Fly ash-based multi-effect catalysts and their preparation methods

Abstract

This application relates to the field of catalyst technology for industrial solid waste resource utilization and air pollution control, specifically disclosing a fly ash-based multi-effect catalyst and its preparation method. The catalyst uses a hierarchical porous support derived from coal fly ash as a matrix, supporting spatially confined copper-iron, vanadium-tungsten-titanium multi-element active nanoclusters, and lanthanum-cerium co-doped zirconium oxide two-dimensional nanosheets as interfacial bridging units. The preparation method includes: constructing the support through magnetic separation, alkali fusion, and hydrothermal synthesis with dual template agents; utilizing steric hindrance effects to achieve selective localization of active components within mesopores and macropores stepwise; and finally, in-situ growth of two-dimensional additives via hydrothermal methods with selective carbon modification. The catalyst of this application utilizes the spatial distribution of components and the regulation of interfacial structure to achieve synergistic catalysis of multiple pollutants. The preparation method of this application, through sequential confined assembly, helps to improve the utilization efficiency of active sites and system stability, and the process route is closely integrated with solid waste resource utilization.

Description

Technical Field

[0001] This application relates to the field of catalyst technology for industrial solid waste resource utilization and air pollution control, and more specifically, it relates to fly ash-based multi-effect catalysts and their preparation methods. Background Technology

[0002] The synergistic purification of multiple pollutants such as nitrogen oxides, volatile organic compounds, and sulfides in industrial waste gas is a crucial requirement in the environmental protection field. Fly ash, as an industrial solid waste, has the advantages of wide availability and low cost. Modifying it to prepare a catalyst support not only enables resource recovery and utilization but also reduces catalyst preparation costs. Therefore, fly ash-based multi-effect catalysts have become a research hotspot in pollutant purification technology. These catalysts must simultaneously possess catalytic activity against multiple pollutants and structural stability during long-term use to adapt to purification requirements under complex operating conditions. The core lies in the synergistic design of the support, active components, and additives. Through rational structural construction and performance regulation, efficient conversion of multiple pollutants and stable catalyst operation can be achieved.

[0003] Existing fly ash-based catalysts generally suffer from insufficient component synergistic design. Specifically, the support pore structure is simple, failing to provide targeted loading and mass transfer space for multiple active components; the active components lack precise spatial separation and ratio control, easily leading to mutual interference and decreased catalytic efficiency; and there is a lack of effective interface bridging and performance regulation mechanisms, resulting in weak synergistic effects among functional units. Ultimately, the catalysts cannot simultaneously achieve multi-effect catalytic performance and structural stability, either only working on a single pollutant or experiencing problems such as active component detachment and pore collapse during long-term use, severely limiting their practical application in industrial multi-pollutant synergistic purification scenarios. Summary of the Invention

[0004] To address the shortcomings of existing fly ash-based catalysts in terms of component synergistic design and the difficulty in balancing multi-effect catalytic performance and structural stability, this application provides a fly ash-based multi-effect catalyst and its preparation method.

[0005] In the first aspect, this application provides a fly ash-based multi-effect catalyst, which adopts the following technical solution:

[0006] A fly ash-based multi-effect catalyst comprises the following components: 100-120 parts of hierarchical porous fly ash support, 15-25 parts of confined multi-element active nanoclusters, and 6-10 parts of interface-modified rare earth additives.

[0007] By employing the above technical solution, this fly ash-based multi-effect catalyst constructs a highly efficient catalytic system through the structural design and synergistic effect of the support, active components, and additives. The support undergoes multi-step modification to form a tertiary porous structure and introduces amino functional groups, providing a structural basis for pollutant transport and active component loading. The confined multi-component active nanoclusters adopt a two-component spatial separation design, achieving selective loading of different pore regions through specific processes, forming functionally complementary catalytic sites. The interface-modified rare earth additives, through structural design and surface modification, construct an interface bridging and performance regulation system. These components, through precise proportioning and structural design, form an integrated system where the support provides structural support, the active components achieve multi-component catalysis, and the additives enhance synergistic effects. Utilizing the interfacial interactions and functional complementarity among the components, a highly efficient and stable multi-effect catalytic mechanism is constructed.

[0008] Preferably, the graded porous fly ash carrier has a three-level pore structure of micropores, mesopores and macropores, and the specific surface area of ​​the graded porous fly ash carrier is 300-600 m² / g.

[0009] By adopting the above technical solution, the hierarchical porous fly ash carrier has a three-level pore structure with micropores smaller than 2 nm, mesopores with a diameter of 2-50 nm, and macropores larger than 50 nm. Mesopores account for 60%-75% of the total pore volume, micropores for 10%-20%, and macropores for 10%-20%. This pore volume ratio and pore size distribution are achieved through the selection and ratio control of the dual-template agent and the precise control of hydrothermal synthesis temperature and time. Cationic surfactants, such as hexadecyltrimethylammonium chloride, are used in combination with nanoparticles, such as silica nanoparticles, as composite dual-template agents. The cationic surfactant directionally induces the formation of the mesoporous structure and dominates the mesopore volume ratio, while the nanoparticle template constructs the macroporous framework. The microporous structure is further refined and pore connectivity optimized through an ion exchange process. Combined with a specific surface area range of 300-600 m² / g, a pore system with mesopores as the core and micropores and macropores working synergistically is formed. The high proportion of mesopores provides ample and uniform loading sites for active components, ensuring their dispersion; micropores enhance the adsorption and capture capacity of small molecule pollutants through their high specific surface area; and macropores reduce the mass transfer resistance of the reaction system through appropriate pore size. The specific pore volume ratio, pore size distribution and specific surface area of ​​the three components work together to meet the loading requirements of active components and ensure the efficient connection of adsorption-catalysis-mass transfer processes, laying the structural foundation for the performance of multi-effect catalysis.

[0010] Preferably, the confined multi-element active nanoclusters include a first active component and a second active component. The first active component is a copper-iron bimetallic nanocluster, wherein the molar ratio of copper to iron is 1:1 to 1:3. The second active component is a vanadium-tungsten-titanium multi-element oxide nanocluster, wherein the molar ratio of vanadium, tungsten and titanium is 1:(0.3-1.5):(2-10).

[0011] By employing the above technical solutions, the two-component structure, particle size regulation, and regioselective distribution of confined multi-element active nanoclusters are achieved through a small-molecule sterically hindered amine-mediated deposition process, a polymer complexing agent-assisted assembly process, and precise control of the molar ratio of each component element. The copper source is selected from copper nitrate or copper chloride, the iron source from ferric nitrate or ferric chloride, the vanadium source from ammonium metavanadate or vanadium acetylacetone, the tungsten source from ammonium tungstate or ammonium metatungstate, and the titanium source from tetrabutyl titanate or titanium oxysulfate. The particle size control of the first active component, copper-iron bimetallic nanoclusters, is achieved through the synergistic effect of the molecular size effect of small-molecule sterically hindered amines and the 1:1 to 1:3 molar ratio of copper to iron. The small-molecule sterically hindered amines form spatial confinement within the mesoporous channels of the support, inhibiting the excessive growth of nanoclusters and resulting in a particle size of 5-25 nm, specifically less than 1 / 2 of the maximum pore size of the mesopore. At the same time, the selective confined distribution of nanoclusters within the mesoporous channels is achieved by the anchoring effect of amino functional groups on the inner wall of the mesopores of the support. The specific molar ratio of copper to iron optimizes the electronic structure of the active sites by adjusting the electronic interactions of the bimetallic components. The particle size of the second active component, vanadium-tungsten-titanium multi-component oxide nanoclusters, is controlled by the volume repulsion effect of the polymeric complexing agent and the molar ratio of vanadium-tungsten-titanium (1:(0.3-1.5):(2-10), resulting in a particle size of 50-100 nm, falling between the maximum pore size of mesopores and the minimum pore size of macropores. The complex formed by the polymeric complexing agent and the active metal precursor cannot penetrate the mesopore channels due to the volume repulsion effect, and can only selectively adsorb onto the inner wall and outer surface of the macropores of the support. The specific molar ratio of vanadium-tungsten-titanium is adjusted by regulating the crystal structure and the number of surface active sites of the multi-component oxides to meet the catalytic reaction requirements of the macroporous region. Through the adaptive design of particle size and support pores, and the targeted control of the elemental molar ratio, the two active components achieve spatial separation and distribution, avoiding mutual interference between different active components and allowing each component to fully exert its catalytic function in its dedicated pore region, ensuring the efficient synergy of the multi-component catalytic process.

