Aerogel-derived ultralow-temperature water-sulfur poisoning-resistant flue gas denitration catalyst and preparation method thereof

Abstract

The invention relates to an aerogel-derived ultralow-temperature water-sulfur poisoning-resistant flue gas denitration catalyst and a preparation method thereof, and belongs to the technical field of air pollution control and environment catalytic material frontier. CeMnNiOx composite oxide is used as an active component of the catalyst, a catalyst precursor gel with a three-dimensional network structure is formed through a sol-gel method, and then the hydrophobic aerogel derivative denitration catalyst with a high specific surface area, low density and a three-dimensional porous structure is obtained through aging, freeze drying and high-temperature heat treatment. The denitration efficiency of the catalyst can reach 90% or above at the temperature of 80-270 DEG C in a complex atmosphere containing 5-10% of water vapor and 50-100 ppm of SO2. The method is suitable for deep purification of NOx in ultralow-temperature and high-humidity SO2-containing complex flue gas after industrial desulfurization and dust removal.

Description

Technical Field

[0001] This invention belongs to the cutting-edge technology field of air pollution control and environmental catalytic materials, specifically relating to an aerogel-derived ultra-low temperature resistant flue gas denitrification catalyst resistant to water-sulfur poisoning and its preparation method, applicable to the denitrification of NO in complex ultra-low temperature flue gas after industrial desulfurization and dust removal. x Deep purification. Background Technology

[0002] NO x It is the formation of PM 2.5 NO is an important precursor to ozone and a key area for air pollution control. x Ultra-low emissions have become a rigid requirement for achieving green and high-quality industrial development. The key to their control lies in the use of ammonia selective catalytic reduction (NH3-SCR) denitrification catalysts. Ultra-low emissions of dust and SO2 have already been achieved in industry. Ultra-low temperature flue gas denitrification after desulfurization and dust removal has become a current focus for industrial NOx control. x The widespread need for in-depth treatment. Currently, the main industrial method used is post-heated SCR denitrification, which is energy-intensive and does not meet the requirements of the "dual carbon" strategy. Therefore, the development of ultra-low temperature resistant denitrification catalysts for complex flue gas NO2 in industrial desulfurization and dust removal has become a priority. x The significant need for in-depth governance.

[0003] Domestic and international scholars have conducted extensive research on low-temperature denitration catalysts, achieving certain research progress. Patent CN119633837A provides a manganese-based multi-element ultra-low temperature denitration catalyst, its preparation method, and its applications. This catalyst has abundant pores, a large specific surface area, and uniform dispersion of active materials and auxiliary elements, exhibiting excellent ultra-low temperature catalytic activity. However, its resistance to water and sulfur is poor, and its stability is inadequate. Patent CN114887618A provides a method for using hydrotalcite-derived MgAlO4. x MnO was supported on a composite oxide substrate. x This highly efficient ultra-low temperature denitrification catalyst uses inexpensive and readily available raw materials, operates under mild conditions, and has a simple preparation process. Furthermore, the catalyst possesses a high specific surface area and adsorption capacity, resulting in a high degree of dispersion of the active components. It can efficiently remove NO at low temperatures. x However, the problem of sulfur resistance and the problem of multivalent state synergy and oxygen vacancy-enhanced redox capacity have not yet been solved.

[0004] Existing low-temperature denitrification catalysts have achieved significant breakthroughs in ultra-low temperature denitrification activity below 150℃; however, the problem of resistance to water sulfur poisoning at ultra-low temperatures remains unresolved and is still a global challenge in the field of flue gas denitrification. Given that aerogels possess a three-dimensional network arrangement, a highly porous structure, and a large surface area (500–1200 m²), [further research is needed]. 2With advantages such as high porosity (80–99.8%), tunable surface chemistry, and the ability to be processed into various shapes and sizes, aerogel-derived ultra-low temperature CeMnNiO has not yet been found. x Research on composite oxide catalysts. To this end, this patent creatively utilizes the sol-gel technology, which offers mild reaction conditions, controllable structure, and simple operation, combined with aging, freeze-drying, and high-temperature heat treatment processes, to prepare a porous, uniformly dispersed, and lightweight aerogel-derived ultra-low temperature denitrification catalyst, significantly improving the efficient utilization of catalyst components and resistance to water and sulfur poisoning. Summary of the Invention

