A method for preparing a composite nanostructured manganese zirconium vanadate denitration catalyst

Abstract

This invention relates to a method for preparing a composite nanostructured manganese zirconium vanadate denitrification catalyst, belonging to the field of industrial flue gas denitrification. The catalyst's nanostructure comprises two or more composite nanostructures, including hollow microspheres, layered structures, granular structures of manganese vanadate, and amorphous manganese, vanadium, and zirconium composite oxides. The main component of the catalyst includes MnO. x , V2O5, MnV2O6, Mn2V2O7, ZrO2, Zr x Mn 1‑x V2O7 and Zr x Mn 1‑x One or more V₂O₆ solid solutions, wherein the atomic molar ratio (x) of metallic zirconium and metallic manganese is 0.4–2, and the atomic molar ratio (y) of metallic manganese and metallic vanadium is 0.5–2. The preparation method employs a stepwise hydrothermal approach, which is simple and low-cost. The composite nanostructure synthesized by this method combines the advantages of manganese-based and vanadium-based catalysts, extending the catalyst's operating temperature to low temperatures, achieving NO production at 150–375℃. x It has a conversion rate of not less than 80%, an N2 selectivity of not less than 95%, and excellent resistance to H2O and SO2 poisoning as well as high thermal stability.

Description

Technical Field

[0001] This invention belongs to the field of flue gas denitrification technology, specifically relating to a method for preparing a composite nanostructured manganese zirconium vanadate denitrification catalyst. Background Technology

[0002] Nitrogen oxides (NO) x Nitrogen oxides, primarily including NO, NO2, and N2O, are the leading air pollutants in my country. Selective catalytic reduction (SCR) is one of the most efficient technologies for removing nitrogen oxides, and the catalyst is the core of SCR technology. Currently, the most widely used commercial denitrification catalyst is the V2O5 / WO3(MoO3) / TiO2 catalyst, which exhibits good denitrification efficiency and selectivity at 300–420℃. However, vanadium-based catalysts still have the following drawbacks: high operating temperature, narrow operating window, easy sublimation and instability of the active component V2O5, and short catalyst life due to high concentrations of dust and heavy metals in high-temperature flue gas, which limits their application.

[0003] Manganese-based catalysts exhibit good low-temperature activity; however, they suffer from poor resistance to SO2 poisoning and low N2 selectivity. Patent (CN115041162 A) discloses a low-temperature denitration catalyst supported on ZrO2 with Mn, Fe, Ce, and Ho. This catalyst shows good denitration activity at 180℃; however, it lacks good resistance to SO2 poisoning, and its N2 selectivity is unknown. In recent years, metal vanadate catalysts have attracted considerable attention due to their good thermal stability, denitration performance, and resistance to SO2 and H2O poisoning. However, vanadate catalysts have high activation temperatures and low denitration efficiency at low temperatures. Patent (CN 103316685A) discloses a low-dimensional nanostructured ferric vanadate denitration catalyst, which exhibits excellent activity, selectivity, thermal stability, and resistance to SO2 poisoning at medium and high temperatures. However, its denitration activity is poor at low temperatures, and the melting point of manganese vanadate (1030℃) is much higher than that of ferric vanadate (850℃) and the melting point of component V2O5 (690℃). Therefore, nanostructures based on vanadates warrant further investigation.

[0004] Manganese-based catalysts exhibit good low-temperature activity, while vanadium-based catalysts demonstrate good sulfur resistance. Composite nanostructures can combine the advantages of both manganese-based and vanadium-based catalysts. The nanostructure morphology of vanadate denitration catalysts has a significant impact on catalytic activity. Hollow microspheres provide a larger specific surface area, offering more active and adsorption sites for the catalytic reaction. Layered nanostructures, due to crystal anisotropy, exhibit different surface energies and chemical coordination states across different crystal faces, resulting in varying physicochemical properties. Amorphous composite oxides possess abundant free oxygen vacancies and active sites. These structural characteristics have a crucial influence on the activity, selectivity, and sulfur poisoning resistance of the catalytic reaction. Therefore, based on structure-activity relationships, it is necessary to construct a composite nanostructure manganese-zirconium vanadate denitration catalyst with both structural and component advantages. By introducing the transition metal zirconium, the nanostructure morphology of manganese vanadate can be further modified to leverage its structural and component advantages, broaden its low-temperature activity, and improve its sulfur and water poisoning resistance. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a composite nanostructured manganese zirconium vanadate denitration catalyst and its preparation method. This preparation method employs an improved stepwise hydrothermal process, and the resulting composite nanostructure combines the advantages of manganese-based catalysts, vanadium-based catalysts, and composite nanostructures. The catalyst prepared by this invention exhibits excellent low-to-medium temperature denitration performance, selectivity, thermal stability, and good resistance to sulfur and water poisoning.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a composite nanostructured manganese zirconate denitration catalyst includes the following steps:

[0008] (1) Dissolve the manganese precursor salt, soluble vanadium salt and auxiliary agent in water respectively, and then mix them according to the ratio;

[0009] (2) Soluble zirconium salt is dissolved in water and then mixed with the heterogeneous mixture containing manganese and vanadium obtained in step (1) according to the ratio. Then, a precipitant is added to adjust the pH value and the mixture is thoroughly mixed.

[0010] (3) The heterogeneous mixture containing manganese, vanadium and zirconium obtained in step (2) is transferred to a polytetrafluoroethylene-lined reactor and subjected to a stepwise hydrothermal reaction to obtain a precipitated mixture containing manganese, vanadium and zirconium;

[0011] (4) The precipitate mixture obtained in step (3) is washed, dried and calcined to obtain a nanostructured manganese zirconium vanadate denitration catalyst.

[0012] The stepwise mixing process allows vanadium to preferentially combine with manganese, and then with zirconium, thus preventing the manganese component from being poisoned and deactivated by contact with sulfur dioxide during the catalytic reaction.

[0013] Further, the manganese precursor salt in step (1) is one or more of manganese nitrate, manganese acetate, and manganese carbonate;

[0014] The soluble vanadium salt is one or more of ammonium metavanadate and vanadium oxyacetate;

[0015] The auxiliary agent is one or more of ethylene glycol, polyvinylpyrrolidone, and hexamethylenetetramine. Ethylene glycol and hexamethylenetetramine are beneficial for forming hollow microspheres and particulate structures, while polyvinylpyrrolidone is beneficial for forming layered structures.

[0016] Further, the soluble zirconium salt in step (2) is one or more of zirconium nitrate, zirconium acetate, and zirconium carbonate; the precipitant is one or two of ammonia and urea. The precipitant adjusts the pH, which can control the amount of amorphous composite oxide generated.

[0017] Furthermore, in step (4), the washing agent is one or both of ethanol and deionized water.

[0018] Furthermore, the composite nanostructured manganese zirconium vanadate denitration catalyst synthesized by this method comprises two or more composite nanostructures, including hollow microspheres, layered structures, granular structures of manganese vanadate, and amorphous manganese, vanadium, and zirconium composite oxides. The components include MnO. x , V2O5, MnV2O6, Mn2V2O7, ZrO2, Zr x Mn 1-x V2O7 and Zr x Mn 1-x One or more V₂O₆ solid solutions. Among them, the oxide MnO x V2O5 and ZrO2 account for 0.1 to 0.7%, and the rest are manganese vanadate and zirconium manganese vanadate solid solutions.

[0019] The amorphous composite oxide structure in the composite nanostructure has a higher specific surface area, more abundant chemically adsorbed oxygen, and stronger redox properties, which is beneficial to improving low-temperature activity. The hollow microspheres, layered structures, and granular structures of manganese vanadate in the composite nanostructure have better stability. Due to the anisotropy of the crystal planes, the surface and chemical coordination states of different crystal planes are different, resulting in differences in surface physicochemical properties. Based on the structure-activity relationship, the N2 selectivity is improved, and the adsorption of SO2 active sites is inhibited, thus giving it good anti-sulfur poisoning performance.

[0020] Furthermore, in the manganese precursor salt, vanadium salt, and zirconium salt, the atomic molar ratio (x) of metallic zirconium and metallic manganese is 0.4–2, the atomic molar ratio (y) of metallic manganese and metallic vanadium is 0.5–2, the concentration of the auxiliary agent is 0.1–0.3 mmol / L, and the pH is 5–8. The precipitant is one or both of ammonia and urea; adjusting the pH with the precipitant controls the amount of amorphous composite oxides generated.

