A rare earth ferrite denitration catalyst and a preparation method thereof

Abstract

The present application relates to the technical field of catalyst preparation, and particularly relates to a rare earth ferrite type denitration catalyst and a preparation method thereof, which comprises the following raw material components in percentage by mass: 66-82% of oxygen defect titanium dioxide, 11-25% of rare earth ferrite type composite oxide and 7-9% of forming agent; the rare earth ferrite type composite oxide is a MeFe2O4 mixture, and Me is one or more of Ce, Nd, La, Pr, Y, Sm and Ho, and Er. By taking the oxygen defect titanium dioxide as a carrier, the denitration activity and sulfur resistance of the catalyst can be enhanced. By taking the rare earth ferrite type composite oxide as an active component, the surface acid point of the denitration catalyst can be improved, and the high-temperature stability and wear resistance of the carrier can be improved. The catalyst does not contain strategic metals vanadium and tungsten, the raw materials are cheap and easy to obtain, the stability is good, the service life is long, the wear resistance is strong, and the economic benefits are better. The problems of the traditional vanadium-based denitration catalyst, such as reduced denitration efficiency, short service life and high cost, are solved.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, specifically to a rare earth ferrite-type denitration catalyst and its preparation method. Background Technology

[0002] In recent years, smog has seriously endangered human health, road traffic safety, and the ecological environment, especially during winter. Nitrogen oxides are one of the main causes of smog, severely impacting human health.

[0003] Currently, SCR denitrification technology is one of the most mature and effective technologies for removing nitrogen oxides, with efficient, low-cost, and long-life denitrification catalysts being key. Existing commercial vanadium-based denitrification catalysts use TiO2 as a support and V2O5 and WO3 as active components; however, vanadium and tungsten are strategic metals and therefore expensive. At temperatures above 400℃, SO2 concentrations reach 10000 mg / Nm³. 3 The above dust content is 50g / Nm³. 3 In the flue gas mentioned above, vanadium-based catalysts are prone to sintering, which leads to a decrease in the specific surface area of ​​the catalyst and severe wear, reducing the chemical life of the catalyst and causing excessive nitrogen oxide emissions. Frequent catalyst replacement is required, which increases the operating cost of denitrification. Summary of the Invention

[0004] To address the problems of reduced denitrification efficiency, short lifespan, and high cost of existing vanadium-based denitrification catalysts due to their sintering tendency in high-temperature, high-sulfur, and high-dust denitrification flue gas, this invention provides a rare-earth ferrite-type denitrification catalyst and its preparation method.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a rare earth ferrite-type denitration catalyst, comprising the following raw material components by mass percentage: 66%–82% oxygen-deficient titanium dioxide, 11%–25% rare earth ferrite-type composite oxide, and 7%–9% forming agent; wherein the rare earth ferrite-type composite oxide is a mixture of MeFe2O4, where Me is one or more of Ce, Nd, La, Pr, Y, Sm, and Ho, and Er.

[0007] Furthermore, in the rare earth ferrite composite oxide, the molar percentage of Er at the Me site is ≥45%.

[0008] Furthermore, the oxygen-deficient titanium dioxide has a particle size of 20–30 nm and a specific surface area of ​​100–120 m². 2 / g, density ≤0.5g / cm³ 3 .

[0009] Furthermore, the molding agent comprises, by mass percentage of the catalyst, 0.5% to 1% activated carbon, 4% to 5% glass fiber, 0.5% to 1% petrolatum, and 1% to 2% methylcellulose.

[0010] This invention also provides a method for preparing the rare earth ferrite-type denitration catalyst as described above, comprising the following steps:

[0011] Preparation of rare earth ferrite-type composite oxides;

[0012] Preparation of oxygen-defective titanium dioxide;

[0013] Oxygen-deficient titanium dioxide, rare-earth ferrite composite oxides, and molding agents are kneaded into a plastic slurry.

[0014] The plastic clay is kneaded, sieved to remove impurities, and aged to obtain aged clay.

[0015] The aged clay is poured into a mold to form a wet body;

[0016] The wet preform is dried and calcined at high temperature to produce a rare earth ferrite-type denitrification catalyst.

[0017] Furthermore, the method for preparing rare earth ferrite-type composite oxides is as follows:

[0018] A soluble salt of one or more elements selected from Er and Ce, Nd, La, Pr, Y, Sm and Ho is mixed with a soluble salt of iron and a gelling agent in deionized water to obtain a mixed solution.

