A biochar-based catalyst and its preparation method and application in removing volatile organic compounds

Abstract

The present invention provides a biochar-based catalyst and a preparation method thereof and an application thereof in removing volatile organic compounds, and relates to the technical field of organic pollutant removal. The present invention uses rare earth metal oxides as an auxiliary agent to wrap porous biochar, and forms a rare earth metal oxide hydrophobic coating on the surface of the porous biochar, which greatly improves the high thermal stability of the biochar-based catalyst and the water resistance in a high-humidity environment and the sulfur resistance in a high-sulfur environment. By loading a variety of transition metals as active components, the catalytic activity of the biochar-based catalyst is improved. The catalyst provided by the present invention not only meets the applicable scope of traditional carbon-based catalysts, but also can meet the catalytic oxidation of VOCs such as toluene in a wide temperature range and high-humidity environment to harmless CO2 and H2O. The applicable temperature can be increased to 400°C, and it is applicable to a high-humidity environment with a water content of 8%, and has a wider application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of organic pollutant removal, and in particular to a biochar-based catalyst, a preparation method thereof, and an application thereof in removing volatile organic matter. Background Art

[0002] Every year, agricultural and forestry production in countries around the world produces a large amount of agricultural and forestry waste such as lotus leaves and lotus leaf stems. Except for some of them being utilized, most of them are randomly discarded or burned in the open air, which not only wastes resources but also causes a lot of environmental pollution problems. Therefore, the reasonable disposal and resource utilization of agricultural and forestry wastes are difficult problems that many countries need to solve urgently.

[0003] Volatile organic compounds (VOCs), represented by toluene, are a common air pollutant that seriously threatens the ecological environment and human health. 3 It is an important precursor of ozone and a major cause of environmental problems such as haze and photochemical smog. Most VOCs, such as toluene, are carcinogenic, teratogenic and mutagenic, and have strong toxic effects on the respiratory tract, nerves, cardiovascular and cerebrovascular systems. Toluene, as a typical VOC, is at the forefront in terms of total emissions, harmfulness and ozone formation potential, which has aroused widespread concern. The current methods for controlling VOCs mainly include adsorption, absorption, membrane separation, thermal catalytic oxidation, photocatalytic oxidation, biodegradation, plasma, etc. Among them, thermal catalytic oxidation oxidizes VOCs to CO under the action of a catalyst. 2 and H 2 O and other harmless or less harmful small molecules, it has the advantages of high efficiency, low energy consumption, no secondary pollution, and a wide range of applications, making it a VOCs control technology with broad application prospects.

[0004] Suitable catalysts are the key to thermal catalytic oxidation of VOCs. At present, the research on catalytic oxidation of VOCs catalysts mainly focuses on precious metal catalysts and transition metal oxide catalysts. Precious metal catalysts have good low-temperature catalytic activity, but their high cost, easy poisoning, and easy sintering at high temperature seriously limit their promotion and application. In contrast, transition metal oxide catalysts are widely available, low-priced and have strong anti-poisoning ability, gradually replacing precious metal catalysts and becoming the focus of research. Among them, mixed metal oxide catalysts composed of multiple active metal oxide components (referring to more than two) are more active and stable than single-component metal oxide catalysts and have attracted much attention. Activated carbon has a high specific surface area, a large pore volume and a three-dimensional pore structure, which is conducive to the dispersion of active metal oxides and the mass transfer and diffusion of reaction gases. Therefore, carbon-based catalysts loaded with mixed metal oxides on activated carbon have become one of the research hotspots for the treatment of VOCs.

[0005] Traditional commercial activated carbon is mainly prepared from fossil raw materials such as lignite, which is non-renewable. However, agricultural and forestry waste biomass has high carbon content and low ash content, and is a type of renewable raw material for preparing activated carbon. Therefore, the preparation of biochar by pyrolysis of agricultural and forestry waste is an effective way to utilize agricultural and forestry waste resources and a research hotspot. Although the preparation of carbon-based catalysts using biochar synthesized from agricultural and forestry waste to treat VOCs can achieve "waste treatment with waste", it has important environmental, social and economic value and significance. However, some problems still need to be solved before it can be widely used. Due to the flammability of carbon materials, thermal stability under high temperature conditions is a major challenge for carbon-based catalysts. In addition, some oxygen-containing functional groups on the surface of ordinary biochar have high oxygen content and strong hydrophilicity. In the high humidity environment in the south, due to the competitive adsorption of polar water molecules, its water resistance is poor, which easily leads to the passivation and deactivation of the catalyst. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a biochar-based catalyst and a preparation method thereof and its application in removing volatile organic compounds. The biochar-based catalyst provided by the present invention has high hydrophobicity and high thermal stability, and can meet the requirements of catalytic oxidation of toluene and other VOCs into harmless CO in a wide temperature range and high humidity environment. 2 and H 2 O, has good catalytic activity.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The invention provides a biochar-based catalyst, comprising a carrier and an active component loaded on the carrier; the carrier is porous biochar wrapped by rare earth metal oxides; the active component is a mixed oxide of multiple transition metals.

