A fly ash-based double-stitched nanosheet SOD zeolite composite catalytic material for ammonia treatment, a preparation method and application thereof

Abstract

The present application belongs to the field of catalytic materials and its application technology, and relates to a fly ash-based double-spliced nanosheet SOD zeolite composite catalytic material for ammonia treatment as well as a preparation method and application thereof. The method comprises the following steps: S1, fly ash pretreatment and activation; S2, preparation of a fly ash-based SOD zeolite; S3, preparation of a Pt nanoparticle liquid; and S4, preparation of a composite catalytic material: titanium glue and the Pt nanoparticle liquid are added into the fly ash-based SOD zeolite, and after mixing, calcination is performed to obtain the fly ash-based double-spliced nanosheet SOD zeolite composite catalytic material for ammonia treatment, namely the composite catalytic material. The fly ash-based double-spliced nanosheet SOD zeolite composite catalytic material for ammonia treatment has significant catalytic activity, wet resistance and improved catalytic oxidation performance on ammonia at normal temperature and pressure.

Description

Technical Field

[0001] This invention belongs to the field of catalytic materials and their application technology, and relates to a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, its preparation method and application. Background Technology

[0002] Currently, with the development of animal husbandry in various regions, intensive pig farming has emerged in large numbers, resulting in a significant increase in manure emissions and a growing problem of foul odor. The odor primarily originates from odorous substances such as ammonia, hydrogen sulfide, indole, and skatole. Excessive odorous substances pollute the environment of pig farms, affecting not only the healthy growth of pigs and the quality of pork but also the health of farm workers. Therefore, it is necessary to control ammonia levels in pig farms.

[0003] Currently, photocatalysis is a widely used method for pollutant treatment. The principle of photocatalysis is based on the redox capabilities of photocatalysts under light. By stimulating active sites on the material surface through light, an oxidation reaction is achieved, thereby purifying pollutants and facilitating substance synthesis and transformation. Therefore, photocatalysis can oxidize ammonia into N2 or nitrates, solving the problem of odor pollution. See patent document CN108854518B, which discloses a method for photocatalytic oxidation of ammonia, specifically using silver phosphate as a catalyst for photocatalytic oxidation of ammonia under visible light. Other studies have shown that plasma and ultraviolet photocatalysis can be used to simultaneously purify ammonia and odor gases. Although existing technologies can treat ammonia, they have the following problems: existing photocatalysts have poor catalytic activity at room temperature and pressure; furthermore, due to the high humidity of aquaculture environments, existing photocatalysts have poor moisture resistance, and moisture in the air significantly affects their performance, making it difficult for them to exert their catalytic performance effectively, leading to a decrease in catalytic performance. Summary of the Invention

[0004] To address the technical problem in existing ammonia treatment processes where photocatalysts exhibit poor catalytic activity, poor moisture resistance, and difficulty in achieving their catalytic performance under normal temperature and pressure, leading to reduced catalytic performance, this invention provides a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, its preparation method, and its application.

[0005] This invention prepares fly ash-based SOD zeolite using fly ash as raw material; further, it forms a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material (hereinafter referred to as composite catalytic material) with titanium glue and Pt nanoparticles for ammonia treatment. The composite catalytic material exhibits significant catalytic activity and moisture resistance at room temperature and pressure, thereby enhancing the catalytic oxidation performance of ammonia.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment includes the following steps:

[0008] S1. Fly ash pretreatment and activation

[0009] Fly ash was subjected to acid washing pretreatment, calcination activation and melt activation in sequence to obtain activated fly ash;

[0010] S2. Preparation of fly ash-based SOD zeolite

[0011] The activated fly ash from step S1 is mixed with sodium hydroxide solution; then it is successively subjected to aging, hydrothermal crystallization reaction, centrifugation and drying to obtain fly ash-based SOD zeolite.

[0012] S3, Preparation of Pt nanoparticle liquid

[0013] Under stirring conditions, chloroplatinic acid solution and polyvinylpyrrolidone were heated and mixed, then cooled, and acetone was added until the supernatant became clear. The mixture was then centrifuged, washed, and dispersed to obtain Pt nanoparticle liquid.

[0014] S4. Preparation of composite catalytic materials

[0015] Titanium colloid and Pt nanoparticle liquid from step S3 are added to the fly ash-based SOD zeolite in step S2, mixed, and then calcined to obtain a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, i.e., a composite catalytic material.

[0016] Further specifying, the specific process of step S1 is as follows:

[0017] S1.1 Mix fly ash with hydrochloric acid solution, and perform acid washing pretreatment at a constant temperature of 80℃-95℃ for 0.5h-1.5h. Then, after centrifugation, dry at 80℃-95℃ and grind to obtain fine powder.

[0018] S1.2 Place the fine powder in a muffle furnace and calcine and activate it at 600℃-900℃ for 0.5h-2h to obtain fly ash powder;

[0019] S1.3 Fly ash powder and sodium hydroxide are ground and mixed at a mass ratio of 1:(1.0-1.5), and then melt-activated at 450℃-550℃ to obtain activated fly ash.

