Layered catalytic article

Abstract

The present invention relates to a catalytic article for treating an exhaust gas stream, the catalytic article comprising:-a substrate having an inlet end and an outlet end defining an axial length; -a first coating extending part or the entire axial length of the substrate, the first coating comprising a first catalyst comprising a vanadium component; -a second coating extending part or the entire axial length of the substrate, the second coating comprising a second catalyst comprising a noble metal component; and-a third coating extending part or the entire axial length of the substrate, the third coating comprising or consisting of an inorganic oxide selected from the group consisting of titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth oxides such as lanthanum oxide and cerium oxide, any combination thereof or a composite oxide thereof, wherein the third coating is positioned as an intermediate layer between the first coating and the second coating over part or the entire axial length of the substrate. The invention also relates to a method and system for treating an exhaust stream containing nitrogen oxides with the catalytic article.

Description

Technical Field

[0001] This invention relates to a layered catalytic article for treating exhaust streams containing nitrogen oxides, the layered catalytic article comprising a layer containing a vanadium-based catalyst and a layer containing a noble metal-based catalyst. The invention also relates to a method and system for treating exhaust streams containing nitrogen oxides. Background Technology

[0002] Engine exhaust primarily consists of particulate matter and gaseous pollutants such as unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Engine exhaust requires treatment by an engine exhaust system before being released into the air. Due to the negative environmental impacts of NOx on ecosystems, humans, animals, and plants, controlling NOx emissions has always been one of the most important issues in exhaust treatment, particularly for diesel engines.

[0003] Various treatment methods (such as catalytic reduction of nitrogen oxides) have been used to reduce NOx in exhaust streams. A typical catalytic reduction method is selective catalytic reduction (SCR), which uses ammonia (NH3) or an ammonia precursor as a reducing agent in the presence of atmospheric oxygen. SCR is considered superior because it achieves high NOx reduction with only a small amount of reducing agent. Typically, nitrogen oxides and the reducing agent NH3 react according to the following equation:

[0004] 4NO + 4NH3 + O2 → 4N2 + 6H2O (Standard SCR reaction)

[0005] 2NO2 + 4NH3 + O2 → 3N2 + 6H2O (slow SCR reaction)

[0006] NO + NO2 + 2NH3 → 2N2 + 3H2O (fast SCR reaction).

[0007] In SCR methods, a stoichiometric excess of the reducing agent NH3 or its precursor is typically added to the exhaust stream to reduce NOx as high a conversion rate as possible. Excess ammonia can leave the vehicle's tailpipe. Another potential scenario for ammonia leaving the tailpipe is the desorption of a significant amount of ammonia that was retained on the surface of the SCR catalyst during the low-temperature phase of a typical drive cycle as operating temperatures rise. If ammonia is released into the air (also known as an ammonia leak), several problems arise. Ammonia leaks are harmful to human health and the environment. Ammonia is known to cause significant eye and throat irritation above 100 ppm, significant skin irritation above 400 ppm, and has an IDLH value of 500 ppm in air. Furthermore, ammonia is caustic, especially in its aqueous form. Condensation of ammonia and water in the cooler areas of the exhaust line downstream of the exhaust treatment catalyst will result in a corrosive mixture that can damage the exhaust line. Ammonia should be removed before entering the tailpipe. Ammonia oxidation (AMOx) catalysts (also known as ammonia leak catalysts (ASC)) installed downstream of SCR catalysts are typically used to convert leaked ammonia into N2.

[0008] Ammonia oxidation (AMOx) catalysts are known to contain noble metal active materials for the oxidation of ammonia, and often also contain SCR active materials. Zeolites are widely used as known SCR active materials, while vanadium-based materials are rarely used due to the significant poisoning effect of vanadium on noble metals.

[0009] US 2014 / 0212350A1 describes a catalytic article for treating exhaust gases, the catalytic article comprising (a) a first catalyst layer having a plurality of consecutive sublayers, wherein each sublayer comprises vanadium oxide on a first refractory metal oxide support; (b) a second catalyst layer comprising one or more precious metals disposed on a second refractory metal oxide support; and (c) a substrate, wherein the first catalyst layer and the second catalyst layer are on and / or within the substrate. In embodiments of this patent application, the catalytic article comprises vanadium oxide and tungsten oxide in the first catalyst layer.

[0010] US2014 / 0178273A1 describes a treatment apparatus configured to receive exhaust gas from a power source. The apparatus includes: a first layer comprising a selective catalytic reduction (SCR) layer; a second layer disposed downstream of the first layer and comprising an oxidation catalyst support; a substrate layer disposed adjacent to the second layer; and an additive disposed between the first and second layers, wherein the additive is operable to substantially inhibit the migration of components from the second layer to the first layer when the exhaust gas is treated by the oxidation catalyst support. The SCR catalyst material may include zeolite components or may include vanadium oxide, tungsten oxide, and / or molybdenum oxide deposited on titanium oxide.

[0011] JP2019035340A describes an exhaust emission control system comprising: an exhaust pipe through which exhaust gas from an internal combustion engine passes; and a composite catalyst device disposed in the exhaust pipe and having a composite catalyst in which at least one of an SCR (Selective Catalytic Reduction) catalyst and a PGM (Platinum Group Metals) catalyst is mixed or multilayered with a copper oxide catalyst. The SCR catalyst may include zeolite or vanadium.

[0012] It would be desirable if low-cost vanadium-based SCR active materials could be used in ammonia oxidation (AMOx) catalysts with little or no poisoning effect on precious metals and thus have the desired NH3 removal efficiency. Summary of the Invention

[0013] One object of the present invention is to provide an AMOx catalyst comprising a vanadium-based SCR catalyst and a noble metal-based catalyst, which undergoes reduced poisoning by the noble metal and thus can provide improved NH3 conversion, especially during the low-temperature operation phase of the exhaust gas treatment system.

[0014] Surprisingly, this objective is achieved by a layered catalytic article that, in addition to layers containing vanadium-based catalysts and layers containing noble metal-based catalysts, also contains layers of inorganic oxide particles.

[0015] Therefore, in a first aspect, the present invention relates to a catalytic article for treating an exhaust stream, the catalytic article comprising:

[0016] - A substrate having an inlet end and an outlet end that define axial lengths.

[0017] - A first coating extending part or all of the axial length of the substrate, the first coating comprising a first catalyst containing a vanadium component;

[0018] - A second coating, extending a portion or the entire axial length of the substrate, comprising a second catalyst containing a noble metal component, and

[0019] - A third coating extending a portion or the entire axial length of the substrate, the third coating comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0020] The third coating is positioned as an intermediate layer between the first and second coatings along a portion or the entire axial length of the substrate.

[0021] In a second aspect, the present invention relates to a system for treating exhaust gas streams, the system comprising a reducing agent source (e.g., NH3 or a precursor thereof), a catalytic product as described in the first aspect of the invention, and optionally one or more of a diesel oxidation catalyst (DOC), a selective catalytic reduction catalyst (SCR), a three-way conversion catalyst (TWC), a four-way conversion catalyst (FWC), a non-catalytic or catalytic smoke filter (CSF), a NOx trap, a hydrocarbon trapping catalyst, a sensor, and a mixer.

[0022] In a third aspect, the present invention relates to a method for treating an exhaust stream containing nitrogen oxides, the method comprising passing the exhaust stream through a system as described in a second aspect of the invention in the presence of NH3 as a reducing agent.

