Ternary platinum alloy having a transition metal for enhanced oxidation activity

Abstract

An oxidation catalyst, an oxidation catalyst composite, a system, and a method for treating an exhaust gas stream to control the emissions of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x ) in the exhaust gas stream of an internal combustion engine are disclosed herein. The oxidation catalyst, the oxidation catalyst composite, the system, and the treatment method include a ternary alloy nanoparticle catalyst, and the ternary alloy nanoparticle catalyst includes a platinum group metal alloyed with at least two transition metal elements.

Description

Technical Field

[0001] This disclosure was made with government support under CHE-2102482 awarded by the National Science Foundation. The government has certain rights in this disclosure.

[0002] This disclosure is directed to oxidation catalysts, systems, and methods for treating an exhaust gas stream to control emissions of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x ) in the exhaust gas stream of an internal combustion engine. The oxidation catalyst, system, and treatment method include a ternary alloy nanoparticle catalyst, which includes a platinum group metal alloyed with at least two transition metal elements.

[0003] The exhaust gas stream of an internal combustion engine contains pollutants such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x ) that contaminate the air. Generally, oxidation catalysts containing noble metals such as platinum group metals (PGMs) dispersed on a refractory metal oxide support such as alumina are used to treat the exhaust of an internal combustion engine by catalyzing the oxidation of gaseous pollutants such as HC and CO to convert these pollutants to carbon dioxide and water. Typically, the oxidation catalyst is formed on a ceramic substrate or a metal substrate, on which one or more catalyst coating compositions are deposited. In addition to the conversion of gaseous HC and CO emissions, the oxidation catalyst containing PGM promotes the oxidation of NO to NO2, which in particular enhances the downstream SCR reaction at lower temperatures (≤250 °C).

[0004] The catalyst is typically defined by its light-off temperature or the temperature at which 50% conversion, also referred to as T 50 is achieved. Catalysts containing only platinum become less active with use, especially after thermal aging, resulting in, for example, a reduction in NO2 formation from NO oxidation, which in turn results in lower downstream SCR activity, most pronounced at lower temperatures (≤250 °C). Also, the NO2 / NO from fresh catalyst to aged catalystx The large change in ratio complicates the calibration of the urea injection rate during the course of catalyst deactivation as a result of hydrothermal aging.

[0005] Oxidation catalysts containing precious metals dispersed on refractory metal oxide supports are known to be used in the treatment of diesel engine exhaust to catalyze the oxidation of gaseous pollutants of hydrocarbons and carbon monoxide, thereby converting these pollutants to carbon dioxide and water. Such catalysts are generally contained in units called diesel oxidation catalysts (DOCs), or more simply catalytic converters, which are placed in the exhaust flowpath from diesel-powered engines to treat the exhaust before it is released into the atmosphere. Typically, diesel oxidation catalysts are formed on ceramic or metal substrate supports (such as flow-through monolith supports as described herein below) on which one or more catalytic coating compositions are deposited. In addition to converting gaseous HC, CO, and particulate matter, oxidation catalysts containing platinum group metals (typically dispersed on refractory oxide supports) promote the oxidation of nitric oxide (NO) to NO2.

[0006] One important factor in DOC design is catalyst deactivation after high temperature exposure. Thermally induced DOC deactivation can occur as a result of sintering of the catalyst components or support. Sintering of catalyst components involves coalescence or crystallite growth of initially well-dispersed catalytic sites. This agglomeration leads to a loss of surface area to volume ratio, reducing catalytic performance. Alternatively, exposure of DOCs to high temperatures can lead to sintering of the catalyst support. This is accompanied by a loss of support pore structure causing a loss of accessibility to catalytically active sites.

[0007] S. Shiyao et al., "Surface oxygenation of multicomponent nanoparticles toward active and stable oxidation catalysts", NATURE COMMUNICATIONS, vol.11, no.1, December 1, 2020 relates to the synthesis of oxidation catalysts for the complete oxidation of hydrocarbons, such as propane, by surface oxygenation of platinum-alloyed multicomponent nanoparticles.

[0008] L. Yang et al., "Role of Support-Nanoalloy Interactions in the Atomic-Scale Structural and Chemical Ordering for Tuning Catalytic Sites", JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, vol.134, no.36, September 12, 2012 discloses alloy nanoparticles as oxidation catalysts, which can be supported on silica, titania, or carbon, and the catalysts are used for the oxidation of CO.

[0009] Therefore, there is still a need for even more efficient catalysts for treating the exhaust gases of internal combustion engines. Specific needs include catalysts that provide excellent conversion of CO, HC, and NO→NO2 oxidation and are stable against thermal aging.

[0010] This disclosure is directed to oxidation catalysts that are ternary alloy nanoparticle catalysts. The ternary alloy nanoparticle catalysts contain a platinum group metal alloyed with at least two transition metal elements. The platinum group metal can be selected from Pt, Pd, Ru, Rh, Ir, and Os, and the at least two transition metal elements can be selected from Ni, Co, Mn, Fe, V, Zn, Cu, Ti, Sc, and Cr. This disclosure is further directed to diesel oxidation catalysts containing the above ternary alloy nanoparticle catalysts.

[0011] The ternary alloy nanoparticle catalyst can be supported on a refractory oxide support, and the refractory oxide support can be selected from silica, δ-alumina, θ-alumina, γ-alumina, Si-doped alumina, alkaline earth metal-stabilized alumina, transition metal-stabilized alumina, zirconia, and titania.

[0012] The platinum group metal content of the ternary alloy nanoparticles can be about 80 atomic% or less of the metal content, and the platinum group metal weight ratio can be about 30 atomic% to about 50 atomic% of the metal content.

[0013] At least two transition metal elements of the ternary alloy nanoparticles can have a total ratio of about 20 atomic% to about 80 atomic% of the metal content.

[0014] The platinum group metal and at least two transition metal elements of the ternary alloy nanoparticle catalyst can be detectable by TEM / EDS (Transmission Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy), X-ray diffraction, or a combination thereof.

[0015] The XRD of the ternary alloy nanoparticles can show a 2-theta value of Pt fcc (111) in the range of about 39.7° to about 42° when incorporating at least two transition metals at different levels.

[0016] The ternary alloy nanoparticle catalyst can be selected from PtNiCo and PtMnFe. The atomic ratio of the PtNiCo ternary alloy nanoparticle catalyst can be about 20 - 80% Pt, about 1 - 50% Ni, and about 5 - 40% Co. The atomic ratio of the PtMnFe ternary alloy nanoparticle catalyst can be about 15 - 40% Pt, about 10 - 50% Mn, and about 10 - 50% Fe.

[0017] The present disclosure also provides a process for preparing a ternary alloy nanoparticle catalyst comprising a platinum group metal alloyed with at least two transition metal elements. The process includes combining a precursor of the platinum group metal and precursors of at least two transition metal elements with a capping agent in an organic solvent to form a solution, introducing a reducing agent into the solution to produce a colloidal suspension of the ternary alloy nanoparticle catalyst, collecting the ternary alloy nanoparticle catalyst and adsorbing it onto a refractory oxide support, and drying and calcining the adsorbed ternary alloy nanoparticle catalyst and refractory oxide support.

[0018] The precursor of the platinum group metal can be selected from platinum(II) acetylacetonate, chloroplatinic acid, platinum(II) hydroxy sulfite, tetraammineplatinum(II) chloride, and tetraammineplatinum(II) nitrate. The precursors of at least two transition metal elements can be selected from nickel(II) acetylacetonate and cobalt(III) acetylacetonate. The capping agent can be selected from citric acid, polyvinylpyrrolidone, oleylamine, oleic acid, and polyethylene glycol. The reducing agent can be selected from sodium borohydride, hydrazine, formic acid, sodium formate, and amine-borane complexes; 1,2-hexadecanediol, and oleylamine. The refractory oxide support can be selected from silica, δ-alumina, θ-alumina, γ-alumina, Si-doped alumina, alkaline earth metal stabilized alumina, transition metal stabilized alumina, zirconia, and titania.

