Flue gas denitration catalyst, its preparation method and application

Abstract

The application relates to the technical field of denitration catalysts, and particularly discloses a flue gas denitration catalyst as well as a preparation method and application thereof. The flue gas denitration catalyst disclosed by the application is composed of the following components in percentage by weight: 70-80 wt% of a composite carrier, 8-12 wt% of an active component, 3-6 wt% of a structure aid, and the balance of a binder; the composite carrier is formed by mixing anatase titanium dioxide and gamma-Al2O3 at a weight ratio of 7-9:1-3; the active component is a ternary system composed of vanadium pentoxide, molybdenum trioxide and cerium dioxide at a molar ratio of 1-3:0.1-0.4:0.02-0.08; and the structure aid is silicon dioxide. The denitration catalyst prepared by the application has excellent denitration catalytic performance, and the denitration catalyst is excellent in sulfur resistance, water resistance and stability.

Description

Technical Field

[0001] This application relates to the technical field of denitrification catalysts, specifically to a flue gas denitrification catalyst, its preparation method, and its application. Background Technology

[0002] Coal combustion produces large amounts of nitrogen oxides and other air pollutants, making it a major source of air pollution and seriously endangering human health and the ecological environment. With increasingly stringent environmental regulations, industrial flue gas denitrification technology has become a key focus of air pollution control. Selective catalytic reduction (SCR) technology is currently the mainstream flue gas denitrification method, and its core lies in the development of highly efficient catalysts. Currently, vanadium-based catalysts are widely used due to their high activity and good stability, but they suffer from problems such as insufficient low-temperature activity and poor resistance to sulfur and water.

[0003] In recent years, researchers have attempted to improve catalyst performance through methods such as support modification and active component optimization, but the aforementioned technical bottlenecks have not yet been completely resolved. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a flue gas denitrification catalyst, its preparation method, and its application.

[0005] In a first aspect, this application provides a flue gas denitrification catalyst, which is composed of the following components by weight percentage: 70-80 wt% composite support, 8-12 wt% active component, 3-6 wt% structural aid, and the balance binder. The composite carrier is composed of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 7-9:1-3; The active component is a ternary system composed of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1-3:0.1-0.4:0.02-0.08. The structural additive is silicon dioxide.

[0006] In the technical solution provided in this application, the composite support serves as the skeletal support for the catalyst. Its core functions are to support active components, provide a stable pore structure, and optimize the distribution of active sites. Anatase titanium dioxide and γ-nitrogen oxides are mixed at a weight ratio of 7-9:1-3, achieving a synergistic advantage of "activity compatibility + structural stability," avoiding the performance defects of a single support: First, it provides a high specific surface area and active loading sites: it can form stable chemical bonds with active components, uniformly disperse active component particles, and ensure sufficient exposure of active components, providing ample active sites for nitrogen oxide adsorption and catalytic reactions. Second, it can optimize low-temperature denitrification activity: by reducing the activation energy of the denitrification reaction, it significantly improves the low-temperature denitrification performance of the catalyst, solving the problem of insufficient low-temperature activity of conventional supports. Third, it enhances sulfur and water resistance: the surface of anatase titanium dioxide is weakly acidic, which can inhibit the reaction of sulfur dioxide in flue gas with active components to form ammonium sulfate / ammonium bisulfate (avoiding blockage of active sites). At the same time, its pore structure can adsorb a small amount of water without damaging its own structure, reducing the inhibitory effect of water vapor on the denitrification reaction.

[0007] The active component is the core functional component of the catalyst for denitrification. A synergistic catalytic system is formed by combining vanadium pentoxide (main active), molybdenum trioxide (co-active), and cerium dioxide (auxiliary synergist) in a molar ratio of 1-3:0.1-0.4:0.02-0.08. This system addresses the shortcomings of single active components, such as low denitrification efficiency, poor resistance to sulfur and water, and poor stability. Molybdenum trioxide can lower the activation energy of the SCR reaction and accelerate the reaction rate of ammonia and nitrogen oxides, especially in the low-temperature range (180-220℃). It can assist vanadium pentoxide in improving denitrification efficiency and compensate for the insufficient activity of vanadium pentoxide at low temperatures. A molar ratio of vanadium trioxide controlled at 0.1-0.4 achieves optimal synergy with vanadium pentoxide. If the ratio is below 0.1, the co-active effect is not significant; if it is above 0.4, it will cover the active sites, thus reducing denitrification efficiency. Cerium dioxide possesses excellent oxygen storage and release capabilities, releasing lattice oxygen in the low-temperature range (180-220℃) to increase the number of active sites. Simultaneously, it can adsorb more nitrogen oxides to form nitrate intermediates, accelerating the catalytic reaction rate. Furthermore, cerium dioxide can synergistically work with molybdenum trioxide to further inhibit the adsorption and deposition of sulfur dioxide at active sites, reducing the formation of ammonium sulfate / ammonium bisulfate. In addition, it can enhance the catalyst's tolerance to water vapor, reducing the inhibition of nitrogen oxide adsorption and catalytic reactions by water vapor, ensuring long-term stable operation of the catalyst under humid and sulfur-containing conditions.

