Nta catalyst, preparation method and application thereof

Abstract

The application provides an NTA catalyst, a preparation method and application thereof, and comprises: (a) a catalytically active center which is a perovskite type oxide co-doped with A and B sites, and has a chemical general formula of La 1‑ x Ce x Co 1‑y M y O3, wherein 0.05<=x<=0.15, 0.05<=y<=0.15, and M is selected from Pd or Pt; (b) a NOx storage component which is BaO; and (c) a porous carrier which is Al2O3; the mass fraction of the catalytically active center is 5%-20% and the mass fraction of the NOx storage component is 15%-25% based on the mass of the porous carrier. The NTA catalyst cost is reduced, the hydrothermal stability of the NTA catalyst is improved, and NH3 is efficiently and selectively generated.

Description

Technical Field

[0001] The present invention relates to the technical field of tail gas catalysis, and particularly relates to an NTA catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] As a zero-carbon power device, the only pollutant emission of a hydrogen engine is nitrogen oxides (NOx). Due to the high water vapor content and wide range of air-fuel ratio variations in the tail gas of hydrogen engines, traditional technologies such as three-way catalysis (TWC), selective catalytic reduction (SCR), and lean NOx trap (LNT) are all difficult to efficiently and economically treat it. Existing NTA catalysts are mostly based on precious metals, and there are problems such as high cost and easy hydrothermal aging. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the present invention provides an NTA catalyst, a preparation method thereof, and an application thereof, aiming to reduce the cost of the NTA catalyst, improve the hydrothermal stability of the NTA catalyst, and efficiently and selectively generate NH₃.

[0004] In a first aspect, an embodiment of the present application provides an NTA catalyst, including: (a) A catalytic active center, which is a perovskite-type oxide co-doped and modified at A-site and B-site, with a chemical general formula of La 1- x Ce x Co 1-y M y O₃, where 0 < x ≤ 0.2, 0 ≤ y ≤ 0.15, and M is selected from Pd or Pt; (b) A NOx storage component, which is BaO; and (c) A porous carrier, which is Al₂O₃; Based on the mass of the porous carrier, the mass fraction of the catalytic active center is 5% - 20%, and the mass fraction of the NOx storage component is 15% - 25%.

[0005] Optionally, 0 < x ≤ 0.2, 0.05 ≤ y ≤ 0.15.

[0006] Optionally, 0.05 < x ≤ 0.15, 0 ≤ y ≤ 0.15.

[0007] Optionally, 0.05 ≤ x ≤ 0.15, 0.05 ≤ y ≤ 0.15.

[0008] Optionally, the chemical formula of the catalytic active center is La₀.₉Ce₀.₁Co₀.₉Pd₀.₁O₃.

[0009] Optionally, the chemical formula of the catalytic active center is La0.9Ce0.1Co0.9Pt0.1O3.

[0010] Optionally, the mass fraction of the catalytic active center is 15%, and the mass fraction of the NOx storage component is 20%.

[0011] Secondly, embodiments of this application provide a method for preparing an NTA catalyst, comprising the following steps: (1) Preparation of modified perovskite active centers: Lanthanum salt, cerium salt, cobalt salt and M salt were dissolved in water according to stoichiometric ratio, a complexing agent was added, the pH was adjusted to 6-7, and the solution was evaporated to dryness in a water bath, dried and calcined to obtain powdered modified perovskite La 1-x Ce x Co 1-y M y O3; where M is selected from Pd or Pt; (2) Loading NOx storage components: Barium salt was dissolved in water and impregnated onto an Al2O3 support, then evaporated in a water bath, dried, and calcined to obtain the BaO / Al2O3 precursor; (3) Loading catalytic active centers: The modified perovskite powder obtained in step (1) is loaded onto the BaO / Al2O3 precursor obtained in step (2) according to the required mass fraction, and then evaporated, dried and calcined in a water bath to obtain the NTA catalyst.

