Manganese-based composite bimetallic catalyst for collaborative desulfurization and denitrification of cremation flue gas and preparation method of manganese-based composite bimetallic catalyst

Abstract

The invention relates to a manganese-based composite bimetallic catalyst for collaborative desulfurization and denitrification of cremation flue gas and a preparation method of the manganese-based composite bimetallic catalyst, and relates to the technical field of cremation flue gas purification. The Mn-Cu / Al2O3 catalyst is obtained by selecting an Al2O3 ceramic membrane as a carrier and loading manganese and copper, the NOx removal rate of the manganese-based composite bimetallic catalyst prepared by the method reaches 72.47% at 200 DEG C, the CO conversion rate exceeds 70%, the manganese-based composite bimetallic catalyst has a remarkable removal effect on SOs in the temperature range of 50-400 DEG C, the removal rate is increased along with temperature rise, the removal rate can reach 30%-70% in the medium and low temperature range (50-250 DEG C), and the removal rate can reach 30%-70% in the medium and low temperature range (50-250 DEG C). The desulfurization function can be stably exerted under the input of different SOconcentrations, the reduction characteristic of inherent CO in flue gas is utilized, under the condition that an ammonia source is not additionally added, SO2 and NOx can be synergistically catalyzed and removed, and the emission level of CO is synchronously reduced.

Description

Technical Field

[0001] This invention relates to the field of flue gas purification technology, and in particular to a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of flue gas in cremation and its preparation method. Background Technology

[0002] Air pollutants generated during cremation are one of the main sources of pollution in the funeral industry. The harmful air pollutants emitted mainly include particulate matter (TSP, PM2.5). 10 PM 2.5 Conventional gaseous pollutants include SO2, NOx, CO, NH3, and HCl; persistent organic pollutants (dioxins), heavy metals, and VOCs. Literature indicates that existing purification processes (such as bag filters and acid removal spraying) are less effective against particulate matter (PM2.5). 2.5 The removal rate of SO2 (97%) and some gaseous pollutants (SO2 removal rate of 38.22%-84.7%) were well controlled, but the overall treatment still faces multiple challenges.

[0003] Existing flue gas purification devices are effective in removing particulate matter and can achieve stable emissions that meet standards. While the desulfurization process and activated carbon adsorption have a certain neutralization and removal effect on SO2, fluctuations in emission concentrations and occasional exceedances still exist. In most actual operating conditions, cremation flue gas purification systems rarely have dedicated NOx control units, leading to significant emission exceedances. It is worth noting that the low-temperature catalytic denitrification technology introduced by a funeral home in Zhejiang Province achieved an average emission reduction efficiency of 64.39%, significantly better than conventional, untargeted emission control methods, indicating that catalytic methods have good technical feasibility in NOx treatment. Furthermore, incomplete combustion during cremation produces a large amount of CO, especially in the early stages when the furnace temperature is low, resulting in a significant increase in CO emission concentration. Currently, CO removal mainly relies on high-temperature combustion in the cremator's recombustion chamber and sufficient flue gas residence time; existing flue gas purification systems generally lack the ability to directly remove it. Summary of the Invention

[0004] The purpose of this invention is to address the above-mentioned problems by providing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas and its preparation method. This catalyst can utilize the inherent reduction characteristics of CO in flue gas to achieve synergistic catalytic removal of SO2 and NOx without the addition of an external ammonia source, and simultaneously reduce CO emission levels.

[0005] The first aspect of this invention provides a method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas, employing the following technical solution:

[0006] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas includes the following steps:

[0007] S1. Carrier pretreatment: Select Al2O3 ceramic membranes, clean them, and dry them for later use;

[0008] S2. Preparation of impregnation solution: Mix manganese nitrate solution and copper nitrate trihydrate solution, then add citric acid and mix to promote metal ion complexation. Continue stirring at pH 6.8±0.2 to obtain the impregnation solution.

[0009] S3, Vacuum Impregnation: The carrier pretreated in S1 is placed in the impregnation solution obtained in S2 and impregnated under vacuum for 1.5 hours. After impregnation, the membrane is taken out and air-dried horizontally, and then placed in an oven to dry. The impregnation is repeated 2 to 3 times.

[0010] S4. Calcination: The Al2O3 ceramic film loaded with active components obtained in S3 is transferred to a tube furnace and calcined in an air atmosphere. After calcination, the product is naturally cooled, and after cooling, a manganese-based composite bimetallic catalyst for co-desulfurization and denitrification of combustion flue gas is obtained.

[0011] By adopting the above technical solution, the pore structure, surface acidity, and interaction with the metal active components of the Al2O3 ceramic film are more conducive to NO... x The adsorption and activation of CO are observed. The outer electrons of metal ions in transition metal oxides are unstable and easily gain or lose electrons. The change in the chemical bonding environment after Cu and Mn form a composite oxide leads to a shift and enhancement of characteristic peaks, directly reflecting the strong interaction of Mn-O-Cu bonds in the CuMn2O4 composite oxide. This synergistic chemical bond provides an efficient electron transfer pathway for the adsorption and activation of NO and the oxidation of CO. CO, as a reducing agent, reduces NOx to harmless N2 under the action of a catalyst, as in the reaction 2CO + 2NO → 2CO2 + N2. This not only improves denitrification efficiency but also reduces secondary CO pollution. In catalytic desulfurization, CO has a relatively weak effect, but SO2 generation can be indirectly reduced by optimizing combustion. By utilizing the inherent reducing properties of CO in flue gas, SO2 and NOx can be synergistically removed without the addition of an external ammonia source, while simultaneously reducing CO emission levels.

[0012] Preferably, in S1, the pore size of the Al2O3 ceramic membrane is 2-70 μm, and more preferably 50 μm.

[0013] Preferably, in the above preparation method, step S2 specifically includes: S2, preparation of impregnation solution: manganese nitrate solution and copper nitrate trihydrate solution are mixed with a certain amount of deionized water and magnetically stirred for 15 minutes to completely dissolve them. Citric acid is then added and magnetically stirred for 30 minutes to promote metal ion complexation. Diluted ammonia water is added dropwise to control the pH of the solution to be stable at 6.8±0.2. Magnetic stirring is continued for 12 hours under the condition of pH 6.8±0.2 to obtain the impregnation solution.

[0014] Preferably, the concentration of the manganese nitrate solution is 0.007–0.07 mol / L, more preferably 0.035 mol / L, and the concentration of the copper nitrate trihydrate solution is 0.003–0.03 mol / L, more preferably 0.015 mol / L.

[0015] Preferably, the total concentration of the manganese nitrate solution and the copper nitrate trihydrate solution is 0.01-0.1 mol / L, more preferably 0.05 mol / L, and the concentration of the citric acid is 0.005-0.05 mol / L, more preferably 0.025 mol / L.

