Improved TWC catalysts for gasoline engine exhaust gas treatment.

Abstract

A catalyst composition comprising a first platinum group metal (PGM) component and a first support material, the first PGM component comprising platinum (Pt) and palladium (Pd) supported on the first support material, the first PGM component having a molar ratio of Pt:Pd of about 5:95 to about 95:5.

Description

[Technical field]

[0001] The present invention relates to catalyzed articles useful for treating exhaust gas emissions from gasoline engines, and in particular to catalyst compositions, catalytic articles, emissions treatment systems, methods for treating exhaust gases, and methods for making catalytic articles. [Background technology]

[0002] In internal combustion engines, the main components of the exhaust gas are hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxide (NO x ). Emissions control systems that include exhaust gas catalytic conversion catalysts are widely used to reduce the amount of these pollutants emitted into the atmosphere. The catalyst typically used to treat the exhaust of gasoline engines is the three way catalyst (TWC). TWCs perform three main functions: (1) oxidation of CO, (2) oxidation of unburned HC, and (3) oxidation of NO. x Reduction of.

[0003] Palladium (Pd) and rhodium (Rh) are widely used in TWC formulations to reduce harmful emissions in gasoline vehicles. In fact, current TWC technology relies heavily on the Pd / Rh system. However, in recent years, the prices of these precious metals have risen and become more expensive due to the increasing demand in the market. Meanwhile, increasingly stringent environmental regulations worldwide are forcing the automotive industry to put more and more precious metals into catalytic converters. As a result, there is a potential market risk due to the recent Pd demand exceeding Pd supply.

[0004] For the time being, platinum (Pt) has become a more attractive candidate for gasoline applications due to its relatively cheap price. During the past 12 months from July 2021, the average prices of Pt and Pd were approximately $1,085 and $2,660 per ounce, respectively (http: / / www.platinum.matthey.com). Thus, there is a huge economic incentive for how to introduce Pt into catalyst formulations to at least partially replace Pd while hoping to maintain comparable catalytic performance.

[0005] Therefore, it is desirable to provide cheaper catalysts for TWC applications that may still have comparable or improved activity compared to conventional TWC catalysts currently in use. Summary of the Invention

[0006] One aspect of the present disclosure is a catalyst composition comprising a first platinum group metal (PGM) component and a first support material, the first PGM component comprising platinum (Pt) and palladium (Pd) supported on the first support material, the first PGM component having a molar ratio of Pt:Pd of about 5:95 to about 95:5.

[0007] Another aspect of the present disclosure is directed to a catalyst article for treating exhaust gases, the catalyst article including a substrate and a first catalytic region including a first platinum group metal (PGM) component and a first support material, the first PGM component including platinum (Pt) and palladium (Pd) supported on the first support material, the first PGM component having a molar ratio of Pt:Pd of about 5:95 to about 95:5.

[0008] The present invention also includes an emission treatment system comprising the catalyst composition or catalyst article described herein.

[0009] Another aspect of the present disclosure is directed to a method of treating an exhaust gas, the method comprising providing a catalyst composition or catalyst article described herein and contacting the catalyst composition or catalyst article with the exhaust gas.

[0010] Another aspect of the present disclosure is a method of making a catalyst article, the method comprising providing a slurry comprising platinum (Pt) ions and palladium (Pd) ions in a molar ratio of about 5:95 to about 95:5 and a support material, disposing the slurry on a substrate, and heating the slurry to form Pt and Pd nanoparticles on the support material.

[0011] The present invention also includes the catalyst articles described herein, which are obtained or obtainable by the methods of making the catalyst articles described herein. [Brief description of the drawings]

[0012] [Figure 1a] FIG. 1 shows an embodiment according to the invention in which a first catalyst region is a top layer and extends over 100% of the axial length L, and a second catalyst region is a bottom layer and extends over 100% of the axial length L. [Figure 1b] FIG. 1b depicts a variant of FIG. 1a. [Figure 2a] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from an inlet end less than 100% of the axial length L, and a second catalyst region extends from an outlet end less than 100% of the axial length L. The combined length of the second catalyst region and the first catalyst region is less than or equal to the axial length L. [Figure 2b] FIG. 2b illustrates a variation of FIG. 2a. [Figure 2c] 1 illustrates an embodiment according to the present invention in which a first catalyst region extends from an inlet end less than 100% of the axial length L, and a second catalyst region extends from an outlet end less than 100% of the axial length L. The combined length of the second catalyst region and the first catalyst region is greater than the axial length L. [Figure 2d] FIG. 2c illustrates a variation of FIG. [Figure 3a] FIG. 1 shows light-off temperature results from Example 1. [Figure 3b] FIG. 1 shows light-off temperature results from Example 1. [Figure 4] FIG. 1 shows light-off temperature results for different CO:H2 ratios in Example 1. [Figure 5a] FIG. 13 shows the discharge results of Example 2. [Figure 5b] FIG. 13 shows the discharge results of Example 2. [Figure 5c] FIG. 13 shows the discharge results of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention aims to address at least some of the problems associated with the prior art, or at least to provide a commercially acceptable alternative solution.

