A low-temperature oxidation adsorbent and its flue gas NO X Deep removal process

Abstract

This invention relates to the field of air pollutant control and environmental protection materials technology, and discloses a low-temperature oxidation adsorbent and its application in flue gas NO. X The deep denitrification process utilizes a low-temperature oxidation adsorbent comprising an amino-functionalized micron-sized diatomite core layer and an aldehyde-functionalized nano-manganese-cerium composite oxide active shell layer. The core layer and the active shell layer are bonded by Schiff base covalent bonds formed by the condensation of amino and aldehyde groups, and C=N covalent bonds are formed at the interface between the two phases, constructing a micro-nano hierarchical composite material with integrated adsorption and catalysis functions. The micro-nano dual-scale rough structure on the surface of this material, along with the synergistic effect of low surface energy phenylsiloxane and diundecyl long-chain hydrophobic groups, endows the catalyst with excellent hydrophobic properties. Under harsh high humidity conditions of 100℃ and 10-20 vol% H2O, the catalyst can still maintain a denitrification rate of over 81%, and the activity loss rate is significantly lower than that of traditional physical mixed catalysts, effectively coping with fluctuations in industrial high-humidity desulfurization flue gas.

Description

Technical Field

[0001] This invention relates to the field of air pollutant control and environmental protection materials technology, and particularly to a low-temperature oxidation adsorbent and its application in flue gas NO. X Deep removal process. Background Technology

[0002] Currently, selective catalytic reduction (SCR) technology is widely used in industrial flue gas denitrification. The basic principle of this technology is to add a reducing agent (such as NH3, CO, H2, or hydrocarbons) to the flue gas under the action of a catalyst, selectively reducing nitrogen oxides to harmless nitrogen (N2) and water (H2O) in the presence of oxygen. Ammonia selective catalytic reduction (NH3-SCR) technology, using ammonia (NH3) as a reducing agent, has become the mainstream technology for stationary source nitrogen oxide emission control due to its high denitrification efficiency and good selectivity.

[0003] Currently, the most widely used SCR denitrification catalyst in commercial applications is the V2O5-WO3 / TiO2 system catalyst. This type of catalyst exhibits excellent catalytic activity within a temperature window of 300-400℃, achieving a denitrification efficiency of over 80%. It has been widely used in large-scale stationary source denitrification projects such as coal-fired power plants. For non-power industries (such as kilns in steel, glass, ceramics, and cement industries), the flue gas temperature is typically below 150℃. If traditional SCR technology is used, the flue gas needs to be reheated to reach the catalyst's optimal operating temperature, which significantly increases operating costs and is economically infeasible.

[0004] Manganese-based catalysts are characterized by having multiple variable valence states (Mn). 2+ Mn 3+ Mn 4+ Cerium-based catalysts readily undergo redox reactions and exhibit excellent catalytic activity at low temperatures, making them highly promising low-temperature SCR catalysts. Cerium-based catalysts, on the other hand, are valued for their excellent oxygen storage and release capabilities (Ce). 4+ / Ce 3+ Redox pairs can effectively regulate the concentration of oxygen species on the catalyst surface, thereby improving reaction efficiency. Manganese-cerium oxide (Mn-Ce-O) is formed by combining manganese-based and cerium-based catalysts. x This combination can produce a significant synergistic effect, improving both low-temperature catalytic activity and enhancing the structural stability of the catalyst. Developing novel integrated adsorption-catalysis low-temperature oxidation adsorbents by combining adsorption properties with manganese-cerium composite oxides has become a current research hotspot.

[0005] Although manganese-cerium-based catalysts exhibit excellent catalytic activity at low temperatures, their application still faces significant challenges. Flue gas from industrial wet desulfurization processes typically contains a high concentration of water vapor (10-20%). At low temperatures (below 150°C), this water vapor readily undergoes capillary condensation within the catalyst pores, forming a liquid water film. Water molecules rapidly occupy the active sites on the catalyst surface, reacting with reactant molecules (NH3, NO...). X Competitive adsorption occurs, leading to a significant decrease in catalytic activity.

