Ammonia oxidation catalyst and exhaust gas treatment method for internal combustion engine

Abstract

The application belongs to the technical field of catalysts, and particularly relates to an ammonia oxidation catalyst and an internal combustion engine tail gas treatment method. The ammonia oxidation catalyst comprises a first carrier and a catalyst coating arranged on the surface of the first carrier. The catalyst coating comprises a first catalyst component and a second catalyst component. The first catalyst component comprises a noble metal active component and an oxide carrier. The second catalyst component comprises a molecular sieve. The molecular sieve comprises a molecular sieve carrier and an active component. The active component comprises a first metal and an M element. The first metal is selected from one of copper or iron. The M element is selected from at least one of zinc, cobalt, silver, vanadium and bismuth. The catalyst at least solves the problem that existing ammonia oxidation catalysts are difficult to simultaneously achieve high ammonia oxidation efficiency and nitrogen selectivity under full working conditions.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, and particularly relates to an ammonia oxidation catalyst and a method for treating internal combustion engine exhaust gas. Background Technology With increasingly stringent emission regulations both domestically and internationally, further reducing diesel engine exhaust pollutant emission limits is a future development trend. NH3-SCR technology is currently the most common exhaust gas purification and denitrification technology, aiming to achieve high NOx emission levels. x High conversion efficiency typically requires a high ammonia-to-nitrogen ratio, leading to NH3 levels in the exhaust gas exceeding emission limits. Installing an ammonia oxidation catalyst (ASC) downstream of the SCR is currently the primary method for handling ammonia leaks. ASCs typically employ a composite structure of a molecular sieve layer / precious metal layer to convert ammonia; however, this process not only generates harmless nitrogen (N2) but also produces a certain amount of nitrogen oxides (NOx). x ) and the strong greenhouse gas nitrous oxide (N2O). N2O is mainly generated through two pathways: one is the direct oxidation of ammonia on the surface of noble metals; the other is the formation of NO as an intermediate product from the oxidation of ammonia. x These byproducts are generated by further reaction with residual ammonia on the catalyst surface. The formation of these byproducts brings new emission control challenges to the ASC system, while addressing the ammonia slip problem.

[0002] Currently, the main technical means to reduce N2O formation in ASCs include optimizing the noble metal composition and adjusting the catalyst coating structure. For example, the reaction selectivity can be adjusted by changing the proportion and dispersion state of noble metals such as platinum and palladium, or by adding metal oxide promoters such as cerium and zirconium. Some studies have also improved the mass transfer process of reactants by designing gradient coatings or adjusting the thickness of double-layer coatings. However, existing methods are difficult to achieve a balance between high ammonia conversion and low N2O selectivity simultaneously. Summary of the Invention

[0003] In view of the above problems, this application provides an ammonia oxidation catalyst and a method for treating internal combustion engine exhaust gases. The catalyst described in this invention at least solves the problem that existing ammonia oxidation catalysts are unable to simultaneously achieve high ammonia oxidation efficiency and nitrogen selectivity under all operating conditions.

[0004] On one hand, the present invention provides an ammonia oxidation catalyst, comprising a first support and a catalyst coating disposed on the surface of the first support; the catalyst coating comprises a first catalyst component and a second catalyst component; the first catalyst component comprises a noble metal active component and an oxide support; the second catalyst component comprises a molecular sieve; The molecular sieve includes a molecular sieve carrier and an active component; the active component includes a first metal and an element M; the first metal is selected from copper or iron; the element M is selected from at least one of zinc, cobalt, silver, vanadium, and bismuth.

[0005] The above-mentioned catalyst system is constructed by combining the efficient ammonia oxidation function of the noble metal active component with the adsorption, retention and catalytic functions of the molecular sieve component, and the special regulatory effect of the M element, to jointly solve the problem that traditional ASC is difficult to suppress the generation of nitrous oxide when efficiently eliminating ammonia.

[0006] The second catalyst component improves the physicochemical properties and reactivity of the molecular sieve by introducing a specific element M to construct a multi-component synergistic system with Cu or Fe. The introduction of element M can modify the molecular sieve framework and active centers: on the one hand, it regulates the distribution and intensity of acidic sites, improving the hydrothermal stability of the molecular sieve support itself; on the other hand, the aforementioned multi-component synergistic system can optimize the adsorption, activation, and conversion pathways of key intermediates (such as nitrate and nitrite species) during the reaction, thereby inhibiting the occurrence of excessive oxidation reactions and reducing the selectivity of N2O byproduct formation while maintaining high nitrogen oxide conversion efficiency.

