Catalyst Articles with High Local Rhodium Concentrations

Abstract

The present invention provides a catalyst article for treating exhaust gases, the catalyst article comprising a substrate having an axial length L and including an inlet end and an outlet end, and a first catalyst region comprising support material particles, at least a portion of the support material particles being rhodium-loaded support material particles having rhodium loaded thereon at a concentration of 0.001 to 3.5 wt % based on the weight of the rhodium-loaded support material particles, the rhodium being present in a loading of up to 20 g / ft3 for the first catalyst region.

Description

[Technical field]

[0001] The present invention relates to a catalytic article, a method for making a catalytic article, a catalytic article obtained or obtainable by the method, an emission treatment system, and a method for treating exhaust gases. [Background technology]

[0002] Three-way catalysts (TWCs) are used to separate CO, HC, and NO from the exhaust of gasoline engines at a stoichiometric air-fuel ratio. x to harmless compounds (about 98%). Specifically, the oxidation of CO and HC to CO2 and water vapor (HO) is primarily catalyzed by Pd, while NO x The reduction of N2 to N2 is primarily catalyzed by Rh. Modern TWCs use supported platinum group metal (PGM) catalysts (Pd, Rh, Pt, etc.) deposited on single, bi- or multi-layer supports, with the support material consisting of high surface area metal oxides, primarily stabilized alumina, and ceria-containing oxygen storage materials. The supported catalysts are washcoated onto ceramic monolith substrates.

[0003] In recent years, as PGM prices have risen significantly and emissions regulations have become stricter, there is a demand to reduce the amount of precious metals used in exhaust gas purification catalysts. Among the precious metals, Rh is the rarest and most expensive species on earth. Therefore, highly activating Rh in particular is desirable to reduce the cost of PGM use while still meeting the strict emission regulations.

[0004] In exhaust purification catalysts, one of the methods to reduce the amount of precious metals used is to support the precious metals on a carrier and use them as fine particles. For example, WO2016123534(A1) reports PGM particle sizes of 10-92 nm. These PGM nanoparticles were obtained by supporting them on nanoscale carriers in the range of 1-100 nm.

[0005] Lower Rh loading (e.g., <20 g / ft 3 In certain exhaust purification catalysts having a high Rh content, very fine Rh particles are formed, which tend to be encapsulated by the support material due to strong metal support interaction (SMSI), resulting in a decrease in catalyst performance during subsequent catalyst life. Exposure to high temperatures in addition to moisture in the feed gas composition is the main reason that causes the fine Rh particles to be encapsulated or dissolved into the support matrix. Thus, the durability of the catalyst is poor.

[0006] However, if the initial Rh particles are large enough, Rh encapsulation / dissolution is less of a problem. This is typically achieved at higher Rh loadings (e.g., 20 g / ft 3 This is observed in catalysts having a molecular weight of 1.0 or more. Summary of the Invention

[0007] One aspect of the present disclosure is directed to providing a catalyst article for treating an exhaust gas, the article comprising a substrate including an inlet end and an outlet end, the substrate having an axial length L, and a first catalytic region comprising support material particles, at least a portion of the support material particles being rhodium-loaded support material particles having rhodium loaded thereon at a concentration of 0.001 to 3.5 weight percent based on the weight of the rhodium-loaded support material particles, the rhodium being present in an amount of up to 20 g / ft 2 for the first catalytic region. 3 is present at a loading of .

[0008] Another aspect of the present disclosure is directed to a method of making a catalyst article, the method comprising providing rhodium-loaded support material particles having rhodium loaded thereon at a concentration of 0.001 to 3.5 weight percent based on the weight of the rhodium-loaded support material particles; providing unsupported support material particles having essentially no rhodium loaded thereon, preferably having no rhodium loaded thereon; forming a washcoat comprising the rhodium-loaded support material particles and the unsupported support material particles; and coating a substrate with the washcoat to provide the catalyst article, wherein the rhodium is present in an amount of up to 20 g / ft. 3 and wherein the catalyst is present in a loading amount of

[0009] Another aspect of the present disclosure is directed to a catalyst article obtained or obtainable by the method of the above aspect.

[0010] The present invention also includes an emission treatment system including the catalytic article described herein and a method of treating an exhaust gas, the method including providing a catalytic article described herein and contacting the catalytic article with an exhaust gas. [Brief description of the drawings]

[0011] [Figure 1] 1 shows one embodiment according to the present invention containing a first catalytic region (single layer) having a length of 100% relative to the axial length L of the substrate. [Figure 2a] 1 shows an embodiment according to the invention in which a first catalyst region extends 100% of the axial length L as a bottom layer and a second catalyst region extends 100% of the axial length L as a top layer. [Figure 2b] 2 illustrates a variation of FIG. 2a. [Figure 3a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from the inlet end less than 100% of the axial length L, and a second catalyst region extends from the outlet end less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to or less than the axial length L. [Figure 3b] 3 illustrates a variation of FIG. 3a. [Figure 3c] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from the inlet end less than 100% of the axial length L, and a second catalyst region extends from the outlet end less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is greater than the axial length L. [Figure 3d] 3 illustrates a variation of FIG. 3c. [Figure 4a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is equal to or less than the axial length L. A third catalyst region extends 100% of the axial length L and is layered as an upper layer onto the first and second catalyst regions. [Figure 4b] 4 illustrates a variation of FIG. 4a. [Figure 4c] 1 illustrates an embodiment according to the invention where the third catalyst region is a bottom layer and extends 100% of the axial length L. 2 illustrates an embodiment according to the invention where the first catalyst region extends less than 100% of the axial length L from the inlet end and the second catalyst region extends less than 100% of the axial length L from the outlet end. 3 illustrates an embodiment according to the invention where the second catalyst region and the first catalyst region extend less than 100% of the axial length L. [Figure 4d] 4 illustrates a variation of FIG. 4c. [Figure 5a] 1 shows an embodiment according to the invention in which a first catalyst region is a bottom layer extending over 100% of the axial length L, a second catalyst region is a middle layer extending over 100% of the axial length L, and a third catalyst region is a top layer extending over 100% of the axial length L. [Figure 5b] 5 illustrates a variation of FIG. 5a. [Figure 5c] 5 illustrates a variation of FIG. 5a. [Figure 6a]1 illustrates an embodiment according to the present invention in which a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is greater than the axial length L. A third catalyst region extends 100% of the axial length L and is layered as an upper layer onto the first and second catalyst regions. [Figure 6b] 6 illustrates a variation of FIG. 6a. [Figure 6c] 6 illustrates a variation of FIG. 6a. [Figure 6d] 6 illustrates a variation of FIG. 6a. [Figure 6e] 6 illustrates a variation of FIG. 6a. [Figure 6f] 6 illustrates a variation of FIG. 6a. [Figure 6g] 1 illustrates an embodiment according to the present invention, where a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region can be less than, equal to, or greater than the axial length L. A third catalyst region extends less than 100% of the axial length L from the inlet end and is at least partially stacked to the first catalyst region and / or the second catalyst region. [Figure 6h] 6 illustrates a variation of FIG. 6g. [Figure 6i] 6 illustrates a variation of FIG. 6g. [Figure 6j] 1 illustrates an embodiment according to the present invention, where a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region can be less than, equal to, or greater than the axial length L. A third catalyst region extends less than 100% of the axial length L from the outlet end and is at least partially stacked to the second and / or first catalyst regions. [Figure 6k] Illustrates a variation of FIG. 6j. [Figure 6l] Illustrates a variation of FIG. 6j. [Figure 7] 1 shows the results of NOx conversion and CO conversion in lambda sweep tests in engine tests for reference catalyst 1 and inventive catalysts 1-3. [Figure 8] 1 shows the results of THC conversion in lambda sweep tests in engine tests for reference catalyst 1 and inventive catalysts 1-3. [Figure 9] 1 shows NOx and CO conversion results of lambda sweep tests in engine tests for reference catalyst 2 and inventive catalysts 4-6. [Figure 10] 1 shows the results of THC conversion in lambda sweep tests in engine tests for reference catalyst 2 and inventive catalysts 4-6. [Figure 11] 1 shows NOx and CO conversion results of lambda sweep tests in engine tests for reference catalyst 3, inventive catalyst 7, and inventive catalyst 8. [Figure 12] 1 shows the THC conversion results of lambda sweep tests in engine tests for reference catalyst 3, inventive catalyst 7, and inventive catalyst 8. [Figure 13] 1 shows the cumulative mass of NOx at a post-catalyst position during a high temperature RDE test in an engine test for a reference catalyst 1 and inventive catalysts 1-3. [Figure 14] 1 shows the cumulative mass of CO at a post-catalyst position during a high temperature RDE test in an engine test for a reference catalyst 1 and inventive catalysts 1-3. [Figure 15] 1 shows the cumulative mass of THC at the post-catalyst position during a high temperature RDE test in an engine test for a reference catalyst 1 and inventive catalysts 1-3. [Figure 16] 1 shows the cumulative mass of NOx at a post-catalyst position during a high temperature RDE test in an engine test for a reference catalyst 2 and inventive catalysts 4 to 6. [Figure 17] 1 shows the cumulative mass of CO at a post-catalyst position during a high temperature RDE test in an engine test for reference catalyst 2 and inventive catalysts 4-6. [Figure 18]1 shows the cumulative mass of THC at the post-catalyst position during a high temperature RDE test in an engine test for reference catalyst 2 and inventive catalysts 4-6. [Figure 19] 1 shows the cumulative mass of NOx at the post-catalyst location during a high temperature RDE test in an engine test for reference catalyst 3, inventive catalyst 7, and inventive catalyst 8. [Figure 20] 1 shows the cumulative mass of CO at the post-catalyst location during a high temperature RDE test in an engine test for reference catalyst 3, inventive catalyst 7, and inventive catalyst 8. [Figure 21] 1 shows the cumulative mass of THC at the post-catalyst location during a high temperature RDE test in an engine test for reference catalyst 3, inventive catalyst 7, and inventive catalyst 8. [Figure 22] 1 shows the cumulative mass of NOx at a post-catalyst position during a high temperature RDE test in an engine test for reference catalyst 4 and inventive catalysts 9 to 11. [Figure 23] 1 shows the cumulative mass of CO at a post-catalyst position during a high temperature RDE test in an engine test for reference catalyst 4 and inventive catalysts 9-11. [Figure 24] 1 shows the cumulative mass of THC at the post-catalyst position during a high temperature RDE test in an engine test for reference catalyst 4 and inventive catalysts 9-11. [Diagram 25] 1 shows the cumulative mass of NOx at the post-catalyst position during a WLTC test in an engine test for reference catalyst 4 and inventive catalysts 9-11. [Figure 26] 4 shows the cumulative mass of CO at the post-catalyst position during a WLTC test in an engine test for reference catalyst 4 and inventive catalysts 9-11. [Figure 27] 1 shows the cumulative mass of THC at the post-catalyst position during a WLTC test in an engine test for reference catalyst 4 and inventive catalysts 9-11. [Figure 28] The concept of enlarging the Rh particle size by locally concentrating Rh in a part of the support material is shown. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention aims to address at least some of the problems associated with the prior art, or at least to provide a commercially acceptable alternative solution.

[0013] In a first aspect, the present invention provides a catalytic article for treating an exhaust gas, the article comprising: a substrate including an inlet end and an outlet end having an axial length L; a first catalyst region comprising support material particles; at least a portion of the support material particles are rhodium-loaded support material particles having rhodium loaded thereon in a concentration of 0.001 to 3.5 weight percent based on the weight of the rhodium-loaded support material particles; Rhodium up to 20g / ft for the first catalytic area 3 is present at a loading of .

[0014] Each aspect or embodiment defined in this specification may be combined with any other aspect or embodiment unless expressly indicated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0015] The first catalytic region Preferably, the rhodium-loaded support material particles have rhodium loaded thereon in a concentration of 0.3 to 3.5% by weight based on the weight of the rhodium-loaded support material particles. More preferably, the rhodium-loaded support material particles have rhodium loaded thereon in a concentration of 0.4 to 3.0% by weight, still more preferably 0.4 to 2.0% by weight, still more preferably 0.4 to 1.5% by weight based on the weight of the rhodium-loaded support material particles. Alternatively, the rhodium-loaded support material particles have rhodium loaded thereon in a concentration of 0.3 to 1.8% by weight, still more preferably 0.4 to 1.2% by weight, still more preferably 0.4 to 1.0% by weight based on the weight of the rhodium-loaded support material particles.

