Method for preparing carbon monoxide oxidation catalyst by using red mud and tungsten-molybdenum smelting slag

Abstract

The invention discloses a method for preparing a carbon monoxide oxidation catalyst by using red mud and tungsten-molybdenum smelting slag, which comprises the following steps of: uniformly stirring and mixing the red mud and the tungsten-molybdenum smelting slag at a high speed, mixing with inorganic strong acid, and performing ultrasonic-assisted stirring to obtain acid leaching slag; the acid leaching residues are subjected to low-temperature plasma activating treatment and then microwave activating treatment, and microwave activated plasma residues are obtained; weighing tricalcium phosphate and microwave activated plasma slag, and uniformly stirring to obtain phosphorus-calcium doped activated slag; weighing an ammonium sulfide solution and the phosphorus-calcium doped activated slag, uniformly stirring, transferring the obtained sulfur-phosphorus-calcium doped activated slag into a hydrothermal reaction kettle, carrying out hydrothermal reaction, carrying out compression molding on the obtained hydrothermal composite material, and carrying out pyrolysis carbonization treatment in an inert gas atmosphere to obtain the phosphorus-calcium doped activated slag. The obtained pyrolysis composite material is soaked with a silane coupling agent solution and then roasted again, and the carbon monoxide oxidation catalyst is obtained. The catalyst prepared by the invention can realize efficient oxidation photocatalysis of carbon monoxide under the conditions of normal temperature and normal pressure.

Description

Technical Field

[0001] This invention belongs to the field of industrial solid waste resource utilization, and relates to a method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag. Background Technology

[0002] Globally, red mud stockpiles are large, but their comprehensive utilization rate is low. The leakage of alkaline solutions from red mud severely pollutes the soil, exacerbating the risk of heavy metal migration. Furthermore, during the mining and smelting of tungsten concentrate, the recovery rate of Mo and W from the smelting slag is still less than 70%, resulting in significant resource waste. Tungsten-molybdenum slag also has polluting characteristics: its sulfate (SO3) content is as high as 10-30%, and direct stockpiling leads to soil acidification, affecting the yield of surrounding crops. Therefore, treating red mud and tungsten-molybdenum slag can reduce the land occupied by stockpiling, lower the risk of environmental pollution, and simultaneously recover valuable metals to generate economic and environmental benefits, achieving a win-win situation.

[0003] At the same time, with increasingly stringent vehicle emission standards and the rapid growth of the automotive industry, there is a huge market demand for low-temperature, high-efficiency catalysts, especially in the field of non-precious metal catalysts.

[0004] In summary, the research on the method of preparing carbon monoxide oxidation catalysts using red mud and tungsten-molybdenum smelting slag is expected to break through the bottleneck of utilizing red mud and tungsten-molybdenum slag alone, realize waste-to-waste conversion, solve the problems of high cost and low added value of single waste treatment, and fill the technological gap in the synergistic preparation of catalysts from multiple solid wastes. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag.

[0006] Technical solution: The present invention provides a method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag, comprising the following steps: (1) Weigh out red mud and tungsten-molybdenum smelting slag separately, stir them evenly, and obtain a preliminary mixed slag; (2) Mix the preliminary mixed residue with an inorganic strong acid, stir with ultrasonic assistance, let stand, separate the supernatant, and obtain acid leaching residue; (3) The acid leaching residue is placed in a low-temperature plasma treatment device for low-temperature plasma activation treatment to obtain plasma activated residue; (4) Placing the plasma-activated slag in a microwave reactor and performing microwave activation treatment to obtain microwave-activated plasma slag; (5) Weigh and mix tricalcium phosphate and microwave-activated plasma slag separately, stir evenly to obtain calcium phosphate-doped activated slag; (6) Mix the ammonium sulfide solution and the phosphorus-calcium activated slag, stir evenly, and obtain the sulfur-phosphorus-calcium activated slag; (7) The sulfur-phosphorus-calcium activated slag is transferred to a hydrothermal reactor for hydrothermal reaction to obtain a hydrothermal composite material; (8) The hydrothermal composite material is pressed into a catalyst blank, and the catalyst blank is subjected to pyrolysis carbonization treatment in an inert gas atmosphere to obtain the pyrolysis composite material. (9) The pyrolysis composite material was soaked in a silane coupling agent solution and then calcined again to obtain a carbon monoxide oxidation catalyst.

[0007] Furthermore, the mass ratio of red mud to tungsten-molybdenum smelting slag in step (1) is 20~70:100.

[0008] Further, in step (1), the weighed red mud and tungsten-molybdenum smelting slag are placed in a high-speed mixer and stirred at a speed of 800~1500r / min for 30~60 minutes to ensure that the two are fully mixed.

[0009] Further, in step (2), the concentration of the inorganic strong acid is 3~9M, and the liquid-solid ratio of the inorganic strong acid to the preliminary mixed residue is (0.3~0.6):1 mL / g.

[0010] Furthermore, in step (2), the inorganic strong acid is any one of hydrochloric acid, sulfuric acid, and nitric acid.

[0011] Furthermore, in step (2), the ultrasonic-assisted stirring time is 20-60 minutes, the ultrasonic frequency is 30-50 kHz, and the standing time is 1-3 hours.

[0012] Furthermore, in step (3), the plasma voltage is 5~75kV, the power is 100~800W, the processing time is 5~35 minutes, and the gas is any one of argon, oxygen, or nitrogen.

[0013] Furthermore, in step (4), the microwave power of the microwave activation treatment is 300~700W, and the microwave time is 5~25 minutes.

