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US20080075651A1 - Vapor-Grown Carbon Fiber and Production Process Thereof - Google Patents

Vapor-Grown Carbon Fiber and Production Process Thereof Download PDF

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Publication number
US20080075651A1
US20080075651A1 US11/662,730 US66273005A US2008075651A1 US 20080075651 A1 US20080075651 A1 US 20080075651A1 US 66273005 A US66273005 A US 66273005A US 2008075651 A1 US2008075651 A1 US 2008075651A1
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Prior art keywords
carbon fiber
vapor
compound
producing
temperature
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US11/662,730
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Tomoyoshi Higashi
Eiji Kambara
Katsuyuki Tsuji
Takanori Aoki
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Resonac Holdings Corp
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Showa Denko KK
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Priority to US11/662,730 priority Critical patent/US20080075651A1/en
Assigned to SHOWA DENKO K.K. reassignment SHOWA DENKO K.K. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: AOKI, TAKANORI, HIGASHI, TOMOYOSHI, KAMBARA, EIJI, TSUJI, KATSUYUKI
Publication of US20080075651A1 publication Critical patent/US20080075651A1/en
Abandoned legal-status Critical Current

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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
    • D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
    • D01F9/127—Carbon filaments; Apparatus specially adapted for the manufacture thereof by thermal decomposition of hydrocarbon gases or vapours or other carbon-containing compounds in the form of gas or vapour, e.g. carbon monoxide, alcohols
    • D01F9/1271—Alkanes or cycloalkanes
    • D01F9/1272—Methane
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C01B32/162—Preparation characterised by catalysts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/34—Length
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/36—Diameter
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2913—Rod, strand, filament or fiber
    • Y10T428/2918—Rod, strand, filament or fiber including free carbon or carbide or therewith [not as steel]

Definitions

  • the present invention relates to a process for efficiently producing a vapor-grown carbon fiber such as a carbon nanotube.
  • the carbon fiber obtained by the vapor-growth process (vapor-grown carbon fiber) can have a large aspect ratio with relative ease. Accordingly, studies thereon have been aggressively done heretofore and there is a large number of reports on the production process.
  • a carbon nanotube (that is, a carbon fiber having a fiber diameter on the nanometer order) has attracted particular attention in recent years and can be synthesized by applying this vapor-growth process.
  • FIG. 1 is a schematic view showing one example of a reaction apparatus for continuously producing a carbon fiber by the vapor-growth process.
  • CO, methane, acetylene, ethylene, benzene, toluene or the like is used as the carbon source which is the raw material of the carbon fiber.
  • a carbon source which is a gas at an ordinary temperature and pressure is supplied, in the gaseous state, by being mixed with a carrier gas.
  • the carbon source is vaporized in a vaporizer 4 and then supplied by being mixed with a carrier gas, or is sprayed in the liquid state into the heating zone 1 .
  • the carrier gas used is, for example, nitrogen gas, which is an inert gas, or hydrogen which is reducing gas.
  • the carbon source is supplied into a depressurized apparatus.
  • a catalyst a supported catalyst in which a metal is supported on a support such as alumina, or an organic metal compound such as ferrocene, is used.
  • the supported catalyst is subjected to a necessary pretreatment by previously locating and heating it in a heating zone 1 , and then a carbon source is supplied and reacted (this is the example shown in FIG. 1 ).
  • the reaction is performed by continuously or pulsedly supplying a supported catalyst which has been pretreated, from outside of the system.
  • an organic metal compound readily dissolvable in a carbon source such as ferrocene
  • a carbon source such as ferrocene
  • the product is collected in the inside of the heating zone 1 heated by a heater 2 or in a collector 3 at the end of the heating zone and, after the completion of reaction, after a predetermined time, recovered.
  • the production process of a carbon fiber by a vapor-phase method is roughly classified into the following three types according to the method of supplying a catalyst or a precursor compound of the catalyst:
  • a substrate or boat comprising an alumina or graphite supporting a catalyst or a precursor compound thereof is placed in a heating zone and contacted with a gas of a carbon source supplied in a vapor phase;
  • a particulate catalyst or a precursor compound thereof is dispersed in a liquid-state carbon source or the like, continuously or pulsedly supplied to a heating zone from outside of the system, and contacted with a carbon source at a high temperature;
  • a metallocene, carbonyl compound and like dissolvable in a liquid-state carbon source is used as the catalyst precursor compound, and a carbon source comprising this catalyst precursor compound dissolved therein is supplied to a heating zone, whereby a catalyst and the carbon source, which is a hydrocarbon or the like, are contacted at a high temperature.
