EP2097168A2 - Method for preparing carbon fibrils and/or nanotubes from a carbon source integrated in the catalyst - Google Patents

Method for preparing carbon fibrils and/or nanotubes from a carbon source integrated in the catalyst

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Publication number
EP2097168A2
EP2097168A2 EP07871964A EP07871964A EP2097168A2 EP 2097168 A2 EP2097168 A2 EP 2097168A2 EP 07871964 A EP07871964 A EP 07871964A EP 07871964 A EP07871964 A EP 07871964A EP 2097168 A2 EP2097168 A2 EP 2097168A2
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EP
European Patent Office
Prior art keywords
catalyst
nanotubes
metal
material according
organic substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP07871964A
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German (de)
French (fr)
Inventor
Dominique Plee
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Arkema France SA
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Arkema France SA
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Publication of EP2097168A2 publication Critical patent/EP2097168A2/en
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    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/74—Iron group metals
    • B01J23/745—Iron
    • 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
    • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
    • B01J21/18—Carbon
    • B01J21/185—Carbon nanotubes
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/74—Iron group metals
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J23/74—Iron group metals
    • B01J23/75—Cobalt
    • 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
    • B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
    • B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
    • B01J31/06—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing polymers
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • 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
    • 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
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
    • B01J23/24—Chromium, molybdenum or tungsten
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • 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
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
    • B01J35/613—
    • B01J35/615—
    • 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
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/0201—Impregnation
    • B01J37/0203—Impregnation the impregnation liquid containing organic compounds
    • 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
    • C01B2202/02—Single-walled nanotubes
    • 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
    • C01B2202/06—Multi-walled nanotubes

Definitions

  • the present invention relates to a process for preparing carbon fibrils and / or nanotubes from a carbon source integrated with the catalyst used for their preparation, as well as the catalyst material and its manufacturing process.
  • Carbon fibrils and carbon nanotubes are recognized today as materials presenting great advantages, because of their mechanical properties, of their relations of form
  • the carbon fibrils generally have a mean diameter ranging from 50 nm to a micron, greater than that of the carbon nanotubes.
  • the fibrils are composed of more or less organized graphitic zones (or turbostratic stacks) whose planes are inclined at variable angles with respect to the axis of the fiber. They are often hollow in the central axis.
  • the carbon nanotubes are terminated by hemispheres consisting of pentagons and hexagons of structure close to fullerenes.
  • nanotubes composed of a single sheet this is called SWNT (acronym for Single Wall Nanotubes) and nanotubes composed of several concentric layers then called MWNT (acronym for Multi Wall Nanotubes).
  • SWNTs are generally more difficult to manufacture than MWNTs.
  • the production of carbon nanotubes may be implemented by various methods such as electrical discharge, the r laser ablation or chemical vapor deposition (CVD)
  • a carbon source is injected at a relatively high temperature over a catalyst, said catalyst being able to consist of a metal supported on an inorganic solid.
  • a metal supported on an inorganic solid iron, cobalt, nickel and molybdenum are preferentially mentioned and among the supports there is often alumina, silica or magnesia.
  • Possible carbon sources are methane, ethane, ethylene, acetylene, ethanol, methanol, acetone or even CO + H2 synthesis gas (HIPCO process).
  • the ashes consist of transition metal and alumina, silica or magnesia.
  • the metal is often encapsulated and little subject to cause undesirable effects, but this is not the case of the mineral support which, if it is not eliminated by a binding acidic treatment, can prove harmful in applications such as thin films or fibers, because of the particle size.
  • US2006 / 0115409 describes a process in which the preparation of carbon nanotubes (CNTs) is carried out by in situ decomposition of a mixture comprising polyethylene glycol as organic material and carbon source, in the presence of a catalyst. metallic.
  • the mixture consisting of the metal catalyst dispersed in the polyethylene glycol is previously prepared in a solvent medium before the CNT formation step which itself is carried out in two stages by heating at temperatures of 200-400 ° C., respectively, at the first time. step then 400-1QOO 0 C in the second step.
  • the invention provides a catalyst material for the preparation of fibrils and / or mono- or multi-walled carbon nanotubes comprising:
  • one or more multivalent transition metals chosen from those of group VIB, chromium Cr, molybdenum Mo, tungsten W, or those of group VIIIB, iron Fe, cobalt Co, nickel Ni, ruthenium Ru, Rh rhodium, Pd palladium, Os osmium, Ir irium, Pt platinum or mixtures thereof, and a solid organic substrate selected from polymers, copolymers and terpolymers which contain only carbon and hydrogen.
  • the organic substrate is a polymer with a BET specific surface area of less than 200 m 2 / g, for example between 0.1 m 2 / g and 50 m 2 / g.
  • a BET specific surface area of less than 200 m 2 / g, for example between 0.1 m 2 / g and 50 m 2 / g.
  • the organic substrate is chosen from polymers, copolymers or terpolymers, in which at least a part of the units comprises butadiene and / or styrene.
  • the organic substrate is selected from core-shell polymers (methacrylate / butadiene / styrene terminology) or crosslinked polystyrene / divinylbenzene polymers.
  • the transition metal may be chosen from iron Fe, cobalt Co, or nickel Ni, or a mixture thereof.
  • the amount of transition metal (s) is advantageously up to 50% by weight of the final catalyst material, preferably from 1 to 30% and more preferably from 1 to 15% by weight of the final catalyst material.
  • the organic substrate is a porous support in which the metal is impregnated, preferably, in which the impregnation rate of the support is up to 40%.
  • the catalyst material according to the invention is in the form of solid particles whose diameter is between 1 micron and 5 mm.
  • the invention also relates to the process for preparing the catalyst material described above by contacting the organic substrate with a solution containing at least one of said transition metal (s) in the form of salt, preferably under a dry gas sweep. This step is usually followed by a reduction of the deposited metal. To do this, the deposited metal is advantageously reduced under a reducing gas scan such as hydrogen.
  • the solution is an aqueous solution metal nitrate, especially iron nitrate.
  • the denitrification of the catalyst takes place under an inert atmosphere.
  • the contacting is carried out at a temperature between room temperature and the boiling temperature of the solution, and the quantity of liquid, at any time, in contact with the substrate is just sufficient to ensure the formation of a film on the surface of the particles.
  • the invention also relates to a process for the preparation of fibrils and / or mono- or multi-walled carbon nanotubes comprising the steps of: a) providing a catalyst material as defined above; b) growth of the carbon fibrils and / or nanotubes by thermal decomposition of the organic substrate by heating the catalyst material at a temperature of between 300 and 1200 ° C. in the presence of a hydrocarbon gas composition optionally comprising a reducing gas; c) cooling and recovery of fibrils and / or carbon nanotubes formed.
  • the invention relates more particularly to a process as described above, wherein the hydrocarbon gas is ethylene, used in the presence of hydrogen as a reducing gas, the gas composition containing at least 20% by volume of hydrogen.
  • step b) is carried out on a fluidized bed in the presence of the hydrocarbon gas and optionally reducing gas, more preferably in the presence of ethylene and hydrogen.
  • the reducing gas is present in step b) of preparing the carbon nanotubes, so that the reduction of the metal of the catalyst material occurs in-situ during step b).
  • the process according to the invention allows the manufacture of carbon fibrils and / or nanotubes both by decomposition of the organic support and chemical vapor deposition, so that its productivity is maximum.
  • the aim of the invention is to provide a catalyst material for the preparation of mono- or multi-walled carbon fibrils and / or nanotubes comprising one or more particular multivalent transition metals and a hydrocarbon polymeric organic substrate.
  • the organic substrate
  • the organic substrate is solid and advantageously porous. It may have a BET specific surface area of less than 200 m 2 / g, and preferably between 1 m 2 / g and 50 m 2 / g.
  • the substrate is chosen from polymers, copolymers or terpolymers which contain only carbon and hydrogen, and which, as a result, lead to a higher yield of ordered fibrils and / or nanotubes.
  • the organic substrate is chosen from polymers, copolymers or terpolymers in which at least part of the units comprise butadiene and / or styrene. More preferably, it is chosen from the core-bark polymers of the methacrylate / butadiene / styrene type or the polystyrene / divinylbenzene type crosslinked polymers or the methacrylate / butadiene / styrene MBS (BET surface area of 1 to 5 m 2 / g) sold in particular by Arkema.
  • BET surface area of 1 to 5 m 2 / g sold in particular by Arkema.