[0023] In a fourth aspect, the present invention relates to a method for mitigating poisoning of a noble metal component in a catalyst article comprising a first coating containing a vanadium-based catalyst and a second coating containing a noble metal-based catalyst, the method comprising at least partially incorporating an inorganic oxide layer between the first coating and the second coating, wherein the inorganic oxide is selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination or composite oxide thereof.

[0024] The inventors have surprisingly discovered that poisoning of the noble metal component in AMOx catalysts containing vanadium-based catalysts and noble metal-based catalysts can be effectively suppressed by a layered structure having an intermediate layer of inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides, any combination thereof, or composite oxides thereof. Attached Figure Description

[0025] Figure 1a A longitudinal cross-sectional view of the layered structure from the inlet end to the outlet end on the substrate of the catalyst articles according to Examples 1 to 5 and Comparative Example 6 is shown schematically.

[0026] Figure 1b A longitudinal cross-sectional view of the layered structure from the inlet end to the outlet end on the substrate of the catalyst according to Comparative Example 7 is shown schematically.

[0027] Figure 2a , Figure 2b , Figure 2c , Figure 3a , Figure 3b , Figure 4a , Figure 4b , Figure 5a and Figure 5b An exemplary longitudinal cross-sectional view of a layered structure from the inlet end to the outlet end is schematically shown on a substrate on which the catalyst product according to the invention may also be used. Detailed Implementation

[0028] The present invention will now be described in detail. It should be understood that the present invention may be embodied in many different ways and should not be construed as being limited to the embodiments set forth herein.

[0029] In this document, the singular forms “a” and “the” include plural indicators unless the context clearly indicates otherwise. The terms “comprising,” “including,” etc., are used interchangeably with “containing,” etc., and are interpreted in a non-restrictive, open-ended manner. That is, additional parts or elements may exist, for example. Expressions such as “consisting of,” “substantially consisting of,” or cognates may be encompassed within “comprising” or cognates.

[0030] As used herein, the term “area” is intended to refer only to a portion of the catalyst that includes the specified material and extends a certain length in the direction of exhaust flow.

[0031] In this paper, in the context of catalysts, the term "vanadium-based" is intended to refer to catalysts containing vanadium-containing active materials such as vanadium oxide.

[0032] In this paper, in the context of catalysts, the term "noble metal-based" is intended to refer to catalysts containing noble metal active materials.

[0033] In this document, any references to “upstream” and “downstream” will be understood as relative positions with respect to the flow direction of the flow (e.g., the flow direction of the exhaust flow).

[0034] In the context of catalysts or coatings, the terms “first” and “second” are not intended to impose any limitation on the arrangement or construction of catalysts or coatings in catalytic articles.

[0035] According to a first aspect, the present invention provides a catalytic article for treating exhaust gas streams, the catalytic article comprising:

[0036] - A substrate having an inlet end and an outlet end that define axial lengths.

[0037] - A first coating extending part or all of the axial length of the substrate, the first coating comprising a first catalyst containing a vanadium component;

[0038] - A second coating, extending a portion or the entire axial length of the substrate, comprising a second catalyst containing a noble metal component, and

[0039] - A third coating extending a portion or the entire axial length of the substrate, the third coating comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0040] The third coating is positioned as an intermediate layer between the first and second coatings along a portion or the entire axial length of the substrate.

[0041] <First Coating>

[0042] The first catalyst in the first coating can be a vanadium-based SCR catalyst, which refers to any material containing vanadium, typically in oxide form, as the main active substance for the selective catalytic reduction of NOx, and which is typically supported on particles of a support. Vanadium-containing materials for the selective catalytic reduction of NOx are well known in the art. There are no particular limitations on the vanadium-based SCR catalyst that can be used in the first coating.

[0043] Vanadium-based SCR catalysts typically contain a vanadium component (e.g., V₂O₅) supported on particles of a support as the main active material and optional additional metal or metalloid components as promoter components, or components thereof. The additional metal or metalloid components may include, but are not limited to, boron (B), aluminum (Al), bismuth (Bi), silicon (Si), tin (Sn), lead (Pb), antimony (Sb), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), cerium (Ce), yttrium (Y), niobium (Nb), molybdenum (Mo), barium (Ba), samarium (Sm), erbium (Er), and tungsten (W). In particular, vanadium-based SCR catalysts contain vanadium oxide and optionally at least one oxide of a metal or metalloid selected from silicon (Si), antimony (Sb), molybdenum (Mo), and tungsten (W). The additional metal or metalloid components may be present in the form of the corresponding oxide or a composite oxide thereof with vanadium and / or another metal or metalloid, or a combination thereof.

[0044] In some embodiments of the invention, the vanadium-based SCR catalyst contains a vanadium component supported on particles of a support and at least one metallic or metalloid component selected from silicon (Si), antimony (Sb), molybdenum (Mo), and tungsten (W), or composed thereof. In particular, the vanadium-based SCR catalyst may contain a vanadium (V) component, an antimony (Sb) component, and optionally other metallic or metalloid components supported on particles of a support.

[0045] It should be understood that the vanadium component and the additional metal or metalloid component (if present) in the first catalyst may be in the form of any composite oxide of two or more of the corresponding oxides, vanadium and additional metal or metalloid components, or any combination thereof, supported on particles of the support.

[0046] For example, in some embodiments, the first catalyst contains vanadium oxide, antimony oxide, and optionally a composite oxide of vanadium and antimony supported on particles of a support.

[0047] In some specific embodiments, the first catalyst contains vanadium oxide, antimony oxide, silicon dioxide, and optionally any of their composite oxides or compositions, supported on particles of a support.

[0048] Useful materials for the support of the vanadium component and optional additional metal or metalloid components in the first catalyst may include, but are not limited to, molecular sieves and oxides of metals or metalloids selected from the group consisting of Ti, Si, W, Al, Ce, Zr, Mg, Ca, Ba, Y, La, Pr, Nb, Mo, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn, and Bi. Preferably, the support may be one or more selected from titanium dioxide (preferably anatase), silicon dioxide, alumina, zirconium oxide, and any doped stable form thereof.

[0049] Based on the total weight of the first catalyst, the first catalyst may contain a vanadium component in an amount of 0.5 wt% to 8 wt% or 1 wt% to 6 wt% calculated as V2O5.

[0050] Based on the total weight of the first catalyst, each of the additional metallic or near-metallic components, when present, may be included in the first catalyst in an amount of 0.1% to 30% by weight, 1% to 15% by weight, or 2% to 10% by weight, calculated as the corresponding oxide.

[0051] Based on the total weight of the first catalyst, the support may be included in the first catalyst in an amount of at least 45 wt%, at least 60 wt%, at least 70 wt%, or at least 75 wt%. Based on the total weight of the first catalyst, the amount of support may be at most 95 wt% or at most 90 wt%.

[0052] In some embodiments, the first catalyst may contain an amount of antimony component of 0.5 wt% to 16 wt% or 2 wt% to 9 wt% calculated as Sb2O3, based on the total weight of the first catalyst.

[0053] In some embodiments, the first catalyst contains or is composed of the following substances:

[0054] (a) 0.5 wt% to 8 wt% vanadium oxide, calculated as V₂O₅,

[0055] (b) 0.5% to 16% by weight of antimony oxide, calculated as Sb₂O₃,

[0056] (c) 1% to 15% by weight of SiO2, and

[0057] (e) 70% to 95% by weight of TiO2

[0058] Each is based on the total weight of the first catalyst.

[0059] In some other embodiments, the first catalyst contains or is composed of the following substances:

[0060] (a) 1% to 6% by weight of vanadium oxide, calculated as V₂O₅

[0061] (b) 2% to 9% by weight of antimony oxide, calculated as Sb₂O₃.

