Improved TWC activity using rhodium / platinum and gallic acid as complexing and reducing agents.

Abstract

1. A method for producing a catalyst article, the method comprising: [Formula 1] JPEG2026500612000007.jpg31128 (wherein R1 is H or C1-C6 alkyl and R2 is H, OH, or O-C1-C4 alkyl) and a PGM comprising rhodium and / or platinum; providing a support material; applying the complex to the support material to form a supported support material; disposing the supported support material on a substrate; and heating the supported support material to form nanoparticles of the PGM 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 this method, an emission treatment system, and a method for treating exhaust gases. [Background technology]

[0002] A three-way catalyst (TWC) removes CO, HC, and NO from the exhaust of a gasoline engine at a stoichiometric air-fuel ratio. x Specifically, the oxidation of CO and HC to CO and water vapor (HO) is primarily catalyzed by Pd, while NO x The reduction of CO to N2 is primarily catalyzed by Rh. Modern TWCs use supported platinum group metal (PGM) catalysts (e.g., Pd, Rh, Pt) deposited on single-, double-, or multi-layer supports. The support materials consist of high-surface-area metal oxides, primarily stabilized 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 PGM elements onto oxide supports by incipient wetness or wet impregnation using solutions of inorganic PGM precursors, such as nitrate, acetate, or chloride salts. To improve TWC performance, promoter salts are often added to the washcoat formulation. Once a monolith substrate is washcoated with the as-prepared slurry, subsequent drying and calcination steps are performed to decompose the inorganic salts and immobilize the PGM and promoter elements on the support material. The performance of supported metal catalysts is known to depend on the structure and composition of the metal nanoparticles and the properties of the support. Conventional TWCs prepared using the above methods often offer limited control over the structure of the catalytically active species (i.e., average PGM particle size and composition, location of the active components, and metal-support interactions). This is primarily due to metal migration and particle growth during the high-temperature calcination process.

[0004] Increasingly stringent environmental regulations require TWCs with higher emission reduction efficiencies. Meanwhile, increasing PGM costs have created an urgent need to reduce PGM loadings without compromising TWC performance. Better control of PGM particle size and metal-support interactions is essential to optimizing TWC performance. Furthermore, a more homogenized PGM particle size distribution can contribute to reducing the degree of metal sintering due to Ostwald ripening, which often occurs during the fuel cutoff process, an engine strategy used to improve fuel economy.

[0005] The catalyst light-off is the minimum temperature required to initiate the catalytic reaction. Specifically, the light-off temperature is the temperature at which 50% conversion is reached. There is a need for catalyst articles with lower light-off temperatures.

[0006] U.S. Patent Application Publication No. 2012 / 0077669(A1) describes the polymer-assisted synthesis of supported metal catalysts for automotive applications. The polymers used in the examples include poly(vinylpyrrolidone), poly(acrylic acid), and poly(ethyleneimine). In the described synthesis procedure, a support (alumina powder) is first impregnated with a polymer-containing aqueous solution. The impregnated support is then separated from the solution by filtration and drying. The dried, impregnated support is further impregnated with a PGM precursor solution by incipient wetness impregnation. The described process involves multiple steps for the formation of the claimed supported metal catalyst, which increases the cost and difficulty of commercial-scale production. U.S. Patent Application Publication No. 2012 / 0077669(A1) indicates that lean-burn engines, such as diesel engines or lean-burn gasoline engines, are preferably used to apply this technology. Summary of the Invention

[0007] One aspect of the present disclosure relates to a method of making a catalytic article, the method comprising:

[0008] [ka] wherein R1 is H or C1-C6 alkyl and R2 is H, OH, or O-C1-C4 alkyl, and a PGM comprising rhodium and / or platinum; providing a support material; applying the complex to the support material to form a supported support material; disposing the supported support material on a substrate; and heating the supported support material to form nanoparticles of the PGM on the support material.

[0009] Another aspect of the present disclosure relates to a catalyst article obtainable by the method of the first aspect.

[0010] The present invention also includes an exhaust system for an internal combustion engine that includes the catalytic article of the second aspect. [Brief explanation of the drawings]

