Composites of manganese oxides and zeolites useful as NH3-SCR catalysts

Abstract

The present invention relates to an NH3-SCR catalyst comprising a complex of manganese oxide, cerium oxide, and molecular sieves, wherein the molecular sieves are present in an amount of 20% to 70% by weight based on the total weight of the complex. The present invention also relates to a sol-gel method for preparing an NH3-SCR catalyst, an SCR catalyst article comprising an NH3-SCR catalyst, and an exhaust gas treatment system equipped with an SCR catalyst article.

Description

[Technical Field]

[0001] The present invention relates to a composite of manganese oxide and zeolite useful as a catalyst for selective catalytic reduction (SCR) of nitrogen oxides in engine exhaust, an SCR catalyst article containing the composite, an exhaust gas treatment system equipped with the SCR catalyst article, and a method for preparing a composite of manganese oxide and zeolite. [Background technology]

[0002] Nitrogen oxides (NOx) are common air pollutants, generally found in exhaust gases from mobile sources such as automobiles and stationary sources such as power plants. Controlling NOx emissions is always one of the most important topics, for example, in the automotive manufacturing sector, due to the adverse environmental impacts of NOx on ecosystems, humans, animals, and plants.

[0003] To reduce air pollution, NO x Various treatment methods have been used to treat gas mixtures containing NOx. One well-known type of treatment method is selective catalytic reduction (SCR), also known as the NH3-SCR method, which uses ammonia or an ammonia precursor as a reducing agent. The NH3-SCR method is considered an excellent method because it can achieve a high degree of NOx reduction with a small amount of reducing agent. In the NH3-SCR method, NOx is reduced in the presence of oxygen in the atmosphere. x It is catalytically reduced by a reducing agent (e.g., ammonia or urea), mainly producing nitrogen and water vapor. 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] NO x A side reaction associated with the selective catalytic reduction is the formation of low-valent nitrogen oxides, particularly nitrous oxide (N2O), from the reducing agent NH3 and oxygen.

[0005] Currently used catalysts in the SCR method include copper-enhanced zeolites (e.g., copper-enhanced CHA). However, regulations in various countries around the world mandate a reduction in emissions from vehicles. NO emissions at low temperatures (below 200°C) x The efficient removal of NO is an unmet need and a major challenge for the entire industry. Cu-enhanced zeolite is the most active type of catalyst in NH3-SCR for diesel vehicles, but such SCR catalysts are insufficient to exhibit sufficient activity at low temperatures, such as below 200°C. At low temperatures, Cu-enhanced zeolite catalysts also have difficulty removing NO. x The catalyst needs to be saturated with ammonia (NH3) before it can effectively reduce the gas, which slows its response to reducing agents (such as urea injection). Vanadium / titania (V2O5 / TiO2) catalysts are another type of current SCR catalyst that requires less NH3 to reach saturation, but are far less active at low temperatures compared to copper-promoted zeolite catalysts. Another drawback of vanadium catalysts is the environmental concern associated with the potential release of V2O5 into the atmosphere with the use of such catalysts.

[0006] Manganese oxide catalysts are known to be useful and effective for NH3-SCR reactions at low temperatures, and these catalysts can be manganese oxide or Mn-based polymetallic oxides. Manganese oxides typically produce large amounts of N2O, resulting in low N2 selectivity. Mn-based polymetallic oxides, such as manganese-cerium composite oxides (also known as "MnCeOx"), have been shown to exhibit excellent SCR activity at low temperatures while reducing N2O emissions. However, given strict emission regulations, N2O emissions remain zero.

[0007] NO is particularly desirable at low temperatures. x There is a need to provide an NH3-SCR catalyst that can demonstrate a conversion level while simultaneously reducing N2O emissions, as well as a method for preparing such an NH3-SCR catalyst. [Overview of the Initiative]

[0008] The object of the present invention is to provide an SCR catalyst that exhibits a desirable NOx conversion level and yields an acceptable level of N2O emissions, particularly at low temperatures (e.g., below 200°C).

[0009] Surprisingly, it was found that this objective could be achieved by a complex of manganese (Mn), cerium (Ce), and zeolite species.

[0010] Another objective of the present invention is high NO x The objective is to provide a method particularly useful for preparing SCR catalysts that exhibit conversion levels and low N2O emissions.

[0011] This objective was achieved by a method including the preparation of manganese (Mn), cerium (Ce), and zeolite complexes using the sol-gel method.

[0012] Accordingly, in a first embodiment, the present invention relates to an NH3-SCR catalyst comprising a complex of manganese oxide, cerium oxide, and molecular sieves, and more particularly to an NH3-SCR catalyst comprising a complex of manganese oxide, cerium oxide, and molecular sieves, wherein the molecular sieves are present in an amount of 20% to 70% by weight based on the total weight of the complex.

[0013] In a second aspect, the present invention relates to a sol-gel method for preparing the NH3-SCR catalyst described herein, (i) A step of preparing a suspension containing molecular sieves, a manganese oxide precursor and a cerium oxide precursor, (ii) A step of heating the suspension to form a gel, (iii) The sol-gel method comprises the steps of drying, grinding and calcining the gel.

[0014] In a third aspect, the present invention relates to an NH3-SCR article comprising an NH3-SCR catalyst described herein, preferably in the form of a molded body or a coating structure.

[0015] In a fourth aspect, the present invention relates to a method for treating exhaust gas containing nitrogen oxides by selective catalytic reduction, comprising contacting the exhaust gas with an NH3-SCR catalyst or NH3-SCR article described herein in the presence of ammonia or an ammonia precursor as a reducing agent.

[0016] In a fifth embodiment, the present invention relates to an exhaust gas treatment system for a combustion engine, comprising a reducing agent source, an NH3-SCR article as described herein, and optionally one or more of the following: a diesel oxidation catalyst (DOC), a ternary converter (TWC), a quaternary converter (FWC), a catalyst-free or catalytic soot filter (CSF), an ammonia oxidation catalyst (AMOx), a NOx trap, a NOx absorption catalyst, a hydrocarbon trap catalyst, a sensor, and a mixer.

[0017] The complex containing manganese oxide, cerium oxide, and molecular sieves exhibits desirable NO production, especially at low temperatures (e.g., below 200°C). x The inventors have found that it is particularly useful as an NH3-SCR catalyst, or in an NH3-SCR catalyst, in providing a conversion level and resulting in an acceptable level of N2O emissions. [Brief explanation of the drawing]

[0018] [Figure 1] The XRD patterns of the NH4+-ZSM-5, MnCeOx composite in its fresh state and after aging, and the manganese oxide, cerium oxide, and NH4+-ZSM-5 composite (Mn / Ce / NH4+-ZSM-5) according to the present invention in its fresh state and after aging are shown, respectively. [Figure 2a] This image shows a fresh SEM-EDS image of the manganese oxide, cerium oxide, and NH4+-ZSM-5 complex (Mn / Ce / NH4+-ZSM-5) according to the present invention. [Figure 2b]The image shows an SEM-EDS image of the manganese oxide, cerium oxide, and NH4+-ZSM-5 composite (Mn / Ce / NH4+-ZSM-5) according to the present invention after aging. [Modes for carrying out the invention]

[0019] The present invention will be described in detail below in this specification. It should be understood that the present invention can be carried out in many different ways and should not be construed as being limited to the embodiments described herein.