[0062] (c) 2% to 10% by weight of SiO2, and

[0063] (e) 75% to 95% by weight of TiO2

[0064] Each is based on the total weight of the first catalyst.

[0065] In each of the cases described herein, the total weight of the first catalyst will be 100 wt%.

[0066] In addition to the first catalyst, the first coating may also contain one or more components, which may be non-catalytically active components, such as processing aids, lubricants, and binders, used to deposit the coating onto the substrate. Other components may also be catalytically active, such as active substances different from those catalysts described herein.

[0067] The first coating may extend a portion or the entire axial length of the substrate. Based on the substrate or substrate region containing or bearing the first coating, the loading of the first catalyst coating can be as low as 0.01 g / in. 3 Up to 20g / in 3 or 0.5g / in 3 Up to 8g / in 3 Within the range. Additionally or alternatively, based on the substrate or substrate region containing or supporting the first coating, the first catalyst can provide 0.005 g / in V₂O₅. 3 Up to 1.5g / in 3 0.01g / in 3 Up to 1.0 g / in 3 or 0.03g / in 3 Up to 0.5g / in 3Vanadium is present in quantity.

[0068] <Second Coating>

[0069] The second catalyst in the second coating can be a noble metal-based oxidation catalyst containing a noble metal component, preferably a platinum group metal component, typically supported on particles of a support. The noble metal component may contain one or more of ruthenium, rhodium, iridium, palladium, platinum, silver, and gold on the particles of the support. Preferably, the noble metal component contains one or more of ruthenium, rhodium, iridium, palladium, and platinum on the particles of the support; more preferably, palladium and platinum; and most preferably, platinum.

[0070] It should be understood that precious metals can exist in any possible valence state, such as the corresponding metal or metal oxide as the catalytically active form, or as, for example, the corresponding metal compound, complex, etc., which will decompose or otherwise transform into the catalytically active form upon calcination or use of a catalyst.

[0071] The useful material for supporting the noble metal in the second catalyst can be any material suitable for receiving and supporting the noble metal, such as molecular sieves, or oxides of metals or metalloids selected from the group consisting of Ti, Si, W, Al, Ce, Zr, Mg, Ca, Ba, Y, La, Pr, Nb, Mo, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn, Sm, Eu, Hf, and Bi. In particular, the noble metal support can be selected from high-surface-area alumina, silica, titanium dioxide, cerium dioxide, zirconium oxide, lanthanum oxide, barium oxide, yttrium oxide, neodymium oxide, praseodymium oxide, titanium dioxide, europium oxide, samarium oxide, hafnium oxide, and any composites or combinations thereof. Exemplary supports can be composite oxides of silica and alumina, composite oxides of silica and titanium dioxide, etc.

[0072] Optionally, in addition to the precious metal component, the second catalyst may also contain zeolite or non-zeolite molecular sieve catalyst components.

[0073] Molecular sieves are framework materials based on a broad three-dimensional network of oxygen ions, typically containing tetrahedral sites and exhibiting a substantially uniform pore distribution. Molecular sieves suitable for the purposes of this invention can be microporous or mesoporous.

[0074] In particular, the molecular sieve can be a zeolite, which is optionally metal-promoted. In this document, the term "metal-promoted" in the context of molecular sieves is intended to refer to the incorporation of a metal capable of improving any properties of the zeolite into and / or onto the zeolite.

[0075] Preferably, suitable molecular sieves may include, but are not limited to, aluminosilicate zeolites with a framework type selected from the group consisting of AEI, AEL, AFI, AFT, AFO, AFX, AFR, ATO, BEA, CHA, DDR, EAB, EMT, ERI, EUO, FAU, FER, GME, HEU, JSR, KFI, LEV, LTA, LTL, LTN, MAZ, MEL, MFI, MOR, MOZ, MSO, MTW, MWW, OFF, RTH, SAS, SAT, SAV, SBS, SBT, SFW, SSF, SZR, TON, TSC, and WEN. More preferably, the molecular sieve comprises a zeolite having a framework type selected from the group consisting of AEI, BEA (e.g., β), CHA (e.g., chalcogenide, SSZ-13), AFT, AFX, FAU (e.g., zeolite Y), MOR, MFI (e.g., ZSM-5), MOR (e.g., mordenite), and MEL, wherein AEI, BEA, and CHA are particularly preferred.

[0076] It should be understood that when zeolites are referred to in this article by the framework type codes generally accepted by the International Zeolite Association (IZA), the intention is to include not only the reference material but also any isomorphic framework material with SCR catalytic activity. Lists of reference and isomorphic framework materials for each framework type code are available from the IZA database (http: / / www.iza-structure.org / databases / ).

[0077] In some embodiments, the second catalyst contains a metal-promoted molecular sieve catalyst component. The promoter metal may be selected from noble metals such as Au and Ag, platinum group metals such as Ru, Rh, Pd, In, and Pt, base metals such as Cr, Zr, Nb, Mo, Fe, Mn, W, V, Al, Ti, Co, Ni, Cu, Zn, Sb, Sn, and Bi, alkaline earth metals such as Ca and Mg, and any combination thereof. The promoter metal is preferably Fe or Cu, or a combination thereof.

[0078] In some illustrative embodiments, the second catalyst contains Cu and / or Fe-promoted zeolites having a framework type of AEI, BEA, CHA, AFT, AFX, FAU, FER, KFI, MOR, MFI, MOR, or MEL as a molecular sieve catalyst component, particularly Cu and / or Fe-promoted zeolites having an AEI, BEA, or CHA framework.

[0079] Based on the total weight of the metal-promoted molecular sieve, the promoter metal may be present in the metal-promoted molecular sieve in an amount of 0.1 wt% to 20 wt%, or 0.5 wt% to 15 wt%, or 1 wt% to 10 wt%, or 2 wt% to 6 wt%, based on the amount of oxides. In some illustrative embodiments where Cu or Fe is used as the promoter metal, the promoter metal is preferably present in an amount of 0.5 wt% to 15 wt%, or 1 wt% to 15 wt%, or 1 wt% to 10 wt%, based on the total weight of the metal-promoted molecular sieve.

[0080] The noble metal component and the molecular sieve catalyst component described for the second catalyst may exist in any possible form, such as as a physical mixture or in separate forms.

[0081] In addition to the second catalyst, the second coating may also contain one or more components, which may be non-catalytically active components, such as processing aids, lubricants, and binders, that can be used to deposit the second coating onto the substrate. The components may also be catalytically active, such as active substances different from those catalysts described herein.

[0082] The second coating can extend a portion or the entire axial length of the substrate. Based on the substrate or substrate region containing or supporting the second coating, the loading of the second catalyst coating can be as low as 0.01 g / in. 3 Up to 20g / in 3 or 0.1g / in 3 Up to 5g / in 3 Within the range. Alternatively or alternatively, based on the substrate or substrate region bearing the second coating, the noble metal component may be 0.01 g / ft calculated according to the corresponding noble metal. 3 Up to 20g / ft 3 Preferably 0.5g / ft 3 Up to 10g / ft 3 The quantity exists.

[0083] Based on the loading of these coatings, the first and second coatings may be included in a weight ratio ranging from 50:1 to 0.5:1, 30:1 to 1:1, or 20:1 to 5:1.

[0084] <Third Coating>

[0085] The inorganic oxide in the third coating may be selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0086] There are no particular restrictions on the specific valence states of those inorganic oxides, which may have any stable valence state as in the corresponding commercially available products and / or as produced by any possible reaction during the manufacture of the catalyst.

