Biochar-doped manganese-based catalysts, methods of making, and use in catalytic degradation of volatile organic compounds

Abstract

This invention discloses a biochar-doped manganese-based catalyst, its preparation method, and its application in the catalytic degradation of volatile organic compounds, belonging to the field of environmental protection technology. A method for preparing a biochar-doped manganese-based catalyst includes the following steps: impregnating agricultural and forestry waste in a first organic solvent to introduce polar groups onto the waste, thus preparing pretreated waste; using the pretreated waste and a manganese-soluble metal salt as raw materials, and organic solvent and water as solvents, carrying out a hydrothermal reaction at 100℃~200℃ to prepare a hydrothermal reactant; calcining the reactant at 400℃~500℃ to form a mixed-crystal phase, thus obtaining the biochar-doped manganese-based catalyst. The mixed-crystal phase biochar-doped manganese-based catalyst prepared by this invention using biochar as a dopant component exhibits excellent catalytic degradation performance of volatile organic compounds.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, and more specifically to biochar-doped manganese-based catalysts, their preparation methods, and their application in the catalytic degradation of volatile organic compounds. Background Technology

[0002] Volatile organic compounds (VOCs) refer to a variety of organic compounds with a saturated vapor pressure greater than 70 Pa at room temperature and a boiling point between 50°C and 260°C at normal pressure. They are part of PM2.5. 2.5 Important precursors to VOCs (volatile organic compounds) not only contribute to urban haze and photochemical smog, but are also often toxic and irritating, causing severe harm to human health and the living environment. Therefore, how to efficiently manage the complex pollution caused by VOCs has become an urgent environmental problem. VOCs treatment methods are mainly divided into two categories: recovery and degradation. Recovery technologies include adsorption, condensation, and membrane separation; degradation technologies include catalytic oxidation, direct combustion, and plasma technology. Among these, catalytic oxidation, with its advantages of high efficiency, energy saving, environmental friendliness, and easy product control, is one of the most promising methods. Catalysts are generally classified into supported noble metal catalysts and transition metal oxide catalysts. Noble metal catalysts have excellent low-temperature catalytic activity, but their high cost, susceptibility to poisoning, and sintering limitations restrict their practical application. Transition metal oxide catalysts, on the other hand, are promising catalytic materials due to their low cost, high thermal stability, and abundant resources. Among transition metal oxides, manganese oxides, with their tunable valence state, morphology, and crystal form, excellent redox performance, and oxygen storage capacity, have become a hot topic in catalytic degradation research of VOCs. In recent years, researchers have employed various methods, such as morphology / structure control, surface modification, atmosphere-assisted heat treatment, and heteroatom doping, to modify catalysts and improve their catalytic performance. Biomass materials, due to their abundant resources, diverse microstructures, well-developed pore structures, rich functional groups, and low cost, have become excellent precursors for constructing biochar doped materials. However, the catalytic degradation of VOCs typically occurs in high-temperature and oxygen-rich environments. The low mechanical strength and poor thermal stability of biochar limit its application in high-temperature catalytic reactions, making it difficult to use as a dopant for the catalytic degradation of VOCs. Summary of the Invention

[0003] To address the above problems, this invention provides a biochar-doped manganese-based catalyst, its preparation method, and its application in the catalytic degradation of volatile organic compounds (VOCs). The mixed-phase manganese-based catalyst prepared by this invention using biochar as a dopant component not only achieves highly efficient degradation of VOCs but also exhibits excellent stability and water resistance. The preparation process of this invention is simple and pollution-free, with high yield and energy-saving and environmentally friendly characteristics, enabling the reuse of agricultural and forestry waste, thereby effectively promoting pollution reduction and carbon reduction efforts.

[0004] The first objective of this invention is to provide a method for preparing a biochar-doped manganese-based catalyst, comprising the following steps:

[0005] Agricultural and forestry waste is impregnated in a first organic solvent to introduce polar groups onto the waste, thus preparing pretreated waste.

