WO2004067171A1 - Petrol engine exhaust catalyst - Google Patents

Petrol engine exhaust catalyst Download PDF

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Publication number
WO2004067171A1
WO2004067171A1 PCT/IB2004/000289 IB2004000289W WO2004067171A1 WO 2004067171 A1 WO2004067171 A1 WO 2004067171A1 IB 2004000289 W IB2004000289 W IB 2004000289W WO 2004067171 A1 WO2004067171 A1 WO 2004067171A1
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WIPO (PCT)
Prior art keywords
ceramic
solution
substrate
ceramic powder
engine exhaust
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PCT/IB2004/000289
Other languages
French (fr)
Inventor
James Anthony Cairns
Graham James Berry
Gary John Callon
Robert Dermot Smith
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Aktina Limited
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Publication of WO2004067171A1 publication Critical patent/WO2004067171A1/en

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    • 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
    • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
    • B01J21/066—Zirconium or hafnium; Oxides or hydroxides thereof
    • 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
    • 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
    • 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
    • B01J35/56—
    • 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
    • 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
    • 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
    • B01J37/0215—Coating
    • B01J37/0225—Coating of metal substrates
    • 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
    • F01N2330/00—Structure of catalyst support or particle filter
    • 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
    • F01N2510/00—Surface coverings
    • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
    • 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 manufacture of an exhaust catalyst comprising a support substrate coated with a ceramic layer having metals or metal oxides dispersed therein. More particularly, the invention relates to a petrol engine exhaust catalyst comprising a zirconia layer incorporating catalytic metal(s), such as palladium or platinum, in highly dispersed form.
  • catalytic material is applied to substrates by immersing the substrate in a washcoat slurry, which may also contain the catalytic material. Lately, organic solutions of metal organic precursors of catalytic material have become widely used instead of slurries.
  • a catalyst is prepared by pre-oxidising a substrate, preparing a solution comprising a ceramic oxide precursor, such as alumina or silica, and a solution containing a catalyst precursor, depositing precursors onto the substrate, such as a fiber board, and thermally treating the board to decompose the precursor into the catalyst.
  • the precursors are deposited by immersing, spraying or the like methods.
  • the metallic fiber board obtained thereby comprises a plurality of metallic fibers, preferably produced from a Fe-Cr-AI alloy, wherein the fibers are coated with a dense oxide covering the surfaces of the fibers, onto which a porous oxide layer is deposited covering the exterior surface of the dense layer, and the catalyst is a noble metal distributed across the exterior surface of the porous oxide layer or incorporated within it.
  • US 5,980,843 discloses another catalytic system obtained from a perforated foil or a metallic grid on which a porous ceramic layer, preferably of alumina or zirconia, is deposited by means of techniques including plasma spraying, flame spraying, and detonation spraying. The ceramic layer is then impregnated with a catalyst precursor solution or suspension. After suitable thermal treatments the final catalytic system is obtained.
  • the production processes described above are disadvantageous in that, predominantly, the ceramic oxide layer formed from precursor solutions has an amorphous structure, and hence, low structural strength, insufficient thermal stability and low adhesion to the substrate.
  • An effective approach has been developed recently by the inventors of the present invention as described in PCT/GB02/04086 filed 30.08.02, the entire disclosure of which application is incorporated herein by reference.
