A denitration catalyst with low SO2 / SO3 conversion rate and a preparation method thereof

Abstract

This invention relates to the field of SCR denitrification catalyst preparation technology, and in particular to a denitrification catalyst with low SO2 / SO3 conversion rate and its preparation method. The denitrification catalyst has a core-shell structure, including an active core and a coating layer; the active core is a V-MoSnLa / TiO2 composite oxide; the coating layer is a Co-P-Si composite; the mass ratio of the active core to the coating layer is 1:(0.1~0.3). By constructing an "active core-coating layer" core-shell structure, this invention can fundamentally achieve extremely low SO2 oxidation rate and excellent resistance to alkali metal poisoning while maintaining or even improving the high denitrification activity of V-based catalysts. Furthermore, the preparation method is controllable and can meet the denitrification requirements of complex industrial flue gas, applicable to NO emission control under flue gas conditions in coal-fired units, steel sintering machines, coking, and building materials industries.

Description

Technical Field

[0001] This invention relates to the field of SCR denitrification catalyst preparation technology, and in particular to a denitrification catalyst with low SO2 / SO3 conversion rate and its preparation method. Background Technology

[0002] Selective catalytic reduction (SCR) technology is currently the most advanced technology for removing nitrogen oxides (NOx) from industrial flue gas. X This is the most mature and widely used technology. Its core is to use ammonia (NH3) as a reducing agent under the action of a catalyst to reduce NO. X It efficiently and selectively reduces to harmless nitrogen (N2) and water (H2O). Currently, V2O5-MoO3 / TiO2 series catalysts are widely used in coal-fired power plants, steel and other industries due to their advantages such as wide temperature window and high denitrification activity.

[0003] However, with increasingly stringent environmental standards and the increasing complexity of industrial flue gas conditions, the inherent defects of traditional V-based SCR catalysts in practical applications are becoming increasingly prominent, mainly in the following two aspects: While catalyzing the NH3-SCR reaction, the V2O5 component also possesses strong oxidizing ability, catalytically oxidizing the large amount of SO2 present in the flue gas to SO3. The generated SO3 reacts with escaped NH3 to produce viscous ammonium bisulfate (NH4HSO4) and ammonium sulfate. These ammonium salts deposit in low-temperature regions (such as the cold end of the air preheater), causing equipment blockage and increased resistance, affecting the safe operation of the system; on the other hand, they cover the catalyst surface, blocking pores, leading to catalyst activity decay and shortening service life. Therefore, inhibiting the SO2 oxidation activity of the catalyst is a long-standing challenge for SCR technology. Furthermore, under conditions involving the combustion of high-alkali coal, biomass, or co-firing of waste, the potassium content in the flue gas... + Na + Alkali metal ions migrate to the catalyst surface and irreversibly bind to the catalyst's acidic active sites (such as V-OH), leading to permanent poisoning and deactivation of the catalyst, which severely limits the catalyst's service life under complex flue gas conditions.

[0004] To address the above problems, existing technologies have made a series of improvement attempts, but all of them have certain limitations.

[0005] For example, Chinese invention patent CN109482181A discloses a catalyst for reducing SO2 / SO3 conversion by adding yttrium trichloride (YCl3). The principle is to utilize the catalytic effect of yttrium to promote the reduction reaction of SO2 / SO3, thus counteracting the oxidation of V2O5. While this method reduces SO2 conversion to some extent (optimally 6.1% in the examples), it essentially introduces another component with the opposite function for "neutralization," failing to fundamentally inhibit the oxidation activity of V2O5. Furthermore, this catalyst has a conventional supported mixed structure, lacking a physical barrier mechanism against alkali metal ions, resulting in limited improvement in anti-poisoning ability. Moreover, its preparation process focuses on the extrusion molding of honeycomb ceramics, potentially leading to insufficient nanoscale uniformity of component dispersion.

[0006] Another Chinese invention patent, CN120460014A, proposes a core-shell structured catalyst for synergistic denitrification and dioxin removal. This design utilizes CeMoLaSnO. X The catalyst uses microspheres as its core and porous SiO2-TiO2@ZSM-5 as its shell, with Fe-Co-Ni-Y oxides supported on the outermost layer. This core-shell structure primarily protects the active core, enables shape-selective catalysis, and supports multiple active components to address challenges related to low-temperature activity and dioxin degradation. However, the catalyst's composition (Ce-based, molecular sieve, transition metal composite oxides) and design goals are mainly aimed at complex flue gas from waste incineration processes involving low temperatures and multiple pollutants (including dioxins), rather than specifically addressing the core challenges of traditional V-based catalysts: inhibiting SO2 oxidation and enhancing resistance to alkali metal poisoning. Its complex shell structure results in high cost, and the mechanism by which it inhibits SO2 oxidation remains unclear.