  • the particle size of the substrate is advantageously chosen to allow good fluidization of the catalyst during the synthesis reaction of carbon fibrils and / or nanotubes. In practice, to ensure correct productivity, it is preferred that the substrate particles have a diameter of between 20 and 500 ⁇ m. Multivalent transition metals.
  • the transition metal is a multivalent metal selected from those of group VIB such as chromium Cr, molybdenum Mo, tungsten W, or those of group VIIIB such as iron Fe, cobalt Co, nickel Ni, ruthenium Ru, rhodium Rh, palladium Pd, osmium Os, Ir irium, platinum Pt or mixtures thereof.
  • the metal is selected from iron Fe, cobalt Co, or nickel Ni, or a mixture thereof.
  • the metal consists of iron only.
  • the catalyst material More preferably still, the metal consists of iron only.
  • the organic substrate represents the support on which the metal is coated.
  • the metal may be in the form of a film, but as otherwise the support is preferably porous, a portion of the metal may also be located in the pores of the catalyst.
  • a catalyst with a metal impregnation rate of up to 40%, preferably 10 to 35% can be obtained.
  • the amount of transition metal (s) generally represents up to 50% by weight of the final catalyst.
  • the amount of metal represents 1 to 30%, or even 1 to 15%, of the weight of the final catalyst.
  • the final catalyst is typically in the form of particles whose diameter is between 1 micron and 5 mm, preferably between 10 and 500 microns.
  • the catalyst is prepared by contacting the organic substrate as described above with a solution containing at least one transition metal (as) as defined above, in salt form.
  • the contacting is in principle carried out at a temperature between room temperature and the boiling point of the solution.
  • the amount of impregnating solution is determined so that at any time the substrate particles are in contact with a sufficient amount of solution to ensure the formation of a surface film on said substrate particles.
  • an impregnation of the substrate occurs when the organic substrate is brought into contact with the solution.
  • the impregnation of the substrate particles is advantageously carried out under a dry gas sweep, for example by means of an aqueous solution of metal in salt form, for example iron nitrate or cobalt acetate or nitrate. cobalt or a mixture of the two metals.
  • metal in salt form for example iron nitrate or cobalt acetate or nitrate. cobalt or a mixture of the two metals.
  • a catalyst material is provided as described above.
  • the growth of fibrils and / or carbon nanotubes is carried out.
  • This is carried out by thermal decomposition, preferably on a fluidized bed, of the organic substrate by heating the catalyst material at a temperature of between 300 and 1200 ° C., preferably between 500 and 700 ° C., in the presence of a composition.
  • hydrocarbon gas optionally comprising a reducing gas such as hydrogen.
  • a hydrocarbon gas is preferably introduced alone or in the presence of hydrogen.
  • the hydrocarbon gas may especially be chosen from: methane, ethane, ethylene, acetylene, ethanol, methanol, acetone and their mixtures, or even synthesis gas CO + H 2 (HIPCO process ). It is preferably a hydrocarbon such as methane, ethane, ethylene or acetylene, with ethylene being preferred for use in the present invention.
  • the hydrocarbon gas, such as ethylene, introduced into the reactor acts as a complementary source of carbon in the preparation of the carbon fibrils and / or nanotubes and can be combined if necessary with hydrogen or with a hydrogen / hydrogen mixture.
  • inert gas such as nitrogen.
  • the gas composition preferably comprises from 20 to 100% hydrogen, from 0% to 85% and more generally from 5 to 80% of hydrocarbon gas such as ethylene and optionally inert gas in addition. It is still preferred that the hydrocarbon gas be present in greater quantity (by volume) than the reducing gas.
  • volume ratio of hydrogen to hydrocarbon gas is advantageously between 1: 2 and 1: 4, better still, between 1:25 and 1:35 and even better, close to 1: 3.
  • Hydrogen allows the cleaning of the catalyst surface, prevents the formation of carbon fibers having an anarchic organization, and promotes the production of ordered carbon fibers and / or carbon nanotubes. It may further allow the reduction of the metal deposited on the catalyst.
  • the reduction of the catalyst takes place in situ in the synthesis reactor of carbon nanotubes, introducing the catalyst at the reaction temperature; thus, the catalyst does not see the air and the metal remains in unoxidized metal form.
  • This process has the advantage of allowing high productivity and obtaining products having a very low ash content of less than 15%, preferably less than 4%.
  • Fibrils and carbon nanotubes mono- or multifilets.
  • the products obtained have lengths ranging from 1 ⁇ m to 7 or 8 ⁇ m.
  • the diameters are between 20 and 250 nm, and particularly for the carbon nanotubes of diameters between 10 and 60 nm. Nanotubes are mainly multifilets.
  • the fibrils and / or nanotubes obtained according to the process of the invention described above can be used as agents for improving the mechanical and / or thermal properties and / or electrical conductivity in polymeric compositions or be used to prepare dispersions in solvents.
  • the fibrils and / or nanotubes obtained can be used in many fields, in particular in electronics (depending on the temperature and their structure, they can be conductors, semiconductors or insulators), in mechanics, for example for the reinforcement of composite materials ( carbon nanotubes are a hundred times stronger and six times lighter than steel) and electromechanical (they can lengthen or contract by charge injection). It is possible, for example, to mention the use of carbon nanotubes in macromolecular compositions intended, for example, for the packaging of electronic components, for the manufacture of fuel lines (fuel oil), antistatic coatings (or coating), in thermistors, electrodes for supercapacities, etc.
  • a catalyst is prepared from methacrylate / butadiene / styrene (MBS) and iron nitrate.
  • MBS methacrylate / butadiene / styrene
  • the MBS sold by Arkema under reference C223 is a core-shell structure, consisting of an elastomeric core of butadiene surrounded by a crown consisting of a layer of methylmethacrylate
  • the median diameter is of the order of 200 to 250 ⁇ m.
  • a 3 1 reactor equipped with a double jacket heated to 100 0 C is introduced 30 g of MBS and nitrogen sweeps from bottom to top.
  • the MBS particles are then in a prefluidization state.
  • a pump 54 g of a solution of iron nitrate nonahydrate containing 5.4 g of iron are then continuously injected.
  • the target ratio (mass of metal / mass of catalyst) being 15% of iron metal
  • the duration of addition of the solution is 2 h
  • the rate of addition of the liquid is substantially equal to the rate of evaporation of the water.
  • the catalyst is then heated to 18O 0 C in the reactor for 4 hours to effect denitrification.
  • the actual iron content of the catalyst at the end of the operation is 13%.
  • the same catalyst is prepared without denitrification; as soon as it is put back into the air, the composition
  • MBS / Fe begins to oxidize slowly, giving off smoke.
  • a black powder consisting of 32% of iron oxide and 68% of carbon.
  • Example 3 Preparation of the Polymeric Metal Catalyst No. 3
  • a catalyst is prepared from the same amount of MBS by adding 160 g of solution of iron nitrate nonahydrate, ie 16 g of iron.
  • the catalyst preparation and the impregnation are carried out in the same manner as in Example 1, with the exception of the duration of addition which is of the order of 6.5 h. Denitrification is continued for 4 hours. The actual iron content of the catalyst is 23% at the end of the operation.
  • This catalyst is prepared from an aqueous solution of cobalt acetate.
  • the actual cobalt content of the catalyst at the end of the operation is 12%.
  • a catalytic test is carried out by introducing a temperature between 600 and 700 ° C, a mass of about 2.5 g of catalyst in a reactor of 5 cm in diameter and 1 m in effective height, equipped with a disengagement to prevent entrainment of fine particles to downstream.
  • the gases are composed of hydrogen and ethylene (25% / 75% vol / vol) with a total flow rate between 100 and 300 Nl / h.
  • the catalyst is introduced in five portions per 0.5 gram to avoid too much gas evolution. Between each introduction, we wait 10 minutes.
  • the gas flow rate is sufficient for the solid to be well above the fluidization limit velocity, while remaining below the rate of flight.
  • the fibers obtained in tests 1 to 4 are well ordered and present either with well-organized graphitic planes parallel to the axis, or with planes inclined with respect to the axis of an angle of about 30 °. fish).
  • Productivity is expressed in grams of carbon produced per gram of metal introduced.

Abstract

The present invention relates to a method for preparing carbon fibrils and/or nanotubes from a carbon source integrated in the catalyst used for their preparation and a source of hydrocarbonated gas, as well as to the catalyst material and to the corresponding method. The catalyst material for preparing mono- or multi-leaved carbon fibrils and/or nanotubes includes one or more given multivalent transition metals and a hydrocarbonated solid organic substrate.

