US20100229542A1 - Texturized purification structure incorporating an electrochemical catalyst system - Google Patents

Texturized purification structure incorporating an electrochemical catalyst system Download PDF

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US20100229542A1
US20100229542A1 US12/681,865 US68186508A US2010229542A1 US 20100229542 A1 US20100229542 A1 US 20100229542A1 US 68186508 A US68186508 A US 68186508A US 2010229542 A1 US2010229542 A1 US 2010229542A1
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inorganic material
grains
texturizing
irregularities
gas
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Patricia Andy
Agnes Princivalle
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Saint Gobain Centre de Recherche et dEtudes Europeen SAS
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Saint Gobain Centre de Recherche et dEtudes Europeen SAS
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    • 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
    • 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
    • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/2429—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material of the honeycomb walls or cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24491—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2425—Honeycomb filters characterized by parameters related to the physical properties of the honeycomb structure material
    • B01D46/24492—Pore diameter
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D46/00—Filters or filtering processes specially modified for separating dispersed particles from gases or vapours
    • B01D46/24—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies
    • B01D46/2403—Particle separators, e.g. dust precipitators, using rigid hollow filter bodies characterised by the physical shape or structure of the filtering element
    • B01D46/2418—Honeycomb filters
    • B01D46/2451—Honeycomb filters characterized by the geometrical structure, shape, pattern or configuration or parameters related to the geometry of the structure
    • B01D46/2482—Thickness, height, width, length or diameter
    • 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
    • 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
    • B01J35/33—Electric or magnetic properties
    • 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
    • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
    • 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
    • B01J37/0215—Coating
    • B01J37/0219—Coating the coating containing organic compounds
    • 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
    • B01J37/0242—Coating followed by impregnation
    • 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
    • B01J37/0246—Coatings comprising a zeolite
    • 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
    • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
    • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
    • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
    • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors, e.g. catalysed diesel particulate filters
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M35/00—Combustion-air cleaners, air intakes, intake silencers, or induction systems specially adapted for, or arranged on, internal-combustion engines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/50—Zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/92—Dimensions
    • B01D2255/9205—Porosity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2279/00—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses
    • B01D2279/30—Filters adapted for separating dispersed particles from gases or vapours specially modified for specific uses for treatment of exhaust gases from IC Engines
    • 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
    • B01J23/02—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the alkali- or alkaline earth metals or beryllium
    • 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
    • B01J23/10—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of rare earths
    • 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
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/18—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the mordenite type
    • B01J29/20—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the mordenite type containing iron group metals, noble metals or copper
    • B01J29/22—Noble metals
    • 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 present invention relates to the field of structures for purifying a gas laden with gaseous pollutants essentially of the NO type. More particularly, the invention relates to honeycomb structures, especially those used to treat exhaust gases of a gasoline engine or preferably a diesel engine, and incorporating a system that combines a reduction catalyst A for reducing said polluting species of the NO type and an oxidation catalyst B for oxidizing hydrocarbons HC and/or for oxidizing soot and/or steam reforming reactions of the HC+H 2 O ⁇ 3/2H 2 +CO type and/or water gas reactions of the CO+H 2 O ⁇ H 2 +CO 2 type.
  • the desorption of the trapped NO x on the catalyst and their catalytic reduction to gaseous nitrogen N 2 can be obtained only in the presence, within the reduction catalyst, of a sufficient quantity of reducing species, in the form of hydrocarbons or carbon monoxide CO or else hydrogen H 2 , the hydrogen itself possibly being obtained by a catalytic reaction between the hydrocarbons HC and steam or between CO and steam.
  • An electrochemical catalysis system is well known from U.S. Pat. No. 6,878,354 which makes it possible in theory to convert the NO even when operating outside stoichiometry.
  • the system comprises the combination of an HC and CO oxidation catalyst and an NO reduction catalyst, the two being coupled on the model of an electrochemical cell by means of metallic or inorganic materials. These materials, which provide the junction between the catalysts, are chosen from electron conductors or ion conductors and deliver “continuously”, into the system, the various charged species (for example electrons and oxygen ions O 2 ⁇ ) necessary for the simultaneous reduction and oxidation reactions.
