Modified biochar catalyst, preparation method and application of modified biochar catalyst in removal of mercury and chlorobenzene

Abstract

The invention provides a preparation method of a modified biochar catalyst. The preparation method comprises the following steps: (1) preparing a sweet potato vine powder raw material; (2) preparing a calcium chloride-urea activation solution with the mass ratio of 1: 1; (3) uniformly stirring the sweet potato vine powder and the calcium chloride-urea activation solution, fully mixing, drying into powder, and putting into a tubular furnace to prepare a carbonized material; (4) impurity removal: repeatedly performing acid pickling, water washing, alkali washing and water washing on the carbonized material for more than ten times to obtain an initial charcoal carrier; (5) high-temperature graphitization treatment: putting the initial biochar carrier into a tubular furnace, graphitizing for 2 hours in a nitrogen-protected 1000 DEG C programmed heating tubular furnace, and cooling to obtain a three-dimensional interconnected hierarchical pore biochar carrier; and (6) preparing the modified biochar catalyst: weighing a proper amount of lanthanum nitrate, cerium nitrate and cobalt nitrate to prepare a precursor solution, taking a proper amount of the three-dimensional interconnected hierarchical porous biochar carrier, soaking the three-dimensional interconnected hierarchical porous biochar carrier in the precursor solution, performing ultrasonic treatment for 2 hours, fully mixing, drying into powder, and calcining the powder for 4 hours at 500 DEG C under the protection of N2 to prepare the modified biochar catalyst XLa alpha Ce beta Co gamma / BC. The invention also provides the modified biochar catalyst prepared by the method and application of the modified biochar catalyst in removal of mercury and chlorobenzene.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of environmental governance functional materials, and particularly relates to a modified biochar catalyst, a preparation method and application thereof in removal of mercury and chlorobenzene. BACKGROUND

[0002] Incineration is widely used as a waste disposal method in the world. During waste incineration, dust, SO2, NO x , heavy metals (Hg, Pb and Cd, etc.), chlorobenzene (CB) and dioxin, etc. volatile organic compounds (VOCs) and other atmospheric pollutants are produced. At present, dust, SO2 and NO x emissions have been successfully controlled, while the emissions of Hg and VOCs are still severe, which gradually become the focus and difficulty of waste incineration flue gas pollutant control.

[0003] The high toxicity, persistence and bioaccumulation of Hg pose a serious threat to human health and ecological environment safety. Excessive accumulation of mercury can cause damage to human internal organs and heart function, and even death. According to research, waste incineration flue gas mercury contains three kinds of oxidized mercury (Hg 2+ ), particulate mercury (Hg P ) and elemental mercury (Hg 0 ), among which Hg 2+ and Hg P can be removed by traditional wet flue gas desulfurization equipment (WFGD) and bag filter (FF) or electrostatic precipitator (ESP) respectively; but the proportion of Hg 0 is large, which is extremely volatile and difficult to dissolve in water, so the existing wet desulfurization system and dust removal equipment have limited removal capacity. Therefore, the key to control mercury emission lies in the removal of elemental mercury (Hg 0 ). Chlorobenzene (CB, usually as a monitoring substitute for dioxin) is a typical representative of VOCs emitted by waste incineration, which has the characteristics of stable chemical properties, carcinogenic, teratogenic and mutagenic properties, is not easily biodegradable and long-term accumulation in the environment, etc., and is also the main inducement of haze, photochemical smog, ozone and PM 2.5 pollution. Therefore, it is of great significance to enhance the control of Hg 0 and CB in waste incineration flue gas for improving the quality of urban atmospheric environment and maintaining the physical and mental health of residents.

[0004] At present, for the removal of Hg 0 and chlorobenzene (CB), dioxin and other VOCs in waste incineration flue gas, the process of “water washing + absorption tower deacidification + activated carbon injection + bag filter” is usually adopted. Although this combined flue gas purification technology can achieve good Hg 0and VOCs removal effect, but it also has the following disadvantages: (1) large space occupation, high equipment investment, and high operation and maintenance cost; (2) due to the limited adsorption capacity of activated carbon, the consumption of activated carbon is quite large, which greatly increases the treatment cost of atmospheric pollutants; (3) activated carbon is easy to be poisoned by Hg 0 and CB, etc. VOCs purification mainly relies on adsorption, and there is a problem of adsorbing Hg 0 and CB, etc. VOCs activated carbon subsequent disposal and Hg 0 and CB, etc. VOCs desorption problem again.

