Catalyst article comprising an SCR catalyst upstream of an ASC acting as a DOC, use of the catalyst article and process using the catalyst article

Abstract

A catalyst article comprising a substrate with an inlet end and an outlet, a first zone comprising a first SCR catalyst, and a second zone comprising an ammonia barrier catalyst (ASC), wherein the ammonia barrier catalyst comprises a second SCR catalyst that differs from the first SCR catalyst with respect to the active component and / or the loading with the active component, and an oxidation catalyst, and the ASC has DOC functionality, wherein the first zone is arranged on the inlet side of the substrate and the second zone is arranged on the outlet side of the substrate, wherein the ASC is a bilayer with a lower layer comprising an oxidation catalyst and an upper cover layer comprising a second SCR catalyst; wherein the oxidation catalyst comprises platinum and palladium in a weight ratio of 1:0.01 to 1:10.

Description

FIELD OF INVENTION:

[0001] The present invention relates to ammonia slip catalysts (ASC), articles containing ammonia slip catalysts, and methods of making and using such articles to reduce ammonia slip. BACKGROUND OF THE INVENTION

[0002] The combustion of hydrocarbons in diesel engines, stationary gas turbines and other systems produces exhaust gas that is used to remove nitrogen oxides (NO X ), the NO (nitric oxide) and NO 2 (Nitrogen dioxide) contain, must be treated, with NO the main part of the formed NO X matters. It is known that NO X causes a number of human health problems, and also causes a number of harmful effects on the environment, including the formation of smog and acid rain. To mitigate the impact of NO on both humans and the environment X in the exhaust gas it is desirable to remove these undesirable components preferably by a process that does not produce any other harmful or toxic substances.

[0003] Exhaust gas produced in lean-burn and diesel engines is generally oxidative. NO X must be selectively reduced with a catalyst and reductant in a process known as Selective Catalytic Reduction (SCR) that uses NO X to elemental nitrogen (N 2 ) and water converts. In an SCR process, a gaseous reductant, typically anhydrous ammonia, aqueous ammonia, or urea, is added to an exhaust gas stream before the exhaust gas contacts the catalyst. The reducing agent is absorbed on the catalyst and the NO X is reduced as the gases flow through or over the catalyzed substrate. To maximize the conversion of NO X it is often necessary to add more than a stoichiometric amount of ammonia to the gas stream. However, the release of the excess ammonia into the atmosphere would be harmful to human health and the environment. In addition, ammonia is basic, especially in its aqueous form. Ammonia and water condensation in areas of the exhaust line downstream of the catalytic converters can create a corrosive mixture that can damage the exhaust system. Therefore, the release of ammonia in the exhaust gas should be prevented. In many conventional exhaust systems, an ammonia oxidation catalyst (also known as an ammonia slip catalyst or "ASC") is installed downstream of the SCR catalyst for removing ammonia from the exhaust gas by converting it to nitrogen. The use of ammonia slip catalysts can NO X -Enable conversions in excess of 90% over a typical diesel drive cycle.

[0004] It would be desirable to have a catalyst capable of both NO X by SCR, as well as selectively converting ammonia to nitrogen, with ammonia conversion occurring over a wide range of temperatures in a vehicle drive cycle, with minimal formation of nitrogen oxides and nitrous oxides by-products. SUMMARY OF THE INVENTION

[0005] In a first aspect, the invention relates to a catalyst article comprising a substrate comprising an inlet end and an outlet, a first zone comprising a first SCR catalyst, and a second zone comprising an ammonia slip catalyst (ASC), wherein the ammonia the slip catalyst comprises a second SCR catalyst and an oxidation catalyst and the ASC has DOC functionality, the first zone being on the inlet side of the substrate and the second zone being on the outlet side of the substrate.

[0006] In another aspect, the invention relates to exhaust systems comprising a catalytic article of the first aspect of the invention and an NH 3 -forming agent 3 included in the exhaust gas.

[0007] In a still further aspect, the invention relates to an engine comprising an exhaust system comprising a catalyst article of the first aspect of the invention and a means for forming NH 33 included in the exhaust gas.

[0008] In yet another aspect, the invention relates to methods of controlling hydrocarbon emissions in an exhaust gas, the method comprising contacting an exhaust gas comprising hydrocarbons with a catalyst article of the first aspect of the invention.

[0009] In another aspect, the invention relates to methods of forming an exotherm in a catalyst treating hydrocarbon emissions in an exhaust gas, the method comprising contacting an exhaust gas comprising hydrocarbons with a catalyst article of the first aspect of the invention.

[0010] In yet another aspect, the invention relates to a method of forming an exotherm in a catalyst treating hydrocarbon emissions in an exhaust gas, the method comprising contacting an exhaust gas comprising hydrocarbons with a catalyst article of the first aspect of the invention.

[0011] In yet another aspect, the invention relates to a method for controlling NO X emissions in an exhaust gas, the method comprising contacting an NO X or NH 3 comprising exhaust gas with a catalyst article of the first aspect of the invention.

[0012] In another aspect, the invention relates to a method for controlling N 2 O emissions in an exhaust gas, the method comprising contacting an NO X or NH 3 comprising exhaust gas with a catalyst article of the first aspect of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] figure 1 shows a configuration in which the SCR is positioned in the exhaust stream before an ASC.

[0014] figure Figure 2 shows a configuration in which the ASC is positioned in the exhaust stream before a bi-layer catalyst comprising an upper layer containing a second SCR catalyst over a lower layer comprising an oxidation catalyst.

[0015] figure 3 shows a configuration in which the SCR is positioned in the exhaust stream before an ASC comprising a mixture of a second SCR catalyst and an oxidation catalyst.

[0016] figure 4 is a diagram showing the NH 3 -conversion, the N 2 O selectivity and the NO X - Shows selectivity when using fresh catalysts.

[0017] figure 5 is a diagram showing the NH 3 -Conversion, N 2 O selectivity and NO X - Shows selectivity when using aged catalysts.

[0018] figure 6 is a graph showing NO conversion using fresh catalysts.

[0019] figure 7 is a graph showing NO conversion using aged catalysts.

[0020] figure Figure 8 is a graph showing CO conversion using fresh catalysts.

[0021] figure Figure 9 is a graph showing CO conversion using aged catalysts.

[0022] figure 10 is a graph showing hydrocarbon (HC) conversion using a fresh comparative catalyst.

[0023] figure Figure 11 is a graph showing hydrocarbon (HC) conversion using a fresh catalyst having a Pt:Pd ratio of 1:5.

[0024] figure Figure 12 is a graph showing hydrocarbon (HC) conversion using a fresh catalyst having a Pt:Pd ratio of 2:1.

[0025] figure 13 is a graph showing hydrocarbon (HC) conversion using an aged comparative catalyst.

