Preparation method and application of CeCo / AC catalyst for removing NO by coupling CO and NH3 at low temperature

Abstract

The invention relates to a preparation method and application of a CeCo / AC catalyst for removing NO by coupling CO and NH3 at a low temperature, and belongs to the technical field of flue gas purification. An A-site doped carrier of the CeCo / AC catalyst is a Co / AC catalyst, A-site doped metal is Ce, the total mass of Co and the A-site doped metal Ce is 2-4% of the mass of the AC carrier, and the molar weight of Co accounts for 20-80% when the total molar weight of Co and the A-site doped metal Ce is 100%. According to the method, Ce is loaded to the Co / AC catalyst to realize A-site doping by adopting surface oxidation pretreatment, an impregnation method, microwave sintering and plasma surface treatment, so that NO is removed by coupling low-temperature CO and NH3, low-temperature activation is realized, and the low-temperature NO removal capability is improved. The catalyst provided by the invention has the characteristics of high NO removal efficiency, environmental protection, no pollution, developed catalyst void structure, good dispersibility of each metal oxide and the like.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a CeCo / AC catalyst for removing NO by coupling CO and NH3 at low temperature, belonging to the technical field of flue gas purification. Background Art

[0002] NO x It is not only easy to cause ecological problems such as smog, acid rain, ozone layer depletion, photochemical pollution, but also easy to cause health problems such as hypoxia of human tissue, emphysema, asthma, etc. According to statistics, the steel industry NO x The emissions account for about 8% of the total emissions in China, and the NO x It accounts for 45-65% of the total emissions in the steel industry. x The most effective and widely used technology is SCR technology, which uses NH3 or CO as a reducing agent to selectively reduce and remove NO. x Using NH3 as a reducing agent has a high NO conversion rate and low pollution, but NH3 itself is a toxic gas, which is expensive and prone to chemical accidents and pipeline corrosion. The advantage of choosing CO as a reducing agent is that CO itself exists in automobile exhaust and industrial waste gas. Using it as a reducing agent to treat NO x It can achieve waste treatment with waste, but it has some bottlenecks that are difficult to break through, such as how to achieve low-temperature activation, how to improve antioxidant capacity, etc. At present, there are studies on coupling the two gases for low-temperature denitrification. The advantage of coupling is that it can utilize the good reducing property of NH3 and the CO carried in the exhaust gas for denitrification, and it can also make up for the disadvantages of denitrification of the two gases separately.

[0003] Activated carbon (AC) is considered to be the most widely used adsorbent and catalyst carrier due to its large surface area, rich pore structure, and flexible working conditions. Among them, coconut shell activated carbon has a more developed pore structure and better adsorption performance, making it one of the most industrially valuable denitrification catalyst carriers at this stage. However, the existing activated carbon loaded with metal active components has a low temperature denitrification performance. x Poor activity to NO x The removal rate is low. Summary of the invention

[0004] Low-temperature removal of NO by existing activated carbon loaded with metal active components x Poor activity to NO xIn order to solve the problems of low removal rate of NO, the present invention provides a preparation method and application of a CeCo / AC catalyst for low-temperature CO and NH3 coupling removal of NO. With cheap coconut shell activated carbon as a primary carrier, Co is loaded on an activated carrier AC activated by a nitric acid solution, and the Co / AC catalyst is prepared by plasma surface treatment. The Co / AC catalyst is used as an A-site doping carrier to load A-site doped metal Ce, and the CeCo / AC catalyst is prepared by plasma surface treatment. The two reducing gases of CO and NH3 are used as mixed reducing agents to remove NO at 100-250°C, and the catalyst is used for the selective catalytic reduction of nitrogen oxides. The present invention solves the technical problems of low NO removal rate, difficulty in low-temperature activation, and short life of SCR process catalysts in existing flue gas removal of NO.