[0006] More seriously, liquid water molecules may hydrate with the active components on the catalyst surface, leading to the dissolution and loss of active components such as manganese and cerium, causing irreversible damage to the catalyst structure and rendering it completely deactivated. This phenomenon, known as water poisoning, is a key bottleneck restricting the industrial application of low-temperature SCR catalysts. Studies have shown that under humid conditions, the interaction between water molecules and the active components of the catalyst accelerates the deactivation process.

[0007] To address the problem of catalyst deactivation under low-temperature and high-humidity conditions, researchers have attempted to modify the catalyst surface with hydrophobicity. Hydrophobic modification is considered an effective approach, as it reduces the hydrophilicity of the catalyst surface, thereby decreasing the adsorption of water molecules at active sites and improving the catalyst's water resistance.

[0008] However, traditional hydrophobic modification methods have significant drawbacks: the hydrophobic layer formed by physical coating has weak adhesion to the catalyst matrix and is prone to detachment during long-term operation; while simple silanization modification can improve surface hydrophobicity, it easily clogs the microporous structure of the catalyst, affecting catalytic activity. Furthermore, selecting a support material with excellent pore structure and low cost to achieve efficient dispersion of active components remains a major challenge restricting the industrial application of catalysts.

[0009] With increasingly stringent environmental protection requirements, NO2 in low-temperature saturated wet flue gas from non-power industries is becoming more critical. X The need for deep denitrification is becoming increasingly urgent. Developing a novel low-temperature denitrification material with a multi-level micro-nano porous structure, robust dispersion of active components, and excellent water resistance has become a key technical problem that urgently needs to be solved in this field. Summary of the Invention

[0010] This invention provides a low-temperature oxidation adsorbent for manganese-cerium / diatomite with a micro / nano hierarchical structure and its preparation method. The method first synthesizes an aldehyde-modified hydrophobic linker integrating phenylsiloxane, a diundecyl long-chain hydrophobic group, and a catechol anchoring group based on a molecular design strategy. This linker achieves stable surface modification by forming multiple non-covalent interactions (including hydrogen bonds, coordination bonds, and hydrophobic interactions) with the surface of the nano-manganese-cerium composite oxide through the catechol group, forming an aldehyde-functionalized nano-manganese-cerium composite oxide. Subsequently, through a Schiff base condensation reaction, the nano-manganese-cerium composite oxide is chemically bonded to surface-amino-modified micron-sized diatomite. This process forms C=N covalent bonds at the interface between the two phases, constructing a micro / nano hierarchical composite material with integrated adsorption and catalysis functions.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: A low-temperature oxidation adsorbent, comprising a core layer and an active shell layer; The core layer is amino-functionalized micron-sized diatomaceous earth; The active shell is an aldehyde-functionalized nano-manganese-cerium composite oxide. The core layer and the active shell layer are bonded by Schiff base covalent bonds formed by the condensation of amino and aldehyde groups, forming a micro-nano porous structure. The aldehyde-functionalized nano-manganese-cerium composite oxide is prepared by surface modification of nano-manganese-cerium composite oxide with an aldehyde-modified hydrophobic catechol binder.

[0012] Preferably, the mass ratio of the core layer to the active shell layer is 1:0.1-0.2.

[0013] Preferably, the mass ratio of the aldehyde-modified hydrophobic catechol binder to the nano-manganese cerium composite oxide is 0.02-0.1:1.

[0014] Preferably, the amino-functionalized micronized diatomaceous earth is prepared by surface modification of micronized diatomaceous earth with 3-aminopropyltriethoxysilane, wherein the mass ratio of 3-aminopropyltriethoxysilane to micronized diatomaceous earth is 0.3-0.8:1.

[0015] Preferably, the preparation method of the aldehyde-modified hydrophobic catechol linker is as follows: Under the action of a platinum catalyst, 1 molar equivalent of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and 2 molar equivalents of undecenol undergo a hydrosilylation reaction to prepare a dihydroxy-functionalized intermediate. Under the action of an esterification catalyst, 1 molar equivalent of dihydroxy intermediate and 1 molar equivalent of glyoxylic acid undergo a hydroxyl-carboxyl esterification reaction to obtain a hydroxyaldehyde-functionalized intermediate. Under the action of a composite catalyst, 1 molar equivalent of hydroxyaldehyde functionalized intermediate and 1 molar equivalent of 3,4-dihydroxyphenylacetic acid undergo a hydroxyl-carboxyl esterification reaction to obtain an aldehyde-modified hydrophobic catechol linker.

