Alkali poisoning resistant honeycomb low-temperature denitration catalyst and preparation method thereof

Abstract

The invention discloses an alkali poisoning-resistant honeycomb low-temperature denitration catalyst and a preparation method thereof. The anti-alkali poisoning honeycomb-shaped low-temperature denitration catalyst comprises an anti-alkali honeycomb ceramic carrier and a denitration coating, wherein the alkali-resistant honeycomb ceramic carrier is prepared by co-extrusion and co-firing, the alkali-resistant honeycomb carrier comprises an alkali capturing component and a carrier matrix, and the alkali capturing component is macroscopically and uniformly dispersed in the carrier matrix; and the denitration coating is coated on the surface of the channel wall of the alkali-resistant honeycomb ceramic carrier. The method comprises the following steps: firstly, introducing alkali capturing components such as attapulgite, AlPO4 and MgAl2O4 in a carrier stage, and forming a honeycomb carrier with alkali fixing capability through co-extrusion and high-temperature sintering; then Mn-Ti is taken as a main body in the active layer, and auxiliaries such as Zr, Nb and Ce are introduced, so that the acidity and the structural stability of Lewis can be enhanced, and the alkali poisoning resistance and the low-temperature activity of the catalyst are jointly improved; and coating, drying and roasting to obtain the monolithic catalyst.

Description

Technical Field

[0001] This invention relates to the field of air pollution control and environmental catalysis technology, and in particular to a honeycomb-shaped low-temperature denitrification catalyst resistant to alkali poisoning and its preparation method. Background Technology

[0002] Selective catalytic reduction (SCR) is a stationary source of NO. X The mainstream technology for pollution control. Existing commercial V2O5-WO3 / TiO2 catalysts typically require high activity and stability at 300–400℃; however, many non-power industry operations occur in the low-temperature range of 150–300℃, with high dust levels and large fluctuations in H2O / SO2. Traditional high-temperature catalysts in this temperature range are prone to insufficient activity, increased pressure drop, and shortened lifespan. Cement kiln operations exhibit significant "rich alkali-low temperature-high dust" characteristics. Alkali / alkaline earth metals such as Na, K, Ca, and Mg in the exhaust gas easily deposit and migrate on the catalyst surface under low-temperature and high-humidity conditions. Alkali metals can cover the catalyst surface and combine with acid centers, leading to a decrease in surface acidity and acid strength, thereby weakening the adsorption and activation of NH3. Therefore, low-temperature SCR for cement kilns needs to simultaneously address the two major challenges of low-temperature activation and alkali resistance durability.

[0003] To address the requirements of low temperature and alkali resistance, existing patents have proposed improvements from different dimensions of the carrier / active layer. However, these improvements still have engineering shortcomings under the overall long-term operating conditions of "rich alkali + high humidity + high dust". For example, CN108654633B uses dry quenching dust to prepare an activated coke carrier and applies it at 180-250℃, expanding the high-value utilization of solid waste. However, its specific surface area is affected by the fluctuation of carbonization temperature, its micropores are easily blocked by by-products, and its hydrophobicity and sulfur resistance are insufficient, making it difficult to operate stably in high-humidity sulfur-containing flue gas for a long time. CN107983354B improves low-temperature activity and alkali resistance through copper-based spinel, but spinel usually requires a high calcination temperature, and there are engineering concerns regarding the low-temperature window and selectivity / cost. CN113522274B discloses a low-temperature manganese-based SCR catalyst resistant to alkali metal poisoning, which remains active under Na / K loading conditions. However, most of these are powders or multi-step processes, and there is still insufficient data on adhesion strength, consistency, and long-term performance under high humidity and high dust conditions when scaled up to a honeycomb-like overall structure.

[0004] In summary, existing solutions mostly focus on surface interception or powder performance verification, lacking an integrated approach that simultaneously considers long-term alkali trapping of the carrier phase, low-temperature high activity of the active layer, and overall manufacturability. There is an urgent need to propose a low-temperature monolithic SCR catalyst and complete process resistant to alkali poisoning, tailored to the characteristics of cement kilns. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a honeycomb-shaped low-temperature denitrification catalyst resistant to alkali poisoning and its preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A honeycomb-shaped low-temperature denitration catalyst resistant to alkali poisoning includes an alkali-resistant honeycomb ceramic carrier and a denitration coating; wherein the alkali-resistant honeycomb ceramic carrier is prepared by co-extrusion and co-firing, the alkali-resistant honeycomb carrier includes an alkali-catching component and a carrier matrix, and the alkali-catching component is macroscopically uniformly dispersed in the carrier matrix; the denitration coating is applied to the channel wall surface of the alkali-resistant honeycomb ceramic carrier.

[0008] The mass ratio of the alkali-catching component to the carrier matrix in the alkali-resistant honeycomb ceramic carrier is 70-95:5-30, and the mass ratio of the denitrification coating to the alkali-resistant honeycomb ceramic carrier is 0.05-0.30:1.