[0012] Preferably, the interface-modified rare earth additive is a two-dimensional nanosheet with zirconium oxide as the matrix and co-doped with lanthanum and cerium, the thickness of which is 3-5 nm, wherein the molar ratio of lanthanum to cerium is 1:2 to 1:5.

[0013] By employing the above technical solution, the two-dimensional nanosheet structure, elemental composition, size control, and spatial distribution of interface-modified rare earth additives are achieved through a hydrothermal in-situ growth process mediated by a structure-directing agent and precise control of the element feed ratio. Lanthanum nitrate or lanthanum chloride is used as the lanthanum source, cerium nitrate or cerium chloride as the cerium source, and zirconium oxychloride or zirconium nitrate as the zirconium source. Using zirconium oxide as the matrix, the two-dimensional nanosheet morphology, with the template-directing effect of the structure-directing agent in the hydrothermal reaction and the control of reaction conditions, allows the lanthanum-cerium-zirconium oxide precursor to grow directionally, forming a sheet-like structure that adheres to the outer surface and macropore inner walls of a hierarchical porous fly ash carrier. The 3-5 nm sheet thickness is achieved through the synergistic control of the spatial confinement effect of the structure-directing agent and the hydrothermal reaction rate. This thin sheet structure ensures a tight bond with the carrier interface while facilitating spatial expansion across different pore regions. The molar ratio of lanthanum to cerium, ranging from 1:2 to 1:5, is achieved through precise control of the feeding ratios of lanthanum, cerium, and zirconium sources. This specific molar ratio optimizes the electronic conductivity and interfacial affinity of the additives by adjusting the electronic interactions between rare earth elements. The two-dimensional nanosheets, through their distribution design that conforms to the inner walls and outer surfaces of the macropores of the carrier, spatially connect the mesoporous region containing the first active component with the macroporous region containing the second active component, forming structural connectivity and functional bridging, thus providing interfacial support for the synergistic effect between active components in different regions.

[0014] Preferably, the two-dimensional nanosheets of the interface-modified rare earth additive are modified with a fullerene carbon layer.

[0015] By employing the above-mentioned technical solution, a fullerene carbon layer is formed on the surface of two-dimensional nanosheets through chemical vapor deposition. Acetylene, methane, and other carbon-containing gases are selected as carbon sources. By controlling the vapor deposition temperature, carbon source concentration, and deposition time, the carbon content is precisely controlled within the range of 0.1%-2%. During deposition, the fullerene carbon layer covers the surface of the two-dimensional nanosheets in a thin and uniform film form. Its unique conjugated structure can alter the electron cloud distribution on the surface of the rare earth additive, thereby regulating the overall electronic properties of the catalyst and optimizing the electron transfer efficiency between the active component and pollutant molecules. Simultaneously, the hydrophobic properties of the fullerene carbon layer can reduce the adsorption capacity of water molecules and polar sulfur species on the catalyst surface, reducing surface hydroxylation and sulfur deposition. The specific range of carbon content ensures a balance between the regulatory effect and catalytic activity. When the carbon content is too low, the electronic property regulation and hydrophobic effect are not significant; when the carbon content is too high, it will cover the active sites and interfacial bridging regions of the rare earth additive, affecting its synergistic effect with the support and active component. This provides surface modification support for improving the catalyst's anti-poisoning performance and catalytic stability.

[0016] Secondly, this application provides a method for preparing a fly ash-based multi-effect catalyst, employing the following technical solution:

[0017] A method for preparing a fly ash-based multi-effect catalyst includes the following steps:

[0018] S1. Carrier construction and pre-modification: Using coal fly ash as raw material, a hierarchical porous fly ash carrier was prepared by magnetic separation, alkali fusion, hydrothermal synthesis in the presence of a dual template agent and ion exchange treatment. Subsequently, the carrier was pretreated with an aminosilane coupling agent to introduce amino functional groups into the inner surface of its pores.

[0019] S2. Mesoporous confined deposition of the first active component: The pretreated hierarchical porous fly ash carrier is immersed in a solution containing copper source, iron source and small sterically hindered amine. The molecular size effect of the sterically hindered amine and the anchoring effect of the amino functional group are used to selectively enter and confine copper and iron ions in the mesopores. After drying, heat treatment is carried out in a weak reducing atmosphere to form copper-iron bimetallic nanoclusters in the mesopores.

[0020] S3. Assembling the second active component in the macroporous region: The product obtained in step S2 is immersed in a solution containing vanadium source, tungsten source, titanium source and polymer complexing agent. The volume repulsion effect of the polymer complexing agent is used to make the active metal precursor complex mainly adsorbed on the outer surface of the carrier and in the macroporous channels. After being dried in a programmed manner, it is calcined in an air atmosphere to form vanadium-tungsten-titanium multi-element oxide nanoclusters.

[0021] S4. In-situ growth interface bridging agent: The product obtained in step S3 is immersed in a hydrothermal system containing lanthanum source, cerium source, zirconium source and structure guiding agent to carry out hydrothermal reaction, so that the lanthanum-cerium-zirconium oxide precursor is directionally grown into two-dimensional nanosheets on the surface of the support and the inner wall of the macropores, and then crystallized in an air atmosphere.

[0022] S5. Functionalization post-processing: The product obtained in step S4 is subjected to vapor deposition in an atmosphere containing a carbon source to generate a fullerene carbon modification layer on the surface of two-dimensional rare earth nanosheets.

[0023] By adopting the above technical solution and through a five-step continuous and synergistic process design, a fly ash-based multi-effect catalyst with specific structure and function is precisely constructed. The core technical means and mechanisms of action of each step are as follows: In S1, magnetic separation removes magnetic impurities from coal fly ash to improve raw material purity; alkaline fusion treatment breaks the original dense structure of fly ash and releases active sites through high-temperature activation; dual template agents induce the formation of tertiary channels; and ion exchange treatment optimizes channel connectivity. Subsequently, the reaction between aminosilane coupling agent and hydroxyl groups on the inner wall of the carrier channels achieves stable grafting of amino functional groups, providing binding sites for selective anchoring of active components. In S2, small-molecule sterically hindered amines restrict the diffusion area of ​​copper and iron ions, and amino functional groups achieve metal ion anchoring. Heat treatment under a weak reducing atmosphere converts metal ions into elemental substances and forms bimetallic nanoclusters with controllable size. In S3, a polymeric complexing agent forms a complex of a specific size with the metal precursor, achieving regioselective adsorption through volume repulsion effect; and programmed drying and calcination in air atmosphere promote the formation and firm binding of oxide nanoclusters. In step S4, a structure-directing agent regulates the growth direction of the oxide precursor, while hydrothermal reaction and crystallization treatment ensure the structural integrity and interfacial bonding strength of the two-dimensional nanosheets. In step S5, carbon species generated from the cracking of carbon-containing gas recombine on the surface of the two-dimensional nanosheets to form a fullerene carbon layer, and the carbon content is precisely controlled through process parameter regulation. Each step of the entire preparation process is interconnected. Precise control of raw material processing, component loading, structural regulation, and surface modification ensures that the structure and spatial distribution of each functional component of the catalyst meet the design requirements, providing process assurance for its multi-effect catalytic performance.

