Classifications

• • 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
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0244—Coatings comprising several layers
• • 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
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/85—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
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/84—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
  • B01J23/85—Chromium, molybdenum or tungsten
  • B01J23/88—Molybdenum
  • B01J23/881—Molybdenum and 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
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
  • B01J37/0205—Impregnation in several steps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82B—NANOSTRUCTURES FORMED BY MANIPULATION OF INDIVIDUAL ATOMS, MOLECULES, OR LIMITED COLLECTIONS OF ATOMS OR MOLECULES AS DISCRETE UNITS; MANUFACTURE OR TREATMENT THEREOF
  • B82B3/00—Manufacture or treatment of nanostructures by manipulation of individual atoms or molecules, or limited collections of atoms or molecules as discrete units
  • B82B3/0004—Apparatus specially adapted for the manufacture or treatment of nanostructural devices or systems or methods for manufacturing the same
• • 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
• • 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
  • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
  • B01J21/04—Alumina
• • 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
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size

Definitions

• the present invention relates to novel bilayer catalysts. BACKGROUND OF THE INVENTION It also relates to the process for preparing these catalysts and their use for the manufacture of nanotubes, especially carbon nanotubes.
• CNTs have been the subject of intensive research aimed at replacing carbon black powder, which is volatile and difficult to handle in all its applications.
• the CNTs furthermore have the advantage of conferring improved mechanical properties and electrical and / or thermal conduction properties on any composite material containing them, at least equal to those of the pulverulent carbon black, at lower contents.
• Their good mechanical properties and especially resistance to elongation are related in part to their very high aspect ratios (length / diameter).
• SWNT synchronym for Single Wall Nanotubes
• MWNT acronym for Multi Wall Nanotubes
• Carbon nanotubes can be manufactured using various processes such as electrical discharge, laser ablation, chemical vapor deposition (CVD in abbreviation) or physical vapor deposition (PVD abbreviation).
• CVD in abbreviation chemical vapor deposition
• PVD abbreviation physical vapor deposition
• the CVD process involves injecting a source of carbon-rich gas into a reactor containing a high temperature metal catalyst. In contact with the metal, the gas source decomposes into graphitic plane NTC and hydrogen.
• the catalyst consists of a catalytic metal such as iron, cobalt, nickel, supported by a solid substrate, in the form of grains, and chemically inert, such as alumina, silica, magnesia or still carbon.
• the gaseous carbon sources generally used are methane, ethane, ethylene, acetylene or benzene.
• CNTs are synthesized by contacting a catalyst containing iron (e.g. Fe3 ⁇ 4, Fe on a carbon support, Fe on an alumina carrier or Fe on a carbon fibril support) with a rich gaseous compound carbon, such as a hydrocarbon, in the presence of another gas capable of reacting with the carbon-rich gaseous compound.
• a catalyst containing iron e.g. Fe3 ⁇ 4, Fe on a carbon support, Fe on an alumina carrier or Fe on a carbon fibril support
• a rich gaseous compound carbon such as a hydrocarbon
• the catalyst has a structure different from that of a supported catalyst since it is obtained by coprecipitation, on the one hand, of a solution of iron salts and molybdenum salts and, on the other hand, a solution of aluminum salts.
• EP 2,077,251 discloses a supported catalyst for the production of single-walled carbon nanotubes.
• This one consists of a substrate plane, made of quartz glass or cordierite, covered with a support based on non-porous alumina, on which catalytic metals (molybdenum and iron) are deposited according to a given process.
• catalytic metals mobdenum and iron
• the present inventors have found that a supported catalyst having a core-shell structure allows this improvement.
• the invention thus aims at providing a catalyst material for the preparation of nanotubes, in particular carbon, said material being in the form of solid particles, said particles comprising (and preferably being constituted by) a porous substrate supporting two superimposed catalytic layers, a first layer (called “core”) directly disposed on the substrate and comprising at least one transition metal, in particular in a reduced state or metal, of column VIB of the Periodic Table, preferably molybdenum, and a second layer (called “bark”), arranged on the first and comprising iron.