[0007] Therefore, in view of the shortcomings of existing technologies, there is an urgent need to develop a new catalyst design method that can fundamentally achieve extremely low SO2 oxidation rate and excellent resistance to alkali metal poisoning while maintaining or even improving the high denitrification activity of V-based catalysts, and whose preparation method is controllable and suitable for industrial production.

[0008] In view of this, the present invention is proposed. Summary of the Invention

[0009] The purpose of this invention is to provide a denitrification catalyst with low SO2 / SO3 conversion rate and its preparation method. This denitrification catalyst has extremely low SO2 oxidation rate and excellent resistance to alkali metal poisoning.

[0010] In a first aspect, the present invention provides a denitrification catalyst with low SO2 / SO3 conversion rate, wherein the denitrification catalyst has a core-shell structure, comprising an active core and a coating layer; The active core is a V-MoSnLa / TiO2 composite oxide; The encapsulation layer is a Co-P-Si composite; The mass ratio of the active core to the encapsulation layer is 1:(0.1~0.3).

[0011] As a preferred embodiment of this technical solution, the mass percentage of each component in the V-MoSnLa / TiO2 composite oxide, calculated as oxides, is as follows: V2O5 1%~5%, MoO3 2%~8%, SnO2 0.1%~1%, La2O3 0.5%~2%, with the remainder being TiO2.

[0012] As a preferred embodiment of this technical solution, the mass percentage of each component in the Co-P-Si composite, calculated as oxides and elements, is: Co3O4 50%~80%, P 0.5%~3%, and the remainder is SiO2.

[0013] As a preferred embodiment of this technical solution, the particle size of the V-MoSnLa / TiO2 composite oxide is 20~50nm.

[0014] Secondly, this invention also discloses a method for preparing a denitrification catalyst with low SO2 / SO3 conversion rate, specifically including the following steps: S1. Dissolve the titanium source in anhydrous ethanol to prepare solution A; dissolve the vanadium source, molybdenum source, tin source and lanthanum source in oxalic acid to prepare solution B; slowly add solution B to solution A, and adjust the pH to 2-4 with oxalic acid, stir to form a sol, and after aging, drying, calcination and grinding, obtain V-MoSnLa / TiO2 composite oxide; S2. Dissolve the silicon source in anhydrous ethanol to prepare solution C; dissolve the cobalt source and phosphorus source in deionized water to prepare solution D; slowly add solution D to solution C, and adjust the pH to 3-5 with oxalic acid, stir, and obtain Co-P-Si composite sol; S3. The V-MoSnLa / TiO2 composite oxide prepared in step S1 is added to the Co-P-Si composite sol prepared in step S2. After ultrasonic dispersion, the mixture is stirred until the solvent is completely evaporated. After drying and calcination, the denitrification catalyst is obtained.

