Preparation method of manganese-carbon composite material, manganese-carbon composite material and application

Abstract

The application belongs to the field of catalytic treatment of volatile organic compounds, and particularly relates to a preparation method of a manganese-carbon composite material, the manganese-carbon composite material and application. The preparation method of the manganese-carbon composite material comprises the following steps: (1) performing full solid-phase high-energy ball milling on beta-MnO2 until the beta-MnO2 phase is converted into a Mn2O3 phase to obtain a ball-milled modified manganese oxide material; performing full solid-phase high-energy ball milling on a carbon material to obtain a ball-milled modified carbon; (2) performing high-energy ball milling mixing on the ball-milled modified manganese oxide material and the ball-milled modified carbon at a mass ratio of (2-7):3 to obtain the manganese-carbon composite material. Through a distribution ball milling method, the catalytic activity of commercial beta-MnO2 is regulated, and the adsorption performance of commercial carbon material is regulated, and then the interface combination of the manganese oxide active center and the carbon is realized by using mixed ball milling to prepare a high-performance room-temperature toluene catalytic oxidation catalyst.

Description

Technical Field

[0001] This invention belongs to the field of catalytic treatment of volatile organic compounds (VOCs), specifically relating to a method for preparing a manganese-carbon composite material, the manganese-carbon composite material, and its applications. Background Technology

[0002] Toluene, a typical volatile organic compound (VOC), is one of the main components of indoor air pollution and industrial waste gas. Long-term exposure to toluene-containing environments can damage the human nervous system, respiratory system, and liver. Toluene is also an important precursor to photochemical smog and ozone formation. Therefore, developing efficient and low-cost toluene removal technologies has significant practical importance and application value.

[0003] Catalytic oxidation, with its advantages of low-temperature operation, high efficiency, and no secondary pollution, is currently the mainstream control technology for toluene. The key lies in the development of green and efficient catalysts. An ideal catalyst should possess the following characteristics: 1) It should be able to achieve efficient oxidation at room temperature or lower to reduce energy consumption; 2) It should have good deep oxidation capabilities, completely mineralizing toluene into CO2 and H2O, avoiding the formation of toxic intermediate products; 3) It should have excellent stability, enabling long-term operation without deactivation; 4) It should have widely available raw materials, a simple preparation process, and low cost.

[0004] Chinese invention patent CN 107952429 B, published on September 29, 2020, discloses a nanocatalyst for the catalytic oxidation of toluene. This nanocatalyst is a mixed-crystal α@β-MnO2, prepared using a one-step hydrothermal method. Oxalic acid solutions of varying concentrations are added dropwise to a potassium permanganate solution as a reducing agent, and the reaction is carried out at 100-240℃ for 12-24 hours. The hydrothermal reaction product is then calcined at 400-700℃ for 5-8 hours. In this method, the gas generated by the thermal decomposition of oxalic acid gives the catalyst a high specific surface area and abundant pore structure, while the hydrothermal method ensures a stable morphology. When catalytically oxidizing toluene, the removal efficiency can reach 99% at around 200℃. However, the catalyst prepared by this method requires maintaining a high temperature of 200℃ during catalytic oxidation, resulting in high overall energy consumption.

[0005] Chinese invention patent application CN 116832805 A, published on October 3, 2023, discloses a graphite-supported manganese dioxide catalyst from spent lithium-ion batteries, its preparation method, and its application. The method involves wet ball milling of spent graphite powder, dispersing the resulting activated graphite in a mixed solution of KMnO4 and MnSO4, and subjecting the reaction to a hydrothermal reaction at 120–180°C for 8–20 hours to obtain the graphite-supported manganese dioxide catalyst from spent lithium-ion batteries. This catalyst utilizes non-metallic and metallic dopants contained in the graphite from spent lithium-ion batteries to provide defect sites for anchoring manganese dioxide, thereby generating highly dispersed and enhanced active manganese dioxide sites to improve formaldehyde catalytic performance. Simultaneously, the formation of manganese dioxide promotes graphite exfoliation, further expanding the surface area of ​​the graphite from spent lithium-ion batteries, which in turn affects the final morphology of the manganese dioxide growth, significantly increasing the active area and thus enhancing the formaldehyde catalytic activity. The catalyst prepared by this method has a formaldehyde removal rate of 80% to 97% within 1 hour.

[0006] The aforementioned methods for preparing manganese oxides all require high-temperature hydrothermal or even calcination steps, resulting in high energy consumption and the generation of wastewater and waste gas, thus failing to achieve green and low-energy catalyst preparation. Furthermore, the obtained catalysts require high-temperature treatment for the catalytic oxidation and removal of toluene, and the toluene removal rate at room temperature needs further improvement. Summary of the Invention

[0007] The first objective of this invention is to provide a method for preparing manganese-carbon composite materials to solve the problem that existing catalysts cannot achieve green and low-consumption preparation.