[0019] Add a dispersant to the mixed solution, heat and stir to evaporate until the mixed solution transforms into a gel;

[0020] The gel was dried to obtain a fluffy, porous solid.

[0021] A loose, porous solid was calcined at high temperature to obtain a rare earth ferrite-type composite oxide.

[0022] Further, the soluble salts of Er and one or more of Ce, Nd, La, Pr, Y, Sm and Ho are one or more of nitrates, sulfates and acetates; the soluble salts of iron are one or more of iron nitrates, sulfates and acetates; the gelling agent is citric acid, and the amount of citric acid added is 1.2 to 1.4 times the total molar amount of Me sites and iron; the dispersant is one of ethylene glycol, polyethylene glycol or polyvinylpyrrolidone, and the amount of dispersant added is 0.12 to 0.23 times the total molar amount of Me sites and iron.

[0023] Furthermore, the heating and stirring temperature is 65℃~70℃; the gel drying temperature is 90℃~110℃, and the drying time is 8~12h; the method for high-temperature calcination of the loose porous solid is as follows: the loose porous solid is heated to 200℃~300℃ at a heating rate of 5℃ / min~10℃ / min and held for 2~3h; then, it is heated to 600℃~700℃ at a heating rate of 10℃ / min~20℃ / min and held for 6~8h to obtain rare earth ferrite composite oxide.

[0024] Furthermore, the method for preparing oxygen-deficient titanium dioxide is as follows:

[0025] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of (1:20) to (1:30) at a temperature of 500℃ to 600℃ for 15 to 25 seconds to obtain oxygen-defective titanium dioxide.

[0026] Furthermore, the high-temperature roasting temperature is 500℃~600℃, and the roasting time is 12~16h.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] This invention discloses a rare-earth ferrite-type denitrification catalyst, comprising oxygen-deficient titanium dioxide, a rare-earth ferrite-type composite oxide, and a forming agent; the rare-earth ferrite-type composite oxide is a mixture of MeFe2O4, where Me is one or more of Ce, Nd, La, Pr, Y, Sm, and Ho, and Er. By using oxygen-deficient titanium dioxide as a support, NO can be effectively denitrated. x The adsorption capacity of NH3 is increased by 15%–20% compared to ordinary titanium dioxide, thereby inhibiting the adsorption of SO2 and enhancing the denitrification activity and sulfur resistance of the catalyst. Using a rare earth ferrite composite oxide, namely a mixture of MeFe2O4, as the active component, with Er and other rare earth elements as the essential elements at the Me sites, it can improve the acidic sites on the surface of the denitrification catalyst, while simultaneously enhancing the high-temperature stability and wear resistance of the support and further promoting iron denitrification activity, resulting in a higher denitrification efficiency. This catalyst does not contain strategic metals vanadium and tungsten, making the raw materials cheaper and more readily available, and free of carcinogens, resulting in lower costs and greater safety. Verification has shown that this catalyst has a catalytic efficiency at least 10% higher than vanadium-based catalysts, and at temperatures above 400°C, SO2 concentrations are 10000 mg / Nm³. 3 The above dust content is 50g / Nm³. 3 The above flue gas exhibits good long-term stability, long service life, and strong wear resistance, resulting in better economic benefits.

[0029] This invention also provides a method for preparing the rare-earth ferrite-type denitration catalyst as described above. This method involves preparing a rare-earth ferrite-type composite oxide; kneading oxygen-deficient titanium dioxide, the rare-earth ferrite-type composite oxide, and a molding agent into a plastic slurry; kneading the plastic slurry, sieving to remove impurities, and aging it to obtain an aged slurry; injecting the aged slurry into a mold to form a wet preform; drying the wet preform and calcining it at high temperature to produce the rare-earth ferrite-type denitration catalyst. The preparation method is simple, suitable for industrialization, and the prepared catalyst exhibits better temperature stability, higher catalytic efficiency, lower cost, and longer service life. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the preparation process of a rare earth ferrite-type denitration catalyst according to the present invention.

[0031] Figure 2 This is a flowchart illustrating the preparation process of the rare earth ferrite-type composite oxide of the present invention.

