Biomass-derived curvature carbon nanotube anchoring atom dispersion metal catalyst and preparation method and application thereof

Abstract

The invention belongs to the technical field of catalysts and catalysis methods, and particularly relates to a biomass-derived curvature carbon nanotube anchoring atom dispersion metal catalyst and a preparation method and application thereof. Furthermore, the invention also discloses a method for catalytic oxidation of sulfur-containing volatile organic pollutants by ozone. The preparation method of the catalyst comprises the following steps: mixing a biomass raw material and a metal salt, carrying out pre-pyrolysis at 450-600 DEG C in a nitrogen atmosphere, then heating to 700-900 DEG C, annealing, and carrying out post-treatment to prepare the biomass-derived curvature carbon nanotube anchoring atom dispersion metal catalyst, the mass percentage of the metal salt in the biomass raw material is 0.8-3.0 wt.%; metal in the metal salt is transition metal; the catalyst comprises a carbon nano tube and metal loaded on the tube wall of the carbon nano tube; and the average diameter of the carbon nanotubes is 8-50 nm. The catalyst provided by the invention has excellent catalytic activity, and shows excellent removal efficiency and stability on S-VOCs.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts and catalytic methods, and particularly relates to a biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Sulfur-containing volatile organic pollutants (S-VOCs), due to the presence of sulfur elements, in addition to having the characteristics of typical VOCs, have an extremely low olfactory threshold, usually accompanied by a foul smell, and are prone to cause acid deposition, posing great harm to the ecological environment and human health. Sulfur-containing volatile organic pollutants are difficult to purify. Due to the easy generation of sulfur-containing by-products during the purification process and the complexity of S-VOCs emission sources and emission categories, the removal of sulfur-containing volatile organic pollutants is quite difficult.

[0003] The heterogeneous ozone catalytic oxidation technology has become one of the most promising S-VOCs removal technologies due to its technical characteristics such as simple operation, high efficiency, low energy consumption, and low secondary pollution. The electrophilic ozone molecules are adsorbed and activated by the active sites in the catalyst at normal temperature and pressure to generate a large number of highly oxidizing reactive oxygen species, thus being able to continuously and efficiently remove S-VOCs. During the removal of S-VOCs, the mass transfer and diffusion behavior of pollutant molecules and oxidant molecules at the catalyst surface and interface, as well as the electronic interaction between the active sites in the catalyst and different molecules, are of great significance for understanding the origin of activity and promoting the long-term use of the catalyst.

[0004] Patent Publication No. CN118237062A discloses a nitrogen-doped carbon nanotube-coated cobalt metal composite. Melamine, graphitic carbon nitride, and inorganic cobalt salts are mixed to obtain a mixed raw material; the mixed raw material is calcined in a protective atmosphere to obtain a calcined material; the calcined material is washed and dried in sequence to obtain a nitrogen-doped carbon nanotube-coated cobalt metal composite. In addition, it is also disclosed that the composite material can be used for the catalytic degradation of methylene blue. However, the above composite material still has a poor removal effect on S-VOCs. Summary of the Invention

[0005] Aiming at the above existing technical problems, the primary object of the present invention is to provide a preparation method of a biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst. The catalyst prepared by the preparation method has excellent catalytic activity during the ozone catalytic oxidation process and exhibits excellent removal efficiency and stability for S-VOCs.

[0006] The second object of the present invention is to provide a biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst prepared by the above preparation method.

[0007] The third object of the present invention is to provide the application of a biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst in the ozonation catalytic oxidation of sulfur-containing volatile organic pollutants.

[0008] The fourth object of the present invention is to provide a method for the ozonation catalytic oxidation of sulfur-containing volatile organic pollutants.

