A catalyst article comprising a vanadium-containing catalyst and an oxidation catalyst

Abstract

The present invention relates to a catalyst article for treating an exhaust stream, the catalyst article comprising a first catalyst containing a vanadium component and an antimony component, and a second catalyst containing a noble metal component, and also relates to a method and a system for treating an exhaust stream containing nitrogen oxides.

Description

Technical Field

[0001] The present invention relates to a catalyst article for treating an exhaust stream containing nitrogen oxides, comprising a vanadium-containing catalyst and an oxidation catalyst. The present invention also relates to a method and a system for treating an exhaust stream containing nitrogen oxides.

Background Art

[0002] Engine exhaust substantially consists of particulate matter and gaseous pollutants such as unburned hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). Engine exhaust needs to be treated in an engine exhaust system before being released into the air. The control of NOx emissions has always been one of the most important topics, especially for the exhaust treatment of diesel engines, due to the environmental adverse effects of NOx on the ecosystem, humans, animals, and plants.

[0003] To reduce NOx in exhaust gas, various treatment processes, such as catalytic reduction of nitrogen oxides, have been used. One typical catalytic reduction process is selective catalytic reduction using ammonia (NH3) or an ammonia precursor as a reducing agent in the presence of oxygen in the atmosphere, which is also referred to as the SCR process. The SCR process is considered excellent because it can achieve a high degree of NOx reduction with a small amount of reducing agent. Typically, nitrogen oxides and the reducing agent NH3 react according to the following equations. 4NO + 4NH3 + O2 → 4N2 + 6H2O (standard SCR reaction) 2NO2 + 4NH3 + O2 → 3N2 + 6H2O (slow SCR reaction) NO + NO2 + 2NH3 → 2N2 + 3H2O (fast SCR reaction).

[0004] In the SCR process, typically, a stoichiometrically excessive reducing agent NH3 or its precursor is administered to the exhaust stream to reduce NOx with as high a conversion rate as possible. Excess ammonia may exit from the tailpipe of an automobile. Another potential scenario where ammonia may exit from the tailpipe is that a significant amount of ammonia held on the surface of the SCR catalyst during the low-temperature portion of a typical operating cycle desorbs from the SCR catalyst when the operating temperature rises. When the release of ammonia into the air, also referred to as ammonia slip, occurs, several problems will arise. Ammonia slip is harmful to human health and the environment. Ammonia can cause significant eye and throat inflammation when it exceeds 100 ppm and may cause significant skin irritation when it exceeds 400 ppm, and the IDLH value of ammonia was known to be 500 ppm in air. In addition, ammonia is caustic, especially in its aqueous form. The condensation of ammonia and water in the low-temperature region of the exhaust line downstream of the exhaust treatment catalyst will result in a corrosive mixture and damage the exhaust line. Ammonia should be removed before entering the tailpipe. An ammonia oxidation (AMOx) catalyst installed downstream of the SCR catalyst, also known as an ammonia slip catalyst (ASC), is generally used to convert the slipped ammonia to N2.

[0005] Ammonia oxidation (AMOx) catalysts are known, which contain noble metal active species for oxidizing ammonia and usually also contain SCR active species. As known SCR active species, zeolites are widely used, but vanadium-based species are hardly applied due to the significant poisoning effect of vanadium species on noble metals.

[0006] U.S. Patent Application Publication No. 2014 / 0212350 (A1) describes a catalyst article for treating exhaust gas, comprising: (a) a first catalyst layer having a plurality of continuous sub-layers, each sub-layer containing vanadium oxide on a first refractory metal oxide support, the first catalyst layer; (b) a second catalyst layer disposed on a second refractory metal oxide support and containing one or more noble metals; and (c) a substrate, wherein the first and second catalyst layers are on and / or within the substrate. The catalyst article in the examples of this patent application contains vanadia and tungsten oxide in the first catalyst layer.

[0007] International Publication No. 2011 / 140251 (A2) describes an integrated SCR and AMOx catalyst system comprising a first zone for reducing nitrogen oxides by selective catalytic reduction, a second zone for oxidizing ammonia, and a third zone for oxidizing carbon monoxide and hydrocarbons. The second zone is obtained by overlapping a first catalyst coating containing a platinum group metal extending from the outlet end to the inlet end of the substrate and a second catalyst coating containing an SCR catalyst extending from the inlet end to the outlet end of the substrate. The SCR catalyst may contain V2O5 and WO3 supported on TiO2.

[0008] International Publication No. 2018 / 178627 (A1) describes a catalyst article for treating the flow of combustion exhaust gas, comprising a substrate formed of an extruded vanadium-containing SCR catalyst material, a first layer provided on at least a part of the substrate, and a second layer provided on at least a part of the first layer, wherein the first layer contains an ammonia slip catalyst composition containing one or more platinum group metals, and the second layer contains an SCR catalyst composition. A preferred substrate is formed from a blend of vanadium / tungsten / titania and iron-promoted ZSM-5 zeolite.

[0009] It would be desirable if low-cost vanadium-based SCR active species could be applied to ammonia oxidation (AMOx) catalysts that are less or not at all poisoned by noble metals.

SUMMARY OF THE INVENTION

[0010] An object of the present invention is to provide an AMOx catalyst article comprising a vanadium-based SCR catalyst and a noble metal-based catalyst, in which poisoning of noble metal species is reduced, and thus an improved NH3 conversion rate can be provided, particularly in the low-temperature operation stage of an exhaust treatment system.

[0011] Surprisingly, this object has been achieved by a catalyst article comprising an SCR catalyst containing vanadium and antimony.

[0012] Accordingly, in a first aspect, the present invention is a catalyst article for treating an exhaust stream, - a first catalyst containing a vanadium component and an antimony component, - a second catalyst containing a noble metal component, and relates to a catalyst article.

