A 40-pore high-temperature SCR denitrification honeycomb catalyst and its preparation method

Abstract

This invention provides a 40-pore high-temperature SCR denitrification honeycomb catalyst and its preparation method. By weight, it comprises 60-70 parts titanium dioxide, 5-10 parts ternary composite agent, 10-18 parts active component, 5-10 parts pore-forming agent, and 3-8 parts binder. The preparation method includes: a) raw material mixing: mixing titanium dioxide, ternary composite agent, active component, pore-forming agent, and binder according to the specified ratio; b) molding treatment: injecting the slurry into a molding die and extruding it under vacuum; c) gradient drying: sequentially performing pre-drying at 250℃ under normal pressure for 48 hours, vacuum drying at 550℃ for 144 hours, and vacuum fine drying at 150℃ for 48 hours. This invention, through innovation in ternary composite agent and mold, solves the technical bottlenecks of poor formability and low strength of honeycomb catalysts, making it suitable for high-temperature flue gas denitrification scenarios in coal-fired power plants, steel metallurgy, etc., and has significant industrialization value.

Description

Technical Field

[0001] This invention relates to the field of denitrification catalyst technology, and in particular to a high-temperature SCR denitrification honeycomb 40-pore catalyst and its preparation method. Background Technology

[0002] SCR (Selective Catalytic Reduction) denitrification technology uses a catalyst to selectively catalytically reduce nitrogen oxides in flue gas with ammonia, producing harmless nitrogen and water. This technology boasts advantages such as high denitrification efficiency and a wide reaction temperature window (280-420℃), making it a mainstream technology in industrial flue gas purification. As a core component, the catalyst's performance directly affects the operating efficiency and economy of the denitrification system. Currently, SCR denitrification catalysts mostly employ a honeycomb structure, using single clays such as kaolin as the molding carrier, and are extruded using traditional molds. However, in actual production, this process has the following prominent problems: The poor plasticity of single clay materials makes them prone to matrix cracking due to stress concentration during extrusion. Simultaneously, the high frictional resistance between the material and the inner wall of the die causes pore deformation and dimensional inconsistencies. Extrusion molding relies on die precision, but traditional die designs do not fully consider the rheological properties of the material, making it difficult to guarantee the uniformity of pore density, affecting flue gas distribution and catalytic reaction efficiency. The clay matrix experiences high shrinkage during high-temperature sintering, easily generating microcracks, resulting in high porosity and insufficient mechanical strength after sintering, making the catalyst prone to breakage and detachment during long-term use. Single carrier materials are prone to crystal phase transformation at high temperatures, leading to a decrease in specific surface area and reduced active components. Reduced dispersion leads to rapid decay of catalytic efficiency; traditional mold flow channel design does not optimize material flow, making localized material accumulation during extrusion easy, resulting in low production efficiency and high energy consumption; to improve molding performance, some studies have attempted to add organic binders (such as polyvinyl alcohol and carboxymethyl cellulose), which, although improving extrusion molding rate in the short term, brings new problems: organic binders are prone to decomposition during high-temperature sintering of the catalyst (>500℃), producing volatile gases, leading to a decrease in matrix porosity (<0.3) and hindering reactant diffusion; poor long-term stability: residual organic matter slowly oxidizes in high-temperature flue gas, releasing acidic gases, corroding the catalyst skeleton, and shortening service life (<3 years).

[0003] In summary, the market urgently needs a high-temperature SCR denitrification honeycomb 40-pore catalyst and its preparation method, which can not only improve the plasticity of materials, avoid cracking and resistance problems, and improve stability, but also replace traditional organic materials and extend catalyst life. Summary of the Invention

[0004] This invention provides a 40-pore high-temperature SCR denitrification honeycomb catalyst and its preparation method, in order to solve the problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, this invention discloses a 40-pore high-temperature SCR denitrification honeycomb catalyst, comprising the following raw materials: titanium dioxide, ternary composite agent, active component, pore-forming agent and binder.

[0006] Furthermore, by weight, the SCR denitrification honeycomb 40-pore high-temperature catalyst comprises the following raw materials: 60-70 parts titanium dioxide, 5-10 parts ternary composite agent, 10-18 parts active component, 5-10 parts pore-forming agent and 3-8 parts binder.

[0007] Furthermore, the ternary composite agent includes the following raw materials: kaolin, montmorillonite, and attapulgite clay.

[0008] Furthermore, the ternary composite agent comprises the following raw materials by weight: 40-45 parts kaolin, 20-30 parts montmorillonite and 20-30 parts attapulgite clay.

[0009] Furthermore, the active component is a V2O5-WO3 / TiO2 composite oxide.

[0010] Furthermore, the pore-forming agent is polyethylene glycol, and the binder is silica sol.