  • the process of (1) comprises steps which must be independently performed, such as a step of coating a catalyst or a precursor thereof on a substrate, a step of, if desired, performing a pretreatment such as reduction, a step of producing a carbon fiber, and a step of taking out the produced carbon fiber after temperature is lowered, and therefore, this process is disadvantageous in that continuous production is difficult and the productivity is low.
  • a pretreatment such as reduction
  • a step of producing a carbon fiber a step of producing a carbon fiber
  • a step of taking out the produced carbon fiber after temperature is lowered
  • this process is disadvantageous in that continuous production is difficult and the productivity is low.
  • continuous production is possible and the productivity is high. Accordingly, a process classified into (2) or (3) is generally employed in industry. However, a sufficiently large amount of carbon fibers cannot be obtained unless a catalyst or a precursor compound thereof is used greatly in excess of the amount necessary for the growth of carbon fiber as a product.
  • the status quo is that an expensive catalyst or catalyst precursor compound is consumed in a large amount and furthermore, a step of removing a by-product due to the excessively added catalyst is provided.
  • the reason why a sufficiently large amount of carbon fibers cannot be obtained is considered to be because the catalyst having high activity is coarsened through aggregation and loses an ability to grow a carbon fiber. This tendency is serious in the case of using a catalyst not supported on a support or the like and, for example, a catalyst produced by supplying a catalyst precursor, such as ferrocene in the gaseous state or in the state of floating in a raw material gas, to the heating zone.
  • the process of (1) is used in many cases, because such a compound is low in the production rate of a carbon fiber.
  • the contact time of a catalyst and a carbon source is as long as from a few minutes to tens of minutes and therefore, the productivity is low.
  • the process of (1) is used in many cases. Also, in the case of a process capable of continuous production, the yield or productivity is low.
  • J. Phys. Chem. B, 1999, 103, 6484-6492 uses the process of (1) and therefore, continuous production is difficult. Further, in the process, the reaction temperature is low, and the throughput of carbon fibers per the amount of methane used or per catalyst is extremely low.
  • Japanese Examined Patent Publication (Kokoku) No. 62-49363 discloses a process of using methane as a raw material of a carbon fiber, but since the methane concentration is low and the reaction temperature is also low, the yield is as low of as 0.1%.
  • Japanese Unexamined Patent Publication (Kokai) No. 1-92423 discloses a process where in the production of a carbon fiber by a vapor phase method, a mixed gas of H 2 , CO and CO 2 is used as a carrier gas.
  • a mixed gas of H 2 , CO and CO 2 is used as a carrier gas.
  • methane is used as a raw material for a carbon fiber, but the main carbon source is benzene, the amount of a catalyst used is large, and the effectiveness of using methane is not described.
  • An object of the present invention is to provide a production process for a vapor-grown carbon fiber, which is simple and effective and in which the effectiveness of a catalyst or a catalyst precursor can be remarkably enhanced and in turn, a carbon fiber can be produced at a low cost.
  • Another object of the present invention is to provide a production process for a vapor-grown carbon fiber, in which a carbon fiber having a long average fiber length can be obtained.
  • the present inventors have found that when methane is used as the main carbon source and is introduced in a high concentration into an atmosphere at a temperature of 1,100° C. or more, the reaction time is shortened and an effectiveness of a catalyst or a catalyst precursor is increased.
  • the present invention has been accomplished based on this finding. In other words, according to the process of the present invention, even in the case of using a very small amount of a catalyst, where a fiber cannot be conventionally produced, a carbon fiber can be obtained at a high yield.
  • the present invention relates to the following (1) to (25).
  • a process for producing a vapor-grown carbon fiber by contacting a carbon source in the supplied raw material with a catalyst and/or a catalyst precursor compound in a heating zone to produce a carbon fiber in a vapor phase, wherein the carbon source at least includes methane, the concentration of methane in the supplied raw material is at or more than 15 mol % to less than 100 mol %, and the temperature in the high-temperature part of the heating zone is from 1,100 to 1,500° C.
  • methane in a high concentration is introduced into an atmosphere at a high temperature of 1,100° C. or more, whereby a carbon fiber can be obtained at high productivity with a very small amount of a catalyst.
  • FIG. 1 is a schematic view showing an example of the general horizontal reaction apparatus for producing a vapor-grown carbon fiber.
  • FIG. 2 is a schematic view showing an example of the vertical reaction apparatus for producing a vapor-grown carbon fiber.
  • the carbon fiber is produced at a low temperature of 1,000° C. or less, particularly about 900° C., and the productivity is low.
  • the catalyst is previously charged into a reaction furnace, for example, by loading it on a support, and the catalyst heated to a temperature of the reaction furnace and methane similarly heated are reacted to produce a carbon fiber.
  • the catalyst supported on a support may undergo aggregation.