[0013] In a second aspect, the present invention is a system for treating an exhaust stream, comprising a reductant source (e.g., NH3 or its precursor), the catalyst article described herein, 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 catalyzed soot filter (CSF), a NOx trap, a hydrocarbon trap catalyst, a sensor, and a mixer, and relates to a system.

[0014] In a third aspect, the present invention is a method for treating an exhaust stream containing nitrogen oxides, comprising contacting the exhaust stream with a catalyst article as described herein in the presence of NH3 as a reductant, or passing the exhaust stream through a system as described herein, and relates to a method.

[0015] In a fourth aspect, the present invention relates to a method for reducing poisoning of a noble metal component in a catalyst article comprising a vanadium-based catalyst and a noble metal-based catalyst, the method comprising incorporating an antimony component into the vanadium-based catalyst.

[0016] Surprisingly, the present inventors have found that poisoning of the noble metal component in an AMOx catalyst article comprising a vanadium-based catalyst and a noble metal-based catalyst can be effectively suppressed by incorporating an antimony component into the vanadium-based catalyst.

BRIEF DESCRIPTION OF THE INVENTION

[0017] The present invention will be described in detail hereinafter. It should be understood that the present invention can be implemented in many different ways and should not be construed as limited to the embodiments described herein.

[0018] As used herein, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Terms such as “comprise,” “comprising,” etc. are used interchangeably with “contain,” “containing,” etc. and should be construed in a non-limiting, open-ended fashion. That is, for example, additional components or elements may be present. The expressions “consists of” or “consists essentially of” or cognates may be subsumed within “comprises” or cognates.

[0019] As used herein, the term “zone” is simply intended to mean a portion of a catalyst article that contains a particular material and extends for a particular length in the flow direction of the exhaust stream.

[0020] As used herein, any reference to “upstream” and “downstream” is also understood to be a relative position with respect to the flow direction of the flow, e.g., the flow direction of the exhaust stream.

[0021] The terms "first catalyst" and "second catalyst" themselves are not intended to impose any limitation on the arrangement or configuration method of the two catalysts in the catalyst article. If the two catalysts are separated from each other, it will be understood that the first catalyst can be arranged either upstream or downstream of the second catalyst, or either above or below the second catalyst. It will also be understood that the first catalyst and the second catalyst may also be applied in a mixed form.

[0022] According to a first aspect, the present invention provides a catalyst article for treating an exhaust stream, - a first catalyst containing a vanadium component and an antimony component, - a second catalyst containing a noble metal component, the catalyst article comprising.

[0023] <The first catalyst> The first catalyst may be a vanadium-based SCR catalyst containing a vanadium component and an antimony component. The vanadium component and the antimony component may exist in the form of their respective oxides and / or their composite oxides, and these are supported on the particles of the support.

[0024] In particular, the vanadium component and the antimony component may be present in the first catalyst in the form of vanadium oxides such as V2O5 and antimony oxides such as Sb2O3. In this case, a composite oxide of vanadium and antimony may be present in the first catalyst. Therefore, the first catalyst may contain vanadium oxide, antimony oxide, and optionally a composite oxide of vanadium and antimony, supported on the particles of the support, as the vanadium component and the antimony component.

[0025] It is also conceivable that the vanadium component and the antimony component may exist in the first catalyst only in the form of a composite oxide of vanadium and antimony.

[0026] The first catalyst may optionally contain at least one additional metal or metalloid. Examples of additional metals or metalloids may include, but are not limited to, boron (B), aluminum (Al), bismuth (Bi), silicon (Si), tin (Sn), lead (Pb), 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).

[0027] In particular, the additional metal or metalloid may be selected from silicon (Si), molybdenum (Mo), and tungsten (W). It will be understood that at least one metal or metalloid may be present in the form of their respective oxides, or these composite oxides with vanadium, antimony, or other additional metals or metalloids, or combinations thereof.

[0028] In some embodiments, the first catalyst contains or consists of vanadium oxide, antimony oxide, and optionally at least one oxide of a metal or metalloid selected from silicon (Si), molybdenum (Mo), and tungsten (W) on the particles of the support. For example, the first catalyst contains or consists of the respective and / or composite oxides of vanadium (V), antimony (Sb), and silicon (Si) on the particles of the support.

[0029] Materials useful as supports for vanadium, antimony, and optionally additional metals or metalloids in the first catalyst may include molecular sieves, and oxides of metals 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, but are not limited thereto. Preferably, the support may be one or more selected from titania (preferably anatase), silica, alumina, zirconia, and any dopant-stabilized forms thereof.

[0030] The first catalyst may contain a vanadium component calculated as V2O5 in an amount of 0.5 to 8 wt% or 1 to 6 wt% based on the total weight of the first catalyst.

[0031] The first catalyst may contain an antimony component calculated as Sb2O3 in an amount of 0.5 to 16 wt% or 2 to 9 wt% based on the total weight of the first catalyst.

[0032] Each of at least one additional metal or metalloid, if present, is calculated as its respective oxide and may be contained in the first catalyst in an amount of 0.1 to 30 wt%, 1 to 15 wt%, or 2 to 10 wt% based on the total weight of the first catalyst.

[0033] The support may be contained 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 the support may be at most 95 wt% or at most 90 wt% based on the total weight of the first catalyst.

[0034] In some embodiments, the first catalyst (a) vanadium oxide calculated as V2O5 in an amount of 0.5 to 8 wt%, and (b) antimony oxide calculated as Sb2O3 in an amount of 0.5 to 16 wt%, and (c) SiO2 in an amount of 1 to 15 wt%, and (e) TiO2 in an amount of 70 to 95 wt%, and consists of or consists of them, each being based on the total weight of the first catalyst.

