Mn-based denitration catalyst and preparation method thereof

Abstract

This invention discloses a Mn-based denitrification catalyst and its preparation method, belonging to the field of low-temperature flue gas denitrification technology. It provides a highly active low-temperature SCR catalyst and its preparation method. The Mn-based denitrification catalyst comprises a sepiolite support and active components attached to the support. The active components include the metal elements Mn, Nb, and Nd, with a molar ratio of Mn:Nb:Nd = 1:(0.05-0.20):(0.05-0.20). Because a ternary metal oxide of Mn, Nb, and Nd is used as the active component, a stable and abundant reactive site is constructed through multi-metal synergy. Therefore, it can effectively alleviate the limitations of current commercial SCR catalysts in water vapor and SO2 environments, which suffer from poisoning and activity decay due to the single active component, and has stronger applicability in industrial denitrification environments.

Description

Technical Field

[0001] This invention belongs to the field of low-temperature flue gas denitrification technology, specifically relating to a Mn-based denitrification catalyst and its preparation method. Background Technology

[0002] Selective catalytic reduction (NH3-SCR) technology is currently the most effective method for controlling NO from stationary sources. x The mainstream emission process. This technology utilizes NH3 as a reducing agent to remove NO from flue gas under the action of a specific catalyst. x It is selectively reduced to N2 and H2O. Therefore, the research on catalysts is the core and key direction in this technical field.

[0003] Currently, the most widely used catalyst system in industrial applications is V2O5-WO3 / TiO2. Although this type of catalyst has high activity and certain anti-poisoning properties, it still has some significant application limitations: its efficient operating temperature usually needs to be higher than 620K, which means that the denitrification reactor must be arranged before the air preheater and dust removal / desulfurization unit. This arrangement exposes the catalyst to complex flue gas with high concentrations of SO2 and dust particles for a long time. This not only aggravates sulfate deposition and pore blockage on the catalyst surface, but also causes irreversible passivation of active sites, significantly affecting the catalyst's efficiency and service life. At the same time, the active components of this type of catalyst are relatively simple, and its adaptability to fluctuations in flue gas composition is limited. It is easily affected by water vapor and SO2, leading to accelerated performance degradation. In addition, high-temperature operating conditions will increase the energy consumption burden of the system and place higher demands on the heat resistance and safety of the equipment materials. Therefore, there is an urgent need to develop highly active low-temperature SCR catalysts. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a Mn-based denitrification catalyst and its preparation method, thereby providing a highly active low-temperature SCR catalyst and its preparation method.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: First, a Mn-based denitration catalyst is provided, comprising a support made of sepiolite and an active component attached to the support, wherein the active component comprises the metal elements Mn, Nb and Nd, and the molar ratio of the metal elements is Mn:Nb:Nd=1:(0.05-0.20):(0.05-0.20).

[0006] Preferably, the molar ratio of the metal elements is Mn:Nb:Nd = 1:0.10:0.10.

[0007] Preferably, the molar ratio of the metal elements is Mn:Nb:Nd = 1:0.10:0.20.

[0008] Preferably, the molar ratio of the metal elements is Mn:Nb:Nd = 1:0.10:0.05.

[0009] In addition, the present invention also provides a method for preparing a Mn-based denitration catalyst, which includes the following steps: Step 1: Acidify the sepiolite. Step 2: Disperse the acidified sepiolite in deionized water to form a suspension slurry, and obtain a sepiolite dispersion after stirring and ultrasonic treatment, as solution I; Step 3: Add the corresponding molar amounts of KMnO4, Nb(NO3)5 and Nd(NO3)3×6H2O solutions to solution I according to the molar ratio and mix thoroughly to obtain mixed solution II; Step 4: Mix the mixed solution II vigorously under water bath conditions, and dry it to obtain a powdered solid; Step 5: Transfer the powdered solid to a heating furnace for heating, and then cool it to room temperature to obtain a low-temperature Mn-based denitration catalyst.

