Catalytic articles having high local rhodium concentrations on ceria-zirconia, emission treatment systems including the catalytic articles, and methods for treating exhaust gases using the catalytic articles

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 some 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 an amount of up to 20 g / ft of the first catalyst region. 3 is present at a loading of .

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to catalytic articles, emission treatment systems, and methods for treating exhaust gases. [Background technology]

[0002] A three-way catalyst (TWC) removes CO, HC, and NO from the exhaust of a gasoline engine at a stoichiometric air-fuel ratio. x The oxidation of CO and HC to CO and water vapor (HO) is primarily catalyzed by Pd, while the oxidation of NO x The reduction of CO to N2 is primarily catalyzed by Rh. Modern TWCs use supported platinum group metal (PGM) catalysts (e.g., Pd, Rh, Pt) deposited on single-, double-, or multi-layer supports. The support materials consist 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 precious metals, Rh is the rarest and most expensive species on Earth. Therefore, highly activated Rh in particular is desirable to reduce the cost of PGM use while still meeting strict emissions regulations.

[0004] In Rh TWC washcoats, Rh is dispersed on a stabilized alumina support, a ceria-containing oxygen storage material support, or a blend of both. It is well known that deactivation of Rh TWC catalysts after high-temperature aging is primarily due to calcination of the Rh metal and the support material. However, at lower Rh loadings (e.g., <20 g / ft), 3In certain TWC catalysts with a high cerium content, Rh atoms or clusters tend to form and be "dissolved" in the support material due to strong metal support interaction (SMSI), resulting in a decrease in active Rh sites and a decline in catalytic performance. Ceria has a high surface energy, which favors strong metal-support interactions when Rh is dispersed on a ceria-zirconia mixed oxide support. The strong interaction between Rh and Ce can suppress Rh combustion, which is beneficial for catalytic performance. However, if the Ce content is too high, Ce can also "decorate" the Rh surface, covering active Rh sites and being detrimental to activity. Therefore, an optimal ceria content is required to maintain ideal Rh-Ce interactions. Typically, a ceria-zirconia mixed oxide containing 20% ​​ceria is used as the Rh support.

[0005] Despite recent TWC developments, there remains a need for improved TWC catalysts with more active Rh sites at lower Rh loadings. The present invention addresses these problems, among others. Summary of the Invention

[0006] One aspect of the present disclosure is directed to providing a catalyst article for treating exhaust gases, 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 some 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 an amount of up to 20 g / ft of the first catalytic region. 3 wherein the support material particles comprise a ceria-zirconia mixed oxide, the ceria-zirconia mixed oxide having a ceria content of at least 20 wt. %.

[0007] The present invention includes an emission treatment system including the catalytic article described herein, and a method of treating an exhaust gas, the method comprising providing a catalytic article described herein and contacting the catalytic article with an exhaust gas. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 shows an embodiment according to the present invention containing a first catalyst region (single layer) having a length of 100% of the axial length L of the substrate. [Figure 2a] FIG. 1 shows an embodiment according to the invention in which a first catalyst region extends as a bottom layer over 100% of the axial length L, and a second catalyst region extends as a top layer over 100% of the axial length L. [Figure 2b] FIG. 2b shows a variation of FIG. 2a. [Figure 3a] 1 illustrates an embodiment according to the present invention in which the first catalyst region extends from the inlet end for less than 100% of the axial length L, and the second catalyst region extends from the outlet end for less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is less than or equal to the axial length L. [Figure 3b] 3b illustrates a variation of FIG. 3a. [Figure 3c] 1 illustrates an embodiment according to the present invention in which the first catalyst region extends from the inlet end for less than 100% of the axial length L, and the second catalyst region extends from the outlet end for 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] 3c illustrates a variation of FIG. [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 combined length of the second catalyst region and the first catalyst region is less than or equal to the axial length L. A third catalyst region extends 100% of the axial length L and is layered as an upper layer on the first and second catalyst regions. [Figure 4b]FIG. 4b shows a variation of FIG. 4a. [Figure 4c] 1 shows an embodiment according to the present invention in which the third catalyst region extends as a bottom layer for 100% of the axial length L. 2 shows an embodiment according to the present invention in which the first catalyst region extends from the inlet end for less than 100% of the axial length L, and the second catalyst region extends from the outlet end for less than 100% of the axial length L. 3 shows an embodiment according to the present invention in which the second catalyst region and the first catalyst region extend for less than 100% of the axial length L. 4 shows an embodiment according to the present invention in which the third catalyst region extends as a bottom layer for 100% of the axial length L. 5 shows an embodiment according to the present invention in which the first catalyst region extends from the inlet end for less than 100% of the axial length L. 6 shows an embodiment according to the present invention in which the first catalyst region extends from the outlet end for less than 100% of the axial length L. 7 shows an embodiment according to the present invention in which the second catalyst region extends from the inlet end for less than 100% of the axial length L. 8 shows an embodiment according to the present invention in which the second catalyst region extends from the inlet end for less than 100% of the axial length L. 9 shows an embodiment according to the present invention in which the second catalyst region extends from the outlet end for less than 100% of the axial length L. 10 shows an embodiment according to the present invention in which the first catalyst region extends from the outlet end for less than 100% of the axial length L. 11 shows an embodiment according to the present invention in which the first catalyst region extends from the outlet end for less than 100% of the axial length L. 12 shows an embodiment according to the present invention in which the second catalyst region extends from the inlet end for less than 100% of the axial length L. 13 shows an embodiment according to the present invention in which the second catalyst region extends from the inlet end for less than 100% of the axial length L. 14 shows an embodiment according to the present invention [Figure 4d] 4c illustrates a variation of FIG. [Figure 5a] 1 shows an embodiment according to the present invention in which a first catalyst region extends 100% of the axial length L as a bottom layer, a second catalyst region extends 100% of the axial length L as a middle layer, and a third catalyst region extends 100% of the axial length L as a top layer. [Figure 5b] 5b illustrates a variation of FIG. 5a. [Figure 5c] 5b 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 combined 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 on the first and second catalyst regions. [Figure 6b] 6b illustrates a variation of FIG. 6a. [Figure 6c] 6b illustrates a variation of FIG. 6a. [Figure 6d] 6b illustrates a variation of FIG. 6a. [Figure 6e] 6b illustrates a variation of FIG. 6a. [Figure 6f] 6b illustrates a variation of FIG. 6a. [Figure 6g]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 combined 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 on the first catalyst region and / or the second catalyst region. [Figure 6h] 6g illustrates a variation of FIG. [Figure 6i] 6g illustrates a variation of FIG. [Figure 6j] 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 combined 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 on the second catalyst region and / or the first catalyst region. [Figure 6k] 6j illustrates a variation of FIG. [Figure 6l] 6j illustrates a variation of FIG. [Figure 7a] 1 shows the cumulative NOx conversion of reference catalyst 1 and inventive catalysts 1-3 during a high temperature RDE cycle. [Figure 7b] 1 shows cumulative CO conversions of reference catalyst 1 and inventive catalysts 1 to 3 during a high-temperature RDE cycle. [Figure 7c] 1 shows the cumulative THC conversion of reference catalyst 1 and inventive catalysts 1-3 during a high temperature RDE cycle. [Figure 8a] 4 shows NOx emissions for reference catalyst 3 and inventive catalyst 6 during a low temperature RDE cycle. [Figure 8b] 1 shows the CO emissions of reference catalyst 3 and inventive catalyst 6 during a low-temperature RDE cycle. [Figure 8c] 1 shows THC emissions for reference catalyst 3 and inventive catalyst 6 during a low temperature RDE cycle. DETAILED DESCRIPTION OF THE INVENTION

[0009] 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.

