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WO2008135373A1 - Revêtement de supports céramiques - Google Patents

Revêtement de supports céramiques Download PDF

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Publication number
WO2008135373A1
WO2008135373A1 PCT/EP2008/054804 EP2008054804W WO2008135373A1 WO 2008135373 A1 WO2008135373 A1 WO 2008135373A1 EP 2008054804 W EP2008054804 W EP 2008054804W WO 2008135373 A1 WO2008135373 A1 WO 2008135373A1
Authority
WO
WIPO (PCT)
Prior art keywords
particles
ceramic
particle
functional
group
Prior art date
Application number
PCT/EP2008/054804
Other languages
German (de)
English (en)
Inventor
Joerg Jockel
Matthias Kruse
Thomas Hauber
Vera Lindemer
Hermann Koch-Groeber
Christoph Saffe
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO2008135373A1 publication Critical patent/WO2008135373A1/fr

Links

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
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/92—Dimensions
    • B01D2255/9202—Linear dimensions
    • 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
    • B01D2255/9207—Specific surface
    • 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 is based on known ceramic functional elements, as they are used in particular in the field of pollutant reduction of exhaust gases.
  • Such ceramic functional elements are used, for example, in the field of catalyst and / or particle filter technology, for example in the context of diesel particulate filters (DPF).
  • DPF diesel particulate filters
  • Such filters generally have a ceramic carrier material, which is usually composed of ceramic materials such as silicon carbide, cordierite, aluminum titanate or a sintered metal.
  • the ceramic functional elements can be used in different structures, which depend on the nature of the exhaust gas purification.
  • the functional elements can be used within the framework of a honeycomb structure, as is frequently found in catalysts or particle filters, for example a honeycomb structure with mutually closed inlet and outlet channels.
  • the carrier material cordierite and also other ceramic support materials have a number of microcracks in the structure due to their manufacturing process. These microcracks are in part desirable, and make a significant contribution, for example, to the filtering effect or catalyst action of the functional elements.
  • the microcracks lead to lower strength of the ceramic support material, at the same time they also lead to a lower modulus of elasticity and to a lower thermal stability. expansion coefficients and contribute to the fact that thermal stresses are reduced in the ceramic and the thermal load capacity is increased. A low coefficient of thermal expansion and a low modulus of elasticity ensure low induced stresses under thermal stress of the substrate. This is due in particular to the fact that the microcracks in the ceramic support material gradually close when the temperature rises, thus forming a buffer for thermal expansion.
  • a catalytic coating is usually applied in the prior art.
  • This coating is often referred to as "washcoat.”
  • ceramic materials such as porous alumina (Al 2 O 3) are often ground to a desired particle size, then a suspension with a certain particle size distribution is generated, and then this suspension (also called slurry) applied to the ceramic carrier.
  • the problem of this known method is that the suspensions also contain the smallest particles which can penetrate into the microcracks of the ceramic carrier. This causes these microcracks can not close to a degree of heating of the ceramic support to the extent described above. This in turn increases the thermal expansion coefficient of the ceramic carrier, and there are unwanted, increased thermal stresses.
  • first particle group of carrier particles having an average particle diameter between 1 micron and 10 microns
  • second particle group of intermediate particles having a mean particle diameter between 50 nanometers and one micrometer
  • third particle group of functional particles having a mean particle diameter between 2 nm and 50 nm.
  • the particles of these three particle groups together form layer particles which each contain at least one particle of each particle group.
  • the basic idea of the invention is that now the catalytic effect of the functional particles and the overall high surface area of the coating are combined with a sufficient Total particle size of the layer particles, so that the microcracks in the ceramic support are no longer or only to a lesser extent blocked.
  • the carrier particles comprise a material which comprises aluminum oxide, silicon oxide, barium oxide, magnesium oxide, calcium oxide, titanium oxide or ceria, or else mixtures of said oxides.
  • a material which comprises aluminum oxide, silicon oxide, barium oxide, magnesium oxide, calcium oxide, titanium oxide or ceria, or else mixtures of said oxides Alternatively or additionally, it is also possible to use mineral substances such as, for example, silicon carbide, cordierite, boehmite or zeolite or mixtures of the materials mentioned. The materials mentioned or mixtures of these materials can also be used for the intermediate particles of the second particle group.
  • the third particle group (functional particles) materials can be used which comprise one or more noble metals from the group of platinum metals (Ru, Rh, Pd, Os, Ir, Pt).
  • the invention is not linked to a specific, catalytically active coating component.
  • Other elements of the eighth to eleventh group of the periodic table may also be used, the use of one or more of the following elements overall being preferred: Pt, Pd, Rh, Fe or Au.
  • one or more elements of the 3rd to 7th group of the periodic table can be used, with the use of one or more of the following elements being particularly preferred: V, Ti, Mo
  • one or more elements of the lanthanides may also be used, with the use of one or more of the following elements being particularly preferred: La, Ce, Pr.
  • one or more the elements of the 1st and 2nd group of the periodic table are used, in particular the elements potassium and / or magnesium. In general, mixtures and / or alloys of these metals may be present.
  • the metals may be metallic or oxide.
  • the functional particles should be arranged at least predominantly on the surfaces of the intermediate particles, and the
  • a second particle group of intermediate particles with a middle particle size can firstly be obtained Particle diameter between 40 nm and 1 .mu.m with a third particle group of functional particles with a mean particle diameter between 2 nm and 50 nm are functionalized in a wet-chemical process.
  • Particle diameter between 40 nm and 1 .mu.m with a third particle group of functional particles with a mean particle diameter between 2 nm and 50 nm are functionalized in a wet-chemical process.
  • the particles thus functionalized can be connected to a first particle group of the carrier particles having an average particle diameter between 1 ⁇ m and 10 ⁇ m by co-sintering.
