Manganese-cerium composite metal oxide catalytic materials, their preparation methods and applications

Abstract

This invention provides a manganese-cerium composite metal oxide catalytic material, its preparation method, and its application, belonging to the field of catalyst technology. The manganese-cerium composite metal oxide catalytic material has a nanorod structure, comprising cerium oxide and manganese dioxide supported on the surface of the cerium oxide, with the cerium oxide surface exposing {100} and {110} crystal planes. The manganese-cerium composite metal oxide catalytic material of this invention can effectively synergistically remove dioxins-like chlorinated aromatic hydrocarbons and nitrogen oxides from flue gas. The catalytic material exposes highly active crystal planes, and utilizing the synergistic effect between cerium and manganese, it exhibits excellent low-temperature activity. Furthermore, it demonstrates excellent resistance to water, sulfur, and chlorine poisoning. The preparation process is simple and low-cost, making it suitable for industrial application.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and more particularly to a manganese-cerium composite metal oxide catalytic material, its preparation method and application, and more specifically to a manganese-cerium composite metal oxide catalytic material and its preparation method, and a method for removing dioxins-like chlorinated aromatics and nitrogen oxides from flue gas. Background Technology

[0002] Flue gas emitted from thermal industrial processes such as municipal solid waste incineration, metal smelting, and coking commonly contains pollutants such as dioxins-like chlorinated aromatic hydrocarbons and nitrogen oxides. Among them, chlorinated aromatic hydrocarbons are highly carcinogenic, bioaccumulative, and environmentally persistent, while nitrogen oxides easily induce acid rain and photochemical smog. Currently, stringent emission limits are imposed on both.

[0003] Existing treatment technologies mostly employ activated carbon adsorption and selective catalytic reduction (SCR) technology to treat two types of pollutants in steps. This not only involves complex equipment layout and large footprint, but activated carbon is also prone to causing secondary pollution. Traditional vanadium-based selective catalytic reduction catalysts need to operate at high temperatures of 250~300℃, requiring secondary heating of the flue gas, resulting in high energy consumption.

[0004] In addition, industrial flue gas often contains components such as water vapor and sulfur dioxide. Water vapor will compete for adsorption on the active sites of the catalyst, while sulfur dioxide is prone to react with the metal active components in the catalyst to form sulfates or sulfites, causing sulfur poisoning of the catalyst and blockage of the pores. Summary of the Invention

[0005] In view of this, the main objective of the present invention is to provide a manganese-cerium composite metal oxide catalytic material, its preparation method and application, in order to at least partially solve at least one of the aforementioned technical problems.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] In one aspect of the present invention, a manganese-cerium composite metal oxide catalytic material is provided, the catalytic material having a nanorod structure comprising cerium oxide and manganese dioxide supported on the surface of cerium oxide, wherein the surface of cerium oxide has exposed {100} crystal planes and {110} crystal planes.

[0008] In some embodiments, the molar ratio of manganese to cerium in the catalytic material is 0.1:9 to 8:2.

[0009] In some embodiments, the molar ratio of manganese to cerium in the catalyst is 3:7.

[0010] In some embodiments, the diameter of the nanorod structure is 6-20 nm and the length is 30-200 nm.

[0011] In another aspect of the present invention, a method for preparing the above-mentioned manganese-cerium composite metal oxide catalytic material is provided. The method includes: mixing a manganese source and a cerium source in water to form a mixed solution; adding an alkaline solution dropwise to the mixed solution to adjust the pH value to 7-13, and then carrying out a hydrothermal reaction at 80-220°C to obtain a hydrothermal reaction product; washing and drying the hydrothermal reaction product, and then calcining it in an air atmosphere at 300-600°C to obtain the manganese-cerium composite metal oxide catalytic material.

[0012] In some embodiments, the manganese source is manganese nitrate or manganese sulfate; the cerium source is cerium nitrate or cerium sulfate; and the alkaline solution is at least one of sodium hydroxide, potassium hydroxide, ammonia, and sodium bicarbonate.

[0013] In some implementations, the hydrothermal reaction time is 6 to 24 hours; the calcination time is 3 to 6 hours.

[0014] In some embodiments, washing and drying includes: washing the hydrothermal reaction product until the pH of the washing solution is 5-7, drying at a temperature of 60-80°C, and drying for 5-12 hours.

[0015] In another aspect of the present invention, a method for removing dioxin-like chlorinated aromatic hydrocarbons and nitrogen oxides from flue gas is provided. The method includes: placing the above-mentioned manganese-cerium composite metal oxide catalyst material in a fixed-bed reactor, heating it, and then introducing flue gas to simultaneously remove dioxin-like chlorinated aromatic hydrocarbons and nitrogen oxides from the flue gas.

[0016] In some embodiments, the total concentration of dioxin-like chlorinated aromatic hydrocarbons and nitrogen oxides in the flue gas is 30-1000 ppm; the amount of manganese-cerium composite metal oxide catalyst is 30-200 mg; the heating temperature is 120-240°C; the relative humidity of the flue gas is 0%-70%; and the concentration of sulfur dioxide in the flue gas is 0-100 mg / m³. 3 .

