Thin-wall denitration catalyst and preparation method thereof

Abstract

The present application relates to the technical field of environmental protection catalytic material, and is a thin-wall denitration catalyst and a preparation method thereof; the thin-wall denitration catalyst raw material comprises titanium tungsten powder, V2O5, WO3, glass fiber, silicon dioxide, clay or kaolin, cellulose, stearic acid, high molecular fiber and deionized water; the present application takes in-situ composite titanium tungsten powder as a carrier, V2O5 as an active component, and WO3 as an additive, so that the obtained thin-wall denitration catalyst has a honeycomb wall thickness of 0.28 mm to 0.42 mm, a gradient structure of the pore, a specific surface area of greater than or equal to 80 m 2 / g, an activity increase of greater than or equal to 22%, a selectivity increase of greater than or equal to 16%, and a single titanium tungsten powder consumption of less than or equal to 386 kg; meanwhile, the present application realizes thin-wall precise forming, significantly reduces the raw material amount, reduces the cost by more than 30%, has excellent mechanical strength, can be industrially produced, and is suitable for efficient denitration of industrial flue gas.

Description

Technical Field

[0001] This invention relates to the field of environmentally friendly catalytic materials technology, specifically a thin-walled denitrification catalyst and its preparation method. Background Technology

[0002] With increasingly stringent environmental standards, selective catalytic reduction (SCR) denitrification technology has become the mainstream technology for flue gas treatment in industries such as coal-fired power plants, chemicals, and steel. Traditional honeycomb denitrification catalysts suffer from problems such as large wall thickness, limited specific surface area, low utilization rate of active components, high raw material consumption, and high production costs. Conventional catalysts can consume about 420 kg of titanium-tungsten powder per cubic meter, resulting in high raw material costs, and the catalytic activity and reaction efficiency are difficult to meet ultra-low emission requirements. Existing thin-walled catalyst preparation technologies often suffer from drawbacks such as difficulty in molding, insufficient mechanical strength, poor wall thickness uniformity, and difficulty in balancing activity and stability, making it difficult to achieve stable industrial production.

[0003] Patent document CN105498749A discloses a high-strength honeycomb thin-walled denitrification catalyst and its preparation method, belonging to the field of industrial denitrification technology. The high-strength honeycomb thin-walled denitrification catalyst is composed of the following components in parts by weight: 80-85 parts TiO2, 1-2 parts SiO2, 5-10 parts Ca(OH)2, 5-10 parts WO3, 50-2 parts V2O, and 1-3 parts glass fiber. Compared with existing technologies, this technical solution reduces bound water in the catalyst by adding Ca(OH)2, enhancing the bonding force between catalyst particles and thus increasing catalyst strength. Simultaneously, the addition of Ca ions can improve the catalyst's reactivity and catalytic efficiency to a certain extent, resulting in beneficial technical effects. This invention also provides a method for preparing the above-mentioned catalyst. This method, compared with existing processes, makes catalyst sludge extrusion easier, reduces production costs, and has broad market prospects.

[0004] Patent document CN104971715A discloses a method for preparing a honeycomb thin-walled denitration catalyst, comprising the following steps: ① mixing raw materials; ② extrusion molding: conveying the material in the mixer to the extruder to extrude a honeycomb preform; ③ drying: drying the preform at 25-65℃ and relative humidity of 10-90% for 8-10 days; ④ calcination: preheating the dried preform to 500-620℃ at a heating rate of 0.4-0.6℃ / min; then maintaining it at 500-620℃ for 5-7 hours; finally cooling to 60-80℃ at a cooling rate of 0.4-0.6℃ / min to obtain the finished product. This invention can mix various raw materials more uniformly, allowing the catalyst to have a thinner wall and larger pore size while maintaining its strength, thus reducing the weight per unit volume; it also shortens the drying and calcination time, improves production efficiency, and saves raw materials and energy.

[0005] Patent document CN201921694U discloses a thin-walled denitrification catalyst, comprising a cuboid catalyst body with a 20×20 square pore array evenly distributed along its long edge for flue gas passage. This invention fills the gap in the industry for thin-walled honeycomb catalyst product specifications, enabling it to better adapt to various flue gas treatment requirements. Simultaneously, it reduces the catalyst wall thickness, resulting in a lower SO2 oxidation rate during denitrification under the same conditions. This catalyst achieves a porosity of up to 80.2% and a geometrical specific surface area of ​​up to 482 m². 2 / m 3 This effectively increases the contact area between flue gas and catalyst. The larger inner diameter and higher porosity also make it less prone to ash blockage during the denitrification process under the same conditions.

