Method for Producing a Catalyst Intermediate

Abstract

A method of producing a catalyst intermediate is provided that includes providing a slurry containing hydrous oxides of one or more of aluminum, cerium, and zirconium, and contacting the hydrous oxide-containing slurry with platinum group metal (PGM) ions to provide a PGM-containing slurry.

Description

[Technical field]

[0001] The present invention relates to new methods of producing catalyst intermediates for use, for example, in washcoat formulations for the preparation of catalyst articles for treating exhaust gases, and in particular to methods of producing catalyst intermediates, catalyst intermediates, washcoat formulations, methods of producing catalyst articles, and catalyst articles. [Background technology]

[0002] In internal combustion engines, the following substances are produced: hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x In gasoline engines, exhaust gases containing various pollutants are produced, including CO2, CO3, and NO3. Emissions control systems that include exhaust gas catalytic conversion catalysts are widely used to reduce the amount of these pollutants emitted into the atmosphere. The catalyst typically used to treat the exhaust gas of gasoline engines is the three way catalyst (TWC). The TWC has three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO2. x A reduction in the amount of

[0003] Such TWCs typically include a substrate and one or more catalytic layers or regions applied thereto. Thus, a typical method of making such TWCs may include applying a washcoat (e.g., a slurry) containing catalytically active particles to the substrate and calcining the particles in the slurry on the substrate. The washcoat typically includes one or more platinum group metals (PGMs) supported on a support material. The support material may include, for example, an inorganic oxide such as ceria, alumina, zirconia, or mixed oxides thereof.

[0004] However, problems associated with such typical methods of manufacturing TWCs, or other catalytic articles for treating exhaust gases, include the difficulty of efficiently supporting the PGMs on the support material. This may be due, for example, to poor incorporation of the PGMs on the inorganic oxide support material. Moreover, the relatively large PGM particles that may form on the surface of such supported support materials are likely to sinter during the calcination step of manufacture and / or during use in the exhaust system. Such sintering means that larger than desired PGM particles may be present on the final catalytic article (e.g., TWC) or may increase during use, which may result in lower catalytic activity of the catalytic article. Such reduced catalytic activity as a result of having larger particles is known and may be a result of having a reduced total PGM surface area compared to smaller PGM particles that have not undergone sintering.

[0005] Thus, there is a need to reduce the likelihood of sintering of PGM particles, particularly rhodium particles, in catalyst articles (e.g., TWCs) as a result of calcination during manufacture and / or the harsh aging conditions in exhaust systems for internal combustion engines, particularly gasoline engines. Summary of the Invention

[0006] One aspect of the present disclosure is directed to a method of making a catalyst intermediate, the method including providing a slurry including hydrous oxides of one or more of aluminum, cerium, and zirconium, and contacting the slurry including hydrous oxides with platinum group metal (PGM) ions to provide a PGM-containing slurry.

[0007] Another aspect of the present disclosure is directed to a catalyst intermediate produced by the method of producing a catalyst intermediate described herein.

[0008] Another aspect of the present disclosure is directed to a catalytic intermediate comprising a hydrous oxide network comprising one or more hydrous oxides of aluminum, cerium, and zirconium, the hydrous oxide network comprising encapsulated PGM ions therein.

[0009] Another aspect of the present disclosure is directed to a washcoat formulation for the preparation of a catalytic article for treating exhaust gases, the washcoat formulation including a catalytic intermediate as described herein.

[0010] Another aspect of the present disclosure is directed to a method of making a catalyst article, the method comprising: providing a catalyst intermediate made by a method described herein or as described herein; providing a slurry comprising the catalyst intermediate; applying the slurry comprising the catalyst intermediate to a substrate; and heating the slurry.

[0011] Another aspect of the present disclosure is directed to a method of making a catalyst article, the method comprising: making a catalyst intermediate by a method described herein or providing a catalyst intermediate described herein; calcining the catalyst intermediate to form a catalyst composition; providing a slurry comprising the catalyst composition; applying the slurry comprising the catalyst composition to a substrate; and heating the slurry.

[0012] Another aspect of the present disclosure is directed to a catalyst article produced by the method of making a catalyst article described herein.

[0013] Another aspect of the present disclosure is directed to an intermediate that includes one or more hydrous oxides of aluminum, cerium, and zirconium, the hydrous oxides having a hydroxyl content greater than 1 μmol / g.

[0014] Another aspect of the present disclosure is directed to a method of making an intermediate, the method including: (1) providing a slurry including one or more hydrous oxides of aluminum, cerium, and zirconium; (2a) heating the slurry of(1); and / or (2b) adjusting the pH of the slurry of(1) to between 7 and 14. [Brief description of the drawings]

[0015] [Figure 1]1 shows NO conversion for Reference Example 1 and Catalyst 1 during powder catalyst TWC light-off testing. [Diagram 2] 1 shows the CO conversion for Reference Example 1 and Catalyst 1 during powder catalyst TWC light-off testing. [Diagram 3] 1 shows the THC conversion for Reference Example 1 and Catalyst 1 during powder catalyst TWC light-off testing. [Figure 4] 1 shows NO conversion for Reference Example 2 and Catalyst 2 during powder catalyst TWC light-off testing. [Diagram 5] 1 shows the CO conversion for Reference Example 2 and Catalyst 2 during powder catalyst TWC light-off testing. [Figure 6] 1 shows the THC conversion for Reference Example 2 and Catalyst 2 during powder catalyst TWC light-off testing. [Figure 7] 1 shows NO conversion for Reference Example 3 and Catalyst 3 during powder catalyst TWC light-off testing. [Figure 8] 1 shows the CO conversion for Reference Example 3 and Catalyst 3 during powder catalyst TWC light-off testing. [Figure 9] 1 shows THC conversion for Reference Example 3 and Catalyst 3 during powder catalyst TWC light-off testing. [Figure 10] Hydroxyl content for solid oxide powders and hydrous oxide powders of equivalent metal composition is shown (Example 2). [Figure 11] 1 shows Rh uptake values ​​at various Rh loadings for solid oxide powders and hydrous oxide powders of equivalent metal composition (Example 2). [Figure 12] 1 shows NO conversion for Reference Example 5, Catalyst 5, and Catalyst 6 during catalyst core TWC light-off testing. [Figure 13] 1 shows the CO conversion for Reference Example 5, Catalyst 5, and Catalyst 6 during catalyst core TWC light-off testing. [Figure 14] 1 shows the THC conversion for Reference Example 5, Catalyst 5, and Catalyst 6 during catalyst core TWC light-off testing. [Figure 15] 1 shows NO conversion for Reference Example 5, Catalyst 5, and Catalyst 6 during catalyst core lambda sweep testing. [Figure 16] 1 shows the CO conversion for Reference Example 5, Catalyst 5, and Catalyst 6 during catalyst core lambda sweep testing. [Figure 17] 1 shows the THC conversion for Reference Example 5, Catalyst 5, and Catalyst 6 during catalyst core lambda sweep testing. [Figure 18] 1 shows cumulative NOx emissions for Reference Example 7 and Catalyst 7 during RDE testing on an engine bench dynamometer. [Figure 19] 1 shows the cumulative CO emissions for Reference Example 7 and Catalyst 7 during the RDE test on an engine bench dynamometer. [Figure 20] 1 shows cumulative THC emissions for Reference Example 7 and Catalyst 7 during RDE testing on an engine bench dynamometer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] 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.

[0017] In a first aspect, the present invention provides a method of producing a catalyst intermediate, the method comprising providing a slurry comprising hydrous oxides of one or more of aluminum, cerium, and zirconium, and contacting the slurry comprising hydrous oxides with platinum group metal (PGM) ions to provide a PGM-containing slurry.

[0018] Each aspect or embodiment defined in this specification may be combined with any other aspect or embodiment unless expressly indicated otherwise. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature indicated as being preferred or advantageous.

[0019] Surprisingly, when used in exhaust gas treatment systems, catalyst articles produced by using the catalyst intermediates produced by the present invention in the preparation of catalyst washcoats exhibit, for example, the following advantageous properties: increased thermal durability of the catalyst article, lower light-off temperature after accelerated aging at high temperatures (total hydrocarbon (THC), CO, and NO x [about]), superior / increased conversion at high temperatures (THC, CO, and NO x Moreover, due in part to the above advantageous properties, particularly increased activity, such catalyst articles may provide an opportunity to de-escalate (i.e., reduce the loading of) PGMs such as rhodium while maintaining the same or higher levels of catalytic activity.

