A method for synthesizing a bifunctional carbon-based catalyst capable of removing VOCs from low-temperature flue gas

Abstract

The present invention discloses a method for synthesizing a bifunctional carbon-based catalyst capable of removing VOCs from low-temperature flue gas, comprising the following steps: step 1) pretreatment of a carbon source; step 2) mixing a metal salt / nitrogen source / carbon source in one step, so that the carbon source is fully mixed with the metal salt and the nitrogen source; step 3) filtering / centrifuging the mixture obtained in step 2). Step 4) placing the mixture obtained in step 3) in an atmosphere tube furnace to catalytically etch and pore-form the carbon source and catalytically graphitize it; step 5) characterizing the physical and chemical properties of the carbon-based catalyst material obtained in step 4) by low-temperature nitrogen adsorption test, X-ray diffraction test, X-ray electro-photon spectroscopy test and the like, and conducting experiments using a fixed bed reactor. The present invention is conducive to the activation of reactant molecules such as oxygen on the catalyst surface, promoting the catalytic oxidation reaction of VOCs at relatively low temperatures; forming a graphite-like microcrystalline structure in the carbon matrix, thereby obtaining excellent thermal stability.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing a carbon-based catalyst, in particular to a method for synthesizing a bifunctional carbon-based catalyst capable of removing VOCs from low-temperature flue gas, and belongs to the technical field of coal-fired / chemical pollutant treatment. Background Art

[0002] Among the many coal-fired and chemical-related pollutants, mature control technologies exist for sulfur and nitrogen oxides. However, volatile organic compounds (VOCs), key precursors to smog and ozone, have also recently gained attention. In 2020, national VOC emissions from industrial sources reached 13.58 million tons, accounting for 56% of the total. Coal-fired power generation, in particular, has an emission factor even higher than that of industries like textiles and rubber. More importantly, load fluctuations during the deep peak-shaving phase of renewable energy production have exacerbated the complexity and volume of VOC emissions from coal-fired flue gas.

[0003] Existing VOCs treatment technologies mainly include two categories: catalytic oxidation and adsorption. As for the adsorption method, whether it is activated carbon or molecular sieve adsorbent, it is limited by the basic principle of physical adsorption intermolecular forces. It mainly exhibits adsorption effects in low-temperature flue gas (such as <180°C), and after a period of time, it reaches adsorption saturation and requires regeneration. The whole process is difficult to sustain for a long time; as for the catalytic oxidation method, it is limited by the activation energy of the thermal catalytic reaction. Whether it is a transition metal oxide catalyst or a precious metal catalyst, its effective working temperature is mostly in the temperature range of 300-450°C. However, taking coal-fired flue gas as an example, according to data from 2021, nearly 60% of coal-fired units in my country have been in low-load operation for a long time, and the flue gas temperature at the SCR (selective catalytic reduction denitrification) is often below 300°C. Therefore, the development of catalyst materials with excellent VOCs removal performance in the entire temperature range (180-450°C) is the key to achieving efficient treatment.

[0004] The metal active components required for catalyst materials should be supported on supports with good thermal stability and high specific surface area. Common supports include TiO2, Al2O3, carbon fibers, and activated carbon. Their functions include: 1) a large surface area provides an excellent dispersion site for active sites, facilitating efficient activity; and 2) a rich pore structure that provides pathways for the diffusion and transport of VOC molecules, providing a location for their storage (adsorption). In summary, based on specific analysis of engineering application requirements, the production cost of catalysts should consider the following two aspects: 1) avoiding the use of precious metals (such as Pt and Au) as active components. By rationally combining transition metals (such as Fe and Mn) and rare earth metal-based materials (such as Ce), the oxygen vacancies and electron transfer-promoting properties of rare earth metal oxides can be exploited to achieve a "1+1>2" effect; and 2) using a low-cost, widely available support. High-specific-surface-area porous carbon is a preferred catalyst support. Therefore, considering the inherent advantages of carbon-based materials and the urgent need to control organic pollutants in flue gas, carbon-based catalysts are an excellent and promising option for VOCs control.