[0011] [Figure 1A] 1 shows the results of NO conversion in a perturbation ignition performance test for Comparative Example 1A and Example 1B. [Figure 1B] 1 shows the THC conversion results of the perturbation ignition performance test for Comparative Example 1A and Example 1B. [Figure 1C] 1 shows the results of CO conversion in a perturbation ignition performance test for Comparative Example 1A and Example 1B. [Figure 2A] 1 shows the results of NO conversion in a perturbation ignition performance test for Comparative Example 1A and Example 1B. [Figure 2B] 1 shows the THC conversion results of the perturbation ignition performance test for Comparative Example 1A and Example 1B. [Figure 2C] 1 shows the results of CO conversion in a perturbation ignition performance test for Comparative Example 1A and Example 1B. [Figure 3A] 1 shows CO conversion results of perturbed lambda sweep performance tests of Comparative Example 1A and Example 1B. [Figure 3B] 1 shows THC conversion results of perturbed lambda sweep performance tests of Comparative Example 1A and Example 1B. [Figure 3C] 1 shows NO conversion results of perturbed lambda sweep performance tests of Comparative Example 1A and Example 1B. [Figure 4A] 1 shows the results of NO conversion in a perturbation ignition performance test for Comparative Example 2A and Example 2B. [Figure 4B] 1 shows the THC conversion results of perturbation ignition performance tests for Comparative Example 2A and Example 2B. [Figure 4C] 1 shows the results of CO conversion in a perturbation ignition performance test for Comparative Example 2A and Example 2B. DETAILED DESCRIPTION OF THE INVENTION

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

[0013] In a first aspect, the present invention provides a method of making a catalytic article, the method comprising: Formula (I):

[0014] [ka] providing a complex of a compound of the formula: wherein R1 is H or C1-C6 alkyl and R2 is H, OH, or O-C1-C4 alkyl with a PGM comprising rhodium and / or platinum; Providing a carrier material; applying the complex to the support material to form a supported support material; disposing the supported support material on a substrate; and heating the supported support material to form nanoparticles of the PGM on the support material.

[0015] Each aspect or embodiment defined herein may be combined with any other aspect or embodiment unless expressly stated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0016] Surprisingly, when used in emissions treatment systems, catalyst articles produced by the methods of the present invention can exhibit favorable catalytic activity, particularly favorable three-way catalytic activity, after aging. For example, the aged catalyst article can 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 can be superior to that exhibited by conventional catalyst articles having the same / similar PGM species(s), loading(s), support(s), and configuration(s).

[0017] Advantageously, such superior performance may facilitate the use of lower loadings of PGMs compared to conventional catalyst articles without compromising catalytic performance, which may be beneficial given the high cost of such metals, particularly rhodium. Furthermore, such superior performance may facilitate partial / complete substitution of high-cost PGMs with lower-cost PGMs or other transition metals without compromising catalytic performance.

[0018] Compared with the method of U.S. Patent Application Publication No. 2012 / 0077669(A1), the method of the present invention is a simpler and more efficient "one-pot" method. The method of the present invention does not require separate impregnation, filtration, and drying steps to deposit polymer molecules on the support material. In contrast, in U.S. Patent Application Publication No. 2012 / 0077669(A1), only a limited amount of polymer can remain on the support after the filtration and washing steps. Furthermore, the catalyst article prepared by the method of the present invention can be used, in particular, as a three-way catalyst for stoichiometric gasoline emission reduction. In contrast, the catalyst article produced by the method of U.S. Patent Application Publication No. 2012 / 0077669(A1) has particular application in lean-burn diesel or gasoline engines.

[0019] As used herein, the term "catalytic article" may include an article having a catalyst supported thereon or therein. 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 catalytic article may be for use in emissions treatment systems, particularly emissions treatment systems for gasoline engines, preferably stoichiometric gasoline engines. The catalytic article may be for use in three-way catalysis.

[0020] Formula (I):

[0021] [ka] Providing a complex of a compound of formula (I) with a PGM typically involves providing the complex in solution, for example an aqueous or alcoholic solution. Providing a complex of a compound of formula (I) with a PGM typically involves mixing an inorganic PGM precursor in pure form or in solution with a compound of formula (I) in an aqueous medium, for example mixing nitrate PGM with a compound of formula (I) in water.

[0022] Preferably, R1 is H. Also preferably, R2 is OH.

[0023] The PGMs include rhodium and / or platinum. Such metals may be particularly suitable for three-way catalysis. In addition, such metals are expensive, which means that it is advantageous to be able to provide similar levels of catalytic activity for the same amount of metal. Furthermore, the use of such metals in the methods of the present invention can result in particularly favorable perturbation ignition performance. The PGMs may be in the form of alloys. In addition to rhodium and / or platinum, the PGMs may include other PGMs, such as, for example, one or more of ruthenium, palladium, osmium, and iridium.

[0024] The complexes may have a PGM atom to ester group ratio of 2:1 to 1:10, preferably 1:1 to 1:8, more preferably 1:2 to 1:5. The complexes may have a rhodium atom to ester group ratio of 2:1 to 1:10, preferably 1:1 to 1:8, more preferably 1:2 to 1:5. The complexes may have a platinum atom to ester group ratio of 2:1 to 1:10, preferably 1:1 to 1:8, more preferably 1:2 to 1:5. The complexes may have a rhodium and platinum atom to ester group ratio of 2:1 to 1:10, preferably 1:1 to 1:8, more preferably 1:2 to 1:5.