[0020] Further specifying, in step S2, the sodium hydroxide solution is composed of sodium hydroxide and water; the mass ratio of activated fly ash, sodium hydroxide and water is 1:(1.4-1.8):(5.0-6.0).

[0021] Further specifying, in step S2, the aging time is 20h-30h; the conditions for the hydrothermal crystallization reaction are: temperature 90℃-120℃, time 12h-24h.

[0022] Further specifying, in step S3, the mass of polyvinylpyrrolidone in each 8 mL of chloroplatinic acid solution is 300 mg-400 mg; the heating conditions are: 120℃-140℃ for 1-2 hours.

[0023] Further specifying, in step S3, hexane is used for washing; methanol is used for dispersion.

[0024] Further specifying that in step S4, the titanium glue is calculated as titanium dioxide and the Pt nanoparticle liquid is calculated as Pt, then the mass ratio of fly ash-based SOD zeolite, titanium dioxide and Pt is (1-4):(1-2):(0.2%-2%).

[0025] Further specifying that in step S4, the temperature is raised to 350℃-450℃ at a heating rate of 5℃ / min under a dry air atmosphere and calcined for 1h-1.5h.

[0026] A method for preparing a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment.

[0027] The application of the aforementioned composite catalytic material as a photocatalyst in the oxidation of gaseous ammonia at room temperature.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. This invention prepares fly ash-based SOD zeolite using fly ash as raw material; further, it forms a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material (hereinafter referred to as composite catalytic material) for ammonia treatment by combining it with titanium dioxide and Pt nanoparticles. This material not only has high catalytic activity, but also has small pores in the SOD-type zeolite. Its micropores can selectively adsorb water molecules into the pores while preventing ammonia molecules from entering, thereby reducing the influence of water molecules on ammonia oxidation and improving the catalytic oxidation efficiency of ammonia at room temperature and pressure.

[0030] 2. Performance testing of this invention confirms that the composite catalytic material contains both SOD zeolite crystalline phase and rutile and anatase TiO2 crystalline phases; and the hollow microspheres with a diameter of 3-5 μm composed of double nanosheets have a hierarchical porous structure, which is more conducive to gas diffusion, thus exhibiting significant catalytic activity for gaseous ammonia at room temperature and pressure, with high catalytic degradation efficiency, and can be well used for the oxidation of gaseous ammonia at room temperature.

[0031] 3. Through performance testing, this invention found that when the ambient humidity increases from 60% to 70%, the ammonia treatment effect of the composite catalytic material prepared in this invention does not decrease significantly, indicating that the composite catalytic material has excellent moisture resistance to moisture in the environment.

[0032] 4. This invention uses fly ash as raw material to prepare SOD zeolite, which not only improves the catalyst performance of the overall composite catalytic material, but also achieves the purpose of treating waste with waste by using industrial solid waste fly ash as a matrix. Attached Figure Description

[0033] Figure 1 X-ray diffraction (XRD) patterns of different composite catalytic materials;

[0034] Figure 2 The image shows a scanning electron microscope (SEM) image of the fly ash-based SOD zeolite prepared in Comparative Example 1.

[0035] Figure 3 The image shows a scanning electron microscope (SEM) image of the composite catalytic material prepared in Example 1.

[0036] Figure 4 The elemental distribution (SEM mapping) of the composite catalytic material prepared in Example 1 is shown.

[0037] Figure 5 The graph shows the effect of different composite catalytic materials on ammonia degradation at an air humidity of 60%.

[0038] Figure 6 The graph shows the effect of the composite catalytic material prepared in Example 1 on ammonia decomposition under different humidity levels.

[0039] Figure 7 The images show the UV-Vis diffuse reflectance (UV-Vis DRS) spectra of the composite catalytic materials of Example 1 and the control example.

[0040] Figure 8 The images show the luminescence (PL) spectra of the composite catalytic materials of Example 1 and the control example. Detailed Implementation

[0041] The technical solution of the present invention will now be further described with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0042] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0043] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0044] This invention provides a method for preparing a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, comprising the following steps:

[0045] S1. Fly ash pretreatment and activation

[0046] Fly ash was subjected to acid washing pretreatment, roasting activation and melting activation in sequence to obtain activated fly ash.

[0047] The specific process of step S1 in this invention is as follows:

[0048] S1.1 Mix fly ash with hydrochloric acid solution and pre-treat it by acid washing at a constant temperature of 80℃-95℃ for 0.5h-1.5h. Then, after centrifugation, dry it at 80℃-95℃ and grind it to obtain fine powder.

[0049] For example, the constant temperature and drying temperature are 80°C, 85°C, 90°C or 95°C; the pickling pretreatment time is 0.5h, 0.75h, 1h, 1.25h or 1.5h.

[0050] S1.2 Place the fine powder in a muffle furnace and calcine it at 600℃-900℃ for 0.5h-2h to obtain fly ash powder.

