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  • 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
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  • 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
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• • 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
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  • B01D2255/20761—Copper
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  • B01D2255/502—Beta zeolites
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01D2257/404—Nitrogen oxides other than dinitrogen oxide
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  • B01D2258/01—Engine exhaust gases
  • B01D2258/012—Diesel engines and lean burn gasoline engines
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/45—Gas separation or purification devices adapted for specific applications
  • B01D2259/4566—Gas separation or purification devices adapted for specific applications for use in transportation means
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
  • B01J23/8933—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
  • B01J23/894—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals also combined with metals, or metal oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
• • B—PERFORMING OPERATIONS; TRANSPORTING
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• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • 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
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/7007—Zeolite Beta
• • B—PERFORMING OPERATIONS; TRANSPORTING
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
  • B01J37/0027—Powdering
  • B01J37/0036—Grinding
• • 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
  • F01N2570/00—Exhaust treating apparatus eliminating, absorbing or adsorbing specific elements or compounds
  • F01N2570/16—Oxygen
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
  • Y02T10/00—Road transport of goods or passengers
  • Y02T10/10—Internal combustion engine [ICE] based vehicles
  • Y02T10/12—Improving ICE efficiencies

Definitions

• gaseous vehicular emissions comprise pollutants such as carbon monoxide (CO), oxides of nitrogen (NO and NO 2 collectively NOx), and unburnt hydrocarbons (HC).
• CO carbon monoxide
• NO and NO 2 collectively NOx oxides of nitrogen
• HC unburnt hydrocarbons
• exhaust after-treatment technologies have been developed for both gasoline and diesel engines. These technologies include, but are not limited to, engine control methodologies /modification, alternate combustion cycles and the use of after-treatment systems e.g. catalytic control devices which eliminate exhaust pollutants by promoting chemical changes to convert unwanted compounds into more benign species.
• the latter devices include the Diesel Oxidation Catalyst (DOC), Diesel NOx Trap /NOx Storage Catalyst (DNT /NSC) and Selective Catalytic Reduction catalyst (SCR) to address emissions of CO, HC (DOC) and NOx and the use of the Catalysed Diesel Particulate Filter (CDPF) for the removal and combustion of entrained solids, also known as particulate matter or soot.
• DOC Diesel Oxidation Catalyst
• DNT /NSC Diesel NOx Trap /NOx Storage Catalyst
• SCR Selective Catalytic Reduction catalyst
• CDPF Catalysed Diesel Particulate Filter
• PGM Precious Group Metal
• PGM Precious Group Metal
• Pt/Pd active Precious Group Metal
• the choice of these metals is based upon their ability to offer the highest turnover (number of reactions per second) with respect to the oxidation of CO and Hydrocarbon to CO 2 and water at low temperatures and low concentrations of active component within the DOC formulation.
• a further and final requirement is that the DOC must maintain this high level of activity after exposure to transient high temperatures in the presence of steam as occurs for a close- coupled catalyst or during the active regeneration strategy required for the DPF, as a result of the exotherm generated in the DOC by the combustion of post-injected hydrocarbons.
• the present invention provides a new class of base metal DOC and base metal modified DOC systems which can address these challenges.
• This improved technology is realised by the inclusion of a new generation of Base Metal Ion Exchanged Oxygen Storage (OS) materials and offers significant performance improvements in an apparatus for the lower temperature catalytic oxidation of CO, either it solely or in combination with conventional PGM containing DOCs.
• OS Base Metal Ion Exchanged Oxygen Storage
• the particular combination of doped OS CO oxidation catalyst with the conventional PGM-based activity provides a synergy which enables high conversion of pollutants at lower temperatures and with increased hydrothermal durability.
• the mode of ion exchange essentially involves the introduction of active metal / cations into the solid solution under chemically basic i.e. conditions of high pH, that is say high OH " / low Hydronium (HsO + ) or proton (H + ) content.
