gas into contact with the transition metal catalyst at the reaction temperature of 400 to 900° C. for reducing the carbon dioxide contained in the reaction gas on the catalyst. Consequently, the carbon nanotube or the like can be produced under a lower temperature and ordinary pressure with no requirement for a specific large sized apparatus.
When bringing the reaction gas containing a carbon compound into contact with the transition metal catalyst at the reaction temperature of 400 to 900° C. for precipitating carbon on the surface of the catalyst, the fine structure of carbon can be controlled under a lower temperature and ordinary pressure while enabling mass production by changing the type of the catalyst or the reaction condition.
The foregoing along with other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawing.
REFERENCES:
patent: 4572813 (1986-02-01), Arakawa
patent: 5780101 (1998-07-01), Nolan et al.
Patent Abstr. of Japan, No. 63159210, Pub. Jul. 1988 (Mitsubishi Heavy Ind. Ltd.).
Database WPI, Section CH, Week 9006, XP002107935, Dec. 21, 1989 (Nippon Steel Corp.).
Patent Abstr. of Japan, No. 05193920, Pub. Aug. 1993 (Hitachi Ltd.).
Database EPODOC, EPO, XP-002107945, Dec. 1997 (Chinese Academy of Metals Inst.).
Armstrong Westerman Hattori McLeland & Naughton LLP
Hendrickson Stuart L.
Research Institute of Innovative Technology for the Earth
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