Hollow rod-shaped denitration catalyst and preparation method thereof
By using a catalyst composed of hollow rod-shaped TiO2 support and holmium-ytterbium and iron-cerium composite oxides, the problems of alkali heavy metal poisoning and fly ash blockage of denitrification catalysts in the cement industry have been solved, thereby improving the denitrification efficiency and stability of the catalyst.
Patent Information
- Application Number
- CN202510918692.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-03
- Publication Date
- 2025-11-21
AI Technical Summary
Existing denitrification catalysts are susceptible to alkali and heavy metal poisoning and fly ash blockage in the cement industry, resulting in reduced denitrification efficiency and an inability to effectively cope with complex cement flue gas conditions.
Hollow rod-shaped TiO2 was used as a support, and holmium-ytterbium composite oxide was used as the main active component and iron-cerium composite oxide was used as the co-catalytic active component. The catalyst was prepared by alcohol thermal method, which increased the specific surface area of the catalyst and improved its alkali resistance.
It improves the denitrification efficiency and stability of the catalyst, prevents metal sintering and agglomeration, enhances the catalyst's alkali resistance, and ensures that it maintains high-efficiency denitrification performance under complex flue gas conditions.
Smart Images
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of denitrification catalyst technology, and particularly relates to a hollow rod-shaped denitrification catalyst and its preparation method. Background Technology
[0002] Nitrogen oxides (NOx) are one of the most significant air pollutants. NOx is a major cause of smog, acid rain, and secondary ozone. It not only pollutes the environment but also seriously harms human health and has biological toxicity to plants and animals.
[0003] Currently, selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR) technologies dominate NOx removal. Considering both technical and economic factors, SCR remains the most effective NOx emission reduction method, and the denitrification catalyst is crucial to its success. In coal-fired power plants and the steel industry, V2O5-WO3 / TiO2 catalysts are the most widely used due to their mature preparation technology and high NOx removal rate. However, compared to coal-fired boiler flue gas, the flue gas conditions in the cement industry are more complex, making denitrification catalysts more susceptible to problems such as alkali heavy metal poisoning and fly ash blockage during use, leading to a decrease in denitrification efficiency.
[0004] Therefore, developing effective SCR catalysts for cement flue gas to reduce NOx emissions in the cement industry has become an important issue in the field of environmental protection. Summary of the Invention
[0005] The purpose of this invention is to address the problems of alkali heavy metal poisoning and fly ash blockage in existing denitrification catalysts by providing a hollow rod-shaped denitrification catalyst and its preparation method. The prepared denitrification catalyst uses hollow rod-shaped TiO2 as a support. The hollow structure is beneficial to increasing the specific surface area of the catalyst and improving the removal efficiency of nitrogen oxides. At the same time, the hollow structure of the catalyst can effectively prevent metal sintering and agglomeration, thereby improving the stability of the catalyst. Ce and Fe composite oxides serve as co-catalytic active components, increasing the content of active sites and acidic sites on the catalyst surface and improving the catalyst's alkali resistance.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] In the first aspect, a hollow rod-shaped denitration catalyst is provided, the catalyst comprising: hollow (micron) rod-shaped TiO2 as a support, holmium-ytterbium composite oxide as the main active component, and iron-cerium composite oxide as a co-catalytic active component;
[0008] Among them, the hollow (micron) rod-shaped TiO2 support is a product prepared by mixing tetrabutyl titanate as a support precursor with a surface activator and a morphology stabilizer in an alcohol solvent and then by an alcohol thermal method.
[0009] Based on the mass of the hollow (micron) rod-shaped TiO2 support, the content of each component of the catalyst is as follows:
[0010] The main active ingredient has a mass percentage content of 5% to 10% (e.g., 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%).
[0011] The mass percentage of the co-catalytic active component is 2% to 5% (e.g., 2.5%, 3%, 3.5%, 4%, 4.5%).
[0012] In some embodiments of the catalyst provided by the present invention, the mass ratio of holmium oxide to ytterbium oxide in the main active component is 1:(0.3 to 0.5), for example, 1:0.32, 1:0.35, 1:0.38, 1:0.4, 1:0.42, 1:0.45, 1:0.46, 1:0.48.
[0013] According to the catalyst provided by the present invention, in some embodiments, the mass ratio of iron oxide to cerium oxide in the co-catalytic active component is 1:(1 to 1.5), for example, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45.