[0009] Preferably, the rare earth metal oxide comprises CeO 2 .

[0010] Preferably, the mass content of rare earth metal oxides in the biochar-based catalyst is 5 to 25%.

[0011] Preferably, the plurality of transition metals include Co and Mn.

[0012] Preferably, the molar ratio of Co to Mn is (1-3): (3-1).

[0013] Preferably, the mass content of active components in the biochar-based catalyst is 5 to 20%.

[0014] The present invention provides a method for preparing the biochar-based catalyst described in the above scheme, comprising the following steps: impregnating porous biochar into a rare earth metal oxide precursor solution, and sequentially drying and first calcining to obtain porous biochar coated with rare earth metal oxide;

[0015] The rare earth metal oxide-wrapped porous biochar is impregnated into an active component precursor solution, and then dried and calcined for a second time to obtain the biochar-based catalyst.

[0016] Preferably, the temperature of the first calcination is 300-550° C., and the holding time is 2-6 hours.

[0017] Preferably, the second calcination temperature is 300-550° C., and the holding time is 2-6 hours.

[0018] The present invention provides the use of the biochar-based catalyst described in the above scheme or the biochar-based catalyst prepared by the preparation method described in the above scheme in the thermal catalytic oxidation removal of volatile organic matter.

[0019] The present invention provides a biochar-based catalyst, comprising a carrier and an active component loaded on the carrier; the carrier is a porous biochar wrapped with a rare earth metal oxide; the active component is a mixed oxide of multiple transition metals. The present invention uses rare earth metal oxides as an auxiliary agent to wrap the porous biochar, and forms a rare earth metal oxide hydrophobic coating on the surface of the porous biochar, which greatly improves the high-temperature thermal stability of the biochar-based catalyst, the water resistance in a high-humidity environment, and the sulfur resistance in a high-sulfur environment, and improves the catalytic activity of the biochar-based catalyst by loading multiple transition metals as active components.

[0020] Conventional carbon-based catalysts are generally only suitable for catalytic degradation of VOCs at low temperatures (below 250°C) under dry conditions. Once the flue gas contains a certain amount of water vapor, the water vapor will compete for active sites, resulting in a decrease in catalytic performance. Once the temperature exceeds 250°C, the high temperature causes the active components of the carbon-based catalyst to catalytically degrade the carbon matrix, resulting in structural damage to the carbon-based catalyst. The catalyst provided by the present invention not only meets the applicable scope of conventional carbon-based catalysts, but also can meet the requirements of catalytic oxidation of toluene and other VOCs into harmless CO in a wide temperature range and high humidity environment. 2 and H 2 O, the applicable temperature can be increased to 400℃, it is suitable for high humidity environment with a water content of 8%, and has a wider application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 For the original BAC, CeO 2 @BAC and different Mn and Co bimetallic oxide loadings of 5% to 20% Mn 0.5 Co 0.5 / CeO 2 @SEM images of BAC catalysts (a: SEM image of original BAC, b: SEM image of CeO 2 @SEM image of BAC, c: 5% Mn 0.5Co 0.5 / CeO 2 @SEM image of BAC, d: 10% Mn 0.5 Co 0.5 / CeO 2 @SEM image of BAC, e: 15% Mn 0.5 Co 0.5 / CeO 2 @SEM image of BAC, f: 20% Mn 0.5 Co 0.5 / CeO 2 @Bac SEM image);

[0022] Figure 2 This is a graph showing the test results of Test Example 1 for investigating the effect of different active components on the removal of toluene from biochar-based catalysts;

[0023] Figure 3 This is a graph showing the test results of Test Example 2 for investigating the effect of different active metal oxide loadings on the removal of toluene from biochar-based catalysts;

[0024] Figure 4 This is a graph showing the performance test results of test example 3 for removing toluene from biochar-based catalysts modified with different molar ratios of active metals Mn and Co;

