Sulfur-containing organic compounds assisted metal nanoparticle synthesis for three-way catalysis applications

Abstract

1. A method of making a catalytic article, the method comprising: providing a slurry comprising a support material, palladium ions, alkaline earth metal ions, and an organic compound, the organic compound comprising a functional group selected from sulfo (-SO3H), sulfonyl (-S(=O)2-), and sulfinyl (-S(=O)-), disposing the slurry on a substrate, and heating the slurry to form palladium nanoparticles and alkaline earth metal sulfate nanoparticles on the support material.

Description

[Technical field]

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

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

[0003] Conventional preparation of TWC washcoat slurries generally involves depositing the PGM elements onto oxide supports by incipient wetness or wet impregnation using solutions of inorganic PGM precursors, such as nitrates, acetates, hydroxides, or chlorides. Promoter salts are often added to the washcoat formulation to improve TWC performance. Once the monolith substrate is washcoated with the as-prepared slurry, drying and calcination steps are subsequently performed to decompose the inorganic salts and fix the PGMs and promoter elements onto the support material. Conventional TWCs prepared using the above methods often offer limited control over the properties of the catalytically active species (i.e., the average particle size of the PGMs and promoters, the association of these active components, and the metal-support interactions). This is primarily due to migration and particle growth during the drying and high-temperature calcination processes.

[0004] Typically, Pd is a catalyzer for the NO x It is known that alkaline earth metals such as barium are good promoters for the catalytic function of Pd. Ba can donate electrons to Pd, which leads to the reduction of Pd. (II) The electron configuration of Pd becomes more similar to that of Rh, which can improve the rich NOx reduction activity of Pd TWC [Non-Patent Document 1]. x Both the adsorption strength of NO and CO were reduced on the Ba-promoted Pd catalyst. x and improved CO conversion [Non-Patent Document 2, Non-Patent Document 3]. Ba also helps stabilize PdO and inhibit sintering due to high temperature exposure during life-time application of three-way catalytic converters. Last but not least, Ba is a good stabilizer for the alumina support material, which helps maintain high dispersion of the Pd species.

[0005] When using Ba components as additives, it is important to control the location and size of both palladium and barium to optimize the synergistic interaction with active Pd, Ba species, and support components. However, in catalysts obtained from known methods, the particle size of alkaline earth metal-containing species is generally large compared to Pd nanoparticles, so that the interaction may not be optimized. Furthermore, this interaction may deteriorate upon aging in catalysts obtained from known methods. Therefore, there is a need to provide a method for producing a catalyst article that allows a more optimized interaction between palladium nanoparticles and alkaline earth metal-containing species in the resulting catalyst article, ideally with comparable particle size and close proximity that allows such improved performance and is less susceptible to aging.

[0006] Significant efforts have been made historically to reduce the particle size of barium species to facilitate closer contact with Pd species that are mostly located within the pores of the support material with nanoscale particle size. Ball / bead milling of BaSO4 compounds is not very effective in making nanoscale barium sulfate species [Patent Document 1, Patent Document 6]. To generate barium sulfate species during the calcination step, sulfuric acid was added to Pd washcoats with Ba acetate or Ba hydroxide as precursors. Smaller BaSO4 particle sizes were obtained. However, this is still at the micron level and far from the nanoscale goal [Patent Documents 2-5]. US Patent Application Publication No. 2020 / 030780 discloses a method of making catalytic articles that involves the use of sulfur-containing organic compounds. However, US Patent Application Publication No. 2020 / 030780 involves first immobilizing both Pd and Ba on the same support using a pre-calcination process. This process is not cost-effective due to the high cost-to-yield ratio of the PGM content. In addition, the particle size of the Ba sulfate species is substantially larger than the Pd particle size. The method of U.S. Patent Application Publication No. 2020 / 030780 also importantly involves starting with a slurry of the support material, to which the other components of the washcoat are added successively.

[0007] Citation List: Patent literature: Patent Document 1: U.S. Patent No. 8,741,799 Patent Document 2: U.S. Patent Application Publication No. 2012 / 0165185 Patent Document 3: U.S. Patent No. 8,545,780 Patent document 4: U.S. Patent No. 8,835,346 Patent Document 5: U.S. Patent Application Publication No. 2014 / 0329669 Patent Document 6: International Publication No. 2014 / 156746 Patent Document 7: U.S. Patent Application Publication No. 2020 / 030780

[0008] Non-patent literature: Non-patent document 1: Applied Catalyst B, 30, 2001, 287 Non-patent document 2: Journal of Molecular Catalysis A: Chemical, 349, 2011, 94 Non-patent document 3: Applied Catalysis A: General403, 2011, 12 Summary of the Invention

[0009] One aspect of the present disclosure is directed to a method of making a catalytic article, the method including providing a slurry including a support material, palladium ions, alkaline earth metal ions, and an organic compound, where the organic compound includes a functional group selected from a sulfo group (-SO3H), a sulfonyl group (-S(=O)2-), and a sulfinyl group (-S(=O)-), disposing the slurry on a substrate, and heating the slurry to form palladium nanoparticles and alkaline earth metal sulfate nanoparticles on the support material.

[0010] Another aspect of the present disclosure is directed to a method of making a catalytic article, the method including providing a solution including palladium ions, alkaline earth metal ions, and an organic compound, where the organic compound includes a functional group selected from a sulfo group (-SO3H), a sulfonyl group (-S(=O)2-), and a sulfinyl group (-S(=O)-), providing a support material, contacting the solution with the support material to form a slurry, disposing the slurry on a substrate, and heating the slurry to form palladium nanoparticles and alkaline earth metal sulfate nanoparticles on the support material.

[0011] Another aspect of the present disclosure is directed to a catalyst article for use in an emissions treatment system, the catalyst article comprising: a substrate; and a first catalytic region on the substrate, the first catalytic region comprising a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles, the alkaline earth metal sulfate nanoparticles having a crystallite size of 0.1 nm to 30 nm.

[0012] Another aspect of the present disclosure is a catalyst article for use in an exhaust treatment system, the catalyst article comprising a substrate and a first catalyst region on the substrate, the first catalyst region comprising a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles, and when a cross section of the first catalyst region of the catalyst article is area-analyzed by FE-EPMA under conditions of a pixel (cross section) size of 0.34 μm×0.34 μm and a measurement pixel (cross section) number of 256×256, a characteristic X-ray intensity (α: cps) of an alkaline earth metal element (Ae) and a characteristic X-ray intensity (β: cps) of palladium (Pd) are measured for each pixel, and a Pearson correlation coefficient calculated using α and β at each pixel obtained is expressed as R Ae / Pd When you specify Ae / Pd is at least 0.75.

[0013] Another aspect of the present disclosure is directed to a catalyst article obtainable by the method of the first aspect.

[0014] The invention also includes an exhaust system for an internal combustion engine comprising a catalytic article of the second, third or fourth aspect.

[0015] Another aspect of the present disclosure is directed to a method of treating an exhaust gas, the method comprising providing a catalytic article of the second, third, or fourth aspect and contacting the catalytic article with the exhaust gas. [Brief description of the drawings]

[0016] The invention will now be described with reference to the following non-limiting drawings.

