Transition metal incorporated alumina for improved three-way catalysts.

Abstract

The present invention relates to a catalytic article comprising a substrate and a catalytic composition disposed on the substrate, the catalytic composition comprising a support material on which one or more platinum group metals (PGMs) and a Ta-polyoxometalate (POM) are supported.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION The present invention relates to catalyzed articles useful for treating exhaust gas emissions from gasoline engines, and particularly to intermediate products in the manufacture thereof. [Background technology]

[0002] In an internal combustion engine, hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x The exhaust gas produced by the engine contains various pollutants, including CO2, CO3, and CO4. Emissions control systems containing exhaust gas catalytic converters are widely used to reduce the amount of these pollutants emitted into the atmosphere. The catalyst typically used to treat the exhaust gas of a gasoline engine is the TWC (three way catalyst). The TWC performs three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO2. x is reduced.

[0003] Despite advances in TWC technology, there remains a need for improved catalytic converters for specific engine platforms that simultaneously improve performance during cold start phases, provide better light-off performance, and provide better OSC performance during hot transient phases with a wide range of Pt, Pd, and / or Rh applications. The present invention addresses these problems, among others. Summary of the Invention

[0004] One aspect of the present disclosure relates to a catalytic article comprising a substrate and a catalytic composition disposed on the substrate, the catalytic composition comprising a support material on which one or more platinum group metals (PGMs) and a Ta-polyoxometallate (POM) are supported.

[0005] The present invention also encompasses a catalyst article obtained or obtainable by calcining a catalyst article according to any of the preceding claims.

[0006] The present invention also encompasses a catalyst article comprising a substrate and a catalyst composition disposed on the substrate, the catalyst composition comprising a support material having one or more platinum group metals (PGMs) and Ta2O5 supported thereon, the catalyst composition obtained or obtainable by a process comprising: providing a support material having one or more PGMs supported thereon; providing a solution comprising Ta-POM; contacting the support material with the solution to provide a support material having Ta-POM supported thereon; and calcining the support material having Ta-POM supported thereon.

[0007] The present invention also includes an exhaust gas treatment system comprising a catalytic article according to the present invention.

[0008] The present invention also includes a fuel combustion and exhaust gas treatment system including an engine and the exhaust gas treatment system of the present invention.

[0009] The present invention also includes a method for treating exhaust gases, comprising passing the exhaust gases through a catalytic article according to the present invention.

[0010] The present invention also encompasses the use of Ta-POM in a method for making a catalyst article comprising one or more PGMs supported on a support material. [Brief explanation of the drawings]

[0011] [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 2] 1 shows an embodiment according to the present invention in which the first catalyst region is a bottom layer and extends 100% of the axial length L. The second catalyst region is a top layer and extends 100% of the axial length L. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention is directed to the catalytic treatment of combustion exhaust gases, such as those produced by gasoline and other engines, and related catalyst compositions, catalyst articles, and systems. More specifically, the present invention relates to the treatment of NO in vehicle exhaust systems. x The present invention relates to the simultaneous treatment of CO, CO, and HC. While most technological developments for improving TWC performance have focused on increasing the thermal stability of alumina support materials by doping with lanthanum or other rare earth elements, the present inventors have surprisingly discovered that the application of Ta to PGM-supported support materials via specific anionic complexes can further impact the improved light-off performance and resulting emission control performance of TWCs. The present inventors have discovered that the potential performance of TWCs under light-off tests and their actual performance under emission control tests are improved by the present invention. The method of the present invention can also significantly reduce the PGM loading in TWCs, conserving valuable natural resources and reducing the cost of the catalyst product.

[0013] One aspect of the present disclosure relates to a catalytic article comprising a substrate and a catalytic composition disposed on the substrate, the catalytic composition comprising a support material on which one or more platinum group metals (PGMs) and a Ta-polyoxometallate (POM) are supported.

[0014] Through intensive research, the present inventors have surprisingly found that applying Ta to a PGM-supported support material via Ta-POM can provide a catalyst composition that can exhibit superior catalytic properties (e.g., using the catalysts described herein, reduced emissions, THC / NMHC, CO, and NO during vehicle testing). x (One or more of the following emissions may be significantly reduced.) More specifically, such catalyst compositions xThe light-off temperatures for NO and THC conversion can be improved even more significantly after redox aging (e.g., 1000-1050°C for 4 hours). This improvement was noted relative to reference catalysts including simple conventional support materials (such as Rh / alumina), support materials supported with TaO by applying TaO (at the same Ta loading), and support materials supported with Nb via Nb-POM, each having Rh supported thereon. The Ta-POM samples of the present invention can provide higher conversion rates at all temperatures, but especially for NO. x and THC, providing higher conversion rates at lower temperatures, i.e., temperatures that reduce light-off temperatures.

[0015] Without being bound by theory, it is believed that by applying Ta to a support material via Ta-POM, due to the high negative charge of the Ta-POM, there may be an electrostatic attraction between the Ta-POM and the PGM (e.g., via an inductive charge interaction or due to a slight positive charge that may exist on the PGM), meaning that the Ta-POM may be located in close proximity to and / or in direct contact with the PGM (particles) on the support material. Thus, during calcination and / or use of the catalyst article at high temperatures in an exhaust gas treatment system, the Ta-POM may form TaO on the surface of and / or in close proximity to the PGM (particles). In this manner, the resulting TaO may impart greater hydrothermal stability to the PGM-supported support material (i.e., compared to a PGM such as Rh supported on simple alumina or pure TaO). This interaction is surprising and unexpected, and has not previously been studied for this use. It is also believed that Ta-POM may offer a greater improvement in light-off temperature compared to Nb-POM, for example, because the oxygen atoms in Ta-POM may have a relatively higher charge than the oxygen atoms on Nb-POM, which is believed to be because Ta is more polarizable than Nb.

