EP2086878A1 - Process for synthesizing nanotubes, especially carbon nanotubes, and their uses - Google Patents

Process for synthesizing nanotubes, especially carbon nanotubes, and their uses

Info

Publication number
EP2086878A1
EP2086878A1 EP07847425A EP07847425A EP2086878A1 EP 2086878 A1 EP2086878 A1 EP 2086878A1 EP 07847425 A EP07847425 A EP 07847425A EP 07847425 A EP07847425 A EP 07847425A EP 2086878 A1 EP2086878 A1 EP 2086878A1
Authority
EP
European Patent Office
Prior art keywords
nanotubes
process according
catalyst
support
alumina
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.)
Withdrawn
Application number
EP07847425A
Other languages
German (de)
French (fr)
Inventor
Dominique Plee
Jean-Luc Dubois
Anne Pigamo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Arkema France SA
Original Assignee
Arkema France SA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from FR0655226A external-priority patent/FR2909369B1/en
Application filed by Arkema France SA filed Critical Arkema France SA
Publication of EP2086878A1 publication Critical patent/EP2086878A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • 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
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/16—Preparation
    • C01B32/162—Preparation characterised by catalysts
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B2202/00—Structure or properties of carbon nanotubes
    • C01B2202/06—Multi-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
    • C01B2202/20—Nanotubes characterized by their properties
    • C01B2202/36—Diameter