[0017] [Figure 1] 1 shows one embodiment according to the present invention containing a first catalytic region (single layer) having a length of 100% relative to the axial length L of the substrate. [Figure 2a] 1 shows an embodiment according to the invention in which a first catalyst region extends 100% of the axial length L as a bottom layer and a second catalyst region extends 100% of the axial length L as a top layer. [Figure 2b]2 illustrates a variation of FIG. 2a. [Figure 3a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from the inlet end less than 100% of the axial length L, and a second catalyst region extends from the outlet end less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is equal to or less than the axial length L. [Figure 3b] 3 illustrates a variation of FIG. 3a. [Figure 3c] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from the inlet end less than 100% of the axial length L, and a second catalyst region extends from the outlet end less than 100% of the axial length L. The total length of the second catalyst region and the first catalyst region is greater than the axial length L. [Figure 3d] 3 illustrates a variation of FIG. 3c. [Figure 4a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is equal to or less than the axial length L. A third catalyst region extends 100% of the axial length L and is layered as an upper layer onto the first and second catalyst regions. [Figure 4b] 4 illustrates a variation of FIG. 4a. [Figure 4c] 1 illustrates an embodiment according to the present invention in which the third catalyst region is a bottom layer and extends 100% of the axial length L. The first catalyst region extends less than 100% of the axial length L from the inlet end and the second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is less than or equal to the axial length L. [Figure 4d] 4 illustrates a variation of FIG. 4c. [Figure 5a]1 illustrates an embodiment according to the invention in which the first catalyst region extends less than 100% of the axial length L from the inlet end and the second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region can be less than, equal to, or greater than the axial length L. The third catalyst region extends less than 100% of the axial length L from the inlet end and the fourth catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the third catalyst region and the fourth catalyst region can be less than, equal to, or greater than the axial length L. The first catalyst region and the second catalyst region constitute a bottom layer and the third catalyst region and the fourth catalyst region constitute a top layer. [Figure 5b] 5 illustrates a variation of FIG. 5a. [Figure 5c] 5 illustrates a variation of FIG. 5a. [Figure 5d] 5 illustrates a variation of FIG. 5a. [Figure 6a] 1 shows an embodiment according to the invention in which a first catalyst region is a bottom layer extending over 100% of the axial length L, a second catalyst region is a middle layer extending over 100% of the axial length L, and a third catalyst region is a top layer extending over 100% of the axial length L. [Figure 6b] 6 illustrates a variation of FIG. 6a. [Figure 6c] 6 illustrates a variation of FIG. 6a. [Figure 7a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region is greater than the axial length L. A third catalyst region extends 100% of the axial length L and is layered as an upper layer onto the first and second catalyst regions. [Figure 7b] 7 illustrates a variation of FIG. 7a. [Figure 7c] 7 illustrates a variation of FIG. 7a. [Figure 7d] 7 illustrates a variation of FIG. 7a. [Figure 7e] 7 illustrates a variation of FIG. 7a. [Figure 7f] 7 illustrates a variation of FIG. 7a. [Figure 7g] 1 illustrates an embodiment according to the present invention, where a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region can be less than, equal to, or greater than the axial length L. A third catalyst region extends less than 100% of the axial length L from the inlet end and is at least partially stacked to the first catalyst region and / or the second catalyst region. [Figure 7h] 7A illustrates a variation of FIG. 7g. [Figure 7i] 7A illustrates a variation of FIG. 7g. [Figure 7j] 1 illustrates an embodiment according to the present invention, where a first catalyst region extends less than 100% of the axial length L from the inlet end and a second catalyst region extends less than 100% of the axial length L from the outlet end. The total length of the second catalyst region and the first catalyst region can be less than, equal to, or greater than the axial length L. A third catalyst region extends less than 100% of the axial length L from the outlet end and is at least partially stacked to the second and / or first catalyst regions. [Figure 7k] Illustrates a variation of FIG. 7j. [Figure 7l] Illustrates a variation of FIG. 7j. [Figure 8] 1 shows NOx and CO conversion at different lambda (air-fuel ratio) values ​​for a reference catalyst and a catalyst of the invention according to the invention. [Figure 9] 1 shows THC (total hydrocarbon) conversion at different lambda values ​​for a reference catalyst and a catalyst of the present invention according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 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.

[0019] In a first aspect, the present invention provides a method of making a catalyst article, the method comprising: providing a slurry comprising a support material, palladium ions, alkaline earth metal ions, and an organic compound, the organic compound comprising a functional group selected from a sulfo group (-SO3H), a sulfonyl group (-S(=O)2-), and a sulfinyl group (-S(=O)-); disposing the slurry on a substrate; and heating the slurry to form palladium nanoparticles and alkaline earth metal sulfate nanoparticles on the support material.

[0020] Each aspect or embodiment defined in this specification may be combined with any other aspect or embodiment unless expressly indicated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0021] The slurry preferably further comprises an inorganic oxide, more preferably a mixed inorganic oxide.

[0022] Providing a slurry comprising a carrier material, palladium ions, alkaline earth metal ions, and an organic compound typically comprises contacting the carrier material, palladium ions, typically in the form of a palladium salt, alkaline earth metal ions, typically in the form of an alkaline earth metal salt, and an organic compound with a solvent, or contacting a first slurry comprising a carrier material, for example, with palladium ions, typically in the form of a palladium salt, alkaline earth metal ions, typically in the form of an alkaline earth metal salt, and an organic compound. The palladium ions, alkaline earth metal ions, and organic compound may be combined with the first slurry in any order, sequentially, or all at once. The solvent is preferably selected such that each of the palladium ions, alkaline earth metal ions, and organic compound has a high solubility in the solvent. Thus, providing a slurry preferably comprises one or more steps of combining two or more of the carrier material, palladium ions, alkaline earth metal ions, organic compound, and optionally inorganic oxide in a solvent. The solvent preferably comprises water. Providing a slurry comprising the support material, palladium ions, alkaline earth metal ions, and the organic compound typically further includes stirring the slurry for an extended period of time, such as at least 30 minutes.

[0023] The method includes a step of disposing the slurry on a substrate. In other words, the slurry provided with its component parts is disposed on a support material. Thus, preferably, the slurry is provided, for example, by mixing its component parts, and then disposed on a substrate. In other words, preferably, there is no intervening step between providing the slurry (for example, by mixing its component parts) and disposing the slurry on a substrate. In particular, the slurry is disposed on a substrate. Thus, preferably, there is no intervening step of drying and calcining the provided slurry to form a powder (of course, likely to form nanoparticles of palladium and / or alkaline earth metal sulfates, and also removing substantially all organics, for example by pyrolysis or combustion), and then providing a further separate slurry by adding such powder to a solvent, which is then disposed on a support material.

[0024] In a second aspect, the present invention provides a method of making a catalyst article, the method comprising: providing a solution comprising palladium ions, alkaline earth metal ions, and an organic compound, the organic compound comprising a functional group selected from a sulfo group (-SO3H), a sulfonyl group (-S(=O)2-), and a sulfinyl group (-S(=O)-); Providing a support material; contacting the solution with a support material to form a slurry; disposing the slurry on a substrate; and heating the slurry to form palladium nanoparticles and alkaline earth metal sulfate nanoparticles on the support material.

[0025] Surprisingly, when used in an emission treatment system, the catalyst article produced by the method of the present invention (e.g., the first or second embodiment) may exhibit favorable catalytic activity, particularly favorable three-way catalytic activity. For example, the catalyst article may exhibit favorable light-off performance, particularly NO, CO, and total hydrocarbon conversion, during three-way catalytic emission reduction of a stoichiometric gasoline engine. Such favorable catalytic activity and light-off performance may be superior to that exhibited by a conventional catalyst article having the same / similar PGM species, loading, support, and configuration. The catalyst article may be more durable compared to a conventional catalyst article. In other words, such favorable catalytic activity may be exhibited even after aging.

[0026] Advantageously, such superior performance may facilitate the use of lower loadings of PGMs and / or promoter metals (such as alkaline earth metals) compared to conventional catalyst articles without compromising catalytic performance, which may be beneficial given the high cost of such metals, such as palladium. Furthermore, such superior performance may facilitate partial / complete replacement of high cost PGMs with lower cost PGMs or other transition metals without compromising catalytic performance.

[0027] Additionally, the catalyst article exhibits surprisingly efficient NO x Conversion performance may be improved because the promoter interactions of alkaline earth metals, such as barium, with palladium may be particularly effective in such catalyst articles.

[0028] Without being bound by theory, it is hypothesized that such superior performance may be provided by the preferred particle size distribution of the palladium nanoparticles and the alkaline earth metal sulfate nanoparticles, and the preferred distribution of the palladium nanoparticles and the alkaline earth metal sulfate nanoparticles relative to each other, i.e., have a high correlation with each other (in other words, have a large number of palladium-alkaline earth metal interactions, by having particularly small particle size and highly uniformly distributed nanoparticles, i.e., a distribution of palladium nanoparticles and alkaline earth metal sulfate nanoparticles with high uniformity). Without being bound by theory, it is hypothesized that the method of the present invention (e.g., the first embodiment or the second embodiment), in which the slurry provided in the method is disposed on a substrate, may help to enable a smaller particle size and a uniform distribution of palladium and alkaline earth metal on the loaded support material and in the final support material formed. It is believed that this may be because, for example, there may be no intervening step in which the prepared slurry is dried and / or calcined and / or calcined before forming a further slurry that is disposed on a substrate. Without being bound by theory, it is also hypothesized that by first providing a solution containing palladium ions, alkaline earth metal ions, and an organic compound, as in the second embodiment, and then mixing such solution with any support material, interactions in the solution (e.g., forming one or more complexes) may further aid in enabling both small particle size and uniform distribution of the palladium and alkaline earth metal on the loaded support material and within the final support material formed. Thus, the cocatalytic activity of the palladium-alkaline earth metal combination may be optimized through a greater number of interactions.

[0029] Furthermore, without being bound by theory, it is assumed that such a method may enable the particle size of palladium and alkaline earth metal sulfate to be comparable, i.e., of similar size. Typically, in conventional methods, alkaline earth metal sulfate nanoparticles may be up to 5, 10, or even 20 times larger than palladium nanoparticles. In the method of the present invention, it may be possible to obtain small nanoparticles of similar size, so the interaction and correlation between palladium and alkaline earth metal may be high. This is because the nanoparticles may thus be located closely adjacent to each other on the support material (e.g., when uniformly distributed), and may, for example, enter pores of the same size in the support material. Thus, a highly uniform distribution of particles of similar size may be provided. This may enable the above-mentioned advantageous effects to be achieved, but optimize the possibility of interaction between palladium and alkaline earth metal promoter species.