[0032] Figure 3 The figure shows the stability test results of the rare earth ferrite denitrification catalyst prepared in Example 1 of the present invention and the catalyst prepared in Comparative Example 1. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. Furthermore, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0039] This invention discloses a rare-earth ferrite-type denitration catalyst, comprising the following raw material components by mass percentage: 66%–82% oxygen-deficient titanium dioxide, 11%–25% rare-earth ferrite-type composite oxide, and 7%–9% forming agent; the rare-earth ferrite-type composite oxide is a mixture of MeFe2O4, where Me is one or more of Ce, Nd, La, Pr, Y, Sm, and Ho, and Er; the forming agent comprises, by mass percentage of the catalyst, 0.5%–1% activated carbon, 4%–5% glass fiber, 0.5%–1% petrolatum, and 1%–2% methylcellulose. In the rare-earth ferrite-type composite oxide, the molar percentage of Er at the Me sites is ≥45%; the oxygen-deficient titanium dioxide has a particle size of 20–30 nm and a specific surface area of ​​100–120 m². 2 / g, density ≤0.5g / cm³ 3 The activated carbon is 2000 mesh; the glass fiber has a diameter of 9-10 μm, a length of 4.5 mm, and a ZrO2 content of >16.5% in its chemical composition; preferably, it is methylcellulose with a viscosity of 300-400 mPa·s, a solution temperature of 20°C, and a mass concentration of 2% in its aqueous solution.

[0040] See Figure 1 The present invention also provides a method for preparing the rare earth ferrite-type denitration catalyst as described above, comprising the following steps:

[0041] S1: Preparation of rare earth ferrite-type composite oxides, see [link to documentation]. Figure 2 Specifically:

[0042] S1.1: A soluble salt of one or more elements selected from Er and Ce, Nd, La, Pr, Y, Sm, and Ho is mixed evenly with a soluble salt of iron and a gelling agent in deionized water to obtain a mixed solution; wherein the soluble salt of one or more elements selected from Er and Ce, Nd, La, Pr, Y, Sm, and Ho is one or more of nitrates, sulfates, and acetates, with a concentration of 5-6 mol / L; the soluble salt of iron is one or more of nitrates, sulfates, and acetates of iron, with a concentration of 10-12.5 mol / L, and the volume ratio of the two soluble salts is (30-40):(80-100); the gelling agent is citric acid, and the amount of citric acid added is 1.2-1.4 times the total molar amount of the Me site and the total molar amount of iron.

[0043] S1.2: Add a dispersant to the mixed solution, heat and stir to evaporate until the mixed solution transforms into a gel; preferably, add it in a water bath and stir at 65℃~70℃, wherein the dispersant is one of ethylene glycol, polyethylene glycol or polyvinylpyrrolidone, and the amount of dispersant added is 0.12~0.23 times the total number of moles of Me and iron elements;

[0044] S1.3: Dry the gel to obtain a fluffy porous solid; the gel drying temperature is 90℃~110℃, and the drying time is 8~12h;

[0045] S1.4: The loose porous solid is calcined at high temperature to obtain rare earth ferrite composite oxide. The loose porous solid is heated to 200℃~300℃ at a heating rate of 5℃ / min~10℃ / min and held for 2~3h. Then, it is heated to 600℃~700℃ at a heating rate of 10℃ / min~20℃ / min and held for 6~8h to obtain rare earth ferrite composite oxide.

[0046] S2: Preparation of oxygen-deficient titanium dioxide, specifically:

[0047] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of (1:20) to (1:30) at a temperature of 500℃ to 600℃ for 15 to 25 seconds to obtain oxygen-defective titanium dioxide.

[0048] S3: Oxygen-deficient titanium dioxide, rare earth ferrite composite oxide and molding agent are kneaded into plastic clay;

[0049] S4: Knead the plastic clay, sieve it to remove impurities, and age it to obtain aged clay; Knead the plastic clay in a clay kneading machine 2 to 4 times, sieve it through a 100 to 200 mesh screen to remove impurities, and age it for 6 to 12 hours to obtain aged clay.

[0050] S5: The aged clay is injected into a mold to form a wet body; preferably, the wet body is honeycomb-shaped;

[0051] S6: Dry the wet preform and calcine it at high temperature to prepare a rare earth ferrite denitration catalyst. Dry the wet preform in a tunnel microwave drying chamber for 12-24 hours and calcine it at high temperature of 500℃-600℃ for 12-16 hours to obtain the rare earth ferrite denitration catalyst.

