A denitration catalyst and a method for preparing the same

Abstract

The present application relates to the field of environmental catalysis technology, and discloses a denitration catalyst and a preparation method thereof, wherein the preparation method is as follows: a modified titanium-silicon composite oxide carrier is added into an active component precursor solution for ultrasonic immersion, evaporative drying, then a promoter precursor solution is added for pulse microwave assisted immersion, and after drying and calcination, a binder is added, kneaded into shape, dried and calcined to obtain the denitration catalyst.The denitration catalyst prepared by the present application has good high-efficiency wide-temperature denitration performance, sulfur resistance, water resistance, and alkali metal and alkaline earth metal resistance.The components synergize to inhibit active phase sintering and phase change, improve structural stability and anti-aging ability, prolong the service life of the denitration catalyst, and reduce operation and maintenance costs.

Description

Technical Field

[0001] This invention relates to the field of environmental catalysis technology, specifically to a denitrification catalyst and its preparation method. Background Technology

[0002] Nitrogen oxides (NOx) are one of the major air pollutants, causing environmental problems such as acid rain and smog, and posing serious threats to ecosystems and human health. Selective catalytic reduction (SCR) technology is currently the most mainstream and efficient method for industrial flue gas denitrification. As the core of the SCR system, the denitrification catalyst's catalytic activity, temperature window, and resistance to poisoning directly determine the denitrification efficiency and equipment lifespan.

[0003] Currently, the most widely used vanadium-tungsten-titanium denitration catalysts in industrial applications, while exhibiting good denitration effects in the medium-to-high temperature range (300-400℃), suffer from insufficient low-temperature activity and a narrow active temperature window, making them unsuitable for low-temperature flue gas conditions. Furthermore, this system has poor resistance to sulfur and water, easily generating ammonium sulfate in sulfur- and water-containing flue gas, clogging pores and poisoning active sites, leading to rapid catalyst deactivation. In addition, alkali metals and alkaline earth metals in the flue gas readily neutralize the acidic sites of the catalyst, causing irreversible poisoning, further shortening its lifespan and increasing maintenance costs. In recent years, non-vanadium denitration catalysts, represented by manganese-based and cerium-based catalysts, have become a research hotspot due to their excellent low-temperature activity and strong environmental friendliness. However, these catalysts still suffer from insufficient support structural stability and limited catalytic efficiency and lifespan.

[0004] Therefore, developing a novel denitrification catalyst with wide temperature range, high efficiency, sulfur and water resistance, and stable structure, along with a green and efficient preparation process, is of great practical significance for promoting the large-scale application of selective catalytic reduction denitrification technology in multiple scenarios and complex flue gas conditions. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a denitrification catalyst and its preparation method. The denitrification catalyst prepared by the present invention has good high-efficiency wide-temperature denitrification performance, sulfur resistance, water resistance and alkali metal and alkaline earth metal resistance.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a denitrification catalyst, comprising a modified titanium-silicon composite oxide as a carrier, a manganese-cerium-zirconium composite oxide as an active component, a molybdenum-tungsten composite oxide as an auxiliary agent, and a rare earth element lanthanum as a modifier; based on the total mass of the denitrification catalyst being 100%, the active component accounts for 8%-15%, the auxiliary agent accounts for 3%-8%, the modifier accounts for 1%-3%, and the remainder is the modified titanium-silicon composite oxide carrier; The catalyst was prepared by a pulsed microwave-assisted impregnation process; The modified titanium-silicon composite oxide carrier has a mesoporous structure with a pore size distribution of 2-10 nm and a specific surface area of ​​180-250 m². 2 / g.

[0007] Furthermore, in the modified titanium-silicon composite oxide carrier, the mass ratio of TiO2 to SiO2 is 7:3-9:1.

[0008] Furthermore, in the active component of the manganese-cerium-zirconium composite oxide, the molar ratio of Mn, Ce, and Zr is 6:3:1-7:2:1; Mn exists in the form of MnO2, Ce exists in the form of CeO2, and Zr exists in the form of ZrO2, forming a solid solution structure.

[0009] Furthermore, in the molybdenum-tungsten composite oxide additive, the molar ratio of Mo to W is 1:1-2:1; Mo exists in the form of MoO3, and W exists in the form of WO3, and the molybdenum-tungsten composite oxide is directionally enriched on the catalyst surface, forming a core-shell distribution.