[0025] The support material may be any material capable of supporting the composite and nanoparticles 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. 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 is typically in the form of a powder having a D50, e.g., of 0.1 to 25 μm, more typically 0.5 to 5 μm, as measured using TEM. Such particle size may facilitate desirable rheological properties of the slurry used to coat the filter. The support material may function as a washcoat. The support material may be the washcoat or may be part of the washcoat.

[0026] 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.

[0027] Applying the complex to the support material typically involves contacting the complex with the support material in the presence of a solvent (typically water) to produce a slurry. As used herein, the term "slurry" can encompass a liquid containing insoluble material, e.g., insoluble particles. The slurry may include (1) the solvent, (2) soluble content, e.g., unreacted compound of Formula (I), inorganic PGM and co-catalyst precursor, and PGM-compound of Formula (I) complex (outside the support), and (3) insoluble content, e.g., support particles that may or may not interact with the compound of Formula (I) and metal precursor. 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 can increase the amount of complex supported on the support material.

[0028] As used herein, the term "loaded support material" can include a support material having a PGM-compound of Formula (I) complex 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 complex is typically immobilized on the support by, for example, electrostatic forces, hydrogen bonding, coordination bonds, covalent bonds, and / or ionic bonds. For example, in the case of oxides, ester functional groups (e.g., carboxylic acid ester functional groups) in the compound of Formula (I) and surface hydroxyl groups on the support can interact via electrostatic forces or hydrogen bond formation.

[0029] 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.

[0030] The supported carrier material can be placed on the substrate using techniques known in the art. Typically, the supported carrier material is placed on the substrate by pouring a slurry of the supported carrier material into the inlet of the substrate in a predetermined amount using a specific forming tool. As discussed in more detail below, subsequent vacuum and drying steps may be used during the placement step. If the carrier is a filter block, the supported carrier material may be placed on the filter wall, within the filter wall (if porous), or both.

[0031] Heating of the supported support material is typically carried out in an oven or furnace, more typically in a belt or static oven or furnace, typically in a unidirectional flow of hot air. Heating can include calcination. Heating can also include drying. The drying and calcination steps can be continuous or sequential. For example, a separate washcoat can be applied after the substrate has already been washcoated and dried with the previous washcoat. The washcoated substrate can also be dried and calcined using one continuous heating program once coating is complete. During heating, the complex can be at least partially, substantially, or completely decomposed. In other words, the ligand of the complex, i.e., the compound of formula (I), is at least partially, substantially, or completely removed or separated from the PGM and removed from the final catalyst article. The particles of PGM so separated can then begin to form metal-metal and metal-oxide bonds. As a result of heating (calcining), the substrate is typically substantially free of compounds of formula (I), more typically completely free of compounds of formula (I).

[0032] As used herein, the term "nanoparticle" can encompass particles having a diameter of 0.01 nm to 100 nm as measured by TEM. Nanoparticles can be of any shape, e.g., spheres, plates, cubes, cylinders, hexagons, or rods, but are typically spherical. The largest dimension of a nanoparticle (i.e., the diameter if the nanoparticle is spherical), as measured by TEM, is typically 0.5 to 10 nm, more typically 1 to 5 nm.

[0033] After the heating step, the substrate is typically cooled, more typically to room temperature. Cooling is typically done in air with or without a coolant / cooling medium, typically without a coolant.

[0034] In some preferred embodiments, compounds of formula (I):

[0035] [ka] The compound is gallic acid.

[0036] Gallic acid can coordinate with metal ions through hydrogen or covalent bonds. The PGM-gallic acid complex may be immobilized on a support, such as a metal oxide support, in a washcoat, and the carboxylic acid functional groups in the gallic acid ligand and the surface hydroxyl groups on the support may interact through electrostatic forces or hydrogen bond formation.

[0037] The PGM preferably comprises, consists essentially of, or consists of rhodium. Rhodium is a particularly expensive PGM and forms a particularly suitable complex with the compounds of formula (I), particularly gallic acid. The PGM preferably comprises, consists essentially of, or consists of platinum. Platinum is a particularly expensive PGM and forms a particularly suitable complex with the compounds of formula (I), particularly gallic acid.

[0038] In preferred embodiments, the PGM comprises, consists essentially of, or consists of rhodium and platinum. The use of such metals in the methods of the present invention can result in particularly favorable perturbation ignition performance.

[0039] The support material preferably comprises an oxide, preferably one or more of Al2O3 (aluminum oxide or alumina), SiO2, TiO2, CeO2, ZrO2, VO5, La2O3, and zeolite. The oxide is preferably a metal oxide. The support material more preferably comprises alumina, even more preferably gamma-alumina. The support material preferably comprises ceria-zirconia. The support material preferably comprises alumina and ceria-zirconia. The alumina and / or ceria-zirconia are preferably doped, more preferably doped with one or more oxides of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, manganese, iron, copper, calcium, barium, strontium, cesium, magnesium, potassium, or sodium, even more preferably doped 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 wt. % to 20 wt. %, and more preferably 0.5 wt. % to 10 wt. %.

