Catalytic article comprising vanadium-containing catalyst and oxidation catalyst

Abstract

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

Description

Technical Field

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

[0002] Engine exhaust basically includes particulate matter and gaseous pollutants such as unburned hydrocarbons (HC), carbon monoxide (CO) and nitrogen oxides (NOx). Engine exhaust needs to be treated by an engine exhaust system before being discharged into the air. Due to the negative environmental impact of NOx on ecosystems, humans, animals and plants, controlling the emission of NOx has always been one of the most important topics in exhaust treatment, especially for diesel engines.

[0003] Various treatment methods, such as catalytic reduction of nitrogen oxides, have been used to reduce NOx in exhaust gas. A typical catalytic reduction method is to use ammonia (NH 3 ) or an ammonia precursor as a reducing agent, which is also called the SCR method. The SCR method is considered to be excellent because a high NOx reduction effect can be achieved with a small amount of reducing agent. 3 The reaction is according to the following equation:

[0004] 4NO+4NH 3 +O 2 →4N 2 +6H 2 O(Standard SCR reaction)

[0005] 2NO 2 +4NH 3 +O 2 →3N 2 +6H 2 O(slow SCR reaction)

[0006] NO+NO 2 +2NH 3 →2N 2 +3H 2 O (fast SCR response).

[0007] In the SCR method, a stoichiometric excess of the reducing agent NH 3Or its precursor is metered into the exhaust gas flow to reduce NOx with the highest possible conversion rate. Excess ammonia can leave the tail pipe of the car. Another potential situation in which ammonia may leave the tail pipe is when the operating temperature rises, and a considerable amount of ammonia that has been retained on the surface of the SCR catalyst during the low temperature part of the typical driving cycle is desorbed from the SCR catalyst. If ammonia is released into the air (this is also called ammonia slip), many problems will arise. Ammonia slip is harmful to human health and the environment. It is known that ammonia can cause significant eye and throat irritation above 100 ppm, significant skin irritation above 400 ppm, and the IDLH value of ammonia in air is 500 ppm. In addition, 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, thereby damaging the exhaust line. Ammonia should be eliminated before entering the tail pipe. An ammonia oxidation (AMOx) catalyst (also called an ammonia slip catalyst (ASC)) installed downstream of the SCR catalyst is generally used to convert the leaked ammonia into N 2 .

[0008] Ammonia oxidation (AMOx) catalysts are known, which contain a noble metal active substance for oxidizing ammonia and usually also contain an SCR active substance. As known SCR active substances, zeolites are widely used, while vanadium-based substances are rarely used due to the significant poisoning effect of vanadium substances on noble metals.

[0009] US2014 / 0212350A1 describes a catalytic article for treating exhaust gases, the catalytic article comprising (a) a first catalyst layer having a plurality of continuous 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. The catalytic article in the examples of the patent application comprises vanadium oxide and tungsten oxide in the first catalyst layer.

[0010] WO 2011 / 140251A2 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 produced by the overlap of a first catalyst coating layer comprising a platinum group metal extending from the outlet end toward the inlet end of the substrate and a second catalyst coating layer comprising an SCR catalyst extending from the inlet end toward the outlet end of the substrate. The SCR catalyst may comprise a catalyst supported on TiO 2 V 2 O 5 and WO 3 .

[0011] WO 2018 / 178627A1 describes a catalytic article for treating a combustion exhaust stream, the catalytic article comprising a substrate formed of an extruded SCR catalyst material containing vanadium, a first layer disposed on at least a portion of the substrate, and a second layer disposed on at least a portion of the first layer, wherein the first layer comprises an ammonia slip catalyst composition containing one or more platinum group metals, and the second layer comprises an SCR catalyst composition. The preferred substrate is formed of a blend of vanadium / tungsten / titanium dioxide and an iron-promoted ZSM-5 zeolite.

[0012] It would be desirable if low-cost vanadium-based SCR-active materials could be applied in ammonia oxidation (AMOx) catalysts with little or no poisoning effect on precious metals. Summary of the invention

[0013] It is an object of the present invention to provide an AMOx catalytic article comprising a vanadium-based SCR catalyst and a precious metal-based catalyst that will experience reduced poisoning of precious metal species and thus can provide improved NH 3 conversion rate, especially during low temperature operation of the exhaust gas treatment system.

[0014] Surprisingly, this object is achieved by a catalytic article comprising an SCR catalyst containing vanadium and antimony.

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

[0016] - a first catalyst comprising a vanadium component and an antimony component, and

[0017] - a second catalyst comprising a precious metal component.

[0018] In a second aspect, the present invention relates to a system for treating an exhaust gas stream, the system comprising a reductant source (e.g., NH 3 or a precursor thereof), a catalytic article as described herein, and optionally 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-catalyzed or catalyzed soot filter (CSF), a NOx trap, a hydrocarbon trap catalyst, a sensor, and one or more of a mixer.

[0019] In a third aspect, the invention relates to a method for treating an exhaust gas stream containing nitrogen oxides, the method comprising: 3 The exhaust gas stream is contacted with a catalytic article as described herein or passed through a system as described herein in the presence of a reductant.

[0020] In a fourth aspect, the present invention is directed to a method for mitigating poisoning of a precious metal component in a catalytic article comprising a vanadium-based catalyst and a precious metal-based catalyst, the method comprising incorporating an antimony component into the vanadium-based catalyst.

