Metal oxide catalysts for selective catalytic reduction

Abstract

A non-vanadium metal oxide catalyst composition is provided, comprising at least one metal oxide, including manganese oxide, dispersed on a support, and a support comprising particles of a composite oxide of aluminum and at least one metal selected from cerium, manganese, and titanium, wherein the aluminum is present in the composite oxide in an amount of 50% to 80% by weight, calculated as Al2O3, based on the total weight of the composite oxide, and the manganese oxide is present in the metal oxide catalyst composition in an amount of 2.5% to 10% by weight, calculated as MnO2, based on the total weight of the metal oxide catalyst composition.

Description

[Technical field]

[0001] The present invention relates to a non-vanadium metal oxide catalyst for selective catalytic reduction, a process for preparing the same, and a method for treating exhaust gases containing nitrogen oxides by selective catalytic reduction. [Background technology]

[0002] Nitrogen oxides (NOx) are common air pollutants and are commonly contained in exhaust gases from mobile sources such as automobiles and stationary sources such as power plants. The control of NOx emissions has always been one of the most important topics, for example in the automobile manufacturing field, due to the adverse environmental effects of NOx on ecosystems, humans, animals and plants.

[0003] In order to reduce NOx in exhaust gas, various treatment methods have been used, such as catalytic reduction of nitrogen oxides. One typical catalytic reduction process is selective catalytic reduction using ammonia (NH3) or ammonia precursor as a reducing agent in the presence of atmospheric oxygen, which is also called SCR process. The SCR process is considered superior because it can obtain a high degree of NOx reduction with a small amount of reducing agent. Typically, nitrogen oxides and the reducing agent NH3 react according to the following equation: 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] A side reaction associated with selective catalytic reduction is the formation of lower valent nitrogen oxides, specifically nitrous oxide (N2O), from the reductant NH3 and oxygen.

[0005] For example, the efficiency of NOx treatment in terms of NOx conversion and N2O formation is highly dependent on the catalyst used in the SCR process. Catalysts useful for selective catalytic reduction of NOx, i.e., SCR catalysts, are well known.

[0006] A typical type of SCR catalyst is a vanadium-based catalyst, which generally comprises vanadium oxide as the active species and, optionally, one or more other metal oxides as promoters, such as WO3, on a support such as TiO2. However, vanadium-based catalysts do not have desirable thermal durability. Once aged, vanadium-based catalysts exhibit fairly low activity at low temperatures (e.g., below 300°C). Another drawback of vanadium-based catalysts is that V2O5 can leak into the environment, causing environmental problems.

[0007] Another type of SCR catalyst is the zeolite-based catalyst, which generally comprises transition metal-exchanged small pore aluminosilicate zeolites. Zeolite-based catalysts exhibit high activity at low temperatures (e.g., 210°C), but suffer from a slow response to the injection of reductant. The slow response is believed to be due to acid sites in the zeolite framework, where the reductant NH3 is absorbed to saturation before it is effectively available for NOx reduction.

[0008] Recently, a class of non-vanadium metal oxides have been proposed as alternatives to zeolite- and vanadium-based catalysts for SCR. These metal oxide catalysts generally comprise one or more oxides of a base metal active species on a support, as described in several prior patent applications.

[0009] JP 2003-326167 describes an SCR catalyst comprising tungsten oxide or molybdenum oxide on a zirconium-based support.

[0010] WO 2009 / 001131 describes an SCR catalyst comprising at least one transition metal dispersed on a mixed oxide or composite oxide or mixtures thereof consisting of cerium and zirconium as support material.

[0011] CN106824173 describes an SCR catalyst containing manganese oxide (MnOx) dispersed on a composite oxide of cerium and aluminum (CeO2-Al2O3) as a support. The support was prepared by co-precipitating cerium and aluminum hydroxides and then calcining to obtain a composite oxide of cerium and aluminum.

[0012] It would be desirable to develop non-vanadium-based metal oxide SCR catalysts that have improved NOx treatment efficiency. Summary of the Invention

[0013] It is an object of the present invention to provide an SCR catalyst that performs well, especially at low temperatures (eg, below 210° C.).

[0014] Surprisingly, it has now been found that this object is achieved by a non-vanadium metal oxide composition comprising manganese (Mn) species dispersed on a support comprising particles of a composite oxide of aluminium (Al) and at least one metal selected from cerium (Ce), manganese and titanium (Ti).

[0015] Another object of the present invention is to provide a process that is particularly useful for preparing non-vanadium metal oxide compositions having improved NOx treatment efficiency.

[0016] This object has been achieved by a process which comprises impregnating, in an aqueous alcoholic solvent, a precursor of Mn species onto a support comprising particles of a composite oxide of aluminium and at least one metal selected from cerium, manganese and titanium.

[0017] Thus, in one aspect, the present invention comprises: at least one metal oxide, including manganese oxide; A support including particles of a composite oxide of aluminum and at least one metal selected from cerium, manganese, and titanium, in which aluminum is present in the composite oxide in an amount of 50% by weight to 80% by weight, calculated as Al2O3, based on the total weight of the composite oxide; Including, At least one metal oxide is dispersed on a support; Manganese oxide relates to non-vanadium metal oxide catalyst compositions present in the metal oxide catalyst composition in an amount of 2.5% to 10% by weight, calculated as MnO2, based on the total weight of the metal oxide catalyst composition.

[0018] In another aspect, the present invention relates to a process for preparing the non-vanadium metal oxide catalyst compositions described herein, comprising impregnating one or more precursors of at least one metal oxide onto a support, particularly in an aqueous alcohol solvent, and calcining.

[0019] In yet another aspect, the present invention relates to a method for treating exhaust gases containing nitrogen oxides by selective catalytic reduction comprising contacting the exhaust gas with a metal oxide catalyst composition described herein in the presence of a reducing agent.

