Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen; Reversible storage of hydrogen
  • C01B3/0005—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes
  • C01B3/001—Reversible storage of hydrogen, e.g. by hydrogen getters or electrodes characterised by the uptaking media; Treatment thereof
  • C01B3/0018—Inorganic elements or compounds, e.g. oxides, nitrides, borohydrides or zeolites; Solutions thereof
  • C01B3/0021—Elemental carbon, e.g. active carbon, carbon nanotubes or fullerenes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J25/00—Catalysts of the Raney type
  • B01J25/02—Raney nickel
• • 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
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/32—Hydrogen storage

Definitions

• the present invention provides a process for the preparation of fibrous carbon which comprises contacting a metallic catalyst with a carbon-containing gas at elevated temperature, characterized in that said catalyst is a porous metal comprising a transition metal or an alloy thereof.
• the metal catalyst used according to the invention preferably is selected from group 5 to 10 metals, eg nickel, iron, cobalt, vanadium, molybdenum, chromium and ruthenium and alloys thereof, eg Fe/Ni, Cu/Ni etc alloys. Lanthanides may also be used. In general the requirement seems to be that the metal is able to form carbides which are unstable at the temperatures used in the CNF production process. Precious metals, such as Pt, Au and Ag may also be deposited on such metals or alloys. Especially preferably the transition metal of the catalyst is nickel, iron or cobalt or a mixture of two or three thereof, eg Ni/Fe.
• Starck include Amperkat SK-NiFe 6816, SK-Ni 3704, SK-Ni 5544, and SK-Ni 5546 which contain respectively 4-7% wt Al : 62-67% wt Ni: 26-30% wt Fe, 4-7% wt Al : 93-96% wt Ni : ⁇ 1% wt Fe, 5-9% wt Al: 90-95% wt Ni : ⁇ 0.6% wt Fe, and 5-9% wt Al : 90-95% wt Ni: ⁇ 0.6% wt Fe .
• These Amperkat catalysts have a grain size of about 80 ⁇ m (i.e.
• the catalyst is preferably particulate, - 4 - conveniently having a particle size as described above, or of from 10 nm to 100 ⁇ m, preferably 50 nm to 1000 nm, especially 80 to 200 nm.
• the catalyst may be a macrostructure having a desired shape (eg tube, ring, rod, etc) , optionally a structure which is- porous only on desired surfaces, eg the catalyst may be tubular with the interior surface porosified or it may be of any desired shape fully porosified.
• CNF growth will yield a tube fully or partially filled with CNF or a predetermined shape consisting substantially entirely of CNF.
• Such CNF-filled tubes could be used as hydrogen reservoirs, eg after capping and provision of a valve.
• Such CNF or CNF-containing structures form a further aspect of the present invention.
• the gas used in the process of the invention may be any carbon-containing gas suitable for CNF production, e 9 ]__ 3 hydrocarbons (such as for example methane, ethene, ethyne, etc) , carbon monoxide, synthesis gas etc.
• the gas is or comprises methane.
• the gas comprises methane and carbon monoxide as this lowers the energy supply needed since the CNF production reaction is less endothermic with carbon monoxide than with methane alone.
• the feed gas comprise methane and carbon monoxide in a mole ratio of 1:99 to 99:1, more particularly 10:90 to 90:10.
• the gas fed into the CNF production reactor should, for at least part of the reaction period, contain a small proportion of hydrogen, e.g. 1 to 20% mole, more preferably 2 to 10% mole. This has the effect of reducing the carbon activity of the catalyst metal (i.e. the rate of carbon uptake by the metal) and serves to prolong CNF production, increase total yield and reduce the weight percentage of the CNF product which is in the form of amorphous carbon.
• Hydrogen can be added to the gas feed to the reactor or off-gas from the reactor (which is hydrogen containing if the feed gas contains a hydrocarbon) may be, at least in part, recycled into the reactor to provide the desired hydrogen content.
• the hydrogen generated by CNF production may be sufficient to provide an appropriate hydrogen content in the CNF/catalyst bed.
• the porous catalyst according to the process of the invention it is possible to use natural gas without requiring unusual purification - this is a novel reagent for CNF production and this use of natural gas represents a further aspect of the invention.