[0035] In some further embodiments, the first catalyst (a) vanadium oxide calculated as V2O5 in an amount of 1 to 6 wt%, and (b) antimony oxide calculated as Sb2O3 in an amount of 2 to 9 wt%, and (c) SiO2 in an amount of 2 to 10 wt%, and (e) containing 75 to 95% by weight of TiO2, or consisting of these, each is based on the total weight of the first catalyst.

[0036] The total weight of the first catalyst in each case as described herein will be 100% by weight.

[0037] <Second catalyst> The second catalyst may be a noble metal-based oxidation catalyst containing a noble metal component, preferably a platinum group metal component. The noble metal component may contain one or more selected from ruthenium, rhodium, iridium, palladium, platinum, silver and gold on the particles of the support. Preferably, the noble metal component contains one or more selected from ruthenium, rhodium, iridium, palladium and platinum, more preferably palladium and platinum, and most preferably platinum on the particles of the support.

[0038] The noble metal may exist in any possible valence state, for example, each metal or metal oxide in the catalytically active form, or, for example, each metal compound, complex, etc., which will be understood to decompose during the calcination or use of the catalyst, or otherwise be converted to the catalytically active form.

[0039] The support for the noble metal in the second catalyst can be any material suitable for receiving and supporting the noble metal, for example, an oxide of a metal selected from the group consisting of molecular sieve, 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 support for the noble metal can be selected from high surface area alumina, ceria, zirconia, lanthana, baria, yttria, neodymia, praseodymia, titania, europia, samaria, hafnia, and any composite or combination thereof. Exemplary supports may be composite oxides such as silica and alumina, silica and titania.

[0040] Optionally, the second catalyst may further contain a zeolite or non-zeolite molecular sieve component. Molecular sieves generally refer to skeletal materials based on a wide three-dimensional network structure of oxygen ions that contain tetrahedral sites and have a substantially uniform pore distribution. Molecular sieves suitable for the purposes of the present invention can be microporous or mesoporous.

[0041] In particular, the molecular sieve may be a zeolite, which is optionally metal-promoted. As used herein, the term "metal-promoted" in the context of molecular sieves is intended to mean that a metal that can also improve any performance of the zeolite is incorporated into and / or on the zeolite.

[0042] Preferably, suitable molecular sieves can include, but are not limited to, aluminosilicate zeolites having 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 includes zeolites having a framework type selected from the group consisting of AEI, BEA (e.g., beta), CHA (e.g., chabazite, SSZ-13), AFT, AFX, FAU (e.g., zeolite Y), MOR, MFI (e.g., ZSM-5), MOR (e.g., mordenite), and MEL, among which AEI, BEA, and CHA are particularly preferred.

[0043] When a zeolite is referred to herein with reference to the framework type code generally accepted by the International Zeolite Association (IZA), it is understood that this is intended to include not only the reference materials but also any isotypic framework materials having SCR catalytic activity. Lists of reference materials and isotypic framework materials for each framework type code are available from the IZA database (http: / / www.iza-structure.org / databases / ).

[0044] In some embodiments, the second catalyst contains a metal-promoted molecular sieve. The promoter metal can 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.

[0045] In some exemplary embodiments, the second catalyst contains a Cu and / or Fe-promoted zeolite having a framework type of AEI, BEA, CHA, AFT, AFX, FAU, FER, KFI, MOR, MFI, MOR, or MEL, particularly a Cu and / or Fe-promoted zeolite having a framework of AEI, BEA, or CHA.

[0046] The promoter metal can be present in the metal-promoted molecular sieve in an amount of 0.1 to 20 wt%, 0.5 to 15 wt%, 1 to 10 wt%, or 2 to 6 wt% on an oxide basis, based on the total weight of the metal-promoted molecular sieve. In some exemplary embodiments where Cu or Fe is used as the promoter metal, the promoter metal is preferably present in an amount of 0.5 to 15 wt%, or 1 to 15 wt%, or 1 to 10 wt% on an oxide basis, based on the total weight of the metal-promoted molecular sieve.

[0047] The noble metal component and the molecular sieve component as described for the second catalyst may be present in any possible form, for example, as a physical mixture thereof, or in separate forms. Alternatively, the noble metal component may be integrated, for example, by distributing the noble metal component on the outer surface of the molecular sieve or within channels, cavities, or cages.

[0048] In some embodiments, the catalyst article according to the present invention may include a substrate.

[0049] <Substrate> As used herein, the term "substrate" generally refers to a structure that is suitable for withstanding the conditions encountered in the exhaust stream, on which the catalyst material is supported in the form of a coating, typically a washcoat. The substrate may have an inlet end and an outlet end that define its axial length, and a plurality of fine parallel gas flow channels extending along the axial length.

[0050] The substrate is usually inert and has conventionally been made from, for example, ceramic or metallic materials and is also known as an "inert substrate". The substrate may alternatively be active and may consist of, for example, extrudates containing catalytically active species.

[0051] The substrate can be a monolithic flow-through structure, which has a plurality of fine parallel gas flow channels extending from the inlet to the outlet end of the substrate. As a result, the channels are open to the fluid flow passing therethrough. The channels, which are essentially straight paths from the fluid inlet to the fluid outlet, are defined by walls to which a catalytic material is applied as a washcoat so that the gas flowing through the channels contacts the catalytic material. The flow channels of the monolithic substrate are thin-walled channels, which can have any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such a structure can contain from 50 to over 900 flow channels (or "cells") per square inch of cross-section. For example, the substrate can have 50 to 600 cells per square inch (cpsi) or 200 to 450 cpsi. The wall thickness of the flow-through substrate can vary, and a typical range is from 2 mils to 0.1 inch.

[0052] The substrate can also be a monolithic wall-flow structure having a plurality of fine parallel gas flow channels extending along the length from the inlet to the outlet end of the substrate, with alternating channels blocked at opposite ends. The channels are defined by walls to which a catalytic material is applied as a washcoat so that the gas flowing through the channels contacts the catalytic material. This configuration requires the gas to flow through the porous walls of the wall-flow substrate to reach the outlet end. The wall-flow substrate can have up to 700 cpsi, for example 100 to 400 cpsi. The flow channels of the monolithic substrate are thin-walled channels, which 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 within a typical range of 2 mils to 0.1 inch.