Description

PROCEDE DE PREPARATION DE FIBRILLES ET/OU NANOTUBES DE CARBONE A PARTIR D7UNE SOURCE DE CARBONE INTEGREE AUFIBRILS FOR PREPARING AND / OR CARBON NANOTUBES FROM 7 SOURCE INTEGRATED CARBON
CATALYSEURCATALYST
Domaine de l'invention.Field of the invention
La présente invention concerne un procédé de préparation de fibrilles et/ou nanotubes de carbone à partir d'une source de carbone intégrée au catalyseur servant à leur préparation, ainsi que le matériau catalyseur et son procédé de fabrication.The present invention relates to a process for preparing carbon fibrils and / or nanotubes from a carbon source integrated with the catalyst used for their preparation, as well as the catalyst material and its manufacturing process.
Arrière plan technologique de l'invention.Technological Background of the Invention
Les fibrilles de carbone et les nanotubes de carbone sont reconnus aujourd'hui comme des matériaux présentant de grands avantages, du fait de leurs propriétés mécaniques, de leurs rapports de formeCarbon fibrils and carbon nanotubes are recognized today as materials presenting great advantages, because of their mechanical properties, of their relations of form
(longueur/diamètre) élevés ainsi que de leurs propriétés électriques .(length / diameter) as well as their electrical properties.
Les fibrilles de carbone ont généralement un diamètre moyen allant de 50 nm au micron, supérieur à celui des nanotubes de carbone.The carbon fibrils generally have a mean diameter ranging from 50 nm to a micron, greater than that of the carbon nanotubes.
Les fibrilles se composent de zones graphitiques plus ou moins organisées (ou empilements turbostratiques) dont les plans sont inclinés à des angles variables par rapport à l'axe de la fibre. Elles sont souvent creuses dans l'axe central.The fibrils are composed of more or less organized graphitic zones (or turbostratic stacks) whose planes are inclined at variable angles with respect to the axis of the fiber. They are often hollow in the central axis.
Les nanotubes de carbone sont terminés par des hémisphères constitués de pentagones et d'hexagones de structure proche des fullerènes. Parmi ces structures, on peut citer entre autres les nanotubes composés d'un seul feuillet : on parle alors de SWNT (acronyme anglais de Single Wall Nanotubes) et les nanotubes composés de plusieurs feuillets concentriques appelés alors MWNT (acronyme anglais de Multi Wall Nanotubes) . Les SWNT sont en général plus difficiles à fabriquer que les MWNT.The carbon nanotubes are terminated by hemispheres consisting of pentagons and hexagons of structure close to fullerenes. Among these structures, there may be mentioned, among others, nanotubes composed of a single sheet: this is called SWNT (acronym for Single Wall Nanotubes) and nanotubes composed of several concentric layers then called MWNT (acronym for Multi Wall Nanotubes). SWNTs are generally more difficult to manufacture than MWNTs.
La production des nanotubes de carbone peut être mise en œuvre selon différents procédés comme la décharge électrique, lr ablation laser ou le dépôt chimique en phase vapeur (CVD)The production of carbon nanotubes may be implemented by various methods such as electrical discharge, the r laser ablation or chemical vapor deposition (CVD)
Parmi ces techniques, cette dernière semble être la seule susceptible de pouvoir assurer la fabrication en quantité importante de nanotubes de carbone, condition essentielle pour assurer un prix de revient permettant de déboucher massivement sur des applications industrielles. Selon cette méthode, on injecte une source de carbone à température relativement élevée sur un catalyseur, ledit catalyseur pouvant être constitué d'un métal supporté sur un solide inorganique. Parmi les métaux, sont cités de manière préférentielle le fer, le cobalt, le nickel, le molybdène et parmi les supports, on retrouve souvent l'alumine, la silice ou la magnésie. Les sources de carbone envisageables sont le méthane, l'éthane, l'éthylène, l'acétylène, l'éthanol, le méthanol, l'acétone, voire le gaz de synthèse CO + H2 (procédé HIPCO) .Among these techniques, the latter seems to be the only one likely to be able to ensure the production of a large quantity of carbon nanotubes, an essential condition to ensure a cost price allowing to emerge massively on industrial applications. According to this method, a carbon source is injected at a relatively high temperature over a catalyst, said catalyst being able to consist of a metal supported on an inorganic solid. Among the metals, iron, cobalt, nickel and molybdenum are preferentially mentioned and among the supports there is often alumina, silica or magnesia. Possible carbon sources are methane, ethane, ethylene, acetylene, ethanol, methanol, acetone or even CO + H2 synthesis gas (HIPCO process).
Mais, si l'on cherche à éviter les étapes de purification après la récupération des nanotubes de carbone en vue de simplifier le procédé et parce que certaines applications ne le nécessitent pas, on sera particulièrement intéressé à augmenter fortement la productivité pour avoir la teneur en cendres la plus faible possible.But, if we try to avoid purification steps after the recovery of carbon nanotubes in order to simplify the process and because some applications do not require it, we will be particularly interested in greatly increasing the productivity to have the content of carbon nanotubes. ash as low as possible.
De plus, avec les catalyseurs de l'art antérieur et dans la grande majorité des cas, les cendres sont constituées de métal de transition et d'alumine, de silice ou de magnésie. En effet, le métal est souvent encapsulé et peu sujet à causer des effets indésirables, mais ce n'est pas le cas du support minéral qui, s'il n'est pas éliminé par un traitement acide contraignant, peut s'avérer dommageable dans des applications telles que les films fins ou les fibres, du fait de la taille des particules.In addition, with the catalysts of the prior art and in the vast majority of cases, the ashes consist of transition metal and alumina, silica or magnesia. Indeed, the metal is often encapsulated and little subject to cause undesirable effects, but this is not the case of the mineral support which, if it is not eliminated by a binding acidic treatment, can prove harmful in applications such as thin films or fibers, because of the particle size.
Il est donc particulièrement désirable d'éviter l'utilisation de matériau inorganique, et ce pour éviter sa décomposition pendant la réaction.It is therefore particularly desirable to avoid the use of inorganic material, and this to prevent its decomposition during the reaction.
Dans ce but, US2006/0115409 décrit un procédé dans lequel la préparation des nanotubes de carbone (NTC) s'effectue par décomposition in situ d'un mélange comprenant du polyéthylène glycol comme matériau organique et source de carbone, en présence d'un catalyseur métallique. Le mélange constitué du catalyseur métallique dispersé dans le polyéthylène glycol est préalablement préparé en milieu solvant avant l'étape de formation des NTC qui elle-même s'effectue en deux étapes par chauffage à des températures respectives de 200-4000C à la première étape puis 400-1QOO0C à la deuxième étape.For this purpose, US2006 / 0115409 describes a process in which the preparation of carbon nanotubes (CNTs) is carried out by in situ decomposition of a mixture comprising polyethylene glycol as organic material and carbon source, in the presence of a catalyst. metallic. The mixture consisting of the metal catalyst dispersed in the polyethylene glycol is previously prepared in a solvent medium before the CNT formation step which itself is carried out in two stages by heating at temperatures of 200-400 ° C., respectively, at the first time. step then 400-1QOO 0 C in the second step.
Néanmoins, l'un des inconvénients de ce procédé réside dans le nombre important d'étapes à mettre en œuvre tant pour la préparation du catalyseur que pour la préparation des NTC. Un autre inconvénient réside dans la nature même du catalyseur sous forme de dispersion ou encore dans la nature du polymère organique, le poiyéthylène glycol (PEG), comme composant du catalyseur. En effet, en raison de la présence d'atomes d'oxygène dans sa structure, le PEG est susceptible d'oxyder d'éventuels gaz utilisés comme source de carbone complémentaire, cette réaction entrant alors en compétition avec la formation des nanotubes de carbone, de sorte que l'utilisation de ces gaz est fortement déconseillée. La productivité du procédé de fabrication de nanotubes de carbone se trouve ainsi fortement limitée, ce qui le rend impropre à une application industrielle.Nevertheless, one of the drawbacks of this process lies in the large number of steps to be implemented both for the preparation of the catalyst and for the preparation of the CNTs. Another disadvantage lies in the very nature of the dispersion catalyst or in the nature of the organic polymer, polyethylene glycol (PEG), as a component of the catalyst. Indeed, because of the presence of oxygen atoms in its structure, the PEG is likely to oxidize any gas used as a complementary carbon source, this reaction then competing with the formation of carbon nanotubes, so the use of these gases is strongly discouraged. The productivity of the process for manufacturing carbon nanotubes is thus greatly limited, which renders it unfit for industrial application.