[0006] The aforementioned publicly available patent documents primarily focus on wall thickness control, component modification, and low-temperature sulfur resistance. The first two patent documents employ Ca(OH)2 chemical reinforcement and a five-step mixing process for thinning, respectively, both involving uniform channels, conventional extrusion, purchased powders, and air calcination. No technical solutions combining gradient channel structures, vacuum-coupled stepwise molding, and in-situ reduction of titanium-tungsten powder were found. Therefore, developing a highly active, low-cost, mechanically strong, and scalable thin-walled SCR catalyst and its molding process has significant engineering value and economic benefits. Summary of the Invention

[0007] This invention provides a thin-walled denitrification catalyst and its preparation method, which overcomes the shortcomings of the prior art and can effectively solve the problems of existing catalysts such as large wall thickness, low activity, high raw material consumption, difficult molding and high cost.

[0008] One of the technical solutions of the present invention is achieved through the following measures: a thin-walled denitrification catalyst, wherein the raw materials, by weight, include 75 to 82 parts of titanium tungsten powder, 1.2 to 2.5 parts of V2O5, 2 to 5 parts of WO3, 3 to 6 parts of glass fiber, 1 to 4 parts of silica, 2 to 5 parts of clay or kaolin, 0.5 to 1.5 parts of cellulose, 0.2 to 1 part of stearic acid, 0.1 to 0.5 parts of polymer fiber, and 25 to 27.5 parts of water.

[0009] The following are further optimizations and / or improvements to one of the above-mentioned technical solutions: The above-mentioned thin-walled denitration catalyst is obtained by the following steps: The first step is in-situ composite activation of titanium-tungsten powder. The required amount of titanium-tungsten powder is activated by wet in-situ co-precipitation. During activation, the pH value is adjusted to 3.5 to 5.0. After activation, a highly dispersed composite carrier is obtained. The second step is to anchor the active components at the interface. By coupling spraying and in-situ deposition, the required amount of V2O5 is prepared into an ammonium metavanadate solution and sprayed onto the surface of a highly dispersed composite carrier to anchor and form a film. The third step is two-stage mixing and plasticizing. The materials obtained in the second step, the required amount of WO3, glass fiber, silica, clay or kaolin, cellulose, stearic acid, polymer fiber and water are added to the two-stage mixing process to obtain a plastic paste. The fourth step is vacuum coupling stepwise extrusion molding. The plastic paste enters the extruder, undergoes primary vacuum preforming, and then secondary precision stepwise extrusion molding to obtain a honeycomb preform. Step 5: Step-temperature controlled drying; the honeycomb embryos are dried under step-temperature controlled conditions. Step 6: Micro-oxygen atmosphere calcination. The dried honeycomb preform is then calcined in a micro-oxygen atmosphere. Step 7: Online inspection and cutting. After the calcined honeycomb preform passes the inspection, it is cut to obtain a thin-walled denitration catalyst.

[0010] In the second step above, the concentration of the ammonium metavanadate solution is 0.6% to 10%; or / and in the third step, the viscosity of the first stage of the two-stage mixing is 2000 cP to 3000 cP, and the viscosity of the second stage is 8000 cP to 12000 cP; or / and in the fourth step, the vacuum degree of the step extrusion is -0.08 MPa to -0.095 MPa; or / and in the fifth step, the honeycomb preform is dried sequentially at 55℃ for 2 h, at 85℃ for 4 h, and at 115℃ for 3 h; or / and in the fifth step, the temperature rise rate of the stepped temperature-controlled drying is ≤5℃ / h.

[0011] In the sixth step above, the honeycomb embryo is calcined at 460°C to 510°C for 2 to 4 hours; or / and, the volume percentage of oxygen in the micro-oxygen atmosphere is 3% to 8%.

[0012] The honeycomb wall thickness of the aforementioned thin-walled denitration catalyst is controlled between 0.28 mm and 0.42 mm; or / and the pore structure of the thin-walled denitration catalyst is a gradient structure, with dense micropores on the surface and interconnected mesopores in the inner layer, and a specific surface area ≥ 80 m². 2 / g.