[0020] Typically in industry, mixed oxide support materials for PGMs are provided by suppliers in their calcined form, i.e. as solid mixed oxide support materials. The mixed oxide support materials may or may not then be reduced to smaller particles by grinding before supporting the PGMs on the support material. However, in contrast to this standard practice, the inventors of the present invention have devised a method for producing a catalyst intermediate for use in preparing washcoat formulations, starting, for example, from the hydrous oxide form of the support material, i.e. before calcination of the support material to obtain the solid oxide form. Such a method may thus advantageously be able to exploit the interesting surface chemistry of the hydrous oxide form and its interaction with the PGM ions before calcination.

[0021] For example, without wishing to be bound by theory, it is hypothesized that the PGM ions strongly interact with the hydroxyl functional groups on the hydrous oxide in the slurry via electrostatic interactions. Indeed, PGM incorporation may be directly correlated to the surface charge of the hydrous oxide, which may allow for easy immobilization of the PGM. This strong interaction may therefore result in strongly immobilized PGM ions that are highly uniformly distributed throughout the hydrous oxide. In the slurry, it is hypothesized that the hydrous oxide at least partially forms a network, e.g., a porous network, which may encapsulate the highly dispersed PGM therein. Calcination of the hydrous oxide may then result in a (mixed) oxide support material with PGM particles encapsulated therein. As a result of the above-mentioned method and the highly dispersed PGM, for example, very small PGM particle sizes may be formed within the mixed oxide due to the strong interactions that keep the PGM ions / particles apart during the process. Moreover, the encapsulation of the PGM particles within the porous network may provide a physical barrier that reduces the possibility of PGM particle sintering during use of the resulting catalyst article or during the calcination process itself.

[0022] It is hypothesized that the above-mentioned advantageous properties are realized for at least these reasons. For example, without wishing to be bound by theory, it is hypothesized that this may be because (i) the particle size of the PGM particles encapsulated within the support material is kept small (i.e., increasing the PGM surface area to volume ratio), and (ii) the PGM particles are less likely to sinter under harsh conditions, such as the high temperatures during calcination and / or during use of such catalyst articles in exhaust systems, which can result in catalyst deactivation.

[0023] This novel starting point for the preparation of the washcoat therefore goes against standard practice in the industry (e.g., simply obtaining a calcined (mixed) oxide support material from a supplier and supporting PGMs thereon) and surprisingly and unexpectedly achieves improved catalytic properties of the final catalyst article prepared using such a technique for preparing a catalyst intermediate.

[0024] The term "catalyst intermediate" as used herein may include precursors for catalytic compositions exhibiting catalytic activity, for example, particularly for use in treating exhaust gases from internal combustion engines, preferably gasoline engines. The term "precursor" as used herein may include compositions formed before being used to provide further target compositions. In other words, the term "intermediate" is used within its ordinary meaning, for example, in the field of chemistry. Thus, a catalyst intermediate may be a precursor for catalytic compositions exhibiting catalytic activity, for example, for use in treating exhaust gases from internal combustion engines, preferably gasoline engines, for example, for treating exhaust gases from internal combustion engines, preferably gasoline engines. x The compound may be a precursor to a catalyst composition capable of demonstrating catalytic activity towards one or more of the following reductions:

[0025] As used herein, the term "slurry" can include a liquid containing insoluble material, e.g., insoluble particles. A slurry can include (1) a solvent or liquid, typically containing water, (2) a soluble portion, and (3) an insoluble portion.

[0026] The term "hydrated oxides" as used herein may include inorganic compounds of metals, hydroxides, and weakly bound water. In other words, the term "hydrated oxides" is used within its ordinary meaning in the art.

[0027] Contacting the slurry containing hydrous oxides with platinum group metal (PGM) ions may typically include, for example, mixing a solution containing PGM ions with the slurry containing hydrous oxides. Alternatively, a PGM precursor, such as a water-soluble PGM salt, may be added to the slurry containing hydrous oxides. The method of contacting the slurry containing hydrous oxides with platinum group metal (PGM) ions is not particularly limited. The PGM ions are typically provided in the form of a suitable PGM salt, such as, for example, a nitrate, sulfate, or chloride.

[0028] The PGM-containing slurry preferably comprises a hydrous oxide network with PGM ions encapsulated therein. As used herein, the term "hydrous oxide network" may include a matrix or lattice structure formed by hydrous oxides. As used herein, the term "encapsulated" may include structures in which the PGM ions are associated with the hydrous oxide network, particularly structures in which the PGM ions are located, for example, within the pores of the network or lattice structure. The PGM ions are typically associated with or coordinated to hydroxyl groups on the hydrous oxide network.

[0029] To promote the formation of a hydrous oxide network with the PGM ions encapsulated therein, the method preferably further comprises heating the PGM-containing slurry. Heating of the PGM-containing slurry is preferably carried out at a temperature of from 20 to 250°C, more preferably at or below 50°C. Without wishing to be bound by theory, it is believed that heating the PGM-containing slurry may increase the rate of formation of the network. Heating may also increase the rate of PGM ion association with the hydrous oxide. Preferably, the heating step does not result in calcination of the hydrous oxide.

[0030] The slurry containing hydrous oxides may also at least partially comprise a hydrous oxide network prior to contacting the slurry with the PGM ions. In order to promote the formation of the hydrous oxide network at this stage of the method, the method preferably further comprises the step of heating the slurry containing hydrous oxides prior to contacting the slurry containing hydrous oxides with the PGM ions. Heating the slurry containing hydrous oxide network is preferably carried out at a temperature of 20-250°C, more preferably 50-200°C, most preferably 100-175°C. Without wishing to be bound by theory, it is believed that heating the slurry containing hydrous oxides may increase the rate of formation of the network. It is essential that the heating at this stage of the method (i.e. prior to the addition of the PGM ions) does not cause substantial calcination of the hydrous oxides so that the desired interaction of the PGM ions with the hydroxyl groups of the hydrous oxides can be achieved.

[0031] While it is still possible to achieve the objectives of the invention with this additional heating step prior to the addition of the PGM ions, it may be preferred to eliminate this step in order to help disperse the PGM ions as uniformly as possible within the hydrous oxide network, i.e., by adding the PGM ions prior to any substantial formation of the hydrous oxide network. Alternatively, in some embodiments it may be preferred to include a heating step prior to contacting the slurry containing hydrous oxides with the PGM ions. This may result in better performance depending, for example, on which hydrous oxide is being used.

[0032] Any of the heating steps preferably includes hydrothermal treatment, which may include increasing the pH above 7, increasing the temperature above room temperature (about 20° C.), and stirring / mixing the slurry. Without wishing to be bound by theory, it is believed that increasing the pH may catalyze network formation, increasing the temperature may increase the rate of network formation, and stirring / mixing may increase the rate of network formation, resulting in a more homogenous network.

[0033] Preferably, the method further comprises adjusting the pH of the hydrous oxide-containing slurry and / or the PGM-containing slurry to 7-14. Preferably, the pH is adjusted to 8-13, more preferably 9-12, even more preferably 10-11. Without wishing to be bound by theory, it is believed that such a high pH may help to facilitate and / or increase the rate of formation of the hydrous oxide network by catalyzing the process, such as, for example, by catalyzing the reaction between hydroxyl groups that may result in the formation of a network. Without wishing to be bound by theory, the process may be considered to be, for example, a balance between consuming hydroxyl groups to form a network while allowing some hydroxyls to remain attached to the PGM ions. The pH may be adjusted using any suitable base, such as, for example, ammonium hydroxide, sodium hydroxide, potassium hydroxide, and / or an organic base, such as ammonium hydroxide, e.g., tetraethylammonium hydroxide. The choice of base is not particularly limited, provided that the material does not, for example, negatively interfere with the method. Moreover, without wishing to be bound by theory, it is believed that increasing the number of hydroxyl groups in the hydrous oxide may result in increased uptake of PGM ions due to an increase in the number of available electrostatic interactions. However, increasing the number of hydroxyl groups in the hydrous oxide may also result in an increase in the viscosity of the slurry. Thus, depending on the application, it may be necessary to find a balance between the described PGM uptake and the viscosity of the slurry.