[0010] In a first aspect, the present invention provides a catalytic article for treating exhaust gases, 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 wt. % based on the weight of the rhodium-loaded support material particles; Rhodium up to 20g / ft for the first catalytic region 3 wherein the support material particles comprise a ceria-zirconia mixed oxide, the ceria-zirconia mixed oxide having a ceria content of at least 20 wt. %.

[0011] Each aspect or embodiment defined herein may be combined with any other aspect or embodiment unless expressly stated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0012] First catalytic region Preferably, the rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.3 to 3.5 wt %, based on the weight of the rhodium-loaded support material particles. More preferably, the rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.4 to 3.0 wt %, even more preferably 0.4 to 2.0 wt %, and even more preferably 0.4 to 1.5 wt %, based on the weight of the rhodium-loaded support material particles. Alternatively, the rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.3 to 1.8 wt %, even more preferably 0.4 to 1.2 wt %, and even more preferably 0.4 to 1.0 wt %, based on the weight of the rhodium-loaded support material particles.

[0013] In known catalyst articles, rhodium is present in the first catalyst region at a maximum of 20 g / ft 3 When 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 this embodiment. This may be because rhodium is typically uniformly, i.e., at a uniform concentration, supported 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.

[0014] However, through extensive research, the present inventors surprisingly discovered that higher ceria content (>20%) ceria-zirconia mixed oxide (CZO) materials are better Rh supports with less concern about Rh dissolution when the initial Rh particles are sufficiently large (e.g., have higher local Rh concentrations). Higher ceria content CZO materials generally have higher oxygen storage capacity, which can provide catalytic performance advantages at high space velocity and dramatic lambda swing conditions within transient test cycles.

[0015] As used herein, the term "catalytic 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 or flow-through filter.

[0016] 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.

[0017] As used herein, the term "catalytic region" can encompass an area on a substrate that is typically obtained by drying and / or calcining a washcoat. A "region" can be disposed or supported on the substrate as, for example, a "layer" or a "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).

[0018] Preferably, the "catalyst region" has a substantially uniform composition (i.e., there is, on average, 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.

[0019] The first catalyst region is preferably disposed on a substrate. The term "disposed on" in the context of this embodiment can encompass both having a catalyst region disposed directly on the substrate, i.e., without intervening materials, and / or having a catalyst region disposed indirectly on the substrate, i.e., with intervening materials. If the substrate is porous, the term "disposed on" can also encompass having a catalyst region disposed therein, for example, within the pores of the substrate, i.e., the catalyst region disposed thereon and / or therein.

[0020] The term "washcoat" as used herein is well known in the art and typically refers to an adherent coating applied to a substrate during catalyst production. Preferably, the first catalyst region is a washcoat layer.

[0021] 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.

[0022] Preferably, the rhodium is not alloyed with other metals.

[0023] Preferably, the rhodium-loaded support material particles are substantially uniformly dispersed throughout the first catalyst region. In this context, the term "substantially uniformly dispersed" can include the concentration of rhodium-loaded support material particles in any one subregion of the first catalyst region being substantially the same as the concentration of rhodium-loaded support material particles in any different subregion of the first catalyst region, e.g., within 5%, within 3%, within 2%, preferably within 1% of the concentration.

[0024] 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 to 3.5 wt %, 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 to 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 to 3.5 wt %, more preferably 0.4 to 3.0 wt %, even more preferably 0.4 to 2.0 wt %, even more preferably 0.4 to 1.8 wt %, even more preferably 0.4 to 1.6 wt %, and even more preferably 0.4 to 1.5 wt %, 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 wt. %, 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 wt. %, based on the weight of the rhodium-loaded support material particles. It will be understood that the invention may encompass preferred subranges consisting of any combination of the above endpoints.

[0025] Without being bound by theory, it is believed that maintaining a similar total amount of support material may allow the thermal durability properties of the support material, such as alumina, to be maintained compared to conventional catalyst regions having uniformly distributed low concentrations of rhodium rather than locally concentrated rhodium-loaded support material. Accordingly, it is preferred that at least a portion of the support material particles are unsupported support material particles that have 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 that have essentially no rhodium loaded thereon, preferably no rhodium loaded thereon.

[0026] As used herein, the term "essentially free of rhodium" may encompass unsupported support material particles having rhodium supported thereon at a concentration of less than 0.001 wt. %, preferably less than 0.0005 wt. %, and more preferably less than 0.0001 wt. %, 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 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. Accordingly, the present invention is intended to encompass unavoidable amounts of rhodium supported on unsupported support material particles.

[0027] 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 benefits 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% of rhodium-loaded support material particles in the first catalyst zone, based on the total amount of support material in the first catalyst zone).

[0028] Preferably, 5 to 80% of the support material particles in the first catalyst zone are rhodium-supported support material particles. In other words, 5 to 80% of the rhodium-supported and unsupported support material particles in the first catalyst zone are rhodium-supported support material particles. In this context, "%" is simply a numerical percentage, which can be measured by TEM or any other suitable means. More preferably, 7 to 60%, even more preferably 10 to 50%, even more preferably 11 to 45%, even more preferably 13 to 40%, and even more preferably 15 to 35% of the support material particles in the first catalyst zone are rhodium-supported support material particles. For example, preferably, 10 to 25% of the support material particles in the first catalyst zone are rhodium-supported support material particles. In another preferred embodiment, 20 to 35% of the support material particles in the first catalyst zone are rhodium-supported support material particles.

[0029] 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 with improved light-off performance and resistance to calcination, for reasons hypothesized herein.

[0030] Preferably, the support material particles, i.e., the support material particles of the first catalyst zone, consist essentially of rhodium-loaded and unloaded support material particles, i.e., the rhodium-loaded and unloaded support particles preferably constitute 90% or more by weight of the support particles, more preferably 95% or more by weight, even more preferably 97% or more by weight, and even more preferably 99% or more by weight. Most preferably, the support material particles, i.e., the support material particles of the first catalyst zone, consist essentially of rhodium-loaded and unloaded support material particles.

[0031] Preferably, the first catalyst region comprises rhodium-loaded support material particles, unloaded support material particles, and optionally a binder. In some preferred embodiments, the ceria-zirconia mixed oxide has a ceria content of 20-45 wt. %. In more preferred embodiments, the ceria-zirconia mixed oxide has a ceria content of 20-40 wt. %, 25-40 wt. %, or even 25-35 wt. %.

[0032] Preferably, the ceria-zirconia mixed oxide is doped, i.e., 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 ceria-zirconia mixed oxide in an amount of 0.001 wt. % to 20 wt. %, and more preferably 0.5 wt. % to 10 wt. %. The weight percentage may be based on the total weight of the ceria-zirconia mixed oxide.

[0033] 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 dynamic light scattering.

[0034] Preferably, rhodium is present in an amount of 1 to 20 g / ft relative to the first catalytic region (e.g., particularly when the first catalytic region extends less than the total length L of the substrate, e.g., 20 to 80%, 30 to 70%, or 40 to 60% of the total 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 3Alternatively, 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 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 benefits 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.

[0035] 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.

[0036] Preferably, the first catalytic region further comprises a first inorganic oxide. The first inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, and 14. The first 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 first inorganic oxide is alumina, lanthanum-alumina, zirconia, or a magnesia / alumina composite oxide. One particularly preferred first inorganic oxide is alumina or lanthanum-alumina.

[0037] Preferably, the first catalyst region further comprises a binder, and 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 to 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 catalyst region is a washcoat layer.

[0038] The catalyst article preferably further comprises one or more additional catalytic regions. The one or more additional catalytic regions may be different from the catalytic regions required by the present invention as 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, it is preferred that the one or more additional catalytic regions 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.

[0039] Second catalytic region The catalytic article may further include a second catalytic region.

[0040] 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.

[0041] 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.

[0042] The second OSC material can 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 can further include one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material can 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.

[0043] The ceria-zirconia mixed oxide has 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 can also have a weight ratio of ceria to zirconia less than 50:50, preferably less than 40:60, more preferably less than 30:70.