• core first layer
• bark second layer
• At least one metal means one or more metals.
• iron and transition metal refers to these metals in the elemental state, that is to say in the oxidation state 0, or in the oxidized state. However, it is preferred that these metals are primarily in the elemental state.
• Such a catalyst material thus has a core-bark structure disposed on a porous substrate.
• the transition metal present in the first layer or core is preferably chromium, molybdenum, tungsten or mixtures thereof.
• molybdenum is used.
• these catalytic metals are known to have a function of initiation of the reaction, and their presence is therefore useful at the beginning of the synthesis reaction of carbon nanotubes.
• Iron, present in the second layer or bark, is known to play a role during the elongation of the chain of carbon nanotubes.
• the present inventors have observed that the synthesis of CNTs was from the inside of the catalyst to the outside and, without wishing to be bound by any theory, they are of the opinion that by disposing the catalytic priming metal closer to the part of the catalyst material in which is initiated, that is to say inwardly of the catalyst material, and the catalytic metal of chain elongation further out, the synthesis of CNTs is favored.
• the core may comprise, in addition to the transition metal of column VIB of the Periodic Table, iron.
• the mass quantity of iron may be less than the mass quantity of transition metal of column VIB of the Periodic Table.
• the bark may also comprise a transition metal of column VIB of the Periodic Table, preferably molybdenum, in addition to iron.
• the mass quantity of transition metal of column VIB of the Periodic Table is generally less than the mass quantity of iron.
• the catalyst according to the invention comprises (or is constituted by) a first catalytic layer comprising, as sole catalytic metal, molybdenum, on which is deposited a second catalytic layer comprising as sole catalytic metal iron.
• the iron content of the catalyst material according to the invention is at least 25%, preferably 30 to 40% by weight of the total mass of the catalyst material.
• the transition metal content of column VIB of the Periodic Table is from 0.5 to 10%, especially from 1.5 to 8%, for example from 2 to 4% by weight of the total mass. catalyst material.
• the porous substrate advantageously has a BET specific surface area greater than 50 m 2 / g, preferably between 70 and 400 m 2 / g.
• BET surface area can be measured by the amount of nitrogen adsorbed by the substrate, a method well known to those skilled in the art.
• the substrate is preferably inert, ie chemically inert with respect to the transition metal and iron and carbon gas source, under the operating conditions of the CVD synthesis process.
• this substrate is made of inorganic material. It represents in particular from 50 to 85%, for example from 52 to 83.5% by weight of the catalyst material.
• the substrate may be chosen from alumina, an activated carbon, silica, a silicate, magnesia, titanium oxide, zirconia, a zeolite or even carbon fibers.
• the substrate is alumina, for example of the gamma or theta type.
• the macroscopic shape of the substrate particles, and particles of catalyst material can be globally substantially spherical or not.
• the invention also applies to grains of macroscopic shape more or less flattened (flakes, discs, etc.) and / or elongated (cylinders, rods, ribbons ...) -
• the substrate is in powder form and not in an agglomerated form, especially flat.
• the shape and size of the particles are adapted to allow the formation of a fluidized bed of the catalyst material.
• the substrate particles have a larger size of between 20 and 500 microns, preferably between 75 and 150 microns. This particle size can be measured by dry or wet laser granulometry.
• the catalyst material is in the form of spherical particles having a unimodal particle size distribution, the equivalent diameter of the particles being between 80% and 120% of the average particle diameter of the catalyst material. .
• the particles may have a bimodal particle size distribution with an equivalent diameter ranging from 30 to 350%.
• the catalyst material according to the invention comprises alumina particles supporting a molybdenum core on which is disposed an iron bark, the mass percentages of the various constituents being 32 for iron, 2 for molybdenum and of 66 for alumina, based on the total mass of the catalyst material.
• the invention extends to a process for preparing the catalyst material described above, which comprises a first step of impregnating the substrate with an impregnating solution comprising a transition metal salt of column VIB of the Periodic Table, preferably molybdenum, and a second impregnation step with an impregnating solution comprising an iron salt.
• Each of the impregnation solutions can be a solution alcoholic or aqueous.
