Preparation method and application of Na and / or K poisoning resistant CO and NH3 coupled denitration catalyst

Abstract

The invention relates to a preparation method and application of a Na and / or K poisoning resistant CO and NH3 coupled denitration catalyst, and belongs to the technical field of flue gas purification. The preparation method comprises the following steps: by taking coconut shell activated carbon (AC) activated by nitric acid as a carrier, preparing a Fe-Mn / AC catalyst through an impregnation method, treating the Fe-Mn / AC catalyst with hydrogen peroxide under a microwave condition to obtain the denitration catalyst resistant to Na and / or K poisoning, and the metal oxide active components of the denitration catalyst are mainly FeOx and MnOy. The anti-Na and / or K poisoning denitration catalyst provided by the invention takes CO and NH3 as a mixed reducing agent to remove nitrogen oxides in Na and / or K-containing flue gas in a coupling manner, and has the characteristic of high removal rate.

Description

Technical Field

[0001] The invention relates to a method for preparing a catalyst for coupling denitration of CO and NH3 resistant to Na and / or K poisoning and application thereof, belonging to the technical field of flue gas purification. Background Art

[0002] Nitrogen oxides (NO x ) is one of the main air pollutants emitted during fuel combustion, causing environmental problems such as acid rain, ozone depletion and photochemical smog. Selective catalytic reduction technology using NH3 as a reducing agent is an important way to control NO x It is an effective means of pollution control, but NH3 itself is a toxic gas with high cost and easy to leak, which can easily cause chemical accidents and other problems. The advantage of denitrification technology using CO as a reducing agent is that CO is commonly present in industrial flue gases such as sintering and coking. CO in the flue gas can be used as a reducing agent to remove NO, and CO and NO can be converted into non-toxic N2 and CO2 at the same time, so as to achieve the purpose of treating waste with waste. However, this technology also has some bottlenecks that are difficult to break through, such as the high denitrification temperature window and the easy oxidation of the reducing agent. Therefore, if the two gases are combined for the removal of NO from medium and low temperature flue gas, it can not only reduce the ammonia escape problem of NH3-SCR technology, but also make up for the narrow temperature range of CO-SCR technology. It is expected to overcome the shortcomings of NO removal alone and give play to their respective technical advantages.

[0003] In addition, the flue gas entering the SCR reactor contains a large amount of dust and metals that will clog the catalyst pores. The metals contained (Zn, Pb, Ca, As, K, Na, etc.) will cause the catalyst to deactivate. In particular, alkali metals are the main components of flue gas. A small amount of Na and K will cause the catalyst to deactivate, reducing its service life and causing an economic burden. Summary of the invention

[0004] In view of the problems of K and Na poisoning and failure of the flue gas denitration catalyst in the prior art, the present invention proposes a method for preparing a CO and NH3 coupled denitration catalyst resistant to Na and / or K poisoning and its application, wherein coconut shell activated carbon activated by nitric acid is used as a carrier, and an Fe-Mn / AC catalyst is prepared by an impregnation method. The Fe-Mn / AC catalyst is treated with hydrogen peroxide under microwave conditions to obtain a denitration catalyst resistant to Na and / or K poisoning. The metal oxide active component of the denitration catalyst is mainly FeO x and MnO y The denitration catalyst resistant to Na and / or K poisoning of the present invention uses CO and NH3 as mixed reducing agents to couple the removal of nitrogen oxides in flue gas containing Na and / or K. It has the characteristics of high removal rate and can solve the problems of low denitration rate, easy pore blockage, easy K and Na poisoning failure, short life and the like of SCR process catalyst in existing flue gas denitration.