[0030] Without being bound by theory, it is also believed that such a distribution of the resulting palladium nanoparticles and alkaline earth metal sulfate nanoparticles may help achieve advantageous aging characteristics, i.e., increased resistance to deactivation during aging (e.g., NOx conversion performance). This may be because, due to the more uniform distribution of small nanoparticles that may be formed, i.e., due to the relatively high number of direct interactions between palladium and alkaline earth metals and the relatively low number of direct interactions between palladium and palladium and alkaline earth metals (i.e., relative to adjacent nanoparticles), upon aging, such catalytic articles may be more resistant to sintering / coalescence of the same type of particles that form the larger nanoparticles, thereby becoming inactivated. This may be due to, for example, a highly uniform distribution of particles that allows the "other" type of nanoparticles to act as a physical barrier against sintering / coalescence of the same type of nanoparticles. Thus, advantageously, catalytic articles having a higher resistance to deactivation during aging may be provided.

[0031] In contrast to the method of the present invention, previous methods such as those described in US Patent Application Publication No. 2020 / 030780 require a pre-calcination powder process, for example, where a slurry is prepared and calcined to provide a powder, followed by preparation of a further slurry from the powder to be used in the washcoating process. Such an additional step may result in a relatively large crystallite size of BaSO4 (e.g., greater than 32 nm). A further advantage may be that in situ BaSO4 may form during the process, taking advantage of the pores of the support material (especially for lanthanum-doped alumina) such that the growth of BaSO4 crystals is limited. Furthermore, in contrast to the method of the second aspect, in which a solution containing palladium ions, alkaline earth metal ions, and an organic compound is provided separately before being mixed with the support material, the method of US Patent Application Publication No. 2020 / 030780 (which also uses a similar organic compound) may not be able to achieve the further advantageous effects mentioned above. In US Patent Application Publication No. 2020 / 030780, the components of the washcoat slurry are each added successively, for example, to the support material. In other words, US Patent Application Publication No. 2020 / 030780 also does not disclose at least one step of providing a solution containing palladium ions, alkaline earth metal ions, and an organic compound, which is believed to be an important factor in achieving the further advantageous effects of the second aspect.

[0032] The term "catalyst article" as used herein may include an article on or in which a catalyst is supported. The article may take the form of, for example, a honeycomb monolith, or a filter, such as a wall-flow filter or a flow-through filter. The catalyst article may be for use in an emission treatment system, particularly an emission treatment system for a gasoline engine, preferably a stoichiometric gasoline engine. The catalyst article may be for use in three-way catalysis.

[0033] Providing a solution containing palladium ions, alkaline earth metal ions, and an organic compound typically includes contacting palladium ions, typically in the form of a palladium salt, alkaline earth metal ions, typically in the form of an alkaline earth metal salt, and an organic compound with a solvent. The solvent is preferably selected such that each of the palladium ions, alkaline earth metal ions, and organic compound has a high solubility in the solvent. Providing a solution containing palladium ions, alkaline earth metal ions, and an organic compound typically further includes stirring the solution for an extended period of time, for example, at least 30 minutes. Without being bound by theory, it is believed that by first providing a solution containing palladium ions, alkaline earth metal ions, and an organic compound, this may allow a complex containing palladium ions, alkaline earth metal ions, and / or an organic compound to form in the solution before contacting the support material. Thus, the solution is preferably free of support material and / or any solids.

[0034] The solution includes palladium ions and alkaline earth metal ions. In the catalytic article produced by the method of the present invention, alkaline earth metal species such as alkaline earth metal sulfates can act as promoters for palladium. Palladium can be particularly suitable for performing three-way catalysis. In addition, palladium is expensive, which means that it is advantageous to be able to provide a similar level of catalytic activity for the same amount of metal. Furthermore, the use of palladium in the method of the present invention can result in particularly favorable perturbation ignition performance. The palladium can be in the form of an alloy. In addition to palladium ions, the solution can include other platinum group metals, such as one or more of rhodium, platinum, ruthenium, osmium, and iridium.

[0035] The support material can be any material capable of supporting palladium ions, alkaline earth metal ions, organic compounds, and / or complexes formed therefrom, as well as nanoparticles thereon or therein. The support material can be in any form, but is typically in the form of a powder, more typically a high surface area powder. When the method of the present invention is used to prepare a catalyzed filter, such as a wall-flow filter or a flow-through filter, the support material will typically be in the form of a powder having a D50, for example, of 0.1 to 30 μm, more typically 0.5 to 25 μm, even more typically 1 to 20 μm, as measured using TEM. Such particle size can facilitate desirable rheological properties of the slurry used to coat the filter. The support material can function as a washcoat. The support material can be a washcoat or can be part of a washcoat.

[0036] The support material may also act as an oxygen storage material, storing and releasing oxygen under fuel-lean and fuel-rich conditions, respectively, to facilitate three-way catalytic conversion.

[0037] Contacting the solution with the support material to form a slurry typically involves either adding free support material to a pre-prepared solution to form the slurry, or contacting a pre-prepared solution with a pre-prepared slurry containing the support material to form the slurry, and mixing the slurry. The term "slurry" as used herein can include a liquid containing insoluble material, e.g., insoluble particles. The slurry can include (1) a solvent, (2) soluble inclusions, e.g., free palladium ions, free alkaline earth metal ions, and free organic compounds (i.e., outside the support), and (3) insoluble inclusions, e.g., support particles that may or may not interact with the components of the solution. The slurry is particularly effective in placing materials on a substrate, particularly to maximize gas diffusion and minimize pressure drop during catalytic conversion. 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. Increasing the contact time and / or stirring time may increase the amount of palladium ions, alkaline earth metal ions, organic compounds, and / or complexes formed therefrom loaded on the support material. Thus, the slurry typically includes a loaded support material. The term "loaded support material" as used herein may include a support material having palladium ions, alkaline earth metal ions, organic compounds, and / or complexes formed therefrom loaded thereon (e.g., on the surface of a high surface area metal oxide support material) and / or loaded therein (e.g., within the pores of a zeolite support material). The palladium ions, alkaline earth metal ions, organic compounds, and / or complexes formed therefrom are typically fixed to the support by, for example, electrostatic forces, hydrogen bonds, coordination bonds, covalent bonds, and / or ionic bonds.

[0038] 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.

[0039] Placing the slurry on the substrate can be done using techniques known in the art. Typically, the slurry is injected into the inlet of the substrate using a specific forming tool in a predetermined amount, whereby the loaded carrier material can be placed on the substrate. As will be discussed in more detail below, a subsequent vacuum and / or air knife and / or drying step can be used during the placing step. If the carrier is a filter block, the loaded carrier material can be placed on the filter wall, in the filter wall (if porous), or both.

[0040] Heating of the slurry is typically carried out in an oven or furnace, more typically in a belt or static oven or furnace, typically in a specific flow of hot air from one direction. Heating may include calcination. Heating may also include drying. The drying and calcination steps may be continuous or sequential. For example, a separate washcoat may be applied after the substrate has already been washcoated and dried together with the previous washcoat. The washcoated substrate may also be dried and calcined using one continuous heating program once coating is complete. During heating, any complexes that may have formed in the solution may be at least partially, substantially, or completely decomposed. In other words, the ligands of such complexes, e.g., ligands of organic compounds, may be at least partially, substantially, or completely removed or separated from the palladium and / or alkaline earth metal and removed from the final catalyst article. The particles of palladium so separated may then begin to form metal-metal and metal-oxide bonds. As a result of heating (calcination), the substrate is typically substantially free of organic compounds, and more typically completely free of organic compounds. It is further believed that particles of alkaline earth metal sulfates are formed by a similar process.

[0041] As used herein, the term "nanoparticles" can include particles having a Rietveld crystallite size of 0.01 nm to 100 nm as measured by XRD. Nanoparticles can be of any shape, e.g., spheres, plates, cubes, cylinders, hexagons, or rods, but are typically spherical.

[0042] After the heating step, the substrate is typically cooled, more typically to room temperature. Cooling is typically performed in air with or without a coolant / cooling medium, typically without a coolant.

[0043] After contacting the solution with the support material to form a slurry and before placing the slurry on the substrate, the method of the second aspect preferably further comprises adding an inorganic oxide, preferably a mixed inorganic oxide, to the slurry. Additionally or alternatively, providing the support material may comprise providing a mixture of the support material and an inorganic oxide, preferably a mixed inorganic oxide, and contacting the solution with the support material to form a slurry comprises contacting the solution with the mixture of the support material and the inorganic oxide. In other words, in one embodiment, the solution may be added to and mixed with the support material (i.e., the first support material) before the inorganic oxide (i.e., the second support material) is added. Alternatively, in another embodiment, the support material and the inorganic oxide (i.e., the first support material and the second support material) may be mixed first, and then the solution is added to the mixture of the support materials. The order of these steps is not particularly limited and may depend on the support material and / or inorganic oxide used.