[0010] Preferably, the acidification treatment method in step 1 is as follows: place the block sepiolite in a reaction vessel, add H2SO4, stir at room temperature, wash with deionized water until neutral, and dry to obtain the acidified sepiolite.

[0011] Preferably, in step 1: the concentration of added H2SO4 is 1 mol / L; and / or, the stirring time is 4 h, and the drying temperature is 70 °C.

[0012] Preferably, in step 2: the stirring time is 4 hours, the ultrasonic treatment time is 30 minutes; and / or, the solid content of the sepiolite dispersion obtained in step 2 is 4 g / 100 ml.

[0013] Preferably, in step 4: the water bath temperature is 80℃, the stirring time is 3 hours, and the drying temperature is 60℃.

[0014] Preferably, in step 5: a muffle furnace is used for heating, the heating temperature is 350℃, and the heating time is 4 hours.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The low-temperature denitrification catalyst of this invention uses ternary metal oxides of Mn, Nb and Nd as active components. Through the synergistic effect of multiple metals, it constructs stable and abundant reactive active sites, which can effectively alleviate the limitations of current commercial SCR catalysts in water vapor and SO2 environments due to the poisoning and activity decay caused by the single active component. It has stronger applicability in industrial denitrification environments.

[0016] 1. Excellent low-temperature activity: Achieves NO activity in the 100–250℃ range. x Highly efficient conversion (90%), significantly broadening the low-temperature activity window of Mn-based catalysts.

[0017] 2. Significantly improved N2 selectivity: Inhibits excessive oxidation of NH3 and formation of N2O byproducts, enhancing the environmental friendliness of the denitrification process.

[0018] 3. Strong structural stability: inhibits the agglomeration and sintering of active components, and extends the service life of the catalyst.

[0019] 4. Enhanced resistance to poisoning: Improved tolerance to SO2, H2O and alkali metals, adapting to complex flue gas conditions.

[0020] 5. Acidity and redox balance: Construct an acid-redox bifunctional site adapted to the SCR reaction, which simultaneously meets the requirements of NH3 adsorption activation and NO redox.

[0021] Mn is used to provide the redox cycle (Mn 4+ ↔Mn 3+ ↔Mn 2+ The three metals are the core of NO oxidation and NH3 activation; Nb regulates the valence state of Mn, enhances acidity, inhibits SO2 poisoning, and stabilizes the structure; Nd improves dispersibility, stabilizes the lattice, optimizes oxygen migration, and enhances low-temperature activity and selectivity. The three metals synergistically construct stable and abundant active sites. (1) Electron synergy: Constructing an efficient electron transfer network and optimizing the valence state of active centers. Nb→Mn electron transfer: Nb 5+ It has strong electron-withdrawing properties and can extract electrons from Mn sites, thereby enhancing Mn. 4 + Ratio (Mn) 4 + is the SCR low-temperature high-activity valence state, which enhances redox capabilities.

[0022] Nd→Mn Electron Compensation: Nd 3+ It has weak electron-donating properties and can supplement electrons to the Mn site to balance Mn. 4 + / Mn 3 The + ratio avoids excessive oxidation of Mn leading to non-selective oxidation of NH3 and improves N2 selectivity.

[0023] Ternary electron cycle: formation of Mn 4 +↔Mn 3 +↔Nb 5 +↔Nd 3 The closed-loop electron transfer of + accelerates electron transfer in the reaction, lowers the reaction energy barrier, and improves catalytic efficiency.

[0024] (2) Structural synergy: inhibits aggregation, stabilizes crystal phase, and enriches the types of active sites. Structural stabilizing effect of Nb: Nb 5+ Can be doped into MnO x The crystal lattice may form Nb-O-Mn bonds, suppressing MnO x Crystallization and aggregation maintain an amorphous / microcrystalline state, exposing more edge and defect active sites.

