Mo-ni bimetallic denitration catalyst and preparation method thereof

Abstract

The application discloses a Mo-Ni bimetallic denitration catalyst and a preparation method thereof, and relates to the technical field of denitration agents, and the preparation method comprises the following steps: firstly, a nickel source, a molybdenum source and an aluminum source are smelted and crushed to obtain a Ni-Mo-Al ternary alloy powder; then, the Ni-Mo-Al ternary alloy powder is added into a mixed alkaline leaching solution containing alkali metal hydroxide, a surfactant and hydrophobic conductive micro powder to perform a dealuminization reaction; hydrogen bubbles generated in-situ by the reaction are used as soft templates, and the hydrophobic conductive micro powder is adsorbed on the bubble interface and assembled in the skeleton through Pickering effect; finally, the catalyst is obtained through washing and drying; the catalyst prepared by the application has a large pore structure with conductive micro powder distributed on the inner wall; the unique structure not only reduces the mass transfer resistance, constructs an electron transmission channel, but also promotes the discharge of product nitrogen through a local hydrophobic environment, and significantly improves the catalytic activity and nitrogen selectivity when treating nitrate-containing wastewater.

Description

Technical Field

[0001] This invention relates to the field of denitrification agent technology, specifically to a Mo-Ni bimetallic denitrification catalyst and its preparation method. Background Technology

[0002] With the rapid development of modern industry, the concentration of nitrogenous pollutants (especially nitrate ions) in industrial wastewater is increasing daily, becoming one of the main factors contributing to water pollution. Nitrate not only leads to eutrophication of water bodies but also poses serious threats to human health. Therefore, developing efficient nitrate wastewater treatment technologies has become an important issue in the field of environmental protection.

[0003] Currently, the main industrial methods for treating nitrate-containing wastewater include biological denitrification, physical adsorption, membrane separation, and catalytic reduction.

[0004] Although biological denitrification is relatively low in cost, it has strict requirements on the C / N ratio of wastewater, a long treatment cycle, a large footprint, and poor treatment effect on high-concentration nitrate wastewater, making it difficult to meet the needs of modern industry for efficient treatment.

[0005] While physicochemical methods such as ion exchange and reverse osmosis have high treatment efficiency, they generally suffer from drawbacks such as high operating costs, secondary pollution, and complex equipment maintenance, making them difficult to promote and apply in large-scale industrial wastewater treatment.

[0006] Catalytic reduction has gradually become a research hotspot due to its advantages such as fast reaction rate and high processing efficiency. This method uses a catalyst and a reducing agent to reduce nitrate ions to harmless nitrogen gas.

[0007] The catalyst systems currently under research mainly include noble metal catalysts and non-noble metal catalysts.

[0008] Although precious metal catalysts (such as palladium-based and platinum-based catalysts) have certain catalytic activity, they are extremely expensive and prone to metal loss leading to deactivation, making it difficult to achieve large-scale industrial application.

[0009] Although non-precious metal catalysts are less expensive, they generally suffer from the following technical problems in the nitrate reduction process:

[0010] (1) Unsatisfactory catalytic selectivity: Existing catalysts often produce a large amount of ammonia nitrogen byproducts when reducing nitrate, resulting in incomplete denitrification and even secondary pollution.

[0011] (2) Catalytic activity needs to be improved: The overall catalytic efficiency of existing catalysts is not high enough, making it difficult to meet the requirements of rapid and efficient treatment of industrial wastewater.

[0012] (3) Limited mass transfer performance: Existing catalysts have mass transfer and diffusion resistance in liquid phase reactions, resulting in low catalyst utilization and affecting the overall treatment effect.

[0013] To address the aforementioned issues, existing technologies have attempted various improvement methods, including support modification and structural regulation. However, these methods generally suffer from problems such as complex preparation processes, high costs, and poor stability, making it difficult to simultaneously solve the technical challenges of catalytic activity and selectivity.

[0014] Especially in terms of catalyst pore structure design and surface modification, existing preparation methods are difficult to achieve precise structural control and cannot effectively balance mass transfer performance and selectivity requirements.

[0015] In summary, existing nitrate catalytic reduction technologies still have significant shortcomings in key technical indicators such as catalytic activity, reaction selectivity, and mass transfer performance, making it difficult to meet the actual needs of modern industrial wastewater treatment.

[0016] Therefore, there is an urgent need to develop a new type of denitrification catalyst and its preparation method to solve the technical problems existing in the current technology, achieve efficient and highly selective nitrate removal, and meet the requirements of industrial applications. Summary of the Invention

[0017] To address the shortcomings of existing technologies, this invention aims to provide a Mo-Ni bimetallic denitrification catalyst and its preparation method. This invention combines alloy smelting with in-situ bubble-forming technology to construct a hierarchical macroporous structure with embedded conductive microparticles while retaining the high specific surface area of ​​Raney Ni. This process is simple and controllable, simultaneously optimizing the catalyst's pore structure, enhancing electron transport capacity, and regulating the local microenvironment. It significantly solves the problems of hindered mass transfer and easy gas accumulation and deactivation in traditional catalysts, greatly improving the activity, nitrogen selectivity, and operational stability of wastewater denitrification.