[0044] The organic compound comprises a functional group selected from a sulfo group (-SO3H), a sulfonyl group (-S(=O)2-), and a sulfinyl group (-S(=O)-). Without being bound by theory, it is believed that such sulfur-containing groups may interact and / or complex with alkaline earth metal ions in solution. Furthermore, it is the presence of such sulfur-containing groups that allows for the formation of nanoparticles of alkaline earth metal sulfates.

[0045] The organic compound preferably further comprises an amine functional group, preferably a primary amine functional group. Without being bound by theory, it is believed that such functional group may interact with palladium ions in solution. Thus, the organic compound may interact and / or form complexes with both palladium ions and alkaline earth metal ions in solution, either separately or, for example, with the same molecule of the organic compound. Without being bound by theory, it is hypothesized that such interactions, if present, may further help to achieve the above-mentioned advantageous effects. That is, such interactions in the preformed solution may help to enable uniform distribution and correlation of the various nanoparticles obtained, since such metal ions are "held" closely together, for example, in the solution, and thus in the slurry on the loaded support material, and finally in the final catalyst article. In this regard, the organic compound preferably comprises a sulfo group and a primary amine group.

[0046] The organic compound may contain 1 to 6 carbon atoms, preferably 2 to 4 carbon atoms, and more preferably 2 carbon atoms. Such organic compounds may provide a good balance between solubility in solution, ability to form complexes with metal species, and ability to decompose upon heating to form nanoparticles of the desired size.

[0047] Specifically, the organic compound preferably comprises one or more of aminomethanesulfonic acid, taurine, homotaurine, 4-aminobutane-1-sulfonic acid, 2-aminopropane-1-sulfonic acid, 2-methyltaurine, dimethylsulfone, sulfonane, cysteic acid, dimethylsulfoxide, and aminobenzenesulfonic acid, more preferably taurine. In certain embodiments, the organic compound (e.g., taurine) and palladium can have a molar ratio of 8:1 or less, preferably 4:1 or less. In alternative embodiments, the organic compound (e.g., taurine) and palladium can have a molar ratio of 8:1 to 2:1, preferably 4:1 to 2:1.

[0048] In the second embodiment, the solution is preferably stirred before contacting the solution with the support material to form a slurry. Preferably, the solution is stirred for at least 30 minutes, more preferably at least 1 hour, and even more preferably at least 2 hours. Without being bound by theory, it is believed that such stirring may help to disperse the components of the solution evenly, allowing sufficient time to form any complexes that may be formed in the solution between the organic compound and one or more of the palladium ions and the alkaline earth metal ions before the support material is introduced and any species formed in the solution may be loaded thereon. For example, if the support material is instead added before the alkaline earth metal ions are added to the solution, the complexes formed between the organic compound and the palladium ions may be loaded onto the support material without, for example, forming interactions with the alkaline earth metal ions. Alternatively, if the support material is instead added before the palladium ions are added to the solution, the complexes formed between the organic compound and the alkaline earth metal ions may be loaded onto the support material without, for example, forming interactions with the palladium ions. However, as explained in the first aspect, this alternative sequence of method steps may also provide a fully effective method.

[0049] Providing the solution and / or slurry preferably comprises contacting the solvent with a palladium salt, preferably the palladium salt comprises one or more of palladium nitrate and palladium acetate, preferably palladium nitrate.

[0050] The alkaline earth metal ions preferably include one or more of calcium ions, strontium ions, and barium ions, preferably barium ions. Barium is known to provide superior cocatalytic activity in combination with palladium. Providing the solution and / or slurry preferably includes contacting the solvent with an alkaline earth metal salt, preferably the alkaline earth metal salt includes one or more of alkaline earth metal hydroxides, alkaline earth metal nitrates, and alkaline earth metal acetates, preferably alkaline earth metal acetates. Preferably, the alkaline earth metal salt includes barium acetate.

[0051] The solution is preferably an aqueous solution, which is consistent with typical washcoating techniques in the art. Therefore, it would be easy to modify the techniques and equipment used in conventional methods to carry out the method of the present invention by using similar components. Therefore, the organic compound is preferably highly water-soluble.

[0052] Providing the support material preferably includes providing a first slurry comprising the support material. The first slurry preferably includes the support material and water. As described herein, the first slurry may include one or more support materials and / or inorganic oxides. Then, contacting the solution with the support material to form a slurry preferably includes mixing the first slurry comprising the support material with the solution. Thus, a loaded support material may be provided as a result.

[0053] The method is preferably a one-pot method. Such a "one-pot" preparation method can be simplified and low-cost compared to conventional methods. This method can also maximize the utilization of organic compounds. Furthermore, such a method avoids the need to dry and calcinate the slurry / suspension to make a powder before reforming the slurry used in the washcoat. This is the method used, for example, in US Patent Application Publication No. 2020 / 030780. In other words, the method of the present invention preferably does not include drying and / or calcining the slurry before the step of placing the slurry on the substrate.

[0054] The support material preferably comprises an oxide. The support material and / or inorganic oxide preferably comprises one or more of Al2O3, SiO2, TiO2, CeO2, ZrO2, CeO2-ZrO2, V2O5, La2O3, and zeolites. Al2O3 (aluminum oxide or alumina), SiO2, TiO2, CeO2, ZrO2, CeO2-ZrO2, V2O5, La2O3, and zeolites. The oxide is preferably a metal oxide. The support material and / or inorganic oxide more preferably comprises alumina, even more preferably gamma-alumina. The support material and / or inorganic oxide preferably comprises ceria-zirconia. The support material and / or inorganic oxide preferably comprises alumina and ceria-zirconia. The alumina and / or ceria-zirconia are preferably doped, more preferably 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, or sodium, and even more preferably with oxides of lanthanum, neodymium, or yttrium. Such doped oxides are particularly useful as support materials. Preferably, the dopant is present in the alumina and / or ceria-zirconia in an amount of 0.001% to 20% by weight, and more preferably 0.5% to 10% by weight.

[0055] The support material preferably comprises alumina, preferably lanthanum doped alumina, and the inorganic oxide comprises an inorganic oxide other than alumina, preferably ceria zirconia.

[0056] The support material and / or inorganic oxide is preferably in the form of a powder having a D90 measured by TEM of 0.1 to 25 μm, preferably 0.5 to 5 μm.

[0057] One or more of a binder, an acid or base, and a thickener may be added to the solution and / or slurry before the slurry is placed on a substrate.

[0058] The binder may include, for example, an oxide material having a small particle size to bind together individual insoluble particles in the washcoat slurry. The use of binders in washcoats is well known in the art.

[0059] The thickener may include, for example, a natural polymer with functional hydroxyl groups that interact with insoluble particles in the washcoat slurry. The thickener serves the purpose of thickening the washcoat slurry for improved coating profile during washcoat coating on the substrate. The thickener is usually baked off during the washcoat calcination. Examples of specific thickeners / rheology modifiers for washcoats include glactoma gum, guar gum, xanthan gum, curdlan schizophyllan, scleroglucan, diutan gum, wheylan gum, hydroxymethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and ethylhydroxycellulose.

[0060] The method preferably involves washcoating. Suitable washcoating techniques are known to those skilled in the art.

[0061] The slurry preferably has a solids content of 10-40%, preferably 15-35%. Such solids content may allow suitable slurry rheology for disposing the loaded carrier material on the substrate. For example, if the substrate is a honeycomb monolith, such solids content may allow deposition of a thin layer of washcoat on the inner wall of the substrate. If the substrate is a wall-flow filter, such solids content may allow the slurry to enter the channels of the wall-flow filter and allow the slurry to enter the walls of the wall-flow filter.

[0062] Placing the slurry on the substrate preferably includes contacting the slurry with the substrate and, optionally, applying a vacuum to the substrate and / or drying the slurry on the substrate. This may result in a favorable distribution of the loaded support material that may be contained in the slurry on the substrate. Drying preferably occurs at a temperature of 60° C. to 200° C., more preferably 70° C. to 130° C., and / or for a period of 10 to 360 minutes, preferably 15 to 60 minutes.

[0063] The substrate preferably comprises cordierite. The substrate may be in the form of a honeycomb monolith, a wall-flow filter, or a flow-through filter. The substrate may be a "blank", i.e., an unwashcoated substrate. Alternatively, the substrate may have one or more washcoats already loaded thereon. In such a situation, the final catalyst article may include multiple layers of different washcoats.

[0064] The heating is preferably carried out at a temperature of 400° C. to 700° C., preferably 400° C. to 600° C., more preferably 450° C. to 600° C., and / or for 10 to 360 minutes, preferably 35 to 120 minutes. The heating preferably includes calcination.

[0065] The palladium nanoparticles preferably have a Rietveld crystallite size of 0.1 nm to 20 nm, preferably 5 to 15 nm. The crystallite size may be measured by X-ray diffraction (XRD). Such particle size may advantageously enable the favorable properties discussed above, such as high activity and resistance to deactivation on aging.

