Alkali-modified bimetallic composite catalyst, preparation method and application thereof
By combining alkali-modified bimetallic composite catalysts with low-temperature plasma technology, the problem of chlorine poisoning and deactivation of catalysts in regenerated non-ferrous metal smelting flue gas was solved, achieving efficient degradation of chlorobenzene and dioxins and improving the stability and degradation efficiency of the catalyst.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CENT SOUTH UNIV
- Filing Date
- 2026-01-30
- Publication Date
- 2026-06-16
Smart Images
Figure CN121607162B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of non-ferrous metal smelting flue gas treatment technology, specifically relating to an alkali-modified bimetallic composite catalyst, its preparation method, and its application. Background Technology
[0002] Recycled non-ferrous metal smelting, by reusing scrap metal resources, is of great significance in conserving mineral resources and reducing energy consumption. However, this green circular process is accompanied by complex environmental pollution problems, especially flue gas emissions. Due to the complexity of raw material sources and the large fluctuations in process conditions, the types and contents of pollutants in the flue gas of recycled non-ferrous metal smelting are extremely complex, among which chlorinated volatile organic pollutants (CVOCs) are one of the characteristic and highly harmful pollutants.
[0003] Under high-temperature smelting conditions of 800–1200℃, organic impurities in raw materials undergo pyrolysis and synthesis reactions with chlorine-containing substances, generating CVOCs represented by chlorobenzenes (such as monochlorobenzene and dichlorobenzene). These compounds are not only highly toxic and environmentally persistent, but more importantly, under specific process windows (such as the temperature range of 500–800℃, oxygen-deficient conditions, or insufficient flue gas residence time), they act as key precursors, synthesizing highly toxic dioxins (PCDD / Fs) through complex reaction pathways. Currently, Chinese standards have set strict limits (0.5 ng TEQ / m³) for dioxins and chlorobenzenes emitted by recycled non-ferrous metal enterprises. However, existing treatment technologies are insufficient in their degradation efficiency of chlorobenzene in flue gas, and their control effect on associated dioxin pollutants is also unsatisfactory.
[0004] In the end-of-pipe treatment of CVOCs, catalytic oxidation technology is considered one of the optimal choices due to its low energy consumption and high purification efficiency, with the core being the development of high-performance catalysts. Manganese-based catalysts have shown application potential in this field due to their excellent low-temperature oxidation activity. However, in the degradation of CVOCs such as chlorobenzene, a critical challenge is that the chlorine species produced in the reaction (such as Cl·, HCl, or metal chlorides) are strongly adsorbed and deposited on the active sites of the catalyst, leading to irreversible chlorine poisoning and deactivation, which severely restricts its long-term operational stability and degradation efficiency. How to systematically optimize the catalyst's resistance to chlorine poisoning, thereby simultaneously improving its catalytic activity and ensuring long-term operational stability, remains a key scientific problem that urgently needs to be solved. Furthermore, from a practical application perspective, the regeneration of non-ferrous metal smelting flue gas requires catalysts that not only efficiently degrade chlorobenzene but also possess the ability to synergistically degrade associated pollutants such as dioxins, the latter of which is often overlooked in existing research. Summary of the Invention
[0005] To address the technical problem of the urgent need for a catalyst with excellent resistance to chlorine poisoning and synergistic control of chlorobenzene and dioxin emissions in the aforementioned commonly used technologies, this invention provides a method for preparing an alkali-modified bimetallic composite catalyst, comprising the following steps:
[0006] The manganese source and the copper source are mixed in the first solvent to obtain the first bimetallic reagent;
[0007] The pseudoboehmite and sodium source are dispersed in a second solvent to obtain a second bimetallic reagent;
[0008] The first bimetallic reagent is mixed with the second bimetallic reagent to obtain a precursor reagent; the proportions of manganese and copper in the total mass of the manganese source, the copper source, the sodium source and the pseudoboehmite are 1%-10%; the molar ratio of sodium, manganese and copper in the precursor reagent is 2-8:2-6:1.
[0009] The precursor reagent was subjected to stirring, aging and calcination treatments in sequence to obtain the alkali-modified bimetallic composite catalyst.
[0010] Furthermore, the manganese source includes manganese acetate tetrahydrate, the copper source includes copper sulfate pentahydrate, and the sodium source includes sodium carbonate.
[0011] Furthermore, the stirring treatment temperature is 50-100℃, and the stirring treatment duration is 1-5h; the aging treatment temperature is 10-50℃, and the aging treatment duration is 10-20h; the calcination treatment temperature is 400-700℃, and the calcination treatment duration is 1-5h.
[0012] This invention provides an alkali-modified bimetallic composite catalyst prepared by any of the above preparation methods, which is applied to the treatment of flue gas from non-ferrous metal smelting.
[0013] The alkali-modified bimetallic composite catalyst exhibits a loose particulate aggregate structure with a rough surface and abundant pores. It consists of a pseudoboehmite support and metal elements supported thereon, including manganese, copper, and sodium. Manganese and copper are synergistically distributed on the surface of the support, while sodium ions form dispersed active sites on the surface of the support.
[0014] The alkali-modified bimetallic composite catalyst has a manganese and copper loading of 1%-10%; the molar ratio of sodium, manganese and copper is 2-8:2-6:1.
[0015] Furthermore, in the alkali-modified bimetallic composite catalyst, the content of weakly basic sites is not less than 1.0 mmol / g;
[0016] The surface of the alkali-modified bimetallic composite catalyst has an atomic percentage of oxygen of not less than 50%, an atomic percentage of copper of not less than 0.8%, and an atomic percentage of manganese of not less than 1.5%.
[0017] Furthermore, in the alkali-modified bimetallic composite catalyst, the molar ratio of sodium, manganese, and copper is 4-8:3-6:1.
[0018] Furthermore, the specific surface area of the alkali-modified bimetallic composite catalyst is 200-300 m². 2 / g, with an average pore size of 3.0-10.0 nm.
[0019] This invention provides an application of an alkali-modified bimetallic composite catalyst prepared by any of the above methods, or an alkali-modified bimetallic composite catalyst as described in any of the above methods, in the treatment of flue gas from non-ferrous metal smelting, comprising the following steps:
[0020] The smelting flue gas is contacted with the alkali-modified bimetallic composite catalyst after being enhanced by plasma; the smelting flue gas contains at least one of chlorobenzene and dioxin;
[0021] In the case where the smelting flue gas contains chlorobenzene, the concentration of chlorobenzene in the smelting flue gas is 50-800 ppm;
[0022] In the case where the smelting flue gas contains dioxins, the concentration of dioxins in the smelting flue gas shall not exceed 20 ng TEQ / m³. 3 .
[0023] Furthermore, the reaction space velocity in the smelting flue gas treatment process is 2000-15000 h⁻¹. -1 .
[0024] Furthermore, the flow rate of the smelting flue gas during the smelting flue gas treatment process is 0.5-10 L / min, and the relationship between the volume of the alkali-modified bimetallic composite catalyst and the volume of the smelting flue gas is 0.1-1 g: 10-500 L.
[0025] Compared with the prior art, the present invention has at least the following advantages:
[0026] This invention provides an alkali-modified bimetallic composite catalyst, which exhibits significant advantages in chlorine poisoning resistance and synergistic control of chlorobenzene and dioxins through the synergistic effect of manganese and copper bimetals and the directional modification of sodium.
