exhaust gas treatment catalyst

Abstract

Improved NO x To provide a catalyst with high conversion efficiency and lower N2O production. A catalyst composition for use as a selective catalytic reduction catalyst comprises small pore molecular sieve particles impregnated with a promoter metal, the small pore molecular sieve particles having a pore structure and a maximum ring size of eight tetrahedral atoms, and metal oxide particles dispersed within the small pore molecular sieve particles and outside the pore structure of the small pore molecular sieve particles, wherein the D of the molecular sieve particles is 0.05 to 0.05. 50 particle size D of the metal oxide particles 50 The catalyst composition has a particle size ratio of greater than 10:1.

Description

[Technical Field]

[0001] The present invention relates to an exhaust gas purification catalyst, a method for producing the catalyst, and a method for using the catalyst. More specifically, the present invention relates to a selective catalytic reduction catalyst comprising a small pore molecular sieve containing a promoter metal.

[0002] background Over a long period of time, nitrogen oxides (NO x ) harmful components are causing air pollution. x is found in exhaust gases such as those from internal combustion engines (eg, in cars and trucks), combustion equipment (eg, power plants heated by natural gas, oil, or coal), and nitric acid production plants.

[0003] NO x Various treatment methods are used in the treatment of nitrogen-containing gas mixtures. One type of treatment requires the catalytic reduction of nitrogen oxides. There are two methods: (1) non-selective reduction, in which carbon monoxide, hydrogen, or lower hydrocarbons are used as reducing agents, and (2) selective reduction, in which ammonia or an ammonia precursor is used as reducing agent. In selective reduction, a high degree of removal of nitrogen oxides can be obtained with a small amount of reducing agent. Selective reduction methods are called SCR (selective catalytic reduction). SCR uses the catalytic reduction of nitrogen oxides with ammonia in the presence of atmospheric oxygen, resulting in the formation of mainly nitrogen and water vapor: 4NO + 4NH3 + O2 → 4N2 + 6H2O (standard SCR reaction) 2NO2 + 4NH3 → 3N2 + 6H2O (slow SCR reaction) NO + NO2 + NH3 → 2N2 + 3H2O (fast SCR reaction).

[0004] Catalysts used in SCR processes should ideally be able to maintain good catalytic activity under hydrothermal conditions over a wide range of temperatures, e.g., from 200°C to over 600°C. Hydrothermal conditions often occur in practice, for example, during the regeneration of soot filters, which are components of exhaust gas treatment systems used for particle removal.

[0005] Molecular sieves, such as zeolites, have been used in the selective catalytic reduction (SCR) of nitrogen oxides in the presence of oxygen using reducing agents such as ammonia, urea, or hydrocarbons. Zeolites are crystalline materials with fairly uniform pore sizes ranging from approximately 3 Å to 10 Å in diameter, depending on the type of zeolite and the type and amount of cations contained in the zeolite lattice. Zeolites with eight-membered ring pore openings and double six-membered ring secondary structural units, particularly zeolites with cage-like structures, have recently attracted interest for use as SCR catalysts. A specific type of zeolite with these properties is chabazite (CHA), a small-pore zeolite with eight-membered ring pore openings (approximately 3.8 Å) accessible through three-dimensional porosity. The cage-like structure is achieved by connecting four double six-membered ring structural units.

[0006] Metal-promoted zeolite catalysts, such as iron-promoted and copper-promoted zeolite catalysts, are known for the selective catalytic reduction of nitrogen oxides with ammonia. Iron-promoted zeolite beta has long been an effective commercial catalyst for the selective reduction of nitrogen oxides with ammonia. Unfortunately, it has been found that under severe hydrothermal conditions, such as those encountered during the regeneration of soot filters, with temperatures exceeding 700°C in some areas, the activity of many metal-promoted zeolites begins to decline. This decline is often attributed to dealumination of the zeolite and the resulting loss of metal-containing active centers within the zeolite.

[0007] Metal-promoted aluminosilicate zeolites having the CHA structure type, particularly copper-promoted zeolites, have recently attracted considerable interest as catalysts for selective catalytic reduction of nitrogen oxides in lean-burn engines using nitrogen-containing reductants. This is due to the wide temperature window of these materials, as well as their excellent hydrothermal durability, as described in U.S. Pat. No. 7,601,662. Prior to the discovery of the metal-promoted zeolites described in U.S. Pat. No. 7,601,662, numerous metal-promoted zeolites had been proposed in the patent and scientific literature for use as SCR catalysts, but each of the proposed materials suffered from one or both of the following drawbacks: (1) insufficient conversion of nitrogen oxides at low temperatures, e.g., temperatures below 350°C, and (2) poor hydrothermal stability, as evidenced by a significant drop in catalytic activity for SCR of nitrogen oxides. Thus, the invention described in U.S. Pat. No. 7,601,662 addressed the urgent and unmet need to provide a material that would provide nitrogen oxide conversion at low temperatures and retain SCR catalytic activity after hydrothermal aging at temperatures above 650° C.

[0008] Although modern catalysts exhibit excellent performance, there is a continuing desire to reduce NO production during SCR reactions. Therefore, improved NO production compared to current technology is required. x Catalysts with higher conversion efficiency and lower N2O production are needed.

[0009] overview The present invention relates to a catalyst composition suitable for use as a selective catalytic reduction catalyst, comprising a homogeneous mixture of small pore molecular sieve particles impregnated with a promoter metal, having a pore structure and a maximum ring size of eight tetrahedral atoms, and metal oxide particles comprising one or more oxides of transition metals or lanthanides of Group 3 or 4 of the Periodic Table. Certain embodiments of the catalyst composition comprising molecular sieve particles having metal oxide particles dispersed therein (but outside the small pore molecular sieve particles) exhibit enhanced NOx at low and / or high temperatures compared to conventional metal-promoted molecular sieves that contain no metal oxide particles or only minimal amounts of metal oxide particles derived from certain binder materials. x It has been found that this can result in reduced NO production at low and / or high temperatures, and the metal oxide is generally present in an amount ranging from about 1% to about 15% by weight, on an oxide basis, based on the total weight of the washcoat.

[0010] The metal oxide particles generally comprise a metal oxide selected from the group consisting of zirconia, alumina, ceria, hafnia, yttria, and combinations thereof. In certain embodiments, the metal oxide particles have an average particle size in the range of about 10 nm to about 500 nm and / or a D greater than 10 times the pore opening of the molecular sieve. 10 In one embodiment, the metal oxide particles have a particle size of about 10 nm or greater. 10 It has a granularity.

[0011] The catalyst composition can include small pore molecular sieve particles having d6r units. Exemplary small pore molecular sieves have a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, LTN, MSO, SAS, SAT, SAV, SFW, and TSC. In one embodiment, the molecular size is SSZ-13.

[0012] The catalyst composition generally contains Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Pr, Ti, Cr, Zn, Sn The catalyst composition of the present invention will comprise a promoter metal selected from the group consisting of Nb, Mo, Hf, Y, W, and combinations thereof. In exemplary embodiments, the promoter metal comprises Cu or Fe, or a combination thereof. Typical amounts of promoter metals are about 1% to about 10%, e.g., about 2% to about 5%, by weight, based on the total weight of the molecular sieve. In another aspect, the present invention provides a catalyst article comprising a substrate selected from a flow-through monolith, a wall-flow filter, a foam, or a mesh, wherein a catalyst composition according to any embodiment of the present disclosure is deposited on the substrate as a washcoat layer. In certain embodiments, the catalyst article of the present invention is characterized by at least 10% by weight lower (or at least 15% by weight lower, or at least 20% by weight lower) NO production compared to a catalyst article comprising the same catalyst composition at the same loading, but without metal oxide particles dispersed within the small pore molecular sieve particles.

[0013] In yet another aspect, the present invention provides a method for producing nitrogen oxides (NO x ), comprising the steps of: xand contacting an exhaust gas stream containing N2O with a catalyst composition or catalyst article according to any embodiment of the present disclosure. In certain embodiments, the amount of N2O produced as a by-product is reduced in the method of the present invention compared to methods practiced with certain conventional catalyst compositions and catalyst articles. For example, in one embodiment, the amount of N2O produced as a by-product in the method of the present invention is reduced compared to the amount of N2O produced in a method using a catalyst article containing a washcoat having the same catalyst composition at the same loading, but without metal oxide particles dispersed within the small pore molecular sieve particles. In yet a further aspect, the present invention provides an exhaust gas treatment system comprising a catalyst composition or catalyst article according to any embodiment of the present disclosure downstream from an engine (e.g., a diesel engine or other lean-burn engine) and an injector that adds a reductant to the exhaust gas stream.

[0014] The present invention also provides a method for producing a catalyst composition, comprising the steps of: dissolving a salt of at least one promoter metal in an aqueous metal oxide sol; a salt of the at least one promoter metal dissociates in the aqueous metal oxide sol to form an aqueous metal salt / metal oxide sol mixture, wherein the metal oxide particles comprise one or more oxides of a transition metal or lanthanide from Group 3 or 4 of the Periodic Table; treating ammonium or proton exchanged small pore molecular sieve particles having a pore structure and a maximum ring size of eight tetrahedral atoms with the aqueous metal salt / metal oxide sol mixture to impregnate the promoter metal into the pore structure of the small pore molecular sieve; drying and calcining the treated small pore molecular sieve particles to form a catalyst composition comprising small pore molecular sieve particles impregnated with a promoter metal and metal oxide particles dispersed within the small pore molecular sieve particles and outside the pore structure of the small pore molecular sieve particles. The promoter metal and molecular sieve can be selected as described in any embodiment herein.

[0015] The metal oxide sol may comprise any of the metal oxides described above with respect to the catalyst composition and may exhibit the same particle size characteristics described above. In certain embodiments, the metal oxide sol is selected from the group consisting of zirconyl hydroxide sol, nano-sized hydrous zirconia sol, alumina sol (e.g., large crystal, thermally stable boehmite sol), zirconia-yttria sol, zirconia-alumina sol, zirconia-ceria sol, organozirconium sol, and mixtures thereof. Advantageously, the metal oxide particles do not enter the pore structure of the small pore molecular sieve during the preparation process (i.e., the metal oxide particles are size-excluded from the pore structure of the molecular sieve).

[0016] The method may further include mixing the catalyst composition with water to form a washcoat slurry, applying the washcoat slurry to a substrate to form a washcoat coating on the substrate, and drying and calcining the substrate to form the catalyst article. In certain embodiments, the method includes adding a water-soluble metal oxide compound (e.g., a zirconium compound) to the washcoat slurry to increase its total metal oxide content.

[0017] The present invention includes, but is not limited to, the following embodiments.

[0018] Embodiment 1: A catalyst composition suitable for use as a selective catalytic reduction catalyst, comprising: small pore molecular sieve particles impregnated with a promoter metal, the small pore molecular sieve particles having a pore structure and a maximum ring size of 8 tetrahedral atoms; and metal oxide particles comprising one or more oxides of a transition metal or lanthanide of Group 3 or 4 of the Periodic Table dispersed within the small pore molecular sieve particles and outside the pore structure of the small pore molecular sieve particles.

[0019] Embodiment 2: The catalyst composition of any of the above or below embodiments, wherein said metal oxide particles comprise a metal oxide selected from the group consisting of zirconia, alumina, ceria, hafnia, yttria, and combinations thereof.

[0020] Embodiment 3: The catalyst composition of any of the above or below embodiments, wherein the metal oxide particles comprise zirconia.

[0021] Embodiment 4: The catalyst composition of any of the above or below embodiments, wherein said metal oxide particles have an average particle size in the range of from about 10 nm to about 500 nm.

[0022] Embodiment 5: The metal oxide particles have a diameter D that is more than 10 times larger than the pore openings of the molecular sieve. 10 10. The catalyst composition of any of the above or below embodiments, having a particle size.

