Adjustable NOx adsorbent

Abstract

The present disclosure relates to a method for reducing nitrogen oxides (NOx) emissions from a diesel or lean-burn gasoline engine after a cold start of the engine. x The present invention is directed to a method for treating a gaseous exhaust stream containing at least one low-temperature NO. x The present disclosure also relates to the NO 2 -containing LT-NA composition, which comprises a rare earth metal component, a platinum group metal (PGM) component, and a dopant. x Adsorption / desorption profile of NO in LT-NA compositions x The present invention is directed to a method for adjusting the temperature range of the catalyst, the desorption temperature range, or both.

Description

Technical Field

[0001] The present invention is directed to a method suitable for treating the exhaust gas flow of an internal combustion engine to reduce the emission of nitrogen oxides (NO x x).

Background Art

[0002] Environmental regulations regarding emissions from internal combustion engines are becoming increasingly stringent worldwide. 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), and NO x x represents various chemical species of nitrogen oxides including nitric oxide and nitrogen dioxide. NO x x is a harmful component of air pollution. Various treatment methods have been used to treat NO x x-containing gas mixtures to reduce air pollution.

[0003] An effective method for reducing NO x x from the exhaust of lean burn engines requires the reaction of NO x 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 reducing agents in the presence of atmospheric oxygen, thereby mainly forming nitrogen and steam: 4NO + 4NH 3 3 + O 2 2 → 4N 2 2 + 6H 2 2O (standard SCR reaction) 2NO 2 2 + 4NH 3 3 + O 2 2 → 3N 2 2 + 6H 2 2O (low-speed SCR reaction) NO + NO 2 2 + 2NH 3→2N 2 +3H 2 O (Fast SCR reaction)

[0004] The 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 can catalytically reduce NO in the exhaust components effectively at temperatures below 600 °C, so that even under low-load conditions typically associated with lower exhaust temperatures, reduced NO x levels can be achieved. x

[0005] The main problem encountered in the treatment of automotive exhaust gas flow is the so-called "cold start" period, which is the period at the start of the treatment process when the exhaust gas flow 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 the 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 N 2 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-term low-speed urban driving. Therefore, there is a strong need for catalyst components that can capture and store such low-temperature NO x emissions and release the NO x emissions at a higher temperature (>200 °C) when the catalyst component (i.e., the SCR catalyst component) becomes effective. As a result, considerable efforts have been made to mitigate this problem.

[0006] There are several ways to minimize NO x emissions during the cold start period. For example, these exhaust gas emissions (i.e., HC, CO, and NO xA capture system has been developed that stores exhaust gas emissions at low temperatures and then releases these exhaust gas emissions at a higher temperature when the remaining catalyst components of the treatment system reach sufficient catalytic activity. One such system is the well-known and commercially proven lean NO x capture (LNT) catalyst.

[0007] The lean NO x capture (LNT) catalyst contains a NO x adsorbent component that captures NO x under specific exhaust conditions. For example, the NO x adsorbent component may contain alkaline earth elements, such as oxides and carbonates of alkaline earth metals, such as Mg, Ca, Sr, and / or Ba oxides. Other LNT catalysts may contain rare earth metal oxides, such as oxides of Ce, La, Pr, and / or Nd, as the NO x adsorbent component. The LNT catalyst further contains a platinum group metal component (PGM), such as platinum, dispersed on a refractory metal oxide (e.g., alumina) support for catalytic NO x oxidation and reduction. The LNT catalyst operates under periodic lean (capture mode) and rich (regeneration mode) exhaust conditions. Under lean conditions, the LNT catalyst captures and stores NO x as inorganic nitrates (e.g., when the NO x adsorbent component is BaO or BaCO x , this is converted to Ba(NO 3 )) 3 ) 2 during the reaction of NO x . The NO x adsorbent component then releases the captured NO x , and the PGM component reduces NO 2 to N 2 under stoichiometric or transient rich engine operating conditions, or under lean engine operation where an external fuel is injected into the exhaust to induce a rich condition. The conversion of NO to NO xAlthough it is a prerequisite for capture, the reaction rate is very slow when the temperature is less than 200 °C, which makes conventional LNT catalysts inefficient for capturing cold start NO x emissions. Furthermore, a rich purge is required to regenerate the LNT catalyst, which reduces fuel consumption, but only minimally. Therefore, a preferred solution would be to provide a NO x absorption / emission component that operates only under lean conditions.

[0008] As exhaust gas regulations are becoming increasingly stringent, it would be highly desirable to provide an improved NO x adsorbent for capturing cold start NO x emissions. Using a catalyst that functions during low temperature operation (<150 °C) can help meet these increasingly stringent emission regulations (e.g., Euro-7 regulations). Since >80% of cold start NO x emissions consist of NO, such an advanced NO x adsorbent material must have excellent efficiency for NO adsorption. Recently, passive lean NO x adsorbents (PNA) using Pd on small pore zeolites as NO X adsorbents have been reported. The drawback of this type of NO x adsorbent is that they are not good at NO 2 adsorption and that the NO x adsorption and desorption windows do not exactly match the transient cold start vehicle requirements. Another type of NO x adsorbent is the low temperature NO x adsorbent (LT-NA) that uses rare earth and / or alkali metal adsorbents. These have the drawback that NO x species tend to adsorb to the NO x adsorbent at a wide range of active sites, thereby broadening the NO x desorption temperature window and not matching the transient cold start vehicle requirements either.

[0009] Therefore, cold start NOx It is highly desirable to provide an improved adjustable LT-NA for capturing emissions, the NO x adsorption / desorption characteristics of which can be adjusted to meet the requirements of each vehicle. SUMMARY OF THE INVENTION

[0010] Low temperature NO x emissions are captured and stored, and when the downstream catalyst component (i.e., SCR catalyst) becomes effective, NO x There is a strong demand for a method of releasing emissions at a higher temperature (>200 °C). Surprisingly, according to the present disclosure, a low temperature NO x adsorbent (LT-NA) composition containing a rare earth metal component, a platinum group metal (PGM) component, and a dopant, wherein the PGM and the dopant are disposed on or impregnated in the rare earth metal component, has been found to be able to adjust the adsorption / desorption characteristics of the composition by selecting the dopant and the loading amounts of the rare earth metal component, the PGM component, and the dopant. Thus, the present disclosure generally relates to a method of treating an NO x containing exhaust stream with an LT-NA component containing such a composition, as well as a method of adjusting one or both of the NO x adsorption / desorption profile and the NO x desorption temperature range of such an LT-NA composition. In particular, the method of utilizing the LT-NA component disclosed herein is suitable for adsorbing NO x at low temperatures and controlling the high temperature for releasing the captured NO x in accordance with individual vehicle requirements.

[0011] Thus, in one aspect, a method for treating a gaseous exhaust stream containing a mixture of nitrogen oxides (NO x ) flowing from the exhaust manifold of a diesel engine or a lean burn gasoline engine during a period after a cold start of the engine, the method comprising passing the gaseous exhaust stream through a low temperature NO containing an LT-NA composition xContact with the adsorbent (LT-NA) component, the LT-NA component is disposed downstream of the exhaust manifold and in fluid communication therewith, the LT-NA composition comprising a rare earth metal component, a platinum group metal (PGM) component, a transition metal oxide, an alkaline earth metal oxide, an oxide of any element of Groups 13-15 of the periodic table, or a dopant selected from combinations thereof, the PGM and the dopant being disposed on or impregnated in the rare earth metal component, the LT-NA component storing NO at a temperature below 200°C x and being effective to release the stored NO x at a predetermined elevated temperature, a method is provided.

[0012] In some embodiments, the rare earth metal component comprises ceria. In some embodiments, the rare earth metal component is ceria.

[0013] In some embodiments, the dopant is a transition metal oxide. In some embodiments, the transition metal oxide is an oxide of manganese. In some embodiments, the dopant is an alkaline earth metal oxide. In some embodiments, the alkaline earth metal oxide is an oxide of magnesium, calcium, or barium. In some embodiments, the dopant is an oxide of any element of Groups 13-15 of the periodic table. In some embodiments, the oxide of any of Groups 13-15 of the periodic table is an oxide of boron, silicon, tin, phosphorus, antimony, or bismuth. In some embodiments, the dopant is an oxide of magnesium, manganese, or tin. In some embodiments, the dopant is an oxide of manganese.

[0014] In some embodiments, the PGM component comprises palladium, platinum, rhodium, rhenium, ruthenium, iridium, or combinations thereof. In some embodiments, the PGM component comprises palladium, platinum, or mixtures thereof.

[0015] In some embodiments, the predetermined NO xThe release temperature is above about 200 °C. In some embodiments, the predetermined temperature is in the temperature range of about 200, about 225, about 250, or about 275 to about 300, about 325, about 350, about 400, or about 450 °C.

[0016] In some embodiments, the LT-NA component includes a substrate and one or more washcoats disposed on at least a portion of the substrate and containing an LT-NA composition. In some embodiments, the one or more washcoats are coated on the substrate in a layered or zoned configuration. In some embodiments, the substrate is a wall flow or flow-through substrate.

[0017] In some embodiments, treating the gaseous exhaust stream includes selectively removing at least a portion of the NO in the gaseous exhaust stream. x In some embodiments, treating the gaseous exhaust stream includes adjusting the distribution of nitrogen monoxide (NO) and nitrogen dioxide (NO 2 ) in the gaseous exhaust stream.

[0018] In some embodiments, the LT-NA component is effective to store one or more of NO and NO 2 at a temperature below about 200 °C and release one or both of NO and NO 2 at a predetermined temperature. In some embodiments, the predetermined temperature is above about 200 °C. In some embodiments, the predetermined temperature is in the temperature range of about 200, about 225, about 250, or about 275 to about 300, about 325, about 350, about 400, or about 450 °C. In some embodiments, the LT-NA component is effective to release one or both of NO and NO 2 at a temperature above about 300 °C. In some embodiments, the LT-NA component is effective to release one or both of NO and NO 2 at a temperature above about 325 °C.

[0019] In some embodiments, the contacting comprises continuously passing a gaseous exhaust stream at an initial temperature of about 150 °C or less into contact with the LT-NA component and gradually warming it during further engine operation, and adsorbing and storing NO from the gaseous exhaust stream until the exhaust gas stream reaches a predetermined temperature, releasing NO into the exhaust gas stream exiting the LT-NA component, and continuously passing the exhaust gas stream exiting the LT-NA component into contact with at least one downstream catalyst material to heat the downstream catalyst materials to an operating temperature of about 200 °C to about 450 °C as the exhaust gas stream increases in temperature, and further oxidizing NO or reducing NO and NO x therefrom. x In another aspect, a method for adjusting one or both of the NO adsorption / desorption profile of an LT-NA composition and the NO desorption temperature range of the LT-NA composition is provided, wherein the LT-NA composition comprises a rare earth metal component, a platinum group metal (PGM) component, and a dopant selected from a transition metal oxide, an alkaline earth metal oxide, an oxide of any element of Groups 13-15 of the periodic table, or combinations thereof, and the PGM component and the dopant are disposed on or impregnated in the rare earth metal component, and the method comprises selecting the dopant and selecting the loading amounts of the rare earth metal component, the PGM component, and the dopant. 2 therefrom.