[0016] In known catalytic articles, rhodium is present in a first catalytic region in an amount of up to 20 g / ft 3When present at a relatively low loading of rhodium, the support material particles having rhodium supported thereon may not have as high a concentration of rhodium supported thereon as required in the present embodiment. This may be because rhodium is typically supported uniformly, i.e., at a uniform concentration, on each support material particle present in a particular catalyst region. In other words, none of the support material particles having rhodium supported thereon may have a locally higher concentration of rhodium.

[0017] Surprisingly, when used in an emission treatment system, the catalyst articles of the present invention having locally higher concentrations of rhodium as defined herein, but still with a lower overall loading of rhodium to reduce PGM usage, exhibit significantly improved light-off performance {i.e., lower light-off temperature, lower specific target species [NO x 50% conversion of rhodium (CO, CO, or total hydrocarbons (THC)) can be achieved. Furthermore, having a locally higher concentration of rhodium while maintaining a low total rhodium loading can result in a larger particle size of rhodium on the rhodium-loaded support material particles, which can surprisingly result in a catalyst article in which the rhodium particles are more resistant to calcination, oxidation, and migration compared to other low rhodium-loaded catalyst articles. However, it has also been found that over-concentrating rhodium on the rhodium-loaded support material particles can result in reduced catalytic activity. Thus, there may be an optimal local rhodium concentration for a particular low total loading of rhodium.

[0018] The above effect may be particularly beneficial for catalytic articles having a low total rhodium loading, but may not be observed for catalytic articles having a higher total rhodium loading. Without being bound by theory, it is believed that this may be because when the total rhodium loading on the support is already high, the local concentration of rhodium on each support material particle is already high, and therefore there may be no need to locally concentrate rhodium on some of the support material. In other words, the present invention may alleviate problems resulting from reducing the total Rh loading on the catalytic article by allowing some of the benefits associated with higher loadings to be present at low total loadings due to the presence of locally concentrated rhodium.

[0019] As used herein, the term "catalyst article" may include an article on or within which a catalyst is supported. The article may take the form of, for example, a honeycomb monolith, or a filter, such as a wall-flow filter or a flow-through filter.

[0020] The term "substrate" as used herein can include, for example, ceramic or metal honeycombs, or filter blocks, such as wall-flow or flow-through filters. Substrates can include ceramic monolith substrates. Substrates can vary in their material composition, size and configuration, cell shape and density, and wall thickness. Suitable substrates are known in the art.

[0021] The term "catalytic region" as used herein can encompass an area on a substrate, typically obtained by drying and / or calcining a washcoat. A "region" can be disposed or supported on the substrate, for example, as a "layer" or "zone." The area or arrangement on the substrate is generally controlled during the process of applying the washcoat to the substrate. A "region" typically has a distinct boundary or edge (i.e., it is possible to distinguish one region from another using conventional analytical techniques).

[0022] Preferably, a "catalyst region" has a substantially uniform composition (i.e., on average, there is no substantial difference in the composition of the washcoat when comparing one portion of the region to another portion of the region). Substantially uniform composition in this context refers to a material (e.g., region) that has a composition difference of 5% or less, usually 2.5% or less, and most commonly 1% or less, when comparing one portion of the region to another portion of the region.

[0023] The first catalytic region is preferably disposed on a substrate. The term "disposed on" in the context of this embodiment can include both having a catalytic region disposed directly on the substrate, i.e., without intervening materials, and / or having a catalytic region disposed indirectly on the substrate, i.e., with intervening materials. If the substrate is porous, the term "disposed on" can also include having a catalytic region disposed therein, for example, within the pores of the substrate, i.e., the catalytic region is disposed thereon and / or therein.

[0024] The term "washcoat" as used herein is well known in the art and typically refers to an adherent coating applied to a substrate during the manufacture of a catalyst. Preferably, the first catalyst region is a washcoat layer.

[0025] The term "support material" as used herein may include any known support material, typically in powder form, that may be used in the field of the present invention to support PGMs. The support material is not particularly limited, and suitable support materials are known in the art. Without wishing to be bound by theory, it is believed that the advantages of the present invention may be independent of the support material. However, preferred support materials are outlined herein.

[0026] In the context of the present invention, "rhodium-loaded support material particles" are support material particles having rhodium loaded thereon. The term "loaded thereon" in this context means that the rhodium, typically in the form of nanoparticles, is in direct contact with and physically and / or chemically bound to the surface of the support material. The term "surface of the support material" may include the surfaces of the pores within the porous support material.

[0027] Preferably, the rhodium is not alloyed with other metals.

[0028] Preferably, the rhodium-loaded support material particles are substantially uniformly dispersed throughout the first catalytic region. In this context, the term "substantially uniformly dispersed" may include that the concentration of rhodium-loaded support material particles in any one subregion of the first catalytic region is substantially the same as the concentration of rhodium-loaded support material particles in any different subregion of the first catalytic region, for example within 5%, within 3%, within 2%, preferably within 1% of the concentration.

[0029] At least a portion of the support material particles are rhodium-loaded support material particles having rhodium loaded thereon at a concentration of 0.001-3.5% by weight based on the weight of the rhodium-loaded support material particles. "Based on the weight of the rhodium-loaded support material particles" means that the weight of rhodium is 0.001-3.5% of the weight of the support material particles (e.g., alumina powder particles). In other words, the term "wt%" relates to the weight of the support material particles, not the total weight of the support material particles and rhodium. Preferably, the rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.3-3.5% by weight, more preferably 0.4-3.0% by weight, even more preferably 0.4-2.0% by weight, even more preferably 0.4-1.8% by weight, even more preferably 0.4-1.6% by weight, even more preferably 0.4-1.5% by weight based on the weight of the rhodium-loaded support material particles. For example, the rhodium-loaded support material particles preferably have rhodium loaded thereon at a concentration of 0.4 to 1.3 weight percent, based on the weight of the rhodium-loaded support material particles. In another preferred embodiment, the rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.4 to 1.8 weight percent, based on the weight of the rhodium-loaded support material particles. It will be understood that the invention may include preferred subranges consisting of combining any of the above endpoints.

[0030] Without being bound by theory, it is believed that maintaining a similar total amount of support material may allow the thermal endurance properties of the support material, such as alumina, to be maintained, as compared to conventional catalyst regions having uniformly distributed low concentrations of rhodium rather than locally concentrated rhodium-loaded support material. It is therefore preferred that at least a portion of the support material particles are unsupported support material particles having essentially no rhodium loaded thereon, preferably no rhodium loaded thereon. In the context of the present invention, "unsupported support material particles" are support material particles having essentially no rhodium loaded thereon, preferably no rhodium loaded thereon.

[0031] The term "essentially free of rhodium" as used herein may include that the unsupported support material particles have rhodium supported thereon at a concentration of less than 0.001% by weight, preferably less than 0.0005% by weight, more preferably less than 0.0001% by weight, based on the weight of the rhodium-supported support material particles. In other words, preferably, the amount of rhodium supported on the unsupported support material particles is negligible. However, it will be understood that in practice, under the high temperature conditions of the intended use of such catalyst articles, small amounts of rhodium may migrate from the rhodium-supported support material particles to the unsupported support material particles. To some extent, this may be unavoidable within technical constraints. Thus, the present invention is intended to include an unavoidable amount of rhodium supported on the unsupported support material particles.

[0032] Additionally, without being bound by theory, it is also believed that the presence of unsupported support material particles can provide a physical barrier and / or create additional distance between rhodium-loaded support material particles, thereby reducing the likelihood of calcination and coalescence of rhodium nanoparticles on different rhodium-loaded support material particles, for example, when the catalyst article is exposed to aging conditions. Such advantages cannot be achieved by simply reducing the total amount of support material in known catalysts while maintaining the same amount of rhodium to obtain a higher rhodium concentration on all support material particles (i.e., having 100% rhodium-loaded support material particles in the first catalyst region, based on the total amount of support material in the first catalyst region).

[0033] Preferably, 5-80% of the support material particles in the first catalyst region are rhodium-loaded support material particles. In other words, 5-80% of the rhodium-loaded support material particles and unloaded support material particles in the first catalyst region are rhodium-loaded support material particles. Percentage in this context is simply a numerical percentage and can be measured by TEM or any other suitable means. More preferably, 7-60%, even more preferably 10-50%, even more preferably 11-45%, even more preferably 13-40%, even more preferably 15-35% of the support material particles in the first catalyst region are rhodium-loaded support material particles. For example, preferably, 10-25% of the support material particles in the first catalyst region are rhodium-loaded support material particles. In another preferred embodiment, 20-35% of the support material particles in the first catalyst region are rhodium-loaded support material particles.

[0034] Without being bound by theory, it is believed that having rhodium supported on only a smaller proportion of the support material particles, as compared to a catalyst article having a similar rhodium loading, but rhodium supported on all of the support material particles, may result in an improved catalyst article having improved light-off performance and resistance to calcination, for reasons hypothesized herein.

[0035] Preferably, the support material particles, i.e. the support material particles of the first catalyst zone, consist essentially of rhodium-loaded and unsupported support material particles, i.e. the rhodium-loaded and unsupported support particles preferably constitute at least 90% by weight of the support particles, more preferably at least 95% by weight, even more preferably at least 97% by weight, even more preferably at least 99% by weight. Most preferably, the support material particles, i.e. the support material particles of the first catalyst zone consist of rhodium-loaded and unsupported support material particles.

[0036] Preferably, the first catalytic region consists of rhodium-loaded support material particles, unloaded support material particles, and optionally a binder.

[0037] The support material particles can be alumina, ceria, zirconia, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium, and mixed oxides or composite oxides thereof. In some embodiments, the support material particles can be an oxygen storage capacity (OSC) material such as cerium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or combinations thereof. In other embodiments, the support material particles can be alumina, lanthanum / alumina composite oxide, or magnesia / alumina composite oxide. Preferably, the support material particles comprise alumina and / or ceria-zirconia mixed oxide. In some preferred embodiments, the support material is alumina. In other preferred embodiments, the support material is ceria-zirconia mixed oxide. Preferably, the alumina and / or ceria-zirconia mixed oxide is doped, the alumina and / or ceria-zirconia mixed oxide being doped with one or more oxides of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, manganese, iron, copper, calcium, barium, strontium, cesium, magnesium, potassium and sodium, preferably with one or more oxides of lanthanum, neodymium and yttrium. Preferably, the dopant is present in the alumina and / or ceria-zirconia mixed oxide in an amount of 0.001% to 20% by weight, and more preferably 0.5% to 10% by weight. The weight percentage may be based on the total weight of the alumina and / or ceria-zirconia mixed oxide.

[0038] Preferably, the support material particles have a D of 0.1 to 25 μm, preferably 0.5 to 5 μm. 90 As used herein, "D 90 The term "contains" up to, but not including, 90% of the total volume of material in a sample. 90 can be measured using any suitable technique, such as TEM.

[0039] Preferably, the support material particles include a ceria-zirconia mixed oxide, and when a cross section of the first catalyst region of the catalyst article is surface-analyzed by FE-EPMA under conditions of a pixel (cross section) size of 0.34 μm×0.34 μm and a measurement pixel (cross section) number of 256×256, the characteristic X-ray intensity (α: cps) of zirconium (Zr) and the characteristic X-ray intensity (β: cps) of rhodium (Rh) are measured for each pixel, and the Pearson correlation coefficient calculated using α and β at each pixel obtained is R Zr / Rh When you specify Zr / Rh The value of R is preferably 0.15 to 0.48. Zr / Rh The value is 0.3 to 0.45.