[0008] As a structural aid, silica plays a key role in optimizing the catalyst's framework structure and inhibiting component aggregation, thus ensuring the full performance of the active components and composite supports, and adapting to the entire catalyst preparation and application process.

[0009] Based on the above technical solution, this application uses anatase titanium dioxide-γ-Al2O3 (7-9:1-3) composite carrier to provide stable framework support and sufficient active loading sites, adapting to the loading requirements of ternary active components; the tandem effect of the vanadium pentoxide-molybdenum trioxide-cerium dioxide ternary system ensures low-temperature and efficient denitrification while improving stability; the silica structural additive optimizes the framework structure and molding performance, and enhances mechanical strength and component dispersibility; the three components work synergistically with the pseudoboehmite binder to ultimately enable the catalyst to achieve the core advantages of "efficient denitrification, sulfur and water resistance, and long lifespan", adapting to the industrial flue gas denitrification needs of industries such as power, coking, steel, and cement.

[0010] Preferably, the flue gas denitrification catalyst is composed of the following components by weight percentage: 72-78 wt% composite carrier, 9-11 wt% active component, 4-5 wt% structural aid, and the balance binder.

[0011] Preferably, the composite carrier is composed of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 7.5-8.5:1.5-2.5.

[0012] In one specific implementation, the weight ratio of tantalum-type titanium dioxide to γ-Al2O3 in the composite carrier can be 7.5:2.5, 8:2, or 8.5:1.5.

[0013] Experimental analysis shows that the composite support composed of titanium dioxide and γ-Al2O3 in a weight ratio can further improve the performance of the denitrification catalyst.

[0014] Preferably, the active component is a ternary system composed of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1.5-2.5:0.2-0.3:0.04-0.06.

[0015] In one specific implementation, the molar ratio of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in the active components can be 1.5:0.2:0.04, 2:0.2:0.04, 2.5:0.2:0.04, 1.5:0.25:0.05, 2:0.25:0.05, 2.5:0.25:0.05, 1.5:0.3:0.06, 2:0.3:0.06, or 2.5:0.3:0.06.

[0016] Experimental analysis shows that the active component composed of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in the above molar ratio can further improve the performance of the denitrification catalyst.

[0017] Preferably, the binder is boehmite.

[0018] Secondly, this application provides a method for preparing the flue gas denitrification catalyst, specifically including the following steps: Raw material mixing: Add the composite carrier and structural aid to the impregnation solution, disperse by ultrasonication, then add the active component, and stir and impregnate at room temperature for 4-6 hours; Molding and curing: Add a binder to the impregnated mixture and stir until a uniform and plastic agglomerate is formed. Prepare a honeycomb preform by extrusion molding, and then dry and calcinate to obtain the flue gas denitrification catalyst.

[0019] Preferably, the impregnation solution is composed of water and monoethanolamine in a volume ratio of 2-5:1, and the amount of impregnation solution used is 1.0-1.5 times the weight of the composite carrier.

[0020] Preferably, the impregnation solution is composed of water and monoethanolamine in a volume ratio of 3-4:1.

[0021] In preparing the flue gas denitrification catalyst, the inventors discovered that using water and monoethanolamine in the aforementioned volume ratio as the impregnation solution can improve the compatibility, dispersion, and loading uniformity among the composite carrier, active components, and structural additives during the impregnation process. This maximizes the synergistic effect of the mixed impregnation solution and is suitable for the overall preparation process of the catalyst of this invention. Simultaneously, monoethanolamine can be completely decomposed into CO2, H2O, and N2 during calcination, leaving no residual impurities. The slight reducing atmosphere generated during decomposition promotes the formation of stable binding sites between the active components and the hydroxyl groups on the carrier surface, enhancing the synergistic effect of the vanadium pentoxide-molybdenum trioxide-cerium dioxide ternary system and improving the catalyst's catalytic activity and sulfur and water resistance. Furthermore, this impregnation solution can improve compatibility with boehmite binders, enhance the plasticity of the material, reduce the risk of cracking and deformation during honeycomb preform extrusion molding, and ensure the dimensional stability of the preform.

