A particulate matter trap with adjustable NO2 content and its application

Abstract

This invention relates to the field of exhaust gas treatment technology, specifically to a particulate matter trap with the function of adjusting the NO2 content and its application. It includes a carrier, a first active coating disposed at the inlet end of the carrier, and a second active coating disposed at the outlet end of the carrier. The second active coating includes a second supporting carrier and a second active component loaded on the second supporting carrier. The second active component includes an oxide of metal M; metal M includes at least one selected from Mo, Co, Mn, Fe, and Ce. The second supporting carrier includes an oxide carrier or a non-precious metal modified oxide thereof; the oxide carrier includes at least one selected from alumina, titanium oxide, silicon oxide, and cerium-zirconium oxide. The second coating enables the targeted catalytic conversion of excess NO2 generated after the upstream DOC reaction, effectively reducing the NO2 content in the exhaust gas by reducing a portion of the NO2 to NO or pollution-free N2.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas treatment technology, and more specifically, to a particulate matter trap with the function of adjusting the NO2 ratio and its application. Background Technology

[0002] In order to improve particulate matter filtration and regeneration efficiency, traditional DPFs require a significant increase in NO2 concentration after the exhaust gas from upstream engines passes through DOC. However, excessively high NO2 concentrations can lead to a significant increase in N2O generation after downstream SCR reactions, causing environmental pollution. Traditional DPFs, on the other hand, have almost no effect on reducing NO2 concentration.

[0003] Therefore, traditional techniques need to be improved. Summary of the Invention

[0004] In view of this, the present invention aims to at least partially solve one of the technical problems in the aforementioned related technologies. To this end, the present invention provides a particulate matter trap with the function of reducing NO2 content, comprising a carrier, a first active coating disposed on the carrier, and a second active coating disposed at the gas outlet end of the carrier; wherein, the second active coating comprises a second loading carrier and a second active component loaded on the second loading carrier; the second active component comprises an oxide of metal M; the metal M comprises at least one of Mo, Co, Mn, Fe, and Ce; the second loading carrier comprises an oxide carrier or a non-precious metal modified oxide thereof; the oxide carrier comprises at least one of alumina, titanium oxide, silicon oxide, and cerium zirconium oxide. The first active coating ensures efficient interception and capture of particulate matter, maintaining the core filtration performance of traditional DPFs. The second active coating at the outlet relies on the catalytic properties of active components such as Mo, Co, and Mn metal oxides loaded on supports such as alumina, titanium dioxide, silicon dioxide, and cerium zirconium oxides. It can catalytically convert excess NO2 generated after the upstream DOC reaction, effectively reducing the proportion of NO2 in the exhaust gas by reducing some NO2 to NO or pollution-free N2. This prevents excessive NO2 from entering the downstream SCR system and causing a large amount of N2O byproducts, thus solving the environmental pollution problem caused by the lack of NO2 control capability in traditional DPFs. Ultimately, this invention achieves precise adaptation of NO2 concentration throughout the entire exhaust gas treatment process without sacrificing particulate matter capture efficiency, significantly improving the environmental performance and operational stability of the overall exhaust gas treatment system.

[0005] To solve the above-mentioned technical problems, the present invention is implemented as follows: In a first aspect, the present invention provides a particulate matter trap with the function of reducing NO2 content, the particulate matter trap including a carrier, a first active coating disposed on the carrier, and a second active coating disposed at the gas outlet end of the carrier; The second active coating includes a second support carrier and a second active component supported on the second support carrier; the second active component includes an oxide of metal M; the metal M includes at least one of Mo, Co, Mn, Fe, and Ce; The second load carrier includes an oxide carrier or a non-precious metal modified oxide thereof; the oxide carrier includes at least one of alumina, titanium oxide, silicon oxide, and cerium zirconium oxide.

[0006] It should be understood that the first active coating can be set at the air inlet end of the carrier, at the air outlet end, or at both the air inlet end and the air outlet end.

[0007] Compared with the prior art, the present invention creatively sets a second active coating at the outlet of the particulate filter DPF. This is because the inventors accidentally discovered that the oxide of metal M in the second active coating has rich variable valence state characteristics as a non-noble metal active site. It can transfer electrons with NO2 through its own reversible valence state change, efficiently break the chemically stable structure of NO2, promote its decomposition to generate NO, and reduce the NO2 concentration at the DPF outlet.

[0008] It should be understood that the first active coating in this invention is the traditional DPF coating, used to ensure the high collection efficiency and regeneration function of the particulate matter trap. The invention further discovers that the first active coating and the second active coating have mutual influence. When the first coating is regenerated, a small amount of reducing agents such as CO and hydrocarbons are generated, which can assist the second coating in reducing the NO2 concentration. Specifically, CO and hydrocarbons (such as C3H6 in the test conditions) can act as reducing agents and react with NO2 at the active sites of the second active coating to undergo redox reactions, further promoting the conversion of NO2 to NO. It can also make the active sites that participated in the reaction return to a low valence state, realize the recycling of active sites, and continuously maintain the NO2 conversion efficiency.

[0009] It is easy to see that, under the premise that the first active coating ensures that the particulate matter capture efficiency and regeneration capacity are not affected, the present invention effectively reduces the NO2 concentration and proportion in the DPF outlet exhaust gas by means of the directional catalytic effect of the second active coating. This not only solves the defect of traditional DPFs that cause a significant increase in N2O generation in the downstream SCR reaction due to excessively high NO2 concentration at the outlet, but also improves the low-temperature reaction performance of SCR, thus achieving synergistic optimization of particulate matter capture, regeneration functions and pollutant emission control.

[0010] Furthermore, the loading of the second active coating on the carrier is 10-200 g / L; preferably 100 g / L. It should be understood that L here refers to the volume of the cordierite honeycomb carrier.

