Heat-aging resistant oxidation catalyst for diesel exhaust control

Abstract

An oxidation catalyst composition is provided, comprising a plurality of platinum group metal particles having a multimodal particle size distribution. The plurality of platinum group metal particles includes a first population of platinum group metal particles having a particle size range of about 0.5 nm to about 3 nm and a second population of platinum group metal particles having a particle size range of about 4 nm to about 15 nm. Methods for preparing and using the catalyst composition are also provided, as are catalyst articles and exhaust gas treatment systems employing such catalyst articles. The catalyst exhibits enhanced stability with respect to oxidation performance after degradation and / or aging, particularly less loss of NOx oxidation performance, compared to conventional oxidation catalysts.

Description

[Technical Field]

[0001] This disclosure generally relates to exhaust gas treatment catalysts, in particular oxidation catalyst compositions comprising platinum group metal particles, methods for preparing and using such catalyst compositions, and catalytic articles and exhaust gas treatment systems employing such catalyst compositions.

[0002] Environmental regulations regarding emissions from internal combustion engines are becoming increasingly stringent worldwide. Lean-burn engines, such as diesel engines, offer users superior fuel efficiency due to their operation at high air / fuel ratios under lean fuel conditions. However, diesel engines also emit particulate matter, unburned hydrocarbons, carbon monoxide (CO), and nitrogen oxides (NOx). x It also emits exhaust gases containing NO x This refers to various chemical species of nitrogen oxides, including nitric oxide (NO) and nitrogen dioxide (NO2) in particular. The two main components of exhaust particulate matter are the soluble organic fraction and the soot fraction. The soluble organic fraction condenses in layers on top of the soot and generally originates from unburned diesel fuel and lubricating oil. Depending on the temperature of the exhaust gas, the soluble organic fraction can be present in diesel exhaust either as vapor or as an aerosol (i.e., fine droplets of liquid condensate). Soot is mainly composed of carbon particles.

[0003] Oxidation catalysts containing noble metals such as platinum group metals dispersed on refractory metal oxide supports are known to be used in treating diesel engine exhaust to convert both hydrocarbon and CO gaseous pollutants by catalyzing the oxidation of these pollutants to carbon dioxide (CO2) and water. Such catalysts may be contained in diesel oxidation catalysts, which are placed in the exhaust flow path from diesel power engines to treat the exhaust gas flow. Typically, diesel oxidation catalysts are prepared on ceramic or metal support substrates on which one or more catalyst coating compositions are deposited.

[0004] Diesel soot removal is achieved through either active or passive regeneration of the soot filter. Active regeneration can be performed by injecting additional diesel fuel at the inlet of the diesel oxidation catalyst. The heat released by the combustion of the fuel significantly increases the temperature at the downstream catalytic soot filter, initiating combustion of soot with O2 according to the equation (C + O2 → CO / CO2). This reaction typically occurs at temperatures above 600°C. Passive soot regeneration utilizes NO2 instead of O2 to oxidize the soot according to the equation (C + NO2 → CO / CO2 + NO). This reaction is efficient at temperatures above 300°C and can often be achieved during normal operation without requiring fuel injection, which would result in fuel consumption disadvantages.

[0005] In addition to the conversion of soluble organic fractions of gaseous hydrocarbons, CO, and particulate matter, platinum-containing oxidation catalysts promote the oxidation of NO to NO2. Platinum (Pt) remains the most effective platinum group metal for oxidizing NO to NO2. Platinum group metals can be incorporated into diesel oxidation catalyst compositions in various forms. For example, certain catalyst compositions incorporate platinum group metals in the form of particles (e.g., nanoparticles). See Paulus et al., J. Electroanal. Chem., 134, 495 (2001), Yoo et al., J. Catalysis, 214, 1-7 (2003), and Jain et al., Acc. Chem. Res., 41, 1578-1586 (2008). For example, size- and shape-controlled Pt nanoparticles offer an excellent opportunity for developing high-performance industrial Pt catalysts. See Zhao et al., Adv. Mater., 11, 217-220 (1999), Oishi et al., React. Funct. Polym. 67, 662-668 (2007), and Peng et al., Nano Lett., 9, 3704-3709 (2009). When platinum group metals are incorporated into catalyst compositions in the form of particles (e.g., nanoparticles), particle growth at high temperatures (i.e., sintering), which leads to a decrease in surface area, is the main deactivation pathway of the catalyst composition. In particular, NO oxidation has been widely reported to be structure-sensitive on Pt, i.e., the turnover frequency (TOF) is strongly dependent on the particle size of Pt (Weiss et al., J. Phys. Chem. C, 2009, 30, 13331-13340). In addition, completely reduced metallic Pt (Pt 0 The surface is most active against NO oxidation.

[0006] For example, the phenomenon of particle sintering in platinum group metal-containing catalyst compositions is thought to proceed by one of two limiting mechanisms: Ostwald aging or particle migration and coalescence. See, for example, Hansen et al., Acc. Chem. Res. 2013, 46(8):1720-30, whose disclosure is incorporated herein by reference. Under the Ostwald aging mechanism, the metal particles are assumed to be immobile, and sintering occurs only by the migration of atoms or clusters from smaller particles to larger particles. Under the particle migration and coalescence sintering mechanism, the particles are understood to move on the carrier surface in a Brownian motion-like manner, with subsequent coalescence leading to particle growth. Significant (often up to 50%) loss of NO oxidation activity can be observed during aging of conventional Pt-based diesel oxidation catalysts by either or both of these mechanisms.

[0007] The addition of palladium (Pd) to a Pt-based diesel oxidation catalyst can prevent Pt sintering and improve the oxidation performance of CO and hydrocarbons after high-temperature aging. However, high Pd concentrations can reduce the activity of Pt in converting hydrocarbons and / or oxidizing NO, especially when used with hydrocarbon storage materials, and can also make the catalyst more susceptible to sulfur poisoning. Therefore, it would be advantageous to provide a catalyst composition containing Pt that is less affected by surface area loss in order to enable consistently high catalytic efficiency under high-temperature operating conditions. Furthermore, it would be beneficial to efficiently utilize metals (e.g., platinum group metals) and enable the oxidation of hydrocarbons and NO over long periods, especially under high-temperature conditions. x There is a continuing need to provide catalyst compositions that remain effective in meeting CO conversion regulations.

[0008] Disclosed herein are catalyst compositions, catalyst articles, and catalyst systems comprising such catalyst articles. In some embodiments, the catalyst compositions, catalyst articles, and catalyst systems comprising such catalyst articles exhibit enhanced aging stability with respect to oxidation performance. In some embodiments, an oxidation catalyst composition comprising a plurality of platinum group metal particles having a multimodal particle size distribution in which the plurality of platinum group metal particles are two distinctly different and clearly defined particle size ranges exhibits less NO after degreening and / or aging compared to an oxidation catalyst composition not having such a multimodal distribution of platinum group metal particles. x This shows the loss of oxidation performance.

[0009] Accordingly, in one embodiment, the oxidation catalyst composition comprises a plurality of platinum group metal particles having a multimodal particle size distribution, wherein the plurality of platinum group metal particles comprises a first group of platinum group metal particles having a particle size range of about 0.5 nm to about 3 nm, and a second group of platinum group metal particles having a particle size range of about 4 nm to about 15 nm.

[0010] In some embodiments, a first group of platinum group metal particles has a particle size distribution characterized by an average particle size of about 1 nm, and at least about 80% of the first group of platinum group metal particles have a particle size within about 1 nm of the average particle size.

[0011] In some embodiments, the second population of platinum group metal particles has a particle size distribution characterized by an average particle size of about 6 nm, and at least about 80% of the second population of platinum group metal particles have a particle size within about 2 nm of the average particle size.

[0012] In some embodiments, the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 10:90 to about 90:10. In some embodiments, the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 50:50 to about 90:10. In some embodiments, the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 50:50 to about 75:25.

[0013] In some embodiments, the multiple platinum group metal particles have an average particle size of about 3 nm to about 12 nm. In some embodiments, the multiple platinum group metal particles have an average particle size of about 3 nm to about 10 nm. In some embodiments, the multiple platinum group metal particles have an average particle size of about 3 nm to about 8 nm. In some embodiments, the multiple platinum group metal particles have an average particle size of about 3 nm to about 6 nm. In some embodiments, the multiple platinum group metal particles have an average particle size of about 3 nm to about 5 nm.

[0014] In some embodiments, at least about 90% of the platinum group metals are in a completely reduced form.

[0015] In some embodiments, the platinum group metals include platinum, palladium, ruthenium, rhodium, iridium, or combinations thereof. In some embodiments, the platinum group metals include platinum, palladium, or combinations thereof. In some embodiments, the platinum group metal is platinum.

[0016] In some embodiments, the oxidation catalyst composition further comprises at least one refractory metal oxide support. In some embodiments, the at least one refractory metal oxide support comprises alumina (Al2O3), silica (SiO2), zirconia (ZrO2), titania (TiO2), ceria (CeO2), or a combination thereof. The combination may be in the form of a physical mixture or a chemical mixture. In some embodiments, the at least one refractory metal oxide support comprises SiO2-doped Al2O3, SiO2-doped TiO2, and / or SiO2-doped ZrO2. In some embodiments, the at least one refractory metal oxide support comprises Al2O3 doped with 1-10% SiO2, TiO2 doped with 1-20% SiO2, and / or ZrO2 doped with 1-30% SiO2.

[0017] In some embodiments, both the first population of platinum group metal particles and the second population of platinum group metal particles are dispersed on the same refractory metal oxide support. In some embodiments, the first population of platinum group metal particles and the second population of platinum group metal particles are each dispersed on a separate refractory metal oxide support, the first population of platinum group metal particles is dispersed on a first refractory metal oxide support, the second population of platinum group metal particles is dispersed on a second refractory metal oxide support, and the first refractory metal oxide support and the second refractory metal oxide support are each independently selected. In some embodiments, both the first refractory metal oxide support and the second refractory metal oxide support comprise the same refractory metal oxide support material. In some embodiments, the refractory metal oxide support material comprises TiO2 or TiO2 doped with SiO2.

[0018] In another aspect, the oxidation catalyst article comprises a substrate having an inlet end and an outlet end defining a total length, and a catalyst coating comprising one or more washcoats disposed thereon, wherein at least one of the washcoats comprises an oxidation catalyst composition as disclosed herein.

[0019] In some embodiments, the substrate is a flow-through monolith or a wall-flow filter.

[0020] In some embodiments, the oxidation catalyst article is a diesel oxidation catalyst article. In some embodiments, the plurality of platinum group metal particles are disposed on the substrate at a loading of from about 5 g / ft 3 to about 200 g / ft 3 .

[0021] In some embodiments, the oxidation catalyst article is a catalytic soot filter article. In some embodiments, the plurality of platinum group metal particles are disposed on the substrate at a loading of from about 0.5 g / ft 3 to about 30 g / ft 3 .

[0022] In some embodiments, the oxidation catalyst article is aged at 650°C for 5 hours, then yields 1.7 g / ft 3 When placed on a 1-inch x 3-inch flow-through substrate with a platinum group metal filling and exposed to a feed gas containing 600 ppm NO, 10% O2, 5% CO2, 5% H2O, and 33 ppm propane at a temperature of 350°C and a space velocity of 50,000 rpm, the sample yielded approximately 40% to approximately 55% NO2 / NO2. x Shows the ratio.

[0023] In some embodiments, the oxidation catalyst article is degraded at 550°C for 5 hours, followed by the first NO2 / NO X It has a ratio, and after aging at 650°C for 5 hours, the second NO2 / NO X It has a ratio, and the second NO2 / NO x The ratio is 1.7 g / ft of oxidation catalyst material. 3 When placed on a 1-inch x 3-inch flow-through substrate with a platinum group metal filling and exposed to a feed gas containing 600 ppm NO, 10% O2, 5% CO2, 5% H2O, and 33 ppm propane at a temperature of 350°C and a space velocity of 50,000 per hour, the first NO2 / NO2 mixture is produced. x The ratio is at least approximately 80%.

[0024] In another embodiment, the exhaust gas treatment system includes an oxidation catalyst article as disclosed herein, which is located downstream of the internal combustion engine and is in fluid communication with the internal combustion engine. In some embodiments, the exhaust gas treatment system includes a urea injector, a selective catalytic reduction (SCR) catalyst, and an ammonia oxidation (AMO) catalyst. x ) Catalyst, low temperature NO X Adsorbent (LT-NA), and lean NO x Further includes one or more catalyst articles selected from the trap (LNT).

[0025] In another embodiment, hydrocarbons, carbon monoxide, and / or NO xA method for treating an exhaust gas stream is provided, comprising passing the exhaust gas stream through a catalytic article or exhaust gas treatment system as disclosed herein. In some embodiments, the exhaust gas stream is hydrocarbons and carbon monoxide, hydrocarbons and NO x , or carbon monoxide and NO x Includes.

[0026] These and other features, aspects, and advantages of the Disclosure will become apparent upon reading the following detailed description together with the accompanying drawings, which are briefly described below. The Disclosure includes any combination of two, three, four, or more of the embodiments described above, and any combination of two, three, four, or more features or elements described herein, whether or not such features or elements are expressly combined in the description of the specific embodiments herein.