[0066] The alkaline earth metal sulfate nanoparticles preferably have a Rietveld crystallite size of 0.1 nm to 30 nm, preferably 5 to 25 nm, more preferably 5 to 20 nm, or 10 to 20 nm, even more preferably 12 to 16 nm. The crystallite size can be measured by XRD. Such a particle size can advantageously enable the favorable properties discussed above, such as high activity and resistance to deactivation upon aging. Moreover, such a size of the nanoparticles, in combination with the size preferred for palladium nanoparticles, can help to achieve the above-mentioned advantageous properties as a result of comparable particle size.

[0067] Unless otherwise stated herein, any crystallite size described herein may be measured by XRD. Suitable techniques are known in the art. For example, such techniques may be described as follows: To obtain X-ray diffraction data, an X'Pert Pro MPD diffractometer was used, as described by Bragg Brentano. HDIt can be used with a mirror, 1 / 4° divergence slit, 20 mm mask, sample spinner, and PIXcel detector. Triple scans can be performed over a range of 5° to 115°, a step size of 0.02°, and a total scan time of 50 minutes. Data can be analyzed using HighScore Plus software. Transition alumina phases can be modeled using the partial or unknown crystal structure method (NVYSCARLETT and ICMADSEN, Quantification of phases with partial or not known crystal structure, Powder Diffraction (2006), 21(4), 278-284, incorporated herein by reference), and all other phases can be modeled using the Rietveld method. Crystallite size and distortion can be measured based on the pseudo-Voight profile function and can be corrected for instrumental broadening. Crystallite size measured by XRD is a common parameter for determining nanoparticle size of such species in the field of the present invention.

[0068] Preferably, M=C±70%, preferably M=C±50%, more preferably M=C±30%, even more preferably M=C±20%, where M is the Rietveld crystallite diameter of the Pd nanoparticles and C is the Rietveld crystallite diameter of the alkaline earth metal sulfate nanoparticles. In other words, the Rietveld crystallite diameter of the Pd nanoparticles and the Rietveld crystallite diameter of the alkaline earth metal sulfate nanoparticles are preferably comparable in size, i.e. of similar magnitude, for the reasons mentioned above.

[0069] In a further aspect, the present invention provides a catalyst article for use in an emissions treatment system, the catalyst article comprising a substrate and a first catalytic region on the substrate, the first catalytic region comprising a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles, the alkaline earth metal sulfate nanoparticles having a Rietveld crystallite size of from 0.1 nm to 30 nm.

[0070] Compared to conventional catalyst articles, such catalyst articles may exhibit favorable light-off performance, particularly for NO, CO, and total hydrocarbons, during three-way catalytic reduction of stoichiometric gasoline engines. The catalyst articles may also exhibit other favorable properties described herein, such as high resistance to deactivation upon aging, and high activity, such as NOx conversion performance at rich conditions.

[0071] The palladium nanoparticles preferably have a crystallite diameter of 0.1 to 20 nm.The palladium nanoparticles preferably have a Rietveld crystallite diameter of 5 nm to 15 nm.

[0072] Preferably, M=C±70%, preferably M=C±50%, more preferably M=C±30%, even more preferably M=C±20%, where M is the crystallite size of the Pd nanoparticles and C is the crystallite size of the alkaline earth metal sulfate nanoparticles.

[0073] Preferably, when a cross section of the first catalyst region of the catalyst article is surface-analyzed by FE-EPMA under conditions of a pixel (cross section) size of 0.34 μm × 0.34 μm and a measurement pixel (cross section) number of 256 × 256, the characteristic X-ray intensity (α: cps) of an alkaline earth metal element (Ae) and the characteristic X-ray intensity (β: cps) of palladium (Pd) are measured for each pixel, and the Pearson correlation coefficient calculated using the obtained α and β at each pixel is R Ae / Pd When you specify Ae / Pd The value of R is at least 0.75. The Pearson correlation coefficient (product-moment correlation coefficient) is known to those skilled in the art and is calculated based on the results of the surface analysis by FE-EPMA. Ae / Pd When the characteristic X-ray intensity of alkaline earth metal elements (Ae) in surface analysis by FE-EPMA is the first variable (α) and the characteristic X-ray intensity of palladium (Pd) is the second variable (β), the formula R Ae / Pd= (covariance) / (standard deviation of α×standard deviation of β). Such calculations are known to those skilled in the art. In other words, preferably, in such catalytic articles, the alkaline earth metal element and palladium are highly correlated. That is, based on the distribution of palladium on the substrate, the alkaline earth metal can be present in a highly dispersed state. Thus, the ability of the alkaline earth metal to act as a promoter species for palladium can be optimized.

[0074] In a further aspect, the present invention relates to a catalyst article for use in an exhaust treatment system, the catalyst article comprising a substrate and a first catalyst region on the substrate, the first catalyst region comprising a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles, and when a cross section of the first catalyst region of the catalyst article is area-analyzed by FE-EPMA under conditions of a pixel (cross section) size of 0.34 μm×0.34 μm and a measurement pixel (cross section) number of 256×256, a characteristic X-ray intensity (α: cps) of an alkaline earth metal element (Ae) and a characteristic X-ray intensity (β: cps) of palladium (Pd) are measured for each pixel, and a Pearson correlation coefficient calculated using α and β at each pixel is expressed as R Ae / Pd When you specify Ae / Pd The catalyst article has a value of at least 0.75. The Pearson correlation coefficient (product moment correlation coefficient) is known to those skilled in the art and is calculated based on the results of the surface analysis by FE-EPMA. The correlation coefficient R Ae / Pd When the characteristic X-ray intensity of alkaline earth metal elements (Ae) in surface analysis by FE-EPMA is the first variable (α) and the characteristic X-ray intensity of palladium (Pd) is the second variable (β), the formula R Ae / Pd = (covariance) / (standard deviation of α×standard deviation of β). Such calculations are known to those skilled in the art. In other words, preferably, in such catalytic articles, the alkaline earth metal element and palladium are highly correlated. That is, based on the distribution of palladium on the substrate, the alkaline earth metal can be present in a highly dispersed state. Thus, the ability of the alkaline earth metal to act as a promoter species for palladium can be optimized.

[0075] Preferably, RAe / Pd is at least 0.76. In other words, the alkaline earth metal and palladium are preferably highly correlated. Such high correlation may not be readily achieved with the larger alkaline earth metal sulfate nanoparticles of conventional catalytic articles, i.e., those having small palladium nanoparticles but much larger alkaline earth metal sulfate nanoparticles.

[0076] Preferably, after aging for 100 hours at 1000°C, the palladium nanoparticles have a Rietveld crystallite size of 60 nm or less and / or any alkaline earth metal-containing species have a Rietveld crystallite size of 50 nm or less, preferably, after aging for 100 hours at 1000°C, the palladium nanoparticles have a Rietveld crystallite size of 40 nm or less and / or any alkaline earth metal-containing species have a Rietveld crystallite size of 30 nm or less.

[0077] The alkaline earth metals preferably include one or more of calcium, strontium, and barium, preferably barium.

[0078] The first catalytic region preferably further comprises an inorganic oxide, preferably a mixed inorganic oxide, more preferably ceria-zirconia.

[0079] The catalyst article may be obtainable by the methods described herein.

[0080] The catalyst article is preferably for use in an emission treatment system.

[0081] The catalyst article is preferably for three-way catalysis.

[0082] The catalyst article preferably has a surface area of ​​1 g / in 3 ~3g / in 3 of support material, palladium nanoparticles, alkaline earth metal sulfate nanoparticles, and optionally inorganic oxide.

[0083] In some embodiments, the catalyst article has a viscosity of 20 to 150 g / ft 3 , preferably 40 to 120 g / ft 3 , more preferably 80 to 120 g / ft 3 Alternatively, the catalyst article may have a Pd loading of 150 g / ft 3 Less than 120g / ft 3 Less than or equal to 100 g / ft 3 The following Pd loadings can be used:

[0084] The substrate preferably comprises a wall-flow filter substrate.The substrate preferably comprises a flow-through substrate.

[0085] The catalytic article preferably comprises a first catalytic region and a second catalytic region, the first catalytic region comprising a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles, and the second catalytic region comprising platinum and / or rhodium.

[0086] Preferably, the first catalytic region forms a first layer on the substrate and the second catalytic region forms a second layer on the substrate, the first layer extending from a first end of the substrate and the second layer extending from a second end of the substrate, and preferably the first catalytic region and the second catalytic region are each disposed directly on the substrate.

[0087] Preferably, the catalytic article further comprises a third catalytic region, the second catalytic region comprising platinum, and optionally the third catalytic region comprising rhodium, disposed on the first catalytic region and / or the second catalytic region such that the first catalytic region and / or the second catalytic region are each located between the third catalytic region and the substrate.

[0088] In another preferred embodiment, the first catalytic region forms a first layer on the substrate and the second catalytic region forms a second layer on the substrate, the first layer being disposed directly on the substrate and the second layer being disposed directly on the first layer. In another preferred embodiment, the first catalytic region forms a first layer on the substrate and the second catalytic region forms a second layer on the substrate, the second layer being disposed directly on the substrate and the first layer being disposed directly on the first layer. In another preferred embodiment, the catalytic article further comprises a third catalytic region, the third catalytic region being disposed directly on the first layer or the second layer, and optionally the second catalytic region comprises platinum and the third catalytic region comprises rhodium.