[0005] A method for preparing a CO and NH3 coupled denitration catalyst resistant to Na and / or K poisoning, the specific steps are as follows:

[0006] (1) washing coconut shell activated carbon (AC) with deionized water, adding it into deionized water, ultrasonically treating it at a temperature of 60 to 70° C., separating the solid from the liquid, and vacuum drying it to obtain pretreated coconut shell activated carbon;

[0007] (2) adding the coconut shell activated carbon pretreated in step (1) to nitric acid, heating to a temperature of 80-90° C. and reflux activation treatment for 2-3 h, cooling and washing with deionized water until neutral, solid-liquid separation, and vacuum drying to obtain activated AC;

[0008] (3) adding the activated AC prepared in step (2) to the precursor solution, ultrasonically impregnating the mixture at a temperature of 60 to 70°C for 2 to 3 hours, stirring and impregnating the mixture at room temperature for 24 to 48 hours, vacuum drying the mixture, and then calcining the mixture at a temperature of 450 to 500°C in a nitrogen atmosphere for 4 to 5 hours to obtain a Fe-Mn / AC catalyst; the precursor solution is a mixed solution of Fe(NO3)3 and Mn(NO3)2;

[0009] (4) The Fe-Mn / AC catalyst is added to deionized water under microwave conditions and stirred evenly to obtain a Fe-Mn / AC catalyst suspension. Under stirring conditions at a temperature of 80 to 90° C., hydrogen peroxide is slowly added to the Fe-Mn / AC catalyst suspension and the reaction is maintained at a temperature of 60 to 100° C. for 1.0 to 2.0 h. The catalyst is cooled to room temperature, the solid and the liquid are separated, and the solid is calcined at a temperature of 200 to 500° C. for 2 to 6 h to obtain a denitration catalyst resistant to Na and / or K poisoning.

[0010] The particle size of the coconut shell activated carbon AC in step (1) is 10 to 20 meshes.

[0011] The concentration of nitric acid in step (1) is 4-5 mol / L.

[0012] The concentration of Fe(NO3)3 in the precursor solution of step (3) is 1.5-2.0 mol / L, and the mass content of Mn element is 2-2.5 times that of Fe element.

[0013] The solid-to-liquid ratio g:L of the activated AC to the precursor solution in step (3) is 2500:1.

[0014] In the step (4), the concentration of the Fe-Mn / AC catalyst suspension under microwave conditions is 70-90 g / L, the volume ratio of hydrogen peroxide to the Fe-Mn / AC catalyst suspension is 1:5; and the mass concentration of the hydrogen peroxide is 25-35%.

[0015] The catalyst can be used to remove NO in flue gas: the flue gas contains Na and / or K, CO and NH3 are used as mixed reducing agents, and the NO removal temperature is 150-300°C.

[0016] The present invention uses activated carbon activated by nitric acid as a carrier, which can greatly improve the surface functional groups of coconut shell activated carbon, increase the specific surface area, and improve the internal pore volume and pore diameter of the activated carbon; ultrasonic impregnation is used to effectively ensure the dispersion of iron and manganese oxides on the catalyst surface, thereby ensuring that it has high NO removal activity and good nitrogen selectivity; hydrogen peroxide is used to treat the catalyst under microwave conditions to improve the catalyst activity and toxicity resistance without introducing other impurities; K and Na are successfully loaded through ultrasonic impregnation of a poisoned solution without introducing new impurities.

[0017] The beneficial effects of the present invention are:

[0018] (1) The present invention adopts CO+NH3 coupling removal of NO technology, uses iron and manganese oxides as active components, coconut shell activated carbon activated by nitric acid as a carrier, and adopts precursor solution ultrasonic impregnation method-microwave inorganic modification method to prepare a denitration catalyst resistant to Na and / or K poisoning, which is used for flue gas denitration and significantly improves the removal of NO x Activity and catalytic ability; can solve the problems of low denitration rate, easy pore blockage, easy K and Na poisoning and failure in the existing SCR process catalyst in flue gas denitration;

[0019] (2) The catalyst of the present invention has a high NO removal rate, and the denitrification rate remains high over time, and has strong anti-poisoning performance;