[0025] The dispersing and stabilizing effects of Nd: Nd 3+ Ionic radius and Mn 2+ / Mn 3+ Matching can act as a "separator" to prevent the sintering of Mn / Nb particles, while stabilizing the pore structure of sepiolite and maintaining a high specific surface area.

[0026] Coexistence of multiple active sites: synergistically forming multiple interface sites such as Mn-O-Mn, Mn-O-Nb, Mn-O-Nd, and Nb-O-Nd, each site has different adsorption and activation capabilities, adapting to the multi-step elementary reaction of SCR (NH3 adsorption, NO oxidation, and intermediate species transformation).

[0027] (3) Acidic synergy: Constructing gradient acidic sites to optimize NH3 adsorption and activation Mn provides medium-to-strong acid sites: responsible for the chemisorption and initial activation of NH3 (forming NH2*).

[0028] Nb introduces strong acid sites: enhances the adsorption strength of NH3, improves NH3 coverage at low temperatures, and inhibits the competitive adsorption of SO2 at active sites, thereby improving sulfur resistance.

[0029] Nd regulation of acidity distribution: Optimize the ratio of weak acid, medium strong acid and strong acid to avoid excessive strong acid sites leading to strong adsorption of NH3 and difficulty in desorption, or insufficient weak acid sites leading to low adsorption capacity, and achieve dynamic balance of NH3 adsorption-activation-reaction-desorption.

[0030] Acidic synergy between carrier and active component: The weak acid sites of sepiolite complement the medium-strong acid / strong acid sites of Mn-Nb-Nd, forming a gradient acidic field that adapts to the NH3 adsorption requirements at different temperatures and broadens the active temperature window.

[0031] (4) Synergistic effect of oxygen species: Optimize the migration and supply of reactive oxygen species and improve the efficiency of redox cycle. Mn provides lattice oxygen (O) latti c e ): Participates in the oxidation of NO to NO2 (fast SCR pathway), and requires oxygen replenishment for regeneration after being reduced.

[0032] Nd promotes oxygen vacancy formation and migration: Nd 3+ Doping introduces lattice defects, increases oxygen vacancy concentration, and accelerates the adsorption and dissociation of gaseous O2 on the surface (forming active adsorbed oxygen O). a d s ), and promote O a d s Migration to Mn active sites, rapid regeneration of Mn 4 +, to maintain the continuity of the redox cycle.

[0033] Nb stabilizes reactive oxygen species: The high bond energy of the Nb-O bond stabilizes surface-adsorbed oxygen (O₂). a d s This prevents premature desorption and inhibits the reaction of SO2 with reactive oxygen species to form sulfate, thus protecting the active sites.

[0034] Therefore, through the above synergistic effect, excellent overall results are achieved: The quantity and quality of active sites are both improved: high dispersion + multi-dimensional interface + gradient acidity + abundant oxygen vacancies, constructing high-density, high-activity, and multi-type reaction sites, and significantly improving low-temperature activity.

[0035] Long-lasting stability: The structural stabilizing effect of Nb and Nd inhibits the sintering and loss of active components, thus extending the catalyst life.

[0036] Selectivity and precision: Electronic synergistic regulation of Mn valence state and acid synergistic optimization of NH3 activation effectively inhibit N2O generation, with N2 selectivity > 95%.

[0037] Enhanced resistance to poisoning: Nb inhibits SO2 adsorption and oxidation, Nd stabilizes the structure and captures toxins, and the sieving effect of sepiolite channels together improve the resistance to SO2, H2O and alkali metals.

[0038] Wide temperature range: Gradient acidity and efficient redox cycle enable the catalyst to maintain high activity at 100–300℃, adapting to a wider range of flue gas temperature conditions.