[0005] At present, representative synthesis methods of carbon-based catalyst materials include: physical activation, chemical activation, hydrothermal synthesis, activation, etc. Based on different synthesis conditions and precursors, the three aspects of porosity, graphitization degree and heterogeneous atom doping can be regulated. For metal-loaded carbon-based catalysts, a multi-step method of porous carbon synthesis-impregnation-calcination is often used to achieve the loading of metal oxides, but there are still problems such as poor anchoring effect between the loaded metal and the carbon-based surface. If a fast, simple, and energy-saving one-step method can be developed to achieve the one-step conversion of carbon precursor-metal-loaded carbon-based catalyst and achieve coordinated regulation of porosity, doping and loading, it will be an important methodological breakthrough in the field of carbon-based catalyst preparation. Summary of the Invention

[0006] This invention aims to develop a low-cost, long-life "dual-functional carbon-based" catalyst material. It proposes a "one-step activation" preparation method for a carbon source-carbon-based catalyst. A transition metal-rare earth metal dual-component oxide is loaded onto porous carbon and pores are formed through high-temperature catalysis. This allows for both VOC adsorption and catalytic oxidation, enabling efficient VOC removal across the entire flue gas temperature range (180-350°C). The resulting carbon-based catalyst is structurally stable and exhibits a very low ignition loss rate in an oxidizing atmosphere. Using toluene as a representative of common flue gas VOCs, the resulting material demonstrates excellent catalytic performance against VOCs across the entire temperature range.

[0007] The technical solution of the present invention is a method for synthesizing a bifunctional carbon-based catalyst capable of removing VOCs from flue gas over the entire temperature range, comprising the following steps:

[0008] Step 1) Carbon source pretreatment: drying, crushing and screening the selected solid carbon source to a suitable particle size; the particle size can range from 20 μm to 2 cm depending on the actual application;

[0009] Step 2) mixing the metal salt / nitrogen source / carbon source in one step, placing the carbon source in an aqueous solution or suspension containing the metal salt and the nitrogen source in a certain proportion, and using ultrasonic dispersion or mechanical stirring, accompanied by heating in a water bath at 60-80° C., so that the carbon source is fully mixed with the metal salt and the nitrogen source;

[0010] Step 3) separation and drying: The mixture obtained in step 2) is filtered / centrifuged, and the resulting solid material is dried by hot air, vacuum dried, or freeze-dried at 80-150°C.

[0011] Step 4) High-temperature activation treatment: The mixture obtained in step 3) is placed in an atmosphere tube furnace and pre-carbonized in a nitrogen atmosphere or an argon inert atmosphere at a temperature range of 600-800°C to achieve the fixation of nitrogen elements in the carbon matrix and the melt dispersion of metal salts. Subsequently, the activation atmosphere is switched to an activation atmosphere containing a certain proportion of water vapor, ammonia or carbon dioxide, and activation is performed at a temperature range of 700-1000°C. The metal salt and the activation atmosphere work together to achieve catalytic etching of the carbon source, pore formation, and catalytic graphitization.

[0012] Step 5) Characterization and testing: The physical and chemical properties of the carbon-based catalyst material obtained in step 4) are characterized by low-temperature nitrogen adsorption test, X-ray diffraction test, X-ray electro-photon spectroscopy test and other methods, and experiments are carried out in a fixed bed reactor to determine the typical VOCs removal efficiency of the sample obtained in step 4) in the temperature range of 180-350°C for a concentration range of 200-2000ppm.

[0013] Furthermore, the selected carbon source may be medium or low-rank coal or biomass (such as straw, cellulose, lignin, and waste rice husk).

