Iron-manganese composite oxide NH3-SCR catalyst and preparation method thereof

Abstract

The invention belongs to the technical field of environmental catalytic materials, and particularly relates to an iron-manganese composite oxide NH3-SCR catalyst and a preparation method thereof. The catalyst is composed of an active component, a molding aid, an auxiliary active component and a carrier, and comprises the following components in percentage by mass: 10%-20% of the active component, 5%-15% of the molding aid, 0.5%-5% of the auxiliary active component and the balance of the carrier. Wherein the active component is a composite metal oxide of iron, manganese and cerium loaded on the carrier; the forming auxiliary agent comprises an inorganic adhesive and inorganic fibers; the auxiliary active component is WO3; the carrier is a carrier; the catalyst is a ZrO2-TiO2 bimetallic oxide carrier. The catalyst has excellent low-temperature catalytic activity, wide active temperature window, high N2 generation selectivity, outstanding hydrothermal aging resistance and good SO2 poisoning resistance, and is suitable for industrial flue gas denitration treatment.

Description

Technical Field

[0001] This invention belongs to the field of environmental catalytic materials technology, specifically relating to an iron-manganese composite oxide NH3-SCR catalyst and its preparation method. Background Technology

[0002] With the rapid development of industrialization and urbanization, nitrogen oxides (NOx) have increased significantly. x NO emissions have become a significant source of air pollution, seriously threatening the ecological environment and human health. SCR (Selective Catalytic Reduction) technology is currently the most effective method for controlling NO emissions. x One method for removing nitrification is NH3-SCR technology, which uses NH3 as a reducing agent. Due to its high denitrification efficiency and good selectivity, it is widely used in the treatment of stationary source flue gas, such as coal-fired power plants and industrial boilers. The core of this technology lies in the high-efficiency catalyst, whose performance directly determines the efficiency, operating cost, and applicability of the denitrification system. Among many denitrification materials, iron-manganese composite oxides have become a research hotspot for non-vanadium-based low-temperature SCR catalysts in recent years due to their excellent low-temperature catalytic activity, environmental friendliness, and relatively low cost, demonstrating the potential to replace traditional vanadium-titanium catalysts.

[0003] Existing technologies for the preparation and modification of iron-manganese composite oxide catalysts mainly focus on the following aspects: First, synthesis through conventional methods such as co-precipitation and sol-gel methods. Their activity is highly dependent on the Fe / Mn ratio, precursor type, and calcination temperature, but they generally suffer from uneven dispersion of active components, limited specific surface area, and insufficient high-temperature hydrothermal stability. Second, the use of support loading strategies (such as TiO2, carbon materials, molecular sieves, etc.) to improve dispersion and mechanical strength. However, the interaction mechanism between the support and the active components is complex, and inappropriate combinations may lead to the covering of active sites or adverse chemical reactions, thus reducing intrinsic activity. Third, doping modification by introducing a third or even fourth metal element (such as Ce, Cu, Co, Zr, etc.) to adjust redox performance and surface acidity. This route has made some progress in improving low-temperature activity or broadening the active temperature window, but it often faces challenges such as complex preparation processes, increased costs, unclear synergistic mechanisms among multiple components, and the potential for elemental segregation or phase transitions during long-term operation, leading to accelerated activity decline. In addition, most existing studies focus on evaluating ideal conditions in the laboratory. The ability of catalysts to resist SO2 and H2O poisoning in actual flue gas remains a common bottleneck restricting their engineering application. Existing modification methods are still significantly insufficient in terms of long-term sulfur and water resistance.

[0004] Therefore, developing an iron-manganese composite oxide NH3-SCR catalyst that combines excellent low-temperature activity, good hydrothermal stability, and outstanding resistance to poisoning, and whose preparation process is simple and controllable, has important practical significance and application needs. Summary of the Invention

[0005] This invention aims to overcome the shortcomings of the prior art and provide an iron-manganese composite oxide NH3-SCR catalyst and its preparation method, solving the problems that existing iron-manganese based low-temperature NH3-SCR catalysts generally have, such as a narrow activity temperature window, poor high-temperature hydrothermal stability, and insufficient sulfur and water resistance, making it difficult to operate stably for a long time under actual complex flue gas conditions.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: 1. A manganese-iron composite oxide NH3-SCR catalyst, wherein the catalyst comprises, by percentage of total catalyst mass: Active component: 10%-20%; molding aid: 5%-15%; auxiliary active component: 0.5%-5%; support: the balance by mass of catalyst; The active component is a composite metal oxide of iron, manganese, and cerium supported on a carrier. In the composite metal oxide, the molar ratio of iron, manganese, and cerium is (1-3):(1-3):(0.1-0.5); The molding aids include inorganic binders and inorganic fibers; The auxiliary active component is WO3; The support is a ZrO2-TiO2 bimetallic oxide support.

