Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
  • B01D53/9454—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific device
• • 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
  • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
  • B01J35/51—Spheres
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/9445—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC]
  • B01D53/945—Simultaneously removing carbon monoxide, hydrocarbons or nitrogen oxides making use of three-way catalysts [TWC] or four-way-catalysts [FWC] characterised by a specific catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
• • 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
• • 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
  • B01J21/005—Spinels
• • 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
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  • 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
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/391—Physical properties of the active metal ingredient
  • B01J35/393—Metal or metal oxide crystallite size
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
• • 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
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
  • B01J37/0027—Powdering
  • B01J37/0045—Drying a slurry, e.g. spray drying
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0215—Coating
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • 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
  • B01J37/0242—Coating followed by impregnation
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/03—Precipitation; Co-precipitation
  • B01J37/031—Precipitation
  • B01J37/033—Using Hydrolysis
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
  • C04B38/0045—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by a process involving the formation of a sol or a gel, e.g. sol-gel or precipitation processes
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
  • C04B38/06—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by burning-out added substances by burning natural expanding materials or by sublimating or melting out added substances
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
  • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
  • F01N3/2832—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support granular, e.g. pellets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/204—Alkaline earth metals
  • B01D2255/2047—Magnesium
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/20—Metals or compounds thereof
  • B01D2255/206—Rare earth metals
  • B01D2255/2061—Yttrium
• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/20715—Zirconium
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/209—Other metals
  • B01D2255/2092—Aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
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  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/92—Dimensions
  • B01D2255/9202—Linear dimensions
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/92—Dimensions
  • B01D2255/9207—Specific surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2258/00—Sources of waste gases
  • B01D2258/01—Engine exhaust gases
  • B01D2258/012—Diesel engines and lean burn gasoline engines
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
  • C04B2111/00474—Uses not provided for elsewhere in C04B2111/00
  • C04B2111/0081—Uses not provided for elsewhere in C04B2111/00 as catalysts or catalyst carriers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
  • F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
  • F01N3/28—Construction of catalytic reactors
  • F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
  • F01N3/2825—Ceramics
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• the invention relates to a device for cleaning the exhaust gases of a heat engine, in particular for a motor vehicle, comprising a support on which at least one catalyst is deposited for the chemical destruction of impurities of the exhaust gas, commonly called "catalytic converter".
• a device for cleaning the exhaust gases of a heat engine in particular for a motor vehicle, comprising a support on which at least one catalyst is deposited for the chemical destruction of impurities of the exhaust gas, commonly called "catalytic converter”.
• Such a device has the function of removing at least part of the pollutant gases contained in the exhaust gases, in particular carbon monoxide, hydrocarbons and nitrogen oxides, by transforming them by reduction or reduction reactions. 'oxidation.
• the invention proposes exhaust gas purification devices comprising oxide ceramic supports adapted to heterogeneous catalysis, the structural characteristics of which give higher performances than those of conventional catalyst oxide supports.
• a heterogeneous gas-solid catalyst is generally an inorganic material consisting of at least one oxide or non-oxide ceramic support on which is dispersed one or more active phases which convert reagents into products through repeated and uninterrupted cycles of elementary phases (adsorption, dissociation, diffusion, reaction-recombination, diffusion, desorption).
• the support may be involved not only from a physical point of view (high pore volume and BET surface area to improve the dispersion of the phases active) but also chemical (accelerate for example the dissociation and diffusion of such or such molecules).
• the catalyst participates in the conversion by returning to its original state at the end of each cycle throughout its lifetime.
• a catalyst modifies / accelerates the reaction mechanism (s) and the associated reaction kinetics without changing the thermodynamics thereof.
• the set of elementary steps are:
• the number of reactive molecules converted into product (s) within a defined time interval is directly related to the accessibility and the number of catalytic sites (s) available. It is therefore necessary to initially increase as much as possible the number of available active sites per unit area. To do this, it is necessary to reduce the size of the metal nanoparticles (from 1.5 to 3 nm) and maximize the dispersion of said active nanoparticles on the surface of the support. In order to reduce the average size of the active phase particles and to maximize the dispersion of the latter, it is necessary to provide a support having itself a maximum specific surface area and a suitable pore volume.