[0013] The second technical solution of the present invention is achieved through the following measures: a method for preparing a thin-walled denitration catalyst, comprising the following steps: The first step is in-situ composite activation of titanium-tungsten powder. The required amount of titanium-tungsten powder is activated by wet in-situ co-precipitation. During activation, the pH value is adjusted to 3.5 to 5.0. After activation, a highly dispersed composite carrier is obtained. The second step is to anchor the active components at the interface. By coupling spraying and in-situ deposition, the required amount of V2O5 is prepared into an ammonium metavanadate solution and sprayed onto the surface of a highly dispersed composite carrier to anchor and form a film. The third step is two-stage mixing and plasticizing. The materials obtained in the second step, the required amount of WO3, glass fiber, silica, clay or kaolin, cellulose, stearic acid, polymer fiber and water are added to the two-stage mixing process to obtain a plastic paste. The fourth step is vacuum coupling stepwise extrusion molding. The plastic paste enters the extruder, undergoes primary vacuum preforming, and then secondary precision stepwise extrusion molding to obtain a honeycomb preform. Step 5: Step-temperature controlled drying; the honeycomb embryos are dried under step-temperature controlled conditions. Step 6: Micro-oxygen atmosphere calcination. The dried honeycomb preform is then calcined in a micro-oxygen atmosphere. Step 7: Online inspection and cutting. After the calcined honeycomb preform passes the inspection, it is cut to obtain a thin-walled denitration catalyst.

[0014] The following are further optimizations and / or improvements to the second technical solution of the above invention: In the second step above, the concentration of the ammonium metavanadate solution is 0.6% to 10%; or / and in the third step, the viscosity of the first stage of the two-stage mixing is 2000 cP to 3000 cP, and the viscosity of the second stage is 8000 cP to 12000 cP; or / and in the fourth step, the vacuum degree of the step extrusion is -0.08 MPa to -0.095 MPa; or / and in the fifth step, the honeycomb preform is dried sequentially at 55℃ for 2 h, at 85℃ for 4 h, and at 115℃ for 3 h; or / and in the fifth step, the temperature rise rate of the stepped temperature-controlled drying is ≤5℃ / h.

[0015] In the sixth step above, the honeycomb embryo is calcined at 460°C to 510°C for 2 to 4 hours; or / and, the volume percentage of oxygen in the micro-oxygen atmosphere is 3% to 8%.

[0016] The honeycomb wall thickness of the aforementioned thin-walled denitration catalyst is controlled between 0.28 mm and 0.42 mm; or / and the pore structure of the thin-walled denitration catalyst is a gradient structure, with dense micropores on the surface and interconnected mesopores in the inner layer, and a specific surface area ≥ 80 m². 2 / g.

[0017] This invention uses in-situ composite titanium-tungsten powder as a carrier, V₂O₅ as the active component, and WO₃ as an additive to obtain a thin-walled denitration catalyst with a honeycomb wall thickness of 0.28 mm to 0.42 mm, a gradient pore structure, and a specific surface area ≥ 80 m². 2 / g, activity increased by ≥22%, selectivity increased by ≥16%, single-unit titanium tungsten powder consumption ≤386kg; at the same time, the present invention achieves thin-walled precision molding, significantly reduces raw material volume, reduces cost by more than 30%, has excellent mechanical strength, can be industrialized, and is suitable for efficient denitrification of industrial flue gas. Detailed Implementation

[0018] This invention is not limited to the following embodiments, and specific implementation methods can be determined according to the technical solutions and actual conditions of this invention. Unless otherwise specified, all chemical reagents and chemical products mentioned in this invention are well-known and commonly used chemical reagents and chemical products in the prior art; unless otherwise specified, all percentages in this invention are mass percentages; unless otherwise specified, all solutions in this invention are aqueous solutions with water as the solvent, for example, hydrochloric acid solution is an aqueous solution of hydrochloric acid.

[0019] The present invention will be further described below with reference to embodiments: Example 1: The thin-walled denitrification catalyst comprises, by weight, 75 to 82 parts of titanium tungsten powder, 1.2 to 2.5 parts of V2O5, 2 to 5 parts of WO3, 3 to 6 parts of glass fiber, 1 to 4 parts of silica, 2 to 5 parts of clay or kaolin, 0.5 to 1.5 parts of cellulose, 0.2 to 1 part of stearic acid, 0.1 to 0.5 parts of polymer fiber, and 25 to 27.5 parts of water.