[0016] Preferably, the platinum catalyst is a Karstedt catalyst or chloroplatinic acid.

[0017] Preferably, the esterification catalyst is p-toluenesulfonic acid or concentrated sulfuric acid.

[0018] Preferably, the composite catalyst is dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.4-0.8.

[0019] A type of smoke NO X The deep removal process includes the following steps: Step 1: Pre-treat the raw flue gas by dust removal and wet desulfurization to reduce the sulfur dioxide concentration in the flue gas to the ultra-low emission standard. Step 2: The saturated wet flue gas after desulfurization is heated to 90°C to 130°C through a heat exchanger, and the maximum temperature is controlled not to exceed 150°C. Step 3: Inject ammonia into the flue gas to fully mix the ammonia with the nitrogen oxides in the flue gas; Step 4: The mixed gas enters a low-temperature SCR reactor filled with low-temperature oxidation adsorption material; The low-temperature oxidation adsorption material is a honeycomb substrate coated with the low-temperature oxidation adsorbent; Step 5: The clean flue gas after nitrogen oxide removal is directly discharged.

[0020] Preferably, the coating load of the honeycomb substrate is 10% to 15% of the mass of the honeycomb substrate.

[0021] The beneficial effects of this invention are as follows: First, the micro-nano rough structure on the surface of the material in this invention is combined with hydrophobic groups (phenylsiloxane, bis(undecyl) long chain) to form a micro-nano dual-scale rough structure. This structure is conducive to forming a Cassie-Baxter wetting state at the gas-liquid-solid interface, that is, a gas-liquid-solid composite contact state in which the droplet is suspended at the top of the rough structure and air is trapped in the gap. While maintaining the gas-solid reaction interface, the residual amino functional groups provide Lewis basic sites, optimize the surface electronic structure and cooperate with the acidic sites of the metal active center, which significantly improves the adsorption activation performance and kinetic efficiency of the low-temperature denitrification reaction. The aforementioned micro-nano dual-scale rough structure, in synergy with low surface energy hydrophobic groups, endows the catalyst with excellent hydrophobic properties (water contact angle >135°). This structure effectively alleviates the competitive adsorption and hydration dissolution of water molecules on the Mn-Ce active components by reducing the direct contact between liquid water and the active sites of the catalyst. Furthermore, the strongly hydrophobic surface reduces the hydration dissolution rate of SO2 on the catalyst surface, thereby inhibiting the liquid-phase formation pathway of ammonium sulfate (NH4)2SO4 and NH4HSO4 from the source, achieving a synergistic effect of water and sulfur resistance.

[0022] Second, the specific surface area of ​​the catalytic materials prepared by this invention is greater than 95 m². 2 / g, under harsh high humidity conditions of 100℃ and 10-20 vol% H2O, the catalyst can still maintain a denitrification rate of more than 81%, and the activity loss rate is significantly lower than that of traditional physical mixed catalysts. Experimental data show that under extreme conditions of 20 vol% water vapor, the denitrification rate of the comparative sample dropped sharply to 31.2%, while that of the present invention remained above 81%, indicating that the micro-nano hydrophobic structure can effectively cope with the fluctuations of industrial high-humidity desulfurization flue gas.

[0023] Third, given that the thermal decomposition initiation temperature of Schiff base bonds (C=N) is approximately 200℃, and that hydrolysis is prone to occur under high-temperature hydrothermal conditions, it is recommended that the continuous operating temperature of this denitrification catalyst be strictly controlled within the range of 90-150℃. Within this temperature range, the covalent bond structure of the Schiff base can remain stable, while the Mn-Ce active component maintains high redox activity. Temperatures exceeding 180℃ are strictly prohibited to prevent structural failure caused by thermal degradation and accelerated hydrolysis of Schiff base bonds. Detailed Implementation Example 1:

[0024] Low-temperature oxidation adsorbent I comprises the following raw materials: 100g micron-sized diatomaceous earth; 50g 3-aminopropyltriethoxysilane; 16g of nano-manganese cerium composite oxide; 0.32g aldehyde-modified hydrophobic catechol binder; The preparation method of low-temperature oxidation adsorbent I includes the following steps: Step S1-1: Preparation of nano-manganese-cerium composite oxide 28.8 g of sodium hydroxide and 80 mL of deionized water were added to a beaker and stirred at 200 r / min until completely dissolved to form solution A. 0.46 mL of 50 wt% manganese nitrate solution was added to 20 mL of deionized water, followed by 2.6 g of cerium nitrate hexahydrate, and stirred until dissolved to form solution B. Solution A was slowly added to solution B, and after stirring for 30 min, the mixture was transferred to a hydrothermal reactor. The temperature was raised to 100 °C, and the hydrothermal reaction was carried out for 24 h. The solid was then separated by centrifugation, washed with deionized water until neutral, and dried in an 80 °C vacuum drying oven for 12 h. After grinding, the solid was poured into a crucible and calcined in a 500 °C muffle furnace for 5 h to obtain nano-manganese cerium composite oxide. Step S1-2: Preparation of aldehyde-functionalized nano-manganese-cerium composite oxide The synthesis mechanism of aldehyde-modified hydrophobic catechol linkers is as follows: Under the action of Karstedt catalyst, 1 molar equivalent of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and 2 molar equivalents of undecenol undergo a hydrosilylation reaction to prepare a dihydroxy-functionalized intermediate. In the presence of p-toluenesulfonic acid, 1 molar equivalent of dihydroxy intermediate and 1 molar equivalent of glyoxylic acid undergo a hydroxyl-carboxyl esterification reaction to obtain a hydroxyaldehyde-functionalized intermediate. Under the action of dicyclohexylcarbodiimide and 4-dimethylaminopyridine, 1 molar equivalent of hydroxyaldehyde functionalized intermediate and 1 molar equivalent of 3,4-dihydroxyphenylacetic acid undergo a hydroxy-carboxyl esterification reaction to prepare an aldehyde-functionalized hydrophobic catechol linker. The specific preparation method of the aldehyde-modified hydrophobic catechol linker includes the following steps: 4 mL of undecenol, 5 drops of Karstedt catalyst, and 30 mL of tetrahydrofuran were added to a round-bottom flask and stirred at 100 rpm for 15 min. 3.34 mL of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane was added dropwise to the round-bottom flask through a dropping funnel, ensuring that the addition was completed within 0.5 h. The temperature was raised to 60 °C and the reaction was maintained at this temperature for 4 h. After cooling to room temperature, tetrahydrofuran was removed by rotary evaporation. The crude product was purified by silica gel column chromatography. First, hexane was used as the eluent to remove impurities. Then, a mixture of hexane and dichloromethane in a volume ratio of 1:1 was used as the eluent. Finally, dichloromethane was used as the eluent and the mixture was rotary evaporated to obtain the dihydroxy functionalized intermediate. 6.73 g of the dihydroxy functionalized intermediate, 1 g of p-toluenesulfonic acid, 1.48 g of 50 wt% glyoxylic acid and 50 mL of cyclohexane were added to a three-necked flask and stirred under reflux for 3 h to remove water. After cooling to room temperature, the mixture was washed three times with deionized water, separated, and the aqueous phase was discarded. The organic layer was washed with saturated sodium bicarbonate solution until neutral, dried with anhydrous magnesium sulfate, filtered, and the solvent was removed by rotary evaporation. The mixture was then dried in a vacuum drying oven at 40 °C for 6 h to obtain the hydroxyaldehyde functionalized intermediate. 7.3 g of a hydroxyaldehyde-functionalized intermediate, 2 g of dicyclohexylcarbodiimide, 1 g of 4-dimethylaminopyridine, and 60 mL of N,N-dimethylformamide were added to a three-necked flask. 1.3 mL of 3,4-dihydroxyphenylacetic acid was added, and the mixture was reacted at 35 °C for 10 h. The mixture was then poured into a separatory funnel, and dichloromethane and deionized water were added. The organic phase was washed three times with saturated brine, dried with anhydrous magnesium sulfate, filtered, and the organic solvent was removed by rotary evaporation. The mixture was then dried in a vacuum oven at 40 °C for 6 h to obtain an aldehyde-functionalized hydrophobic catechol linker. Its chemical structural formula is as follows: ; The 1H NMR characterization results of the aldehyde-modified hydrophobic catechol linker are as follows: 1 H NMR (400MHz, DMSO-D6, δ, ppm): 0.03 (s, 12H), 0.79-0.82 (t, 4H), 1.25-1.39 (m, 32H), 1.58-1.69 (m, 4H), 3.57 (s, 2H), 4.07-4. 