[0051] For example, the calcination activation temperature is 600℃, 650℃, 700℃, 750℃, 800℃, 850℃ or 900℃; and the time is 0.5h, 0.75h, 1h, 1.25h, 1.5h, 1.75h or 2h.

[0052] S1.3 Fly ash powder and sodium hydroxide are ground and mixed at a mass ratio of 1:(1.0-1.5), and then melt-activated at 450℃-550℃ to obtain activated fly ash.

[0053] For example, the mass ratio of fly ash powder to sodium hydroxide is 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5; and the melting activation temperature is 450℃, 480℃, 500℃, 520℃ or 550℃.

[0054] S2. Preparation of fly ash-based SOD zeolite

[0055] The activated fly ash from step S1 is mixed with sodium hydroxide solution, and then subjected to aging, hydrothermal crystallization reaction, centrifugation and drying in sequence to obtain fly ash-based SOD zeolite.

[0056] In step S2 of this invention, the sodium hydroxide solution is composed of sodium hydroxide and water; the mass ratio of activated fly ash, sodium hydroxide and water is 1:(1.4-1.8):(5.0-6.0).

[0057] For example, the mass ratio of activated fly ash, sodium hydroxide, and water is 1:1.4:5.0, 1:1.4:5.5, 1:1.4:6.0, 1:1.6:5.0, 1:1.6:5.5, 1:1.6:5.7, 1:1.6:6.0, 1:1.8:5.0, 1:1.8:5.5, or 1:1.8:6.0.

[0058] In step S2 of this invention, the aging time is 20h-30h; the conditions for the hydrothermal crystallization reaction are: temperature 90℃-120℃, time 12h-24h.

[0059] For example, the aging time is 20h, 22h, 24h, 26h, 28h, or 30h. The hydrothermal crystallization reaction temperature is 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, or 120℃, and the time is 12h, 14h, 15h, 18h, 20h, 22h, or 24h.

[0060] S3, Preparation of Pt nanoparticle liquid

[0061] Under stirring conditions, chloroplatinic acid solution and polyvinylpyrrolidone were heated and mixed, then cooled; acetone was added until the supernatant became clear, and then centrifuged, washed and dispersed to obtain Pt nanoparticle liquid.

[0062] In step S3 of this invention, the mass of polyvinylpyrrolidone in each 8 mL chloroplatinic acid solution is 300 mg-400 mg; the heating conditions are: temperature 120℃-140℃ for 1-2 hours.

[0063] For example, in each 8 mL of chloroplatinic acid solution, the mass of polyvinylpyrrolidone is 300 mg, 320 mg, 350 mg, 380 mg, or 400 mg; the heating conditions are: temperature 120°C, 125°C, 130°C, 135°C, or 140°C, held for 1 h, 1.5 h, or 2 h.

[0064] In step S3 of this invention, hexane is used for washing; methanol is used for dispersion.

[0065] S4. Preparation of composite catalytic materials

[0066] Titanium colloid and Pt nanoparticle liquid from step S3 are added to the fly ash-based SOD zeolite in step S2, mixed, and then calcined to obtain a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, i.e., a composite catalytic material.

[0067] In step S4 of this invention, the titanium glue is calculated as titanium dioxide and the Pt nanoparticle liquid is calculated as Pt. Therefore, the mass ratio of fly ash-based SOD zeolite, titanium dioxide and Pt is (1-4):(1-2):(0.2%-2%).

[0068] For example, the mass ratio of fly ash-based SOD zeolite, titanium dioxide and Pt is (1:1:0.2%), (1:1:1%), (1:1:2%), (1:2:0.2%), (1:2:1%), (1:2:2%), (2:1:0.2%), (2:1:1%), (2:1:2%), (4:1:0.2%), (4:1:1%), (4:1:2%), (4:2:0.2%), (4:2:1%) or (4:2:2%).

[0069] In step S4 of this invention, the temperature is raised to 350℃-450℃ in a dry air atmosphere at a heating rate of 5℃ / min and calcined for 1h-1.5h. For example, the temperature is 350℃, 380℃, 400℃, 420℃ or 450℃, and the calcination time is 1h, 1.25h or 1.5h.

[0070] This invention also provides a composite catalytic material prepared using the above-mentioned method for preparing fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment. The composite catalytic material is used as a photocatalyst in the oxidation of gaseous ammonia at room temperature.