[0025] Figure 5 Compare SO for Test Case 4 2 and water to 10% Mn 0.5 Co 0.5 / CeO 2 @BAC, 10% Mn 0.5 Co 0.5 15% Ce / BAC and 10% Mn 0.5 Co 0.5 / BAC toluene removal performance test results diagram;

[0026] Figure 6 10% Mn 0.5 Co 0.5 / CeO 2 @BAC and 10%Mn 0.5 Co 0.5 / BAC in SFG and SFG+300ppmSO 2 +8%H 2 Toluene removal rate (E toluene ) and toluene conversion (S c )’s performance test result graph;

[0027] Figure 7 For the original BAC, CeO 2 @BAC, 10%Mn / CeO2 @BAC, 10% Co / CeO 2 @BAC and 10%Mn 0.5 Co 0.5 / CeO 2 XRD pattern of @BAC. DETAILED DESCRIPTION

[0028] The invention provides a biochar-based catalyst, comprising a carrier and an active component loaded on the carrier; the carrier is porous biochar wrapped by rare earth metal oxides; the active component is a mixed oxide of multiple transition metals.

[0029] In the present invention, the rare earth metal preferably includes CeO 2 The mass content of rare earth metal oxide in the biochar-based catalyst is preferably 5 to 25%, more preferably 10 to 20%, and further preferably 15%.

[0030] In the present invention, the multiple transition metals preferably include Co and Mn, and the molar ratio of Co and Mn is preferably (1-3): (3-1), specifically 1:1, 1:2, 1:3, 2:1 or 3:1, which are not listed here. When the multiple transition metals are Co and Mn, the mixed oxide of the multiple transition metals preferably includes MnO x 、CoO x and MnCo composite oxides; the MnO x Preferably including MnO 2 , Mn 2 O 3 , MnO and Mn 3 O 4 One or more of the following: x Preferably including Co 3 O 4 The present invention does not make any special requirements on the specific type of the MnCo composite oxide, for example, it can be CoMnO 3 The composite oxide may be other MnCo composite oxides.

[0031] In the present invention, the mass content of the active components in the biochar-based catalyst is preferably 5 to 20%, more preferably 8 to 17%, and further preferably 10 to 12%.

[0032] The present invention uses rare earth metal oxides as additives to wrap porous biochar, forming a rare earth metal oxide hydrophobic coating on the surface of the porous biochar, greatly improving the high thermal stability of the biochar-based catalyst, the water resistance in a high-humidity environment, and the sulfur resistance in a high-sulfur environment, and improving the catalytic activity of the biochar-based catalyst by loading a variety of transition metals as active components.

[0033] The present invention provides a method for preparing the biochar-based catalyst described in the above scheme, comprising the following steps: impregnating porous biochar into a rare earth metal oxide precursor solution, and sequentially drying and first calcining to obtain porous biochar coated with rare earth metal oxide;

[0034] The rare earth metal oxide-wrapped porous biochar is impregnated into an active component precursor solution, and then dried and calcined for a second time to obtain the biochar-based catalyst.

[0035] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known in the art.

[0036] In the present invention, the porous biochar is preferably prepared by itself, and the preparation method of the porous biochar preferably includes the following steps: placing the biomass raw material in an activator solution for immersion activation, drying (referred to as the first drying) and pyrolyzing the obtained activated material to obtain porous biochar.

[0037] In the present invention, the biomass raw materials preferably include lotus leaves and lotus stems; before the impregnation, the present invention preferably washes, dries, crushes and sieves the biomass raw materials. In the present invention, the mass ratio of the lotus leaves and lotus stems is preferably 1:1. The present invention adopts pyrolysis of lotus leaves and lotus stems to prepare porous biochar (BAC), which has a three-dimensional multi-level pore structure, a high specific surface area, a large pore volume, and a multi-level pore structure with a specific ratio of micropores, mesopores and macropores, which is beneficial to the mass transfer and diffusion of reactants and products, and is beneficial to promote the adsorption and catalytic oxidation of VOCs reactants such as toluene, thereby improving its removal efficiency.

[0038] In the present invention, the activator solution is preferably obtained by dissolving the activator in water; the activator preferably includes ZnCl 2 , KOH, NaOH or H 3 PO 4 , more preferably ZnCl 2 The present invention does not impose any special limitation on the concentration of the activator solution, and any concentration of the activator solution known in the art may be used. In the present invention, when the activator is ZnCl 2 The concentration of the activator solution is preferably 1 g / mL. The present invention has no special requirements on the amount of the activator solution, as long as it can completely immerse the biomass raw material.