[0024] Preferably, in step S1, the aminosilane coupling agent is 3-aminopropyltriethoxysilane, and the pretreatment temperature is 70-90°C.

[0025] By adopting the above technical solution, in the pretreatment process of step S1, 3-aminopropyltriethoxysilane is selected as the aminosilane coupling agent. Combined with a pretreatment temperature of 70-90℃, the efficient and uniform grafting of amino functional groups onto the inner wall of the carrier pores is achieved through precise reagent selection and temperature control. The ethoxy group at one end of the 3-aminopropyltriethoxysilane molecule can undergo a hydrolysis reaction under this temperature condition to generate a reactive silanol group. The silanol group further undergoes a dehydration condensation reaction with the hydroxyl groups on the inner wall of the hierarchical porous fly ash carrier pores to form a stable Si-O-Si covalent bond, which firmly anchors the coupling agent molecule to the carrier surface. The amino group at the other end of the molecule remains active and exposed in the pores, providing specific binding sites for the subsequent coordination and anchoring of metal ions. The temperature range of 70-90℃ can meet the kinetic requirements of ethoxy hydrolysis and condensation reactions, promote the full reaction, and ensure the grafting density of amino functional groups. At the same time, it can avoid the coupling agent molecules from self-polymerization or decomposition due to excessively high temperature, and prevent the reaction rate from being too slow and the grafting from being too low temperature. Finally, through the synergistic regulation of reagents and temperature, the uniform distribution of amino functional groups in the pores of the support can be achieved, providing a reliable interfacial basis for the selective confined deposition of the first active component.

[0026] Preferably, in step S2, the small molecule sterically hindered amine is triethylamine or N,N-diisopropylethylamine; the weak reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 5-10%, and the temperature of the heat treatment is 350-450℃.

[0027] By adopting the above technical solution, in step S2, triethylamine or N,N-diisopropylethylamine is selected as a small-molecule sterically hindered amine. Combined with a weak reducing atmosphere with a hydrogen gas integral of 5-10% and a heat treatment temperature of 350-450℃, the precise confinement preparation of copper-iron bimetallic nanoclusters is achieved through the synergistic control of reagent properties and process parameters. Both triethylamine and N,N-diisopropylethylamine have molecular sizes that adapt to the differences in pore size between mesopores and macropores of the carrier. During impregnation, their molecules can form a spatial barrier at the entrance and inside of the mesopore channels of the carrier, preventing copper and iron ions from diffusing into the macropore region through the steric hindrance effect, allowing only selective entry of ions into the mesopore channels. At the same time, they synergistically interact with the amino functional groups on the inner wall of the carrier channels to enhance the anchoring effect on metal ions. A weak reducing atmosphere is constructed through a reasonable ratio of hydrogen and inert gas. The inert gas dilutes the hydrogen and moderates the reduction reaction. A hydrogen gas fraction of 5-10% provides sufficient reducing power to reduce copper and iron ions in the mesopores to elemental form, while avoiding over-reduction that could lead to metal particle agglomeration or sintering. The heat treatment temperature of 350-450℃ is synergistically matched with the weak reducing atmosphere. This temperature range satisfies the kinetic requirements of the metal ion reduction reaction, promoting the formation of bimetallic nanoclusters, while also inhibiting excessive growth of nanoclusters through the spatial confinement effect of the mesopore channels, ensuring a particle size of 5-25 nm. At the same time, it avoids excessive temperature causing decomposition of amino functional groups or damage to the carrier pore structure, ultimately achieving a stable confined distribution of copper-iron bimetallic nanoclusters within the mesopores.

[0028] Preferably, in step S3, the polymeric complexing agent is polyvinylpyrrolidone or polyacrylic acid; and the calcination temperature is 400-500℃.

[0029] By adopting the above technical solution, in step S3, polyvinylpyrrolidone or polyacrylic acid is selected as a polymeric complexing agent, and a calcination temperature of 400-500℃ is used. Through the synergistic control of reagent structural characteristics and process temperature, the precise assembly of vanadium-tungsten-titanium multi-component oxide nanoclusters in specific regions is achieved. Both polyvinylpyrrolidone and polyacrylic acid have good coordination ability and large molecular volume. After combining with metal ions in vanadium, tungsten, and titanium sources, they form metal precursor complexes with a size of 50-100 nm. Due to the volume repulsion effect, these complexes cannot penetrate mesoporous channels and can only selectively adsorb onto the inner wall and outer surface of the macropores of the carrier, laying the foundation for the subsequent regional distribution of oxide nanoclusters. The calcination temperature of 400-500℃ precisely matches the requirements for the decomposition of complexes and the formation of oxides. Under this temperature condition, the polymer complexing agent can be completely decomposed and volatilized, while driving the metal precursor to undergo an oxidative polymerization reaction, transforming it into structurally stable vanadium-tungsten-titanium multi-element oxide nanoclusters. Moreover, this temperature will not destroy the hierarchical pore structure of the support and the first active component that has been deposited in a confined space, and can also strengthen the interfacial bonding strength between the oxide nanoclusters and the surface of the support, ultimately achieving the stable anchoring of the second active component in the designated area.

[0030] Preferably, in step S4, the structure directing agent is hexadecyltrimethylammonium chloride or ammonium fluoride; the temperature of the hydrothermal reaction is 120-180℃; the temperature of the crystallization treatment is 500-600℃; and in step S5, the temperature of the vapor deposition is 600-800℃, and the deposition time is 10-20 minutes.

[0031] By adopting the above technical solution, in step S4, hexadecyltrimethylammonium chloride or ammonium fluoride is selected as the structure directing agent. Combined with a hydrothermal reaction temperature of 120-180℃ and a crystallization treatment temperature of 500-600℃, the directional growth and structural stabilization of two-dimensional nanosheets are achieved through reagent template effect and temperature gradient control. Hexadecyltrimethylammonium chloride, leveraging the molecular structure characteristics of a cationic surfactant, self-assembles into rod-shaped micelle templates in the hydrothermal system, guiding the lanthanum, cerium, and zirconium oxide precursors to grow directionally along the template into a sheet-like structure. Ammonium fluoride, by controlling the pH and ionic environment of the system, induces directional crystallization of the precursor. Both structure directing agents are adaptable to the growth environment on the carrier surface and the inner wall of the macropores, ensuring the adherent growth of the two-dimensional nanosheets. The hydrothermal reaction temperature of 120-180℃ provides suitable kinetic conditions for the dissolution, diffusion, and directional growth of the precursor, promoting the full reaction of the oxide precursor to form a sheet-like morphology while avoiding excessive temperature leading to collapse of the carrier pore structure or excessive aggregation of the precursor. A crystallization temperature of 500-600℃ further enhances the crystalline structure order of the two-dimensional nanosheets, strengthening their mechanical stability and interfacial bonding strength, while avoiding damage to the loaded active components, thus ensuring the structural integrity and functional reliability of the additive. In step S5, a vapor deposition temperature of 600-800℃ and a deposition time of 10-20 minutes work synergistically to achieve precise modification of the fullerene carbon layer on the surface of the two-dimensional nanosheets. The temperature range of 600-800℃ drives the carbon source gas to decompose, generating reactive carbon species. These carbon species are rapidly adsorbed, recombined, and form a fullerene-structured carbon layer on the surface of the two-dimensional nanosheets. This temperature range ensures efficient carbon source decomposition and successful carbon layer formation, while avoiding excessive temperature that could lead to nanosheet oxidation or over-deposition of the carbon layer. The deposition time of 10-20 minutes is precisely matched with the temperature. By controlling the growth cycle of carbon species on the surface, the carbon content can be precisely controlled within the range of 0.1%-2%, ensuring that the carbon layer is thin and uniform. This allows the electronic properties to be fully utilized for regulation and hydrophobic effects, without covering the active sites of the two-dimensional nanosheets or affecting their interface bridging function. Ultimately, this achieves efficient surface functionalization modification of interface-modified rare earth additives.