[0040] The support material is preferably in the form of a powder having a D90 of 0.1 to 25 μm, more preferably 0.5 to 5 μm.

[0041] The supported support material is preferably disposed on the substrate in the form of a slurry, which is particularly effective in disposing the material on the substrate to maximize gas diffusion and minimize pressure drop during catalytic conversion.

[0042] Providing a complex of a compound of formula (I) and a PGM preferably comprises synthesizing the complex in situ in a slurry.

[0043] The slurry preferably comprises: contacting a PGM salt with a compound of formula (I) in water to form a complex of the compound of formula (I) and the PGM in aqueous solution, wherein the PGM salt comprises rhodium and / or platinum; applying the complex to the support material by contacting the support material with an aqueous solution to form a supported support material; Optionally, adding one or more of an oxygen storage material, preferably ceria-zirconia, a promoter salt, a binder, an acid or base, a thickener, and a reducing agent to the aqueous solution.

[0044] Such a "one-pot" preparation method may be simplified and less costly than conventional methods, and may also maximize utilization of the compound of formula (I).

[0045] In other words, the steps of providing a complex of a compound of formula (I) and a PGM, providing a support material, applying the complex to the support material to form a supported support material, and disposing the supported support material on a substrate comprise: contacting a PGM salt with a compound of formula (I) in water to form a complex of the compound of formula (I) and the PGM in aqueous solution, wherein the PGM salt comprises rhodium and / or platinum; adding the support material to an aqueous solution to form a slurry of the supported support material; Optionally, adding one or more of an oxygen storage material, preferably ceria-zirconia, a promoter salt, a binder, an acid or base, a thickener, and a reducing agent to the slurry; and disposing the slurry on a substrate.

[0046] The support may include a washcoating.

[0047] The slurry preferably has a solids content of 10-40%, preferably 15-35%. Such a solids content can enable a suitable slurry rheology for disposing the supported support material on a substrate. For example, if the substrate is a honeycomb monolith, such a solids content can enable deposition of a thin layer of washcoat on the inner wall of the substrate. If the substrate is a wall-flow filter, such a solids content can enable the slurry to enter the channels of the wall-flow filter and the walls of the wall-flow filter.

[0048] Preferably, the slurry comprises: an oxygen storage material, preferably ceria-zirconia; promoter salts, binder, Acids or bases, thickeners, and Further comprising one or more of the following reducing agents:

[0049] Other promoters may include, for example, non-PGM transition metal elements, rare earth elements, alkali group elements, and / or combinations of two or more of the foregoing elements in the same or different groups of the periodic table. The promoter salt may be a salt of such elements.

[0050] 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.

[0051] Thickeners may include, for example, natural polymers with functional hydroxyl groups that interact with insoluble particles in the washcoat slurry. The thickener serves the purpose of thickening the washcoat slurry to improve the coating profile during washcoat application onto a substrate. The thickener is typically burned off during washcoat calcination. Examples of specific thickeners / rheology modifiers for washcoats include glactomanna gum, guar gum, xanthan gum, curdlan schizophyllan, scleroglucan, diutan gum, wheelan gum, hydroxymethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and ethylhydroxycellulose.

[0052] The term "reducing agent" as used herein may include compounds capable of reducing PGM cations to their metallic state particles in situ during washcoat preparation.

[0053] Organic acids can be added to act as reducing agents for the PGMs and / or create a reducing environment during the subsequent heating / calcination step. Examples of suitable organic acids include citric acid, succinic acid, oxalic acid, ascorbic acid, acetic acid, formic acid, and combinations thereof.

[0054] In a preferred embodiment, the PGM comprises rhodium, the support material comprises alumina, and the slurry further comprises ceria-zirconia. In another preferred embodiment, the PGM comprises rhodium, the support material comprises ceria-zirconia, and the slurry further comprises alumina. In another preferred embodiment, the PGM comprises rhodium, and the support material comprises alumina and ceria-zirconia.

[0055] The method preferably further comprises disposing a further slurry on the substrate, the further slurry comprising one or more of a further support material, an oxygen storage material, a promoter salt, a binder, an acid or base, a thickener, and a reducing agent, prior to disposing the support material on the substrate and / or after heating the supported support material to form PGM nanoparticles on the support material. This can result in a catalyst article having multiple layers of different washcoats, e.g., a bottom washcoat containing, inter alia, rhodium nanoparticles supported on alumina, and a top washcoat containing, inter alia, rhodium nanoparticles supported on alumina. Further examples of such multiple layers are discussed in more detail below.

