A dual-effect catalyst for simultaneous removal of NH3 and N2O, its preparation method and application

Abstract

This invention provides a dual-effect catalyst for the simultaneous removal of NH3 and N2O, comprising a support and a coating applied to the surface of the support. The coating includes an inner coating and an outer coating. The inner coating adheres closely to the surface of the support, and the outer coating covers the surface of the inner coating. The inner coating comprises the following components: Pt, Co3O4, BaO, Al2O3, and TiO2. The outer coating comprises Cu-SSZ-13 and a binder. This invention uses barium-modified cobalt oxide to obtain a highly active N2O removal material. Simultaneously, the use of an Al2O3 and TiO2 composite coating combines the anti-poisoning properties of TiO2 with the high-temperature resistance of Al2O3, and reduces the N2O generation of traditional ASC catalysts. By combining the two catalysts and coating them on the same support, a dual-effect catalyst capable of simultaneously removing NH3 and N2O is obtained. This invention also provides a method for preparing the dual-effect catalyst for the simultaneous removal of NH3 and N2O. Research on the selection of catalyst precursors, component ratios, and post-treatment methods yields a highly active dual-effect catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalysis technology, and in particular to a dual-effect catalyst for the simultaneous removal of NH3 and N2O, its preparation method, and its application. Background Technology

[0002] According to the emission standards "Limits and Measurement Methods for Pollutant Emissions from Light-Duty Vehicles (China VI)" and "Limits and Measurement Methods for Pollutant Emissions from Heavy-Duty Diesel Vehicles (China VI)," the commonly adopted China VI emission technology routes are mostly in the form of "EGR+DOC+DPF+SCR+ASC," or DDPF (DOC and DPF integrated), SDPF (SCR and DPF integrated), and CDPF (DPF loaded with a small amount of precious metals to promote active regeneration). Among these, EGR (Exhaust Gas Recirculation) is a technology that separates a portion of the exhaust gas after combustion in an internal combustion engine and introduces it into the intake side for re-combustion, which can suppress the generation of nitrogen oxides and improve fuel economy; DOC (Diesel Oxidation Gas Recirculation)... The diesel engine oxidation catalyst (Catalyst) is typically the first stage in a three-stage exhaust manifold, usually using precious metals or ceramics as the catalyst carrier. Its main function is to oxidize carbon monoxide and hydrocarbons in the exhaust gas, converting them into carbon dioxide and water. It can also absorb soluble organic components and some carbon particles, reducing PM (particulate matter) emissions, and oxidize nitrogen monoxide to nitrogen dioxide. The diesel particulate filter (DPF), the second stage in the three-stage exhaust manifold, primarily captures PM particles, reducing them by approximately 90%. Once the DPF has captured a sufficient amount of particulate matter, to prevent further damage... Blockage will dissolve the captured particulate matter; this process is called DPF regeneration. SCR (Selective Catalytic Reduction) technology, the final stage in the exhaust pipe, uses urea as a reducing agent. It uses a catalyst to chemically react with nitrogen oxides, converting them into nitrogen and water. ASC (Ammonia Slip Catalyst) prevents ammonia escape. Because vehicles may experience urea leaks or low reaction efficiency, the ammonia produced by urea decomposition may not participate in the reaction and be directly emitted into the atmosphere. ASC reduces the ammonia leaking from the exhaust after SCR through catalytic oxidation. The main function of ASC is to oxidize excess NH3 into N2, N2O, and NOx, while simultaneously catalyzing the reaction of NOx with NH3 to N2.

[0003] However, increasingly stringent engine emission standards, with the Euro 7 standard already implemented and adding emission limits for NH3 and N2O, and the upcoming China VII standard inevitably having corresponding emission limits, pose a significant challenge to existing after-treatment technologies. Current engine after-treatment technologies include ASC catalysts (ammonia slip catalysts) specifically for NH3, but lack treatment devices for N2O. Adding additional treatment devices would require significant space. If NH3 and N2O could be removed simultaneously from the existing ASC, the existing after-treatment process could be utilized to the maximum extent, simplifying the future China VII standard after-treatment system and reducing costs. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a dual-effect catalyst for the simultaneous removal of NH3 and N2O, a preparation method and application, so as to obtain a new treatment technology that can remove NH3 and N2O at the same time.