[0020] In some embodiments, the rare earth metal component comprises ceria. In some embodiments, the rare earth metal component is ceria. x In some embodiments, NO x adsorption / desorption profiles and NO

[0021] desorption temperature ranges of the LT-NA composition are provided.

[0022] In some embodiments, NO xThe desorption temperature range is about 150, about 175, about 200, about 225, or about 250 to about 275, about 300, about 325, about 350, or about 400 °C. In some embodiments, NO is desorbed over a temperature range of about 150, about 175, about 200, about 225, or about 250 to about 275, about 300, about 325, about 350, or about 400 °C. In some embodiments, NO 2 is desorbed over a temperature range of about 150, about 175, about 200, about 225, or about 250 to about 275, about 300, about 325, about 350, or about 400 °C.

[0023] In some embodiments, NO x Adjusting the adsorption / desorption profile involves adjusting the ratio of NO desorbed at a given temperature over the desorption temperature range of the LT-NA composition to NO x and NO 2 and.

[0024] In another aspect, a rare earth metal component, a platinum group metal (PGM) component, a dopant selected from a transition metal oxide, an alkaline earth metal oxide, an oxide of any element of Groups 13-15 of the periodic table, or a combination thereof, wherein the PGM and the dopant are disposed on or impregnated in the rare earth metal component, and the LT-NA composition stores NO at a temperature below 200 °C x and is effective to release the stored NO x at a predetermined temperature, a low temperature NO x adsorbent (LT-NA) composition is provided. In some embodiments, the rare earth metal component includes ceria.

[0025] In another aspect, an LT-NA article is provided that includes a substrate and one or more washcoats disposed on at least a portion of the substrate and including the LT-NA composition disclosed herein. In some embodiments, the one or more washcoats are coated on the substrate in a layered or zoned configuration. In some embodiments, the substrate is a wall flow or flow-through substrate.

[0026] The present disclosure includes, but is not limited to, the following embodiments.

[0027] Embodiment 1: A method for treating a gaseous exhaust stream containing a mixture of nitrogen oxides (NOx) flowing from an exhaust manifold of a diesel engine or a lean-burn gasoline engine during a period after a cold start of the engine, the method comprising contacting the gaseous exhaust stream with a low-temperature NOx adsorbent (LT-NA) component containing an LT-NA composition, the LT-NA component being disposed downstream of the exhaust manifold and in fluid communication therewith, the LT-NA composition comprising a rare earth metal component, a platinum group metal (PGM) component, a transition metal oxide, an alkaline earth metal oxide, an oxide of any element of Groups 13-15 of the periodic table, or a combination thereof, as a dopant, the PGM and the dopant being disposed on or impregnated in the rare earth metal component, the LT-NA component being effective to store NOx at a temperature below 200°C and release the stored NOx at a predetermined temperature.

[0028] Embodiment 2: The method according to Embodiment 1, wherein the rare earth metal component comprises ceria.

[0029] Embodiment 3: The method according to Embodiment 1 or 2, wherein the dopant is a transition metal oxide.

[0030] Embodiment 4: The method according to Embodiment 3, wherein the transition metal oxide is an oxide of manganese.

[0031] Embodiment 5: The method according to any one of Embodiments 1-4, wherein the dopant is an alkaline earth metal oxide.

[0032] Embodiment 6: The method according to Embodiment 5, wherein the alkaline earth metal oxide is an oxide of magnesium, calcium, or barium.

[0033] Embodiment 7: The method according to Embodiment 1 or 2, wherein the dopant is an oxide of any element of Groups 13-15 of the periodic table.

[0034] Embodiment 8: The method according to Embodiment 7, wherein the oxide of any one of Groups 13 to 15 of the periodic table is an oxide of boron, silicon, tin, phosphorus, antimony, or bismuth.

[0035] Embodiment 9: The method according to Embodiment 1 or 2, wherein the dopant is an oxide of magnesium, manganese, or tin.

[0036] Embodiment 10: The method according to Embodiment 1 or 2, wherein the dopant is an oxide of manganese.

[0037] Embodiment 11: The method according to any one of Embodiments 1 to 10, wherein the PGM component comprises palladium, platinum, rhodium, rhenium, ruthenium, iridium, or a combination thereof.

[0038] Embodiment 12: The method according to any one of Embodiments 1 to 11, wherein the PGM component comprises palladium, platinum, or a mixture thereof.

[0039] Embodiment 13: The stored NO x The method according to any one of Embodiments 1 to 12, wherein the predetermined temperature for releasing is above about 200°C.

[0040] Embodiment 14: The stored NO x The method according to any one of Embodiments 1 to 13, wherein the predetermined temperature for releasing is in the temperature range of about 200, about 225, about 250, or about 275 to about 300, about 325, about 350, about 400, or about 450°C.

[0041] Embodiment 15: The method according to any one of Embodiments 1 to 14, wherein the LT-NA component comprises a substrate and one or more washcoats disposed on at least a portion of the substrate and containing an LT-NA composition.

[0042] Embodiment 16: The method according to embodiment 15, wherein one or more washcoats are coated on a substrate in a layered or zoned configuration.

[0043] Embodiment 17: The method according to embodiment 15 or 16, wherein the substrate is a wall flow or flow-through substrate.

[0044] Embodiment 18: The method according to any one of embodiments 1 to 17, wherein treating the exhaust gas stream further comprises selectively removing at least a portion of NO in the gaseous exhaust stream. x

[0045] Embodiment 19: The method according to any one of embodiments 1 to 17, wherein treating the exhaust gas stream further comprises adjusting the distribution of nitrogen monoxide (NO) and nitrogen dioxide (NO₂) in the gaseous exhaust stream. 2

[0046] Example 20: The method according to any one of embodiments 1 to 19, wherein the LT-NA component is effective to store one or more of NO and NO₂ at a temperature below about 200 °C and release one or both of NO and NO₂ at a predetermined temperature. 2 2

[0047] Embodiment 21: The method according to embodiment 20, wherein the predetermined temperature for releasing NO, NO₂, or both is above about 200 °C. 2

[0048] Embodiment 22: The method according to embodiment 20 or 21, wherein the predetermined temperature for releasing NO, NO₂, or both is in the temperature range of about 200, about 225, about 250, or about 275 to about 300, about 325, about 350, about 400, or about 450 °C. 2

[0049] Embodiment 23: The method according to any one of embodiments 1 to 22, wherein the LT-NA component is effective to release one or both of NO and NO₂ at a temperature above about 300 °C.

[0050] Embodiment 24: The method according to any one of Embodiments 1 to 23, wherein the LT-NA component is effective in releasing one or both of NO and NO2 at a temperature above about 325°C.

[0051] Embodiment 25: Contacting the gaseous exhaust stream with the LT-NA component, continuously passing an exhaust gas stream at an initial temperature of about 150°C or less in contact with the LT-NA component, and gradually warming it during further engine operation; and adsorbing and storing NO from the exhaust gas stream until the exhaust gas stream reaches a predetermined temperature, releasing NO into the exhaust gas stream exiting the LT-NA component, and continuously passing the exhaust gas stream exiting the LT-NA component in contact with at least one downstream catalyst material to further oxidize nitric oxide or reduce nitric oxide and nitrogen dioxide, the method according to any one of Embodiments 1 to 24. x by adsorbing and storing it, x releasing NO into the exhaust gas stream exiting the LT-NA component, and heating the exhaust gas stream exiting the LT-NA component to an operating temperature of about 200 to about 450°C for each downstream catalyst material as the temperature of the exhaust gas stream rises, continuously passing the exhaust gas stream exiting the LT-NA component in contact with at least one downstream catalyst material to further oxidize nitric oxide or reduce nitric oxide and nitrogen dioxide, the method according to any one of Embodiments 1 to 24.

[0052] Embodiment 26: Injecting ammonia or an ammonia precursor into the exhaust stream downstream of the LT-NA component and upstream of the selective catalytic reduction (SCR) catalyst article, further comprising adjusting the timing and duration of the injection according to the NO x release profile of the LT-NA component, the method according to any one of Embodiments 1 to 25.

[0053] Embodiment 27: The NO x adsorption / desorption profile of the LT-NA composition and the NO xA method for adjusting one or both of the desorption temperature ranges, wherein the LT-NA composition comprises a rare earth metal component, a platinum group metal (PGM) component, a transition metal oxide, an alkaline earth metal oxide, an oxide of any element of Groups 13-15 of the periodic table, or a combination thereof. A method, wherein the PGM component and the dopant are disposed on or impregnated in the rare earth metal component, the method comprising selecting a dopant and selecting the loading amounts of the rare earth metal component, the PGM component, and the dopant.

[0054] Embodiment 28: The method according to embodiment 27, wherein the rare earth metal component comprises ceria.

[0055] Embodiment 29: NO x The method according to embodiment 27 or 28, wherein the desorption temperature range is about 150, about 175, about 200, about 225, or about 250 to about 275, about 300, about 325, about 350, or about 400 °C.

[0056] Embodiment 30: NO is desorbed over a temperature range of about 150, about 175, about 200, about 225, or about 250 to about 275, about 300, about 325, about 350, or about 400 °C, according to any one of embodiments 27-29.

[0057] Embodiment 31: NO 2 is desorbed over a temperature range of about 150, about 175, about 200, about 225, or about 250 to about 275, about 300, about 325, about 350, or about 400 °C, according to any one of embodiments 27-30.

[0058] Embodiment 32: NO x Adjusting the adsorption / desorption profile comprises adjusting the ratio of NO desorbed at a given temperature over the NOx desorption temperature range of the LT-NA composition to NO 2 and NO, according to any one of embodiments 27-31.

[0059] Embodiment 33: A low-temperature NOx adsorbent (LT-NA) composition comprising a rare earth metal component, a platinum group metal (PGM) component, a dopant selected from a transition metal oxide, an alkaline earth metal oxide, an oxide of any element of Groups 13 to 15 of the periodic table, or a combination thereof, wherein the PGM and the dopant are disposed on or impregnated in the rare earth metal component, and the LT-NA composition stores NOx at a temperature below 200°C and is effective for releasing the stored NO x at a predetermined temperature. x

[0060] Embodiment 34: The LT-NA composition according to Embodiment 33, wherein the rare earth metal component contains ceria.

[0061] Embodiment 35: A low-temperature NOx adsorbent (LT-NA) article comprising a substrate and one or more washcoats disposed on at least a part of the substrate, the one or more washcoats comprising the LT-NA composition according to Embodiment 33 or 34.

[0062] Embodiment 36: The LT-NA article according to Embodiment 35, wherein the one or more washcoats are coated on the substrate in a layered or zoned configuration.

[0063] Embodiment 37: The LT-NA article according to Embodiment 35 or 36, wherein the substrate is a wall flow or flow-through substrate.

[0064] ​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, unless the context clearly indicates otherwise, it is intended that the separable features or elements of the disclosed invention be combinable in any of its various aspects and embodiments. Other aspects and advantages of the present invention will become apparent below.