[0056] Placing the supported support material on the substrate preferably involves contacting a slurry with the substrate (e.g., injecting the slurry into an inlet of the substrate), and optionally: applying a vacuum to the substrate, and / or and drying the slurry on the substrate.

[0057] This allows for a favorable distribution of the supported support material on the substrate.

[0058] Drying is preferably carried out as follows. at a temperature between 60°C and 200°C, preferably between 70°C and 130°C, and / or The heating is carried out for 10 to 360 minutes, preferably 15 to 60 minutes.

[0059] The substrate may be a "blank," i.e., a substrate that has not been washcoated. Alternatively, the substrate may have one or more washcoats already deposited thereon. In such a situation, the final catalyst article may include multiple layers of different washcoats.

[0060] The substrate preferably comprises cordierite, which is particularly suitable for use in catalytic articles.

[0061] The substrate is preferably in the form of a honeycomb monolith, a wall-flow filter or a flow-through filter.

[0062] The heating is preferably carried out as follows. at a temperature of 400°C to 700°C, preferably 400°C to 600°C, more preferably 450°C to 600°C, and / or The heating is carried out for 10 to 360 minutes, preferably 35 to 120 minutes.

[0063] Lower temperatures and / or shorter heating times may result in insufficient decomposition of the complex and / or high levels of the compound of formula (I) may remain in the substrate. Higher temperatures and / or longer heating times may result in PGM particles with undesirably large particle sizes, possibly due to sintering. Higher temperatures and longer heating times may also result in damage to the catalyst article.

[0064] Heating preferably includes calcination. As used herein, the term "calcination" can include a heat treatment process in the absence or limited supply of air or oxygen to cause thermal decomposition.

[0065] The nanoparticles preferably have a D50 of 0.1 nm to 10 nm, more preferably 0.2 to 5 nm, and even more preferably 0.2 to 4 nm. D50 can be measured by TEM. Such particle size can provide a desirable level of catalytic activity.

[0066] In a further aspect, the present invention provides a catalyst article obtainable by the methods described herein, the catalyst article being for use in an emissions treatment system.

[0067] Compared to conventional catalyst articles, catalyst articles obtainable by the methods described herein can contain PGM particles having advantageously small particle sizes and favorable particle size distributions (e.g., D50 of 0.2 to 4 nm). Furthermore, compared to conventional catalyst articles, catalyst articles obtainable by the methods described herein can exhibit a more uniform distribution of PGM particles throughout the substrate.

[0068] When used in emissions treatment systems, the catalyst article can exhibit favorable light-off performance, particularly for NO, CO, and total hydrocarbons, during three-way catalytic conversion for stoichiometric gasoline emission reduction.

[0069] The catalyst is preferably for a three-way catalyst.

[0070] The catalyst article is 1 g / in 3 ~3g / in 3 Such catalyst articles may exhibit similar or higher catalytic activity compared to conventional catalyst articles, but may be less expensive given the lower levels of PGM used.

[0071] The substrate preferably comprises a wall-flow filter substrate or a flow-through substrate.

[0072] In a preferred embodiment, the catalyst article comprises a bottom layer of support material having rhodium thereon and a top layer of support material having palladium thereon. In another preferred embodiment, the catalyst article comprises a bottom layer of support material having palladium thereon and a top layer of support material having rhodium thereon. As used herein, the term "bottom layer" may include a layer (e.g., a washcoat layer) that is closest to or in contact with the substrate (i.e., the substrate wall). As used herein, the term "top layer" 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.

[0073] In such a preferred embodiment, the support material preferably comprises alumina and ceria-zirconia.

[0074] The catalyst article, inter alia, in such preferred embodiments, preferably has a surface roughness of 2 g / ft 3 ~15g / ft 3 of rhodium, more preferably 5 g / ft 3 ~10g / ft 3 Advantageously, such rhodium levels can be lower than those of conventional catalyst articles, without impairing catalytic activity.

[0075] The catalyst article, particularly in such preferred embodiments, preferably has a coating weight of 50 g / ft 3 ~200g / ft 3 of palladium, more preferably 80 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.

[0076] In a preferred embodiment, the supported support material is disposed on a substrate in the form of a slurry, wherein the PGM comprises rhodium, the support material comprises alumina, and the slurry further comprises ceria-zirconia. In another preferred embodiment, the supported support material is disposed on a substrate in the form of a slurry, wherein the PGM comprises rhodium, the support material comprises ceria-zirconia, and the slurry further comprises alumina. In another preferred embodiment, the supported support material is disposed on a substrate in the form of a slurry, wherein the PGM comprises rhodium, and the support material comprises alumina and ceria-zirconia.

[0077] In a further aspect, the present invention provides an emissions treatment system comprising the catalytic article described herein.

[0078] The emission treatment system is preferably for a gasoline engine.