[0026] figure 14 is a graph showing hydrocarbon (HC) conversion using an aged catalyst with a Pt:Pd ratio of 1:5.

[0027] figure 15 is a graph showing hydrocarbon (HC) conversion using an aged catalyst with a Pt:Pd ratio of 2:1.

[0028] figure16 is a graph showing the temperature at various points in an exhaust system containing a comparative catalyst with Pt as the sole PGM.

[0029] figure 17 is a graph showing the temperature at various points in an exhaust system containing a comparative catalyst with Pt and Pd at a loading of 1:5.

[0030] figure Figure 18 is a graph showing the temperature at various points in an exhaust system containing a comparative catalyst with Pt and Pd at a 2:1 loading. DETAILED DESCRIPTION OF THE INVENTION

[0031] As used in the present specification and the appended claims, the singular forms "a", "an" and "the" include the corresponding plural forms unless the context clearly dictates otherwise . Thus, for example, reference to "a catalyst" includes a mixture of two or more catalysts and the like.

[0032] The term "ammonia slip" means the amount of unreacted ammonia that passes through the SCR catalyst.

[0033] The term "support" means the material to which the catalyst is affixed.

[0034] The term "a support having low ammonia storage" means a support containing less than 0.001 mmol NH 3 per m 3 of the carrier stores. The low ammonia storage support is preferably a molecular sieve or zeolite having a framework type selected from the group consisting of AEI, ANA, ATS, BEA, CDO, CFI, CHA, CON, DDR, ERI, FAU, FER, GON, IFR, IFW, IFY, IHW, IMF, IRN, IRY, ISV, ITE, ITG, ITN, ITR, ITW, IWR, IWS, IWV, IWW, JOZ, LTA, LTF, MEL, MEP, MFI, MRE, MSE, MTF, MTN, MTT, MTW, MVY, MWW, NON, NSI, RRO, RSN, RTE, RTH, RUT, RWR, SEW, SFE, SFF, SFG, SFH, SFN, SFS, SFV, SGT, SOD, SSF, SSO, SSY, STF, STO, STT, SVR, SVV, TON, TUN, UOS, UOV, UTL, UWY, VET, VNI. More preferably the molecular sieve or zeolite has a framework type selected from the group consisting of BEA, CDO, CON, FAU, MEL, MFI and MWW, even more preferably the framework type is selected from the group consisting of BEA and MFI exists.

[0035] The term "calcinate" or "calcination" means heating the material in air or oxygen. This definition is consistent with the IUPAC definition of a calcination. (IUPAC. Compendium of Chemical Terminology, 2nd Edition ("Gold Book"). Prepared by A.D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Corrected XML online version: http: / / goldbook.iupac.org (2006-), generated by M. Nic, J. Jirat, B. Kosata; updates generated by A. Jenkins. ISBN 0-9678550-9-8. Doi:10.1351 / goldbook.) The calcination is performed to to decompose a metal salt and to promote the exchange of metal ions in the catalyst and also to attach the catalyst to a substrate. The temperatures used in the calcination depend on the components in the material to be calcined and generally range from about 400°C to about 900°C for about 1 to 8 hours. In some cases, calcination can be carried out up to a temperature of about 1200°C. In applications involving the methods described herein, the calcinations are generally carried out at temperatures from about 400°C to about 700°C for about 1 to 8 hours, preferably at temperatures from about 400°C to about 650°C for about 1 hour carried out up to 4 hours.

[0036] The term "about" means "approximately" and refers to a range that is optionally ±25%, preferably ±10%, more preferably ±5%, or most preferably ±1% of the value to which the term is associated.

[0037] When a range or ranges is (are) provided for various numeric elements, the range or ranges may include the values ​​unless otherwise noted.

[0038] The term "N 2 -Selectivity" means the percent conversion of ammonia to nitrogen.

[0039] The term "diesel oxidation catalyst" (DOC) is a well-known term in the art to describe a type of catalyst used to treat hydrocarbon-containing exhaust gases from combustion processes.

[0040] The term "platinum group metal" or "PGM" refers to platinum, palladium, ruthenium, rhodium, osmium and iridium. The platinum group metals are preferably platinum, palladium, ruthenium or rhodium.

[0041] The term "active component loading" or "active component loading" refers to the weight of the support of platinum + the weight of the platinum + the weight of the first SCR catalyst in the mixture. Platinum can be present in the catalyst with an active component loading from about 0.01 wt% to about 0.25 wt% inclusive Preferably, platinum may be present in the catalyst at an active component loading of from 0.04 wt% to 0.2 wt% inclusive More preferably, platinum may be present in the catalyst at an active component loading of from 0.07 wt% to 0.17 wt% inclusive Most preferably, platinum may be present in the catalyst at an active component loading of from 0.05 wt% to including 0.15% by weight.

[0042] The terms "downstream" and "upstream" describe the orientation of a catalyst or substrate where the flow of exhaust gas is from the inlet end to the outlet end of the substrate or article.

[0043] In the first aspect of the invention, a catalyst article comprises a substrate comprising an inlet end and an outlet, a first zone comprising a first SCR catalyst and a second zone comprising an ammonia slip catalyst (ASC), the ammonia slip catalyst having a second SCR -catalyst and an oxidation catalyst and the ASC has a DOC functionality, wherein the first zone is on the inlet side of the substrate and the second zone is in the outlet side of the substrate. The catalyst article can generate an exotherm. The first zone and the second zone may be on the same substrate, with the first zone being located on the inlet side of the substrate and the second zone being located on the outlet side of the substrate.

[0044] The catalyst article may further comprise a second substrate, wherein the first zone is on a first substrate and the second zone is on the second substrate, and wherein the first substrate is located upstream of the second substrate. The catalyst article may include a first part and a second part, wherein the first zone is located in the first part and the second zone is located in the second part, and the first part is located upstream of the second part.

[0045] The first zone includes a first SCR catalyst. The second zone includes an ASC catalyst that includes an oxidation catalyst and a second SCR catalyst. The ASC may be a dual layer with a lower layer comprising an oxidation catalyst and an upper cover layer comprising a second SCR catalyst. The ASC catalyst may be a single layer comprising a mixture of an oxidation catalyst and a second SCR catalyst. SCR catalytic converters

[0046] The compositions include two SCR catalysts: a first SCR catalyst in the SCR zone and a second SCR catalyst as part of the ammonia slip catalyst (ASC). The first SCR catalyst may differ from the second SCR catalyst in that it includes a different active component, as described below, in having a different loading of the active component, or both.