[0005] In contrast, catalytic oxidation method is one of the most promising VOCs treatment technologies due to its high VOCs degradation efficiency, no secondary pollution, low energy consumption, and wide application range; it can catalytically oxidize CB, etc. VOCs to CO2, water and HCl, etc. non-toxic or less toxic small molecules, which is an economic and environmental "green" VOCs treatment technology. In addition, although Hg 0 volatile and difficult to dissolve in water, which is destined to be difficult to collect and control, but its oxidation product Hg 2+ high water solubility is easy to be absorbed and removed by the subsequent wet flue gas desulfurization system (WFGD). Therefore, if a new type of economic and efficient catalyst for catalytic oxidation of Hg 0 and CB is developed on the basis of the widely installed dust and SO2 purification equipment, CB and Hg 0 can be converted into harmless or less harmful CO2, H2O and HCl, respectively, and Hg 2+ which is easy to be treated by subsequent flue gas treatment equipment, which will be a multiple pollution control process and method with double the result with half the effort.

[0006] In catalytic oxidation method, catalyst is the core of catalytic oxidation reaction, which plays a key function in the catalytic reaction process, can adsorb reactant molecules, effectively reduce the energy barrier of the reaction, and then speed up the reaction rate. The catalyst usually consists of active components, carriers and promoters, and according to the different active components, the catalyst can be divided into three categories: noble metal catalyst, rare earth-transition metal oxide catalyst and their mixed catalyst. Among them, noble metal catalysts such as Pt, Pd, Rh, Au, Ag, etc. have empty d orbitals, which are easy to adsorb and activate reactant molecules, so they have high oxidation activity, which is beneficial to the catalytic oxidation of Hg 0 and CB; but noble metal resources are scarce and expensive, noble metals are easy to agglomerate and volatilize under high temperature conditions, and are easy to be poisoned by halogen during use. In contrast, rare earth-transition metal oxide catalysts are abundant in reserves, cheap, thermally stable and strong in anti-poisoning ability, and are considered as an ideal choice to replace noble metal catalysts, so rare earth-transition metal oxide catalysts are used to catalytically oxidize and remove Hg 0And VOCs gradually become a research hotspot.

[0007] As disclosed in Chinese patent CN114210314B, a rare earth metal Ce and transition metal Cr / Mn / Fe modified biochar catalyst is used to synergistically remove formaldehyde and Hg 0 However, the catalyst is not suitable for removing chlorobenzene (CB) and Hg 0 from incineration flue gas, and the reasons are mainly two, one is that the catalyst has relatively few surface / interface active sites, and the activity of synergistically removing Hg 0 and VOCs is slightly insufficient, and the other is that compared with simple-structured formaldehyde, more energy is needed to degrade chlorobenzene and other VOCs (more difficult to degrade) containing benzene rings, and the reaction temperature needed is relatively high, while the above-mentioned biochar catalyst has poor thermal stability.

[0008] In order to solve the above problems, people have been seeking an ideal technical solution. SUMMARY

[0009] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a modified biochar catalyst with high thermal stability and many active sites, which can synergistically catalyze the oxidation of CB and Hg 0 respectively into harmless CO2, H2O, HCl and Hg 2+ which can be treated by subsequent flue gas treatment equipment, a preparation method thereof and its application in removing mercury and chlorobenzene.