[0020] (3) The present invention uses nitric acid to activate coconut shell activated carbon, improves the surface active functional groups of coconut shell activated carbon, increases the specific surface area, improves the pore volume and pore size inside the activated carbon, and greatly improves the dispersibility of iron and manganese oxides on the surface of Fe-Mn / AC catalyst that resists Na and K poisoning;

[0021] (4) The Fe-Mn / AC catalyst of the present invention is treated with hydrogen peroxide under microwave conditions and then calcined to improve the NO conversion rate of the catalyst, optimize the pore distribution, and increase the number of micropores and mesopores;

[0022] (5) The present invention uses CO and NH3 as a mixed reducing gas, with high NO removal efficiency. The reducing agent of the CO-SCR NO removal technology comes from the flue gas itself, which can achieve the advantages of synergistic removal of CO and NO by waste treatment, and overcome the shortcomings of NH3-SCR technology such as poor N2 selectivity at high temperature, SO2 poisoning leading to irreversible deactivation of the catalyst, and poor reaction activity of CO-SCR technology under oxygen-rich conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is the NO removal curve of the catalyst at different temperatures, different times, and before and after modification;

[0024] Figure 2 The SEM images of the catalyst before and after modification;

[0025] Figure 3 is the EDS graph of the catalyst before and after modification;

[0026] Figure 4 N2 adsorption-desorption curves and average pore size diagrams of the catalysts before and after modification;

[0027] Figure 5 XRD patterns of catalysts before and after modification;

[0028] Figure 6 XPS graphs of catalysts before and after modification;

[0029] Figure 7 FTIR images of the catalyst before and after modification. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below in conjunction with specific implementation modes, but the protection scope of the present invention is not limited to the described contents.

[0031] The catalytic reactor used in the implementation of the present invention is a CHY-1200 fixed bed reactor. The raw gas containing K and / or Na is preheated before entering the reactor. The reaction temperature is 150-300°C, the total gas flow rate is 1000 ml / min, and the GHSV is 30000 h -1 ;

[0032] Simulated flue gas composition: NO flow rate is 4 ml min -1 (4×10 3 ppm), O2 volume concentration is 9% (volume ratio), N2 is the balance gas, K and / or Na are mixed in the simulated flue gas, and the flow rate of reducing gas NH3 is 4 ml min -1 (4×10 3 ppm), the reducing gas CO flow rate is 16 ml min -1 (1.6×10 4 ppm), the simulated flue gas was mixed and sent into the fixed bed reactor, and the gas flow was controlled by LZB-4DKF rotor flowmeter;

[0033] The NO concentration at the inlet and outlet of the fixed bed reactor evaluation device was detected by a Testo-340 flue gas analyzer;

[0034] The purity of CO, NO, N2 and O2 used in the present invention is 99.99%, and the ammonia gas composition in nitrogen is 99% N2 and 1% NH3;

[0035] The NO removal activity of the catalyst was evaluated by NO conversion rate, and the calculation method is as follows:

[0036]

[0037] Where:

[0038] NO in ------NO concentration at reactor inlet, ppm;

[0039] NO out -----NO concentration at reactor outlet, ppm.

[0040] Example 1: A method for preparing a catalyst for coupled denitration of CO and NH3 that is resistant to Na and / or K poisoning, the specific steps are as follows:

[0041] (1) Coconut shell activated carbon AC was washed with deionized water, then added to deionized water, ultrasonically treated at 60°C for 2 h, solid-liquid separation was performed, and vacuum dried at 110°C for 24 h to obtain pretreated coconut shell activated carbon;

[0042] (2) adding the coconut shell activated carbon pretreated in step (1) to 4 mol / L nitric acid, heating to 80° C. and reflux activation treatment for 3 h, cooling and washing with deionized water until the washing liquid is neutral, separating the solid and the liquid, and placing under vacuum drying at 110° C. for 24 h to obtain activated AC;