[0011] Through extensive experimental verification, the inventors discovered that the loading of the second active coating directly determines the effective loading of the second active component and the coating's dispersibility: if the loading is below 10 g / L, the loading of the active component is insufficient, the coating cannot form continuous and sufficient active sites, the contact probability between NO2 in the exhaust gas and the active sites is greatly reduced, making it difficult to achieve efficient conversion of NO2 to NO and failing to achieve the core objective of reducing the proportion of NO2 at the downstream SCR; if the loading is above 200 g / L, on the one hand, it will lead to an excessively thick coating, reducing the cross-sectional area of ​​the DPF carrier's pores, increasing exhaust gas flow resistance, raising back pressure, and thus affecting the engine. On the one hand, excessive coating material can cause the active components to agglomerate, reducing their dispersibility. This not only fails to further improve catalytic efficiency but also increases production costs and wastes resources. It may also interfere with the filtration and regeneration functions of the first active coating. The present invention further limits the loading of the second active coating to 10-200 g / L, which can ensure that the active components in the second active coating are uniformly dispersed, forming sufficient and efficient active sites. This ensures sufficient contact and reaction with NO2 in the exhaust gas, and prevents abnormal back pressure due to excessive coating thickness, thus ensuring that the original filtration and regeneration functions of the DPF are not affected.

[0012] The further optimization of the loading of 100 g / L is based on the optimal balance of activity efficiency, flowability and economy. At this loading, the active components can achieve the best dispersion state, the density of active sites is moderate, and the catalytic decomposition of NO2 can be maximized. At the same time, the coating thickness is just right, and the exhaust gas flow resistance is minimal. It does not require additional sacrifice of engine performance and avoids material waste. This allows the DPF to achieve excellent NO2 ratio control while having the economy and reliability for industrial applications.

[0013] Furthermore, the second active component accounts for 1 wt% to 50 wt% of the mass of the second active coating.

[0014] The ratio of the second active component to the second support directly determines the dispersibility of the active component, the exposure degree of the catalytic active center, and the stability of the coating structure. If the mass ratio of the second active component is too low, the loading of the second active component on the surface of the second support will be insufficient, and it will be unable to form uniform and sufficient effective active sites. The contact probability between NO2 in the exhaust gas and the active sites will be greatly reduced, making it difficult to achieve efficient conversion of NO2 to NO, and it may even fail to meet the basic requirement of reducing the proportion of NO2 at the downstream SCR. If the mass ratio of the second active component is too high, the excess component is prone to agglomeration and accumulation on the surface of the second support, causing some active sites to be wrapped and unable to contact the exhaust gas. This will not only fail to improve the catalytic efficiency, but also reduce the utilization rate of the active component and increase production costs. At the same time, the excess active component may damage the bonding force between the coating and the support, causing the coating to fall off and affecting the service life of the DPF. Therefore, by adopting the above-mentioned mass ratio, the present invention can make full use of the high specific surface area characteristics of the second load carrier to allow the second active component to be uniformly dispersed on the surface of the second load carrier, forming fully exposed and appropriately dense active sites. This not only ensures the efficient reaction with NO2, but also ensures the integrity and durability of the second active coating structure through the stable bearing effect of the second load carrier.

[0015] Further, the first active coating includes a first support carrier and a first active component loaded on the first support carrier; preferably, the first support carrier includes at least one of alumina, silicon oxide, and cerium zirconium oxide; preferably, the first active component includes a Pt / Pd mixture.

[0016] Compared with the prior art, the present invention clarifies the specific composition of the first active coating. On the one hand, by utilizing the high specific surface area and good dispersibility of the selected support carrier, the Pt / Pd mixture can be uniformly loaded and form efficient catalytic sites. On the other hand, the synergistic effect of Pt / Pd can precisely ensure the efficient capture and regeneration function of particulate matter, which not only maintains the core basic performance of DPF, but also provides a stable working condition for the second active coating at the outlet to play the role of NO2 conversion, thus realizing the synergistic optimization of filter regeneration-NO2 ratio control.

[0017] Furthermore, the concentration of the Pt / Pd mixture in the first active coating is 1 g / ft. 3 ~5g / ft 3 Preferably, the mass ratio of Pt to Pd in ​​the Pt / Pd mixture is 10:1 to 1:10; more preferably, it is 2:1.

[0018] Compared with the prior art, the present invention further limits the concentration of the Pt / Pd mixture and the mass ratio of Pt to Pd. This is because the high oxidation activity of Pt and the stability of Pd can form a synergistic catalytic effect. If the concentration is too low, the catalytic sites of the first active coating will be insufficient, and the particulate matter oxidation and DPF regeneration cannot be completed efficiently. If the concentration is too high, it will increase the amount of precious metals used and the production cost, and may also cause excessive oxidation reaction that interferes with the exhaust gas components. The mass ratio of 10:1 to 1:10 can adapt to the regeneration requirements under different working conditions, and can maximize the synergistic effect of the two. This ensures that the particulate matter capture and regeneration function of the DPF core is stable and reliable, and avoids the NO2 conversion efficiency of the downstream second active coating due to the imbalance of catalytic activity.

[0019] Furthermore, the loading of the first active coating on the carrier is 1 g / L to 50 g / L; preferably 10 g / L.

[0020] Compared with the prior art, the present invention further limits the loading of the first active coating to 1g / L~50g / L. This is because the loading of the first active coating is directly related to the effective loading of Pt / Pd active components and the permeability of the coating: if the loading is less than 1g / L, the loading of precious metal active components is insufficient, the catalytic sites are scarce, and it is impossible to efficiently complete the oxidation of carbon soot particles and the active / passive regeneration of DPF, making it difficult to guarantee the core function of particulate matter capture; if the loading is greater than 50g / L, the coating is too thick, which will cause the carrier pores to be blocked, the exhaust gas flow resistance will increase, the back pressure will rise, and the engine power and fuel economy will be affected. At the same time, excessive precious metals will significantly increase the production cost, and the coating accumulation may also interfere with the contact reaction between the second active coating at the exhaust end and the exhaust gas. The loading range of 1 g / L to 50 g / L ensures that the Pt / Pd components are uniformly dispersed and form sufficient catalytic sites, which can stably perform the functions of particulate matter capture and regeneration, while avoiding abnormal back pressure and cost waste. The optimal loading of 10 g / L has been verified by experiments as the best balance point, which can maximize the synergistic performance of the core basic function of DPF and the downstream NO2 regulation function, further improving the practicality and industrial value of the technical solution.

