Method for degrading toluene by low-temperature plasma and mn / nitrogen-doped porous carbon catalyst

Abstract

This invention discloses a method for the degradation of toluene using a low-temperature plasma-assisted Mn / N-C catalyst, specifically implemented according to the following steps: Step 1, a mixture of zinc acetate dihydrate, polyvinylpyrrolidone, and methanol is poured into a mixture of 2-methylimidazole and methanol and mixed uniformly, then aged, centrifuged, washed with methanol, and dried to obtain ZIF-8 solid; Step 2, the ZIF-8 solid is dispersed in a glucose solution, then placed in a high-pressure reactor and heated, the resulting precipitate is centrifuged, washed with methanol, dried, and then placed in a tube furnace and reacted at 750℃ for 1 h to obtain N-C material; Step 3, N-C is dispersed in a potassium permanganate aqueous solution, treated with ultrasonic vibration, then manganese sulfate aqueous solution is added dropwise and stirred vigorously, then allowed to stand, centrifuged, washed with methanol, and dried to obtain the Mn / N-C catalyst.

Description

Technical Field

[0001] This invention belongs to the field of chemical catalyst technology, specifically relating to a method for the degradation of toluene using a low-temperature plasma-assisted Mn / nitrogen-doped porous carbon catalyst. Background Technology

[0002] Volatile organic pollutants (VOCs) are common air pollutants, widely present in the environment and complex in composition. Their main components include aromatic hydrocarbons and their derivatives, alkanes, alkenes, halogenated hydrocarbons, alcohols, esters, aldehydes, and ketones. They have small molecular weights and low boiling points, are easily volatilized at room temperature and pressure, and possess strong irritant, genotoxic, and carcinogenic properties, posing a significant health threat to humans and animals. Toluene, a typical VOC, was identified as a carcinogen by the World Health Organization (WHO) in 1999. It mainly originates from industrial processes such as petrochemical plants, paint factories, and automobile painting. Prolonged exposure to high concentrations of toluene (>0.087 mg / m³) can lead to serious health problems. 3 In environments where toluene is present, it can cause chronic poisoning, leading to headaches, memory loss, liver and kidney damage, and even carcinogenic effects. Furthermore, even low concentrations of toluene emissions and accumulation can harm the atmospheric environment, causing phenomena such as photochemical smog. Therefore, toluene pollution control is of great significance for improving the human living environment.

[0003] Currently, VOCs degradation technologies mainly include adsorption, absorption, biodegradation, catalytic combustion, photocatalysis, and low-temperature plasma methods. Among these, adsorption requires further treatment of the adsorbed pollutants and is only suitable for low-concentration pollutants; absorption methods have high absorbent costs and generate waste solvents; biodegradation is unsuitable for high-concentration or highly toxic VOCs and requires large equipment footprints; catalytic combustion requires high temperatures for the catalyst reaction, resulting in high economic costs; and photocatalysis has a slow reaction rate, low light utilization, and the photocatalyst is prone to deactivation. Low-temperature plasma technology has broad application prospects in VOCs pollution control due to its advantages of simple operation, convenient maintenance, and high VOCs degradation rate at room temperature and pressure. However, current plasma technology for VOCs degradation still suffers from low energy efficiency and the easy generation of byproducts. To overcome these problems, researchers have introduced catalysts into the low-temperature plasma reaction system, developing low-temperature plasma synergistic catalysis technology. This technology not only possesses the high reactivity of low-temperature plasma and the high product selectivity of catalysts, but also the synergistic effect between the two can significantly promote VOCs degradation.

[0004] In plasma-assisted catalysis systems, commonly used catalysts include noble metal (such as Ru, Rh, Pd, Pt) and transition metal (such as Mn, Fe, Co, Ni, etc.) catalysts. Among them, manganese-based catalysts are favored due to their advantages such as good low-temperature activity, wide availability, and low cost. Currently, low-temperature plasma-assisted catalysis systems still cannot meet industrial requirements due to low energy efficiency and low selectivity for target products. To address this problem, this invention designs a Mn / nitrogen-doped porous carbon catalyst with a large specific surface area, abundant pore structure, and strong oxygen transport capacity to enhance the synergistic effect between plasma and catalyst, and to develop a green and efficient method for the low-temperature plasma-assisted catalytic degradation of toluene. Summary of the Invention

[0005] The purpose of this invention is to provide a green and efficient method for degrading toluene using low-temperature plasma synergistic with Mn / nitrogen-doped porous carbon (Mn / NC) catalysts, which solves the problems of low energy efficiency and low selectivity of target products in current low-temperature plasma catalytic technology for degrading toluene.