[0009] To achieve the above objects, the present invention is realized through the following technical solutions: A preparation method of a biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst, comprising the following steps: mixing a biomass raw material and a metal salt, pre-carbonizing at 450-600 °C in a nitrogen atmosphere, and then heating to 700-900 °C for annealing, and post-treating to obtain a biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst; The mass percentage of the metal salt in the biomass raw material is 0.8-3.0 wt.%; the metal in the metal salt is a transition metal; The biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst comprises carbon nanotubes and a metal supported on the tube walls of the carbon nanotubes; the average diameter of the carbon nanotubes is 8-50 nm.

[0010] Traditional planar carbon carrier-supported atomically dispersed catalysts have a highly symmetric in-plane ordered structure, and there is a strong electronic interaction between the carrier and the metal active sites, which inhibits the reactivity between the catalytic active sites and pollutant molecules, resulting in low catalytic activity. In the present invention, biomass and transition metals with rich d-orbital electron structures are selected as the carbon source and metal precursor, which can effectively introduce different mesoscopic and microscopic structures, and can form a flexible and adjustable curvature structure and atomic state, thereby promoting the accessibility and reactivity of the active sites. Specifically: In the present invention, by controlling the average diameter of the carbon nanotubes, the carbon nanotubes have a specific curvature structure. Compared with the planar graphite structure, the carbon nanotube structure can improve the mass transfer efficiency of each molecule in the catalytic process, reduce the accumulation of surface carbon-containing species and sulfur-containing species, enable the catalyst to maintain excellent catalytic activity and cycle stability, and the catalyst can be repeatedly regenerated by simple annealing treatment. It is very important to control the average diameter of the carbon nanotubes within a specific range. When the average diameter of the carbon nanotubes is small, the molecular diffusion rate is too high and the catalytic activity is low; when the average diameter of the carbon nanotubes is large, the ineffective collision between molecules increases and the catalytic activity is still low.

[0011] Furthermore, the atomically dispersed metal is anchored on the tube walls of the carbon nanotubes, and an asymmetric metal-carbon coordination structure is formed by using its curvature effect. The curved surface metal sites are enriched with charges, enhancing the electron utilization rate and effectively improving the O3 activation ability, and thus can significantly improve the catalytic activity.

[0012] Furthermore, the mass percentage of the metal salt and the biomass raw material also greatly affects the catalytic performance of the catalyst for S-VOCs. Excellent catalytic oxidation effects are difficult to achieve when the mass percentage is either too low or too high.

[0013] Furthermore, in the present invention, preliminary pre-pyrolysis is first carried out at a relatively low temperature. Since the types and concentrations of oxygen-containing groups (-OH, -COOH, -O) on the surfaces of different biomasses are not the same, the oxygen-containing groups can complex with transition metal atoms to varying degrees during the preliminary pre-pyrolysis process and form complex intermediates, which can prevent the aggregation of metal atoms. When the pre-pyrolysis temperature is too low, effective complexation of metal atoms is difficult to occur, resulting in a low loading amount and low atomic utilization rate; when the pre-pyrolysis temperature is too high, the oxygen-containing groups will be destroyed, causing the metal ions to agglomerate and be coated in the carbon nanotubes, affecting the exposure of their active sites.

[0014] After the complex intermediate is pre-pyrolyzed, annealing treatment is carried out to promote the complete carbonization of the biomass and induce its thermal polymerization and radial self-assembly at high temperatures, forming a nanotube curvature structure with a specific average diameter. At the same time, the oxygen-containing groups complexing with the metal atoms are volatilized, enabling the metal atoms to be fully exposed on the surface of the carbon nanotubes. Moreover, the degree of polymerization can be effectively regulated by selecting a specific biomass, thus forming a biomass-derived curvature carbon nanotube anchored atom-dispersed metal catalyst with different diameters.