[0039] The Nb molar ratio is set at 0.05–0.20, which effectively regulates the Mn valence state, enhances acidity, and stabilizes the structure. Too low a ratio results in insufficient effect, while too high a ratio will cover Mn active sites and reduce overall activity. The Nd molar ratio is also set at 0.05–0.20, which improves dispersibility, optimizes oxygen migration, and enhances low-temperature activity. Too low a ratio weakens the stabilizing effect, while too high a ratio leads to decreased acidity and reduced activity. This Mn:Nb:Nd molar ratio achieves a ternary balance, optimally matching electron transfer, structural stability, acidity regulation, and oxygen supply, which is key to maximizing the synergistic effect.

[0040] Furthermore, the catalytic system prepared by this invention exhibits stable denitrification capability within a temperature range of 150-400℃, and especially demonstrates high NO content in the low-temperature region below 300℃. x With its high conversion efficiency and excellent resistance to water and sulfur, it can adapt to temperature fluctuations and load changes during industrial operation, achieving stable and efficient denitrification in low-temperature flue gas.

[0041] Furthermore, the Mn-based denitration catalyst used in this invention employs natural sepiolite as a support. The synthesis route is simple, the process is environmentally friendly, and there are no additional pollutant emissions, aligning with the current trend of green chemistry. Sepiolite provides the active components with high specific surface area, ordered pores, surface acidity, and structural stability, forming the physical and chemical basis for the synergistic effect. Sepiolite supports possess high specific surface area and porous structure, providing numerous loading sites to promote high dispersion of Mn-Nb-Nd, prevent aggregation, and expose more active surfaces. Sepiolite supports themselves contain Lewis and Brønsted acid sites, which can pre-adsorb and activate NH3, synergizing with the acidic sites of the active components. Sepiolite exhibits structural stability and good thermal stability: it is resistant to high temperatures and hydrothermal aging, preventing the sintering of active components and maintaining long-term structural integrity. Furthermore, sepiolite supports possess ion exchange and anchoring properties: the Mg framework... 2+ Can be used with Mn 2+ / Nd 3+ Exchange enhances the binding force between active components and the carrier, thereby improving stability.

[0042] The Mn-based denitrification catalyst provided by this invention can be applied to the flue gas emitted from gas turbines and coal-fired boilers in the low-temperature range to achieve NO reduction. x The efficient removal of nitrogen can significantly improve denitrification efficiency, nitrogen selectivity, and resistance to poisoning within the operating temperature range. Using the Mn-based denitrification catalyst prepared according to this invention can facilitate the transfer of the SCR denitrification reactor bed to the tail flue of the thermal power plant, thereby reducing waste heat loss and system energy consumption, and improving the overall economic efficiency and engineering adaptability of the thermal power plant.

[0043] The specific technical solution of the present invention and its beneficial effects will be described in detail in the following specific embodiments. Detailed Implementation

[0044] This invention provides a Mn-based denitration catalyst and a corresponding method for preparing the Mn-based denitration catalyst, through which a Mn-based denitration catalyst can be obtained.

[0045] In implementing this invention, the catalytic testing used a 4100-type fixed-bed microreactor manufactured by Zhejiang Fantai Instrument Co., Ltd., with a reaction tube outer diameter of 16 mm and a length of 480 mm. The raw material gas was preheated before being fed into the reactor. The operating temperature was set between 150 and 400°C, the gas flow rate was controlled at 1000 mL / min, and the reaction space velocity was 216000 h⁻¹.

[0046] In the embodiments of the present invention, the simulated flue gas used consists of the following components: 500 ppm NO, 500 ppm NH3, 5% O2, with Ar as the balance gas for the remaining gases. The flow rate of each gas is adjusted using a CS200 mass flow meter manufactured by Beijing Sevenstar Electronics Co., Ltd.

[0047] In the embodiments of the present invention, the O2 and Ar used are 99.99% pure and were purchased from Jiangnan Mixed Gas Co., Ltd.