[0006] Hydrothermal reactants were prepared by using pretreated waste and manganese soluble metal salts as raw materials and organic solvents and water as solvents in a hydrothermal reaction at 100℃~200℃.

[0007] The hydrothermal reactants were calcined at 400℃~500℃ to form a mixed crystal phase, resulting in a biochar-doped manganese-based catalyst.

[0008] For example, the solvothermal temperatures are 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, etc.

[0009] The calcination temperatures are 400℃, 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, etc., but are not limited to the listed values. Other unlisted values ​​within the above range are also applicable, and will not be elaborated here.

[0010] In a preferred embodiment of the present invention, the ratio of pretreated waste to manganese soluble metal salt is 0.5g to 1g:0.1mol. For example, the ratio of pretreated waste to manganese soluble metal salt is 0.5g:0.1mol, 0.6g:0.1mol, 0.7g:0.1mol, 0.8g:0.1mol, 0.9g:0.1mol, 1g:0.1mol, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable, and will not be described in detail here.

[0011] In a preferred embodiment of the present invention, the ratio of pretreated waste to the second organic solvent is 0.5-1 g:7 mL; for example, the ratio of pretreated waste to the second organic solvent is 0.5 g:7 mL, 0.6 g:7 mL, 0.7 g:7 mL, 0.8 g:7 mL, 0.9 g:7 mL, 1 g:7 mL, etc.

[0012] The ratio of manganese soluble metal salt to water is 0.1 mol: 18 mL to 20 mL. For example, the ratio of manganese soluble metal salt to water is 0.1 mol: 18 mL, 0.1 mol: 18.5 mL, 0.1 mol: 19 mL, 0.1 mol: 19.5 mL, 0.1 mol: 20 mL, etc., but it is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable, and will not be elaborated here.

[0013] In a preferred embodiment of the present invention, the solvothermal reaction time is 2h to 12h. For example, the solvothermal reaction time is 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable, and will not be described in detail here.

[0014] In a preferred embodiment of the present invention, the calcination time is 3h to 12h. For example, the calcination time is 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable, and will not be described in detail here.

[0015] In a preferred embodiment of the present invention, the ratio of agricultural and forestry waste to the first organic solvent is 0.5g to 1g:14mL. For example, the ratio of agricultural and forestry waste to the first organic solvent is 0.5g:14mL, 0.6g:14mL, 0.7g:14mL, 0.8g:14mL, 0.9g:14mL, 1g:14mL, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable, and will not be described in detail here.

[0016] In a preferred embodiment of the present invention, the second organic solvent is ethylene glycol, methanol, or isopropanol.

[0017] The first organic solvent is ethylene glycol, isopropanol, or glacial acetic acid.

[0018] In a preferred embodiment of the present invention, the manganese soluble metal salt is one or more selected from manganese nitrate, manganese acetate, manganese chloride, and manganese sulfate.

[0019] The plants used in agricultural and forestry waste are one or more of the following: sycamore, paulownia, corn, and pine. The parts of the plants used can be roots, branches, leaves, flowers, fruits, etc.

[0020] A second objective of this invention is to provide a biochar-doped manganese-based catalyst prepared by the above-described method.

[0021] A third objective of this invention is to provide the application of the above-mentioned biochar-doped manganese-based catalyst in the catalytic degradation of volatile organic compounds.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) This invention uses pretreated agricultural and forestry waste and manganese-soluble metal as raw materials, and generates biochar through hydrothermal reaction to prevent the agglomeration of metal particles, promote the dispersion and stability of the metal phase, and provide conditions for the formation of mixed crystal phase. The reactants are calcined to prepare biochar-doped manganese-based catalysts. During the calcination process, the content of mixed crystal phase in the biochar-doped manganese-based catalysts is controlled by changing the calcination temperature. This not only achieves efficient degradation of VOCs, but also has excellent stability and water resistance.

