Biochar-doped manganese-based catalyst as well as preparation method and application thereof in catalytic degradation of volatile organic compounds

Abstract

The invention discloses a charcoal-doped manganese-based catalyst, a preparation method thereof and application of the charcoal-doped manganese-based catalyst in catalytic degradation of volatile organic compounds, and belongs to the technical field of environmental protection. The preparation method of the biochar-doped manganese-based catalyst comprises the following steps: impregnating agricultural and forestry wastes in a first organic solvent, and introducing polar groups to the agricultural and forestry wastes to prepare pretreated wastes; taking the pretreated waste and a manganese soluble metal salt as raw materials, taking an organic solvent and water as solvents, and carrying out hydrothermal reaction at 100-200 DEG C to prepare a hydrothermal reactant; and calcining the reactant at 400-500 DEG C to form a mixed crystal phase, thereby obtaining the charcoal-doped manganese-based catalyst. The manganese-based catalyst doped with the mixed crystal phase biochar, which is prepared by taking the biochar as a doping component, has excellent performance of catalytically degrading volatile organic compounds.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental protection, and more specifically to a biochar-doped manganese-based catalyst, a preparation method thereof, and an application thereof in catalytic degradation of volatile organic compounds. Background Art

[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 of 50°C to 260°C at normal pressure. 2.5 It is an important precursor substance formed by VOCs and O3, which not only produces urban haze and photochemical smog, but also is often toxic and irritating, which will have a bad impact on human health and living environment. Therefore, how to efficiently control the complex pollution caused by VOCs has become an environmental problem that needs to be solved urgently. The treatment methods of VOCs 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 them, catalytic oxidation has become one of the most promising methods with the advantages of high efficiency, energy saving, environmental protection and easy product control. Generally, catalysts are mainly divided into supported precious metal catalysts and transition metal oxide catalysts. Precious metal catalysts have excellent low-temperature catalytic activity, but their high cost, easy poisoning and easy sintering limit their application in practice. Transition metal oxide catalysts have become very potential catalytic materials due to their low cost, high thermal stability and abundant resources. Among transition metal oxides, manganese oxide has the properties of adjustable valence, morphology and crystal form, excellent redox performance and oxygen storage capacity, and has become a hot spot in the study of catalytic degradation of VOCs. In recent years, researchers have used a variety of methods such as morphology / structure regulation, surface modification, atmosphere-assisted heat treatment, and heteroatom doping to modify catalysts to improve catalytic performance. Biomass materials have become excellent precursors for constructing biochar doping due to their abundant resources, diverse micromorphologies, developed pore structures, rich functional groups, and low costs. However, the catalytic degradation of VOCs is usually a high-temperature and oxygen-rich environment. The low mechanical strength and poor thermal stability of biochar limit its application in high-temperature catalytic reactions, making it difficult to use it as a doping component for the catalytic degradation of VOCs. Summary of the invention

[0003] In view of the above problems, the present invention provides a biochar-doped manganese-based catalyst, a preparation method and an application in catalytic degradation of volatile organic compounds. The mixed-crystal phase manganese-based catalyst prepared by the present invention using biochar as a doping component not only achieves efficient degradation of volatile organic compounds, but also has excellent stability and water resistance. The preparation process of the present invention is simple and pollution-free, the yield is high, and it is energy-saving and environmentally friendly, realizing the reuse of agricultural and forestry wastes, thereby effectively promoting pollution reduction and carbon reduction.

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

[0005] The agricultural and forestry waste is immersed in a first organic solvent, polar groups are introduced into the agricultural and forestry waste, and pre-treated waste is prepared.

[0006] The pre-treated waste and manganese soluble metal salt are used as raw materials, an organic solvent and water are used as solvents, and a hydrothermal reaction is carried out at 100 DEG C to 200 DEG C to prepare a hydrothermal reactant.

[0007] The hydrothermal reactants are calcined at 400° C. to 500° C. to form a mixed crystal phase, thereby obtaining a biochar-doped manganese-based catalyst.

[0008] For example, the solvothermal temperature is 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc.

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

[0010] In a preferred embodiment of the present invention, the ratio of pretreated waste to manganese soluble metal salt is 0.5g~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 is not limited to the listed values. Other unlisted values ​​within the above numerical range are also applicable and will not be repeated here.