[0005] To achieve the above and other related objectives, the present invention provides a dual-effect catalyst for the simultaneous removal of NH3 and N2O, comprising a support and a coating applied to the surface of the support, the coating comprising an inner coating and an outer coating; the inner coating is in close contact with the surface of the support, and the outer coating covers the surface of the inner coating; the inner coating, on a dry weight basis, comprises the following components in the following mass percentages: Pt 0.05-0.08%; Co3O4 16-19%; BaO 1-4%; Al2O3 15-16% and TiO2 63-64%; the outer coating, on a dry weight basis, comprises the following components in the following mass percentages: Cu-SSZ-13 96-99%; binder 1-4%.

[0006] Preferably, the carrier is selected from honeycomb cordierite.

[0007] Preferably, the adhesive is selected from one or more of boehmite, liquid silica gel, and aluminum hydroxide sol.

[0008] Preferably, the mass percentage of BaO in the total amount of Co3O4 and BaO is 5%-20%.

[0009] Preferably, the loading of the inner coating is 80-120 g / L.

[0010] Preferably, the loading of the outer coating is 80-120 g / L.

[0011] The present invention also provides a method for preparing a dual-effect catalyst for the simultaneous removal of NH3 and N2O as described above, comprising the following steps:

[0012] a. Preparation of the slurry for the inner coating: Barium metal oxide or salt solution is impregnated onto cobalt metal oxide or salt, and calcined to prepare active powder; Platinum, aluminum, and titanium metal oxides or salts are dissolved in a solvent, and the active powder is added, mixed, and the solid content and pH are adjusted to obtain the slurry for the inner coating.

[0013] b. Preparation of the slurry for the outer coating: Grind Cu-SSZ-13, add binder, mix, and adjust the solid content and pH to obtain the slurry for the outer coating;

[0014] c. Coating: The slurry of the inner coating layer is coated onto the carrier, the dry loading of the inner coating slurry is controlled, and after drying and calcination, the slurry of the outer coating layer is coated, the dry loading of the outer coating slurry is controlled, and after drying and calcination again, the dual-effect catalyst is obtained.

[0015] The present invention also provides an application of the dual-effect catalyst for simultaneous removal of NH3 and N2O as described above in the field of engine exhaust gas treatment.

[0016] As described above, the present invention has the following beneficial effects:

[0017] 1) The dual-effect catalyst for the simultaneous removal of NH3 and N2O in this invention uses barium-modified cobalt oxide to obtain a highly active N2O removal material. At the same time, it uses an Al2O3 and TiO2 composite coating, which combines the anti-poisoning properties of TiO2 and the high-temperature resistance of Al2O3, and reduces the N2O generation of traditional ASC catalysts. Pt is used to oxidize NH3, and combined with Cu molecular sieve coating, NH3 and the generated NO react again to generate N2 and H2O. In this invention, the two catalysts are coated on the same support in an internal and external coating manner and in an appropriate ratio to obtain a dual-effect catalyst that can simultaneously remove NH3 and N2O.

[0018] 2) The preparation method of the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, through the study of the selection of catalyst precursor, component ratio and post-treatment method, obtained a highly active dual-effect catalyst.

[0019] 3) The dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention can directly integrate N2O removal into the ASC compared with the existing EGR→DOC→DPF→SCR→ASC after-treatment system, without the need to add a separate device, thus avoiding space occupation and saving the additional costs of carrier and packaging. It achieves pollutant control under the condition that the system remains unchanged, thereby simplifying the system and reducing costs. Attached Figure Description

[0020] Figure 1 The figure shows the removal rate of N2O by the dual-effect catalyst of the present invention for simultaneously removing NH3 and N2O as a function of temperature.

[0021] Figure 2 The figure shows the NH3 removal rate of the dual-effect catalyst for the simultaneous removal of NH3 and N2O of the present invention as a function of temperature. Detailed Implementation

[0022] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0023] Please refer to the accompanying drawings. It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0024] The first aspect of this invention provides a dual-effect catalyst for the simultaneous removal of NH3 and N2O, comprising a support and a coating applied to the surface of the support, the coating comprising an inner coating and an outer coating; the inner coating is in close contact with the surface of the support, and the outer coating covers the surface of the inner coating; the inner coating, on a dry weight basis, comprises the following components in the following mass percentages: Pt 0.05-0.08%; Co3O4 16-19%; BaO 1-4%; Al2O3 15-16% and TiO2 63-64%; the outer coating, on a dry weight basis, comprises the following components in the following mass percentages: Cu-SSZ-13 96-99%; binder 1-4%.

