Integrated emission control system including a diesel oxidation catalyst and a lean NOX adsorbent

Abstract

The present disclosure relates to the oxidation of hydrocarbons and carbon monoxide, and NO in the exhaust stream of a lean-burn engine. x 1. An emission treatment system for abatement, the emission treatment system comprising a cryogenic NO 3 mitigation system, the cryogenic NO 3 mitigation system comprising a molecular sieve impregnated with at least one PGM component positioned in fluid communication with the exhaust stream. x The present invention is directed to an emissions treatment system comprising an adsorbent (LT-NA) and an oxidation catalyst comprising a platinum-impregnated manganese-containing refractory metal oxide support positioned in fluid communication with an exhaust stream, the LT-NA and oxidation catalyst each disposed on a substrate. The present invention provides a catalyst article combining the oxidation catalyst with the LT-NA, and related methods for treating exhaust gases.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority from U.S. Provisional Patent Application No. 62 / 851,392, filed on May 22, 2019, which is hereby incorporated by reference in its entirety.

[0002] The present invention is directed to a catalytic article, an exhaust control system, and a method suitable for treating an exhaust gas stream of an internal combustion engine to reduce emissions of nitrogen oxides (NO x x).

Background Art

[0003] Environmental regulations regarding emissions from internal combustion engines are becoming increasingly stringent worldwide. For example, the operation of lean - burn engines such as diesel engines provides excellent fuel economy to users by operating at a high air - fuel ratio under fuel - lean conditions. However, diesel engines also emit exhaust gas emissions containing particulate matter (PM), unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NO x) x), where NO x x represents various chemical species of nitrogen oxides including nitric oxide and nitrogen dioxide. NO x is a harmful component of air pollution. Various treatment methods have been used to treat NO x - containing gas mixtures to reduce air pollution.

[0004] An effective method for reducing NO x x from the exhaust of lean - burn engines requires the reaction of NO x under lean - burn engine operating conditions using a suitable reducing agent in the presence of a selective catalytic reduction (SCR) catalyst component. The SCR process typically uses ammonia or hydrocarbons as a reducing agent in the presence of atmospheric oxygen, thereby forming mainly nitrogen and steam. 4NO + 4NH3+O2→4N2+6H2O (Standard SCR reaction) 2NO2 + 4NH3 + O2 → 3N2 + 6H2O (Low-speed SCR reaction) NO + NO2 + 2NH3 → 2N2 + 3H2O (High-speed SCR reaction)

[0005] Current catalysts used in the SCR process include molecular sieves such as zeolites ion-exchanged with catalytic metals such as iron or copper. Useful SCR catalyst components are effective in catalyzing the reduction of exhaust components at temperatures below 600 °C, thereby reducing NO x levels can be achieved even under low-load conditions typically associated with lower exhaust temperatures. x

[0006] One problem encountered in the treatment of automotive exhaust gas streams is the so-called "cold start" period, which is the period at the start of the treatment process when the exhaust gas stream and the exhaust gas treatment system are at low temperatures (i.e., below 150 °C). At these low temperatures, the exhaust gas treatment system generally does not exhibit sufficient catalytic activity to effectively treat emissions of hydrocarbons (HC), nitrogen oxides (NO x ), and / or carbon monoxide (CO). Generally, catalyst components such as SCR catalyst components are very effective in converting NO x to N2 at temperatures above 200 °C but do not exhibit sufficient performance in the lower temperature range (<200 °C) as seen during cold starts or long periods of low-speed urban driving.

[0007] Another problem encountered with SCR catalysts is that the SCR reaction is sensitive to the ratio of NO2 to total NO x in the feed gas to the SCR catalyst. In diesel systems, this ratio typically depends strongly on the composition of the diesel oxidation catalyst (DOC) placed upstream of the SCR catalyst.

[0008] It would be highly desirable to provide an improved emissions treatment system that provides very efficient SCR catalyst performance over a wide range of operating temperatures. Summary of the Invention​

[0009] This disclosure is directed to the use of a lean NO x adsorbent (LT-NA) in combination with the use of a diesel oxidation catalyst (DOC) that exhibits enhanced NO2 production to efficiently remove the desorbed NO x from the LT-NA by a downstream SCR component from NO in the exhaust gas at low temperature. More specifically, the DOC advantageously comprises a manganese-containing support material (e.g., Mn / Al2O3) that increases the NO2 / NO x ratio of the treated exhaust gas to improve the downstream operation of the SCR catalyst. x In one aspect, the disclosure is an emissions treatment system for the oxidation of hydrocarbons and carbon monoxide and the reduction of NO

[0010] in the exhaust stream of a lean burn engine, the emissions treatment system comprising a low temperature NO x adsorbent molecular sieve impregnated with at least one PGM component positioned to be in fluid communication with the exhaust stream xAn adsorbent (LT-NA) and an oxidation catalyst comprising a platinum-impregnated manganese-containing refractory metal oxide support positioned in fluid communication with an exhaust stream, wherein the LT-NA and the oxidation catalyst are each disposed on a substrate, to provide an emissions treatment system. In certain embodiments, the LT-NA and the oxidation catalyst are (1) layered on the same substrate, with the LT-NA present in a first layer and the oxidation catalyst present in a second layer, the first layer being positioned closer to the substrate than the second layer and at least partially overlapping the second layer, or (2) in a zoned configuration on the same substrate, with the LT-NA in an upstream zone and the oxidation catalyst in a downstream zone, or (3) the LT-NA is present on a first substrate and the oxidation catalyst is present on a second substrate, the first substrate being positioned upstream of the second substrate. The emissions treatment system may further include at least one selective catalytic reduction (SCR) catalyst positioned downstream of both the LT-NA and the oxidation catalyst, and optionally one or more of the following: an ammonia or ammonia precursor injection component, a catalyzed soot filter (CSF), and an ammonia oxidation (AMOX) catalyst.

[0011] For example, the LT-NA and the oxidation catalyst may be disposed on the same substrate in a zoned configuration, the substrate having an inlet end and an outlet end defining a total length, the LT-NA may extend from the inlet end for a length of about 20% to about 100% of the total length and be disposed on the substrate, and the oxidation catalyst may extend from the outlet end for a length of about 20% to about 100% of the total length and be disposed on the substrate, and the oxidation catalyst may optionally overlap at least a portion of the LT-NA. In certain embodiments, the LT-NA extends from the inlet end for a length of about 40% to about 100% of the total length and is disposed on the substrate, and the oxidation catalyst extends from the outlet end for a length of about 40% to about 100% of the total length and is disposed on the substrate. Both the LT-NA and the oxidation catalyst may be disposed, for example, on a flow-through substrate in the form of a honeycomb having a plurality of longitudinally extending gas flow paths extending from the inlet to the outlet.

[0012] Optionally, the oxidation catalyst is zone coated with a second oxidation catalyst comprising a refractory metal oxide support impregnated with one or more platinum group metal (PGM) components, the second oxidation catalyst being substantially manganese-free and located upstream of the oxidation catalyst.

[0013] Molecular sieves can have a framework type selected from the group consisting of 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, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EZT, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, IFY, IHW, IMF, IRN, ISV, ITE, ITG, ITH, ITW, IWR, IWS, IWV, IWW, JBW, JRY, JSR, JST, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LTF, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MSO, MTF, MTN, MTT, MVY, MTW, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, PAR, PAU, PCR, PHI, PON, PUN, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SCO, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGF, SGT, SIV, SOD, SOF, SOS, SSF, SSY, STF, STI, STO, STT, STW, SVR, SZR, TER, THO, TON, TSC, TUN, UEI, UFI, UOS, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, and mixtures or twins thereof. In certain embodiments, the molecular sieve has a framework type selected from the group consisting of LEV, CHA, and FER. Advantageously, the molecular sieve is an aluminosilicate zeolite.In certain embodiments, the molecular sieve comprises channels defined by at least 10-membered rings.

[0014] The oxidation catalyst may also include palladium, rhodium, or combinations thereof. Exemplary oxidation catalysts include platinum in an amount in the range of about 10 g / ft 3 ~100 g / ft 3 impregnated on a manganese-containing refractory metal oxide support, for example, at least about 40 g / ft 3 (or at least about 45, or at least about 50, or at least about 55, or at least about 60, or at least about 65, or at least about 70, or at least about 75, or at least about 80) of platinum. In some embodiments, the platinum impregnated on the manganese-containing refractory metal oxide support is in the form of nanoparticles having an average particle size in the range of about 1 to about 10 nm. LT-NA may, in certain embodiments, contain palladium as the sole PGM component.

[0015] Refractory metal oxide supports typically include alumina, silica, zirconia, titania, ceria, or combinations thereof. In certain embodiments, the manganese content of the refractory metal oxide support is in the range of about 0.1 wt% to about 30 wt%, for example, in the range of about 3 to about 10 wt%, based on the total weight of the support. Manganese is typically present in a form selected from the group consisting of Mn-containing solid solutions having a refractory metal oxide, Mn surface-dispersed on the refractory metal oxide by impregnation, and discrete manganese oxide particles on the particles of the refractory metal oxide.

[0016] In another aspect, the present disclosure provides a method for oxidizing hydrocarbons and reducing NO in the exhaust stream from a lean burn engine, the method comprising contacting the exhaust gas stream with an emissions treatment system according to any of the embodiments described herein. x The method includes contacting the exhaust gas stream with an emissions treatment system according to any of the embodiments described herein.

[0017] In yet another aspect, the present disclosure is a catalytic article for treating exhaust from a lean burn engine, comprising a substrate having an inlet end and an outlet end defining a total length, and a molecular sieve impregnated with at least one PGM component disposed on the substrate for low temperature NO x adsorbent (LT-NA) (such as any embodiment of LT-NA disclosed herein) and an oxidation catalyst disposed on the substrate and comprising a platinum-impregnated manganese-containing refractory metal oxide support (such as any embodiment of the oxidation catalyst disclosed herein), wherein the LT-NA and the oxidation catalyst are (1) layered on the substrate, the LT-NA is present in a first layer, the oxidation catalyst is present in a second layer, the first layer is positioned closer to the substrate than the second layer and at least partially overlaps the second layer, or (2) in a zoned configuration on the same substrate, the LT-NA is in an upstream zone and the oxidation catalyst is in a downstream zone. For example, the LT-NA and the oxidation catalyst are disposed on the substrate in a zoned configuration, the substrate has an inlet end and an outlet end defining a total length, the LT-NA extends from the inlet end over a length of about 20% to about 100% of the total length and is disposed on the substrate, the oxidation catalyst extends from the outlet end over a length of about 20% to about 100% of the total length and is disposed on the substrate, and the oxidation catalyst optionally overlaps at least a portion of the LT-NA. In some embodiments, the LT-NA extends from the inlet end over a length of about 40% to about 100% of the total length and is disposed on the substrate, and the oxidation catalyst extends from the outlet end over a length of about 40% to about 100% of the total length and is disposed on the substrate. In some embodiments, the oxidation catalyst is zone-coated with a second oxidation catalyst comprising a refractory metal oxide support impregnated with one or more platinum group metal (PGM) components, the second oxidation catalyst is substantially manganese-free and is located upstream of the oxidation catalyst.