[0032] In summary, this application has the following beneficial effects:

[0033] 1. Because this application adopts a hierarchical porous fly ash carrier, a confined multi-element active nanoclusters and an interface-modified rare earth additive, the carrier provides a three-level pore mass transfer structure, the two active components form functional complementary sites through spatial separation and molar ratio regulation, the rare earth additive realizes interface bridging and performance regulation, and the precise ratio of each component and the structural design work together to achieve the effect of multi-effect catalysis and structural stability.

[0034] 2. In this application, a hierarchical porous fly ash carrier with a three-level pore structure and a specific surface area of ​​300-600 m² / g is preferred. It is prepared by magnetic separation, alkali fusion, hydrothermal synthesis with dual template agents and ion exchange process, which lays the structural foundation for pollutant adsorption and mass transfer and uniform loading of active components, and achieves the effect of improving the kinetic efficiency of catalytic reaction.

[0035] 3. In this application, the confined multi-component active nanoclusters achieve selective distribution of mesoporous and macroporous regions by controlling the specific molar ratio of copper and iron and the molar ratio of vanadium, tungsten and titanium, combined with the steric hindrance and volume repulsion effect, avoiding interference between components, and each component plays a targeted catalytic role, thus achieving the effect of synergistic purification of multiple pollutants.

[0036] 4. In this application, the interface-modified rare earth additive uses lanthanum and cerium co-doped two-dimensional nanosheets and modifies fullerene carbon layers. Lanthanum and cerium optimize electron conduction, carbon layers regulate surface properties, and the layered structure strengthens interface bridging, thereby achieving the effect of improving the synergistic effect and anti-interference ability of the components.

[0037] 5. The preparation method of this application adopts a five-step continuous process, combined with the selection of specific reagents and precise control of parameters such as temperature and time, to achieve the orderly connection of support pretreatment, active component deposition, auxiliary agent growth and functional modification, and obtain the effect of stable and controllable catalyst structure and performance. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method for preparing a fly ash-based multi-effect catalyst provided in this application. Detailed Implementation

[0039] The present application will be further described in detail below with reference to embodiments and comparative examples. Unless otherwise specified, the experimental methods used below are conventional methods. Unless otherwise specified, the materials, reagents, methods and instruments used are all conventional materials, reagents, methods and instruments in the art, which can be obtained by those skilled in the art through commercial channels or prepared according to literature methods.

[0040] Technical concept:

[0041] In existing technologies, the preparation of catalysts using fly ash often focuses on achieving a single function or simple component blending, such as primarily for denitrification or treating a single type of organic matter. These methods often fail to fully utilize the complex composition and structural plasticity of fly ash, resulting in catalysts with randomly distributed active sites and a lack of effective spatial organization and synergistic mechanisms between different functional components. When treating flue gas with similar compositions, it is difficult to achieve simultaneous and efficient removal of multiple pollutants such as nitrogen oxides, volatile organic compounds, and heavy metals. Furthermore, the long-term stability and poisoning resistance of the catalyst are often limited by the agglomeration and sintering of the active components.

[0042] This technical solution constructs a hierarchical porous fly ash support with a three-tiered pore structure of micropores, mesopores, and macropores, providing differentiated spatial loading sites for different active components. Furthermore, utilizing the molecular size effect of sterically hindered amines and polymeric complexing agents, copper-iron bimetallic nanoclusters and vanadium-tungsten-titanium multi-element oxide nanoclusters are selectively and stepwise confined within the mesopores and macropores of the support, respectively. Simultaneously, two-dimensional sheet-like lanthanum-cerium-zirconium composite oxides are introduced as interface modification aids, growing in situ on the support surface and pore walls, connecting the different spatially distributed active sites. This design enables multiple active components to form an ordered and stable spatial distribution architecture, aiming to promote synergy between different catalytic functions through a structured approach.

[0043] Preparation Example 1

[0044] The specific method for preparing the graded porous fly ash carrier is as follows:

[0045] Take 100g of coal fly ash with a particle size of 50-100μm, remove magnetic impurities by magnetic separation in an 8000Gs magnetic field, mix with 50g of sodium hydroxide and place in a muffle furnace, alkali melt at 800℃ for 2h, cool, pulverize and pass through a 200-mesh sieve, add 2L of deionized water, stir to dissolve and filter. Mix the filter residue with a composite dual-template agent solution containing 0.05mol / L hexadecyltrimethylammonium chloride and 0.1g / mL silica nanoparticles, transfer to a hydrothermal reactor and immerse in water at 160℃. The reaction was thermally synthesized for 8 hours. After the reaction was completed, the product was filtered and placed in 0.5 mol / L hydrochloric acid solution for ion exchange at room temperature for 2 hours. After washing with deionized water until neutral, the product was dried at 110℃ for 12 hours to obtain a hierarchical porous fly ash support. Subsequently, the support was immersed in an ethanol solution containing 5 wt% 3-aminopropyltriethoxysilane for pretreatment for 4 hours. After filtration, the product was dried at 100℃ for 6 hours to obtain a modified hierarchical porous fly ash support with amino functional groups grafted onto the inner surface of the pores and possessing a three-level structure of micropores-mesopores-macropores.

[0046] The following are the main raw materials and reagents used in the preparation examples, embodiments, and comparative examples, and their sources and specifications are as follows; unless otherwise specified, all reagents are commercially available analytical grade or higher products:

[0047] 1. 3-Aminopropyltriethoxysilane was purchased from Suzhou Yake Technology Co., Ltd., item number: A0005;

[0048] 2. Triethylamine was purchased from Shandong Mingyu Supply Chain Management Co., Ltd., CAS: 121-44-8;

[0049] 3. N,N-Diisopropylethylamine was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., CAS: 7087-68-5;

[0050] 4. Polyvinylpyrrolidone was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S30268;

[0051] 5. Polyacrylic acid was purchased from Hubei Hengjingrui Chemical Co., Ltd., CAS: 9003-01-4;

[0052] 6. Cetyltrimethylammonium chloride was purchased from Shanghai Yuanye Biotechnology Co., Ltd., product number: S15002.

[0053] Example 1

[0054] This application provides a fly ash-based multi-effect catalyst, which, by mass parts, comprises the following components: 110 parts of hierarchical porous fly ash support, 20 parts of confined multi-element active nanoclusters, and 8 parts of interface-modified rare earth additives.

[0055] Among them, the graded porous fly ash carrier has a three-level pore structure of micropores, mesopores and macropores, and the specific surface area of ​​the graded porous fly ash carrier is 450m² / g.