[0020] Example 2: The thin-walled denitrification catalyst comprises, by weight, 75 to 82 parts of titanium tungsten powder, 1.2 to 2.5 parts of V2O5, 2 to 5 parts of WO3, 3 to 6 parts of glass fiber, 1 to 4 parts of silica, 2 to 5 parts of clay or kaolin, 0.5 to 1.5 parts of cellulose, 0.2 to 1 part of stearic acid, 0.1 to 0.5 parts of polymer fiber, and 25 to 27.5 parts of deionized water.

[0021] Example 3: The thin-walled denitrification catalyst comprises, by weight, 75 or 82 parts of titanium tungsten powder, 1.2 or 2.5 parts of V2O5, 2 or 5 parts of WO3, 3 or 6 parts of glass fiber, 1 or 4 parts of silica, 2 or 5 parts of clay or kaolin, 0.5 or 1.5 parts of cellulose, 0.2 or 1 part of stearic acid, 0.1 or 0.5 parts of polymer fiber, and 25 or 27.5 parts of water.

[0022] Example 4: The thin-walled denitrification catalyst comprises, by weight, 75 or 82 parts of titanium tungsten powder, 1.2 or 2.5 parts of V2O5, 2 or 5 parts of WO3, 3 or 6 parts of glass fiber, 1 or 4 parts of silica, 2 or 5 parts of clay or kaolin, 0.5 or 1.5 parts of cellulose, 0.2 or 1 part of stearic acid, 0.1 or 0.5 parts of polymer fiber, and 25 or 27.5 parts of deionized water.

[0023] Example 5: The thin-walled denitration catalyst was obtained according to the following steps: The first step is in-situ composite activation of titanium-tungsten powder. The required amount of titanium-tungsten powder is activated by wet in-situ co-precipitation. During activation, the pH value is adjusted to 3.5 to 5.0. After activation, a highly dispersed composite carrier is obtained. The second step is to anchor the active components at the interface. By coupling spraying and in-situ deposition, the required amount of V2O5 is prepared into an ammonium metavanadate solution and sprayed onto the surface of a highly dispersed composite carrier to anchor and form a film. The third step is two-stage mixing and plasticizing. The materials obtained in the second step, the required amount of WO3, glass fiber, silica, clay or kaolin, cellulose, stearic acid, polymer fiber and water are added to the two-stage mixing process to obtain a plastic paste. The fourth step is vacuum coupling stepwise extrusion molding. The plastic paste enters the extruder, undergoes primary vacuum preforming, and then secondary precision stepwise extrusion molding to obtain a honeycomb preform. Step 5: Step-temperature controlled drying; the honeycomb embryos are dried under step-temperature controlled conditions. Step 6: Micro-oxygen atmosphere calcination. The dried honeycomb preform is then calcined in a micro-oxygen atmosphere. Step 7: Online inspection and cutting. After the calcined honeycomb preform passes the inspection, it is cut to obtain a thin-walled denitration catalyst.

[0024] Example 6, as an optimization of the above example, in the second step, the concentration of the ammonium metavanadate solution is 0.6% to 10%; or / and in the third step, the viscosity of the first stage of the two-stage mixing is 2000 cP to 3000 cP, and the viscosity of the second stage is 8000 cP to 12000 cP; or / and in the fourth step, the vacuum degree of the step extrusion is -0.08 MPa to -0.095 MPa; or / and in the fifth step, the honeycomb preform is dried sequentially at 55°C for 2 h, at 85°C for 4 h, and at 115°C for 3 h; or / and in the fifth step, the temperature rise rate of the stepped temperature-controlled drying is ≤5°C / h.

[0025] The wet in-situ co-precipitation activation of titanium-tungsten powder is a well-known and widely used method.