[0006] To achieve the above objectives, the technical solution adopted in this invention is: to develop a controllable construction method for low-temperature, high-efficiency, and stable Mn / NC catalysts, and to construct a highly synergistic low-temperature plasma-coupled Mn / NC system for green and efficient removal of toluene.

[0007] As a preferred technical solution of the present invention, a low-temperature, high-efficiency, and stable Mn / NC catalyst is prepared by a glucose-assisted hydrothermal method combined with a chemical deposition method, specifically according to the following steps:

[0008] Step 1: Weigh zinc acetate dihydrate, polyvinylpyrrolidone, and methanol. The total volume ratio of zinc acetate dihydrate and polyvinylpyrrolidone to methanol is 1:50. Pour the zinc acetate dihydrate and polyvinylpyrrolidone into methanol to obtain mixed solution A. Then, weigh 2-methylimidazole and methanol at the same volume ratio of 1:50. Pour the 2-methylimidazole into methanol to obtain mixed solution B. The amount of methanol used in mixed solution A and mixed solution B is the same. After mixing mixed solution A and mixed solution B evenly, place them at room temperature for aging reaction.

[0009] Step 2: The precipitate obtained in Step 1 is centrifuged, washed with methanol, and dried overnight to finally obtain the zeolite imidazole framework material (ZIF-8);

[0010] Step 3: Disperse ZIF-8 solid in glucose solution and stir thoroughly for 1-10 hours; weigh 0.1-1 g of ZIF-8 solid for every 30 mL of glucose solution;

[0011] Step 4: Place the solution obtained in Step 3 into a high-pressure reactor and heat it at 60-180℃ for 2-20 hours;

[0012] Step 5: The precipitate obtained in Step 4 is centrifuged, washed with methanol, and dried.

[0013] Step 6: Place the dried sample obtained in step 5 into a tube furnace and react it at 600-900℃ for 1-5 hours in a nitrogen atmosphere to obtain ZIF-8 derived carbon material (NC).

[0014] Step 7: Weigh the NC sample and disperse it in a potassium permanganate aqueous solution, then perform ultrasonic vibration treatment to obtain a suspension; each 100 mL of potassium permanganate aqueous solution corresponds to 0.01-0.1 g of NC sample;

[0015] Step 8: Prepare a manganese sulfate aqueous solution, add it dropwise to the above suspension and stir vigorously, and let the mixed reaction solution stand at room temperature for 6-20 hours; each 100 mL of potassium permanganate aqueous solution corresponds to 10-100 mL of manganese sulfate aqueous solution;

[0016] Step 9: Centrifuge the suspension obtained in Step 8, wash it several times with methanol, and dry the washed black solid material at 60-100℃ for 6-20 hours.

[0017] In a preferred embodiment of the present invention, in step 1, the volume ratio of zinc acetate dihydrate to polyvinylpyrrolidone is 0.2-5:1.

[0018] In a preferred embodiment of the present invention, the aging reaction time in step 1 is 10-30 hours.

[0019] As a preferred technical solution of the present invention, in step 8, the standing time is 6-20 hours.

[0020] As a preferred embodiment of the present invention, a built-in reaction system is constructed by combining a Mn / NC catalyst with a dielectric barrier discharge plasma reactor for green, low-temperature, and efficient toluene removal. The dielectric material of the dielectric barrier discharge reactor has an outer diameter of 1-3 cm, an inner diameter of 0.5-2 cm, a thickness of 0.2-0.8 cm, and a length of 15-80 cm. The high-voltage electrode has a diameter of 1-5 mm, the grounding electrode is a metal mesh, the discharge gap of the reactor is 0.2-1 cm, and the effective discharge length is 10-60 cm.

[0021] As a preferred embodiment of the present invention, the high-voltage electrode is made of stainless steel or copper, the grounding electrode is made of stainless steel or copper, and the dielectric material includes ceramic, glass, or quartz.