Il existe donc un besoin de disposer d'autres procédés plus simples, plus efficaces pour fabriquer des nanotubes et/ou des fibrilles de carbone. Dans ce but, il existe aussi un besoin de disposer de nouvelles structures de catalyseur métallique polymérique pour préparer ces fibrilles ou nanotubes de carbone, ainsi que des procédés permettant de réaliser de telles structures.There is therefore a need for other simpler, more efficient processes for making nanotubes and / or carbon fibrils. For this purpose, there is also a need for new polymeric metal catalyst structures to prepare these carbon fibrils or nanotubes, as well as methods for making such structures.
Résumé de l'Invention. Ainsi, l'invention propose un matériau catalyseur pour la préparation de fibrilles et/ou de nanotubes de carbone mono- ou multifeuillets comprenant :Summary of the Invention Thus, the invention provides a catalyst material for the preparation of fibrils and / or mono- or multi-walled carbon nanotubes comprising:
- un ou plusieurs métaux de transition multivalents, choisis parmi ceux du groupe VIB, le chrome Cr, le molybdène Mo, le tungstène W, ou ceux du groupe VIIIB, le fer Fe, le cobalt Co, le nickel Ni, le ruthénium Ru, le rhodium Rh, le palladium Pd, l'osmium Os, l'iridium Ir, le platine Pt ou leurs mélanges, et un substrat organique solide choisi parmi les polymères, copolymères et terpolymères qui ne contiennent que du carbone et de l'hydrogène.one or more multivalent transition metals, chosen from those of group VIB, chromium Cr, molybdenum Mo, tungsten W, or those of group VIIIB, iron Fe, cobalt Co, nickel Ni, ruthenium Ru, Rh rhodium, Pd palladium, Os osmium, Ir irium, Pt platinum or mixtures thereof, and a solid organic substrate selected from polymers, copolymers and terpolymers which contain only carbon and hydrogen.
De préférence, le substrat organique est un polymère, de surface spécifique BET inférieure à 200 m2/g, par exemple comprise entre 0,1 m2/g et 50 m2/g. Par "compris (e) entre", on n'entend pas exclure, au sens de la présente invention, les valeurs citées comme bornes inférieure et supérieure de la plage concernée.Preferably, the organic substrate is a polymer with a BET specific surface area of less than 200 m 2 / g, for example between 0.1 m 2 / g and 50 m 2 / g. By "included (e) between", it is not intended to exclude, within the meaning of the present invention, the values cited as the lower and upper limits of the range concerned.
De préférence, le substrat organique est choisi parmi les polymères, copolymères ou terpolymères, dans lesquels au moins une partie des motifs comprend du butadiène et/ou du styrène.Preferably, the organic substrate is chosen from polymers, copolymers or terpolymers, in which at least a part of the units comprises butadiene and / or styrene.
De préférence encore, le substrat organique est choisi parmi les polymères cœur-écorce (en terminologie anglaise : « core-shell ») de type méthacrylate/butadiène/styrène ou les polymères réticulés de type polystyrène/divinylbenzène .More preferably, the organic substrate is selected from core-shell polymers (methacrylate / butadiene / styrene terminology) or crosslinked polystyrene / divinylbenzene polymers.
Selon l'invention, le métal de transition peut être choisi parmi le fer Fe, le cobalt Co, ou le nickel Ni, ou un de leurs mélanges.According to the invention, the transition metal may be chosen from iron Fe, cobalt Co, or nickel Ni, or a mixture thereof.
La quantité de métal (aux) de transition représente avantageusement jusqu'à 50% en poids du matériau catalyseur final, de préférence de 1 à 30% et plus préférentiellement de 1 à 15 % du poids du matériau catalyseur final .The amount of transition metal (s) is advantageously up to 50% by weight of the final catalyst material, preferably from 1 to 30% and more preferably from 1 to 15% by weight of the final catalyst material.
Selon un mode de réalisation, le substrat organique est un support poreux dans lequel le métal est imprégné, de préférence, dans lequel le taux d'imprégnation du support va jusqu'à 40%.According to one embodiment, the organic substrate is a porous support in which the metal is impregnated, preferably, in which the impregnation rate of the support is up to 40%.
Selon un mode de réalisation, le matériau catalyseur selon l'invention est sous forme de particules solides dont le diamètre est compris entre 1 micron et 5 mm.According to one embodiment, the catalyst material according to the invention is in the form of solid particles whose diameter is between 1 micron and 5 mm.
L' invention concerne aussi le procédé de préparation du matériau catalyseur décrit ci-dessus par mise en contact du substrat organique avec une solution contenant au moins un desdits métal (aux) de transition sous forme de sel, de préférence sous balayage de gaz sec. Cette étape est généralement suivie d'une réduction du métal déposé. Pour ce faire, le métal déposé est avantageusement réduit sous balayage de gaz réducteur tel que l'hydrogène.The invention also relates to the process for preparing the catalyst material described above by contacting the organic substrate with a solution containing at least one of said transition metal (s) in the form of salt, preferably under a dry gas sweep. This step is usually followed by a reduction of the deposited metal. To do this, the deposited metal is advantageously reduced under a reducing gas scan such as hydrogen.
De préférence, la solution est une solution aqueuse de nitrate de métal, notamment de nitrate de fer. De préférence, la dénitrification du catalyseur s'opère sous atmosphère inerte.Preferably, the solution is an aqueous solution metal nitrate, especially iron nitrate. Preferably, the denitrification of the catalyst takes place under an inert atmosphere.
Selon un mode de réalisation, la mise en contact s'effectue à une température comprise entre la température ambiante et la température d'ébullition de la solution, et la quantité de liquide, à tout moment, en contact avec le substrat est juste suffisante pour assurer la formation d'un film à la surface des particules.According to one embodiment, the contacting is carried out at a temperature between room temperature and the boiling temperature of the solution, and the quantity of liquid, at any time, in contact with the substrate is just sufficient to ensure the formation of a film on the surface of the particles.
L' invention concerne également un procédé de préparation de fibrilles et/ou de nanotubes de carbone mono- ou multifeuillets comprenant les étapes de : a) fourniture d'un matériau catalyseur tel que défini précédemment ; b) croissance des fibrilles et/ou nanotubes de carbone par décomposition thermique du substrat organique par chauffage du matériau catalyseur à une température comprise entre 300 et 12000C en présence d'une composition de gaz hydrocarboné comprenant éventuellement un gaz réducteur ; c) refroidissement et récupération des fibrilles et/ou nanotubes de carbone formés.The invention also relates to a process for the preparation of fibrils and / or mono- or multi-walled carbon nanotubes comprising the steps of: a) providing a catalyst material as defined above; b) growth of the carbon fibrils and / or nanotubes by thermal decomposition of the organic substrate by heating the catalyst material at a temperature of between 300 and 1200 ° C. in the presence of a hydrocarbon gas composition optionally comprising a reducing gas; c) cooling and recovery of fibrils and / or carbon nanotubes formed.
L' invention concerne plus particulièrement un procédé tel que décrit ci-dessus, dans lequel le gaz hydrocarboné est l'éthylène, utilisé en présence d'hydrogène comme gaz réducteur, la composition de gaz renfermant au moins 20% en volume d'hydrogène.The invention relates more particularly to a process as described above, wherein the hydrocarbon gas is ethylene, used in the presence of hydrogen as a reducing gas, the gas composition containing at least 20% by volume of hydrogen.
De préférence, l'étape b) est effectuée sur lit fiuidisé en présence du gaz hydrocarboné et éventuellement du gaz réducteur, plus préférentiellement en présence d'éthylène et d'hydrogène.Preferably, step b) is carried out on a fluidized bed in the presence of the hydrocarbon gas and optionally reducing gas, more preferably in the presence of ethylene and hydrogen.
De préférence, le gaz réducteur est présent dans l'étape b) de préparation des nanotubes de carbone, de sorte que la réduction du métal du matériau catalyseur s'opère in-situ pendant l'étape b) .Preferably, the reducing gas is present in step b) of preparing the carbon nanotubes, so that the reduction of the metal of the catalyst material occurs in-situ during step b).
On comprend donc que le procédé selon 1 ' invention permet la fabrication de fibrilles et/ou nanotubes de carbone à la fois par décomposition du support organique et dépôt chimique en phase vapeur, de sorte que sa productivité est maximale.It is therefore understood that the process according to the invention allows the manufacture of carbon fibrils and / or nanotubes both by decomposition of the organic support and chemical vapor deposition, so that its productivity is maximum.