  • a thin film stabilised porous ceramic such as zirconia, can be effectively used in making catalysts and gas sensors.
  • This process includes introducing the stabilising moiety into the precursor solution, so that the transformation of the amorphous porous ceramic layer into a crystalline structure occurs at lower temperatures and relatively milder conditions than usually employed to effect such a transformation. The result is that the porous oxide layer is bonded strongly to the substrate and has a high structural strength that avoids the necessity of providing additional treatment of the composite material.
  • Still one more objective is to provide a catalytic member for combustion of gases, having a high thermal conductivity and low flow resistivity but at the same time improved mass transfer characteristics and high catalytic activity.
  • a method for making a petrol engine exhaust catalyst comprising the steps of: - preparing a solution by admixing to a ceramic precursor solution a nanoscale ceramic powder as the major constituent to the ceramic precursor solution; - contacting a substrate with a solution so as to form a coating directly on the substrate,
  • a petrol engine exhaust catalyst comprising - a substrate supported layer of porous ceramic incorporating nanoscale ceramic particles and one or more catalytic metals, the ceramic layer being strongly adhered directly to the substrate.
  • the nanoscale ceramic powder is composed primarily of ceria and zirconia, with the addition of a small percentage of the oxides of lanthanum and neodymium.
  • the surface area of the coating is increased and thereby the efficiency of interaction between the coating and the exhaust gas is improved.
  • Thermal stability of an engine exhaust catalyst is an important consideration, as the device can be exposed to temperatures of up to 1000°C under certain operating conditions and to even higher temperatures if an engine fault should develop.
  • a catalyst must be able to withstand such conditions for an operational lifetime of at least 100000 miles (160000km).
  • Washcoat A solution is made up of zirconium propionate dissolved in tetrahydrofuran at a concentration of between 20g and 200g of zirconium propionate per litre of solution, preferably between 50 and 100g per litre. To this is added a quantity of the ceria/zirconia/lanthana/neodymia powder mentioned above, of between 100 and 300g per litre of solution, and preferably between 120 and 180g per litre.
  • the mixture thus created is deposited onto a suitable substrate, such as a Fecralloy steel monolith, which is then dried to remove the solvent and heated to a temperature of at least 300°C to decompose the zirconium propionate and achieve good adhesion of the washcoat layer to the substrate.
  • a suitable substrate such as a Fecralloy steel monolith
  • a solution of palladium acetate and rhodium acetate in tetrahydrofuran is made up, comprising between 2 and 5g of rhodium acetate per litre of solution, preferably between 2.4 and 3g per litre, and between 0.5 and 5g of palladium acetate per litre of solution, preferably between 0.7 and 2.5g per litre.
  • This is applied to the monolith coated with washcoat and then dried to remove the solvent and heated to a temperature of at least 300°C to decompose the precursors and form metallic rhodium and palladium.
  • a solution was prepared consisting of 25g zirconium propionate per litre of tetrahydrofuran. To this was added 150g of nanoscale powder per litre.
  • the nanoscale powder was composed of zirconium oxide (47.10%), cerium oxide (45.95%), lanthanum oxide (1.87%) and neodymium oxide (5.08%).
  • the catalyst prepared as above was tested in the exhaust system of a stationary 1.81 4-cylinder 8-valve Volkswagen petrol engine connected to a dynamometer. Two load conditions were employed. The first was a standard load condition using an engine speed of 2500rpm and a torque of 100Nm. The second was a full-throttle high load condition using an engine speed of 3300rpm and 130Nm of torque. The results are shown below in table 1 :
  • the catalyst was then subjected to accelerated ageing by heating it in air at 900°C for four hours. After cooling it was tested again, and showed only a small degradation, as can be seen from table 2:

Abstract

The present invention relates to the manufacture of an exhaust catalyst comprising a support substrate coated with a ceramic layer having metals or metal oxides dispersed therein. A process for the production of a ceramic-metal catalyst comprises the steps of coating the substrate with a solution comprising ceramic precursors, and subsequent thermal treatment of the coated substrate, wherein a nanoscale ceramic powder is added as the major constituent to the ceramic precursor solution prior to thermally treating said substrate to decompose the precursor compounds. The porous ceramic layer obtained thereby is further impregnated with one or more catalytic metals or metal oxides.

Description

PETROL ENGINE EXHAUST CATALYST
TECHNICAL FIELD
The present invention relates to the manufacture of an exhaust catalyst comprising a support substrate coated with a ceramic layer having metals or metal oxides dispersed therein. More particularly, the invention relates to a petrol engine exhaust catalyst comprising a zirconia layer incorporating catalytic metal(s), such as palladium or platinum, in highly dispersed form.
BACKGROUND OF THE INVENTION Contemporary pollution problems demand the development of new highly effective exhaust catalysts, capable of withstanding high temperatures and yet remaining active and highly durable whilst providing steadily decreasing levels of pollutants, due to more severe requirements pertaining to the quality of purification of effluent gases and lower concentration limits applicable to vehicle catalysts. For this reason, much of the development work is directed at catalysts applied on substrates, such as metallic or ceramic substrates. The substrates need to have very open structures in order to allow gas mixtures to interact with them efficiently. For instance, wire meshes, metallic or ceramic bodies provided with holes, and boards or meshes made of metallic or ceramic fibers have all been used. To further increase the boundary surface of heterogeneous catalysts, composite materials are widely used, which comprise a substrate as mentioned above coated with a porous ceramic layer incorporating or having applied thereon a catalytic metal or metals.
Conventionally, catalytic material is applied to substrates by immersing the substrate in a washcoat slurry, which may also contain the catalytic material. Lately, organic solutions of metal organic precursors of catalytic material have become widely used instead of slurries.
Thus, according to US 6,303,538, a catalyst is prepared by pre-oxidising a substrate, preparing a solution comprising a ceramic oxide precursor, such as alumina or silica, and a solution containing a catalyst precursor, depositing precursors onto the substrate, such as a fiber board, and thermally treating the board to decompose the precursor into the catalyst. The precursors are deposited by immersing, spraying or the like methods.
The metallic fiber board obtained thereby comprises a plurality of metallic fibers, preferably produced from a Fe-Cr-AI alloy, wherein the fibers are coated with a dense oxide covering the surfaces of the fibers, onto which a porous oxide layer is deposited covering the exterior surface of the dense layer, and the catalyst is a noble metal distributed across the exterior surface of the porous oxide layer or incorporated within it. US 5,980,843 discloses another catalytic system obtained from a perforated foil or a metallic grid on which a porous ceramic layer, preferably of alumina or zirconia, is deposited by means of techniques including plasma spraying, flame spraying, and detonation spraying. The ceramic layer is then impregnated with a catalyst precursor solution or suspension. After suitable thermal treatments the final catalytic system is obtained.
The production processes described above, however, are disadvantageous in that, predominantly, the ceramic oxide layer formed from precursor solutions has an amorphous structure, and hence, low structural strength, insufficient thermal stability and low adhesion to the substrate. An effective approach has been developed recently by the inventors of the present invention as described in PCT/GB02/04086 filed 30.08.02, the entire disclosure of which application is incorporated herein by reference. According to this approach, a thin film stabilised porous ceramic, such as zirconia, can be effectively used in making catalysts and gas sensors. This process includes introducing the stabilising moiety into the precursor solution, so that the transformation of the amorphous porous ceramic layer into a crystalline structure occurs at lower temperatures and relatively milder conditions than usually employed to effect such a transformation. The result is that the porous oxide layer is bonded strongly to the substrate and has a high structural strength that avoids the necessity of providing additional treatment of the composite material.
Though the above approach proved to be highly effective for producing a composite material having excellent catalytic properties, some problems remained, associated with loss of surface area of the ceramic when subjected to prolonged exposure to high temperatures. Therefore there was a strong motivation to modify the existing process in order to improve the thermal stability of the catalyst. A further motivation was to simplify the synthetic route, if possible. SUMMARY OF THE INVENTION
It is an objective of the present invention to provide a relatively simple and cost- effective method of preparing porous ceramic-metal catalysts having high temperature stability and structural integrity.
Still one more objective is to provide a catalytic member for combustion of gases, having a high thermal conductivity and low flow resistivity but at the same time improved mass transfer characteristics and high catalytic activity.
These and other objectives are surprisingly achieved by modifying the process for preparing a catalyst material composed of a substrate coated with a porous ceramic layer, such as zirconia, incorporating one or more catalytic metals, in a way eliminating the complexity of preparing organic precursors of stabilising chemical moieties to the zirconia propionate solution, whilst offering a relatively inexpensive and simple method providing yet thermally stable composite catalyst structures.