Definitions

  • the subject of the present invention is a process for synthesizing nanotubes, especially carbon nanotubes, by chemical vapour deposition employing a fluidized catalyst bed.
  • the subject of the invention is also the nanotubes synthesized and their use for improving the mechanical and/or electrical and/or thermal properties of materials, especially polymeric materials.
  • Inorganic or carbon nanotubes are recognized at the present time as being materials having great advantages because of their mechanical properties, their very high aspect ratio (length/diameter ratio) and their electrical and thermal conduction properties.
  • Nanotubes based on boron, nitrogen and/or carbon are composed of graphite sheets that are wound up and terminated by hemispheres consisting of pentagons and hexagons with a structure similar to fullerenes.
  • Nanotubes are known to be composed of either a single sheet - they are then referred to as single-walled nanotubes or SWNTs - or several concentric sheets - called multi-walled nanotubes or MWNTs.
  • Boron, nitrogen and/or carbon nanotubes may be produced by various processes, such as electrical discharge, laser ablation or chemical vapour deposition (CVD).
  • CVD chemical vapour deposition
  • metal-based nanotubes sol-gel processes are used.
  • CVD seems to be the only one capable of manufacturing boron, nitrogen and/or carbon nanotubes in large quantity, an essential condition for achieving a cost price allowing them to be used industrially in bulk in materials based on polymers and/or resins, used in various industries, such as the automobile, electronics, optoelectronics, aeronautical and thermal or electrical protection industries.
  • a source of nitrogen-containing, boron-containing and/or carbon-containing gas is injected at a relatively high temperature high temperature onto a catalyst, said catalyst possibly consisting of a metal supported on an inorganic solid.
  • catalyst metals mention may preferably be made of iron, cobalt, nickel, molybdenum, and among supports, alumina, silica and magnesia, or even carbon, are found.
  • Carbon sources that may be envisaged are methane, ethane, ethylene, acetylene, benzene, ethanol, methanol, acetone or even CO/H 2 synthesis gas (the HIPCO process).
  • the gaseous source of boron is for example borane (B 2 H 6 ), and the gaseous source of nitrogen is especially pyridine, ammonia or ethylenediamine.
  • the reader may refer to the doctoral thesis of Marie Castignolles: "Etudes de Ia synthese et de Ia structure par microscopie et spectroscopie electroniques de nanotubes de carbone purs et dopes a I'azote [Studies on the synthesis and structure, using electron microscopy and spectroscopy, of pure and nitrogen-doped carbon nanotubes]", University of affiliated II, defended on 15 June 2006.
  • CNTs carbon nanotubes
  • a catalyst containing iron for example Fe 3 O 4 , iron on a carbon support, iron on an alumina support or iron on a carbon-containing fibril support
  • a carbon-containing gaseous compound preferably CO or one or more hydrocarbons
  • the catalysts are prepared by dry impregnation, by precipitation or by wet impregnation of a support.
  • this article mentions that the CNTs synthesized using a Co/AI 2 O 3 or Fe/AI 2 O 3 catalyst in the presence of acetylene have a diameter ranging from 20 to 40 nm, whereas they are finer (8 to 12 nm diameter) if an Fe-Co/ AI 2 O 3 catalyst is used.
  • the object of the present invention is to provide a novel process that is effective for manufacturing nanotubes, especially carbon nanotubes, having good weight productivity and good reproducibility. This process also makes it easier to purify the nanotubes, should this step be necessary for their application.
  • the subject of the present invention is a process for synthesizing nanotubes, especially carbon nanotubes, by decomposition of a gas source, at a temperature ranging from 400 to 1200 0 C in a reactor, by bringing it into contact with at least one (one or more) multivalent transition metals, the transition metal or metals being supported on a support having a specific surface area determined by the BET method of greater than 50 m 2 /g.
  • the BET method is based on the molecular multilayer adsorption of gas at low temperature, well known to those skilled in the art.
  • the catalyst is brought into contact with the gases in a fluidized bed.
  • the specific surface area of the support is chosen to be in the range from 70 m 2 /g to 400 m 2 /g.
  • inorganic supports for example a support consisting of at least one alumina, the intraparticle porosity of which is multimodal, as determined by the mercury porosimetry method.
  • the support is a multimodal alumina (having 2 or more than 2 porosity peaks), the total mercury pore volume of which is greater than 0.9 cm 3 /g, said alumina having at least one porosity peak in the range from 50 to 3000 nm.
  • the supports can be impregnated with an amount of transition metal(s) ranging up to 50% by weight of the final catalyst and especially in a range from 10 to 50% by weight of the final catalyst.
  • the size of the support particles is chosen so as to allow good fluidization of the catalyst during the CNT synthesis reaction.
  • the support particles preferably have a mean diameter D 50 ranging from 20 to 500 ⁇ m.
  • the catalyst is prepared by impregnating the support particles, especially in a stream of dry gas, with an impregnation solution containing at least one transition metal salt, especially an iron and/or cobalt and/or molybdenum salt, at a temperature lying within the range from room temperature to the boiling point of the solution.
  • the amount of impregnation solution is chosen so that the support particles are, at all times, in contact with a sufficient amount of solution to ensure formation of a film of the impregnation solution on the surface of the support particles.
  • the iron impregnation solution may be an aqueous iron nitrate solution.
  • the catalyst is calcined in a furnace, especially at a temperature between 300 and 750 0 C, for the purpose of purifying them and, for example, denitrifying them.
  • aqueous discharges for example aqueous nitrate discharges when the impregnation solution contains iron nitrate; after impregnation, the product obtained is heated to between 300 0 C and 400 0 C in a gas, whether inert or not, in order to remove the nitrates.