[0008] The second objective of this invention is to provide a manganese-carbon composite material prepared by the above method to address the problem that the removal rate of toluene by existing catalysts needs to be improved.

[0009] The third objective of this invention is to provide the application of the above-mentioned manganese-carbon composite material in the catalytic oxidation removal of toluene, so as to solve the problem of how to achieve efficient removal of toluene at room temperature.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for preparing a manganese-carbon composite material includes the following steps: (1) β-MnO2 was subjected to all-solid-phase high-energy ball milling until the β-MnO2 phase was transformed into the Mn2O3 phase to obtain ball-milled modified manganese oxide material; carbon material was subjected to all-solid-phase high-energy ball milling to obtain ball-milled modified carbon. (2) Ball-milled modified manganese oxide material and ball-milled modified carbon are mixed by high-energy ball milling at a mass ratio of (2~7):3 to obtain manganese-carbon composite material.

[0011] This invention is an improved invention. By using a distributed ball milling method, the catalytic activity of commercial β-MnO2 and the adsorption performance of commercial carbon materials are first regulated. Then, by using mixed ball milling, the interfacial bonding between the active centers of manganese oxide and carbon is achieved, thus preparing a high-performance room-temperature toluene catalytic oxidation catalyst.

[0012] This method involves no organic or water solvents and requires no high-temperature hydrothermal synthesis or high-temperature calcination. The catalyst can be prepared simply by solid-phase ball milling, making it green, environmentally friendly, and generating no waste.

[0013] The room-temperature toluene catalytic oxidation catalyst prepared by the above method can be used at room temperature (25°C) and gas hourly space velocity (GHSV) of 750,000 h⁻¹. -1 Under these conditions, the toluene removal rate can reach 92.4%~99.5%, with no CO byproducts generated. This method demonstrates excellent performance in both toluene removal and product safety.

[0014] Preferably, in step (1), the ball-to-material ratio of the all-solid-phase high-energy ball mill is (100~150):1, the rotation speed is 700~900 rpm, and the effective ball milling time is 4~8 h; in step (2), the ball-to-material ratio of the all-solid-phase high-energy ball mill is (100~150):1, the rotation speed is 700~900 rpm, and the effective ball milling time is 1~4 h. Under the above ball milling conditions, the adsorption performance and catalytic activity can be quickly controlled, further improving the preparation efficiency.

[0015] More preferably, the all-solid-phase high-energy ball milling in step (1) adopts a forward and reverse rotation mode, switching between forward and reverse rotation every 15-20 minutes, with a resting time of 2-5 minutes in between. One complete forward and reverse rotation constitutes one cycle, and a total of 8-16 cycles are performed. By adopting the above forward and reverse rotation ball milling method, the structure of the catalytically active components of manganese oxide can be avoided, and efficient ball milling modification can be achieved.

[0016] More preferably, the all-solid-phase high-energy ball milling in step (2) adopts a forward and reverse rotation mode, switching between forward and reverse rotation every 15-20 minutes, with a resting time of 2-5 minutes in between. One complete forward and reverse rotation constitutes one cycle, and a total of 2-8 cycles are performed. By adopting the above forward and reverse rotation ball milling method, a tightly bonded structure at the manganese-carbon interface can be formed more efficiently.

[0017] Preferably, the diameter of the grinding balls used in the all-solid-phase high-energy ball milling in steps (1) and (2) is 10~15mm; both the grinding balls and the grinding jar are made of zirconium oxide. Using a grinding jar and grinding balls made of zirconium oxide results in high grinding efficiency and avoids the introduction of external contaminants.

[0018] A manganese-carbon composite material prepared using the above-described preparation method.

[0019] The manganese-carbon composite material prepared by the above method forms a manganese-carbon heterogeneous interface, generates a large number of oxygen vacancies and introduces abundant carbon defects, optimizes the valence state distribution of Mn, thereby significantly improving the catalytic oxidation activity of toluene and effectively increasing the toluene removal rate.

[0020] Preferably, the manganese-carbon composite material has an Mn₂O₃ / carbon composite phase structure, with low-valence Mn accounting for 0.67~0.70% of the total Mn, a surface adsorbed oxygen to lattice oxygen ratio of 4.09~5.82, an average manganese oxidation state of 2.62~2.81, and low-valence Mn being Mn 2+ and Mn 3+ ;I D / I G The value is 1.14~1.21. By controlling the above-mentioned composite phase structure, the proportion of low-valent manganese, the average oxidation state of manganese, and the ratio of adsorbed oxygen on the surface to lattice oxygen, a stable adsorption-catalytic synergistic structure can be constructed to ensure the stability of toluene removal capacity.