[0014] According to the catalyst provided by the present invention, in some embodiments, the preparation method of the hollow (micron) rod-shaped TiO2 support includes the following steps:
[0015] Tetrabutyl titanate was added as a carrier precursor to an alcohol solvent (such as ethanol) and mixed thoroughly. Then, a surfactant (such as stearic acid) and a morphology stabilizer (such as a mixture of lauric acid and octadecylamine) were added. The resulting suspension was stirred at room temperature for 20-60 min (e.g., 25 min, 30 min, 40 min, 50 min), transferred to a reaction apparatus, and reacted at 140-180℃ (e.g., 150℃, 160℃, 170℃) for 8-15 h (e.g., 10 h, 12 h, 14 h) to obtain a precipitate.
[0016] The precipitate was then washed, dried, and calcined in air to obtain a hollow rod-shaped TiO2 support.
[0017] According to the catalyst provided by the present invention, in some embodiments, the method for preparing the hollow (micron) rod-shaped TiO2 support,
[0018] The alcohol solvent is selected from one or more of ethanol, isopropanol, and n-butanol;
[0019] The surfactant is selected from one or more of stearic acid, palmitic acid and lauric acid;
[0020] The morphology stabilizer is a mixture of lauric acid and octadecylamine.
[0021] In some embodiments, the mass ratio of lauric acid to octadecylamine in the morphology stabilizer is 1:(3-5), for example, 1:3.5, 1:3.8, 1:4, 1:4.2, 1:4.5, 1:4.8.
[0022] In a second aspect, a method for preparing the hollow rod-shaped denitration catalyst as described above is provided, comprising the following steps:
[0023] (1) Preparation of catalyst support
[0024] Tetrabutyl titanate was added to an alcohol solvent as a carrier precursor and mixed thoroughly. Then, a surfactant and a morphology stabilizer were added. The resulting suspension was stirred at room temperature for 20-60 min (e.g., 30 min, 40 min, 50 min), transferred to a reaction apparatus, and reacted at 140-180℃ (e.g., 150℃, 160℃, 170℃) for 8-15 h (e.g., 10 h, 12 h, 14 h) to obtain a precipitate.
[0025] The precipitate was then washed, dried, and calcined in air to obtain a hollow rod-shaped TiO2 support.
[0026] (2) Preparation of precursor solution of main active component
[0027] Holmium salt and ytterbium salt were added to deionized water and stirred until homogeneous to obtain precursor solution A of the main active component;
[0028] (3) Preparation of precursor solution of co-catalytic active component
[0029] Iron salt and cerium salt were added to deionized water and stirred until homogeneous to obtain catalyst precursor solution B;
[0030] (4) Catalyst preparation
[0031] The hollow rod-shaped TiO2 support obtained in step (1) is immersed in a mixed solution of solution A obtained in step (3) and solution B obtained in step (4), and stirred at 70-90℃ (such as 75℃, 80℃, 85℃) until the water is basically evaporated. The material is then removed, dried, and finally calcined to obtain the hollow rod-shaped denitrification catalyst.
[0032] According to the preparation method provided by the present invention, in some embodiments, the preparation method of the hollow rod-shaped denitration catalyst includes the following steps:
[0033] (1) Preparation of catalyst support
[0034] The precursor of the support (such as tetrabutyl titanate) was added to an alcohol solvent (such as ethanol) and mixed thoroughly. A surfactant (such as stearic acid) and a morphology stabilizer (such as a mixture of lauric acid and octadecylamine) were added. The resulting suspension was placed in a stirrer and stirred at room temperature for 30 min. It was then transferred to a polytetrafluoroethylene beaker and placed in an oven at 160 °C for 12 h. The resulting precipitate was repeatedly washed with deionized water and dried in a forced-air drying oven. It was then calcined in a muffle furnace under an air atmosphere to obtain a hollow rod-shaped TiO2 support.