[0014] In a first aspect, the present invention provides a catalyst composition comprising a first platinum group metal (PGM) component and a first support material, the first PGM component comprising platinum (Pt) and palladium (Pd) supported on the first support material, the first PGM component having a molar ratio of Pt:Pd of about 5:95 to about 95:5.

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

[0016] Surprisingly, the catalyst composition of the present invention provides equivalent or improved catalytic (i.e., TWC) activity compared to conventional catalyst compositions containing Pd without Pt substitution. It is known that Pt has a lower catalytic (i.e., TWC) activity compared to Pd for a wide range of TWC operating conditions. Therefore, it is surprising that replacing any amount of Pd with Pt in a catalyst composition does not adversely affect its catalytic activity. However, the present inventors have surprisingly found that by replacing about 5 mol % to about 95 mol % of Pd in ​​such catalyst composition with Pt (i.e., to desirably provide a less expensive catalyst composition), a catalyst composition having equivalent or even improved catalytic (i.e., TWC) activity is provided. As described in more detail herein, at certain ratios of Pt to Pd (i.e., replacing an amount of Pd with Pt within the above ranges), a catalyst composition can be obtained that may actually have improved catalytic (i.e., TWC) activity compared to a catalyst composition containing Pd without Pt substitution. Such catalyst compositions may also exhibit lower light-off temperatures as compared to catalyst compositions containing Pd without Pt substitution.

[0017] Moreover, it has been surprisingly found that such catalyst compositions may be more robust to changes in exhaust gas conditions, such as lean to rich conditions, and different aging conditions, which, together with increased catalyst (i.e., TWC) activity, may be particularly advantageous properties for use in exhaust systems currently in common use.

[0018] In particular, when used in exhaust systems, the catalyst composition of the present invention can surprisingly provide a combination of significantly improved reduction in CO emissions, improved NOx conversion, and equivalent or improved reduction in hydrocarbon (HC) emissions. Thus, not only can the catalyst composition described herein be desirably cheaper than conventionally used catalyst compositions that include Pd without Pt substitution, but such catalyst compositions can also exhibit desirably improved catalytic performance. Without being bound by theory, it is hypothesized that the improved performance with respect to CO emissions can be the result of Pd being less poisoned by CO or having better CO oxidation activity due to the presence of Pt and its interaction with Pd.

[0019] Without being bound by theory, it is also hypothesized that Pt-Pd alloys may be formed in the catalyst composition, where the alloy substantially maintains the Pd properties (e.g., because it contains a majority of Pd). It is believed that this may contribute to the improved or equivalent performance that may be provided by the catalyst composition described herein. In other words, such alloys maintaining the Pd properties may mean that the catalytic (i.e., TWC) activity of the catalyst composition is not reduced when Pd is replaced with the less active Pt. For example, the presence of Pt may induce electronic modification of Pd such that the adsorption / dissociation energy of contaminants on the metal is altered while substantially maintaining the properties of Pd. This may result in the advantageous properties described above, without being bound by theory.

[0020] The term "catalyst composition" as used herein may include compositions that exhibit catalytic activity, particularly for use in the treatment of exhaust gases, preferably from gasoline engines. In other words, the catalyst composition is capable of oxidizing CO, oxidizing unburned HC, and oxidizing NO. x The catalyst composition may exhibit catalytic activity for one or more of the following reductions:

[0021] Unless otherwise specified, terms such as "first," "second," "third," etc., used herein are for clarity purposes only and are used as labels to help distinguish particular features from one another. This language is not intended, for example, to limit any particular ordering of features or components or to indicate whether one feature is preferred over another.

[0022] As used herein, the term "platinum group metals (PGM)" may include metals selected from the group consisting of Ru, Rh, Pd, Os, Ir, and Pt, preferably metals selected from the group consisting of Ru, Rh, Pd, Ir, and Pt. In general, the term "PGM" preferably refers to metals selected from the group consisting of Rh, Pt, and Pd.

[0023] The first PGM component comprises Pt and Pd. Preferably, the first PGM component consists essentially of or even consists of Pt and Pd. In addition to Pt and Pd, the first catalyst component may comprise PGMs other than Pt and Pd.

[0024] As used herein, the phrase "consisting essentially of" limits the scope of a feature to include the specified materials or steps and any other materials or steps, e.g., trace impurities, that do not substantially affect the basic properties of the feature. "Consisting essentially of" encompasses the phrase "consisting of."

[0025] As used herein, the term "support material" may encompass any material capable of supporting the first PGM component thereon or therein. The support material may take any form, but is typically in the form of a powder, more typically a high surface area powder. When the catalyst composition of the invention is used to prepare a catalyzed filter, such as a wall-flow filter or a flow-through filter, the support material will typically have a D of, for example, 0.1 to 30 μm, more typically 0.5 to 25 μm, even more typically 1 to 20 μm, as measured using TEM. 50Such particle size may facilitate desirable rheological properties of the slurry used to coat the filter. The carrier material may function as a washcoat. The carrier material may be the washcoat or may be part of the washcoat.

[0026] The support material may also act as an oxygen storage material, storing and releasing oxygen under fuel-lean and fuel-rich conditions, respectively, to facilitate three-way catalytic conversion.