[0010] Furthermore, the modifier lanthanum exists in the form of La2O3.

[0011] Furthermore, the preparation method of the denitration catalyst is as follows: Step 1: Dissolve titanium source and silicon source in anhydrous ethanol, adjust pH and mix, add lanthanum nitrate and carbonaceous template agent, ultrasonically disperse to form gel, dry and calcine to obtain modified titanium-silicon composite oxide carrier. Step 2: Dissolve manganese nitrate tetrahydrate, cerium nitrate hexahydrate, and zirconium nitrate pentahydrate in deionized water, add citric acid, adjust the pH, and obtain the active component precursor solution. Step 3: Dissolve ammonium molybdate tetrahydrate and ammonium metatungstate in deionized water, heat to dissolve, and obtain the auxiliary agent precursor solution; Step 4: The modified titanium-silicon composite oxide support is added to the active component precursor solution for ultrasonic impregnation and evaporation drying. Then, the auxiliary agent precursor solution is added for pulsed microwave-assisted impregnation, followed by drying and calcination. Finally, a binder is added, the mixture is kneaded and shaped, dried, and calcined to obtain the denitrification catalyst.

[0012] Furthermore, in step one, the titanium source is tetrabutyl titanate and the silicon source is tetraethyl orthosilicate; the calcination process is divided into two steps: the first step is to keep warm at 300℃ for 1 hour, and the second step is to calcine at 550-650℃ for 3-5 hours; the carbonaceous template agent is coconut shell carbon powder with a particle size of 50-100nm, and the amount added is 5%-10% of the carrier mass.

[0013] In this step, the carbonaceous template agent is oxidized and decomposed during the high-temperature calcination stage and escapes in gaseous form, thereby generating a mesoporous structure in situ within the composite oxide framework.

[0014] Furthermore, in step two, the total molar ratio of citric acid to metal ions is 1.2:1, and the pH is adjusted to 5-6.

[0015] In this step, the pH of the system is strictly controlled between 5 and 6, which allows citric acid to fully complex free metal ions and effectively prevents the metal precursor from undergoing non-uniform single hydroxide precipitation. This ensures that the three metal ions, Mn, Ce, and Zr, are uniformly mixed at the atomic level, providing the necessary precursor conditions for the formation of a uniform manganese-cerium-zirconium ternary solid solution structure during the subsequent calcination process. After stirring evenly, the active component precursor solution is obtained.

[0016] Furthermore, in step four, the parameters for pulsed microwave-assisted impregnation are: microwave power of 700-900W, pulse mode of 3-5 seconds on / 9-15 seconds off, processing time of 10-15 minutes; calcination temperature of 450-550℃, and calcination time of 2-3 hours.

[0017] In this step, intermittent heating with pulsed microwaves can avoid local overheating and component agglomeration caused by continuous microwaves, promote the migration of molybdenum-tungsten additives to the outer layer of the carrier, and make the molybdenum-tungsten composite additives directionally enriched in the outer layer of the carrier, forming a core-shell distribution.

[0018] Furthermore, in step four, the binder is silica sol, and the amount added is 5%-8% of the sample mass.

[0019] Compared with the prior art, the present invention has the following beneficial technical effects: This invention uses modified titanium-silicon composite oxide as a support and a manganese-cerium-zirconium ternary solid solution as the active component. A pulsed microwave-assisted impregnation process is employed to directionally enrich molybdenum-tungsten additives on the support surface, forming a core-shell distribution. Combined with the acid-modifying effect of rare earth lanthanum, this significantly broadens the catalyst's active temperature window, enhancing the high-efficiency, wide-temperature denitrification performance of the denitrification catalyst. Under pulsed microwave irradiation, the molybdenum-tungsten additives form a core-shell enrichment layer on the catalyst surface. Combined with the high specific surface area of ​​the mesoporous support and the optimization of surface acidity by lanthanum modification, this effectively suppresses the effects of SO2 and H2O on the catalyst's activity. The competitive adsorption and poisoning of acidic sites enhance the sulfur and water resistance of the denitrification catalyst. Rare earth lanthanum modification increases the number and strength of acidic sites on the catalyst surface. When impacted by alkali or alkaline earth metals, these acidic sites effectively neutralize and contain the alkaline poisons, protecting the active components from damage and endowing the denitrification catalyst with excellent resistance to alkali and alkaline earth metal poisoning. The synergistic effect of all components inhibits sintering and phase transformation of the active phase, improving structural stability and anti-aging capabilities, extending the service life of the denitrification catalyst, and reducing operation and maintenance costs. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In the following embodiments, as the loading of the active component and the silicon-to-titanium ratio of the carrier change, the specific parameters of the pulsed microwave and the calcination temperature are adjusted accordingly to ensure that the precursors with different ratios can obtain suitable microwave processing conditions.