[0034] Preferably, the catalyst intermediate is for use in a washcoat formulation for the preparation of a catalyst article for treating exhaust gases. More preferably, the catalyst article is for three-way catalysis.

[0035] Preferably, the hydrous oxide is not calcined. Calcination of the hydrous oxide may form a solid inorganic oxide of the metal, i.e., substantially free of hydroxyl functional groups for the PGM ions to interact with and substantially free of the ability to form a hydroxide network. Thus, sintering the hydrous oxide may not realize the advantages discussed above with respect to the differences between the use of hydrous oxides and sintered inorganic oxides.

[0036] As used herein, the term "platinum group metals (PGM)" refers to the metals ruthenium, rhodium, palladium, osmium, iridium, and platinum. The PGM ions preferably include platinum ions, palladium ions, rhodium ions, or combinations thereof, more preferably rhodium ions. For example, the PGM ions preferably consist of rhodium ions. Such PGMs are particularly suitable for use in forming TWCs and may be particularly compatible with the methods of the present invention. In some embodiments, the PGM loading is 0.02-20 wt.% based on the weight of the hydrous oxide. In further embodiments, the PGM loading is 0.1-10 wt.% based on the weight of the hydrous oxide. In certain embodiments, the PGM (e.g., Rh) loading is 0.02-5 wt.% based on the weight of the hydrous oxide. In further embodiments, the PGM (e.g., Rh) loading is 0.1-4 wt.%, 0.1-3 wt.%, 0.1-2 wt.%, or 0.1-1 wt.%, based on the weight of the hydrous oxide. As used herein, PGM loading is calculated based on elemental PGM metal (e.g., Rh).

[0037] The hydrous oxide preferably comprises a mixed hydrous oxide of cerium and zirconium. Upon calcination, the use of such a mixed hydrous oxide results in a ceria / zirconia mixed oxide, which may be a particularly advantageous support material for PGMs, for example, for use in TWCs. This is because such support materials may exhibit high oxygen storage capacity. Such properties are known to be advantageous for use in TWCs. The hydrous oxide preferably further comprises a dopant selected from the group consisting 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, more preferably one or more of lanthanum, neodymium, praseodymium, and yttrium. Such doped hydrous oxides, upon calcination, result in a doped oxide, which may be particularly effective as a support material. Preferably, the dopant is present in the hydrous oxide in an amount of 0.001% to 20% by weight, preferably 0.5% to 18% by weight, more preferably 1% to 17% by weight, even more preferably 2% to 16% by weight.

[0038] The term "mixed oxide" as used herein generally refers to a mixture of oxides in a single phase, as is conventionally known in the art.

[0039] Providing a slurry containing hydrous oxides preferably comprises contacting an aqueous solution containing one or more of aluminum ions, cerium ions, and zirconium ions with a basic aqueous solution. The aluminum ions, cerium ions, and zirconium ions may be provided in the form of a suitable metal salt, such as, for example, a nitrate, sulfate, or chloride. Suitable methods for making such hydrous oxides may be known in the art. If a dopant is present, the aqueous solution may further comprise ions of the dopant.

[0040] In a further aspect, the present invention provides a catalytic intermediate produced by the methods described herein.

[0041] In a further aspect, the present invention provides a catalytic intermediate comprising a hydrous oxide network comprising one or more hydrous oxides of aluminium, cerium and zirconium, the hydrous oxide network comprising encapsulated PGM ions therein.

[0042] The catalyst intermediate is preferably for use in a washcoat formulation for the preparation of a catalyst article for treating exhaust gases, more preferably the catalyst article is for three-way catalysis.

[0043] Preferably, the hydrous oxide network is not calcined.

[0044] The PGM ions preferably include platinum ions, palladium ions, rhodium ions, or a combination thereof, and more preferably, the PGM ions include rhodium ions. For example, the PGM ions preferably consist of rhodium ions. In some embodiments, the PGM loading is 0.02-20 wt.% based on the weight of the hydrous oxide. In further embodiments, the PGM loading is 0.1-10 wt.% based on the weight of the hydrous oxide. In certain embodiments, the PGM (e.g., Rh) loading is 0.02-5 wt.% based on the weight of the hydrous oxide. In further embodiments, the PGM (e.g., Rh) loading is 0.1-4 wt.%, 0.1-3 wt.%, 0.1-2 wt.%, or 0.1-1 wt.% based on the weight of the hydrous oxide. As used herein, the PGM loading is calculated based on elemental PGM metal (e.g., Rh).

[0045] The hydrous oxide preferably comprises a mixed hydrous oxide of cerium and zirconium. The hydrous oxide preferably further comprises a dopant selected from the group consisting 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, more preferably one or more of lanthanum, neodymium, praseodymium, and yttrium. Preferably, the dopant is present in the hydrous oxide in an amount of 0.001% to 20% by weight, preferably 0.5% to 18% by weight, more preferably 1% to 17% by weight, and even more preferably 2% to 16% by weight.

[0046] The hydrous oxides may preferably have a hydroxyl content (as measured using the method described in Example 2) of greater than 1 μmol / g, more preferably at least 2 μmol / g, and most preferably at least 3 μmol / g. Alternatively, the hydrous oxides may preferably have a hydroxyl content of 2 to 20 μmol / g, more preferably 3 to 18 μmol / g, and most preferably 4 to 16 μmol / g.

[0047] In a further aspect, the present invention provides a washcoat formulation for the preparation of a catalyst article for treating exhaust gases, the washcoat formulation comprising a catalyst intermediate as described herein. Preferably, the catalyst article is a TWC and / or the exhaust gas is from a gasoline engine. The washcoat formulation is typically in the form of a slurry.

[0048] In a further aspect, the present invention provides a method of making a catalyst article, the method comprising: producing a catalyst intermediate by a method described herein or providing a catalyst intermediate as described herein; providing a slurry comprising the catalyst intermediate; applying the slurry comprising the catalyst intermediate to a substrate; and heating the slurry.

[0049] In a further aspect, the present invention provides a method of making a catalyst article, the method comprising: making a catalyst intermediate by a method described herein or providing a catalyst intermediate described herein; calcining the catalyst intermediate to form a catalyst composition; providing a slurry comprising the catalyst composition; applying the slurry comprising the catalyst composition to a substrate; and heating the slurry.

[0050] In other words, the present invention encompasses methods of making catalytic articles that may or may not involve calcining the catalytic intermediate prior to application of the catalytic intermediate or its calcined product to a substrate. If the catalytic intermediate is not calcined prior to application to a substrate, the catalytic intermediate may be further calcined during the step of heating the slurry.

[0051] The term "catalyst article" as used herein may include an article on which or in which a catalyst is supported. The article may preferably take the form of, for example, a honeycomb monolith, or a filter, for example, preferably a wall-flow filter or a flow-through filter. The catalyst article may be for use in an emission treatment system, particularly an emission treatment system for a gasoline engine, preferably a stoichiometric gasoline engine. The catalyst article may be for use in three-way catalysis. In other words, the catalyst article may be a TWC.

[0052] The term "substrate" as used herein may include, for example, ceramic or metal honeycombs, or filter blocks, such as, preferably, wall-flow or flow-through filters. Substrates may include ceramic monolith substrates. Substrates may vary in their material composition, size and configuration, cell shape and density, and wall thickness. Suitable substrates are known in the art.

[0053] Providing the slurry comprising the catalyst intermediate can include providing a PGM-containing slurry as described herein. Alternatively, if the catalyst intermediate is separated from the PGM-containing slurry, providing the slurry comprising the catalyst intermediate can include contacting the separated catalyst intermediate with a liquid, preferably water, to provide the slurry.

[0054] Calcining the catalyst intermediate to form the catalyst composition typically involves heating the catalyst intermediate at a temperature between 400°C and 700°C, preferably between 400°C and 600°C, more preferably between 450°C and 600°C, and / or for 10 minutes to 360 minutes, preferably between 35 minutes to 120 minutes. However, calcination may be carried out by any calcination technique known in the art. The calcination process may convert the hydrous oxide (network) to the solid oxide form of the support material. As used herein, the term "calcination" or "calcining" may include a process of heat treating a material, preferably for the purpose of causing a chemical and / or physical change in the material and / or for the purpose of removing impurities. As used herein, the term "calcination" or "calcining" may include heat treating a material in air.

