Palladium immobilization using gallic acid or derivatives thereof

Abstract

A method of making a catalyst article, the method comprising: providing a complex of a compound # imgabs0 # of formula (I) with PGM, R1 being H or C1-C6 alkyl, R2 being H, OH or O-C1-C4 alkyl, the PGM comprising palladium; providing a carrier material; applying the complex to the support material to form a supported support material; disposing the loaded carrier material on a substrate; and heating the loaded 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 catalyst product, a catalyst product obtainable by the method, an emission treatment system and a method for treating exhaust gases. Background Art

[0002] Three-way catalyst (TWC) removes CO, HC and NO from gasoline engine exhaust. x The oxidation of CO and HC to CO2 and steam (H2O) is mainly catalyzed by Pd, while NO x The reduction to N2 is mainly catalyzed by Rh. Modern TWC uses supported platinum group metal (hereinafter referred to as "PGM") catalysts (Pd, Rh, Pt, etc.) deposited on a single-layer, double-layer or multi-layer support, wherein the support material consists of a metal oxide with a high specific surface area, mainly stable γ-alumina and an oxygen storage material containing ceria. The supported catalyst support coating is applied on a ceramic single substrate.

[0003] Conventional preparation of TWC carrier coating slurries generally involves the use of solutions of inorganic PGM precursors (e.g., nitrates, acetates, hydroxides, or chloride salts) to deposit PGM elements on oxide supports via an initial impregnation process or a wet impregnation process. Promoter salts are also generally added to the carrier coating formulation to obtain enhanced TWC performance. Once a single substrate is coated with the slurry carrier coating so prepared, a drying and calcining step is then used to decompose the inorganic salts and to fix the PGM and promoter elements to the support material. The performance of known supported metal catalysts depends on the structure and composition of the metal nanoparticles and the properties of the support. Conventional TWCs prepared using the above methods generally provide only limited control over the structure of the catalytically active material (i.e., average PGM particle size and composition, location of active components, and metal-support interactions). This is primarily due to metal migration and grain growth during the high temperature calcination process.

[0004] With increasingly stringent environmental regulations, TWCs with higher emission reduction efficiency are needed. On the other hand, with the increase in PGM costs, there is an urgent need to reduce PGM loading without compromising TWC performance. Better control of PGM particle size and metal-support interactions is essential for optimizing TWC performance. In addition, a uniform PGM particle size distribution can help reduce the extent of metal sintering caused by Ostwald ripening, which often occurs during fuel cut-off processes (engine strategies for enhancing fuel economy).

[0005] US2012 / 0077669 A1 describes a polymer-assisted synthesis of a supported metal catalyst for automotive applications. The polymers used in the examples include poly(vinylpyrrolidone), poly(acrylic acid), and poly(ethyleneimine). In the synthesis process, the support (aluminum oxide powder) is first impregnated with an aqueous solution containing the polymer. Then, through filtration and drying steps, the impregnated support is separated from the above solution. Through incipient wetness impregnation, the dried impregnated support is further impregnated with a PGM precursor solution. The method includes multiple steps for forming the claimed supported metal catalyst, which increases the cost and difficulty of production on a commercial scale. US2012 / 0077669 A1 states that for the application of this technology, lean-burn engines such as diesel engines or lean-burn gasoline engines are preferably used. SUMMARY OF THE INVENTION

[0006] One aspect of the present disclosure relates to a method for manufacturing a catalyst article, the method comprising: providing a compound of formula (I) a complex with PGM, where R1 is H or C1-C6 alkyl, R2 is H, OH, or O-C1-C4 alkyl, and the PGM comprises palladium; 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.

[0007] Another aspect of the present disclosure relates to a catalyst article obtainable by the method in the first aspect.

[0008] The present invention also encompasses an exhaust system for an internal combustion engine, the exhaust system comprising the catalyst article in the second aspect.

[0009] Another aspect of the present disclosure relates to a method for treating exhaust gas, the method comprising: providing the catalyst article in the second aspect; and contacting the catalyst article with the exhaust gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 Shows Pd uptake on alumina at various pHs for Comparative Example 1A and Comparative Example 1B and Example 1C.

[0011] Figure 2 Shows Pd uptake on CZO at various pHs for Comparative Example 2A and Comparative Example 2B and Example 2C.

[0012] Figure 3A Shows SEM imaging mapping of Pd for Comparative Example 3A; Figure 3B Shows the SEM mapping image of Pd for Example 3B; Figure 3C Shows the SEM mapping image of Pd for Example 3C; andFigure 3D Shows the SEM mapping image of Pd of Example 3C.

[0013] Figure 4 Shows the quantitative elemental correlation of Pd-Al and Pd-Zr of Comparative Example 3A and Examples 3B to 3D by EPMA.

[0014] Figure 5A Shows the comparison of NO x conversion rate between aged Comparative Example 4A and Examples 4B to 4D samples during the TWC light-off test; Figure 5B Shows the comparison of CO conversion rate between aged Comparative Example 4A and Examples 4B to 4D samples during the TWC light-off test; and Figure 5C Shows the comparison of THC conversion rate between aged Comparative Example 4A and Examples 4B to 4D samples during the TWC light-off test.

[0015] Figure 6A Shows the NO x cumulative emissions between aged Comparative Example 5A and Example 5B during the engine bench test; Figure 6B Shows the CO cumulative emissions between aged Comparative Example 5A and Example 5B during the engine bench test; and Figure 6C Shows the THC cumulative emissions between aged Comparative Example 5A and Example 5B during the engine bench test. Detailed Description

[0016] The present invention attempts to solve at least some problems associated with the prior art or at least provide a commercially acceptable alternative solution thereto.

[0017] In a first aspect, the present invention provides a method for manufacturing a catalyst article, the method comprising:

[0018] providing a compound of formula (I) a complex with PGM, wherein R1 is H or C1-C6 alkyl, R2 is H, OH or O-C1-C4 alkyl, and the PGM comprises palladium;

[0019] providing a carrier material;

[0020] applying the complex to the carrier material to form a loaded carrier material;

[0021] disposing the loaded carrier material on a substrate; and

[0022] heating the loaded carrier material to form nanoparticles of the PGM on the carrier material.

[0023] Unless expressly indicated to the contrary, each aspect or embodiment as defined herein may be combined with any other aspect or embodiment. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0024] Surprisingly, when used in an emissions treatment system, the catalyst article made by the method of the present invention can exhibit favorable catalytic activity, particularly favorable three-way catalytic activity. For example, the catalyst article can exhibit favorable light-off performance during three-way catalytic reduction in a stoichiometric gasoline engine, particularly the conversion rates of NO, CO, and total hydrocarbons. Such favorable catalytic activity and light-off performance can be superior to those exhibited by conventional catalyst articles having the same / similar PGM species, loading, carrier, and configuration. The catalyst article can be more durable compared to conventional catalyst articles. In other words, such favorable catalytic activity can still be exhibited even after aging.

[0025] Advantageously, compared to conventional catalyst articles, such excellent performance can facilitate the use of a lower loading of PGM without compromising catalytic performance. This can be beneficial given the high cost of such metals (such as palladium). In addition, such excellent performance can facilitate the partial or complete replacement of high-cost PGM with lower-cost PGM or other transition metals without compromising catalytic performance.