[0043] (3) adding the activated AC obtained in step (2) to a precursor solution (a mixed solution of Fe(NO3)3 and Mn(NO3)2), ultrasonically impregnating the mixture at 60°C for 2 h, stirring and impregnating the mixture at room temperature for 24 h, vacuum drying the mixture at 110°C for 24 h, and calcining the mixture at 450°C in a nitrogen atmosphere for 4 h to obtain a Fe-Mn / AC catalyst (denoted as 3.5Fe-7.0Mn / AC); the Fe(NO3)3 concentration in the precursor solution was 1.5 mol / L; the Fe content by mass of the Fe element in the Fe-Mn / AC catalyst was 3.5%, and the Mn content by mass of the Mn element was 7.0%;

[0044] (4) adding Fe-Mn / AC catalyst to deionized water under microwave conditions and stirring uniformly to obtain Fe-Mn / AC catalyst suspension, slowly adding hydrogen peroxide to the Fe-Mn / AC catalyst suspension under stirring conditions at 80° C. and maintaining the reaction at a temperature of 60° C. for 1 hour, cooling to room temperature after the reaction, separating the solid and the liquid, and calcining the solid at a temperature of 400° C. for 2 hours to obtain Fe-Mn / AC catalyst resistant to Na and / or K poisoning (denoted as H-3.5Fe-7.0Mn / AC); the concentration of the Fe-Mn / AC catalyst suspension is 70 g / L, the volume ratio of hydrogen peroxide to the Fe-Mn / AC catalyst suspension is 1:5; the mass concentration of the hydrogen peroxide is 25%;

[0045] The catalyst (H-3.5Fe-7.0Mn / AC) for coupled denitration of CO and NH3 resistant to Na and / or K poisoning of this embodiment and 3.5Fe-7.0Mn / AC of comparative example 1 which has not been modified with microwave hydrogen peroxide were used, and NH3+CO was used as a reducing agent to couple and remove NO from Na-containing flue gas (Na content of 0.1%) at 150-300°C, and the catalyst loading amount was 8g; before the start of the experimental test, N2 was introduced into the fixed bed reactor to discharge other gases in the reactor to avoid interference from other gases; then simulated flue gas was introduced for 8h; under the action of the coupled denitration catalyst of CO and NH3 resistant to Na poisoning, NO was reduced to N2 under the joint reduction of CO and NH3; the reacted gas was discharged into the atmosphere after absorbing unreacted NO and CO through a limestone solution, and the NO concentration at the inlet and outlet was detected by a flue gas analyzer, as shown in Table 1;

[0046] Table 1 DeNO efficiency of H-3.5Fe-7.0Mn / AC catalysts of this example and 3.5Fe-7.0Mn / AC catalysts of the comparative example

[0047]

[0048]

[0049] As can be seen from Table 1, the catalyst H-3.5Fe-7.0Mn / AC of this embodiment and the comparative example 3.5Fe-7.0Mn / AC were used to remove NO from flue gas at a temperature of 150-300°C. It was found that the catalyst of the embodiment had a high NO removal rate, and as time went by, the denitrification rate always remained highly efficient, and had strong resistance to Na poisoning. The NO conversion rate of the corresponding catalysts after modification was significantly improved, and the NO conversion rate curve became flat, and the NO conversion rate decreased slowly.

[0050] Example 2: A method for preparing a catalyst for coupled denitration of CO and NH3 that is resistant to Na and / or K poisoning, the specific steps are as follows:

[0051] (1) Coconut shell activated carbon AC was washed with deionized water, then added to deionized water, ultrasonically treated at 65°C for 1.8 h, solid-liquid separation was performed, and vacuum dried at 100°C for 36 h to obtain pretreated coconut shell activated carbon;

[0052] (2) adding the coconut shell activated carbon pretreated in step (1) to 4.5 mol / L nitric acid, heating to 85° C. and reflux activation treatment for 2.5 h, cooling and washing with deionized water until the washing liquid is neutral, separating the solid from the liquid, and drying under vacuum at 100° C. for 36 h to obtain activated AC;