[0011] In a preferred embodiment of the present invention, the ratio of the pretreated waste to the second organic solvent is 0.5 to 1 g:7 mL; for example, the ratio of the 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 is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable and will not be repeated here.

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

[0015] In a preferred embodiment of the present invention, the ratio of agricultural and forestry waste to the first organic solvent is 0.5 g to 1 g: 14 mL. For example, the ratio of agricultural and forestry waste to the first organic solvent is 0.5 g: 14 mL, 0.6 g: 14 mL, 0.7 g: 14 mL, 0.8 g: 14 mL, 0.9 g: 14 mL, 1 g: 14 mL, etc., but is not limited to the listed values. Other values ​​not listed in the above numerical range are also applicable, and will not be repeated 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 of manganese nitrate, manganese acetate, manganese chloride and manganese sulfate.

[0019] The plants used as agricultural and forestry wastes are one or more of sycamore, paulownia, corn and pine, and the parts of the plants used can be roots, branches, leaves, flowers, fruits and the like.

[0020] The second object of the present invention is to provide a biochar-doped manganese-based catalyst prepared by the above preparation method.

[0021] The third object of the present invention is to provide the use of the above-mentioned biochar-doped manganese-based catalyst in catalytic degradation of volatile organic compounds.

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

[0023] (1) The present invention uses pre-treated agricultural and forestry waste and manganese-soluble metal as raw materials, generates biochar by hydrothermal reaction to prevent the agglomeration of metal particles, promotes the dispersion and stability of the metal phase, and provides conditions for the formation of a mixed crystal phase. The reactants are calcined to prepare a biochar-doped manganese-based catalyst. During the calcination process, the calcination temperature is changed to control the content of the mixed crystal phase in the biochar-doped manganese-based catalyst, which can not only achieve 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, is energy-saving and environmentally friendly, achieves the purpose of treating waste with waste, and helps promote the synergistic effect of pollution reduction and carbon reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the thermogravimetric diagram of the sycamore fruit hairs, which are agricultural and forestry wastes used in the present invention, in air.

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

[0027] Figure 3 The catalytic performance diagram of the samples prepared by Examples 1-3 and Comparative Examples 1-2 in the catalytic oxidation reaction of toluene is shown.

[0028] Figure 4 This is a performance diagram of the temperature rise and fall cycle test of the sample obtained in Example 2.

[0029] Figure 5 This is a performance diagram of the stability and water resistance test of the sample obtained in Example 2.

[0030] Figure 6 The catalytic performance diagram of the samples prepared by Example 2, Examples 4-5 and Comparative Example 1 in the catalytic oxidation reaction of toluene is shown.

[0031] Figure 7 The catalytic performance diagram of the samples prepared by Example 6 and Comparative Example 1 in the catalytic oxidation reaction of toluene. DETAILED DESCRIPTION

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] Biochar can not only effectively prevent the agglomeration of metal particles and promote the dispersion and stabilization of metal phases, but also has the function of transferring, supplying and accepting electrons, accelerating the redox cycle of metals, and thus improving the catalytic degradation performance. Usually, the catalytic degradation of VOCs is carried out in a high temperature and oxygen-rich environment. However, biochar has the characteristics of low mechanical strength and poor thermal stability, which limits its application in high-temperature catalytic reactions, making it difficult to use biochar as a doping component for the catalytic degradation of VOCs.

[0034] To address this problem, the present invention innovatively uses pretreated agricultural and forestry waste as a biochar precursor, mixes it with a manganese soluble salt, prepares a hydrothermal reactant by a simple hydrothermal method, and then calcines the hydrothermal reactant to obtain a biochar-doped manganese-based catalyst of a mixed crystal phase. In the biochar-doped manganese-based catalyst, the presence of a small amount of biochar can not only induce the formation of a mixed crystal phase interface, but also facilitate the improvement of catalyst activity and stability. This not only achieves efficient degradation of VOCs, but also provides a way for the reuse of agricultural and forestry waste, thereby effectively promoting pollution reduction and carbon reduction.