• HsO + Hydronium
• H + proton
• the resultant materials demonstrate high activity and hydrothermal durability in contrast to any promotion realised by conventional impregnation of an acidic metal e.g. metal nitrate, where formation of bulk oxide phases in fresh materials and rapid sintering of such oxide phases, with resultant deactivation, is the norm.
• the proposed exchange of the H + species by metal ions enables the incorporation and stabilisation of specific mono-valent (e.g.
• the choice of base metals thus incorporated can be based upon oxides known to be active for reactions of especial interest or catalytic importance.
• Metals of specific catalytic significance include Ag, Cu, Co, Mn, Fe, alkali metals, alkaline earth metals or transitions metals, or other metal or metalloid known to form a stable nitrate NOx adS which can undergo subsequent decomposition and reduction to N 2 under conditions within the conventional operational window of the vehicle exhaust.
• transition metal refers to the 38 elements in Groups 3-12 of the Periodic Table of Elements.
• Oxygen Storage (OS) materials are well known solid electrolytes based on, for example, Ceria-Zirconia (CeZrO x ) solid solutions. They are a ubiquitous component of aftertreatment catalysts for gasoline vehicles due to their ability to 'buffer' the active components in the catalyst against local fuel rich (reducing) or fuel lean (oxidising) conditions. OS materials do this by releasing active oxygen from their 3-D structure in a rapid and reproducible manner under oxygen-depleted transients, regenerating this 'lost' oxygen by adsorption from the gaseous phase when oxygen rich conditions arise.
• CeZrO x Ceria-Zirconia
• This reduction-oxidation (hereafter redox) chemistry is attributed to the Ce 4+ ⁇ -> Ce 3+ redox couple, with the oxidation state of Ce depending upon local O 2 content.
• This high availability of oxygen is critical for the promotion of generic oxidation / reduction chemistries e.g. CO / NO chemistry for the gasoline three-way catalyst, or more recently for the direct catalytic oxidation of particulate matter (soot) in the catalysed diesel particulate filter (CDPF) e.g. US2005 0282698 Al.
• Benefits and features include: a) Provision of a 'stand-alone' base metal DOC or of a base metal component able to operate in a synergistic manner within a conventional DOC technology to promote lower temperature oxidation of CO. b) Improved CO oxidation performance ascribed to the high dispersion of the promoting base metal sites within the CeZrO x resulting in high accessibility of the gaseous reactants to active O species.
• an oxidation catalyst can comprise a catalytic material disposed on a support.
• the catalyst will additionally comprise about 10 wt% to 50 wt% of a base metal modified Cubic Fluorite Ce-Zr mixed oxide component and about 10 wt% to about 50 wt% Zeolite based upon the total weight of the catalyst formulation.
• a catalytic device can comprise a housing disposed around a substrate with a compression ignition oxidation catalyst disposed on the substrate.
• the method for treating a compression ignition exhaust stream can comprise: introducing a diesel exhaust stream to a compression ignition oxidation catalyst; and oxidising an exhaust stream component.
• the catalyst materials can be included in the formulation by combining alumina, or other appropriate support, with other catalyst materials to form a mixture, drying (actively or passively), and optionally calcining. More specifically, a slurry can be formed by combining alumina, doped OS powder and water, and optionally pH control agents (such as inorganic or organic acids and bases) and/or other components.
• the catalytic materials e.g. catalytic metals, such as Pt
• This slurry can then be washcoated onto a suitable substrate.
• the washcoated product can be dried and heat treated to fix the washcoat onto the substrate.
• the catalyst can further comprise a Zeolite.
• Zeolites include Y-type Zeolite, beta Zeolite ( ⁇ ), ZSM-5, silica alumina phosphate (SAPO e.g. SAPO34) and the like, as well as combinations comprising at least one of the foregoing Zeolites.
• SAPO silica alumina phosphate
• the Zeolite can, for example, have a silica to alumina ratio (Si:Al) of about 15 to about 80, or, more specifically, about 35 to about 60. If the Zeolite is employed, it can be added to the slurry along with the catalytic material (e.g., before the catalytic material has been calcined).