[0015] Preferably, the biomass raw material is selected from one or more of coconut shell, oil-tea fruit shell, orange peel or pomelo peel. More preferably, the biomass raw material is selected from oil-tea fruit shell. The inventors need to further clarify that the type of the biomass raw material also has a significant impact on the catalytic activity of the finally prepared catalyst. By selecting a specific biomass raw material, the surface curvature of the carbon nanotubes can be optimized, and the one-dimensional radial confinement structure of carbon nanotubes with different curvatures can regulate the mass transfer and diffusion behaviors of gaseous pollutant molecules, effectively avoiding catalyst carbon deposition and sulfur poisoning, and thus maintaining the high activity and high stability of the catalyst.

[0016] Preferably, the average diameter of the carbon nanotubes is 15 - 50 nm. More preferably, the average diameter of the carbon nanotubes is 15 - 25 nm. Most preferably, the average diameter of the carbon nanotubes is 20 nm. Specifically, the average diameter of the carbon nanotubes can be 10nm, 15 nm, 20 nm, 15nm, 30 nm, 35 nm, 40 nm, 50 nm, etc., or the interval ranges formed by any of the above values, such as 15 - 40 nm, 15 - 25 nm, etc. The present invention is not limited thereto. The test method for the average diameter of the carbon nanotubes is: statistically calculate the average diameter of the carbon nanotubes in the scanning electron microscope image and take its arithmetic mean.

[0017] Preferably, the mass percentage of the metal salt in the biomass raw material is 0.8 - 2.0 wt.%. Further preferably, the mass percentage of the metal salt in the biomass raw material is 1.0 - 1.5 wt.%. More preferably, the mass percentage of the metal salt in the biomass raw material is 1.0 - 1.2 wt.%. Most preferably, the mass percentage of the metal salt in the biomass raw material is 1.0 wt.%. Specifically, the mass percentage of the metal salt in the biomass raw material can be 1.0 wt.%, 1.1 wt.%, 1.2 wt.%, 1.3 wt.%, 1.4 wt.%, 1.5 wt.%, 1.6 wt.%, 1.7 wt.%, 1.8 wt.%, 1.9 wt.%, 2.0 wt.%, 2.1 wt.%, 2.2 wt.%, 2.3 wt.%, 2.4 wt.%, 2.5 wt.%, 2.6 wt.%, 2.7 wt.%, 2.8 wt.%, 2.9 wt.%, etc., or the range formed by any of the above numerical values. The present invention is not limited thereto.

[0018] Preferably, the metal salt is selected from one or more of copper salts, manganese salts, iron salts, and cobalt salts. Further preferably, the metal salt is selected from copper salts.

[0019] Preferably, at least one of the following (a) to (d) is selected: (a) The copper salt is selected from one or more of Cu(NO3)2·3H2O, CuCl2·4H2O, CuSO4·5H2O, and Cu(CH3COO)2·H2O; (b) The manganese salt is selected from one or more of Mn(NO3)2·4H2O, MnCl2·4H2O, MnSO4, and Mn(CH3COO)2·H2O; (c) The iron salt is selected from one or more of Fe(NO3)3·9H2O, FeCl3, FeSO4, and Fe(CH3COO)2·4H2O; (d) The cobalt salt is selected from one or more of Co(NO3)2·6H2O, CoCl2·6H2O, CoSO4, and (CH3COO)2Co·4H2O.

[0020] Preferably, the time for pre - pyrolysis is 1 - 4 h; and / or, the time for annealing is 1 - 4 h.

[0021] Further preferably, the time for pre - pyrolysis is 2 - 3 h; most preferably, the time for pre - pyrolysis is 2 h.

[0022] Further preferably, the time for annealing is 2 - 3 h; most preferably, the time for annealing is 3 h.

[0023] Preferably, pre-pyrolysis is carried out at 480 - 520 °C under a nitrogen atmosphere; most preferably, pre-pyrolysis is carried out at 500 °C under a nitrogen atmosphere.

[0024] Preferably, annealing is carried out by heating to 750 - 850 °C; more preferably, annealing is carried out by heating to 780 - 820 °C; most preferably, annealing is carried out by heating to 800 °C.