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

[0036] The agricultural and forestry waste is immersed in a first organic solvent, polar groups are introduced into the agricultural and forestry waste, and pre-treated waste is prepared.

[0037] The pre-treated waste and manganese soluble metal salt are used as raw materials, a second organic solvent and water are used as solvents, and a hydrothermal reaction is carried out at 100 DEG C to 200 DEG C to prepare a hydrothermal reactant.

[0038] The hydrothermal reactants are calcined at 400° C. to 500° C. to remove unstable carbon on the reactants during the hydrothermal reaction, thereby obtaining a biochar-doped manganese-based catalyst.

[0039] In the preparation process of the present invention, polar groups are first introduced into agricultural and forestry wastes to increase the hydrophilicity of agricultural and forestry wastes, which is conducive to the full contact between soluble manganese salts and wastes. The polar groups can be hydroxyl groups, carboxyl groups, etc. Then, pre-treated wastes and manganese soluble metals are used as raw materials for hydrothermal reaction. Biochar is generated during the hydrothermal reaction. Biochar can effectively prevent the agglomeration of metal particles, promote the dispersion and stability of the metal phase, and provide conditions for the formation of a mixed crystal phase. The hydrothermal reactants are calcined to prepare biochar-doped manganese-based catalysts. The unstable carbon on the hydrothermal reactants is calcined to remove the unstable carbon on the hydrothermal reactants, and the biochar-doped manganese-based catalysts are regulated to generate mixed crystal phases by changing the calcination temperature during the calcination process. Compared with the single crystal phase, there are abundant defects near the interface of the mixed crystal phase, which can effectively increase the active sites of the catalyst, thereby promoting O2 activation and VOCs cracking. In this way, the mixed crystal phase catalyst often exhibits better activity and stability under high temperature conditions.

[0040] During the preparation process, changes in hydrothermal temperature will affect the generation of hydrothermal products, and hydrothermal time will affect the yield of hydrothermal products.

[0041] During the preparation process, if the raw material ratio is high, it may cause raw material waste; if the raw material ratio is low, the hydrothermal product may not be generated.

[0042] The methods of the present invention are conventional methods unless otherwise specified. The raw materials can be obtained from public commercial channels unless otherwise specified. The 50wt% manganese nitrate aqueous solution used in the present invention is a conventional commercial specification with a density of 1.54g / mL.

[0043] Example 1

[0044] Step 1: Wash the sycamore cones with pure water, dry them, and remove the sycamore fruit hair (FHP). Weigh 1g of FHP, add 14mL of ethylene glycol to completely immerse the fruit hair, place it in a constant temperature oscillator, and oscillate it at 55°C and 150r / min for 2h. Rinse the FHP with pure water to remove surface impurities, and dry it at 70°C for 48 hours to obtain pre-treated waste.

[0045] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

[0046] Preparation of the second mixed solution: 23.24 mL of 50 wt% manganese nitrate aqueous solution was drawn into the polytetrafluoroethylene reactor lining, 19.76 mL of deionized water was added, and the mixture was stirred at 500 r / min for 30 min and set aside.

[0047] The first mixed solution was added to the second mixed solution, and after being stirred evenly, the reactor was placed in an oven at 150°C for 12 hours, and after cooling to room temperature, it was taken out and washed alternately with water and ethanol three times, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0048] Step 3: The reactants were heated to 400°C at a heating rate of 10°C / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst, which was recorded as MnC-400-12.

[0049] Example 2

[0050] Step 1: Wash the sycamore cones with pure water, dry them, and remove the sycamore fruit hairs. Weigh 1g of FHP, add 14mL of ethylene glycol to completely immerse the fruit hairs, place in a constant temperature oscillator, and oscillate at 55°C and 150r / min for 2h. Rinse the FHP with pure water to remove surface impurities, and dry at 70°C for 48 hours to obtain pre-treated waste.

[0051] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

[0052] Preparation of the second mixed solution: 23.24 mL of 50 wt% manganese nitrate aqueous solution was drawn into the polytetrafluoroethylene reactor lining, 19.76 mL of deionized water was added, and the mixture was stirred at 500 r / min for 30 min and set aside.