[0022] The beneficial effects of this invention are: (1) Low cost: The Mn / NC catalyst prepared by this invention has good degradation activity using only transition metals, and the preparation method is simple, greatly reducing the preparation cost of the catalyst and making it easy to industrialize. (2) Good performance: The nitrogen-doped carbon prepared by this invention has the advantages of rich pore structure and large specific surface area, and is a high-performance support material, while manganese has rich valence states and excellent oxygen transport capacity. The low-temperature plasma synergistic Mn / NC catalyst system constructed by this invention has high catalytic activity, selectivity and stability for toluene under low energy consumption. In this invention, the highest toluene degradation efficiency reached 100%, and CO x The selectivity of (CO+CO2) reached 100%, and the energy efficiency was as high as 23.05 g / kWh, both of which are superior to previous patents in terms of target product selectivity and energy efficiency. In the plasma catalysis system, there is a synergistic effect between plasma and catalyst. Low-temperature plasma generates a large number of active species, including high-energy electrons, excited-state N2 molecules, and free radicals such as ·O and ·N, which can activate toluene molecules and reduce the reaction activation energy of the catalyst. The introduction of the catalyst not only enhances the electric field and generates many micro-discharges in its channels, but also increases the residence time of toluene, which greatly increases the reaction probability between toluene and the active particles generated by the discharge and the active species on the catalyst surface, thus greatly improving the complete mineralization rate of toluene. Attached Figure Description

[0023] Figure 1 A schematic diagram of an experimental setup for the low-temperature plasma catalytic degradation of toluene gas.

[0024] Icons: 1-Air; 2-Mass flow meter; 3-Thermostatic magnetic stirrer; 4-Low-temperature plasma reactor; 5-Low-temperature plasma power supply; 6-Oscilloscope; 7-Gas chromatograph.

[0025] Figure 2 The X-ray diffraction pattern of the ZIF-8, NC, and 6% Mn / NC catalysts of this invention is shown. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] Figure 1A schematic diagram of the experimental setup for the low-temperature plasma catalytic degradation of toluene gas is shown below: A bubbling flask containing toluene is placed in a 0°C ice-water bath. High-pressure pure air is used as the gas source, and the toluene concentration is adjusted by a mass flow meter and fixed at 100 ppm. The low-temperature plasma reactor is a dielectric barrier discharge reactor. The high-voltage electrode of the dielectric barrier discharge reactor is a stainless steel rod with a diameter of 0.4 cm. The dielectric material is a quartz tube with an outer diameter of 1.4 cm, an inner diameter of 1 cm, a thickness of 0.2 cm, and a length of 30 cm. The grounding electrode is a stainless steel mesh outside the quartz tube. The discharge gap of the reactor is 0.3 cm, and the effective discharge length is 20 cm. The concentrations of toluene before and after degradation, as well as the concentrations of the products, are analyzed online using a gas chromatograph. In each experiment, the catalyst and quartz sand are thoroughly mixed at a ratio of 1:2 and then filled into the discharge area.

[0028] Example 1

[0029] The Mn / NC catalyst is prepared according to the following steps:

[0030] Step 1: Weigh zinc acetate dihydrate, polyvinylpyrrolidone (PVP), and methanol. The total volume ratio of zinc acetate dihydrate and PPVP to methanol is 1:50, and the volume ratio of zinc acetate dihydrate to PPVP is 1:1. Pour the zinc acetate dihydrate and PPVP into methanol to obtain mixed solution A. Then, weigh 2-methylimidazole and methanol at a volume ratio of 1:50, and pour the 2-methylimidazole into methanol to obtain mixed solution B. The amount of methanol used in mixed solution A and mixed solution B is the same. After mixing mixed solution A and mixed solution B evenly, place them at room temperature for an aging reaction for 20 hours.

[0031] Step 2: The precipitate obtained in Step 1 is centrifuged, washed with methanol, and dried overnight to finally obtain ZIF-8 solid;

[0032] Step 3: Disperse 0.5g of ZIF-8 solid in 30mL of glucose solution and stir thoroughly for 10h;

[0033] Step 4: Place the solution obtained in Step 3 into a high-pressure reactor and heat it at 120°C for 11 hours;

[0034] Step 5: The precipitate obtained in Step 4 is centrifuged, washed with methanol, and dried.

