Nitrogen-doped manganese-supported layered double hydroxide and its manufacture and use

Abstract

In relation to the technology for treating methanethiol exhaust gas, specifically, the present invention provides nitrogen-doped manganese-supported layered double hydroxides and their production and use. [Solution] A method for producing nitrogen-doped manganese-supported layered double hydroxide is provided, which includes ultrasonic mixing of layered double hydroxide and manganese salt in water to obtain a mixed solution, adding melamine and water to the mixed solution and ultrasonic mixing again to obtain a precursor, and calcining the precursor to obtain nitrogen-doped manganese-supported layered double hydroxide. Nitrogen-doped manganese-supported layered double hydroxide has two active sites, nitrogen and manganese, and exhibits excellent effect on ozone catalytic oxidation treatment of methanethiol.

Description

[Technical Field]

[0001] The present invention relates to the technology of methanethiol exhaust gas treatment, and more specifically to nitrogen-doped manganese-supported layered double hydroxide and its production and use. [Background technology]

[0002] Methanethiol (CH3SH) is a sulfur-containing volatile organic pollutant with a strong odor reminiscent of rotten vegetables, and its olfactory threshold is extremely low, at only 0.0021 ppm. Methanethiol is widely present 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 not only have harmful effects on the human nervous system but can also cause acid rain, equipment corrosion, and catalyst deactivation in the chemical industry. As environmental protection efforts in China continue to strengthen, strengthening the treatment and prevention of methanethiol exhaust gases has become an urgent necessity. Therefore, research and development of efficient methanethiol exhaust gas / flue gas treatment technologies have significant practical importance.

[0003] Currently, methods for removing methanethiols mainly include adsorption, chemical absorption, biological methods, and catalytic decomposition. Of these, catalytic decomposition is considered the most appropriate method due to its high conversion efficiency, low cost, and ability to convert contaminating methanethiols into useful chemical products (CH4, CO, etc.). In recent years, cerium-based catalysts, precious metal catalysts, molecular sieves, and their modifying catalysts have been commonly used for the catalytic decomposition of methanethiols.

[0004] While existing catalysts have shown some effectiveness in the catalytic decomposition of methanethiols, they still face the following challenges: 1) High ozone consumption; in catalytic decomposition processes, high ozone consumption not only increases operating costs but can also cause the generation of by-products, potentially affecting the purity and quality of the final product. 2) High catalyst usage; achieving ideal catalytic effect requires the use of large amounts of conventional catalysts, increasing processing costs and potentially making catalyst recovery and reuse difficult, further increasing the environmental burden. 3) Cost issues; while precious metal catalysts offer superior catalytic efficiency, their high cost and the difficulty in recovering precious metals increase environmental protection costs. 4) Coke buildup and inactivation. Therefore, developing novel catalysts that are easy to manufacture, have higher activity, consume less energy and ozone, and require less catalyst is a crucial challenge that needs to be addressed in the field of methanethiol exhaust gas treatment. This will contribute to improving the efficiency of methanethiol removal, reducing treatment costs, and promoting the development of environmental protection technologies. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] China Patent Publication No. CN109173978A [Patent Document 2] Japanese Patent Publication No. 2018-067494 [Overview of the project]

[0006] This invention provides nitrogen-doped manganese-supported layered double hydroxide and its production and use. The nitrogen-doped manganese-supported layered double hydroxide can be used as a catalyst for methanethiol treatment. In the usage process, the nitrogen-doped manganese-supported layered double hydroxide exhibits high activity, and achieves a methanethiol conversion efficiency of 95% with an O3 / CH3SH molar ratio of only 0.8, while the amount of nitrogen-doped manganese-supported layered double hydroxide used is only 0.1 g / L. Furthermore, after continuous use for 4 hours, the conversion efficiency of the nitrogen-doped manganese-supported layered double hydroxide to methanethiol still remains above 90%, demonstrating that the nitrogen-doped manganese-supported layered double hydroxide exhibits a small performance decay range and high stability.

[0007] To achieve the above objectives, the present invention employs the following technical solutions.