16(m, 4H), 6.68-6.77(m, 3H), 7.26-7.30(m, 4H), 7.34-7.39(m, 2H), 7.45-7.47(m, 4H), 8.30(s, 1H), 8.71(s, 1H), 9.10(s, 1H); 16g of nano-manganese cerium composite oxide was added to 600mL of N,N-dimethylformamide and ultrasonically dispersed for 30min to form a uniform dispersion. 0.32g of aldehyde-functionalized hydrophobic catechol linker was added to the dispersion. After stirring at room temperature for 12h, the mixture was centrifuged, washed three times with deionized water, and dried in a vacuum drying oven at 60℃ for 6h to obtain aldehyde-functionalized nano-manganese cerium composite oxide. Steps S1-3: Preparation of amino-functionalized micron-sized diatomaceous earth 100g of micron-sized diatomaceous earth (average particle size of 7.8μm) and 1L of 5mol / L hydrochloric acid were mixed and added to a beaker. The temperature was raised to 100℃ and stirred at 200r / min for 3h. This process was repeated 3 times. After centrifugation, the mixture was washed with deionized water until the solution was neutral. The solution was then dried in a vacuum drying oven at 100℃ for 8h to obtain acid-treated diatomaceous earth. 100g of acid-treated diatomaceous earth and 2L of ethanol were added to a beaker and stirred at 200r / min for 1h. 50g of 3-aminopropyltriethoxysilane was slowly added dropwise to the beaker. The temperature was raised to 80℃ and the reaction was maintained at this temperature for 8h. After cooling to room temperature, the mixture was filtered, washed three times with ethanol, and then washed three times with deionized water. The mixture was then dried in a vacuum drying oven at 60℃ for 8h to obtain amino-functionalized micronized diatomaceous earth. Steps S1-4: Construction of core-shell composite particles 100g of amino-functionalized micronized diatomaceous earth was added to 1L of N,N-dimethylformamide and stirred at 200r / min for 1h. Then, 15g of aldehyde-functionalized nano-manganese cerium composite oxide was added, the temperature was raised to 65℃, and stirring was continued for 5h. After cooling to room temperature, the mixture was centrifuged, washed 3 times with N,N-dimethylformamide, and then washed 3 times with deionized water. The mixture was then dried in a vacuum drying oven at 60℃ for 10h to obtain low-temperature oxidation adsorbent I. The preparation method of low-temperature oxidation adsorption material I includes the following steps: Step S2-1: Material selection: Cordierite honeycomb ceramic: Φ100 mm×100 mm, 300 cpsi, wall thickness 0.25 mm, porosity 40%, specific surface area 1.2 m² / g, dry weight W0=85.2 g; Step S2-2 Slurry preparation: Add 200 mL of anhydrous ethanol, 12.5 g of alcohol-soluble nano-silica sol (SiO2 content 30 wt%, particle size 18 nm), 50 g of low-temperature oxidation adsorbent I, solid content 25%, ultrasonically disperse for 25 min, viscosity 85 mPa·s; Step S2-3 Coating: Immersion for 2.5 min, lifting speed 2.5 cm / s, purging pressure 0.28 MPa, purging time 18 s, distance 90 mm; Step S2-4 Drying and curing: Surface dry at room temperature for 2 h, then heat to 100℃ at 2℃ / min and hold for 8 h to obtain low-temperature oxidation adsorption material I; Results: The single coating load was 6.8%, with no pore blockage and a uniform coating; after two repeated coatings, the total coating load was 13.6%. NO smoke X The deep removal process includes the following steps: Step S3-1: Front-end pretreatment: The raw flue gas discharged from the boiler / kiln first passes through an electrostatic precipitator / bag filter, and then enters a wet desulfurization tower (FGD) to minimize particulate matter in the flue gas and reduce SO2 concentration to ultra-low emission standards (e.g., <35mg / Nm³). 3 ); Step S3-2: Mild temperature adjustment: The flue gas after wet desulfurization is usually saturated wet flue gas (containing a large amount of water vapor) with a temperature of about 50℃-70℃; the flue gas temperature is finely adjusted and raised to the optimal catalytic temperature range of the material (usually set at 90℃-130℃) by using a steam heater. Step S3-3: Ammonia gas is evenly injected into the straight pipe section at the front end of the SCR reactor. An appropriate amount of ammonia (NH3) is injected through the ammonia injection grid (AIG) and static mixer, allowing it to react with NO in the flue gas. X Mix thoroughly; Step S3-4: Core reaction: The mixed gas enters the low-temperature SCR reactor filled with low-temperature oxidation adsorption material I; Process: NO and NH3 molecules in flue gas pass through the gaps in the monolayer hydrophobic layer and are captured by the diatomaceous earth core-manganese cerium shell with a high specific surface area; nano-manganese cerium composite oxide catalyzes the conversion of NO and NH3 into N2 and H2O, and the products are discharged with the flue gas flow; Step S3-5: Clean emission: NO removal X The clean flue gas is then directly discharged into the atmosphere through the chimney without the need for subsequent desorption or secondary treatment. Example 2:

[0025] Preparation method of low-temperature oxidation adsorption material II and NO in flue gas X Deep removal process, preparation method of low-temperature oxidation adsorption material I and NO in flue gas X The only difference in the deep removal process is that the amount of nano-manganese cerium composite oxide is adjusted from 16g to 18g; the amount of aldehyde-based hydrophobic catechol binder is adjusted from 0.32g to 0.9g, and the coating is repeated twice, with a total loading of 13.5%. Example 3:

[0026] Preparation method of low-temperature oxidation adsorption material III and NO in flue gas X Deep removal process, preparation method of low-temperature oxidation adsorption material I and NO in flue gas X The only difference in the deep removal process is that the amount of nano-manganese cerium composite oxide is adjusted from 16g to 19g; the amount of aldehyde-based hydrophobic catechol binder is adjusted from 0.32g to 1.52g, and the coating is repeated twice, with a total loading of 13.8%. Example 4:

[0027] Preparation method of low-temperature oxidation adsorption material IV and its application in flue gas NO X Deep removal process, preparation method of low-temperature oxidation adsorption material I and NO in flue gas XThe only difference in the deep removal process is that the amount of nano-manganese cerium composite oxide is adjusted from 16g to 20g; the amount of aldehyde-modified hydrophobic catechol binder is adjusted from 0.2g to 2g, and the coating is repeated twice, with a total loading of 13.7%. Comparative example:

[0028] The preparation method of the low-temperature oxidation adsorbent is as follows: 18g of nano-manganese cerium composite oxide was added to 1L of deionized water and stirred at 1500r / min for 30min. Then 100g of diatomaceous earth was added and placed in a 50℃ water bath environment. After stirring for 12h, the mixture was centrifuged and then dried in a 120℃ vacuum drying oven for 12h to obtain a low-temperature oxidation adsorbent. The preparation method of the low-temperature oxidation adsorption material is the same as that of low-temperature oxidation adsorption material I, with repeated coating twice, and the total loading is 13.9%. NO smoke X The deep removal process is the same as the removal process in Example 1.

[0029] I. Surface area and pore structure testing 1g of low-temperature oxidizing adsorbent was placed in a sample tube, degassed under vacuum, and then dried in a 90℃ vacuum drying oven for 8 hours to remove moisture. After cooling to room temperature, the N2 adsorption-desorption isotherm of the low-temperature oxidizing adsorbent was measured in liquid nitrogen using a specific surface area and porosity analyzer. The specific surface area of ​​the low-temperature oxidizing adsorbent was calculated according to the BET model. The pore volume was calculated based on the N2 adsorption amount of the low-temperature oxidizing adsorbent at a relative pressure ρ / ρ0=0.99. The average pore size was calculated based on the N2 adsorption amount of the low-temperature oxidizing adsorbent in the adsorption section selected according to the thermodynamic model. The results are shown in Table 1. Table 1. Test results of specific surface area and pore structure parameters of low-temperature oxidation adsorbent