[0005] A method for preparing a CeCo / AC catalyst for coupling removal of NO by CO and NH3 at low temperature, wherein the A-site doping carrier of the CeCo / AC catalyst is a Co / AC catalyst, the A-site doping metal is Ce, the total mass of Co and the A-site doping metal Ce is 2-4% of the mass of the AC carrier, and the molar amount of Co accounts for 20-80% based on the total molar amount of Co and the A-site doping metal Ce as 100%;

[0006] The specific steps of the preparation method are as follows:

[0007] (1) The coconut shell activated carbon was washed with deionized water, then ultrasonically vibrated in a water bath at a temperature of 60 to 80° C. for 2 to 4 h, solid-liquid separation was performed, and the pretreated activated carbon AC was obtained by drying;

[0008] (2) adding the pretreated activated carbon AC into a HNO3 solution for surface oxidation activity treatment, then washing with deionized water until neutral, solid-liquid separation, and drying to obtain activated activated carbon HNO3 / AC;

[0009] (3) adding activated carbon HNO3 / AC to cobalt nitrate solution, immersing at 60-80°C for 2-4 hours, standing at room temperature for 24-48 hours, and then vacuum drying to obtain a Co / AC precursor;

[0010] (4) placing the Co / AC precursor in a microwave high temperature sintering furnace, uniformly heating the temperature to 450-470° C. and microwave vacuum sintering for 90-110 min, and then performing plasma surface treatment to obtain a Co / AC catalyst;

[0011] (5) adding the Co / AC catalyst as the A-site doping carrier into a cerium nitrate solution, immersing at a temperature of 60 to 80° C. for 2 to 4 hours, standing at room temperature for 24 to 48 hours, and then vacuum drying to obtain a CeCo / AC precursor;

[0012] (6) The CeCo / AC precursor is placed in a microwave high temperature sintering furnace, the temperature is uniformly raised to 450-470°C and microwave vacuum sintered for 90-110 min, and then the A-doped CeCo / AC catalyst is obtained by plasma surface treatment.

[0013] Preferably, in step (2), the concentration of the HNO3 solution is 4 to 6 mol / L, the temperature of the surface oxidation activation treatment is 80 to 90°C, and the time is 2 to 3 hours.

[0014] Preferably, the concentration of the cobalt nitrate solution in step (3) is 0.025-0.4 mol / L.

[0015] Preferably, in step (4) and step (6), the microwave power is 2-4 kW, the plasma surface treatment power is 200-300 W, the treatment time is 10-20 min, and the plasma discharge gas is a hydrogen-nitrogen mixture.

[0016] More preferably, the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixed gas is 1-2:10, and the flow rate of the hydrogen-nitrogen mixed gas is 10-14 ml / min.

[0017] Preferably, the concentration of the cerium nitrate solution in step (5) is 0.05 to 0.1 mol / L.

[0018] The CeCo / AC catalyst is used in the low-temperature coupling removal of NO by CO and NH3: the reducing gas is CO and NH3, and the temperature for removing NO is 100-250°C.

[0019] The NO removal performance test of CeCo / AC catalyst of the present invention:

[0020] (1) N2 was introduced to purge the A-site doped CeCo / AC catalyst, and the temperature of the NO removal fixed bed reactor was raised to 100 °C;

[0021] (2) The mixed flue gas (simulated gas) to be deNOxed is fed into a fixed bed reactor, the reaction temperature is controlled at 100-250°C, and the NO flow rate in the mixed flue gas (simulated gas) to be deNOxed is 4 ml min -1 (4×10 3 ppm), O2 volume concentration is 1.5% (volume ratio), 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 total flow rate of the mixed gas is 1000 ml min -1 (1×10 6ppm), N2 is the balance gas, CO and NH3 in the flue gas reduce NO to N2 gas under the action of CeCo / AC catalyst doped at the A site;

[0022] (3) The flue gas analyzer records various components in the flue gas before and after the NO removal process over the A-site doped CeCo / AC catalyst, and calculates the NO removal efficiency;

[0023] (4) The gas after the reaction is discharged into the atmosphere after the unreacted NO, CO and NH3 are absorbed by the limestone solution.