[0044] The second OSC material (e.g., ceria-zirconia mixed oxide) can be 10-90 wt % based on the total washcoat loading of the second catalyst region, preferably 25-75 wt %, and more preferably 30-60 wt % based on the total washcoat loading of the second catalyst region.

[0045] 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 catalyst 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.

[0046] The second alkali metal or alkaline earth metal is preferably barium, strontium, or a mixed oxide or composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. % barium or strontium, more preferably 3 to 10 wt. % barium or strontium, based on the total weight of the second catalyst region.

[0047] Even more preferably, the second alkali metal or alkaline earth metal is strontium, which, when present, is preferably present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the second catalyst region.

[0048] 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 wt %, more preferably 3 to 10 wt %, 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.

[0049] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0050] The second inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, and 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 preferred is alumina, lanthanum-alumina, zirconia, or a magnesia / alumina composite oxide. One particularly preferred second inorganic oxide is alumina or lanthanum-alumina.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] The total washcoat loading of the second catalyst region was 3.5 g / in 3 Less than 3.0 g / in 3 or 2.5 g / in 3 Alternatively, the total washcoat loading of the first catalyst region may be between 0.5 and 3.5 g / in 3 Preferably, it is 0.6 to 3 g / in 3 or 0.7 to 2.5 g / in 3 It could be.

[0055] The second catalyst region can extend over 100 percent of the axial length L (see, eg, Figures 2a, 2b, and 6a-6c).

[0056] 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 combined 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).

[0057] 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 3c and 3d; 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 combined length of the second catalyst region and the first catalyst region can be equal to the axial length L (see, e.g., Figures 3a and 3b). In yet another alternative, the combined 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.

[0058] 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.

[0059] The third catalytic region The catalytic article may further include a third catalytic region.

[0060] The third catalyst region may further comprise a third PGM component, a third oxygen storage capacity (OSC) material, a third alkali metal component or alkaline earth metal component, and / or a third inorganic oxide.

[0061] 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.

[0062] 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 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.

[0063] The ceria-zirconia mixed oxide may have a weight ratio of ceria to zirconia of at least 50:50, preferably greater than 60:40, more preferably greater than 75:25, or alternatively, may have a weight ratio of ceria to zirconia of less than 50:50, preferably less than 40:60, more preferably less than 25:75.

[0064] The third OSC material (e.g., 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.

[0065] 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 catalyst 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.

[0066] 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 or less than 2g / in 3 It can be the following:

[0067] The third alkali metal or alkaline earth metal is preferably barium, strontium, or a mixed oxide or composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. % barium or strontium, more preferably 3 to 10 wt. % barium or strontium, based on the total weight of the third catalytic region.

[0068] Even more preferably, the third alkali metal or alkaline earth metal is strontium, which, when present, is preferably present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the third catalyst region.

[0069] 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 wt %, more preferably 3 to 10 wt %, based on the total weight of the third catalyst region. More preferably, the third alkali metal or alkaline earth metal is a composite oxide of barium and strontium.

[0070] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0071] The third inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, and 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 preferred is alumina, lanthanum-alumina, zirconia, or magnesia / alumina composite oxide. One particularly preferred third inorganic oxide is alumina or lanthanum-alumina.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] The third catalyst region can extend over 100 percent of the axial length L (see, eg, Figures 4a-4d and 6a-6c).

[0076] The third catalyst region can be less than the axial length L, for example, 95%, 90%, 80%, or 70% or less of the axial length L (see, for example, Figures 5a-5d and 7g-7l).

[0077] 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).

[0078] Preferably, the catalyst article comprises a substrate, a first catalytic region as described herein, and a second catalytic region. In other words, the catalyst 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.

[0079] The first catalyst region is preferably disposed directly on the second catalyst region, preferably on the second catalyst region. For example, the second catalyst region is preferably disposed directly on the substrate, and the first catalyst region is preferably disposed directly on the second catalyst region. In these embodiments, the first catalyst region and the second catalyst region are preferably washcoat layers, each of which is preferably applied over the entire length of the substrate.

[0080] In another preferred embodiment, a catalytic article includes a substrate and a first catalytic region described herein, a second catalytic region, and a third catalytic region. In other words, the catalytic article preferably further includes a second catalytic region and a third catalytic region. The second catalytic region and the third catalytic region preferably have compositions different from the composition of the first catalytic region. Furthermore, the second catalytic region preferably has a composition different from the composition of the third catalytic region.

[0081] Preferably, the second catalyst region in this embodiment is as described in another preferred embodiment above. However, in this embodiment, the first catalyst region and the third catalyst region are preferably arranged on the second catalyst region in the form of a zone, preferably directly on the second catalyst region. In particular, the second catalyst region is preferably arranged directly on the substrate, and the first catalyst region and the third catalyst region are preferably arranged directly on the second catalyst region, respectively. The second catalyst region is preferably arranged over the entire length of the substrate, and the first catalyst region and the third catalyst region are preferably arranged on the second catalyst region in the form of a zone. In these preferred embodiments, the first catalyst region, the second catalyst region, and the third catalyst region are preferably in the form of a washcoat layer.

[0082] In these preferred embodiments, the first catalyst region is preferably located in the rear zone, i.e., at the intended outlet end of the catalyst article, and the third catalyst region is preferably located in the front zone, i.e., at the intended inlet end of the catalyst article.

[0083] The third catalytic zone preferably comprises rhodium supported on a support material. The rhodium is preferably distributed on all of 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.

[0084] When the first catalyst region and the third catalyst region are zoned, the two zones together preferably extend over the entire length of the substrate (which is preferably the entire length of the second catalyst region).

[0085] Such a preferred arrangement of the first catalyst region, the second catalyst region, and optionally the third catalyst region surprisingly results in improved NOx, particularly during cold start conditions. x and lower light-off temperatures. Improved CO and / or THC reduction may also be observed. Improved aged OSC characteristics may also be observed.

[0086] The fourth catalytic region The catalytic article may further include a fourth catalytic region.

[0087] The fourth catalyst region may further comprise a fourth PGM component, a fourth oxygen storage capacity (OSC) material, a fourth alkali or alkaline earth metal component, and / or a fourth inorganic oxide.

[0088] The fourth PGM component may be selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof, hi some embodiments, the fourth PGM component may be Pd, Rh, or mixtures thereof.

[0089] The fourth OSC material may be cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the fourth OSC material includes ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. In addition, the fourth OSC material may further include one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the fourth OSC material may function as a support material for the fourth PGM component. In some embodiments, the fourth OSC material includes ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0090] The ceria-zirconia mixed oxide may have a weight ratio of ceria to zirconia of at least 50:50, preferably greater than 60:40, more preferably greater than 75:25, or alternatively, may have a weight ratio of ceria to zirconia of less than 50:50, preferably less than 40:60, more preferably less than 25:75.

[0091] The fourth OSC material (e.g., 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 fourth catalyst region.

[0092] The loading of the fourth OSC material in the fourth catalyst region is 1.5 g / in 3 In some embodiments, the loading of the fourth OSC material in the second catalyst 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.

[0093] The total washcoat loading of the fourth catalyst region was 3.5 g / in 3 Less than 3.0 g / in3 Below 2.5g / in 3 or less than 2g / in 3 It can be the following:

[0094] The fourth alkali metal or alkaline earth metal is preferably barium, strontium, or a mixed oxide or composite oxide thereof. Preferably, the barium or strontium, if present, is in an amount of 0.1 to 15 wt. % barium or strontium, more preferably 3 to 10 wt. % barium or strontium, based on the total weight of the fourth catalytic region.

[0095] Even more preferably, the fourth alkali or alkaline earth metal is strontium, which, when present, is preferably present in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, based on the total weight of the fourth catalyst region.