[0017] Compared with existing technologies, the technical solution provided by the embodiments of the present invention has at least the following beneficial effects: The manganese-cerium composite metal oxide catalytic material of the present invention has a nanorod structure, with cerium oxide preferentially exposing the {100} and {110} highly active crystal faces. The catalytic material has sufficient oxygen vacancies and excellent active oxygen migration ability. The manganese and cerium components construct a synergistic redox system, effectively increasing the surface acidic sites and effectively improving the overall catalytic activity. It can achieve the synergistic degradation of dioxin-like chlorinated aromatic hydrocarbons and nitrogen oxides in the low temperature range of 120~240℃. The manganese-cerium composite metal oxide catalytic material also has good resistance to water, sulfur, and chlorine poisoning, can be adapted to complex industrial flue gas conditions, and has strong long-term operational stability. In addition, the present invention adopts a hydrothermal reaction combined with calcination preparation process, which is simple in procedure, easy to control in process parameters, and has low production cost, making it suitable for industrial-scale production. Attached Figure Description

[0018] Figure 1 This is a transmission electron microscope characterization image of the manganese-cerium composite metal oxide catalytic material in Example 1 of the present invention;

[0019] Figure 2 This is a schematic diagram illustrating the catalytic activity of the manganese-cerium composite metal oxide catalytic material for chlorobenzene in Example 1 of the present invention;

[0020] Figure 3 This is a schematic diagram of the catalytic activity of the cerium metal oxide catalytic material for chlorobenzene in Comparative Example 1 of the present invention;

[0021] Figure 4 This is a schematic diagram illustrating the catalytic activity of the manganese-cerium composite metal oxide catalytic material for nitrogen oxides in Example 1 of the present invention;

[0022] Figure 5 This is a schematic diagram of the catalytic activity of the cerium metal oxide catalytic material for nitrogen oxides in Comparative Example 1 of the present invention;

[0023] Figure 6 This is a schematic diagram illustrating the synergistic catalytic activity of the manganese-cerium composite metal oxide catalytic material in Example 1 of the present invention on chlorobenzene and nitrogen oxides under aqueous conditions;

[0024] Figure 7 This is a schematic diagram of the synergistic catalytic activity of the cerium metal oxide catalytic material in Comparative Example 1 of the present invention for chlorobenzene and nitrogen oxides under aqueous conditions;

[0025] Figure 8 This is a schematic diagram of the synergistic catalytic activity of the manganese-cerium composite metal oxide catalytic material in Example 1 of the present invention on chlorobenzene and nitrogen oxides under aqueous and sulfur dioxide conditions;

[0026] Figure 9 This is a schematic diagram illustrating the synergistic catalytic activity of the cerium metal oxide catalytic material in Comparative Example 1 of the present invention for chlorobenzene and nitrogen oxides under conditions containing water and sulfur dioxide. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0028] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] Existing flue gas purification technologies mostly employ stepwise processes to treat dioxins-like chlorinated aromatics and nitrogen oxides. Traditional catalysts operate at high temperatures (250~300 °C), consume a lot of energy, and are easily poisoned and deactivated in complex flue gas containing water vapor and sulfur dioxide. Commonly used cerium dioxide catalysts mainly expose the {111} low surface energy crystal plane, resulting in insufficient oxygen vacancies and active oxygen, and their low-temperature catalytic performance and surface acidity are insufficient to meet the requirements for the synergistic removal of multiple pollutants. Therefore, there is an urgent need to develop integrated purification catalytic materials with high low-temperature activity and strong anti-interference capabilities.

[0031] In the process of realizing this invention, it was discovered that the nanorod structure can preferentially expose the {110} and {100} highly active crystal faces of cerium dioxide, significantly improving the oxygen vacancy concentration and oxygen mobility. However, the problems of missing acidic sites and insufficient low-temperature reaction efficiency still exist. Based on this, this invention loads manganese components onto the surface of nanorod-shaped cerium dioxide and utilizes the strong interactions generated at the two-phase interface to construct Ce 3+ / Ce 4+ With Mn 3+ / Mn 4+ A coupled synergistic redox cycle system. The combination of the two can produce a positive synergistic effect: on the one hand, it replenishes a large number of surface acidic sites, reduces the activation energy of the catalytic reaction, and comprehensively improves the low-temperature reaction efficiency; on the other hand, it inhibits the erosion of active sites by components such as sulfur, chlorine, and water vapor through interfacial electron transfer, effectively enhancing the catalytic material's resistance to poisoning. This invention uses a hydrothermal process to precisely control the crystal morphology and the exposure state of the dominant crystal faces, and achieves high dispersion loading of manganese species on specific crystal faces by optimizing the metal element ratio. Through the synergistic effect of crystal facets and the cerium-manganese interface, a unique dual redox cycle system is formed. The prepared catalytic material can efficiently and synergistically remove dioxin-like chlorinated aromatics and nitrogen oxides from flue gas in a low-temperature range of 120~240℃, while also exhibiting good resistance to water, sulfur, and chlorine poisoning. The entire preparation process is simple and controllable, with low production costs, making it very suitable for industrial mass production and field application.