[0025] The mass percentage of Pt in the inner coating can be 0.05–0.06%, 0.06–0.07%, or 0.07–0.08%. In a preferred embodiment of the present invention, the mass percentage of Pt is 0.07%.

[0026] The mass percentage of Co3O4 in the inner coating can be 16–17%, 17–18%, or 18–19%.

[0027] The mass percentage of BaO in the inner coating can be 1-2%, 2-3%, or 3-4%.

[0028] The mass percentage of Al2O3 in the inner coating can be 15–15.1%, 15.1–15.2%, 15.2–15.3%, 15.3–15.4%, 15.4–15.5%, 15.5–15.6%, 15.6–15.7%, 15.7–15.8%, 15.8–15.9%, or 15.9–16%. In a preferred embodiment of the present invention, the mass percentage of Al2O3 is 15.99%.

[0029] The mass percentage of TiO2 in the inner coating can be 63–63.1%, 63.1–63.2%, 63.2–63.3%, 63.3–63.4%, 63.4–63.5%, 63.5–63.6%, 63.6–63.7%, 63.7–63.8%, 63.8–63.9%, or 63.9–64%. In a preferred embodiment of the present invention, the mass percentage of TiO2 is 63.94%.

[0030] In a preferred embodiment of the present invention, the mass percentage ratio of Al2O3 to TiO2 is 1:4.

[0031] In a preferred embodiment of the present invention, the sum of the mass percentages of Co3O4 and BaO is 20%.

[0032] In a preferred embodiment of the present invention, the mass percentage of BaO in the total amount of Co3O4 and BaO is 5%-20%. For example, it is 5%-6%, 6%-7%, 7%-8%, 8%-9%, 9%-10%, 10%-11%, 11%-12%, 12%-13%, 13%-14%, 14%-15%, 15%-16%, 16%-17%, 17%-18%, 18%-19%, or 19%-20%.

[0033] The mass percentage of Cu-SSZ-13 in the outer coating can be 96-97%, 97-98%, or 98-99%. In a preferred embodiment of the present invention, the mass percentage of Cu-SSZ-13 is 98%. The Cu-SSZ-13 is a Cu-SSZ-13 molecular sieve.

[0034] The mass percentage of the adhesive in the outer coating can be 1-2%, 2-3%, or 3-4%. In a preferred embodiment of the present invention, the mass percentage of the adhesive is 2%.

[0035] In the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, the support is selected from honeycomb cordierite.

[0036] In the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, the binder is selected from one or more of boehmite, liquid silica gel, and aluminum hydroxide sol.

[0037] In the dual-effect catalyst for the simultaneous removal of NH3 and N2O of the present invention, the loading of the inner coating is 80–120 g / L. For example, it is 80–85 g / L, 85–90 g / L, 90–95 g / L, 95–100 g / L, 100–105 g / L, 105–110 g / L, 110–115 g / L, or 115–120 g / L. In a preferred embodiment of the present invention, the loading of the inner coating is 100 g / L.

[0038] In the dual-effect catalyst for the simultaneous removal of NH3 and N2O of the present invention, the loading of the outer coating is 80–120 g / L. For example, it is 80–85 g / L, 85–90 g / L, 90–95 g / L, 95–100 g / L, 100–105 g / L, 105–110 g / L, 110–115 g / L, or 115–120 g / L. In a preferred embodiment of the present invention, the loading of the outer coating is 100 g / L.

[0039] The loading amount refers to the mass of catalyst attached to a unit volume of carrier.

[0040] A second aspect of this invention provides a method for preparing the above-mentioned dual-effect catalyst for simultaneous removal of NH3 and N2O, comprising the following steps:

[0041] a. Preparation of the slurry for the inner coating: Barium metal oxide or salt solution is impregnated onto cobalt metal oxide or salt, and calcined to prepare active powder; Platinum, aluminum, and titanium metal oxides or salts are dissolved in a solvent, and the active powder is added, mixed, and the solid content and pH are adjusted to obtain the slurry for the inner coating.