Exposé détaillé des modes de réalisation de l'invention.DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION
L' invention vise à proposer un matériau catalyseur pour la préparation de fibrilles et/ou de nanotubes de carbone mono- ou multifeuillets comprenant un ou plusieurs métaux de transition multivalents particuliers et un substrat organique polymérique hydrocarboné. Le substrat organique .The aim of the invention is to provide a catalyst material for the preparation of mono- or multi-walled carbon fibrils and / or nanotubes comprising one or more particular multivalent transition metals and a hydrocarbon polymeric organic substrate. The organic substrate
Le substrat organique est solide et avantageusement poreux. Il peut présenter une surface spécifique BET inférieure à 200 m2/g, et, de préférence, comprise entre 1 m2/g et 50 m2/g.The organic substrate is solid and advantageously porous. It may have a BET specific surface area of less than 200 m 2 / g, and preferably between 1 m 2 / g and 50 m 2 / g.
Le substrat est choisi parmi les polymères, copolymères ou terpolymères qui ne contiennent que du carbone et de l'hydrogène, et qui, de ce fait, conduisent à un rendement supérieur en fibrilles et/ou nanotubes ordonnés.The substrate is chosen from polymers, copolymers or terpolymers which contain only carbon and hydrogen, and which, as a result, lead to a higher yield of ordered fibrils and / or nanotubes.
De préférence, le substrat organique est choisi parmi les polymères, copolymères ou terpolymères dans lesquels une partie au moins des motifs comprend du butadiène et/ou du styrène. De préférence encore, il est choisi parmi les polymères coeur-écorce de type méthacrylate/butadiène/styrène ou les polymères réticulés de type polystyrène/divinylbenzène ou les méthacrylate/butadiène/styrène MBS (surface BET de 1 à 5 m2/g) vendus notamment par la société Arkema.Preferably, the organic substrate is chosen from polymers, copolymers or terpolymers in which at least part of the units comprise butadiene and / or styrene. More preferably, it is chosen from the core-bark polymers of the methacrylate / butadiene / styrene type or the polystyrene / divinylbenzene type crosslinked polymers or the methacrylate / butadiene / styrene MBS (BET surface area of 1 to 5 m 2 / g) sold in particular by Arkema.
La taille des particules du substrat est avantageusement choisie pour permettre une bonne fluidisation du catalyseur lors de la réaction de synthèse des fibrilles et/ou nanotubes de carbone. Dans la pratique, pour assurer une productivité correcte, on préfère que les particules de substrat aient un diamètre compris entre 20 et 500 μm. Les métaux de transition multivalents .The particle size of the substrate is advantageously chosen to allow good fluidization of the catalyst during the synthesis reaction of carbon fibrils and / or nanotubes. In practice, to ensure correct productivity, it is preferred that the substrate particles have a diameter of between 20 and 500 μm. Multivalent transition metals.
Le métal de transition est un métal multivalent choisi parmi ceux du groupe VIB comme le chrome Cr, le molybdène Mo, le tungstène W, ou ceux du groupe VIIIB comme le fer Fe, le cobalt Co, le nickel Ni, le ruthénium Ru, le rhodium Rh, le palladium Pd, l'osmium Os, l'iridium Ir, le platine Pt ou leurs mélanges.The transition metal is a multivalent metal selected from those of group VIB such as chromium Cr, molybdenum Mo, tungsten W, or those of group VIIIB such as iron Fe, cobalt Co, nickel Ni, ruthenium Ru, rhodium Rh, palladium Pd, osmium Os, Ir irium, platinum Pt or mixtures thereof.
De préférence, le métal est choisi parmi le fer Fe, le cobalt Co, ou le nickel Ni, ou un de leurs mélanges.Preferably, the metal is selected from iron Fe, cobalt Co, or nickel Ni, or a mixture thereof.
Plus préférentiellement encore, le métal est constitué de fer uniquement. -Le matériau catalyseur.More preferably still, the metal consists of iron only. The catalyst material.
Dans le catalyseur, le substrat organique représente le support sur lequel est enrobé le métal. Le métal peut être sous forme de film, mais comme par ailleurs, le support est de préférence poreux, une partie du métal peut aussi se trouver située dans les pores du catalyseur. Ainsi, on peut obtenir un catalyseur avec un taux d'imprégnation en métal allant jusqu'à 40%, de préférence de 10 à 35%. La quantité de métal (aux) de transition représente généralement jusqu'à 50% en poids du catalyseur final. De préférence et en vue d'augmenter la productivité en fibrilles et/ou nanotubes de carbone, la quantité de métal représente de 1 à 30 %, voire de 1 à 15 %, du poids du catalyseur final.In the catalyst, the organic substrate represents the support on which the metal is coated. The metal may be in the form of a film, but as otherwise the support is preferably porous, a portion of the metal may also be located in the pores of the catalyst. Thus, a catalyst with a metal impregnation rate of up to 40%, preferably 10 to 35% can be obtained. The amount of transition metal (s) generally represents up to 50% by weight of the final catalyst. Preferably and in order to increase the productivity of carbon fibrils and / or nanotubes, the amount of metal represents 1 to 30%, or even 1 to 15%, of the weight of the final catalyst.
Le catalyseur final se présente typiquement sous forme de particules dont le diamètre est compris de 1 micron et 5 mm, de préférence entre 10 et 500 μm. Le procédé de préparation du matériau catalyseur.The final catalyst is typically in the form of particles whose diameter is between 1 micron and 5 mm, preferably between 10 and 500 microns. The process for preparing the catalyst material
La préparation du catalyseur s'effectue par mise en contact du substrat organique tel que décrit plus haut avec une solution contenant au moins un métal (aux) de transition tel que défini précédemment, sous forme de sel .The catalyst is prepared by contacting the organic substrate as described above with a solution containing at least one transition metal (as) as defined above, in salt form.
La mise en contact s'effectue en principe à une température comprise entre la température ambiante et la température d'ébullition de la solution. La quantité de solution d'imprégnation est déterminée pour qu'à tout moment, les particules de substrat soient en contact avec une quantité de solution suffisante pour assurer la formation d'un film de surface sur lesdites particules de substrat. De préférence, lorsque le substrat est poreux, une imprégnation du substrat se produit lors de la mise en contact du substrat organique avec la solution.The contacting is in principle carried out at a temperature between room temperature and the boiling point of the solution. The amount of impregnating solution is determined so that at any time the substrate particles are in contact with a sufficient amount of solution to ensure the formation of a surface film on said substrate particles. Preferably, when the substrate is porous, an impregnation of the substrate occurs when the organic substrate is brought into contact with the solution.
L' imprégnation des particules de substrat est avantageusement mise en oeuvre sous balayage de gaz sec, par exemple au moyen d'une solution aqueuse de métal sous forme de sel, comme par exemple le nitrate de fer ou l'acétate de cobalt ou le nitrate de cobalt ou un mélange des deux métaux.The impregnation of the substrate particles is advantageously carried out under a dry gas sweep, for example by means of an aqueous solution of metal in salt form, for example iron nitrate or cobalt acetate or nitrate. cobalt or a mixture of the two metals.
Le fait de travailler «à sec», c'est-à-dire en ayant à tout moment juste la quantité de liquide nécessaire pour créer un film liquide en surface des particules de substrat catalytique est un avantage car cela permet, en chauffant sous balayage d'air sec, d'éviter les rejets aqueux (par exemple les rejets aqueux de nitrates lorsque la solution d'imprégnation contient des nitrates). La dénitrification du catalyseur s'opère ensuite sous atmosphère inerte, par exemple par chauffage vers 200°C. .Le procédé de préparation de fibrilles et/ou de nanotubes de carbone mono- ou multifeuillets .The fact of working "dry", that is to say having at any time just the amount of liquid necessary to create a liquid film on the surface of the catalytic substrate particles is an advantage because it allows, by heating under scanning dry air, avoid discharges aqueous (for example aqueous releases of nitrates when the impregnating solution contains nitrates). The denitrification of the catalyst is then carried out under an inert atmosphere, for example by heating to 200 ° C. The process for the preparation of fibril and / or mono- or multi-walled carbon nanotubes.
Dans une première étape, on fournit un matériau catalyseur tel que décrit ci-dessus.In a first step, a catalyst material is provided as described above.
