Bifunctional catalysts for synergistic purification of nitrogen oxides and CO, their preparation and application

Abstract

This invention discloses a bifunctional catalyst suitable for the synergistic purification of nitrogen oxides and CO, its preparation method, and its applications. The bifunctional catalyst has a core-shell structure, wherein the core comprises Cu-ZSM-5, and the shell comprises a copper-cerium composite metal oxide; the mass ratio of Cu-ZSM-5 to the copper-cerium composite metal oxide is (0.25~4):1; the molar ratio of copper to cerium in the copper-cerium composite metal oxide is (0.2~3):1. The bifunctional catalyst of this invention can be used in the temperature range of 200~450℃ and at a volume hourly space velocity of 40000 h⁻¹. ‑1 Under these conditions, more than 90% of NO can be obtained. x Conversion rate, CO oxidation rate and N2 selectivity.

Description

Technical Field

[0001] This invention relates to the fields of air pollution control technology and catalyst preparation technology, specifically to a catalyst suitable for nitrogen oxides (NOx). x Bifunctional catalysts for the synergistic purification of NO and carbon monoxide (CO), their preparation methods, and applications. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] NO x NOx and CO are major air pollutants in industrial flue gas and vehicle exhaust, directly harming human health and the ecological environment. Ammonia selective catalytic reduction (NH3-SCR) technology is currently the most mature flue gas denitrification technology, widely used in coal-fired power plants, steel sintering, cement kilns, and diesel vehicle exhaust treatment. For CO, efficient oxidation removal is typically achieved using CO oxidation technology. In the context of environmental technology upgrades aimed at reducing pollution and carbon emissions, improving quality and efficiency, the synergistic removal of NOx is crucial. x CO is of great significance.

[0004] At present, regarding NO x Co-removal of NO and CO often employs CO-SCR (Selective Catalytic Reduction of CO) technology. However, actual industrial flue gas is mostly in an oxygen-rich environment, which significantly reduces the denitrification efficiency of CO-SCR. Simultaneous NH3-SCR and CO oxidation reactions on the same catalyst can effectively avoid these problems, thus becoming a method for the synergistic removal of NO. x Effective methods for dealing with CO.

[0005] Currently, researchers have attempted to develop bifunctional catalysts capable of simultaneously achieving NH3-SCR and CO oxidation. However, existing technologies still have the following shortcomings: (1) Competition for active sites: On a single catalyst, the NH3-SCR reaction and the CO oxidation reaction often compete for active oxygen species and active sites, resulting in mutual constraints on the efficiency of the two reactions.

[0006] (2) Temperature window mismatch: Traditional NH3-SCR catalysts (such as Cu-ZSM-5) need to have matching acidity and redox properties to ensure the efficient conduction of denitrification reactions in the medium-high temperature range (250~400℃). For example, the patent specification with publication number CN106732757A discloses a method for preparing Cu-ZSM-5 denitrification catalyst by one-step hydrothermal synthesis using a dual-template approach, which can be used for NH3-SCR reactions. However, CO oxidation catalysts only require strong redox centers to promote efficient activation of oxygen, which makes it difficult for the same catalyst to achieve efficient synergy between NH3-SCR and CO oxidation within the same temperature window.

[0007] (3) Dependence on precious metals: Some bifunctional catalysts that combine NH3-SCR and CO oxidation activities depend on precious metal components such as Pt and Pd, which are costly and limit their large-scale industrial application.

[0008] Therefore, NO with a wide temperature window, high activity, and low cost was developed. x The synergistic effect of catalysts with CO removal has significant practical and economic value. Summary of the Invention

[0009] To address the aforementioned technical problems and shortcomings in the field, this invention provides a method suitable for NO x A bifunctional catalyst for synergistic CO purification, its preparation method, and its application. The bifunctional catalyst of this invention has a core-shell structure, with a Cu ion-exchanged HZSM-5 molecular sieve (Cu-ZSM-5) as the core and a copper-cerium composite metal oxide (CuCeO) as the core. x ) as the outer shell, utilizing the outer shell CuCeO x The initial activation of NH3 and the exothermic effect of CO oxidation, combined with the efficient NH3-SCR reaction on the core Cu-ZSM-5, achieve synergistic effects of NH3-SCR and CO oxidation. The catalyst developed in this invention exhibits both high synergistic purification performance and product selectivity over a wide temperature window, while its low cost makes it suitable for industrial application.