[0021] Furthermore, in the axial direction of the carrier, the length of the first active coating is greater than or equal to the length of the second active coating; preferably, the length of the first active coating accounts for 50% to 100% of the axial length of the carrier; preferably, the length of the second active coating accounts for 10% to 50% of the axial length of the carrier.

[0022] Compared with the prior art, the present invention further features the above-mentioned technical characteristics. This is because the core function of the first active coating is particulate matter capture and regeneration, which requires sufficient axial length to ensure full contact between the Pt / Pd catalytic sites and the exhaust gas and soot particles to achieve efficient oxidation and regeneration. The second active coating only needs to complete the NO2 conversion before the exhaust gas is discharged. If it is too long, it will encroach on the effective space of the first coating and increase the back pressure. If it is too short, it cannot guarantee sufficient reaction with the exhaust gas. This limitation not only strengthens the core performance of the DPF through the reasonable length of the first coating, but also accurately exerts the NO2 regulation function with the appropriate length of the second coating, avoiding functional conflicts or insufficient effects of the two coatings. At the same time, it controls the exhaust gas flow resistance, realizing spatial synergy and performance balance of filtration regeneration and NO2 ratio regulation, further enhancing the reliability and industrial adaptability of the technical solution.

[0023] Furthermore, the carrier is made of at least one of cordierite and silicon carbide; the carrier shape includes circular or square.

[0024] Compared with existing technologies, when using the above-mentioned materials to make the carrier, it can adapt to the complex working environment of high temperature and multiple pollutants in engine exhaust gas, stably support the first and second active coatings, avoid coating peeling or carrier failure, and ensure the continuous stability of filter regeneration and NO2 conversion functions; while the circular or square shape design can flexibly adapt to the installation space and assembly requirements of different engine exhaust gas treatment systems, avoiding the application limitations of traditional single-shape carriers.

[0025] Secondly, the present invention provides a method for treating engine exhaust gas, wherein the engine exhaust gas is treated by the particulate matter trap described above.

[0026] Furthermore, in the step of treating the simulated engine exhaust gas, the O2 injection rate is controlled at 5%~10%, the CO2 injection rate at 5%~8%, the H2O mass percentage at 8%~15%, the NO2 concentration at 200ppm~300ppm, the NO concentration at 200ppm~500ppm, the C3H6 concentration at 30ppm~80ppm, and the balance is N2, with a space velocity of 30000h. -1 ~80000 h -1 .

[0027] Compared with the prior art, the present invention applies the above-mentioned dual-coated particulate matter trap with both particulate matter capture and regeneration and NO2 ratio regulation functions to engine exhaust gas treatment, and precisely limits the reaction operating parameters to achieve full-chain synergistic optimization of efficient particulate matter removal, directional NO2 conversion, SCR efficiency improvement and N2O emission reduction. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0029] Appendix Figure 1 This is a schematic diagram of the particulate matter trap provided in Example 1.

[0030] Appendix Figure 2 This is a schematic diagram of the particulate matter trap provided in Example 2.

[0031] Appendix Figure 3 This is a schematic diagram of the particulate matter trap provided in Example 3.

[0032] The accompanying drawings have illustrated specific embodiments of the invention, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0033] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0034] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0035] In the description of this application, "same chemical composition" should be interpreted broadly, that is, the main components of the two have the same chemical composition, or the two have substantially the same chemical composition, but may have errors or impurities within the acceptable range that can be understood by those skilled in the art.

[0036] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0037] Unless otherwise specified, the terms "comprising" and "including" as used in this invention can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0038] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0039] Unless otherwise specified, all technical features and optional technical features of this invention can be combined to form new technical solutions.

[0040] Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0041] During the research and development process, the inventors of this invention discovered that, for the active components, the catalytic effects of single oxides and composite oxides of Mo, Co, Mn, Fe, and Ce were tested. It was found that these non-noble metal oxides can efficiently promote NO2 decomposition through valence state changes and electron transfer. Based on this, this invention provides a particulate matter trap with the function of reducing NO2 content, comprising a support, a first active coating disposed on the support, and a second active coating disposed at the gas outlet end of the support; wherein, the second active coating comprises a second supported support and a second active component loaded on the second supported support; the second active component comprises an oxide of metal M; the metal M includes at least one of Mo, Co, Mn, Fe, and Ce; the second supported support includes an oxide support or a non-noble metal modified oxide thereof; the oxide support includes at least one of alumina, titanium oxide, silicon oxide, and cerium-zirconium oxide. The first active coating ensures efficient interception and capture of particulate matter, maintaining the core filtration performance of traditional DPFs. The second active coating at the outlet relies on the catalytic properties of active components such as Mo, Co, and Mn metal oxides loaded on supports like alumina, titanium dioxide, silicon dioxide, and cerium-zirconium oxides. It can catalytically convert excess NO2 generated after the upstream DOC reaction, effectively reducing the proportion of NO2 in the exhaust gas by reducing some of it to NO or harmless N2. This prevents excessive NO2 from entering the downstream SCR system and causing a large amount of N2O byproducts, thus solving the environmental pollution problem caused by the lack of NO2 control capability in traditional DPFs. Ultimately, this invention achieves precise adaptation of NO2 concentration throughout the entire exhaust gas treatment process without sacrificing particulate matter capture efficiency, significantly improving the overall environmental performance and operational stability of the exhaust gas treatment system. Specifically, this invention adopts the following technical solution: In a first aspect, embodiments of the present invention provide a particulate matter trap with the function of reducing NO2 content. The particulate matter trap includes a carrier, a first active coating disposed on the carrier, and a second active coating disposed at the outlet end of the carrier. The second active coating includes a second load carrier and a second active component loaded on the second load carrier. The second active component includes an oxide of metal M. Metal M includes at least one of Mo, Co, Mn, Fe, and Ce. The second load carrier includes an oxide carrier or a non-precious metal modified oxide thereof. The oxide carrier includes at least one of alumina, titanium oxide, silicon oxide, and cerium zirconium oxide. It should be understood that the first active coating in the present invention is a conventional DPF coating, used to ensure the high collection efficiency and regeneration function of the particulate matter trap. The first active coating can be disposed at the inlet end of the carrier, or at the outlet end, or simultaneously at both the inlet and outlet ends.