[0024] The present invention uses activated carbon activated by nitric acid surface oxidation pretreatment and modified by cobalt nitrate as a carrier to increase the specific surface area of ​​the catalyst, improve the internal pore volume and pore diameter of the activated carbon, and greatly increase the oxygen-containing functional groups on the surface of coconut shell activated carbon; the equal volume impregnation method can improve the dispersibility of Co and Ce elements on the catalyst surface, effectively reduce the agglomeration of metal oxides on the catalyst surface, thereby ensuring that it has a high NO removal activity; microwave sintering technology can enrich the pore structure of the catalyst and improve the uniformity of the dispersion of active components; plasma surface treatment can promote the transformation of the valence state of metal active components and generate more oxygen vacancies. The present invention prepares the A-site doped CeCo / AC catalyst by surface oxidation pretreatment-impregnation method-microwave sintering-plasma surface treatment, and its preparation process is simple, easy to operate, low energy consumption, environmentally friendly and pollution-free, high NO removal efficiency, and convenient for industrial promotion.

[0025] The beneficial effects of the present invention are:

[0026] (1) The present invention prepares an A-site doped CeCo / AC catalyst by loading the A-site doped metal Ce onto the Co / AC catalyst, which has good low-temperature NO removal activity; can realize the removal of NO at 100-250°C using two reducing gases, CO and NH3, as mixed reducing agents; can solve the technical problems of low NO removal rate, difficulty in low-temperature activation, and short life of the SCR process catalyst in the existing flue gas NO removal;

[0027] (2) The present invention uses activated carbon pre-treated with nitric acid surface oxidation and modified with cobalt nitrate as a carrier to increase the specific surface area of ​​the catalyst, improve the internal pore volume and pore diameter of the activated carbon, and significantly increase the oxygen-containing functional groups on the surface of coconut shell activated carbon; the equal volume impregnation method can improve the dispersion of Co and Ce elements on the catalyst surface, effectively reduce the agglomeration of metal oxides on the catalyst surface, thereby ensuring that it has a high NO removal activity; microwave sintering technology can enrich the pore structure of the catalyst and improve the uniformity of the dispersion of active components; plasma surface treatment can promote the transformation of the valence state of metal active components and generate more oxygen vacancies;

[0028] (3) The present invention uses CO and NH3 as a mixed reducing gas, which not only utilizes the good reducing property of NH3, but also utilizes the CO carried in the exhaust gas for denitrification. It can also make up for the shortcomings of the two gases when they are denitrified separately, such as weak low-temperature activation ability and antioxidant ability, so that the denitrification effect is better, and can provide a theoretical basis for the low-temperature and high-efficiency development of denitrification catalysts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The NO removal curve of CoCe / AC catalyst with different loading ratios at different temperatures in Example 1;

[0030] Figure 2 This is a diagram of the test device for the removal of NO activity by CoCe / AC catalyst;

[0031] Figure 3 The SEM and EDS mappings of the CoCe / AC catalysts with different loading ratios in Example 1;

[0032] Figure 4 The pore structure characteristics of the CoCe / AC catalyst with different loading ratios in Example 1: (a) N2 adsorption-desorption curve; (b) pore size distribution diagram;

[0033] Figure 5 The XRD spectra of CoCe / AC catalysts with different loading ratios in Example 1;

[0034] Figure 6 The XPS graphs of CoCe / AC catalysts with different loading ratios in Example 1;

[0035] Figure 7 FTIR spectra of CoCe / AC catalysts with different loading ratios in Example 1. DETAILED DESCRIPTION

[0036] 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.