[0010] The specific technical solution of this invention is as follows: In a first aspect, the present invention provides a bifunctional catalyst suitable for the synergistic purification of nitrogen oxides and CO, having a core-shell structure, wherein the core comprises a Cu ion-exchanged HZSM-5 molecular sieve (Cu-ZSM-5), and the outer shell comprises a copper-cerium composite metal oxide (CuCeO). x The mass ratio of Cu-ZSM-5 to copper-cerium composite metal oxide (the mass of the copper-cerium composite metal oxide is based on CuO+CeO2) is (0.25~4):1, for example 0.4:1, 0.5:1, 0.6:1, 1:1, etc., preferably (0.4~1):1. Under preferred conditions, the NO content of the catalyst...x The catalyst exhibits superior conversion rate, CO oxidation rate, and N2 selectivity. The molar ratio of copper to cerium in the copper-cerium composite metal oxide is (0.2~3):1, for example, 0.5:1, 1:1, 1.5:1, etc., preferably (0.5~1.5):1. Under these preferred conditions, the catalyst exhibits better NO conversion efficiency, CO oxidation rate, and N2 selectivity. x It has better conversion rate, CO oxidation rate and N2 selectivity.

[0011] Cu-ZSM-5 serves as the active center for the NH3-SCR reaction, enabling the efficient and selective reduction of NO by NH3. x CuCeO x Coated on the surface of Cu-ZSM-5, it serves as an active center for the initial activation of NH3 and the oxidation of CO, and is used to catalyze the initial activation and dehydrogenation of NH3 and the catalytic oxidation of CO.

[0012] In some preferred embodiments, the bifunctional catalyst Cu-ZSM-5 has a Cu loading of 1wt% to 8wt%, such as 3wt%, 3.5wt%, 4wt%, etc., preferably 3wt% to 4wt%. Under preferred conditions, the catalyst has a NO content of 1wt% to 8wt%. x It has better conversion rate, CO oxidation rate and N2 selectivity.

[0013] In some preferred embodiments, the bifunctional catalyst Cu-ZSM-5 has a silicon-to-aluminum ratio (Si / Al) of 10 to 50, preferably 20 to 30.

[0014] Secondly, the present invention provides a method for preparing the bifunctional catalyst described in the first aspect, using either method one or method two; Method 1 includes: mixing cerium source, copper source and citric acid in water to obtain a sol-gel mixture, and then adding HZSM-5 molecular sieve (preferably with a specific surface area ≥300 m²). 2 (g) Continue stirring to evaporate the solvent and form a mixed gel. Dry, calcine once, exchange copper ions, and calcine twice to obtain the bifunctional catalyst. Method 2 includes: mixing cerium source, copper source and citric acid in water and stirring to obtain a sol-gel mixture, then adding Cu-ZSM-5 and continuing stirring to evaporate the solvent to form a mixed gel, drying and calcining to obtain the bifunctional catalyst.

[0015] In some preferred embodiments, the preparation method of the bifunctional catalyst involves copper and cerium concentrations in the sol-gel mixture being independently 0.1~0.6 mol / L.

[0016] In some preferred embodiments, the ratio of the total molar number of copper in the copper source and cerium in the cerium source to the molar number of citric acid in the preparation method of the bifunctional catalyst is (0.5~2):1.

[0017] In some preferred embodiments, the method for preparing the bifunctional catalyst includes cerium source comprising one or more of cerium nitrate, cerium chloride, and cerium sulfate.

[0018] In some preferred embodiments, the copper source in the method for preparing the bifunctional catalyst includes one or more of copper nitrate, copper chloride, copper sulfate, and copper acetate.

[0019] In some preferred embodiments, the temperature of the volatile solvent in the preparation method of the bifunctional catalyst is 40~90°C.

[0020] In some preferred embodiments, the drying temperature in the preparation method of the bifunctional catalyst is 100~150°C.

[0021] In some preferred embodiments, the preparation method of the bifunctional catalyst involves calcination at a temperature of 300–700°C (e.g., 400°C, 450°C, 500°C, etc.) for a time of 2–6 h (e.g., 3 h, 4 h, etc.). The above-mentioned limitations on calcination temperature and time apply to the single-stage calcination, double-stage calcination, and calcination in Method 1, Method 2, and the calcination in the Cu-ZSM-5 acquisition method described below.