  • Such systems appear to be advantageous as they enable an electrochemical reaction to take place between a reduction catalyst A and an oxidation catalyst B that are connected together, independently of the conditions of the gaseous medium. According to that publication, such a system makes it possible in particular to increase the catalytic conversion of the polluting species, especially when an engine is operating with a lean mixture.
  • the efficiency of converting the polluting species may also be substantially limited by the intrinsic characteristics of the materials used as ion and electron conductors. More precisely, since the electrochemical system consists of small particles randomly disposed with respect to one another, its efficiency is necessarily limited, on the one hand, by the connections between the particles, and, on the other hand, by the small quantity of conducting species (electrons and/or ions) that are available for the electrochemical catalyst system to operate properly.
  • the procedures for depositing catalysts A and B in the pores of the support appear to be very difficult to determine, experience showing that an ideal distribution of the active sites promoting successive contacts of the ADB or BDA or ACB or BCA type, necessary for the optimum operation of the electrochemical system, is very difficult to implement and to reproduce.
  • the object of the structure according to the invention is to solve the abovementioned problems by providing an electrocatalyzed support that is particularly suitable for filtering applications and has an improved purification performance, especially in respect of the amount of NO x reduced, especially when the engine is operating in lean mixture mode, the pressure drop and the aging resistance.
  • the present invention relates to a structure, preferably a honeycomb structure, for the purification of a polluted gas, for example an exhaust gas of a diesel or gasoline engine, comprising:
  • said irregularities take for example the form of beads, crystallites, polycrystalline clusters, or even rods or acicular structures, hollows or craters, said irregularities having a mean diameter d of between about 10 nm and about 5 microns and a mean height h or a mean depth p of between about 10 nm and about 5 microns.
  • mean diameter d is understood within the meaning of the present description to be the mean diameter of the irregularities, these being individually defined from the plane tangential to the surface of the grain or of the grain boundary on which they are located.
  • mean height h is understood within the meaning of the present description to be the mean distance between the top of the relief formed by the texturizing and the aforementioned plane.
  • mean depth p is understood within the meaning of the present description to be the mean distance between, on the one hand, the deepest point formed by the impression, for example the hollow or crater of the texturizing, and, on the other hand, the aforementioned plane.
  • the mean diameter d of the irregularities is between 100 nm and 2.5 microns.
  • the mean height h or the mean depth p of the irregularities is between 100 nm and 2.5 microns.
  • the texturizing material covers at least 10% of the total surface of the grains and possibly of the grain boundaries of the inorganic material constituting the porous matrix. Preferably, the texturizing material covers at least 15% of the total surface of the grains and possibly of the grain boundaries of the inorganic material constituting the porous matrix.
  • the mean equivalent diameter d and/or the mean height h or the mean depth p of the irregularities are/is smaller than the mean size of the grains of the inorganic material constituting the matrix by a factor of between 1 ⁇ 2 and 1/1000.
  • the mean equivalent diameter d and/or the mean height h or the mean depth p of the irregularities are/is smaller than the mean size of the grains of the inorganic material constituting the matrix by a factor of between 1 ⁇ 5 and 1/100.
  • the texturizing material is of the same nature as the inorganic material constituting the matrix.
  • the texturizing material and the inorganic material constituting the matrix are based on one and the same compound, for example SiC, that is to say that said compound (e.g. SiC) is present in an amount of at least 25% by weight in both materials, preferably at least 45% by weight in both materials and very preferably at least 70% by weight in both materials.
  • said compound e.g. SiC
  • the inorganic material constituting the matrix is for example based on silicon carbide SiC.
  • the inorganic material may be based on doped SiC, for example doped with aluminum or with nitrogen, in such a way that its electronic resistivity is less than 20 ⁇ cm at 400° C.
  • the irregularities are formed by crystallites or by a cluster of crystallites of a fired or sintered material on the surface of the grains of the porous matrix.
  • the irregularities essentially consist of beads of an electron-conductive and/or ion-conductive material.
  • the irregularities may also take the form of craters hollowed out in a fired or sintered material on the surface of the grains of the porous matrix.