[0042] b. Preparation of the slurry for the outer coating: Grind Cu-SSZ-13, add binder, mix, and adjust the solid content and pH to obtain the slurry for the outer coating;

[0043] c. Coating: The slurry of the inner coating layer is coated onto the carrier, the dry loading of the inner coating slurry is controlled, and after drying and calcination, the slurry of the outer coating layer is coated, the dry loading of the outer coating slurry is controlled, and after drying and calcination again, the dual-effect catalyst is obtained.

[0044] In the preparation method of the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, in step a, the barium metal oxide or salt solution is selected from one or more of barium acetate solution or barium hydroxide solution.

[0045] In step a, the cobalt metal oxide or salt is selected from cobalt carbonate.

[0046] In step a, the metal oxide or salt of platinum is selected from platinum nitrate.

[0047] In step a, the aluminum metal oxide or salt is selected from boehmite.

[0048] In step a, the titanium metal oxide or salt is selected from titanium dioxide.

[0049] In the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, the calcination temperature in step a is 450–500°C. For example, it is 450–455°C, 455–460°C, 460–465°C, 465–470°C, 470–475°C, 475–480°C, 480–485°C, 485–490°C, 490–495°C, or 495–500°C.

[0050] In step a, the calcination time is 1 to 3 hours. For example, it is 1 to 2 hours or 2 to 3 hours.

[0051] In step a, the solvent is deionized water.

[0052] In step a, the solid content is 30-40%. For example, it is 30-31%, 31-32%, 32-33%, 33-34%, 34-35%, 35-36%, 36-37%, 37-38%, 38-39%, or 39-40%. In a preferred embodiment of the present invention, in step a, the solid content is 33-35%.

[0053] In step a, the pH is 6 to 7.

[0054] In the preparation method of the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, the specific process of preparing the slurry of the inner coating includes: impregnating barium acetate solution onto cobalt carbonate, calcining at 450°C for 2 hours to obtain active powder; adding platinum nitrate solution to an appropriate amount of deionized water, stirring evenly, adding titanium dioxide and boehmite, mixing, adding the active powder, stirring and adjusting the slurry solid content to 30-40% and pH 6-7 to obtain the slurry of the inner coating.

[0055] In the dual-effect catalyst for the simultaneous removal of NH3 and N2O of the present invention, in step b, the grinding is performed until D50 ≤ 3 μm. For example, D50 ≤ 0.5 μm, D50 is 0.5–1.0 μm, D50 is 1.0–1.5 μm, D50 is 1.5–2.0 μm, D50 is 2.0–2.5 μm, or D50 is 2.5–3.0 μm.

[0056] In step b, the solid content is 25-35%. For example, it can be 25-26%, 26-27%, 27-28%, 28-29%, 29-30%, 30-31%, 31-32%, 32-33%, 33-34%, or 34-35%. In a preferred embodiment of the invention, in step b, the solid content is 29%-31%.

[0057] In step b, the pH is 5 to 6.

[0058] In the preparation method of the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, the specific process of preparing the slurry of the outer coating includes: adding Cu-SSZ-13 to an appropriate amount of water, stirring evenly and grinding until D50≤3μm, adding a binder and stirring, adjusting the solid content of the slurry to 25-35% and pH 5-6, to obtain the slurry of the outer coating.

[0059] In the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, in steps a and b, the pH adjuster is selected from one or more of tartaric acid or tetramethylamine hydroxide.

[0060] In the dual-effect catalyst for the simultaneous removal of NH3 and N2O of the present invention, in step c, the dry loading of the slurry of the inner coating layer is 80–120 g / L. For example, it is 80–85 g / L, 85–90 g / L, 90–95 g / L, 95–100 g / L, 100–105 g / L, 105–110 g / L, 110–115 g / L, or 115–120 g / L. In a preferred embodiment of the present invention, the dry loading of the slurry of the inner coating layer is 100 g / L.