[0012] Optionally, the complexing agent in step (1) is ethylenediaminetetraacetic acid and citric acid.

[0013] Optionally, the total molar number of the metal ions is in a molar ratio of ethylenediaminetetraacetic acid and citric acid of 1:1:1.5.

[0014] Optionally, the calcination conditions in step (1) are: calcination at 700~900℃ for 3~6 hours; Optionally, the calcination conditions described in steps (2) and (3) are: calcination at 500~700℃ for 3~6 hours.

[0015] Optionally, the temperature of the water bath evaporation in step (1) is 70–90°C.

[0016] Optionally, the drying temperature is 100–120°C and the time is 10–15 hours.

[0017] Optionally, the barium salt in step (2) is barium acetate.

[0018] Optionally, the mass ratio of Al2O3 to BaO is 1:0.15~0.25.

[0019] Thirdly, this application provides an application of an NTA catalyst in the purification of hydrogen engine exhaust gas, wherein the NTA catalyst is used to react nitrogen oxides in the exhaust gas of a hydrogen engine with hydrogen to selectively generate ammonia.

[0020] This application has the following beneficial effects: This application effectively modulates the electronic structure and redox properties of perovskite through co-doping of Ce at the A-site and / or Pd / Pt at the B-site, increasing oxygen vacancies and surface-adsorbed oxygen species. Experiments show that at H2 / NO = 2.5 and a temperature of 350°C, the optimal catalyst achieves an NH3 selectivity of 64.9%, demonstrating efficient and selective NH3 generation. The NO conversion rate is close to 100%, and its performance is comparable to that of noble metal-based catalysts, but with a significantly reduced noble metal content, thus lowering the cost of NTA catalysts.

[0021] In this application, the BaO component in the NTA catalyst reacts with the Al2O3 support during high-temperature aging to form a new species, BaAl2O4. This species still possesses certain NOx adsorption and catalytic activity, thereby mitigating the negative impact of thermal aging on the catalyst. Simultaneously, the high-temperature stability of the perovskite structure itself ensures the catalyst's durability and improves the hydrothermal stability of the NTA catalyst.

[0022] The NTA catalyst of this application exhibits good NOx conversion capability in a temperature range of 250°C to 500°C, especially with excellent NH3 selectivity under medium and low temperature conditions (250°C to 350°C), which is very suitable for the typical exhaust temperature of hydrogen engines.

[0023] This application uses non-precious metals (Ce, Co) and a small amount of Pd to replace traditional Pt-based catalysts, which greatly reduces the cost of catalysts. Attached Figure Description

[0024] 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.

[0025] Figure 1 La in an NTA catalyst provided in an embodiment of this application 1-x Ce x XRD pattern of CoO3 material.

[0026] Figure 2 LaCo in an NTA catalyst provided in an embodiment of this application 0.9 M 0.1XRD patterns of O3 (M=Co,Pd,Pt) materials.

[0027] Figure 3 La in an NTA catalyst provided in an embodiment of this application 1-x Ce x Co 0.9 M 0.1 XRD patterns of O3 (M=Co,Pd,Pt) materials.

[0028] Figure 4 The NTA catalyst curve for H2 reduction and saturation adsorption of NOx in an embodiment of this application is shown.

[0029] Figure 5 The XRD patterns of NTA catalysts with different active site loading ratios provided in an embodiment of this application are shown. Detailed Implementation

[0030] 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.

[0031] 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.

[0032] Unless otherwise stated, all percentages, parts, ratios, etc. in this document are by weight.

[0033] The materials, methods, and embodiments described herein are exemplary and should not be construed as limiting unless otherwise stated.

[0034] Unless otherwise specified, all raw materials or reagents in the following embodiments can be obtained through commercial purchases or prepared using conventional methods in the art.

[0035] 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.

[0036] 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.

[0037] Figure 1 In the diagram, 'a' represents undoped, pure-phase LaCoO3 perovskite material (x=0), used 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:Ce doping level 15% sample (x=0.15). d is La 0.8 Ce 0.2 Sample with CoO3:Ce doping of 20% (x=0.2).