[0047] The active component in the first and second SCR catalysts may be independently selected from the group consisting of a base metal, an oxide of a base metal, a molecular sieve, a metal exchanged molecular sieve, or a mixture thereof. The base metal may be selected from the group consisting of vanadium (V), molybdenum (Mo), tungsten (W), chromium (Cr), cerium (Ce), manganese (Mn), iron (Fe), cobalt (Co ), nickel (Ni), copper (Cu) and zirconium (Zr) and mixtures thereof. SCR compositions consisting of vanadium supported on a refractory metal oxide such as alumina, silica, zirconia, titania, ceria, and combinations thereof are well known and widely used commercially in mobile applications. Typical compositions are described in US Patent Nos. 4,010,238 and 4,085,193, the entire contents of which are incorporated herein by reference. Compositions used commercially - particularly in mobile applications - include TiO 2 , on the WHERE 3 and V 2 O 5 at concentrations ranging from 5 to 20 weight percent (wt%) and 0.5 to 6 wt%, respectively. The second SCR catalyst can be Nb-Ce-Zr or Nb on MnO 2 include. These catalysts can contain other inorganic materials such as SiO 2 and ZrO 2 included, which act as binders and promoters.

[0048] When the SCR catalyst is a base metal, the catalyst article may further comprise at least one base metal promoter. As used herein, a "promoter" is understood to mean a substance that when added to a catalyst increases the activity of the catalyst. The base metal promoter may be in the form of a metal, an oxide of the metal, or a mixture thereof. The at least one base metal catalyst promoter may be selected from neodymium (Nd), barium (Ba), cerium (Ce), lanthanum (La), praseodymium (Pr), magnesium (Mg), calcium (Ca), manganese (Mn), zinc (Zn), niobium (Nb), zirconium (Zr), molybdenum (Mo), tin (Sn), tantalum (Ta), strontium (Sr) and oxides thereof. The at least one base metal catalyst promoter may preferably be MnO 2 , Mn 2 O 3 , Fe 2 O 3 , SnO 2 , CuO, CoO, CeO 2 and mixtures thereof. The at least one base metal catalyst promoter may be added to the catalyst in the form of a salt in an aqueous solution, such as a nitrate or an acetate. The at least one base metal catalyst promoter and the at least one base metal catalyst, e.g. copper, may be impregnated from an aqueous solution onto the oxide support material(s), may be incorporated into a washcoat comprising the oxide support material(s). added or can be impregnated into a carrier previously coated with the washcoat.

[0049] The SCR catalyst may comprise a molecular sieve or a metal exchanged molecular sieve. As used herein, the term "molecular sieve" is intended to mean a metastable material containing small pores of a precise and uniform size that can be used as an absorbent for gases or liquids. The molecules small enough to pass through the pores are adsorbed, while the larger molecules are not. The molecular sieve can be a zeolitic molecular sieve, a non-zeolitic molecular sieve, or a mixture thereof.

[0050] A zeolitic molecular sieve is a microporous aluminosilicate having any of the framework structures listed in the Database of Zeolite Structures published by the International Zeolite Association (IZA). The framework structures include but are not limited to those of the CHA, FAU, BEA, MFI, MOR types. Non-limiting examples of zeolites having these structures include chabazite, faujasite, zeolite Y, ultrastable zeolite Y, beta zeolite, mordenite, silicalite, zeolite X, and ZSM-5. Aluminosilicate zeolites can have a silica to alumina molar ratio (SAR) (defined as SiO 2 / Al 2 O 3) of at least about 5, preferably at least about 20, with suitable ranges of about 10-200.

[0051] Any of the SCR catalysts may comprise a small pore, medium pore, or large pore molecular sieve, or combinations thereof. A "small pore molecular sieve" is a molecular sieve containing a maximum ring size of 8 tetrahedral atoms. A "medium pore molecular sieve" is a molecular sieve containing a maximum ring size of 10 tetrahedral atoms. A "large pore molecular sieve" is a molecular sieve that has a maximum ring size of 12 tetrahedral atoms. The second SCR catalyst may comprise a small pore molecular sieve selected from the group consisting of aluminosilicate molecular sieves, metal-substituted aluminosilicate molecular sieves, aluminophosphate (AlPO) molecular sieves, metal-substituted aluminophosphate (MeAlPO) molecular sieves, silicoaluminophosphate (SAPO) molecular sieves, and metal-substituted silicoaluminophosphate( MeAPSO) molecular sieves and mixtures thereof.

[0052] Any of the SCR catalysts may comprise a small pore molecular sieve selected from the group of framework types consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT , EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SFW, SIV, THO, TSC , UEI, UFI, VNI, YUG and ZON as well as mixtures and / or adhesions thereof. Preferably, the small pore molecular sieve is selected from the group of framework types consisting of CHA, LEV, AEI, AFX, ERI, SFW, KFI, DDR and ITE.

[0053] Any of the SCR catalysts may comprise a medium pore molecular sieve selected from the group of framework types consisting of AEL, AFO, AHT, BOF, BOZ, CGF, CGS, CHI, DAC, EUO, FER, HEU, IMF, ITH , ITR, JRY, JSR, JST, LAU, LOV, MEL, MFI, MFS, MRE, MTT, MVY, MWW, NAB, NAT, NES, OBW, PAR, PCR, PON, PUN, RRO, RSN, SFF, SFG , STF, STI, STT, STW, SVR, SZR, TER, TON, TUN, UOS, VSV, WEI and WEN as well as mixtures and / or adhesions thereof. Preferably, the medium pore molecular sieve is selected from the group of framework types consisting of MFI, FER and STT.

[0054] Any of the SCR catalysts may comprise a large pore molecular sieve selected from the group of framework types consisting of AFI, AFR, AFS, AFY, ASV, ATO, ATS, BEA, BEC, BOG, BPH, BSV, CAN, CON , CZP, DFO, EMT, EON, EZT, FAU, GME, GON, IFR, ISV, ITG, IWR, IWS, IWV, IWW, JSR, LTF, LTL, MAZ, MEI, MOR, MOZ, MSE, MTW, NPO , OFF, OKO, OSI, RON, RWY, SAF, SAO, SBE, SBS, SBT, SEW, SFE, SFO, SFS, SFV, SOF, SOS, STO, SSF, SSY, USI, UWY and VET and mixtures and / or adhesions thereof. Preferably, the large pore molecular sieve is selected from the group of framework types consisting of MOR, OFF and BEA.

[0055] A metal-exchanged molecular sieve can have at least one metal from one of Groups VB, VIB, VIIB, VIIIB, IB, or IIB of the Periodic Table deposited at extra-framework sites on the outer surface or within the channels, cavities, or cages of the molecular sieves. The metals can be in any of several forms including, but not limited to, zero-valent metal atoms or clusters, isolated cations, mononuclear or polynuclear oxycations, or extended metal oxides. Preferably, the metals can be iron, copper, and mixtures or combinations thereof.