[0014] Furthermore, the selected external nitrogen source may be nitrogen-containing substances such as urea, melamine, ammonium nitrate, and ethylenediaminetetraacetic acid; the selected external metal salt may be an alkali metal salt, a transition metal salt, or a mixture of the two, specifically including manganese nitrate, ferric nitrate, ferrous nitrate, manganese chloride, ferric chloride, cupric chloride, as well as cerium nitrate, cerium chloride, cerium acetate, etc.

[0015] Furthermore, the mass ratio of the selected added metal salt to the carbon source is in the range of 0.02:1 to 0.2:1, and the mass ratio of the added nitrogen source to the carbon source is in the range of 0.5:1 to 1:1. When the above-mentioned three types of substances, metal salt, carbon source and nitrogen source, exist at the same time, the mass ratios between the above-mentioned substances are still applicable.

[0016] Furthermore, the activation gas selected during the high-temperature activation treatment is a mixture of an activator and an inert gas, wherein the activator includes water vapor, ammonia or carbon dioxide, and the inert gas includes high-purity nitrogen, argon, helium, etc.; the ratio of the volume fraction of the activator to the inert gas ranges from 0.1:1 to 0.8:1.

[0017] Furthermore, the transition metal and rare earth metal contents in the obtained carbon-based catalyst were determined by elemental analysis, X-ray photoelectron spectroscopy and other means, and the mass fraction of the above metal elements was in the range of 1% to 10%; the atomic percentage of nitrogen was in the range of 4at% to 10at%.

[0018] Furthermore, the specific surface area of ​​the obtained carbon-based catalyst was determined by nitrogen adsorption at liquid nitrogen temperature and calculated by BET theory multi-point method, which was located at 250m 2 / g to 800m 2 / g range, and the ratio of the micropore volume (ie, diameter <2nm) to the total pore volume is in the range of 30% to 70%.

[0019] Furthermore, the obtained carbon-based catalyst exhibits catalytic oxidation effect on typical benzene-based VOCs at 200°C. In the space velocity range of 15,000 to 25,000 h-1, the catalytic oxidation efficiency of toluene at 200°C is not less than 50%, and the catalytic oxidation efficiency of toluene at 300°C is not less than 70%.

[0020] Compared with the prior art, the carbon-based catalyst obtained in the present invention has a lower overall cost than traditional pure metal-based catalysts such as VW-Ti and MnO2, and has a relatively lower operating temperature range, demonstrating catalytic oxidation ability for toluene at flue gas temperatures below 300°C. The reasons are: 1) the developed specific surface area and pore structure of the carbon-based catalyst not only provide an adsorption site for VOCs molecules, but also provide a carrier for the dispersion of metal oxides, thereby enhancing the dispersion of metal active sites and providing a high loading per unit specific surface area, thereby promoting the efficient catalytic oxidation reaction of VOCs; 2) the heterogeneous atom doping structure such as nitrogen functional groups in the carbon-based catalyst promotes electron transfer on the basal plane and strengthens the carrier-metal interaction between the carbon material and the metal oxide, thereby facilitating the activation of reactant molecules such as oxygen on the catalyst surface and promoting the catalytic oxidation reaction of VOCs at lower temperatures; in addition, the addition of transition metal salts (such as manganese chloride) during the preparation process can promote graphitization of the carbon structure at high temperatures, forming a graphite-like microcrystalline structure within the carbon matrix, thereby achieving excellent thermal stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the low-temperature nitrogen adsorption test isotherm of the sample in Example 1.

[0022] Figure 2 This is the X-ray diffraction pattern of the sample in Example 1.

[0023] Figure 3 This is the peak separation result of N element in the X-ray photoelectron spectrum of the sample in Example 1.

[0024] Figure 4 This is the Ce element peak separation result in the X-ray photoelectron spectrum of the sample in Example 1.

[0025] Figure 5 This is the peak separation result of Mn element in the X-ray photoelectron spectrum of the sample in Example 1.

[0026] Figure 6 This is the low-temperature nitrogen adsorption test isotherm of the sample in Example 2.