[0014] Furthermore, in step (5), the mass ratio of tricalcium phosphate to microwave-activated plasma slag is 1~5:100.

[0015] Further, in step (6), the liquid-to-solid ratio of ammonium sulfide solution and calcium phosphate activated slag is (0.1~0.3):1 mL / g, and the concentration of ammonium sulfide solution is 0.1~0.5 mol / L.

[0016] Furthermore, in step (7), the hydrothermal temperature is 150~250℃ and the hydrothermal time is 4~12 hours.

[0017] Further, in step (8), the inert gas is either nitrogen or argon. After heating to 400~700℃, the temperature is maintained for 2~6 hours, and after cooling, a pyrolysis composite material is obtained.

[0018] Further, in step (9), the silane coupling agent is any one of γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, polyol titanate, or zirconium aluminate coupling agent.

[0019] Furthermore, in step (9), the mass fraction of the silane coupling agent solution is 0.5%~2.5%, and the soaking time is 2~6 hours.

[0020] Furthermore, in step (9), the second roasting is carried out in an air atmosphere, with the roasting temperature set at 500~800℃ and the roasting time at 3~6 hours.

[0021] Reaction mechanism: Red mud and tungsten-molybdenum smelting slag are mixed and stirred at high speed to ensure full contact and form a homogeneous preliminary mixture. This mixture is then mixed with a strong inorganic acid. Under ultrasonic assistance, the acid penetrates the internal pores of the mixture, undergoing acid-base neutralization and acidolysis reactions with the metal oxides and other components. This process leaches some metal elements into the liquid phase and simultaneously disrupts the original structure of the raw materials, exposing more active sites. After settling, the supernatant is separated, yielding an acid-leached slag rich in undissolved solid particles. These particles retain some of the original structure and active components, while the acid leaching process creates more defects and active sites on their surface, providing a foundation for subsequent reactions. The acid-leached slag is then placed in a low-temperature plasma treatment device. High-energy particles in the plasma collide and interact with the surface of the acid-leached slag. This plasma treatment causes structural distortions in some metal oxides on the surface of the acid-leached slag, forming unsaturated coordinated metal atoms. These atoms have stronger electron-donating or accepting abilities, thus facilitating subsequent chemical reactions with other substances. Microwave fields can cause polar molecules in acid leaching residues to move rapidly and generate frictional heat, leading to a rapid increase in the internal temperature of the material. This accelerates the diffusion and migration of components in the residues, promoting coordination reactions between metal ions and surrounding ligands to form new compounds or complexes. Simultaneously, the thermal and non-thermal effects of microwaves may also trigger local phase transitions and crystal transformations, making the material's structure more ordered or disordered, thereby altering its physicochemical properties and further enhancing its activity. Tricalcium phosphate can react with metal ions in the acid leaching residues to generate phosphate compounds with specific structures and properties. These phosphate compounds can regulate the acidity and alkalinity of catalysts, provide new active sites, and act as structure-directing agents, influencing the morphology and crystal structure of products in subsequent hydrothermal reactions. The addition of ammonium sulfide solution introduces sulfide ions, which can react with metal ions in the acid leaching residues to form metal sulfides. Under hydrothermal conditions, the higher temperature and pressure alter the properties of water, making it an excellent solvent and reaction medium. In a hydrothermal system, acid leaching residue, tricalcium phosphate, and ammonium sulfide undergo complex chemical reactions, including dissolution, recrystallization, coordination, and precipitation. Under high temperature and pressure, aluminum ions in the acid leaching residue react with phosphate ions to form compounds such as aluminum hydroxyphosphate. Simultaneously, sulfides react with metal oxides to form composite materials with specific structures. These reactions enable thorough mixing and reaction of the components at the atomic or molecular level, resulting in composite materials with specific crystal structures and morphologies, which is beneficial for improving the catalytic performance of the catalyst. By pressing the hydrothermal reaction products into catalyst preforms with specific shapes and strengths, this step primarily aims to improve the mechanical strength of the catalyst and facilitate subsequent processing and use. The preforms maintain the dispersion and active structure of the components, providing a stable support for subsequent pyrolysis and carbonization processes.In an inert gas atmosphere, the catalyst preform undergoes pyrolysis and carbonization. As the temperature rises, the organic matter in the preform undergoes thermal decomposition and carbonization reactions, generating carbonaceous substances. These carbonaceous substances deposit on the surface and in the pores of the catalyst, forming a carbon coating layer. This carbon coating layer possesses good electrical conductivity, which improves the electron transfer efficiency of the catalyst and promotes electron transfer processes in the catalytic reaction. Simultaneously, the carbon coating layer stabilizes the internal structure of the catalyst, preventing the active components from agglomerating or sintering under high-temperature conditions, thereby improving the catalyst's stability and lifespan. The pyrolyzed and carbonized catalyst is then immersed in a silane coupling agent solution. The silane coupling agent undergoes chemical adsorption and reaction at the active sites on the catalyst surface, forming an organosilane film. This film improves the hydrophilicity and wettability of the catalyst surface, allowing for better dispersion and contact with the reactant gases, thus improving the adsorption and diffusion efficiency of reactants on the catalyst surface. Furthermore, the silane coupling agent also acts as a coupling agent, enhancing the interaction between the catalyst and other substances that may be added subsequently, further improving the overall performance of the catalyst. The catalyst treated with the coupling agent is calcined in an air atmosphere. This calcination process further removes residual organic matter, moisture, and other impurities from the catalyst, making its structure more compact and stable. During calcination, some metal sulfides may undergo oxidation reactions to generate corresponding metal oxides or oxysulfides. These products may possess better catalytic performance or synergistically enhance the catalytic activity and stability of the catalyst with other components.