[0022] Preferably, the drying process parameters are: air drying at room temperature for 12-24 hours, followed by drying at 100-110℃ for 4-6 hours; The calcination process parameters are as follows: the dried green body is heated to 500-600℃ at a heating rate of 2-8℃ / min, calcined at a constant temperature for 3-4 hours, and then naturally cooled to room temperature to obtain the flue gas denitrification catalyst product.

[0023] Thirdly, this application provides the application of the aforementioned flue gas denitrification catalyst in flue gas denitrification in the power, coking, steel, and cement industries, applicable to a temperature range of 180-450℃. In summary, the technical solution of this application has the following effects: Innovative composite carrier structure: Anatase titanium dioxide and γ-Al2O3 are used as a composite carrier to ensure high dispersion of active components and selectively adsorb alkali metal ions (K⁺, Na⁺) in flue gas, avoiding poisoning of active components; at the same time, the mechanical strength and stability are enhanced, solving the defects of poor component compatibility and single function of traditional composite carriers.

[0024] Synergistic Enhancement of Ternary Active System: The active system is constructed using vanadium pentoxide-molybdenum trioxide-cerium dioxide ternary powders. By precisely controlling the molar ratio, the precursor decomposition and conversion steps are eliminated, shortening the preparation process and avoiding the loss of active components during the conversion process. Cerium dioxide can enhance the catalyst's adsorption and oxidation capacity for nitrogen oxides, while molybdenum trioxide improves the stability and sulfur resistance of the active components. The synergistic effect of the three enables the catalyst to achieve a denitrification efficiency that is significantly better than that of existing active component systems and catalysts prepared by the precursor method at a loading of 8-12 wt%, with a low-temperature (180-220℃) denitrification efficiency of over 95%.

[0025] Structural additive modification: Silica is dispersed in the support skeleton, which not only greatly increases the specific surface area of ​​the catalyst, but also inhibits the aggregation of active components and pore collapse, while enhancing the catalyst's resistance to sulfur and water poisoning and extending its service life.

[0026] Preparation process optimization: Three-dimensional dispersion of silica and impregnation of active components are carried out sequentially, which simplifies the process while ensuring uniform bonding of each component. The calcination activation process precisely controls the heating rate and temperature, further enhancing the interaction between the active components and the support, making the catalyst performance stable and controllable, and easy to scale up for industrial production.

[0027] The denitrification catalyst prepared in this application has excellent denitrification catalytic performance, and the denitrification catalyst has excellent sulfur and water resistance and stability. Detailed Implementation

[0028] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0029] Example

[0030] Example 1

[0031] Example 1 provides a flue gas denitrification catalyst and its preparation method.

[0032] The specific information of the raw materials in Example 1 is as follows: the average particle size of anatase titanium dioxide is 10nm-30nm, and the specific surface area is 30-50m². 2 / g; the average particle size of γ-Al2O3 is 20nm-50nm, and the specific surface area is 150-200m². 2 / g; silica sol (solid content 30wt%, particle size 15±5nm, solvent is water) is from Jining Benok Biotechnology Co., Ltd.; pseudoboehmite is from Zibo Nuoda Chemical Co., Ltd. (brand name: P-DF-09-HSi), with pore volume of 0.9-1.2cm³ / g and specific surface area of ​​320m² / g.

[0033] The preparation method of the flue gas denitrification catalyst in the above embodiments is as follows: Raw material mixing: 75g of composite carrier (composed of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 8.5:1.5) and 5g of structural aid silica (using 16.7g of silica sol, with a solid content of 30wt%, a particle size of 15±5nm, and water as the solvent) were added to 90g of impregnation solution (the impregnation solution was composed of water and monoethanolamine in a volume ratio of 3:1, and the amount used was 1.2 times the weight of the composite carrier). The mixture was ultrasonically dispersed (power 350W, time 30min). Then, 10g of active component (composed of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1.5:0.3:0.04) was added and the mixture was stirred and impregnated at room temperature for 5h.

[0034] Molding and Curing: 10g of boehmite binder was added to the impregnated mixture, and the mixture was stirred until a uniform and plastic agglomerate was formed. A honeycomb preform was prepared by extrusion molding (specifications: square through-holes, pore density 20 pores / cm², wall thickness 0.8-1.2mm; overall dimensions 150mm×150mm×100mm, length×width×height). After drying and calcination, the flue gas denitrification catalyst was obtained. The drying process parameters were: air drying at room temperature for 18 hours, followed by drying at 105℃ for 5 hours; the calcination process parameters were: the dried preform was placed in a muffle furnace, heated to 550℃ at a heating rate of 5℃ / min, calcined at a constant temperature for 3 hours, and then naturally cooled to room temperature to obtain the finished flue gas denitrification catalyst.