[0026] Furthermore, due to the improved fixation of Pd to the support material achievable by the method of the present invention, significantly less Pd or the support coating layer is observed to wick through the substrate and / or mix with the support coating layer. In other words, compared to catalyst articles made by conventional methods, the catalyst article made by the method of the present invention can exhibit stronger / more reliable fixation of PGM to the support material. In addition to the aesthetic improvement in such catalyst articles, the catalyst article made by the method of the present invention can thus also exhibit improved catalytic activity. This is at least because the mixing of catalytically active PGM between any different support coating layers in the catalyst article can be reduced, and this reduction can thereby lower the likelihood of deactivation of any support coating layer in the support coating layer. This in turn can help maintain the catalytic activity of the entire catalyst article as high as expected when the catalyst article is fresh and after aging. Keeping the PGM of any different support coating layers within their intended respective layers can be important for maintaining their intended catalytic purposes (such as for oxidation or reduction). For example, it is known that the direct interaction between Pd and Rh can reduce the catalytic activity of the individual components, particularly the catalytic function of the Rh component.

[0027] In addition, depending on the order of steps and the order of addition of the support materials, the method of the present invention can be used to immobilize PGM (e.g., Pd) onto any standard support material. In other words, if there are multiple different support materials in the support coating, the method of the present invention can be used to target PGM (e.g., Pd) to the desired support material by controlling the order of steps (such as whether the support material is combined with the PGM precursor first or with the complex of polyphenol and PGM first).

[0028] Compared with the method of US2012 / 0077669 A1, the method of the present invention is a simpler and more efficient "one-pot" method, for example, no pH adjustment is required. The method of the present invention does not require separate impregnation, filtration, and drying steps for depositing polymer molecules onto the support material. In contrast, in US 2012 / 0077669A1, only a limited amount of polymer can remain on the support after the filtration and washing steps. In addition, the catalyst article prepared by the method of the present invention can be specifically used as a three-way catalyst for stoichiometric gasoline emission reduction. In contrast, the catalyst article prepared by the method of US2012 / 0077669 A1 has specific applications in lean-burn diesel or gasoline engines.

[0029] The term "catalyst article" as used herein can cover an article on or in which a catalyst is loaded. The article can take the form of, for example, a honeycomb monolith or a filter, such as a wall-flow filter or a flow-through filter. The catalyst article can be used in an emissions treatment system, particularly for gasoline engines, preferably for the emissions treatment system of a stoichiometric gasoline engine. The catalyst article can be used in three-way catalysis.

[0030] Provide a compound of formula (I) The complex with PGM generally involves providing the complex in solution form, such as an aqueous solution or an alcohol solution. Providing the complex of the compound of formula (I) with PGM generally involves mixing an inorganic PGM precursor and the compound of formula (I) in pure or solution form in an aqueous medium, such as mixing PGM nitrate and the compound of formula (I) in water.

[0031] Preferably, R1 is H. Preferably, R2 is OH.

[0032] The PGM contains palladium. Palladium can be particularly suitable for performing three-way catalysis. In addition, palladium is expensive, meaning that it would be advantageous to be able to provide a similar level of catalytic activity for the same amount of metal. In addition, using palladium in the method of the present invention can result in particularly favorable perturbation light-off performance. The PGM can be in the form of an alloy. In addition to palladium, the PGM can also contain other PGMs, such as one or more of rhodium, platinum, ruthenium, osmium, and iridium.

[0033] The ratio of the PGM atoms to the ester groups of the complex can be from 2:1 to 1:10, preferably from 1:1 to 1:8, more preferably from 1:2 to 1:5. The ratio of the palladium atoms to the ester groups of the complex can be from 2:1 to 1:10, preferably from 1:1 to 1:8, more preferably from 1:2 to 1:5.

[0034] The support material can be any material capable of loading the complex and the nanoparticles thereon or therein. The support material can take any form, but is typically in the form of a powder, more typically a high surface area powder. The powder can be further ground by dry or wet grinding to obtain a desired particle size range. When preparing a catalytic filter (such as a wall-flow filter or a flow-through filter) using the method of the present invention, the support material will typically be in the form of a powder in its original, dry-ground or wet-ground form, and the D50, as measured using TEM, is, for example, from 0.1 μm to 30 μm, more typically from 0.5 μm to 25 μm, even more typically from 1 μm to 20 μm. Such particle sizes can be beneficial for the desired rheology of the slurry used to coat the filter. The support material can be used as a support coating. The support material can be a support coating or can be part of a support coating.

[0035] The support material can also be used as an oxygen storage material that stores and releases oxygen under lean fuel and rich fuel conditions, respectively, to promote three-way catalytic conversion.

[0036] Applying the complex to the support material generally involves contacting the complex with the support material in the presence of a solvent (usually water) to produce a slurry. As used herein, the term "slurry" can encompass a liquid containing insoluble materials (such as insoluble particles). The slurry can contain (1) a solvent; (2) soluble contents, such as unreacted compounds of formula (I), inorganic PGMs and promoter precursors, and complexes of PGM-compounds of formula (I) (outside the support); and (3) insoluble contents, such as support particles with and without interaction with the compounds of formula (I) and metal precursors. The slurry is typically stirred, more typically stirred for at least 10 minutes, more typically stirred for at least 30 minutes, even more typically stirred for at least one hour. Increasing the contact and / or stirring time can increase the amount of the complex loaded onto the support material.

[0037] As used herein, the term "support material for the load" can encompass a support material having a complex of a compound of formula (I) of PGM 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, for example, by electrostatic forces, hydrogen bonds, coordination bonds, covalent bonds, and / or ionic bonds. For example, in the case of an oxide, the ester functional group (e.g., a carboxylate functional group) in the compound of formula (I) can interact with the surface hydroxyl groups on the support through electrostatic forces or hydrogen bond formation.

[0038] As used herein, the term "substrate" can encompass, for example, a ceramic or metal honeycomb or a filter block (e.g., a wall-flow filter or a flow-through filter). The substrate can include a ceramic monolith. The substrate can vary in its material composition, dimensions and configuration, pore shape and density, and wall thickness. Suitable substrates are known in the art.

[0039] The support material for the load can be disposed on the substrate using techniques known in the art. Generally, the support material for the load is disposed on the substrate by pouring a slurry of the support material for the load into the inlet of the substrate in a predetermined amount using a specific molding tool. As discussed in more detail below, subsequent vacuum and drying steps can be employed during this disposition step. When the support is a filter block, the support material for the load can be disposed on the filter walls, within the filter walls (if porous), or both.

[0040] Heating the support material for the load is typically carried out in an oven or furnace, more typically in a belt or static oven or furnace, usually in a specific flow of hot air from one direction. The heating can include calcination. The heating can also include drying. The drying step and the calcination step can be continuous or sequential. For example, a separate support coating can be applied after the substrate has been coated with a previous support coating and dried. If the coating is complete, a single continuous heating program can also be used to dry and calcine the substrate coated with the support coating. During heating, the complex can be at least partially, substantially, or completely decomposed. In other words, the ligands of the complex (i.e., the compounds of formula (I)) are at least partially, substantially, or completely removed or separated from the PGM and removed from the final catalyst article. Then, particles of such separated PGM can begin to form metal-metal bonds and metal-oxide bonds. As a result of heating (calcination), the substrate is typically substantially free of the compound of formula (I), more typically completely free of the compound of formula (I).

