COMBINATION OF NOx ABSORBER AND SCR CATALYST

Abstract

To provide a catalyst article for performing efficient NOx conversion in combination with an SCR catalyst, and a method for treating a flow of an exhaust gas using the article.SOLUTION: A catalyst article includes a base material both a selective catalytic reduction (SCR) catalyst composition and a nitrogen oxide (NOx) absorber composition arranged thereon, wherein the NOx absorber composition contains an alkali earth metal component, and the SCR catalyst composition contains a mixed metal oxide component selected from a group consisting of FeTiO3, FeAl2O3, MgTiO3, MgAlO3, MnOX / TiO2, CuTiO3, CeZrO2, TiZrO2, V2O5 / TiO2 and mixtures thereof.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates generally to the field of selective catalytic reduction (SCR) catalysts and nitrogen oxide (NOx) absorbers, and methods for preparing and using such catalysts in treating NOx-containing exhaust gas streams. [Background technology]

[0002] Nitrogen oxides (NOx) are harmful components of air pollution. They are found in exhaust gases from internal combustion engines (e.g., in cars and trucks), combustion facilities (e.g., power plants heated by natural gas, oil, or coal), and nitric acid production plants.

[0003] Various treatment methods are used to reduce NOx (i.e., NO and NO2) in exhaust gases, thereby reducing air pollution. One type of treatment involves catalytic reduction of nitrogen oxides using a reducing agent such as a hydrocarbon or ammonia. The use of ammonia or an ammonia precursor in combination with a suitable catalyst can achieve a high degree of nitrogen oxide removal with a minimal amount of reducing agent. This is called selective catalytic reduction, because the reducing agent, such as ammonia (NH3), reacts almost exclusively with NOx.

[0004] The selective reduction process using ammonia is called the NH3-SCR (selective catalytic reduction) process, or often simply SCR. The SCR process uses the catalytic reduction of nitrogen oxides with a reducing agent (e.g., ammonia (NH3) or an ammonia precursor) in the presence of atmospheric oxygen, resulting in the formation of primarily nitrogen (N2) and steam (H2O). 4NO+4NH3+O2→4N2+6H2O (standard SCR reaction) 2NO2+4NH3→3N2+6H2O (slow SCR reaction) NO+NO2+NH3→2N2+3H2O (fast SCR reaction)

[0005] The SCR process is one of the most viable technologies for removing nitrogen oxides from engine exhaust gases. In a typical exhaust gas, nitrogen oxides consist mainly of NO (>90%), which is converted to nitrogen and water by the SCR catalyst in the presence of ammonia (standard SCR reaction). Ammonia is one of the most effective reducing agents, but urea can also be used as an ammonia precursor.

[0006] Generally, catalysts used in SCR processes have good catalytic activity at higher operating temperatures (i.e., about 200°C to 600°C), but are much less efficient at lower operating temperatures. The lower operating temperatures typically occur after engine start-up and during engine and catalyst pre-heating. This time is generally referred to as the "cold start" time, during which the operating temperature of the exhaust gas treatment system at start-up is too low to initially develop sufficient catalytic activity to efficiently treat the hydrocarbons (HC), nitrogen oxides (NOx) and / or carbon monoxide (CO) present in the engine exhaust gas. Various trapping systems (e.g., NOx absorbers) are used to store only the initial exhaust gas emissions emitted by the engine during this cold start period, and then sequentially release them (i.e., HC, CO and NOx gases) at higher temperatures when the catalytic components of the engine treatment system (e.g., SCR catalyst) have reached sufficient catalytic activity.

[0007] For example, NOx absorbers are used to capture NOx at temperatures below 200°C and release NOx at temperatures above 200°C. These materials typically contain oxides of alkaline earth metals (such as Ba, Ca, Sr, and Mg) or cerium oxide, which form inorganic nitrates (e.g., BaO or BaCO3 converted to Ba(NO3)2) when absorbing NOx gases at low temperatures. At higher temperatures, the inorganic nitrates decompose into NO and / or NO2 and release them back into the exhaust gas stream. NOx absorbers are generally located as separate catalytic components upstream of the SCR catalyst in the engine processing system. In many cases, the operating temperatures of the NOx absorber and the SCR catalyst differ due to their separate locations in the engine processing system; for example, the NOx absorber is often located closer to the engine and will increase in temperature at a faster rate than the SCR catalyst located downstream. This temperature difference between the two catalyst components often results in premature release of NOx gases from the NOx absorber, before the SCR catalyst has reached its optimum operating temperature to perform efficient NOx conversion.

[0008] In addition, the presence of traces of sulfur-containing impurities in diesel or gasoline fuels has a large effect on the catalytic activity of the NOx absorber. Oxidation catalysts located upstream of the NOx absorber in engine treatment systems can oxidize sulfur dioxide (SO2) in the exhaust gas to sulfur trioxide (SO3), which exacerbates sulfur poisoning. Alkaline earth metal sulfates (e.g., barium oxide or carbonate reacts with sulfur trioxide (SO3) to form barium sulfate (BaSO4)) are formed upon contact of oxygenated sulfur compounds with the surface of the NOx absorber. Unfortunately, these alkaline earth metal sulfates are more stable than the alkaline earth metal nitrates (e.g., Ba(NO3)2) that are generated upon contact with NOx gases, and therefore require higher temperatures (>650°C) for removal from the NOx absorber using desulfurization methods. The extreme conditions required for desulfurization can lead to a short life of the NOx absorber.

[0009] Due to increasingly stringent emission regulations, it is highly desirable to provide an emission treatment system including a sulfur-tolerant NOx absorber that exhibits essentially the same operating temperatures as an SCR catalyst to provide efficient NOx conversion (e.g., of NOx released from the absorbed NOx absorber during cold start) in combination with an SCR catalyst. Summary of the Invention

[0010] The present invention relates to a catalyst article having a selective catalytic reduction (SCR) catalyst composition and a nitrogen oxide (NOx) absorber composition arranged on the same substrate in a layered or zoned configuration. Integrating the NOx absorber composition into the SCR catalyst article ensures that the SCR catalyst composition has an operating temperature at least as high as the NOx absorber composition. Thus, any premature release of NOx from the NOx absorber composition before the SCR catalyst composition reaches its optimal operating temperature will be minimized. For this reason, some engine treatment systems mount the SCR catalyst article of the present invention as close to the engine exhaust as possible to utilize exhaust heat, allowing the article to heat up faster. Integrating the NOx absorber composition into the SCR catalyst article of the present invention eliminates the need for a separate catalyst brick for the NOx absorber, which would otherwise be located upstream of the SCR catalyst article. In addition, the NOx absorber composition does not interfere with the catalytic activity of the SCR catalyst composition, for example, the NOx absorber composition does not oxidize the ammonia reductant used in the SCR process. Ammonia actually protects the NOx absorbent composition against sulfur poisoning from trace amounts of sulfur-containing impurities present in the fuel by forming ammonium sulfate, thus preventing sulfate species in the exhaust from reacting with the SCR catalyst composition or the NOx absorbent composition.

[0011] One aspect of the invention relates to a catalyst article that includes a substrate having both a selective catalytic reduction (SCR) catalyst composition and a nitrogen oxide (NOx) absorber composition disposed thereon. In some embodiments, the selective catalytic reduction (SCR) catalyst composition and the nitrogen oxide (NOx) absorber composition are mixed in a single layer on the substrate. In some embodiments, on the substrate, the selective catalytic reduction (SCR) catalyst composition is in a first layer and the nitrogen oxide (NOx) absorber composition is in a second layer, the second layer is directly on the substrate, and the first layer is on the second layer. In some embodiments, the selective catalytic reduction (SCR) catalyst composition and the NOx absorber composition are disposed on the substrate in an axially zoned configuration, the substrate having an axial length with an inlet end and an outlet end, and the second layer is disposed on a first zone that extends from the inlet end of the substrate over a range of about 5 to about 95% of the axial length of the substrate.

[0012] In some embodiments, the NOx absorbent composition is substantially free of platinum. In some embodiments, the NOx absorbent composition comprises a platinum group metal component selected from Ru, Pd, Rh and combinations thereof impregnated on a support material. In some embodiments, the support material is a molecular sieve or a metal oxide. In some embodiments, the molecular sieve is a zeolite and the metal oxide support comprises ceria. In some embodiments, the metal oxide is doped with at least one lanthanide group metal.

[0013] In some embodiments, the NOx absorbent composition further comprises an alkaline earth metal component. In some embodiments, the alkaline earth metal component comprises a barium component. In some embodiments, the SCR catalyst composition comprises a metal-promoted molecular sieve. In some embodiments, the metal is selected from Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Mo, Hf, Y, W, and combinations thereof. In some embodiments, the molecular sieve is optionally a zeolite having a structure type selected from AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB, EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE, RTH, SAS, SAT, SAV, SFW, TSC, and UFI, and combinations thereof.