[0015] In the preparation method of the denitrification catalyst with low SO2 / SO3 conversion rate of the present invention, for the preparation of the active core of V-MoSnLa / TiO2 composite oxide, anhydrous ethanol is first used instead of water to dissolve the titanium source, which can effectively control the hydrolysis rate of the titanium source and form a uniform sol; at the same time, oxalic acid is used to dissolve the vanadium source, molybdenum source, tin source and lanthanum source. Oxalic acid, as a strong complexing agent, can react with V 5+ Mo 6+ Sn 4+ La 3+To ensure the uniform mixing of active components at the molecular level, stable soluble complexes are formed by the metal ions, preventing individual precipitation or segregation of any component in subsequent processes. Solution B is then slowly added to solution A, and the pH is adjusted to 2-4 using oxalic acid. Under these conditions, titanium alkoxide slowly hydrolyzes and condenses to form a Ti-O-Ti network, while the metal-oxalic acid complex gradually releases metal ions, which are then embedded into the growing TiO2 network in an atomically dispersed manner. This not only improves the uniformity of the active components but also lays the foundation for the subsequent synergistic effect of SnO2 and V2O5, as well as the embedding of La2O3 into the TiO2 lattice, and pre-anchoring of potentially infiltrated alkali metal ions. For the preparation of Co-P-Si composite sol, anhydrous ethanol is first used to dissolve the silicon source to form a uniform and continuous SiO2 network framework; simultaneously, water is used to dissolve the cobalt and phosphorus sources. Then, solution D is slowly added to solution C, and the pH is adjusted to 3-5 using oxalic acid. Under these conditions, silanol (Si-OH) and cobalt (Co) ions generated by silane hydrolysis... 2+ ) and phosphate / phosphate ions (such as H2PO4) - Complex interactions occur between them: Co 2+ Co-O-Si bonds are formed with Si-OH, and phosphate ions are connected to the silicon-oxygen network through PO-Si bonds, or form Co-OP bonds with Co. This method effectively ensures that the subsequently formed coating layer is not a simple physical mixture of Co3O4 particles and SiO2 powder, but a chemically bonded, homogeneous composite oxide phase. Finally, the core-shell structure is constructed through ultrasonic dispersion, dissolution and slow evaporation, and secondary calcination. Therefore, the denitrification catalyst prepared by this invention can fundamentally achieve extremely low SO2 oxidation rate and excellent resistance to alkali metal poisoning while maintaining or even improving the high denitrification activity of V-based catalysts.

[0016] As a preferred embodiment of this technical solution, the present invention does not strictly limit the specific types of titanium sources, vanadium sources, molybdenum sources, tin sources, lanthanum sources, silicon sources, cobalt sources, and phosphorus sources involved. For example, the titanium source includes any one or two of tetrabutyl titanate and isopropyl titanate; the vanadium source includes any one or more of vanadium oxysulfate, ammonium metavanadate, and vanadium oxyoxalate; the molybdenum source includes any one or two of ammonium heptamolybdate and molybdenum oxalate; the tin source includes any one or two of stannous chloride and stannous oxalate; the lanthanum source includes any one or two of lanthanum nitrate and lanthanum chloride; the silicon source includes any one or two of tetrabutyl titanate and isopropyl titanate; the cobalt source includes any one or two of cobalt nitrate and cobalt acetate; and the phosphorus source includes any one or two of phosphoric acid and ammonium dihydrogen phosphate.

[0017] As a preferred embodiment of this technical solution, in step S1, the temperature is controlled at 60~80℃ during stirring.

[0018] As a preferred embodiment of this technical solution, in step S1, the calcination is carried out at 400~500℃ for 3~6 hours.

[0019] At this temperature, calcination causes the oxalate complex to decompose, and oxides or composite oxides of V, Mo, Sn, and La are firmly loaded or doped onto the TiO2 surface and near the surface in a highly dispersed state, forming abundant VO-Ti, Mo-O-Ti, and other active interfaces. Calcination temperatures that are too low can lead to organic residues and insufficient crystallinity, while calcination temperatures that are too high are detrimental to the formation of the optimal carrier crystal form (anatase TiO2) and can cause problems such as sintering and aggregation of active components, and a sharp drop in specific surface area.

[0020] As a preferred embodiment of this technical solution, in step S2, the temperature is controlled at 50~70℃ during stirring.

[0021] As a preferred embodiment of this technical solution, in step S3, the temperature is controlled at 70~90℃ during stirring.

[0022] Stirring at 70-90℃ until the solvent evaporates completely, the system concentration increases as the solvent evaporates, and the adsorption-concentration-gelation process of the coating sol on the surface of the active core particles proceeds slowly, which helps to form a continuous, complete, dense but porous gel film on the particle surface.

[0023] As a preferred embodiment of this technical solution, in step S3, the drying process involves drying at 100~120℃ for 4~8 hours to remove surface moisture.

[0024] As a preferred embodiment of this technical solution, in step S3, the calcination is carried out at 400~500℃ for 2~5 hours.

[0025] Calcination at this temperature not only promotes the transformation of the gel-state Co-P-Si precursor into the target oxide phase, but also enhances the mechanical strength and thermal stability of the core-shell structure.