[0048] In the embodiments of the present invention, the molar concentrations of NO and NH3 used are both 1%, and the remaining components are made up with Ar, which were purchased from Shanghai Weichuang Standard Gas Co., Ltd.

[0049] In the embodiments of the present invention, all the medicines used were purchased from Aladdin.

[0050] The low-temperature Mn-based denitration catalyst comprises a sepiolite support and an active component attached to the support. The active component includes the metal elements Mn, Nb, and Nd, and the molar ratio of Mn:Nb:Nd is 1:(0.05-0.20):(0.05-0.20). For example, Mn:Nb:Nd=1:0.10:0.10, Mn:Nb:Nd=1:0.10:0.20, Mn:Nb:Nd=1:0.10:0.05.

[0051] The preparation method of the above-mentioned low-temperature Mn-based denitration catalyst includes the following steps: Step 1: Acidify the sepiolite. Step 2: Disperse the acidified sepiolite in deionized water to form a suspension slurry, and obtain a sepiolite dispersion after stirring and ultrasonic treatment, as solution I; Step 3: Add the corresponding molar amounts of KMnO4, Nb(NO3)5 and Nd(NO3)3×6H2O solutions to solution I according to the molar ratio and mix thoroughly to obtain mixed solution II; Step 4: Mix the mixed solution II vigorously under water bath conditions, and dry it to obtain a powdered solid; Step 5: Transfer the powdered solid to a heating furnace for heating, and then cool it to room temperature to obtain a low-temperature Mn-based denitration catalyst.

[0052] The Mn-based denitrification catalyst provided in this embodiment can be applied to flue gas emitted from gas turbines and coal-fired boilers in the low-temperature range to achieve efficient NOx removal. Using the Mn-based denitrification catalyst prepared by this invention can facilitate the transfer of the SCR denitrification reaction bed to the tail flue of the thermal power plant, thereby reducing waste heat loss and system energy consumption, and improving the overall economic efficiency and engineering adaptability of the thermal power plant.

[0053] Example 1: In this embodiment, the Mn-based denitration catalyst A is prepared with a molar ratio of Mn, Nb, and Nd of 1:0.10:0.20. The preparation process includes the following steps: Step 1: Place the block sepiolite in a beaker, add 250 mL of 1 mol / L H2SO4, stir at room temperature for 4 h, wash with deionized water until neutral, and dry at 70 °C to obtain acidified sepiolite.

[0054] Step 2: Place the acidified sepiolite in a beaker and disperse it in deionized water to form a suspension slurry. Stir at room temperature for 4 h and sonicate for 30 min to obtain a sepiolite dispersion with a solid content of 4 g / 100 ml, i.e., solution I.

[0055] Step 3: Add 1 mol of KMnO4, 0.10 mol of Nb(NO3)5 and 0.20 mol of Nd(NO3)3×6H2O solution to solution I and mix thoroughly to obtain mixed solution II.

[0056] Step 4: Stir mixed solution II in an 80°C water bath for 3 hours, and dry it at 60°C to obtain a powdered solid.

[0057] Step 5: Transfer the powdered solid to a muffle furnace, heat at 350°C for 4 hours, and cool to room temperature to obtain the Mn-based denitration catalyst A of this embodiment.

[0058] The Mn-based denitration catalyst A prepared in this embodiment was analyzed using a MAX2200V X-ray diffractometer manufactured by Rigaku Corporation, Japan. Analysis revealed that the Mn-based denitration catalyst A consists of two parts: a support and an active component. The support is sepiolite, and the active component is a mixture of Mn, Nb, and Nd elements.

[0059] To highlight the advantages of Mn-based denitration catalyst A in this embodiment, a conventional catalyst produced by Chengdu Oriental Katery Co., Ltd. was used as a control. This conventional catalyst is a denitration catalyst composed of tungsten trioxide, nano-titanium dioxide, and vanadium pentoxide.