[0020] In this specification, the singular forms "a," "an," and "the" refer to multiple objects unless the context clearly indicates otherwise. Terms such as "comprise" and "comprising" are used interchangeably with "contain" and "containing" and should be interpreted in a non-restrictive, open manner; that is, for example, there may be further components or elements. The expressions or cognates of "consists of" or "consists essentially of" may be encompassed by "comprises" or cognates.

[0021] As used herein, the term "molecular sieve" refers to skeletal materials such as zeolites and other skeletal materials (e.g., isomorphosimilated materials) that can be used as catalysts in particulate form in combination with one or more promoter metals. Molecular sieves are materials based on a broad three-dimensional network structure of oxygen ions, containing substantially tetrahedral moieties and having a substantially uniform pore distribution.

[0022] As used herein, the term “zeolite” refers to a specific example of a molecular sieve. Generally, a zeolite is defined as an aluminosilicate having an open three-dimensional skeletal structure composed of TO4 tetrahedra sharing corners, where T is, for example, Al or Si. The cations that balance the charge of the anionic skeleton are loosely associated with the skeletal oxygen. For the purposes of this disclosure, the term “aluminosilicate zeolite” does not include phosphorus or other metals isomorphically substituted in the skeleton. In other words, “aluminosilicate zeolites” do not include aluminophosphate materials such as SAPO, AlPO, and MeA1PO, although the broader term “zeolite” includes aluminosilicates and aluminophosphates.

[0023] As used herein, the term “composite” refers to a material comprising manganese species, cerium species, and molecular sieve species that are combined with each other in a uniformly dispersed state, rather than existing as dispersed individual elements as determined by SEM-EDS. Physical mixtures of these species obtained by physical means, such as mechanical mixing or blending, are not included in this term.

[0024] As used herein, the term “manganese oxide” is intended to encompass all possible oxidation states of manganese, such as MnO, Mn2O3, Mn3O4, MnO2, MnO3, Mn2O7, or any combination thereof.

[0025] Furthermore, the term "cerium oxide" is intended to encompass all possible oxidation states of cerium, such as CeO2, Ce2O3, Ce3O4, or any combination thereof.

[0026] As used herein, the term “catalytic article” refers to an article of a particular shape having catalytic function, and is not necessarily a single entity. In other words, a catalytic article may be a single entity or may consist of two or more separable bodies.

[0027] In a first aspect, the present invention provides an NH3-SCR catalyst comprising a composite of manganese oxide, cerium oxide and molecular sieve, particularly consisting of a composite of manganese oxide, cerium oxide and molecular sieve, wherein the molecular sieve is present in an amount of 20% to 70% by weight based on the total weight of the composite.

[0028] In some embodiments, the NH3-SCR catalyst consists of a composite of manganese oxide, cerium oxide, and molecular sieve, and the molecular sieve is present in an amount of 20% to 70% by weight based on the total weight of the composite.

[0029] According to the present invention, the molecular sieve is preferably present in the composite of manganese oxide, cerium oxide and molecular sieve in an amount of 20% to 50% by weight, more preferably 35% to 45% by weight, based on the total weight of the composite.

[0030] In the composite described herein, manganese oxide and cerium oxide are present in a molar ratio in the range of 4:1 to 1:4, preferably in the range of 7:3 to 3:7, more preferably in the range of 3:2 to 2:3, calculated as Mn element and Ce element.

[0031] For the purposes of the present invention, suitable molecular sieves are ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFV, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, -CHI, -CLO, CON, CSV, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, *-EWT, EZT, FAR, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFO, IFR, -IFU, IFW, IFY, IHW, IMF, IRN, IRR, -IRY, ISV, ITE, ITG, ITH, * -ITN, ITR, ITT, -ITV, ITW, IWR, IWS, IWV, IWW, JBW, JNT, JOZ, JRY, JSN, JSR, JST, JSW, KFI, LAU, LEV, LIO, -LIT, LOS, LOV, LTA, LTF, LTJ, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, * MRE, MSE, MSO, MTF, MTN, MTT, MTW, MVY, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, -PAR, PAU, PCR, PHI, PON, POS, PSI, PUN, RHO, -RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBN, SBS, SBT, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, * SFV, SFW, SGT, SIV, SOD, SOF, SOS, SSF, * -SSO, SSY, STF, STI, * STO, STT, STW, -SVR, SVV, SZR, TER, THO, TOL, TON, TSC, TUN, UEI, UFI, UOS, UOV, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WEI, -WEN, YUG, ZON, and may include, but is not limited to, zeolites having a framework type selected from the group consisting of any combination thereof.

[0032] In particular, preferred molecular sieves may be zeolites having a skeleton 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, WEN, and any combination thereof.

[0033] Where zeolite is referred to herein with reference to the framework codes generally accepted by the International Zeolite Association (IZA), it will be understood that this is intended to include not only the reference material but also any isomorphic framework material having SCR catalytic activity. A list of reference materials and isomorphic framework materials for each framework code is available from the IZA database (http: / / www.iza-structure.org / databases / ).

[0034] There are no particular limitations on the cations that balance the charge of the anionic skeleton in the zeolite useful as molecular sieves in the composites described herein. In other words, the zeolite described above is H-type, NH4 + It may be a metal ion exchange type such as a copper and / or iron exchange type, or any other preferred form.

[0035] In some embodiments, the molecular sieves in the composites described herein are zeolites having a skeleton type selected from the group consisting of BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite). In particular, the molecular sieves in the composites described herein are zeolites having an MFI skeleton, for example, ZSM-5, preferably H-type ZSM-5 (H-ZSM-5) or NH4+ Type ZSM-5(NH4 + -ZSM-5), especially NH4 + It is the ZSM-5 model.

[0036] Zeolites useful as molecular sieves in the composites described herein may have an SiO2 / Al2O3 molar ratio (SAR) in the range of 5:1 to 150:1, preferably 5:1 to 50:1.

[0037] Molecular sieves, when measured according to DIN 66131, must be at least 150 m 2 / g, at least 250m 2 / g, or at least 300m 2 It may have a BET surface area of ​​ / g.