• This slurry can be dried and heat treated, e.g., at temperatures of about 500 0 C to about 1,000 0 C, or more specifically about 500 0 C to about 700 0 C, to form the finished catalyst formulation.
• the slurry can be washcoated onto the substrate and then heat treated as described above, to adjust the surface area and crystalline nature of the support.
• catalyst metals may optionally be disposed on the support. The catalyst metals, therefore, can be added after the washcoat is fixed onto the substrate by additional washcoat steps and/or by exposing the washcoated substrate to a liquid containing the catalytic metal.
• the supported catalyst can comprise a PGM (Pt, Pd, Rh etc.), (modified) alumina, and Zeolite, optionally silica to which the metal doped OS is added.
• the amounts of these components in the supported catalyst can be: about 0.1 wt % to about 10 wt % PGM, about 50 wt % to about 80 wt % (modified) alumina, about 10 wt % to about 50 wt % metal doped OS, and about 10 wt % to about 50 wt % Zeolite; or, more specifically, about 1 wt % to about 5 wt % PGM, about 40 wt % to about 60 wt % modified alumina, about 25 wt % to about 45 wt % of metal doped OS, and about 25 wt % to about 45 wt % Zeolite.
• the supported catalyst can be disposed on a substrate.
• the substrate can comprise any material designed for use in the desired environment, e.g., a compression ignition engine (e.g., a diesel engine) environment.
• a compression ignition engine e.g., a diesel engine
• Some possible materials include cordierite, silicon carbide, metal, metal oxides (e.g., alumina, and the like), glasses, and the like, and mixtures comprising at least one of the foregoing materials.
• These materials can be in the form of packing material, extrudates, foils, perform, mat, fibrous material, monoliths (e.g., a honeycomb structure, and the like), other porous structures (e.g., porous glasses, sponges), foams, molecular sieves, and the like (depending upon the particular device), and combinations comprising at least one of the foregoing materials and forms, e.g., metallic foils, open pore alumina sponges, and porous ultra-low expansion glasses.
• these substrates can be coated with oxides and/or hexaaluminates, such as stainless steel foil coated with a hexaaluminate scale.
• the substrate can have any size or geometry, the size and geometry are preferably chosen to optimise geometric area in the given exhaust emission control device design parameters.
• the substrate has a honeycomb geometry, with the combs through-channel having any multi-sided or rounded shape, with substantially square, triangular, pentagonal, hexagonal, heptagonal, or octagonal or similar geometries preferred due to ease of manufacturing and increased surface area.
• the substrate can be disposed in a housing to form the converter.
• the housing can have any design and comprise any material suitable for the application. Suitable materials for the housing can comprise metals, alloys, and the like, such as ferritic stainless steels (including stainless steels such as, e.g., the 400-Series such as SS-409, SS-439, and SS-441), and other alloys (e.g. those containing nickel, chromium, aluminium, yttrium and the like, e.g., to permit increased stability and/or corrosion resistance at operating temperatures or under oxidising or reducing atmospheres).
• ferritic stainless steels including stainless steels such as, e.g., the 400-Series such as SS-409, SS-439, and SS-441
• other alloys e.g. those containing nickel, chromium, aluminium, yttrium and the like, e.g., to permit increased stability and/or corrosion resistance at operating temperatures or under oxidising or
• end cone(s), end plate(s), exhaust manifold cover(s), and the like can be concentrically fitted about the one or both ends and secured to the housing to provide a gas tight seal.
• These components can be formed separately (e.g., moulded or the like), or can be formed integrally with the housing using methods such as, e.g., a spin forming, or the like.
• a suitable device is illustrated in Nunan, U.S. 2005/0129588 Al.
• the retention material Disposed between the housing and the substrate can be a retention material.
• the retention material which may be in the form of a mat, particulates, or the like, may be an intumescent material e.g., a material that comprises vermiculite component, i.e., a component that expands upon the application of heat, a non-intumescent material, or a combination thereof.