[0037] The test device for the removal of NO by CoCe / AC catalyst in the embodiment of the present invention is shown in FIG. Figure 2 The catalytic reactor is a fixed bed reactor. The raw gas enters the reactor after preheating. The reaction temperature is 100-250℃, the total gas flow rate is 1000ml / min, and the GHSV is 30000h -1 ;

[0038] Simulated flue gas composition: NO flow rate is 4 ml min -1 (4×10 3 ppm), O2 volume concentration is 1.5% (volume ratio), 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), N2 is the balance gas, and the simulated flue gas is mixed and sent into the fixed bed reactor, and the gas flow is controlled by a rotor flowmeter;

[0039] 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;

[0040] The catalyst activity for NO removal was evaluated by NO conversion and N2 selectivity, and the calculation method is as follows:

[0041]

[0042] Where:

[0043] NO in ------NO concentration at reactor inlet, ppm.

[0044] NO out -----NO concentration at reactor outlet, ppm.

[0045] Example 1: The A-site doping carrier of the CeCo / AC catalyst in this example is a Co / AC catalyst, the A-site doping metal is Ce, the total mass of Co and the A-site doping metal Ce is 2% of the mass of the AC carrier, and the total molar amount of Co and the A-site doping metal Ce is 100%, and the molar amount of Co accounts for 20%, 50% and 80%, respectively, which are recorded as 2%Ce 0.8 Co 0.2 / AC catalyst, 2% Ce 0.5 Co 0.5 / AC catalyst, 2% Ce 0.2 Co 0.8 / AC catalyst;

[0046] A method for preparing a CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3, the specific steps are as follows:

[0047] (1) The coconut shell activated carbon was washed with deionized water for 7 times, then ultrasonically shaken in a water bath at 60°C for 2 h, solid-liquid separation was performed, and dried for 24 h to obtain pretreated activated carbon AC;

[0048] (2) adding the pretreated activated carbon AC to a HNO3 solution with a concentration of 4 mol / L, performing surface oxidation activity treatment at a temperature of 80°C for 2 h, then washing with deionized water until neutral, separating the solid and the liquid, and drying to obtain activated activated carbon HNO3 / AC;

[0049] (3) adding activated carbon HNO3 / AC to cobalt nitrate solutions with concentrations of 0.1 mol / L, 0.2 mol / L, and 0.025 mol / L, respectively, immersing at 60°C for 2 h, standing at room temperature for 24 h, and then vacuum drying at 110°C for 24 h to obtain a Co / AC precursor;

[0050] (4) The Co / AC precursor was placed in a microwave high temperature sintering furnace, the temperature was uniformly raised to 450°C and microwave vacuum sintered for 90 minutes, and then plasma surface treated for 10 minutes to obtain a Co / AC catalyst; the microwave power was 2 kW, the plasma surface treatment power was 200 W, the plasma discharge gas was a hydrogen-nitrogen mixture, the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture was 1:10, and the flow rate of the hydrogen-nitrogen mixture was 10 ml / min (1×10 4 ppm);

[0051] (5) adding the Co / AC catalyst as the A-site doping carrier into cerium nitrate solutions with concentrations of 0.1 mol / L, 0.05 mol / L, and 0.1 mol / L, respectively, according to the cerium doping amount, immersing at 60°C for 2 h, standing at room temperature for 24 h, and then vacuum drying at 110°C for 24 h to obtain a CeCo / AC precursor;

[0052] (6) The CeCo / AC precursor was placed in a microwave high temperature sintering furnace, the temperature was uniformly raised to 450°C and microwave vacuum sintered for 90 min, and then plasma surface treated for 10 min to obtain the A-doped CeCo / AC catalyst, which was recorded as 2% Ce and 2% AC. 0.8 Co 0.2 / AC catalyst, 2% Ce 0.5 Co 0.5 / AC catalyst, 2% Ce 0.2 Co 0.8 / AC catalyst; the microwave power is 2KW, the plasma surface treatment power is 200W, the plasma discharge gas is a hydrogen-nitrogen mixture, the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture is 1:10, and the flow rate of the hydrogen-nitrogen mixture is 10ml / min (1×10 4 ppm);