[0032] Specifically, according to one aspect of the present invention, a manganese-cerium composite metal oxide catalytic material is provided, the catalytic material having a nanorod structure, including cerium oxide and manganese dioxide supported on the surface of cerium oxide, and the surface of cerium oxide has exposed {100} crystal planes and {110} crystal planes.

[0033] According to embodiments of the present invention, the manganese-cerium composite metal oxide catalytic material of the present invention optimizes the catalytic material through crystal facet control and metal component doping synergistically, thereby improving the comprehensive catalytic performance, anti-interference ability and operational stability of the catalytic material, as detailed below.

[0034] The catalytic activity of cerium oxide mainly depends on the redox pair of trivalent and tetravalent cerium ions (Ce). 3+ / Ce 4+ The reversible oxidation and dynamic oxygen vacancy of the manganese-cerium composite metal oxide catalytic material of this invention are achieved. The material possesses a nanorod-like structure, preferentially exposing the {110} and {100} crystal planes of cerium oxide. Compared to the thermodynamically stable {111} crystal plane, the {110} and {100} crystal planes have lower oxygen vacancy formation energies, resulting in higher oxygen vacancy concentrations and better oxygen mobility. This effectively enhances the redox capacity and active oxygen supply capacity of the catalytic material without altering its chemical composition. Simultaneously, these highly active crystal planes provide ample interfacial interaction sites, offering a superior structural basis for subsequent manganese doping and the construction of composite catalytic systems.

[0035] Introducing manganese into cerium oxide allows manganese oxide to be dispersed and loaded onto the cerium oxide surface, effectively strengthening the cerium-manganese (Ce-Mn) interfacial interaction and constructing a Ce-Mn composite structure. 3+ / Ce 4+ With Mn 3+ / Mn 4+ Synergistic dual redox cycle. During the catalytic reaction, continuous and reversible electron transfer occurs between ions: when the system is in an oxidizing atmosphere, the lower valence state Ce... 3+ With Mn 3+ They lose electrons and are oxidized to Ce. 4+ and Mn 4+ This process simultaneously releases reactive oxygen species, creating oxygen vacancies on the crystal surface. When the system switches to a reducing atmosphere, the high-valence Ce... 4+ The electrons are reduced to Ce 3+ Meanwhile, Mn 4+ It also accepts electrons and transforms into Mn 3+ This process enables the storage of active oxygen and the dynamic regeneration of oxygen vacancies. The aforementioned valence state transformation process continues cyclically at the manganese-cerium interface, forming a stable redox system. On the one hand, continuous electron transfer effectively enhances the overall redox capacity of the catalytic material, continuously supplying active oxygen and ensuring the oxidative degradation of dioxin-like chlorinated aromatic hydrocarbons. On the other hand, this cycle can synergistically activate ammonia adsorbed on the material surface, efficiently driving the selective catalytic reduction reaction of nitrogen oxides. Furthermore, the electron exchange between the interfaces can regulate the surface charge distribution of active sites, effectively inhibiting the combination of toxic components such as sulfur dioxide and chloride ions with the active metal, thus enhancing the catalytic material's resistance to sulfur and chloride poisoning.

[0036] The manganese-cerium composite metal oxide catalytic material provided by this invention, through the composite modification of manganese and cerium, forms a strong interfacial interaction between the cerium and manganese components, altering the surface microstructure and electronic state of the material, and inducing the generation of a large number of acidic sites. This not only further enhances the redox capacity, active oxygen content, and migration efficiency of the catalytic material, but also increases the number of surface acidic sites. In the reaction system, the Ce-Mn synergistic active centers organically combine the acidic sites with the redox sites, efficiently promoting the denitrification reaction while effectively resisting the competitive adsorption and poisoning effects of components such as chlorobenzene, water vapor, and sulfur dioxide on the active sites. Especially when the reaction temperature increases, the active hydroxyl groups generated by the activation of water molecules can promote the breaking of C-Cl bonds in chloroaromatic molecules and accelerate the desorption of chlorinated species, continuously maintaining the activity of the catalytic material.

[0037] According to embodiments of the present invention, the molar ratio of manganese to cerium in the catalytic material is 0.1:9 to 8:2, for example, 0.1:9.9, 0.5:9.5, 1:9, 2:8, 3:7, 4:6, 5:5, 7:3, 8:2, etc. By adjusting the molar ratio of manganese to cerium, uniform dispersion of manganese species on the surface of cerium dioxide can be ensured. This avoids the problem of insufficient synergistic effect and limited catalytic activity improvement when the manganese content is too low, and also prevents particle agglomeration and coverage of active sites caused by an excessively high manganese ratio. This molar ratio range can fully construct Ce 3+ / Ce 4+ With Mn 3+ / Mn 4+ Synergistic redox cycle, leveraging the catalytic advantages of bimetallic components.