[0009] The alkali-catching component is selected from one or more of attapulgite, aluminum phosphate (AlPO4), and spinel MgAl2O4;

[0010] The coating comprises, on a solids basis, 1.0–6.0 wt% MnO2, 2–18 wt% ZrO2 and / or 0.2–2.0 wt% Nb2O5, 0–3.0 wt% CeO2, wherein the contents of ZrO2 and Nb2O5 cannot be 0 at the same time, and the balance is TiO2.

[0011] The alkali-resistant honeycomb carrier has a pore density of 200–300 cpsi, a wall thickness of 0.35–0.40 mm, a total porosity of ≥35%, and an axial compressive strength of ≥3 MPa.

[0012] The alkali-resistant honeycomb low-temperature denitrification catalyst of the present invention is particularly suitable for NH3-SCR denitrification of industrial flue gas containing alkali (alkaline earth) metal components such as Na, K, Ca, and Mg at 150–300°C.

[0013] The preparation method of the above-mentioned alkali-resistant honeycomb low-temperature denitration catalyst includes the following steps:

[0014] S1: Co-extrusion and co-firing preparation of alkali-resistant honeycomb ceramic carrier: The carrier raw material, namely cordierite precursor powder, is mixed with the alkali-catching component at a mass ratio of 70-95:5-30. Additives and water are added to form an extrusion slurry. After extrusion into a honeycomb green body, sintering is performed to obtain an alkali-resistant honeycomb ceramic carrier in which the alkali-catching component is macroscopically and uniformly dispersed in the carrier matrix. The additives can be binders, pore-forming agents, and regulators. The amount of binder is 2-3% of the carrier raw material, the amount of pore-forming agent is 1.2-12% of the carrier raw material, and the amount of regulator is 0.3% of the carrier raw material. Here, the carrier raw material refers to the sum of the mass of cordierite precursor powder and the alkali-catching component.

[0015] S2: Apply the coating liquid to the channel wall surface of the alkali-resistant honeycomb ceramic carrier;

[0016] S3: The alkali-resistant honeycomb ceramic carrier obtained in step S2 is dried and cured to obtain the alkali-resistant honeycomb low-temperature denitrification catalyst.

[0017] It should be noted that in order to achieve a mass ratio of 0.05 to 0.30:1 between the denitrification coating and the alkali-resistant honeycomb ceramic carrier, multiple coating and curing processes can be performed.

[0018] In step S1, the sintering temperature is 1200–1300℃, and the holding time is 2–4 hours. Preferably, a drying process is included before the sintering process. The drying temperature in step S1 is 60℃–110℃, and the drying time is 0.5 hours–4 hours (preferably 1.3–4 hours). More preferably, the drying process in step S1 is specifically drying at 60–70℃ for 0.8–2 hours, and then drying at 100–110℃ for 0.5–2 hours.

[0019] In step S2, the coating solution is prepared by dispersing the raw material powders in an aqueous system; the pH of the coating solution is 2.5 to 4.5, the solid content is 45 to 55 wt%, and the viscosity at 25°C is 800 to 1500 mPa·s.

[0020] The adhesive solvent in the aqueous dispersion system is nitric acid, and the coating liquid also contains boehmite, the amount of which is 1.0 to 5.0 wt% of the total mass of the raw material powder.

[0021] The raw material powder includes one or more of TiO2 powder, Zr precursor, Nb precursor, Mn precursor, and Ce precursor; the Zr precursor is selected from one or more of zirconium oxychloride, zirconium-based nitrate, or zirconium carboxylate; the Nb precursor is selected from niobium ammonium oxalate or niobium sol; and the Mn precursor is selected from manganese nitrate or manganese acetate.

[0022] In step S2, a dispersing / complexing agent is added to the coating liquid. The dispersing / complexing agent is polyacrylic acid and citric acid. The amount of polyacrylic acid added is 0.2 to 0.6 wt% of the mass of the raw material powder, and the amount of citric acid added is 0.2 to 0.6 wt% of the total mass of the coating liquid.

[0023] In step S2, the coating is performed using vacuum extraction coating, wherein the vacuum degree of the vacuum extraction coating is -0.02 to -0.08 MPa and the extraction time is 1 to 5 min.

[0024] The drying temperature in step S3 is 60℃~110℃, and the drying time is 0.5h~1.5h (preferably 1.3~1.5h). More preferably, the drying in step S3 is specifically drying at 60~70℃ for 0.5~0.8h, and then drying at 100~110℃ for 0.5~1h. The curing temperature is 380~420℃, and the time is 2~4h.