[0027] The first PGM component is supported on a first support material. As used in this context, the term "supported on" can encompass situations where the first PGM component is loaded onto the external surface of the support material (e.g., on the surface of a high surface area metal oxide support material) or is contained within the support material, for example within its pores (e.g., within the pores of a zeolitic support material).

[0028] The first PGM component has a molar ratio of Pt:Pd of about 5:95 to about 95:5. In other words, the first PGM component has about 5 to about 50 mole % Pt, based on the total moles of Pt and Pd. Thus, if the first PGM component consists of Pt and Pd, the first PGM component contains about 5 to about 50 mole % Pt, based on the total moles of the first PGM component.

[0029] The molar ratio of Pt:Pd is preferably about 5:95 to about 90:10, more preferably about 5:95 to about 75:25, even more preferably about 10:90 to about 50:50, even more preferably about 10:90 to about 35:65, and most preferably about 10:90 to about 25:75. For example, preferably about 7:93 to about 15:85, about 7:93 about 8:92 to about 15:85, about 8:92 to about 14:86, about 8:92 to about 13:87, about 7:93 to about 12:88, about 7:93 to about 11:89, about 8:92 to about 15:85, about 8:92 to about 14:86, about 8:92 to about 13:87, about 8:92 to about 12:88, about 8:92 to about 11:89, about 9:91 to about 14:86, or about 9:91 to about 13:87. In some preferred embodiments, the molar ratio of Pt:Pd can be about 9:91 to about 11:89.

[0030] The inventors have also surprisingly found that replacing Pt with Pt approaching about 10 mol% in a Pd-containing catalyst, such as a TWC catalyst, can provide the improved catalytic performance described herein, while also providing a less expensive catalyst composition due to the current price difference between Pt and Pd. As demonstrated in the examples below, the best benefits are shown when the molar ratio of Pt:Pd approaches about 10:90. However, throughout the claimed range (e.g., when the molar ratio of Pt:Pd approaches 95:5), a less expensive catalyst can still be provided that can unexpectedly provide at least the same, but preferably improved, catalytic (i.e., TWC) performance.

[0031] Pt and Pd are preferably at least partially alloyed, more preferably substantially alloyed, and even more preferably completely alloyed. The terms "alloy" or "alloyed" as used herein have their usual meaning in the art. TEM and XRD characterization techniques may be used to help determine whether a Pt-Pd alloy has formed, using techniques known to those skilled in the art. Without wishing to be bound by theory, it is hypothesized that the formation of such an alloy may contribute to the achievement of advantageous properties such as comparable or improved catalytic activity, lower light-off temperature, and aging resistance, as described and demonstrated herein. Such an alloy of Pt and Pd may be formed during the preparation of the catalyst composition, for example, during a calcination and / or heating step that may be performed. Alternatively, such an alloy may form during use (e.g., aging) of the catalyst composition due to high temperatures experienced, for example, in an exhaust system. That is, a mixture of Pt nanoparticles and Pd nanoparticles that may be in close proximity on a support material may coalesce and form an alloy at such temperatures.

[0032] As used herein, the term "substantially alloyed" refers to at least 75% of the PGMs contained within a catalyst region of interest being present as an alloy phase. As used herein, the term "partially alloyed" refers to at least 25% of the PGMs contained within a catalyst region of interest being present as an alloy phase.

[0033] The likelihood of such potentially beneficial alloying occurring can be increased by using, during preparation of the catalyst composition, methods that help ensure, for example, uniform distribution of Pt and Pd on the support material, preferably also uniform distribution of Pt and Pd nanoparticles on the support material having small particle sizes, such as less than 50 nm, less than 30 nm, or even less than 20 nm, in terms of average particle size as determined by TEM. In other words, the close proximity of small Pt and Pd nanoparticles on the support material can help increase the likelihood of alloying of Pt and Pd in ​​the first PGM component. The first PGM component preferably consists of an alloy of Pt and Pd.

[0034] The first support material preferably comprises an inorganic oxide. The inorganic oxide is preferably selected from one or more of cerium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, alumina, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium oxide, and mixed or composite oxides thereof, or zeolites. The inorganic oxide is preferably a metal oxide. The first support material is preferably selected from alumina, preferably gamma-alumina, ceria-zirconia mixed oxide, or combinations thereof. In other words, the first PGM component is preferably supported on alumina and / or ceria-zirconia. Any number of support materials may be present, provided that the Pt and Pd of the first PGM component are both supported on or in the same, together, to allow for an interaction between Pt and Pd.

[0035] The alumina and / or ceria-zirconia mixed oxide is preferably doped. The alumina and / or ceria-zirconia mixed oxide is preferably doped with one or more oxides of lanthanum, neodymium, yttrium, niobium, praseodymium, hafnium, molybdenum, titanium, vanadium, zinc, cadmium, manganese, iron, copper, calcium, barium, strontium, cesium, magnesium, potassium and sodium, preferably with one or more oxides of lanthanum, neodymium, praseodymium and yttrium, more preferably with an oxide of lanthanum. Such doped oxides are particularly useful as support materials. Preferably, the dopant is present in the alumina and / or ceria-zirconia mixed oxide in an amount of 0.001% to 20% by weight, and preferably 0.5% to 10% by weight.