[0021] More preferably, the proportion of low-valent Mn to total Mn is 0.68~0.70, the ratio of adsorbed oxygen to lattice oxygen is 5.72~5.82, and the average oxidation state of manganese is 2.62~2.72; D / I G The value is 1.19~1.21. Under the above-mentioned preferred structural parameters, the removal rate of toluene is increased to over 99%.

[0022] Preferably, the BET specific surface area of ​​the manganese-carbon composite material is 22.7~62.4 m². 2 / g, pore volume 0.03~0.048 cm³ 3 / g. The corresponding specific surface area and pore volume, in conjunction with other structural parameters, jointly determine the excellent catalytic oxidation performance of manganese-carbon composite materials.

[0023] More preferably, the BET specific surface area of ​​the manganese-carbon composite material is 22.7~43.0 m². 2 / g, pore volume 0.03~0.043 cm³ 3 / g. It exhibits superior toluene removal capability within the aforementioned BET specific surface area and pore volume.

[0024] The above-mentioned manganese-carbon composite material is used in the catalytic oxidation removal of toluene.

[0025] The aforementioned manganese-carbon composite material possesses excellent room-temperature toluene catalytic oxidation performance and cycle stability, making it widely applicable to various room-temperature toluene treatment scenarios, such as industrial VOCs waste gas treatment and indoor air purification.

[0026] Preferably, the application uses a fixed-bed reactor, and the treatment temperature is room temperature. The fixed-bed reactor method is a mature technology with high treatment efficiency. Attached Figure Description

[0027] Figure 1 SEM images of the manganese-carbon composite materials obtained in Examples 1-4 of this invention: (a) original carbon material; (b) original MnO2; (c) C&MnO2-2; (d) C&MnO2-4; (e) C&MnO2-6; and (f) C&MnO2-8; Figure 2 The XRD patterns of the manganese-carbon composite materials obtained in Examples 1-4 of this invention are shown below. Figure 3 The Raman spectra of the manganese-carbon composite materials obtained in Examples 1-4 of this invention are shown below. Figure 4 The results show the toluene removal capacity test results of the manganese-carbon composite materials obtained in Examples 1-4 of this invention. Detailed Implementation

[0028] (I) Preferred embodiments of the preparation method of the manganese-carbon composite material of the present invention and its application. This invention provides a ball milling preparation method for a manganese-carbon composite catalyst for the catalytic oxidation of toluene at room temperature. The method adopts a solid-phase ball milling process, with no solvent involved throughout the process, and no need for high-temperature hydrothermal and calcination steps. By controlling the mechanical energy input through distributed ball milling, the method achieves directional regulation of the catalyst interface structure, defect concentration, Mn valence state distribution, and surface active oxygen.

[0029] Specifically, the preparation method of the above-mentioned manganese-carbon composite material adopts the following steps: (1) β-MnO2 is subjected to all-solid-phase high-energy ball milling until the β-MnO2 phase is transformed into the Mn2O3 phase to obtain ball-milled modified manganese oxide material; carbon material is subjected to all-solid-phase high-energy ball milling to obtain ball-milled modified carbon.

[0030] In this step, commercially available β-MnO2 and carbon materials are used as raw materials, and the two materials are directionally modified by ball milling using the mechanical impact and shearing action of a planetary ball mill. The average particle size of commercially available β-MnO2 can be 8~15μm; in the examples below, it was purchased from Zhongkexin Science and Technology (Hubei) Co., Ltd., with an average particle size of 12μm (microscopic morphology of blocky). The commercially available carbon material is preferably activated carbon. For example, activated carbon used as an adsorbent material in air purifiers; this type of activated carbon material belongs to conventional adsorbent consumables. The average particle size can be 5~10μm. D / I G =1.0~1.1. In the following examples, the commercially available carbon materials are all activated carbon with an average particle size of 8 μm.

[0031] For β-MnO2, mechanical force is used to gradually induce lattice distortion in MnO2, generating a large number of oxygen vacancies, while simultaneously promoting the growth of Mn. 4+ Towards lower valence state Mn 3+ Mn 2+ The conversion and optimization of the valence state distribution of Mn were carried out. The ball-to-material ratio of the all-solid-phase high-energy ball mill was controlled at (100~150):1, the rotation speed was 700~900 rpm, and the effective ball milling time was 4~8h.