[0079] Gasoline engines preferably operate under stoichiometric conditions.

[0080] In a further aspect, the present invention provides a method for treating exhaust gases, the method comprising: providing a catalyst article as described herein; and contacting the catalytic article with the exhaust gas.

[0081] The exhaust gas is preferably exhaust gas from a gasoline engine. The catalytic article is particularly suitable for treating such exhaust gas. The gasoline engine preferably operates under stoichiometric conditions. [Example]

[0082] The invention will now be described with reference to the following non-limiting examples.

[0083] A number of catalyst articles were prepared according to the following examples.

[0084] Comparative Example 1A: Pt-TWC (containing Pt nitrate) washcoat catalyst 1. Prepare a Pt nitrate slurry (Pt loading 11 g / ft 3 ). 2. Stabilized alumina support (0.5 g / in 3 ) Add the slurry and mix for 1 hour. 3. Ceria-zirconia support (0.8 g / in 3 ) and mix for 30 minutes. 4. Adjust the solids content to the target (e.g., about 23%). 5. Add the appropriate amount of thickener and mix overnight. 6. Coat the single dose target only 1.2 inches from the entrance. 7. Fire the bricks in a static oven at 500°C / 30 minutes.

[0085] Example 1B: Pt-TWC (with Pt modified by gallic acid) washcoat catalyst 1. Prepare a Pt nitrate slurry (Pt loading 11 g / ft 3 ). 2. Stabilized alumina support (0.5 g / in 3 ) Add the slurry and mix for 1 hour. 3. Ceria-zirconia support (0.8 g / in 3 ) and mix for 30 minutes. Add the required amount of gallic acid (GA) to target a 4.18:1 gallic acid:Pt mass ratio. 5. Adjust the solids content to the target (e.g., about 23%). 6. Add the appropriate amount of thickener and mix overnight. 7. Coat the single dose target only 1.2 inches from the entrance. 8. Fire the bricks in a static oven at 500°C / 30 minutes.

[0086] Perturbed ignition performance Aging conditions: Rich long-term redox aging 1A to 1C show a comparison of NO, THC, and CO light-off conversion rates between Comparative Example 1A and Example 1B after redox aging at 1000°C for 40 hours. After rich pretreatment, the catalysts were aged at light-off temperatures of 150 to 600°C, perturbations of 0.96 to 1.04 (at a frequency of 1 Hz), and GHSV of 200,000 hours. -1 Compared to the formulated Pt reference catalyst without gallic acid modification (Comparative Example 1A), Inventive Example 1B showed significantly improved TWC light-off performance. The maximum TWC values ​​for THC and CO for the Pt catalyst with GA modification were 50 The reductions were 21°C and 35°C, respectively. 20 The reduction was 73° C. and the NO conversion did not exceed 25% for the Pt reference catalyst.

[0087] Aging conditions: Lean long-term redox aging 2A to 2C show the comparison of NO, THC, and CO light-off conversion between Comparative Example 1A and Example 1B after redox aging at 1000°C for 40 hours. After lean pretreatment, the catalysts were aged at light-off temperatures of 150 to 600°C, perturbation frequency of 0.96 to 1.04 (frequency of 1 Hz), and GHSV of 200,000 hours. -1 Compared to the formulated Pt reference catalyst without gallic acid modification (Comparative Example 1A), Inventive Example 1B showed significantly improved TWC light-off performance. The maximum T values ​​for NO, THC, and CO for the Pt catalyst with GA modification were 50 The reductions were 30°C, 24°C, and 32°C, respectively.

[0088] Perturbation lambda sweep performance Figures 3A-3C show a comparison of NO, THC, and CO conversion between Comparative Example 1A and Example 1B under lambda sweep conditions between 0.98 and 1.04, respectively, after 40 hours of redox aging at 1000°C. Compared to the formulated Pt reference catalyst without gallic acid modification (Comparative Example 1A), Example 1B of the present invention showed significantly improved TWC performance, with the greatest improvement occurring at leaner conditions. The maximum reductions for CO, THC, and NO at lambda 1.04 were 15%, 10%, and 12%, respectively. The maximum reductions for CO, THC, and NO at lambda 1.01 were 13%, 20%, and 3%, respectively. The maximum reductions for CO, THC, and NO at lambda 0.98 were -3%, 0%, and 2%, respectively.

[0089] Comparative Example 2A: Pt-Rh TWC (Containing Pt Nitrate and Rh Nitrate) Washcoat Catalyst 1. Prepare a slurry of ceria-zirconia support (1 g / in 3 ). 2. The required amount of Rh nitrate (Rh loading is 2g / ft 3 ) and Pt nitrate (Pt loading 2g / ft 3 ) and add. 3. Adjust the pH of the washcoat to a target pH of approximately 6-7. 4. Stabilized alumina support (1 g / in3 ) Add the slurry and mix for 1 hour. 5. Adjust the solids content to the target (e.g., about 30%). 6. Add the appropriate amount of thickener and mix overnight. 7. Coat the single dose target only 1.2 inches from the entrance. 8. Fire the bricks in a static oven at 500°C / 30 minutes.