[0025] The beneficial effects of this invention are as follows:

[0026] 1) The present invention utilizes a bulk alkali-trapping and poisoning-delaying carrier. This invention employs an alkali-resistant honeycomb ceramic carrier prepared through a co-extrusion and co-firing process. The alkali-resistant components are macroscopically and uniformly dispersed within the honeycomb matrix, forming stable bulk chemical fixation sites throughout the carrier structure. These fixation sites preferentially react with alkali metals such as Na, K, Ca, and Mg, as well as alkaline earth metals, in the flue gas, effectively immobilizing and intercepting them, thereby inhibiting their migration and coverage into the catalyst active layer and significantly slowing down the catalyst poisoning rate. Simultaneously, the bulk alkali-trapping mechanism also reduces the risk of blockage caused by alkali metal accumulation in the pore structure, effectively suppressing the rapid increase in pressure drop over operating time, and extending the overall service life and stable operating cycle of the catalyst.

[0027] 2) The denitrification coating of this invention enhances acidity and low-temperature activation. In the coating formulation, TiO2 is used as the main framework and carrier, and MnO is utilized. x This process endows the system with excellent low-temperature redox activity, enabling it to maintain strong NO to NO2 conversion and reactive oxygen species generation capabilities even at relatively low reaction temperatures. Simultaneously, the introduction of ZrO2 and Nb2O5 into the system significantly modulates the number and strength of Lewis acid centers, enhancing the adsorption and activation efficiency of NH3 molecules at acidic sites and improving the resistance of the active layer to alkali metal poisoning to some extent. The synergistic effect of the multiple components not only strengthens the acidic environment and reaction driving force of the active layer but also inhibits phase transformation and active site loss at high temperatures, thus balancing reactivity and structural durability, ensuring sustained and efficient conversion performance within the low-temperature SCR reaction window.

[0028] 3) The alkali-poisoning-resistant honeycomb low-temperature denitrification catalyst of this invention is adapted for cement kiln applications. Considering the low-temperature conditions of 150–300°C in cement kiln flue gas, and the complex environmental factors commonly present in the flue gas such as high alkali content, high humidity, and high dust levels, the catalyst prepared by this invention can maintain a high NO content even under multiple harsh conditions. xThe catalyst exhibits high conversion efficiency and stable long-term operational performance. Its integrated structure effectively resists the risks of deactivation caused by alkali metal poisoning and moisture cover, while also meeting low pressure drop requirements, reducing system energy consumption and operational resistance. Simultaneously, the tight bonding between the denitrification coating and the substrate enhances resistance to mechanical erosion and thermal shock, enabling stable operation even in the high-dust, high-airflow-impact environment of cement kiln flues. In summary, the catalyst of this invention can achieve highly efficient denitrification in low-temperature SCR in engineering applications and meets the stringent adaptation requirements for long-term continuous operation of cement kilns. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0030] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available.

[0031] Example 1:

[0032] A method for preparing a honeycomb-shaped low-temperature denitration catalyst resistant to alkali poisoning specifically includes the following steps:

[0033] S0: Preparation - Coating Solution Preparation: Take approximately 900 g of deionized water in a dispersion tank and slowly adjust the pH to 3 with dilute nitric acid. Then, add 837 g of TiO2 powder, 262 g of zirconium oxychloride (ZrOCl2·8H2O, equivalent to approximately 100 g of ZrO2), 101 g of manganese nitrate (Mn(NO3)2·4H2O, equivalent to approximately 35 g of MnO2), and 25 g of cerium nitrate (Ce(NO3)3·6H2O, equivalent to approximately 10 g of CeO2). Add 18 g of AlOOH as an inorganic binder, and simultaneously supplement with 4 g of polyacrylic acid and 4 g of citric acid as dispersing and complexing agents. After planetary dispersion for 20 min, transfer the mixture to a sand mill and grind with zirconia beads for 30 min. Then, add deionized water until the viscosity is controlled at 1000-1200 mPa·s at 25 °C to obtain the coating solution.

[0034] S1: Preparation of Alkali-Resistant Honeycomb Ceramic Carrier by Co-extrusion and Co-firing: 850 g of cordierite precursor powder was weighed and mixed with 80 g of attapulgite, 40 g of AlPO4 powder and 30 g of MgAl2O4 powder. After passing through a 100-mesh sieve, the mixture was dry-mixed for 10 min. 30 g of boehmite was added as a binder, along with 120 g of starch as a pore-forming agent and 3 g of CMC as a water-retaining rheology modifier. Deionized water was added slowly in two batches until the moisture content reached approximately 30 wt%. After vacuum kneading for 20 min, a honeycomb preform with a wall thickness of 0.40 mm and a density of 200 cpsi was obtained in a honeycomb extruder. After standing at room temperature for 2 h, the preform was dried successively at 60 ℃ for 2 h and 110 ℃ for 2 h, and then dried at 2 ℃·min. -1 The temperature was raised to 1250 ℃, held for 3 h, and then cooled to obtain an alkali-resistant honeycomb ceramic carrier.

[0035] S2: Coating: After preheating the alkali-resistant honeycomb ceramic carrier to 120 ℃ and holding it at that temperature for 30 min, place it into a coating tank containing coating liquid. Keep it under a vacuum of -0.06 MPa for 2 min to complete the coating. After removing it, blow away the excess slurry with compressed air at 0.2 MPa.