[0038] According to embodiments of the present invention, the molar ratio of manganese to cerium in the catalytic material is preferably 3:7. At this molar ratio, the interaction between the cerium and manganese interfaces is stronger, resulting in better redox capabilities and a greater number of surface acidic sites in the catalytic material. This leads to higher synergistic removal efficiency of chlorinated aromatics and nitrogen oxides, while also exhibiting superior resistance to water, sulfur, and chlorine poisoning.

[0039] According to embodiments of the present invention, the diameter of the nanorod structure is 6-20 nm, for example, 6 nm, 8 nm, 10 nm, 12 nm, 15 nm, 18 nm, 20 nm, etc.; the length is 30-200 nm, for example, 30 nm, 50 nm, 70 nm, 100 nm, 150 nm, 180 nm, 200 nm, etc. If the size is too small, the nanorods are prone to sintering instability; if the size is too large, it will lead to a decrease in specific surface area and a reduction in the number of active sites. Nanorods in this size range have regular morphology and are not prone to aggregation, providing a large specific surface area, effectively increasing the contact area between the catalytic material and flue gas pollutants, and enhancing mass transfer efficiency. At the same time, this size can stably maintain the exposure state of the {100} crystal plane and {110} crystal plane, ensuring sufficient oxygen vacancies and active oxygen species, while taking into account structural stability and catalytic activity, and can be adapted to the industrial flue gas catalytic reaction conditions.

[0040] According to another embodiment of the present invention, a method for preparing the above-mentioned manganese-cerium composite metal oxide catalytic material is provided, comprising: mixing a manganese source and a cerium source in water to form a mixed solution; adding an alkaline solution dropwise to the mixed solution to adjust the pH value to 7-13, and then carrying out a hydrothermal reaction at 80-220°C to obtain a hydrothermal reaction product; washing and drying the hydrothermal reaction product, and then calcining it in an air atmosphere at 300-600°C to obtain the manganese-cerium composite metal oxide catalytic material.

[0041] In some specific embodiments, the pH value can be adjusted to 7, 8, 9, 10, 11, 12, 13, etc. after adding alkaline solution; the hydrothermal reaction temperature can be, for example, 80℃, 100℃, 150℃, 180℃, 200℃, 220℃, etc.; the calcination temperature can be, for example, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, etc.

[0042] According to embodiments of the present invention, the preparation method of the catalytic material is simple, requires no complex equipment, and features mild and controllable process conditions, meeting the requirements for industrial-scale mass production. This preparation method utilizes a hydrothermal reaction combined with high-temperature calcination to prepare the catalytic material: in an alkaline (pH 7-13) hydrothermal system, hydroxide ions selectively adsorb onto the crystal surface, altering the surface energy of different crystal faces, inhibiting radial crystal growth, and promoting anisotropic development along specific axes, thereby forming a nanorod-like structure and directionally exposing highly active crystal faces such as {100} and {110}; combined with the hydrothermal reaction, the Ostwald ripening effect is used to regulate crystal nucleation and growth, ensuring stable microstructure. Subsequent calcination completely decomposes the precursor and completes the phase transformation, further solidifying the crystal structure, optimizing pore characteristics and redox properties while perfectly preserving the original morphology and target crystal faces, ultimately yielding a catalytic material with abundant surface active sites.

[0043] According to an embodiment of the present invention, the manganese source is manganese nitrate or manganese sulfate; the cerium source is cerium nitrate or cerium sulfate. Both types of metal salts are highly soluble and can form a uniform and stable mixed salt solution in water, ensuring that the manganese and cerium components are uniformly mixed at the molecular scale. Furthermore, the above salts undergo complete thermal decomposition, leaving no difficult-to-decompose impurities after calcination.

[0044] The alkaline solution is at least one of sodium hydroxide, potassium hydroxide, ammonia, and sodium bicarbonate. Among them, sodium hydroxide and potassium hydroxide are strongly alkaline, which can effectively create a strongly alkaline hydrothermal environment to meet the conditions for directional crystal growth. Various alkaline solutions can be used alone or in combination to adapt to different process parameter requirements, correspondingly control the pH value of the reaction system, and will not introduce harmful impurities that are difficult to remove after the reaction, leaving no toxic or harmful components, thus ensuring that the original performance of the catalytic material is not disturbed.

[0045] According to an embodiment of the present invention, the hydrothermal reaction time is 6-24 h. Insufficient time (<6 h) will lead to insufficient crystal nucleation and growth, resulting in incomplete rod-shaped morphology; excessive time (>24 h) will cause excessive crystal growth and increased grain size. This hydrothermal reaction time range allows the crystals to develop fully, resulting in a catalytic material with a regular morphology and uniform size of nanorod-shaped structure.