[0008] The present invention provides a method for producing nitrogen-doped manganese-supported layered double hydroxide, comprising ultrasonically mixing a layered double hydroxide and a manganese salt in water to obtain a mixed solution, adding melamine and water to the mixed solution and ultrasonically mixing again to obtain a precursor, and calcining the precursor to obtain nitrogen-doped manganese-supported layered double hydroxide.

[0009] This invention utilizes the non-hydrophilic properties of layered double hydroxides. First, it mixes with a manganese salt in an aqueous solution, during which the manganese salt solution is encased in the layered structure of the layered double hydroxide. Melamine is then added, and because the manganese salt solution is encased in the layered structure, the melamine cannot come into direct contact with the manganese salt. Finally, during the calcination process, the melamine is converted into ammonia gas at high temperatures, enters the layered structure, and completes nitrogen doping and manganese loading.

[0010] The order of addition of the raw materials in this invention plays a crucial role in the structure of the final nitrogen-doped manganese-supported layered double hydroxide. If melamine is added first, followed by the manganese salt, the initial sequestering effect between melamine and the manganese salt is not achieved, leading to a decrease in the utilization rate of the manganese salt and nitrogen element. As a result, the proportion of active sites (manganese sites and nitrogen sites) in the synthesized composite material becomes too small, reducing the catalytic activity of the composite material. More importantly, the manganese metal ions are not fixed to the layered double hydroxide, making stable catalytic decomposition impossible.

[0011] The sustained-release synthesis method described in this application helps to effectively fix free manganese ions to layered double hydroxides and, after fixation, allows for uniform dispersion of the manganese ions in the layered structure and on the surface of the layered double hydroxides. At the same time, the layered structure of the layered double hydroxides can serve to fix the active sites, preventing the problem of a significant decrease in catalyst conversion efficiency due to the desorption of 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 of manganese to the layered double hydroxide in the manganese salt is (5-10):100.

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

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

[0016] Preferably, the firing temperature is 500-600°C, the firing heating rate is 10-15°C / min, and the firing time is 0.5-2 hours.

[0017] The present invention further provides a nitrogen-doped manganese-supported layered double hydroxide produced by the above manufacturing method. With respect to the weight of the nitrogen-doped manganese-supported layered double hydroxide, the nitrogen doping amount is 1 to 10 wt%, and the manganese loading amount is 5 to 10 wt%.

[0018] The present invention further provides the use of the nitrogen-doped manganese-supported layered double hydroxide produced by the above manufacturing method or the above nitrogen-doped manganese-supported layered double hydroxide in the ozone catalytic oxidation treatment of methanethiol in flue gas / exhaust gas at room temperature.

[0019] The mechanism by which the nitrogen-doped manganese-supported layered double hydroxide catalyzes the oxidation of methanethiol by ozone is as follows. First, ozone molecules (O3) are adsorbed and activated on the surface of the nitrogen-doped manganese-supported layered double hydroxide. Nitrogen and manganese provide abundant active sites, enabling effective adsorption and activation of ozone. Along with this, ozone molecules are decomposed into active oxygen species (e.g., ·O2 - or ·O) as the main oxidizing agent. Then, the sulfur atom in the methanethiol (CH3SH) molecule is adsorbed on the surface of the nitrogen-doped manganese-supported layered double hydroxide, and the manganese center provides an adsorption site to localize the methanethiol molecule. The active oxygen species react with the adsorbed methanethiol, causing the oxidation of methanethiol. The initial oxidation product is methanethiol radical (CH3S - ), and the further oxidation product is methylthiosulfoxide (CH3SO2 - ), which is finally oxidized to produce sulfur dioxide (SO2) and other by-products. The products generated in these oxidation processes desorb from the surface of the nitrogen-doped manganese-supported layered double hydroxide, thereby regenerating the surface of the nitrogen-doped manganese-supported layered double hydroxide and enabling continuous adsorption and activation of new ozone and methanethiol molecules to achieve 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 to 0.8):1.

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

[0022] When the amount of the nitrogen-doped manganese supported layered double hydroxide used is 0.2 g / L, the conversion rate of methanethiol is close to 100%. With the increase in the usage amount, the conversion efficiency also increases. However, considering the actual use and economic problems, setting it at 0.05 to 0.3 g / L can almost meet the usage needs. Although a considerable effect can also be achieved with a usage amount exceeding 0.3 g / L, it is not selected considering the cost. Therefore, the actual usage amount range in this application should be regarded as exceeding 0.05 g / L.