  • the above-described layer particles can be generated, which can be stored, for example, as a particle mixture and produced on an industrial scale, and which can then be used for functional coating of ceramic functional elements for pollutant reduction of exhaust gases.
  • the particle mixture thus obtained with the layer particles can then be applied to the ceramic carrier.
  • a known suspension method can be used, in which the particle mixture is first slurried with the layer particles, for example in an aqueous suspension, then applied to the ceramic support and dried there and / or subjected to a heat treatment.
  • wet-chemical processes can be used, such as, for example, an impregnation process and / or a sol-gel process.
  • the particles thus functionalized may then be subjected to a drying and / or sintering step prior to co-sintering with the carrier particles.
  • the ceramic functional element, the described method and the use of the particle mixture according to the above description in one of the variants have the advantage over conventional methods that on the one hand coatings are produced with a high surface area, which is particularly important for the filter and catalyst effect of considerable importance.
  • the functional elements thus produced have comparatively low coefficients of thermal expansion, low moduli of elasticity and have comparatively low thermal stresses even at high temperatures.
  • the method described is cost-effective due to the comparatively simple feasibility and can be implemented on an industrial scale.
  • Figure 1 is a scanning electron micrograph of cordierite as a ceramic carrier
  • Figure 2 is a scanning electron micrograph of coated with a conventional washcoat method cordierite
  • FIG. 3 shows the effect of the penetration of coating particles into a microcrack
  • FIG. 4 shows a ceramic functional coating according to the invention.
  • FIGS. 1 to 3 show the effects of conventional washcoat coatings on the thermal behavior of conventional ceramic support materials.
  • 1 shows a scanning electron micrograph of cordierite. Typical surface irregularities of this support material are in the range of 1 to several micrometers. It can be seen clearly in FIG. 1 that the cordierite has a microcrack 110. This microcrack 110 has a width that is typically less than 1 ⁇ m at room temperature.
  • FIG. 2 shows a scanning electron micrograph of particle-coated cordierite.
  • the cordierite was coated with a washcoat coating. It can already be seen from this photograph that smaller particles of the particle distribution of the coating penetrate into the microcrack 110.
  • FIG. 4 schematically shows a ceramic functional element according to the invention for pollutant reduction of exhaust gases, which can be used, for example, in diesel particulate filters.
  • the illustration in FIG. 4 is greatly simplified, but clearly illustrates the functional principle of the coating according to the invention.
  • the coating takes place here with large layer particles 118.
  • These large layer particles 118 are composed of three particle groups: the carrier particles 120, which ensure by their comparatively large particle diameter (above 1 ⁇ m) that no substantial penetration of the layer particles 118 into the microcracks 110 the ceramic carrier 112, the intermediate particles 122, which essentially serve to increase the total surface area of the layer particles 118, and finally the functional particles 124, which have, for example, catalytic action and which are applied to the surface of the intermediate particles 122.
  • the following method can be used, for example:
  • the intermediate particles 122 are produced.
  • Al 2 O 3 particles are used, which are ground to a particle diameter of, for example, 500 nm by means of a suitable milling method.
  • conventional ceramic mills may be used for this milling process, such as jet mills or other types of known mills.
  • laser measurement techniques can be used to monitor the particle diameter.
  • a corresponding selection of the particle diameter can be made to further restrict the width of the diameter distributions.
  • the intermediate particles 122 thus obtained can then be functionalized with the functional particles 124 in a subsequent process step.
  • the intermediate particles 122 may, for example, be immersed in one or more noble metal-containing impregnating solutions, for example in hexachloroplatinic acid, Pt-ethanolamine.
  • the solvent of the impregnation solution is removed by drying (for example, about 120 ° C. for about one hour).
  • the functionalized intermediate particles 122 are then sintered at a temperature of about 400 0 C for about 1 hour.
  • the functionalized intermediate particles 122 thus produced are mixed with carrier particles 120.
  • carrier particles 120 may, for example, in turn comprise Al 2 O 3 particles, which in turn have been previously ground to a desired average particle diameter by a suitable milling method. Again, a selection process may follow the milling step to further restrict the particle diameter.
  • the average particle diameter may be in the range of about 5 microns.
  • the functionalized carrier particles 120 and the layered particles 118 are mixed together, for example, by stirring or in a stream of air and connected together at a temperature of about 900 0 C for a period of about 30 minutes by co-sintering.
  • layer particles 118 are produced according to Figure 4, which have the catalytically active particle specification. These layer particles 118 can be manufactured and stored in various specifications in order subsequently to be able to produce various ceramic functional coatings of various properties.
  • a ceramic carrier 112 for example cordierite according to the above examples, is immersed in an aqueous suspension of the layer particles 118.
  • an aqueous suspension having a solids content of 10-20% by weight, a binder content (e.g., boehmite) of 1-3% by weight and an acetic acid content of 1-3% by weight may be used.
  • a further heat treatment can be carried out in order to drive off the water of the suspension on the one hand (for example by a heat treatment at 200 0 C for about 1 hour, followed by a further, optional sintering step, for example at 300 to 600 0 C for about 60 minutes to solidify the bond between the layered particles 118 and the surface of the ceramic substrate 112.
  • This last process step of applying the functional coating to the ceramic carrier 112 may preferably be carried out after the ceramic carrier 112 has already been brought into its desired shape, for example the honeycomb structure of a diesel particulate filter described above.
  • the ceramic carrier with the functional coating can also be subsequently processed, for example by additional shaping steps, heat treatments or other coatings.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (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)
  • Chemical Kinetics & Catalysis (AREA)
  • Catalysts (AREA)