  • a part of the methane is thermally decomposed to produce an aliphatic hydrocarbon such as ethylene and propylene, or an aromatic compound having an aromatic ring.
  • a large number of patent documents disclose a technique of producing a carbon fiber at a high temperature of 1,100° C. or more by using an aromatic compound.
  • a carbon fiber can be produced, and particularly in a large amount, at a high temperature of 1,100° C. or more by using an aliphatic hydrocarbon. This infers that a carbon fiber is not successfully produced when an aliphatic hydrocarbon such as ethylene and propylene is contacted with a catalyst at a high temperature of 1,100° C. or more.
  • the production of a carbon fiber from methane starts from a low temperature, in other words, the production of a fiber starts before the catalyst particles are aggregated and coarsened to lose a catalytic ability, whereby the effectiveness of the catalyst or catalyst precursor is remarkably enhanced and the fiber continuously grows in the diameter direction at a high temperature.
  • the methane concentration is high, production of non-fibrous matters is suppressed and high productivity can be achieved.
  • a carbon fiber having a long fiber length can be obtained as compared with the case of using an aromatic compound as a raw material carbon source of a carbon fiber.
  • the carbon source at least includes methane, and preferably the main carbon source is methane.
  • the “carbon source” means a compound having a carbon atom. Accordingly, when the catalyst precursor compound has a carbon atom, the catalyst precursor compound is also included in the “carbon source”. However, carbon monoxide and carbon dioxide show a behavior different from that of an aliphatic hydrocarbon or an aromatic hydrocarbon and therefore, are not included in the “carbon source” as concerns the present invention.
  • the “main carbon source” means a carbon source having a largest number of carbons when the total amount of carbons in each carbon source contained in the supplied raw material is compared obviously, only methane may be used as the carbon source.
  • a carbon source other than methane cannot be used as the main carbon source.
  • a carbon source other than methane cannot be used as the main carbon source.
  • an aliphatic hydrocarbon such as ethane, propane and butane
  • a mixture of a fine carbon fiber and a non-fibrous product is obtained, and the yield of a carbon fiber becomes low, and a large amount of a non-fibrous material is contained.
  • an aromatic hydrocarbon such as benzene and toluene is used, a carbon fiber cannot be obtained unless a large amount of a catalyst is used.
  • the methane concentration in the supplied raw material is preferably is at or more than 15 mol % to less than 100 mol %, more preferably from 30 to 95 mol %, still more preferably from 45 to 90 mol %. If the methane concentration in the raw material is excessively low, the productivity of a carbon fiber decreases, whereas if the methane concentration is excessively high, a non-fibrous product may be produced.
  • the “supplied raw material” means a composition containing a carbon source, a catalyst and/or catalyst precursor, and a carrier gas described below, i.e. includes all components supplied to the heated zone, as concerns the present invention.
  • the carbon source other than methane, which is used along with methane, is preferably not used in an excessively large amount, because if used in a large amount, the carbon source inhibits the properties of methane.
  • the carbon source other than methane is used in such an amount that the total amount of carbon atoms contained in such a carbon source is preferably 60% or less, more preferably 40% or less, still more preferably 20% or less, further still more preferably 10% or less, and most preferably 5% or less, based on the total amount of carbon atoms contained in methane. If the carbon source other than methane is used in an excess amount, the amount of a non-fibrous solid matter produced abruptly increases.
  • the catalyst used for the present invention is not particularly limited as long as it is a substance capable of accelerating the growth of a carbon fiber.
  • the catalyst is, for example, at least one metal (particularly, a fine particle thereof) selected from the group consisting of Groups 3 to 12 of the 18 Groups-Type Periodic Table of Elements recommended by IUPAC in 1990, preferably at least one metal selected from the group consisting of Groups 3, 5, 6, 8, 9 and 10, more preferably iron, nickel, cobalt, ruthenium, rhodium, palladium, platinum or a rare earth element.
  • the “catalyst precursor compound” means a compound which is thermally decomposed upon heating and, in some cases, further reduced to provide the catalyst.
  • the catalyst precursor compound includes an organic metal compound, a metal salt, etc.
  • ferrocene which is a catalyst precursor compound is thermally decomposed upon heating to provide iron fine particles which work as a catalyst. Accordingly, as for the catalyst precursor compound, a compound of providing the above-described metal can be suitably used.
  • the catalyst precursor compound is, for example, a metal compound containing at least one element selected from the group consisting of Groups 3 to 12, preferably a compound containing at least one element selected from the group consisting of Groups 3, 5, 6, 8, 9 and 10, and most preferably a compound containing iron, nickel, cobalt, ruthenium, rhodium, palladium, platinum or a rare earth element.