[0023] Embodiment 6: The metal oxide particles have a D of about 10 nm or greater. 10 10. The catalyst composition of any of the above or below embodiments, having a particle size.

[0024] Embodiment 7: The catalyst composition of any of the above or below embodiments, wherein the small pore molecular sieve has d6r units.

[0025] Embodiment 8: The catalyst composition of any of the above or below embodiments, wherein the small pore molecular sieve has a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, LTN, MSO, SAS, SAT, SAV, SFW, and TSC.

[0026] Embodiment 9: The promoter metal is Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Pr, Ti, Cr, Zn, Sn , Nb, Mo, Hf, Y, W, and combinations thereof.

[0027] Embodiment 10: The catalyst composition of any of the above or below embodiments, wherein the small pore molecular sieve has a CHA structure type.

[0028] Embodiment 11: The catalyst composition of any of the above or below embodiments, wherein the promoter metal comprises Cu or Fe, or a combination thereof.

[0029] Embodiment 12: The catalyst composition of any of the above or below embodiments, wherein the promoter metal is present in an amount in the range of about 1 wt.% to about 10 wt.%, based on the total weight of the molecular sieve.

[0030] Embodiment 13: The catalyst composition of any of the above or below embodiments, wherein the promoter metal is present in an amount in the range of about 2% to about 5% by weight, based on the total weight of the molecular sieve.

[0031] Embodiment 14: The catalyst composition of any of the above or below embodiments, wherein the metal oxide is present in an amount in the range of about 1 wt.% to about 15 wt.%, on an oxide basis, based on the total weight of the washcoat.

[0032] Embodiment 15: A catalyst article comprising a substrate selected from a flow-through monolith, a wall-flow filter, a foam, or a mesh, wherein the catalyst composition according to any of the above or below embodiments is deposited on the substrate as a washcoat layer.

[0033] Embodiment 16: The catalyst article of any of the above or below embodiments, wherein the washcoat is disposed on a flow-through monolith or a wall-flow filter.

[0034] Embodiment 17: The catalyst article of any of the above or below embodiments, wherein said catalyst article is characterized by at least 10% by weight lower NO production compared to a catalyst article comprising the same catalyst composition at the same loading, but without metal oxide particles dispersed within the small pore molecular sieve particles.

[0035] Embodiment 18: Nitrogen oxides (NO x ), comprising the steps of: x contacting an exhaust gas stream containing the compound with the catalytic article of any of the above or below embodiments.

[0036] Embodiment 19: The process of any of the above or below embodiments, wherein the amount of NO produced as a by-product is reduced compared to the amount of NO produced in a process using a catalyst article comprising a washcoat having the same catalyst composition at the same loading, but without metal oxide particles dispersed within the small pore molecular sieve particles.

[0037] Embodiment 20: An exhaust gas treatment system comprising the catalyst article of any of the above or below embodiments downstream from an engine and an injector that adds a reductant to the exhaust gas stream.

[0038] Embodiment 21: A method for producing a catalyst composition, comprising: dissolving a salt of at least one promoter metal in an aqueous metal oxide sol; a salt of the at least one promoter metal dissociates in the aqueous metal oxide sol to form an aqueous metal salt / metal oxide sol mixture, wherein the metal oxide particles comprise one or more oxides of a transition metal or lanthanide from Group 3 or 4 of the Periodic Table; treating ammonium or proton exchanged small pore molecular sieve particles having a pore structure and a maximum ring size of eight tetrahedral atoms with the aqueous metal salt / metal oxide sol mixture to impregnate the promoter metal into the pore structure of the small pore molecular sieve; drying and calcining the treated small pore molecular sieve particles to form a catalyst composition comprising small pore molecular sieve particles impregnated with a promoter metal and metal oxide particles dispersed within the small pore molecular sieve particles and outside the pore structure of the small pore molecular sieve particles. A method comprising:

[0039] Embodiment 22: The method of any of the above or below embodiments, wherein the metal oxide is selected from the group consisting of zirconia, alumina, ceria, hafnia, yttria, and combinations thereof.

[0040] Embodiment 23: The method of any of the above or below embodiments, wherein the metal oxide comprises zirconia.

[0041] Embodiment 24: The method of any of the above or below embodiments, wherein the metal oxide sol has an average particle size in the range of about 10 nm to about 500 nm.

[0042] Embodiment 25: The metal oxide sol has a D of more than 10 times larger than the pore openings of the molecular sieve. 10 10. The method of any preceding or following embodiment, having a particle size.

[0043] Embodiment 26: The metal oxide sol has a D of about 10 nm or greater. 10 10. The method of any preceding or following embodiment, having a particle size.

[0044] Embodiment 27: The promoter metal is Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Pr, Ti, Cr, Zn, Sn , Nb, Mo, Hf, Y, W, and combinations thereof.

[0045] Embodiment 28: The method of any of the above or below embodiments, wherein the metal oxide sol is selected from the group consisting of zirconyl hydroxide sol, nanosized hydrous zirconia sol, alumina sol, zirconia-yttria sol, zirconia-alumina sol, zirconia-ceria sol, organozirconium sol, and mixtures thereof.

[0046] Embodiment 29: The method of any of the above or below embodiments, wherein the metal oxide particles do not penetrate into the pore structure of the small pore molecular sieve.

[0047] Embodiment 30: The method of any of the above or below embodiments, wherein the small pore molecular sieve has d6r units.

[0048] Embodiment 31: The method of any of the above or below embodiments, wherein the small pore molecular sieve has a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, LTN, MSO, SAS, SAT, SAV, SFW, and TSC.

[0049] Embodiment 32: The method of any of the above or below embodiments, wherein said small pore molecular sieve has a CHA crystalline structure.

[0050] Embodiment 33: The method of any of the above or below embodiments, wherein the promoter metal comprises Cu, Fe, or a combination thereof.

[0051] Embodiment 34: The method of any of the above or below embodiments, further comprising the steps of mixing the catalyst composition with water to form a washcoat slurry, applying the washcoat slurry to a substrate to form a washcoat coating on the substrate, and drying and calcining the substrate to form a catalyst article.

[0052] Embodiment 35: The method of any of the above or below embodiments, further comprising adding a water soluble metal oxide compound to the washcoat slurry to increase its total metal oxide content.

[0053] The above and other features, aspects, and advantages of the present disclosure will be clearly understood from the following detailed description read in conjunction with the accompanying drawings, which are briefly described below. The present invention encompasses combinations of two, three, four, or more of the above-described embodiments, as well as combinations of any two, three, four, or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined in the description of a particular embodiment herein. The present disclosure is to be read as a whole such that any separable features or elements in any of its various aspects and embodiments of the disclosed invention should be considered to be construed as capable of being combined unless the context clearly dictates otherwise. [Brief explanation of the drawings]

[0054] [Figure 1] 1 is a graph of NOx conversion and N2O production versus temperature for catalyst materials according to examples. [Figure 2] 1 is an SEM image of a catalyst material according to an example. [Figure 3] 1 is an SEM image of a catalyst material according to an example. [Figure 4] 1 is a bar graph of NOx efficiency for catalyst materials according to examples. [Figure 5] 1 is an SEM image of a catalyst material according to an example. [Figure 6] 6A-6D are a collection of SEM images of catalyst materials according to examples. [Figure 7] 7A-7D are a collection of SEM images of catalyst materials according to examples. [Figure 8] 1 is a bar graph of NOx reduction for catalyst materials according to examples. [Figure 9] 1 is a bar graph of NH3 slip, NH3 storage, and N2O production for catalyst materials according to examples. [Figure 10] 10A-10D are a collection of SEM images of catalyst materials according to examples. [Figure 11]1 is a graph of NOx conversion versus temperature for catalyst materials according to examples. [Figure 12] 1 is a graph of N2O production versus temperature for a catalyst material according to an example. [Figure 13] 1 is a graph of NOx conversion and N2O production versus temperature for catalyst materials according to examples compared to prior art materials. [Figure 14] 1 is a graph of NOx conversion versus temperature for catalyst materials according to examples compared to prior art materials. [Figure 15] 1 is a perspective view of a honeycomb-shaped substrate support that may include a catalyst composition according to the present invention. [Figure 16] 1 shows a schematic diagram of one embodiment of an exhaust gas treatment system in which the catalyst composition of the present invention is used.

[0055] Detailed Description Before describing several exemplary embodiments of the invention, it is to be understood that the invention is not limited to the details of construction or method steps set forth in the following detailed description. The invention is capable of other embodiments and of being practiced or carried out in various ways.

[0056] NO for light and heavy vehicles due to government regulations x The use of reduction technology is mandatory. NO using urea x Selective catalytic reduction (SCR) of NO x In order to meet government regulations, SCR catalysts with improved performance compared to current Cu-SSZ-13 based baseline technology are needed. In certain embodiments, improved NO emissions are achieved compared to current Cu-SSZ-13 based baseline technology. x A catalyst with high conversion efficiency and lower NO production is provided that effectively promotes the reaction of ammonia with nitrogen oxides to selectively form nitrogen and HO over a temperature range of 200°C to 600°C.

[0057] Embodiments of the present invention relate to selective catalytic reduction catalysts comprising a small pore molecular sieve and a zirconia-containing layer. It has surprisingly been found that modification of the small pore molecular sieve with zirconia results in lower NO production and an improved low- to high-temperature performance window. In certain embodiments, the present invention provides a catalyst composition in the form of a homogeneous mixture of small pore molecular sieve particles and metal oxide (e.g., zirconia) particles impregnated with a promoter metal. The metal oxide particles are sized such that most of the metal oxide particles are prevented from penetrating into the pore structure of the molecular sieve. Instead, the metal oxide particles essentially provide a surface coating on the molecular sieve particles. The presence of the metal oxide particles enhances low-temperature NO production and improves NO production. x It has been found to improve reduction and reduce N2O production.

[0058] The following definitions are provided for terms used in this disclosure.

[0059] As used herein, the term "catalyst" or "catalyst composition" or "catalytic material" refers to a material that promotes a reaction.

[0060] As used herein, the term "catalytic article" refers to an element used to promote a desired reaction. For example, the catalytic article may include a washcoat including a catalytic species, e.g., a catalyst composition, on a substrate.

[0061] As used herein, the term "selective catalytic reduction (SCR)" refers to a catalytic process for reducing nitrogen oxides to dinitrogen (N2) using a nitrogen-containing reducing agent.

[0062] As used herein, the term "washcoat" has its conventional meaning in the art of a thin, adherent coating of catalytic or other material applied to a support substrate material, such as a honeycomb-type support element, that is sufficiently porous to permit the passage of a gas stream to be treated. As understood in the art, a washcoat is obtained from a dispersion of particles in a slurry that is applied to a substrate, dried, and calcined to provide a porous washcoat.

[0063] In one or more embodiments, the selective catalytic reduction catalyst is a washcoat comprising a small pore molecular sieve having a pore structure and a maximum ring size of 8 tetrahedral atoms and comprising a promoter metal, and a zirconia-containing layer on the small pore molecular sieve comprising the promoter metal, the zirconia-containing layer comprising a washcoat having zirconia particles having a particle size in the range of about 10 nm to about 500 nm.

[0064] molecular sieve As used herein, the term "molecular sieve" refers to framework materials such as zeolites and other framework materials (e.g., isomorphous replacement materials) that can be used as catalysts in particulate form and in combination with one or more promoter metals. Molecular sieves are materials based on an extensive three-dimensional network of oxygen ions that generally contain tetrahedral sites and have an essentially uniform pore distribution with an average pore size of 20 Å or less. The pore size is defined by the ring size. As used herein, the term "zeolite" refers to a specific example of a molecular sieve containing silicon and aluminum atoms. According to one or more embodiments, it should be understood that the definition of molecular sieves by their structural type is intended to include that structural type as well as any and all isomorphous framework materials, such as SAPO, ALPO, and MeAPO, that have the same structural type as the zeolite material.