[0018] To achieve the above objectives, the present invention adopts the following technical solution:

[0019] A method for preparing a Mo-Ni bimetallic denitration catalyst includes the following steps:

[0020] (1) Preparation of ternary alloy precursor powder: Nickel source (such as nickel ingot or nickel powder), molybdenum source (such as molybdenum powder or molybdenum-aluminum master alloy), and aluminum source (such as aluminum ingot) are batched according to the mass ratio Ni:Mo:Al = 35~45:0.5~5:50~60. The mixture is then melted into a homogeneous alloy ingot at 1300~1500℃ in a high-temperature induction furnace or electric arc furnace under inert gas protection. After the ingot cools, it is mechanically crushed and ground using a ball mill, then sieved and classified to select Ni-Mo-Al ternary alloy powder with a particle size range of 100~300 mesh for later use. This particle size range ensures a suitable reaction specific surface area and also helps the bubbles to adhere stably to the particle surface.

[0021] (2) Constructing a bubble-stabilized system with dispersed microparticles: Prepare a mixed alkaline leachate. First, dissolve an alkali metal hydroxide (preferably sodium hydroxide or potassium hydroxide) in deionized water to prepare an alkaline solution with a concentration of 15-25 wt%. Add a surfactant (at least one of cationic surfactant, anionic surfactant, or nonionic surfactant, preferably hexadecyltrimethylammonium bromide or sodium dodecyl sulfate) to the alkaline solution, with the concentration controlled at 0.05-0.5 wt%; simultaneously add hydrophobic conductive microparticles (at least one of hydrophobic modified carbon nanotubes, graphene, carbon black, graphite powder, or conductive polymer microspheres, preferably hydrophobic modified multi-walled carbon nanotubes or graphene), so that its content in the leachate is 0.1-2.0 g / L. Treat the mixture with an ultrasonic disperser or a high-shear disperser for 10-30 min to overcome the agglomeration of the hydrophobic conductive microparticles, so that they are uniformly suspended in the alkaline solution to form a stable dispersion system.

[0022] (3) In-situ bubble formation and micro powder assembly: The Ni-Mo-Al ternary alloy powder obtained in step (1) is slowly added to the mixed alkaline leaching solution prepared in step (2), and the solid-liquid ratio is controlled at 1g:10~20mL. The reaction system is placed in a constant temperature water bath, and the dealumination reaction temperature is controlled at 60~90℃, and the reaction time is 1~4h.

[0023] During this process, aluminum reacts with a strong alkali to release hydrogen bubbles in situ. To utilize these bubbles as pore-forming templates, intermittent low-speed stirring (e.g., <100 r / min) or static leaching is employed in the initial stage after adding the alloy powder (e.g., the first 20-60 minutes) to control the rheology of the reaction system and maintain the residence time of the hydrogen bubbles at the solid-liquid interface. At this time, the synergistic adsorption effect (Pickering effect) of surfactants and hydrophobic conductive microparticles at the gas-liquid interface is utilized to stabilize the micron-sized hydrogen bubbles and allow them to occupy the framework space. As the metal framework rearranges and solidifies, the hydrophobic conductive microparticles are anchored at the bubble interface, ultimately constructing a connected macroporous structure with conductive microparticles distributed on the inner wall within the catalyst.

[0024] (4) Post-treatment: After the reaction, the solid product was separated by filtration. First, the solid was repeatedly washed with deionized water until the pH of the washing solution dropped to 7-8; then it was washed 2-3 times with anhydrous ethanol to replace the water in the pores and reduce the surface tension. Finally, the wet sample was placed in a vacuum drying oven (vacuum degree < -0.08MPa) or dried at 40-60℃ for 6-12h under nitrogen / argon gas protection to obtain the Mo-Ni bimetallic denitration catalyst.

[0025] This invention also provides a Mo-Ni bimetallic denitration catalyst prepared by the above method:

[0026] This catalyst possesses a three-dimensional interconnected hierarchical pore structure, including mesopores formed by aluminum dissolution and macropores formed by hydrogen bubble templates. The inner walls of the macropores are distributed with hydrophobic conductive microparticles that provide both electrical conductivity and support. Its chemical composition contains 0.5–10% Mo by mass, 0.1–5.0% hydrophobic conductive microparticles by mass, 2.0–12.0% residual Al by mass, and the balance being Ni and unavoidable impurities.