Brief Description of the Drawings

[0065] To provide an understanding of the embodiments of the present invention, reference is made to the accompanying drawings, in which reference numerals indicate components of typical embodiments of the present invention. The drawings are merely examples and should not be construed as limiting the present invention. The disclosure described herein is shown in the accompanying drawings by way of example, and not as a limitation. For the sake of brevity and clarity, the features shown in the drawings 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.

[0066]

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DETAILED DESCRIPTION OF THE INVENTION

[0067] NO x Adsorption can be divided into two categories: adsorption of nitric oxide (NO) and nitrogen dioxide (NO 2 2). As described above, a new class of NO X adsorption / desorption materials is needed. Surprisingly, according to the present disclosure, a low-temperature NO containing a rare earth metal component, a platinum group metal (PGM) component, and a dopant xIt has been discovered that the adsorption / desorption properties of adsorbent (LT-NA) compositions, in which a PGM and a dopant are disposed on or impregnated into a rare earth metal component, can be tailored by selecting the dopant and the loadings of the rare earth metal component, the PGM component, and the dopant.

[0068] Thus, the present disclosure generally relates to, for example, adjusting a NO to suit a particular vehicle requirement. x It can narrow the temperature window for adsorption and subsequent heat release of NO from the engine exhaust to facilitate downstream SCR function. x NO and NO 2 Provided are LT-NA compositions, components, and methods that allow for tailoring of the component distribution.

[0069] The present invention will now be described more fully hereinafter. However, the present invention may 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.

[0070] definition The articles "a" and "an" herein refer to one or more than one (e.g., at least one) of the grammatical object. All ranges cited herein are inclusive. The term "about" used throughout is used to express and account for small variations. For example, "about" can mean that a numerical value may vary by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1%, or ±0.05%. All numerical values ​​are modified by the term "about", whether or not expressly stated. Numeric values ​​modified by the term "about" include the specific identified value. For example, "about 5.0" includes 5.0.

[0071] The term "reduction" refers to a decrease in amount caused by any means.

[0072] The term "adsorbent" refers to a material that adsorbs and / or absorbs a desired substance, in this disclosure NO x and / or absorbs. An adsorbent can advantageously adsorb and / or absorb (store) a substance at a specific temperature and desorb (release) the substance at a higher temperature.

[0073] The term "associated" means, for example, "comprising", "connected to", or "in communication with", for example, "electrically connected" or "in fluid communication with", or connected to perform a function. The term "associated" can mean directly associated or indirectly associated, for example, via one or more other articles or elements.

[0074] The average particle size is synonymous with D50, that is, it means that half of the number of particles have a size larger than this and half have a size smaller than this. The particle size refers to primary particles. The particle size may be measured by laser light scattering technology using a dispersion or dry powder according to ASTM method D4464.

[0075] The term "catalyst" refers to a material that promotes a chemical reaction. A catalyst includes a "catalytically 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 catalytically active species are also called "promoters" to promote chemical reactions. For example, the present palladium-containing rare earth metal component can be called a Pd-promoted rare earth metal component. The "promoted rare earth metal component" refers to a rare earth metal component to which a catalytically active species is intentionally added.

[0076] The term "catalyst article" in the present invention refers to an article including a substrate having a catalyst coating composition.

[0077] The term "configured" as used in the specification and claims is intended to be an open-ended term, similar to the terms "comprising" or "containing". The term "configured" is not meant to exclude other possible articles or elements. The term "configured" may be equivalent to "adapted".

[0078] As used herein, "crystal size" means the length of one edge of a face of a crystal, preferably the longest edge, provided that the crystal is not acicular. Direct measurement of crystal size can be carried out using microscopy such as SEM and TEM. For example, in the measurement by SEM, it involves examining the morphology of the material at a high magnification (typically 1000 times to 10,000 times). The SEM method can be carried out by distributing a representative portion of the zeolite powder on a suitable mount, whereby the individual particles are spread moderately uniformly over the entire field of view at a magnification of 1000 times to 10,000 times. From this population, a statistically significant sample (e.g., 50 to 200) of random individual crystals is examined, and the longest dimension of the individual crystals parallel to the horizontal line of the linear edge is measured and recorded. Particles that are clearly large polycrystalline aggregates are not included in the measurement. Based on these measurements, the arithmetic mean of the crystal size of the sample is calculated.

[0079] "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, where the inlet channels are plugged into the outlet ends and the outlet channels are plugged into the inlet ends. The exhaust gas flow carrying soot entering the inlet channels is passed through the filter walls before exiting through the outlet channels. In addition to soot filtration and regeneration, ACSF oxidizes CO and HC to CO 2 and H 2 O, or promotes the oxidation of soot particles at a lower temperature, or accelerates the downstream SCR catalyst, or oxidizes NO to NO 2It may carry an oxidation catalyst for oxidation. The SCR catalyst composition can also be directly coated on a wall flow filter called SCRoF.

[0080] "DOC" refers to a diesel oxidation catalyst that converts hydrocarbons and carbon monoxide in the exhaust gas of a diesel engine. Typically, DOC contains one or more platinum group metals such as palladium and / or platinum, a carrier material such as alumina, zeolite for HC storage, and optionally promoters and / or stabilizers.

[0081] Generally, the term "effective" means having an effect of, for example, about 35% to 100% with respect to the defined catalytic activity or storage / release activity in weight or mole, for example, having an effect of 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%.

[0082] 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 specific non-gaseous components such as droplets, solid particles, etc., in the exhaust of a lean burn engine. The exhaust gas stream of a combustion engine typically contains combustion products (CO 2 and H 2 O), incomplete combustion products (carbon monoxide (CO) and hydrocarbons (HC)), nitrogen oxides (NO x) It further contains combustibles and / or carbonaceous particulate matter (soot), as well as unreacted oxygen and nitrogen. As used herein, the terms "upstream" and "downstream" refer to the relative directions according to the flow of the engine exhaust gas from the engine towards the tailpipe, with the engine in the upstream position and the tailpipe and any pollutant reduction articles such as filters and catalysts downstream of the engine. The inlet end of the substrate is synonymous with the "upstream" end or the "front" end. The outlet end is synonymous with the "downstream" end or the "rear" end. The upstream zone is upstream of the downstream zone. The upstream zone may be near the engine or the manifold, and the downstream zone may be further away from the engine or the manifold.

[0083] The term "in fluid communication" is used to refer to articles positioned in the same exhaust line, i.e., a common exhaust flow 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 "washcoat monoliths".

[0084] The term "functional article" in the present invention means an article that includes a substrate on which a functional coating composition, particularly a catalyst and / or adsorbent coating composition, is disposed.

[0085] As used herein, "impregnated" or "impregnation" refers to permeating a catalytic material into the porous structure of a support material.

[0086] The terms "on" and "above" related to the coating layer can be used synonymously. The term "directly on" means in direct contact. The disclosed articles are referred to in certain embodiments as including one coating layer "on" 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., "on" is not equivalent to "directly on").

[0087] As used herein, the term "promoted" refers to a component intentionally added to a rare earth metal component as contrasted with impurities inherent to the rare earth metal component. A "promoter" is a metal that enhances the activity towards a desired chemical reaction or function.

[0088] As used herein, the term "nitrogen oxides" or "NO x " refers to nitrogen oxides such as NO, NO 2 , or N 2 O.

[0089] As used herein, the term "flow" broadly refers to any combination of flowing gases that may contain particulate matter of solids or liquids. The terms "gas flow" or "exhaust gas flow" mean a flow of gaseous components such as the exhaust of a combustion engine, which may include entrained non-gaseous components such as droplets, solid particles, etc. The exhaust gas flow of a combustion engine typically includes combustion products (CO 2 and H 2 O), incomplete combustion products (carbon monoxide (CO) and hydrocarbons (HC)), nitrogen oxides (NO x ), combustible and / or carbonaceous particulate matter (soot), and unreacted oxygen and nitrogen.

[0090] "Substantially free of" means "little or none" or "not intentionally added" and also means containing only trace and / or incidental 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.

[0091] As used herein, the term "substrate" refers to a monolithic material onto which a catalyst material, i.e., a catalyst coating, is typically disposed in the form of a washcoat. In one or more embodiments, the substrate is a flow-through monolith and a monolithic wall flow filter. Flow-through and wall flow substrates are also disclosed, for example, in International Patent Application No. WO2016 / 070090, which is incorporated herein by reference. A washcoat is formed by preparing a slurry containing a catalyst with a specific solids content (e.g., 30 wt% to 90 wt%) in a liquid, then coating this onto the substrate and drying to provide a washcoat layer. Reference to a "monolithic substrate" means a homogeneous and continuous single structure from an inlet to an outlet. A washcoat is formed by preparing a slurry containing particles with a specific solids content (e.g., 20% to 90 wt%) in a liquid vehicle, then coating this onto the substrate and drying to provide a washcoat layer.

[0092] As used herein, the terms "upstream" and "downstream" refer to relative directions in accordance with the flow of engine exhaust gas from the engine towards the tailpipe, with the engine in an upstream position and the tailpipe and any pollutant reduction articles such as filters and catalysts downstream of the engine.

[0093] 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 allow 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 a lower washcoat layer. The 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, such as particle size or crystallite phase, can be different), and / or the chemical catalytic function can be different.

[0094] Unless otherwise indicated, "weight percent (wt%)" is based on the entire composition exclusive of volatile matter, i.e., the dry solids content. Unless otherwise indicated, all parts and percentages are by weight.

[0095] All methods described herein can be performed in any suitable order, unless otherwise indicated herein or unless clearly inconsistent with the context. The use of any and all examples or exemplary language (e.g., "such as") provided herein is intended only to better illustrate 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.

[0096] In a first aspect, a method for treating a gaseous exhaust stream containing a mixture of nitrogen oxides (NO x ) flowing from the exhaust manifold of a diesel engine or a lean burn gasoline engine during a period after a cold start of the engine, the method comprising contacting the gaseous exhaust stream with a low temperature NO x adsorbent (LT-NA) component, the LT-NA component being disposed downstream of the exhaust manifold and in fluid communication therewith, is provided. Such an LT-NA component is effective to store NO x at a temperature below 200°C and release the stored NO x at a predetermined temperature. Further provided is a method for adjusting one or both of the NO x adsorption / desorption profile of the LT-NA composition and the NO x desorption temperature range of the LT-NA composition.

[0097] LT-NA composition The LT-NA compositions of the present disclosure include a rare earth metal component, a platinum group metal (PGM) component, and a dopant selected from a transition metal oxide, an alkaline earth metal oxide, an oxide of any element of Groups 13-15 of the periodic table, or combinations thereof. The PGM and dopant are disposed on or impregnated in the rare earth metal component. Individual components comprising the LT-NA composition are disclosed herein below.