[0065] In more specific embodiments, reference to an aluminosilicate zeolite structure type limits the material to molecular sieves that do not contain phosphorus or other metals substituted in the framework. However, for clarity, as used herein, "aluminosilicate zeolite" excludes aluminophosphate materials such as SAPO, ALPO, and MeAPO materials, and the broad term "zeolite" is intended to include aluminosilicates and aluminophosphates. Zeolites are crystalline materials with fairly uniform pore sizes, with diameters ranging from about 3 Å to 10 Å, depending on the type of zeolite and the type and amount of cations contained in the zeolite lattice. Zeolites generally have a silica-to-alumina (SAR) molar ratio of 2 or greater.

[0066] The term "aluminophosphate" refers to another example of a molecular sieve that contains aluminum atoms and phosphate. Aluminophosphates are crystalline materials with fairly uniform pore sizes.

[0067] Aluminosilicates generally contain an open three-dimensional framework structure composed of corner-sharing TO4 tetrahedra, where T is Al or Si or optionally P. Anionic framework charge-compensating cations are loosely associated with framework oxygens, and the remaining pore volume is filled with water molecules. Non-framework cations are generally exchangeable, and water molecules are removable.

[0068] In one or more embodiments, the small pore molecular sieve comprises SiO / AlO tetrahedra, which are connected by common oxygen atoms to form a three-dimensional network. In other embodiments, the molecular sieve components comprise SiO / AlO / PO tetrahedra. The small pore molecular sieves of one or more embodiments are primarily classified by the morphology of the voids formed by the tight network of (SiO) / AlO or SiO / AlO / PO tetrahedra. The entrances to the voids are formed from 6, 8, 10, or 12 ring atoms relative to the atoms forming the entrance opening. In one or more embodiments, the molecular sieve has a ring size of 8 or less, e.g., 6 and 8.

[0069] According to one or more embodiments, the molecular sieve may be based on a framework topology that defines the structure. Generally, any structural type of zeolite, such as ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, SCO, CFI, SG F, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EMT, EON, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, IHW, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LIT, LOS , LOV, LTA, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MSO, MTF, MTN, MTT, MTW, MWW, NAB, N AT, NES, NON, NPO, NSI, OBW, OFF, OSI, OSO, OWE, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, Zeolites of the structural type SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SGT, SOD, SOS, SSY, STF, STI, STT, TER, THO, TON, TSC, UEI, UFI, UOZ, USI, UTL, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON or combinations thereof can be used.

[0070] In one or more embodiments, the molecular sieve comprises an 8-ring small-pore aluminosilicate zeolite. As used herein, "small pore" refers to a pore opening smaller than about 5 Å, e.g., on the order of about 3.8 Å. The term "8-ring" zeolite refers to a zeolite having an 8-ring pore opening and double 6-ring secondary structural units, and a cage-like structure obtained by connecting the double 6-ring structural units by four rings. Zeolites are composed of secondary structural units (SBUs) and composite structural units (CBUs), which exist in many different framework structures. The secondary structural units contain up to 16 tetrahedral atoms and are non-chiral. The composite structural units need not be achiral and need not necessarily be used to constitute the entire framework. For example, one group of zeolites has single 4-ring (s4r) composite structural units in its framework structure. In the four-membered ring, the "4" refers to the position of the silicon and aluminum atoms in the tetrahedron, with the oxygen atoms located between the tetrahedral atoms. Other complex building blocks include, for example, the single six-membered ring (s6r) unit, the double four-membered ring (d4r) unit, and the double six-membered ring (d6r) unit. A d4r unit is formed by linking two s4r units. A d6r unit is formed by linking two s6r units. In a d6r unit, there are 12 tetrahedral atoms. Zeolite structure types with d6r secondary structure units include AEI, AFT, AFX, CHA, EAB, EMT, ERI, FAU, GME, JSR, KFI, LEV, LTL, LTN, MOZ, MSO, MWW, OFF, SAS, SAT, SAV, SBS, SBT, SFW, SSF, SZR, TSC, and WEN.

[0071] In one or more embodiments, the molecular sieve is a small pore molecular sieve having a pore structure and a maximum ring size of eight tetrahedral atoms. In other embodiments, the small pore molecular sieve has a d6r unit. Thus, in one or more embodiments, the small pore molecular sieve has a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, LTN, MSO, SAS, SAT, SAV, SFW, TSC, and combinations thereof. In other specific embodiments, the molecular sieve has a structure type selected from the group consisting of CHA, AEI, AFX, ERI, KFI, LEV, and combinations thereof. In even further specific embodiments, the small pore molecular sieve has a structure type selected from CHA, AEI, and AFX. In one or more very specific embodiments, the small pore molecular sieve component has a CHA structure type.

[0072] Chabazite-type zeolites are naturally occurring members of the zeolite family, with the approximate formula: (Ca,Na,K,Mg)AlSiO 126H2O (e.g., hydrated calcium aluminum silicate). Three synthetic forms of chabazite-type zeolites are described in "Zeolite Molecular Sieves" by D.W. Breck, published by John Wiley & Sons in 1973, which is incorporated herein by reference. The three synthetic forms reported by Breck are Zeolite KG, described in J. Chem. Soc., p. 2822 (1956), Barrer et al., Zeolite D, described in British Patent No. 868,846 (1961), and Zeolite R, described in U.S. Patent No. 3,030,181, which is incorporated herein by reference. The synthesis of another synthetic form of chabazite-type zeolite, SSZ-13, is described in U.S. Patent No. 4,544,538, which is incorporated herein by reference. The synthesis of a synthetic form of molecular sieve, silicoaluminophosphate 34 (SAPO-34), having the chabazite crystal structure is described in U.S. Patent Nos. 4,440,871 and 7,264,789, which are incorporated herein by reference. A method for producing yet another synthetic molecular sieve, SAPO-44, having the chabazite structure, is described in U.S. Patent No. 6,162,415, which is incorporated herein by reference.

[0073] In one or more embodiments, the molecular sieve can include any aluminosilicate, borosilicate, gallosilicate, MeAPSO, and MeAPO composition, including, but not limited to, SSZ-13, SSZ-62, natural chabazite, zeolite KG, Linde D, Linde R, LZ-218, LZ-235, LZ-236, ZK-14, SAPO-34, SAPO-44, SAPO-47, ZYT-6, CuSAPO-34, CuSAPO-44, and CuSAPO-47.

[0074] The silica-to-alumina ratio of the aluminosilicate molecular sieve can vary over a wide range. In one or more embodiments, the molecular sieve has a silica-to-alumina molar ratio (SAR) in the range of 2 to 300, e.g., 5 to 250, 5 to 200, 5 to 100, and 5 to 50. In one or more specific embodiments, the molecular sieve has a silica-to-alumina molar ratio (SAR) in the range of 10 to 200, 10 to 100, 10 to 75, 10 to 60, and 10 to 50, 15 to 100, 15 to 75, 15 to 60, and 15 to 50, 20 to 100, 20 to 75, 20 to 60, and 20 to 50.

[0075] In one or more specific embodiments, the small pore molecular sieve has a CHA structure type and a silica-to-alumina ratio of from 2 to 300, e.g., from 5 to 250, from 5 to 200, from 5 to 100, and from 5 to 50, from 10 to 200, from 10 to 100, from 10 to 75, from 10 to 60, and from 10 to 50, from 15 to 100, from 15 to 75, from 15 to 60, and from 15 to 50, from 20 to 100, from 20 to 75, from 20 to 60, and from 20 to 50. In one specific embodiment, the small pore molecular sieve comprises SSZ-13. In one very specific embodiment, the SSZ-13 has a silica to alumina ratio of from 2 to 300, e.g., from 5 to 250, from 5 to 200, from 5 to 100, and from 5 to 50, from 10 to 200, from 10 to 100, from 10 to 75, from 10 to 60, and from 10 to 50, from 15 to 100, from 15 to 75, from 15 to 60, and from 15 to 50, from 20 to 100, from 20 to 75, from 20 to 60, and from 20 to 50.

[0076] The synthesis of zeolites and related microporous and mesoporous materials varies depending on the structural type of the zeolite material, but generally involves combining several components (e.g., silica, alumina, phosphorus, alkali, organic template, etc.) to form a synthesis gel, which is then hydrothermally crystallized to form the final product. The structure directing agent (SDA) is either an organic cation, i.e., tetraethylammonium hydroxide (TEAOH), or an inorganic cation, i.e., Na + Or K + During crystallization, multiple tetrahedral units organize around the SDA to form the desired framework, and the SDA is often embedded within the pore structure of the zeolite crystal. In one or more embodiments, crystallization of the molecular sieve material can be achieved by the addition of structure-directing agents / templates, nuclei, or elements. In some cases, crystallization can be carried out at temperatures below 100°C. Molecular sieves having the CHA structure can be prepared by various techniques known in the art, such as those described in U.S. Patent Nos. 4,544,538 (Zones) and 6,709,644 (Zones), which are incorporated herein by reference in their entireties.

[0077] Optionally, the resulting alkali metal zeolite is exchanged with NH to form NH-chabazite. NH ion exchange can be carried out according to various techniques known in the art, such as Bleken, F.; Bjorgen, M.; Palumbo, L.; Bordiga, S.; Svelle, S.; Lillerud, K.-P., and Olsbye, U. Topics in Catalysis 52, (2009), 218-228.

[0078] Promoter Metal As used herein, "promoted" refers to a component intentionally added to the molecular sieve, as opposed to an impurity inherent in the molecular sieve. Thus, the intentional addition of a promoter enhances the activity of the catalyst compared to a catalyst without the intentional addition of a promoter. To promote SCR of oxides of nitrogen, in one or more embodiments, a suitable metal is exchanged into the molecular sieve component. Thus, the molecular sieve of one or more embodiments may be subsequently ion-exchanged with one or more promoter metals, such as copper (Cu), cobalt (Co), nickel (Ni), lanthanum (La), manganese (Mn), iron (Fe), vanadium (V), silver (Ag), and cerium (Ce), neodymium (Nd), praseodymium (Pr), titanium (Ti), chromium (Cr), zinc (Zn), tin (Sn), niobium (Nb), molybdenum (Mo), hafnium (Hf), yttrium (Y), and tungsten (W). In specific embodiments, the molecular sieve component is promoted with Cu, Fe, and combinations thereof. In very specific embodiments, the molecular sieve component is promoted with Cu.

[0079] The promoter metal content of the molecular sieve component, calculated as oxide, in one or more embodiments, is at least about 0.1 wt.%, reported on a non-volatile basis. In one or more embodiments, the promoter metal is present in an amount in all cases within the range of about 1 wt.% to about 10 wt.%, e.g., within the range of about 2 wt.% to about 5 wt.%, based on the total weight of the molecular sieve. In one or more specific embodiments, the promoter metal comprises Cu, and the Cu content, calculated as CuO, is in the ranges of up to about 10 wt.%, e.g., 9 wt.%, 8 wt.%, 7 wt.%, 6 wt.%, 5 wt.%, 4 wt.%, 3 wt.%, 2 wt.%, 1 wt.%, 0.5 wt.%, and 0.1 wt.%, based on the total weight of the calcined molecular sieve component and reported on a non-volatile basis, respectively, on an oxide basis. In specific embodiments, the Cu content, calculated as CuO, is in the range of about 2 wt.% to about 5 wt.%.