[0036] S3: Curing: The alkali-resistant honeycomb ceramic carrier obtained in step S2 is dried at 60 ℃ for 0.5 h, then dried at 110 ℃ for 1 h, and finally cured at 2 ℃·min. -1 The temperature was raised to 400 ℃ and held for 2 h for curing to obtain a honeycomb-shaped low-temperature denitrification catalyst resistant to alkali poisoning with a coating / carrier mass ratio of 0.20:1.

[0037] Example 2:

[0038] A method for preparing a honeycomb-shaped low-temperature denitration catalyst resistant to alkali poisoning specifically includes the following steps:

[0039] S0: Preparation - Coating Solution Preparation: Take approximately 850g of deionized water in a dispersion tank and slowly adjust the pH to 3.0 with dilute nitric acid. Then, add 974g of TiO2 powder, 3.3g of niobium ammonium oxalate solution (equivalent to approximately 10g of Nb2O5), 58g of manganese nitrate Mn(NO3)2·4H2O (equivalent to approximately 20g of MnO2), and 12.6g of cerium nitrate Ce(NO3)3·6H2O (equivalent to approximately 5g of CeO2). Add 50g of pseudoboehmite as an inorganic binder, and simultaneously add 2g of polyacrylic acid and 2g of citric acid as dispersing and complexing agents. After planetary dispersion for 15 min, transfer the slurry to a sand mill and grind it with zirconia beads for 20 min. Then, add deionized water until the viscosity at 25℃ is 900-1100 mPa·s, thus obtaining the coating solution.

[0040] S1: Preparation of alkali-resistant honeycomb ceramic carrier by co-extrusion and co-firing: 900 g cordierite precursor powder and 100 g attapulgite were mixed, sieved evenly, and then 20 g AlOOH, 100 g starch, and 3 g CMC were added. Water was gradually added until the moisture content was 30 wt%. After vacuum kneading for 20 min, the mixture was extruded into a honeycomb blank with a wall thickness of 0.35 mm and a wall thickness of 300 cpsi. The blank was dried at 70 ℃ for 0.8 h and at 100 ℃ for 0.5 h, and then fired at 1200 ℃ for 4 h to obtain an alkali-resistant honeycomb ceramic carrier that meets the mechanical and porosity requirements.

[0041] S2: Coating: After preheating the alkali-resistant honeycomb ceramic carrier to 120 ℃ and holding it at that temperature for 30 min, place it into a coating tank containing the coating liquid and coat it under a vacuum of -0.08 MPa for 1 min. After removing it, sweep away the excess slurry.

[0042] S3: Curing: The alkali-resistant honeycomb ceramic carrier obtained in step S2 is dried at 70 ℃ for 0.8 h and at 100 ℃ for 0.5 h in sequence, and then calcined at 400 ℃ for 3 h to obtain a finished product with a coating / carrier mass ratio of 0.05:1.

[0043] Example 3:

[0044] A method for preparing a honeycomb-shaped low-temperature denitration catalyst resistant to alkali poisoning specifically includes the following steps:

[0045] S0: Preparation - Coating Solution Preparation: Take approximately 800 g of deionized water in a dispersion tank and slowly adjust the pH to 3.5 with dilute nitric acid. Then, add 835 g of TiO2 powder, 500 g of zirconium oxychloride (ZrOCl2·8H2O, equivalent to approximately 190 g of ZrO2), and 130 g of manganese nitrate (Mn(NO3)2·4H2O, equivalent to approximately 45 g of MnO2). Next, add 23.6 g of pseudoboehmite as the inorganic binder phase, and simultaneously add 4 g of polyacrylic acid and 4 g of citric acid as dispersing and complexing agents. After the mixture is homogenized by high-speed stirring, transfer it to a sand mill and grind it with zirconia beads for 30 min. Then, add deionized water until the viscosity of the coating solution measured at 25 ℃ is 1300-1500 mPa·s, thus obtaining the coating solution.

[0046] S1: Preparation of alkali-resistant honeycomb ceramic carrier by co-extrusion and co-firing: 800g cordierite precursor powder and 200g AlPO4 powder were mixed, sieved evenly, and then 30g boehmite, 12g starch and 3g CMC were added. Water was added to a moisture content of about 30wt%. After vacuum refining, a honeycomb blank with a wall thickness of 200 cpsi and 0.40 mm was extruded. After drying at 60 ℃ for 2 h and at 110 ℃ for 2 h, it was fired at 1260 ℃ for 3 h to obtain the alkali-resistant honeycomb ceramic carrier.

[0047] S2: Coating: After preheating the alkali-resistant honeycomb ceramic carrier to 110 ℃ and holding it at that temperature for 30 min, place it into a coating tank containing coating liquid and coat it at -0.06 MPa for 3 min, and then perform sweep blowing.