[0053] SEM and EDS mappings of CoCe / AC catalysts with different loading ratios are shown in Figure 3 ; Pore structure characteristics of CoCe / AC catalysts with different loading ratios: (a) N2 adsorption-desorption curve; (b) pore size distribution diagram Figure 4 ; XRD spectra of CoCe / AC catalysts with different loading ratios are shown in Figure 5 ; XPS graphs of CoCe / AC catalysts with different loading ratios are shown in Figure 6 ; FTIR spectra of CoCe / AC catalysts with different loading ratios are shown in Figure 7 ,from Figure 3-7 It can be seen that as the Ce doping ratio increases, the tensile force exerted by Ce on the metal oxide grain boundary inhibits grain growth, thereby refining the grains and improving dispersion, as inferred from the Scherrer formula; the average pore size is negatively correlated with the Ce doping amount; according to the Braggs equation, Ce doping expands the CoO 1.29 and Ce2Co 17 Lattice structure; Ce 3+ Inducing charge imbalance to generate more oxygen vacancies and chemically adsorbed oxygen, however, the excess Ce in the reduced state 3+ It will inhibit the generation of oxygen vacancies and chemically adsorbed oxygen. As the Co doping ratio increases, the increase of CoO causes the pores to collapse and expand the pore size; 2+ Co 3+ -O-Ce 3+ Ion pair substitution can promote low-temperature SCR reaction;

[0054] In this embodiment, CeCo / AC catalysts with different A-site doping were used for NO removal reaction at 100-250°C, and the catalyst loading amount was 8g. Before 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, NO in the simulated flue gas was introduced for 1h to allow the low-temperature CO and NH3 to couple the A-site doped CeCo / AC catalyst for NO removal to adsorb NO to saturation, thereby reducing experimental errors.

[0055] The total flow rate of simulated gas is 1000ml / min, and the GHSV is 30000h -1 , NO flow rate is 4 ml min -1 (4×10 3 ppm), O2 volume concentration is 1.5% (volume ratio), 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), N2 is the balance gas; after the simulated gas is mixed in the gas mixing box, it is sent to the fixed bed reactor, and under the action of the A-site doped CeCo / AC catalyst for low-temperature CO+NH3 coupling to remove NO, the mixed reductant of CO and NH3 reduces NO to N2. The gas after the reaction is discharged into the atmosphere after the unreacted NO, CO, and NH3 are absorbed by the limestone solution, and the NO concentration at the inlet and outlet is detected by a flue gas analyzer;

[0056] The NO removal efficiencies of A-site doped CeCo / AC catalysts with different Co molar contents are shown in Tables 1 and Figure 1 ,

[0057] Table 1 NO removal efficiency of A-site doped CeCo / AC catalysts with different Co molar contents

[0058] Temperature(℃) <![CDATA[2%Ce 0.8 Co 0.2 / AC Catalyst]]> <![CDATA[2%Ce 0.5 Co 0.5 / AC Catalyst]]> <![CDATA[2%Ce 0.2 Co 0.8 / AC Catalyst]]> 100 70 89 92 110 68 77 85 120 67 76 84 130 59 74 82 140 58 74 82 150 55 71 80 160 54 70 80 170 54 70 80 180 53 69 77 190 49 65 73 200 44 60 69 210 42 60 68 220 40 60 66 230 38 60 64 240 42 63 71 250 43 66 73

[0059] From Table 1 and Figure 1 It can be seen that under the same temperature conditions, Ce 0.2 Co 0.8 / AC catalyst has the highest activity in coupling removal of NO by CO and NH3. Figure 3-Figure 7 Characterization shows that its larger specific surface area and total pore volume provide more active sites for NO removal, more oxygen vacancies promote the adsorption and activation of reactive gases, higher mobility of chemically adsorbed oxygen and more strongly oxidizing Co 3+ Promote SCR reaction. Co and Ce have a synergistic effect, which not only makes the catalyst produce more metal ion channels, but also -Ce-O-Co- solid solution transfers from metal ions, enhances the electronic interaction between components, facilitates electron migration, and promotes SCR reaction.