[0035] Examples 2-4 Examples 2-4 provide a flue gas denitrification catalyst and its preparation method, respectively.

[0036] The difference between the above embodiments and Embodiment 1 is that the types of composite carriers are different, as shown below.

[0037] In Example 2: The composite carrier is a mixture of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 7.5:2.5.

[0038] In Example 3: The composite carrier is a mixture of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 7:3.

[0039] In Example 4: The composite carrier is a mixture of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 9:1.

[0040] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0041] Examples 5-7 Examples 5-7 provide a flue gas denitrification catalyst and its preparation method, respectively.

[0042] The difference between the above embodiments and Embodiment 1 is that the types of active components are different, as detailed below.

[0043] In Example 5: the active component is composed of vanadium pentoxide, molybdenum trioxide and cerium dioxide in a molar ratio of 2.5:0.2:0.06.

[0044] In Example 6: The active component is composed of vanadium pentoxide, molybdenum trioxide and cerium dioxide in a molar ratio of 1:0.4:0.02.

[0045] In Example 7: the active component is composed of vanadium pentoxide, molybdenum trioxide and cerium dioxide in a molar ratio of 3:0.1:0.08.

[0046] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0047] Examples 8-11 Examples 8-11 provide a flue gas denitrification catalyst and its preparation method, respectively.

[0048] The difference between the above embodiments and Embodiment 1 is that the type of impregnation liquid is different, as shown below.

[0049] In Example 8: the impregnation solution was composed of water and diethanolamine in a volume ratio of 3:1.

[0050] In Example 9: the impregnation solution was composed of water and monoethanolamine in a volume ratio of 1:1.

[0051] In Example 10: the impregnation solution was composed of water and monoethanolamine in a volume ratio of 2:1.

[0052] In Example 11: the impregnation solution was composed of water and monoethanolamine in a volume ratio of 5:1.

[0053] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0054] Comparative Example Comparative Example 1 Comparative Example 1 provides a flue gas denitrification catalyst and its preparation method.

[0055] The difference between Comparative Example 1 and Example 1 is that the types of composite carriers are different, as shown below.

[0056] In Comparative Example 1: The composite carrier was formed by mixing anatase titanium dioxide and γ-Al2O3 in a weight ratio of 2.5:7.5.

[0057] All other process parameters in the above comparative examples are the same as those in Example 1.

[0058] Comparative Examples 2-3 Comparative Examples 2 and 3 respectively provide a flue gas denitrification catalyst and its preparation method.

[0059] The difference between the above comparative example and Example 1 is that the types of active components are different, as detailed below.

[0060] In Comparative Example 2: the active component is composed of vanadium pentoxide, molybdenum trioxide and cerium dioxide in a molar ratio of 4:0.3:0.04.

[0061] In Comparative Example 3, the active component was composed of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1.5:0.04:0.3.

[0062] In the comparative examples above, all other process parameters are the same as in Example 1.

[0063] Performance testing test 2 (1) Catalytic activity test of denitrification catalyst: The catalyst was placed in a fixed bed reactor; the flue gas was composed of 1500ppm NO, 1500ppm NH3, 8% O2 and N2 as balance gases; the space velocity was controlled at 5000h. -1 The flue gas flow rate was 200 mL / min, and the catalyst denitrification efficiency was tested at 200℃. The results are shown in Table 1.

[0064] (2) Water and sulfur resistance test of denitrification catalyst: The catalyst was placed in a fixed-bed reactor; the flue gas was composed of 1500ppm NO, 1500ppm NH3, 8% O2, 10% H2O, 500ppm SO2 and N2 as balance gases; the space velocity was controlled at 5000 h⁻¹. -1 The flue gas flow rate was 200 mL / min, and the catalyst denitrification efficiency was tested at 200℃. The results are shown in Table 1.

[0065] (3) Stability test of denitrification catalyst: The catalyst was placed in a fixed-bed reactor; the flue gas was composed of 1500ppm NO, 1500ppm NH3, 8% O2, 10% H2O, 500ppm SO2 and N2 as balance gases; the space velocity was controlled at 5000 h⁻¹. -1The flue gas flow rate was 200 mL / min, and the catalyst was continuously operated at 200℃ for 1000 h to test its denitrification efficiency. The results are shown in Table 1.

[0066] Test results are shown in Table 1.