[0020] In a further aspect, the present invention relates to a system for the treatment of exhaust gases, particularly from an internal combustion engine, comprising a reductant source, a metal oxide catalyst composition as described herein, and optionally one or more of a diesel oxidation catalyst (DOC), a three-way conversion catalyst (TWC), a four-way conversion catalyst (FWC), an uncatalyzed or catalyzed soot filter (CSF), an ammonia oxidation catalyst (AMOx), a NOx trap, a NOx absorber catalyst, a hydrocarbon trap catalyst, a sensor, and a mixer.

[0021] The present inventors have found that the metal oxide catalyst composition according to the present invention has improved NOx treatment efficiency, which is particularly useful for treating exhaust gas from automobile engines, especially heavy-duty diesel engines. The metal oxide catalyst composition according to the present invention combines good SCR performance at low temperatures (e.g., below 210°C) with desirable thermal stability. [Brief description of the drawings]

[0022] [Figure 1] 1 shows an XRD pattern of a fresh composite oxide support material used in the examples. [Diagram 2] 1 shows the XRD pattern of the aged composite oxide support material used in the examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present invention will be described in detail herein 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.

[0024] As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Terms such as "comprise," "comprising," and the like are used interchangeably with "contain," "containing," and the like, and are to be interpreted in an open, non-restrictive manner; that is, for example, additional components or elements may be present. The phrases "consists of" or "consists essentially of" or cognates may be included within "comprises" or cognates.

[0025] The term "complex oxide" as used herein refers to an oxide material consisting of oxides of two or more elements that can be identified as separate oxides and crystalline phases by X-ray diffraction, where the individual oxides are in intimate contact but are not a physical mixture of the oxides obtained by physical means, such as mechanical mixing or blending.

[0026] As used herein, the term "non-vanadium-based" refers to a metal oxide catalyst composition that does not contain vanadium (e.g., in the form of vanadium) intentionally incorporated into the composition. The terms "non-vanadium-based metal oxide catalyst composition" and "metal oxide catalyst composition" are used interchangeably herein.

[0027] The term "catalytic article" as used herein is intended to mean an article of a particular shape having a catalytic function, not necessarily a single object, in other words, the catalytic article may be a single body or may consist of two or more separable bodies.

[0028] In a first aspect, the present invention provides a method for producing a composition comprising the steps of: at least one metal oxide, including manganese oxide; A support including particles of a composite oxide of aluminum and at least one metal selected from cerium, manganese, and titanium, in which aluminum is present in the composite oxide in an amount of 50% by weight to 80% by weight, calculated as Al2O3, based on the total weight of the composite oxide; Including, At least one metal oxide is dispersed on a support; Manganese oxide relates to non-vanadium metal oxide catalyst compositions present in the metal oxide catalyst composition in an amount of 2.5% to 10% by weight, calculated as MnO2, based on the total weight of the metal oxide catalyst composition.

[0029] The at least one metal oxide dispersed on the support may further comprise an oxide of titanium (Ti), iron (Fe), magnesium (Mg) or aluminum (Al), or any combination thereof. Each of the oxides of Ti, Fe, Mg and Al, when present, may be included in the metal oxide catalyst composition according to the present invention in an amount of 10% by weight or less, 8% by weight or less, or 6% by weight or less, calculated as the respective oxide, based on the total weight of the metal oxide catalyst composition.

[0030] In some embodiments, the at least one metal oxide dispersed on the support comprises manganese oxide, and the manganese oxide is present in the metal oxide catalyst composition in an amount of from 2.5% to 10% by weight, or from 3% to 8% by weight, calculated as MnO2, based on the total weight of the metal oxide catalyst composition.

[0031] In some embodiments, the at least one metal oxide dispersed on the support comprises or consists of manganese oxide and titanium oxide. In these embodiments, it is preferred that the manganese oxide is present in an amount of 2.5% to 10% by weight, or 3% to 8% by weight, calculated as MnO2, and the titanium oxide is present in an amount of 1% to 6% by weight, or 2% to 4% by weight, calculated as TiO2, each based on the total weight of the metal oxide catalyst composition. Specifically, the manganese oxide and titanium oxide may be present in a weight ratio of 1:1 to 3:1, or 1.2:1 to 2.5:1, or 1.5:1 to 2:1.

[0032] In some embodiments, the at least one metal oxide dispersed on the support comprises or consists of manganese oxide and iron oxide. In these embodiments, it is preferred that the manganese oxide is present in an amount of 2.5% to 10% by weight, or 3% to 8% by weight, calculated as MnO2, and the iron oxide is present in an amount of 1 to 5% by weight, or 3 to 5% by weight, calculated as Fe2O3, each based on the total weight of the metal oxide catalyst composition. Specifically, the manganese oxide and iron oxide may be present in a weight ratio of 1:1 to 2:1, or 1:1 to 1.5:1.

[0033] In some further embodiments, the at least one metal oxide dispersed on the support comprises or consists of manganese oxide, titanium oxide, and iron oxide. In these embodiments, it is preferred that the manganese oxide is present in an amount of 2.5% to 10% or 3% to 8% by weight, calculated as MnO2, the titanium oxide is present in an amount of 1% to 6% or 2% to 4% by weight, calculated as TiO2, and the iron oxide is present in an amount of 1% to 5% or 3% to 5% by weight, calculated as Fe2O3, each based on the total weight of the metal oxide catalyst composition.

[0034] The support is in the form of particles in which at least one metal oxide described herein can be dispersed (also referred to as "supported"). The composite oxide particles have a fresh average particle size of 50 to 200 μm. 2 / g.

[0035] The particles may be modified with a dopant, for example Ti, Si, Zr, La or Ba. In this case, the support may comprise particles of the composite oxide and the dopant. The dopant may be present in an amount of 1 to 10% by weight, alternatively 3 to 6% by weight, calculated as the respective oxide, based on the total weight of the metal oxide catalyst composition.