[0038] 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.

[0039] (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.

[0040] (3) Place the mixture in an ultrasonic cleaner and sonicate for 30 minutes to fully dissolve the complexing agent.

[0041] (4) Add 25-28% ammonia water dropwise to adjust the pH of the solution to 6-7.

[0042] (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.

[0043] (6) Transfer the gel to a forced-air drying oven and dry at 110°C for 12 hours to obtain a fluffy dry gel.

[0044] (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.

[0045] Ce doping increases H2 consumption, but the reduction peak temperature does not change significantly. The additional H2 consumption comes from the reduction of oxygen on the CeO2 surface, indicating that Ce doping increases the material's oxygen storage capacity, which is beneficial to the redox cycle of the H2 / NO reaction and improves the redox performance of the H2 / NO reaction.

[0046] Ce doping significantly improves the NO-to-NO2 conversion rate below 300°C, with the smallest decrease above 300°C. NO2 is a key intermediate for the rapid storage of nitrates; improving NO oxidation capacity can accelerate NOx adsorption, providing more active species for subsequent H2 reduction and thus enhancing NO-to-NO2 oxidation capacity.

[0047] The Ce-doped NTA catalyst exhibits an increased NO-TPD low-temperature desorption peak area and a higher total NO adsorption capacity. More oxygen vacancies promote the oxidation of NO to NO2, which is then rapidly stored as nitrate at Ba sites, improving NOx capture efficiency and thus enhancing NOx adsorption capacity.

[0048] Heat aging treatment on 15% La 0.9 Ce 0.1 Co 0.9 Pd 0.1 Effect of O3-Ba / Al2O3 catalyst on the selectivity of H2 / NO reaction products. After thermal aging, the NO conversion rate of the Ce-doped catalyst was slightly higher at low H2 concentrations than that in the fresh state, and the formation of the byproduct N2O decreased. During thermal aging, Ce stabilized the perovskite structure and formed BaAl2O4 spinel with Ba and Al. The latter still has NOx adsorption activity, mitigating aging deactivation.

[0049] As shown in Table 1, O a d s / (O a d s +O latThe content of Ce increased from 61.11% in LaCoO3 to 81.70% in La0.9Ce0.1CoO3. XPS directly proved that Ce doping introduced more oxygen vacancies, which are beneficial to O2 activation and NO oxidation, thus improving redox performance.

[0050] Table 1 shows La 1-x Ce x Co 0.9 M 0.1 In O3 (M = Co, Pd, Pt) material [Co+Pd / Pt] / [La+Ce+Co +Pd / Pt], Co 2+ / [Co 2+ +Co 3+ ], Ce 3+ / [Ce 3+ +Ce 4+ ] and O ads / [O ads +O lat ]percentage LaCoO3 perovskite material serves as the redox active center in NTA catalysts, and its redox capability directly determines the catalyst's catalytic performance. H2-TPR experiments can provide information on the oxidizing properties of metal ions and the surface-adsorbed oxygen (O2). ad and lattice oxygen O lat The activity and stability of the catalyst were also observed. The LaCoO3 sample curve showed three main reduction peaks: one near 438℃ (reduction of surface-adsorbed oxygen species), and another near 462℃ (Co). 3+ →Co 2+ The reduction (2LaCoO3 + H2 → 2LaCoO) 2.5 +H2O), at which point the LaCoO3 perovskite structure remains unchanged; and Co is located near 629℃. 2+ →Reduction of Co0 (2LaCoO) 2.5 +2H2→La2O3+2Co 0 +2H₂O), at which point the perovskite structure collapses. The low-temperature reduction peak is contributed by the consumption of H₂ by surface-adsorbed oxygen, while the high-temperature peak is obtained by the elimination of lattice oxygen by H₂. The reduction of Co ions often requires breaking the Co-Olat bond, thus requiring high energy. With different proportions of Ce doping, the positions of the three reduction peaks shift to varying degrees, but the corresponding temperature changes are irregular. Integrating the reduction peaks reveals that H₂ consumption gradually increases with increasing Ce doping, possibly because Ce doping brings more O₂. ad and O latThis leads to increased H2 consumption. CeO2 has a large specific surface area and a high density of oxygen vacancies; increasing the Ce content can improve the oxygen storage capacity of the prepared sample material. The incorporation of Ce has little effect on the reducibility of LaCoO3 material itself, but rather increases the O content on the material surface. ads and O lat This improves the oxygen vacancy concentration and oxygen mobility on the surface, thereby enhancing the redox properties of the material.