[0026] The preparation of ammonium metavanadate solution is a well-known and commonly used method, and it can also be prepared as follows: (1) Add deionized water to the ammonium metavanadate dissolving tank to ensure that the tank is not contaminated; (2) Add monoethanolamine to the ammonium metavanadate dissolving tank; (3) Start the stirrer of the ammonium metavanadate dissolving tank and start the heating device at the same time; (4) When the heating temperature is displayed as 90℃, add ammonium metavanadate; (5) Continue heating until the temperature display shows 98℃, and maintain this temperature for about 30 minutes; (6) Adjust the temperature to cool it down to 60℃; (7) Before transferring the ammonium metavanadate solution, add deionized water to adjust the solution volume to the specified volume; (8) Turn off the stirring and heating devices of the ammonium metavanadate dissolving tank.

[0027] The ammonium metavanadate ratio ranges from 0.6% to 10%, with approximately 6-10 kg per batch.

[0028] To control the viscosity of the two-stage mixing process, carboxymethyl cellulose and polyoxyethylene can be added to adjust the viscosity. At low speed (300r), 2.4kg of carboxymethyl cellulose, 2.7kg of polyoxyethylene, 20L of ammonia, and 10L of water can be added sequentially (with the exhaust valve and air supply valve closed). The ratio should be between 0.5% and 1% (the proportion of carboxymethyl cellulose and polyoxyethylene in the raw materials).

[0029] Example 7, as an optimization of the above examples, in the sixth step, the honeycomb embryo is calcined at 460°C to 510°C for 2 to 4 hours.

[0030] Example 8, as an optimization of the above examples, shows that the volume percentage of oxygen in the micro-oxygen atmosphere is 3% to 8%.

[0031] Example 9, as an optimization of the above examples, the honeycomb wall thickness of the thin-walled denitration catalyst is controlled between 0.28 mm and 0.42 mm.

[0032] Example 10, as an optimization of the above examples, features a thin-walled denitration catalyst with a gradient pore structure, densely packed micropores on the surface, interconnected mesopores in the inner layer, and a specific surface area ≥80 m². 2 / g.

[0033] In this invention, the mold structure and key parameters are as follows: The molding die adopts a two-stage split precision honeycomb extrusion die, and the whole adopts a coaxial positioning structure, which has the characteristics of automatic self-alignment, high rigidity and high stability.

[0034] Mold material: H13 hot work die steel, integral forging, tempered hardness HRC48–52, working area surface nitriding treatment, nitriding layer depth 0.15–0.25mm, surface hardness HV900–1100, roughness Ra≤0.025μm.

[0035] Primary preforming mold: Inlet hole type: spiral diversion type, number of diversion holes: 36 / 48 / 60 holes optional, single hole diameter Φ2.5–3.5mm; diversion cone angle: 30°–45°, compression ratio: 1.8–2.5:1; outlet forming gap width: 0.40–0.50mm; total mold thickness: 60–80mm, positioning stop tolerance H7 / g6.

[0036] Secondary precision forming mold: Hole arrangement: dense hexagonal arrangement, hole center distance 5.0mm / 5.5mm / 6.0mm; Mold pin diameter: 4.60mm / 5.05mm / 5.55mm, mold pin length-to-diameter ratio 8–12:1; Mold opening forming gap: 0.28–0.42mm, wall thickness uniformity error control ≤±0.02mm; Mold pin end face chamfer: R0.10–R0.15mm, entrance guide angle 15°–20°; Template flatness: ≤0.01mm / 100mm, parallelism ≤0.015mm / 100mm; Effective forming section: 150mm×150mm / 200mm×200mm.

[0037] Mold matching process parameters: Mold preheating temperature: 45–60℃; Mold closing pressure: 10–16MPa; Extrusion line speed: 1.0–2.0m / min; Mold head vacuum degree: -0.08~-0.095MPa.

[0038] Example 11 The difference from Example 5 is that, in this case, the required amount of titanium-tungsten powder was taken and activated by wet in-situ co-precipitation to prepare a composite support; a vanadium precursor solution (ammonium metavanadate solution) was prepared and loaded using spray-in-situ deposition coupling to obtain catalyst powder; molding aids, lubricants, and pore-forming agents (the remaining raw materials) were added, and the mixture was mixed in two stages for 2 hours to obtain a plastic paste; vacuum coupling stepwise extrusion was used to control the wall thickness to 0.35 mm; step temperature controlled drying: 55℃ / 2h → 85℃ / 4h → 115℃ / 3h; calcination was carried out in a micro-oxygen atmosphere at 490℃ for 2 hours to obtain a thin-walled catalyst. Performance testing showed a 24% increase in activity, a 17% increase in selectivity, a wall thickness of 0.35 mm, a titanium-tungsten powder consumption of 385 kg per cubic meter, and an axial compressive strength of 1.9 MPa, meeting the performance requirements.