[0052] Example 1

[0053] Erbium nitrate and cerium nitrate were dissolved in deionized water at a molar ratio of 45:55 to obtain a first solution with an erbium nitrate concentration of 5 mol / L. Ferric nitrate was dissolved in deionized water to obtain a second solution with a concentration of 10 mol / L. The first and second solutions were mixed at a volume ratio of 40:100, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.2 times the total molar amount of Me and iron.

[0054] Add 0.12 times the total molar amount of ethylene glycol (Me and iron) to the mixed solution, stir continuously in a 65°C water bath, and gradually evaporate until a gel is formed.

[0055] The gel was dried at 90°C for 12 hours to form a fluffy, porous solid.

[0056] The loose, porous solid was heated to 200℃ at a heating rate of 5℃ / min and held for 3 hours, and then heated to 600℃ at a heating rate of 10℃ / min and held for 8 hours to obtain rare earth ferrite composite oxide.

[0057] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:20 at 500℃ for 25s to obtain oxygen-defective titanium dioxide.

[0058] 82 kg of oxygen-deficient titanium dioxide, 11 kg of rare earth ferrite composite oxide, 0.5 kg of activated carbon, 5 kg of glass fiber, 0.5 kg of petrolatum, and 1 kg of methylcellulose were kneaded into a plastic clay.

[0059] The plastic clay was kneaded twice in a clay kneading machine, and impurities were removed by passing it through a 100-mesh sieve. The clay was then aged for 6 hours to obtain aged clay.

[0060] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0061] The wet preform was dried in a tunnel microwave drying chamber for 12 hours and calcined at 600℃ for 12 hours to prepare a rare earth ferrite denitration catalyst.

[0062] Example 2

[0063] Erbium acetate and neodymium sulfate were dissolved in deionized water at a molar ratio of 50:50 to obtain a first solution with an erbium acetate concentration of 6 mol / L. Ferric nitrate was dissolved in deionized water to obtain a second solution with a concentration of 10 mol / L. The first and second solutions were mixed at a volume ratio of 30:100, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.3 times the total molar amount of Me and iron.

[0064] Add polyethylene glycol at 0.13 times the total molar amount of Me and iron to the mixed solution, stir continuously in a 70°C water bath, and gradually evaporate until a gel is formed, thus transforming into a gel.

[0065] The gel was dried at 110°C for 8 hours to form a fluffy, porous solid.

[0066] The loose porous solid was heated to 300℃ at a heating rate of 10℃ / min and held for 3h, and then heated to 700℃ at a heating rate of 20℃ / min and held for 8h to obtain rare earth ferrite composite oxide.

[0067] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:25 at 600℃ for 15s to obtain oxygen-defective titanium dioxide.

[0068] 66 kg of oxygen-deficient titanium dioxide, 25 kg of rare earth ferrite composite oxide, 1 kg of activated carbon, 5 kg of glass fiber, 1 kg of petrolatum, and 2 kg of methylcellulose were kneaded into a plastic clay.

[0069] The plastic clay was kneaded four times in a clay kneading machine, then passed through a 200-mesh sieve to remove impurities, and aged for 12 hours to obtain aged clay.

[0070] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0071] The wet preform was dried in a tunnel microwave drying chamber for 24 hours and calcined at 500℃ for 12 hours to prepare a rare earth ferrite denitration catalyst.

[0072] Example 3

[0073] Erbium sulfate and lanthanum nitrate were dissolved in deionized water at a molar ratio of 45:55 to obtain a first solution with an erbium sulfate concentration of 5 mol / L. Ferric acetate was dissolved in deionized water to obtain a second solution with a concentration of 12.5 mol / L. The first and second solutions were mixed at a volume ratio of 40:85, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.4 times the total molar amount of Me and iron.

[0074] Add 0.15 times the total number of moles of Me and iron to the mixed solution, stir continuously in a 70°C water bath, and gradually evaporate until a gel is formed, thus transforming into a gel.

[0075] The gel was dried at 100°C for 10 hours to form a fluffy, porous solid.

[0076] The loose, porous solid was heated to 200℃ at a heating rate of 10℃ / min and held for 3 hours, and then heated to 700℃ at a heating rate of 10℃ / min and held for 8 hours to obtain rare earth ferrite composite oxide.

[0077] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:30 at 550℃ for 20s to obtain oxygen-defective titanium dioxide.