[0046] The calcination time is 3-6 hours. Sufficient calcination time ensures complete decomposition of hydrothermal reaction products and full transformation of crystal phases, forming a structurally stable catalytic material. If the calcination time is too short, the thermal decomposition reaction will be insufficient, the formation of the target oxide crystal phase will be hindered, and impurities will remain inside the catalytic material. This will not only fail to fully solidify the microstructure and active crystal faces, but also weaken the reactivity and structural stability of the catalytic material. If the calcination time is too long, it will exacerbate grain sintering, resulting in a decrease in the activity of the catalytic material.

[0047] According to an embodiment of the present invention, the washing and drying process includes: washing the hydrothermal reaction product until the pH of the washing solution is 5-7, which can thoroughly remove residual alkali and free salt ions in the reaction system, and prevent residual impurities from covering active sites and causing poisoning of the catalytic material. The drying temperature is 60-80°C, and the drying time is 5-12 hours. Through low-temperature and slow drying conditions, the rod-shaped microstructure of the hydrothermal reaction product can be protected while removing free water, preventing structural collapse and particle agglomeration caused by rapid high-temperature drying.

[0048] According to another aspect of the present invention, a method for removing dioxin-like chlorinated aromatic hydrocarbons and nitrogen oxides from flue gas is provided, comprising: placing the above-mentioned manganese-cerium composite metal oxide catalyst material in a fixed-bed reactor, heating it, and then introducing flue gas to simultaneously remove dioxin-like chlorinated aromatic hydrocarbons and nitrogen oxides from the flue gas.

[0049] According to embodiments of the present invention, a fixed-bed reaction process is employed to simultaneously achieve the synergistic removal of dioxin-like chlorinated aromatics and nitrogen oxides from flue gas using a manganese-cerium composite metal oxide catalytic material. The catalytic material of this invention has a nanorod structure, preferentially exposing the {100} and {110} highly active crystal faces, possessing abundant oxygen vacancies and excellent oxygen migration capabilities. Combined with dispersed manganese-cerium dual-active components, a dual redox cycle is constructed, forming numerous surface acidic sites, providing a reaction basis for the simultaneous conversion of dioxin-like chlorinated aromatics and nitrogen oxides.

[0050] For nitrogen oxides, the acidic sites on the surface of the catalytic material can adsorb ammonia reducing agents, and the redox active sites further drive selective catalytic reduction reactions, converting nitrogen oxides in flue gas into harmless nitrogen and water, thus completing the denitrification treatment. For dioxin-like chlorinated aromatics, the active oxygen species on the material surface can oxidize and destroy the aromatic molecular skeleton; at the same time, water molecules in the flue gas generate active hydroxyl groups under the action of active sites, effectively breaking the C-Cl chemical bonds in the molecules and promoting the rapid desorption of chlorine species, avoiding the accumulation of chlorine components that could lead to poisoning of the catalytic material, and achieving the complete degradation of chlorinated aromatics.

[0051] Compared to setting up two separate devices for denitrification and dioxin removal, the method of the present invention can complete the integrated purification of two pollutants with a single catalytic material and a single set of equipment, which greatly simplifies the flue gas treatment process and reduces equipment investment, land area and operation and maintenance costs.

[0052] According to embodiments of the present invention, the total concentration of dioxins, chlorinated aromatic hydrocarbons, and nitrogen oxides in the flue gas is 30-1000 ppm, which covers the actual pollution load of industrial flue gas from municipal solid waste incineration, metallurgy, and other industries. The dosage of manganese-cerium composite metal oxide catalyst is 30-200 mg, ensuring a reasonable ratio between the number of active sites of the catalyst and the total number of pollutant molecules in the flue gas. This ensures sufficient active sites for pollutant removal while avoiding resource waste and increased bed resistance caused by excessive catalyst dosage. In practical applications, the dosage can be flexibly adjusted according to the flue gas flow rate and pollutant concentration, effectively controlling treatment costs while ensuring purification effects.

[0053] The heating temperature is 120~240℃, for example, 120℃, 150℃, 180℃, 200℃, 220℃, 240℃, etc. The {100} and {110} crystal planes on the surface of the catalytic material provide a large number of oxygen vacancies and highly mobile active oxygen, significantly reducing the activation energy of the reaction. The manganese-cerium synergistic redox system and surface acidic sites can efficiently adsorb and activate ammonia in this low-temperature range (120~240℃), promoting the redox reaction, thereby simultaneously removing dioxin-like chlorinated aromatics and nitrogen oxides, eliminating the need for flue gas reheating and reducing operating energy consumption. In addition, the low-temperature environment can also prevent grain sintering, ensuring the microstructure and active sites of the catalytic material, and ensuring the long-term stable operation of the system.

[0054] The relative humidity of the flue gas is 0%–70%, for example, it can be 0%, 10%, 20%, 30%, 50%, 70%, etc., which can cover the common humidity range of industrial flue gas. The catalytic material of this invention has excellent water resistance; within this humidity range, water molecules will not occupy active sites in large quantities. Moderate moisture can also generate active hydroxyl groups during the reaction, promoting the breaking of C–Cl bonds in chlorinated aromatic hydrocarbon molecules, accelerating the desorption of chlorinated species, and helping to improve the pollutant removal efficiency.