[0056] The metal can be combined with the zeolite using a mixture or solution of the metal precursor in a suitable solvent. The term "metal precursor" means any compound or complex that can be distributed on the zeolite to yield a catalytically active metal component. Preferably the solvent is water due to both economic and environmental concerns in using other solvents. When copper, a preferred metal, is used, suitable complexes or compounds include, but are not limited to, anhydrous and hydrated copper sulfate, copper nitrate, copper acetate, copper acetylacetonate, copper oxide, copper hydroxide, and salts of copper amines (e.g., [Cu(NH 3 ) 4 ] 2+). The present invention is not limited to metal precursors of any particular type, composition, or purity. The molecular sieve can be added to the metal component solution to form a suspension which is then allowed to react so that the metal component is distributed on the zeolite. The metal can be distributed in the pore channels as well as on the outer surface of the molecular sieve. The metal can be distributed in ionic form or in the form of a metal oxide. For example, copper can be distributed in the form of copper(II) ions, copper(I) ions, or in the form of copper oxide. The molecular sieve containing the metal can be separated from the liquid phase of the suspension, washed and dried. The resulting metal-containing molecular sieve can then be calcined to fix the metal in the molecular sieve. Preferably, the SCR catalysts comprise a Cu-SCR, a Fe-SCR, vanadium, a mixed oxide, supported Ce-Zr or supported MnO 2 .

[0057] A metal-exchanged molecular sieve can contain a Group VB, VIB, VIIB, VIIIB, IB, or IIB metal in the range of about 0.10% to about 10% by weight, concentrated at extra-framework sites on the outer Surface or located in the channels, cavities or cages of the molecular sieve. Preferably, the extra-framework metal can be present in an amount ranging from about 0.2% to about 5% by weight.

[0058] The metal-exchanged molecular sieve can be a copper (Cu) or iron (Fe) supported molecular sieve having from about 0.1 to about 20 weight percent copper or iron based on the total weight of the catalyst. More preferably, the copper or iron is present from about 0.5% to about 15% by weight of the total weight of the catalyst. Most preferably, copper or iron is present from about 1% to about 9% by weight of the total weight of the catalyst.

[0059] The second SCR catalyst may be a Cu SCR catalyst, an Fe SCR catalyst, a base metal, an oxide of a base metal, or a mixed oxide, or a vanadium catalyst. The Cu SCR catalyst includes copper and a small pore molecular sieve and the Fe SCR catalyst includes iron and a small pore molecular sieve. The small pore molecular sieve can be an aluminosilicate, an aluminophosphate (AlPO), a silicoaluminophosphate (SAPO), or mixtures thereof. The small pore molecular sieve can be selected from the group of framework types consisting of ACO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATT, CDO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, GIS, GOO, IHW, ITE, ITW, LEV, KFI, MER, MON, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG and ZON and Mixtures and / or adhesions thereof. Preferably, the small pore molecular sieve can be selected from the group of framework types consisting of AEI, AFX, CHA, DDR, ERI, ITE, KFI, LEV and SFW. The ratio of the amount of the first SCR catalyst to the amount of platinum on the low ammonia storage support may be in the range of at least one of the following (ranges): (a) 0:1 up to and including 300:1, (b) 3: 1 to 300:1 inclusive, (c) 7:1 to 100:1 inclusive and (d) 10:1 to 50:1 inclusive by weight of these components. Platinum may be present in at least one of the following ranges: (a) 0.01% up to and including 0.3% by weight, (b) 0.03% up to and including 0.2% by weight , (c) from 0.05% to 0.17% by weight inclusive and (d) from 0.07% to 0.15% by weight inclusive, based on the weight of the platinum + support the weight of platinum + the weight of the first SCR catalyst in the mix. Ammonia Slip Catalyst

[0060] The ammonia slip catalyst may be a dual layer having a bottom layer comprising an oxidation catalyst and a top cover layer comprising a second SCR catalyst. The ammonia slip catalyst may be a single layer comprising a mixture of an oxidation catalyst and a second SR catalyst.

[0061] The oxidation catalyst is preferably a platinum group metal, preferably platinum or palladium or a mixture thereof. Platinum can be used in an amount of about 0.1 g / ft 3 up to about 20 g / ft 3be present in the ASC zone. Palladium can be used in an amount of about 0.1 g / ft 3 up to about 20 g / ft 3 be present in the ASC zone. When both platinum and palladium are present in the ASC zone, Pt and Pd are present in a ratio of from about 1:0.01 to about 1:10 by weight.

[0062] An ammonia slip catalyst comprising a bilayer preferably comprises a lower layer comprising platinum and an upper layer comprising a copper zeolite, preferably a copper chabazite, with palladium also being present in the lower layer or the upper layer or in both the upper and lower layers. The top layer may further include palladium. When palladium is present in the top layer, it is preferably present in a mixture with the copper zeolite, the palladium being supported when mixed with the copper zeolite to form a mixture. These compositions can help improve the exothermic performance of the catalyst.

[0063] When the second zone comprises a mixture of an oxidation catalyst and the second SCR catalyst, the oxidation catalyst may comprise platinum on a low ammonia storage support. The low ammonia storage support can be a silicate support. The silicate support may comprise a silica or a zeolite having a silica to alumina ratio of at least one of the following: (a) at least 100, (b) at least 200, (c) at least 250, (d) at least 300, ( e) at least 400, (f) at least 500, (g) at least 750, and (h) at least 1000. The siliceous support may comprise a molecular sieve having a BEA, CDO, CON, FAU, MEL, MFI or MWW framework type. The ratio of the amount of SCR catalyst to the amount of platinum on the low ammonia storage support may be in the range of 0:1 to 300:1, preferably 3:1 to 300:1, more preferably 7:1 to 100:1 and most preferably 10:1 to 50:1, each of the endpoints being included in the ratio by weight of these components. The mixture can further Pd, Nb-Ce-Zr or Nb on MnO 2 include.

[0064] The catalysts described herein can be used in SCR treatment of exhaust gases from various engines. One of the properties of a catalyst comprising a mixture of platinum on a siliceous support with a first SCR catalyst, wherein the first SCR catalyst is a Cu-SCR or a Fe-SCR catalyst, is that it is an improvement regarding the N 2 yield from ammonia at a temperature of about 250°C to about 350°C compared to a catalyst comprising a comparable formulation where the first SCR catalyst is in the form of a first layer and platinum supported on it a layer that stores ammonia is present in a second layer, and NH 3 gas comprising flows through the first layer before flowing through the second layer. Another property of a catalyst comprising a mixture of platinum on a low ammonia storage support with a first SCR catalyst, wherein the first SCR catalyst is a Cu SCR catalyst or a Fe SCR catalyst is that he reduced formation of N 2 O from NH 3 compared to a catalyst comprising a comparable formulation in which the first SCR catalyst is present in the form of a first layer and platinum supported on a carrier that stores ammonia is present in a second layer, and NH 3 3 gas comprising passes through the first layer before passing through the second layer.