[0035] Step 6: Place the dried sample obtained in step 5 into a tube furnace and carbonize it at 900°C for 3 hours in a nitrogen atmosphere to obtain NC material.

[0036] Step 7: Weigh 0.1g of NC sample and disperse it in 30mL of potassium permanganate aqueous solution, then perform ultrasonic vibration treatment to obtain a suspension;

[0037] Step 8: Prepare 40 mL of manganese sulfate aqueous solution, add it dropwise to the above suspension and stir vigorously, and let the mixed reaction solution stand at room temperature for 20 h;

[0038] Step 9: Centrifuge the suspension obtained in Step 8, wash it several times with methanol, and dry the washed black solid material at 80°C for 12 hours.

[0039] Example 2

[0040] The Mn / NC catalyst is prepared according to the following steps:

[0041] Step 1: Weigh zinc acetate dihydrate, polyvinylpyrrolidone (PVP), and methanol. The total volume ratio of zinc acetate dihydrate and PPVP to methanol is 1:50, and the volume ratio of zinc acetate dihydrate to PPVP is 1:5. Pour the zinc acetate dihydrate and PPVP into methanol to obtain mixed solution A. Then, weigh 2-methylimidazole and methanol at a volume ratio of 1:50, and pour the 2-methylimidazole into methanol to obtain mixed solution B. The amount of methanol used in mixed solution A and mixed solution B is the same. After mixing mixed solution A and mixed solution B evenly, place them at room temperature for an aging reaction for 20 hours.

[0042] Step 2: The precipitate obtained in Step 1 is centrifuged, washed with methanol, and dried overnight to finally obtain ZIF-8 solid;

[0043] Step 3: Disperse 0.5g of ZIF-8 solid in 30mL of glucose solution and stir thoroughly for 10h;

[0044] Step 4: Place the solution obtained in Step 3 into a high-pressure reactor and heat it at 120°C for 11 hours;

[0045] Step 5: The precipitate obtained in Step 4 is centrifuged, washed with methanol, and dried.

[0046] Step 6: Place the dried sample obtained in step 5 into a tube furnace and carbonize it at 900°C for 3 hours in a nitrogen atmosphere to obtain NC material.

[0047] Step 7: Weigh 0.1g of NC sample and disperse it in 30mL of potassium permanganate aqueous solution, then perform ultrasonic vibration treatment to obtain a suspension;

[0048] Step 8: Prepare 40 mL of manganese sulfate aqueous solution, add it dropwise to the above suspension and stir vigorously, and let the mixed reaction solution stand at room temperature for 20 h;

[0049] Step 9: Centrifuge the suspension obtained in Step 8, wash it several times with methanol, and dry the washed black solid material at 80°C for 12 hours.

[0050] Example 3

[0051] The Mn / NC catalyst is prepared according to the following steps:

[0052] Step 1: Weigh zinc acetate dihydrate, polyvinylpyrrolidone (PVP), and methanol. The total volume ratio of zinc acetate dihydrate and PPVP to methanol is 1:50, and the volume ratio of zinc acetate dihydrate to PPVP is 5:1. Pour the zinc acetate dihydrate and PPVP into methanol to obtain mixed solution A. Then, weigh 2-methylimidazole and methanol at a volume ratio of 1:50, and pour the 2-methylimidazole into methanol to obtain mixed solution B. The amount of methanol used in mixed solution A and mixed solution B is the same. After mixing mixed solution A and mixed solution B evenly, place them at room temperature for an aging reaction for 20 hours.

[0053] Step 2: The precipitate obtained in Step 1 is centrifuged, washed with methanol, and dried overnight to finally obtain ZIF-8 solid;

[0054] Step 3: Disperse 0.5g of ZIF-8 solid in 30mL of glucose solution and stir thoroughly for 10h;

[0055] Step 4: Place the solution obtained in Step 3 into a high-pressure reactor and heat it at 120°C for 11 hours;

[0056] Step 5: The precipitate obtained in Step 4 is centrifuged, washed with methanol, and dried.