[0005] This invention addresses the widespread need for denitrification of complex SO2-containing flue gas after industrial desulfurization and dust removal at ultra-low temperatures. It creatively develops an aerogel-derived ultra-low temperature, water-sulfur poisoning-resistant flue gas denitrification catalyst, overcoming the bottleneck of existing low-temperature denitrification catalysts' limited applicability. Another objective of this invention is to provide a method for preparing the aforementioned catalyst. A further objective is to provide applications for the catalyst, aiming to address the issue of NO2 in industrial flue gas in my country. x It provides feasible key technical support for ultra-low temperature and ultra-clean treatment.

[0006] The technical solution of this invention is: an aerogel-derived ultra-low temperature flue gas denitrification catalyst resistant to water-sulfur poisoning, characterized in that: the catalyst is CeMnNiO x The composite oxide is used as the active component. A hydrophobic aerogel-derived denitration catalyst with a three-dimensional porous structure is formed through a sol-gel method combined with aging, freeze-drying, and high-temperature heat treatment. The catalyst has a specific surface area of ​​200–350 m². 2 / g, with a pore size distribution of 20–50 nm; the CeMnNiO x The molar ratio of Ce, Mn and Ni in the active components is 1:(5~8):(0.1~0.5).

[0007] The present invention also provides a method for preparing the above-mentioned catalyst, the specific steps of which are as follows:

[0008] (1) Weigh the soluble cerium salt, manganese salt and nickel salt according to the molar ratio of Ce, Mn and Ni as 1:(5~8):(0.1~0.5), dissolve them in an ethanol aqueous solution, stir evenly, and prepare a mixed solution for later use.

[0009] (2) Add stabilizer and dispersant to the mixed solution in step (1), and add gel initiator dropwise to form wet gel, wherein the volume of stabilizer accounts for 10-25% of the volume of mixed solution, the volume of dispersant accounts for 5-10% of the volume of mixed solution, and the volume of gel initiator accounts for 5-10% of the volume of mixed solution.

[0010] (3) Immerse the wet gel obtained in step (2) in a mixed solution of hydrophobic agent and ethanol. Replace the residual water with ethanol to allow the hydrophobic agent to penetrate evenly into the gel pores. Then place it in a water bath for aging to promote the condensation reaction between the hydrophobic agent and the hydroxyl groups on the gel surface, forming a chemically bonded hydrophobic layer, and obtain the hydrophobic modified gel.

[0011] (4) The hydrophobic modified gel obtained in step (3) is freeze-dried in a freeze dryer, and then treated in air at a temperature of 2–5 °C / min to 400–500 °C for 2–4 hours to obtain an aerogel-derived denitration catalyst. The hydrophobic agent is transformed into a stable structure during high-temperature heat treatment, ultimately yielding CeMnNiO with high specific surface area and strong hydrophobicity. x Composite oxide aerogel-derived catalyst.

[0012] In preferred step (1), the soluble cerium salt, manganese salt, and nickel salt are soluble nitrates, acetates, or sulfates.

[0013] The volume concentration of the ethanol aqueous solution in step (1) is preferably 30% to 60%.

[0014] In preferred step (2), the stabilizer is formamide; the dispersant is polyethylene glycol 400; and the gel initiator is propylene oxide.

[0015] In preferred step (3), the hydrophobic agent is polydimethylsiloxane; the mass of the hydrophobic agent in the mixed solution of the hydrophobic agent and ethanol accounts for 2-5% of the mass of the mixed solution.

[0016] In the preferred step (3), the aging temperature is 40–80°C and the aging time is 3–5 days.

[0017] In preferred step (3), the freeze-drying temperature is -20 to 0°C, and the freeze-drying time is 18 to 24 hours.