[0022] The reagents used in the following specific embodiments are of analytical grade. Additionally: Manganese nitrate is manganese nitrate tetrahydrate [Mn(NO3)2·4H2O], Cerium nitrate is cerium nitrate hexahydrate [Ce(NO3)3·6H2O], Zirconium nitrate is zirconium oxynitrate pentahydrate [ZrO(NO3)2·5H2O], Ammonium molybdate is ammonium molybdate tetrahydrate [(NH4)6Mo7O 24 ·4H2O], Ammonium tungstate is ammonium metatungstate [(NH4)6H2W] 12 O 40 ·xH2O], Lanthanum nitrate is lanthanum nitrate hexahydrate [La(NO3)3·6H2O].

[0023] Example 1

[0024] This embodiment provides a denitrification catalyst, which uses a modified titanium-silicon composite oxide as a support, a manganese-cerium-zirconium composite oxide as an active component, a molybdenum-tungsten composite oxide as an auxiliary agent, and La2O3 as a modifier. Based on the total mass of the denitrification catalyst as 100%, the active component accounts for 8%, the auxiliary agent accounts for 3%, the modifier accounts for 1%, and the balance is the modified titanium-silicon composite oxide support. The preparation method is as follows: (1) Weigh 84.2 g of tetrabutyl titanate and 22.5 g of tetraethyl orthosilicate, dissolve them separately in 100 mL of anhydrous ethanol, and stir until homogeneous to obtain a titanium source solution and a silicon source solution; add 7 mL of glacial acetic acid to the titanium source solution to adjust the pH to 3.5, stir for 45 min, then slowly add the silicon source solution, and continue stirring for 1.5 h to obtain a mixed precursor solution; weigh 1 g of lanthanum nitrate, dissolve it in 50 mL of deionized water, add it to the mixed precursor solution, and stir for 30 min; then add coconut shell carbon powder with a particle size of 50 nm, the amount added is... 8% of the carrier mass was ultrasonically dispersed for 25 min to form a gel system. The gel system was dried in a 70℃ oven for 18 h to obtain a dry gel. The dry gel was placed in a muffle furnace and heated to 300℃ at a rate of 5℃ / min and held for 1 h. Then, the temperature was increased to 600℃ at a rate of 3℃ / min and calcined for 4 h. After cooling to room temperature, the gel was pulverized and passed through a 90-mesh sieve to obtain a modified titanium-silicon composite oxide carrier with a mesoporous structure. The mass ratio of TiO2 to SiO2 was approximately 7.5:2.5, the pore size distribution was 2 nm, and the specific surface area was 210 m². 2 / g.

[0025] (2) Weigh 24.5g of manganese nitrate tetrahydrate, 17.3g of cerium nitrate hexahydrate, and 4.2g of zirconium nitrate pentahydrate, dissolve them in 100mL of deionized water, and stir until completely dissolved to obtain a metal salt solution; add 22.5g of citric acid to the metal salt solution, stir for 30min, and adjust the pH to 5.5 with dilute ammonia water to obtain an active component precursor solution.

[0026] (3) Weigh 5.4g of ammonium molybdate tetrahydrate and 6.2g of ammonium metatungstate, dissolve them in 80mL of deionized water, heat to 55℃, and stir until completely dissolved to obtain the precursor solution of the auxiliary agent. (4) Add 88g of modified titanium-silicon composite oxide support to the active component precursor solution prepared in step (2), ultrasonically impregnate for 45min, and then place it in a 70℃ water bath and stir to evaporate to dryness to obtain an active component loaded intermediate; then add the active component loaded intermediate to the auxiliary agent precursor solution prepared in step (3), and use pulsed microwave assisted impregnation with a microwave power of 800W and a pulse mode of 4 seconds on / 12 seconds off for 12min to make the molybdenum-tungsten composite auxiliary agent directionally enriched on the outer layer of the support; then place it in a 110℃ oven to dry for 3h; place the dried sample in a muffle furnace and heat it to 500℃ at a rate of 4℃ / min, calcine for 2.5h, and cool to room temperature; add silica sol equivalent to 6% of the powder mass and 20mL of deionized water, knead evenly, extrude to form a honeycomb catalyst, and then place it in a 120℃ oven to dry for 5h and calcine at 500℃ for 2h to obtain a denitrification catalyst.