[0061] In step c, the dry loading of the slurry for the outer coating is 80–120 g / L. For example, it can be 80–85 g / L, 85–90 g / L, 90–95 g / L, 95–100 g / L, 100–105 g / L, 105–110 g / L, 110–115 g / L, or 115–120 g / L. In a preferred embodiment of the invention, the dry loading of the slurry for the outer coating is 100 g / L.

[0062] In step c, the dry loading amount refers to the loading amount calculated based on the mass after the sizing is completed and the material is dried and calcined.

[0063] In step c, the drying and calcination involves raising the temperature from room temperature to 180–220°C within 30 minutes, for example, 180–185°C, 185–190°C, 190–195°C, 195–200°C, 200–205°C, 205–210°C, 210–215°C, or 215–220°C, holding at this temperature for 1 hour, and then raising the temperature to 530–580°C within 60 minutes, for example, 530–535°C, 535–540°C, 540–545°C, 545–550°C, 550–555°C, 555–560°C, 560–565°C, 565–570°C, 570–575°C, or 575–580°C, holding at this temperature for 2 hours, and then allowing it to cool naturally. In a preferred embodiment of the present invention, the drying and calcination involves raising the temperature from room temperature to 200°C within 30 minutes, holding it at that temperature for 1 hour, raising the temperature to 550°C within 60 minutes, holding it at that temperature for 2 hours, and then allowing it to cool naturally.

[0064] In step c, the drying and calcination are carried out in a muffle furnace.

[0065] In step c, the coating process employs a bottom-feeding vacuum method. In this invention, bottom-feeding refers to the slurry passing over the carrier from bottom to top.

[0066] In the dual-effect catalyst for simultaneous removal of NH3 and N2O of the present invention, the mass percentage ratio of Pt, Co3O4, BaO, Al2O3 and TiO2 in the inner coating of the dual-effect catalyst is: (0.05~0.08):(16-19):(1-4):(15~16):(63~64).

[0067] In this invention, a dual-effect catalyst for the simultaneous removal of NH3 and N2O is prepared using a cobalt precursor modified with barium. The Hedvall effect during the decomposition of CoCO3 promotes the migration of alkali into the Co3O4 lattice. Therefore, after calcination, alkali ions are distributed not only on the surface of the catalyst but also within the catalyst bulk. The alkali on the surface is inactive, while the alkali components migrating into the bulk affect the electronic structure of Co3O4, thereby promoting the catalytic activity of Co3O4 for the direct decomposition of N2O. Using TiO2 to partially replace traditional Al2O3 reduces the formation of N2O during the NH3 oxidation process. Simultaneously, controlling the ratio of TiO2 to Al2O3 and the method of Al2O3 addition solves the sintering problem of TiO2 at high temperatures.

[0068] A third aspect of the present invention provides the application of the dual-effect catalyst for simultaneous removal of NH3 and N2O as described above in the field of engine exhaust gas treatment.

[0069] Example 1

[0070] Preparation of a dual-effect catalyst for simultaneous removal of NH3 and N2O:

[0071] a. Preparation of the slurry for the inner coating: Dissolve 5g of barium acetate in 10g of deionized water, impregnate it onto 40.0g of cobalt carbonate, and calcine at 450℃ for 2h to obtain active powder; add 0.85g of platinum nitrate solution (platinum content 12.5%) to 280g of deionized water, stir evenly, add 110.9g of titanium dioxide and 30.0g of boehmite, stir for 10min, add the active powder, continue stirring for 30min, adjust the slurry solid content to 33%-35%, pH 6-7, to obtain the slurry for the inner coating;

[0072] b. Preparation of slurry for outer coating: Add 150g Cu-SSZ13 to 280g deionized water, stir evenly and grind to D50 = 2.76μm, add 3g pseudoboehmite and stir for 30min; adjust the solid content to 29%-31% and pH 5-6 to obtain the slurry for outer coating;

[0073] c. Coating: Apply the inner coating slurry to the honeycomb cordierite, with a carrier size of [missing information]. The dry loading is 100 g / L; after drying and calcination, the slurry is coated with an outer coating, with a loading of 100 g / L. After drying and calcination, a dual-effect catalyst for the simultaneous removal of NH3 and N2O can be obtained.