• the invention provides a process for the production of fibrous carbon which comprises contacting a particulate catalyst comprising a transition metal or an alloy thereof with a carbon- containing gas at elevated temperature, characterized in - 6 - that said gas comprises natural gas .
• natural gas methane- containing gas from a hydrocarbon well, optionally treated to remove hydrocarbons having four or more carbon atoms per molecule, water, nitrogen and carbon dioxide, and preferably treated to remove catalyst poisons, e.g. sulphur compounds and possibly halogens. Conventional means for poison removal may be used.
• catalyst poisons e.g. sulphur compounds and possibly halogens.
• Conventional means for poison removal may be used.
• the methane content of such natural gas will generally lie in the range 80 to 95% mole.
• Liquefied natural gas LNG or LPG
• LPG Liquefied natural gas
• CNF production is preferably effected so as to yield carbon in an amount of at least lg carbon per gram metal catalyst, more preferably at least lOg/g, still more preferably at least 50g/g, especially at least lOOg/g, more especially at least 150g/g, eg 100 to 400 g/g, typically 150 to 250 g/g-
• the process of the invention will typically be effected by flowing the carbon-containing gas past the catalyst .
• the CNF growth results in hydrogen release where the gas contains a hydrocarbon such as methane and the hydrogen generated is an important by-product of the process.
• the hydrogen produced may be separated out of the gas flow from the catalyst. However it may also be burned to provide a heat source for the reaction. Moreover it is preferred that the gas flow to the catalyst should contain hydrogen, eg 1 to 20% mole, for example 5 to 15% mole, preferably 8 to 11%, and to this end it is preferred that a part of the gas flow from the catalyst be drawn off and mixed with the carbon- containing gas flow to the catalyst .
• the hydrogen produced may also be separated out from the gas flow inside the reactor.
• One option is to separate the hydrogen from the catalyst bed by use of membranes (for - 7 - example ceramic membranes) followed by a subsequent separation and discharge of the carbon product. This is of particular interest if high purity hydrogen is a desired by-product of the process.
• the lower wall of the reactor may be provided with a downward slope in at least one portion following the initial location of the catalyst bed.
• Such a horizontal reactor design has the benefit that the carbon product compacts .naturally during production without any significant adverse effect on carbon yield.
• the carbon may compact in this way to a density of about 0.4 to 0.9 g/cm 3 , more typically 0.5 to 0.7 g/cm 3 .
• the catalyst/carbon bed may be mechanically agitated, for example to improve gas and heat distribution and/or to facilitate flow of the CNF product towards an outlet.
• the process of the invention may be .performed continuously or batchwise.
• the reactor in which the process is carried out is preferably provided with means for introducing fresh catalyst at the downstream end of the catalyst bed and for removing CNF from the upstream end of the catalyst bed, eg isolatable settling legs of the type commonly provided in the loop reactors used for olefin polymerization.
• a reactor design similar to the reactor designs used in the polyolefin- industry could be used. These reactors are designed to achieve a favourable mass transport and enhance the reactivity of the reacting gas molecules at the " catalytically active metal surfaces.
• the reactor used in the process of the invention will conveniently have a volume of 10 to 100m 3 , preferably 50 to 70 m 3 allowing a total product content in the thousands of kilograms.
• methane feed rates of 500 to 2000 kg/hour, eg 1000 to 1500 kg/hour, and carbon removal rates of 200 to 2000 kg/hour, eg 750 to 1250 kg/hour may thus typically be achieved.
• the energy supply necessary to operate such a reactor will typically be in the hundreds of kW, eg 100 to 1000 kW, more typically 500 to 750kW.
• the energy demand will typically be in the range 1 to 5 kW/kgC, e.g.
• energy supply into the reactor may be achieved by external heating of the reactors or by inclusion within the reactor of heating means or heat exchange elements connected to a heat source.
• heated feed gas is preferably fed into an agitated catalyst/carbon bed at a plurality of points or over the entire undersurface of a gas- fluidized bed.