[0071] This invention uses fly ash as the main raw material, combining it with titanium dioxide and Pt nanoparticles to form a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment. SOD zeolite is formed by the coplanar connections between SOD cages, making it a small-pore molecular sieve. The standard pore size of SOD zeolite is 0.28 nm. Scale-wise, the diameter of water vapor molecules is less than 0.28 nm (0.28 nm < the internal molecular pore size of the molecular sieve < the critical diameter of ammonia molecules approximately 0.37 nm), allowing relatively small water molecules to enter the pores and be effectively adsorbed, while ammonia molecules are retained outside the pores and removed by catalysis. This precise pore size matching allows the SOD zeolite molecular sieve pores to selectively adsorb water molecules in odorous gases, thereby reducing the impact of water molecules on the ammonia catalytic effect. The SOD zeolite molecular sieve also has a significant adsorption capacity, capable of adsorbing a large number of water molecules at once, thus reducing the water content outside the odorous gas pores to an extremely low level, further reducing the impact of water molecules on ammonia catalysis and improving the catalytic effect. Furthermore, since the pore size of SOD zeolite molecular sieves is comparable to the diameter of water vapor molecules, the diffusion resistance of water vapor molecules in the SOD micropores is relatively large. Constructing hierarchical porous molecular sieves can significantly improve the diffusion effect of molecules. At the same time, the composite catalytic material has a special double-layered nanosheet spherical structure. Its complex hierarchical porous structure and the combined effect of TiO2 and Pt particles made of titanium dioxide loaded on its surface enable the composite catalytic material to greatly improve the oxidation efficiency of ammonia at room temperature and pressure.

[0072] This invention also provides the application of fly ash-based SOD zeolite composite catalytic material as a photocatalyst in room temperature gaseous ammonia oxidation.

[0073] The technical solution provided by the present invention will be described in detail below with several embodiments, and the performance of the prepared composite catalytic material will be studied through testing.

[0074] It should be noted that, unless otherwise specified, the chemicals and reagents used in the following embodiments are all commercially available products commonly used in the field.

[0075] It should be noted that, unless otherwise specified, the operations used in the following embodiments are all conventional operations; for example, the operating temperature is always at room temperature unless otherwise specified. The test methods are all existing standard test methods in the art unless otherwise specified.

[0076] It should be noted that in the following examples, the mass of TiO2 contained in the purchased titanium glue is 3g per 100mL of titanium glue, and fly ash-based composite catalyst material is prepared using this as an example.

[0077] Example 1

[0078] This embodiment provides a method for preparing a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, including the following steps:

[0079] S1. Fly ash pretreatment and activation

[0080] Fly ash is subjected to acid washing pretreatment, calcination activation, and melt activation in sequence to obtain activated fly ash. The specific process is as follows:

[0081] S1.1 Place the fly ash raw material in a 10% hydrochloric acid solution, and then perform acid washing pretreatment at a constant temperature of 85℃ for 1 hour. After acid washing, centrifuge, dry at a constant temperature of 85℃, and grind to obtain fine powder.

[0082] S1.2 Place the fine powder in a muffle furnace and calcine and activate it at a high temperature of 700℃ for 1.5h to obtain fly ash powder;

[0083] S1.3 Fly ash powder and sodium hydroxide are ground and mixed at a mass ratio of 1:1.0, and then melted and activated at 500℃ to obtain activated fly ash.

[0084] S2. Preparation of fly ash-based SOD zeolite

[0085] In step S1, the activated fly ash was mixed with sodium hydroxide solution and aged at room temperature for 25 hours with stirring to obtain a precursor solution. The precursor solution was then transferred to a polytetrafluoroethylene reactor and subjected to hydrothermal crystallization in a 100°C constant temperature oven for 15 hours. After the reaction, the mixture was centrifuged and dried to obtain fly ash-based SOD zeolite.

[0086] S3, Preparation of Pt nanoparticle liquid

[0087] 8 mL of a 10 mg / mL solution of chloroplatinic acid (H₂PtCl₆·6H₂O) and 350 mg of polyvinylpyrrolidone (k29-32, Mw=58000) were sequentially added to a 100 mL round-bottom flask containing 25 mL of ethylene glycol to form a yellow solution. The yellow solution was then heated to 130 °C under magnetic stirring and held at this temperature for 1 hour to form a dark brown solution. After the dark brown solution cooled to room temperature, 60-80 mL of acetone was slowly added to it while shaking until the turbidity of the solution increased significantly. The solution was washed with n-hexane, and the precipitate was centrifuged to precipitate a black oily substance. Finally, the precipitate was dispersed in 20 mL of methanol to obtain a PtNPs solution with a concentration of 1.48 mg / mL, denoted as PtNPs.

[0088] S4. Preparation of composite catalytic materials

[0089] 18g of fly ash-based SOD zeolite was weighed and added to 300mL of titanium glue and 61mL of Pt nanoparticle liquid. After mixing and stirring, the mixture was transferred to a muffle furnace and heated to 400℃ at a heating rate of 5℃ / min under dry air atmosphere and calcined for 1h. Finally, a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment was obtained, namely the composite nanomaterial, denoted as SOD-TiO2-Pt (2:1:1%).

[0090] In this step, the mass of fly ash-based SOD zeolite is 18g, and each 100mL of titanium glue contains 3g of TiO2. Since the volume of the titanium glue is 300mL, the mass of TiO2 is 9g. The concentration of the Pt nanoparticle liquid is 1.48mg / mL, and the volume is 61mL, so the mass of the Pt nanoparticles is 1%. Therefore, the mass ratio of fly ash-based SOD zeolite, TiO2, and Pt nanoparticles is 2:1:1%.