[0022] In some preferred embodiments, the method for preparing the bifunctional catalyst, wherein the copper ion exchange comprises: placing the calcined product in a copper ion solution and stirring, and repeating this process multiple times (e.g., 3-5 times). More preferably, the copper ion solution comprises one or more of copper nitrate solution, copper chloride solution, copper sulfate solution, and copper acetate solution. More preferably, the copper ion concentration in the copper ion solution is 0.01~0.05 mol / L.

[0023] In Method 2, Cu-ZSM-5 can be obtained by the following method: HZSM-5 molecular sieve (preferably with a specific surface area ≥ 300 m²) is used. 2 The copper ion solution (g) is placed in a copper ion solution and stirred, and this process is repeated multiple times (e.g., 3-5 times) to complete the copper ion exchange, followed by drying and calcination. More preferably, the copper ion solution includes one or more of copper nitrate solution, copper chloride solution, copper sulfate solution, and copper acetate solution. More preferably, the copper ion concentration in the copper ion solution is 0.01~0.05 mol / L.

[0024] In some preferred embodiments, the temperature for copper ion exchange is 50-90°C (e.g., 60°C, 80°C, etc.), and the time is 2-12 hours (e.g., 3 hours, 6 hours, 9 hours, etc.).

[0025] Thirdly, the present invention provides the application of the bifunctional catalyst described in the first aspect for the synergistic purification of nitrogen oxides and CO.

[0026] Fourthly, the present invention provides a method for synergistically purifying nitrogen oxides and CO, using the bifunctional catalyst described in the first aspect to conduct a catalytic reaction in a gaseous environment in which nitrogen oxides, NH3, CO and O2 coexist, thereby synergistically purifying nitrogen oxides and CO.

[0027] In some preferred embodiments, the catalytic reaction temperature of the method for synergistic purification of nitrogen oxides and CO is 150~450℃, such as 200℃, 250℃, 300℃, 350℃, 400℃, etc.

[0028] In some preferred embodiments, the method for synergistically purifying nitrogen oxides and CO involves a bifunctional catalyst with a volume space velocity of 5000~150000 h⁻¹ during the catalytic reaction. -1 For example, 40000 h -1 wait.

[0029] In some preferred embodiments, the method for synergistically purifying nitrogen oxides and CO is wherein the NO volume concentration in the gaseous environment is 100-1000 ppm.

[0030] In some preferred embodiments, the method for synergistically purifying nitrogen oxides and CO is wherein the volume concentration of NH3 in the gaseous environment is 100-1000 ppm.

[0031] In some preferred embodiments, the method for synergistically purifying nitrogen oxides and CO is wherein the NH3 / NO molar ratio in the gaseous environment is 0.8 to 1.2.

[0032] In some preferred embodiments, the method for synergistically purifying nitrogen oxides and CO is wherein the CO volume concentration in the gaseous environment is 1,000 to 20,000 ppm, for example, 10,000 ppm.

[0033] In some preferred embodiments, the method for synergistically purifying nitrogen oxides and CO is wherein the volume concentration of O2 in the gaseous environment is 3% to 10%.

[0034] In some preferred embodiments, the method for synergistically purifying nitrogen oxides and CO further includes a gaseous environment containing water vapor. More preferably, the water vapor volume concentration in the gaseous environment is 5% to 10%.

[0035] The bifunctional catalyst of this invention can operate at temperatures ranging from 200 to 450°C and with a volume hourly space velocity of 40,000 h⁻¹. -1 Under these conditions, more than 90% of NO can be obtained. x Conversion rate, CO oxidation rate and N2 selectivity.