[0098] Rare earth metal component As mentioned above, the LT-NA compositions disclosed herein contain a rare earth metal component. The term "rare earth metal component" typically refers to the metals of the lanthanide series as defined in the periodic table, which are typically in the form of oxides. Examples of lanthanide series metals include cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium. Particularly preferred rare earth metal components include one or more oxides of lanthanum, cerium, neodymium, yttrium, praseodymium, and mixtures thereof. These can include various oxidation states of rare earth metals such as monoxide, dioxide, trioxide, tetraoxide, etc., depending on the valence of the specific transition metal. In some embodiments, the rare earth metal component comprises cerium oxide (CeO 2 ; ceria). In some embodiments, the rare earth metal component is ceria.

[0099] Platinum group metal (PGM) component As mentioned previously, the LT-NA compositions disclosed herein include a platinum group metal (PGM) component. The term "PGM component" refers to any component that includes a PGM (e.g., Ru, Rh, Os, Ir, Pd, Pt, and / or Au). References to the "PGM component" take into account the presence of PGMs 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 includes palladium, platinum, rhodium, rhenium, ruthenium, iridium, or combinations thereof. In some embodiments, the PGM component includes palladium, platinum, or mixtures thereof. In some embodiments, the PGM component is palladium. In some embodiments, the PGM component is platinum.

[0100] The PGM component may be present in an amount in the range of about 0.01 to about 5 wt% or about 0.1 to about 3 wt% on a metal basis, based on the weight of the rare earth metal component. In some embodiments, the PGM is present at about 0.5 to about 2.5 wt% (e.g., about 2 wt%) of the rare earth metal component.

[0101] Dopant As mentioned previously, the LT-NA compositions disclosed herein include a dopant. The dopant may be selected from transition metal oxides, alkaline earth metal oxides, oxides of any element in Groups 13 - 15 of the periodic table, or combinations thereof.

[0102] In some embodiments, the dopant is a transition metal oxide. As used herein, the term "transition metal oxide" refers to any oxide of a transition metal. These oxides can include various oxidation states of the transition metal, such as monoxide, dioxide, trioxide, tetraoxide, etc., depending on the valence of the specific transition metal. As used herein, the term "transition metal" refers to any element within the d-block of the periodic table, which includes Groups 3 to 12 of the periodic table. Examples of transition metals include, for example, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, silver, cadmium, lanthanum, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, silver, gold, and mercury. Particularly suitable transition metals for use as dopants disclosed herein include one or more of chromium, manganese, iron, cobalt, nickel, copper, zinc, molybdenum, and tungsten. In some embodiments, the transition metal oxide is an oxide of manganese. In some embodiments, the transition metal oxide is MnO, Mn 2 , Mn 2 O 3 , and manganese oxide selected from the group consisting of mixtures thereof.

[0103] In some embodiments, the dopant is an alkaline earth metal oxide. As used herein, the term "alkaline earth metal oxide" refers to an oxide of a Group II metal. In some embodiments, the alkaline earth metal oxide is selected from the group consisting of oxides of barium, calcium, magnesium, strontium, and mixtures thereof. In some embodiments, the alkaline earth metal oxide is an oxide of barium, calcium, or magnesium. In some embodiments, the alkaline earth metal oxide is an oxide of magnesium.

[0104] In some embodiments, the dopant is an oxide of any element from Group 13 to Group 15 of the periodic table. As used herein, the term "oxide of any element from Group 13 to Group 15 of the periodic table" refers to any oxide of any element from Group 13 to Group 15 of the periodic table. These may include various oxidation states of the element such as monoxide, dioxide, trioxide, tetroxide, etc., depending on the valence of the specific element. "Any element from Group 13 to Group 15 of the periodic table" means any element included in Group 13, 14, or 15 described in the periodic table, for example, boron, aluminum, gallium, indium, thallium, carbon, silicon, germanium, tin, lead, nitrogen, phosphorus, arsenic, antimony, bismuth, oxygen, sulfur, selenium, and tellurium. Particularly suitable elements from Group 13 to Group 15 of the periodic table for use as dopants as disclosed herein include one or more of boron, silicon, tin, phosphorus, antimony, bismuth, and mixtures thereof. In some embodiments, the oxide of any element from Group 13 to Group 15 of the periodic table is selected from the group consisting of oxides of boron, silicon, tin, phosphorus, antimony, bismuth, and mixtures thereof. In some embodiments, the oxide of any element from Group 13 to Group 15 of the periodic table is an oxide of tin.

[0105] In some embodiments, the total amount of the dopant metal is in the range of about 0.1 wt% to about 10 wt% or about 0.5 wt% to about 5 wt% based on the weight of the rare earth metal component (e.g., less than 10 wt%, less than 9 wt%, less than 8 wt%, less than 7 wt%, less than 6 wt%, less than 5 wt%, less than 4 wt%, less than 3 wt%, less than 2 wt%, less than 1 wt%, or less than 0.5 wt% based on the weight of the rare earth metal component). In some embodiments, the dopant is present in an amount of about 0.5 wt% based on the weight of the rare earth metal component. In some embodiments, the dopant is present in an amount of about 1 wt% based on the weight of the rare earth metal component. In some embodiments, the dopant is present in an amount of about 2 wt% based on the weight of the rare earth metal component. In some embodiments, the dopant is present in an amount of about 5 wt% based on the weight of the LT-NA composition.

[0106] The foregoing description provides some preferred ranges or amounts for the PGM component and the dopant component of the LT-NA composition. However, it should be noted that the ranges or amounts disclosed for one of these components may be combined with the ranges or amounts disclosed for the other components, respectively, to form new ranges or sub-ranges. Such embodiments are also clearly contemplated by the present invention.

[0107] Preparation of LT-NA Composition The preparation of the LT-NA composition described herein generally involves treating (impregnating) rare earth metal oxides in particulate form, individually or as a mixture, with a solution containing the PGM component and the dopant. In some embodiments, the disclosed LT-NA compositions can be prepared by the incipient wetness impregnation method. The incipient wetness impregnation technique, also called capillary impregnation or dry impregnation, is generally used in the synthesis of heterogeneous materials, i.e., catalysts. Typically, a metal precursor (e.g., the PGM component and / or the dopant disclosed herein) is dissolved in an aqueous or organic solution, and then the metal-containing solution is added to a material (e.g., rare earth metal oxide) that contains the same pore volume 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 calcined to remove the volatile components in the solution and deposit active species (e.g., metal or its oxide) 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 in the pores during impregnation and drying.

[0108] In some embodiments, the PGM component is impregnated in or disposed on the rare earth metal component. The PGM component can be introduced into or onto the rare earth metal oxide by any suitable means, such as incipient wetness, co-precipitation, or other methods known in the art. In some embodiments, a suitable method for impregnating the PGM into the rare earth metal component or disposing the PGM on the rare earth metal component is to prepare a mixture of a solution of a desired PGM precursor (e.g., a platinum compound and / or a palladium compound) and the rare earth component to produce a slurry. Non-limiting examples of suitable PGM precursors include palladium nitrate, tetraammine palladium nitrate, tetraammine platinum acetate, and platinum nitrate. During the firing step or at least during the initial stages of use of the composite, such compounds are converted to the catalytically active form of the metal or its compound. In one or more embodiments, the slurry is acidic, for example, having a pH of from about 2 to less than about 7. The pH of the slurry may be reduced by adding an appropriate amount of an inorganic or organic acid to the slurry. Considering the compatibility of the acid and the raw materials, a combination of both can be used. Examples of inorganic acids include, but are not limited to, nitric acid. Examples of organic acids include, but are not limited to, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutamic acid, fatty acids, maleic acid, fumaric acid, phthalic acid, tartaric acid, citric acid, etc. In some embodiments, the slurry is dried and fired to provide a PGM rare earth metal component catalyst powder. In some embodiments, the catalyst powder comprises ceria with Pd impregnated or disposed thereon. The PGM component can be described as being dispersed, impregnated, disposed, or contained in the rare earth metal oxide.

[0109] In some embodiments, in the second step, the dopant is impregnated in or disposed on the PGM-containing rare earth metal component catalyst powder. In some embodiments, a suitable method for impregnating the dopant into the PGM-containing rare earth metal component or disposing the dopant on the PGM-containing rare earth metal component is to prepare a mixture of solutions of the desired dopant precursors. Non-limiting examples of suitable dopant precursors include salts of alkaline earth metals, salts of transition metals, and salts of Group 13-15 elements. Suitable salts include, for example, nitrates, acetates, sulfates, chlorides, and the like. During the firing step or at least during the initial stages of use of the composite material, such compounds are converted to the active form of the metal or its compound, such as an oxide. In one or more embodiments, the slurry is acidic, for example, having a pH of from about 2 to less than about 7. The pH of the slurry may be decreased by adding an appropriate amount of an inorganic or organic acid to the slurry. Considering the compatibility of the acid and the raw materials, a combination of both can be used. Examples of inorganic acids include, but are not limited to, nitric acid. Examples of organic acids include, but are not limited to, acetic acid, propionic acid, oxalic acid, malonic acid, succinic acid, glutamic acid, fatty acids, maleic acid, fumaric acid, phthalic acid, tartaric acid, citric acid, and the like. In some embodiments, the slurry is dried and fired to provide a PGM rare earth metal oxide dopant catalyst powder. In some embodiments, the catalyst powder comprises ceria impregnated with Pd and any one of magnesium, manganese, or tin. The dopant can be described as being dispersed, impregnated, disposed, or contained in the rare earth metal oxide. In some embodiments, the order of steps may be reversed, introducing the dopant into the rare earth metal oxide first and subsequently introducing the PGM component. The dopant can be introduced into or onto the rare earth metal oxide by any suitable means, such as incipient wetness, co-precipitation, or other methods known in the art.

[0110] In some embodiments, the same method is used to introduce the PGM component and the dopant, respectively. In some embodiments, the PGM component and the dopant are each introduced using individual and different methods. In some embodiments, both the PGM component and the dopant are impregnated in or disposed on the rare earth metal component in the same step (e.g., the PGM precursor and the dopant precursor are combined in one solution and added to the rare earth metal component, e.g., by co-impregnation).

[0111] LT-NA component In one or more embodiments, the present LT-NA composition is disposed (coated) on a substrate to form an LT-NA component (i.e., a catalyst article). Such a component is part of an exhaust gas treatment system (e.g., the catalyst article includes, but is not limited to, the LT-NA composition disclosed herein). As used herein, the terms catalyst article and component are synonymous.

[0112] Coating composition To manufacture an LT-NA component, the substrate disclosed herein is coated with the LT-NA composition disclosed herein. The coating is a "catalyst coating composition" or a "catalyst coating". The terms "catalyst composition" and "catalyst coating composition" are synonymous. The LT-NA composition disclosed herein includes a binder, e.g., a suitable precursor, e.g., ZrO derived from zirconyl acetate or any other suitable zirconium precursor, e.g., zirconyl nitrate 2It can be prepared using a binder. Zirconyl acetate binder, for example, provides a homogeneous and intact coating after thermal aging when the catalyst is exposed to high temperatures of at least about 600 °C, such as about 800 °C or higher, and a steam environment of about 5% or more. Other potentially suitable binders include, but are not limited to, alumina and silica. Alumina binders include aluminum oxide, aluminum hydroxide, and aluminum oxyhydroxide. Aluminum salts and colloidal forms of alumina may also be used. Silica binders include various forms of SiO 2 including. The binder composition can include any combination of zirconia, alumina, and silica. Other exemplary binders include boehmite, gamma alumina, or delta / theta alumina, as well as silica sols. When present, the binder is typically used in an amount of about 1 - 5 wt% of the total washcoat loading. Alternatively, the binder can be zirconia-based or silica-based, such as zirconium acetate, zirconia sol, or silica sol. When present, the alumina binder is typically used in an amount of about 0.05 g / in 3 ~ about 1 g / in 3 amount. In some embodiments, the binder is alumina.