[0060] In this embodiment, the denitrification reaction performance of Mn-based denitrification catalyst A and ordinary catalyst were compared at different temperatures of 150℃, 200℃, 250℃, 300℃ and 350℃.

[0061] The experimental comparison process is as follows: Before the test, NO in the simulated flue gas was introduced into the fixed bed microreactor for 0.5 to 1 hour to ensure that NO reached saturation in the reactor and to prevent the NO content from decreasing due to adsorption by Mn-based denitrification catalyst A and ordinary catalyst.

[0062] Subsequently, 3 mL of Mn-based denitrification catalyst A or a conventional catalyst was loaded into the fixed-bed microreactor evaluation device. Simulated flue gas (flowing in at a rate of 1000 mL / min, with the following composition and concentration: NO 500 ppm, NH3 500 ppm, O2 5%, and the remainder Ar) was thoroughly mixed in the mixing chamber before entering the fixed-bed microreactor evaluation device. Under the action of Mn-based denitrification catalyst A or a conventional catalyst, NH3 and NO react to produce N2 and H2O. After the reaction, the unreacted NH3 is absorbed by a phosphoric acid solution, and the treated gas is discharged into the atmosphere through the exhaust pipe. The NO concentration at the reactor inlet and outlet was measured using a Thermo Fisher Scientific Model 60i flue gas analyzer. The denitrification efficiency of each catalyst at different reaction temperatures was calculated using the following formula: The experimental results obtained through calculation are shown in Table 1.

[0063] Table 1. Denitrification efficiency of Mn-based denitrification catalyst A and ordinary catalyst at different reaction temperatures. The Mn-based denitrification catalyst A prepared in this embodiment was tested for flue gas denitrification under the same conditions as a conventional catalyst. Table 1 shows that the Mn-based denitrification catalyst A exhibits a significantly higher denitrification efficiency than the conventional catalyst. Within the reaction temperature range of 150–350℃, the Mn-based denitrification catalyst A achieved a denitrification efficiency of 86.2%–98.3%. Particularly at 300℃, the denitrification efficiency of the Mn-based denitrification catalyst A reached 98.3%.

[0064] Example 2: In this embodiment, the Mn-based denitration catalyst B is prepared with a molar ratio of Mn, Nb, and Nd of 1:0.10:0.05. The preparation process includes the following steps: Step 1: Place the block sepiolite in a beaker, add 250 mL of 1 mol / L H2SO4, stir at room temperature for 4 h, wash with deionized water until neutral, and dry at 70 °C to obtain acidified sepiolite.

[0065] Step 2: Place the acidified sepiolite in a beaker and disperse it in deionized water to form a suspension slurry. Stir at room temperature for 4 h, and after ultrasonic treatment for 30 min, obtain a sepiolite dispersion with a solid content of 4 g / 100 ml, thus obtaining solution I.

[0066] Step 3: Add 1 mol of KMnO4, 0.10 mol of Nb(NO3)5 and 0.05 mol of Nd(NO3)3×6H2O solution to solution I and mix thoroughly to obtain mixed solution II.

[0067] Step 4: Stir mixed solution II in an 80°C water bath for 3 hours, and dry it at 60°C to obtain a powdered solid.

[0068] Step 5: Transfer the powdered solid to a muffle furnace, heat at 350°C for 4 hours, and cool to room temperature to obtain the Mn-based denitration catalyst B of this embodiment.

[0069] The Mn-based denitration catalyst B prepared in this embodiment was analyzed using a MAX2200V X-ray diffractometer manufactured by Rigaku Corporation, Japan. Analysis revealed that the Mn-based denitration catalyst B consists of two parts: a support and an active component. The support is sepiolite, and the active component is a mixture of Mn, Nb, and Nd elements.

[0070] In this embodiment, as in Example 1, the denitrification reaction performance of the prepared Mn-based denitrification catalyst B and the ordinary catalyst were compared at 150℃, 200℃, 250℃, 300℃ and 350℃. The experimental results obtained after calculation are shown in Table 2.