[0087] In some embodiments, the inorganic oxide may be selected from titanium dioxide, silicon dioxide, cerium dioxide, zirconium oxide, lanthanum oxide, silicon-titanium composite oxide, tungsten-titanium composite oxide, lanthanum-zirconium composite oxide, or any combination thereof.

[0088] In some other embodiments, the inorganic oxide may be selected from zirconium oxide, cerium dioxide, lanthanum-zirconium composite oxide, a combination of titanium dioxide and silicon dioxide, a combination of silicon dioxide and silicon-titanium composite material, or a combination of silicon dioxide and tungsten-titanium composite oxide.

[0089] Typically, inorganic oxides can exist in the third coating in particulate form. The particles of inorganic oxides can have a particle size D ranging from 1 micrometer (μm) to 100 μm. 90 .

[0090] Preferably, the third coating does not contain any vanadium-based SCR catalyst components or noble metal-based oxidation catalyst components. In some embodiments, the third coating consists of inorganic oxides as described herein in the context of the third coating.

[0091] The third coating is positioned as an intermediate layer between the first and second coatings along a portion or the entire axial length of the substrate. Based on the substrate or substrate region containing or supporting the third coating, the loading of the third coating can be as low as 0.01 g / in. 3 Up to 20g / in 3 Preferably 0.1 g / in 3 Up to 5g / in 3 Within the range.

[0092] It has been surprisingly found that by applying inorganic oxides as an intermediate layer to the catalyst, the NH3 removal performance of catalysts including vanadium-based catalyst layers and noble metal-based catalyst layers for treating exhaust streams containing nitrogen oxides has been improved.

[0093] <Base>

[0094] As used herein, the term "substrate" generally refers to a structure suitable for withstanding the conditions encountered in the exhaust flow, on which a coating, typically in the form of a wash-out coating, is carried. The substrate may have an inlet end and an outlet end defining its axial length, as well as multiple narrow parallel gas flow channels extending along the axial length.

[0095] The substrate is typically inert and is usually made of materials such as ceramics or metals, and is also known as an "inert substrate". Alternatively, the substrate can be active and can consist of, for example, an extrusion containing a catalytically active substance.

[0096] The substrate can be a monolithic flow-through structure with multiple finely parallel flow channels extending from the inlet end of the substrate to the outlet end, allowing the channels to be open to the fluid flowing through them. The flow paths, which are essentially straight paths from the fluid inlet to the fluid outlet, are defined by walls on which a catalytic material is applied as a wash coating, allowing the flow through the channels to contact the catalytic material. The flow paths of the monolithic substrate are thin-walled channels that can have any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such structures can contain 50 to 900 or more flow paths (or “channels”) per square inch of cross-section. For example, the substrate can have 50 to 600 channels per square inch (“cpsi”) or 200 to 450 cpsi. The wall thickness of the flow-through substrate can vary, typically ranging from 2 mils to 0.1 inches.

[0097] The substrate can also be a monolithic wall-flow structure with multiple fine, parallel gas flow paths extending from the inlet end of the substrate to the outlet end, where alternating paths are blocked at opposite ends. The paths are defined by walls, on which a catalytic material is applied as a wash coating, allowing the flow through the paths to contact the catalytic material. This configuration requires the flow to pass through the porous walls of the wall-flow substrate to reach the outlet end. Wall-flow substrates can have a maximum capacity of 700 cpsi, for example, from 100 cpsi to 400 cpsi. The flow paths of the monolithic substrate are thin-walled channels that can have any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. The wall thickness of the wall-flow substrate can vary, typically ranging from 2 mils to 0.1 inches.

[0098] The term "wash-coating" has its usual meaning in the art, referring to a thin, adhesive coating of catalytic material or other material applied to a substrate. Wash-coatings are typically formed as follows: a slurry containing the desired material and optional processing aids, such as a binder having a certain solids content (e.g., 15% to 60% by weight), is prepared, then applied to the substrate, dried, and calcined to provide the wash-coating. Wash-coatings in single or multilayer forms are typically applied at a density of 0.1 g / in. 3 Up to 10g / in 3 For example, 0.5g / in 3 Up to 7g / in 3 The quantity is loaded onto the substrate.

[0099] <Catalyst Structure>

[0100] In the catalytic article according to the invention, the first coating, the second coating, and the third coating may be included in any suitable layered structure known in the art, such as those conventional structures of AMOx catalytic articles that include an SCR catalyst layer and an oxidation catalyst layer, provided that the third coating is positioned as an intermediate layer between the first coating and the second coating over a portion or the entire axial length of the substrate.

[0101] Preferably, the first coating, i.e., the coating containing a first catalyst comprising a vanadium component, is positioned as the top layer. More preferably, the first coating extends the entire axial length of the substrate. The second coating may be positioned as the bottom layer and extend part or all of the axial length of the substrate.

[0102] In some embodiments, both the first and second coatings extend the entire axial length of the substrate. Preferably, the first coating, i.e., a coating containing a first catalyst comprising a vanadium component, is positioned as the top layer; the second coating, i.e., a coating containing a second catalyst comprising a noble metal component, is positioned as the bottom layer; and the third coating, i.e., a coating containing an inorganic oxide as described herein, is positioned as an intermediate layer between the first and second coatings over a portion or the entire axial length of the substrate.

[0103] In some specific embodiments, the catalyst according to the invention comprises:

[0104] - A substrate having an inlet end and an outlet end that define axial lengths.

[0105] - A first coating, which serves as the top layer extending the entire axial length of the substrate, contains a first catalyst comprising a vanadium component.

[0106] - A second coating, which serves as the bottom layer extending the entire axial length of the substrate, comprises a second catalyst containing a noble metal component, and

[0107] - A third coating extending the entire axial length of the substrate, comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0108] The third coating is positioned as an intermediate layer between the first and second coatings.

[0109] Figure 1a A longitudinal cross-sectional view of the aforementioned layered structure from the inlet end to the outlet end on a substrate of the catalyst is schematically shown.

[0110] In some other specific embodiments, the catalyst according to the invention comprises:

[0111] - A substrate having an inlet end and an outlet end that define axial lengths.

[0112] - A first coating, which serves as the top layer extending the entire axial length of the substrate, contains a first catalyst comprising a vanadium component.

[0113] - A second coating, which serves as the bottom layer extending the entire axial length of the substrate, comprises a second catalyst containing a noble metal component, and

[0114] - A third coating extending a portion of the axial length of the substrate, the third coating comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0115] The third coating is positioned as an intermediate layer between the first coating and the second coating, extending along a portion of the axial length of the substrate from the inlet or outlet end toward the opposite end, preferably from the outlet end toward the opposite end.

[0116] Figure 2a and Figure 2b An exemplary longitudinal cross-sectional view of the above-described layered structure from the inlet end to the outlet end on a substrate of the catalyst is schematically shown.

[0117] It is also anticipated that the catalyst article according to the present invention may include:

[0118] - A substrate having an inlet end and an outlet end that define axial lengths.

[0119] - A first coating, which serves as the top layer extending the entire axial length of the substrate, contains a first catalyst comprising a vanadium component.

[0120] - A second coating, which serves as the bottom layer extending the entire axial length of the substrate, comprises a second catalyst containing a noble metal component, and

[0121] - A third coating extending a portion of the axial length of the substrate, the third coating comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0122] The third coating is positioned as an intermediate layer between the first and second coatings, located at a certain distance from both the inlet and outlet ends along a portion of the axial length of the substrate.

[0123] Figure 2c An exemplary longitudinal cross-sectional view of the above-described layered structure from the inlet end to the outlet end on a substrate of the catalyst is schematically shown.