[0024] (2) The preparation method of the present invention is simple, has a high yield and is energy-saving and environmentally friendly, and achieves the purpose of treating waste with waste, which helps to promote the synergistic effect of pollution reduction and carbon reduction. Attached Figure Description

[0025] Figure 1 Thermogravimetric analysis of the fruit hairs of the sycamore tree, an agricultural and forestry waste used in this invention, in air.

[0026] Figure 2 The images show X-ray powder diffraction patterns of the samples obtained in Examples 1-3 and Comparative Examples 1-2.

[0027] Figure 3 The graph shows the catalytic performance of the samples prepared using Examples 1-3 and Comparative Examples 1-2 in the catalytic oxidation of toluene.

[0028] Figure 4 The graph shows the performance of the sample obtained in Example 2 under temperature cycling test.

[0029] Figure 5 The graph shows the stability and water resistance performance of the sample obtained in Example 2.

[0030] Figure 6 The graph shows the catalytic performance of the samples prepared in Examples 2, 4-5 and Comparative Example 1 in the catalytic oxidation of toluene.

[0031] Figure 7 The graph shows the catalytic performance of the samples prepared in Example 6 and Comparative Example 1 in the catalytic oxidation of toluene. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Biochar not only effectively prevents the aggregation of metal particles and promotes the dispersion and stabilization of the metal phase, but also possesses the functions of electron transfer, supply, and acceptance, accelerating the redox cycle of metals and thus improving catalytic degradation performance. Typically, the catalytic degradation of VOCs takes place in a high-temperature and oxygen-rich environment. However, biochar's low mechanical strength and poor thermal stability limit its application in high-temperature catalytic reactions, making it difficult to use as a dopant in the catalytic degradation of VOCs.

[0034] To address this problem, this invention innovatively uses pretreated agricultural and forestry waste as a biochar precursor, mixes it with manganese-soluble salts, and prepares a hydrothermal reactant via a simple hydrothermal method. The hydrothermal reactant is then calcined to obtain a mixed-crystal phase biochar-doped manganese-based catalyst. In this biochar-doped manganese-based catalyst, the presence of a small amount of biochar not only induces the formation of a mixed-crystal phase interface but also enhances the catalyst's activity and stability. This not only enables efficient VOCs degradation but also provides a pathway for the reuse of agricultural and forestry waste, thereby effectively promoting pollution reduction and carbon reduction efforts.

[0035] This invention provides a method for preparing a biochar-doped manganese-based catalyst, comprising the following steps:

[0036] Agricultural and forestry waste is impregnated in a first organic solvent to introduce polar groups onto the waste, thus preparing pretreated waste.

[0037] Hydrothermal reactants were prepared by using pretreated waste and manganese soluble metal salt as raw materials, and a second organic solvent and water as solvents, and by carrying out a hydrothermal reaction at 100℃~200℃.

[0038] The hydrothermal reactants were calcined at 400℃~500℃ to remove the unstable carbon on the reactants during the hydrothermal reaction, resulting in a biochar-doped manganese-based catalyst.

[0039] This invention first introduces polar groups into agricultural and forestry waste to increase its hydrophilicity, facilitating full contact between soluble manganese salts and the waste. These polar groups can be hydroxyl, carboxyl, etc. Then, a hydrothermal reaction is carried out using the pretreated waste and soluble manganese metal as raw materials. Biochar is generated during the hydrothermal reaction, effectively preventing metal particle aggregation, promoting the dispersion and stability of the metal phase, and providing conditions for the formation of a mixed-crystal phase. The hydrothermal reactants are then calcined to prepare a biochar-doped manganese-based catalyst. Calcination removes unstable carbon from the hydrothermal reactants, and the formation of the mixed-crystal phase is controlled by changing the calcination temperature. Compared to the single-crystal phase, the mixed-crystal phase has abundant defects near the interface, effectively increasing the active sites of the catalyst and promoting O2 activation and VOCs decomposition. Thus, the mixed-crystal phase catalyst often exhibits superior activity and stability at high temperatures.