  • a metal compound containing at least one element selected from the group consisting of Groups 1 to 17 as a modification component (so-called co-catalyst), to the main component to modify the catalytic performance of the main component metal.
  • the catalyst and/or catalyst precursor compound may also be used, if desired, by loading it on a support.
  • the support is preferably a compound stable in the heating zone, and examples of such a compound include alumina, silica, zeolite, magnesia, titania, zirconia, graphite, activated carbon and carbon fiber.
  • this support compound must be introduced together with a carbon source, etc. into a heated furnace without previously charging it into a reaction furnace.
  • the amount of the catalyst or catalyst precursor compound to be used is, in terms of the ratio between the atomic number of an a catalyst element (for example, Fe) and the number of carbon atoms in the carbon source, preferably 0.000005 to 0.0015, more preferably from 0.00001 to 0.001, still more preferably from 0.00002 to 0.0005, and most preferably from 0.00004 to 0.0004. If this ratio is less than 0.000005, the amount of catalyst is too small and the number of fibers may decrease or the fiber diameter may increase, whereas if the ratio exceeds 0.0015, not only the profitability is low but also coarsened catalyst particles, not functioning as a catalyst, may be mixed in the fiber.
  • an a catalyst element for example, Fe
  • the carbon atoms of the carbon source in the raw material when the catalyst precursor compound contains a carbon, the carbon atoms thereof are also included. That is, the total number of carbon atoms is a total amount of all carbon atoms excluding carbons contained in the carbon monoxide and carbon dioxide in the supplied raw material.
  • the method of supplying the raw material is not particularly limited.
  • the methane and/or carbon source other than methane and the catalyst and/or catalyst precursor compound may be vaporized and supplied in the gaseous state, or a part or all thereof may be supplied in the liquid state.
  • these raw materials are preferably vaporized before the production of carbon fiber starts, thoroughly mixed as gaseous materials and then supplied.
  • the gaseous materials are preferably thoroughly mixed at 700° C. or less, more preferably 600° C. or less, and most preferably 400° C. or less.
  • the catalyst and/or catalyst precursor compound is in a solid or a liquid state at an ordinary temperature and pressure in many cases.
  • the effectiveness of the catalyst is high and the amount to be used may be a small amount, even in the case of a liquid, it is sometimes difficult to supply the catalyst or catalyst precursor compound as-is to the heating zone.
  • the catalyst and/or catalyst precursor compound or the like may be supplied by dissolving or dispersing it in a compound which is a liquid at an ordinary temperature and pressure.
  • a carbon source which is a liquid at an ordinary temperature and pressure may be used.
  • the solubility is preferably high.
  • a compound which is a liquid at an ordinary temperature and pressure and in which the solubility of the catalyst precursor compound at 25° C. is preferably 1 g or more, more preferably 5 g or more, and still more preferably 10 g or more per 100 g of the compound which is in a liquid state at an ordinary temperature and pressure may be used.
  • ferrocene often employed as the catalyst precursor compound as the compound which is a liquid at an ordinary temperature and pressure, a compound which is a liquid at an ordinary temperature and pressure and in which the solubility of ferrocene at 25° C. is 5 g or more per 100 g of the compound which is in a liquid state at an ordinary temperature is preferably used, and specifically benzene, toluene and tetrahydrofuran may be used.
  • the compound which is a liquid at an ordinary temperature and pressure is preferably a compound having a boiling point of 115° C. or more in which the solubility of the catalyst precursor at 25° C. is 1 g or more per 100 g of the compound which is a liquid at an ordinary temperature and pressure.
  • the compound includes aromatic compounds such as o-xylene, m-xylene, p-xylene, ethylbenzene, stylene; esters such as methyllactate, methyl pyruvate; ketone compounds such as 4-methyl-2-pentanone, 2-hexanone, 3-hexanone, cyclopentanone, hydroxyacetone, 3-heptanone, 4-hepatanone; and ether compounds such as propyleneglycolmonomethylether, propyleneglycolmonoethylether.
  • aromatic compounds such as o-xylene, m-xylene, p-xylene, ethylbenzene, stylene
  • esters such as methyllactate, methyl pyruvate
  • ketone compounds such as 4-methyl-2-pentanone, 2-hexanone, 3-hexanone, cyclopentanone, hydroxyacetone, 3-heptanone, 4-hepatanone
  • ether compounds
  • the compound which is a liquid at an ordinary temperature and pressure is preferably a compound having a boiling point of 150° C. or more in which the solubility of the catalyst precursor at 25° C. is 1 g or more per 100 g of the compound which is a liquid at an ordinary temperature and pressure.