[0007] Preferably, the catalyst comprises, by percentage of the total mass of the catalyst: Active component: 12%-18%; molding aid: 8%-12%; auxiliary active component: 1%-3%; support: the balance of catalyst mass.

[0008] Preferably, in the composite metal oxide, the molar ratio of iron, manganese and cerium is (1.8-2.2):(1.8-2.2):(0.25-0.35).

[0009] Preferably, in the molding aid, the mass ratio of inorganic binder to inorganic fiber is (6-10):1; The inorganic binder is selected from at least one of silica sol and alumina sol; The inorganic fibers include glass fibers.

[0010] Preferably, the inorganic binder is added in liquid form during the preparation process, and the amount of liquid inorganic binder meets the following requirements: the percentage of solid components in the liquid inorganic binder to inorganic fibers in the final calcined catalyst product is 5%-15% of the total mass of the catalyst, and the mass ratio of solid components in the liquid inorganic binder to inorganic fibers is (6-10):1.

[0011] Preferably, the percentage of solid components in the liquid inorganic binder to inorganic fibers in the final calcined catalyst product is 8%-12% of the total catalyst mass, and the mass ratio of solid components in the liquid inorganic binder to inorganic fibers is (6-10):1.

[0012] Preferably, the molar ratio of titanium to zirconium in the ZrO2-TiO2 bimetallic oxide composite carrier is 1:1, and ZrO2 and TiO2 exist in the form of TiZrO4 solid solution.

[0013] This invention also discloses a method for preparing the iron-manganese composite oxide NH3-SCR catalyst as described above, comprising the following steps: S1. Preparation of ZrO2-TiO2 bimetallic oxide composite support: Titanium source and zirconium source were prepared by co-precipitation method according to the molar ratio of titanium to zirconium of 1:1. After drying and calcination, ZrO2-TiO2 bimetallic oxide composite support with TiZrO4 solid solution structure was obtained. S2, Loading active components and auxiliary active components: The support obtained in step S1 is added to an impregnation solution containing soluble iron salt, soluble manganese salt, soluble cerium salt and soluble tungsten salt for impregnation. After impregnation, it is dried and calcined to obtain the catalyst precursor. S3. Molding: Add the inorganic binder and inorganic fiber from the molding aid to the catalyst precursor obtained in step S2, mix and age, and then extrude to obtain the catalyst preform. S4. Calcination and activation: The catalyst preform obtained in step S3 is dried and then calcined and activated in an air atmosphere. After cooling, the supported iron-manganese composite oxide NH3-SCR catalyst is obtained.

[0014] Preferably, in step S1, the titanium source includes titanium tetrachloride or titanium sulfate, the zirconium source includes zirconium oxychloride, and the calcination conditions are: calcination at 450-650℃ for 3-6 hours.

[0015] Preferably, in step S2, the soluble iron salt includes ferric nitrate, the soluble manganese salt includes manganese nitrate, the soluble cerium salt includes cerium nitrate, and the soluble tungsten salt includes ammonium metatungstate hydrate. The calcination conditions are: calcination at 350-550℃ for 3-5 hours.

[0016] Preferably, in step S3, the mixing time is 30-90 minutes; the aging time is 12-24 hours.

[0017] Preferably, in step S4, the calcination activation conditions are: heating to 450-600℃ at a heating rate of 1-5℃ / min, and maintaining this temperature for 4-8 hours.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: In this invention, the precise construction of the active component and the support achieves a breakthrough improvement in low-temperature activity. The core lies in using a Fe-Mn-Ce composite oxide with a specific molar ratio of (1-3):(1-3):(0.1-0.5) as the active phase, supported on a unique TiZrO4 solid solution support. The combination of Fe and Mn is the foundation for high activity at low temperatures, while the introduction of trace amounts of Ce not only optimizes the surface redox cycle, but its oxygen storage and release capabilities also produce a strong synergistic effect with the support. The ZrO2-TiO2 composite support used is not a simple mixture; the TiZrO4 solid solution formed through co-precipitation and calcination has superior surface acidity and thermal stability compared to single TiO2 or ZrO2. The strongly acidic surface greatly promotes the adsorption and activation of NH3, while the active oxygen provided by Ce in the active component is efficiently transferred through the support, thereby achieving NO adsorption at low temperatures (e.g., 150-250℃). x The high efficiency and rapid reduction of vanadium catalysts overcomes the bottleneck of insufficient low-temperature activity of traditional vanadium-based catalysts. In this invention, the auxiliary introduction of WO3, synergistically with the support, endows the catalyst with excellent hydrothermal stability and resistance to sulfur and alkali metal poisoning. As an auxiliary active component, WO3, when introduced into the catalyst system, can form dispersed acidic sites on the surface of the active component. These sites, working together with the acidic sites of the TiZrO4 solid solution structure ZrO2-TiO2 composite support, effectively inhibit the low-temperature deposition and accumulation of byproducts such as ammonium sulfate during the reaction. Furthermore, WO3 can form strong interactions with Mn and Ce in the active component, stabilizing their high valence states and preventing irreversible sintering and phase transformation under high-temperature hydrothermal conditions, thereby maintaining the integrity and dispersion of the active surface. Simultaneously, the presence of WO3 can competitively capture K in the flue gas. + Na + Alkali metal ions provide shielding protection for active sites, enabling the catalyst to maintain long-term activity under complex flue gas conditions. In this invention, inorganic binders and inorganic fibers are introduced into the catalyst system as molding aids. The addition of inorganic fibers constructs a three-dimensional network framework within the catalyst preform, effectively offsetting the internal stress that may result from the loading of highly active components and multiple calcinations. This gives the molded catalyst excellent crush resistance and wear resistance. The silicon or aluminum oxide network formed by the inorganic binder after high-temperature calcination not only provides strong bonding but also its porous structure helps maintain the macroscopic porosity of the catalyst, ensuring that reactant gases can fully diffuse to the internal active sites. Through integrated control of strength, porosity, and activity, the catalyst of this invention can directly meet the long-term operating requirements of industrial honeycomb or plate catalysts. Attached Figure Description