Puis, dans une deuxième étape, on effectue la croissance des fibrilles et/ou nanotubes de carbone. Celle-ci s'effectue par décomposition thermique, de préférence sur lit fluidisé, du substrat organique par chauffage du matériau catalyseur à une température comprise entre 300 et 12000C, de préférence de 500 à 7000C, en présence d'une composition de gaz hydrocarboné comprenant éventuellement un gaz réducteur tel que 1 ' hydrogène .Then, in a second step, the growth of fibrils and / or carbon nanotubes is carried out. This is carried out by thermal decomposition, preferably on a fluidized bed, of the organic substrate by heating the catalyst material at a temperature of between 300 and 1200 ° C., preferably between 500 and 700 ° C., in the presence of a composition. hydrocarbon gas optionally comprising a reducing gas such as hydrogen.
Ainsi on introduit, de préférence, un gaz hydrocarboné seul ou en présence d'hydrogène. Le gaz hydrocarboné peut notamment être choisi parmi : le méthane, l'éthane, l'éthylène, l'acétylène, l'éthanol, le méthanol, l'acétone et leurs mélanges, voire du gaz de synthèse CO + H2 (procédé HIPCO) . Il s'agit de préférence d'un hydrocarbure tel que le méthane, l'éthane, l'éthylène ou l'acétylène, l'éthylène étant préféré pour une utilisation dans la présente invention .Thus, a hydrocarbon gas is preferably introduced alone or in the presence of hydrogen. The hydrocarbon gas may especially be chosen from: methane, ethane, ethylene, acetylene, ethanol, methanol, acetone and their mixtures, or even synthesis gas CO + H 2 (HIPCO process ). It is preferably a hydrocarbon such as methane, ethane, ethylene or acetylene, with ethylene being preferred for use in the present invention.
Le gaz hydrocarboné, tel que l'éthylène, introduit dans le réacteur joue le rôle de source complémentaire de carbone dans la préparation des fibrilles et/ou nanotubes de carbone et peut être si nécessaire combiné à de l'hydrogène ou à un mélange hydrogène/gaz inerte comme 1' azote . La composition de gaz comprend en volume de préférence de 20 à 100% d'hydrogène, de 0% à 85% et plus généralement de 5 à 80% de gaz hydrocarboné tel que l'éthylène et éventuellement du gaz inerte en complément. On préfère encore que le gaz hydrocarboné soit présent en plus grande quantité (en volume) que le gaz réducteur.The hydrocarbon gas, such as ethylene, introduced into the reactor acts as a complementary source of carbon in the preparation of the carbon fibrils and / or nanotubes and can be combined if necessary with hydrogen or with a hydrogen / hydrogen mixture. inert gas such as nitrogen. The gas composition preferably comprises from 20 to 100% hydrogen, from 0% to 85% and more generally from 5 to 80% of hydrocarbon gas such as ethylene and optionally inert gas in addition. It is still preferred that the hydrocarbon gas be present in greater quantity (by volume) than the reducing gas.
Plus particulièrement, le rapport volumique de l'hydrogène au gaz hydrocarboné est avantageusement compris entre 1:2 et 1:4, mieux, entre 1:25 et 1:35 et, encore mieux, voisin de 1:3.More particularly, the volume ratio of hydrogen to hydrocarbon gas is advantageously between 1: 2 and 1: 4, better still, between 1:25 and 1:35 and even better, close to 1: 3.
L'hydrogène permet le nettoyage de la surface du catalyseur, empêche la formation de fibres de carbone ayant une organisation anarchique, et favorise la production de fibrilles et/ou nanotubes de carbone ordonnés. Il peut en outre permettre la réduction du métal déposé sur le catalyseur.Hydrogen allows the cleaning of the catalyst surface, prevents the formation of carbon fibers having an anarchic organization, and promotes the production of ordered carbon fibers and / or carbon nanotubes. It may further allow the reduction of the metal deposited on the catalyst.
Puis, après refroidissement on récupère les fibrilles et/ou nanotubes de carbone formés.Then, after cooling, the fibrils and / or carbon nanotubes formed are recovered.
Selon un mode de réalisation préféré, la réduction du catalyseur s'opère in-situ dans le réacteur de synthèse des nanotubes de carbone, en introduisant le catalyseur à la température de réaction ; ainsi, le catalyseur ne revoit pas l'air et le métal reste sous forme métallique non oxydée . Ce procédé a l'avantage de permettre une forte productivité et l'obtention de produits ayant une teneur en cendres très faible, inférieure à 15%, de préférence inférieure à 4%.According to a preferred embodiment, the reduction of the catalyst takes place in situ in the synthesis reactor of carbon nanotubes, introducing the catalyst at the reaction temperature; thus, the catalyst does not see the air and the metal remains in unoxidized metal form. This process has the advantage of allowing high productivity and obtaining products having a very low ash content of less than 15%, preferably less than 4%.
.Les fibrilles et les nanotubes de carbone mono- ou multifeuillets .Fibrils and carbon nanotubes mono- or multifilets.
Les produits obtenus ont des longueurs allant de Iμm à 7 ou 8 μm. Les diamètres sont compris entre 20 et 250 nm, et particulièrement pour les nanotubes de carbone des diamètres compris entre 10 et 60 nm. Les nanotubes sont principalement multifeuillets .The products obtained have lengths ranging from 1 μm to 7 or 8 μm. The diameters are between 20 and 250 nm, and particularly for the carbon nanotubes of diameters between 10 and 60 nm. Nanotubes are mainly multifilets.
Les fibrilles et/ou nanotubes obtenus selon le procédé de l'invention décrit ci-dessus peuvent être utilisés comme agents d'amélioration des propriétés mécaniques et/ou thermiques et/ou de conductivité électrique dans des compositions polymériques ou être utilisés pour préparer des dispersions en solvants.The fibrils and / or nanotubes obtained according to the process of the invention described above can be used as agents for improving the mechanical and / or thermal properties and / or electrical conductivity in polymeric compositions or be used to prepare dispersions in solvents.
Les fibrilles et/ou nanotubes obtenus peuvent être utilisés dans de nombreux domaines, notamment en électronique (selon la température et leur structure, ils peuvent être conducteurs, semi-conducteurs ou isolants), en mécanique, par exemple pour le renfort des matériaux composites (les nanotubes de carbone sont cent fois plus résistants et six fois plus légers que l'acier) et en électromécanique (ils peuvent s'allonger ou se contracter par injection de charge) . On peut, par exemple, citer l'utilisation de nanotubes de carbone dans des compositions macromoléculaires destinées par exemple à l'emballage de composants électroniques, à la fabrication de conduites d'essence (fuel une), de revêtements antistatiques (ou coating) , dans des thermistors, des électrodes pour supercapacités, etc.The fibrils and / or nanotubes obtained can be used in many fields, in particular in electronics (depending on the temperature and their structure, they can be conductors, semiconductors or insulators), in mechanics, for example for the reinforcement of composite materials ( carbon nanotubes are a hundred times stronger and six times lighter than steel) and electromechanical (they can lengthen or contract by charge injection). It is possible, for example, to mention the use of carbon nanotubes in macromolecular compositions intended, for example, for the packaging of electronic components, for the manufacture of fuel lines (fuel oil), antistatic coatings (or coating), in thermistors, electrodes for supercapacities, etc.
EXEMPLES :EXAMPLES
Les exemples qui suivent visent à illustrer l'invention sans en limiter la portée.The following examples are intended to illustrate the invention without limiting its scope.
Exemple 1 : préparation du catalyseur métallique polymérique n° 1Example 1 Preparation of the Polymeric Metal Catalyst No. 1
On prépare un catalyseur à partir de Méthacrylate/Butadiène/Styrène (MBS) et de nitrate de fer. Le MBS vendu par Arkema sous la référence C223 est une structure cœur-écorce, constituée d'un cœur élastomérique de butadiène entouré par une couronne constituée d'une couche de méthylméthacrylateA catalyst is prepared from methacrylate / butadiene / styrene (MBS) and iron nitrate. The MBS sold by Arkema under reference C223 is a core-shell structure, consisting of an elastomeric core of butadiene surrounded by a crown consisting of a layer of methylmethacrylate
(36%) /butylacrylate (4%), puis par une seconde couche de polystyrène (50%) et par une troisième couche de méthacrylate de méthyle (10%). Selon les proportions des différents polymères, on peut obtenir un caractère élastomérique plus ou moins prononcé. Le diamètre médian est de l'ordre de 200 à 250 μm. Dans un réacteur de 3 1 muni d'une double enveloppe chauffé à 100 0C, on introduit 30 g de MBS et on balaye à l'azote de bas en haut. Les particules de MBS sont alors dans un état de préfluidisation. Au moyen d'une pompe, on injecte alors en continu 54 g d'une solution de nitrate de fer nonahydrate, contenant 5,4 g de fer. Le ratio visé (masse de métal / masse de catalyseur) étant de 15 % en fer métal, la durée d'addition de la solution est de 2 h et la vitesse d'ajout du liquide est sensiblement égale à la vitesse d' évaporation de l'eau. Le catalyseur est ensuite porté à 18O0C dans le réacteur pendant 4 h afin d'opérer la dénitrification .(36%) / butylacrylate (4%), followed by a second layer of polystyrene (50%) and a third layer of methyl methacrylate (10%). Depending on the proportions of the different polymers, a more or less pronounced elastomeric character can be obtained. The median diameter is of the order of 200 to 250 μm. In a 3 1 reactor equipped with a double jacket heated to 100 0 C, is introduced 30 g of MBS and nitrogen sweeps from bottom to top. The MBS particles are then in a prefluidization state. By means of a pump, 54 g of a solution of iron nitrate nonahydrate containing 5.4 g of iron are then continuously injected. The target ratio (mass of metal / mass of catalyst) being 15% of iron metal, the duration of addition of the solution is 2 h and the rate of addition of the liquid is substantially equal to the rate of evaporation of the water. The catalyst is then heated to 18O 0 C in the reactor for 4 hours to effect denitrification.
