Preparation method of Mn-Fe / activated carbon low-temperature denitration catalyst based on hydrogen modification

Abstract

The invention relates to the technical field of environmental catalytic materials and waste gas treatment, and discloses a preparation method of a Mn-Fe / activated carbon low-temperature denitration catalyst based on hydrogen modification, which comprises the following steps: (1) pretreatment of an activated carbon carrier: granular activated carbon is sequentially subjected to acid pickling treatment, alkali liquor soaking treatment and high-temperature inert gas shielding heat treatment; and (2) loading the active component: dipping the pretreated active carbon carrier in a mixed solution containing a manganese salt and an iron salt, keeping the total concentration of metal ions in the mixed solution at 0.5-2.0 mol / L, keeping the temperature of the solution at 40-60 DEG C in the dipping process, continuously stirring, and dipping for 4-8 hours. The low-temperature denitration activity of the catalyst is remarkably improved through hydrogen modification treatment, the chemical valence state and the surface structure of active components are effectively regulated and controlled in the hydrogen reduction process, the oxidation-reduction capacity of the catalyst is enhanced, and the catalyst can still keep excellent NO conversion efficiency under the low-temperature condition.

Description

TECHNICAL FIELD

[0001] The application relates to the field of environmental catalytic materials and waste gas treatment technology, and particularly relates to a preparation method of a Mn-Fe / activated carbon low-temperature denitration catalyst based on hydrogen modification. BACKGROUND

[0002] With the increasingly stringent environmental protection requirements in China, the emission control of nitrogen oxides (NO x ) in industrial flue gas has become a focus of atmospheric pollution control, and the selective catalytic reduction (SCR) technology is one of the most widely used denitration technologies at present, in which a catalyst is the core of the SCR system.

[0003] Traditional commercial SCR catalysts (such as V2O5-WO3 / TiO2) have excellent denitration performance in the medium-high temperature section (300-400 DEG C), but in the non-electricity industries such as steel, cement and glass, the flue gas temperature is generally low (150-250 DEG C), the activity of the traditional catalysts is significantly reduced, and the traditional catalysts are difficult to be directly applied, in addition, the vanadium-based catalysts have the problems of biological toxicity, easy sintering at high temperature and narrow active window.

[0004] In order to solve the problem of low-temperature denitration, researchers have developed low-temperature SCR catalysts based on transition metals (such as Mn, Fe, Cu and the like), among which the Mn-based catalysts are concerned due to their excellent low-temperature oxidation-reduction performance, and the introduction of Fe can adjust the acid sites and improve the N2 selectivity, and the activated carbon as a carrier has the advantages of large specific surface area, rich pore structure and adjustable surface functional groups.

[0005] However, the existing Mn-Fe / AC catalysts still have problems such as uneven dispersion of active components, insufficient low-temperature activity, poor hydrothermal stability and the like, especially under the conditions of high humidity or SO2-containing complex flue gas, the catalysts are easy to be deactivated, which limits the industrial application of the catalysts. SUMMARY

[0006] The application aims to provide a preparation method of a Mn-Fe / activated carbon low-temperature denitration catalyst based on hydrogen modification, so as to solve the problems in the background art.

[0007] In order to achieve the above-mentioned purpose, the application provides the following technical scheme: a preparation method of a Mn-Fe / activated carbon low-temperature denitration catalyst based on hydrogen modification, comprising the following steps: (1) Pretreatment of the activated carbon carrier: granular activated carbon is sequentially subjected to acid washing treatment, alkali immersion treatment and high-temperature inert gas protection heat treatment; (2) Loading of active components: The pretreated activated carbon carrier is impregnated in a mixed solution containing manganese salt and iron salt. The total concentration of metal ions in the mixed solution is 0.5-2.0 mol / L. During the impregnation process, the solution temperature is kept at 40-60℃ and the mixture is stirred continuously. The impregnation time is 4-8 hours. (3) Hydrogen modification treatment: The catalyst precursor loaded with active components is placed in a tube furnace and reduced in a mixed atmosphere of hydrogen and nitrogen, wherein the hydrogen gas fraction is 10-30%, the heating rate is 2-5℃ / min, and it is kept at 300-500℃ for 2-4 hours, and then cooled to room temperature at a cooling rate of 1-3℃ / min. (4) Post-processing: The catalyst modified by hydrogen is dried under vacuum at a temperature of 80-120°C for 6-12 hours. Then, it is surface stabilized under a carbon dioxide atmosphere at a temperature of 200-300°C for 1-2 hours.