[0036] The first support material or the inorganic oxide of the first support material preferably has a D of 0.1 to 25 μm, preferably 0.5 to 5 μm, as measured by TEM. 90 It is in the form of a powder having the formula:

[0037] The term "mixed oxide" as used herein generally refers to a mixture of oxides in a single phase, as is conventionally known in the art. The term "complex oxide" as used herein generally refers to a composition of oxides having two or more phases, as is conventionally known in the art.

[0038] The catalyst composition preferably further comprises a second PGM component and a second support material. The second PGM component preferably comprises rhodium (Rh), a Rh alloy, Pt, a Pt alloy, a Rh-Pt alloy, or a mixture thereof. The second PGM component preferably comprises Rh. Thus, the catalyst composition is preferably a trimetallic (i.e., Pt, Pd, and Rh) catalyst composition, preferably a TWC. For example, when Rh is present, it may offset any (albeit slight) deterioration in performance of a catalyst composition in which a higher percentage of Pd is replaced by, for example, more than about 25 mole % Pd. In other words, the catalyst composition further comprising Rh may achieve the same or improved catalytic performance even if the Pt content in the first PGM component is higher (e.g., even if the Pt:Pd molar ratio approaches 95:5), even if a larger amount of Pt may result in minimal change in catalytic performance. Furthermore, such a catalyst composition may have a lower cost first PGM component.

[0039] In a further aspect, the present invention provides a catalytic article for treating an exhaust gas, the catalytic article comprising: A substrate; a first catalyst region comprising a first platinum group metal (PGM) component and a first support material, the first PGM component comprising platinum (Pt) and palladium (Pd) supported on the first support material; The first PGM component has a molar ratio of Pt:Pd of from about 5:95 to about 95:5.

[0040] The term "catalyst article" as used herein may include an article on which or in which a catalyst is supported. The article may preferably take the form of, for example, a honeycomb monolith, or a filter, for example, preferably a wall-flow filter or a flow-through filter. The catalyst article may be for use in an emission treatment system, particularly an emission treatment system for a gasoline engine, preferably a stoichiometric gasoline engine. The catalyst article may be for use in three-way catalysis. In other words, the catalyst article may be a TWC.

[0041] The term "substrate" as used herein may include, for example, ceramic or metal honeycombs, or filter blocks, such as, preferably, wall-flow or flow-through filters. Substrates may include ceramic monolith substrates. Substrates may vary in their material composition, size and configuration, cell shape and density, and wall thickness. Suitable substrates are known in the art.

[0042] Unless otherwise stated, the preferences, embodiments, and definitions set forth above for the first aspect (the catalyst composition described herein) in relation to the first PGM component and the first support material apply equally to this aspect (the catalyst article).

[0043] The term "region" or "catalyst region" as used herein refers to an area on a substrate containing a catalyst, typically obtained by drying and / or calcining a washcoat. A "region" may be disposed or supported on the substrate as, for example, a "layer" or a "zone." The area or arrangement on the substrate is generally controlled during the process of applying the washcoat to the substrate. A "region" typically has a distinct boundary or edge (i.e., it is possible to distinguish one region from another using conventional analytical techniques).

[0044] Typically, a "region" has a substantially uniform length. Reference to a "substantially uniform length" in this context refers to a length that does not deviate from its average value by more than 10% (e.g., the difference between the maximum and minimum length), preferably a length that does not deviate from its average value by more than 5%, and more preferably a length that does not deviate from its average value by more than 1%.

[0045] Each "region" preferably has a substantially uniform composition (i.e., there is no substantial difference in the composition of the washcoat when comparing one portion of the region to another portion of the region). Substantially uniform composition in this context refers to a material (e.g., region) that has a composition difference of 5% or less, usually 2.5% or less, and most commonly 1% or less, when comparing one portion of the region to another portion of the region.

[0046] As used herein, the term "zone" refers to a region having a length that is less than the entire length of the substrate, such as a length that is 75% or less of the entire length of the substrate. A "zone" typically has a length that is at least 5% (e.g., 5% or more) of the entire length of the substrate (i.e., a substantially uniform length).

[0047] The catalyst article preferably further comprises a second catalyst region. The second catalyst region preferably comprises a second PGM component and a second support material. The second PGM component preferably comprises rhodium (Rh), an Rh alloy, Pt, a Pt alloy, an Rh-Pt alloy, or a mixture thereof. The second PGM component preferably comprises Rh. Thus, the catalyst article is preferably a trimetallic (i.e., Pt, Pd, and Rh) catalyst composition, preferably a TWC. As with conventional TWC catalysts, the Rh-containing catalyst region is a different catalyst region from the Pd-based catalyst region (i.e., the first catalyst region described herein). For example, when Rh is present, it can offset the reduced performance of a catalyst composition in which a higher percentage (e.g., greater than about 25 mol%) of Pd is replaced by Pd. In other words, for catalyst compositions further comprising Rh, equivalent or improved catalytic performance may be achieved even with higher Pt content in the first PGM component (e.g., even with Pt:Pd molar ratios approaching 95:5), even though higher amounts of Pt may result in minimal change in catalytic performance. Moreover, such catalyst articles may have lower cost first PGM components.

[0048] The catalyst composition, the first catalyst region, and / or the second catalyst may include additional components such as, for example, one or more of an accelerator, a binder, and a thickener.

