Classifications

• • 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
  • F01N3/18—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 methods of operation; Control
• • 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
• • 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]
  • B01D53/945—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
  • 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
  • B01J23/005—Spinels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/54—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/56—Platinum group metals
  • B01J23/63—Platinum group metals with rare earths or actinides
• • B—PERFORMING OPERATIONS; TRANSPORTING
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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
  • 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
  • B01J23/83—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 rare earths or actinides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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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
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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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
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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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
• • 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
  • F01N3/2825—Ceramics
• • 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
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/1021—Platinum
• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2255/1026—Ruthenium
• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2258/012—Diesel engines and lean burn gasoline engines
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2258/014—Stoichiometric gasoline engines
• • C—CHEMISTRY; METALLURGY
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  • 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
• • 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
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  • 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, commonly called “ catalytic converter ", in particular for a motor vehicle, a device comprising a support on which at least one catalyst is deposited for the chemical destruction of impurities in the exhaust gases.
• the function of such a device is to eliminate, at least in part, the gases pollutants contained in the exhaust gases, in particular carbon monoxide, hydrocarbons and nitrogen oxides, by transforming them by reduction or oxidation reactions.
• the invention proposes exhaust gas purification devices comprising oxide ceramic supports and active metal particles whose structural characteristics and the anchoring of the particles in the support give superior performances to those of the catalyst oxide supports. conventional.
• 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 can in some cases intervene no only from a physical point of view (high pore volume and high BET surface to improve the dispersion of the active phases) but also chemical (accelerate for example the adsorption, dissociation, diffusion and desorption of such and 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 kinetics of the associated reaction (s) without changing the thermodynamics thereof.
• the set of elementary steps are:
• a catalytic converter consists of a stainless conversion chamber in which the exhaust gas is introduced. These gases pass through a ceramic structure generally consisting of a ceramic honeycomb substrate of oxide nature (cordierite, mullite, ). On the walls of the ceramic substrate (honeycomb) is deposited a so-called three-way catalyst (TWC: Three Ways Catalysts). The catalyst accelerates the conversion kinetics of the reagents into products.
• the objective is to limit the release of toxic gases (CO, NOx and unburned hydrocarbons) by transforming them mainly into water, C0 2 and nitrogen.
• a 3-way catalyst is able to provide 3 types of reactions simultaneously:
• Oxidation reactions (requiring a high partial pressure of oxygen) and reduction (low partial pressure of oxygen) add stresses. They require a very precise amount of air to add to the fuel.
• a lambda probe placed on the exhaust measures the amount of oxygen output.
• a servo loop makes it possible to control the air / fuel ratio very precisely by keeping it at an ideal value.
• the catalytic converter is effective only from 250-300 ° C. That's why small trips are problematic.
• the ceramic architectures of catalytic converters for automotive pollution control are generally substrates in honeycombs and are for the most part made of cordierite (2 MgO-2 Al 2 O 3 -5 SiO 2 ) or mullite. These architectures develop a low surface area (a few m 2 / g) with a volume porosity of 20% to 40%.
• the supports of the classical active phases are oxides: alumina for its low temperature thermo-chemical stability ( ⁇ 800 ° C), ceria for its oxygen redox properties and zirconia for its chemical affinity with rhodium.
• alumina for its low temperature thermo-chemical stability ( ⁇ 800 ° C)
• ceria for its oxygen redox properties
• zirconia for its chemical affinity with rhodium.
• the specific surface development has been sought from alumina in its forms ⁇ , ⁇ and ⁇ (from 50 to 250 m 2 / g). Since then, supports ceria and zirconia developing from 20 to 100 m 2 / g have been made.
• the support collapses thermally after a few cycles inducing a drop in the specific surface, a drop in the pore volume and an acceleration of migration / diffusion / coalescence phenomena of the metal nanoparticles.
• the oxide supports In order to minimize these phenomena of thermal collapse under operating conditions of the oxide supports, the latter have been stabilized by additions of elements such as yttrium, gadolinium, lanthanum, etc. La-Al 2 0 3 is thus used . CeGdO, ZrYO, CeZrYO, ... This limits their thermal collapses but does not minimize the phenomena of migration / sintering of the metal particles.
• the noble metals and the support oxide of the active phases (for example the migration of the Rh 3+ ion in a structure ⁇ A1 2 0 3 ).
• a problem that arises is to provide a device for cleaning the exhaust gas of a heat engine comprising an improved catalyst capable of to stabilize, under conditions similar to those encountered during methane steam reforming, nanoparticles of active phases, so as to improve its performance.
• a solution of the invention is a device for cleaning the exhaust gases 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 substantially of the same size, same isodiametric morphology and same chemical composition in which each crystallite is in point contact or almost punctual with the crystallites which the surround, and
• an active phase for the chemical destruction of impurities in the exhaust gas comprising metal particles mechanically anchored in said catalytic support in such a way that the coalescence and mobility of each particle are limited to a maximum volume corresponding to that of a crystallite said catalytic ceramic support.