[0008] As a preferred embodiment of the present invention, the pickling treatment involves reflux treatment with a nitric acid solution of concentration ranging from 5-15% at 60-80°C for 2-4 hours, the alkaline soaking treatment involves ultrasonic oscillation treatment with a sodium hydroxide solution of concentration ranging from 3-8% at room temperature for 1-2 hours, and the high-temperature inert gas protection heat treatment involves heating to 600-800°C at a heating rate of 5-10°C / min under an argon atmosphere and holding for 2-3 hours.

[0009] As a preferred embodiment of the present invention, the manganese salt is selected from any one of manganese nitrate, manganese acetate or manganese chloride, and the iron salt is selected from any one of ferric nitrate, ferric sulfate or ferric chloride, and the molar ratio of manganese salt to iron salt is 1:0.5-2.

[0010] As a preferred embodiment of the present invention, the activated carbon carrier in step (1) has a particle size of 0.5-2.0 mm and a specific surface area of ​​800-1200 m². 2 / g, pore volume is 0.4-0.8cm 3 / g, the high-temperature inert gas protected heat treatment process also includes a step of introducing water vapor into the reaction system for surface modification after the heat treatment is completed, wherein the water vapor introduction time is 30-60 minutes and the water vapor flow rate is 0.1-0.5 mL / min.

[0011] As a preferred technical solution of the present invention, the impregnation process in step (2) adopts a step-by-step equal-volume impregnation method. First, the activated carbon carrier is impregnated in a manganese salt solution and stirred at 50-70°C for 2-3 hours. Then, it is impregnated in an iron salt solution and stirred at the same temperature for 2-3 hours. Between the two impregnations, the carrier needs to be dried in an intermediate manner. The drying temperature is 80-100°C and the drying time is 1-2 hours.

[0012] As a preferred technical solution of the present invention, the mixed solution in step (2) further includes an organic complexing agent, which is selected from citric acid, ethylenediaminetetraacetic acid or tartaric acid. The molar ratio of the organic complexing agent to the metal ions is 1:1-2, and the pH value of the solution is controlled to be 4-6 during the impregnation process. Ammonia or dilute nitric acid is used to adjust the pH value.

[0013] As a preferred technical solution of the present invention, the hydrogen modification treatment in step (3) adopts the programmed temperature reduction method, which specifically includes the following stages: first, in a nitrogen atmosphere, the temperature is raised from room temperature to 150-200℃ at a heating rate of 2-3℃ / min and held for 0.5-1 hour; then, in a mixed atmosphere of hydrogen and nitrogen, the temperature is raised to the target temperature at a heating rate of 3-5℃ / min, and the hydrogen concentration is changed every 30 minutes during the holding period of the target temperature, with the hydrogen concentration changing in the range of 10-30%.

[0014] As a preferred technical solution of the present invention, microwave-assisted treatment is also introduced in the hydrogen modification process in step (3). The microwave power is 300-500W, the microwave frequency is 2.45GHz, the intermittent irradiation method is adopted, the irradiation time is 5-10 minutes, the interval time is 10-15 minutes, and the total number of irradiations is 3-6 times.

[0015] As a preferred technical solution of the present invention, the surface stabilization treatment under carbon dioxide atmosphere in step (4) adopts a programmed temperature rise method, specifically including: firstly, raising the temperature from room temperature to 150-200℃ at a heating rate of 2-4℃ / min under carbon dioxide atmosphere and holding it for 0.5-1 hours, then continuing to raise the temperature to the final temperature at a heating rate of 1-2℃ / min, and periodically changing the carbon dioxide gas flow rate during the holding period of the final temperature, with the gas flow rate varying from 50-200mL / min.