[0041] As used herein, the term "nanoparticle" can encompass particles having a diameter of 0.01 nm to 100 nm as measured by TEM. The nanoparticles can be of any shape, such as spherical, plate-shaped, cubic-shaped, cylindrical, hexagonal, or rod-shaped, but are typically spherical. The maximum size of the nanoparticles (i.e., the diameter if the nanoparticles are spherical) will typically be 0.5 nm to 10 nm, more typically 1 nm to 5 nm, as measured by TEM.

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

[0043] In some preferred embodiments, the compound of formula (I) is gallic acid:

[0044]

[0045] Gallic acid can coordinate with metal ions through hydrogen bonds or covalent bonds. The PGM-gallic acid complex can be immobilized on a support (such as a metal oxide support) in a carrier coating, where the carboxylic acid functional group in the gallic acid ligand and the surface hydroxyl groups on the support can form interactions through electrostatic forces or hydrogen bonds.

[0046] The PGM contains palladium. Preferably, the PGM consists essentially of palladium, more preferably of palladium. Palladium is a particularly expensive PGM and forms a particularly suitable complex with the compound of formula (I), especially gallic acid. The use of such a metal in the method of the present invention can result in particularly advantageous perturbation ignition performance. The PGM can mainly contain palladium, i.e., at least 50 wt% palladium, typically at least 80 wt% palladium, more typically at least 95 wt% palladium, and even more typically at least 99 wt% palladium based on the total weight of the PGM.

[0047] After heating the loaded support material, the substrate preferably contains 10 g / ft 3 to 200 g / ft 3 of PGM, more preferably 30 g / ft 3 to 150 g / ft 3 of PGM, and even more preferably 80 g / ft 3 to 150 g / ft 3 of PGM. In other words, the concentration of the PGM applied to the substrate via the loaded support material can be such that after heating the loaded support material, the substrate contains 10 g / ft 3 to 200 g / ft 3 of PGM, more preferably 30 g / ft 3 to 150 g / ft 3of PGM, and even more preferably 80 g / ft 3 to 150 g / ft 3 of PGM. By, for example, using a higher or lower concentration of the complex of the compound of formula (I) with PGM and / or a higher or lower ratio of PGM atoms to ester groups, those skilled in the art will readily achieve obtaining such PGM loadings on the substrate. In other words, it is entirely within the capabilities of those skilled in the art to provide a substrate having a desired level of PGM loading via the method of the present invention. For example, in the step of applying the complex to the carrier material to form the loaded carrier material, 10 g / ft 3 to 200 g / ft 3 of PGM, more preferably 30 g / ft 3 to 150 g / ft 3 of PGM, and even more preferably 80 g / ft 3 to 150 g / ft 3 of PGM can be applied to the carrier material.

[0048] The carrier material preferably comprises an oxide, preferably one or more of Al2O3 (aluminum oxide or alumina), SiO2, TiO2, CeO2, ZrO2, CeO2-ZrO2, V2O5, La2O3, and zeolite. The oxide is preferably a metal oxide. The carrier material more preferably comprises alumina, even more preferably γ-alumina. The carrier material preferably comprises cerium dioxide-zirconium dioxide. The carrier material preferably comprises alumina and cerium dioxide-zirconium dioxide. Alumina and / or cerium dioxide-zirconium dioxide are preferably doped, more preferably doped with oxides of one or more of the following: 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 effective as carrier materials. Preferably, the dopant is present in alumina and / or cerium dioxide-zirconium dioxide in an amount of 0.001 wt% to 20 wt%, still more preferably 0.5 wt% to 10 wt%.

[0049] The carrier material is preferably in the form of a powder having a D90 of 0.1 μm to 25 μm, more preferably 0.5 μm to 5 μm.

[0050] The loaded carrier material is preferably provided on the substrate in the form of a slurry. The slurry is particularly effective when setting the material on the substrate, especially for maximizing gas diffusion and minimizing pressure drop during catalytic conversion.

[0051] Providing the complex of the compound of formula (I) with PGM preferably comprises in-situ synthesizing the complex in the slurry.

[0052] The slurry is preferably prepared by a method comprising the following steps:

[0053] Contacting a PGM salt with a compound of formula (I) in water to form a complex of the compound of formula (I) and PGM in an aqueous solution, the PGM salt comprising palladium; and

[0054] Applying the complex to the carrier material by contacting the carrier material with the aqueous solution to form a loaded carrier material;

[0055] Optionally adding one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or base; a thickener; and a reducing agent to the aqueous solution. The optional step of adding one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or base; a thickener; and a reducing agent to the aqueous solution can be carried out during any of the steps of the preferred method of preparing the slurry.

[0056] In an alternative preferred embodiment, the slurry can be prepared by a method comprising the following steps:

[0057] Contacting a carrier material with an aqueous solution of a PGM salt to form a slurry comprising a carrier material loaded with the PGM salt, the PGM salt comprising palladium;

[0058] Applying a complex of the compound of formula (I) and PGM to the carrier material by contacting the slurry comprising the carrier material loaded with the PGM salt with the compound of formula (I) in water to form a loaded carrier material;

[0059] Optionally adding one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or base; a thickener; and a reducing agent to the aqueous solution or to the slurry comprising the carrier material loaded with the PGM salt. The optional step of adding one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or base; a thickener; and a reducing agent to the aqueous solution can be carried out during any of the steps of the preferred method of preparing the slurry, but is preferably carried out during the step of supplying the carrier material in each case.

[0060] Preferably, in each alternative method of preparing the slurry, the steps of contacting the PGM salt with the compound of formula (I) in water and contacting the slurry comprising the support material loaded with the PGM salt with the compound of formula (I) in water include allowing sufficient reaction time for complexation to occur between the compound of formula (I) and the PGM cation, for example such steps are typically carried out for at least 10 minutes, more typically for at least 30 minutes, even more typically for at least 1 hour, preferably with stirring. Without wishing to be bound by theory, it is believed that after the step of applying the complex of the compound of formula (I) with PGM to the support material to form the loaded support material by contacting the slurry comprising the support material loaded with the PGM salt with the compound of formula (I) in water in the second alternative method of preparing the slurry, subsequent reduction and precipitation of the PGM metal species on the support material may occur.

[0061] In other words, the method of preparing the slurry may include first providing a complex of the compound of formula (I) with PGM in an aqueous solution, followed by adding the support and other optional components, or alternatively may include first adding the support material and other optional components to an aqueous solution of the PGM precursor (i.e., the PGM salt), followed by adding the compound of formula (I).

[0062] Compared with conventional methods, such “one-pot” preparation methods can be simplified and less costly. It can also maximize the utilization rate of the compound of formula (I).