  • the compound includes aromatic compounds such as cumene, anisol, 4-methoxytoluene; ester compounds such as ethyl lactate, 2-ethoxyethyl acetate, propyleneglycolmonoethylether acetate, dimethyl malonate, propyleneglycol diacetate, ⁇ -butylolactone; ketone compounds such as 4-methoxy-4-methyl-2-pentanone, 4-hydroxy-4-methyl-2-pentanone, cyclohexanone, 2,6-dimethyl-4-heptanone, 3-methylcyclohexanone, 3-methoxy-1-butanol, ethyleneglycol monoisobutyl ether, ethyleneglycol monomethyl ether, diethyleneglycol dimethyl ether, propyleneglycol mono-n-buthyl ether, ethyleneglycol mono-n-buthyl ether, 3-methoxy-3-methyl-1-butanol, tetrahydrol,
  • the method for supplying a compound which is a liquid at an ordinary temperature and pressure and in which the catalyst and/or catalyst precursor compound or the like is dissolved or dispersed is not particularly limited.
  • this compound may be supplied by spraying it in the liquid state with use of a nozzle or the like, but in order to attain thorough mixing with a gas component such as methane at a lower temperature, the compound is preferably introduced after vaporization at a temperature where all components can be thoroughly vaporized, more preferably in the state that the gases are thoroughly mixed before introduction.
  • a carrier gas in addition to the above-described composition.
  • the carrier gas hydrogen, nitrogen, helium, argon, krypton or a mixed gas thereof may be used, but a gas containing an oxygen molecule (that is, oxygen in the molecular state (O 2 )), such as air, is not suited.
  • the catalyst precursor compound for use in the present invention is sometimes in the oxidized state and in such a case, a hydrogen-containing gas is preferably used as the carrier gas.
  • the carrier gas is preferably a gas containing hydrogen at a concentration of 1 vol % or more, more preferably 30 vol % or more, and most preferably 85 vol % or more, and this is, for example, a gas of 100 vol % hydrogen or a gas of hydrogen diluted with nitrogen.
  • the hydrogen gas concentration used here is based only on the carrier gas, but the amounts of methane and/or carbon source other than methane, the gasified catalyst and/or catalyst precursor compound and the like are not considered.
  • a sulfur compound considered to be effective in controlling the carbon fiber diameter may be used in combination.
  • the sulfur compound which can be used in the present invention includes sulfur; thiophene; hydrogen sulfide; carbon sulfide; mercaptans such as methyl mercaptan, tert-butyl mercaptan; sulfides such as dimethyl sulfide; and disulfides such as dimethyl disulfide.
  • the preferred sulfur compound includes thiophene, carbon disulfide, dimethyl sulfide and dimethyl disulfide, and more preferred sulfur compound includes dimethyl sulfide and dimethyl disulfide.
  • a compound such as sulfur, thiophene, hydrogen sulfide, carbon sulfide, mercaptans such as tert-butyl mercaptan, sulfides such as dimethyl sulfide, and disulfides such as dimethyl disulfide may be supplied in the gaseous state or by dissolving it in a solvent.
  • the total molar number of sulfur supplied is suitably 100 times or less, preferably 10 times or less, more preferably 2 times or less, the molar number of a catalyst element. If the amount of sulfur supplied is excessively large, this is not only unprofitable but also it also inhibits the growth of a carbon fiber, and is not preferred.
  • the synthesis of a vapor-grown carbon fiber is achieved by supplying the raw materials described above and, if desired, a carrier gas to a heating zone, and contacting these under heating.
  • the reactor heating zone
  • the reactor is not particularly limited as long as predetermined residence time and heating temperature are obtained, but a vertical or horizontal tubular furnace is preferred in view of the supply of raw material and the control of residence time.
  • the carbon source As methane, which is a stable compound, is used as the carbon source, preferably as the main carbon source, if the temperature in the heating zone is too low, a solid product as well as a carbon fiber is not produced at all or is produced in an extremely small amount, whereas if the temperature is excessively high, a carbon fiber does not grow or only a thick fiber is obtained. Therefore, the temperature in the high-temperature part of the heating zone is preferably from 1,100 to 1,500° C., more preferably from 1,150 to 1,350° C.
  • the main component of the carbon source in the gas after the reaction is preferably methane.
  • a part of the carbon becomes carbon monoxide or carbon dioxide but, as described above, these are not included in the carbon source.
  • the gas after reaction satisfies the composition comprising methane and a carbon source other than methane and can be circulated and reused by again supplying all or a part of the gas, as-is or after adding methane and/or a carbon source other than methane, to the heating zone.
  • the reused gas and the components additionally added in combination form the reaction raw material and therefore, this raw material must satisfy the raw material composition of the present invention.
  • FIG. 2 shows one example of the reaction apparatus.