[0096] The fourth alkali 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 wt %, more preferably 3 to 10 wt %, based on the total weight of the fourth catalyst region. More preferably, the fourth alkali or alkaline earth metal is a composite oxide of barium and strontium.

[0097] Preferably, the barium or strontium is present as BaCO or SrCO. Such materials can be prepared by any method known in the art, such as incipient wetness impregnation or spray drying.

[0098] The fourth inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, and 14. The fourth inorganic oxide is preferably selected from the group consisting of alumina, magnesia, silica, zirconia, barium oxide, and mixed oxides or composite oxides thereof. Particularly preferred is alumina, lanthanum-alumina, zirconia, or magnesia / alumina composite oxide. One particularly preferred fourth inorganic oxide is alumina or lanthanum-alumina.

[0099] The fourth OSC material and the fourth 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.

[0100] Alternatively, the fourth OSC material and the fourth 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.

[0101] In some embodiments, the fourth OSC material and the fourth inorganic oxide can have a weight ratio of 2:1 or less. In further embodiments, the fourth OSC material and the fourth inorganic oxide can have a weight ratio of 10:1 or less. In other further embodiments, the fourth OSC material and the fourth inorganic oxide can have a weight ratio of 20:1 or more, or 30:1 or more. In yet other further embodiments, the fourth OSC material and the fourth inorganic oxide can have a weight ratio of 40:1 or more, or 50:1 or more.

[0102] In some embodiments, the fourth catalyst region can extend over 100% of the axial length L. In other embodiments, the fourth catalyst region can extend over less than the axial length L, for example, no more than 95%, 90%, 80%, or 70% of the axial length L.

[0103] The term "zone," as used herein, refers to a region having a length less than the entire length of the substrate, such as a length of 75% or less of the entire length of the substrate. A "zone" typically has a length of at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).

[0104] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0105] As used herein, any reference to a "zone disposed at the inlet end of the substrate" refers to a zone disposed on or carried by a substrate that 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, as used herein, any reference to a "zone disposed at the outlet end of the substrate" refers to a zone disposed on or carried by a substrate that 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.

[0106] Preferably, the first catalytic region is a single washcoat layer disposed on a substrate. The single washcoat layer may be coated along the entire length of the substrate or over only a portion thereof. For example, the single washcoat layer is preferably coated from one end of the substrate (e.g., the inlet end or outlet end relative to the direction of intended use in the exhaust system), and preferably covers less than 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% of the length of the substrate. Preferably, the single washcoat layer is coated directly on the substrate. In another preferred embodiment, there are one or more intervening washcoat layers positioned 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 catalytic action. In other words, the catalytic article preferably further comprises one or more additional washcoat layers.

[0107] 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.

[0108] Preferably, the catalyst article is for three-way catalysis, in other words, the catalyst article is preferably a TWC.

[0109] Base material Preferably, the substrate is a flow-through monolith. Alternatively, the substrate may be a wall-flow filter.

[0110] 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., wall surfaces defining each channel). Each of the plurality of channels has an opening in the first surface and an opening in the second surface. For the avoidance of doubt, the flow-through monolith substrate is not a wall-flow filter.

[0111] The first surface is typically at the inlet end of the substrate and the second surface is at the outlet end of the substrate.

[0112] The channels may be of constant width, and each of the plurality of channels may have a uniform channel width.

[0113] 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 the open first channels and closed second channels is 600 to 700 channels per square inch. These channels can have cross sections that are rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shapes.

[0114] 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.

[0115] It should be noted that the flow-through monolith substrates described herein are single components (i.e., a single brick). Nevertheless, when forming waste treatment systems, the substrates used may be formed by bonding multiple channels together, or by bonding multiple smaller substrates together as described herein. Such techniques, along with suitable casings and configurations of waste treatment systems, are well known in the art.

[0116] In embodiments in which the catalyst article of the present invention comprises a ceramic substrate, the ceramic substrate can 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.

[0117] In embodiments in which the catalytic article of the present invention comprises 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.

[0118] Preferably, the substrate comprises a wall-flow filter substrate. In an alternative 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 deposited thereon. In such a situation, the final catalyst article may comprise multiple layers of different washcoats. The substrate preferably comprises cordierite. However, the composition of the substrate is not particularly limited.

[0119] 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; 1. Coating a substrate with a washcoat to provide a catalyst article, wherein the rhodium is present in an amount of up to 20 g / ft of the substrate. 3 and wherein the catalyst is present in a loading amount of 0.1 to 1.0.

[0120] 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 further catalytic region, the support material particles generally, the substrate, and the catalyst article as a whole, apply equally to this aspect.

[0121] Providing rhodium-loaded support material particles having rhodium loaded thereon may include providing support material particles and loading rhodium thereon. Such methods are known in the art and any suitable technique may be used.

[0122] Forming a washcoat containing rhodium-loaded and unloaded support material particles preferably includes combining the rhodium-loaded and unloaded support material particles with water in any order to form a slurry. As used herein, the term "slurry" 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.

[0123] Coating a substrate with a washcoat can be carried out using techniques known in the art. Typically, the washcoat is injected into the inlet of the substrate using a specific molding tool in a predetermined amount, thereby coating the substrate with the washcoat. Alternatively, coating a substrate with the washcoat can be carried out by immersing the substrate in the washcoat. Subsequent vacuum and / or air knife and / or drying steps can be used during the coating process. If the substrate is a filter block, the washcoat can be coated on the filter walls, within the filter walls (if porous), or both.

[0124] By coating the substrate with a washcoat, rhodium can be added at up to 20g / ft of substrate. 3 It is essential to obtain a catalyst article in which the rhodium is present at a loading of about 1000 sq. m. It is readily within the skill of the art to appropriately plan the relative amounts of each component (e.g., washcoat and substrate) used in the present process to achieve such a desired rhodium loading.

[0125] Preferably, 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.

[0126] 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.

[0127] 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 perform a suitable incipient wetness impregnation method without further instruction.

[0128] 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.

[0129] After coating the substrate with the washcoat, the resulting catalyst article (or coated substrate) is preferably dried and / or calcined.

[0130] Preferably, the catalyst article of this embodiment is according to the first embodiment.

[0131] In a further aspect, the present invention provides a catalyst article obtained or obtainable by the method of the above aspect.

[0132] Surprisingly, when used in emissions treatment systems, catalyst articles of the present embodiment having locally higher concentrations of rhodium as defined herein, but still having a low overall rhodium loading to reduce PGM usage, exhibit significantly improved light-off performance {i.e., lower light-off temperatures, lower release of specific target species [NO x , CO, or total hydrocarbons (THC)] reaches 50%. 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 reduce catalytic activity. Thus, there may be an optimal local rhodium concentration for a particular low total rhodium loading.

[0133] The above effect may be particularly beneficial for catalyst articles having a low total rhodium loading, but may not be observed for 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 is no need to locally concentrate rhodium in parts of the support material.

[0134] 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.

[0135] In a further aspect, the present invention provides a method of treating exhaust gas, the method comprising providing a catalytic article as described herein and contacting the catalytic article with exhaust gas. Preferably, the exhaust gas is from a gasoline engine. Preferably, the gasoline engine is operated under stoichiometric conditions.

[0136] The invention will now be described with reference to the following non-limiting examples.

[0137] Catalyst Article Manufacturing A number of catalyst articles were prepared according to the following examples.