[0042] When employing the above technical solution, the oxide of metal M in the second active coating, as a non-noble metal active site, possesses abundant variable valence state characteristics. It can reversibly change its valence state to transfer electrons with NO2, efficiently breaking the chemically stable structure of NO2 and promoting its decomposition to generate NO, thus reducing the NO2 concentration at the DPF outlet. Simultaneously, the regeneration of the first coating generates small amounts of reducing agents such as CO and hydrocarbons, which can assist the second coating in reducing NO2 concentration and continuously maintain NO2 conversion efficiency. Therefore, this invention, while ensuring that the particulate matter capture efficiency and regeneration capacity are not affected by the first active coating, effectively reduces the NO2 concentration and proportion in the DPF outlet exhaust gas through the directional catalytic effect of the second active coating. This solves the defect of traditional DPFs where excessively high outlet NO2 concentration leads to a significant increase in N2O generation in the downstream SCR reaction, and also improves the low-temperature reaction performance of SCR, achieving synergistic optimization of particulate matter capture, regeneration functions, and pollutant emission control.

[0043] In some embodiments, the loading of the second active coating on the carrier is 10-200 g / L; preferably 100 g / L. It should be understood that L here refers to the volume of the cordierite honeycomb carrier.

[0044] For example, the loading of the second active coating on the carrier can be specifically selected as a range of values ​​consisting of 10 g / L, 50 g / L, 80 g / L, 120 g / L, 150 g / L, 200 g / L or any point values, preferably 80 g / L to 150 g / L; more preferably 100 g / L.

[0045] When the above technical solution is adopted, the synergistic unity of NO2 conversion efficiency, DPF flow performance, production cost and original filtration and regeneration function is achieved, ensuring the stability and practicality of the particulate matter trap in controlling the NO2 ratio, and providing a more reliable technical guarantee for improving downstream SCR efficiency and reducing N2O generation.

[0046] In some embodiments, the second active component accounts for 1 wt% to 50 wt% of the mass of the second active coating.

[0047] For example, the mass percentage of the second active component in the second active coating is a range of values ​​consisting of 1 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt%, 40 wt%, or any point value, preferably 2 wt% to 30 wt%.

[0048] By adopting the above technical solution, the catalytic performance and structural stability of the second active coating are further optimized. While maximizing the NO2 conversion efficiency, the waste of active components and the risk of coating peeling are avoided, reducing the cost of industrial application. This achieves a synergistic unity of catalytic activity, structural stability and economy, and provides a more stable and reliable ratio support for the core function of adjusting the NO2 ratio, further strengthening the technical advantages and practical application value of the present invention.

[0049] In some embodiments, the first active coating includes a first support carrier and a first active component loaded on the first support carrier; preferably, the first support carrier includes at least one of alumina, silicon oxide, and cerium zirconium oxide; the first active component includes a Pt / Pd mixture.

[0050] When the above technical solution is adopted, on the one hand, the high specific surface area and good dispersibility of the support carrier can enable the Pt / Pd mixture to be uniformly loaded and form efficient catalytic sites. On the other hand, the synergistic effect of Pt / Pd can accurately ensure the efficient capture and regeneration function of particulate matter, which not only maintains the core basic performance of DPF, but also provides a stable working condition for the second active coating at the outlet to play the role of NO2 conversion, thus realizing the synergistic optimization of filtration regeneration-NO2 ratio control.

[0051] In some embodiments, the concentration of the Pt / Pd mixture in the first active coating is 1 g / ft. 3 ~5g / ft 3 Preferably, in the Pt / Pd mixture, the mass ratio of Pt to Pd is 10:1 to 1:10; more preferably, it is 2:1.

[0052] For example, the concentration of the Pt / Pd mixture in the first active coating can be specifically selected as 1 g / ft. 3 1.5g / ft 32g / ft 3 5g / ft 3 Or a range of values ​​composed of any points, preferably 1.5 g / ft. 3 ~2g / ft 3 .

[0053] For example, the mass ratio of Pt to Pd can be specifically selected as 10:1, 5:1, 2:1, 1:10, 1:5 or any range of points, preferably 10:1 to 2:1.

[0054] When using the above technical solution, the high oxidation activity of Pt and the stability of Pd can form a synergistic catalytic effect. If the concentration is too low, the catalytic sites of the first active coating will be insufficient, and the particulate matter oxidation and DPF regeneration cannot be completed efficiently. If the concentration is too high, the amount of precious metal used will increase the production cost, and may also cause excessive oxidation reaction that interferes with the exhaust gas components. The mass ratio of 10:1 to 1:10 can adapt to the regeneration requirements under different working conditions, and can maximize the synergistic effect of the two. This ensures that the particulate matter capture and regeneration function of the DPF core is stable and reliable, and avoids the NO2 conversion efficiency of the downstream second active coating due to the imbalance of catalytic activity.

[0055] In some embodiments, the loading of the first active coating on the carrier is 1 g / L to 50 g / L.

[0056] For example, the loading of the first active coating on the carrier can be specifically selected as a range of values ​​consisting of 1 g / L, 5 g / L, 10 g / L, 20 g / L, 30 g / L, 50 g / L or any point value, preferably 5 g / L to 10 g / L, more preferably 10 g / L.