[0078] 74 kg of oxygen-deficient titanium dioxide, 18 kg of rare earth ferrite composite oxide, 0.8 kg of activated carbon, 4.5 kg of glass fiber, 0.7 kg of petrolatum, and 2 kg of methyl cellulose were kneaded into a plastic clay.

[0079] The plastic clay was kneaded three times in a clay kneading machine, then passed through a 150-mesh sieve to remove impurities, and aged for 8 hours to obtain aged clay.

[0080] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0081] The wet preform was dried in a tunnel microwave drying chamber for 18 hours and calcined at 500℃ for 16 hours to prepare a rare earth ferrite denitration catalyst.

[0082] Example 4

[0083] Erbium nitrate and praseodymium nitrate were dissolved in deionized water at a molar ratio of 70:30 to obtain a first solution with an erbium nitrate concentration of 5.5 mol / L. Ferric acetate was dissolved in deionized water to obtain a second solution with a concentration of 11 mol / L. The first and second solutions were mixed at a volume ratio of 35:90, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.25 times the total molar amount of Me and iron.

[0084] Add polyethylene glycol at 0.23 times the total molar amount of Me and iron to the mixed solution, stir continuously in a 70°C water bath, and gradually evaporate until a gel is formed, thus transforming into a gel.

[0085] The gel was dried at 90°C for 10 hours to form a fluffy, porous solid.

[0086] The loose, porous solid was heated to 250℃ at a heating rate of 8℃ / min and held for 3 hours, and then heated to 650℃ at a heating rate of 15℃ / min and held for 7 hours to obtain rare earth ferrite composite oxide.

[0087] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:28 at 580℃ for 18s to obtain oxygen-defective titanium dioxide.

[0088] 70 kg of oxygen-deficient titanium dioxide, 24 kg of rare earth ferrite composite oxide, 0.5 kg of activated carbon, 4 kg of glass fiber, 0.5 kg of petrolatum, and 1 kg of methylcellulose were kneaded into a plastic mud.

[0089] The plastic clay was kneaded three times in a clay kneading machine, then passed through a 200-mesh sieve to remove impurities, and aged for 10 hours to obtain aged clay.

[0090] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0091] The wet preform was dried in a tunnel microwave drying chamber for 16 hours and calcined at 550°C for 12 hours to prepare a rare earth ferrite-type denitration catalyst.

[0092] Example 5

[0093] Erbium acetate and yttrium nitrate were dissolved in deionized water at a molar ratio of 80:20 to obtain a first solution with an erbium acetate concentration of 6 mol / L. Ferric sulfate was dissolved in deionized water to obtain a second solution with a concentration of 12 mol / L. The first and second solutions were mixed at a volume ratio of 40:100, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.4 times the total molar amount of Me and iron.

[0094] Add 0.2 times the total number of moles of Me and iron to the mixed solution, stir continuously in a 70°C water bath, and gradually evaporate until a gel is formed, thus transforming into a gel.

[0095] The gel was dried at 100°C for 8 hours to form a fluffy, porous solid.

[0096] The loose, porous solid was heated to 200℃ at a heating rate of 10℃ / min and held for 3 hours, and then heated to 650℃ at a heating rate of 20℃ / min and held for 7 hours to obtain rare earth ferrite composite oxide.

[0097] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:30 at 600℃ for 15s to obtain oxygen-defective titanium dioxide.

[0098] 80 kg of oxygen-deficient titanium dioxide, 24 kg of rare earth ferrite composite oxide, 0.5 kg of activated carbon, 4 kg of glass fiber, 0.5 kg of petrolatum, and 1 kg of methylcellulose were kneaded into a plastic mud.

[0099] The plastic clay was kneaded three times in a clay kneading machine, then passed through a 200-mesh sieve to remove impurities, and aged for 10 hours to obtain aged clay.

[0100] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0101] The wet preform was dried in a tunnel microwave drying chamber for 16 hours and calcined at 500℃ for 12 hours to prepare a rare earth ferrite denitration catalyst.

[0102] Example 6

[0103] Erbium nitrate and samarium sulfate were dissolved in deionized water at a molar ratio of 50:50 to obtain a first solution with an erbium nitrate concentration of 5 mol / L. Ferric nitrate was dissolved in deionized water to obtain a second solution with a concentration of 12.5 mol / L. The first and second solutions were mixed at a volume ratio of 40:80, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.2 times the total molar amount of Me and iron.