[0019] The calcination step of the process can include calcining the ternary alloy nanoparticle catalyst and refractory oxide support at about 800 °C for about 2 hours in a hydrogen atmosphere, followed by heating in air at about 260 °C for about 1 hour and heating in air at about 590 °C for about 1 hour.

[0020] The nanoparticles of the ternary alloy catalyst can have an average particle size in the range of about 2 nm to about 10 nm.

[0021] The total platinum group metal content of the ternary alloy nanoparticle catalyst can be about 0.1 wt% to about 5 wt% of the metal content.

[0022] The nanoparticles of the ternary alloy catalyst generally retain the original atomic ratios of the individual elements. The transition metal elements are present throughout the nanoparticles but are often concentrated on the particle surface, presumably due to the acidophilic nature of the transition metals when calcined in air.

[0023] After hydrothermal aging, the nanoparticles of the ternary alloy catalyst have a further concentration of the Pt composition (more than 90 atomic %), and the transition metal elements are less than 10 atomic %. All three elements appear to be uniform throughout the particles.

[0024] The present disclosure further provides an exhaust gas treatment system comprising the ternary alloy nanoparticle catalyst described herein, preferably an oxidation catalyst composite according to any of the specific preferred embodiments described herein. The ternary alloy nanoparticle catalyst is positioned downstream of an internal combustion engine and can be in fluid communication with the internal combustion engine.

[0025] The present disclosure also provides a method of treating an exhaust gas stream comprising HC and / or CO and / or NO→NO2 oxidation. The method can include passing the exhaust gas stream through the ternary alloy nanoparticle catalyst or oxidation catalyst composite or exhaust gas treatment system described herein.

Brief Description of the Drawings

[0026] To provide an understanding of embodiments of the present disclosure, reference is made to the accompanying drawings. The drawings are exemplary and should not be construed as limiting the present disclosure.

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[0027] Here, the present disclosure is more fully described. However, the present disclosure can be embodied in many different forms and should not be construed as limited to the embodiments described herein.

[0028] As used herein, the term "a" or "an" entity refers to one or more of that entity. For example, "a catalyst" refers to one or more catalysts or at least one catalyst unless otherwise specified. Thus, the terms "a" (or "an"), "one or more", and "at least one" are used interchangeably herein.

[0029] As used herein, the term "about" means approximately, nearly, substantially, or around. When the term "about" is used in conjunction with a numerical range, it modifies that range by extending the boundaries above and below the recited numerical values. Generally, the term "about" is used herein to modify the numerical values above and below the recited value by a variation of 10%.

[0030] As used herein, the term "alloy" refers to a material composed of two or more metallic elements combined by atomic bonding. The properties exhibited by the alloys of the present disclosure are different from the individual properties of the elements that make up the alloy. The distribution of each element in the alloy can be affected by external processing, often resulting in a concentration of a particular element that is seen on the particle surface.

[0031] As used herein, the term "stream" broadly refers to any combination of flowing gases that may contain particulate matter of solids or liquids. The terms "gas stream" or "exhaust stream" or "exhaust gas stream" mean the flow of gaseous constituents such as the exhaust of a combustion engine, which may contain entrained non-gaseous components such as droplets, solid particulates, etc. The exhaust gas stream of a combustion engine typically further contains combustion products (CO2 and H2O), products of incomplete combustion (carbon monoxide (CO) and hydrocarbons (HC)), nitrogen oxides (NO x x), combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen.

[0032] As used herein, "impregnated" or "impregnation" refers to the penetration of a catalyst material into the porous structure of a carrier material.

[0033] The catalyst of the present invention is suitable for the treatment of exhaust gas streams of internal combustion engines, such as gasoline, light diesel, and heavy diesel engines. In some embodiments, such a catalyst can, in combination with other components, such as other catalyst compositions, provide compositions and articles suitable for use as diesel oxidation catalysts or catalyzed soot filters. The catalyst is also suitable for the treatment of emissions from stationary industrial processes, the removal of harmful or toxic substances from indoor air, or catalysis in chemical reaction processes.

[0034] This disclosure is directed to ternary alloy nanoparticle catalysts comprising a platinum group metal alloyed with at least two transition metal elements. In some embodiments, the ternary alloy nanoparticle catalyst comprises two transition metal elements. In some embodiments, the ternary alloy nanoparticle catalyst comprises three transition metal elements. In some embodiments, the ternary alloy nanoparticle catalyst comprises four transition metal elements.

[0035] As used herein, the term "platinum group metal" (PGM) refers to platinum group metals or their oxides such as, for example, platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), oxides of any of the foregoing, and mixtures of any of the foregoing. In some embodiments, the PGM can be in any valence state.

[0036] In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is selected from Pt, Pd, Ru, Rh, Ir, and Os. In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is Pt. In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is Pd. In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is a combination of Pt and Pd. In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is Ru. In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is Rh. In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is selected from Ir. In some embodiments, the platinum group metal of the ternary alloy nanoparticle catalyst is Os.

[0037] In some embodiments, at least two transition metals of the ternary alloy nanoparticles catalyst are selected from nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), vanadium (V), zinc (Zn), copper (Cu), titanium (Ti), scandium (Sc), and chromium (Cr). In some embodiments, the at least two transition metals are Ni and Co. In some embodiments, the at least two transition metals are Ni and Mn. In some embodiments, the at least two transition metals are Ni and Fe. In some embodiments, the at least two transition metals are Ni and V. In some embodiments, the at least two transition metals are Ni and Zn. In some embodiments, the at least two transition metals are Ni and Cu. In some embodiments, the at least two transition metals are Ni and Ti. In some embodiments, the at least two transition metals are Ni and Sc. In some embodiments, the at least two transition metals are Ni and Cr. In some embodiments, the at least two transition metals are Co and Mn. In some embodiments, the at least two transition metals are Co and Fe. In some embodiments, the at least two transition metals are Co and V. In some embodiments, the at least two transition metals are Co and Zn. In some embodiments, the at least two transition metals are Co and Cu. In some embodiments, the at least two transition metals are Co and Ti. In some embodiments, the at least two transition metals are Co and Sc. In some embodiments, the at least two transition metals are Co and Cr. In some embodiments, the at least two transition metals are Mn and Fe. In some embodiments, the at least two transition metals are Mn and V. In some embodiments, the at least two transition metals are Mn and Zn. In some embodiments, the at least two transition metals are Mn and Cu. In some embodiments, the at least two transition metals are Mn and Ti. In some embodiments, the at least two transition metals are Mn and Sc. In some embodiments, the at least two transition metals are Mn and Cr.In some embodiments, the at least two transition metals are Fe and V. In some embodiments, the at least two transition metals are Fe and Zn. In some embodiments, the at least two transition metals are Fe and Cu. In some embodiments, the at least two transition metals are Fe and Ti. In some embodiments, the at least two transition metals are Fe and Sc. In some embodiments, the at least two transition metals are Fe and Cr. In some embodiments, the at least two transition metals are V and Zn. In some embodiments, the at least two transition metals are V and Cu. In some embodiments, the at least two transition metals are V and Ti. In some embodiments, the at least two transition metals are V and Sc. In some embodiments, the at least two transition metals are V and Cr. In some embodiments, the at least two transition metals are Zn and Cu. In some embodiments, the at least two transition metals are Zn and Ti. In some embodiments, the at least two transition metals are Zn and Sc. In some embodiments, the at least two transition metals are Zn and Cr. In some embodiments, the at least two transition metals are Cu and Ti. In some embodiments, the at least two transition metals are Cu and Sc. In some embodiments, the at least two transition metals are Cu and Cr. In some embodiments, the at least two transition metals are Ti and Sc. In some embodiments, the at least two transition metals are Ti and Cr. In some embodiments, the at least two transition metals are Sc and Cr.