[0027] The present invention further provides the application of the above-mentioned Mo-Ni bimetallic denitrification catalyst in the treatment of nitrate-containing wastewater: the application is to use the catalyst as a reduction catalyst to efficiently reduce nitrate ions in wastewater to nitrogen gas under normal temperature and pressure or mild conditions.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Existing conventional Raney Ni catalysts mainly consist of micropores and mesopores formed by dealumination, with narrow and tortuous pore channels, making it difficult for reactants and products to enter and exit. This invention creatively utilizes hydrogen bubbles released in situ from the aluminum-alkali reaction as a soft template to construct three-dimensionally interconnected micron-sized macropores within the catalyst. This "macropore-mesopore" hierarchical structure greatly shortens the path for nitrate ions to contact active sites, significantly reducing liquid-phase mass transfer resistance, allowing the catalyst to maintain an extremely high reaction rate even when treating high-concentration nitrate wastewater.

[0030] 2. This invention utilizes the synergistic self-assembly (Pickering effect) of hydrophobic conductive microparticles and hydrogen bubbles at the interface to achieve simultaneous optimization of catalyst structure and function: Hydrogen bubbles act as soft templates, opening up micron-sized mass transfer macropores while guiding the microparticles to oriented and construct a conductive network within the macropore walls. During catalytic reduction, electrons can transfer more rapidly from the reducing agent or current collector to the deeper Ni-Mo active centers, effectively reducing the reaction overpotential and improving catalytic activity. This simultaneously solves the two major bottlenecks of hindered liquid-phase diffusion and low electron transfer efficiency within the same pore structure. Furthermore, the microparticle shell enhances bubble stability, ensuring the integrity of the macroporous structure.

[0031] 3. The ideal product of the denitrification reaction is nitrogen gas, but bubbles easily adhere to the surface of hydrophilic metal catalysts, blocking active sites and forcing the reaction to stop or redirect to the formation of ammonia nitrogen. The hydrophobic microparticles introduced in this invention construct a localized hydrophobic environment within the macroporous channels. Hydrophobic nitrogen molecules tend to migrate and aggregate towards the hydrophobic regions before being expelled. This "gas-repellent" mechanism accelerates the desorption of nitrogen gas, prevents active sites from being covered by bubbles, thereby significantly improving the selectivity for nitrogen and reducing the formation rate of the byproduct ammonia nitrogen.

[0032] 4. This invention optimizes the adsorption energy of intermediate species (such as nitrite) in the denitration reaction by introducing Mo during the alloy smelting stage and utilizing the electronic interaction between Mo and Ni (d-band center regulation). Appropriate Mo doping promotes NO bond breaking and prevents excessive adsorption of intermediate products from poisoning the catalyst, further improving the catalyst's stability and conversion frequency.

[0033] 5. Compared to traditional methods that require the addition of hard templates such as polystyrene microspheres to create pores, this invention utilizes self-generated hydrogen bubbles as "soft templates," eliminating the need for subsequent complex calcination or solvent removal steps, making the process greener and simpler. Furthermore, by adjusting the ratio of surfactant and micropowder in the leachate, the pore size distribution and micropowder loading can be flexibly controlled, facilitating large-scale industrial production. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some schematic diagrams of certain embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a SEM image of the Mo-Ni bimetallic denitration catalyst prepared in Example 1 of this invention;

[0036] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the Mo-Ni bimetallic denitration catalyst prepared in Example 1 of this invention.

[0037] Figure 3 This is the Fourier transform infrared (FT-IR) spectrum of the Mo-Ni bimetallic denitration catalyst prepared in Example 1 of this invention;

[0038] Figure 4 XPS Ni is the Mo-Ni bimetallic denitration catalyst prepared in Example 1 of this invention. 2p and Mo3d Detailed spectrum. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. Of course, the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0040] Unless otherwise specified, all chemical reagents and materials used in this invention are purchased from the market or synthesized from raw materials purchased from the market. The purity of the metal raw materials, such as nickel blocks, molybdenum powder, and aluminum ingots, is better than 99.5%; the chemical reagents, such as sodium hydroxide, potassium hydroxide, and anhydrous ethanol, are all analytical grade or industrial grade; the hydrophobic and conductive micropowders, such as multi-walled carbon nanotubes (MWCNTs) or graphene, are purchased from conventional nanomaterial suppliers and can be pretreated with conventional hydrophobicity treatment as needed before use, or commercially available hydrophobic modified products can be used directly.

[0041] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0042] (1) Alloy smelting and powder preparation: Weigh out the nickel source, molybdenum source, and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo, and Al is 35~45:0.5~5:50~60. Put the above raw materials into a smelting furnace (such as an induction furnace or an electric arc furnace), heat and melt them under inert gas protection (e.g., 1200~1500℃), and obtain Ni-Mo-Al ternary alloy ingots after cooling. Crush, grind, and sieve the ingots, and select alloy powder with a particle size in the range of 100~300 mesh as the precursor.