[0027] Figure 7 This is the X-ray diffraction pattern of the sample in Example 2.

[0028] Figure 8 This is the N element peak separation result in the X-ray photoelectron spectrum of the sample in Example 2.

[0029] Figure 9 The peak separation results of Ce element in X-ray photoelectron spectrum of sample 2 in Example 2 are as follows:

[0030] Figure 10 This is the peak separation result of Mn element in the X-ray photoelectron spectrum of the sample in Example 2.

[0031] Figure 11 This is the low-temperature nitrogen adsorption test isotherm of the comparative example sample.

[0032] Figure 12 The X-ray diffraction pattern of the sample of the comparative example is shown in FIG.

[0033] Figure 13 The figure shows the peak separation results of Ce element in X-ray photoelectron spectrum of the comparative example samples.

[0034] Figure 14 The figure shows the peak separation results of Mn element in X-ray photoelectron spectrum of the samples in the comparative example. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0036] Example 1:

[0037] The following steps were taken to prepare the carbon-based catalyst supported by manganese and cerium bimetallic oxides:

[0038] 1) Carbon source pretreatment: The selected domestic low- and medium-rank coal blocks were dried, crushed and screened to a suitable particle size with an average particle size of 96 μm;

[0039] 2) One-step mixing of metal salt / nitrogen source / carbon source: The carbon source described in step 1 is placed in an aqueous solution containing metal salts manganese chloride, cerium chloride, and a nitrogen source ethylenediaminetetraacetic acid. In the preparation of the above solution, the mass of manganese chloride and cerium chloride is each 5wt% of the mass of the solid carbon source, and the mass of ethylenediaminetetraacetic acid is equal to the mass of the solid carbon source. Subsequently, ultrasonic dispersion is performed while heating in a constant temperature water bath at 60°C to fully mix the solution and the carbon source.

[0040] 3) Separation and drying: After the mixture is separated by suction filtration, the obtained solid material is dried in a hot air drying oven at 80°C.

[0041] 4) High-temperature activation treatment: The mixture is placed in an atmosphere tube furnace and activated at 750°C in an activation atmosphere containing 40% high-purity carbon dioxide and 60% high-purity nitrogen. The metal salt and the activation atmosphere work together to achieve catalytic etching, pore formation, and catalytic graphitization of the carbon source.

[0042] 5) Characterization and testing: The physical and chemical properties of the carbon-based catalyst material obtained in step 4 were characterized by low-temperature nitrogen adsorption test, X-ray diffraction test, X-ray electron photon spectroscopy test, etc., and experiments were conducted using a fixed bed reactor to determine the catalytic oxidation efficiency of the sample obtained in step 4) for 250 ppm toluene in an air atmosphere at temperatures of 200, 250, 300 and 350°C.

[0043] The obtained catalyst has the following properties and effects:

[0044] The pore structure is as follows:

[0045]

[0046] Figure 1 This is the low-temperature nitrogen adsorption test isotherm of the sample in Example 1; Figure 2 The X-ray diffraction pattern of the sample in Example 1 shows characteristic peaks of different crystal forms such as MnO2, Mn3O4, and CeO2, proving that the above-mentioned metal oxides are successfully loaded inside the carbon-based catalyst.

[0047] Figure 3 This is the N element peak analysis result from the X-ray photoelectron spectrum of the sample in Example 1. The XPS data indicate that the atomic percentage of nitrogen in the sample obtained in this example is 4.0%. The characteristic N1s peak can be separated and fitted into three peak types: pyridinic nitrogen (pyridinic N), pyrrolic nitrogen (pyrrolic N), and graphitic nitrogen (graphitic N). The atomic percentages of these three types are 36%, 46%, and 16%, respectively. Figure 4 This is the Ce element peak separation result in the X-ray photoelectron spectrum of the sample in Example 1. Figure 5 This is the peak separation result of Mn element in the X-ray photoelectron spectrum of the sample in Example 1.