[0038] In some embodiments, the ternary alloy nanoparticle catalyst is supported on a refractory oxide support selected from silica, δ-alumina, θ-alumina, γ-alumina, Si-doped alumina, alkaline earth metal stabilized alumina, transition metal stabilized alumina, zirconia, and titania. In some embodiments, the refractory oxide support is silica. In some embodiments, the refractory oxide support is δ-alumina. In some embodiments, the refractory oxide support is θ-alumina. In some embodiments, the refractory oxide support is γ-alumina. In some embodiments, the refractory oxide support is Si-doped alumina. In some embodiments, the Si-doped alumina contains SiO2 in the range of about 1% to about 20%. In some embodiments, the Si-doped alumina contains about 1% SiO2. In some embodiments, the Si-doped alumina contains about 5% SiO2. In some embodiments, the Si-doped alumina contains about 10% SiO2. In some embodiments, the Si-doped alumina contains about 15% SiO2. In some embodiments, the Si-doped alumina contains about 20% SiO2. In some embodiments, the refractory oxide support is alkaline earth metal stabilized alumina. In some embodiments, the alkaline earth stabilized alumina is Mn-stabilized alumina. In some embodiments, the refractory oxide support is transition metal stabilized alumina. In some embodiments, the transition metal stabilized alumina is Zr-doped alumina. In some embodiments, the transition metal stabilized alumina is Ti-doped alumina. In some embodiments, the refractory oxide support is zirconia. In some embodiments, the refractory oxide support is titania.

[0039] In some embodiments, the platinum group metal content of the ternary alloy nanoparticle catalyst is about 80 atomic % or less of the metal content. In some embodiments, the platinum group metal content is about 20 atomic % of the metal content. In some embodiments, the platinum group metal content is about 25 atomic % of the metal content. In some embodiments, the platinum group metal content is about 30 atomic % of the metal content. In some embodiments, the platinum group metal content is about 35 atomic % of the metal content. In some embodiments, the platinum group metal content is about 40 atomic % of the metal content. In some embodiments, the platinum group metal content is about 45 atomic % of the metal content. In some embodiments, the platinum group metal content is about 50 atomic % of the metal content. In some embodiments, the platinum group metal content is about 55 atomic % of the metal content. In some embodiments, the platinum group metal content is about 60 atomic % of the metal content. In some embodiments, the platinum group metal content is about 65 atomic % of the metal content. In some embodiments, the platinum group metal content is about 70 atomic % of the metal content. In some embodiments, the platinum group metal content is about 75 atomic % of the metal content. In some embodiments, the platinum group metal content is about 80 atomic % of the metal content.

[0040] In some embodiments, the platinum group metal ratio of the ternary alloy nanoparticle catalyst is from about 30 atomic % to about 50 atomic % of the metal content. In some embodiments, the platinum group metal weight ratio is about 30 atomic % of the metal content. In some embodiments, the platinum group metal weight ratio is about 35 atomic % of the metal content. In some embodiments, the platinum group metal weight ratio is about 40 atomic % of the metal content. In some embodiments, the platinum group metal weight ratio is about 45 atomic % of the metal content. In some embodiments, the platinum group metal weight ratio is about 50 atomic % of the metal content.

[0041] In some embodiments, at least two transition metal elements of the ternary alloy nanoparticle catalyst have a total ratio of about 20 atomic % to about 80 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 20 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 25 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 30 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 35 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 40 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 45 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 50 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 55 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 60 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 65 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 70 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 75 atomic % of the metal content. In some embodiments, at least two transition metal elements have a total weight ratio of about 80 atomic % of the metal content.

[0042] In some embodiments, the platinum group metal and at least two transition metal elements of the ternary alloy nanoparticle catalyst are detectable by TEM / EDS. In some embodiments, the platinum group metal and at least two transition metal elements of the ternary alloy nanoparticle catalyst are detectable by X-ray diffraction. In some embodiments, XRD shows a 2-theta value of Pt fcc(111) in the range of about 39.7° to about 42° when incorporating at least two transition metals at different levels.

[0043] In some embodiments, the ternary alloy nanoparticle catalyst is PtNiCo. In some embodiments, the atomic ratio of the PtNiCo ternary alloy nanoparticle catalyst is about 20% - 80% Pt, about 1% - 50% Ni, and about 5% - 40% Co. In some embodiments, the atomic ratio is about 30% - 60% Pt, about 20% - 40% Ni, and about 10% - 30% Co.

[0044] In some embodiments, the ternary alloy nanoparticle catalyst is PtMnFe. In some embodiments, the atomic ratio of the PtMnFe ternary alloy nanoparticle catalyst is about 15% - 40% Pt, about 10% - 50% Mn, and about 10% - 50% Fe. In some embodiments, the atomic ratio is about 30% - 40% Pt, about 30% - 40% Mn, and about 30% - 40% Fe.

[0045] In some embodiments, an oxidation catalyst composite for reducing exhaust gas emissions from a lean - burn engine is provided, which includes the above - mentioned ternary alloy nanoparticle catalyst. In some embodiments, the lean - burn engine is a lean - burn gasoline engine or a diesel engine, preferably a diesel engine.

[0046] In some embodiments, the oxidation catalyst composite includes a carrier substrate having a length, an inlet end, and an outlet end, and an oxidation catalyst material including the ternary alloy nanoparticle catalyst, and the oxidation catalyst material is provided on the carrier substrate.

[0047] In some embodiments, the oxidation catalyst material includes, preferably consists of, a washcoat layer including the ternary alloy nanoparticle catalyst. In some embodiments, the washcoat layer includes zeolite.

[0048] In some embodiments, the washcoat layer contains, calculated as an element, 5 - 500 g / ft 3 of platinum group metals from the ternary alloy nanoparticle catalyst, preferably 10 - 300 g / ft 3, more preferably 20 to 200 g / ft 3 , more preferably 40 to 150 g / ft 3 , more preferably 60 to 120 g / ft 3 , more preferably 80 to 100 g / ft 3 contains a platinum group metal. In some embodiments, the oxidation catalyst catalyst material includes, preferably consists of, a lower washcoat layer and an upper washcoat layer. The lower washcoat layer is provided on a carrier substrate, and the upper washcoat layer is provided on the lower washcoat layer. In some embodiments, the lower washcoat layer, the upper washcoat layer, or both the lower washcoat layer and the upper washcoat layer contain a ternary alloy nanoparticle catalyst.

[0049] In some embodiments, the lower washcoat layer or the upper washcoat layer contains a ternary alloy nanoparticle catalyst, and the lower washcoat layer or the upper washcoat layer contains 5 to 500 g / ft 3 of platinum group metal, preferably 10 to 300 g / ft 3 , more preferably 20 to 200 g / ft 3 , more preferably 40 to 150 g / ft 3 , more preferably 60 to 120 g / ft 3 , more preferably 80 to 100 g / ft 3 of platinum group metal.

[0050] In some embodiments, the lower washcoat layer and the upper washcoat layer contain a ternary alloy nanoparticle catalyst, and the total amount of platinum group metal in the lower washcoat layer and the upper washcoat layer from the ternary alloy nanoparticle catalyst contained in the lower washcoat layer and the upper washcoat layer, calculated as an element, is 5 to 500 g / ft 3 , preferably 10 to 300 g / ft 3 , more preferably 20 to 200 g / ft 3 , more preferably 40 to 150 g / ft 3 , more preferably 60 to 120 g / ft 3, more preferably in the range of 80 to 100 g / ft 3 is.

[0051] In some embodiments, the upper washcoat layer or the lower washcoat layer contains zeolite, preferably, the upper washcoat layer contains zeolite. In some embodiments, the upper washcoat layer contains zeolite and the lower washcoat layer is substantially free of zeolite. In some embodiments, the lower washcoat layer contains zeolite and the upper washcoat layer is substantially free of zeolite. Within the scope of the present invention, "substantially free of" means that the washcoat layer contains less than 1% by weight of zeolite, preferably less than 0.5% by weight, more preferably less than 0.1% by weight, more preferably less than 0.05% by weight, more preferably less than 0.01% by weight, more preferably less than 0.005% by weight, more preferably less than 0.001% by weight of zeolite.