[0027] To provide an understanding of embodiments of this disclosure, accompanying drawings are referenced, the reference numbers of which point to components of exemplary embodiments of this disclosure. The drawings are illustrative only and should not be construed as limiting to this disclosure. The disclosures described herein are illustrated in the accompanying drawings as examples, not as limitations. For the sake of brevity and clarity, the features illustrated in the drawings are not necessarily drawn to a constant scale. Furthermore, where appropriate, reference marks are repeated between the drawings to indicate corresponding or similar elements. [Brief explanation of the drawing]

[0028] [Figure 1] A perspective view of a honeycomb substrate, which may contain a catalyst (i.e., a selective catalytic reduction catalyst) washcoat composition according to several exemplary embodiments, is depicted. [Figure 2] A cross-sectional view of an exemplary wall flow filter substrate is depicted. [Figure 3A] A cross-sectional view of an exemplary embodiment of a layered catalyst article is depicted. [Figure 3B]A cross-sectional view of an exemplary embodiment of a zoned catalyst article is depicted. [Figure 3C] A cross-sectional view of exemplary embodiments of layered and zoned catalyst articles is depicted. [Figure 4] A description of an emissions treatment system, including an exemplary diesel oxidation catalyst article, is presented. [Figure 5] This describes the NO2 generation and decomposition in an exemplary embodiment. [Figure 6] The decomposition of NO2 at various temperatures is described for exemplary embodiments. [Figure 7] The NO oxidation performance of an exemplary embodiment is described. [Figure 8] The changes in NO oxidation performance are described for exemplary degraded and aged embodiments. [Figure 9] The oxidizing performance of hydrocarbons and carbon monoxide is described for exemplary degraded and aged embodiments. [Figure 10] This paper describes the changes in NO oxidation performance for exemplary degraded and aged embodiments across multiple engine test cycles.

[0029] Disclosed herein are catalysts, catalytic articles, and one or more exhaust gas components (e.g., CO, hydrocarbons, and NO). x This is a catalyst system comprising such a catalyst article suitable for the oxidation of ). In some embodiments, there are catalysts comprising multiple platinum group metal particles having a multimodal particle size distribution and exhibiting enhanced stability with respect to oxidation performance after degradation and / or aging compared to conventional oxidation catalysts.

[0030] Definition: As used herein, the entity "a" or "an" refers to one or more such entities; for example, "a compound" refers to one or more compounds or at least one compound unless otherwise stated. Thus, the terms "a" (or "an"), "one or more," and "at least one" are used synonymously herein.

[0031] Any ranges cited herein are inclusive. The term “about” used throughout is used to represent and describe small variations. For example, “about” may mean that a number can be modified by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1%, or ±0.05%. A number modified by the term “about” includes a specific identified value. For example, “about 5.0” includes 5.0.

[0032] The term "reduction" means a decrease in quantity caused by any means.

[0033] The term “associated” means, for example, “equipped with,” “connected to,” or “communicating with,” for example, “electrically connected,” or “fluidly connected to,” or otherwise connected in a way that performs a function. The term “associated” can mean being directly associated, or being indirectly associated, for example, through one or more other articles or elements.

[0034] The term "catalyst" refers to a material that facilitates a chemical reaction. A catalyst includes a "catalytically active species" and a "carrier" that carries or supports the active species. For example, refractory metal oxide particles can be carriers for platinum group metal catalyst species.

[0035] In this disclosure, the term "catalyst article" means an article comprising a substrate having a catalyst coating composition.

[0036] As used herein, the phrase “catalytic soot filter” refers to a wall-flow monolith. A wall-flow filter consists of alternating inlet and outlet channels, with the inlet channel inserted over the outlet end and the outlet channel inserted over the inlet end. The exhaust gas flow carrying soot entering the inlet channel is forced to pass through the filter wall before exiting through the outlet channel. In addition to filtering and regenerating soot, a catalytic soot filter may carry an oxidation catalyst, oxidizing CO and hydrocarbons to CO2 and H2O, or NO to NO2, to accelerate a downstream SCR catalyst or promote the oxidation of soot particles at lower temperatures. SCR catalyst compositions may also be coated directly onto a wall-flow filter, which is called an SCRoF.

[0037] As used herein, the phrase “catalytic system” means a combination of two or more catalysts, for example, a first low-temperature NO x This refers to a combination of an adsorbent (LT-NA) catalyst and a second catalyst, which may be a diesel oxidation catalyst, LNT, or SCR catalyst article. Alternatively, the catalyst system may take the form of a washcoat, where the two catalysts are mixed together or coated in separate layers.

[0038] As used in descriptions and claims, the term “configured” is intended to be unrestrictive, as is the term “includes” or “contains.” The term “configured” is not intended to exclude other possible articles or elements. The term “configured” may be equivalent to “adapted.”

[0039] As used herein, “diesel oxidation catalyst” converts hydrocarbons and carbon monoxide in the exhaust gas of a diesel engine, and oxidizes nitric oxide (NO) to nitrogen dioxide (NO2). For example, a diesel oxidation catalyst may comprise one or more platinum group metals such as palladium and / or platinum, a carrier material such as alumina, a zeolite for hydrocarbon storage, and optionally, an accelerator and / or stabilizer.

[0040] Generally, the term "effective" means that, for example, in weight ratio or molar ratio, it is effective at approximately 35% to 100% with respect to the defined catalytic activity or storage / release activity, for example, at approximately 40%, 45%, 50%, or 55% to 60%, 65%, 70%, 75%, 80%, 85%, 90%, or 95%.

[0041] The term “exhaust flow” or “exhaust gas flow” refers to any combination of flowing gases that may contain solid or liquid particulate matter. The flow may be the exhaust of a lean-burn engine, containing gaseous components and certain non-gaseous components such as droplets, solid particles, and equivalents. The exhaust gas flow of a combustion engine contains combustion products (CO2 and H2O), products of incomplete combustion (carbon monoxide (CO) and hydrocarbons), and nitrogen oxides (NOx). x ), flammable and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen may further be included. As used herein, the terms “upstream” and “downstream” refer to the relative direction according to the flow of engine exhaust gases from the engine to the tailpipe, with the engine in the upstream position and the tailpipe and any contamination mitigation articles such as filters and catalysts in the downstream position. The inlet end of the substrate is synonymous with the “upstream” end or “front” end. The outlet end is synonymous with the “downstream” end or “rear” end. The upstream zone is upstream of the downstream zone. The upstream zone may be closer to the engine or manifold, and the downstream zone may be further away from the engine or manifold.

[0042] The term "fluid communication" is used to refer to articles located on the same exhaust line, i.e., a common exhaust flow passes through articles that are in fluid communication with each other. Fluid-communicating articles may be adjacent to each other within the exhaust line. Alternatively, fluid-communicating articles may be separated by one or more articles, also referred to as a "washcoat monolith."

[0043] The term “functional article” in this disclosure means an article comprising a substrate having a functional coating disposed thereon, such as a catalyst and / or adsorbent coating composition.

[0044] As used herein, “impregnated” or “impregnated” refers to the penetration of a catalyst material into the porous structure of a carrier material.

[0045] As used herein, "LNT" refers to platinum group metals, ceria, and NO during lean conditions. x Lean NO is a catalyst containing an alkaline earth trapping material (e.g., BaO or MgO) suitable for adsorbing. x It refers to a trap. Under abundant conditions, NO x However, it is released and reduced to nitrogen.

[0046] As used herein, "nitrogen oxides" or "NO x The term "nitrogen oxides" refers to nitrogen oxides such as NO, NO2, or N2O.

[0047] The terms “on” and “above” in relation to coating layers may be used as synonyms. The term “directly on” means in direct contact. In certain embodiments, the disclosed articles are indicated to include one coating layer “on” a second coating layer, and such wording is intended to encompass embodiments involving intervening layers where direct contact between coating layers is not required (i.e., “on” is not equivalent to “directly on”).

[0048] As used herein, the term “enhanced” refers to components that are intentionally added to the molecular sieve material, for example, through ion exchange, as opposed to impurities inherent in the molecular sieve.

[0049] As used herein, the term “selective catalytic reduction” (SCR) refers to a catalytic process that uses a nitrogenous reducing agent to reduce nitrogen oxides to dinitrogen (N2).

[0050] "Substantially absent" means "almost none or none at all" or "not intentionally added," and also allows for only trace and / or accidental amounts. For example, in certain embodiments, "substantially absent" means less than 2% by weight (wt%, weight%), less than 1.5% by weight, less than 1.0% by weight, less than 0.5% by weight, 0.25% by weight, or less than 0.01% by weight, based on the total weight of the composition shown.

[0051] As used herein, the term “substrate” refers to a monolithic material on which a catalyst composition, i.e., a catalyst coating, is disposed, for example, in the form of a wash coat. In one or more embodiments, the substrate is a flow-through monolith and a monolithic wall-flow filter. Flow-through and wall-flow substrates are also taught, for example, in International Patent Application Publication No. 2016 / 070090, which is incorporated herein by reference. A wash coat is formed by preparing a slurry containing a specific solid content (e.g., 30–90 wt%) of catalyst in a liquid, then coating this onto the substrate and drying to provide a wash coat layer. The reference to “monolithic substrate” means a single structure that is homogeneous and continuous from inlet to outlet. A wash coat is formed by preparing a slurry containing a specific solid content (e.g., 20–90 wt%) of particles in a liquid vehicle, then coating this onto the substrate and drying to provide a wash coat layer.

[0052] As used herein, the term “carrier” refers to any high-surface-area material, typically a refractory metal oxide material, to which the catalytic noble metal is applied.

[0053] As used herein, the term “washcoat” has its usual meaning in the art of a thin, adhesive coating of a catalyst or other material applied to a substrate material, such as a honeycomb substrate, which is sufficiently porous to allow the passage of the gas flow being treated. Washcoats containing platinum group metal particles may optionally contain a binder selected from silica, alumina, titania, zirconia, ceria, or a combination thereof. The amount of binder filling is about 0.1 to 10% by weight, based on the weight of the washcoat. As used herein and as described in Heck, Ronald and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp. 18-19, the washcoat layer includes a monolithic substrate or a layer of material compositionally distinct from the underlying washcoat layer, placed on the surface. The substrate may contain one or more wash coat layers, each wash coat layer may differ in some respect (e.g., its physical properties such as particle size) and / or its chemical catalytic function may differ.

[0054] "Weight percentage (W%)" is based on the entire composition excluding any volatile substances, i.e., on the dry solids content, unless otherwise specified. Unless otherwise specified, all parts and proportions are by weight.

[0055] As used herein, “space velocity” is the number of volumes of gas or liquid that pass through or exceed one unit volume (e.g., as a catalyst) per unit time.

[0056] A selective catalytic reduction catalyst is a catalyst capable of selectively reducing nitrogen oxides.

[0057] An ammonia oxidation catalyst is a catalyst capable of oxidizing ammonia.

[0058] Low-temperature NOx adsorbents absorb NOx at low temperatures typically associated with the cold start period of diesel engines, and release the absorbed NOx at high temperatures typically associated with more efficient reduction by selective catalytic reduction catalysts.

[0059] All methods described herein may be carried out in any preferred order, unless otherwise indicated herein or otherwise clearly contradicted by the context. The use of any examples or illustrative language provided herein (e.g., "etc.") is intended solely to better illustrate the materials and methods and does not impose any limitation on their scope unless otherwise requested. Nothing in this specification should be construed as indicating that any unclaimed element is essential to the practice of the disclosed materials and methods. All U.S. patent applications, pre-grant publications, and patents referenced herein are incorporated herein by reference in their entirety.

[0060] Oxidation catalyst composition In one embodiment, the oxidation catalyst composition comprises a plurality of platinum group metal particles having a multimodal particle size distribution, wherein the plurality of platinum group metal particles comprises a first group of platinum group metal particles having a particle size range of about 0.5 to about 3 nm and a second group of platinum group metal particles having a particle size range of about 4 to about 15 nm.

[0061] Platinum group metals (PGM) Platinum group metals include platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), and mixtures thereof. Platinum group metals can be in a metallic form with zero valency, or they can be in an oxide form. In some embodiments, platinum group metals are metals or their oxides (including, but not limited to, platinum or its oxides). Advantageously, platinum group metals are in a substantially completely reduced form, meaning that at least about 90% of the platinum group metal content is reduced to a metallic form (platinum group metal (0)). In some embodiments, the amount of platinum group metals in a completely reduced form is even higher, for example, at least about 92%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% of the platinum group metals are in a completely reduced form. The amount of platinum group metal (0) can be determined using ultrafiltration followed by inductively coupled plasma / emission spectroscopy (ICP-OES) or X-ray photoelectron spectroscopy (XPS).

[0062] In some embodiments, the platinum group metals include platinum, palladium, ruthenium, rhodium, iridium, or combinations thereof. Exemplary weight ratios of such Pt / Pd combinations include Pt:Pd weight ratios ranging from approximately 1:10 to approximately 10:1, such as Pt:Pd of about 1:1 or greater, Pt:Pd of about 1.5:1 or greater, or Pt:Pd of about 2:1 or greater. In certain embodiments, the platinum group metal is Pd. In certain embodiments, the platinum group metal is Pt.

[0063] The concentration of platinum group metals (e.g., Pt and / or Pd) present in the oxidation catalyst composition may vary, but can range from about 1% to about 10% by weight relative to the weight of the composition.