[0027] The introduction of copper effectively inhibited manganese particle agglomeration, promoting the formation of smaller particle size and higher specific surface area in the catalyst, increasing surface active sites, as verified by BET test results. Meanwhile, Cu... 2+ / Cu+ With Mn 3+ / Mn 4+ A dynamic synergy exists between redox couples, maintaining the efficient cycle of the catalytic reaction. CuO x With MnO x A strong interaction occurs between them through Cu-O-Mn bridging bonds, prompting electrons to move from MnO... x To CuO x Migration promotes the formation of high-valence manganese species, thereby enhancing overall oxidation capacity.
[0028] The introduction of sodium enhances the effect through multiple mechanisms. Sodium ions form highly dispersed active sites on the surface, preferentially binding chlorine species to protect the manganese active center from chlorine poisoning and delay deactivation. Its electron-donating effect regulates the electronic structure of manganese, promoting its conversion to higher valence states (Mn). 4+ Sodium transforms and enhances catalytic oxidation efficiency. Furthermore, sodium promotes oxygen vacancy formation, increasing the concentration and mobility of surface reactive oxygen species, which contributes to the deep mineralization of pollutants such as chlorobenzene.
[0029] Sodium also optimizes the catalyst surface properties: on the one hand, it increases weakly basic sites, forming a multi-intensity distribution of basic centers, promoting the conversion of chlorine species into easily desorbable HCl or Cl2, and reducing chlorine accumulation; on the other hand, it restructures the distribution of acidic sites, moderately reducing weakly acidic sites and enhancing moderately strong acidic sites, thereby improving chlorine resistance while maintaining activity. Sodium is highly dispersed in the catalyst and does not form an independent crystalline phase, which facilitates its full reaction with chlorine to form NaCl, blocking the chlorine poisoning pathway. In summary, sodium modification synergistically improves the activity and stability of the catalyst in chlorobenzene degradation through multiple pathways, including enhancing basicity, regulating acidity, promoting the formation of high-valence manganese, protecting active centers, and improving oxygen migration.
[0030] In the treatment of flue gas from non-ferrous metal smelting, this alkali-modified bimetallic catalyst is coupled with low-temperature plasma technology to form a synergistic degradation system. Plasma-excited free radicals (such as ·OH and ·O) and ozone, along with active oxygen on the catalyst surface, preferentially break the C-Cl bond in chlorobenzene and initiate ring opening. The intermediate products are then deeply oxidized in the catalyst's abundant oxygen vacancies and acid-base site network, ultimately mineralizing into CO2 and H2O. This system not only efficiently degrades chlorobenzene but also exhibits good adsorption and degradation capabilities for dioxin-like pollutants, meeting the needs of synergistic control of multiple pollutants in complex smelting flue gas. Attached Figure Description
[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0032] Figure 1 The images show the morphological characteristics and surface element distribution of different alkali-modified catalysts in Example 1 of this invention, where (a) is a SEM image of Na-MnCuOx and (b) is a SEM image of CaO-MnCuOx.
[0033] Figure 2 The Mn element distribution diagram of Na-MnCuOx in Example 1 of this invention is shown.
[0034] Figure 3 The Cu element distribution diagram of Na-MnCuOx in Example 1 of this invention is shown.
[0035] Figure 4 The XRD patterns are of different alkali-modified catalysts in Example 1 of this invention.
[0036] Figure 5 This is a comparison chart of the chlorobenzene degradation efficiency of CaO-MnCuOx under different mass ratios in Example 3 of this invention.
[0037] Figure 6 This is a comparison chart of the chlorobenzene degradation efficiency of different catalysts in Example 3 of the present invention.
[0038] Figure 7 This is a comparison chart of the chlorobenzene degradation efficiency of different catalysts in Example 3 of the present invention.
[0039] Figure 8 This is a comparison chart of the chlorobenzene degradation efficiency of different catalysts in Example 3 of the present invention.
[0040] Figure 9 The stability test diagram of Na-MnCuOx under different space velocity conditions is shown in Example 4 of this invention.
[0041] Figure 10 This is a comparison chart of the catalytic degradation performance of Na-MnCuOx under different initial chlorobenzene concentrations in Example 5 of this invention.
[0042] Figure 11 To analyze the catalytic degradation performance of the MnCuOx catalyst in Example 5 of this invention under different initial concentrations of chlorobenzene.
[0043] Figure 12 The stability test diagram of Na-MnCuOx in Example 6 of this invention is shown.
[0044] Figure 13 (a) is the CO2-TPD diagram of the catalyst before and after sodium modification in Analytical Example 7 of the present invention; (b) is the CO2-TPD diagram of the Na-MnCuOx reaction before and after in Analytical Example 7 of the present invention.
[0045] Figure 14 (a) is the NH3-TPD diagram of the catalyst before and after alkali modification in Example 7 of the present invention, and (b) is the NH3-TPD diagram of the MnCuOx-PB reaction before and after in Example 7 of the present invention.
[0046] Figure 15 The XRD patterns before and after the MnCuOx-PB reaction in Example 7 of this invention are shown.
[0047] Figure 16 XPS plots showing the changes in surface elements before and after the MnCuOx-PB reaction in Example 7 of this invention.
[0048] Figure 17 XPS diagrams showing the surface elemental changes of the catalyst before and after sodium modification in Example 7 of the present invention; wherein, (a) is the Mn 2p spectrum before and after the Na-MnCuOx reaction in Example 7 of the present invention; (b) is the Mn 2p spectrum of MnCuOx and before the Na-MnCuOx reaction in Example 7 of the present invention.
[0049] Figure 18 The O2-TPD diagrams of the catalyst before and after modification in Example 7 of this invention are shown.
[0050] Figure 19 This is a GC-MS analysis diagram of the tail gas from the chlorobenzene degradation reaction in Example 8 of this invention. Detailed Implementation
[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0052] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.
[0053] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of the invention, may be implemented using any prior art methods, devices, and materials similar to or equivalent to the methods, devices, and materials in the embodiments of the present invention.
[0054] This invention provides an alkali-modified bimetallic composite catalyst for the treatment of flue gas from non-ferrous metal smelting.
[0055] The alkali-modified bimetallic composite catalyst exhibits a loose particulate aggregate structure with a rough surface and abundant pores. It is composed of a pseudoboehmite support and metal elements supported thereon, including manganese, copper, and sodium. Manganese and copper elements are synergistically distributed on the surface of the support, while sodium ions form dispersed active sites on the surface of the support.
[0056] In this invention, the loading of manganese and copper in the alkali-modified bimetallic composite catalyst is 1%-10%; the molar ratio of manganese to copper is 2-6:1.
[0057] In some embodiments of the present invention, the manganese and copper loadings in the alkali-modified bimetallic composite catalyst are 1%-5% or 2-5% or 3-5% or 1%-4% or 2%-4% or 1%-8% or 1%-7% or 2%-8% or 2%-7% or 2%-6% or 1%-6%.
[0058] In some embodiments, the molar ratio of manganese to copper can be 3-5:1, 3-6:1, 3.1-5:1, or 3.5-4.5:1. In some embodiments, the molar ratio of sodium, manganese, and copper in the alkali-modified bimetallic composite catalyst can be 2-8:2-6:1, 2-8:3-5:1, 2-8:3-6:1, 2-8:3.1-5:1, or 2-8:3.5-4.5:1.
[0059] In some other embodiments of the present invention, the molar ratio of sodium, manganese and copper can be 2-6:2-6:1 or 2-6:3-5:1 or 2-6:3-6:1 or 2-6:3.1-5:1 or 2-6:3.5-4.5:1.