[0010] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: a preparation method of a modified biochar catalyst, comprising the following steps:

[0011] (1) Raw material treatment: after washing and drying the raw material of sweet potato vine, crushing and sieving, the sweet potato vine powder is obtained;

[0012] (2) Preparation of activation solution: weigh anhydrous calcium chloride and urea with a mass ratio of 1:1, and dissolve them in an appropriate amount of water to obtain a calcium chloride-urea activation solution;

[0013] (3) Carbonization reaction: weigh an appropriate amount of the sweet potato vine powder and pour it into the calcium chloride-urea activation solution and stir uniformly, wherein the mass ratio of the sweet potato vine powder, the anhydrous calcium chloride and the urea is 1:2:2, and after mixing thoroughly, dry it into powder, and then put it into a tubular furnace, and carbonize it in the tubular furnace under N2 protection at 800℃ for 2 hours, and then cool it to room temperature under N2 protection to obtain carbonized material;

[0014] (4) Impurity removal: repeat the acid washing-water washing-alkali washing-water washing of the carbonized material for more than ten times to wash away the impurities in the carbonized material, and finally dry the obtained product to obtain the initial biochar carrier;

[0015] (5) High-temperature graphitization treatment: the initial biochar carrier is put into a tubular furnace, and after 2 hours of programmed temperature rising tubular furnace graphitization at 1000 DEG C under nitrogen protection, the three-dimensional interconnected multi-level pore biochar carrier is prepared by cooling to room temperature;

[0016] (6) Preparation of modified biochar catalyst: an appropriate amount of lanthanum nitrate, cerium nitrate and cobalt nitrate is weighed to prepare a precursor solution, and an appropriate amount of the three-dimensional interconnected multi-level pore biochar carrier is immersed in the precursor solution, ultrasonic treatment is performed for 2 hours, and after sufficient mixing, the powder is dried, and the powder is calcined at 500 DEG C under N2 protection for 4 hours to prepare a rare earth metal oxide LaO x and CeO x and a transition metal oxide CoO x co-modified biochar catalyst XLa α Ce β Co γ / BC.

[0017] Based on the above, the mixed solution stirred uniformly in step (3) and the mixed solution after ultrasonic treatment in step (6) need to be placed at room temperature for 24 hours to ensure sufficient mixing.

[0018] Based on the above, in step (3), the mixed solution after standing is placed in a 105 DEG C drying oven for drying for 24 hours to obtain a dry powder; and in step (6), the mixed solution after standing is placed in a 105 DEG C drying oven for drying until a constant weight is obtained to obtain a dry powder.

[0019] Based on the above, in step (4), the acid washing is performed by immersing the carbonized material in a 5-6 mol / L dilute nitric acid solution for 30 minutes, and then rinsing with deionized water several times until neutral; and the alkali washing is performed by immersing the carbonized material in a 5-6 mol / L dilute NaOH solution for 30 minutes, and then rinsing with deionized water several times until neutral.

[0020] Based on the above, in step (1), the sweet potato vine raw material is cleaned with deionized water, and the drying is performed by first placing in a 105 DEG C drying oven for drying, and then cooling to room temperature.

[0021] The application also provides a modified biochar catalyst prepared by the modified biochar catalyst preparation method described above.

[0022] Based on the above, the XLa α Ce β Co γ / BC is specifically 10% La 0.2 Ce 0.3 Co 0.5 / BC.

[0023] The application further provides a modified biochar catalyst for removing mercury and chlorobenzene, and the modified biochar catalyst is used for catalytic oxidation of waste incineration flue gas.

[0024] Based on the above, the reaction temperature of catalytic oxidation is 80-400 DEG C.

[0025] Based on the above, the reaction temperature of catalytic oxidation is 280 DEG C.

[0026] The application has the following advantages compared with the prior art:

[0027] (1) The modified biochar catalyst (XLa α Ce β Co γ / BC) adopts various rare earth-transition metal oxides to modify the biochar, optimize the surface / interface physicochemical properties, and the various metal oxides can not only produce various catalytic active sites, reduce the catalytic efficiency reduction caused by the competition for active sites in the multi-pollutant synergistic removal process, but also can produce synergistic effect through the strong interaction between the multiple metals, induce the formation of lattice defects and oxygen vacancies, produce more active oxygen species, and promote the deep oxidation of Hg 0 And CB.

[0028] (2) The sweet potato vine is used as raw material, and the excellent pore structure of the sweet potato vine itself is utilized, so that the three-dimensional porous structure of the prepared biochar is more excellent.