[0043] (2) Preparation of Functionalized Leachate: Prepare a mixed alkaline leachate containing alkali metal hydroxide, surfactant, and hydrophobic conductive micropowder. The concentration of the alkali metal hydroxide (such as NaOH or KOH) is 15-25 wt%; the concentration of the surfactant (such as hexadecyltrimethylammonium bromide, sodium dodecyl sulfate, polyethylene glycol, or polyvinylpyrrolidone) is 0.05-0.5 wt%; and the content of the hydrophobic conductive micropowder (such as hydrophobically modified multi-walled carbon nanotubes or hydrophobically modified graphene) is 0.1-2.0 g / L. The hydrophobic conductive micropowder is dispersed in the alkaline solution by means of ultrasound or mechanical stirring to form a uniform suspension.

[0044] (3) Reaction pore formation and micropowder assembly: The Ni-Mo-Al ternary alloy powder obtained in step (1) is added to the mixed alkaline leaching solution in step (2), and the solid-liquid ratio is controlled at 1g:10~20mL. The dealumination reaction is carried out at a temperature of 60~90℃ for 1~4h. During the reaction, especially in the early stage of the reaction, a fluid control method that can maintain bubble stability (such as intermittent low-speed stirring or standing) is adopted. The hydrogen bubbles released by the reaction of aluminum and alkali are used as templates, and the hydrophobic conductive micropowder is adsorbed on the bubble interface with the help of surfactants, thereby constructing a macroporous structure with micropowder embedded in the inner wall in the formed porous framework.

[0045] (4) Post-processing: After the reaction is completed, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7~8), and then washed with anhydrous ethanol. Finally, it is dried at 40~60℃ under vacuum (e.g., vacuum degree <-0.08 MPa) or inert gas protection to obtain the Mo-Ni bimetallic denitration catalyst.

[0046] This embodiment also relates to the Mo-Ni bimetallic denitration catalyst prepared by the above method and its application:

[0047] The catalyst has a hierarchical porous structure, with a Mo content of 0.5-10%, a hydrophobic conductive microparticle content of 0.1-5.0%, and a residual Al content of 2.0-12.0%. This catalyst can be used to treat nitrate-containing wastewater, reducing nitrate ions to nitrogen gas.

[0048] The present invention will be further described below through specific embodiments.

[0049] Example 1

[0050] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0051] (1) Weigh out the nickel source, molybdenum source and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo and Al is 45:0.5:54.5. Put the above raw materials into an electric arc furnace and heat them to melt at 1300°C under inert gas protection. After cooling, obtain Ni-Mo-Al ternary alloy ingot. Crush, grind and sieve the ingot, and select alloy powder with a particle size of 200 mesh as the precursor.

[0052] (2) Prepare a mixed alkaline leachate containing alkali metal hydroxide NaOH, surfactant and hydrophobic conductive micro powder, wherein the concentration of NaOH is 20wt%; the concentration of surfactant (hexadecyltrimethylammonium bromide) is 0.5wt%; and the content of hydrophobic conductive micro powder (hydrophobic modified multi-walled carbon nanotubes) is 2.0g / L. Dispersion is carried out by means of ultrasonic or mechanical stirring to form a uniform suspension of the hydrophobic conductive micro powder in the alkaline solution.

[0053] (3) The Ni-Mo-Al ternary alloy powder obtained in step (1) is added to the mixed alkaline leaching solution in step (2), and the solid-liquid ratio is controlled at 1g:20mL. The aluminum removal reaction is carried out at 90℃ for 1 hour. In the initial stage of the reaction (first 20min), intermittent low-speed stirring is used. The hydrogen bubbles released by the reaction of aluminum and alkali are used as templates, and the hydrophobic conductive micropowder is adsorbed on the bubble interface with the help of surfactants, thereby constructing a macroporous structure with micropowder embedded in the inner wall in the formed porous skeleton.

[0054] (4) After the reaction is complete, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7), and then washed with anhydrous ethanol. Finally, it is dried at 50°C under a vacuum of <-0.08 MPa to obtain the Mo-Ni bimetallic denitration catalyst.

[0055] The catalyst has a hierarchical pore structure, with a Mo content of 1.1%, a hydrophobic conductive microparticle content of 2.2%, a residual Al content of 4.5%, and the balance being Ni and unavoidable impurities.

[0056] Example 2

[0057] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0058] (1) Weigh out the nickel source, molybdenum source and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo and Al is 40:4:56. Put the above raw materials into an electric arc furnace and heat them to melt at 1300°C under inert gas protection. After cooling, obtain Ni-Mo-Al ternary alloy ingot. Crush, grind and sieve the ingot, and select alloy powder with a particle size of 200 mesh as the precursor.

[0059] (2) Prepare a mixed alkaline leachate containing alkali metal hydroxide NaOH, surfactant and hydrophobic conductive micro powder, wherein the concentration of NaOH is 20wt%; the concentration of surfactant (sodium dodecyl sulfate) is 0.3wt%; and the content of hydrophobic conductive micro powder (hydrophobic modified multi-walled carbon nanotubes) is 1.5g / L. Dispersion is carried out by means of ultrasonic or mechanical stirring to form a uniform suspension of the hydrophobic conductive micro powder in the alkaline solution.