[0018] This invention also provides the above-mentioned ultra-low temperature resistant sulfur-poisoning flue gas denitrification catalyst for use in industrial desulfurization and dust removal of complex flue gas containing SO2 at ultra-low temperature and high humidity. x Applications in deep purification.

[0019] The denitrification performance evaluation method of the catalyst of this invention:

[0020] Simulated flue gas composition, NO x The inlet gas concentration was 1000 ppm, the NH3 inlet concentration was 1000 ppm, the O2 content was 10%, the H2O content was 5 vol.% (added during use), and the SO2 content was 50–100 ppm (added during use), with N2 as the balance gas. The reaction space velocity (GHSV) was set to 50,000 h⁻¹, and the reaction temperature range was set to 60–300 °C. A flue gas analyzer was used to monitor NO levels before and after the reaction online. x The concentration change.

[0021]

[0022] Beneficial effects:

[0023] This invention utilizes aerogel derivatization technology to prepare catalysts with hierarchical porous structures, achieving NO reduction within the temperature range of 80–270 °C. x This highly efficient catalytic reduction catalyst maintains a stable denitrification efficiency of over 90%, achieving a breakthrough by solving the performance degradation problem of traditional catalysts in high-humidity, sulfur-containing flue gas. Under simulated real-world conditions with 5–10% water vapor and 50–100 ppm SO2, the catalyst exhibits excellent resistance to water-sulfur poisoning. This performance advantage allows the system to be deployed directly after the desulfurization and dust removal process, achieving NO reduction without additional heating. x This technology achieves deep purification, reducing heat energy consumption by over 40% compared to commercially available low-temperature catalysts. It is a method for removing NO from industrial flue gas after desulfurization and dust removal. x Ultra-low temperature and ultra-clean treatment provides key technical support and is particularly suitable for ultra-low temperature flue gas denitrification treatment in non-power industries such as steel and cement. It has significant environmental and economic benefits and engineering application value. Attached Figure Description

[0024] Figure 1 The aerogel-derived ultra-low temperature water-sulfur poisoning resistant flue gas denitrification catalyst NH3-SCR for NO removal prepared in Examples 1-6 of this invention x Efficiency diagram;

[0025] Figure 2 The aerogel-derived ultra-low temperature water-sulfur poisoning resistant flue gas denitrification catalyst NH3-SCR for NO removal prepared in Examples 7-10 of this invention. x Efficiency diagram;

[0026] Figure 3 The graph shows the long-term stability test curves of the catalysts prepared in Example 2 and Comparative Example 1 of this invention against water-sulfur denitrification at 120°C. Detailed Implementation

[0027] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto.

[0028] The following examples illustrate the method for evaluating the denitrification performance of catalysts:

[0029] Simulated flue gas composition, NO xThe inlet gas concentration was 1000 ppm, the NH3 inlet concentration was 1000 ppm, the O2 content was 10%, the H2O content was 5 vol.% (added during use), and the SO2 content was 50–100 ppm (added during use), with N2 as the balance gas. The reaction space velocity (GHSV) was set to 50,000 h⁻¹, and the reaction temperature range was set to 60–300 °C. A flue gas analyzer was used to monitor NO levels before and after the reaction online. x The concentration change.

[0030]

[0031] Example 1

[0032] (1) Preparation of precursor solution

[0033] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.1, dissolve them in an ethanol aqueous solution with a volume concentration of 60%, and stir to form a homogeneous mixed solution.

[0034] (2) Sol-gel process

[0035] Formamide as a stabilizer and polyethylene glycol 400 as a dispersant were added to the mixed solution. After stirring evenly, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer accounted for 10% of the volume of the mixed solution, the volume of the dispersant accounted for 10% of the volume of the mixed solution, and the volume of propylene oxide accounted for 5% of the volume of the mixed solution. The wet gel was immersed in a mixed solution of 3% polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate evenly into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 5 days to strengthen the three-dimensional network structure.