It has been now discovered by the inventors that it is possible to significantly enhance the thermal stability of ceramic-metal catalyst structures by using a powder which is comprised of the essential components of the catalyst support: ceria, zirconia, lanthana and neodymia. It has been found also that, to achieve a noticeable stabilising effect, it is important that the powder be in the form of small particulates (typically less than 50nm diameter). When this powder is mixed with an organic precursor of zirconia (zirconium propionate), the coating adheres well to a range of substrates, including metal substrates. Larger diameter powder (e.g. with particle sizes of the order of 500nm) exhibits poorer adhesion and lower thermal stability.
Thus, according to the present invention, a method for making a petrol engine exhaust catalyst is provided comprising the steps of: - preparing a solution by admixing to a ceramic precursor solution a nanoscale ceramic powder as the major constituent to the ceramic precursor solution; - contacting a substrate with a solution so as to form a coating directly on the substrate,
- thermally treating said substrate with the coating at a temperature sufficient to decompose said precursor compounds to form a stabilised porous ceramic layer, incorporating ceramic powder particles; and
- impregnating the porous ceramic layer obtained thereby with one or more catalyst metals or metal oxides.
In another aspect of the invention, a petrol engine exhaust catalyst is provided comprising - a substrate supported layer of porous ceramic incorporating nanoscale ceramic particles and one or more catalytic metals, the ceramic layer being strongly adhered directly to the substrate.
Preferably, the nanoscale ceramic powder is composed primarily of ceria and zirconia, with the addition of a small percentage of the oxides of lanthanum and neodymium.
As a result of the method according to the invention, the surface area of the coating is increased and thereby the efficiency of interaction between the coating and the exhaust gas is improved.
The method of production of an improved petrol engine exhaust catalyst is described hereinbelow.
Results obtained from testing the catalyst are also provided.
DETAILED DESCRIPTION OF THE INVENTION
Thermal stability of an engine exhaust catalyst is an important consideration, as the device can be exposed to temperatures of up to 1000°C under certain operating conditions and to even higher temperatures if an engine fault should develop. A catalyst must be able to withstand such conditions for an operational lifetime of at least 100000 miles (160000km). We have demonstrated here that by modifying the formulation of the catalyst coating such that the inherent particle size is of the order of tens of nanometres, the resistance of the catalyst to thermal degradation is much improved. This is achieved by the use of a nanoscale powder composed primarily of ceria and zirconia, with the addition of a small percentage of the oxides of lanthanum and neodymium, as the major constituent of the washcoat onto which the catalytic metals are impregnated.
Washcoat: A solution is made up of zirconium propionate dissolved in tetrahydrofuran at a concentration of between 20g and 200g of zirconium propionate per litre of solution, preferably between 50 and 100g per litre. To this is added a quantity of the ceria/zirconia/lanthana/neodymia powder mentioned above, of between 100 and 300g per litre of solution, and preferably between 120 and 180g per litre. The mixture thus created is deposited onto a suitable substrate, such as a Fecralloy steel monolith, which is then dried to remove the solvent and heated to a temperature of at least 300°C to decompose the zirconium propionate and achieve good adhesion of the washcoat layer to the substrate.
Active layer: A solution of palladium acetate and rhodium acetate in tetrahydrofuran is made up, comprising between 2 and 5g of rhodium acetate per litre of solution, preferably between 2.4 and 3g per litre, and between 0.5 and 5g of palladium acetate per litre of solution, preferably between 0.7 and 2.5g per litre. This is applied to the monolith coated with washcoat and then dried to remove the solvent and heated to a temperature of at least 300°C to decompose the precursors and form metallic rhodium and palladium.
Example 1 :
A solution was prepared consisting of 25g zirconium propionate per litre of tetrahydrofuran. To this was added 150g of nanoscale powder per litre. The nanoscale powder was composed of zirconium oxide (47.10%), cerium oxide (45.95%), lanthanum oxide (1.87%) and neodymium oxide (5.08%).
100ml of this mixture was applied to a Fecralloy steel monolith purchased from Emitec GmbH. This was allowed to dry at room temperature then heated in air to 400°C to decompose the zirconium propionate and consolidate the coating. A further solution comprising 2.5g of rhodium (II) acetate and 2.33g of palladium (II) acetate per litre of tetrahydrofuran was prepared. 60ml of this solution was then applied to the coated monolith whereupon it was allowed to dry at room temperature and then heated in air to 400°C to decompose the acetates to their metallic constituents. The loading of precious metal on the monolith was approximately 140mg of palladium and 75mg of rhodium, which equates to a total loading of approximately 6g per cubic foot, in the units typically used by the industry.
Test results from example 1 :
The catalyst prepared as above was tested in the exhaust system of a stationary 1.81 4-cylinder 8-valve Volkswagen petrol engine connected to a dynamometer. Two load conditions were employed. The first was a standard load condition using an engine speed of 2500rpm and a torque of 100Nm. The second was a full-throttle high load condition using an engine speed of 3300rpm and 130Nm of torque. The results are shown below in table 1 :
Table 1 - Test results for fresh catalyst.
Figure imgf000007_0001
The catalyst was then subjected to accelerated ageing by heating it in air at 900°C for four hours. After cooling it was tested again, and showed only a small degradation, as can be seen from table 2:
Table 2 - Test results for aged catalyst.
Figure imgf000007_0002