[0063] In other words, the steps of providing a complex of the compound of formula (I) with PGM; providing a support material; applying the complex to the support material to form a loaded support material; and disposing the loaded support material on a substrate may include:

[0064] Contacting a PGM salt with the compound of formula (I) in water to form a complex of the compound of formula (I) with PGM in an aqueous solution, the PGM salt comprising palladium;

[0065] Adding the support material to the aqueous solution to form a slurry of the loaded support material;

[0066] Optionally adding one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or base; a thickener; and a reducing agent to the slurry; and

[0067] Drying the slurry on the substrate.

[0068] Alternatively, the steps of providing a complex of the compound of formula (I) with PGM; providing a support material; applying the complex to the support material to form a loaded support material; and disposing the loaded support material on a substrate may include:

[0069] Contact a carrier material with an aqueous solution of a PGM salt to form a slurry comprising the carrier material loaded with the PGM salt, the PGM salt comprising palladium;

[0070] Add a compound of formula (I) to the slurry comprising the carrier material loaded with the PGM salt to form a slurry of the loaded carrier material;

[0071] Optionally add one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or a base; a thickening agent; and a reducing agent to the aqueous solution or to the slurry of the carrier material loaded with the PGM salt; and

[0072] Dry the slurry on the substrate.

[0073] Loading may include carrier coating.

[0074] The solids content of the slurry is preferably from 10% to 40%, preferably from 15% to 35%. Such a solids content can render the rheology of the slurry suitable for setting the loaded carrier material onto the substrate. For example, if the substrate is a honeycomb monolith, such a solids content can enable a thin layer of the carrier coating to be deposited on the inner walls 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 can enable the slurry to enter the walls of the wall-flow filter.

[0075] Preferably, the slurry further comprises one or more of the following substances:

[0076] An oxygen storage material, preferably cerium-zirconium oxide;

[0077] A promoter salt;

[0078] A binder;

[0079] An acid or a base;

[0080] A thickening agent; and

[0081] A reducing agent.

[0082] The promoter may include, for example, non-PGM transition metal elements, rare earth elements, alkali or alkaline earth group elements and / or a combination of two or more of the above elements within the same or different groups of the periodic table. The promoter salt can be a salt of such elements. A particularly preferred promoter is barium, and particularly preferred salts thereof are barium acetate, barium citrate and barium sulfate or a combination thereof, more preferably barium citrate.

[0083] The binder may comprise, for example, an oxide material having a small particle size to bind together the individual insoluble particles in the carrier coating slurry. The use of a binder in the carrier coating is well known in the art.

[0084] The thickener may include, for example, natural polymers having functional hydroxyl groups that interact with the insoluble particles in the carrier coating slurry. It is used for the purpose of thickening the carrier coating slurry to improve the coating profile during the application of the carrier coating to the substrate. It is typically burned off during the calcination of the carrier coating. Examples of specific thickeners / rheology modifiers for the carrier coating include guar gum, guar gum, xanthan gum, gellan gum, schizophyllan, scleroglucan, diutan gum, welan gum, hydroxyethyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose, methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, and ethyl hydroxyethyl cellulose.

[0085] The term "reducing agent" as described herein may encompass compounds that can in-situ reduce PGM cations to their reduced state or even metallic state during the preparation of the carrier coating.

[0086] Organic acids can be added, which act as reducing agents for PGM and / or create a reducing environment at ambient temperature or elevated temperature (<100 °C) over a period of time during the preparation of the carrier coating. Examples of suitable organic acids may include citric acid, succinic acid, oxalic acid, ascorbic acid, acetic acid, formic acid, tannic acid, and combinations thereof.

[0087] In a preferred embodiment, the carrier material comprises alumina and the slurry further comprises cerium-zirconium oxide. In another preferred embodiment, the carrier material comprises cerium-zirconium oxide and the slurry further comprises alumina. In another preferred embodiment, the carrier material comprises alumina and cerium-zirconium oxide.

[0088] The method preferably further comprises disposing an additional slurry on the substrate, the additional slurry comprising one or more of the following: additional carrier material; oxygen storage material; promoter salt; binder; acid or base; thickener; and reducing agent, wherein disposing the additional slurry on the substrate is carried out before disposing the carrier material on the substrate and / or after heating the loaded carrier material to form the PGM nanoparticles on the carrier material. This can result in a catalyst article having multiple layers of different carrier coatings, such as a bottom carrier coating containing, in particular, palladium nanoparticles supported on alumina and a top carrier coating containing, in particular, palladium nanoparticles supported on alumina. Additional embodiments of such multi-layers are discussed in more detail below.

[0089] Disposing the loaded carrier material on the substrate preferably includes contacting the slurry with the substrate (e.g., pouring the slurry into the inlet of the substrate) and optionally:

[0090] Applying a vacuum to the substrate, and / or

[0091] Drying the slurry on the substrate.

[0092] This can result in a favorable distribution of the carrier material of the load on the substrate.

[0093] Drying is preferably carried out under the following conditions:

[0094] at a temperature of from 60 °C to 200 °C, more preferably from 70 °C to 130 °C; and / or

[0095] for from 10 minutes to 360 minutes, preferably from 15 minutes to 60 minutes.

[0096] The substrate can be "blank", i.e., a substrate not coated with a carrier coating. Alternatively, the substrate can have one or more carrier coatings already loaded thereon. In this case, the final catalyst article can comprise multiple layers of different carrier coatings.

[0097] The substrate preferably comprises cordierite. A cordierite substrate is particularly suitable for catalyst articles.

[0098] The substrate is preferably in the form of a honeycomb monolith, a wall-flow filter or a flow-through filter.

[0099] Heating is preferably carried out under the following conditions:

[0100] at a temperature of from 400 °C to 700 °C, preferably from 400 °C to 600 °C, more preferably from 450 °C to 600 °C; and / or

[0101] for from 10 minutes to 360 minutes, preferably from 35 minutes to 120 minutes.

[0102] Lower temperatures and / or shorter heating times can result in insufficient decomposition of the complex and / or can result in high levels of the compound of formula (I) remaining in the substrate. Higher temperatures and / or longer heating times can result in the PGM particles having an unfavorable large particle size, presumably due to sintering. Higher temperatures and longer heating times can also result in damage to the catalyst article.

[0103] Heating preferably includes calcination. As used herein, the term "calcination" can encompass a heat treatment process in the absence or limited supply of air or oxygen to effect thermal decomposition.

[0104] The D50 of the nanoparticles is preferably from 0.1 nm to 30 nm, more preferably from 0.5 nm to 25 nm, even more preferably from 1 nm to 20 nm. The D50 can be measured by TEM. Such particle sizes can result in a favorable level of catalytic activity.

[0105] In another aspect, the present invention provides a catalyst article obtainable by the method described herein, the catalyst article for use in an emissions treatment system.

[0106] Compared with conventional catalyst articles, the catalyst articles obtainable by the methods described herein can contain PGM particles having, in their fresh state, a favorably larger particle size and a favorable particle size distribution (e.g., D50 from 1 nm to 20 nm). In addition, compared with conventional catalyst articles, the catalyst articles obtainable by the methods described herein can exhibit a more uniform dispersion of PGM particles throughout the substrate.