[0022] Beneficial Effects: This invention enables the efficient resource utilization of red mud and tungsten-molybdenum smelting slag. The entire preparation process, through the synergistic effect of various physicochemical treatment methods and additives, transforms the useful components in red mud and tungsten-molybdenum smelting slag into a composite catalyst with highly efficient carbon monoxide oxidation catalytic performance. Each step is closely related and mutually influential, working together to optimize the catalyst's performance. The catalyst prepared by this invention can achieve highly efficient photocatalytic oxidation of carbon monoxide under ambient temperature and pressure conditions. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation method of the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Red mud: provided by Shandong Zibo Zhengheng Aluminum Co., Ltd., the main tested components include: 38.52% Fe2O3, 27.83% Al2O3, 12.49% SiO2, 11.36% Na2O, 5.61% TiO2, 0.57% CaO, 0.34% SO3 and other components (unavoidable impurities and loss on ignition); Tungsten-molybdenum smelting slag: provided by Luoyang Luanchuan Molybdenum Group Co., Ltd., the main components tested include: 58.19% SiO2, 12.56% Al2O3, 21.38% FeO, 3.95% CaO, 0.34% Mo and other components (unavoidable impurities and loss on ignition).

[0026] Example 1: Effect of the mass ratio of red mud to tungsten-molybdenum smelting slag on the performance of the prepared carbon monoxide oxidation catalyst.

[0027] Red mud and tungsten-molybdenum smelting slag were weighed at mass ratios of 5:100, 10:100, 15:100, 20:100, 45:100, 70:100, 75:100, 80:100, and 85:100, and placed in a high-speed mixer. The mixture was stirred at 800 rpm for 30 minutes to ensure thorough mixing and obtain a preliminary mixed slag. This preliminary mixed slag was then mixed with a 3M inorganic strong acid (hydrochloric acid) at a liquid-to-solid ratio of 0.3:1 (mL / g). The mixture was ultrasonically stirred for 20 minutes at a frequency of 30 kHz in an ultrasonic cleaner, followed by settling for 1 hour. The supernatant was then separated to obtain an acid-leached slag. This acid-leached slag was then placed in a low-temperature plasma treatment device to obtain a plasma-activated slag. The plasma voltage was 5 kV, the power was 100 W, the treatment time was 5 minutes, and the gas used was argon. The plasma-activated slag was placed in a microwave reactor, and microwave power was set to 300W for 5 minutes for microwave activation treatment to obtain microwave-activated plasma slag. Tricalcium phosphate and microwave-activated plasma slag were weighed and mixed at a mass ratio of 1:100 and stirred evenly to obtain calcium phosphate-doped activated slag. Ammonium sulfide solution and calcium phosphate-doped activated slag were mixed at a liquid-to-solid ratio of 0.1:1 (mL / g) and stirred evenly to obtain calcium phosphate-sulfurized activated slag, wherein the concentration of ammonium sulfide solution was 0.1 mol / L. The calcium phosphate-sulfurized activated slag was transferred to a hydrothermal reactor, and the hydrothermal temperature was set to 150℃ for 4 hours to obtain a hydrothermal composite material. The hydrothermal composite material was removed, allowed to cool naturally to room temperature, and then thoroughly washed with deionized water until neutral, followed by filtration. The filter cake was then placed in a molding device and pressed under a pressure of 10 MPa to obtain a catalyst preform with a certain shape and strength. The catalyst preform was placed in a tube furnace and subjected to pyrolysis and carbonization treatment under an inert gas atmosphere to obtain a pyrolysis composite material. The inert gas could be nitrogen. The temperature was raised to 400℃ and held for 2 hours. After pyrolysis and carbonization, the pyrolysis composite material was removed and cooled to room temperature. It was then immersed in a 0.5% (mass fraction) silane coupling agent solution for 2 hours. The silane coupling agent was γ-aminopropyltriethoxysilane. The catalyst treated with the coupling agent was then placed back into the tube furnace and calcined in air to obtain a carbon monoxide oxidation catalyst. The calcination temperature was set at 500℃ and the calcination time was 3 hours.

[0028] Carbon monoxide oxidation test: The gas source used in the test was CO (1% v / v, N2 balance, steel cylinder, including flame arrester); syngas (21% O2, N2 balance); high-purity N2 (99.999%). All gas cylinders were fixed to steel cylinder racks and equipped with flashback arresters, pressure reducing valves, and 0~0.6MPa pressure gauges; all piping and valve bodies were made of 316L stainless steel and passed a 10MPa water pressure test; the fume hood surface velocity was ≥0.5 m / s. -1The fixed-bed reactor uses a quartz U-shaped tube with an inner diameter of 6mm and a length of 250mm, with a sintered glass frit core in the middle. The tube furnace is controlled by PID temperature control with an accuracy of ±1°C; a K-type thermocouple is inserted into the center of the catalyst bed. Weigh 100±1mg of catalyst (40~60 mesh), dilute it with an equal volume of quartz sand (60~80 mesh), and load it into the constant-temperature zone of the reaction tube. Secure both ends with quartz wool to prevent pulverization and blow-out. The equipment connection sequence is: gas cylinder → pressure reducing valve → mass flow controller (MFC, 0~100mL / min). -1 (Accuracy ±1%) → Three-way mixing valve → Reactor → Condenser → FTIR online analysis → Tail gas treatment. Introduce 100 mL of N2 per minute. -1 Purge at room temperature for 10 min to replace air. Incubate the catalyst in N2 at 5°C for [time missing]. -1 The temperature was raised to 150°C and held for 30 minutes to remove water, then lowered to 25°C to pretreat the catalyst. Subsequently, 100 mL of the catalyst was bubbled through the catalyst. -1 The CO gas (CO 1%, O2 1%, N2 equilibrium) in STP has a space velocity (GHSV) of approximately 60,000 mL g. -1 h -1 The temperature was raised to 250℃ and held for 30 minutes. The concentrations of CO, CO2, and O2 at the outlet were continuously monitored using FTIR. The CO conversion rate was calculated as: X = (C0 – C) / C0 × 100%, and the highest CO conversion rate was recorded. After the experiment, the CO cylinder was shut off, and synthesis air was continuously purged for 5 minutes to ensure complete oxidation of residual CO. The furnace was then shut off and cooled to <40℃ under N2 protection.