[0060] It should be understood that in the alkali-modified bimetallic composite catalyst described in this invention, "manganese and copper loading" specifically refers to the percentage of the total mass of the active components manganese (Mn) and copper (Cu) relative to the total mass of the catalyst. For ease of description and to maintain a consistent calculation standard, the trace losses of manganese and copper sources and the boehmite support that may occur during the preparation process will be ignored in the following description. Accordingly, the manganese and copper loading is theoretically calculated using the following formula:
[0061] Manganese and copper loading (%) = (mass of manganese in manganese source + mass of copper in copper source) / (mass of manganese source + mass of copper source + mass of sodium source + mass of boehmite) × 100%.
[0062] This calculation method can clearly and precisely define the total content of active metals in the catalyst, making it easy for those skilled in the art to repeat and accurately understand.
[0063] In this invention, the content of weakly basic sites in the alkali-modified bimetallic composite catalyst is not less than 1.0 mmol / g; in some embodiments, the content of weakly basic sites in the alkali-modified bimetallic composite catalyst can be 1.0-2.0 mmol / g, 1.0-1.6 mmol / g, or 10-1.5 mmol / g.
[0064] In this invention, the oxidation state distribution of manganese in the alkali-modified bimetallic composite catalyst is as follows: Mn 4+ / Mn 3+ It can be 80%-90%.
[0065] In this invention, the atomic percentage of oxygen on the surface of the alkali-modified bimetallic composite catalyst can be no less than 50%; the atomic percentage of copper can be no less than 0.8%; and the atomic percentage of manganese can be no less than 1.5%.
[0066] For example, the atomic percentage of oxygen on the surface of the alkali-modified bimetallic composite catalyst can be 50-70% or 50-60%; for example, the atomic percentage of oxygen on the surface of the alkali-modified bimetallic composite catalyst can be 0.8-1.2%; for example, the atomic percentage of manganese on the surface of the alkali-modified bimetallic composite catalyst can be 1.5-2.0%.
[0067] In this invention, the specific surface area of the alkali-modified bimetallic composite catalyst can be 200-300 m². 2 / g, with an average pore size of 3.0-10.0 nm. In some embodiments, the specific surface area of the alkali-modified bimetallic composite catalyst provided by the present invention is 225-300 m² / g. 2 / g, with an average pore size of 6.0-7.5 nm; for example, the alkali-modified bimetallic composite catalyst provided by the present invention has a specific surface area of 225-280 m².2 / g; The average pore size of the alkali-modified bimetallic composite catalyst provided by this invention is 6.0-7.0 nm.
[0068] As another example, the alkali-modified bimetallic composite catalyst provided by the present invention has a specific surface area of 225-260 m². 2 / g.
[0069] This invention provides a method for preparing the alkali-modified bimetallic composite catalyst as described in any one of the above claims, comprising the following steps:
[0070] S1. Mix the manganese source and the copper source in the first solvent to obtain the first bimetallic reagent.
[0071] In this invention, the first solvent may include water, specifically deionized water.
[0072] In this invention, the mass-to-volume ratio of the manganese source, the copper source, and the first solvent can be 0.01-0.5 g / mL, such as 0.01-0.1 g / mL, 0.01-0.05 g / mL, or 0.01-0.03 g / mL.
[0073] In this invention, the manganese source includes manganese acetate tetrahydrate, and the copper source includes copper sulfate pentahydrate.
[0074] S2. Disperse boehmite and sodium source in a second solvent to obtain a second bimetallic reagent; the proportion of manganese and copper elements in the total mass of manganese source, copper source and boehmite is 1%-10%, and the molar ratio of sodium, manganese and copper elements is 2-8:2-6:1.
[0075] In this invention, the molar ratio of sodium, manganese and copper in the precursor reagent can be 2-8:3-5:1, 2-8:3-6:1, 2-8:3.1-5:1 or 2-8:3.5-4.5:1.
[0076] In other embodiments of the present invention, the molar ratio of sodium, manganese and copper in the precursor reagent can be 2-6:2-6:1 or 2-6:3-5:1 or 2-6:3-6:1 or 2-6:3.1-5:1 or 2-6:3.5-4.5:1.
[0077] In this invention, the sodium source includes sodium carbonate.
[0078] In this invention, the second solvent may include ethanol.
[0079] In this invention, the mass-to-volume ratio between boehmite and the second solvent can be 0.01-0.5 g / mL, such as 0.05-0.10 g / mL, 0.05-0.15 g / mL, or 0.01-0.15 g / mL.
[0080] S3. Mix the first bimetallic reagent with the second bimetallic reagent to obtain the precursor reagent;
[0081] S4. The precursor reagent is subjected to stirring, aging and calcination treatment in sequence to obtain the alkali-modified bimetallic composite catalyst.
[0082] In this invention, the temperature of the stirring treatment can be 50-100℃, such as 50-80℃, 50-90℃, or 60-90℃. The duration of the stirring treatment can be 1-5 hours, such as 1-3 hours or 3-5 hours.
[0083] In this invention, the aging treatment temperature can be 10-50℃, such as 10-30℃, 20-50℃, or 20-30℃. The aging treatment duration can be 10-20 hours, such as 10-15 hours.
[0084] In this invention, the calcination temperature can be 400-700℃, such as 400-600℃, 450-600℃, or 450-650℃. The calcination duration is 1-5 hours, such as 2-5 hours or 2-4 hours.
[0085] This invention also provides the application of the alkali-modified bimetallic composite catalyst prepared by any of the above-described methods in the treatment of flue gas from non-ferrous metal smelting, comprising the following steps:
[0086] The smelting flue gas is contacted with the alkali-modified bimetallic composite catalyst after being enhanced by plasma; the smelting flue gas contains at least one of chlorobenzene and dioxin;
[0087] In cases where the smelting flue gas contains chlorobenzene, the concentration of chlorobenzene in the smelting flue gas is 50-800 ppm; in some embodiments, the concentration of chlorobenzene in the smelting flue gas may be 100-800 ppm, 50-500 ppm, 100-600 ppm, or 50-600 ppm.
[0088] In the case where the smelting flue gas contains dioxins, the concentration of dioxins in the smelting flue gas shall not exceed 20 ng TEQ / m³. 3 In some embodiments, where the smelting flue gas contains dioxins, the concentration of dioxins in the smelting flue gas can be 1-20 ng TEQ / m³. 3Or 5-20ng TEQ / m 3 Or 10-20ng TEQ / m 3 Or 1-10ng TEQ / m 3 Or 5-15ng TEQ / m 3 .
[0089] In some embodiments, the sodium-modified alkali-modified bimetallic composite catalyst provided by the present invention has a dioxin degradation rate of not less than 99%.
[0090] It should be noted that low-temperature plasma combined with catalysis is a feasible method for VOCs emission reduction in flue gas, which can improve carbon dioxide selectivity and suppress the formation of reaction byproducts ozone and nitrogen oxides. Furthermore, compared to other forms of plasma, dielectric barrier discharge plasma can not only discharge at atmospheric pressure, reducing operational steps and avoiding pipeline corrosion, but also has advantages such as high average electron energy and high electron density. Moreover, due to the flexibility of reactor configuration, it is more suitable for combination with catalysts for gas degradation.
[0091] In this invention, the experimental apparatus used in the treatment of flue gas from non-ferrous metal smelting can consist of a gas distribution system, a chlorobenzene generation system, a reaction system, and a tail gas analysis system.