[0051] 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.

[0052] 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).

[0053] 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.

[0054] (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.

[0055] (3) Place the mixture in an ultrasonic cleaner and sonicate for 30 minutes to fully dissolve the complexing agent.

[0056] (4) Add 25-28% ammonia water dropwise to adjust the pH of the solution to 6-7.

[0057] (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.

[0058] (6) Transfer the gel to a forced-air drying oven and dry at 110°C for 12 hours to obtain a fluffy dry gel.

[0059] (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 LaCo0.9Pd0.1O3 and LaCo0.9Pt0.1O3 samples.

[0060] After Pd doping, the low-temperature H2 consumption peak decreased from 437°C to 219°C (ΔT = 218°C). 0 First, reduction is performed at low temperature, where H2 dissociates into H on the Pd surface. + And overflows to Co sites, promoting Co 3+ →Co 2+ →Co 0 Reduction significantly lowers the ignition temperature and greatly reduces the H2 reduction temperature.

[0061] At 250°C, the B-site doped catalyst achieved nearly 100% NO conversion at H2 / NO = 2.5, while the undoped catalyst achieved <40%. At low temperatures, H2 overflow generated a large amount of H2. + It rapidly reduces adsorbed NOx, achieving high-efficiency conversion at low temperatures and improving the NO conversion rate at low temperatures.

[0062] The increased area of ​​the high-temperature desorption peak of NO-TPD in the B-site-doped NTA catalyst indicates that the nitrate species are more stable. Pd / Pt promotes the oxidation of NO to NO2 and strongly adsorbs it onto the Ba site in the form of bidentate nitrate, thereby increasing the storage capacity and improving the NOx adsorption capacity.

[0063] At 350°C and H2 / NO = 2.5, the NH3 selectivity of the LaCo0.9Pd0.1O3-based catalyst is approximately 50%, while that of the undoped catalyst is almost zero; H2 overflow generates a high concentration of H2. + This promotes the stepwise hydrogenation of N to NH3 (path: N→NH→NH2→NH3), thus enhancing the NH3 generation capacity.

[0064] Compared with 1.5% Pt-Ba / Al2O3, the LaCo0.9Pd0.1O3-based catalyst has comparable NH3 selectivity at 350°C (~50% vs ~55%), but the amount of noble metal used is reduced by about 90%. B-site doping allows the noble metal to be atomically dispersed in the perovskite lattice, resulting in extremely high utilization. It replaces traditional high-loaded noble metal catalysts and achieves high performance with extremely low noble metal usage.

[0065] 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, on the basis of preliminary screening, La0.9Ce0.1Co0.9Pd0.1O3 and La0.9Ce0.1Co0.9Pt0.1O3 materials were synthesized (as Figure 3 shown). As Figure 3 shown by the XRD pattern, La0.9Ce0.1Co0.9Pd0.1O3 has the optimal comprehensive performance and is thus selected as the active center of the NTA catalyst.

[0066] 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 solutions in stoichiometric ratios, keeping 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.

[0067] (2) Weigh the corresponding masses 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.

[0068] (3) Place the mixed solution in an ultrasonic cleaner and ultrasonically treat it for 30 minutes to fully dissolve the complexing agent.