[0016] In other words, it is believed that the relatively strong interaction between the negative charges of Ta-POM and one or more PGMs (preferably Rh) influences the initial state of the one or more PGMs, which can improve the TWC performance of the catalyst even after aging.

[0017] Of course, this means that the catalyst article of the first embodiment may be considered an intermediate or "fresh" product for use in an exhaust gas treatment system. This is because Ta-POM may not be thermally stable at the operating temperatures of the exhaust gas catalyst. Thus, Ta-POM may decompose to Ta2O5 upon heating. Indeed, as explained above, this may be the cause of the technical advantages described herein. In other words, the catalyst article of the first embodiment may be included in an exhaust gas treatment system in a "fresh" state, but then form the final catalyst article during use. Alternatively, the catalyst article may be calcined before first use as described herein.

[0018] As is conventional in the art, the term "light-off temperature" of a catalyst as used herein may refer to the temperature at which the catalyst reaches 50% conversion of a particular pollutant.

[0019] Preferably, the catalytic article is for treating exhaust gases from an internal combustion engine, more preferably a gasoline engine. Preferably, the catalytic article is a TWC article. The catalytic article is characterized by the beneficial NOx reduction exhibited by the catalytic article as described herein. x and THC conversion may be particularly suitable for such applications.

[0020] Preferably, the Ta-POM comprises Ta-hexametallate, which is [TaO 19 ] 8-Precursors of Ta-POM may include its alkali metal salts, such as its potassium salt. Ta-hexametallate has been shown to be particularly effective in providing the benefits described herein. Ta-POM and its preparation are known to those skilled in the art.

[0021] Preferably, the one or more PGMs comprise one or more of Pt, Pd, Rh, and mixtures or alloys thereof, more preferably the one or more PGMs comprise Pd and / or Rh, even more preferably the one or more PGMs comprise Rh, and even more preferably the one or more PGMs consist of Rh. In a further embodiment, the catalyst composition is preferably substantially free of PGMs other than Rh.

[0022] Preferably, one or more PGMs comprise nanoparticles. The term "nanoparticles" as used herein can encompass particles having an average particle size of 0.01 to 1000 nm, for example, as measured by CO pulse adsorption. Preferably, one or more PGMs comprise nanoparticles having an average particle size of 0.1 to 10 nm, preferably 0.5 to 9 nm, more preferably 1 to 8 nm, even more preferably 2 to 7 nm, even more preferably 3 to 6 nm, and most preferably 4.5 to 6 nm. The average particle size can be measured by CO pulse adsorption. While catalyst compositions comprising a wide range of particle sizes can still provide the benefits described herein, surprisingly, the NO 2 content of aged catalyst compositions according to the present invention is significantly reduced. x It has been found that the effect on increasing THC conversion can be greater for larger PGM (such as Rh) particle sizes, e.g., about 5.3 nm compared to about 0.8 nm. In other words, the NO 3 content for aged catalysts is significantly higher than that for aged catalysts. xIt has been found that the light-off temperature for THC conversion and THC activity can be lower when the particle size is larger and within the preferred range. This is surprising and unexpected. For example, it may be typical to favor smaller PGM particle sizes for increased activity / conversion, limiting the effects of PGM-nanoparticle sintering, due to the higher surface area provided by such smaller particles. In contrast, in the present invention, activity and light-off temperature can be improved for larger PGM nanoparticles compared to smaller PGM nanoparticles. Without being bound by theory, it is believed that this may be because, sterically, there may be more space for more Ta-POM ions to interact with each Rh nanoparticle.

[0023] Preferably, the support material comprises one or more of an alumina and ceria-containing mixed oxide, preferably alumina and / or ceria-zirconia mixed oxide, more preferably alumina. The catalyst composition has been shown to be particularly effective on alumina-based support materials.

[0024] In certain embodiments, the alumina preferably comprises gamma alumina, while in other embodiments, the alumina preferably comprises theta alumina.

[0025] Preferably, the support material further comprises a dopant comprising one or more of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, copper, silicon, calcium, barium, strontium, cesium, magnesium, potassium, and sodium, more preferably one or more of lanthanum, neodymium, praseodymium, hafnium, and yttrium, even more preferably lanthanum. Preferably, the dopant is present in the support material in an amount of 0.001 to 20 wt.%, preferably 0.5 to 10 wt.%, based on the total weight of the support material. More preferably, the dopant is present in the support material in an amount of 0.5 to 10.0 wt.%, more preferably 1.0 to 8.0 wt.%, even more preferably 1.5 to 7.0 wt.%, even more preferably 2.0 to 6.0 wt.%, and even more preferably 3.0 to 6.0 wt.%, based on the total weight of the support material. Throughout this application, "wt. %" with respect to dopants is calculated based on, for example, metal oxide. Preferably, the support material is a mixed oxide.

[0026] Preferably, the support material comprises La-doped alumina, preferably containing about 4 wt. % La based on the total weight of the support material.

[0027] Accordingly, a particularly preferred embodiment of the present invention is a catalyst article comprising a substrate and a catalyst composition disposed on the substrate, the catalyst composition comprising alumina having Rh and Ta-hexametallate supported thereon, preferably the alumina further comprising La as a dopant.

[0028] Preferably, at least a portion of the Ta-POM is in direct contact with at least a portion of the one or more PGMs. As described herein, this interaction may be facilitated by electrostatic interactions between the one or more PGMs and the negative charges on the oxygen atoms of the Ta-POM.