[0060] Example 2: The A-site doping carrier of the CeCo / AC catalyst in this example is a Co / AC catalyst, the A-site doping metal is Ce, and the total mass of Co and the A-site doping metal Ce is 2%, 3%, and 4% of the mass of the AC carrier, respectively. Taking the total molar amount of Co and the A-site doping metal Ce as 100%, the molar amount of Co accounts for 80%, which is recorded as 2%Ce, respectively. 0.2 Co 0.8 / AC catalyst, 3% Ce 0.2 Co 0.8 / AC catalyst, 4% Ce 0.2 Co 0.8 / AC catalyst;

[0061] A method for preparing a CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3, the specific steps are as follows:

[0062] (1) The coconut shell activated carbon was washed with deionized water for 7 times, then ultrasonically shaken in a water bath at 70°C for 3 h, solid-liquid separation was performed, and dried for 24 h to obtain pretreated activated carbon AC;

[0063] (2) adding the pretreated activated carbon AC to a HNO3 solution with a concentration of 5 mol / L, performing surface oxidation activity treatment at a temperature of 85°C for 2.5 h, then washing with deionized water until neutral, separating the solid from the liquid, and drying to obtain activated activated carbon HNO3 / AC;

[0064] (3) adding the activated carbon HNO3 / AC to cobalt nitrate solutions with concentrations of 0.2 mol / L, 0.3 mol / L, and 0.4 mol / L, respectively, immersing at 70°C for 3 h, standing at room temperature for 36 h, and then vacuum drying at 120°C for 24 h to obtain a Co / AC precursor;

[0065] (4) placing the Co / AC precursor in a microwave high-temperature sintering furnace, uniformly heating the temperature to 460°C and microwave vacuum sintering for 100 minutes, and then subjecting the precursor to plasma surface treatment for 15 minutes to obtain a Co / AC catalyst; the microwave power is 3KW, the plasma surface treatment power is 250W, the plasma discharge gas is a hydrogen-nitrogen mixture, the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture is 1.5:10, and the flow rate of the hydrogen-nitrogen mixture is 12ml / min;

[0066] (5) adding the Co / AC catalyst as the A-site doping carrier into cerium nitrate solutions with concentrations of 0.05 mol / L, 0.08 mol / L, and 0.1 mol / L according to the cerium doping amount, immersing at 70°C for 3 h, standing at room temperature for 36 h, and then vacuum drying at 110°C for 24 h to obtain a CeCo / AC precursor;

[0067] (6) placing the CeCo / AC precursor in a microwave high-temperature sintering furnace, uniformly heating the temperature to 460°C and microwave vacuum sintering for 100 min, and then subjecting the precursor to plasma surface treatment for 15 min to obtain an A-doped CeCo / AC catalyst; the microwave power is 3 KW, the plasma surface treatment power is 250 W, the plasma discharge gas is a hydrogen-nitrogen mixture, and the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture is 1.5:10;

[0068] In this embodiment, CeCo / AC catalysts with different total CeCo contents were used for NO removal reaction at 100-250°C, and the catalyst loading was 8g. Before 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, NO in the simulated flue gas was introduced for 1h to allow the low-temperature CO and NH3 to couple and remove NO to the A-site doped CeCo / AC catalyst to adsorb NO to saturation, thereby reducing experimental errors.