[0048] S3: Curing: The alkali-resistant honeycomb ceramic carrier obtained in step S2 is dried at 60℃ for 0.5 h and at 110℃ for 1.5 h, and then calcined at 420℃ for 2.5 h to cure, resulting in a finished product with a coating / carrier ratio of 0.30:1.

[0049] Example 4:

[0050] A method for preparing a honeycomb-shaped low-temperature denitration catalyst resistant to alkali poisoning specifically includes the following steps:

[0051] S0: Preparation - Coating Solution Preparation: Take about 850 g of deionized water in a dispersion tank and slowly adjust the pH to 3.2 with dilute nitric acid. Then, add 895 g of TiO2 powder, 209 g of zirconium oxychloride ZrOCl2·8H2O (equivalent to about 80 g of ZrO2), 4.3 g of ammonium niobate oxalate (equivalent to about 5 g of Nb2O5), 87 g of manganese nitrate Mn(NO3)2·4H2O (equivalent to about 30 g of MnO2), and 37.8 g of cerium nitrate Ce(NO3)3·6H2O (equivalent to about 15 g of CeO2). Add 17.7 g of pseudoboehmite as an inorganic binder phase, and simultaneously add 4 g of polyacrylic acid and 4 g of citric acid as dispersing and complexing agents. The mixture is first stirred at high speed until uniform, then dispersed by planetary dispersion for 15 min, and then ground with zirconia beads in a sand mill for 25 min. After that, deionized water is added until the viscosity is controlled at 1000-1200 mPa·s at 25 ℃, thus obtaining the coating liquid.

[0052] S1: Preparation of alkali-resistant honeycomb ceramic carrier by co-extrusion and co-firing: 700 g cordierite precursor powder, 250 g MgAl2O4 and 50 g attapulgite were mixed and sieved evenly. Then, 25 g AlOOH, 12 g starch and 3 g CMC were added to adjust the moisture content to 30 wt%. After vacuum kneading for 20 min, a honeycomb green body with a wall thickness of 0.35 mm and a density of 300 cpsi was extruded. After drying at 60 ℃ for 2 h and at 110 ℃ for 1 h, the green body was fired at 1250 ℃ for 3 h to obtain an alkali-resistant honeycomb ceramic carrier with qualified mechanical and porosity properties.

[0053] S2: Coating: After preheating the alkali-resistant honeycomb ceramic carrier to 130℃ and holding it at that temperature for 30 min, place it into a coating tank containing the coating liquid and vacuum coat it for 2 min at -0.06 MPa, then sweep away any excess slurry.

[0054] S3: Curing: The alkali-resistant honeycomb ceramic carrier obtained in step S2 is dried at 60 ℃ for 0.5 h, dried at 110 ℃ for 1 h, and calcined at 400 ℃ for 3 h to obtain a finished product with a coating / carrier ratio of 0.18:1.

[0055] Example 5:

[0056] A method for preparing a honeycomb-shaped low-temperature denitration catalyst resistant to alkali poisoning specifically includes the following steps:

[0057] S0: Preparation - Coating Solution Preparation: Take about 880 g of deionized water in a dispersion tank and slowly adjust the pH to 4 with dilute nitric acid. Then, add 934 g of TiO2 powder, 52 g of zirconium oxychloride ZrOCl2·8H2O (equivalent to about 20 g of ZrO2), 18 g of ammonium niobate oxalate (equivalent to about 21 g of Nb2O5), 159 g of manganese nitrate Mn(NO3)2·4H2O (equivalent to about 55 g of MnO2), and 75.6 g of cerium nitrate Ce(NO3)3·6H2O (equivalent to about 30 g of CeO2). Add 15.3 g of pseudoboehmite as an inorganic binder phase, and simultaneously add 6 g of polyacrylic acid and 6 g of citric acid as dispersing and complexing agents. The obtained slurry is first stirred evenly, then planetarily dispersed for 15 min, and then transferred to a sand mill and ground with zirconia beads with an inner diameter of 0.5 mm for 25 min. After that, deionized water is added until the viscosity of the coating solution is maintained at 800-900 mPa·s at 25 ℃, and the coating solution is obtained.

[0058] S1: Preparation of alkali-resistant honeycomb ceramic carrier by co-extrusion and co-firing: Weigh 950 g of cordierite precursor powder, 25 g of attapulgite and 25 g of AlPO4, mix them, sieve them evenly and then add 30 g of AlOOH, 100 g of starch and 3 g of CMC. Add water in batches to make a plastic mud with a moisture content of 30wt%. After vacuum refining, extrude a honeycomb blank with a wall thickness of 0.40 mm at 200 cpsi. After drying at 60 ℃ for 2 h and 110 ℃ for 2 h, fire at 1300 ℃ for 2 h to obtain an alkali-resistant honeycomb ceramic carrier that meets the porosity and mechanical properties.