[0036] Compared with the prior art, the beneficial effects of this invention are as follows: This invention develops a core-shell structure Cu-ZSM-5@CuCeOx A bifunctional catalyst achieves highly efficient synergistic effects between CO oxidation and NH3-SCR denitrification by constructing a spatially separated reaction system. This catalyst uses Cu-ZSM-5 as its core and CuCeO as its catalyst core. x The outer shell of the catalyst primarily confines the CO oxidation and initial NH3 activation processes to the outer shell region, while limiting the NH3-SCR reaction mainly to the core region. This effectively avoids competition for active sites and reactive oxygen species between CO oxidation and the NH3-SCR reaction in traditional catalysts. The outer shell is CuCeO. x It exhibits excellent redox properties, and its surface Cu 2+ / Cu + and Ce 4+ / Ce 3+ Redox cycles promote CO oxidation and NH3 activation. The heat released by CO oxidation increases the local temperature of the catalyst, which is beneficial for enhancing the low-temperature SCR reaction activity and broadening the catalyst's active temperature window. Simultaneously, active intermediates such as -NH2 generated by NH3 activation can further diffuse to the core Cu-ZSM-5 surface, promoting the SCR reaction and increasing NO content. x Removal efficiency. The core Cu-ZSM-5 has abundant acidic sites and Cu active centers, enabling it to remove NO. x The core-shell structure provides highly efficient reduction. Its spatial isolation effect effectively inhibits excessive oxidation of NH3 on the outer shell, reducing the formation of byproducts such as NO, NO2, and N2O, and improving N2 selectivity and NH3 utilization. Furthermore, this invention uses non-noble metals such as Cu and Ce as active components, avoiding the use of noble metals such as Pt, Pd, and Ru. This significantly reduces catalyst preparation costs while ensuring excellent catalytic performance, demonstrating promising prospects for industrial application. Attached Figure Description

[0037] Figure 1 The catalysts of Examples 1-3 and Comparative Examples 1-6 were used for NO at different reaction temperatures in the specific implementation embodiments. x NO synergistically purified with CO x Conversion rate results chart.

[0038] Figure 2 The catalysts of Examples 1-3 and Comparative Examples 1-6 were used for NO at different reaction temperatures in the specific implementation embodiments. x A graph showing the CO oxidation rate results of synergistic purification with CO.

[0039] Figure 3 The catalysts of Examples 1-3 and Comparative Examples 1-6 were used for NO at different reaction temperatures in the specific implementation embodiments. x The N2 selectivity results of co-purification with CO. Detailed Implementation

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Operating methods not specifically specified in the following embodiments are generally performed under conventional conditions or as recommended by the manufacturer.

[0041] In the following examples, HZSM-5 molecular sieves are commercially available industrial products with a silicon-to-aluminum ratio (Si / Al) of 20-30 and a specific surface area ≥300 m². 2 / g, particle size <200 mesh.

[0042] Example 1: 1. Catalyst preparation: A type of NO x A bifunctional catalyst for synergistic CO purification, featuring a core-shell structure, wherein the core comprises Cu-ZSM-5 and the outer shell comprises CuCeO. x The resulting bifunctional catalyst contains Cu-ZSM-5 and CuCeO x The theoretical mass ratio is approximately 0.5.

[0043] The preparation method of the bifunctional catalyst in this embodiment includes the following steps: (1) 8.68 g (0.02 mol) cerium nitrate Ce(NO3)3·6H2O, 4.83 g (0.02 mol) copper nitrate Cu(NO3)2·3H2O, and 11.53 g (0.06 mol) citric acid C6H8O7 were added to 100 mL of deionized water. After stirring continuously at room temperature for 3 hours, a sol-gel mixture was obtained. Then, 2.5 g of HZSM-5 molecular sieve was added and stirred continuously for 2 hours to obtain a mixture. The resulting mixture was transferred to an 80 ℃ water bath and stirred until the solvent evaporated and a mixed gel was formed. The gel was placed in a 120 ℃ oven and dried for 20 h to obtain a solid mixture. After grinding, it was calcined in a muffle furnace at 500 ℃ for 4 h (heating rate of 5 ℃ / min) to obtain HZSM-5@CuCeO x -0.5 sample.

[0044] (2) The prepared HZSM-5@CuCeO x -0.5 μL of the sample was placed in a 0.025 mol / L copper nitrate solution and stirred at 80 °C for 3 hours for ion exchange. This exchange process was repeated three times (with fresh copper nitrate solution each time). After the exchange was completed, the sample was repeatedly washed with deionized water until the filtrate was neutral (pH ≈ 7) and dried at 100 °C for 12 hours. Subsequently, it was calcined at 450 °C for 3 hours (heating rate of 10 °C / min) to obtain Cu-ZSM-5@CuCeO. x-0.5 wt% catalyst. The Cu loading in Cu-ZSM-5 is 3.5 wt%.

[0045] 2. Performance Testing: 2.3 mL of powdered catalyst with a particle size of 40-60 mesh was placed in a fixed-bed quartz tube reactor with an inner diameter of 1 cm. The initial gas composition (by volume) was: NO 1000 ppm, NH3 1000 ppm, CO 10000 ppm, O2 3%, water vapor 5%, and the remainder nitrogen. The reaction temperature was 150–450 °C, and the volume hourly space velocity (VHSV) was 40000 h⁻¹. -1 .