• the carbon monoxide is preferably introduced at a lower temperature (e.g. ⁇ 300°C) , for example through a separate feed line, e.g. to avoid dusting of ferrous metal feed lines.
• the present invention provides a process for the production of particulate carbon by contacting a carbon-containing gas with a transition metal catalyst at elevated temperature, which process comprises selecting the temperature and gas pressure at which gas: catalyst contact occurs so as to produce particulate carbon having a desired ratio of graphitic to amorphous carbon.
• the process may thus be subject to feedback control, whereby carbon is removed from the catalyst bed in the reactor, its graphite to amorphous carbon weight ratio determined, eg by X-ray diffraction, and the temperature, pressure and/or carbon-containing gas:hydrogen ratio adjusted if the ratio is above or below the desired value.
• the ratio is too high the temperature should be increased and/or - 12 - the pressure increased (or the temperature should be decreased and/or the pressure should be decreased if the ratio is too low) .
• a reactor may be used to produce successive batches of carbon with different desired graphite : amorphous carbon ratios, or in the case of "continuous reactor operation the changeover period between production of carbon with two different desired values of the ratio may be controlled to minimize wastage, ie material not meeting the desired ratio requirements .
• a desired graphitic:amorphous carbon ratio of at least 5:95 may readily be achieved.
• a ratio of 5:95 to 90:10, especially 50:50 to 80:20 particularly 50:50 to 70:30 is especially preferred.
• -the catalyst is subjected to an initiation or pretreatment .
• This serves to increase CNF production rate and CNF yield and may be achieved with any CNF production catalyst, i.e. not just porous metal catalysts, by a limited period of exposure to a feed gas with reduced or no hydrogen content at a lower temperature than the reaction temperature in the main CNF production stage.
• Such pretreatment is preferably under process conditions under which the carbon activity of the catalyst is greater than in the main CNF production stage.
• the invention provides a process for the preparation of carbon nanofibres which comprises in a first stage contacting a catalyst for carbon nanofibre production with a first carbonaceous gas at a first temperature for a first time period and subsequently contacting said catalyst with a second carbonaceous gas at a second temperature for a second time period, characterized in that said first gas has a lower hydrogen (H 2 ) mole percentage than said second gas, said first temperature is lower than said second temperature, and said first period is shorter than said second - 13 - period. If a higher graphitic contact of the CNF product is desired, the first temperature may be reduced and/or the second temperature may be increased.
• the catalyst is preferably a transition or lanthanide metal or an alloy thereof, especially a transition metal and more especially a porous metal, in particular a nickel containing metal, especially a Raney metal.
• the temperature, pressure and gas composition, in the second period are preferably as described above for CNF production.
• the temperature in the first period is preferably in the range 400 to 600°C, especially 450 to 550°C, more especially 460 to 500°C.
• the hydrogen mole percentage in the first period is preferably 0 to 2% mole, especially 0 to 1% mole, more especially 0 to
• the pressure in the first period is preferably 5 to 10 bar, especially 6 to 9 bar.
• the duration of the first period is preferably 1 to 60 minutes, more especially 2 to 40 minutes, particularly 5 to 15 minutes.
• This pretreatment or initiation of the catalyst causes the catalyst to become a catalyst/carbon agglomerate comprising particles of a carbon-containing metal having carbon on the surfaces thereof.
• the catalyst may if desired be treated with hydrogen at elevated temperature, e.g. to reduce any surface oxide.
• the invention provides a metal catalyst comprising particles of a carbon- containing metal having deposits of carbon on the surfaces thereof, prepared by exposure of said metal to a gas comprising methane and/or carbon monoxide for a period of 1 to 60 minutes at a temperature of 400 to 600°C and a pressure of 5 to 10 bar, said gas containing - 14 - less than 2% mole of hydrogen and preferably less than 10% mole of other carbonaceous compounds, especially less than 2% mole of other carbonaceous compounds.