[0092] In some embodiments, the gas mixing system may consist of high-purity air (20% oxygen, the remainder nitrogen) and a mass flow meter, with the flow rate set to 1 L / min. The chlorobenzene generation system may consist of a syringe pump, a micro-syringe (500 μL), and a temperature control system. The micro-syringe injects the chlorobenzene solution at a constant rate, causing the chlorobenzene to rapidly vaporize at 120°C and be carried by air to the reaction system for further reaction. The reaction can occur in a self-made quartz tube reactor with an inner diameter of 8.1 cm. Suitable quartz wool is placed in the reaction tube, and a catalyst (0.1-0.3 g) is placed on top of the quartz wool. After the reaction, the tail gas is subjected to gas chromatography-mass spectrometry (GC-MS) to analyze incompletely degraded chlorobenzene and other reaction products.
[0093] In this invention, the plasma discharge voltage during the smelting flue gas treatment process is not lower than 16V. In some embodiments, the plasma discharge voltage during the smelting flue gas treatment process may be not lower than 18V. In some embodiments, the plasma discharge voltage during the smelting flue gas treatment process may be 16-24V, such as 18-24V or 18-22V.
[0094] In this invention, the reaction space velocity in the smelting flue gas treatment process can be 2000-15000 h⁻¹. -1In some embodiments, the reaction space velocity in the smelting flue gas treatment process can be 4000-12000 h⁻¹. -1 For example, 5000-12000 h -1 Or 6000-12000 h -1 .
[0095] In this invention, the flow rate of the smelting flue gas during the smelting flue gas treatment process can be 0.5-10 L / min, such as 0.5-8 L / min, 0.5-5 L / min, or 0.5-3 L / min.
[0096] In this invention, the relationship between the alkali-modified bimetallic composite catalyst and the volume of the smelting flue gas can be 0.1-1 g: 20-500 L.
[0097] To facilitate a further understanding of the present invention by those skilled in the art, the following examples are provided:
[0098] The reagents used in the embodiments and analytical examples of this invention are shown in Table 1.
[0099] Table 1 Main experimental reagents
[0100]
[0101] The names, specifications, and manufacturers of the instruments used in the embodiments and analysis examples of this invention are shown in Table 2.
[0102] Table 2 Main Experimental Instruments
[0103]
[0104] Example 1
[0105] Preparation of alkali-modified bimetallic composite catalysts.
[0106] An alkali-modified bimetallic composite catalyst (Na-MnCuOx) was prepared by impregnation. First, 0.1339 g of manganese acetate tetrahydrate (manganese source) and 0.0341 g of copper sulfate pentahydrate (copper source) were dissolved in 10 mL of deionized water to obtain the first bimetallic reagent. Then, 1.1412 g of boehmite and 0.042 g of sodium carbonate (sodium source) were added to 15 mL of ethanol to obtain the second bimetallic reagent. The first and second bimetallic reagents were mixed under stirring to obtain the precursor reagent. The obtained precursor reagent was stirred at 80 °C for 2 h, aged at room temperature for 12 h, dried at 100 °C for 12 h, and calcined in air at 550 °C for 3 h. The sample was passed through a 60-mesh sieve to obtain the Na-MnCuOx catalyst sample (manganese and copper loading approximately 3%, Na, Mn, and Cu molar ratio 5.8:4:1).
[0107] Comparative Example 1
[0108] Meanwhile, a catalyst without metal components was prepared using the same method as a comparison, referred to as Na-PB.
[0109] 1.1412 g of boehmite and 0.042 g of sodium carbonate (sodium source) were added to 15 mL of ethanol. After stirring at 80 °C for 2 h, the mixture was aged at room temperature for 12 h, dried at 100 °C for 12 h, and calcined in air at 550 °C for 3 h. The sample was then passed through a 60-mesh sieve to obtain the Na-PB sample.
[0110] Comparative Example 2
[0111] MnCuOx-PB was prepared by impregnation. First, 0.1339 g of manganese acetate tetrahydrate (manganese source) and 0.0341 g of copper sulfate pentahydrate (copper source) were dissolved in 10 mL of deionized water to obtain a first mixture. Then, 1.1412 g of boehmite was added to 15 mL of ethanol to obtain a second mixture. The first and second mixtures were mixed under stirring to obtain the precursor reagent. The obtained precursor reagent was stirred at 80 °C for 2 h, aged at room temperature for 12 h, dried at 100 °C for 12 h, and calcined in air at 550 °C for 3 h. The sample was passed through a 60-mesh sieve to obtain the MnCuOx-PB catalyst sample (manganese and copper loading approximately 3%, Mn:Cu molar ratio 4:1).
[0112] By adjusting the molar ratio of manganese in the manganese source to copper in the copper source to 3:1, while maintaining the same total molar amount as the bimetallic molar amount in MnCuOx-PB, and following the same preparation process as described above for MnCuOx-PB, a bimetallic composite catalyst Mn was obtained. 0.75 Cu 0.25 Ox:
[0113] Bimetallic composite catalyst Mn was prepared by impregnation method. 0.75 Cu 0.25 0x. First, 0.1255 g of manganese acetate tetrahydrate (manganese source) and 0.04275 g of copper sulfate pentahydrate (copper source) were dissolved in 10 mL of deionized water to obtain the first mixture; then, 1.1412 g of boehmite was added to 15 mL of ethanol to obtain the second mixture. The first and second mixtures were mixed under stirring to obtain the precursor reagent. The obtained precursor reagent was stirred at 80°C for 2 h, aged at room temperature for 12 h, dried at 100°C for 12 h, and calcined in air at 550°C for 3 h. The sample was passed through a 60-mesh sieve to obtain Mn. 0.75 Cu 0.25Ox (manganese and copper loading is about 3%, and the molar ratio of Mn to Cu is 3:1).
[0114] Comparative Example 3
[0115] Compared to Comparative Example 2, only the molar ratio of manganese in the manganese source to copper in the copper source was adjusted to 1:1. The total molar amount was the same as the bimetallic molar amount in MnCuOx-PB, and the other steps were the same as the preparation process of MnCuOx-PB, thus obtaining Mn 0.5 Cu 0.5 Ox:
[0116] Bimetallic composite catalyst Mn was prepared by impregnation method. 0.5 Cu 0.5 0x. First, 0.0837 g of manganese acetate tetrahydrate (manganese source) and 0.0854 g of copper sulfate pentahydrate (copper source) were dissolved in 10 mL of deionized water to obtain the first mixture. Then, 1.1412 g of boehmite was added to 15 mL of ethanol to obtain the second mixture. The first and second mixtures were mixed under stirring to obtain the precursor reagent. The obtained precursor reagent was stirred at 80 °C for 2 h, aged at room temperature for 12 h, dried at 100 °C for 12 h, and calcined in air at 550 °C for 3 h. The sample was passed through a 60-mesh sieve to obtain Mn. 0.5 Cu 0.5 Ox (manganese and copper loading is about 3%, and the molar ratio of Mn to Cu is 1:1).