[0021] Further, in step (3), the stepwise hydrothermal reaction is carried out as follows: the first step hydrothermal reaction temperature is 90-110°C and the hydrothermal time is 6-12h; the second step hydrothermal reaction temperature is 120-180°C and the hydrothermal reaction time is 6-12h; the drying temperature is 85-110°C and the drying time is 2-8h; the calcination atmosphere is air or nitrogen, the calcination temperature is 400-550°C and the calcination time is 2-6h.

[0022] The first step of the hydrothermal reaction process involves sufficient aging, which promotes the formation of amorphous composite precipitates; the second step of the hydrothermal reaction process forms composite nanostructures.

[0023] Based on the first hydrothermal process, the two-step hydrothermal process enables the catalyst to exhibit a more stable manganese vanadate nanostructure.

[0024] The beneficial effects of this invention are:

[0025] (1) The composite nanostructured manganese zirconium vanadate denitration catalyst provided by the present invention adopts an improved stepwise hydrothermal method. The synthesized composite nanostructure combines the advantages of manganese-based catalysts, vanadium-based catalysts and composite nanostructures. The catalyst achieves excellent low-temperature activity and has good anti-sulfur poisoning performance. The composite nanostructure improves the N2 stability of the catalyst and improves both low-temperature activity and anti-sulfur poisoning performance.

[0026] (2) The preparation method of the composite nanostructured manganese zirconium vanadate denitration catalyst provided by the present invention allows vanadium to preferentially combine with manganese in a stepwise mixing process, and then allows vanadium zirconium to coat the manganese component, effectively blocking the poisoning effect of sulfur dioxide on the manganese component, thereby extending the catalyst life.

[0027] (3) The preparation method of the composite nanostructured manganese zirconium vanadate denitration catalyst provided by the present invention forms a dual-function composite nanostructure in a two-step hydrothermal process, including an amorphous composite oxide structure with higher low-temperature activity and a manganese vanadate structure with good stability and sulfur resistance. Based on the structure-activity relationship, the low-temperature denitration performance, stability and sulfur poisoning resistance of the catalyst are improved.

[0028] (4) The preparation method of the composite nanostructured manganese zirconium vanadate denitration catalyst of the present invention has the advantages of short preparation process, wide operating window, good thermal stability and good resistance to sulfur and water poisoning, and is easy to industrialize and promote application. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the preparation method of a composite nanostructured manganese zirconium vanadate denitration catalyst in an embodiment of the present invention.

[0030] Figure 2 This is a SEM image of a composite nanostructured manganese zirconium vanadate denitration catalyst in an embodiment of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0032] Conversely, this invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of the invention as defined in the claims. Furthermore, to provide a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0033] Implementation Case 1

[0034] Manganese carbonate, ammonium metavanadate, and zirconium nitrate in a molar ratio of 1:0.5:2.5 were dissolved in water, and 0.3 mmol ethylene glycol solutions were prepared. All solutions except the zirconium nitrate solution were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 7, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 12 hours, followed by a further hydrothermal reaction at 160°C for 12 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 90°C for 6 hours, and then calcined at 500°C for 2 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 150–280°C, NO… x Conversion rate over 95%, N2 selectivity over 99%; for flue gas containing 50ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 93%.

[0035] Implementation Case 2

[0036] Manganese carbonate, ammonium metavanadate, and zirconium acetate in a molar ratio of 1:0.5:1.5 were dissolved in water, and then a 0.15 mmol ethylene glycol solution was prepared. The solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 6, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90℃ for 8 hours, followed by a further hydrothermal reaction at 160℃ for 8 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 85℃ for 8 hours, and then calcined at 500℃ for 2 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 150–300℃, NO… x Conversion rate over 95%, N2 selectivity over 95%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 90.0%.

[0037] Implementation Case 3

[0038] Manganese carbonate, vanadium oxyacetate, and zirconium acetate in a molar ratio of 1:0.5:1 were dissolved in water, and 0.1 mmol ethylene glycol solutions were prepared. These solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 7, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 100°C for 8 hours, followed by a hydrothermal reaction at 180°C for 6 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 90°C for 6 hours, and then calcined at 450°C for 3 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 180–300°C, NO… x Conversion rate over 92%, N2 selectivity over 95%; for flue gas containing 50ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 90.0%.