[0016] Preferably, the molar ratio of manganese to copper in the impregnation solution is 7:3.

[0017] Preferably, in step S3, the conditions for a single vacuum impregnation are: vacuum degree (-0.08 MPa) and impregnation time of 1.5 hours.

[0018] Preferably, in step S4, the calcination temperature is 350–450°C, more preferably 450°C, and the calcination time is 4 hours.

[0019] By adopting the above technical solution, the performance of the catalyst can be synergistically regulated by multiple dimensions such as the type of support, the metal concentration in the impregnation solution, the membrane pore size and the calcination temperature. By optimizing the steps and parameters of the preparation method, a manganese-based composite bimetallic catalyst with better performance for co-desulfurization and denitrification of combustion flue gas can be obtained.

[0020] A second aspect of the present invention provides a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas, which is prepared by any of the preparation methods described above.

[0021] The third aspect of the present invention provides the application of the above-mentioned manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas in the field, wherein the optimal operating conditions of the manganese-based composite bimetallic catalyst are: a CO to NO concentration ratio of 3 and an O2 concentration of 3% at medium and low temperature (50 to 250°C).

[0022] In summary, this application includes at least one of the following beneficial technical effects:

[0023] 1. The pore structure, surface acidity, and interaction with the active metal components of the Al2O3 ceramic membrane are more conducive to NO... x The adsorption and activation of CO are observed. The outer electrons of metal ions in transition metal oxides are unstable and easily gain or lose electrons. The change in the chemical bonding environment after Cu and Mn form a composite oxide leads to a shift and enhancement of characteristic peaks, directly reflecting the strong interaction of Mn-O-Cu bonds in the CuMn2O4 composite oxide. This synergistic chemical bond provides an efficient electron transfer pathway for the adsorption and activation of NO and the oxidation of CO. CO, as a reducing agent, reduces NOx to harmless N2 under the action of a catalyst, as in the reaction 2CO + 2NO → 2CO2 + N2. This not only improves denitrification efficiency but also reduces secondary CO pollution. In catalytic desulfurization, CO has a relatively weak effect, but SO2 generation can be indirectly reduced by optimizing combustion. By utilizing the inherent reducing properties of CO in flue gas, SO2 and NOx can be synergistically removed without the addition of an external ammonia source, while simultaneously reducing CO emission levels.

[0024] 2. The manganese-based composite bimetallic catalyst prepared by this method exhibits NO content at 200℃. x The removal rate reaches 72.47%, the CO conversion rate exceeds 70%, and it has a significant removal effect on SO2 in the temperature range of 50-400℃. The removal rate increases with the increase of temperature. In the medium and low temperature range (50~250℃), the removal rate can reach 30%~70%. It can stably perform desulfurization function under different SO2 concentration inputs.

[0025] 3. The manganese-based composite bimetallic catalyst prepared by this method exhibits NO reduction under SO2-free conditions in the medium-low temperature range (50–200℃). x The removal rate remained stable at 55%–75%; although the denitrification activity was inhibited by SO2, it was not deactivated, and the denitrification rate was still around 50% at 50 ppm SO2 + 250℃, demonstrating good sulfur resistance stability.

[0026] 4. The manganese-based composite bimetallic catalyst prepared by this method has good adaptability to operating conditions. Under suitable operating conditions of CO / NO ratio of 3 and O2 concentration of 3%, the simultaneous treatment efficiency is optimal. Even when faced with complex situations such as fluctuations in CO / NO ratio and changes in O2 concentration in flue gas, it can still maintain stable synergistic removal performance, which is fully adaptable to the actual scenario of dynamic changes in combustion flue gas concentration. Thus, it provides feasible support for the synergistic control of multiple pollutants in complex sulfur-containing flue gas environments. Attached Figure Description

[0027] Figure 1 This is the gas purification performance testing device used in this application, wherein Figure 1 a is a schematic diagram of the overall structure. Figure 1 b is a schematic diagram of the stainless steel membrane reactor structure;

[0028] Figure 2 This is a comparison chart of the catalytic efficiency of the catalyst prepared in this application at different flue gas residence times, where, Figure 2 a is NO X A comparison chart of removal rates. Figure 2 b is a comparison chart of CO conversion rates;

[0029] Figure 3 This is a comparison chart of the catalytic efficiency of the catalyst prepared in this application at different CO / NO concentration ratios, where, Figure 3 a is NO X Removal rate comparison chart Figure 3 b is a comparison chart of CO conversion rates;

[0030] Figure 4 This is a comparison chart of the catalytic efficiency of the catalyst prepared in this application at different O2 concentration ratios, where, Figure 4 a is NO X Removal rate comparison chart Figure 4 b is a comparison chart of CO conversion rates;

[0031] Figure 5 This is a comparison chart of the catalytic efficiency of the catalyst prepared in this application at different SO2 concentration ratios, where, Figure 5 a is NO X Removal rate comparison chart Figure 5 b is a comparison chart of CO conversion rates. Figure 5 c is a comparison chart of SO2 removal rates;

[0032] Figure 6 These are scanning electron microscope (SEM) images of the catalysts prepared in Examples 1 and 7-8 of this application, wherein... Figure 6 a is a SEM image of the catalyst from Example 7. Figure 6 b is a SEM image of the catalyst from Example 1. Figure 6 c is a SEM image of the catalyst in Example 8;

[0033] Figure 7 These are scanning electron microscope (SEM) images of the catalysts used in Examples 1 and 4-6 of this application, wherein... Figure 7 a is a SEM image of the catalyst in Example 4. Figure 7 b is a SEM image of the catalyst in Example 5. Figure 7 c is an SEM image of the catalyst from Example 1. Figure 7 d is a SEM image of the catalyst in Example 6;

[0034] Figure 8 These are the XRD patterns of the catalysts in Examples 1-3 of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Modifications or equivalent substitutions made by those skilled in the art based on their understanding of the technical solutions of this invention, without departing from the spirit and scope of the invention, should be covered within the protection scope of this invention.

[0036] Information on the reagents, instruments, and equipment used in the following examples is shown in Tables 1.1 and 1.2. All reagents and chemicals were used as is without further processing. Other specific conditions not specified were performed according to conventional conditions or the manufacturer's recommendations. Reagents or instruments whose manufacturers are not specified are all commercially available products. Unless otherwise specified, all chemical abbreviations mentioned in the examples and comparative examples of this application are based on common industry knowledge.

[0037] Table 1.1 Information on Reagents Used

[0038]

[0039] Table 1.2 Information on Instruments and Equipment Used

[0040]

[0041] The manganese-based composite bimetallic catalysts for synergistic desulfurization and denitrification of combustion flue gas prepared in all embodiments of this application are collectively referred to as Mn-Cu / Al2O3 catalysts.