[0055] The term "catalyst composition" as used herein may include compositions that exhibit catalytic activity, particularly for use in the treatment of exhaust gases, preferably from gasoline engines. In other words, the catalyst composition is capable of oxidizing CO, oxidizing unburned HC, and oxidizing NO. x The catalytic composition may demonstrate catalytic activity for one or more of the following: reduction of cerium, cerium, zirconium, and / or cerium-containing oxides. Preferably, the catalytic composition is for three-way catalysis. In other words, the catalytic composition may be a three-way catalyst. Thus, in the present invention, the catalytic composition may be one or more PGMs supported on and / or in an inorganic oxide, the inorganic oxide comprising an oxide of aluminum, cerium, zirconium, or mixtures thereof.

[0056] Providing a slurry comprising the catalyst composition typically involves contacting the catalyst composition with a liquid, preferably water, to provide a slurry.

[0057] Applying the slurry containing the catalytic intermediate or the slurry containing the catalytic composition to the substrate can be carried out using techniques known in the art. Typically, the slurry can be injected into the inlet or outlet of the substrate using a specific forming tool in a predetermined amount, thereby disposing the catalytic intermediate or the catalytic composition on the substrate. Alternatively or additionally, the substrate can be at least partially immersed in the slurry. Subsequent vacuum, air knife and drying steps can be used during the application step. For example, once the slurry is injected into the inlet or outlet, or once the substrate is immersed in the slurry, a vacuum and / or an air knife can be applied to the inlet and / or outlet to distribute the slurry throughout the substrate and / or remove excess slurry from the substrate. If the carrier is a filter block, the catalytic intermediate or the catalytic composition can be disposed on the filter wall, within the filter wall (if porous), or both.

[0058] The slurry is particularly effective in disposing the material on the substrate, particularly for maximizing gas diffusion and minimizing pressure drop during catalytic conversion. Prior to disposing on the substrate, 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.

[0059] The catalyst article is preferably for three-way catalysis.

[0060] Preferably, the method further comprises contacting the slurry comprising the catalyst intermediate or the slurry comprising the catalyst composition with a binder, preferably a slurry comprising a binder. The binder preferably comprises alumina, preferably gamma alumina. The alumina is 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, and sodium, more preferably one or more oxides of lanthanum, neodymium, praseodymium, and yttrium. The dopant is preferably present in the alumina in an amount of 0.001% to 20% by weight, preferably 0.01% to 18% by weight, more preferably 0.1% to 15% by weight, and most preferably 0.5% to 10% by weight. Such additional ingredients for slurry / washcoat formulations are typical, for example, in the manufacture of TWCs.

[0061] The method may further include adjusting the pH of the slurry containing the catalyst intermediate or the slurry containing the catalyst composition to 8 or less. This is a typical step during a washcoating procedure and may be primarily to adjust the rheology (e.g., viscosity) of the slurry so that it can be more easily coated onto the substrate. However, in the method of the present invention, particularly in embodiments where the catalyst intermediate is not calcined before being applied to the substrate, such a step of lowering the pH may not be required. The rheology (e.g., viscosity) may be adjusted in other ways.

[0062] Preferably, the method further comprises adjusting the viscosity of the slurry containing the catalyst intermediate or the slurry containing the catalyst composition prior to applying said slurry to the substrate. Suitable techniques for adjusting the viscosity of the slurry are known in the art and may include one or more of adjusting the temperature, adjusting the pH, and adding a thickening agent to provide a suitable viscosity for coating the substrate using standard coating techniques.

[0063] Preferably, the method further comprises introducing one or more of a promoter salt, an acid or base, and a thickener to the slurry containing the catalyst intermediate or to the slurry containing the catalyst composition.

[0064] The promoter may include, for example, a non-PGM transition metal element, a rare earth element, an alkali or alkaline earth group element, and / or a combination of two or more of the above elements in the same or different groups of the periodic table. The promoter may be a salt of such an element. A particularly preferred promoter is barium, the particularly preferred salts of which are barium acetate, barium citrate, and barium sulfate, or combinations thereof, more preferably barium citrate.

[0065] The thickener may include, for example, a natural polymer with functional hydroxyl groups that interact with insoluble particles in the washcoat slurry. The thickener serves the purpose of thickening the washcoat slurry for improved coating profile during washcoat coating on the substrate. The thickener is usually baked off during the washcoat bake. Examples of specific thickeners / rheology modifiers for washcoats include glactoma gum, guar gum, xanthan gum, curdlan schizophyllan, scleroglucan, diutan gum, wheylan gum, hydroxymethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and ethylhydroxycellulose.

[0066] Applying the slurry containing the catalyst intermediate or the slurry containing the catalyst composition to the substrate preferably includes contacting the slurry with the substrate (e.g., injecting the slurry into an inlet and / or outlet of the substrate and / or at least partially immersing the substrate in the slurry) and, optionally, applying a vacuum to the substrate and / or drying the slurry on the substrate. This can result in a favorable distribution of the supported support material on the substrate. Preferably, drying occurs at a temperature between 60°C and 200°C, preferably between 70°C and 130°C, and / or for a period of 10 to 360 minutes, preferably between 15 to 60 minutes.

[0067] The substrate may be a "blank", i.e., an unwashcoated substrate. 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.

[0068] The substrate preferably comprises cordierite. Cordierite substrates are particularly suitable for use in catalytic articles.

[0069] The substrate is preferably in the form of a honeycomb monolith, a wall-flow filter or a flow-through filter.

[0070] Heating the slurry is preferably carried out at a temperature of 400° C. to 700° C., preferably 400° C. to 600° C., more preferably 450° C. to 600° C., and / or for 10 to 360 minutes, preferably 35 to 120 minutes. Heating the slurry preferably includes calcining.

[0071] In a further aspect, the present invention provides a catalyst article made by the method of making a catalyst article described herein. Preferably, the catalyst article is for three-way catalysis.

[0072] In a further aspect, the present disclosure is directed to an intermediate comprising one or more hydrous oxides of aluminum, cerium, and zirconium, the hydrous oxides having a hydroxyl content greater than 1 μmol / g.

[0073] The hydrous oxide preferably comprises a mixed hydrous oxide of cerium and zirconium. The hydrous oxide preferably further comprises a dopant selected from the group consisting 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, more preferably one or more of lanthanum, neodymium, praseodymium, and yttrium. Preferably, the dopant is present in the hydrous oxide in an amount of 0.001% to 20% by weight, preferably 0.5% to 18% by weight, more preferably 1% to 17% by weight, and even more preferably 2% to 16% by weight.

[0074] The hydrous oxides can preferably have a hydroxyl content (as measured using the method described in Example 2) of greater than 1 μmol / g, more preferably at least 2 μmol / g, and most preferably at least 3 μmol / g. Alternatively, the hydrous oxides can preferably have a hydroxyl content of 2-20 μmol / g, more preferably 3-18 μmol / g, and most preferably 4-16 μmol / g. In some embodiments, the hydrous oxides can have a hydroxyl content of 2-14 μmol / g, 3-12 μmol / g, or 4-10 μmol / g.

[0075] In another aspect, the invention provides a method of making an intermediate, the method comprising: (1) providing a slurry comprising one or more hydrous oxides of aluminum, cerium, and zirconium; and (2a) heating the slurry of(1); and / or (2b) adjusting the pH of the slurry of(1) to 7-14.

[0076] In (1), the slurry is heated at a temperature of preferably 20 to 250°C, more preferably 50 to 200°C, and most preferably 100 to 175°C.

[0077] The heating step preferably comprises hydrothermal treatment, which may include increasing the pH above 7, increasing the temperature above room temperature (about 20° C.), and stirring / mixing the slurry.

[0078] Preferably, the method further comprises adjusting the pH of the slurry containing the hydroxide oxide to 8 to 13, more preferably 9 to 12, even more preferably 10 to 11. The pH can be adjusted using any suitable base, such as, for example, ammonium hydroxide, sodium hydroxide, potassium hydroxide, and / or an organic base, such as ammonium hydroxide, e.g., tetraethylammonium hydroxide. The choice of base is not particularly limited, provided that the material does not, for example, negatively interfere with the method.

[0079] Preferably, the intermediate can have a hydroxyl content (as measured using the method described in Example 2) of greater than 1 μmol / g, more preferably at least 2 μmol / g, and most preferably at least 3 μmol / g. Alternatively, the intermediate can have a hydroxyl content of preferably 2-20 μmol / g, more preferably 3-18 μmol / g, and most preferably 4-16 μmol / g. In some embodiments, the intermediate can have a hydroxyl content of 2-14 μmol / g, 3-12 μmol / g, or 4-10 μmol / g.