[0104] Add 0.16 times the total number of moles of Me and iron to the mixed solution, stir continuously in a 65°C water bath, and gradually evaporate until a gel is formed.

[0105] The gel was dried at 110°C for 10 hours to form a fluffy, porous solid.

[0106] The loose porous solid was heated to 300℃ at a heating rate of 5℃ / min and held for 3h, and then heated to 600℃ at a heating rate of 10℃ / min and held for 6h to obtain rare earth ferrite composite oxide.

[0107] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:20 at 600℃ for 17s to obtain oxygen-defective titanium dioxide.

[0108] 72 kg of oxygen-deficient titanium dioxide, 20 kg of rare earth ferrite composite oxide, 1 kg of activated carbon, 5 kg of glass fiber, 1 kg of petrolatum, and 1 kg of methylcellulose were kneaded into a plastic clay.

[0109] The plastic clay was kneaded three times in a clay kneading machine, then passed through a 200-mesh sieve to remove impurities, and aged for 10 hours to obtain aged clay.

[0110] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0111] The wet preform was dried in a tunnel microwave drying chamber for 16 hours and calcined at 550°C for 16 hours to prepare a rare earth ferrite-type denitration catalyst.

[0112] Example 7

[0113] Erbium nitrate and samarium nitrate were dissolved in deionized water at a molar ratio of 50:50 to obtain a first solution with an erbium nitrate concentration of 6 mol / L. Ferric nitrate was dissolved in deionized water to obtain a second solution with a concentration of 12.5 mol / L. The first and second solutions were mixed at a volume ratio of 40:95, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.4 times the total molar amount of Me and iron.

[0114] Add 0.14 times the total number of moles of Me and iron to the mixed solution, stir continuously in a 70°C water bath, and gradually evaporate until a gel is formed, thus transforming into a gel.

[0115] The gel was dried at 90°C for 12 hours to form a fluffy, porous solid.

[0116] The loose, porous solid was heated to 300℃ at a heating rate of 10℃ / min and held for 3 hours, and then heated to 700℃ at a heating rate of 20℃ / min and held for 6 hours to obtain rare earth ferrite composite oxide.

[0117] Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of 1:30 at 500℃ for 25s to obtain oxygen-defective titanium dioxide.

[0118] 82 kg of oxygen-deficient titanium dioxide, 11 kg of rare earth ferrite composite oxide, 0.5 kg of activated carbon, 4 kg of glass fiber, 0.5 kg of petrolatum, and 2 kg of methylcellulose were kneaded into a plastic mud.

[0119] The plastic clay was kneaded twice in a clay kneading machine, impurities were removed by passing it through a 100-mesh sieve, and it was aged for 12 hours to obtain aged clay.

[0120] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0121] The wet preform was dried in a tunnel microwave drying chamber for 12 hours and calcined at 550°C for 12 hours to prepare a rare earth ferrite-type denitration catalyst.

[0122] Comparative Example 1

[0123] Mix 82 kg of commercial titanium dioxide, 1 kg of ammonium metavanadate, 10 kg of ammonium metatungstate, 0.5 kg of activated carbon, 5 kg of glass fiber, 0.5 kg of petrolatum, and 1 kg of methylcellulose into a plastic slurry.

[0124] The plastic clay was kneaded twice in a clay kneading machine, then passed through a 100-mesh sieve to remove impurities, and then aged for 6 hours to obtain aged clay.

[0125] The aged clay material is extruded into a honeycomb mold to form a honeycomb wet body with 18×18 holes and a length of 1000mm;

[0126] The wet preform was dried in a tunnel microwave drying chamber for 12 hours and calcined at 600℃ for 12 hours to prepare a commercial vanadium-tungsten-titanium honeycomb denitration catalyst.

[0127] Comparative Example 2

[0128] Mix 82 kg of defective titanium dioxide, 1 kg of ammonium metavanadate, 10 kg of ammonium metatungstate, 0.5 kg of activated carbon, 5 kg of glass fiber, 0.5 kg of petrolatum, and 1 kg of methylcellulose into a plastic slurry.

[0129] The plastic clay was kneaded twice in a clay kneading machine, then passed through a 100-mesh sieve to remove impurities, and then aged for 6 hours to obtain aged clay.

[0130] The aged mud material is extruded into a honeycomb mold to form a honeycomb wet body with 18×18 holes and a length of 1000mm;

[0131] The wet preform was dried in a tunnel microwave drying chamber for 12 hours and calcined at 600℃ for 12 hours to prepare a commercial vanadium-tungsten-titanium honeycomb denitration catalyst.