[0027] Example 2

[0028] This embodiment provides a denitrification catalyst, which uses a modified titanium-silicon composite oxide as a support, a manganese-cerium-zirconium composite oxide as an active component, a molybdenum-tungsten composite oxide as an auxiliary agent, and La2O3 as a modifier. Based on the total mass of the denitrification catalyst being 100%, the active component accounts for 12%, the auxiliary agent accounts for 5%, the modifier accounts for 2%, and the remainder is the modified titanium-silicon composite oxide support. The preparation method is as follows: (1) Weigh 89.5g of tetrabutyl titanate and 13.2g of tetraethyl orthosilicate, dissolve them in 110mL of anhydrous ethanol, stir well to obtain titanium source solution and silicon source solution; add 8mL of glacial acetic acid to the titanium source solution to adjust the pH to 3.8, stir for 50min, then slowly add silicon source solution, continue stirring for 1.8h to obtain mixed precursor solution; weigh 2.2g of lanthanum nitrate, dissolve it in 55mL of deionized water, add it to the mixed precursor solution, stir for 30min; then add coconut shell carbon powder with a particle size of 80nm, the amount added is... The substrate, at 8% of its mass, was ultrasonically dispersed for 28 min to form a gel system. The gel system was then dried in a 75℃ oven for 16 h to obtain a dry gel. The dry gel was placed in a muffle furnace and heated to 300℃ at a rate of 5℃ / min, held at that temperature for 1 h, and then heated to 600℃ at a rate of 3℃ / min for 4 h. After cooling to room temperature, the gel was pulverized and passed through a 90-mesh sieve to obtain a modified titanium-silicon composite oxide support with a mesoporous structure. The mass ratio of TiO2 to SiO2 was approximately 8.5:1.5, the pore size distribution was 8 nm, and the specific surface area was 220 m². 2 / g. (2) Weigh 28.6g of manganese nitrate tetrahydrate, 15.6g of cerium nitrate hexahydrate and 3.8g of zirconium nitrate pentahydrate, dissolve them in 110mL of deionized water, stir until completely dissolved to obtain a metal salt solution; add 24.8g of citric acid to the metal salt solution, stir for 30min, adjust the pH to 5.8 with dilute ammonia water to obtain an active component precursor solution.

[0029] (3) Weigh 7.8g of ammonium molybdate tetrahydrate and 5.9g of ammonium metatungstate, dissolve them in 90mL of deionized water, heat to 58℃, and stir until completely dissolved to obtain the precursor solution of the auxiliary agent. (4) 79g of modified titanium-silicon composite oxide support was added to the active component precursor solution prepared in step (2), ultrasonically impregnated for 50min, and then placed in a 75℃ water bath and stirred to evaporate to dryness to obtain an active component loaded intermediate; then the active component loaded intermediate was added to the auxiliary agent precursor solution prepared in step (3), and pulsed microwave assisted impregnation was performed with a microwave power of 800W and a pulse mode of 4 seconds on / 12 seconds off for 12min to make the molybdenum-tungsten composite auxiliary agent directionally enriched on the outer layer of the support; then it was placed in a 115℃ oven to dry for 2.5h; the dried sample was placed in a muffle furnace and heated to 500℃ at a rate of 4℃ / min, calcined for 2.5h, and cooled to room temperature; silica sol equivalent to 6.5% of the powder mass and 22mL of deionized water were added, kneaded evenly, extruded into a honeycomb catalyst, and then placed in a 120℃ oven to dry for 4.5h and calcined at 500℃ for 2h to obtain a denitrification catalyst.