[0071] Table 2. Denitrification efficiency of Mn-based denitrification catalyst B and ordinary catalyst at different reaction temperatures. The Mn-based denitrification catalyst B prepared in this embodiment was tested for flue gas denitrification under the same conditions as a conventional catalyst. Table 2 shows that the Mn-based denitrification catalyst B exhibits a significantly higher denitrification efficiency than the conventional catalyst. Within the reaction temperature range of 150–350℃, the Mn-based denitrification catalyst B achieved a denitrification efficiency of 82.1%–97.1%. Particularly at 350℃, the denitrification efficiency of the Mn-based denitrification catalyst B reached 97.1%.

[0072] As shown in Examples 1 and 2, the Mn-based denitrification catalyst prepared by this invention maintains good denitrification efficiency over a wide temperature range of 150–350°C, especially at a low temperature of around 150°C. Therefore, the Mn-based denitrification catalyst prepared by this invention has a wider activity window of 150–350°C, which is more conducive to installing SCR denitrification devices in the tail flue of thermal power plants, thereby reducing waste heat loss and system energy consumption, and improving the overall economic efficiency and engineering adaptability of the thermal power plant. Furthermore, the prepared Mn-based denitrification catalyst exhibits optimal SCR activity when the molar ratio of the metal elements Mn, Nb, and Nd is 1:0.10:0.20.

[0073] XPS analysis, XRD analysis, and in-situ infrared analysis were performed on the Mn-based denitration catalysts A and B prepared in Examples 1 and 2. The specific characterization results are as follows: XPS characterization results show that the interaction of Mn, Nb, and Nd elements in the catalyst promotes the formation of Mn4+ species. The introduction of this species not only increases the number of oxygen vacancies and NH4+-Bronsted acid sites on the catalyst surface, enhancing the adsorption and activation capacity of reactant molecules, but also accelerates the oxidation conversion of NO to NO2 and promotes the occurrence of a fast SCR reaction pathway. Simultaneously, the presence of Mn4+ species helps improve the electronic structure and chemical environment of the catalyst surface, enhancing its structural stability and corrosion resistance under acidic flue gas conditions, and slowing down the loss of active components and performance degradation.

[0074] XRD characterization results show that doping with Mn, Nb, and Nd improves the dispersion of active components on the catalyst surface, increasing the specific surface area and pore size of the catalyst. This process facilitates mass transfer and diffusion of reactants within the catalyst channels, increases the number of accessible active sites, and enhances the adsorption capacity of reactants.

[0075] In-situ infrared characterization results show that the Mn-based denitrification catalyst prepared in this invention follows both the LH and ER mechanisms in the NH3-SCR reaction. In the low-temperature range, the LH mechanism dominates the reaction. Doping with Mn, Nb, and Nd promotes the chemisorption of ammonia on the catalyst surface, while also facilitating the formation and stabilization of highly reactive nitrite groups and inhibiting the accumulation of thermally stable nitrate species. This process reduces the kinetic hindrance of the low-temperature reaction and mitigates the inert coverage of intermediate species on the surface, thus maintaining high NO reduction catalytic activity at low temperatures and effectively performing flue gas denitrification.

[0076] Furthermore, mechanistic analysis of in-situ infrared characterization experiments revealed that the number of NH4+-Bronsted acid sites in the Mn-based denitration catalyst prepared in this invention significantly increased in the low-temperature range, a finding consistent with XPS conclusions.