• the iron salt may be iron nitrate, and in particular iron nitrate nonahydrate.
• the molybdenum salt may be ammonium molybdate, and in particular ammonium molybdate tetrahydrate.
• the first impregnation solution is an aqueous solution of ammonium molybdate and the second solution is an aqueous solution of iron nitrate nonahydrate.
• Each impregnation step is preferably carried out under a dry gas sweep, preferably under a sweep of air. It is carried out at a temperature measured in situ ranging from 100 to 150 ° C., preferably about 120 ° C.
• the quantity of impregnation solution, at any time, in contact with the substrate or the underlying layer is generally just sufficient to provide film formation on the surface of the substrate particles or the underlying layer.
• the process for preparing the catalytic material according to the invention further comprises, after the impregnation steps, a drying step at a temperature ranging, for example, from 150 to 250 ° C., measured in situ, advantageously followed by a denitrification step. preferably under an inert atmosphere at a temperature ranging from 350 to 450 ° C., measured in situ.
• the invention also extends to a catalyst material obtained by a process according to the invention as defined above.
• the invention also extends to a method for manufacturing nanoparticles of material chosen from silicon, carbon or boron and a mixture of these elements, optionally associated with nitrogen or doped with nitrogen, characterized in that at least one catalyst material according to the invention is used.
• it is a reaction for the selective production of carbon nanotubes by thermal decomposition of a source of gaseous carbon.
• the invention more particularly relates to a method of manufacturing carbon nanotubes by decomposition of a carbon source in the gaseous state, comprising the following steps:
• step b) contacting a carbon source (alkane or alkene), preferably ethylene, with the catalyst material of step b), to form carbon nanotubes and carbon nanotubes at the surface of said catalyst material; hydrogen by catalytic decomposition of said carbon source;
• a carbon source alkane or alkene
• the carbon source may be an alkane such as methane or ethane or preferably an alkene which may be selected from the group consisting of ethylene, isopropylene, propylene, butene, butadiene, and mixtures thereof.
• This carbon source may be of renewable origin as described in patent application EP 1 980 530.
• the alkene preferably used is ethylene.
• the carbon source and preferably ethylene, is mixed in step c) with a stream of hydrogen.
• the carbon / hydrogen source ratio can in this case be between 90/10 and 60/40, preferably between 70/30 and 80/20.
• step c) is carried out with an ethylene / hydrogen mixture in a ratio of 75/25.
• the different steps are preferably carried out simultaneously and continuously in the same reactor.
• this process may comprise other steps (preliminary, intermediate or subsequent), as long as they do not adversely affect the production of carbon nanotubes.
• the catalyst material is reduced in situ in the CNT synthesis reactor.
• the catalyst layers are in the reduced state at the moment the catalyst is used.
• a step of grinding the nanotubes in situ or ex situ of the reactor may be considered, before or after step d). It is also possible to provide a step of chemical purification and / or thermal nanotubes before or after step d).
• the productivity obtained with the process of the invention is particularly high, since it is always greater than 20, even greater than 25, said productivity being calculated as the ratio of the mass of carbon formed to the mass of catalyst used.
• the carbon nanotubes formed are less likely to agglomerate than in the processes of the prior art.
• the invention also extends to carbon nanotubes, which can be obtained according to the process described above. It is advantageously multi-walled nanotubes, comprising for example from 5 to 15, and preferably from 7 to 10, graphene sheets wound concentrically.
• the nanotubes obtained according to the invention usually have a mean diameter ranging from 0.1 to 200 nm, preferably from 0.4 to 100 nm, more preferably from 0.4 to 50 nm and better still from 1 to 30 nm and advantageously a length of more than 0.1 microns and advantageously from 0.1 to 20 microns, for example about 6 microns.
• Their length / diameter ratio is advantageously greater than 10 and most often greater than 100.
• Their specific surface area is for example between 100 and 600 m 2 / g and their apparent density may especially be between 0.01 and 0.5 g. / cm 3 and more preferably between 0.07 and 0.2 g / cm 3 .