  • the invention also relates to the intermediate structure for obtaining a catalytic filter for the treatment of solid particles and gaseous pollutants according to one of the above embodiments and comprising a porous matrix consisting of an inorganic material, in the form of grains that are interconnected so as to provide cavities between them, such that the open porosity is between 20 and 70% and the median pore diameter is between 5 and 40 ⁇ m, said grains of the inorganic material being covered over at least part of their surface with a texturizing material according to one of the preceding claims.
  • the invention also relates to a process for obtaining a filter as described above and comprising the following steps:
  • the texturizing material is deposited by the application of a slip of said material for covering the surface of the grains, followed by a firing or sintering heat treatment, by the application of a sol-gel solution that includes a filler in the form of inorganic beads or particles, followed by a firing or sintering heat treatment or else by the application of a sol-gel solution that includes a filler in the form of organic beads or particles, followed by a firing or sintering heat treatment.
  • the texturizing process according to the invention may be obtained either:
  • Texturizing methods may also be employed according to the invention, such as heat treatment in a gas (for example O 2 or N 2 in the case of a substrate based on SiC).
  • a gas for example O 2 or N 2 in the case of a substrate based on SiC.
  • Plasma etching or chemical etching processes may also be used to obtain the texturizing according to the invention, depending on the operating conditions and on the nature of the substrate.
  • the catalytic coating according to the invention is typically obtained by impregnation with one or more successive solutions comprising the catalysts of the electrochemical system according to the invention in the form of the support material or its precursors and of an active phase or a precursor of the active phase.
  • the precursors used take the form of organic or mineral salts or compounds, dissolved or in suspension in an aqueous or organic solution.
  • the impregnation is followed by a heat treatment for the purpose of obtaining the final coating of a solid and catalytically active phase in the pores of the filter.
  • Catalyst A used for the reduction reaction is chosen from the catalysts that are well known in the art for their activity and preferably for their selectivity with respect to NO x reduction reactions. They may in particular be chosen from compounds of the alkali metal or alkaline earth or rare earth type, which also act as NO x traps, for example such as those described in application EP 1 566 214, in that they are deposited as a mixture with an active principle that includes precious metals (Pt, Pd, Rh) by adsorption on the surface of a powder having a high specific surface area, for example alumina powder.
  • precious metals Pt, Pd, Rh
  • Catalyst B used for the hydrocarbon oxidation reaction is chosen from the catalysts well known in the art for their activity and preferably their selectivity with respect to hydrocarbon oxidation reactions.
  • reforming and steam reforming catalysts used in the petrochemical and refining field may be used according to the invention.
  • the arrangement according to the invention has, compared with the nontexturized structures known hitherto, many advantages, among which:
  • the porous inorganic material comprises or is formed by an electron-conductive inorganic material of the carbide type, for example SiC, or of the silicide type, for example MoSi 2 , or a boride, for example TiB 2 , or of the La 1-x Sr x MnO 3 family or of the mixed cerium gadolinium oxide (CGO) type.
  • an electron-conductive inorganic material of the carbide type for example SiC
  • the silicide type for example MoSi 2
  • a boride for example TiB 2
  • La 1-x Sr x MnO 3 family or of the mixed cerium gadolinium oxide (CGO) type.
  • the porous inorganic material may also comprise or be formed by an inorganic material that conducts by oxygen ions, of the fluorite structure, for example zirconia stabilized by CaO or by Y 2 O 3 , or mixed cerium gadolinium oxides, or of perovskite structure, for example a gallate, compounds based on lanthanum of the LaAlO 3 or LaGaO 3 or La 1-x Sr x Ga 1-y Mg y O 3 type or of the BIMEVOX structure, for example Bi 2 V 1-x Me x O z or of the LAMOX structure, for example La 2 Mo 2 O 9 , or else of the apatite structure, for example Me 10 (XO 4 ) 6 Y 2 , or of the mixed cerium gadolinium oxide (CGO) type.
  • CGOs have the advantage of being both ion conductors and electron conductors.
  • the porous inorganic material may comprise or be formed by an inorganic proton-conductive material of the perovskite type, for example SrCe 1-x M x O 3- ⁇ where M is a rare earth, typically the compound SrCe x Yb 1-x O 3- ⁇ , or of the BaCe 1-x M x O 3- ⁇ type, for example the compound BaCeO 3 , or else a compound of the La x Sr 1-x ScO 3- ⁇ family, for example La 0.9 Sr 0.1 ScO 3- ⁇ .