[0056] The confined multi-element active nanoclusters include a first active component and a second active component. The first active component is a copper-iron bimetallic nanocluster, in which the molar ratio of copper to iron is 1:2. The second active component is a vanadium-tungsten-titanium multi-element oxide nanocluster, in which the molar ratio of vanadium, tungsten and titanium is 1:0.9:6.

[0057] Among them, the interface-modified rare earth additive is a two-dimensional nanosheet with zirconium oxide as the matrix and co-doped with lanthanum and cerium, with a sheet thickness of 4 nm and a molar ratio of lanthanum to cerium of 1:3.5.

[0058] Among them, the two-dimensional nanosheets of the interface-modified rare earth additive are modified with a fullerene carbon layer with a carbon content of 1.5%, which is used to adjust the electronic properties and hydrophobicity of the catalyst surface.

[0059] The above-mentioned method for preparing a fly ash-based multi-effect catalyst includes the following steps:

[0060] S1. Carrier construction and pre-modification: Using coal fly ash as raw material, a hierarchical porous fly ash carrier was prepared by magnetic separation, alkali fusion, hydrothermal synthesis in the presence of a dual template agent and ion exchange treatment. Subsequently, the carrier was pretreated with an aminosilane coupling agent to introduce amino functional groups into the inner surface of its pores.

[0061] The aminosilane coupling agent is 3-aminopropyltriethoxysilane, and the pretreatment temperature is 80°C.

[0062] S2. Mesoporous confined deposition of the first active component: The pretreated hierarchical porous fly ash carrier is immersed in a solution containing copper source, iron source and small sterically hindered amine. The molecular size effect of the sterically hindered amine and the anchoring effect of the amino functional group are used to selectively enter and confine copper and iron ions in the mesopores. After drying, heat treatment is carried out in a weak reducing atmosphere to form copper-iron bimetallic nanoclusters in the mesopores.

[0063] The small-molecule sterically hindered amine is triethylamine; the weak reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 7.5%, and the heat treatment temperature is 400℃.

[0064] S3. Assembling the second active component in the macroporous region: The product obtained in step S2 is immersed in a solution containing vanadium source, tungsten source, titanium source and polymer complexing agent. The volume repulsion effect of the polymer complexing agent is used to make the active metal precursor complex mainly adsorbed on the outer surface of the carrier and in the macroporous channels. After being dried in a programmed manner, it is calcined in an air atmosphere to form vanadium-tungsten-titanium multi-element oxide nanoclusters.

[0065] The polymeric complexing agent is polyvinylpyrrolidone; the calcination temperature is 450℃.

[0066] S4. In-situ growth interface bridging agent: The product obtained in step S3 is immersed in a hydrothermal system containing lanthanum source, cerium source, zirconium source and structure directing agent to carry out hydrothermal reaction, so that the lanthanum-cerium-zirconium oxide precursor is directionally grown into two-dimensional nanosheets on the surface of the support and the inner wall of the macropores; then crystallization treatment is carried out in an air atmosphere.

[0067] The structure-directing agent is hexadecyltrimethylammonium chloride; the hydrothermal reaction temperature is 150°C; and the crystallization treatment temperature is 550°C.

[0068] S5. Functionalization post-processing: The product obtained in step S4 is subjected to vapor deposition in an atmosphere containing a carbon source to generate a fullerene carbon modification layer on the surface of two-dimensional rare earth nanosheets.

[0069] The vapor deposition temperature is 700℃ and the deposition time is 15 minutes.

[0070] Example 2

[0071] This application provides a fly ash-based multi-effect catalyst, which, by mass parts, comprises the following components: 120 parts of hierarchical porous fly ash carrier, 15 parts of confined multi-element active nanoclusters, and 10 parts of interface-modified rare earth additives.

[0072] Among them, the graded porous fly ash carrier has a three-level pore structure of micropores, mesopores and macropores, and the specific surface area of ​​the graded porous fly ash carrier is 600m² / g.

[0073] The confined multi-element active nanoclusters include a first active component and a second active component. The first active component is a copper-iron bimetallic nanocluster, in which the molar ratio of copper to iron is 1:1. The second active component is a vanadium-tungsten-titanium multi-element oxide nanocluster, in which the molar ratio of vanadium, tungsten and titanium is 1:1.5:10.

[0074] Among them, the interface-modified rare earth additive is a two-dimensional nanosheet with zirconium oxide as the matrix and co-doped with lanthanum and cerium, with a sheet thickness of 5 nm and a molar ratio of lanthanum to cerium of 1:5.

[0075] Among them, the two-dimensional nanosheets of the interface-modified rare earth additive are modified with a fullerene carbon layer with a carbon content of 2%, which is used to adjust the electronic properties and hydrophobicity of the catalyst surface.

[0076] The above-mentioned method for preparing a fly ash-based multi-effect catalyst includes the following steps:

[0077] S1. Carrier construction and pre-modification: Using coal fly ash as raw material, a hierarchical porous fly ash carrier was prepared by magnetic separation, alkali fusion, hydrothermal synthesis in the presence of a dual template agent and ion exchange treatment. Subsequently, the carrier was pretreated with an aminosilane coupling agent to introduce amino functional groups into the inner surface of its pores.

[0078] The aminosilane coupling agent is 3-aminopropyltriethoxysilane, and the pretreatment temperature is 90°C.

[0079] S2. Mesoporous confined deposition of the first active component: The pretreated hierarchical porous fly ash carrier is immersed in a solution containing copper source, iron source and small sterically hindered amine. The molecular size effect of the sterically hindered amine and the anchoring effect of the amino functional group are used to selectively enter and confine copper and iron ions in the mesopores. After drying, heat treatment is carried out in a weak reducing atmosphere to form copper-iron bimetallic nanoclusters in the mesopores.

[0080] The small sterically hindered amine is N,N-diisopropylethylamine; the weak reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 5%, and the heat treatment temperature is 350°C.

[0081] S3. Assembling the second active component in the macroporous region: The product obtained in step S2 is immersed in a solution containing vanadium source, tungsten source, titanium source and polymer complexing agent. The volume repulsion effect of the polymer complexing agent is used to make the active metal precursor complex mainly adsorbed on the outer surface of the carrier and in the macroporous channels. After being dried in a programmed manner, it is calcined in an air atmosphere to form vanadium-tungsten-titanium multi-element oxide nanoclusters.

[0082] The polymeric complexing agent is polyacrylic acid; the calcination temperature is 500℃.

[0083] S4. In-situ growth interface bridging agent: The product obtained in step S3 is immersed in a hydrothermal system containing lanthanum source, cerium source, zirconium source and structure directing agent to carry out hydrothermal reaction, so that the lanthanum-cerium-zirconium oxide precursor is directionally grown into two-dimensional nanosheets on the surface of the support and the inner wall of the macropores; then crystallization treatment is carried out in an air atmosphere.

[0084] The structure-directing agent is ammonium fluoride; the hydrothermal reaction temperature is 180℃; and the crystallization treatment temperature is 600℃.

[0085] S5. Functionalization post-processing: The product obtained in step S4 is subjected to vapor deposition in an atmosphere containing a carbon source to generate a fullerene carbon modification layer on the surface of two-dimensional rare earth nanosheets.

[0086] The vapor deposition temperature is 800℃ and the deposition time is 20 minutes.

[0087] Example 3

[0088] This application provides a fly ash-based multi-effect catalyst, which, by mass parts, comprises the following components: 100 parts of hierarchical porous fly ash carrier, 25 parts of confined multi-element active nanoclusters, and 6 parts of interface-modified rare earth additives.