[0018] These and other features, aspects, and advantages of the present disclosure will become apparent from the following detailed description, along with the accompanying drawings described briefly below. The present invention includes any combination of two, three, four, or more of the above-described embodiments, and any combination of any two, three, four, or more features or elements described in the present disclosure, regardless of whether such features or elements are explicitly combined in the description of a particular embodiment herein. In the present disclosure, it is intended to be read as a whole that separable features or elements of the disclosed invention should be considered combinable in any of its various aspects and embodiments, unless the context clearly indicates otherwise. Other aspects and advantages of the present invention will become apparent below.

Brief Description of the Drawings

[0019] To provide an understanding of embodiments of the present invention, reference is made to the accompanying drawings, in which reference numerals indicate components of exemplary embodiments of the present invention. The drawings are merely examples and are not to be construed as limiting the present invention. The disclosure described herein is shown in the accompanying figures by way of example, and not as a limitation. For the sake of brevity and clarity, the features shown in the figures are not necessarily drawn to scale. For example, the dimensions of some features may be exaggerated relative to other features for clarity. Further, reference numerals may be repeated in multiple drawings to indicate corresponding or similar elements where appropriate.

[0020]

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Mode for Carrying Out the Invention

[0021] Hereinafter, the present invention will be more fully described. However, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

[0022] Definitions As used herein, the articles "a" and "an" refer to one or more than one (e.g., at least one) of the grammatical object. All ranges recited herein are inclusive. The term "about" is used throughout to express and account for minor variations. For example, "about" can mean that a numerical value can vary by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1%, or ±0.05%. All numerical values, whether or not explicitly indicated as such, are modified by the term "about". Numerical values modified by the term "about" include the specifically identified value. For example, "about 5.0" includes 5.0.

[0023] The term "reduce" means a decrease in amount caused by any means.

[0024] The term "adsorbent" refers to a material that adsorbs and / or absorbs a desired substance, in this disclosure NO x and / or. An adsorbent can advantageously adsorb and / or absorb (store) a substance at a particular temperature and desorb (release) the substance at a higher temperature.

[0025] The term "associated" means, for example, "comprising", "connected to", or "in communication with", for example, "electrically connected to" or "in fluid communication with", or connected to perform a function. The term "associated" can mean directly or indirectly associated, for example, through one or more other articles or elements.

[0026] The term "catalyst" refers to a material that promotes a chemical reaction. A catalyst includes a "catalytic active species" and a "support" that transports or supports the active species. For example, zeolite is a support for palladium active catalyst species. Similarly, refractory metal oxide particles can be a support for platinum group metal catalyst species. The catalytic active species is also called an "accelerator" to promote a chemical reaction.

[0027] The term "catalyst article" in the present invention refers to an article including a substrate having a catalyst coating composition.

[0028] The term "comprised of" used in the specification and claims is intended to be an open-ended term similar to the terms "including" or "containing". The term "comprised of" does not mean excluding other possible articles or elements. The term "comprised of" may be equivalent to "adapted to".

[0029] "CSF" refers to a catalyzed soot filter that is a wall flow monolith. The wall flow filter consists of alternately positioned inlet channels and outlet channels. The inlet channels are inserted into the outlet ends, and the outlet channels are inserted into the inlet ends. The exhaust gas flow carrying soot entering the inlet channels is passed through the filter walls before exiting from the outlet channels. In addition to soot filtration and regeneration, the CSF may carry an oxidation catalyst for oxidizing CO and HC to CO2 and H2O, or for oxidizing NO to NO2, in order to accelerate a downstream SCR catalyst or to promote the oxidation of soot particles at a lower temperature. The SCR catalyst composition can also be directly coated on a wall flow filter called SCRoF.

[0030] "DOC" refers to a diesel oxidation catalyst that converts hydrocarbons and carbon monoxide in the exhaust gas of a diesel engine. Typically, the DOC includes one or more platinum group metals such as palladium and / or platinum, a support material such as alumina, zeolite for HC storage, and optionally an accelerator and / or a stabilizer.

[0031] Generally, the term "effective" means, with respect to a defined catalytic activity or storage / release activity in weight or mole, for example, having an effect of about 35% to 100%, for example, having an effect from about 40%, about 45%, about 50% or about 55% to about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90% or about 95%.

[0032] The term "exhaust stream" or "exhaust gas stream" refers to any combination of flowing gases that may contain solid or liquid particulate matter. The stream contains gaseous components and may contain certain non-gaseous components such as, for example, droplets, solid particles, etc., in the exhaust of a lean burn engine. The exhaust gas stream of a combustion engine typically contains combustion products (CO2 and H2O), incomplete combustion products (carbon monoxide (CO) and hydrocarbons (HC)), nitrogen oxides (NO x )), combustible and / or carbonaceous particulate matter (soot), and further contains unreacted oxygen and nitrogen. As used herein, the terms "upstream" and "downstream" refer to the relative direction according to the flow of the engine exhaust gas stream from the engine towards the tail pipe, with the engine in the upstream position and the tail pipe and any pollution reduction articles such as filters and catalysts downstream of the engine. The inlet end of the substrate is synonymous with the "upstream" end or "front" end. The outlet end is synonymous with the "downstream" end or "rear" end. The upstream zone is upstream of the downstream zone. The upstream zone may be near the engine or manifold, and the downstream zone may be further away from the engine or manifold.

[0033] The term "in fluid communication" is used to refer to articles positioned in the same exhaust line, i.e., a common exhaust stream passes through articles that are in fluid communication with each other. Articles in fluid communication may be adjacent to each other in the exhaust line. Alternatively, articles in fluid communication may be separated by one or more articles, also referred to as a "washcoat monolith".

[0034] As used herein, "impregnated" or "impregnation" refers to permeating a catalytic material into the porous structure of a carrier material.

[0035] The terms "above," "upper," and "overlying" associated with the coating layer can be used synonymously. The term "directly above" means in direct contact. The disclosed article, in certain embodiments, is referred to as including one coating layer "above" a second coating layer, but such terminology is intended to encompass embodiments having intervening layers where direct contact between the coating layers is not required (i.e., "above" is not equivalent to "directly above").

[0036] As used herein, the term "nitrogen oxide" or "NO x " refers to nitrogen oxides such as NO, NO2, or N2O.

[0037] "Substantially free of" means "little or no" or "not intentionally added," and also means having only trace amounts and / or accidental amounts. For example, in certain embodiments, "substantially free of" means less than 2 weight percent (wt%), less than 1.5 wt%, less than 1.0 wt%, less than 0.5 wt%, less than 0.25 wt%, or less than 0.01 wt% based on the weight of the total composition shown.

[0038] As used herein, the term "washcoat" has its ordinary meaning in the art of a thin adherent coating of a catalyst or other material applied to a substrate material that is sufficiently porous to permit passage of the gas stream being processed, such as a honeycomb-type substrate. As used herein, and as described in Heck, Ronald, and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp. 18-19, a washcoat layer comprises a compositionally distinct layer of material disposed on the surface of a monolith substrate or underlying washcoat layer. A substrate can contain one or more washcoat layers, and each washcoat layer can differ in some way (e.g., the physical properties of the washcoat can differ, such as particle size or crystallite phase) and / or can have a different chemical catalytic function. A washcoat is typically formed by preparing a slurry containing a catalyst having a particular solids content (e.g., 30 wt% to 90 wt%) in a liquid, then coating this onto the substrate and drying to provide the washcoat layer.

[0039] Unless otherwise indicated, "weight percent (wt%)" is based on the total composition exclusive of volatiles, i.e., the dry solids content. Unless otherwise specified, all parts and percentages are by weight.

[0040] All of the methods described in this specification can be performed in any suitable order, unless otherwise indicated herein or unless clearly inconsistent by context. The use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better explain the materials and methods and is not limiting of the scope unless otherwise claimed. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed materials and methods. All U.S. patent applications, published pre-grant publications, and patents referred to herein are incorporated herein by reference in their entirety.

[0041] In a first aspect, the present invention provides an emissions treatment system adapted for the oxidation of hydrocarbons and carbon monoxide in an exhaust stream and the reduction of NOx in the exhaust stream. The emissions treatment system of the present invention includes an oxidation catalyst (i.e., a diesel oxidation catalyst or DOC) capable of enhancing the activity of a downstream SCR catalyst, which oxidizes hydrocarbons and carbon monoxide and also promotes NO2 formation, and a low-temperature NO x adsorbent (LT-NA) capable of effecting the adsorption of NO x at a temperature below the efficient operating temperature of the downstream SCR catalyst. Acting together, the oxidation catalyst and the LT-NA can reduce the NO x emissions downstream of the SCR catalyst. The present invention also provides a catalyst article comprising both a DOC and an LT-NA composition as described herein.

[0042] Diesel oxidation catalyst (DOC) The DOC composition used in the present invention contains a PGM component impregnated in a porous refractory metal oxide support. As used herein, "platinum group metal" or "PGM" refers to platinum group metals or their oxides, including platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), and mixtures thereof. In certain embodiments, the platinum group metals include a combination of platinum and palladium in a weight ratio of about 1:10 to about 10:1, more typically, platinum to palladium in a ratio of about 1.5:1 or greater, about 2:1 or greater, or about 5:1 or greater. The concentration of the PGM component (e.g., Pt, Pd, or a combination thereof) can vary, but is typically about 0.1 wt% to about 10 wt% (e.g., about 1 wt% to about 6 wt% with respect to the refractory oxide support) based on the weight of the porous refractory oxide support material. The DOC may further include a hydrocarbon adsorbent such as zeolite (e.g., Fe-beta zeolite), and / or a stabilizer or promoter (e.g., barium oxide).