[0107] When used in an emission treatment system, 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. The catalyst article can also exhibit other favorable properties described herein, such as a lower fresh OSC capacity and a lower fresh-to-aged OSC difference (in other words, more stable OSC performance to aging).

[0108] The catalyst is preferably used for three-way catalysis.

[0109] The catalyst article can have a washcoat loading of 1 g / in 3 to 3 g / in 3 Compared with conventional catalyst articles, such catalyst articles can exhibit similar or higher catalytic activity but lower cost in view of the lower level of PGM employed.

[0110] The substrate preferably comprises a wall-flow filter substrate or a flow-through substrate.

[0111] In a preferred embodiment, the catalyst article includes a bottom layer of a carrier material having rhodium thereon and a top layer of a carrier material having palladium thereon. In such a catalyst article, for example, the bottom layer can be provided by a method similar to those described herein or by any conventional method. In another preferred embodiment, the catalyst article includes a bottom layer of a carrier material having palladium thereon and a top layer of a carrier material having rhodium thereon. In such a catalyst article, for example, the top layer can be provided by a method similar to those described herein or by any conventional method. As used herein, the term "bottom layer" can encompass the layer (e.g., a carrier coating layer) closest to or in contact with the substrate (i.e., the substrate wall). As used herein, the term "top layer" can encompass the layer that is further from the substrate (i.e., the substrate wall) than the bottom layer and can be located on top of the bottom layer (e.g., a carrier coating layer). In such a layered catalyst article, the top layer of the carrier material and / or the bottom layer of the carrier material can have additional PGM thereon, such as platinum. In such a layered catalyst article, the top layer and / or the bottom layer can contain multiple PGMs, i.e., can be bimetallic (e.g., containing Pd-Rh or Pd-Pt) or trimetallic (e.g., Pd-Rh-Pt). The catalyst article can include two or more catalyst zones, such as an upstream zone and a downstream zone. These zones can differ from each other by having different PGMs (e.g., Rh upstream and Pd downstream, or vice versa), or by the amount of different types of PGMs (e.g., monometallic, bimetallic, or trimetallic).

[0112] In such preferred embodiments, the carrier material preferably comprises alumina and ceria-zirconia.

[0113] The catalyst article, particularly in such preferred embodiments, preferably contains from 2 g / ft 3 to 15 g / ft 3 of rhodium, more preferably from 5 g / ft 3 to 10 g / ft 3 of rhodium. Advantageously, such rhodium levels can be lower than those of conventional catalyst articles without compromising catalytic activity.

[0114] The catalyst article, particularly in such preferred embodiments, preferably contains from 50 g / ft 3 to 200 g / ft 3 of palladium, more preferably from 80 g / ft 3 to 150 g / ft 3 of palladium. Advantageously, such palladium levels can be lower than those of conventional catalyst articles without compromising catalytic activity.

[0115] In a preferred embodiment, the supported carrier material is disposed on the substrate in the form of a slurry, the PGM comprises palladium, the carrier material comprises alumina, and the slurry further comprises cerium-zirconium oxide. In another preferred embodiment, the supported carrier material is disposed on the substrate in the form of a slurry, the PGM comprises palladium, the carrier material comprises cerium-zirconium oxide, and the slurry further comprises alumina. In another preferred embodiment, the supported carrier material is disposed on the substrate in the form of a slurry, the PGM comprises palladium, and the carrier material comprises alumina and cerium-zirconium oxide.

[0116] In yet another aspect, the present invention provides an emissions treatment system comprising the catalyst article described herein.

[0117] The emissions treatment system is preferably for a gasoline engine.

[0118] The gasoline engine is preferably operated under stoichiometric conditions.

[0119] In yet another aspect, the present invention provides a method of treating exhaust gas, the method comprising:

[0120] providing a catalyst article as described herein; and

[0121] contacting the catalyst article with the exhaust gas.

[0122] The exhaust gas is preferably exhaust gas from a gasoline engine. The catalyst article is particularly suitable for treating such exhaust gas. The gasoline engine is preferably operated under stoichiometric conditions.

[0123] The present invention will now be described in connection with the following non-limiting examples.

[0124] Pd Uptake Test

[0125] Comparative Example 1A: Pd Uptake on Alumina at Various pH (2, 4, 6, 8, and 10)

[0126] 1. Add the required amounts of palladium nitrate, water, and alumina, targeting 3.75 wt% Pd on alumina and 30% solids. Mix for 1 hour.

[0127] Pd and 30% solids. Mix for 1 hour.

[0128] 2. Measure the pH and adjust to the target pH using ammonium hydroxide. Mix for 1 hour.

[0129] 3. Centrifuge and collect the supernatant.

[0130] 4. Use the supernatant sample for ICP analysis of Pd concentration.

[0131] Comparative Example 1B: Pd Uptake on Alumina at Different pH (2, 4, 6, 8, and 10) in the Presence of Tannic Acid Example 1C: Pd Uptake on Alumina at Different pH (2, 4, 6, 8, and 10) in the Presence of Gallic Acid

[0132] 1. Add the required amounts of palladium nitrate, water, and alumina, aiming for 3.75 wt% Pd on the alumina and 30% solids. Mix for 1 hour.

[0133] Pd and 30% solids. Mix for 1 hour.

[0134] 2. Add tannic acid, aiming for a TA:Pd mass ratio of 2:1; mix for 2 hours.

[0135] 3. Measure the pH and adjust to the target pH using ammonium hydroxide. Mix for 1 hour.

[0136] 4. Centrifuge and collect the supernatant.

[0137] 5. Use the supernatant sample for ICP analysis of the Pd concentration.

[0138] Comparative Example 2A: Pd Uptake on CZO at Various pH (2, 4, 6, 8, and 10) Comparative Example 2B: Pd Uptake on CZO at Different pH (2, 4, 6, 8, and 10) in the Presence of Tannic Acid

[0139] 1. Add the required amounts of palladium nitrate, water, and alumina, aiming for 3.75 wt% Pd on the alumina and 30% solids. Mix for 1 hour.

[0140] Pd and 30% solids. Mix for 1 hour.

[0141] 2. Add gallic acid, aiming for a GA:Pd mass ratio of 2:1; mix for 2 hours.

[0142] 3. Measure the pH and adjust to the target pH using ammonium hydroxide. Mix for 1 hour.

[0143] 4. Centrifuge and collect the supernatant.

[0144] 5. Use the supernatant sample for ICP analysis of the Pd concentration.

[0145] Example 2C: Pd Uptake on CZO at Different pH (2, 4, 6, 8, and 10) in the Presence of Gallic Acid

[0146] 1. Add the required amounts of palladium nitrate, water, and CZO, aiming for 3.75 wt% Pd on the CZO and 30% solids. Mix for 1 hour.

[0147] 2. Measure the pH and adjust to the target pH using ammonium hydroxide. Mix for 1 hour.

[0148] 3. Centrifuge and collect the supernatant.

[0149] 4. Use the supernatant sample for ICP analysis of the Pd concentration.

[0150] Figure 1

[0151] 1. Add the required amounts of palladium nitrate, water, and CZO, aiming for 3.75 wt% Pd on the CZO and 30% solids. Mix for 1 hour.