[0030] Example 3

[0031] This embodiment provides a denitrification catalyst, which uses a modified titanium-silicon composite oxide as a support, a manganese-cerium-zirconium composite oxide as an active component, a molybdenum-tungsten composite oxide as an auxiliary agent, and La2O3 as a modifier. Based on the total mass of the denitrification catalyst as 100%, the active component accounts for 15%, the auxiliary agent accounts for 8%, the modifier accounts for 3%, and the balance is the modified titanium-silicon composite oxide support. The preparation method is as follows: (1) Weigh 93.8g of tetrabutyl titanate and 8.8g of tetraethyl orthosilicate, dissolve them in 120mL of anhydrous ethanol, stir well to obtain titanium source solution and silicon source solution; add 9mL of glacial acetic acid to the titanium source solution to adjust the pH to 4.0, stir for 60min, then slowly add silicon source solution, continue stirring for 2h to obtain mixed precursor solution; weigh 3.3g of lanthanum nitrate, dissolve it in 60mL of deionized water, add it to the mixed precursor solution, stir for 30min; then add coconut shell carbon powder with a particle size of 100nm, the amount added is... A 10% (by weight of the carrier) mixture was ultrasonically dispersed for 30 min to form a gel system. The gel system was then dried in an 80℃ oven for 12 h to obtain a dry gel. The dry gel was placed in a muffle furnace and heated to 300℃ at a rate of 5℃ / min, held for 1 h, then heated to 650℃ at a rate of 3℃ / min and calcined for 3 h. After cooling to room temperature, the gel was pulverized and passed through a 90-mesh sieve to obtain a modified titanium-silicon composite oxide carrier with a mesoporous structure. The mass ratio of TiO2 to SiO2 was approximately 9:1, the pore size distribution was 9 nm, and the specific surface area was 250 m². 2 / g.

[0032] (2) Weigh 30.2g of manganese nitrate tetrahydrate, 16.8g of cerium nitrate hexahydrate and 4.5g of zirconium nitrate pentahydrate, dissolve them in 120mL of deionized water, stir until completely dissolved to obtain a metal salt solution; add 26.3g of citric acid to the metal salt solution, stir for 30min, adjust the pH to 6.0 with dilute ammonia water to obtain an active component precursor solution.

[0033] (3) Weigh 8.5g of ammonium molybdate tetrahydrate and 6.8g of ammonium metatungstate, dissolve them in 100mL of deionized water, heat to 60℃, and stir until completely dissolved to obtain the precursor solution of the auxiliary agent.

[0034] (4) 74g of modified titanium-silicon composite oxide support was added to the active component precursor solution prepared in step (2), ultrasonically impregnated for 55min, and then placed in an 80℃ water bath and stirred and evaporated to dryness to obtain an active component loaded intermediate; then the active component loaded intermediate was added to the auxiliary agent precursor solution prepared in step (3), and pulsed microwave assisted impregnation was performed with a microwave power of 900W and a pulse mode of 5 seconds on / 15 seconds off for 15min to make the molybdenum-tungsten composite auxiliary agent directionally enriched on the outer layer of the support; then it was placed in a 120℃ oven to dry for 2h; the dried sample was placed in a muffle furnace and heated to 550℃ at a rate of 4℃ / min, calcined for 2h, and cooled to room temperature; silica sol equivalent to 8% of the powder mass and 25mL of deionized water were added, kneaded evenly, extruded into a honeycomb catalyst, and then placed in a 120℃ oven to dry for 4h and calcined at 500℃ for 2h to obtain a denitrification catalyst.

[0035] Example 4

[0036] This embodiment provides a denitrification catalyst, which uses a modified titanium-silicon composite oxide as a support, a manganese-cerium-zirconium composite oxide as an active component, a molybdenum-tungsten composite oxide as an auxiliary agent, and La2O3 as a modifier. Based on the total mass of the denitrification catalyst being 100%, the active component accounts for 12%, the auxiliary agent accounts for 5%, the modifier accounts for 2%, and the remainder is the modified titanium-silicon composite oxide support.

