A multi-layer core-shell structure synchronous desulfurization and denitrification SCR catalyst, a preparation method and application thereof

Abstract

The application discloses a kind of multilayer core-shell structure simultaneously desulfurization denitration SCR catalyst and its preparation method and application, belong to flue gas catalyst preparation field.The catalyst includes denitration active core, complex intermediate layer and surface hydrophobic protective layer;The denitration active core is formed by manganese oxide and cerium oxide loaded on TiO2 carrier;The complex intermediate layer has mesoporous structure, and the material forming the complex intermediate layer is the complex of metal ion M and nitrogen-containing organic ligand.The catalyst of the application has outstanding denitration desulfurization performance, excellent stability, longer service life and water resistance and sulfur poisoning resistance in complex flue gas environment, and is applied to flue gas desulfurization and / or denitration, which can simultaneously achieve desulfurization and denitration in the same temperature range, get rid of the dependence on complex series process, and avoid the problems of blockage and corrosion of downstream heat exchanger and flue in series process.

Description

Technical Field

[0001] This invention relates to a multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst, its preparation method and application, belonging to the field of flue gas catalyst preparation. Background Technology

[0002] Nitrogen oxides are one of the major air pollutants. Large emissions of nitrogen oxides can cause environmental problems such as acid rain, photochemical smog and ozone layer depletion. Long-term inhalation may also lead to changes in the structure of the human lungs and seriously endanger health.

[0003] Currently, most desulfurization and denitrification processes widely used in industry rely on single-function catalysts or absorbents. For example, commercial SCR catalysts (such as V2O5-WO3 / TiO2) are mainly used for denitrification, but they are easily poisoned and deactivated by SO2 in flue gas; while desulfurization methods such as limestone-gypsum have no denitrification capability at all. To achieve simultaneous control of multiple pollutants, equipment with different functions can only be physically connected in series and stacked, resulting in lengthy purification systems, large footprints, complex piping, and high investment and operating costs. Moreover, there is a lack of intrinsic functional synergy between units at the material level, making it difficult to achieve efficient and synchronous conversion of pollutants on a single material. In addition, efficient SCR denitrification requires high temperatures of 300~400℃, while wet desulfurization operates at low temperatures of 50~60℃. The typical series-connected denitrification and desulfurization process forces a significant cooling of the high-temperature flue gas. During this process, ammonia escaping from the SCR stage reacts with SO3 in the flue gas to form viscous ammonium bisulfate (ABS), which easily clogs and corrodes downstream heat exchangers and flue ducts, becoming a serious problem affecting the long-term stable operation of the system. At the same time, in order to increase the emission elevation of the saturated wet flue gas after desulfurization, a large amount of energy is often required for reheating, resulting in significant energy waste.

[0004] Existing technologies lack a method for simultaneously and efficiently removing SO2 and NO within the same mild temperature range. x The catalysts used in traditional catalysts are often insufficient to achieve truly efficient and low-energy-consumption single-tower or single-bed purification processes. Furthermore, the stability of traditional catalysts faces two major challenges: sulfur poisoning and hydrothermal deactivation. On the one hand, SO2 in the flue gas readily undergoes irreversible reactions with the active sites of the denitrification catalyst, generating thermally stable sulfates that lead to permanent deactivation. On the other hand, water vapor competes with reactants for adsorption at the active sites, severely inhibiting the reaction.

[0005] Therefore, it is necessary to develop a method that can realize SO2 and NO under medium and low temperature conditions. x Catalyst materials that can simultaneously remove pollutants and are resistant to water and sulfur poisoning are of great significance for achieving integrated, compact, and low-energy-consumption operation of flue gas treatment systems. Summary of the Invention

[0006] To address the aforementioned problems with existing SCR catalysts, the first objective of this invention is to provide a multi-layered core-shell structured SCR catalyst for simultaneous desulfurization and denitrification. Through the synergistic effect of the denitrification active core, the complex intermediate layer, and the surface hydrophobic protective layer, the catalyst exhibits outstanding denitrification and desulfurization performance, excellent stability, long service life, and resistance to water and sulfur poisoning in complex flue gas environments.