[0030] II. Water Resistance Test (1) Surface wetting performance: The contact angle meter was used to measure the low-temperature oxidation adsorbent. Water droplets were placed on the surface of the prepared sample, and the contact angle was tested at three different locations. The average value was taken. The test was conducted under normal temperature and pressure conditions and the flatness of the surface of the low-temperature oxidation adsorbent was ensured. The test results are shown in Table 2. Table 2. Surface wetting performance test results of low-temperature oxidation adsorbents

[0031] As shown in Table 2, compared with the comparative example, the low-temperature oxidation adsorbent prepared by the present invention introduces phenylsiloxane and long alkyl chain hydrophobic groups and constructs a micro-nano hydrophobic structure, with water contact angles all greater than 135°, and the hydrophobic effect is greatly improved.

[0032] (2) Water resistance test: The low-temperature oxidation adsorption material was tested in a fixed-bed quartz reactor with simulated flue gas composition: 500ppm NO, 500ppm NH3, 3vol% O2, N2 equilibrium, temperature 100℃, anhydrous conditions, and space velocity 30000h. -1 The concentration of each gas component was detected using a flue gas analyzer, and NO was calculated according to the formula. X Conversion rate (denitrification rate %) = [C NOX(in) -C NOX(out) ] / C NOX(in) ×100%; C NOX(in) NO inlet concentration; C NOX(out) The NO outlet concentration is used as the initial activity, denoted as NO. X0 Under the same conditions, adjust the water content to 15 vol% or 20 vol%, and test the denitrification rate, which is recorded as NO. X1 ; with NO X The percentage of conversion loss, also known as the percentage of activity loss, indicates the water resistance of the low-temperature oxidation adsorbent. The smaller the activity loss, the better the water resistance. The formula is: Y = [(NO...] X0 -NO X1 ) / NO X0 The test results are shown in Table 3, calculated as 100% × 100%. III. Denitrification Rate Test The low-temperature oxidation adsorption material was tested. Based on the water resistance test conditions, the denitrification rate was tested under 15 vol%H2O and 20 vol%H2O conditions. The results are shown in Table 3. IV. Stability Performance Test The low-temperature oxidation adsorption material was tested under water resistance test conditions, with 15 vol% H2O continuously introduced into the reaction gas for 30 h, and the denitrification rate was tested. The results are shown in Table 3. Table 3 Performance test results of low-temperature oxidation adsorption materials

[0033] The test results show that the low-temperature oxidation adsorption materials prepared in Examples 1 to 4 exhibit excellent low-temperature denitrification activity and water resistance.

[0034] In an anhydrous initial state, the denitrification rates of Examples 1-4 ranged from 89.2% to 92.4%, slightly better than the 85.3% of the comparative example. When high concentrations of water vapor were introduced, the performance differences among the samples significantly increased. Under 15 vol% H2O conditions, the denitrification rates of Examples 1-4 remained at 84.6%~88.7%, with a loss rate of only 4.0%~5.2% relative to the initial activity; while the denitrification rate of the comparative example dropped sharply to 52.6%, with an activity loss rate as high as 38.3%.

[0035] Furthermore, even under harsh conditions where the water vapor concentration was increased to 20 vol% H2O, the example samples still maintained high catalytic activity, with denitrification rates remaining between 81.3% and 85.6%. Calculations showed that the activity loss rate for Examples 1-4 under this condition was only 7.4% to 8.9% (with Example 3 showing the best performance at a loss rate of 7.4%). In contrast, the comparative sample experienced severe deactivation, with the denitrification rate dropping to 31.2%, and the calculated activity loss rate reaching as high as 63.4%.

[0036] The above data indicate that the hydrophobic properties of the sample surface in the examples constitute an effective barrier layer. This hydrophobic surface significantly reduces the competitive adsorption probability of water molecules on the catalyst micropores and active sites, inhibits capillary condensation, and thus ensures the reactants (NO) under high humidity conditions. X Effective contact between the active sites and the water vapor is achieved; conversely, due to the lack of effective hydrophobic modification, the active sites are occupied by water molecules or the structure collapses under the scouring of high-concentration water vapor, resulting in a sharp decline in performance.