[0077] The low-temperature denitrification catalyst involved in this embodiment uses ternary metal oxides of Mn, Nb, and Nd as active components. Through the synergistic effect of multiple metals, it constructs stable and abundant reactive active sites, effectively alleviating the limitations of current commercial SCR catalysts in water vapor and SO2 environments, which suffer from poisoning and activity decay due to the single active component. This makes it more suitable for industrial denitrification environments. Furthermore, the catalytic system prepared in this invention exhibits stable denitrification capability within a temperature range of 150-400℃, especially demonstrating high NOx conversion efficiency and excellent resistance to water and sulfur in the low-temperature region below 300℃. It can adapt to temperature fluctuations and load changes during industrial operation, achieving stable and efficient denitrification in low-temperature flue gas. In addition, the Mn-based denitrification catalyst used in this embodiment uses natural sepiolite as a support, with a simple synthesis route, environmentally friendly process, and no additional pollutant emissions, aligning with the current trend of green chemistry. The Mn-based denitrification catalyst provided in this embodiment can be applied to achieve efficient NOx removal in flue gas emitted from gas turbines and coal-fired boilers in the low-temperature range. It can significantly improve the denitrification efficiency, nitrogen selectivity and anti-poisoning ability within the operating temperature range. Using the Mn-based denitrification catalyst prepared in this embodiment can facilitate the transfer of the SCR denitrification reaction bed to the tail flue of the thermal power plant, thereby reducing waste heat loss and system energy consumption, and improving the overall economic efficiency and engineering adaptability of the thermal power plant.

[0078] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A Mn-based denitration catalyst, characterized in that, The product includes a carrier made of sepiolite and active components attached to the carrier. The active components include the metal elements Mn, Nb and Nd, and the molar ratio of the metal elements is Mn:Nb:Nd=1:(0.05-0.20):(0.05-0.20).

2. The Mn-based denitration catalyst according to claim 1, characterized in that, The molar ratio of the metal elements is Mn:Nb:Nd = 1:0.10:0.

10.

3. The Mn-based denitration catalyst according to claim 1, characterized in that, The molar ratio of the metal elements is Mn:Nb:Nd = 1:0.10:0.

20.

4. The Mn-based denitration catalyst according to claim 1, characterized in that, The molar ratio of the metal elements is Mn:Nb:Nd = 1:0.10:0.

05.

5. A method for preparing a Mn-based denitration catalyst, used to prepare the Mn-based denitration catalyst according to claim 1, characterized in that, Includes the following steps: Step 1: Acidify the sepiolite. Step 2: Disperse the acidified sepiolite in deionized water to form a suspension slurry, and obtain a sepiolite dispersion after stirring and ultrasonic treatment, as solution I; Step 3: Add the corresponding molar amounts of KMnO4, Nb(NO3)5 and Nd(NO3)3×6H2O solutions to solution I according to the molar ratio and mix thoroughly to obtain mixed solution II; Step 4: Mix the mixed solution II vigorously under water bath conditions, and dry it to obtain a powdered solid; Step 5: Transfer the powdered solid to a heating furnace for heating, and then cool it to room temperature to obtain a low-temperature Mn-based denitration catalyst.

6. The method for preparing a Mn-based denitration catalyst according to claim 5, characterized in that, The acidification process in step 1 is as follows: place the block sepiolite in a reaction vessel, add H2SO4, stir at room temperature, wash with deionized water until neutral, and dry to obtain the acidified sepiolite.

7. The method for preparing a Mn-based denitration catalyst according to claim 6, characterized in that, In step 1: the concentration of added H2SO4 is 1 mol / L; and / or, the stirring time is 4 h, and the drying temperature is 70℃.

8. The method for preparing a Mn-based denitration catalyst according to claim 5, characterized in that, In step 2: the stirring time is 4 hours, the ultrasonic treatment time is 30 minutes; and / or, the solid content of the sepiolite dispersion obtained in step 2 is 4 g / 100 ml.

9. The method for preparing a Mn-based denitration catalyst according to claim 5, characterized in that, In step 4: the water bath temperature is 80℃, the stirring time is 3 hours, and the drying temperature is 60℃.

10. The method for preparing a Mn-based denitration catalyst according to claim 5, characterized in that, In step 5: a muffle furnace is used for heating at a temperature of 350℃ for 4 hours.

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