[0060] (3) The Ni-Mo-Al ternary alloy powder obtained in step (1) is added to the mixed alkaline leaching solution in step (2), and the solid-liquid ratio is controlled at 1g:18mL. The aluminum removal reaction is carried out at 80℃ for 2 hours. In the initial stage of the reaction (first 30min), intermittent low-speed stirring is used. The hydrogen bubbles released by the reaction of aluminum and alkali are used as templates, and the hydrophobic conductive micropowder is adsorbed on the bubble interface with the help of surfactants, thereby constructing a macroporous structure with micropowder embedded in the inner wall in the formed porous skeleton.

[0061] (4) After the reaction is complete, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7), and then washed with anhydrous ethanol. Finally, it is dried at 50°C under a vacuum of <-0.08 MPa to obtain the Mo-Ni bimetallic denitration catalyst.

[0062] The catalyst has a hierarchical pore structure, with a Mo content of 7.5%, a hydrophobic conductive microparticle content of 1.6%, a residual Al content of 4.2%, and the balance being Ni and unavoidable impurities.

[0063] Example 3

[0064] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0065] (1) Weigh out the nickel source, molybdenum source and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo and Al is 40:2:58. Put the above raw materials into an electric arc furnace and heat them to melt at 1300℃ under inert gas protection. After cooling, obtain Ni-Mo-Al ternary alloy ingot. Crush, grind and sieve the ingot, and select alloy powder with a particle size of 200 mesh as the precursor.

[0066] (2) Prepare a mixed alkaline leachate containing alkali metal hydroxide NaOH, surfactant and hydrophobic conductive micro powder, wherein the concentration of NaOH is 20wt%; the concentration of surfactant (polyethylene glycol) is 0.2wt%; and the content of hydrophobic conductive micro powder (hydrophobic modified graphene) is 1.0g / L. Dispersion is carried out by means of ultrasonic or mechanical stirring to form a uniform suspension of the hydrophobic conductive micro powder in the alkaline solution.

[0067] (3) The Ni-Mo-Al ternary alloy powder obtained in step (1) is added to the mixed alkaline leaching solution in step (2), and the solid-liquid ratio is controlled at 1g:15mL. The aluminum removal reaction is carried out at 70℃ for 3 hours. In the initial stage of the reaction (first 60min), intermittent low-speed stirring is used. The hydrogen bubbles released by the reaction of aluminum and alkali are used as templates, and the hydrophobic conductive micropowder is adsorbed on the bubble interface with the help of surfactants, thereby constructing a macroporous structure with micropowder embedded in the inner wall in the formed porous skeleton.

[0068] (4) After the reaction is complete, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7), and then washed with anhydrous ethanol. Finally, it is dried at 50°C under a vacuum of <-0.08 MPa to obtain the Mo-Ni bimetallic denitration catalyst.

[0069] The catalyst has a hierarchical pore structure, with a Mo content of 3.8%, a hydrophobic conductive microparticle content of 1.1%, a residual Al content of 4.0%, and the balance being Ni and unavoidable impurities.

[0070] Example 4

[0071] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0072] (1) Weigh out the nickel source, molybdenum source and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo and Al is 35:5:60. Put the above raw materials into an electric arc furnace and heat them to melt at 1300°C under inert gas protection. After cooling, obtain Ni-Mo-Al ternary alloy ingot. Crush, grind and sieve the ingot, and select alloy powder with a particle size of 200 mesh as the precursor.

[0073] (2) Prepare a mixed alkaline leachate containing alkali metal hydroxide NaOH, surfactant and hydrophobic conductive micro powder, wherein the concentration of NaOH is 20wt%; the concentration of surfactant (polyvinylpyrrolidone) is 0.05wt%; and the content of hydrophobic conductive micro powder (hydrophobic modified graphene) is 0.5g / L. Dispersion means such as ultrasonic or mechanical stirring are used to make the hydrophobic conductive micro powder form a uniform suspension in the alkaline solution.

[0074] (3) The Ni-Mo-Al ternary alloy powder obtained in step (1) is added to the mixed alkaline leaching solution in step (2), and the solid-liquid ratio is controlled at 1g:10mL. The aluminum removal reaction is carried out at 60℃ for 4 hours. In the initial stage of the reaction (first 60min), intermittent low-speed stirring is used. The hydrogen bubbles released by the reaction of aluminum and alkali are used as templates, and the hydrophobic conductive micropowder is adsorbed on the bubble interface by the help of surfactants, thereby constructing a macroporous structure with micropowder embedded in the inner wall in the formed porous skeleton.

[0075] (4) After the reaction is complete, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7), and then washed with anhydrous ethanol. Finally, it is dried at 50°C under a vacuum of <-0.08 MPa to obtain the Mo-Ni bimetallic denitration catalyst.