[0029] Preferably, at least 70 wt. % of the Ta-POM supported on the support material is in direct contact with at least a portion of one or more PGMs, based on the total weight of the Ta-POM supported on the support material. Without being bound by theory, the Ta-POM that may be preferably supported by impregnation in the present invention may be, for example, hydrated tantalum oxide, protonated [TaO 19 ] 8- , and K + / [Ta6O 19 ] 8- HO separated ion pairs, which can be measured, for example, by extended X-ray absorption fine structure (EXAFS) and / or X-ray absorption near edge structure (XANES) spectroscopy. Preferably, at least 80 wt. %, more preferably at least 90 wt. %, and even more preferably at least 95 wt. % of the Ta-POM supported on the support material is in direct contact with at least a portion of the one or more PGMs, based on the total weight of the Ta-POM supported on the support material.

[0030] Preferably, the molar ratio of Ta-POM to one or more PGMs supported on the support material is 1:1 to 100:1, preferably 3:1 to 70:1, more preferably 5:1 to 50:1, even more preferably 10:1 to 50:1, and even more preferably 15:1 to 50:1. In certain embodiments, the molar ratio of Ta-POM to one or more PGMs supported on the support material can be 1:1 to 70:1 or 1:1 to 50:1. Because the Ta-POM is preferably Ta-hexametallate, the molar ratio of Ta atoms to one or more PGMs is therefore preferably six times this. Catalyst compositions having such ratios can promote the advantages described herein.

[0031] Preferably, the catalyst composition comprises 0.01 to 2.0 wt. % of one or more PGMs, preferably 0.05 to 1.0 wt. % of one or more PGMs, and more preferably 0.07 to 0.5 wt. % of one or more PGMs, based on the total weight of the support material. Catalyst compositions having such wt. % of one or more PGMs can promote the benefits described herein.

[0032] Preferably, the catalyst composition comprises 0.01 to 20 wt% Ta, preferably 0.1 to 15 wt% Ta, more preferably 0.2 to 10 wt% Ta, even more preferably 1.0 to 10.0 wt%, and even more preferably 2.0 to 10.0 wt% Ta, based on the total weight of the support material. Catalyst compositions having such wt% Ta can promote the benefits described herein.

[0033] Preferably, the substrate is a flow-through monolith or a wall-flow filter, more preferably a flow-through monolith.

[0034] Preferably, the catalyst composition of the catalyst article comprises: providing a support material having one or more PGMs supported thereon; providing a solution containing Ta-POM; contacting the support material with a solution.

[0035] Preparing the catalyst article in this manner has been found to be particularly effective.

[0036] Preferably, the solution containing Ta-POM is an aqueous solution containing Ta-POM. Preferably, the solution contains 1 to 5 M Ta-POM. The aqueous solution can help facilitate the advantageous electrostatic interaction between Ta-POM and PGM discussed herein.

[0037] Preferably, providing a support material having one or more PGMs supported thereon comprises pretreating the support material having one or more PGMs supported thereon at a temperature of 300-500°C for 1-3 hours. In other words, the one or more PGMs are preferably immobilized on the support material prior to the addition of the Ta-POM. Preferably, the pretreatment is at about 400°C for about 2 hours. Preferably, the atmosphere during the pretreatment comprises about 3% H2 and the balance N2. Preferably, after contacting the support material with the solution, the resulting slurry is stirred for about 1 minute to about 30 minutes, preferably about 10 minutes, preferably under a nitrogen atmosphere. Preferably, the formed catalyst composition is then collected by vacuum filtration, preferably in air. Preferably, the recovered catalyst composition is then washed with water and dried.

[0038] When the support material contains alumina, the specific surface area (SSA) of the alumina is preferably 80 to 220 m as measured by the Brunauer-Emmett-Teller (BET) method. 2 / g, more preferably 100 to 200m 2 / g, and even more preferably 130 to 180 m 2 / g. The crystallite size of the alumina is preferably 5 to 30 nm, more preferably 10 to 25 nm, and even more preferably 15 to 20 nm. Furthermore, the alumina has a D50 of preferably 10 to 20 nm, more preferably 12 to 18, even more preferably 14 to 16 nm, and even more preferably about 15 nm. D50 can be measured by TEM. In a specific embodiment, after hydrothermal aging at 1000°C for 4 hours in air containing 10% water vapor, the SSA of the alumina is preferably 1 to 150 nm as measured by BET. 2 / g, more preferably 10 to 130 m 2 / g, and even more preferably 20 to 110 m 2 / g In some embodiments, the aged alumina preferably has a crystallite size of 50 to 300 nm, more preferably 80 to 200 nm, and even more preferably 100 to 150 nm.

[0039] First catalytic region The catalyst composition may be present in a first catalyst region. In other words, the catalyst article may include a substrate and a first catalyst region disposed on the substrate, the first catalyst region comprising the catalyst composition described herein. Unless otherwise indicated, the first catalyst region may be disposed directly on the substrate, i.e., without an intervening material, and / or may be disposed indirectly on the substrate, i.e., using an intervening material. If the substrate is porous, the catalyst composition may be disposed therein, for example, within the pores of the substrate, i.e., the catalyst composition is disposed thereon and / or therein. The catalyst composition is typically disposed on the substrate in the form of a washcoat. As used herein, the term "washcoat" is well known in the art and typically refers to an adherent coating applied to a substrate during catalyst production.

[0040] Preferably, the first catalytic region further comprises a first oxygen storage capacity (OSC) material and / or a first alkali and / or alkaline earth metal component.

[0041] Preferably, the first OSC material comprises cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the first OSC material comprises ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. Preferably, the ceria-zirconia mixed oxide further comprises a dopant, such as lanthanum, neodymium, praseodymium, or yttrium oxide. In some embodiments, the first OSC material preferably comprises ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0042] Preferably, the first catalytic region further comprises a first alkali metal and / or alkaline earth metal.

[0043] The first alkali metal or alkaline earth metal is preferably barium or strontium, and mixed oxides or composite oxides thereof. Preferably, the barium or strontium, if present, is supported in an amount of 0.1 to 15 wt %, more preferably 3 to 10 wt %, barium or strontium, based on the total weight of the first catalyst region.