• intumescent material e.g., a material that comprises vermiculite component, i.e., a component that expands upon the application of heat
• non-intumescent material a non-intumescent material
• These materials may comprise ceramic materials e.g., ceramic fibres and other materials such as organic and inorganic binders and the like, or combinations comprising at least one of the foregoing materials.
• the coated monolith containing the metal doped OS augmented DOC is incorporated into the exhaust flow of the compression ignition engine.
• This provides a means for treating said compression ignition exhaust stream to reduce the concentrations of environmental toxins by passing said diesel exhaust stream after the aforementioned compression ignition oxidation catalyst under net oxidising conditions (oxygen rich) to facilitate catalytic conversion / oxidation into more environmentally benign products.
• Figure 1 compares the H 2 Temperature Programmed Reduction performance of a CeZrLaPrO 2 . ⁇ mixed oxide (OS3) before and after post-synthetic basic exchange of 2wt%Cu (hereafter all samples will be referred to a XMe-OS"Z" e.g.2Cu-OSl).
• OS3 CeZrLaPrO 2 . ⁇ mixed oxide
• XMe-OS XMe-OS
• Z e.g.2Cu-OSl
• the incorporation of Copper (Cu) results in a dramatic promotion of the redox properties of the OS, with the exchanged material exhibiting high redox function at T ⁇ 300 0 C cf. the non- exchanged material which exhibits a redox maximum at ca. 575 °C.
• FIG. 1 reports Synthetic Gas Bench (SGB) performance data for the oxidation of a simulated diesel stream. Test conditions were selected to mimic a Euro V exhaust and comprised lOOOppm CO, 600 ppm Cl n-Octane, 180 ppm Cl Methyl-Benzene, 75 ppm Cl Propene, 75 ppm Cl Methane, 80 ppm NO, 3.5% CO 2 , 13% O 2 , 3.5% H 2 O, Balance N 2 , Ramp 12 °C / min and total flow 5 1 /min.
• SGB Synthetic Gas Bench
• the testing was performed using 0.5g Zeolite ⁇ (Silica Alumina Ratio 40) powder, positioned at the inlet of the reactor and 1.5g base metal oxidation catalyst powder material (fresh) positioned at the outlet i.e. behind the Zeolite HC trap.
• the data confirms the efficacy of both the Cu and Ag doped OSl for the catalytic oxidation of both CO and HC, with the former exhibiting an especial benefit with respect to CO oxidation.
• Figure 3 examines the impact of OS composition on catalytic performance in standard SGB testing, using the conditions described in Figure 2, for 5%Cu doped OSl and OS2. Again both samples demonstrate fresh activity for the oxidation of CO and HC, even in the absence of PGM. In this instance the oxidation of CO is favoured using 5%- OSl, consistent with the high Ce content of this material and consistent with the aforementioned concept of high redox activity coupling with the CO oxidation reaction.
• Figure 4 summarises the CO light-off temperatures for a range of ion exchanged OS materials in SGB testing, again using the conditions outlined in Figure 2.
• Figure 7 further demonstrates the promise of the 5%Cu-OS3 - 35 gcf Pt sample on the SGB.
• the sample against at 120 gcf Pt DOC again using the aging and testing protocols defined in Figure 5.
• the high loaded Pt DOC exhibits superior performance under all conditions, but only at considerable expense in terms of PGM content.
• Analysis of Figures 5-7 suggests that based upon SGB screening and aging the performance benefit of the 5Cu-OS3 equates to ca. 60 gcf Pt content on a conventional DOC, a considerable potential saving.
• Core A comprised a DOC with 60 gcf Pt/Pd (60 @ 2:1 i.e. 40 gcf Pt and 20 gcf Pd) to which a second layer comprising 2Cu-OS3 + Zeolite ⁇ was added.
• Core B used an identical composition and architecture except the PGM content was 60 gcf at 1:5 i.e. 10 gcf Pt and 50 gcf Pd.
• Core C employed the same architecture and base metal oxide ratios except this sample contained 0 gcf PGM. Prior to testing all samples were 'stabilised' by aging Ih at 650 C in the reactive gas mixture without SO 2 .
• the data ( Figure 8) illustrates some very salient issues.
