A method for online regulation of NH3 generation in hydrogen engine aftertreatment catalyst

Abstract

This invention provides a method for controlling the online NH3 generation of a hydrogen engine aftertreatment catalyst, comprising: mixing NOx contained in the exhaust gas of a hydrogen engine with hydrogen, and then passing the mixture into a reactor containing an NTA catalyst; controlling the selectivity of NH3 in the NOx reduction products by adjusting the molar ratio of H2 to NO. This application utilizes H2 to generate NH3 in situ on the NTA catalyst, avoiding the problems of low-temperature crystallization and NH3 leakage. It achieves highly selective conversion of NOx reduction products to NH3 over a wide temperature and concentration range.

Description

Technical Field

[0001] This invention relates to the field of exhaust gas catalysis technology, specifically to a method for online regulation of NH3 generation in hydrogen engine aftertreatment catalysts. Background Technology

[0002] Hydrogen engines, as a zero-carbon internal combustion engine technology, are one of the important pathways to achieving carbon neutrality in the transportation sector. The main combustion product of hydrogen is water vapor, producing no CO, HC, or particulate matter. However, due to its high combustion temperature, it generates a large amount of thermal nitrogen oxides (NOx). Unlike traditional gasoline or diesel engines, hydrogen engines typically operate under lean-burn conditions (excess air coefficient λ>2), resulting in high oxygen concentration and water vapor content in the exhaust, along with a wide range of exhaust temperature fluctuations (approximately 200℃~500℃). These characteristics pose significant challenges to NOx after-treatment technologies.

[0003] Currently, the mainstream NOx after-treatment technologies include the following four: Three-way catalytic converters (TWCs) can only simultaneously purify CO, HC, and NOx under conditions of an equivalence ratio (λ≈1). Hydrogen engines mostly operate under lean-burn conditions, and TWCs cannot effectively reduce NOx. Furthermore, the precious metals in TWCs are prone to hydrothermal aging in high-temperature and high-humidity environments, leading to a decrease in activity.

[0004] Selective catalytic reduction (SCR) uses NH3, generated from urea hydrolysis, as a reducing agent to reduce NOx to N2 under oxygen-rich conditions. However, SCR requires an additional urea supply system, which carries risks of low-temperature urea crystallization and NH3 leakage. Furthermore, the urea hydrolysis process increases system complexity and cost. For hydrogen engines, the high water vapor content in the exhaust makes urea nozzles prone to clogging, and urea hydrolysis efficiency is low under low-temperature conditions.

[0005] Lean-burn NOx capture (LNT) achieves NOx adsorption and reduction through alternating lean and rich combustion conditions. However, LNT requires frequent switching of the air-fuel ratio in the engine, affecting fuel economy and drivability, and produces higher emissions of byproducts N2O and NH3. Furthermore, the precious metals in LNT catalysts also face the problem of hydrothermal aging and deactivation.

[0006] Hydrogen selective catalytic reduction (H2-SCR) directly uses H2 as a reducing agent to reduce NOx. However, H2-SCR is prone to side reactions between H2 and O2 under lean-burn conditions, and the product selectivity is poor. At high temperatures, the ratio of N2O and NH3 formation is difficult to control.

[0007] To overcome the aforementioned shortcomings, researchers have recently proposed the NTA-SCR coupling technology route: first, an NTA (NOx to Ammonia) catalyst is used to convert some of the NOx in the exhaust gas into NH3 in an H2 atmosphere; then, the generated NH3 is used to reduce the remaining NOx on a downstream SCR catalyst. This route eliminates the need for an external supply of NH3, avoiding urea crystallization and leakage problems, and fully utilizes unburned H2 in the exhaust gas of hydrogen engines as a reducing agent.