[0117] Comparative Example 4
[0118] Compared to Comparative Example 2, only the molar ratio of manganese in the manganese source to copper in the copper source was adjusted to 9:1. The total molar amount was the same as the bimetallic molar amount in MnCuOx-PB, and the other steps were the same as the preparation process of MnCuOx-PB, thus obtaining Mn 0.9 Cu 0.1 Ox:
[0119] Mn was prepared by impregnation method 0.9 Cu 0.1 0x. First, 0.1506 g of manganese acetate tetrahydrate (manganese source) and 0.0170 g of copper sulfate pentahydrate (copper source) were dissolved in 10 mL of deionized water. Then, 1.1412 g of boehmite was added to 15 mL of ethanol, and the mixture was slowly poured in while stirring to obtain the precursor reagent. The obtained precursor reagent was stirred at 80°C for 2 h, aged at room temperature for 12 h, dried at 100°C for 12 h, and calcined in air at 550°C for 3 h. The sample was passed through a 60-mesh sieve to obtain Mn. 0.9 Cu 0.1 Ox (manganese and copper loading is about 3%, and the molar ratio of Mn to Cu is 9:1).
[0120] Comparative Example 5
[0121] Compared to Comparative Example 2, a manganese-cerium bimetallic catalyst (referred to as MnCeOx-PB, with a metal loading of approximately 3% and a Mn:Ce ratio of 4:1) was prepared by impregnation. First, 0.1057 g of manganese acetate tetrahydrate (manganese source) and 0.0468 g of cerium nitrate hexahydrate (cerium source) were dissolved in 10 mL of deionized water. Then, 1.1412 g of boehmite was added to 15 mL of ethanol, and the mixture was slowly poured in while stirring to obtain the precursor reagent. The obtained precursor reagent was stirred at 80 °C for 2 h, aged at room temperature for 12 h, dried at 100 °C for 12 h, and calcined in air at 550 °C for 3 h. The sample was passed through a 60-mesh sieve to obtain MnCeOx-PB.
[0122] Comparative Example 6
[0123] A manganese-aluminum composite catalyst (MnOx-PB, 3% manganese loading) with boehmite as the support was prepared by impregnation method. First, 0.1339 g of manganese acetate tetrahydrate was dissolved in a mixed solution of 15 mL ethanol and 10 mL deionized water. Then, 1.1412 g of boehmite was added to the solution under stirring. After stirring at 80 °C for 2 h, the mixture was aged at room temperature for 12 h, dried at 100 °C for 12 h, and calcined in air at 550 °C for 3 h. The sample was then passed through a 60-mesh sieve to obtain the MnOx-PB catalyst sample.
[0124] By simply changing the amount of manganese acetate tetrahydrate added to adjust the manganese loading, samples with manganese loadings of 1%, 10%, 15% and 20% were prepared as controls and labeled as MnOx-PB1, MnOx-PB10, MnOx-PB15 and MnOx-PB20, respectively.
[0125] By simply changing the type of aluminum support, replacing boehmite with commercial alumina, a catalyst (referred to as MnOx-Al2O3) using commercial alumina as the support was prepared.
[0126] Unsupported MnOx boehmite is abbreviated as PB.
[0127] Comparative Example 7
[0128] The MnCuOx-PB prepared in Comparative Example 2 was ball-milled with calcium oxide powder at different mass ratios (1:1, 2:1, 3:1, 4:1). The ball mill was set to a running speed of 200 rpm and a running time of 10 min. The resulting sample was denoted as CaO-MnCuOx.
[0129] It should be noted that the Na-MnCuOx described below are all derived from Example 1 of this invention;
[0130] The Na-PB described below are all derived from Comparative Example 1 of this invention;
[0131] The following MnCuOx-PB, Mn 0.75 Cu 0.25 All Ox values are derived from Comparative Example 2 of this invention;
[0132] The following Mn 0.5 Cu 0.5 All Ox were derived from Comparative Example 3 of this invention;
[0133] The following Mn 0.9 Cu 0.1 All Ox values are derived from Comparative Example 4 of this invention;
[0134] The MnCeOx-PB described below are all derived from Comparative Example 5 of this invention;
[0135] The MnOx-PB, MnOx-PB1, MnOx-PB10, MnOx-PB15, MnOx-PB20, MnOx-Al2O3, and PB described below are all derived from Comparative Example 6 of this invention.
[0136] Analysis example 1
[0137] The morphological characteristics and surface elemental distribution of different alkali-modified catalysts were analyzed by SEM-EDS, such as... Figure 1 As shown, (a) is the SEM image of Na-MnCuOx and (b) is the SEM image of CaO-MnCuOx. The modified catalyst samples all exhibit a loose particulate aggregate structure with a rough surface and abundant pores, which is conducive to the diffusion of reactant molecules and their contact with catalytic active sites.
[0138] like Figure 2 , Figure 3 The EDS spectrum of Na-MnCuOx is shown in the figure. Figure 2 This is a diagram showing the Mn elemental distribution in Na-MnCuOx. Figure 3 The image shows the Cu elemental distribution of Na-MnCuOx. EDS results (Table 3) indicate that sodium modification significantly increases the oxygen content on the catalyst surface, along with a marked increase in Mn and Cu contents, suggesting that more metal active sites may be exposed on the surface. Calcium modification also results in a high oxygen content, but a decrease in surface Mn and Cu contents, indicating that the addition of CaO may cover the exposed active sites.
[0139] Table 3 Elemental Analysis of EDS
[0140]
[0141] The phase structure of the catalyst was analyzed using XRD, such as... Figure 4 As shown, sodium does not form an independent crystalline phase. This state facilitates the contact between sodium ions and chloride ions to form NaCl, preventing chloride species from poisoning the metal components. Combined with EDS data, it can be seen that the dispersed sites formed by sodium ions on the catalyst surface can anchor active metal particles, preventing their migration and sintering under high-temperature reaction conditions, and maintaining the specific surface area and number of active sites of the catalyst.
[0142] The CaO-MnCuOx catalyst exhibited multiple sharp CaO diffraction peaks, indicating high crystallinity and significant alteration of the alumina support's crystal structure, suggesting that the ball milling process disrupted the original structure. The presence of a distinct new crystalline phase indicates that calcium oxide exists as an independent phase, potentially resisting chlorine poisoning through steric hindrance. However, this could also block catalyst pores or cover surface active sites, thereby reducing the catalyst's catalytic activity.
[0143] Analysis example 2
[0144] The changes in the pore structure of the catalyst were analyzed by N2 adsorption-desorption. As the Cu content increased, the specific surface area of the catalyst gradually decreased.
[0145] Table 4 lists the pore structure parameters of catalysts with different manganese-copper doping ratios. After introducing copper, the specific surface area of MnCuOx-PB is 235.9 m². 2 / g, compared to MnOx-PB (219.5 m 2 / g) and CuOx (215.2 m 2 The pore size ( / g) of the copper-to-manganese ratio catalyst was significantly improved, and the enhanced specific surface area provided more adsorption and catalytic reaction active sites, which is crucial for the degradation of chlorobenzene. The average pore size of MnCuOx-PB decreased from 8.1 nm to 6.2 nm compared to MnOx-PB, and was also the smallest among all manganese-copper ratio catalysts. This indicates that copper doping optimized the dispersion of the metal oxide on the boehmite support, forming a denser and more uniform mesoporous structure. The smaller pore size may enhance the confinement effect of chlorobenzene molecules within the pores, increasing residence time and reaction probability, and allowing for more efficient utilization of active species. Furthermore, the pore volume showed a small change (0.44 → 0.43 cm⁻¹). 3 The ( / g) test confirmed the maintenance of pore connectivity, providing a stable channel for reactant transport and product desorption.
[0146] Table 4 Catalyst pore structure parameters
[0147]
[0148] Analysis example 3
[0149] The reaction conditions were: plasma discharge voltage 18 V, simulated flue gas flow rate 1 L / min, initial chlorobenzene concentration 300 ppm, and initial dioxin concentration 10 ng TEQ / m³. 3 The degradation efficiency of the catalyst for chlorobenzene and dioxins was studied when the catalyst dosage was 0.2 g.