[0124] In some other embodiments, the first coating extends the entire axial length of the substrate, and the second and third coatings extend a portion of the axial length of the substrate. Preferably, the first coating, i.e., a coating containing a first catalyst comprising a vanadium component, is positioned as the top layer extending the entire axial length of the substrate; the second coating, i.e., a coating containing a second catalyst comprising a noble metal component, is positioned as the bottom layer extending from the inlet or outlet end of the substrate along a portion of its length; and the third coating, i.e., a coating containing an inorganic oxide as described herein, is positioned as an intermediate layer extending within the region where the second coating is positioned, with an extension length equal to or less than the length of the second coating.

[0125] In some specific embodiments, the catalyst according to the invention comprises:

[0126] - A substrate having an inlet end and an outlet end that define axial lengths.

[0127] - A first coating, which serves as the top layer extending the entire axial length of the substrate, contains a first catalyst comprising a vanadium component.

[0128] - A second coating, which serves as a base layer extending a portion of the axial length of the substrate, comprising a second catalyst containing a noble metal component, and

[0129] - A third coating extending a portion of the axial length of the substrate, the third coating comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0130] The third coating is positioned as an intermediate layer between the first and second coatings, and both the second and third coatings extend along the same axial length of the substrate from the inlet or outlet end of the substrate toward the opposite end, preferably from the outlet end of the substrate toward the opposite end.

[0131] Figure 3a and Figure 3b An exemplary longitudinal cross-sectional view of the above-described layered structure from the inlet end to the outlet end on a substrate of the catalyst is schematically shown.

[0132] In some other specific embodiments, the catalyst according to the invention comprises:

[0133] - A substrate having an inlet end and an outlet end that define axial lengths.

[0134] - A first coating, which serves as the top layer extending the entire axial length of the substrate, contains a first catalyst comprising a vanadium component.

[0135] - A second coating, which serves as a base layer extending a portion of the axial length of the substrate, comprising a second catalyst containing a noble metal component, and

[0136] - A third coating extending a portion of the axial length of the substrate, the third coating comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0137] The third coating is positioned as an intermediate layer between the first and second coatings, wherein both the second and third coatings extend from the inlet or outlet end of the substrate toward the opposite end, preferably from the outlet end of the substrate toward the opposite end, and wherein the axial length of the third coating is less than the axial length of the second coating.

[0138] Figure 4a and Figure 4b An exemplary longitudinal cross-sectional view of the above-described layered structure from the inlet end to the outlet end on a substrate of the catalyst is schematically shown.

[0139] It is also anticipated that the catalyst article according to the present invention may include:

[0140] - A substrate having an inlet end and an outlet end that define axial lengths.

[0141] - A first coating, which serves as the top layer extending the entire axial length of the substrate, contains a first catalyst comprising a vanadium component.

[0142] - A second coating, which serves as a base layer extending a portion of the axial length of the substrate, comprising a second catalyst containing a noble metal component, and

[0143] - A third coating extending a portion of the axial length of the substrate, the third coating comprising an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0144] The third coating is positioned as an intermediate layer between the first coating and the second coating. The second coating extends from the inlet or outlet end of the substrate toward the opposite end, preferably from the outlet end of the substrate toward the opposite end. The third coating is positioned at a certain distance from the inlet and outlet ends of the substrate, and the axial length extending within the area where the second coating is positioned is less than the axial length of the second coating.

[0145] Figure 5a and Figure 5b An exemplary longitudinal cross-sectional view of the above-described layered structure from the inlet end to the outlet end on a substrate of the catalyst is schematically shown.

[0146] The catalytic articles according to the invention can be used to treat exhaust streams from internal combustion engines of automobiles, particularly diesel engines. The catalytic articles according to the invention are particularly effective at treating exhaust streams from heavy-duty diesel engines (including highway and off-road heavy-duty diesel engines).

[0147] Therefore, in a second aspect, the present invention relates to a system for treating exhaust streams, particularly those originating from heavy-duty diesel engines (including highway and off-road heavy-duty diesel engines), the system comprising a reducing agent source (e.g., NH3 or a precursor thereof) and a catalyst as described in the first aspect above.

[0148] Systems used to treat exhaust gases may also include one or more conventional exhaust gas treatment elements. Conventional exhaust gas treatment elements include, but are not limited to, diesel oxidation catalysts (DOC), selective catalytic reduction catalysts (SCR), three-way conversion catalysts (TWC), four-way conversion catalysts (FWC), non-catalytic or catalytic smoke filters (CSF), NOx traps, hydrocarbon capture catalysts, sensors, and mixers.

[0149] In some embodiments, the system for treating the exhaust flow further includes a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) catalyst located downstream of the engine and upstream of the catalytic articles as described in the first aspect above. Preferably, the system for treating the exhaust flow further includes a diesel oxidation catalyst (DOC), a selective catalytic reduction (SCR) catalyst, and a catalytic smoke filter (CSF) located upstream of the catalytic articles as described in the first aspect above.

[0150] In a third aspect, the present invention relates to a method for treating an exhaust stream containing nitrogen oxides, the method comprising passing the exhaust stream through a system as described in the second aspect in the presence of NH3 as a reducing agent.

[0151] In some implementations, the method can be used to treat exhaust streams originating from diesel engines, particularly heavy-duty diesel engines such as highway and off-road heavy-duty diesel engines.

[0152] In a fourth aspect, the present invention relates to a method for mitigating poisoning of a noble metal component in a catalyst article comprising a first coating containing a vanadium-based catalyst and a second coating containing a noble metal-based catalyst, the method comprising at least partially incorporating an inorganic oxide layer between the first coating and the second coating, wherein the inorganic oxide is selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination or composite oxide thereof.

[0153] Implementation Plan

[0154] Various embodiments are listed below. It should be understood that the embodiments listed below can be combined with all aspects of the invention and other embodiments.

[0155] 1. A catalytic article for treating exhaust gas streams, the catalytic article comprising:

[0156] - A substrate having an inlet end and an outlet end that define axial lengths.

[0157] - A first coating that extends part or all of the axial length of the substrate, the first coating comprising a first catalyst containing a vanadium component;

[0158] - A second coating, extending a portion or the entire axial length of the substrate, comprising a second catalyst containing a noble metal component, and

[0159] - A third coating extending a portion or the entire axial length of the substrate, the third coating comprising, or consisting of, an inorganic oxide selected from, titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination thereof, or composite oxides thereof.

[0160] The third coating is positioned as an intermediate layer between the first coating and the second coating along a portion or the entire axial length of the substrate.

[0161] 2. The catalyst product according to embodiment 1, wherein the substrate is a flow-through substrate or a wall-flow substrate.

[0162] 3. The catalyst product according to embodiment 2, wherein the substrate is a flow-through substrate.

[0163] 4. The catalyst article according to any one of the foregoing embodiments, wherein both the first coating and the second coating extend the entire axial length of the substrate.

[0164] 5. The catalyst article according to any one of the foregoing embodiments, wherein the first coating is a top layer extending the entire axial length of the substrate, and the second coating is a bottom layer.

[0165] 6. The catalyst article according to embodiment 5, wherein the second layer and the third coating extend the entire axial length of the substrate.

[0166] 7. The catalyst article according to embodiment 5, wherein the third coating extends a portion of the axial length of the substrate.

[0167] 8. The catalyst article according to embodiment 7, wherein the second coating extends the entire axial length of the substrate, and the third coating extends a portion of the axial length of the substrate from the outlet end toward the opposite end.