[0053] (3) adding the activated AC obtained in step (2) to a precursor solution (a mixed solution of Fe(NO3)3 and Mn(NO3)2), ultrasonically impregnating the mixture at 65°C for 2.5 h, stirring and impregnating the mixture at room temperature for 36 h, vacuum drying the mixture at 110°C for 24 h, and then calcining the mixture at 480°C in a nitrogen atmosphere for 4.5 h to obtain a Fe-Mn / AC catalyst (denoted as 3.7Fe-7.6Mn / AC); the Fe(NO3)3 concentration in the precursor solution was 1.8 mol / L; the Fe content by mass of the Fe element in the Fe-Mn / AC catalyst was 3.7%, and the Mn content by mass of the Mn element was 7.6%;

[0054] (4) adding Fe-Mn / AC catalyst to deionized water under microwave conditions and stirring uniformly to obtain Fe-Mn / AC catalyst suspension, slowly adding hydrogen peroxide to the Fe-Mn / AC catalyst suspension under stirring conditions at 85° C. and maintaining the reaction at a temperature of 80° C. for 1.5 hours, cooling to room temperature after the reaction, separating the solid from the liquid, and calcining the solid at a temperature of 450° C. for 4 hours to obtain Fe-Mn / AC catalyst resistant to Na and / or K poisoning (denoted as H-3.7Fe-7.6Mn / AC); the concentration of the Fe-Mn / AC catalyst suspension is 80 g / L, the volume ratio of hydrogen peroxide to the Fe-Mn / AC catalyst suspension is 1:5; the mass concentration of the hydrogen peroxide is 30%;

[0055] The CO and NH3 coupled denitration catalyst (H-3.7Fe-7.6Mn / AC) resistant to Na and / or K poisoning in this embodiment and 3.7Fe-7.6Mn / AC without microwave hydrogen peroxide modification in comparative example 2 were used, and NH3+CO was used as a reducing agent to couple and remove NO from K-containing flue gas (K content was 1.0%) at 150-300°C, with a catalyst loading of 8g; before the start of the experimental test, N2 was introduced into the fixed bed reactor to discharge other gases in the reactor to avoid interference from other gases; then simulated flue gas was introduced for 8h; under the action of the CO and NH3 coupled denitration catalyst resistant to K poisoning, NO was reduced to N2 under the joint reduction of CO and NH3; the reacted gas was discharged into the atmosphere after absorbing unreacted NO and CO through a limestone solution, and the NO concentration at the inlet and outlet was detected by a flue gas analyzer, as shown in Table 2;

[0056] Table 2 NO removal efficiency of H-3.7Fe-7.6Mn / AC catalysts of this example and 3.7Fe-7.6Mn / AC catalysts of the comparative example

[0057]

[0058]

[0059] As can be seen from Table 2, the catalyst H-3.7Fe-7.6Mn / AC of this embodiment and the comparative example 3.7Fe-7.6Mn / AC were used to remove NO from flue gas at a temperature of 150-300°C. It was found that the catalyst of the embodiment had a high NO removal rate, and as time went by, the denitrification rate always remained highly efficient, and had strong resistance to K poisoning. The NO conversion rate of the corresponding catalysts after modification was significantly improved, and the NO conversion rate curve became flat, and the NO conversion rate decreased slowly.

[0060] Example 3: A method for preparing a CO and NH3 coupled denitration catalyst resistant to Na and / or K poisoning, the specific steps are as follows:

[0061] (1) Coconut shell activated carbon AC was washed with deionized water, then added to deionized water, ultrasonically treated at 70°C for 1.5h, solid-liquid separation was performed, and vacuum dried at 120°C for 48h to obtain pretreated coconut shell activated carbon;

[0062] (2) adding the coconut shell activated carbon pretreated in step (1) to 5 mol / L nitric acid, heating to 90° C. and reflux activation treatment for 2 h, cooling and washing with deionized water until the washing liquid is neutral, separating the solid and the liquid, and placing under vacuum drying at 120° C. for 48 h to obtain activated AC;