[0065] In one aspect of the invention, various configurations of catalysts comprising a mixture of platinum on a low ammonia storage support with a first SCR catalyst can be prepared. The portion of the catalyst comprising a mixture of platinum on a non-ammonia storage support with a first SCR catalyst is referred to as "mixture" in the figures described below.

[0066] In a first configuration, a catalyst article comprises a substrate having an inlet and an outlet, a first zone comprising an SCR catalyst, and a second zone comprising an ammonia slip catalyst (ASC), the first zone being disposed on the inlet side of the substrate and the second zone is located downstream of the first zone and on the outlet side of the substrate. figure Figure 1 shows a configuration in which the SCR is positioned at the inlet of the article in the exhaust flow and the ASC is positioned at the outlet of the article.

[0067] In a second configuration, a catalyst article comprises a substrate having an inlet and an outlet, a first zone comprising a first SCR catalyst, a second zone comprising an ammonia slip catalyst (ASC), the ASC comprising a bilayer having a top, one a second layer comprising SCR catalyst and a lower layer comprising an oxidation catalyst, wherein the first zone is arranged on the inlet side of the substrate, the second zone is arranged downstream of the first zone and is arranged on the outlet side of the substrate. This configuration is similar to the first configuration in that the ASC is a dual layer with an upper layer comprising a second SCR catalyst and a lower layer comprising an oxidation catalyst. figure Figure 2 shows a configuration in which the first zone is positioned at the inlet of the article in the exhaust flow, the second zone comprising an ASC which is a bilayer with an upper layer comprising a second SCR catalyst and a lower layer comprising an oxidation catalyst comprising layer, is positioned downstream of the first zone and is positioned at the outlet of the article. The top layer may include palladium in addition to the second SCR catalyst.

[0068] In a third configuration, a catalyst article includes a substrate having an inlet and an outlet, a first zone including a first SCR catalyst, and a second zone including an ammonia slip catalyst (ASC), wherein the ammonia slip catalyst is a mixture of a second SCR catalyst and an oxidation catalyst and the first zone is arranged on the inlet side of the substrate and the second zone is arranged downstream of the first zone and is arranged on the outlet side of the substrate. This configuration is similar to the first configuration in that the ASC is a mixture of a second SCR catalyst and an oxidation catalyst. figure 3 shows a configuration in which the SCR zone comprising a first SCR catalyst is positioned at the inlet of the article in the exhaust flow and the ASC zone is composed of a mixture of a second SCR catalyst and an oxidation catalyst and the ASC zone is downstream the SCR zone is positioned at the outlet of the article.

[0069] In any of the above configurations, each of the zones can be on the same substrate, or there can be two or more substrates with one or more zones on each substrate. In an exhaust system, when two or more substrates are used, one or more substrates may be disposed in a single housing or fairing, or in different housings or fairings.

[0070] When the second zone in the catalytic article comprises a mixture of the oxidation catalyst and the second SCR catalyst, the catalytic article may have one or more properties associated with the N 2 -Yield, reducing NO X -formation and reduction of the N 2 O formation are connected, have. The catalyst article can show an improvement in N 2 -provide yield from ammonia at a temperature of about 250°C to about 350°C compared to a catalyst comprising a comparable formulation in which the first SCR catalyst is in the form of a first coating and platinum on a support with low ammonia storage is present in a second coating, and NH 3comprising gas flows through the first coating before flowing through the second coating. The catalyst article can provide at least one of the following: (a) an improvement in N 2 - yield from ammonia at a temperature from about 350°C to about 450°C and (b) a reduction in NO X - formation at a temperature of about 350°C to about 450°C, compared to a catalyst comprising a comparable formulation in which the first SCR catalyst is present in the form of a first coating and the supported platinum is in a second coating is present and NH 3 gas comprising passes through the first coating before passing through the second coating. The catalyst article can have a reduced N 2 O formation from NH 3 compared to a catalyst comprising a comparable formulation in which the first SCR catalyst is present in the form of a first coating and the supported platinum is present in a second coating and NH 3 gas comprising passes through the first coating before passing through the second coating.

[0071] The substrate for the catalyst can be any material typically used in the manufacture of automotive catalysts that includes a flow-through or filter structure, such as a honeycomb, an extruded body, a metallic substrate, or a SCRF. Preferably, the substrate has a plurality of fine, parallel gas flow passages extending from an inlet to an outlet side of the substrate such that passages are open to the flow of fluid. Such monolithic supports can contain up to about 700 or more flow passages (or "cells") per square inch of diameter, although far fewer can be used. For example, the support can have about 7 to 600, more usually about 100 to 400 cells per square inch ("cpsi"). The passages, which are essentially straight paths from their fluid inlet to their fluid outlet, are defined by walls on which the SCR catalyst is "washcoated" so that the gases flowing through the passages are in contact with the catalytic material reach. The flow passages of the monolithic substrate are thin-walled channels that can have any suitable cross-sectional shape, such as trapezoidal, rectangular, square, triangular, sinusoidal, hexagonal, oval, circular, and so on. The invention is not limited to any particular type, material, or geometry of substrate.

[0072] Ceramic substrates can be made of any suitable refractory material such as cordierite, cordierite-α-alumina, α-alumina, silicon carbide, silicon nitride, zirconia, mullite, spodumene, alumina-silica-magnesia, zirconium silicate, sillimanite, magnesium silicates, zircon, petalite, aluminosilicates and mixtures thereof.

[0073] Wall-flow substrates can also be formed from ceramic fiber composite materials, such as those formed from cordierite and silicon carbide. Such materials are able to withstand the environmental conditions, particularly the high temperatures, encountered when treating the exhaust streams.

[0074] The substrates can be highly porous substrates. The term "highly porous substrate" refers to a substrate that has a porosity of between about 40% and about 80%. The highly porous substrate can have a porosity of preferably at least about 45%, more preferably at least about 50%. The highly porous substrate can have a porosity, preferably less than about 75%, more preferably less than about 70%. The term "porosity" as used herein refers to total porosity, preferably as measured by mercury porosimetry.

[0075] Preferably, the substrate may be cordierite, a highly porous cordierite, a metallic substrate, an extruded SCR, a wall-flow filter, a filter, or an SCRF.

[0076] A washcoat comprising a mixture of platinum on a low ammonia storage support, preferably a siliceous support, and a first SCR catalyst, wherein the first SCR catalyst is preferably a Cu SCR catalyst or a Fe SCR catalyst, can be applied to the inlet side of the substrate using any method known in the art. After application of the washcoat, the composition can be dried and calcined. When the composition includes a second SCR, the second SCR can be applied in a separate washcoat to a calcined article having the bottom layer as described above. After application of the second washcoat, it can be dried and calcined as was done with the first coat.