[0053] The term "washcoat" has its ordinary meaning in the art and refers to a thin adhesive coating of a catalyst material or other material applied to a substrate. A washcoat is generally formed by preparing a slurry containing the desired material and processing aids such as a binder having an optional specific solids content (e.g., 15 - 60 wt%), then applying the slurry onto the substrate, drying it, and firing it to provide a washcoat layer. The washcoat is generally filled onto the substrate in an amount of 0.1 - 10 g / in 3 , for example, 0.5 - 7 g / in 3 of the substrate.

[0054] <Configuration of Catalytic Articles> In the catalytic article according to the present invention, the first catalyst and the second catalyst can be included in any suitable configuration without any particular limitation. Suitable configurations are known in the art and are, for example, the conventional configurations of AMOx catalytic articles including an SCR catalyst component and an oxidation catalyst component.

[0055] For example, the first catalyst and the second catalyst may be included in the catalytic article according to the present invention in a mixed form. In some embodiments, the catalytic article includes a substrate on which a coating layer containing the first catalyst and the second catalyst is supported.

[0056] The first catalyst and the second catalyst may also be included in the catalytic article according to the present invention in separate forms. For example, the first catalyst may be included in an extrudate as a substrate, and the second catalyst may be included as a layer on the extrudate. Thus, in some embodiments, the catalytic article includes an extrudate containing the first catalyst as a substrate, on which the second catalyst is supported as a coating layer.

[0057] As used herein, the term "extrudate" generally refers to a shaped body formed by extrusion. The extrudate can have any suitable structure for passing a gas stream, preferably a honeycomb structure. The honeycomb structure can have flow channels as described hereinafter in the present specification for monolithic flow-through structures and wall flow structures.

[0058] Alternatively, the first catalyst and the second catalyst may be included in the catalyst article according to the present invention in their respective regions. In this case, the catalyst article will have a zoned configuration. In some embodiments, the catalyst article includes a substrate, on which a coating containing the first catalyst is carried and extends from one end (e.g., the inlet end) to the opposite end of the substrate over a partial axial length of the substrate, and a coating containing the second catalyst is carried and extends from the opposite end (e.g., the outlet end) over at least a partial axial length of the substrate. The coating containing the first catalyst and the coating containing the second catalyst may be adjacent to or overlap each other. The catalyst article may include two or more substrate pieces, and it may be contemplated that the first catalyst and the second catalyst are carried on their respective substrates.

[0059] Furthermore, the first catalyst and the second catalyst may be included in the catalyst article according to the present invention in their respective coating layers. In this case, the catalyst article will have a layered configuration including a first coating layer containing the first catalyst and a second coating layer containing the second catalyst. In some embodiments, the catalyst article includes a substrate, on which a first coating layer containing the first catalyst and a second coating layer containing the second catalyst are carried. The first coating layer may overlap with, be superposed on, or cover the second coating layer. In particular, the first coating may be at least partially on or under the second coating, preferably at least partially on the second coating. Preferably, the second coating layer extends from the outlet end towards the inlet end over at least a partial axial length of the substrate.

[0060] In some exemplary embodiments, the catalyst article according to the present invention comprises - a substrate, - a first coating layer comprising a first catalyst, and - a second coating layer comprising a second catalyst, and the first coating layer is on and covers the second coating layer. The first coating layer is on and covers the second coating layer.

[0061] In some further exemplary embodiments, the catalyst article according to the present invention comprises - a substrate, - a first coating layer comprising a first catalyst, and - a second coating layer comprising a second catalyst, and the first coating layer is on and covers the second coating layer, and both the first coating layer and the second coating layer extend over the entire axial length of the substrate. The first coating layer is on and covers the second coating layer, and both the first coating layer and the second coating layer extend over the entire axial length of the substrate.

[0062] Any of the coating layers comprising the first catalyst and / or the second catalyst as described herein, or the extrudate comprising the first catalyst, may contain one or more components in addition to the catalyst, which may be processing aids useful in the preparation of the catalyst article, such as non-catalytically active components, for example, lubricants and binders. Other components may also be catalytically active, for example, active species other than the catalysts as described herein.

[0063] The first catalyst may be present in an amount providing from 0.005 to 1.5 g / in calculated as V2O5, based on the substrate or substrate region containing or supporting the first catalyst. 3 of vanadium, from 0.01 to 1.0 g / in 3 , or from 0.03 to 0.5 g / in 3 of vanadium.

[0064] Additionally or alternatively, the first catalyst may be present in an amount providing from 0.005 to 2.5 g / in calculated as Sb2O3, based on the substrate or substrate region containing or supporting the first catalyst. 3antimony of 0.01 to 1.5 g / in 3 or an amount of antimony of 0.02 to 1.2 g / in 3 may be present.

[0065] Based on the substrate or substrate region supporting the second catalyst, the noble metal component may be present in an amount of 0.01 to 20 g / ft 3 , preferably 0.5 to 10 g / ft 3 in terms of each noble metal calculated as such.

[0066] The first catalyst and the second catalyst may be included in a weight ratio in the range of 50:1 to 0.5:1, 30:1 to 1:1, or 20:1 to 5:1 based on the weights of these components.

[0067] The catalyst article according to the present invention can be used to treat the exhaust stream from an automotive combustion engine, particularly a diesel engine. The catalyst article according to the present invention can be particularly effective in treating the exhaust stream from a robust diesel engine including on-road and off-road large diesel engines.