[0053] The first mixed solution was added to the second mixed solution, and after being stirred evenly, the reactor was placed in an oven at 150°C for 12 hours, and after cooling to room temperature, it was taken out and washed alternately with water and ethanol three times, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0054] Step 3: The reactants were heated to 450°C at a heating rate of 10°C / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst, which was recorded as MnC-450-12.

[0055] Example 3

[0056] Step 1: Wash the sycamore cones with pure water, dry them, and remove the sycamore fruit hairs. Weigh 1g of FHP, add 14mL of ethylene glycol to completely immerse the fruit hairs, place in a constant temperature oscillator, and oscillate at 55°C and 150r / min for 2h. Rinse the FHP with pure water to remove surface impurities, and dry at 70°C for 48 hours to obtain pre-treated waste.

[0057] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

[0058] Preparation of the second mixed solution: 23.24 mL of 50 wt% manganese nitrate aqueous solution was drawn into the polytetrafluoroethylene reactor lining, 19.76 mL of deionized water was added, and the mixture was stirred at 500 r / min for 30 min and set aside.

[0059] The first mixed solution was added to the second mixed solution, and after being stirred evenly, the reactor was placed in an oven at 150°C for 12 hours, and after cooling to room temperature, it was taken out and washed alternately with water and ethanol three times, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0060] Step 3: The reactants were heated to 500°C at a heating rate of 10°C / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst, which was recorded as MnC-500-12.

[0061] Comparative Example 1

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

[0063] Step 1: 23.24 mL of 50 wt% manganese nitrate aqueous solution is taken into a polytetrafluoroethylene reactor lining, 19.76 mL of deionized water and 7 mL of ethylene glycol are added, and after being stirred evenly, the mixture is placed in an oven and kept at 150° C. for 12 h, and then taken out after cooling to room temperature, and washed alternately with water and ethanol three times. The mixture is dried in an oven at 80° C. for 12 h to obtain a hydrothermal reactant.

[0064] Step 2: The reactants were heated to 450°C in an air atmosphere at a heating rate of 10°C / min and calcined for 3 h to obtain a manganese oxide catalyst, denoted as MnO x .

[0065] Example 4

[0066] Step 1: Wash the sycamore cones with pure water, dry them, and remove the sycamore fruit hairs. Weigh 1g of FHP, add 14mL of ethylene glycol to completely immerse the fruit hairs, place in a constant temperature oscillator, and oscillate at 55°C and 150r / min for 2h. Rinse the FHP with pure water to remove surface impurities, and dry at 70°C for 48 hours to obtain pre-treated waste.

[0067] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

[0068] Preparation of the second mixed solution: 23.24 mL of 50 wt% manganese nitrate aqueous solution was drawn into the polytetrafluoroethylene reactor lining, 19.76 mL of deionized water was added, and the mixture was stirred at 500 r / min for 30 min for later use.

[0069] The first mixed solution was added to the second mixed solution, and after being stirred evenly, the reactor was placed in an oven at 150°C for 3 hours, and after cooling to room temperature, it was taken out and washed alternately with water and ethanol three times, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0070] Step 3: The reactants were heated to 450°C at a heating rate of 10°C / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst, recorded as MnC-450-3.

[0071] Example 5

[0072] Step 1: Wash the sycamore cones with pure water, dry them, and remove the sycamore fruit hairs. Weigh 1g of FHP, add 14mL of ethylene glycol to completely immerse the fruit hairs, place in a constant temperature oscillator, and oscillate at 55°C and 150r / min for 2h. Rinse the FHP with pure water to remove surface impurities, and dry at 70°C for 48 hours to obtain pre-treated waste.

[0073] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

[0074] Preparation of the second mixed solution: 23.24 mL of 50 wt% manganese nitrate aqueous solution was drawn into the polytetrafluoroethylene reactor lining, 19.76 mL of deionized water was added, and the mixture was stirred at 500 r / min for 30 min and set aside.

[0075] The first mixed solution was added to the second mixed solution, and after being stirred evenly, the reactor was placed in an oven at 150°C for 6 hours, and after cooling to room temperature, it was taken out and washed alternately with water and ethanol three times, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0076] Step 3: The reactants were heated to 450°C at a heating rate of 10°C / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst, recorded as MnC-450-6.