[0040] During the preparation process, changes in hydrothermal temperature can affect the formation of hydrothermal products, and the duration of hydrothermal treatment can affect the harvest of hydrothermal products.

[0041] During the preparation process, a high ratio of raw materials may lead to waste of raw materials; if the ratio of raw materials is low, hydrothermal products may not be generated.

[0042] Unless otherwise specified, all methods described in this invention are conventional methods. All raw materials, unless otherwise specified, are commercially available. The 50 wt% manganese nitrate aqueous solution used in this invention is a commercially available standard with a density of 1.54 g / mL.

[0043] Example 1

[0044] Step 1: After washing and drying the sycamore cones with pure water, remove the fruit hairs (FHP). Weigh 1g of FHP and add 14mL of ethylene glycol to completely immerse the fruit hairs. Place the mixture in a constant temperature shaker and shake at 55℃ and 150r / min for 2 hours. Rinse the FHP with pure water to remove surface impurities and dry at 70℃ for 48 hours to obtain the pretreated waste.

[0045] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under constant temperature conditions at 55℃.

[0046] Preparation of the second mixed solution: Pipette 23.24 mL of 50 wt% manganese nitrate aqueous solution into the liner of a polytetrafluoroethylene reactor, add 19.76 mL of deionized water, and stir at 500 r / min for 30 min.

[0047] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 150°C for 12 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0048] Step 3: The reactants are calcined at 400°C for 3 hours in air at a heating rate of 10°C / min to obtain a biochar-doped manganese-based catalyst, denoted as MnC-400-12.

[0049] Example 2

[0050] Step 1: Wash and dry the sycamore cones with pure water, then remove the fruit hairs. Weigh 1g of FHP (Fluorescent Hydroxide), add 14mL of ethylene glycol to completely impregnate the fruit hairs, and place in a constant temperature shaker. Shake at 55℃ and 150r / min for 2 hours. Rinse the FHP with pure water to remove surface impurities, and dry at 70℃ for 48 hours to obtain the pretreated waste.

[0051] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under constant temperature conditions at 55℃.

[0052] Preparation of the second mixed solution: Pipette 23.24 mL of 50 wt% manganese nitrate aqueous solution into the liner of a polytetrafluoroethylene reactor, add 19.76 mL of deionized water, and stir at 500 r / min for 30 min.

[0053] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 150°C for 12 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0054] Step 3: The reactants are calcined at 450°C for 3 hours in air at a heating rate of 10°C / min to obtain a biochar-doped manganese-based catalyst, denoted as MnC-450-12.

[0055] Example 3

[0056] Step 1: Wash and dry the sycamore cones with pure water, then remove the fruit hairs. Weigh 1g of FHP (Fluorescent Hydroxide), add 14mL of ethylene glycol to completely impregnate the fruit hairs, and place in a constant temperature shaker. Shake at 55℃ and 150r / min for 2 hours. Rinse the FHP with pure water to remove surface impurities, and dry at 70℃ for 48 hours to obtain the pretreated waste.

[0057] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under constant temperature conditions at 55℃.

[0058] Preparation of the second mixed solution: Pipette 23.24 mL of 50 wt% manganese nitrate aqueous solution into the liner of a polytetrafluoroethylene reactor, add 19.76 mL of deionized water, and stir at 500 r / min for 30 min.

[0059] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 150°C for 12 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0060] Step 3: The reactants are calcined in air at a heating rate of 10℃ / min to 500℃ for 3 hours to obtain a biochar-doped manganese-based catalyst, denoted as MnC-500-12.