[0023] Preferably, after continuously using the nitrogen-doped manganese supported layered double hydroxide for 4 h, the conversion rate of methanethiol in the flue gas / exhaust gas is 90% or more.

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

[0025] (1) The present invention provides a nitrogen-doped manganese supported layered double hydroxide, which has two active sites of nitrogen and manganese and has excellent effects on the ozone catalytic oxidation treatment of methanethiol.

[0026] (2) The present invention provides a method for manufacturing a nitrogen-doped manganese supported layered double hydroxide, which utilizes a sustained-release synthesis method, has a high utilization rate of manganese ions and can fix manganese metal sites, and contributes to the high-efficiency and stable use of the nitrogen-doped manganese supported layered double hydroxide by using this characteristic.

[0027] (3) The nitrogen-doped manganese supported 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 at this time, the amount of the nitrogen-doped manganese supported layered double hydroxide used is as low as 0.1 g / L.

[0028] (4) After continuous use for 4 hours, the nitrogen-doped manganese-supported layered double hydroxide provided by the present invention still maintains a conversion efficiency of 90% or more to methanethiol, which demonstrates that the nitrogen-doped manganese-supported layered double hydroxide has a small performance decay range and high stability. [Brief explanation of the drawing]

[0029] [Figure 1] This figure shows the methanethiol conversion ability of each catalyst material under liquid phase conditions. [Figure 2] This figure shows the methanethiol conversion ability of each catalyst material under gas phase conditions. [Figure 3] This figure shows the effects of layered double hydroxide compounds on nitrogen-doped iron-supported and manganese-supported catalysts. [Figure 4] This figure shows the methanethiol conversion ability of different catalyst materials. [Figure 5] This figure shows the methanethiol conversion ability of Mn LDH-M at different catalyst concentrations. [Figure 6] This figure shows the methanethiol conversion ability of Mn LDH-M under different ozone concentrations. [Figure 7] This figure shows the methanethiol conversion ability of Mn LDH-M under different liquid environments. [Figure 8] This figure shows the methanethiol conversion ability of Mn LDH-M under different methanethiol concentrations. [Figure 9] This figure shows the results of the stability test of Mn LDH-M. [Modes for carrying out the invention]

[0030] The present invention will be further described below with reference to specific examples. Those skilled in the art can implement the present invention based on these descriptions. In addition, the examples of the present invention described below are only some examples of the present invention and not all examples. Therefore, all other examples obtained by those skilled in the art without creative efforts based on the examples of the present invention should belong to the protection scope of the present invention.

Example

[0031] Manganese(II) nitrate tetrahydrate, melamine, and iron(III) nitrate in this part were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. The layered hydroxide was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., abbreviated as LDH, and the general formula is [M(II) 1-x M(III) x (OH)2] x +(An - ) x / n ·mH2O, where M(II) represents divalent metal cations (such as Mg 2+ , Ni 2+ , Zn 2+ , Cu 2+ , etc.), M(III) represents trivalent metal cations (such as Al 3+ , Fe 3+ , Cr 3+ , etc.), An - represents an interlayer exchangeable anion (such as CO3 2- , NO3 - , Cl - , etc.), x is the molar fraction of M(III) in the total metal ions (usually, the value range is between 0.2 and 0.33), and m is the number of interlayer water molecules. Montmorillonite was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., which is montmorillonite k-10, abbreviated as MMT.

[0032] Example 1 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 uniformly, and sonicated for 20 mins. Then, 0.5 g of melamine (4 mmol) and 1 mL of deionized water were added, stirred uniformly, and sonicated for 10 mins. The temperature was raised from room temperature to 550 °C at a heating rate of 13 °C / min and held for 1 hour to obtain nitrogen-doped manganese-supported layered double hydroxide, where the nitrogen doping amount was 3-4 wt% and the manganese supporting amount was 7.5 wt%, and the product was designated Mn LDH-M (Note: The amount of nitrogen doping could not be accurately measured due to instrument limitations, so it is expressed as a range value).