[0077] Example 6

[0078] Step 1: Wash the paulownia branches with pure water, dry them and crush them to obtain 40-60 mesh paulownia branch powder. Weigh 1g of paulownia branch powder, add 14mL of ethylene glycol to completely immerse the paulownia branch powder, place it in a constant temperature oscillator, and oscillate it at 55°C and 150r / min for 2h. Then rinse the paulownia branch powder in pure water to remove surface impurities, and dry it in an oven at 70°C for 48 hours to obtain pre-treated waste.

[0079] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

[0080] Preparation of the second mixed solution: 23.24 mL of 50 wt% manganese nitrate aqueous solution was drawn into the polytetrafluoroethylene reactor lining, 19.76 mL of deionized water was added, and the mixture was stirred at 500 r / min for 30 min and set aside.

[0081] The first mixed solution was added to the second mixed solution, stirred evenly, and the reactor was placed in an oven at 150°C for 12 hours, and after cooling to room temperature, it was taken out and washed three times with water and ethanol alternately, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0082] Step 3: The reactants were heated to 450°C at a heating rate of 10°C / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst, which was recorded as MnC(PF)-450-12.

[0083] Example 7

[0084] Step 1: Wash the corn stalks with pure water, dry them and crush them to obtain corn stalk powder of 40-60 mesh. Weigh 0.5g corn stalk powder, add 14mL of ethylene glycol to completely immerse the corn stalk powder, place it in a constant temperature oscillator, and oscillate it at 55°C and 150r / min for 2h. Rinse the corn stalk powder with pure water to remove surface impurities, and dry it at 70°C for 48 hours to obtain pre-treated waste.

[0085] Step 2, preparation of the first mixed solution: weigh 0.8 g of the pretreated waste obtained in step 1, add 7 mL of glacial acetic acid, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

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

[0087] The first mixed solution was added to the second mixed solution, stirred evenly, and the reactor was placed in an oven at 100°C for 10 hours, taken out after cooling to room temperature, and washed three times with water and ethanol alternately, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0088] Step 3: The reactants are heated to 450° C. at a heating rate of 10° C. / min in an air atmosphere and calcined for 12 h to obtain a biochar-doped manganese-based catalyst, which is stored for later use.

[0089] Example 8

[0090] Step 1: Wash the pine sawdust with pure water, dry and crush it to obtain 40-60 mesh pine sawdust strip powder. Weigh 0.8g of pine sawdust powder, add 14mL of methanol to completely immerse the pine sawdust powder, place it in a constant temperature oscillator, and oscillate at 55°C and 150r / min for 2h. Rinse the pine sawdust powder with pure water to remove surface impurities, and dry it at 70°C for 48 hours to obtain pre-treated waste.

[0091] Step 2, preparation of the first mixed solution: weigh 7 g of the pretreated waste obtained in step 1, add 7 mL of isopropanol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

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

[0093] The first mixed solution was added to the second mixed solution, stirred evenly, the reactor was placed in an oven at 200°C for 2 hours, taken out after cooling to room temperature, and washed with water and ethanol alternately three times, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0094] Step 3: The reactants are heated to 450° C. at a heating rate of 10° C. / min under an air atmosphere and calcined for 10 h to obtain a biochar-doped manganese-based catalyst.

[0095] Example 9

[0096] Step 1: Wash the sycamore cones with pure water, dry them, and remove the sycamore fruit hairs. Weigh 1g of FHP, add 14mL of isopropanol to completely immerse the fruit hairs, place in a constant temperature oscillator, and oscillate at 55°C and 150r / min for 2h. Rinse the FHP with pure water to remove surface impurities, and dry at 70°C for 48 hours to obtain pre-treated waste.

[0097] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

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

[0099] The first mixed solution was added to the second mixed solution, stirred evenly, and the reactor was placed in an oven at 180°C for 3 hours, and after cooling to room temperature, it was taken out and washed with water and ethanol alternately three times, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0100] Step 3: The reactants are heated to 400° C. at a heating rate of 10° C. / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst.