[0077] The substrate with the platinum-containing layer can be dried and calcined at a temperature in the range of 300°C to 1200°C, preferably 400°C to 700°C, and more preferably 450°C to 650°C. The calcination is preferably carried out under dry conditions, but it can also be carried out hydrothermally, i.e. in the presence of some moisture content. The calcination can be conducted for a period of between about 30 minutes and about 4 hours, preferably between about 30 minutes and about 2 hours, more preferably between about 30 minutes and about 1 hour.

[0078] An exhaust system may include a catalyst article of the first aspect of the invention and a first NH 3 -forming agent 3 in the exhaust gas or to introduce NH 3 in the exhaust gas, wherein the first means for forming NH 3 in the exhaust gas or to introduce NH 3 is located in the exhaust gas before the catalytic article. When two or more substrates are used in an exhaust system, one or more substrates may be located in a single housing or canister or in different housings or canisters. The exhaust system may further include a catalyzed soot filter (CSF) or SCRF (SCR on a filter), where the CSF or SCRF is positioned downstream of the catalytic article. If the system includes a SCRF, there is a second means of forming NH 3 in the exhaust gas or to introduce NH 3 into the exhaust between the catalytic article and the SCRF. The catalyzed soot filter may include a high PGM loading in the front of the filter. A high PGM loading means a loading of at least 5 g / ft 3 in heavy duty diesel engines and from about 10 g / ft 3 up to about 205 g / ft 3 for light-duty diesel engines, approximately the front 5 to 50 mm of the filter.

[0079] An engine may have an exhaust system comprising a catalyst article of the first aspect of the invention and an NH 3 -forming agent 3 in the exhaust gas or to introduce NH 3 included in the exhaust gas. The engine may be a diesel engine in a vehicle, a diesel engine on a stationary source, or a diesel engine on a watercraft such as a ship.

[0080] In yet another aspect of the invention, a method for controlling hydrocarbon emissions in an exhaust gas comprises contacting an exhaust gas comprising hydrocarbons with a catalyst article of the first aspect of the invention.

[0081] In another aspect of the invention, a method of forming an exotherm in a catalyst treating hydrocarbon emissions in an exhaust gas comprises contacting an exhaust gas comprising hydrocarbons with a catalyst article of the first aspect of the invention.

[0082] In yet another aspect of the invention, a method for controlling NO X -Emissions in an exhaust gas contacting an NO X or NH 3 comprising exhaust gas with a catalyst article of the first aspect of the invention.

[0083] In another aspect of the invention, a method for controlling N 2 O emissions in an exhaust gas contacting an NO X or NH 3comprising exhaust gas with a catalyst article of the first aspect of the invention. Preferably, the catalyst article of the first aspect of the invention is not part of an exhaust system comprising a DOC.

[0084] The following examples only serve to illustrate the invention; those skilled in the art will recognize numerous variations that fall within the spirit of the invention and the scope of the claims. EXAMPLESExample 1

[0085] Catalyst articles were prepared on a cordierite substrate (400 cpsi) by initially applying a washcoat comprising a PGM on alumina to the substrate to form an underlayer and then drying the washcoat. A top layer was constructed onto the bottom layer by applying a copper chabazite (Cu-CHA) (120 g / ft 3 Cu) applied comprehensive washcoats and subsequent drying of the top layer. After drying the top layer, the article was calcined.

[0086] A comparative article containing only platinum as the PGM at a loading of 3 g / ft 3 contained was manufactured. A sample comprising Pt and Pd as the PGM was tested with a total PGM loading of 18 g / ft 3 and made with a Pt:Pd ratio of 1:5. A sample comprising Pt and Pd as the PGM was tested with a total PGM loading of 18 g / ft 3 and made with a Pt:Pd ratio of 2:1.

[0087] Samples were tested fresh and after hydrothermal aging at 580°C for 100 hours.

[0088] First became N 2 - Gas flowed over 1" x 1" cores of the samples while raising the temperature from room temperature to 150°C. Subsequently, gas containing NH 3 = 500ppm, CO 2 = 4.5%, H 2 O = 5%, CO = 200ppm, O 2 = 12% and the remainder N 2 contained, at SV = 150000 h –1 was passed over the samples while the temperature was increased from 150°C to 500°C at a (heating) rate of 10°C / minute. The concentrations of NH 3 , NO X , N 2 O, CO and CO 2 were measured by FTIR at the outlet from the system.

[0089] the figure 4 and figure 5 show the NH 3 -Conversion, N 2 O selectivity and NO X -Selectivity from the three samples at temperatures from 200 °C to 500 °C in fresh and aged samples. The catalyst with Pt and Pd in ​​a 2:1 ratio gave better low-temperature NH 3 3 -conversion than the Pt only comparison sample, while the Pt and Pd catalyst in a 1:5 ratio has a lower NH 3 -transformation below about 350 °C. The catalyst with Pt and Pd in ​​a ratio of 2:1 gave a higher N 2 O selectivity than the Pt only control or the catalyst with Pt and Pd in ​​a 1:5 ratio. The three catalysts provided similar NO X -Selectivity. These results apply to both fresh and aged samples.

[0090] the figure 6 and figure 7 show the NO conversions from the three samples at temperatures from 150°C to 500°C for fresh and aged samples. Again, the fresh and aged samples provided similar results, with the 2:1 mixture of Pt:Pd providing a conversion equal to or greater than the comparative sample with only Pt as the PGM.

[0091] the figure 8 and figure 9 show the CO conversions from the three samples at temperatures from 150°C to 500°C for fresh and aged samples. Again, the fresh and aged samples provided similar results, with the 2:1 mixture of Pt:Pd providing a conversion equal to or greater than the control sample with only Pt as the PGM, with the 2:1 mixture of Pt :Pd provided a conversion equal to or greater than the control with only Pt as the PGM.

[0092] the figure 10- figure 12 and figure 13– figure15 show the HC transformations from the three samples at temperatures from 150°C to 500°C for fresh and aged samples, respectively. Again, the fresh and aged samples gave similar results. The comparative samples containing only Pt as the PGM showed a maximum HC conversion of about 70% at about 450°C to 500°C. In contrast, the two samples containing mixtures of Pt and Pd gave about 70% HC conversion at about 375°C and 90% or higher HC conversion at 500°C. This shows that a mixture of Pt and Pd in ​​an ASC is able to oxidize many more hydrocarbons than using Pt alone. example 2

[0093] Samples of catalysts prepared as described in Example 1 were placed in an exhaust system along with a diesel oxidation catalyst (DOC) and a catalyzed soot filter (CSF). The catalysts were arranged in the exhaust system in the order SCR:ASC:DOC:CSF. The exhaust system was connected to an engine and urea was injected into the exhaust stream before the SCR catalyst. The outlet from a fuel injector was also in the system before the SCR. The system was conditioned by running the engine at 450°C for one hour and then reducing the speed of the engine to allow the engine temperature to stabilize at around 300°C. After the temperature stabilized, fuel was injected into the exhaust system before the SCR catalyst to raise the temperature to around 450 °C after the CSF. After keeping the temperature behind the CSF constant for about 15 minutes, the addition of fuel to the exhaust system was stopped and the temperature was allowed to return to about 300°C.