[0036] As used herein, the terms "modified" or "modifying" in the context of a support refers to treating a particle of a complex oxide to incorporate a dopant into the particle, in other words, the dopant is not incorporated during the formation of the complex oxide.

[0037] In some embodiments, the support comprises or consists of particles of a composite oxide of aluminum, cerium, and optionally manganese and / or titanium. In particular, the support consists of particles of a composite oxide of aluminum and cerium, and optionally a dopant. The composite oxide of aluminum and cerium may comprise a phase of Al2O3 and a phase of CeO2, and the crystallite size is at least 5 nm, preferably at least 9 nm, at least 9.5 nm, or at least 10 nm, as measured by X-ray powder diffraction (XRD) analysis in the fresh state. Cerium may be present in the composite oxide in an amount of 20% to 50% by weight, 20% to 40% by weight, or 20% to 30% by weight, calculated as CeO2, based on the total weight of the composite oxide.

[0038] The metal oxide catalyst composition according to the present invention may further comprise a coating metal oxide, such as titanium oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, or any combination thereof, which may be useful for improving the catalyst's resistance to sulfur poisoning or for improving the thermal stability of the catalyst.

[0039] As used herein, the term "coating" refers to a component that is incorporated into a metal oxide catalyst composition by dispersing it or its precursor on the surface of a catalyst particle. The coating metal oxide may be in the form of a gas-permeable layer or partial layer or isolated islands on the surface of the catalyst particle. The coating metal oxide may be incorporated onto the catalyst by post-treatment or by co-impregnation with the active component.

[0040] The coating metal oxide may be present in the metal oxide catalyst composition in an amount of from 0.5 wt % to 10 wt %, from 1 wt % to 5 wt %, or from 0.8 wt % to 3 wt %, based on the total weight of the metal oxide catalyst composition.

[0041] When the metal oxide catalyst composition according to the present invention comprises titanium in two or more of the at least one metal oxide, dopant and coating metal oxide components, the titanium may be present in an amount up to a total of 6 wt. %, calculated as TiO2, based on the total weight of the metal oxide catalyst composition.

[0042] In some embodiments, the metal oxide catalyst composition according to the present invention comprises titanium in only one of the at least one metal oxide component, the dopant and the coating metal oxide component in the respective amounts described herein above.

[0043] In some exemplary embodiments, the metal oxide catalyst composition comprises: at least one metal oxide, comprising or consisting of manganese oxide or manganese oxide and titanium oxide, a support comprising particles of a composite oxide of aluminum and cerium, and optionally a dopant, in which the cerium is present in the composite oxide in an amount of 20% to 40% by weight or 20% to 30% by weight, calculated as CeO2, based on the total weight of the composite oxide; Including, At least one metal oxide is dispersed on a support; Manganese oxide is present in the metal oxide catalyst composition in an amount of from 2.5% to 10% by weight, calculated as MnO2, based on the total weight of the metal oxide catalyst composition.

[0044] In certain other exemplary embodiments, the metal oxide catalyst composition comprises: at least one metal oxide consisting of manganese oxide or manganese oxide and titanium oxide, a support comprising particles of a composite oxide of aluminum and cerium, and optionally a dopant, in which the cerium is present in the composite oxide in an amount of 20% to 40% by weight or 20% to 30% by weight, calculated as CeO2, based on the total weight of the composite oxide; Including, At least one metal oxide is dispersed on a support; Manganese oxide is present in the metal oxide catalyst composition in an amount of from 3% to 8% by weight, calculated as MnO2, based on the total weight of the metal oxide catalyst composition.

[0045] In some further exemplary embodiments, the metal oxide catalyst composition comprises: at least one metal oxide consisting of manganese oxide or manganese oxide and titanium oxide, a support comprising particles of a composite oxide of aluminum and cerium, and optionally a dopant, in which the cerium is present in the composite oxide in an amount of 20% to 40% by weight or 20% to 30% by weight, calculated as CeO2, based on the total weight of the composite oxide; Including, At least one metal oxide is dispersed on a support; The manganese oxide is present in the metal oxide catalyst composition in an amount of from 3 wt. % to 8 wt. %, calculated as MnO2, based on the total weight of the metal oxide catalyst composition; The composite oxide of aluminum and cerium may include a phase of Al2O3 and a phase of CeO2, with a crystallite size of at least 9 nm, at least 9.5 nm, or at least 10 nm, as measured by X-ray powder diffraction (XRD) analysis in the fresh state.

[0046] The metal oxide catalyst compositions can be prepared conventionally, for example, by impregnating one or more precursors of at least one metal oxide onto the support.

[0047] Thus, in a second aspect, the present invention provides a process for preparing a non-vanadium metal oxide catalyst composition as described herein, comprising the steps of impregnating one or more precursors of at least one metal oxide onto a support, preferably in a water-soluble alcoholic solvent, and then optionally impregnating one or more precursors of a coating metal oxide.

[0048] In particular, the present invention provides a process for preparing the non-vanadium based metal oxide catalyst compositions described herein, the process comprising: - impregnating one or more precursors of at least one metal oxide onto support particles in a water-soluble alcoholic solvent to obtain supported particles; - calcining the supported particles to obtain calcined particles; - optionally impregnating one or more precursors of a coating metal oxide onto the calcined particles, followed by calcination; Includes.

[0049] Suitable water-soluble alcohols as a solvent for impregnating one or more precursors of at least one metal oxide can include, but are not limited to, methanol, ethanol, n-propanol, and isopropanol.

[0050] The at least one metal oxide, the support and the coating metal oxide are as described above for the metal oxide catalyst composition. The precursors of the at least one metal oxide and the coating metal oxide are not particularly limited. The precursors may be inorganic or organic soluble salts, complexes or other compounds of the metal.

[0051] The support may comprise or consist of particles of a composite oxide as described above for the metal oxide catalyst composition of the first aspect, in particular the support consists of particles of a composite oxide as described above for the metal oxide catalyst composition, optionally with a dopant such as Ti, Si, Zr, La or Ba.