[0150] The MnCuOx bimetallic catalyst was compounded with CaO by ball milling, with the aim of utilizing the strong Cl- content of CaO. - The adsorption capacity alleviates the "chlorine poisoning" problem during the degradation of chlorobenzene. The catalytic activity of chlorobenzene at different mass ratios was compared, such as... Figure 5 As shown in the figure. Experimental results show that the degradation efficiency of chlorobenzene with different mass ratios of MnCuOx:CaO (1:1 to 4:1) did not significantly improve, and even decreased to varying degrees compared with the bimetallic catalyst. The speculated reason may be that physical ball milling may have resulted in CaO and MnCuOx only surface mixing, without forming a tight interfacial interaction, thus reducing the degradation efficiency of chlorobenzene by CaO. - The adsorption sites of Cl are spatially isolated from the catalytic active sites of MnCuOx. - CaO preferentially adsorbs onto the MnCuOx surface, failing to effectively alleviate "chlorine poisoning." Furthermore, the ball milling process may cause CaO to coat the MnCuOx nanoparticles, resulting in CaO covering the catalyst's active sites and thus reducing catalytic efficiency.
[0151] The degradation efficiency of chlorobenzene before and after sodium modification of the catalyst was compared, such as Figure 6 As shown in the figure, the performance of each catalyst in terms of chlorobenzene degradation efficiency is as follows: Na-MnCuOx-PB (99.5%) > MnCuOx-PB (93%) > Na-PB (89%) > MnOx-PB (85%) > PB (67%). Na-MnCuOx-PB showed a catalytic efficiency increase of approximately 6.5 percentage points compared to unmodified MnCuOx-PB, reaching a degradation rate close to 100%, indicating that sodium modification effectively enhanced the activity of the manganese-copper catalyst. Sodium-modified alumina support (Na-PB) alone could increase the degradation efficiency from 68% to 90%, approaching the performance of MnCuOx-PB, indicating that the alkalinity modification of the support has a crucial impact on the reaction. The results of Na-PB and Na-MnCuOx-PB show that the synergistic effect of the active metal and sodium modification increased the catalytic efficiency from 89% to 99.5%, indicating that the optimal catalytic system requires both a suitable alkaline environment and highly efficient redox active centers. In addition, as shown in Table 5, the catalyst also has a good decomposition effect on dioxins, with Na-MnCuOx-PB achieving a purification efficiency of up to 99.3% for dioxins in flue gas.
[0152] Sodium, as an alkali metal, can significantly increase the number and intensity of basic sites on the catalyst surface. During the reaction of chlorobenzene, these basic sites can neutralize chlorine-containing species such as HCl generated in the reaction, reducing poisoning to active metal sites and promoting the polarization of C-Cl bonds in chlorobenzene, thus lowering the activation energy required for their breakage. In addition, the presence of sodium may alter the surface energy of metal oxides, improving their thermal stability, reducing sintering under high-temperature reaction conditions, and can also donate electrons to manganese-copper oxides, promoting the redox cycle of Mn and Cu and enhancing catalytic activity.
[0153] like Figure 7 As shown, the degradation efficiency of chlorobenzene increased from 85% to 93% after the addition of copper. This is attributed to the strong electronic synergistic effect of the Cu-Mn bimetallic compound: the introduction of copper altered the electronic structure of manganese oxide, enhanced the oxygen activity on the catalyst surface, and the copper ions (Cu... 2+ / Cu + ) and manganese ions (Mn 4+ / Mn 3+ Electron transfer between the two accelerated the catalytic cycle, thereby promoting the catalytic degradation of chlorobenzene. However, the addition of cerium actually reduced the catalytic degradation efficiency of chlorobenzene from 85% to 80%. This is presumably because there was no strong interaction between cerium oxide and manganese oxide, and the addition of cerium actually reduced the dispersion of manganese oxide.
[0154] like Figure 8 As shown, copper doping improved the degradation efficiency of chlorobenzene by varying degrees compared to the single-metal catalyst, further verifying that the introduction of copper enhanced the catalytic activity of the catalyst for chlorobenzene. The degradation efficiency of the manganese-copper bimetallic catalyst for chlorobenzene showed a trend of first increasing and then decreasing with increasing copper content. 0.9 Cu 0.1 Although the catalytic activity of Ox on chlorobenzene was improved compared to MnOx-PB, the increase was small, only from 85% to 87%. Further increasing the copper content, when Mn:Cu = 4:1, the degradation efficiency of MnCuOx-PB on chlorobenzene reached 93%. However, further increasing the copper content led to a decrease in the degradation efficiency. When Mn:Cu = 1:1, the degradation efficiency of MnCuOx-PB decreased. 0.5 Cu 0.5 The degradation efficiency of chlorobenzene by Ox decreased to 83%. This indicates that the appropriate introduction of copper can promote the degradation activity of chlorobenzene by the catalyst.
[0155] Table 5. Degradation efficiency of catalysts for dioxins
[0156]
[0157] Analysis example 4
[0158] The reaction conditions were: plasma discharge voltage 18 V, simulated flue gas flow rate 1 L / min, initial chlorobenzene concentration 300 ppm, and initial dioxin concentration 10 ng TEQ / m³. 3 The stability of Na-MnCuOx under chlorobenzene catalytic degradation was tested for 2.5 h under different space velocity conditions by varying the amount of catalyst used to change the reaction space velocity. Figure 9 As shown, the Na-MnCuOx catalyst exhibits excellent catalytic stability under three different space velocity conditions. Throughout the 2.5 h test, even at higher space velocities (12000 h), the catalytic stability remained stable. -1 Under these conditions, the catalyst's degradation efficiency for chlorobenzene still exceeds 95%, indicating its good resistance to chlorine poisoning and catalytic stability. Changes in the space velocity do not significantly affect the overall catalytic ability of chlorobenzene; at this point, the space velocity has almost no impact on the chlorobenzene degradation reaction. A smaller amount of catalyst is needed to achieve higher degradation efficiency, significantly saving costs.
[0159] It is worth noting that at a maximum airspeed of 12,000 h / h -1 Under these conditions, the catalyst exhibited the most stable activity, with an initial conversion of approximately 97%, which remained between 96-99.5% throughout the test, showing relatively small fluctuations. Compared to the other two space velocity conditions, the stability of the catalyst performance at high space velocities indicates that the Na-MnCuOx catalyst possesses excellent resistance to diffusion confinement and high utilization of active sites. Furthermore, at a space velocity of 4000 h⁻¹, the catalyst showed... -1 Under these conditions, the catalyst achieves a maximum decomposition efficiency of 100% for chlorobenzene.
[0160] Analysis example 5
[0161] The reaction conditions were: plasma discharge voltage 18 V, simulated flue gas flow rate 1 L / min, and initial dioxin concentration 10 ng TEQ / m³. 3 With a catalyst dosage of 0.2 g, the initial chlorobenzene concentration was varied from 150 to 600 ppm by changing the injection rate of the syringe pump. The reaction gas flow rate (20% oxygen, the remainder nitrogen) was maintained at 1 L / min, and the catalyst dosage was 0.2 g. The catalytic degradation performance of Na-MnCuOx under three different initial chlorobenzene concentrations was investigated, with a reaction time of 2.5 h. Figure 10 As shown; in comparison, the catalytic degradation performance of the MnCuOx catalyst under different initial chlorobenzene concentrations is as follows: Figure 11 As shown.