[0080] Metal oxides on the surface of molecular sieves According to one or more embodiments, the catalyst composition comprises a molecular sieve containing a promoter metal and a metal oxide on the surface of the molecular sieve. The metal oxide is present in a homogeneous mixture with the molecular sieve, resulting in a dispersed metal oxide phase within the molecular sieve material. In certain embodiments, the dispersion of the metal oxide throughout the molecular sieve material may be relatively uniform. However, in some embodiments, at least a portion of the metal oxide may be found in enriched regions at the surface of the washcoat layer containing the catalyst composition of the present invention, typically as a result of the amount of water-soluble zirconium compounds (or other metal oxide compounds) that migrate to the washcoat layer surface and are decomposed / oxidized in air during the substrate coating process.

[0081] For ease of reference, much of this disclosure focuses on zirconium oxide (and related zirconium precursors). However, other metal oxides, such as metal oxides containing one or more oxides of transition metals or lanthanides from Groups 3 or 4 of the periodic table, can be used without departing from the invention. Specific examples include zirconia, alumina, ceria, hafnia, yttria, and combinations thereof, although minor amounts of other metal oxides may be present. In certain embodiments, the predominant (greater than 50 wt. % based on the weight of the total metal oxide) metal oxide is zirconia, alumina, ceria, hafnia, yttria, or combinations thereof. In certain preferred embodiments, the metal oxide is primarily zirconia, including composites of zirconia with other metal oxides, such as ceria, alumina, hafnia, or yttria. In other embodiments, the metal oxide is alumina, e.g., a large crystal boehmite material, e.g., boehmite having a crystallite size of about 20 nm or greater.

[0082] In certain embodiments, the metal oxide content of the catalyst composition is defined, at least in part, by a mixture of a metal oxide sol containing metal oxide microparticles or nanoparticles and a molecular sieve. The introduction of the metal oxide material in a relatively insoluble form allows for the formation of a metal oxide material at high temperature using NO 3 as a precursor, as opposed to the use of a water-soluble precursor that is subsequently calcined to the oxide form. x This can help prevent migration of promoter metals within the catalyst composition, which can interfere with reduction. Thus, the benefits of increased metal oxide content (reduced NO production and increased low-temperature NO x Reduction) can be achieved without adversely affecting high temperature performance.

[0083] For example, in some embodiments, zirconia is introduced using an aqueous zirconia sol. As used herein, the term "aqueous zirconia sol" refers to a colloidal suspension of small solid particles of zirconia or hydrous zirconia in a continuous liquid (water) medium. In one or more embodiments, the aqueous zirconia sol is selected from the group consisting of zirconyl hydroxide sol, nano-sized hydrous zirconia sol, zirconia-yttria sol, zirconia-alumina sol, zirconia-ceria sol, organozirconium sol, and mixtures thereof. As indicated herein, aqueous alumina sols, such as large crystal boehmite sol, can also be used in certain embodiments.

[0084] In some embodiments, the aqueous zirconia sol may include one or more promoter metals in the form of aqueous metal salts. That is, the molecular sieve may be impregnated with the promoter metals and mixed with the metal oxide particles in the same process step. As used herein, "promoted" refers to a component intentionally added to the aqueous zirconia sol, as opposed to an impurity inherent in the aqueous zirconia sol. In this manner, the intentional addition of a promoter increases the activity of the aqueous zirconia sol compared to an aqueous zirconia sol to which no promoter was intentionally added. In one or more embodiments, the aqueous zirconia sol comprises a promoter metal selected from the group consisting of lanthanum (La), cerium (Ce), neodymium (Nd), praseodymium (Pr), copper (Cu), manganese (Mn), iron (Fe), nickel (Ni), titanium (Ti), chromium (Cr), zinc (Zn), tin (Sn), vanadium (V), niobium (Nb), molybdenum (Mo), hafnium (Hf), tungsten (W), yttrium (Y), and combinations thereof.

[0085] In one or more embodiments, the zirconium sol (or other metal oxide sol) referred to herein has zirconia (or other metal oxide) particles with an average particle size ranging from about 10 nm to about 500 nm, e.g., from about 10 nm to about 400 nm, from about 10 nm to about 300 nm, or from about 10 nm to about 250 nm. As used herein, "average particle size" refers to the average diameter of the zirconia particles (or other metal oxide particles) measured using a CILAS 1064 laser particle size analyzer in the liquid mode recommended by the manufacturer, with a measurement range of 0.04 microns to 500 microns. The particle size of nano-sized sol components can be measured using a CILAS 1064 laser particle size analyzer in the liquid mode recommended by the manufacturer, with a measurement range of 0.04 microns to 500 microns. For particles smaller than 40 nm, such particle sizes can be measured using the Malvern Zetasizer Nano ZS, a high performance two-angle particle and molecular size analyzer that uses dynamic light scattering with "NIBS" optics for the measurement of small or dilute samples and very low or high concentration samples, as well as enhanced detection of condensates.

[0086] In one or more embodiments, the molecular sieve and zirconia (or other metal oxide) particles have an average or mean particle size distribution ratio of greater than about 10:1, e.g., greater than about 100:1, greater than about 1000:1, greater than about 10000:1. As used herein, the terms "average particle size distribution ratio" and "average particle size distribution ratio" refer to a ratio of D 50 (50% = value).

[0087] Without being bound by theory, the zirconia (or other metal oxide) is advantageously in nano-sized particles, D 10It is believed that the zeolite should contain particles of a size such that the D value is greater than 10 times (10x) the pore opening of the zeolite and the particles do not penetrate the pores of the small pore molecular sieve. In one or more embodiments, the zirconia particles (and / or the zirconia particles in the starting zirconia sol) have a D value greater than 10 times the pore opening of the small pore molecular sieve. 10 D 10 References to particle size refer to a particle distribution having 10% by weight of particles with a diameter below a given threshold. In certain embodiments, the zirconia particles have a D of about 10 nm or greater, about 15 nm or greater, or about 20 nm or greater. 10 It has a value.

[0088] Surprisingly, it has been found that the presence of zirconia reduces NO production. In one or more embodiments, for certain catalyst articles of the present invention, NO production is reduced by more than about 10% by weight, e.g., more than about 15%, more than about 20%, more than about 25%, more than about 30%, more than about 35%, and more than about 40%, when compared to a catalyst article including the same small pore molecular sieve / promoter metal washcoat but without the zirconia-containing layer (at the same catalyst and promoter metal loadings). Exemplary test conditions for measuring NO production can be found in Example 3.

[0089] In one or more embodiments, the zirconia (or other metal oxide) is present in an amount ranging from about 1% to about 20% by weight, e.g., about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, about 10%, about 11%, about 12%, about 13%, about 14%, and about 15% by weight, based on the total weight of the washcoat in all cases, on an oxide basis. As used herein, the term "total weight of the washcoat" refers to the weight of all components in the washcoat, including molecular sieves, promoter metals, and zirconia, after the washcoat has been dried and calcined. In certain embodiments, the zirconia (or other metal oxide) is present in an amount of at least about 5%, at least about 6%, at least about 7%, at least about 8%, at least about 9%, or at least about 10% by weight, based on the total weight of the washcoat.

[0090] In certain embodiments, the metal oxide content is provided by using a water-soluble metal oxide precursor that is added to the washcoat slurry during the washcoat application process. In one embodiment, the entire metal oxide is provided as described above, although it is preferred that at least some of the metal oxide content be derived from the relatively insoluble source described above. As shown in the examples, the use of large amounts of water-soluble metal oxide precursor can cause undesirable promoter metal migration within the washcoat. Therefore, it is desirable to either minimize the contribution of the water-soluble metal oxide precursor to the total metal oxide content and / or to minimize the solubility of the promoter metal by calcining the metal-promoted molecular sieve material (e.g., calcining in air at a temperature of at least about 300°C) prior to contact with the water-soluble metal oxide precursor.

[0091] Washcoat slurries are typically prepared using abundant amounts of water, and therefore, aqueous-based washcoat slurries are commonly used as well. The zirconium compound that migrates to the washcoat surface must be soluble in water and also in the slurry. In one or more embodiments, the zirconium compound is at least 15% by weight soluble in water, e.g., at least about 20% by weight soluble, at least about 30% by weight soluble, at least about 40% by weight soluble, at least about 50% by weight soluble, at least about 60% by weight soluble, at least about 70% by weight soluble, at least about 80% by weight soluble, and at least about 90% by weight soluble. In other embodiments, the zirconium compound has a water solubility of about 15% to about 100%, for example, within the range of about 15% to about 85%, about 20% to about 100%, about 20% to about 85%, about 30% to about 100%, about 30% to about 85%, about 40% to about 100%, about 40% to about 85%, about 50% to about 100%, and about 50% to about 85% solubility. References to solubility in terms of weight percent refer to the percentage of the zirconium compound dissolved in the aqueous washcoat composition at room temperature (25° C.) and 1 atmosphere pressure.

[0092] As used herein, "water-soluble zirconia component," "water-soluble zirconium compound," and the like refer to the respective water-soluble zirconium-containing compounds, complexes, precursors, and the like that are decomposed, oxidized, or otherwise converted to the catalytically active form, typically the metal or metal oxide (i.e., zirconia), upon calcination or use of the catalyst. As noted above, water-soluble precursors of other metal oxides may be used in place of the zirconium compound.

[0093] In one or more embodiments, a salt, such as NH4NO3 or NHOAc, is added to the aqueous washcoat composition containing the zirconium compound to increase the ionic strength, and the pH is then adjusted / controlled, for example, to about pH 4-5, to ensure that the zirconium compound, such as a zirconyl salt, e.g., zirconyl acetate, is water soluble and migrates during drying.

[0094] In one or more embodiments, the zirconium compound is selected from the group consisting of ionic zirconium salts, covalently bound organozirconium complexes, covalently bound organozirconyl compounds, and mixtures thereof. As used herein, the term "organozirconium salt, compound, or complex" refers to any zirconium salt, compound, or complex that is a covalently bound organozirconyl compound. 4+ and any anionic organic ligands, which may also include polymeric species. In one or more embodiments, the water-soluble zirconium compound is selected from the group consisting of zirconium acetate, zirconium citrate, zirconium tartrate, zirconium lactate, zirconium adipate, and mixtures thereof. As used herein, the term "organic zirconyl salt, compound, or complex" refers to a complex formed by covalently bonding ZrO 2+ and any anionic organic ligands, which may also include polymeric species. In one or more embodiments, the water-soluble zirconium compound is selected from the group consisting of zirconium nitrate, zirconium chloride, zirconium sulfate, zirconyl nitrate, zirconyl chloride, zirconyl sulfate, zirconyl acetate, zirconyl citrate, zirconyl tartrate, zirconyl lactate, zirconyl adipate, and mixtures thereof.

[0095] Particle shape and size Catalysts according to embodiments of the present invention may be provided in the form of powders or atomized materials from separation techniques including decantation, filtration, centrifugation, or atomization.

[0096] Generally, the powder or sprayed material can be formed, without any other compounds, for example by suitable compression molding, to obtain a desired shape of molding, such as a tablet, cylinder, sphere, etc.

[0097] For example, the powder or sprayed material may be mixed with or coated with a suitable modifier well known in the art. For example, modifiers such as silica, alumina, zeolite, or a refractory binder (e.g., a zirconium precursor) may be used. The powder or sprayed material, optionally after mixing with or coating with a suitable modifier, may be formed into a slurry, for example with water, which is then deposited on a suitable refractory support, such as a flow-through honeycomb substrate support or a wall-flow honeycomb substrate support.

[0098] Catalysts according to embodiments of the present invention may also be provided in the form of extrudates, pellets, tablets or particles of any other suitable shape for use as a packed bed of particulate catalyst or as shaped articles such as plates, saddles, tubes, etc.