[0080] The hydrous oxide preferably comprises a mixed hydrous oxide of cerium and zirconium. Upon calcination, the use of such a mixed hydrous oxide results in a ceria / zirconia mixed oxide, which may be a particularly advantageous support material for PGMs, for example, for use in TWCs. This is because such support materials may exhibit high oxygen storage capacity. Such properties are known to be advantageous for use in TWCs. The hydrous oxide preferably further comprises a dopant selected from the group consisting 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, more preferably one or more of lanthanum, neodymium, praseodymium, and yttrium. Such doped hydrous oxides, upon calcination, result in a doped oxide, which may be particularly effective as a support material. Preferably, the dopant is present in the hydrous oxide in an amount of 0.001% to 20% by weight, preferably 0.5% to 18% by weight, more preferably 1% to 17% by weight, even more preferably 2% to 16% by weight.

[0081] Providing a slurry containing hydrous oxides preferably comprises contacting an aqueous solution containing one or more of aluminum ions, cerium ions, and zirconium ions with a basic aqueous solution. The aluminum ions, cerium ions, and zirconium ions may be provided in the form of a suitable metal salt, such as, for example, a nitrate, sulfate, or chloride. Suitable methods for making such hydrous oxides may be known in the art. If a dopant is present, the aqueous solution may further comprise ions of the dopant.

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

[0083] General preparation of hydrous oxides A solution of metal ions was prepared by mixing the following metal salt solution (6.3 kg of cerium (IV) nitrate (19.1 wt% CeO2), 0.3 kg of lanthanum (III) nitrate (29.4 wt% La2O3), 0.7 kg of neodymium (III) nitrate (29.1 wt% Nd2O3), and 12.5 kg of zirconium (IV) oxynitrate (19.7 wt% ZrO2, 0.43 wt% HfO2)) in 60 kg of deionized (DI) water. The metal salt solution was heated to a temperature of 70° C. and mechanically stirred. Ammonium hydroxide solution was added to the metal ion solution over 45 minutes to achieve a final pH of about 8. The mixture was stirred at 70° C. for an additional 4 hours. The solution was then cooled to less than 50° C. The hydrous oxide precipitate was then filtered in a filter press and washed with DI water until the exiting solution was measured to have a conductivity of <5 mS. A small amount of the final hydrous oxide precipitate was dissolved in acidic medium and its gravimetric composition determined by inductively coupled plasma optical emission spectroscopy (ICP-OES) to be 62.5% ZrO2, 30.0% CeO2, 4.8% Nd2O3, 1.5% La2O3, and 1.2% HfO2.

[0084] Preparation of powder catalyst of the reference example 100 g of the hydrous oxide (dry basis) was dispersed in 900 g of DI water to form a slurry. A solution of ammonium hydroxide was added to the slurry to adjust the pH to about 10-11. The mixture was then sealed in a Hastelloy autoclave, heated to 150°C, and mechanically stirred for 2 hours. After cooling, the treated hydrous oxide was filtered and washed with DI water until the exiting filtrate reached a neutral pH of about 7. The hydrous oxide was then dried at 90°C for 16 hours, crushed into a powder, and further dried at 120°C for 2 hours. After drying, the hydrous oxide was calcined at 500°C in air to remove hydroxyls and convert the hydrous oxide to a solid oxide.

[0085] Reference Example 1: 10 g of the calcined solid oxide (dry basis) was dispersed in 90 g of DI water with mechanical mixing to form a slurry. The pH of the solution was raised to about 10-11 by the addition of ammonium hydroxide solution. 0.04 g of Rh was then added to the slurry in the form of a rhodium (III) nitrate solution. A solution of ammonium hydroxide was added to the slurry to readjust the pH to about 10-11 and the slurry was mixed for 30 minutes. The slurry was then transferred to a crucible and dried at 90° C. for at least 16 hours. The dried powder was ground using a mortar and pestle. The ground powder was calcined at 500° C. to form Reference Example 1.

[0086] Reference Example 2: 10 g of the calcined solid oxide (dry basis) was dispersed in 90 g of DI water with mechanical mixing to form a slurry. The pH of the solution was raised to about 10-11 by the addition of an aqueous solution of tetraethylammonium hydroxide. 0.3 g of Pd was then added to the slurry in the form of a palladium (II) nitrate solution. A solution of tetraethylammonium hydroxide was added to the slurry to readjust the pH to about 10-11, and the slurry was mixed for 30 minutes. The slurry was then transferred to a crucible and dried at 90° C. for at least 16 hours. The dried powder was ground using a mortar and pestle. The ground powder was calcined at 500° C. to form Reference Example 2.

[0087] Reference Example 3: 10 g of the calcined solid oxide (dry basis) was dispersed in 90 g of DI water with mechanical mixing to form a slurry. The pH of the solution was raised to about 10-11 by the addition of an aqueous solution of tetraethylammonium hydroxide. 0.3 g of Pd was then added to the slurry in the form of a platinum (II) nitrate solution. A solution of tetraethylammonium hydroxide was added to the slurry to readjust the pH to about 10-11 and the slurry was mixed for 30 minutes. The slurry was then transferred to a crucible and dried at 90° C. for at least 16 hours. The dried powder was ground using a mortar and pestle. The ground powder was calcined at 500° C. to form Reference Example 3.

[0088] Preparation of the Powder Catalyst of the Present Invention 100 g of hydrous oxide (dry basis) was dispersed in 900 g of DI water to form a slurry. A solution of ammonium hydroxide was added to the slurry to adjust the pH to approximately 10-11. The mixture was then sealed in a Hastelloy autoclave, heated to 150°C, and mechanically stirred for 2 hours. After cooling, the treated hydrous oxide was filtered and washed with DI water until the exiting filtrate reached a neutral pH of approximately 7.

[0089] Catalyst 1: 10 g of hydrous oxide (dry basis) was dispersed in 90 g of DI water with mechanical mixing to form a slurry. The pH of the solution was raised to about 10-11 by the addition of ammonium hydroxide solution. 0.04 g of Rh was then added to the slurry in the form of a rhodium (III) nitrate solution. A solution of ammonium hydroxide was added to the slurry to readjust the pH to about 10-11 and the slurry was mixed for 30 minutes. The slurry was then transferred to a crucible and dried at 90°C for at least 16 hours. The dried powder was ground using a mortar and pestle. The ground powder was calcined at 500°C to form Catalyst 1.

[0090] Catalyst 2: 10 g of hydrous oxide (dry basis) was dispersed in 90 g of DI water with mechanical mixing to form a slurry. The pH of the solution was raised to about 10-11 by the addition of an aqueous solution of tetraethylammonium hydroxide. 0.3 g of Pd was then added to the slurry in the form of a palladium (II) nitrate solution. A solution of tetraethylammonium hydroxide was added to the slurry to readjust the pH to about 10-11 and the slurry was mixed for 30 minutes. The slurry was then transferred to a crucible and dried at 90°C for at least 16 hours. The dried powder was ground using a mortar and pestle. The ground powder was calcined at 500°C to form Catalyst 2.

[0091] Catalyst 3: 10 g of hydrous oxide (dry basis) was dispersed in 90 g of DI water with mechanical mixing to form a slurry. The pH of the solution was raised to about 10-11 by the addition of an aqueous solution of tetraethylammonium hydroxide. 0.3 g of Pd was then added to the slurry in the form of a platinum(II) nitrate solution. A solution of tetraethylammonium hydroxide was added to the slurry to readjust the pH to about 10-11 and the slurry was mixed for 30 minutes. The slurry was then transferred to a crucible and dried at 90°C for at least 16 hours. The dried powder was ground using a mortar and pestle. The ground powder was calcined at 500°C to form Catalyst 3.