[0089] Among them, the graded porous fly ash carrier has a three-level pore structure of micropores, mesopores and macropores, and the specific surface area of ​​the graded porous fly ash carrier is 300m² / g.

[0090] The confined multi-element active nanoclusters include a first active component and a second active component. The first active component is a copper-iron bimetallic nanocluster, wherein the molar ratio of copper to iron is 1:3; the second active component is a vanadium-tungsten-titanium multi-element oxide nanocluster, wherein the molar ratio of vanadium, tungsten and titanium is 1:0.3:2.

[0091] Among them, the interface-modified rare earth additive is a two-dimensional nanosheet with zirconium oxide as the matrix and co-doped with lanthanum and cerium, with a sheet thickness of 3nm and a molar ratio of lanthanum to cerium of 1:2.

[0092] Among them, the two-dimensional nanosheets of the interface-modified rare earth additive are modified with a fullerene carbon layer with a carbon content of 1%, which is used to adjust the electronic properties and hydrophobicity of the catalyst surface.

[0093] The above-mentioned method for preparing a fly ash-based multi-effect catalyst includes the following steps:

[0094] S1. Carrier construction and pre-modification: Using coal fly ash as raw material, a hierarchical porous fly ash carrier was prepared by magnetic separation, alkali fusion, hydrothermal synthesis in the presence of a dual template agent and ion exchange treatment. Subsequently, the carrier was pretreated with an aminosilane coupling agent to introduce amino functional groups into the inner surface of its pores.

[0095] The aminosilane coupling agent is 3-aminopropyltriethoxysilane, and the pretreatment temperature is 70°C.

[0096] S2. Mesoporous confined deposition of the first active component: The pretreated hierarchical porous fly ash carrier is immersed in a solution containing copper source, iron source and small sterically hindered amine. The molecular size effect of the sterically hindered amine and the anchoring effect of the amino functional group are used to selectively enter and confine copper and iron ions in the mesopores. After drying, heat treatment is carried out in a weak reducing atmosphere to form copper-iron bimetallic nanoclusters in the mesopores.

[0097] The small-molecule sterically hindered amine is triethylamine; the weak reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 10%, and the heat treatment temperature is 450°C.

[0098] S3. Assembling the second active component in the macroporous region: The product obtained in step S2 is immersed in a solution containing vanadium source, tungsten source, titanium source and polymer complexing agent. The volume repulsion effect of the polymer complexing agent is used to make the active metal precursor complex mainly adsorbed on the outer surface of the carrier and in the macroporous channels. After being dried in a programmed manner, it is calcined in an air atmosphere to form vanadium-tungsten-titanium multi-element oxide nanoclusters.

[0099] The polymeric complexing agent is polyvinylpyrrolidone; the calcination temperature is 400℃.

[0100] S4. In-situ growth interface bridging agent: The product obtained in step S3 is immersed in a hydrothermal system containing lanthanum source, cerium source, zirconium source and structure directing agent to carry out hydrothermal reaction, so that the lanthanum-cerium-zirconium oxide precursor is directionally grown into two-dimensional nanosheets on the surface of the support and the inner wall of the macropores; then crystallization treatment is carried out in an air atmosphere.

[0101] The structure-directing agent is hexadecyltrimethylammonium chloride; the hydrothermal reaction temperature is 120°C; and the crystallization treatment temperature is 500°C.

[0102] S5. Functionalization post-processing: The product obtained in step S4 is subjected to vapor deposition in an atmosphere containing a carbon source to generate a fullerene carbon modification layer on the surface of two-dimensional rare earth nanosheets.

[0103] The vapor deposition temperature is 600℃ and the deposition time is 10 minutes.

[0104] Comparative Example 1

[0105] The only difference between this comparative example and Example 1 is that the graded porous fly ash carrier is replaced with a common alkali-fused fly ash carrier that has not undergone hydrothermal synthesis and ion exchange treatment with dual template agents. The specific surface area of ​​the common alkali-fused fly ash carrier is 120 m² / g, and it does not have a tertiary pore structure. The other raw material components, proportions and preparation processes are the same as in Example 1.

[0106] Comparative Example 2

[0107] The only difference between this comparative example and Example 1 is that: the entire step S5 is omitted, and the final catalyst is obtained after the crystallization treatment in step S4 is completed; the surface of the interface-modified rare earth additive of this catalyst does not contain a fullerene carbon layer; the remaining raw material components, proportions and preparation processes are the same as in Example 1.

[0108] Comparative Example 3

[0109] The only difference between this comparative example and Example 1 is that the confined deposition and regional assembly processes in steps S2 and S3 are omitted. Instead, copper, iron, vanadium, tungsten, and titanium sources are simultaneously impregnated onto the support pretreated in step S1. After drying and calcination, a catalyst with randomly distributed active components is obtained. The total mass fraction of the active components remains the same as in Example 1. The remaining raw material components, proportions, and preparation processes are the same as in Example 1.

[0110] Comparative Example 4

[0111] The only difference between this comparative example and Example 1 is that, in step S4, a hydrothermal system containing a structure-directing agent is not used to grow two-dimensional nanosheets; instead, an equal-volume impregnation method is used to load the same molar amounts of soluble salts of lanthanum, cerium, and zirconium onto the product obtained in step S3, which is then dried and directly calcined at high temperature to obtain a traditional granular lanthanum-cerium-zirconium composite oxide additive; the remaining raw material components, ratios, and preparation processes are the same as in Example 1.

[0112] Comparative Example 5

[0113] This comparative example does not involve preparation; a commercially available V2O5-WO3 / TiO2 honeycomb SCR denitration catalyst was directly selected as the comparison sample. Its active components partially overlap with those of this invention, but the support and structural design are completely different.

[0114] Comparative Example 6

[0115] The only difference between this comparative example and Example 1 is that a conventional fly ash utilization method is used; the fly ash is simply acid-washed and alkali-melted as a carrier, and a salt solution of copper, iron, vanadium and tungsten is loaded onto it in one step using a common impregnation method, and then dried and calcined to obtain a catalyst.

[0116] Experiment 1: Evaluation of Synergistic Catalytic Performance of Multiple Pollutants

[0117] Referring to the relevant testing standards of GB / T31590-2015 "Denitrification Catalysts for Coal-fired Flue Gas", HJ583-2010 "Determination of Benzene Series Compounds in Ambient Air: Solid Adsorption / Thermal Desorption-Gas Chromatography", and HJ685-2014 "Determination of Lead in Exhaust Gas from Stationary Sources: Flame Atomic Absorption Spectrophotometry", a fixed-bed reactor was used to conduct multi-pollutant synergistic catalytic performance tests.

[0118] This experiment targeted all catalyst samples from Examples 1-3 and Comparative Examples 1-6. 5g of each catalyst sample was taken, crushed, sieved to a particle size of 2.5-4.5mm, and then packed into the core reaction section of the reactor. The reaction temperature was set at 250℃, the mass hourly space velocity (HSV) was 20000mL・g⁻¹・h⁻¹, and simulated coal-fired flue gas was introduced, with a nitrogen monoxide concentration of 500ppm, a toluene concentration of 100ppm, a gaseous mercury concentration of 50μg / m³, a sulfur dioxide concentration of 800ppm, an oxygen volume fraction of 6%, and nitrogen as the balance gas. The total gas flow rate was stably controlled at 500mL / min. After the system stabilized following two hours of continuous operation, the concentrations of nitric oxide at the inlet and outlet were measured using a "42i-HL" flue gas analyzer, the concentrations of toluene at the inlet and outlet were measured using a gas chromatograph, and the concentrations of gaseous mercury at the inlet and outlet were measured using an atomic absorption spectrophotometer. The removal rate of nitric oxide, the degradation rate of toluene, and the adsorption rate of gaseous mercury for each catalyst were calculated. The temperature changes of the catalyst bed and the stability of the gas flow rate were recorded simultaneously during the reaction.