[0036] (3) Freeze drying and calcination

[0037] The aged gel was freeze-dried at -20°C for 18 hours in a freeze dryer to obtain a low-density aerogel. The aerogel was then heated to 450°C (air atmosphere, 2°C / min) in a muffle furnace and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 235 m². 2 / g, pore size is 45nm.

[0038] (4) Denitrification rate test

[0039] The simulated flue gas composition and the measured results are as follows: Figure 1 The denitrification rate of Example 1 shown is >90% in the range of 145-265℃, and the denitrification efficiency is 100% in the range of 180-240℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 92% for 12 hours.

[0040] Example 2

[0041] (1) Preparation of precursor solution

[0042] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.3, dissolve them in an alcohol-water solution with a volume concentration of 60%, and stir to form a homogeneous mixed solution;

[0043] (2) Sol-gel process

[0044] Formamide as a stabilizer and polyethylene glycol 400 as a dispersant were added to the mixed solution. After stirring evenly, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer accounted for 15% of the volume of the mixed solution, the volume of the dispersant accounted for 10% of the volume of the mixed solution, and the volume of propylene oxide accounted for 8% of the volume of the mixed solution. The wet gel was immersed in a mixed solution of 5% polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate evenly into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 5 days to strengthen the three-dimensional network structure.

[0045] (3) Freeze drying and calcination

[0046] The aged gel was freeze-dried at 0°C for 24 hours to obtain a low-density aerogel. The aerogel was then heated to 450°C (air atmosphere, 2°C / min) in a muffle furnace and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 300 m². 2 / g, pore size is 50nm.

[0047] (4) Denitrification rate test

[0048] The simulated flue gas composition and the measured results are as follows: Figure 1 As shown, Example 2 exhibits a denitrification rate >90% within the temperature range of 80–270℃, and a denitrification efficiency of 100% within the temperature range of 150–245℃. Its 12-hour resistance to water and sulfur is as follows: Figure 3 As shown, it can maintain a denitrification activity of over 98%.

[0049] Example 3

[0050] (1) Preparation of precursor solution

[0051] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.5, dissolve them in an alcohol-water solution with a volume concentration of 60%, and stir to form a homogeneous mixed solution;

[0052] (2) Sol-gel process

[0053] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer, dispersant, and propylene oxide was 25% and 10% of the mixed solution, respectively. The wet gel was then immersed in a mixed solution of 2% polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate uniformly into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 5 days to strengthen the three-dimensional network structure.

[0054] (3) Freeze drying and calcination

[0055] The aged gel was freeze-dried at -10°C for 20 hours to obtain a low-density aerogel. The aerogel was then heated to 450°C (air atmosphere, 2°C / min) in a muffle furnace and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 240 m². 2 / g, pore size is 40nm.

[0056] (4) Denitrification rate test

[0057] The simulated flue gas composition and the measured results are as follows: Figure 1 As shown, Example 3 has a denitrification rate of >90% in the range of 145-265℃ and a denitrification efficiency of 100% in the range of 180-240℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 90% for 12 hours.

[0058] Example 4

[0059] (1) Preparation of precursor solution

[0060] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:5:0.3, dissolve them in an alcohol-water solution with a volume concentration of 50%, and stir to form a homogeneous mixed solution;

[0061] (2) Sol-gel process

[0062] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer, dispersant, and propylene oxide constituted 10% and 5% of the mixed solution, respectively. The wet gel was then immersed in a 5% (w / w) mixed solution of polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate uniformly into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 4 days to strengthen the three-dimensional network structure.

[0063] (3) Freeze drying and calcination

[0064] The aged gel was freeze-dried at -10°C for 22 hours to obtain a low-density aerogel. The aerogel was then heated to 450°C (air atmosphere, 3°C / min) in a muffle furnace and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 200 m². 2 / g, pore size is 50nm.

[0065] (4) Denitrification rate test

[0066] The simulated flue gas composition and the measured results are as follows: Figure 1 As shown, Example 4 has a denitrification rate of >90% in the range of 120-270℃ and a denitrification efficiency of 100% in the range of 150-240℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 95% for 12 hours.