  • a quartz-made reaction tube 1 used as a heating zone is equipped with a heater 2 and, at the top, is connected to a supply line of mixing and supplying raw material components such as carrier gas and methane as well as a raw material liquid component containing a catalyst and/or a catalyst precursor compound.
  • a vaporizer 4 is disposed at the bottom of the reaction tube 1 .
  • a receiver 3 for collecting the produced carbon fibers is provided at the bottom of the reaction tube 1 .
  • the heater 2 is set to a predetermined temperature of 1,100° C. or more and raw materials are introduced from the introduction line 4 and reacted.
  • the characteristic feature of the present invention is to efficiently recover the supplied carbon source as carbon fibers.
  • the fundamental mechanism thereof is mainly such that a carbon fiber produced upon contact of methane with a catalyst at a low temperature of 1,000° C. or less is effectively grown in the diameter direction at a high temperature of 1,000° C. or more by using a carbon source, for example, methane, an aliphatic hydrocarbon such as ethylene and propylene and/or an aromatic hydrocarbon such as benzene, which all are a decomposition product of methane.
  • the temperature at the raw material-introducing part from which a raw material is induced into the reaction tube must be kept lower than the temperature in the high-temperature part of the heating zone.
  • the temperature of the raw material-introducing part is preferably 700° C. or less, more preferably 600° C. or less, still more preferably 400° C. or less.
  • the residence at 1,000° C. or less must be kept to a certain period of time by introducing the raw material into the low-temperature region.
  • the residence time at 600 to 1,000° C. is important and the raw material is preferably caused to stay in this temperature range for 0.05 seconds or more, preferably 0.5 seconds ore more, still more preferably from 1.0 to 30 seconds.
  • this residence time can be arbitrarily determined depending on the desired fiber length, raw material concentration, temperature of the supplied raw material, catalyst concentration or the like.
  • the temperature used here is a value obtained, for example, by inserting a platinum-platinum•13% rhodium alloy thermocouple capable of measuring even a temperature of 1,000° C. or more into the heating zone. To be precise, this measured value is affected by radiation and does not necessarily agree with the gas temperature but can be satisfactorily used as an index for specifying the preferred condition of the present invention.
  • the residence time in the temperature range of 600 to 1,000° C. is a time of passage of the raw material gas through a region where the temperature measured as above on the inlet side of the reaction apparatus elevates from 600° C. to 1,000° C.
  • the residence time is calculated on the assumption that the raw material gas creates a plug flow in this region and the temperature of the raw material gas is elevated to the temperature measured as above.
  • the residence time is a residence time in the region from the upstream end of heating zone or the ejection part of a nozzle or the like to a part where the temperature is elevated to 1,000° C.
  • the residence time is calculated on the assumption that the raw material creates a plug flow in this region and the temperature of the raw material gas is elevated to the temperature measured as above.
  • the residence time at a temperature of 1,100° C. or more can be determined in the same manner as the residence time in the temperature range of 600 to 1,000° C., and this residence time is, for example, 0.001 second or more, preferably 0.01 second or more, more preferably from 0.1 to 30 seconds.
  • the residence time at a temperature of 1,100° C. or more can be arbitrarily determined depending on the desired fiber thickness, raw material concentration, temperature in the high-temperature part, or the like.
  • the fundamental mechanism of the present invention is mainly such that a carbon fiber produced at a low temperature of 1,000° C. or less is grown in the diameter direction at a high temperature of 1,000° C. or more.
  • a high temperature of 1,100° C. or more is particularly used here.
  • the production process of the present invention is particularly suited for the production of a relatively thick fiber rather than the production of a carbon fiber having a very small outer diameter, such as single wall or dual wall carbon fiber.
  • the production process of the present invention is optimal as a production process of a carbon fiber having an average outer diameter of 10 nm or more, preferably 50 nm or more, and most preferably 100 nm or more.
  • the outer diameter of a carbon fiber as used herein can be determined, for example, by measuring the outer diameter of the images of about 100 fibers in a photograph from an SEM.
  • the present invention is characterized in that, despite it being a production process with high productivity, a carbon fiber having a long fiber length can be produced as compared with the case of using a carbon source such as benzene capable of producing a carbon fiber with similarly high productivity. That is, the production process of the present invention is optimal as a production process of a carbon fiber having an average fiber length of 10 ⁇ m or more, preferably 13 ⁇ m or more, and most preferably 15 ⁇ m or more.
  • the length of a carbon fiber as used herein can be determined, for example, by measuring the length of the images of about 100 fibers in a photograph from an SEM similarly to the case of the outer diameter.
  • the effectiveness of a catalyst or a catalyst precursor can be remarkably enhanced. That is, a carbon fiber can be efficiently obtained even with a small amount of a catalyst.