[0037] The preparation method is as follows: (1) Weigh 75g of tetrabutyl titanate and 35.2g of tetraethyl orthosilicate, dissolve them in 110mL of anhydrous ethanol, stir well to obtain titanium source solution and silicon source solution; add 8mL of glacial acetic acid to the titanium source solution to adjust the pH to 3.8, stir for 50min, then slowly add silicon source solution, continue stirring for 1.8h to obtain mixed precursor solution; weigh 2.2g of lanthanum nitrate, dissolve it in 55mL of deionized water, add it to the mixed precursor solution, stir for 30min; then add coconut shell carbon powder with a particle size of 80nm, add... The amount of TiO2 was 8% of the carrier mass, and the mixture was ultrasonically dispersed for 28 min to form a gel system. The gel system was then dried in a 75℃ oven for 16 h to obtain a dry gel. The dry gel was placed in a muffle furnace and heated to 300℃ at a rate of 5℃ / min and held for 1 h. Then, the temperature was increased to 600℃ at a rate of 3℃ / min and calcined for 4 h. After cooling to room temperature, the mixture was pulverized and passed through a 90-mesh sieve to obtain a modified titanium-silicon composite oxide carrier with a mesoporous structure. The mass ratio of TiO2 to SiO2 was approximately 7:3, the pore size distribution was 7 nm, and the specific surface area was 205 m². 2 / g.

[0038] (2) Weigh 28.6g of manganese nitrate tetrahydrate, 15.6g of cerium nitrate hexahydrate and 3.8g of zirconium nitrate pentahydrate, dissolve them in 110mL of deionized water, stir until completely dissolved to obtain a metal salt solution; add 24.8g of citric acid to the metal salt solution, stir for 30min, adjust the pH to 5.8 with dilute ammonia water to obtain an active component precursor solution.

[0039] (3) Weigh 7.8g of ammonium molybdate tetrahydrate and 5.9g of ammonium metatungstate, dissolve them in 90mL of deionized water, heat to 58℃, and stir until completely dissolved to obtain the precursor solution of the auxiliary agent.

[0040] (4) 79g of modified titanium-silicon composite oxide support was added to the active component precursor solution prepared in step (2), ultrasonically impregnated for 50min, and then placed in a 75℃ water bath and stirred to evaporate to dryness to obtain an active component loaded intermediate; then the active component loaded intermediate was added to the auxiliary agent precursor solution prepared in step (3), and pulsed microwave assisted impregnation was performed with a microwave power of 700W and a pulse mode of 3 seconds on / 9 seconds off for 12min to make the molybdenum-tungsten composite auxiliary agent directionally enriched on the outer layer of the support; then it was placed in a 115℃ oven to dry for 2.5h; the dried sample was placed in a muffle furnace and heated to 500℃ at a rate of 4℃ / min, calcined for 2.5h, and cooled to room temperature; silica sol equivalent to 6.5% of the powder mass and 22mL of deionized water were added, kneaded evenly, extruded into a honeycomb catalyst, and then placed in a 120℃ oven to dry for 4.5h and calcined at 500℃ for 2h to obtain a denitrification catalyst.

[0041] Comparative Example 1 The main difference between this comparative example and Example 4 is that, in step (4), the loading of the additive was not carried out using a pulsed microwave-assisted impregnation process. Specifically, after the active component loading intermediate was added to the additive precursor solution, it was impregnated by conventional water bath heating and stirring. The mixture was continuously stirred for 2 hours in a constant temperature water bath at 60°C, followed by drying and calcination. The remaining steps and parameters were consistent with those in Example 4.

[0042] Comparative Example 2 The main difference between this comparative example and Example 4 is that no carbonaceous template agent (coconut shell carbon powder) was added when preparing the modified titanium-silicon composite oxide carrier in step (1). The remaining steps and parameters are consistent with those of Example 4.

[0043] Comparative Example 3 The main difference between this comparative example and Example 4 is that the catalyst does not contain the rare earth element lanthanum modifier. Specifically, lanthanum nitrate is not added when preparing the support in step (1), and the remaining steps and parameters are consistent with those in Example 4.

[0044] Comparative Example 4 The main difference between this comparative example and Example 4 is that the active component does not contain zirconium (Zr), but is only a manganese-cerium binary composite oxide. Specifically, in step (2), zirconium nitrate is not added, and its corresponding molar amount is distributed to manganese nitrate and cerium nitrate in the original proportion. The remaining steps and parameters are consistent with those in Example 4.