[0052] In some embodiments, one or more washcoat layers containing ternary alloy nanoparticle catalysts are substantially free of barium, preferably, one or more washcoat layers containing ternary alloy nanoparticle catalysts are substantially free of alkaline earth metals. Within the scope of the present invention, "substantially free of" means that the washcoat layer contains less than 1% by weight of barium or alkaline earth metal, preferably less than 0.5% by weight, more preferably less than 0.1% by weight, more preferably less than 0.05% by weight, more preferably less than 0.01% by weight, more preferably less than 0.005% by weight, more preferably less than 0.001% by weight of barium or alkaline earth metal element, calculated as each element. In some embodiments, the carrier substrate is a wall flow substrate or a flow-through substrate, preferably a flow-through substrate, more preferably a honeycomb monolith substrate.

[0053] The present disclosure also relates to a process for preparing a ternary alloy nanoparticle catalyst comprising a platinum group metal alloyed with at least two transition metal elements. For example, the present disclosure is a process for preparing a ternary alloy nanoparticle catalyst comprising a platinum group metal alloyed with at least two transition metal elements, the process comprising: (a) combining a salt of the platinum group metal and salts of at least two transition metal elements with a capping agent in an organic solvent to form a slurry; (b) introducing a reducing agent into the slurry to produce a colloidal suspension of the ternary alloy nanoparticle catalyst; (c) collecting the ternary alloy nanoparticle catalyst and adsorbing it onto a refractory oxide support; and (d) drying and calcining the adsorbed ternary alloy nanoparticle catalyst and the refractory oxide support.

[0054] In some embodiments, the process comprises (a) combining a precursor of the platinum group metal and precursors of two transition metal elements with a capping agent in an organic solvent to form a solution. In some embodiments, the precursor of the platinum group metal is platinum(II) acetylacetonate. In some embodiments, the precursor of the platinum group metal is chloroplatinic acid. In some embodiments, the precursor of the platinum group metal is platinum(II) hydroxy sulfite. In some embodiments, the precursor of the platinum group metal is tetraammineplatinum(II) chloride. In some embodiments, the precursor of the platinum group metal is tetraammineplatinum(II) nitrate. In some embodiments, the precursors of the at least two transition metal elements are nickel(II) acetylacetonate and cobalt(III) acetylacetonate. In some embodiments, the capping agent is citric acid. In some embodiments, the capping agent is polyvinylpyrrolidone. In some embodiments, the capping agent is oleylamine. In some embodiments, the capping agent is oleic acid. In some embodiments, the capping agent is polyethylene glycol.

[0055] In some embodiments, the process includes (b) introducing a reducing agent into the solution to produce a colloidal suspension of the ternary alloy nanoparticle catalyst. In some embodiments, the reducing agent is sodium borohydride. In some embodiments, the reducing agent is hydrazine. In some embodiments, the reducing agent is formic acid. In some embodiments, the reducing agent is sodium formate. In some embodiments, the reducing agent is an amine-borane complex. In some embodiments, the reducing agent is 1,2-hexadecanediol. In some embodiments, the reducing agent is oleylamine.

[0056] In some embodiments, the process includes (c) collecting the ternary alloy nanoparticle catalyst and adsorbing it onto a refractory oxide support. In some embodiments, the process includes (d) drying and firing the adsorbed ternary alloy nanoparticle catalyst and the refractory oxide support. In some embodiments, the firing step includes firing the ternary alloy nanoparticle catalyst and the refractory oxide support at about 800 °C for about 2 hours in a hydrogen atmosphere, followed by heating in air at about 260 °C for about 1 hour and heating in air at about 590 °C for about 1 hour.

[0057] In some embodiments, the nanoparticles of the ternary alloy nanoparticle catalyst have an average particle size of about 2 nm to about 10 nm when supported on an inorganic refractory oxide. In some embodiments, the nanoparticles of the ternary alloy nanoparticle catalyst have an average particle size of about 2 nm to about 5 nm. In some embodiments, the nanoparticles have an average particle size of about 2 nm. In some embodiments, the nanoparticles have an average particle size of about 3 nm. In some embodiments, the nanoparticles have an average particle size of about 4 nm. In some embodiments, the nanoparticles have an average particle size of about 5 nm.

[0058] As used herein, the term "particle size" refers to the smallest diameter sphere that completely encloses a particle, and this measurement relates to individual particles rather than aggregates of two or more particles. The particle size can be measured, for example, by laser light scattering techniques with a dispersion or dry powder according to ASTM method D4464. The particle size can also be measured by scanning electron microscopy (SEM) or transmission electron microscopy (TEM) for sub-micron sized particles, or by a particle size analyzer for carrier-containing particles (micron size). In addition to TEM, carbon monoxide (CO) chemisorption can be used to determine the average PGM particle size. This technique only determines the average particle size without distinguishing between various PGM species (e.g., Pt, Pd, etc. as compared to XRD, TEM, and SEM).

[0059] In some embodiments, the total platinum group metal content of the ternary alloy nanoparticle catalyst is from about 0.1 wt% to about 5 wt% of the metal content. In some embodiments, the total platinum group metal content of the ternary alloy nanoparticle catalyst is from about 0.5 wt% to about 2 wt% of the metal content. In some embodiments, the total platinum group metal content is about 0.5 wt% of the metal content. In some embodiments, the total platinum group metal content is about 1.0 wt% of the metal content. In some embodiments, the total platinum group metal content is about 1.5 wt% of the metal content. In some embodiments, the total platinum group metal content is about 2 wt% of the metal content. In some embodiments, the total platinum group metal content is about 2.5 wt% of the metal content. In some embodiments, the total platinum group metal content is about 3 wt% of the metal content. In some embodiments, the total platinum group metal content is about 3.5 wt% of the metal content. In some embodiments, the total platinum group metal content is about 4 wt% of the metal content. In some embodiments, the total platinum group metal content is about 4.5 wt% of the metal content. In some embodiments, the total platinum group metal content is about 5 wt% of the metal content.

[0060] In another aspect of the present disclosure, an exhaust gas treatment system is provided that includes the ternary alloy nanoparticle catalyst of any one of the foregoing embodiments, is positioned downstream of an internal combustion engine, and is in fluid communication with the internal combustion engine.

[0061] In some embodiments, the internal combustion engine is a lean burn engine, preferably a lean burn gasoline engine or a diesel engine, preferably a diesel engine. In some embodiments, the exhaust gas treatment system is in fluid communication with the internal combustion engine via an exhaust conduit.

[0062] In some embodiments, the exhaust gas treatment system further includes a catalyzed soot filter and / or an SCR catalyst component containing an SCR catalyst composition, preferably a catalyzed soot filter and an SCR catalyst component containing an SCR catalyst composition.

[0063] In some embodiments, the catalyzed soot filter and / or the SCR catalyst component is located downstream of the ternary alloy nanoparticle catalyst, preferably a catalytic oxidation complex, and more preferably both the catalyzed soot filter and the SCR catalyst component are located downstream of the ternary alloy nanoparticle catalyst, preferably a catalytic oxidation complex.

[0064] In yet another aspect of the present disclosure, a method of treating an exhaust gas stream containing hydrocarbons and / or carbon monoxide and / or NO x is provided, the method including passing the exhaust gas stream through the ternary alloy nanoparticle catalyst of any one of the foregoing embodiments or the exhaust gas treatment system.

Examples

[0065] Comparative Example 1: A Pt reference sample was prepared via incipient wetness impregnation. A support material such as alumina was impregnated with a Pt ammine precursor solution, followed by drying at 110°C and calcination at 590°C.

[0066] Comparative Example 2: A Pt reference sample was prepared in the same manner as in Comparative Example 1, except that a colloidal Pt precursor having an average Pt particle size of 1 to 3 nm was used.

[0067] Example 1 The synthesis of PtNiCo nanoparticles (NP) involved the reduction and decomposition of three metal precursors, Pt II (acac)2, Ni II (acac)2, and Co III (acac)3 at a controlled molar ratio in dioctyl ether solvent at high temperature. Pt 41 Ni 36 Co 23 For the synthesis of the nanoparticles, 397 mg of Pt II (acac)2, 256 mg of Ni II (acac)2, and 356 mg of Co III (acac)3 were dissolved in 100 ml of dioctyl ether at room temperature, followed by the addition of 1.0 ml of oleylamine, 1.0 ml of oleic acid, and 1,000 g of 1,2-hexadecanediol. The mixture was purged with N2 gas to remove ambient air, and then the temperature was raised stepwise to 105 °C in 20 minutes, then further to 180 °C in 20 minutes until it turned completely dark brown. Finally, the temperature was raised to 270 °C and refluxed for 40 minutes. After cooling to room temperature, the resulting solution was diluted with ethanol to a volume ratio of 1:2.5. After crystallization overnight (about 12 hours), the supernatant was discarded, and the remaining precipitate was dried by purging with N2 gas for 10 minutes. The precipitated black powder was redispersed in a hexane solution before further use.