[0040] The Pearson correlation coefficient (product moment correlation coefficient) is known to those skilled in the art and is calculated based on the results of area analysis by FE-EPMA (field emission electron probe analysis). Zr / Rh When the characteristic X-ray intensity of zirconium (Zr) in the surface analysis by FE-EPMA is the first variable (α) and the characteristic X-ray intensity of rhodium (Rh) is the second variable (β), the formula R Zr / Rh = (covariance) / (standard deviation of α×standard deviation of β). Such calculations are known to those skilled in the art. In other words, zirconium and rhodium are preferably not highly correlated in such catalytic articles. That is, rhodium is preferably not highly dispersed with respect to zirconium in the support material. This may be due to a higher localized concentration of rhodium on certain support material particles, followed by the presence of unsupported support material particles. Thus, this may be a convenient way of characterizing the preferred distribution of rhodium on the support material in the present invention, which may enable the technical advantages mentioned above.

[0041] Preferably, rhodium is present in an amount of 1 to 20 g / ft 2 of the first catalytic region (e.g., particularly when the first catalytic region extends over less than the entire length L of the substrate, e.g., 20 to 80%, 30 to 70%, or 40 to 60% of the entire length L). 3 , more preferably 2 to 18 g / ft 3 , and even more preferably 3 to 16 g / ft 3, and even more preferably 4 to 16 g / ft 3 Alternatively, the rhodium may be present at a loading of 1 to 20 g / ft relative to the first catalytic region (e.g., particularly when the first catalytic region extends over the entire length L of the substrate). 3 , more preferably 2 to 15 g / ft 3 , and even more preferably 3 to 10 g / ft 3 , and even more preferably 4 to 10 g / ft 3 The advantages described herein can be particularly strong at such low loadings. Moreover, such low loadings are consistent with the general desire in the field to reduce PGM usage.

[0042] Preferably, the support material particles are present in a concentration of 0.5 to 3 g / in relative to the first catalyst region. 3 Methods for calculating such loadings are known to those skilled in the art. More preferably, the support material particles are present in a loading of 0.5 to 2 g / in relative to the first catalyst region. 3 , and even more preferably 0.6 to 2 g / in 3 , and even more preferably 0.75 to 2 g / in 3 , and even more preferably 0.8 to 2 g / in 3 In some preferred embodiments, the support material particles are present at a loading of about 1 g / in relative to the first catalyst region. 3 Such loadings may be particularly suitable for obtaining the advantages described herein at the particular rhodium loadings required by the claims.

[0043] Preferably, the first catalytic region further comprises a binder, preferably the binder comprises a further alumina species such as alumina, preferably gamma alumina, more preferably lanthanum doped gamma alumina such as 4% La-Al2O3. The binder is preferably present in an amount of 0.5-2 g / in of the substrate. 3 , more preferably about 1.0 g / in 3 The presence of such additional binder may be particularly suitable, for example, when the first catalytic region is a washcoat layer.

[0044] The catalytic article preferably further comprises one or more additional catalytic regions. The one or more additional catalytic regions may be different from the catalytic region required by the present invention described herein. For example, the one or more additional catalytic regions may be any suitable additional catalytic region known to those skilled in the art. In particular, the one or more additional catalytic regions preferably comprise one or more catalytic regions for three-way catalysis. Preferably, one or more of the additional catalytic regions comprises platinum and / or palladium. The platinum and / or palladium may be supported on a support material. Suitable support materials are known in the art.

[0045] The second catalytic region The catalytic article may further include a second catalytic region.

[0046] The second catalyst region may further comprise a second PGM component, a second oxygen storage capacity (OSC) material, a second alkali metal or alkaline earth metal component, and / or a second inorganic oxide.

[0047] The second PGM component may be selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof, hi some embodiments, the second PGM component may be Pd, Rh, or mixtures thereof.

[0048] The second OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the second OSC material includes ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the second OSC material may further include one or more of dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material may function as a support material for the second PGM component. In some embodiments, the second OSC material includes ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0049] The ceria-zirconia mixed oxide may have a weight ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, more preferably greater than 70:30.Alternatively, the ceria-zirconia mixed oxide may also have a weight ratio of ceria to zirconia less than 50:50, preferably less than 40:60, more preferably less than 30:70.

[0050] The second OSC material (eg, ceria-zirconia mixed oxide) can be 10-90 wt %, preferably 25-75 wt %, more preferably 30-60 wt %, based on the total washcoat loading of the second catalyst region.

[0051] The loading of the second OSC material in the second catalyst region is 2 g / in 3 In some embodiments, the loading of the second OSC material in the second catalytic region can be less than 1.5 g / in 3 Below, 1.2g / in 3 Below, 1g / in 3 Below, 0.8g / in 3 or less than 0.7g / in 3 The following is the result.

[0052] The second alkali or alkaline earth metal is preferably barium, strontium, a mixed oxide or a composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. %, more preferably 3 to 10 wt. %, barium or strontium, based on the total weight of the second catalytic region.

[0053] It is even more preferred that the second alkali or alkaline earth metal is strontium, which, when present, is preferably present in an amount of from 0.1 to 15 wt %, more preferably from 3 to 10 wt %, based on the total weight of the second catalyst region.

[0054] Also, the second alkali metal or alkaline earth metal is preferably a mixed oxide or composite oxide of barium and strontium. Preferably, the mixed oxide or composite oxide of barium and strontium is present in an amount of 0.1 to 15% by weight, more preferably 3 to 10% by weight, based on the total weight of the second catalyst region. More preferably, the second alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0055] Preferably, the barium or strontium is present as BaCO3 or SrCO3. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0056] The second inorganic oxide is preferably an oxide of an element of group 2, group 3, group 4, group 5, group 13, and group 14. The second inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, zirconia, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferably, the second inorganic oxide is alumina, lanthanum-alumina, zirconia, or magnesia / alumina composite oxide. One particularly preferred second inorganic oxide is alumina or lanthanum-alumina.

[0057] The second OSC material and the second inorganic oxide can have a weight ratio of 10:1 or less, preferably 8:1 or 5:1 or less, more preferably 4:1 or 3:1 or less, and most preferably 2:1 or less.

[0058] Alternatively, the second OSC material and the second inorganic oxide can have a weight ratio of 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5, more preferably 4:1 to 1:4 or 3:1 to 1:3, and most preferably 2:1 to 1:2.

[0059] In some embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 2:1 or greater. In further embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 10:1 or greater. In other further embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 20:1 or greater, or 30:1 or greater. In yet other further embodiments, the second OSC material and the second inorganic oxide can have a weight ratio of 40:1 or greater, or 50:1 or greater.

[0060] The total washcoat loading of the second catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2.5g / in 3 Alternatively, the total washcoat loading of the first catalyst region may be between 0.5 and 3.5 g / in 3 and preferably, 0.6 to 3 g / in 3 Or 0.7 to 2.5 g / in 3 It could be.

[0061] The second catalytic region can extend over 100 percent of the axial length L (see, eg, Figures 2a, 2b, and 6a-6c).

[0062] The second catalyst region can extend over 30 to 70 percent of the axial length L. Preferably, it can extend over 40 to 60 percent, more preferably 45 to 55 percent, of the axial length L, and most preferably the total length of the second region and the first region is equal to or greater than the axial length L (see, e.g., Figures 3a-5d and 7a-7l).

[0063] The second catalyst region can overlap the first catalyst region over 0.1 to 99 percent of the axial length L (see, e.g., FIGS. 3c and 3d, where the first catalyst region can be stacked on the second catalyst region, or the second catalyst region can be stacked on the first catalyst region). Alternatively, the total length of the second catalyst region and the first catalyst region can be equal to the axial length L (see, e.g., FIGS. 3a and 3b). In yet another alternative, the total length of the second catalyst region and the first catalyst region can be less than the axial length L, e.g., 95%, 90%, 80%, or 70% or less of the axial length L.

[0064] In some embodiments, the first catalytic region may be supported / deposited directly on the substrate. In certain embodiments, the second catalytic region may be supported / deposited directly on the substrate.

[0065] The third catalytic area The catalytic article may further include a third catalytic region.

[0066] The third catalyst region may further comprise a third PGM component, a third oxygen storage capacity (OSC) material, a third alkali metal or alkaline earth metal component, and / or a third inorganic oxide.

[0067] The third PGM component may be selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof, hi some embodiments, the third PGM component may be Pd, Rh, or mixtures thereof.

[0068] The third OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the third OSC material includes ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the third OSC material may further include one or more of dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the third OSC material may function as a support material for the third PGM component. In some embodiments, the third OSC material includes ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0069] The ceria-zirconia mixed oxide may have a weight ratio of zirconia to ceria of at least 50:50, preferably greater than 60:40, more preferably greater than 75:25, or alternatively, the ceria-zirconia mixed oxide may have a weight ratio of ceria to zirconia less than 50:50, preferably less than 40:60, more preferably less than 25:75.

[0070] The third OSC material (eg, ceria-zirconia mixed oxide) can be 10-90 wt %, preferably 25-75 wt %, more preferably 30-60 wt %, based on the total washcoat loading of the third catalyst region.

[0071] The loading of the third OSC material in the third catalyst region is 1.5 g / in 3 In some embodiments, the loading of the third OSC material in the second catalytic region can be less than 1.2 g / in 3 Below, 1.0g / in 3 Below, 0.9g / in 3 Below, 0.8g / in 3 or less than 0.7g / in 3 The following is the result.

[0072] The total washcoat loading of the third catalyst region was 3.5 g / in 3 Less than 3.0 g / in3 Below 2.5g / in 3 Less than or equal to 2g / in 3 It can be the following:

[0073] The third alkali or alkaline earth metal is preferably barium, strontium, a mixed oxide or a composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. %, more preferably 3 to 10 wt. %, barium or strontium, based on the total weight of the third catalytic region.

[0074] It is even more preferred that the third alkali or alkaline earth metal is strontium, which, when present, is preferably present in an amount of from 0.1 to 15 wt %, more preferably from 3 to 10 wt %, based on the total weight of the third catalytic region.

[0075] Also, the third alkali metal or alkaline earth metal is preferably a mixed oxide or composite oxide of barium and strontium. Preferably, the mixed oxide or composite oxide of barium and strontium is present in an amount of 0.1 to 15% by weight, more preferably 3 to 10% by weight, based on the total weight of the third catalytic region. More preferably, the third alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0076] Preferably, the barium or strontium is present as BaCO3 or SrCO3. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0077] The third inorganic oxide is preferably an oxide of an element of group 2, group 3, group 4, group 5, group 13, and group 14. The third inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, zirconia, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferably, the third inorganic oxide is alumina, lanthanum-alumina, zirconia, or magnesia / alumina composite oxide. One particularly preferred third inorganic oxide is alumina or lanthanum-alumina.

[0078] The third OSC material and the third inorganic oxide can have a weight ratio of 10:1 or less, preferably 8:1 or 5:1 or less, more preferably 4:1 or 3:1 or less, and most preferably 2:1 or less.

[0079] Alternatively, the third OSC material and the third inorganic oxide can have a weight ratio of 10:1 to 1:10, preferably 8:1 to 1:8 or 5:1 to 1:5, more preferably 4:1 to 1:4 or 3:1 to 1:3, and most preferably 2:1 to 1:2.

[0080] In some embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 2:1 or greater. In further embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 10:1 or greater. In other further embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 20:1 or greater, or 30:1 or greater. In yet other further embodiments, the third OSC material and the third inorganic oxide can have a weight ratio of 40:1 or greater, or 50:1 or greater.

[0081] The third catalytic region can extend over 100 percent of the axial length L (see, for example, Figures 4a-4d and 6a-6c).

[0082] The third catalytic region can be less than the axial length L, for example, less than or equal to 95%, 90%, 80%, or 70% of the axial length L (see, for example, Figures 5a-5d and 7g-7l).

[0083] The second catalyst region can overlap the first catalyst region over 0.1 to 99 percent of the axial length L (see, e.g., Figures 7a-7l), the first catalyst region can be stacked on the second catalyst region, or the second catalyst region can be stacked on the first catalyst region). Alternatively, either the second region or the first region can extend over 30 to 70 percent of the axial length L. Preferably, it can extend over 40 to 60 percent, more preferably 45 to 55 percent, of the axial length L, and most preferably the total length of the second region and the first region is equal to or less than the axial length L (see, e.g., Figures 4a-4d).