[0138] Reference catalyst 1 1. Pre-milled ceria zirconia mixed oxide (CZO) containing 20% ​​ceria was added at 1.0 g / in 3 The slurry was prepared with the target loading amount of 10 ... 2. 4g / ft 3 A calculated amount of Rh nitrate was added to the slurry (1) with the goal of Rh metal. 3. Ammonia was added to the washcoat (2) to adjust the pH to 7. 4. Add the slurry to a solution of 1.0 g / in 3The target loading was a 4% La2O3-Al2O3 slurry, which was then blended with the 4% La2O3-Al2O3 slurry. 5. The solids content was adjusted to thicken the washcoat. 6. First, the substrate was coated with washcoat (5) from one side, aiming for a coverage of 50% to 55%. This was dried with hot air until more than 80% of the moisture was removed. Next, the other side of the substrate was coated, aiming for a coverage of 50% to 55% of the original length, followed by drying and calcination again. 7. The final catalyst is 1.0 g / in 3 20% ceria containing CZO, 1.0 g / in 3 of 4% La2O3-Al2O3, and 4g / ft 3 Contains Rh metal.

[0139] Catalyst 1 of the present invention 1. Pre-milled CZO containing 20% ​​ceria (the same material used in step 1 of Reference Catalyst 1) was added at 0.15 g / in 3 The slurry was prepared with the target loading amount of 10 ... 2. 4g / ft 3 A calculated amount of Rh nitrate was added to the slurry (1) with the goal of Rh metal. 3. Ammonia was added to the washcoat (2) to adjust the pH to 7. 4. 0.86g / in 3 An additional amount of CZO slurry was added to the reference catalyst 1 (1.0 g / in 3 The CZO material used in this step contains 20% ceria, the same as in step 1 of Reference Catalyst 1. However, in this washcoat, Rh is locally concentrated on approximately 15.4% of the CZO support, which contains 20% CeO, while the remainder of the CZO support contains no Rh. This was mixed continuously. 5. Add the slurry to a solution of 1.0 g / in 3 The target loading was a 4% La2O3-Al2O3 slurry, which was then blended with the 4% La2O3-Al2O3 slurry. 6. The solids content was adjusted to thicken the washcoat. 7. First, the substrate was coated with washcoat (6) from one side, aiming for a coating length of 50% to 55%. This was dried with hot air until more than 80% of the moisture was removed. Next, the other side of the substrate was coated, aiming for a coating length of 50% to 55%, followed by drying and calcination again. 8. The final catalyst is 1.0 g / in 3 20% ceria containing CZO, 1.0 g / in 3 of 4% La2O3-Al2O3, and 4g / ft 3 Contains Rh metal.

[0140] Catalyst 2 of the present invention 1. Pre-milled CZO containing 30% ceria was added at 0.15 g / in 3 The slurry was prepared with the target loading amount of 10 ... 2. 4g / ft 3 A calculated amount of Rh nitrate was added to the slurry (1) with the goal of Rh metal. 3. Ammonia was added to the washcoat (2) to adjust the pH to 7. 4. 0.86g / in 3 An additional amount of CZO slurry was added to the reference catalyst 1 (1.0 g / in 3 The CZO material used in this step contained 20% ceria, the same as in step 1 of Reference Catalyst 1. However, in this washcoat, Rh was concentrated locally on approximately 15.4% of the CZO support, which contained 30% CeO, while the remainder of the CZO support was free of Rh. This was mixed continuously. 5. Add the slurry to a solution of 1.0 g / in 3 The target loading was a 4% La2O3-Al2O3 slurry, which was then blended with the 4% La2O3-Al2O3 slurry. 6. The solids content was adjusted to thicken the washcoat. 7. First, the substrate was coated with washcoat (6) from one side, aiming for a coating length of 50% to 55%. This was dried with hot air until more than 80% of the moisture was removed. Next, the other side of the substrate was coated, aiming for a coating length of 50% to 55%, followed by drying and calcination again. 8. The final catalyst is 0.15 g / in 3 30% ceria containing CZO, 0.85 g / in 3 20% ceria containing CZO, 1.0 g / in 3 of 4% La2O3-Al2O3, and 4g / ft 3 Contains Rh metal.

[0141] Catalyst 3 of the present invention 1. Pre-milled CZO containing 45% ceria was added at 0.15 g / in 3 The slurry was prepared with the target loading amount of 10 ... 2. 4g / ft 3 A calculated amount of Rh nitrate was added to the slurry (1) with the goal of Rh metal. 3. Ammonia was added to the washcoat (2) to adjust the pH to 7. 4. 0.86g / in 3 An additional amount of CZO slurry was added to the reference catalyst 1 (1.0 g / in 3 The CZO material used in this step contains 20% ceria, the same as in step 1 of Reference Catalyst 1. However, in this washcoat, Rh is concentrated locally on approximately 15.4% of the CZO support, which contains 45% CeO, while the remainder of the CZO support is Rh-free. This was mixed continuously. 5. Add the slurry to a solution of 1.0 g / in 3 The target loading was a 4% La2O3-Al2O3 slurry, which was then blended with the 4% La2O3-Al2O3 slurry. 6. The solids content was adjusted to thicken the washcoat. 7. First, the substrate was coated with washcoat (6) from one side, aiming for a coating length of 50% to 55%. This was dried with hot air until more than 80% of the moisture was removed. Next, the other side of the substrate was coated, aiming for a coating length of 50% to 55%, followed by drying and calcination again. 8. The final catalyst is 0.15 g / in 3 45% ceria containing CZO, 0.85 g / in 3 20% ceria containing CZO, 1.0 g / in 3of 4% La2O3-Al2O3, and 4g / ft 3 Contains Rh metal.

[0142] Example 1: High temperature RDE test in engine test Reference Catalyst 1 and Inventive Catalysts 1, 2, and 3 were engine bench aged for 50 hours in a stoic / fuel-cut aging cycle targeting a peak catalyst bed temperature of 1000°C. The catalysts were tested using a 2.0L engine bench dynamometer and subjected to a custom OEM-designed real-world driving (RDE) cycle including acceleration and fuel-cut conditions representative of 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 period between them. The catalyst bed temperature remains elevated while the engine is at operating temperature. The advantage of performing high-temperature RDE with low-temperature RDE as the precondition is the very good repeatability of engine emissions. NO at pre- and post-catalyst locations was measured. x Emissions of CO, THC, and HCl were measured, and the cumulative mass of each species was calculated over the entire cycle. To avoid discrepancies in engine-out emissions between experiments, cumulative conversion was further calculated by comparing the cumulative mass of pre-catalyst emissions with the cumulative mass at the catalyst outlet. The values ​​for the three high-temperature RDE experiments were plotted against time and are shown in the figure below.

[0143] FIG. 7a shows the NO 3 concentration of the reference catalyst 1 and the catalysts 1 to 3 of the present invention during the high-temperature RDE cycle. x The cumulative conversions are compared. All catalysts of the present invention show significantly improved performance compared to Reference Catalyst 1, with over 10% higher NO at the end of the cycle. x Therefore, the increase in the size of the Rh particles at a local Rh concentration of 1.5% is more resistant to calcination, migration, or segregation of the Rh cations into the CeO2 lattice, resulting in a higher NO x This can result in cumulative conversion.

[0144] Among the three inventive catalysts, inventive catalyst 2 provided the highest conversion throughout the entire test cycle. The high surface energy of CeO2 favors metal-support interactions. Therefore, the more ceria in CZO, the stronger the Rh-support interaction. However, too much ceria in CZO also leads to Rh dissolution into the bulk ceria after high-temperature treatment. Therefore, the 30% ceria content of CZO in inventive catalyst 2 may provide optimal metal-support interactions. However, a lower ceria-CZO content in inventive catalyst 1 or a higher ceria-CZO content in inventive catalyst 3 deteriorates catalytic activity, although still higher than that of reference catalyst 1. CO emissions and THC emissions are shown in Figures 7b and 7c, respectively. Inventive catalysts 1-3 all clearly demonstrate 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 lower ceria-CZO in Inventive Catalyst 1 or the higher ceria-CZO in Inventive Catalyst 3 begins to decrease CO and THC conversion compared to Inventive Catalyst 2 due to less than optimal Rh-support interaction.