[0008] However, the product selectivity (N2O, N2, NH3) of existing NTA catalysts in the H2 / NO reaction is affected by various factors, including reaction temperature, H2 concentration, and catalyst composition. In actual hydrogen engine exhaust, NOx concentration and residual H2 vary in real time with operating conditions, and a simple, operable, and highly selective online NH3 generation control strategy is lacking. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention proposes an online NH3 generation control method for hydrogen engine aftertreatment catalysts, aiming to achieve highly selective conversion of NOx reduction products to NH3 over a wide temperature and concentration range.

[0010] In a first aspect, embodiments of this application provide a method for controlling the online NH3 generation of a hydrogen engine aftertreatment catalyst, comprising: The NOx contained in the exhaust gas of the hydrogen engine is mixed with hydrogen and then passed into a reactor containing an NTA catalyst. By adjusting the molar ratio of H2 to NO to be greater than 1, the selectivity of NH3 in the NOx reduction product is controlled.

[0011] Optionally, the molar ratio of H2 / NO is adjustable between 1.5 and 5.0.

[0012] Optionally, the molar ratio of H2 / NO is 2.5.

[0013] Optionally, the reaction between NOx and H2 in the exhaust gas is carried out at a temperature range of 150°C to 500°C.

[0014] Optionally, the reaction between NOx and H2 in the exhaust gas is carried out at a temperature range of 250°C to 350°C.

[0015] Optionally, the NTA catalyst includes a perovskite active center, a Ba-based NOx storage unit, and an Al2O3 support.

[0016] Optionally, the perovskite active center is a LaCoO3-based material modified with metals at the A-site and / or B-site.

[0017] Optionally, the perovskite active center is a LaCoO3-based material with simultaneous A / B site modification.

[0018] Optionally, the perovskite active center is La0.9Ce0.1Co0.9Pd0.1O3 or La0.9Ce0.1Co0.9Pt0.1O3.

[0019] Optionally, the loading ratio of the perovskite active sites in the NTA catalyst is 15 wt%.

[0020] This application also provides a method for catalytic reduction of NOx in H2 engine exhaust gas, including a method for regulating NH3 generation; it further includes: using an SCR catalyst to catalytically reduce the generated NH3 with the remaining NOx in the exhaust gas to generate N2 and H2O.

[0021] Optionally, the SCR catalyst is a metal-modified molecular sieve SCR catalyst.

[0022] Optionally, the SCR catalyst is a Ce and Zr modified Cu-ZSM-5 catalyst.

[0023] Optionally, the SCR catalyst is 6%Ce-2%Zr / Cu-ZSM-5.

[0024] This application utilizes H2 to generate NH3 in situ over an NTA catalyst, avoiding the problems of low-temperature crystallization and NH3 leakage. It achieves highly selective conversion of NOx reduction products to NH3 over a wide temperature and concentration range. Attached Figure Description

[0025] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale.

[0026] Figure 1 In an embodiment of this application, the online NH3 generation control method for hydrogen engine aftertreatment catalysts provides a method for controlling La. 1-x Ce x XRD pattern of CoO3 material.

[0027] Figure 2 LaCo is used in the online NH3 generation control method of the hydrogen engine aftertreatment catalyst provided in an embodiment of this application. 0.9 M 0.1 XRD patterns of O3 (M=Co,Pd,Pt) materials.

[0028] Figure 3 In an embodiment of this application, the online NH3 generation control method for hydrogen engine aftertreatment catalysts provides a method for controlling La. 1-x Ce x Co 0.9 M 0.1 XRD patterns of O3 (M=Co,Pd,Pt) materials.

[0029] Figure 4 The XRD patterns of NTA catalysts with different active center loading ratios in the online NH3 generation control method for hydrogen engine aftertreatment catalysts provided in an embodiment of this application.

[0030] Figure 5 This is a selectivity diagram of H2 / NO reaction products of NTA catalysts with different active center loading ratios in an online NH3 generation control method for hydrogen engine aftertreatment catalysts provided in an embodiment of this application.