• the active species in the context of the automobile depollution reaction and of the steam reforming reaction can be noble metal (s) (Ruthenium, Rhenium, Rhodium, Palladium, Osmium, Iridium, Platinum) or an alloy between one, two or three of these noble metals or a transition metal and a two or three noble metals.
• noble metal Ruthenium, Rhenium, Rhodium, Palladium, Osmium, Iridium, Platinum
• Nickel, silver, gold, copper, zinc and cobalt are mentioned as transition metals.
• the ideal is to disperse nanometric active phases ( ⁇ 5 nm) on the surface of a ceramic support in general.
• phase change is usually accompanied by a destructuration.
• Alumina ⁇ is conventionally used especially in automotive pollution control as a catalytic support stabilized or not with lanthanum, cerium, zirconium ... In all cases however, after a few automobile stop-start cycles, the specific surface of stabilized or non-stabilized gamma alumina collapses inducing / promoting migration of active particles resulting in coalescence of the latter. Catalyst manufacturers deposit larger quantities of noble metals in order to avoid catalytic performance deactivation too quickly in order to minimize the impact related to the degradation of the structural properties of the ceramic support.
• Silica is the first mesoporous material to have been synthesized in 1992.
• US2003 / 0039744A1 discloses from the method of self-assembly induced by evaporation how to obtain a mesoporous silica support.
• the main problem is the non-stability under operating conditions of the synthesized support materials related to thermal cycling (300-1000 ° C.) and atmosphere containing a mixture of exhaust gases (CO, H 2 O, NO, N 2 , C ⁇ H). y , 0 2 , N 2 0 . It collapsed the specific surface of the oxide support, from 50 to 200 m 2 / g to less than 10 m 2 / g after a few thermal cycles (see Table 1: effect of the calcination temperature on the BET surface). oxides).
• a problem that arises is to provide a device for cleaning the exhaust gases of a thermal engine comprising a catalytic ceramic support having good physicochemical stability under the severe operating conditions (ie amplitude of the changes in temperature and atmosphere modification)
• a solution of the invention is a device for cleaning the exhaust gas of a heat engine comprising a catalytic ceramic support comprising an arrangement of crystallites of the same size, same isodiametric morphology and same chemical composition or of substantially the same size, even Isodiametric morphology and same chemical composition in which each crystallite is in point or near-point contact with crystallites surrounding it, and on which is deposited at least one active phase for the chemical destruction of impurities in the exhaust gas.
• the catalytic ceramic support implemented in the purification device according to the invention has the first advantage of developing a large available surface area, typically greater than or equal to 20 m 2 / g and up to several hundred m 2 /boy Wut. Furthermore, it is stable in terms of specific surface area at least up to 1000 ° C under an atmosphere containing an exhaust gas mixture (CO, H 2 O, NO, N 2 , C x H y , O 2 , N 2 0 ).
• an exhaust gas mixture CO, H 2 O, NO, N 2 , C x H y , O 2 , N 2 0 .
• Figure la schematically shows a catalytic support according to the state of the art. It is more precisely a mesoporous structure.
• Figure lb schematically shows a catalytic support implemented in the purification device according to the invention. In this figure each crystallite is in contact with 6 other crystallites in a plane (ie compact stack).
• the catalytic ceramic support implemented in the purification device according to the invention may have one or more of the following characteristics:
• the crystallite arrangement is a hexagonal compact or cubic face-centered stack in which each crystallite is in point or almost point contact with at most 12 other crystallites in a 3-dimensional space.
• said arrangement is made of alumina (Al 2 O 3 ), or of cerine (CeO 2 ) stabilized or not with gadolinium oxide, or of zirconia (ZrO 2 ) stabilized or not with yttrium oxide or in phase spinel or lanthanum oxide (La 3 O 3 ) or in a mixture of one or more of these compounds.
• the crystallites are of substantially spherical shape.
• the crystallites have a mean equivalent diameter of between 2 and 20 nm, preferably between 5 and 15 nm.
• said support comprises a substrate and a film on the surface of said substrate comprising said arrangement of crystallites.
• said ceramic support comprises granules comprising said arrangement of crystallites.
• the granules are of substantially spherical shape.