[0091] Example 2

[0092] This embodiment provides a method for preparing a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, including the following steps:

[0093] S1, fly ash activation

[0094] The fly ash was subjected to acid washing pretreatment, roasting activation, and melt activation in sequence to obtain activated fly ash. The specific process was the same as in Example 1.

[0095] S2. Preparation of fly ash-based SOD zeolite

[0096] In step S1, the activated fly ash was mixed with sodium hydroxide solution and aged at room temperature for 25 hours with stirring to obtain a precursor solution. The precursor solution was then transferred to a polytetrafluoroethylene reactor and subjected to hydrothermal crystallization in a 100°C constant temperature oven for 15 hours. After the reaction, the mixture was centrifuged and dried to obtain fly ash-based SOD zeolite.

[0097] S3. Preparation of Pt nanoparticle liquid

[0098] 8 mL of chloroplatinic acid solution and 350 mg of polyvinylpyrrolidone were sequentially added to a round-bottom flask containing 25 mL of ethylene glycol. The mixture was magnetically stirred in an oil bath and heated to 130 °C for 1 hour, allowing the solution color to gradually change from light yellow to dark brown. After the round-bottom flask cooled naturally to room temperature, acetone was slowly added until the supernatant became clear. The mixture was then centrifuged and washed with n-hexane. The resulting product was dispersed in 20 mL of methanol to prepare a Pt nanoparticle liquid with a concentration of 1.48 mg / mL, denoted as Pt NPs.

[0099] S4. Preparation of composite catalytic materials

[0100] 18g of fly ash-based SOD zeolite was weighed and added to 300mL of titanium glue and 30.5mL of Pt nanoparticle liquid. After mixing and stirring, the mixture was transferred to a muffle furnace and heated to 400℃ at a heating rate of 5℃ / min under dry air atmosphere and calcined for 1h. Finally, a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment was obtained, namely the composite nanomaterial, denoted as SOD-TiO2-Pt (2:1:0.5%).

[0101] In this step, the mass of fly ash-based SOD zeolite is 18g, and each 100mL of titanium glue contains 3g of TiO2. Since the volume of the titanium glue is 300mL, the mass of TiO2 is 9g. The concentration of the Pt nanoparticle liquid is 1.48mg / mL, and the volume is 30.5mL, so the mass of the Pt nanoparticles is 0.5%. Therefore, the mass ratio of fly ash-based SOD zeolite, TiO2, and Pt nanoparticles is 2:1:0.5%.

[0102] Example 3

[0103] This embodiment provides a method for preparing a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, including the following steps:

[0104] S1. Fly ash pretreatment and activation

[0105] The fly ash was subjected to acid washing pretreatment, roasting activation, and melt activation in sequence to obtain activated fly ash. The specific process was the same as in Example 1.

[0106] S2. Preparation of fly ash-based SOD zeolite

[0107] In step S1, the activated fly ash was mixed with sodium hydroxide solution and aged at room temperature for 25 hours with stirring to obtain a precursor solution. The precursor solution was then transferred to a polytetrafluoroethylene reactor and subjected to hydrothermal crystallization in a 100°C constant temperature oven for 15 hours. After the reaction, the mixture was centrifuged and dried to obtain fly ash-based SOD zeolite.

[0108] S3, Preparation of Pt nanoparticle liquid

[0109] 8 mL of chloroplatinic acid solution and 350 mg of polyvinylpyrrolidone were sequentially added to a round-bottom flask containing 25 mL of ethylene glycol. The mixture was magnetically stirred in an oil bath and heated to 130 °C for 1 hour, allowing the solution color to gradually change from light yellow to dark brown. After the round-bottom flask cooled naturally to room temperature, acetone was slowly added until the supernatant became clear. The mixture was then centrifuged and washed with n-hexane. The resulting product was dispersed in 20 mL of methanol to prepare a Pt nanoparticle liquid with a concentration of 1.48 mg / mL, denoted as PtNPs.

[0110] S4. Preparation of composite catalytic materials

[0111] 18g of fly ash-based SOD zeolite was weighed and added to 300mL of titanium glue and 122mL of Pt nanoparticle liquid. After mixing and stirring, the mixture was transferred to a muffle furnace and heated to 400℃ at a heating rate of 5℃ / min under dry air atmosphere and calcined for 1h. Finally, a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment was obtained, namely the composite nanomaterial, denoted as SOD-TiO2-Pt(2:1:2%).

[0112] In this step, the mass of fly ash-based SOD zeolite is 18g, and each 100mL of titanium glue contains 3g of TiO2. Since the volume of the titanium glue is 300mL, the mass of TiO2 is 9g. The concentration of the Pt nanoparticle liquid is 1.48mg / mL, and the volume is 122mL, so the mass of the Pt nanoparticles is 2%. Therefore, the mass ratio of fly ash-based SOD zeolite, TiO2, and Pt nanoparticles is 2:1:2%.