[0021] The present inventors have surprisingly found that poisoning of the noble metal component in an AMOx catalytic article comprising a vanadium-based catalyst and a noble metal-based catalyst can be effectively inhibited by incorporating an antimony component into the vanadium-based catalyst. DETAILED DESCRIPTION

[0022] The present invention is described in detail below. It should be understood that the present invention can be embodied in many different ways and should not be construed as being limited to the embodiments set forth herein.

[0023] As used herein, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. The terms "comprising", "including", and the like are used interchangeably with "containing", and are to be interpreted in a non-limiting, open-ended manner. That is, for example, additional components or elements may be present. The expression "consisting of" or "consisting essentially of" or cognates may be encompassed by "comprising" or cognates.

[0024] As used herein, the term "region" is intended to refer only to a portion of the catalytic article that includes the designated material and extends a certain length in the direction of flow of the exhaust gas stream.

[0025] In this document, any references to "upstream" and "downstream" are to be understood as relative positions with respect to the flow direction of a flow, such as the flow direction of an exhaust gas flow.

[0026] The terms "first catalyst" and "second catalyst" are not intended to impose any restrictions on the arrangement or configuration of the two catalysts in the catalytic article. It should be understood that if the two catalysts are separated from each other, the first catalyst can be arranged upstream or downstream of the second catalyst, above or below the second catalyst. It should also be understood that the first catalyst and the second catalyst can also be applied in a mixed form.

[0027] According to a first aspect, the present invention provides a catalytic article for treating an exhaust gas stream, the catalytic article comprising:

[0028] - a first catalyst comprising a vanadium component and an antimony component, and

[0029] - A second catalyst comprising a precious metal component.

[0030] <First Catalyst>

[0031] 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 be present in the form of corresponding oxides and / or composite oxides thereof, and the corresponding oxides and / or composite oxides thereof are supported on particles of a carrier.

[0032] In particular, the vanadium component and the antimony component may be in the form of vanadium oxide (such as V 2 O 5 ) and antimony oxides (such as Sb 2 O 3 ) is present in the first catalyst in the form of. In this case, a composite oxide of vanadium and antimony may also 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 particles of a carrier as the vanadium component and the antimony component.

[0033] It is also conceivable that the vanadium component and the antimony component may be present in the first catalyst only in the form of a composite oxide of vanadium and antimony.

[0034] 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).

[0035] Specifically, the additional metal or metalloid can be selected from silicon (Si), molybdenum (Mo) and tungsten (W). It should be understood that the at least one additional metal or metalloid can be present in the form of a corresponding oxide or a composite oxide thereof with vanadium, antimony or other additional metal or metalloid, or a combination thereof.

[0036] In some embodiments, the first catalyst contains vanadium oxide, antimony oxide and optionally at least one metal or metalloid oxide selected from silicon (Si), molybdenum (Mo) and tungsten (W) on particles of a carrier, or consists of them. For example, the first catalyst contains corresponding and / or composite oxides of vanadium (V), antimony (Sb) and silicon (Si) on particles of a carrier, or consists of them.

[0037] Useful materials as supports for vanadium, antimony and optional additional metals or metalloids in the first catalyst may include, but are not limited to, 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. Preferably, the support may be one or more selected from titania (preferably anatase), silica, alumina, zirconia and any doped stable form thereof.

[0038] The first catalyst may contain 0.5 wt % to 8 wt % or 1 wt % to 6 wt % of the total weight of the first catalyst. 2 O 5 Calculated vanadium composition.

[0039] The first catalyst may contain Sb in an amount of 0.5 wt % to 16 wt % or 2 wt % to 9 wt % based on the total weight of the first catalyst. 2 O 3 Calculated antimony composition.

[0040] Each of the at least one additional metal or metalloid, when present, may be included in the first catalyst in an amount of 0.1 wt % to 30 wt %, 1 wt % to 15 wt %, or 2 wt % to 10 wt %, calculated as the corresponding oxide, based on the total weight of the first catalyst.

[0041] Based on the total weight of the first catalyst, the carrier can 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 the carrier can be up to 95 wt% or up to 90 wt%.

[0042] In some embodiments, the first catalyst comprises or consists of:

[0043] (a) 0.5 to 8 wt% of vanadium oxide, V 2 O 5 calculate,

[0044] (b) 0.5 to 16 wt% of antimony oxide, as Sb 2 O 3 calculate,

[0045] (c) 1 to 15 wt% SiO 2 ,and

[0046] (e) 70 to 95 wt% TiO 2 ,

[0047] Each is based on the total weight of the first catalyst.

[0048] In some additional embodiments, the first catalyst comprises or consists of:

[0049] (a) 1 to 6 wt% of vanadium oxide, V 2 O 5 calculate,

[0050] (b) 2 to 9 wt% of antimony oxide, as Sb 2 O 3 calculate,

[0051] (c) 2 to 10 wt% SiO 2 ,

[0052] (e) 75 wt% to 95 wt% TiO 2 ,

[0053] Each is based on the total weight of the first catalyst.

[0054] In each case as described herein, the total weight of the first catalyst will be 100 weight percent.

[0055] <Second Catalyst>

[0056] 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 carrier. Preferably, the noble metal component contains one or more selected from ruthenium, rhodium, iridium, palladium and platinum on the particles of the carrier, more preferably palladium and platinum, most preferably platinum.