[0168] 9. The catalyst article according to embodiment 7, wherein both the second layer and the third coating extend from the outlet end of the substrate toward the opposite end along the same portion of the axial length of the substrate.

[0169] 10. The catalyst article according to any one of the foregoing embodiments, wherein, based on the total weight of the first catalyst, the first catalyst contains an amount of the vanadium component from 0.5% to 8% by weight, calculated as V2O5.

[0170] 11. The catalyst article according to embodiment 10, wherein, based on the total weight of the first catalyst, the first catalyst contains a vanadium component in an amount of 1% to 6% by weight, calculated as V2O5.

[0171] 12. The catalyst article according to any one of the foregoing embodiments, wherein the first catalyst contains an antimony component.

[0172] 13. The catalyst article according to embodiment 12, wherein, based on the total weight of the first catalyst, the first catalyst contains an amount of antimony component from 0.5% to 16% by weight, calculated as Sb2O3.

[0173] 14. The catalyst article according to embodiment 13, wherein, based on the total weight of the first catalyst, the first catalyst contains an amount of antimony component of 2% to 9% by weight, calculated as Sb2O3.

[0174] 15. The catalyst article according to any one of the foregoing embodiments, wherein the first catalyst comprises vanadium oxide, antimony oxide, and optionally a composite oxide of vanadium and antimony supported on particles of a support.

[0175] 16. The catalyst article according to embodiment 15, wherein the support comprises a molecular sieve and one or more oxides of a metal or metalloid selected from the group consisting of Ti, Si, W, Al, Ce, Zr, Mg, Ca, Ba, Y, La, Pr, Nb, Mo, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn and Bi.

[0176] 17. The catalyst article according to any one of the foregoing embodiments, wherein the noble metal component comprises one or more of ruthenium, rhodium, iridium, palladium and platinum supported on particles of a support, more preferably palladium and platinum, and most preferably platinum.

[0177] 18. The catalyst article according to embodiment 17, wherein the support in the noble metal component is one or more of a molecular sieve and an oxide of a metal or metalloid selected from the group consisting of Ti, Si, W, Al, Ce, Zr, Mg, Ca, Ba, Y, La, Pr, Nb, Mo, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn, Sm, Eu, Hf and Bi.

[0178] 19. The catalyst article according to any one of the foregoing embodiments, wherein, in addition to the precious metal component, the second catalyst further contains a zeolite or non-zeolite molecular sieve catalyst component.

[0179] 20. The catalyst article according to any one of the foregoing embodiments, wherein the third coating comprises, or is composed of, an inorganic oxide selected from titanium dioxide, silicon dioxide, cerium dioxide, zirconium oxide, lanthanum oxide, silicon-titanium composite oxide, tungsten-titanium composite oxide, lanthanum-zirconium composite oxide, or any combination thereof.

[0180] 21. The catalyst article according to any one of the foregoing embodiments, wherein the third coating is at a concentration of 0.01 g / in 3 Up to 20g / in 3 Preferably 0.1 g / in 3 Up to 5g / in 3 The quantity exists.

[0181] 22. The catalyst article according to any one of the foregoing embodiments, wherein the first coating is at a concentration of 0.01 g / in 3 Up to 20g / in 3 Preferably 0.5g / in 3 Up to 8g / in 3 The quantity exists.

[0182] 23. The catalyst article according to any one of the foregoing embodiments, wherein the second coating is applied at a concentration of 0.01 g / in 3 Up to 20g / in 3 Preferably 0.1 g / in 3 Up to 5g / in 3 The quantity exists.

[0183] 24. The catalyst article according to any one of the foregoing embodiments, wherein the precious metal component is expressed at a concentration of 0.01 g / ft for each precious metal. 3 Up to 20g / ft 3 Preferably 0.5g / ft 3 Up to 10g / ft 3 The quantity exists.

[0184] 25. A system for treating exhaust gas streams, the system comprising a reducing agent source (e.g., NH3 or a precursor thereof), a catalytic article according to any one of the preceding embodiments, and optionally one or more of a diesel oxidation catalyst (DOC), a selective catalytic reduction catalyst (SCR), a three-way conversion catalyst (TWC), a four-way conversion catalyst (FWC), a non-catalytic or catalytic smoke filter (CSF), a NOx trap, a hydrocarbon capture catalyst, a sensor, and a mixer.

[0185] 26. The system according to embodiment 25, wherein the exhaust flow originates from an internal combustion engine, particularly a diesel engine.

[0186] 27. A method for treating an exhaust stream containing nitrogen oxides, the method comprising passing the exhaust stream through a system as defined in embodiment 25 or embodiment 26 in the presence of NH3 as a reducing agent.

[0187] 28. A method for mitigating poisoning of a noble metal component in a catalyst article comprising a first coating containing a vanadium-based catalyst and a second coating containing a noble metal-based catalyst, the method comprising at least partially incorporating an inorganic oxide layer between the first coating and the second coating, wherein the inorganic oxide is selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination or composite oxide thereof.

[0188] The present invention will be further illustrated by the following embodiments, which illustrate particularly advantageous implementations. Although embodiments are provided to illustrate the invention, they are not intended to limit the invention.

[0189] Example

[0190] Example 1

[0191] Step 1.1 Apply a bottom coating containing a Pt-based catalyst to the substrate.

[0192] A Cu-CHA slurry was prepared by mixing 218.7 g of Cu-CHA zeolite from Zeolyst and 6.2 g of Al2O3 powder into 300 g of deionized (DI) water. The Cu-CHA zeolite had a SiO2 to Al2O3 molar ratio of 28, a CuO weight content of 3.2%, an X-ray crystallinity of 98%, and a pH of 750 μm. 2 / g BET surface area and 5 micrometers D 90 .

[0193] A Pt slurry was prepared by mixing 69g of a colloidal Pt solution with a Pt content of 2% by weight with 100g of deionized water to form a homogeneous mixture. This Pt slurry was then immersed in 207g of 8% SiO2-doped TiO2 powder and stirred for 30 minutes. The pH was adjusted to 4 with tartaric acid, and the powder was then ground to a particle size D. 90 The particle size is 5 micrometers, as measured using a Sympatec particle size analyzer.

[0194] Cu-CHA slurry was mixed with Pt slurry, adjusted to pH 5 with tartaric acid, and then stirred for 20 minutes to obtain a homogeneous slurry. The resulting slurry was coated onto a 300 cpsi, 5 mil thick, monolithic cordierite substrate by immersing the substrate in the slurry. Excess slurry was carefully blown off with an air knife, followed by drying at 130°C and calcining at 550°C. After cooling to room temperature, the impregnation, drying, and calcination process was repeated until 0.5 g / in was obtained on the substrate. 3 The total coating loading, of which the Cu-CHA loading was 0.25 g / in. 3 The Pt loading is 3 g / ft 3 .

[0195] Step 1.2 Apply an intermediate wash coating containing TiO2 particles

[0196] 150 g of anatase TiO2 with a titanium content of 95.9 wt% (calculated as TiO2) was added to 200 g of deionized water at room temperature. The resulting suspension was stirred for 30 minutes, and the pH was adjusted to 7.0 using a 25% ammonia solution. Then, 15 g of a SiO2 solution with a SiO2 content of 40 wt% was added. After stirring for 1 hour, particle size D was obtained. 90 A homogeneous slurry with a thickness of less than 15 microns is used to impregnate a substrate with a bottom wash coating obtained in step 1.1 to load sufficient slurry. Excess slurry is carefully blown off with an air knife, followed by drying with hot air at 150°C for 15 minutes, and then calcining in air at 450°C for 1 hour. The impregnation, drying, and calcination process is repeated until 1.0 g / in is obtained on the substrate. 3 The total load of the intermediate wash coating.