[0044] 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.

[0045] The first catalytic region can extend over 100 percent of the axial length of the substrate (see, e.g., Figures 1 and 2).

[0046] The total washcoat loading of the first catalyst region is preferably 3.5 g / in 3 More preferably, it is less than 3.0 g / in 3 less than, and even more preferably 2.5 g / in 3 Alternatively, the total washcoat loading of the first catalyst region is preferably from 0.5 to 3.5 g / in 3 More preferably, it is 0.6 to 3 g / in 3 , and even more preferably 0.7 to 2.5 g / in 3 is.

[0047] Second catalytic region Preferably, the catalytic article further comprises a second catalytic region disposed on the substrate.

[0048] Preferably, the second catalyst region further comprises a second PGM component, a second oxygen storage capacity (OSC) material, a second alkali and / or alkaline earth metal component, and / or a second inorganic oxide.

[0049] The second PGM component preferably comprises one or more of platinum, palladium, rhodium, and mixtures or alloys thereof, hi some embodiments, the second PGM component preferably comprises Pd, Pt, or mixtures or alloys thereof.

[0050] Preferably, the second OSC material comprises cerium oxide, zirconium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. More preferably, the second OSC material comprises ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, or a combination thereof. Furthermore, the second OSC material preferably further comprises one or more dopants such as lanthanum, neodymium, praseodymium, yttrium, etc. Furthermore, the second OSC material preferably functions as a support material for the second PGM component. In some embodiments, the second OSC material preferably comprises ceria-zirconia mixed oxide and alumina-ceria-zirconia mixed oxide.

[0051] The ceria-zirconia mixed oxide preferably 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.

[0052] The second catalyst region preferably comprises the second OSC material (e.g., ceria-zirconia mixed oxide) in an amount of 10-90 wt%, preferably 25-75 wt%, more preferably 30-60 wt%, based on the total washcoat loading of the second catalyst region.

[0053] The loading of the second OSC material in the second catalyst region is preferably 2 g / in 3 In some embodiments, the loading of the second OSC material in the second catalyst region is preferably less than 1.5 g / in 3Less than or equal to 1.2 g / in, preferably 1.2 g / in 3 or less, and even more preferably 1 g / in 3 or less, and even more preferably 0.8 g / in 3 or less, and even more preferably 0.7 g / in 3 The following is the result.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The second inorganic oxide is preferably an oxide of an element of Groups 2, 3, 4, 5, 13, or 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, lanthania-alumina, zirconia, or a silica / alumina composite oxide. More preferably, the second inorganic oxide is alumina, lanthania-alumina, or a silica / alumina composite oxide. One particularly preferred second inorganic oxide is alumina or lanthania-alumina. In some embodiments, the second inorganic oxide is lanthania-alumina (e.g., lanthanum-stabilized alumina), and lanthania is present in an amount of up to 10% by weight of the second inorganic oxide, preferably 2-8, 3-7, or 4-6% by weight.

[0059] In some embodiments, the second inorganic oxide is doped with at least 5 wt. % of a second dopant, and the second dopant is selected from the group consisting of Zr, Ta, Mo, W, Ti, Nb, and combinations thereof. In further embodiments, the second dopant can be selected from the group consisting of Zr, Ta, Ti, Nb, and combinations thereof. In even further embodiments, the second dopant can be Ti, Nb, or combinations thereof. In yet other further embodiments, the second dopant can be Ti or Nb. In certain embodiments, the second dopant can be Ti. In other embodiments, the second dopant can be Nb. In certain embodiments, the content of the second dopant in the second inorganic oxide (e.g., alumina) can be 5 wt. % to 90 wt. In some further embodiments, the content of the second dopant in the second inorganic oxide can be 5 wt. % to 20 wt. In other further embodiments, the content of the second dopant in the second inorganic oxide can be 20 wt. % to 80 wt.

[0060] Preferably, the total washcoat loading of the second catalyst region is 3.5 g / in 3 More preferably, it is less than 3.0 g / in 3less than, and even more preferably 2.5 g / in 3 Alternatively, the total washcoat loading of the first catalyst region is preferably from 0.5 to 3.5 g / in 3 More preferably, it is 0.6 to 3 g / in 3 , and even more preferably 0.7 to 2.5 g / in 3 is.

[0061] The second catalytic region can extend over 100 percent of the axial length L (see, eg, FIG. 2).

[0062] In some embodiments, the first catalytic region is preferably supported / deposited directly on the substrate, and then the second catalytic region is preferably supported / deposited directly on the first catalytic region. In certain embodiments, the second catalytic region is preferably supported / deposited directly on the substrate, and then the first catalytic region is preferably supported / deposited directly on the second catalytic region.

[0063] The catalyst article of the present invention may contain additional components known to those skilled in the art. For example, the composition of the present invention may further comprise at least one binder and / or at least one surfactant. When a binder is present, a dispersible alumina binder is preferred.

[0064] Base material Preferably, the substrate is a flow-through monolith. Alternatively, the substrate may be a wall-flow filter.

[0065] The flow-through monolith substrate may have a first surface and a second surface defining a longitudinal direction therebetween. The flow-through monolith substrate may have a plurality of channels extending between the first surface and the second surface. The plurality of channels may 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, a flow-through monolith substrate is not a wall-flow filter.

[0066] The first surface is typically at the inlet end of the substrate, and the second surface may be at the outlet end of the substrate.

[0067] The channels may be of constant width, and each of the plurality of channels may have a uniform channel width.

[0068] 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 preferably 600 to 700 channels per square inch. The channels can have cross sections that are rectangular, square, circular, oval, triangular, hexagonal, or other polygonal shapes.