[0057] It should be understood that the noble metal can be present in any possible valence state, for example as the corresponding metal or metal oxide in a catalytically active form, or can be, for example, a corresponding metal compound, complex, etc., which will decompose or otherwise convert to a catalytically active form upon calcination or use of the catalyst.

[0058] Useful materials as carriers of the noble metal in the second catalyst may be any material suitable for receiving and supporting the noble metal, such as molecular sieves, 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. In particular, the carrier of the noble metal may be selected from high surface area alumina, silica, titania, cerium dioxide, zirconium oxide, lanthanum oxide, barium oxide, yttrium oxide, neodymium oxide, praseodymium oxide, titanium oxide, europium oxide, samarium oxide, hafnium oxide and any composite or combination thereof. Exemplary carriers may be composite oxides of silica and alumina, silica and titania, and the like.

[0059] Optionally, the second catalyst may also contain a zeolite or non-zeolite molecular sieve component. Molecular sieve refers to a framework material based on a broad three-dimensional network of oxygen ions, which generally contains tetrahedral sites and has a substantially uniform pore distribution. Molecular sieves suitable for the purposes of the present invention may be microporous or mesoporous.

[0060] In particular, the molecular sieve may be a zeolite, which is optionally metal promoted.Herein, the term "metal promoted" in the context of a molecular sieve is intended to mean that a metal capable of improving any property of the zeolite has been incorporated into and / or onto the zeolite.

[0061] Preferably, suitable molecular sieves may 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 comprises a zeolite having a framework type selected from the group consisting of AEI, BEA (e.g., β), 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, with AEI, BEA and CHA being particularly preferred.

[0062] It should be understood that when zeolites are referred to herein by citing the framework type codes generally accepted by the International Zeolite Association (IZA), it is intended to include not only the reference material, but also any isotype framework material having SCR catalytic activity. A list of reference materials and isotype framework materials for each framework type code can be obtained from the IZA database (http: / / www.iza-structure.org / databases / ).

[0063] In some embodiments, the second catalyst contains a metal-promoted molecular sieve. 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.

[0064] In some illustrative 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, and in particular a Cu and / or Fe promoted zeolite having a framework of AEI, BEA or CHA.

[0065] 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 % calculated as oxide, based on the total weight of the metal-promoted molecular sieve. 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 % calculated as oxide, based on the total weight of the metal-promoted molecular sieve.

[0066] The noble metal component and the molecular sieve component described for the second catalyst can exist in any possible form, for example as a physical mixture thereof or in a separate form. Alternatively, the noble metal component can be integrated, for example, by distributing the noble metal component on the outer surface or in the channels, cavities or cages of the molecular sieve.

[0067] In some embodiments, catalytic articles according to the present invention may include a substrate.

[0068] <Base>

[0069] As used herein, the term "substrate" generally refers to a structure suitable for withstanding conditions encountered in an exhaust gas flow, on which a catalytic material, typically in the form of a washcoat, is carried. The substrate may have an inlet end and an outlet end defining its axial length and a plurality of thin parallel gas flow passages extending along the axial length.

[0070] The substrate is usually inert and is usually made of, for example, ceramic or metallic materials, which are also referred to as “inert substrates.” Alternatively, the substrate may be active and may consist, for example, of extrudates containing catalytically active substances.

[0071] The substrate can be a monolithic flow-through structure having a plurality of thin parallel gas flow passages extending from the inlet end of the substrate to the outlet end, so that the passages are open to the fluid flowing therethrough. The passages, which are substantially straight paths from its fluid inlet to its fluid outlet, are defined by walls, on which catalytic materials are applied as washcoats so that the gas flowing through the passages contacts the catalytic materials. The flow passages of the monolithic substrate are thin-walled channels, which may have any suitable cross-sectional shape and size, such as trapezoidal, rectangular, square, sinusoidal, hexagonal, elliptical, circular, etc. Such structures may contain 50 to 900 or more flow passages (or "pores") per square inch of cross section. For example, the substrate may have 50 to 600 pores / square inch ("cpsi") or 200 cpsi to 450 cpsi. The wall thickness of the flow-through substrate may vary, typically in the range of 2 mils to 0.1 inches.

[0072] The substrate can also be an integral wall-flow structure with a plurality of thin parallel gas flow passages extending along the inlet end of the substrate to the outlet end, wherein the alternating passages are blocked at the opposite end. The passage is defined by a wall, and the catalytic material is applied to these walls as a washcoat so that the gas flowing through the passage contacts the catalytic material. This construction requires the gas to flow through the porous walls of the wall-flow substrate to reach the outlet end. The wall-flow substrate may have up to 700 cpsi, for example, 100 cpsi to 400 cpsi. The flow passage of the integral substrate is a thin-walled channel, which may have any suitable cross-sectional shape and size, such as a trapezoid, rectangle, square, sinusoidal, hexagonal, elliptical, circular, etc. The wall thickness of the wall-flow substrate may vary, typically in the range of 2 mils to 0.1 inches.

[0073] The term "washcoat" has its usual meaning in the art and refers to a thin, adherent coating of catalytic material or other material applied to a substrate. The washcoat is typically formed by preparing a slurry containing the desired materials and optional processing aids such as a binder having a certain solid content (e.g., 15% to 60% by weight), then applying the slurry to the substrate, drying and calcining to provide the washcoat. The washcoat, in the form of one or more layers, is typically applied at 0.1 g / in3 Up to 10g / in 3 , for example 0.5g / in 3 Up to 7g / in 3 amount is loaded on the substrate.