[0042] I. Implementation Examples

[0043] Example 1

[0044] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas includes the following steps:

[0045] S1. Carrier pretreatment: Select Al2O3 ceramic membranes, clean them, and dry them for later use.

[0046] Specifically, an Al2O3 ceramic membrane with a pore size of 50 μm was selected, ultrasonically cleaned with deionized water for 30 min to remove surface impurities, and then dried in an oven at 120℃ for 2 h for later use.

[0047] S2. Preparation of impregnation solution: Mix manganese nitrate solution and copper nitrate trihydrate solution, then add citric acid and mix to promote metal ion complexation. Continue stirring at pH 6.8±0.2 to obtain the impregnation solution.

[0048] Specifically, a manganese nitrate solution with a concentration of 0.035 mol / L and a copper nitrate trihydrate solution with a concentration of 0.015 mol / L were prepared. The manganese nitrate solution and the copper nitrate solution were mixed in a 7:3 ratio, at which point the total concentration of the manganese nitrate solution and the copper nitrate trihydrate solution in the solution was 0.05 mol / L. A certain amount of deionized water was added (to a final volume of 100 mL), and the mixture was magnetically stirred for 15 min to ensure complete dissolution. Citric acid was then added, and the concentration of citric acid in the mixture was 0.025 mol / L. After adding citric acid, the mixture was magnetically stirred for 30 min to promote the complexation of metal ions. After stirring, the pH was measured, and diluted ammonia water was added dropwise as needed to control the pH of the impregnation solution to be stable at 6.8 ± 0.2. Under these conditions, magnetic stirring was continued for 12 h to obtain the impregnation solution for later use.

[0049] S3. Vacuum impregnation: Place the carrier pretreated in S1 into the impregnation solution obtained in S2 and impregnate it under vacuum for 1.5 hours. After impregnation, take out the membrane and air dry it horizontally, then place it in an oven to dry. Repeat the impregnation 2-3 times.

[0050] Specifically, the Al2O3 ceramic membrane obtained in S1 is placed in the impregnation solution prepared in S2 and impregnated for 1.5 hours under a vacuum of -0.08 MPa to allow the active components to be fully adsorbed onto the membrane pores and surface. After impregnation, the membrane is removed and air-dried horizontally for 0.5 hours, and then placed in an oven at 120°C for 3 hours. This process is repeated twice to obtain an Al2O3 ceramic membrane loaded with active components.

[0051] S4. Calcination: The Al2O3 ceramic film loaded with active components obtained in S3 is transferred to a tube furnace and calcined in an air atmosphere. After calcination, the product is naturally cooled, and after cooling, a manganese-based composite bimetallic catalyst for co-desulfurization and denitrification of combustion flue gas is obtained.

[0052] Specifically, the Al2O3 ceramic film loaded with active components obtained in S3 is transferred into a crucible, and the crucible is placed in a tube furnace and calcined at 450°C for 4 hours in an air atmosphere to decompose, fix and form a catalytic active phase. After calcination, the product is naturally cooled to obtain a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas.

[0053] The manganese-based composite bimetallic catalyst prepared in this embodiment for synergistic desulfurization and denitrification of combustion flue gas can participate in the catalytic reaction by being placed directly in the reactor during combustion flue gas purification.

[0054] Example 2

[0055] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas is different from that in Example 1, the calcination temperature in S4 is 350℃, while the remaining steps are the same as in Example 1. The manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas prepared in this example can be directly placed in the reactor to participate in the catalytic reaction during combustion flue gas purification.

[0056] Example 3

[0057] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas is different from that in Example 1, the calcination temperature in S4 is 400℃, while the remaining steps are the same as in Example 1. The manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas prepared in this example can be directly placed in the reactor to participate in the catalytic reaction during combustion flue gas purification.

[0058] Example 4

[0059] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas differs from Example 1 in that the pore size of the Al2O3 ceramic membrane in S1 is 2 μm and the calcination temperature in S4 is 400℃.

[0060] The manganese-based composite bimetallic catalyst prepared in this embodiment for synergistic desulfurization and denitrification of combustion flue gas can participate in the catalytic reaction by being placed directly in the reactor during combustion flue gas purification.

[0061] Example 5

[0062] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas differs from Example 1 in that the pore size of the Al2O3 ceramic membrane in S1 is 30 μm and the calcination temperature in S4 is 400 °C.

[0063] The manganese-based composite bimetallic catalyst prepared in this embodiment for synergistic desulfurization and denitrification of combustion flue gas can participate in the catalytic reaction by being placed directly in the reactor during combustion flue gas purification.

[0064] Example 6

[0065] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas differs from Example 1 in that the pore size of the Al2O3 ceramic membrane in S1 is 70 μm and the calcination temperature in S4 is 400 °C.

[0066] The manganese-based composite bimetallic catalyst prepared in this embodiment for synergistic desulfurization and denitrification of combustion flue gas can participate in the catalytic reaction by being placed directly in the reactor during combustion flue gas purification.

[0067] Example 7

[0068] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas, differing from Example 1 in that the pore size of the Al2O3 ceramic membrane in S1 is 2 μm.

[0069] The preparation method of the impregnation solution in S2 is as follows: Prepare a manganese nitrate solution with a concentration of 0.007 mol / L and a copper nitrate trihydrate solution with a concentration of 0.003 mol / L. Mix the manganese nitrate solution and the copper nitrate solution in a ratio of 7:3. At this time, the total concentration of the manganese nitrate solution and the copper nitrate trihydrate solution in the solution is 0.01 mol / L. Add a certain amount of deionized water (make up to 100 mL with water) and stir magnetically for 15 min to completely dissolve it. Then add citric acid. The concentration of citric acid in the mixture is 0.005 mol / L. After adding, stir magnetically for 30 min to promote the complexation of metal ions. After stirring, measure the pH. Add diluted ammonia water dropwise as needed to control the pH of the impregnation solution to be stable at 6.8 ± 0.2. Under this condition, continue to stir magnetically for 12 h to obtain the impregnation solution for later use.

[0070] S3 is the same as in Example 1, and the calcination temperature in S4 is 400°C.

[0071] The manganese-based composite bimetallic catalyst prepared in this embodiment for synergistic desulfurization and denitrification of combustion flue gas can participate in the catalytic reaction by being placed directly in the reactor during combustion flue gas purification.

[0072] Example 8

[0073] A method for preparing a manganese-based composite bimetallic catalyst for synergistic desulfurization and denitrification of combustion flue gas, differing from Example 1 in that the pore size of the Al2O3 ceramic membrane in S1 is 2 μm.