[0014] In some embodiments, the SCR catalyst composition optionally comprises FeTiO3, FeAl2O3, MgTiO3, MgAlO3, MnO X In some embodiments, the mixed metal oxide component comprises titania and vanadia. In some embodiments, the substrate is a honeycomb substrate selected from the group consisting of a flow-through substrate and a wall flow filter. In some embodiments, the NOx absorber composition does not substantially oxidize ammonia. In some embodiments, the catalytic article is effective in reducing NOx from an engine exhaust gas stream.

[0015] Another aspect of the invention relates to a method for treating an exhaust gas stream comprising contacting the gas with a catalytic article of the invention such that NOx in the exhaust gas stream is reduced.

[0016] Another aspect of the invention relates to an emissions treatment system for treating an exhaust gas stream, the emissions treatment system comprising an engine generating an exhaust gas stream, a catalytic article of the invention positioned downstream of the engine in fluid communication with the exhaust gas stream and adapted to reduce NOx in the exhaust gas stream to form a treated exhaust gas stream, and an injector positioned upstream of the catalytic article and adapted to add a reductant to the exhaust gas stream. In some embodiments, the emissions treatment system further comprises one or both of a diesel oxidation catalyst positioned upstream of the catalytic article and a soot filter positioned downstream of the catalytic article.

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

[0018] Embodiment 1: A catalytic article comprising a substrate having both a selective catalytic reduction (SCR) catalyst composition and a nitrogen oxide (NOx) absorber composition disposed thereon.

[0019] Embodiment 2: The catalyst article of embodiment 1, wherein the SCR catalyst composition and the NOx absorbent composition are mixed in a single layer on the substrate.

[0020] Embodiment 3: A catalyst article as described in embodiment 1 or 2, wherein the SCR catalyst composition is in a first layer and the NOx absorbent composition is in a second layer on a substrate, the second layer is directly on the substrate, and the first layer is on the second layer.

[0021] Embodiment 4: A catalyst article according to any of embodiments 1-3, wherein the SCR catalyst composition and the NOx absorber composition are disposed on the substrate in an axially zoned configuration, the substrate having an axial length having an inlet end and an outlet end, and the second layer is disposed on a first zone extending from the inlet end of the substrate over a range of about 5 to about 95% of the axial length of the substrate.

[0022] Embodiment 5: The catalyst article of any one of embodiments 1-4, wherein the NOx absorbent composition is substantially free of platinum.

[0023] Embodiment 6: The catalytic article of any of embodiments 1-5, wherein the NOx absorbent composition comprises a platinum group metal (PGM) component selected from Ru, Pd, Rh and combinations thereof impregnated on a support material.

[0024] Embodiment 7: The catalytic article of any one of embodiments 1 to 6, wherein the support material is a molecular sieve or a metal oxide.

[0025] Embodiment 8: The catalytic article of any one of embodiments 1-7, wherein the molecular sieve is a zeolite and the metal oxide support comprises ceria.

[0026] Embodiment 9: The catalytic article of any one of embodiments 1-8, wherein the metal oxide is doped with at least one lanthanide group metal.

[0027] Embodiment 10: The catalyst article of any one of embodiments 1-9, wherein the NOx absorbent composition further comprises an alkaline earth metal component.

[0028] Embodiment 11: The catalytic article of any one of embodiments 1-10, wherein the alkaline earth metal component comprises a barium component.

[0029] Embodiment 12: The catalyst article of any one of embodiments 1-11, wherein the SCR catalyst composition comprises a metal-promoted molecular sieve.

[0030] Embodiment 13: The catalytic article of any one of embodiments 1 to 12, wherein the metal is selected from Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Mo, Hf, Y, W, and combinations thereof.

[0031] Embodiment 14: The catalytic article of any one of embodiments 1 to 13, wherein the metal-promoted molecular sieve is optionally a zeolite having a structure type selected from AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB, EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE, RTH, SAS, SAT, SAV, SFW, TSC, and UFI, and combinations thereof.

[0032] Embodiment 15: The catalyst article of any one of embodiments 1 to 14, wherein the SCR catalyst composition optionally comprises a mixed metal oxide component selected from FeTiO3, FeAl2O3, MgTiO3, MgAlO3, MnOx / TiO2, CuTiO3, CeZrO2, TiZrO2, V2O5 / TiO2, and mixtures thereof.

[0033] Embodiment 16: The catalytic article of any one of embodiments 1-15, wherein the mixed metal oxide component comprises titania and vanadia.

[0034] Embodiment 17: The catalytic article of any one of embodiments 1-16, wherein the substrate is a honeycomb substrate selected from the group consisting of a flow-through substrate and a wall-flow filter.

[0035] Embodiment 18: The catalyst article of any one of embodiments 1-17, wherein the NOx absorbent composition does not substantially oxidize ammonia.

[0036] Embodiment 19: The catalytic article of any one of embodiments 1-18, wherein the catalytic article is effective for reducing NOx from an engine exhaust gas stream.

[0037] Embodiment 20: A method for treating an exhaust gas stream, comprising contacting the gas with the catalytic article of any of embodiments 1-19, such that NOx in the exhaust gas stream is reduced.

[0038] Embodiment 21: An emission treatment system for treating an exhaust gas stream, comprising: an engine generating an exhaust gas stream; a catalytic article according to any of embodiments 1-20 positioned downstream of the engine in fluid communication with the exhaust gas stream and adapted to reduce NOx in the exhaust gas stream to form a treated exhaust gas stream; and an injector positioned upstream of the catalytic article and adapted to add a reducing agent to the exhaust gas stream.

[0039] Embodiment 22: The emissions treatment system of embodiment 21, further comprising one or both of a diesel oxidation catalyst located upstream of the catalyst article, and a catalyzed soot filter located downstream of the catalyst article.

[0040] These and other features, aspects, and advantages of the present disclosure will become apparent from reading the following detailed description in conjunction with the accompanying drawings, which are briefly described below. The present invention includes any combination of two, three, four, or more of the above-described embodiments, as well as combinations of two, three, four, or more features or elements described in the present disclosure, whether or not such features or elements are explicitly combined in the description of a particular embodiment herein. The present disclosure is intended to be read in its entirety such that any 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 from the following. [Brief description of the drawings]

[0041] To provide an understanding of embodiments of the present invention, reference is made to the accompanying drawings, which are not necessarily drawn to scale, and in which reference numerals designate components of exemplary embodiments of the present invention. The drawings are merely illustrative and should not be construed as limiting the present invention.

[0042] [Figure 1]1 is a perspective view of a honeycomb-type substrate that may include a catalytic article washcoat composition according to the present invention. [Diagram 2] 2 is a partial cross-sectional view enlarged relative to FIG. 1 and taken along a plane parallel to the end face of the substrate of FIG. 1 representing a monolithic flow-through substrate, showing an enlarged view of multiple gas flow paths shown in FIG. 1. [Diagram 3] 2 is an enlarged cross-sectional cutaway view relative to FIG. 1, in which the honeycomb-type substrate represents a wall-flow filter substrate monolith. [Figure 4] 1 shows a cross-sectional view of a zoned catalyst article of the present invention. [Diagram 5] A cross-sectional view of a layered catalyst article of the present invention is shown in which an outer layer (107) is disposed over a portion of an inner layer (106) that is disposed directly over the entire length of a substrate (100). [Figure 6] A cross-sectional view of a layered catalyst article of the present invention is shown in which an inner layer (115) is disposed over a portion of a substrate (100) and an outer layer (114) is disposed over the remainder of the substrate (100) and the inner layer (115). [Figure 7] 1 shows a schematic diagram of an embodiment of an emissions treatment system in which a catalytic article of the present invention is utilized, the catalytic article being positioned downstream of a catalyzed soot filter (CSF). [Figure 8] 1 shows a schematic diagram of an embodiment of an emissions treatment system in which a catalytic article of the present invention is utilized, the catalytic article being positioned upstream of a catalyzed soot filter (CSF). [Figure 9] 1 shows a schematic diagram of an embodiment of an emissions treatment system in which a catalytic article of the present invention is utilized, the catalytic article of the present invention being located immediately downstream of an engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] The present invention will now be described more fully below. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth 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. As used in this specification and claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0044] The present invention relates to a catalyst article having a selective catalytic reduction (SCR) catalyst composition and a nitrogen oxide (NOx) absorber composition disposed on the same substrate. Integrating the NOx absorber composition into the SCR catalyst article provides the same operating temperature for both catalyst components. This ensures that the SCR catalyst composition is at least as hot as the NOx absorber composition. The NOx absorber composition can be designed to release NOx at a temperature at which the SCR catalyst composition is active, thus preventing premature release of NOx from the NOx absorber composition before the SCR catalyst composition reaches its optimal operating temperature. As mentioned above, the SCR catalyst composition does not exhibit efficient catalytic activity at low operating temperatures (e.g., below 200°C), and during this period, the engine exhaust gas is primarily processed by the NOx absorber composition, which removes NOx from the exhaust gas stream by absorbing and storing NOx. As the engine warms up and the temperature of the engine exhaust gas increases, the operating temperatures of the NOx absorber composition and the SCR catalyst composition of the present invention increase at substantially the same rate. Thus, upon reaching high temperatures, the NOx absorbent composition releases NOx, which is immediately converted by the SCR catalyst composition located in close proximity, using ammonia as a reductant. The catalytic activity of the SCR catalyst composition is not affected by the NOx absorbent composition located on the same substrate (e.g., in a zoned or layered configuration). In particular, the NOx absorbent composition of the present invention is inert to the presence of ammonia and does not react with ammonia to interfere with the SCR process, e.g., does not oxidize ammonia. The presence of ammonia actually provides a beneficial effect on the NOx absorbent composition from trace amounts of sulfur-containing impurities present in the fuel. Without being bound by theory, it is believed that any oxidized sulfur-containing impurities (e.g., sulfur trioxide species) react with ammonia to form ammonium sulfate, which readily decomposes back to sulfur trioxide and ammonia at high temperatures. In particular, when the SCR catalyst composition has a high ammonia storage capacity at low operating temperatures, any sulfur trioxide species in the engine exhaust gas will be able to react with the absorbed ammonia before contacting the NOx absorber composition, especially when the SCR catalyst composition is layered over the NOx absorber composition on the same substrate.Such a layered configuration will protect the NOx absorbent composition from any contact with sulfur-containing trace impurities, such as sulfur trioxide, that may contaminate the catalyst composition.