[0039] Example 12 The difference from Example 5 is that titanium and tungsten sources (titanium-tungsten powder) were used and activated by wet in-situ co-precipitation, with pH controlled at 4.0, to prepare a highly dispersed composite support. A vanadium-tungsten mixed precursor solution was prepared and loaded using spray-in-situ deposition coupling at a loading temperature of 60°C. Molding aids, lubricants, and pore-forming agents were added, and the mixture was mixed in two stages: the first stage for 30 minutes and the second stage for 90 minutes. Vacuum coupling stepwise extrusion was used, controlling the wall thickness to 0.30 mm and the vacuum degree to -0.09 MPa. Stepwise temperature-controlled drying was performed: 55°C / 2h → 85°C / 4h → 115°C / 3h. The catalyst was calcined at 500°C for 2 hours in a micro-oxygen atmosphere to obtain a thin-walled catalyst. Performance testing showed a 25% increase in activity, an 18% increase in selectivity, a wall thickness of 0.30 mm, a titanium-tungsten powder consumption of 383 kg per cubic meter, and an axial compressive strength of 1.85 MPa, meeting the required specifications.

[0040] Example 13 The difference from Example 5 is that titanium and tungsten sources were used, and wet in-situ co-precipitation activation was performed, controlling the pH at 3.8; the vanadium component was anchored using spray-in-situ deposition at a loading temperature of 55°C; the two-stage mixing viscosities were 2400 cP and 10000 cP, respectively; an H13 nitriding precision mold was used, with a vacuum degree of -0.095 MPa and an extrusion wall thickness of 0.28 mm; step drying and micro-oxygen calcination at 480°C for 2 hours were performed. Test results: specific surface area 87 m² / s. 2 / g, activity increased by 26%, selectivity increased by 18%, titanium tungsten powder consumption 382kg / cubic meter, axial compressive strength 1.83MPa, wall thickness uniformity error ±0.018mm, qualified.

[0041] Example 14 The difference from Example 5 is that titanium and tungsten sources were used for in-situ co-precipitation at pH 4.5; the two-stage mixing viscosity was 2800 cP and 11000 cP; the vacuum degree was -0.085 MPa; the extrusion wall thickness was 0.42 mm; and the mixture was calcined at 510℃ under micro-oxygen conditions for 2 hours. Test results: specific surface area 82 m² / g. 2 / g, activity increased by 23%, selectivity increased by 16.5%, titanium tungsten powder consumption was 385kg / cubic meter, axial compressive strength was 1.92MPa, qualified.

[0042] Comparative Example 1 (conventional uniform channel, no gradient) The process is the same as in Example 11, only using a conventional uniform pore structure without the surface micropore + inner mesopore gradient design. Result: Specific surface area 68m² 2 / g, activity increased by 12%, selectivity increased by 10%, easy to clog ash, compressive strength 1.7MPa.

[0043] Comparative Example 2 (Conventional single vacuum extrusion, non-step extrusion) The process was the same as in Example 12, but only a single vacuum extrusion was used, without primary preforming + secondary precision shaping. Results: wall thickness uniformity error ±0.06mm, molding qualification rate 82%, cracking rate 11%, activity improvement 14%, compressive strength 1.5MPa.

[0044] Comparative Example 3 (Purchased titanium-tungsten powder, without in-situ composite activation) The process was the same as in Example 11, using purchased titanium-tungsten powder directly without in-situ co-precipitation activation. Results: Specific surface area 72 m² / g, activity increased by 15%, titanium-tungsten powder consumption 418 kg / m³, and cost not significantly reduced.

[0045] Comparative Example 4 (conventional air roasting, without micro-oxygen control) The process was the same as in Example 12, using conventional air atmosphere calcination without micro-oxygen control. Results: Abnormal crystal phase, specific surface area 70 m². 2 / g, activity increased by 13%, selectivity increased by 11%, some pores were blocked.

[0046] Comparative Example 5 (Ordinary mold, without high-precision nitriding treatment) The process was the same as in Example 13, using ordinary 45# steel molds, without nitriding or high-precision machining. Results: Large wall thickness deviation, uniform error ±0.07mm, numerous surface burrs, a forming pass rate of 83%, and uneven strength.