[0031] Figure 6 This diagram illustrates the selectivity of the H2 / NO reaction products of the NTA catalyst under different temperature conditions in the online NH3 generation control method for hydrogen engine aftertreatment catalysts provided in an embodiment of this application. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are merely descriptive and not limiting, and should not be used to limit the scope of protection of the present invention.

[0033] When a quantity, concentration, or other value or parameter is described as a range, preferred range, or preferred upper and lower limits, it should be understood that it is equivalent to specifically disclosing any range by combining any pair of upper or preferred values ​​with any lower or preferred values, regardless of whether the range is specifically disclosed. Unless otherwise stated, the numerical range values ​​listed herein include the endpoints of the range and all integers and fractions within that range.

[0034] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0035] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0036] In the following embodiments, unless otherwise specified, all raw materials or reagents can be obtained through commercial purchases or prepared using conventional methods in the art.

[0037] In this embodiment, a series of modified LaCoO3 perovskite materials were synthesized using the sol-gel method to screen out the active centers with the best redox performance.

[0038] Example 1: Preparation of A-site doped modified perovskite oxides (preparation of La) 1-x Ce x CoO3 (x=0,0.05,0.1,0.15,0.2)) La was synthesized by A-site doping. 1-x Ce x CoO3 material (x=0, 0.05, 0.1, 0.15, 0.2). XRD (e.g.) Figure 1 As shown in the figure, it was found that when the Ce doping amount x=0.1, the material (La0.9Ce0.1CoO3) has the best microstructure properties and the highest oxygen mobility. 4+ The introduction of increases surface adsorption of oxygen (O) a The proportion of ds) is increased, thereby improving its redox performance.

[0039] Figure 1 In the diagram, 'a' represents undoped Ce pure-phase LaCoO3 perovskite material (x=0), serving as a baseline. 'b' represents La... 0.95 Ce 0.05 CoO3: Sample with 5% Ce doping (x=0.05). c represents La. 0.9 Ce 0.1 CoO3: Sample with 10% Ce doping (x=0.1). d represents La. 0.85 Ce 0.15 CoO3: Sample with 15% Ce doping (x=0.15). e represents La. 0.8 Ce 0.2 Sample with CoO3:Ce doping of 20% (x=0.2).

[0040] For Ce-doped La at site A 1-x Ce x CoO3 materials were prepared by using the sol-gel method to prepare La with different Ce doping ratios. 1-x Ce x CoO3 (x=0, 0.05, 0.1, 0.15, 0.2) material: (1) Weigh La(NO3)3·6H2O, Co(NO3)2·6H2O and Ce(NO3)3·6H2O according to the stoichiometric ratio, add an appropriate amount of deionized water to prepare a mixed salt solution with a total metal ion concentration of 0.2 mol / L.

[0041] (2) Weigh out the corresponding mass of EDTA and CA and add them to the above solution according to the molar ratio of metal cation: ethylenediaminetetraacetic acid (EDTA): citric acid (CA) = 1:1:1.5.

[0042] (3) Place the mixture in an ultrasonic cleaner and sonicate for 30 minutes to fully dissolve the complexing agent.

[0043] (4) Add 25-28% ammonia water dropwise to adjust the pH of the solution to 6-7.

[0044] (5) Place the pH-adjusted solution in an 80°C constant temperature water bath and stir continuously to evaporate the water until a viscous gel is formed.

[0045] (6) Transfer the gel to a forced-air drying oven and dry at 110°C for 12 hours to obtain a fluffy dry gel.

[0046] (7) Place the dry gel in a muffle furnace and heat it to 400°C at a heating rate of 5°C / min. Hold it at that temperature for 2 hours, then continue heating to 800°C and calcining for 4 hours. Allow it to cool naturally to room temperature and grind it to obtain a powder sample.