[0113] Substrate A useful substrate is three-dimensional and has a length, diameter, and volume similar to a cylinder. The shape does not necessarily have to match a cylinder exactly. The length is the axial length defined by the inlet end and the outlet end.

[0114] According to one or more embodiments, the substrate for the disclosed components may be composed of any material typically used to prepare automotive catalysts, typically including a metal or ceramic honeycomb structure. The substrate typically provides a plurality of walls to which the washcoat composition is applied and adhered, thereby functioning as a substrate for the catalyst composition.

[0115] 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, lischite, alumina-silica-magnesia, zircon silicate, sillimanite, magnesium silicate, zircon, petalite, α-alumina, aluminosilicate, etc.

[0116] The substrate can also be a metal and include one or more metals or metal alloys. The metal substrate can include any metal substrate having an opening or "punch out" in the channel wall. The metal substrate can be used in various shapes such as pellets, corrugated sheets, or monolithic foams. Specific examples of the metal substrate 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 preferably, in any case, at least about 15 wt% (weight percent) of the alloy based on the weight of the substrate, for example, about 10 to about 25 wt% of chromium, about 1 to about 8 wt% of aluminum, and 0 to about 20 wt% of nickel. Examples of the metal substrate 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. In particular, the metal substrate is preferably used in a closely bonded position in certain embodiments, thereby enabling rapid heating of the substrate and, correspondingly, rapid heating of the catalyst composition (e.g., LT-NA composition) coated therein.

[0117] Any suitable substrate for the catalytic articles disclosed herein may be used, such as a monolithic substrate of the type having fine parallel gas flow channels extending through from an end face of an inlet or outlet of a substrate so as to be open to a flowing fluid stream ("flow-through substrate"). 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 and wall flow substrates are also disclosed, for example, in International Application No. WO2016 / 070090, which is hereby incorporated by reference in its entirety.

[0118] In some embodiments, the substrate comprises a honeycomb substrate in the form of a wall flow filter or a flow-through substrate. In some embodiments, the substrate is a wall flow filter. The flow-through substrate and the wall flow filter will be further described below.

[0119] 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 parallel gas flow channels extending from the inlet end to the outlet end of the substrate such that the channels are open to the flow of fluid. The channels, which are a substantially straight path from the fluid inlet to the fluid outlet, are defined by walls on which a catalytic coating is disposed such that the gas flowing through the channels contacts the catalytic material. The flow channels of the flow-through substrate are thin-walled channels and can be of 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.

[0120] The flow-through substrate is, for example, from about 50 in 3 to about 1200 in 3It has a volume, a cell density (inlet openings) 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.

[0121] The LT-NA component can be provided by applying an LT-NA composition coating as a washcoat to a substrate (e.g., as disclosed herein). Figures 1A and 1B illustrate an exemplary substrate 2 in the form of a through-flow substrate coated with an LT-NA composition as described herein. Referring to Figure 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 Figure 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 Figure 1B, the walls 12 are dimensioned and configured such that the gas flow paths 10 have a substantially regular polygonal shape. As shown, the LT-NA composition can be applied in a plurality of separate layers as needed. In the illustrated embodiment, the LT-NA composition consists of both a separate bottom layer 14 adhered to the wall 12 of the carrier member and a second separate top layer 16 coated above the bottom layer 14. The present invention can be implemented to include one or more (e.g., 2, 3, or 4 or more) LT-NA composition layers and is not limited to the two-layer embodiment illustrated in Figure 1B. Further coating configurations are disclosed herein below.

[0122] 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 may have about 7 to 600, more typically about 100 to 400 cells per square inch ("cpsi"). The cells can have rectangular, square, circular, elliptical, triangular, hexagonal, or other polygonal cross-sections.

[0123] Figure 2 is a perspective view of an exemplary wall flow filter. A cross-sectional view of the monolithic wall flow filter substrate portion is shown in Figure 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 arrows across the porous cell walls 104 represent that the exhaust gas flow enters the open cell ends, diffuses through the porous cell walls 104, and exits from the open outlet cell ends. The blocked ends 100 impede the gas flow and promote diffusion through the cell walls. Each cell wall has an inlet side 104a and an outlet side 104b. The passages are surrounded by the cell walls.

[0124] The wall flow filter article substrate is 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 at 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 may have a volume of. 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.

[0125] 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 applying a functional coating, and the average pore diameter is at least about 5 microns. For example, the wall flow filter article substrate 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 of about 50%, about 60%, about 65% or about 70% to about 75%, about 80% or about 85%, and an average pore diameter of 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 applying the catalyst coating. The terms "wall porosity" and "substrate porosity" have the same meaning and are interchangeable. Porosity is the ratio of the void volume to 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 a high loading of the catalyst composition without excessive backpressure during operation.

[0126] Coating To form the LT-NA component, the substrate is coated with the LT-NA composition disclosed herein. The coating may include one or more thin, adherent coating layers disposed on and attached to at least a portion of the substrate. In some embodiments, the LT-NA component of the present invention may include the use of one or more LT-NA composition layers, and a combination of one or more LT-NA composition layers. The LT-NA composition may be present only on the inlet side, only on the outlet side, both on the inlet and outlet sides of the substrate wall, or the wall itself may be composed entirely or partially of catalytic material. The LT-NA composition 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 phrase "catalytic coating disposed on the substrate" means on any surface, e.g., on the wall surface and / or on the pore surface. The catalytic coating layer may include individual functional components, i.e., the LT-NA composition described herein.

[0127] LT-NA compositions typically contain active species (e.g., NO of the LT-NA composition). x The catalyst material may be applied in the form of a washcoat containing a support material having a sorbent component thereon. The washcoat is formed by preparing a slurry containing a particular solids content (e.g., about 10 to about 60 wt%) in a liquid vehicle, which is then applied to the substrate, dried and fired to provide a coating layer. If multiple coating layers are applied, the substrate is dried and fired after each layer is applied and / or after multiple layers as desired are applied. In one or more embodiments, the catalyst material is applied to the substrate as a washcoat. A binder may also be used as described above.

[0128] The above LT-NA composition is generally mixed with water independently to form a slurry for coating a catalyst substrate such as a honeycomb type substrate. In addition to the catalyst particles, the 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 (anionic, cationic, nonionic, or amphoteric surfactant). 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.

[0129] The slurry can be milled to improve the mixing of the particles and the formation of a homogeneous material. Milling can be accomplished with a ball mill, a continuous mill, or other similar equipment, and the solids content of the slurry can be, for example, from about 20 to 60 wt%, more specifically from about 20 to 40 wt%. In one embodiment, the milled slurry has a D 90 particle size characterized by from about 10 to about 40 microns, preferably from 10 to about 30 microns, more preferably from about 10 to about 15 microns.

[0130] The slurry is then coated onto the substrate using any washcoat technique known in the art. In one embodiment, the substrate is dipped one or more times into the slurry or otherwise coated with the slurry. 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 3 hours) and then fired by heating, for example, at 400 - 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.

[0131] After firing, the washcoat loading obtained by the washcoat technique described above 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 generating the washcoat can be repeated as necessary to build the coating to the desired loading level or thickness, i.e., apply more than one washcoat.

[0132] The washcoat 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 (but rather in contact with 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 stream or atmosphere (but rather in contact with the overcoat).

[0133] The different coating layers may be in direct contact with each other without an "intermediate" overlapping zone. Alternatively, the different coating layers may be provided with a "gap" between two zones and not in direct contact. In the case of an "undercoat" or "overcoat", the gap between different layers is called an "intermediate layer". The undercoat is the layer "under" the coating layer, the overcoat is the layer "over" 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.

[0134] The catalyst coating can include more than one thin adherent layer, layers adhering to each other, and a coating adhering to the substrate. The entire coating includes individual "coating layers". The catalyst coating may advantageously be "zoned" and may include zoned catalyst 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. Different coating layers may be adjacent to each other and may not overlay each other. Alternatively, different layers may overlay 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, such as about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, or about 70% of the substrate length.

[0135] The different layers may each extend over the entire length of the substrate or each may extend over a portion of the substrate length and may partially or wholly overlay or underlay each other. The different layers may each extend from either the inlet end or the outlet end.

[0136] The zones of the present disclosure are defined by the relationship of the coating layers. For different coating layers, there are several possible zone configurations. For example, there may be an upstream zone and a downstream zone, there may be an upstream zone, an intermediate zone, and a downstream zone, or there may be four different zones. When two layers are adjacent and do not overlap, there are an upstream zone and a downstream zone. When two layers overlap to some extent, there are upstream, downstream, and intermediate zones. For example, when a coating layer extends over the entire length of a substrate, a different coating layer extends from an outlet end by a certain length and overlays a part of the first coating layer, there are upstream and downstream zones. The present catalyst coating may include more than one identical layer.

[0137] Figures 3A, 3B, and 3C show some possible coating layer configurations having two coating layers (however, the present disclosure is not limited thereto, and the catalyst may include any number of layers). A monolithic wall flow filter substrate wall 200 on which coating layers 201 and 202 are disposed is shown. This is a simplified diagram, and in the case of a porous wall flow substrate, pores and coatings adhering to the pore walls are not shown, and blocked ends are not shown. In Figure 3A, coating layer 201 extends over approximately 50% of the substrate length from the inlet towards the outlet. Coating layer 202 extends over approximately 50% of the substrate length from the outlet towards the inlet, and the coating layers are adjacent to each other, providing an inlet upstream zone 203 and an outlet downstream zone 204. In Figure 3B, coating layer 202 extends over approximately 50% of the substrate length from the outlet, layer 201 extends over more than 50% of the length from the inlet, and overlays a part of layer 202, providing an upstream zone 203, an intermediate zone 205, and a downstream zone 204. In Figure 3C, coating layers 201 and 202 each extend over the entire length of the substrate such that layer 201 overlays layer 202. The substrate of Figure 3C does not contain a zoned coating configuration. Figures 3A, 3B, and 3C may be useful for illustrating the configuration of the coating composition on the wall-through substrate. Figures 3A, 3B, and 3C may further be useful for illustrating the configuration of the coating composition on the flow-through substrate, as described hereinafter in this specification. The configuration of such coating layers is not limited.

[0138] The loading amount of this LT-NA coating on the substrate depends on substrate properties such as porosity and wall thickness. Typically, the wall flow filter loading amount is lower than the loading amount on the flow-through substrate. The catalytic wall flow filter is disclosed, for example, in U.S. Patent No. 7,229,597, which is hereby incorporated by reference in its entirety. This LT-NA composition generally, based on the substrate, is, for example, about 0.3 - 5.5 g / in 3 , or about 0.4 g / in 3 , about 0.5 g / in3 , 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 ~ 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 is present on the substrate at a concentration of. The concentration of the LT-NA composition or any other composition on the substrate refers to the concentration per any one three-dimensional cross-section or zone, e.g., per cross-section of the substrate or the entire substrate.