[0099] SCR activity In one or more embodiments, the coated substrate comprising the selective catalytic reduction catalyst of one or more embodiments is heated to a gas hourly space velocity of 80,000 h -1 NO after aging at 200°C x In a specific embodiment, the catalyst exhibits a conversion of at least 50%. -1 NO after aging at 450°C measured at x The conversion rate is at least 70%. More specifically, the gas hourly volumetric space velocity is 80,000 h -1 Under steady-state conditions, maximum NH3 slip was measured in a gas mixture of 500 ppm NO, 500 ppm NH3, 10% O2, 5% H2O, balance N2, and NO after aging at 200°C. x The conversion may be at least 55%, at least 75% at 450°C, and even more specifically, at least 75% after aging at 200°C. x The conversion is at least 60% and at least 80% at 450°C. The coated substrate or "core" is heated in a tube furnace at a space velocity of 4000 h in a gas stream containing 10% H2O, 10% O2, and the balance N2.-1 The mixture was then hydrothermally aged at 750°C for 5 hours.

[0100] SCR activity measurements have been documented in the literature (see, for example, PCT Application Publication No. WO2008 / 106519).

[0101] Additionally, according to one or more embodiments, the catalyst is effective in lowering N2O production.

[0102] Base material In one or more embodiments, the catalyst composition may be applied to a substrate as a washcoat. As used herein, the term "substrate" refers to a monolithic material onto which the catalyst is disposed, typically in the form of a washcoat. The washcoat is formed by preparing a slurry containing a specific solids content (e.g., 30% to 90% by weight) of the catalyst in a liquid vehicle, which is then coated onto the substrate and dried to obtain a washcoat layer.

[0103] In one or more embodiments, the substrate is selected from one or more of a flow-through honeycomb monolith, a wall-flow filter, a foam, or a mesh, and the catalyst is applied to the substrate as a washcoat.

[0104] According to one or more embodiments, the substrate for the catalyst composition may be made from any material commonly used for the manufacture of automotive catalysts, and is generally believed to comprise a metal or ceramic honeycomb structure. The substrate generally provides a plurality of walls onto which the catalyst composition is applied and adhered, thereby acting as a support for the catalyst composition.

[0105] Exemplary metallic substrates include heat-resistant metals and metal alloys, such as titanium and stainless steel, as well as other alloys in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and / or aluminum, the combined amount of which may advantageously comprise at least about 15% by weight of the alloy, e.g., about 10% to 25% by weight chromium, about 3% to 8% by weight aluminum, and up to 20% by weight nickel. The alloy may also contain small or trace amounts of one or more other metals, such as manganese, copper, vanadium, titanium, etc. Surfaces or metal supports may be oxidized at high temperatures, e.g., above 1000°C, to form an oxide layer on the substrate surface, improving the corrosion resistance of the alloy and promoting the adhesion of washcoat layers to the metal surface.

[0106] The ceramic material used to make the substrate can include any suitable refractory material, such as cordierite, mullite, cordierite-α-alumina, silicon nitride, zirconia-mullite, spodumene, alumina-silica-magnesia, zirconium silicate, sillimanite, magnesium silicate, zirconium, petalite, α-alumina, aluminosilicates, and the like.

[0107] Any suitable substrate can be used, such as a monolithic flow-through substrate, having fine, parallel gas flow passages extending from the inlet face to the outlet face of the substrate, thus leaving the passages open for fluid flow. The passages, which are essentially straight-line paths from the inlet to the outlet, are defined by walls coated with a catalytic material as a washcoat, so that gas flowing through the passages comes into contact with the catalytic material. The flow paths of the monolithic substrate are thin-walled passages, which may have any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such structures may contain from about 60 to about 1200 or more gas inlet openings (i.e., "cells") per square inch of cross-sectional area (cpsi), more typically about 300-600 cpsi. The wall thickness of the flow-through substrate can vary, typically between 0.002 inches and 0.1 inches. Typical commercially available flow-through substrates are cordierite substrates having 400 cpsi and a 6 mil wall thickness, or 600 cpsi and a 4 mil wall thickness, however, it will be understood that the present invention is not limited to any particular substrate type, material, or shape.

[0108] In an alternative embodiment, the substrate may be a wall-flow substrate, in which each passage is plugged with a nonporous plug at one end of the substrate body, with alternating passages plugged at the opposite end. This requires that gas flow reach the outlet through the porous walls of the wall-flow substrate. Such monolithic substrates may have a pressure of about 700 cpsi or more, e.g., about 100 to 400 cpsi, more typically about 200 to about 300 cpsi. The cross-sectional shape of the cells may vary, as described above. Wall-flow substrates generally have wall thicknesses between 0.002 inches and 0.1 inches. Typical commercially available wall-flow substrates are made from porous cordierite, one example of which has 200 cpsi and a 10-mil wall thickness, or 300 cpsi with an 8-mil wall thickness, and a wall porosity of between 45% and 65%. Other ceramic materials, such as aluminum titanate, silicon carbide, and silicon nitride, have also been used as wall-flow filter substrates. However, it will be understood that the present invention is not limited to a particular substrate type, material, or shape. It should be noted that when the substrate is a wall-flow substrate, the DOC composition, in addition to being disposed on the wall surface, may penetrate into the pore structure of the porous wall (i.e., partially or completely block the pore openings).

[0109] FIG. 15 illustrates an exemplary substrate 2 in the form of a honeycomb monolith coated with a catalyst composition described herein. The exemplary substrate 2 has a cylindrical shape, with a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 identical to end surface 6. The substrate 2 has a plurality of narrow, parallel gas passages 10 formed therein. In the case of a flow-through monolith, the passages 10 are generally unblocked, allowing a fluid, such as a gas stream, to flow longitudinally through the substrate 2 through the gas passages 10. Alternatively, the substrate 2 may be in the form of a wall-flow filter, as described in detail above. In one such embodiment, each gas passage 10 is blocked at either the inlet or outlet end, and the walls of the passages are porous, allowing gas to pass from one gas passage to the adjacent gas passage, as understood in the art. If desired, the catalyst composition can be applied in many different layers. The present invention can be practiced with one or more (e.g., two, three, or four) washcoat layers.

[0110] To coat a substrate with one or more embodiment catalysts, the substrate is immersed vertically in a portion of the catalyst slurry so that the top of the substrate is just above the surface of the slurry. This allows the slurry to contact the inlet face of each honeycomb wall but prevents contact with the outlet face of each wall. The sample is allowed to sit in the slurry for approximately 30 seconds. The substrate is removed from the slurry, and excess slurry is removed from the substrate by first allowing it to flow through the channels, then blowing compressed air (against the direction of penetration of the slurry), and then applying a vacuum from the direction of penetration of the slurry. Using this technique, in the case of wall-flow substrates, the catalyst slurry penetrates the walls of the substrate but does not block the pores to the extent that excessive back pressure is created in the finished substrate. As used herein, the term "infiltrate," when used to describe the dispersion of catalyst slurry on a substrate, means that the catalyst composition is dispersed throughout the substrate walls, thereby at least partially blocking the pores in the walls.

[0111] The coated substrate is typically dried at about 100°C and calcined at a higher temperature (e.g., 300°C to 450°C). After calcination, the catalyst loading can be determined by calculating the coated weight of the substrate and its uncoated weight. As will be apparent to those skilled in the art, the catalyst loading can be varied by changing the solids content of the coating slurry. Alternatively, repeated immersion of the substrate in the coating slurry can be performed, followed by removal of excess slurry as described above.

[0112] Catalyst production According to one or more embodiments, there is provided a method for synthesizing a selective catalytic reduction catalyst. More specifically, the catalyst comprises a small pore molecular sieve having a pore structure and a maximum ring size of eight tetrahedral atoms and containing a promoter metal, and a zirconia-containing layer on the small pore molecular sieve containing the promoter metal, wherein the zirconia-containing layer generally has zirconia particles having an average particle size within the range of about 10 nm to about 500 nm.

[0113] For ease of reference, the above description focuses on the use of zirconia sol. However, it is understood that other metal oxides can be used without departing from the present invention. In one embodiment, the catalyst can be prepared by dissolving a metal salt (e.g., a nitrate or acetate salt) in an aqueous zirconia sol, such as, but not limited to, colloidal zirconyl hydroxide. In one or more embodiments, the metal salt is a salt of at least one metal selected from the group consisting of La, Ce, Nd, Pr, Cu, Mn, Fe, Ni, Ti, Cr, Zn, Sn, V, Nb, Mo, Hf, Y, and W. The metal salt dissolves and dissociates in the aqueous zirconia sol to form a soluble aqueous metal salt / zirconia sol mixture. Exemplary metal salts include copper(II) nitrate, copper(II) acetate, iron(III) nitrate, and iron(III) acetate. The aqueous zirconia sol has zirconia particles with an average particle size ranging from about 10 nm to about 500 nm. An aqueous metal salt (i.e., promoter metal) / zirconia sol mixture is formed having an initial moisture concentration of about 50% to 100%. In one or more embodiments, higher initial moisture concentrations, particularly those approaching 100%, are desirable.

[0114] The ammonium- or proton-exchanged molecular sieve is then impregnated with the metal salt / zirconia-based sol mixture. Impregnation can be carried out in any of a variety of mixers known in the art for mixing powders with solutions or dispersions, such as ribbon or planetary mixers equipped with nozzles for spraying the liquid into the mixer. The impregnated material is dried and calcined in air to form a catalyst comprising the metal-exchanged / promoted molecular sieve with a zirconia-containing layer. Calcination of the impregnated material can be carried out using a variety of techniques known in the art, including box calcination, calcination in a rotary kiln, or calcination using a fluidized-bed calciner. Flash drying and calcination in a single step (e.g., using a fluidized-bed calciner) are preferred in certain embodiments because such methods provide short residence times and uniform drying / calcination at the particle level.

[0115] Without being bound by theory, it is believed that upon drying and calcination, the metal from the metal salt penetrates the pores of the small pore molecular sieve, migrates to Bronsted acid sites via a concentration gradient effect in the presence or absence of HO vapor, and then acts as a promoter metal, while the zirconia (or other metal oxide) particles do not penetrate the pore structure of the molecular sieve. Instead, the zirconia forms an enriched layer (zirconia-containing layer) on and / or between the small pore molecular sieve particles, which then bond together to form agglomerates of metal-promoted zeolite particles.

[0116] In one or more embodiments, at least one binder compound is added to the aqueous washcoat formulation after the addition and dispersion of the zirconia-enriched molecular sieve powder. The washcoat containing the binder is then applied to a substrate, dried, and calcined to produce the final catalyst material. The one or more additional binders can be selected from any binder known to those skilled in the art. In one or more embodiments, the additional binder can be a titania binder, an alumina binder, a zirconia binder, or a silica binder known to those skilled in the art. For example, but not limited to, the binder can be selected from titanium oxychloride (TiOCl), titanium oxysulfate (TiOSO), aluminum trihydrate (Al(OH)), boehmite (AlO(OH)), aluminum nitrate Al(NO), SiO sol (e.g., commercially available Nalco® 1034A), and a zirconia compound.

[0117] NO x Reduction methods and exhaust gas treatment systems Generally, the molecular sieve material having the zirconia-containing layer can be used as a molecular sieve, an adsorbent, a catalyst, a catalyst support, or a binder thereof. In one or more embodiments, the material is used as a catalyst.

[0118] Another aspect of the present invention relates to a method of catalyzing a chemical reaction, wherein the catalyst of one or more embodiments can be used to catalyze a chemical reaction, wherein the catalyst is used as a catalytically active material.

[0119] Among others, the catalyst is preferably used for the treatment of nitrogen oxides (NO x It can be used as a catalyst for the selective reduction (SCR) of NH3, for the oxidation of NH3, especially for the oxidation of NH3 slip in diesel systems.