[0064] PGM particles Platinum group metal particles are particles containing one or more platinum group metals. The size of platinum group metal particles in catalyst compositions such as those disclosed herein can vary. As disclosed herein, an oxidation catalyst composition contains a plurality of platinum group metal particles having a multimodal particle size distribution.

[0065] As used herein, “particle size” refers to the smallest diameter sphere that completely encloses a particle, and this measurement relates to individual particles, as opposed to aggregations of two or more particles. Particle size can be measured, for example, by laser light scattering techniques using dispersed or dried powder, according to ASTM method D4464. Particle size can also be measured by scanning electron microscopy (SEM) or transmission electron microscopy (TEM) for submicron-sized particles, or by particle size analyzer for carrier-containing particles (micron size).

[0066] In addition to TEM, carbon monoxide (CO) chemiadsorption can be used to determine the average particle size. This technique may not distinguish between various platinum group metal species (e.g., Pt, Pd, etc., compared to XRD, TEM, and SEM) and only determines the average particle size. To determine the average particle size by CO chemiadsorption, a sample of the catalyst washcoat was pulverized, and a small amount (approximately 100 mg) was analyzed using pulsed CO implantation as follows: pretreatment: drying at 150°C in helium, followed by heating at 400°C in 5% hydrogen in a nitrogen atmosphere; CO chemiadsorption: the sample was pulsed at room temperature using 10% CO in helium.

[0067] As used herein, “particle size distribution” defines the relative quantity of particles in a population of particles having a particle size within a given range.

[0068] As used herein, “multimodal particle size distribution” refers to a continuous probability distribution with two or more modes that appear as two or more distinctly different peaks (maxima) in the probability density function. This can be visualized by plotting the frequency against the logarithm of the particle size of the particle population. The distribution and proportion of particle sizes within a specific size range can be determined, for example, by coating a substrate with calcined supported platinum group metal particles using TEM or SEM. For example, calcined supported platinum group metal particles on a substrate can be analyzed directly by TEM or SEM (viewing the coated substrate), or by scraping or otherwise removing at least a portion of the calcined supported platinum group metal particles from the substrate and obtaining an image of the scraped / removed supported platinum group metal particles.

[0069] In some embodiments, the plurality of platinum group metal particles comprises a first group and a second group of platinum group metal particles having different size ranges. In some embodiments, the plurality of platinum group metal particles comprises a first group having a particle size range of about 0.5 nm to about 3 nm and a second group having a particle size range of about 4 nm to about 15 nm. In some embodiments, the second group of platinum group metal particles may be colloidal platinum group metal particles.

[0070] In some embodiments, a first group of platinum group metal particles and a second group of platinum group metal particles each have an average particle size. In some embodiments, the first group of platinum group metal particles has an average particle size of about 1 nm. In some embodiments, the second group of platinum group metal particles has an average particle size of about 6 nm.

[0071] As used herein, the term “average particle size” refers to a particle characteristic that indicates the average diameter of the particles. 50 This is synonymous with meaning that half of the particles in the collection have a particle size above this point, and the other half have a particle size below it. 90The particle size distribution indicates that 90% (by number) of the particles have a ferret diameter below a certain size. The average particle size can be measured, for example, by transmission electron microscopy (TEM), by visually examining the TEM image, measuring the diameter of the particles in the image, and calculating the average particle size of the measured particles based on the magnification of the TEM image.

[0072] References to average particle size in this specification reflect the average particle size of fresh and / or calcined material, determined, for example, after calcination of the particles but before aging of the particles. "Fresh" means that the particles have not been exposed to temperatures above about 500°C. In some embodiments, the oxidation catalyst composition is fresh. In other embodiments, the oxidation catalyst composition may be referred to as degraded. As used herein, the term "degraded" refers to a catalyst composition that has been exposed to temperatures of about 500–550°C for a period of time (e.g., about 1–5 hours) using engine exhaust or simulated exhaust gas. In some embodiments, the oxidation catalyst composition may be referred to as aged. As used herein, the term "aged" refers to a catalyst composition that has been exposed to temperatures of about 650°C or higher (e.g., about 650°C, 700°C, 800°C, 900°C, or 1000°C) for a period of time (e.g., about 5 hours to about 100 hours, or about 100 hours to about 1000 hours). As will be recognized by those skilled in the art, exposure of platinum group metal particles to degradation or aging conditions can induce changes in particle size as described above herein.

[0073] In some embodiments, the particle population may be characterized in that at least 80% of the particles have a particle size within 50 percent, 20 percent, 15 percent, 10 percent, or 5 percent of the average particle size of the particle population (i.e., at least 80% of all particles in the population have a particle size within a given percentage range of the average particle size). In other embodiments, at least 85%, 90%, 95%, 96%, 97%, 98%, or 99% of all particles fall within these ranges. In some embodiments, the particle population includes particles in which at least 80% of the particles have a particle size within approximately 1 nm of the average particle size, or within approximately 2 nm of the average particle size.

[0074] In some embodiments, a first population of platinum group metal particles has a particle size distribution characterized by an average particle size of about 1 nm, and at least 80% (or at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) of the first population of platinum group metal particles have a particle size within 1 nm of the average particle size, for example, in the range of about 0.001 nm, about 0.01 nm, or about 0.1 nm to about 2 nm.

[0075] In some embodiments, the second population of platinum group metal particles has a particle size distribution characterized by an average particle size of about 6 nm, and at least about 80% (or at least 85%, 90%, 95%, 96%, 97%, 98%, 99%, or 100%) of the second population of platinum group metal particles have particle sizes within about 2 nm of the average particle size, for example, in the range of about 4 nm, about 5 nm, about 6 nm, about 7 nm, or about 8 nm.

[0076] The relative amounts of the two groups of platinum group metal particles can vary. In some embodiments, the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 10:90 to about 90:10. In some embodiments, the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 50:50 to about 90:10. In some embodiments, the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 50:50 to about 75:25.

[0077] The average particle size of multiple platinum group metal particles (i.e., the overall average size of the particles in two combined populations) can vary depending on both the ratio of the two populations and the average size of the particles within each population. In some embodiments, the multiple platinum group metal particles have an average particle size of about 3 to about 12 nm, for example, about 3 to about 10 nm, about 3 to about 8 nm, about 3 to about 6 nm, or about 3 to about 5 nm.

[0078] Fire-resistant metal oxide support material In some embodiments, the oxidation catalyst composition further comprises at least one refractory metal oxide support material. As used herein, “refractory metal oxide” refers to a porous metal-containing oxide material that exhibits chemical and physical stability at high temperatures, such as those associated with diesel engine exhaust. Exemplary refractory oxides include alumina, silica, zirconia, titania, ceria, and physical mixtures or chemical combinations thereof, including atomically doped combinations and containing high surface area or activated compounds such as activated alumina. Exemplary aluminas include large-pore boehmite, gamma-alumina, and delta / theta-alumina. Useful commercially available aluminas include high-bulk-density gamma-alumina, low- or medium-bulk-density large-pore gamma-alumina, and activated aluminas such as low-bulk-density large-pore boehmite and gamma-alumina.

[0079] High-surface-area refractory oxide supports, such as alumina support materials, also known as "gamma alumina" or "activated alumina," have a surface area of ​​60m². 2 In most cases, exceeding / g, up to approximately 200m 2 It can exhibit a BET surface area of ​​60-350 m² / g or more. Such activated alumina is usually a mixture of the gamma and delta phases of alumina, but may also contain substantial amounts of eta, kappa, and theta alumina phases. "BET surface area" has its usual meaning referring to the Brunauer, Emmett, Teller method for determining surface area by N2 adsorption. In some embodiments, the activated alumina may have a BET surface area of ​​60-350 m² / g or more.2 / g, in some embodiments, 90-250m 2 It has a specific surface area of ​​ / g.

[0080] In some embodiments, the refractory metal oxides include alumina (Al2O3), silica (SiO2), zirconia (ZrO2), titania (TiO2), ceria (CeO2), or combinations thereof. The combinations may be in the form of physical or chemical mixtures. Mixed metal oxides include, but are not limited to, zirconia-alumina, ceria-zirconia, ceria-alumina, lantana-alumina, barrier-alumina, and silica-alumina.

[0081] In certain embodiments, metal oxide supports useful in the oxidation catalyst compositions disclosed herein are doped alumina materials such as Si-doped trialumina materials (containing 1-10% SiO2-Al2O3, but not limited thereto), doped titania materials such as Si-doped titania materials (containing 1-10% SiO2-TiO2, but not limited thereto), or doped zirconia materials such as Si-doped ZrO2 (containing 5-30% SiO2-ZrO2, but not limited thereto). Thus, in some embodiments, at least one refractory metal oxide support comprises SiO2-doped Al2O3, SiO2-doped TiO2, and / or SiO2-doped ZrO2.

[0082] The oxidation catalyst composition may contain any of the above-mentioned refractory metal oxides in any amount. For example, the refractory metal oxide in the catalyst composition may contain about 15% by weight, about 20% by weight, about 25% by weight, about 30% by weight, about 35% by weight, about 40% by weight, about 45% by weight, or about 50% to about 55% by weight, about 60% by weight, about 65% by weight, about 70% by weight, about 75% by weight, about 80% by weight, about 85% by weight, about 90% by weight, about 95% by weight, or about 99% by weight. The catalyst composition may contain, for example, about 10 to 99% by weight of TiO2 or SiO2-doped TiO2, about 15 to 95% by weight of TiO2 or SiO2-doped TiO2, or about 20 to 85% by weight of TiO2 or SiO2-doped TiO2.

[0083] In some embodiments, both a first group of platinum group metal particles and a second group of platinum group metal particles are dispersed on the same refractory metal oxide carrier. In some embodiments, the first group of platinum group metal particles and the second group of platinum group metal particles are dispersed on separate refractory metal oxide carriers, where the first group of platinum group metal particles is dispersed on a first refractory metal oxide carrier and the second group of platinum group metal particles is dispersed on a second refractory metal oxide carrier, where the first and second refractory metal oxide carriers are selected independently.

[0084] In some embodiments, the first refractory metal oxide support and the second refractory metal oxide support are two different refractory metal oxide materials (for example, in a non-limiting example, the first refractory metal oxide support may be alumina and the second refractory metal oxide support may be titania). In some embodiments, both the first and second refractory metal oxide support comprise the same refractory metal oxide support material. In some embodiments, both the first and second refractory metal oxide support comprise TiO2 or TiO2 doped with SiO2.

[0085] Platinum group metal particles are dispersed on a refractory metal oxide support. Oxidation catalyst compositions such as those disclosed herein may comprise one or more carrier materials, for example, a refractory metal oxide carrier and two groups of platinum group metal particles associated with it. The method for dispersing the platinum group metal particles on the refractory metal oxide carrier may vary, for example, depending on the size range of the platinum group metal particles.

[0086] In some embodiments, a first population of platinum group metal particles having a particle size range of about 0.5 to about 3 nm is dispersed on a refractory metal oxide support. In some embodiments, such supported particles are prepared by impregnating a refractory metal oxide support material in particulate form with a platinum group metal precursor solution, such as an aqueous solution of a water-soluble platinum group metal compound or complex, such as palladium or platinum, in the form of nitrates, acetates, tetraammine complexes (e.g., nitrate chlorides, acetates, and equivalents), or combinations thereof. After impregnation and drying, calcination is optionally performed to convert the platinum group metal compound into a more catalytically active zero-valent form. Multiple platinum group metals (e.g., platinum and palladium) can be impregnated simultaneously or separately, for example, by using an initial wetting technique to impregnate the same refractory metal oxide support particles or separate refractory metal oxide support particles.

[0087] The initial wet impregnation technique, also known as capillary impregnation or dry impregnation, is commonly used in the synthesis of such dissimilar materials, i.e., catalysts. In some embodiments, an aqueous solution of a platinum group metal compound is added to a refractory metal oxide carrier containing the same pore volume as the volume of the added solution. Capillary action draws the solution into the pores of the refractory metal oxide carrier. If the solution is added beyond the carrier pore volume, the solution transport may shift from a capillary process to a much slower diffusion process. In some embodiments, the carrier particles are sufficiently dry to absorb substantially all of the solution and form a wet solid.

[0088] In some embodiments, the impregnated refractory metal oxide support can then be dried by heat-treating the particles at a high temperature (e.g., 100-150°C) for a set period of time (e.g., 1-3 hours) to expel volatile components in the solution, and then calcined to convert the platinum group metal components into a more catalytically active form, depositing the active platinum group metals onto the surface of the refractory metal oxide support. An exemplary calcination process involves heat treatment in air at a temperature of approximately 400-550°C for 0.5-3 hours. The maximum filling amount may be limited by the solubility of the precursor in the solution. The concentration profile of the impregnated material may depend on the mass transfer conditions in the pores during impregnation and drying. The above process can be repeated as needed to achieve the desired level of platinum group metal impregnation.

[0089] In some embodiments, a second population of platinum group metal particles having a particle size range of about 4 to about 15 nm is dispersed on a refractory metal oxide support. Dispersion can be achieved during the production of the platinum group metal particles (direct dispersion) and / or after the production of the platinum group metal particles (subsequent dispersion). Each method is outlined below in this specification.