[0063] (3) adding the activated AC obtained in step (2) to a precursor solution (a mixed solution of Fe(NO3)3 and Mn(NO3)2), ultrasonically impregnating the mixture at 70°C for 3 h, stirring and impregnating the mixture at room temperature for 48 h, vacuum drying the mixture at 120°C for 48 h, and then calcining the mixture at 500°C in a nitrogen atmosphere for 5 h to obtain a Fe-Mn / AC catalyst (denoted as 3.9Fe-8.0Mn / AC); the Fe(NO3)3 concentration in the precursor solution was 2.0 mol / L; the Fe content by mass of the Fe element in the Fe-Mn / AC catalyst was 3.9%, and the Mn content by mass of the Mn element was 8.0%;

[0064] (4) adding Fe-Mn / AC catalyst to deionized water under microwave conditions and stirring uniformly to obtain Fe-Mn / AC catalyst suspension, slowly adding hydrogen peroxide to the Fe-Mn / AC catalyst suspension under stirring conditions at 90° C. and maintaining the reaction at a temperature of 100° C. for 2.0 h, cooling to room temperature after the reaction, separating the solid from the liquid, and calcining the solid at a temperature of 500° C. for 6 h to obtain Fe-Mn / AC catalyst resistant to Na and / or K poisoning (denoted as H-3.9Fe-8.0Mn / AC); the concentration of the Fe-Mn / AC catalyst suspension is 90 g / L, the volume ratio of hydrogen peroxide to the Fe-Mn / AC catalyst suspension is 1:5; the mass concentration of the hydrogen peroxide is 35%;

[0065] The CO and NH3 coupled denitrification catalysts resistant to Na and / or K poisoning of Examples 1 to 3 (Example 1 (H-3.5Fe-7.0Mn / AC), Example 2 (H-3.7Fe-7.6Mn / AC), Example 3 (H-3.9Fe-8.0Mn / AC)) and the corresponding catalysts of Comparative Example 1 (3.5Fe-7.0Mn / AC), Comparative Example 2 (3.7Fe-7.6Mn / AC), and Comparative Example 3 (3.9Fe-8.0Mn / AC) that were not treated with microwave hydrogen peroxide were used, and NH3+CO was used as a reducing agent. NO in flue gas containing K and Na (K content of 0.05%, Na content of 0.05%) was removed by coupling at 50-300°C, and the catalyst loading was 8g; before the start of the experimental test, N2 was introduced into the fixed bed reactor to discharge other gases in the reactor to avoid interference from other gases; then simulated flue gas was introduced for 8h; under the action of CO and NH3 coupled denitrification catalyst resistant to K and Na poisoning, NO was reduced to N2 under the joint reduction of CO and NH3; the gas after the reaction was discharged into the atmosphere after the unreacted NO and CO were absorbed by limestone solution, and the NO concentration at the inlet and outlet was detected by a flue gas analyzer, see Figure 1 and Table 3;

[0066] Table 3 DeNO efficiency of catalysts of Examples 1 to 3 and Comparative Examples 1 to 3