[0045] As used herein, the term "catalyst" or "catalyst composition" refers to a material that promotes a reaction.

[0046] As used herein, the term "absorber" refers to a material that reacts with gas species to form chemically absorbed species, surface complexes, or compounds that can be readily converted back to the original gas species by some combination of elevated temperature and / or changes in gas composition, for example, by changing the exhaust gas composition from net lean to net rich.

[0047] As used herein, the terms "upstream" and "downstream" refer to relative directions relative to the flow of engine exhaust gas stream from the engine toward the exhaust pipe, with the engine being at the upstream location and the exhaust pipe and any pollution reduction articles, such as filters and catalysts, being downstream of the engine.

[0048] As used herein, the term "stream" broadly refers to any combination of flowing gases that may contain solid or liquid particulate matter. The term "gaseous stream" or "exhaust gas stream" refers to a mixture of gaseous components, such as the exhaust gas of a combustion engine, which may also contain entrained non-gaseous components, such as liquid droplets, solid particles, etc. Combustion engine exhaust gas streams typically further include combustion products (CO2 and HO), incomplete combustion products (carbon monoxide (CO) and hydrocarbons (HC)), nitrogen oxides (NOx), combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen.

[0049] As used herein, the term "substrate" refers to a monolithic material upon which the catalyst composition is disposed.

[0050] As used herein, the term "support" refers to any high surface area material, usually a metal oxide material, to which a platinum group metal component is applied.

[0051] As used herein, the term "washcoat" has its usual meaning in the art of a thin, adherent coating of catalyst or other material applied to a substrate material, such as a honeycomb-type carrier member, that is sufficiently porous to permit the passage of a stream of gas to be treated. Washcoats are formed by preparing a slurry containing a particular solids content (e.g., 30% to 90% by weight) of particles in a liquid vehicle, which is then coated onto the substrate and dried to provide the washcoat layer.

[0052] As used herein, the term "catalyst article" refers to an element used to promote a desired reaction. For example, the catalyst article may include a washcoat containing a catalyst composition on a substrate. The catalyst article may also primarily include a catalyst composition formed into a monolithic honeycomb or other solid shape for use in a packed bed reactor.

[0053] As used herein, "impregnated" or "impregnation" refers to the infiltration of a catalytic material into the porous structure of a support material.

[0054] The term "reduction" refers to a decrease in amount, caused by any means.

[0055] SCR catalyst composition The SCR catalyst composition of the present invention includes a mixed metal oxide component or a metal-promoted molecular sieve. With respect to an SCR catalyst composition that includes a mixed metal oxide component, the term "mixed metal oxide component" as used therein refers to an oxide that contains cations of two or more chemical elements or cations of a single element in several oxidation states. In one or more embodiments, the mixed metal oxide is selected from the group consisting of Fe / titania (e.g., FeTiO3), Fe / alumina (e.g., FeAl2O3), Mg / titania (e.g., MgTiO3), Mg / alumina (e.g., MgAl2O3), Mn / alumina (e.g., MnO3), Mg / titania (e.g., MgTiO3), Mg / alumina (e.g., MgAl2O3), Mn / alumina (e.g., MnO3), Mg / titania (e.g., MgTiO3), Mg / alumina (e.g., MgAl2O3), Mn / alumina (e.g., MnO3), Mn ...titania (e.g., MgTi x / Al2O3), Mn / titania (e.g., MnO xIn some embodiments, the mixed metal oxide component comprises vanadia / titania. In some embodiments, the amount of vanadia present in the mixed metal oxide component ranges from about 1 wt.% to about 10 wt.%, based on the total weight of the mixed metal oxide component (with a lower limit of 0 wt.%, up to about 10 wt.%, about 9 wt.%, about 8 wt.%, about 7 wt.%, about 6 wt.%, about 5 wt.%, about 4 wt.%, about 3 wt.%, about 2 wt.%, or about 1 wt.%, based on the total weight of the mixed metal oxide component). In some embodiments, the mixed metal oxide component may be activated or stabilized. For example, in some embodiments, vanadia / titania oxide may be activated or stabilized with tungsten (e.g., WO3) to provide V2O5 / TiO2 / WO3. In some embodiments, the amount of tungsten present in the mixed metal oxide component (e.g., V2O5 / TiO2 / WO3) ranges from about 0.5% to about 10% by weight based on the total weight of the mixed metal oxide component (with a lower limit of 0% by weight, up to about 10% by weight, about 9% by weight, about 8% by weight, about 7% by weight, about 6% by weight, about 5% by weight, about 4% by weight, about 3% by weight, about 2% by weight, or about 1% by weight based on the total weight of the mixed metal oxide component). In some embodiments, vanadia is activated or stabilized with tungsten (e.g., WO3). Tungsten may be dispersed at a concentration ranging from about 0.5% to about 10% by weight based on the total weight of vanadia (with a lower limit of 0% by weight, up to about 10% by weight, about 9%, about 8%, about 7%, about 6%, about 5%, about 4%, about 3%, about 2%, or about 1% by weight based on the total weight of vanadia).For examples of mixed metal oxides as SCR catalyst compositions, see U.S. Patent Application Publication No. 2001 / 0049339 to Schafer-Sindelindger et al., U.S. Pat. No. 4,518,710 to Brennan et al., U.S. Pat. No. 5,137,855 to Hegedus et al., U.S. Pat. No. 5,476,828 to Kapteijn et al., U.S. Pat. No. 8,685,882 to Hong et al., and U.S. Pat. No. 9,101,908 to Jurng et al., all of which are incorporated herein by reference in their entireties.

[0056] For SCR catalyst compositions including metal-promoted molecular sieves, the term "molecular sieve" refers to framework materials such as zeolites and other framework materials (e.g., isomorphously substituted materials). Molecular sieves are generally materials based on an extensive three-dimensional network of oxygen ions containing tetrahedral-type sites and having a substantially uniform pore distribution with an average pore size of 20 Å or less. The pore size is defined by the ring size. It will be understood that by defining molecular sieves by their framework type, according to one or more embodiments, it is intended to include any and all zeolites or isomorphous framework materials such as SAPO, ALPO and MeAPO, Ge silicates, all-silica, and similar materials having the same framework type.

[0057] In general, molecular sieves, e.g., zeolites, are defined as aluminosilicates with 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 anion framework change are loosely associated with framework oxygens, and the remaining pore volume is filled with water molecules. Non-framework cations are generally exchangeable, and water molecules are removable.

[0058] As used herein, the term "zeolite" refers to a specific example of a molecular sieve that contains silicon and aluminum atoms. Zeolites are crystalline materials with very uniform pore sizes ranging from about 3 to 10 angstroms in diameter, depending on the type of zeolite and the type and amount of cations contained in the zeolite lattice. The silica to alumina molar ratio (SAR) of zeolites and other molecular sieves can vary over a very wide range, but is usually 2 or greater. In one or more embodiments, the molecular sieves have a SAR molar ratio in the ranges of about 2 to about 300, about 5 to about 250, about 5 to about 200, about 5 to about 100, and about 5 to about 50. In one or more specific embodiments, the molecular sieve has a SAR molar ratio in the range of about 10 to about 200, about 10 to about 100, about 10 to about 75, about 10 to about 60, and about 10 to about 50, about 15 to about 100, about 15 to about 75, about 15 to about 60, and about 15 to about 50, about 20 to about 100, about 20 to about 75, about 20 to about 60, and about 20 to about 50.

[0059] In more specific embodiments, reference to an aluminosilicate zeolite framework type limits the material to molecular sieves that do not contain phosphorus or other metals substituted within the framework. However, for clarity, as used herein, "aluminosilicate zeolite" excludes aluminophosphate materials such as SAPO, ALPO, and MeAPO materials, and the broader term "zeolite" is intended to include aluminosilicates and aluminophosphates. The term "aluminophosphate" refers to another specific example of a molecular sieve that contains aluminum and phosphate atoms. Aluminophosphates are crystalline materials with very uniform pore sizes.