[0038] In some exemplary embodiments, the NH3-SCR catalyst according to the present invention comprises a complex of manganese oxide, cerium oxide, and a molecular sieve, wherein the molecular sieve is present in an amount of 20% to 70% by weight based on the total weight of the complex, and the molecular sieve is a zeolite having a skeletal structure selected from the group consisting of BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite).

[0039] In these exemplary embodiments, the molecular sieves are preferably present in an amount of 20% to 50% by weight based on the total weight of the complex. In these exemplary embodiments, the molecular sieves are more preferably present in an amount of 35% to 45% by weight based on the total weight of the complex.

[0040] In some specific embodiments, the NH3-SCR catalyst according to the present invention comprises a complex of manganese oxide, cerium oxide, and molecular sieves, wherein the molecular sieves are present in an amount of 20% to 50% by weight based on the total weight of the complex, and the molecular sieves are of type H or NH4 +The zeolite has a skeleton type selected from the group consisting of BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite).

[0041] More specifically, the NH3-SCR catalyst according to the present invention consists of a complex of manganese oxide, cerium oxide, and molecular sieves, wherein the molecular sieves are present in an amount of 35% to 45% by weight based on the total weight of the complex, and the molecular sieves are NH4 + This is a zeolite having a specific MFI skeleton type (e.g., ZSM-5).

[0042] In some other exemplary embodiments, the NH3-SCR catalyst according to the present invention comprises a complex of manganese oxide, cerium oxide, and molecular sieves. Molecular sieves are present in amounts ranging from 20% to 70% by weight, based on the total weight of the complex. Manganese oxide and cerium oxide are present in molar ratios ranging from 4:1 to 1:4. Molecular sieves are zeolites having a skeleton type selected from the group consisting of BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite).

[0043] Preferably, the NH3-SCR catalyst according to the present invention consists of a composite of manganese oxide, cerium oxide, and molecular sieves. Molecular sieves are present in amounts ranging from 20% to 50% by weight, based on the total weight of the complex. Manganese oxide and cerium oxide are present in molar ratios ranging from 7:3 to 3:7. Molecular sieves are zeolites having a skeleton type selected from the group consisting of BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite).

[0044] More preferably, the NH3-SCR catalyst according to the present invention comprises a composite of manganese oxide, cerium oxide, and molecular sieves. Molecular sieves are present in amounts of 35% to 45% by weight, based on the total weight of the complex. Manganese oxide and cerium oxide are present in molar ratios ranging from 3:2 to 2:3. Molecular sieves are zeolites having a skeleton type selected from the group consisting of BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite).

[0045] Most preferably, the NH3-SCR catalyst according to the present invention consists of a composite of manganese oxide, cerium oxide, and molecular sieves. Molecular sieves are present in amounts of 35% to 45% by weight, based on the total weight of the complex. Manganese oxide and cerium oxide are present in molar ratios ranging from 3:2 to 2:3. Molecular sieves are NH4 + This is a zeolite with an MFI skeleton type (e.g., ZSM-5).

[0046] In some embodiments, the composites described herein contain a CeO2(

[0111] ) phase having a crystallite size of 3.5 nm or less, e.g., 3.2 nm or less, in a fresh state, and / or having a crystallite size of 6.5 nm or less, e.g., 6.0 nm or less, after hydrothermal aging at 650°C for 50 hours in an air atmosphere containing 10% water vapor. The crystallite size of CeO2(

[0111] ) is determined by X-ray powder diffraction (XRD) analysis.

[0047] The composite described herein should be consumed in a fresh state at least 100 ml 2 / g, for example, at least 150m 2 Having a BET specific surface area of ​​ / g and / or having at least 50m after hydrothermal aging at a temperature of 650°C for 50 hours in an air atmosphere containing 10% water vapor. 2 / g, for example, at least 75m 2 / g or at least 100m 2 It may have a BET specific surface area of ​​ / g.

[0048] The complexes described herein, namely the manganese oxide, cerium oxide, and molecular sieve complexes, can be prepared by any suitable method capable of providing the complex from a manganese precursor, a cerium precursor, and a molecular sieve. Preferably, the manganese oxide, cerium oxide, and molecular sieve complexes can be prepared by coprecipitation or sol-gel method, more preferably by sol-gel method.

[0049] Surprisingly, the inventors found that a composite of manganese oxide, cerium oxide, and molecular sieves prepared by the sol-gel method is particularly advantageous in terms of low-temperature catalytic performance when used in the NH3-SCR method.

[0050] Therefore, in a second aspect, the present invention relates to a sol-gel method for preparing the NH3-SCR catalyst described in the first aspect, (i) A step of preparing a suspension containing molecular sieves, a manganese oxide precursor and a cerium oxide precursor, (ii) A step of heating the suspension to form a gel (iii) A sol-gel method is provided, comprising the steps of drying, grinding and calcining the gel.

[0051] Molecular sieves suitable for the sol-gel method according to the present invention are generally preferred as described in the first embodiment above.

[0052] As used herein, the term “precursor” refers to a material that can be decomposed or otherwise converted into its respective catalytically active species (i.e., manganese oxide and cerium oxide, respectively) during calcination or catalyst use.

[0053] A manganese oxide precursor suitable for the sol-gel method according to the present invention may be any inorganic or organic water-soluble or water-dispersible compound of manganese, such as manganese salts and complexes. Similarly, a cerium oxide precursor suitable for the sol-gel method according to the present invention may be any inorganic or organic water-soluble or water-dispersible compound of cerium, such as cerium salts and complexes.

[0054] In particular, the suspension in step (i) further comprises an aqueous medium, preferably water, more preferably deionized water (DI water) or demineralized water.

[0055] The suspension in step (i) may further contain a complexing agent such as citric acid.

[0056] In step (i), the suspension may be provided by preparing a mixture containing molecular sieves, a manganese oxide precursor, and a cerium oxide precursor, and then dissolving the mixture in an aqueous medium, preferably DI water. The mixture may also contain a complexing agent such as citric acid.

[0057] In step (ii), the suspension obtained from step (i) is preferably heated under stirring to form a gel. The heating may be carried out at a temperature in the range of 70°C to 100°C, for example, in the range of 80°C to 90°C.

[0058] In step (iii), the gel obtained in step (ii) is dried, pulverized, and calcined. Drying, pulverization, and calcination can be carried out by any conventional method and conditions well known in the art. In particular, drying can be carried out at a temperature in the range of 40 to 100°C, for example, 60 to 80°C, to remove the aqueous medium. The resulting solid can be further pulverized to obtain a powder having a suitable particle size. The powder is then calcined at a temperature in the range of 300 to 500°C, for example, 300°C or 400°C, to obtain a composite of manganese oxide, cerium oxide, and molecular sieves.