  • the catalyst is reduced in situ in the synthesis reactor and the catalyst does not see air again before the synthesis of the nanotubes. The iron thus remains in metallic form.
  • the carbon source may be chosen from any type of carbon-containing material, such as methane, ethane, propane, butane or any other aliphatic alkane containing more than 4 carbon atoms, cyclohexane, ethylene, propylene, butane, isobutene or any other aliphatic alkane containing more than 4 carbon atoms, benzene, toluene, xylene, cymene, ethyl benzene, naphthalene, phenanthrene, anthracene, acetylene or any other alkyne containing more than 4 carbon atoms, formaldehyde, acetaldehyde, acetone, methanol, ethanol, carbon monoxide, by themselves or as a mixture.
  • carbon-containing material such as methane, ethane, propane, butane or any other aliphatic alkane containing more than 4 carbon atoms, cyclohexan
  • the boron source is for example borane (B 2 H 6 ).
  • the nitrogen source is for example pyridine, ammonia or ethylenediamine.
  • the gas source and its composition fixes the composition of the nanotubes.
  • a carbon source allows carbon nanotubes to be manufactured.
  • the subject of the present invention is also nanotubes, especially carbon nanotubes, obtained by the above process.
  • the nanotubes thus obtained are multi-walled nanotubes having an external diameter lying within the range from 10 to 30 nm.
  • These nanotubes may be used as agents for improving the mechanical and/or electrical and/or thermal conductivity properties, especially in compositions based on polymers and/or resins. These nanotubes may be used in many fields, especially in electronics (depending on the use temperature and their structure, they may be conductors, semiconductors or insulators); in the mechanical field, for example for the reinforcement of composites, for example in the automotive field, aeronautical field (CNTs are one hundred times stronger and six times lighter than steel) and in the electromechanical field (they can elongate or contract by charge injection).
  • CNTs in macromolecular compositions intended for example for the packaging of electronic components, for the manufacture of fuel (petrol or diesel) lines, antistatic coatings, in thermistors, in electrodes for the energy sector, especially for supercapacitors, as agents dispersed in aqueous media, such as electromagnetic screening, etc.
  • the method of purifying the nanotubes, in order to remove the catalyst residues, for example using an acid solution is made easier owing to greater accessibility to the support.
  • the instrument used for carrying out the BET specific surface area measurements was a Micromeritics ASAP ® 2000 machine.
  • a catalyst containing 35% iron by weight was prepared by impregnation of
  • the particles of this alumina had a median diameter of about 85 ⁇ m and the surface area and porosity characteristics indicated below: BET surface area (m 2 /g) 148
  • An alumina was prepared by spray drying, without prior micronization, a suspension consisting of water, a calcined alumina (Sasol Puralox ® UF 5/230) and a pseudoboehmite (Sasol Dispersal ® 40). After calcination to convert the pseudoboehmite into ⁇ -alumina, the catalyst was prepared as explained in the counter-example.
  • An alumina was prepared by milling a bimodal alumina from Norton, supplied in the form of extrudates 5 mm in length having a BET surface area of 252 m 2 /g.
  • An alumina was prepared by spray drying, with prior micronization, a suspension consisting of water, a calcined alumina (Sasol Puralox ® UF 5/230) and a pseudoboehmite (Eurosupport Versal ® 250). The solids content was 21.3% by weight. After calcination to convert the pseudoboehmite into ⁇ -alumina, the catalyst was prepared as explained in the counter-example.
  • An alumina was prepared by spray drying, with prior micronization, a suspension consisting of water, a calcined alumina (Sasol Puralox ® UF 5/230) and a pseudoboehmite (Sasol Pural ® 400). The solids content was 42.5% by weight. After calcination to convert the pseudoboehmite into ⁇ -alumina, the catalyst was prepared as explained in the counter-example.
  • An alumina was prepared by spray drying, without prior micronization, a suspension consisting of water and a pseudoboehmite (Sasol Versal ® 250). The solids content was 26% by weight. After calcination to convert the pseudoboehmite into ⁇ -alumina, the catalyst was prepared as explained in the counter-example.
  • Example 6 (Ref: 2017 C93) (according to the invention) (according to the invention) (according to the invention) An alumina was prepared by spray drying, without prior micronization, a suspension consisting of water and a pseudoboehmite (Sasol Versal ® 250). The solids content was 15% by weight. After calcination to convert the pseudoboehmite into ⁇ -alumina, the catalyst was prepared as explained in the counter-example.
  • An alumina was prepared by milling a bimodal alumina in the form of extrudates 1.2 mm in length from Norton.
  • D 50 Apparent mean diameter of 50% of the particle population.
  • Example 9 (according to the invention) The denitrification operations, corresponding to the step of purifying the catalysts obtained according to the counter-example and examples 1 to 8, were carried out at 350 0 C in an oven under a stream of air for 2 h. About 2.5 g of catalyst thus denitrified was introduced, as a layer, into a reactor having a diameter of 5 cm and an effective height of 1 m, fitted with a separator intended to prevent fine particles from being entrained towards the top of the reactor. The reactor was heated for about 30 minutes up to 650 0 C and then the catalysts were reduced under 25 vol% H 2 /75 vol% N 2 for 30 minutes. The nitrogen was then replaced with ethylene, the reaction was left to continue for 1 hour and then the nanotubes formed were collected. In all cases, the total N 2 , H 2 /N 2 or C 2 H 2 /H 2 flow rates were constant at 160 Sl/min.
  • the productivity was determined by loss of ignition of the CNTs and the quality of the CNTs determined by electron microscopy.
  • MWNT multi-walled nanotubes
  • 0 diameter of the nanotubes.
  • Table 2 shows that the best productivity is obtained with catalysts having a multimodal porosity.
  • Table 2 also shows that the combination of iron and cobalt results in better CNT productivity and smaller CNTs. It may also be seen that the amount of catalyst has no influence on the productivity nor on the reproducibility of the CNTs in terms of diameter and structure.