[0025] Preferably, in the pre-pyrolysis step and the annealing step, the heating rate is 3 - 8 °C min -1 ; and / or the nitrogen flow rate is 20 - 60 mL min -1 .

[0026] Preferably, the post-treatment includes the following steps: dispersing the annealed product into an alkali solution for mixing, removing excess metal salts, washing, and drying.

[0027] Preferably, the mixing time is 6 - 18 h. Preferably, deionized water is used for washing until the pH is about 7.0.

[0028] Furthermore, the present invention claims the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst prepared by the above preparation method.

[0029] Furthermore, the present invention claims the application of the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst in the catalytic ozonation of sulfur-containing volatile organic pollutants.

[0030] In the process of catalytic ozonation for removing S-VOCs provided by the present invention, the catalyst not only has excellent removal efficiency for pollutants, but also effectively avoids catalyst surface carbon deposition and sulfur poisoning, maintaining excellent stability while achieving high-efficiency removal of S-VOCs. And the unique surface curvature effect can maximize the utilization of metal atoms and significantly enhance the utilization efficiency of ozone. The ozone concentration in the tail gas is significantly lower than the national standard, causing little secondary pollution to the environment. It is a new type of environmentally friendly material with the unique advantages of low cost, easy preparation, and environmental friendliness.

[0031] Furthermore, the present invention claims a method for catalytic ozonation of sulfur-containing volatile organic pollutants, in which, in the presence of ozone, the above biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst is used to catalytically oxidize sulfur-containing volatile organic pollutants.

[0032] Preferably, the sulfur-containing volatile organic pollutants are selected from one or more of methanethiol (CH3SH), ethanethiol (CH3CH2SH), hydrogen sulfide (H2S), dimethyl sulfide (CH3SCH3), and carbon disulfide (CS2).

[0033] Preferably, the concentration of ozone in the catalytic oxidation reaction system is 10 - 40 ppm. Preferably, the concentration of sulfur-containing volatile organic pollutants is 30 - 100 ppm.

[0034] Compared with the prior art, the present invention has the following beneficial effects: (1) The catalyst provided by the present invention can achieve the efficient utilization of ozone molecules, show excellent removal efficiency for S-VOCs, and have extremely low secondary pollution, being more environmentally friendly and green.

[0035] (2) The radial confinement structure of the carbon nanotubes of the catalyst provided by the present invention can improve the mass transfer efficiency of molecules, enhance the accessibility of active sites, and at the same time can promote the rapid transfer of sulfur-containing intermediate products, avoiding catalyst deactivation caused by the accumulation of sulfur-containing species, and thus can maintain excellent cyclic stability.

[0036] (3) For the catalyst provided by the present invention, the raw materials for preparation are biomass raw materials with wide sources, and the preparation method is simple and the structural stability is good. At the same time, the curvature effect of the carbon nanotubes anchors metal atoms in an atomically dispersed state, which can maximize the utilization of metal atoms, significantly reduce the addition amount of metal precursors, and reduce the preparation cost of the catalyst. Description of the Drawings

[0037] Figure 1 are the scanning electron microscope images of the catalysts prepared in Comparative Example 1 and Example 1. Among them, Figure 1 (a) in is the scanning electron microscope image of the catalyst prepared in Comparative Example 1; Figure 1 (b) in is the scanning electron microscope image of the catalyst prepared in Example 1.

[0038] Figure 2 is the scanning electron microscope image of the catalyst prepared in Comparative Example 4.

[0039] Figure 3 are the X-ray diffraction patterns of the catalysts prepared in Comparative Example 1 and Example 1.

[0040] Figure 4 are the Raman spectra of the catalysts prepared in Comparative Example 1 and Example 1.