[0039] In the present invention, the impregnation activation time is preferably more than 24 hours, more preferably 24 hours. The present invention performs impregnation activation on biomass raw materials, which is beneficial to improving the yield of biomass carbon, expanding pores, and increasing the pore volume and specific surface area of ​​activated carbon.

[0040] The present invention has no special requirements for the first drying conditions, and the drying conditions known in the art can be used. In an embodiment of the present invention, the first drying temperature is 100° C. and the time is 48 hours.

[0041] In the present invention, the pyrolysis temperature is preferably 550-900°C, more preferably 600-850°C, and further preferably 650-800°C; the pyrolysis holding time is preferably 0.5-3 hours, more preferably 1-2.5 hours, and further preferably 1.5-2 hours. In the present invention, the pyrolysis is preferably carried out under the protection of flowing nitrogen.

[0042] After completing the pyrolysis, the present invention preferably further comprises alternately acid-washing-alkali-washing the obtained pyrolysis product, and finally washing with deionized water until the supernatant is neutral, and drying (referred to as the second drying) to obtain the porous biochar.

[0043] In the present invention, the pickling solution used in the pickling is preferably HNO 3 solution, the HNO 3 The concentration of the solution is preferably 3-10 mol / L; the alkaline washing solution used in the alkaline washing is preferably a NaOH solution, and the concentration of the NaOH solution is preferably 3-10 mol / L. The material obtained after pyrolysis contains not only the biochar matrix but also acidic impurities, alkaline impurities, neutral impurities and residual activating agent. The present invention uses acid washing, water washing and alkaline washing to wash away alkaline impurities, water-soluble impurities and acidic impurities respectively.

[0044] In the present invention, the temperature of the second drying is preferably 105° C.; the present invention has no special requirements on the time of the second drying, and drying to constant weight is sufficient.

[0045] After obtaining the porous biochar, the present invention impregnates the porous biochar (referred to as the first impregnation) into a rare earth metal oxide precursor solution, and sequentially performs drying (referred to as the third drying) and a first calcination to obtain the rare earth metal oxide-coated porous biochar.

[0046] In the present invention, the rare earth metal oxide precursor is preferably a nitrate of a rare earth metal; when the rare earth metal oxide is CeO 2 When the rare earth metal oxide precursor is preferably Ce(NO 3 ) 3 6H 2O. In the present invention, the first impregnation is preferably an equal volume impregnation; the first impregnation is preferably carried out under ultrasonic assisted conditions. In the present invention, the content of rare earth elements in the rare earth metal oxide precursor solution is determined according to the content of rare earth elements in the biochar-based catalyst. In the present invention, the first impregnation is preferably carried out under ultrasonic conditions; the time of the first impregnation is preferably 1 to 6 hours, more preferably 2 to 4 hours. Through the first impregnation, the present invention allows the auxiliary rare earth metal oxide precursor to be fully impregnated into the inner and outer surfaces of the porous biochar.

[0047] The present invention has no special requirements for the conditions of the third drying, and it can be dried to constant weight. In the present invention, the temperature of the first calcination is preferably 300-550°C, more preferably 350-500°C, and further preferably 400-450°C; the insulation time of the first calcination is preferably 2-6 hours, more preferably 3-5 hours; the first calcination is preferably carried out under the protection of flowing nitrogen. In the present invention, the first calcination is preferably carried out by microwave heating. After the first calcination, the rare earth metal oxide precursor of the present invention is decomposed into rare earth metal oxides, which are coated on the surface of the porous biochar to form rare earth metal oxide-coated porous biochar.

[0048] After obtaining the rare earth metal oxide-coated porous biochar, the present invention impregnates (referred to as the second impregnation) the rare earth metal oxide-coated porous biochar into an active component precursor solution, and sequentially performs drying (referred to as the fourth drying) and a second calcination to obtain the bio-based catalyst.

[0049] In the present invention, the active component precursor solution is preferably obtained by dissolving corresponding multiple transition metal salts in water. The present invention has no special requirements on the specific types of each transition metal salt, as long as it can be soluble in water. In the present invention, when the multiple transition metals are Co and Mn, the transition metal salt is preferably Mn(CH 3 COO 2 ·4H 2 O and Co(NO 3 ) 2 6H 2 O. In the present invention, the second impregnation is preferably equal volume impregnation; the second impregnation time is preferably 20 to 30 hours, more preferably 24 hours. In the present invention, the temperature of the fourth drying is preferably 105°C. The present invention has no special requirements for the time of the fourth drying, and it can be dried to constant weight.