[0152] 2. Add tannic acid with the aim of a TA:Pd mass ratio of 2:1; mix for 2 hours.

[0153] 3. Measure the pH and adjust to the target pH using ammonium hydroxide. Mix for 1 hour.

[0154] 4. Centrifuge and collect the supernatant.

[0155] 5. Use the supernatant sample for ICP analysis of Pd concentration.

[0156] Figure 2

[0157] 1. Add the required amounts of palladium nitrate, water, and CZO with the aim of 3.75 wt% Pd and 30% solids on CZO. Mix for 1 hour.

[0158] 2. Add gallic acid with the aim of a GA:Pd mass ratio of 2:1; mix for 2 hours.

[0159] 3. Measure the pH and adjust to the target pH using ammonium hydroxide. Mix for 1 hour.

[0160] 4. Centrifuge and collect the supernatant.

[0161] 5. Use the supernatant sample for ICP analysis of Pd concentration.

[0162] These Pd uptake results on alumina or CZO are shown in Pd Distribution Test and Comparative Example 3A: Fully Formulated Monolayer Pd Support Coating without Pd Fixation . Although both tannic acid and gallic acid significantly improved Pd fixation, the effectiveness of tannic acid on the CZO support was much lower, especially at higher pH conditions. In contrast, gallic acid was much more effective in fixing Pd regardless of the support and pH conditions.

[0163] Example 3B: Fully Formulated Monolayer Pd Support Coating with Pd Fixed by Gallic Acid in the Presence of Both Alumina and CZO

[0164] Example 3C: Fully Formulated Monolayer Pd Support Coating with Pd Fixed on Alumina by GA before CZO Addition

[0165] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading of 130 g / ft 3 ).

[0166] 2. Add stabilized alumina (1 g / in 3 ) and CZO (1 g / in 3 ) to the batch.

[0167] 3. Add barium acetate (400 g / ft 3 ) to the batch.

[0168] 4. Adjust the solids to the target (recommended ~30%)

[0169] 5. Add an appropriate amount of thickener and mix overnight.

[0170] 6. Coat the single-dose target 1.2 inches from the inlet.

[0171] 7. Place the brick in a static oven and bake at 500 °C for 30 minutes.

[0172] Example 3D: Fully Formulated Monolayer Pd Support Coating with Pd Fixed on CZO by GA before Alumina Addition Figures 3A to 3D

[0173] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading is 130 g / ft 3 ).

[0174] 2. Add stabilized alumina (1 g / in 3 ) and CZO (1 g / in 3 ) to the batch.

[0175] 3. Add gallic acid with the goal of a GA:Pd mass ratio of 2.

[0176] 4. Add barium acetate (400 g / ft 3 ) to the batch.

[0177] 5. Adjust the solids to the target (recommended about 30%)

[0178] 6. Add an appropriate amount of thickener and mix overnight.

[0179] 7. Coat the single-dose target 1.2 inches from the inlet.

[0180] 8. Place the brick in a static oven and bake at 500 °C for 30 minutes.

[0181] Figure 3A Figure 3B

[0182] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading is 130 g / ft 3 ).

[0183] 2. Add stabilized alumina (1 g / in 3 ) to the batch.

[0184] 3. Add gallic acid with the goal of a GA:Pd mass ratio of 2.

[0185] 4. Add CZO (1 g / in 3 ) to the batch.

[0186] 5. Add barium acetate (400 g / ft 3 ).

[0187] 6. Adjust the solids to the target (recommended about 30%)

[0188] 7. Add an appropriate amount of thickener and mix overnight.

[0189] 8. Coat a single-dose target 1.2 inches from the inlet

[0190] 9. Place the brick in a static oven and calcine at 500 °C for 30 minutes.

[0191] Figure 3C Figure 3D

[0192] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading is 130 g / ft 3 ).

[0193] 2. Add CZO (1 g / in 3 ) to the batch.

[0194] 3. Add gallic acid with the goal of a GA:Pd mass ratio of 2.

[0195] 4. Add stabilized alumina (1 g / in 3 ) to the batch.

[0196] 5. Add barium acetate (400 g / ft 3 ) to the batch.

[0197] 6. Adjust the solids to the target (recommended about 30%)

[0198] 7. Add an appropriate amount of thickener and mix overnight.

[0199] 8. Coat a single-dose target 1.2 inches from the inlet

[0200] 9. Place the brick in a static oven and calcine at 500 °C for 30 minutes.

[0201] EPMA Analysis Shows SEM (scanning electron microscope) mapping of Pd in the Pd-TWC single-layer washcoat in Comparative Example 3A and Examples 3B to 3D. Comparison Figure 4 and Catalyst Light-off Performance , clearly show that Pd is concentrated on the surface of the washcoat in the reference catalyst, while Pd is more evenly distributed throughout the washcoat layer when gallic acid is added. Thus, gallic acid helps to immobilize Pd in the washcoat. Comparative Example 4A: Fully Formulated Monolayer Pd Support Coating without Pd Fixation and Example 4B: Fully Formulated Monolayer Pd Support Coating of Pd-GA (GA:Pd mass ratio of 1.3) show elemental mapping of Pd compared to Al or Pd compared to Zr in the same washcoat sample; which shows that Pd is immobilized on alumina or CZO by adding gallic acid and controlling the addition sequence during washcoat preparation.

[0202] Example 4C: Fully Formulated Monolayer Pd Support Coating of Pd-GA×1.5 (GA:Pd mass ratio of 2)

[0203] Compare Comparative Example 3A and Examples 3B to 3D by EPMA analysis to quantitatively analyze the proximity between elements. A higher / positive correlation number indicates a higher statistical likelihood of two elements being in close proximity; and a lower / negative correlation number indicates a lower statistical likelihood of two elements being in close proximity. Therefore, the relative amount of alumina compared to Pd on the CZO support can be determined by analyzing the correlation of Pd-Al and Pd-Zr using this method. And the analysis is shown in Example 4D: Fully Formulated Monolayer Pd Support Coating of Pd-GA×2.0 (GA:Pd mass ratio of 2.7) .

[0204] The results show that in Comparative Example 3A, Pd is uniformly distributed on alumina and CZO. And when fixed by gallic acid, Pd preferentially adsorbs on alumina, which may be due to the higher surface area and pore volume of alumina compared to CZO. However, by changing the addition order, Pd can be selectively fixed on alumina or CZO using gallic acid.

[0205] Figure 5A

[0206] Figure 5B

[0207] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading is 100 g / ft 3 ).

[0208] 2. Add stabilized alumina (1 g / in 3 ) and CZO (1 g / in 3 ) to the batch.

[0209] 3. Add barium acetate (300 g / ft 3 ) to the batch.

[0210] 4. Adjust the solids to the target (recommended about 30%)

[0211] 5. Add an appropriate amount of thickener and mix overnight.

[0212] 6. Coat a single-dose target 1.2 inches from the inlet

[0213] 7. Place the brick in a static oven and calcine at 500 °C for 30 minutes.

[0214] Figure 5C

[0215] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading is 100 g / ft 3 ).