[0048] The Ce 3d XPS spectrum and the Mn 2p XPS spectrum of the sample indicate that the atomic percentages of Mn and Ce in the sample obtained in this example are 2.0% and 2.1%, respectively. Furthermore, based on the above spectra, the valence states of each element can be calculated, as shown in the following table:

[0049]

[0050] A fixed bed reactor was used to test the catalytic oxidation efficiency of the sample obtained in step 4) for 250 ppm toluene at 200, 250, 300, and 350° C. in an air atmosphere. The flow rate was 200 ml / min. The catalytic oxidation efficiencies are summarized as follows:

[0051]

[0052] Example 2:

[0053] The following steps were taken to prepare the carbon-based catalyst supported by manganese and cerium bimetallic oxides:

[0054] 1) Carbon source pretreatment: The selected domestic low- and medium-rank coal blocks were dried, crushed and screened to a suitable particle size with an average particle size of 96 μm;

[0055] 2) One-step mixing of metal salt / nitrogen source / carbon source: The carbon source described in step 1 is placed in an aqueous solution containing metal salts manganese nitrate and cerium nitrate. In the process of preparing the above solution, the mass of manganese chloride and cerium chloride is each 5wt% of the mass of the solid carbon source. The nitrate in the above nitrate is used to replace the ethylenediaminetetraacetic acid in the above embodiment to achieve nitrogen doping of the carbon material. Subsequently, ultrasonic dispersion is performed while heating in a constant temperature water bath at 60°C to fully mix the solution and the carbon source.

[0056] 3) Separation and drying: After the mixture is separated by suction filtration, the obtained solid material is dried in a hot air drying oven at 80°C.

[0057] 4) High-temperature activation treatment: The mixture is placed in an atmosphere tube furnace and activated at 750°C in an activation atmosphere containing 40% high-purity carbon dioxide and 60% high-purity nitrogen. The metal salt and the activation atmosphere work together to achieve catalytic etching, pore formation, and catalytic graphitization of the carbon source.

[0058] 5) Characterization and testing: The physical and chemical properties of the carbon-based catalyst material obtained in step 4 were characterized by low-temperature nitrogen adsorption test, X-ray diffraction test, X-ray electron photon spectroscopy test, etc., and experiments were conducted using a fixed bed reactor to determine the catalytic oxidation efficiency of the sample obtained in step 4) for 250 ppm toluene in an air atmosphere at temperatures of 200, 250, 300 and 350°C.

[0059] The obtained catalyst has the following properties and effects:

[0060] Pore ​​structure:

[0061]

[0062] Figure 6 This is the low-temperature nitrogen adsorption test isotherm of the sample in Example 2. Figure 7 The X-ray diffraction pattern of the sample in Example 2 shows characteristic peaks of different crystal forms such as MnO2, Mn3O4, and CeO2, proving that the above-mentioned metal oxides are successfully loaded inside the carbon-based catalyst.

[0063] Figure 8 This is the N element peak analysis result from the X-ray photoelectron spectrum of the sample from Example 2. The XPS data indicate that the atomic percentage of nitrogen in the sample obtained from this example is 4.0%. The characteristic N1s peak can be separated and fitted into three peak types: pyridinic nitrogen (pyridinic N), pyrrolic nitrogen (pyrrolic N), and graphitic nitrogen (graphitic N). The atomic percentages of these three types are 24%, 48%, and 27%, respectively. Figure 9 This is the Ce element peak separation result in the X-ray photoelectron spectrum of the sample in Example 2. Figure 10 This is the peak separation result of Mn element in the X-ray photoelectron spectrum of the sample in Example 2.