[0067] Time (h) Temperature(℃) Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 0 150 75.0％ 73.0％ 70.0％ 82.0％ 81.2％ 77.0％ 0.4 160 74.6％ 72.5％ 69.7％ 80.0％ 78.0％ 75.0％ 0.8 170 74.2％ 72.3％ 69.5％ 78.5％ 75.5％ 73.5％ 1.2 180 74.0％ 72.0％ 69.2％ 75.0％ 72.0％ 71.4％ 1.6 190 73.9％ 71.7％ 69.0％ 71.0％ 69.3％ 68.1％ 2.0 200 73.5％ 71.3％ 68.7％ 68.0％ 66.5％ 66.0％ 2.4 210 73.3％ 71.1％ 68.5％ 66.0％ 60.9％ 60.0％ 2.8 220 73.1％ 70.8％ 68.2％ 63.0％ 59.4％ 58.2％ 3.2 230 72.8％ 70.6％ 68.0％ 61.5％ 58.5％ 57.3％ 3.6 240 73.0％ 70.9％ 68.3％ 62.3％ 60.3％ 59.2％ 4.0 250 73.2％ 71.2％ 68.6％ 62.9％ 60.9％ 59.7％ 4.4 260 73.5％ 71.5％ 68.8％ 63.3％ 61.3％ 60.3％ 4.8 270 73.8％ 71.8％ 69.0％ 63.5％ 61.8％ 60.7％ 5.2 280 73.9％ 72.0％ 69.3％ 63.9％ 62.2％ 61.0％ 5.6 290 74.1％ 72.3％ 69.4％ 64.3％ 62.7％ 61.3％ 6.0 300 74.3％ 72.5％ 69.6％ 64.8％ 63.1％ 61.7％ 6.4 300 74.2％ 71.9％ 69.1％ 64.0％ 62.2％ 61.4％ 6.8 300 74.0％ 71.5％ 68.9％ 63.5％ 61.8％ 60.1％ 7.2 300 73.7％ 71.1％ 68.7％ 63.0％ 61.2％ 59.2％ 7.6 300 73.5％ 71.0％ 68.4％ 62.5％ 61.0％ 58.6％ 8.0 300 73.0％ 70.3％ 68.0％ 61.5％ 60.5％ 57.8％

[0068] from Figure 1 As can be seen from Table 3, the catalysts of Examples 1 to 3 and Comparative Examples 1 to 3 were used to remove NO from flue gas at a temperature of 150 to 300° C. It was found that the catalysts of the examples had a high NO removal rate, and as time went on, the denitration rate remained highly efficient, and had strong resistance to Na and K poisoning. The NO conversion rates of the corresponding catalysts after modification were significantly improved, and the NO conversion rate curve became flat, and the NO conversion rate decreased slowly;

[0069] SEM images of different catalysts after denitrification are shown in Figure 2 , wherein a to f are catalysts of Examples 1 to 3 and Comparative Examples 1 to 3, respectively, Figure 2 It can be seen that the presence of Na or K in the flue gas makes the catalyst surface rough and blocks the pores. Na and K make the catalyst surface seriously rough, seriously destroy the pore structure, and affect the pore development. After modification, the catalyst surface becomes obviously smooth and the pore development is uniform.

[0070] EDS diagrams after denitration with different catalysts are shown in Figure 3 , wherein a to f are catalysts of Examples 1 to 3 and Comparative Examples 1 to 3, respectively, Figure 3It can be seen that the presence of Na and / or K in the flue gas successfully attached Na and K elements to the catalyst, and Na2CO3 and K2CO3 were deposited on the catalyst surface; after modification, the deposited salt on the catalyst surface was reduced, and the content of Na and K elements was significantly reduced;

[0071] N2 adsorption-desorption curves and average pore size diagrams of different catalysts are shown in Figure 4 ,from Figure 4 It can be seen that the pore structure is almost not affected before and after modification;

[0072] XRD spectra of different catalysts are shown in Figure 5 ,from Figure 5 It can be seen that the presence of Na and / or K in the flue gas makes the catalyst contain the active component FeO x and MnO y The diffraction peak gradually weakened, and metal carbonate was generated; after modification, the active component contained FeO x and MnO y And the diffraction peak gradually strengthens;

[0073] XPS pictures of different catalysts are shown in Figure 6 ,from Figure 6 It can be seen that the presence of Na and / or K in the flue gas increases the content of low-valent Fe and Mn ions in the catalyst, which has a higher mobility O α The content gradually decreases; after modification, the content of high-valent Fe and Mn ions increases, and O α The content gradually increases;

[0074] FTIR spectra of different catalysts are shown in Figure 7 ,from Figure 7 It can be seen that the presence of Na and / or K in the flue gas reduces the number of oxygen-containing functional group carboxyl and lactone groups of the catalyst, and reduces the number of OH and C=O. After modification, the number of oxygen-containing functional group carboxyl and lactone groups increases.