[0060] In one or more embodiments, the molecular sieve comprises SiO4 / AlO4 tetrahedra that are linked by common oxygen atoms to form a three-dimensional network independently. In other embodiments, the molecular sieve comprises SiO4 / AlO4 / PO4 tetrahedra. The molecular sieves of one or more embodiments can be distinguished according to the geometry of the voids formed primarily by the rigid network of SiO4 / AlO4, or SiO4 / AlO4 / PO4 tetrahedra. The entrances to the voids are formed from 6, 8, 10, or 12 ring atoms relative to the atoms forming the entrance opening. In one or more embodiments, the molecular sieve comprises ring sizes of 12 or less, including 6, 8, 10, and 12.

[0061] According to one or more embodiments, the molecular sieve may be based on a framework topology from which the structure is identified. Typically, the molecular sieve is based on a framework topology 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, 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, G ME, GON, GOO, HEU, IFR, IFY, IHW, IRN, ISV, ITE, ITH, ITW, IWR, IWW, JBW, KFI, LAU, LEV, LIO, LIT, LOS, LOV, LTA, LT L, 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, Zeolites of any framework type may be used, such as framework types 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 combinations thereof. In some embodiments, the molecular sieve comprises a framework structure type selected from AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB, EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE, RTH, SAS, SAT, SAV, SFW, TSC, and UFI.

[0062] In one or more embodiments, the molecular sieve comprises an 8-ring small pore aluminosilicate zeolite. As used herein, the term "small pore" refers to a pore opening that is smaller than about 5 angstroms, for example, about 3.8 angstroms. The phrase "8-ring" zeolite refers to a zeolite with an 8-ring pore opening and a double 6-ring secondary building unit, with a cage structure resulting from the connection of the double 6-ring building unit by 4 rings. In one or more embodiments, the molecular sieve is a small pore molecular sieve with a maximum ring size of 8 tetrahedral atoms.

[0063] As noted above, in one or more embodiments, the molecular sieve may include all aluminosilicate, borosilicate, gallosilicate, MeAPSO, and MeAPO compositions, including, but not limited to, SSZ-13, SSZ-62, natural chabazite, zeolite KG, Linde D, Linde R, LZ-218, LZ-235, LZ-236, ZK-14, SAPO-34, SAPO-44, SAPO-47, ZYT-6, CuSAPO-34, CuSAPO-44, Ti-SAPO-34, and CuSAPO-47.

[0064] As mentioned hereinabove, the disclosed SCR catalyst composition generally comprises a metal promoted molecular sieve (e.g., zeolite). As used herein, "promoted" refers to a molecular sieve that includes one or more components that are intentionally added, as opposed to including impurities that may be inherent to the molecular sieve. Thus, a promoter is a component that is intentionally added to enhance the activity of the catalyst compared to a catalyst that does not have the promoter intentionally added. To promote the SCR of nitrogen oxides, in one or more embodiments according to the present disclosure, a suitable metal is exchanged into the molecular sieve. Copper is involved in the conversion of nitrogen oxides and therefore may be a particularly useful metal for exchange. Thus, in certain embodiments, a catalyst composition is provided that includes a copper promoted molecular sieve, e.g., Cu-CHA. However, the present invention is not intended to be limited thereto, and catalyst compositions that include other metal promoted molecular sieves are also encompassed by the present invention.

[0065] The promoter metal may generally be selected from the group consisting of alkali metals, alkaline earth metals, transition metals of groups IIIB, IVB, VB, VIB, VIIB, VIIIB, IB, and IIB, group IIIA elements, group IVA elements, lanthanides, actinides, and combinations thereof. In various embodiments, additional promoter metals that may be used to prepare metal-promoted molecular sieves include, but are not limited to, copper (Cu), cobalt (Co), nickel (Ni), lanthanum (La), manganese (Mn), iron (Fe), vanadium (V), silver (Ag), cerium (Ce), neodymium (Nd), praseodymium (Pr), titanium (Ti), chromium (Cr), zinc (Zn), tin (Sn), niobium (Nb), molybdenum (Mo), hafnium (Hf), yttrium (Y), tungsten (W), and combinations thereof. Such combinations of metals can be used, for example, copper and iron, to give a mixed Cu-Fe promoted molecular sieve, for example, Cu-Fe-CHA.

[0066] In one or more embodiments, the promoter metal content of the metal-promoted molecular sieve, calculated as oxide, ranges from about 0.1 wt.% to about 10 wt.%, about 0.1 wt.% to about 5 wt.%, about 0.5 wt.% to about 4 wt.%, about 2 wt.% to about 5 wt.%, or about 1 wt.% to about 3 wt.%, based on the total weight of the calcined molecular sieve (including promoter) and reported on a volatiles-free basis. In some embodiments, the promoter metal of the molecular sieve comprises Cu, Fe, or a combination thereof.

[0067] For examples of SCR catalyst compositions containing metal-promoted molecular sieves, see U.S. Pat. No. 9,480,976 to Rivas-Cardona et al., U.S. Pat. No. 9,352,307 to Stiebels et al., U.S. Pat. No. 9,321,009 to Wan et al., U.S. Pat. No. 9,199,195 to Andersen et al., U.S. Pat. No. 9,138,732 to Bull et al., U.S. Pat. No. 9,011,807 to Mohanan et al., U.S. Pat. No. 8,715,618 to Turkhan et al., U.S. Pat. No. 8,293,182 to Boorse et al., U.S. Pat. No. 8,119,088 to Boorse et al., U.S. Pat. No. 8,101,146 to Fedeyko et al., and U.S. Pat. No. 7,220,692 to Marshall et al., all of which are incorporated herein by reference in their entireties.

[0068] NOx absorbent composition The NOx absorber composition of the present invention includes a platinum group metal component impregnated on a support material. As used herein, "platinum group metal component" or "PGM component" refers to platinum group metals or oxides thereof, including palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir) and mixtures thereof. The concentration of the platinum group metal component can vary, but is typically about 0.01% to about 10% by weight based on the total weight of the impregnated metal oxide support. In some embodiments, the NOx absorber composition is substantially free of platinum. As used herein, the term "substantially free of platinum" means that there is no additional platinum intentionally added to the NOx absorber composition, and that there is less than about 0.01% by weight of platinum metal present in the NOx absorber composition. In some embodiments, the NOx absorber composition specifically excludes platinum. In other embodiments, the platinum group metal component includes two platinum group metals, for example, in a weight ratio of about 1:10 to about 10:1. For example, in some embodiments, the platinum group metal component includes ruthenium and palladium.

[0069] The platinum group metal component may be supported on any suitable material. In some embodiments, the support material is a metal oxide support. As used herein, "metal oxide support" refers to a metal-containing oxide material that exhibits chemical and physical stability at high temperatures, such as temperatures associated with diesel engine exhaust. Exemplary metal oxides may include, but are not limited to, ceria, alumina, silica, zirconia, titania, or combinations thereof. For example, in some embodiments, the metal oxides alumina, silica, zirconia, or titania may be combined as a physical mixture or chemical combination with ceria to form a metal oxide support. In some embodiments, the metal oxide support comprises more than 50 wt. % ceria, based on the total weight of the NOx absorbent composition. In further embodiments, the metal oxide support comprises more than about 60 wt. %, more than about 70 wt. %, more than about 80 wt. %, or more than about 90 wt. % ceria, based on the total weight of the NOx absorbent composition. In additional embodiments, the metal oxide support comprises from about 50% to about 99.9%, from about 60% to about 99.5%, or from about 80% to about 99.0% by weight of ceria, based on the total weight of the NOx absorbent composition.

[0070] In some embodiments, the metal oxide support comprises a combination of atomically doped metal oxides. For example, in some embodiments, the metal oxide support is modified to contain an oxidized form of a dopant metal, such as, but not limited to, a lanthanide group metal selected from La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Si, Nb, Zr, and combinations thereof. In some embodiments, the dopant metal is Pr, Gd, Zr, or combinations thereof. In some embodiments, the total amount of the dopant metal or combinations thereof ranges from about 0.1% to about 15% by weight based on the total weight of the NOx absorber composition. Exemplary metal oxides include, but are not limited to, mixtures of two metal oxides such as alumina-zirconia, ceria-zirconia, alumina-ceria-zirconia, lanthana-alumina, lanthana-zirconia-alumina, baria-alumina, baria-lanthana-alumina, baria-lanthana-neodymia alumina, and alumina-ceria. Exemplary aluminas include large pore boehmite, gamma-alumina, and delta / theta alumina. Useful commercially available aluminas include high bulk density gamma-alumina, low or medium bulk density large pore gamma-alumina, and activated aluminas such as low bulk density large pore boehmite and gamma-alumina.