• Figure 9a and Figure 9b illustrate the dynamometer (hereafter dyno) performance of full size parts (4" round by 6" long, 400 cells per square inch) of DOC washcoats A,B and C versus a 70 gcf Pt reference technology.
• AU parts were tested after oven aging (700 0 C, 10% steam, air for 25 hours), after aging 20 hours on the dyno in an exhaust stream from a combustion cycle using a fuel source with 500 ppm S, and finally after a de-sulfation / further hydrothermal aging again on the dyno, exposing the sample for 5 hours to hot exhaust gases at a DOC inlet temperature of 650 0 C (note.
• Figure 10 confirms the dyno performance of the parts tested in Figure 9a/9b in vehicle testing (the data reports the activity after 700 °C aging oven cycle). Again the base metal only sample (Part C) displays poor activity for CO and HC. In contrast Part A (2Cu- OS3 with 60 Pt/Pd @ 2:1) shows a definite CO performance advantage, this being derived from superior ECE performance i.e. cold start / light-off benefit. Finally Part B (2Cu-OS3 + 60 Pt/Pd @ 1 :5) shows a fair performance, again inconsistent with the PGM type and content.
• FIG. 11 illustrates the CO light-off curves after initial oven aging, sulfation and de-sulfation. While the impact of sulphur is clear and unambiguous, it is also apparent that after hydrothermal aging almost full activity is recovered. This effect we ascribe to the facile de-sulfation of both the PGM centres and especially the 2Cu-OS3. This effect will be examined in more detail in later Figures.
• the performance of the 70 gcf Pt 3"/ 2Cu-OS3 3" shows clear advantages to either the 70 gcf Pt 3" or 2Cu-OS3 3" / 70 gcf Pt 3" thereby confirming that the conventional DOC zone affords 'protection' of the active base metal catalyst sites to the toxic components in the exhaust stream, thereby facilitating the second (base metal only) brick to provide additional CO oxidation function.
• the same is not true for the reverse configuration with the activity of the 2Cu-OS3 3"/ 70 gcf Pt 3" and 70 gcf Pt 3" systems being within experimental variation.
• Figure 15 compares the technologies from Figure 14 in standard vehicle performance testing.
• the benefit of the Part A 60 gcf @ 2:1 with 2Cu-OS3 base metal
• the 60 gcf @ 2:1 without base metal is confirmed (testing performed after oven agjng).
• the enhanced activity is attributed to superior conversion efficiency during the ECE i.e. enhanced light-off activity.
• Figure 17 compares the dyno aging and testing performance of Part F (30 @ 2:1 with a secondary layer of 2Cu-OS3 and Zeolite) versus a commercial reference technology Part G (also 30 @ 2:1) versus Part H ( 30 @ 2:1 with 2Cu-OS3 in the same layer as the PGM, alumina and Zeolite, but at 50% content cf. Part F).
• Part F a commercial reference technology
• Part G also 30 @ 2:1
• Part H 30 @ 2:1 with 2Cu-OS3 in the same layer as the PGM, alumina and Zeolite, but at 50% content cf. Part F.
• the reference is outperformed by the 2Cu-OS3 -containing parts after oven aging with Part F displaying the best performance, consistent with the higher loading of promoter.
• SOx aging all parts are equal, consistent with poisoning of the base metal function i.e.
• both base metal containing samples exhibited weaker performance than the reference after 2Oh SOx aging.
• SOx aging penalty for the Pt only reference is also a fraction of that for parts J and K, this higher poisoning tolerance is attributed solely to the absence of the 2Cu-OS3 modifier.
• the previous level of high activity of both samples are restored. Since this regeneration occurs for both PtPd and Pt only samples, the effect cannot be ascribed to the typical regeneration seen for PtPd after DeSOx cycles but must instead be due to De- SOx of the 2Cu-OS3.
• Figure 19 and Figure 20 further illustrate the SOx and De-SOx characteristics of the 2Cu-OS 3 material.
• the impact of zone coating, and more specifically the direction of zone coating on the CO oxidation performance vs SOx are examined.