[0068] Comparative Example 3 A colloidal Pt 51 Ni 49 solution was prepared in the same manner as in Example 1, except that no Co precursor was added.

[0069] Comparative Example 4 A colloidal Pt 62 Co 38 solution was prepared in the same manner as used in Example 1, except that no Ni precursor was added.

[0070] Example 2 Colloidal Pt 33 Mn 34 Fe 33 The solution was prepared in the same manner as that used in Example 1, and Pt II (acac)2, Mn2(CO) 10 , and Fe(CO)5 were precursors used in a controlled molar ratio.

[0071] Comparative Example 5 Pt 46 Mn 54 / Al2O3 sample was prepared via one-pot synthesis. Along with the Al2O3 support, Pt II (acac)2, and Mn II (acac)2 were first suspended in a DMF solvent and then transferred to a Teflon autoclave and reacted for 12 hours. The resulting powder was washed with ethanol, filtered, and then calcined at 590 °C in air for 1 hour.

[0072] Example 3 The colloidal PtNiCo solution (10 - 20 mg / mL hexane) (Example 1) was added to an inorganic support material (0.5 - 10 g) suspended in a 5 - 30 mL pre-mixed isopropanol / hexane (volume ratio 1:9) solution to prepare a PtNiCo catalyst supported on alumina. The mixture was sonicated for 20 minutes and then purged with N2 to remove the solvent. The dried fine powder was then calcined at 800 °C in a H2 atmosphere for 2 hours, followed by continuous calcination at 260 °C in air for 1 hour and then again at 590 °C for 1 hour. This protocol resulted in all samples maintaining substantially the same ternary metal composition with a slight enrichment in Pt% compared to that of the nanoparticle precursors.

[0073] Comparative Example 6 Supported Pt 51 Ni 49 / Al2O3 catalyst was prepared in the same manner as that used in Example 3, except that the colloidal PtNi solution (Comparative Example 3) was used.

[0074] Comparative Example 7 Supported Pt 63 Co 37 The supported Pt / Al2O3 catalyst was prepared in the same manner as that used in Example 3, except that a colloidal PtCo (Comparative Example 4) solution was used.

[0075] Example 4 Supported Pt 37 Mn 50 Fe 13 The supported PtMnFe / Al2O3 catalyst was prepared in the same manner as that used in Example 3, except that a colloidal PtMnFe solution (Example 2) was used.

[0076] Example 5 (High-Throughput Powder Test) The powder catalyst was crushed, sieved into a size range of 250 - 500 μm, and 100 mg was diluted to a volume of about 1 mL with corundum. The samples were loaded into a high-throughput test unit and each sample was tested at 125 °C, 135 °C, 150 °C, 165 °C, 180 °C, 195 °C, 210 °C, 225 °C, 250 °C, and 300 °C. The feed gas composition was 500 ppm of NO, 300 ppm of CO, 40 ppm of propene, 60 ppm of C1 HC (toluene / decan = 1 / 2 on a C1 basis), 10% of O2, 10% of CO2, and 10% of H2O, and the space velocity (simulating 1 mL of the coated catalyst) was 45000 / h.

[0077] Example 6 (Single Powder Test) The powder catalyst was sieved into 200 - 500 μm, and 30 mg of the sample was tested in a simulated exhaust gas mixture with a flow rate of 250 ml / min of 200 ppm of NO + 167 ppm of C3H6 + 333 ppm of CO + 10% of O2 + 10% of H2O + the balance N2.

[0078] Figure 1 shows a comparison of the sizes of the synthesized PtNiCo [(Figure 1A) and (Figure 1D)], PtNi (Figure 1B), and PtCo (Figure 1C) nanoparticles. Ternary alloy Example 1 (Pt 41 Ni 36 Co 23) showed a minimum particle size average of 2.9 - 3.6 nm. Binary alloy Comparative Example 3 (Pt 45 Ni 55 ) and Comparative Example 4 (Pt 63 Co 37 ) appeared with sizes of 9 - 10 nm and 4 - 5 nm respectively. When deposited on alumina [Example 3, Pt 41 Ni 36 Co 23 / Al2O3 (Figure 1D)], several larger PtNiCo nanoparticles with an increased size range of 2 nm - 10 nm appeared.

[0079] Figure 2 shows the effect of the Pt / Mn / Fe ratio on the size of the nanoparticles. Pt 13 Mn 27 Fe 60 NPs (Figure 2A) show a mixture of small particles with an average size of 2.8 ± 0.6 nm and large nanoparticles with a diameter of 6.4 ± 1.7 nm. Figure 2B shows a representative image of Pt 38 Mn 29 Fe 33 nanoparticles with an average size of about 4.0 ± 0.5 nm, while in Figure 2C, the average size of Pt 86 Mn1Fe 13 nanoparticles was estimated to be about 6.1 ± 1.0 nm. These results suggest that the particle size and morphology strongly depend on the metal composition. The smallest particles are found at an intermediate Pt level of about 40 atomic %. Figure 2D shows the size of Pt 38 Mn 29 Fe 33 alloy particles supported on Al2O3, estimated to be about 4.2 ± 0.7 nm, indicating that neither the original Pt / Mn / Fe ratio nor the particle size changes upon deposition on alumina.

[0080] Figure 3 shows the X-ray diffraction pattern of Example 1 (isolated PtNiCo nanoparticles). The broad peak at about 41.4° is due to Pt(111), which is shifted from 39.7° in the case of only Pt, caused by alloying with Ni and Co. For equal weight % of Pt dispersed on alumina, Example 3 (PtNiCo / Al2O3) shows a Pt(111) peak at 40.8° compared to 39.9° of Example 1, indicating that the alloy-structured PtNiCo particles remain unchanged.

[0081] The EDS mapping of fresh Example 3 in Figure 1D shows the enrichment of Ni and Co on the Pt particles, but the decomposition is significantly limited due to the small particle size and low concentrations of Ni and Co. The close Pt-Ni-Co association is more easily confirmed in Example 3 aged at 650 °C / 50 h. Figure 4 shows the elemental line profiles across two PtNiCo particles (particles A and B) as indicated by the arrow lines in the TEM image. Here, each particle is dominated by the Pt signal, and the Ni and Co signals are observed consistently across the particle, although at levels significantly lower than the original PtNiCo nanoparticles (Pt 41 Ni 36 Co 23 ) before aging. Here, the atomic ratios change to Pt 96.34 / Ni 0.56 / Co 3.10 for particle A and Pt 95.90 / Ni 1.95 / Co 2.16 for particle B. This observation suggests that a significant amount of Ni / Co may have separated from Pt during aging and dispersed into the alumina support. The remaining trace amounts of Ni and Co may continue to play an important role in modifying the Pt chemistry. Since Ni and Co are acidic at the particle-support interface, they could help to more strongly anchor the ternary alloy particles to the support and retard aging. On the particle surface, Ni and Co can promote the activation of O2 and enhance the oxidation reaction.

[0082] Figure 5 compares the NO oxidation activity to NO between Example 3 and Comparative Example 1 before and after aging. Example 3 showed lower activity in the fresh state, but remained stable after 650°C / 50h HT aging compared to the reference, i.e. Comparative Example 1.

[0083] The higher stability of Example 3 is clearly demonstrated in FIG. 6, which shows the NO2 / NO x The change in the ratio was compared at 210°C, 225°C, and 250°C, respectively. At each temperature, Example 3 showed significantly less decay in activity due to aging. The largest deactivation was observed in Comparative Example 2, which used colloidal Pt precursor. Despite the significant change in Pt / Ni / Co ratio and particle sintering after aging, Example 3 maintained NO oxidation activity to a significant extent, suggesting that the remaining small amount of Ni and Co plays an important role in enhancing NO oxidation. Meanwhile, Example 3 showed similar CO and HC light-off activity to Comparative Examples 1 and 2, except that a higher CO light-off activity was observed for fresh Example 3, as shown in Figure 7. The presence of Ni / Co in Pt appears to have the greatest impact on maintaining NO oxidation activity after hydrothermal aging.