[0035] (2) Preparation of precursor solution of main catalytic active component
[0036] Holmium salt and ytterbium salt were added to deionized water and stirred until homogeneous to obtain active component precursor solution A;
[0037] (3) Preparation of precursor solution of co-catalytic active component
[0038] Iron and cerium salts were added to deionized water and stirred until homogeneous to obtain catalyst precursor solution B;
[0039] (4) Catalyst preparation
[0040] The carrier obtained in step (1) is immersed in a mixture of solution A obtained in step (3) and solution B obtained in step (4), transferred to a constant temperature stirrer and stirred at 80°C until the water is basically evaporated, taken out and placed in an oven to dry to constant weight, and finally placed in a muffle furnace for calcination to obtain a hollow rod-shaped denitration catalyst.
[0041] According to the preparation method provided by the present invention, in some embodiments, the alcohol solvent in step (1) is ethanol, and the concentration (mass fraction) of ethanol can be 95%.
[0042] In some implementations, in step (1), the mass ratio of the carrier precursor, alcohol solvent, surfactant, and morphology stabilizer is 20:(20-40):(3-5):(2-4). That is, 1:(1-2):(0.15-0.25):(0.1-0.2).
[0043] For example, the mass ratio of the support precursor to the alcohol solvent can be 1:1.5, 1:1.8, 1:1, or 1:2. The mass ratio of the support precursor to the surfactant can be 1:0.15, 1:0.18, 1:0.2, 1:0.24, or 1:0.25. The mass ratio of the support precursor to the morphology stabilizer can be 1:0.12, 1:0.14, 1:0.15, 1:0.18, or 1:0.2.
[0044] According to the preparation method provided by the present invention, in some embodiments, the drying process conditions in step (1) include: a drying temperature of 105℃~130℃ (e.g., 110℃, 115℃, 120℃, 125℃) and a drying time of 3~6h (e.g., 3.5h, 4h, 4.5h, 5h, 5.5h).
[0045] In some implementations, the roasting process conditions in step (1) include: a roasting temperature of 400-500°C (e.g., 420°C, 440°C, 450°C, 460°C, 480°C) and a roasting time of 2-3 hours (e.g., 2.5 hours).
[0046] According to the preparation method provided by the present invention, in some embodiments, the holmium salt in step (2) is holmium chloride hexahydrate, and the ytterbium salt is ytterbium chloride hexahydrate.
[0047] According to the preparation method provided by the present invention, in some embodiments, the iron salt in step (3) is ferric chloride and the cerium salt is cerium nitrate hexahydrate.
[0048] According to the preparation method provided by the present invention, in some embodiments, the calcination process conditions in step (4) include: a calcination temperature of 400-600℃ (e.g., 420℃, 440℃, 450℃, 460℃, 480℃, 500℃, 520℃, 540℃, 550℃, 580℃), and a calcination time of 3-6h (e.g., 3.5h, 4h, 4.5h, 5h, 5.5h).
[0049] In some implementations, the drying temperature in step (4) can be 60°C to 90°C (e.g., 70°C, 80°C, 85°C).
[0050] In this invention, the reaction conditions for evaluating the catalytic performance of the catalyst are as follows: 0.4 g of the catalyst to be evaluated is loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device is 5 mm, and a reaction gas is introduced for activity evaluation. The simulated gas composition is: NO (500 ppm), NH3 (600 ppm), O2 (2%), H2O (10%), with N2 as the carrier gas. The total gas flow rate is 320 mL / min, and the catalytic reaction test temperature range is 300–380 °C.
[0051] The hollow rod-shaped denitrification catalyst prepared by this invention has a denitrification efficiency of more than 90% at a temperature of 300-380℃ for 30 minutes.
[0052] This invention uses hollow rod-shaped TiO2 obtained by alcohol thermal method as a support to prepare a denitrification catalyst. Compared with block and granular supports, the hollow structure of the hollow rod-shaped TiO2 support of this denitrification catalyst is conducive to increasing the specific surface area of the catalyst, increasing the contact area between the reactants and the catalyst, making the reaction more complete, and improving the catalytic denitrification efficiency; (2) The main active component and the co-catalytic active component are impregnated in the hollow rod-shaped TiO2 support by impregnation method to prepare a denitrification catalyst with holmium-ytterbium composite oxide as the main active component and iron-cerium composite oxide as the co-catalytic active component. By controlling the content and ratio of holmium-ytterbium composite oxide in the main active component and the content and ratio of iron-cerium composite oxide in the co-catalytic active component, and using cerium-iron composite oxide as the co-catalytic active component, the number of acidic sites on the catalyst surface is increased, and the alkali resistance of the catalyst is improved.