[0019] Figure 1 The XRD pattern of the ZrO2-TiO2 bimetallic oxide composite support prepared in Example 1 of the present invention; Figure 2 When testing the catalytic activity of the NH3-SCR catalysts prepared in Examples 1-3 and Comparative Examples 1-4 of this invention, NO x Graph showing the results of the conversion rate measurement; Figure 3 The graph shows the results of the activity retention rate at 250°C and 350°C during the hydrothermal aging resistance test of the NH3-SCR catalysts prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention. Figure 4 The graph shows the results of strength retention rate determination during hydrothermal aging resistance tests of the NH3-SCR catalysts prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention. Figure 5 The graph shows the results of the determination of activity retention rate and activity recovery rate of the NH3-SCR catalysts prepared in Examples 1-3 and Comparative Examples 1-4 of the present invention during SO2 poisoning resistance tests. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Example

[0021] This embodiment discloses a method for preparing an iron-manganese composite oxide NH3-SCR catalyst, comprising the following steps: S1. Preparation of ZrO2-TiO2 bimetallic oxide composite support: Titanium tetrachloride (TiCl4) and zirconium oxychloride (ZrOCl2·8H2O) were weighed out as titanium source and zirconium source, respectively, and the molar ratio of titanium to zirconium was controlled at 1:1. Titanium tetrachloride and zirconium oxychloride were dissolved together in deionized water, and the amount of deionized water was 6 times the sum of the masses of titanium tetrachloride and zirconium oxychloride to obtain a mixed salt solution. Under the stirring condition of 600 r / min, 25 wt% ammonia water was slowly added dropwise to the mixed salt solution until the pH value was 9. The stirring speed was maintained at 600 r / min and the stirring was continued for 2 h to carry out the co-precipitation reaction. After the reaction was completed, the mixture was filtered, and the precipitate was repeatedly washed with deionized water until the filtrate was free of chloride ions to obtain the precursor. The precursor was vacuum dried at 50 °C to constant weight, calcined at 450 °C for 6 h, and ground after natural cooling to obtain ZrO2-TiO2 bimetallic oxide composite carrier powder with TiZrO4 solid solution structure. S2, Loaded active components and auxiliary active components: Weigh out ferric nitrate nonahydrate (Fe(NO3)3·9H2O), 50wt% manganese nitrate (Mn(NO3)2) aqueous solution, cerium nitrate hexahydrate (Ce(NO3)3·6H2O), and ammonium metatungstate hydrate ((NH4)6H2W). 12 O 40 The dosage relationships of ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate meet the following conditions: The molar ratio of iron in ferric nitrate nonahydrate, manganese in 50wt% manganese nitrate aqueous solution, and cerium in cerium nitrate hexahydrate is 1:1:0.1. Based on the final total mass of the catalyst, the content of the composite metal oxide of active component iron, manganese, and cerium is 10%, and the content of auxiliary active component WO3 is 0.5%. Ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate were dissolved together in deionized water. The amount of deionized water used was 6 times the total mass of ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate to obtain the impregnation solution. The composite carrier powder obtained in step S1 is added to the impregnation liquid and stirred to form a slurry. The slurry is left to stand overnight for impregnation. After impregnation, it is dried at 80°C for 12 hours and then placed in a muffle furnace. Under an air atmosphere, the temperature is increased to 350°C at 2°C / min and calcined at 350°C for 5 hours. After natural cooling, it is ground to obtain catalyst precursor powder loaded with active components and auxiliary active components. S3, Molding: Weigh out silica sol with a solid content of 30% and chopped glass fibers. The ratio of the amounts of silica sol with a solid content of 30% and chopped glass fibers should meet the following conditions: The mass percentage of the solid components in the 30% solid content silica sol to the chopped glass fibers in the final calcined catalyst product is 5% of the total mass of the catalyst, and the mass ratio of the solid components in the 30% solid content silica sol to the chopped glass fibers is 10:1. Short glass fibers and silica sol with 30% solid content were added to the catalyst precursor powder obtained in step S2. The mixture was continuously mixed in a mixer for 30 minutes. The mixed mud was sealed and aged at room temperature for 12 hours. The aged mud was then extruded into shape using a honeycomb mold on an extruder to obtain a honeycomb catalyst preform with square channels in cross section. The catalyst preform has 18×18 pores, a cross-section of 150mm×150mm, an inner wall thickness of 1.2mm, and an outer wall thickness of 1.8mm. S4, Calcination activation: After drying the catalyst preform at 50℃ and 45% relative humidity for 12 hours, it was transferred to a muffle furnace and activated by programmed temperature rise in air: the temperature was raised to 450℃ at a rate of 1℃ / min and held at 450℃ for 8 hours. After the program was completed, it was naturally cooled to room temperature to obtain the honeycomb iron-manganese composite oxide NH3-SCR catalyst. Example