[0084] 8 and 9 show the effect of Pt atomic ratio in Example 3 on the stability of NO2 production from fresh to aged, where the highest stability was achieved near an intermediate Pt level of about 41%. The amount of Ni may also be a consideration, as high stability was observed when Ni was present in a molar amount similar to Co.

[0085] Figure 10 shows a comparison of the activity of bimetallic alloys PtNi (Comparative Example 6) and PtCo (Comparative Example 7) supported on alumina. Comparative Example 6 showed similar activity to Comparative Example 1, while Comparative Example 7 showed very high fresh activity that deteriorated significantly after aging. Thus, the ternary alloy PtNiCo has a mechanism for enhancing NO oxidation that cannot be achieved with the bimetallic alloys.

[0086] Figure 11 shows the comparison of the activity of Example 4 (Pt 37 Mn 50 Fe 13 / Al2O3) with respect to Comparative Example 1. Example 4 showed lower NO oxidation activity in the fresh state, and the activity deteriorated to the same extent as Comparative Example 1 after aging. Characterization data (TEM and EDS) showed that significant phase separation occurred after aging, and as a result, Mn and Fe separated from the Pt particles and integrated into the alumina support.

[0087] Figure 12 shows the comparison of the fresh activity of binary metal PtMn alloy particles (Comparative Example 5) supported on alumina with respect to Comparative Example 1. The mere presence of Mn in the alloy seems to have significantly decreased the NO oxidation activity. Based on the fact that ternary Pt alloy samples tend to result in better or equivalent NO2 stability, it suggests that the negative effect of a single transition metal changes significantly in the presence of a second transition metal, resulting in enhanced activity especially in the case of PtNiCo catalysts.

[0088] DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy) studies of the CO adsorption experiments for the comparative examples and Example 3 indicate that, prior to aging, both comparative examples have a higher available Pt surface for CO adsorption than Example 3. This is likely due to the following two factors: (1) the PtNiCo alloy nanoparticle precursors have a larger average particle size than the initial Pt particles obtained in the comparative examples, and (2) the ternary PtNiCo alloy nanoparticles are also found to be enriched with Ni and Co on the surface, reducing the available Pt on the surface for CO adsorption. After hydrothermal aging at 650 °C for 50 hours, all the catalysts show a significantly reduced CO adsorption intensity, but the reduction in Comparative Examples 1 and 2 is much more prominent. Example 3 now has the highest available Pt surface for CO adsorption (see the inset in Figure 13), indicating that Example 3 is more resistant to hydrothermal aging due to the presence of Ni and Co. Since Ni and Co are acidophilic, they can improve the adhesion of the ternary nanoalloy particles to the inorganic oxide support, and thus can slow down particle growth and aggregation. On the nanoparticle surface, Ni and Co can more efficiently activate O2 and promote the oxidation reaction.