[0026] The denitrification catalyst with low SO2 / SO3 conversion rate of the present invention has at least the following beneficial effects: 1. The present invention provides a denitrification catalyst with low SO2 / SO3 conversion rate, comprising an active core and a coating layer. The active core is a V-MoSnLa / TiO2 composite oxide, and the coating layer is a Co-P-Si composite. The core function of the V-MoSnLa / TiO2 composite oxide active core is to catalyze the NH3-SCR reaction with high selectivity and high rate; the Co-P-Si composite coating layer serves to selectively permeate, pre-activate the reaction, and enhance mechanical properties. 2. The denitrification catalyst with low SO2 / SO3 conversion rate of the present invention has the effect of synergistically inhibiting SO2 oxidation. Specifically, firstly, SnO2 and V2O5 in the active core form a synergistic effect, which reduces the thermodynamic driving force and kinetic rate of SO2 oxidation reaction from the source; secondly, the outer Co-P-Si coating layer forms a physical barrier, reducing the probability of SO2 contact with the active core. The dual effect greatly reduces the SO2 oxidation rate of the catalyst. 3. The denitration catalyst with low SO2 / SO3 conversion rate of this invention possesses high denitration activity and a wide temperature window. Specifically, firstly, TiO2 not only provides a support but also forms a stable acidic-redox bifunctional active center with V and Mo species; while MoO3 not only broadens the temperature window but also synergizes with V2O5 to assist its redox cycle, ensuring efficient denitration reaction. Secondly, the Co-P-Si coating layer has certain acidic sites, which can promote the adsorption and activation of NH3, effectively maintaining the wide temperature window and high activity of the denitration catalyst. Studies have shown that the denitration catalyst of this invention can maintain a denitration efficiency of over 90% within a temperature window of 220~420℃. 4. The denitrification catalyst with low SO2 / SO3 conversion rate of the present invention possesses excellent resistance to alkali metals. Specifically, firstly, La2O3 can stabilize the catalyst structure and pre-anchor any alkali metal ions that may penetrate, thereby improving the catalyst's resistance to alkali metals; secondly, the outer Co-P-Si coating layer can effectively block K+. + Na + Alkali metal ions diffuse to the active sites, significantly enhancing the catalyst's alkali metal poisoning ability.

[0027] Therefore, the denitrification catalyst of the present invention can fundamentally achieve extremely low SO2 oxidation rate and excellent resistance to alkali metal poisoning while maintaining or even improving the high denitrification activity of V-based catalysts. Detailed Implementation

[0028] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application. As used herein, the singular form includes the plural form unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this description, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0030] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0031] Example 1 S1, Preparation of Active Core Dissolve the titanium source (corresponding to a TiO2 content of 86.9%) in anhydrous ethanol to prepare solution A; Take vanadium source (corresponding to V2O5 content 4.2%), molybdenum source (corresponding to MoO3 content 6.5%), tin source (corresponding to SnO2 content 0.6%), and lanthanum source (corresponding to La2O3 content 1.8%), dissolve them together in oxalic acid solution, and sonicate for 15 min to prepare solution B; Solution B was slowly added dropwise to solution A, and the pH was adjusted to 2.5 with oxalic acid solution. The solution was then stirred in a 70°C water bath to form a homogeneous sol. The sol was aged at room temperature for 18 hours, dried at 90°C for 8 hours, and then calcined at 490°C for 4.5 hours. After natural cooling, the sol was ground to obtain V-MoSnLa / TiO2 active core particles of 30-40 nm.

[0032] S2, Preparation of coating layer precursor solution Dissolve the silicon source (corresponding to 20% SiO2 content) in anhydrous ethanol and stir until homogeneous to prepare solution C; Dissolve a cobalt source (corresponding to a Co3O4 content of 78%) and a phosphorus source (corresponding to a P content of 2%) in deionized water and stir until completely dissolved to prepare solution D; Solution D was slowly added to solution C and stirred continuously for 30 minutes. The pH was adjusted to 4 with oxalic acid solution and then stirred in a 60°C water bath for 2 hours to form a stable Co-P-Si composite sol.

[0033] S3, Core-shell structure construction The active core particles were added to the Co-P-Si composite sol and ultrasonically dispersed for 30 minutes to ensure uniform particle dispersion. The mixture was placed in an 80°C oil bath and magnetically stirred until the solvent was completely evaporated, resulting in a loose solid precursor. The precursor was dried in an oven at 110℃ for 6 hours, and then calcined in a muffle furnace at 450℃ for 3 hours. After cooling, a denitrification catalyst with low SO2 / SO3 conversion rate was obtained, wherein the mass ratio of the coating layer to the active core was 1:0.25.