[0067] Example 5

[0068] (1) Preparation of precursor solution

[0069] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:8:0.3, dissolve them in an alcohol-water solution with a volume concentration of 30%, and stir to form a homogeneous mixed solution;

[0070] (2) Sol-gel process

[0071] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer accounted for 10% of the mixed solution volume, the volume of the dispersant accounted for 5% of the mixed solution volume, and the volume of propylene oxide accounted for 10% of the mixed solution volume. The wet gel was then placed in a mixed solution of 4% polydimethylsiloxane and ethanol. The residual water was replaced with ethanol, allowing the hydrophobic agent to uniformly penetrate into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 4 days to strengthen the three-dimensional network structure.

[0072] (3) Freeze drying and calcination

[0073] The aged gel was freeze-dried at -20°C for 24 hours to obtain a low-density aerogel. The aerogel was then heated to 450°C (air atmosphere, 3°C / min) in a muffle furnace and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 260 m². 2 / g, with a pore size of 42nm.

[0074] (4) Denitrification rate test

[0075] The simulated flue gas composition and the measured results are as follows: Figure 1As shown, Example 5 has a denitrification rate of >90% in the range of 85-240℃ and a denitrification efficiency of 100% in the range of 180-225℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 93% for 12 hours.

[0076] Example 6

[0077] (1) Preparation of precursor solution

[0078] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.3, dissolve them in an alcohol-water solution with a volume concentration of 60%, and stir to form a homogeneous mixed solution;

[0079] (2) Sol-gel process

[0080] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer accounted for 15% of the mixed solution volume, the volume of the dispersant accounted for 10% of the mixed solution volume, and the volume of propylene oxide accounted for 8% of the mixed solution volume. The wet gel was then immersed in a mixed solution of 3% polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate uniformly into the gel pores. The wet gel was then transferred to a mold and aged in a 40°C water bath for 3 days to strengthen the three-dimensional network structure.

[0081] (3) Freeze drying and calcination

[0082] The aged gel was freeze-dried at 0°C for 18 hours in a freeze dryer to obtain a low-density aerogel. The aerogel was then heated to 450°C (air atmosphere, 2°C / min) in a muffle furnace and held for 2 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 220 m². 2 / g, pore size is 35nm.

[0083] (4) Denitrification rate test

[0084] The simulated flue gas composition was measured, and the results are as follows: Figure 1 As shown, Example 6 has a denitrification rate of >90% in the range of 150-250℃ and a denitrification efficiency of 100% in the range of 180-240℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 90% for 12 hours.

[0085] Example 7

[0086] (1) Preparation of precursor solution

[0087] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.3, dissolve them in an alcohol-water solution with a volume concentration of 60%, and stir to form a homogeneous mixed solution;

[0088] (2) Sol-gel process

[0089] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer, dispersant, and propylene oxide constituted 10% and 5% of the mixed solution, respectively. The wet gel was then immersed in a 3% (w / w) mixed solution of polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate uniformly into the gel pores. The wet gel was then transferred to a mold and aged in an 80°C water bath for 5 days to strengthen the three-dimensional network structure.

[0090] (3) Freeze drying and calcination

[0091] The aged gel was freeze-dried at 0°C for 24 hours to obtain a low-density aerogel. The aerogel was then heated to 450°C (air atmosphere, 5°C / min) in a muffle furnace and held for 4 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 200 m². 2 / g, pore size is 45nm.

[0092] (4) Denitrification rate test

[0093] The simulated flue gas composition was measured, and the results are as follows: Figure 2 As shown, Example 7 has a denitrification rate of >90% in the range of 120-240℃ and a denitrification efficiency of 100% in the range of 180-240℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 94% for 12 hours.

[0094] Example 8

[0095] (1) Preparation of precursor solution

[0096] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.3, dissolve them in a 60% ethanol aqueous solution, and stir to form a homogeneous mixed solution;

[0097] (2) Sol-gel process

[0098] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer accounted for 25% of the mixed solution volume, the volume of the dispersant accounted for 10% of the mixed solution volume, and the volume of propylene oxide accounted for 5% of the mixed solution volume. The wet gel was immersed in a mixed solution of 3% polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate uniformly into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 5 days to strengthen the three-dimensional network structure.