Mode for Carrying Out the Invention

[0089] The present invention is further illustrated by the following series of embodiments, as well as combinations of embodiments resulting from the dependencies and cross-references as shown. In particular, in each case where the scope of an embodiment is mentioned, for example, in the context of terms such as "any one of the catalysts of Embodiments 1 to 4", it should be noted that all embodiments within this scope are explicitly disclosed to those skilled in the art, that is, the expression of this term is understood by those skilled in the art to be synonymous with "any one of the catalysts of Embodiments 1, 2, 3, and 4". Furthermore, it should be clearly noted that the following series of embodiments do not represent a series of claims determining the scope of protection, but rather appropriately structured parts of the description targeting the general and preferred aspects of the present invention. 1. A ternary alloy nanoparticle catalyst comprising a platinum group metal alloyed with at least two transition metal elements. 2. The ternary alloy nanoparticle catalyst according to Embodiment 1, comprising two transition metal elements. 3. The ternary alloy nanoparticle catalyst according to Embodiment 1, comprising three transition metal elements. 4. The ternary alloy nanoparticle catalyst according to Embodiment 1, comprising four transition metal elements. 5. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 4, wherein the platinum group metal is selected from Pt, Pd, Ru, Rh, Ir, and Os. 6. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 5, wherein the platinum group metal is selected from Pt, Pd, and Ru. 7. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 6, wherein the platinum group metal is selected from Pt and Pd. 8. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 7, wherein the platinum group metal is a combination of Pt and Pd. 9. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 7, wherein the platinum group metal is Pt. 10. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 9, wherein at least two transition metal elements are selected from Ni, Co, Mn, Fe, V, Zn, Cu, Ti, Sc, and Cr. 11. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 10, wherein at least two transition metal elements are selected from Ni, Co, Mn, and Fe. 12. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 11, wherein at least two transition metal elements are Ni and Co. 13. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 11, wherein at least two transition metal elements are Mn and Fe. 14. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 13, wherein the ternary alloy nanoparticles are supported on a refractory oxide support selected from silica, δ-alumina, θ-alumina, γ-alumina, Si-doped alumina, alkaline earth metal-stabilized alumina, transition metal-stabilized alumina, zirconia, and titania. 15. The ternary alloy nanoparticles catalyst according to Embodiment 14, wherein the refractory oxide support is Si-doped alumina containing SiO2 in the range of about 1% to about 20%. 16. The ternary alloy nanoparticles catalyst according to Embodiment 14, wherein the refractory oxide support is Mn-stabilized alumina. 17. The ternary alloy nanoparticles catalyst according to Embodiment 14, wherein the refractory oxide support is Zr-doped alumina. 18. The ternary alloy nanoparticles catalyst according to Embodiment 14, wherein the refractory oxide support is Ti-doped alumina. 19. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 18, wherein the platinum group metal content of the alloy is about 80 atomic% or less of the metal content. 20. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 19, wherein the platinum group metal content of the alloy is about 80 atomic% of the metal content. 21. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 19, wherein the platinum group metal content of the alloy is about 70 atomic% of the metal content. 22. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 19, wherein the platinum group metal weight ratio is about 60 atomic% of the metal content. 23. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 19, wherein the platinum group metal content of the alloy is about 50 atomic% of the metal content. 24. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 19, wherein the platinum group metal content of the alloy is about 40 atomic% of the metal content. 25. The ternary alloy nanoparticles catalyst according to any one of Embodiments 1 to 19, wherein the platinum group metal weight ratio is about 30 atomic% of the metal content. 26. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 19, wherein the platinum group metal content of the alloy is about 20 atomic% of the metal content. 27. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 26, wherein at least two transition metal elements have a total weight ratio of about 20 atomic% to about 80 atomic% of the metal content. 28. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 27, wherein at least two transition metal elements have a total weight ratio of about 20 atomic% of the metal content. 29. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 27, wherein at least two transition metal elements have a total weight ratio of about 30 atomic% of the metal content. 30. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 27, wherein at least two transition metal elements have a total weight ratio of about 40 atomic% of the metal content. 31. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 27, wherein at least two transition metal elements have a total weight ratio of about 50 atomic% of the metal content. 32. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 27, wherein at least two transition metal elements have a total weight ratio of about 60 atomic% of the metal content. 33. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 27, wherein at least two transition metal elements have a total weight ratio of about 70 atomic% of the metal content. 34. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 27, wherein at least two transition metal elements have a total weight ratio of about 80 atomic% of the metal content. 35. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 34, wherein the platinum group metal and at least two transition metal elements are detectable by TEM / EDS (transmission electron microscopy combined with energy-dispersive X-ray spectroscopy), X-ray diffraction, or a combination thereof. 36. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 35, wherein XRD shows a 2-theta value of Pt fcc (111) in the range of about 39.7° to about 42° when incorporating at least two transition metals at different levels. 37. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 36, wherein the ternary alloy nanoparticle catalyst is PtNiCo. 38. The ternary alloy nanoparticle catalyst according to Embodiment 37, wherein the atomic ratio of the PtNiCo ternary alloy nanoparticle catalyst is 20% to 80% Pt, 1% to 50% Ni, and 5% to 40% Co. 39. The ternary alloy nanoparticle catalyst according to Embodiment 37, wherein the atomic ratio of the PtNiCo ternary alloy nanoparticle catalyst is 30% to 60% Pt, 20% to 40% Ni, and 10% to 30% Co. 40. The ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 36, wherein the ternary alloy nanoparticle catalyst is PtMnFe. 41. The ternary alloy nanoparticle catalyst according to Embodiment 40, wherein the atomic ratio of the PtMnFe ternary alloy nanoparticle catalyst is 15% to 40% Pt, 10% to 50% Mn, and 10% to 50% Fe. 42. The ternary alloy nanoparticle catalyst according to Embodiment 40, wherein the atomic ratio of the PtMnFe ternary alloy nanoparticle catalyst is 30% to 40% Pt, 30% to 40% Mn, and 30% to 40% Fe. 43. An oxidation catalyst composite for reducing exhaust gas emissions from a lean burn engine, comprising the ternary alloy nanoparticle catalyst according to any one of Embodiments 1 to 42, preferably, the lean burn engine is a lean burn gasoline engine or a diesel engine, more preferably a diesel engine. 44. The oxidation catalyst composite, comprises a carrier substrate having a length, an inlet end, and an outlet end, and an oxidation catalyst material containing the ternary alloy nanoparticle catalyst, wherein the oxidation catalyst material is provided on the carrier substrate. The oxidation catalyst composite according to Embodiment 43. 45. The oxidation catalyst composite according to Embodiment 44, wherein the oxidation catalyst material comprises a washcoat layer containing the ternary alloy nanoparticle catalyst, preferably consisting of it. 46. The oxidation catalyst composite of Embodiment 45, wherein the washcoat layer contains zeolite. 47. The washcoat layer contains, calculated as an element, from 5 to 500 g / ft of platinum group metal from the ternary alloy nanoparticle catalyst, preferably from 10 to 300 g / ft 3 , more preferably from 20 to 200 g / ft 3 , still more preferably from 40 to 150 g / ft 3 , still more preferably from 60 to 120 g / ft 3 , still more preferably from 80 to 100 g / ft 3 , and still more preferably from 80 to 100 g / ft 3 of platinum group metal, and is the oxidation catalyst composite according to Embodiment 45 or 46. 48. The oxidation catalyst material includes, preferably consists of, a lower washcoat layer and an upper washcoat layer. The lower washcoat layer is provided on the carrier substrate, and the upper washcoat layer is provided on the lower washcoat layer, and is the oxidation catalyst composite according to Embodiment 44. 49. The oxidation catalyst composite according to Embodiment 48, wherein the lower washcoat layer, the upper washcoat layer, or both the lower washcoat layer and the upper washcoat layer contain the ternary alloy nanoparticle catalyst. 50. The lower washcoat layer or the upper washcoat layer contains the ternary alloy nanoparticle catalyst, and the lower washcoat layer or the upper washcoat layer contains, calculated as an element, from 5 to 500 g / ft of platinum group metal from the ternary alloy nanoparticle catalyst, preferably from 10 to 300 g / ft 3 , more preferably from 20 to 200 g / ft 3 , still more preferably from 40 to 150 g / ft 3 , still more preferably from 40 to 150 g / ft 3 , still more preferably from 60 to 120 g / ft 3 , still more preferably from 80 to 100 g / ft 3 of platinum group metal, and is the oxidation catalyst composite according to Embodiment 49. 51. The lower washcoat layer and the upper washcoat layer contain the ternary alloy nanoparticle catalyst, and the total amount of platinum group metal in the lower washcoat layer and the upper washcoat layer from the ternary alloy nanoparticle catalyst contained in the lower washcoat layer and the upper washcoat layer is from 5 to 500 g / ft, calculated as an element, preferably from 10 to 300 g / ft 3 , preferably from 10 to 300 g / ft 3, more preferably 20 to 200 g / ft 3 , more preferably 40 to 150 g / ft 3 , more preferably 60 to 120 g / ft 3 , more preferably 80 to 100 g / ft 3 The oxidation catalyst composite according to Embodiment 49, which is in the range of 52. The oxidation catalyst composite according to any one of Embodiments 48 to 51, wherein the upper washcoat layer or the lower washcoat layer contains zeolite, and preferably, the upper washcoat layer contains zeolite. 53. The oxidation catalyst composite according to Embodiment 52, wherein the upper washcoat layer contains zeolite and the lower washcoat layer does not substantially contain zeolite. 54. The oxidation catalyst composite according to Embodiment 52, wherein the lower washcoat layer contains zeolite and the upper washcoat layer does not substantially contain zeolite. 55. One or more washcoat layers containing a ternary alloy nanoparticle catalyst substantially do not contain barium, and preferably, one or more washcoat layers containing a ternary alloy nanoparticle catalyst substantially do not contain alkaline earth metals. The oxidation catalyst composite according to any one of Embodiments 45 to 54. 56. The oxidation catalyst composite according to any one of Embodiments 44 to 55, wherein the carrier substrate is a wall flow substrate or a flow-through substrate, preferably a flow-through substrate, and more preferably a honeycomb monolith substrate. 57. A process for preparing a ternary alloy nanoparticle catalyst containing a platinum group metal alloyed with at least two transition metal elements, the process comprising (a) Combining a precursor of a platinum group metal and a precursor of at least two transition metal elements with a capping agent in an organic solvent to form a slurry; (b) Introducing a reducing agent into the solution to generate a colloidal suspension of the ternary alloy nanoparticle catalyst; (c) Collecting the ternary alloy nanoparticle catalyst and adsorbing it onto a refractory oxide support; (d) Drying and firing the adsorbed ternary alloy nanoparticle catalyst and the refractory oxide support. 58. The process according to embodiment 57, wherein the precursor of the platinum group metal is selected from platinum(II) acetylacetonate, chloroplatinic acid, platinum(II) hydroxy sulfite, tetraammineplatinum(II) chloride, and tetraammineplatinum(II) nitrate. 59. The process according to embodiment 57 or 58, wherein the precursors of at least two transition metal elements are selected from nickel(II) acetylacetonate and cobalt(III) acetylacetonate. 60. The process according to any one of embodiments 57 to 59, wherein the capping agent is selected from citric acid, polyvinylpyrrolidone, oleylamine, oleic acid, and polyethylene glycol. 61. The process according to any one of embodiments 57 to 60, wherein the reducing agent is selected from sodium borohydride, hydrazine, formic acid, sodium formate, and amine-borane complex; 1,2-hexadecanediol, and oleylamine. 62. The process according to any one of embodiments 57 to 61, wherein the refractory oxide support is selected from silica, δ-alumina, θ-alumina, γ-alumina, Si-doped alumina, alkaline earth metal stabilized alumina, transition metal stabilized alumina, zirconia, and titania. 63. The process according to embodiment 62, wherein the refractory oxide support is Si-doped alumina containing SiO2 in the range of about 1% to about 20%. 64. The process according to embodiment 62, wherein the refractory oxide support is Mn-stabilized alumina. 65. The process according to embodiment 62, wherein the refractory oxide support is Zr-doped alumina. 66. The process according to embodiment 62, wherein the refractory oxide support is Ti-doped alumina. 67. The process according to any one of embodiments 57 to 66, wherein the firing step includes firing the ternary alloy nanoparticle catalyst and the refractory oxide support at about 800 °C for about 2 hours in a hydrogen atmosphere, followed by heating in air at about 260 °C for about 1 hour and heating in air at about 590 °C for about 1 hour. 68. The process according to any one of embodiments 57 to 67, wherein the nanoparticles of the ternary alloy nanoparticle catalyst have an average particle size in the range of about 2 nm to about 10 nm. 69. The process according to any one of embodiments 57 to 67, wherein the nanoparticles of the ternary alloy nanoparticle catalyst have an average particle size in the range of about 2 nm to about 5 nm. 70. The process according to any one of embodiments 57 to 69, wherein the total platinum group metal content of the ternary alloy nanoparticle catalyst is about 0.1 wt% to about 5 wt% of the metal content. 71. The process according to any one of embodiments 57 to 70, wherein the total platinum group metal content of the ternary alloy nanoparticle catalyst is about 0.5 wt% to about 2 wt% of the metal content. 72. An exhaust gas treatment system comprising the ternary alloy nanoparticle catalyst according to any one of the foregoing embodiments, preferably comprising the oxidation catalyst composite according to any one of embodiments 57 to 70, which is positioned downstream of an internal combustion engine and in fluid communication with the internal combustion engine. 73. The exhaust gas treatment system according to embodiment 72, wherein the internal combustion engine is a lean burn engine, preferably a lean burn gasoline engine or a diesel engine, preferably a diesel engine. 74. The exhaust gas treatment system according to embodiment 72 or 73, wherein the exhaust gas treatment system is in fluid communication with the internal combustion engine via an exhaust duct. 75. The exhaust gas treatment system according to any one of embodiments 72 to 74, further comprising a catalyzed soot filter and / or an SCR catalyst component containing an SCR catalyst composition, preferably a catalyzed soot filter and an SCR catalyst component containing an SCR catalyst composition. 76. The exhaust gas treatment system according to embodiment 75, wherein the catalyzed soot filter and / or the SCR catalyst component is located downstream of the ternary alloy nanoparticle catalyst, preferably the oxidation catalyst composite, and more preferably both the catalyzed soot filter and the SCR catalyst component are located downstream of the ternary alloy nanoparticle catalyst, preferably the oxidation catalyst composite. 77. Hydrocarbon and / or carbon monoxide and / or NO xA method for treating an exhaust gas stream containing, the method comprising passing the exhaust gas stream through the ternary alloy nanoparticle catalyst described in any one of the preceding embodiments, or the oxidation catalyst composite described in any of embodiments 43 to 56, or the exhaust gas treatment system described in any one of the preceding embodiments. 78. The exhaust gas stream contains NO x , preferably carbon monoxide and NO x , more preferably hydrocarbons, carbon monoxide, and NO x The method according to embodiment 77, which contains. 79. Use of the ternary alloy nanoparticle catalyst described in any one of embodiments 1 to 42, or the oxidation catalyst composite described in any of embodiments 43 to 56, or the exhaust gas treatment system described in any of embodiments 72 to 76, for the treatment of exhaust gas from a lean burn gasoline engine or a diesel engine, preferably from a diesel engine.