[0050] In the present invention, the temperature of the second calcination is preferably 300-550°C, more preferably 350-500°C, and further preferably 400-450°C; the holding time of the second calcination is preferably 2-6 hours, more preferably 3-5 hours, and further preferably 4 hours; the second calcination is preferably carried out under a flowing nitrogen atmosphere. In the present invention, the heating method of the second calcination is preferably microwave heating. After the second calcination, the transition metal salt is converted into an oxide of the transition metal.

[0051] The present invention provides the use of the biochar-based catalyst described in the above scheme or the biochar-based catalyst prepared by the preparation method described in the above scheme in the thermal catalytic oxidation removal of volatile organic matter.

[0052] In the present invention, the volatile organic compounds preferably include toluene. The present invention has no special requirements on the source and concentration of the volatile organic compounds, and any concentration known in the art can be used. In the embodiment of the present invention, a simulated flue gas (SFG) is used, wherein the concentration of toluene is 300 ppm, 2 The volume content is 6%, using N 2 As a balance gas. In the present invention, the temperature of the thermal catalytic oxidation is preferably below 400°C, more preferably 80-400°C; the ambient humidity of the thermal catalytic oxidation is preferably ≤8%, more preferably 3-8%.

[0053] Conventional carbon-based catalysts are generally only suitable for catalytic degradation of VOCs at low temperatures (below 250°C) under dry conditions. Once the flue gas contains a certain amount of water vapor, the water vapor will compete for active sites, resulting in a decrease in catalytic performance. Once the temperature exceeds 250°C, the high temperature causes the active components of the carbon-based catalyst to catalytically degrade the carbon matrix, resulting in structural damage to the carbon-based catalyst. The catalyst provided by the present invention not only meets the applicable scope of conventional carbon-based catalysts, but also can meet the requirements of catalytic oxidation of toluene and other VOCs into harmless CO in a wide temperature range and high humidity environment. 2 and H 2 O, the applicable temperature can be increased to 400℃, it is suitable for high humidity environment with a water content of 8%, and has a wider application prospect.

[0054] The biochar-based catalyst provided by the present invention, its preparation method and its application in removing volatile organic compounds are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0055] Example 1

[0056] In this embodiment, lotus leaves and lotus stems are washed, dried and crushed to obtain corresponding raw material particles, which are fully mixed to obtain a mixed precursor material (the mass ratio of lotus leaves to lotus stems is 1:1). Take 500 g of the mixed precursor material and add the activator ZnCl2 Weigh 500g ZnCl with a mass ratio of 1:1 to the precursor powder 2 Dissolve in 500 mL of deionized water to prepare ZnCl 2 The precursor material was then placed in an activator solution for activation for 24 hours, dried, and pyrolyzed in a microwave oven at 700 °C for 2 hours under flowing nitrogen protection. 3 Solution, deionized water and 4.5 mol / L NaOH solution were alternately soaked and rinsed for multiple times, and then dried and sieved to obtain the original biochar carrier (referred to as BAC). 2 Taking 15% mass fraction as an example, weigh an appropriate amount of Ce(NO 3 ) 3 6H 2 O solution was prepared, and an appropriate amount of BAC was ultrasonically treated in the above precursor solution for 24 h. 2 Rare earth metal oxide CeO was obtained by heating to 450℃ under microwave protection for 4 hours. 2 The fully encapsulated modified biochar carrier (denoted as CeO 2 @BAC).

[0057] The above CeO 2 @BAC is used as a carrier, and an appropriate amount of Mn(CH 3 COO 2 ·4H 2 O and Co(NO 3 ) 2 6H 2 O was dissolved in deionized water to form the corresponding precursor solution, and CeO 2 @BAC was immersed in the corresponding precursor solution, and after being immersed and allowed to stand for 24 hours, it was placed in a 105°C drying oven and dried to constant weight. 2 The double transition metal oxide MnO was obtained by calcining at 450 °C for 4 hours in a microwave-heated tube furnace under protection. x and CoO x Modified CeO 2 @BAC’s biochar-based catalyst, denoted as 10% Mn 0.5 Co 0.5 / CeO 2 @BAC.