[0029] (3) The modified biochar catalyst (XLa α Ce β Co γ / BC) has a carrier which is graphitized at a high temperature of 1000 DEG C, which not only reconstructs the pore structure of the biochar carrier at a high temperature, increases the specific surface area, optimizes the ratio of micropore-mesopore-macropore (the mesopore specific surface area is greater than 424 m 2 / g), promotes the diffusion and mass transfer of reactants and products, but also can enhance the thermal stability and water resistance of the biochar catalyst, and improve its advantages in the catalytic field.

[0030] (4) The strong hydrophobicity of the three-dimensional interconnected biochar carrier after high-temperature graphitization and the unique electronic structure of the rare earth metals such as La and Ce inhibit the formation of hydrogen bonds between the catalyst and the interface water vapor, thereby improving the water resistance of the biochar catalyst; in addition, the rare earth metals such as Ce and La can act as a sacrificial agent to preferentially react with SO2, thereby improving the sulfur resistance of the biochar catalyst, so that the biochar catalyst has good industrial application potential and prospect. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1is a test result graph in the present application embodiment 1.

[0032] Figure 2 is a SEM and TEM characterization result graph in the present application embodiment 2.

[0033] Figure 3 is a test result graph in the present application embodiment 2.

[0034] Figure 4 is a test result graph in the present application embodiment 3.

[0035] Figure 5 is a test result graph in the present application embodiment 4. DETAILED DESCRIPTION

[0036] The technical solutions of the present application are further described in detail below through specific embodiments.

[0037] Embodiment 1

[0038] A modified biochar catalyst preparation method comprises the following steps:

[0039] (1) Raw material treatment: Deionized water washes the agricultural waste sweet potato vine clean, and then is placed in a 105℃ drying oven for drying. After cooling to room temperature, it is crushed and sieved to obtain sweet potato vine powder, which is stored in a sealed bag for use;

[0040] (2) Preparation of activation solution: An appropriate amount of anhydrous calcium chloride and urea are weighed, wherein the mass ratio of the anhydrous calcium chloride to the urea is 1:1. After dissolving in an appropriate amount of water, a calcium chloride-urea activation solution is obtained;

[0041] (3) Carbonization reaction: An appropriate amount of the sweet potato vine powder is weighed and poured into the calcium chloride-urea activation solution and stirred uniformly, wherein the mass ratio of the sweet potato vine powder, the anhydrous calcium chloride and the urea is 1:2:2. After being placed at room temperature for 24 hours, it is then placed in a 105℃ drying oven for drying for 24 hours. Then it is put into a tubular furnace and carbonized in an N2-protected programmed temperature tubular furnace at 800℃ for 2 hours. After that, the carbonized material is cooled to room temperature under nitrogen protection for standby use;

[0042] (4) Impurity removal: The carbonized material is soaked in a 5-6mol / L dilute nitric acid solution for 30 minutes, and then rinsed with deionized water several times until neutral. Then it is soaked in a 5-6mol / L dilute NaOH solution for 30 minutes, and then rinsed with deionized water several times until neutral. The above-mentioned acid washing-water washing-alkali washing-water washing steps are repeated for more than ten times to wash away the impurities in the carbonized material. Finally, the obtained product is dried to obtain an initial biochar carrier;

[0043] (5) High-temperature graphitization treatment: the initial biochar carrier was put into a tubular furnace, and after 2 hours of programmed temperature tubular furnace graphitization at 1000℃ under nitrogen protection, it was cooled to room temperature to obtain a three-dimensional interconnected multi-level pore biochar carrier;

[0044] (6) Preparation of modified biochar catalyst: an appropriate amount of lanthanum nitrate (La(NO3)3 . 6H2O), cerium nitrate (Ce(NO3)3 . 6H2O), and cobalt nitrate (Co(NO3)2 . 6H2O) were weighed to prepare a precursor solution, and an appropriate amount of the three-dimensional interconnected multi-level pore biochar carrier was immersed in the precursor solution, ultrasonic treatment was performed for 2h, then it was left to stand at room temperature for 24 hours, and then dried to constant weight in a 105℃ drying oven, followed by calcination at 500℃ under N2 protection for 4 hours to obtain a biochar catalyst co-modified by rare earth metal oxides LaO x and CeO x and transition metal oxides CoO x (XLa α Ce β Co γ / BC).

