Application of nitrogen-doped bamboo activated carbon in room-temperature oxidation of methyl mercaptan

Abstract

The invention discloses application of nitrogen-doped bamboo activated carbon in room-temperature oxidation of methyl mercaptan, and belongs to the technical field of sulfur-containing foul pollutant treatment. According to the catalyst, bamboo charcoal is used as a carbon source, 1, 10-phenanthroline or ammonia gas and 1, 10-phenanthroline are used as nitrogen sources, and the nitrogen-doped bamboo activated carbon catalyst is prepared through mixed grinding and high-temperature calcination. The nitrogen-doped bamboo activated carbon prepared by the method has abundant topological defects and structural alkaline sites, and has remarkable advantages in the aspect of oxidative degradation of methyl mercaptan at room temperature. The catalyst can realize catalytic degradation of methyl mercaptan at room temperature, can still keep the degradation rate of 85% or above after continuous reaction for 150 hours, and shows excellent catalytic activity and stability.

Description

Technical Field

[0001] This invention belongs to the field of sulfur-containing odor pollutant treatment technology, specifically involving the application of nitrogen-doped bamboo activated carbon in the room temperature oxidation of methanethiol. Background Technology

[0002] Malodor, one of the world's seven major environmental hazards, not only irritates and harms the human respiratory, sensory, and central nervous systems, but is also a significant contributing factor to environmental problems such as haze and photochemical smog. Sulfur-containing volatile organic compounds (VOCs) are typical malodorous substances, characterized by high toxicity, low odor threshold, and strong corrosiveness. They are widely present in industries such as petrochemicals, wastewater treatment, and livestock farming, seriously impacting air quality and human health. Methanethiol (CH3SH), as a sulfur-containing VOC, has an extremely low odor threshold; trace amounts of CH3SH (10⁻¹⁰) can cause odor problems. -9 Even at ppb levels, it can produce an unpleasant rotten cabbage smell; high concentrations of CH3SH (10 ppb) can also produce this smell. -6 High concentrations (in ppm) can be harmful to human health, causing mild irritation to the skin, upper respiratory tract mucosa, and eyes, and severe paralysis of the central nervous system, leading to suffocation and symptoms such as headache and nausea. Therefore, using CH3SH as a representative of malodorous substances in research has significant practical implications.

[0003] Currently, odor pollution control technologies in my country mainly fall into several categories, including catalytic combustion, absorption / adsorption, low-temperature plasma, biodegradation, and advanced oxidation, each with its own advantages, disadvantages, and application areas. Catalytic combustion and absorption / adsorption show excellent performance in treating high concentrations of sulfur-containing volatile organic compounds, but traditional combustion methods suffer from secondary pollution problems (such as SO2). x (Emissions). For the purification of low-concentration malodors, low-temperature plasma technology is energy-intensive and carries potential risks, while biotechnology is limited by factors such as low efficiency, large processing equipment, and high investment costs. In recent years, advanced oxidation technologies (AOPs) have received widespread attention as an effective method for removing recalcitrant organic pollutants. Room temperature advanced oxidation technologies refer to the use of highly reactive free radicals (such as ·OH, ·O2) generated by strong oxidants or catalysts at room temperature (20℃-25℃). , 1 Advanced oxidation technologies (AOPs) are techniques that oxidize and decompose organic pollutants into non-toxic and harmless small molecules (such as CO2 and H2O). AOPs are characterized by simple systems, mild reaction conditions, high operability, and economic safety, and can significantly improve the removal rate and efficiency of pollutants, demonstrating great potential in the treatment of CH3SH pollution in the environment.

[0004] Previous studies have found that surface defects (especially oxygen vacancies) are the main active sites for triggering the activation of O2 into reactive oxygen species (ROS) and inducing the catalytic decomposition of organic molecules at room temperature. Therefore, the construction of highly defective catalysts is key to achieving efficient degradation of CH3SH at room temperature through advanced oxidation. However, the preparation process of defective catalysts for room temperature advanced oxidation technologies is still relatively complex, and the activity of the materials needs further improvement. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide nitrogen-doped bamboo activated carbon and its application in the room temperature oxidation of methanethiol.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The present invention first provides a nitrogen-doped bamboo activated carbon catalyst, wherein the catalyst is prepared by mixing, grinding and high-temperature calcination using bamboo charcoal as a carbon source and 1,10-phenanthroline or ammonia and 1,10-phenanthroline as nitrogen sources. The mass fraction of nitrogen in the catalyst can be 0-5%, but the endpoint 0 is not acceptable.