• the invention also relates to the use of nanotubes, which can be obtained as described above, in composite materials, to impart improved electrical and / or thermal conduction properties and / or mechanical properties, in particular resistance to 1 elongation, improved.
• CNTs can be used in macromolecular compositions intended for the packaging of electronic components or the manufacture of fuel lines (fuel oil) or antistatic coatings or paints, or in thermistors or electrodes. for supercapacities, or for the manufacture of structural parts in the aeronautical, nautical or automotive fields.
• FIGURE illustrates a catalyst particle according to the invention covered with a film of carbon nanotubes.
• Example 1 3% molybdenum under the conditions of Example 1 by first injecting the 520 ml of the iron nitrate solution and then the 150 ml of the solution of iron nitrate and ammonium molybdate.
• a 32 Fe 2 Mo / Al 2 O 3 catalyst containing 32% iron and 2 mol% of molybdenum is prepared under the conditions of Example 1, by first injecting the 90 ml of a solution of ammonium molybdate at 60 g / L of Mo then 650 mL of iron nitrate solution at 535 g / L.
• a 32Fe / Al 2 O 3 catalyst is prepared from Puralox® SCCa-5/150 alumina having a median diameter of approximately 85 ⁇ m and a specific surface area of 160 m 2 / g.
• 100 g of alumina are introduced and the mixture is swept in air. Thanks to 630 ml of a solution of iron nitrate containing 535 g / l of iron nitrate nonahydrate is then continuously injected into a pump.
• the target ratio (iron mass / catalyst mass) being 32%, the duration of addition is fixed at 25 h.
• the catalyst is then heated in situ at 20 ° C. under a dry air sweep for 8 hours and then placed in a muffle furnace at 400 ° C. for 8 hours.
• a catalytic test is carried out by putting a mass of about 2.3 g of catalyst in a layer in a reactor of 5 cm in diameter and 1 meter in effective height. It is heated at 650 ° C. under 2.66 L / min of nitrogen for 30 minutes and then a reduction stage is maintained for 30 minutes under 2 L / min of nitrogen and 0.66 L / min of hydrogen. Once this plateau is over, an ethylene flow rate of 2 L / min and 0.66 L / min of hydrogen are set. After 60 minutes, the heating was stopped and the reactor was cooled under a nitrogen flow of 2.66 L / min. The amount of product formed is evaluated by calculating the mass remaining after a calcination of about 2 g of the composite at 800 ° C. for 6 hours.
• the catalysts in accordance with the invention make it possible to obtain a productivity of carbon nanotubes and a higher activity than those obtained with the catalysts of the comparative examples.
• the attached figure also illustrates a catalyst grain according to the invention, coated with a carbon nanotube film formed by a method similar to that described above. As shown in this figure, the nanotube film has a thickness greater than 100 microns. To obtain a film thickness value more representative of the whole sample tested, we carried out a particle size analysis of the catalyst grains at the end of the reaction. After subtraction of the average diameter (D50) of the catalyst grains before reaction, it was deduced that the average thickness of the nanotube film was, for this sample, about 200 microns.
• D50 average diameter
• the nanotubes obtained according to the invention may be introduced into a polymer matrix in order to produce composite materials with improved mechanical and / or thermal and / or conductive properties.

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• 2009
  • 2009-08-17 FR FR0955692A patent/FR2949074B1/fr not_active Expired - Fee Related
• 2010
  • 2010-08-16 US US13/391,100 patent/US20120149551A1/en not_active Abandoned
  • 2010-08-16 KR KR1020127004259A patent/KR20120051019A/ko not_active Withdrawn
  • 2010-08-16 EP EP10766080A patent/EP2467205A2/de not_active Withdrawn
  • 2010-08-16 WO PCT/FR2010/051717 patent/WO2011020971A2/fr not_active Ceased
  • 2010-08-16 CN CN2010800364686A patent/CN102470351A/zh active Pending
  • 2010-08-16 BR BR112012003679A patent/BR112012003679A2/pt not_active IP Right Cessation
  • 2010-08-16 JP JP2012525192A patent/JP2013502309A/ja active Pending
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