• the catalytic ceramic support implemented in the purification device according to the invention can be deposited (washcoated) on a ceramic and / or metal substrate optionally coated with ceramic of various architectures such as honeycomb structures, barrels, monoliths. , honeycomb structures, spheres, multi-scale structured reactors-reactors (reactors) ...
• the present invention also relates to a method of cleaning the exhaust gas of a heat engine in which said exhaust gas is circulated through a device according to the invention.
• the heat engine is preferably a motor vehicle engine, in particular a gasoline or diesel engine.
• a sol comprising salts of nitrate and / or aluminum carbonate and / or magnesium and / or cerium and / or zirconium and / or yttrium and / or gadolinium and / or lanthanum a surfactant and solvents such as water, ethanol and ammonia; b) Soaking a substrate in the soil prepared in step a);
• step c) Calcining the gelled composite material of step c) at a temperature between 500 ° C and 1000 ° C, preferably between 700 ° C and 900 ° C, more preferably at a temperature of 900 ° C.
• the substrate used in this first synthesis process is dense alumina or cordierite or mullite or silicon carbide.
• a sol comprising salts of nitrate and / or aluminum carbonate and / or magnesium and / or cerium and / or zirconium and / or yttrium and / or gadolinium and / or lanthanum a surfactant and solvents such as water, ethanol and ammonia; b) Atomization of the soil in contact with a stream of hot air so as to evaporate the solvent and form a micron powder;
• the two methods of synthesis of the catalytic ceramic supports may have one or more of the following characteristics:
• the soil prepared in step a) is aged in a ventilated oven at a temperature of between 15 and 35 ° C. for a period of 24 hours.
• the soil prepared in the two processes for synthesizing the ceramic supports mentioned above preferably comprises four main constituents:
• Inorganic precursors for reasons of cost limitation, it has been chosen to use nitrates of magnesium, aluminum, cerium, zirconium, yttrium, gadolinium, lanthanum. The stoichiometry of these nitrates can be verified by Induced Coupled Plasma (ICP), before their solubilization in osmosis water. Any other chemical precursor (carbonate, chloride, etc.) can be used in the production process.
• ICP Induced Coupled Plasma
• the surfactant otherwise called surfactant. It is possible to use a Pluronic F 127 triblock copolymer of the EO-PO-EO type. It has two hydrophilic blocks (EO) and a hydrophobic central block (PO).
• the surfactant is solubilized in an ammoniacal solution which makes it possible to create hydrogen bonds between the hydrophilic blocks and the inorganic species.
• the first step is to solubilize the surfactant (0.9g) in absolute ethanol (23 mL) and in an ammoniacal solution (4.5 mL). The mixture is then refluxed for 1 hour. Then, the nitrate solution previously prepared (20 mL) is added dropwise to the mixture. The whole is refluxed for 1 h and then cooled to room temperature. The soil thus synthesized is aged in a ventilated oven whose ambient temperature (20 ° C) is precisely controlled.
• soaking consists in immersing a substrate in the soil and removing it at a constant speed.
• the movement of the substrate causes the liquid forming a surface layer. This layer divides in two, the inner part moves with the substrate while the outer part falls into the container. The progressive evaporation of the solvent leads to the formation of a film on the surface of the substrate.
• the quenched substrates are then baked at 30 ° C to 70 ° C for a few hours. A gel is then formed. Calcination of substrates under air eliminates nitrates but also decomposes the surfactant and thus release porosity.
• the atomization technique makes it possible to transform a sol into a solid dry form (powder) by the use of a hot intermediate (FIG. 3).
• the principle is based on spraying fine droplets of soil 3, in a chamber 4 in contact with a stream of hot air 2 in order to evaporate the solvent.
• the powder obtained is entrained by the heat flow 5 to a cyclone 6 which will separate the air 7 from the powder 8.
• the apparatus that can be used in the context of the present invention is a reference commercial model "190 Mini Spray Dryer” brand Buchi.
• the powder recovered after the atomization is dried in an oven at 70 ° C and then calcined.
• the precursors i.e. in this example magnesium and aluminum nitrate salts, are partially hydrolysed (Equation 2).
• the surfactants used are copolymers which have two parts of different polarities: a hydrophobic body and hydrophilic ends. These copolymers are part of the family of block copolymers consisting of poly (alkylene oxide) chains.