[0059] S2: Coating: After preheating the alkali-resistant honeycomb ceramic carrier to 120 ℃ and holding it at that temperature for 30 min, place it into a coating tank containing coating liquid and coat it under a vacuum of -0.02 MPa for 5 min, then sweep away any excess slurry.

[0060] S3: Curing: The alkali-resistant honeycomb ceramic carrier obtained in step S2 is dried at 60 ℃ for 0.5 h, dried at 110 ℃ for 1 h, and calcined at 380 ℃ for 4 h to obtain a finished product with a coating / carrier ratio of 0.20:1.

[0061] Comparative Example 1:

[0062] The preparation process of Comparative Example 1 is the same as that of Example 1, except that step S1 does not include the alkali-resistant component, i.e., 1000 g of cordierite precursor powder is weighed.

[0063] Comparative Example 2:

[0064] The preparation process of Comparative Example 2 is the same as that of Example 1, except that no Zr or Nb components are introduced into the coating solution in step S20.

[0065] Specifically, the preparation steps of the coating solution in Comparative Example 2 are as follows: Take approximately 950 g of deionized water, adjust the pH to 3 with dilute nitric acid, then add 965 g of TiO2 powder and 101 g of Mn(NO3)2·4H2O (equivalent to approximately 35 g of MnO2), without introducing any Zr or Nb components. Next, add 18 g of AlOOH (equivalent to approximately 15 g of Al2O3) as an inorganic binder phase, and simultaneously add 4 g of polyacrylic acid and 4 g of citric acid. After planetary dispersion for 20 min, mill for 30 min, and add water to a total mass of 2000 g to obtain a coating solution with a solid content of 50 wt% and a viscosity of 1000-1200 mPa·s at 25 ℃.

[0066] Comparative Example 3:

[0067] In Comparative Example 3, an alkali-resistant component was added to the coating. The specific steps included the following:

[0068] S1: Preparation of honeycomb ceramic carrier: Weigh 1000 g of cordierite precursor powder, pass it through a 100-mesh sieve, dry mix for 10 min, add 30 g of AlOOH as a binder, and simultaneously add 120 g of starch as a pore-forming agent and 3 g of CMC as a water-retaining rheology modifier. Add deionized water in two slow additions until the moisture content is about 30 wt%. After vacuum kneading for 20 min, obtain a honeycomb preform with a thickness of 200 cpsi and a wall thickness of 0.40 mm in a honeycomb extruder. After standing at room temperature for 2 h, dry at 60 ℃ for 2 h and 110 ℃ for 2 h respectively, and then at 2 ℃·min -1 The temperature was raised to 1250 ℃, held for 3 h, and then cooled to obtain the honeycomb ceramic carrier.

[0069] S20: Preparation of coating solution: Take about 900 g of deionized water in a dispersion tank, slowly adjust the pH to 3 with dilute nitric acid, and add 80 g of attapulgite, 40 g of AlPO4 powder and 30 g of MgAl2O4 powder, 837 g of TiO2 powder, 262 g of zirconium oxychloride ZrOCl2·8H2O (equivalent to about 100 g of ZrO2), 101 g of manganese nitrate Mn(NO3)2·4H2O (equivalent to about 35 g of MnO2), 25 g of cerium nitrate Ce(NO3)3·6H2O (equivalent to about 10 g of CeO2), and add 18 g of AlOOH (equivalent to about 15 g of Al2O3) as an inorganic binder phase. At the same time, add 4 g of polyacrylic acid and 4 g of citric acid as dispersing and complexing agents. After the mixed slurry is dispersed by planetary dispersion for 20 min, it is transferred to a sand mill and ground with zirconia beads for 30 min. Then, deionized water is added until the viscosity is controlled at 1000-1200 mPa·s at 25 °C to obtain the coating liquid.

[0070] S2: Coating: After preheating the honeycomb ceramic carrier to 120 ℃ and holding it at that temperature for 30 min, place it into the coating tank and maintain it under a vacuum of -0.06 MPa for 2 min to complete the coating. After removing it, blow away the excess slurry with compressed air at 0.2 MPa.

[0071] S3: Curing: The honeycomb ceramic carrier obtained in step S2 is dried at 60 ℃ for 0.5 h, then dried at 110 ℃ for 1 h, and finally cured at 2 ℃·min. -1 The temperature was raised to 400 ℃ and held for 3 h to cure, resulting in a honeycomb-shaped low-temperature denitrification catalyst resistant to alkali poisoning with a coating / carrier mass ratio of 0.20:1.

[0072] Catalyst denitrification activity test:

[0073] (a) Basic activity test:

[0074] The reaction was conducted in a fixed-bed reactor at a temperature of 150-300 °C. The simulated flue gas consisted of 1000 ppm NH3 + 1000 ppm NO + 5% O2, with the remainder being N2 in equilibrium. The pressure was atmospheric pressure. The volumetric hourly space velocity (VHSV) was calculated to be 5000 mL·mg based on the sample mass. -1 ·h -1 The NO conversion rate was used as an indicator of denitrification activity, and the exhaust gas was analyzed online using a KM9506 flue gas analyzer.