[0016] As a preferred technical solution of the present invention, the vacuum drying process in step (4) adopts a multi-stage drying process, specifically including: firstly drying for 2-3 hours under an absolute pressure of 10-20 kPa and a temperature of 80-100℃, then drying for 2-3 hours under an absolute pressure of 5-10 kPa and a temperature of 100-120℃, and finally drying for 2-3 hours under an absolute pressure of 1-5 kPa and a temperature of 60-80℃, with a 30-minute transition period between each stage for slowly adjusting the drying conditions.

[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention significantly improves the low-temperature denitrification activity of the catalyst through hydrogen modification treatment. The hydrogen reduction process effectively regulates the chemical valence state and surface structure of the active components, enhances the redox ability of the catalyst, and enables it to maintain excellent NO conversion efficiency under low-temperature conditions.

[0018] 2. The catalyst exhibits excellent N2 selectivity. By optimizing the impregnation process and introducing organic complexing agents, the occurrence of side reactions is effectively suppressed, the proportion of the target product N2 generated is increased, and the risk of secondary pollution is reduced.

[0019] 3. The pretreatment process of the activated carbon carrier effectively improves the dispersibility and binding strength of the active components. The combination of acid washing, alkali washing and high-temperature treatment not only removes impurities from the carrier surface, but also introduces abundant surface functional groups, providing favorable conditions for the uniform anchoring of the metal active components.

[0020] 4. The multi-stage drying and CO2 stabilization treatment enhances the structural stability and moisture resistance of the catalyst. This post-treatment process effectively protects the pore structure of the catalyst and improves its service life in complex flue gas environments. Attached Figure Description

[0021] Figure 1 This is an overall flow chart of the preparation method of a hydrogen-modified Mn-Fe / activated carbon low-temperature denitrification catalyst according to the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1 Please see Figure 1This invention provides a method for preparing a low-temperature denitrification catalyst based on hydrogen-modified Mn-Fe / activated carbon, comprising the following steps: (1) Pretreatment of activated carbon carrier: The granular activated carbon is subjected to acid washing, alkaline soaking and high-temperature inert gas protection heat treatment in sequence. (2) Loading of active components: The pretreated activated carbon carrier is impregnated in a mixed solution containing manganese salt and iron salt. The total concentration of metal ions in the mixed solution is 0.5-2.0 mol / L. During the impregnation process, the solution temperature is kept at 40-60℃ and the mixture is stirred continuously. The impregnation time is 4-8 hours. (3) Hydrogen modification treatment: The catalyst precursor loaded with active components is placed in a tube furnace and reduced in a mixed atmosphere of hydrogen and nitrogen, wherein the hydrogen gas fraction is 10-30%, the heating rate is 2-5℃ / min, and it is kept at 300-500℃ for 2-4 hours, and then cooled to room temperature at a cooling rate of 1-3℃ / min. (4) Post-processing: The catalyst modified by hydrogen is dried under vacuum at a temperature of 80-120°C for 6-12 hours. Then, it is surface stabilized under a carbon dioxide atmosphere at a temperature of 200-300°C for 1-2 hours.

[0024] Furthermore, the pickling treatment involves reflux treatment with a nitric acid solution of concentration ranging from 5-15% at 60-80℃ for 2-4 hours, the alkaline immersion treatment involves ultrasonic oscillation treatment with a sodium hydroxide solution of concentration ranging from 3-8% at room temperature for 1-2 hours, and the high-temperature inert gas protection heat treatment involves heating to 600-800℃ at a heating rate of 5-10℃ / min under an argon atmosphere and holding for 2-3 hours.