[0057] When the above technical solution is adopted, it can ensure that the Pt / Pd components are uniformly dispersed and form sufficient catalytic sites, which can not only stably perform the particulate matter capture and regeneration functions, but also avoid abnormal back pressure and cost waste. The preferred loading of 10 g / L has been verified by experiments as the optimal balance point, which can maximize the synergistic performance of the core basic function of DPF and the downstream NO2 regulation function, and further enhance the practicality and industrial value of the technical solution.

[0058] In some embodiments, the length of the first active coating is greater than or equal to the length of the second active coating in the axial direction of the carrier; preferably, the length of the first active coating accounts for 50% to 100% of the axial length of the carrier, and the length of the second active coating accounts for 10% to 50% of the axial length of the carrier.

[0059] For example, the proportion of the length of the first active coating to the axial length of the carrier can be specifically selected as a range of values ​​consisting of 50%, 80%, 90%, 100%, or any point values.

[0060] For example, the length of the second active coating as a percentage of the axial length of the carrier is a range of values ​​consisting of 10%, 20%, 50%, or any point values.

[0061] It should be understood that the core function of the first active coating is particulate matter capture and regeneration. It needs sufficient axial length to ensure full contact between the Pt / Pd catalytic sites and the exhaust gas and soot particles to achieve efficient oxidation and regeneration. The second active coating only needs to complete the NO2 conversion before the exhaust gas is discharged. If it is too long, it will encroach on the effective space of the first coating and increase the back pressure. If it is too short, it cannot guarantee sufficient reaction with the exhaust gas. This limitation not only strengthens the core performance of the DPF through the reasonable length of the first coating, but also accurately exerts the NO2 regulation function with the appropriate length of the second coating. It avoids functional conflicts or insufficient effects between the two coatings, and controls the exhaust gas flow resistance. It achieves spatial synergy and performance balance between filtration regeneration and NO2 ratio regulation, and further enhances the reliability and industrial adaptability of the technical solution.

[0062] In some embodiments, the carrier is made of at least one of cordierite and silicon carbide; the carrier shape includes circular or square.

[0063] When adopting the above technical solution, it can adapt to the complex working environment of high temperature and multiple pollutants in engine exhaust gas, stably support the first and second active coatings, avoid coating peeling or carrier failure, and ensure the continuous stability of filter regeneration and NO2 conversion functions. The circular or square shape design can flexibly adapt to the installation space and assembly requirements of different engine exhaust gas treatment systems, avoiding the application limitations of traditional single-shaped carriers. It is clear that this limitation not only provides solid support for the function of the two active coatings through adaptable materials, but also improves the industrial adaptability of the technical solution with a universal shape, achieving a synergy of carrier structural stability, functional adaptability, and application flexibility, further ensuring the reliability and practicality of the overall technical solution.

[0064] Secondly, embodiments of the present invention provide a method for treating engine exhaust gas, wherein the engine exhaust gas is treated using the particulate matter trap described above.

[0065] In some embodiments, the steps for treating engine exhaust gas include controlling the O2 intake to be 5%–10%, the CO2 intake to be 5%–8%, the H2O mass percentage to be 8%–15%, the NO2 concentration to be 200 ppm–300 ppm, the NO concentration to be 200 ppm–500 ppm, the C3H6 concentration to be 30 ppm–80 ppm, the balance to be N2, and the air velocity to be 30,000 h⁻¹. -1 ~80000 h -1 .

[0066] It should be understood that by applying the above-mentioned dual-coated particulate matter trap, which combines particulate matter capture and regeneration with NO2 ratio regulation, to engine exhaust gas treatment and precisely limiting the reaction operating parameters, the entire chain of efficient particulate matter removal, directional NO2 conversion, SCR efficiency improvement, and N2O emission reduction is synergistically optimized.

[0067] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0068] To illustrate the technical solution of the present invention in more detail, the following specific embodiments are provided. It should be understood that, unless otherwise stated, all raw materials used in the following embodiments are commercially available.

[0069] Example 1 This embodiment provides a particulate matter trap with the function of reducing NO2 content. The particulate matter trap includes a carrier, a first active coating disposed at the air inlet end of the carrier, and a second active coating disposed at the air outlet end of the carrier. The second active coating includes a second load carrier and a second active component loaded on the second load carrier. The second active component is cobalt oxide. The second load carrier is a mixture of aluminum oxide and titanium oxide.

[0070] The second active coating has a loading of 80 g / L on the carrier; it is composed of cobalt oxide, aluminum oxide, and titanium oxide, with the mass ratios of cobalt oxide, aluminum oxide, and titanium oxide being 15 wt%, 42.5 wt%, and 42.5 wt%, respectively. The first active coating includes a first support and a first active component loaded on the first support; the first support is alumina; the first active component is a Pt / Pd mixture; the Pt / Pd mixture is... The concentration of the first active coating is 2g / ft. 3 The mass ratio of Pt to Pd is 2:1; the loading of the first active coating on the carrier is 20 g / L; In the axial direction of the carrier, the length of the first active coating accounts for 90% of the axial length of the carrier; the length of the second active coating accounts for 10% of the axial length of the carrier; the carrier material is cordierite.

[0071] The preparation process of the above-mentioned particulate matter trap is as follows: according to Figure 1 The coating scheme shown involves coating a Pt / Pd slurry (with alumina as the support) onto a DPF wall-flow cordierite honeycomb ceramic support from the inlet end. The coating amount is controlled at 10 g / L to obtain a first active coating. The length of the first active coating accounts for 90% of the axial length of the support, and the Pt / Pd ratio in the first active coating is 10:1 with a concentration of 2 g / ft. 3 ; A slurry containing cobalt nitrate, alumina, and titanium oxide at mass ratios of 15 wt%, 42.5 wt%, and 42.5 wt%, respectively, with a Co oxide concentration of 15 wt%, was thoroughly mixed. The mixture was then coated from the outlet end of the DPF, with the coating amount controlled at 80 g / L, to obtain a second active coating. The length of the second active coating accounted for 10% of the axial length of the carrier. The target particulate matter collector is obtained by sequentially drying the particulate matter collector coated with the first active coating and the second active coating at 120°C for 1 hour and calcining it at 550°C for 3 hours.