[0216] 2. Add stabilized alumina (1 g / in 3 ) and CZO (1 g / in 3 ) to the batch.

[0217] 3. Add gallic acid with the target of a GA:Pd mass ratio of 1.3.

[0218] 4. Add barium acetate (300 g / ft 3 ) to the batch.

[0219] 5. Adjust the solids to the target (recommended at about 30%)

[0220] 6. Add an appropriate amount of thickener and mix overnight.

[0221] 7. Coat the single-dose target 1.2 inches from the inlet

[0222] 8. Place the brick in a static oven and calcine at 500 °C for 30 minutes.

[0223] Catalyst Engine Performance

[0224] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading of 100 g / ft 3 ).

[0225] 2. Add stabilized alumina (1 g / in 3 ) and CZO (1 g / in 3 ) to the batch.

[0226] 3. Add gallic acid with the target of a GA:Pd mass ratio of 2.0.

[0227] 4. Add barium acetate (300 g / ft 3 ) to the batch.

[0228] 5. Adjust the solids to the target (recommended at about 30%)

[0229] 6. Add an appropriate amount of thickener and mix overnight.

[0230] 7. Coat the single-dose target 1.2 inches from the inlet

[0231] 8. Place the brick in a static oven and calcine at 500 °C for 30 minutes.

[0232] Comparative Example 5A: Fully Formulated Monolayer Pd Support Coating without Pd Fixation

[0233] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading of 100 g / ft 3 ).

[0234] 2. Add stabilized alumina (1 g / in3 ) and CZO (1 g / in 3 ) are added to this batch.

[0235] 3. Add gallic acid, with the target of a GA:Pd mass ratio of 2.7.

[0236] 4. Add barium acetate (300 g / ft 3 ) to this batch.

[0237] 5. Adjust the solids to the target (recommended at about 30%)

[0238] 6. Add an appropriate amount of thickener and mix overnight.

[0239] 7. Coat the single-dose target 1.2 inches from the inlet

[0240] 8. Place the bricks in a static oven and calcine at 500 °C for 30 minutes.

[0241] Example 5B: Fully Formulated Monolayer Pd Support Coating with Pd Fixed by Gallic Acid 、 Figure 6A and Figure 6B respectively show the comparison of NO x , CO and THC light-off conversion rates between Comparative Example 4A and Examples 4B, 4C and 4D after redox aging at 1000 °C for 40 hours. After rich burn pretreatment, and at light-off temperatures between 150 °C and 600 °C, at a perturbation λ (frequency of 1 Hz) between 0.96 and 1.04, and at a GHSV of 200,000 hr -1 the catalysts are evaluated. Compared with the unfixed fully formulated Pd reference catalyst (Comparative Example 4A), the Pd catalysts fixed with different amounts of gallic acid (Examples 4B to 4D, with GA:Pd mass ratios of 1.3, 2.0 and 2.7 respectively) show improved low-temperature NO x light-off performance and improved CO and THC performance.

[0242] Figure 6C

[0243] ​

[0244] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading of 149 g / ft 3 ).

[0245] 2. Add stabilized alumina (1 g / in 3 ) and CZO (1 g / in 3 ) to this batch.

[0246] 3. Add barium acetate (400 g / ft 3 ) to this batch.

[0247] 4. Adjust the solid to the target (recommended at about 30%).

[0248] 5. Add an appropriate amount of thickener and mix overnight.

[0249] 6. Coat 50% of the dose length from the inlet and cure dry with air.

[0250] 7. Then coat 50% of the dose length from the outlet and cure dry with air to obtain the bottom-coated component.

[0251] 8. Prepare a solution with the required amount of rhodium nitrate (Pd loading is 6 g / ft 3 ).

[0252] 9. Add stabilized alumina (1 g / in 3 ) to the above solution.

[0253] 10. Adjust the pH of the above mixture to 6 - 7 and mix for at least 1 hour.

[0254] 11. Add CZO (1 g / in 3 ) to the above mixture.

[0255] 12. Add an appropriate amount of thickener to the above mixture and stir overnight.

[0256] 13. Coat 50% of the dose length from the inlet of the coated component in step 7 and cure dry with air.

[0257] 14. Then coat 50% of the dose length from the outlet and cure dry with air to obtain the double-coated component.

[0258] 15. Place the brick in a static oven and calcine at 500 °C for 30 minutes.

[0259] ​

[0260] 1. Prepare a solution with the required amount of palladium nitrate (Pd loading is 149 g / ft 3 ).

[0261] 2. Add stabilized alumina (1 g / in 3 ) and CZO (1 g / in 3 ) to the batch.

[0262] 3. Add gallic acid with the target of a GA:Pd mass ratio of 2.0.

[0263] 4. Add barium acetate (400 g / ft 3 ) to the batch.

[0264] 5. Adjust solids to target (recommended about 30%)

[0265] 6. Add appropriate amount of thickener and mix overnight.

[0266] 7. Apply 50% of the dosage length from the entrance and air cure to dry.

[0267] 8. Then apply 50% of the dose length from the exit and air cure to obtain a basecoated part.

[0268] 9. Prepare a solution with the required amount of rhodium nitrate (Pd loading of 6 g / ft 3 ).

[0269] 10. Stabilized alumina (1g / in 3 ) was added to the above solution.

[0270] 11. Adjust the pH of the above mixture to 6-7 and mix for at least 1 hour.

[0271] 12. Add CZO (1g / in 3 ) was added to the above mixture.

[0272] 13. Add appropriate amount of thickener to the above mixture and stir overnight.

[0273] 14. Apply 50% of the dosage length from the entrance of the coated part in step 8 and dry with air curing.

[0274] 15. Then apply 50% of the dose length from the exit and dry with air curing to obtain a double-coated part.

[0275] 16. The bricks were placed in a static oven and fired at 500°C for 30 minutes.

[0276] ​ , ​ and ​ The NO values ​​of Comparative Example 5A and Example 5B during the engine bench test after 50 hours of engine-redox aging at 950°C are shown respectively. x , CO and THC emissions. Compared to the fully formulated Pd-Rh bilayer catalyst without Pd immobilization (Comparative Example 5A), Example 5B shows improved TWC performance with less NO x , CO and THC emissions.

[0277] The foregoing detailed description has been presented by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to those of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A method of manufacturing a catalyst article, the method comprising: To provide a compound of formula (I) A complex with PGM, where R1 is H or C1-C6 alkyl, R2 is H, OH or O-C1-C4 alkyl, and the PGM contains palladium; 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.

2. The method according to claim 1, wherein R2 is OH.

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

4. The method according to any one of the preceding claims, wherein the PGM consists of palladium.

5. The method according to any one of the preceding claims, wherein after heating the carrier material of the load, the substrate comprises from 50 g / ft 3 to 200 g / ft 3 of the PGM.

6. The method according to claim 5, wherein after heating the carrier material of the load, the substrate comprises from 10 g / ft 3 to 150 g / ft 3 of the PGM.

7. The method according to any one of the preceding claims, wherein the support material comprises an oxide, preferably one or more of Al2O3, SiO2, TiO2, CeO2, ZrO2, CeO2-ZrO2, V2O5, La2O3 and zeolite.