[0090] Direct dispersion on a carrier material In some embodiments, platinum group metal particles can be dispersed on a refractory metal oxide support material during the production of platinum group metal particles. One exemplary method for producing platinum group metal particles in a desired size range (e.g., about 4 to about 15 nm) is described in International Patent Application Publication 2016 / 057692, which is incorporated herein by reference in its entirety. Briefly, as disclosed herein, a platinum group metal precursor (e.g., a salt of a platinum group metal) is combined with a dispersion medium and a polymer suspension stabilizer, and the resulting solution is combined with a reducing agent to provide a platinum group metal particle colloidal dispersion. To disperse platinum group metal particles on a refractory metal oxide support material, the refractory metal oxide support material can be added to the dispersion at any stage of the process (e.g., together with the platinum group metal precursor or together with the reducing agent) so that the particles can be dispersed on the refractory metal oxide support material. Prior to this addition, the dispersion of platinum group metal particles can be optionally concentrated or diluted. Exemplary methods for impregnating a carrier with a colloidal platinum group metal material are described in US2017 / 0304805 by Xu et al. and US2019 / 0015781 by Wei et al., both of which are incorporated herein by reference in their entirety.

[0091] In some embodiments, platinum group metal particles are isolated and then dispersed on a refractory metal oxide support material. Methods for isolating particles from a dispersion are generally known, and in some embodiments, isolated platinum group metal particles can be obtained by heating the dispersion containing the particles and / or applying a vacuum thereto, or by otherwise treating the dispersion to ensure the removal of at least a large portion of the solvent therefrom. Following the isolation of the platinum group metal particles, the platinum group metal particles and the refractory metal oxide support can be mixed (e.g., with water) to form a dispersion in which the platinum group metal particles can be dispersed on the refractory metal oxide support material. Such methods for providing a dispersion on a refractory metal oxide support material after the formation of platinum group metal particles are generally described as an initial wetting technique. This process may be repeated several times to achieve a target platinum group metal concentration on the support.

[0092] Colloidal platinum group metals (e.g., platinum) can be prepared from platinum group metal precursors by reduction, as described above. In some embodiments, the platinum group metal precursor can be selected from ammine complex salts, hydroxyl salts, nitrates, carboxylates, ammonium salts, and oxides (e.g., selected from Pt(NH3)4(OH)2, Pt nitrate, Pt citrate, and equivalents).

[0093] The reducing agent can be any reagent effective for reducing platinum group metals to their metallic (platinum group metal (0)) form and is favorably soluble in a dispersion medium (e.g., water-soluble). In certain embodiments, the reducing agent may be an organic reducing agent, but is not limited thereto. Suitable reducing agents include, for example, hydrogen, hydrazine, urea, formaldehyde, formic acid, ascorbic acid, citric acid, glucose, sucrose, xylitol, mesoerythritol, sorbitol, glycerol, maltitol, or oxalic acid. Furthermore, monohydric alcohols from the group including methanol, ethanol, 1-propanol, isopropanol, 1-butanol, 2-butanol, 2-methylpropan-1-ol, allyl alcohol, and diacetone alcohol, as well as mixtures and combinations thereof, may be employed. Even more preferred liquid reducing agents are dihydric alcohols such as ethylene glycol, propylene glycol, diethylene glycol, tetraethylene glycol, or dipropylene glycol. Other reducing agents include hydrazine-based reducing agents such as formic acid hydrazide and hydroxyethylhydrazine, as well as natural plant-based polyphenolic acids such as tannic acid and garlicic acid. In some embodiments, the reducing agent is ascorbic acid. The reducing agent may be present in the dispersion in an amount of about 1 to 10% by weight.

[0094] The dispersion medium may be at least one polar solvent selected from, for example, water, alcohol (including polyols), dimethylformamide (DMF), and combinations thereof. In some embodiments, the alcohol may be selected from methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butanol, hexanol, octanol, and combinations thereof. In some embodiments, the polyol may be selected from glycerol, glycol, ethylene glycol, diethylene glycol, triethylene glycol, butanediol, tetraethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentadiol, 1,2-hexadiol, and combinations thereof. In some embodiments, the dispersion medium includes water. In some embodiments, the dispersion medium is an aqueous colloidal dispersion.

[0095] The stabilizer may be a polymer suspension stabilizer that is soluble in the dispersion medium and / or used to improve the dispersion of platinum group metal particles (for example, if the dispersion medium contains water, the stabilizer may be a water-soluble polymer suspension stabilizer). The composition and size of the polymer (e.g., weight-average molecular weight, M) are also important. w ) can vary. In some embodiments, the polymer has a M of 10,000 to 60,000 Da. w M2,000-2,000,000 Da (measured using gel permeation chromatography (GPC)) w The polymers have the following properties. Suitable polymers include, for example, polyvinylpyrrolidone (PVP), copolymers containing vinylpyrrolidone as the first polymerization unit, and fatty acid-substituted or unsubstituted polyoxyethylenes. Polyvinylpyrrolidone may be useful as a polymer suspension stabilizer. The polymer suspension stabilizer may be present in an amount of about 0.1 to 20 parts by weight, such as about 5 to 10 parts by weight, based on 100 parts by weight of the dispersion medium.

[0096] In some embodiments, a refractory metal oxide support material dispersed with platinum group metal particles is then dried at a high temperature (e.g., 100-150°C) for a certain period (e.g., 1-3 hours). Optionally, the refractory metal oxide support material dispersed with platinum group metal particles is calcined to remove volatile components. An exemplary calcination process involves heat treatment in air at a temperature of approximately 400-550°C for 1-3 hours. The above process can be repeated as needed to achieve the desired level of impregnation.

[0097] In some embodiments, two groups of platinum group metal particles may be dispersed on the same refractory metal oxide carrier, or on separate refractory metal oxide carrier materials which may have the same or different compositions. In embodiments in which two groups of platinum group metal particles are dispersed on the same refractory metal oxide carrier material, the dispersion may be carried out sequentially in any order (e.g., impregnation with a platinum group metal solution followed by colloidal platinum group metal impregnation, or colloidal platinum group metal impregnation followed by impregnation with a platinum group metal solution). Furthermore, after the dispersion of each platinum group metal, calcination, grinding, both, or neither may be carried out.

[0098] catalyst article In another embodiment, the oxidation catalyst article comprises a substrate having an inlet end and an outlet end defining its overall length, and a catalyst coating disposed on at least a portion thereof, comprising an oxidation catalyst composition as disclosed herein.

[0099] Base material In some embodiments, the oxidation catalyst composition is placed on a substrate to form a catalyst article. The catalyst article, including the substrate, can be employed as part of an exhaust gas treatment system (for example, catalyst articles include, but are not limited to, articles containing the oxidation catalyst compositions disclosed herein). In some embodiments, the useful substrate is three-dimensional, having length, diameter, and volume, similar to a cylinder. The shape does not necessarily have to match a cylinder. In some embodiments, the length is the axial length defined by the inlet and outlet ends.

[0100] In some embodiments, the substrate for the disclosed composition may consist of any material typically used to prepare automotive catalysts and may include a metal or ceramic honeycomb structure. In some embodiments, the substrate may provide a plurality of wall surfaces to which the washcoat composition is applied and adhered, thereby acting as a substrate for the catalyst composition.

[0101] The ceramic substrate may be made from any suitable refractory material, such as cordierite, cordierite-α-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon mullite, scia pyroxene, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, feldspar, α-alumina, aluminosilicate, and equivalents.

[0102] The substrate may also be metal, comprising one or more metals or metal alloys. Metal substrates may include any metal substrate, such as those having openings or "punchouts" in the channel walls. Metal substrates may be employed in various forms, such as pellets, compressed metal fibers, corrugated sheets, and monolithic forms. Specific examples of metal substrates include heat-resistant base metal alloys, in particular those in which iron is substantial or the main component. Such alloys may contain one or more of nickel, chromium, and aluminum, and the sum of these metals may, advantageously, on the weight of the substrate in each case, contain at least about 15 wt% (weight percent) of the alloy, e.g., about 10 to about 25 wt% of chromium, about 1 to about 8 wt% of aluminum, and 0 to about 20 wt% of nickel. Examples of metal substrates include those having linear channels, those having blades protruding along the axial channels to obstruct gas flow and open communication of gas flow between channels, and those also having holes to improve gas transport between channels, allowing radial gas transport across the blades and the entire monolith.

[0103] Any suitable substrate for the catalyst article disclosed herein may be employed, such as a monolithic substrate of the type having fine parallel gas channels extending through it from an inlet or outlet surface of the substrate ("flow-through substrate"), such that the channels are open to the fluid flow through them. Another exemplary substrate is of the type having a plurality of fine substantially parallel gas channels extending along the longitudinal axis of the substrate, where, for example, each channel may be blocked at one end of the substrate body and alternating channels may be blocked at the opposite end surface ("wall-flow filter"). Flow-through and wall-flow substrates are also taught, for example, in International Patent Application Publication No. 2016 / 070090, which is incorporated herein in its entirety by reference.

[0104] In some embodiments, the catalyst substrate includes a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate. In some embodiments, the substrate is a wall-flow filter. In some embodiments, the substrate is a flow-through substrate. Flow-through substrates and wall-flow filters are discussed further below herein.

[0105] Flow-through substrate In some embodiments, the substrate is a flow-through substrate (e.g., a monolithic substrate including a flow-through honeycomb monolithic substrate). The flow-through substrate has fine, parallel gas channels extending from the inlet end to the outlet end of the substrate, such that the channels are open to fluid flow. The channels, which may be essentially straight paths from their fluid inlets to their fluid outlets, are defined by walls on or within them, where a catalyst coating is positioned so that the gas flowing through the channels comes into contact with the catalyst material. The channels of the flow-through substrate may be thin-walled channels, which may be any preferred cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, or circular. The flow-through substrate may be ceramic or metal, as described above.

[0106] Flow-through substrates are, for example, about 50 inches. 3 ~About 1200in3 It can have a volume of approximately 60 cells per square inch (cpsi) to approximately 500 cpsi, or up to 900 cpsi, for example, a cell density (inlet opening) of approximately 200 to 400 cpsi, and a wall thickness of approximately 50 to approximately 200 microns or approximately 400 microns.

[0107] Wall flow filter substrate In some embodiments, the substrate is a wall flow filter having a plurality of fine, substantially parallel gas channels extending along the longitudinal axis of the substrate. In some embodiments, each channel is blocked at one end of the substrate body, and alternating channels are blocked at the opposite end face. Such a monolithic wall flow filter substrate may contain up to about 900 or more channels (or “cells”) per square inch of cross-section. For example, the substrate may have about 7 to 600, more typically about 100 to 400 cells (“cpsi”) per square inch. The cells may have cross-sections that are rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal. The wall flow filter substrate may be ceramic or metal as described above.

[0108] Referring to Figure 1, an exemplary wall flow filter substrate has a cylindrical shape and a cylindrical outer surface having a diameter D and an axial length L. A cross-sectional view of the monolithic wall flow filter substrate is illustrated in Figure 2, showing alternating closed and open passages (cells). The closed or blocked ends 100 alternate with the open passages 101, with each opposing end being open and closed, respectively. The filter has an inlet end 102 and an outlet end 103. Arrows crossing the porous cell walls 104 represent exhaust gas flow entering the open cell end, diffusing through the porous cell walls 104, and exiting from the open outlet cell end. The closed ends 100 obstruct the gas flow and facilitate diffusion through the cell walls. Each cell wall has an inlet side 104a and an outlet side 104b. The passages are surrounded by cell walls.

[0109] The wall flow filter article substrate is, for example, about 50 cm 3Approximately 100 inches 3 Approximately 200 inches 3 , about 300in 3 Approximately 400 inches 3 Approximately 500 inches 3 Approximately 600 inches 3 Approximately 700 inches 3 Approximately 800 inches 3 Approximately 900 inches 3 , or about 1000in 3 ~About 1500in 3 Approximately 2000 in 3 , about 2500in 3 , about 3000in 3 , about 3500in 3 Approximately 4000 in 3 Approximately 4500 in 3 , or approximately 5000 in 3 The volume may be such that the wall flow filter substrate may have a wall thickness of approximately 50 microns to approximately 2000 microns, for example, approximately 50 microns to approximately 450 microns, or approximately 150 microns to approximately 400 microns.

[0110] The walls of a wall flow filter may be porous and may have at least about 40% or at least about 50% wall porosity with an average pore diameter of at least about 10 microns prior to the placement of the functional coating. For example, the wall flow filter article substrate in some embodiments may have a porosity of ≥40%, ≥50%, ≥60%, ≥65%, or ≥70%. For example, the wall flow filter article substrate may have a wall porosity of about 50%, about 60%, about 65%, or about 70% to about 75% prior to the placement of the catalyst coating, and an average pore diameter of about 10 microns or about 20 to about 30 microns or about 40 microns. The terms “wall porosity” and “substrate porosity” mean the same thing and are interchangeable. Porosity is the ratio of void volume (or pore volume) to the total volume of the substrate material. Pore diameter and pore diameter distribution can be determined, for example, by Hg porosimetry.

[0111] Substrate coating process In some embodiments, a substrate as described herein is coated with an oxidation catalyst composition as disclosed herein. The coating is a “catalytic coating composition” or “catalytic coating.” “Catalyst composition” and “catalytic coating composition” are synonyms.