[0052] When the support consists of particles of a complex oxide modified with a dopant, the modification may also be carried out by a process comprising impregnating one or more precursors of the dopant onto the particles of the complex oxide, preferably in a water-soluble alcoholic solvent, drying and optionally calcining.

[0053] Thus, the process according to the invention optionally comprises a step of impregnating one or more precursors of a dopant onto the particles of the composite oxide, preferably in a water-soluble alcoholic solvent, drying and optionally calcining, prior to impregnation with one or more precursors of at least one metal oxide.

[0054] In the process according to the present invention, the impregnation and calcination operations may be carried out in any conventional manner and under conditions well known in the art, except that a water-soluble alcohol solvent may be used to impregnate one or more precursors of at least one metal oxide onto the support particles.

[0055] In some embodiments, impregnation of the dopant and / or coating metal oxide precursor is also carried out in a water-soluble alcohol solvent.

[0056] As is well known in the art, the calcination step in the process according to the invention may follow the drying step.

[0057] Metal oxide catalyst compositions according to the present invention have been found to exhibit desirable thermal stability and improved NOx treatment efficiency as compared to conventional catalysts.

[0058] Without being bound by any theory, it is believed that the thermal stability may be related to the well-defined micro-structure of the complex oxide used as the support in the metal oxide catalyst composition. It is further believed that the improvement in NOx treatment efficiency may be related to the well-defined composition of the metal oxides involved, and also to the well-defined micro-structure of the complex oxide.

[0059] It has also been surprisingly found that catalysts prepared by impregnating one or more precursors of at least one metal oxide onto support particles in an aqueous alcohol solvent exhibit improved NOx conversion compared to catalysts prepared in the same manner except that water was used as the solvent instead of the aqueous alcohol.

[0060] In a third aspect, the present invention provides a method for treating an exhaust gas containing nitrogen oxides by selective catalytic reduction comprising contacting the exhaust gas with a metal oxide catalyst composition described herein in the presence of a reducing agent.

[0061] The metal oxide catalyst composition may be used in any conventional form in the process for the treatment of exhaust gases, for example, as a powder or extrudate, or as a washcoat on a substrate.

[0062] The metal oxide catalyst composition can be used as a powder having an average particle size of generally 1 to 100 microns (μm). The particle size of the metal oxide catalyst composition can be adjusted, for example, by grinding and / or sieving.

[0063] The metal oxide catalyst composition may be used as extrudates, i.e. shaped bodies obtained by extrusion. The extrudates may have any suitable structure for passing exhaust gas flow, preferably a honeycomb structure. The honeycomb structure may have flow channels as described herein below for the monolithic flow-through and wall-flow structures.

[0064] The metal oxide catalyst composition may be used as a washcoat on a substrate. The term "substrate" generally refers to a structure suitable for withstanding the conditions encountered in an exhaust stream, on which the metal oxide catalyst composition is supported in the form of a washcoat.

[0065] The substrate may be a monolithic flow-through structure having a plurality of fine parallel gas flow passages extending from an inlet face to an outlet face of the substrate such that the passages are open for fluid flow therethrough. The passages, which are essentially straight-line paths from their fluid inlets to their fluid outlets, are defined by walls to which a catalytic material is applied as a washcoat such that gas flowing through the passages contacts the catalytic material.

[0066] The substrate may alternatively be a monolithic wall-flow structure with a plurality of fine parallel gas flow passages extending from the inlet face along the outlet face of the substrate, with alternating passages being blocked at opposite ends. The passages are defined by walls to which a catalytic material is applied as a washcoat such that gas flowing through the passages contacts the catalytic material. This configuration requires that gas flow through the porous walls of the wall-flow substrate to reach the outlet face.

[0067] The term "washcoat" has its ordinary meaning in the art and refers to a thin, adherent coating of catalytic or other material applied to a substrate. Washcoats are generally formed by preparing a slurry containing the desired materials and, optionally, processing aids such as binders having a particular solids content (e.g., 15-60% by weight), then coating the slurry on the substrate, drying, and firing to provide the washcoat.

[0068] Thus, in a fourth aspect, the present invention provides a catalyst article comprising a metal oxide catalyst composition according to the present invention.

[0069] In a fifth aspect, the present invention provides a system for the treatment of exhaust gases, particularly from an internal combustion engine, comprising a reductant source, a catalyst article as described herein, and optionally one or more of a diesel oxidation catalyst (DOC), a three-way conversion catalyst (TWC), a four-way conversion catalyst (FWC), an uncatalyzed or catalyzed soot filter (CSF), an ammonia oxidation catalyst (AMOx), a NOx trap, a NOx absorber catalyst, a hydrocarbon trap catalyst, a sensor, and a mixer.

[0070] The catalyst article according to the present invention may be located downstream of an internal combustion engine, such as a diesel engine, particularly a heavy duty diesel engine, in a close-coupled position, downstream of a close-coupled position, or both. It is preferred that the catalyst article according to the present invention is located downstream of the internal combustion engine in a close-coupled position.

[0071] The exhaust gas treatment system preferably further comprises a diesel oxidation catalyst located downstream of the engine and upstream of the catalytic article according to the present invention. In some embodiments, the exhaust gas treatment system preferably comprises both a diesel oxidation catalyst and a catalyzed soot filter located upstream of the catalytic article according to the present invention.