[0068] Accordingly, in a second aspect, the present invention relates to a system for treating an exhaust stream derived from a large diesel engine, particularly including on-road and off-road large diesel engines, the system including a reducing agent source (e.g., NH3 or its precursor) and a catalyst article as described in the first aspect above.

[0069] The system for treating the exhaust stream may further include one or more exhaust stream treatment elements. Conventional exhaust stream treatment elements include, but are not limited to, diesel oxidation catalysts (DOCs), selective catalytic reduction catalysts (SCRs), three-way conversion catalysts (TWCs), four-way conversion catalysts (FWCs), non-catalytic or catalytic soot filters (CSFs), NOx traps, hydrocarbon trap catalysts, sensors, and mixers.

[0070] In some embodiments, a system for treating an exhaust stream further includes a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) catalyst that are located downstream of the engine and upstream of a catalyst article as described in the first aspect above. Preferably, a system for treating an exhaust stream further includes a diesel oxidation catalyst (DOC), a selective catalytic reduction (SCR) catalyst, and a catalyst soot filter (CSF) that are located upstream of a catalyst article as described in the first aspect above.

[0071] In a third aspect, the present invention relates to a method for treating an exhaust stream containing nitrogen oxides, the method including contacting the exhaust stream with a catalyst article as described in the first aspect in the presence of NH3 as a reducing agent, or passing the exhaust stream through a system as described in the second aspect.

[0072] In some embodiments, the method is useful for treating exhaust streams derived from diesel engines, particularly large diesel engines, such as on-road and off-road large diesel engines.

[0073] In a fourth aspect, the present invention relates to a method for reducing poisoning of a noble metal component in a catalyst article containing a vanadium-based catalyst and a noble metal-based catalyst, the method including incorporating an antimony component into the vanadium-based catalyst. The vanadium-based catalyst is as described above with respect to the first catalyst.

[0074] In some embodiments, the vanadium-based catalyst may contain a vanadium component calculated as V2O5 in an amount of 0.5 to 8 wt% or 1 to 6 wt% based on the total weight of the vanadium-based catalyst. Alternatively or additionally, the vanadium-based catalyst may contain an antimony component calculated as Sb2O3 in an amount of 0.5 to 16 wt% or 2 to 9 wt% based on the total weight of the vanadium-based catalyst.

[0075] Embodiments Various embodiments are listed below. It will be understood that the embodiments listed below may be combined with all aspects and other embodiments in accordance with the scope of the present invention.

[0076] 1. A catalyst article for treating an exhaust stream, - a first catalyst containing a vanadium component and an antimony component, - a second catalyst containing a noble metal component, the catalyst article comprising. 2. The catalyst article according to embodiment 1, wherein the first catalyst is contained in an extrudate as a substrate, and the second catalyst is supported thereon as a coating layer. 3. The catalyst article according to embodiment 1, comprising a substrate having an inlet end and an outlet end defining an axial length, and a plurality of fine parallel gas flow channels extending along the axial length, preferably a flow-through substrate or a wall-flow substrate. 4. The catalyst article according to embodiment 3, comprising a coating layer containing the first catalyst and the second catalyst on the substrate. 5. The catalyst article according to embodiment 3, comprising a coating containing a first catalyst supported and extending from one end to the opposite end over a partial axial length of the substrate, and a coating containing a second catalyst supported and extending from the opposite end over at least a partial axial length of the substrate, the two coatings being adjacent or overlapping each other. 6. The catalyst article according to embodiment 3, comprising a first coating layer containing the first catalyst and a second coating layer containing the second catalyst on the substrate. 7. The catalyst article according to embodiment 6, wherein the first coating layer is at least partially above or below the second coating, preferably at least partially above the second coating. 8. The catalyst article according to embodiment 6 or 7, wherein the second coating layer extends from the outlet end to the inlet end over at least a partial axial length of the substrate. 9. The catalyst article according to any one of embodiments 6 to 8, wherein the first coating layer overlaps with, is superimposed on, or covers the second coating layer. 10. - A substrate, - A first coating layer containing a first catalyst, - A second coating layer containing a second catalyst, and The catalyst article according to embodiment 9, wherein the first coating layer is on the second coating layer and covers the second coating layer. 11. The catalyst article according to embodiment 10, wherein both the first coating layer and the second coating layer extend over the entire axial length of the substrate. 12. The catalyst article according to any one of embodiments 1 to 11, wherein the first catalyst contains a vanadium component calculated as V2O5 in an amount of 0.5 to 8% by weight or 1 to 6% by weight based on the total weight of the first catalyst. 13. The catalyst article according to any one of embodiments 1 to 12, wherein the first catalyst contains an antimony component calculated as Sb2O3 in an amount of 0.5 to 16% by weight or 2 to 9% by weight based on the total weight of the first catalyst. 14. The catalyst article according to any one of embodiments 1 to 13, wherein the first catalyst contains vanadium oxide, antimony oxide, and optionally a composite oxide of vanadium and antimony, supported on the particles of the support. 15. The catalyst article according to embodiment 14, wherein the support contains one or more of molecular sieves and oxides of metals 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. 16. The catalyst article according to any one of embodiments 1 to 15, wherein the noble metal component contains one or more selected from ruthenium, rhodium, iridium, palladium, and platinum, more preferably palladium and platinum, and most preferably platinum, supported on the particles of the support. 17. The catalyst article according to embodiment 16, wherein the support in the noble metal component is one or more of molecular sieves and oxides of metals 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. 18. The catalyst article according to any one of embodiments 1 to 17, wherein the second catalyst contains a zeolite or non-zeolite molecular sieve component. 19. The noble metal component is present in an amount of 0.01 to 20 g / ft 3 , preferably 0.5 to 10 g / ft 3 , as calculated for each noble metal, of the catalyst article according to any one of embodiments 1 to 18. 20. The catalyst article according to any one of embodiments 1 to 19, wherein the first catalyst and the second catalyst can be included in a weight ratio in the range of 50:1 to 0.5:1, 30:1 to 1:1, or 20:1 to 5:1. 21. A system for treating an exhaust stream, comprising a reductant source (e.g., NH3 or its precursor), the catalyst article according to any one of embodiments 1 to 20, 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 soot filter (CSF), a NOx trap, a hydrocarbon trap catalyst, a sensor, and a mixer. 22. The system according to embodiment 21, wherein the exhaust stream is derived from an internal combustion engine, particularly a diesel engine. 23. A method for treating an exhaust stream containing nitrogen oxides, comprising contacting the exhaust stream with a catalyst article as defined in any one of embodiments 1 to 20 in the presence of NH3 as a reductant, or passing the exhaust stream through a system as defined in embodiment 21 or 22. 24. A method for reducing the poisoning of a noble metal component in a catalyst article containing a vanadium-based catalyst and a noble metal-based catalyst, comprising incorporating an antimony component into the vanadium-based catalyst. 25. The method according to embodiment 24, wherein the vanadium-based catalyst contains a vanadium component calculated as V2O5 in an amount of 0.5 to 8% by weight or 1 to 6% by weight based on the total weight of the vanadium-based catalyst. 26. The method according to embodiment 24 or 25, wherein the vanadium-based catalyst contains an antimony component calculated as Sb2O3 in an amount of 0.5 to 16% by weight or 2 to 9% by weight based on the total weight of the vanadium-based catalyst.