[0007] Specifically, the first carrier may be made of materials known in the art, such as ceramics or ceramic-like materials, such as cordierite, α-alumina, aluminosilicate, cordierite-alumina, silicon carbide, aluminum titanate, silicon nitride, zircon, mullite, zircon, zircon-mullite, zirconium silicate, sillimanite, magnesium silicate, petalite, spodumene, alumina-silica-magnesium oxide, or zirconium silicate, etc. In addition, it may be a metal, such as heat-resistant metals or metal alloys, specifically such as titanium or stainless steel.

[0008] Specifically, the noble metal active component includes one or more of platinum or palladium; the oxide support includes one or more of aluminum oxide, titanium oxide, or silicon oxide.

[0009] Pt or Pd exhibit intrinsic activity for NH3 adsorption-dehydrogenation, while Al2O3, TiO2, and SiO2 supports can provide high specific surface area and acidity, stabilizing the dispersion of noble metals, thereby maintaining the initial activity and durability of the catalyst over a wide temperature range.

[0010] Furthermore, based on the total mass of the molecular sieve carrier, the first metal loading is ≥1 wt%.

[0011] The above range can balance the low-temperature activity and high-temperature stability of the catalyst. Too low a loading will result in insufficient active sites; too high a loading will easily cause agglomeration and sintering of active components under harsh conditions, which is not conducive to long-term stable operation.

[0012] Preferably, based on the total mass of the molecular sieve support, the first metal loading can be, for example, 1 wt%, 1.5 wt%, 2 wt%, 2.3 wt%, 2.6 wt%, 2.8 wt%, 3.0 wt%, 3.4 wt%, 3.5 wt%, 4.0 wt%, 5.0 wt%, 7.0 wt%, 9.0 wt%, or 10.0 wt%.

[0013] Preferably, based on the total mass of the molecular sieve support, the loading of element M is ≥0.1wt%. Controlling the loading of element M within this range achieves a balance between improving hydrothermal stability and maintaining high main reaction activity, while effectively suppressing the formation of byproducts such as N₂O. The aforementioned loading level of element M can stabilize the first metal Cu / Fe sites and the molecular sieve framework, while avoiding pore blockage or acidic site coverage due to excessive loading.

[0014] Preferably, based on the total mass of the molecular sieve support, the loading of element M can be, for example, 0.1 wt%, 0.3 wt%, 0.5 wt%, 1.0 wt%, 1.2 wt%, 1.3 wt%, 1.5 wt%, 1.8 wt%, 2.0 wt%, or 3.0 wt%.

[0015] Preferably, the M element is present in the catalyst coating in at least one of the following ways: (a) Loaded on the molecular sieve support; (b) Dispersed in the catalyst coating as an additive.

[0016] The introduction of element M primarily functions in two ways: firstly, it acts as a modifier, entering the molecular sieve framework or forming synergistic active sites with copper or iron; secondly, it acts as a dispersant distributed within the coating. When element M is used as a modifier, it can finely modulate the electronic structure and acidity of the molecular sieve's active sites, enhancing the molecular sieve's resistance to ammonia and NO. x The adsorption and activation capabilities of M element promote the efficient SCR reaction and direct the reaction pathway to generate nitrogen (N2). When M element is used as a dispersant in the coating, it may affect the surface state of adjacent noble metal active centers through electronic or geometric effects, thereby regulating its oxidation selectivity, adjusting the oxidation depth of ammonia, and inhibiting the further oxidation of NH3 to NO. x And the resulting excessive oxidation of N2O by side reactions.

[0017] It should be noted that the preparation methods of the M-element modified catalyst in this invention include, but are not limited to, one or a combination of several of the following preparation methods: liquid phase ion exchange (stepwise ion exchange, ion co-exchange), solid phase ion exchange, equal volume impregnation, excess impregnation, rotary evaporation impregnation, and mechanical grinding.

