Nitrogen-doped supported manganese layered double hydroxide and preparation and application thereof

Abstract

The present application relates to methyl mercaptan waste gas treatment technical field, specifically to a kind of nitrogen-doped supported manganese layered double hydroxide and its preparation and application.The present application provides a kind of preparation method of nitrogen-doped supported manganese layered double hydroxide, comprising: layered double hydroxide is mixed with manganese salt in water ultrasonic to obtain mixed solution, then melamine and water are added in mixed solution again ultrasonic to obtain precursor, and the precursor is calcined to obtain nitrogen-doped supported manganese layered double hydroxide.Nitrogen-doped supported manganese layered double hydroxide has nitrogen and manganese double active sites, and has good ozone catalytic oxidation treatment effect on methyl mercaptan.

Description

Technical Field

[0001] This invention relates to the field of methanethiol waste gas treatment technology, specifically to a nitrogen-doped supported manganese layered double hydroxide and its preparation and application. Background Technology

[0002] Methanethiol (CH3SH) is a sulfur-containing volatile organic pollutant with a strong, rotten vegetable odor and an extremely low odor threshold of only 0.0021 ppm. Methanethiol is widely found in environments such as the petroleum industry, wastewater treatment plants, and sanitary landfills, with concentrations ranging from tens to hundreds of ppm. High concentrations of methanethiol are not only toxic to the human nervous system but can also lead to acid rain, equipment corrosion, and catalyst deactivation in the chemical industry. With my country's increasing emphasis on environmental protection, strengthening the treatment and prevention of methanethiol exhaust gas has become a top priority. Therefore, researching and developing efficient technologies for treating methanethiol waste gas / flue gas is of significant practical importance.

[0003] Currently, methods for removing methanethiol mainly include adsorption, chemical absorption, biological methods, and catalytic decomposition. Among these, catalytic decomposition is considered the most suitable method due to its high conversion efficiency, low cost, and ability to convert polluting methanethiol into valuable chemical products (such as CH4 and CO). In recent years, cerium-based catalysts, noble metal catalysts, molecular sieves, and their modified catalysts have been frequently used for the catalytic decomposition of methanethiol.

[0004] Although existing catalysts have shown some effectiveness in the catalytic decomposition of methanethiol, they still face the following problems: 1) High ozone consumption: During the catalytic decomposition process, high ozone consumption not only increases operating costs but may also lead to the formation of byproducts, affecting the purity and quality of the final product. 2) Large catalyst dosage: To achieve the ideal catalytic effect, existing catalysts often require a large dosage, which not only increases processing costs but may also lead to difficulties in catalyst recovery and reuse, further increasing the environmental burden. 3) Cost issues: Although precious metal catalysts have high catalytic efficiency, their cost is high, and the difficulty in recovering precious metals increases environmental safety costs. 4) Carbon deposition and deactivation.

[0005] Therefore, developing a novel catalyst that is simple to prepare, has higher activity, lower energy consumption, lower ozone depletion, and requires less catalyst dosage is a key issue that urgently needs to be addressed in the field of methanethiol tail gas treatment. This will help improve the removal efficiency of methanethiol, reduce treatment costs, and promote the development of environmental protection technologies. Summary of the Invention

[0006] This invention provides a nitrogen-doped supported manganese layered double hydroxide, its preparation, and its application. The nitrogen-doped supported manganese layered double hydroxide can be used as a catalyst for methanethiol treatment. During application, it exhibits high activity, achieving a methanethiol conversion efficiency of only 95% with an O3 / CH3SH molar ratio of only 0.8, and requiring a dosage of only 0.1 g / L. Furthermore, after 4 hours of continuous use, the methanethiol conversion efficiency of the nitrogen-doped supported manganese layered double hydroxide remains above 90%, demonstrating its low performance degradation and high stability.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing nitrogen-doped loaded manganese layered double hydroxides, comprising: ultrasonically mixing the layered double hydroxides and manganese salts in water to obtain a mixed solution; subsequently adding melamine and water to the mixed solution and ultrasonically mixing again to obtain a precursor; and calcining the precursor to obtain nitrogen-doped loaded manganese layered double hydroxides.