[0084] Preferably, the catalytic article comprises a substrate, a first catalytic region as described herein, and a second catalytic region. In other words, the catalytic article preferably further comprises a second catalytic region. The second catalytic region preferably has a composition different from that of the first catalytic region. Preferably, the second catalytic region comprises a PGM supported on a support material, and optionally one or more of a binder and a promoter. The PGM preferably comprises palladium. The support material preferably comprises alumina and / or a ceria-zirconia mixed oxide as described herein. The binder preferably comprises alumina. The promoter preferably comprises barium.

[0085] The first catalytic region is preferably disposed on the second catalytic region, preferably directly on the second catalytic region. For example, the second catalytic region is preferably disposed directly on the substrate, and the first catalytic region is disposed directly on the second catalytic region. In these embodiments, the first catalytic region and the second catalytic region are preferably washcoat layers, each of which is preferably applied over the entire length of the substrate.

[0086] In another preferred embodiment, the catalytic article comprises a substrate and a first catalytic region as described herein, a second catalytic region, and a third catalytic region. In other words, the catalytic article preferably further comprises a second catalytic region and a third catalytic region. The second catalytic region and the third catalytic region preferably have a composition different from that of the first catalytic region. Furthermore, the second catalytic region preferably has a composition different from that of the third catalytic region.

[0087] Preferably, the second catalytic region in this embodiment is as described in another preferred embodiment above. However, in this embodiment, the first catalytic region and the third catalytic region are preferably arranged on the second catalytic region in the form of a zone, preferably directly on the second catalytic region. In particular, the second catalytic region is preferably arranged directly on the substrate, and the first catalytic region and the third catalytic region are preferably arranged directly on the second catalytic region, respectively. The second catalytic region is preferably arranged over the entire length of the substrate, and the first catalytic region and the third catalytic region are preferably arranged on the second catalytic region in the form of a zone. In these preferred embodiments, the first catalytic region, the second catalytic region and the third catalytic region are preferably in the form of a washcoat layer.

[0088] In these preferred embodiments, the first catalyst region is preferably in the rear zone, i.e., located at the intended outlet end of the catalyst article, and the third catalyst region is preferably in the front zone, i.e., located at the intended inlet end of the catalyst article.

[0089] The third catalytic zone preferably comprises rhodium supported on a support material. The rhodium is preferably arranged on all the support material particles, i.e. as in a standard catalytic zone. The support material is preferably alumina and / or a ceria-zirconia mixed oxide as described herein. If the support material of the rhodium-supported support material particles in the first catalytic zone comprises alumina, the support material of the third catalytic zone preferably comprises ceria-zirconia mixed oxide. If the support material of the rhodium-supported support material particles in the first catalytic zone comprises ceria-zirconia mixed oxide, the support material of the third catalytic zone preferably comprises alumina.

[0090] When the first and third catalytic regions are zoned, the two zones together are preferably applied over the entire length of the substrate, which is preferably the entire length of the second catalytic region.

[0091] Such a preferred arrangement of the first catalytic region, the second catalytic region, and optionally the third catalytic region surprisingly results in improved NO emission, particularly during cold start-up conditions. x and lower light-off temperature. Improved CO and / or THC reduction may also be observed. Improved aged OSC characteristics may also be observed.

[0092] As used herein, the term "zone" refers to a region having a length that is less than the entire length of the substrate, such as a length that is 75% or less of the entire length of the substrate. A "zone" typically has a length that is at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).

[0093] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0094] Any reference herein to a "zone disposed at the inlet end of a substrate" refers to a zone disposed on or supported by a substrate, which is closer to the inlet end of the substrate than to the outlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the inlet end of the substrate than to the outlet end of the substrate. Similarly, any reference herein to a "zone disposed at the outlet end of a substrate" refers to a zone disposed on or supported by a substrate, which is closer to the outlet end of the substrate than to the inlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the outlet end of the substrate than to the inlet end of the substrate.

[0095] When the substrate is a wall-flow filter, generally any reference to "a zone disposed at the inlet end of the substrate" refers to a zone disposed on or supported by the substrate, (a) a zone that is closer to the inlet end (e.g., an open end) of an inlet channel of the substrate than to the closed end (e.g., a blocked or plugged end) of the inlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an outlet channel of a substrate than to the outlet end (e.g., open end) of the outlet channel.

[0096] Thus, the midpoint of the zone (i.e., the point at half its length) is (a) closer to the inlet end of the inlet channel of the substrate than to the closed end of the inlet channel, and / or (b) closer to the closed end of the outlet channel of the substrate than to the outlet end of the outlet channel.

[0097] Similarly, where the substrate is a wall-flow filter, any reference to a "zone disposed at the outlet end of the substrate" refers to a zone disposed on or carried by the substrate, (a) a zone that is closer to the outlet end (e.g., an open end) of the outlet channel of the substrate than to the closed end (e.g., a blocked or plugged end) of the outlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an inlet channel of a substrate than to the inlet end (e.g., open end) of the inlet channel.

[0098] Thus, the midpoint of the zone (i.e., the point at half its length) is (a) closer to the outlet end of the outlet channel of the substrate than to the closed end of the outlet channel, and / or (b) closer to the closed end of the inlet channel of the substrate than to the inlet end of the inlet channel.

[0099] If a washcoat is present on the wall of a wall-flow filter (ie, the zone is within the wall), the zone may satisfy both (a) and (b).

[0100] Preferably, the first catalytic region is a single washcoat layer disposed on the substrate. The single washcoat layer may be coated along the entire length of the substrate or over only a portion thereof. For example, preferably, the single washcoat layer is coated from one end of the substrate (e.g., the inlet end or the outlet end with respect to the direction of intended use in the exhaust system), and preferably coats less than 90%, less than 80%, less than 70%, less than 60%, less than 50%, less than 40%, less than 30%, less than 20%, or less than 10% of the substrate's length. Preferably, the single washcoat layer is coated directly on the substrate. In another preferred embodiment, there are one or more intervening washcoat layers located between the single washcoat layer of the present invention and the substrate. The one or more intervening washcoat layers in this embodiment may be any suitable washcoat layer known to those skilled in the art. Preferably, the one or more intervening washcoat layers may be suitable for three-way catalysis. In other words, the catalytic article preferably further comprises one or more additional washcoat layers.

[0101] Preferably, the first catalytic region further comprises platinum and / or palladium. The platinum and / or palladium may be supported on a support material. Suitable support materials are known in the art.

[0102] Preferably, the catalyst article is for three-way catalysis, in other words, the catalyst article is preferably a TWC.

[0103] Base material Preferably, the substrate is a flow-through monolith. Alternatively, the substrate can be a wall-flow filter.

[0104] The flow-through monolith substrate has a first surface and a second surface defining a longitudinal direction therebetween. The flow-through monolith substrate has a plurality of channels extending between the first surface and the second surface. The plurality of channels extend longitudinally and provide a plurality of interior surfaces (e.g., surfaces of walls defining each channel). Each of the plurality of channels has an opening at the first surface and an opening at the second surface. For the avoidance of doubt, the flow-through monolith substrate is not a wall-flow filter.

[0105] The first surface is typically at an inlet end of the substrate and the second surface is at an outlet end of the substrate.

[0106] The channels may be of constant width, and each of the multiple channels may have a uniform channel width.

[0107] Preferably, in a plane perpendicular to the longitudinal direction, the monolith substrate has 300 to 900 channels per square inch, preferably 400 to 800 channels per square inch. For example, on the first face, the density of open first channels and closed second channels is 600 to 700 channels per square inch. The channels may have cross-sections that are rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shapes.

[0108] The monolith substrate acts as a support to hold the catalytic material. Suitable materials for forming the monolith substrate include ceramic-like materials such as cordierite, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica magnesia or zirconium silicate, or porous refractory metals. Such materials and their use in the manufacture of porous monolith substrates are well known in the art.

[0109] It should be noted that the flow-through monolith substrates described herein are unitary components (i.e., a single brick). Nevertheless, when forming an emission treatment system, the substrates used may be formed by bonding together multiple channels, or by bonding together multiple smaller substrates as described herein. Such techniques, along with suitable casings and configurations of emission treatment systems, are well known in the art.

[0110] In embodiments in which the catalytic article of the present invention includes a ceramic substrate, the ceramic substrate may be made of any suitable refractory material, such as alumina, silica, ceria, zirconia, magnesia, zeolites, silicon nitride, silicon carbide, zirconium silicate, magnesium silicate, aluminosilicates and metalloaluminosilicates (such as cordierite and spodumene), or mixtures or mixed oxides of any two or more thereof. Cordierite, magnesium aluminosilicate, and silicon carbide are particularly preferred.

[0111] In embodiments in which the catalytic article of the present invention includes a metal substrate, the metal substrate may be made of any suitable metal, particularly heat-resistant metals and metal alloys such as titanium and stainless steel, and ferritic alloys containing iron, nickel, chromium, and / or aluminum in addition to other trace metals.

[0112] Preferably, the substrate comprises a wall-flow filter substrate. In another preferred embodiment, the substrate comprises a flow-through substrate. The substrate may be a "blank", i.e., a substrate that has not been washcoated. Alternatively, the substrate may have one or more washcoats already supported on top. In such a situation, the final catalyst article may include multiple layers of different washcoats. The substrate preferably comprises cordierite. However, the composition of the substrate is not particularly limited.

[0113] In a further aspect, the present invention provides a method of making a catalyst article, the method comprising: providing rhodium-loaded support material particles having rhodium loaded thereon in a concentration of 0.001 to 3.5 weight percent based on the weight of the rhodium-loaded support material particles; providing unsupported support material particles having essentially no rhodium supported thereon, preferably having no rhodium supported thereon; forming a washcoat comprising rhodium-loaded and unloaded support material particles; Coating a substrate with a washcoat to provide a catalytic article, the washcoat comprising a catalyst and a rhodium content of up to 20 g / ft 2 of the substrate. 3 and wherein the catalyst is present in a loading amount of

[0114] Unless otherwise stated, the preferred features and embodiments relating to the first aspect, in particular any preferred features of the rhodium-loaded support material particles, the unloaded support material particles, the first catalytic region and / or the further catalytic region, the support material particles generally, the substrate, and the catalyst article as a whole, apply equally to this aspect.

[0115] Providing rhodium-supported support material particles having rhodium supported thereon may include providing support material particles and supporting rhodium thereon. Such methods are known in the art and any suitable technique may be used.

[0116] Forming the washcoat comprising rhodium-loaded and unloaded carrier material particles preferably comprises combining the rhodium-loaded and unloaded carrier material particles with water in any order to form a slurry. The term "slurry" as used herein can include a liquid containing insoluble materials, such as insoluble particles. The slurry is typically stirred, more typically for at least 10 minutes, more typically for at least 30 minutes, and even more typically for at least 1 hour. Such washcoat preparation methods are known in the art, and the technique is not particularly limited.

[0117] Coating the substrate with the washcoat can be done using techniques known in the art. Typically, the washcoat is injected into the inlet of the substrate using a specific forming tool in a predetermined amount, thereby coating the substrate with the washcoat. Alternatively, coating the substrate with the washcoat can be done by immersing the substrate in the washcoat. Subsequent vacuum and / or air knife and / or drying steps can be used during the coating step. If the substrate is a filter block, the washcoat can be coated on the filter walls, in the filter walls (if porous), or both.

[0118] By coating the substrate with a washcoat, rhodium can be applied at up to 20g / ft2 of substrate. 3 It is essential that the resulting catalyst article has a rhodium loading of about 100%. It is readily within the skill of the art to plan the relative amounts of each component (e.g., washcoat and substrate) used in the process to achieve such a desired rhodium loading.

[0119] Preferably, the rhodium-loaded support material particles have rhodium loaded thereon in a concentration of from 0.3 to 3.5 weight percent based on the weight of the rhodium-loaded support material particles.