[0025] Furthermore, the manganese salt is selected from any one of manganese nitrate, manganese acetate, or manganese chloride, and the iron salt is selected from any one of ferric nitrate, ferric sulfate, or ferric chloride. The molar ratio of manganese salt to iron salt is 1:0.5-2.

[0026] Furthermore, in step (1), the activated carbon carrier has a particle size of 0.5-2.0 mm and a specific surface area of ​​800-1200 m². 2 / g, pore volume is 0.4-0.8cm 3 / g, the high-temperature inert gas protected heat treatment process also includes a step of introducing water vapor into the reaction system for surface modification after the heat treatment is completed, wherein the water vapor introduction time is 30-60 minutes and the water vapor flow rate is 0.1-0.5 mL / min.

[0027] Furthermore, in step (2), the impregnation process adopts a stepwise equal-volume impregnation method. First, the activated carbon carrier is impregnated in a manganese salt solution and stirred at 50-70°C for 2-3 hours. Then, it is impregnated in an iron salt solution and stirred at the same temperature for another 2-3 hours. Between the two impregnations, the carrier needs to be dried in between. The drying temperature is 80-100°C and the drying time is 1-2 hours.

[0028] Furthermore, the mixed solution in step (2) also contains an organic complexing agent, which is selected from citric acid, ethylenediaminetetraacetic acid or tartaric acid. The molar ratio of the organic complexing agent to the metal ions is 1:1-2, and the pH value of the solution is controlled to be 4-6 during the impregnation process. Ammonia or dilute nitric acid is used to adjust the pH value.

[0029] Furthermore, in step (3), the hydrogen modification treatment adopts the temperature-programmed reduction method, which specifically includes the following stages: first, in a nitrogen atmosphere, the temperature is raised from room temperature to 150-200℃ at a heating rate of 2-3℃ / min and held for 0.5-1 hour; then, in a mixed atmosphere of hydrogen and nitrogen, the temperature is raised to the target temperature at a heating rate of 3-5℃ / min, and the hydrogen concentration is changed every 30 minutes during the holding period of the target temperature, with the hydrogen concentration changing in the range of 10-30%.

[0030] Furthermore, in step (3), microwave-assisted treatment is introduced during the hydrogen modification process. The microwave power is 300-500W, the microwave frequency is 2.45GHz, and an intermittent irradiation method is adopted. The irradiation time is 5-10 minutes, the interval time is 10-15 minutes, and the total number of irradiations is 3-6 times.

[0031] Furthermore, the surface stabilization treatment under carbon dioxide atmosphere in step (4) adopts a programmed temperature rise method, specifically including: first, raising the temperature from room temperature to 150-200℃ at a heating rate of 2-4℃ / min under carbon dioxide atmosphere and holding it for 0.5-1 hours, then continuing to raise the temperature to the final temperature at a heating rate of 1-2℃ / min, and periodically changing the carbon dioxide gas flow rate during the holding period of the final temperature, with the gas flow rate changing in the range of 50-200mL / min.

[0032] Furthermore, in step (4), the vacuum drying process adopts a multi-stage drying process, specifically including: first, drying for 2-3 hours under an absolute pressure of 10-20 kPa and a temperature of 80-100℃; then drying for 2-3 hours under an absolute pressure of 5-10 kPa and a temperature of 100-120℃; and finally drying for 2-3 hours under an absolute pressure of 1-5 kPa and a temperature of 60-80℃. A 30-minute transition period is provided between each stage to slowly adjust the drying conditions.

[0033] Example 2 Implementation location: Taking the flue gas treatment of a coal-fired power plant in an industrial zone in North China as an example, the denitrification performance of the catalyst of this invention at low temperature (150℃) was verified.

[0034] Preparation steps: 1. Pretreatment of activated carbon carrier: Pickling: 10% nitric acid, reflux at 70°C for 3 hours; Alkali washing: 5% NaOH, sonicated at room temperature for 1.5 hours; High-temperature treatment: under argon protection, the temperature is increased to 700℃ at 8℃ / min and held for 2.5 hours. After the treatment, water vapor is introduced (0.3mL / min, 40 minutes).