[0009] This application utilizes the hydrophobic properties of layered double hydroxides, first mixing them with manganese salts in an aqueous solution. During this process, the manganese salt solution is encapsulated within the layered structure of the double hydroxides. Melamine is then added; however, because the manganese salt solution is encapsulated by the layered structure, the melamine cannot directly contact the manganese salt. Finally, during calcination, the melamine is converted into ammonia gas at high temperature, entering the layered structure and completing nitrogen doping and manganese loading.

[0010] The order in which raw materials are added in this application plays a crucial role in the structure of the final nitrogen-doped supported manganese layered double hydroxide. Adding melamine before manganese salt fails to achieve the initial isolation effect between melamine and manganese salt, leading to decreased utilization of manganese and nitrogen. This results in a low proportion of active sites (manganese and nitrogen sites) in the synthesized composite material, thus reducing its catalytic activity. More importantly, manganese ions cannot be immobilized on the layered double hydroxide, hindering stable catalytic degradation.

[0011] The slow-release synthesis method proposed in this application can help free manganese ions to be effectively anchored on the layered double hydroxide, and after anchoring, they are uniformly dispersed on the layered structure and surface of the layered double hydroxide. At the same time, the layered structure of the layered double hydroxide can play a role in fixing the active sites, and will not cause a significant decrease in catalytic conversion efficiency due to detachment from the active metal during long-term use.

[0012] Preferably, the solid-liquid ratio in the mixed solution is (0.5-0.7) g: 1 mL.

[0013] Preferably, the mass ratio between manganese in the manganese salt and the layered double hydroxide is (5-10):100.

[0014] Preferably, the molar ratio of manganese in the manganese salt to melamine is (0.4-1):4.

[0015] Preferably, the manganese salt is manganese nitrate.

[0016] Preferably, the calcination temperature is 500–600°C, the calcination heating rate is 10–15°C / min, and the calcination time is 0.5–2 h.

[0017] The present invention also provides a nitrogen-doped loaded manganese layered double hydroxide prepared by the above preparation method, wherein the nitrogen doping amount is a to b wt% and the manganese loading amount is 5 to 10 wt% based on the weight of the nitrogen-doped loaded manganese layered double hydroxide.

[0018] This invention also provides the application of the nitrogen-doped loaded manganese layered double hydroxide prepared by the above preparation method, or the above nitrogen-doped loaded manganese layered double hydroxide, in the ozone catalytic oxidation treatment of methanethiol in flue gas / exhaust gas at room temperature.

[0019] The mechanism by which nitrogen-doped manganese-supported layered double hydroxides catalyze the ozone oxidation of methanethiol is as follows: First, ozone molecules (O3) are adsorbed and activated on the surface of the nitrogen-doped manganese-supported layered double hydroxides. Nitrogen and manganese provide abundant active sites, which can effectively adsorb and activate ozone. Subsequently, the ozone molecules decompose into active oxygen species (such as ·O2). - (Or ·O) is used as the main oxidant. Subsequently, the sulfur atoms in the methanethiol (CH3SH) molecule are adsorbed on the surface of a nitrogen-doped, manganese-supported layered double hydroxide, with the manganese center providing adsorption sites for the methanethiol molecule. Reactive oxygen species react with the adsorbed methanethiol, leading to its oxidation. The initial oxidation product is a methanethiol radical (CH3S). - Further oxidation produces methylthioperoxide (CH3SO2). - The oxidation process ultimately produces sulfur dioxide (SO2) and other byproducts. These products can desorb from the surface of nitrogen-doped manganese-supported layered double hydroxides, regenerating the surface of the nitrogen-doped manganese-supported layered double hydroxides. This allows the surface to continue adsorbing and activating new ozone and methanethiol molecules, thus achieving a continuous reaction.

[0020] Preferably, in the ozone catalytic oxidation treatment, the molar ratio of ozone to methanethiol in the flue gas / exhaust gas is (0.6-0.8):1.

[0021] Preferably, in the ozone catalytic oxidation treatment, the amount of nitrogen-doped supported manganese layered double hydroxide is 0.05–0.3 g / L.

[0022] When the nitrogen-doped supported manganese layered double hydroxide is used at a concentration of 0.2 g / L, the conversion of methanethiol is close to 100%, and the conversion efficiency increases with increasing concentration. However, considering practical use and economic factors, a concentration of 0.05–0.3 g / L is generally sufficient to meet the requirements. Concentrations exceeding 0.3 g / L can also achieve comparable results, but this is not chosen for cost reasons. Therefore, the actual concentration range in this application should be considered to be greater than 0.05 g / L.