[0043] As used herein, "porous refractory metal oxide" refers to a porous metal-containing oxide material that exhibits chemical and physical stability at elevated temperatures, e.g., temperatures associated with the exhaust of a diesel engine. Exemplary refractory oxides include alumina, silica, zirconia, titania, ceria, and physical mixtures or chemical combinations thereof, including atom-doped combinations and high surface area or activated compounds such as activated alumina. Exemplary combinations of metal oxides include alumina-zirconia, ceria-zirconia, alumina-ceria-zirconia, lanthana-alumina, lanthana-zirconia-alumina, baria-alumina, barialanthana-alumina, barialanthana-neodymia alumina, and alumina-ceria. Exemplary aluminas include macroporous boehmite, gamma-alumina, and delta / theta alumina. Useful commercially available aluminas include high bulk density gamma-alumina, low or medium bulk density macroporous gamma-alumina, and activated aluminas such as low bulk density macroporous boehmite and gamma-alumina.

[0044] A high-surface area refractory oxide support, such as an alumina support material, also referred to as "gamma alumina" or "activated alumina", typically has a BET surface area of greater than 60 m 2 / g, often up to about 200 m 2 / g or more. Such activated alumina is usually a mixture of the gamma and delta phases of alumina, but may also contain significant amounts of the eta, kappa, and theta alumina phases. "BET surface area" has its usual meaning related to the Brunauer, Emmett, Teller method of determining surface area by N2 adsorption. Desirably, the activated alumina has a specific surface area of 60 to 350 m 2 / g, typically 90 to 250 m 2 / g.

[0045] At least a portion of the refractory metal oxide support used in the DOC of the present invention contains manganese, and the manganese-containing refractory metal oxide support is impregnated with platinum. The manganese content of such a refractory metal oxide support is typically in the range of about 0.1 wt% to about 30 wt% (including 0.1, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 15.0, and 20.0 wt%) based on the total weight of the refractory metal oxide support. In certain embodiments, the Mn content is in the range of about 3 to about 10 wt%. Without intending to be bound by theory, it is believed that manganese can beneficially interact with platinum to promote NO2 formation, thereby improving the performance of downstream SCR catalysts. In one or more embodiments, the combination of platinum supported on manganese and manganese on the manganese-containing support results in a synergistic effect that improves NO oxidation and increases NO2 formation. A method for forming a manganese-containing refractory metal oxide support is described in US2015 / 0165422 to Sung et al., which is hereby incorporated by reference in its entirety.

[0046] Mn can be incorporated into the refractory metal oxide support either in bulk or surface form, or as discrete manganese oxide forms. In one or more embodiments, Mn is derived from soluble Mn species selected from manganese acetate, manganese nitrate, manganese sulfate, or combinations thereof. In other embodiments, Mn is derived from bulk manganese oxides selected from MnO, Mn2O3, MnO2, and combinations thereof.

[0047] According to one or more embodiments, the refractory metal oxide support is impregnated with an Mn salt. As used herein, the term "impregnated" means that an Mn-containing solution is placed into the pores of a material such as a refractory metal oxide support. In certain embodiments, the impregnation is achieved by incipient wetness, wherein the volume of the diluted Mn-containing solution is approximately equal to the pore volume of the support body. Incipient wetness impregnation generally distributes the precursor solution substantially uniformly throughout the pore system of the material.

[0048] In other embodiments, manganese and the refractory oxide support precursor are co-precipitated and then the co-precipitated material is calcined such that the refractory oxide support material and manganese form a solid solution together, thereby incorporating manganese with the refractory oxide support. Thus, according to one or more embodiments, a mixed oxide containing oxides of manganese, aluminum, cerium, silicon, zirconium, and titanium can be formed. Manganese can also be dispersed on the surface of the refractory oxide support as discrete manganese oxide particles.

[0049] The amount of platinum incorporated into the manganese-containing support can vary, but the amount of platinum is known to be a factor that determines the overall efficiency of NO x reduction in an emissions treatment system incorporating the oxidation catalyst. In certain embodiments, the amount of platinum is at least about 40 g / ft (based on the volume of the underlying substrate on which the catalyst is disposed) 3 , at least about 45 g / ft 3 , at least about 50 g / ft 3 , at least about 55 g / ft3 , at least about 60 g / ft 3 , at least about 65 g / ft 3 , at least about 70 g / ft 3 , at least about 75 g / ft 3 , or at least about 80 g / ft 3 including ranges such as about 10 g / ft 3 ~100 g / ft 3 . The concentration of platinum or any other composition on the substrate refers to the concentration per cross-section of any one three-dimensional part or zone, for example, of the substrate or the entire substrate, typically in g / ft 3 or g / in 3 and is expressed in.

[0050] The oxidation catalyst of the present invention may include an additional refractory metal oxide in addition to the manganese-containing carrier, and such an additional refractory metal oxide may also have a PGM component impregnated thereon. For example, in certain embodiments, the oxidation catalyst includes a two-zone coated composition, namely, a front or upstream zone including one or more PGM components impregnated on a refractory metal oxide carrier that is usually substantially manganese-free (and including optional additional components such as hydrocarbon adsorbents, stabilizers, promoters, etc.), and a rear or downstream zone including a manganese-containing refractory metal oxide carrier impregnated with platinum (and including optional additional components such as hydrocarbon adsorbents, stabilizers, promoters, etc.). Alternatively, a plurality of refractory oxide carriers (including manganese-containing carriers) containing PGM components can be included in a single homogeneous composition.

[0051] The oxidation catalyst is generally, based on the volume of the substrate, for example, about 0.3 to 2.5 g / in 3 , or about 0.4 g / in 3 , about 0.5 g / in 3 , about 0.6 g / in 3 , about 0.7 g / in 3 , about 0.8 g / in 3 , about 0.9 g / in 3 or about 1.0 g / in 3 to about 1.5 g / in 3 , about 1.7 g / in 3, at a concentration of about 1.8 g / in 3 , at a concentration of about 1.9 g / in 3 , at a concentration of about 2.0 g / in 3 , at a concentration of about 2.1 g / in 3 , at a concentration of about 2.2 g / in 3 , at a concentration of about 2.3 g / in 3 or at a concentration of about 2.5 g / in 3 and are present on the substrate.

[0052] Method for producing a DOC composition The preparation of the PGM-impregnated refractory oxide material typically involves impregnating a refractory oxide support material in particulate form with a PGM solution such as one or more of a platinum solution and a palladium solution. Multiple PGM components (e.g., platinum and palladium) may be impregnated simultaneously or separately, and may be impregnated onto the same support particles or separate support particles using the incipient wetness technique. The support particles are typically dry enough to absorb substantially all of the solution to form a wet solid. Typically, an aqueous solution of a water-soluble compound or complex of the PGM component such as palladium nitrate or platinum nitrate, tetraamminepalladium nitrate or platinum nitrate, or tetraamminepalladium acetate or platinum acetate is utilized.

[0053] After treating the support particles with the PGM solution, the particles are dried, for example, by heat-treating the particles at a high temperature (e.g., 100 - 150 °C) for a certain period (e.g., 1 - 3 hours), and then calcined to convert the PGM component into a more catalytically active form. An exemplary calcination process involves heat-treating in air at a temperature of about 400 - 550 °C for 1 - 3 hours. The above process may be repeated as necessary to reach the desired level of PGM impregnation. The resulting material can be stored as a dry powder or in slurry form.

[0054] Alternatively, the PGM starting material can be in the form of a colloidal dispersion of PGM nanoparticles rather than in solution form. Such a colloidal suspension can be applied to the support in the incipient wetness technique as described above. Methods for impregnating the support with the colloidal PGM material are described in US2017 / 0304805 by Xu et al. and US2019 / 0015781 by Wei et al., both of which are hereby incorporated by reference in their entirety.

[0055] The average size of the PGM nanoparticles in the colloidal dispersion can vary. In some embodiments, the PGM nanoparticles in a given colloidal dispersion can have an average particle size of from about 1 nm to about 10 nm, such as an average particle size of from about 1 nm to about 6 nm, such as an average particle size of about 1 nm, about 2 nm, about 3 nm, about 4 nm, or about 5 nm. Particular embodiments can have an average particle size of from about 1 - 2 nm, about 1 - 3 nm, about 1 - 4 nm, about 1 - 5 nm, about 1 - 6 nm, about 2 - 3 nm, about 2 - 4 nm, about 2 - 5 nm, about 2 - 6 nm, about 3 - 4, about 3 - 5 nm, about 3 - 6 nm, about 4 - 5 nm, about 4 - 6 nm, or about 5 - 6 nm.

[0056] Advantageously, the PGM nanoparticles in the colloidal dispersions disclosed herein are substantially monodisperse. In certain embodiments, the particles can be considered monodisperse, which means that the population of PGM nanoparticles is very uniform with respect to particle size. Certain monodisperse particle populations useful in the present invention can be characterized in that at least 95%, or within 50 percent, or within 20 percent, or within 15 percent, or within 10 percent of the average particle size of the particle population, of the particles consist of particles having a particle size (i.e., at least 95% of all the particles in the population have a particle size within a given percentage range of approximately the average particle size). In other embodiments, at least 96%, 97%, 98%, or 99% of all the particles are within these ranges. In one exemplary embodiment, the average particle size is about 2 nm, and at least 95% (or at least 96%, 97%, 98%, 99%, or 100%) of all the particles in the population have a particle size in the range of about 1 nm to about 3 nm (i.e., within about 50 percent of the average particle size). Certain PGM nanoparticle dispersions can include substantially monodisperse dispersions having average PGM nanoparticle particle sizes of about 2 nm, about 3 nm, about 4 nm, and about 5 nm.

[0057] The particle size and size distribution of the PGM nanoparticles can be determined using a transmission electron microscope (TEM). Such values can be found by visually examining the TEM image, measuring the diameter of the particles in the image, and calculating the average particle size of the measured particles based on the magnification of the TEM image. The particle size refers to the smallest diameter sphere that completely encloses the particle, and this measurement relates to individual particles as opposed to the aggregation of two or more particles. The above size ranges are the average values of particles having a size distribution.