[0057] Step 6: Place the dried sample obtained in step 5 into a tube furnace and carbonize it at 900°C for 3 hours in a nitrogen atmosphere to obtain hollow nitrogen-doped carbon material.

[0058] Step 7: Weigh 0.1g of hollow nitrogen-doped carbon sample and disperse it in 30mL of potassium permanganate aqueous solution, then perform ultrasonic vibration treatment to obtain a suspension;

[0059] Step 8: Prepare 40 mL of manganese sulfate aqueous solution, add it dropwise to the above suspension and stir vigorously, and let the mixed reaction solution stand at room temperature for 20 h;

[0060] Step 9: Centrifuge the suspension obtained in Step 8, wash it several times with methanol, and then dry the washed black solid material at 100°C for 12 hours.

[0061] When the ZIF-8 carbonization temperature is 900℃, the carbonization time is 3h, the Mn loading is 6wt%, the discharge power is 10W, and the total flow rate is 2L / min, the degradation efficiency of the plasma catalytic system and CO2 are as follows: x The selectivity is shown in Table 1.

[0062] Table 1. Toluene degradation rate and CO2 corresponding to Mn / NC catalysts prepared with different ratios of zinc acetate dihydrate to polyvinylpyrrolidone dihydrate. x Selective

[0063] Ratio of zinc acetate dihydrate to polyvinylpyrrolidone Toluene degradation rate (%) <![CDATA[CO x Selectivity (%) Example 1 1：1 97.9 85.4 Example 2 1：5 72.5 61.3 Example 3 5：1 67.6 59.1

[0064] Preferably, taking the Mn / NC catalyst prepared with zinc acetate dihydrate and polyvinylpyrrolidone in a 1:1 ratio as an example, the plasma catalytic performance at different ZIF-8 carbonization temperatures is listed.

[0065] Comparative Example 1

[0066] The catalyst was prepared according to the steps and conditions of Example 1, with the carbonization temperature of ZIF-8 changed to 600°C.

[0067] Comparative Example 2

[0068] The catalyst was prepared according to the steps and conditions of Example 1, with the carbonization temperature of ZIF-8 changed to 750°C.

[0069] When the ratio of zinc acetate dihydrate to polyvinylpyrrolidone is 1:1, the ZIF-8 carbonization time is 3 h, the Mn loading is 6 wt%, the discharge power is 10 W, and the total flow rate is 2 L / min, the degradation efficiency of the plasma catalytic system and CO2 are as follows: x The selectivity is shown in Table 2.

[0070] Table 2. Toluene degradation rate and CO2 corresponding to Mn / NC catalysts prepared at different ZIF-8 carbonization temperatures. x Selective

[0071] ZIF-8 carbonization temperature (°C) Toluene degradation rate (%) <![CDATA[CO x Selectivity (%) Example 1 900 97.9 85.4 Comparative Example 1 600 87.2 81.2 Comparative Example 2 750 91.3 83.4

[0072] Preferably, taking the Mn / NC catalyst prepared at a ZIF-8 carbonization temperature of 900℃ as an example, the plasma catalytic performance under different ZIF-8 carbonization times is listed.

[0073] Comparative Example 3

[0074] The catalyst was prepared according to the steps and conditions of Example 1, with the ZIF-8 carbonization time changed to 1 h. Comparative Example 4

[0075] The catalyst was prepared according to the steps and conditions of Example 1, with the ZIF-8 carbonization time changed to 5 h. When the ratio of zinc acetate dihydrate to polyvinylpyrrolidone was 1:1, the ZIF-8 carbonization temperature was 900℃, the Mn loading was 6wt%, the discharge power was 10W, and the total flow rate was 2L / min, the degradation efficiency of the plasma catalytic system and CO were... x The selectivity is shown in Table 3.

[0076] Table 3. Toluene degradation rate and CO2 corresponding to Mn / NC catalysts prepared with different ZIF-8 carbonization times. x Selective

[0077] ZIF-8 carbonization time (h) Toluene degradation rate (%) <![CDATA[CO x Selectivity (%) Example 1 3 97.9 85.4 Comparative Example 3 1 75.4 73.2 Comparative Example 4 5 95.1 82.7

[0078] Preferably, taking the Mn / NC catalyst with a ZIF-8 carbonization time of 3h as an example, the plasma catalytic performance under different Mn loadings is listed.