[0018] Preferably, the molecular sieve support is selected from one or more of the following topologies: ACO, AEI, AEL, AEN, AFI, AFN, AFT, AFX, ANA, APC, APD, ATT, BEA, BIK, CDO, CHA, DDR, DFT, DON, EAB, EDI, EPI, ERI, ESV, ETL, FAU, FER, GIS, GOO, IHW, ITE, ITW, LEV, LTA, KFI, MER, MFI, MON, MOR, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, SOD, THO, TSC, UEI, UFI, VFI, VNI, YUG, ZON, and / or eutectic molecular sieves or commensal organisms having the above topologies. All of the above molecular sieve topologies possess suitable pore structures and ion exchange capacities, providing a stable site environment for Cu / Fe and M elements. Among them, the small-pore CHA, AEI, and AFX structures perform well in diesel vehicle exhaust SCR applications due to their eight-membered ring pores and excellent hydrothermal stability; while the large-pore BEA and FAU structures are suitable for processing reactant systems with larger molecular sizes.

[0019] For example, the silica-to-alumina ratio of the molecular sieve support ranges from 3 to 200. Controlling the silica-to-alumina ratio of the molecular sieve framework between 3 and 200 helps to balance its structural stability, acidity, and ion exchange capacity, providing a suitable environment for the effective loading and stable existence of active metals.

[0020] In one possible implementation, the catalyst coating is a single-layer structure, and the first catalyst component and the second catalyst component are uniformly mixed in the catalyst coating.

[0021] Preferably, the catalyst coating has a double-layer structure, comprising a first coating close to the first support and a second coating away from the first support; the first coating comprises the first catalyst component; optionally, the first coating further comprises the second catalyst component; the second coating comprises the second catalyst component. In some embodiments, the structural design of the catalyst coating can more effectively leverage the improvement effect of introducing the M element on the molecular sieve catalyst.

[0022] In a monolayer hybrid structure, the M-element modified molecular sieve is uniformly dispersed and in close contact with the noble metal component. This structure promotes the rapid capture and conversion of intermediate products (such as NO and NO2) generated from ammonia oxidation by adjacent molecular sieve active sites, enhancing the coupling between ammonia oxidation and SCR reactions through microscale synergistic effects. The introduction of the M element helps optimize the properties of the molecular sieve active sites, thereby guiding the main reaction pathway towards nitrogen (N2) generation and suppressing side reaction pathways that may form N2O, achieving efficient ammonia conversion while maintaining good selectivity.

[0023] In the bilayer structure, spatial stratification further enhances the functional positioning of the M-element modified molecular sieve. The top layer (second coating) typically concentrates the M-element modified molecular sieve, primarily responsible for the adsorption, storage, and subsequent SCR reaction of ammonia; the bottom layer (first coating) is mainly composed of noble metals, responsible for the initial oxidation of ammonia. This separation design allows the reactants to undergo a sequential process of "adsorption-oxidation-re-reaction," which is beneficial for controlling the reaction process. When the bottom layer is a pure noble metal layer, the functional zoning is clear, and the system stability is good; when the bottom layer is a mixed layer of noble metals and molecular sieves, a functional gradient transition is formed, which can improve the overall efficiency of the reaction. The concentration of M element in the top layer can more effectively improve the microenvironment of the SCR reaction and enhance the NO removal process. x The ability to convert intermediates into N2 and effectively suppress N2O formation is enhanced. Therefore, the bilayer structure provides an effective design approach for achieving higher nitrogen selectivity and lower N2O emissions.

[0024] On the other hand, the present invention also provides a method for treating exhaust gas from an internal combustion engine, wherein exhaust gas containing escaped ammonia is contacted with the ammonia oxidation catalyst, and under the action of the catalyst, the escaped ammonia is selectively oxidized and the formation of nitrous oxide is suppressed.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects: 1. This invention addresses the problem of traditional ASCs' inability to suppress nitrous oxide formation during efficient ammonia removal by synergistically combining the high-efficiency ammonia oxidation function of the noble metal active component with the adsorption, retention, and catalytic functions of the molecular sieve component, and further incorporating the special regulatory effect of element M. The second catalyst component, through the introduction of a specific element M and the construction of a multi-component synergistic system with Cu or Fe, improves the physicochemical properties and reactivity of the molecular sieve. The introduction of element M modifies the molecular sieve framework and active centers: on the one hand, it regulates the distribution and intensity of acidic sites, enhancing the hydrothermal stability of the molecular sieve support itself; on the other hand, the aforementioned multi-component synergistic system optimizes the adsorption, activation, and conversion pathways of key intermediates (such as nitrates and nitrites) during the reaction, thereby maintaining high nitrogen oxide conversion efficiency while inhibiting excessive oxidation reactions and reducing the selectivity of N2O byproduct formation.