[0092] Example 1: Accelerated aging of powder catalyst in reactor and three-way catalysis (TWC) light-off test Powder catalysts of Reference Examples 1-3 and Catalysts 1-3 were subjected to high temperature redox conditions to simulate long term operation in a vehicle. The powders were placed in a tube furnace and heated to 1050°C at a rate of 10°C / min under a stoichiometric gas mixture of 1.2% CO, 0.4% H2, 0.8% O2, 10% H2O, 10% CO2, balance N2 flowing at 5 L / min. The temperature was then held at 1050°C for 40 hours, during which the flowing gas mixture was changed every 5 minutes in the order listed below. 1.Stoichiometry: 1.2%CO, 0.4%H2, 0.8%O2, 10%H2O, 10%CO2, balance N2 2. Lean: 1.2%CO, 0.4%H2, 1.6%O2, 10%H2O, 10%CO2, balance N2 3.Stoichiometry: 1.2%CO, 0.4%H2, 0.8%O2, 10%H2O, 10%CO2, balance N2 4. Rich: 2.4%CO, 0.8%H2, 0.8%O2, 10%H2O, 10%CO2, balance N2

[0093] After 40 hours, the coated cores were cooled under the rich gas mixture from 1050°C to below 400°C, and then cooled from 400°C to room temperature under N2 only.

[0094] After being subjected to the accelerated aging conditions described above, the catalysts of Reference Example 1 and Catalyst 1 were subjected to a TWC light-off test. In this test, 0.05 g of powdered catalyst mixed with 0.25 g of crushed cordierite was loaded into a reactor apparatus capable of heating and flowing a gas mixture designed to simulate gasoline exhaust conditions. 3 The temperature was increased from 150 to 600 °C at a rate of 5 °C / min under a gas mixture flowing at 1000 ppm / min. The volumetric composition of the gas was 1% CO, 1500 ppm C3H6 (propene), 400 ppm NO, 0.65% O2, 6% H2O, balance N2. The conversions of NO, CO, and total hydrocarbons (composed of THC and C3H6) as a function of temperature are reported in Figures 1 to 3, respectively.

[0095] A useful metric for quantifying the performance of a catalyst during light-off testing is T 50 value, which is defined herein as the lowest temperature at which 50% conversion is achieved. 50 The temperatures indicate which catalysts demonstrate improved catalytic activity. For each pollutant (NO, CO, and THC), the catalytic activity is the T achieved by each catalyst. 50 As evidenced by the T values, the conversion rates of NO, CO, and THC were greater for Catalyst 1 than for Reference Example 1. Catalyst 1 had T values ​​of NO, CO, and THC that were 8° C., 11° C., and 20° C. lower than Reference Example 1, respectively. 50 These results demonstrate that the Rh-containing catalyst 1 of the present invention exhibits improved catalytic activity compared to Reference Example 1 and is suitable as a catalyst in gasoline vehicle emission systems.

[0096] After being subjected to the above accelerated aging conditions, the catalysts of Reference Example 2 and Catalyst 2 were subjected to TWC light-off tests. The conversions of NO, CO, and total hydrocarbons (composed of THC, C3H6) as a function of temperature are reported in Figures 4 to 6, respectively.

[0097] For each pollutant (NO, CO, and THC), the catalytic activity is the T achieved by each catalyst. 50As evidenced by the T values, Catalyst 2 had NO, CO, and THC conversions that were 33° C., 51° C., and 40° C. lower than Reference Example 2, respectively. 50 These results demonstrate that the Pd-containing catalyst 2 of the present invention exhibits improved catalytic activity compared to Reference Example 2 and is suitable as a catalyst in gasoline vehicle emission systems.

[0098] After being subjected to the above accelerated aging conditions, the catalysts of Reference Example 3 and Catalyst 3 were subjected to TWC light-off tests. The conversions of NO, CO, and total hydrocarbons (composed of THC and C3H6) as a function of temperature are reported in Figures 7 to 9, respectively.

[0099] For each pollutant (NO, CO, and THC), the catalytic activity is the T achieved by each catalyst. 50 As evidenced by the T values, Catalyst 3 had NO, CO, and THC conversions that were 21° C., 20° C., and 21° C. lower than Reference Example 3, respectively. 50 These results demonstrate that the Pt-containing catalyst 3 of the present invention exhibits improved catalytic activity compared to Reference Example 3 and is suitable as a catalyst in gasoline vehicle emission systems.

[0100] Example 2: Hydroxyl content measurement and Rh uptake test Reference Example 4: 100 g of hydrous oxide (dry basis) was dispersed in 900 g of DI water to form a slurry. A solution of ammonium hydroxide was added to the slurry to adjust the pH to about 10-11. The mixture was then sealed in a Hastelloy autoclave, heated to 150°C, and mechanically stirred for 2 hours. After cooling, the treated hydrous oxide was filtered and washed with DI water until the exiting filtrate reached a neutral pH of about 7. The hydrous oxide was then dried at 90°C for 16 hours, crushed into a powder, and further dried at 120°C for 2 hours. After drying, the hydrous oxide was calcined at 500°C in air to remove hydroxyls and convert the hydrous oxide to a solid oxide.

[0101] Precatalyst 4: 100 g of hydrous oxide (dry basis) was dispersed in 900 g of DI water to form a slurry. A solution of ammonium hydroxide was added to the slurry to adjust the pH to approximately 10-11. The mixture was then sealed in a Hastelloy autoclave, heated to 150 °C, and mechanically stirred for 2 hours. After cooling, the treated hydrous oxide was filtered and washed with DI water until the exiting filtrate reached a neutral pH of approximately 7.

[0102] Reference Example 4 and Precatalyst 4 were then analyzed for hydroxyl content via thermogravimetric analysis (TGA). The powders were heated from room temperature to 120°C under nitrogen flow. The powders were then held isothermally at 120°C for 2 hours to desorb the weakly adsorbed water. The samples were then heated from 120°C to 500°C under nitrogen flow and the weight loss of each sample was measured. The weight loss was attributed to a condensation reaction between the two pendant hydroxyls contained in the solid oxide and hydrous oxide powders, as shown below.

[0103]

number

[0104]

number

[0105] 10 depicts the hydroxyl content of Reference Example 4 and Precatalyst 4. Precatalyst 4 contained about 6.7 μmol / g of hydroxyl compared to Reference Example 4, which contained only about 1.0 μmol / g of hydroxyl. These results demonstrate that Precatalyst 4 contained a significantly higher amount of hydroxyl than Reference Example 4.

[0106] Reference Example 4 and the pre-catalyst powder sample were also subjected to Rh uptake testing using the following procedure: 10 g (dry basis) of solid oxide powder or hydrous oxide powder was dispersed in 90 g of DI water by mechanical mixing for 2 hours at room temperature. Rhodium (III) nitrate was added to the solution to target various Rh loadings on the solid oxide (0.6 wt%, 1.7 wt%, and 3.1 wt%, respectively) or hydrous oxide support (0.5 wt%, 1.4 wt%, and 3.1 wt%, respectively). The solution was then centrifuged and decanted to remove most of the solid material. Finally, the solution was filtered using a 0.1 μm filter syringe. The centrifuged and filtered solution was analyzed by ICP-OES to determine the amount of free Rh remaining in the solution. The Rh uptake of the solid oxide and hydrous oxide was determined using the following equation:

[0107]

number

[0108] The results of the Rh uptake experiments are summarized in FIG. 11. At all Rh loadings, it was observed that precatalyst 4, with the same metal composition as Reference Example 4, was able to adsorb much more Rh amounts from simple mixing in solution, as evidenced by the Rh uptake values. At a target Rh loading of 3 wt%, the hydrous oxide of precatalyst 4 was able to adsorb more than 90% of the Rh, while the calcined solid oxide of Reference Example 4 only adsorbed about 22%. Without wishing to be bound by theory, this higher Rh uptake of the hydrous oxide is tentatively attributed to the favorable electrostatic interaction between the Rh ions and the higher hydroxyl content present on the hydrous oxide. The strong driving force for the interaction between the Rh ions and the hydrous oxide allowed for the stabilization of isolated Rh atoms and / or small Rh particles.

[0109] Preparation of catalyst-coated substrate cores Reference Example 5: 100 g of hydrous oxide (dry basis) was dispersed in 900 g of DI water to form a slurry. A solution of ammonium hydroxide was added to the slurry to adjust the pH to about 10-11. The mixture was then heated to 75° C. and mechanically stirred for 4 hours. After cooling, the treated hydrous oxide was filtered and washed with DI water until the exiting filtrate reached a neutral pH of about 7. The hydrous oxide was then dried at 90° C. for 16 hours, crushed into powder, and further dried at 120° C. for 2 hours. After drying, the hydrous oxide was calcined at 500° C. in air to remove hydroxyls and convert the hydrous oxide to a solid oxide.