Malgré la température élevée, les grains de MBS gardent parfaitement leur morphologie.Despite the high temperature, the grains of MBS keep perfectly their morphology.
Le taux réel en fer du catalyseur, en fin d'opération, est de 13%.The actual iron content of the catalyst at the end of the operation is 13%.
Exemple 2 : préparation du catalyseur métallique polymérique n° 2Example 2 Preparation of the Polymeric Metal Catalyst No. 2
On prépare le même catalyseur sans opérer la dénitrification ; dès la remise à l'air, la compositionThe same catalyst is prepared without denitrification; as soon as it is put back into the air, the composition
MBS/Fe commence à s'oxyder lentement en dégageant une fumée. A la fin de l'opération, on récupère une poudre noire, constituée de 32 % d'oxyde de fer et 68 % de carbone .MBS / Fe begins to oxidize slowly, giving off smoke. At the end of the operation, a black powder consisting of 32% of iron oxide and 68% of carbon.
Exemple 3 : préparation du catalyseur métallique polymérique n° 3 On prépare un catalyseur à partir de la même quantité de MBS en y ajoutant 160 g de solution de nitrate de fer nonahydrate, soit 16 g de fer.Example 3 Preparation of the Polymeric Metal Catalyst No. 3 A catalyst is prepared from the same amount of MBS by adding 160 g of solution of iron nitrate nonahydrate, ie 16 g of iron.
La préparation du catalyseur et l'imprégnation sont faites de la même manière qu'à l'exemple 1, à l'exception de la durée d'addition qui est de l'ordre de 6,5 h. La dénitrification est poursuivie pendant 4 h. Le taux réel en fer du catalyseur est de 23% en fin d'opération.The catalyst preparation and the impregnation are carried out in the same manner as in Example 1, with the exception of the duration of addition which is of the order of 6.5 h. Denitrification is continued for 4 hours. The actual iron content of the catalyst is 23% at the end of the operation.
Exemple 4 : préparation du catalyseur métallique polymérique n° 4Example 4 Preparation of the Polymeric Metal Catalyst No. 4
Ce catalyseur est préparé à partir d'une solution aqueuse d'acétate de cobalt.This catalyst is prepared from an aqueous solution of cobalt acetate.
Dans un réacteur de 3 1 muni d'une double enveloppe chauffé à 100 0C, on introduit 30 g de MBS et on balaye à l'azote de bas en haut. Les particules de MBS sont alors dans un état de préfluidisation. Au moyen d'une pompe, on injecte alors en continu 100 ml d'une solution d'acétate de cobalt tétrahydrate, contenant 5,3 g de cobalt. Le ratio visé (masse de métal / masse de catalyseur) étant de 15 % en métal, la durée d'addition de la solution est de 2 h et la vitesse d'ajout du liquide est sensiblement égale à la vitesse d' évaporation de l'eau.In a 3 1 reactor equipped with a double jacket heated to 100 0 C, is introduced 30 g of MBS and nitrogen sweeps from bottom to top. The MBS particles are then in a prefluidization state. By means of a pump, 100 ml of a solution of cobalt acetate tetrahydrate, containing 5.3 g of cobalt, are then continuously injected. The target ratio (mass of metal / mass of catalyst) being 15% of metal, the duration of addition of the solution is 2 h and the rate of addition of the liquid is substantially equal to the evaporation rate of the metal. 'water.
Le taux réel en cobalt du catalyseur, en fin d'opération, est de 12%.The actual cobalt content of the catalyst at the end of the operation is 12%.
Exemple 5 : préparation de fibrilles et/ou nanotubes de carboneExample 5 Preparation of Carbon Fibers and / or Nanotubes
On pratique un test catalytique en introduisant à une température comprise entre 600 et 700°C, une masse d'environ 2,5 g de catalyseur dans un réacteur de 5 cm de diamètre et 1 m de hauteur efficace, équipé d'un désengagement destiné à éviter l'entraînement de fines particules vers l'aval. Les gaz sont composés d'hydrogène et d'éthylène (25%/75% vol. /vol.) avec un débit total compris entre 100 et 300 Nl/h.A catalytic test is carried out by introducing a temperature between 600 and 700 ° C, a mass of about 2.5 g of catalyst in a reactor of 5 cm in diameter and 1 m in effective height, equipped with a disengagement to prevent entrainment of fine particles to downstream. The gases are composed of hydrogen and ethylene (25% / 75% vol / vol) with a total flow rate between 100 and 300 Nl / h.
Le catalyseur est introduit en cinq fois par parties de 0,5 gramme afin d'éviter un trop fort dégagement gazeux. Entre chaque introduction, on attend 10 minutes.The catalyst is introduced in five portions per 0.5 gram to avoid too much gas evolution. Between each introduction, we wait 10 minutes.
On constate qu'à chaque introduction, apparaît en chromatographie gazeuse un pic de méthane un peu plus intense qu'en régime établi.It is found that at each introduction, appears in gas chromatography a peak of methane a little more intense than in steady state.
Le débit gazeux est suffisant pour que le solide soit largement au-delà de la vitesse limite de fluidisation, tout en restant en dessous de la vitesse d' envolement .The gas flow rate is sufficient for the solid to be well above the fluidization limit velocity, while remaining below the rate of flight.
Après une certaine durée de réaction, on arrête le chauffage et on évalue la quantité de produit formée.After a certain reaction time, the heating is stopped and the amount of product formed is evaluated.
Parallèlement, une estimation de la qualité des fibrilles et nanotubes de carbone produits est faite par microscopie à transmission.At the same time, an estimate of the quality of the carbon fibrils and nanotubes produced is made by transmission microscopy.
Les conditions opératoires et résultats des 7 essais effectués sont réunis dans le tableau 1 ci-dessous : The operating conditions and results of the 7 tests carried out are shown in Table 1 below:
Tableau 1Table 1
Les fibres obtenues dans les essais 1 à 4 sont bien ordonnées et se présentent, soit avec des plans graphitiques bien organisés parallèles à l'axe, soit avec des plans inclinés par rapport à l'axe d'un angle environ 30° (arête de poisson) . The fibers obtained in tests 1 to 4 are well ordered and present either with well-organized graphitic planes parallel to the axis, or with planes inclined with respect to the axis of an angle of about 30 °. fish).
La productivité est exprimée en grammes de carbone produit par gramme de métal introduit.Productivity is expressed in grams of carbon produced per gram of metal introduced.
Les conditions des essais 1 et 5 permettent d'obtenir les meilleures productivité et teneur en cendres. Ces productivités sont tout à fait étonnantes et nettement supérieures à celles obtenues généralement dans l'art antérieur. Ces résultats démontrent que la présence du substrat organique a un effet sur la productivité de fibrilles et/ou nanotubes de carbone. De plus, le fait d'avoir brûlé le substrat permet de récupérer des fibrilles et/ou des nanotubes de carbone exempts de support minéral autre que le métal catalytique . The conditions of tests 1 and 5 make it possible to obtain the best productivity and ash content. These productivities are quite surprising and clearly superior to those generally obtained in the prior art. These results demonstrate that the presence of the organic substrate has an effect on the productivity of carbon fibrils and / or nanotubes. In addition, the fact of having burned the substrate makes it possible to recover fibrils and / or carbon nanotubes free of mineral support other than the catalytic metal.