[0055] The concentration of sulfur dioxide in the flue gas is 0–100 mg / m³. 3 For example, it can be 0 mg / m 3 20 mg / m 3 40 mg / m 3 50 mg / m 3 60 mg / m 3 80 mg / m 3 100 mg / m 3The manganese-cerium composite system in the catalytic material of this invention possesses excellent sulfur resistance, effectively resisting sulfur poisoning caused by sulfur dioxide. Sulfur dioxide is unlikely to combine with the active metal components of manganese and cerium in the catalytic material to form stable sulfates. Within the aforementioned concentration range, the catalytic material can consistently maintain a stable pollutant removal efficiency, solving the problem of traditional catalysts (such as vanadium-based SCR catalysts and single cerium oxide catalysts) being easily poisoned by sulfur dioxide and experiencing rapid activity decline, thus ensuring the long-term continuous and stable operation of the treatment system.

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. Unless otherwise specified, specific techniques or conditions in the embodiments are conventional methods, which can be performed according to the techniques or conditions described in the literature in this field or according to the product instructions. It should be noted that, unless otherwise specified, the methods provided by this invention are conventional methods, and the reactants and reagents can be obtained from publicly available commercial sources unless otherwise specified.

[0057] Example 1

[0058] This embodiment 1 provides a manganese-cerium composite metal oxide catalytic material, and the preparation method of the catalytic material is as follows.

[0059] 1.736 g of cerium nitrate hexahydrate and 0.81 mL of 50% manganese nitrate solution were added together to 10 mL of deionized water and stirred magnetically at room temperature for 10 min until completely dissolved to form a mixed salt solution.

[0060] Take 19.2 g of sodium hydroxide and add it to 70 mL of deionized water. Stir until completely dissolved to prepare a strongly alkaline solution. Under vigorous magnetic stirring, slowly add the sodium hydroxide solution dropwise to the mixed salt solution. After the addition is complete, continue stirring for 30 min to ensure the system is homogeneous. Adjust the pH of the mixed salt solution to 12.

[0061] The pH-adjusted mixed salt solution was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and sealed. It was then placed in a constant-temperature drying oven and subjected to hydrothermal reaction at 100℃ for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was removed and washed repeatedly by centrifugation with deionized water until the pH of the washing solution approached 7. The washed solid product was placed in a petri dish and dried in a 60℃ forced-air drying oven for 12 h. Subsequently, the dried solid product was placed in a muffle furnace and calcined at 500℃ for 4 h in air to obtain the manganese-cerium composite metal oxide catalyst.

[0062] Figure 1These are transmission electron microscope (TEM) images of the manganese-cerium composite metal oxide catalytic material in Example 1 of this invention. Specifically, a is a TEM image of the manganese-cerium composite metal oxide catalytic material; b is a high-resolution TEM image of the manganese-cerium composite metal oxide catalytic material.

[0063] like Figure 1 As shown, the manganese-cerium composite metal oxide catalytic material in Example 1 is a nanorod-like structure with regular morphology and uniform size. High-resolution transmission electron microscopy (HRTEM) images reveal clear lattice fringes, where the interplanar spacings of 0.191 nm and 0.192 nm correspond to the {110} crystal plane of cerium dioxide, and 0.264 nm corresponds to the {100} crystal plane. This indicates that the catalytic material directionally exposes the highly active {100} and {110} crystal planes.

[0064] Comparative Example 1

[0065] Comparative Example 1 provides a cerium metal oxide catalytic material, and the preparation method of the catalytic material is as follows.

[0066] 1.736 g of cerium nitrate hexahydrate was added to 10 mL of deionized water and magnetically stirred at room temperature for 10 min until completely dissolved to obtain a cerium salt solution.

[0067] Take 19.2 g of sodium hydroxide and add it to 70 mL of deionized water. Stir until completely dissolved to prepare a strongly alkaline solution. Under vigorous magnetic stirring, slowly add the sodium hydroxide solution dropwise to the cerium salt solution. After the addition is complete, continue stirring for 30 min to ensure the system is homogeneous. Adjust the pH of the cerium salt solution to 12.

[0068] The pH-adjusted cerium salt solution was transferred to a 100 mL polytetrafluoroethylene-lined high-pressure reactor and sealed. It was then placed in a constant-temperature drying oven and subjected to hydrothermal reaction at 100℃ for 24 h. After the reaction, the mixture was allowed to cool naturally to room temperature. The precipitate was removed and washed repeatedly by centrifugation with deionized water until the pH of the washing solution approached 7. The washed solid product was placed in a petri dish and dried in a 60℃ forced-air drying oven for 12 h. Subsequently, the dried solid product was placed in a muffle furnace and calcined at 500℃ for 4 h in air to obtain the cerium metal oxide catalyst.