Abstract

The subject of the present invention is a process for synthesizing nanotubes, especially carbon nanotubes, by decomposition of a gas source, at a temperature ranging from 400 to 1200 °C in a reactor, by bringing it into contact with at least one (one or more) multivalent transition metals, the transition metal(s) being supported on a support having a specific surface area determined by the BET method of greater than 50 m2/g, especially within the range from 70 m2/g to 400 m2/g. The support according to the invention is especially an inorganic support, for example an alumina having a multimodal porosity. The subject of the invention is also the nanotubes thus obtained and their use for improving the mechanical and/or electrical and/or thermal properties of materials, especially polymeric materials.

Description

PROCESS FOR SYNTHESIZING NANOTUBES, ESPECIALLY CARBON NANOTUBES, AND THEIR USES
(Field of the Invention)
The subject of the present invention is a process for synthesizing nanotubes, especially carbon nanotubes, by chemical vapour deposition employing a fluidized catalyst bed. The subject of the invention is also the nanotubes synthesized and their use for improving the mechanical and/or electrical and/or thermal properties of materials, especially polymeric materials.
(Prior art and the technical problem)
Inorganic or carbon nanotubes are recognized at the present time as being materials having great advantages because of their mechanical properties, their very high aspect ratio (length/diameter ratio) and their electrical and thermal conduction properties. In particular, these nanotubes are nanotubes consisting of carbon, boron, nitrogen, metal dichalocogenide MX2 (M = Mo, Nb, Hf, W; X= S, Se), metal oxide MOx, such as TiO2, ZnO, ..., by themselves or combined. Nanotubes based on boron, nitrogen and/or carbon are composed of graphite sheets that are wound up and terminated by hemispheres consisting of pentagons and hexagons with a structure similar to fullerenes.
Nanotubes are known to be composed of either a single sheet - they are then referred to as single-walled nanotubes or SWNTs - or several concentric sheets - called multi-walled nanotubes or MWNTs.
Boron, nitrogen and/or carbon nanotubes may be produced by various processes, such as electrical discharge, laser ablation or chemical vapour deposition (CVD). In the case of metal-based nanotubes, sol-gel processes are used. Among these techniques, CVD seems to be the only one capable of manufacturing boron, nitrogen and/or carbon nanotubes in large quantity, an essential condition for achieving a cost price allowing them to be used industrially in bulk in materials based on polymers and/or resins, used in various industries, such as the automobile, electronics, optoelectronics, aeronautical and thermal or electrical protection industries.
In this CVD method, a source of nitrogen-containing, boron-containing and/or carbon-containing gas is injected at a relatively high temperature high temperature onto a catalyst, said catalyst possibly consisting of a metal supported on an inorganic solid. Among catalyst metals, mention may preferably be made of iron, cobalt, nickel, molybdenum, and among supports, alumina, silica and magnesia, or even carbon, are found. Carbon sources that may be envisaged are methane, ethane, ethylene, acetylene, benzene, ethanol, methanol, acetone or even CO/H2 synthesis gas (the HIPCO process).
The gaseous source of boron is for example borane (B2H6), and the gaseous source of nitrogen is especially pyridine, ammonia or ethylenediamine. As prior art relating to the various types of nanotubes and their manufacture, the reader may refer to the doctoral thesis of Marie Castignolles: "Etudes de Ia synthese et de Ia structure par microscopie et spectroscopie electroniques de nanotubes de carbone purs et dopes a I'azote [Studies on the synthesis and structure, using electron microscopy and spectroscopy, of pure and nitrogen-doped carbon nanotubes]", University of Montpellier II, defended on 15 June 2006.
As an example of the CVD method, the process described in document WO 86/03455A1 from Hyperion Catalysis International Inc. may be mentioned. The synthesis of carbon nanotubes (CNTs) is carried out by bringing a catalyst containing iron (for example Fe3O4, iron on a carbon support, iron on an alumina support or iron on a carbon-containing fibril support) into contact with a carbon-containing gaseous compound (preferably CO or one or more hydrocarbons), advantageously in the presence of a compound capable of reacting with carbon in order to produce gaseous products (for example CO, H2 or H2O). The catalysts are prepared by dry impregnation, by precipitation or by wet impregnation of a support.
The desire to increase the productivity by weight (quantity of nanotubes produced relative to the quantity of gas and catalyst used) or to achieve better control of the quality of the nanotubes formed has led several authors to consider Co/Fe catalyst mixtures.
Thus, the article "Metal mixtures catalyzed carbon nanotubes", by Z. Konya, N. Nagaraju, A. Fonseca, J. B. Nagy, A. Tamasi and K.M. Mukhopadhyay, AIP Conference Proceedings, (1999), 486, 249-253, may be mentioned. This document explains that the Fe/Co catalyst mixtures are more effective for synthesizing MWNTs than Co or Fe by themselves on the aluminas used. These aluminas were prepared from hydrolysed aluminium isopropoxide or commercial alumina having a low specific surface area determined by the BET method.
Z. Fonseca et al. in "Synthesis of SWNT by catalytic decomposition of hydrocarbons", Chem. Commun. (1999), 1344-1344, teach that a Co/Fe catalyst mixture on silica or alumina results in better CNT yields than Fe by itself and that alumina is a better catalyst support than silica. Controlling the diameter of nanotubes is mentioned in "XPS characterization of catalysts during production of multiwall carbon nanotubes" by Z. Konya, J. Kiss, A. Oszko, A. Siska and I. Kiricsi, Physical Chemistry, Chemical Physics (2001 ), βϋL 155-158. Thus, this article mentions that the CNTs synthesized using a Co/AI2O3 or Fe/AI2O3 catalyst in the presence of acetylene have a diameter ranging from 20 to 40 nm, whereas they are finer (8 to 12 nm diameter) if an Fe-Co/ AI2O3 catalyst is used.