[0072] Example 2 This embodiment provides a particulate matter trap with the function of reducing NO2 content. The particulate matter trap includes a carrier, a first active coating disposed at the air inlet end of the carrier, and a second active coating disposed at the air outlet end of the carrier. The second active coating includes a second load carrier and a second active component loaded on the second load carrier. The second active component is an oxide of Mo. The second load carrier is a mixture of alumina and titanium oxide.

[0073] The second active coating has a loading of 150 g / L on the carrier; the mass ratios of molybdenum oxide, aluminum oxide and titanium oxide are 10 wt%, 45 wt%, and 45 wt%, respectively.

[0074] The first active coating includes a first support carrier and a first active component loaded on the first support carrier; the first support carrier is alumina and cerium zirconium oxide; the first active component is a Pt / Pd mixture; the concentration of the Pt / Pd mixture in the first active coating is 1 g / ft. 3 In the Pt / Pd mixture, the mass ratio of Pt to Pd is 5:1; the loading of the first active coating on the carrier is 5 g / L. In the axial direction of the carrier, the length of the first active coating accounts for 80% of the axial length of the carrier; the length of the second active coating accounts for 20% of the axial length of the carrier; the carrier is made of silicon carbide; and the carrier is square in shape.

[0075] The preparation process of the above-mentioned particulate matter trap is as follows: according to Figure 2 The coating scheme shown involves coating a Pt / Pd slurry (with a 1:1 mass ratio of alumina and cerium zirconium oxide as the support) onto a DPF wall-flow cordierite honeycomb ceramic support from the inlet end. The coating amount is controlled at 1 g / L to obtain a first active coating. The length of the first active coating accounts for 80% of the axial length of the support, and the Pt / Pd ratio in the first active coating is 5:1 with a concentration of 1 g / ft. 3 ; A slurry of ammonium molybdate, alumina, and titanium oxide in a mass ratio of 10wt%, 45wt%, and 45wt% was thoroughly mixed, with a molybdenum oxide concentration of 10wt%. The mixture was then coated from the gas outlet of the DPF, with the coating amount controlled at 150g / L, to obtain a second active coating. The length of the second active coating accounted for 10% of the axial length of the carrier. The target particulate matter collector is obtained by sequentially drying the particulate matter collector coated with the first active coating and the second active coating at 120°C for 1 hour and calcining it at 550°C for 3 hours.

[0076] Example 3 This embodiment provides a particulate matter trap with the function of reducing NO2 content. The particulate matter trap includes a carrier, a first active coating disposed at the air inlet end of the carrier, and a second active coating disposed at the air outlet end of the carrier. The second active coating includes a second load carrier and a second active component loaded on the second load carrier. The second active component is molybdenum oxide and ferric oxide in a mass ratio of 1:1. The second load carrier is titanium oxide.

[0077] The second active coating has a loading of 120 g / L on the carrier; the mass percentages of the mixture of molybdenum oxide and ferric oxide and titanium oxide are 15 wt% and 85 wt%, respectively.

[0078] The first active coating includes a first support and a first active component loaded on the first support; the first support is alumina; the first active component is a Pt / Pd mixture; the concentration of the Pt / Pd mixture in the first active coating is 1.5 g / ft. 3 In the Pt / Pd mixture, the mass ratio of Pt to Pd is 2:1; the loading of the first active coating on the carrier is 10 g / L. In the axial direction of the carrier, the length of the first active coating is greater than or equal to the length of the second active coating; the length of the first active coating accounts for 50% of the axial length of the carrier; the length of the second active coating accounts for 50% of the axial length of the carrier; the carrier is made of cordierite; and the carrier is square in shape.

[0079] The preparation process of the above-mentioned particulate matter trap is as follows: according to Figure 3 The coating scheme shown involves coating a Pt / Pd slurry (with alumina as the support) onto a DPF wall-flow cordierite honeycomb ceramic support from the inlet end. The coating amount is controlled at 5 g / L to obtain a first active coating. The length of the first active coating accounts for 50% of the axial length of the support, and the Pt / Pd ratio in the first active coating is 2:1 with a concentration of 1.5 g / ft. 3 ; A slurry containing ammonium molybdate, ferric nitrate, and titanium oxide at mass ratios of 10 wt%, 5 wt%, and 85 wt% was thoroughly mixed to achieve molybdenum oxide and ferric oxide concentrations of 10 wt% and 5 wt%, respectively. The mixture was then coated from the outlet end of the DPF, with the coating amount controlled at 120 g / L, to obtain a second active coating. The length of the second active coating accounted for 50% of the axial length of the carrier. The target particulate matter collector is obtained by sequentially drying the particulate matter collector coated with the first active coating and the second active coating at 120°C for 1 hour and calcining it at 550°C for 3 hours.

[0080] Example 4 This embodiment provides a particulate matter trap with the function of reducing NO2 content. The particulate matter trap includes a carrier, a first active coating disposed at the air inlet end of the carrier, and a second active coating disposed at the air outlet end of the carrier. The second active coating includes a second load carrier and a second active component loaded on the second load carrier. The second active component is cerium oxide. The second load carrier is silicon oxide.

[0081] The second active coating has a loading of 200 g / L on the carrier; the mass ratio of cerium oxide and silicon oxide is 20 wt% and 80 wt%, respectively.

[0082] The first active coating includes a first support and a first active component loaded on the first support; the first support is cerium zirconium oxide; the first active component is a Pt / Pd mixture; the concentration of the Pt / Pd mixture in the first active coating is 5 g / ft. 3 In the Pt / Pd mixture, the mass ratio of Pt to Pd is 1:10; the loading of the first active coating on the carrier is 50 g / L. In the axial direction of the carrier, the length of the first active coating is greater than or equal to the length of the second active coating; the length of the first active coating accounts for 50% of the axial length of the carrier; the length of the second active coating accounts for 50% of the axial length of the carrier; the carrier is made of cordierite; and the carrier is square in shape.