[0007] The second objective of this invention is to provide a method for preparing a multi-layered core-shell structured SCR catalyst for simultaneous desulfurization and denitrification. By in-situ coating, strong chemical bonding between the layers is achieved, avoiding the peeling and detachment of the shell during use, ensuring the integrity of the core-shell structure. The entire process has good repeatability, is easy to scale up, and has significant potential for industrial application.

[0008] The third objective of this invention is to provide an application of a multi-layered core-shell structure SCR catalyst for simultaneous desulfurization and denitrification, which is applied to the desulfurization and / or denitrification of flue gas, enabling the catalyst to simultaneously achieve desulfurization and denitrification within the same temperature range, eliminating dependence on complex series processes, and avoiding the problems of blockage and corrosion in downstream heat exchangers and flues during series processes.

[0009] To achieve the above-mentioned technical objectives, this invention provides a multi-layered core-shell structured SCR catalyst for simultaneous desulfurization and denitrification. The catalyst comprises a denitrification active core, a complex intermediate layer, and a hydrophobic protective layer. The denitrification active core is composed of manganese oxide and cerium oxide supported on a TiO2 support. The complex intermediate layer has a mesoporous structure, and the material constituting the complex intermediate layer is a complex formed by a metal ion M and a nitrogen-containing organic ligand. The metal ion M is selected from Zn. 2+ Cu 2+ Co 2+ and Ni 2+ At least one of them.

[0010] The SCR catalyst of this invention achieves simultaneous desulfurization and denitrification within the same temperature range through synergistic design of components and structure, eliminating dependence on complex series processes. Specifically, when flue gas flows through the catalyst, it first contacts the outermost hydrophobic protective layer, which effectively blocks the erosion of poisoning molecules such as water vapor and SO2 in the flue gas to the internal active sites, significantly improving the catalyst's resistance to poisoning in complex flue gas environments. Subsequently, the flue gas enters the intermediate shell of the complex, which has a rich mesoporous structure. This shell, through its abundant coordination sites and mesoporous channels, physically adsorbs and chemically anchors acidic poisoning molecules such as sulfur dioxide in the flue gas, effectively delaying their diffusion to the core. Finally, the flue gas further reaches the Mn and Ce supported by the mesoporous structure of the intermediate complex layer. The denitrification active core, constructed on a TiO2 support, provides ample active centers and efficient mass transfer channels for the efficient reduction of nitrogen oxides, ensuring high-efficiency denitrification activity. More importantly, compared to existing SCR catalysts, the denitrification active core exhibits a wider and lower denitrification temperature range. Furthermore, the introduction of the complex intermediate layer, through interfacial synergy with the core, modulates the electronic structure of the core's active sites, further stimulating its low-temperature catalytic activity. This allows the catalyst of this invention to simultaneously achieve desulfurization and denitrification within the same temperature range. In addition, the core-shell structure of this invention effectively inhibits the sintering and loss of active components (especially the denitrification active core) during use, exhibiting excellent catalytic stability and significantly extending catalyst lifespan.

[0011] Furthermore, the denitrification active core of this invention employs a co-support of manganese oxide and cerium oxide on a TiO2 support. This utilizes the variable valence of Mn to provide highly efficient denitrification active sites, while Ce's oxygen storage and release capabilities promote the redox cycle of Mn, lower the activation energy, and significantly enhance denitrification activity at medium and low temperatures. Simultaneously, the high specific surface area of ​​the TiO2 support enables highly dispersed bimetallic loading, preventing active site aggregation and providing an efficient channel for reactant mass transfer, thus laying a stable structural foundation for subsequent core-shell coating. In this invention, manganese oxide refers to Mn2O3, and cerium oxide refers to CeO2.

[0012] As a preferred embodiment, the nitrogen-containing organic ligand comprises 3-amino-1,2,4-triazole; the metal ion M is Zn. 2+ In this invention, the intermediate layer is further preferably Zn. 2+ At the same time, it has better desulfurization and denitrification effects.

[0013] As a preferred embodiment, the porosity of the intermediate layer of the complex is 30-60%, and the pore size is 5-12 nm. Within the preferred porosity range of the intermediate layer of the complex in this invention, while ensuring good desulfurization effect, it is also beneficial to ensure that the flue gas further enters the active core reaction of denitrification. However, the pore size of the intermediate layer of the complex in this invention should not be too large. More preferably, the porosity of the intermediate layer of the complex is 45-55%. As a preferred embodiment, the TiO2 support is a mesoporous TiO2 support. When a mesoporous TiO2 support is used, it has a higher specific surface area than a non-mesoporous TiO2 support, which can improve the dispersion and loading of the active components.