[0064] The Ce 3d XPS spectrum and the Mn 2p XPS spectrum of the sample indicate that the atomic percentages of Mn and Ce in the sample obtained in this example are 2.7% and 2.5%, respectively. Furthermore, based on the above spectra, the valence states of each element can be calculated, as shown in the following table:

[0065]

[0066] A fixed bed reactor was used to test the catalytic oxidation efficiency of the sample obtained in step 4) for 250 ppm toluene at 200, 250, 300, and 350° C. in an air atmosphere. The flow rate was 200 ml / min. The catalytic oxidation efficiencies are summarized as follows:

[0067]

[0068] Comparison of Examples:

[0069] The carbon-based catalyst used as a control group was prepared by the following steps:

[0070] 1) Carbon source pretreatment: The selected domestic low- and medium-rank coal blocks were dried, crushed and screened to a suitable particle size with an average particle size of 96 μm;

[0071] 2) One-step mixing of metal salt / carbon source: The carbon source described in step 1 is placed in an aqueous solution containing metal salts manganese chloride and cerium chloride. During the preparation of the above solution, the mass of manganese chloride and cerium chloride is each 5wt% of the mass of the solid carbon source. Subsequently, ultrasonic dispersion is performed while heating in a constant temperature water bath at 60°C to ensure that the solution and carbon source are fully mixed.

[0072] 3) Separation and drying: After the mixture is separated by suction filtration, the obtained solid material is dried in a hot air drying oven at 80°C.

[0073] 4) High-temperature activation treatment: The mixture is placed in an atmosphere tube furnace and activated at 750°C in an activation atmosphere containing 40% high-purity carbon dioxide and 60% high-purity nitrogen. The metal salt and the activation atmosphere work together to achieve catalytic etching, pore formation, and catalytic graphitization of the carbon source.

[0074] 5) Characterization and testing: The physical and chemical properties of the carbon-based catalyst material obtained in step 4 were characterized by low-temperature nitrogen adsorption test, X-ray diffraction test, X-ray electron photon spectroscopy test, etc., and experiments were conducted using a fixed bed reactor to determine the catalytic oxidation efficiency of the sample obtained in step 4) for 250 ppm toluene in an air atmosphere at temperatures of 200, 250, 300 and 350°C.

[0075] Pore ​​structure:

[0076]

[0077] Figure 11 This is the low-temperature nitrogen adsorption test isotherm of the comparative example sample. Figure 12 The X-ray diffraction pattern of the sample in Example 2 shows characteristic peaks of different crystal forms such as MnO2, Mn3O4, and CeO2, proving that the above-mentioned metal oxides are successfully loaded inside the carbon-based catalyst.

[0078] Figure 13 The figure shows the peak separation results of Ce element in X-ray photoelectron spectrum of the comparative example samples. Figure 14The following table shows the peak separation results of the Mn element in the X-ray photoelectron spectrum of the comparative example sample. The data indicate that the atomic percentages of Mn and Ce in the sample obtained in this example are 1.1% and 1.1%, respectively, indicating a lower metal loading capacity than in Examples 1 and 2. Furthermore, based on the above spectrum, the valence states of each element can be calculated, as shown in the following table:

[0079]

[0080]

[0081] A fixed bed reactor was used to test the catalytic oxidation efficiency of the sample obtained in step 4) for 250 ppm toluene at 200, 250, 300, and 350° C. in an air atmosphere. The flow rate was 200 ml / min. The catalytic oxidation efficiencies are summarized as follows:

[0082]

[0083] Its catalytic oxidation efficiency of toluene is lower than that of Example 1.

[0084] Thus far, various embodiments of the present invention have been described in detail. To avoid obscuring the concept of the present invention, some details well known in the art have not been described. Based on the above description, those skilled in the art can fully understand how to implement the technical solutions of the present invention.

[0085] All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. The above drawings and specific embodiments are intended only to illustrate the present invention and are not intended to limit the present invention. Minor changes to the present invention within the spirit and scope of the invention as defined by the claims of the present invention are also within the scope of protection of the present invention.