[0069] The catalytic activities of the manganese-cerium composite metal oxide catalytic material in Example 1 and the cerium metal oxide catalytic material in Comparative Example 1 on dioxin-like chlorobenzene, nitrogen oxides, synergistic catalytic activity of chlorobenzene and nitrogen oxides, synergistic catalytic activity of chlorobenzene and nitrogen oxides under aqueous conditions, and synergistic catalytic activity of chlorobenzene and nitrogen oxides under aqueous and sulfur dioxide conditions were tested respectively.

[0070] (1) Catalytic activity of chlorobenzene, a model pollutant of dioxin-like chlorinated aromatic hydrocarbons

[0071] The catalytic activity of the manganese-cerium composite metal oxide catalyst in Example 1 and the cerium metal oxide catalyst in Comparative Example 1 was evaluated using a fixed-bed reactor coupled with gas chromatography / flame ionization detector. The experimental conditions were as follows: the manganese-cerium composite metal oxide catalyst was weighed and placed in a fixed-bed reactor, heated to 240°C, and a mixed gas of nitrogen (N2), oxygen (O2), and chlorobenzene (CB) was introduced at a total flow rate of 80 mL / min, wherein the chlorobenzene concentration was 50 ppm, the O2 volume content was 10%, and the space velocity was 15000 h⁻¹. -1 The degradation rate of CB by the catalytic material was detected using a GC-FID (gas chromatography-flame ionization detector) device.

[0072] Figure 2 This is a schematic diagram illustrating the catalytic activity of the manganese-cerium composite metal oxide catalytic material for chlorobenzene in Example 1 of the present invention;

[0073] like Figure 2 As shown, the manganese-cerium composite metal oxide catalytic material exhibits high degradation activity for chlorobenzene at 240℃, with a degradation rate of over 85%.

[0074] Figure 3 This is a schematic diagram of the catalytic activity of the cerium metal oxide catalytic material for chlorobenzene in Comparative Example 1 of this invention.

[0075] like Figure 3 As shown, the cerium metal oxide catalytic material of Comparative Example 1 exhibits a degradation activity of only 37.81% for chlorobenzene at 240℃, which is significantly lower than that of the manganese-cerium composite metal oxide catalytic material.

[0076] (2) Catalytic activity for nitrogen oxides

[0077] The manganese-cerium composite metal oxide catalyst from Example 1 and the cerium metal oxide catalyst from Comparative Example 1 were weighed separately and placed in a fixed-bed reactor. The reactors were heated at 120°C and 240°C, respectively. A mixed gas of N2, O2, NO, and NH3 was introduced at a total flow rate of 80 mL / min, wherein the NO concentration was 250 ppm, the NH3 concentration was 250 ppm, the O2 volume content was 10%, and the space velocity was 15000 h⁻¹. -1 The NO concentration after the reaction was detected using a nitrogen oxide analyzer.

[0078] Figure 4 This is a schematic diagram of the catalytic activity of the manganese-cerium composite metal oxide catalytic material for nitrogen oxides in Example 1 of the present invention.

[0079] like Figure 4As shown, the manganese-cerium composite metal oxide catalytic material of Example 1 exhibits high degradation activity for nitrogen oxides at both 120℃ and 240℃, with degradation rates exceeding 90%.

[0080] Figure 5 This is a schematic diagram of the catalytic activity of the cerium metal oxide catalytic material for nitrogen oxides in Comparative Example 1 of the present invention.

[0081] like Figure 5 As shown, the cerium metal oxide catalytic material of Comparative Example 1 exhibited degradation activities of only 20.3% and 43.12% for nitrogen oxides at 120℃ and 240℃, respectively, which were significantly lower than the activity of the manganese-cerium composite metal oxide catalytic material.

[0082] (3) Synergistic catalytic activity of p-chlorobenzene and nitrogen oxides in the presence of water

[0083] The manganese-cerium composite metal oxide catalyst from Example 1 and the cerium metal oxide catalyst from Comparative Example 1 were weighed and placed in a fixed-bed reactor. The heating temperature was set at 240°C. Water was introduced into the reaction system using nitrogen gas at a certain flow rate as a carrier, and the relative humidity of the overall gas flow was controlled to be 5% by changing the nitrogen gas flow rate. Then, a mixed gas of N2, O2, chlorobenzene, NO, and NH3 with a total flow rate of 80 mL / min was introduced, wherein the concentration of chlorobenzene was 50 ppm, the concentration of NO was 250 ppm, the concentration of NH3 was 250 ppm, the volume content of O2 was 10%, and the space velocity was 15000 h⁻¹. -1 .

[0084] Figure 6 This is a schematic diagram illustrating the synergistic catalytic activity of the manganese-cerium composite metal oxide catalytic material for chlorobenzene and nitrogen oxides under aqueous conditions in Example 1 of this invention.

[0085] like Figure 6 As shown, the manganese-cerium composite metal oxide catalytic material of Example 1 still exhibits high degradation activity for chlorobenzene and nitrogen oxides at 5% relative humidity, and has good water resistance.

[0086] Figure 7 This is a schematic diagram illustrating the synergistic catalytic activity of the cerium metal oxide catalytic material in Comparative Example 1 of the present invention for chlorobenzene and nitrogen oxides under aqueous conditions.