[0034] Example 2 S1, Preparation of Active Cores Dissolve the titanium source (corresponding to a TiO2 content of 96.4%) in anhydrous ethanol to prepare solution A; Take vanadium source (corresponding to 1% V2O5 content), molybdenum source (corresponding to 2.0% MoO3 content), tin source (corresponding to 0.1% SnO2 content), and lanthanum source (corresponding to 0.5% La2O3 content), dissolve them together in oxalic acid solution, and sonicate for 15 min to prepare solution B; Solution B was slowly added dropwise to solution A, and the pH was adjusted to 2 with oxalic acid solution. The solution was then stirred in a 60°C water bath for 3 hours to form a homogeneous sol. The sol was aged at room temperature for 18 hours, dried at 90°C for 8 hours, and then calcined at 400°C for 3 hours. After natural cooling, the sol was ground to obtain V-MoSnLa / TiO2 active core particles of 20~30 nm.

[0035] S2, Preparation of coating layer precursor solution Dissolve the silicon source (corresponding to a SiO2 content of 49.5%) in anhydrous ethanol and stir until homogeneous to prepare solution C; Dissolve a cobalt source (corresponding to 50% Co3O4 content) and a phosphorus source (corresponding to 0.5% P content) in deionized water and stir until completely dissolved to prepare solution D; Solution D was slowly added to solution C and stirred continuously for 30 minutes. The pH was adjusted to 3 with oxalic acid solution and then stirred in a 50°C water bath for 2 hours to form a stable Co-P-Si composite sol.

[0036] S3, Core-shell structure construction The active core particles were added to the Co-P-Si composite sol and ultrasonically dispersed for 20 minutes to ensure uniform particle dispersion. The mixture was placed in a 70°C oil bath and magnetically stirred until the solvent was completely evaporated, resulting in a loose solid precursor. The precursor was dried in an oven at 100°C for 4 hours, and then calcined in a muffle furnace at 400°C for 2 hours. After cooling, a denitrification catalyst with low SO2 / SO3 conversion rate was obtained, wherein the mass ratio of the coating layer to the active core was 1:0.1.

[0037] Example 3 S1, Preparation of Active Cores Dissolve the titanium source (corresponding to a TiO2 content of 84.0%) in anhydrous ethanol to prepare solution A; Take vanadium source (corresponding to V2O5 content 5.0%), molybdenum source (corresponding to MoO3 content 8.0%), tin source (corresponding to SnO2 content 1.0%), and lanthanum source (corresponding to La2O3 content 2.0%), dissolve them together in oxalic acid solution, and sonicate for 15 min to prepare solution B; Solution B was slowly added dropwise to solution A, and the pH was adjusted to 4.0 with oxalic acid solution. The solution was then stirred in an 80°C water bath for 3 hours to form a homogeneous sol. The sol was aged at room temperature for 18 hours, dried at 90°C for 8 hours, and then calcined at 500°C for 6 hours. After natural cooling, the sol was ground to obtain V-MoSnLa / TiO2 active core particles of 40~50 nm.

[0038] S2, Preparation of coating layer precursor solution Dissolve the silicon source (corresponding to a SiO2 content of 17.0%) in anhydrous ethanol and stir until homogeneous to prepare solution C; Dissolve a cobalt source (corresponding to 80% Co3O4 content) and a phosphorus source (corresponding to 3% P content) in deionized water and stir until completely dissolved to prepare solution D; Solution D was slowly added to solution C and stirred continuously for 30 minutes. The pH was adjusted to 5 with oxalic acid solution and then stirred in a 70°C water bath for 2 hours to form a stable Co-P-Si composite sol.

[0039] S3, Core-shell structure construction The active core particles were added to the Co-P-Si composite sol and ultrasonically dispersed for 40 minutes to ensure uniform particle dispersion. The mixture was placed in a 90°C oil bath and magnetically stirred until the solvent was completely evaporated, resulting in a loose solid precursor. The precursor was dried in an oven at 120°C for 8 hours, and then calcined in a muffle furnace at 500°C for 5 hours. After cooling, a denitrification catalyst with low SO2 / SO3 conversion rate was obtained, wherein the mass ratio of the coating layer to the active core was 1:0.3.