[0045] The modified biochar catalyst prepared by the above method was prepared using agricultural waste sweet potato vine as raw material, anhydrous calcium chloride and urea as activating agent, and three-dimensional interconnected porous biochar as carrier (BC) after activation, carbonization and 1000℃ high-temperature graphitization treatment, and loaded with various rare earth-transition metal oxides (La, Ce and Co) to prepare a biochar catalyst with high thermal stability and multiple active sites (XLa α Ce β Co γ / BC), the content of the corresponding active components was calculated according to the respective oxides, and the amount of required nitrate was converted, as shown in Table 1:

[0046] Table 1 Required amount of raw materials for 10% La 0.2 Ce 0.3 Co 0.5 / BC

[0047]

[0048] The specific surface area of the 10% La 0.2 Ce 0.3 Co 0.5 / BC was 424.87m 2 / g, the total pore volume was 0.095cm 3 / g, and the average pore size was 5.446nm.

[0049] For comparison, 10% Co / BC and 10% La 0.4 Ce 0.6 / BC were prepared by the same method after changing the formula ratio 0.2 Ce 0.3 Co 0.5 / BC, 10% Co / BC and 10% La 0.4 Ce 0.6 / BC were prepared by the same method after changing the formula ratio 3 Hg 0 (g), 120 ppm CB (g), 6% O2, 94% N2.

[0050] As Figure 1 shown, the test results show that they show similar performance trends, in low temperature cases, the synergistic removal of Hg 0 and CB performance of the sample increases with the increase of reaction temperature, after 280℃, continue to increase the reaction temperature, the sample removal Hg 0 and CB performance slightly decreased, at 280℃, the best performance of synergistic catalytic oxidation removal of CB and Hg 0 . 10% La 0.2 Ce 0.3 Co 0.5 / BC is significantly better than 10% Co / BC and 10% La 0.4 Ce 0.6 / BC. This may be due to the multi-rare earth-metal oxide modified biochar catalyst, which can produce a stronger synergistic effect, optimize the physicochemical properties of the sample, provide more active sites, and can obtain better synergistic catalytic oxidation removal of Hg 0 and CB performance. At 280℃, 10% La 0.2 Ce 0.3 Co 0.5 / BC can obtain 99.3% Hg 0 removal rate and 91.8% CB removal rate.

[0051] Example 2

[0052] The preparation method is the same as example 1, without changing the carrier, appropriately changing the loading amount or molar ratio of the active component to prepare modified biochar catalyst materials with different active component loading amounts or molar ratios, metal oxides account for biochar catalyst (XLa α Ce β Co γThe mass percentage of / BC) is 5%, 10%, 15%, and 20%; the molar ratio of metal La:Ce:Co is 0.2:0.3:0.5, 0.3:0.2:0.5, 0.25:0.25:0.5, 0.4:0.1:0.5, and 0.1:0.4:0.5. Applications are as follows:

[0053] Using 0.25g of biochar catalyst from this invention as the experimental subject, within a temperature range of 80–400°C, a normal simulated flue gas atmosphere (SFG) including 100 μg / m³ was observed. 3 Hg 0 (g), 120ppm CB(g), 6% O2, 94% N2. Test results show that suitable metal oxide loading and a suitable La:Ce:Co molar ratio are both beneficial to Hg. 0 The synergistic catalytic oxidation removal of Hg with CB, however, can be hindered by an inappropriate molar ratio and insufficient or excessive metal oxide loading. 0 The removal effect of CB is reduced.

[0054] In addition, such as Figure 2 As shown in the figure, the SEM and TEM characterization results reveal that the introduction of metal oxides significantly alters the surface morphology of the original BC: Figure a shows the SEM image of the original BC, and figure b shows the SEM image of 5% La... 0.2 Ce 0.3 Co 0.5 SEM image of / BC, c is 10% La 0.2 Ce 0.3 Co 0.5 SEM image of / BC, d is 15% La 0.2 Ce 0.3 Co 0.5 SEM image of / BC, TEM image of 10% Co / BC, f image of 10% La 0.4 Ce 0.6 TEM image of / BC, g is 10% La 0.2 Ce 0.3 Co 0.5 TEM image of / BC, h is 10% La 0.2 Ce 0.3 Co 0.5 The EDX plot of / BC shows that when the metal oxide loading is 5%, some of the biochar support surface remains unutilized, while in the sample with an excessive loading of 20%, a large amount of metal oxide aggregates appear, even clogging some pores. Meanwhile, the 10% La... 0.2 Ce 0.3 Co 0.5 The metal oxides on / BC are relatively uniformly distributed, providing sufficient adsorption and catalytic active sites for the catalytic reaction, thus exhibiting the highest Hg.0 The efficiency of synergistic catalytic oxidation removal with CB.