[0099] (3) Freeze drying and calcination

[0100] The aged gel was freeze-dried at 0°C for 24 hours to obtain a low-density aerogel. The temperature was then programmed to 400°C (at air, 5°C / min) and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 350 m². 2 / g, pore size is 20nm.

[0101] (4) Denitrification rate test

[0102] The simulated flue gas composition was measured, and the results are as follows: Figure 2 As shown, Example 8 has a denitrification rate of >90% in the range of 90-270℃ and a denitrification efficiency of 100% in the range of 150-240℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 93% for 12 hours.

[0103] Example 9

[0104] (1) Preparation of precursor solution

[0105] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.3, dissolve them in a 60% ethanol aqueous solution, and stir to form a homogeneous mixed solution;

[0106] (2) Sol-gel process

[0107] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer, dispersant, and propylene oxide constituted 10% and 5% of the mixed solution, respectively. The wet gel was then immersed in a 3% (w / w) mixed solution of polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate uniformly into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 5 days to strengthen the three-dimensional network structure.

[0108] (3) Freeze drying and calcination

[0109] The aged gel was freeze-dried at 0°C for 24 hours to obtain a low-density aerogel. The temperature was then programmed to 500°C (at air, 2°C / min) and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 235 m². 2 / g, pore size is 45nm.

[0110] (4) Denitrification rate test

[0111] The simulated flue gas composition was measured, and the results are as follows: Figure 2 As shown, Example 9 has a denitrification rate of >90% in the range of 90-270℃ and a denitrification efficiency of 100% in the range of 150-240℃. It was also found that the water and sulfur resistance performance can maintain a denitrification activity of over 93% for 12 hours.

[0112] Example 10

[0113] (1) Preparation of precursor solution

[0114] Weigh out cerium nitrate, manganese acetate, and nickel acetate according to Ce / Mn / Ni = 1:7:0.1, dissolve them in a 60% ethanol aqueous solution, and stir to form a homogeneous mixed solution;

[0115] (2) Sol-gel process

[0116] Formamide was added as a stabilizer and polyethylene glycol 400 as a dispersant to a mixed solution. After stirring until homogeneous, propylene oxide was added dropwise as a gel initiator to form a wet gel. The volume of the stabilizer, dispersant, and propylene oxide constituted 10% and 5% of the mixed solution, respectively. The wet gel was then immersed in a 3% (w / w) mixed solution of polydimethylsiloxane and ethanol. The residual water was replaced by ethanol, allowing the hydrophobic agent to penetrate uniformly into the gel pores. The wet gel was then transferred to a mold and aged in a 60°C water bath for 5 days to strengthen the three-dimensional network structure.

[0117] (3) Freeze drying and calcination

[0118] The aged gel was freeze-dried at 0°C for 24 hours to obtain a low-density aerogel. The temperature was then programmed to 450°C (at air, 2°C / min) and held for 3 hours to decompose nitrates into oxides and simultaneously create stable oxygen vacancies. The measured surface area was 280 m². 2 / g, with a pore size of 38nm.

[0119] (4) Denitrification rate test

[0120] The simulated flue gas composition was measured, and the results are as follows: Figure 2 As shown, Example 10 has a denitrification rate of >90% in the range of 90-270℃, a denitrification efficiency of 100% in the range of 150-240℃, and its water and sulfur resistance performance can be maintained at over 95% of denitrification activity after 12 hours.

[0121] Comparative Example 1

[0122] (1) Preparation of precursor solution

[0123] Weigh out cerium nitrate, manganese nitrate, and nickel nitrate according to Ce / Mn / Ni = 1:7:0.3, dissolve them in a mixed solution of 10 ml glycerol and 60 ml isopropanol, and stir thoroughly to obtain an active component precursor solution.