[0120] The method preferably further comprises adding a binder to the washcoat prior to coating the substrate with the washcoat. Preferred binders are described elsewhere herein. Preferably, the method further comprises adding one or more of an acid, a base, a thickener, and a reducing agent to the washcoat prior to coating the substrate with the washcoat.

[0121] Preferably, providing rhodium-loaded support material particles comprises loading rhodium onto the support material particles using incipient wetness impregnation, a technique well known to those skilled in the art, who will be able to carry out a suitable incipient wetness impregnation method without further instruction.

[0122] Preferably, providing the rhodium-loaded support material particles further comprises drying and calcining the rhodium-loaded support material particles, the drying and calcining steps preferably occurring prior to forming the washcoat.

[0123] After coating the substrate with the washcoat, the resulting catalyst article (or coated substrate) is preferably dried and / or calcined.

[0124] Preferably, the catalyst article of this embodiment is according to the first embodiment.

[0125] In a further aspect, the present invention provides a catalyst article obtained or obtainable by the method of the above aspect.

[0126] Surprisingly, when used in an emission treatment system, the catalyst articles of the present embodiment having locally higher concentrations of rhodium as defined herein, but still with a lower overall loading of rhodium to reduce PGM usage, exhibit significantly improved light-off performance {i.e., lower light-off temperature, lower specific target species [NO x50% conversion of rhodium, CO, or total hydrocarbons (THC). Furthermore, having a locally higher concentration of rhodium while maintaining a low total rhodium loading may result in a larger particle size of rhodium on the rhodium-loaded support material particles, which may surprisingly result in a catalyst article in which the rhodium particles are more resistant to calcination, oxidation, and migration compared to other low rhodium-loaded catalyst articles. However, it has also been found that over-concentrating rhodium on the rhodium-loaded support material particles may result in reduced catalytic activity. Thus, there may be an optimal local rhodium concentration for a particular low total loading of rhodium.

[0127] The above effect may be particularly beneficial for catalyst articles having a low total rhodium loading, but may not be observed in catalyst articles having a higher total rhodium loading. Without being bound by theory, it is believed that this may be because when the total rhodium loading on the support is already high, the local concentration of rhodium on each support material particle is already high, and therefore there may be no need to locally concentrate rhodium in parts of the support material.

[0128] In a further aspect, the present invention provides an emission treatment system comprising the catalytic article described herein. Preferably, the emission treatment system is for a gasoline engine. Preferably, the gasoline engine operates under stoichiometric conditions.

[0129] In a further aspect, the present invention provides a method of treating an exhaust gas, the method comprising providing a catalytic article as described herein and contacting the catalytic article with an exhaust gas. Preferably, the exhaust gas is from a gasoline engine. Preferably, the gasoline engine operates under stoichiometric conditions.

[0130] The invention will now be described with reference to the following non-limiting examples.

[0131] Manufacturing of catalytic articles A number of catalyst articles were prepared according to the following examples.

[0132] Reference catalyst 1 1. Rh-Ceria Zirconia mixed oxide (CZO) preloaded powder was prepared by incipient wetness impregnation of CZO with Rh nitrate solution to obtain a Rh concentration of 0.23 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground.

[0133] 2.1.0g / in 3 CZO and 4g / ft 3 Calculated amounts of milled Rh CZO preloaded powder were slurred for each of the Rh targets.

[0134] 3. Blend the slurry with 4% La-Al2O3 slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0135] 4. The solids content was adjusted to thicken the washcoat.

[0136] 5. First, the substrate is coated with washcoat (4) from one side, aiming at 50%-55% dose length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% dose length, followed by drying and calcination again.

[0137] Catalyst 1 of the present invention 1. Rh-ceria-zirconia mixed oxide (CZO) preloaded powder was prepared by incipient wetness impregnation of CZO with Rh nitrate solution to obtain a Rh concentration of 0.75 wt %. The powder was dried at 80 °C overnight, calcined at 500 °C for 2 h, and subsequently milled.

[0138] 2.0.3g / in 3 CZO and 4g / ft 3 Calculated amounts of ground Rh CZO pre-immobilized powder were slurried to target Rh of each.

[0139] 3.0.7g / in 3 An additional amount of CZO slurry was added to the reference catalyst 1 (1.0 g / in 3 In this washcoat, Rh is locally concentrated on approximately 31% of the CZO support, while the remainder of the CZO support is Rh-free, and this is continuously mixed.

[0140] 4. Blend the slurry with 4% La-Al2O3 slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0141] 5. The solids content was adjusted to thicken the washcoat.

[0142] 6. First, the substrate is coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0143] Catalyst 2 of the present invention 1. Rh-ceria-zirconia mixed oxide (CZO) preloaded powder was prepared by incipient wetness impregnation of CZO with Rh nitrate solution to obtain a Rh concentration of 1.5 wt %. The powder was dried at 80 °C overnight, calcined at 500 °C for 2 h, and subsequently ground.

[0144] 2.0.15g / in 3 CZO and 4g / ft 3 Calculated amounts of ground Rh CZO pre-immobilized powder were slurried to target Rh of each.

[0145] 3.0.85g / in 3 An additional amount of CZO slurry was added to the reference catalyst 1 (1.0 g / in 3 In this washcoat, Rh is locally concentrated on approximately 15% of the CZO support, while the remainder of the CZO support is Rh-free, and this is continuously mixed.

[0146] 4. Blend the slurry with 4% La-Al2O3 slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0147] 5. The solids content was adjusted to thicken the washcoat.

[0148] 6. First, the substrate is coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0149] Catalyst 3 of the present invention 1. Rh-ceria-zirconia mixed oxide (CZO) preloaded powder was prepared by incipient wetness impregnation of CZO with Rh nitrate solution to obtain a Rh concentration of 3 wt %. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently milled.

[0150] 2.0.08g / in 3 CZO and 4g / ft 3 Calculated amounts of ground Rh CZO pre-immobilized powder were slurried to target Rh of each.

[0151] 3.0.92g / in 3 An additional amount of CZO slurry was added to the reference catalyst 1 (1.0 g / in 3 In this washcoat, Rh is locally concentrated on approximately 8% of the CZO support, while the remainder of the CZO support is Rh-free, and this is continuously mixed.

[0152] 4. Blend the slurry with 4% La-Al2O3 slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0153] 5. The solids content was adjusted to thicken the washcoat.

[0154] 6. First, the substrate is coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0155] Reference catalyst 2 1. Rh La-stabilized alumina preloaded powder was prepared by incipient wetness impregnation of La-stabilized alumina (La-Al2O3) with Rh nitrate solution to obtain a Rh concentration of 0.2 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground.

[0156] 2.1.0g / in 3 of La-Al2O3 and 4g / ft 3 Calculated amounts of ground RhLa-Al2O3 pre-fixed powder were slurried to target Rh of each.

[0157] 3. Blend the slurry with ceria-zirconia mixed oxide (CZO) slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0158] 4. The solids content was adjusted to thicken the washcoat.

[0159] 5. First, the substrate is coated with washcoat (4) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0160] Catalyst 4 of the present invention 1. Rh La-stabilized alumina preloaded powder was prepared by incipient wetness impregnation of La-stabilized alumina (La-Al2O3) with Rh nitrate solution to obtain a Rh concentration of 0.75 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground.

[0161] 2.0.3g / in 3 of La-Al2O3 and 4g / ft 3 Calculated amounts of ground RhLa-Al2O3 pre-fixed powder were slurried to target Rh of each.

[0162] 3.0.7g / in 3 An additional amount of La-AlO slurry was added to the reference catalyst 2 (1.0 g / in 3 In this washcoat, Rh was locally concentrated on approximately 31% of the La-Al2O3 support, while the remainder of the La-Al2O3 support was free of Rh, and was mixed continuously.

[0163] 4. Blend the slurry with ceria-zirconia mixed oxide (CZO) slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0164] 5. The solids content was adjusted to thicken the washcoat.

[0165] 6. First, the substrate is coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0166] Catalyst 5 of the present invention 1. Rh La-stabilized alumina preloaded powder was prepared by incipient wetness impregnation of La-stabilized alumina (La-Al2O3) with Rh nitrate solution to obtain a Rh concentration of 1.5 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground using a pestle and mortar.

[0167] 2.0.15g / in 3 of La-Al2O3 and 4g / ft 3Calculated amounts of ground RhLa-Al2O3 pre-fixed powder were slurried to target Rh of each.

[0168] 3.0.85g / in 3 An additional amount of La-AlO slurry was added to the reference catalyst 2 (1.0 g / in 3 In this washcoat, Rh was locally concentrated on approximately 15% of the La-Al2O3 support, while the remainder of the La-Al2O3 support was free of Rh, and this was continuously mixed.

[0169] 4. Blend the slurry with ceria-zirconia mixed oxide (CZO) slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0170] 5. The solids content was adjusted to thicken the washcoat.

[0171] 6. First, the substrate is coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0172] Catalyst 6 of the present invention 1. Rh La-stabilized alumina preloaded powder was prepared by incipient wetness impregnation of La-stabilized alumina (La-Al2O3) with Rh nitrate solution to obtain a Rh concentration of 3 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground.

[0173] 2.0.08g / in 3 of La-Al2O3 and 4g / ft 3 Calculated amounts of ground RhLa-Al2O3 pre-fixed powder were slurried to target Rh of each.

[0174] 3.0.92g / in 3An additional amount of La-AlO slurry was added to the reference catalyst 2 (1.0 g / in 3 In this washcoat, Rh is locally concentrated on approximately 8% of the La-Al2O3 support, while the remainder of the La-Al2O3 support is free of Rh, and this is continuously mixed.

[0175] 4. Blend the slurry with ceria-zirconia mixed oxide (CZO) slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0176] 5. The solids content was adjusted to thicken the washcoat.

[0177] 6. First, the substrate is coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0178] Reference catalyst 3 1. Rh La-stabilized alumina preloaded powder was prepared by incipient wetness impregnation of La-stabilized alumina (La-Al2O3) with Rh nitrate solution to obtain a Rh concentration of 0.5 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground.

[0179] 2.1.3g / in 3 of La-Al2O3 and 10g / ft 3 Calculated amounts of ground RhLa-Al2O3 pre-fixed powder were slurried to target Rh of each.

[0180] 3. Blend the slurry with ceria-zirconia mixed oxide (CZO) slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0181] 4. The solids content was adjusted to thicken the washcoat.

[0182] 5. First, the substrate is coated with washcoat (4) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0183] Catalyst 7 of the present invention 1. Rh La-stabilized alumina preloaded powder was prepared by incipient wetness impregnation of La-stabilized alumina (La-Al2O3) with Rh nitrate solution to obtain a Rh concentration of 0.9 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground.

[0184] 2.0.6g / in 3 of La-Al2O3 and 10g / ft 3 Calculated amounts of ground RhLa-Al2O3 pre-fixed powder were slurried to target Rh of each.

[0185] 3.0.6g / in 3 An additional amount of La-AlO slurry was added to the total La-AlO of reference catalyst 3 (1.3 g / in 3 In this washcoat, Rh is locally concentrated on approximately 50% of the La-Al2O3 support, while the remainder of the La-Al2O3 support is free of Rh, and this is continuously mixed.

[0186] 4. Blend the slurry with ceria-zirconia mixed oxide (CZO) slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0187] 5. The solids content was adjusted to thicken the washcoat.

[0188] 6. First, the substrate is coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It is dried with hot air until more than 80% of the moisture is removed. Then, the other side of the substrate is coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0189] Catalyst 8 of the present invention 1. Rh La-stabilized alumina preloaded powder was prepared by incipient wetness impregnation of La-stabilized alumina (La-Al2O3) with Rh nitrate solution to obtain a Rh concentration of 1.9 wt%. The powder was dried at 80°C overnight, calcined at 500°C for 2 h, and subsequently ground using a pestle and mortar.

[0190] 2.0.3g / in 3 of La-Al2O3 and 10g / ft 3 Calculated amounts of ground RhLa-Al2O3 pre-fixed powder were slurried to target Rh of each.