• An example is the copolymer (EO) n- (PO) m- (EO) n, constituted by the chain of polyethylene oxide (EO), hydrophilic at the ends and in its central part propylene oxide (PO), hydrophobic.
• the polymer chains remain dispersed in solution at a concentration below the critical micelle concentration (CMC). CMC is defined as the limiting concentration beyond which occurs the phenomenon of self-arrangement of surfactant molecules in the solution.
• the chains of the surfactant tend to be grouped by hydrophilic / hydrophobic affinity.
• the hydrophobic bodies are grouped together and form spherical micelles.
• the ends of the polymer chains are pushed outwardly of the micelles, and associate during the evaporation of the volatile solvent (ethanol) with the ionic species in solution which also have hydrophilic affinities.
• This phenomenon of self-arrangement occurs during c) drying stages of the synthesis processes of the ceramic supports mentioned above.
• the substrate coated with a thin film was calcined under air at 500 ° C. for 4 hours, with a temperature rise rate of 1 ° C./min.
• the sample is observed using a high-resolution scanning electron microscope (SEM-FEG) and an Atomic Force Microscope (AFM).
• SEM-FEG high-resolution scanning electron microscope
• AFM Atomic Force Microscope
• the Atomic Force microscope allows to account for the surface topography of a sample with an ideally atomic resolution.
• the principle consists in sweeping the surface of the sample with a tip whose end is of atomic dimension, while measuring the interaction forces between the end of the tip and the surface. By keeping the interaction constant, it is possible to measure the topography of the sample.
• FIG. 4 The AFM images produced over a surface of 500 nm (FIG. 4) and the SEM-FEG micrographs (FIG. 5) reveal the formation of a mesostructured deposit at this calcination temperature.
• Figure 4a) is a topography image while Figure 4b is an auto-correlation image.
• the mesostructuration of the material is due to a progressive concentration within the deposition of the aluminum and magnesium precursors, as well as the surfactant, to a micellar concentration greater than the critical concentration, which results from the evaporation of the solvents.
• FIG. 8 corresponds to 3 SEM-FEG micrographs of the catalytic support with 3 different magnifications.
• D is the size of the crystallites (nm)
• ⁇ is the wavelength of the Cu Ka line (1.5406 ⁇ )
• ⁇ corresponds to the width at mid-height of the line (in rad)
• ⁇ corresponds to the diffraction angle
• the microstructure of this powder is identical to that obtained on the deposit, namely an ultra-divided and porous micro structure with a crystallite size of the same order of magnitude.
• the specific surface area of the powder measured by the BET method, is 50 m 2 / g.
• the morphology of the powder was compared with that of a spinel phase powder of the trade name Puralox MG30, supplied by Sasol (FIG. 11). This powder has a specific surface area of 30 m 2 / g.
• the particles of the commercial powder are not spherical and their particle size distribution is wide, which will potentially promote a particle enlargement (physical deactivation) during aging under automotive conditions (temperature between 300 and 1000 ° C, stop-start cycles, specific atmosphere).
• Catalytic ceramic substrates obtained by dipping the soil on a substrate, in other words comprising a substrate and a film, as well as the catalytic ceramic supports obtained by atomization of the soil, in other words comprising granules, have been aged under the operating conditions of the catalytic converters, that is to say a temperature of 900 ° C for 100 h under an atmosphere containing a mixture of exhaust gases (CO, H 2 0, NO, N 2 , C x H y , O 2 , N 2 O ).
• the specific surface of the aged powder is 41 m 2 / g, thus showing a very low abatement of the specific surface area.
• spinel support with the associated production methods can be extended to other families of ceramic support such that said support is alumina (Al 2 O 3 ), or cerine (CeO 2 ) stabilized or no to gadolinium oxide, or zirconia (ZrO 2 ) stabilized or otherwise with yttrium oxide (such as YSZ 4 and 7-10%) or lanthanum oxide (La 2 0 3 ) or spinel phase (for example MgAl 2 0 4 ) or in a mixture of one, or two or three or four of these compounds. It is also possible to mention compounds based on alumina stabilized with cerium and / or zirconium and / or lanthanum at a level of 2-20% by mass.
• the microstructures obtained are identical to those described in the example detailed above.

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