[0058] In the present invention, the single or double transition metal oxide MnO x and / or CoO x Modified CeO 2 @BAC's biochar-based catalyst (YMn / CeO 2 @BAC, YCo / CeO 2 @BAC and YMnz Co 1-z / CeO 2 @BAC, where Y represents the mass percentage of the single or double metal oxide in the total catalyst, and Z and 1-Z represent the proportion of Mn and Co in the total molar amount of Mn+Co, respectively).

[0059] Comparative Example 1

[0060] The only difference from Example 1 is that Mn(CH 3 COO 2 ·4H 2 Preparation of single transition metal oxides MnO x Modified CeO 2 @BAC’s biochar-based catalyst, denoted as 10% Mn / CeO 2 @BAC.

[0061] Comparative Example 2

[0062] The only difference from Example 1 is that Co(NO 3 ) 2 6H 2 Preparation of single transition metal oxide CoO x Modified CeO 2 @BAC’s biochar-based catalyst, denoted as 10% Co / CeO 2 @BAC.

[0063] Comparative Examples 3-4

[0064] Using BAC as a carrier, the method of Example 1 was used to prepare 10% Mn 0.5 Co 0.5 15% Ce / BAC and 10% Mn 0.5 Co 0.5 / BAC, of ​​which 10%Mn 0.5 Co 0.5 15% Ce / BAC means that BAC is used as a carrier to load Mn, Co and Ce at the same time.

[0065] In the present invention, YMn / BAC, YCo / BAC and YMn z Co 1-z / BAC、YMn z Co 1-z 15% Ce / BAC catalyst, similarly, Y represents the mass percentage of the single or double metal oxide in the total catalyst, and Z and 1-Z represent the total molar proportions of Mn and Co in Mn+Co, respectively.

[0066] Embodiments 2 to 4

[0067] The preparation method is the same as that in Example 1, except that the loading amount of the metal oxide of the active component is changed to obtain different loading amounts of MnO x and CoO x Co-modified CeO 2 @BAC's biochar-based catalyst (MnCo / CeO 2 @BAC), transition metal oxides account for the carbon-based catalyst Mn 0.5 Co 0.5 / CeO 2 The mass percentages of @BAC are 5%, 15% and 20% respectively.

[0068] Embodiments 5 to 8

[0069] The preparation method is the same as that of Example 1, except that the molar ratio of the active components Mn and Co is changed to obtain carbon-based catalysts with different molar ratios of active components. The molar ratios of Mn and Co are 2:1, 1:2, 3:1 and 1:3 respectively.

[0070] Test Example 1

[0071] In order to investigate the effect of active components on the toluene removal performance of biochar-based catalysts, 0.3 g of the original BAC, 10% Mn / CeO 2 @BAC, 10% Co / CeO 2 @BAC, 10% Mn 0.5 Co 0.5 / CeO 2 @BAC, 10% Mn 0.5 Co 0.5 15% Ce / BAC and 10% Mn 0.5 Co 0.5 / BAC for comparative study, in the temperature range of 80 ~ 400 ℃, the simulated flue gas atmosphere (SFG) includes 300ppm toluene, 6% O 2 and balance gas N 2 (99.99%). Test results show 10% Mn 0.5 Co 0.5 / CeO 2 @BAC has better toluene removal performance in the whole temperature range, and the toluene removal efficiency is the best at 240℃, which is 97.5%. Compared with 10% Mn / CeO 2 @BAC and 10%Co / CeO 2 @BAC, 10% Mn over the entire temperature range 0.5 Co 0.5 / CeO 2@BAC has better toluene removal performance, which may be due to the synergistic effect of Mn and Co, which can promote the dispersion of metal oxides, inhibit their agglomeration, and provide sufficient adsorption and catalytic active sites for adsorption and catalytic reactions. 0.5 Co 0.5 15% Ce / BAC and 10% Mn 0.5 Co 0.5 / BAC, 10%Mn 0.5 Co 0.5 / CeO 2 @BAC has better performance in the whole temperature range, especially in the high temperature range, mainly because CeO 2 Fully encapsulating BAC can greatly reduce the damage caused by the oxidation of the carrier carbon matrix by the active metal oxide under high temperature conditions, thus increasing the Mn 0.5 Co 0.5 / CeO 2 @BAC's high temperature thermal stability and catalytic performance. For specific test results, see Figure 2 and Table 1.