[0197] Step 1.3 Apply a top wash coating containing a V-based catalyst

[0198] 132.8 g of anatase TiO2 (95.9 wt% titanium content, calculated as TiO2), 57.1 g of vanadium oxalate solution (10.8 wt% vanadium content, calculated as V2O5), and 9.0 g of Sb2O3 were mixed in 200 g of deionized water at room temperature. The resulting suspension was stirred for 30 minutes, and then 25% ammonia solution was added to raise the pH of the system to 7.0. Then, 25.5 g of SiO2 solution (30.1 wt% SiO2 content) was added. After stirring for 1 hour, a homogeneous slurry for the V-based catalyst was obtained. A substrate with two wash-out layers, as obtained in step 1.2, was impregnated into this homogeneous slurry to load sufficient slurry. The extra slurry was carefully blown off with an air knife, followed by drying with hot air at 150°C for 15 minutes, and then calcined in air at 450°C for 1 hour. Based on the total weight of the V-based catalyst, the V-based catalyst has a vanadium content of 4.0% by weight, calculated as V2O5.

[0199] Repeat the impregnation, drying, and calcination process until 3.0 g / in is obtained. 3 The total load of the top wash coating to provide a coating with the following properties: Figure 1a The catalyst product shown has a three-layer wash coating structure.

[0200] Example 2

[0201] Step 2.1 Apply a bottom coating containing a Pt-based catalyst to the substrate.

[0202] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom wash coating.

[0203] Step 2.2 Apply an intermediate wash coating containing SiO2-doped TiO2 particles.

[0204] 150 g of anatase-doped TiO2 with a solid content of 95 wt% (SiO2 / TiO2) and 5 wt% (SiO2-to-TiO2) was added to 200 g of deionized water at room temperature. The resulting suspension was stirred for 30 minutes, and the pH was adjusted to 7.0 using a 25% ammonia solution. Then, 15 g of a SiO2 solution with a SiO2 content of 40 wt% was added. After stirring for 1 hour, particle size D was obtained. 90 A homogeneous slurry with a thickness of less than 15 microns is used to impregnate a substrate with a bottom wash coating obtained in step 2.1 to load sufficient slurry. Excess slurry is carefully blown off with an air knife, followed by drying with hot air at 150°C for 15 minutes, and then calcining in air at 450°C for 1 hour. The impregnation, drying, and calcination process is repeated until a slurry of 1.0 g / in is obtained. 3 The total load of the intermediate wash coating.

[0205] Step 2.3 Apply a top wash coating containing the V-based catalyst

[0206] Repeat the procedure according to step 1.3 above on the coating substrate obtained in step 2.2 to provide a coating having the following properties. Figure 1a The catalyst product shown has a three-layer wash coating structure.

[0207] Example 3

[0208] Step 3.1 Apply a bottom coating containing a Pt-based catalyst to the substrate.

[0209] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom wash coating.

[0210] Step 3.2 Apply an intermediate wash coating containing WO3-doped TiO2 particles.

[0211] 150 g of WO3-doped TiO2 in anatase form (96 wt% solids, calculated as WO3 / TiO2) and 10 wt% WO3-doped TiO2 was added to 200 g of deionized water at room temperature. The resulting suspension was stirred for 30 minutes, and the pH was adjusted to 7.0 using a 25% ammonia solution. Then, 15 g of a SiO2 solution (40 wt% SiO2 content) was added. After stirring for 1 hour, particle size D was determined. 90 A homogeneous slurry with a thickness of less than 15 microns is used to impregnate a substrate with a bottom wash coating obtained in step 3.1 to load sufficient slurry. Excess slurry is carefully blown off with an air knife, followed by drying with hot air at 150°C for 15 minutes, and then calcining in air at 450°C for 1 hour. The impregnation, drying, and calcination process is repeated until a slurry of 1.0 g / in is obtained. 3 The total load of the intermediate wash coating.

[0212] Step 3.3 Apply a top wash coating containing the V-based catalyst

[0213] Repeat the procedure according to step 1.3 above on the coating substrate obtained in step 3.2 to provide a coating having the following properties. Figure 1a The catalyst product shown has a three-layer wash coating structure.

[0214] Example 4

[0215] Step 4.1 Apply a bottom coating containing a Pt-based catalyst to the substrate.

[0216] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom wash coating.

[0217] Step 4.2 Apply an intermediate wash coating containing CeO2 particles

[0218] 300 g of CeO2 with a solid content of 98 wt% (calculated as CeO2) was added to 550 g of deionized water at room temperature. After stirring the resulting suspension for 30 minutes, particle size D was provided. 90A homogeneous slurry with a thickness of less than 15 microns is used to impregnate a substrate with a bottom wash coating obtained in step 4.1 to load sufficient slurry. Excess slurry is carefully blown off with an air knife, followed by drying with hot air at 150°C for 15 minutes, and then calcining in air at 450°C for 1 hour. The impregnation, drying, and calcination process is repeated until a slurry of 1.0 g / in is obtained. 3 The total load of the intermediate wash coating.

[0219] Step 4.3 Apply a top wash coating containing the V-based catalyst

[0220] Repeat the procedure according to step 1.3 above on the coated substrate obtained in step 4.2 to provide a coating having the following properties. Figure 1a The catalyst product shown has a three-layer wash coating structure.

[0221] Example 5

[0222] Step 5.1 Apply a bottom coating containing a Pt-based catalyst to the substrate.

[0223] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom wash coating.

[0224] Step 5.2 Apply an intermediate wash coating containing ZrO2 particles

[0225] 300 g of ZrO2 with a solid content of 97 wt% (calculated as ZrO2) was added to 550 g of deionized water at room temperature. After stirring the resulting suspension for 30 minutes and milling, particle size D was provided. 90 A homogeneous slurry with a thickness of less than 15 microns is used to impregnate a substrate with a bottom wash coating obtained in step 5.1 to load sufficient slurry. Excess slurry is carefully blown off with an air knife, followed by drying with hot air at 150°C for 15 minutes, and then calcining in air at 450°C for 1 hour. The impregnation, drying, and calcination process is repeated until 1.0 g / in is obtained. 3 The total load of the intermediate wash coating.

[0226] Step 5.3 Apply a top wash coating containing the V-based catalyst

[0227] Repeat the procedure according to step 1.3 above on the coating substrate obtained in step 5.2 to provide a coating having the following properties. Figure 1a The catalyst product shown has a three-layer wash coating structure.

[0228] Example 6 - (Comparative Example)

[0229] Step 6.1 Apply a bottom coating containing a Pt-based catalyst to the substrate.

[0230] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom wash coating.

[0231] Step 6.2 Apply an intermediate wash coating containing Al2O3 particles

[0232] 300 g of Al2O3 with a solid content of 97 wt% (calculated as Al2O3) was added to 550 g of deionized water at room temperature. After stirring the resulting suspension for 30 minutes, particle size D was provided. 90 A homogeneous slurry with a thickness of less than 15 microns is used to impregnate a substrate with a bottom wash coating obtained in step 6.1 to load sufficient slurry. Excess slurry is carefully blown off with an air knife, followed by drying with hot air at 150°C for 15 minutes, and then calcining in air at 450°C for 1 hour. The impregnation, drying, and calcination process is repeated until a slurry of 1.0 g / in is obtained. 3 The total load of the intermediate wash coating.