[0162] It is evident that the Na-MnCuOx catalyst exhibits high catalytic activity and good stability for chlorobenzene at different concentrations. Although the catalytic activity decreases somewhat with increasing initial chlorobenzene concentration, the conversion efficiency remains above 90% even at the highest concentration (600 ppm) throughout the reaction. This indicates that sodium modification enhances the degradation capacity of the bimetallic catalyst for higher concentrations of chlorobenzene, suggesting a preliminary resistance to chlorine poisoning. Simultaneously, the catalyst also achieves a dioxin purification efficiency of 99.3% under these conditions.
[0163] At 150 ppm, Na-MnCuOx exhibited optimal performance, achieving a high conversion rate of approximately 100% from the initial reaction stage and remaining stable with minimal fluctuations throughout the 2.5 h reaction period. When the concentration increased to 300 ppm, the initial catalyst activity (approximately 95%) decreased compared to 150 ppm, but the activity rapidly increased with the reaction proceeding and reached a stable state of around 97-100% after approximately 0.75 h. At 600 ppm, the initial activity of the Na-MnCuOx catalyst decreased significantly to approximately 91%, likely due to the competitive occupancy of active sites by high-concentration chlorobenzene and the rapid accumulation of chlorine species in the early stages of the reaction. However, the conversion rate rapidly increased with the reaction proceeding, reaching nearly 97% after approximately 0.75 h. This process indicates a brief activation period for the catalyst, presumably due to the rapid saturation of active sites on the catalyst surface caused by high-concentration chlorobenzene and the resulting competitive adsorption.
[0164] Analysis example 6
[0165] The fixed reaction conditions were: initial chlorobenzene concentration of 450 ppm, reaction gas flow rate (20% oxygen, the remainder nitrogen) of 1 L / min, catalyst dosage of 0.2 g, and reaction space velocity of 6000 h⁻¹. -1 The stability of the sodium-modified bimetallic catalyst for the catalytic combustion of chlorobenzene was investigated at a discharge voltage of 18 V. Figure 12 As shown in the figure, the bimetallic catalyst, after sodium modification, still exhibits excellent stability after 5.5 hours, with the chlorobenzene degradation efficiency remaining at around 95%. This also verifies that the catalyst was not poisoned or deactivated during the reaction and can continue to function. Simultaneously, the plasma continuously provides high-energy electrons and active free radicals, which synergistically work with the catalyst to maintain a high degradation efficiency.
[0166] Analysis example 7
[0167] Analysis of the mechanism by which sodium-modified catalysts resist chlorine poisoning.
[0168] Basicity site analysis: CO2-TPD was used to analyze the changes in basicity sites on the catalyst surface before and after sodium modification, such as... Figure 13 As shown in (a). Sodium content remained at only 200 before and after modification. o The CO2 desorption peaks within the C-base region all correspond to weakly basic sites. Before sodium modification, the content of weakly basic sites in MnCuOx was 0.34 mmol / g. After sodium introduction, the content of weakly basic sites in Na-MnCuOx increased to 1.36 mmol / g. Sodium increased the content of weakly basic sites on the catalyst surface, and as an electron donor, it created basic centers capable of strongly adsorbing acidic CO2 molecules. Furthermore, the CO2 desorption peak of the sodium-modified catalyst extended from approximately 50℃ to 250℃, exhibiting a wider temperature distribution, indicating the formation of basic sites of varying strengths on the catalyst surface. The increased basic sites can convert acidic chlorine species generated during the reaction into easily desorbable HCl or Cl2 through acid-base neutralization and oxidation reactions, reducing Cl accumulation on the surface and thus preventing catalyst deactivation due to chlorine poisoning.
[0169] The CO2-TPD spectra before and after the Na-MnCuOx reaction were compared, such as... Figure 13 As shown in (b), the content of weak bases after the reaction decreased from 1.36 mmol / g to 0.41 mmol / g compared to before the reaction, which once again demonstrates the important role of basic sites on the catalyst surface in the degradation of chlorobenzene.
[0170] Acidic site analysis: The NH3-TPD spectra of the catalyst before and after alkali modification were analyzed by examining changes in acidic sites, such as... Figure 14 As shown in (a); the NH3-TPD spectra before and after the MnCuOx-PB reaction were also analyzed, as shown in (a). Figure 14As shown in (b), the MnCuOx-PB exhibits a distinct low-temperature peak at 130°C, with a content of 7.21 mmol / g. After the addition of sodium, the Na-MnCuOx sample shows multiple distinct desorption peaks at 130°C, 330°C, and 440°C, corresponding to weak acid sites, moderate acid sites, and strong acid sites, respectively, with contents of 5.73 mmol / g, 0.18 mmol / g, and 0.28 mmol / g. This indicates that sodium modification alters the type and distribution of acidic sites in the catalyst, reducing the number of weak acid sites but increasing the content of moderate and strong acids. The new acidic sites may be new active centers formed by the interaction between sodium and Mn and Cu. These newly formed sites can provide alternative adsorption sites, maintaining catalytic activity under chlorine poisoning conditions. Sodium modification, by redistributing acidic sites, retains some weak acid sites to maintain high catalytic activity while creating new moderate and strong acid sites to enhance chlorine resistance. The CaO-MnCuOx only has a very weak desorption peak at 130°C, and the weak acid content is 0.23 mmol / g. This indicates that calcium oxide neutralizes most of the acidic sites, thereby achieving anti-chlorine poisoning by greatly reducing the number of acidic sites. However, it also reduces the catalytically active sites, which has an adverse effect on the degradation of chlorobenzene.
[0171] Crystal structure analysis: XRD was used to analyze the phase structure before and after the catalyst reaction, such as... Figure 15 As shown, the catalyst structure remains stable during the chlorobenzene degradation reaction, and the addition of sodium mainly affects the surface properties of the support without altering the catalyst's crystal structure. Sodium does not form an independent crystalline phase, a state that facilitates the contact between sodium ions and chloride ions to form NaCl, preventing the poisoning of metal components by chloride species. Furthermore, the dispersed sites formed by sodium ions on the catalyst surface anchor active metal particles, preventing their migration and sintering under high-temperature reaction conditions, thus maintaining the catalyst's specific surface area and the number of active sites, thereby improving the catalyst's stability in degrading chlorobenzene.
[0172] Surface chloride analysis: XPS was used to analyze the changes in surface elements of Na-MnCuOx before and after the reaction, such as... Figure 16 As shown in Table 6, the characteristic peak of Na-MnCuOx at 197 eV, attributed to Cl 2p, was extremely low after the reaction. Compared with before modification, the proportion of chlorine on the catalyst surface decreased from 3.91% to 0.59% (Table 6), indicating that the amount of chlorine deposited was extremely small, which is consistent with the catalyst stability data. This further proves that sodium modification improves the catalyst's resistance to chlorine poisoning.
[0173] Table 6. Surface chlorine ratio before and after alkali modification and before and after catalyst reaction
[0174]
[0175] Surface elemental valence state analysis: XPS was used to analyze the surface elements of the catalyst before and after sodium modification, such as... Figure 17 As shown. The XPS spectra of Mn 2p before and after sodium addition were compared. 3 / 2 Region (640-644 eV) and Mn 2p 1 / 2 The peak shape variations in the region (650-660 eV) all confirmed the presence of Mn. 4+ The relative content of Mn increased significantly after sodium modification. 4+ / Mn 3+ The increase in the ratio to 85.40% indicates that the oxidation degree of the catalyst surface is improved, the manganese valence state distribution is more diversified, and a richer number of catalytic active sites may be formed.