[0022] This embodiment discloses a method for preparing an iron-manganese composite oxide NH3-SCR catalyst, comprising the following steps: S1. Preparation of ZrO2-TiO2 bimetallic oxide composite support: Titanium sulfate (Ti(SO4)2) and zirconium oxychloride (ZrOCl2·8H2O) were weighed out as titanium source and zirconium source, respectively, and the molar ratio of titanium to zirconium was controlled at 1:1. Titanium sulfate and zirconium oxychloride were dissolved together in deionized water, and the amount of deionized water was 10 times the sum of the masses of titanium sulfate and zirconium oxychloride to obtain a mixed salt solution. Under the stirring condition of 1000 r / min, 25 wt% ammonia water was slowly added dropwise to the mixed salt solution until the pH value was 10. The stirring speed was maintained at 1000 r / min and the stirring was continued for 1 h to carry out the co-precipitation reaction. After the reaction was completed, the mixture was filtered, and the precipitate was repeatedly washed with deionized water until the filtrate was free of chloride ions to obtain the precursor. The precursor was vacuum dried at 50 °C to constant weight, calcined at 650 °C for 3 h, and ground after natural cooling to obtain ZrO2-TiO2 bimetallic oxide composite carrier powder with TiZrO4 solid solution structure. S2, Loaded active components and auxiliary active components: Weigh out ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate. The relationship between the amounts of ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate should meet the following conditions: The molar ratio of iron in ferric nitrate nonahydrate, manganese in 50wt% manganese nitrate aqueous solution, and cerium in cerium nitrate hexahydrate is 3:3:0.5. Based on the final total mass of the catalyst, the content of the composite metal oxide of active components iron, manganese, and cerium is 20%, and the content of auxiliary active component WO3 is 5%. Ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate were dissolved together in deionized water. The amount of deionized water used was 10 times the sum of the masses of ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate to obtain the impregnation solution. The composite carrier powder obtained in step S1 is added to the impregnation liquid and stirred to form a slurry. The slurry is left to stand overnight for impregnation. After impregnation, it is dried at 120°C for 6 hours and then placed in a muffle furnace. Under air atmosphere, the temperature is increased to 550°C at 4°C / min and calcined at 550°C for 3 hours. After natural cooling, it is ground to obtain catalyst precursor powder loaded with active components and auxiliary active components. S3, Molding: Weigh out aluminum sol with a solid content of 20% and chopped glass fibers. The ratio of the amounts of aluminum sol with a solid content of 20% and chopped glass fibers should meet the following conditions: The mass percentage of the solid components in the 20% solid content aluminum sol to the chopped glass fibers in the final calcined catalyst product is 15% of the total mass of the catalyst, and the mass ratio of the solid components in the 20% solid content aluminum sol to the chopped glass fibers is 6:1. Short glass fibers and 20% solid content aluminum sol were added to the catalyst precursor powder obtained in step S2. The mixture was continuously mixed in a mixer for 90 minutes. The mixed mud was sealed and aged at room temperature for 24 hours. The aged mud was then extruded into shape using a honeycomb mold on an extruder to obtain a honeycomb catalyst preform with square channels in cross section. The catalyst preform has 18×18 pores, a cross-section of 150mm×150mm, an inner wall thickness of 1.2mm, and an outer wall thickness of 1.8mm. S4, Calcination activation: After drying the catalyst preform at 50℃ and 45% relative humidity for 12 hours, it was transferred to a muffle furnace and activated by programmed temperature rise in air: the temperature was raised to 600℃ at a rate of 5℃ / min and held at 600℃ for 4 hours. After the program was completed, it was naturally cooled to room temperature to obtain the honeycomb iron-manganese composite oxide NH3-SCR catalyst. Example