[0011] Furthermore, the titanium dioxide contains 98% TiO2 and 5% rutile phase, with a specific surface area of ​​8 m². 2 / g; the WO3 loading in the active component is 9%; the molecular weight of the pore-forming agent is 4000-6000; the SiO2 content of the binder is 30-40wt%, and the particle size distribution D50 is 10-15nm.

[0012] Furthermore, the preparation method of the SCR denitrification honeycomb 40-pore high-temperature catalyst includes the following steps:

[0013] a) Raw material mixing: Mix titanium dioxide, ternary composite agent, active component, pore-forming agent and binder according to the formula ratio, and add water to make plastic mud;

[0014] b) Molding process: The clay is injected into a molding die with a 30° chamfer and then extruded under vacuum.

[0015] c) Gradient drying: sequentially perform pre-drying at 250℃ and atmospheric pressure for 48 hours, vacuum drying at 550℃ for 144 hours, and vacuum fine drying at 150℃ for 48 hours.

[0016] Furthermore, in step a), the moisture content of the mud is controlled at 25%, the aging time is 18-24 hours, and it is filtered through a 200-mesh sieve and vacuum defoamed.

[0017] Furthermore, the SCR denitrification honeycomb 40-pore high-temperature catalyst has an axial compressive strength ≥3.5MPa and a specific surface area ≥35m².2 / g, porosity 40-45%, denitrification efficiency ≥95% under operating conditions of 300-400℃.

[0018] Compared with the prior art, the present invention provides a high-temperature SCR denitrification honeycomb 40-pore catalyst and its preparation method, which has the following beneficial effects:

[0019] 1. Synergistic effect of the formulation of this invention: Kaolin provides plasticity, montmorillonite enhances bonding, and attapulgite clay strengthens the skeleton, thereby increasing the compressive strength of the catalyst unit strip to 2.5 MPa (compared to 1.2 MPa of kaolin alone);

[0020] 2. This invention employs a chamfered mold design, reducing extrusion pressure by 20% and achieving a honeycomb channel integrity rate of >98%. Through innovation in ternary composite agents and molds, this invention solves the technical bottlenecks of poor formability and low strength in honeycomb catalysts. Microstructure optimization is achieved through a gradient drying process: free water is removed during the 250℃ pre-drying stage to prevent stress cracking during subsequent high-temperature drying; the 550℃ main drying stage causes irreversible dehydration of clay minerals to form a stable framework structure; and 150℃ fine drying eliminates residual stress. This invention is suitable for high-temperature flue gas denitrification scenarios such as coal-fired power plants and steel metallurgy, possessing significant industrialization value. It solves the problem of uneven dispersion of active components due to insufficient carrier porosity in traditional SCR catalysts, as well as the honeycomb structure cracking caused by stress concentration during high-temperature drying.

[0021] 3. Kaolin provides basic plasticity and high-temperature stability, while montmorillonite enhances adhesion through interlayer cation exchange; attapulgite clay, with its fibrous structure, forms a three-dimensional framework, improving compressive strength and porosity. In the ternary composite agent, montmorillonite interlayer cations (Ca... 2+ / Na + It forms a -Si-O-Si- network structure with silica sol. Detailed Implementation

[0022] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0023] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0024] Unless otherwise specified, the examples and comparative examples are parallel experiments with the same components, component content, preparation steps, and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. Unless otherwise specified, the experimental materials used in the following examples are analytical reagents (AR) and were all purchased from commercial channels.

[0025] The kaolin was SX-90A, with a D50 of 0.9μm; the attapulgite clay was purchased from Lingshou County Kaixin Mineral Products Processing Plant, with a mesh size of 2500; the titanium dioxide was purchased from Zhenjiang Diyang New Material Technology Co., Ltd.; the polyethylene glycol was BASF Yangtze Pluriol E400; the silica sol was Huihe Yongsheng, model: S-1430 / S-1440, with a SiO2 content of 30wt%; and the mesoporous template agent F127 was of high purity. F127, EO 106 PO 70 EO 106 .

[0026] Preparation method of active component V2O5-WO3 / TiO2 composite oxide (WO3 loading 9%): Take 100g of commercial anatase TiO2 (specific surface area 80m²) 2 (g, particle size 50nm) was mixed with 12g of mesoporous template agent F127, and the pH was adjusted to 2.5 with 0.5mol / L hydrochloric acid solution. The mixture was ultrasonically treated (40kHz, 800W) for 30min, hydrothermally crystallized at 100℃ for 8h, and calcined at 550℃ for 4h (heating rate 2℃ / min) to obtain a hierarchical porous TiO2 support (pore size distribution: 3nm mesopores + 25nm macropores, BET = 145nm). 2 / g).