[0061] Comparative Example 1

[0062] This invention provides a comparative example of MnO without biochar. x The preparation method of the catalyst specifically includes the following steps:

[0063] Step 1: Pipette 23.24 mL of a 50 wt% manganese nitrate aqueous solution into the lining of a polytetrafluoroethylene (PTFE) reactor. Add 19.76 mL of deionized water and 7 mL of ethylene glycol. Stir well and place in an oven at 150°C for 12 hours. After cooling to room temperature, remove and wash three times alternately with water and ethanol. Dry in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0064] Step two: The reactants were calcined in air at a heating rate of 10℃ / min to 450℃ for 3 hours to obtain a manganese oxide catalyst, denoted as MnO. x .

[0065] Example 4

[0066] Step 1: Wash and dry the sycamore cones with pure water, then remove the fruit hairs. Weigh 1g of FHP (Fluorescent Hydroxide), add 14mL of ethylene glycol to completely impregnate the fruit hairs, and place in a constant temperature shaker. Shake at 55℃ and 150r / min for 2 hours. Rinse the FHP with pure water to remove surface impurities, and dry at 70℃ for 48 hours to obtain the pretreated waste.

[0067] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under the condition of 55℃, for later use.

[0068] Preparation of the second mixed solution: Pipette 23.24 mL of 50 wt% manganese nitrate aqueous solution into the liner of a polytetrafluoroethylene reactor, add 19.76 mL of deionized water, stir at 500 r / min for 30 min, and set aside.

[0069] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 150°C for 3 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0070] Step 3: The reactants are calcined at 450°C for 3 hours in air at a heating rate of 10°C / min to obtain a biochar-doped manganese-based catalyst, denoted as MnC-450-3.

[0071] Example 5

[0072] Step 1: Wash and dry the sycamore cones with pure water, then remove the fruit hairs. Weigh 1g of FHP (Fluorescent Hydroxide), add 14mL of ethylene glycol to completely impregnate the fruit hairs, and place in a constant temperature shaker. Shake at 55℃ and 150r / min for 2 hours. Rinse the FHP with pure water to remove surface impurities, and dry at 70℃ for 48 hours to obtain the pretreated waste.

[0073] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under constant temperature conditions at 55℃.

[0074] Preparation of the second mixed solution: Pipette 23.24 mL of 50 wt% manganese nitrate aqueous solution into the liner of a polytetrafluoroethylene reactor, add 19.76 mL of deionized water, and stir at 500 r / min for 30 min.

[0075] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 150°C for 6 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0076] Step 3: The reactants are calcined at 450°C for 3 hours in air at a heating rate of 10°C / min to obtain a biochar-doped manganese-based catalyst, denoted as MnC-450-6.

[0077] Example 6

[0078] Step 1: Wash and dry the paulownia branches with pure water, then crush them to obtain paulownia branch powder of 40-60 mesh. Weigh 1g of paulownia branch powder and add 14mL of ethylene glycol to completely impregnate the powder. Place the powder in a constant temperature shaker and shake at 55℃ and 150r / min for 2 hours. Then rinse the paulownia branch powder with pure water to remove surface impurities and dry it in an oven at 70℃ for 48 hours to obtain pretreated waste.

[0079] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under 55℃.

[0080] Preparation of the second mixed solution: Pipette 23.24 mL of 50 wt% manganese nitrate aqueous solution into the liner of a polytetrafluoroethylene reactor, add 19.76 mL of deionized water, and stir at 500 r / min for 30 min.

[0081] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 150°C for 12 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0082] Step 3: The reactants are heated to 450℃ for 3 hours in air at a heating rate of 10℃ / min to obtain a biochar-doped manganese-based catalyst, denoted as MnC(PF)-450-12.

[0083] Example 7

[0084] Step 1: Wash and dry the corn stalks with pure water, then crush them to obtain corn stalk powder of 40-60 mesh. Weigh 0.5g of corn stalk powder and add 14mL of ethylene glycol to completely impregnate the powder. Place the powder in a constant temperature shaker and shake at 55℃ and 150r / min for 2 hours. Rinse the corn stalk powder with pure water to remove surface impurities, and dry it at 70℃ for 48 hours to obtain pretreated waste.