[0112] In some embodiments, the catalyst composition is prepared as described herein and coated onto a substrate. In some embodiments, this method may include mixing the catalyst composition (or one or more components of the catalyst composition) as generally disclosed herein with a solvent (e.g., water) to form a slurry for the purpose of coating a catalyst substrate. In addition to the catalyst composition, the slurry may optionally contain a variety of additional components. Additional components may include, for example, binders as described above herein, such as additives for controlling the pH and viscosity of the slurry. Additional components may include hydrocarbon storage components (e.g., zeolites), associative thickeners, and / or surfactants (including anionic, cationic, nonionic, or amphoteric surfactants). An exemplary pH range for the slurry is about 3 to about 6. Addition of acidic or basic species to the slurry may be carried out to adjust the pH accordingly. For example, in some embodiments, the pH of the slurry is adjusted by the addition of aqueous acetic acid.

[0113] The slurry can be ground to reduce particle size and improve particle mixing and the formation of a homogeneous material. Grinding can be achieved with a ball mill, continuous mill, or other similar equipment, and the solid content of the slurry can be, for example, about 20-60% by weight or about 20-40% by weight. In some embodiments, the slurry after grinding has particles of about 1-40 microns, such as about 2-20 microns or about 4-15 microns. 90 It is characterized by its particle size.

[0114] In some embodiments, the oxidation catalyst composition may be applied in the form of one or more wash coats. A wash coat may be formed by preparing a slurry containing a specific solid content (e.g., about 10 to about 60 wt%) of the catalyst composition (or one or more components of the catalyst composition) in a liquid vehicle, which may then be applied to a substrate using any wash coat technique known in the art, and dried and calcined to provide a coating layer. When multiple coatings are applied, the substrate may be dried and / or calcined after each wash coat has been applied and / or after a desired number of wash coats have been applied. In some embodiments, the catalyst material is applied to the substrate as a wash coat.

[0115] A washcoat can be formed by preparing a slurry containing a specific solid content (e.g., 30–90 wt%) of catalyst material in a liquid vehicle, which is then coated onto a substrate (e.g., multiple substrates) and dried to provide a washcoat layer. To coat a wall-flow substrate with the catalyst material of some embodiments, the substrate can be immersed perpendicularly in a portion of the catalyst slurry such that the top of the substrate is positioned directly above the surface of the slurry. In this way, the slurry contacts the inlet surface of each honeycomb wall but is prevented from contacting the outlet surface of each wall. The sample may be left in the slurry for about 30 seconds. The substrate can be removed from the slurry, and excess slurry can be removed from the wall-flow substrate by first draining it from the channels, then by blowing compressed air (against the direction of slurry penetration), and then by drawing a vacuum from the direction of slurry penetration. Using this technique, the catalyst slurry can penetrate the walls of the substrate, but the pores cannot be blocked to the extent that excessive back pressure accumulates within the finished substrate. As used herein, the term “penetrates” means that the catalyst composition is dispersed throughout the walls of the substrate when used to describe the dispersion of a catalyst slurry on a substrate.

[0116] In some embodiments, the coated substrate is dried at a high temperature (e.g., 100-150°C) for a certain period (e.g., 1-3 hours), and then calcined by heating at, for example, 400-600°C for about 10 minutes to about 3 hours. After drying and calcining, the final washcoat coating layer can be considered substantially solvent-free. After calcining, the catalyst load can be determined by calculating the difference between the coated and uncoated weights of the substrate. As will be obvious to those skilled in the art, the catalyst load can be modified, for example, by altering the rheology of the slurry. In addition, the coating / drying / calcining process can be repeated as needed to build the coating to a desired load level or thickness.

[0117] After firing, the amount of catalyst filling obtained by the wash-coat technique described above can be determined by calculating the difference between the coated and uncoated weights of the substrate. As will be obvious to those skilled in the art, the amount of catalyst filling can be modified, for example, by altering the rheology of the slurry. In addition, the coating / drying / firing process for producing the wash-coat layer (coating layer) can be repeated as needed to build up the coating to the desired filling level or thickness, meaning that more than one wash-coat may be applied.

[0118] In some embodiments, the catalyst coating may comprise one or more coating layers, each containing at least one layer of the catalyst composition or one or more components of the catalyst composition. The catalyst coating may comprise one or more thin adhesive coating layers positioned on and adhering to at least a portion of the substrate. The entire coating may comprise individual coating layers.

[0119] In some embodiments, the oxidation catalyst article may include the use of one or more catalyst layers and combinations of one or more catalyst layers. The catalyst material may be present only on the inlet side of the substrate wall, only on the outlet side, on both the inlet and outlet sides, or the wall itself may be composed entirely or partially of the catalyst material. The catalyst coating may be on the substrate wall surface and / or within the pores of the substrate wall, i.e., "inside" and / or "on" the substrate wall. Thus, the phrase "wash coat placed on the substrate" means on any surface, e.g., on the wall surface and / or on the pore surface.

[0120] The wash coat can be applied so that different coating layers can come into direct contact with the substrate. In some embodiments, one or more “undercoats” may be present so that at least a portion of the catalyst coating layer or a coating layer does not come into direct contact with the substrate, but rather comes into contact with the undercoat. One or more “overcoats” may also be present so that at least a portion of one or more coating layers does not come into direct contact with the gas flow or atmosphere, but rather comes into contact with the overcoat.

[0121] In some embodiments, the oxidation catalyst composition may be located within an upper coating layer above a bottom coating layer. The catalyst composition may be located within both the upper and bottom layers. Either layer may extend along the entire axial length of the substrate; for example, the bottom layer may extend along the entire axial length of the substrate, and the upper layer may also extend along the entire axial length of the substrate above the bottom layer. In some embodiments, each of the upper and bottom layers may extend from either the inlet end or the outlet end.

[0122] For example, both the bottom and top coating layers may extend from the same substrate edge, the top layer may partially or completely overlay the bottom layer, the bottom layer may extend along a portion or the entire length of the substrate, and the top layer may extend along a portion or the entire length of the substrate. In some embodiments, the top layer may overlay a portion of the bottom layer. For example, the bottom layer may extend along the entire length of the substrate, and the top layer may extend from either the inlet or outlet end to about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the length of the substrate.

[0123] In some embodiments, the bottom layer may extend from either the inlet or outlet end to about 10%, 15%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 95% of the length of the substrate, and the top layer may extend from either the inlet or outlet end to about 10%, 15%, 25%, 30%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 95% of the length of the substrate, with at least a portion of the top layer overlaying the bottom layer. This "overlay" zone may extend, for example, to about 5% to about 80% of the length of the substrate, for example, about 5%, 10%, 20%, 30%, 40%, 50%, 60%, or 70% of the length of the substrate.

[0124] In some embodiments, the catalyst coating may be advantageously zoned, comprising a zoned catalyst layer, and may be “zoned,” i.e., the catalyst coating contains various compositions over the axial length of the substrate. This may be described as “zoned laterally.” For example, a layer may extend from the inlet end to the outlet end, extending about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the length of the substrate. Another layer may extend from the outlet end to the inlet end, extending about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the length of the substrate. Different coating layers may be adjacent to each other and may not overlay each other. In some embodiments, different layers may overlay parts of each other, providing a third “intermediate” zone. The intermediate zone may extend, for example, to about 5% to about 80% of the length of the substrate, for example, about 5%, 10%, 20%, 30%, 40%, 50%, 60%, or 70% of the length of the substrate.

[0125] Zones can be defined by the relationship between the coating layers. Several possible zoning configurations exist with respect to different coating layers. For example, there may be an upstream zone and a downstream zone, an upstream zone, an intermediate zone, and a downstream zone, or four different zones. If two layers are adjacent and do not overlap, an upstream zone and a downstream zone exist. If the two layers overlap to some extent, upstream, downstream, and intermediate zones exist. For example, if one coating layer extends along the entire length of the substrate, and a different coating layer extends a certain length from the exit end and overlays a portion of the first coating layer, then upstream and downstream zones exist.

[0126] In some embodiments, a first wash coat is placed on the catalyst substrate from the inlet end to a length of approximately 10% to 50% of the total length, and a second wash coat is placed on the catalyst substrate from the outlet end to a length of approximately 50% to 90% of the total length.

[0127] Figures 3a, 3b, and 3c depict exemplary coating layer configurations with two coating layers. A substrate wall 200 is shown, on which coating layers 201 (top coat) and 202 (bottom coat) are located. This is a simplified diagram, and in the case of porous wall-flow substrates, coatings adhering to pores and pore walls are not shown, and closed ends are not shown. In Figure 3a, coating layers 201 and 202 each extend along the entire length of the substrate, with the top layer 201 overlaying the bottom layer 202. The substrate in Figure 3a does not contain a zoned coating configuration. Figure 3b illustrates a zoned configuration having a coating layer 202 extending from the outlet to about 50% of the length of the substrate to form a downstream zone 204, and a coating layer 201 extending from the inlet to about 50% of the length of the substrate to provide an upstream zone 203. In Figure 3c, the bottom coating layer 202 extends approximately 50% of the substrate length from the outlet, and the top coating layer 201 extends beyond 50% of the length from the inlet, overlaying a portion of layer 202 and providing an upstream zone 203, an intermediate overlay zone 205, and a downstream zone 204. Figures 3a, 3b, and 3c may be useful to illustrate SCR catalyst composition coatings on wall-through or flow-through substrates.

[0128] The amount of catalyst coating packed onto a substrate may depend on substrate properties such as porosity and wall thickness. For example, the catalyst packed into a wall-flow filter may be lower than the catalyst packed into a flow-through substrate. A catalyst wall-flow filter is disclosed, for example, in U.S. Patent No. 7,229,597, which is incorporated herein by reference in its entirety. When describing the amount of wash coat or catalyst metal component or other components of a composition, it may be convenient to use units of weight of the component per unit volume of the catalyst substrate. Thus, the unit, i.e., grams per cubic inch ("g / in"), may be used. 3 "), and grams per cubic foot ("g / ft") 3 In this specification, "g / L" is used to mean the weight of the component per unit volume of the substrate, including the volume of voids in the substrate. Other units of weight per unit volume, such as g / L, may also be used. The concentration of the catalyst composition or any other component on the substrate refers to the concentration per any three-dimensional cross-section or zone, e.g., the substrate or any cross-section of the entire substrate. The total platinum group metal filling of a platinum group metal particle-containing composition (e.g., multiple Pt particles) on a catalyst substrate such as a monolithic flow-through substrate is, for example, about 0.5 g / ft 3 ~about 200g / ft 3 It is possible.

[0129] In some embodiments, the oxidation catalyst article is a diesel oxidation catalyst article. In some embodiments, multiple platinum group metal particles are present at approximately 5 g / ft 3 ~about 200g / ft 3 (For example, about 5g / ft 3 ~50g / ft 3 In certain embodiments, approximately 10 g / ft 3 ~approximately 50g / ft 3 , or approximately 10g / ft 3 ~about 100g / ft 3 It is placed on the substrate with a filling amount of ).

[0130] In some embodiments, the oxidation catalyst article is a catalytic soot filter article. In some embodiments, a plurality of platinum group metal particles are present at approximately 0.5 g / ft 3~about 30 g / ft 3 、for example, about 0.5 g / ft 3 、about 1.0 g / ft 3 、about 1.5 g / ft 3 、about 2.0 g / ft 3 / / 这里原内容有误,推测为 3 ~about 2.5 g / ft 3 、about 3.0 g / ft 3 、or about 3.5 g / ft 3 ~about 5 g / ft 3 、about 10 g / ft 3 、about 15 g / ft 3 、about 20 g / ft 3 、about 25 g / ft 3 、or about 30 g / ft 3 are disposed on a substrate at a loading of. In some embodiments, a plurality of platinum group metal particles are about 1.2 g / ft 3 ~about 3.6 g / ft 3 、about 1.5 g / ft 3 ~about 2.7 g / ft 3 、or about 1.7 g / ft 3 ~about 2.2 g / ft[[ID=..]] 3 / / 这里原内容有误,推测为 3 are disposed on a substrate at a loading of. ]

[0131] These weights per unit volume can be calculated by weighing the catalyst substrate before and after treatment with the catalyst washcoat composition. Since the treatment process involves drying and firing the catalyst substrate at high temperature, these weights represent a catalyst coating that is essentially solvent-free because essentially all of the water in the washcoat slurry has been removed.

[0132] In some embodiments, the level of hydrocarbons, such as methane, or CO present in the exhaust gas stream is at least about 30%, or at least about 50%, or at least about 70%, or at least about 75%, or at least about 80%, or at least about 90%, or at least about 95% reduced compared to the level of hydrocarbons or CO present in the exhaust gas stream prior to contact with the catalyst article. In some embodiments, the temperature for converting hydrocarbons, such as methane, or CO using the catalyst article described in this embodiment can be in the range of about 250 °C to about 650 °C, about 300 °C to about 600 °C, or about 350 °C to about 550 °C.

[0133] In some embodiments, the efficiency for reducing hydrocarbon and / or CO levels is measured in terms of conversion efficiency. In some embodiments, the conversion efficiency is measured as a function of the light-off temperature (i.e., T 50 ). The light-off temperature is the temperature at which the catalyst composition can convert 50% of hydrocarbons or carbon monoxide to carbon dioxide and water. Typically, the lower the measured light-off temperature of a given catalyst composition, the more efficient the catalyst composition is for carrying out catalytic reactions, such as hydrocarbon conversion.