[0079] Comparative Example 5

[0080] The catalyst was prepared according to the steps and conditions of Example 1, with the Mn loading changed to 9 wt%.

[0081] Comparative Example 6

[0082] The catalyst was prepared according to the steps and conditions of Example 1, with the Mn loading changed to 12 wt%.

[0083] When the ratio of zinc acetate dihydrate to polyvinylpyrrolidone is 1:1, the ZIF-8 carbonization temperature is 900℃, the carbonization time is 3h, the discharge power is 10W, and the total flow rate is 2L / min, the degradation efficiency of the plasma catalytic system and CO2 are [data missing]. x The options are shown in Table 4.

[0084] Table 4. Toluene degradation rate and CO2 corresponding to Mn / NC catalysts prepared with different Mn loadings. x Selective

[0085] Mn loading (wt%) Toluene degradation rate (%) <![CDATA[CO x Selectivity (%) Example 1 6 97.9 85.4 Comparative Example 5 9 89.3 70.9 Comparative Example 6 12 92.4 77.1

[0086] Figure 2 XRD results for ZIF-8, NC, and 6% Mn-loaded Mn / NC are presented. The prepared ZIF-8 exhibits strong characteristic diffraction peaks at 2θ = 7.4°, 10.4°, 12.7°, 17.9°, and 26.6°, indicating that the synthesized ZIF-8 has a complete structure. However, no characteristic diffraction peaks of ZIF-8 were found in the prepared NC and 6% Mn / NC catalysts, indicating that ZnO was completely decomposed during synthesis. The diffraction peaks of NC at 2θ = 24.56° and 44.24° are attributed to the (002) and (101) planes of the carbon material, which are typical characteristics of graphitic carbon. After loading manganese oxide, the typical diffraction peaks of the NC material are still present, and characteristic peaks of Mn2O3 (JCPDS 41-1442) and Mn3O4 (JCPDS 75-1560) species are detected, indicating that the crystal structure of NC is not destroyed and Mn is well loaded on the NC surface.

[0087] Preferably, taking the Mn / NC catalyst prepared with a Mn loading of 6% as an example, the plasma catalytic performance under different discharge powers is listed.

[0088] Comparative Example 7

[0089] The catalyst was prepared according to the steps and conditions of Example 1, with the discharge power changed to 15W.

[0090] Comparative Example 8

[0091] The catalyst was prepared according to the steps and conditions of Example 1, with the discharge power changed to 20W.

[0092] When the ratio of zinc acetate dihydrate to polyvinylpyrrolidone is 1:1, the ZIF-8 carbonization temperature is 900℃, the carbonization time is 3h, the Mn loading is 6wt%, and the total flow rate is 500mL / min, the degradation efficiency and CO2 of the plasma catalytic system are as follows: x Selectivity and energy efficiency are shown in Table 5.

[0093] Table 5. Toluene degradation rate and CO2 corresponding to Mn / NC catalyst at different discharge powers. x Selectivity and energy efficiency

[0094] Discharge power (W) Toluene degradation rate (%) <![CDATA[CO x Selectivity (%) Energy efficiency (g / kWh) Example 1 10 97.9 85.4 23.05 Comparative Example 7 15 99.1 91.2 15.64 Comparative Example 8 20 100 100 7.52

[0095] Experimental results show that when the discharge power is 10W, the energy efficiency of the reaction is 23.05g / kWh. Therefore, taking the discharge power of 10W as an example, the reaction performance of three systems are listed: single plasma system, single catalytic system and plasma catalytic system.

[0096] Comparative Example 9

[0097] Compared to Example 1, toluene degradation was carried out using only a 6% Mn / NC catalyst without the use of plasma.

[0098] Comparative Example 10

[0099] Compared to Example 1, toluene degradation was carried out using only plasma without a catalyst.

[0100] When the ratio of zinc acetate dihydrate to polyvinylpyrrolidone is 1:1, the ZIF-8 carbonization temperature is 900℃, the carbonization time is 3h, the Mn loading is 10wt%, the discharge power is 10W, and the total flow rate is 2L / min, the degradation efficiency and CO2 of different systems are compared. x The options are shown in Table 6.