[0074] Comparative Example 1

[0075] Preparation of a dual-effect catalyst for simultaneous removal of NH3 and N2O:

[0076] a. Preparation of the slurry for the inner coating: 44.4g of cobalt carbonate was calcined at 450℃ for 2h to obtain active powder, which did not contain BaO; 0.85g of platinum nitrate solution (platinum content 12.5%) was added to 280g of deionized water and stirred evenly. Then, 110.9g of titanium dioxide and 30.0g of boehmite were added and stirred for 10min. The active powder was then added and stirred for another 30min. The solid content of the slurry was adjusted to 33%-35% and the pH was 6-7 to obtain the slurry for the inner coating.

[0077] b. Preparation of slurry for outer coating: Add 150g Cu-SSZ13 to 280g deionized water, stir evenly and grind to D50 = 2.76μm, add 3g pseudoboehmite and stir for 30min; adjust the solid content to 29%-31% and pH 5-6 to obtain the slurry for outer coating;

[0078] c. Coating: Apply the inner coating slurry to the honeycomb cordierite, with a carrier size of [missing information]. The dry loading is 100 g / L; after drying and calcination, the slurry is coated with an outer coating, with a loading of 100 g / L. After drying and calcination, a dual-effect catalyst for the simultaneous removal of NH3 and N2O can be obtained.

[0079] Comparative Example 2

[0080] Preparation of a dual-effect catalyst for simultaneous removal of NH3 and N2O:

[0081] a. Preparation of the slurry for the inner coating: Dissolve 12.5g of barium acetate in 10g of deionized water, impregnate it onto 33.3g of cobalt carbonate, and calcine at 450℃ for 2h to obtain active powder. The proportion of BaO in the obtained active powder is 25%. Add 0.85g of platinum nitrate solution (platinum content 12.5%) to 280g of deionized water, stir evenly, add 110.9g of titanium dioxide and 30.0g of boehmite, stir for 10min, add the active powder, continue stirring for 30min, adjust the solid content of the slurry to 33%-35%, and pH 6-7 to obtain the slurry for the inner coating.

[0082] b. Preparation of slurry for outer coating: Add 150g Cu-SSZ13 to 280g deionized water, stir evenly and grind to D50 = 2.76μm, add 3g pseudoboehmite and stir for 30min; adjust the solid content to 29%-31% and pH 5-6 to obtain the slurry for outer coating;

[0083] c. Coating: Apply the inner coating slurry to the honeycomb cordierite, with a carrier size of [missing information]. The dry loading is 100 g / L; after drying and calcination, the slurry is coated with an outer coating, with a loading of 100 g / L. After drying and calcination, a dual-effect catalyst for the simultaneous removal of NH3 and N2O can be obtained.

[0084] Comparative Example 3

[0085] Preparation of a dual-effect catalyst for simultaneous removal of NH3 and N2O:

[0086] a. Preparation of the slurry for the inner coating: Dissolve 5g of barium acetate in 10g of deionized water, impregnate it onto 27g of cobalt tetroxide, and calcine at 450℃ for 2h to obtain active powder; add 0.85g of platinum nitrate solution (platinum content 12.5%) to 280g of deionized water, stir evenly, add 110.9g of titanium dioxide and 30.0g of boehmite, stir for 10min, add the active powder, continue stirring for 30min, adjust the slurry solid content to 33%-35%, pH 6-7, and obtain the slurry for the inner coating;

[0087] b. Preparation of slurry for outer coating: Add 150g Cu-SSZ13 to 280g deionized water, stir evenly and grind to D50 = 2.76μm, add 3g pseudoboehmite and stir for 30min; adjust the solid content to 29%-31% and pH 5-6 to obtain the slurry for outer coating;

[0088] c. Coating: Apply the inner coating slurry to the honeycomb cordierite, with a carrier size of [missing information]. The dry loading is 100 g / L; after drying and calcination, the slurry is coated with an outer coating, with a loading of 100 g / L. After drying and calcination, a dual-effect catalyst for the simultaneous removal of NH3 and N2O can be obtained.

[0089] Comparative Example 4

[0090] Preparation of a dual-effect catalyst for simultaneous removal of NH3 and N2O:

[0091] The proportions of each component were adjusted so that the sum of the mass percentages of Co3O4 and BaO in the prepared dual-effect catalyst was 15%.