[0040] Example 4 S1, Preparation of Active Cores Dissolve the titanium source (corresponding to a TiO2 content of 92.2%) in anhydrous ethanol to prepare solution A; Take vanadium source (corresponding to V2O5 content 3.0%), molybdenum source (corresponding to MoO3 content 3.0%), tin source (corresponding to SnO2 content 1.0%), and lanthanum source (corresponding to La2O3 content 0.8%), dissolve them together in oxalic acid solution, and sonicate for 15 min to prepare solution B; Solution B was slowly added dropwise to solution A, and the pH was adjusted to 3.0 with oxalic acid solution. The solution was then stirred in a 72°C water bath for 3 hours to form a homogeneous sol. The sol was aged at room temperature for 18 hours, dried at 90°C for 8 hours, and then calcined at 450°C for 5 hours. After natural cooling, the sol was ground to obtain V-MoSnLa / TiO2 active core particles of 30~50 nm.

[0041] S2, Preparation of coating layer precursor solution Dissolve the silicon source (corresponding to a SiO2 content of 27.5%) in anhydrous ethanol and stir until homogeneous to prepare solution C; Dissolve a cobalt source (corresponding to a Co3O4 content of 70%) and a phosphorus source (corresponding to a P content of 2.5%) in deionized water and stir until completely dissolved to prepare solution D; Solution D was slowly added to solution C and stirred continuously for 30 minutes. The pH was adjusted to 3.5 with oxalic acid solution and then stirred in a 65°C water bath for 2 hours to form a stable Co-P-Si composite sol.

[0042] S3, Core-shell structure construction The active core particles were added to the Co-P-Si composite sol and ultrasonically dispersed for 25 minutes to ensure uniform particle dispersion. The mixture was placed in a 75°C oil bath and magnetically stirred until the solvent was completely evaporated, resulting in a loose solid precursor. The precursor was dried in an oven at 115℃ for 6.5 h, and then calcined in a muffle furnace at 470℃ for 5 h. After cooling, a denitrification catalyst with low SO2 / SO3 conversion rate was obtained, wherein the mass ratio of the coating layer to the active core was 1:0.15.

[0043] Example 5 S1, Preparation of Active Cores Dissolve the titanium source (corresponding to a TiO2 content of 89.5%) in anhydrous ethanol to prepare solution A; Take vanadium source (corresponding to V2O5 content 1.5%), molybdenum source (corresponding to MoO3 content 7.0%), tin source (corresponding to SnO2 content 0.2%), and lanthanum source (corresponding to La2O3 content 1.8%), dissolve them together in oxalic acid solution, and sonicate for 15 min to prepare solution B; Solution B was slowly added dropwise to solution A, and the pH was adjusted to 3.5 with oxalic acid solution. The solution was then stirred in a 65°C water bath for 3 hours to form a homogeneous sol. The sol was aged at room temperature for 18 hours, dried at 90°C for 8 hours, and then calcined at 430°C for 4.5 hours. After natural cooling, the sol was ground to obtain V-MoSnLa / TiO2 active core particles with a diameter of 20-40 nm.

[0044] S2, Preparation of coating layer precursor solution Dissolve the silicon source (corresponding to a SiO2 content of 36.2%) in anhydrous ethanol and stir until homogeneous to prepare solution C; Dissolve a cobalt source (corresponding to a Co3O4 content of 62%) and a phosphorus source (corresponding to a P content of 1.8%) in deionized water and stir until completely dissolved to prepare solution D; Solution D was slowly added to solution C and stirred continuously for 30 minutes. The pH was adjusted to 4.5 with oxalic acid solution and then stirred in a 72°C water bath for 2 hours to form a stable Co-P-Si composite sol.

[0045] S3, Core-shell structure construction The active core particles were added to the Co-P-Si composite sol and ultrasonically dispersed for 35 minutes to ensure uniform particle dispersion. The mixture was placed in an 85°C oil bath and magnetically stirred until the solvent was completely evaporated, resulting in a loose solid precursor. The precursor was dried in an oven at 113℃ for 7 hours, and then calcined in a muffle furnace at 430℃ for 4.5 hours. After cooling, a denitrification catalyst with low SO2 / SO3 conversion rate was obtained, wherein the mass ratio of the coating layer to the active core was 1:0.26.

[0046] Compare with Example 1 This comparative example is basically the same as Example 1, except that the V-MoSnLa / TiO2 active core prepared in step S1 is used directly as the catalyst.