[0029] The test results of this embodiment are shown in Table 1.

[0030] Table 1: Effects of red mud and tungsten-molybdenum smelting slag on the performance of the prepared carbon monoxide oxidation catalyst:

[0031] As shown in Table 1, when the mass ratio of red mud to tungsten-molybdenum smelting slag is less than 20:100 (e.g., in Table 1, the mass ratios of red mud to tungsten-molybdenum smelting slag are 15:100, 10:100, 5:100, and even lower ratios not listed in Table 1), the addition of less red mud results in insufficient reaction between the red mud and the tungsten-molybdenum smelting slag, leading to a significant decrease in the highest CO conversion rate as the mass ratio of red mud to tungsten-molybdenum smelting slag decreases. When the mass ratio of red mud to tungsten-molybdenum smelting slag is equal to 20~70:100 (e.g., in Table 1, the mass ratios of red mud to tungsten-molybdenum smelting slag are 20:100, 45:100, and 70:100), high-speed stirring of the mixture ensures sufficient contact between the two, forming a uniform preliminary mixed slag. Next, it is mixed with a strong inorganic acid. Under ultrasonic assistance, the acid penetrates into the internal pores of the mixed slag, undergoing acid-base neutralization and acidolysis reactions with the metal oxides and other components. This leaches some metal elements into the liquid phase and simultaneously disrupts the original structure of the raw materials, exposing more active sites. After settling, the supernatant is separated, yielding an acid-leached slag rich in undissolved solid particles. These particles retain some of the original material's structure and active components, while the acid leaching treatment creates more defects and active sites on their surface, providing a foundation for subsequent reactions. The acid-leached slag is then placed in a low-temperature plasma treatment device. High-energy particles in the plasma collide and interact with the surface of the acid-leached slag. Plasma treatment can cause structural distortion of some metal oxides on the surface of the acid-leached slag, forming unsaturated coordinated metal atoms. These atoms have stronger electron-donating or accepting abilities, thus facilitating subsequent chemical reactions with other substances. Microwave fields can cause polar molecules in acid leaching residues to move rapidly and generate frictional heat, leading to a rapid increase in the internal temperature of the material. This accelerates the diffusion and migration of components in the acid leaching residues, promotes coordination reactions between metal ions and surrounding ligands, and forms new compounds or complexes. Simultaneously, the thermal and non-thermal effects of microwaves may also trigger some local phase transitions and crystal transformations, making the material's structure more ordered or disordered, thereby altering its physicochemical properties and further enhancing its activity. Ultimately, the highest CO conversion rate was higher than 91%. When the mass ratio of red mud to tungsten-molybdenum smelting slag is greater than 70:100 (as shown in Table 1, the mass ratios of red mud to tungsten-molybdenum smelting slag are 75:100, 80:100, 85:100, and higher ratios not listed in Table 1), the excessively high mass ratio of red mud to tungsten-molybdenum smelting slag results in excessive red mud addition and an imbalance in the reaction between the red mud and tungsten-molybdenum smelting slag. Consequently, the highest CO conversion rate decreases significantly with further increases in the mass ratio of red mud to tungsten-molybdenum smelting slag. Therefore, considering both benefits and costs, a mass ratio of red mud to tungsten-molybdenum smelting slag of 20-70:100 is most conducive to improving the oxidation performance of the prepared catalyst for CO.

[0032] Example 2: Effect of inorganic strong acid and liquid-solid ratio of mixed slag on the performance of the prepared carbon monoxide oxidation catalyst.