[0090] Example 2B: Pt-RhTWC (with Pt modified by gallic acid) washcoat catalyst 1. Prepare a slurry of ceria-zirconia support (1 g / in 3 ). 2. The required amount of Pt nitrate (Pt loading 2g / ft 3 ) is added to the slurry. Add the required amount of gallic acid (GA) to target a 3.15:1 gallic acid:Pt mass ratio. 4. The required amount of Rh nitrate (Rh loading 2g / ft 3 ) is added to the slurry. 5. Adjust the pH of the washcoat to a target pH of approximately 6-7. 6. Stabilized alumina support (1 g / in 3 ) Add the slurry and mix for 1 hour. 7. Adjust the solids content to the target (e.g., about 30%). 8. Add the appropriate amount of thickener and mix overnight. 9. Coat the single dose target only 1.2 inches from the entrance. 10. Fire the bricks in a static oven at 500°C / 30 minutes.

[0091] After aging, the catalyst articles of Example 2B and Comparative Example 2A were tested for perturbed light-off performance versus TWC conversion under simulated gasoline exhaust conditions. (Aging conditions: 1000°C / redox / 40 hours. Reaction conditions: rich pretreatment, 150-700°C, λ=0.96-1.04, GHSV=200,000 hours) -1The results for NO, CO, and THC conversion are shown in Figures 4A-4C. In each case, TWC activity was greater in Example 2B than in Comparative Example 2A. NO in Example 2B x , CO and THC maximum T 50 The reductions were 15°C, 22°C and 33°C, respectively.

[0092] The foregoing detailed description has been provided for purposes of illustration and example, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments set forth herein will be apparent to those skilled 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: Formula (I): 【Chemistry 1】 (Wherein R1 is H or C １ -C ６ alkyl, and R2 is H, OH, or O—C １ -C ４ providing a complex of a compound of formula (I) wherein the compound is an alkyl group, with a PGM comprising rhodium and / or platinum; Providing a carrier material; applying the complex to the support material to form a supported support material; placing the supported support material on a substrate; and heating the supported support material to form nanoparticles of the PGM on the support material.

2. The method of claim 1, wherein R2 is OH.

3. 3. The method of claim 1 or claim 2, wherein R1 is H.

4. The method of any one of claims 1 to 3, wherein the PGM comprises rhodium.

5. The method of any one of claims 1 to 4, wherein the PGM comprises platinum.

6. The method of any one of claims 1 to 5, wherein the PGM comprises rhodium and platinum.

7. The support material is an oxide, preferably 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.

8. The method of any one of claims 1 to 7, wherein the support material comprises alumina, preferably gamma-alumina.

9. The method of any one of claims 1 to 8, wherein the support material comprises ceria-zirconia.

10. The method of any one of claims 1 to 9, wherein the support material comprises alumina and ceria-zirconia.

11. A method according to any one of claims 8 to 10, wherein the alumina and / or ceria-zirconia is doped.

12. 12. The method of claim 11, wherein the alumina and / or ceria-zirconia is doped with one or more oxides of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, manganese, iron, copper, calcium, barium, strontium, cesium, magnesium, potassium, and sodium, preferably with one or more oxides of lanthanum, neodymium, and yttrium.

13. A method according to claim 11 or claim 12, wherein the dopant is present in the alumina and / or ceria-zirconia in an amount of from 0.001% to 20% by weight, preferably from 0.5% to 10% by weight.

14. A method according to any one of the preceding claims, wherein the support material is in the form of a powder having a D90 of 0.1 to 25 μm, preferably 0.5 to 5 μm.

15. The method of any one of claims 1 to 14, wherein the supported carrier material is disposed on the substrate in the form of a slurry.

16. 16. The method of claim 15, wherein providing the complex of the compound of formula (I) and the PGM comprises synthesizing the complex in situ in the slurry.

17. the slurry comprises contacting a PGM salt with a compound of formula (I) in water to form the complex of the compound of formula (I) and PGM in aqueous solution, wherein the PGM salt comprises rhodium and / or platinum; applying the complex to the support material by contacting the support material with the aqueous solution to form a supported support material; and optionally adding one or more of an oxygen storage material, preferably ceria-zirconia, a promoter salt, a binder, an acid or a base, a thickener, and a reducing agent to the aqueous solution.

18. The method of any one of claims 1 to 17, wherein the supporting comprises a washcoating.

19. A method according to any one of claims 15 to 18, wherein the slurry has a solids content of 10 to 40%, preferably 15 to 35%.