  • an inorganic proton-conductive material of the perovskite type for example SrCe 1-x M x O 3- ⁇ where M is a rare earth, typically the compound SrCe x Yb 1-x O 3- ⁇ , or of the BaCe 1-x M x O 3- ⁇ type, for example the compound BaCeO 3 , or else a compound of the La x Sr 1-x ScO 3- ⁇ family, for example La 0.9 Sr 0.1 ScO 3- ⁇
  • the porous inorganic material is based on silicon carbide SiC, preferably recrystallized at a temperature between 2100 and 2400° C.
  • the inorganic material may be based on doped SiC, for example doped with aluminum or with nitrogen, and in such a way that its electronic resistivity is preferably less than 20 ⁇ cm, more preferably less than 15 ⁇ cm and even more preferably less than 10 ⁇ cm at 400° C.
  • the expression “based on silicon carbide” is understood, within the context of the present description, to mean that the material consists of at least 25%, preferably at least 45% and very preferably at least 70% by weight of SiC.
  • the porous inorganic material may also comprise or be formed by a mixture of optionally doped silicon carbide and at least one inorganic material conducted by oxygen ions, for example of the fluorite structure (for example, zirconia stabilized by CaO or by Y 2 O 3 , mixed cerium gadolinium oxides), or of perovskite structure (a gallate, or compounds based on lanthanum, for example LaAlO 3 or LaGaO 3 or La 1-x Sr x Ga 1-x Mg y O 3 ), or of the BIMEVOX structure (for example Bi 2 V 1-x Me x O z ), or of the LAMOX structure (for example La 2 Mo 2 O 9 ), or of apatite structure (for example Me 10 (XO 4 ) 6 Y 2 ).
  • the fluorite structure for example, zirconia stabilized by CaO or by Y 2 O 3 , mixed cerium gadolinium oxides
  • perovskite structure a gallate, or compounds
  • the porous inorganic material comprises or is formed by a mixture of optionally doped silicon carbide and at least one inorganic proton-conductive material, for example of the perovskite type (for example SrCe 1-x M x O 3- ⁇ , where M is a rare earth, for example the compound SrCe x Yb 1-x O 3- ⁇ ) or of the BaCe 1-x M x O 3- ⁇ type (for example the compound BaCeO 3 ), or else a compound of the La x Sr 1-x ScO 3- ⁇ family (for example La 0.9 Sr 0.1 ScO 3- ⁇ ).
  • the perovskite type for example SrCe 1-x M x O 3- ⁇
  • M is a rare earth
  • BaCe 1-x M x O 3- ⁇ type for example the compound BaCeO 3
  • a compound of the La x Sr 1-x ScO 3- ⁇ family for example La 0.9 Sr 0.1 ScO 3- ⁇
  • the porous inorganic material comprises or is formed by optionally doped silicon carbide, in the pores of which a mixture of reduction catalyst A, of oxidation catalyst B and of at least one inorganic oxygen-ion-conductive material D, for example of fluorite structure (such as zirconia stabilized by CaO or Y 2 O 3 or mixed cerium gadolinium oxides), or of perovskite structure (gallate, lanthanum-based compounds of the LaAlO 3 or LaGaO 3 or La 1-x Sr x Ga 1-y Mg y O 3 type), or of BIMEVOX structure (for example Bi 2 V 1-x Me x O z ), or of LAMOX structure (for example La 2 Mo 2 O 9 ) or of apatite structure (for example Me 10 (XO 4 ) 6 Y 2 ), is deposited.
  • fluorite structure such as zirconia stabilized by CaO or Y 2 O 3 or mixed cerium gadolinium oxides
  • perovskite structure gal
  • the porous inorganic material comprises or is formed by optionally doped silicon carbide in the pores of which a mixture of reduction catalyst A, of oxidation catalyst B and of at least one inorganic proton-conductive material D, for example of the perovskite type (for example SrCe 1-x M x O 3- ⁇ where M is a rare earth, for example the compound SrCe x Yb 1-x O 3- ⁇ ) or of the BaCe 1-x M x O 3- ⁇ type (for example the compound BaCeO 3 ), or else a compound of the La x Sr 1-x ScO 3 , family (for example La 0.9 Sr 0.1 ScO 3- ⁇ ), is deposited.