• the invention also extends to the products of the process of the invention. Viewed from this aspect the invention provides a carbon article formed from carbon generated in a process according to the invention. Viewed from another aspect the invention provides an article comprising a metal substrate bearing on a surface thereof carbon generated in a process according to the invention.
• the carbon produced in the process of the invention may be processed after removal from the reactor, eg to remove catalyst material, to separate CNF from amorphous material, to mix in additives, or by compaction.
• Catalyst removal typically may involve acid or base treatment;
• CNF separation may for example involve dispersion in a liquid and sedimentation (eg centrifugation) , possibly in combination with other steps such as magnetic separation;
• additive treatment may for example involve deposition of a further catalytically active material on the carbon, especially the CNF, whereby the carbon will then act as a catalyst carrier, or absorption of hydrogen into the carbon; and compaction may be used to produce shaped carbon items, eg pellets, rods, etc.
• Catalyst removal from the CNF product may also be - 15 - effected by exposure to a flow of carbon monoxide, preferably at elevated temperature and pressure, e.g. at least 50°C and at least 20 bar, preferably 50 to 200°C and 30 to 60 bar.
• the CO stream may be recycled after deposition of any entrained metal carbonyls at an increased temperature, e.g. 230° to 400°C.
• the invention provides nanofibrous carbon having a metal content of less than 0.2% wt, especially less than 0.1% wt, particularly less than 0.05% wt, more particularly less than 0.01% wt, e.g. as low as 0.001% wt.
• a metal content of less than 0.2% wt especially less than 0.1% wt, particularly less than 0.05% wt, more particularly less than 0.01% wt, e.g. as low as 0.001% wt.
• Carbon containing gas (90% mol methane and 10% mol hydrogen) at a pressure of 5 bar was introduced at a flow rate of 400 mL/minute and a temperature of 550 °C into a horizontal tubular reactor having a conical section increasing in cross-section in the flow direction.
• a aluminium-leached nickel : aluminium intermetal catalyst (Amperkat ® SK Ni 3704 from H.C. Starck GmbH & Co KG, Goslar, Germany) was placed at the narrowest point of the reactor. The gas flow was maintained for 30 hours by which time CNF generation had ceased.
• Carbon containing gas (90% mol methane and 10% mol hydrogen) at a pressure of 5 bar was introduced at a flow rate of 400 mL/minute and a temperature of 550 °C into a horizontal tubular reactor having a conical section increasing in cross-section in the flow direction.
• a aluminium-leached 68% Nickel/32% Iron: aluminium intermetal catalyst (Amperkat ® SK Ni Fe 6816 from H.C. Starck GmbH & ' Co KG, Goslar, Germany) was placed at the narrowest point of the reactor. The gas flow was maintained for 30 hours by which time CNF generation had ceased.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Nanotechnology (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Physics & Mathematics (AREA)
• General Chemical & Material Sciences (AREA)
• Condensed Matter Physics & Semiconductors (AREA)
• General Physics & Mathematics (AREA)
• Composite Materials (AREA)
• Crystallography & Structural Chemistry (AREA)
• Textile Engineering (AREA)
• Combustion & Propulsion (AREA)
• Inorganic Chemistry (AREA)
• Thermal Sciences (AREA)
• Carbon And Carbon Compounds (AREA)
• Catalysts (AREA)
• Inorganic Fibers (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9937200

Family Applications (1)

Country Status (7)

Cited By (1)

Families Citing this family (26)

Family Cites Families (11)

• 2002
  • 2002-05-22 GB GBGB0211789.3A patent/GB0211789D0/en not_active Ceased
• 2003
  • 2003-05-22 AU AU2003234019A patent/AU2003234019A1/en not_active Abandoned
  • 2003-05-22 US US10/514,238 patent/US20060013757A1/en not_active Abandoned
  • 2003-05-22 WO PCT/GB2003/002221 patent/WO2003097910A2/en not_active Ceased
  • 2003-05-22 CA CA2486153A patent/CA2486153C/en not_active Expired - Fee Related
  • 2003-05-22 EP EP03727689A patent/EP1506330A2/de not_active Withdrawn
• 2004
  • 2004-11-19 NO NO20045044A patent/NO20045044L/no not_active Application Discontinuation

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events