[0032] For carbon materials, mechanical force disrupts the graphitized lattice, introducing abundant carbon defects and oxygen-containing functional groups on the surface, thereby enhancing the adsorption capacity of carbon materials for toluene and their interfacial electron transport capabilities. The ball-to-material ratio for all-solid-phase high-energy ball milling is controlled at (100~150):1, the rotation speed at 700~900 rpm, and the effective milling time at 4~8 hours. The effective milling time refers to the time the ball mill is in the grinding state, excluding resting time.

[0033] (2) Ball-milled modified manganese oxide material and ball-milled modified carbon are mixed by high-energy ball milling at a mass ratio of (2~7):3 to obtain manganese-carbon composite material.

[0034] Step (1) The initial structures of MnO2 and carbon materials are controlled by pre-ball milling, and then composite ball milling is performed. Through the mechanical force of the ball milling process, the MnO2 particles are refined and highly dispersed on the surface of the carbon material, forming a manganese-carbon heterogeneous interface with atomic-level close contact. This effectively inhibits the aggregation of MnO2 particles and strengthens the electron transfer between the carbon material and manganese oxide, providing a structural basis for the adsorption-catalysis synergistic effect.

[0035] In this step, the ball-to-material ratio of the all-solid-phase high-energy ball mill is controlled at (100~150):1, the rotation speed is 700~900 rpm, and the effective ball milling time is 1~4h.

[0036] In the ball milling process of steps (1) and (2), a planetary ball mill can be used in forward and reverse ball milling mode. The forward and reverse rotation is switched every 15 to 20 minutes, and the resting time is 2 to 5 minutes in between. One complete forward and reverse rotation is one cycle. In step (1), the number of cycles for both materials is controlled to be 8 to 16 times; in step (2), the number of cycles is controlled to be 2 to 8 times.

[0037] In the ball milling process of steps (1) and (2), grinding balls with a diameter of 10-15 mm can be used. Grinding balls and grinding jars made of zirconia material should be used to avoid the introduction of impurities.

[0038] The manganese-carbon composite catalyst prepared by the above method differs from existing catalysts in terms of microstructure, such as defect concentration, Mn valence state distribution, and surface active oxygen content, and exhibits unique adsorption and catalytic performance.

[0039] Specifically, the aforementioned manganese-carbon composite material has an Mn₂O₃ / carbon composite phase structure, with low-valence Mn accounting for 0.67~0.70% of the total Mn, a surface adsorbed oxygen to lattice oxygen ratio of 4.09~5.82, an average manganese oxidation state of 2.62~2.81, and low-valence Mn being Mn 2+ and Mn 3+ ;I D / I G The value is 1.14~1.21. The specific surface area of ​​BET is 22.7~62.4 m². 2 / g, pore volume 0.03~0.048 cm³ 3 / g. The corresponding structural parameters are significantly different from those of the original material.

[0040] Within a certain range of ball milling parameters, the above structural parameters exhibit a regular change with the increase of the number of cycles. With a target toluene removal rate of greater than 99% via room temperature catalytic oxidation, the following structural parameters can be optimized: the proportion of low-valent Mn to total Mn is 0.68~0.70, the ratio of surface adsorbed oxygen to lattice oxygen is 5.72~5.82, and the average oxidation state of manganese is 2.62~2.72; D / I G The value is 1.19~1.21. The specific surface area of ​​BET is 22.7~43.0 m². 2 / g, pore volume 0.03~0.043 cm³ 3 / g.

[0041] In the catalytic oxidation removal of toluene, the existing fixed-bed reactor process can be used to achieve efficient removal and deep mineralization of toluene under conditions of room temperature, no additional heating, and high space velocity. The method generates no CO byproducts and demonstrates good process safety.

[0042] The preferred embodiments described above will be illustrated below with specific examples.

[0043] Examples 1-4 The preparation methods of the manganese-carbon composite materials in Examples 1-4 are as follows: (1) Independent ball milling of β-MnO2 and carbon materials Preparation of C-BM: Zirconia grinding balls with a diameter of 15 mm and 2 g of commercial carbon material (C) were placed in a zirconia grinding jar, maintaining a ball-to-material ratio of 100:1. The grinding jar was then placed in a planetary ball mill, with the rotation speed set to 700 rpm. The ball milling process adopted an alternating forward and reverse rotation mode, switching between forward and reverse rotation every 15 minutes, with a 2-minute rest period in between. The time for one complete forward and reverse rotation cycle was 34 minutes, and a total of 8 cycles were performed. The product was denoted as C-BM.