[0076] The catalyst has a hierarchical pore structure, with a Mo content of 8.8%, a hydrophobic conductive microparticle content of 0.5%, a residual Al content of 3.8%, and the balance being Ni and unavoidable impurities.

[0077] Comparative Example 1

[0078] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0079] (1) Weigh out the nickel source, molybdenum source and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo and Al is 45:0.5:54.5. Put the above raw materials into an electric arc furnace and heat them to melt at 1300°C under inert gas protection. After cooling, obtain Ni-Mo-Al ternary alloy ingot. Crush, grind and sieve the ingot, and select alloy powder with a particle size of 200 mesh as the precursor.

[0080] (2) Prepare a mixed alkaline leachate, wherein the concentration of NaOH in the leachate is 20 wt%; the concentration of surfactant (hexadecyltrimethylammonium bromide) is 0.5 wt%; and form a uniform solution by mechanical stirring and dispersion.

[0081] (3) Add the Ni-Mo-Al ternary alloy powder obtained in step (1) to the mixed alkaline leaching solution in step (2), control the solid-liquid ratio to be 1g:20mL, carry out the aluminum removal reaction at 90℃ for 1h; in the initial stage of the reaction (first 20min), use intermittent low-speed stirring.

[0082] (4) After the reaction is complete, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7), and then washed with anhydrous ethanol. Finally, it is dried at 50°C under a vacuum of <-0.08 MPa to obtain the Mo-Ni bimetallic denitration catalyst.

[0083] The catalyst has a porous structure, with a Mo content of 1.1%, a hydrophobic conductive microparticle content of 0%, a residual Al content of 4.5%, and the balance being Ni and unavoidable impurities.

[0084] Comparative Example 2

[0085] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0086] (1) Weigh out the nickel source, molybdenum source and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo and Al is 45:0.5:54.5. Put the above raw materials into an electric arc furnace and heat them to melt at 1300°C under inert gas protection. After cooling, obtain Ni-Mo-Al ternary alloy ingot. Crush, grind and sieve the ingot, and select alloy powder with a particle size of 200 mesh as the precursor.

[0087] (2) Prepare a mixed alkaline leachate, wherein the concentration of NaOH in the leachate is 20wt%; the content of hydrophobic conductive micropowder (hydrophobic modified multi-walled carbon nanotubes) is 2.0g / L, and the hydrophobic conductive micropowder is dispersed by ultrasonic means to form a suspension in the alkaline solution;

[0088] (3) Add the Ni-Mo-Al ternary alloy powder obtained in step (1) to the mixed alkaline leaching solution in step (2), control the solid-liquid ratio to be 1g:20mL, carry out the aluminum removal reaction at 90℃ for 1h; in the initial stage of the reaction (first 20min), use intermittent low-speed stirring.

[0089] (4) After the reaction is complete, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7), and then washed with anhydrous ethanol. Finally, it is dried at 50°C under a vacuum of <-0.08 MPa to obtain the Mo-Ni bimetallic denitration catalyst.

[0090] The catalyst has a porous structure, with a Mo content of 1.1%, a hydrophobic conductive microparticle content of <0.1%, a residual Al content of 4.5%, and the balance being Ni and unavoidable impurities.

[0091] Comparative Example 3

[0092] A method for preparing a Mo-Ni bimetallic denitration catalyst, which mainly includes the following steps:

[0093] (1) Weigh out the nickel source, molybdenum source and aluminum source according to the mass ratio, wherein the mass ratio of Ni, Mo and Al is 45:0.5:54.5. Put the above raw materials into an electric arc furnace and heat them to melt at 1300°C under inert gas protection. After cooling, obtain Ni-Mo-Al ternary alloy ingot. Crush, grind and sieve the ingot, and select alloy powder with a particle size of 200 mesh as the precursor.

[0094] (2) Prepare a mixed alkaline leachate, wherein the concentration of NaOH in the leachate is 20 wt%;

[0095] (3) Add the Ni-Mo-Al ternary alloy powder obtained in step (1) to the mixed alkaline leaching solution in step (2), control the solid-liquid ratio to be 1g:20mL, and carry out the dealumination reaction at 90℃ for 1h.

[0096] (4) After the reaction is complete, the solid product is subjected to solid-liquid separation. The solid is washed with deionized water until neutral (pH=7), and then washed with anhydrous ethanol. Finally, it is dried at 50°C under a vacuum of <-0.08 MPa to obtain the Mo-Ni bimetallic denitration catalyst.

[0097] The catalyst has a porous structure, with a Mo content of 1.1%, a hydrophobic conductive microparticle content of 0%, a residual Al content of 4.5%, and the balance being Ni and unavoidable impurities.

[0098] (I) Characterization of the structure and composition of catalysts

[0099] 1. Microscopic morphology analysis (corresponding appendix) Figure 1 )

[0100] Figure 1 Scanning electron microscope (SEM) image of the Mo-Ni bimetallic denitration catalyst prepared in the embodiments of the present invention.