[0014] This invention also provides a method for preparing a multi-layer core-shell structured simultaneous desulfurization and denitrification SCR catalyst, comprising the following steps:

[0015] S1 In a weakly acidic solution environment, cerium source, manganese source and complexing agent are mixed evenly, and then TiO2 support is added for impregnation. The resulting solid is then oxidized and calcined to obtain a denitrification active core.

[0016] S2 After surface amino modification of the denitrification active core, it undergoes an in-situ coating reaction with a metal ion source M and a nitrogen-containing organic ligand under the action of a structure-directing agent to obtain a core-shell structure intermediate; the metal ion source M is selected from at least one of zinc source, copper source, cobalt source and nickel source;

[0017] The core-shell structure intermediate described in S3 is obtained by surface hydrophobic treatment.

[0018] The preparation method of this invention first involves uniformly impregnating and oxidizing a TiO2 support with a cerium and manganese source under a weakly acidic environment using a complexing agent, thereby loading highly dispersed and stable denitrification active centers on the support surface, providing abundant active sites for selective catalytic reduction (SCR) reactions. Subsequently, the core is modified with amino groups, and an organic framework intermediate is generated using amino groups, a metal ion source (M), and a nitrogen-containing organic ligand under the action of a structure-directing agent, and then in situ coated to form a core-shell structure intermediate. Simultaneously, amino modification enhances the chemical bonding between the core and shell interfaces, ensuring structural stability. Finally, a hydrophobic surface treatment introduces low surface energy groups onto the outer surface of the shell, effectively suppressing competitive adsorption of water vapor without compromising the synergistic desulfurization and denitrification function of the core and shell, thus significantly improving the long-term operational stability of the catalyst in water-containing and sulfur-containing flue gas environments.

[0019] As a preferred embodiment, in S1, the molar ratio of the cerium source and manganese source, calculated as Mn and Ce, is (0.3~0.6):1. When the molar ratio is below 0.3:1, there are insufficient core denitrification active sites based on Mn, and excessive Ce dilutes the density of active sites, weakening the Mn-Ce electronic synergistic effect and significantly reducing the low-temperature denitrification activity of the catalyst. Conversely, when the molar ratio is above 0.6:1, the Mn component is prone to agglomeration and sintering, hindering the redox cycle and causing a rapid decline in denitrification activity. At the same time, irreversible sulfates are easily generated, significantly reducing the resistance to sulfur poisoning.

[0020] As a preferred embodiment, the cerium source includes at least one of cerium acetate and cerium nitrate; the manganese source includes at least one of manganese nitrate and manganese acetate; and the complexing agent includes at least one of citric acid and EDTA.

[0021] As a preferred embodiment, the weakly acidic solution environment refers to a pH of 5-6. In a weakly acidic environment, not only can the hydrolysis and precipitation of metal ions be inhibited, but the complexation stability of the complexing agent is also maintained.

[0022] As a preferred embodiment, the specific surface area of ​​the TiO2 support is not less than 100 m². 2 / g.

[0023] As a preferred embodiment, the immersion time is 2 to 6 hours.

[0024] As a preferred embodiment, the total mass ratio of the TiO2 support to the cerium source and manganese source is 1:(2~10). Within the mass ratio range of this invention, it is beneficial to ensure the loading of the cerium source and manganese source, thereby ensuring the denitrification effect.

[0025] As a preferred embodiment, the oxidative calcination conditions are: temperature 400~600℃ and time 2~6h. The temperature and time of oxidative calcination directly affect the phase structure and surface properties of the catalyst core. When the temperature is too low or the time is too short, the organic complexes in the precursor are difficult to decompose completely, and the metal salts are not fully oxidized, resulting in low dispersion of Mn and Ce active components, making it difficult to form efficient denitrification active centers. However, the temperature should not be too high, and the calcination time should not be too long, to avoid thermal sintering and reduced catalyst activity.