[0023] Preferably, after continuous use for 4 hours, the nitrogen-doped loaded manganese layered double hydroxide achieves a conversion rate of over 90% for methanethiol in flue gas / exhaust gas.

[0024] Therefore, the present invention has the following beneficial effects:

[0025] (1) The present invention provides a nitrogen-doped loaded manganese layered double hydroxide with nitrogen and manganese dual active sites, which has a good ozone catalytic oxidation effect on methanethiol.

[0026] (2) This invention provides a method for preparing nitrogen-doped loaded manganese layered double hydroxides. By using a slow-release synthesis method, the utilization rate of manganese ions is high and manganese metal sites can be fixed. This characteristic can help the efficient and stable use of nitrogen-doped loaded manganese layered double hydroxides.

[0027] (3) The nitrogen-doped manganese layered double hydroxide provided by the present invention can achieve a methanethiol conversion efficiency of 95% when the O3 / CH3SH molar ratio is 0.8, and the amount of nitrogen-doped manganese layered double hydroxide is as low as 0.1 g / L.

[0028] (4) After continuous use for 4 hours, the nitrogen-doped manganese layered double hydroxide provided by the present invention can still maintain a conversion efficiency of more than 90% for methanethiol, which proves that the performance degradation of nitrogen-doped manganese layered double hydroxide is small and the stability is high. Attached Figure Description

[0029] Figure 1 The graph shows the methanethiol conversion capacity of various catalytic materials under liquid phase conditions.

[0030] Figure 2 The graph shows the methanethiol conversion capacity of various catalytic materials under gas-phase conditions.

[0031] Figure 3 An effect diagram of the layered double hydroxide compound of nitrogen-doped supported iron and supported manganese catalysts;

[0032] Figure 4 The graph shows the methanethiol conversion capacity of different catalytic materials;

[0033] Figure 5The graph shows the methanethiol conversion capacity of Mn LDH-M under different catalyst dosages;

[0034] Figure 6 The graph shows the methanethiol conversion capacity of Mn LDH-M under different ozone concentrations.

[0035] Figure 7 The graph shows the methanethiol conversion capacity of Mn LDH-M under different liquid conditions.

[0036] Figure 8 The graph shows the methanethiol conversion capacity of Mn LDH-M at different methanethiol concentrations.

[0037] Figure 9 The figure shows the stability test results of Mn LDH-M. Detailed Implementation

[0038] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0039]

Example

[0040] Manganese nitrate tetrahydrate, melamine, and ferric nitrate in this section were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Layered hydroxides were also purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; abbreviated as LDH, with the general formula [M(II)]. 1-x M(III) x (OH)2] x +(An - ) x / n ·mH2O, where M(II) represents a divalent metal cation (such as Mg). 2+ Ni 2+ Zn 2+ Cu 2+ (etc.), M(III) represents a trivalent metal cation (such as Al), 3+ Fe 3+ Cr 3+ (etc.), An - For interlayer exchangeable anions (such as CO3) 2- NO3 - Cl -(etc.), where x is the mole fraction of M(III) in the total metal ions (usually ranging from 0.2 to 0.33), and m is the number of interlayer water molecules. Montmorillonite was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., montmorillonite K-10, abbreviated as MMT.

[0041] Example 1

[0042] 0.5 g of layered hydroxide (6.6 mmol) and 0.173 g of manganese nitrate tetrahydrate (0.7 mmol) were mixed in 1 mL of deionized water, shaken thoroughly, and sonicated for 20 min. Then, 0.5 g of melamine (4 mmol) and 1 mL of deionized water were added, stirred thoroughly, and sonicated for 10 min. The temperature was increased from room temperature to 550 °C at a rate of 13 °C / min and held for 1 h to obtain nitrogen-doped loaded manganese layered double hydroxide, with a nitrogen doping amount of 3–4 wt% and a manganese loading of 7.5 wt%, denoted as Mn LDH-M (Note: the nitrogen doping amount could not be accurately measured due to equipment limitations, so it is written as a range value).