[0071] In some embodiments, the support material is a molecular sieve, e.g., a zeolite. In some embodiments, the NOx absorber composition further comprises an alkaline earth metal component. As used herein, the term "alkaline earth metal component" refers to one or more chemical elements defined in the Periodic Table of Elements, including beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). In one or more embodiments, the alkaline earth metal component may be incorporated into the NOx absorber composition as a salt and / or oxide (e.g., BaCO3). In one or more embodiments, the alkaline earth metal component comprises barium. The alkaline earth metal component may be present in the NOx absorber composition in an amount of about 1% to about 30% by weight, 1% to about 20% by weight, or 5% to about 10% by weight, on an oxide basis.

[0072] For additional examples of NOx absorbent compositions, see U.S. Pat. No. 5,750,082 to Hephurn et al., U.S. Pat. No. 8,105,559 to Melville et al., U.S. Pat. No. 8,475,752 to Wan et al., U.S. Pat. No. 8,592,337 to Holgendorff et al., U.S. Pat. No. 9,114,385 to Briskley et al., U.S. Pat. No. 9,486,791 to Swallow et al., U.S. Pat. No. 9,610,564 to Xue et al., U.S. Pat. No. 9,610,564 to Wan et al., U.S. Pat. No. 9,770,621 to Wan et al., which are incorporated by reference in their entireties. See U.S. Patent No. 9,662,611 to Bender et al., U.S. Patent Application No. 2002 / 0077247 to Bender et al., U.S. Patent Application No. 2011 / 0305615 to Hilgendorff et al., U.S. Patent Application No. 2015 / 0157982 to Rajaram et al., U.S. Patent Application No. 2015 / 0158019 to Rajaram et al., U.S. Patent Application No. 2016 / 0228852 to Biberger et al., and International Patent Application No. WO2016 / 141142 to Grubert et al.

[0073] Base material The substrate for the catalytic articles of the present invention may be constructed from any material typically used to prepare automotive catalysts, and will typically include a metal or ceramic honeycomb structure. The substrate typically provides a plurality of walls to which the catalytic article washcoat composition is applied and adhered, thereby acting as a support for one or more catalyst compositions.

[0074] Exemplary metal substrates include heat-resistant metals and metal alloys such as titanium and stainless steels and other alloys in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and / or aluminum, and the total amount of these metals may advantageously comprise at least 15% by weight of the alloy, e.g., 10-25% by weight chromium, 3-8% by weight aluminum, and up to 20% by weight nickel. The alloys may also contain small or trace amounts of one or more other metals, such as manganese, copper, vanadium, titanium, and the like. The surface of the metal substrate may be oxidized at high temperatures, e.g., 1000° C. or higher, to form an oxide layer on the surface of the substrate, improving the corrosion resistance of the alloy and facilitating adhesion of a washcoat layer to the metal surface.

[0075] The ceramic material used to construct the substrate may include any suitable refractory material, such as cordierite, mullite, cordierite-alpha alumina, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, alpha alumina, aluminosilicates, and the like.

[0076] In some embodiments, the substrate can be constructed from one or more catalyst compositions that form a honeycomb structure or any other solid shape that can be used in, for example, a packed bed reactor. For example, the substrate can be constructed from a first catalyst composition that is coated with a washcoat composition that includes a second catalyst composition. In another example, the first and second catalyst compositions can be co-extruded to form the substrate.

[0077] Any suitable substrate may be used, such as a monolithic flow-through substrate having a plurality of fine, parallel gas flow passages extending from the inlet to the outlet face of the substrate such that the flow passages are open to the fluid flow. The flow passages, which are essentially straight-line paths from the inlet to the outlet, are defined by walls on which a catalytic material is coated as a washcoat such that gas flowing through the flow passages contacts the catalytic material. The flow passages of the monolithic substrate are thin-walled channels that may be of any suitable cross-sectional shape, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such structures may contain from about 60 to about 1200 or more gas inlet openings (i.e., "cells") per square inch of cross section (cpsi), more commonly about 300 to 600 cpsi. The wall thickness of the flow-through substrate may vary, with a typical range being 0.002 to 0.1 inches. A representative commercially available flow-through substrate is a cordierite substrate having a wall thickness of 6 mils at 400 cpsi, or 4 mils at 600 cpsi. However, it will be understood that the present invention is not limited to any particular substrate type, material, or geometry.

[0078] In an alternative embodiment, the substrate may be a wall flow substrate, with each flow passage plugged at one end of the substrate body with a non-porous plug, and alternate flow passages plugged at the opposite end face. This requires the gas flow to pass through the porous walls of the wall flow substrate to reach the outlet. Such monolithic substrates may contain up to about 700 or more cpsi, such as about 100 to 400 cpsi, more typically about 200 to about 300 cpsi. The cross-sectional geometry of the cells may vary as described above. Wall flow substrates typically have wall thicknesses of 0.002 to 0.1 inches. Representative commercially available wall flow substrates are constructed from porous cordierite, examples of which have wall thicknesses of 10 mils at 200 cpsi, or 8 mils at 300 psi, and wall porosities of 45 to 65%. Other ceramic materials, such as aluminum titanate, silicon carbide, and silicon nitride, are also used as wall flow filter substrates. However, it will be understood that the present invention is not limited to a particular substrate type, material, or geometry. It should be noted that if the substrate is a wall flow substrate, the catalyst composition, in addition to being disposed on the surface of the wall, may penetrate into the pore structure of the porous wall (i.e., partially or completely block the pore openings).

[0079] 1 and 2 illustrate an exemplary substrate 2 in the form of a flow-through substrate coated with a washcoat composition described herein. Referring to FIG. 1, the exemplary substrate 2 has a cylindrical shape, with a cylindrical outer surface 4, an upstream end surface 6, and a corresponding downstream end surface 8 identical to end surface 6. The substrate 2 has a plurality of fine, parallel gas flow passages 10 formed therein. As seen in FIG. 2, the flow passages 10 are formed by walls 12 and extend through the substrate 2 from the upstream end surface 6 to the downstream end surface 8, and the flow passages 10 are unobstructed to allow the flow of a fluid, e.g., a gas stream, to pass longitudinally through the substrate 2 through the gas flow passages 10. As can be more easily seen in FIG. 2, the walls 12 are so dimensioned and configured such that the gas flow passages 10 have a substantially regular polygonal shape. As shown, the washcoat composition can be applied in multiple separate layers, if desired. In the illustrated embodiment, the washcoat is comprised of both a separate bottom washcoat layer 14 adhered to the wall 12 of the substrate member and a second separate top washcoat layer 16 coated over the bottom washcoat layer 14. The invention may be practiced with one or more (e.g., 2, 3, or 4) washcoat layers and is not limited to the illustrated two-layer embodiment. Alternatively, the catalyst compositions of the invention (i.e., the SCR catalyst composition and the NOx absorber composition) may be homogenously mixed within the same washcoat layer.

[0080] For example, in one embodiment, the catalyst article includes multiple layers of catalyst material, with each layer having a different catalyst composition. The bottom layer (e.g., layer 14 in FIG. 2) can include the NOx absorber composition of the present invention, and the top layer (e.g., layer 16 in FIG. 2) can include the SCR catalyst composition of the present invention. In some embodiments, the catalyst article includes a catalyst material, with the bottom layer (e.g., layer 14 in FIG. 2) including the SCR catalyst composition of the present invention, and the top layer (e.g., layer 16 in FIG. 2) including the NOx absorber composition of the present invention.

[0081] In another example, the catalyst article includes a catalyst material having one or more layers, and the substrate is constructed from one or more catalyst compositions. In one embodiment, the substrate is constructed from an inventive NOx absorber composition coated with a washcoat composition including an inventive SCR catalyst composition. In some embodiments, two or more layers of an inventive SCR catalyst composition are applied to the substrate (e.g., layers 14 and 16 in FIG. 2).

[0082] In another example, a substrate is constructed from an SCR catalyst composition of the present invention coated with a washcoat composition comprising a NOx absorbent composition of the present invention. In some embodiments, two or more layers of the NOx absorbent composition of the present invention are applied to the substrate (e.g., layers 14 and 16 in FIG. 2).

[0083] In another example, a substrate is constructed by co-extruding the SCR catalyst composition and the NOx absorber composition of the present invention and is not coated with a washcoat composition.

[0084] The relative amounts of the SCR catalyst composition and the NOx absorber composition can vary. For example, the relative amounts of the PGM components in the NOx absorber composition in the exemplary dual layer coating can each comprise about 10-90 wt. % based on the total weight of the NOx absorber composition in the bottom layer (adjacent to the substrate surface), and the SCR catalyst composition is present at about 10-90 wt. % based on the total weight of the SCR catalyst composition in the top layer. The same proportions can be applied when the SCR catalyst composition is in the bottom layer and the NOx absorber composition is on the top layer.

[0085] FIG. 3 illustrates an exemplary substrate 2 in the form of a wall-flow filter substrate coated with a washcoat composition described herein. As seen in FIG. 3, the exemplary substrate 2 has a plurality of flow channels 52. The flow channels are tubularly surrounded by the inner wall 53 of the filter substrate. The substrate has an inlet end 54 and an outlet end 56. Alternate flow channels are blocked at the inlet end with inlet plugs 58 and at the outlet end with outlet plugs 60 to form an opposing checkerboard pattern at the inlet 54 and outlet 56. Gas flow 62 enters through the unblocked channel inlet 64, is stopped by the outlet plugs 60, and diffuses through the channel wall 53 (which is porous) to the outlet side 66. Gas cannot pass back to the inlet side of the wall because of the inlet plugs 58. The porous wall-flow filters used in the present invention are catalyzed in that the walls of the element have one or more catalytic materials on or within them. The catalytic material may be present only on the inlet side, only on the outlet side, on both the inlet and outlet sides of the element walls, or the walls themselves may be composed entirely or in part of the catalytic material. The present invention includes the use of one or more layers of catalytic material on the inlet and / or outlet walls of the element.