[0132] Comparative Example 3

[0133] Erbium nitrate and cerium nitrate were dissolved in deionized water at a molar ratio of 50:50 to obtain a first solution with an erbium nitrate concentration of 6 mol / L. Ferric nitrate was dissolved in deionized water to obtain a second solution with a concentration of 12 mol / L. The first and second solutions were mixed at a volume ratio of 40:90, and citric acid was added and stirred until homogeneous to form a mixed solution. The amount of citric acid added was 1.4 times the total molar amount of Me and iron.

[0134] Add 0.14 times the total number of moles of Me and iron to the mixed solution, stir continuously in a 70°C water bath, and gradually evaporate until a gel is formed, thus transforming into a gel.

[0135] The gel was dried at 90°C for 12 hours to form a fluffy, porous solid.

[0136] The loose porous solid was heated to 300℃ at a heating rate of 5℃ / min and held for 3h, and then heated to 600℃ at a heating rate of 10℃ / min and held for 8h to obtain rare earth ferrite composite oxide.

[0137] 82 kg of commercial titanium dioxide, 11 kg of rare earth ferrite composite oxide, 0.5 kg of activated carbon, 5 kg of glass fiber, 0.5 kg of petrolatum, and 1 kg of methylcellulose were kneaded into a plastic mud.

[0138] The plastic clay was kneaded twice in a clay kneading machine, and impurities were removed by passing it through a 100-mesh sieve. The clay was then aged for 6 hours to obtain aged clay.

[0139] The aged clay material is poured into a mold to form a honeycomb-shaped wet body; the honeycomb-shaped wet body is 1000mm long and has 18*18 holes;

[0140] The wet preform was dried in a tunnel microwave drying chamber for 12 hours and calcined at 600℃ for 12 hours to prepare a rare earth ferrite denitration catalyst.

[0141] The catalysts prepared in Examples 1-7 and Comparative Examples 1-3 were tested in a fixed-bed reactor.

[0142] Test conditions: NO 500 mg / Nm 3 O2 10%, SO2 10000mg / Nm 3 The concentrations of NO at the inlet and outlet were measured using a Testo portable flue gas analyzer at 400℃, 450℃, 500℃, and 550℃, with 10% H2O, an NH3 / NO molar ratio of 1.0, N2 as the balance gas, an Av of 18 m / h, and a catalyst length of 500 mm. The results are shown in the table below.

[0143]

[0144]

[0145] It is evident that, compared with the commercial vanadium-tungsten-titanium honeycomb denitrification catalysts of Comparative Examples 1, 2, and 3, the rare earth ferrite-type denitrification catalysts prepared in Examples 1-7 of this invention have higher denitrification efficiency. This indicates that the honeycomb denitrification catalyst of this invention, which uses oxygen-deficient titanium dioxide as a support and rare earth ferrite-type composite oxide as the active component, is superior to the commercial vanadium-tungsten-titanium catalyst.

[0146] The catalysts of Example 1 and Comparative Example 1 were subjected to wear strength testing according to GB / T 38219-2019 "Technical Specification for Testing Catalysts for Flue Gas Denitrification in Thermal Power Plants". The test results are shown in the table below:

[0147] catalyst Abrasion strength (%) / kg National Standard (%) / kg Example 1 0.065 0.15 Comparative Example 1 0.088 0.15

[0148] The catalysts prepared in Example 1 and Comparative Example 1 were subjected to a stability test at 500°C for 168 hours. The results are shown in [reference needed]. Figure 3 It can be seen that the rare earth ferrite denitrification catalyst prepared in Example 1 of the present invention has significantly better wear strength than the commercial vanadium-tungsten-titanium honeycomb denitrification catalyst prepared in Comparative Example 1 and meets national standards. The denitrification efficiency remains basically unchanged after 168 hours. Moreover, the denitrification efficiency of the catalyst of the present invention in high-temperature, high-sulfur, and high-dust flue gas is more than 10% higher than that of existing vanadium-based catalysts.

[0149] In summary, this invention provides a rare-earth ferrite-type denitration catalyst and its preparation method. Using oxygen-deficient titanium dioxide as a support and a mixture of rare-earth ferrite-type composite oxides (MeFe2O4) as the active component, it can improve the acidic sites on the catalyst surface, enhance the high-temperature stability and wear resistance of the support, and further promote iron denitration activity, resulting in a catalyst with higher denitration efficiency. This catalyst does not contain strategic metals vanadium and tungsten, and the raw materials are cheaper and more readily available, leading to lower costs and greater safety.