[0074] The preparation method of the impregnation solution in S2 is as follows: Prepare a manganese nitrate solution with a concentration of 0.07 mol / L and a copper nitrate trihydrate solution with a concentration of 0.03 mol / L. Mix the manganese nitrate solution and the copper nitrate solution in a ratio of 7:3. At this time, the total concentration of the manganese nitrate solution and the copper nitrate trihydrate solution in the solution is 0.1 mol / L. Add a certain amount of deionized water (make up to 100 mL with water) and stir magnetically for 15 min to completely dissolve it. Then add citric acid. The concentration of citric acid in the mixture is 0.05 mol / L. After adding, stir magnetically for 30 min to promote the complexation of metal ions. After stirring, measure the pH. Add diluted ammonia water dropwise as needed to control the pH of the impregnation solution to be stable at 6.8±0.2. Under this condition, continue to stir magnetically for 12 h to obtain the impregnation solution for later use.

[0075] S3 is the same as in Example 1, and the calcination temperature in S4 is 400°C.

[0076] The manganese-based composite bimetallic catalyst prepared in this embodiment for synergistic desulfurization and denitrification of combustion flue gas can participate in the catalytic reaction by being placed directly in the reactor during combustion flue gas purification.

[0077] II. Comparative Example

[0078] Comparative Example 1

[0079] The preparation method of Mn-M / TiO2 catalyst includes the following steps: First, the TiO2 support is pretreated by drying it in an oven at 100℃ for 2 hours to remove moisture. Next, the impregnation solution is prepared by accurately weighing the required amounts of manganese nitrate solution, metal nitrate, and titanium dioxide (TiO2) support. In this comparative example, Co is used as the metal M. The total mass of the prepared Mn-Co / TiO2 catalyst is 5g, and the total mass fraction of the active metal element is 10% (i.e., m). Mn +m M =10%m 总 The molar ratio of Mn to Co metal elements was 7:3. A 100mL beaker was then used as the reaction vessel. The weighed metal nitrate was first added to the beaker and mixed thoroughly. Then, 25mL of deionized water was added, and finally, TiO2 support (m...) was added. TiO2 =90%m 总 Continue stirring to fully disperse and dissolve the solid.

[0080] The above mixture was placed in an ultrasonic device and ultrasonically treated at 30°C for 30 min. After ultrasonic treatment, the beaker was transferred to an 80°C constant temperature water bath and heated for about 2.5 h until the water was completely evaporated to obtain a solid product. The solid product was placed in an oven and dried at 100°C for 12 h. The dried catalyst was ground and transferred to a crucible, placed in a tube furnace, and calcined at 500°C for 4 h in an air atmosphere. After calcination, the product was ground again and sieved through a 60-80 mesh standard sieve to finally obtain the metal-based / TiO2 catalyst.

[0081] The catalyst prepared in this comparative example is denoted as Mn-Co / TiO2.

[0082] Comparative Example 2

[0083] The preparation method of the Mn-M / TiO2 catalyst differs from that of Comparative Example 1 in that the metal M used in this comparative example is Fe, and the catalyst prepared in this comparative example is denoted as Mn-Fe / TiO2.

[0084] Comparative Example 3

[0085] The preparation method of the Mn-M / TiO2 catalyst differs from that of Comparative Example 1 in that the metal M used in this comparative example is Cu, and the catalyst prepared in this comparative example is denoted as Mn-Cu / TiO2.

[0086] Comparative Example 4

[0087] The commercially available powdered Fe-Beta catalyst was purchased from Raodong Molecular Sieves Enterprise Store.

[0088] Comparative Example 5

[0089] The commercially available Cu-ZSM-5 molecular sieve catalyst was purchased from Raodong Molecular Sieves Enterprise Store.

[0090] III. Performance Test Experiments and Results

[0091] 1. Gas purification performance test

[0092] 1.1 Test Apparatus and Methods

[0093] Gas purification performance testing device such as Figure 1 As shown in Figure a, the system mainly consists of three parts: The first part is the gas distribution system, which, taking into account the composition of the combustion flue gas and the test conditions, is equipped with five gas cylinders to adjust the concentration of various gases online to prepare the simulated flue gas. The gas composition and specifications of each gas cylinder are shown in Table 2. The second part is the simulated flue gas preheating and catalytic reaction system, which is mainly used for preheating the simulated flue gas and carrying out desulfurization and denitrification reactions, including mixers, tubular furnaces, and reactors. The third part is the flue gas testing system, which uses a Testo 350 flue gas analyzer to test the content of simulated flue gas before and after the reaction.

[0094] Table 2 Gas composition and specifications of the gas distribution system

[0095]

[0096] Testing Procedure: The powder sample was tested using a quartz tube reactor. The dried powder sample was spread evenly on the lower wall of the reactor, with the tail end filled with quartz wool to prevent the catalyst from escaping with the airflow. The quartz tube reactor had a diameter of 1 cm and a length of 50 cm. The temperature range for catalyst performance testing was 50–200℃.

[0097] The membrane catalyst was tested using a stainless steel membrane reactor: the calcined membrane sample was placed inside the reactor and tightened securely. The reactor's thin tube had a diameter of 2 cm and a total length of 50 cm, while the wide component had a diameter of 4.2 cm and a length of 10 cm. A schematic diagram of the stainless steel membrane reactor is shown below. Figure 1 As shown in b.

[0098] NO is calculated using the following formula. XThe removal rate of CO, the conversion rate of CO, and the removal rate of SO2.

[0099]

[0100]

[0101]

[0102] in, , and They refer to NO respectively x Removal rate, CO conversion rate and SO2 removal rate, % These refer to the NOx concentration in the inlet and outlet gases, respectively, in ppm. This refers to the CO concentration in the inlet and outlet gases, expressed in ppm. This refers to the concentration of SO2 in the inlet and outlet gases, expressed in ppm.

[0103] 1.2 Denitrification efficiency testing of different carriers

[0104] 1.2.1 Comparison of efficiency between TiO2 support and commercial catalyst

[0105] The powdered catalysts prepared in Comparative Examples 1-3 and the commercially available catalysts purchased in Comparative Examples 4-5 were tested according to the test method in 1.1. The reaction system of CO+NO+N2 was used (reaction conditions were T=200℃, 2500ppmCO, 500ppmNO, and equilibrium gas N2). The test results are shown in Table 3.

[0106] Table 3. Efficiency Comparison between TiO2 Support and Commercial Catalyst

[0107]

[0108] Table 3 shows that the NO content of commercial Fe-Beta and commercial Cu-ZSM-5 catalysts... x The removal rate was relatively low, while the removal rate of Mn-based catalysts modified with transition metal doping increased sequentially, with Mn-Co / TiO2 showing the most outstanding performance, significantly higher than the other two. Regarding CO conversion, the conversion rate of commercial catalysts was at a low level, while the CO conversion rate of Mn-based catalysts modified with transition metal doping was improved to varying degrees, with Mn-Cu / TiO2 and Mn-Fe / TiO2 showing the best performance. This demonstrates the positive impact of transition metal doping and the catalyst system on the reaction process, and further illustrates that commercial molecular sieve catalysts can remove NO in this experimental system. x The results were unsatisfactory.