[0077] The present invention will be further illustrated by the following examples which describe particularly advantageous embodiments. The examples are provided to illustrate the present invention but are not intended to limit the present invention.

Examples

[0078] Example 1 Step 1.1 Apply a bottom washcoat containing a Pt-based catalyst onto a substrate A Cu-CHA slurry was prepared by mixing 218.7 g of Cu-CHA zeolite and 6.2 g of Al2O3 powder from Zeolyst in 300 g of deionized (DI) water. The Cu-CHA zeolite has a SiO2 to Al2O3 molar ratio of 28, a CuO weight content of 3.2%, an X-ray crystallinity of 98%, a BET surface area of 750 m 2 / g, and a D of 5 microns 90 and has.

[0079] A Pt slurry was prepared by mixing 45.6 g of a colloidal Pt solution having a Pt content of 2% by weight with 100 g of DI water to form a homogeneous mixture, impregnating this into 207 g of 8% SiO2-doped TiO2 powder, stirring for 30 minutes, adjusting the pH to 4 with tartaric acid, and then grinding to a D of 5 microns 90 particle size as measured by a Sympatec particle size analyzer.

[0080] The Cu-CHA slurry and the Pt slurry were mixed and adjusted to pH 4 with tartaric acid, followed by stirring for 20 minutes to obtain a uniform slurry. The resulting slurry was coated on a 300 cpsi flow-through cordierite monolith substrate having a wall thickness of 5 mils by immersing the substrate in the slurry. The excess filled slurry was carefully blown off with an air knife and subsequently dried at 130 °C and calcined at 550 °C. After cooling to room temperature, the process of immersion, drying, and calcination was repeated until a total washcoat filling amount of 0.5 g / in 3 was obtained on the substrate. The Cu-CHA filling amount was 0.25 g / in 3 and the Pt filling amount was 2 g / ft 3 .

[0081] Step 1.2: Applying an upper washcoat containing a V / Sb-based catalyst 140.6 g of anatase-form TiO2 having a titanium content of 95.9 wt% calculated as TiO2, 28.6 g of a vanadyl oxalate solution having a vanadium content of 10.8 wt% calculated as V2O5, and 4.5 g of Sb2O3 were mixed in 200 g of DI water at room temperature. After stirring the resulting suspension for 30 minutes, the pH was adjusted to 7.0 using 25% aqueous ammonia solution. Then, 25.5 g of SiO2 sol having a SiO2 content of 30.1 wt% was added. After stirring for 1 hour, a homogeneous slurry for the V / Sb-based catalyst was obtained, into which the substrate having the bottom washcoat obtained from Step 1.1 was immersed to fill it with sufficient slurry. The excess filled slurry was carefully blown off with an air knife and subsequently dried with hot air at 150 °C for 15 minutes and then calcined in air at 450 °C for 1 hour.

[0082] 3.0 g / in 3 The process of immersion, drying, and calcination was repeated until a total washcoat filling amount on the substrate was obtained. The V / Sb-based catalyst had a vanadium content of 2.0 wt% calculated as V2O5 based on the total weight of the V / Sb-based catalyst.

[0083] Example 2 Apply a bottom washcoat containing a Pt-based catalyst onto a substrate Repeat the procedure of Step 1.1 above to provide a substrate with a bottom washcoat

[0084] Apply an upper washcoat containing a V / Sb-based catalyst 132.8 g of anatase-form TiO2 having a titanium content of 95.9 wt% calculated as TiO2, 57.1 g of a vanadyl oxalate solution having a vanadium content of 10.8 wt% calculated as V2O5, and 9.0 g of Sb2O3 were mixed in 200 g of DI water at room temperature. After stirring the resulting suspension for 30 minutes, a 25% aqueous ammonia solution was further added to raise the pH of the system to 7.0. Then, 25.5 g of a SiO2 sol having a SiO2 content of 30.1 wt% was added. After stirring for 1 hour, a homogeneous slurry for the V / Sb-based catalyst was obtained, into which a substrate with the bottom washcoat obtained from Step 2.1 was immersed to fill it with sufficient slurry. The excess filled slurry was carefully blown off with an air knife and then dried with hot air at 150 °C for 15 minutes, and then calcined in air at 450 °C for 1 hour

[0085] 3.0 g / in on the substrate 3 The processes of immersion, drying, and calcination were repeated until a total washcoat filling amount of was obtained. The V / Sb-based catalyst has a vanadium content of 4.0 wt% calculated as V2O5 based on the total weight of the V / Sb-based catalyst