[0145] Example 2: Light-off performance 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 then tested in a gasoline engine. Light-off performance was measured under typical conditions: gas volumetric space velocity of 216 K / h, temperature gradient of 20°C / min, and air-fuel ratio (AFR) lambda of 14.56, perturbed with an amplitude of 0.5 and a frequency of 1 Hz. THC conversion, CO conversion, and NO conversion were measured. 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 x Conversion, CO conversion, and THC conversion were calculated by comparing the concentrations of the feed gas with the concentrations of the gas at the outlet of the catalyst.

[0146] T 50 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 1. The data clearly show that inventive catalysts 1-3 all provide significantly improved light-off performance when compared to reference catalyst 1. Therefore, the optimal Rh particle size at 1.5% Rh local concentration may be more resistant to calcination, migration, or dissolution into the bulk ceria lattice, resulting in early light-off performance. Both inventive catalysts 1 and 2 provide significantly improved light-off performance when compared to reference catalyst 1. x About 65°C lower T 50 , about 80 °C lower T for CO 50 , and about 45°C lower T for THC 50 However, when the ceria content of the CZO in inventive catalyst 3 is too high, it 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, although this is still an improvement over reference catalyst 1.

[0147] [Table 1]

[0148] Reference catalyst 2 The bottom layer front zone washcoat slurry was prepared by the following: 1. A solution of palladium nitrate and a solution of dilute barium acetate were mixed. 2. Taurine was added to the above mixed solution (i) and the mixture was maintained. 3. 4% La2O3-doped alumina was ground and a slurry containing this was prepared separately. 4. The pre-solution in step (2) was added to the pre-milled 4% La2O3 doped alumina slurry (3) and mixing was continued. 5. A mixed oxide of ceria and zirconia was ground and a slurry containing the mixed oxide was prepared separately. 6. The resulting ceria-zirconia mixed oxide slurry (5) was added to the batch in step (4). 7. The washcoat slurry in (6) was thickened with a rheology modifier.

[0149] The final composition of the bottom layer front zone washcoat was a ceria-zirconia composite of 0.4 g / in 3 , 4% La2O3 doped alumina 0.8g / in 3 , Ba element 150g / ft 3 , and Pd element 9g / ft 3 It contained:

[0150] The bottom layer rear zone washcoat slurry was prepared by the following: 1. Pre-milled CZO containing 5% ceria was added at 1.5 g / in 3 The slurry was prepared with the target loading amount of 10 ... 2. 10g / ft 3 A calculated amount of Rh nitrate was added to the slurry (1) with the goal of Rh metal. 3. Ammonia was added to the washcoat (2) to adjust the pH to 7. 4. Add the slurry to a volume of 0.5 g / in 3 The target loading was a 4% La2O3-Al2O3 slurry, which was then blended with the 4% La2O3-Al2O3 slurry. 5. The solids content was adjusted to thicken the washcoat.

[0151] The final composition of the bottom layer rear zone washcoat was 1.5 g / in of total ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.5g / in 3 , and Rh element 10g / ft 3 It contained:

[0152] The top layer front zone washcoat was prepared by the following. 1. Mixed oxides of ceria and zirconia were ground. 2. A slurry containing 4% La2O3 doped alumina was milled separately. 3. The above two slurries (1) and (2) were blended. 4. Platinum nitrate was added to the slurry (3) and mixed. 5. Gallic acid was added and mixing was continued. 6. Barium sulfate powder was added and mixed continuously. 7. Adjust the pH to 7.0 or higher 8. Washcoat (7) was thickened with a rheology modifier.

[0153] The final composition of the top layer front zone washcoat was a ceria-zirconia composite at 0.4 g / in 3 , 4% La2O3 doped alumina 0.8g / in 3 , Ba element 150g / ft 3 , and Pd element 131 g / ft 3 It contained:

[0154] Washcoat coating on flow-through monolith substrate: 1. First, apply the bottom layer front zone to 75%-80% of the coating length using a precision coating method. Dry until more than 80% of the moisture has been removed. 2. Bake. 3. Apply the bottom layer rear zone wash coat to a target application length of 75%-80%. Dry until at least 80% of the water has been removed. 4. Apply the top layer to the front zone using a precision coating method, aiming for a 30%-35% application length. Dry until 80% or more of the moisture has been removed. 5. Bake again.

[0155] Catalyst 4 of the present invention The bottom layer front zone washcoat slurry was prepared in the same manner as Reference Catalyst 2. The bottom layer rear zone washcoat slurry was prepared by the following: 1. Pre-milled CZO containing 5% ceria was added at 0.56 g / in 3 The slurry was prepared with the target loading amount of 10 ... 2. 10g / ft 3A calculated amount of Rh nitrate was added to the slurry (1) with the goal of Rh metal. 3. Ammonia was added to the washcoat (2) to adjust the pH to 7. 4. 0.94g / in 3 An additional amount of CZO slurry was added to the reference catalyst 2 (1.5 g / in 3 ) The CZO material used in this step contains 5% ceria, the same as in step 1 of Reference Catalyst 2. However, in this washcoat, Rh is locally concentrated on approximately 37.3% of the CZO support containing 5% CeO, while the remainder of the CZO support is Rh-free. This was mixed continuously. 5. Add the slurry to a volume of 0.5 g / in 3 The target loading was a 4% La2O3-Al2O3 slurry, which was then blended with the 4% La2O3-Al2O3 slurry. 6. The solids content was adjusted to thicken the washcoat.

[0156] The final composition of the bottom layer rear zone washcoat was 1.5 g / in of total ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.5g / in 3 , and Rh element 10g / ft 3 All ceria-zirconia composites contained 5% ceria.

[0157] The top front zone washcoat was prepared in the same manner as Reference Catalyst 2. The washcoat coating on the flow-through monolith substrate was the same as for Reference Catalyst 2.

[0158] Catalyst 5 of the present invention The bottom layer front zone washcoat slurry was prepared in the same manner as Reference Catalyst 2. The bottom layer rear zone washcoat slurry was prepared by the following: 1. Pre-milled CZO containing 30% ceria was added at 0.56 g / in 3 The slurry was prepared with the target loading amount of 10 ... 2. 10g / ft3 A calculated amount of Rh nitrate was added to the slurry (1) with the goal of Rh metal. 3. Ammonia was added to the washcoat (2) to adjust the pH to 7. 4. 0.94g / in 3 An additional amount of CZO slurry was added to the reference catalyst 2 (1.5 g / in 3 However, the CZO material used in this process contains 30% ceria. In this washcoat, Rh is locally concentrated on approximately 37.3% of the CZO support containing 30% CeO, while the remainder of the CZO support is Rh-free. This was mixed continuously. 5. Add the slurry to a volume of 0.5 g / in 3 The target loading was a 4% La2O3-Al2O3 slurry, which was then blended with the 4% La2O3-Al2O3 slurry. 6. The solids content was adjusted to thicken the washcoat.

[0159] The final composition of the bottom layer rear zone washcoat was 1.5 g / in of total ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.5g / in 3 , and Rh element 10g / ft 3 Each of the ceria-zirconia composites contained 30% ceria.

[0160] The top front zone washcoat was prepared in the same manner as Reference Catalyst 2. The washcoat coating on the flow-through monolith substrate was the same as for Reference Catalyst 2.

[0161] Example 3: Light-off performance test in engine test All catalysts were engine bench aged for 108 hours in 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 95 K / h, temperature gradient of 10°C / min, and lambda of the air-to-fuel ratio (AFR) perturbed with an amplitude of 0.5 at 14.55. The conversions of NOx, CO, and THC were calculated by comparing the concentrations of the feed gas with those at the catalyst outlet, and the T 50 is defined as the temperature at which 50% conversion of the pollutant is achieved. 50 The lower the temperature, the better the catalyst.