[0027] Solution A was prepared by dissolving 3.4 g ammonium metavanadate and 6.3 g oxalic acid in 200 mL deionized water, and solution B was prepared by dissolving 12.7 g ammonium metatungstate in 150 mL deionized water. The hierarchical pore TiO2 support was immersed in solution A and stirred at 60 °C for 2 h. Solution B was then added and stirred for 3 h. The mixture was dried under supercritical CO2 at 100 MPa and 40 °C and calcined at 380 °C for 3 h under N2 atmosphere to obtain a preform. One part of the preform was immersed in five parts of 0.1 mol / L thiourea solution for 30 min, dried under vacuum at 120 °C, annealed in H2 / N2 (5% N2) at 400 °C for 1 h, and calcined at 480 °C for 6 h to obtain the active component V2O5-WO3 / TiO2 composite oxide. The final WO3 loading was determined to be 9% by ICP-OES.

[0028] Example 1

[0029] A ternary composite agent was prepared by mixing 42 parts kaolin, 26 parts montmorillonite, and 23 parts attapulgite clay at 45°C and stirring at 400 rpm for 40 minutes. 65 parts titanium dioxide (98% TiO2, 5% rutile phase, specific surface area 8 m²) was then added. 2 Mix 8 parts of ternary composite agent, 15 parts of active component V2O5-WO3 / TiO2 composite oxide (WO3 loading 9%), 8 parts of pore-forming agent polyethylene glycol and 5 parts of binder silica sol, add water and heat to prepare a plastic mud with a moisture content of 25%, age for 20 hours, filter and defoam, inject the mud into a chamfered mold with a 30° chamfer at the mold inlet, vacuum extrude to form, pre-dry at 250℃ and normal pressure in a kiln for 2 days, main dry at 550℃ and vacuum degree of -0.05MPa for 6 days, and fine dry at 150℃ and -0.08MPa for 2 days to obtain SCR denitrification honeycomb 40-pore high-temperature catalyst.

[0030] Example 2

[0031] A ternary composite agent was prepared by mixing 40 parts kaolin, 20 parts montmorillonite, and 20 parts attapulgite clay at 45°C and stirring at 400 rpm for 40 minutes. 60 parts titanium dioxide (98% TiO2, 5% rutile phase, specific surface area 8 m²) was then added. 2 Mix 5 parts of ternary composite agent, 10 parts of active component V2O5-WO3 / TiO2 composite oxide (WO3 loading 9%), 5 parts of pore-forming agent polyethylene glycol and 3 parts of binder silica sol, add water and heat to prepare a plastic mud with a moisture content of 25%, age for 18 hours, filter and defoam, inject the mud into a chamfered mold with a 30° chamfer at the mold inlet, vacuum extrude to form, pre-dry at 250℃ and normal pressure in a kiln for 2 days, main dry at 550℃ and vacuum degree of -0.05MPa for 6 days, and fine dry at 150℃ and -0.08MPa for 2 days to obtain SCR denitrification honeycomb 40-pore high-temperature catalyst.

[0032] Example 3

[0033] A ternary composite agent was prepared by mixing 45 parts kaolin, 30 parts montmorillonite, and 30 parts attapulgite clay at 45°C and stirring at 400 rpm for 40 minutes. 70 parts titanium dioxide (98% TiO2, 5% rutile phase, specific surface area 8 m²) was then added. 2 Mix 10 parts of ternary composite agent, 18 parts of active component V2O5-WO3 / TiO2 composite oxide (WO3 loading 9%), 10 parts of pore-forming agent polyethylene glycol and 8 parts of binder silica sol, add water and heat to prepare a plastic mud with a moisture content of 25%, age for 24 hours, filter and defoam, inject the mud into a chamfered mold with a 30° chamfer at the mold inlet, vacuum extrude to form, pre-dry at 250℃ and normal pressure in a kiln for 2 days, main dry at 550℃ and vacuum degree of -0.05MPa for 6 days, and fine dry at 150℃ and -0.08MPa for 2 days to obtain SCR denitrification honeycomb 40-pore high-temperature catalyst.

[0034] Comparative Example 1

[0035] The difference from Example 1 is that it lacks an equal weight of ternary composite agent, otherwise it is the same.

[0036] Comparative Example 2

[0037] The difference from Example 1 is that it lacks an equal part by weight of V2O5-WO3 / TiO2 composite oxide, otherwise it is the same.

[0038] Comparative Example 3

[0039] The difference from Example 1 is that an equal part by weight of montmorillonite was missing when preparing the ternary composite agent; otherwise, they are the same.

[0040] Comparative Example 4

[0041] The difference from Example 1 is that an equal weight of attapulgite clay was missing when preparing the ternary composite agent; otherwise, they are the same.