• the first advantage of the proposed solution relates to the ultra-divided mesoporous catalytic ceramic support of active phase (s). Indeed, it develops a large available surface area greater than or equal to 20 m 2 / g, due to the size of its nanoscale particles which constitutes it and their respective arrangement. Furthermore, the support is stable under the operating conditions of the catalytic converters; that is, the support is stable at temperatures between 600 ° C and 1000 ° C in 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 .
• This thermal stability is directly related to the microstructure of the synthesized material (arrangement of crystallites of the same size, same isodiametric morphology and same chemical composition or substantially of the same size, same isodiametric morphology and same chemical composition in which each crystallite is in point contact or almost punctual with surrounding crystallites) and associated synthesis method (s).
• the particular architecture of the catalytic support has a direct influence on the stability of the metal nanoparticles.
• the arrangement of the crystallites and the porosity makes it possible to develop a mechanical anchoring of said metallic nanoparticles on the surface of the support.
• the excellent dispersion of the active phases thus obtained makes it possible to envisage a significant reduction in the amount of noble metals employed without loss of catalytic performance.
• FIG. 2 illustrates the mechanical blocking of the metal particles by the catalytic ceramic support. Firstly, it is clear that the elementary active particles will be at most the size of a support crystallite. Second, their movement under the combined effect of a high temperature and an atmosphere rich in water vapor is still limited to potential wells that represents the space between two crystallites. The arrows represent the only possible movement of the metal particles.
• the device according to the invention may have one or more of the following characteristics:
• said arrangement is alumina (Al 2 O 3 ) stabilized or not with lanthanum, cerium or zirconium, or cerine (CeO 2 ) stabilized or not stabilized with gadolinium oxide, or zirconia (ZrO 2 ) stabilized or otherwise with yttrium oxide or spinel phase or lanthanum oxide (La 3 O 3 ) or a mixture of one or more of these compounds,
• the metal particles are chosen:
• noble metals selected from Ruthenium, Rhodium, Palladium, Silver, Osmium, Iridium, Platinum or an alloy between one, two or three of these noble metals, or
• transition metals selected from nickel, silver, gold, cobalt, and copper or an alloy between one, two or three of these transition metals, or
• the crystallites have a mean equivalent diameter of between 2 and 20 nm, preferably between 5 and 15 nm, and the metal particles have a mean equivalent diameter of between 2 and 20 nm, preferably less than 10 nm.
• the active phase support crystallite arrangement (s) is at best a hexagonal compact or cubic face-centered stack in which each crystallite is in punctual or near-point contact with at most 12 other crystallites in a 3-dimensional space.
• the catalytic assembly (substrate + catalyst) used in the purification device according to the invention may comprise a substrate of various architectures such as honeycomb structures, barrels, monoliths, honeycomb structures. bees, spheres, multi-scale structured reactors-reactors (reactors), ... of a ceramic or metallic or metallic nature coated with ceramics, and on which the active phase support (s) can be deposited (washcoat) .
• 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 diesel engine or a gasoline engine.
• a method for preparing a support assembly (s) ceramic (s) - phase (s) active (s) may include the following steps:
• a catalytic ceramic support comprising an arrangement of crystallites of the same size, same morphology and same chemical composition or substantially the same size, same morphology and same chemical composition in which each crystallite is in point contact or almost punctual with the crystallites who surround him,
• calcination in air of the impregnated catalyst at a temperature of between 350 ° C. and 1000 ° C., preferably at a temperature of between 450 ° C. and 700 ° C., still more preferably at a temperature of 500 ° C., so as to obtain an active phase (s) oxidized (s) deposited on the surface (s) support (s) ceramic (s) catalytic (s); and d) optionally reducing the oxidized active phase (s) between 300 ° C and 1000 ° C, preferably at a temperature between 300 ° C and 600 ° C, even more preferably at a temperature of 300 ° C.
• this method may include one or more of the following features:
• step b) of impregnation is carried out under vacuum for a period of between 5 and 60 minutes;
• the active phase solution (s) is a solution of rhodium nitrate (Rh (NO 3 ) 3 , 2H 2 O) or a solution of nickel nitrate (Ni (NO 3 ) 2 , 6H 2 O) or palladium ((Pd (NO 3 ) 3 , 2H 2 O) or platinum ((Pt (NO 3 ) x ), yH 2 O) or a mixture thereof.
• said method comprises, after step d) optionally a step e) of aging under operating conditions or close to the operating conditions of the catalyst.
• the first operating cycle stop / start
• the catalytic ceramic support described in step a) of the process for preparing the ceramic support-active phase (s) assembly (s) implemented in the purification device according to the invention can be prepared by two methods.