[0069] (4) Slowly add 25 - 28% ammonia water dropwise to adjust the pH value of the solution to 6 - 7.

[0070] (5) Place the solution with adjusted pH in an 80°C constant temperature water bath, continuously stir, and evaporate the water until a viscous gel is formed.

[0071] (6) Transfer the gel to a forced-air drying oven and dry it at 110°C for 12 hours to obtain a fluffy dry gel.

[0072] (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.

[0073] At 350°C, the selectivity of NH3 was ~45% at the A-site alone, ~50% at the B-site alone, and 64.9% with A / B co-doping; Ce at the A-site increased oxygen vacancies and O. ads Pd at site B provides H2 overflow, and the two work together to promote efficient conversion of NO→NO2→nitrate→N*→NH3 throughout the entire pathway.

[0074] like Figure 4 As shown, when H2 reduces saturated NOx adsorption, the A / B co-doped catalyst has the largest NH3 signal area, while N2O is almost invisible. Under transient conditions, the co-doped catalyst converts almost all adsorbed NOx into NH3 with very few byproducts, making it highly practical. The A / B co-doped catalyst exhibits excellent NOx adsorption-reduction transient performance.

[0075] After thermal aging, the A / B co-doped catalyst showed a slightly higher NO conversion rate at low H2 concentrations than the fresh catalyst; the NO-TPD high-temperature peak area decreased the least after aging. Ce stabilized the perovskite structure, while Pd promoted the formation of BaAl2O4, and the two synergistically maintained the catalytic activity after aging. The A / B co-doped catalyst exhibited the best resistance to thermal aging.

[0076] In the cycle test of powdered NTA-SCR, the peak NO2 and N2O emissions of the A / B co-doped catalyst at 250, 350, and 500°C were significantly lower than those of the unmodified catalyst. High NH3 selectivity means that more N atoms are converted to NH3 rather than N2O or NO2, making it suitable for coupling with downstream SCR and achieving extremely low byproduct emissions.

[0077] As shown in Table 2, the A / B co-doped catalyst has the lowest activation energy (15.0 kJ / mol) and the highest pre-exponential factor (960.9 s⁻¹). -1 The reaction kinetics show that the H2 / NO reaction barrier is lowest and the reaction rate is fastest on the surface of the co-doped catalyst, which is also the highest NH3 selectivity.

[0078] Table 2. Activation energy and pre-exponential factor of H2 / NO reaction with NTA catalyst 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.

[0079] (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.

[0080] (3) The obtained solid was placed in a 110°C drying oven and dried for 12 hours.

[0081] (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.

[0082] 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 by impregnation. 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.

[0083] Comparative experiments revealed that when the active site loading was 15%, the catalyst showed better XRD (e.g., α-ray diffraction) performance. Figure 5 The catalyst (shown in the figure) exhibits optimal dispersibility. A unique O2 formation peak appears at 505°C with a 15% loading, due to H... + The catalyst preferentially reacts with N to generate NH3, leading to the accumulation and bonding of O to form O2. This phenomenon directly proves that the H / N ratio on the catalyst surface is most favorable for NH3 formation. Therefore, the optimal NTA catalyst is determined to be 15%La0.9Ce0.1Co0.9Pd0.1O3-Ba / Al2O3.

[0084] Figure 5 In the figures, a is the XRD pattern of 5% LaCoO3-Ba / Al2O3 (with a loading of 5 wt% of LaCoO3 perovskite active centers); b is the XRD pattern of 10% LaCoO3-Ba / Al2O3; c is the XRD pattern of 15% LaCoO3-Ba / Al2O3; and d is the XRD pattern of 20% LaCoO3-Ba / Al2O3.

[0085] Example 5: Preparation and optimization of SCR catalyst (6%Ce-2%Zr / Cu-ZSM-5) I. Preparation of SCR catalyst: (1) Using Cu-ZSM-5 molecular sieve (Cu content 4wt%, Nankai University Catalyst Factory) as the base, weigh Ce(NO3)3·6H2O and Zr(NO3)4·5H2O according to the target loading (Ce: 2%, 4%, 6%, 8%; Zr: 2%), dissolve them in an appropriate amount of deionized water, and prepare an impregnation solution.