[0047] Compare with Example 2 This comparative example is basically the same as Example 1, except that: in step S1, no tin source and lanthanum source are added, and the active core components are V2O 52%, MoO 36%, and TiO 292%, while the other steps remain unchanged.

[0048] Compare with Example 3 This comparative example uses a conventional V-Mo / TiO2 catalyst, which is prepared as follows: 0.8 g of ammonium metavanadate and 2.4 g of ammonium molybdate were dissolved in deionized water, and 40 g of TiO2 support was added. The mixture was stirred and impregnated for 4 h, dried at 90 °C for 8 h, and calcined at 500 °C for 4 h to obtain the V2O5-MoO3 / TiO2 catalyst.

[0049] Compare with Example 4 This comparative example is basically the same as Example 1, except that: in step S2, ammonium dihydrogen phosphate is not added, and the coating layer composition is 50% Co3O4 and 50% SiO2, while the other steps remain unchanged.

[0050] Compare with Example 5 This comparative example is basically the same as Example 1, except that the precursors of the active core components (V, Mo, Sn, La, Ti) and the coating layer components (Co, P, Si) are directly mixed, and a sol-gel and calcination process similar to that in Example 1 is used to prepare a composite oxide catalyst with "the same composition but uniform structure" (denoted as V-MoSnLa-Co-P-Si / TiO2).

[0051] To verify the performance of the denitrification catalysts prepared in the above examples and comparative examples, the present invention tested the denitrification efficiency, SO2 oxidation rate and alkali metal resistance of the catalysts obtained in Examples 1-5 and Comparative Examples 1-5.

[0052] The testing method is as follows: The catalyst prepared above was crushed and sieved to 40-60 mesh, and 1.0g was loaded into a fixed-bed reactor.

[0053] The test conditions were as follows: simulated flue gas composition: NH3 500ppm (not added when testing SO2 / SO3 conversion rate), NO 500ppm, O2 5%, SO2 2000 ppm (added during use), H2O 15%, N2 balance gas, and space velocity GHSV = 60000 h⁻¹. -1 The volume fractions of NO and NO2 in the post-reaction mixture were analyzed using a GA-21plus flue gas analyzer, and the denitrification efficiency ηNO (%) was calculated. The results are detailed in Table 1. Table 1 Test Results

[0054] As shown in Table 1, the denitrification catalyst prepared in this invention has a significant synergistic effect in inhibiting SO2 oxidation. For example, the SO2 / SO3 conversion rate of Example 1 at 380℃ was only 0.8%, far lower than all control examples; the conversion rate of Control Example 1 (without coating layer) increased to 2.8%, indicating that the Co-P-Si coating layer, as a physical barrier, effectively blocked SO2 from contacting the active core, which is the key to reducing SO2 oxidation; the conversion rate of Control Example 2 (without Sn, La) (1.9%) was higher than that of Example 1 but lower than that of Control Example 1, indicating that the synergistic effect of SnO2 and V2O5 in the active core can also inhibit oxidation, but the effect is weaker than that of the coating layer; the conversion rate of Control Example 4 (without P) (1.5%) was higher than that of Example 1, indicating that the introduction of P in the coating layer has a positive effect on optimizing the coating layer structure and enhancing the barrier effect; Control Example 5 (same composition but homogeneous structure) lost the protection of the coating layer and Sn 4+ Precise control of the V active sites restored the catalyst's inhibition of SO2 oxidation to its original state. Example 1 of this invention achieved the "dual effect" of active core modification and shell barrier, resulting in the best effect.

[0055] Furthermore, the denitrification catalyst prepared by this invention also possesses high denitrification activity and a wide temperature window. For example, the active temperature window (>90%) of all catalysts in all embodiments of this invention is wider than 220-420℃, with Example 1 having the widest window (200-440℃), completely covering the typical SCR operating range from medium to high temperature; Control Example 3 (conventional catalyst) has the narrowest window (250-380℃); Control Example 5 (same composition but homogeneous structure) shows that different components are more likely to migrate and sinter at high temperatures, resulting in a reduction in active surface area and a decrease in high-temperature activity and stability. This indicates that the V-MoSnLa / TiO2 active core and the Co-P-Si coating layer together provide more abundant and efficient active sites and acidic sites, promoting the adsorption and activation of NH3, thereby broadening the reaction window and maintaining high activity.