[0109] 1.2.2 Comparison of efficiency between Mn-Cu / Al2O3 catalyst and Mn-Cu / TiO2 catalyst

[0110] The denitrification efficiency of the catalysts prepared in Example 1 and Comparative Example 1 was compared. The reaction system of CO+NO+N2 was used (reaction conditions were T=50~200℃, 2500ppm CO, 500ppm NO, and balance gas N2). The test results are shown in Table 4.

[0111] Table 4. Efficiency Comparison of Mn-Cu / Al2O3 and Mn-Cu / TiO2 Catalysts

[0112]

[0113] As shown in Table 4, in NO x In terms of removal performance, Mn-Cu / Al2O3 showed a significant advantage over TiO2 support, with the former removing NO at 200℃. x The removal rate reached approximately 55%, significantly higher than the 37% of Mn-Cu / TiO2; however, in terms of CO conversion rate, Mn-Cu / TiO2 performed better, achieving approximately 70% CO conversion at 200℃, higher than the nearly 60% of Mn-Cu / Al2O3. This result indicates that the pore structure, surface acidity, and interaction with active components of the Al2O3 ceramic membrane are more conducive to NO removal. x The adsorption and activation of CO; while the TiO2 support may have a more suitable interface effect in the construction of the reaction pathway for CO conversion.

[0114] 1.2.3 Catalytic efficiency of Mn-Cu / Al2O3 prepared with supports of different membrane sizes

[0115] The catalysts prepared in Examples 1 and 4-6 were used to test their catalytic efficiency. The reaction system of CO+NO+N2 was used (reaction conditions were T=50~400℃, 1000ppm CO, 500ppm NO, balance gas N2, and flue gas residence time of 2min). The test results are shown in Table 5.

[0116] Table 5. Comparison of catalytic efficiencies of Mn-Cu / Al2O3 prepared with different membrane size supports.

[0117]

[0118] Table 5 shows that the effect of pore size on catalytic activity exhibits a "first increases, then decreases" pattern: the NO in the 50 μm pore size system... x The removal rate and CO conversion rate were optimal across the entire temperature range, with NO at 200℃ being the highest. xThe highest removal rate was 69.16%, and the CO conversion rate exceeded 70%. The 30μm pore size system was the second best, with performance slightly lower than the 50μm system but significantly higher than the 2μm and 30μm systems. The 2μm small pore size system had the lowest catalytic efficiency due to its narrow pores, resulting in greater mass transfer resistance and difficulty for reactants to diffuse rapidly to the active sites inside the support. Although the 70μm large pore size system had low mass transfer resistance, the excessively large pores reduced the specific surface area of ​​the support, decreased the loading density of the active components, and resulted in a short residence time of reactants within the pores, making it difficult for them to react fully. Therefore, its performance was inferior to that of the medium pore size system.

[0119] 1.2.4 Comparison of catalytic efficiencies of Mn-Cu / Al2O3 prepared with different impregnation solutions

[0120] The concentration of the metal precursor solution (i.e., the total concentration of manganese nitrate solution and copper nitrate trihydrate solution in the impregnation solution) directly determines the loading and dispersion state of the active components (Mn, Cu) on the Al2O3 support, and thus significantly affects the catalytic performance. The catalysts prepared in Examples 1 and 7-8 were used to test the catalytic efficiency (total concentrations of 0.05, 0.01 and 0.1 mol / L, respectively). The reaction system of CO+NO+N2 was used (reaction conditions were T=50~400℃, 1000ppm CO, 500ppm NO, balance gas N2, and flue gas residence time of 1 min). The test results are shown in Table 6.

[0121] Table 6. Comparison of catalytic efficiencies of Mn-Cu / Al2O3 prepared with different impregnation solutions

[0122]

[0123] Table 6 shows that, with increasing reaction temperature, the catalytic membranes with 2 μm pore size prepared by calcination at 400℃ using three concentrations (0.01, 0.05, and 0.1 mol / L) exhibited the following NO reduction rates under conditions of 1 min of flue gas residence time: x Both the removal rate and CO conversion rate showed an upward trend, with the performance difference being particularly significant in the low-temperature range (50-200℃).

[0124] Among them, the 0.05 mol / L concentration system exhibited the best overall catalytic activity: its NO content was [missing value] across the entire temperature range. x The removal rate was consistently higher than that of the 0.01 mol / L and 0.1 mol / L systems, especially in the high-temperature region (350-400℃) for NO removal. x The removal rate is close to 60%; the CO conversion rate also shows a similar pattern, reaching over 80% in the high-temperature zone.

[0125] In contrast, the 0.01 mol / L concentration system suffers from insufficient metal ion supply and low loading of active components, resulting in a scarcity of active sites and low NO concentration across the entire temperature range.x The removal rate and CO conversion rate were the lowest. Although the 0.1 mol / L concentration system had sufficient active component loading, the excessively high ion concentration easily caused Mn and Cu oxide particles to agglomerate, and some active sites were encapsulated. The catalytic efficiency was actually lower than that of the 0.05 mol / L system, showing the effect of "excessive concentration inhibiting activity".

[0126] 1.2.5 Comparison of catalytic efficiencies of Mn-Cu / Al2O3 prepared at different calcination temperatures

[0127] Calcination temperature is a key parameter for controlling the structure and performance of Mn–Cu / Al2O3 catalysts. It affects the catalytic denitrification activity by influencing the crystal phase, dispersion, and interactions of the active components. Catalytic efficiency was tested using the catalysts prepared in Examples 1-3, employing a CO+NO+N2 reaction system (reaction conditions: T=50~400℃, 1000ppm CO, 500ppm NO, equilibrium gas N2, flue gas residence time 2min). The test results are shown in Table 7, where the horizontal temperature represents the calcination temperature and the vertical temperature represents the reaction temperature.

[0128] Table 7 Comparison of catalytic efficiencies of Mn-Cu / Al2O3 prepared at different calcination temperatures

[0129]

[0130] Table 7 shows that, under the CO+NO+N2 conditions (1000 ppm CO, 500 ppm NO, and equilibrium gas N2), the catalysts with a pore size of 50 μm prepared at three calcination temperatures (350℃, 400℃, and 450℃) exhibited the following NO content: x Both the removal rate and CO conversion rate increased with increasing reaction temperature; among them, the catalyst calcined at 450℃ showed the best catalytic activity, while the NO removal rate was lower at 200℃. x The highest removal rate was 72.47%, covering the entire temperature range for NO removal. x The removal rate and CO conversion rate were both higher than those of the samples calcined at 350℃ and 400℃; the catalysts calcined at 350℃ and 400℃ had relatively low activity, and the performance difference between the two at different temperature ranges was not significant.