[0058] Advantageously, according to the present disclosure, the PGM in the colloidal dispersion that is useful is in a substantially fully reduced form, which means that at least about 90% of the platinum group metal content (i.e., the majority of the nanoparticles) is reduced to the metallic form (PGM(0)). In some embodiments, the amount of PGM in the fully reduced form is even higher, for example, at least about 92%, at least about 94%, at least about 95%, at least about 96%, at least about 97%, at least about 98%, or at least about 99% of the PGM is in the fully reduced form. The amount of PGM(0) can be determined using ultrafiltration followed by inductively coupled plasma / optical emission spectrometry (ICP-OES). In this method, the un-reduced PGM species in the colloidal dispersion can be separated from the PGM(0) nanoparticles, and then the PGMNP can be quantified by ICP-OES.

[0059] Low-temperature NO x Adsorbent (LT-NA) The LT-NA disclosed herein includes a molecular sieve containing a platinum group metal (PGM) component. Such LT-NA components are effective for storing NO at temperatures below 200 °C and releasing the stored NO at higher temperatures. x and releasing the stored NO x at higher temperatures.

[0060] As used herein, the term "molecular sieve", for example, zeolites and other zeolite framework materials (e.g., isomorphous substitution materials), generally refers to materials based on an extensive three-dimensional network structure of oxygen anions connected to metal atoms (e.g., Si, Al, etc.) that are in tetrahedral sites and have a substantially uniform pore distribution with an average pore diameter of 20 angstroms (Å) or less.

[0061] Molecular sieves can be mainly distinguished according to the shape of the voids formed by the robust network structure of (SiO4) / AlO4 tetrahedrons. The entrances to the voids are surrounded by rings containing 6, 8, 10, 12, or 14 oxygen atoms, which include 6, 8, 10, 12, or 14 (SiO4) / AlO4 tetrahedrons that form the entrance openings. A molecular sieve is a crystalline material with a fairly uniform pore diameter in the range of about 3 to 10 Å, depending on the type of molecular sieve and the type and amount of cations contained in the molecular sieve lattice. The expression "eight-ring" molecular sieve refers to a molecular sieve having eight-ring pore openings and a double six-ring secondary building unit, and having a cage-like structure resulting from the connection of double six-ring building units by four rings. Molecular sieves include small-pore, medium-pore, and large-pore molecular sieves or combinations thereof. The pore diameter is defined by the ring diameter.

[0062] Small-pore molecular sieves contain channels defined by a maximum of eight tetrahedral atoms. As used herein, the term "small pore" refers to pore openings smaller than about 5 angstroms, for example, pore openings on the order of about 3.8 angstroms. Exemplary small-pore molecular sieves include framework types 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, ZON, and mixtures or twins thereof.

[0063] Mesoporous molecular sieves contain channels defined by 10-membered rings. Exemplary mesoporous molecular sieves include framework types 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, WEN, and mixtures or twins thereof.

[0064] Macroporous molecular sieves contain channels defined by 12-membered rings. Exemplary macroporous molecular sieves include framework types 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, LTL4, 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, VET, and mixtures or twins thereof.

[0065] Typically, any framework type of molecular sieve can be used, 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, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOG, BPH, BRE, CAN, CAS, SCO, CFI, SGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, IFY, IHW, IRN, 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, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OSI, OSO, OWE, PAR, PAU, PHI, PON, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SFE, SFF, SFG, SFH, SFN, SFO, SFW, 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 a combination of these framework types. For example, in certain embodiments, the molecular sieve can include a framework type selected from the group consisting of CHA (chabazite), FER (ferrierite), and LEV (levyne).

[0066] As used herein, the term "zeolite" refers to a particular example of a molecular sieve containing silicon and aluminum atoms. Generally, zeolites are defined as aluminosilicates having an open three-dimensional framework structure composed of corner-sharing TO4 tetrahedra, where T is Al or Si, or optionally P. Cations that balance the charge of the anionic framework are loosely associated with the framework oxygen, and the remaining pore volume is filled with water molecules. Non-framework cations are generally exchangeable, and water molecules are removable. The aluminosilicate zeolite structure does not contain phosphorus or other metals that are isomorphously substituted in the framework. That is, "aluminosilicate zeolite" excludes aluminophosphate materials such as SAPO, AlPO, and MeAlPO materials, while the broader term "zeolite" includes aluminosilicates and aluminophosphates. For the purposes of this disclosure, SAPO, AlPO, and MeAlPO materials are considered non-zeolite molecular sieves.

[0067] Zeolites can include SiO4 / AlO4 tetrahedra that are bonded by common oxygen atoms to form a three-dimensional network structure. The molar ratio of silica to alumina ("SAR") of this zeolite can vary over a wide range and is generally 2 or more. For example, the zeolite of the present invention can have an SAR of about 5 to about 1000, such as about 10 to about 100, or about 10 to about 50, or about 15 to about 30.

[0068] The molecular sieve of LT-NA is impregnated with a PGM component. As used herein, reference to impregnation with a PGM component includes any form of association of the PGM component with the molecular sieve, such as when the PGM component is present at either the ion exchange sites of the molecular sieve or other internal locations within the molecular sieve, or where the PGM is present on the surface of the molecular sieve, or any combination of the above locations.

[0069] The term "PGM component" refers to any component containing PGM (e.g., Ru, Rh, Os, Ir, Pd, Pt). References to "PGM component" take into account the presence of PGM in any valence state. For example, the PGM may be in the metallic form with a valence of zero, or the PGM may be in the oxide form. Terms such as "platinum (Pt) component", "rhodium (Rh) component", "palladium (Pd) component", "iridium (Ir) component", "ruthenium (Ru) component", etc. refer to the respective platinum group metal compounds, complexes, etc. that decompose or otherwise convert to the catalytically active form, usually a metal or metal oxide, when the catalyst is calcined or used. In some embodiments, the PGM component is palladium as the sole PGM component, but mixtures of PGM components can also be used.

[0070] The concentration of the PGM component can vary, but will typically be from about 0.01 wt% to about 6 wt% based on the total dry weight of the molecular sieve. The PGM component can be present in the molecular sieve, based on the total dry weight of the molecular sieve, at, for example, about 0.1 wt%, about 0.2 wt%, about 0.5 wt%, about 0.7 wt%, about 0.9 wt%, or about 1.0 wt% to about 1.5 wt%, about 2.0 wt%, about 2.5 wt%, about 3.0 wt%, about 3.5 wt%, about 4.0 wt%, about 4.5 wt%, about 5.0 wt%, or about 6 wt%. Measure the weight of the PGM component and report it as the metal (e.g., the weight of palladium). The total dry weight of the molecular sieve includes any added / exchanged metals (i.e., palladium).

[0071] Alternatively, the amount of the PGM component in the LT-NA composition can be expressed as the weight per unit volume of the substrate. For example, in certain embodiments, the amount of the PGM component in the LT-NA is about 10 g / ft 3 ~140 g / ft 3 or about 40 g / ft 3 ~ about 100 g / ft 3 and is.

[0072] The LT-NA composition is generally, based on the volume of the substrate, for example, about 0.3 to 5.5 g / in 3 or about 0.4 g / in 3 about 0.5 g / in 3 about 0.6 g / in 3 about 0.7 g / in 3 about 0.8 g / in 3 about 0.9 g / in 3 or about 1.0 g / in 3 to about 1.5 g / in 3 about 2.0 g / in 3 about 2.5 g / in 3 about 3.0 g / in 3 about 3.5 g / in 3 about 4.0 g / in 3 about 4.5 g / in 3 about 5.0 g / in 3 or about 5.5 g / in 3 and is present on the substrate at a concentration of.

[0073] Preparation of the LT-NA Composition The LT-NA disclosed herein can be readily prepared by processes well known in the art. The disclosed LT-NA can, in some embodiments, be prepared by the incipient wetness impregnation method. Typically, a metal precursor (e.g., the PGM component) is dissolved in an aqueous or organic solution, and then the metal-containing solution is added to a material (e.g., a molecular sieve) that contains a pore volume essentially the same as the volume of the added solution to be impregnated. By capillary action, the solution is drawn into the pores of the material. The addition of a solution in excess of the pore volume of the material causes the solution transport to change from the capillary action process to a much slower diffusion process. The impregnated material can then be dried and optionally calcined to remove volatile components in the solution and deposit the metal on the surface of the material. The maximum filling amount is limited by the solubility of the precursor in the solution. The concentration profile of the impregnated material depends on the mass transfer conditions within the pores during impregnation and drying.

[0074] For example, a PGM component precursor (e.g., palladium nitrate, etc.) can be supported on a molecular sieve by impregnation, adsorption, ion exchange, incipient wetness, precipitation, etc. Non-limiting examples of suitable PGM precursors include palladium nitrate, tetraamminepalladium nitrate, tetraammineplatinum acetate, and platinum nitrate. Alternatively, a PGM colloid dispersion as discussed above can be used. During the firing step, or at least during the initial stages of use of the catalyst, such compounds are converted to the catalytically active form of the metal or its compound.

[0075] Substrate The DOC and LT-NA compositions of the present invention are typically disposed on a substrate. Useful substrates are three-dimensional and have a length, diameter, and volume similar to a cylinder. The shape does not necessarily have to conform exactly to a cylinder. The length is the axial length defined by the inlet end and the outlet end.

[0076] According to one or more embodiments, the substrate for the disclosed components may be composed of any material typically used to prepare automotive catalysts, and typically includes a metal or ceramic honeycomb structure. The substrate typically provides a plurality of wall surfaces to which a washcoat composition is applied and adhered, thereby functioning as a substrate for the catalyst composition. In some embodiments, the substrate includes a honeycomb substrate in the form of a wall flow filter or a flow-through substrate.

[0077] The ceramic substrate can be made from any suitable refractory material, such as cordierite, cordierite-α-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon mullite, rhodonite, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, α-alumina, aluminosilicate, etc.