  • a catalyst e.g., iron
  • the carbon fiber produced is subjected to firing (at around 1,500° C.) or graphitization treatment (at 2,000 to 3,000° C.) in an inert gas so as to enhance the physical properties.
  • a part of iron or the like as the catalyst is vaporized or transpired by this treatment and the catalyst residual amount decreases in the carbon fiber after graphitization treatment.
  • the catalyst content in the carbon fiber can be extremely decreased even in the state not subjected to a treatment such as firing and graphitization.
  • a carbon fiber having a catalyst content of 5,000 ppm or less or, under preferred conditions, a catalyst content of 500 ppm or less can be obtained in the state not subjected to a treatment such as firing and graphitization, and depending on usage, the graphitization treatment is not necessary.
  • the average outer diameter of the fiber obtained tends to change by varying the ratio of the catalyst and/or catalyst precursor compound to methane. That is, the fiber diameter becomes small when the ratio of the catalyst and/or catalyst precursor compound is increased, and becomes large when the ratio is decreased.
  • the average outer diameter of the carbon fiber obtained can be controlled merely by changing the composition of a raw material carbon source and a catalyst without changing the reaction apparatus or detailed conditions. For example, a carbon fiber having a fiber outer diameter of 80 to 150 nm can be very easily produced.
  • Carbon disulfide Wako Pure Chemical Industries, Ltd.
  • a vertical furnace equipped with a heating zone 1 of the quartz-made reaction tube (inner diameter: 31 mm, outer diameter: 36 mm, length of heating zone: about 400 mm) shown in FIG. 2 was used.
  • the temperature of the heating zone 1 was elevated to 1,200° C. with an N 2 stream, the supply of N 2 was then stopped, and H 2 as a carrier gas was instead flowed into the heating zone 1 at 1 NL/min.
  • H 2 as a carrier gas was instead flowed into the heating zone 1 at 1 NL/min.
  • benzene, ferrocene and thiophene were dissolved and mixed with each other, and the resulting solution was introduced into a vaporizer 4 heated at 200° C. to introduce each component in the amount shown in Table 1, vaporized and then entrained in H 2 .
  • NL as used herein indicates a volume (liter) in the standard state (0° C., 1 atm).
  • the temperature was elevated to 1,200° C. with a He stream at 1 NL/min and when the temperature was stabilized, the inside temperature of the quartz tube was measured by using a platinum-platinum•13% rhodium alloy thermocouple. As a result, the temperature was 600° C. at 24 cm from the top of the quartz tube and 1,000° C. at 29 cm. The residence time therebetween was determined and found to be 0.59 seconds. The temperature was higher than 1,100° C. at 33 cm from the top of the quartz tube and was lower than 1,1000° C. at 60 cm. The residence time therebetween was determined and found to be 2.25 seconds.
  • ratios of a total amount of carbon atom in carbon sources supplied other than methane to a total amount of carbon atom in methane supplied are calculated according to the following equation, and shown in Table 2:
  • the cobweb-like product was observed by a scanning electron microscope. Out of the product, the average outer diameter and the average length were examined on about 100 pieces, as a result, the product was found to be a fibrous material having an average outer diameter of 200 nm and an average length of 20 ⁇ m.
  • the reaction was performed according to the method of Example 1 except for setting the reaction temperature to 1,250° C. and changing the composition of the solution prepared by dissolving and mixing benzene, ferrocene and thiophene with together.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 53% and the product was a fibrous material having an average outer diameter of 170 nm and an average length of 15 ⁇ m.
  • the reaction was performed according to the method of Example 2 except for changing the flow rates of H 2 and methane to 0.64 NL/min and 0.36 NL/min, respectively.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 34% and the product was a fibrous material having an average outer diameter of 170 nm.
  • the reaction was performed according to the method of Example 2 except for changing the flow rates of H 2 and methane to 0.82 NL/min and 0.18 NL/min, respectively.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 15% and the product was a fibrous material having an average outer diameter of 150 nm.
  • the reaction was performed according to the method of Example 1 except for changing the flow rates of H 2 and methane to 0.25 NL/min and 0.75 NL/min, respectively.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 45% and the product was a fibrous material having an average outer diameter of 250 nm.
  • the reaction was performed according to the method of Example 2 except for the flow rate of the solution prepared by dissolving and mixing benzene, ferrocene and thiophene with each other.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 55% and the product was a fibrous material having an average outer diameter of 200 nm.
  • the reaction was performed according to the method of Example 6 except for using toluene in place of benzene and setting the introduced amount thereof to 0.10 mmol/min.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 56% and the product was a fibrous material having an average outer diameter of 200 nm.
  • the reaction was performed according to the method of Example 6 except for using tetrahydrofuran in place of benzene and setting the introduced amount thereof to 0.13 mmol/min.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 51% and the product was a fibrous material having an average outer diameter of 200 nm.