[0092] Comparative Example 5

[0093] Preparation of a dual-effect catalyst for simultaneous removal of NH3 and N2O:

[0094] The proportions of each component were adjusted so that the sum of the mass percentages of Co3O4 and BaO in the prepared dual-effect catalyst was 25%.

[0095] Comparative Example 6

[0096] Preparation of a dual-effect catalyst for simultaneous removal of NH3 and N2O:

[0097] a. Preparation of the slurry for the inner coating: Add 0.85g of platinum nitrate solution (platinum content 12.5%) to 280g of deionized water, stir evenly, add 110.9g of titanium dioxide and 30.0g of boehmite, stir for 10min, add active powder, continue stirring for 30min, adjust the slurry solid content to 33%-35%, pH 6-7, and obtain the slurry for the inner coating;

[0098] b. Preparation of slurry for outer coating: Add 150g Cu-SSZ13 to 280g deionized water, stir evenly, and grind to D50 = 2.76μm. Add 3g binder and stir for 30min. Adjust the solid content to 29%-31% and pH 5-6 to obtain the slurry for outer coating.

[0099] c. Coating: Apply the inner coating slurry to the honeycomb cordierite, with a carrier size of [missing information]. The dry loading is 100 g / L; after drying and calcination, the slurry is coated with an outer coating, with a loading of 100 g / L. After drying and calcination, a dual-effect catalyst for the simultaneous removal of NH3 and N2O can be obtained.

[0100] The dual-effect catalysts for simultaneous removal of NH3 and N2O prepared in Example 1 and Comparative Examples 1-6 were subjected to hydrothermal aging at 800°C for 16 hours, followed by a space velocity of 60,000 h⁻¹. -1The denitrification performance was tested at 150-400℃, with H2O: 7%, O2: 10%, N2O: 500ppm, NH3: 500ppm, a heating rate of 10℃ / min, and an initial stable temperature of 120℃.

[0101] The test method is as follows: Using a blank carrier, adjust the parameters of each flow meter according to the above flue gas conditions to reach the required values. After stabilizing at 120℃, record the NH3 and N2O concentrations at the reactor outlet as the calculated values ​​of NH3 and N2O concentrations at the inlet of the test sample. Replace the blank carrier with the test sample, set the heating rate after stabilizing at 120℃, and use a Fourier transform infrared flue gas analyzer to monitor the outlet flue gas parameters online. Calculate the efficiency based on these two values ​​and obtain the temperature-efficiency relationship curve.

[0102] Test results are as follows Figure 1 , Figure 2 As shown, compared with Example 1, Comparative Example 1, without Ba modification of Co, had a lower N2O removal performance of the prepared catalyst; Comparative Example 2, with excessive Ba addition, resulted in a loss of N2O removal performance; Comparative Example 3, by directly replacing the cobalt precursor with Co3O4, also had lower performance of the prepared sample; Comparative Examples 4 and 5 mainly adjusted the mass ratio of active powder to the overall coating. It can be found that when the proportion of active powder 1 is low, the N2O removal performance of the dual-effect catalyst product is low; when the proportion of active powder is too high, the N2O removal performance of the product is not improved, but the NH3 removal performance is lost; Comparative Example 6, without the addition of active powder 1, only had NH3 removal ability, while N2O was generated.

[0103] The dual-effect catalyst for simultaneous removal of NH3 and N2O in Example 1 of this invention exhibits high synergistic removal performance of NH3 and N2O. The main reason is that the Hedvall effect during the decomposition of CoCO3 promotes the migration of Ba into the Co3O4 lattice. Therefore, after calcination, Ba ions are not only distributed on the surface of the catalyst but also in the bulk of Co3O4. These Ba ions promote the direct decomposition reaction of N2O. The use of a composite support of titanium oxide and alumina maximizes the performance of the active components while possessing good high-temperature resistance and anti-poisoning properties.