[0078] The substrate can also be a metal and includes one or more metals or metal alloys. The metal substrate can include any metal substrate having openings or "punch-outs" in the channel walls. The metal substrate can be used in various shapes such as pellets, corrugated sheets, or monolithic foams. Specific examples of metal substrates include base metal alloys with heat resistance, particularly alloys in which iron is a substantial or major component. Such alloys can contain one or more of nickel, chromium, and aluminum, and the total of these metals is advantageously, in any case, at least about 15 weight% (weight percent) of the alloy based on the weight of the substrate, for example, about 10 to about 25 weight% chromium, about 1 to about 8 weight% aluminum, and 0 to about 20 weight% nickel. Examples of metal substrates include those having straight channels, those having blades protruding along the axial channels to obstruct the gas flow and open the communication of the gas flow between the channels, and those having holes for improving the gas transport between the channels to enable radial gas transport across the blades and the monolith as a whole. In particular, the metal substrate is advantageously used in a closely bonded position in certain embodiments, thereby enabling rapid heating of the substrate and, correspondingly, rapid heating of the catalyst composition coated therein.

[0079] Any suitable substrate for the catalyst articles disclosed herein can be used, such as a type of monolithic substrate ("flow-through substrate") having fine parallel gas flow channels extending through from the end face of the inlet or outlet of the substrate so as to be open to the flowing fluid stream. Another suitable substrate is of the type having a plurality of fine substantially parallel gas flow channels extending along the longitudinal axis of the substrate, typically with each channel blocked at one end of the substrate body and every other channel blocked at the opposite end face ("wall-flow filter"). Flow-through substrates and wall-flow substrates are also taught, for example, in US2017 / 0333883 to Mohanan et al., which is hereby incorporated by reference in its entirety.

[0080] Flow-through substrate In some embodiments, the substrate is a flow-through substrate (e.g., a monolithic flow-through substrate including a monolithic flow-through honeycomb substrate). The flow-through substrate has fine and parallel gas flow channels extending from an inlet end of the substrate to an outlet end such that the channels are open to the flow of fluid. The channels, which are essentially straight paths from a fluid inlet to a fluid outlet, are defined by walls on which a catalyst coating is disposed so that the gas flowing through the channels contacts the catalyst material. The flow channels of the flow-through substrate are thin-walled channels and can have any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. The flow-through substrate can be ceramic or metal as described above.

[0081] The flow-through substrate is, for example, about 50 in 3 ~ about 1200 in 3 in volume, and has a cell density (inlet opening) of about 60 cells per square inch (cpsi) to about 500 cpsi or up to 900 cpsi, for example, about 200 to about 400 cpsi, and a wall thickness of about 50 to about 200 microns or about 400 microns.

[0082] Figures 1A and 1B illustrate an exemplary substrate 2 in the form of a through-flow substrate coated with a coating composition as described herein. Referring to FIG. 1A, the exemplary substrate 2 has a cylindrical shape and a cylindrical outer surface 4, an upstream end face 6, and a corresponding downstream end face 8 that is identical to the end face 6. The substrate 2 has a plurality of fine and parallel gas flow paths 10 formed therein. As seen in FIG. 1B, the flow paths 10 are formed by walls 12 and extend through the carrier 2 from the upstream end face 6 to the downstream end face 8, and the passages 10 are not blocked so as to allow a fluid, e.g., a gas flow, to flow longitudinally through the carrier 2 via its gas flow paths 10. As more readily seen in FIG. 1B, the walls 12 are sized and configured such that the gas flow paths 10 have a substantially regular polygonal shape. As shown, the coating composition can be applied in a plurality of distinct layers if desired. In the illustrated embodiment, the coating composition consists of both a separate bottom layer 14 (e.g., an LT-NA composition) adhered to the wall 12 of the carrier member, and a second separate top layer 16 (e.g., a DOC composition) coated above the bottom layer 14. The present invention can be implemented to comprise one or more (e.g., two, three, or four or more) composition layers and is not limited to the two-layer embodiment illustrated in FIG. 1B. Further coating configurations are disclosed herein below.

[0083] Wall flow filter substrate In some embodiments, the substrate is a wall flow filter, which generally has a plurality of fine and substantially parallel gas flow paths extending along the longitudinal axis of the substrate. Typically, each passage is blocked at one end of the substrate body, and every other passage is blocked at the opposite end face. Such a monolithic wall flow filter substrate may contain up to about 900 or more flow paths (or "cells") per square inch of cross-section, although far fewer numbers may be used. For example, the substrate can have from about 7 to 600, more typically from about 100 to 400 cells per square inch ("cpsi"). The cells can have a rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal cross-section.

[0084] A cross-sectional view of the monolithic wall flow filter substrate portion is illustrated in FIG. 2, which shows alternately blocked and open passages (cells). The blocked or closed ends 100 and the open passages 101 are alternately positioned, with the opposite ends of each being open and blocked, respectively. The filter has an inlet end 102 and an outlet end 103. The arrow across the porous cell wall 104 represents that the exhaust gas flow enters the open cell end, diffuses through the porous cell wall 104, and exits from the open outlet cell end. The blocked end 100 impedes the gas flow and promotes diffusion through the cell wall. Each cell wall has an inlet side 104a and an outlet side 104b. The passages are surrounded by the cell walls.

[0085] The wall flow filter article substrate can have a volume of, for example, about 50 cm 3 , about 100 cm 3 , about 200 cm 3 , about 300 cm 3 , about 400 cm 3 , about 500 cm 3 , about 600 cm 3 , about 700 cm 3 , about 800 cm 3 , about 900 cm 3 , or about 1000 cm 3 to about 1500 cm 3 , about 2000 cm 3 , about 2500 cm 3 , about 3000 cm 3 , about 3500 cm 3 , about 4000 cm 3 , about 4500 cm 3 , or about 5000 cm 3 . The wall flow filter substrate typically has a wall thickness of about 50 microns to about 2000 microns, for example, about 50 microns to about 450 microns, or about 150 microns to about 400 microns.

[0086] The walls of the wall flow filter are porous and generally have a wall porosity of at least about 50% or at least about 60% before disposing a functional coating thereon, and an average pore diameter of at least about 5 microns. For example, the wall flow filter article substrates in some embodiments will have a porosity of ≧50%, ≧60%, ≧65%, or ≧70%. For example, the wall flow filter article substrate has a wall porosity from about 50%, about 60%, about 65% or about 70% to about 75%, about 80% or about 85% and an average pore diameter from about 5 microns, about 10, about 20, about 30, about 40 or about 50 microns to about 60 microns, about 70, about 80, about 90 or about 100 microns before disposing a catalyst coating thereon. The terms “wall porosity” and “substrate porosity” have the same meaning and are interchangeable. Porosity is the ratio of the void volume divided by the total volume of the substrate. The pore diameter may be determined according to the ISO15901-2 (static volume) procedure for nitrogen pore diameter analysis. The nitrogen pore diameter may be determined on a Micromeritics TRISTAR 3000 series instrument. The nitrogen pore diameter may be determined using BJH (Barrett-Joyner-Halenda) calculations and 33 desorption points. Useful wall flow filters have a high porosity and allow for a high loading of the catalyst composition without imposing excessive backpressure during operation.

[0087] Coating LT-NA and DOC compositions as disclosed herein are coated on a substrate such as the substrates referred to herein. The coating may include one or more thin adherent coating layers disposed on and adhered to at least a portion of the substrate. The coating may be on the substrate wall surface and / or within the pores of the substrate wall, i.e., “in” and / or “on” the substrate wall. Thus, the expression “coating disposed on a substrate” means on any surface, e.g., on the wall surface and / or on the pore surface.

[0088] The LT-NA and DOC compositions are typically applied in the form of a washcoat. The washcoat is formed by preparing a slurry containing a specific solids content (e.g., about 10 to about 60% by weight) in a liquid vehicle, then applying this to a substrate and drying and firing it to provide a coating layer. When multiple coating layers are applied, typically the substrate is dried and fired after each layer is applied and / or after the desired multiple layers are applied.

[0089] The washcoat slurry may optionally contain a binder (e.g., alumina, silica), a water-soluble or water-dispersible stabilizer, an accelerator, an associative thickener, and / or a surfactant (including anionic, cationic, non-ionic, or amphoteric surfactants). For example, the washcoat may contain a ZrO2 binder derived from a suitable precursor such as zirconyl acetate or any other suitable zirconium precursor such as zirconyl nitrate. The zirconyl acetate binder provides a homogeneous and intact coating after thermal aging. Other potentially suitable binders include, but are not limited to, alumina and silica. Examples of alumina binders include aluminum oxide, aluminum hydroxide, and aluminum oxyhydroxide. Aluminum salts, and colloidal forms of alumina may be used. The silica binder includes various forms of SiO2, including silicates and colloidal silica. The binder composition may include any combination of zirconia, alumina, and silica. When present, the binder is typically used in an amount of about 1 to 5% by weight of the total washcoat loading.

[0090] Optionally, as described above, the slurry containing the DOC composition may contain one or more hydrocarbon (HC) storage components for adsorbing hydrocarbons (HC). Any known hydrocarbon storage material can be used, such as a microporous material like zeolite or zeolite-like material. Preferably, the hydrocarbon storage material is zeolite. Zeolite can be a natural or synthetic zeolite such as faujasite, chabasite, clinoptilolite, mordenite, silicalite, zeolite X, zeolite Y, ultrastable zeolite Y, ZSM-5 zeolite, offretite, or beta zeolite. Preferred zeolite adsorbent materials have a high silica to alumina ratio. Zeolite can have a silica / alumina molar ratio of at least about 25:1, preferably at least about 50:1, and useful ranges are about 25:1 to 1000:1, 50:1 to 500:1, and about 25:1 to 300:1. Preferred zeolites include ZSM-5, Y, and beta zeolite. Particularly preferred adsorbents can include beta zeolite of the type disclosed in U.S. Patent No. 6,171,556, which is hereby incorporated by reference in its entirety. When present, the zeolite or other HC storage component is typically in an amount of about 0.05 g / in 3 ~ about 1 g / in 3 .

[0091] The typical pH range of the slurry is from about 3 to about 6. Acidic or basic species may be added to the slurry to adjust the pH thereby. For example, in some embodiments, the pH of the slurry is adjusted by the addition of aqueous ammonium hydroxide or nitric acid.

[0092] The slurry can be pulverized to improve the mixing of particles and the formation of a homogeneous material. The pulverization can be achieved with a ball mill, a continuous mill, or other similar devices, and the solids content of the slurry can be, for example, about 20 to 60 wt%, more specifically, about 20 to 40 wt%. In one embodiment, the pulverized slurry is characterized by a D90 particle size of about 10 to about 40 microns, preferably 10 to about 30 microns, more preferably about 10 to about 15 microns.