[0046] Example 2: The only difference from Example 1 is that the amount of HZSM-5 molecular sieve added is 1.25 g; all other aspects are the same, including Cu-ZSM-5 and CuCeO. x The theoretical mass ratio is approximately 0.25, and the resulting bifunctional catalyst is Cu-ZSM-5@CuCeO. x -0.25.

[0047] Example 3: The only difference from Example 1 is that the amount of HZSM-5 molecular sieve added is 20 g; all other aspects are the same, including Cu-ZSM-5 and CuCeO. x The theoretical mass ratio is approximately 4.0, and the resulting bifunctional catalyst is Cu-ZSM-5@CuCeO. x -4.0.

[0048] Comparative Example 1: The only difference from Example 1 is that HZSM-5 molecular sieve is not added and the ion exchange in step (2) is not performed; all other aspects are the same, and the resulting catalyst is CuCeO alone. x .

[0049] Comparative Example 2: The only difference from Example 1 is that cerium nitrate, copper nitrate and citric acid are not added in step (1), and the rest are the same. The catalyst obtained is Cu-ZSM-5 alone.

[0050] Comparative Example 3: The only difference from Example 1 is that in step (1), the amount of cerium nitrate Ce(NO3)3·6H2O added is 0 mol (0 g), the amount of copper nitrate Cu(NO3)2·3H2O added is 0.063 mol (15.22 g), and the amount of citric acid C6H8O7 added is 0.095 mol (18.25 g). All other steps are the same, and the resulting catalyst is Cu-ZSM-5@CuO. x -0.5.

[0051] Comparative Example 4: The only difference from Example 1 is that in step (1), the amount of copper nitrate Cu(NO3)2·3H2O added is 0 mol (0 g), the amount of cerium nitrate Ce(NO3)3·6H2O added is 0.029 mol (12.59 g), and the amount of citric acid C6H8O7 added is 0.044 mol (8.45 g). All other steps are the same, and the resulting catalyst is Cu-ZSM-5@CeO. x -0.5.

[0052] Comparative Example 5: The only difference from Example 1 is that HZSM-5 in step (1) is replaced with Cu-ZSM-5 after ion exchange (obtained according to Comparative Example 2). The ion exchange operation in step (2) is not performed thereafter. All other steps are the same, resulting in Cu-ZSM-5@CuCeO. x -0.5-R catalyst.

[0053] Comparative Example 6: The only difference from Example 1 is that the CuCeO of Comparative Example 1 was mixed by grinding. x Cu-ZSM-5 / CuCeO was obtained from Comparative Example 2. x -0.5 catalyst (of which Cu-ZSM-5 and CuCeO x The theoretical mass ratio is approximately 0.5, and all other mass ratios are the same.

[0054] Examples 1-3 and Comparative Examples 1-6: Catalysts for NO x NO synergistically purified with CO x Conversion rate, etc. Figure 1 As shown, the CO oxidation rate is as follows: Figure 2 As shown, N2 selectivity is as follows Figure 3 As shown.

[0055] Comparing the data of Example 1 with those of Comparative Examples 1-2, it can be seen that in NO x In the synergistic purification process with CO, the Cu-ZSM-5 catalyst alone exhibits excellent NH3-SCR reactivity and N2 selectivity, but its low-temperature CO oxidation performance is poor. This is mainly due to its weak redox properties, which prevent it from effectively activating gaseous oxygen. Meanwhile, CuCeO alone... x The oxide exhibits acceptable CO oxidation activity, but it does not show good NH3-SCR reactivity and N2 selectivity over a wide temperature window. This is mainly due to its excessively strong redox properties, leading to over-oxidation of NH3. However, the Cu-ZSM-5@CuCeO provided in this invention... xThe catalyst can enhance its low-temperature CO oxidation performance through the strong synergistic effect between the two, while also exhibiting excellent NH3-SCR reactivity and N2 selectivity, ultimately demonstrating good NO oxidation performance over a wide temperature window. x It has synergistic purification performance with CO.