[0045] Comparative Example 5 The main difference between this comparative example and Example 4 is that in step (4), continuous microwave-assisted impregnation is used instead of pulsed microwave. Specifically, after adding the active component-loaded intermediate to the auxiliary agent precursor solution, microwave treatment is performed continuously for 3.75 minutes at a power of 700W (equal to the cumulative on-time of pulsed microwave in Example 4), without any interruption. The remaining steps, raw material ratios, and process parameters are completely consistent with those of Example 4.

[0046] Performance testing The denitrification catalysts prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to performance tests.

[0047] (1) Denitrification efficiency determination: The simulated flue gas composition was: NOx (1500 mg / m³) 3 The composition of the gas is as follows: NH3 (NH3 / NOx molar ratio = 1:1.03), O2 (17%), H2O (8%), with N2 as the balance gas and a space velocity of 10000 h⁻¹. -1The reaction temperature is controlled between 150-450℃, with test points including 150℃, 200℃, 250℃, 300℃, 350℃, 400℃, and 450℃. The flow rate of each gas is controlled by a mass flow meter. Before entering the reactor, the gas is first mixed in a gas mixer and then preheated in a preheater. NO at the inlet and outlet... x The concentration was measured by a flue gas analyzer. The system started collecting data 60 minutes after it had been running stably for ventilation. The test results are shown in Table 1.

[0048] Table 1: Denitrification efficiency determination

[0049] As can be seen from Table 1, the denitrification catalysts prepared in Examples 1-4 all exhibited excellent denitrification efficiency within a wide temperature window of 150~450℃, reaching the optimal activity at 300℃, with the highest NOx conversion rate reaching 98.5%.

[0050] (2) Determination of sulfur and water resistance: The simulated flue gas composition was: NOx (1500 mg / m³) 3 The composition of the gas is as follows: NH3 (NH3 / NOx molar ratio = 1:1.03), O2 (17%), SO2 (1000 mg / m3), H2O (8%), with N2 as the balance gas and a space velocity of 10000 h⁻¹. -1 The reaction temperatures were controlled at 120℃, 200℃, and 300℃, respectively. The flow rates of each gas were controlled by mass flow meters. Before entering the reactor, the gas was mixed in a gas mixer and then preheated in a preheater. The NOx concentrations at the inlet and outlet were measured by a flue gas analyzer. Testing began 30 minutes after the system had stabilized during operation; the results are shown in Table 2.

[0051] Table 2: Determination of sulfur resistance and water resistance

[0052] As can be seen from Table 2, the denitrification catalysts prepared in Examples 1-4 still maintain a denitrification efficiency of over 80% under complex flue gas conditions containing SO2 and high H2O, demonstrating excellent sulfur and water resistance.

[0053] (3) Determination of resistance to alkali metals and alkaline earth metals: Two test blocks of each of the denitrification catalysts prepared in Examples 1-3 and Comparative Examples 1-4 were placed in a 2% potassium hydroxide + 2% sodium hydroxide mixed solution and a 2% calcium hydroxide + 2% magnesium hydroxide mixed solution, respectively. After soaking in a sealed container at 100°C for 72 hours, the catalysts were removed, dried in a forced-air drying oven at 120°C for 3 hours, and then calcined in a muffle furnace at 400°C for 3 hours. After removal, the denitrification efficiency was tested under the same conditions as performance test (1), with the reaction temperature controlled at 150°C and 300°C. The test results are shown in Table 3.

[0054] Table 3: Test results of resistance to alkali metals and alkaline earth metals

[0055] As can be seen from Table 3, the denitrification catalysts prepared in Examples 1-4 still maintained a denitrification efficiency of over 77% after being subjected to accelerated poisoning by alkali metals / alkaline earth metals, demonstrating excellent resistance to poisoning.

[0056] The comparison reveals that neither conventional water bath impregnation (Comparative Example 1) nor continuous microwave-assisted processes (Comparative Example 5) can provide a localized non-thermal alternation effect, easily leading to agglomeration and sintering of molybdenum-tungsten additives. This prevents the construction of an ideal core-shell protective layer on the support surface, resulting in a significant reduction in effective active sites. Regarding the support framework, the absence of carbonaceous template agents (Comparative Example 2) directly caused severe sintering during the high-temperature calcination stage, with the collapse of the pore network hindering the mass transfer of reactant gases. The absence of lanthanum (Comparative Example 3) weakens the density of acidic sites on the surface, making it highly susceptible to neutralization and poisoning when subjected to alkaline poisoning. Furthermore, the lack of zirconium doping (Comparative Example 4) severely hinders the formation of highly active solid solution lattice defects within the manganese-cerium system, fundamentally limiting the intrinsic electron transfer rate of the catalyst.