[0072] Table 1 Effect data of test example 1

[0073]

[0074] Test Example 2

[0075] The effect of active metal oxide loading on the toluene removal performance of biochar-based catalysts was investigated.

[0076] With 0.3 g of MnCo / CeO in Examples 1 to 4 of the present invention 2 @BAC catalyst is the experimental object (specifically 5% Mn 0.5 Co 0.5 / CeO 2 @BAC, 10% Mn 0.5 Co 0.5 / CeO 2 @BAC, 15% Mn 0.5 Co 0.5 / CeO 2 @BAC and 20%Mn 0.5 Co 0.5 / CeO 2 @BAC), in the temperature range of 80~400℃, the simulated flue gas atmosphere (SFG) includes 300ppm toluene, 6%O 2 and balance gas N 2(99.99%). The test results show that the removal rate of toluene by each catalyst at different temperatures is more than 85%, but the appropriate amount of Mn and Co mixed metal oxide loading is more conducive to the removal of toluene, while too little or too much metal oxide will reduce the removal effect of toluene. In addition, through SEM characterization results ( Figure 1 ) It can be seen that the introduction of Mn and Co mixed metal oxides greatly changes the CeO 2 Modified lotus leaf-lotus stem biochar (CeO 2 @BAC) surface structure, when the metal oxide loading is 5%, part of the carbon surface is still unused, while the samples with excessive loading of 15% and 20% show a large amount of agglomeration of Mn and Co mixed metal oxides, which will inevitably block some pores, and 10% Mn 0.5 Co 0.5 / CeO 2 The metal oxides on @BAC are evenly distributed, providing sufficient adsorption and catalytic activity sites for the catalytic reaction, thus achieving the highest toluene removal efficiency. Figure 3 and Table 2.

[0077] Table 2 Effect data of test example 2

[0078]

[0079] Test Example 3

[0080] The effect of Mn / Co molar ratio on the toluene removal performance of biochar-based catalysts was investigated.

[0081] With 0.3 g of 10% Mn in Example 1 and Examples 5 to 8 of the present invention z Co 1-z / CeO 2 @BAC catalyst is the experimental object (10% Mn 0.5 Co 0.5 / CeO 2 @BAC, 10% Mn 0.25 Co 0.75 / CeO 2 @BAC, 10% Mn 0.75 Co 0.25 / CeO 2 @BAC, 10% Mn 0.33 Co 0.67 / CeO 2 @BAC and 10%Mn 0.67 Co 0.33 / CeO 2@BAC), in the temperature range of 80~400℃, the simulated flue gas atmosphere (SFG) includes 300ppm toluene, 6%O 2 and balance gas N 2 (99.99%). The test results show that the molar ratio of Mn to Co affects the performance of the catalyst in removing toluene. Compared with other molar ratios of Mn and Co, the sample with a molar ratio of Mn to Co of 1:1 and 10% Mn 0.5 Co 0.5 / CeO 2 @BAC has the best toluene removal performance, which is mainly due to the fact that 1:1 is the optimal molar ratio of Mn and Co, which produces the strongest synergistic effect, induces the most lattice defects and oxygen vacancies, greatly promotes the absorption and oxidation of toluene, and thus has the highest toluene removal efficiency. See the specific test results for details. Figure 4 and Table 3.

[0082] Table 3 Effect data of test example 3

[0083]

[0084] Test Example 4

[0085] Comparative study of 10% Mn 0.5 Co 0.5 / CeO 2 @BAC, 10% Mn 0.5 Co 0.5 15% Ce / BAC and 10% Mn 0.5 Co 0.5 / BAC in water or SO 2 The removal performance of toluene under different conditions.

[0086] The applications are as follows:

[0087] In the present invention, 0.3 g of 10% Mn 0.5 Co 0.5 / CeO 2 @BAC, 0.3g of 10% Mn 0.5 Co 0.5 15% Ce / BAC and 0.3g of 10% Mn 0.5 Co 0.5 The BAC catalyst was used as the experimental object. The temperature range was 80-400℃, and the simulated flue gas atmosphere (SFG) included 300ppm toluene, 6% O 2 and balance gas N 2 (99.99%). Add appropriate concentration of SO as needed. 2or water vapor, the results show that compared with 10% Mn 0.5 Co 0.5 / BAC and 10%Mn 0.5 Co 0.5 15% Ce / BAC, 10% Mn 0.5 Co 0.5 / CeO 2 @BAC has better resistance to water and SO 2 performance, more suitable for high humidity environment and high SO 2 Environmental applications, mainly because CeO 2 Fully wrap BAC and form a hydrophobic CeO layer on its surface 2 coating, thereby increasing 10% Mn 0.5 Co 0.5 / CeO 2 @BAC has good water resistance in high humidity environment; in addition, the additive CeO 2 Can be used with some SO 2 The reaction protects the active components Mn and Co, thereby enhancing the 10% Mn 0.5 Co 0.5 / CeO 2 @BAC's Anti-SO 2 Performance. See the specific results Figure 5 .