[0059] In some exemplary embodiments, the present invention relates to a sol-gel method for preparing the NH3-SCR catalyst described in the first aspect, (i) A step of preparing a suspension in an aqueous medium (preferably water) containing molecular sieves, a manganese oxide precursor, a cerium oxide precursor, and a complexing agent, (ii) A step of heating the suspension to form a gel, (iii) A sol-gel method is provided, comprising the steps of drying, grinding and calcining the gel.

[0060] In particular, the present invention relates to a sol-gel method for preparing the NH3-SCR catalyst described in the first embodiment, (i) A step of preparing a suspension in water containing molecular sieves, a water-soluble salt of manganese, a water-soluble salt of cerium, and citric acid, (ii) A step of heating the suspension to form a gel, (iii) A sol-gel method is provided, comprising the steps of drying, grinding and calcining the gel.

[0061] NH3-SCR catalysts prepared by the sol-gel method produce less N2O compared to their counterparts prepared by the coprecipitation method, and produce less low-temperature NO compared to their counterparts prepared by the impregnation method. x It has a high conversion rate and produces low-temperature NO compared to the counterpart prepared by mixing Mn / Ce composite oxide with molecular sieves. x It was found that the conversion rate is high and the amount of N2O produced can be reduced.

[0062] An NH3-SCR catalyst described in the first aspect of the present invention, or an NH3-SCR catalyst obtained by the sol-gel method described in the second aspect of the present invention, can be used in exhaust gas treatment applications in any conventional form. For example, the NH3-SCR catalyst may be used as a powder, processed into a molded body by conventional methods, or coated onto a substrate.

[0063] Accordingly, in a third aspect, the present invention provides an NH3-SCR article comprising an NH3-SCR catalyst obtained from the NH3-SCR catalyst described in the first aspect or from the sol-gel method described in the second aspect, preferably in the form of a molded article or a coating structure.

[0064] NH3-SCR articles may be in the form of molded articles, such as extruded articles, particularly granular extruded articles or monolithic extruded articles. Granular extruded articles may be in various shapes such as pellets, beads, rings, spheres, cylinders, trefoils, and tetrafoils. Monolithic extruded articles may have any suitable structure, preferably a honeycomb structure, that allows exhaust gas flow to pass through. The honeycomb structure may have flow channels as described below herein for monolithic flow-through and wall-flow structures. This form of NH3-SCR article may comprise an NH3-SCR catalyst and optionally other conventional functional components or processing aids, such as binders or lubricants.

[0065] Alternatively, the NH3-SCR article may take the form of a coating structure containing the NH3-SCR catalyst within a coating on a substrate. The substrate generally refers to a structure suitable for withstanding the conditions encountered in exhaust gas flow, on which the NH3-SCR catalyst is supported as a coating, particularly as a wash coat.

[0066] A suitable substrate may have a monolithic flow-through structure, having multiple fine parallel gas channels extending from an inlet surface to an outlet surface of the substrate, thereby open to allow fluid to flow through these channels. The channels, which are essentially straight paths from the fluid inlet to the fluid outlet, are defined by walls to which the catalytic material is applied as a coating, particularly a wash coat, so that the gas flowing through the channels comes into contact with the catalytic material.

[0067] Alternatively, the substrate may have a monolithic wall-flow structure with multiple fine parallel gas channels extending from the inlet surface to the outlet surface of the substrate, in which case the alternating channels are blocked at both ends. The channels are defined by walls to which the catalyst material is applied as a coating, particularly as a wash coat, so that the gas flowing through the channels comes into contact with the catalyst material. This configuration requires the gas to flow through the porous walls of the wall-flow substrate to reach the outlet surface.

[0068] The term "wash coat" has its common meaning in the art and refers to a thin, adhesive coating of a catalytic material or other material applied to a substrate. Wash coats are generally formed by preparing a slurry containing a desired catalytic material and, optionally, a processing aid such as a binder having a specific solid content (e.g., 15-60% by weight), then applying the slurry to a substrate, drying, and firing to provide the wash coat.

[0069] The NH3-SCR articles according to the present invention can be used, for example, to treat exhaust gases from stationary combustion devices such as power plants and heating systems for buildings and private buildings, as well as from mobile combustion devices such as combustion engines in vehicles, particularly diesel engines. The NH3-SCR articles according to the present invention may be particularly effective in treating exhaust gases from internal combustion engines, such as diesel engines.

[0070] The NH3-SCR article according to the present invention can be positioned downstream of an internal combustion engine such as a diesel engine, at a close-coupled position, downstream of the close-coupled position, or both. Preferably, the catalyst article according to the present invention is positioned downstream of the internal combustion engine at a close-coupled position.

[0071] Accordingly, in a fourth aspect, the present invention relates to a method for treating exhaust gas containing nitrogen oxides by selective catalytic reduction, comprising contacting the exhaust gas with an NH3-SCR catalyst or NH3-SCR article described herein in the presence of ammonia or an ammonia precursor as a reducing agent.

[0072] Furthermore, in a fifth embodiment, the present invention provides an exhaust gas treatment system for a combustion engine comprising a reducing agent source, an NH3-SCR article as described herein, and optionally one or more of the following: a diesel oxidation catalyst (DOC), a ternary converter (TWC), a quaternary converter (FWC), a catalyst-free or catalytic soot filter (CSF), an ammonia oxidation catalyst (AMOx), a NOx trap, a NOx absorption catalyst, a hydrocarbon trap catalyst, a sensor, and a mixer.

[0073] The exhaust gas treatment system preferably further comprises a diesel oxidation catalyst located downstream of the engine and upstream of the NH3-SCR article according to the present invention. In some embodiments, the exhaust gas treatment system preferably comprises both a diesel oxidation catalyst and a catalytic soot filter located upstream of the catalytic article according to the present invention.

[0074] Embodiment Various embodiments are listed below. It will be understood that the embodiments listed below can be combined with all aspects and other embodiments in accordance with the scope of the present invention.