[0023] This embodiment discloses a method for preparing an iron-manganese composite oxide NH3-SCR catalyst, comprising the following steps: S1. Preparation of ZrO2-TiO2 bimetallic oxide composite support: Titanium sulfate (Ti(SO4)2) and zirconium oxychloride (ZrOCl2·8H2O) were weighed out as titanium source and zirconium source, respectively, and the molar ratio of titanium to zirconium was controlled at 1:1. Titanium sulfate and zirconium oxychloride were dissolved together in deionized water, and the amount of deionized water was 8 times the sum of the masses of titanium sulfate and zirconium oxychloride to obtain a mixed salt solution. Under the stirring condition of 800 r / min, 25 wt% ammonia water was slowly added dropwise to the mixed salt solution until the pH value was 9.5. The stirring speed was maintained at 800 r / min and the stirring was continued for 1.5 h to carry out the co-precipitation reaction. After the reaction was completed, the mixture was filtered, and the precipitate was repeatedly washed with deionized water until the filtrate was free of chloride ions to obtain the precursor. The precursor was vacuum dried at 50 °C to constant weight, calcined at 550 °C for 4.5 h, and ground after natural cooling to obtain ZrO2-TiO2 bimetallic oxide composite carrier powder with TiZrO4 solid solution structure. S2, Loaded active components and auxiliary active components: Weigh out ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate. The relationship between the amounts of ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate should meet the following conditions: The molar ratio of iron in ferric nitrate nonahydrate, manganese in 50wt% manganese nitrate aqueous solution, and cerium in cerium nitrate hexahydrate is 2:2:0.3. Based on the final total mass of the catalyst, the content of the composite metal oxide of active component iron, manganese, and cerium is 15%, and the content of auxiliary active component WO3 is 2.5%. Ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate were dissolved together in deionized water. The amount of deionized water used was 8 times the total mass of ferric nitrate nonahydrate, 50wt% manganese nitrate aqueous solution, cerium nitrate hexahydrate, and ammonium metatungstate hydrate to obtain the impregnation solution. The composite carrier powder obtained in step S1 is added to the impregnation liquid and stirred to form a slurry. The slurry is left to stand overnight for impregnation. After impregnation, it is dried at 100°C for 9 hours and then placed in a muffle furnace. Under an air atmosphere, the temperature is increased to 450°C at 3°C / min and calcined at 450°C for 4 hours. After natural cooling, it is ground to obtain catalyst precursor powder loaded with active components and auxiliary active components. S3, Molding: Weigh out silica sol with a solid content of 30% and chopped glass fibers. The ratio of the amounts of silica sol with a solid content of 30% and chopped glass fibers should meet the following conditions: The mass percentage of the solid components in the 30% solid content silica sol to the chopped glass fibers in the final calcined catalyst product is 10% of the total mass of the catalyst, and the mass ratio of the solid components in the 30% solid content silica sol to the chopped glass fibers is 8:1. Short glass fibers and silica sol with 30% solid content were added to the catalyst precursor powder obtained in step S2. The mixture was continuously mixed in a mixer for 60 minutes. The mixed mud was sealed and aged at room temperature for 18 hours. The aged mud was then extruded into shape using a honeycomb mold on an extruder to obtain a honeycomb catalyst preform with square channels in cross section. The catalyst preform has 18×18 pores, a cross-section of 150mm×150mm, an inner wall thickness of 1.2mm, and an outer wall thickness of 1.8mm. S4, Calcination activation: After drying the catalyst preform at 50℃ and 45% relative humidity for 12 hours, it was transferred to a muffle furnace and activated by programmed temperature rise in air: the temperature was raised to 550℃ at a rate of 3℃ / min and held at 550℃ for 6 hours. After the program was completed, it was naturally cooled to room temperature to obtain the honeycomb iron-manganese composite oxide NH3-SCR catalyst.

[0024] Comparative Example 1 Compared with Example 3, the only difference in the preparation of the iron-manganese composite oxide NH3-SCR catalyst in Comparative Example 1 is that the active component is only iron oxide, without manganese oxide and cerium oxide. The content of iron oxide as the active component is 15% based on the final total mass of the catalyst.

[0025] Comparative Example 2 Compared with Example 3, the only difference in Comparative Example 2 in preparing the iron-manganese composite oxide NH3-SCR catalyst is that the active component is only manganese oxide, without iron oxide and cerium oxide. The content of manganese oxide as the active component is 15% based on the final total mass of the catalyst.

[0026] Comparative Example 3 Compared with Example 3, the only difference in Comparative Example 3 in preparing the iron-manganese composite oxide NH3-SCR catalyst is that the molar ratio of iron, manganese and cerium in the composite metal oxide of active components is 2:2:1.