[0191] 3.1.0g / in 3 An additional amount of La-AlO slurry was added to the total La-AlO of reference catalyst 3 (1.3 g / in 3 In this washcoat, Rh is locally concentrated on approximately 25% of the La-Al2O3 support, while the remainder of the La-Al2O3 support is free of Rh, and this is continuously mixed.

[0192] 4. Blend the slurry with ceria-zirconia mixed oxide (CZO) slurry and add 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0193] 5. The solids content was adjusted to thicken the washcoat.

[0194] 6. First, the substrate was coated with washcoat (5) from one side, aiming at 50%-55% of the coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side of the substrate was coated, aiming at 50%-55% of the coating length, followed by drying and calcination.

[0195] Reference catalyst 4 The bottom layer washcoat was prepared by the following.

[0196] 1. Grind and prepare a slurry containing 4% La2O3 doped alumina.

[0197] 2. The mixture was ground to prepare a slurry containing ceria and zirconia mixed oxide (CZO).

[0198] 3. The two slurries were blended together.

[0199] 4. Add barium hydroxide and palladium nitrate to the slurry (3).

[0200] 5. Adjust the solids content of the wash coat (4) and thicken it with a rheology modifier.

[0201] 6. The final composition of the bottom layer washcoat is La-Al2O3 1.0 g / in 3 , ceria-zirconia composite 1.0g / in 3 , Ba element 400g / ft 3 , and Pd element 149g / ft 3 Contains:

[0202] 7. First, the substrate was coated with washcoat (6) from one side, aiming at 50%-55% of the coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side of the substrate was coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0203] The top layer washcoat was prepared by the following.

[0204] 1. La-stabilized alumina (La-Al2O3) was pulverized and a slurry containing this was prepared.

[0205] 2.1.0g / in 3 of La-Al2O3 and 6g / ft 3 A calculated amount of rhodium nitrate solution was added to the slurry (1) for each of the Rh targets.

[0206] 3. The pH of slurry (2) was increased to 6-7 with ammonia to obtain a local Rh concentration of 0.35%.

[0207] 4. Blend the slurry (3) with pre-milled ceria-zirconia mixed oxide (CZO) slurry to a concentration of 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0208] 5. The solid content of the washcoat (4) was adjusted with a rheology modifier to increase viscosity.

[0209] 6. The final composition of the top layer washcoat is 1.0 g / in of 4% La2O3 doped alumina. 3 , ceria-zirconia composite 1.0g / in 3 , and Rh element 6g / ft 3 Contains:

[0210] 7. First, the washcoat (5) was applied to the bottom layer of coated bricks from one side, aiming at 50%-55% coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side was coated, aiming at 50%-55% coating length, followed by drying and calcination again to obtain the finished catalyst article.

[0211] Catalyst 9 of the present invention (see, for example, FIG. 2b). The bottom layer washcoat (second catalyst region in FIG. 2b) was prepared and coated in the same manner as the bottom layer of Reference Catalyst 4.

[0212] The top layer washcoat (first catalyst region in FIG. 2b) was prepared by:

[0213] 1. La-stabilized alumina (La-Al2O3) was pulverized and a slurry containing this was prepared.

[0214] 2.0.35g / in 3 of La-Al2O3 and 6g / ft 3 A calculated amount of rhodium nitrate solution was added to the slurry (1) for each of the Rh targets.

[0215] 3. The pH of the slurry (2) was increased to 6-7 with ammonia.

[0216] 4.0.65g / in 3 An additional amount of La-AlO slurry was added to the total La-AlO of reference catalyst 4 (1.0 g / in 3 In this washcoat, Rh was locally concentrated on approximately 35% of the La-Al2O3 support at a concentration of 1%, while the remainder of the La-Al2O3 support was free of Rh and was continuously mixed.

[0217] 5. Blend the slurry (4) with pre-milled ceria-zirconia mixed oxide (CZO) slurry to a concentration of 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0218] 6. The solid content of the washcoat (5) was adjusted with a rheology modifier to increase viscosity.

[0219] 7. The final composition of the top layer washcoat was the same as that of Reference Catalyst 4, 1.0 g / in of 4% La2O3-doped alumina. 3 , ceria-zirconia composite 1.0g / in 3 , and Rh element 6g / ft 3 Contains:

[0220] 8. First, the washcoat (7) was applied to the bottom layer of coated bricks from one side, targeting 50%-55% coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side was coated, targeting 50%-55% coating length, followed by drying and calcination again to obtain the finished catalyst article.

[0221] A catalyst 10 of the present invention having a zone configuration (see, for example, FIG. 4d). The bottom layer washcoat (third catalyst region in FIG. 4d) was prepared and coated in the same manner as the bottom layer of Reference Catalyst 4.

[0222] The upper layer of the catalyst 10 of the present invention has a zoned configuration.

[0223] The inlet zone washcoat (second catalyst region in Figure 4d) was prepared in the same manner as the top layer washcoat of reference catalyst 4. The washcoat was then applied to the bottom layer coated bricks, aiming for a coating length of 50%-55% from the inlet side. It was then dried with hot air until more than 80% of the moisture was removed.

[0224] The outlet zone washcoat (first catalyst region in Figure 4d) was prepared in the same manner as the top layer washcoat of inventive catalyst 9. The washcoat was then applied to the bottom layer coated bricks, targeting a coating length of 50%-55% from the outlet side. It was dried with hot air until more than 80% of the moisture was removed. Finally, the bricks were calcined to obtain the finished catalyst article.

[0225] A catalyst 11 of the present invention having a zone configuration (see, for example, FIG. 4d). The bottom layer washcoat (third catalyst region in FIG. 4d) was prepared and coated in the same manner as the bottom layer of Reference Catalyst 4.

[0226] The upper layer of the catalyst 11 of the present invention has a zone configuration.

[0227] The inlet zone washcoat (second catalyst region in Figure 4d) was prepared in the same manner as the top layer washcoat of reference catalyst 4. The washcoat was then applied to the bottom layer coated bricks, aiming for a coating length of 50%-55% from the inlet side. It was then dried with hot air until more than 80% of the moisture was removed.

[0228] The exit zone washcoat (first catalyst region in FIG. 4d) was prepared as follows.

[0229] 1. The material was ground to prepare a slurry containing ceria-zirconia mixed oxide (CZO).

[0230] 2.0.35g / in 3 CZO and 6g / ft 3 A calculated amount of rhodium nitrate solution was added to the slurry (1) for each of the Rh targets.

[0231] 3. The pH of the slurry (2) was increased to 6-7 with ammonia.

[0232] 4.0.65g / in 3 An additional amount of ceria-zirconia mixed oxide (CZO) slurry was added to the control catalyst 4 (1.0 g / in 3 In this washcoat, Rh was locally concentrated at a concentration of 1% on approximately 35% of the ceria-zirconia mixed oxide (CZO) support, while the remainder of the CZO support was free of Rh, and this was mixed continuously.

[0233] 5. Slurry (4) was blended with the pre-milled La-Al2O3 slurry to obtain a 1.0 g / in 3 The target loading amount was 1.0 μg / kg. This was mixed continuously.

[0234] 6. The solid content of the washcoat (5) was adjusted with a rheology modifier to increase viscosity.

[0235] 7. The final composition of the top layer washcoat was the same as that of Reference Catalyst 4, 1.0 g / in of 4% La2O3-doped alumina. 3 , ceria-zirconia composite 1.0 g / in 3 , and Rh element 6g / ft 3 Contains:

[0236] 8. Next, a washcoat (7) was applied to the bottom layer of coated bricks, aiming for 50%-55% of the coating length from the outlet side. It was dried with hot air until more than 80% of the moisture was removed. Finally, the bricks were calcined to obtain the finished catalyst article.

[0237] Reference catalyst 5 The bottom layer washcoat was prepared by the following.

[0238] Alumina doped with 1.4% La2O3 was ground and a slurry containing this was prepared.

[0239] 2. Ceria and zirconia mixed oxide (CZO) was pulverized and a slurry containing it was prepared.

[0240] 3. The two slurries were blended together.

[0241] 4. Add barium hydroxide and palladium nitrate to the slurry (3).

[0242] 5. Adjust the solids content of the wash coat (4) and thicken it with a rheology modifier.

[0243] 6. The final composition of the bottom layer washcoat is La-Al2O3 0.9 g / in 3 , ceria-zirconia composite 0.9g / in 3 , Ba element 300g / ft 3 , and Pd element 36g / ft 3 Contains:

[0244] 7. First, the substrate was coated with washcoat (6) from one side, aiming at 50%-55% of the coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side of the substrate was coated, aiming at 50%-55% of the coating length, followed by drying and calcination again.

[0245] The top layer washcoat was prepared by the following.

[0246] 1. La-stabilized alumina (La-Al2O3) was pulverized and a slurry containing this was prepared.

[0247] 2. Ceria and zirconia mixed oxide (CZO) was pulverized and a slurry containing it was prepared.

[0248] 3. Blend the two slurries together, keeping the weight ratio of La-Al2O3 to CZO at 1:3.

[0249] 4.0.4g / in 3 of La-Al2O3, 1.1g / in 3 CZO, and 4g / ft 3 A calculated amount of rhodium nitrate solution was added to the slurry (3) to target Rh of each.

[0250] 5. The pH of the slurry (4) was increased to 6-7 with ammonia to obtain a local Rh concentration of 0.15%.

[0251] 6. The solid content of the washcoat (5) was adjusted with a rheology modifier to increase viscosity.

[0252] 7. The final composition of the top layer washcoat is 1.0 g / in of 4% La2O3 doped alumina. 3 , ceria-zirconia composite 1.0g / in 3 , and Rh element 6g / ft 3 Contains:

[0253] 8. First, the washcoat (5) was applied to the bottom layer of coated bricks from one side, aiming at 50%-55% coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side was coated, aiming at 50%-55% coating length, followed by drying and calcination again to obtain the finished catalyst article.

[0254] Catalyst 12 of the present invention (see, for example, FIG. 2b). The bottom layer washcoat (second catalyst region in FIG. 2b) was prepared and coated in the same manner as the bottom layer of Reference Catalyst 5.

[0255] The top layer washcoat (first catalyst region in FIG. 2b) was prepared by:

[0256] 1. La-stabilized alumina (La-Al2O3) was pulverized and a slurry containing this was prepared.

[0257] 2. Ceria and zirconia mixed oxide (CZO) was pulverized and a slurry containing it was prepared.

[0258] 3. Blend the two slurries together, keeping the weight ratio of La-Al2O3 to CZO at 1:3.

[0259] 4.0.2g / in 3 La-Al2O3, 0.6g / in 3 CZO, and 4g / ft 3 A calculated amount of rhodium nitrate solution was added to the partial slurry (3) for each of the Rh targets. The resulting slurry was continuously mixed.

[0260] 5. For Rh hydrolysis, the pH of the slurry (4) was raised to 6-7 with ammonia to obtain a local Rh concentration of 0.31%. This was mixed continuously.

[0261] 6.0.2g / in 3 La-Al2O3 slurry and 0.6g / in 3An additional amount of slurry 3 containing 1.0 g / in CZO slurry was added to increase the total La-AlO and CZO content to 1.0 g / in 3 In this washcoat, Rh was locally concentrated to a concentration of 0.3% on approximately 50% of the mixed La-Al2O3 and CZO supports, while the remainder of the La-Al2O3 and CZO supports were free of Rh, which were mixed continuously.

[0262] 7. The solid content of the washcoat (5) was adjusted with a rheology modifier to increase viscosity.

[0263] 8. The final composition of the top layer washcoat was the same as that of Reference Catalyst 5, 0.4 g / in 4% La2O3-doped alumina. 3 , ceria-zirconia composite 1.1 g / in 3 , and Rh element 4g / ft 3 Contains:

[0264] 9. First, the washcoat (7) was applied to the bottom layer of coated bricks from one side, targeting 50%-55% coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side was coated, targeting 50%-55% coating length, followed by drying and calcination again to obtain the finished catalyst article.