  • the perovskite type for example SrCe 1-x M x O 3- ⁇ where M is a rare earth, for example the compound SrCe x Yb 1-x O 3- ⁇
  • BaCe 1-x M x O 3- ⁇ type for example the compound BaCeO 3
  • the present invention is most particularly applicable in the structures used for the purification and filtration of a diesel engine exhaust gas.
  • Such structures generally referred to as particulate filters, comprise at least one and preferably a plurality of honeycomb monoliths.
  • said monolith or monoliths comprise a plurality of adjacent ducts or channels having mutually parallel axes separated by porous walls, said ducts or channels being closed off by plugs at one or other of their ends in order to define inlet ducts opening onto a gas intake face and outlet ducts opening onto a gas discharge face, in such a way that the gas flows through the porous walls.
  • Examples of such assembled or non-assembled structures are for instance described in the publications EP 0 816 065, EP 1 142 619, EP 1 306 358 or EP 1 591 430.
  • Such a system also helps to improve the efficiency in regenerating the filter by promoting a higher rate of soot oxidation.
  • the filtering structure is obtained by assembling silicon carbide filtering elements that were firstly extruded, dried, and then fired, using well-known techniques, and bonded together using a jointing cement according to the techniques described for example in patent EP 1 142 619.
  • the filtering parts were characterized by a plurality of adjacent ducts or channels having mutually parallel axes separated by porous walls, said ducts or channels being closed off by plugs at one or other of their ends in order to define inlet ducts opening onto a gas intake face and outlet ducts opening onto a gas discharge face, in such a way that the gas passes through the porous walls.
  • a first fraction had a median diameter d 50 of between 5 ⁇ m and 50 ⁇ m, at least 10% by weight of the grains making up this fraction having a diameter greater than 5 ⁇ m.
  • the second fraction had a median grain diameter of less than 5 ⁇ m.
  • the two fractions were mixed in a mass ratio of 1 with a temporary binder of the methyl cellulose type and a polyethylene organic pore-forming agent.
  • Catalysts A and B and the ion-conductive compound D were synthesized in the following manner.
  • the ion conductor D used was a YSZ powder (zirconia powder, basic grade TZ), sold by Tosoh.
  • Particle size of the powders of catalysts A, B and ion conductor D was adapted and chosen according to the porosity of the porous ceramic body.
  • the median diameter of these powders was in particular chosen to be less than 5 ⁇ m.
  • the as-formed filter structure was then immersed in a bath of an aqueous solution containing catalysts A, B and compound D, in proportions making it possible to obtain about 2% by weight, relative to the total weight of the support, of each compound on the SiC support.
  • the filter was impregnated with the solution according to a method of implementation similar to that described in U.S. Pat. No. 5,866,210. Next, the filter was dried at about 150° C. and then heated at a temperature of about 500° C. A reference electrocatalytic filter was thus obtained.
  • the as-formed structure obtained according to Example 1 was subjected to a first texturizing treatment before the incorporation of catalysts A and B and of ion conductor D.
  • a texturizing material was introduced into the pores of the filter in the form of a slip. More precisely, a suspension based on SiC doped with about 200 ppm of aluminum was prepared.
  • the suspension comprised, in percent by weight, 96% water, 0.1% of a nonionic dispersant, 1% of a PVA (polyvinyl alcohol) binder and 2.8% of an SiC powder of 0.5 ⁇ m median diameter, the purity of said powder being greater than 98% by weight.
  • Such a doping level makes it possible, according to a first advantage, to obtain a structure having a substantially improved surface electronic conductivity, i.e. a resistivity of less than 10 ⁇ cm at 400° C.
  • the texturized structure thus exhibited surface electronic conductivity and thus constituted element C of the system.
  • the slip or suspension was prepared according to the following steps:
  • the dispersant was introduced into a tank, kept stirred and containing the PVA dissolved in water, before being followed by the SiC powder until a homogeneous suspension was obtained.