[0026] As a preferred embodiment, in S2, the surface amino modification involves dispersing the denitrification active core in an organic solvent and then adding a silane coupling agent for modification, resulting in a surface-modified denitrification active core. Treatment with the silane coupling agent allows for the modification of amino groups onto the denitrification active core, thereby achieving in-situ coating of the complex intermediate layer.

[0027] As a preferred embodiment, the silane coupling agent is γ-aminopropyltriethoxysilane; the metal ion source M is a zinc source, and more preferably, the zinc source is zinc nitrate.

[0028] As a preferred embodiment, the organic solvent includes N,N-dimethylformamide.

[0029] As a preferred embodiment, the structure directing agent is a mixture of oxalic acid and triethylamine, with a molar ratio of zinc source, nitrogen-containing organic ligand, oxalic acid, and triethylamine of 1:(0.8~1.2):(0.1~0.3):(0.05~0.15). In this invention, oxalic acid acts as a competitive ligand, competing with the nitrogen-containing organic ligand for coordination, effectively regulating the nucleation rate of the zinc source, inhibiting excessive crystal growth, and thus forming a rich mesoporous structure. If the amount of oxalic acid is too low, the crystal growth is too rapid, leading to a decrease in porosity; if the amount of oxalic acid is too high, it will lead to difficulty in forming a dense film. Triethylamine acts as a buffer to maintain the pH value of the reaction system and promotes the deprotonation of the nitrogen-containing organic ligand to enhance its coordination ability. By using oxalic acid and triethylamine as a composite structure directing agent, this invention effectively regulates the growth and micromorphology of the intermediate shell of the coordination compound, resulting in a shell with a rich mesoporous structure.

[0030] As a preferred embodiment, the in-situ coating reaction conditions are: temperature 20~60℃ and time 5~12h. The in-situ coating reaction conditions of the present invention are mild and can be achieved at room temperature.

[0031] As a preferred embodiment, the mass ratio of the surface-modified denitrification active core to the zinc source is (0.4~5):1.

[0032] As a preferred embodiment, in step S3, the surface hydrophobic treatment process involves dispersing the core-shell structure intermediate in an alcohol solvent, followed by adding a silanizing agent and ammonia to initiate a hydrolysis-condensation reaction. In this process, ammonia acts as a catalyst, enriching the core-shell surface with hydroxyl groups and catalyzing the hydrolysis of the silanizing agent to generate silanols. These silanols condense with the hydroxyl groups on the core-shell surface to form strong covalent bonds, thereby uniformly grafting the hydrophobic groups at the ends of the silane reagent onto the material surface. Further, the alcohol solvent is ethanol.

[0033] As a preferred embodiment, the mass ratio of the core-shell intermediate, the silanizing agent, and ammonia is 100:(0.5~10):(0.01~1). Within the preferred mass ratio range of this invention, a catalyst with better surface hydrophobicity can be obtained.

[0034] As a preferred embodiment, the silanizing agent comprises tetraethyl orthosilicate.

[0035] As a preferred embodiment, the conditions for the hydrolysis-condensation reaction are: temperature of 20~35℃ and time of 1~2h.

[0036] Finally, this invention also provides an application of a multi-layer core-shell structured SCR catalyst for simultaneous desulfurization and denitrification of flue gas. This catalyst can simultaneously achieve desulfurization and denitrification within the same temperature range (especially the medium- and low-temperature range), eliminating reliance on complex series processes and avoiding the problems of blockage and corrosion in downstream heat exchangers and flue ducts during series processes. It is particularly suitable for the simultaneous desulfurization and denitrification treatment of complex flue gas compositions.

[0037] As a preferred embodiment, the temperature range is 90~240℃.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The SCR catalyst provided by this invention achieves a significant improvement in denitrification activity through the synergistic design of components and structure. Under optimal reaction conditions, the catalyst can stably achieve a nitrogen oxide removal efficiency of over 90%. Moreover, the core-shell structure effectively inhibits the sintering and loss of active components during use, exhibiting excellent catalytic stability and extending the catalyst's service life.

[0040] (2) The catalyst of the present invention has outstanding denitrification and desulfurization performance, excellent stability, long service life and resistance to water and sulfur poisoning in complex flue gas environments through the synergistic effect of the denitrification active core, the complex intermediate layer and the surface hydrophobic protective layer.