[0265] Catalyst 13 of the present invention (see, for example, FIG. 2b). The bottom layer washcoat (second catalyst region in FIG. 2b) was prepared and coated in the same manner as the bottom layer of Reference Catalyst 4.

[0266] The top layer washcoat (first catalyst region in FIG. 2b) was prepared by:

[0267] 1. La-stabilized alumina (La-Al2O3) was pulverized and a slurry containing this was prepared.

[0268] 2. Ceria and zirconia mixed oxide (CZO) was pulverized and a slurry containing it was prepared.

[0269] 3. Blend the two slurries together, keeping the weight ratio of La-Al2O3 to CZO at 1:3.

[0270] 4.0.1g / in 3 La-Al2O3, 0.3g / in 3 CZO, and 4g / ft 3 A calculated amount of rhodium nitrate solution was added to the partial slurry (3) for each of the Rh targets. The resulting slurry was continuously mixed.

[0271] 5. For Rh hydrolysis, the pH of the slurry (4) was raised to 6-7 with ammonia to obtain a local Rh concentration of 0.6%. This was mixed continuously.

[0272] 6.0.3g / in 3 La-Al2O3 slurry and 0.8g / in 3 An additional amount of slurry 3 containing 1.5 g / in CZO slurry was added to increase the total La-AlO and CZO content to 1.5 g / in 3 In this washcoat, Rh was locally concentrated at a concentration of 0.6% on approximately 25% of the mixed La-Al2O3 and CZO supports, while the remainder of the La-Al2O3 and CZO supports were free of Rh, which were mixed continuously.

[0273] 7. The solid content of the washcoat (5) was adjusted with a rheology modifier to increase viscosity.

[0274] 8. The final composition of the top layer washcoat was the same as that of Reference Catalyst 5, 0.4 g / in 4% La2O3-doped alumina. 3 , ceria-zirconia composite 1.2g / in 3 , and Rh element 4g / ft 3 Contains:

[0275] 9. First, the washcoat (7) was applied to the bottom layer of coated bricks from one side, targeting 50%-55% coating length. It was dried with hot air until more than 80% of the moisture was removed. Then, the other side was coated, targeting 50%-55% coating length, followed by drying and calcination again to obtain the finished catalyst article.

[0276] All catalysts are listed in Table 1 along with the corresponding Rh local concentration, target support, and total Rh loading.

[0277] [Table 1]

[0278] Example 1: FE-EPMA analysis of the interaction of RH with ZR or AL Characterization of Rh nanoparticles at very low Rh loading is a very challenging task. HRTEM is the most used technique so far. However, because the Rh particle size is very fine, it is difficult to identify these Rh particles, and the standard deviation (error) is very large. Also, when Rh is supported on CZO, the contrast between Rh and Zr is very close, and it is not possible to distinguish the Rh particles from the support. H2-TPR is another technique that is frequently used to measure the Rh support interaction or the Rh "relative" particle size. However, both Rh and Ce can be reduced by H2 at the same time, and it is impossible to separate them from each other. In the case of CO chemisorption method, CO is used to measure the Rh support interaction or Rh "relative" particle size in Rh / Al2O3 and Rh / CZO. 0Rh can only be chemisorbed onto the CeO2 surface. In non-reduced Rh samples, CO uptake is negligible. Typically, the Rh species in the as-prepared TWC catalysts is in an oxidized state (Rh2O3), meaning that it is not possible to measure the as-prepared Rh dispersion by CO chemisorption. There may be an overestimation of the metal particle dispersion by measuring the CO chemisorption of Rh / CZO, due to the formation of carbonate species on the CeO2 surface even at low temperatures (323 K) and the possibility of multiple CO molecules adsorbing on the Rh itself. In this work, we have demonstrated that Rh dispersions on CZO or La-Al2O3 supports can be achieved at very low loadings (0.23% on a single support or 4 g / ft2 in the TWC formulation). 3 ) to effectively test the

[0279] The Pearson correlation coefficient (product-moment correlation coefficient) was calculated based on the results of the area analysis by FE-EPMA, and the Rh-Zr correlation coefficient or the Rh-Al correlation coefficient is listed in Table 2.

[0280] 4g / ft 3 Reference catalyst 1, in which Rh is pre-fixed on all of the CZO support, shows a high coefficient of 0.5, indicating very high Rh dispersion and very fine Rh particles. In contrast, inventive catalyst 1 and inventive catalyst 2 demonstrate lower Rh-Zr coefficients than reference catalyst 1. This means that by concentrating Rh on a portion of the CZO support (31% or 15%, respectively), the Rh particle size can be successfully enlarged even though the total Rh loading remains the same. Further increasing the Rh local concentration to 3% by fixing Rh on 7.7% of the total CZO material resulted in an extremely low Rh-Zr coefficient of 0.17. In this case, Rh is overly concentrated and the Rh dispersion is too low. The hypothesis is that some of the Rh atoms may be buried inside the Rh particles and therefore not utilized. This concept is well illustrated in FIG. 28.

[0281] Similar trends in Rh local concentrations and Rh-Al Pearson correlation coefficients were observed at 4 g / ft 3is observed for the reference catalyst 2, in which Rh is pre-immobilized on the La-Al2O3 support, as well as for the inventive catalysts 4, 5, and 6. Local enrichment of Rh to 3% by immobilizing Rh on 7.7% of the total La-Al2O3 material (inventive catalyst 6) resulted in a very low Rh-Al coefficient of 0.17. In this case, Rh is overly concentrated and the Rh dispersion is too low. The assumption is that some of the Rh atoms are buried inside the Rh particles and therefore not utilized. In contrast, the inventive catalyst 5 by enriching Rh on the 15% La-Al2O3 support demonstrates a reasonable Pearson correlation coefficient of 0.43, resulting in the assumed optimal Rh nanoparticle size, i.e., Rh dispersion.

[0282] As demonstrated by Reference Catalyst 3, Inventive Catalyst 7, and Inventive Catalyst 8, total Rh loadings of 10 g g / ft 3 As the local Rh concentration increases from 0.46% to 1.86%, the relationship between the local Rh concentration and the Pearson correlation coefficient becomes flatter, with the Pearson correlation coefficient leveling off at 0.38-0.36 as the local Rh concentration increases from 0.46% to 1.86%. The technique is not sensitive enough at high Rh loadings.

[0283] [Table 2]

[0284] Example 2: Light-off performance test in engine test All catalysts were engine bench aged for 100 hours with a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C and tested in a gasoline engine. Light-off performance was measured under typical conditions, gas volumetric space velocity of 216K / hr, temperature gradient of 20°C / min, and lambda of the air and fuel ratio (AFR) of 14.56 perturbed with an amplitude of 0.5 and a frequency of 1Hz. THC conversion, CO conversion, and NO x Decrease catalyst inlet temperature until conversion is less than 10%. Allow to stabilize for 2 minutes. Increase catalyst inlet temperature at 20°C / min until inlet temperature reaches 500°C. NO xThe conversion, CO conversion, and THC conversion were calculated by comparing the concentrations of the feed gas and the gas at the outlet of the catalyst.

[0285] T 50 T is the temperature at which the conversion rate reaches 50% and is typically used to compare catalyst performance. 50 The lower the T, the better the catalyst. 50 The light-off temperatures are listed in Table 3. The data clearly show that both inventive catalyst 1 and inventive catalyst 2 provide significantly improved light-off performance compared to reference catalyst 1, both with no significant reduction in NO x T is about 30℃ lower 50 , and CO has a T that is approximately 33°C lower. 50 , and THC is about 30°C lower 50 and , respectively. Thus, the optimal Rh particle size may be more resistant to calcination and migration, resulting in early light-off performance. However, the over-enrichment of Rh in inventive catalyst 3, which is further improved compared to reference catalyst 1, begins to slow the conversion of all three pollutants by about 25° C. and reduce the catalytic activity when compared to inventive catalysts 1 and 2.

[0286] 4g / ft 3 Similar light-off performance benefits are observed in the reference catalyst 2 and the inventive catalysts 4, 5 and 6, in which 100% of Rh is pre-immobilized on the La-Al2O3 support. When Rh is locally enriched on a portion of the La-Al2O3 support (31% or 15%, respectively), the inventive catalysts 4 and 5 clearly show significantly improved light-off performance compared to the reference catalyst 2, possibly due to the optimal Rh particle size, which may be more resistant to calcination and migration. However, again, the over-enrichment of Rh in the inventive catalyst 3, although further improved compared to the reference catalyst 1, starts to decrease the conversion of all three pollutants compared to the inventive catalysts 1 and 2.

[0287] Interestingly, the total Rh loading was 10 g / ft 3, inventive catalyst 7 shows no benefit in light-off performance compared to reference catalyst 3. It is possible that the Rh particle size / Rh dispersion is already at an optimal level in reference catalyst 3 with a Rh local concentration of 0.46% for the light-off test conditions. Further enrichment of Rh to 1.86% in inventive catalyst 8 becomes detrimental.

[0288] [Table 3]

[0289] Example 3: Lambda Sweep Test in Engine Test All catalysts were engine bench aged for 100 hours in a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C and tested in a gasoline engine. The lambda sweep test was performed under typical conditions, where the gas volumetric space velocity was 216 K / hr, the temperature was fixed at 400°C, and the air-fuel ratio (AFR) lambda was swept from 15.5 to 13.5 with an amplitude of 0.5 perturbed during the sweep. The concentrations of THC, CO, and NO were measured. x The conversion was calculated from the comparison of the feed gas concentration with the gas concentration at the catalyst outlet.

[0290] CO conversion trace and NO x Conversion traces are shown in Figure 7. The data show that both Inventive Catalyst 1 and Inventive Catalyst 2 showed significantly improved NO conversion over the entire range of lambda conditions. x The results clearly show that the THC conversion and CO conversion are significantly improved by the inventive catalyst 1. The THC conversion traces are shown in FIG. 8. Both inventive catalyst 1 and inventive catalyst 2 have higher THC conversion within the entire range of lambda conditions and are more active than reference catalyst 1. The improved activity of the inventive catalysts is believed to be related to the optimal Rh particle size, and thus the Rh particles are more resistant to calcination and migration, which may provide performance benefits. However, the over-enrichment of Rh in inventive catalyst 3 is further improved compared to reference catalyst 1, but still results in NO2 conversion and CO2 conversion compared to inventive catalysts 1 and 2. x There is a significant decrease in conversion, CO conversion, and THC conversion.

[0291] 4g / ft 3 Similar lambda sweep performance benefits are observed for reference catalyst 2 and inventive catalysts 4-6, in which 100% of Rh was pre-anchored on the La-Al2O3 support. x The conversion traces are shown in Figure 9. The THC conversion traces are shown in Figure 10. When Rh was locally enriched on a portion of the La-Al2O3 support (31% or 15%, respectively), inventive catalyst 4 and inventive catalyst 5 showed significantly improved NO conversion over the entire lambda range compared to reference catalyst 2. x Conversion, CO conversion, and THC conversion are clearly shown, possibly due to the optimal Rh particle size, which may be more resistant to calcination and migration. However, again, the over-enrichment of Rh in inventive catalyst 6, although further improved compared to reference catalyst 2, begins to decrease the conversion of all three pollutants compared to inventive catalysts 4 and 5.

[0292] Total Rh loading is 10g / ft 3 , neither inventive catalyst 7 nor inventive catalyst 8 show any lambda sweep light-off performance advantage compared to reference catalyst 3. x The conversion traces are shown in Figure 11. The THC conversion traces are shown in Figure 12. The Rh particle size / Rh dispersion may already be at an optimal level in reference catalyst 3 with a Rh local concentration of 0.46% for the lambda sweep test conditions. Further enrichment of Rh to either 0.93% or 1.86% in inventive catalysts 7 or 8 would be detrimental to the lambda sweep test at 400°C.