[0072] 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. 1. A non-vanadium metal oxide catalyst composition comprising: at least one metal oxide, including manganese oxide; A support including particles of a composite oxide of aluminum and at least one metal selected from cerium, manganese, and titanium, in which aluminum is present in the composite oxide in an amount of 50% by weight to 80% by weight, calculated as Al2O3, based on the total weight of the composite oxide; Including, At least one metal oxide is dispersed on a support; A non-vanadium based metal oxide catalyst composition, wherein manganese oxide is present in the metal oxide catalyst composition in an amount of from 2.5% by weight to 10% by weight, calculated as MnO2, based on the total weight of the metal oxide catalyst composition. 2. The non-vanadium metal oxide catalyst composition of embodiment 1, wherein the at least one metal oxide further comprises an oxide of titanium (Ti), iron (Fe), magnesium (Mg), or aluminum (Al), or any combination thereof. 3. The non-vanadium metal oxide catalyst composition of embodiment 2, wherein each of the oxides of Ti, Fe, Mg, and Al is present in an amount of 10 wt. % or less, 8 wt. % or less, or 6 wt. % or less, calculated as the respective oxide, based on the total weight of the metal oxide catalyst composition. 4. The non-vanadium metal oxide catalyst composition of any of embodiments 1-3, wherein the manganese oxide is present in an amount of 3 wt. % to 8 wt. %, calculated as MnO2, based on the total weight of the metal oxide catalyst composition. 5. The non-vanadium metal oxide catalyst composition of any one of embodiments 1 to 4, wherein the at least one metal oxide further comprises titanium oxide, which is preferably present in an amount of 1 to 6 wt. %, or 2 to 4 wt. %, calculated as TiO2, based on the total weight of the catalyst composition. 6. The non-vanadium metal oxide catalyst composition of any of the preceding embodiments, wherein the at least one metal oxide further comprises iron oxide, and the iron oxide is preferably present in an amount of 1 to 5 wt. %, or 3 to 5 wt. %, calculated as Fe2O3, based on the total weight of the metal oxide catalyst composition. 7. The non-vanadium metal oxide catalyst composition according to any one of the preceding embodiments, wherein the support comprises particles of a composite oxide and a dopant selected from Ti, Si, Zr, La and Ba, the dopant being preferably present in an amount of 1 to 10% by weight, or 3 to 6% by weight, calculated as the respective oxide, based on the total weight of the metal oxide catalyst composition. 8. The non-vanadium metal oxide catalyst composition according to any one of the preceding embodiments, wherein the support comprises particles of a composite oxide of aluminum, cerium, and optionally manganese and / or titanium. 9. The non-vanadium metal oxide catalyst composition according to embodiment 7, wherein the support consists of particles of a composite oxide of aluminum and cerium, and optionally a dopant. 10. The non-vanadium metal oxide catalyst composition of embodiment 8 or 9, wherein cerium is present in the composite oxide in an amount of 20% to 50% by weight, 20% to 40% by weight, or 20% to 30% by weight, calculated as CeO2, based on the total weight of the composite oxide. 11. The non-vanadium metal oxide catalyst composition of embodiment 10, wherein the composite oxide of aluminum and cerium comprises a phase of Al2O3 and a phase of CeO2, and has a crystallite size of at least 5 nm, preferably at least 9 nm, at least 9.5 nm, or at least 10 nm, as measured by XRD analysis in the fresh state. 12. The non-vanadium metal oxide catalyst composition of any of the preceding embodiments, further comprising a coating metal oxide, such as titanium oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, or any combination thereof. 13. A process for preparing the non-vanadium metal oxide catalyst composition according to any of the preceding embodiments, comprising impregnating one or more precursors of at least one metal oxide onto a support, and then, optionally, impregnating one or more precursors of a coating metal oxide. 14. The process according to embodiment 13, wherein the impregnation of one or more precursors of at least one metal oxide onto the support is carried out in a water-soluble alcoholic solvent. 15. The process of embodiment 13 or 14, wherein the water-soluble alcoholic solvent is selected from methanol, ethanol, n-propanol and isopropanol. 16. The process according to any one of embodiments 13 to 15, further comprising the step of impregnating one or more precursors of a dopant onto the particles of the composite oxide, preferably in a water-soluble alcoholic solvent, prior to impregnation with one or more precursors of at least one metal oxide. 17. A method for the treatment of an exhaust gas containing nitrogen oxides by selective catalytic reduction, comprising contacting the exhaust gas with a metal oxide catalyst composition according to any one of embodiments 1 to 12 in the presence of a reducing agent. 18. The method of embodiment 17, wherein the exhaust gas originates from an internal combustion engine, such as a diesel engine, in particular a heavy-duty diesel engine. 19. A catalyst article comprising the metal oxide catalyst composition of any of embodiments 1-12, for example in the form of a powder or extrudate, or in the form of a washcoat on a substrate. 20. The catalytic article of embodiment 19, wherein the substrate is a monolithic flow-through structure or a monolithic wall-flow structure. 21. A system, particularly for the treatment of exhaust gases from an internal combustion engine, comprising a reductant source, a catalyst article according to embodiment 19 or 20, and optionally one or more of a diesel oxidation catalyst (DOC), a three-way catalyst (TWC), a four-way catalyst (FWC), an uncatalyzed or catalyzed soot filter (CSF), an ammonia oxidation catalyst (AMOx), a NOx trap, a NOx absorber catalyst, a hydrocarbon trap catalyst, a sensor, and a mixer. 22. The system of embodiment 21, wherein the catalyst article is positioned downstream of an internal combustion engine, such as a diesel engine, particularly a heavy-duty diesel engine, in a close-coupled position, downstream of a close-coupled position, or both, preferably in a close-coupled position.

[0073] The present invention will be further illustrated by the following examples which set forth particularly advantageous embodiments. The examples are provided to illustrate the invention, but they are not intended to limit the invention. EXAMPLES

[0074] I. Preparation Examples Example 1 - Preparation of vanadium-based metal oxide catalyst (3V@8W-TiO2) 0.1909g of ammonium metatungstate was dissolved in 30mL of deionized water and stirred uniformly, to which 2g of anatase-type TiO2 was added and stirred for 1 hour. The resulting solution was transferred to a rotary evaporator and dried at 60°C. The resulting product was then calcined in a muffle furnace at 500°C for 3 hours with a heating rate of 2°C / min to obtain a WO3-modified TiO2 support. 0.0867g of NH4VO3 was dissolved in a solution of 0.5g of oxalic acid in 30mL of deionized water. The above obtained WO3 modified TiO2 support was then added to the solution and stirred for 1 hour. The mixed solution was transferred to a rotary evaporator and dried at 60°C. The obtained product was then calcined in a muffle furnace at 500°C for 3 hours with a heating rate of 2°C / min.