[0162] NO x , CO, and THC 50 The light-off temperatures are shown in Table 2. The data clearly show that both Inventive Catalyst 4 and Inventive Catalyst 5 provide significantly improved light-off performance when compared to Reference Catalyst 2. Typically, the rear portion of the catalyst brick has a greater impact on the light-off function of a TWC catalyst. Therefore, the application of Rh distribution technology in the rear zone of the bottom layer in this catalyst design undoubtedly contributed to Inventive Catalyst 4 having a T that was 17-22°C lower than Reference Catalyst 2. 50 This benefit was demonstrated by showing that the optimum Rh particle size at 1.0% Rh local concentration is therefore more resistant to calcination, migration, or dissolution into the bulk ceria lattice, potentially resulting in early light-off performance. In particular, inventive catalyst 5 was even more active than inventive catalyst 4, demonstrating that all T 50s is several degrees lower. Therefore, it is possible that the 30% ceria content of CZO in inventive catalyst 5 may provide stronger metal-support interaction than the 5% ceria in inventive catalyst 4. More OSC capacity is another factor for the earlier light-off activity. Clearly, inventive catalyst 5 has higher OSC capacity due to the use of 30% ceria-containing CZO.

[0163] [Table 2]

[0164] Example 4: Warm-up test in engine test All catalysts were engine bench aged for 108 hours in a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C and then tested in a gasoline engine. Warm-up tests were typically conducted at a gas hourly space velocity of 95K. Pollutants from the engine out were preheated to 490°C and then directed onto the cold catalyst. Total hydrocarbons, carbon monoxide, and NO were measured. x The time to reach 50% conversion of T 50 H.C., T. 50 CO, and T 50 NO x THC, CO, and NO x The conversion was calculated by comparing the concentration of the feed gas with the concentration of the gas at the outlet of the catalyst.

[0165] The data in Table 3 clearly show that both Inventive Catalyst 4 and Inventive Catalyst 5 warm up a little faster than Reference Catalyst 2, with no significant difference between Inventive Catalyst 4 and Catalyst 5. Previous studies have shown that the front zone of a TWC catalyst has a greater impact on warm-up performance than the rear zone. Therefore, it is not surprising that the warm-up activity of all catalysts is quite similar when only the Rh-containing rear zone is modified.

[0166] [Table 3]

[0167] Reference catalyst 3 The bottom layer front zone washcoat was prepared by the following. 1. 4% La2O3-doped alumina was ground and a slurry containing this was prepared. 2. Ceria and CZO were pulverized to prepare a slurry containing them. 3. The two slurries were blended together. 4. Barium hydroxide and palladium nitrate were added to the slurry (3). 5. Addition of tannic acid to the slurry (4) 6. Adjust the solids content of the washcoat (5) and thicken it with a rheology modifier. 7. The final composition of the bottom layer washcoat is La-Al2O3 1.0 g / in 3 , ceria-zirconia composite 1.0 g / in 3 , Ba element 400g / ft 3 , and Pd element 31 g / ft 3 Contains:

[0168] The bottom layer rear zone washcoat was prepared by the following. 1. 4% La2O3-doped alumina was ground and a slurry containing this was prepared. 2. Ceria and CZO were pulverized to prepare a slurry containing them. 3. The two slurries were blended together. 4. Add platinum nitrate to the slurry (3). 5. Adjust the solids content of the washcoat (4) and thicken it with a rheology modifier. 6. The final composition of the bottom layer washcoat is La-Al2O3 1.0 g / in 3 , ceria-zirconia composite 1.0 g / in 3 , and Pt element 28g / ft 3 Contains:

[0169] The top layer washcoat was prepared by the following. 1. La-stabilized alumina (La-Al2O3) was pulverized and a slurry containing it was prepared. 2. 1.0g / in 3 of La-Al2O3, 5g / ft 3 Rh, 2.4g / ft 3 Calculated amounts of rhodium nitrate solution and platinum nitrate solution were added to the slurry (1) with the target of Pt of each. 3. The pH of the slurry (2) was increased to 6-7 with ammonia to obtain a local Rh concentration of 0.29%. 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 was 40% ceria. This was mixed continuously. The CZO material used in this process contains 40% ceria. 5. The solid content of the washcoat (4) was adjusted with a rheology modifier to increase viscosity. 6. The final composition of the top layer washcoat is 1.0 g / in of 4% La2O3-doped alumina. 3 , ceria-zirconia composite 1.0 g / in 3 , and Rh element 5g / ft 3 and the CZO material used contains 40% ceria.

[0170] Washcoat coating on flow-through monolith substrate: 1. First apply the bottom layer front zone to 50%-55% of the coating length using a precision coating method. Dry until more than 80% of the moisture has been removed. 2. Apply the bottom layer rear zone washcoat to a target application length of 50%-55%. Dry until at least 80% of the water has been removed. 3. Bake. 4. Apply the top layer washcoat from the front zone using a precision coating method targeting a 50%-55% application length. Dry to 80% or more moisture removal. 5. Apply the top layer washcoat from the rear zone using a precision coating method targeting a 50%-55% application length. Dry to 80% or more moisture removal. 6. Bake again.

[0171] Catalyst 6 of the present invention having a zone configuration in the upper layer The bottom layer washcoat was prepared and coated in the same manner as the bottom layer of Reference Catalyst 3.

[0172] The upper layer of the catalyst 6 of the present invention has a zone configuration.

[0173] The inlet zone washcoat was prepared by the following. 1. Grinding was performed to prepare a slurry containing CZO. The CZO material used in this step contained 40% ceria, the same as in step 4 of Reference Catalyst 3. 2. 0.65g / in 3 of CZO and 5g / ft 3 A calculated amount of rhodium nitrate solution was added to the slurry (1) with the target Rh content of each. 3. The pH of the slurry (2) was increased to 6-7 with ammonia. 4. Add the slurry (3) to the slurry (3) at a rate of 0.65 g / in 3 The La-Al2O3 slurry was blended with pre-ground La-Al2O3 slurry with the target loading of 10 ... 5. The solid content of the washcoat (5) was adjusted with a rheology modifier to increase viscosity. 6. The final composition of the top layer inlet zone washcoat is 0.65 g / in of 4% La2O3-doped alumina. 3 , ceria-zirconia composite 0.65 g / in 3 , and Rh element 5g / ft 3 The washcoat loading was 35% less than that of Reference Catalyst 3.

[0174] The exit zone washcoat was prepared by the following. 1. Grinding was performed to prepare a slurry containing CZO. The CZO material used in this step contained 40% ceria, the same as in step 4 of Reference Catalyst 3. 2. 0.19g / in 3 of CZO and 5g / ft 3 A calculated amount of rhodium nitrate solution was added to the slurry (1) with the target Rh content of each. 3. The pH of the slurry (2) was increased to 6-7 with ammonia. 4. 0.46g / in 3 An additional amount of CZO slurry was added to increase the total CZO to the upper layer inlet zone (0.65 g / in 3 In this washcoat, Rh was locally concentrated on approximately 41.3% of the CZO support containing 40% CeO, while the remainder of the CZO support was free of Rh. This was then mixed continuously. 5. Add the slurry (4) to the slurry (4) at a rate of 0.65 g / in 3 The La-Al2O3 slurry was blended with pre-ground La-Al2O3 slurry with the target loading of 10 ... 6. The solid content of the washcoat (5) was adjusted with a rheology modifier to increase viscosity. 7. The final composition of the top layer inlet zone washcoat is 0.65 g / in of 4% La2O3-doped alumina. 3 , ceria-zirconia composite 0.65 g / in 3 , and Rh element 5g / ft 3 The washcoat loading was 35% less than that of Reference Catalyst 3.