[0041] (3) In the formation process of the complex intermediate layer of the present invention, the growth and microstructure of the complex intermediate layer are effectively regulated by using oxalic acid and triethylamine as composite structure directing agents, resulting in an outer shell with a rich mesoporous structure. This pore structure ensures that the reactant gas can diffuse efficiently to the core active sites and ensures the rapid discharge of reaction products, effectively reducing the risk of pore blockage and thus ensuring the continuous and stable progress of the catalytic reaction. In addition, the complex intermediate layer can not only protect the core but also act as a sulfur dioxide molecular sieve, producing a desulfurization effect, and can further stimulate the low-temperature catalytic activity of the core.

[0042] (4) The preparation method provided by this invention has mild conditions, clear steps, and does not require complex and expensive equipment. The core preparation adopts the conventional impregnation-calcination method; the shell coating is carried out at near room temperature, with low energy consumption; the hydrophobic treatment uses alcohol solvents instead of toxic toluene, which is safer and more environmentally friendly. The entire process has good repeatability, is easy to scale up, and has significant potential for industrial application.

[0043] (5) The catalyst of the present invention is applied to the desulfurization and / or denitrification of flue gas, achieving desulfurization and denitrification simultaneously in the same temperature range, eliminating the dependence on complex series processes, and avoiding the problems of blockage and corrosion of downstream heat exchangers and flues in series processes. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the overall structure of the SCR catalyst of the present invention.

[0045] Figure 2 This is a schematic diagram illustrating the reaction mechanism of the SCR catalyst of the present invention. Detailed Implementation

[0046] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments. Obviously, the embodiments described below are only a part of the embodiments, and all other embodiments obtained by those skilled in the art without creative effort are still within the scope of protection of the present invention.

[0047] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0048] Example 1

[0049] A method for preparing a multi-layered core-shell structured simultaneous desulfurization and denitrification SCR catalyst comprises the following steps:

[0050] Preparation of S1 denitrification active core:

[0051] Weigh 0.01 mol cerium acetate (3.12 g) and 0.004 mol manganese nitrate tetrahydrate (1.09 g), place them in a beaker, add 25 mL of deionized water, and stir magnetically for 5 min until completely dissolved. Then add 0.6 g citric acid and continue stirring for 5 min. Adjust the pH of the solution to 5.5 dropwise with concentrated ammonia to obtain a clear solution A. Add 0.75 g of mesoporous TiO2 (specific surface area ≥150 m² / g) to solution A and stir magnetically for 3 h. Then place the mixed slurry in an 80℃ forced-air drying oven and dry under normal pressure for 6 hours. Grind the dried solid into powder and place it in a muffle furnace for oxidation calcination. The muffle furnace is heated from room temperature to 500℃ at a rate of 5℃ / min and held at 500℃ for 4 h, then naturally cooled to room temperature to obtain 2.9 g of Mn-Ce / TiO2 cores.

[0052] S2 in-situ coated intermediate layer of complex:

[0053] Take 2.5g of the above-prepared denitrification active core, disperse it in 25mL of N,N-dimethylformamide, then add 0.25g of γ-aminopropyltriethoxysilane, and stir magnetically at room temperature for 2h. Separate by centrifugation at 4000rpm for 5min, and dry the solid at 80℃ for 0.5h to obtain the surface-modified denitrification active core.

[0054] In a conical flask, 25 mL of DMF, 2.28 g of zinc nitrate, 0.645 g of 3-amino-1,2,4-triazole, 0.18 g of oxalic acid, and 0.1 mL of triethylamine were added sequentially. The mixture was magnetically stirred for 5 min until the solid was basically dissolved. Then, 2.5 g of the surface-modified denitrification active core was added, and the mixture was magnetically stirred at room temperature for 8 h. After the reaction was completed, the solid was collected by centrifugation, washed twice with anhydrous ethanol, and dried in an 80 °C oven at normal pressure for 8 h to obtain a core-shell structure intermediate (porosity 50%, pore size 9-11 nm, thickness 200 nm).

[0055] (3) Surface hydrophobic treatment:

[0056] 5.0 g of the core-shell structured intermediate was dispersed in 25 mL of anhydrous ethanol, and then 0.25 g of tetraethyl orthosilicate and 0.05 mL of 25% ammonia solution were added. The mixture was magnetically stirred for 1.5 h. After the reaction, the solid was collected by centrifugation and dried in an oven at 80 °C for 6.5 h to obtain a multilayer core-shell structured simultaneous desulfurization and denitrification SCR catalyst, named Mn-Ce@TiO2 core@Zn-ATZ-OH shell coating@hydrophobic layer treatment, abbreviated as M.