[0043] Comparative Example 1

[0044] 0.5 g of layered hydroxide (6.6 mmol), 0.5 g of melamine (4 mmol), and 1 mL of deionized water were stirred until homogeneous and sonicated for 20 min. Then, 0.173 g of manganese nitrate tetrahydrate (0.7 mmol) and 1 mL of deionized water were added, stirred until homogeneous, and sonicated for 10 min. The temperature was increased from room temperature to 550 °C at a rate of 13 °C / min and held for 1 h to obtain nitrogen-doped supported manganese layered double hydroxide, denoted as Mn-M / LDH.

[0045] Comparative Example 2

[0046] This comparative example is basically the same as Example 1, except that the layered hydroxide is replaced by an equal mass of montmorillonite, 0.5 g montmorillonite (2 mmol), denoted as Mn MMT-M.

[0047] Comparative Example 3

[0048] This comparative example is basically the same as Example 1, except that manganese nitrate tetrahydrate is replaced with equimolar ferric nitrate nonahydrate, 0.283g ferric nitrate nonahydrate (0.7mmol), denoted as Fe LDH-M.

[0049] Comparative Example 4

[0050] This comparative example is basically the same as Example 1, except that the addition of manganese nitrate tetrahydrate, denoted as LDH-M, is omitted.

[0051] Comparative Example 5

[0052] This comparative example is basically the same as Example 1, except that the addition of the layered double hydroxide, denoted as Mn-M, is omitted.

[0053] [Performance Testing]

[0054] 1. Methanethiol conversion capacity of different catalyst supports

[0055] 70 mg of Mn MMT-M and montmorillonite (MMT), and 35 mg of Mn LDH-M and layered hydroxide (LDH) were taken for testing under liquid phase conditions. 70 mg of Mn MMT-M, montmorillonite (MMT), Mn LDH-M and layered hydroxide (LDH) were taken for testing under gas phase conditions.

[0056] The performance of the above catalysts in catalyzing the oxidation of methanethiol by ozone was investigated. Gas phase experimental parameters 1: 180 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min. Gas phase experimental parameters 2: 240 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min. Liquid phase experimental parameters 1: 180 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL. Liquid phase experimental parameters 2: 240 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL.

[0057] After the reaction, the conversion rate of methanethiol during the ozone catalytic oxidation process was detected by liquid chromatography / gas chromatography, respectively. The results are shown in the figure. Figures 1-2 .

[0058] Figure 1The results show that the performance of MMT declined after nitrogen doping and manganese loading, while the performance of LDH was effectively improved after nitrogen doping and manganese loading. Both MMT and LDH theoretically possess layered structures and have similar physicochemical properties, so their performance after doping and loading should theoretically be similar. However, the applicant's experiments revealed that although their performances were similar, the results were drastically different. This is speculated to be because layered double hydroxides have a larger interlayer spacing and contain exchangeable anions and water molecules in the interlayer. After nitrogen doping and manganese loading, these anions and water molecules can effectively regulate the interlayer environment, resulting in a uniform distribution of manganese ions and maintaining high catalytic activity. In contrast, montmorillonite has a smaller interlayer spacing, and the interlayer mainly contains water molecules and a small amount of exchangeable cations. Nitrogen doping and manganese loading may lead to crowding of the interlayer space, affecting the free movement of interlayer ions and thus reducing its catalytic activity.

[0059] In this study, the applicant first conducted exploratory experiments in the liquid phase at a catalyst dosage of 70 mg to evaluate the catalytic activity of Mn LDH-M and LDH. The experimental results showed that both substances exhibited good reactivity at this dosage. Based on these preliminary results, the applicant further optimized the catalyst dosage of Mn LDH-M and LDH in the liquid phase, finding that reducing the catalyst dosage to 35 mg still maintained high reactivity.

[0060] 2. Differences in methanethiol conversion capacity due to different active metal centers

[0061] 35 mg of each of Mn LDH-M and Fe LDH-M were tested under liquid phase conditions to explore the performance of the above catalysts in catalyzing the oxidation of methanethiol by ozone. Liquid phase experimental parameters: 240 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N 265 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL.

[0062] After the reaction was completed, the conversion rate of methanethiol during the ozone catalytic oxidation process was detected by liquid chromatography. The results are shown in the figure. Figure 3 .