[0124] (2) Preparation of cerium manganese nickel composite oxide catalyst

[0125] The solution obtained in step (1) was transferred to a 100 ml reactor and hydrothermally reacted at 180 °C for 12 h. The precipitate was then collected by centrifugation (10000 rpm, 2 min) and washed with deionized water and anhydrous ethanol. The resulting sample was then vacuum dried at 80 °C for 12 h and calcined at 450 °C for 3 h to obtain a cerium-manganese-nickel composite oxide catalyst with a measured surface area of ​​71 m². 2 / g, with a pore size of 25nm. Catalysts with a particle size of 40-60 mesh were sieved for denitrification performance testing;

[0126] (3) Denitrification rate test

[0127] The simulated flue gas composition was measured, and the results are as follows: Figure 2 As shown, Comparative Example 1 exhibits a denitrification rate >90% in the temperature range of 90–270℃ and a denitrification efficiency of 100% in the temperature range of 150–240℃. Its 12-hour resistance to water and sulfur is as follows: Figure 3 As shown, the catalyst can maintain a denitrification activity of over 80%.

Claims

1. An aerogel-derived ultra-low temperature flue gas denitrification catalyst resistant to water-sulfur poisoning, characterized in that: The catalyst is CeMnNiO x The composite oxide is used as the active component. A hydrophobic aerogel-derived denitration catalyst with a three-dimensional porous structure is formed through a sol-gel method combined with aging, freeze-drying, and high-temperature heat treatment. The catalyst has a specific surface area of ​​200–350 m². 2 / g, with a pore size distribution of 20–50 nm; the CeMnNiO x The molar ratio of Ce, Mn and Ni in the active components is 1:(5~8):(0.1~0.5).

2. A method for preparing the catalyst as described in claim 1, comprising the following specific steps: (1) Weigh the soluble cerium salt, manganese salt and nickel salt according to the molar ratio of Ce, Mn and Ni as 1:(5~8):(0.1~0.5), dissolve them in an ethanol aqueous solution, stir evenly, and prepare a mixed solution for later use. (2) Add stabilizer and dispersant to the mixed solution in step (1), and add gel initiator dropwise to form wet gel, wherein the volume of stabilizer accounts for 10-25% of the volume of mixed solution, the volume of dispersant accounts for 5-10% of the volume of mixed solution, and the volume of gel initiator accounts for 5-10% of the volume of mixed solution. (3) Immerse the wet gel obtained in step (2) in a mixed solution of hydrophobic agent and ethanol. Replace the residual water with ethanol to allow the hydrophobic agent to penetrate evenly into the gel pores. Then age it in a water bath to obtain a hydrophobic modified gel. (4) The hydrophobic modified gel obtained in step (3) is freeze-dried in a freeze dryer, and then treated in an air atmosphere at a temperature of 2-5℃ / min to 400-500℃ for 2-4 hours to obtain an aerogel-derived denitrification catalyst.

3. The method according to claim 2, characterized in that: In step (1), the soluble cerium salt, manganese salt, and nickel salt are soluble nitrates, acetates, or sulfates.

4. The method according to claim 2, characterized in that: In step (1), the volume concentration of the ethanol aqueous solution is 30% to 60%.

5. The method according to claim 2, characterized in that: In step (2), the stabilizer is formamide; the dispersant is polyethylene glycol 400; and the gel initiator is propylene oxide.

6. The method according to claim 2, characterized in that: In step (3), the hydrophobic agent is polydimethylsiloxane; the mass of the hydrophobic agent in the mixed solution of hydrophobic agent and ethanol accounts for 2-5% of the mass of the mixed solution.

7. The method according to claim 2, characterized in that: In step (3), the aging temperature is 40–80℃ and the aging time is 3–5 days.

8. The method according to claim 2, characterized in that: In step (3), the freeze-drying temperature is -20 to 0°C, and the freeze-drying time is 18 to 24 hours.

9. A low-temperature resistant flue gas denitrification catalyst as described in claim 1, applied to complex flue gas containing SO2 at low temperatures and high humidity after industrial desulfurization and dust removal. x Applications in deep purification.

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