[0035] 2. Active component loading The stepwise equal-volume impregnation method was adopted, first impregnating with manganese nitrate solution (70℃, 2.5 hours), drying in between (90℃, 1.5 hours), and then impregnating with ferric nitrate solution (70℃, 2.5 hours). Total metal concentration: 1.2 mol / L, Mn:Fe = 1:1; Citric acid was added as a complexing agent at a molar ratio of 1:1.5 with the metal ions, and the pH was controlled at 5.

[0036] 3. Hydrogen modification treatment: Programmed temperature reduction: Heat to 180℃ in N2 (2.5℃ / min) and hold for 0.8 hours; Switch to an H2 / N2 mixture (H2 20%), raise the temperature to 400℃ at 4℃ / min, hold for 3 hours, and adjust the H2 concentration (15%~25%) every 30 minutes. Microwave assistance was introduced: power 400W, irradiation for 8 minutes / time, 12 minutes interval, for a total of 4 times.

[0037] Post-processing: Vacuum multi-stage drying: First stage: 15 kPa, 90℃, 2.5 hours; Second stage: 8 kPa, 110℃, 2.5 hours; Third stage: 3 kPa, 70℃, 2.5 hours.

[0038] CO2 stabilization: The temperature was increased to 180℃ at 3℃ / min and held for 0.8 hours, then increased to 250℃ at 1.5℃ / min and held for 1.5 hours. The CO2 flow rate was periodically varied (80-150 mL / min).

[0039] Example 3 Implementation location: Taking the treatment of nitric acid tail gas in a chemical plant in Southwest China as an example, the stability of the catalyst under low temperature and high humidity conditions was verified.

[0040] Preparation steps: 1. Pretreatment of activated carbon carrier: Pickling: 12% nitric acid, reflux at 75°C for 2.5 hours; Alkali washing: 6% NaOH, sonicated at room temperature for 1 hour; High-temperature treatment: under argon protection, the temperature is increased to 750℃ at 7℃ / min and held for 2 hours, with water vapor passed through (0.2mL / min, 50 minutes).

[0041] 2. Active component loading: One-step impregnation method: Mn:Fe = 1:1.5, total concentration 1.5 mol / L; Add EDTA as a complexing agent at a molar ratio of 1:2 with metal ions, and control the pH at 5.5. The immersion temperature is 50℃ and the time is 6 hours.

[0042] 3. Hydrogen modification treatment: Programmed temperature reduction: Heat to 160℃ in N2 (2℃ / min) and hold for 1 hour; The H2 / N2 mixture (H2 25%) was heated to 450℃ at a rate of 3℃ / min and held for 2.5 hours. The H2 concentration varied between 20% and 30% every 30 minutes. No microwave assistance.

[0043] 4. Post-processing: Vacuum drying: 100℃, 10 hours; CO2 stabilization: Increase to 200℃ at 2℃ / min, hold for 1 hour, and keep the CO2 flow rate constant at 100mL / min.

[0044] Comparative Example 1 (without hydrogen modification) Preparation steps: It is basically the same as Example 1, but step (3) hydrogen modification treatment is omitted. After loading the active component, it is directly vacuum dried and CO2 stabilized.

[0045] Comparative Example 2 (without activated carbon pretreatment) Preparation steps: It is basically the same as Example 1, but step (1) activated carbon pretreatment is omitted, and the original activated carbon is used directly for loading.

[0046] Experimental data and performance testing Test conditions: Reaction temperature: 150℃; Airspeed: 20000h -1 ; Simulated flue gas composition: NO 500ppm, NH3 550ppm, O2 5%, H2O 10%, N2 balance; Test duration: 6 hours.