[0053] Compared with the prior art, the beneficial effects of the technical solution of the present invention are at least as follows:
[0054] The denitration catalyst prepared in this invention uses hollow rod-shaped TiO2 as a support. The hollow structure is beneficial to increasing the specific surface area of the catalyst and the contact area between the reactant gas and the catalyst, ensuring complete reaction and improving the removal efficiency of nitrogen oxides. At the same time, the catalyst with a hollow structure can effectively prevent metal sintering and agglomeration, thus improving catalytic stability. In addition, Ce and Fe composite oxides, as co-catalytic active components, increase the content of active sites and acidic sites on the catalyst surface, thereby improving the catalyst's resistance to alkali. Attached Figure Description
[0055] Figure 1 This is a SEM image of the catalyst prepared in Example 1.
[0056] Figure 2 The image shows a SEM image of the catalyst prepared in Comparative Example 1.
[0057] Figure 3 This is a schematic diagram comparing the denitrification efficiency of the catalysts obtained in Examples 1-3 and Comparative Examples 1-3.
[0058] Figure 4 This is a schematic diagram comparing the denitrification efficiency of the catalysts obtained in Examples 1-3 and Comparative Examples 1-3 after alkali metal poisoning treatment. Detailed Implementation
[0059] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments of the invention are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.
[0060] Unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the examples are assumed to be commercially available.
[0061] Example 1
[0062] The preparation method of hollow rod-shaped denitration catalyst includes the following steps:
[0063] (1) Preparation of catalyst support
[0064] Measure 42.61g of tetrabutyl titanate solution and add it to 42.61g of ethanol solvent and mix thoroughly. Add 6.39g of stearic acid, 1.07g of lauric acid and 3.19g of octadecylamine to the mixture. Place the resulting suspension in a stirrer and stir at room temperature for 30min. Transfer the suspension to a polytetrafluoroethylene beaker and place it in an oven at 160℃ for 12h to obtain a precipitate.
[0065] The precipitate was repeatedly washed with deionized water and then dried in a forced-air drying oven at 105°C for 6 hours. After that, it was placed in a muffle furnace and calcined at 400°C in air for 3 hours to obtain hollow rod-shaped TiO2 support.
[0066] (2) Preparation of precursor solution of main catalytic active component
[0067] Weigh 0.38 g of holmium chloride hexahydrate and 0.12 g of ytterbium chloride hexahydrate, add them to 10 mL of deionized water and stir well to obtain the active component precursor solution A;
[0068] (3) Preparation of precursor solution of co-catalytic active component
[0069] Weigh 0.10 g of anhydrous ferric chloride and 0.25 g of cerium nitrate hexahydrate, add them to 10 mL of deionized water and stir well to obtain catalyst precursor solution B;
[0070] (4) Catalyst preparation
[0071] Weigh 10g of the hollow rod-shaped TiO2 support obtained in step (1), immerse it in a mixed solution of solution A obtained in step (2) and solution B obtained in step (3), transfer it to a constant temperature stirrer and stir at 80℃ until the water is basically evaporated, remove the material and place it in an oven to dry at 80℃ to constant weight, and finally place it in a muffle furnace and calcine at 400℃ for 6h to obtain a hollow rod-shaped denitration catalyst (its structure is as follows). Figure 1 As shown in the figure, its specific surface area is 71.148 m². 2 / g.
[0072] Of the catalysts prepared, based on the mass of the hollow rod-shaped TiO2 support, the following is included:
[0073] The content of holmium oxide is 3.8 wt%, and the content of ytterbium oxide is 1.2 wt%.
[0074] The content of iron oxide is 1 wt%, and the content of cerium oxide is 1 wt%.
[0075] (5) Catalytic activity test
[0076] 0.4 g of the hollow rod-shaped catalyst prepared above was placed into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10 mm. Reaction gas was introduced for activity evaluation. The simulated gas composition was: NO (500 ppm), NH3 (600 ppm), O2 (2%), H2O (10%), with N2 as the carrier gas. The total gas flow rate was 320 mL / min, and the catalytic reaction test temperature range was 300–380 °C. The test results showed that the denitrification efficiency of the catalyst was greater than 90% at 300–380 °C for 30 min. Figure 3 As shown.