The article "Control of the outer diameter of thin carbon nanotubes synthesized by catalytic decomposition of hydrocarbons", by J. Willems, Z. Konya, JF. Colomer, G. van Tenderloo, N. Nagaraju, A. Fonseca and J. B. Nagy, CP 544, Electronic Properties of Novel Materials-Molecular Nanostructures, published by Kuzmany et al., (2000), 242-245, shows that the outside diameter of the CNTs is controlled by the metal.
The object of the present invention is to provide a novel process that is effective for manufacturing nanotubes, especially carbon nanotubes, having good weight productivity and good reproducibility. This process also makes it easier to purify the nanotubes, should this step be necessary for their application.
(Detailed description of the Invention)
The subject of the present invention is a process for synthesizing nanotubes, especially carbon nanotubes, by decomposition of a gas source, at a temperature ranging from 400 to 1200 0C in a reactor, by bringing it into contact with at least one (one or more) multivalent transition metals, the transition metal or metals being supported on a support having a specific surface area determined by the BET method of greater than 50 m2/g.
The BET method is based on the molecular multilayer adsorption of gas at low temperature, well known to those skilled in the art.
In particular, the catalyst is brought into contact with the gases in a fluidized bed.
According to one embodiment of the invention, the specific surface area of the support is chosen to be in the range from 70 m2/g to 400 m2/g.
Among supports according to the invention, it is particularly useful to use inorganic supports, for example a support consisting of at least one alumina, the intraparticle porosity of which is multimodal, as determined by the mercury porosimetry method.
According to one particular embodiment of the invention, the support is a multimodal alumina (having 2 or more than 2 porosity peaks), the total mercury pore volume of which is greater than 0.9 cm3/g, said alumina having at least one porosity peak in the range from 50 to 3000 nm.
According to one particular embodiment, the supports can be impregnated with an amount of transition metal(s) ranging up to 50% by weight of the final catalyst and especially in a range from 10 to 50% by weight of the final catalyst.
Advantageously, the size of the support particles is chosen so as to allow good fluidization of the catalyst during the CNT synthesis reaction. In practice, to ensure correct productivity, the support particles preferably have a mean diameter D50 ranging from 20 to 500 μm. According to one particular embodiment of the process of the invention, the catalyst is prepared by impregnating the support particles, especially in a stream of dry gas, with an impregnation solution containing at least one transition metal salt, especially an iron and/or cobalt and/or molybdenum salt, at a temperature lying within the range from room temperature to the boiling point of the solution. The amount of impregnation solution is chosen so that the support particles are, at all times, in contact with a sufficient amount of solution to ensure formation of a film of the impregnation solution on the surface of the support particles. In particular, when the transition metal is iron, the iron impregnation solution may be an aqueous iron nitrate solution.
According to the invention, before the nanotubes are synthesized, the catalyst is calcined in a furnace, especially at a temperature between 300 and 750 0C, for the purpose of purifying them and, for example, denitrifying them.
The fact of working "dry", that is to say having at all times just the quantity of liquid needed to create a liquid film on the surface of the catalyst support particles, prevents aqueous discharges (for example aqueous nitrate discharges when the impregnation solution contains iron nitrate; after impregnation, the product obtained is heated to between 3000C and 4000C in a gas, whether inert or not, in order to remove the nitrates). According to one particular embodiment of the invention, the catalyst is reduced in situ in the synthesis reactor and the catalyst does not see air again before the synthesis of the nanotubes. The iron thus remains in metallic form.
According to the invention, the carbon source may be chosen from any type of carbon-containing material, such as methane, ethane, propane, butane or any other aliphatic alkane containing more than 4 carbon atoms, cyclohexane, ethylene, propylene, butane, isobutene or any other aliphatic alkane containing more than 4 carbon atoms, benzene, toluene, xylene, cymene, ethyl benzene, naphthalene, phenanthrene, anthracene, acetylene or any other alkyne containing more than 4 carbon atoms, formaldehyde, acetaldehyde, acetone, methanol, ethanol, carbon monoxide, by themselves or as a mixture.
According to the invention, the boron source is for example borane (B2H6). According to the invention, the nitrogen source is for example pyridine, ammonia or ethylenediamine. The gas source and its composition fixes the composition of the nanotubes. Thus, a carbon source allows carbon nanotubes to be manufactured.
The subject of the present invention is also nanotubes, especially carbon nanotubes, obtained by the above process. The nanotubes thus obtained are multi-walled nanotubes having an external diameter lying within the range from 10 to 30 nm.
These nanotubes may be used as agents for improving the mechanical and/or electrical and/or thermal conductivity properties, especially in compositions based on polymers and/or resins. These nanotubes may be used in many fields, especially in electronics (depending on the use temperature and their structure, they may be conductors, semiconductors or insulators); in the mechanical field, for example for the reinforcement of composites, for example in the automotive field, aeronautical field (CNTs are one hundred times stronger and six times lighter than steel) and in the electromechanical field (they can elongate or contract by charge injection). For example, mention may be made of the use of CNTs in macromolecular compositions intended for example for the packaging of electronic components, for the manufacture of fuel (petrol or diesel) lines, antistatic coatings, in thermistors, in electrodes for the energy sector, especially for supercapacitors, as agents dispersed in aqueous media, such as electromagnetic screening, etc.