• Figure 19 we compare 4 parts, all of which contain 30 gcf PtPd @ 2:1 Pt:Pd, one is a commercial reference without 2Cu-OS3 while the other three all contain a 50% second layer zone of the base metal promoter.
• Part L in its 'correct' orientation i.e. zone of base metal / Zeolite at the inlet
• Part L in a 'reverse' orientation i.e.
• the present invention relates to the development and use of base metal promoters for emission treatment catalysts.
• the base metal promoter is derived from a substantially phase pure cubic fluorite (as determined by XRD) of the CeZrO x type which is well known in the art. This parent material is subsequently modified by the introduction of base metal e.g. transition or other metal as defined in US applications 12/363,310 and 12/363,329.
• This modification is proposed to arise, whilst not wishing to be bound by theory, from an ion exchange of the Ce 3+ -OH hydroxyls, present in both the surface and to a lessor extent in the bulk of the crystal, by the base metal element / ion selected for this purpose and results in a significant promotion of the redox / oxygen ion conductivity of the CeZrO x .
• the base metal promoted CeZrOx materials / base metal promoter may be applied advantageously to an emission control catalyst for a diesel (or other fuel lean) application.
• the particular example described herein is for the application of these materials in the area of catalytic oxidation of (especially) CO and HC.
• This new generation of modified OS materials has been demonstrated as having particular benefit in affecting the low temperature oxidation of CO and HC as compared to non-modified OS materials.
• the method for producing the metal promoter is referred to as the basic exchange for enhanced redox process.
• This process describes a method for the modification of conventional cerium-zirconium-based mixed oxides, also known as, oxygen storage materials (OSM).
• OSM oxygen storage materials
• the process involves the treatment of the OSM with a basic, where possible an ammoniacal solution of the dopant metal.
• Base metals i.e. common metals, currently being employed in this process include, but are not limited to, transition metals, e.g. silver, copper and cobalt; alkali metals e.g. potassium; alkaline earth metals e.g. calcium, strontium, barium.
• transition metal as used herein means the 38 elements in groups 3 through 12 of the Periodic Table of the Elements.
• the variables in the process include (1) the OSM / mixed oxide selected, (2) the base metal used, and (3) the concentration of that metal. Metal concentrations successfully employed have ranged from 0.02 to 5.0 wt%. However, at higher metal exchange levels bulk metal oxides may be formed which do not retain the synergistic coupling with the OSM. Hence, the most preferred range for ion exchange is 0.1 to 2.5 wt%.
• the base metals are typically received as a metal salt or solution of salt e.g. nitrate. As indicated, most base metals form a water-soluble complex with ammonium hydroxide. In those instances wherein the ammoniacal complex is unstable an organic amine e.g. tri- ethanolamine may be employed instead.
• the solution of an acidic metal solution is converted to a chemically basic form by addition of the ammoniacal base. The chemistry and amounts of base used vary with the metal used.
• the resulting solution is then used to impregnate the mixed oxide powder, thereby ion-exchanging the surface and sub-surface Ce-OH hydroxyls (surface terminations and bulk defects which act as acidic centres under the conditions of synthesis).
• the impregnated mixed oxide must first be calcined at sufficient temperature to drive off the inorganic anions (e.g. nitrate and ammonium ions), typically >350 0 C. After calcination the metal that was added is now bound to the former Ce-OH centres.
• inorganic anions e.g. nitrate and ammonium ions
• the mixed oxide / OSM material of this invention comprises any known or predicted Cerium-containing or Ce-Zr-based stable solid solution.
• the solid solution contains a cationic lattice with a single-phase, as determined by standard X-ray Diffraction method. More preferably this single-phase is a cubic structure, with a cubic fluorite structure being most preferred.
• the ion exchange process may be performed without formation of additional bulk phases, as determined by XRD, providing the concentration of exchanged cation does not exceed the Ce-OH 'concentration' of the cubic fluorite lattice.
• the OS material may include those OS materials disclosed in U.S. Pat.