[0077] The hollow rod-shaped catalyst prepared above was subjected to potassium sulfate alkali metal poisoning treatment, and then its catalyst activity was tested according to the above procedure. The test results are as follows. Figure 4 As shown.
[0078] Example 2
[0079] The preparation method of hollow rod-shaped denitration catalyst includes the following steps:
[0080] (1) Preparation of catalyst support
[0081] Measure 42.61g of tetrabutyl titanate solution and add it to 85.22g of ethanol solvent and mix thoroughly. Add 10.65g of stearic acid, 1.42g of lauric acid and 7.1g of octadecylamine to the mixture. Place the resulting suspension in a stirrer and stir at room temperature for 30min. Transfer the suspension to a polytetrafluoroethylene beaker and place it in an oven at 160℃ for 12h to obtain a precipitate.
[0082] The precipitate was repeatedly washed with deionized water and then dried in a forced-air drying oven at 130°C for 3 hours. After that, it was placed in a muffle furnace and calcined at 500°C in air for 2 hours to obtain hollow rod-shaped TiO2 support.
[0083] (2) Preparation of precursor solution of main catalytic active component
[0084] Weigh 0.67 g of holmium chloride hexahydrate and 0.32 g of ytterbium chloride hexahydrate, add them to 10 mL of deionized water and stir well to obtain the active component precursor solution A;
[0085] (3) Preparation of precursor solution of co-catalytic active component
[0086] Weigh 0.20 g of anhydrous ferric chloride and 0.76 g of cerium nitrate hexahydrate, add them to 10 mL of deionized water and stir well to obtain catalyst precursor solution B;
[0087] (4) Catalyst preparation
[0088] Weigh 10g of the hollow rod-shaped TiO2 support obtained in step (1), immerse it in a mixed solution of solution A obtained in step (2) and solution B obtained in step (3), transfer it to a constant temperature stirrer and stir at 80℃ until the water is basically evaporated, remove the material and place it in an oven to dry at 80℃ to constant weight, and finally place it in a muffle furnace and calcine at 600℃ for 3h to obtain a hollow rod-shaped denitration catalyst with a specific surface area of 76.229m². 2 / g.
[0089] Of the catalysts prepared, based on the mass of the hollow rod-shaped TiO2 support, the following is included:
[0090] The content of holmium oxide is 6.7 wt%, and the content of ytterbium oxide is 3.3 wt%.
[0091] The content of iron oxide is 2 wt%, and the content of cerium oxide is 3 wt%.
[0092] (5) Catalytic activity test
[0093] 0.4 g of the hollow rod-shaped catalyst prepared above was loaded into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10 mm. Reaction gas was introduced for activity evaluation. The simulated gas composition was: NO (500 ppm), NH3 (600 ppm), O2 (2%), H2O (10%), with N2 as the carrier gas. The total gas flow rate was 320 mL / min, and the catalytic reaction test temperature range was 300–380 °C. The test results showed that the denitrification efficiency of the catalyst was greater than 95% at 300–380 °C for 30 min. Figure 3 As shown.
[0094] The hollow rod-shaped catalyst prepared above was subjected to potassium sulfate alkali metal poisoning treatment, and then its catalyst activity was tested according to the above procedure. The test results are as follows. Figure 4 As shown.
[0095] Example 3
[0096] The preparation method of hollow rod-shaped denitration catalyst includes the following steps:
[0097] (1) Preparation of catalyst support
[0098] Measure 42.61g of tetrabutyl titanate solution and add it to 63.92g of ethanol solvent and mix thoroughly. Add 8.52g of stearic acid, 1.28g of lauric acid and 5.12g of octadecylamine to the mixture. Place the resulting suspension in a stirrer and stir at room temperature for 30min. Transfer the suspension to a polytetrafluoroethylene beaker and place it in an oven at 160℃ for 12h to obtain a precipitate.
[0099] The obtained precipitate was repeatedly washed with deionized water and then dried in a forced-air drying oven at 120°C for 4 hours. After that, it was placed in a muffle furnace and calcined at 450°C for 2.5 hours in air atmosphere to obtain hollow rod-shaped TiO2 support.