Because the catalyst support has multimodal porosity, the method of purifying the nanotubes, in order to remove the catalyst residues, for example using an acid solution, is made easier owing to greater accessibility to the support.
The present invention will now be illustrated by particular examples of its implementation described below. It should be pointed out that the purpose of these examples is not in any way to limit the scope of the present invention.
EXAMPLES:
The instrument used for carrying out the BET specific surface area measurements was a Micromeritics ASAP® 2000 machine.
The machine used to carry out the mercury porosimetry measurement was a Micromeritics AUTOPORE® machine operating from 3 to 4000 bar. > Preparation of the catalysts:
Counter-example
A catalyst containing 35% iron by weight was prepared by impregnation of
Puralox® SCCA 5-150 alumina from Sasol using the following protocol: 300 g of alumina were introduced into a jacketed 3-litre reactor heated to
1000C, a stream of air being passed therethrough. By means of a pump, 1600 ml of an iron solution containing 545 g/l of iron nitrate nonahydrate was then continuously injected. Since the intended (mass of metal/mass of final catalyst) ratio was 35% by weight of iron in metallic form, the iron solution was added over a period of 23 h and the rate of addition of this solution was equal to the rate of evaporation of the water. The catalyst was then heated at 100 0C in an oven for
16 h.
Initially, the particles of this alumina had a median diameter of about 85 μm and the surface area and porosity characteristics indicated below: BET surface area (m2/g) 148
Hg total pore volume (cm3/g) 0.87
Example 1 (Ref: 2017 C27) (according to the invention)
An alumina was prepared by spray drying, without prior micronization, a suspension consisting of water, a calcined alumina (Sasol Puralox® UF 5/230) and a pseudoboehmite (Sasol Dispersal® 40). After calcination to convert the pseudoboehmite into γ-alumina, the catalyst was prepared as explained in the counter-example.
Example 2 (Ref: 2017 COD (according to the invention)
An alumina was prepared by milling a bimodal alumina from Norton, supplied in the form of extrudates 5 mm in length having a BET surface area of 252 m2/g.
Example 3 (Ref: 2017 C54) (according to the invention)
An alumina was prepared by spray drying, with prior micronization, a suspension consisting of water, a calcined alumina (Sasol Puralox® UF 5/230) and a pseudoboehmite (Eurosupport Versal® 250). The solids content was 21.3% by weight. After calcination to convert the pseudoboehmite into γ-alumina, the catalyst was prepared as explained in the counter-example.
Example 4 (Ref: 2017 C70) (according to the invention)
An alumina was prepared by spray drying, with prior micronization, a suspension consisting of water, a calcined alumina (Sasol Puralox® UF 5/230) and a pseudoboehmite (Sasol Pural® 400). The solids content was 42.5% by weight. After calcination to convert the pseudoboehmite into γ-alumina, the catalyst was prepared as explained in the counter-example.
Example 5 (Ref: 2017 C94) (according to the invention)
An alumina was prepared by spray drying, without prior micronization, a suspension consisting of water and a pseudoboehmite (Sasol Versal® 250). The solids content was 26% by weight. After calcination to convert the pseudoboehmite into γ-alumina, the catalyst was prepared as explained in the counter-example.
Example 6 (Ref: 2017 C93) (according to the invention) An alumina was prepared by spray drying, without prior micronization, a suspension consisting of water and a pseudoboehmite (Sasol Versal® 250). The solids content was 15% by weight. After calcination to convert the pseudoboehmite into γ-alumina, the catalyst was prepared as explained in the counter-example.
Example 7 (Ref: 1870 C161 ) (according to the invention)
An alumina was prepared by milling a bimodal alumina in the form of extrudates 1.2 mm in length from Norton.
The main data regarding these aluminas are given in Table 1 below. Table 1
D50: Apparent mean diameter of 50% of the particle population.
Example 8 (according to the invention)
An alumina was prepared by spray drying, without prior micronization, a suspension consisting of water and a pseudoboehmite (Sasol Versal® 250). The solids content was 15% by weight. After calcination to convert the pseudoboehmite into γ-alumina, the catalyst was prepared by adding a solution composed of cobalt acetate dihydrate and iron nitrate, so as to have a total metal content of 35 wt% with a Co/Fe ratio = 1.
> Preparation of the carbon nanotubes:
Example 9 (according to the invention) The denitrification operations, corresponding to the step of purifying the catalysts obtained according to the counter-example and examples 1 to 8, were carried out at 3500C in an oven under a stream of air for 2 h. About 2.5 g of catalyst thus denitrified was introduced, as a layer, into a reactor having a diameter of 5 cm and an effective height of 1 m, fitted with a separator intended to prevent fine particles from being entrained towards the top of the reactor. The reactor was heated for about 30 minutes up to 6500C and then the catalysts were reduced under 25 vol% H2/75 vol% N2 for 30 minutes. The nitrogen was then replaced with ethylene, the reaction was left to continue for 1 hour and then the nanotubes formed were collected. In all cases, the total N2, H2/N2 or C2H2/H2 flow rates were constant at 160 Sl/min.
After the nanotubes formed were discharged and collected, the productivity was determined by loss of ignition of the CNTs and the quality of the CNTs determined by electron microscopy.
The results are given in Table 2 below:
Table 2
MWNT: multi-walled nanotubes; 0: diameter of the nanotubes.
Except for the counter-example, all the other catalysts were γ-alumina/iron catalysts exhibiting two peaks in the region of pores smaller in size than 5 μm.
Table 2 shows that the best productivity is obtained with catalysts having a multimodal porosity.
Table 2 also shows that the combination of iron and cobalt results in better CNT productivity and smaller CNTs. It may also be seen that the amount of catalyst has no influence on the productivity nor on the reproducibility of the CNTs in terms of diameter and structure.