• the OS materials modified by the basic exchange method comprise a composition having a balance of sufficient amount of zirconium to decrease the reduction energies of Ce 4+ and the activation energy for mobility of 'O' within the lattice and a sufficient amount of cerium to provide the desired oxygen storage capacity.
• the OS shall contain a sufficient amount of stabiliser e.g. yttrium, rare earth (La/Pr etc.) or combination thereof to stabilise the solid solution in the preferred cubic crystalline phase.
• the OS materials modified by the basic exchange method shall preferably be characterised by a substantially cubic fluorite structure, as determined by conventional XRD methods.
• the percentage of the OS material having the cubic structure, both prior and post exchange, is preferably greater than about 95%, with greater than about 99% typical, and essentially 100% cubic structure generally obtained (i.e. an immeasurable amount of tetragonal phase based upon current measurement technology).
• the exchanged OS material is further characterised in that it possess large improvements in durable redox activity with respect to facile oxygen storage and increased release capacity as described in detail in US applications 12/363,310 and 12/363,329.
• the base metal material may be advantageously applied either solely, or more preferably with a conventional PGM containing catalyst.
• the base metal material can thusly be applied in a variety of configurations e.g. in a single 'pass' i.e. as an intimate mixture with the PGM-containing formulation, as a separate layer coated prior to or more preferably subsequent to the conventional PGM formulation.
• the base metal material may be applied as a homogeneous coating, or as a partial or zone-coating covering a fraction of the entire monolith length.
• the base metal material may be employed in a separate, second monolith brick situated downstream of the conventional PGM containing DOC. In all of these configurations appreciable performance benefits are realised and improvements in the hydrothermal durability of the subsequent emission control catalyst are also observed.
• Parts A and B employed as test technologies is as follows: Slurry Alumina at pH ca. 4.5 and mill to dso (diameter of 50% of the particles) of 4-6 microns, confirm dr ⁇ . Next take the required concentration of Pt nitrate solution and slowly dilute with rheology modifier as required prior to adding solution dropwise to milled Alumina slurry. Slurry must be at a pH lower than 6.0 prior to metal addition and during Pt addition, monitor pH and prevent slurry from going to pH values below 3.0 with the judicious use of base. After metal addition, adjust to 3.5 with base and stir slurry for 2 hours.
• Part C As employed as a test technology is as follows: Slurry Alumina at pH ca. 4.5 and mill to dso (diameter of 50% of the particles) of 4-6 microns, confirm d9o. Then coat monolith in 1 pass and calcine at temperatures > 540 0 C for > 1 hour.
• Part A Pass 1 67.1g/l HP14/15020Pd 40Pt Pass 2 91.5g/l 2CuOS3 30.5g/l ⁇ SAR40
• Part B Pass 1 67.1g/l HP14/150 50Pd 10 Pt Pass 2 91.5g/l 2CuOS3 30.5g/l ⁇ SAR40
• Part D Commercial DOC @ 60 gcf 2:1 Pt:Pd
• Part E Pass 1 67.1g/l HP14/150 7Pd 14Pt Pass 2 91.5g/l 2CuOS3 30.5g/l ⁇ SAR40
• Part F Pass 1 67.1g/l HP14/150 lOPd 20Pt Pass 2 91.5g/l 2CuOS3 30.5g/l ⁇ SAR40
• Part G Commercial DOC @ 30 gcf 2:1 Pt:Pd
• Part H Pass 1 61 ⁇ HP14/150 lOPd 20Pt 91.5g/l 2CuOS3 30.5g/l ⁇ SAR40
• Part J Pass 1 67.2g/l HP14/15030Pd 90Pt Pass 2 91.65g/12Cu-OS3 30.5g/l ⁇ SAR40
• Part K Pass 1 85.5 HP15/150 Zr5 70Pt 47.78g/l ⁇ SAR40 Pass 2 48.9g/l 2Cu-OS3
• Part L Pass 1 85.5g/l HP14/150 Zr5 lOPd 20Pt 18.33g/l ⁇ SAR40

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