[0134] In some embodiments, the reduction of NO x levels is measured in terms of the NO2 / NO x ratio. In some embodiments, the oxidation catalyst article, after aging at 650 °C for 5 hours, is disposed on a 1 inch × 3 inch through-flow substrate at a platinum group metal loading of 1.7 g / ft 3 and exhibits a NO2 / NO x ratio of about 40% to about 55% when exposed to a feed gas containing 600 ppm of NO, 10% of O2, 5% of CO2, 5% of H2O, and 33 ppm of propane at a temperature of 350 °C and a space velocity of 50,000 per hour.

[0135] In some embodiments, the oxidation catalyst article, after being deteriorated at 550 °C for 5 hours, has a first NO2 / NO XIt has a ratio, and after aging at 650°C for 5 hours, the second NO2 / NO X It has a ratio, and the second NO2 / NO x The ratio is 1.7 g / ft of oxidation catalyst material. 3 When placed on a 1-inch x 3-inch flow-through substrate with a platinum group metal filling and exposed to a feed gas containing 600 ppm NO, 10% O2, 5% CO2, 5% H2O, and 33 ppm propane at a temperature of 350°C and a space velocity of 50,000 per hour, the first NO2 / NO2 mixture is produced. x The ratio is at least approximately 80%.

[0136] Exhaust gas treatment system In some embodiments, the exhaust gas treatment system includes an oxidation catalyst article such as those disclosed herein. The engine may be a diesel engine operating under combustion conditions with more air than required for stoichiometric combustion, i.e., lean conditions. In other embodiments, the engine may be a gasoline engine (e.g., a lean-burn gasoline engine) or an engine associated with a fixed power source (e.g., a generator or pumping station). The exhaust gas treatment system may include one or more catalyst articles positioned downstream of the engine in fluid communication with the exhaust gas flow. The system may include, for example, an oxidation catalyst article such as those disclosed herein (e.g., a diesel oxidation catalyst), a selective catalytic reduction catalyst (SCR), and / or a reducing agent injector, a soot filter, an ammonia oxidation catalyst (AMOx), or lean NO x The system may contain one or more articles, including a trap (LNT). Articles containing a reducing agent injector are reducing articles. The reduction system includes a reducing agent injector and / or a pump and / or a reservoir, etc. The treatment system may further include a soot filter and / or an ammonia oxidation catalyst. Soot filters, such as catalytic soot filters disclosed herein, may be non-catalyzed or catalyzed. For example, the treatment system may include, from upstream to downstream, articles containing a diesel oxidation catalyst, catalytic soot filters, urea injectors, SCR articles, and articles containing AMOx. Lean NO xTraps (LNT) may also be included.

[0137] The relative arrangement of the various catalytic components present within the exhaust treatment system can vary. In some embodiments, the exhaust gas flow is received into the article or treatment system by entering at the upstream end and exiting at the downstream end. The inlet end of the substrate or article is synonymous with the “upstream” end or “front” end. The outlet end is synonymous with the “downstream” end or “rear” end. The treatment system is, for example, located downstream of an internal combustion engine and is in fluid communication with the internal combustion engine.

[0138] One exemplary emissions treatment system is illustrated in Figure 4, which depicts a schematic diagram of emissions treatment system 20. As shown, the emissions treatment system may include a plurality of catalytic components in series downstream of an engine 22, such as a lean-burn engine. One or more of the catalytic components may include the oxidation catalyst compositions of the Disclosure described herein (e.g., diesel oxidation catalysts, catalytic soot filters, or both). The oxidation catalyst compositions of the Disclosure may be combined with additional catalytic materials and may be placed in various positions relative to the additional catalytic materials. Figure 4 illustrates five catalytic components 24, 26, 28, 30, and 32 in series, but the total number of catalytic components may vary, and the five components are merely examples.

[0139] For example, Table 1 shows various exhaust gas treatment system configurations. Note that each catalyst may be connected to the next catalyst via the exhaust conduit, for example, if the engine is upstream of catalyst A, which is upstream of catalyst B, which is upstream of catalyst C, which is upstream of catalyst D, and which is upstream of catalyst E. References to components A-E in the table can be cross-referenced using the same symbols in Figure 4.

[0140] The LNT catalysts listed in Table 1 are NO x The trap may be any conventionally used catalyst, comprising a base metal oxide (BaO, MgO, CeO2, and equivalents) and a platinum group metal (e.g., Pt and Rh) for the oxidation and reduction of NO by the catalyst.x It may include an adsorbent composition.

[0141] The LT-NA catalysts listed in Table 1 are NO catalysts that produce NO at low temperatures (<250°C). x It can be any catalyst that can adsorb (e.g., NO or NO2) and release it into a gas stream at high temperatures (>250°C). X These can be converted to N2 and H2O above the downstream SCR or SCRoF catalyst. For example, LT-NA catalysts include Pd-promoted zeolite or Pd-promoted refractory metal oxides.

[0142] References to SCR in the table refer to SCR catalysts. References to SCRoF (or SCR on a filter) refer to particulate or soot filters (e.g., wall-flow filters) that may contain an SCR catalyst composition.

[0143] References to AMOx in the table refer to ammonia oxidation catalysts, which may be provided downstream of an oxidation catalyst to remove ammonia that has leaked through an exhaust gas treatment system, for example. In some embodiments, the AMOx catalyst may include a platinum group metal component. In some embodiments, the AMOx catalyst may include a bottom coat with platinum group metals and a top coat with SCR functionality.

[0144] As will be recognized by those skilled in the art, in the configurations listed in Table 1, one or more of components A, B, C, D, or E may be placed on a particulate filter such as a wall-flow filter or on a flow-through honeycomb substrate. In some embodiments, the engine exhaust system includes one or more catalytic compositions mounted near the engine (directly connected position, CC) with additional catalytic compositions located below the vehicle body (underbody position, UF). In some embodiments, the exhaust gas treatment system may further include a urea injection component. [Table 1]

[0145] Methods for treating exhaust gas flow In another embodiment, hydrocarbons and / or carbon monoxide (CO), and / or NO x A method for treating an engine exhaust gas flow is provided, including the following. In some embodiments, this method includes bringing the exhaust gas flow into contact with a catalytic article of the Disclosure or an exhaust treatment system of the Disclosure.

[0146] In some embodiments, hydrocarbons and CO present in the exhaust gas stream of any engine can be converted to carbon dioxide (CO2) and water. For example, hydrocarbons present in the engine exhaust gas stream may include C1-C6 hydrocarbons (i.e., lower hydrocarbons) such as methane, but higher hydrocarbons (above C6) may also be present. In some embodiments, this method involves contacting the gas stream with a catalytic article or exhaust gas treatment system of the Disclosure for a sufficient time and temperature to reduce the levels of CO and hydrocarbons in the gas stream.

[0147] In some embodiments, NOs such as NO present in the engine exhaust gas flow x The CO can be converted (oxidized) to NO2. In some embodiments, this method involves contacting the gas stream with the catalyst article or exhaust gas treatment system of the Disclosure for a sufficient time and temperature to oxidize at least a portion of the CO present in the gas stream to NO2.

[0148] The articles, systems, and methods may be suitable for treating exhaust gas flows from mobile exhaust sources such as trucks and automobiles. In some embodiments, the articles, systems, and methods are also suitable for treating exhaust flows from stationary sources such as power plants.

[0149] Some additional exemplary embodiments include, but are not limited to, the following:

[0150] 1. An oxidation catalyst composition comprising a plurality of platinum group metal particles having a multimodal particle size distribution, wherein the plurality of platinum group metal particles comprises a first group of platinum group metal particles having a particle size range of about 0.5 nm to about 3 nm, and a second group of platinum group metal particles having a particle size range of about 4 nm to about 15 nm.

[0151] 2. The oxidation catalyst composition according to Embodiment 1, wherein a first group of platinum group metal particles has a particle size distribution characterized by an average particle size of about 1 nm, and at least about 80% of the first group of platinum group metal particles have a particle size within about 1 nm of the average particle size.

[0152] 3. The oxidation catalyst composition according to Embodiment 1 or 2, wherein the second group of platinum group metal particles has a particle size distribution characterized by an average particle size of about 6 nm, and at least about 80% of the second group of platinum group metal particles have a particle size within about 2 nm of the average particle size.

[0153] 4. The oxidation catalyst composition according to any one of Embodiments 1 to 3, wherein the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 10:90 to about 90:10.

[0154] 5. The oxidation catalyst composition according to any one of Embodiments 1 to 4, wherein the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 50:50 to about 90:10.

[0155] 6. The oxidation catalyst composition according to any one of Embodiments 1 to 5, wherein the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is about 50:50 to about 75:25.

[0156] 7. The oxidation catalyst composition according to any one of Embodiments 1 to 6, wherein the plurality of platinum group metal particles have an average particle size of about 3 nm to about 12 nm.

[0157] 8. The oxidation catalyst composition according to any one of Embodiments 1 to 7, wherein the plurality of platinum group metal particles have an average particle size of about 3 nm to about 10 nm, about 3 nm to about 8 nm, about 3 nm to about 6 nm, or about 3 nm to about 5 nm.

[0158] 9. An oxidation catalyst composition according to any one of embodiments 1 to 8, wherein at least about 90% of one or more platinum group metals from the first and second groups of platinum group metal particles are in a completely reduced form.

[0159] 10. An oxidation catalyst composition according to any one of Embodiments 1 to 9, wherein one or more platinum group metals from the first and second groups of platinum group metal particles include platinum, palladium, ruthenium, rhodium, iridium, or a combination thereof.

[0160] 11. The oxidation catalyst composition according to any one of Embodiments 1 to 10, wherein one or more platinum group metals from the first and second groups of platinum group metal particles include platinum, palladium, or a combination thereof.

[0161] 12. The oxidation catalyst composition according to any one of embodiments 1 to 11, wherein one or more platinum group metals from the first and second groups of platinum group metal particles are platinum.

[0162] 13. An oxidation catalyst composition according to any one of embodiments 1 to 12, further comprising at least one refractory metal oxide support.

[0163] 14. The oxidation catalyst composition according to Embodiment 13, wherein at least one refractory metal oxide support comprises alumina (Al2O3), silica (SiO2), zirconia (ZrO2), titania (TiO2), ceria (CeO2), or a combination thereof.

[0164] 15. The oxidation catalyst composition according to Embodiment 13 or 14, wherein at least one refractory metal oxide support comprises SiO2-doped Al2O3, SiO2-doped TiO2, or SiO2-doped ZrO2.

[0165] 16. An oxidation catalyst composition according to any one of embodiments 13 to 15, wherein at least one refractory metal oxide support comprises Al2O3 doped with 1 to 10% SiO2, TiO2 doped with 1 to 20% SiO2, or ZrO2 doped with 1 to 30% SiO2.

[0166] 17. The oxidation catalyst composition according to any one of embodiments 13 to 16, wherein both a first group of platinum group metal particles and a second group of platinum group metal particles are dispersed on the same refractory metal oxide support.

[0167] 18. An oxidation catalyst composition according to any one of embodiments 14 to 17, wherein a first group of platinum group metal particles and a second group of platinum group metal particles are each dispersed on separate refractory metal oxide carriers, the first group of platinum group metal particles is dispersed on a first refractory metal oxide carrier, the second group of platinum group metal particles is dispersed on a second refractory metal oxide carrier, and the first refractory metal oxide carrier and the second refractory metal oxide carrier are each independently selected.

[0168] 19. The oxidation catalyst composition according to Embodiment 18, wherein both the first refractory metal oxide support and the second refractory metal oxide support comprise the same refractory metal oxide support material.

[0169] 20. The refractory metal oxide support material is the oxidation catalyst composition according to Embodiment 19, comprising TiO2 or TiO2 doped with SiO2.

[0170] 21. An oxidation catalyst article comprising a substrate having an inlet end and an outlet end defining its overall length, and a catalyst coating disposed on at least a portion thereof, comprising an oxidation catalyst composition according to any one of embodiments 1 to 20.

[0171] 22. The oxidation catalyst article according to Embodiment 21, wherein the substrate is a flow-through monolith or a wall-flow filter.

[0172] 23. The oxidation catalyst article according to Embodiment 21 or 22, wherein the oxidation catalyst article is a diesel oxidation catalyst article.

[0173] 24. Multiple PGM particles are approximately 5 g / ft 3 ~about 200g / ft 3 A diesel oxidation catalyst article according to Embodiment 23, which is disposed on a substrate in a filled amount.

[0174] 25. The oxidation catalyst article is an oxidation catalyst article according to Embodiment 21 or 22, wherein the oxidation catalyst article is an oxidation catalyst soot filter article.

[0175] 26. Multiple PGM particles are present at approximately 0.5 g / ft 3 ~about 30g / ft 3 A catalyst soot filter article according to Embodiment 25, which is arranged on a substrate in a filling amount.

[0176] 27. After aging the oxidation catalyst article at 650°C for 5 hours, the oxidation catalyst article was exposed to a feed gas containing 600 ppm NO, 10% O2, 5% CO2, 5% H2O, and 33 ppm propane at a temperature of 350°C and a space velocity of 50,000 per hour, resulting in an oxidation of approximately 40% to approximately 55% NO2 / NO2. x An oxidation catalyst article according to any one of embodiments 21 to 26, showing a ratio.