[0119] Experiment 2: Hydrothermal Aging and Sulfur Poisoning Resistance Test

[0120] Referring to the durability test method in GB / T31590-2015 "Coal-fired Flue Gas Denitrification Catalyst", HJ / T389-2007 "Environmental Protection Product Technical Requirements for Coal-fired Flue Gas Denitrification Catalyst", and the industry's sulfur poisoning resistance performance evaluation standard, a continuous test mode of hydrothermal aging and sulfur poisoning resistance was adopted to ensure that the test duration meets the industrial catalyst evaluation standard.

[0121] This experiment targeted all catalyst samples from Examples 1-3 and Comparative Examples 1-6. First, each catalyst sample was placed in a hydrothermal aging apparatus, with 10% (by volume) water vapor introduced, nitrogen used as the equilibrium gas, and the temperature set at 450°C, pressure at 0.1 MPa, and aging time at 200 hours, simulating high-temperature and high-humidity industrial conditions for accelerated aging. After hydrothermal aging, the samples were transferred to a fixed-bed reactor, using the same reaction apparatus and simulated flue gas components as in Experiment 1, but with the reaction duration extended to 1000 hours, during which the sulfur dioxide concentration was maintained at a stable 800 ppm. At 0, 200, 400, 600, 800, and 1000 hours of reaction operation, the removal efficiency of each catalyst for nitric oxide, toluene, and gaseous mercury was determined according to the detection method in Experiment 1. Performance data at each time point were recorded, and the performance decay rate after 1000 hours was calculated. Simultaneously, scanning electron microscopy was used to observe the changes in the surface morphology of the catalyst before and after aging, X-ray diffraction was used to analyze the stability of the crystal structure of the active component, and inductively coupled plasma atomic emission spectrometry was used to detect the amount of sulfur deposited on the catalyst surface. The long-term operational stability and anti-poisoning ability of the catalyst in this application under high temperature, high humidity, and sulfur-containing atmosphere were comprehensively evaluated. The test duration fully meets the industry evaluation standards, and the data comparison is more convincing.

[0122] Experiment 3: Characterization of Active Component Dispersion and Surface Acidity

[0123] Referring to the relevant standards of GB / T5816-1995 "Method for Determination of Dispersion of Active Components in Catalysts" and HG / T4860-2015 "Method for Determination of Surface Area and Pore Structure of Catalysts", characterization tests were carried out using a chemical adsorption instrument and a temperature-programmed desorption instrument.

[0124] This experiment targeted all catalyst samples from Examples 1-3 and Comparative Examples 1-6. In the active component dispersion test, carbon monoxide was used as the adsorption probe molecule. The catalyst sample was purged with inert gas at 300°C for 1 hour to remove surface impurities. After cooling to 50°C, carbon monoxide adsorption gas was introduced until saturation, and then the temperature was increased to 600°C at a rate of 10°C / min. The desorption curves were recorded, and the dispersion of active components such as copper, iron, and vanadium was calculated. For the surface acidity test, an ammonia-programmed desorption method was used. The catalyst sample was pretreated with inert gas at 300°C for 1 hour, cooled to 50°C, and then ammonia adsorption was introduced until saturation. The temperature was increased to 600°C at a rate of 15°C / min, and the desorption curves were recorded. The number and distribution of weak, moderate, and strong acid sites on the catalyst surface were analyzed. Simultaneously, X-ray photoelectron spectroscopy was used to determine the chemical valence state of the active components.

[0125] The experimental data for evaluating the synergistic catalytic performance of multiple pollutants are shown in Table 1.

[0126] Table 1:

[0127] Sample Name NO removal rate (%) Toluene degradation rate (%) Gaseous mercury adsorption rate (%) Example 1 88.6 80.2 86.5 Example 2 91.3 84.7 89.8 Example 3 86.4 78.5 90.3 Comparative Example 1 54.8 39.6 48.2 Comparative Example 2 82.1 71.3 72.6 Comparative Example 3 67.3 55.8 65.4 Comparative Example 4 75.9 66.2 70.1 Comparative Example 5 82.5 21.7 30.5 Comparative Example 6 58.7 42.3 52.8

[0128] The hydrothermal aging and sulfur poisoning resistance durability test data are shown in Table 2.

[0129] Table 2:

[0130] Sample Name NO removal rate attenuation rate (%) Toluene degradation rate attenuation rate (%) Attenuation rate of gaseous mercury adsorption (%) Sulfur deposition (mg / g) Example 1 7.2 8.5 9.3 1.86 Example 2 6.5 7.8 8.1 1.62 Example 3 8.1 9.2 7.5 1.75 Comparative Example 1 28.6 32.4 35.7 4.28 Comparative Example 2 18.3 20.7 24.5 3.51 Comparative Example 3 22.5 25.3 28.9 3.87 Comparative Example 4 15.7 17.9 21.3 3.14 Comparative Example 5 12.8 45.6 58.2 2.93 Comparative Example 6 33.4 38.9 42.6 4.75

[0131] The experimental data on the dispersion of active components and surface acidity are shown in Table 3.

[0132] Table 3:

[0133] Sample Name Copper dispersion (%) Iron dispersion (%) Vanadium dispersion (%) Total number of acidic sites (μmol / g) Example 1 42.8 40.3 38.6 326.5 Example 2 45.2 43.7 41.8 358.2 Example 3 41.5 39.6 37.2 312.8 Comparative Example 1 21.7 19.5 23.3 156.3 Comparative Example 2 40.6 38.2 36.9 301.7 Comparative Example 3 25.3 23.8 27.5 198.4 Comparative Example 4 32.4 30.1 31.7 245.9 Comparative Example 5 - - 43.5 286.4 Comparative Example 6 23.1 20.8 24.6 172.5

[0134] Based on Examples 1-3 and Comparative Example 1, and referring to Tables 1-3, it can be seen that replacing the hierarchical porous fly ash support with a conventional alkali-fused fly ash support that has not undergone hydrothermal synthesis and ion exchange treatment with dual-template agents leads to a comprehensive decline in catalyst performance. The conventional alkali-fused fly ash support lacks an ordered tertiary pore structure and has a low specific surface area. This results in the inability to achieve effective spatial confinement and high dispersion loading of subsequent active components and additives. Simultaneously, the mass transfer and diffusion process of reactants is hindered, and the number of acidic sites provided on the support surface is significantly reduced.

[0135] Based on Examples 1-3 and Comparative Example 2, and referring to Tables 1-3, it can be seen that omitting the step of generating a fullerene carbon layer on the surface of the interface-modified rare earth additive affects the catalyst's performance, particularly its long-term stability in a sulfur-containing atmosphere. The lack of fullerene carbon layer modification weakens the modulating effect on the catalyst's surface electronic properties, reducing its ability to resist the adsorption and conversion of acidic gases such as sulfur dioxide. Simultaneously, its surface hydrophobicity may change, affecting its structural stability in high-temperature and high-humidity environments.

[0136] As can be seen from Examples 1-3 and Comparative Example 3, and Tables 1-3, changing the loading process of the active components, replacing the stepwise mesoporous confined deposition and macroporous region assembly with a one-time co-impregnation, significantly reduces catalyst performance. The one-time impregnation process cannot achieve the selective spatial distribution of copper-iron bimetallic nanoclusters and vanadium-tungsten-titanium multi-element oxide nanoclusters within pores of different scales, leading to random aggregation of the active components, decreased dispersion, weakened synergistic effects between different active sites, and greater susceptibility to sintering and deactivation under harsh reaction conditions.