[0041] Figure 5 are the structural models of the catalysts prepared in Comparative Example 1 and Example 1. Among them, Figure 5 (a) in is the structural model of the catalyst prepared in Comparative Example 1; Figure 5 (b) in is the structural model of the catalyst prepared in Example 1. Detailed Embodiments

[0042] The present invention will be further described below in conjunction with the specification and specific embodiments. However, the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0043] Example 1 Preparation of 1.0% Cu-BCNT-M Catalyst (1) Wash the oil-tea fruit shells, dry them in an oven, and sieve them to 400 mesh. Dry them in a vacuum oven for 12 h to remove moisture, and then store them in a drying vessel for later use.

[0044] (2) Then weigh 0.03 g of Cu(NO3)2·3H2O and 3.0 g of oil-tea fruit shell powder, mix them evenly, and transfer them to a tubular furnace. Pre-calcine them at 500 °C for 2 h in a nitrogen atmosphere (heating rate: 5 °C / min, N2 flow rate: 30 mL / min). Then raise the temperature to 800 °C and anneal for 3 h (heating rate: 5 °C / min, N2 flow rate: 20 mL / min) to obtain a black product. -1 , N2 flow rate: 30 mL / min -1 ), and then raise the temperature to 800 °C and anneal for 3 h (heating rate: 5 °C / min -1 , N2 flow rate: 20 mL / min -1 ), to obtain a black product.

[0045] (3) Collect the obtained black product and stir it in a 3.0 mol / L NaOH solution for 12 h to remove excess metal salts. Then wash it repeatedly with deionized water until the pH is about 7.0, and dry it overnight in a vacuum oven to obtain the final catalyst sample, named 1.0% Cu-BCNT-M, where the average diameter of the carbon nanotubes is 20 nm. -1 of NaOH solution for 12 h to remove excess metal salts, and then wash it repeatedly with deionized water until the pH is about 7.0. Dry it overnight in a vacuum oven to obtain the final catalyst sample, named 1.0% Cu-BCNT-M, where the average diameter of the carbon nanotubes is 20 nm.

[0046] Example 2 Preparation of 2.0% Cu-BCNT-M Catalyst The difference between this example and Example 1 is that in step (2), 0.06 g of Cu(NO3)2·3H2O is weighed.

[0047] Example 3 Preparation of 3.0% Cu-BCNT-M Catalyst The difference between this example and Example 1 is that in step (2), 0.09 g of Cu(NO3)2·3H2O is weighed.

[0048] Example 4 Preparation of 1.0% Cu-BCNT-M Catalyst The difference between this example and Example 1 is that in step (2), the temperature is raised to 800 °C and annealed for 1 h, and the average diameter of the carbon nanotubes is 30 nm.

[0049] Example 5 Preparation of 1.0% Cu-BCNT-M Catalyst The difference between this example and Example 1 is that in step (2), it is annealed at 800 °C for 4 h, and the average diameter of the carbon nanotubes is 8 nm.

[0050] Preparation of 1.0% Mn-BCNT-M catalyst The difference between this example and Example 1 is that Cu(NO3)2·3H2O is replaced with an equal amount of Mn(NO3)2·4H2O.

[0051] Preparation of 1.0% Fe-BCNT-M catalyst The difference between this example and Example 1 is that Cu(NO3)2·3H2O is replaced with an equal amount of Fe(NO3)3·9H2O.

[0052] Preparation of 1.0% Co-BCNT-M catalyst The difference between this example and Example 1 is that Cu(NO3)2·3H2O is replaced with an equal amount of Co(NO3)2·6H2O.

[0053] Preparation of 1.0% Cu-BCNT-H catalyst The difference between this example and Example 1 is that in step (1), the oil-tea fruit shell is replaced with a coconut shell.

[0054] Preparation of 1.0% Cu-BCNT-L catalyst The difference between this example and Example 1 is that in step (1), the oil-tea fruit shell is replaced with orange peel.

[0055] Preparation of 1.0% Cu-BCNT-UL catalyst The difference between this example and Example 1 is that in step (1), the oil-tea fruit shell is replaced with pomelo peel.

[0056] Preparation of BCNT-M catalyst in Comparative Example 1 The difference between this comparative example and Example 1 is that no metal salt precursor is added, and the average tube diameter of the carbon nanotubes derived from the oil-tea fruit shell is 20 nm.