[0100] (2) Preparation of precursor solution of main catalytic active component
[0101] Weigh 0.54 g of holmium chloride hexahydrate and 0.21 g of ytterbium chloride hexahydrate, add them to 10 mL of deionized water and stir well to obtain the active component precursor solution A;
[0102] (3) Preparation of precursor solution of co-catalytic active component
[0103] Weigh 0.16g of anhydrous ferric chloride and 0.48g of cerium nitrate hexahydrate, add them to 10mL of deionized water and stir well to obtain catalyst precursor solution B;
[0104] (4) Catalyst preparation
[0105] Weigh 10g of the hollow rod-shaped TiO2 support obtained in step (1), immerse it in a mixed solution of solution A obtained in step (2) and solution B obtained in step (3), transfer it to a constant temperature stirrer and stir at 80℃ until the water is basically evaporated, remove the material and place it in an oven to dry at 80℃ to constant weight, and finally place it in a muffle furnace and calcine at 600℃ for 3h to obtain a hollow rod-shaped denitration catalyst with a specific surface area of 72.093m². 2 / g.
[0106] Of the catalysts prepared, based on the mass of the hollow rod-shaped TiO2 support, the following is included:
[0107] The content of holmium oxide is 5.4 wt%, and the content of ytterbium oxide is 2.1 wt%.
[0108] The content of iron oxide is 1.6 wt%, and the content of cerium oxide is 1.9 wt%.
[0109] (5) Catalytic activity test
[0110] 0.4 g of the hollow rod-shaped catalyst prepared above was placed into a catalyst performance evaluation reaction device. The inner diameter of the quartz tube in the evaluation reaction device was 10 mm. Reaction gas was introduced for activity evaluation. The simulated gas composition was: NO (500 ppm), NH3 (600 ppm), O2 (2%), H2O (10%), with N2 as the carrier gas. The total gas flow rate was 320 mL / min, and the catalytic reaction test temperature range was 300–380 °C. The test results showed that the denitrification efficiency of the catalyst was greater than 90% at 300–380 °C for 30 min. Figure 3 As shown.
[0111] The hollow rod-shaped catalyst prepared above was subjected to potassium sulfate alkali metal poisoning treatment, and then its catalyst activity was tested according to the above procedure. The test results are as follows. Figure 4 As shown.
[0112] Comparative Example 1
[0113] The preparation method of the denitration catalyst includes the following steps:
[0114] (1) Preparation of catalyst support
[0115] In step (1), no stearic acid is added to the reaction system, and other conditions are the same as in Example 1;
[0116] (2) The preparation of the precursor solution of the main catalytic active component is the same as in Example 1;
[0117] (3) The preparation of the precursor solution of the co-catalytic active component is the same as in Example 1;
[0118] (4) Catalyst preparation: same as in Example 1; a denitrification catalyst with a specific surface area of 62.107 m² was obtained. 2 / g.
[0119] (5) Catalyst activity test
[0120] 0.4g of the catalyst prepared above was loaded into a catalyst performance evaluation reaction apparatus. The quartz tube in the evaluation reaction apparatus had an inner diameter of 10mm. Reaction gas was introduced for activity evaluation. The simulated gas composition was: NO (500ppm), NH3 (600ppm), O2 (2%), H2O (10%), with N2 as the carrier gas. The total gas flow rate was 320mL / min, and the catalytic reaction test temperature range was 300–380℃. The test results showed that the denitrification efficiency of this catalyst was less than 90% at 300℃ for 30 minutes. Figure 3 As shown.
[0121] The hollow rod-shaped catalyst prepared above was subjected to potassium sulfate alkali metal poisoning treatment, and then its catalyst activity was tested according to the above procedure. The test results are as follows. Figure 4 As shown.
[0122] Compared to Example 1, in the preparation of the catalyst in Comparative Example 1, no surface activator stearic acid was added in step (1). The resulting TiO2 support exhibited a solid rod-like morphology. Although catalyst grains could grow, the catalyst did not form a porous structure (e.g., Figure 2 As shown in the figure, the specific surface area decreases, thus causing a decrease in activity.
[0123] Comparative Example 2
[0124] The preparation method of the denitration catalyst includes the following steps:
[0125] (1) The preparation of the catalyst support is the same as in Example 2;
[0126] (2) Preparation of precursor solution of main catalytic active component
[0127] In step (2), holmium chloride hexahydrate is not added, and other conditions are the same as in Example 2;
[0128] (3) The preparation of the precursor solution of the co-catalytic active component is the same as in Example 2;
[0129] (4) Catalyst preparation: same as in Example 2; a denitrification catalyst with a specific surface area of 65.172 m² was obtained. 2 / g.