[0074] <Structure of Catalytic Products>

[0075] In the catalytic article according to the present invention, the first catalyst and the second catalyst may be included in any suitable configuration without any particular limitation. Suitable configurations are known in the art, such as those conventional configurations of AMOx catalytic articles including an SCR catalyst component and an oxidation catalyst component.

[0076] For example, the first catalyst and the second catalyst may be included in a mixed form in a catalytic article according to the present invention. In some embodiments, the catalytic article includes a substrate on which a coating including the first catalyst and the second catalyst is supported.

[0077] The first catalyst and the second catalyst may also be included in the catalytic article according to the present invention in a separate form. For example, the first catalyst may be included in the extrudate as a substrate, and the second catalyst may be included as a layer on the extrudate. Thus, in some embodiments, the catalytic article comprises an extrudate comprising the first catalyst as a substrate, and the second catalyst is supported on the substrate as a coating.

[0078] As used herein, the term "extrudate" generally refers to a shaped body formed by extrusion. The extrudate may have any suitable structure that allows gas to flow through, preferably a honeycomb structure. The honeycomb structure may have flow passages as described below for integral flow-through and wall-flow structures.

[0079] Alternatively, the first catalyst and the second catalyst may be contained in corresponding regions in the catalytic article according to the present invention. In this case, the catalytic article will have a partitioned structure. In some embodiments, the catalytic article includes a substrate, a coating containing the first catalyst is carried on the substrate and extends from one end of the substrate (e.g., the inlet end) toward the opposite end of the substrate over a portion of the axial length of the substrate, and a coating containing the second catalyst is carried on the substrate and extends from the opposite end (e.g., the outlet end) over at least a portion of the 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. It is contemplated that the catalytic article may include two or more substrates, and the first catalyst and the second catalyst are carried on corresponding substrates.

[0080] In addition, the first catalyst and the second catalyst may be included in the corresponding coatings in the catalytic article according to the present invention. In this case, the catalytic article will have a layered structure, and the layered structure includes a first coating comprising the first catalyst and a second coating comprising the second catalyst. In some embodiments, the catalytic article includes a substrate, and the first coating comprising the first catalyst and the second coating comprising the second catalyst are carried on the substrate. The first coating can overlap, overlap, or cover the second coating. In particular, the first coating can be at least partially above or below the second coating, preferably at least partially above the second coating. Preferably, the second coating extends from the outlet end toward the inlet end on at least part of the axial length of the substrate.

[0081] In some illustrative embodiments, a catalytic article according to the present invention comprises:

[0082] - substrate,

[0083] - a first coating comprising a first catalyst, and

[0084] - a second coating layer comprising a second catalyst, wherein the first coating layer is on top of and covers the second coating layer.

[0085] In some additional illustrative embodiments, catalytic articles according to the present invention include:

[0086] - substrate,

[0087] - a first coating comprising a first catalyst, and

[0088] - a second coating comprising a second catalyst, wherein the first coating is over and covers the second coating, and wherein both the first coating and the second coating extend the entire axial length of the substrate.

[0089] In addition to the catalyst, any of the coatings comprising the first catalyst and / or the second catalyst as described herein or the extrudate comprising the first catalyst may also include one or more components, which may be non-catalytically active components, such as processing aids used to prepare catalytic articles, such as lubricants and adhesives. Other components may also be catalytically active, such as active materials other than those catalysts as described herein.

[0090] Based on the substrate or substrate region containing or supporting the first catalyst, the first catalyst can be provided in an amount of V 2 O 5 Calculated 0.005g / in 3 Up to 1.5g / in 3 Vanadium, 0.01g / in 3 Up to 1.0g / in 3or 0.03g / in 3 Up to 0.5g / in 3 The amount of vanadium present.

[0091] Additionally or alternatively, based on the substrate or substrate region containing or supporting the first catalyst, the first catalyst may be provided in the form of 2 O 3 Calculated 0.005g / in 3 Up to 2.5g / in 3 Antimony, 0.01g / in 3 Up to 1.5g / in 3 or 0.02g / in 3 Up to 1.2g / in 3 The amount of antimony present.

[0092] The precious metal component may be present in an amount of 0.01 g / ft2 calculated as the corresponding precious metal based on the substrate or substrate region supporting the second catalyst. 3 Up to 20g / ft 3 , preferably 0.5g / ft 3 Up to 10g / ft 3 The amount exists.

[0093] The first catalyst and the second catalyst 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, based on the weight of these components.

[0094] Catalytic articles according to the present invention may be used to treat exhaust gas streams from automotive internal combustion engines, especially diesel engines. Catalytic articles according to the present invention are particularly effective in treating exhaust gas streams from heavy duty diesel engines, including both on-highway and off-highway heavy duty diesel engines.

[0095] Thus, in a second aspect, the present invention relates to a system for treating an exhaust gas stream, in particular originating from a heavy-duty diesel engine (including both on-road and off-road heavy-duty diesel engines), the system comprising a source of a reductant (e.g., NH 3 or a precursor thereof) and a catalytic article as described above in the first aspect.

[0096] The system for treating the exhaust gas flow may also include one or more exhaust gas flow treatment elements. Conventional exhaust gas flow 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-catalyzed or catalyzed soot filters (CSFs), NOx traps, hydrocarbon trap catalysts, sensors, and mixers.