[0057] Example 2

[0058] The only difference between this embodiment and Example 1 is that the mass of the surface-modified denitrification active core in S2 is changed to 1.0 g, and the magnetic stirring time at room temperature is changed to 2 h. All other steps and conditions are the same, resulting in a core-shell structure intermediate and a multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst, referred to as M-1. The core-shell structure intermediate has a porosity of 38%, a pore size of 5-8 nm, and a thickness of 500 nm.

[0059] Example 3

[0060] The only difference between this embodiment and Example 1 is that the molar amount of cerium acetate in S1 is changed to 0.02 mol, the molar amount of manganese nitrate is changed to 0.012 mol, and the mass of mesoporous TiO2 is changed to 1 g. All other steps and conditions are the same, resulting in a core-shell structure intermediate and a multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst, referred to as M-2.

[0061] Example 4

[0062] The only difference between this embodiment and Example 1 is that the amount of the core-shell structure intermediate in S3 is changed to 4.5g, and the magnetic stirring time is changed to 0.5h. All other steps and conditions are the same, resulting in a core-shell structure intermediate and a multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst, referred to as M-3.

[0063] Example 5

[0064] The only difference between this embodiment and Example 1 is that the oxidation calcination temperature in S1 is changed to 600℃ and the time is changed to 6h. All other steps and conditions are the same, resulting in a core-shell structure intermediate and a multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst, referred to as M-4.

[0065] Comparative Example 1: Washing activated carbon with nitric acid alone

[0066] Commercial activated carbon was soaked in nitric acid solution (5 wt%) at 60°C for 2 hours, then washed with deionized water until neutral, and dried to obtain nitric acid-washed activated carbon. This material represents conventional modified activated carbon and is not loaded with any metal components.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 1 is that only S1 is performed to obtain the Mn-Ce / TiO2 core.

[0069] Comparative Example 3

[0070] The only difference between this comparative example and Example 1 is that the structure-directing agent oxalic acid is not added in S2; all other steps and conditions are the same, resulting in a core-shell structure intermediate and a multi-layer core-shell structure SCR catalyst for simultaneous desulfurization and denitrification. The porosity of the obtained core-shell structure intermediate is greater than 60%, and the pore size is greater than 20 nm.

[0071] Comparative Example 4

[0072] The only difference between this comparative example and Example 1 is that the S3 surface hydrophobic treatment step is omitted, and the core-shell structure intermediate obtained in S2 is used directly as the catalyst. All other steps and conditions are the same.

[0073] Catalyst activity evaluation

[0074] The catalyst activity testing and evaluation system consists of a gas cylinder, mass flow meter, shut-off valve, check valve, mixing cylinder, tubular furnace, and flue gas analyzer. During testing, the temperature is set between 90 and 240℃. The inlet gas composition is: 200 ppm NO, 100 ppm SO2, 5% O2, 5% H2O, and N2 as a balance gas, with a total flow rate of 1 L / min. When loading the catalyst, the quartz reaction tube has an inner diameter of 8 mm and a length of 535 mm. The catalyst dosage is 0.2 g, dispersed with an equal volume of quartz sand, and the gas hourly space velocity is 30,000 h⁻¹.-1 The simulated flue gas, after mixing, undergoes a denitrification reaction in a fixed-bed reactor. The concentration of the tail gas is detected by a Laoying 3012H flue gas analyzer, and the efficiency is calculated using the following formula:

[0075]

[0076] NO xin The concentration of nitrogen oxides at the inlet is expressed in ppm; NO xout η represents the nitrogen oxide outlet concentration in ppm; η represents the denitrification efficiency in ppm.

[0077] The catalysts used in the examples and comparative examples were used for flue gas denitrification reactions, and the NOx conversion rates at 210°C for 80 h are shown in Table 1.

[0078]

[0079] As can be seen from Table 1, the embodiments of the present invention have good denitrification and desulfurization effects.