[0089] In other words, a catalyst article comprising a catalyst region formed by the method of the present invention may have such a catalyst layer as, for example, a top layer, a middle layer, or a bottom layer. The term "bottom layer" as used herein may include a layer (e.g., a washcoat layer) that is closest to or in contact with the substrate (i.e., the substrate wall). The term "top layer" as used herein may include a layer (e.g., a washcoat layer) that is further from the substrate (i.e., the substrate wall) than the bottom layer and may be located above the bottom layer. In such layered catalyst articles, the top and / or bottom layers of support material may have additional PGMs thereon, such as platinum. In such layered catalyst articles, the top and / or bottom layers may include multiple PGMs, i.e., bimetallic (e.g., containing Pd-Rh or Pd-Pt) or trimetallic (e.g., Pd-Rh-Pt). The catalyst article may include two or more catalyst zones, such as an upstream zone and a downstream zone. The zones may differ from one another by having different PGMs (eg, Rh upstream and Pd downstream, or vice versa), or may differ by the amount of different types of PGMs, eg, monometallic, bimetallic, or trimetallic.

[0090] In any of the above preferred embodiments, the first catalytic region, the second catalytic region, and / or the third catalytic region may be in the form of a zone, such a zone covering less than 100% of the substrate, such as 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less. The zone may extend from an inlet end or an outlet end of the substrate.

[0091] The substrate can have a first end having an axial length L and a second end.

[0092] The first catalyst region can extend over 100 percent of the axial length L (see, e.g., FIGS. 1, 2a, 2b, and 6a-6c). In some embodiments, the first catalyst region can extend over 20-99%, 30-90%, or 40-80% of the axial length L. Alternatively, the first catalyst region can extend over 30-70 percent of the axial length L. Preferably, the first catalyst region can extend over 40-60 percent, and more preferably, over 45-55 percent of the axial length L (see, e.g., FIGS. 3a-5d and 7a-7l).

[0093] The second catalytic region can extend over 100 percent of the axial length L (see, eg, Figures 2a, 2b, and 6a-6c).

[0094] The second catalyst region can extend over 30 to 70 percent of the axial length L. Preferably, it can extend over 40 to 60 percent, more preferably 45 to 55 percent, of the axial length L, and most preferably the total length of the second region and the first region is equal to or greater than the axial length L (see, e.g., Figures 3a-5d and 7a-7l).

[0095] The second catalyst region can overlap the first catalyst region over 0.1 to 99 percent of the axial length L (see, e.g., FIGS. 3c and 3d, where the first catalyst region can be stacked on the second catalyst region, or the second catalyst region can be stacked on the first catalyst region). Alternatively, the total length of the second catalyst region and the first catalyst region can be equal to the axial length L (see, e.g., FIGS. 3a and 3b). In yet another alternative, the total length of the second catalyst region and the first catalyst region can be less than the axial length L, e.g., 95%, 90%, 80%, or 70% or less of the axial length L.

[0096] The third catalytic region can extend over 100 percent of the axial length L (see, for example, Figures 4a-4d and 6a-6c).

[0097] The third catalytic region can be less than the axial length L, for example, less than or equal to 95%, 90%, 80%, or 70% of the axial length L (see, for example, Figures 5a-5d and 7g-7l).

[0098] 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).

[0099] The support material preferably comprises alumina and / or ceria-zirconia, preferably alumina. The alumina preferably comprises doped alumina, preferably lanthanum doped alumina.

[0100] The catalyst article preferably has a surface area of ​​10 g / ft 3 ~250g / ft 3 of palladium, preferably 20 g / ft 3 ~150g / ft 3 Advantageously, such palladium levels can be lower than those of conventional catalyst articles, yet do not impair catalytic activity.

[0101] In a further aspect, the present invention provides an emissions treatment system comprising the catalytic article described herein.

[0102] The emission treatment system is preferably for a gasoline engine.

[0103] Gasoline engines preferably operate under stoichiometric conditions.

[0104] In a further aspect, the present invention provides a method of treating an exhaust gas, the method comprising providing a catalytic article as described herein and contacting the catalytic article with the exhaust gas.

[0105] The exhaust gas is preferably from a gasoline engine. The catalytic article is particularly suitable for treating such exhaust gas. Furthermore, exhaust from a gasoline engine is typically more severe than exhaust from a diesel engine. Thus, the advantageous aging characteristics of the catalytic articles described herein are particularly beneficial therefor. The gasoline engine preferably operates under stoichiometric conditions.

[0106] The term "region" as used herein refers to an area on a substrate that is typically obtained by drying and / or calcining a washcoat. A "region" can be disposed or carried on a 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).

[0107] Typically, a "region" has a substantially uniform length. Reference to a "substantially uniform length" in this context refers to a length that does not deviate from its average value by more than 10% (e.g., the difference between the maximum and minimum length), preferably a length that does not deviate from its average value by more than 5%, and more preferably a length that does not deviate from its average value by more than 1%.

[0108] Each "region" preferably has a substantially uniform composition (i.e., there is no substantial difference in the composition of the washcoat when comparing one portion of the region to another portion of the region). Substantially uniform composition in this context refers to a material (e.g., region) that has a compositional difference of 5% or less, usually 2.5% or less, and most usually 1% or less, when comparing one portion of the region to another portion of the region.

[0109] As used herein, the term "zone" refers to a region having a length that is less than the entire length of the substrate, such as a length that is 75% or less of the entire length of the substrate. A "zone" typically has a length that is at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).

[0110] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0111] Any reference herein to a "zone disposed at the inlet end of a substrate" refers to a zone disposed on or supported by a substrate, which is closer to the inlet end of the substrate than to the outlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the inlet end of the substrate than to the outlet end of the substrate. Similarly, any reference herein to a "zone disposed at the outlet end of a substrate" refers to a zone disposed on or supported by a substrate, which is closer to the outlet end of the substrate than to the inlet end of the substrate. Thus, the midpoint of the zone (i.e., a point at half its length) is closer to the outlet end of the substrate than to the inlet end of the substrate.

[0112] When the substrate is a wall-flow filter, generally any reference to "a zone disposed at the inlet end of the substrate" refers to a zone disposed on or supported by the substrate, (a) a zone that is closer to the inlet end (e.g., an open end) of an inlet channel of the substrate than to the closed end (e.g., a blocked or plugged end) of the inlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an outlet channel of a substrate than to the outlet end (e.g., open end) of the outlet channel.

[0113] Thus, the midpoint of the zone (i.e., the point at half its length) is (a) closer to the inlet end of the inlet channel of the substrate than to the closed end of the inlet channel, and / or (b) closer to the closed end of the outlet channel of the substrate than to the outlet end of the outlet channel.

[0114] Similarly, where the substrate is a wall-flow filter, any reference to a "zone disposed at the outlet end of the substrate" refers to a zone disposed on or carried by the substrate, (a) a zone that is closer to the outlet end (e.g., an open end) of the outlet channel of the substrate than to the closed end (e.g., a blocked or plugged end) of the outlet channel; and / or (b) Refers to a zone that is closer to the closed end (e.g., blocked or plugged end) of an inlet channel of a substrate than to the inlet end (e.g., open end) of the inlet channel.

[0115] Thus, the midpoint of the zone (i.e., the point at half its length) is (a) closer to the outlet end of the outlet channel of the substrate than to the closed end of the outlet channel, and / or (b) closer to the closed end of the inlet channel of the substrate than to the inlet end of the inlet channel.

[0116] If the washcoat is present on the wall of a wall-flow filter (ie, the zone is intramural), the zone may satisfy both (a) and (b).

[0117] The term "washcoat" is well known in the art and typically refers to an adherent coating that is applied to a substrate during the production of a catalyst.

[0118] The acronym "PGM" as used herein refers to "platinum group metals." The term "platinum group metals" generally refers to metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, and Pt, preferably metals selected from the group consisting of Ru, Rh, Pd, Ir, and Pt. In general, the term "PGM" preferably refers to metals selected from the group consisting of Rh, Pt, and Pd.

[0119] The term "mixed oxide" as used herein generally refers to a mixture of oxides in a single phase, as is conventionally known in the art. The term "complex oxide" as used herein generally refers to a composition of oxides having two or more phases, as is conventionally known in the art.

[0120] As used herein, any reference to an amount of dopant expressed as weight percent, particularly a total amount, refers to the weight of the support material or refractory metal oxide thereof.

[0121] As used herein, the term "loading" refers to g / ft2 on a metal weight basis. 3 Refers to the measurement in units of .

[0122] When reference is made herein to "a" or "an," this includes the singular and the plural.

[0123] The following non-limiting examples are merely illustrative of the present invention. Those skilled in the art will recognize many variations that are within the spirit of the invention and scope of the claims.