[0101] Comparative Example 2

[0102] Step 1: Wash the sycamore cones with pure water, dry them, and remove the sycamore fruit hairs. Weigh 1g of FHP, add 14mL of ethylene glycol to completely immerse the fruit hairs, place in a constant temperature oscillator, and oscillate at 55°C and 150r / min for 2h. Rinse the FHP with pure water to remove surface impurities, and dry at 70°C for 48 hours to obtain pre-treated waste.

[0103] Step 2, preparation of the first mixed solution: weigh 0.5 g of the pretreated waste obtained in step 1, add 7 mL of ethylene glycol, place in a constant temperature oscillator, oscillate at 55° C. and 150 r / min for 30 min, and set aside.

[0104] Preparation of the second mixed solution: 23.24 mL of 50 wt% manganese nitrate aqueous solution was drawn into the polytetrafluoroethylene reactor lining, 19.76 mL of deionized water was added, and the mixture was stirred at 500 r / min for 30 min and set aside.

[0105] The first mixed solution was added to the second mixed solution, stirred evenly, and the reactor was placed in an oven at 150°C for 12 hours, and after cooling to room temperature, it was taken out and washed three times with water and ethanol alternately, and dried in an oven at 80°C for 12 hours to obtain a hydrothermal reactant.

[0106] Step 3: The reactants were heated to 800°C at a heating rate of 10°C / min under air atmosphere and calcined for 3 h to obtain a biochar-doped manganese-based catalyst, which was recorded as MnC-800-12.

[0107] Example 10

[0108] 50 mg of the sample catalysts prepared in Examples 1 to 6 and Comparative Examples 1 to 2 were respectively taken and placed in a quartz tube reactor with an inner diameter of 6 mm and a length of 400 mm.

[0109] The experimental conditions are: 1000ppm toluene + 20% O2 (N2 balance gas), total flow rate 50mL / min, mass space velocity (WHSV) 60000mL / (g cat h). The toluene content in the tail gas at different temperatures was measured by Techcomp GC-7980 after stabilization at 10°C for 30 minutes. The catalytic activity of the catalyst was expressed by the conversion rate of toluene.

[0110] Figure 1 This is the thermogravimetric diagram of the fruit hair of the plane tree used in the present invention in an air atmosphere. Figure 1 It can be seen that as the temperature increases from 30°C to 240°C, the weight of the fruit hair of the sycamore tree decreases slightly. However, as the calcination temperature continues to increase, the weight of the fruit hair is severely lost, from 89.4% at 240°C to 1.5% at 468°C, and then remains stable. Therefore, in order to explore the effect of biochar on the catalyst, the calcination (400, 450 and 500°C) was carried out around 468°C, the inflection point of severe fruit hair loss in the sycamore tree, to obtain biochar-doped manganese oxide catalysts, and the calcined sample at 800°C was selected for comparison.

[0111] Figure 2 The X-ray powder diffraction (XRD) diagrams of the samples obtained in Examples 1 to 3 and Comparative Examples 1 to 2 are shown in FIG. Figure 2 It can be seen that MnC-400-12, MnC-450-12 and MnC-500-12 all detected characteristic diffraction peaks belonging to MnO2 (PDF#24-0735), Mn2O3 (PDF#24-0508) and Mn5O8 (PDF#39-1218), and as the calcination temperature increases from 400°C to 500°C, the characteristic diffraction peaks belonging to MnO2 gradually weaken, while the diffraction peaks of Mn2O3 gradually increase. When the temperature is further increased to 800°C, the MnC-800-12 sample obtained only presents a single Mn2O3 crystal form. In Comparative Example 1, the catalyst without the addition of sycamore fruit hairs is mainly MnO2 crystal form except for a small amount of Mn5O8, but no diffraction peaks of Mn2O3 are detected. This may be because biochar can prevent the agglomeration of metal particles, promote the dispersion and stability of the metal phase, and provide conditions for the formation of mixed crystal phases. Therefore, the introduction of agricultural and forestry wastes and calcination at an appropriate temperature can regulate the formation of MnO2 and Mn2O3 mixed crystal phases, thereby controlling the formation of defective interface structures, which plays a vital role in the catalytic degradation of VOCs.