[0101] Table 6. Toluene degradation rate and CO2 for different systems x Selective

[0102] reaction system Toluene degradation rate (%) <![CDATA[CO x Selectivity (%) Example 1 Plasma catalysis 97.9 85.4 Comparative Example 9 Single catalyst 9.3 1.2 Comparative Example 10 Single plasma 45.2 12.1

[0103] Experimental results show that the degradation rate of toluene and CO in the plasma catalytic system are... x The selectivity is much greater than the sum of the single catalyst and single plasma, demonstrating the good synergistic effect between plasma and catalyst.

[0104] In summary, in this invention, the highest toluene removal rate is 100%, and CO... x With 100% selectivity and a power of 10W, the energy efficiency can reach 23.05 g / kWh, indicating that low-temperature plasma combined with Mn / NC catalyst has great application prospects in toluene degradation.

Claims

1. A method for the degradation of toluene using low-temperature plasma in conjunction with a Mn / NC catalyst, characterized in that, A Mn / NC catalyst with abundant pore structure, large specific surface area and strong oxygen transport capacity was prepared and introduced into a low-temperature plasma discharge system to enhance the synergistic effect between the Mn / NC catalyst and the low-temperature plasma, so as to be used for green and efficient degradation of toluene at low temperature. The Mn / NC catalyst is prepared according to the following steps: Step 1: Weigh zinc acetate dihydrate, polyvinylpyrrolidone (PVP), and methanol. The total volume ratio of zinc acetate dihydrate and PPVP to methanol is 1:

50. Pour the zinc acetate dihydrate and PPVP into methanol to obtain mixed solution A. Then, weigh 2-methylimidazole and methanol at a volume ratio of 1:

50. Pour the 2-methylimidazole into methanol to obtain mixed solution B. The amount of methanol used in mixed solution A and mixed solution B is the same. After mixing mixed solution A and mixed solution B evenly, place them at room temperature for aging reaction. The volume ratio of zinc acetate dihydrate to PPVP is 0.2-5:1, and the aging reaction time is 10-30 h. Step 2: The precipitate obtained in Step 1 is centrifuged, washed with methanol, and dried overnight to finally obtain ZIF-8 solid; Step 3: Disperse ZIF-8 solid in glucose solution and stir thoroughly for 1-10 h; weigh 0.1-1 g of ZIF-8 solid for every 30 mL of glucose solution; Step 4: Place the solution obtained in Step 3 into a high-pressure reactor and heat it at 60-180 °C for 2-20 h; Step 5: The precipitate obtained in Step 4 is centrifuged, washed with methanol, and dried. Step 6: Place the dried sample obtained in step 5 into a tube furnace and react it at 600-900 °C for 1-5 h in a nitrogen atmosphere to obtain hollow nitrogen-doped carbon material. Step 7: Weigh out the hollow nitrogen-doped carbon sample and disperse it in a potassium permanganate aqueous solution, then perform ultrasonic vibration treatment to obtain a suspension; each 100 mL of potassium permanganate aqueous solution corresponds to 0.01-0.1 g of hollow nitrogen-doped carbon sample; Step 8: Prepare a manganese sulfate aqueous solution, add it dropwise to the above suspension and stir vigorously, and let the mixed reaction solution stand at room temperature for 6-20 h; each 100 mL of potassium permanganate aqueous solution corresponds to 10-100 mL of manganese sulfate aqueous solution; Step 9: Centrifuge the suspension obtained in Step 8, wash it several times with methanol, and dry the washed black solid material at 60-100 °C for 6-20 h.

2. The method for low-temperature plasma-assisted degradation of toluene using a Mn / NC catalyst according to claim 1, characterized in that, Toluene is degraded using a dielectric barrier discharge reactor. For a single discharge unit, the high-voltage electrode of the dielectric barrier discharge reactor has a diameter of 1-5 mm, an outer diameter of 1-3 cm, an inner diameter of 0.5-2 cm, a thickness of 0.2-0.8 cm, and a length of 15-80 cm. The grounding electrode is a metal mesh, the discharge gap of the reactor is 0.2-1 cm, and the effective discharge length is 10-60 cm. The high-voltage electrode is made of stainless steel or copper, the grounding electrode is made of stainless steel or copper, and the dielectric material includes ceramic, glass, or quartz.

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