Claims

1. Process for synthesizing nanotubes, especially carbon nanotubes, by decomposition of a gas source, at a temperature of between 400 and 1200 0C, by bringing it into contact with at least one or more multivalent transition metals, characterized in that the transition metal or metals are supported on a support having a BET specific surface area of greater than 50 m2/g.
2. Nanotube synthesis process according to Claim 1 , characterized in that the transition metal or metals are supported on a support having a BET specific surface area lying within the range from 70 m2/g to 400 m2/g.
3. Nanotube synthesis process according to Claim 1 or 2, characterized in that the transition metal or metals are supported on an inorganic support.
4. Process according to one of the preceding claims, characterized in that the support consists of at least one alumina whose intraparticle porosity is multimodal.
5. Process according to one of the preceding claims, characterized in that the support is an alumina, the total mercury pore volume of which is greater than 0.9 cm3/g, said alumina having at least one porosity peak in the range from 50 to 3000 nm.
6. Process according to one of the preceding claims, characterized in that the amount of transition metal(s) represents up to 50% by weight of the final catalyst.
7. Process according to one of the preceding claims, characterized in that the amount of transition metal(s) lies within the range from 10 to 50% by weight of the final catalyst.
8. Process according to one of the preceding claims, characterized in that the support particles have a mean diameter lying within the range from 20 to 500 μm.
9. Process according to one of the preceding claims, characterized in that the catalyst is prepared by impregnating the support particles with an impregnation solution containing at least one transition metal salt.
10. Process according to one of the preceding claims, characterized in that said catalyst is prepared by impregnating the support particles at a temperature lying within the range from room temperature to the boiling point of the solution, the support particles being at all times in contact with a sufficient amount of impregnation solution to ensure formation of a film of the impregnation solution on the surface of the support particles.
11. Process according to one of the preceding claims, characterized in that the catalyst is prepared by impregnating the support particles with an iron impregnation solution.
12. Process according to one of the preceding claims, characterized in that the catalyst is calcined in a furnace before the nanotubes are synthesized.
13. Process according to one of the preceding claims, in which the catalyst is reduced in situ and does not see air again before the synthesis of the nanotubes.
14. Process according to any one of the preceding claims, characterized in that the gas source is a carbon source.
15. Nanotubes that can be obtained by the process as defined in any one of the preceding claims.
16. Use of the nanotubes, especially carbon nanotubes, obtained according to any one of Claims 1 to 14 as agents for improving the mechanical and/or electrical and/or thermal conductivity properties, especially in compositions based on polymers and/or resins.
17. Use according to the preceding claim of the compositions based on polymers in fuel lines, antistatic coatings or in electrodes for the energy sector.
EP07847425A 2006-11-30 2007-11-27 Process for synthesizing nanotubes, especially carbon nanotubes, and their uses Withdrawn EP2086878A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR0655226A FR2909369B1 (en) 2006-11-30 2006-11-30 PROCESS FOR THE SYNTHESIS OF NANOTUBES, IN PARTICULAR CARBON, AND USES THEREOF
US87882707P 2007-01-05 2007-01-05
PCT/EP2007/062900 WO2008065121A1 (en) 2006-11-30 2007-11-27 Process for synthesizing nanotubes, especially carbon nanotubes, and their uses

Publications (1)

Publication Number Publication Date
EP2086878A1 true EP2086878A1 (en) 2009-08-12

Family

ID=39189838

Family Applications (1)

Application Number Title Priority Date Filing Date
EP07847425A Withdrawn EP2086878A1 (en) 2006-11-30 2007-11-27 Process for synthesizing nanotubes, especially carbon nanotubes, and their uses

Country Status (3)

Country Link
EP (1) EP2086878A1 (en)
KR (1) KR20090087454A (en)
WO (1) WO2008065121A1 (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101007184B1 (en) * 2008-10-17 2011-01-12 제일모직주식회사 Supported Catalyst for Synthesizing Carbon Nanotubes, Method for Preparing thereof and Carbon Nanotube Using the Same
KR101007183B1 (en) * 2008-10-23 2011-01-12 제일모직주식회사 Supported Catalyst for Synthesizing Carbon Nanotubes, Method for Preparing thereof and Carbon Nanotube Using the Same
US20150011380A1 (en) * 2012-02-22 2015-01-08 Mitsubishi Heavy Industries, Ltd. Catalyst for carbon nanotube production
CN104718170A (en) 2012-09-04 2015-06-17 Ocv智识资本有限责任公司 Dispersion of carbon enhanced reinforcement fibers in aqueous or non-aqueous media
KR101785773B1 (en) * 2015-02-06 2017-10-17 주식회사 엘지화학 Catalyst having circular shaped alpha-alumina for obtaining carbon nanotube, and process for preparing same