[0033] Red mud and tungsten-molybdenum smelting slag were weighed at a mass ratio of 70:100 and placed in a high-speed mixer. The mixture was stirred at 1150 r / min for 45 minutes to ensure thorough and uniform mixing, yielding a preliminary mixed slag. This preliminary mixed slag was then mixed with a 6M inorganic strong acid, with liquid-to-solid ratios controlled at 0.15:1 (mL / g), 0.2:1 (mL / g), 0.25:1 (mL / g), 0.3:1 (mL / g), 0.45:1 (mL / g), 0.6:1 (mL / g), 0.65:1 (mL / g), 0.7:1 (mL / g), and 0.75:1 (mL / g). The inorganic strong acid was sulfuric acid. The mixture was ultrasonically stirred for 40 minutes in an ultrasonic cleaner at a frequency of 40 kHz. Afterward, the mixture was allowed to settle for 2 hours, and the supernatant was separated to obtain the acid-leached slag. The acid leaching residue was placed in a low-temperature plasma treatment device to obtain plasma-activated residue. The plasma voltage was 40kV, the power was 450W, the treatment time was 20 minutes, and the gas was oxygen. The plasma-activated residue was placed in a microwave reactor, and the microwave power was set to 500W for 15 minutes for microwave activation treatment to obtain microwave-activated plasma residue. Tricalcium phosphate and microwave-activated plasma residue were weighed and mixed at a mass ratio of 3:100 and stirred evenly to obtain calcium phosphate-doped activated residue. Ammonium sulfide ((NH4)2S) solution and calcium phosphate-doped activated residue were mixed at a liquid-to-solid ratio of 0.2:1 (mL / g) and stirred evenly to obtain calcium phosphate-doped activated residue, where the concentration of ammonium sulfide solution was 0.3mol / L. The calcium phosphate-doped activated residue was transferred to a hydrothermal reactor, and the hydrothermal temperature was set to 200℃ for 8 hours to obtain a hydrothermal composite material. The hydrothermal composite material was removed, allowed to cool naturally to room temperature, washed thoroughly with deionized water until neutral, and then separated by vacuum filtration. Next, the filter cake is placed in a molding device and pressed under a pressure of 20 MPa to obtain a catalyst preform with a certain shape and strength. The catalyst preform is placed in a tube furnace and subjected to pyrolysis carbonization treatment in an inert gas atmosphere to obtain a pyrolysis composite material, wherein the inert gas can be argon. The temperature is raised to 550℃ and held for 4 hours. After the pyrolysis carbonization is completed, the pyrolysis composite material is taken out and cooled to room temperature. Then, it is immersed in a silane coupling agent solution with a concentration of 1.5% (mass fraction) for 4 hours. The silane coupling agent is vinyltrimethoxysilane. The catalyst treated with the coupling agent is then placed back into the tube furnace and calcined in an air atmosphere to obtain a carbon monoxide oxidation catalyst. The calcination temperature is set at 650℃ and the calcination time is 4.5 hours.

[0034] The carbon monoxide oxidation test and the calculation of the highest CO conversion rate were the same as in Example 1. The test results of this example are shown in Table 2.

[0035] Table 2: Effect of inorganic strong acid and mixed slag liquid-solid ratio on the performance of the prepared carbon monoxide oxidation catalyst:

[0036] As shown in Table 2, when the ratio of inorganic strong acid to mixed slag liquid-solid is less than 0.3:1 (mL / g) (as shown in Table 2, when the ratio of inorganic strong acid to mixed slag liquid-solid is 0.25:1 (mL / g), 0.2:1 (mL / g), 0.15:1 (mL / g), and even lower ratios not listed in Table 2), less inorganic strong acid is added, and the reaction between inorganic strong acid and mixed slag is insufficient, resulting in a significant decrease in the highest CO conversion rate as the ratio of inorganic strong acid to mixed slag liquid-solid decreases. When the ratio of inorganic strong acid to the liquid-solid mixture of the slag is 0.3~0.6:1 (mL / g) (as shown in Table 2, where the ratios are 0.3:1 (mL / g), 0.45:1 (mL / g), and 0.6:1 (mL / g)), under ultrasonic assistance, the acid can penetrate into the internal pores of the slag, undergoing acid-base neutralization and acidolysis reactions with the metal oxides and other components. This leaches some metal elements into the liquid phase and simultaneously disrupts the original structure of the raw materials, exposing more active sites. After settling, the supernatant is separated, and the resulting acid-leached residue is rich in undissolved solid particles. These particles retain some of the original material's structure and active components, while the acid leaching treatment creates more defects and active sites on their surface, providing a foundation for subsequent reactions. When acid leaching residue is placed in a low-temperature plasma treatment device, high-energy particles in the plasma collide and interact with the surface of the residue. Plasma treatment can cause structural distortions in certain metal oxides on the surface of the residue, forming unsaturated coordinated metal atoms. These atoms have stronger electron-donating or accepting abilities, thus facilitating subsequent chemical reactions with other substances. Microwave energy causes rapid movement and frictional heating of polar molecules in the acid leaching residue, leading to a rapid increase in the internal temperature of the material. This accelerates the diffusion and migration of components in the residue, promoting coordination reactions between metal ions and surrounding ligands to form new compounds or complexes. Simultaneously, the thermal and non-thermal effects of microwaves may also trigger local phase transitions and crystal transformations, making the material's structure more ordered or disordered, thereby altering its physicochemical properties and further enhancing its activity. Ultimately, the highest CO conversion rate exceeded 93%. When the ratio of inorganic strong acid to mixed slag liquid-solid is greater than 0.6:1 (mL / g) (as shown in Table 2, where the ratios are 0.65:1 (mL / g), 0.7:1 (mL / g), 0.75:1 (mL / g), and higher ratios not listed in Table 2), excessive addition of inorganic strong acid leads to an imbalance in the reaction between the inorganic strong acid and the mixed slag. This results in a significant decrease in the maximum CO conversion rate as the ratio of inorganic strong acid to mixed slag liquid-solid further increases. Therefore, considering both efficiency and cost, a ratio of inorganic strong acid to mixed slag liquid-solid of 0.3–0.6:1 (mL / g) is most beneficial for improving the CO oxidation performance of the prepared catalyst.

[0037] Example 3: Effect of the mass ratio of tricalcium phosphate and microwave-activated plasma slag on the performance of the prepared carbon monoxide oxidation catalyst.