[0086] In some embodiments, a substrate may be coated with at least two layers contained in separate washcoat slurries in an axially zoned configuration. For example, the same substrate may be coated with one layer of washcoat slurry and another layer of washcoat slurry, each layer being different. This may be more easily understood by reference to FIG. 4, which shows one embodiment in which a first washcoat zone 102 and a second washcoat zone 103 are located side-by-side along the length of the substrate 100. The first washcoat zone 102 of certain embodiments extends from a front or inlet end 100a of the substrate 100 through a range of about 5% to about 95%, about 5% to about 75%, about 5% to about 50%, or about 10% to about 35% of the length of the substrate 100. The second washcoat zone 103 extends from the rear or outlet end 100b of the substrate 100 through about 5% to about 95%, about 5% to about 75%, about 5% to about 50%, or about 10% to about 35% of the total axial length of the substrate 100. As described herein, the catalyst compositions of at least two components in the treatment system can be zoned on the same substrate. In some embodiments, the NOx absorber composition and the SCR catalyst composition are zoned on the same substrate. For example, referring again to FIG. 4, the first washcoat zone 102 represents the NOx absorber composition and extends from the front or inlet end 100a of the substrate through about 5% to about 95% of the length of the substrate 100. Thus, the second washcoat zone 103, which includes the SCR catalyst composition, is located alongside the zone 102 that extends from the rear or outlet 100b of the substrate 100. In another embodiment, the first washcoat zone 102 may represent an SCR catalyst composition and the second washcoat zone 103 may include a NOx absorbent composition.

[0087] In some embodiments, as seen in FIG. 5, the substrate 100 may be coated with a first coating layer 106 extending from a front or inlet end 100a of the substrate 100 to a rear or outlet end 100b of the substrate 100, and a second coating layer 107 coated on the first coating layer 106 proximate the front or inlet end 100a of the substrate 100 and extending over only a partial length of the substrate 100 (i.e., terminating before reaching the rear or outlet end 100b of the substrate 100). In some embodiments, the first coating layer 106 may include an SCR catalyst composition and the second coating layer 107 may include a NOx absorber composition. In another embodiment, the first coating layer may include a NOx absorber composition and the second coating layer may include an SCR catalyst composition.

[0088] In some embodiments, as seen in FIG. 6, the substrate 100 may be coated with a first coating layer 115 that is proximate the rear or outlet end 100b of the substrate 100 and extends only partially along the length of the substrate 100 (i.e., terminates before reaching the front or inlet end 100a of the substrate 100). The substrate 100 may be coated with a second coating layer 114. As seen in FIG. 6, the second coating layer 114 extends from the front or inlet end 100a of the substrate 100 to the rear or outlet end 100b of the substrate 100 (and thus is completely coated over the first coating layer 115). In some embodiments, the first coating layer 115 may include a NOx absorber composition and the second coating layer 114 may include a SCR catalyst composition. In another embodiment, the first coating layer may include a SCR catalyst composition and the second coating layer may include a NOx absorber composition. It is understood that the above embodiments are provided as examples, and further combinations of catalytic coatings are encompassed.

[0089] In describing the amount of washcoat of catalytic metal components and other components of the composition, it is convenient to use units of weight of the component per unit volume of catalytic substrate. Thus, the unit grams per cubic inch ("g / in 3" ) and grams per cubic foot (" g / ft 3 " is used herein to mean the weight of a component per volume of substrate, including the volume of void space in the substrate. Other units of weight per volume, such as g / L, may also be used. The total loading of the catalyst article (i.e., NOx absorber composition and SCR catalyst composition) on the substrate is typically from about 0.5 to about 6 g / in 3 , more typically about 1 to about 5 g / in 3 , or about 1 to about 3 g / in 3 The total content of PGMs without support material (e.g., only PGM components) is typically about 0.1 to about 200 g / ft of the catalyst article. 3 , about 0.1~about 100g / ft 3 , about 1 to about 50g / ft 3 , about 1~30g / ft 3 , or about 5 to about 25 g / ft 3 It should be noted that these weights per unit volume are typically calculated by weighing the substrate before and after treatment with the catalytic washcoat composition, and because the treatment process involves drying and calcining the substrate at high temperatures, these weights represent the essentially solvent-free catalytic coating when essentially all of the water in the washcoat slurry has been removed.

[0090] In some embodiments, the catalytic material on the filter of the CSF disclosed herein includes two or more catalytic compositions with different catalytic compositions (e.g., selective oxidation catalytic composition and SCR material). Such catalytic compositions are contained in separate washcoat slurries when coating a wall-flow filter, for example, in an axially zoned configuration, where the wall-flow filter is coated with a washcoat slurry of one catalytic composition and a washcoat slurry of another catalytic composition. This can be more easily understood by referring to FIG. 3, which shows an embodiment of a zoned coated wall-flow filter 20 in which a first washcoat zone 24 and a second washcoat zone 26 are located side-by-side along the length of a substrate 28 having an upstream end 25 and a downstream end 27. In this zoned configuration, the first washcoat zone 24 is located upstream of the second washcoat zone 26 (or the second washcoat zone 26 is located downstream of the first washcoat zone 24).

[0091] For example, in some embodiments, the catalytic material of the catalyzed soot filter includes a selective oxidation catalyst composition and a second SCR material, which are disposed on the substrate in an axially zoned configuration. In some embodiments, the washcoat zone 24 represents a selective oxidation catalyst composition as disclosed herein and the second washcoat zone 26 represents a second SCR material as disclosed herein to provide a catalyzed soot filter, with the second SCR material disposed downstream of the selective oxidation catalyst composition. In another embodiment, the first washcoat zone 24 represents a second SCR material as disclosed herein and the second washcoat zone 26 represents a selective oxidation catalyst composition as disclosed herein to provide a catalyzed soot filter, with the selective oxidation catalyst composition disposed downstream of the second SCR.

[0092] In another example, the catalytic material of the catalyzed soot filter includes a selective oxidation catalyst composition and a second SCR material mixed in the same washcoat and disposed on a substrate in a layered configuration.

[0093] Method for preparing a catalyst composition Preparation of PGM component-impregnated support materials for NOx absorbent compositions typically involves impregnating a support material in particulate form with an active metal solution, such as a palladium and / or ruthenium precursor solution. The active metals may be impregnated into the same support particles or into separate support particles using incipient wetness techniques. In some embodiments, the support material is a metal oxide support.

[0094] Incipient wetness impregnation technique, also called capillary impregnation or dry impregnation, is commonly used in the synthesis of heterogeneous materials, e.g., catalysts. Typically, metal precursors are dissolved in an aqueous or organic solution, and then the metal-containing solution is added to a catalyst support that contains the same pore volume as the volume of the added solution. Capillary action draws the solution into the pores of the support. The solution added beyond the pore volume of the support changes the solution transport from a capillary action process to a much slower diffusion process. The catalyst is then dried and calcined to remove volatile components in the solution, depositing the metal on the surface of the catalyst support. The concentration profile of the impregnated material depends on the mass transfer conditions in the pores during impregnation and drying.

[0095] The carrier particles are typically dry enough to absorb substantially all of the solution and form a wet solid. An aqueous solution of a water-soluble compound or complex of the active metal (i.e., PGM component), such as ruthenium chloride, ruthenium nitrate (e.g., Ru(NO) and its salts), ruthenium hexaammine chloride, or a combination thereof, is typically utilized. An aqueous solution of a water-soluble compound having palladium as the active metal includes a metal precursor, such as palladium nitrate, palladium tetraamine, palladium acetate, or a combination thereof.

[0096] After treatment of the support particles with the active metal solution, the particles are dried by heat treating the particles at an elevated temperature (e.g., 100-150° C.) for a period of time (e.g., 1-3 hours) and then calcined to convert the active metal to a more catalytically active form. An exemplary calcination process involves heat treatment in air at a temperature of about 400-550° C. for 10 minutes to 3 hours. The above process may be repeated as necessary to reach the desired level of active metal impregnation. For additional examples of preparation of NOx absorbent compositions, see U.S. Pat. No. 5,472,673 to Goto et al., U.S. Pat. No. 5,599,758 to Guth et al., U.S. Pat. No. 5,750,082 to Hepburn et al., U.S. Pat. No. 8,105,559 to Melville et al., U.S. Pat. No. 8,475,752 to Wan et al., U.S. Pat. No. 8,592,337 to Holgendorff et al., U.S. Pat. No. 9,114,385 to Briskley et al., and U.S. Pat. No. 9,486,791 to Swallow et al., which are incorporated by reference in their entireties. No. 9,662,611 to Wan et al., U.S. Patent Application No. 2002 / 0077247 to Bender et al., U.S. Patent Application No. 2011 / 0305615 to Hilgendorff et al., U.S. Patent Application No. 2015 / 0157982 to Rajaram et al., U.S. Patent Application No. 2015 / 0158019 to Rajaram et al., U.S. Patent Application No. 2016 / 0228852 to Biberger et al., and International Patent Application No. WO2016 / 141142 to Grubert et al.