[0075] The specific implementation modes of the present invention are described in detail above, but the present invention is not limited to the above implementation modes, and various changes can be made within the knowledge scope of ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. A CO and NH 2 solution resistant to Na and / or K poisoning 3 Method for preparing a catalyst for coupled denitration, It is characterized in that The specific steps are as follows: (1) Coconut shell activated carbon AC is washed with deionized water, then added into deionized water, ultrasonically treated at a temperature of 60 to 70° C., solid-liquid separation is performed, and vacuum drying is performed to obtain pretreated coconut shell activated carbon; (2) adding the coconut shell activated carbon pretreated in step (1) to nitric acid, heating to a temperature of 80-90° C. and reflux activation treatment for 2-3 h, cooling and washing with deionized water until neutral, solid-liquid separation, and vacuum drying to obtain activated AC; (3) adding the activated AC prepared in step (2) to the precursor solution, ultrasonically impregnating the mixture at a temperature of 60 to 70°C for 2 to 3 hours, stirring and impregnating the mixture at room temperature for 24 to 48 hours, vacuum drying, and then calcining the mixture at a temperature of 450 to 500°C in a nitrogen atmosphere for 4 to 5 hours to obtain a Fe-Mn / AC catalyst; the precursor solution is Fe(NO 3 ) 3 and Mn(NO 3 ) 2 A mixed solution; (4) The Fe-Mn / AC catalyst is added to deionized water under microwave conditions and stirred evenly to obtain a Fe-Mn / AC catalyst suspension. Under stirring conditions at a temperature of 80 to 90° C., hydrogen peroxide is slowly added to the Fe-Mn / AC catalyst suspension and the reaction is maintained at a temperature of 60 to 100° C. for 1.0 to 2.0 h. The catalyst is cooled to room temperature, the solid and the liquid are separated, and the solid is calcined at a temperature of 200 to 500° C. for 2 to 6 h to obtain a denitration catalyst resistant to Na and / or K poisoning.

2. The CO and NH according to claim 1 that are resistant to Na and / or K poisoning 3 Method for preparing a catalyst for coupled denitration, Features: The particle size of the coconut shell activated carbon AC in step (1) is 10 to 20 meshes.

3. The CO and NH according to claim 1 which are resistant to Na and / or K poisoning 3 Method for preparing a catalyst for coupled denitration, Features: The concentration of the nitric acid in step (1) is 4-5 mol / L.

4. The CO and NH according to claim 1 which are resistant to Na and / or K poisoning 3 Method for preparing a catalyst for coupled denitration, Features: Step (3) Fe(NO 3 ) 3 The concentration is 1.5-2.0 mol / L, and the mass content of Mn element is 2-2.5 times that of Fe element.

5. The CO and NH according to claim 1 which are resistant to Na and / or K poisoning 3 Method for preparing a catalyst for coupled denitration, Features: In step (3), the Fe-Mn / AC catalyst has an Fe content of 3.5-4.0% by mass and a Mn content of 7.0-8.0% by mass.

6. The CO and NH according to claim 1 which are resistant to Na and / or K poisoning 3 Method for preparing a catalyst for coupled denitration, Features: In step (4), under microwave conditions, the concentration of the Fe-Mn / AC catalyst suspension is 70-90 g / L, the volume ratio of hydrogen peroxide to the Fe-Mn / AC catalyst suspension is 1:5; and the mass concentration of the hydrogen peroxide is 25-35%.

7. Use of the catalyst prepared by the preparation method according to any one of claims 1 to 7 in removing NO from flue gas, Features: Flue gas contains Na and / or K, in the form of CO and NH 3 For mixed reducing agent, the NO removal temperature is 150-300℃.

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