[0137] As can be seen from Examples 1-3 and Comparative Example 4, and in conjunction with Tables 1-3, the catalyst performance deteriorates when the process of growing two-dimensional nanosheet rare earth additives using the structure-directing hydrothermal method is replaced with the traditional impregnation-calcination method to prepare particulate additives. The dispersibility and interfacial contact effect of particulate additives on the support surface are inferior to those of two-dimensional nanosheet structures. Their efficiency in bridging different active regions and promoting electron transfer and mass transfer is reduced, thus affecting the catalytic reaction and the overall stability of the catalytic system.

[0138] As can be seen from Examples 1-3 and Comparative Example 5, and in conjunction with Tables 1-3, when comparing with commercially available single-function denitrification catalysts, their performance exhibits inconsistencies in the synergistic removal of multiple pollutants. The material system and structural design of this commercial catalyst are primarily aimed at nitrogen oxide removal; its support and active component composition lack synergistic catalytic and adsorption capabilities for multiple pollutants such as volatile organic compounds and heavy metals like mercury. This underscores the necessity of the specific material and structural design employed in this application for multi-effect treatment.

[0139] As can be seen from Examples 1-3 and Comparative Example 6, and Tables 1-3, the performance indicators of the catalyst prepared by simple fly ash treatment and conventional impregnation methods are all at a low level. This method failed to construct a hierarchical porous support, nor did it achieve the confined distribution of active components and the nanosheet structure modification of the additives. Its technical solution failed to comprehensively utilize multiple means such as support design, spatial confinement, and interface modification, and therefore could not achieve the technical effects achieved in this application.

[0140] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A fly ash-based multi-effect catalyst, characterized in that: By mass fraction, it includes the following components: 100-120 parts of graded porous fly ash carrier, 15-25 parts of confined multi-element active nanoclusters, and 6-10 parts of interface-modified rare earth additives. The graded porous fly ash carrier has a three-level pore structure of micropores, mesopores and macropores, and the specific surface area of ​​the graded porous fly ash carrier is 300-600m² / g. The confined multi-element active nanoclusters include a first active component and a second active component. The first active component is a copper-iron bimetallic nanocluster, wherein the molar ratio of copper to iron is 1:1 to 1:3, and the copper-iron bimetallic nanocluster is selectively confined within the mesopores of the hierarchical porous fly ash carrier. The second active component is a vanadium-tungsten-titanium multi-element oxide nanocluster, wherein the molar ratio of vanadium, tungsten, and titanium is 1:(0.3-1.5):(2-10), and the vanadium-tungsten-titanium multi-element oxide nanocluster is selectively distributed on the macropore inner wall and outer surface of the hierarchical porous fly ash carrier. The interface-modified rare earth additive is a two-dimensional nanosheet with zirconium oxide as the matrix and co-doped with lanthanum and cerium. The thickness of the nanosheet is 3-5 nm, and the molar ratio of lanthanum to cerium is 1:2 to 1:

5. The two-dimensional nanosheet is grown in situ on the surface and macropore inner wall of the hierarchical porous fly ash carrier, bridging the first active component in the mesopore and the second active component in the macropore. The two-dimensional nanosheets of the interface-modified rare earth additive are modified with a fullerene carbon layer.

2. The fly ash-based multi-effect catalyst according to claim 1, characterized in that: The graded porous fly ash carrier has micropores with a diameter of less than 2 nm, mesopores with a diameter of 2-50 nm, and macropores with a diameter of greater than 50 nm; wherein the mesopore volume accounts for 60%-75% of the total pore volume, the micropore volume accounts for 10%-20% of the total pore volume, and the macropore volume accounts for 10%-20% of the total pore volume.

3. The fly ash-based multi-effect catalyst according to claim 1, characterized in that: The copper-iron bimetallic nanoclusters have a particle size of 5-25 nm, and the vanadium-tungsten-titanium multi-element oxide nanoclusters have a particle size of 50-100 nm.

4. The fly ash-based multi-effect catalyst according to claim 1, characterized in that: The carbon content of the fullerene carbon layer accounts for 0.1%-2% of the mass of the interface-modified rare earth additive.

5. A method for preparing a fly ash-based multi-effect catalyst, characterized in that, The fly ash-based multi-effect catalyst according to any one of claims 1-4 comprises the following steps: S1. Carrier construction and pre-modification: Using coal fly ash as raw material, a hierarchical porous fly ash carrier was prepared by magnetic separation, alkali fusion, hydrothermal synthesis in the presence of a dual template agent and ion exchange treatment. Subsequently, the carrier was pretreated with an aminosilane coupling agent to introduce amino functional groups into the inner surface of its pores. S2. Mesoporous confined deposition of the first active component: The pretreated hierarchical porous fly ash carrier is immersed in a solution containing copper source, iron source and small sterically hindered amine. The molecular size effect of the sterically hindered amine and the anchoring effect of the amino functional group are used to selectively enter and confine copper and iron ions in the mesopores. After drying, heat treatment is carried out in a weak reducing atmosphere to form copper-iron bimetallic nanoclusters in the mesopores. S3. Assembling the second active component in the macroporous region: The product obtained in step S2 is immersed in a solution containing vanadium source, tungsten source, titanium source and polymer complexing agent. The volume repulsion effect of the polymer complexing agent is used to make the active metal precursor complex mainly adsorbed on the outer surface of the carrier and in the macroporous channels. After being dried in a programmed manner, it is calcined in an air atmosphere to form vanadium-tungsten-titanium multi-element oxide nanoclusters. S4. In-situ growth interface bridging agent: The product obtained in step S3 is immersed in a hydrothermal system containing lanthanum source, cerium source, zirconium source and structure guiding agent to carry out hydrothermal reaction, so that the lanthanum-cerium-zirconium oxide precursor is directionally grown into two-dimensional nanosheets on the surface of the support and the inner wall of the macropores, and then crystallized in an air atmosphere. S5. Functionalization post-processing: The product obtained in step S4 is subjected to vapor deposition in an atmosphere containing a carbon source to generate a fullerene carbon modification layer on the surface of two-dimensional rare earth nanosheets.

6. The method for preparing a fly ash-based multi-effect catalyst according to claim 5, characterized in that: In step S1, the aminosilane coupling agent is 3-aminopropyltriethoxysilane, and the pretreatment temperature is 70-90℃.

7. The method for preparing a fly ash-based multi-effect catalyst according to claim 5, characterized in that: In step S2, the small molecule sterically hindered amine is triethylamine or N,N-diisopropylethylamine; the weak reducing atmosphere is a mixture of hydrogen and an inert gas, wherein the volume fraction of hydrogen is 5-10%, and the heat treatment temperature is 350-450℃.

8. The method for preparing a fly ash-based multi-effect catalyst according to claim 5, characterized in that: In step S3, the polymeric complexing agent is polyvinylpyrrolidone or polyacrylic acid; the calcination temperature is 400-500℃.

9. The method for preparing a fly ash-based multi-effect catalyst according to claim 5, characterized in that: In step S4, the structure directing agent is hexadecyltrimethylammonium chloride or ammonium fluoride; the temperature of the hydrothermal reaction is 120-180℃; the temperature of the crystallization treatment is 500-600℃; in step S5, the temperature of the vapor deposition is 600-800℃, and the deposition time is 10-20 minutes.

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