[0097] In some embodiments, the system for treating the exhaust flow also includes a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) catalyst located downstream of the engine and upstream of the catalytic product as described in the first aspect above. Preferably, the system for treating the exhaust flow also includes a diesel oxidation catalyst (DOC), a selective catalytic reduction (SCR) catalyst and a catalytic soot filter (CSF) located upstream of the catalytic product as described in the first aspect above.

[0098] In a third aspect, the invention relates to a method for treating an exhaust gas stream containing nitrogen oxides, the method comprising: 3 The exhaust gas stream is contacted with a catalytic article as described in the first aspect or passed through a system as described in the second aspect in the presence of a reductant.

[0099] In some embodiments, the method may be used to treat exhaust streams originating from diesel engines, particularly heavy duty diesel engines, such as on-highway and off-road heavy duty diesel engines.

[0100] In a fourth aspect, the invention relates to a method for mitigating poisoning of a precious metal component in a catalytic article comprising a vanadium-based catalyst and a precious metal-based catalyst, the method comprising incorporating an antimony component into the vanadium-based catalyst. The vanadium-based catalyst is as described above for the first catalyst.

[0101] In some embodiments, the vanadium-based catalyst may contain vanadium in an amount of 0.5 wt % to 8 wt % or 1 wt % to 6 wt % based on the total weight of the vanadium-based catalyst. 2 O 5 Alternatively or additionally, the vanadium-based catalyst may contain Sb in an amount of 0.5 wt % to 16 wt % or 2 wt % to 9 wt %, based on the total weight of the vanadium-based catalyst. 2 O 3 Calculated antimony composition.

[0102] Implementation

[0103] Various embodiments are listed below. It should be understood that the embodiments listed below can be combined with all aspects of the scope of the present invention and other embodiments.

[0104] 1. A catalytic article for treating an exhaust gas stream, the catalytic article comprising

[0105] - a first catalyst comprising a vanadium component and an antimony component, and

[0106] - a second catalyst comprising a precious metal component.

[0107] 2. The catalytic article according to embodiment 1, wherein the first catalyst is contained in an extrudate as a substrate and the second catalyst is supported as a coating on the substrate.

[0108] 3. The catalytic product according to embodiment 1 comprises a substrate having an inlet end and an outlet end defining its axial length and a plurality of thin parallel gas flow passages extending along the axial length, preferably a flow-through substrate or a wall-flow substrate.

[0109] 4. The catalytic article according to embodiment 3 comprises a coating on the substrate comprising the first catalyst and the second catalyst.

[0110] 5. According to the catalytic product described in embodiment 3, the catalytic product includes a coating containing the first catalyst on the substrate and extending from one end toward the opposite end over a portion of the axial length of the substrate, and a coating containing the second catalyst on the substrate and extending from the opposite end over at least a portion of the axial length of the substrate, and the two coatings are adjacent to or overlap each other.

[0111] 6. The catalytic article according to embodiment 3 comprises, on the substrate, a first coating layer comprising the first catalyst and a second coating layer comprising the second catalyst.

[0112] 7. The catalytic article according to embodiment 6, wherein the first coating is at least partially above or below the second coating, preferably at least partially above the second coating.

[0113] 8. The catalytic article of embodiment 6 or 7, wherein the second coating extends from the outlet end toward the inlet end over at least a portion of the axial length of the substrate.

[0114] 9. The catalytic article according to any one of embodiments 6 to 8, wherein the first coating overlaps, superimposes, or covers the second coating.

[0115] 10. The catalytic article according to embodiment 9, comprising

[0116] - substrate,

[0117] - a first coating comprising a first catalyst, and

[0118] - a second coating comprising a second catalyst,

[0119] The first coating is on top of and covers the second coating.

[0120] 11. The catalytic article of embodiment 10, wherein the first coating and the second coating both extend the entire axial length of the substrate.

[0121] 12. The catalytic article according to any one of embodiments 1 to 11, wherein the first catalyst contains 0.5 wt.% to 8 wt.% or 1 wt.% to 6 wt.% of V 2 O 5 The vanadium component was calculated.

[0122] 13. The catalytic article according to any one of embodiments 1 to 12, wherein the first catalyst contains Sb in an amount of 0.5 wt.% to 16 wt.% or 2 wt.% to 9 wt.%, based on the total weight of the first catalyst. 2 O 3 Calculate the antimony component.

[0123] 14. The catalytic 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 particles of a carrier.

[0124] 15. The catalytic article according to embodiment 14, wherein the support comprises a molecular sieve and one or more oxides of a metal 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.

[0125] 16. The catalytic article according to any one of embodiments 1 to 15, wherein the precious metal component contains one or more selected from ruthenium, rhodium, iridium, palladium and platinum, more preferably palladium and platinum, most preferably platinum, supported on particles of a carrier.

[0126] 17. The catalytic product according to embodiment 16, wherein the support in the precious metal component is one or more of a molecular sieve and an oxide of a metal 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.

[0127] 18. The catalytic article according to any one of embodiments 1 to 17, wherein the second catalyst contains a zeolite or a non-zeolitic molecular sieve component.

[0128] 19. The catalyst article according to any one of embodiments 1 to 18, wherein the precious metal component is present at 0.01 g / ft 3 Up to 20g / ft 3, preferably 0.5g / ft 3 Up to 10g / ft 3 The amount exists.

[0129] 20. The catalytic article according to any one of embodiments 1 to 19, wherein 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.