[0177] After degradation at 28.550°C for 5 hours, the oxidation catalyst article was first NO2 / NO X Having a ratio, after aging at 650°C for 5 hours, the oxidation catalyst article has a second NO2 / NO2 ratio. X It has a ratio, and the second NO2 / NO x The ratio is NO2 / NO2 for the first group. x The ratio is at least about 80%, and the first and second NO2 / NO2 xThe ratio is determined by exposing the oxidation catalyst article to a supply gas containing 600 ppm NO, 10% O2, 5% CO2, 5% H2O, and 33 ppm propane at a temperature of 350°C and a space velocity of 50,000 per hour, according to any one of embodiments 21 to 27.

[0178] 29. An exhaust gas treatment system comprising an oxidation catalyst article according to any one of embodiments 21 to 28, wherein the oxidation catalyst article is located downstream of an internal combustion engine and is in fluid communication with the internal combustion engine.

[0179] 30. Urea injectors, selective catalytic reduction (SCR) catalysts, ammonia oxidation (AMO) x ) Catalyst, low temperature NO X Adsorbent (LT-NA), and lean NO x The exhaust gas treatment system according to Embodiment 29, further comprising one or more catalytic articles selected from traps (LNTs).

[0180] 31. Hydrocarbons, carbon monoxide, and / or NO x A method for treating an exhaust gas flow, comprising passing the exhaust gas flow through a catalytic article according to any one of embodiments 21 to 28 or an exhaust gas treatment system according to embodiment 29 or 30.

[0181] 32. Multiple platinum group metal particles are present at approximately 0.5 g / ft 3 ~about 5g / ft 3 An oxidation catalyst article according to Embodiment 18, which is arranged on a substrate in a filling amount.

[0182] It will be readily apparent to those skilled in the art that suitable modifications and adaptations to the compositions, methods, and uses described herein can be made without departing from the scope of any embodiment or its manifestations. The compositions and methods provided are illustrative and are not intended to limit the scope of the claimed embodiments. All of the various exemplary embodiments, manifestations, and options disclosed herein can be combined in all variations. The scope of the compositions, formulations, methods, and processes described herein includes all actual or potential combinations of the embodiments, manifestations, options, examples, and preferences herein. All patents and publications cited herein are incorporated herein by reference with respect to their specific teachings, as described herein, unless other specific descriptions incorporating them are specifically provided. [Examples]

[0183] The following examples are illustrative and not intended to limit the scope of the disclosure in any way. Unless otherwise stated, all parts and percentages are by weight, and all weight percentages are expressed on a dry basis, meaning that water content is excluded unless otherwise indicated.

[0184] Examples 1A-E In Examples 1A-E, a colloidal suspension of Pt was prepared, dispersed on a titania support material, and pulverized. The catalyst soot filter article was then coated with the resulting titania-supported Pt by coating the wall-flow soot filter substrate with 1.2 g / ft of Pt. 3 ~3.6g / ft 3 It was prepared with the following Pt filling amount.

[0185] Specifically, octanol (1 g) was added to water (820 g) with gentle stirring. Titania carrier material (310 g) was gradually added to the water / octanol mixture with stirring. A dispersant (4 g) was added to promote the dispersion of the carrier in the aqueous phase. Subsequently, tartaric acid (2.3 g) was added to lower the pH to 3.8. Mixing was then continued for 30 minutes. The resulting well-dispersed slurry of carrier material had a particle size of approximately 5 microns. 90 To reduce it further, it was transferred into a mill. The ground slurry was transferred into a clean container and the aqueous portion of the pre-formed Pt material was prepared according to US2017 / 0304805 and US2019 / 001578, with various target Pt filling amounts (g / ft 3 It was added (measured at [location]). The average Pt particle size was 5.9 nm, with a P particle size range of 4 nm to 15 nm. The resulting slurry was then 0.15 g / in 3 The wash coat was coated onto the wall flow filter substrate in a drying gain, followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour. The Pt filling amounts for each example are provided in Table 2. [Table 2]

[0186] Example 2 In Example 2, the titania carrier material was impregnated with a Pt solution and then pulverized. The catalyst soot filter article was then constructed by coating the wall-flow soot filter substrate with the pulverized Pt-impregnated titania carrier, resulting in a concentration of 2.8 g / ft. 3 It was prepared with the following Pt filling amount.

[0187] Specifically, titania carrier material (255 g) was impregnated with a solution of tetraamine platinum(II) complex (13.2 g) by dropwise addition onto dry powder during mixing. The Pt-impregnated carrier mixture was then added to water (260 g) to form a well-dispersed slurry. A dispersant (up to 1.5% of the solids) was added if necessary. The pH of the slurry was adjusted to 4.2 using tartaric acid. The well-dispersed slurry was then processed to produce particles with a particle size of approximately 5 microns. 90 It was loaded into the mill to reduce it to a certain size. The resulting slurry is then 0.15 g / in 3 The coating was applied to a wall-flow filter substrate using a wash coat drying gain. This was followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour. The average Pt particle size was 1.3 nm, with a range of Pt particle sizes from 0.5 nm to 3 nm.

[0188] Examples 3-6 The catalyst compositions of Examples 3 to 6 were prepared by impregnating a titania support material with a Pt solution, and then arranging Pt particles from a colloidal Pt suspension onto the impregnated titania support material using the following procedure. For the composition of each example, the ratio of impregnated Pt (referred to herein as "Pt A") to deposited colloidal Pt (referred to herein as "Pt B") is provided in Table 3.

[0189] Examples 3-5 were prepared by impregnating titania carrier material with a Pt solution. The resulting material was pulverized and used to prepare a slurry adjusted to a pH of less than 5. Colloidal Pt was then dispersed on the titania carrier.

[0190] Specifically, titania carrier material (260 g) was impregnated with tetraamine platinum(II) complex solution (3.4 g, 6.7 g, and 10.1 g for Examples 3-5, respectively). The Pt solution was added to the dry powder as a wet mist in a sealed container at a moderate mixing rate. After the addition of the Pt solution was complete, mixing was continued for 30 minutes. A slurry was prepared by mixing the impregnated carrier with water (575 g), a dispersant (3.5 g), and octanol (1 g) while stirring. Subsequently, tartaric acid (2.1 g) was added to lower the pH to 3.9, followed by mixing for 30 minutes. The well-dispersed mixture was then loaded into a mill, and the particle size was measured to approximately 5 microns. 90 The slurry was reduced to the desired target Pt filling amount (g / ft). The crushed slurry was transferred to a clean container and the aqueous portion of the preformed Pt material was prepared according to US2017 / 0304805 and US2019 / 001578. 3 To achieve the measured value, 90g, 60g, and 30g of silica sol binder were added for Examples 3, 4, and 5, respectively. 10.5g of silica sol binder was then added, and the resulting slurry was then measured at 0.15g / in. 3 The wash coat was coated onto the wall flow filter substrate in a drying gain. This was followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour.

[0191] Example 6 was prepared by impregnating a titania carrier material with a Pt solution as follows: Water (680 g), octanol (1 g), and a dispersant (3.3 g) were thoroughly mixed with stirring for 30 minutes. The pH of the mixture was adjusted to 6.5 using monoethylamine. A tetraamine platinum(II) complex solution (2.3 g) was added to the mixture, and the pH was adjusted to 4.3 using tartaric acid. Colloidal Pt (60 g) was then added with stirring. The well-dispersed mixture was loaded into a mill, and the particle size was measured to approximately 5 microns. 90It was reduced to this size. The crushed slurry was transferred to a clean container, and silica sol binder (8.2 g) was added, and the resulting slurry was then 2.8 g / ft 3 With a Pt filling amount of 0.15 g / in 3 The wash coat was coated onto the wall flow filter substrate in a drying gain. This was followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour.

[0192] Examples 7-12 The catalyst compositions of Examples 7 to 12 were prepared by impregnating a titania support material with a Pt solution and dispersing colloidal Pt on a separate titania support using the following procedure. The Pt A to Pt B ratios for each example composition are provided in Table 3.

[0193] Example 7 A tetraamine platinum complex solution (4.4 g) was diluted with 110 g of water and added as a wet mist to 200 g of dry titania carrier material powder in a sealed container at a moderate mixing rate. Mixing was continued for 30 minutes after the addition of the Pt solution was complete. Water (365 g), octanol (0.6 g), and dispersant (2.6 g) were thoroughly mixed with stirring, and the wet Pt-impregnated carrier material was added to the mixture with stirring. The pH was adjusted to 3.9 using tartaric acid (1 g), and the mixture was stirred for 30 minutes. The well-dispersed mixture was loaded into a mill, and the particle size was measured to approximately 5 microns. 90 It was reduced to this size.

[0194] Separately, the carrier material (133.5 g), slurry water (295 g), and dispersant (1.65 g) were mixed together with stirring for 30 minutes. Tartaric acid was added to lower the pH to 3.9, and the slurry was mixed to a depth of approximately 5 microns. 90 It was ground to this slurry. To this slurry, preformed platinum group metal material (118g), prepared according to US2017 / 0304805 and US2019 / 001578, was added at 15g / ft 3 It was added at the target platinum group metal filling amount.

[0195] Two separate slurries were combined, and a silica sol binder was added (19.5 g). The resulting slurry was then 0.85 g / in 3 The wash coat was coated onto the flow-through substrate with a drying gain, followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour, as described above.

[0196] Example 8 A tetraamine platinum complex solution (10.8 g) was diluted with 130 g of water and added as a wet mist to the dry powder of the carrier material (205 g) in a sealed container at a moderate mixing rate. Mixing was continued for 30 minutes after the addition of the Pt solution was complete. Water (395 g), octanol (0.6 g), and dispersant (2.6 g) were thoroughly mixed with stirring, and the wet Pt-impregnated carrier material was added to the mixture with stirring. The pH was adjusted to 4.7 using tartaric acid (1.8 g), and the mixture was stirred for 30 minutes. The well-dispersed mixture was loaded into a mill, and the particle size was measured to approximately 5 microns. 90 It was reduced to this size.

[0197] Separately, the carrier material (205 g), slurry water (480 g), and dispersant (2.6 g) were mixed together with stirring for 30 minutes. Tartaric acid (1 g) was added to lower the pH to 4.1, and the slurry was mixed to a thickness of approximately 5 microns. 90 It was ground to this slurry. To this slurry, preformed platinum group metal material (96g), prepared according to US2017 / 0304805 and US2019 / 001578, was added at 15g / ft 3 It was added at the target platinum group metal filling amount.

[0198] Two separate slurries were combined, and a silica sol binder was added (19.5 g). The resulting slurry was then 0.85 g / in 3The wash coat was coated onto the flow-through substrate with a drying gain, followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour, as described above.

[0199] Example 9 A tetraamine platinum complex solution (13.4 g) was diluted with 155 g of water and added as a wet mist to the dry powder of the carrier material (260 g) in a sealed container at a moderate mixing rate. Mixing was continued for 30 minutes after the addition of the Pt solution was complete. The wet Pt-impregnated carrier powder was diffused onto a ceramic tray and calcined in a 500°C oven for 5 hours. Water (640 g), octanol (0.8 g), and dispersant (3.2 g) were thoroughly mixed with stirring, and the calcined Pt-impregnated carrier material was added to the mixture with stirring. The pH was adjusted to 4.7 using tartaric acid (1.8 g), followed by 30 minutes of stirring. The well-dispersed mixture was loaded into a mill, and the particle size was approximately 5 microns. 90 It was reduced to this size.

[0200] Separately, the carrier material (260g), slurry water (610g), and dispersant (3.3g) were mixed together with stirring for 30 minutes. Tartaric acid (1g) was added to lower the pH to 4.1, and the slurry was mixed to a thickness of approximately 5 microns. 90 It was ground to this slurry. A preformed platinum group metal material (120g), prepared according to US2017 / 0304805 and US2019 / 001578), was added at 15g / ft 3 The target platinum group metals were added. Two separate slurries were combined, and a silica sol binder was added (23.2 g). The resulting slurry was then 0.85 g / in 3 The coating was applied to the flow-through substrate with a wash-coat drying gain. This was followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour.

[0201] Example 10 A tetraamine platinum complex solution (10.8 g) was diluted with 120 g of water and added as a wet mist to the dry powder of the carrier material (200 g) in a sealed container at a moderate mixing rate. Mixing was continued for 30 minutes after the addition of the Pt solution was complete. The wet Pt-impregnated carrier powder was diffused onto a ceramic tray and calcined in a 550°C oven for 5 hours. Water (440 g), octanol (0.6 g), and dispersant (2.5 g) were thoroughly mixed with stirring, and the calcined Pt-impregnated carrier material was added to the mixture with stirring. The pH was adjusted to 4.7 using tartaric acid (1.8 g), followed by 30 minutes of stirring. The well-dispersed mixture was loaded into a mill, and the particle size was approximately 5 microns. 90 It was reduced to this size.