[0027] Comparative Example 4 This comparative example discloses a method for preparing an iron-manganese composite oxide NH3-SCR catalyst, comprising the following steps: S1. Preparation of TiO2 support: Titanium sulfate was weighed as the titanium source and dissolved in deionized water at a volume of 8 times the mass of titanium sulfate to obtain a titanium sulfate solution. Under stirring at 800 r / min, 25 wt% ammonia was slowly added dropwise to the mixed salt solution until the pH value reached 9.5. The stirring was continued at 800 r / min for 1.5 h to carry out the co-precipitation reaction. After the reaction was completed, the solution was filtered, and the precipitate was repeatedly washed with deionized water until the filtrate was free of chloride ions to obtain the precursor. The precursor was vacuum dried at 50 °C to constant weight, calcined at 550 °C for 4.5 h, and ground after natural cooling to obtain TiO2 support powder. S2, Loaded active component: Weigh out ferric nitrate nonahydrate and a 50wt% manganese nitrate aqueous solution. The relationship between the amounts of ferric nitrate nonahydrate and the 50wt% manganese nitrate aqueous solution should meet the following conditions: The molar ratio of iron in ferric nitrate nonahydrate to manganese in a 50wt% manganese nitrate aqueous solution is 2:2. Based on the final total mass of the catalyst, the content of the active component, iron-manganese composite metal oxide, is 15%. Ferric nitrate nonahydrate and 50wt% manganese nitrate aqueous solution were dissolved together in deionized water. The amount of deionized water was 8 times the mass of the ferric nitrate nonahydrate and 50wt% manganese nitrate aqueous solution to obtain the impregnation solution. The TiO2 support powder obtained in step S1 was added to the impregnation solution and stirred to form a slurry. The slurry was left to stand overnight for impregnation. After impregnation, it was dried at 100°C for 9 hours and then placed in a muffle furnace. Under an air atmosphere, the temperature was increased to 450°C at 3°C / min and calcined at 450°C for 4 hours. After natural cooling, it was ground to obtain catalyst precursor powder loaded with active components. S3, Molding: Weigh out attapulgite, the amount of which is 10% of the total mass of the catalyst; The catalyst precursor powder obtained in step S2 was mixed with attapulgite, and water with a mass of 3 times that of attapulgite was added. The mixture was continuously mixed in a mixer for 60 minutes. The mixed mud was sealed and aged at room temperature for 18 hours. The aged mud was then extruded into shape using a honeycomb mold on an extruder to obtain a honeycomb catalyst preform with square channels in cross section. The catalyst preform has 18×18 pores, a cross-section of 150mm×150mm, an inner wall thickness of 1.2mm, and an outer wall thickness of 1.8mm. S4, Calcination activation: After drying the catalyst preform at 50℃ and 45% relative humidity for 12 hours, it was transferred to a muffle furnace and activated by programmed temperature rise in air: the temperature was raised to 550℃ at a rate of 3℃ / min and held at 550℃ for 6 hours. After the program was completed, it was naturally cooled to room temperature to obtain the honeycomb iron-manganese composite oxide NH3-SCR catalyst.

[0028] In the above examples and comparative examples, the molecular weight of ammonium metatungstate hydrate was 2956.3; the pH value of the 30% solid content silica sol was 9-11, and the particle size of the nano silica was 15±5nm; the pH value of the 20% solid content aluminum sol was 9-10, and the particle size of the nano alumina was 10nm; the length of the chopped glass fiber was 3mm.

[0029] Test case The NH3-SCR catalysts prepared in Examples 1-3 and Comparative Examples 1-4 were cut into cylindrical catalyst samples with a diameter of 20 mm and a length of 60 mm (ensuring the integrity of the pores) for performance testing. Test (1), Catalytic activity test: Each cylindrical catalyst sample was loaded into a tubular reactor, ensuring that the gas flow passed parallel through the honeycomb channels. The simulated flue gas composition was: 500 ppm NO, 500 ppm NH3, 5 vol.% O2, with N2 as the balance gas and a volume hourly space velocity of 20,000 h⁻¹. -1 NO was tested in the range of 150-450℃ (at one point every 50℃). x Conversion rate and N2 selectivity (considering only N2O as the main byproduct) were analyzed by recording data after stabilizing at each temperature point for 1 hour.

[0030] NO x The results of the conversion rate and N2 generation selectivity are shown in Table 1, and the results of the pressure drop and axial compressive strength are shown in Table 2. Table 1 As shown in Table 1, the iron-manganese composite oxide NH3-SCR catalyst prepared in this invention exhibits good catalytic activity and a wide active temperature window, covering the NO range of 150-450°C. xConversion rate ≥90%, N2 generation selectivity ≥95%. Compared with Example 3, in Comparative Example 1, the absence of manganese and cerium resulted in limited redox ability of the single Fe oxide at low temperatures, and the lack of high low-temperature activity of Mn and oxygen storage and electronic modulation effect of Ce led to a significant decrease in low-temperature activity. In Comparative Example 2, the absence of iron and cerium resulted in a single Mn oxide exhibiting certain low-temperature activity, but its excessive oxidizing power exacerbated the non-selective oxidation of NH3 at high temperatures, leading to the large-scale generation of byproducts such as N2O, a sharp deterioration in N2 generation selectivity, and a significant decrease in high-temperature activity. In Comparative Example 3, the excessively high Ce content would overly cover the acidic sites on the support surface and may form an inert complex phase with Fe and Mn, leading to excessive oxidation of NH3 at low temperatures to generate byproducts such as N2O, while simultaneously reducing the activity against NO. x The effective adsorption and activation capacity of the TiZrO4 solid solution resulted in a decrease in both low-temperature catalytic activity and N2 generation selectivity. In Comparative Example 4, the support was a pure TiO2 support, which lacked the synergistic stabilizing effect and optimized surface properties provided by the TiZrO4 solid solution structure. This resulted in insufficient high-temperature dispersibility and thermal stability of the active components, which manifested as a significant decrease in both high-temperature catalytic activity and N2 generation selectivity.