[0130] 21. A system for treating an exhaust gas stream, the system comprising a source of a reductant (e.g., NH 3 or a precursor thereof), a catalytic product according to any one of the preceding embodiments, and optionally 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-catalyzed or catalyzed soot filter (CSF), a NOx trap, a hydrocarbon trap catalyst, a sensor and a mixer. One or more.

[0131] 22. A system according to embodiment 21, wherein the exhaust gas flow originates from an internal combustion engine, in particular a diesel engine.

[0132] 23. A method for treating an exhaust gas stream containing nitrogen oxides, the method comprising: 3 The exhaust gas stream is contacted with a catalytic article as described in any one of embodiments 1 to 20 in the presence of a reductant or passed through a system as described in any one of embodiments 21 or 22.

[0133] 24. A method for mitigating poisoning of a precious metal component in a catalytic article comprising a vanadium-based catalyst and a precious metal-based catalyst, the method comprising incorporating an antimony component into the vanadium-based catalyst.

[0134] 25. The method according to embodiment 24, wherein the vanadium-based catalyst contains 0.5 wt % to 8 wt % or 1 wt % to 6 wt % of V based on the total weight of the vanadium-based catalyst. 2 O 5 Calculated vanadium composition.

[0135] 26. The method according to embodiments 24 to 25, wherein the vanadium-based catalyst contains Sb in an amount of 0.5 wt.% to 16 wt.% or 2 wt.% to 9 wt.%, based on the total weight of the vanadium-based catalyst. 2 O 3 Calculate the antimony component.

[0136] The present invention will be further illustrated by the following examples, which illustrate particularly advantageous embodiments.While the examples are provided to illustrate the present invention, they are not intended to limit the present invention.

[0137] Example

[0138] Example 1

[0139] Step 1.1 Applying a bottom washcoat layer containing a Pt-based catalyst on a substrate

[0140] By mixing 218.7 g Cu-CHA zeolite from Zeolyst and 6.2 g Al 2 O 3 The powder was mixed into 300 g of deionized (DI) water to prepare a Cu-CHA slurry, wherein the Cu-CHA zeolite had a SiO 2 With Al 2 O 3 molar ratio, 3.2% CuO weight content, 98% X-ray crystallinity, 750m 2 / g BET surface area and 5 μm D 90 .

[0141] Pt slurry was prepared by mixing 45.6 g of colloidal Pt solution having a Pt content of 2 wt % with 100 g of deionized water to form a homogeneous mixture, and the Pt slurry was soaked in 207 g of 8% SiO 2 Doped TiO 2 The powder was stirred for 30 minutes, adjusted to pH 4 with tartaric acid, and then ground to D 90 The particle size is 5 microns as measured with a Sympatec particle size analyzer.

[0142] The Cu-CHA slurry was mixed with the Pt slurry, adjusted to pH 4 with tartaric acid, and then stirred for 20 minutes to obtain a homogenous slurry. The obtained slurry was coated on a 300 cpsi, 5 mil wall thickness flow-through cordierite monolithic substrate by dipping the substrate into the slurry. The extra loading of 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 process of impregnation, drying and calcination was repeated until 0.5 g / in 3 The total washcoat loading was 0.25 g / in 3 , Pt loading is 2g / ft 3 .

[0143] Step 1.2 Application of top washcoat layer containing V / Sb-based catalyst

[0144] 140.6 g of TiO 2 The calculated titanium content is 95.9 wt% in the anatase form of TiO 2 , 28.6gV 2 O5 The calculated vanadium content is 10.8 wt% of the vanadyl oxalate solution and 4.5 g of Sb 2 O 3 Mix in 200 g of DI water at room temperature. After stirring the obtained suspension for 30 minutes, a 25% aqueous ammonia solution was used to adjust the pH to 7.0. Then 25.5 g of SiO 2 The content of SiO is 30.1% by weight 2 After stirring for 1 hour, a homogeneous slurry for the V / Sb-based catalyst was obtained, and the substrate with the bottom washcoat layer obtained from step 1.1 was immersed in the homogeneous slurry to load sufficient slurry. The extra loaded 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.

[0145] The process of impregnation, drying and calcination was repeated until a 3.0 g / in 3 Based on the total weight of the V / Sb-based catalyst, the V / Sb-based catalyst has a total washcoat loading of V 2 O 5 Calculated vanadium content of 2.0 wt%.

[0146] Example 2

[0147] Step 2.1 Applying a bottom washcoat layer containing a Pt-based catalyst on a substrate

[0148] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom washcoat layer.

[0149] Step 2.2 Application of top washcoat layer containing V / Sb-based catalyst

[0150] 132.8 g of TiO 2 The calculated titanium content is 95.9 wt% in the anatase form of TiO 2 , 57.1gV 2 O 5 The calculated vanadium content is 10.8 wt% of the vanadyl oxalate solution and 9.0 g of Sb 2 O 3 The mixture was mixed in 200 g of DI water at room temperature. After stirring the obtained 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 SiO 2 The content of SiO is 30.1% by weight 2After stirring for 1 hour, a homogeneous slurry for the V / Sb-based catalyst was obtained, and the substrate with the bottom washcoat layer obtained from step 2.1 was immersed in the homogeneous slurry to load sufficient slurry. The extra loaded 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.

[0151] The process of impregnation, drying and calcination was repeated until a 3.0 g / in 3 Based on the total weight of the V / Sb-based catalyst, the V / Sb-based catalyst has a total washcoat loading of V 2 O 5 Calculated vanadium content of 4.0 wt%.