Claims

1. An exhaust gas treatment system comprising a diesel oxidation catalyst, which includes a ternary alloy nanoparticle catalyst positioned downstream of an internal combustion engine and in fluid communication with the internal combustion engine, wherein the ternary alloy nanoparticle catalyst includes a platinum group metal alloyed with at least two transition metal elements.

2. The exhaust gas treatment system according to claim 1, wherein the platinum group metal is selected from Pt, Pd, Ru, Rh, Ir, and Os.

3. The exhaust gas treatment system according to claim 1 or 2, wherein the at least two transition metal elements are selected from Ni, Co, Mn, Fe, V, Zn, Cu, Ti, Sc, and Cr.

4. The exhaust gas treatment system according to claim 1 or 2, wherein the ternary alloy nanoparticles are supported on a refractory oxide support selected from silica, δ-alumina, θ-alumina, γ-alumina, Si-doped alumina, alkaline earth metal-stabilized alumina, transition metal-stabilized alumina, zirconia, and titania.

5. The exhaust gas treatment system according to claim 1 or 2, wherein the platinum group metal content of the alloy is about 80 atomic percent or less of the total metal content.

6. The exhaust gas treatment system according to claim 1 or 2, wherein the weight ratio of platinum group metals is approximately 30 atomic% to approximately 50 atomic% of the metal content.

7. The exhaust gas treatment system according to claim 1 or 2, wherein the at least two transition metal elements have a total ratio of about 20 atomic% to about 80 atomic% of the metal content.

8. The exhaust gas treatment system according to claim 1 or 2, wherein the platinum group metal and the at least two transition metal elements are detectable by TEM / EDS (transmission electron microscopy combined with energy-dispersive X-ray spectroscopy), X-ray diffraction, or a combination thereof.

9. The exhaust gas treatment system according to claim 8, wherein the XRD exhibits a two-theta value of Pt fcc(111) in the range of about 39.7° to about 42° when different levels of the at least two transition metals are incorporated.

10. The exhaust gas treatment system according to claim 1 or 2, wherein the ternary alloy nanoparticle catalyst is selected from PtNiCo and PtMnFe.

11. The exhaust gas treatment system according to claim 10, wherein the atomic ratio of the PtNiCo ternary alloy nanoparticle catalyst is about 20-80% Pt, about 1-50% Ni, and about 5-40% Co.

12. The exhaust gas treatment system according to claim 10, wherein the atomic ratio of the PtMnFe ternary alloy nanoparticle catalyst is about 15-40% Pt, about 10-50% Mn, and about 10-50% Fe.

13. A process for preparing the ternary alloy nanoparticle catalyst for an exhaust gas treatment system according to claim 1 or 2, comprising at least two transition metal elements and a platinum group metal alloyed with it, wherein the process comprises (a) Combining the platinum group metal precursor and the precursor of at least two transition metal elements with a capping agent in an organic solvent to form a slurry, (b) Introducing a reducing agent into the solution to produce a colloidal suspension of the ternary alloy nanoparticle catalyst, (c) Collecting the ternary alloy nanoparticle catalyst and adsorbing it onto a refractory oxide support, (d) A process comprising drying and calcining the adsorbed ternary alloy nanoparticle catalyst and refractory oxide support.

14. - The precursor of the platinum group metal is selected from platinum(II) acetylacetonate, chloroplatinic acid, platinum(II) hydroxysulfite, tetraammineplatinum(II) chloride, and tetraamineplatinum(II) nitrate. - The precursors of the at least two transition metal elements are selected from nickel(II) acetylacetonate and cobalt(III) acetylacetonate. - The capping agent is selected from citric acid, polyvinylpyrrolidone, oleylamine, oleic acid, and polyethylene glycol. - The reducing agent is selected from sodium borohydride, hydrazine, formic acid, sodium formate, and amine-borane complexes; 1,2-hexadecanediol, and oleylamine. - The process according to claim 13, wherein the refractory oxide carrier is selected from silica, δ-alumina, θ-alumina, γ-alumina, Si-doped alumina, alkaline earth metal-stabilized alumina, transition metal-stabilized alumina, zirconia, and titania.

15. The process according to claim 13, wherein the firing step includes firing the ternary alloy nanoparticle catalyst and the refractory oxide support at approximately 800°C for approximately 2 hours in a hydrogen atmosphere, followed by heating in air at approximately 260°C for approximately 1 hour, and then heating in air at approximately 590°C for approximately 1 hour.

16. The process according to claim 13, wherein the nanoparticles of the ternary alloy nanoparticle catalyst have an average particle size in the range of about 2 nm to about 10 nm.

17. The process according to claim 13, wherein the total platinum group metal content of the ternary alloy nanoparticle catalyst is about 0.1% by weight to about 5% by weight of the metal content.

18. The exhaust gas treatment system according to claim 1, wherein the exhaust gas treatment system is in fluid communication with the internal combustion engine via an exhaust conduit.

19. The exhaust gas treatment system according to claim 1 or 18, wherein the exhaust gas treatment system further comprises an SCR catalyst component containing a catalytic soot filter and / or an SCR catalyst composition.

20. The exhaust gas treatment system according to claim 19, wherein the catalytic soot filter and / or the SCR catalyst component is located downstream of the ternary alloy nanoparticle catalyst.

21. hydrocarbons and / or carbon monoxide and / or NO ｘ A method for processing an exhaust gas flow containing a gas, wherein the method includes passing the exhaust gas flow through an exhaust gas processing system according to any one of claims 1, 2, and 18.

22. Use of the exhaust gas treatment system according to any one of claims 1, 2, and 18 for treating exhaust gases from a diesel engine.

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