[0086] (2) Add the impregnation solution drop by drop to 10g Cu-ZSM-5 powder while stirring to ensure uniform impregnation.

[0087] (3) Place the impregnated sample on a magnetic stirrer and stir continuously for 12 hours under sealed conditions.

[0088] (4) Transfer the sample to a rotary evaporator and evaporate the water in an 80°C water bath.

[0089] (5) Place the dried sample in a 110°C forced-air drying oven and dry for 12 hours.

[0090] (6) Place the dried sample in a muffle furnace, heat it to 500°C at 5°C / min, calcine for 4 hours, and cool it naturally to obtain Ce or Ce-Zr modified SCR catalyst powders with different proportions (such as 2%Ce / Cu-ZSM-5, 4%Ce / Cu-ZSM-5, 6%Ce / Cu-ZSM-5, 8%Ce / Cu-ZSM-5 and 6%Ce-2%Zr / Cu-ZSM-5).

[0091] (7) Compress, crush, and sieve the powder sample to obtain 40-60 mesh particles for later use.

[0092] Example 6: NOx purification effect of powder-type NTA-SCR catalytic system I. Catalyst loading Following the gas flow direction, 1.5 mL of 15% La0.9Ce0.1Co0.9Pd0.1O3-Ba / Al2O3NTA catalyst (40-60 mesh) and 1.5 mL of 6%Ce-2%Zr / Cu-ZSM-5SCR catalyst (40-60 mesh) were sequentially loaded into a quartz tube fixed-bed reactor with an inner diameter of 7 mm. The two catalyst layers were separated by quartz wool.

[0093] Two-cycle test condition An alternating oxygen-enriched / oxygen-deficient cycle test was conducted, with 8 cycles performed at each temperature point. Operating parameters are shown in Table 3. Table 3. Cyclic Test Conditions for Supported NTA-SCR Catalysts Lean phase: 500 ppm NO, 8 vol% O2, Ar equilibrium, total flow rate 1,134 mL / min, duration 80 seconds.

[0094] Rich phase: 100 ppm NO, 0.5 vol% O2, 2,500 ppm H2, Ar equilibrium, total flow rate 1,134 mL / min, duration 80 seconds.

[0095] Total gas hourly space velocity (GHSV) maintained at 40,000 h -1 .

[0096] III. Activity Test 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.

[0097] IV. NOx Conversion Rate: At reaction temperatures of 250°C, 350°C, and 500°C, the NO conversion rates of this NTA-SCR system reached as high as 99.4%, 82.3%, and 59.1%, respectively. Compared with traditional noble metal-based catalysts (1.5% Pt-Ba / Al2O3+SCR), the NTA catalyst of this invention exhibits higher NO conversion rates at medium and low temperatures (250-350°C), comparable performance at high temperatures (500°C), and a significantly reduced amount of noble metals required.

[0098] 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.

[0099] Based on the above embodiments and comparative examples, the NTA catalyst proposed in this invention achieves the following significant and unexpected technical effects: This application presents a technical route that utilizes unburned H2 from hydrogen engine exhaust to generate NH3 in situ on an NTA catalyst, which is then coupled with a downstream SCR catalyst for NOx purification. This eliminates the need for external reducing agents such as urea, fundamentally solving the problems of urea crystallization, ammonia leakage, and additional carbon emissions inherent in traditional SCR technology.

[0100] The NTA catalyst described in this application, through synergistic modification of A / B site metals, 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.

[0101] The BaAl2O4 species generated in situ during the thermal aging process of the NTA catalyst also possess certain NOx adsorption activity, thus mitigating 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.