[0120] One or more embodiments may include nitrogen oxides (NO xIn one or more embodiments, the method comprises the step of selectively reducing NO x and contacting an exhaust gas stream containing the compound with one or more of the catalysts of the present invention. In particular, the selective reduction of nitrogen oxides of the present invention, wherein the selective catalytic reduction catalyst comprises a small pore molecular sieve having a pore structure and a maximum ring size of eight tetrahedral atoms and comprising a promoter metal, and a zirconia (or other metal oxide)-containing layer on the small pore molecular sieve comprising the promoter metal, is used as the catalytically active material in a reaction carried out in the presence of ammonia or urea.

[0121] While ammonia is the reducing agent of choice for stationary power plants, urea is the reducing agent of choice for mobile SCR systems. SCR systems are typically incorporated into the exhaust gas treatment system of a vehicle and typically include the following major components: a selective catalytic reduction catalyst according to an embodiment of the present invention, including a small pore molecular sieve having a pore structure and a maximum ring size of eight tetrahedral atoms and including a promoter metal; a zirconia (or other metal oxide)-containing layer on the small pore molecular sieve including the promoter metal; and an injector for injecting a reducing agent, such as ammonia or an ammonia precursor (e.g., urea), located upstream from the SCR catalyst article. In a specific embodiment, the system may include a urea storage tank, a urea pump, a urea metering system, a urea injector / nozzle, and respective control units.

[0122] In other embodiments, an SCR catalyst according to one or more embodiments is used as an SCR catalyst in an exhaust gas treatment system for a lean-burn gasoline direct injection (GDI) engine. In such cases, the SCR catalyst according to one or more embodiments acts as a passive ammonia SCR catalyst and can effectively store ammonia at temperatures above 400°C.

[0123] As used herein, the term "stream" generally refers to any combination of flowing gases containing solid or liquid particulate matter. The term "gas stream" or "exhaust gas stream" refers to a stream of gaseous components, e.g., an exhaust gas stream of a lean-burn engine (i.e., an engine that burns fuel in the presence of excess oxygen), which may contain entrained non-gaseous components such as liquid droplets, solid particulate matter, etc. The exhaust gas stream of a lean-burn engine generally further contains products of combustion, products of incomplete combustion, nitrogen oxides, combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen.

[0124] As used in the context of embodiments of the present invention, nitrogen oxides NO x The term denotes oxides of nitrogen, in particular nitrous oxide (N2O), nitric oxide (NO), nitrogen trioxide (N2O3), nitrogen dioxide (NO2), nitrogen tetroxide (N2O4), nitrogen pentoxide (N2O5), and nitrogen peroxide (NO3).

[0125] A further aspect of the present invention relates to an exhaust gas treatment system. In one or more embodiments, the exhaust gas treatment system comprises an exhaust gas stream optionally containing a reducing agent such as ammonia, urea, and / or hydrocarbons, in one specific embodiment, ammonia and / or urea, and a selective catalytic reduction catalyst comprising a washcoat according to one or more embodiments comprising a small pore molecular sieve having a pore structure and a maximum ring size of eight tetrahedral atoms and containing a promoter metal, and a zirconia (or other metal oxide)-containing layer on the small pore molecular sieve containing the promoter metal. The catalyst is effective for destroying at least a portion of the ammonia in the exhaust gas stream.

[0126] In one or more embodiments, the catalyst may be disposed on a substrate, such as a soot filter. A catalyzed or uncatalyzed soot filter may be present upstream or downstream of the catalyst. In one or more embodiments, the system may further include a diesel oxidation catalyst. In specific embodiments, the diesel oxidation catalyst is disposed upstream of the catalytic material. In other specific embodiments, the diesel oxidation catalyst and the catalyzed soot filter are upstream from the catalytic material.

[0127] In a specific embodiment, the exhaust gas is conveyed from the engine to a downstream location in the exhaust system, and the exhaust gas is, in a more specific embodiment, a mixture of NO x wherein a reducing agent, for example urea, is added and the exhaust gas stream together with the added reducing agent is conveyed to the catalyst.

[0128] For example, catalyzed soot filters, diesel oxidation catalysts, and reductants are described in WO 2008 / 106519, which is incorporated herein by reference. In a specific embodiment, the soot filter comprises a wall-flow filter substrate with alternating blocked passages such that gas flows into the passages in one direction (the inlet direction), through the passage walls, and out the passages in the other direction (the outlet direction).

[0129] An ammonia oxidation catalyst (AMOx) may be provided downstream of one or more of the catalyst embodiments to remove any slip ammonia from the system. In specific embodiments, the AMOx catalyst may comprise a platinum group metal, such as platinum, palladium, rhodium, or a combination thereof.

[0130] Such AMOX catalysts are useful in exhaust gas treatment systems that include SCR catalysts. As discussed in commonly assigned U.S. Patent No. 5,516,497 (the entire contents of which are incorporated herein by reference), a gas stream containing oxygen, nitrogen oxides, and ammonia may be passed sequentially through a first catalyst and a second catalyst, where the first catalyst is responsible for reducing the nitrogen oxides and the second catalyst is responsible for oxidizing or otherwise decomposing excess ammonia. As described in U.S. Patent No. 5,516,497, the first catalyst may be a zeolite-containing SCR catalyst, and the second catalyst may be a zeolite-containing AMOX catalyst.

[0131] One or more AMOx and / or SCR catalyst compositions may be coated onto a flow-through or wall-flow filter. If a wall-flow substrate is utilized, the resulting system may also be capable of removing particulate matter along with gaseous pollutants. The wall-flow filter substrate may be fabricated from materials commonly known in the art, such as cordierite, aluminum titanate, or silicon carbide. It will be appreciated that the loading of catalyst composition on a wall-flow substrate depends on substrate characteristics, such as porosity and wall thickness, and is generally lower than the loading on a flow-through substrate.

[0132] One exemplary exhaust gas treatment system is illustrated in Figure 16, which shows a schematic diagram of an exhaust gas treatment system 32. As shown, an exhaust gas stream containing gaseous pollutants and particulate matter is conveyed from an engine 34 (e.g., a diesel engine, a lean GDI engine, or other lean-burn engine) via an exhaust pipe 36, through a diesel oxidation catalyst (DOC) 38, through a catalyzed soot filter (CSF), and to a selective reduction catalyst (SRC) coated with the washcoat composition of the present invention. In the DOC 38, unburned gaseous non-volatile hydrocarbons (i.e., SOF) and carbon monoxide are substantially combusted to form carbon dioxide and water. Additionally, NOx is released from the exhaust gas 34, which is then passed through a catalyzed soot filter (CSF) and ... xA proportion of the component NO can be oxidized to NO2 in the DOC.

[0133] The exhaust gas stream is then conveyed via exhaust pipe 40 to a catalyzed soot filter (CSF) 42, which captures particulate matter present in the exhaust gas stream. The CSF 42 is optionally catalyzed for passive or active soot regeneration. The CSF 42 optionally captures NO present in the exhaust gas. x The SRC composition of the present invention may be included for the conversion of

[0134] After removing particulate matter via CSF 42, the exhaust gas stream is conveyed via exhaust pipe 44 to a downstream selective catalytic reduction component 46 of the present invention, which further reduces NO x The exhaust gas passes through the SCR component 46 where the catalyst composition treats and / or converts NO in the exhaust gas at a predetermined temperature. x The SCR component 46 passes through the exhaust gas treatment system at a flow rate that allows sufficient time for the CSF 42 to reduce the level of NO. The SCR component 46 may optionally be included in the exhaust gas treatment system if the CSF 42 already contains an SCR catalyst composition. An injector 50 for introducing a nitrogen-containing reductant into the exhaust gas stream is located upstream of the SCR 46. The nitrogen-containing reductant introduced into the exhaust gas stream reduces NO. x to N2, and water is exposed as a gas to the catalyst composition. If the CSF 42 also contains an SCR catalyst, the injector 50 can be moved to a position upstream of the CSF.

[0135] The present invention will now be described with reference to the following examples. Before describing certain exemplary embodiments of the present invention, it is to be understood that the present invention is not limited to the details of construction or method steps set forth in the following detailed description. The present invention is capable of other embodiments and of being practiced or carried out in various ways.

[0136] Example Example 1 - 10% ZrO as zirconyl acetate added to slurry 2 Cu-exchanged CHA (3.25 wt% CuO, SAR 28) was dispersed in water and recirculated through a 50 Hz in-line homogenizer to break down large agglomerates, resulting in a D90 of less than 14 μm. Zirconyl acetate binder was then added to achieve a total binder loading of 10 wt% based on the calcined washcoat. The final pH of the resulting slurry was approximately 4.0. The mixture was then coated onto a cordierite substrate, dried, and calcined at 450°C to form an active catalytic coating. Drying was performed using a forced-draft oven to promote flow through the part. Because zirconyl acetate is highly soluble, it migrated through the washcoat during drying, forming an enriched layer on the surface of the CHA. The final washcoat composition after coating, drying, and calcination was 2.9% CuO, 87.1% CHA, and 10% ZrO.

[0137] Referring to Figure 1, the SCR conversion is relatively unchanged at the low temperature end, 200°C to 300°C, for 10% ZrO2 (versus the same washcoat made with only 5% ZrO2), and slightly higher than at the high temperature end.

[0138] The zirconyl acetate solution also contains excess acetic acid for stabilization (acetic acid / ZrO2 molar ratio about 1.6), which allows more CuO to become soluble and migrate to the surface. This explains the observed change in selectivity between 450 and 600 °C, where the performance of 10% ZrO2 drops off, since free CuO (outside the exchange sites) oxidizes NH3, providing more NO for reduction than is already there. x is known to be formed in practice.

[0139] As shown in Figure 1, enrichment of ZrO2 on the washcoat surface leads to reduced NO production at all temperatures (200°C-600°C). This experiment illustrates the correlation between zirconium oxide concentration in the washcoat and NO production, with higher zirconium oxide amounts resulting in reduced NO production.

[0140] Example 2 - 5% Zirconyl Acetate and Higher Slurry Conductivity To investigate the effect of more soluble Zr, one slurry batch was prepared similar to Example 1, but with the addition of only 5 wt. % ZrO2 as zirconyl acetate. After the addition of zirconyl acetate, the slurry was split into two samples designated Sample 1 and Sample 2. Sample 1 was not further modified and therefore had the same composition as one of the compositions in Example 1.

[0141] 0.1% ammonium nitrate (NH4NO3) was added to Sample 2 to increase the conductivity (measured using Cole Parmer product number EW-19601-04). The conductivity increased from 870 μS / cm to 2200 μS / cm, and the final pH of both slurries was 4.4 (see Table 1).

[0142] Table 1: Solubility of Cu and Zr in the aqueous liquid phase after centrifugation of the washcoat slurry [Table 1]

[0143] Using the same method as in Example 1, the mixture was then coated onto a cordierite substrate, dried, and calcined at 450°C to form an active catalytic coating. Drying was performed using a forced draft oven to promote flow through the element. Table 1 shows that the Zr solubility of Sample 2 was two times higher than that of Sample 1. Solubility was measured by taking a slurry sample, adding it to a centrifuge tube, and subjecting it to 7800 rpm for 2 hours using a Thermo Electron Corporation IEC CL40R centrifuge. The resulting clear, water-white to blue supernatant (Cu 2+The solubility of Zr in the slurry phase (which depends on how soluble it was) was analyzed using inductively coupled plasma (ICP) to measure the parts per million concentration in the liquid phase, and the % soluble fraction of a given element in the liquid phase was calculated based on the slurry solids content and washcoat elemental composition. Tables 1 and 2 (see Example 3) confirm that the solubility of Zr needs to be greater than 15% and approach 100% soluble in the slurry phase to facilitate migration of the soluble species (i.e., zirconium compounds) to the surface of the washcoat during drying.