[0044] Preparation of β-MnO2-BM: Zirconia grinding balls with a diameter of 15 mm and 2 g of commercially available β-MnO2 were placed in a zirconia grinding jar, maintaining a ball-to-material ratio of 100:1. The grinding jar was then placed in a planetary ball mill, with the rotation speed set to 700 rpm. The ball milling process adopted an alternating forward and reverse rotation mode, switching between forward and reverse rotation every 15 min, with a 2 min rest period in between. The time for one complete forward and reverse rotation cycle was 34 min, and a total of 8 cycles were performed. The product was denoted as β-MnO2-BM.

[0045] (2) Mixing ball milling C&MnO2 preparation: Zirconia balls with a diameter of 15 mm, 1 g of β-MnO2-BM, and 1 g of C-BM were placed in a zirconia grinding jar, maintaining a ball-to-material ratio of 100:1. The grinding jar was then placed in a planetary ball mill, with the rotation speed set to 700 rpm. The ball milling process employed an alternating forward and reverse rotation mode, switching between forward and reverse rotation every 15 minutes, with a 2-minute rest period in between, meaning one complete forward and reverse rotation cycle took 34 minutes. By setting different cycle numbers, a series of C@MnO2-y were obtained, where y represents the number of ball milling cycles, which were 2, 4, 6, and 8 (corresponding to Examples 1-4, respectively).

[0046] The manganese-carbon composite materials in Examples 1-4 have a Mn₂O₃ / carbon composite phase structure, and a relatively tight bonding interface is formed between the two phases during the ball milling process. The BET specific surface area (S) of different examples... BET ), pore volume and I D / I G The values ​​are summarized in Table 1. The proportion of low-priced Mn to total Mn is [(Mn)] 2+ +Mn 3+ [Total Mn], the ratio of adsorbed oxygen to lattice oxygen (O) ads / O latt The average oxidation state (AOS) of manganese is summarized in Table 2.

[0047] Table 1 Structural parameters of Examples 1-4 S BET (m 2 / g)]]> Pore volume (cm 3 / g)]]> I D / I G values [C & MnO2-2] 62.4 0.048 1.14 [C & MnO2-4] 54.1 0.045 1.15 [C & MnO2-6] 43.0 0.043 1.19 [C & MnO2-8] 22.7 0.03 1.21

[0048] Table 2 Chemical states of Mn and O in Examples 1-4 (Mn 2+ +Mn 3+ ) / total Mn O ads / O latt ]]> AOS [C & MnO2-2] 0.67 4.09 2.81 [C & MnO2-4] 0.68 5.21 2.74 [C & MnO2-6] 0.68 5.72 2.72 [C & MnO2-8] 0.70 5.82 2.62

[0049] Example 5 The application of the manganese-carbon composite material in the catalytic oxidation removal of toluene in this embodiment was evaluated in a fixed-bed reactor. Specifically, at 25°C, 40 mg of catalyst was loaded into a quartz reaction tube, and toluene standard gas with nitrogen as the carrier was introduced at a flow rate of 500 mL / min, a toluene concentration of 100 ppm, and a gas hourly space velocity (GHSV) of 750,000 h⁻¹. -1 A handheld portable VOC detector was used to measure and record the toluene concentration at the inlet and outlet in real time. A multi-analyzer was used to measure and record the carbon dioxide and carbon monoxide concentrations at the outlet.

[0050] Toluene removal rate (%) is calculated using the following formula:

[0051] Among them, C in (ppm) and C out (ppm) represents the concentration of toluene in the inlet gas and the outlet gas, respectively.

[0052] Carbon dioxide production (%) is calculated using the following formula:

[0053] Carbon monoxide production (%) is calculated using the following formula:

[0054] C CO2 (ppm) and C CO (ppm) indicates the concentration of carbon dioxide and carbon monoxide in the outlet gas, while C in This represents the concentration of toluene in the inlet gas.

[0055] (II) Experimental Examples Experimental Example 1: Structural Characterization 1.1 SEM Analysis SEM analysis was performed on the C&MnO2-y (y=2, 4, 6 and 8) composite materials obtained in Examples 1-4, and the results are as follows: Figure 1 As shown.

[0056] Depend on Figure 1 It can be seen that the stable C&MnO2-y composite materials prepared in Examples 1-4 exhibit the morphological characteristics of carbon materials and MnO2 being mutually composite, and a relatively tight bonding interface is formed between the two phases.

[0057] 1.2 XRD Analysis XRD analysis was performed on the C&MnO2-y (y=2, 4, 6 and 8) composite materials obtained in Examples 1-4, and the results are as follows: Figure 2 As shown.