[0049] The promoter may include, for example, a non-PGM transition metal element, a rare earth element, an alkali or alkaline earth group element, and / or a combination of two or more of the above elements in the same or different groups of the periodic table. The promoter may be a salt of such an element. A particularly preferred promoter is barium, the particularly preferred salts of which are barium acetate, barium citrate, and barium sulfate, or combinations thereof, more preferably barium citrate.

[0050] The binder may include, for example, an oxide material having a small particle size to bind together individual insoluble particles in the washcoat slurry. The use of binders in washcoats is well known in the art.

[0051] The thickener may include, for example, a natural polymer with functional hydroxyl groups that interact with insoluble particles in the washcoat slurry. The thickener serves the purpose of thickening the washcoat slurry for improved coating profile during washcoat coating on the substrate. The thickener is usually baked off during the washcoat calcination. Examples of specific thickeners / rheology modifiers for washcoats include gluctomannan gum, guar gum, xanthan gum, curdlan schizophyllan, scleroglucan, diutan gum, wheylan gum, hydroxymethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, methylcellulose, methylhydroxyethylcellulose, methylhydroxypropylcellulose, and ethylhydroxycellulose.

[0052] Preferably, the first and second catalytic regions form separate layers, and the second catalytic region is deposited directly on the first catalytic region. That is, the first catalytic region is sandwiched between the second catalytic region and a substrate (e.g., a filter wall). In another preferred embodiment, the first and second catalytic regions form separate layers, and the first catalytic region is deposited directly on the second catalytic region.

[0053] The first catalytic region may be supported / deposited directly on the substrate, i.e., the first catalytic region is in direct contact with the substrate. Alternatively, the second catalytic region may be supported / deposited directly on the substrate.

[0054] Typically, the substrate has a first end and a second end having an axial length L. In some preferred embodiments, the first catalyst region extends over the entire axial length L, and / or the second catalyst region extends over the entire axial length L (e.g., FIG. 1a and FIG. 1b). In other preferred embodiments, the first catalyst region extends over less than the axial length L, and / or the second catalyst region extends over less than the axial length L (e.g., FIG. 2a-FIG. 2d). When the first catalyst region extends over less than the axial length L, the first catalyst region may extend from the first end or the second end. When the second catalyst region extends over less than the axial length L, the second catalyst region may extend from the first end or the second end. When the first or second catalytic region extends less than the axial length L, the first or second catalytic region may extend, for example, over 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% of the axial length L, such as over 10%-90%, or 10%-50%, or 10%-30%, or 30%-90%, or 50%-90%, or 70%-90%, or 20%-80%, or 30%-70%, or 40%-60%. The first and second catalytic regions may overlap completely, at least partially, partially, or not at all. Each configuration provides certain advantages depending on the intended application of the catalytic article.

[0055] In some preferred embodiments, the first end is an inlet end and the second end is an outlet end of the catalytic article. As used herein, the terms "outlet end" and "inlet end" are used with reference to the relative intended direction of exhaust flow when the catalytic article is disposed within an exhaust system, e.g., the intended direction of exhaust gas is from the inlet end toward the outlet end.

[0056] The first catalyst region preferably has a surface roughness of 20 g / ft 3 ~400g / ft 3 The total amount of Pt and Pd is preferably 30 g / ft 3 ~250g / ft 3 , or 40g / ft 3 ~200g / ft3 The second catalytic region preferably contains a total amount of Pt and Pd of 2 g / ft 3 ~200g / ft 3 of Rh, preferably 5 g / ft 3 ~100g / ft 3 Contains Rh.

[0057] In some preferred embodiments, the first catalytic region of the catalyst article of the present embodiment is a catalyst composition according to the first embodiment. In other words, in some preferred embodiments, the first catalytic region of the catalyst article of the present embodiment is formed from a catalyst composition according to the first embodiment.

[0058] In a further aspect, the present invention provides an emission treatment system comprising the catalyst composition or catalyst article described herein.

[0059] The emission treatment system is preferably for a gasoline engine.

[0060] Gasoline engines preferably operate under stoichiometric conditions.

[0061] In a further aspect, the present invention provides a method of treating an exhaust gas comprising providing a catalyst composition or catalyst article described herein and contacting the catalyst composition or catalyst article with the exhaust gas.

[0062] The exhaust gas is preferably from a gasoline engine. The catalytic article is particularly suitable for treating such exhaust gas. Furthermore, exhaust from a gasoline engine is typically more severe, e.g., hotter, than exhaust from a diesel engine. Thus, the advantageous aging characteristics of the catalytic articles described herein are particularly beneficial therefor. The gasoline engine preferably operates under stoichiometric conditions.

[0063] In a further aspect, the present invention provides a method of making a catalyst article, the method comprising: A slurry comprising: Platinum (Pt) ions and palladium (Pd) ions in a molar ratio of about 5:95 to about 95:5, and providing a slurry comprising a support material; disposing the slurry on a substrate; and heating the slurry to form Pt and Pd nanoparticles on the support material.