[0057] Preparation of 1.0% Cu-BCNT-M catalyst in Comparative Example 2 The difference between this comparative example and Example 1 is that in step (2), it is annealed at 800 °C for 0.5 h, and the average diameter of the carbon nanotubes is 150 nm.

[0058] Preparation of 1.0% Cu-BCNT-M catalyst in Comparative Example 3 The difference between this comparative example and Example 1 is that in step (2), annealing is carried out at 800 °C for 6 h, and the average diameter of the carbon nanotubes is 4 nm.

[0059] Preparation of 1.0% Cu-CNT Catalyst for Comparative Example 4 Weigh 1.5 g of melamine, 1.5 g of g-C3N4 and 0.03 g of Cu(NO3)2·3H2O, grind them evenly, and then transfer them to a tubular furnace. Anneal at 500 °C for 2 h under a nitrogen atmosphere (heating rate: 5 °C min -1 , N2 flow rate: 30 mL min -1 ), then raise the temperature to 800 °C and continue annealing for 3 h (heating rate: 5 °C min -1 , N2 flow rate: 20 mL min -1 ). Obtain the primary product. Collect the obtained black product and stir it in a 3.0 mol L -1 NaOH solution for 12 h to remove excess metal salts, then wash it repeatedly with deionized water until the pH is about 7.0, and dry it overnight in a vacuum oven to obtain the final catalyst sample, named 1.0% Cu-CNT, and the average diameter of the carbon nanotubes is 200 nm.

[0060] Comparative Example 5 Commercial MnO2 Catalyst (99.0%) The commercial MnO2 catalyst was purchased from Shanghai Macklin Biochemical Co., Ltd.

[0061] Preparation of 0.1% Cu-BCNT-M Catalyst for Comparative Example 6 The difference between this comparative example and Example 1 is that in step (2), 0.003 g of Cu(NO3)2·3H2O is weighed.

[0062] Preparation of 0.5% Cu-BCNT-M Catalyst for Comparative Example 7 The difference between this comparative example and Example 1 is that in step (2), 0.015 g of Cu(NO3)2·3H2O is weighed.

[0063] Test Example 1 Experimental materials: Catalysts prepared in each example and comparative example.

[0064] (1) Pollutant removal efficiency: Weigh 30.0 mg of the prepared catalyst respectively and place it in a continuous flow reactor. Generate high-purity ozone by ionizing oxygen with an ozone generator, and control the initial concentration of ozone (C O3 ) entering the reactor to 20.0 ppm, and the flow rate is 10 ml min -1CH3SH was diluted to 50.0 ppm with high-purity nitrogen, and a mass flowmeter was used to control the total mass flow rate of the feed gas at 100 ml min -1 , corresponding to a space velocity of 200000 mg h -1 g -1 . At the same time, a sensor was used to detect the initial concentration (C0) of CH3SH at the reactor inlet and the real-time concentration (C t ) at the outlet.

[0065] The catalytic activity was evaluated by the removal rate of methanethiol (η = 1 - C t / C0), and the results are shown in Table 1 below.

[0066] (2) Cycling stability: 30.0 mg of the catalyst was taken and placed in a continuous flow reaction device, and a cycling test was carried out for 5 cycles by the test method of the pollutant removal efficiency in (1) above.

[0067] The test results were expressed as the removal efficiency of methanethiol, and the results are shown in Table 2 below.

[0068] (3) Ozone utilization efficiency: The test process was based on the test process of the pollutant removal efficiency in (1) above, and at the same time, the concentration of ozone (C t- o3) at the reactor outlet was measured at the end of the reaction.

[0069] The ozone utilization efficiency was expressed as the decomposition rate of ozone (η O3 = 1 - C t- o3 / C O3 ), and the results are shown in Table 3 below.