[0086] Example 3 Apply a bottom washcoat containing a Pt-based catalyst onto a substrate Repeat the procedure of Step 1.1 above to provide a substrate with a bottom washcoat

[0087] Apply an upper washcoat containing a V / Sb-based catalyst 125.0 g of anatase-form TiO₂ with a titanium content of 95.9 wt% calculated as TiO₂, 85.7 g of a vanadyl oxalate solution with a vanadium content of 10.8 wt% calculated as V₂O₅, and 13.5 g of Sb₂O₃ were mixed in 200 g of DI water at room temperature. After the resulting suspension was stirred for 30 minutes, a 25% aqueous ammonia solution was further added to raise the pH of the system to 7.0. Then, 25.5 g of a SiO₂ sol with a SiO₂ content of 30.1 wt% was added. After stirring for 1 hour, a homogeneous slurry for the V / Sb-based catalyst was obtained, into which a substrate having the bottom washcoat obtained from Step 3.1 was immersed to fill it with sufficient slurry. The excess-filled slurry was carefully blown off with an air knife and then dried with hot air at 150 °C for 15 minutes and then calcined in air at 450 °C for 1 hour.

[0088] 3.0 g / in 3 The process of immersion, drying, and calcination was repeated until the total washcoat filling amount on the substrate of was obtained. The V / Sb-based catalyst has a vanadium content of 6.0 wt% calculated as V₂O₅ based on the total weight of the V / Sb-based catalyst.

[0089] Example 4 (Comparative Example) Step 4.1 Apply a bottom washcoat containing a Pt-based catalyst onto the substrate The procedure according to Step 1.1 above was repeated to provide a substrate with a bottom washcoat.

[0090] Step 4.2 Apply a top washcoat containing a V / W-based catalyst 147.4 g of WO₃-doped TiO₂ having a solid content of 95.0 wt% and containing 10 wt% of WO₃, and 28.6 g of vanadyl oxalate solution having a vanadium content of 10.8 wt% calculated as V₂O₅ were mixed in 200 g of DI water at room temperature. The resulting suspension was stirred for 30 minutes, and then 25% aqueous ammonia solution was added to raise the pH of the system to 7.0. Then, 17.3 g of SiO₂ sol having a SiO₂ content of 40.0 wt% was added. After stirring for 1 hour, a homogeneous slurry for the V / W-based catalyst was obtained, into which a substrate having the bottom washcoat obtained from Step 4.1 was immersed to fill it with sufficient slurry. The excess filled slurry was carefully blown off with an air knife and then dried with hot air at 150 °C for 15 minutes and then calcined at 450 °C in air for 1 hour.

[0091] 3.0 g / in 3 The process of immersion, drying, and calcination was repeated until the total washcoat filling amount on the substrate of was obtained. The V / W-based catalyst has a vanadium content of 2.0 wt% calculated as V₂O₅ based on the total weight of the V / Sb-based catalyst.

[0092] Example 5 (Comparative Example) Step 5.1 Apply a bottom washcoat containing a Pt-based catalyst onto the substrate The procedure according to the above Step 1.1 was repeated to provide a substrate having a bottom washcoat.

[0093] Step 5.2 Apply a top washcoat containing a V / W-based catalyst 144.3 g of WO3-doped TiO2 with a solid content of 95.0 wt% containing 10 wt% WO3 and 57.1 g of vanadyl oxalate solution with a vanadium content of 10.8 wt% calculated as V2O5 were mixed in 200 g of DI water at room temperature. The resulting suspension was stirred for 30 minutes, and then 25% aqueous ammonia solution was added to raise the pH of the system to 7.0. Then, 17.3 g of SiO2 sol with a SiO2 content of 40.0 wt% was added. After stirring for 1 hour, a homogeneous slurry for the V / W-based catalyst was obtained, and a substrate having the bottom washcoat obtained from Step 5.1 was immersed therein to fill it with sufficient slurry. The excess filled slurry was carefully blown off with an air knife and then dried with hot air at 150 °C for 15 minutes and then calcined in air at 450 °C for 1 hour.

[0094] 3.0 g / in 3 The process of dipping, drying, and calcining was repeated until the total washcoat filling amount on the substrate of was obtained. The V / W-based catalyst has a vanadium content of 4.0 wt% calculated as V2O5 based on the total weight of the V / Sb-based catalyst.

[0095] Example 6 (Comparative Example) Step 6.1 Apply a bottom washcoat containing a Pt-based catalyst onto the substrate The procedure according to Step 1.1 above was repeated to provide a substrate having a bottom washcoat.

[0096] Step 6.2 Apply an upper washcoat containing a V / W-based catalyst 141.1 g of WO3-doped TiO2 with a solid content of 95.0 wt% containing 10 wt% WO3 and 85.7 g of vanadyl oxalate solution with a vanadium content of 10.8 wt% calculated as V2O5 were mixed in 200 g of DI water at room temperature. The resulting suspension was stirred for 30 minutes, and then 25% aqueous ammonia solution was added to raise the pH of the system to 7.0. Then, 17.3 g of SiO2 sol with a SiO2 content of 40.0 wt% was added. After stirring for 1 hour, a homogeneous slurry for the V / W-based catalyst was obtained, and a substrate having the bottom washcoat obtained from Step 6.1 was immersed therein to fill it with sufficient slurry. The excess filled slurry was carefully blown off with an air knife and then dried with hot air at 150 °C for 15 minutes and then calcined in air at 450 °C for 1 hour.

[0097] 3.0 g / in 3 The process of immersion, drying, and calcination was repeated until the total washcoat filling amount on the substrate of was obtained. The V / W-based catalyst has a vanadium content of 6.0 wt% calculated as V2O5 based on the total weight of the V / Sb-based catalyst.