[0063] observe Figure 3It is evident that, under the same reaction conditions, Fe LDH-M with Fe as the active metal center exhibits significantly lower methanethiol conversion capacity compared to Mn LDH-M with Mn as the active metal center. This indicates that Mn, as the active metal center, possesses superior performance in the catalytic oxidation of methanethiol. This may be due to the electronic structure and chemical properties of Mn, which, when synergistically interacting with nitrogen-doped supported layered double hydroxides, can more effectively activate ozone molecules and promote the reaction between methanethiol molecules and reactive oxygen species. Further research revealed that the influence of different active metal centers on catalytic performance may be related to their ability to regulate the generation and stability of reactive oxygen species. Mn may be more conducive to generating highly reactive oxygen species and can maintain appropriate stability of these reactive oxygen species on the catalyst surface, thereby enhancing the oxidation capacity of methanethiol. Fe, on the other hand, performs relatively weakly in this regard, resulting in lower efficiency in catalytic methanethiol conversion. This result provides an important reference for further optimization of catalyst design, namely, selecting a suitable active metal center is crucial for improving the catalytic oxidation performance of nitrogen-doped supported layered double hydroxides for methanethiol. Further research could delve into the synergistic mechanisms between Mn and other elements, and how to further optimize the loading and distribution of Mn to achieve higher catalytic activity and selectivity. Simultaneously, combining Mn with other materials possessing specific functions could be considered to develop higher-performance methanethiol treatment catalysts, providing a more effective technical means to address the problem of methanethiol waste gas pollution.

[0064] 3. Synergistic effect of nitrogen and manganese active sites

[0065] 35 mg of each of Mn LDH-M, Mn-M, LDH-M, Mn-M / LDH, and layered hydroxide (LDH) were tested under liquid phase conditions to explore the performance of these catalysts in catalyzing the oxidation of methanethiol by ozone. Liquid phase experimental parameters 1: 180 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL. Liquid phase experimental parameters 2: 210 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL. Liquid phase experimental parameters 3: 240 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL.

[0066] After the reaction was completed, the conversion rate of methanethiol during the ozone catalytic oxidation process was detected by liquid chromatography. The results are shown in the figure. Figure 4 .

[0067] observe Figure 4 It is evident that the ability of LDH-M materials to catalyze methanethiol significantly decreases after losing manganese sites, demonstrating a synergistic effect between manganese and nitrogen sites, while the manganese sites themselves also play a role in the catalysis of methanethiol. Furthermore, the ability of Mn-M / LDH materials to catalyze methanethiol is also affected by changing the order of addition.

[0068] 4. Performance Testing of Mn LDH-M

[0069] ① Catalyst dosage

[0070] To explore the performance of the above catalysts in catalyzing the oxidation of methanethiol by ozone.

[0071] Liquid phase experimental parameters 1: 180ppm O3; 300ppm CH3SH; room temperature; gas flow rates: N2 65mL / min, CH3SH 30mL / min, O3 5mL / min, water 350mL, and the amount of catalyst was controlled at 0.175g, 0.35g, and 0.70g respectively.

[0072] Liquid phase experimental parameters 2: 240ppm O3; 300ppm CH3SH; room temperature; gas flow rates: N2 65mL / min, CH3SH 30mL / min, O3 5mL / min, water 350mL, and the amount of catalyst was controlled at 0.175g, 0.35g, and 0.70g respectively.

[0073] After the reaction was completed, the conversion rate of methanethiol during the ozone catalytic oxidation process was detected by liquid chromatography. The results are shown in the figure. Figure 5 .

[0074] observe Figure 5 It can be seen that the catalytic efficiency of methanethiol is improved with the increase of catalyst dosage. When the catalyst dosage is 0.1 g / L, the conversion rate reaches more than 95%.

[0075] ②Ozone concentration

[0076] The performance of the above-mentioned catalyst in the ozone-catalyzed oxidation of methanethiol was investigated. Liquid chromatography experimental parameters: catalyst dosage 35 mg; CH3SH 300 ppm; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, water 350 mL; ozone concentrations 90 ppm, 180 ppm, 240 ppm, 270 ppm, and 360 ppm. After the experiment, the conversion rate of methanethiol during the ozone-catalyzed oxidation of methanethiol was detected by liquid chromatography. The results are shown below. Figure 6 .

[0077] observe Figure 6It can be seen that the catalytic efficiency of methanethiol increases with increasing ozone concentration, reaching over 95% when the ozone concentration is 240 ppm. At this point, the O3 / CH3SH molar ratio is 0.8.