[0233] Step 6.3 Apply a top wash coating containing the V-based catalyst

[0234] Repeat the procedure according to step 1.3 above on the coating substrate obtained by step 6.2 to provide a coating having the following properties: Figure 1a The catalyst product shown has a three-layer wash coating structure.

[0235] Example 7 - (Comparative Example)

[0236] Step 7.1 Apply a bottom coating containing a Pt-based catalyst to the substrate.

[0237] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom wash coating.

[0238] Step 7.2 Apply a top wash coating containing the V-based catalyst

[0239] Repeat the procedure according to step 1.3 above on the substrate with the bottom wash coating obtained by step 7.1 to provide a substrate with the following properties: Figure 1b The catalyst product shown has a two-layer wash coating structure.

[0240] Performance testing

[0241] The catalysts prepared as in each example were subjected to hydrothermal treatment at 550°C for 100 hours in 10% water / air to provide aged catalysts. Cores with a diameter of 1 inch and a length of 3 inches were cut from the aged catalysts as test samples and placed in a fixed laboratory simulator for testing.

[0242] The feed gas contains 500 ppm NH3, 7% H2O, 10% O2, 8% CO2, and the balance N2 by volume. The test is conducted over 100,000 h⁻¹. -1 The gas space velocity and the temperature as shown in Table 1.

[0243]

[0244]

[0245] MC: Intermediate Wash Coating

[0246] It can be seen that the aged catalyst with an intermediate layer according to the present invention exhibits higher NH3 conversion performance than the comparative counterparts (i.e., the catalysts of Examples 6 and 7). Without being bound by any theory, it is believed that the lower NH3 conversion of the catalysts of Examples 6 and 7 is due to more severe platinum poisoning caused by vanadium during aging.

[0247] Although the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatus of the invention without departing from the spirit and scope of the invention. Therefore, the invention is intended to include modifications and variations within the scope of the appended claims and their equivalents.

Claims

1. A catalytic article for treating an exhaust gas stream, the catalytic article comprising - a substrate having an inlet end and an outlet end defining an axial length, - a first coating extending part or the entire axial length of the substrate, the first coating comprising a first catalyst comprising a vanadium component; - a second coating extending part or the entire axial length of the substrate, the second coating comprising a second catalyst comprising a noble metal component, and - a third coating extending part or the entire axial length of the substrate, the third coating comprising or consisting of an inorganic oxide selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanium oxide and cerium oxide, any combination thereof or a composite oxide thereof, wherein the third coating is positioned as an intermediate layer between the first coating and the second coating over part or the entire axial length of the substrate.

2. The catalytic article according to claim 1, wherein the substrate is a flow-through substrate or a wall-flow substrate, preferably a flow-through substrate.

3. The catalytic article according to claim 1 or 2, wherein both the first coating and the second coating extend the entire axial length of the substrate.

4. The catalytic article according to any one of the preceding claims, wherein the first coating is a top layer extending the entire axial length of the substrate and the second coating is a bottom layer.

5. The catalytic article according to claim 4, wherein the second layer and the third coating extend the entire axial length of the substrate.

6. The catalytic article according to claim 4, wherein the third coating extends part of the axial length of the substrate.

7. The catalytic article according to claim 6, wherein the second coating extends the entire axial length of the substrate and the third coating extends part of the axial length of the substrate from the outlet end of the substrate towards the opposite end.

8. The catalytic article according to claim 6, wherein both the second layer and the third coating extend from the outlet end of the substrate towards the opposite end over the same part of the axial length of the substrate.

9. The catalytic article according to any one of the preceding claims, wherein the first catalyst contains the vanadium component in an amount of 0.5 to 8 wt.%, or 1 to 6 wt.% calculated as V2O5, based on the total weight of the first catalyst.

10. The catalytic article according to any one of the preceding claims, wherein the first catalyst contains a antimony component in an amount of preferably 0.5 to 16 wt.%, or 2 to 9 wt.% calculated as Sb2O3, based on the total weight of the first catalyst.

11. The catalytic article according to any one of the preceding claims, wherein the first catalyst contains vanadium oxide, antimony oxide and optionally a composite oxide of vanadium and antimony supported on particles of a carrier.

12. The catalytic article according to claim 11, wherein the support comprises a molecular sieve and one or more of the oxides of metals or metalloids selected from the group consisting of Ti, Si, W, Al, Ce, Zr, Mg, Ca, Ba, Y, La, Pr, Nb, Mo, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn and Bi.

13. The catalytic article according to any one of the preceding claims, wherein the noble metal component contains one or more selected from ruthenium, rhodium, iridium, palladium and platinum, more preferably palladium and platinum, most preferably platinum, supported on the particles of the support.

14. The catalytic article according to claim 13, wherein the support in the noble metal component is a molecular sieve and one or more of the oxides of metals or metalloids selected from the group consisting of Ti, Si, W, Al, Ce, Zr, Mg, Ca, Ba, Y, La, Pr, Nb, Mo, Mn, Fe, Co, Ni, Cu, Zn, Ga, Sn, Sm, Eu, Hf and Bi.

15. The catalytic article according to any one of the preceding claims, wherein the second catalyst contains, in addition to the noble metal component, a zeolitic or non-zeolitic molecular sieve catalyst component.

16. The catalytic article according to any one of the preceding claims, wherein the third coating comprises or consists of an inorganic oxide selected from titanium dioxide, silicon dioxide, cerium dioxide, zirconium oxide, lanthanum oxide, silicon-titanium composite oxides, tungsten-titanium composite oxides, lanthanum-zirconium composite oxides, or any combination thereof.

17. The catalytic article according to any one of the preceding claims, wherein the third coating is present in an amount of 0.01 g / in 3 to 20 g / in 3 , preferably 0.1 g / in 3 to 5 g / in 3 .

18. The catalytic article according to any one of the preceding claims, wherein the first washcoat is present in an amount of 0.01 g / in 3 to 20 g / in 3 , preferably 0.5 g / in 3 to 8 g / in 3 .

19. The catalytic article according to any one of the preceding claims, wherein the second coating is present in an amount of 0.01 g / in 3 to 20 g / in 3 , preferably 0.1 g / in 3 to 5 g / in 3 .

20. The catalytic article according to any one of the preceding claims, wherein the noble metal component is present in an amount of 0.01 g / ft 3 to 20 g / ft 3 , preferably 0.5 g / ft 3 to 10 g / ft 3 , calculated per noble metal.

21. A system for treating an exhaust gas stream, the system comprising a source of a reductant (e.g. NH3 or a precursor thereof), a catalytic article according to any one of the preceding claims, and optionally one or more of a diesel oxidation catalyst (DOC), a selective catalytic reduction catalyst (SCR), a three-way conversion catalyst (TWC), a four-way conversion catalyst (FWC), a non-catalysed or catalysed soot filter (CSF), a NOx trap, a hydrocarbon trap catalyst, a sensor and a mixer.

22. The system according to claim 21, wherein the exhaust gas stream originates from an internal combustion engine, in particular a diesel engine.

23. A method for treating an exhaust gas stream containing nitrogen oxides, the method comprising passing the exhaust gas stream through a system as defined in claim 21 or 22 in the presence of NH3 as a reductant.

24. A method for mitigating poisoning of a noble metal component in a catalytic article comprising a first coating comprising a vanadium-based catalyst and a second coating comprising a noble metal-based catalyst, the method comprising at least partially interposing an inorganic oxide layer between the first coating and the second coating, wherein the inorganic oxide is selected from titanium oxide, silicon oxide, zirconium oxide, tungsten oxide, rare earth metal oxides such as lanthanum oxide and cerium oxide, any combination or composite oxide thereof.

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