[0047] Comparative Example 6 (stepless drying, conventional constant temperature drying) The process was the same as in Example 11, using a constant temperature of 105℃ for single-stage drying without step-up heating. Results: The cracking rate of the billet was 13%, the deformation was large, the yield was 85%, and the strength fluctuated greatly.

[0048] Advantages of this invention over existing technologies: (1) Performance improvement: The thin-walled denitrification catalyst of the present invention has more than 22% higher activity and more than 16% higher selectivity than the existing technology, and has higher denitrification efficiency, and is suitable for a wide temperature range.

[0049] (2) Significant cost reduction: This invention saves more than 720 yuan in raw material costs per unit. Based on an annual output of 2,000 cubic meters, the annual cost savings exceed 1.44 million yuan.

[0050] (3) Excellent strength and stability: The thin-walled denitrification catalyst of the present invention has a thin-walled structure that does not crack or collapse, and has excellent wear resistance and poisoning resistance.

[0051] (4) Green and low carbon: This invention reduces raw material consumption and energy consumption, which is in line with the "dual carbon" goal and the development direction of the environmental protection industry.

[0052] (5) Strong industrial adaptability: The process route of this invention is simple and can be implemented on existing SCR production lines, making it suitable for large-scale continuous production.

[0053] Table 1 shows a comparison of the defects of existing conventional SCR catalysts with those of the thin-walled catalyst of this invention; Table 2 shows a comparison of this invention with existing technical solutions; Table 3 shows the control range and technical effects of the core process parameters in this invention; Table 4 shows a comparison of the economic benefits and performance of this invention with traditional processes; Table 5 shows a summary of the performance test results of the embodiments of this invention; and Table 6 shows a performance comparison between the comparative examples and the embodiments of this invention.

[0054] The above technical features constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Unnecessary technical features can be added or removed according to actual needs to meet the needs of different situations.

Claims

1. A thin-walled denitration catalyst, characterized in that... The raw materials, by weight, include 75 to 82 parts of titanium tungsten powder, 1.2 to 2.5 parts of V2O5, 2 to 5 parts of WO3, 3 to 6 parts of glass fiber, 1 to 4 parts of silicon dioxide, 2 to 5 parts of clay or kaolin, 0.5 to 1.5 parts of cellulose, 0.2 to 1 part of stearic acid, 0.1 to 0.5 parts of polymer fiber, and 25 to 27.5 parts of water.

2. The thin-walled denitration catalyst according to claim 1, characterized in that... The thin-walled denitration catalyst is obtained by the following steps: The first step is in-situ composite activation of titanium-tungsten powder. The required amount of titanium-tungsten powder is activated by wet in-situ co-precipitation. During activation, the pH value is adjusted to 3.5 to 5.

0. After activation, a highly dispersed composite carrier is obtained. The second step is to anchor the active components at the interface. By coupling spraying and in-situ deposition, the required amount of V2O5 is prepared into an ammonium metavanadate solution and sprayed onto the surface of a highly dispersed composite carrier to anchor and form a film. The third step is two-stage mixing and plasticizing. The materials obtained in the second step, the required amount of WO3, glass fiber, silica, clay or kaolin, cellulose, stearic acid, polymer fiber and water are added to the two-stage mixing process to obtain a plastic paste. The fourth step is vacuum coupling stepwise extrusion molding. The plastic paste enters the extruder, undergoes primary vacuum preforming, and then secondary precision stepwise extrusion molding to obtain a honeycomb preform. Step 5: Step-temperature controlled drying; the honeycomb embryos are dried under step-temperature controlled conditions. Step 6: Micro-oxygen atmosphere calcination. The dried honeycomb preform is then calcined in a micro-oxygen atmosphere. Step 7: Online inspection and cutting. After the calcined honeycomb preform passes the inspection, it is cut to obtain a thin-walled denitration catalyst.