8. The method according to any one of the preceding claims, wherein the support material comprises alumina, preferably γ-alumina.

9. The method according to any one of the preceding claims, wherein the support material comprises cerium dioxide-zirconia.

10. The method according to any one of the preceding claims, wherein the support material comprises alumina and cerium dioxide-zirconia.

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

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

13. The method according to claim 11 or claim 12, wherein the dopant is present in the alumina and / or cerium dioxide-zirconia in an amount of 0.001 wt% to 20 wt%, preferably 0.5 wt% to 10 wt%.

14. The 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 μm to 30 μm, preferably 1 μm to 20 μm.

15. The method according to any one of the preceding claims, wherein the supported support material is disposed on the substrate in the form of a slurry.

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

17. The method according to claim 15, wherein the slurry is prepared by a method comprising the steps of: 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 an aqueous solution, the PGM salt comprising palladium; applying the complex to the support material by contacting the support material with the aqueous solution to form a supported support material; Optionally, one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or a base; a thickener; and a reducing agent are added to the aqueous solution.

18. The method according to claim 15, wherein the slurry is prepared by a method comprising the steps of: contacting a support material with an aqueous solution of a PGM salt to form a slurry comprising the support material loaded with the PGM salt, the PGM salt comprising palladium; By contacting the slurry of the carrier material comprising the supported PGM salt with the compound of formula (I) in water, the compound of formula (I) is applied to the carrier material to form a supported carrier material; Optionally, one or more of an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt; a binder; an acid or a base; a thickener; and a reducing agent are added to the aqueous solution or the slurry comprising the support material loaded with the PGM salt.

19. The method according to any one of the preceding claims, wherein the loading comprises support coating.

20. The method according to any one of claims 15 to 19, wherein the solid content of the slurry is from 10% to 40%, preferably from 15% to 35%.

21. The method according to any one of claims 15 to 20, wherein the slurry further comprises one or more of the following substances: an oxygen storage material, preferably cerium-zirconium oxide; a promoter salt, preferably barium acetate, barium sulfate, barium citrate or a combination thereof; a binder; an acid or a base; a thickener; and a reducing agent.

22. The method according to any one of claims 15 to 21, wherein the support material comprises alumina and the slurry further comprises cerium-zirconium oxide.

23. The method according to any one of claims 15 to 21, wherein the support material comprises cerium-zirconium oxide and the slurry further comprises alumina.

24. The method according to any one of claims 15 to 21, wherein the support material comprises alumina and cerium-zirconium oxide.

25. The method according to any one of claims 15 to 24, the method further comprising disposing an additional slurry on the substrate, the additional slurry comprising one or more of the following substances: an additional support material; an oxygen storage material; a promoter salt, preferably barium acetate, barium sulfate, barium citrate or a combination thereof; a binder; an acid or a base; a thickener; and a reducing agent, wherein disposing the additional slurry on the substrate is performed before and / or after disposing the support material on the substrate and heating the loaded support material to form the nanoparticles of the PGM on the support material.

26. The method according to any one of claims 15 to 25, wherein disposing the loaded support material on the substrate comprises contacting the slurry with the substrate and optionally: applying a vacuum to the substrate, and / or drying the slurry on the substrate.

27. The method according to claim 26, wherein the drying occurs under the following conditions: at a temperature of 60°C to 200°C, preferably 70°C to 130°C; and / or for 10 minutes to 360 minutes, preferably 15 minutes to 60 minutes.

28. The method according to any one of the preceding claims, wherein the substrate comprises cordierite.

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

30. The method according to any one of the preceding claims, wherein the heating is carried out under the following conditions: at a temperature of 400 °C to 700 °C, preferably 400 °C to 600 °C, more preferably 450 °C to 600 °C; and / or for 10 minutes to 360 minutes, preferably 35 minutes to 120 minutes.

31. The method according to any one of the preceding claims, wherein the heating includes calcination.

32. The method according to any one of the preceding claims, wherein the D50 of the nanoparticles is 0.1 nm to 30 nm, preferably 0.5 nm to 25 nm, more preferably 1 nm to 20 nm.

33. A catalyst article capable of being obtained by the method according to any one of the preceding claims, the catalyst article being used in an emission treatment system.

34. The catalyst article according to claim 33, the catalyst article being used for three-way catalysis.

35. The catalyst article according to claim 33 or claim 34, wherein the support coating loading of the catalyst article is 1 g / in 3 to 3 g / in 3 .

36. The catalyst article according to any one of claims 33 to 35, wherein the substrate includes a wall-flow filter substrate.

37. The catalyst article according to any one of claims 33 to 35, wherein the substrate includes a flow-through substrate.

38. The catalyst article according to any one of claims 33 to 37, the catalyst article including a bottom layer of a carrier material having rhodium thereon and a top layer of a carrier material having palladium thereon.

39. The catalyst article according to any one of claims 33 to 37, the catalyst article including a bottom layer of a carrier material having palladium thereon and a top layer of a carrier material having rhodium thereon.

40. The catalyst article according to claim 38 or 39, wherein the top layer of the carrier material and / or the bottom layer of the carrier material further has platinum thereon.

41. The catalyst article according to any one of claims 38 to 40, wherein the top layer of the carrier material and / or the bottom layer of the carrier material has a plurality of PGMs thereon.

42. The catalyst article according to any one of claims 38 to 41, the catalyst article including two or more catalyst zones, wherein the two or more catalyst zones are different from each other by including different PGMs or different amounts of PGMs.

43. The catalyst article according to claim 38 or claim 42, wherein the carrier material includes alumina and ceria-zirconia.

44. The catalyst article according to any one of claims 33 to 43, the catalyst article comprising from 2 g / ft 3 to 15 g / ft 3 of rhodium, preferably from 5 g / ft 3 to 10 g / ft 3 of rhodium.

45. The catalyst article according to any one of claims 38 to 44, the catalyst article comprising from 10 g / ft 3 to 200 g / ft 3 of palladium, preferably from 80 g / ft 3 to 150 g / ft 3 of palladium.

46. The catalyst article according to any one of claims 33 to 45, wherein the loaded carrier material is provided on the substrate in the form of a slurry, the PGM includes palladium, the carrier material includes alumina, and the slurry further includes ceria-zirconia.

47. The catalyst article according to any one of claims 33 to 45, wherein the loaded carrier material is provided on the substrate in the form of a slurry, the PGM includes palladium, the carrier material includes ceria-zirconia, and the slurry further includes alumina.

48. The catalyst article according to any one of claims 34 to 45, wherein the supported carrier material is provided on the substrate in the form of a slurry, the PGM comprises palladium, and the carrier material comprises alumina and ceria-zirconia.

49. An emissions treatment system, the emissions treatment system comprising the catalyst article according to any one of claims 33 to 48.

50. The emissions treatment system according to claim 49, the emissions treatment system being for a gasoline engine.

51. The emissions treatment system according to claim 50, wherein the gasoline engine is operated under stoichiometric conditions.

52. A method of treating exhaust gas, the method comprising: providing the catalyst article according to any one of claims 33 to 48; and contacting the catalyst article with the exhaust gas.

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

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

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