[0093] Subsequently, any washcoat technology known in the art is used to coat the slurry onto a substrate. In one embodiment, the substrate is immersed one or more times in the slurry or otherwise coated with the slurry. Thereafter, the coated substrate is dried at a high temperature (e.g., 100 to 150 °C) for a certain period (e.g., 10 minutes to 3 hours) and then fired by heating, for example, at 400 to 600 °C typically for about 10 minutes to about 3 hours. After drying and firing, the final washcoat coating layer can be considered to be substantially free of solvent.

[0094] After firing, the washcoat loading obtained by the above washcoat technology can be determined by calculating the difference between the coated weight and the uncoated weight of the substrate. As will be apparent to those skilled in the art, the loading can be adjusted by changing the rheology of the slurry. Further, the coating / drying / firing process for producing the washcoat can be repeated as necessary to build up the coating to the desired loading level or thickness, i.e., more than one washcoat may be applied.

[0095] The wash coat can be applied such that different coating layers are in direct contact with the substrate. Alternatively, one or more "undercoats" may be present such that the catalyst or adsorbent coating layer or at least a portion of the coating layer is not in direct contact with the substrate (rather, it contacts the undercoat). One or more "overcoats" may be present such that at least a portion of the coating layer is not directly exposed to the gas flow or atmosphere (rather, it contacts the overcoat).

[0096] The different coating layers may be in direct contact with each other. Alternatively, the different coating layers may not be in direct contact with each other. The various coating layers can be regarded as undercoats, overcoats, or intermediate layers. The undercoat is the layer "below" the coating layer, the overcoat is the layer "above" the coating layer, and the intermediate layer is the layer "between" two coating layers. The intermediate layer, undercoat, and overcoat may or may not contain one or more functional compositions.

[0097] The various coatings (e.g., DOC coating and LT-NA coating) may advantageously be "zoned" and include zoned layers. This may be expressed as "laterally zoned". For example, the layer may extend from the inlet end to the outlet end and may extend over about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the substrate length. Another layer may extend from the outlet end to the inlet end and may extend over about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the substrate length. The different coating layers may be adjacent to each other and may not overlap each other. Alternatively, the different layers may overlap a portion of each other to provide a third "intermediate" zone. The intermediate zone may extend, for example, over about 5% to about 80% of the substrate length, for example, about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, or about 70% of the substrate length.

[0098] Figures 3A - 3E show some possible coating layer configurations having two coating materials (however, the present disclosure is not limited thereto). A monolithic substrate wall 200 extending from an inlet 102 to an outlet 103 is shown, on which coating layers 201 and 202 are disposed. This is a simplified diagram, and in the case of a porous wall flow-through substrate, pores and coatings adhering to the pore walls are not shown, and blocked ends are not shown.

[0099] Figure 3A illustrates a layered configuration in which both coating layer 201 (for example, a coating layer containing an LT-NA composition) and coating layer 202 (for example, a DOC coating layer) extend along the entire length of the substrate 200.

[0100] Figure 3B is the same as Figure 3A except that the top layer is zone-coated in the upstream zone 202a and the downstream zone 202b. This configuration can be used, for example, when layer 201 contains an LT-NA composition and the downstream zone 202b is a DOC composition containing a platinum and manganese-containing carrier. The upstream zone 202b can be a second DOC composition containing a refractory metal oxide carrier and one or more PGM components but not a manganese-containing carrier.

[0101] Figure 3C illustrates a zoned coating configuration in which coating layer 201 (for example, a coating layer containing an LT-NA composition) extends from the inlet 102 over a part of the substrate length, and coating layer 202 (for example, a DOC coating layer) extends from the outlet 103 over a part of the substrate length, with the coating layers adjacent to each other, thereby providing an inlet upstream zone 203 and an outlet downstream zone 204. Figure 3D is the same as Figure 3C except that coating layer 202 overlaps coating layer 201, thereby creating an intermediate overlapping zone.

[0102] In FIG. 3E, the coating layer 202 (e.g., DOC coating layer) extends from the outlet over a portion of the substrate length, and the layer 201 (e.g., coating layer containing LT-NA composition) extends over the entire length of the substrate 200.

[0103] In some embodiments, the LT-NA and the oxidation catalyst are disposed on the substrate in a zoned configuration (i.e., on the same substrate), the substrate has an inlet end and an outlet end defining the entire length, the LT-NA extends from the inlet end over a length of about 20% to about 100% of the entire length and is disposed on the substrate, and the oxidation catalyst extends from the outlet end over a length of about 20% to about 100% of the entire length and is disposed on the substrate.

[0104] In some embodiments, the LT-NA coating layer is disposed directly on the substrate, and the oxidation catalyst coating layer is disposed directly on the substrate (i.e., there is no overlap between the two coating layers). In some embodiments, the oxidation catalyst coating layer partially overlaps the LT-NA coating layer. In certain embodiments, the LT-NA layer extends from the inlet end over a length of about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, or about 80% of the entire length and is disposed on the substrate, and the oxidation catalyst coating layer extends from the outlet end over a length of about 20%, about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, or about 80% of the entire length and is disposed on the substrate. In some embodiments, the LT-NA is disposed directly on the substrate covering 100% of the entire length, and the oxidation catalyst is disposed on the LT-NA covering about 20% to about 80% of the entire length.

[0105] Exhaust gas treatment system In another aspect of the present disclosure, an emission treatment system for treating exhaust gas emissions from a diesel engine or a lean-burn gasoline engine is provided, the emission treatment system including the LT-NA and DOC components disclosed herein. The emission treatment system may further include one or more additional catalyst components, such as a selective catalytic reduction (SCR) catalyst component. Examples of additional components include a soot filter (which may be catalyzed or uncatalyzed), an ammonia or ammonia precursor injection component, an ammonia oxidation catalyst (AMOX), and combinations thereof. The relative locations of the various components of the emission treatment system can be varied, but the LT-NA and DOC components of the present disclosure should be located upstream of any SCR catalyst components.

[0106] SCR components suitable for use in emissions treatment systems are capable of producing NO at temperatures as high as 650°C. x Advantageously, the SCR component can effectively catalyze the reduction of exhaust components by reducing NO x At least 50% of the (e.g., NO) components can be converted to N2. Another desirable property of an SCR component is the ability to catalyze the reaction of O2 with any excess NH3 to form N2, so that NH3 is not released to the atmosphere. Useful SCR components for use in emissions treatment systems should also be thermally resistant to temperatures above 650°C. Such high temperatures may be encountered during regeneration of catalyzed soot filters. Suitable SCR catalyst components are described, for example, in U.S. Pat. Nos. 4,961,917 and 5,516,497, both of which are incorporated herein by reference in their entirety. Exemplary SCR catalysts are iron- or copper-containing zeolites, such as Fe-CHA or Cu-CHA.

[0107] The exhaust treatment system can use a soot filter to remove particulate matter. The soot filter can be located upstream or downstream of the DOC, but typically, the soot filter will be located downstream of the DOC. In some embodiments, the soot filter is a catalyzed soot filter (CSF). The CSF can include a substrate coated with washcoat particles containing one or more catalysts for burning the captured soot and / or oxidizing the emissions of the exhaust gas stream. Generally, the soot combustion catalyst can be any known catalyst for soot combustion. For example, the CSF can be coated with one or more high surface area refractory oxides (e.g., aluminum oxide or ceria-zirconia) to burn CO and unburned hydrocarbons and to some extent particulate matter. The soot combustion catalyst can be an oxidation catalyst containing one or more noble metal catalysts (e.g., platinum and / or palladium).

[0108] One exemplary exhaust treatment system is illustrated in FIG. 4, which shows a schematic of a non-limiting exhaust gas treatment system according to an embodiment of the present disclosure. As shown, the exhaust treatment system 20 can include a plurality of catalyst components in series downstream of an engine 22, such as a lean burn gasoline engine or a diesel engine. At least one (or two if located on a separate substrate) of the catalyst components will include a DOC catalyst and an LT-NA composition as described herein. FIG. 4 illustrates five catalyst components 24, 26, 28, 30, 32 in series, but the total number of catalyst components can vary and the five components are merely an example.

[0109] Without limitation, Table 1 presents various exhaust gas treatment system configurations of one or more embodiments. Note that each catalyst is connected to the next catalyst via an exhaust duct such that the engine is upstream of catalyst A, which is upstream of catalyst B, which is upstream of catalyst C, which is upstream of catalyst D, which is upstream of catalyst E (if present). References to components A - E in the table can be cross-referenced with the same symbols in FIG. 4.

[0110] References to DOC or LT-NA refer to the DOC or LT-NA described herein, and DOC / LT-NA refers to a DOC composition and an LT-NA composition on the same substrate. References to SCR in the table refer to an SCR catalyst. References to SCRoF (or SCR on filter) refer to a particulate filter or soot filter (e.g., a wall flow filter) with an SCR catalyst coated thereon. References to AMOx in the table refer to an ammonia oxidation catalyst that may be provided downstream of the SCR to remove any leaked ammonia from the exhaust gas treatment system. As will be recognized by those skilled in the art, in the configurations listed in Table 1, any one or more of components A, B, C, D, or E can be disposed on a particulate filter such as a wall flow filter or on a flow-through honeycomb substrate. In one or more embodiments, the engine exhaust system includes one or more catalyst compositions attached at a location near the engine (a direct connection location, CC), and additional catalyst compositions are at a location under the vehicle body (an underfloor location, UF). In one or more embodiments, the exhaust gas treatment system may further include an ammonia or ammonia precursor injection component that is typically disposed upstream of any SCR catalyst present within the system.

Table 1

[0111] Method for treating an exhaust stream In another aspect, a method is provided for treating a gaseous exhaust stream flowing from an exhaust manifold of a diesel engine or a lean burn gasoline engine, the gaseous exhaust stream comprising a mixture of nitrogen oxides (NO x ), as well as hydrocarbons and carbon monoxide. Specifically, the method includes contacting the gaseous exhaust stream with a low temperature NO x adsorbent (LT-NA) component and an oxidation catalyst component as disclosed herein, which are disposed downstream of the exhaust manifold and in fluid communication therewith.

[0112] In some embodiments, the LT-NA component is effective in releasing one or both of NO and NO2 at temperatures above about 300°C. In some embodiments, the LT-NA component is effective in releasing one or both of NO and NO2 at temperatures above about 325°C. In some embodiments, the oxidation catalyst composition of the present invention is effective in oxidizing hydrocarbons and carbon monoxide in the exhaust stream and simultaneously converting NO, including NO released from LT-NA, to NO2. The two compositions act together in an integrated form and adsorb NO at low temperatures x to improve the downstream SCR catalyst performance by producing a higher NO2 to NOx ratio.