[0139] This LT-NA component, which may include the flow-through or wall-flow filter substrate disclosed herein, provides desirable NO x adsorption and desorption characteristics, e.g., adsorbing NO x at low temperatures and releasing the trapped NO x at high temperatures. Preferably, the LT-NA component stores NO x at temperatures below 200°C and is effective in releasing the stored NO x at a predetermined temperature.

[0140] Exhaust gas treatment system In another aspect of the present disclosure, there is provided an exhaust gas treatment system for treating exhaust gas emissions from a diesel engine or a lean-burn gasoline engine, the exhaust gas treatment system including the LT-NA component disclosed herein. The exhaust gas treatment system may further include one or more additional catalyst components such as a diesel oxidation catalyst (DOC) and / or a selective catalytic reduction (SCR) catalyst component. The exhaust gas treatment system may also further include a soot filter component and / or additional catalyst components.

[0141] The relative arrangement of the various components of the exhaust treatment system can be changed, but the LT-NA component of the present disclosure must be located upstream of any catalyst component involved in the conversion of NO x released from the LT-NA component.

[0142] The exhaust treatment system may further include a diesel oxidation catalyst (DOC) component. The DOC component may be located upstream of, for example, the SCR component and / or the soot filter. A DOC suitable for use in an exhaust treatment system can effectively catalyze the oxidation of CO and HC to carbon dioxide (CO 2 2). Preferably, the DOC can convert at least 50% of the CO or HC components present in the exhaust gas.

[0143] In addition to treating exhaust gas emissions by using a DOC, the exhaust treatment system can use a soot filter for removing 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 trapped soot and / or oxidizing the emissions of the exhaust gas stream. Generally, the soot combustion catalyst can be any known catalyst for the combustion of soot. For example, the CSF can be coated with one or more high surface area refractory oxides (such as 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 (such as platinum and / or palladium).

[0144] The emissions treatment system disclosed herein may further include a selective catalytic reduction (SCR) component. The SCR catalyst component may be located upstream or downstream of the DOC and / or soot filter. As noted above, the SCR must be located downstream of the LT-NA component disclosed herein. An SCR component suitable for use in an emissions treatment system is effective in catalytically reducing NO x exhaust components at a high temperature of 650 °C. Further, the SCR component must be active for the reduction of NO x even under low load conditions typically associated with lower exhaust temperatures. Preferably, the SCR component is capable of converting at least 50% of the NO x (e.g., NO) component to N 2 depending on the amount of reducing agent added to the system. Another desirable characteristic of the SCR component is the ability to catalyze the reaction of O 2 with any excess NH 3 to form N 2 , so that NH 3 is not released to the atmosphere. A useful SCR component for use in an emissions treatment system should also have heat resistance to temperatures above 650 °C. Such high temperatures can occur during the regeneration of a catalyzed soot filter. Suitable SCR catalyst components are described, for example, in U.S. Patent Nos. 4,961,917 and 5,516,497, both of which are hereby incorporated by reference in their entirety.

[0145] The gaseous exhaust stream to be treated according to the method disclosed herein may optionally be treated with at least a DOC and / or CSF component. Further, the LT-NA component need not be located within a separate catalyst component but may be included in another component such as a DOC, CSF, or SCR component, and the catalyst composition of each such component is applied to a substrate having a zoned or layered configuration as described herein.

[0146] The illustrated emissions treatment system can be more readily understood by referring to FIGS. 4A - 4D, which show non - limiting schematic views of an exhaust gas treatment system according to an embodiment of the present invention. Referring to FIG. 4A, an emissions treatment system 320 is shown in which an exhaust gas stream containing gaseous contaminants (e.g., unburned hydrocarbons, carbon monoxide, and NO x ) and particulate matter is conveyed from an engine 321 via line 322 to a diesel oxidation catalyst (DOC) 323. In the DOC 323, most of the unburned gaseous and non - volatile hydrocarbons and carbon monoxide are combusted to form carbon dioxide and water. Next, the exhaust stream is conveyed via line 324 to a lean NO x adsorbent (LT - NA 325) for adsorption and / or storage of NO x . The treated exhaust gas stream 326 is then conveyed to a catalyzed soot filter (CSF) 327, which captures particulate matter present in the exhaust gas stream. After removing particulate matter via the CSF 327, the exhaust gas stream is conveyed via line 328 to a downstream SCR catalyst 329, thereby effecting treatment and / or conversion of NO x . The exhaust gas passes through the SCR component 329 at a flow rate that allows the catalyst composition sufficient time to reduce the level of NO x in the exhaust gas (in combination with a reductant) at a predetermined temperature in the exhaust gas before exiting the system.

[0147] Another embodiment of the exhaust gas treatment system of the present invention is shown in FIG. 4B, which shows a schematic view of an exhaust gas treatment system 330. Referring to FIG. 4B, an exhaust gas stream is conveyed from an engine 331 via line 332 to a lean NO x adsorbent (LT - NA) 333. Next, the exhaust stream is conveyed via line 334 to a DOC 335 and then via line 336 to a CSF 337. The treated exhaust gas stream 338 is conveyed to an SCR 339 before being released to the atmosphere.

[0148] Another embodiment of the exhaust gas treatment system of the present invention is shown in FIG. 4C, which shows a schematic diagram of the emissions treatment system 340. Referring to FIG. 4C, the exhaust gas stream is carried from the engine 341 through line 342 to the DOC 343, and further to the lean NO x absorbent (LT-NA) 345 via exhaust gas stream 344. Next, the exhaust stream is carried to the SCR 347 via line 346 and further to the CSF 349 via line 348. The treated exhaust gas stream 338 is carried to the SCR 339 before exiting the system.

[0149] Another embodiment of the exhaust gas treatment system of the present invention is shown in FIG. 4D, which shows a schematic diagram of the exhaust gas treatment system 350. Referring to FIG. 4D, the exhaust gas stream is carried from the engine 351 through line 352 to the lean NO x adsorbent (LT-NA) 353 and further to the DOC 355 via the gas exhaust line 354. The exhaust gas line 356 is carried to the SCR catalyst 357, and the exhaust stream 358 is carried to the CSF 359 before exiting the system.

[0150] After any of the exemplified emissions treatment systems shown in FIGS. 4A - 4D, a selective ammonia oxidation catalyst (AMOx) may be provided to remove the NH 3 released from the SCR and selectively oxidize this NH 3 to N 2 . Although not shown in the emissions treatment systems of FIGS. 4A - 4D, those skilled in the art will recognize that where an SCR catalyst article is present in an emissions treatment system, a source of reducing agent and means for introducing the reducing agent upstream of the SCR catalyst article will be required. Typically, ammonia or an ammonia precursor (e.g., urea) is introduced by an injection article for reaction with the NO x in contact with the SCR catalyst article.

[0151] Method for treating a gaseous exhaust stream In one aspect, a method is provided for treating a gaseous exhaust stream containing a mixture of nitrogen oxides (NO x ) flowing from an exhaust manifold of a diesel engine or a lean burn gasoline engine during a period after a cold start of the engine. Specifically, the method involves contacting the gaseous exhaust stream with a low temperature NO x adsorbent (LT-NA) component disposed downstream of the exhaust manifold and in fluid communication therewith as disclosed herein.

[0152] In some embodiments, treating the gaseous exhaust gas stream involves selectively removing at least a portion of the NO x present in the gaseous exhaust stream. In some embodiments, treating the gaseous exhaust stream involves adjusting the distribution of nitric oxide (NO) and nitrogen dioxide (NO 2 ) in the gaseous exhaust stream.

[0153] In some embodiments, the LT-NA component is effective to release one or both of NO and NO 2 at a temperature above about 300°C. In some embodiments, the LT-NA component is effective to release one or both of NO and NO 2 at a temperature above about 325°C.

[0154] In some embodiments, contacting the gaseous exhaust stream with the LT-NA component disclosed herein involves continuously passing an exhaust gas stream at an initial temperature of about 150°C or less through and into contact with the LT-NA component (e.g., in the form of a catalyst article which may or may not contain other catalyst compositions on top), gradually warming it during further engine operation, and adsorbing and storing NO x from the exhaust gas stream until the exhaust gas stream reaches a temperature of about 200°C, where NO xReleasing it into the exhaust gas stream exiting the LT-NA component, and since the exhaust gas stream rises in temperature and heats each downstream catalyst material to the operating temperature, continuously passing the exhaust gas stream exiting the LT-NA component into contact with at least one downstream catalyst material to further oxidize nitrogen monoxide or reduce nitrogen monoxide and nitrogen dioxide. In some embodiments, the operating temperature is from about 200 to about 450 °C.

[0155] In some embodiments, the method further comprises injecting ammonia or an ammonia precursor (e.g., urea) upstream of the SCR catalyst article, and the injection timing, frequency, and duration of the ammonia or ammonia precursor can be adjusted according to the unique NO x emission profile of the upstream LT-NA component disclosed herein.

[0156] NO X adsorption / desorption profile and / or the NO of the LT-NA composition X Method for adjusting the desorption temperature range In another aspect, a method is provided for adjusting one or both of the NO x adsorption / desorption profile of the LT-NA composition disclosed herein and the NO x desorption temperature range of the LT-NA composition disclosed herein. Surprisingly, doping the LT-NA composition containing rare earth metal and PGM components with a dopant (described in detail above) changes one or both of the NO x adsorption / desorption profile and / or the NO x desorption temperature range, providing an "adjustable" LT-NA composition. By adjusting the NO X adsorption / desorption profile and / or the NO x desorption temperature range, the LT-NA composition can be adjusted to meet the desired requirements of the OEM. Thus, NO xThe components can be selectively desorbed over various temperature ranges and in response to requirements. For example, by varying the identity and concentration of the dopant species, the temperature ranges at which NO and NO 2 are each adsorbed and released can be adjusted to affect the performance of a downstream catalyst article (e.g., an SCR catalyst).

[0157] In some embodiments, the NO x desorption temperature range is about 150, about 175, about 200, about 225, or about 250 - about 275, about 300, about 325, about 350, or about 400 °C. In some embodiments, NO is desorbed over a temperature range of about 150, about 175, about 200, about 225, or about 250 - about 275, about 300, about 325, about 350, or about 400 °C. In some embodiments, NO 2 is desorbed over a temperature range of about 150, about 175, about 200, about 225, or about 250 - about 275, about 300, about 325, about 350, or about 400 °C.

[0158] In some embodiments, adjusting the NO x adsorption / desorption profile involves adjusting the ratio of NO desorbed at a given temperature over the NO x desorption temperature range of the LT-NA composition to NO 2 and.

[0159] The compositions, components, systems, and methods are suitable for treating exhaust gas streams from mobile emission sources such as trucks and automobiles. The compositions, components, systems, and methods are also suitable for treating exhaust streams from stationary sources such as power plants.