[0102] This application effectively modulates the electronic structure and redox properties of perovskite through co-doping of Ce at the A-site and Pd / Pt at the B-site, increasing oxygen vacancies and surface-adsorbed oxygen species. Experiments show that at H2 / NO=2.5 and a temperature of 350°C, the optimal catalyst achieves an NH3 selectivity of 64.9% and a NO conversion rate close to 100%, exhibiting performance comparable to noble metal-based catalysts, but with a significantly reduced amount of noble metal required.

[0103] In the NTA catalyst of this application, the BaO component reacts with the Al2O3 support during high-temperature aging to form a new species, BaAl2O4. This species still possesses certain NOx adsorption and catalytic activity, thereby mitigating the negative impact of thermal aging on the catalyst. Simultaneously, the high-temperature stability of the perovskite structure itself ensures the catalyst's durability.

[0104] The NTA catalyst of this application exhibits good NOx conversion capability in a temperature range of 250°C to 500°C, especially with excellent NH3 selectivity under medium and low temperature conditions (250°C to 350°C), which is very suitable for the typical exhaust temperature of hydrogen engines.

[0105] This application uses non-precious metals (Ce, Co) and a small amount of Pd to replace traditional Pt-based catalysts, which greatly reduces the cost of catalysts.

[0106] 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. An NTA catalyst, characterized in that, include: (a) catalytically active centers which are A-site and / or B-site co-doped modified perovskite oxides of the general formula La 1- x Ce x Co 1-y M y O3, wherein 0 < x < 0.2, 0 < y < 0.15, M is selected from Pd or Pt; (b) The NOx storage component is BaO; and (c) Porous support, which is Al2O3; Based on the mass of the porous support, the mass fraction of the catalytic active center is 5% to 20%, and the mass fraction of the NOx storage component is 15% to 25%.

2. The NTA catalyst according to claim 1, characterized in that, The 0 <x≤0.2,0.05≤y≤0.15。 3. The NTA catalyst according to claim 2, characterized in that The values ​​are 0.05≤x≤0.15 and 0.05≤y≤0.

15.

4. The NTA catalyst according to claim 3, characterized in that The chemical formula of the catalytic active center is La0.9Ce0.1Co0.9Pd0.1O3.

5. The NTA catalyst according to claim 3, characterized in that, The chemical formula of the catalytic active center is La0.9Ce0.1Co0.9Pt0.1O3.

6. The NTA catalyst of claim 1, wherein, The mass fraction of the catalytic active center is 15%, and the mass fraction of the NOx storage component is 20%.

7. The process for producing an NTA catalyst according to any one of claims 1 to 6, characterized by, Includes the following steps: (1) Preparation of modified perovskite active centers: Lanthanum salt, cerium salt, cobalt salt and M salt were dissolved in water according to stoichiometric ratio, a complexing agent was added, the pH was adjusted to 6-7, and the solution was evaporated to dryness in a water bath, dried and calcined to obtain powdered modified perovskite La 1-x Ce x Co 1-y M y O3; where M is selected from Pd or Pt; (2) Loading NOx storage components: Barium salt was dissolved in water and impregnated onto an Al2O3 support, then evaporated in a water bath, dried, and calcined to obtain the BaO / Al2O3 precursor; (3) Loading catalytic active centers: The modified perovskite powder obtained in step (1) is loaded onto the BaO / Al2O3 precursor obtained in step (2) according to the required mass fraction, and then evaporated, dried and calcined in a water bath to obtain the NTA catalyst.

8. The method of claim 7, wherein the NTA catalyst is prepared by the steps of: The complexing agents mentioned in step (1) are ethylenediaminetetraacetic acid and citric acid.

9. The method of claim 5, wherein the NTA catalyst is prepared by the steps of: The barium salt mentioned in step (2) is barium acetate.

10. Use of the NTA catalyst according to any one of claims 1 to 4 for the purification of exhaust gases from hydrogen engines, characterized in that, The NTA catalyst is used to react nitrogen oxides in the exhaust gas of a hydrogen engine with hydrogen to selectively generate ammonia.

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