[0047] Example 2: Preparation of B-site doped perovskite oxides (Preparation of LaCo0.9M0.1O3 (M=Co,Pd,Pt)) LaCo0.9M0.1O3 (M=Co,Pd,Pt) materials were synthesized through B-site doping (e.g., ...). Figure 2 As shown in the figure). XRD shows that Pd / Pt doping causes lattice distortion. After doping with Pd or Pt, the reduction peak temperature of the material shifts significantly to the low-temperature region (for example, the low-temperature reduction peak of LaCo0.9Pd0.1O3 drops from 437°C to 219°C), indicating that its redox performance is significantly improved.

[0048] Figure 2 In the diagram, a represents undoped Ce pure-phase LaCoO3 perovskite material (M=0), used as a reference. b represents LaCo0.9Pd0.1O3 perovskite material (M=Pd). c represents LaCo0.9Pd0.1O3 perovskite material (M=Pt).

[0049] For the preparation of B-site noble metal-doped LaCo0.9M0.1O3 (M=Pd,Pt) materials via the sol-gel method: (1) Weigh out La(NO3)3·6H2O, Co(NO3)2·6H2O and Pd(NO3)2·2H2O or Pt(NO3)4 solution according to stoichiometric ratio, keeping the molar ratio of metal at site A to site B at 1:1; add an appropriate amount of deionized water to prepare a mixed salt solution with a total metal ion concentration of 0.2 mol / L.

[0050] (2) Weigh out the corresponding mass of EDTA and CA and add them to the above solution according to the molar ratio of metal cation: ethylenediaminetetraacetic acid (EDTA): citric acid (CA) = 1:1:1.5.

[0051] (3) Place the mixed solution in an ultrasonic cleaner and perform ultrasonic treatment for 30 minutes to fully dissolve the complexing agent.

[0052] (4) Slowly add 25 - 28% ammonia water drop by drop to adjust the pH value of the solution to 6 - 7.

[0053] (5) Place the solution with adjusted pH in a constant temperature water bath at 80 °C, continuously stir, and evaporate the water until a viscous gel is formed.

[0054] (6) Transfer the gel to a blast drying oven and dry it at 110 °C for 12 hours to obtain a fluffy dry gel.

[0055] (7) Place the dry gel in a muffle furnace, heat it at a heating rate of 5 °C / min to 400 °C, hold for 2 hours, continue to heat to 800 °C, hold for 4 hours for roasting, naturally cool to room temperature, and grind to obtain LaCo0.9Pd0.1O3 and LaCo0.9Pt0.1O3 samples.

[0056] Example 3: Preparation of A / B-site co-doped perovskite-type oxides (Preparation of La 1-x Ce x Co 1-y M y O3, where 0 < x ≤ 0.2, 0 ≤ y ≤ 0.15, M = Pd or Pt) Through A / B-site co-doping, based on the previous screening, La0.9Ce0.1Co0.9Pd0.1O3 and La0.9Ce0.1Co0.9Pt0.1O3 materials were synthesized (as Figure 3 shown). As shown in the XRD pattern in Figure 3 shown, La0.9Ce0.1Co0.9Pd0.1O3 has the optimal comprehensive performance and is therefore selected as the active center of the NTA catalyst.

[0057] For the preparation of A / B-site co-doped noble metal-doped LaCo0.9M0.1O3 (M = Pd, Pt) materials by the sol-gel method: (1) Weigh La(NO3)3·6H2O, Ce(NO3)3·6H2O, Co(NO3)2·6H2O, and Pd(NO3)2·2H2O or Pt(NO3)4 solution according to the stoichiometric ratio, and keep the total molar ratio of A-site (La + Ce) to B-site (Co + Pd / Pt) at 1:1, where Ce accounts for 10% of the A-site and Pd / Pt accounts for 10% of the B-site. Add an appropriate amount of deionized water to prepare a mixed salt solution with a total metal ion concentration of 0.2 mol / L.

[0058] (2) Weigh out the corresponding mass of EDTA and CA and add them to the above solution according to the molar ratio of metal cation: ethylenediaminetetraacetic acid (EDTA): citric acid (CA) = 1:1:1.5.

[0059] (3) Place the mixture in an ultrasonic cleaner and sonicate for 30 minutes to fully dissolve the complexing agent.