[0160] It will be readily apparent to those skilled in the relevant arts 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 options 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, options, examples, and preferences of this specification. 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

[0161] The present invention is illustrated in more detail by the following examples which are presented to illustrate the invention and should not be construed as limiting the invention. Unless otherwise specified, all parts and percentages are by weight, and all weight percentages are expressed on a dry basis, i.e., the water content is excluded unless otherwise indicated.

[0162] Example 1: Reference article (CeO 2 2% Pd above; 1 g / in 3 ) Preparation of 2% Pd on ceria powder Palladium nitrate (29 grams) was diluted with 75 grams of deionized water. This solution was added to 300 grams of ceria (CeO 2 ). Using a mixer, this mixture was homogenized. The resulting powder was dried at 120 °C for 4 hours and calcined at 500 °C for 1 hour.

[0163] Preparation of washcoat slurry of 2% Pd on ceria 200 grams of 2% Pd / CeO was added to 240 grams of deionized water 2was added. The slurry was carefully mixed with a homogenizer. The pH of the slurry was 4.1. The resulting slurry was continuously milled until it had a D 90 particle size of approximately 13 microns and a pH value of approximately 4.2. An alumina binder was added and this combination was carefully mixed.

[0164] Preparation of 2% Pd sample on ceria core Two 1-inch diameter × 3-inch length ceramic substrate cores with a cell density of 400 cells per square inch were immersed in Pd / CeO 2 / Al 2 O 3 slurry. An air gun was used to blow off the excess slurry. The coated cores were dried at 200 °C for 5 - 10 minutes using a hot air blower and then fired in an oven at 500 °C for 1 hour. The total washcoat loading of the cores was 1 g / in 3 .

[0165] Preparation of core samples for testing One of the core samples was subjected to an accelerated aging protocol to simulate in-service use of a vehicle. The aging conditions were set at 800 °C for 16 hours in an atmosphere of 10% water, 10% oxygen, and 80% nitrogen. The second core sample was tested without aging.

[0166] Example 1a: Reference article (1% Pd on ceria; 2 g / in 3 ) Preparation of 1% Pd on ceria powder The catalyst powder was prepared according to the procedure of Example 1, except that the amount of Pd was reduced by half during powder impregnation.

[0167] Preparation of washcoat slurry of 1% Pd on ceria The washcoat slurry was prepared according to the procedure of Example 1, except that 2% Pd on ceria was replaced with 1% Pd on ceria.

[0168] Preparation of 2% Pd sample on ceria core The catalyst core was prepared according to the procedure of Example 1, except that a 1% Pd slurry on ceria was used with a washcoat loading of 2 g / in 3 .

[0169] Preparation of Core Samples for Testing Core samples for testing were prepared according to the procedure of Example 1, except that a 1% Pd on ceria was used with a washcoat loading of 2 g / in 3 .

[0170] Example 1b: Reference Article (2% Pd on Ceria; 2 g / in 3 ) Preparation of 2% Pd on Ceria Powder The catalyst powder was prepared according to the procedure of Example 1

[0171] Preparation of Samples of 2% Pd on Ceria Core The catalyst core was prepared according to the procedure of Example 1, except that a washcoat loading of 2 g / in 3 was used

[0172] Preparation of Core Samples for Testing Core samples for testing were prepared according to the procedure of Example 1, except that a 2% Pd on ceria was used with a washcoat loading of 2 g / in 3 .

[0173] Example 1c: Reference Article (4% Pd on Ceria; 2 g / in 3 ) Preparation of 4% Pd on Ceria Powder The catalyst powder was prepared according to the procedure of Example 1, except that the amount of Pd was doubled during powder impregnation

[0174] Preparation of Washcoat Slurry of 4% Pd on Ceria The washcoat slurry was prepared according to the procedure of Example 1, except that 4% Pd on ceria powder was used

[0175] Preparation of 4% Pd Sample on Ceria Core The catalyst core was prepared according to the procedure of Example 1, except that a 4% Pd slurry on ceria powder was used with a washcoat filling amount of 2 g / in 3 .

[0176] Preparation of Core Samples for Testing The core samples for testing were prepared according to the procedure of Example 1, except that a 4% Pd on ceria powder was used with a washcoat filling amount of 2 g / in 3 .

[0177] Example 2: Catalyst Article of the Invention (2% Pd / 0.5% Mg / CeO 2 ) Preparation of LT-NA Composition Powder (2% Pd + 0.5% Mg on Ceria) Ceria powder (283 g) was added to a mixing container. Palladium nitrate (27.4 g) was mixed with 35 ml of deionized H 2 2O. Magnesium nitrate (6.8 g) was added to the palladium nitrate solution and mixed. Inside the mixing container, the ceria powder was impregnated with the Pd / Mg solution.

[0178] Preparation of LT-NA Composition Washcoat Slurry The Pd / Mg-impregnated ceria powder was mixed with deionized H 2 2O (202 g). The pH of the slurry was 1.07 and the particle size was 15 μm. The resulting slurry was milled until it had a D 90 particle size of about 11 microns and a pH value of about 1.2. An alumina binder was added and mixed well.

[0179] Preparation of LT-NA Component Core Samples Similar to Example 1, a 2% Pd / 0.5% Mg / CeO 2 slurry was used.

[0180] Preparation of LT-NA Component Core Samples for Testing Similar to Example 1, a 2% Pd / 0.5% Mg / CeO 2 slurry was used.

[0181] Example 3: The catalyst article of the present invention (2% Pd / 1% Sn / CeO 2 ) Preparation of 1% Sn on ceria powder Tin acetate ((Sn(OAc) 4 , 5 g) was diluted with acetic acid (25 g) and deionized water (50 g). This solution was mixed for 3 minutes to homogenize the liquid. This became a beige-colored colloidal solution. Ceria (251 g) was added to this solution. The slurry was mixed for 3 minutes. The resulting powder was grayish-brown. The powder was dried at 120 °C for 4 hours and calcined at 500 °C for 1 hour to provide 1% Sn on CeO 2 .

[0182] Palladium nitrate (20 grams) was diluted with deionized water (40 g). 1% Sn (200 g) on CeO 2 powder was added to the Pd solution and mixed for 3 minutes to homogenize the powder. The powder turned golden. The powder was dried at 120 °C for 4 hours and calcined at 500 °C for 1 hour to provide 2% Pd on 1% Sn / 99% ceria.

[0183] Preparation of LT-NA composition washcoat slurry To deionized water (210 g), 2% Pd (177 g) on 1% Sn / 99% ceria powder was added. The slurry was carefully mixed with a homogenizer. The pH of the slurry was 7.2. The pH of the slurry was adjusted to 5.3 with nitric acid (1.6 g). The slurry was milled to a particle size of about 7 microns and a pH value of about 5.7. An alumina binder was added and mixed well.

[0184] Preparation of LT-NA component core sample Two 1-inch diameter × 3-inch long ceramic substrate cores with a cell density of 400 cells per square inch were coated with Pd / Sn / CeO 2It was immersed in the washcoat slurry. An air gun was used to blow off the excess slurry. The coated core was dried at 200 °C for 5 to 10 minutes using a hot air blower, and then fired in an oven at 500 °C for 1 hour.

[0185] Preparation of test LT-NA component core samples One of the core samples was subjected to an accelerated aging protocol to simulate in-vehicle use. The aging conditions were set at 800 °C for 16 hours in an atmosphere of 10% water, 10% oxygen, and 80% nitrogen. A second core sample was tested without aging.

[0186] Example 4: Catalyst article of the present invention (2% Pd / 1% Mn / CeO 2 ) 1% Mn / 99% CeO 2 Preparation of 2% Pd on powder Palladium nitrate (29 g) was diluted with deionized water (70 g). The palladium nitrate solution was added to 1 wt% Mn (302 g) on ceria powder in a mixer and mixed for 3 minutes to homogenize the powder. The powder was dried at 120 °C for 4 hours and fired at 500 °C for 1 hour.

[0187] Preparation of LT-NA composition washcoat slurry 2% Pd / 1% Mn / CeO was added to deionized water (225 g) 2 powder (168 g), and it was thoroughly mixed with a homogenizer. The pH of the slurry was 4.7. The slurry was ball milled to a particle size of about 9 microns over 40 minutes. The pH value of the resulting slurry was 4.9. An alumina binder was added and mixed thoroughly.

[0188] Preparation of LT-NA component core samples Two ceramic substrate cores with a diameter of 1 inch and a length of 3 inches and a cell density of 400 cells per square inch were coated with 2% Pd / 1% Mn / CeO 2It was immersed in the slurry. Excess slurry was blown off using an air gun. The coated core was dried at 200 °C for 5 to 10 minutes using a hot air blower and then fired in an oven at 500 °C for 1 hour.

[0189] Preparation of LT-NA component core samples for testing One of the cores was subjected to an accelerated aging protocol to simulate in-service use of the vehicle. The aging conditions were set at 800 °C for 16 hours in an atmosphere of 10% water, 10% oxygen, and 80% nitrogen. The second core was tested as is.

[0190] Example 5: Catalyst article of the present invention (2% Pd / 5% Mn / CeO 2 , 400 cpsi) All processes were carried out as in Example 4, except that 2% Pd / 1% Mn / CeO 2 was replaced with 2% Pd / 5% Mn / CeO 2 and executed.

[0191] Example 6: Catalyst article of the present invention (2% Pd / 5% Mn / CeO 2 , 600 cpsi) All processes were carried out as in Example 5, except that the substrate used (cell density of 600 cpsi instead of 400 cpsi).

[0192] Example 7: Reactor testing of core samples (steady-state conditions): Both new and aged samples were evaluated in a laboratory reactor under the preset conditions listed below.

Table 1

[0193] Example 8: Catalyst article of the present invention (Pd / 5% Mn / CeO 2 , 400 cpsi vs. 600 cpsi, adsorption) It is generally observed that a catalyst coated on a 600 cells per square inch (cpsi) honeycomb has better activity compared to a 400 cpsi honeycomb. However, the purpose of this example was to confirm whether the same advantage could be seen in NO x adsorption. The results shown in Figure 5 indicated that there was no difference in NO x adsorption between the 600 cpsi and 400 cpsi substrates after aging.

[0194] Example 9: Catalyst article of the present invention (Pd / 5%Mn / CeO 2 , 400 cpsi vs 600 cpsi, desorption) Using the protocol of Example 7, equivalent results were observed during the desorption test (Figure 6).

[0195] Example 10: Reactor tests of various Pd / CeO 2 core samples (Pd loading effect, steady-state NO x adsorption, 400 cpsi) In this example, the effect of Pd loading on ceria was investigated based on the same washcoat loading (WCL), i.e., all based on 2 g / in 3 of ceria. The Pd loadings expressed in g / ft 3 were 34, 68, and 138 g / ft 3 . The results shown in Figure 7 indicated that the higher the palladium loading, the better the total NO x adsorption. However, a plateau was reached when the Pd concentration exceeded 2%.