  • the slip was deposited in the filter by simple immersion, the excess suspension being removed by vacuum suction, under a residual pressure of 10 mbar.
  • the filter thus obtained underwent a drying step at 120° C. for 16 hours followed by a sintering heat treatment at 1700° C. for 3 h in argon.
  • FIG. 2 shows an SEM photograph, in cross section, of the filtering walls of the texturized filter thus obtained, showing the irregularities on the surface of the SiC grains constituting the porous matrix.
  • the irregularities take the form of SiC crystallites or clusters of crystallites.
  • the measured parameter d corresponds to the mean diameter, within the meaning described above, of the crystallites present on the surface of the SiC grains, i.e. about 0.5 ⁇ m.
  • the parameter h corresponds to the mean height h of said crystallites, i.e. about 0.5 ⁇ m. This coating covers about 18% of the total offered surface area of the SiC grains.
  • the as-formed filter structure was then immersed in a bath of an aqueous solution containing catalysts A and B and compound D, in the same proportions and under the same principles and operating method as Example 1.
  • the filter was impregnated, dried and heated using the same operating method as in the case of Example 1.
  • the structure was again dried at 150° C. then heated at a temperature of about 500° C. in air so as to obtain a structure according to the invention.
  • the performance of the filter was measured at a temperature of 400° C. using two synthetic gas mixtures according to Table 2, these being characteristic of the exhaust gases for a diesel engine operating with a lean mixture (mixture 1 ) and for a diesel engine operating with a rich mixture (mixture 2 ).
  • the test was carried out in the following manner: the lean gas mixture 1 firstly flowed over the catalyzed filter maintained in an electric furnace at 400° C. Every two minutes, the gas composition was switched onto the rich gas mixture 2 for 5 seconds, before being switched back to the mixture 1 , and so on. The composition of the gases leaving the furnace was analyzed after stabilization so as to determine the amount of NO x converted.
  • Example 1 non texturized filter
  • Example 2 texturized filter
  • the pressure drop was measured on the filter according to the prior art, for an air flow rate of 600 m 3 /h in a stream of ambient air.
  • the term “pressure drop” is understood, within the context of the present invention, to mean the pressure difference that exists between the upstream side and the downstream side of the filter.
  • the filters were placed in a furnace at 800° C. in a wet air atmosphere for a period of 5 hours, such that the molar concentration of water was kept constant at 3%.
  • the degree of NO x conversion on the filters thus aged was measured using the same experimental protocol as previously (see test 1).

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  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Geometry (AREA)
  • Combustion & Propulsion (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Environmental & Geological Engineering (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Catalysts (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US12/681,865 2007-10-08 2008-10-02 Texturized purification structure incorporating an electrochemical catalyst system Abandoned US20100229542A1 (en)

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FR0758154A FR2921848B1 (fr) 2007-10-08 2007-10-08 Structure de purification texturee incorporant un systeme de catalyse electrochimique
PCT/FR2008/051791 WO2009053590A2 (fr) 2007-10-08 2008-10-02 Structure de purification texture incorporant un systeme de catalyse electrochimique

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US8735217B2 (en) * 2012-02-07 2014-05-27 Intermolecular, Inc. Multifunctional electrode