[0069] The monolith substrate can act as a support for holding 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Another aspect of the invention relates to a catalyst article obtained or obtainable by calcining a catalyst article according to the first aspect.

[0074] All preferred features and embodiments of the other aspects apply equally to this aspect, where appropriate.

[0075] As used herein, the terms "calcining," "sintering," "firing," and the like can encompass a heat treatment process in the absence or limited supply of air or oxygen to effect thermal decomposition or transformation. Typically, however, calcining in this context involves heating in air in an oven. Preferably, calcining involves heating (in air in an oven) at a temperature of 350-1100°C, preferably 400-900°C, more preferably 450-800°C, for 1-8 hours, preferably 2-5 hours.

[0076] Without being bound by theory, it is believed that the calcination step may cause the thermal decomposition of Ta-POM to Ta2O5. That is, it is believed that the catalyst article of this embodiment is substantially free of Ta-POM. Due to the location of Ta-POM relative to the PGM particles in the intermediate product, it is believed that Ta2O5 typically forms in the vicinity of and / or as a coating that at least partially coats one or more PGMs. The Ta2O5 is then believed to provide a PGM-loaded support material with increased hydrothermal stability. However, as described herein and shown in the examples, the simple addition of Ta2O5 (without via Ta-POM) can significantly reduce the amount of NO x and THC conversion, at least to the same extent as the present invention. For this reason, it is believed that the catalytic article of this embodiment can be distinguished from a catalytic article in which Ta2O5 is simply disposed on a PGM-supported support material by the distribution of Ta2O5 on the support material. This is because, in the present invention, Ta2O5 may be primarily present on and / or around the PGM particles present on the support material. This can be measured, for example, by TEM, which can show the distribution of Ta on alumina. X-ray diffraction can also be useful. Furthermore, EXAFS can be useful to determine the ratio of Rh-Rh, Rh-Ta, and Ta-Ta interactions in the catalytic article.

[0077] Preferably, the catalyst article comprises particles of Ta2O5 supported on one or more PGMs. "Supported on one or more PGMs" in this context means that the particles of Ta2O5 are in direct contact with (particles of) one or more PGMs. The Ta2O5 may also be in direct contact with the support material. However, the Ta2O5 may also be in direct contact only with one or more PGMs.

[0078] In another aspect, a catalyst article is provided that includes a substrate and a catalyst composition disposed on the substrate, the catalyst composition including a support material having thereon one or more platinum group metals (PGMs), and Ta2O5 and is supported, The catalyst composition comprises: providing a support material having one or more PGMs supported thereon; providing a solution containing Ta-POM; contacting a support material with the solution to provide a support material including Ta-POM supported thereon; It has been obtained or is obtainable by a method comprising: calcining a support material having Ta-POM supported thereon; and calcining a support material comprising Ta-POM supported thereon.

[0079] All preferred features and embodiments of the other aspects apply equally to this aspect, where appropriate.

[0080] Of course, after contacting the support material with the solution, the support material still comprises one or more PGMs supported thereon. Typically, the support material comprising Ta-POM supported thereon can be recovered, typically by filtration or the like, from the mixture or slurry formed in the step of contacting the support material with the solution. The support material comprising Ta-POM supported thereon may then be further washed, preferably with water, before calcining the support material comprising Ta-POM supported thereon. The calcined support material may then be cooled, for example, to room temperature, or may be cooled after calcination. Contacting the support material with the solution may include mixing or stirring the resulting slurry, preferably under an inert nitrogen atmosphere, for a period of about 1 minute to about 30 minutes, preferably about 10 minutes.

[0081] Another aspect of the invention relates to an exhaust gas treatment system comprising the catalytic article described herein in any aspect. All preferred features and embodiments of the other aspects apply equally to this aspect, where appropriate.

[0082] Another aspect of the invention relates to a fuel combustion and exhaust gas treatment system comprising an engine and an exhaust gas treatment system of the above aspect. Preferably, the engine is a gasoline engine. All preferred features and embodiments of the other aspects apply equally to this aspect, where appropriate.

[0083] Another aspect of the invention relates to a method of treating exhaust gases, comprising passing the exhaust gases through a catalyst article of any of the aspects described herein, preferably a Ta-POM pyrolyzed embodiment, and preferably an exhaust gas treatment system of the above aspects. All preferred features and embodiments of the other aspects apply equally to this aspect, where appropriate.

[0084] Another aspect of the invention relates to the use of Ta-POM in a method for producing a catalytic article comprising one or more PGMs supported on a support material. All preferred features and embodiments of the other aspects apply equally to this aspect, where appropriate. Preferably, the use is to improve the TWC performance of the catalytic article. In the context of this aspect, the term "TWC performance" refers to the ability to improve the TWC performance of at least THC and / or NO. x It is intended to encompass conversion rate and / or light-off temperature (ie, increasing conversion rate and decreasing light-off temperature).

[0085] In alternative embodiments contemplated herein, Ta-POM is replaced by Nb-POM. In other words, in such embodiments, Nb is used instead of Ta. Similar advantages, although to a lesser extent, have been observed with the use of Nb-POM.

[0086] The following numbered clauses are also provided herein: All preferred features and embodiments of other aspects apply equally to these clauses, where appropriate. I. A method for producing a catalyst composition, the method comprising: providing a support material having one or more PGMs supported thereon; providing a solution containing Ta-POM; contacting the support material with a solution. II. The method of clause I, wherein the catalyst composition is for three-way catalysis. III. The method of clause I or clause II, further comprising calcining the catalyst composition. IV. A method of making a catalyst article, the method comprising: preparing a catalyst composition according to the method of any one of clauses I-III; and disposing the catalyst composition on a substrate.

[0087] definition As used herein, the terms "article" or "catalyst article" 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.