20. The slurry an oxygen storage material, preferably ceria-zirconia; promoter salts, binder, Acids or bases, thickeners, and 20. The method of any one of claims 15 to 19, further comprising one or more of the following reducing agents:

21. The method of any one of claims 15 to 20, wherein the PGM comprises rhodium, the support material comprises alumina, and the slurry further comprises ceria-zirconia.

22. The method of any one of claims 15 to 20, wherein the PGM comprises rhodium, the support material comprises ceria-zirconia, and the slurry further comprises alumina.

23. The method of any one of claims 15 to 20, wherein the PGM comprises rhodium and the support material comprises alumina and ceria-zirconia.

24. 24. The method of any one of claims 15 to 23, further comprising disposing a further slurry on the substrate, the further slurry comprising one or more of a further support material, an oxygen storage material, a promoter salt, a binder, an acid or base, a thickener, and a reducing agent, and wherein disposing the further slurry on the substrate occurs before disposing the support material on the substrate and / or after heating the supported support material to form nanoparticles of the PGM on the support material.

25. Disposing the supported support material on a substrate comprises contacting the slurry with the substrate, and optionally applying a vacuum to the substrate; and / or The method of any one of claims 15 to 24, comprising drying the slurry on the substrate.

26. The drying at a temperature of 60°C to 200°C, preferably 70°C to 130°C, and / or 26. The method of claim 25, carried out for 10 to 360 minutes, preferably 15 to 60 minutes.

27. The method of any one of claims 1 to 26, wherein the substrate comprises cordierite.

28. The method of any one of claims 1 to 27, wherein the substrate is in the form of a honeycomb monolith, a wall-flow filter, or a flow-through filter.

29. The heating at a temperature of 400°C to 700°C, preferably 400°C to 600°C, more preferably 450°C to 600°C, and / or 29. The method according to any one of claims 1 to 28, carried out for 10 to 360 minutes, preferably 35 to 120 minutes.

30. The method of any one of claims 1 to 29, wherein the heating comprises calcining.

31. 31. The method of any one of claims 1 to 30, wherein the nanoparticles have a D50 of 0.1 nm to 10 nm, preferably 0.2 to 5 nm, more preferably 0.2 to 4 nm.

32. A catalytic article obtainable by the method of any one of claims 1 to 31, for use in an emission treatment system.

33. 33. The catalytic article of claim 32 for three-way catalysis.

34. 1 g / in ３ ~3g / in ３ 34. The catalyst article of claim 32 or claim 33, having a washcoat loading of

35. The catalytic article of any one of claims 32 to 34, wherein the substrate comprises a wall-flow filter substrate.

36. The catalytic article of any one of claims 32 to 34, wherein the substrate comprises a flow-through substrate.

37. 37. The catalyst article of any one of claims 32 to 36, comprising a bottom layer of support material having rhodium thereon and a top layer of support material having palladium thereon.

38. 37. The catalyst article of any one of claims 32 to 36, comprising a bottom layer of support material having palladium thereon and a top layer of support material having rhodium thereon.

39. 39. The catalytic article of claim 37 or claim 38, wherein the support material comprises alumina and ceria-zirconia.

40. 2 g / ft ３ ~15g / ft ３ of rhodium, preferably 5 g / ft ３ ~10g / ft ３ 40. The catalytic article of any one of claims 32 to 39, comprising:

41. 50g / ft ３ ~200g / ft ３ of palladium, preferably 80 g / ft ３ ~150g / ft ３ 41. The catalytic article of any one of claims 37 to 40, comprising palladium of

42. 42. The catalyst article of any one of claims 32-41, wherein the supported support material is disposed on the substrate in the form of a slurry, the PGM comprising rhodium, the support material comprising alumina, and the slurry further comprising ceria-zirconia.

43. 42. The catalyst article of any one of claims 32-41, wherein the supported support material is disposed on the substrate in the form of a slurry, the PGM comprising rhodium, the support material comprising ceria-zirconia, and the slurry further comprising alumina.

44. 42. The catalyst article of any one of claims 32-41, wherein the supported support material is disposed on the substrate in the form of a slurry, the PGM comprises rhodium, and the support material comprises alumina and ceria-zirconia.

45. An emissions treatment system comprising the catalytic article of any one of claims 32 to 44.

46. 46. ​​The emission treatment system of claim 45 for a gasoline engine.

47. 47. The emission treatment system of claim 46, wherein the gasoline engine operates under stoichiometric conditions.

48. 1. A method for treating an exhaust gas, said method comprising: Providing a catalyst article according to any one of claims 32 to 44; contacting the catalytic article with an exhaust gas.

49. 49. The method of claim 48, wherein the exhaust gas is from a gasoline engine.

50. 50. The method of claim 49, wherein the gasoline engine is operated under stoichiometric conditions.

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