[0064] The term "slurry" as used herein may include a liquid containing insoluble material, e.g., insoluble particles. The slurry may include (1) a solvent, (2) soluble matter, e.g., free Pt and Pd ions (i.e., outside the support), and (3) insoluble matter, e.g., particles to be supported. The slurry is particularly effective in placing the material on the substrate, particularly to maximize gas diffusion and minimize pressure drop during catalytic conversion. The slurry is typically stirred, more typically for at least 10 minutes, more typically for at least 30 minutes, and even more typically for at least 1 hour. Thus, the slurry typically includes a loaded support material (i.e., the support material is preferably a loaded support material). The term "loaded support material" as used herein may include a support material having Pt and Pd ions loaded thereon (e.g., on the surface of a high surface area metal oxide support material) and / or loaded therein (e.g., within the pores of a zeolite support material). The Pt and Pd ions are typically immobilized on the support by, for example, electrostatic forces, hydrogen bonds, coordinate bonds, covalent bonds, and / or ionic bonds. The support material is preferably the first support material described herein.

[0065] Providing the slurry typically involves mixing a solvent, a support material, and Pt and Pd ions (eg, from a Pt and / or Pd salt, such as Pt nitrate or Pd nitrate).

[0066] The disposing of the slurry on the substrate can be performed using techniques known in the art. Typically, the slurry is injected into the inlet of the substrate using a specific forming tool in a predetermined amount, thereby disposing the loaded carrier material on the substrate. Subsequent vacuum and drying steps may be used during the disposing step. If the substrate is a filter block, the loaded carrier material can be disposed on the filter wall, within the filter wall (if porous), or both.

[0067] Heating of the slurry is typically performed in an oven or furnace, more typically in a belt or static oven or furnace, typically in a specific flow of hot air from one direction. Heating may include calcination. Heating may also include drying. The drying and calcination steps may be continuous or sequential. For example, a separate washcoat may be applied after the substrate has already been washcoated and dried together with the previous washcoat. The washcoated substrate may also be dried and calcined using one continuous heating program once coating is complete. During heating, any complexes that may have formed in the slurry may at least partially, substantially, or completely decompose. In other words, such complexes, e.g., ligands of organic compounds, are at least partially, substantially, or completely removed or separated from the Pt and Pd and removed from the final catalyst article. The particles of Pt and Pd so separated may then begin to form metal-metal bonds and metal-oxide bonds. As a result of heating (calcination), the substrate is typically substantially free of organic compounds, more typically completely free of organic compounds.

[0068] As used herein, the term "nanoparticle" can encompass particles having a diameter between 0.01 nm and 100 nm as measured by TEM. Nanoparticles can be of any shape, e.g., spheres, plates, cubes, cylinders, hexagons, or rods, but are typically spherical.

[0069] After the heating step, the substrate is typically cooled, more typically to room temperature. Cooling is typically performed in air with or without a coolant / cooling medium, typically without a coolant.

[0070] The slurry preferably comprises one or more of glyoxime, glyoxime derivatives, salicylaldimine, and salicylaldimine derivatives. Without being bound by theory, it is believed that complexes can be formed that include such molecules and Pt and / or Pd. It has been surprisingly found that such compounds are useful for enabling uniform distribution of Pt and Pd, for example, to achieve the advantageous properties described and demonstrated herein.

[0071] The catalytic articles described herein are preferably obtained or obtainable by the method of this aspect, however, alternative methods known to those skilled in the art may also be used to produce the catalytic articles described herein, although the method of this aspect may be particularly preferred.

[0072] The invention will now be described with reference to the following non-limiting examples.

[0073] Example 1: Light-off performance in synthetic catalyst activity test A series of Pd-Pt supported ceria-zirconia catalysts with a total PGM loading of 1 wt% were prepared by the incipient wetness method using Pd(NO3)3 and Pt(NO3)3 precursors. After drying, they were calcined at 650°C for 2 hours. The molar ratios of Pd and Pt are 100:0 (for Pd only reference), 95:5, 90:10, 79:21, 65:35, 47:53, and 0:100 (for Pt only reference), as shown in Table 1 below.

[0074] [Table 1] Table 1: PGM loading of catalyst in Example 1

[0075] The catalysts were aged according to the TWC aging conditions in Table 2 and tested under a continuous gas mixture with a typical TWC gas composition. The catalysts in Table 1 were tested from 110 to 500 °C using a ramp rate of 10 °C / min. The total flow rate used was 5 L / min for 0.2 g of catalyst mixed with 0.2 g of cordierite placed in a fixed bed reactor. The gases used and their concentrations are listed in Table 3.

[0076] [Table 2] Table 2: Aging conditions of the catalyst of Example 1

[0077] [Table 3] Table 3: Gas mixture composition for light-off experiments in Example 1

[0078] The results are shown in Figures 3a and 3b, which show the light-off temperature (T 60 ) are shown. Figure 3a shows the aging conditions after a lean shutdown, and Figure 3b shows the aging conditions after a rich shutdown. Catalyst 3 (with a Pd-Pt molar ratio of 90:10) showed better performance after both rich and lean shutdown conditions after aging treatment compared to Comparative Catalysts 1 and 7.