[0097] The preparation of metal-promoted molecular sieves for the SCR catalyst composition of the present invention generally involves ion-exchanging a metal (e.g., copper) into the molecular sieve. The ion-exchange process involves the molecular sieve in particulate form with a metal precursor solution. For example, a copper salt can be used to provide the copper. Such metals are generally ion-exchanged into an alkali metal or NH4 molecular sieve (e.g., NH4 into an alkali metal molecular sieve by methods known in the art, as disclosed in Bleken, F. et al. Topics in Catalysis 2009, 52, 218-228, which is incorporated herein by reference). -(Can be prepared by ion exchange).

[0098] For additional promotion of the SCR catalyst composition, in some embodiments, the molecular sieve may be promoted with two or more metals (e.g., copper in combination with one or more other metals). When two or more metals are included in the metal ion promoted molecular sieve material, multiple metal precursors (e.g., copper and iron precursors) may be ion exchanged simultaneously or separately. In certain embodiments, a second metal may be exchanged into a molecular sieve material first promoted with a first metal (e.g., a second metal may be exchanged into a molecular sieve material promoted with copper). The second molecular sieve material may vary and in some embodiments may be iron or an alkaline earth or alkali metal. Suitable alkaline earth or alkali metals may include, but are not limited to, barium, magnesium, beryllium, calcium, strontium, and combinations thereof. For examples of the preparation of SCR catalyst compositions containing metal-promoted molecular sieves, see U.S. Pat. No. 9,480,976 to Rivas-Cardona et al., U.S. Pat. No. 9,352,307 to Stiebels et al., U.S. Pat. No. 9,321,009 to Wan et al., U.S. Pat. No. 9,199,195 to Andersen et al., U.S. Pat. No. 9,138,732 to Bull et al., U.S. Pat. No. 9,011,807 to Mohanan et al., U.S. Pat. No. 9,011,807 to Tu et al., all of which are incorporated by reference in their entireties. See U.S. Patent No. 8,715,618 to rkhan et al., U.S. Patent No. 8,293,182 to Boorse et al., U.S. Patent No. 8,119,088 to Boorse et al., U.S. Patent No. 8,101,146 to Fedeyko et al., U.S. Patent No. 7,220,692 to Marshall et al., U.S. Patent No. 4,961,917 to Byrne et al., U.S. Patent No. 4,010,238 to Shiraishi et al., and U.S. Patent No. 4,085,193 to Nakajima et al.

[0099] For the preparation of SCR catalyst compositions containing mixed metal oxides, see, e.g., U.S. Pat. No. 4,518,710 to Brennan et al., U.S. Pat. No. 5,137,855 to Hegedus et al., U.S. Pat. No. 5,476,828 to Kapteijn et al., U.S. Pat. No. 8,685,882 to Hong et al., and U.S. Pat. No. 9,101,908 to Jurng et al., which are incorporated by reference in their entireties.

[0100] Substrate Coating Process The catalyst compositions described above are typically prepared in the form of catalyst particles, as described above, which may be mixed with water to form a slurry for the purpose of coating a catalytic substrate, such as a honeycomb-type substrate.

[0101] In addition to the catalyst particles, the slurry may optionally contain a binder in the form of alumina, silica, zirconium acetate, colloidal zirconia, or zirconium hydroxide, an associative thickener, and / or a surfactant, including anionic, cationic, nonionic, or amphoteric surfactants. Other exemplary binders include bohemite, gamma-alumina, or delta / theta alumina, and silica sol. When present, binders are typically used in an amount of about 1-5% by weight of the total washcoat content.

[0102] The addition of acidic or basic species to the slurry may be performed to adjust the pH accordingly. For example, in some embodiments, the pH of the slurry is adjusted by the addition of aqueous ammonium hydroxide or nitric acid. A typical pH range for the slurry is about 3-6.

[0103] The slurry may be milled to reduce particle size and enhance particle mixing. Milling may be accomplished in a ball mill, continuous mill, or other similar equipment, and the solids content of the slurry may be, for example, about 20-60% by weight, more specifically, about 20-40% by weight. In one embodiment, the slurry after milling is characterized by a D90 particle size of about 10 to about 40 microns, preferably 10 to about 30 microns, and more preferably about 10 to about 15 microns. D90 is determined using a dedicated particle size analyzer. The instrument was manufactured by Sympatec in 2010 and uses laser diffraction to measure the particle size of a small amount of slurry. D90 typically means that 90% of the particles by number have a diameter less than the estimated value, in microns.

[0104] The slurry is coated onto a substrate using any washcoat technique known in the art. In one embodiment, the substrate is dipped into or otherwise coated with the slurry one or more times. The coated substrate is then dried at an elevated temperature (e.g., 100-150° C.) for a period of time (e.g., 10 minutes to about 3 hours) and then calcined, for example, by heating at 400-600° C. for typically about 10 minutes to about 3 hours. After drying and calcination, the final washcoat coating layer can be considered essentially solvent-free.

[0105] After calcination, the catalyst content obtained by the above washcoat technique can be determined by calculating the difference between the coated and uncoated weights of the substrate. As will be apparent to those skilled in the art, the catalyst content can be altered by changing the slurry rheology. In addition, the washcoat coating / drying / calcining process can be repeated as necessary to build up the coating to a desired content level or thickness, meaning that more than one washcoat can be applied.

[0106] Waste Treatment Systems The present invention also provides an emission treatment system incorporating the catalytic article described herein. The catalytic article of the present invention is typically used in an integrated emission treatment system with one or more additional components for the treatment of exhaust gas emissions, for example, exhaust gas emissions from a diesel engine. For example, the emission treatment system may further include a catalyzed soot filter (CSF) and / or a diesel oxidation catalyst (DOC). The catalytic article of the present invention is typically located upstream or downstream of the soot filter and downstream of the diesel oxidation catalyst component, although the relative placement of the various components of the emission treatment system may vary. The treatment system may include further components, such as a reductant injector for the ammonia precursor, and may optionally include any additional particle filtering components. The above list of components is merely illustrative and should not be construed as limiting the scope of the present invention.

[0107] One exemplary emission treatment system is illustrated in FIG. 7, which illustrates a schematic diagram of an emission treatment system 32. As shown, a stream of exhaust gas containing gaseous pollutants and particulate matter is conveyed from an engine 34 via an exhaust pipe 36 to a diesel oxidation catalyst (DOC) 38, a catalyzed soot filter (CSF) 42, and a catalyst article of the present invention (i.e., SCR / NOxAd component 46). In the DOC 38, most of the unburned gaseous and non-volatile hydrocarbons (SOF) and carbon monoxide are combusted to form carbon dioxide and water. In addition, a certain percentage of NO of the NOx component may be oxidized to NO2 in the DOC.

[0108] The exhaust stream is then conveyed via exhaust pipe 40 to a catalyzed soot filter (CSF) 42, which traps particulate matter present in the exhaust gas stream. The CSF 42 is optionally catalyzed for passive or active soot regeneration. The CSF 42 may optionally include an SCR catalyst composition for conversion of NOx present in the exhaust gas.

[0109] After removal of particulate matter, the exhaust gas stream is conveyed via the CSF 42 to a downstream catalyst article of the present invention (i.e., SCR / NOxAd component 46) via exhaust pipe 44 for further processing and / or conversion of NOx. The exhaust gas passes through component 46 at a flow rate that allows sufficient time for the catalyst composition to reduce the level of NOx in the exhaust gas at a given temperature. An injector 50 for introducing a nitrogen-containing reductant into the exhaust stream is located upstream of the SCR / NOx component 46. The nitrogen-containing reductant introduced into the gas exhaust stream promotes the reduction of NOx to N2 and water when the gas is exposed to the catalyst composition at 46. In the case of an emission treatment system where the CSF 42 already contains an SCR catalyst composition, the injector 50 for introducing a nitrogen-containing reductant into the exhaust stream is located upstream of the CSF 42. Alternatively, for an emissions system including a CSF 42 with an SCR catalyst and an SCR / NOxAd component 46, one and / or two injectors 50 may be included upstream of the CSF 42 and / or the SCR / NOxAd component 46. The nitrogen-containing reductant introduced into the gas exhaust stream promotes the reduction of NOx to N2 and water when the gas is exposed to the catalyst composition.

[0110] Additionally, the nitrogen-containing reductant may be introduced into the exhaust gas prior to contact with the SCR / NOxAd component 46 for treatment of NOx. Generally, the reductant for the SCR process broadly refers to any compound that facilitates the reduction of NOx in the exhaust gas. Examples of such reductants include ammonia, hydrazine, or any suitable ammonia precursor, such as urea ((NH2)2CO), ammonium carbonate, ammonium carbamate, ammonium bicarbonate, or ammonium formate.