[0152] Example 3

[0153] Step 3.1 Applying a bottom washcoat layer containing a Pt-based catalyst on a substrate

[0154] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom washcoat layer.

[0155] Step 3.2 Application of top washcoat layer containing V / Sb-based catalyst

[0156] 125.0 g of TiO 2 The calculated titanium content is 95.9 wt% in the anatase form of TiO 2 , 85.7gV 2 O 5 The calculated vanadium content is 10.8 wt% of the vanadyl oxalate solution and 13.5 g of Sb 2 O 3 The mixture was mixed in 200 g of DI water at room temperature. After stirring the obtained 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 SiO 2 The content of SiO is 30.1% by weight 2 After stirring for 1 hour, a homogeneous slurry for the V / Sb-based catalyst was obtained, and the substrate with the bottom washcoat layer obtained from step 3.1 was immersed in the homogeneous slurry to load sufficient slurry. The extra loaded 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.

[0157] The process of impregnation, drying and calcination was repeated until a 3.0 g / in 3 Based on the total weight of the V / Sb-based catalyst, the V / Sb-based catalyst has a total washcoat loading of V 2 O 5 Calculated vanadium content of 6.0 wt%.

[0158] Example 4 (Comparative Example)

[0159] Step 4.1 Applying a bottom washcoat layer containing a Pt-based catalyst on a substrate

[0160] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom washcoat layer.

[0161] Step 4.2 Application of top washcoat layer containing V / W-based catalyst

[0162] At room temperature, 147.4 g of a solid content of 95.0 wt % (including 10 wt % WO 3 ) of WO 3 Doped TiO 2 and 28.6g with V 2 O 5 A vanadyl oxalate solution with a calculated vanadium content of 10.8 wt% was mixed in 200 g of DI water. After the obtained suspension was stirred for 30 minutes, a 25% ammonia solution was further added to raise the pH of the system to 7.0. Then 17.3 g of SiO 2 The content of SiO is 40.0 wt%. 2 After stirring for 1 hour, a homogeneous slurry for the V / W-based catalyst was obtained, and the substrate with the bottom washcoat layer obtained from step 4.1 was immersed in the homogeneous slurry to load sufficient slurry. The extra loaded 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.

[0163] The process of impregnation, drying and calcination was repeated until a 3.0 g / in 3 Based on the total weight of the V / Sb-based catalyst, the V / W-based catalyst has a total washcoat loading of V 2 O 5 Calculated vanadium content of 2.0 wt%.

[0164] Example 5 (Comparative Example)

[0165] Step 5.1 Applying a bottom washcoat layer containing a Pt-based catalyst on a substrate

[0166] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom washcoat layer.

[0167] Step 5.2 Application of top washcoat layer containing V / W-based catalyst

[0168] At room temperature, 144.3 g of a solid content of 95.0 wt % (including 10 wt % WO 3 ) of WO 3 Doped TiO 2 and 57.1g with V 2 O 5A vanadyl oxalate solution with a calculated vanadium content of 10.8 wt% was mixed in 200 g of DI water. After the obtained suspension was stirred for 30 minutes, a 25% ammonia solution was further added to raise the pH of the system to 7.0. Then 17.3 g of SiO 2 The content of SiO is 40.0 wt%. 2 After stirring for 1 hour, a homogeneous slurry for the V / W-based catalyst was obtained, and the substrate with the bottom washcoat layer obtained from step 5.1 was immersed in the homogeneous slurry to load sufficient slurry. The extra loaded 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.

[0169] The process of impregnation, drying and calcination was repeated until a 3.0 g / in 3 Based on the total weight of the V / Sb-based catalyst, the V / W-based catalyst has a total washcoat loading of V 2 O 5 Calculated vanadium content of 4.0 wt%.

[0170] Example 6 (Comparative Example)

[0171] Step 6.1 Applying a bottom washcoat layer containing a Pt-based catalyst on a substrate

[0172] Repeat the procedure according to step 1.1 above to provide a substrate with a bottom washcoat layer.

[0173] Step 6.2 Application of top washcoat layer containing V / W-based catalyst

[0174] At room temperature, 141.1 g of a 95.0 wt% solids content (including 10 wt% WO 3 ) of WO 3 Doped TiO 2 and 85.7g with V 2 O 5 A vanadyl oxalate solution with a calculated vanadium content of 10.8 wt% was mixed in 200 g of DI water. After the obtained suspension was stirred for 30 minutes, a 25% ammonia solution was further added to raise the pH of the system to 7.0. Then 17.3 g of SiO 2 The content of SiO is 40.0 wt%. 2 After stirring for 1 hour, a homogeneous slurry for the V / W-based catalyst was obtained, and the substrate with the bottom washcoat layer obtained from step 6.1 was immersed in the homogeneous slurry to load sufficient slurry. The extra loaded 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.

[0175] The process of impregnation, drying and calcination was repeated until a 3.0 g / in 3 Based on the total weight of the V / Sb-based catalyst, the V / W-based catalyst has a total washcoat loading of V 2 O 5 Calculated vanadium content of 6.0 wt%.

[0176] Performance Testing

[0177] Cores having a diameter of 1 inch and a length of 3 inches were cut from the fresh and aged catalytic articles of each example as test specimens and placed in a stationary laboratory simulator for testing.