[0058] Depend on Figure 2 It can be seen that the C&MnO2-y series samples also exhibited the (002) crystal plane of graphite near 26.52°, but the diffraction peaks at 23.12°, 32.93°, and 38.31° belonged to the (211), (222), and (400) crystal planes of Mn2O3, respectively. During the first ball milling process, mechanical force induced a crystal transformation of β-MnO2, resulting in the formation of the Mn2O3 phase. After the second ball milling treatment, the characteristic diffraction peak positions of Mn2O3 in the samples did not change significantly. This indicates that in this preparation system, the crystal transformation of manganese dioxide mainly occurred in the first ball milling stage, while subsequent ball milling processes primarily affected the dispersion state and interfacial contact of the material, with a relatively limited impact on the already formed Mn2O3 crystal phase structure. Based on the spectral results, the introduction of carbon materials may have altered the crystal phase evolution path during the ball milling process to some extent. On the one hand, carbon materials may act as a buffer or lubricant during ball milling, reducing the intensity of direct collisions between particles; on the other hand, their good thermal conductivity also helps to disperse local heat, thereby inhibiting further structural reconstruction or crystal transformation to some extent. Therefore, in the composite system, the Mn2O3 crystal phase remains relatively stable during the second ball milling process.

[0059] 1.3 Specific surface area and pore structure analysis BET specific surface area (S) of C&MnO2-y series samples BET The pore volume analysis results are shown in Table 1.

[0060] As shown in Table 1, when the number of cycles increased from 2 to 8, the specific surface area increased from 62.4 m². 2 / g gradually decreased to 22.7 m 2 / g, pore volume from 0.048 cm³ 3 / g decreased to 0.03 cm 3 / g. This phenomenon indicates that MnO2 gradually adheres to the surface of carbon materials and enters part of the pore structure during the cyclic ball milling process, thereby occupying or covering the original adsorption sites and reducing the effective pore structure parameters of the material.

[0061] 1.4 Raman Analysis Raman analysis was performed on C&MnO2-y series samples. The Raman spectra of different materials are as follows: Figure 3 As shown.

[0062] I of original carbon materials D / I G =1.00, by Figure 3 It can be seen that the C&MnO2-y series samples, when the number of cycles is 2, 4, 6 and 8, correspond to I... D / IG The values ​​were 1.14, 1.15, 1.19, and 1.21, respectively, showing a gradual increase with the number of cycles. This indicates that under step-by-step ball milling conditions, mechanical force can still effectively disrupt the ordered structure of carbon materials, introducing more structural defects, and the defect density continues to increase with the number of ball milling cycles.

[0063] 1.5 XPS Analysis XPS analysis was performed on C&MnO2-y series samples to determine (Mn 2+ +Mn 3+ The ratio of total Mn to surface adsorbed oxygen to lattice oxygen (O) ads / O latt The average oxidation state of manganese, AOS, is given by AOS = 8.956 - 1.126ΔE3s, where ΔE3s represents the splitting of the Mn3s energy level.

[0064] The results showed that the (Mn) content of the C&MnO2-y series samples obtained by stepwise ball milling was significantly higher than that of the MnO2-y series samples. 2+ +Mn 3+ The Mn / total Mn ratio increased from 0.67 to 0.70. Simultaneously, analysis of the oxidation state of Mn on the MnO2 catalyst surface using Mn 3s was conducted. The binding energy differences between the two Mn 3s peaks for different catalysts were: C&MnO2-2 (5.46 eV), C&MnO2-4 (5.52 eV), C&MnO2-6 (5.54 eV), and C&MnO2-8 (5.63 eV), with corresponding AOS values ​​of 2.81, 2.74, 2.72, and 2.62, respectively. C&MnO2-8 exhibited the lowest AOS value, suggesting the potential presence of more Mn on its surface. 3+ It has more surface defects.

[0065] O in C&MnO2-y series samples prepared by stepwise ball milling ads / O latt The ratio also increases with the number of milling cycles (from 4.09 for C&MnO2-2 to 5.82 for C&MnO2-8).

[0066] Experimental Example 2: Comparison of Toluene Catalytic Oxidation Removal Capacity The toluene removal performance was evaluated under the conditions of Example 5. The results of the toluene removal capacity of the C&MnO2-y series materials at room temperature are as follows: Figure 4 As shown.

[0067] Depend on Figure 4It can be seen that the removal rates were 92.4%, 97.3%, 99.3%, and 99.5% for 2, 4, 6, and 8 cycles, respectively, increasing with the number of cycles. Analysis of the reaction products revealed no CO, only CO2, with yields of 37.4%, 48.8%, 52.9%, and 53.6%, respectively. C&MnO2-8 exhibited the highest removal rate and CO2 yield.