[0042] Comparative Example 5

[0043] The difference from Example 1 is that an equal part by weight of kaolin was missing when preparing the ternary composite agent; otherwise, they are the same.

[0044] Performance testing

[0045] 1. The compressive strength of the catalysts prepared in the examples and comparative examples was tested using the test method of "Test Method for Strength of Wood-based Activated Carbon" (GB / T 12496.6-1999), and the results are shown in Table 1.

[0046] Table 1

[0047] Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 compressive strength (MPa) 3.5 1.8 2.0 2.2 1.5 1.1

[0048] 2. The denitrification and anti-poisoning performance of the catalysts prepared in the examples and comparative examples were tested. The simulated flue gas inlet was: CO = 2000 ppm, NO = 1000 ppm, SO2 = 50 ppm, H2O = 10%, O2 = 5%, N2 was the balance gas, and the space velocity was 20000 h⁻¹. -1 The total gas flow rate was 1 L / min. The system operated continuously at 350℃ for 2000 hours, with data recorded every hour after the flow stabilized. The results are shown in Table 2.

[0049] Table 2

[0050]

[0051] As shown in Table 2, due to the lack of the active component V2O5-WO3 / TiO2, the catalyst has no denitrification activity and is completely deactivated after 2000 h. The lack of the ternary composite component leads to structural deterioration, pore blockage, or sintering of the active component, resulting in a significant decrease in conversion rate.

[0052] 3. The thermomechanical properties of the catalysts prepared in the examples and comparative examples were tested. A Netzsch DIL402C thermal expansion meter was used with a heating rate of 5℃ / min to test the thermal expansion behavior in the range of 25-600℃. The results are shown in Table 3.

[0053] Table 3

[0054]

[0055]

[0056] Table 3 shows that the absence of any clay component (Comparative Examples 3-5) leads to an increase in the coefficient of thermal expansion of 30%-88%, demonstrating the synergistic stabilizing effect of kaolin (plasticity), montmorillonite (bonding), and attapulgite clay (skeleton). Example 1 maintained a denitrification efficiency of 94.1% after 2000 hours, compared to the traditional process (which decreased to 61.2% in Comparative Example 1), proving the effectiveness of gradient drying in optimizing the microstructure.

[0057] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of the claims of this invention and their equivalents, then this invention is also intended to include these modifications and variations.

Claims

1. An SCR De-NOx honeycomb 40-cell high temperature catalyst characterized by, The SCR denitration honeycomb 40-hole high-temperature catalyst The SCR denitration honeycomb 40-hole high-temperature catalyst The ternary composite agent comprises the following raw materials: kaolin, montmorillonite, and attapulgite clay. The active component is a V2O5-WO3 / TiO2 composite oxide. The pore-forming agent is polyethylene glycol, and the binder is silica sol. The preparation method of the SCR denitration honeycomb 40-hole high-temperature catalyst comprises the following steps: a) Raw material mixing: mix the titanium white, the ternary composite agent, the active component, the pore-forming agent, and the binder according to the proportion, and add water to prepare a plastic mud; b) Molding treatment: inject the mud into a molding mold with a 30° chamfer, and perform vacuum extrusion molding; c) Gradient drying: sequentially perform 250°C normal-pressure pre-drying for 48 hours, 550°C vacuum drying for 144 hours, and 150°C vacuum fine drying for 48 hours.

2. The SCR De-NOx honeycomb 40-cell high temperature catalyst of claim 1, wherein, The ternary composite agent comprises the following raw materials according to weight parts: 40-45 parts of kaolin, 20-30 parts of montmorillonite, and 20-30 parts of attapulgite clay.

3. The SCR De-NOx honeycomb 40-cell high temperature catalyst of claim 1, wherein, The titanium white powder comprises 98% TiO2 and a rutile phase content of 5%, a specific surface area of 8 m 2 / g; the WO3 loading in the active component is 9%; the molecular weight of the pore-forming agent is 4000-6000; the SiO2 content of the binder is 30-40 wt%, and the particle size distribution D50 is 10-15 nm.

4. The SCR De-NOx honeycomb 40-cell high temperature catalyst of claim 1, wherein, In the step a), the water content of the mud is controlled to be 25%, the aging time is 18-24 hours, the mud is filtered through a 200-mesh screen, and vacuum defoaming treatment is performed.

5. The SCR De-NOx honeycomb 40-cell high temperature catalyst of any of claims 1-4, wherein, The axial compression strength of the SCR denitration honeycomb 40-hole high-temperature catalyst is greater than or equal to 3.5 MPa, the specific surface area is greater than or equal to 35 m 2 / g, the porosity is 40-45%, and the denitration efficiency is greater than or equal to 95% under the working condition of 300-400 DEG C.

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