[0111] Another exemplary emissions treatment system is illustrated in FIG. 8, which illustrates a schematic diagram of an emissions treatment system 72. As shown, the exhaust gas flow is conveyed from an engine 74 to a diesel oxidation catalyst (DOC) 78 via an exhaust pipe 76. The exhaust flow is then conveyed via an exhaust pipe 80 to a catalyst article of the present invention (i.e., SCR / NOxAd component 82) located upstream of a catalyzed soot filter (CSF) 86. The CSF 86 may optionally include an SCR catalyst composition for conversion of NOx present in the exhaust gas. The exhaust gas flow then exits the SCR / NOxAd component 82 via an exhaust pipe 84 that leads to the CSF 86. An injector 70 for introducing a nitrogen-containing reductant into the exhaust flow is located upstream of the SCR / NOxAd component 82. Alternatively, in the case of an emissions treatment system including a CSF 86 with an SCR catalyst and an SCR / NOxAd component 82 , one and / or two injectors 70 may be included upstream of the CSF 86 and / or the SCR / NOxAd component 82 .

[0112] Another exemplary emissions treatment system is illustrated in FIG. 9, which illustrates a schematic diagram of an emissions treatment system 90. As shown, a flow of exhaust gas is conveyed from an engine 91 to a catalyst article of the present invention (i.e., SCR / NOxAd component 94) via an exhaust pipe 92. An injector 93 for introducing a nitrogen-containing reductant into the exhaust flow is located upstream of the SCR / NOxAd component 94. The exhaust flow is then conveyed via an exhaust pipe 95 to a catalyst component A (96) located upstream of the SCR / NOxAd component 94. Catalyst component A can be, but is not limited to, a diesel oxidation catalyst, a catalyzed soot filter, or a selective catalytic reduction catalyst. The exhaust flow then exits catalyst component A via an exhaust pipe 97, which leads to catalyst component B (98), if present. The presence of catalyst component B is optional and can be, but is not limited to, a catalyzed soot filter, a diesel oxidation catalyst, or a selective catalytic reduction catalyst.

[0113] With respect to this SCR process, a method is provided herein for the reduction of NOx in an exhaust gas, the method comprising contacting the exhaust gas with a catalytic article of the present invention (i.e., a combination of an SCR catalyst and a NOx absorbent composition), optionally in the presence of a reducing agent, for a time and at a temperature sufficient to catalytically reduce NOx, thereby reducing the concentration of NOx in the exhaust gas. In certain embodiments, the temperature range is from about 200° C. to about 600° C. The catalytic article of the present invention can be fresh or hydrothermally aged. The amount of NOx reduction depends on the contact time of the exhaust gas stream with the catalytic article, and thus on the space velocity. The contact time and space velocity are not particularly limited herein. Thus, the catalytic article may perform well at high space velocities, which are desirable in certain applications. In some embodiments, the amount of NOx (i.e., a mixture of NO and NO2) in the exhaust gas stream that is converted to nitrogen and water ranges from about 50% to about 99.9% by weight, preferably from about 75% to about 99.9% by weight, based on the total amount of NOx present in the exhaust gas stream. In some embodiments, the amount of NOx converted may be at least 50%, 60%, 70%, 80%, 90%, or 95% by weight based on the total amount of NOx present in the exhaust gas stream, with each value being understood to have an upper limit of 100%.

[0114] In some embodiments, a method for reducing NOx in an exhaust gas includes contacting the exhaust gas with a catalytic article of the present invention, wherein the SCR catalyst composition and the NOx absorber composition are disposed on the same substrate such that both compositions are at substantially the same operating temperature. The amount of NOx levels reduced by the catalytic article of the present invention is higher compared to a combination of a catalytic article having the same NOx absorber composition and SCR catalyst composition disposed on separate substrates.

[0115] Regarding the process of absorbing and releasing NOx of the catalyst article of the present invention, a method for absorbing NOx (NO, NO2, or mixtures thereof) in an exhaust gas stream is provided. Such a method may include contacting the gas stream with a NOx absorbent composition as described herein for a time and at a temperature sufficient to reduce the level of NOx in the exhaust gas stream. In some embodiments, the amount of NOx absorbed from the exhaust gas stream is about 15% to about 99.9% by weight, preferably about 30% to about 99.9% by weight, based on the total amount of NOx present in the exhaust gas stream. The amount of NOx absorbed may be, in some embodiments, at least 15%, 25%, 35%, 45%, 55%, 65%, 75%, 85%, or 95% by weight, based on the total amount of NOx present in the exhaust gas stream, each value being understood to have an upper limit of 100%. In some embodiments, the temperature is less than about 200° C., less than about 150° C., or less than about 100° C.

[0116] Another aspect of the invention is directed to a method for releasing NOx (i.e., a mixture of NO and NO2) from a NOx absorbent composition into an exhaust gas stream at a temperature sufficient for an SCR catalyst composition (located in the same substrate as the NOx absorbent composition in an exhaust gas treatment system) to convert NO to N2. In some embodiments, the amount of NO released back into the exhaust gas stream is at least about 55% to about 100%, or at least about 75% to about 100% (alternatively at least about 55%, at least about 65%, at least about 75% by weight, at least about 85% by weight, at least about 95% by weight, or at least about 99.9% by weight) based on the total amount of NO absorbed in the NOx absorbent. In some embodiments, the temperature of release of NO from the NOx absorbent composition ranges from about 170°C to about 350°C, preferably from about 250°C to about 350°C.

Claims

1. A substrate, a selective catalytic reduction (SCR) catalyst composition and a nitrogen oxide (NOx) absorber composition are both disposed on the substrate; the NOx absorbent composition comprises an alkaline earth metal component; The SCR catalyst composition comprises FeTiO ３ , FeAl ２ O ３ , MgTiO ３ , MgAlO ３ , MnO Ｘ / TiO ２ , CuTiO ３ , CeZrO ２ , TiZrO ２ , V ２ O ５ / TiO ２ and mixtures thereof; on said substrate, said SCR catalyst composition being in a first layer, said NOx absorbent composition being in a second layer, at least a portion of said second layer being directly on said substrate, and at least a portion of said first layer being on said second layer; a first layer disposed on the substrate, the first layer extending from the first end of the substrate to a first region of the substrate, the second layer extending from the first region ...

2. A catalyst article as described in claim 1, wherein the NOx absorbent composition does not contain platinum or the platinum metal present in the NOx absorbent composition is less than 0.01 weight percent.

3. 10. The catalytic article of claim 1, wherein the NOx sorbent composition comprises a platinum group metal (PGM) component selected from Ru, Pd, Rh and combinations thereof impregnated on a support material.

4. The catalytic article of claim 3 , wherein the support material is a molecular sieve or a metal oxide.

5. 5. The catalytic article of claim 4, wherein the molecular sieve is a zeolite and the metal oxide support comprises ceria.

6. The catalytic article of claim 5 , wherein the metal oxide is doped with at least one lanthanide group metal.

7. The catalytic article of claim 1 , wherein the alkaline earth metal component comprises a barium component.

8. The catalyst article of claim 1 , wherein the SCR catalyst composition comprises a metal promoted molecular sieve.

9. 9. The catalytic article of claim 8, wherein the metal of the metal-promoted molecular sieve is selected from Cu, Co, Ni, La, Mn, Fe, V, Ag, Ce, Nd, Mo, Hf, Y, W, and combinations thereof.

10. 10. The catalyst article of claim 8, wherein the metal-promoted molecular sieve is a zeolite having a structure type selected from AEI, AFT, AFV, AFX, AVL, CHA, DDR, EAB, EEI, ERI, IFY, IRN, KFI, LEV, LTA, LTN, MER, MWF, NPT, PAU, RHO, RTE, RTH, SAS, SAT, SAV, SFW, TSC, and UFI, and combinations thereof.

11. The catalytic article of claim 1 , wherein the mixed metal oxide component comprises titania and vanadia.

12. 10. The catalytic article of claim 1, wherein the substrate is a honeycomb substrate selected from the group consisting of a flow-through substrate and a wall flow filter.

13. The catalytic article of claim 1 , wherein the catalytic article is effective for reducing NOx from an engine exhaust gas stream.

14. 13. A method for treating an exhaust gas stream comprising contacting the exhaust gas stream with the catalytic article of claim 1 such that NOx in the exhaust gas stream is reduced.

15. 1. An emissions treatment system for treating an exhaust gas stream, comprising: an engine generating a stream of exhaust gas; 10. The catalytic article of claim 1 , positioned downstream of the engine in fluid communication with the exhaust gas stream and adapted for reducing NOx within the exhaust gas stream to form a treated exhaust gas stream; an injector positioned upstream of the catalytic article and adapted to add a reductant to the exhaust gas stream.

16. 16. The emissions treatment system of claim 15, further comprising one or both of a diesel oxidation catalyst located upstream of the catalyst article, and a catalyzed soot filter located downstream of the catalyst article.

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