[0075] 1. An NH3-SCR catalyst comprising a complex of manganese oxide, cerium oxide, and molecular sieves, particularly a complex of manganese oxide, cerium oxide, and molecular sieves, wherein the molecular sieves are present in an amount of 20% to 70% by weight based on the total weight of the complex. 2. The NH3-SCR catalyst according to Embodiment 1, wherein molecular sieves are present in the complex of manganese oxide, cerium oxide, and molecular sieves in an amount of 20% to 50% by weight, more preferably 35% to 45% by weight, based on the total weight of the complex. 3. The NH3-SCR catalyst according to Embodiment 1 or 2, wherein manganese oxide and cerium oxide are present in a molar ratio of 4:1 to 1:4, preferably 7:3 to 3:7, and more preferably 3:2 to 2:3, calculated as Mn and Ce elements. 4. Molecular sieves include ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFV, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC , BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, -CHI, -CLO, CON, CSV, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, * -EWT, EZT, FAR, FAU, FER, FRA, GIS, GIU, GME, GON, GOO, HEU, IFO, IFR, -IFU, IFW, IFY, IHW, IMF, IRN, IRR, -IRY, ISV, ITE, ITG, ITH, * -ITN, ITR, ITT, -ITV, ITW, IWR, IWS, IWV, IWW, JBW, JNT, JOZ, JRY, JSN, JSR, JST, JSW, KFI, LAU, LEV , LIO, -LIT, LOS, LOV, LTA, LTF, LTJ, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, *MRE, MSE, MSO, MTF, MTN, MTT, MTW, MVY, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, -PAR, PAU, PCR, PHI, PON, PO S, PSI, PUN, RHO, -RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBN, SBS, SBT, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, * SFV, SFW, SGT, SIV, SOD, SOF, SOS, SSF, * -SSO, SSY, STF, STI, * An NH3-SCR catalyst according to any one of Embodiments 1 to 3, selected from zeolites having the skeleton types STO, STT, STW, -SVR, SVV, SZR, TER, THO, TOL, TON, TSC, TUN, UEI, UFI, UOS, UOV, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WEI, -WEN, YUG, and ZON. 5. An NH3-SCR catalyst according to any one of Embodiments 1 to 4, wherein the molecular sieve is selected from zeolites having the skeleton types 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. 6. Zeolites are H-type, NH4 + The NH3-SCR catalyst according to Embodiment 4 or 5, which is a metal ion exchange type such as a copper and / or iron exchange type. 7. Molecular sieves are BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite), preferably MFI (e.g., ZSM-5), more preferably NH4+ An NH3-SCR catalyst according to any one of Embodiments 1 to 6, wherein the zeolite has a skeletal type selected from the group consisting of morphological MFIs (e.g., ZSM-5). 8. An NH3-SCR catalyst according to any one of Embodiments 1 to 7, wherein a complex of manganese oxide, cerium oxide, and molecular sieves is prepared by coprecipitation or sol-gel method, more preferably by sol-gel method. 9. A sol-gel method for preparing an NH3-SCR catalyst according to any one of Embodiments 1 to 8, (i) A step of preparing a suspension containing molecular sieves, a manganese oxide precursor and a cerium oxide precursor, (ii) A step of heating the suspension to form a gel, (iii) A sol-gel method comprising the steps of drying, grinding and calcining the gel. 10. The sol-gel method according to Embodiment 9, wherein the suspension in step (i) comprises an aqueous medium, preferably water. 11. The sol-gel method according to Embodiment 9 or 10, wherein the suspension in step (i) contains a complexing agent such as citric acid. 12. The method according to any one of Embodiments 9 to 11, wherein the heating in step (ii) is performed at a temperature in the range of 70°C to 100°C. 13. The method according to any one of Embodiments 9 to 12, wherein the firing in step (iii) is carried out at a temperature in the range of 300°C to 500°C, for example, 300°C or 400°C. 14. An NH3-SCR article comprising an NH3-SCR catalyst described in any one of Embodiments 1 to 8, or an NH3-SCR catalyst obtained by a sol-gel method described in any one of Embodiments 9 to 13. 15. An NH3-SCR article according to Embodiment 14, in the form of a molded body such as an extruded product, or a coated structure. 16. The NH3-SCR article according to Embodiment 15, in the form of a granular extruded or monolithic extruded product. 17. The NH3-SCR article according to Embodiment 15, which has a coating structure in which an NH3-SCR catalyst is contained within a coating on a substrate. 18. The NH3-SCR article according to Embodiment 17, wherein the substrate is a monolithic flow-through structure or a monolithic wall-flow structure. 19. A method for treating exhaust gas containing nitrogen oxides by selective catalytic reduction, comprising contacting the exhaust gas with an NH3-SCR catalyst according to any one of Embodiments 1 to 8, an NH3-SCR article obtained from a sol-gel method according to any one of Embodiments 9 to 13, or an NH3-SCR article according to any one of Embodiments 14 to 18, in the presence of ammonia or an ammonia precursor as a reducing agent. 20. An exhaust gas treatment system for a combustion engine, comprising a reducing agent source, an NH3-SCR article described in any one of embodiments 14 to 18, and optionally one or more of the following: a diesel oxidation catalyst (DOC), a three-way converter catalyst (TWC), a four-way converter catalyst (FWC), a catalyst-free or catalytic soot filter (CSF), an ammonia oxidation catalyst (AMOx), a NOx trap, a NOx absorption catalyst, a hydrocarbon trap catalyst, a sensor, and a mixer. 21. The exhaust gas treatment system according to Embodiment 20, comprising a diesel oxidation catalyst located downstream of the engine and upstream of the NH3-SCR article. 22. An exhaust gas treatment system according to embodiment 20 or 21, comprising a diesel oxidation catalyst and a catalytic soot filter located downstream of the engine and upstream of the NH3-SCR article.

[0076] The present invention will be further illustrated by the following embodiments, which describe particularly advantageous embodiments. The embodiments are provided to illustrate the present invention, but are not intended to limit it. [Examples]

[0077] I. Material

[0078] [Table 1]

[0079] II. General Preparation Procedure II.1 Preparation of Mn-Ce composite oxide (MnCeOx) by sol-gel method A mixture of Mn(NO3)4·4H2O, Ce(NO3)3·6H2O, and citric acid in a molar ratio of 1:1:2 was dissolved in deionized water at a weight ratio of 1:50 while stirring, and heated at a temperature below 90°C until a gel was formed. The gel was dried overnight in an oven at 80°C. The resulting solid was pulverized to a powder with a particle size of 40-60 mesh and calcined in a muffle at 300°C for 4 hours.

[0080] II.2 Preparation of Mn / Ce / zeolite complexes by coprecipitation method For each composite sample, a mixture of specified amounts of Mn(NO3)4·4H2O, Ce(NO3)3·6H2O, and zeolite was prepared. The mixture was dissolved in deionized (DI) water at a weight ratio of 1:50. Ammonia was then added to the resulting suspension to adjust the pH to 11, and the mixture was stirred at room temperature until a precipitate formed. The precipitate was separated by filtration and washing, and then dried overnight in an oven. Finally, the resulting solid was pulverized to a particle size of 40-60 mesh and calcined in a muffle at 300°C for 4 hours. A composite of manganese oxide, cerium oxide, and zeolite was obtained, such as Mn / Ce / zeolite, e.g., Mn / Ce / NH4 + It was named -ZSM-5.