[0178] Aged test samples were prepared by hydrothermal treatment of the catalytic article as prepared in each example at 550°C in 10 vol% water / air for 100 hours.

[0179] The feed gas contained 500 ppm NH 3 , 7% H 2 O, 10% O 2 , 8% CO 2 and the remainder N 2 . Tested at 100,000h -1 The gas space velocity and the temperature are shown in Table 1.

[0180] NH 3 The results of conversion and test temperature are listed in Table 1.

[0181] Table 1

[0182]

[0183] nd: not determined

[0184] It can be seen that the catalytic article comprising a vanadium component and an antimony component according to the present invention has a retained NH 3 The conversion performance of the comparative counterpart, i.e. the catalytic article comprising a vanadium component and a tungsten component, showed significantly lower NH 3 conversion or even no NH 3 conversion rate, which is caused by more severe platinum poisoning caused by vanadium.

Claims

1. A catalytic article for treating an exhaust gas stream, the catalytic article comprising - a first catalyst, said first catalyst comprising a vanadium component and an antimony component, and - A second catalyst, said second catalyst comprising a noble metal component.

2. The catalytic article of claim 1, wherein the first catalyst is contained in an extrudate as a substrate and the second catalyst is supported as a coating on the substrate.

3. The catalytic article according to claim 1, comprising a substrate, preferably a flow-through substrate or a wall-flow substrate, having an inlet end and an outlet end defining its axial length and a plurality of thin parallel gas flow passages extending along the axial length.

4. The catalytic article of claim 3, comprising a coating on the substrate comprising the first catalyst and the second catalyst.

5. The catalytic product according to claim 3 comprises a coating layer containing the first catalyst carried on the substrate and extending from one end toward the opposite end over a portion of the axial length of the substrate, and a coating layer containing the second catalyst carried on the substrate and extending from the opposite end over at least a portion of the axial length of the substrate, and the two coating layers are adjacent to or overlap each other.

6. The catalytic article of claim 3, comprising a first coating layer comprising the first catalyst and a second coating layer comprising the second catalyst on the substrate.

7. The catalytic article according to claim 6, wherein the first coating is at least partially above or below the second coating, preferably at least partially above the second coating.

8. The catalytic article of claim 6 or 7, wherein the second coating extends over at least part of the axial length of the substrate from the outlet end toward the inlet end.

9. The catalytic article of any one of claims 6 to 8, wherein the first coating overlaps, superimposes, or covers the second coating.

10. The catalytic article of claim 9, comprising: - substrate, - a first coating layer, said first coating layer comprising said first catalyst, and - a second coating layer, said second coating layer comprising said second catalyst, The first coating layer is on top of and covers the second coating layer.

11. The catalytic article of claim 10, wherein the first coating and the second coating each extend the entire axial length of the substrate.

12. The catalytic article according to any one of claims 1 to 11, wherein the first catalyst contains the vanadium component calculated as V2O5 in an amount of 0.5 wt% to 8 wt% or 1 wt% to 6 wt%, based on the total weight of the first catalyst.

13. The catalytic article according to any one of claims 1 to 12, wherein the first catalyst contains the antimony component calculated as Sb2O3 in an amount of 0.5 wt% to 16 wt% or 2 wt% to 9 wt%, based on the total weight of the first catalyst.

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

15. The catalytic article of claim 14, wherein the support comprises one or more of a molecular sieve and an oxide of a metal 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 precious metal component contains one or more selected from ruthenium, rhodium, iridium, palladium and platinum, more preferably palladium and platinum, most preferably platinum, supported on particles of a carrier.

17. The catalytic article of claim 16, wherein the support in the precious metal component is one or more of a molecular sieve and an oxide of a metal 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 of any one of claims 1 to 17, wherein the second catalyst comprises a zeolite or a non-zeolitic molecular sieve component.

19. The catalyst product according to any one of claims 1 to 18, wherein the precious metal component is present in an amount of 0.01 g / ft 3 Up to 20g / ft 3 , preferably 0.5g / ft 3 Up to 10g / ft 3 The amount exists.

20. The catalytic article of any one of claims 1 to 19, wherein the first catalyst and the second catalyst 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.

21. A system for treating an exhaust gas stream, the system comprising a reductant source (e.g., NH3 or a precursor thereof), a catalytic article according to any of the preceding claims, and optionally 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-catalyzed or catalyzed soot filter (CSF), a NOx trap, a hydrocarbon trap catalyst, a sensor and one or more of a mixer.

22. System according to claim 21, wherein the exhaust gas flow 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 contacting the exhaust gas stream with a catalytic article according to any one of claims 1 to 20 in the presence of NH3 as a reducing agent or passing the exhaust gas stream through a system according to any one of claims 21 or 22.

24. A method for mitigating poisoning of a precious metal component in a catalytic article comprising a vanadium-based catalyst and a precious metal-based catalyst, the method comprising incorporating an antimony component into the vanadium-based catalyst.

25. The method according to claim 24, wherein the vanadium-based catalyst contains the vanadium component calculated as V2O5 in an amount of 0.5 wt% to 8 wt% or 1 wt% to 6 wt%, based on the total weight of the vanadium-based catalyst.

26. The method according to claims 24 to 25, wherein the vanadium-based catalyst contains the antimony component calculated as Sb2O3 in an amount of 0.5 wt% to 16 wt% or 2 wt% to 9 wt%, based on the total weight of the vanadium-based catalyst.

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