[0085] Step 2, Preparation of the first mixed solution: Weigh 0.8g of the pretreated waste obtained in Step 1, add 7mL of glacial acetic acid, place in a constant temperature shaker, and shake for 30min at 150r / min under 55℃.

[0086] Preparation of the second mixed solution: Weigh 24.50g of C4H6MnO4·4H2O into the liner of a polytetrafluoroethylene reactor, add 18mL of deionized water, and stir at 500r / min for 30min.

[0087] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 100°C for 10 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0088] Step 3: The reactants are calcined in air at a heating rate of 10℃ / min to 450℃ for 12 hours to obtain a biochar-doped manganese-based catalyst, which is then stored for later use.

[0089] Example 8

[0090] Step 1: Wash and dry the pine sawdust with pure water, then crush it to obtain pine sawdust strips of 40-60 mesh. Weigh 0.8g of pine sawdust powder, add 14mL of methanol to completely impregnate the powder, and place it in a constant temperature shaker at 55℃ and 150r / min for 2 hours. Rinse the pine sawdust powder with pure water to remove surface impurities, and dry it at 70℃ for 48 hours to obtain pretreated waste.

[0091] Step 2, Preparation of the first mixed solution: Weigh 7g of the pretreated waste obtained in Step 1, add 7mL of isopropanol, place in a constant temperature shaker, and shake for 30min at 150r / min under constant temperature conditions at 55℃.

[0092] Preparation of the second mixed solution: Weigh 16.90g MnSO4·H2O into the liner of a polytetrafluoroethylene reactor, add 20mL of deionized water, and stir at 500r / min for 30min.

[0093] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was placed in an oven at 200°C for 2 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0094] Step 3: The reactants are calcined in air at a heating rate of 10℃ / min to 450℃ for 10h to obtain biochar-doped manganese-based catalyst.

[0095] Example 9

[0096] Step 1: Wash and dry the sycamore cones with pure water, then remove the fruit hairs. Weigh 1g of FHP and add 14mL of isopropanol to completely impregnate the fruit hairs. Place the mixture in a constant temperature shaker and shake at 55℃ and 150r / min for 2 hours. Rinse the FHP with pure water to remove surface impurities, and dry at 70℃ for 48 hours to obtain the pretreated waste.

[0097] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under 55℃.

[0098] Preparation of the second mixed solution: Weigh 19.79g of MnCl2·4H2O into the liner of a polytetrafluoroethylene reactor, add 19.76mL of deionized water, and stir at 500r / min for 30min.

[0099] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 180°C for 3 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0100] Step 3: The reactants are heated to 400℃ for 3 hours in air at a heating rate of 10℃ / min to obtain a biochar-doped manganese-based catalyst.

[0101] Comparative Example 2

[0102] Step 1: Wash and dry the sycamore cones with pure water, then remove the fruit hairs. Weigh 1g of FHP (Fluorescent Hydroxide), add 14mL of ethylene glycol to completely impregnate the fruit hairs, and place in a constant temperature shaker. Shake at 55℃ and 150r / min for 2 hours. Rinse the FHP with pure water to remove surface impurities, and dry at 70℃ for 48 hours to obtain the pretreated waste.

[0103] Step 2, Preparation of the first mixed solution: Weigh 0.5g of the pretreated waste obtained in Step 1, add 7mL of ethylene glycol, place in a constant temperature shaker, and shake for 30min at 150r / min under 55℃.

[0104] Preparation of the second mixed solution: Pipette 23.24 mL of 50 wt% manganese nitrate aqueous solution into the liner of a polytetrafluoroethylene reactor, add 19.76 mL of deionized water, and stir at 500 r / min for 30 min.

[0105] The first mixed solution was added to the second mixed solution and stirred until homogeneous. The reaction vessel was then placed in an oven at 150°C for 12 hours. After cooling to room temperature, it was removed and washed three times alternately with water and ethanol. The mixture was then dried in an oven at 80°C for 12 hours to obtain the hydrothermal reactant.