[0075] Example 2 - Preparation of non-vanadium metal oxide catalyst with alumina support (MnCeTi@Al) First, a given amount of γ-Al2O3 support was prepared in a 25 mL crucible. The calculated amount of Ce(NO3)3·6H2O and Mn(NO3)2·4H2O were dissolved in 1.44 mL of absolute ethanol under ultrasonication for 10 seconds in a 5 mL beaker. Then, the calculated amount of tetrabutyl titanate was added to the solution. This solution was then added to the crucible along with the γ-Al2O3 support under stirring to reach incipient wetness. The mixture in the crucible was dried in an oven at 80 °C for 2 hours and calcined at 500 °C for 3 hours with a heating rate of 2 °C / min. The calcined powder was naturally cooled to room temperature to obtain the catalyst. The formulations of the different samples are listed in Table 1 below.

[0076] [Table 1] * The percentages refer to the amounts (wt%) of Mn, Ce and Ti in total, calculated as their respective oxides, based on the total weight of the catalyst.

[0077] Example 3 - Preparation of non-vanadium metal oxide catalysts (Mn@AlCe, MnTi@AlCe) A crucible was charged with a certain amount of aluminum and cerium composite oxide (AlCe10, AlCe20, AlCe30 or AlCe50) as a support. A calculated amount of Mn(NO3)2·4H2O was dissolved in 1.44mL of absolute ethanol in a 5mL beaker under ultrasonication for 10 seconds. When titanium was also supported, a calculated amount of tetrabutyl titanate was added to the above solution. Thus, the impregnation solution was prepared.

[0078] The solution for impregnation was added to the crucible along with the carrier under stirring to reach incipient wetness. The mixture in the crucible was dried in an oven at 80°C for 2 hours. The dried powder was heated to 500°C at a rate of 2°C / min and held for 3 hours to obtain the calcined powder. The calcined powder was naturally cooled to room temperature to obtain the catalyst. The formulations of the different samples are listed in Table 2 below.

[0079] Example 4 - Preparation of non-vanadium metal oxide catalyst (7Mn@AlCe20(H2O)) in water Catalyst samples were prepared in the same manner as described in Example 3, except that absolute ethanol was replaced with an equal amount of deionized water.

[0080] Example 5 - Preparation of non-vanadium metal oxide catalyst (8Mn@Ti-AlCe20) with Ti-modified support A predetermined amount of aluminum and cerium composite oxide (AlCe20) was placed in a crucible as a support. A calculated amount of tetrabutyl titanate was dissolved in 1.44 mL of absolute ethanol under ultrasonication until it became transparent. This solution was then added to the crucible along with AlCe20 under stirring to reach an incipient wetness state. The mixture in the crucible was dried in an oven at 80 °C for 2 hours to obtain the Ti-modified AlCe20 support. A calculated amount of Mn(NO3)2·4H2O was then dissolved in 1.44 mL of absolute ethanol in a 5 mL beaker under ultrasonication for 10 seconds. This solution was then added to the crucible along with the support under stirring to reach an incipient wetness state. The powder was heated to 500 °C at a rate of 2 °C / min and held for 3 hours to obtain the calcined powder. The calcined powder was naturally cooled to room temperature to obtain the catalyst. The composition of the samples is also listed in Table 2 below.

[0081] [Table 2] * The numbers before Mn and Ti represent their amounts (wt%) calculated as their respective oxides based on the total weight of the catalyst, and the number after Ce represents their amount (wt%) calculated as CeO2 based on the weight of the composite oxide of Al and Ce.

[0082] ** "(H2O)" refers to the solvent for the synthesis.

[0083] Example 6 - Preparation of non-vanadium metal oxide catalysts (5Fe6.5Mn3.3Ti@AlCe20, 5Fe7Mn@AlCe20) A given amount of AlCe20 was placed in a crucible as a support. Calculated amounts of Mn(NO3)2·4H2O and Fe(NO3)3·9H2O were dissolved in 1.44mL of absolute ethanol in a 5mL beaker under ultrasonic waves for 10 seconds. When titanium was also loaded, a calculated amount of tetrabutyl titanate was added to the above solution. Thus, the impregnation solution was prepared.

[0084] The solution for impregnation was added to the crucible along with the AlCe20 support under stirring to reach incipient wetness. The mixture in the crucible was dried in an oven at 80°C for 2 hours. The dried powder was heated to 500°C at a rate of 2°C / min and held for 3 hours to obtain the calcined powder. The calcined powder was then naturally cooled to room temperature to obtain the catalyst. The formulations of the different samples are listed in Table 3 below.

[0085] [Table 3] * The numbers before Fe, Mn, and Ti represent their amounts (wt%) calculated as their respective oxides based on the total weight of the catalyst, and the number after Ce represents their amount (wt%) calculated as CeO2 based on the weight of the composite oxide of Al and Ce.

[0086] Example 7 - Preparation of TiO2-coated metal oxide catalysts (TiO2-coated 7Mn@AlCe20, Al2O3-coated 7Mn@AlCe20) 1 g of catalyst 7Mn@AlCe20 was first prepared in the same manner as described in Example 1.

[0087] A given amount of diisopropyl bis(triethanolamine) titanate (M=466.4) or aluminum isopropoxide was dissolved in 1.44 mL of absolute ethanol under ultrasonic until it became clear. Then, this solution was added to the crucible with catalyst 7Mn@AlCe20 under stirring to reach incipient wetness. The mixture in the crucible was dried in an oven at 80°C for 2 hours. The dried powder was heated to 500°C at a rate of 2°C / min and held for 3 hours to obtain the calcined powder. The calcined powder was then naturally cooled to room temperature to obtain the catalyst with coating. The formulations of the different samples are listed in Table 4 below.