[0007] By adjusting the mass ratio of carbon source to nitrogen source, a series of nitrogen-doped bamboo activated carbon catalysts with different nitrogen contents were obtained.

[0008] The present invention also provides a method for preparing the above-mentioned nitrogen-doped bamboo activated carbon catalyst.

[0009] The method includes the following steps: 1) Mixing and grinding Weigh out bamboo charcoal and 1,10-phenanthroline, grind them until they are evenly mixed, and obtain a powder; 2) High-temperature calcination The powder obtained in step 1) is calcined at high temperature in an N2 atmosphere or an N2 and NH3 atmosphere to obtain nitrogen-doped bamboo activated carbon.

[0010] In step 1) of the above method, the mass ratio of bamboo charcoal to 1,10-phenanthroline can be 1:1 to 1:5, specifically 1:1, 1:3 or 1:5; In step 2) of the above method, the conditions for high-temperature calcination are: a heating rate of 2-10℃ / min, specifically 5℃ / min, and holding at 700-900℃ for 1-2 hours, specifically 2 hours at 900℃.

[0011] In the obtained nitrogen-doped bamboo activated carbon, the mass fraction of nitrogen can be 0-5%, and the endpoint 0 is not acceptable.

[0012] The application of nitrogen-doped bamboo activated carbon in the room temperature oxidative degradation of methanethiol is also within the scope of protection of this invention.

[0013] In the aforementioned application, the conditions for the room-temperature oxidative degradation reaction of methanethiol can be: CH3SH concentration of 0-100 ppm, O2 concentration of 10-20%, reaction temperature of 20-25℃, and gas flow rate of 50-60 L·g. -1 ·h -1 The reaction time is 0~150 h (the endpoint 0 is not acceptable).

[0014] The beneficial effects of this invention are: 1. The nitrogen-doped bamboo activated carbon catalyst provided by this invention uses bamboo activated carbon, a low-cost and readily available biomass-derived carbon material, as a precursor, effectively reducing production costs. Furthermore, the catalyst is simple to prepare and easy to operate.

[0015] 2. The nitrogen-doped bamboo activated carbon catalyst provided by this invention is a non-metallic heterogeneous catalyst. By adjusting the type of nitrogen source and the ratio of carbon source to nitrogen source, nitrogen-containing carbon materials with a nitrogen element mass fraction of 0 to 5% can be prepared, thereby achieving the controllability of nitrogen doping amount and thus controlling its catalytic activity.

[0016] 3. This invention demonstrates for the first time the highly efficient catalytic performance of nitrogen-doped bamboo activated carbon catalysts in the room-temperature oxidation of CH3SH. The high-temperature activated catalyst possesses a large specific surface area and a well-developed pore structure; abundant surface defects enhance the catalyst's adsorption and activation capacity for oxygen, increasing the amount of reactive oxygen species. Pyridine nitrogen acts as a structural basic site during the reaction, synergistically working with topological defects to promote the degradation of CH3SH.

[0017] 4. The nitrogen-doped bamboo activated carbon catalyst prepared by this invention not only exhibits good catalytic performance for the room temperature oxidation of CH3SH, but also has excellent stability, maintaining a degradation rate of over 85% even after 150 hours of continuous reaction. Attached Figure Description

[0018] Figure 1 The image shows a SEM image of the nitrogen-doped bamboo activated carbon prepared in Comparative Example 1.

[0019] Figure 2 This is a SEM image of the nitrogen-doped bamboo activated carbon prepared in Example 3 of the present invention.

[0020] Figure 3 The diagram shows the CH3SH degradation activity of nitrogen-doped bamboo activated carbon prepared in Comparative Examples 1, 2, and 3 of this invention.