[0130] Of the catalysts prepared, based on the mass of the hollow rod-shaped support, the following is included:
[0131] The content of holmium oxide is 0 wt%, and the content of ytterbium oxide is 3.3 wt%.
[0132] The content of iron oxide is 2 wt%, and the content of cerium oxide is 3 wt%.
[0133] (5) Catalyst activity test
[0134] 0.4g of the catalyst prepared above was loaded into a catalyst performance evaluation reaction apparatus. The quartz tube in the evaluation reaction apparatus had an inner diameter of 10mm. Reaction gas was introduced for activity evaluation. The simulated gas composition was: NO (500ppm), NH3 (600ppm), O2 (2%), H2O (10%), with N2 as the carrier gas. The total gas flow rate was 320mL / min, and the catalytic reaction test temperature range was 300–380℃. The test results showed that the denitrification efficiency was less than 90% at 300℃ for 30 minutes. Figure 3 As shown.
[0135] The hollow rod-shaped catalyst prepared above was subjected to potassium sulfate alkali metal poisoning treatment, and then its catalyst activity was tested according to the above procedure. The test results are as follows. Figure 4 As shown.
[0136] Compared with Example 2, in the preparation of the catalyst in Comparative Example 2, holmium chloride hexahydrate was not added in step (2), and the catalytic active component became pure ytterbium oxide, which is not a holmium-ytterbium composite oxide. As a result, the redox performance of the catalyst decreased, and the catalyst activity was reduced.
[0137] Comparative Example 3
[0138] The preparation method of the denitration catalyst includes the following steps:
[0139] (1) The preparation of the catalyst support is the same as in Example 3;
[0140] (2) The preparation of the precursor solution of the main catalytic active component is the same as in Example 3;
[0141] (3) Preparation of precursor solution of co-catalytic active component
[0142] In step (3), cerium nitrate hexahydrate is not added, and other conditions are the same as in Example 3;
[0143] (4) Catalyst preparation: same as in Example 3; a denitrification catalyst with a specific surface area of 64.748 m² was obtained. 2 / g.
[0144] Of the catalysts prepared, based on the mass of the hollow rod-shaped support, the following is included:
[0145] The content of holmium oxide is 5.4 wt%, and the content of ytterbium oxide is 2.1 wt%.
[0146] The content of iron oxide is 1.6 wt%, and the content of cerium oxide is 0 wt%.
[0147] (5) Catalyst activity test
[0148] 0.4g of the catalyst prepared above was loaded into a catalyst performance evaluation reaction apparatus. The quartz tube in the evaluation reaction apparatus had an inner diameter of 10mm. Reaction gas was introduced for activity evaluation. The simulated gas composition was: NO (500ppm), NH3 (600ppm), O2 (2%), H2O (10%), with N2 as the carrier gas. The total gas flow rate was 320mL / min, and the catalytic reaction test temperature range was 300–380℃. The test results showed that the denitrification efficiency was less than 90% at 300℃ for 30 minutes. Figure 3 As shown.
[0149] The hollow rod-shaped catalyst prepared above was subjected to potassium sulfate alkali metal poisoning treatment, and then its catalyst activity was tested according to the above procedure. The test results are as follows. Figure 4 As shown.
[0150] Compared with Example 3, in the preparation of the catalyst in Comparative Example 3, cerium nitrate hexahydrate was not added in step (3), and the co-catalytic active component was pure iron oxide, not iron-cerium composite oxide. The number of active sites on the catalyst surface was reduced, thus causing a decrease in catalyst activity.
[0151] Figure 4 The comparison results of the catalytic denitrification efficiency of the catalysts obtained in each embodiment and comparative example after alkali metal poisoning are shown. After potassium sulfate alkali metal poisoning treatment, the catalyst activity of the catalysts prepared in each embodiment and comparative example was tested at a test temperature of 380℃. It can be seen that the catalysts prepared in Examples 1-3 still maintain high denitrification activity after poisoning, and the denitrification efficiency is still greater than 90% after 16 hours of continuous operation; while the catalysts prepared in Comparative Examples 1-3 show a decrease in initial activity after poisoning, and the denitrification efficiency is less than 80% after 16 hours of continuous operation. This indicates that the technical solution of the present invention can improve the alkali resistance and stability of the catalyst.