[0083] The preparation process of the above-mentioned particulate matter trap is as follows: according to Figure 3 The coating scheme shown involves coating a Pt / Pd slurry (with cerium-zirconium oxide as the support) onto a DPF wall-flow cordierite honeycomb ceramic support from the inlet end. The coating amount is controlled at 50 g / L to obtain a first active coating. The length of the first active coating accounts for 50% of the axial length of the support, and the Pt / Pd ratio in the first active coating is 1:10 with a concentration of 5 g / ft. 3 ; A slurry of 20% and 80% cerium nitrate and silica by mass was thoroughly mixed to achieve a cerium oxide concentration of 20 wt%. The mixture was then applied from the outlet end of the DPF, with the coating amount controlled at 200 g / L, to obtain a second active coating. The length of the second active coating accounted for 50% of the axial length of the carrier. The target particulate matter collector is obtained by sequentially drying the particulate matter collector coated with the first active coating and the second active coating at 120°C for 1 hour and calcining it at 550°C for 3 hours.

[0084] Example 5 This embodiment provides a particulate matter trap with the function of reducing NO2 content. The particulate matter trap includes a carrier, a first active coating disposed at the air inlet end of the carrier, and a second active coating disposed at the air outlet end of the carrier. The second active coating includes a second load carrier and a second active component loaded on the second load carrier. The second active component is molybdenum oxide and manganese oxide. The second load carrier is silicon oxide.

[0085] The second active coating has a loading of 10 g / L on the carrier; the mass ratios of molybdenum oxide, manganese oxide, and silicon oxide are 10 wt%, 5 wt%, and 85 wt%, respectively.

[0086] The first active coating includes a first support and a first active component loaded on the first support; the first support is cerium zirconium oxide; the first active component is a Pt / Pd mixture; the concentration of the Pt / Pd mixture in the first active coating is 5 g / ft. 3 In the Pt / Pd mixture, the mass ratio of Pt to Pd is 1:5; the loading of the first active coating on the carrier is 30 g / L. In the axial direction of the carrier, the length of the first active coating is greater than or equal to the length of the second active coating; the length of the first active coating accounts for 50% of the axial length of the carrier; the length of the second active coating accounts for 50% of the axial length of the carrier; the carrier is made of cordierite; and the carrier is square in shape.

[0087] The preparation process of the above-mentioned particulate matter trap is as follows: according to Figure 3 The coating scheme shown involves coating a Pt / Pd slurry (with cerium-zirconium oxide as the support) onto a DPF wall-flow cordierite honeycomb ceramic support from the inlet end. The coating amount is controlled at 50 g / L to obtain a first active coating. The length of the first active coating accounts for 50% of the axial length of the support, and the Pt / Pd ratio in the first active coating is 1:5 with a concentration of 5 g / ft. 3 ; A slurry containing a certain proportion of ammonium molybdate, manganese nitrate, and silica is thoroughly mixed to achieve a molybdenum oxide concentration of 10 wt% and a manganese oxide concentration of 5%. The mixture is then coated from the gas outlet end of the DPF, with the coating amount controlled at 10 g / L, to obtain a second active coating. The length of the second active coating accounts for 50% of the axial length of the carrier. The target particulate matter collector is obtained by sequentially drying the particulate matter collector coated with the first active coating and the second active coating at 120°C for 1 hour and calcining it at 550°C for 3 hours.

[0088] Comparative Example 1 In Comparative Example 1, the only difference from Example 3 is that there is no second active coating, and the length of the first active coating accounts for 100% of the length along the axial direction of the carrier.

[0089] Comparative Example 2 In Comparative Example 2, the only difference from Example 3 is that there is no first active coating, and the length of the second active coating accounts for 100% of the length along the axial direction of the carrier.

[0090] Comparative Example 3 In Comparative Example 3, the only difference from Example 3 is that the length of the second active coating accounts for 80% of the length of the carrier axial direction, while the length of the first active coating accounts for 20% of the length of the carrier axial direction.

[0091] Performance testing The particulate matter traps 1 to 8 prepared in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to catalyst performance testing. The test conditions were: simulated engine exhaust gas composition, 8% O2, 6% CO2, 10% H2O, 200ppm NO2, 300ppm NO, 50ppm C3H6, and the remainder N2, with a space velocity of 50,000 h⁻¹. -1 The test was conducted in a syngas reactor. Starting from room temperature, the temperature was increased to 600℃ at a rate of 10℃ / min, and the changes in gas composition were recorded. The test results are shown in Table 1.