[0293] Example 4: High temperature RDE test in engine test All catalysts were engine bench aged for 100 hours in a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C. A 2.0L engine bench dynamometer was used to test the catalysts and a custom OEM designed real-world driving (RDE) cycle was performed including acceleration and fuel cut conditions representing cold city, highway, and hot city speed phases. The cycle length was 2700 seconds from ambient soak conditions, reaching a peak catalyst bed temperature of approximately 650°C and a mass air flow rate of 250 kg / hr. The low temperature RDE test was used as the precondition cycle. Three high temperature RDE cycles were then repeated with a 5 minute soak time in between. The catalyst bed temperature is still high while the engine is at operating temperature. The advantage of running the high temperature RDE with the low temperature RDE as the precondition is the very good repeatability of the engine emissions. NO at the post-catalyst position x , CO, and THC emissions were measured and the cumulative mass of each species was calculated over the cycle. The average of three high temperature RDE runs was plotted against time and is shown in the figure below.

[0294] FIG. 13 shows the NOx profiles of the reference catalyst 1 and the catalysts 1 to 3 of the present invention during a high-temperature RDE cycle. x The data shows that the catalyst 2 of the present invention emits approximately 5g less NOx in the exhaust pipe. x It is clearly shown that the optimum Rh particle size at 1.5% Rh local concentration provides the most significant improvement in performance compared to the reference catalyst 1 in terms of NO emissions. Therefore, the optimum Rh particle size at 1.5% Rh local concentration can be the most resistant to calcination and migration, and has the lowest NO emissions. x However, the lower concentration of Rh in the inventive catalyst 1 or the overconcentration of Rh in the inventive catalyst 3 reduces the catalytic activity, resulting in about 2.5 or 3.5 g more NO emissions compared to the inventive catalyst 2, although still less than the reference catalyst 1. xThe CO and THC emissions are shown in Figures 14 and 15, respectively. Both inventive catalyst 1 and inventive catalyst 2 clearly show significantly improved performance compared to reference catalyst 1, likely due to the optimal Rh particle size, which may be more resistant to calcination and migration. However, again, the over-enrichment of Rh in inventive catalyst 3 starts to decrease the CO and THC conversions compared to inventive catalyst 1.

[0295] 4g / ft 3 Similar performance benefits are observed in Reference Catalyst 2 and Inventive Catalysts 4-6, in which 100% of Rh is pre-immobilized on the La-Al2O3 support. When Rh is locally concentrated on a portion of the La-Al2O3 support (31% or 15%, respectively), Inventive Catalyst 4 and Inventive Catalyst 5 clearly show significantly improved emission control of CO (Figure 17) and THC (Figure 18) compared to Reference Catalyst 2, possibly due to the optimal Rh particle size, which may be more resistant to calcination and migration. However, over-concentration of Rh in Inventive Catalyst 6 starts to reduce performance compared to Inventive Catalyst 4 and Inventive Catalyst 5. Although not as obvious as CO and THC, NO emission control for all three Rh-concentrated formulations is also observed, as shown in Figure 16. x There is still an emission control benefit.

[0296] Surprisingly, the total Rh loading was 10 g / ft 3 Catalyst 7 of the invention and catalyst 8 of the invention still show benefits in controlling emissions of CO (FIG. 20) and THC (FIG. 21) compared to reference catalyst 3, but show NO emissions comparable to those of reference catalyst 3. x (Figure 19) Has emissions.

[0297] Example 5: Low temperature RDE test in engine test All catalysts were engine bench aged for 100 hours in a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C. Catalysts were tested using a 2.0L bi-turbo, 4-cylinder Eu(VI)b calibrated engine bench dynamometer and a custom OEM designed real road driving (RDE) cycle including acceleration and fuel cut-off conditions representative of cold start city, highway, and hot city speed phases. The cycle length was 2700 seconds from ambient soak conditions, reaching a peak catalyst temperature of approximately 700°C at a vehicle speed of approximately 140 km / hr and a mass air flow rate of 400 kg / hr. NOx, CO, and THC emissions at post-catalyst locations were measured and the cumulative mass of each species was calculated over the entire cycle. Three experiments were performed for each catalyst formulation and the average of the three experiments against time was plotted and is shown in the figure below.

[0298] FIG. 22 shows the NOx profiles of the reference catalyst 4 and the catalysts 9 to 11 of the present invention during a low-temperature RDE cycle. x The catalyst 10 of the present invention having a zone configuration with 1% Rh enriched on the La-Al2O3 in the rear zone achieved the lowest NO emissions over the entire low temperature RDE driving cycle. x It is very clear that the Rh split variants result in better CO or THC emission control than the baseline. Other formulations such as inventive catalyst 9 with uniform distribution of 1% Rh concentrated on the La-Al2O3 in the top layer, or inventive catalyst 11 with a zoned configuration but with 1% Rh concentrated on the CZO in the rear zone appear to be comparable to the reference catalyst 4. The CO and THC emissions are shown in Figures 23 and 24, respectively. Although the rankings are slightly different, all the Rh split variants are better than the baseline for either CO or THC emission control.

[0299] Example 6: WLTC test in engine testing All catalysts were engine bench aged for 100 hours in a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C. Catalysts were tested using a 2.0L bi-turbo, 4-cylinder Eu(VI)b calibrated engine bench dynamometer, running a standard World Harmonized Light-Duty Test Cycle (WLTC) including acceleration and fuel cut-off conditions representing urban, rural, highway and motorway speed stages. The cycle length was 1800 seconds from ambient soak conditions, reaching a peak catalyst temperature of approximately 600°C at a vehicle speed of approximately 130 km / h and a mass air flow rate of approximately 200 kg / h. NO at post-catalyst position x , CO, and THC emissions were measured and the cumulative mass of each species was calculated over the cycle. Three experiments were performed for each catalyst formulation and the average of the three experiments was plotted against time and is shown in the figures below.

[0300] FIG. 25 shows the NOx of the reference catalyst 4 and the catalysts 9 to 11 of the present invention during the WLTC cycle. x The catalyst 10 of the present invention (zoned with 1% Rh concentrated on the La-Al2O3 in the rear zone) and the catalyst 11 of the present invention (zoned but with 1% Rh concentrated on the CZO in the rear zone) performed equally well, both giving the lowest NO emissions over the entire WLTC driving cycle. x The uniform distribution of 1% Rh concentrated on La-Al2O3 in inventive catalyst 9 appears to be comparable to reference catalyst 4. The CO and THC emissions are shown in Figures 26 and 27, respectively. Although the rankings are slightly different, all Rh split variants are better than the baseline for either CO or THC emission control.

[0301] Example 7: Vehicle Testing Bench aged samples of inventive catalysts 12 and 13, and comparative catalyst 5 were tested in a 1.5 liter engine vehicle using the World Wide Harmonized Exhaust Emissions and Fuel Economy Test Procedure (WLTP). Bench aging was performed in a 6.1 liter engine with a catalyst peak bed temperature of about 980°C, a 4-mode aging cycle, and the same 150 hour run. Vehicle exhaust dilution bag data results for the bench aged parts are shown in Table 4. Inventive catalysts 12 and 13 of the present invention show superior activity for THC and NMHC emission control compared to comparative catalyst 5. (e.g., THC and NMHC performance improved by about 11% and 12%, respectively, versus comparative catalyst 5).

[0302] [Table 4]

[0303] Example 8: Light-off performance test in engine test The bench-aged catalysts 12 and 13 of the present invention and the comparative catalyst 5 were tested separately on a gasoline engine. The light-off performance was typical conditions of exhaust gas flow rate of 80 kg / h, temperature gradient of 30°C / min, and lambda of air and fuel ratio (AFR) of 14.45. The conversion of THC and CO was calculated by comparing the concentration of the feed gas and the gas at the outlet of the catalyst. Before the engine light-off test, the catalysts 12 and 13 of the present invention and the comparative catalyst 5 were bench-aged for 150 hours. The bench-aging was performed under the same 6.1L engine with the same 150-hour run, with a peak catalyst bed temperature of about 980°C and a four-mode aging cycle.

[0304] HC, CO and NO of Catalysts 12 and 13 of the Invention and Comparative Catalyst 5 x T 50 Light-off temperature (T 50 The results are shown in Table 5. (where t is the temperature at which the conversion reaches 50%). The data show that catalysts 12 and 13 of the present invention have a significantly improved conversion of HC, NO, and NO xCatalyst 13 of the present invention showed improved light-off performance compared to Comparative Catalyst 5 (e.g., NO x ,CO,HC T 50 decreased by 13°C, 11°C, and 8°C, respectively).

[0305] [Table 5]

[0306] The foregoing detailed description has been provided for purposes of explanation and illustration and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments described herein will be apparent to those of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. 1. A catalytic article for treating exhaust gases, comprising: a substrate including an inlet end and an outlet end having an axial length L; a first catalyst region comprising support material particles; at least a portion of the support material particles are rhodium-loaded support material particles having rhodium loaded thereon in a concentration of 0.001 to 3.5 wt. % based on the weight of the rhodium-loaded support material particles; The rhodium is present in an amount of up to 20 g / ft relative to the first catalytic region. ３ the catalyst article being present at a loading of

2. 10. The catalyst article of claim 1, wherein the rhodium-loaded support material particles have rhodium loaded thereon in a concentration of 0.3 to 3.5 wt. %, 0.4 to 3.0 wt. %, 0.4 to 2.0 wt. %, or 0.4 to 1.5 wt. %, based on the weight of the rhodium-loaded support material particles.

3. 3. The catalyst article of claim 1 or claim 2, wherein at least some of the support material particles are unsupported support material particles having essentially no rhodium supported thereon, preferably having no rhodium supported thereon.

4. 3. The catalyst article of claim 1 or claim 2, wherein 5 to 80% of the support material particles in the first catalyst region are rhodium-loaded support material particles.

5. 3. The catalytic article of claim 1 or claim 2, wherein the support material particles comprise alumina and / or ceria-zirconia mixed oxide.

6. the support material particles comprise a ceria-zirconia mixed oxide; When a cross section of the first catalyst region of the catalyst article is analyzed by FE-EPMA under the conditions of a pixel (cross section) size of 0.34 μm×0.34 μm and a measurement pixel (cross section) number of 256×256, the characteristic X-ray intensity (α: cps) of zirconium (Zr) and the characteristic X-ray intensity (β: cps) of rhodium (Rh) are measured for each pixel, and the Pearson correlation coefficient calculated using the α and β at each pixel is defined as R Ｚｒ／Ｒｈ When specifying Ｚｒ／Ｒｈ The catalyst article according to claim 1 or claim 2, wherein the value of is 0.15 to 0.

48.

7. The rhodium is present in an amount of 1 to 20 g / ft of the first catalytic region. ３ 3. The catalyst article of claim 1 or claim 2, wherein the catalyst is present at a loading of

8. The carrier material particles have a density of 0.5 to 3 g / in ３ 3. The catalyst article of claim 1 or claim 2, wherein the catalyst is present at a loading of

9. 3. The catalytic article of claim 1 or claim 2, further comprising a second catalytic region, said second catalytic region comprising a second PGM component, a second OSC material, and / or a second inorganic oxide.

10. 10. The catalytic article of claim 9, further comprising a third catalytic region, said third catalytic region comprising a third PGM component, a third OSC material, and / or a third inorganic oxide.

11. 1. A method of making a catalyst article, said method comprising: providing rhodium-loaded support material particles having rhodium loaded thereon in a concentration of 0.001 to 3.5 weight percent based on the weight of the rhodium-loaded support material particles; providing unsupported support material particles having essentially no rhodium supported thereon, preferably having no rhodium supported thereon; forming a washcoat comprising the rhodium-loaded support material particles and the unloaded support material particles; coating a substrate with the washcoat to provide a catalytic article, wherein the rhodium is present in an amount of up to 20 g / ft of the substrate; ３ and wherein the compound is present in a loading amount of

12. 12. The method of claim 11, wherein the rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.3 to 3.5 weight percent based on the weight of the rhodium-loaded support material particles.

13. 13. The method of claim 11 or claim 12, wherein the catalyst article is as defined in claim 1 or claim 2.

14. An emission treatment system comprising the catalytic article of claim 1 or claim 2.

15. 1. A method for treating an exhaust gas, said method comprising: Providing a catalyst article according to claim 1 or claim 2; contacting the catalytic article with an exhaust gas.

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