[0031] Test (2) Hydrothermal aging resistance test: Each cylindrical catalyst sample was placed in a tube furnace and treated at 600°C for 24 hours in an atmosphere of 10 vol.% H2O / air. 2.1 Following the activity test method in test (1), the NO content of the catalyst before and after aging was measured at 250℃ and 350℃ respectively. x Conversion rate, and calculate activity retention rate; 2.2 Using a material testing machine, the axial compressive strength of the catalyst samples before and after aging was tested. The maximum pressure (MPa) at the time of breakage was recorded, and the compressive strength retention rate was calculated. The damage to the overall structural strength caused by hydrothermal aging was assessed based on the compressive strength retention rate. The results of the activity determination and the axial compressive strength determination are shown in Tables 2 and 3, respectively. Table 2

[0032] Table 3

[0033] As shown in Tables 2 and 3, the iron-manganese composite oxide NH3-SCR catalyst prepared by this invention has good resistance to hydrothermal aging. After hydrothermal aging treatment, the catalyst retains high activity retention rate and compressive strength retention rate, with an activity retention rate as high as 92% and a compressive strength retention rate both reaching >90%. Compared with Example 3, in Comparative Example 1, the absence of manganese and cerium elements resulted in insufficient microstructural stability between the single Fe oxide and the support and molding aids, making it more prone to sintering and phase separation under high-temperature hydrothermal conditions, leading to a significant decrease in both activity retention rate and strength retention rate. In Comparative Example 2, the absence of iron and cerium elements resulted in poor structural stability of the single Mn oxide under high-temperature hydrothermal conditions, making it prone to crystal transformation or migration, which not only led to a significant decrease in activity retention rate but also severely weakened its bonding force with the support and binder phase, resulting in a significant decrease in mechanical strength retention rate. In Comparative Example 3, although the excessively high Ce content alleviated the problem to some extent through its oxygen storage capacity... While the activity decayed, excessive Ce may exist as an independent crystalline phase, which may lead to a mismatch in the thermal expansion coefficients with other components and the support at high temperatures, or generate stress at the interface, thereby damaging the integrity of the system and significantly reducing its strength retention rate. In Comparative Example 4, the support is a pure TiO2 support, which lacks the high-temperature phase stability and stronger interaction with the active component provided by the TiZrO4 solid solution structure. Under high-temperature hydrothermal conditions, the pure TiO2 support itself is prone to grain growth and phase transformation. At the same time, the interface between it and the active component and the attapulgite binder is also more unstable, which together lead to the most severe decrease in its activity retention rate and strength retention rate.

[0034] Test (3) SO2 poisoning test: In a base atmosphere containing 10% H2O at 250°C, 100ppm SO2 was introduced to conduct a poisoning experiment on each catalyst sample, and the NOx conversion rate was measured after 12h of poisoning. After stopping the introduction of SO2, the sample was purged with clean flue gas at 250°C, and the NOx conversion rate was measured after 5h of purging. The activity recovery was observed, and the initial NOx conversion rate was compared to calculate the activity retention rate after 12h of poisoning and the activity recovery rate after 5h of purging. The results of the activity retention rate and activity recovery rate are shown in Table 4. Table 4

[0035] As shown in Table 4, the iron-manganese composite oxide NH3-SCR catalyst prepared by this invention has good resistance to SO2 poisoning. The activity retention rate after poisoning is above 83%, and the activity recovery rate after purging is ≥90%, showing strong resistance to poisoning and reversibility of poisoning. Compared to Example 3, in Comparative Example 1, the absence of manganese and cerium means that while the single Fe oxide exhibits some sulfur resistance, its low-temperature activity is low. Furthermore, under conditions of coexistence of SO2 and H2O, it lacks Ce's oxygen storage and electronic modulation functions to effectively mitigate the formation and deposition of ammonium sulfate, and also lacks Mn's optimization effect on the reaction pathway, resulting in low activity retention and recovery rates after poisoning. In Comparative Example 2, the absence of iron and cerium means that the single Mn oxide, due to its strong oxidizing properties, readily reacts with SO2 to form thermally stable manganese sulfate, leading to rapid, deep, and difficult-to-recover poisoning of active sites, thus significantly reducing its activity retention and recovery rates. In Comparative Example 3, while the excessively high Ce content improves oxygen storage capacity, excessive Ce may overly cover acidic sites on the support surface and potentially form isosulfates, reducing the catalyst's resistance to NH3 and NO. x The adsorption and activation capacity of the catalyst was reduced, which also weakened the kinetics of SO2 conversion and removal on the surface, resulting in a significant decrease in the activity retention rate and recovery rate after poisoning. In Comparative Example 4, the support was a pure TiO2 support, which lacked the strong surface acidic sites provided by the TiZrO4 solid solution structure and the stronger metal-support interaction with the active components. This reduced the competitive adsorption capacity of the catalyst surface for NH3, making it easier for SO2 to attack and poison the active center. It was also not conducive to the thermal decomposition and removal of surface sulfates after poisoning. Therefore, its activity retention rate and recovery rate were the worst.