[0075] (II) Evaluation of alkali poisoning resistance:

[0076] To simulate the long-term effects of alkaline conditions on the catalyst, an accelerated poisoning method of "mixed salt solution impregnation-drying-calcination" was used to prepare an "alkali metal poisoning catalyst," which was then compared with a baseline sample. The specific steps are as follows: A mixed solution of NaCl and KCl (0.1 mol·L⁻¹ each) was prepared. -1 The samples to be evaluated (examples and comparative examples) were completely immersed in a mixed salt solution at room temperature. The sample volume: solution volume = 1:3, and the immersion time was 30 min. The samples were then removed and the surface free liquid was drained. The samples were first allowed to stand and air dry for 12 h, then dried in a muffle furnace at 120 ℃, and then calcined at 500 ℃ for 4 h to obtain the "alkali metal poisoning catalyst".

[0077] Table 1. Catalyst Reaction Activity Results

[0078]

[0079] As can be seen from the data in Table 1, the alkali-resistant honeycomb low-temperature denitrification catalyst prepared in this invention already exhibits high activity in the low-temperature region before alkali poisoning: at 150 ℃, Examples 1-5 have 88%, 86%, 90%, 89%, and 87% respectively, with Examples 3 and 4 leading; as the temperature rises to 300 ℃, Examples 1-5 reach 92%, 92%, 94%, 93%, and 93% respectively. In contrast, Comparative Examples 1 and 2 have only 87% and 82% at 150 ℃, and only 89% at 300 ℃, showing a stable difference from the examples. This indicates that the formulation of this invention (Mn-Ti as the main component, with the introduction of Zr / Nb / Ce and control of coating loading) has higher denitrification efficiency within the 120–300 ℃ window.

[0080] After alkali soaking, the activity decrease in the examples was significantly less than that in the comparative examples. At 150 °C, the activity of Examples 1-5 was 77%, 73%, 83%, 80%, and 75%, respectively, while that of Comparative Examples 1 and 2 decreased to 61% and 49%. At 300 °C, the activity of Examples 1-5 was 81%, 78%, 86%, 84%, and 80%, respectively, while that of Comparative Examples 1 and 2 was only 62% and 53%. In the medium-high temperature range (240-300 °C), Examples 3 and 4 maintained a level of 88 / 86-86 / 84%, while the two comparative examples were only 64-62% and 55-53% in the same temperature range, showing a clear difference.

[0081] This yields a clear alkali resistance retention rate: Example 3 maintains approximately 92% at various temperatures (e.g., 83 / 90 at 150℃; 86 / 94 at 300℃), Example 4 approximately 90%, Example 1 approximately 88%, Example 5 approximately 86%, and Example 2 approximately 85%; while Comparative Examples 1 and 2 maintain only approximately 70% and 60%, respectively. This aligns with two design features of this invention: firstly, the bulk alkali-trapping structure of attapulgite / AlPO4 / MgAl2O4 in the carrier is uniformly dispersed, preferentially fixing Na / K and reducing migration to the active layer; secondly, Zr / Nb acidification combined with Ce synergistically enhances NH3 adsorption and low-temperature activation, and improves the alkali resistance of acid sites. Therefore, the samples of this invention can maintain an activity retention rate of 85-92% even under alkali-rich conditions, significantly better than the control samples. Furthermore, Comparative Example 3 exhibits the worst alkali resistance because the "co-coating of alkali-resistant components and active components" process failed to form a bulk alkali-fixing site.

[0082] The preparation method of the alkali-resistant honeycomb low-temperature denitrification catalyst of the present invention first introduces alkali-capturing components such as attapulgite, AlPO4, and MgAl2O4 into the support stage, and forms a honeycomb support with alkali fixation ability through co-extrusion and high-temperature sintering. Subsequently, Mn-Ti is mainly used in the coating, and Zr, Nb, Ce and other additives are introduced to enhance Lewis acidity and structural stability, thereby jointly improving the catalyst's alkali-resistant performance and low-temperature activity. After coating, drying and calcination, a monolithic catalyst is obtained. This catalyst can maintain a high NO conversion efficiency in the presence of alkali metals, which is significantly better than that of traditional systems, demonstrating good alkali-resistant performance. The catalyst of the present invention is suitable for the denitrification treatment of low-temperature alkaline flue gas, especially suitable for the long-term stable operation of flue gas in non-power industries such as glass, metallurgy, and cement, and has strong industrial application prospects.

[0083] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0084] The parts of this invention not described in detail are well-known in the art. The above embodiments are provided merely for the purpose of describing the invention and are not intended to limit the scope of the invention. The scope of the invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principles of the invention should be covered within the scope of the invention.