Claims

1. A multi-layered core-shell structured simultaneous desulfurization and denitrification SCR catalyst, characterized in that: It includes a denitrification active core, a complex intermediate layer, and a surface hydrophobic protective layer; The denitrification active core is composed of manganese oxide and cerium oxide supported on a TiO2 carrier; The intermediate layer of the complex has a mesoporous structure, and the material constituting the intermediate layer is a complex formed by a metal ion M and a nitrogen-containing organic ligand; the metal ion M is selected from Zn. 2+ Cu 2+ Co 2+ and Ni 2+ At least one of them.

2. The multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst according to claim 1, characterized in that: The TiO2 support is a mesoporous TiO2 support.

3. The multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst according to claim 2, characterized in that: The porosity of the intermediate layer of the complex is 30-60%, and the pore size is 5-12 nm; The nitrogen-containing organic ligand comprises 3-amino-1,2,4-triazole; the metal ion M is Zn. 2+ .

4. A method for preparing a multi-layer core-shell structured simultaneous desulfurization and denitrification SCR catalyst as described in any one of claims 1 to 3, characterized in that: Includes the following steps: S1 In a weakly acidic solution environment, cerium source, manganese source and complexing agent are mixed evenly, and then TiO2 support is added for impregnation. The resulting solid is then oxidized and calcined to obtain a denitrification active core. S2 modifies the surface of the denitrification active core with amino groups, and then performs an in-situ coating reaction with a metal ion source M and a nitrogen-containing organic ligand under the action of a structure-directing agent to obtain a core-shell structure intermediate; the metal ion source M is selected from at least one of zinc source, copper source, cobalt source and nickel source; The core-shell structure intermediate described in S3 is obtained by surface hydrophobic treatment.

5. The preparation method of the multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst according to claim 4, characterized in that: In S1, The molar ratio of the cerium source and manganese source, calculated as Mn and Ce, is (0.3~0.6):1; The cerium source includes at least one of cerium acetate and cerium nitrate; The manganese source includes at least one of manganese nitrate and manganese acetate; The complexing agent includes at least one of citric acid and EDTA; The weakly acidic solution environment refers to a pH of 5-6; The specific surface area of ​​the TiO2 support is not less than 100 m². 2 / g; The total mass ratio of the TiO2 support to the cerium source and manganese source is 1:(2~10). The conditions for the oxidative calcination are: temperature of 400~600℃ and time of 2~6h.

6. The preparation method of the core-shell structured simultaneous desulfurization and denitrification SCR catalyst according to claim 4, characterized in that: In S2, The surface amino modification involves dispersing the denitrification active core in an organic solvent and then adding a silane coupling agent for modification, resulting in a surface-modified denitrification active core; the silane coupling agent is γ-aminopropyltriethoxysilane. The metal ion source M is a zinc source, and the structure directing agent is a mixture of oxalic acid and triethylamine. The molar ratio of zinc source, nitrogen-containing organic ligand, oxalic acid and triethylamine is 1:(0.8~1.2):(0.1~0.3):(0.05~0.15). The conditions for the in-situ coating reaction are: temperature of 20~60℃ and time of 5~12h.

7. The preparation method of the core-shell structured simultaneous desulfurization and denitrification SCR catalyst according to claim 6, characterized in that: The mass ratio of the surface-modified denitrification active core to the zinc source is (0.4~5):

1.

8. The method for preparing the core-shell structured simultaneous desulfurization and denitrification SCR catalyst according to claim 4 or 5, characterized in that: In S3 The process of surface hydrophobic treatment is as follows: the core-shell structure intermediate is dispersed in an alcohol solvent, and then a silanizing agent and ammonia are added to carry out a hydrolysis and condensation reaction.

9. The preparation method of the core-shell structured simultaneous desulfurization and denitrification SCR catalyst according to claim 8, characterized in that: The mass ratio of the core-shell intermediate, the silanizing agent, and ammonia is 100:(0.5~10):(0.01~1); The silanizing agent includes tetraethyl orthosilicate; The conditions for the hydrolysis-condensation reaction are: temperature 20~35℃, time 1~2h.

10. The application of a multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst as described in any one of claims 1 to 3, or a multi-layer core-shell structure simultaneous desulfurization and denitrification SCR catalyst prepared by any one of claims 4 to 9, characterized in that: It is used for desulfurization and / or denitrification of flue gas.

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