3. The thin-walled denitration catalyst according to claim 2, characterized in that... In the second step, the concentration of the ammonium metavanadate solution is 0.6% to 10%; or / and in the third step, the viscosity of the first stage of the two-stage mixing is 2000 cP to 3000 cP, and the viscosity of the second stage is 8000 cP to 12000 cP; or / and in the fourth step, the vacuum degree of the step extrusion is -0.08 MPa to -0.095 MPa; or / and in the fifth step, the honeycomb preform is dried sequentially at 55℃ for 2 h, at 85℃ for 4 h, and at 115℃ for 3 h; or / and in the fifth step, the temperature rise rate of the stepped temperature-controlled drying is ≤5℃ / h.

4. The thin-walled denitration catalyst according to claim 2 or 3, characterized in that... In step six, the honeycomb embryo is calcined at 460°C to 510°C for 2 to 4 hours; or / and, the volume percentage of oxygen in the micro-oxygen atmosphere is 3% to 8%.

5. The thin-walled denitration catalyst according to claim 2 or 3, characterized in that... The honeycomb wall thickness of the thin-walled denitration catalyst is controlled between 0.28 mm and 0.42 mm; or / and the pore structure of the thin-walled denitration catalyst is a gradient structure, with dense micropores on the surface and interconnected mesopores in the inner layer, and a specific surface area ≥ 80 m². 2 / g.

6. The thin-walled denitration catalyst according to claim 4, characterized in that... The honeycomb wall thickness of the thin-walled denitration catalyst is controlled between 0.28 mm and 0.42 mm; or / and the pore structure of the thin-walled denitration catalyst is a gradient structure, with dense micropores on the surface and interconnected mesopores in the inner layer, and a specific surface area ≥ 80 m². 2 / g.

7. A method for preparing a thin-walled denitration catalyst according to claim 1, characterized in that... Follow these steps: The first step is in-situ composite activation of titanium-tungsten powder. The required amount of titanium-tungsten powder is activated by wet in-situ co-precipitation. During activation, the pH value is adjusted to 3.5 to 5.

0. After activation, a highly dispersed composite carrier is obtained. The second step is to anchor the active components at the interface. By coupling spraying and in-situ deposition, the required amount of V2O5 is prepared into an ammonium metavanadate solution and sprayed onto the surface of a highly dispersed composite carrier to anchor and form a film. The third step is two-stage mixing and plasticizing. The materials obtained in the second step, the required amount of WO3, glass fiber, silica, clay or kaolin, cellulose, stearic acid, polymer fiber and water are added to the two-stage mixing process to obtain a plastic paste. The fourth step is vacuum coupling stepwise extrusion molding. The plastic paste enters the extruder, undergoes primary vacuum preforming, and then secondary precision stepwise extrusion molding to obtain a honeycomb preform. Step 5: Step-temperature controlled drying; the honeycomb embryos are dried under step-temperature controlled conditions. Step 6: Micro-oxygen atmosphere calcination. The dried honeycomb preform is then calcined in a micro-oxygen atmosphere. Step 7: Online inspection and cutting. After the calcined honeycomb preform passes the inspection, it is cut to obtain a thin-walled denitration catalyst.

8. The method for preparing the thin-walled denitration catalyst according to claim 7, characterized in that... In the second step, the concentration of the ammonium metavanadate solution is 0.6% to 10%; or / and in the third step, the viscosity of the first stage of the two-stage mixing is 2000 cP to 3000 cP, and the viscosity of the second stage is 8000 cP to 12000 cP; or / and in the fourth step, the vacuum degree of the step extrusion is -0.08 MPa to -0.095 MPa; or / and in the fifth step, the honeycomb preform is dried sequentially at 55℃ for 2 h, at 85℃ for 4 h, and at 115℃ for 3 h; or / and in the fifth step, the temperature rise rate of the stepped temperature-controlled drying is ≤5℃ / h.

9. The method for preparing the thin-walled denitration catalyst according to claim 7 or 8, characterized in that... In step six, the honeycomb embryo is calcined at 460°C to 510°C for 2 to 4 hours; or / and, the volume percentage of oxygen in the micro-oxygen atmosphere is 3% to 8%.

10. The method for preparing the thin-walled denitration catalyst according to claim 7, 8, or 9, characterized in that... The honeycomb wall thickness of the thin-walled denitration catalyst is controlled between 0.28 mm and 0.42 mm; or / and the pore structure of the thin-walled denitration catalyst is a gradient structure, with dense micropores on the surface and interconnected mesopores in the inner layer, and a specific surface area ≥ 80 m². 2 / g.

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