[0037] In the stability test after 30 hours of continuous reaction, the denitrification rates of Examples 1-4 stabilized at 82.5%~85.2%, retaining most of the initial activity without significant irreversible deactivation. In contrast, the comparative example showed a denitrification rate of only 36.4% after 30 hours. This confirms that the low-temperature oxidation adsorption material described in this application possesses good structural stability and tolerance under simulated continuous industrial flue gas operation conditions, meeting the requirements of long-term engineering applications.

Claims

1. A low-temperature oxidation adsorbent, characterized in that, Includes a core layer and an active shell; The core layer is amino-functionalized micron-sized diatomaceous earth; The active shell is an aldehyde-functionalized nano-manganese-cerium composite oxide. The core layer and the active shell layer are bonded by Schiff base covalent bonds formed by the condensation of amino and aldehyde groups, forming a micro-nano porous structure. The aldehyde-functionalized nano-manganese-cerium composite oxide is prepared by surface modification of nano-manganese-cerium composite oxide with an aldehyde-functionalized hydrophobic catechol binder. The chemical structural formula of the aldehyde-modified hydrophobic catechol linker is: 。 2. The low-temperature oxidation adsorbent according to claim 1, characterized in that, The mass ratio of the core layer to the active shell layer is 1:0.1-0.

2.

3. The low-temperature oxidation adsorbent according to claim 1, characterized in that, The mass ratio of the aldehyde-based hydrophobic catechol binder to the nano-manganese cerium composite oxide is 0.02-0.1:

1.

4. The low-temperature oxidation adsorbent according to claim 1, characterized in that, The amino-functionalized micron-sized diatomaceous earth is prepared by surface modification of micron-sized diatomaceous earth with 3-aminopropyltriethoxysilane, wherein the mass ratio of 3-aminopropyltriethoxysilane to micron-sized diatomaceous earth is 0.3-0.8:

1.

5. The low-temperature oxidation adsorbent according to claim 1, characterized in that, The preparation method of the aldehyde-modified hydrophobic catechol linker is as follows: Under the action of a platinum catalyst, 1 molar equivalent of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and 2 molar equivalents of undecenol undergo a hydrosilylation reaction to prepare a dihydroxy-functionalized intermediate. Under the action of an esterification catalyst, 1 molar equivalent of dihydroxy intermediate and 1 molar equivalent of glyoxylic acid undergo a hydroxyl-carboxyl esterification reaction to obtain a hydroxyaldehyde-functionalized intermediate. Under the action of a composite catalyst, 1 molar equivalent of hydroxyaldehyde functionalized intermediate and 1 molar equivalent of 3,4-dihydroxyphenylacetic acid undergo a hydroxyl-carboxyl esterification reaction to obtain an aldehyde-modified hydrophobic catechol linker.

6. The low-temperature oxidation adsorbent according to claim 5, characterized in that, The platinum catalyst is either a Karstedt catalyst or chloroplatinic acid.

7. The low-temperature oxidation adsorbent according to claim 5, characterized in that, The esterification catalyst is p-toluenesulfonic acid or concentrated sulfuric acid.

8. The low-temperature oxidation adsorbent according to claim 5, characterized in that, The composite catalyst is dicyclohexylcarbodiimide and 4-dimethylaminopyridine in a mass ratio of 1:0.4-0.

8.

9. A type of flue gas NO X The deep removal process is characterized by, Includes the following steps: Step 1: Pre-treat the raw flue gas by dust removal and wet desulfurization to reduce the sulfur dioxide concentration in the flue gas to the ultra-low emission standard. Step 2: The saturated wet flue gas after desulfurization is heated to 90°C to 130°C through a heat exchanger, and the maximum temperature is controlled not to exceed 150°C. Step 3: Inject ammonia into the flue gas to fully mix the ammonia with the nitrogen oxides in the flue gas; Step 4: The mixed gas enters a low-temperature SCR reactor filled with low-temperature oxidation adsorption material; Wherein, the low-temperature oxidation adsorption material is a honeycomb substrate coated with the low-temperature oxidation adsorbent according to any one of claims 1 to 8; Step 5: The clean flue gas after nitrogen oxide removal is directly discharged.

10. A flue gas NO according to claim 9 X The deep removal process is characterized by, The coating load of the honeycomb substrate is 10% to 15% of the mass of the honeycomb substrate.

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