[0026] 2. This invention synergistically designs the macroscopic structure of the catalyst coating and the introduction method of element M. In the monolayer mixed structure, the element M-modified molecular sieve and the noble metal component are uniformly dispersed and in close contact, promoting the rapid capture and conversion of intermediate products (such as NO and NO2) generated by ammonia oxidation by the adjacent active sites of the molecular sieve, thus realizing the oxidation of NH3 and NO. x The reduced "short-range rapid coupling" facilitates the rapid elimination of ammonia over a wide temperature range while maintaining good N2 selectivity, and the process is simple. In the bilayer structure, spatial stratification further enhances the functional positioning of the M-element modified molecular sieve. By preferentially concentrating the M element (especially in the form of a molecular sieve support) on the top layer, an ideal "adsorption-oxidation-re-reaction" reaction pathway is established: the top layer is mainly responsible for the adsorption, storage, and subsequent SCR reaction of ammonia, while the bottom layer, primarily composed of noble metals, is responsible for the initial oxidation of ammonia. This separation design optimizes the spatiotemporal distribution of reactants and intermediates; the concentration of the M element on the top layer more effectively improves the microenvironment of the SCR reaction, enhancing the reduction of NO. x The ability to convert intermediates into N2 is enhanced, particularly at high temperatures where the formation of N2O is more effectively suppressed. Different underlying designs (pure noble metal layers or mixed layers of noble metals and molecular sieves) can further modulate the reaction gradient and low-temperature activity. Therefore, the design of the coating structure, combined with the directional introduction of the M element, constitutes a multi-level performance optimization strategy from microscopic active sites to macroscopic reaction engineering. Detailed Implementation

[0027] The embodiments of the technical solution of this application will be described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0029] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] The ammonia oxidation catalyst and its application of the present invention will be described below with reference to specific embodiments.

[0032] Example 1 This embodiment provides an ammonia oxidation catalyst with a bilayer structure.

[0033] In this embodiment, the catalyst includes a first support and a double-layer catalyst coating disposed on the surface of the first support: the first coating closer to the first support includes a first catalyst component (Pt / Al2O3), and the second coating farther from the first support includes a second catalyst component (Cu-M-SSZ-13 molecular sieve). The M element is zinc (Zn) supported on the molecular sieve support; the Zn loading is 1.3 wt% by weight of the molecular sieve, and the first metal Cu loading is 3.4 wt%.

[0034] The preparation process includes: preparing Pt-containing oxide support slurry and Zn-modified molecular sieve slurry, respectively, and coating them sequentially onto a cordierite honeycomb ceramic first support, followed by drying and calcination to form a bilayer structure. The first coating has a loading of approximately 30 g / L, and the second coating has a loading of approximately 150 g / L.

[0035] Example 2 This embodiment provides an ammonia oxidation catalyst with a double-layer-bottom layer mixed coating structure.

[0036] Unlike Example 1, in this example, the first coating of the catalyst is a mixture of the first catalyst component and the second catalyst component (i.e., a mixed coating of Pt / Al2O3 and Cu-Zn-SSZ-13), and the second coating is still the second catalyst component (Cu-Zn-SSZ-13). The Cu loading and Zn loading (1.3 wt%, molecular sieve loading) are the same as in Example 1.

[0037] The preparation process includes: mixing the first catalyst component with a portion of the second catalyst component to prepare a bottom slurry, coating and drying it, then coating it with the second catalyst component slurry as the top layer, and finally drying and calcining it. The total loading of the two layers is comparable to that in Example 1.

[0038] Example 3 This embodiment provides an ammonia oxidation catalyst with a single-layer-mixed coating structure.

[0039] In this embodiment, the catalyst coating has a single-layer structure, and the first catalyst component (Pt) and the second catalyst component (Cu-Zn-SSZ-13) are uniformly mixed in the coating. The Cu loading is 3.4 wt%, and the Zn exists in the molecular sieve with a loading of 1.3 wt%, with a total coating amount of approximately 180 g / L.

[0040] The preparation method includes: mixing a Pt-containing oxide support with a Zn-modified molecular sieve to prepare a uniform slurry, coating it onto a first support in one step, and then drying and calcining it to obtain a single-layer mixed structure catalyst.