[0088] Example 8 - Preparation of SiO2-coated metal oxide catalyst (SiO2-coated 7Mn@AlCe20) 1 g of catalyst 7Mn@ / AlCe20 catalyst, prepared in the same manner as described in Example 1, was dispersed in 100 mL of deionized water, and then the pH was adjusted to 8 with ammonium hydroxide. o When heated at 100°C, a predetermined amount of tetraethyl orthosilicate was added with vigorous stirring for 1 h. The formed precipitate was then separated and washed with 1 L of deionized water until the pH was 7. The wet mixture was dried in an oven at 80°C for 2 h. The dried powder was heated to 500°C at a rate of 2°C / min and held for 3 h to obtain the calcined powder. The calcined powder was then naturally cooled to room temperature to obtain the catalyst with coating. The formulations of the different samples are also listed in Table 4 below.

[0089] [Table 4] * The ratios in brackets refer to molar ratios.

[0090] Example 9 - Preparation of MgO-coated metal oxide catalyst (MgO-coated 7Mn@AlCe20) 1 g of catalyst 7Mn@AlCe20 was first prepared in the same manner as described in Example 1. 0.1908 g of Mg(NO3)2·4H2O was dissolved in 1.44 mL of absolute ethanol in a 5 mL beaker under ultrasonication for 10 seconds. This solution was added to the crucible with catalyst 7Mn@AlCe20 under stirring to reach incipient wetness. The mixture in the crucible was dried in an oven at 80 °C for 2 hours. The dried powder was heated to 500 °C at a rate of 2 °C / min and held for 3 hours to obtain the calcined powder. The calcined powder was naturally cooled to room temperature to obtain the catalyst.

[0091] Example 10 - Preparation of non-vanadium metal oxide catalyst based on Al and Ce composite oxide (10Mn@AlCe52) with high Ce content A composite oxide of Al and Ce was prepared according to Example 1 of Chinese Patent Publication No. 106824173. The obtained composite oxide AlCe52 was impregnated with Mn(NO3)2·4H2O in the same manner as in Example 3.

[0092] II.SCR performance measurement II.1 General Procedure The SCR performance measurements were performed using a fixed-bed quartz flow reactor (inner diameter = 4 mm). The reactor was packed with 0.15 g of a catalyst sample with 40-60 mesh (approximately 250-400 μm) and cordierite particles as a diluent up to a total length of 32 mm. The measurements were performed in the temperature range of 90-480°C.

[0093] The gas feed consisted of 500 vppm NO, 500 vppm NH, 10 vol% O, 5 vol% H0, 5 vol% CO, and the balance N. The total flow rate was 150,000 h. -1 The gas hourly space velocity (GHSV) was controlled at 475 mL / min, which corresponds to a gas hourly space velocity (GHSV) of 1000 mL / min. The GHSV was calculated based on the catalyst volume. Cordierite was fixed as an auxiliary agent so that the volume of all catalysts was the same.

[0094] The gas concentrations of NO, NO2, NH3, H2O, and N2O were simultaneously monitored by an FTIR spectrometer (Thermo Fisher). The SCR catalyst activity was recorded after the reaction system reached a steady state. The NO conversion was calculated according to the following equation:

[0095]

number

[0096] Catalyst aging conditions: 10% H2O in air at 650℃ for 50 hours.

[0097] Sulfation conditions: 0.15 g of 40-60 mesh catalyst was packed into a fixed-bed quartz flow reactor (inner diameter = 4 mm). The sulfation process was carried out at a temperature of 300 °C. The gas feed consisted of 40 vppm SO2, 10 vol.% O2, 5 vol.% H2O, 5 vol.% CO2, and the balance N2. The total flow rate was 75,000 h -1 235 mL min -1 was controlled.

[0098] Desulfation conditions: The desulfation process was carried out at a temperature of 600 °C for 3 h with 475 mL / min of N2 as the balance gas. The total flow rate was 150,000 h -1 475 mL min -1 was controlled.

[0099] II.2 Test Results The test results are summarized in the table below.

[0100] [Table 5]

[0101] As can be seen from the results, the catalyst according to the invention exhibits higher NO conversion at temperatures up to 210° C. than the conventional vanadium-based catalyst and the catalyst having a composition not according to the invention.

[0102] [Table 6]

[0103] [Table 7]

[0104] As can be seen from the results, the catalysts according to the invention have desirable thermal stability without significant loss of activity upon aging. The catalysts with the coating even show improved activity upon aging.

[0105] [Table 8]

[0106] III. Characterization of composite oxides as supports The composite oxides as supports in the above catalysts were characterized by XRD. The patterns of each sample are shown in Figures 1 and 2, and the d values ​​shown for each sample are 2θ=28.5. o The composite oxide and CeO2 crystallite size of each sample obtained from the XRD pattern are summarized in Table 9 below.

[0107] The composite oxides were also characterized for surface area by BET method, pore volume by BJH method and pore diameter, the measurements are also summarized in Table 9 below.

[0108] [Table 9] * Aging: 50 hours at 650℃ in air containing 10% H2O.

[0109] All the composite oxides as supports show an increased crystallite size upon aging. The smaller the increase in crystallite size, the more stable the composite oxide. It can be seen that the composite oxides with at least 50% aluminum (calculated as Al2O3) used in the catalyst according to the invention show a higher hydrothermal stability than the composite oxide AlCe52.

[0110] Although the present invention has been described herein with reference to specific embodiments and examples, it should be understood that these embodiments and examples are merely illustrative 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 compositions and processes of the present invention without departing from the spirit and scope of the present invention. Therefore, the present invention is intended to include modifications and variations that come within the scope of the appended claims and their equivalents.