[0176] Sodium, as an alkali metal, has low electronegativity and a strong electron-donating ability. When sodium ions are incorporated into a catalyst, they transfer electrons to oxygen atoms, creating an electron transfer effect with manganese through an oxygen bridge. This promotes the oxidation of manganese, causing it to change from its lower valence state (Mn) to a higher valence state. 2+ ) transformed into Mn 4+ The dominant high-valence manganese ions (Mn) 3+ and Mn 4+ ).
[0177] This electronic effect can be expressed as the following electronic balance: Na + +Mn 2+ → Na + +(O 2- ) → Mn 3+ / Mn 4+ High-valent manganese can more effectively activate oxygen molecules and promote the activity of oxygen on the catalyst surface. When byproduct chloride species come into contact with the catalyst surface, high-valent manganese (Mn)... 4+ It can rapidly convert it into chloride ions, which are then captured by sodium. In addition, sodium modification increases Mn. 4+ / Mn 3+ The proportion was increased from 60% (before sodium modification, i.e., MnCuOx-PB) to 85% (after sodium modification, i.e., Na-MnCuOx), promoting the formation of oxygen vacancies on the catalyst surface. These vacancies serve as new active centers for adsorbing and activating oxygen molecules, enhancing the catalyst's oxidation capacity while also acting as adsorption sites for chlorine. The synergistic effect of sodium ions and high-valence manganese enables the sodium-modified manganese-copper catalyst to exhibit excellent resistance to chlorine poisoning while maintaining good catalytic activity.
[0178] Oxygen vacancy analysis: O2-TPD was used to analyze the changes in oxygen vacancies in the catalyst before and after sodium modification, such as... Figure 18As shown, after sodium modification, the catalyst exhibited a distinct desorption peak at 340°C, corresponding to surface-adsorbed oxygen. The desorption intensity was significantly higher than before modification, indicating a substantial increase in the number of active oxygen species. This suggests that the introduction of sodium altered the adsorption state and desorption energy barrier of oxygen species on the catalyst surface. Sodium modification enhanced the oxygen migration capacity within the catalyst, facilitating the oxidation and removal of adsorbed chlorine species through the formation of volatile chlorine oxides. The sodium-modified catalyst showed a more concentrated distribution of active oxygen species, particularly in the high-temperature region (300-400°C), indicating the formation of specific high-binding-energy oxygen species beneficial to catalytic activity.
[0179] Analysis example 8
[0180] Analysis of decomposition products: GC-MS analysis was performed on the tail gas from the chlorobenzene degradation reaction after the MnCuOx-PB reaction, such as... Figure 19 As shown, apart from undegraded chlorobenzene (peak time 4.3 min), almost no other reaction byproducts appeared in the reaction tail gas, further demonstrating that sodium modification improved the catalyst's resistance to chlorine poisoning while maintaining high catalytic activity.
[0181] The above technical solutions of the present invention are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made under the technical concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included in the patent protection scope of the present invention.
Claims
1. A method for preparing an alkali-modified bimetallic composite catalyst, characterized in that, Including the following steps: The manganese source and the copper source are mixed in the first solvent to obtain the first bimetallic reagent; The pseudoboehmite and a sodium source are dispersed in a second solvent to obtain a second bimetallic reagent; the sodium source includes sodium carbonate. The first bimetallic reagent is mixed with the second bimetallic reagent to obtain a precursor reagent; the proportions of manganese and copper in the total mass of the manganese source, the copper source, the sodium source and the pseudoboehmite are 1%-10%; the molar ratio of sodium, manganese and copper in the precursor reagent is 2-8:2-6:
1. The precursor reagent was subjected to stirring, aging and calcination treatments in sequence to obtain the alkali-modified bimetallic composite catalyst.
2. The method for preparing the alkali-modified bimetallic composite catalyst according to claim 1, characterized in that, The manganese source includes manganese acetate tetrahydrate, and the copper source includes copper sulfate pentahydrate.
3. The method for preparing the alkali-modified bimetallic composite catalyst according to claim 1, characterized in that, The stirring treatment is performed at a temperature of 50-100℃ for 1-5 hours; the aging treatment is performed at a temperature of 10-50℃ for 10-20 hours; and the calcination treatment is performed at a temperature of 400-700℃ for 1-5 hours.
4. An alkali-modified bimetallic composite catalyst prepared by the preparation method according to any one of claims 1-3, characterized in that, Applications include the treatment of flue gas from non-ferrous metal smelting. The alkali-modified bimetallic composite catalyst exhibits a loose particulate aggregate structure with a rough surface and abundant pores. It is composed of a pseudoboehmite support and metal elements supported thereon, including manganese, copper, and sodium. Manganese and copper elements are synergistically distributed on the surface of the support, and sodium ions form dispersed active sites on the surface of the support. The alkali-modified bimetallic composite catalyst has a manganese and copper loading of 1%-10%; the molar ratio of sodium, manganese and copper is 2-8:2-6:
1. Wherein, the manganese and copper loading amount = (mass of manganese element in manganese source + mass of copper element in copper source) / (mass of manganese source + mass of copper source + mass of sodium source + mass of boehmite) × 100%.
5. The alkali-modified bimetallic composite catalyst according to claim 4, characterized in that, In the alkali-modified bimetallic composite catalyst, the content of weakly basic sites is not less than 1.0 mmol / g; The surface of the alkali-modified bimetallic composite catalyst has an atomic percentage of oxygen of not less than 50%, an atomic percentage of copper of not less than 0.8%, and an atomic percentage of manganese of not less than 1.5%.
6. The alkali-modified bimetallic composite catalyst according to claim 4, characterized in that, In the alkali-modified bimetallic composite catalyst, the molar ratio of sodium, manganese, and copper is 4-8:3-6:
1.
7. The alkali-modified bimetallic composite catalyst according to claim 4, characterized in that, The alkali-modified bimetallic composite catalyst has a specific surface area of 200-300 m². 2 / g, with an average pore size of 3.0-10.0 nm.
8. The application of an alkali-modified bimetallic composite catalyst prepared by the preparation method according to any one of claims 1-3 or the alkali-modified bimetallic composite catalyst according to any one of claims 4-7 in the treatment of flue gas from non-ferrous metal smelting, characterized in that, Including the following steps: The smelting flue gas is contacted with the alkali-modified bimetallic composite catalyst after being enhanced by plasma; the smelting flue gas contains at least one of chlorobenzene and dioxin; In the case where the smelting flue gas contains chlorobenzene, the concentration of chlorobenzene in the smelting flue gas is 50-800 ppm; In the case where the smelting flue gas contains dioxins, the concentration of dioxins in the smelting flue gas shall not exceed 20 ngTEQ / m³. 3 .
9. The application of the alkali-modified bimetallic composite catalyst according to claim 8 in the treatment of flue gas from non-ferrous metal smelting, characterized in that, The reaction space velocity in the smelting flue gas treatment process is 2000-15000 h⁻¹ -1 .
10. The application of the alkali-modified bimetallic composite catalyst according to claim 8 in the treatment of flue gas from non-ferrous metal smelting, characterized in that, The flow rate of the smelting flue gas during the smelting flue gas treatment process is 0.5-10 L / min, and the relationship between the volume of the alkali-modified bimetallic composite catalyst and the volume of the smelting flue gas is 0.1-1 g: 10-500 L.