[0113] Furthermore, the performance of the fly ash-based dual-layer nanosheet SOD zeolite composite catalyst material for ammonia treatment prepared in the above embodiments was tested. At the same time, in order to highlight the advantages of the fly ash-based composite catalyst material of the present invention, the following comparative examples were designed.

[0114] Compare with Example 1

[0115] This comparative example provides a method for preparing fly ash-based SOD zeolite, comprising the following steps:

[0116] S1. Place the fly ash raw material in a 10% hydrochloric acid solution and pre-treat it by acid washing at a constant temperature of 85℃ for 1 hour. After acid washing, the sample is centrifuged, dried at a constant temperature of 85℃, and ground to obtain fine powder.

[0117] S2. Place the fine powder in a muffle furnace and calcine and activate it at a high temperature of 700℃ for 1.5 hours to obtain fly ash powder;

[0118] S3. Fly ash powder and sodium hydroxide are ground and mixed at a mass ratio of 1:1.0, and then melted and activated at 500℃ to obtain activated fly ash.

[0119] S4. Activated fly ash is mixed with sodium hydroxide solution and aged at room temperature for 25 hours with stirring to obtain a precursor solution;

[0120] S5. The precursor solution from step S4 is transferred to a polytetrafluoroethylene reactor and subjected to hydrothermal crystallization reaction in a constant temperature oven at 100℃ for 15 hours. After the reaction is completed, centrifugation and drying are performed to obtain fly ash-based SOD zeolite, denoted as SOD.

[0121] Compare with Example 2

[0122] This comparative example provides a method for preparing a TiO2 catalytic material, including the following steps:

[0123] Measure 300 mL of titanium colloid and transfer it into a muffle furnace. Under a dry air atmosphere, raise the temperature to 400 °C at a heating rate of 5 °C / min and calcine for 1 h to obtain TiO2 catalyst material, denoted as TiO2.

[0124] Compare with Example 3

[0125] This comparative example provides a method for preparing a mixed material of SOD zeolite and TiO2, including the following steps:

[0126] S1. Place the fly ash raw material in a 10% hydrochloric acid solution and pre-treat it by acid washing at a constant temperature of 85℃ for 1 hour. After acid washing, the sample is centrifuged, dried at a constant temperature of 85℃, and ground to obtain fine powder.

[0127] S2. Place the fine powder from step S1 in a muffle furnace and calcine and activate it at a high temperature of 700℃ for 1.5 hours to obtain fly ash powder.

[0128] S3. Grind and mix the fly ash powder from step S2 with sodium hydroxide at a mass ratio of 1:1.0, and then melt and activate it at 500℃ to obtain activated fly ash.

[0129] S4. The activated fly ash from step S3 is mixed with sodium hydroxide solution and aged at room temperature for 25 hours to obtain a precursor solution.

[0130] S5. The precursor solution from step S4 is transferred to a polytetrafluoroethylene reactor and subjected to hydrothermal crystallization reaction in a constant temperature oven at 100℃ for 15 hours. After the reaction, centrifugation and drying are performed to prepare fly ash-based SOD zeolite.

[0131] S6: Weigh 18g of fly ash-based SOD zeolite and add it to 300mL of titanium glue. After mixing and stirring, transfer it to a muffle furnace and calcine it at a heating rate of 5℃ / min under dry air atmosphere until the temperature reaches 400℃ and is calcined for 1h. Finally, a mixed material of SOD zeolite and TiO2 is obtained, namely a composite catalyst material, denoted as SOD-TiO2 (2:1).

[0132] The following experimental study was conducted to test the performance of a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material (hereinafter referred to as catalytic material) for ammonia treatment.

[0133] Experiment 1, XRD

[0134] The catalytic materials prepared in Examples 1, 2, 3, Comparative Example 1, and Comparative Example 2 were used as test samples. The crystal structure of the test samples was analyzed by X-ray diffraction (XRD), and the results are as follows: Figure 1 As shown.

[0135] See Figure 1 On the abscissa of the test sample SOD-TiO2-Pt (2:1:1%) in Example 1: 14.024°, 24.434°, 31.703° and 34.742° correspond to the (110), (211), (310) and (222) crystal planes of SOD zeolite (PDF#37-0196-Sodalite), respectively; 27.44°, 36.078° and 54.323° correspond to the (110), (101) and (211) crystal planes of rutile TiO2 (PDF#99-0090-Rutile), respectively; 25.685° corresponds to the (101) crystal plane of anatase TiO2 (PDF#75-1537-Anatase). This indicates that the sample contains both SOD zeolite crystal phase and rutile and anatase TiO2 crystal phases.

[0136] Experiment 2, SEM

[0137] Using fly ash-based SOD zeolite from Comparative Example 1 and the composite catalyst (SOD-TiO2-Pt (2:1:1%)) prepared in Example 1 as test samples, morphology images of each test sample at a certain magnification were obtained using scanning electron microscopy (SEM). The results are as follows: Figure 2 , Figure 3 , Figure 4 As shown.