[0101] As shown in the figure, the catalyst exhibits a typical three-dimensional porous framework structure with numerous interconnected macropores, primarily ranging in size from 5 to 50 μm. These interconnected macropores are formed through a synergistic process of hydrogen bubble template method and alkaline dealumination, effectively reducing mass transfer resistance and improving the utilization rate of the catalyst's internal surface. Simultaneously, the relatively rough framework surface, with nanoscale protrusions, provides a good foundation for the anchoring of hydrophobic microparticles and the distribution of reactive sites. This hierarchical porous structure and surface microstructure collectively endow the catalyst with excellent liquid-phase mass transfer and highly efficient denitrification performance.

[0102] 2. Phase structure analysis (see attached document) Figure 2 )

[0103] Figure 2The image shows the XRD pattern of the Mo-Ni bimetallic denitration catalyst prepared in Example 1 of this invention.

[0104] As can be seen from the figure, the sample exhibits sharp characteristic diffraction peaks near diffraction angles 2θ of 44.5°, 51.8°, and 76.4°, corresponding to the (111), (200), and (220) crystal planes of face-centered cubic nickel (Ni), respectively. This indicates that the catalyst has good crystallinity and forms a framework structure dominated by metallic nickel. Furthermore, no obvious single molybdenum oxide diffraction peaks are observed in the spectrum. Combined with the peak shift phenomenon, this indicates that Mo atoms have successfully entered the Ni lattice or exist in a highly dispersed amorphous state, forming a stable Ni-Mo solid solution alloy structure.

[0105] 3. Surface functional group analysis (see corresponding appendix) Figure 3 )

[0106] Figure 3 The FT-IR infrared spectrum of the Mo-Ni bimetallic denitration catalyst prepared in this embodiment of the invention is shown. This spectrum reveals the chemical environment of the catalyst surface. Besides the low-frequency absorption of the metal framework, there are also absorptions in the fingerprint region and high-frequency region (e.g., 2800–3000 cm⁻¹). -1 Distinct characteristic absorption peaks were observed within the range, corresponding to vibrations of organic functional groups such as CH bonds. This directly confirms that the hydrophobic conductive micropowders (such as hydrophobically modified carbon nanotubes) and surfactant molecules added during the preparation process have been successfully modified or anchored on the catalyst framework surface, thereby creating a localized hydrophobic environment inside the catalyst that is conducive to nitrogen desorption.

[0107] 4. Surface elemental valence state analysis (see corresponding appendix) Figure 4 )

[0108] Figure 4 This is a fine XPS spectrum of the catalyst of the present invention, where (a) is Ni 2p Spectrum, (b) is Mo 3d Spectrum. By Figure 4 (a) It can be seen that nickel on the catalyst surface is mainly in the metallic state (Ni). 0 It exists in the form of ) and constitutes the conductive framework of the catalyst. (By...) Figure 4 (b) It can be seen that Mo 3d The peak splitting is obvious, and the binding energy positions show that the Mo element exhibits Mo on the surface. 4+ and Mo 6+ The mixed valence state indicates that the Mo species, acting as an electronic promoter, has a strong electronic interaction with the Ni framework, and this synergistic effect is key to improving catalytic activity.

[0109] (II) Performance Testing and Result Analysis

[0110] To verify the technical effect of the Mo-Ni bimetallic denitrification catalyst prepared in this invention, the samples prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to simulated wastewater nitrate reduction tests.

[0111] 1. Experimental Methods

[0112] Simulated wastewater preparation: Prepare a potassium nitrate aqueous solution with an initial nitrate ion concentration of 100 mg / L (as N), and adjust the pH of the solution to 6.0.

[0113] Catalytic reaction process: 0.5 g of the catalyst sample to be tested was placed in a reactor containing 200 mL of simulated wastewater. Under normal temperature (25℃) and normal pressure conditions, high-purity hydrogen gas was continuously introduced as a reducing agent at a flow rate of 100 mL / min, the mechanical stirring speed was set to 400 r / min, and the reaction time lasted for 60 min.

[0114] Detection and analysis: After the reaction was completed, the supernatant was taken and the concentration of residual nitrate was detected by ultraviolet spectrophotometry, and the concentration of by-product ammonium ions was detected by Nessler's reagent spectrophotometry.

[0115] Calculation formula: Nitrate conversion rate (%) = (c0 - ct) / c0 × 100%;

[0116] N2 selectivity (%) = [1 - cn / (c0 - ct)] × 100%;

[0117] Where c0 is the initial concentration, ct is the concentration at time t, and cn is the generated NH4. + Ammonium concentration.

[0118] The catalytic performance test data for each group of samples are shown in the table below:

[0119] Table 1 Comparison of denitrification performance data for each catalyst sample

[0120]

[0121] Based on the data in Table 1 and the aforementioned characterization results, the technical effects of the present invention are analyzed as follows:

[0122] The reaction rate constant of Example 1 (0.082 min) -1 ) is the comparison example 3 (0.035min -1 This is 2.3 times that of the previous invention. This directly proves that the hierarchical pore structure constructed using the bubble template in this invention greatly eliminates the resistance to mass transfer in the liquid phase, allowing nitrate ions to contact the active sites more quickly.