[0094] The temperatures at the inlet to the SCR and at the outlets from the ASC, DOC and CSF were measured. These temperatures are in the figure 16– figure 18 for the Pt only comparative sample, the catalyst at 18 g / ft 3 on PGM with a Pt:Pd loading of 1:5 or the catalyst with 18 g / ft 3 demonstrated on PGM with a Pt:Pd loading of 2:1. figure 16 shows that using a catalyst containing only Pt as the PGM resulted in the outlet temperature at the ASC reaching a maximum of about 350°C at about time 1250 seconds and then dropping to about 300°C at about 1600 seconds. In contrast, in the two systems using a combination of Pt and Pd, the outlet temperatures at the ASC reached a maximum of about 390°C at about 1250 seconds and the temperature remained at about 390°C to about 2200 seconds, indicating that each of these two catalysts produced an exotherm. This stable exotherm was not observed with the reference catalyst containing only Pt as the PGM. This shows that when using an SCR in front of an ASC, the SCR did not produce a stable exotherm. Example 3: Omission of the DOC catalyst from a system

[0095] A catalyst article is made by applying a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. The loading of vanadium in the washcoat is preferably between 0.5% and 5% by weight inclusive. A second zone extending from the outlet end of the flow-through substrate is formed by first placing a washcoat comprising platinum on the flow-through substrate to form a first layer and then placing a washcoat comprising Cu-CHA over the first layer. Preferably, copper is present in / on the chabazite in an amount of between 1% and 5% by weight inclusive and the Cu-CHA is present in the layer in an amount of about 60 g / ft 3 up to about 300 g / ft 3 present. Platinum is present in the layer in an amount of about 10 g / ft 3 up to about 20 g / ft 3 present in the ASC zone.

[0096] The catalyst article is placed first in the exhaust aftertreatment system before a CSF and the system does not contain a DOC. Example 4: Omission of the DOC catalyst from a system

[0097] A catalyst article is made by placing a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. A second zone extending from the outlet end of the flow-through substrate is formed by first placing a washcoat comprising platinum on the flow-through substrate to form a first layer, then placing a washcoat comprising Cu-CHA over the first layer. The amounts of vanadium, copper and chabazite that can be used are described in Example 3.

[0098] The catalyst article is placed first in the exhaust aftertreatment system before a SCRF and the system does not include a DOC. Example 5: Omission of the DOC catalyst from a system

[0099] A catalyst article is made by placing a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. A second zone extending from the outlet end of the flow-through substrate is formed by first placing a washcoat comprising platinum and palladium on the flow-through substrate to form a first layer, then placing a washcoat comprising Cu-CHA over the first layer. Platinum and palladium are in the layer in a combined amount of 10 g / ft 3 up to 20 g / ft 3 present in the ASC zone with Pt and Pd present in a ratio of 1:1 to 1:10 by weight. The amounts of vanadium, copper and chabazite that can be used are described in Example 3.

[0100] The catalyst article is first placed in the exhaust aftertreatment system before a CSF and the system does not contain a DOC. Example 6: Omission of the DOC catalyst from a system

[0101] A catalyst article is prepared as described in Example 5, with palladium also present in the washcoat comprising Cu-CHA placed over the first layer. Example 7: Omission of the DOC catalyst from a system

[0102] A catalyst article is made by placing a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. A second zone extending from the outlet end of the flow-through substrate is formed by first placing a washcoat comprising platinum and palladium on the flow-through substrate to form a first layer, then placing a washcoat comprising Cu-CHA over the first layer. Platinum and palladium are in the layer in a combined amount of 10 g / ft 3 up to 20 g / ft 3 present in the ASC zone with Pt and Pd present in a ratio of 1:1 to 1:10 by weight. The amounts of vanadium, copper and chabazite that can be used are described in Example 3.

[0103] The catalyst article is first placed in the exhaust aftertreatment system before a SCRF and the system does not contain a DOC. Example 8: Omission of the DOC catalyst from a system

[0104] A catalyst article is prepared as described in Example 7, with palladium also present in the washcoat comprising Cu-CHA placed over the first layer. Example 9: Omission of the DOC catalyst from a system

[0105] A catalyst article is made by placing a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. A second zone extending from the outlet end of the flow-through substrate is prepared by placing a washcoat comprising a mixture (mixture) of platinum and Cu-CHA onto the flow-through substrate to form a layer. Platinum is present in the layer at 10 g / ft 3 up to 20 g / ft 3 present in the ASC zone. The amounts of vanadium, copper and chabazite that can be used are described in Example 3.

[0106] The catalyst article is first placed in the exhaust aftertreatment system before a CSF and the system does not contain a DOC. Example 10: Omission of the DOC catalyst from a system

[0107] A catalyst article is made by placing a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. A second zone extending from the outlet end of the flow-through substrate is prepared by placing a washcoat comprising a mixture (mixture) of platinum and Cu-CHA onto the flow-through substrate to form a layer. Platinum is present in the layer at 10 g / ft 3 up to 20 g / ft 3 present in the ASC zone. The amounts of vanadium, copper and chabazite that can be used are described in Example 3.

[0108] The catalyst article is first placed in the exhaust aftertreatment system before a SCRF and the system does not contain a DOC. Example 11: Omission of the DOC catalyst from a system

[0109] A catalyst article is made by placing a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. A second zone extending from the outlet end of the flow-through substrate is prepared by placing a washcoat comprising a mixture (mixture) of platinum, palladium, and Cu-CHA onto the flow-through substrate to form a layer. Platinum and palladium are in the layer in a combined amount of about 10 g / ft 3 up to about 20 g / ft 3 present in the ASC zone with Pt and Pd present in a ratio of from about 1:1 to about 1:10 by weight. The amounts of vanadium, copper and chabazite that can be used are described in Example 3.