[0060] (4) Add 25-28% ammonia water dropwise to adjust the pH of the solution to 6-7.

[0061] (5) Place the pH-adjusted solution in an 80°C constant temperature water bath and stir continuously to evaporate the water until a viscous gel is formed.

[0062] (6) Transfer the gel to a forced-air drying oven and dry at 110°C for 12 hours to obtain a fluffy dry gel.

[0063] (7) The dry gel was placed in a muffle furnace and heated to 400°C at a heating rate of 5°C / min. It was kept at this temperature for 2 hours, then heated to 800°C and kept at this temperature for 4 hours. It was then cooled to room temperature and ground to obtain La0.9Ce0.1Co0.9Pd0.1O3 and La0.9Ce0.1Co0.9Pt0.1O3 samples.

[0064] Example 4: Preparation of NTA catalyst 1. Preparation of Ba / Al2O3 support (1) Weigh 10g of Al2O3 powder and calculate and weigh barium acetate ((CH3COO)2Ba) reagent according to the mass ratio of Al2O3:BaO=1:0.2.

[0065] (2) Dissolve barium acetate in 50 mL of deionized water, add Al2O3 powder, stir for 8 hours in an 80°C water bath, and evaporate the water.

[0066] (3) The obtained solid was placed in a 110°C drying oven and dried for 12 hours.

[0067] (4) The dried sample was placed in a muffle furnace and heated to 600°C at a heating rate of 5°C / min. The sample was calcined for 4 hours and then cooled naturally to obtain the Ba / Al2O3 precursor.

[0068] 2. Preparation of NTA catalysts with different loading ratios La0.9Ce0.1Co0.9Pd0.1O3 perovskite powder was weighed according to Al2O3:perovskite mass ratios of 1:0.05, 1:0.10, 1:0.15, and 1:0.20. The perovskite was loaded onto the Ba / Al2O3 precursor using a stepwise impregnation method. After drying and calcination (600°C, 4 hours), catalysts with different loading ratios of 5%, 10%, 15%, and 20% La0.9Ce0.1Co0.9Pd0.1O3-Ba / Al2O3 were obtained.

[0069] Comparative experiments revealed that when the active site loading was 15%, the catalyst showed better XRD (e.g., α-ray diffraction). Figure 4 The optimal dispersibility was observed in the sample (shown). The optimal NTA catalyst was determined to be 15%La0.9Ce0.1Co0.9Pd0.1O3-Ba / Al2O3.

[0070] Figure 4 In the examples, a represents 5% LaCoO3-Ba / Al2O3 (with a loading of 5wt% for the active LaCoO3 perovskite centers); b represents 10% LaCoO3-Ba / Al2O3; c represents 15% LaCoO3-Ba / Al2O3; and d represents 20% LaCoO3-Ba / Al2O3.

[0071] Example 5: NH3 generation performance of basic NTA catalyst (15% LaCoO3-Ba / Al2O3) Catalyst preparation: NTA catalysts with different LaCoO3 loading ratios were prepared by a stepwise impregnation method. First, Ba(CH3COO)2 was supported on Al2O3 with a fixed BaO content of 20 wt%, and calcined at 600°C for 4 h to obtain a Ba / Al2O3 precursor. Then, LaCoO3 perovskite material was impregnated onto the Ba / Al2O3 surface according to the target loading (5%, 10%, 15%, 20%), and calcined at 600°C for 4 h to obtain x% LaCoO3-Ba / Al2O3 catalysts.

[0072] The activity test conditions were as follows: reaction temperature 350°C, NO inlet concentration 500 ppm, H2 concentration adjusted between 100 and 2500 ppm (H2 / NO = 0.2–5.0), and space velocity 40,000 h⁻¹. -1 .