Claims

1. A honeycomb-shaped low-temperature denitration catalyst resistant to alkali poisoning, characterized in that, The alkali poisoning-resistant honeycomb low-temperature denitration catalyst comprises an alkali-resistant honeycomb ceramic carrier and a denitration coating; wherein the alkali-resistant honeycomb ceramic carrier is prepared by co-extrusion and co-sintering, the alkali-resistant honeycomb carrier comprises an alkali-trapping component and a carrier matrix, and the alkali-trapping component is macroscopically uniformly dispersed in the carrier matrix; the denitration coating is coated on the channel wall surface of the alkali-resistant honeycomb ceramic carrier. The mass ratio of the alkali-trapping component to the alkali-trapping component is 5-30:70-95, and the mass ratio of the denitration coating to the alkali-resistant honeycomb ceramic carrier is 0.05-0.30:

1.

2. The alkali poisoning-resistant honeycomb low-temperature de-NOx catalyst according to claim 1, characterized by, The alkali-trapping component is selected from one or more of attapulgite, aluminum phosphate and spinel. The denitration coating comprises, in terms of solid content, 1.0-6.0 wt% of MnO2, 0-18 wt% of ZrO2 and / or 0-2.0 wt% of Nb2O5, 0-3.0 wt% of CeO2, and the content of ZrO2 and Nb2O5 cannot be 0 at the same time, and the balance is TiO2.

3. The alkali poisoning-resistant honeycomb low-temperature de-NOx catalyst according to claim 1 or 2, characterized by, The pore density of the alkali-resistant honeycomb carrier is 200-300 cpsi, the wall thickness of the alkali-resistant honeycomb carrier is 0.35-0.40 mm, the total porosity of the alkali-resistant honeycomb carrier is ≥35%, and the axial compressive strength of the alkali-resistant honeycomb carrier is ≥3 MPa.

4. The method for producing the alkali poisoning-resistant honeycomb low-temperature desulfurization catalyst according to any one of claims 1 to 3, characterized by, The method comprises the following steps: S1: co-extrusion and co-sintering to prepare an alkali-resistant honeycomb ceramic carrier: mixing cordierite precursor powder and an alkali-trapping component at a mass ratio of 70-95:5-30, adding additives and water to prepare extrusion mud, extruding into a honeycomb body, and then performing sintering treatment to obtain an alkali-resistant honeycomb ceramic carrier in which the alkali-trapping component is macroscopically uniformly dispersed in the carrier matrix; S2: coating a coating liquid on the channel wall surface of the alkali-resistant honeycomb ceramic carrier; S3: performing drying treatment and solidification treatment on the alkali-resistant honeycomb ceramic carrier obtained in step S2 to obtain the alkali poisoning-resistant honeycomb low-temperature denitration catalyst.

5. The method of producing a honeycomb low-temperature denitration catalyst resistant to alkali poisoning according to claim 4, characterized by, The sintering temperature in step S1 is 1200-1300°C, and the holding time is 2-4 h.

6. The preparation method of the alkali-resistant honeycomb low-temperature denitration catalyst according to claim 4, characterized in that, The coating liquid used in step S2 is prepared by dispersing each raw material powder in a water dispersion system; the pH of the coating liquid is 2.5-4.5, the solid content is 45-55 wt%, and the viscosity at 25°C is 800-1500 mPa·s.

7. The method of producing an alkali poisoning-resistant honeycomb low-temperature denitration catalyst according to claim 6, characterized by, The peptizing agent in the water dispersion system is nitric acid, and pseudoboehmite is further added to the coating liquid, and the addition amount of the pseudoboehmite is 1.0-5.0 wt% of the mass of the raw material powder.

8. The method for preparing the alkali-poison-resistant honeycomb low-temperature denitration catalyst according to claim 6, characterized in that, The raw material powder comprises one or more of TiO2 powder, Zr precursor, Nb precursor, Mn precursor and Ce precursor; the Zr precursor is selected from one or more of zirconium oxychloride, zirconium nitrate or zirconium carboxylate, the Nb precursor is selected from ammonium niobium oxalate or niobium sol, and the Mn precursor is selected from manganese nitrate or manganese acetate.

9. The method for preparing the alkali-poison-resistant honeycomb low-temperature denitration catalyst according to claim 6, characterized in that, The coating liquid in step S2 further comprises a dispersing / complexing agent, which is polyacrylic acid and citric acid, the polyacrylic acid is added in an amount of 0.2-0.6wt% of the mass of the raw material powder, and the citric acid is added in an amount of 0.2-0.6wt% of the total mass of the coating liquid.

10. The method of producing a honeycomb low-temperature denitration catalyst against alkali poisoning according to any one of claims 4 to 9, characterized by, The coating in step S2 is vacuum extraction coating, the vacuum degree is -0.02 to -0.08 MPa, and the extraction time is 1-5 min. The drying treatment in step S3 is at a temperature of 60-110℃, the drying treatment time is 0.5-1.5h, the curing treatment is at a temperature of 380-420℃, and the time is 2-4h.

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