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2634757B1 (en) * 1988-07-29 1992-09-18 Rhone Poulenc Chimie PROCESS FOR MANUFACTURING ALUMINUM AGGLOMERATES AND AGGLOMERATES OBTAINED
FR2826646B1 (en) * 2001-06-28 2004-05-21 Toulouse Inst Nat Polytech PROCESS FOR THE SELECTIVE MANUFACTURE OF ORDINATED CARBON NANOTUBES IN FLUIDIZED BED
ES2437194T3 (en) * 2003-02-18 2014-01-09 Arkema France Use of carbon nanotubes in mixtures of polyamide and polyolefin
US7186757B2 (en) * 2003-10-16 2007-03-06 Conocophillips Company Silica-alumina catalyst support with bimodal pore distribution, catalysts, methods of making and using same
FR2872150B1 (en) * 2004-06-23 2006-09-01 Toulouse Inst Nat Polytech PROCESS FOR THE SELECTIVE MANUFACTURE OF ORDINATED CARBON NANOTUBES
FR2875716B1 (en) * 2004-09-28 2007-08-03 Inst Francais Du Petrole NEW ALUMINUM COMPOSITE SUPPORTS ON ALUMINA

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO2008065121A1 *

Also Published As

Publication number Publication date
KR20090087454A (en) 2009-08-17
WO2008065121A1 (en) 2008-06-05

Similar Documents

Publication Publication Date Title
US7799246B2 (en) Method for synthesis of carbon nanotubes
Esteves et al. Carbon nanotubes as catalyst support in chemical vapor deposition reaction: A review
US7622059B2 (en) Method for synthesis of carbon nanotubes
EP1558524B1 (en) Cvd synthesis of carbon nanotubes
Pham-Huu et al. Large scale synthesis of carbon nanofibers by catalytic decomposition of ethane on nickel nanoclusters decorating carbon nanotubes
EP3053877B1 (en) Method for manufacturing bundle-type carbon nanotubes having a large specific surface area
Awadallah et al. Effect of progressive Co loading on commercial Co–Mo/Al2O3 catalyst for natural gas decomposition to COx-free hydrogen production and carbon nanotubes
US8562937B2 (en) Production of carbon nanotubes
JP5702043B2 (en) Catalyst for producing carbon nanotubes by decomposing gaseous carbon compounds with heterogeneous catalysts
Li et al. Graphene nanosheets supporting Ru nanoparticles with controlled nanoarchitectures form a high-performance catalyst for CO x-free hydrogen production from ammonia
JP2013502309A (en) Bilayer catalyst, process for its production and its use in the production of nanotubes
US20160214863A1 (en) Method for manufacturing carbon nanotube agglomerate having controlled bulk density
Xu et al. One-step preparation of highly dispersed metal-supported catalysts by fluidized-bed MOCVD for carbon nanotube synthesis
Miniach et al. Growth of carbon nanofibers from methane on a hydroxyapatite-supported nickel catalyst
WO2008065121A1 (en) Process for synthesizing nanotubes, especially carbon nanotubes, and their uses
Gong et al. Preparation of carbon nanotubes (CNTs)-cordierite monoliths by catalytic chemical vapor deposition as catalyst supports for ammonia synthesis
FR2881734A1 (en) Preparation of carbon nanotubes comprises decomposition of a carbon source by contacting in a fluidized bed reactor with multivalent transition metals supported on inorganic substrate having a defined surface area
JP2008529941A (en) Carbon nanotube synthesis method
CN101541675A (en) Process for synthesizing nanotubes, especially carbon nanotubes, and their uses
Louis et al. Advances in the use of carbon nanomaterials in catalysis
Setyopratomo et al. Carbon nanotubes synthesis using Fe-Co-Mo/MgO tri-metallic catalyst: study the effect of reaction temperature, reaction time and catalyst weight
KR20230017835A (en) An improved catalyst for MWCNT production
Onu et al. Comparative Investigation of Yield and Quality of Carbon Nanotubes by Catalytic Conversion of Recycled Polypropylene and Polyethylene Plastics over Fe-Co-Mo/CaCO3 Based on Chemical Vapour Deposition
JP2024510823A (en) Method for producing catalyst for producing carbon nanotubes
KR20230061633A (en) Method for Preparing Catalyst for Manufacturing Carbon Nanotubes

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 20090512

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IS IT LI LT LU LV MC MT NL PL PT RO SE SI SK TR

DAX Request for extension of the european patent (deleted)
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20090630