[0124] A number of catalytic articles were prepared according to the following examples, specifically, a number of catalytic articles were prepared in which each method required a different order of addition of the components of the washcoat, in order to demonstrate the surprising results of the present invention.

[0125] Reference catalyst 1 - standard washcoat (no taurine).

[0126] The bottom layer front zone washcoat slurry was prepared by the following: (i) grinding to produce a slurry containing ceria and zirconia mixed oxide; (ii) adding barium acetate and palladium nitrate to the slurry (i); (iii) adding ground 4% La2O3 doped alumina to the above mixed slurry (ii); (iv) The washcoat (iii) is thickened with a rheology modifier.

[0127] The final composition of the bottom layer front zone washcoat was 1.6 g / in of ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.7g / in 3 , Ba element 300g / ft 3 , and Pd element 98g / ft3 It contained.

[0128] The bottom layer rear zone washcoat slurry was prepared by the following. (i) grinding to produce a slurry containing 4% La2O3 doped alumina; (ii) adding platinum nitrate to the slurry (i) and mixing; (iii) Milling the ceria and zirconia mixed oxide. (iv) Blending the above two slurries (ii) and (iii). (v) The washcoat (iv) is thickened with a rheology modifier.

[0129] The final composition of the bottom layer rear zone washcoat was 1.6 g / in of ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.7g / in 3 , and Pt element 98g / ft 3 It contained.

[0130] The top layer washcoat was prepared by the following. (i) grinding to produce a slurry containing ceria and zirconia mixed oxide; (ii) adding a rhodium nitrate solution to the slurry (i); (iii) adjusting the pH of the slurry (ii) to precipitate Rh onto the mixed oxide; (iv) adding milled 4% La2O3 doped alumina to the slurry (iii); (v) The washcoat (iv) is thickened with a rheology modifier.

[0131] The final composition of the top layer washcoat was 1.0 g / in of ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.35g / in 3 , and Rh element 2g / ft 3 It contained.

[0132] Washcoat coating on follow-through substrate (i) Use precision coating method with the rear zone dose first at 50%-55% dose length. Dry to 80% or more moisture removal. (ii) Coat front zone washcoat to 50%-55% dosage length target. Dry to 80% or more water removal. (iii) Calcining. (iv) Apply to the top layer by precision coating method targeting 50%-55% dose length. Dry to 80% or more moisture removal between inlet and outlet dose. (v) Calcining.

[0133] Reference catalyst 2 - pre-calcined powder containing Pd, BaSO4, and support material The bottom layer front zone washcoat slurry was prepared by the following: (i) grinding to produce a slurry containing 4% La2O3 doped alumina; (ii) adding a Pd nitrate solution to the stirred slurry; (iii) adding barium acetate to the stirred slurry (ii); (iv) adding taurine to the stirred slurry (iii); (v) drying the slurry (iv) in air at 110° C. overnight and calcining at 500° C. for 2 hours; (vi) grinding, sieving and forming a slurry of the pre-calcined powder from (v); (vii) grinding to produce a ceria and zirconia mixed oxide slurry; (viii) mixing the slurries from (vi) and (vii) together to form a washcoat slurry; (ix) The washcoat slurry in (viii) is thickened with a rheology modifier.

[0134] The final composition of the pre-calcined powder (v) contained 8.1% Pd and 24.5% Ba on 4% lanthanide doped alumina. The final composition of the washcoat was 1.6 g / in of ceria zirconia composite. 3 , 4% La2O3 doped alumina 0.7g / in 3, Ba metal 300g / ft 3 , and Pd metal 98g / ft 3 It is.

[0135] The bottom layer rear zone washcoat slurry of Reference Catalyst 2 and the top layer washcoat of Reference Catalyst 2 were prepared in the same manner as Reference Catalyst 1, respectively.

[0136] The application of the washcoat coating was the same as for Reference Catalyst 1.

[0137] The catalyst of the present invention 1-taurine direct batch addition The bottom layer front zone washcoat slurry was prepared by the following: (i) grinding to produce a slurry containing ceria and zirconia mixed oxide; (ii) grinding in a separate container to produce a slurry containing 4% La2O3 doped alumina slurry; (iii) blending the two slurries (i) and (ii) together with continuous mixing; (iv) adding palladium nitrate to the slurry of (iii) above and mixing; (v) adding barium acetate to the slurry (iv) and mixing; (vi) adding taurine to the slurry (v) and mixing; (vii) The washcoat slurry in (vi) is thickened with a rheology modifier.

[0138] The final composition of the bottom layer front zone washcoat was 1.6 g / in of ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.7g / in 3 , Ba metal 300g / ft 3 , and Pd metal 98g / ft 3 It contained.

[0139] The bottom layer rear zone washcoat slurry of Inventive Catalyst 1 and the top layer washcoat of Inventive Catalyst 1 were prepared in the same manner as Reference Catalyst 1, respectively.

[0140] The application of the washcoat coating was the same as for Reference Catalyst 1.

[0141] Preliminary solution of catalyst 2-Pd, Ba acetate, and taurine of the present invention The bottom layer front zone washcoat slurry was prepared by the following: (i) mixing a solution of palladium nitrate and barium acetate; (ii) adding taurine to the above mixed solution (i) and maintaining mixing; (iii) grinding and separately preparing a slurry containing 4% La2O3 doped alumina; (iv) adding and mixing the pre-solution from step (ii) to the pre-milled 4% La2O3 doped alumina slurry (iii); (v) grinding to separately prepare a slurry containing ceria and zirconia mixed oxide; (vi) adding the resulting ceria-zirconia mixed oxide slurry (v) to the batch of step (iv); (vii) The washcoat slurry in (vi) is thickened with a rheology modifier.

[0142] The final composition of the bottom layer front zone washcoat was 1.6 g / in of ceria-zirconia composite. 3 , 4% La2O3 doped alumina 0.7g / in 3 , Ba element 300g / ft 3 , and Pd element 98g / ft 3 It contained.

[0143] The bottom layer rear zone washcoat slurry of inventive catalyst 2 and the top layer washcoat of inventive catalyst 2 were prepared in the same manner as reference catalyst 1, respectively.

[0144] The application of the washcoat coating was the same as for Reference Catalyst 1.

[0145] Example 1: XRD analysis of BA and PD species The crystallite sizes of Ba species in all catalysts were analyzed by XRD, and the results are shown in Table 1.

[0146] [Table 1]

[0147] Witherite (BaCO3) was detected in Reference Catalyst 1 because it was made by a process that did not contain taurine. The estimated crystallite size of BaCO3 was about 36 nm with a standard deviation of 5 nm. Barite (BaSO4) was detected in Reference Catalyst 2 and the two inventive catalysts in which taurine was present in the washcoat batch. The BaSO4 crystallite size of the two inventive catalysts is about 16 nm, which is much smaller than Reference Catalyst 2 (about 32 nm) made by the pre-calcined powder process. They are also significantly smaller than Reference Catalyst 1 (about 36 nm) prepared by the standard batch process that does not contain taurine. There were no XRD peaks originating from Pd species (Pd or PdO) in the fresh catalyst, indicating that the Pd species are highly dispersed.

[0148] Ba is a well-known Pd promoter in TWC technology. Ba can donate electrons to Pd, which allows the Pd (II) The Pd-rich NOx reduction function can be improved because the electronic configuration of Pd becomes more similar to Rh. In order to maximize this promotion effect, intimate Ba-Pd contact is desirable. Typically, Pd species are highly dispersed (not measurable by XRD in this study) and are mostly located in the pores of the support material. Smaller particle size Ba species are preferred, among other things, because they are more likely to enter the pores of the support, resulting in closer proximity of Ba to Pd. The two catalysts of the present invention obtain fresh Ba species with about half the size of the reference ones, and thus are expected to improve Pd-Ba interaction and rich NOx conversion.

[0149] All catalysts were engine bench aged for 100 hours with a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature at 1000° C. Washcoat scraped from the coated monoliths was used for XRD measurements.

[0150] Multiple Ba species were detected in the aged catalysts, including Ba aluminum oxide (BaAl2O4), hexacelsian (BaAl2Si2O8), and witherite (BaCO3). Each of them has a concentration below the detection limit for accurate size measurement. Crystalline PdO was detected in the aged samples, and the crystallite sizes are reported in Table 1. The smaller Rietveld crystallite size of PdO in both inventive catalysts means that sintering of Pd species is suppressed. The results are consistent with other literature reports where the addition of Ba increases the thermal stability of PdO species. The smaller the PdO crystallite size, the higher the thermal stability.

[0151] Example 2: FE-EPMA analysis of the interaction of PD with BA The Pearson correlation coefficients (product moment correlation coefficients) were calculated based on the results of the areal analysis by FE-EPMA and are shown in Table 2. All fresh catalysts have similarly high Pd-Ba coefficients, which are about 0.7-0.8. However, aged inventive catalyst 1 and inventive catalyst 2 demonstrate much higher Pd-Ba co-location than the reference catalyst. This means that the alkaline earth metal elements and palladium are highly correlated in the inventive catalysts, even after TWC aging. Thus, the ability of alkaline earth metals to act as promoter species for palladium is optimized.