[0152] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the spirit of the invention.
Claims
1. A hollow rod-shaped denitration catalyst, characterized in that, The catalyst comprises: hollow rod-shaped TiO2 as a support, holmium-ytterbium composite oxide as the main active component, and iron-cerium composite oxide as a co-catalytic active component; The hollow rod-shaped TiO2 support is prepared by mixing tetrabutyl titanate as a precursor with a surface activator and a morphology stabilizer in an alcohol solvent via an alcoholic method. The component contents of the catalyst are as follows, based on the mass of the hollow rod-shaped TiO2 support: The main active ingredient has a mass percentage content of 5% to 10%. The mass percentage of the co-catalytic active component is 2% to 5%.
2. The catalyst according to claim 1, characterized in that, In the main active components, the mass ratio of holmium oxide to ytterbium oxide is 1:(0.3-0.5). In the co-catalytic active component, the mass ratio of iron oxide to cerium oxide is 1:(1-1.5).
3. The catalyst according to claim 1 or 2, characterized in that, The preparation method of the hollow rod-shaped TiO2 support includes the following steps: Tetrabutyl titanate was added to an alcohol solvent as a carrier precursor and mixed thoroughly. Then, a surface activator and a morphology stabilizer were added. The resulting suspension was stirred at room temperature for 20-60 min, transferred to a reaction apparatus, and reacted at 140-180℃ for 8-15 h to obtain a precipitate. The precipitate was then washed, dried, and calcined in air to obtain a hollow rod-shaped TiO2 support.
4. The catalyst according to claim 3, characterized in that, In the preparation method of the hollow rod-shaped TiO2 support, The alcohol solvent is selected from one or more of ethanol, isopropanol, and n-butanol; The surfactant is selected from one or more of stearic acid, palmitic acid and lauric acid; The morphology stabilizer is a mixture of lauric acid and octadecylamine; In the morphology stabilizer, the mass ratio of lauric acid to octadecylamine is 1:(3-5).
5. The method for preparing the hollow rod-shaped denitrification catalyst according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Preparation of catalyst support Tetrabutyl titanate was added to an alcohol solvent as a carrier precursor and mixed thoroughly. Then, a surface activator and a morphology stabilizer were added. The resulting suspension was stirred at room temperature for 20-60 min, transferred to a reaction apparatus, and reacted at 140-180℃ for 8-15 h to obtain a precipitate. The precipitate was then washed, dried, and calcined in air to obtain a hollow rod-shaped TiO2 support. (2) Preparation of precursor solution of main active component Holmium salt and ytterbium salt were added to deionized water and stirred until homogeneous to obtain precursor solution A of the main active component; (3) Preparation of precursor solution of co-catalytic active component Iron salt and cerium salt were added to deionized water and stirred until homogeneous to obtain catalyst precursor solution B; (4) Catalyst preparation The hollow rod-shaped TiO2 support obtained in step (1) is immersed in a mixed solution of solution A obtained in step (3) and solution B obtained in step (4), and stirred at 70-90℃ until the water is basically evaporated. The material is then removed, dried, and finally calcined to obtain the hollow rod-shaped denitrification catalyst.
6. The preparation method according to claim 5, characterized in that, In step (1), the mass ratio of the carrier precursor, alcohol solvent, surfactant, and morphology stabilizer is 20:(20-40):(3-5):(2-4).
7. The preparation method according to claim 5, characterized in that, The drying process conditions in step (1) include: drying temperature of 105℃~130℃ and drying time of 3~6h; The roasting process conditions in step (1) include: roasting temperature of 400-500℃ and roasting time of 2-3h.
8. The preparation method according to claim 5, characterized in that, The holmium salt in step (2) is holmium chloride hexahydrate, and the ytterbium salt is ytterbium chloride hexahydrate.
9. The preparation method according to claim 5, characterized in that, The iron salt in step (3) is ferric chloride, and the cerium salt is cerium nitrate hexahydrate.
10. The preparation method according to any one of claims 5-9, characterized in that, The roasting process conditions in step (4) include: roasting temperature of 400-600℃ and roasting time of 3-6h.