[0073] like Figure 5As shown, at a 5% loading rate: NO conversion reaches 100% when H2 / NO = 4.0; NH3 selectivity is 0 when H2 / NO = 2.5. At a 10% loading rate: NO conversion reaches 100% when H2 / NO = 3.0; NH3 selectivity is 0 when H2 / NO = 2.5. At a 15% loading rate: NO conversion reaches 100% when H2 / NO = 1.5; NH3 selectivity reaches a relatively high value (approximately 40% at 350°C) when H2 / NO = 2.5. At a 20% loading rate: NO conversion reaches 100% when H2 / NO = 1.5, but NH3 selectivity is lower than at a 15% loading rate. Therefore, a 15% loading rate is the optimal active site loading ratio, balancing high NO conversion rate and high NH3 selectivity.

[0074] Example 6: Optimization of Ce doping ratio at site A Catalyst preparation: La was prepared using the sol-gel method. 1-x Ce x CoO3 (x=0, 0.05, 0.1, 0.15, 0.2) perovskite materials were used to prepare NTA catalysts with a 15% loading.

[0075] Example 7: Comparison of B-position precious metal types Catalyst preparation: LaCo0.9M0.1O3 (M = Co, Pd, Pt) perovskite material was prepared by sol-gel method, and then NTA catalyst was prepared with a 15% loading.

[0076] Example 8: Catalyst with simultaneous modification at A / B sites Catalyst preparation: La0.9Ce0.1Co0.9Pd0.1O3 and La0.9Ce0.1Co0.9Pt0.1O3 perovskite materials were prepared by sol-gel method, and then NTA catalyst was prepared with a 15% loading.

[0077] Activity testing conditions: temperature 250°C, 350°C, 500°C; H2 / NO ratio 0.2~5.0; NO inlet concentration 500ppm; space velocity 40,000 h⁻¹ -1 .

[0078] Table 1. Performance of catalysts simultaneously modified at A / B sites like Figure 6 As shown in Table 1, under the conditions of 350°C and H2 / NO=2.5, the Pd-doped catalyst La0.9Ce0.1Co0.9Pd0.1O3 exhibited the highest NH3 selectivity (64.9%).

[0079] Example 9: Fine-tuning of different H2 / NO ratios Experimental conditions: Optimal catalyst: 15% La0.9Ce0.1Co0.9Pd0.1O3-Ba / Al2O3; temperature 350°C; NO inlet 500 ppm; H2 / NO ratio set to 0.2, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0 respectively.

[0080] like Figure 6 As shown, at H2 / NO = 0.2: N2O selectivity is 58.2%, NH3 selectivity is 0. At H2 / NO = 0.5: N2O selectivity decreases, N2 selectivity increases. At H2 / NO = 1.0: N2 selectivity is highest. At H2 / NO = 1.5: NH3 selectivity begins to increase significantly. At H2 / NO = 2.5: NH3 selectivity is 64.9%, N2O selectivity is below 10%. At H2 / NO = 5.0: NH3 selectivity is approximately 70%, but NO conversion remains 100%. Therefore, an H2 / NO ratio between 2.5 and 3.0 represents the optimal economic range for NH3 production.

[0081] Activity test of NOx purification effect of powder NTA-SCR catalytic system Cyclic tests were conducted at three temperature conditions: 250°C, 350°C, and 500°C. The concentrations of NO (m / z=30), NO2 (m / z=46), N2O (m / z=44), NH3 (m / z=17), and H2 (m / z=2) in the outlet gas were recorded in real time using an Analyses online mass spectrometer.

[0082] The NOx conversion rate was tested, and the results showed that the NO conversion rates of this NTA-SCR system were as high as 99.4%, 82.3%, and 59.1% at reaction temperatures of 250°C, 350°C, and 500°C, respectively. Compared with traditional noble metal-based catalysts (1.5% Pt-Ba / Al2O3+SCR), the NTA catalyst of this invention has a higher NO conversion rate at medium and low temperatures (250-350°C), comparable performance at high temperatures (500°C), and a significantly reduced amount of noble metal.