[0098] Performance Test Cores having a diameter of 1 inch and a length of 3 inches were cut from fresh catalyst articles and aged catalyst articles from each example as test samples and placed in a fixed laboratory simulator for testing.

[0099] The aged test samples were prepared by hydrothermally treating the catalyst articles prepared in each example at 550 °C for 100 hours in 10 vol% water / air.

[0100] The feed gas contains, by volume, 500 ppm NH3, 7% H2O, 10% O2, 8% CO2, and the balance is N2. The tests were conducted at a gas hourly space velocity of 100,000 h -1 and the temperatures shown in Table 1.

[0101] The results of NH3 conversion and the test temperatures are shown in Table 1.

[0102]

Table 1

[0103] As can be seen, the catalyst article containing vanadium and antimony components according to the present invention had NH3 conversion performance retained after aging, while the comparative counterpart, i.e., the catalyst article containing vanadium and tungsten components, exhibited significantly lower NH3 conversion or, in the case of a vanadium content of 6 wt%, did not exhibit NH3 conversion, which resulted from more severe platinum poisoning by vanadium.

Claims

Claim 1 A catalyst article for treating an exhaust stream, comprising: - a first catalyst containing a vanadium component and an antimony component; and - a second catalyst containing a noble metal component. Claim 2 The catalyst article according to claim 1, wherein the first catalyst is contained in an extrudate as a substrate, and the second catalyst is supported thereon as a coating layer. Claim 3 The catalyst article according to claim 1, comprising a substrate having an inlet end and an outlet end defining an axial length, and a plurality of fine parallel gas flow channels extending along the axial length, preferably a flow-through substrate or a wall-flow substrate. Claim 4 The catalyst article according to claim 3, comprising a coating layer containing the first catalyst and the second catalyst on the substrate. Claim 5 The catalyst article according to claim 3, comprising a coating containing the first catalyst supported and extending from one end to the opposite end over a partial axial length of the substrate, and a coating containing the second catalyst supported and extending from the opposite end over at least a partial axial length of the substrate, the two coatings being adjacent to or overlapping each other. Claim 6 The catalyst article according to claim 3, comprising a first coating layer containing the first catalyst and a second coating layer containing the second catalyst on the substrate. Claim 7 The catalyst article according to claim 6, wherein the first coating layer is at least partially above or below the second coating, preferably at least partially above the second coating. Claim 8 The catalyst article according to claim 6 or 7, wherein the second coating layer extends from the outlet end towards the inlet end over at least a partial axial length of the substrate. Claim 9 The catalyst article according to any one of claims 6 to 8, wherein the first coating layer overlaps with, is superposed on, or covers the second coating layer. Claim 10 - a substrate; - a first coating layer containing the first catalyst; and - a second coating layer containing the second catalyst, The catalyst article according to claim 9, wherein the first coating layer is above the second coating layer and covers the second coating layer. Claim 11 The catalytic article according to claim 10, wherein both the first coating layer and the second coating layer extend over the entire axial length of the substrate.

12. The first catalyst contains the vanadium component calculated as V ２ O ５ in an amount of 0.5 to 8% by weight or 1 to 6% by weight based on the total weight of the first catalyst, the catalyst article according to any one of claims 1 to 11.

13. wherein the first catalyst contains the antimony component calculated as Sb ２ O ３ in an amount of 0.5 to 16% by weight or 2 to 9% by weight based on the total weight of the first catalyst, the catalyst article according to any one of claims 1 to 12.

14. The catalytic article according to any one of claims 1 to 13, wherein the first catalyst contains vanadium oxide, antimony oxide, and optionally a composite oxide of vanadium and antimony, supported on particles of a support.

15. The catalytic article according to claim 14, wherein the support contains one or more of molecular sieves and oxides of metals 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.

16. The catalytic article according to any one of claims 1 to 15, wherein the noble metal component contains one or more selected from ruthenium, rhodium, iridium, palladium, and platinum, more preferably palladium and platinum, and most preferably platinum, supported on particles of a support.

17. The catalytic article according to claim 16, wherein the support in the noble metal component is one or more of molecular sieves and oxides of metals 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.

18. The catalytic article according to any one of claims 1 to 17, wherein the second catalyst contains a zeolite or a non-zeolite molecular sieve component.

19. The noble metal component is present in an amount of 0.01 to 20 g / ft calculated as each noble metal ３ , preferably 0.5 to 10 g / ft ３ The catalyst article according to any one of claims 1 to 18, present in an amount of

20. The catalytic article according to any one of claims 1 to 19, wherein the first catalyst and the second catalyst can be included in a weight ratio in the range of 50:1 to 0.5:1, 30:1 to 1:1, or 20:1 to 5:

1.

21. A system for treating an exhaust stream, comprising a reductant source (e.g., NH ３ or a precursor thereof), a catalyst article according to any one of claims 1 to 20, 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 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 stream is derived from an internal combustion engine, particularly a diesel engine.

23. A method for treating an exhaust stream containing nitrogen oxides, comprising contacting the exhaust stream with a catalyst article as defined in any one of claims 1 to 20 in the presence of NH as a reducing agent, or passing the exhaust stream through a system as defined in claim 21 or 22. ３ ​

24. A method for reducing poisoning of a noble metal component in a catalytic article containing a vanadium-based catalyst and a noble metal-based catalyst, the method including incorporating an antimony component into the vanadium-based catalyst.

25. The vanadium-based catalyst contains a vanadium component calculated as V ２ O ５ in an amount of 0.5 to 8% by weight or 1 to 6% by weight based on the total weight of the vanadium-based catalyst, according to the method of claim 24.

26. wherein the vanadium-based catalyst contains the antimony component calculated as Sb ２ O ３ in an amount of 0.5 to 16% by weight or 2 to 9% by weight based on the total weight of the vanadium-based catalyst, the method according to claim 24 or 25.

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