[0123] The activity of Example 1 was also superior to that of Comparative Example 1 (without micronized powder, 0.058 min). -1This indicates that the introduction of conductive micropowder not only alters the pore properties but may also enhance the electron transfer efficiency on the framework surface, further promoting the reduction reaction.

[0124] Although Comparative Example 1 achieved a decent conversion rate (91.5%) by forming macropores with surfactants, its nitrogen selectivity was only 62.8%, resulting in a large amount of ammonia nitrogen byproducts (34.0 mg / L). In contrast, Example 1, by embedding hydrophobic conductive microparticles into the pore walls, achieved a selectivity of 94.5%.

[0125] This significant difference confirms that the hydrophobic microparticles create a localized hydrophobic microenvironment within the pores. Since the intermediate product nitrogen is hydrophobic, while nitrate and ammonium ions are hydrophilic, the hydrophobic pores facilitate the rapid desorption and discharge of nitrogen from the catalyst surface, preventing excessive hydrogenation and reduction of nitrogen to ammonia. This solves the technical challenge of "high activity accompanied by high ammonia production" in traditional Raney nickel catalysts.

[0126] Although Comparative Example 2 included micronized powder, it did not include a surfactant, resulting in the micronized powder failing to assemble onto the pore walls using the Pickering effect (finished product micronized powder content <0.1%). As a result, the activity (81.2%) and selectivity (58.4%) were significantly lower than in Example 1, almost degenerating to levels comparable to the traditional Comparative Example 3. This fully demonstrates that the "surfactant-assisted bubble template method" described in this invention is a necessary technical means for achieving high-performance catalyst preparation.

[0127] The above description is only a preferred embodiment of the present invention, but 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 Mo-Ni bimetallic catalyst for the catalytic reduction of nitrates, characterized in that, Includes the following steps: (1) The nickel source, molybdenum source and aluminum source are melted in proportion, cooled, crushed, ground and sieved to obtain Ni-Mo-Al ternary alloy powder; (2) Prepare a mixed alkaline leachate containing alkali metal hydroxide, surfactant and hydrophobic conductive micro powder, and suspend the hydrophobic conductive micro powder uniformly by dispersion means. (3) Add Ni-Mo-Al ternary alloy powder to a mixed alkaline leaching solution and carry out a dealuminization reaction under heating conditions; (4) After the reaction is complete, the solid product is subjected to solid-liquid separation, washing and drying to obtain the Mo-Ni bimetallic catalyst; In step (1), the mass ratio of Ni, Mo and Al in the Ni-Mo-Al ternary alloy powder is 35~45:0.5~5:50~60.

2. The preparation method according to claim 1, characterized in that, In step (1), the particle size range after crushing and grinding is 100~300 mesh.

3. The preparation method according to claim 1, characterized in that, In step (2), the alkali metal hydroxide is sodium hydroxide or potassium hydroxide, and its concentration in the mixed alkaline leachate is 15~25wt%; the surfactant is at least one of cationic surfactant, anionic surfactant or nonionic surfactant, and its concentration is 0.05~0.5wt%; the hydrophobic conductive micropowder is at least one of hydrophobic modified carbon nanotubes, graphene, carbon black, graphite powder or conductive polymer microspheres, and its content in the mixed alkaline leachate is 0.1~2.0g / L.

4. The preparation method according to claim 1, characterized in that, In step (3), the solid-liquid ratio of the Ni-Mo-Al ternary alloy powder to the mixed alkaline leachate is 1g:10~20mL.

5. The preparation method according to claim 1, characterized in that, In step (3), the temperature of the dealumination reaction is 60~90℃ and the reaction time is 1~4h.

6. The preparation method according to claim 1, characterized in that, In step (3), intermittent low-speed stirring or static leaching is used in the initial stage of adding alloy powder to maintain the residence of hydrogen bubbles at the solid-liquid interface.

7. The preparation method according to claim 1, characterized in that, In step (4), the washing refers to washing with deionized water and anhydrous ethanol in sequence until the pH value of the washing solution is 7~8; the drying is carried out at 40~60°C under vacuum of less than -0.08 MPa or under inert gas protection.

8. A Mo-Ni bimetallic catalyst prepared by the method according to any one of claims 1 to 7, characterized in that, The catalyst has a macroporous structure with the hydrophobic conductive microparticles distributed on the inner wall; the catalyst contains 0.5-10% Mo by mass, 0.1-5.0% hydrophobic conductive microparticles by mass, 2.0-12.0% residual Al by mass, and the balance is Ni and unavoidable impurities.

9. The application of the Mo-Ni bimetallic catalyst as described in claim 8 in the treatment of nitrate-containing wastewater.

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