[0038] Red mud and tungsten-molybdenum smelting slag were weighed at a mass ratio of 70:100 and placed in a high-speed mixer. The mixture was stirred at 1500 r / min for 60 minutes to ensure thorough mixing and obtain a preliminary mixed slag. This preliminary mixed slag was then mixed with a 9M inorganic strong acid (nitric acid) at a liquid-to-solid ratio of 0.6:1 (mL / g). The mixture was ultrasonically stirred for 60 minutes at a frequency of 50 kHz in an ultrasonic cleaner. After settling for 3 hours, the supernatant was separated to obtain an acid-leached slag. This acid-leached slag was then placed in a low-temperature plasma treatment device to obtain a plasma-activated slag. The plasma voltage was 75 kV, the power was 800 W, the treatment time was 35 minutes, and the gas used was nitrogen. Finally, the plasma-activated slag was placed in a microwave reactor with a microwave power of 700 W and a microwave time of 25 minutes for microwave activation treatment to obtain a microwave-activated plasma slag. Tricalcium phosphate and microwave-activated plasma slag were weighed and mixed at mass ratios of 0.25:100, 0.5:100, 0.75:100, 1:100, 3:100, 5:100, 5.5:100, 6:100, and 6.5:100, respectively, and stirred evenly to obtain calcium phosphate-doped activated slag. Ammonium sulfide ((NH4)2S) solution and calcium phosphate-doped activated slag were mixed at a liquid-to-solid ratio of 0.3:1 (mL / g) and stirred evenly to obtain calcium phosphate-sulfurized activated slag, wherein the concentration of the ammonium sulfide solution was 0.5 mol / L. The calcium phosphate-sulfurized activated slag was transferred to a hydrothermal reactor, and the hydrothermal temperature was set to 250℃ for 12 hours to obtain a hydrothermal composite material. The hydrothermal composite material was removed, allowed to cool naturally to room temperature, washed thoroughly with deionized water until neutral, and then separated by vacuum filtration. Next, the filter cake is placed in a molding device and pressed under a pressure of 30 MPa to obtain a catalyst preform with a certain shape and strength. The catalyst preform is placed in a tube furnace and subjected to pyrolysis carbonization treatment in an inert gas atmosphere to obtain a pyrolysis composite material, wherein the inert gas can be argon. The temperature is raised to 700℃ and held for 6 hours. After the pyrolysis carbonization is completed, the pyrolysis composite material is taken out and cooled to room temperature. Then, it is immersed in a silane coupling agent solution with a concentration of 2.5% (mass fraction) for 6 hours. The silane coupling agent is a polyol titanate. The catalyst treated with the coupling agent is then placed back into the tube furnace and calcined in an air atmosphere to obtain a carbon monoxide oxidation catalyst. The calcination temperature is set at 800℃ and the calcination time is 6 hours.

[0039] The carbon monoxide oxidation test and the calculation of the highest CO conversion rate were the same as in Example 1. The test results of this example are shown in Table 3.

[0040] Table 3: Effect of the mass ratio of tricalcium phosphate and microwave-activated plasma slag on the performance of the prepared carbon monoxide oxidation catalyst:

[0041] As shown in Table 3, when the mass ratio of tricalcium phosphate to microwave-activated plasma slag is less than 1:100 (as shown in Table 3, when the liquid-to-solid ratio of inorganic strong acid to mixed slag is 0.75:100, 0.5:100, 0.25:100, and even lower ratios not listed in Table 3), the addition of tricalcium phosphate is insufficient, resulting in incomplete reaction between tricalcium phosphate and microwave-activated plasma slag. This leads to a significant decrease in the highest CO conversion rate as the mass ratio of tricalcium phosphate to microwave-activated plasma slag decreases. When the mass ratio of tricalcium phosphate to microwave-activated plasma slag is 1~5:100 (mL / g) (as shown in Table 3, when the mass ratio of tricalcium phosphate to microwave-activated plasma slag is 1:100, 3:100, and 5:100), tricalcium phosphate can react with metal ions in the acid leaching slag to generate phosphate compounds with specific structures and properties. These phosphate compounds can regulate the acidity and alkalinity of the catalyst, provide new active sites, and act as structure-directing agents, influencing the morphology and crystal structure of the products in subsequent hydrothermal reactions. The addition of ammonium sulfide solution introduces sulfide ions, which can react with metal ions in the acid leaching residue to form metal sulfides. Under hydrothermal conditions, the higher temperature and pressure alter the properties of water, making it an excellent solvent and reaction medium. Complex chemical reactions occur in the hydrothermal system involving acid leaching residue, tricalcium phosphate, and ammonium sulfide, including dissolution, recrystallization, coordination, and precipitation. Under high temperature and pressure, aluminum ions in the acid leaching residue react with phosphate ions to form compounds such as aluminum hydroxyphosphate. Ultimately, the highest CO conversion rate exceeds 95%. When the mass ratio of tricalcium phosphate to microwave-activated plasma slag is greater than 5:100 (as shown in Table 3, the mass ratios of tricalcium phosphate to microwave-activated plasma slag are 5.5:100, 6:100, 6.5:100, and higher ratios not listed in Table 3), excessive tricalcium phosphate is added, leading to an imbalance in the reaction between tricalcium phosphate and microwave-activated plasma slag. This results in a significant decrease in the highest CO conversion rate as the mass ratio of tricalcium phosphate to microwave-activated plasma slag further increases. Therefore, considering both benefits and costs, a mass ratio of tricalcium phosphate to microwave-activated plasma slag of 1~5:100 (mL / g) is most favorable for improving the oxidation performance of the prepared catalyst for CO.

[0042] Comparative example: The effect of different preparation processes on the performance of the prepared carbon monoxide oxidation catalyst.