[0088] 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 or metal monolithic substrates. Substrates can vary in their material composition, size and configuration, cell shape and density, and wall thickness. Suitable substrates (such as cordierite) are known in the art.

[0089] As used herein, the term "catalyst composition" may include compositions that exhibit catalytic activity, particularly towards substances present in exhaust gases, preferably gasoline exhaust gases.

[0090] As used herein, the term "disposed on" can include having the catalyst composition disposed directly on the substrate, i.e., without intervening materials, and / or indirectly on the substrate, i.e., with intervening materials. If the substrate is porous, the term "disposed on" can also include having the catalyst composition disposed therein, e.g., within the pores of the substrate, i.e., the catalyst composition is disposed on and / or within. The catalyst composition is typically disposed on the substrate in the form of a washcoat. As used herein, the term "washcoat" is well known in the art and typically refers to an adherent coating applied to a substrate during catalyst production.

[0091] As used herein, the term "polyoxometallate" or "POM" takes its ordinary meaning in the art, e.g., it can be a polyatomic ion, usually an anion, consisting of three or more transition metal oxyanions bonded together by shared oxygen atoms to form a closed three-dimensional framework.

[0092] As used herein, the term "support material" may encompass any material capable of supporting at least one or more PGMs and Ta-POMs thereon or therein. The support material may take any form but is typically in the form of a powder, more typically a high surface area powder. For example, the support material may be in the form of a powder having a D50, as measured using TEM, of, for example, 0.1 to 30 μm, more typically 0.5 to 25 μm, and even more typically 1 to 20 μm. Such particle size may facilitate desirable rheological properties of the slurry used to coat the substrate. The support material may function as a washcoat. The support material may be the washcoat or may be part of the washcoat. The support material may also serve as an oxygen storage material, storing and releasing oxygen under fuel-lean and fuel-rich conditions, respectively, to facilitate three-way catalytic conversion.

[0093] The term "supported thereon," as used herein in the context of the present invention, can include one or more PGMs (typically in the form of nanoparticles) in direct contact with at least a portion of the surface of the support material, and the Ta-POM either in direct contact with at least a portion of the surface of the support material or indirectly supported on the support material via one or more PGMs. Preferably, the Ta-POM is in direct contact with at least a portion of the surface of the one or more PGMs.

[0094] Preferably, the substrate includes an inlet end and an outlet end having an axial length L. As used herein, the term "inlet end" may encompass an end of the substrate intended to be disposed in an upstream direction. In contrast, as used herein, the term "outlet end" may encompass an end of the substrate intended to be disposed in a downstream direction. As used herein, the term "upstream" refers to a direction in the system toward the exhaust gas source. In contrast, as used herein, the term "downstream" refers to a direction in the system away from the exhaust gas source.

[0095] The term "region," as used herein, refers to an area on a substrate that is typically obtained by drying and / or baking a washcoat. A "region" can be disposed or carried 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).

[0096] 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 (e.g., the difference between the maximum and minimum length) by more than 10%, 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%.

[0097] Preferably, each "region" 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 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.

[0098] 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).

[0099] The overall length of a substrate is the distance between its inlet end and its outlet end (eg, both ends of the substrate).

[0100] 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.

[0101] 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 carried by the substrate, (a) a zone that is closer to the inlet end (e.g., open end) of an inlet channel of a substrate than to the closed end (e.g., 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.

[0102] 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.

[0103] Similarly, when the substrate is a wall-flow filter, any reference to "a zone disposed at the outlet end of the substrate" includes a zone disposed on or carried by the substrate, (a) a zone that is closer to the outlet end (e.g., open end) of the outlet channel of the substrate than to the closed end (e.g., 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.

[0104] 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.

[0105] When the washcoat is present on the wall of a wall-flow filter (ie, the zone is within the wall), the zone may satisfy both (a) and (b).

[0106] The term "washcoat" is well known in the art and typically refers to an adherent coating applied to a substrate during the production of a catalyst.

[0107] 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. Generally, the term "PGM" preferably refers to metals selected from the group consisting of Rh, Pt, and Pd.

[0108] The term "mixed oxide," as used herein, generally refers to a mixture of oxides in a single phase, as 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 conventionally known in the art.

[0109] The phrase "consisting essentially of," as used herein, limits the scope of a feature to include the specified materials or steps and any other materials or steps, e.g., trace impurities, that do not substantially affect the basic properties of the feature. The phrase "consisting essentially of" encompasses the phrase "consisting of."

[0110] The phrase "substantially free," as used herein with respect to a material, typically in the context of the content of a region, layer, or zone, means that the material is present in small amounts, such as 5% by weight or less, preferably 2% by weight or less, more preferably 1% by weight or less, even more preferably 0.5% by weight or less, even more preferably 0.1% by weight or less, and even more preferably 0.01% by weight or less. The phrase "substantially free" encompasses the phrase "free."

[0111] The term "loading" as used herein refers to g / ft on a metal weight basis. 3 Refers to a measurement in units of .

[0112] Unless otherwise specified or implied, the use of terms such as "first," "second," etc. are intended as labels only and are not intended to indicate the relative position or location of particular features.

[0113] The following examples are merely illustrative of the present invention, and those skilled in the art will recognize many variations that are within the spirit and scope of the claims. [Example]

[0114] material All materials were commercially available and obtained from known sources unless otherwise stated.

[0115] General Preparation of Catalytic Washcoat Rh, about 200m 2 Commercially available La-stabilized γ-AlO powder with a surface area of ​​1 / g was impregnated with the powder and calcined in an oven at 500 °C. For the POM-doped Rh washcoat, hexaniobate (Nb-POM) or hexanthalate (Ta-POM) salts were impregnated into the Rh washcoat powder, and the powder was then washed with water and subsequently calcined in an oven at 500 °C.