[0039] Implementation Case 4

[0040] Manganese acetate, vanadium oxyacetate, and zirconium acetate in a molar ratio of 1:0.5:0.5 were dissolved in water, and 0.1 mmol ethylene glycol solutions were prepared. These solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium acetate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 8, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 110°C for 6 hours, followed by hydrothermal reaction at 150°C for 10 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 95°C for 4 hours, and then calcined at 450°C for 4 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 180–300°C, NO… x Conversion rate over 90%, N2 selectivity over 90%; for flue gas containing 50ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 85%.

[0041] Implementation Case 5

[0042] Manganese nitrate, ammonium metavanadate, and zirconium nitrate in a molar ratio of 1:1:1.5 were dissolved in water separately, and then a 0.1 mmol solution of polyvinylpyrrolidone was prepared. The solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Urea was then added to adjust the pH to 7, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 6 hours, followed by a hydrothermal reaction at 180°C for 6 hours to obtain the reaction product. The precipitate was then washed once with ethanol, twice with water, dried at 100°C for 2 hours, and then calcined at 400°C for 6 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 200–350°C, NO… x Conversion rate over 95%, N2 selectivity over 95%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 92%.

[0043] Implementation Case 6

[0044] Manganese nitrate, ammonium metavanadate, and zirconium nitrate in a molar ratio of 1:1:1 were dissolved in water separately, and then a 0.1 mmol solution of polyvinylpyrrolidone was prepared. The solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 8, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 6 hours, followed by a further hydrothermal reaction at 160°C for 6 hours to obtain the reaction product. The precipitate was then washed once with ethanol, twice with water, dried at 100°C for 2 hours, and then calcined at 450°C for 3 hours to obtain a composite nanostructured manganese-zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 225–375°C, NO… x Conversion rate over 95%, N2 selectivity over 95%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 90%.

[0045] Implementation Case 7

[0046] Manganese carbonate, vanadium oxyacetate, and zirconium nitrate in a molar ratio of 1:0.5:2.5 were dissolved in water, and 0.1 mmol of ethylene glycol and 0.1 mmol of polyvinylpyrrolidone solution were prepared. These solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 8, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 8 hours, followed by hydrothermal reaction at 160°C for 12 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 110°C for 2 hours, and then calcined at 500°C for 2 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 150–325°C, NO… x Conversion rate over 90%, N2 selectivity over 98%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 92%.

[0047] Implementation Case 8

[0048] Manganese nitrate, vanadium oxyacetate, and zirconium nitrate in a molar ratio of 1:1:1.5 were dissolved in water, and 0.1 mmol solutions of ethylene glycol and polyvinylpyrrolidone were prepared. These solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 7, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 6 hours, followed by hydrothermal reaction at 160°C for 8 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 85°C for 6 hours, and then calcined at 500°C for 2 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 150–350°C, NO… x Conversion rate over 90%, N2 selectivity over 95%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 90%.

[0049] Implementation Case 9

[0050] Manganese nitrate, ammonium metavanadate, and zirconium nitrate in a molar ratio of 1:2:2.5 were dissolved in water separately, and a 0.2 mmol solution of hexamethylenetetramine was prepared. The solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Urea was added to adjust the pH to 5, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 110°C for 6 hours, followed by hydrothermal reaction at 150°C for 8 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 90°C for 6 hours, and then calcined at 550°C for 2 hours to obtain a composite nanostructured manganese-zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 225–375°C, NO… x Conversion rate over 90%, N2 selectivity over 99%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 85%.

[0051] Implementation Case 10

[0052] Manganese nitrate, ammonium metavanadate, and zirconium nitrate in a molar ratio of 1:2:1.5 were dissolved in water separately, and a 0.2 mmol solution of hexamethylenetetramine was prepared. The solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Urea was added to adjust the pH to 6, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 6 hours, followed by hydrothermal reaction at 150°C for 8 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 90°C for 6 hours, and then calcined at 500°C for 2 hours to obtain a composite nanostructured manganese-zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 225–350°C, NO… x Conversion rate over 95%, N2 selectivity over 95%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 90%.