[0202] Separately, the carrier material (200g), slurry water (460g), and dispersant (2.6g) were mixed together with stirring for 30 minutes. Tartaric acid (2.1g) was added to lower the pH to 3.5, and the slurry was mixed to a thickness of approximately 5 microns. 90 It was ground to this slurry. To this slurry, preformed platinum group metal material (93g), prepared according to US2017 / 0304805 and US2019 / 001578), was added at 15g / ft 3 The target platinum group metals were added. Two separate slurries were combined, and a silica sol binder was added (18.2 g). The resulting slurry was then 0.85 g / in 3 The coating was applied to the flow-through substrate with a wash-coat drying gain. This was followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour.

[0203] Example 11 A tetraamine platinum complex solution (10.8 g) was diluted with 120 g of water and added as a wet mist to the dry powder of the carrier material (200 g) in a sealed container at a moderate mixing rate. Mixing was continued for 30 minutes after the addition of the Pt solution was complete. The wet Pt-impregnated carrier powder was diffused onto a ceramic tray and calcined in a 600°C oven for 5 hours. Water (495 g), octanol (0.6 g), and a dispersant (2.6 g) were thoroughly mixed with stirring, and the calcined Pt-impregnated carrier material was added to the mixture with stirring for 30 minutes.

[0204] Separately, the carrier material (200g), slurry water (520g), and dispersant (2.6g) were mixed together with stirring for 30 minutes. Tartaric acid (2.1g) was added to lower the pH to 3.8, and the slurry was mixed to a thickness of approximately 5 microns. 90 It was ground to this slurry. To this slurry, preformed platinum group metal material (95g), prepared according to US2017 / 0304805 and US2019 / 001578, was added at 15g / ft 3 The target platinum group metals were added. Two separate slurries were combined, and a silica sol binder was added (18.2 g). The resulting slurry was then 0.85 g / in 3 The coating was applied to the flow-through substrate with a wash-coat drying gain. This was followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour.

[0205] Example 12 A tetraamine platinum complex solution (15.7 g) was diluted with 185 g of water and added as a wet mist to the dry powder of the carrier material (303.4 g) in a sealed container at a moderate mixing rate. Mixing was continued for 30 minutes after the addition of the Pt solution was complete. The batch was divided into three equal parts, and each part of the wet Pt-impregnated carrier powder was diffused onto a separate ceramic tray. The wet powders were separately calcined in a furnace at 500°C for 5 hours, 550°C for 5 hours, and 600°C for 5 hours, respectively. During calcination, all powders were combined into a single batch and thoroughly mixed. Water (650 g), octanol (0.9 g), and dispersant (3.9 g) were thoroughly mixed with stirring, and the calcined Pt-impregnated carrier material was added to the mixture with stirring for 30 minutes. The mixture was loaded into a mill, and the particle size was measured to approximately 5 microns. 90 It was reduced to this size.

[0206] Separately, the carrier material (303.2 g), slurry water (600 g), and dispersant (3.9 g) were mixed together with stirring for 30 minutes. Tartaric acid (1.3 g) was added to lower the pH to 4.1, and the slurry was mixed to a diameter of approximately 5 microns. 90 It was ground to this slurry. To this slurry, preformed platinum group metal material (140g), prepared according to US2017 / 0304805 and US2019 / 001578), was added at 15g / ft 3 The target platinum group metals were added. Two separate slurries were combined, and a silica sol binder was added (19.4 g). The resulting slurry was then 0.85 g / in 3 The wash coat was coated onto the flow-through substrate with a drying gain, followed by drying at 120°C for 2 hours and firing at 590°C for 1 hour. [Table 3]

[0207] Example 13. Diesel oxidation catalyst coated article Articles according to Examples 1-11 of the diesel oxidation catalyst coating configuration were evaluated for NO2 synthesis and decomposition at 300°C (Figure 5). Core samples of each article were tested in a laboratory reactor employing synthesis gas consisting of 10% oxygen, 5% carbon dioxide, 100 ppm CO, 600 ppm NO, 100 ppm hydrocarbons, and 5% H2O, along with equilibrium nitrogen. Each sample was tested in a fresh state, a degraded state, and after aging at 600°C for 20 hours. NO oxidation stability against aging was the main focus, and the decrease in activity for NO conversion to NO2 was calculated as NO2 synthesis and decomposition. Example 3 showed the least NO2 synthesis and decomposition, followed by Examples 2, 7, 8, 6, and 10.

[0208] Example 14. Results of a catalytic soot filter article (aged) Articles according to Examples 3 and 10 of the catalytic soot filter coating configuration were aged at 550°C for 100 hours, and then evaluated for NO2 generation loss over a temperature range of 200–350°C. Stable NO2 generation was observed for both articles, with a 5–8% loss of NO2 generation during aging (Figure 6 and Table 4). [Table 4]

[0209] Example 15. NO oxidation rate after aging Catalyst soot filter articles (Examples 1A-E, 3, and 10) were evaluated for NO oxidation rates at 250°C, 300°C, and 350°C after aging at 650°C for 5 hours. Example 3 yielded the highest NO2 production (31-44%) after aging, while Example 10 yielded 0.5 g / ft 3 This was comparable to Example 1E (23-37%), which had a high platinum group metal filling content (Figure 7). The change in maximum NO oxidation of the degraded catalyst compared to the aged catalyst is illustrated in Figure 8, demonstrating that Examples 3 and 10 resulted in almost unchanged NO2 production after aging.

[0210] Example 16. Light-off of CO and hydrocarbons The catalytic soot filter articles (Examples 1A-E, 3, and 10) showed degradation and aging after T 50 The light-off temperatures of hydrocarbons and carbon monoxide (CO) were evaluated. Examples 3 and 10 show the T of hydrocarbons and CO after aging. 50 It showed only a slight increase (Figure 9).

[0211] Example 17. Engine test results of a full-size catalytic soot filter article. A full-size catalytic soot filter article (a catalytic composition coated on a wall-flow substrate measuring 10.5 inches in diameter and 10 inches in length) was prepared and evaluated under engine test conditions. The full-size catalytic soot filter article of Example 1 yielded 1.7 g / ft according to Example 1. 3 The Pt-filled amounts were prepared. The full-size catalyst soot filter articles of Examples 3 and 10 were prepared according to Examples 3 and 10, with concentrations of 1.7 and 2.2 g / ft, respectively. 3 The samples were prepared with the specified Pt filling amount. The changes in NO oxidation performance of degraded and aged samples over six engine test cycles are provided in Figure 10, illustrating that the full-size catalyst soot filter article of Example 10 performed best, followed by the full-size catalyst soot filter article of Example 3, and finally the full-size catalyst soot filter article of Example 1.

Claims

1. An oxidation catalyst composition comprising a plurality of platinum group metal particles having a multimodal particle size distribution, wherein the plurality of platinum group metal particles are A first group of platinum group metal particles having a particle size range of 0.5 nm to 3 nm, It comprises a second group of platinum group metal particles having a particle size range of 4 nm to 15 nm, The first group of platinum group metal particles has a particle size distribution characterized by an average particle size of 1 nm, and at least 80% of the first group of platinum group metal particles have a particle size within 1 nm of the average particle size. An oxidation catalyst composition wherein the second group of platinum group metal particles has a particle size distribution characterized by an average particle size of 6 nm, and at least 80% of the second group of platinum group metal particles have a particle size within 2 nm of the average particle size.

2. The oxidation catalyst composition according to claim 1, wherein the weight ratio of the first group of platinum group metal particles to the second group of platinum group metal particles is 10:90 to 90:10, 50:50 to 90:10, or 50:50 to 75:

25.

3. The oxidation catalyst composition according to claim 1 or 2, wherein the plurality of platinum group metal particles have an average particle size of 3 to 12 nm, 3 nm to 10 nm, 3 nm to 8 nm, 3 nm to 6 nm, or 3 nm to 5 nm.

4. The oxidation catalyst composition according to any one of claims 1 to 3, wherein at least 90% of one or more of the platinum group metals from the first and second groups of platinum group metal particles are in a completely reduced form.

5. The oxidation catalyst composition according to any one of claims 1 to 4, wherein one or more of the first and second groups of platinum group metal particles include platinum, palladium, ruthenium, rhodium, iridium, or a combination thereof.

6. The oxidation catalyst composition according to any one of claims 1 to 5, wherein one or more of the first and second groups of platinum group metal particles are platinum.

7. The oxidation catalyst composition according to any one of claims 1 to 6, further comprising at least one refractory metal oxide support.

8. The at least one refractory metal oxide support is alumina (Al ２ O ３ ), silica (SiO ２ ), Zirconia (ZrO ２ ), Titania (TiO ２ ), Celia (CeO ２ The oxidation catalyst composition according to claim 7, comprising ), or a combination thereof.

9. The at least one refractory metal oxide support is Al doped with 1 to 10% SiO ２ O ２ O[[ID=C5]] ３ TiO doped with 1 to 20% SiO ２ O ２ or ZrO doped with 1 to 30% SiO ２ O ２ The oxidation catalyst composition according to claim 7 or 8, comprising

10. The oxidation catalyst composition according to any one of claims 7 to 9, wherein both the first group of platinum group metal particles and the second group of platinum group metal particles are dispersed on the same refractory metal oxide support.

11. The oxidation catalyst composition according to any one of claims 7 to 9, wherein the first group of platinum group metal particles and the second group of platinum group metal particles are each dispersed on separate refractory metal oxide carriers, the first group of platinum group metal particles is dispersed on a first refractory metal oxide carrier, the second group of platinum group metal particles is dispersed on a second refractory metal oxide carrier, and the first refractory metal oxide carrier and the second refractory metal oxide carrier are each independently selected.

12. The oxidation catalyst composition according to claim 11, wherein both the first refractory metal oxide carrier and the second refractory metal oxide carrier comprise the same refractory metal oxide carrier material.

13. The aforementioned fire-resistant metal oxide support material is TiO ２ or SiO ２ TiO doped ２ The oxidation catalyst composition according to claim 12, comprising:

14. An oxidation catalyst article comprising a substrate having an inlet end and an outlet end defining its overall length, and a catalyst coating disposed on at least a portion thereof, comprising the oxidation catalyst composition according to any one of claims 1 to 13.

15. The oxidation catalyst article according to claim 14, wherein the substrate is a flow-through monolith or a wall-flow filter.

16. The oxidation catalyst article according to claim 14 or 15, wherein the oxidation catalyst article is a diesel oxidation catalyst article or a catalytic soot filter article.

17. The aforementioned plurality of platinum group metal particles are 5 g / (30.48 cm) ３ ~200g / (30.48cm) ３ The diesel oxidation catalyst article according to claim 16, wherein the filling amount is arranged on the substrate.

18. The aforementioned plurality of platinum group metal particles are 0.5 g / (30.48 cm) ３ ~30g / (30.48cm) ３ The catalyst soot filter article according to claim 16, wherein the fill amount is arranged on the substrate.

19. The aforementioned plurality of platinum group metal particles are 0.5 g / (30.48 cm) ３ ~5g / (30.48cm) ３ The oxidation catalyst article according to claim 16, wherein the filling amount is arranged on the substrate.

20. The oxidation catalyst article after aging at 650°C for 5 hours is as follows: The substrate of the oxidation catalyst article before aging is a flow-through substrate with a diameter of 2.54 cm × a length of 7.62 cm, and the oxidation catalyst article before aging has a concentration of 1.7 g / (30.48 cm) ３ The platinum group metal filling content is such that, before aging, the oxidation catalyst article contains 600 ppm NO and 10% O at a temperature of 350°C and a space velocity of 50,000 per hour. ２ , 5% CO ２ , 5% H ２ When exposed to a supply gas containing 0 and 33 ppm propane, 40% to 55% NO ２ / NO ｘ An oxidation catalyst article according to any one of claims 14 to 19, showing a ratio.

21. After degrading the oxidation catalyst article at 550°C for 5 hours, the oxidation catalyst article is converted to first NO ２ / NO Ｘ Having a ratio, after aging the oxidation catalyst article at 650°C for 5 hours, the oxidation catalyst article is second NO ２ / NO Ｘ The ratio of the second NO ２ / NO ｘ The ratio is the first NO ２ / NO ｘ The ratio is at least 80%, and the first and second NO2 / NOx ratios are such that the substrate in the oxidation catalyst article before aging is a flow-through substrate with a diameter of 2.54 cm × a length of 7.62 cm, and the oxidation catalyst article before aging is 1.7 g / (30.48 cm) ３ When the platinum group metal filling content is such that the oxidation catalyst article before aging is subjected to aging at a temperature of 350°C and a space velocity of 50,000 per hour, with 600 ppm NO and 10% O ２ , 5% CO ２ , 5% H ２ An oxidation catalyst article according to any one of claims 14 to 20, determined by exposure to a supply gas containing 0 and 33 ppm propane.

22. An exhaust gas treatment system comprising an oxidation catalyst article according to any one of claims 14 to 21, wherein the oxidation catalyst article is located downstream of an internal combustion engine and is in fluid communication with the internal combustion engine.

23. Urea injector, selective catalytic reduction (SCR) catalyst, ammonia oxidation (AMO) ｘ ) Catalyst, low-temperature NO Ｘ Adsorbent (LT-NA), and lean NO ｘ The exhaust gas treatment system according to claim 22, further comprising one or more catalytic articles selected from traps (LNTs).

24. Hydrocarbons, carbon monoxide, and / or NO ｘ A method for treating an exhaust gas flow, comprising passing the exhaust gas flow through a catalyst article according to any one of claims 14 to 21 or an exhaust gas treatment system according to claim 22 or 23.

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