[0079] Catalyst 3 (with a Pd-Pt molar ratio of 90:10) was then tested across six additional TWC gas mixtures with varying H2:CO ratios and the results were compared to comparative catalyst 1 (Pd only). Catalyst 3 performed better in all cases, especially as the H2 concentration increased, and showed a greater H2 promotion effect on activity in the case of the Pd-Pt alloy, as shown in Figure 4. This data suggests that the Pd-Pt alloy is more robust to a variety of TWC gas conditions.

[0080] Example 2: Vehicle Testing Procedures and Results General Synthesis of Catalyst Articles Catalyst articles having 100:0, 90:10, 50:50, and 27:73 mole % Pd:Pt were prepared according to standard washcoat procedures (known to those skilled in the art) except that a Pd-DMG (dimethylglyoxime) basic solution was added to the washcoat in small increments along with HNO3 solution to reduce and maintain the pH below 7. The fully formulated catalysts were weighed at 100 g / ft 3 of Pd or Pd+Pt and 16g / ft 3 of Rh with a Pd top layer in the following structure: Top layer: La-doped alumina (0.7 g / ft 3 ), rare earth doped ceria zirconia (0.7g / ft 3 ), Pd(+Pt)-DMG(100g / ft 3 ), BaSO4(200g / ft 3 ), and Lower layer: La-doped alumina (0.7 g / ft 3 ), rare earth doped ceria zirconia (0.7g / ft 3 ), Rhodium (16g / ft 3 ).

[0081] [Table 4] Table 4: Top layer PGM loading of catalyst article in Example 2

[0082] The catalyst articles in Table 4 were aged using gasoline engine bench aging, finished under a stoichiometric gas mixture. Engine bench aging was performed using a 4.6 L engine for 50 hours using a four mode aging cycle with a peak bed temperature of about 1000°C on the catalyst. The catalysts were tested on a 2.4 L vehicle via an FTP drive cycle and emissions were measured immediately after the catalyst (placed in a close coupled system). The results of the vehicle testing are summarized in Figures 5a-c.

[0083] As shown in Figures 5a-c, the results show similar trends to those observed for the catalyst of Example 1. Catalyst Article B showed approximately 12% improvement in total cumulative CO emissions and slightly better NO emissions compared to Comparative Catalyst Article A. x Conversion rate (less than 5%) was observed, and there was no deterioration in HC performance.

[0084] Within this series of catalyst articles, Pd can be replaced with Pt up to 50 mol % without significantly changing the total emissions, with a significant benefit observed for catalyst article B (having a Pd-Pt molar ratio of 90:10).

[0085] Example 3: Vehicle Testing Procedures and Results Comparative catalyst article E First catalytic region: The first catalytic region consisted of Pd supported on a washcoat of CeZr mixed oxide, La-stabilized alumina, and Ba promoter, and Pd nitrate solution was used as the Pd source during the washcoat slurry preparation. The washcoat loading of the first catalytic region was about 1.8 g / in 3 and the Pd loading is 42g / ft 3 It was.

[0086] This washcoat was then coated using standard coating procedures onto a ceramic substrate (600 cpsi, 4.3 mil wall thickness, 118.4 mm diameter, and 91 mm length) from the inlet face with a target coating depth of 80% of the substrate's length and dried at 100°C.

[0087] Second catalytic region: The second catalytic region consisted of Rh supported on a washcoat of CeZr mixed oxide and La-stabilized alumina. The washcoat loading of the second catalytic region was about 1.3 g / in 3 and the Rh loading is 8g / ft 3 It was.

[0088] This second washcoat was then coated using standard coating procedures from the outlet face of the ceramic substrate containing the first catalytic region with a coating depth targeted to 80% of the substrate length, dried at 100°C, and calcined at 500°C for 45 minutes.

[0089] Catalyst article F Catalyst article F according to the invention has a viscosity of 34 g / ft 3 Pd loading of 8g / ft 3 Comparative catalyst article E was prepared according to a similar procedure to Comparative catalyst article E, except for partial Pd replacement with Pt in the first catalyst region having a Pt loading of about 11:10 and a Pt:Pd molar ratio of about 11:89.

[0090] The second catalyst region was the same as Comparative Catalyst Article E.

[0091] The new comparative catalyst article E and catalyst article F were tested on a commercial vehicle equipped with a 1.6L turbo engine under the Worldwide Light Duty Testing Procedure (WLTP) with the bricks placed in a close coupling position. The vehicle exhaust dilution bag data are shown in Table 5.

[0092] In addition to cost savings, the inventive catalyst article F surprisingly reduces NO x It showed excellent activity in controlling excretion (e.g., NO x (See performance improvement of about 37%)

[0093] [Table 5] Table 5: Emissions results from vehicle dilution bag data

[0094] Example 4: Vehicle Testing Procedures and Results Comparative catalyst article G First catalytic region: The first catalytic region consisted of Pd supported on a washcoat of rare earth doped CeZr mixed oxide, La stabilized alumina, and Ba promoter, and Pd nitrate solution was used as the Pd source during the washcoat slurry preparation. The washcoat loading of the first catalytic region was about 2.0 g / in 3 and the Pd loading is 68g / ft 3 It was.

[0095] This washcoat was then coated onto a ceramic substrate (600 cpsi, 3 mil wall thickness, 118.4 mm diameter and 114.3 mm length) using standard coating procedures, followed by drying at 100°C.