[0021] Figure 4This is a CH3SH degradation stability diagram of the nitrogen-doped bamboo activated carbon prepared in Examples 1-3 of this invention. BC represents the original bamboo charcoal in Comparative Example 3, BC-N2 represents the bamboo charcoal calcined in a nitrogen atmosphere prepared in Comparative Example 2, BC-NH3 represents the bamboo charcoal calcined in an ammonia atmosphere prepared in Comparative Example 1, BC-1 represents the nitrogen-doped bamboo activated carbon prepared in Example 1, BC-3 represents the nitrogen-doped bamboo activated carbon prepared in Example 2, and BC-5 represents the nitrogen-doped bamboo activated carbon prepared in Example 3. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0024] Comparative Example 1 0.2 g of raw bamboo charcoal was placed in a corundum boat in a horizontal tube furnace and heated from room temperature to 900℃ at a heating rate of 5℃ / min under a nitrogen atmosphere (60 mL / min). Then it was kept under an ammonia atmosphere (60 mL / min) for 2 h and finally cooled to room temperature under a nitrogen atmosphere (60 mL / min) to obtain a nitrogen-doped bamboo activated carbon catalyst with a nitrogen doping amount of 1.75%. Figure 1 The image shows a SEM image of the nitrogen-doped bamboo activated carbon prepared.

[0025] Example 1 0.2 g of raw bamboo charcoal and 0.2 g of 1,10-phenanthroline were ground in a mortar until uniformly mixed. The mixture was then transferred to a corundum boat in a horizontal tube furnace and heated from room temperature to 900°C at a rate of 5°C / min under a nitrogen atmosphere (60 mL / min). The temperature was then maintained at 2 h under an ammonia atmosphere (60 mL / min) and finally cooled to room temperature under a nitrogen atmosphere (60 mL / min) to obtain a nitrogen-doped bamboo activated carbon catalyst with a nitrogen doping amount of 3.21%.

[0026] Example 2 0.2 g of raw bamboo charcoal and 0.6 g of 1,10-phenanthroline were ground in a mortar until uniformly mixed. The mixture was then transferred to a corundum boat in a horizontal tube furnace and heated from room temperature to 900°C at a rate of 5°C / min under a nitrogen atmosphere (60 mL / min). The temperature was then maintained at 2 h under an ammonia atmosphere (60 mL / min) and finally cooled to room temperature under a nitrogen atmosphere (60 mL / min) to obtain a nitrogen-doped bamboo activated carbon catalyst with a nitrogen doping content of 3.97%.

[0027] Example 3 0.2 g of raw bamboo charcoal and 1.0 g of 1,10-phenanthroline were ground in a mortar until uniformly mixed. The mixture was then transferred to a corundum boat in a horizontal tube furnace and heated from room temperature to 900°C at a rate of 5°C / min under a nitrogen atmosphere (60 mL / min). The temperature was then maintained at 2 h under an ammonia atmosphere (60 mL / min) and finally cooled to room temperature under a nitrogen atmosphere (60 mL / min) to obtain a nitrogen-doped bamboo activated carbon catalyst with a nitrogen doping amount of 5.03%. Figure 2 The image shows a SEM image of the nitrogen-doped bamboo activated carbon prepared.

[0028] Depend on Figure 1 and Figure 2 It is known that after ammonia etching and nitrogen doping, the surface of bamboo charcoal becomes rougher, with obvious pores appearing on the longitudinal pore walls, which is conducive to molecular transport and diffusion. Adding 1,10-phenanthroline as a second nitrogen source results in high-temperature decomposition of 1,10-phenanthroline to produce gaseous products, enhancing the pore etching effect and nitrogen doping amount. However, excessive nitrogen doping can cause pore sintering to some extent. Figure 2 It can be seen that some pores are sintered, which will reduce the material's ability to degrade methanethiol.

[0029] Comparative Example 2 0.2 g of raw bamboo charcoal was placed in a corundum boat of a horizontal tube furnace and heated from room temperature to 900℃ at a heating rate of 5℃ / min under a nitrogen atmosphere (60 mL / min). The temperature was maintained for 2 h and then cooled to room temperature to obtain a bamboo activated carbon catalyst with 0% nitrogen doping.

[0030] Comparative Example 3 Take 0.2 g of raw bamboo charcoal without any treatment.

[0031] Example 4: CH3SH Catalytic Degradation Experiment The catalytic degradation of CH3SH was carried out in a fixed-bed reactor at atmospheric pressure. In the standard experiment, the sample was packed into a quartz reactor (Φ1.2 cm). The entire reaction was conducted at room temperature (25 °C) with an inlet CH3SH concentration of 50 ppm and an O2 concentration of 10% (premixed in a mixer from CH3SH cylinder gas (100 ppm, carrier gas N2) and synthesis air cylinder gas (20% O2, the remainder N2)). The reaction space velocity was controlled at 60 L·g⁻¹. -1 ·h -1 The gas flow rate is controlled by a mass flow controller, and the reaction temperature is controlled by a K-type thermocouple furnace. A mass spectrometer (Hiden, HPR-20) is used for online detection of CH3SH and other gaseous product signals in the outlet gas.