[0043] The process of this invention is as follows: Red mud and tungsten-molybdenum smelting slag are weighed at a mass ratio of 20:100 and placed in a high-speed mixer. The mixture is stirred at 1500 r / min for 45 minutes to ensure thorough and uniform mixing, resulting in a preliminary mixed slag. This preliminary mixed slag is then mixed with a 9M inorganic strong acid, with a liquid-to-solid ratio controlled at 0.6:1 (mL / g). The inorganic strong acid is nitric acid. The mixture is ultrasonically stirred for 60 minutes in an ultrasonic cleaner at a frequency of 50 kHz. Afterward, it is allowed to settle for 3 hours, and the supernatant is separated to obtain an acid-leached slag. This acid-leached slag is then placed in a low-temperature plasma treatment device to obtain a plasma-activated slag. The plasma voltage is 75 kV, the power is 800 W, the treatment time is 35 minutes, and the gas used is nitrogen. The plasma-activated slag is then placed in a microwave reactor, with the microwave power set to 700 W and the microwave time set to 25 minutes for microwave activation treatment, resulting in a microwave-activated plasma slag. Tricalcium phosphate and the microwave-activated plasma slag are weighed and mixed at a mass ratio of 3:100 and stirred evenly to obtain a calcium phosphate-doped activated slag. Ammonium sulfide ((NH4)2S) solution and calcium phosphate-doped activated slag were mixed at a liquid-to-solid ratio of 0.3:1 (mL / g) and stirred until homogeneous to obtain calcium phosphate-doped activated slag, wherein the concentration of ammonium sulfide solution was 0.5 mol / L. The calcium phosphate-doped activated slag was transferred to a hydrothermal reactor, and the hydrothermal temperature was set to 250℃ for 12 hours to obtain a hydrothermal composite material. The hydrothermal composite material was removed, allowed to cool naturally to room temperature, and then thoroughly washed with deionized water until neutral, followed by filtration. The filter cake was then placed in a molding device and pressed under a pressure of 30 MPa to obtain a catalyst preform with a certain shape and strength. The catalyst preform was placed in a tube furnace and subjected to pyrolysis carbonization treatment in an inert gas atmosphere, wherein the inert gas could be argon, and the temperature was raised to 700℃ and held for 6 hours. After pyrolysis and carbonization are completed, the pyrolysis composite material is taken out and cooled to room temperature. It is then immersed in a silane coupling agent solution with a concentration of 2.5% (mass fraction) for 6 hours. The silane coupling agent is a zirconium aluminate coupling agent. The catalyst treated with the coupling agent is then placed back into a tube furnace and calcined in an air atmosphere to obtain a carbon monoxide oxidation catalyst. The calcination temperature is set at 800℃ and the calcination time is 6 hours.

[0044] Comparative Process 1: Red mud and tungsten-molybdenum smelting slag were weighed at a mass ratio of 20:100 and placed in a high-speed mixer. The mixture was stirred at 1500 r / min for 45 minutes to ensure thorough mixing and obtain a preliminary mixed slag. This preliminary mixed slag was then mixed with a 9M inorganic strong acid (nitric acid) at a liquid-to-solid ratio of 0.6:1 (mL / g). The mixture was ultrasonically stirred for 60 minutes at a frequency of 50 kHz in an ultrasonic cleaner. After settling for 3 hours, the supernatant was separated to obtain an acid-leached slag. This acid-leached slag was then placed in a low-temperature plasma treatment device to obtain a plasma-activated slag. The plasma voltage was 75 kV, the power was 800 W, the treatment time was 35 minutes, and the gas was nitrogen. The plasma-activated slag was then placed in a microwave reactor with a microwave power of 700 W and a microwave time of 25 minutes for microwave activation treatment to obtain a microwave-activated plasma slag. Tricalcium phosphate and the microwave-activated plasma slag were weighed and mixed at a mass ratio of 3:100 and stirred thoroughly to obtain a calcium phosphate-doped activated slag. Ammonium sulfide ((NH4)2S) solution and calcium phosphate-doped activated slag were mixed at a liquid-to-solid ratio of 0.3:1 (mL / g) and stirred until homogeneous to obtain calcium phosphate-doped activated slag, wherein the concentration of ammonium sulfide solution was 0.5 mol / L. The calcium phosphate-doped activated slag was transferred to a hydrothermal reactor, and the hydrothermal temperature was set to 250℃ for 12 hours to obtain a hydrothermal composite material. The hydrothermal composite material was removed, allowed to cool naturally to room temperature, and then thoroughly washed with deionized water until neutral, followed by filtration. The filter cake was then placed in a molding device and pressed under a pressure of 30 MPa to obtain a catalyst preform with a certain shape and strength. The catalyst preform was placed in a tube furnace and subjected to pyrolysis carbonization treatment in an inert gas atmosphere, wherein the inert gas could be argon, and the temperature was raised to 700℃ and held for 6 hours. After the pyrolysis and carbonization are completed, the pyrolysis composite material is taken out and put back into the tube furnace for calcination in air atmosphere to obtain a carbon monoxide oxidation catalyst. The calcination temperature is set at 800℃ and the calcination time is 6 hours.