[0070] (4) Average diameter of the catalyst: The prepared catalyst was placed under a scanning electron microscope, adjusted to an appropriate magnification, and the morphology of the catalyst was photographed. Then, ImageJ software was used to statistically analyze the diameters of the carbon nanotubes in the scanning electron microscope image. After sufficient numbers were counted, the arithmetic mean was calculated and used as the average diameter of the catalyst.

[0071] Table 1 Comparison of CH3SH removal efficiency

[0072] As can be seen from Table 1, the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst provided by the present invention has excellent removal effect on CH3SH, and the removal rate of CH3SH ≥ 84.7%; further preferably, the removal rate of CH3SH ≥ 90.8%; most preferably, the removal rate of CH3SH is 99.6%.

[0073] It can be seen from Example 1, Example 2, Example 3, Comparative Example 6 and Comparative Example 7 that the proportion of metal and biomass raw materials in the catalyst has a great influence on the removal rate of CH3SH. When the mass percentage of metal salt in the biomass raw material is within a specific range, it has an excellent removal rate of CH3SH.

[0074] It can be seen from Example 1, Example 4, Example 5, Comparative Example 2 and Comparative Example 3 that the average diameter of carbon nanotubes in the catalyst has a great influence on the removal rate of CH3SH. When the average diameter of carbon nanotubes in the catalyst is within a specific range, it has an excellent removal rate of CH3SH.

[0075] It can be seen from Example 1, Example 9, Example 10 and Example 11 that when the biomass raw material is oil-tea fruit shell, it has a more excellent removal rate of CH3SH compared with other biomass raw materials.

[0076] It can be seen from Example 1, Comparative Example 4 and Comparative Example 5 that compared with the existing catalysts, the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst provided by the present invention has a more excellent removal effect on CH3SH.

[0077] Table 2 Results of cyclic stability test

[0078] It can be seen from Table 2 above that the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst provided by the present invention has excellent cyclic stability. After being reused 5 times, the removal rate of CH3SH decreases by ≤2.7%. After the catalyst prepared in the comparative example is reused 5 times, the removal rate of CH3SH decreases significantly, by ≥4.7%.

[0079] Table 3 Comparison of ozone utilization efficiency

[0080] It can be seen from Table 3 above that the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst provided by the present invention has excellent ozone utilization efficiency.

[0081] Test Example 2 Figure 1 are the scanning electron microscope images of BCNT-M (Comparative Example 1) and 1.0% Cu-BCNT-M (Example 1). From Figure 1 it can be seen that the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst obtained in Example 1 is a uniform nanotube structure with an average diameter of about 20 nm. After anchoring Cu atoms, its morphology does not change significantly, indicating that the curved structure of the carbon nanotubes remains unchanged.

[0082] Figure 2This is a scanning electron microscope image of 1.0% Cu-CNT (Comparative Example 4). Figure 2 It can be seen that the diameter of 1.0% Cu-CNT is about 200 nm. The larger diameter of ordinary carbon nanotubes makes it difficult to effectively regulate the mass transfer and diffusion behavior of gaseous molecules, resulting in poor catalytic activity, which also effectively confirms the importance of specific biomass selection for the preparation of carbon nanotubes with appropriate curvature effect. Therefore, the biomass-derived curvature carbon nanotube anchored atomic dispersed metal catalyst of the present invention can achieve efficient utilization of O3 and promote effective mass transfer of gaseous molecules.

[0083] Figure 3 X-ray diffraction patterns of BCNT-M (Comparative Example 1) and 1.0% Cu-BCNT-M (Example 1). As can be seen from the figure, the characteristic peak at 23.2° belongs to the (002) arrangement structure of graphite carbon. After anchoring the Cu atoms, the diffraction peak shifts to a small angle, which indicates that the coordination of Cu with the graphite carbon atoms on the tube wall only affects the local microenvironment of the curved surface. In addition, after anchoring the Cu atoms, no diffraction peak of Cu is observed, indicating that Cu is in an atomically dispersed state and does not destroy the microstructure of the biomass-derived carbon nanotubes.