[0131] contrast Figure 8 XRD patterns of catalysts at different calcination temperatures. Cu2O, MnO2, and trace amounts of CuMn2O4 and Cu were detected in Mn-Cu / Al2O3 calcined at 350℃. 1.5 Mn 1.5 Characteristic diffraction peaks of O4; in the sample calcined at 400℃, CuMn2O4 and Cu 1.5 Mn 1.5The characteristic diffraction peak intensities of the O4 composite oxide were significantly enhanced, and no obvious characteristic peaks of Cu2O or MnO2 single oxides were observed. In the sample calcined at 450℃, the characteristic peak intensities of the composite oxide were weakened, and no new impurity phase diffraction peaks appeared. This indicates that the active component did not completely form the target composite oxide during calcination at 350℃, and the calcination temperature of 400℃ was more conducive to the formation of a stable spinel-type composite oxide between Mn and Cu. Although calcination at 450℃ weakened the characteristic peak intensities of the composite oxide, it still maintained the phase structure of the target composite oxide.

[0132] 2. Effect of operating conditions on the catalytic efficiency of Mn-Cu / Al2O3

[0133] 2.1 Comparison of residence time with the catalytic efficiency of Mn-Cu / Al2O3

[0134] The residence time of flue gas, as a key parameter of reaction kinetics, directly affects the sufficiency of contact between reactants (NO, CO) and the active sites of the catalyst. The experiment selected the catalyst prepared in Example 1 to investigate the effects of three residence times: 30 s, 60 s, and 120 s. The reaction system of CO + NO + N2 was used (reaction conditions: T = 200-400℃, 1000ppm CO, 500ppm NO, and equilibrium gas N2).

[0135] Test results are as follows Figure 2 As shown, where, Figure 2 a is NO X A comparison chart of removal rates. Figure 2 b is a comparison chart of CO conversion rates (for easy differentiation, the catalyst prepared in Example 1 is represented as Mn-Cu / Al2O3-0.05 in the chart, where 0.05 refers to the concentration of the metal precursor solution. Depending on the observation time, the test groups are recorded as Mn-Cu / Al2O3-0.05-30s, Mn-Cu / Al2O3-0.05-60s, and Mn-Cu / Al2O3-0.05-120s, respectively).

[0136] Depend on Figure 2 It can be seen that as the residence time increases, the NO of the catalyst increases. x Both the removal rate and CO conversion rate showed a significant upward trend, with the increase being more pronounced in the low-temperature range (200-250℃). When the residence time was extended from 30 s to 120 s, the NO removal rate at 250℃ was significantly higher. xThe removal rate increased by approximately 30%, and the CO conversion rate increased by nearly 20%. Although there was still an improvement in the high-temperature region (above 350℃), the increase gradually narrowed. This phenomenon indicates that within a short residence time, NO and CO do not completely diffuse to the active sites of the catalyst and react before leaving the system, resulting in incomplete reaction. Extending the residence time ensures sufficient contact between the reactants and the active sites, and optimizing the residence time is even more critical for performance improvement, especially in the low-temperature region where the reaction rate is relatively slow.

[0137] 2.2 Effect of CO / NO concentration ratio on the activity of Mn-Cu / Al2O3 catalyst

[0138] In tests of different CO / NO concentration ratios, the catalyst prepared in Example 1 was selected for testing. The experimental conditions were set as a CO+NO+N2 system, with the NO concentration fixed at 500 ppm and the CO concentration adjusted to 500 ppm, 1000 ppm, and 1500 ppm, corresponding to CO / NO ratios of 1, 3, and 5, respectively. The equilibrium gas was N2, and the reaction temperature covered the range of 50-400℃. This was to investigate the effect of the sufficiency of reducing agent on the optimal activity of the Mn-Cu / Al2O3 catalyst. The experimental results are as follows: Figure 3 As shown, where, Figure 3 a is NO X Removal rate comparison chart Figure 3 b is a comparison chart of CO conversion rates.

[0139] Based on the experimental results, the catalyst's NO... x The removal rate exhibits a unique variation pattern related to the CO / NO ratio, not simply increasing or decreasing monotonically with the ratio, but rather showing an overall trend of "first increasing, then decreasing": across the entire temperature range, when CO / NO=3, NO... x The removal rate was best when CO / NO=1, followed by the lowest when CO / NO=5. Meanwhile, NO... x The removal activity exhibits a consistent characteristic with temperature changes, gradually increasing first, reaching a peak, and then stabilizing. The highest removal rate of 64.39% is achieved in the medium-high temperature range (50-250℃). This trend indicates that the catalyst can catalyze NO more efficiently within a suitable temperature range. x Reduction reaction. With NO xThe removal rates showed different patterns. The CO conversion rate showed a continuous increasing trend with the increase of the CO / NO ratio. Specifically, when CO / NO=5, the CO conversion rate reached over 50% in the medium-high temperature range (150-350℃), significantly higher than the conditions with CO / NO=1 and 3. This phenomenon indicates that sufficient reducing agent (CO) not only provides ample substrate for the CO-SCR denitrification reaction, promoting the forward reaction, but also creates more favorable conditions for the oxidation reaction of CO itself, thereby improving the efficiency of CO oxidation and decomposition. However, it is worth noting that when the CO / NO ratio is too high (e.g., 5), excess CO may compete with NO for adsorption at the catalyst active sites, thus inhibiting NO adsorption. x The reduction reaction leads to NO x The removal rate decreased, therefore the CO / NO ratio is a measure that takes into account NO removal efficiency. x The optimal ratio of removal to CO conversion.

[0140] 2.3 Effect of O2 concentration on the activity of Mn-Cu / Al2O3 catalyst

[0141] The tests at different O2 concentrations used a CO+NO+N2 reaction system. The catalyst prepared in Example 1 was selected for testing. The CO concentration was set at 1000 ppm, the NO concentration at 500 ppm, and the O2 concentration was adjusted to 1%, 3%, and 5%, respectively. N2 was used as the equilibrium gas, and the reaction temperature covered the range of 50-400℃. The aim was to explore the influence mechanism of oxygen content on the optimal activity of the Mn-Cu / Al2O3 catalyst. The test results are as follows: Figure 4 As shown, where Figure 4 a is NO X Removal rate comparison chart Figure 4 b is a comparison chart of CO conversion rates.