  • the reaction was performed according to the method of Example 2 except for using dimethyl sulfide in place of thiophene.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 55%, and the product was a fibrous material having an average outer diameter of 250 nm and an average length of 32 ⁇ m.
  • the reaction was performed according to the method of Example 2 except for using dimethyl disulfide in place of thiophene.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 51%, and the product was a fibrous material having an average outer diameter of 200 nm and an average length of 18 ⁇ m.
  • the reaction was performed according to the method of Example 2 except for using hydrogen disulfide in place of thiophene.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 54%, and the product was a fibrous material having an average outer diameter of 250 nm.
  • the powdery product was observed by a scanning electron microscope.
  • the solid matter was mostly spherical particles, and almost no fibrous material was obtained with the catalyst amount on the same level as in Examples 1 to 5.
  • the reaction was performed according to the method of Comparative Example 1 except for changing the composition of the solution prepared by dissolving and mixing benzene, ferrocene and thiophene with each other.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 39%, and the product was a fibrous material having an outer diameter of 100 nm and an average length of 7 ⁇ m. Although a fibrous material was obtained by increasing the catalyst amount, the fiber length was short.
  • the reaction was performed according to the method of Example 2 except for changing the flow rates of H 2 and methane to 0.91 NL/min and 0.09 NL/min, respectively.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 0%. This is because the methane concentration was excessively low.
  • the reaction was performed according to the method of Example 2 except for setting the reaction temperature to 1,000° C.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • the carbon recovery percentage was 0%. This is because the reaction temperature was excessively low.
  • the reaction was performed according to the method of Comparative Example 4 except for not passing H 2 and changing the flow rate of methane to 1 NL/min.
  • the conditions and results of the test are shown in Tables 1 and 2.
  • a brown smoky matter was produced in the gas at the outlet of the reaction furnace and a black sticky material was attached to the inner wall of the reaction tube, but a recoverable solid deposit was not obtained. Namely, the carbon recovery percentage was 0%.
  • the reaction temperature is excessively low, a carbon fiber is not obtained even if the methane concentration is elevated.

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US20080031803A1 (en) * 2004-06-08 2008-02-07 Showa Denko K.K. Vapor Grown Carbon Fiber, Production Method Thereof and Composite Material Containing the Carbon Fiber
US20090008611A1 (en) * 2007-03-26 2009-01-08 Showa Denko K.K. Carbon nanofiber, production process and use
US20100150815A1 (en) * 2008-12-17 2010-06-17 Alfredo Aguilar Elguezabal Method and apparatus for the continuous production of carbon nanotubes
US8308990B2 (en) 2007-05-31 2012-11-13 Showa Denko K.K. Carbon nanofiber, production process and use
US9506194B2 (en) 2012-09-04 2016-11-29 Ocv Intellectual Capital, Llc Dispersion of carbon enhanced reinforcement fibers in aqueous or non-aqueous media

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CN104246030B (zh) * 2012-03-08 2016-02-24 旭碳株式会社 碳纤维制造方法
CN103496687B (zh) * 2013-09-18 2015-08-12 福州大学 竹原纤维纳米碳颗粒的高温制备装置
WO2015177401A1 (fr) * 2014-05-23 2015-11-26 Canatu Oy Procédé et appareil de production de nanomatériau
JP7760773B1 (ja) 2024-06-07 2025-10-27 住友化学株式会社 カーボンナノチューブ集合体、カーボンナノチューブ分散液、導電材料、電極、二次電池、平面状集合体、及び組成物

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WO2003002789A1 (fr) * 2001-06-28 2003-01-09 Showa Denko K.K. Procede et appareil de production de fibre de carbone obtenue a la vapeur

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US20080031803A1 (en) * 2004-06-08 2008-02-07 Showa Denko K.K. Vapor Grown Carbon Fiber, Production Method Thereof and Composite Material Containing the Carbon Fiber
US8206678B2 (en) 2004-06-08 2012-06-26 Showa Denko K.K. Vapor grown carbon fiber, production method thereof and composite material containing the carbon fiber
US20090008611A1 (en) * 2007-03-26 2009-01-08 Showa Denko K.K. Carbon nanofiber, production process and use
US7879261B2 (en) * 2007-03-26 2011-02-01 Showa Denko K.K. Carbon nanofiber, production process and use
US8308990B2 (en) 2007-05-31 2012-11-13 Showa Denko K.K. Carbon nanofiber, production process and use
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US9506194B2 (en) 2012-09-04 2016-11-29 Ocv Intellectual Capital, Llc Dispersion of carbon enhanced reinforcement fibers in aqueous or non-aqueous media

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