[0055] like Figure 3 As shown, for a loading of 10%, samples with different molar ratios synergistically catalytically oxidatively removed Hg. 0 The performance of CB also differs. The optimal La:Ce:Co molar ratio is 0.2:0.3:0.5. This is likely because the metal oxides exhibit the strongest synergistic effect in this optimal molar ratio, inducing more lattice defects and oxygen vacancies, increasing the quantity and mobility of reactive oxygen species, and resulting in stronger redox performance, which is most favorable for CB and Hg. 0 Catalytic oxidation.

[0056] Example 3

[0057] The preparation method is the same as in Example 1, using the optimal loading of 10% and the optimal molar ratio of La:Ce:Co of 0.2:0.3:0.5 as standards, and using BC before graphitization as the standard. 0 Using graphitized BC as a carrier, 10% La was prepared. 0.2 Ce 0.3 Co 0.5 / BC 0 and 10%La 0.2 Ce 0.3 Co 0.5 / BC. Applications are as follows:

[0058] The 10% La prepared using 0.25g of the present invention 0.2 Ce 0.3 Co 0.5 / BC 0 and 10%La 0.2 Ce 0.3 Co 0.5 / BC was used as the experimental subject. Within a temperature range of 80–400℃, the normal simulated flue gas atmosphere (SFG) included 100 μg / m³. 3 Hg 0 (g), 120ppm CB(g), 6%O2, 94%N2.

[0059] like Figure 4 As shown, 10% La 0.2 Ce 0.3 Co 0.5 / BC ratio 10% La 0.2 Ce 0.3 Co 0.5 / BC 0 Possesses better synergistic catalytic oxidation of Hg 0and CB, which can be attributed to the reconstruction of the pore structure of the support caused by high-temperature graphitization, which not only increases the specific surface area and adjusts the ratio of micropores-mesopores-macropores, optimizes the surface / interface properties and physicochemical properties, but also is conducive to increasing the number of accessible active sites and the timely mass transfer and diffusion of reactants and products, and is conducive to the synergistic catalytic oxidation of Hg 0 and CB.

[0060] Example 4

[0061] The preparation method is the same as that in Example 1, and under the premise of ensuring the optimal reaction temperature of 280℃, the performance of 10% La 0.2 Ce 0.3 Co 0.5 / BC in the synergistic catalytic oxidation removal of Hg 0 and CB, and the selectivity of CO2, and the performance of 10% La 0.2 Ce 0.3 Co 0.5 / BC in SFG and SFG+8% H2O(g)+200ppm SO2 flue gas conditions, in order to evaluate its water and sulfur resistance. The following is applied:

[0062] 0.25g of 10% La 0.2 Ce 0.3 Co 0.5 / BC in the present application is taken as the experimental object, the temperature is kept at 280℃, and the flue gas atmosphere (SFG) includes 100μg / m 3 Hg 0 (g), 120ppm CB(g), 6% O2, 94% N2, and 8% H2O(g) and 200ppm SO2 are added as needed.

[0063] As Figure 5 shown, after running for 36h under SFG conditions, the removal efficiency of CB can still reach 89.4%, the removal efficiency of Hg 0 can still maintain at 93.2%, and the selectivity of CO2 can reach 93.4%; under SFG+8% H2O(g)+200ppm SO2 conditions, 10% La 0.2 Ce 0.3 Co 0.5 / BC can still obtain a CB removal efficiency of 81.7%, a Hg 0 removal efficiency of 83.1%, and the selectivity of CO2 can reach 89.5%. It shows that the biochar catalyst designed in the present application has excellent performance in the synergistic catalytic oxidation removal of Hg 0 and CB, has good stability and selectivity, and has outstanding water and sulfur resistance.