[0047] Experimental results table:

[0048] Experimental Data Analysis Explanation 1. The key role of hydrogen modification A comparison of Comparative Example 1 and Examples 1-3 shows that hydrogen modification significantly improves the denitrification performance of the catalyst. The NO conversion rate of Comparative Example 1 (without hydrogen modification) was only 78.6%, while that of Examples 1-3 all exceeded 93%. Hydrogen reduction treatment can partially reduce the oxides of Mn and Fe to lower valence states (such as Mn). 3+ Fe 2+ These low-valence metal ions have higher redox capabilities and more surface oxygen vacancies, which are beneficial to the NH3-SCR reaction. In addition, hydrogen reduction can remove some surface impurities, enhance the dispersibility of active components, and improve the low-temperature activity of the catalyst.

[0049] 2. The Importance of Activated Carbon Pretreatment The performance of Control Example 2 (without pretreatment) was significantly worse, with a NO conversion rate of only 65.4%, and a specific surface area and pore volume that were also significantly lower than those of other examples. Acid washing, alkali washing and high-temperature treatment of activated carbon can effectively remove ash, open pores and increase surface functional groups, providing more anchoring points for the uniform loading of metal active components. Water vapor modification further enhances the hydrophilicity and pore size distribution of the surface, which is beneficial to the diffusion and adsorption of reactant molecules.

[0050] 3. The role of step-by-step impregnation and complexing agents Example 2 uses stepwise impregnation with the addition of citric acid as a complexing agent, which results in the highest NO conversion rate and N2 selectivity (96.8% and 94.1%, respectively). Stepwise impregnation can avoid competitive adsorption of Mn and Fe ions during the loading process and improve the dispersion. The complexing agent, by coordinating with metal ions, prevents them from precipitating prematurely during the impregnation process and promotes the uniform distribution of active components on the carrier surface.

[0051] 4. Synergistic effect of microwave-assisted and programmed temperature reduction In Example 2, microwave-assisted treatment was introduced, which has a better specific surface area and pore volume than other examples. Microwaves can quickly and uniformly heat the catalyst bulk phase, promote the reduction and dispersion of metal particles, and avoid the local overheating problem that may occur in traditional heating. The programmed temperature rise reduction combined with the periodic change of hydrogen concentration further optimizes the kinetic conditions of the reduction process and enhances the reduction uniformity of the catalyst.

[0052] 5. Stability assurance through CO2 stabilization and multi-stage drying Example 2 employed multi-stage vacuum drying and CO2 programmed temperature stabilization. The catalyst exhibited stable performance during a 6-hour test, showing no significant performance degradation. Multi-stage drying prevents the collapse of the catalyst's pore structure during rapid dehydration; CO2 stabilization forms stable carbonate or carboxyl functional groups on the surface, enhancing the catalyst's structural stability in humid environments.

[0053] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a low-temperature denitrification catalyst based on hydrogen-modified Mn-Fe / activated carbon, characterized in that, Includes the following steps: (1) Pretreatment of activated carbon carrier: The granular activated carbon is subjected to acid washing, alkaline soaking and high-temperature inert gas protection heat treatment in sequence. (2) Loading of active components: The pretreated activated carbon carrier is impregnated in a mixed solution containing manganese salt and iron salt. The total concentration of metal ions in the mixed solution is 0.5-2.0 mol / L. During the impregnation process, the solution temperature is kept at 40-60℃ and the mixture is stirred continuously. The impregnation time is 4-8 hours. (3) Hydrogen modification treatment: The catalyst precursor loaded with active components is placed in a tube furnace and reduced in a mixed atmosphere of hydrogen and nitrogen, wherein the hydrogen gas fraction is 10-30%, the heating rate is 2-5℃ / min, and it is kept at 300-500℃ for 2-4 hours, and then cooled to room temperature at a cooling rate of 1-3℃ / min. (4) Post-processing: The catalyst modified by hydrogen is dried under vacuum at a temperature of 80-120°C for 6-12 hours. Then, it is surface stabilized under a carbon dioxide atmosphere at a temperature of 200-300°C for 1-2 hours.