[0033] Comparative Example 1 0.5 g of layered hydroxide (6.6 mmol), 0.5 g of melamine (4 mmol), and 1 mL of deionized water were uniformly stirred and sonicated for 20 minutes. Then, 0.173 g of manganese nitrate tetrahydrate (0.7 mmol) and 1 mL of deionized water were added, uniformly stirred, and sonicated for 10 minutes. The temperature was raised from room temperature to 550°C at a heating rate of 13°C / min and held for 1 hour to obtain nitrogen-doped manganese-supported layered double hydroxide, which was then prepared as Mn-M / LDH.

[0034] Comparative Example 2 This comparative example is basically the same as Example 1, the only difference being that the layered hydroxide was replaced with an equal mass of montmorillonite, i.e., 0.5 g of montmorillonite (2 mmol), resulting in Mn MMT-M.

[0035] Comparative Example 3 This comparative example is basically the same as Example 1, the only difference being that manganese nitrate tetrahydrate was replaced with equimolar iron nitrate nonahydrate, i.e., 0.283 g of iron nitrate nonahydrate (0.7 mmol), and was named Fe LDH-M.

[0036] Comparative Example 4 This comparative example is basically the same as Example 1, the only difference being that manganese nitrate tetrahydrate was not added, and it was named LDH-M.

[0037] Comparative Example 5 This comparative example is basically the same as Example 1, the only difference being that layered double hydroxide was not added, and the combination was Mn-M. <Performance Test> 1. Methanethiol conversion ability of different catalyst supports 70 mg each of Mn MMT-M and montmorillonite (MMT), and 35 mg each of Mn LDH-M and layered hydroxide (LDH) were taken and tested under liquid-phase conditions. 70 mg each of Mn MMT-M, montmorillonite (MMT), Mn LDH-M, and layered hydroxide (LDH) were taken and tested under gas-phase conditions.

[0038] The catalytic performance of the above catalyst for ozone-catalyzed oxidation of methanethiol was investigated. Gas phase experimental parameters 1: 180 ppm O3, 300 ppm CH3SH, room temperature, gas flow rate: N265 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 rate: N265 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 rate: N265 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.

[0039] After the reaction was complete, the conversion rate of methanethiol during the catalytic oxidation process with ozone was detected using liquid-phase / gas chromatography, and the detection results are shown in Figures 1 and 2.

[0040] As can be seen from the results in Figure 1, the performance of MMT decreased after nitrogen doping and manganese loading, while the performance of LDH effectively improved after nitrogen doping and manganese loading. Theoretically, both MMT and LDH have a layered structure and similar physicochemical properties, so theoretically, the performance expressions after doping and loading should be similar. However, according to the applicant's experiments, although the performance of the two is similar, the results shown are completely different. The reason for this is that layered double hydroxides have large interlayer spacings and contain exchangeable anions and water molecules between the layers. After nitrogen doping and manganese loading, these anions and water molecules can effectively regulate the interlayer environment, thereby uniformly distributing manganese ions and maintaining high catalytic activity. In contrast, montmorillonite has small interlayer spacings and contains mainly water molecules and small amounts of exchangeable cations between the layers. Nitrogen doping and manganese loading may cause congestion in the interlayer space, affecting the free movement of ions between the layers, and thereby reducing its catalytic activity.

[0041] In this study, the applicant first conducted exploratory experiments in the liquid phase with a catalyst dose of 70 mg to evaluate the catalytic activity of Mn LDH-M and LDH. As can be seen from the experimental results, both substances showed good reaction activity at this dose. Based on these initial results, the applicant further optimized the amount of catalyst used in the liquid phase of Mn LDH-M and LDH and found that high reaction activity could be maintained even when the catalyst dose was reduced to 35 mg.

[0042] 2. Differences in methanethiol conversion ability due to different active metal centers. 35 mg each of Mn LDH-M and Fe LDH-M were taken and tested under liquid-phase conditions. The catalytic performance of the above catalysts for ozone-catalyzed oxidation of methanethiol was investigated. Liquid-phase experimental parameters: 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.

[0043] After the reaction was complete, liquid-phase chromatography was used to detect the conversion rate of methanethiol during the catalytic oxidation process with ozone. The results are shown in Figure 3.