[0110] Calcined solid oxide (0.5g / in 3 ) was dispersed in DI water with mechanical mixing to form a slurry. The slurry was then heated to a temperature of 75° C. with mechanical stirring. 3 ) was added to the slurry in the form of a rhodium(III) nitrate solution. A solution of ammonium hydroxide was added to the slurry to readjust the pH to about 7-8, and the slurry was mixed for 30 minutes. The slurry was then cooled to less than 40°C. Alumina binder (0.5 g / in 3 The slurry was then sprayed onto a cylindrical ceramic substrate (400 cells / in2 square, square channel, W / D=4.16 in, H=3.0 in) at 1.0 g / in2. 3 The coated ceramic substrate was fired at 500° C. A core measuring 1 inch×3 inches was cut from the ceramic substrate to form Example 5.

[0111] Catalyst 5: Hydrous oxide (0.5 g / in 3 ) was dispersed in DI water to form a slurry. The slurry was then heated to a temperature of 75° C. with mechanical stirring. Rh (3.5 g / ft 3) was added to the slurry in the form of a rhodium(III) nitrate solution. A solution of ammonium hydroxide was added to the slurry to adjust the pH to about 7-8, and the slurry was mixed for 30 minutes. A solution of ammonium hydroxide was then added to the slurry to readjust the pH to about 10-11, and the slurry was mixed for 4 hours. The slurry was then cooled to below 40°C. An alumina binder (0.5 g / in 3 The slurry was then sprayed onto a cylindrical ceramic substrate (400 cells / in2 square, square channel, W / D=4.16 in, H=3.0 in) at 1.0 g / in2. 3 The coated ceramic substrate was calcined at 500° C. A core measuring 1 inch×3 inches was cut from the ceramic substrate to form catalyst 5.

[0112] Catalyst 6: Hydrous oxide (0.5 g / in 3 ) was dispersed in DI water to form a slurry. The slurry was then heated to a temperature of 75° C. with mechanical stirring. A solution of ammonium hydroxide was then added to the slurry to adjust the pH to about 10-11, and the slurry was mixed for 2 hours. Rh (3.5 g / ft 3 ) was added to the slurry in the form of a rhodium(III) nitrate solution. The slurry was mixed at elevated temperature for an additional 2.5 hours. The slurry was then cooled to below 40°C. Alumina binder (0.5 g / in 3 The slurry was then sprayed onto a cylindrical ceramic substrate (400 cells / in2 square, square channel, W / D=4.16 in, H=3.0 in) at 1.0 g / in2. 3 The coated ceramic substrate was calcined at 500° C. A core measuring 1 inch×3 inches was cut from the ceramic substrate to form catalyst 6.

[0113] Example 3: Accelerated aging of catalyst cores in reactors and three-way catalysis (TWC) light-off testing Reference Example 5, Catalyst 5, and Catalyst 6 were subjected to high temperature aging to simulate long term operation in a vehicle. The cores were placed in a tube furnace and heated to 1050°C at a rate of 10°C / min under a stoichiometric gas mixture of 1.2% CO, 0.4% H2, 0.8% O2, 10% H2O, 10% CO2, balance N2 flowing at 5 L / min. The temperature was then held at 1050°C for 40 hours, during which the flowing gas mixture was changed every 5 minutes in the order listed below. 1.Stoichiometry: 1.2%CO, 0.4%H2, 0.8%O2, 10%H2O, 10%CO2, balance N2 2. Lean: 1.2%CO, 0.4%H2, 1.6%O2, 10%H2O, 10%CO2, balance N2 3.Stoichiometry: 1.2%CO, 0.4%H2, 0.8%O2, 10%H2O, 10%CO2, balance N2 4. Rich: 2.4%CO, 0.8%H2, 0.8%O2, 10%H2O, 10%CO2, balance N2

[0114] After 40 hours, the coated cores were cooled from 1050°C to 400°C under the rich gas mixture, and then cooled from 400°C to room temperature under N2 only.

[0115] After being subjected to the above aging conditions, 1 inch by 3 inch cores of catalyst articles of Reference Example 5, Catalyst 5, and Catalyst 6 were subjected to a typical TWC light-off test under simulated gasoline exhaust conditions, with a GHSV of 200,000 hours. -1The temperature was ramped from 150°C to 600°C at a rate of 50°C / min under a flowing gas mixture designed to simulate the exhaust of a gasoline vehicle at 1000 rpm. The gas composition was perturbed at a frequency of 1 Hz between the following compositions: 1) 1080 ppm propene, 120 ppm isopentane, 2.28% CO, 0.17% H2, 500 ppm NO, 0.49% O2, 14% CO2, 10% H2O, and 2) 1080 ppm propene, 120 ppm isopentane, 0.5% CO, 0.17% H2, 500 ppm NO, 1.28% O2, 14% CO2, 10% H2O. The light-off test results for NO, CO, and total hydrocarbon (composed of THC, propene, and isopentane) conversion, respectively, are shown in Figures 12-14.

[0116] A useful metric for quantifying catalyst performance is T 20 value, which is defined herein as the lowest temperature at which 20% conversion is achieved. 20 The temperatures indicate catalysts that demonstrate enhanced catalytic activity. In each case, the catalytic activity was measured by the T 20 As evidenced by the values, the T values ​​of NO, CO, and THC conversion rates were higher for Catalyst 5 and Catalyst 6 than for Reference Example 5. As shown in Figures 12 to 14, Catalyst 5 had T values ​​of NO, CO, and THC conversion rates that were 37°C, 50°C, and 46°C lower than Reference Example 5, respectively. 20 Catalyst 6 achieved T values ​​for NO, CO, and THC conversion rates that were 45° C., 60° C., and 61° C. lower than those of Reference Example 5, respectively. 20 value was achieved.

[0117] Another useful metric for quantifying catalyst performance is the final conversion value that each catalyst can achieve at the maximum temperature (600°C in this test). As shown in Figures 12-14, at the maximum temperature, catalyst 5 achieved NO, CO, and THC conversion rates that were 38%, 40%, and 25% higher, respectively, than the conversion rate achieved by Reference Example 5. At the maximum temperature, catalyst 6 achieved NO, CO, and THC conversion rates that were 48%, 47%, and 31%, respectively, higher than the conversion rate achieved by Reference Example 5. Thus, the metrics determined from the typical TWC light-off test demonstrate that the catalysts prepared in CATALYST 5 and CATALYST 6 exhibit superior performance as gasoline vehicle emission catalysts compared to Reference Example 5.

[0118] Example 4: Catalyst Core Lambda Sweep Testing During the operation of a gasoline vehicle, the air-fuel ratio is always within a flow rate due to the variability of user inputs during real driving conditions. The optimal air-fuel ratio for converting harmful emissions (NO, CO, THC) is known as the stoichiometric point. The variability of the air-fuel ratio from the ideal stoichiometric point is often calculated using a coefficient known as lambda (λ). Therefore, it is useful and meaningful to measure the performance of the catalyst under a wide range of varying λ values ​​to understand the behavior of the catalyst in real-world conditions on a vehicle.

[0119] The factor λ is defined herein as the ratio of the actual air / fuel ratio to the stoichiometric air / fuel ratio and is expressed as:

[0120]

number

[0121] After being subjected to the aging conditions described in Example 3, 1 inch by 3 inch cores of catalyst articles of Reference Example 5, Catalyst 5, and Catalyst 6 were subjected to lambda sweep testing under simulated gasoline exhaust conditions, with a GHSV of 100,000 hours. -1 The temperature was held isothermally at 500°C under a flowing gas mixture designed to simulate the exhaust of a gasoline vehicle at 1000 rpm. Over a period of 45 minutes, λ was stepped down at regular intervals (every 1 second) from an average value of 1.04 to an average value of 0.98 by varying the O2 concentration while oscillating at a frequency of 1 Hz and an amplitude of 0.05. The average gas composition at the start of the test (λ=1.04) was 600 ppm propene, 600 ppm propane, 1.0% CO, 0.33% H2, 2000 ppm NO, 1.5% O2, 14% CO2, 10% H2O. The average gas composition at the end of the test (λ = 0.98) was 600 ppm propene, 600 ppm propane, 1.0% CO, 0.33% H2, 2000 ppm NO, 0.375% O2, 14% CO2, and 10% H2O.