[0083] The system exhibits extremely low byproduct emissions. At 250°C and 350°C, the peak NO2 emissions were only 0 ppm and 36.7 ppm, respectively, significantly lower than the 20.6 ppm and 100.6 ppm emitted using the unmodified NTA catalyst (15% LaCoO3-Ba / Al2O3). Simultaneously, the peak N2O emissions also decreased substantially, from 11.1 ppm and 115.5 ppm in the control group to 3.4 ppm and 34.1 ppm. This demonstrates that the catalytic system of this invention possesses excellent product selectivity.

[0084] Comparative Example 1: Performance Comparison of NTA Catalysts with Different Active Site Loading Ratios (1) In accordance with Example 4, 5%, 10%, and 20% LaCoO3-Ba / Al2O3 (unmodified) catalysts were prepared as comparative examples.

[0085] (2) Following the experimental method of Example 14, the NO conversion rate and product selectivity were tested at 350°C and H2 / NO = 2.5 (as shown in Figure 5). Figure 5 The NO concentration in the medium is 500 ppm.

[0086] (3) The results showed that the NO conversion rates of the catalysts with loadings of 5%, 10% and 20% were 35%, 60% and 75%, respectively, which were all lower than the 99.4% of the preferred catalyst of the present invention (15%La0.9Ce0.1Co0.9Pd0.1O3-Ba / Al2O3).

[0087] This application utilizes unburned H2 (or injected fuel H2) from hydrogen engine exhaust to generate NH3 in situ on an NTA catalyst. This avoids the problems of low-temperature crystallization and NH3 leakage. It achieves highly selective conversion of NOx reduction products to NH3 over a wide temperature and concentration range.

[0088] The NTA catalyst described in this application, through synergistic modification with A / B site metals (Ce, Pd), exhibits NH3 generation capacity comparable to traditional noble metal (Pt)-based catalysts under medium-low temperature (250-350°C) conditions. This breaks the dependence of traditional LNT / NTA catalysts on noble metals such as Pt, significantly reducing catalyst costs while ensuring high performance, and possesses extremely high commercial application prospects.

[0089] Meanwhile, the BaAl2O4 species generated in situ during the thermal aging process of the NTA catalyst also possess certain NOx adsorption activity, reducing the impact of thermal aging on the reaction activity. This allows the entire catalytic system to adapt well to the harsh exhaust environment of hydrogen engines characterized by high temperature and high humidity.

[0090] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for controlling the online NH3 generation of a hydrogen engine aftertreatment catalyst, characterized in that, include: The NOx contained in the exhaust gas of the hydrogen engine is mixed with hydrogen and then passed into a reactor containing an NTA catalyst. By adjusting the molar ratio of H2 to NO to be greater than 1, the selectivity of NH3 in the NOx reduction product is controlled.

2. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 1, characterized in that, The molar ratio of H2 / NO is adjustable between 1.5 and 5.

0.

3. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 2, characterized in that, The molar ratio of H2 / NO is 2.

5.

4. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 1, characterized in that, The reaction between NOx and H2 in the exhaust gas is carried out at a temperature range of 150°C to 500°C.

5. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 4, characterized in that, The reaction between NOx and H2 in the exhaust gas is carried out in a temperature range of 250°C to 350°C.

6. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 1, characterized in that, The NTA catalyst comprises a perovskite active center, a Ba-based NOx storage unit, and an Al2O3 support.

7. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 6, characterized in that, The perovskite active center is a LaCoO3-based material modified with metals at the A-site and / or B-site.

8. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 7, characterized in that, The perovskite active center is a LaCoO3-based material with simultaneous A / B site modification.

9. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 8, characterized in that, The active centers of the perovskite are La0.9Ce0.1Co0.9Pd0.1O3 or La0.9Ce0.1Co0.9Pt0.1O3.

10. The method for controlling the online NH3 generation of the hydrogen engine aftertreatment catalyst according to claim 1, characterized in that, The loading ratio of the perovskite active sites in the NTA catalyst is 15 wt%.

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