[0081] II.3 Preparation of Mn / Ce / zeolite complexes by sol-gel method A mixture of Mn(NO3)4·4H2O, Ce(NO3)3·6H2O, and citric acid was prepared in a molar ratio of (Mn+Ce) to citric acid of 1:2, and a certain amount of zeolite was added to the mixture. The mixture was dissolved with deionized (DI) water at a weight ratio of 1:50 mixture to water while stirring, and heated at less than 90°C until a gel was formed. The gel was dried overnight in an oven at 80°C. The resulting solid was pulverized to a powder with a particle size of 40-60 mesh and calcined in a muffle at 300°C or 400°C for 4 hours. A composite of manganese oxide, cerium oxide, and zeolite was obtained, such as Mn / Ce / zeolite, e.g., Mn / Ce / NH4 + It was named -ZSM-5.

[0082] II.4 MnCeO x MnCeO x Preparation of a kneaded mixture of zeolite and (grinding method) A mixture of Mn(NO3)4·4H2O, Ce(NO3)3·6H2O, and citric acid was prepared in a molar ratio of (Mn+Ce) to citric acid of 1:2. Then, with deionized water, the mixture was dissolved in water in a weight ratio of 1:0.3 while stirring, and heated at less than 90°C until a gel was formed. The gel was dried overnight in an oven at 80°C. The resulting solid was pulverized into a powder and calcined in a muffle at 300°C for 4 hours to form a Mn / Ce composite oxide (i.e., MnCeO). x ) was obtained. A certain amount of MnCeO x It was mixed with zeolite and pulverized to produce a powder with a particle size of 40-60 mesh. MnCeO x A kneaded mixture of MnCeO and zeolite is obtained. x / Zeolite, for example, MnCeO x / NH4 + It was named -ZSM-5.

[0083] II.5 MnCeO by water mixing method x Preparation of a kneaded mixture of zeolite and A mixture of Mn(NO3)4·4H2O, Ce(NO3)3·6H2O, and citric acid in a molar ratio of 1:1:2 was prepared. Then, with deionized water, the mixture was dissolved with stirring at a weight ratio of 1:50 to water, and heated at a temperature below 90°C until a gel was formed. The gel was dried overnight in an oven at 80°C. The resulting solid was pulverized into a powder and calcined in a muffle at 300°C for 4 hours to form a Mn / Ce composite oxide (i.e., MnCeO). x Next, a certain amount of MnCeO was obtained. x Mix the zeolite with an appropriate amount of deionized water and MnCeO x The zeolite was highly dispersed. The resulting precipitate was filtered, washed, and dried overnight in an oven at 80°C. The resulting solid was pulverized to a particle size of 40-60 mesh and calcined in a muffle at less than 300°C for 4 hours. MnCeO x A kneaded mixture of MnCeO and zeolite is obtained. x / Zeolite, for example, MnCeO x / NH4 + It was named -ZSM-5.

[0084] II.6 Preparation of Mn / Ce / zeolite composites by impregnation method A mixture of Mn(NO3)4·4H2O and Ce(NO3)3·6H2O in a molar ratio of 1:1 was dissolved in deionized water at a weight ratio of 1:0.3 to water. A certain amount of zeolite was added to the resulting solution and stirred for 2 hours. The resulting precipitate was then filtered, washed, and dried overnight in an oven at 80°C. The resulting solid was pulverized to a powder with a particle size of 40-60 mesh and calcined in a muffle at 300°C for 4 hours. A composite of manganese oxide, cerium oxide, and zeolite was obtained, such as Mn / Ce / zeolite, e.g., Mn / Ce / NH4 + It was named -ZSM-5.

[0085] III.Characterization method X-ray diffraction (XRD) experiments were performed using a Rigaku D / MAS-RB X-ray diffractometer with Cu Kα (40kV, 40mA) radiation. XRD patterns were recorded in a 2θ range of 10° to 90° at a scanning speed of 8° / min.

[0086] SEM-EDS characterization was performed using a field emission scanning electron microscope (FE-SEM, SIGMA-3000). Energy-dispersive spectroscopy (EDS) mapping of the catalyst was completed using Oxford Instruments EDS.

[0087] Nitrogen adsorption-desorption tests were performed using a USQuantachrome ASAP 2020M nitrogen adsorption apparatus at 77K, and the specific surface area was calculated using the Brunaue-Emmett-Teller (BET) method. Before the experiment, the samples were degassed at 200°C for 10 hours.

[0088] IV.SCR performance measurement SCR performance was evaluated using a fixed-bed quartz flow reactor (inner diameter = 4 mm) and 0.15 g of 40-60 mesh catalyst. SCR activity measurements were performed in a temperature range of 90-480°C.

[0089] The gas flow used consists of 500 vppm NO, 500 vppm NH3, 10 vol% O2, 5 vol% H2O, 5 vol% CO2, and the remainder as N2 gas. The total flow rate is 200,000 mL·g. -1 ·h -1 Gas space velocity per hour (GHSV, by mass), 150,000 h -1 475 mL·min, corresponding to GHSV (volume) -1 The temperature was controlled, and cordierite was used to make the volume of all catalysts the same.

[0090] To measure the aged samples, freshly prepared samples were hydrothermally treated at 650°C for 50 hours in an air atmosphere containing 10% H2O before measurement.

[0091] The gas concentrations of NO, NO2, NH3, H2O, and N2O were simultaneously monitored using an FTIR spectrometer (Themo Fisher). SCR catalytic activity was recorded after the reaction system reached a steady state. The NOx conversion rate was calculated using the following formula.

[0092]

number

[0093] The test results are summarized in the table below.

[0094] [Table 2]

[0095] All manganese oxide, cerium oxide, and zeolite composites shown in Table 1 have a total mass ratio of manganese oxide and cerium oxide to zeolite of 1.5:1, and a molar ratio of Mn:Ce of 1:1. These were prepared by the gel-sol method according to the general procedure described in II.3 above, with a calcination temperature of 300°C. Mn / Co / NH4 + -ZSM-5 and Mn / Sm / NH4 + - The ZSM-5 complex is prepared according to the same procedure, with a total mass ratio of manganese oxide and cobalt oxide (or total manganese oxide and samarium oxide) to zeolite of 1.5:1 and a molar ratio of Mn:Co (or Sm) of 1:1.

[0096] The test results shown in Table 1 demonstrate that the manganese oxide, cerium oxide, and zeolite composite according to the present invention exhibits a much higher low-temperature NOx conversion rate than conventional Cu-SSZ-13. x The conversion rate is the same as with conventional MnCeO x Although equivalent to or slightly lower than conventional MnCeO, the amount of N2O produced is x It's much lower.