[0113] The present compositions, components, systems, and methods are suitable for treating exhaust gas streams from mobile emission sources such as trucks and automobiles. The present compositions, components, systems, and methods are also suitable for treating exhaust gas streams from stationary sources such as power plants.

[0114] It will be readily apparent to those of ordinary skill in the relevant art that suitable modifications and adaptations to the compositions, methods, and uses described herein can be made without departing from the scope of any embodiment or aspects thereof. The compositions and methods provided are exemplary and are not intended to limit the scope of the claimed embodiments. All of the various embodiments, aspects, and alternatives disclosed herein can be combined in all variations. The scope of the compositions, formulations, methods, and processes described herein includes all actual or potential combinations of all of the embodiments, aspects, alternatives, examples, and preferences herein. All patents and publications cited herein are incorporated herein by reference for their specific teachings as described, unless a specific incorporation of other descriptions is specifically provided.

Examples

[0115] The present invention will be illustrated in more detail by the following examples which are shown for the purpose of exemplifying the present invention and should not be construed as limiting the present invention. Unless otherwise specified, all parts and percentages are by weight, and all weight percentages are expressed on a dry basis, that is, the water content is excluded unless otherwise indicated.

[0116] Example 1 A cordierite honeycomb substrate (total volume 1.85 L) was coated with a bottom coat of H-FER (ferrierite) zeolite impregnated with palladium and fired at 590 °C in air. The concentration of palladium was 60 g / ft 3 and the total washcoat loading was 2.85 g / in 3 . An alumina binder layer was coated thereon (0.7 g / in 3 ).

[0117] An alumina support material containing 5 wt% Mn was impregnated with platinum and palladium (weight ratio 9:1) using the incipient wetness technique. A top coat containing this material was applied to the substrate, and the washcoat contained Fe-beta and barium promoter. The top coat contained 72 g / ft 3 of platinum and 8 g / ft 3 of palladium. The total washcoat loading was 1.95 g / in 3 . This substrate is hereinafter referred to as substrate A.

[0118] A second cordierite honeycomb substrate (total volume 1.85 L) was coated with a bottom coat in the same manner as substrate A above, except that the palladium loading was 80 g / ft 3 and the total washcoat loading was 3 g / in 3 . Further, the bottom coat contained a zirconia binder.

[0119] A conventional oxidation catalyst composition (total washcoat loading of 1.0 g / in 3 on silica-stabilized alumina at 37 g / ft 3of platinum and 3.7 g / ft 3 An inlet zone (50% of the length) containing palladium) and platinum (1.1 g / in impregnated on an alumina support material containing 5 wt% Mn 3 With a total washcoat loading of 80 g / ft 3 Platinum loading) of the outlet zone (50% of the length), and a topcoat was applied to the second substrate having. Both zones contained Fe-beta as a hydrocarbon adsorbent. This substrate will be referred to hereinafter as substrate B.

[0120] Substrate A and substrate B, and a comparative substrate coated only with the bottom coat of substrate A (designated as Comparative A) were aged at 800 °C in 10% steam / air and then tested for a diesel engine in the Worldwide harmonized Light vehicle Test Cycle (WLTC). The test was carried out using an SCR catalyst article containing copper-impregnated chabazite downstream of the above substrates. Figure 5 shows the test results, where the solid line corresponds to the NO x Measurement (labeled "post NA-DOC" in the figure caption), and the dotted line corresponds to the NOx measurement after the downstream SCR (labeled "post SCRoF" in the figure caption). All formulations adsorb most of the NO x In the exhaust from the engine up to about 800 seconds. However, after about 800 seconds, NO x Begins to be released from the formulations containing the DOC top layer (substrates A and B), while the formulations without the DOC top layer (Comparative A) continue to adsorb NOx for about 100 seconds and then desorption also begins.

[0121] In the presence of DOC, NO from Pd / FER xDesorption seems to be accelerated. It should be noted that when desorption starts, there is little difference between the solid line and the dotted line for each formulation. This indicates that the downstream SCR has not reached a temperature high enough to function. However, soon after, the dotted line begins to branch off from the solid line and flatten out, while the solid line continues to increase. This indicates that the SCR catalyst is becoming active for NO x removal.

[0122] Furthermore, the formulation containing the DOC top layer starts to desorb NO x earlier by itself than Pd / FER, but the downstream SCR becomes more active for NO x removal when Pt-Pd / Mn-Al2O3 DOC is present. By the end of the test, the NO x emission is significantly lower compared to the formulation containing only Pd / FER. The reason for this improvement in NO x reduction performance is that NO2 formation is improved in the formulation containing Pt-Pd / Mn-Al2O3 DOC. As illustrated in Figure 6, the NO2 formation in Pd / FER (Comparison A) after 800 seconds is substantially zero, while the NO2 formation in the formulations containing Pt-Pd / Mn-Al2O3 DOC (Substrates A and B) is high, and the ratio of NO2 to NO x reaches 0.7.

[0123] Further insights from this experiment are related to the structure or design of the DOC top layer. When the DOC layer containing Mn is coated over the entire length of the coated monolith, NO2 formation is lower than when the DOC layer containing Mn is coated only on the second half of the monolith (i.e., rear zone coating). Referring again to FIGS. 5 and 6 for substrate A, the DOC top layer extends over the entire length of the catalytic monolith. In the case of substrate B, two different DOC formulations are coated on top of the Pd / FER layer, but each is coated only on half of the monolith length (i.e., zoned DOC top layer). The front zone contains Pt-Pd / Si-Al2O3 and Fe-beta zeolite, and the rear zone contains Pt-Pd / Mn-Al2O3 and Fe-beta zeolite. Compared to substrate A, NO2 formation in the WLTC is higher for the zoned formulation. The improvement in NO2 formation is due to the concentration of the Pt-Pd / Mn-Al2O3 DOC component in the rear zone, despite the overall lower Pt-Pd loading in the top layer of substrate B vs substrate A (60 vs 80 g / ft 3 ). The higher NO2 formation is directly interpreted as better performance after downstream SCR.

[0124] Example 2 The amount of Pt associated with the Mn-Al2O3 support in the top DOC layer also plays an important role. To illustrate this point, two additional coated substrates were prepared. The substrates were prepared in substantially the same manner as substrate B above and designated as substrate C in this example. Similar to substrate C, but increasing the amount of palladium in the bottom coat (120 g / ft 3 vs 80 g / ft 3 ) and decreasing the amount of platinum in the rear zone of the top coat (40 g / ft 3 vs 80 g / ft 3 ), a further substrate was prepared and designated as substrate D. These substrates were aged and tested as described in Example 1.

[0125] The results are shown in FIGS. 7 and 8. FIG. 7 plots the total NO destruction performance over the WLTC test cycle in a diesel engine for substrates C and D. The solid line corresponds to the NO measurement after the test substrate, and the dotted line corresponds to the NO measurement after the downstream SCR. Both test substrates adsorb most of the NO in the exhaust from the engine until about 800 seconds, and then start to release NO after 800 seconds. However, in the case of substrate D with 120 g / ft of Pd in the zeolite bottom coat, the release of NO is slower than in the case of substrate C with 80 g / ft of Pd in the zeolite bottom coat. The higher Pd loading in substrate D allows for more efficient storage of NO, resulting in lower NO emissions until 1500 seconds. Note that at the start of NO desorption at about 800 seconds, there is little difference between the solid and dotted lines for each formulation. This indicates that the downstream SCR has not reached a temperature high enough to function. However, shortly thereafter, the dotted line begins to diverge from and flatten out while the solid line continues to increase. This indicates that the SCR catalyst is becoming active for NO removal. x The solid line corresponds to the NO measurement after the test substrate, and the dotted line corresponds to the NO measurement after the downstream SCR. x The solid line corresponds to the NO measurement after the test substrate, and the dotted line corresponds to the NO measurement after the downstream SCR. x Both test substrates adsorb most of the NO in the exhaust from the engine until about 800 seconds, and then start to release NO after 800 seconds. x Both test substrates adsorb most of the NO in the exhaust from the engine until about 800 seconds, and then start to release NO after 800 seconds. x However, in the case of substrate D with 120 g / ft of Pd in the zeolite bottom coat, the release of NO is slower than in the case of substrate C with 80 g / ft of Pd in the zeolite bottom coat. 3 However, in the case of substrate D with 120 g / ft of Pd in the zeolite bottom coat, the release of NO is slower than in the case of substrate C with 80 g / ft of Pd in the zeolite bottom coat. x The higher Pd loading in substrate D allows for more efficient storage of NO, resulting in lower NO emissions until 1500 seconds. 3 The higher Pd loading in substrate D allows for more efficient storage of NO, resulting in lower NO emissions until 1500 seconds. x The higher Pd loading in substrate D allows for more efficient storage of NO, resulting in lower NO emissions until 1500 seconds. x Note that at the start of NO desorption at about 800 seconds, there is little difference between the solid and dotted lines for each formulation. x Note that at the start of NO desorption at about 800 seconds, there is little difference between the solid and dotted lines for each formulation. x This indicates that the downstream SCR has not reached a temperature high enough to function.

[0126] Furthermore, formulations with less Pd in the zeolite bottom coat desorb NO earlier than formulations with more Pd in the zeolite bottom coat, but in the former case, the downstream SCR becomes more active for NO removal. x Furthermore, formulations with less Pd in the zeolite bottom coat desorb NO earlier than formulations with more Pd in the zeolite bottom coat, but in the former case, the downstream SCR becomes more active for NO removal. x By the end of the test, the NO emissions are significantly lower for the formulations containing more Pd in the zeolite bottom coat. x By the end of the test, the NO emissions are significantly lower for the formulations containing more Pd in the zeolite bottom coat. xThe reason for this improvement in the reduction performance is that NO2 formation is improved in substrate C having twice the amount of Pt in the rear zone of the DOC top layer. As illustrated in Figure 8, the NO2 formation in substrate C after 800 seconds is higher than that in the case of substrate D.