US20140217348A1 (en) * 2012-02-07 2014-08-07 Intermolecular Inc. Transition Metal Oxide Bilayers
WO2014183337A1 (fr) 2013-05-13 2014-11-20 Dalian Institute Of Chemical Physics, Chinese Academy Of Sciences Synthèse d'oléfines à partir d'une conversion directe sans oxygène de méthane, et catalyseurs de cette synthèse
JPWO2016136560A1 (ja) * 2015-02-27 2017-11-30 株式会社豊田中央研究所 排ガス浄化用触媒、その製造方法、及び、それを用いた排ガス浄化方法
US20190381453A1 (en) * 2016-12-07 2019-12-19 Solvay Sa MULTI-POLLUTANT GAS PURIFICATION PROCESS WITH ALKALI SORBENT AND DeNOx SUPPORTED CATALYST COMPRISING Ca-DEFICIENT HYDROXYAPATITE
US10702854B2 (en) 2013-05-13 2020-07-07 Dalian Institute Of Chemical Physics, Chinese Academy Of Sciences Oxygen-free direct conversion of methane and catalysts therefor
CN114345127A (zh) * 2021-12-31 2022-04-15 中国海洋大学 一种船舶烟气电催化还原脱硝方法

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Cited By (19)

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Publication number Priority date Publication date Assignee Title
US20120183725A1 (en) * 2009-09-28 2012-07-19 Ngk Insulators, Ltd. Honeycomb structure
US8530030B2 (en) * 2009-09-28 2013-09-10 Ngk Insulators, Ltd. Honeycomb structure
US8906736B1 (en) * 2012-02-07 2014-12-09 Intermolecular, Inc. Multifunctional electrode
US8987697B2 (en) * 2012-02-07 2015-03-24 Intermolecular, Inc. Transition metal oxide bilayers
US20140224645A1 (en) * 2012-02-07 2014-08-14 Intermolecular Inc. Multifunctional electrode
US8859328B2 (en) * 2012-02-07 2014-10-14 Intermolecular, Inc. Multifunctional electrode
US20140217348A1 (en) * 2012-02-07 2014-08-07 Intermolecular Inc. Transition Metal Oxide Bilayers
US20140357046A1 (en) * 2012-02-07 2014-12-04 Intermolecular Inc. ReRAM Cells Including TaXSiYN Embedded Resistors
US8735217B2 (en) * 2012-02-07 2014-05-27 Intermolecular, Inc. Multifunctional electrode
US20140374240A1 (en) * 2012-02-07 2014-12-25 Intermolecular Inc. Multifunctional electrode
US8969129B2 (en) * 2012-02-07 2015-03-03 Intermolecular, Inc. ReRAM cells including TaXSiYN embedded resistors
WO2014183337A1 (fr) 2013-05-13 2014-11-20 Dalian Institute Of Chemical Physics, Chinese Academy Of Sciences Synthèse d'oléfines à partir d'une conversion directe sans oxygène de méthane, et catalyseurs de cette synthèse
EP2997000A1 (fr) * 2013-05-13 2016-03-23 Dalian Institute Of Chemical Physics, Chinese Academy Of Sciences Synthèse d'oléfines à partir d'une conversion directe sans oxygène de méthane, et catalyseurs de cette synthèse
EP2997000A4 (fr) * 2013-05-13 2017-04-05 Dalian Institute Of Chemical Physics, Chinese Academy Of Sciences Synthèse d'oléfines à partir d'une conversion directe sans oxygène de méthane, et catalyseurs de cette synthèse
US10702854B2 (en) 2013-05-13 2020-07-07 Dalian Institute Of Chemical Physics, Chinese Academy Of Sciences Oxygen-free direct conversion of methane and catalysts therefor
JPWO2016136560A1 (ja) * 2015-02-27 2017-11-30 株式会社豊田中央研究所 排ガス浄化用触媒、その製造方法、及び、それを用いた排ガス浄化方法
US20190381453A1 (en) * 2016-12-07 2019-12-19 Solvay Sa MULTI-POLLUTANT GAS PURIFICATION PROCESS WITH ALKALI SORBENT AND DeNOx SUPPORTED CATALYST COMPRISING Ca-DEFICIENT HYDROXYAPATITE
US10661226B2 (en) * 2016-12-07 2020-05-26 Solvay Sa Multi-pollutant gas purification process with alkali sorbent and deNOx supported catalyst comprising Ca-deficient hydroxyapatite
CN114345127A (zh) * 2021-12-31 2022-04-15 中国海洋大学 一种船舶烟气电催化还原脱硝方法

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ZA201001896B (en) 2010-12-29
KR20100064379A (ko) 2010-06-14
FR2921848B1 (fr) 2011-03-18
WO2009053590A3 (fr) 2009-10-08
EA201070440A1 (ru) 2010-10-29
CA2701391A1 (fr) 2009-04-30
CN101820976A (zh) 2010-09-01
EP2197567B1 (fr) 2011-06-15
WO2009053590A2 (fr) 2009-04-30
JP2010540248A (ja) 2010-12-24
EP2197567A2 (fr) 2010-06-23
ATE512708T1 (de) 2011-07-15

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