Claims

1. A method for synthesizing a bifunctional carbon-based catalyst for removing VOCs from flue gas over the entire temperature range, characterized in that: The steps include: Step 1) Carbon source pretreatment: The selected solid carbon source is dried, crushed and sieved to a suitable particle size; the suitable particle size is 20 μm‒2 cm; Step 2) One-step mixing of the metal salt, nitrogen source, and carbon source: The carbon source is placed in an aqueous solution or suspension containing the metal salt and nitrogen source in a certain proportion, and ultrasonic dispersion or mechanical stirring is used, accompanied by heating in a water bath at 60-80°C to ensure that the carbon source, metal salt, and nitrogen source are fully mixed. Step 3) Isolation and Drying: The mixture obtained in step 2) is separated by filtration, and the resulting solid material is hot-air dried, vacuum-dried, or freeze-dried at 80-150°C; Step 4) High-temperature activation treatment: The mixture obtained in step 3) is placed in an atmosphere tube furnace and pre-carbonized in a nitrogen atmosphere or an argon inert atmosphere at a temperature range of 600-800 °C to achieve the fixation of nitrogen elements in the carbon matrix and the melt dispersion of metal salts. Subsequently, the mixture is switched to an activation atmosphere containing a certain proportion of water vapor or carbon dioxide and activated at a temperature range of 700-1000 °C. The metal salt and the activation atmosphere work together to achieve catalytic etching of the carbon source, pore formation, and catalytic graphitization. Step 5) Characterization and Testing: The physical and chemical properties of the carbon-based catalyst material obtained in step 4) are characterized by low-temperature nitrogen adsorption test, X-ray diffraction test, and X-ray photoelectron spectroscopy test methods. Experiments are conducted using a fixed bed reactor to determine the typical VOCs removal efficiency of the sample obtained in step 4) in the temperature range of 180-350 °C for a concentration range of 200-2000 ppm. The selected carbon source is low- and medium-rank coal. The metal salt is a mixture of rare earth metal salts and transition metal salts, the rare earth metal salts include cerium nitrate, cerium chloride, and cerium acetate, and the transition metal salts include manganese nitrate and manganese chloride.

2. The method for synthesizing a bifunctional carbon-based catalyst for removing VOCs from flue gas over the entire temperature range according to claim 1, characterized in that: The nitrogen sources are urea, melamine, ammonium nitrate and ethylenediaminetetraacetic acid.

3. The method for synthesizing a bifunctional carbon-based catalyst for removing VOCs from flue gas over the entire temperature range according to claim 1, characterized in that: The mass ratio of the metal salt to the carbon source is in the range of 0.02:1 to 0.2:1, and the mass ratio of the nitrogen source to the carbon source is in the range of 0.5:1 to 1:

1.

4. The method for synthesizing a bifunctional carbon-based catalyst for removing VOCs from flue gas over the entire temperature range according to claim 1, characterized in that: The activation gas selected during the high-temperature activation treatment is a mixture of an activator and an inert gas, wherein the activator includes water vapor or carbon dioxide, and the inert gas includes argon and helium; the volume fraction ratio of the activator to the inert gas ranges from 0.1:1 to 0.8:

1.

5. The method for synthesizing a bifunctional carbon-based catalyst for removing VOCs from flue gas in the full temperature range according to claim 1, characterized in that: The specific surface area of ​​the obtained carbon-based catalyst was determined by nitrogen adsorption at liquid nitrogen temperature and calculated by BET theory multi-point method, which was located at 250 m 2 / g to 800 m 2 / g range, and the ratio of micropore volume to total pore volume is in the range of 30% to 70%.

6. The method for synthesizing a bifunctional carbon-based catalyst for removing VOCs from flue gas over the entire temperature range according to claim 1, characterized in that: The obtained carbon-based catalyst showed catalytic oxidation effect on typical benzene-based VOCs at 200°C, and the catalytic oxidation effect was very good at a space velocity of 15000 to 25000 h ‒1 The catalytic oxidation efficiency of toluene at 200°C is not less than 50%, and the catalytic oxidation efficiency of toluene at 300°C is not less than 70%.

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