[0175] 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, performing a custom OEM-designed real-road driving (RDE) cycle including acceleration and fuel cut-off conditions representing cold-start city, highway, and hot city speed phases. The cycle length was 2700 seconds from ambient soak conditions, achieving a peak catalyst temperature of approximately 700°C at a vehicle speed of approximately 140 km / h and a mass air flow rate of 400 kg / h. NO at post-catalyst locations x Emissions of , CO, and THC 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 cumulative mass of each polluting species for the three experiments against time was plotted and is shown in the figure below.

[0176] FIG. 8a shows the NO 3 and inventive catalyst 6 during a low-temperature RDE cycle. x The inventive catalyst 6, with a zone configuration enriched with 1.5% Rh on the CZO material in the rear zone, has a 35% reduced washcoat loading but produces similar NO emissions as the reference catalyst 4 over the entire low-temperature RDE driving cycle. xCO and THC emissions are shown in Figures 8b and 8c, respectively. Although there is some variability from run to run, inventive catalyst 6, with 35% less washcoat loading, still performs very close to the benchmark for either CO or THC emissions regulations.

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 wherein said support material particles comprise a ceria-zirconia mixed oxide, said ceria-zirconia mixed oxide having a ceria content of at least 20 wt. %.

2. 10. The catalyst article of claim 1, wherein said 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 said rhodium-loaded support material particles.

3. 3. The catalyst article of claim 2, wherein said rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.4 to 3.0 weight percent based on the weight of said rhodium-loaded support material particles.

4. 4. The catalyst article of claim 3, wherein said rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.4 to 2.0 weight percent based on the weight of said rhodium-loaded support material particles.

5. 5. The catalyst article of claim 4, wherein said rhodium-loaded support material particles have rhodium loaded thereon at a concentration of 0.4 to 1.5 weight percent based on the weight of said rhodium-loaded support material particles.

6. 6. A catalyst article according to any one of claims 1 to 5, wherein at least some of the support material particles are unsupported support material particles having essentially no rhodium supported thereon, preferably no rhodium supported thereon.

7. 7. The catalyst article of any one of claims 1 to 6, wherein 5 to 80% of the support material particles in the first catalyst region are rhodium-loaded support material particles.

8. 8. The catalytic article of claim 7, wherein 7 to 60% of the support material particles in the first catalytic region are rhodium-loaded support material particles.

9. 9. The catalytic article of claim 8, wherein 10 to 50% of the support material particles in the first catalytic region are rhodium-loaded support material particles.

10. 10. The catalytic article of claim 9, wherein 15 to 35% of the support material particles in the first catalytic region are rhodium-loaded support material particles.

11. Catalyst article according to any one of claims 1 to 10, wherein said ceria-zirconia mixed oxide has a ceria content of up to 45% by weight.

12. Catalyst article according to any one of claims 1 to 11, wherein said ceria-zirconia mixed oxide is doped.

13. 13. The catalytic article of claim 12, wherein the ceria-zirconia mixed oxide is 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.

14. 14. The catalytic article of claim 13, wherein said dopant is present in said ceria-zirconia mixed oxide in an amount of from 0.001% to 20% by weight, preferably from 0.5% to 10% by weight.

15. The carrier material particles have a D of 0.1 to 25 μm, preferably 0.5 to 5 μm ９０ The catalyst article of any one of claims 1 to 14, having

16. Catalyst article according to any one of the preceding claims, wherein said ceria-zirconia mixed oxide has a ceria content of 20 to 40 wt%.

17. 17. The catalytic article of claim 16, wherein said ceria-zirconia mixed oxide has a ceria content of 25 to 40 wt. %.

18. The rhodium is present in an amount of 1 to 20 g / ft of the first catalytic region. ３ 18. The catalyst article of any one of claims 1 to 17, wherein the catalyst is present at a loading of

19. The rhodium is present in an amount of 2 to 18 g / ft of the first catalyst region. ３ 20. The catalyst article of claim 18, wherein the catalyst is present at a loading of

20. The carrier material particles have a density of 0.5 to 3 g / in ３ 20. The catalyst article of any one of claims 1 to 19, wherein the catalyst is present at a loading of

21. The carrier material particles have a density of 0.5 to 2 g / in ３ 21. The catalytic article of claim 20, wherein the catalyst is present at a loading of

22. The carrier material particles have a density of 0.75 to 1.5 g / in ３ 22. The catalytic article of claim 21, wherein the catalyst is present at a loading of

23. The catalytic article of any one of claims 1 to 22, further comprising a second catalytic region.

24. 24. The catalytic article of claim 23, wherein the second catalytic region comprises a second PGM component.

25. 20. The catalytic article of claim 18, wherein the second PGM component is selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof.

26. The catalytic article of any one of claims 23 to 25, wherein the second catalytic region further comprises a second OSC material and / or a second inorganic oxide.

27. 27. The catalytic article of claim 26, wherein the second OSC material is cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof.

28. 27. The catalytic article of claim 26, wherein the second inorganic oxide is selected from the group consisting of alumina, magnesia, silica, zirconia, lanthanum, cerium, neodymium, praseodymium, yttrium oxides, and mixed or composite oxides thereof.

29. The catalytic article of any one of claims 1 to 28, wherein the first catalytic region extends over the axial length L.

30. The catalytic article of any one of claims 23 to 29, wherein the second catalytic region extends over the axial length L.

31. The catalytic article of any one of claims 1 to 30, wherein the first catalytic region is supported / deposited directly on the substrate.

32. The catalytic article of any one of claims 23 to 30, wherein the second catalytic region is supported / deposited directly on the substrate.

33. The catalytic article of any one of claims 1 to 28, wherein the first catalytic region extends over less than the axial length L.

34. The catalytic article of any one of claims 23 to 29, wherein the second catalytic region extends over less than the axial length L.

35. 35. The catalytic article of claim 33 or 34, wherein the first catalytic region is supported / deposited directly on the substrate.

36. 35. The catalytic article of claim 33 or claim 34, wherein the second catalytic region is supported / deposited directly on the substrate.

37. The catalytic article of any one of claims 23 to 36, further comprising a third catalytic region.

38. 38. The catalytic article of claim 37, wherein the third catalytic region comprises a third PGM component.

39. 39. The catalytic article of claim 38, wherein the third PGM component is selected from the group consisting of platinum, palladium, rhodium, and mixtures thereof.

40. 40. The catalytic article of any one of claims 37 to 39, wherein the third catalytic region further comprises a third OSC material and / or a third inorganic oxide.

41. 41. The catalytic article of claim 40, wherein the third OSC material is cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof.

42. 41. The catalytic article of claim 40, wherein the third inorganic oxide is selected from the group consisting of alumina, magnesia, silica, zirconia, lanthanum, cerium, neodymium, praseodymium, yttrium oxides, and mixed or composite oxides thereof.

43. The catalytic article of any one of claims 37 to 42, wherein the third catalytic region extends across the axial length L.

44. The catalytic article of any one of claims 37 to 42, wherein the third catalytic region extends over less than the axial length L.

45. The catalytic article of any one of claims 1 to 44, wherein the first catalytic region further comprises platinum and / or palladium.

46. A catalytic article according to any one of claims 1 to 45 for three-way catalysis.

47. The catalytic article of any one of claims 1 to 46, wherein the substrate comprises a wall-flow filter substrate.

48. The catalytic article of any one of claims 1 to 46, wherein the substrate comprises a flow-through substrate.

49. An emissions treatment system comprising the catalytic article of any one of claims 1 to 48.

50. 50. The emission treatment system of claim 49 for a gasoline engine.

51. 51. The emission treatment system of claim 50, wherein the gasoline engine operates under stoichiometric conditions.

52. 1. A method for treating an exhaust gas, the method comprising: Providing a catalyst article according to any one of claims 1 to 48; contacting the catalytic article with an exhaust gas.

53. 52. The method of claim 51, wherein the exhaust gas is from a gasoline engine.

54. 54. The method of claim 53, wherein the gasoline engine is operated under stoichiometric conditions.

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