[0144] Figures 2 and 3 are scanning electron microscope (SEM) images focused on a portion of the washcoat at the corner of a coated substrate cell for Sample 1 and Sample 2, respectively. The EDS tabulated results in Figure 2 (Sample 1) and Figure 3 (Sample 2) both show higher concentrations of Zr and Cu elements on the surface. However, Figure 3 shows visible enriched zones containing higher Cu and Cr, which directly correlates with the amount of each element soluble in the aqueous slurry phase, as demonstrated in Table 1.

[0145] Figure 4 shows the NO2 emission when each sample was used in a specific exhaust gas treatment system. x 4 is a bar graph comparing Sample 2 and Sample 1 in terms of efficiency (results are reported as two measurements per sample and their average). Figure 4 shows that Sample 2 (higher Zr and Cu on the surface, Figure 3) has improved performance compared to Sample 1 (Figure 2). The results for the system are consistent with the use of the same / normalized (constant) DOC (6.5" diameter x 8" length at 70g / ft) as the primary catalyst in the system. 3The system included a 6.7L engine with a diesel oxidation catalyst (DOC) outlet at 750°C. Efficiency was measured using the EPA 75 test cycle and reported as weighted modal data from the DOC to the SCR outlet without any regeneration step. The temperatures at which data was generated ranged from 180°C to 220°C, with the average data recorded being approximately 200°C.

[0146] This example demonstrates that the presence of soluble zirconium species in the washcoat results in enhanced migration of zirconium to the washcoat surface, which is then converted to low temperature NO x However, as mentioned above, the increase in soluble zirconium species in the outer portion of the washcoat also coincides with an increased copper concentration in the same region, which contributes to increased copper migration during the washcoat coating process. Such copper migration is due to the high temperature NO x This may impair conversion.

[0147] Example 3 - 8% ZrO 2 / 3.25% CuO / CHA Step 1: 1.7 kg of copper (II) nitrate crystals were dissolved in 3.6 kg of commercially available nitric acid-based zirconia sol with a ZrO2 content of 15% by weight by mixing at room temperature.

[0148] Step 2: The solution from step 1 was impregnated onto 18.8 kg of spray-dried NH4 / CHA powder, followed by simultaneous drying and calcination. The product of this step, a 3% ZrO2 / 3.25% CuO / CHA powder, is shown as a scanning electron microscope (SEM) image at 10,000x magnification in Figure 5. The SEM image shows the presence of surrounding zirconium particles (lighter colored material) and dispersed zeolite particles (darker, larger particles).

[0149] Step 3: The calcined powder from step 2 was then dispersed in water and recirculated through a 50 Hz in-line homogenizer to break down large agglomerates, resulting in a D90 of less than 14 μm. An additional 5 wt. % zirconyl acetate as a binder was added to reach a total ZrO2 loading of approximately 8 wt. % based on the washcoat after calcination. The final pH of the resulting slurry was 3.8.

[0150] The mixture was then coated onto a cordierite substrate, dried, and calcined at 450°C to form an active catalytic coating. Drying was performed using a forced-draft oven to promote flow through the part. The final washcoat composition after coating, drying, and calcination was 3.1% CuO, 89.1% CHA, and 7.8% ZrO2, and is designated Sample 3 in Table 2. Table 2 shows that Sample 3 had low Cu and Zr solubility due to the pre-preparation, which included rapid drying / calcination of the 3%ZrO2 / 3.25%CuO / CHA powder manufacturing process. This rapid drying and calcination in air produced a rapid concentration gradient in less than 1.5 seconds, which resulted in the formation of Cu. 2+ This generated a driving force for the transfer of Brønsted acid to the Brønsted acid site.

[0151] Sample 4 was prepared by dispersing Cu-exchanged CHA (3.25 wt% CuO, SAR 28) in water and recirculating it through a 50 Hz in-line homogenizer to break down large agglomerates, resulting in a D of less than 14 μm. 90A zirconyl acetate binder was then added to achieve a total binder loading of 5 wt. % based on the calcined washcoat. The final pH of the resulting slurry was approximately 4.3. The mixture was then coated onto a cordierite substrate, dried, and calcined at 450°C to form an active catalytic coating. The final composition of Sample 4 was 3.1% CuO / 5.0% ZrO2 / 91.9% CHA. Sample 4 contained higher soluble Cu and Zr in the slurry phase compared to Sample 3.

[0152] Table 2: Solubility of Cu and Zr in the aqueous liquid phase after centrifugation of the washcoat slurry [Table 2]

[0153] Figures 6A-6D are a collection of scanning electron microscope (SEM) images of Sample 4 material. The box in the upper left (6A) is an SEM micrograph showing the distribution of the washcoat within a unit substrate cell at 50x magnification. Continuing counterclockwise, the box in the lower left (6B) shows the distribution of Cu in the washcoat using electron dispersive spectroscopy (EDS) mapping, illustrating that Cu is uniformly distributed throughout the washcoat with slight enrichment at the coating surface. Continuing counterclockwise, the micrograph in the lower right corner (6C) shows the Zr distribution by EDS. A distinctive Zr-enriched band is present at the washcoat surface, which correlates with the Zr solubility in Table 2. In the upper right corner is another SEM micrograph (6D) at 10,000x magnification, focusing on the Zr-enriched layer on the surface, approximately 1 μm to 3 μm thick. 6A-6D demonstrate the enrichment of ZrO2 on the washcoat surface, as also observed for Examples 1 and 2.

[0154] Figures 7A-7D are a collection of scanning electron microscope (SEM) images of the Sample 3 material. These figures confirm that the sample with reduced amounts of soluble Cu and Zr did not form any enriched layer, but some layering and interparticle bonding due to nano-ZrO2 is shown, and the washcoat also appears to be more porous. The box in the upper left corner (7A) shows the distribution of the washcoat within a unit substrate cell at 50x magnification. Continuing counterclockwise, the box in the lower left corner (7B) confirms that Cu is uniformly dispersed throughout the washcoat. The box in the lower right corner (7C) shows that Zr is dispersed throughout the washcoat, with regions of higher concentration (lighter colored regions) that are also present in the other samples but become more prevalent as the Zr concentration increases. Zr enrichment is not evident on the surface of the washcoat layer. Finally, in the upper right corner (7D), Zr is clearly visible on the surface of some particles, forming bridges between them. The coating also appears more porous. The CHA fine particles are likely bonded together with larger particles during the flash drying / calcination step during the fabrication of the ZrO2 / Cu / CHA composite powder. Zirconyl acetate, added later during the slurry preparation / washcoat fabrication step, further bonds the particles together during the drying and calcination steps of the coated substrate, forming a final 7.8% ZrO2 / 3.1% CuO, 89.1% CHA washcoat layer.

[0155] Table 3 outlines the reactor gas composition and test protocol.

[0156] Table 3: SCR CAEF [Table 3]

[0157] FIG. 8 shows the NO 3 at 200°C, 250°C, and 525°C for the material of Sample 3 compared to Sample 4, which contains Zr enrichment on the surface of the washcoat. x8 is a bar graph showing the reduction of NO at 200°C and 250°C. The samples were first aged at 700°C for 4 hours in 10% steam and air. The samples were then tested in a reactor according to Table 3. x The reduction of NO was slightly improved. x The conversion is confirmed to be significantly higher at 525°C. The wider performance window exhibited by sample 3 (with higher zirconium loading and lower soluble zirconium species) is due to the interaction of Cu with Bronsted acid sites. 2+ This is an indication of improved exchange and is an advantage of the process of thermally fixing the 3%ZrO2 / 3.25%CuO / CHA powder before introducing it to produce a final washcoat with the composition 7.8%ZrO2 / 3.1%CuO / 89.1%CHA on the N400 / 4 substrate.

[0158] Figure 9 is a bar graph showing NH3 slip, NH3 occlusion, and NO production at various temperatures for the material of Example 3. Figure 9 confirms that NO was further reduced for the material of Sample 3 compared to the material of Sample 4. This is due to the higher ZrO2 concentration (8% versus 5% for Sample 4) with enrichment at the particle level, and reduced soluble Cu and Zr in the slurry phase. 2+ This example demonstrates the benefits of increasing zirconium oxide concentration in the washcoat (e.g., reduced NO production and improved NO production at low temperatures). x This indicates that the reduction can be achieved by reducing the reliance on soluble zirconium species to obtain enhanced zirconium oxide concentrations without causing undesired copper migration.

[0159] Example 4 - 5% nano-ceria / zirconia on 3.25% CuO / CHA 3.8 kg of 3.25% CuO / CHA was first dispersed in 6.2 kg of water and recirculated through a 50 Hz in-line homogenizer to break down large agglomerates and produce D particles less than 20 μm. 90 To this mixture, 794 grams of Ce as defined in Table 4 is added.45 Nd5Zr 50 An aqueous dispersion of 02 was added and recirculation through the homogenizer was continued until the particle size distribution had a D90<14 μm. The pH of the final slurry was 4.6.

[0160] The mixture was then coated onto a cordierite substrate, dried, and calcined at 450°C to form an active catalytic coating. Drying was performed using a forced-draft oven to promote flow through the element. The final washcoat composition after coating, drying, and calcination was 2.25% CeO, 0.25% NdO, 2.51% ZrO, 3.09% CuO, and 91.91% CHA, which is designated Sample 5 in Table 5.

[0161] Sample 6 was prepared by dispersing Cu-exchanged CHA (3.25 wt% CuO, SAR 28) in water and recirculating it through a 50 Hz in-line homogenizer to break down large agglomerates, resulting in a D of less than 14 μm. 90 A zirconyl acetate binder was then added to achieve a total binder loading of 5 wt. % based on the calcined washcoat. The final pH of the resulting slurry was approximately 4.3. The mixture was then coated onto a cordierite substrate, dried, and calcined at 450°C to form an active catalytic coating. The final composition of Sample 6 was 3.1% CuO / 5.0% ZrO2 / 91.9% CHA.

[0162] Table 4: CeO 2 and Nd 2 O 3 Doped ZrO 2 Aqueous dispersion of particles less than 1 μm in size [Table 4]

[0163] Table 5: Solubility of Cu and Zr in the aqueous liquid phase after centrifugation of the washcoat slurry [Table 5]

[0164] Figures 10A-10D are a collection of scanning electron microscope (SEM) images of Sample 5 material. The top left box (10A) is an SEM micrograph showing the distribution of the washcoat within a multi-unit substrate cell at 25x magnification. Continuing counterclockwise, the bottom left box (10B) shows the distribution of Ce in the washcoat using electron dispersive spectroscopy (EDS) mapping, indicating that Ce is uniformly distributed throughout the washcoat. Both Zr and Nd are inferred to be well dispersed based on the sol composition specified in Table 4. Continuing counterclockwise, the bottom right micrograph (10C) shows that Cu is uniformly distributed throughout the washcoat, and finally the top right micrograph (10D) shows that porosity in the coating becomes apparent when magnified 500x.

[0165] Referring to FIG. 11, SCR conversion was slightly improved between 200°C and 250°C, but Sample 5 was slightly inferior to Sample 6 at temperatures between 250°C and 600°C. FIG. 12 shows that Sample 5 was slightly inferior to Sample 6 in terms of NO production. Without being bound by theory of operation, it is believed that the oxidative properties of CeO are at least partially responsible for this result. However, it is believed that the use of a ceria-zirconia composite has improved properties with respect to soot oxidation during regeneration, thereby minimizing zeolite fouling. Furthermore, metal oxide composites incorporating greater amounts of zirconia compared to ceria were able to achieve the desired reduction in NO production.