[0116] Example 1: Synthesis of POM-doped Rh / alumina materials and light-off performance in catalytic activity testing Comparative catalyst A Comparative Catalyst A was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in 3 The Rh loading is 0.9 g / ft 3 It was.

[0117] Comparative catalyst B Comparative Catalyst B was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Nb-POM-doped Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading was 0.9 g / ft 3 The Nb loading was 23 g / ft 3 It was.

[0118] Catalyst C Catalyst C was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Ta-POM-doped Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading was 0.9 g / ft 3 The Ta loading was 79 g / ft 3 It was.

[0119] Comparative Catalyst A, Comparative Catalyst B, and Catalyst C were tested separately in a Synthetic Catalytic Activity Test (SCAT) apparatus. The catalyst was 10% by volume H2O + 15% by volume CO2 + 1260 ppm C3H6 + 0.2% by volume H2 + 0.6% by volume CO + 0.53% by volume O2 + 1000 ppm NO2, balanced with N2 (space velocity: 60,000 h2). -1 The light-off performance was tested in a gas flow of THC, CO, and NO at a temperature gradient of 30°C / min. x The conversion of was calculated by comparing the concentration of the feed gas with the concentration of the gas at the catalyst outlet. Conversion is the concentration of a particular species after passing through the catalyst article as a percentage of the input concentration (i.e., the concentration of the species in the feed gas). A series of comparative catalysts A and B, as well as catalyst C, were hydrothermally aged at 1050°C for 4 hours under the redox conditions shown in Table 1.

[0120] [Table 1]

[0121] HC, CO, and NO of aged Comparative Catalyst A, Comparative Catalyst B, and Catalyst C x T 50 The light-off temperatures are shown in Table 2. The data surprisingly show that inventive catalyst C (i.e., prepared using the Ta-POM described herein) provided significantly improved light-off performance when compared to comparative catalyst A (Rh / Al2O3) and comparative catalyst B (Nb-POM-added Rh / Al2O3). The impact of the improved light-off performance was observed for catalyst C with Ta-POM-added Rh / Al2O3 compared to comparative catalyst A with Rh / Al2O3, with significantly improved CO, HC, and NO, respectively. x About 9℃, 21℃ and 11℃ lower T 50 (T 50 (The temperature at which 50% conversion is reached, as known to those skilled in the art, is the temperature at which 50% conversion is reached.) The effect of Nb-TOM-added Rh / Al2O3 Comparative Catalyst B on Rh / Al2O3 Comparative Catalyst A was also observed, with CO, HC, and NO x T 50 The addition of both Ta-POM and Nb-POM can improve the light-off performance of Rh / Al2O3, but the effect is more significant for Ta-POM.

[0122] [Table 2]

[0123] Example 2: Synthesis of Ta oxide and Ta-POM doped Rh / alumina materials Light-off performance in catalytic activity test Comparative catalyst D Comparative Catalyst D was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in 3 The Rh loading is 0.9 g / ft 3 It was.

[0124] Comparative catalyst E Comparative Catalyst E was a single-layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of solid TaO-doped Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading was 0.9 g / ft 3 The Ta loading is 9 g / ft 3 It was.

[0125] Catalyst F Catalyst F was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Ta-POM-doped Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading was 0.9 g / ft 3 The Ta loading was 79 g / ft 3 It was.

[0126] Comparative Catalysts D and E and Catalyst F were tested separately in a Synthetic Catalytic Activity Test (SCAT) apparatus under the redox conditions shown in Table 1 after hydrothermal aging at 1050° C. for 4 hours.

[0127] HC, CO, and NO for aged comparative catalysts D and E and catalyst F x T 50 The light-off temperatures are shown in Table 3. The data surprisingly show that inventive catalyst F (i.e., prepared using Ta-POM as described herein) also provided significantly improved light-off performance when compared to comparative catalyst E (TaO-doped Rh / AlO, i.e., not via the Ta-POM route). The impact of the improved light-off performance was seen in the reduction of CO, HC, and NO for the Ta-POM-doped Rh / AlO catalyst F compared to the Ta-POM-doped Rh / AlO comparative catalyst E. x T values ​​are approximately 47°C, 64°C, and 54°C lower, respectively. 50 This effect was not observed in the Ta2O5-doped Rh / Al2O3 comparative catalyst E compared to the Rh / Al2O3 comparative catalyst D.

[0128] [Table 3]

[0129] Example 3: Light-off performance in the synthesis catalytic activity test for different amounts of Ta-POM-doped Rh / alumina materials Comparative catalyst G Comparative Catalyst G was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading is 0.9 g / ft 3 It was.

[0130] Catalyst H Catalyst H was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Ta-POM-doped Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading was 0.9 g / ft 3 The Ta loading was 1.7 g / ft 3 It was.

[0131] Catalyst I Catalyst I was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Ta-POM-doped Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading was 0.9 g / ft 3 The Ta loading was 8.6 g / ft 3 It was.

[0132] Catalyst J Catalyst J was a single layer TWC coated on a ceramic substrate (400 cpsi, 4.0 mil wall thickness). The catalyst layer consisted of Ta-POM-doped Rh supported on a washcoat of La-stabilized alumina. The washcoat loading was approximately 0.6 g / in. 3 The Rh loading was 0.9 g / ft 3 The Ta loading was 43 g / ft 3 It was.

[0133] Comparative Catalyst G and Catalyst HJ were tested separately in a Synthetic Catalyst Activity Test (SCAT) apparatus under the redox conditions shown in Table 1 after hydrothermal aging at 1050° C. for 4 hours.