[0084] Figure 4 The Raman spectra of BCNT-M (Comparative Example 1) and 1.0% Cu-BCNT-M (Example 1) are shown in FIG. Figure 4 It can be seen that at 1390 cm -1 and 1580 cm -1 The vibration peaks at 1 and 2 are respectively attributed to the disordered vibration D band in the form of defects in the graphite structure and the sp 2 The G band formed by the hybridized carbon bonding. D / I G Ratio (I D / I G = 1.30) indicates that more carbon defects are introduced after the biomass-derived carbon nanotubes anchor Cu atoms. These defects may be due to the Cu atoms occupying some C atom sites to form a Cu-C coordination structure, which effectively enhances the bonding strength between Cu and carbon nanotubes.

[0085] Figure 5 The structural models of BCNT-M (Comparative Example 1) and 1.0% Cu-BCNT-M (Example 1). Figure 5It can be seen that the C arrangement of the graphite structure forms a nanotube structure, and its curvature effect can effectively anchor Cu atoms and present an atomically dispersed state, thereby significantly improving the utilization efficiency of Cu atoms. During the catalytic ozonation process, biomass-derived carbon nanotubes with medium curvature can also effectively enhance the mass transfer efficiency of oxidant molecules (O3) and pollutant molecules (CH3SH), increase the molecular accessibility of active sites, and achieve efficient and stable removal of sulfur-containing volatile organic pollutants.

[0086] The foregoing examples are merely illustrative and are used to explain some features of the method of the present invention. The appended claims are intended to claim the broadest scope conceivable, and the examples presented herein are supported by the applicant's actual test results. Therefore, the applicant's intention is that the appended claims not be limited by the selection of examples that illustrate the features of the present invention. Some of the numerical ranges used in the claims also include sub-ranges within them, and variations within these ranges should also be interpreted, where possible, as being covered by the appended claims.

Claims

1. A preparation method of a biomass-derived curvature carbon nanotube-anchored atomically dispersed metal catalyst, characterized in that, It includes the following steps: mixing biomass raw materials and metal salts, pre-pyrolyzing at 450 - 600 °C under a nitrogen atmosphere, then heating to 700 - 900 °C for annealing, and performing post-treatment to prepare a biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst; The mass percentage of the metal salt in the biomass raw materials is 0.8 - 3.0 wt.%; the metal in the metal salt is a transition metal; The biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst includes carbon nanotubes and the metal supported on the tube walls of the carbon nanotubes; the average diameter of the carbon nanotubes is 8 - 50 nm.

2. The preparation method according to claim 1, wherein The biomass raw materials are selected from one or more of coconut shells, oil-tea fruit shells, orange peels, or pomelo peels.

3. The preparation method according to claim 2, characterized in that, The biomass raw material is an oil-tea fruit shell.

4. The preparation method according to claim 3, wherein, The average diameter of the carbon nanotubes is 15 - 25 nm.

5. The preparation method according to claim 4, characterized in that, The mass percentage of the metal salt in the biomass raw materials is 0.8 - 2.0 wt.%.

6. According to the preparation method described in claim 1, characterized in that, The time for pre-pyrolysis is 1 - 4 h; and / or, the time for annealing is 1 - 4 h.

7. According to the preparation method described in claim 1, characterized in that, The metal salt is selected from one or more of copper salts, manganese salts, iron salts, and cobalt salts.

8. A biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst prepared by the preparation method according to any one of claims 1 - 7.

9. Use of the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst according to claim 8 in the catalytic oxidation of sulfur-containing volatile organic pollutants by ozone.

10. A method for catalytic oxidation of sulfur-containing volatile organic pollutants by ozone, characterized in that, In the presence of ozone, the sulfur-containing volatile organic pollutants are catalytically oxidized using the biomass-derived curved carbon nanotube-anchored atomically dispersed metal catalyst according to claim 8.

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