[0041] Example 4 This embodiment provides an ammonia oxidation catalyst with a bilayer structure.

[0042] In this embodiment, element M is dispersed in the coating as an additive. The catalyst structure is the same as in Example 1 (the first coating is Pt / Al2O3, and the second coating is a molecular sieve layer), but the second coating uses Cu-SSZ-13 molecular sieve without Zn loading (Cu loading 3.4 wt%), and Zn is dispersed in the second coating slurry as zinc nitrate as an additive. The Zn content is 1.3 wt% based on the mass of the molecular sieve.

[0043] The preparation process includes: preparing a molecular sieve slurry containing Zn additive, coating it onto the substrate in the same manner as in Example 1, and then drying and calcining it.

[0044] Example 5 This embodiment provides an ammonia oxidation catalyst with a bilayer structure.

[0045] Element M is introduced synergistically through two methods: loading onto the molecular sieve and acting as a slurry additive. The catalyst structure is the same as in Example 1, except that in the molecular sieve used for the second coating, the Cu loading is 3.4 wt%; Zn is loaded at 1.0 wt% onto the molecular sieve framework, and at the same time, it is dispersed in the coating at 0.3 wt% as an additive, with a total Zn content of 1.3 wt%, consistent with Examples 1-4.

[0046] The preparation process includes: first, loading a portion of Zn onto a molecular sieve via ion exchange, then adding the remaining Zn as an additive to the slurry to prepare a second coating slurry, and coating and calcining it according to the method in Example 1.

[0047] Example 6 This embodiment provides an ammonia oxidation catalyst with a bilayer structure.

[0048] The only difference between this embodiment and Embodiment 1 is that the element M is cobalt (Co), and the Co loading is 1.3 wt% and the Cu loading is 3.4 wt% based on the molecular sieve mass.

[0049] Example 7 This embodiment provides an ammonia oxidation catalyst with a bilayer structure.

[0050] The only difference between this embodiment and Embodiment 1 is that the M element is a combination of zinc (Zn) and cobalt (Co), wherein the Zn loading is 0.8 wt%, the Co loading is 0.5 wt%, the total M element loading is 1.3 wt%, and the Cu loading is 3.4 wt%.

[0051] Comparative Example 1 This comparative example provides a conventional ammonia oxidation catalyst.

[0052] This comparative catalyst has the same bilayer structure as that of Example 1 (the first coating is Pt / Al2O3, and the second coating is a molecular sieve layer), but the second coating uses unmodified Cu-SSZ-13 molecular sieve with a Cu loading of 3.4 wt% and no M element is introduced.

[0053] The preparation process includes: preparing a second coating slurry using unmodified Cu-SSZ-13 molecular sieve, and the rest is the same as in Example 1.

[0054] The ion exchange method, slurry coating method, and additive dispersion method described in the above embodiments and comparative examples are all conventional technical means in the art for preparing molecular sieve modified catalysts and monolithic coated catalysts. Those skilled in the art can flexibly adjust the process parameters and operating steps according to the actual production conditions and equipment, without being limited to the specific values ​​mentioned above.

[0055] [Performance Testing] The catalysts provided in the above examples and comparative examples were first pretreated under simulated aging conditions (treated at 750°C for 12 hours in air containing 10% water vapor). Subsequently, their ammonia oxidation performance was evaluated in a fixed-bed reactor.

[0056] The test conditions were as follows: the reaction gas composition was 300 ppm NH3, 10% O2, 7% H2O, with N2 as the equilibrium gas, and the gas hourly space velocity (GHSV) was 200,000 h⁻¹. -1 The temperature was programmed to rise, and tests were conducted within a temperature range of 200℃ to 550℃. After stabilization at each temperature point, the composition of the inlet and outlet gases was analyzed.

[0057] The formulas for calculating the NH3 conversion rate and N2O selectivity are as follows: NH3 conversion rate (%) = [(Inlet NH3 concentration - Outlet NH3 concentration) / Inlet NH3 concentration] × 100% N2O selectivity (%) = [(2 × outlet N2O concentration) / (inlet NH3 concentration - outlet NH3 concentration)] × 100% The results are shown in Table 1.

[0058] Table 1

[0059] Analysis of the examples and comparative examples shows that all examples (1-7) incorporating element M exhibited significantly lower N2O selectivity than Comparative Example 1 (which did not contain M) after rigorous aging, confirming the crucial role of element M in inhibiting N2O formation. In particular, loading M as an active component onto the molecular sieve to form Cu-M bimetallic sites (Examples 1-3) was more effective than using M solely as a slurry additive (Example 4).