Claims

1. 1. A non-vanadium-based metal oxide catalyst composition comprising: at least one metal oxide, including manganese oxide; - containing particles of a composite oxide of aluminum and at least one metal selected from cerium, manganese and titanium, wherein the aluminum is contained in the composite oxide in an amount of Al based on the total weight of the composite oxide. ２ O ３ a carrier present in an amount of 50% to 80% by weight, calculated as Including, the at least one metal oxide is dispersed on the support; Manganese oxide is present in the metal oxide catalyst composition in an amount of MnO based on the total weight of the metal oxide catalyst composition. ２ The non-vanadium based metal oxide catalyst composition is present in an amount of from 2.5% to 10% by weight, calculated as

2. 2. The non-vanadium metal oxide catalyst composition of claim 1, wherein the at least one metal oxide further comprises an oxide of titanium (Ti), iron (Fe), magnesium (Mg), or aluminum (Al), or any combination thereof.

3. 3. The non-vanadium metal oxide catalyst composition of claim 2, wherein each of the oxides of Ti, Fe, Mg, and Al is present in an amount of 10 wt. % or less, 8 wt. % or less, or 6 wt. % or less, calculated as the respective oxide, based on the total weight of the metal oxide catalyst composition.

4. manganese oxide is MnO based on the total weight of the metal oxide catalyst composition ２ 4. The non-vanadium metal oxide catalyst composition of any one of claims 1 to 3, wherein the non-vanadium metal oxide catalyst composition is present in an amount of from 3% to 8% by weight, calculated as

5. The at least one metal oxide further comprises titanium oxide, which preferably comprises TiO ２ 4. The non-vanadium metal oxide catalyst composition of any one of claims 1 to 3, wherein the non-vanadium metal oxide catalyst composition is present in an amount of from 1 to 6 wt. %, or from 2 to 4 wt. %, calculated as

6. The at least one metal oxide further comprises iron oxide, and the iron oxide preferably comprises Fe, based on the total weight of the metal oxide catalyst composition. ２ O ３ 4. The non-vanadium metal oxide catalyst composition of any one of claims 1 to 3, wherein the non-vanadium metal oxide catalyst composition is present in an amount of from 1 to 5 wt. %, or from 3 to 5 wt. %, calculated as

7. 4. The non-vanadium metal oxide catalyst composition according to claim 1, wherein the support comprises particles of the composite oxide and a dopant selected from Ti, Si, Zr, La and Ba, and the dopant is preferably present in an amount of 1 to 10 wt. %, or 3 to 6 wt. %, calculated as the respective oxide, based on the total weight of the metal oxide catalyst composition.

8. 4. The non-vanadium metal oxide catalyst composition according to claim 1, wherein the support comprises particles of a composite oxide of aluminum, cerium, and optionally manganese and / or titanium.

9. 8. The non-vanadium metal oxide catalyst composition according to claim 7, wherein the support comprises particles of a composite oxide of aluminum and cerium, and optionally a dopant.

10. Cerium is contained in the composite oxide in an amount of CeO based on the total weight of the composite oxide. ２ 9. The non-vanadium metal oxide catalyst composition of claim 8, wherein the non-vanadium metal oxide catalyst composition is present in an amount of from 20 to 50 wt. %, from 20 to 40 wt. %, or from 20 to 30 wt. %, calculated as

11. The composite oxide of aluminum and cerium is Al ２ O ３ phase and CeO ２ and having a crystallite size of at least 5 nm, preferably at least 9 nm, at least 9.5 nm, or at least 10 nm, as measured by XRD analysis in the fresh state.

12. 4. The non-vanadium metal oxide catalyst composition of any one of claims 1 to 3, further comprising a coating metal oxide, such as titanium oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, or any combination thereof.

13. 4. A process for preparing the non-vanadium metal oxide catalyst composition of any one of claims 1 to 3, comprising the steps of impregnating one or more precursors of said at least one metal oxide onto said support, and then optionally impregnating one or more precursors of said coating metal oxide.

14. 14. The process of claim 13, wherein the impregnation of one or more precursors of at least one metal oxide onto a support is carried out in an aqueous alcoholic solvent.

15. 14. The process of claim 13, wherein the water-soluble alcoholic solvent is selected from methanol, ethanol, n-propanol, and isopropanol.

16. 14. The process according to claim 13, further comprising the step of impregnating one or more precursors of a dopant onto the particles of the composite oxide, preferably in an aqueous alcohol solvent, prior to impregnation with one or more precursors of the at least one metal oxide.

17. 4. A method for the treatment of an exhaust gas containing nitrogen oxides by selective catalytic reduction, the method comprising contacting the exhaust gas with the metal oxide catalyst composition of any one of claims 1 to 3 in the presence of a reducing agent.

18. 18. The method of claim 17, wherein the exhaust gas originates from an internal combustion engine, such as a diesel engine, in particular a heavy-duty diesel engine.

19. A catalyst article comprising the metal oxide catalyst composition of any one of claims 1 to 3, for example in the form of a powder or extrudate, or in the form of a washcoat on a substrate.

20. 20. The catalytic article of claim 19, wherein the substrate is a monolithic flow-through structure or a monolithic wall-flow structure.

21. 20. A system for the treatment of exhaust gases, particularly from an internal combustion engine, comprising a reductant source, the catalyst article of claim 19, and optionally one or more of a diesel oxidation catalyst (DOC), a three-way catalyst (TWC), a four-way catalyst (FWC), an uncatalyzed or catalyzed soot filter (CSF), an ammonia oxidation catalyst (AMOx), a NOx trap, a NOx absorber catalyst, a hydrocarbon trap catalyst, a sensor, and a mixer.

22. 22. The system of claim 21, wherein the catalytic article is positioned downstream of an internal combustion engine, such as a diesel engine, particularly a heavy-duty diesel engine, in a close-coupled position, downstream of a close-coupled position, or both, preferably in a close-coupled position.

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