[0045] Comparative Process 2: Red mud and tungsten-molybdenum smelting slag were weighed at a mass ratio of 20:100 and placed in a high-speed mixer. The mixture was stirred at 1500 r / min for 45 minutes to ensure thorough and uniform mixing, yielding a preliminary mixed slag. This preliminary mixed slag was then mixed with a 9M inorganic strong acid (nitric acid) at a liquid-to-solid ratio of 0.6:1 (mL / g). The mixture was ultrasonically stirred for 60 minutes at a frequency of 50 kHz in an ultrasonic cleaner. After settling for 3 hours, the supernatant was separated to obtain an acid-leached slag. This acid-leached slag was then placed in a low-temperature plasma treatment device to obtain plasma-activated slag. The plasma voltage was 75 kV, the power was 800 W, the treatment time was 35 minutes, and the gas used was nitrogen. Finally, the plasma-activated slag was placed in a microwave reactor with a microwave power of 700 W and a microwave time of 25 minutes for microwave activation treatment, yielding a microwave-activated plasma slag. Ammonium sulfide ((NH4)2S) solution and microwave-activated plasma slag were mixed at a liquid-to-solid ratio of 0.3:1 (mL / g) and stirred until homogeneous to obtain sulfur-doped activated slag, wherein the concentration of ammonium sulfide solution was 0.5 mol / L. The sulfur-doped activated slag was transferred to a hydrothermal reactor, and the hydrothermal temperature was set to 250℃ for 12 hours to obtain a hydrothermal composite material. The hydrothermal composite material was removed, allowed to cool naturally to room temperature, and then thoroughly washed with deionized water until neutral, followed by filtration. The filter cake was then placed in a molding device and pressed under a pressure of 30 MPa to obtain a catalyst preform with a specific shape and strength. The catalyst preform was placed in a tube furnace and subjected to pyrolysis carbonization treatment in an inert gas atmosphere (argon, for example) to obtain a pyrolysis composite material. The temperature was raised to 700℃ and held for 6 hours. After pyrolysis and carbonization are completed, the pyrolysis composite material is taken out and cooled to room temperature. It is then immersed in a silane coupling agent solution with a concentration of 2.5% (mass fraction) for 6 hours. The silane coupling agent is a zirconium aluminate coupling agent. The catalyst treated with the coupling agent is then placed back into a tube furnace and calcined in an air atmosphere to obtain a carbon monoxide oxidation catalyst. The calcination temperature is set at 800℃ and the calcination time is 6 hours.

[0046] The carbon monoxide oxidation test and the calculation of the highest CO conversion rate were the same as in Example 1. The results of this comparative test are shown in Table 4.

[0047] Table 4: Effect of different preparation processes on the performance of the prepared carbon monoxide oxidation catalyst:

[0048] As shown in Table 4, the carbon monoxide oxidation efficiency achieved by the catalyst prepared by the process of the present invention is significantly higher than that of comparative process 1 and comparative process 2, and is higher than the sum of the two.

Claims

1. A method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag, characterized in that, Includes the following steps: (1) Weigh out red mud and tungsten-molybdenum smelting slag separately, stir them evenly, and obtain a preliminary mixed slag; (2) Mix the preliminary mixed residue with an inorganic strong acid, stir with ultrasonic assistance, let stand, separate the supernatant, and obtain acid leaching residue; (3) The acid leaching residue is placed in a low-temperature plasma treatment device for low-temperature plasma activation treatment to obtain plasma activated residue; (4) Placing the plasma-activated slag in a microwave reactor and performing microwave activation treatment to obtain microwave-activated plasma slag; (5) Weigh and mix tricalcium phosphate and microwave-activated plasma slag separately, stir evenly to obtain calcium phosphate-doped activated slag; (6) Mix the ammonium sulfide solution and the phosphorus-calcium activated slag, stir evenly, and obtain the sulfur-phosphorus-calcium activated slag; (7) The sulfur-phosphorus-calcium activated slag is transferred to a hydrothermal reactor for hydrothermal reaction to obtain a hydrothermal composite material; (8) The hydrothermal composite material is pressed into a catalyst blank, and the catalyst blank is subjected to pyrolysis carbonization treatment in an inert gas atmosphere to obtain the pyrolysis composite material. (9) The pyrolysis composite material was soaked in a silane coupling agent solution and then calcined again to obtain a carbon monoxide oxidation catalyst.

2. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, The mass ratio of red mud to tungsten-molybdenum smelting slag in step (1) is 20~70:

100.

3. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, In step (2), the concentration of the inorganic strong acid is 3~9M, and the liquid-solid ratio of the inorganic strong acid to the preliminary mixed residue is (0.3~0.6):1 mL / g.

4. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, In step (2), the inorganic strong acid is any one of hydrochloric acid, sulfuric acid, and nitric acid.

5. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, In step (3), the plasma voltage is 5~75kV, the power is 100~800W, the processing time is 5~35 minutes, and the gas is any one of argon, oxygen, or nitrogen.

6. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, In step (5), the mass ratio of tricalcium phosphate to microwave-activated plasma slag is 1~5:

100.

7. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, In step (6), the liquid-solid ratio of ammonium sulfide solution and calcium phosphate activated slag is (0.1~0.3):1 mL / g, and the concentration of ammonium sulfide solution is 0.1~0.5 mol / L.

8. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, Step (9) The silane coupling agent is any one of γ-aminopropyltriethoxysilane, vinyltrimethoxysilane, polyol titanate, or zirconium aluminate coupling agent.

9. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, In step (9), the mass fraction of the silane coupling agent solution is 0.5% to 2.5%, and the soaking time is 2 to 6 hours.

10. The method for preparing a carbon monoxide oxidation catalyst using red mud and tungsten-molybdenum smelting slag according to claim 1, characterized in that, In step (9), the second roasting is carried out in an air atmosphere, with the roasting temperature set at 500~800℃ and the roasting time at 3~6 hours.

Images