[0097] The Fresh Composite Mn / Ce / NH4 according to the present invention + -ZSM-5 is a fresh complex Mn / Sm / NH4 + -ZSM-5 has a much higher temperature NO x The conversion rate is shown, and the fresh complex Mn / Co / NH4 +-It can also be seen that it produces a much lower amount of N2O than ZSM-5. Furthermore, the aged composite Mn / Ce / NH4 according to the present invention + -ZSM-5 is a composite Mn / Co / NH4 after aging. + -ZSM-5 and Mn / Sm / NH4 + -ZSM-5 has a much higher temperature NO x It shows both the conversion rate and the small amount of N2O produced. Therefore, Mn / Ce / NH4 + -ZSM-5 complex is used as a catalyst for SCR applications, Mn / Co / NH4 + -ZSM-5 and Mn / Sm / NH4 + -It performs better than the ZSM-5.

[0098] [Table 3]

[0099] All manganese oxide, cerium oxide, and zeolite composites shown in Table 2 have a total mass ratio of manganese oxide and cerium oxide to zeolite of 1.5:1, and a molar ratio of Mn:Ce of 1:1. These were prepared by the gel-sol method according to the general procedure described in II.3 above, and the calcination temperature was 400°C.

[0100] From the test results shown in Table 2, the manganese oxide, cerium oxide, and zeolite composite according to the present invention, prepared at a higher calcination temperature, is superior to conventional MnCeO x Low-temperature NO equivalent to or slightly lower than x The conversion rate is shown, and the amount of N2O produced is compared to conventional MnCeO x It can be seen that it is much lower.

[0101] [Table 4]

[0102] The composites of manganese oxide, cerium oxide and zeolite shown in Table 3 all have the mass ratio of the total of manganese oxide and cerium oxide shown in parentheses to zeolite, and the molar ratio of Mn:Ce is 1:1. These were prepared by the sol-gel method according to the general procedure described in II.3 above, and the calcination temperature was 300 °C.

[0103] From the results shown in Table 3, the composites of manganese oxide, cerium oxide and various forms of ZSM-5 according to the present invention have good low-temperature NO x conversion rate and lower N2O production amount than MnCeO x Among them, the composite Mn / Ce / NH4 + -ZSM-5 is found to be better for SCR applications.

[0104]

Table 5

[0105] All of the Mn / Ce / NH4 <P + -ZSM-5 composites shown in Table 4 have the mass ratio of the total of the shown manganese oxide and cerium oxide to zeolite, and the molar ratio of Mn:Ce is 1:1. These were prepared by the sol-gel method according to the general procedure described in II.3 above, and the calcination temperature was 300 °C.

[0106] From the results shown in Table 4, all of the composites of manganese oxide, cerium oxide and NH4 + -ZSM-5 with various MnCeO x :zeolite mass ratios can show better low-temperature NO x conversion rate and lower N2O production amount than MnCeO x Among them, it can be seen that the composite Mn / Ce / NH4 with the mass ratio of the total of manganese oxide and cerium oxide to zeolite being 1.5:1 is the best. + -ZSM-5 is found to be the best.

[0107]

Table 6

[0108] The MnCe+NH4 shown in Table 5 + All of the composites of -ZSM-5 have a mass ratio of the total of manganese oxide and cerium oxide to zeolite of 1.5:1 and have the indicated Mn:Ce molar ratio. These were prepared by the sol-gel method according to the general procedure described in II.3 above, and the calcination temperature was 300 °C.

[0109] From the results shown in Table 5, the composites of MnCe / NH4 + -ZSM-5 with various Mn:Ce molar ratios all show good low-temperature NO x conversion rate and a lower N2O production amount than MnCeO x Among them, it can be seen that the composite Mn / Ce / NH4 with a Mn:Ce molar ratio of 1:1 + -ZSM-5 is the best.

[0110]

Table 7

[0111] All of the composites or kneaded mixtures shown in Table 6 have a mass ratio of the total of manganese oxide and cerium oxide to zeolite of 1.5:1 and a Mn:Ce molar ratio of 1:1. These were prepared by the respective methods shown, and the calcination temperature was 300 °C.

[0112] From the results shown in Table 6, it can be seen that the composite Mn / Ce / NH4 prepared from the sol-gel method + -ZSM-5 shows the lowest N2O production amount among all the samples. The sol-gel method is the best method for preparing the composite of manganese oxide, cerium oxide and zeolite according to the present invention.

[0113] V. Characterization Results N2 Adsorption and Desorption The composite Mn / Ce / NH4 for determining N2 adsorption and desorption characteristics +-ZSM-5 is a combination of manganese oxide and cerium oxide and NH4 + -The mass ratio with ZSM-5 is 1.5:1, and the molar ratio of Mn:Ce is 1:1. This was prepared by the gel-sol method at a calcination temperature of 300°C. MnCeO x It was prepared by a gel-sol method with a Mn:Ce molar ratio of 1:1.

[0114] The results are summarized in Table 7.

[0115] [Table 8]

[0116] Analysis of N2 adsorption and desorption revealed that MnCeO x Specific surface area (80m 2 g -1 ) After aging, 35m 2 g -1 It decreases significantly to Mn / Ce / NH4 + -Specific surface area of ​​ZSM-5 (174 m²) 2 g -1 ) is 147m after aging. 2 g -1 It only decreases up to this point. Complex Mn / Ce / NH4 + - Note that the ZSM-5 maintained a high specific surface area after aging.

[0117] XRD analysis and SEM-EDS analysis Mn / Ce / NH4 complex for XRD analysis and SEM-EDS + -ZSM-5 is a combination of manganese oxide and cerium oxide and NH4 + -The mass ratio with ZSM-5 is 1.5:1, and the molar ratio of Mn:Ce is 1:1. This was prepared by the gel-sol method at a calcination temperature of 300°C. MnCeO x It was prepared by a gel-sol method with a Mn:Ce molar ratio of 1:1.

[0118] The XRD results are shown in Table 8 and Figure 1, and the SEM-EDS images are shown in Figures 2a and 2b.

[0119] [Table 9]

[0120] While the present invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative examples of the principles and applications of the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the methods and apparatus of the present invention without departing from the spirit and scope of the invention. Accordingly, the present invention is intended to include modifications and variations that fall within the scope of the appended claims and their equivalents.

Claims

1. A composite of manganese oxide, cerium oxide, and molecular sieves, particularly an NH comprising the composite of manganese oxide, cerium oxide, and molecular sieves. ３ - An SCR catalyst wherein the molecular sieve is present in an amount of 20% to 70% by weight based on the total weight of the composite, NH ３ -SCR catalyst.

2. The NH according to claim 1, wherein the molecular sieve is present in the composite of manganese oxide, cerium oxide, and molecular sieve in an amount of 20% to 50% by weight, more preferably 35% to 45% by weight, based on the total weight of the composite. ３ -SCR catalyst.