[0196] Example 11: Reactor tests of various Pd / CeO 2 core samples (Pd loading effect, desorption, 400 cpsi) As shown in Figure 8, during the desorption stage, the higher the Pd concentration, the more NO x desorbed at lower temperatures.

[0197] Example 12: Reactor tests of various Pd / CeO 2Reactor tests of core samples (Pd loading effect, desorption, NO only) To confirm whether this desorption temperature shift is related to the adsorbed species (NO or NO 2 ) as shown in Figure 9, desorption plots for NO only were created. These results demonstrate that the more Pd there is on the ceria surface, the more NO is adsorbed and NO is released at a lower temperature than NO 2 . This observation was further confirmed through the NO desorption plot shown as Figure 10. 2

[0198] Example 13: Reactor tests of various Pd / CeO 2 core samples (Pd loading effect, desorption, NO 2 only) These results demonstrated that the NO x release temperature and species were controlled by the Pd concentration. At Pd concentrations above 2%, the adsorption / release of NO onto the ceria support was minimized, and NO adsorption was enhanced by converting some of the NO to NO at 120 °C. 2 2

[0199] Example 14: Reactor tests of fresh Pd / CeO 2 core samples (Pd loading effect, desorption, NO 2 only) Again, the more Pd loading there is, the less NO desorption there is even for fresh samples (Figure 11). 2

[0200] Example 15: Reactor tests of various core samples with different amounts of ceria loading (adsorption) NO x To further demonstrate the effect of ceria on the NO adsorption / release profile, two LT-NA component samples were tested with the same protocol (Example 7). One sample had a ceria washcoat loading of 2 g / in 3 and 1% Pd on the ceria, with a total Pd loading of 34 g / ft 3 ​​​​On the other hand, the Pd concentration on ceria was 2%, but since the ceria filling amount was 1 g / in 3 , the total Pd filling amount was the same (34 g / ft 3 ). The results shown in Fig. 13 indicate that the ceria sample with 2 g / in 3 had a higher NO 3 adsorption capacity than the ceria sample with 1 g / in x , despite having the same Pd filling amount.

[0201] Example 16: Reactor tests of various Pd / CeO 2 core samples (effect of ceria filling, desorption, 400 cpsi) Regarding desorption, both new and aged samples were evaluated. Samples with a higher ceria filling amount (2 g / in 3 ) demonstrated a higher NOx desorption peak and a higher desorption temperature for the second peak, regardless of whether they were new or aged (Fig. 13).

[0202] To identify whether the second peak (higher desorption temperature) is NO or NO 2 , desorption plots for both NO (Fig. 14) and NO 2 (Fig. 15) were created. These results demonstrate that all samples had a similar NO adsorption capacity, indicating that Pd was involved in NO adsorption and that this type of adsorption was weak as it released the adsorbed NO at a lower temperature. In contrast, the strength of NO 2 adsorption was much stronger than that of NO adsorption. As a result, the desorption of NO 2 occurred at a higher temperature (Fig. 15). Also, NO 2 adsorption mainly occurred on ceria.

[0203] Example 17: Reactor tests of various ceria core samples with different dopants (adsorption, 400 cpsi): Since it was demonstrated that Pd reduces the release of NO 2 at high temperatures but enhances NO desorption at low temperatures, to meet OEM requirements, NO and NO 2The possibility of using other dopants to adjust the release of NO was investigated. The effects of doping ceria with Mg, Sn, and Mn were evaluated. x Conversion to NO x Plots of storage capacity (Figure 16) showed that Sn had the least effect on the storage capacity, especially at the initial adsorption stage, while Mn had the greatest effect on the storage capacity. x

[0204] Example 18: Reactor tests of various doped ceria core samples with different dopants (desorption, 400 cpsi): As shown in Figure 17, for desorption, when Mn was added to ceria, the high-temperature NO x release peak decreased. The decreased NO x release portion was shown to be NO x (Figure 18). 2

[0205] Example 19: Reactor tests of samples with various Mn-doped ceria core samples (adsorption, 600 cpsi): To evaluate the effect of dopant concentration, two Mn-doped ceria samples were tested (Figure 19). It was observed that the higher the Mn loading, the faster the NO x conversion curve decreased.

[0206] Example 20: Reactor tests of samples with different Mn dopant concentrations (desorption, 600 cpsi): For NO x desorption, in the case of fresh samples, the higher the Mn loading, the more the high-temperature NO x release peak decreased. As shown in Figure 20, after aging, even a small amount of manganese (1%) reduced almost all the sites of NO 2 adsorption.

[0207] Example 21: Reactor tests of samples with different dopant concentrations (desorption, 600 cpsi, NO 2 only): As shown in Fig. 21, the higher the Mn filling amount, the more the high-temperature NO 2 emission peak decreased.

Claims

1. A method for treating an exhaust gas stream containing a mixture of nitrogen oxides (NO ｘ ), which flows from an exhaust manifold of a diesel engine or a lean burn gasoline engine during a period after a cold start of the engine, comprising contacting the exhaust gas stream with a low temperature NO ｘ adsorbent (LT-NA) component containing an LT-NA composition, the LT-NA component being disposed downstream of the exhaust manifold and in fluid communication therewith, the LT-NA composition being a rare earth metal component, a platinum group metal (PGM) component, and a predetermined dopant wherein the PGM and the dopant are disposed on or impregnated in the rare earth metal component, The LT-NA component stores NO at a temperature below 200 °C ｘ and is effective in releasing the stored NO ｘ at a predetermined temperature, and and the dopant is an oxide of boron, tin, phosphorus, antimony, or bismuth.

2. The method according to claim 1, wherein the dopant comprises an oxide of tin.

3. The method according to claim 1 or 2, wherein the rare earth metal component comprises ceria.

4. The method according to any one of claims 1 to 3, wherein the PGM component comprises palladium, platinum, rhodium, rhenium, ruthenium, iridium, or a combination thereof.

5. The method according to claim 4, wherein the PGM component comprises palladium, platinum, or a mixture thereof.

6. the stored NO ｘ The method according to any one of claims 1 to 5, wherein the predetermined temperature for releasing is above 200°C.

7. the stored NO ｘ The method according to any one of claims 1 to 6, wherein the predetermined temperature for releasing the ｘ is in a temperature range of 200, 225, 250, or 275 to 300, 325, 350, 400, or 450 °C.

8. The LT-NA component comprises a substrate, and one or more washcoats comprising the LT-NA composition disposed on at least a part of the substrate, and the method according to any one of claims 1 to 7.

9. The method according to claim 8, wherein the one or more washcoats are coated on the substrate in a layered or zoned configuration.

10. The method according to claim 8 or 9, wherein the substrate is a wall flow or flow through substrate.

11. Processing the exhaust stream further includes selectively removing at least a portion of the NO in the gaseous exhaust stream ｘ The method according to any one of claims 1 to 10

12. Processing the exhaust stream further includes adjusting the distribution of nitric oxide (NO) and nitrogen dioxide (NO ２ ) in the gaseous exhaust stream, the method according to any one of claims 1 to 10.

13. The LT-NA component stores one or more of NO and NO ２ at a temperature below 200°C and is effective for releasing one or both of NO and NO ２ at a predetermined temperature. The method according to any one of claims 1 to 12.

14. NO, NO ２ The method according to claim 13, wherein the predetermined temperature for releasing NO, NO ２ , or both, is above 200 °C.

15. NO, NO ２ The method according to claim 13, wherein the predetermined temperature for releasing NO, NO ２ , or both is in the temperature range of 200, 225, 250, or 275 to 300, 325, 350, 400, or 450 °C.

16. The method according to claim 13, wherein the LT-NA component is effective for releasing one or both of NO and NO ２ at a temperature above 300 °C.

17. The method according to claim 13, wherein the LT-NA component is effective in releasing one or both of NO and NO ２ at a temperature above 325°C.

18. contacting the exhaust stream with the LT-NA component comprises continuously passing the exhaust stream at an initial temperature of 150 °C or lower in contact with the LT-NA component and gradually warming it during further engine operation, Adsorbing and storing NO from the exhaust gas until the exhaust gas reaches a predetermined temperature, and releasing the NO ｘ to the exhaust gas exiting the LT-NA component ｘ are included. and since the exhaust stream rises in temperature to heat each downstream catalyst material to an operating temperature of 200 to 450 °C, continuously passing the exhaust stream exiting the LT-NA component in contact with at least one downstream catalyst material to further oxidize nitrogen monoxide or reduce nitrogen monoxide and nitrogen dioxide, and the method according to any one of claims 1 to 17.

19. Injecting ammonia or an ammonia precursor into the exhaust stream downstream of the LT-NA component and upstream of the selective catalytic reduction (SCR) catalyst article, further comprising adjusting the timing and duration of the injection according to the NOx emission profile of the LT-NA component, the method according to claim 18.

20. NO of the LT-NA composition ｘ Adsorption / desorption profile and NO of the LT-NA composition ｘ A method for adjusting one or both of the desorption temperature ranges, wherein the LT-NA composition is A rare earth metal component, A platinum group metal (PGM) component, A dopant that is an oxide of boron, tin, phosphorus, antimony, or bismuth Including, wherein the PGM component and the dopant are disposed on or impregnated in the rare earth metal component, The method includes selecting the dopant and selecting the filling amounts of the rare earth metal component, the PGM component, and the dopant.

21. The method according to claim 20, wherein the rare earth metal component includes ceria.

22. The NO ｘ The method according to claim 20 or 21, wherein the temperature range for removal is 150, 175, 200, 225, or 250 to 275, 300, 325, 350, or 400 °C.

23. NO is desorbed over a temperature range of 150, 175, 200, 225, or 250 - 275, 300, 325, 350, or 400 °C, the method according to claim 22.

24. NO ２ The method according to claim 22, wherein the ２ is desorbed over a temperature range of 150, 175, 200, 225, or 250 to 275, 300, 325, 350, or 400 °C.

25. Said NO ｘ Adjusting the adsorption / desorption profile is the NO of the LT-NA composition ｘ The ratio between NO desorbed at a given temperature over the desorption temperature range of NO and NO ２ The method according to claim 20 or 21, comprising adjusting the ratio between.

26. A rare earth metal component, A platinum group metal (PGM) component, A dopant that is an oxide of boron, tin, phosphorus, antimony, or bismuth Including, wherein the PGM and the dopant are disposed on or impregnated in the rare earth metal component, The LT-NA composition stores NO at a temperature below 200 °C and is effective in releasing the stored NO at a predetermined temperature, which is a low-temperature NO adsorbent (LT-NA) composition. ｘ and is effective in releasing the stored NO ｘ at a predetermined temperature, which is a low-temperature NO ｘ adsorbent (LT-NA) composition.

27. The LT-NA composition according to claim 26, wherein the rare earth metal component includes ceria.

28. A substrate, One or more washcoats comprising the LT-NA composition according to claim 26 or 27 disposed on at least a portion of the substrate, and comprising, low temperature NO ｘ adsorbent (LT-NA) article.

29. The LT-NA article according to claim 28, wherein the one or more washcoats are coated on the substrate in a layered or zoned configuration.

30. The LT-NA article according to claim 29, wherein the substrate is a wall flow or flow-through substrate.

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