[0166] Example 5 - 6% ZrO on 3.25% CuO / CHA 2 1.7 kg of copper(II) nitrate crystals were dissolved in 7.2 kg of commercially available nitric acid-based zirconia sol (ZSL-15N, available from Daiichi Kigenso Kagaku Kogyo Co., Ltd.) with a ZrO content of 15% by weight by mixing at room temperature. The resulting solution was impregnated onto 18.2 kg of spray-dried NH4 / CHA powder in a mixer, followed by simultaneous drying and calcination. The product of this process is a 6% ZrO2 / 3.25% CuO / CHA powder. The calcined powder was then dispersed in water and recirculated through a 50 Hz in-line homogenizer to break down large agglomerates, resulting in a D90 of less than 14 μm. This rapid drying and calcination in air creates a rapid concentration gradient in less than 1.5 seconds, and, without being bound by theory, it is believed that this is the cause of the CuO 2+ This is thought to generate a driving force for the transfer of the Brønsted acid site.

[0167] FIG. 13 shows the powder reactor temperature curves comparing the standard 3.25% ion-exchanged Cu / CHA material with the 6%ZrO2 / 3.25%CuO / CHA prepared in this example, where the left-hand y-axis represents NO x The graph shows the % conversion of NO for the zirconia modified material, and the right hand y-axis shows the NO production in ppm. x The squares indicate the NO conversion of the comparative Cu / CHA material. x Conversion is shown, with circles indicating NO production for the zirconia-modified material and diamonds indicating NO production for the comparative CuCHA material. As shown, the zirconia modification of the CHA material resulted in improved low temperature NO production. x This results in slightly increased conversion and NO production at low temperatures. x Performance is roughly the same for both materials, with the zirconia modified material providing improved N2O production at higher temperatures.

[0168] Example 6 - 6% Al on 3.25% CuO / CHA 2 O 3 1.7 kg of copper(II) nitrate crystals were dissolved in 5.4 kg of commercially available nitric acid-based alumina sol with a 20% Al2O3 content by weight (Dispal 23N4-20, available from Sasol), a large crystal boehmite material, by mixing at room temperature. The resulting solution was impregnated onto 18.2 kg of spray-dried NH4 / CHA powder by spraying the solution onto the CHA powder in a mixer, followed by simultaneous drying and calcination. The product of this process is 6% Al2O3 / 3.25% CuO / CHA powder. The calcined powder was then dispersed in water and recirculated through a 50 Hz in-line homogenizer to break down large agglomerates, resulting in a D90 of less than 14 μm. This rapid drying and calcination in air creates a rapid concentration gradient in less than 1.5 seconds, and, without being bound by theory, it is believed that this is the cause of the CuO / CHA powder. 2+ This is thought to generate a driving force for the transfer of the Brønsted acid site.

[0169] The catalyst materials of Examples 5 and 6 were hydrothermally aged at 800°C for 6 hours in the presence of 10% HO to improve NO production compared to unmodified CuO / CHA material aged under the same conditions. x The conversion performance of the CHA materials was tested. The results are shown in Figure 14, where the CuO / CHA material without zirconia sol or alumina sol is represented by diamonds. The catalyst material of Example 5 (6% ZrO2 / 3.25% CuO / CHA) is represented by triangles, and the catalyst material of Example 6 (6% Al2O3 / 3.25% CuO / CHA) is represented by squares. As shown in the figure, the CHA materials modified with zirconia or alumina outperform the unmodified material at higher temperatures.

[0170] Example 7 - 8% ZrO on 4.4% CuO / CHA 2 / 2% of Y 2 O 3 0.5 kg of a commercially available 60 / 40 ZrO2 / Y2O3 mixed sol was dispersed in 41 kg of deionized water containing 0.17 kg of 90% acetic acid. 2.2 kg of a commercially available nitric acid-based zirconia sol (ZSL-15N, Daiichi Kigenso Kagaku Kogyo Co., Ltd.) with a ZrO2 content of 15% by weight was added to the dispersion prepared in the previous step by mixing at room temperature. 5.4 kg of spray-dried 4.91% CuO / CHA was added to the resulting dispersion, thus producing 8%ZrO2 / 2%Y2O3 / 4.40%CuO / CHA. The resulting mixture from the previous step was recirculated through a 50 Hz in-line homogenizer to break down large agglomerates, resulting in a D90 of less than 14 μm. The resulting slurry was then coated onto a 400 / 4 cordierite substrate, dried, and calcined at 450 °C to produce 2.75 g / in. 3 A drying increment of

[0171] The use of the terms "a," "an," and "the" and similar referents in connection with the description of materials and methods discussed herein (particularly in the context of the claims that follow) should be construed to include both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Designations of ranges of values ​​herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated, and each separate value is incorporated herein as if that value were individually indicated herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context. Any and all examples or exemplary language (e.g., "such as") provided herein are intended merely to better describe the materials and methods and do not pose a limitation on their scope unless specifically stated in the claims. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the disclosed materials and methods.

[0172] References throughout this specification to "one embodiment," "a particular embodiment," "one or more embodiments," or "an embodiment" mean that a particular feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of the present invention. Thus, the appearances of phrases such as "in one or more embodiments," "a particular embodiment," "in one embodiment," or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment of the present invention. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments.

[0173] Although the present invention has been described herein with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the method and apparatus of the present invention without departing from the spirit and scope of the invention. Therefore, it is intended that the present invention cover such modifications and variations provided they come within the scope of the appended claims and their equivalents. [Explanation of symbols]

[0174] 2 substrate, 4 cylinder outer surface, 6 upstream end face, 8 downstream end face, 10 passage, 32 exhaust gas treatment system, 34 engine, 36 exhaust pipe, 38 diesel oxidation catalyst, 40 exhaust pipe, 42 CSF, 44 exhaust pipe, 46 SCR component, 50 injector

Claims

1. A catalyst composition for use as a selective catalytic reduction catalyst, comprising: small pore molecular sieve particles impregnated with a promoter metal, the small pore molecular sieve particles having a pore structure and a maximum ring size of eight tetrahedral atoms; and metal oxide particles not penetrating the pore structure of the small pore molecular sieve particles and dispersed on the surface of the small pore molecular sieve particles, wherein the D of the molecular sieve particles is ５０ The particle size of the metal oxide particles D ５０ A catalyst composition wherein the ratio of D10 to particle size is greater than 10:1, and the metal oxide particles comprise zirconia or alumina, and the metal oxide particles have a D10 particle size greater than 10 times the pore openings of the molecular sieve.

2. The catalyst composition of claim 1 , wherein the metal oxide particles comprise zirconia.

3. 10. The catalyst composition of claim 1, wherein the metal oxide particles have an average particle size in the range of 10 nm to 500 nm.

4. The metal oxide particles have a D of 10 nm or more. 10 The catalyst composition of claim 1 having a particle size.

5. 5. The catalyst composition of claim 1, wherein the small pore molecular sieve has d6r units.

6. 5. The catalyst composition of claim 1, wherein the small pore molecular sieve has a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, LTN, MSO, SAS, SAT, SAV, SFW, and TSC.

7. 5. The catalyst composition of any one of claims 1 to 4, wherein the promoter metal is selected from the group consisting of Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Pr, Ti, Cr, Zn, Sn, Nb, Mo, Hf, Y, W, and combinations thereof.

8. 5. The catalyst composition of claim 1, wherein the small pore molecular sieve has a CHA structure type.

9. 5. The catalyst composition of claim 1, wherein the promoter metal comprises Cu or Fe or a combination thereof.

10. 5. The catalyst composition of claim 1, wherein the promoter metal is present in an amount in the range of 1% to 10% by weight, based on the total weight of the molecular sieve.

11. 5. The catalyst composition of claim 1, wherein the promoter metal is present in an amount in the range of 2% to 5% by weight, based on the total weight of the molecular sieve.

12. 5. The catalyst composition of any one of claims 1 to 4, wherein the metal oxide is present in an amount in the range of 1 wt% to 15 wt%, on an oxide basis, based on the total weight of the washcoat.

13. 10. A catalyst article comprising a substrate selected from a flow-through monolith, a wall-flow filter, a foam, or a mesh, wherein the catalyst composition of any one of claims 1 to 4 is deposited on the substrate as a washcoat layer.

14. 14. The catalytic article of claim 13, wherein the washcoat is disposed on a flow-through monolith or a wall-flow filter.

15. The catalyst article has at least 10 wt. % less N than a catalyst article containing a washcoat having the same catalyst composition at the same loading but without metal oxide particles dispersed on the small pore molecular sieve particle surfaces. 2 14. The catalytic article of claim 13 characterized by O production.

16. Nitrogen oxides (NO x ), comprising the steps of: x contacting an exhaust gas stream containing the catalyst with the catalytic article of claim 13.

17. N produced as a by-product 2 The amount of O is compared to the amount of N produced in a process using a catalyst article containing a washcoat having the same catalyst composition at the same loading, but without metal oxide particles dispersed on the surface of the small pore molecular sieve particles. 2 17. The method of claim 16, wherein the amount of O is reduced compared to the amount of O.

18. 14. An exhaust gas treatment system comprising the catalyst article of claim 13 downstream from an engine and an injector that adds a reductant to the exhaust gas stream.

19. 1. A method for producing a catalyst composition for selective catalytic reduction, comprising: dissolving a salt of at least one promoter metal in an aqueous metal oxide sol; a salt of the at least one promoter metal dissociates in the aqueous metal oxide sol to form an aqueous metal salt / metal oxide sol mixture; treating ammonium or proton exchanged small pore molecular sieve particles having a pore structure and a maximum ring size of eight tetrahedral atoms with the aqueous metal salt / metal oxide sol mixture to impregnate the promoter metal into the pore structure of the small pore molecular sieve; drying and calcining the treated small pore molecular sieve particles to form a catalyst composition comprising small pore molecular sieve particles impregnated with a promoter metal and metal oxide particles dispersed on the surface of the small pore molecular sieve particles but not penetrating the pore structure of the small pore molecular sieve particles. The metal oxide sol is selected from the group consisting of zirconyl hydroxide sol, nano-sized hydrous zirconia sol, alumina sol, zirconia-yttria sol, zirconia-alumina sol, zirconia-ceria sol, and mixtures thereof, and the D of the molecular sieve particles ５０ The particle size of the metal oxide particles D ５０ The method of claim 1, wherein the metal oxide sol has a D 10 particle size that is more than 10 times larger than the pore openings of the molecular sieve.

20. 20. The method of claim 19, wherein the metal oxide comprises zirconia.

21. 20. The method of claim 19, wherein the metal oxide sol has an average particle size in the range of 10 nm to 500 nm.

22. The metal oxide sol has a D of 10 nm or more. 10 20. The method of claim 19, wherein the particle size is

23. 23. The method of any one of claims 19 to 22, wherein the promoter metal is selected from the group consisting of Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Pr, Ti, Cr, Zn, Sn, Nb, Mo, Hf, Y, W, and combinations thereof.

24. 23. The method of any one of claims 19 to 22, wherein the metal oxide particles do not penetrate into the pore structure of the small pore molecular sieve.

25. 23. The method of any one of claims 19 to 22, wherein the small pore molecular sieve has d6r units.

26. 23. The method of any one of claims 19 to 22, wherein the small pore molecular sieve has a structure type selected from AEI, AFT, AFX, CHA, EAB, ERI, KFI, LEV, LTN, MSO, SAS, SAT, SAV, SFW, and TSC.

27. 23. The method of any one of claims 19 to 22, wherein the small pore molecular sieve has a CHA crystal structure.

28. 23. The method of any one of claims 19 to 22, wherein the promoter metal comprises Cu, Fe, or a combination thereof.

29. 23. The method of any one of claims 19 to 22, further comprising the steps of mixing the catalyst composition with water to form a washcoat slurry, applying the washcoat slurry to a substrate to form a washcoat coating on the substrate, and drying and calcining the substrate to form a catalyst article.

30. 30. The method of claim 29, further comprising adding a water-soluble metal oxide compound to the washcoat slurry to increase its total metal oxide content.

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