[0057] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0059] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A denitrification catalyst, characterized in that, The catalyst uses a modified titanium-silicon composite oxide as a carrier, a manganese-cerium-zirconium composite oxide as an active component, a molybdenum-tungsten composite oxide as an auxiliary agent, and a rare earth element lanthanum as a modifier. Based on the total mass of the denitrification catalyst as 100%, the active component accounts for 8%-15%, the auxiliary agent accounts for 3%-8%, the modifier accounts for 1%-3%, and the remainder is the modified titanium-silicon composite oxide carrier. The catalyst was prepared by a pulsed microwave-assisted impregnation process; The modified titanium-silicon composite oxide carrier has a mesoporous structure with a pore size distribution of 2-10 nm and a specific surface area of ​​180-250 m². 2 / g.

2. The denitrification catalyst according to claim 1, characterized in that, In the modified titanium-silicon composite oxide carrier, the mass ratio of TiO2 to SiO2 is 7:3-9:

1.

3. The denitrification catalyst according to claim 1, characterized in that, In the active component of the manganese-cerium-zirconium composite oxide, the molar ratio of Mn, Ce, and Zr is 6:3:1-7:2:1; Mn exists in the form of MnO2, Ce exists in the form of CeO2, and Zr exists in the form of ZrO2, forming a solid solution structure.

4. The denitrification catalyst according to claim 1, characterized in that, In the molybdenum-tungsten composite oxide additive, the molar ratio of Mo to W is 1:1-2:1; Mo exists in the form of MoO3 and W exists in the form of WO3, and the molybdenum-tungsten composite oxide is directionally enriched on the catalyst surface, forming a core-shell distribution.

5. The denitrification catalyst according to claim 1, characterized in that, The modifier lanthanum exists in the form of La2O3.

6. A method for preparing a denitrification catalyst as described in any one of claims 1-5, characterized in that, The preparation method of the denitration catalyst is as follows: Step 1: Dissolve titanium source and silicon source in anhydrous ethanol, adjust pH and mix, add lanthanum nitrate and carbonaceous template agent, ultrasonically disperse to form gel, dry and calcine to obtain modified titanium-silicon composite oxide carrier. Step 2: Dissolve manganese nitrate tetrahydrate, cerium nitrate hexahydrate, and zirconium nitrate pentahydrate in deionized water, add citric acid, adjust the pH, and obtain the active component precursor solution. Step 3: Dissolve ammonium molybdate tetrahydrate and ammonium metatungstate in deionized water, heat to dissolve, and obtain the auxiliary agent precursor solution; Step 4: The modified titanium-silicon composite oxide support is added to the active component precursor solution for ultrasonic impregnation and evaporation drying. Then, the auxiliary agent precursor solution is added for pulsed microwave-assisted impregnation, followed by drying and calcination. Finally, a binder is added, the mixture is kneaded and shaped, dried, and calcined to obtain the denitrification catalyst.

7. The method for preparing the denitrification catalyst according to claim 6, characterized in that, In step one, the titanium source is tetrabutyl titanate and the silicon source is tetraethyl orthosilicate. The calcination process is divided into two steps: the first step is to keep warm at 300℃ for 1 hour, and the second step is to calcine at 550-650℃ for 3-5 hours. The carbon template agent is coconut shell carbon powder with a particle size of 50-100nm, and the amount added is 5%-10% of the carrier mass.

8. The method for preparing the denitrification catalyst according to claim 6, characterized in that, In step two, the total molar ratio of citric acid to metal ions is 1.2:1, and the pH is adjusted to 5-6.

9. The method for preparing the denitration catalyst according to claim 6, characterized in that, In step four, the parameters for pulsed microwave-assisted impregnation are: microwave power of 700-900W, pulse mode of 3-5 seconds on / 9-15 seconds off, processing time of 10-15 minutes; calcination temperature of 450-550℃, and calcination time of 2-3 hours.

10. The method for preparing the denitration catalyst according to claim 6, characterized in that, In step four, the binder is silica sol, and the amount added is 5%-8% of the sample mass.

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