[0106] Step 3: The reactants are calcined in air at a heating rate of 10℃ / min to 800℃ for 3 hours to obtain a biochar-doped manganese-based catalyst, denoted as MnC-800-12.

[0107] Example 10

[0108] Take 50 mg of the sample catalyst prepared in Examples 1 to 6 and Comparative Examples 1 to 2 respectively, and place it in a quartz tube reactor with an inner diameter of 6 mm and a length of 400 mm.

[0109] The experimental conditions were: 1000 ppm toluene + 20% O2 (N2 balance gas), total flow rate 50 mL / min, and mass hourly space velocity (WHSV) 60000 mL / (g) cat h). The temperature was stabilized at 10°C for 30 min at different temperatures. The toluene content in the exhaust gas at different temperatures was measured using a Techcomp GC-7980. The catalytic activity of the catalyst was expressed as the toluene conversion rate.

[0110] Figure 1 This is a thermogravimetric analysis (TGA) of the sycamore fruit hairs used in this invention in air. Figure 1 It was observed that the weight of the sycamore fruit hairs decreased slightly as the temperature increased from 30℃ to 240℃. However, with further increases in calcination temperature, the weight loss of the fruit hairs became severe, decreasing from 89.4% at 240℃ to 1.5% at 468℃, and then remaining stable. Therefore, to investigate the effect of biochar on the catalyst, calcination was carried out around 468℃, the inflection point where the loss of sycamore fruit hairs was most severe, at 400, 450, and 500℃ to obtain biochar-doped manganese oxide catalysts. Samples calcined at 800℃ were used for comparison.

[0111] Figure 2 The images show X-ray powder diffraction (XRD) patterns of the samples obtained in Examples 1-3 and Comparative Examples 1-2. Figure 2 It was found that characteristic diffraction peaks belonging to MnO2 (PDF#24-0735), Mn2O3 (PDF#24-0508), and Mn5O8 (PDF#39-1218) were detected in MnC-400-12, MnC-450-12, and MnC-500-12. Furthermore, as the calcination temperature increased from 400℃ to 500℃, the characteristic diffraction peaks belonging to MnO2 gradually weakened, while the diffraction peaks of Mn2O3 gradually strengthened. Further increasing the temperature to 800℃ resulted in MnC-800-12 sample exhibiting only a single Mn2O3 crystal form. In Comparative Example 1, the catalyst without sycamore fruit hairs showed a small amount of Mn5O8, but was predominantly MnO2, and no Mn2O3 diffraction peaks were detected. This may be because biochar can prevent the agglomeration of metal particles, promote the dispersion and stabilization of the metal phase, and provide conditions for the formation of a mixed-phase phase. Therefore, introducing agricultural and forestry waste and calcining it at a suitable temperature can regulate the formation of mixed crystal phases of MnO2 and Mn2O3, thereby controlling the formation of defective interface structures, which plays a crucial role in the catalytic degradation of VOCs.

[0112] Figure 3The graphs show the catalytic performance of the samples obtained in Examples 1-3 and Comparative Example 1. Figure 3 As can be seen, the MnC-450-12 catalyst calcined at 450℃ exhibits the best catalytic activity. Decreasing or increasing the temperature by 50℃ both induce a decrease in the mixed-crystal phase content, leading to a reduction in catalytic activity. The single-crystal MnC-800-12 sample shows the worst catalytic efficiency. This is because the mixed-crystal phase interface structure contains abundant defects, which facilitates oxygen activation and the formation of reactive oxygen species, thus effectively improving the catalytic degradation performance of toluene. For MnO without the addition of sycamore fruit hairs... x The catalyst exhibited significantly lower activity than the MnC-450-12 sample, even showing catalytic performance comparable to that of the MnC-400-12 and MnC-500-12 samples. This indicates that the MnC-450-12 sample calcined at a suitable temperature possesses the optimal catalytic activity. This can be attributed to the addition of biochar inducing the formation of more mixed-phase structures, leading to the formation of defect-state interface structures.