[0053] Implementation Case 11

[0054] Manganese carbonate, ammonium metavanadate, and zirconium nitrate in a molar ratio of 1:0.5:1.5 were dissolved in water, and 0.1 mmol of ethylene glycol and 0.1 mmol of hexamethylenetetramine solution were prepared. These solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 8, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 6 hours, followed by a hydrothermal reaction at 180°C for 6 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 100°C for 2 hours, and then calcined at 500°C for 2 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 200–350°C, NO… x Conversion rate over 90%, N2 selectivity over 95%; for flue gas containing 100ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 90%.

[0055] Implementation Case 12

[0056] Manganese carbonate, ammonium metavanadate, and zirconium nitrate in a molar ratio of 1:1:2.5 were dissolved in water, and 0.1 mmol of ethylene glycol and 0.1 mmol of hexamethylenetetramine solution were prepared. These solutions (except for the zirconium nitrate solution) were mixed thoroughly to obtain a heterogeneous mixture containing manganese and vanadium. The zirconium nitrate solution was then added and mixed thoroughly. Ammonia was added to adjust the pH to 8, and the mixture was stirred thoroughly to obtain a heterogeneous mixture containing manganese, vanadium, and zirconium. This mixture was then transferred to a polytetrafluoroethylene-lined reactor and hydrothermally reacted at 90°C for 6 hours, followed by a hydrothermal reaction at 180°C for 6 hours to obtain the reaction product. The precipitate was then washed twice with ethanol and twice with water, dried at 100°C for 2 hours, and then calcined at 500°C for 2 hours to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst. This catalyst exhibits good denitration efficiency, selectivity, and resistance to SO2 and H2O poisoning. At 200–375°C, NO… x Conversion rate over 95%, N2 selectivity over 98%; for flue gas containing 50ppm SO2 and 2 vol.% H2O, NO x The conversion rate is over 92%.

Claims

1. A method for preparing a composite nanostructured manganese zirconium vanadate denitration catalyst, characterized in that, Includes the following steps: (1) The precursor salt of manganese, the soluble vanadium salt and the auxiliary agent are dissolved in water respectively, and then mixed according to the ratio; the auxiliary agent is selected from ethylene glycol, polyvinylpyrrolidone and hexamethylenetetramine; (2) Soluble zirconium salt is dissolved in water and then mixed with the heterogeneous mixture containing manganese and vanadium obtained in step (1) according to the ratio. Then, a precipitant is added to adjust the pH value and the mixture is thoroughly mixed. (3) The heterogeneous mixture containing manganese, vanadium and zirconium obtained in step (2) is transferred to a polytetrafluoroethylene-lined reactor and subjected to a stepwise hydrothermal reaction to obtain a precipitate mixture containing manganese, vanadium and zirconium; the stepwise hydrothermal reaction is carried out at a temperature of 90-110°C for 6-12 hours for the first step and at a temperature of 120-180°C for 6-12 hours for the second step. (4) The precipitate mixture obtained in step (3) is washed, dried, and calcined to obtain a composite nanostructured manganese zirconium vanadate denitration catalyst; the oxide MnO in the composite nanostructured manganese zirconium vanadate denitration catalyst... x V2O5 and ZrO2 account for 0.1 to 0.7%, and the rest are manganese vanadate and zirconium manganese vanadate solid solutions.

2. The preparation method of the composite nanostructured manganese zirconium vanadate denitration catalyst according to claim 1, characterized in that, The manganese precursor salt in step (1) is selected from manganese nitrate, manganese acetate, and manganese carbonate; The soluble vanadium salt is selected from ammonium metavanadate and vanadium oxyacetate.

3. The method for preparing a composite nanostructured manganese zirconium vanadate denitration catalyst according to claim 1, characterized in that, The soluble zirconium salt in step (2) is selected from zirconium nitrate and zirconium acetate; The precipitant is one or both of ammonia and urea.

4. The preparation method of the composite nanostructured manganese zirconium vanadate denitration catalyst according to claim 1, characterized in that, The washing process described in step (4) uses one or both of the following detergents: ethanol and deionized water.

5. The method for preparing a composite nanostructured manganese zirconium vanadate denitration catalyst according to claim 1, characterized in that, In step (4), the drying temperature is 85-110°C and the drying time is 2-8h; the calcination atmosphere is air or nitrogen, the calcination temperature is 400-550°C and the calcination time is 2-6h.

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