[0134] HC and NO of aged comparative catalyst G and catalyst HJ x T 50 The light-off temperatures are shown in Table 4. The data surprisingly show that catalyst H of the present invention (i.e., about 1.7 g / ft 3 8.6 g / ft) were compared with Comparative Catalyst G (Rh / AlO, i.e., no Ta loading) and Catalyst I (i.e., about 8.6 g / ft). 3 Catalyst J (i.e., prepared using the Ta-POM described herein having a Ta loading of about 43 g / ft 3 The results show that catalyst H gave the best light-off performance when compared to catalyst H prepared using the Ta-POM described herein with a Ta loading of 1000 ppm or less. x T 50 were about 14° C. and 8° C. lower, respectively, than Comparative Catalyst G. The benefit of higher Ta loadings in Catalyst I and Catalyst J is relatively limited with respect to catalyst light-off performance.

[0135] [Table 4]

Claims

1. 1. A catalytic article comprising a substrate and a catalytic composition disposed on the substrate, the catalytic composition comprising a support material having thereon: one or more platinum group metals (PGMs), and Ta-polyoxometallate (POM), and a supported catalytic article.

2. 10. The catalytic article of claim 1, wherein the catalytic article is for treating exhaust gases from an internal combustion engine, and preferably the catalytic article is a three-way catalyst (TWC) article.

3. The catalytic article of claim 1 or claim 2, wherein the Ta-POM comprises Ta-hexametallate.

4. 4. The catalytic article of any one of claims 1 to 3, wherein the one or more PGMs comprise one or more of Pt, Pd, Rh, and mixtures or alloys thereof, preferably the one or more PGMs comprise Rh.

5. 5. The catalytic article of any one of claims 1 to 4, wherein the one or more PGMs comprise nanoparticles having an average particle size of 0.1 to 10 nm, preferably 0.5 to 9 nm, more preferably 1 to 8 nm, even more preferably 2 to 7 nm, and still more preferably 3 to 6 nm.

6. 6. A catalyst article according to any one of claims 1 to 5, wherein the support material comprises one or more of an alumina and ceria-containing mixed oxide, preferably alumina and / or ceria-zirconia mixed oxide, more preferably alumina.

7. 7. The catalytic article of claim 6, wherein the support material further comprises a dopant comprising one or more of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, copper, silicon, calcium, barium, strontium, cesium, magnesium, potassium, and sodium, more preferably one or more of lanthanum, neodymium, praseodymium, hafnium, and yttrium.

8. 8. The catalytic article of claim 7, wherein the dopant is present in the support material in an amount of 0.001 to 20 wt. %, preferably 0.5 to 10 wt. %, based on the total weight of the support material.

9. 9. The catalytic article of any one of claims 1 to 8, wherein at least a portion of the Ta-POM is in direct contact with at least a portion of the one or more PGMs.

10. 10. The catalytic article of claim 9, wherein at least 70 wt. % of the Ta-POM supported on the support material is in direct contact with at least a portion of the one or more PGMs, based on the total weight of the Ta-POM supported on the support material.

11. 11. The catalytic article according to any one of claims 1 to 10, wherein the molar ratio of the Ta-POM to the one or more PGMs supported on the support material is from 1:1 to 100:1, preferably from 3:1 to 70:1, more preferably from 5:1 to 50:

1.

12. 12. The catalyst article of any one of claims 1 to 11, wherein the catalyst composition comprises 0.01 to 2.0 wt.% of the one or more PGMs, preferably 0.05 to 1.0 wt.% of the one or more PGMs, more preferably 0.07 to 0.5 wt.% of the one or more PGMs, based on the total weight of the support material.

13. 13. The catalyst article of any one of claims 1 to 12, wherein the catalyst composition comprises 0.01 to 20 wt% Ta, preferably 0.1 to 15 wt% Ta, more preferably 0.2 to 10 wt% Ta, based on the total weight of the support material.

14. The catalytic article of any one of claims 1 to 13, wherein the substrate is a flow-through monolith or a wall-flow filter.

15. The catalyst composition of the catalyst article, wherein the catalyst composition of the catalyst article comprises: providing a support material comprising one or more PGMs supported thereon; providing a solution comprising Ta-POM; A catalytic article according to any one of claims 1 to 14 obtained or obtainable by a process comprising contacting said support material with said solution.

16. The catalytic article of claim 15, wherein the solution containing Ta-POM is an aqueous solution containing Ta-POM.

17. 17. The catalytic article of claim 15 or 16, wherein providing the support material having one or more PGMs supported thereon comprises pretreating the support material having one or more PGMs supported thereon at a temperature of from 300 to 500°C for from 1 to 3 hours.

18. A catalyst article obtained or obtainable by calcining a catalyst article according to any one of claims 1 to 17.

19. Ta supported on said one or more PGMs ２ O ５ 20. The catalytic article of claim 18, comprising particles of:

20. 1. A catalytic article comprising a substrate and a catalytic composition disposed on the substrate, the catalytic composition comprising a support material having thereon one or more platinum group metals (PGMs), and Ta ２ O ５ and is supported, The catalyst composition comprises: providing a support material comprising one or more PGMs supported thereon; providing a solution comprising Ta-POM; contacting said support material with said solution to provide a support material comprising said Ta-POM supported thereon; and calcining a support material comprising said Ta-POM supported thereon.

21. An exhaust gas treatment system comprising the catalytic article of any one of claims 1 to 20.

22. 22. A fuel combustion and exhaust gas treatment system comprising an engine and the exhaust gas treatment system of claim 21.

23. 23. The fuel combustion and exhaust gas treatment system of claim 22, wherein the engine is a gasoline engine.

24. 22. A method for treating exhaust gases, said method comprising passing exhaust gases through a catalytic article according to any one of claims 1 to 20, preferably an exhaust gas treatment system according to claim 21.

25. Use of Ta-POM in a method for producing a catalytic article comprising one or more PGMs supported on a support material.

26. 26. The use of claim 25, wherein the use is to improve the TWC performance of the catalyst article.

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