[0142] As shown in the figure, O2 concentration has an effect on NO x The effect of O2 concentration on NO removal rate exhibits a significant temperature-dependent pattern, generally showing the characteristic of "low concentration (3%) promoting growth in the low-temperature range, and even lower concentration (1%) being more effective in the medium- and high-temperature ranges": In the low-temperature range (50-150℃), when the O2 concentration is 3%, the catalyst's NO removal rate is significantly higher. x The removal effect was optimal, reaching 63.83% at 150℃; however, in the medium-high temperature range (200-400℃), the condition with an O2 concentration of 1% showed even better denitrification performance, with NO at 250℃. xThe removal rate reached 76.93%, significantly higher than that at O2 concentrations of 3% and 5%. This phenomenon indicates that the O2 concentration requirement of the SCR denitrification reaction is closely related to the reaction temperature: under low-temperature conditions, an appropriate amount of O2 (3%) can provide the necessary oxidation environment for the formation of active species on the catalyst surface (such as high-valence Mn and Cu oxides), thereby enhancing NO removal. x The reduction reaction occurs; however, as the temperature rises, excessive O2 (3%, 5%) intensifies the competition between the CO oxidation reaction and the SCR denitrification reaction for catalyst active sites, leading to a decrease in denitrification efficiency. A lower O2 concentration (1%) can effectively alleviate this competitive effect, making the denitrification reaction more favorable in the medium- and high-temperature stages. (The text abruptly shifts to a seemingly unrelated topic about NO.) x The changes in removal rates differed. CO conversion rate showed a clear monotonic increasing trend with increasing O2 concentration: CO conversion was optimal at an O2 concentration of 5%, with a conversion rate approaching 80% in the medium-high temperature range (200-350℃); CO conversion efficiency was lowest at an O2 concentration of 1%, less than 50% at 50℃. This result fully confirms that O2 is the key limiting reactant in the CO oxidation reaction. Sufficient O2 supply can significantly accelerate the oxidative decomposition process of CO, while insufficient O2 concentration will significantly inhibit the CO oxidation reaction.

[0143] 2.4 Effect of SO2 concentration on the activity of Mn-Cu / Al2O3 catalyst

[0144] As shown in the preceding experiments, Example 1 is the optimal example, and the catalyst prepared therefrom exhibits the best performance. Therefore, the catalyst prepared in Example 1 was used for synergistic testing of desulfurization and denitrification. The tests at different SO2 concentrations used a CO + NO + N2 reaction system. The CO concentration was set at 1000 ppm, the NO concentration at 500 ppm, and the SO2 concentration was adjusted to 0 ppm, 50 ppm, 100 ppm, and 200 ppm, respectively, with N2 as the equilibrium gas.

[0145] The reaction temperature ranged from 50 to 400℃, and the study focused on the effects of sulfur corrosion and poisoning environment in flue gas on the desulfurization and denitrification performance of the optimal Mn-Cu / Al2O3 catalyst.

[0146] The test results are shown in Table 8 and Figure 5 As shown, where Figure 5 a is NO X Removal rate comparison chart Figure 5 b is a comparison chart of CO conversion rates. Figure 5 c is a comparison chart of SO2 removal rates.

[0147] Table 8. Test Results of Catalyst for Simultaneous Desulfurization and Denitrification

[0148]

[0149] From Table 8 and Figure 5 It can be seen that the introduction of SO2 significantly inhibits the denitrification activity of the catalyst, and this inhibitory effect gradually intensifies with increasing SO2 concentration: under conditions without SO2 intervention, the NO content of the catalyst... x It exhibits the best removal rate, consistently achieving a high removal efficiency of 55%–75% within the medium-low temperature range (50-200℃); when the SO2 concentration increases to 50 ppm, NO… x The removal rate declined significantly, dropping to around 50% at 250℃. As the SO2 concentration further increased to 100 ppm and 200 ppm, the denitrification effect continued to weaken. However, it is noteworthy that even under high SO2 concentration stress of 200 ppm, the catalyst could still maintain 20%-30% NO removal in the medium-to-high temperature range (250-400℃). x The removal rate was not completely lost, and it showed a certain degree of sulfur resistance stability.

[0150] The trend of CO conversion rate affected by SO2 concentration is similar to that of NO. x The removal rate remained largely consistent, gradually decreasing with increasing SO2 concentration, but the inhibition was relatively mild. In the medium-high temperature range (250-350℃), it maintained a conversion level of 30%-50%, indicating that SO2 had a limited inhibitory effect on the catalyst's CO oxidation activity, and the catalyst could still effectively promote CO oxidation and decomposition in sulfur-containing environments. Simultaneously, this optimal Mn-Cu / Al2O3 catalyst exhibited a clear desulfurization capability, showing significant SO2 removal effects across the entire temperature range. The SO2 removal rate showed a clear upward trend with increasing reaction temperature: in the medium-low temperature range (50-250℃), the SO2 removal rate reached 30%-70%. Even with different SO2 input concentrations, the catalyst could still stably perform its desulfurization function, successfully achieving the goal of simultaneous desulfurization and denitrification—"desnitrification effect inhibited by SO2 but not deactivated, desulfurization performance stable and effective"—providing feasible support for the synergistic control of multiple pollutants in complex sulfur-containing flue gas environments.

[0151] 3. Structural Characterization

[0152] 3.1 Analysis of the apparent morphology of Mn–Cu / Al2O3 prepared with different impregnation solution concentrations

[0153] Electron microscopy was performed on the catalysts prepared in Examples 1 and 7-8, and the results are as follows: Figure 6 As shown, where, Figure 6 a is a SEM image of the catalyst from Example 7. Figure 6 b is a SEM image of the catalyst from Example 1. Figure 6c is an SEM image of the catalyst from Example 8.

[0154] Depend on Figure 6 It can be seen that when the concentration is 0.01 mol / L, the active component particles on the Al2O3 support surface are sparse and unevenly distributed, with some areas having almost no obvious particle adhesion, directly corresponding to its low loading and low activity characteristics. When the concentration is increased to 0.05 mol / L, a uniform and dense film of active components is formed on the support surface, with small particle size and excellent dispersion, and no obvious agglomeration. This morphological feature maximizes the exposure of active sites, providing a sufficient interface for reactant adsorption and activation, which corresponds to the optimal catalytic activity of the system. When the concentration is increased to 0.1 mol / L, a large number of agglomerates appear on the support surface, and the particle size is significantly increased (far exceeding that of the 0.05 mol / L system). The formation of agglomerates not only reduces the effective exposure of active sites, but also hinders the contact between reactants and active centers, resulting in a decrease in catalytic performance, which corresponds to the catalytic performance detection experiments.

[0155] 3.2 Analysis of the apparent morphology of Mn-Cu / Al2O3 prepared on membrane supports with different pore sizes

[0156] Electron microscopy was performed on the catalysts from Examples 1 and 4-6, and the results are as follows: Figure 7 As shown, where, Figure 7 a is a SEM image of the catalyst in Example 4. Figure 7 b is a SEM image of the catalyst in Example 5. Figure 7 c is an SEM image of the catalyst from Example 1. Figure 7 d is a SEM image of the catalyst in Example 6.