[0122] Lambda sweep test results for NO, CO, and THC (composed of propene and isopentane) conversion rates are shown in Figures 15-17, respectively. Both Catalyst 5 and Catalyst 6 were able to achieve higher conversion rates for all three emissions (NO, CO, and THC) than Reference Example 5 over the entire lambda operating window (1.04 ≦ λ ≦ 0.98). Under so-called "lean" conditions (λ > 1), Catalyst 5 was able to achieve 6%, 31%, and 14% higher NO, CO, and THC conversion rates than those achievable by Reference Example 5. Under so-called "rich" conditions (λ < 1), Catalyst 5 was able to achieve 36%, 20%, and 22% higher NO, CO, and THC conversion rates than those achievable by Reference Example 5. Under so-called "lean" conditions (λ > 1), Catalyst 6 was able to achieve 9%, 39%, and 20% higher NO, CO, and THC conversion rates than those achievable by Reference Example 5. Under so-called "rich" conditions (λ<1), Catalyst 6 was able to achieve NO, CO, and THC conversions that were 42%, 30%, and 29% higher than those achievable by Reference Example 5. Thus, both Catalyst 5 and Catalyst 6 exhibited superior performance under real-world varying exhaust gas conditions compared to Reference Example 5.

[0123] Preparation of fully formulated catalyst coated substrates Example 6 (Ceramic Substrate Containing Underlayer Catalyst Washcoat): An example underlayer of washcoat was prepared by forming a slurry of Pd in ​​the form of Pd(II) nitrate, rare earth doped ceria-zirconia mixed oxide, Ba in the form of Ba(II) hydroxide, and gamma alumina. The washcoat was applied at 2.1 g / in 2 onto a cylindrical ceramic substrate (750 cells / in 2 square, hexagonal channels, W / D=4.66 in, H=2.93 in). 3 The pre-coated ceramic substrate was then used in the preparation of Reference Example 7 and Catalyst 7.

[0124] Precatalyst 7: 100 g of hydrous oxide (dry basis) was dispersed in 900 g of DI water to form a slurry. A solution of ammonium hydroxide was added to the slurry to adjust the pH to approximately 10-11. The mixture was then sealed in a Hastelloy autoclave, heated to 150°C, and mechanically stirred for 2 hours. After cooling, the treated hydrous oxide was filtered and washed with DI water until the exiting filtrate reached a neutral pH of approximately 7. Hereafter, this material is referred to as Precatalyst 7.

[0125] Reference Example 7: Precatalyst 7 was dried at 90° C. for 16 hours, crushed into powder, and further dried at 120° C. for 2 hours. After drying, the hydrous oxide was calcined at 500° C. in air to remove hydroxyls and convert the hydrous oxide to a solid oxide.

[0126] Calcined solid oxide (1.0 g / in 3 ) was dispersed in DI water with mechanical agitation to form a slurry. The pH of the slurry was raised to about 10-11 using an aqueous ammonium nitrate solution. 3 ) was added to the slurry in the form of a Rh(III) nitrate solution and the solution was mixed for 30 minutes. Then, γ-alumina (0.3 g / in 3 ) was added to the slurry. The washcoat was applied at 1.3 g / in 3 The coated ceramic substrate was fired at 500° C. to form Example 7.

[0127] Catalyst 7: Precatalyst 7 (1.0 g / in 3 ) was dispersed in DI water with mechanical agitation to form a slurry. The pH of the slurry was raised to about 10-11 using an aqueous ammonium nitrate solution. 3 ) was added to the slurry in the form of a Rh(III) nitrate solution and the solution was mixed for 30 minutes. Then, γ-alumina (0.3 g / in 3 ) was added to the slurry. The washcoat was applied at 1.3 g / in 3The coated ceramic substrate was calcined at 500° C. to form catalyst 7.

[0128] Example 5: Real-World Driving Emissions (RDE) Testing of Catalyst Coated Substrates on an Engine Reference Example 7 and Catalyst 7 were subjected to high temperature aging on an engine bench to simulate long-term operation on a vehicle. All catalysts were engine bench aged for 150 hours while being subjected to a cycle of 40 sec stoichiometric / 6 sec rich / 14 sec lean exhaust gas conditions targeting an inlet catalyst temperature of 875°C.

[0129] After engine aging, Reference Example 7 and Catalyst 7 were tested using a 2.0L engine bench dynamometer and a custom original equipment manufacturer designed real world driving emissions (RDE) cycle including acceleration and fuel cut-off conditions representative of cold city, highway, and hot city speed phases. The cycle length was 2700 seconds from ambient soak conditions, reaching a peak catalyst bed temperature of approximately 700°C and a mass air flow rate of 250 kg / hr. NO at post-catalyst position x , CO, and THC emissions were measured and the cumulative mass of each species was calculated over the cycle.

[0130] NO for Reference Example 7 and Catalyst 7 x The cumulative emissions of NO, CO, and THC are shown in Figures 18-20, respectively. A catalyst that can more effectively convert engine exhaust emissions to less harmful products will emit lower total emissions. As shown in Figures 18-20, Catalyst 7 emitted 22% lower NO than Reference Example 7. x , 26% lower CO, and 16% lower THC emissions. These results demonstrate that the catalyst 7 of the present invention exhibits improved catalytic activity compared to Reference Example 7 and is suitable as a catalyst in gasoline vehicle emission systems.

[0131] The foregoing detailed description has been provided for purposes of explanation and illustration and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to those of ordinary skill in the art and will still fall within the scope of the appended claims and their equivalents.

Claims

1. 1. A method for producing a catalyst intermediate, comprising: providing a slurry comprising one or more hydrous oxides of aluminum, cerium, and zirconium; contacting the slurry containing the hydrous oxide with platinum group metal (PGM) ions to provide a PGM-containing slurry.

2. The method of claim 1 further comprising heating the PGM-containing slurry.

3. 3. The method of claim 1 or 2, further comprising the step of heating the slurry containing the hydrous oxides before contacting the slurry containing the hydrous oxides with PGM ions.

4. The method according to claim 1 or 2, further comprising adjusting the pH of the slurry containing the hydrous oxide and / or the PGM-containing slurry to 7 to 14.

5. 3. The method of claim 1 or 2, wherein the hydrous oxide is not calcined.

6. 3. The method of claim 1 or 2, wherein providing a slurry comprising a hydrous oxide comprises contacting an aqueous solution comprising one or more of aluminum ions, cerium ions, and zirconium ions with a basic aqueous solution.

7. A catalytic intermediate, A catalytic intermediate comprising a hydrous oxide network comprising one or more hydrous oxides of aluminum, cerium, and zirconium, the hydrous oxide network comprising PGM ions encapsulated therein.

8. 8. The catalytic intermediate of claim 7, wherein the hydrous oxide network is uncalcined.

9. 1. A method of making a catalyst article, comprising: Producing a catalytic intermediate according to claim 1 or 2 or providing a catalytic intermediate according to claim 7 or 8; providing a slurry comprising the catalyst intermediate; applying the slurry containing the catalyst intermediate to a substrate; and heating the slurry.

10. 1. A method of making a catalyst article, comprising: Producing a catalytic intermediate according to claim 1 or 2 or providing a catalytic intermediate according to claim 7 or 8; calcining the catalyst intermediate to form a catalyst composition; providing a slurry comprising the catalyst composition; applying the slurry containing the catalyst composition to a substrate; and heating the slurry.

11. The method of claim 9 , wherein the catalyst article is for three-way catalysis.

12. An intermediate, An intermediate comprising one or more hydrous oxides of aluminum, cerium, and zirconium, said hydrous oxides having a hydroxyl content greater than 1 mmol / g.

13. 13. The intermediate of claim 12, wherein the hydrous oxide comprises a mixed hydrous oxide of cerium and zirconium.

14. 14. The intermediate of claim 12 or 13, wherein the hydrous oxide has a hydroxyl content of 2 to 20 mmol / g.

15. 14. The intermediate of claim 12 or 13, wherein the hydrous oxide further comprises a dopant selected from the group consisting 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.

16. 1. A method for producing an intermediate, comprising: (1) providing a slurry containing one or more hydrous oxides of aluminum, cerium, and zirconium; (2a) heating the slurry of (1), and / or (2b) adjusting the pH of the slurry of (1) to 7 to 14.

17. 17. The method of claim 16, wherein the intermediate has a hydroxyl content of greater than 1 mmol / g.

Images