[0067] Table 1 Performance test results of the denitrification catalysts in the examples and comparative examples

[0068] As can be seen from the test results in Table 1 above, the denitrification catalyst prepared using the technical solution provided in this application has excellent denitrification catalytic performance; and the denitrification catalytic activity decay rate is ≤3% in flue gas containing 10% H2O and 500ppm SO2, and the denitrification catalytic activity decay rate is ≤6% after 1000h of continuous operation, indicating that the denitrification catalyst prepared in this application has excellent sulfur and water resistance and stability.

[0069] By comparing the test results of Examples 1-4 and Comparative Example 1, it can be seen that the type of composite support has a significant impact on the performance of the denitration catalyst. In Comparative Example 1, the composite support was a mixture of anatase titanium dioxide and γ-Al₂O₃ at a weight ratio of 2.5:7.5, resulting in a denitration catalyst with poor performance. In contrast, the denitration catalyst prepared using a composite support with a weight ratio of 7-9:1-3 in this application exhibits superior performance.

[0070] By comparing the test results of Examples 1, 5-7, and Comparative Examples 2-3, it can be seen that the type of active component has a significant impact on the performance of the denitrification catalyst. In Comparative Example 2, the active component consisted of a mixture of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 4:0.3:0.04. In Comparative Example 3, the active component consisted of a mixture of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1.5:0.04:0.3. The denitrification catalysts prepared in these examples showed poor performance. In contrast, the present application utilizes a ternary system composed of a mixture of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1-3:0.1-0.4:0.02-0.08 as the active component, resulting in a denitrification catalyst with excellent performance.

[0071] By comparing the test results of Examples 1 and 8-11, it can be seen that in the process of preparing the flue gas denitrification catalyst, the impregnation solution composed of water and monoethanolamine with a volume ratio of 2-5:1 can further improve the performance of the denitrification catalyst.

[0072] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A flue gas denitrification catalyst, characterized in that, It consists of the following components by weight percentage: 70-80 wt% composite carrier, 8-12 wt% active component, 3-6 wt% structural additive, and balance binder; The composite carrier is composed of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 7-9:1-3; The active component is a ternary system composed of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1-3:0.1-0.4:0.02-0.

08. The structural additive is silicon dioxide.

2. The flue gas denitrification catalyst according to claim 1, characterized in that, It consists of the following components by weight percentage: 72-78 wt% composite carrier, 9-11 wt% active component, 4-5 wt% structural additive, and balance binder.

3. The flue gas denitrification catalyst according to claim 1, characterized in that, The composite carrier is composed of anatase titanium dioxide and γ-Al2O3 in a weight ratio of 7.5-8.5:1.5-2.

5.

4. The flue gas denitrification catalyst according to claim 1, characterized in that, The active component is a ternary system composed of vanadium pentoxide, molybdenum trioxide, and cerium dioxide in a molar ratio of 1.5-2.5:0.2-0.3:0.04-0.

06.

5. The flue gas denitrification catalyst according to claim 1, characterized in that, The binder is boehmite.

6. The method for preparing the flue gas denitrification catalyst according to any one of claims 1-5, characterized in that, Specifically, the following steps are included: Raw material mixing: Add the composite carrier and structural aid to the impregnation solution, disperse by ultrasonication, then add the active component, and stir and impregnate at room temperature for 4-6 hours; Molding and curing: Add a binder to the impregnated mixture and stir until a uniform and plastic agglomerate is formed. Prepare a honeycomb preform by extrusion molding, and then dry and calcinate to obtain the flue gas denitrification catalyst.

7. The method for preparing the flue gas denitrification catalyst according to claim 6, characterized in that, The impregnation solution is composed of water and monoethanolamine in a volume ratio of 2-5:1, and the amount of impregnation solution used is 1.0-1.5 times the weight of the composite carrier.

8. The method for preparing the flue gas denitrification catalyst according to claim 6, characterized in that, The impregnation solution is composed of a mixture of water and monoethanolamine in a volume ratio of 3-4:

1.

9. The method for preparing the flue gas denitrification catalyst according to claim 6, characterized in that, The drying process parameters are: air-drying at room temperature for 12-24 hours, followed by drying at 100-110℃ for 4-6 hours; The calcination process parameters are as follows: the dried green body is heated to 500-600℃ at a heating rate of 2-8℃ / min, calcined at a constant temperature for 3-4 hours, and then naturally cooled to room temperature to obtain the flue gas denitrification catalyst product.

10. The application of the flue gas denitrification catalyst as described in any one of claims 1-5 in flue gas denitrification in the power, coking, steel, and cement industries, characterized in that, Suitable for temperatures ranging from 180 to 450℃.

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