3. The NH according to claim 1 or 2, wherein manganese oxide and cerium oxide are present in a molar ratio in the range of 4:1 to 1:4, preferably in the range of 7:3 to 3:7, and more preferably in the range of 3:2 to 2:3, calculated as Mn and Ce elements. ３ -SCR catalyst.

4. The molecular sieve is ABW, ACO, AEI, AEL, AEN, AET, AFG, AFI, AFN, AFO, AFR, AFS, AFT, AFV, AFX, AFY, AHT, ANA, APC, APD, AST, ASV, ATN, ATO, ATS, ATT, ATV, AVL, AWO, AWW, BCT, BEA, BEC, BIK, BOF, BOG, BOZ, BPH, BRE, BSV, CAN, CAS, CDO, CFI, CGF, CGS, CHA, -CHI, -CLO, CON, CSV, CZP, DAC, DDR, DFO, DFT, DOH, DON, EAB, EDI, EEI, EMT, EON, EPI, ERI, ESV, ETR, EUO, ＊ -EWT, EZT, FAR, FAU, FER, FRA, GIS, GUI, GME, GON, GOO, HEU, IFO, IFR, -IFU, IFW, IFY, IHW, IMF, IRN, IRR, -IRY, ISV, ITE, ITG, ITH, ＊ -ITN, ITR, ITT, -ITV, ITW, IWR, IWS, IWV, IWW, JBW, JNT, JOZ, JRY, JSN, JSR, JST, JSW, KFI, LAU, LEV, LIO, -LIT, LOS, LOV, LTA, LTF, LTJ, LTL, LTN, MAR, MAZ, MEI, MEL, MEP, MER, MFI, MFS, MON, MOR, MOZ, ＊ MRE, MSE, MSO, MTF, MTN, MTT, MTW, MVY, MWF, MWW, NAB, NAT, NES, NON, NPO, NPT, NSI, OBW, OFF, OKO, OSI, OSO, OWE, -PAR, PAU, PCR, PHI, PON, POS, PSI, PUN, RHO, -RON, RRO, RSN, RTE, RTH, RUT, RWR, RWY, SAF, SAO, SAS, SAT, SAV, SBE, SBN, SBS, SBT, SEW, SFE, SFF, SFG, SFH, SFN, SFO, SFS, ＊ SFV, SFW, SGT, SIV, SOD, SOF, SOS, SSF, ＊ -SSO, SSY, STF, STI, ＊ NH according to any one of claims 1 to 3, selected from zeolites having the skeleton types STO, STT, STW, -SVR, SVV, SZR, TER, THO, TOL, TON, TSC, TUN, UEI, UFI, UOS, UOV, UOZ, USI, UTL, UWY, VET, VFI, VNI, VSV, WEI, -WEN, YUG, and ZON ３ -SCR catalyst.

5. The molecular sieve is selected from zeolites having the skeleton types 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, according to any one of claims 1 to 4. ３ -SCR catalyst.

6. The aforementioned zeolites are H-type and NH ４ ＋ The NH according to claim 4 or 5, which is a metal ion exchange type such as a copper and / or iron exchange type. ３ -SCR catalyst.

7. The molecular sieve is BEA (e.g., beta), CHA (e.g., chabazite), FAU (e.g., zeolite Y), FER (e.g., ferrielite), MFI (e.g., ZSM-5), and MOR (e.g., mordenite), preferably MFI (e.g., ZSM-5), more preferably NH ４ ＋ NH according to any one of claims 1 to 6, which is a zeolite having a skeleton type selected from the group consisting of type MFI (e.g., ZSM-5) ３ -SCR catalyst.

8. The NH according to any one of claims 1 to 7, wherein the composite of manganese oxide, cerium oxide, and molecular sieve is prepared by coprecipitation or sol-gel method, more preferably by sol-gel method. ３ -SCR catalyst.

9. NH according to any one of claims 1 to 8 ３ - A sol-gel method for preparing SCR catalysts, (i) A step of preparing a suspension containing molecular sieves, a manganese oxide precursor and a cerium oxide precursor, (ii) A step of heating the suspension to form a gel, (iii) A sol-gel method comprising the steps of drying, grinding and calcining the gel.

10. The sol-gel method according to claim 9, wherein the suspension in step (i) comprises an aqueous medium, preferably water.

11. The sol-gel method according to claim 9 or 10, wherein the suspension in step (i) contains a complexing agent such as citric acid.

12. The sol-gel method according to any one of claims 9 to 11, wherein the heating in step (ii) is performed at a temperature in the range of 70°C to 100°C.

13. The sol-gel method according to any one of claims 9 to 12, wherein the calcination in step (iii) is carried out at a temperature in the range of 300°C to 500°C, for example, 300°C or 400°C.

14. NH according to any one of claims 1 to 8 ３ - SCR catalyst, or NH obtained from the sol-gel method according to any one of claims 9 to 13 ３ - Contains SCR catalyst, NH ３ -SCR articles.

15. The NH according to claim 14 is in the form of a molded body such as an extruded product, or a coated structure. ３ -SCR articles.

16. The NH according to claim 15 is in the form of a granular extruded material or a monolithic extruded material. ３ -SCR articles.

17. The NH within the coating on the substrate ３ - The NH according to claim 15, which is a coating structure containing an SCR catalyst. ３ -SCR articles.

18. The NH according to claim 17, wherein the substrate is a monolithic flow-through structure or a monolithic wall-flow structure. ３ -SCR articles.

19. A method for treating exhaust gas containing nitrogen oxides by selective catalytic reduction, wherein the exhaust gas is treated by selective catalytic reduction according to any one of claims 1 to 8, in the presence of ammonia or an ammonia precursor as a reducing agent. ３ - SCR catalyst, NH obtained from the sol-gel method according to any one of claims 9 to 13 ３ - SCR article, or NH as described in any one of claims 14 to 18 ３ - A method including contact with an SCR article.

20. An exhaust gas treatment system for a combustion engine, comprising a reducing agent source, and NH as described in any one of claims 14 to 18. ３ - An exhaust gas treatment system comprising SCR articles, and optionally one or more of the following: diesel oxidation catalyst (DOC), ternary converter (TWC), quaternary converter (FWC), catalyst-free or catalytic soot filter (CSF), ammonia oxidation catalyst (AMOx), NOx trap, NOx absorption catalyst, hydrocarbon trap catalyst, sensor, and mixer.

21. Downstream of the engine and the NH ３ - An exhaust gas treatment system according to claim 20, comprising a diesel oxidation catalyst located upstream of the SCR article.

22. Downstream of the engine and the NH ３ - An exhaust gas treatment system according to claim 20 or 21, comprising a diesel oxidation catalyst and a catalytic soot filter located upstream of the SCR article.

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