[0044] As can be seen from Figure 3, Fe LDH-M, which has Fe as the active metal center, had significantly lower methanethiol conversion ability than Mn LDH-M, which has Mn as the active metal center, under the same reaction conditions. This indicates that using Mn as the active metal center has superior performance for catalytic oxidation of methanethiol. It is presumed that this is because, due to the electronic structure and chemical properties of Mn, when it acts synergistically with nitrogen-doped supported layered double hydroxide, it more effectively activates ozone molecules and promotes the reaction between methanethiol molecules and reactive oxygen species. Further research revealed that the effect 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 is advantageous because it generates highly reactive oxygen species and can maintain appropriate stability of these reactive oxygen species on the catalyst surface, thereby improving the oxidation ability to methanethiol. However, Fe's behavior in this respect is relatively weak, which is thought to be the reason why its efficiency in catalyzing methanethiol conversion was low. These results provide important reference points for further optimizing catalyst design, namely, the selection of appropriate active metal centers is crucial for improving the catalytic oxidation performance of nitrogen-doped supported layered double hydroxides for methanethiols. Subsequent research should investigate the synergistic mechanisms between Mn and other elements in detail, and explore how to optimize the Mn load and distribution to achieve higher catalytic activity and selectivity. Simultaneously, it is possible to consider combining Mn with other materials possessing specific functions to develop methanethiol treatment catalysts with superior performance, providing more effective technical means to solve the problem of pollution by methanethiol exhaust gases.

[0045] 3. Synergistic effect of nitrogen and manganese active sites 35 mg each of Mn LDH-M, Mn-M, LDH-M, Mn-M / LDH, and layered hydroxide (LDH) were taken and tested under liquid-phase conditions. The catalytic performance of the above catalysts for ozone-catalyzed oxidation of methanethiol was investigated. Liquid-phase experimental parameters 1: 180 ppm O3, 300 ppm CH3SH, room temperature, gas flow rate: N265 mL / min, CH3SH 30 mL / min, O35 mL / min, water 350 mL. Liquid-phase experimental parameters 2: 210 ppm O3, 300 ppm CH3SH, room temperature, gas flow rate: N265 mL / min, CH3SH 30 mL / min, O35 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.

[0046] After the reaction was complete, the conversion rate of methanethiol during the catalytic oxidation process with ozone was detected using liquid-phase chromatography, and the results are shown in Figure 4.

[0047] As can be seen in Figure 4, the LDH-M material that lost manganese sites showed a significant decrease in catalytic activity for methanethiol. This demonstrates that a synergistic effect exists between manganese and nitrogen sites, and that manganese sites themselves have catalytic activity for methanethiol. Furthermore, the catalytic activity for methanethiol of the Mn-M / LDH material obtained after changing the addition order was also affected.

[0048] 4. Performance testing of Mn LDH-M <1> Catalyst usage The catalytic performance of the above catalyst for ozone-catalyzed oxidation of methanethiol was investigated.

[0049] The experimental parameters for the liquid phase were 180 ppm O3, 300 ppm CH3SH, room temperature, and gas flow rates of N265 mL / min, CH3SH 30 mL / min, and O35 mL / min. The amount of water was 350 mL, and the catalyst amounts were controlled to 0.175 g, 0.35 g, and 0.70 g, respectively.

[0050] 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, and catalyst amounts controlled to 0.175 g, 0.35 g, and 0.70 g, respectively.

[0051] After the reaction was complete, liquid-phase chromatography was used to detect the conversion rate of methanethiol during the catalytic oxidation process with ozone. The results are shown in Figure 5.

[0052] As can be seen in Figure 5, the catalytic efficiency for methanethiol improved with increasing catalyst usage, and the conversion rate reached over 95% when the catalyst usage was 0.1 g / L.

[0053] <2> Ozone concentration The catalytic performance of the above catalyst for ozone-catalyzed oxidation of methanethiol was investigated. Liquid-phase experimental parameters: Catalyst amount 35 mg, 300 ppm CH3SH, room temperature, gas flow rate: N2 65 mL / min, CH3SH 30 mL / min, water 350 mL, ozone concentration 90 ppm, 180 ppm, 240 ppm, 270 ppm, 360 ppm. After the reaction was complete, the conversion rate of methanethiol during the catalytic oxidation process with ozone was detected using liquid-phase chromatography, and the detection results are shown in Figure 6.