Claims

REVENDICATIONS
1. Matériau catalyseur pour la préparation de fibrilles et/ou de nanotubes de carbone mono- ou multifeuillets comprenant :Catalyst material for the preparation of mono- or multi-walled carbon fibrils and / or nanotubes comprising:
- un ou plusieurs métaux de transition multivalents choisis parmi ceux du groupe VIB, le chrome Cr, le molybdène Mo, le tungstène W, ou ceux du groupe VIIIB, le fer Fe, le cobalt Co, le nickel Ni, le ruthénium Ru, le rhodium Rh, le palladium Pd, l'osmium 0s, l'iridium Ir, le platine Pt ou leurs mélanges, et un substrat organique solide choisi parmi les polymères, copolymères et terpolymères qui ne contiennent que du carbone et de l'hydrogène.one or more multivalent transition metals chosen from those of group VIB, chromium Cr, molybdenum Mo, tungsten W, or those of group VIIIB, iron Fe, cobalt Co, nickel Ni, ruthenium Ru, rhodium Rh, palladium Pd, osmium Os, Ir irium, platinum Pt or mixtures thereof, and a solid organic substrate selected from polymers, copolymers and terpolymers which contain only carbon and hydrogen.
2. Matériau selon la revendication 1 dans lequel le substrat organique est un polymère de surface spécifique BET inférieure à 200 m2/g.2. Material according to claim 1 wherein the organic substrate is a BET surface area polymer of less than 200 m 2 / g.
3. Matériau selon la revendication 1 ou 2 dans lequel le substrat organique a une surface spécifique BET comprise entre 0,1 m2/g et 50 m2/g.3. Material according to claim 1 or 2 wherein the organic substrate has a BET specific surface area of between 0.1 m 2 / g and 50 m 2 / g.
4. Matériau selon l'une des revendications 1 à 3 dans lequel le substrat organique est choisi parmi les polymères, copolymères ou terpolymères, dans lesquels une partie au moins des motifs comprend du butadiène et/ou du styrène.4. Material according to one of claims 1 to 3 wherein the organic substrate is selected from polymers, copolymers or terpolymers, wherein at least a portion of the units comprises butadiene and / or styrene.
5. Matériau selon l'une des revendications 1 à 4 dans lequel le substrat organique est choisi parmi les polymères cœur-écorce de type Méthacrylate/butadiène/Styrène et les polymères réticulés de type polystyrène/divinylbenzène .5. Material according to one of claims 1 to 4 wherein the organic substrate is selected from core-bark polymers of methacrylate / butadiene / Styrene type and crosslinked polystyrene / divinylbenzene polymers.
6. Matériau selon l'une des revendications 1 à 5 dans lequel le métal est choisi parmi le fer Fe, le cobalt Co, ou le nickel Ni, ou un de leurs mélanges.6. Material according to one of claims 1 to 5 wherein the metal is selected from Fe iron, the cobalt Co, or nickel Ni, or a mixture thereof.
7. Matériau selon l'une des revendications 1 à 6 dans lequel la quantité de métal (aux) de transition représente jusqu'à 50% en poids du matériau catalyseur final, de préférence de 1 à 30 % et plus préférentiellement de 1 à 15 % du poids du matériau catalyseur final.7. Material according to one of claims 1 to 6 wherein the amount of metal (s) transition represents up to 50% by weight of the final catalyst material, preferably from 1 to 30% and more preferably from 1 to 15 % of the weight of the final catalyst material.
8. Matériau selon l'une des revendications 1 à 7 dans lequel le substrat organique est un support poreux dans lequel le métal est imprégné.8. Material according to one of claims 1 to 7 wherein the organic substrate is a porous support in which the metal is impregnated.
9. Matériau selon la revendication 8 dans lequel le taux d'imprégnation du support va jusqu'à 40%.9. Material according to claim 8 wherein the impregnation rate of the support is up to 40%.
10. Matériau selon l'une des revendications 1 à 9 sous forme de particules solides dont le diamètre est compris entre 1 micron et 5 mm.10. Material according to one of claims 1 to 9 in the form of solid particles whose diameter is between 1 micron and 5 mm.
11. Procédé de préparation du matériau catalyseur selon l'une des revendications 1 à 10 par mise en contact du substrat organique avec une solution contenant au moins un desdits métal (aux) de transition sous forme de sel, de préférence sous balayage de gaz sec.11. Process for preparing the catalyst material according to one of claims 1 to 10 by bringing the organic substrate into contact with a solution containing at least one of said transition metal (s) in the form of salt, preferably under a dry gas sweep. .
12. Procédé selon la revendication 11 dans lequel la solution est une solution aqueuse de nitrate de métal, de préférence de fer.12. The method of claim 11 wherein the solution is an aqueous solution of metal nitrate, preferably iron.
13. Procédé selon la revendication 11 ou 12 dans lequel la mise en contact s'effectue à une température comprise entre la température ambiante et la température d'ébullition de la solution, et en ce que la quantité de liquide, à tout moment, en contact avec le substrat est juste suffisante pour assurer la formation d'un film à la surface des particules .13. The method of claim 11 or 12 wherein the contacting is carried out at a temperature between room temperature and the boiling temperature of the solution, and in that the amount of liquid, at any time, in contact with the substrate is just sufficient to ensure the formation of a film on the surface of the particles.
14. Procédé selon la revendication 12 dans lequel la dénitrification du catalyseur s'opère sous atmosphère inerte.14. Process according to claim 12, in which the denitrification of the catalyst is carried out under inert atmosphere.
15. Procédé de préparation de fibrilles et/ou de nanotubes de carbone mono- ou multifeuillets comprenant les étapes de : a) fourniture d'un matériau catalyseur selon l'une quelconque des revendications 1 à 10 ; b) croissance des fibrilles et/ou nanotubes de carbone par décomposition thermique du substrat organique par chauffage du matériau catalyseur à une température comprise entre 300 et 12000C en présence d'une composition de gaz hydrocarboné comprenant éventuellement un gaz réducteur ; et c) refroidissement et récupération des fibrilles et/ou nanotubes de carbone formés. A process for preparing single or multi-walled carbon fibrils and / or nanotubes comprising the steps of: a) providing a catalyst material according to any one of claims 1 to 10; b) growth of the carbon fibrils and / or nanotubes by thermal decomposition of the organic substrate by heating the catalyst material at a temperature of between 300 and 1200 ° C. in the presence of a hydrocarbon gas composition optionally comprising a reducing gas; and c) cooling and recovering the formed fibrils and / or carbon nanotubes.
16. Procédé selon la revendication 15, caractérisé en ce que le gaz hydrocarboné est l'éthylène, utilisé en présence d'hydrogène comme gaz réducteur, la composition de gaz renfermant au moins 20% en volume d' hydrogène . 16. The method of claim 15, characterized in that the hydrocarbon gas is ethylene, used in the presence of hydrogen as a reducing gas, the gas composition containing at least 20% by volume of hydrogen.
17. Procédé selon la revendication 15 ou 16, dans lequel l'étape b) est effectuée sur lit fluidisé en présence du gaz hydrocarboné et éventuellement de gaz réducteur, de préférence en présence d' éthylène et d'hydrogène. 17. The method of claim 15 or 16, wherein step b) is carried out on a fluidized bed in the presence of hydrocarbon gas and optionally reducing gas, preferably in the presence of ethylene and hydrogen.
18. Procédé selon l'une des revendications 15 à 17 dans lequel le matériau catalyseur de l'étape a) est préparé selon le procédé de l'une des revendications 11 à 14.18. Method according to one of claims 15 to 17 wherein the catalyst material of step a) is prepared according to the method of one of claims 11 to 14.
19. Procédé selon la revendication 15, dans lequel le métal du matériau catalyseur est réduit in-situ pendant l'étape b) de préparation des nanotubes de carbone .The method of claim 15, wherein the metal of the catalyst material is reduced in situ during step b) of preparing the carbon nanotubes.
20. Utilisation de fibrilles et/ou nanotubes de carbone obtenus suivant le procédé selon l'une quelconque des revendications 15 à 19 comme agents d'amélioration des propriétés mécaniques et/ou thermiques et/ou de conductivité électrique dans des compositions polymériques . 20. Use of carbon fibrils and / or nanotubes obtained according to the process according to any one of claims 15 to 19 as agents for improving the mechanical and / or thermal properties and / or electrical conductivity in polymeric compositions.
EP07871964A 2006-12-18 2007-12-18 Method for preparing carbon fibrils and/or nanotubes from a carbon source integrated in the catalyst Withdrawn EP2097168A2 (en)

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