[0092] NO2 conversion rate = (Inlet NO2 concentration - Outlet NO2 concentration) / Inlet NO2 concentration 100% Table 1 Catalyst Efficiency As shown in Table 1, Examples 1-5 all adopt the core technical solution of this invention, namely, a first active coating containing a Pt / Pd mixture is set on a cordierite / silicon carbide support, and a second active coating containing at least one metal oxide from Mo / Co / Mn / Fe / Ce is set at the gas outlet end. The design principle of the first coating's axial length being greater than or equal to that of the second coating is strictly followed. The loading and component ratio of each coating are also within the optimal range defined by this invention. Based on this design, the first active coating can achieve efficient particulate matter capture and regeneration, and the reducing agents such as CO and hydrocarbons generated during its regeneration process can also assist the metal oxides in the second active coating in activation. The sites undergo electron transfer with NO2 through reversible changes in their valence state, efficiently breaking the chemically stable structure of NO2 and promoting its decomposition. Simultaneously, hydrocarbons such as C3H6 in the exhaust gas can act as reducing agents to further promote the reduction reaction of NO2. Furthermore, a well-designed coating length ratio ensures that the first coating fully completes the particulate matter treatment process, guaranteeing that the second coating fully contacts and catalyzes the reaction with NO2 before the exhaust gas is discharged. Therefore, Examples 1-5 all exhibit excellent NO2 conversion performance, with NO2 conversion rates reaching 73%~86% at 250℃, 33%~46% at 400℃, and a maximum NO2 conversion rate of 75%~89%. Example 3, employing a Mo / Fe composite oxide as the second active component and featuring a 50% axial ratio for both the first and second coatings, achieved the best conversion performance among all examples, reaching an NO2 conversion rate of 86% at 250℃, with a maximum conversion rate of 89%. Comparative Example 1, lacking a second active coating and consisting solely of a first active coating covering the support, lacked dedicated metal oxide active sites for directional NO2 catalysis. Relying solely on the exhaust gas components, it could not achieve efficient NO2 conversion, and without any reducing agent to assist the reaction, its NO2 conversion performance was significantly inferior to all other examples, with a conversion rate of only 6% at 250℃. The results of 0%, 19% at 400℃, and a maximum conversion rate of only 67% directly highlight the necessity of the second active coating as the core for directional NO2 conversion. Comparative Example 2 did not have a first active coating and only had the second active coating covering the carrier. Although it retained the active sites for NO2 conversion and achieved a NO2 conversion rate of 80% at 250℃, 35% at 400℃, and a maximum conversion rate of 80%, which was better than Comparative Example 1, it lacked the particulate matter capture and regeneration function of the first coating and did not have the reducing agent generated by the regeneration of the first coating to assist the catalytic reaction of the second coating. Its NO2 conversion performance was still significantly lower than that of the examples, especially the maximum conversion rate was much lower than that of the samples in Examples 3 and 5. This fully demonstrates the synergistic effect between the first and second active coatings. Only by working together can the NO2 conversion efficiency be maximized while achieving particulate matter capture and treatment.Although Comparative Example 3 retained the dual-coating structure design, it violated the core requirement of this invention that the length of the first coating must be greater than or equal to that of the second coating. The axial proportion of the first coating was reduced to 20%, and the second coating was increased to 80%. The excessively short first coating could not fully complete the capture and regeneration of particulate matter, resulting in insufficient amount of reducing agent. Furthermore, the excessively long second coating not only encroached on the effective working space of the first coating but also increased the flow resistance of the exhaust gas. At the same time, the exhaust gas contacted the second coating before it had fully completed particulate matter treatment, which also interfered with the catalytic reaction process of NO2 to some extent. Therefore, although its NO2 conversion rate of 79% at 250℃, 38% at 400℃, and a maximum conversion rate of 83% was better than that of Comparative Examples 1 and 2, it was still significantly lower than that of Examples 1-5. This result highlights the scientific and rational nature of this invention's limitation of the axial proportion of the first coating to 50%~90% and the second coating to 10%~50%. The appropriate coating length proportion is an important prerequisite for the dual coatings to fully exert their synergistic effect and ensure NO2 conversion performance. In summary, the test results in Table 1 fully verify the necessity and scientific validity of the dual-coating structure, coating functional components, and axial length ratio design of this invention. Only by simultaneously setting up complementary first and second active coatings and adhering to the spatial design principle that the length of the first coating is greater than or equal to that of the second coating can the synergistic optimization of particulate matter capture and regeneration and NO2 directional conversion be achieved. Deviating from any core design will lead to a decrease in NO2 conversion performance, making it impossible to simultaneously meet the dual requirements of particulate matter treatment and NO2 ratio control.

[0093] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0094] In the foregoing description of this specification, references to terms such as "one embodiment," "another embodiment," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment is included in at least one embodiment of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples, without contradiction. Additionally, it should be noted that in this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A particulate matter trap with the function of reducing NO2 content, characterized in that, The particulate matter collector includes a carrier, a first active coating disposed on the carrier, and a second active coating disposed at the air outlet end of the carrier; The second active coating includes a second support carrier and a second active component supported on the second support carrier; the second active component includes an oxide of metal M; the metal M includes at least one of Mo, Co, Mn, Fe, and Ce; The second load carrier includes an oxide carrier or a non-precious metal modified oxide thereof; the oxide carrier includes at least one of alumina, titanium oxide, silicon oxide, and cerium zirconium oxide.

2. The particulate matter trap with NO2 reduction function according to claim 1, characterized in that, The loading of the second active coating on the cellular carrier is 10-200 g / L; preferably 100 g / L.

3. The particulate matter trap with NO2 reduction function according to claim 1, characterized in that, The second active component accounts for 1 wt% to 50 wt% of the mass of the second active coating.

4. The particulate matter trap with NO2 reduction function according to claim 1, characterized in that, The first active coating includes a first support carrier and a first active component loaded on the first support carrier; Preferably, the first load carrier includes at least one of alumina, silicon oxide, and cerium zirconium oxide; Preferably, the first active component comprises a Pt / Pd mixture.

5. The particulate matter trap with NO2 reduction function according to claim 4, characterized in that, The concentration of the Pt / Pd mixture in the first active coating is 1 g / ft. 3 ~5g / ft 3 ; Preferably, the mass ratio of Pt to Pd in ​​the Pt / Pd mixture is 10:1 to 1:10; more preferably, it is 2:

1.

6. The particulate matter trap with NO2 reduction function according to claim 4, characterized in that, The loading of the first active coating on the carrier is 1 g / L to 50 g / L; preferably 10 g / L.

7. The particulate matter trap with NO2 reduction function according to claim 1, characterized in that, In the axial direction of the carrier, the length of the first active coating is greater than or equal to the length of the second active coating.

8. The particulate matter trap with NO2 reduction function according to claim 1, characterized in that, The length of the first active coating accounts for 50% to 100% of the axial length of the carrier; the length of the second active coating accounts for 10% to 50% of the axial length of the carrier.

9. The particulate matter trap with NO2 reduction function according to any one of claims 1 to 8, characterized in that, The carrier material includes at least one of cordierite and silicon carbide; and / or, The carrier used can be circular or square.

10. A method for treating engine exhaust gas, characterized in that, The particulate matter trap according to any one of claims 1 to 9 is used to treat engine exhaust gas.

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