[0157] As shown in the figure, the 2μm small-pore support has dense and uniform pores, but poor channel connectivity, which can easily hinder the diffusion of reactants. The 30μm and 50μm pore supports both exhibit catalyst particle distribution on their surfaces. The catalyst particles on the 50μm pore support are even smaller and have excellent dispersion, creating a better environment for the catalytic reaction. The 70μm large-pore support has large and unevenly distributed pores, with some areas exhibiting a "hollow" structure, which makes it difficult to uniformly load the active components and results in insufficient residence time of reactants in the pores, ultimately affecting the catalytic efficiency. This result is consistent with the aforementioned catalytic performance testing results.

[0158] In summary, this method uses Al2O3 ceramic membranes as a carrier. The pore structure, surface acidity, and interaction with the active metal components of the Al2O3 ceramic membrane are more conducive to NO removal. xThe adsorption and activation of CO are observed. The outer electrons of metal ions in transition metal oxides are unstable and easily gain or lose electrons. The change in the chemical bonding environment after Cu and Mn form a composite oxide leads to a shift and enhancement of characteristic peaks, directly reflecting the strong interaction of Mn-O-Cu bonds in the CuMn2O4 composite oxide. This synergistic chemical bond provides an efficient electron transfer pathway for the adsorption and activation of NO and the oxidation of CO. CO, as a reducing agent, reduces NOx to harmless N2 under the action of a catalyst, as in the reaction 2CO + 2NO → 2CO2 + N2. This not only improves denitrification efficiency but also reduces secondary CO pollution. In catalytic desulfurization, CO has a relatively weak effect, but SO2 generation can be indirectly reduced by optimizing combustion. By utilizing the inherent reducing properties of CO in flue gas, SO2 and NOx can be synergistically removed without the addition of an external ammonia source, while simultaneously reducing CO emission levels.

[0159] The optimal preparation conditions for the catalyst are: a metal precursor concentration of 0.05 mol / L in the impregnation solution, an Al2O3 membrane pore size of 50 μm, and a calcination temperature of 450 ℃. Under these conditions, the active components of the catalyst are uniformly dispersed and show no significant agglomeration. NO at 200 ℃... x The removal rate reached 72.47%, and the CO conversion rate exceeded 70%, with basic performance far surpassing the initial system. The optimal Mn-Cu / Al2O3 catalyst was obtained. Under SO2-free conditions, the optimal Mn-Cu / Al2O3 catalyst exhibited the best NO removal performance in the medium-low temperature range (50-200℃). x The removal rate remained stable at 55%-75%; although the denitrification activity was inhibited by SO2, it was not deactivated, and the denitrification rate still reached about 50% at 50 ppm SO2 + 250℃, demonstrating good sulfur resistance stability; in terms of desulfurization performance, the optimal Mn-Cu / Al2O3 catalyst showed significant SO2 removal effect across the entire temperature range, and the removal rate increased with increasing temperature, reaching 30%-70% in the medium and low temperature range (50-250℃), and could stably perform desulfurization function under different SO2 concentration inputs; moreover, the optimal Mn-Cu / Al2O3 catalyst had good operating condition adaptability, and under suitable operating conditions of CO / NO ratio of 3 and O2 concentration of 3%, the simultaneous treatment efficiency was optimal; facing complex situations such as fluctuations in CO / NO ratio and changes in O2 concentration in flue gas, it could still maintain stable synergistic removal performance, fully adapting to the actual scenario of dynamic changes in combustion flue gas concentration, thus providing feasible support for the synergistic control of multiple pollutants in complex sulfur-containing flue gas environments.

Claims

1. A method for preparing a manganese-based composite bimetallic catalyst for simultaneous desulfurization and denitrification of crematory flue gas, characterized in that: Includes the following steps: S1. Carrier pretreatment: Select Al2O3 ceramic membranes, clean them, and dry them for later use; S2. Preparation of impregnation solution: Mix manganese nitrate solution and copper nitrate trihydrate solution, then add citric acid and mix to promote metal ion complexation. Continue stirring at pH 6.8±0.2 to obtain the impregnation solution. S3, Vacuum Impregnation: The carrier pretreated in S1 is placed in the impregnation solution obtained in S2 and impregnated under vacuum for 1.5 hours. After impregnation, the membrane is taken out and air-dried horizontally, and then placed in an oven to dry. The impregnation is repeated 2 to 3 times. S4. Calcination: The Al2O3 ceramic film loaded with active components obtained in S3 is transferred to a tube furnace and calcined in an air atmosphere. After calcination, the product is naturally cooled, and after cooling, a manganese-based composite bimetallic catalyst for co-desulfurization and denitrification of combustion flue gas is obtained.

2. The method of claim 1, wherein: In S1, the pore size of the Al2O3 ceramic membrane is 2 to 70 μm, preferably 50 μm.

3. The method of claim 1, wherein: S2. Preparation of impregnation solution: Mix manganese nitrate solution and copper nitrate trihydrate solution with a certain amount of deionized water, stir magnetically for 15 minutes to completely dissolve them, then add citric acid and stir magnetically for 30 minutes to promote metal ion complexation. Add diluted ammonia water dropwise to control the pH of the solution to be stable at 6.8±0.

2. Continue to stir magnetically for 12 hours under the condition of pH 6.8±0.

2. The impregnation solution is obtained after stirring.

4. The method of claim 3, wherein: The concentration of the manganese nitrate solution is 0.007–0.07 mol / L, preferably 0.035 mol / L, and the concentration of the copper nitrate trihydrate solution is 0.003–0.03 mol / L, preferably 0.015 mol / L.

5. The method of claim 4, wherein: The total concentration of the manganese nitrate solution and the copper nitrate trihydrate solution is 0.01–0.1 mol / L, preferably 0.05 mol / L, and the concentration of the citric acid is 0.005–0.05 mol / L, preferably 0.025 mol / L.

6. The method of claim 5, wherein: The molar ratio of manganese to copper in the impregnation solution is 7:

3.

7. The method of claim 1, wherein: In S3, the conditions for a single vacuum impregnation are: vacuum degree (-0.08 MPa) and impregnation time of 1.5 h.

8. The method of claim 1, wherein: In S4, the calcination temperature is 350-450℃, preferably 450℃, and the calcination time is 4h.

9. A manganese-based composite bimetallic catalyst for the synergistic desulfurization and denitrification of crematory flue gas, characterized by: It is prepared by the preparation method according to any one of claims 1-8.

10. The use of the manganese-based composite bimetallic catalyst for cremation flue gas synergistic desulfurization and denitrification according to claim 9 in the field of cremation flue gas purification, characterized in that: The optimal operating conditions for the manganese-based composite bimetallic catalyst are: a CO to NO concentration ratio of 3 and an O2 concentration of 3% at medium and low temperatures (50–250°C).

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