[0112] Figure 3The catalytic performance diagram of the samples obtained in Examples 1 to 3 and Comparative Example 1 is shown in FIG. Figure 3 It can be seen that the MnC-450-12 catalyst calcined at 450°C exhibits the best catalytic activity, while decreasing or increasing the temperature by 50°C will induce a decrease in the content of the mixed crystal phase, resulting in a decrease in catalytic activity, while the single crystal MnC-800-12 sample exhibits the worst catalytic efficiency. This is because the mixed crystal phase interface structure has abundant defects, which is conducive to oxygen activation and active oxygen formation, thereby effectively improving the performance of catalytic degradation of toluene. For MnO without the addition of Platanus fruit hairs x The activity of the catalyst is significantly lower than that of the MnC-450-12 sample, and even shows a catalytic performance comparable to that of the MnC-400-12 and MnC-500-12 samples. It can be seen that the MnC-450-12 sample calcined at an appropriate temperature has the best catalytic activity, which can be attributed to the addition of biochar inducing the formation of more mixed crystal phase structures, leading to the formation of defective interface structures.

[0113] Figure 4 and Figure 5 The temperature rise and fall cycle, stability and water resistance test of the MnC-450-12 sample obtained in Example 2 are as follows: Figure 4 It can be seen that the prepared MnC-450-12 catalyst exhibits excellent heating and cooling cycle performance. Figure 5 It can be seen that the toluene conversion rate of the MnC-450-12 catalyst is still stable at about 95.0% after 24 hours of continuous testing at 320°C, indicating good thermal stability; after the introduction of 1% and 3% water vapor, the toluene conversion rate of the catalyst dropped to 92.0% and 88.0%, respectively, but when the introduction of water vapor was stopped, the toluene conversion rate quickly recovered to 94.2% and remained stable. Therefore, it can be seen that the biochar-doped manganese-based catalyst prepared by this method can not only achieve efficient degradation of VOCs, but also has excellent stability and water resistance.

[0114] Figure 6 The catalytic performance diagram of the samples obtained in Examples 4-5 and 2. Figure 6 It can be seen that the MnC-450-3, MnC-450-6 and MnC-450-12 catalysts obtained with hydrothermal times of 3h, 6h and 12h respectively showed similar catalytic performance for toluene degradation, which indicates that the hydrothermal reaction time has little effect on the catalytic degradation performance of toluene.

[0115] Figure 7 The catalytic performance diagram of the samples obtained in Example 6 and Comparative Example 1 is shown in FIG. Figure 7 It can be seen that compared with the MnO prepared without adding Paulownia xCompared with the catalyst, the MnC(PF)-450-12 catalyst doped with paulownia biochar obtained at a calcination temperature of 450°C exhibited better catalytic performance. It can be seen that the introduction of paulownia biochar can also promote the improvement of catalytic efficiency.

[0116] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0117] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing a biochar-doped manganese-based catalyst, characterized in that: The following steps are involved: The agricultural and forestry waste is immersed in a first organic solvent to introduce polar groups into the agricultural and forestry waste to prepare pretreated waste; Using pretreated waste and manganese soluble metal salt as raw materials, using a second organic solvent and water as solvents, performing a hydrothermal reaction at 100° C. to 200° C. to prepare a hydrothermal reactant; The hydrothermal reactants are calcined at 400° C. to 500° C. to form a mixed crystal phase, thereby obtaining a biochar-doped manganese-based catalyst.

2. The method for preparing a biochar-doped manganese-based catalyst according to claim 1, characterized in that: The ratio of the pretreated waste to the manganese soluble metal salt is 0.5 g to 1 g: 0.1 mol.

3. The method for preparing a biochar-doped manganese-based catalyst according to claim 1, characterized in that: The ratio of pre-treated waste to the second organic solvent is 0.5 g to 1 g: 7 mL; The ratio of manganese soluble metal salt to water is 0.1 mol:18 mL to 20 mL.

4. The method for preparing a biochar-doped manganese-based catalyst according to claim 1, characterized in that: The solvent thermal reaction time is 2h to 12h.

5. The method for preparing a biochar-doped manganese-based catalyst according to claim 1, characterized in that: The calcination time is 3h to 12h.

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

7. 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.

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

9. A biochar-doped manganese-based catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the biochar-doped manganese-based catalyst according to claim 9 in catalytic degradation of volatile organic compounds.

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