[0088] Test Example 5

[0089] Comparative study of 10% Mn 0.5 Co 0.5 / CeO 2 @BAC and 10%Mn 0.5 Co 0.5 / BAC in SFG and SFG+300ppmSO 2 +8%H 2 Toluene removal rate (E toluene ) and toluene conversion (S c ) removal performance.

[0090] With 0.3g 10% Mn of the present invention 0.5 Co 0.5 / CeO 2 @BAC and 0.3g 10%Mn 0.5 Co 0.5 / BAC catalyst was used as the experimental object. At 240℃, SFG and SFG+300ppmSO 2 +8%H 2 The performance test was carried out continuously for 30 hours under the condition of O. The simulated flue gas atmosphere (SFG) included 300ppm toluene, 6% O 2and balance gas N 2 (99.99%). The results show that compared with 10% Mn 0.5 Co 0.5 / BAC, 10%Mn 0.5 Co 0.5 / CeO 2 @BAC has better resistance to water and SO 2 After 30 hours of performance testing, the latter still has better toluene removal performance (E toluene ) and toluene conversion (S c ), more suitable for high humidity environment and high SO 2 Environmental applications, mainly the latter rare earth metal oxide hydrophobic coating, greatly improves the high temperature thermal stability of biochar-based catalysts and water resistance in high humidity environments and sulfur resistance in high sulfur environments, and has better catalytic stability. Specific results are shown in Figure 6 .

[0091] Test Example 6

[0092] For the original BAC, CeO 2 @BAC, 10%Mn / CeO 2 @BAC, 10% Co / CeO 2 @BAC and 10%Mn 0.5 Co 0.5 / CeO 2 @BAC conducted XRD test, the results are shown in Figure 7 .Depend on Figure 7 It can be seen that CeO 2 It is tightly bound to BAC, compared with 10% Mn / CeO 2 @BAC and 10%Co / CeO 2 @BAC's Mn and Co metal oxides have better crystal form, 10% Mn 0.5 Co 0.5 / CeO 2 The Mn and Co oxides in @BAC are better dispersed and exist more in an amorphous state, which suggests better catalytic activity.

[0093] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A biochar-based catalyst, characterized in that: It comprises a carrier and an active component loaded on the carrier; the carrier is porous biochar wrapped with rare earth metal oxide; the active component is a mixed oxide of multiple transition metals; The rare earth metal oxide is CeO2; the mass content of the rare earth metal oxide in the biochar-based catalyst is 5-25%; The multiple transition metals are Co and Mn; the molar ratio of Co to Mn is (1-3): (3-1); the mass content of the active component in the biochar-based catalyst is 5-20%; The preparation method of the biochar-based catalyst comprises the following steps: impregnating porous biochar into a rare earth metal oxide precursor solution, and sequentially drying and first calcining to obtain porous biochar coated with rare earth metal oxide; The rare earth metal oxide-wrapped porous biochar is impregnated into an active component precursor solution, and then dried and calcined for a second time to obtain the biochar-based catalyst.

2. The method for preparing the biochar-based catalyst according to claim 1, characterized in that: The following steps are involved: The porous biochar is impregnated into a rare earth metal oxide precursor solution, and then dried and first calcined to obtain the rare earth metal oxide-coated porous biochar; The rare earth metal oxide-wrapped porous biochar is impregnated into an active component precursor solution, and then dried and calcined for a second time to obtain the biochar-based catalyst.

3. The preparation method according to claim 2, characterized in that: The temperature of the first calcination is 300-550° C., and the holding time is 2-6 hours.

4. The preparation method according to claim 2, characterized in that: The second calcination temperature is 300-550° C., and the heat preservation time is 2-6 hours.

5. Use of the biochar-based catalyst according to claim 1 or the biochar-based catalyst prepared by the preparation method according to any one of claims 2 to 4 in the thermal catalytic oxidation removal of volatile organic compounds.

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