[0078] ③ Liquid environment

[0079] The performance of the above-mentioned catalyst in the ozone-catalyzed oxidation of methanethiol was investigated. Liquid chromatography experimental parameters: catalyst dosage 35 mg; 240 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min; controlled water environments were ultrapure water and tap water, respectively. After the reaction, the conversion rate of methanethiol during the ozone-catalyzed oxidation of methanethiol was detected by liquid chromatography. The results are shown below. Figure 7 .

[0080] observe Figure 7 It is evident that the Mn LDH-M prepared in this application exhibits excellent performance in both tap water and ultrapure water, with its methanethiol conversion rate remaining above 95%.

[0081] ④ Methanethiol concentration

[0082] The performance of the above-mentioned catalyst in the ozone-catalyzed oxidation of methanethiol was investigated. Liquid chromatography experimental parameters: catalyst dosage 35 mg; 240 ppm O3; room temperature; gas flow rates: N2 65 mL / min, O3 5 mL / min, water 350 mL; methanethiol concentrations controlled at 100 ppm, 300 ppm, and 500 ppm. After the reaction, the conversion rate of methanethiol during the ozone-catalyzed oxidation process was detected by liquid chromatography. The results are shown below. Figure 8 .

[0083] observe Figure 8 It can be seen that as the concentration of methanethiol increases, the catalytic efficiency of methanethiol decreases, but its conversion rate remains above 90%.

[0084] ⑤ Stability

[0085] The performance of the above catalyst in catalyzing the oxidation of methanethiol by ozone was investigated. Liquid phase experimental parameters: catalyst dosage 35 mg; 240 ppm O3; 300 ppm CH3SH; room temperature; gas flow rates: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL.

[0086] After the reaction was completed, the conversion rate of methanethiol during the ozone catalytic oxidation process was detected by liquid chromatography. The results are shown in the figure. Figure 9 .

[0087] observe Figure 9 It can be seen that after continuous use for 4 hours, the conversion efficiency of Mn LDH-M to methanethiol can still be maintained at over 90%, proving that the performance degradation of nitrogen-doped loaded manganese layered double hydroxide is small and the stability is high.

Claims

1. A method for preparing a nitrogen-doped supported manganese layered double hydroxide, characterized in that, include: Layered double hydroxides and manganese salts were ultrasonically mixed in water to obtain a mixed solution. Melamine and water were then added to the mixed solution and ultrasonically mixed again to obtain a precursor. The precursor was calcined to obtain nitrogen-doped manganese-loaded layered double hydroxides.

2. The preparation method according to claim 1, characterized in that, The solid-liquid ratio in the mixed solution is (0.5-0.7) g: 1 mL.

3. The preparation method according to claim 1, characterized in that, The mass ratio between manganese in the manganese salt and the layered double hydroxide is (5-10):

100.

4. The preparation method according to claim 1, characterized in that, The molar ratio of manganese in the manganese salt to melamine is (0.4–1):

4.

5. The preparation method according to claim 1, characterized in that, The calcination temperature is 500–600℃, the heating rate is 10–15℃ / min, and the calcination time is 0.5–2h.

6. The nitrogen-doped supported manganese layered double hydroxide prepared by the preparation method according to any one of claims 1 to 5, characterized in that, The nitrogen doping amount is 1 to 10 wt% and the manganese loading amount is 5 to 10 wt% based on the weight of nitrogen-doped loaded manganese layered double hydroxide.

7. The application of the nitrogen-doped supported manganese layered double hydroxide prepared by the preparation method according to any one of claims 1 to 5, or the nitrogen-doped supported manganese layered double hydroxide as described in claim 6, in the ozone catalytic oxidation treatment of methanethiol in flue gas / exhaust gas at room temperature.

8. The application as described in claim 7, characterized in that, In the ozone catalytic oxidation treatment, the molar ratio of ozone to methanethiol in the flue gas / exhaust gas is (0.6-0.8):

1.

9. The application as described in claim 7, characterized in that, In the ozone catalytic oxidation treatment, the amount of nitrogen-doped loaded manganese layered double hydroxide is 0.05–0.3 g / L.

10. The application as described in claim 7, characterized in that, After continuous use for 4 hours, the nitrogen-doped loaded manganese layered double hydroxide exhibits a conversion rate of over 90% for methanethiol in flue gas / exhaust gas.

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