[0054] As can be seen in Figure 6, the catalytic efficiency for methanethiol improved with increasing ozone concentration, and at an ozone concentration of 240 ppm, the conversion rate reached over 95%. At this time, the O3 / CH3SH molar ratio was 0.8.

[0055] <3> liquid environment The catalytic performance of the above catalyst for ozone-catalyzed oxidation of methanethiol was investigated. Liquid-phase experimental parameters: catalyst amount 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. The water environment was controlled to ultrapure water and tap water, respectively. After the reaction was complete, liquid-phase chromatography was used to detect the conversion rate of methanethiol during the ozone-catalyzed oxidation process. The detection results are shown in Figure 7.

[0056] As can be seen in Figure 7, the Mn LDH-M produced in this invention exhibits ideal performance in both tap water and ultrapure water, and the methanethiol conversion rate remained above 95% in both cases.

[0057] <4> Methanethiol concentration The catalytic performance of the above catalyst for ozone-catalyzed oxidation of methanethiol was investigated. Liquid-phase experimental parameters: catalyst amount 35 mg, 240 ppm O3, room temperature, gas flow rates: N265 mL / min, O35 mL / min, water 350 mL, and methanethiol concentrations controlled to 100 ppm, 300 ppm, and 500 ppm, respectively. After the reaction was complete, liquid-phase chromatography was used to detect the conversion rate of methanethiol during the catalytic oxidation process with ozone. The detection results are shown in Figure 8.

[0058] As can be seen in Figure 8, the catalytic efficiency for methanethiol decreased with increasing methanethiol concentration, but the conversion rate remained above 90% in all cases.

[0059] <5> stability The catalytic performance of the above catalyst for ozone-catalyzed oxidation of methanethiol was investigated. Liquid phase experimental parameters: Catalyst amount 35 mg, 240 ppm O3, 300 ppm CH3SH, room temperature, gas flow rate: N2 65 mL / min, CH3SH 30 mL / min, O3 5 mL / min, water 350 mL.

[0060] After the reaction was complete, liquid-phase chromatography was used to detect the conversion rate of methanethiol during the catalytic oxidation process with ozone. The results are shown in Figure 9.

[0061] As can be seen in Figure 9, after continuous use for 4 hours, the conversion efficiency of Mn LDH-M to methanethiol still remained above 90%, demonstrating that the nitrogen-doped manganese-supported layered double hydroxide exhibits a small performance decay and high stability.

Claims

1. A method for producing nitrogen-doped manganese-supported layered double hydroxide, A manufacturing method characterized by comprising ultrasonically mixing a layered double hydroxide and a manganese salt in water to obtain a mixed solution, adding melamine and water to the mixed solution and ultrasonically mixing again to obtain a precursor, and calcining the precursor to obtain a nitrogen-doped manganese-supported layered double hydroxide.

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

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

100.

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

4.

5. The manufacturing method according to claim 1, characterized in that the firing temperature is 500 to 600°C, the firing heating rate is 10 to 15°C / min, and the firing time is 0.5 to 2 hours.

6. A nitrogen-doped manganese-supported layered double hydroxide produced by the manufacturing method described in any one of claims 1 to 5, A nitrogen-doped manganese-supported layered double hydroxide wherein the amount of nitrogen doping is 1 to 10 wt% and the amount of manganese supported is 5 to 10 wt% relative to the weight of the nitrogen-doped manganese-supported layered double hydroxide.

7. Use of a nitrogen-doped manganese-supported layered double hydroxide produced by the manufacturing method described in any one of claims 1 to 5, or the nitrogen-doped manganese-supported layered double hydroxide described in claim 6, for ozone-catalyzed oxidation treatment of methanethiols in flue gas / exhaust gas at room temperature.

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

1.

9. The use according to claim 7, characterized in that the amount of nitrogen-doped manganese-supported layered double hydroxide used in the ozone catalytic oxidation treatment is 0.05 to 0.3 g / L.

10. The use according to claim 7, characterized in that, after using the nitrogen-doped manganese-supported layered double hydroxide continuously for 4 hours, the conversion rate to methanethiol in the flue gas / exhaust gas is 90% or more.

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