[0032] Depend on Figure 3 It is evident that ammonia-activated bamboo charcoal (Comparative Example 1) exhibits significantly enhanced CH3SH degradation performance. This is because ammonia activation constructs structural alkaline sites on the material surface, facilitating the adsorption and activation of CH3SH. High-temperature calcination removes nitrogen atoms, which were initially doped into the carbon lattice at low temperatures, from the carbon framework, leading to lattice distortion and the generation of topological defects. This increases the defect concentration on the material surface, thereby enhancing the ability to activate oxygen and generate ROS. However, its 95% degradation rate of CH3SH was maintained for only 2.8 hours, subsequently declining rapidly. Figure 4 It can be seen that adding 1,10-phenanthroline to the ammonia activation further increases the nitrogen content and defect concentration on the material surface, thereby further improving the catalytic oxidation performance of CH3SH. The nitrogen-doped bamboo activated carbon obtained in Example 1 maintained a 100% degradation rate for 7.5 h; the nitrogen-doped bamboo activated carbon obtained in Example 2 showed the best performance, maintaining a 100% degradation rate for 18 h; the nitrogen-doped bamboo activated carbon obtained in Example 3 maintained a 100% degradation rate for 12.5 h, possibly because excessive nitrogen doping led to a decrease in the material defect concentration, affecting the oxidation of CH3SH. It is noteworthy that after a 150 h stability test, all three types of nitrogen-doped bamboo activated carbon maintained a CH3SH degradation rate of over 85%.

[0033] This invention uses ammonia as an activator and nitrogen source, and adds 1,10-phenanthroline as a second nitrogen source. The nitrogen-doped bamboo activated carbon obtained by high-temperature calcination not only exhibits excellent room-temperature catalytic oxidation ability for CH3SH, but also demonstrates outstanding stability. This is because the combined effect of ammonia and 1,10-phenanthroline creates a rich porous structure and topological defects on the bamboo charcoal surface. The entry of nitrogen atoms constructs a large number of structural basic sites on the material surface, and the synergistic effect of defects and basic sites promotes the degradation of CH3SH.

[0034] The present invention has been described in detail above. Those skilled in the art will recognize that the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. While specific embodiments have been provided, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein.

Claims

1. A nitrogen-doped bamboo activated carbon catalyst, wherein the catalyst is prepared by mixing and grinding and high-temperature calcination with bamboo charcoal as a carbon source and 1, 10-phenanthroline or ammonia and 1, 10-phenanthroline as a nitrogen source.

2. The catalyst according to claim 1, characterized in that, The mass fraction of nitrogen in the catalyst is 0-5%, and the end point 0 is not desirable. 3.A method for preparing the catalyst of claim 1 or 2, comprising the following steps: 1) mixing and grinding Weighing bamboo charcoal and 1, 10-phenanthroline, grinding until mixed evenly to obtain a powder; 2) high-temperature calcination The powder obtained in step 1) is calcined at high temperature in N2 atmosphere or N2 and NH3 atmosphere to obtain a nitrogen-doped bamboo activated carbon.

4. The method of claim 3, wherein, In step 1), the mass ratio of bamboo charcoal to 1, 10-phenanthroline is 1: 1-1:

5.

5. The method of claim 3, wherein, In step 2), the high-temperature calcination conditions are as follows: the heating rate is 2-10 ℃ / min, and the temperature is kept at 700-900 ℃ for 1-2 h. 6.The application of the nitrogen-doped bamboo activated carbon catalyst of claim 1 or 2 in the oxidative degradation of methyl mercaptan at room temperature.

7. Use according to claim 6, characterized in that, In the application, the conditions of the oxidation degradation reaction of methyl mercaptan at room temperature are: CH3SH concentration is 0-100 ppm, O2 concentration is 10-20%, reaction temperature is 20-25℃, gas flow is 50-60L·g -1 ·h -1 , and reaction time is 0-150 h (endpoint 0 is not acceptable).

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