[0056] Finally, the denitration catalyst prepared in this invention also exhibits excellent resistance to alkali metal (K) poisoning. For example, after simulating alkali metal poisoning by loading 1.0% K₂O, Example 1 still maintained a denitration efficiency of 88.5% at 380°C, demonstrating the strongest resistance to poisoning; while the efficiency of Control Example 1 (without the coating layer) dropped significantly to 72.4%, directly proving that the Co-P-Si coating layer can effectively block K. + The physical protection effect of diffusion into the internal active sites; the efficiency of Control Example 2 (without La) (78.6%) was lower than that of Example 1 but higher than that of Control Example 1, indicating that the introduction of La2O3 did indeed enhance the alkali metal resistance of the active core itself; Control Example 3 (conventional catalyst) had the worst resistance to K poisoning (65.0%); Control Example 5 (same composition but homogeneous structure) exhibited alkali poisoning similar to that of conventional catalysts due to the loss of the protective coating. This further demonstrates that Example 1 of the present invention, through the synergy of the "La2O3 modified core" and the "Co-P-Si protective shell," achieved a significant improvement in alkali metal resistance.

[0057] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A denitrification catalyst with low SO2 / SO3 conversion rate, characterized in that, The denitration catalyst has a core-shell structure, including an active core and a coating layer; The active core is a V-MoSnLa / TiO2 composite oxide; The encapsulation layer is a Co-P-Si composite; Preferably, the mass ratio of the active core to the encapsulation layer is 1:(0.1~0.3).

2. The denitrification catalyst with low SO2 / SO3 conversion rate according to claim 1, characterized in that, In the V-MoSnLa / TiO2 composite oxide, the mass percentage of each component as oxide is: V2O5 1%~5%, MoO3 2%~8%, SnO2 0.1%~1%, La2O3 0.5%~2%, and the remainder is TiO2.

3. The denitrification catalyst with low SO2 / SO3 conversion rate according to claim 1, characterized in that, In the Co-P-Si composite, the mass percentage of each component, calculated as oxides and elements, is: Co3O4 50%~80%, P 0.5%~3%, and the remainder is SiO2.

4. The denitrification catalyst with low SO2 / SO3 conversion rate according to claim 1, characterized in that, The particle size of the V-MoSnLa / TiO2 composite oxide is 20~50nm.

5. A method for preparing a denitrification catalyst with low SO2 / SO3 conversion rate, characterized in that, Includes the following steps: S1. Dissolve the titanium source in anhydrous ethanol to prepare solution A; dissolve the vanadium source, molybdenum source, tin source and lanthanum source in oxalic acid to prepare solution B; slowly add solution B to solution A, and adjust the pH to 2-4 with oxalic acid, stir to form a sol, and after aging, drying, calcination and grinding, obtain V-MoSnLa / TiO2 composite oxide; S2. Dissolve the silicon source in anhydrous ethanol to prepare solution C; dissolve the cobalt source and phosphorus source in deionized water to prepare solution D; slowly add solution D to solution C, and adjust the pH to 3-5 with oxalic acid, stir, and obtain Co-P-Si composite sol; S3. The V-MoSnLa / TiO2 composite oxide prepared in step S1 is added to the Co-P-Si composite sol prepared in step S2. After ultrasonic dispersion, it is stirred until the solvent is completely evaporated. After drying and calcination, the denitration catalyst is obtained. There is no restriction on the order of steps S1 and S2.

6. The method for preparing the denitrification catalyst with low SO2 / SO3 conversion rate according to claim 5, characterized in that, In step S1, the temperature is controlled at 60~80℃ during stirring.

7. The method for preparing the denitrification catalyst with low SO2 / SO3 conversion rate according to claim 5, characterized in that, In step S1, the calcination is carried out at 400~500℃ for 3~6 hours.

8. The method for preparing the denitrification catalyst with low SO2 / SO3 conversion rate according to claim 5, characterized in that, In step S2, the temperature is controlled at 50~70℃ during stirring.

9. The method for preparing the denitrification catalyst with low SO2 / SO3 conversion rate according to claim 5, characterized in that, In step S3, the temperature is controlled at 70~90℃ during stirring.

10. The method for preparing the denitrification catalyst with low SO2 / SO3 conversion rate according to claim 5, characterized in that, In step S3, the drying process is carried out at 100~120℃ for 4~8 hours; During the calcination process, the calcination temperature is 400-500℃ for 2-5 hours.

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