[0056] Comparing the data of Example 1 with those of Comparative Examples 3-4, it can be seen that in NO x During the co-purification process with CO, CuCeO on the outer shell is removed. x Replace with CuO x (Comparative Example 3) and CeO x (Comparative Example 4) results in poor low-temperature denitration and CO oxidation activity of the catalyst, mainly due to CuO alone. x or CeO x Unable to complete Cu 2+ / Cu + and Ce 4+ / Ce 3+ The redox cycle leads to a decrease in the redox performance of the catalyst, which is insufficient to effectively activate NH3 and gaseous oxygen at low temperatures.

[0057] Comparing the data from Example 1 and Comparative Example 5, it can be seen that copper ion exchange is performed first, followed by CuCeO. x Cu-ZSM-5@CuCeO prepared by shell coating x -0.5-R also has similar NO x The synergistic purification performance with CO confirms that changing the preparation order does not significantly affect the performance of the catalyst.

[0058] Comparing the data from Example 1 and Comparative Example 6, it can be seen that grinding and mixing CuCeO... x Cu-ZSM-5 / CuCeO obtained from Cu-ZSM-5 x -0.5 catalyst cannot produce good NO x The synergistic purification performance with CO confirms that non-core-shell structures cannot effectively avoid the inhibition of CO oxidation by strongly acidic Cu-ZSM-5 and the strong oxidizing effect of CuCeO. x Excessive oxidation of NH3.

[0059] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A bifunctional catalyst suitable for the synergistic purification of nitrogen oxides and CO, characterized in that, It has a core-shell structure, wherein the core consists of Cu-ZSM-5 and the shell consists of copper-cerium composite metal oxide; the mass ratio of Cu-ZSM-5 to copper-cerium composite metal oxide is (0.25~4):1; the molar ratio of copper to cerium in the copper-cerium composite metal oxide is (0.2~3):

1.

2. The bifunctional catalyst according to claim 1, characterized in that, The Cu loading in Cu-ZSM-5 is 1wt%~8wt%.

3. The bifunctional catalyst according to claim 1, characterized in that, The silicon-to-aluminum ratio of Cu-ZSM-5 is 10~50, preferably 20~30.

4. The method for preparing the bifunctional catalyst according to any one of claims 1 to 3, characterized in that, Use either method one or method two; Method 1 includes: mixing cerium source, copper source and citric acid in water and stirring to obtain a sol-gel mixture, then adding HZSM-5 molecular sieve and continuing stirring, evaporating the solvent to form a mixed gel, drying, first calcination, copper ion exchange, and second calcination to obtain the bifunctional catalyst; Method 2 includes: mixing cerium source, copper source and citric acid in water and stirring to obtain a sol-gel mixture, then adding Cu-ZSM-5 and continuing stirring to evaporate the solvent to form a mixed gel, drying and calcining to obtain the bifunctional catalyst.

5. The preparation method according to claim 4, characterized in that, The ratio of the total molar number of copper in the copper source and cerium in the cerium source to the molar number of citric acid is (0.5~2):1; The cerium source includes one or more of cerium nitrate, cerium chloride, and cerium sulfate; The copper source includes one or more of copper nitrate, copper chloride, copper sulfate, and copper acetate; The copper ion exchange includes: placing the calcined product in a copper ion solution and stirring, and repeating the process multiple times.

6. The preparation method according to claim 4, characterized in that, The roasting temperature is 300~700℃, and the time is 2~6 hours; The temperature for copper ion exchange is 50~90℃, and the time is 2~12 h.

7. The bifunctional catalyst according to any one of claims 1 to 3 for the synergistic purification of nitrogen oxides and CO.

8. A method for synergistically purifying nitrogen oxides and CO, characterized in that, Using the bifunctional catalyst according to any one of claims 1 to 3, a catalytic reaction occurs in a gaseous environment where nitrogen oxides, NH3, CO and O2 coexist, synergistically purifying nitrogen oxides and CO.

9. The method for synergistic purification of nitrogen oxides and CO according to claim 8, characterized in that, The catalytic reaction temperature is 150~450℃; The bifunctional catalyst has a volume space velocity of 5000~150000 h⁻¹ during the catalytic reaction. -1 ; The NO volume concentration in the gaseous environment is 100~1000 ppm; The volume concentration of NH3 in the gaseous environment is 100~1000 ppm; The NH3 / NO molar ratio in the gaseous environment is 0.8~1.2; The CO volume concentration in the gaseous environment is 1000~20000 ppm; The volume concentration of O2 in the gaseous environment is 3%~10%.

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