[0110] The catalyst article is first placed in the exhaust aftertreatment system before a CSF and the system does not contain a DOC. Example 12: Omission of the DOC catalyst from a system

[0111] A catalyst article is made by placing a washcoat comprising vanadium in a first zone extending from the inlet end of a flow-through substrate. A second zone extending from the outlet end of the flow-through substrate is prepared by placing a washcoat comprising a mixture (mixture) of platinum, palladium, and Cu-CHA onto the flow-through substrate to form a layer. Platinum and palladium are in the layer in a combined amount of about 10 g / ft 3 up to about 20 g / ft 3 present in the ASC zone with Pt and Pd present in a ratio of from about 1:1 to about 1:10 by weight. The amounts of vanadium, copper and chabazite that can be used are described in Example 3.

[0112] The catalyst article is first placed in the exhaust aftertreatment system before a SCRF and the system does not contain a DOC. Comparative example 1

[0113] In a comparison system, a DOC is placed after the ASC and before the rest of the aftertreatment system.

[0114] The catalyst articles of Examples 3-12 are used in systems without a DOC. By omitting the DOC, a reduced cost and space are required since the DOC is omitted. The following additional benefits may also result from using the articles described in Examples 3-12.

[0115] The relatively high loading of noble metals supports the generation of the desired exotherm.

[0116] In Examples 5-8, 11 and 12, the incorporation of Pd with Pt in the ASC promotes the generation of an exotherm with less impact on the NH 3 -Oxidation compared to an article using only Pt to generate the exotherm.

[0117] By providing the improved exothermic properties, the catalyst articles also result in a reduction in hydrocarbons.

[0118] The use of one or more PGMs in the ASC increases the formation of NO 2 , reducing the need for a DOC.

[0119] Reducing the thickness of the top layer in the ASC zone can help generate an exotherm in the bottom layer. The NO 2 -Improve education.

[0120] In Examples 9-12, the use of a single layer comprising a mixture (blend) of one or more PGMs and the SCR catalyst as the ASC results in a further improvement in exotherm performance and a reduction in cost and can the formation of NO 2 to enhance.

[0121] The use of Pd in ​​the top layer leads to an improvement in the exothermic properties of the article as well as an improvement in the formation of NO 2 and a reduction in hydrocarbon emissions.

[0122] The system described in the examples can use the N 2 Reduce O formation by eliminating the use of a DOC. When a DOC is present in a traditional system, NH 3 escape from a system upstream of a DOC and enter a N 2 cause O formation. Example 13: Zoned systems

[0123] The systems described in Examples 3-10 are modified to provide zoning in the ASC where the PGM loading is higher in the outlet end of the ASC. Zoning is accomplished either in the layered system described in Examples 3-6 or in the combined single layer in Examples 7-10 by placing two or more washcoats side-by-side with increasing levels of one or more PGMs in the zone or zone, respectively. generated in the zones closest to the outlet.

[0124] The systems described in Examples 3 through 10 can be modified to provide different top layer thicknesses in the ASC zone when using a dual layer ASC zone.

[0125] The composition of the ASC in the systems described in Examples 3 to 10 can be modified to include one or more PGMs in the top layer towards the outlet end of the tail of the catalyst article.

[0126] The foregoing examples are for illustrative purposes only, the claims that follow define the scope of the invention. QUOTES INCLUDED IN DESCRIPTION

[0127] This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Patent Literature Cited

[0128] U.S.4010238

[0047] US4085193

[0047] Non-patent Literature Cited

[0129] IUPAC. Compendium of Chemical Terminology, 2nd Edition ("Gold Book"). Prepared by A.D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Corrected XML online version: http: / / goldbook.iupac.org (2006-), generated by M. Nic, J. Jirat, B. Kosata; the updates were generated by A. Jenkins. ISBN 0-9678550-9-8. Doi:10.1351 / goldbook.

[0035]

Claims

[1] Catalyst article comprising a substrate comprising an inlet end and an outlet, a first zone comprising a first SCR catalyst and a second zone comprising an ammonia barrier catalyst (ASC), wherein the ammonia barrier catalyst comprises a second SCR catalyst and an oxidation catalyst and the ASC has DOC functionality, wherein the first zone is arranged on the inlet side of the substrate and the second zone is arranged on the outlet side of the substrate. [2] Catalyst article according to claim 1, wherein the first zone and the second zone are arranged on the same substrate and the first zone is arranged on the inlet side of the substrate and the second zone is arranged on the outlet side of the substrate. [3] Catalyst article according to claim 1, further comprising a second substrate, wherein the first zone is arranged on a first substrate and the second zone is arranged on the second substrate and the first substrate is arranged upstream of the second substrate. [4] Catalyst article according to claim 1, wherein the ASC is a double layer comprising a lower layer comprising an oxidation catalyst and an upper cover layer comprising a second SCR catalyst. [5] Catalyst article according to claim 1, wherein the second zone comprises a mixture of the oxidation catalyst and the second SCR catalyst. [6] Catalyst article according to claim 1, wherein the oxidation catalyst comprises a platinum group metal. [7] Catalyst article according to claim 1, wherein the oxidation catalyst comprises platinum or palladium or mixtures thereof. [8] Catalyst article according to claim 1, wherein the first SCR catalyst is a base metal, an oxide of a base metal, a molecular sieve, a metal-exchanged molecular sieve or a mixture thereof. [9] Catalyst article according to claim 1, wherein the second SCR catalyst is a Cu-SCR catalyst, an Fe-SCR catalyst, a base metal, an oxide of a base metal or a mixed oxide or a vanadium catalyst. [10] Catalyst article according to claim 5, wherein the oxidation catalyst comprises platinum on a support with low ammonia storage. [11] Catalyst article according to claim 5, wherein the catalyst article provides an improvement in the N2 yield from ammonia at a temperature of about 250 °C to about 350 °C compared to a catalyst comprising a comparable formulation in which the first SCR catalyst is present in the form of a first coating and the platinum is present on a support with low ammonia storage in a second coating and NH3-containing gas passes through the first coating before passing through the second coating. [12] Catalyst article according to claim 5, wherein the catalyst article provides for at least one of the following: (a) an improvement in the N2 yield from ammonia at a temperature of about 350 °C to about 450 °C and (b) a reduction in NO x-Formation at a temperature of approximately 350 °C to approximately 450 °C compared to a catalyst comprising a comparable formulation in which the first SCR catalyst is present in the form of a first coating and the supported platinum is present in a second coating and NH3-containing gas passes through the first coating before passing through the second coating. [13] Catalyst article according to claim 5, wherein the catalyst article provides reduced N2O formation from NH3 compared to a catalyst comprising a comparable formulation in which the first SCR catalyst is present in the form of a first coating and the supported platinum is present in a second coating and NH3-containing gas passes through the first coating before passing through the second coating. [14] Catalyst article according to claim 1, wherein the catalyst article generates an exothermic. [15] Methods for controlling NO x -Emissions in an exhaust gas, wherein the process involves bringing an NO into contact x or exhaust gas comprising NH3 with a catalyst article according to claim 1.

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