[0096] Second catalytic region: The second catalytic region consisted of rare earth doped CeZr mixed oxide and Rh supported on a washcoat of La stabilized alumina. The washcoat loading of the second catalytic region was about 2.0 g / in 3 and the Rh loading is 6g / ft 3 It was.

[0097] This second washcoat was then coated onto the ceramic substrate containing the first catalytic region above using standard coating procedures, dried at 100° C., and calcined at 500° C. for 45 minutes.

[0098] Catalyst article H Catalyst article H according to the invention has a viscosity of 51 g / ft 3 Pd loading of 17g / ft 3 (the molar ratio of Pt:Pd was about 15:85) and Pd-DMG and Pt-DMG were used instead of Pd nitrate.

[0099] The second catalyst region was the same as Comparative Catalyst Article G.

[0100] Catalyst article I The catalytic article I according to the invention has a viscosity of 34 g / ft 3 Pd loading of 34g / ft 3 (the molar ratio of Pt:Pd was about 35:65) and Pd-DMG and Pt-DMG were used instead of Pd nitrate.

[0101] The second catalyst region was the same as Comparative Catalyst Article G.

[0102] Comparative catalyst article G and catalyst articles H, I were aged using gasoline engine bench aging. Engine bench aging was performed using a 4.0L engine using a lean spike aging cycle with a peak bed temperature of about 1030°C on the catalyst for 100 hours. The catalysts were tested on a 2.0L engine bench via an RDE-compatible driving cycle and emissions were measured immediately after the catalyst (located in a close-coupled system). A summary of the vehicle exhaust modal bag data is shown in Table 6.

[0103] In addition to cost savings, the catalyst articles H and I of the present invention surprisingly reduced the amount of THC, CO, and NO compared to the comparative catalyst article G. x They showed comparable activity in controlling efflux.

[0104] [Table 6] Table 6: Emissions results from vehicle modal data

[0105] The foregoing detailed description has been provided for purposes of explanation and illustration and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments described herein will be apparent to those of ordinary skill in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A catalyst composition comprising a first platinum group metal (PGM) component and a first support material, wherein the first PGM component comprises platinum (Pt) and palladium (Pd) and is supported on the first support material; and A catalyst composition wherein the first PGM component has a molar ratio of Pt:Pd of from about 5:95 to about 95:

5.

2. 10. The catalyst composition of claim 1, wherein the Pt and the Pd are at least partially alloyed, preferably substantially alloyed.

3. 3. The catalyst composition of claim 1 or 2, wherein the first support material comprises an inorganic oxide.

4. 4. The catalyst composition according to claim 3, wherein the inorganic oxide is selected from one or more of cerium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, alumina, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium oxide, and mixed or composite oxides thereof, or zeolites.

5. 3. The catalyst composition of claim 1 or 2, further comprising a second PGM component and a second support material.

6. 6. The catalyst composition of claim 5, wherein the second PGM component comprises rhodium (Rh), a Rh alloy, Pt, a Pt alloy, a Rh-Pt alloy, or a mixture thereof.

7. 1. A catalytic article for treating exhaust gases, comprising: A substrate; a first catalyst region comprising a first platinum group metal (PGM) component and a first support material, the first PGM component comprising platinum (Pt) and palladium (Pd) supported on the first support material; A catalyst article wherein the first PGM component has a molar ratio of Pt:Pd of from about 5:95 to about 95:

5.

8. 8. The catalytic article of claim 7, wherein the Pt:Pd molar ratio is from about 5:95 to about 25:75, preferably from about 7:93 to about 20:80, more preferably from about 9:91 to about 15:85, even more preferably from about 9:91 to about 12:88, and most preferably about 10:

90.

9. 9. The catalytic article of claim 7 or 8, wherein the Pt and the Pd are at least partially alloyed, preferably substantially alloyed.

10. 9. The catalytic article of claim 7 or 8, wherein the first support material comprises an inorganic oxide.

11. 11. The catalytic article of claim 10, wherein the inorganic oxide is selected from one or more of cerium oxide, ceria-zirconia mixed oxide, alumina-ceria-zirconia mixed oxide, alumina, magnesia, silica, lanthanum, neodymium, praseodymium, yttrium oxide, and mixed or composite oxides thereof, or zeolites.

12. 9. The catalytic article of claim 7 or 8, further comprising a second catalytic region.

13. The catalytic article of claim 12 , wherein the second catalytic region comprises a second PGM component and a second support material.

14. 9. An emissions treatment system comprising the catalyst composition of claim 1 or 2 or the catalyst article of claim 7 or 8.

15. 1. A method for treating an exhaust gas, the method comprising: Providing a catalyst composition according to claim 1 or 2 or a catalyst article according to claim 7 or 8; contacting the catalyst composition or the catalyst article with an exhaust gas.

16. 1. A method of making a catalyst article, the method comprising: platinum (Pt) ions and palladium (Pd) ions in a molar ratio of about 5:95 to about 95:5; a support material; and providing a slurry comprising: disposing the slurry on a substrate; heating the slurry to form nanoparticles of the Pt and Pd on the support material; A method comprising:

17. 17. The method of claim 16, wherein the slurry comprises one or more of glyoxime, glyoxime derivatives, salicylaldimine, and salicylaldimine derivatives.

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