[0138] Depend on Figure 2 It can be seen that fly ash-based SOD zeolite is composed of hollow microspheres with a diameter of 3-5 μm, consisting of double-layered nanosheets with a width of 1 μm and a thickness of 0.05 μm, exhibiting a hierarchical porous structure. Figure 3 It can be seen that TiO2 particles have been loaded onto the surface of the SOD zeolite in the composite catalytic material. Figure 4 The image shown is a SEM mapping of the composite catalytic material prepared in Example 1. It can be seen that the composite catalytic material contains four elements: Si, Al, Ti, and Pt, and each element is evenly distributed on the surface of the material, indicating that the material has been successfully composited.

[0139] Experiment 3: Ammonia treatment performance

[0140] Composite catalytic materials prepared in Example 1, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were used as test samples, and the treatment effect of each test sample on ammonia under different air humidity was obtained.

[0141] The test method is as follows: each composite catalyst material is oxidized with NH3 under ultraviolet light; ammonia gas with a fixed concentration (40ppm), flow rate (100mL / min) and humidity is introduced into the dynamic photocatalytic experimental device by a flow distribution device, and glass fiber filter membranes of each fly ash-based composite catalyst material are placed in the photocatalytic reaction device in advance. The degradation efficiency and catalytic activity are calculated by observing the concentration change of the ammonia gas detection device at the tail end.

[0142] (1) The air humidity was adjusted to 60%, and the effect of each test sample on ammonia treatment under 60% air humidity was tested. The results are shown in Figure 5.

[0143] from Figure 5 It can be seen that after 2 hours of treatment, the catalytic oxidation efficiency of ammonia by the fly ash-based SOD zeolite (SOD) in Control Example 1 was around 30%, the catalytic oxidation efficiency of ammonia by the catalytic material (TiO2) in Control Example 2 reached 50%, and the treatment efficiency of ammonia by the composite catalytic material (SOD-TiO2(2:1)) in Control Example 3 was 70%. However, the catalytic oxidation efficiency of ammonia by the composite catalytic material (SOD-TiO2-Pt (2:1:1%)) in Example 1 reached over 87%. This indicates that the fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material prepared in this invention exhibits a synergistic effect between TiO2 and Pt on the surface of the fly ash-based SOD zeolite carrier, greatly enhancing the catalytic treatment performance of ammonia, thus enabling its efficient treatment.

[0144] (2) Following the above method, the air humidity was varied at 60%, 63%, 67%, 70%, and 80% to test the treatment effect of the composite catalyst material (SOD-TiO2-Pt (2:1:1%)) in Example 1. The results are as follows: Figure 6 As shown.

[0145] from Figure 6It can be seen that when the air humidity is 60%, 63%, 67%, 70%, and 80% for 120 minutes, the corresponding removal efficiencies are approximately 85%, 80%, 78%, 70%, and 55%, respectively. When the ambient humidity increases from 60% to 80%, the ammonia removal efficiency decreases; however, when the ambient humidity is between 60% and 67%, the ammonia removal efficiency decreases by 7%, which is not significant. When the ambient humidity continues to increase to 70%, the ammonia removal efficiency decreases by 15%, but still remains at 70%. When the ambient humidity continues to increase to 80%, the ammonia removal efficiency continues to decrease. However, since a humidity of 70%-80% is considered a high-humidity environment, and the normal humidity in pig farms is generally between 60% and 70%, from the perspective of removal efficiency, within the normal humidity range (60%-70%), the reduction in the ammonia treatment effect of SOD-TiO2-Pt (2:1:1%) is not significant, and it also has a good catalytic oxidation effect on ammonia, indicating that the moisture in the farm environment has little impact on the catalyst. This demonstrates that the fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material prepared by this invention has excellent moisture resistance.

[0146] Experiment 4, Photochemical Performance

[0147] The photochemical performance of the composite catalytic material (SOD-TiO2-Pt(2:1:1%)) prepared in Example 1, the catalytic material (SOD) of Control Example 1, the catalytic material (TiO2) of Control Example 2, and the composite catalytic material (SOD-TiO2(2:1)) of Control Example 3 were tested.

[0148] The test method involved measuring its absorption characteristics using ultraviolet-visible diffuse reflectance absorption spectroscopy (UV-Vis DRS, TU-1901, Japan), with BaSO4 used as a blank control at 0.6 nm•s. -1 The scanning rate was measured within the scanning range of 240 nm to 800 nm. The results are as follows: Figure 7 As shown.

[0149] from Figure 7 As can be seen, compared with Comparative Examples 1-3, the composite catalytic material (SOD-TiO2-Pt (2:1:1%)) prepared in this invention has the strongest light absorption performance in both the ultraviolet and visible regions, thus ensuring the improvement of its photocatalytic performance.

[0150] Experiment 5, PL spectrum

[0151] This experiment utilizes photoluminescence (PL) spectroscopy to further investigate the charge carrier recombination behavior of fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material (hereinafter referred to as composite catalytic material) used for ammonia treatment.