[0036] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A manganese-iron composite oxide NH3-SCR catalyst, characterized in that, The catalyst, by percentage of the total mass of the catalyst, comprises: Active component: 10%-20%; molding aid: 5%-15%; auxiliary active component: 0.5%-5%; support: the balance by mass of catalyst; The active component is a composite metal oxide of iron, manganese, and cerium supported on a carrier. In the composite metal oxide, the molar ratio of iron, manganese, and cerium is (1-3):(1-3):(0.1-0.5); The molding aids include inorganic binders and inorganic fibers; The auxiliary active component is WO3; The support is a ZrO2-TiO2 bimetallic oxide support.

2. The iron-manganese composite oxide NH3-SCR catalyst according to claim 1, characterized in that, The catalyst, by percentage of the total mass of the catalyst, comprises: Active component: 12%-18%; molding aid: 8%-12%; auxiliary active component: 1%-3%; support: the balance of catalyst mass.

3. The iron-manganese composite oxide NH3-SCR catalyst according to claim 1, characterized in that, In the composite metal oxide, the molar ratio of iron, manganese and cerium is (1.8-2.2):(1.8-2.2):(0.25-0.35).

4. The iron-manganese composite oxide NH3-SCR catalyst according to claim 1, characterized in that, In the molding aid, the mass ratio of inorganic binder to inorganic fiber is (6-10):1; The inorganic binder is selected from at least one of silica sol and alumina sol; The inorganic fibers include glass fibers.

5. The iron-manganese composite oxide NH3-SCR catalyst according to claim 1, characterized in that, The molar ratio of titanium to zirconium in the ZrO2-TiO2 bimetallic oxide composite carrier is 1:1, and ZrO2 and TiO2 exist in the form of TiZrO4 solid solution.

6. A method for preparing the iron-manganese composite oxide NH3-SCR catalyst according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Preparation of ZrO2-TiO2 bimetallic oxide composite support: Titanium source and zirconium source were prepared by co-precipitation method according to the molar ratio of titanium to zirconium of 1:

1. After drying and calcination, ZrO2-TiO2 bimetallic oxide composite support with TiZrO4 solid solution structure was obtained. S2, Loading active components and auxiliary active components: The support obtained in step S1 is added to an impregnation solution containing soluble iron salt, soluble manganese salt, soluble cerium salt and soluble tungsten salt for impregnation. After impregnation, it is dried and calcined to obtain the catalyst precursor. S3. Molding: Add the inorganic binder and inorganic fiber from the molding aid to the catalyst precursor obtained in step S2, mix and age, and then extrude to obtain the catalyst preform. S4. Calcination and activation: The catalyst preform obtained in step S3 is dried and then calcined and activated in an air atmosphere. After cooling, the supported iron-manganese composite oxide NH3-SCR catalyst is obtained.

7. The method for preparing an iron-manganese composite oxide NH3-SCR catalyst according to claim 6, characterized in that, In step S1, the titanium source includes titanium tetrachloride or titanium sulfate, the zirconium source includes zirconium oxychloride, and the calcination conditions are: calcination at 450-650℃ for 3-6 hours.

8. The method for preparing an iron-manganese composite oxide NH3-SCR catalyst according to claim 6, characterized in that, In step S2, the soluble iron salt includes ferric nitrate, the soluble manganese salt includes manganese nitrate, the soluble cerium salt includes cerium nitrate, and the soluble tungsten salt includes ammonium metatungstate hydrate. The calcination conditions are: calcination at 350-550℃ for 3-5 hours.

9. The method for preparing an iron-manganese composite oxide NH3-SCR catalyst according to claim 6, characterized in that, In step S3, the mixing time is 30-90 minutes; the aging time is 12-24 hours.

10. The method for preparing an iron-manganese composite oxide NH3-SCR catalyst according to claim 6, characterized in that, In step S4, the calcination activation conditions are: heating to 450-600℃ at a heating rate of 1-5℃ / min, and maintaining this temperature for 4-8 hours.

Images