[0113] Figure 4 and Figure 5 For the temperature cycling, stability, and water resistance tests of the MnC-450-12 sample obtained in Example 2, from... Figure 4 It can be seen that the prepared MnC-450-12 catalyst exhibits excellent heating and cooling cycle performance. From Figure 5 It can be seen that the toluene conversion rate of the MnC-450-12 catalyst remained stable at around 95.0% after 24 hours of continuous testing at 320℃, indicating good thermal stability. After introducing 1% and 3% water vapor, the toluene conversion rate of the catalyst decreased to 92.0% and 88.0%, respectively, but upon stopping the water vapor introduction, the toluene conversion rate rapidly recovered to 94.2% and remained stable. Therefore, it can be seen that the biochar-doped manganese-based catalyst prepared by this method not only achieves efficient VOCs degradation but also exhibits excellent stability and water resistance.

[0114] Figure 6 The graphs show the catalytic performance of the samples obtained in Examples 4-5 and Example 2. Figure 6 It can be seen that the MnC-450-3, MnC-450-6 and MnC-450-12 catalysts obtained with hydrothermal durations of 3h, 6h and 12h respectively all exhibited similar catalytic performance for toluene degradation, indicating that the hydrothermal reaction time has little effect on the catalytic degradation performance of toluene.

[0115] Figure 7 The images show the catalytic performance of the samples obtained in Example 6 and Comparative Example 1. Figure 7 As can be seen from this, compared to MnO prepared without the addition of paulownia, xCompared with other catalysts, the MnC(PF)-450-12 catalyst doped with paulownia biochar, obtained at a calcination temperature of 450℃, exhibited better catalytic performance. This demonstrates that the introduction of paulownia biochar can also promote improved catalytic efficiency.

[0116] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0117] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method of preparing a biochar-doped manganese-based catalyst, characterized by, Includes the following steps: Agricultural and forestry waste is impregnated in a first organic solvent to introduce polar groups onto the agricultural and forestry waste, thereby preparing pretreated waste; Hydrothermal reactants were prepared by using pretreated waste and manganese soluble metal salt as raw materials, and a second organic solvent and water as solvents, and by carrying out a hydrothermal reaction at 100℃~200℃. The hydrothermal reactants were calcined at 400℃~500℃ to form a mixed crystalline phase, resulting in a biochar-doped manganese-based catalyst. The ratio of pretreated waste to manganese soluble metal salt is 0.5g~1g:0.1mol; The ratio of pretreated waste to the second organic solvent is 0.5g~1g:7mL; The ratio of manganese soluble metal salt to water is 0.1 mol: 18 mL to 20 mL; The solvothermal reaction time is 2h~12h; The calcination time is 3h~12h.

2. The method for preparing a biochar-doped manganese-based catalyst according to claim 1, characterized in that, The ratio of agricultural and forestry waste to the first organic solvent is 0.5g~1g:14mL.

3. The method for preparing a biochar-doped manganese-based catalyst according to claim 1, characterized in that, The second organic solvent is ethylene glycol, methanol, or isopropanol; The first organic solvent is ethylene glycol, isopropanol, or glacial acetic acid.

4. The method for preparing a biochar-doped manganese-based catalyst according to claim 1, characterized in that, The soluble metal salts of manganese are one or more of manganese nitrate, manganese acetate, manganese chloride, and manganese sulfate; The plants used in agricultural and forestry waste are one or more of the following: sycamore, paulownia, corn, and pine.

5. A biochar-doped manganese-based catalyst prepared by the preparation method according to any one of claims 1 to 4.

6. The application of the biochar-doped manganese-based catalyst of claim 5 in the catalytic degradation of volatile organic compounds.

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