Abstract

L'invention concerne un élément fonctionnel céramique servant à réduire les polluants des gaz d'échappement, cet élément présentant un support céramique (112) et un revêtement fonctionnel céramique. Ledit revêtement fonctionnel céramique présente au moins trois groupes de particules : un premier groupe composé de particules supports (120) présentant un diamètre moyen de particule compris entre 1 μm et 10 μm; un deuxième groupe composé de particules intermédiaires (122) présentant un diamètre moyen de particule compris entre 50 nm et 1 μm; et un troisième groupe composé de particules fonctionnelles (124) présentant un diamètre moyen de particule compris entre 2 nm et 50 nm. Ce revêtement fonctionnel présente ainsi des particules stratifiées (118) qui comprennent chacune au moins une particule de chaque groupe.
PCT/EP2008/054804 2007-05-04 2008-04-21 Revêtement de supports céramiques WO2008135373A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102007020962A DE102007020962A1 (de) 2007-05-04 2007-05-04 Beschichtung keramischer Träger
DE102007020962.4 2007-05-04

Publications (1)

Publication Number Publication Date
WO2008135373A1 true WO2008135373A1 (fr) 2008-11-13

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ID=39628759

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2008/054804 WO2008135373A1 (fr) 2007-05-04 2008-04-21 Revêtement de supports céramiques

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DE (1) DE102007020962A1 (fr)
WO (1) WO2008135373A1 (fr)

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008061644B4 (de) * 2008-12-12 2014-01-02 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Zellulärer Werkstoff für Hochtemperaturanwendungen und Verfahren zu seiner Herstellung

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1175935A2 (fr) * 2000-07-27 2002-01-30 Kabushiki Kaisha Toyota Chuo Kenkyusho Oxyde mixte, procédé pour sa préparation, catalyseur pour purifier un gaz d'échappement, et procédé de production
WO2005102933A2 (fr) * 2004-04-27 2005-11-03 Toyota Jidosha Kabushiki Kaisha Particule d’oxyde métallique, processus de production de celle-ci et catalyseur de purification des gaz d’évacuation
JP2006255610A (ja) * 2005-03-17 2006-09-28 Nissan Motor Co Ltd 排気ガス浄化用触媒及びその製造方法
WO2007011062A1 (fr) * 2005-07-21 2007-01-25 Kabushiki Kaisha Toyota Chuo Kenkyusho Materiau composite, base d'un materiau composite, liquide de dispersion d'un materiau composite, et leurs procedes de fabrication
WO2008061847A1 (fr) * 2006-11-24 2008-05-29 Robert Bosch Gmbh Composition pour la fabrication d'un matériau céramique, contenant des nanoparticules formant des pores

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1175935A2 (fr) * 2000-07-27 2002-01-30 Kabushiki Kaisha Toyota Chuo Kenkyusho Oxyde mixte, procédé pour sa préparation, catalyseur pour purifier un gaz d'échappement, et procédé de production
WO2005102933A2 (fr) * 2004-04-27 2005-11-03 Toyota Jidosha Kabushiki Kaisha Particule d’oxyde métallique, processus de production de celle-ci et catalyseur de purification des gaz d’évacuation
JP2006255610A (ja) * 2005-03-17 2006-09-28 Nissan Motor Co Ltd 排気ガス浄化用触媒及びその製造方法
WO2007011062A1 (fr) * 2005-07-21 2007-01-25 Kabushiki Kaisha Toyota Chuo Kenkyusho Materiau composite, base d'un materiau composite, liquide de dispersion d'un materiau composite, et leurs procedes de fabrication
WO2008061847A1 (fr) * 2006-11-24 2008-05-29 Robert Bosch Gmbh Composition pour la fabrication d'un matériau céramique, contenant des nanoparticules formant des pores

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE WPI Week 200671, Derwent World Patents Index; AN 2006-683642 *
DATABASE WPI Week 200727, Derwent World Patents Index; AN 2007-282990 *

Also Published As

Publication number Publication date
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