[0127] Example 3 A further aspect of the present invention relates to the source or form of Pt used in combination with Mn-Al2O3 in the DOC layer. To explain this point, two additional coated substrates were prepared. A bottom coat of an alumina support material containing 5 wt% Si on alumina was coated on a cordierite honeycomb substrate (total volume 1.85 L) by sequentially impregnating with Pd nitrate followed by a water-soluble Pt complex (MEA-stabilized Pt(OH)6) using the incipient wetness technique. The bottom coat contained 29.5 g / ft 3 of platinum and 20.5 g / ft 3 of palladium and also contained a Ba promoter. The total washcoat loading was 1.65 g / in 3 Another alumina support containing a physical mixture of 5 wt% Mn on alumina and 5 wt% Si on alumina was similarly impregnated with platinum and palladium using the incipient wetness technique. A top coat containing this material was applied to the substrate, and the washcoat also contained an Fe-beta and a Ba promoter. The top coat contained 38 g / ft 3 of platinum and 2 g / ft 3 of palladium. The total washcoat loading was 1.42 g / in 3 This substrate is hereinafter referred to as substrate E.

[0128] A bottom coat and a top coat were coated on a second cordierite honeycomb substrate (total volume 1.85 L) in the same manner as substrate E above, except that a colloidal Pt precursor containing Pt metal particles with a size of less than 5 nm was used instead of the water-soluble Pt precursor. This substrate is hereinafter referred to as substrate F.

[0129] As shown in Fig. 9, the NO oxidation performance measured in the tail pipe of a diesel engine over the EUDC portion of the NEDC test cycle is lower for substrate E using a water-soluble Pt complex than for substrate F using a colloidal Pt precursor containing Pt metal particles with a size of less than 5 nm.

Claims

1. Oxidation of hydrocarbons and carbon monoxide, and reduction of NO in the exhaust stream of a lean burn engine, an emissions treatment system for ｘ which the emissions treatment system comprises A low-temperature NO adsorbent (LT-NA) comprising a molecular sieve impregnated with at least one PGM component positioned to be in fluid communication with the exhaust stream ｘ and, An oxidation catalyst comprising a platinum-impregnated manganese-containing refractory metal oxide support positioned in fluid communication with the exhaust stream, and the LT-NA and the oxidation catalyst are each disposed on a substrate, the LT-NA and the oxidation catalyst are configured to be zoned on the same substrate, the LT-NA is in an upstream zone, and the oxidation catalyst is in a downstream zone, the manganese content of the refractory metal oxide support is in the range of 3 to 10% by weight based on the total weight of the support, and the refractory metal oxide support further contains palladium, and the weight ratio of platinum to palladium is 5:1 or more, An exhaust treatment system.

2. the LT-NA and the oxidation catalyst are disposed on the same substrate in a zoned configuration, the substrate having an inlet end and an outlet end defining an overall length, the LT-NA extends from the inlet end over a length of about 20% to about 100% of the overall length and is disposed on the substrate, the oxidation catalyst extends from the outlet end over a length of about 20% to about 100% of the overall length and is disposed on the substrate, and the oxidation catalyst optionally overlaps at least a portion of the LT-NA, the exhaust treatment system according to claim 1.

3. the LT-NA extends from the inlet end over a length of about 40% to about 100% of the overall length and is disposed on the substrate, and the oxidation catalyst extends from the outlet end over a length of about 40% to about 100% of the overall length and is disposed on the substrate, the exhaust treatment system according to claim 2.

4. the oxidation catalyst is zone-coated with a second oxidation catalyst comprising a refractory metal oxide support impregnated with one or more platinum group metal (PGM) components, the second oxidation catalyst being substantially manganese-free and positioned upstream of the oxidation catalyst, the exhaust treatment system according to claim 2.

5. The exhaust treatment system according to claim 1, further comprising at least one selective catalytic reduction (SCR) catalyst positioned downstream of both the LT-NA and the oxidation catalyst.

6. One or more of the following: an ammonia or ammonia precursor injection component, a catalyzed soot filter (CSF), and an ammonia oxidation (AMOX) catalyst, the exhaust treatment system according to any one of claims 1-5.

7. The exhaust gas treatment system according to any one of claims 1 to 5, wherein both the LT-NA and the oxidation catalyst are disposed on a flow-through substrate in the form of a honeycomb having a plurality of longitudinally extending gas flow paths extending from an inlet to an outlet.

8. The molecular sieve has a framework type selected from the group consisting of 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, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, CHI, CLO, CON, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, EZT, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFR, IFY, IHW, IMF, IRN, ISV, ITE, ITG, ITH, ITW, IWR, IWS, IWV, IWW, JBW, JRY, JSR, JST, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LTF, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, MRE, MSE, MSO, MTF, MTN, MTT, MVY, MTW, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, PAR, PAU, PCR, PHI, PON, PUN, RHO, RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBS, SBT, SCO, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, SFW, SGF, SGT, SIV, SOD, SOF, SOS, SSF, SSY, STF, STI, STO, STT, STW, SVR, SZR, TER, THO, TON, TSC, TUN, UEI, UFI, UOS, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WIE, WEN, YUG, ZON, and mixtures or twins thereof, and the exhaust gas treatment system according to any one of claims 1 to 5.

9. The molecular sieve has a framework type selected from the group consisting of LEV, CHA, and FER, and the exhaust gas treatment system according to any one of claims 1 to 5.

10. The exhaust gas treatment system according to any one of claims 1 to 5, wherein the molecular sieve is an aluminosilicate zeolite.

11. The exhaust gas treatment system according to any one of claims 1 to 5, wherein the molecular sieve contains channels defined by at least 10-membered rings.

12. The exhaust gas treatment system according to any one of claims 1 to 5, wherein the oxidation catalyst further contains palladium, rhodium, or a combination thereof.

13. The exhaust gas treatment system according to any one of claims 1 to 5, wherein the LT-NA contains palladium as the only PGM component.

14. The oxidation catalyst contains platinum in an amount in the range of about 10 g / ft ３ to 100 g / ft ３ on the manganese-containing refractory metal oxide support, and the exhaust gas treatment system according to any one of claims 1 to 5.

15. The oxidation catalyst is at least about 40 g / ft impregnated on the manganese-containing refractory metal oxide support ３ The exhaust gas treatment system according to any one of claims 1 to 5, comprising platinum.

16. The exhaust gas treatment system according to any one of claims 1 to 5, wherein the refractory metal oxide carrier contains alumina, silica, zirconia, titania, ceria, or a combination thereof.

17. The exhaust gas treatment system according to any one of claims 1 to 5, wherein the manganese exists in a form selected from the group consisting of an Mn-containing solid solution having the refractory metal oxide, Mn surface-dispersed on the refractory metal oxide by impregnation, and discrete manganese oxide particles on the particles of the refractory metal oxide.

18. The exhaust gas treatment system according to any one of claims 1 to 5, wherein the platinum impregnated on the manganese-containing refractory metal oxide carrier is in the form of nanoparticles having an average particle size of about 1 to about 10 nm.

19. A method for oxidizing hydrocarbons and reducing NO in an exhaust stream from a lean burn engine, the method comprising contacting the exhaust gas stream with an emissions treatment system according to any one of claims 1 to 18. ｘ A method, wherein the method comprises contacting the exhaust gas stream with an emissions treatment system according to any one of claims 1 to 18.

20. A catalyst article for treating exhaust gas from a lean burn engine, a substrate having an inlet end and an outlet end defining an overall length, A low-temperature NO adsorbent (LT-NA) comprising a molecular sieve impregnated with at least one PGM component disposed on the substrate ｘ and, and an oxidation catalyst including a manganese-containing refractory metal oxide carrier impregnated with platinum, disposed on the substrate, wherein the LT-NA and the oxidation catalyst are configured to be zonated on the same substrate, the LT-NA is in an upstream zone, and the oxidation catalyst is in a downstream zone, the manganese content of the refractory metal oxide carrier is in the range of 3 to 10% by weight based on the total weight of the carrier, and the refractory metal oxide carrier further contains palladium, and the weight ratio of platinum to palladium is 5:1 or more. Catalyst article.

21. The LT-NA and the oxidation catalyst are disposed on the substrate in a zoned configuration, and the substrate has an inlet end and an outlet end defining an overall length. The LT-NA extends from the inlet end to a length of about 20% to about 100% of the total length and is disposed on the substrate. The oxidation catalyst extends from the outlet end to a length of about 20% to about 100% of the total length and is disposed on the substrate, and the oxidation catalyst optionally overlaps at least a part of the LT-NA. The catalyst article according to claim 20.

22. The LT-NA extends from the inlet end to a length of about 40% to about 100% of the total length and is disposed on the substrate, and the oxidation catalyst extends from the outlet end to a length of about 40% to about 100% of the total length and is disposed on the substrate. The catalyst article according to claim 21.

23. The oxidation catalyst is zone-coated with a second oxidation catalyst comprising a refractory metal oxide support impregnated with one or more platinum group metal (PGM) components, and the second oxidation catalyst substantially does not contain manganese and is located upstream of the oxidation catalyst. The catalyst article according to claim 20.

24. The molecular sieve has a framework type selected from the group consisting of LEV, CHA, and FER. The catalyst article according to any one of claims 20 to 23.

25. The molecular sieve is an aluminosilicate zeolite. The catalyst article according to any one of claims 20 to 23.

26. The oxidation catalyst further comprises palladium, rhodium, or a combination thereof. The catalyst article according to any one of claims 20 to 23.

27. The LT-NA contains palladium as the only PGM component. The catalyst article according to any one of claims 20 to 23.

28. The oxidation catalyst is impregnated on the manganese-containing refractory metal oxide carrier with platinum in an amount in the range of about 10 g / ft ３ to 100 g / ft ３ The catalyst article according to any one of claims 20 to 23, which contains platinum in an amount in the range of

29. The oxidation catalyst is at least about 40 g / ft impregnated on the manganese-containing refractory metal oxide support ３ The catalyst article according to any one of claims 20 to 23, comprising platinum.

30. The refractory metal oxide support comprises alumina, silica, zirconia, titania, ceria, or a combination thereof. The catalyst article according to any one of claims 20 to 23.

31. The manganese content of the refractory metal oxide support is in the range of about 0.1 wt% to about 30 wt% based on the total weight of the support. The catalyst article according to any one of claims 20 to 23.

32. The manganese content of the refractory metal oxide support is in the range of about 3 to about 10 wt%. The catalyst article according to claim 31.

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