[0150] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A rare earth ferrite-type denitration catalyst, characterized in that, The raw material components, by mass percentage, are as follows: 66%–82% oxygen-defective titanium dioxide, 11%–25% rare earth ferrite composite oxide, and 7%–9% forming agent; wherein the rare earth ferrite composite oxide is a mixture of MeFe2O4, where Me is one or more of Ce, Nd, La, Pr, Y, Sm, and Ho, and Er; wherein, in the rare earth ferrite composite oxide, the molar percentage of Er at the Me site is ≥45%.

2. The rare earth ferrite-type denitration catalyst according to claim 1, characterized in that, The oxygen-defect titanium dioxide has a particle size of 20–30 nm and a specific surface area of ​​100–120 m². 2 / g, density ≤0.5g / cm³ 3 .

3. The rare earth ferrite-type denitration catalyst according to claim 1, characterized in that, The molding agent comprises, by mass percentage of the catalyst, 0.5% to 1% activated carbon, 4% to 5% glass fiber, 0.5% to 1% petrolatum, and 1% to 2% methylcellulose.

4. The method for preparing the rare earth ferrite-type denitration catalyst according to any one of claims 1-3, characterized in that, Includes the following steps: Preparation of rare earth ferrite-type composite oxides; Preparation of oxygen-defective titanium dioxide; Oxygen-deficient titanium dioxide, rare-earth ferrite composite oxides, and molding agents are kneaded into a plastic slurry. The plastic clay is kneaded, sieved to remove impurities, and aged to obtain aged clay. The aged clay is poured into a mold to form a wet body; The wet preform is dried and calcined at high temperature to produce a rare earth ferrite-type denitrification catalyst.

5. The preparation method of the rare earth ferrite-type denitration catalyst according to claim 4, characterized in that, The method for preparing rare earth ferrite-type composite oxides is as follows: A soluble salt of one or more elements selected from Er and Ce, Nd, La, Pr, Y, Sm and Ho is mixed with a soluble salt of iron and a gelling agent in deionized water to obtain a mixed solution. Add a dispersant to the mixed solution, heat and stir to evaporate until the mixed solution transforms into a gel; The gel was dried to obtain a fluffy, porous solid. A loose, porous solid was calcined at high temperature to obtain a rare earth ferrite-type composite oxide.

6. The preparation method of the rare earth ferrite-type denitration catalyst according to claim 5, characterized in that, The soluble salts of one or more of Er and Ce, Nd, La, Pr, Y, Sm and Ho are one or more of nitrates, sulfates and acetates; the soluble salts of iron are one or more of iron nitrates, sulfates and acetates; the gelling agent is citric acid, and the amount of citric acid added is 1.2 to 1.4 times the total molar amount of Me sites and iron; the dispersant is one of ethylene glycol, polyethylene glycol or polyvinylpyrrolidone, and the amount of dispersant added is 0.12 to 0.23 times the total molar amount of Me sites and iron.

7. The preparation method of the rare earth ferrite-type denitration catalyst according to claim 5, characterized in that, The heating and stirring temperature is 65℃~70℃; the gel drying temperature is 90℃~110℃, and the drying time is 8~12h; the method for high-temperature calcination of the loose porous solid is as follows: the loose porous solid is heated to 200℃~300℃ at a heating rate of 5℃ / min~10℃ / min and held for 2~3h; then, it is heated to 600℃~700℃ at a heating rate of 10℃ / min~20℃ / min and held for 6~8h to obtain rare earth ferrite composite oxide.

8. The method for preparing the rare earth ferrite-type denitration catalyst according to claim 4, characterized in that, The method for preparing oxygen-deficient titanium dioxide is as follows: Commercial anatase titanium dioxide was calcined in a mixed atmosphere of hydrogen and argon with a volume ratio of (1:20) to (1:30) at a temperature of 500℃ to 600℃ for 15 to 25 seconds to obtain oxygen-defective titanium dioxide.

9. The preparation method of the rare earth ferrite-type denitration catalyst according to claim 4, characterized in that, The high-temperature roasting temperature is 500℃~600℃, and the roasting time is 12~16h.

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