[0060] A comparison of Examples 6 (Co), 7 (Zn+Co combination) with Example 1 (Zn) shows that low N2O selectivity can be achieved regardless of whether the M element is Zn or Co.

[0061] Regarding the catalyst coating structure, Example 1, employing a bilayer catalyst structure, exhibits the best NH3 conversion rate due to its sequential "adsorption-oxidation-re-reaction" reaction pathway, which more effectively promotes the ordered conversion of ammonia at noble metal active sites. Example 2, using a bilayer-bottom layer mixed coating structure, shows the lowest N2O selectivity, indicating that while retaining the advantages of sequential reaction, it significantly suppresses N2O generation by forming a functional gradient transition through the bottom layer mixed coating and combining this with the rapid capture of intermediate products by the top layer molecular sieve. Example 3, with a single-layer mixed coating structure, demonstrates high ammonia conversion and N2 selectivity, indicating that its highly dispersed and closely contacted active sites facilitate efficient "oxidation-reduction" reaction coupling. These results demonstrate that the coating structure design of this invention can be flexibly optimized for different performance focuses (conversion rate, selectivity, or overall balance).

[0062] In summary, by introducing element M into the second catalyst component and combining it with an optimized coating structure design (double layer or single layer), this invention can synergistically achieve lower N2O selectivity while ensuring ultra-high NH3 conversion efficiency, thus effectively solving the problem that traditional ASC catalysts cannot achieve both high activity and high selectivity.

[0063] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An ammonia oxidation catalyst, characterized in that, It includes a first support and a catalyst coating disposed on the surface of the first support; the catalyst coating includes a first catalyst component and a second catalyst component; The first catalyst component includes a noble metal active component and an oxide support; The second catalyst component includes a molecular sieve; The molecular sieve includes a molecular sieve support and an active component; the active component includes a first metal and element M. The first metal is selected from copper or iron; the M element is selected from at least one of zinc, cobalt, silver, vanadium, and bismuth.

2. The catalyst according to claim 1, characterized in that, The noble metal active component includes one or more of platinum or palladium.

3. The catalyst according to claim 1, characterized in that, The oxide support includes one or more of aluminum oxide, titanium oxide, or silicon oxide.

4. The catalyst according to claim 1, characterized in that, Based on the total mass of the molecular sieve carrier, the first metal loading is ≥1 wt%, and the loading of the M element is ≥0.1 wt%.

5. The catalyst according to claim 1, characterized in that, The M element is present in the catalyst coating in at least one of the following ways: (a) Loaded on the molecular sieve support; (b) Dispersed in the catalyst coating as an additive.

6. The catalyst according to claim 1, characterized in that, The molecular sieve carrier is selected from one or more of the following topological structures: ACO, AEI, AEL, AEN, AFI, AFN, AFT, AFX, ANA, APC, APD, ATT, BEA, BIK, CDO, CHA, DDR, DFT, DON, EAB, EDI, EPI, ERI, ESV, ETL, FAU, FER, GIS, GOO, IHW, ITE, ITW, LEV, LTA, KFI, MER, MFI, MON, MOR, NSI, OWE, PAU, PHI, RHO, RTH, SAT, SAV, SIV, SOD, THO, TSC, UEI, UFI, VFI, VNI, YUG, ZON and / or eutectic molecular sieves or commensal organisms having the above topological structures.

7. The catalyst according to claim 6, characterized in that, The silicon-aluminum molar ratio of the molecular sieve support ranges from 3 to 200.

8. The catalyst according to claim 1, characterized in that, The catalyst coating has a single-layer structure, and the first catalyst component and the second catalyst component are uniformly mixed in the catalyst coating.

9. The catalyst according to claim 1, characterized in that, The catalyst coating has a double-layer structure, including a first coating close to the first support and a second coating away from the first support; The first coating includes the first catalyst component; Optionally, the first coating further includes the second catalyst component; The second coating comprises the second catalyst component.

10. A method for treating exhaust gases from an internal combustion engine, characterized in that, The tail gas containing escaped ammonia is contacted with the ammonia oxidation catalyst as described in any one of claims 1-9, and the escaped ammonia is selectively oxidized under the action of the catalyst.

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