[0068] (III) Comparative Example Comparative Example 1: Physical Mixing The preparation process of the toluene catalytic oxidation catalyst in this comparative example is as follows: 1 g of β-MnO2 and 1 g of carbon were simply physically mixed in a mortar, denoted as C+MnO2. Characterization revealed that carbon and MnO2 largely retained their original morphologies, coexisting mainly in a simple stacking manner with no obvious interfacial recombination; no new phase formation was observed. D / I G =1.05, significantly lower than the ball-milled sample.

[0069] The removal rate of toluene by carbon materials alone was 38.7%, that of β-MnO2 alone was 26.1%, and that of the physically mixed sample (C+MnO2) was 47.5%, significantly lower than that of the ball-milled composite sample. Therefore, simple physical mixing cannot create tight interfacial contact and effective structural control, thus failing to achieve efficient synergy between adsorption and catalysis.

[0070] Comparative Example 2: Simple Grinding The preparation process of the toluene catalytic oxidation catalyst in this comparative example is as follows: 1 g of β-MnO2 and 1 g of carbon material were manually ground in a mortar for 30 minutes, denoted as C / MnO2. Characterization revealed that although the microstructure changed to some extent, the overall structure remained similar to the original material, and the interaction between the two phases was still relatively limited; no new phase formation was observed; ID / IG = 1.12, slightly higher than that of the physically mixed sample, but significantly lower than that of the ball-milled sample.

[0071] The simple grinding sample (C / MnO2) achieved a toluene removal rate of 56.6%, which is slightly better than the physically mixed sample, but still significantly lower than the ball-milled composite sample. Therefore, low-intensity grinding is insufficient to induce significant phase changes and structural defects, and cannot construct an efficient adsorption-catalytic synergistic reaction center.

[0072] Comparative Example 3: Effect of different mass ratios of β-MnO2-BM and C-BM on the toluene removal capacity of the resulting C&MnO2-8 With a fixed number of cycles of 8, and the masses of β-MnO2-BM and C-BM being 0.2 g and 1.8 g respectively, and other parameters being the same as in Example 4, the resulting C&MnO2-8 achieved a toluene removal rate of 84.6%.

[0073] With a fixed number of cycles of 8, and the masses of β-MnO2-BM and C-BM being 0.4 g and 1.6 g respectively, and other parameters being the same as in Example 4, the resulting C&MnO2-8 achieved a toluene removal rate of 87.3%.

[0074] With a fixed number of cycles of 8, and the masses of β-MnO2-BM and C-BM being 0.6 g and 1.4 g respectively, and other parameters being the same as in Example 4, the resulting C&MnO2-8 achieved a toluene removal rate of 87.5%.

[0075] With a fixed number of cycles of 8, and the masses of β-MnO2-BM and C-BM being 0.8 g and 1.2 g respectively, and other parameters being the same as in Example 4, the resulting C&MnO2-8 achieved a toluene removal rate of 93.2%.

[0076] With a fixed number of cycles of 8, and the masses of β-MnO2-BM and C-BM being 1.2 g and 0.8 g respectively, and other parameters being the same as in Example 4, the resulting C&MnO2-8 achieved a toluene removal rate of 93.4%.

[0077] With a fixed number of cycles of 8, and the masses of β-MnO2-BM and C-BM being 1.4 g and 0.6 g respectively, and other parameters being the same as in Example 4, the resulting C&MnO2-8 achieved a toluene removal rate of 92.6%.

[0078] With a fixed number of cycles of 8, the masses of β-MnO2-BM and C-BM were 1.6 g and 0.4 g, respectively, and other parameters were the same as in Example 4. The resulting C&MnO2-8 achieved a toluene removal rate of 90.8%.

[0079] With a fixed number of cycles of 8, and the masses of β-MnO2-BM and C-BM being 0.2 g and 1.8 g respectively, and other parameters being the same as in Example 4, the resulting C&MnO2-8 achieved a toluene removal rate of 82.7%.

[0080] The comparative experiments above show that, under the same conditions as in Example 4, changing the ball-milled modified MnO2 (β-MnO2-BM) and the ball-milled modified carbon material (C-BM) can achieve a toluene removal rate of over 80%. Specifically, when β-MnO2-BM accounts for 40%-80% of the total mass of β-MnO2-BM and C-BM, the toluene removal rate can reach over 90%; when β-MnO2-BM accounts for 40%-70% of the total mass of β-MnO2-BM and C-BM, the toluene removal rate can reach over 93%.

[0081] Based on the above experimental findings, this invention has the following key features: 1. The process adopts a solid-phase ball milling process, with no solvent involved and no wastewater, waste gas or solid waste generated, which fully meets the requirements of green chemical industry; it does not require high-energy-consuming steps such as high-temperature hydrothermal or calcination, and can be completed by ball milling at room temperature. Compared with the traditional hydrothermal-calcination process, it greatly reduces energy consumption and shortens the production cycle.