Claims

1. A process for the production of a petrol engine exhaust ceramic-metal catalyst, comprising the steps of: - preparing a solution by admixing a nanoscale ceramic powder as the major constituent to a ceramic precursor solution;
- contacting a substrate with the solution so as to form a coating directly on the substrate,
- thermally treating said substrate with the coating to form a stabilised porous ceramic strongly adhered directly to the substrate, incorporating therein said nanoscale ceramic powder; and
- impregnating the porous ceramic layer obtained thereby with one or more catalytic metals or metal oxides.
2. A process according to claim 1 , wherein the ceramic powder is less than 50nm in diameter.
3. A process according to claims 1 or 2, wherein the ceramic powder is composed primarily of ceria and zirconia.
4. A process according to claim 3, wherein the ceramic powder comprises small percentage of the oxides of lanthanum and neodymium.
5. A process according to any one of claims 1 to 4, wherein the solution comprises zirconium propionate in a concentration from about 20g to about 200g per litre of solution, preferably from about 50 to about 100g per litre.
6. A process according to any one of claims 1 to 5, wherein the quantity of ceramic powder is from about 100 to about 300g per litre of solution, preferably from about 120 to about 180g per litre of solution.
7. A process according to any one of claims 1 to 6, wherein the substrate coated with solution is dried to remove the solvent and heated to a temperature of at least 300°C to decompose the zirconium propionate.
8. A petrol engine exhaust catalyst comprising: a substrate supported layer of porous ceramic, incorporating nanoscale ceramic particles and one or more catalytic metals, the ceramic layer being strongly adhered directly to the substrate.
9. A petrol engine exhaust catalyst according to claim 8, wherein the individual particles within the ceramic powder are less than 50nm in average diameter.
10. A petrol engine exhaust catalyst according to claims 8 or 9, wherein the ceramic powder is composed primarily of ceria and zirconia.
11. A petrol engine exhaust catalyst according to any one of claims 8 to 10, wherein the ceramic powder comprises a small percentage of lanthana and neodymia.
12. A petrol engine exhaust catalyst according to any one of claims 8 to 11 , wherein the quantity of the ceramic powder is from about 100 to about 300g per litre of solution, preferably from about 120 to about 180g per litre.
PCT/IB2004/000289 2003-01-31 2004-01-29 Petrol engine exhaust catalyst WO2004067171A1 (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8034738B2 (en) * 2007-03-14 2011-10-11 Taiyo Nippon Sanso Corporation Process for producing catalyst body for production of brush-shaped carbon nanostructure
CN107849962A (en) * 2015-05-19 2018-03-27 巴斯夫公司 For being passivated the catalysis soot filter of SCR

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5888464A (en) * 1997-04-08 1999-03-30 Engelhard Corporation Catalyst composition containing an intimately combined cerium-zirconium oxide
EP0955267A1 (en) * 1996-12-27 1999-11-10 Anan Kasei Co., Ltd Composite zirconium-cerium oxide, process for the preparation thereof, and cocatalyst for cleaning exhaust gas
US6040265A (en) * 1996-02-21 2000-03-21 Asec Manufacturing General Partnership Methods of making highly dispersed substantially uniform cerium and zirconium mixed-metal-oxide composite supports for exhaust conversion catalysts
WO2003082740A1 (en) * 2002-03-28 2003-10-09 Utc Fuel Cells, Llc Ceria-based mixed-metal oxide structure including method of making and use

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6040265A (en) * 1996-02-21 2000-03-21 Asec Manufacturing General Partnership Methods of making highly dispersed substantially uniform cerium and zirconium mixed-metal-oxide composite supports for exhaust conversion catalysts
EP0955267A1 (en) * 1996-12-27 1999-11-10 Anan Kasei Co., Ltd Composite zirconium-cerium oxide, process for the preparation thereof, and cocatalyst for cleaning exhaust gas
US5888464A (en) * 1997-04-08 1999-03-30 Engelhard Corporation Catalyst composition containing an intimately combined cerium-zirconium oxide
WO2003082740A1 (en) * 2002-03-28 2003-10-09 Utc Fuel Cells, Llc Ceria-based mixed-metal oxide structure including method of making and use

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US8034738B2 (en) * 2007-03-14 2011-10-11 Taiyo Nippon Sanso Corporation Process for producing catalyst body for production of brush-shaped carbon nanostructure
US8530374B2 (en) 2007-03-14 2013-09-10 Taiyo Nippon Sanso Corporation Catalyst body for production of brush-shaped carbon nanostructure
CN107849962A (en) * 2015-05-19 2018-03-27 巴斯夫公司 For being passivated the catalysis soot filter of SCR

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