• a first method will result in a catalytic ceramic support comprising a substrate and a film on the surface of said substrate comprising an arrangement of crystallites of the same size, same isodiametric morphology and same or substantially the same chemical composition, same isodiametric morphology and same chemical composition in which each crystallite is in point or almost punctual contact with the crystallites which surround it.
• a second process will lead to a catalytic ceramic support comprising granules comprising an arrangement of crystallites of the same size, same isodiametric morphology and same chemical composition or substantially of the same size, same isodiametric morphology and same chemical composition in which each crystallite is in point contact or almost punctual with the crystallites that surround it.
• the granules are substantially spherical.
• the first method of preparing the catalytic ceramic support comprises the following steps:
• a sol comprising salts of nitrates and / or carbonates of aluminum 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; ii) Soaking a substrate in the soil prepared in step i);
• step iv) Calcining the gelled composite material of step iii) at a temperature typically between 500 ° C and 1000 ° C in air.
• the substrate used in this first process for preparing the catalytic ceramic support is of dense alumina.
• the second method of preparing the catalytic ceramic support comprises the following steps:
• a sol comprising salts of nitrates and / or carbonates of aluminum 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; ii) Atomising the soil in contact with a hot air stream so as to evaporate the solvent and form a micron powder;
• the soil prepared in the two processes for preparing the catalytic ceramic support preferably comprises four main constituents:
• Inorganic precursors for reasons of cost limitation, we have chosen to use nitrates of magnesium and aluminum, cerium, zirconium, yttrium or a mixture of these nitrate salts. Other inorganic precursors can be used (carbonates, sulfonates, chlorides, ...) alone or mixed in the process.
• the surfactant otherwise called surfactant.
• the solvent absolute ethanol
• 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.
• This invention applies to substrates of various architectures such as honeycomb structures, barrels, monoliths, honeycomb structures, spheres, multi-scale structured reactors-reactors (reactors), etc. of ceramic or metallic nature, or ceramic coated metal, and on which said support is removable (wash coat).
• 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.
• Equation 1 e ⁇ ⁇ v 2/3
• 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 the spraying of fine droplets soil 3, in a chamber 4 in contact with a hot air stream 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.
• These support particles of active phase (s) with a size of the order of ten nanometers display a very narrow granulometric distribution centered around 12 nm.
• the average spinel crystallite size in this example is 12 nm (measured by small angle X-ray diffraction, Figure 5). This size corresponds to that of the elementary particles observed in scanning electron microscopy indicating that the elementary particles are monocrystalline.
• 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 catalytic ceramic support is then impregnated with a solution of precursor Rh, and / or Pt, and / or Pd and / or Ni.
• the catalyst studied is the 3-way catalyst for use in catalytic converters.
• Rh (N0 3 ) 3 , 2H 2 O) nitrate was retained as the inorganic precursor of Rh.
• the concentration of Rh in the nitrate solution was set at 0.1 g / L.
• the catalyst is calcined under air at 500 ° C. for 4 hours.
• the reduction of the active phase is carried out under Ar-H 2 (3% vol) at 300 ° C. for 1 h.
• FIG. 6a In order to observe the size and the metallic dispersion at the surface of the support, observations by transmission electron microscopy were carried out (FIG. 6a). The latter reveal the presence of particles of Rh in the elemental state of a size of the order of a nanometer. These small particles are concentrated around the spinel particles of the support.
• Rh particles coalesce to a size of 5 nm (FIG. 6b).
• a Rh particle is stabilized on a spinel support particle, which greatly reduces the possibility of future coalescence of the metal particles during catalyst operation.
• the impregnation of the support is carried out with a solution of Ni nitrate (Ni (NO 3 ) 2 , 6H 2 0).
• Ni concentration in this solution can be set at 5g / L.
• the catalyst can be calcined in air at 500 ° C. for 4 hours and then reduced under Ar-H 2 (3% vol) at 700 ° C. for 2 hours.
• the AlMg + Rh catalyst was aged for 20 days while being subjected to a temperature of the order of 650 ° C. and another sample was subjected to a temperature of the order of 850 ° C.
• the ultra-divided spinel phase support (catalytic ceramic support) is preserved after aging and the magnification of the spinel particles is very limited.
• the size of the metal particles after aging remains generally less than or equal to the size of the elemental crystallites of the spinel support.
• reaction concerns the pollution control of exhaust gases.
• This invention can be extended to various applications in heterogeneous catalysis by adapting (s) phase (s) active (s) to the desired catalytic reaction (SMR, chemical reactions, petrochemical, environmental, ...) on a catalytic ceramic support ultra-divided spinel base, alumina, ceria, zirconia (stabilized with yttrium or not) or a mixture of these compounds.

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