[0152] The composite catalytic material prepared in Example 1 (denoted as SOD-TiO2-Pt(2:1:1%)), the catalytic material (TiO2) of Control Example 2, and the composite catalytic material (SOD-TiO2(2:1)) of Control Example 3 were used as test samples for testing.

[0153] The testing method was as follows: Electron-hole recombination was determined using atomic emission spectroscopy (PL, F-7000 type, Hitachi High-Tech Corporation). The operating voltage was 250V, the excitation wavelength was 300nm, the initial wavelength was 900nm, the bandwidth was 3.5nm, and the scan speed was 1500nm / min within the range of 200nm-900nm. The results are as follows: Figure 8 As shown.

[0154] from Figure 8 As can be seen, compared with Comparative Example 2 and Comparative Example 3, the composite catalytic material (SOD-TiO2-Pt(2:1:1%)) prepared in this invention has the lowest fluorescence intensity, indicating that its electron-hole recombination degree is the lowest, thereby ensuring the improvement of its photocatalytic performance.

[0155] The above performance tests were verified using the fly ash-based dual-layer nanosheet SOD zeolite composite catalyst materials for ammonia treatment prepared in Examples 1 to 3. When the raw material ratios and preparation conditions specified in this invention are replaced, the prepared fly ash-based dual-layer nanosheet SOD zeolite composite catalyst materials for ammonia treatment also exhibit the same or similar performance. Structurally, they are hollow microspheres with a diameter of 3-5 μm composed of dual-layer nanosheets and have a hierarchical porous structure. In terms of performance, they have excellent catalytic activity and moisture resistance, achieving efficient ammonia treatment at room temperature and pressure.

[0156] The specific embodiments described above are only used to explain the present invention. The scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, characterized in that, Includes the following steps: S1. Fly ash pretreatment and activation Fly ash was subjected to acid washing pretreatment, calcination activation and melt activation in sequence to obtain activated fly ash; The specific process of step S1 is as follows: S1.1 Mix fly ash with hydrochloric acid solution, and perform acid washing pretreatment at a constant temperature of 80℃-95℃ for 0.5h-1.5h. Then, after centrifugation, dry at 80℃-95℃ and grind to obtain fine powder. S1.2 Place the fine powder in a muffle furnace and calcine and activate it at 600℃-900℃ for 0.5h-2h to obtain fly ash powder; S1.3 Fly ash powder and sodium hydroxide are ground and mixed at a mass ratio of 1:(1.0-1.5), and then melted and activated at 450℃-550℃ to obtain activated fly ash; S2. Preparation of fly ash-based SOD zeolite Mix the activated fly ash from step S1 with a sodium hydroxide solution; Then, after aging, hydrothermal crystallization reaction, centrifugation and drying, fly ash-based SOD zeolite is obtained. The sodium hydroxide solution is composed of sodium hydroxide and water; the mass ratio of activated fly ash, sodium hydroxide and water is 1:(1.4-1.8):(5.0-6.0); the aging time is 20h-30h; the conditions for hydrothermal crystallization reaction are: temperature 90℃-120℃, time 12h-24h; S3. Preparation of Pt nanoparticle liquid Under stirring conditions, chloroplatinic acid solution and polyvinylpyrrolidone were heated and mixed, then cooled, and acetone was added until the supernatant became clear. The mixture was then centrifuged, washed and dispersed to obtain Pt nanoparticle liquid. S4. Preparation of composite catalytic materials Titanium colloid and Pt nanoparticle liquid from step S3 are added to the fly ash-based SOD zeolite in step S2, mixed, and then calcined to obtain a fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment, namely, a composite catalytic material. In step S4, the titanium adhesive is calculated as titanium dioxide, and the Pt nanoparticle liquid is calculated as Pt. Therefore, the mass ratio of fly ash-based SOD zeolite, titanium dioxide, and Pt is (1-4):(1-2):(0.2%-2%). In step S4, the temperature is raised to 350℃-450℃ in a dry air atmosphere at a heating rate of 5℃ / min and then calcined for 1h-1.5h.

2. The preparation method of the fly ash-based dual-layer nanosheet SOD zeolite composite catalyst for ammonia treatment according to claim 1, characterized in that, In step S3, the mass of polyvinylpyrrolidone in each 8 mL of chloroplatinic acid solution is 300 mg-400 mg; the heating conditions are: 120℃-140℃ for 1-2 hours.

3. The preparation method of the fly ash-based dual-layer nanosheet SOD zeolite composite catalyst for ammonia treatment according to claim 1, characterized in that, In step S3, hexane is used for washing; methanol is used for dispersion.

4. A composite catalytic material prepared by the method for preparing fly ash-based dual-layer nanosheet SOD zeolite composite catalytic material for ammonia treatment as described in claim 1.

5. The application of the composite catalytic material as described in claim 4 as a photocatalyst in the oxidation of gaseous ammonia at room temperature.

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