[0064] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not to limit the present application; although the present application has been described in detail with reference to the preferred embodiments, it is understood by those skilled in the art that the specific embodiments of the present application can be modified or some technical features can be replaced by equivalent ones; without departing from the spirit of the technical solutions of the present application, all of which should be covered in the technical solution range of the present application claimed by the present application.

Claims

1. A method for preparing a modified biochar catalyst, characterized by, The method comprises the following steps: (1) raw material treatment: washing, drying, crushing and sieving sweet potato vine raw materials to obtain sweet potato vine powder; (2) preparation of activation solution: weighing anhydrous calcium chloride and urea in a mass ratio of 1:1, dissolving in an appropriate amount of water to obtain a calcium chloride-urea activation solution; (3) carbonization reaction: weighing an appropriate amount of sweet potato vine powder and stirring uniformly in the calcium chloride-urea activation solution, wherein the mass ratio of the sweet potato vine powder, the anhydrous calcium chloride and the urea is 1:2:2, after sufficient mixing, drying into powder, and then putting into a tubular furnace for carbonization at 800℃ in a N2-protected programmed temperature tubular furnace for 2 hours, and cooling to room temperature under N2 protection to obtain carbonized material; (4) impurity removal: repeatedly performing acid washing-water washing-alkali washing-water washing on the carbonized material for more than ten times to wash away impurities in the carbonized material, and finally drying the obtained product to obtain an initial biochar carrier; (5) high-temperature graphitization treatment: putting the initial biochar carrier into a tubular furnace, and after graphitization at 1000℃ in a N2-protected programmed temperature tubular furnace for 2 hours, cooling to room temperature to obtain a three-dimensional interconnected multi-level pore biochar carrier; (6) Preparation of modified biochar catalyst: an appropriate amount of lanthanum nitrate, cerium nitrate and cobalt nitrate are weighed to prepare a precursor solution, an appropriate amount of the three-dimensional interconnected multi-level pore biochar carrier is immersed in the precursor solution, ultrasonic treatment is performed for 2 h, after sufficient mixing, the powder is dried, and the powder is calcined at 500°C for 4 hours under N2 protection to prepare a rare earth metal oxide LaO x and CeO x and a transition metal oxide CoO x co-modified biochar catalyst XLa α Ce β Co γ / BC.

2. The method of claim 1, wherein: The mixed solution stirred uniformly in step (3) and the mixed solution after ultrasonic treatment in step (6) need to be placed at room temperature for 24 hours to ensure sufficient mixing.

3. The method of claim 2, wherein: In step (3), the mixed solution after standing is placed in a 105℃ drying box for drying for 24 hours to obtain a dry powder; in step (6), the mixed solution after standing is placed in a 105℃ drying box and dried to constant weight to obtain a dry powder.

4. The method of claim 1, wherein: In step (4), the carbonized material is soaked in 5-6 mol / L dilute nitric acid solution for 30 minutes, and then rinsed with deionized water several times until neutral, and the alkali washing adopts 5-6 mol / L dilute NaOH solution for 30 minutes, and then rinsed with deionized water several times until neutral.

5. The method of claim 1, wherein: In step (1), the sweet potato vine raw material is washed with deionized water, and drying is first placed in a 105℃ drying oven, and then cooled to room temperature.

6. A modified biochar catalyst characterized by: The modified biochar catalyst is prepared by the method according to any one of claims 1-5.

7. The modified biochar catalyst of claim 6, wherein: The XLa α Ce β Co γ / BC is specifically 10% La 0.2 Ce 0.3 Co 0.5 / BC.

8. Use of a modified biochar catalyst for removal of mercury and chlorobenzene, characterized by: The modified biochar catalyst according to claim 6 or 7 is used for catalytic oxidation of waste incineration flue gas.

9. The use of a modified biochar catalyst to remove mercury and chlorobenzene according to claim 8, characterized by: The reaction temperature of catalytic oxidation is 80-400℃.

10. The use of a modified biochar catalyst to remove mercury and chlorobenzene according to claim 9, characterized by: The reaction temperature of catalytic oxidation is 280℃.

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