[0087] like Figure 7 As shown, the cerium metal oxide catalytic material of Comparative Example 1 exhibited synergistic degradation activities of 17.78% and 32.61% for chlorobenzene and nitrogen oxides, respectively, in the presence of water at 240°C.

[0088] (4) Synergistic catalytic activity of chlorobenzene and nitrogen oxides under conditions of coexistence of water and sulfur dioxide

[0089] The manganese-cerium composite metal oxide catalyst material prepared in Example 1 was weighed and placed into a fixed-bed reactor. The heating temperature was set at 240°C. Water was introduced into the reaction system using nitrogen gas at a certain flow rate as a carrier, and the relative humidity of the overall gas flow was controlled to be 5% by changing the nitrogen gas flow rate. Then, a mixed gas of N2, O2, chlorobenzene, NO, NH3, and SO2 was introduced at a total flow rate of 80 mL / min, wherein the concentration of chlorobenzene was 50 ppm, the concentration of NO was 250 ppm, the concentration of NH3 was 250 ppm, the concentration of SO2 was 20 ppm, the volume content of O2 was 10%, and the space velocity was 15000 h⁻¹. -1 .

[0090] Figure 8 This is a schematic diagram illustrating the synergistic catalytic activity of the manganese-cerium composite metal oxide catalytic material in Example 1 of this invention for chlorobenzene and nitrogen oxides under aqueous and sulfur dioxide conditions.

[0091] like Figure 8 As shown, the degradation efficiency of the manganese-cerium composite metal oxide catalytic material in Example 1 was only slightly reduced, but it could still reach more than 80%, showing good resistance to water and sulfur dioxide interference.

[0092] Figure 9 This is a schematic diagram illustrating the synergistic catalytic activity of the cerium metal oxide catalytic material in Comparative Example 1 of the present invention for chlorobenzene and nitrogen oxides under conditions containing water and sulfur dioxide.

[0093] like Figure 9 As shown, the cerium metal oxide catalytic material of Comparative Example 1 exhibited synergistic degradation activities of 4.38% and 7.29% for chlorobenzene and nitrogen oxides, respectively, in the presence of water and sulfur dioxide at 240℃, indicating severe interference from water and sulfur dioxide.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A manganese-cerium composite metal oxide catalytic material, characterized in that, The catalytic material has a nanorod structure, including cerium oxide and manganese dioxide supported on the surface of the cerium oxide, and the surface of the cerium oxide has exposed {100} crystal planes and {110} crystal planes.

2. The manganese-cerium composite metal oxide catalytic material according to claim 1, characterized in that, The molar ratio of manganese to cerium in the catalytic material is 0.1:9.9~8:

2.

3. The manganese-cerium composite metal oxide catalytic material according to claim 1, characterized in that, The molar ratio of manganese to cerium in the catalytic material is 3:

7.

4. The manganese-cerium composite metal oxide catalytic material according to claim 1, characterized in that, The nanorod-like structure has a diameter of 6-20 nm and a length of 30-200 nm.

5. A method for preparing a manganese-cerium composite metal oxide catalytic material as described in any one of claims 1 to 4, characterized in that, The preparation method includes: Manganese source and cerium source are mixed in water to form a mixed solution; After adjusting the pH value to 7-13 by adding an alkaline solution dropwise to the mixed solution, a hydrothermal reaction is carried out at 80-220°C to obtain the hydrothermal reaction product. After washing and drying the hydrothermal reaction product, it is calcined in air at 300~600℃ to obtain a manganese-cerium composite metal oxide catalytic material.

6. The preparation method according to claim 5, characterized in that, The manganese source is manganese nitrate or manganese sulfate; The cerium source is cerium nitrate or cerium sulfate; The alkaline solution is at least one of sodium hydroxide, potassium hydroxide, ammonia, and sodium bicarbonate.

7. The preparation method according to claim 5, characterized in that, The hydrothermal reaction time is 6-24 h; The roasting time is 3-6 hours.

8. The preparation method according to claim 5, characterized in that, The washing and drying process includes: washing the hydrothermal reaction product until the pH of the washing solution is 5-7, drying at a temperature of 60-80°C, and drying for 5-12 hours.

9. A method for removing dioxins-like chlorinated aromatic hydrocarbons and nitrogen oxides from flue gas, characterized in that, The method includes: The manganese-cerium composite metal oxide catalytic material according to any one of claims 1 to 4 is placed in a fixed-bed reactor, heated, and then introduced into flue gas to simultaneously remove dioxin-like chlorinated aromatics and nitrogen oxides from the flue gas.

10. The method according to claim 9, characterized in that, The total concentration of dioxins, chlorinated aromatic hydrocarbons and nitrogen oxides in the flue gas is 30~1000 ppm; The amount of the manganese-cerium composite metal oxide catalytic material used is 30~200 mg; The heating temperature is 120~240℃; The relative humidity of the flue gas is 0% to 70%; The concentration of sulfur dioxide in the flue gas is 0–100 mg / m³. 3 .

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