[0082] 2. By using the number of ball milling cycles as the core control parameter, the mechanical energy input can be precisely controlled, and the interfacial bonding strength, defect concentration, Mn valence state distribution and surface active oxygen content of the catalyst can be directionally adjusted, resulting in small deviations in the structure and performance of the catalyst between batches.

[0083] 3. The manganese-carbon composite catalyst prepared by this method can achieve efficient removal and deep mineralization of toluene at room temperature, without additional heating, and under high space velocity conditions. It can be widely applied to various room temperature toluene treatment scenarios such as industrial VOCs waste gas treatment and indoor air purification.

[0084] 4. The preparation process of this invention has short steps, simple operation, and low requirements for production equipment. Only a planetary ball mill is needed to complete the entire preparation process. It can realize continuous and batch production, with small scale-up effect and broad prospects for industrial application.

[0085] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a manganese-carbon composite material, characterized in that, Includes the following steps: (1) β-MnO2 was subjected to all-solid-phase high-energy ball milling until the β-MnO2 phase was transformed into the Mn2O3 phase to obtain ball-milled modified manganese oxide material; carbon material was subjected to all-solid-phase high-energy ball milling to obtain ball-milled modified carbon. (2) Ball-milled modified manganese oxide material and ball-milled modified carbon are mixed by high-energy ball milling at a mass ratio of (2~7):3 to obtain manganese-carbon composite material.

2. The method for preparing the manganese-carbon composite material as described in claim 1, characterized in that, Step (1) The ball-to-material ratio of the all-solid-phase high-energy ball mill is (100~150):1, the rotation speed is 700~900rpm, and the effective ball milling time is 4~8h; Step (2) The ball-to-material ratio of the all-solid-phase high-energy ball mill is (100~150):1, the rotation speed is 700~900rpm, and the effective ball milling time is 1~4h.

3. The method for preparing the manganese-carbon composite material as described in claim 2, characterized in that, The all-solid-phase high-energy ball milling in step (1) adopts a forward and reverse rotation mode. The forward and reverse rotation is switched every 15 to 20 minutes, and the middle is left to stand for 2 to 5 minutes. One complete forward and reverse rotation is one cycle, and a total of 8 to 16 cycles are performed.

4. The method for preparing the manganese-carbon composite material as described in claim 2, characterized in that, Step (2) of the all-solid phase high-energy ball mill adopts a forward and reverse rotation mode. The forward and reverse rotation is switched every 15 to 20 minutes, and the middle is left to stand for 2 to 5 minutes. One complete forward and reverse rotation is one cycle, and a total of 2 to 8 cycles are performed.

5. The method for preparing the manganese-carbon composite material according to any one of claims 1 to 4, characterized in that, The diameter of the grinding balls used in the all-solid-phase high-energy ball milling in steps (1) and (2) is 10~15mm; the grinding balls and grinding jars are both made of zirconium oxide.

6. A manganese-carbon composite material prepared by any one of claims 1 to 5.

7. The manganese-carbon composite material as described in claim 6, characterized in that, The manganese-carbon composite material has an Mn2O3 / carbon composite phase structure, with low-valence Mn accounting for 0.67~0.70% of the total Mn, a surface adsorbed oxygen to lattice oxygen ratio of 4.09~5.82, an average manganese oxidation state of 2.62~2.81, and low-valence Mn being Mn2O3. 2+ and Mn 3+ ;I D / I G The value is 1.14~1.

21.

8. The manganese-carbon composite material as described in claim 7, characterized in that, The proportion of low-valence Mn in the total Mn is 0.68~0.70, the ratio of adsorbed oxygen on the surface to lattice oxygen is 5.72~5.82, and the average oxidation state of manganese is 2.62~2.72; I D / I G The value is 1.19~1.

21.

9. The manganese-carbon composite material as described in claim 6 or 7, characterized in that, The BET specific surface area of ​​the manganese-carbon composite material is 22.7~62.4 m². 2 / g, pore volume 0.03~0.048 cm³ 3 / g.

10. The manganese-carbon composite material as described in claim 9, characterized in that, The BET specific surface area of ​​the manganese-carbon composite material is 22.7~43.0 m². 2 / g, pore volume 0.03~0.043 cm³ 3 / g.

11. The manganese-carbon composite material prepared by the method of any one of claims 1 to 5, and the application of the manganese-carbon composite material of any one of claims 6 to 10 in the catalytic oxidation removal of toluene.

12. The application as described in claim 11, characterized in that, The application uses a fixed-bed reactor and the processing temperature is room temperature.

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