[0152] [Table 2]

[0153] Example 3: Ignition 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 tested in a gasoline engine. Ignition performance was measured under typical conditions, with a gas volumetric space velocity of 115K / hr, a temperature gradient of 30°C / min, and an air and fuel ratio (AFR) lambda of 14.45 perturbed with an amplitude of 0.5. 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.

[0154] HC, CO, and NO x T 50 The light-off temperatures are shown in Table 3. The data clearly show that both inventive catalyst 1 and inventive catalyst 2 provide significantly improved light-off performance when compared to the two reference catalysts. Specifically, inventive catalyst 2 is more active than inventive catalyst 1, with a T 50 is about 15 to 20 degrees lower (T 50 is the temperature at which the conversion reaches 50%).

[0155] [Table 3]

[0156] Example 4: Lambda Sweep Test in Engine Test The lambda sweep test is a typical condition, the gas volumetric space velocity is 115 K / h, the temperature is fixed at 400 °C, the air-fuel ratio (AFR) lambda is swept from 15.5 to 13.5, and an amplitude of 0.5 is perturbed during the sweep. x The conversion of was calculated by comparing the concentration of the feed gas with that of the gas at the catalyst outlet. All catalysts were engine bench aged for 100 hours with a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature of 1000°C and tested in a gasoline engine.

[0157] CO and NO xThe conversion traces are shown in Figure 8. The data shows that both inventive catalyst 1 and inventive catalyst 2 show significantly improved NO conversion at rich conditions when lambda is less than 0.985. x Specifically, catalyst 2 of the present invention provides a conversion at the stoichiometric point (CO-NO x Approximately 10% higher CO and NO at the crossover point x The catalysts also show a wider lambda window than the two reference catalysts. The THC conversion trace is shown in FIG. 9. The catalyst 2 of the present invention is more active than the reference catalysts 1 and 2, and has a higher THC conversion on the rich side when lambda is less than 0.99. The improved rich activity of the catalysts of the present invention is believed to be related to the closer Pd-Ba interaction.

[0158] Example 5: Warm-up test in engine test All catalysts were engine bench aged for 100 hours with a stoic / fuel cut aging cycle targeting a peak catalyst bed temperature at 1000°C and tested in a gasoline engine. Warm-up tests were typically performed at a gas hourly space velocity of 95K. Pollutants from the engine out were preheated to 490°C and then directed to the cold catalyst. The time to reach 50% conversion of total hydrocarbons, carbon monoxide, and NOx, respectively, was recorded and calculated as T 50 H.C.,T. 50 CO, and T 50 NO x THC, CO, and NO x The conversion of was calculated by comparing the concentration of the feed gas with the concentration of the gas at the catalyst outlet. Similarly, the time to reach 75% for each pollutant was also recorded and T 75 H.C.,T. 75 CO, and T 75 NO x and named it.

[0159] The data in Table 4 clearly show that both inventive catalyst 1 and inventive catalyst 2 warm up faster than the two reference catalysts. Specifically, inventive catalyst 2 is more active than inventive catalyst 1, showing the shortest time to reach a certain conversion level.

[0160] [Table 4]

[0161] The foregoing detailed description has been provided for purposes of explanation and illustration and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments described herein will be apparent to those of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. 1. A method of making a catalyst article, said method comprising: A slurry is provided comprising a support material, palladium ions, alkaline earth metal ions, and an organic compound, wherein the organic compound has a sulfo group (—SO ３ H), sulfonyl group (-S(=O) ２ a functional group selected from a sulfinyl group (—S(═O)—), and a sulfinyl group (—S(═O)—); disposing the slurry on a substrate; heating the slurry to form nanoparticles of the palladium and nanoparticles of the alkaline earth metal sulfate on the support material.

2. The method of claim 1 , wherein the slurry further comprises an inorganic oxide, preferably a mixed inorganic oxide.

3. 3. The method of claim 1 or 2, wherein providing a slurry comprises one or more steps of combining two or more of the support material, palladium ions, alkaline earth metal ions, an organic compound, and optionally an inorganic oxide in a solvent.

4. 1. A method of making a catalyst article, said method comprising: A solution containing palladium ions, alkaline earth metal ions, and an organic compound is provided, wherein the organic compound has a sulfo group (—SO ３ H), sulfonyl group (-S(=O) ２ a functional group selected from a sulfinyl group (—S(═O)—), and a sulfinyl group (—S(═O)—); Providing a carrier material; contacting the solution with the support material to form a slurry; disposing the slurry on a substrate; heating the slurry to form nanoparticles of the palladium and nanoparticles of the alkaline earth metal sulfate on the support material.

5. the method further comprising adding an inorganic oxide, preferably a mixed inorganic oxide, to the slurry after contacting the solution with the support material to form the slurry and before disposing the slurry on the substrate; and / or 5. The method of claim 4, wherein providing the support material comprises providing a mixture of the support material and an inorganic oxide, preferably a mixed inorganic oxide, and contacting the solution with the support material to form a slurry comprises contacting the solution with the mixture of the support material and the inorganic oxide.

6. 2. The method of claim 1, wherein the organic compound comprises one or more of aminomethanesulfonic acid, taurine, homotaurine, 4-aminobutane-1-sulfonic acid, 2-aminopropane-1-sulfonic acid, 2-methyltaurine, dimethyl sulfone, sulfonane, cysteic acid, dimethyl sulfoxide, and aminobenzenesulfonic acid, preferably taurine.

7. 2. The method of claim 1, wherein the alkaline earth metal ions comprise one or more of calcium ions, strontium ions, and barium ions, preferably barium ions.

8. 2. The method of claim 1, wherein providing the solution and / or slurry comprises contacting a solvent with an alkaline earth metal salt, preferably wherein the alkaline earth metal salt comprises one or more of an alkaline earth metal hydroxide, an alkaline earth metal nitrate, and an alkaline earth metal acetate, preferably an alkaline earth metal acetate.

9. The method of claim 8 wherein the alkaline earth metal salt comprises barium acetate.

10. The method of claim 1 , wherein the method does not include drying and / or calcining the slurry prior to the step of disposing the slurry on the substrate.

11. The support material and / or inorganic oxide is Al ２ O ３ , SiO ２ , TiO ２ , CeO ２ , ZrO ２ , CeO ２ -ZrO ２ , V ２ O ５ , La ２ O ３ and zeolite.

12. 1. A catalytic article for use in an emissions treatment system, said catalytic article comprising: A substrate; a first catalytic region on the substrate; the first catalytic region comprises a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles; The catalytic article, wherein the alkaline earth metal sulfate nanoparticles have a crystallite size of 0.1 nm to 30 nm.

13. 13. The catalytic article of claim 12, wherein the palladium nanoparticles have a crystallite size of 5 nm to 15 nm.

14. 1. A catalytic article for use in an emissions treatment system, said catalytic article comprising: A substrate; a first catalytic region on the substrate; the first catalytic region comprises a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles; When a cross section of the first catalyst region of the catalyst article is analyzed by FE-EPMA under the conditions of a pixel (cross section) size of 0.34 μm×0.34 μm and a measurement pixel (cross section) number of 256×256, the characteristic X-ray intensity (α: cps) of the alkaline earth metal element (Ae) and the characteristic X-ray intensity (β: cps) of the palladium (Pd) are measured for each pixel, and the Pearson correlation coefficient calculated using the obtained α and β for each pixel is defined as R Ａｅ／Ｐｄ When specifying Ａｅ／Ｐｄ A catalytic article having a value of at least 0.

75.

15. 15. The catalyst article of any one of claims 12 to 14, wherein after aging at 1000°C for 100 hours, the palladium nanoparticles have a Rietveld crystallite size of 60 nm or less and / or any alkaline earth metal-containing species have a crystallite size of 50 nm or less, preferably after aging at 1000°C for 100 hours, the palladium nanoparticles have a crystallite size of 40 nm or less and / or any alkaline earth metal-containing species have a crystallite size of 30 nm or less.

16. a first catalyst region and a second catalyst region; the first catalytic region comprises a support material, palladium nanoparticles, and alkaline earth metal sulfate nanoparticles; The catalytic article of claim 12 , wherein the second catalytic region comprises platinum and / or rhodium.

17. 17. The catalytic article of claim 16, wherein the first catalytic region forms a first layer on the substrate and the second catalytic region forms a second layer on the substrate, the first layer extending from a first end of the substrate and the second layer extending from a second end of the substrate, preferably the first catalytic region and the second catalytic region each being disposed directly on the substrate.

18. and a third catalytic region, said second catalytic region comprising platinum, and optionally 17. The catalytic article of claim 16, wherein the third catalytic region comprises rhodium and is disposed on the first catalytic region and / or the second catalytic region such that the first catalytic region and / or the second catalytic region are each located between the third catalytic region and the substrate.

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