[0104] In summary, the dual-effect catalyst for the simultaneous removal of NH3 and N2O of this invention utilizes Ba-modified cobalt oxide to obtain a highly active N2O removal material. The Al2O3 and TiO2 composite coating combines the anti-poisoning properties of TiO2 with the high-temperature resistance of Al2O3, while reducing the N2O generation of traditional ASC catalysts. By combining the two catalysts and coating them on the same support, a dual-effect catalyst capable of simultaneously removing NH3 and N2O is obtained. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0105] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A dual-function catalyst for simultaneous removal of NH3 and N2O, characterized in that, The catalyst comprises a carrier and a coating layer coated on the surface of the carrier, the coating layer comprises an inner coating layer and an outer coating layer; the inner coating layer is close to the surface of the carrier, and the outer coating layer covers the surface of the inner coating layer; the inner coating layer comprises the following components in mass percentage based on dry weight: Pt 0.05~0.08%; Co3O4 16~19%; BaO 1~4%; Al2O3 15~16% and TiO2 63~64%; the outer coating layer comprises the following components in mass percentage based on dry weight: Cu-SSZ-13 96~99%; a binder 1~4%; and a preparation method of the dual-effect catalyst, comprising the following steps: a. Preparation of slurry of inner coating layer: impregnating a barium source solution on a cobalt salt, and preparing active powder by calcination; dissolving a platinum source, an aluminum source and a titanium source in a solvent, and adding the active powder to obtain the slurry of the inner coating layer by mixing and adjusting solid content and pH; the cobalt salt is selected from cobalt carbonate; the barium source solution is selected from one or both of barium acetate solution and barium hydroxide solution; the platinum source is selected from platinum nitrate; the aluminum source is selected from pseudoboehmite; and the titanium source is selected from titanium white powder; b. Preparation of slurry of outer coating layer: grinding Cu-SSZ-13, adding a binder, and mixing to obtain the slurry of the outer coating layer by adjusting solid content and pH; c. Coating slurry: coating the slurry of the inner coating layer on the carrier, controlling the dry loading amount of the slurry of the inner coating layer, drying and calcining, coating the slurry of the outer coating layer, controlling the dry loading amount of the slurry of the outer coating layer, drying and calcining again to obtain the dual-effect catalyst. The carrier is selected from honeycomb cordierite; 2. The dual function catalyst for simultaneous removal of NH3 and N20 according to claim 1, characterized in that, and / or, the binder is selected from one or more of pseudoboehmite, liquid silica gel and aluminum hydroxide sol; and / or, the mass percentage of BaO in the total amount of Co3O4 and BaO is 5%~20%; and / or, the loading amount of the inner coating layer is 80~120g / L; and / or, the loading amount of the outer coating layer is 80~120g / L. In step a, the calcination temperature is 450~500℃; 3. The dual function catalyst for simultaneous removal of NH3 and N20 according to claim 1, characterized in that, and / or, in step a, the calcination time is 1~3h; and / or, in step a, the solvent is deionized water; and / or, in step a, the solid content is 30~40%; and / or, in step a, the pH is 6~7. In step b, the grinding is ground to D50≤3μm; 4. The dual function catalyst for simultaneous removal of NH3 and N20 according to claim 1, characterized in that, and / or, in step b, the solid content is 25~35%; and / or, in step b, the pH is 5~6. In steps a and b, the pH adjusting agent used for adjusting pH is selected from one or more of tartaric acid or tetramethylammonium hydroxide.

5. The dual function catalyst for simultaneous removal of NH3 and N20 according to claim 1, characterized in that, In step c, the loading amount of the slurry of the inner coating layer is 80~120g / L; 6. The dual function catalyst for simultaneous removal of NH3 and N20 according to claim 1, characterized in that, and / or, in step c, the loading amount of the slurry of the outer coating layer is 80~120g / L; and / or, in step c, the drying and calcination is to increase the temperature from room temperature to 180~220℃ for 30min, to increase the temperature to 530~580℃ within 60min after keeping the temperature for 1h, and then to keep the temperature for 2h, and then to naturally cool down; and / or, in step c, the drying and calcination is carried out in a muffle furnace; and / or, in step c, the coating adopts the way of feeding from the bottom and vacuumizing. ​ 7. The dual function catalyst for simultaneous removal of NH3 and N20 according to claim 1, characterized in that, The mass percentage ratio of Pt, Co3O4, BaO, Al2O3 and TiO2 in the inner coating of the dual-effect catalyst is: 0.05-0.08:(16-19):(1-4):(15-16):(63-64).

8. Use of the dual-effect catalyst for simultaneously removing NH3 and N2O according to any one of claims 1-7 in the field of engine exhaust treatment.

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