2. The preparation method of a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, The pickling treatment involves reflux treatment with a nitric acid solution of concentration ranging from 5-15% at 60-80°C for 2-4 hours. The alkaline immersion treatment involves ultrasonic oscillation treatment with a sodium hydroxide solution of concentration ranging from 3-8% at room temperature for 1-2 hours. The high-temperature inert gas protection heat treatment involves heating to 600-800°C at a heating rate of 5-10°C / min under an argon atmosphere and holding for 2-3 hours.

3. The preparation method of a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, The manganese salt is selected from any one of manganese nitrate, manganese acetate, or manganese chloride, and the iron salt is selected from any one of ferric nitrate, ferric sulfate, or ferric chloride. The molar ratio of manganese salt to iron salt is 1:0.5-2.

4. The preparation method of a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, In step (1), the activated carbon carrier has a particle size of 0.5-2.0 mm and a specific surface area of ​​800-1200 m². 2 / g, pore volume is 0.4-0.8cm 3 / g, the high-temperature inert gas protected heat treatment process also includes a step of introducing water vapor into the reaction system for surface modification after the heat treatment is completed, wherein the water vapor introduction time is 30-60 minutes and the water vapor flow rate is 0.1-0.5 mL / min.

5. The method for preparing a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, The impregnation process in step (2) adopts a step-by-step equal-volume impregnation method. First, the activated carbon carrier is impregnated in a manganese salt solution and stirred at 50-70℃ for 2-3 hours. Then, it is impregnated in an iron salt solution and stirred at the same temperature for another 2-3 hours. Between the two impregnations, the carrier needs to be dried in an intermediate manner at a temperature of 80-100℃ for 1-2 hours.

6. The method for preparing a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, The mixed solution in step (2) also contains an organic complexing agent, which is selected from citric acid, ethylenediaminetetraacetic acid or tartaric acid. The molar ratio of the organic complexing agent to the metal ions is 1:1-2, and the pH value of the solution is controlled to be 4-6 during the impregnation process. Ammonia or dilute nitric acid is used to adjust the pH value.

7. The method for preparing a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, In step (3), the hydrogen modification treatment adopts a programmed temperature reduction method, specifically... The process includes the following stages: First, the temperature is increased from room temperature to 150-200℃ at a rate of 2-3℃ / min under a nitrogen atmosphere and held for 0.5-1 hour. Then, the temperature is increased to the target temperature at a rate of 3-5℃ / min under a mixed atmosphere of hydrogen and nitrogen. During the holding period at the target temperature, the hydrogen concentration is changed every 30 minutes, with the hydrogen concentration varying from 10-30%.

8. The method for preparing a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, In step (3), microwave-assisted treatment is also introduced during the hydrogen modification process. The microwave power is 300-500W, the microwave frequency is 2.45GHz, and an intermittent irradiation method is adopted. The irradiation time is 5-10 minutes, the interval time is 10-15 minutes, and the total number of irradiations is 3-6 times.

9. The method for preparing a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, The surface stabilization treatment in step (4) under carbon dioxide atmosphere adopts a programmed temperature rise method, which specifically includes: first, raising the temperature from room temperature to 150-200℃ at a heating rate of 2-4℃ / min under carbon dioxide atmosphere and holding it for 0.5-1 hour, then continuing to raise the temperature to the final temperature at a heating rate of 1-2℃ / min, and periodically changing the carbon dioxide gas flow rate during the holding period of the final temperature, with the gas flow rate varying from 50-200mL / min.

10. The method for preparing a hydrogen-modified Mn-Fe / activated carbon low-temperature denitration catalyst according to claim 1, characterized in that, The vacuum drying process in step (4) adopts a multi-stage drying process, which includes: first drying for 2-3 hours under an absolute pressure of 10-20 kPa and a temperature of 80-100℃, then drying for 2-3 hours under an absolute pressure of 5-10 kPa and a temperature of 100-120℃, and finally drying for 2-3 hours under an absolute pressure of 1-5 kPa and a temperature of 60-80℃. A 30-minute transition period is provided between each stage to slowly adjust the drying conditions.

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