[0069] The total flow rate of simulated gas is 1000ml / min, and the GHSV is 30000h -1 , NO flow rate is 4 ml min -1 (4×10 3 ppm), O2 volume concentration is 1.5% (volume ratio), and the flow rate of reducing gas NH3 is 4 ml min -1 (4×10 3ppm), the reducing gas CO flow rate is 16 ml min -1 (1.6×10 4 ppm), N2 is the balance gas; after the simulated gas is mixed in the gas mixing box, it is sent to the fixed bed reactor, and under the action of the A-site doped CeCo / AC catalyst for low-temperature CO+NH3 coupling to remove NO, the mixed reductant of CO and NH3 reduces NO to N2. The gas after the reaction is discharged into the atmosphere after the unreacted NO, CO, and NH3 are absorbed by the limestone solution, and the NO concentration at the inlet and outlet is detected by a flue gas analyzer;

[0070] The NO removal efficiency of A-site doped CeCo / AC catalysts with different total CeCo contents is shown in Table 2.

[0071] Table 2 NO removal efficiency of A-site doped CeCo / AC catalysts with different Co molar contents

[0072]

[0073]

[0074] From Table 2, we can see that under the same temperature conditions, 4% Ce 0.2 Co 0.8 / AC catalyst has the highest activity for coupling removal of NO by CO and NH3, and 2% Ce 0.2 Co 0.8 The CO and NH3 coupling removal of NO by the / AC catalyst is the lowest, indicating that Co and A-site doping with metal Ce can improve the denitrification performance of the catalyst, but the total loading mass of Co and A-site doped with metal Ce is too small, which is not conducive to catalyst modification and hinders the SCR reaction.

[0075] Example 3: The A-site doping carrier of the CeCo / AC catalyst of this example is a Co / AC catalyst, the A-site doping metal is Ce, the total mass of Co and the A-site doping metal Ce is 4% of the mass of the AC carrier, and the total molar amount of Co and the A-site doping metal Ce is 100%, and the molar amount of Co accounts for 80%;

[0076] A method for preparing a CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3, the specific steps are as follows:

[0077] (1) The coconut shell activated carbon was washed with deionized water for 8 times, then ultrasonically shaken in a water bath at 80°C for 4 h, solid-liquid separation was performed, and dried for 24 h to obtain pretreated activated carbon AC;

[0078] (2) adding the pretreated activated carbon AC to a HNO3 solution with a concentration of 6 mol / L, performing surface oxidation activity treatment at a temperature of 90°C for 3 h, then washing with deionized water until neutral, separating the solid from the liquid, and drying to obtain activated activated carbon HNO3 / AC;

[0079] (3) adding the activated carbon HNO3 / AC to a cobalt nitrate solution with a concentration of 0.4 mol / L, immersing at 80°C for 4 h, standing at room temperature for 48 h, and then vacuum drying at 120°C for 24 h to obtain a Co / AC precursor;

[0080] (4) placing the Co / AC precursor in a microwave high-temperature sintering furnace, uniformly heating the temperature to 470°C and microwave vacuum sintering for 110 min, and then subjecting the precursor to plasma surface treatment for 10 min, 15 min, and 20 min, respectively, to obtain a Co / AC catalyst; the microwave power is 4 kW, the plasma surface treatment power is 300 W, the plasma discharge gas is a hydrogen-nitrogen mixture, the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture is 2:10, and the flow rate of the hydrogen-nitrogen mixture is 14 ml / min;

[0081] (5) adding the Co / AC catalyst as the A-site doping carrier into a 0.1 mol / L cerium nitrate solution, immersing at 80°C for 4 h, standing at room temperature for 48 h, and then vacuum drying at 110°C for 24 h to obtain a CeCo / AC precursor;

[0082] (6) placing the CeCo / AC precursor in a microwave high-temperature sintering furnace, uniformly heating the temperature to 470°C and microwave vacuum sintering for 110 min, and then subjecting the precursor to plasma surface treatment for 10 min, 15 min, and 20 min, respectively, to obtain an A-doped CeCo / AC catalyst; the microwave power is 4 kW, the plasma surface treatment power is 300 W, the plasma discharge gas is a hydrogen-nitrogen mixture, and the volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixture is 2:10;

[0083] The CeCo / AC catalysts with different plasma surface treatment times are listed in Table 3;

[0084]

[0085] In this embodiment, CeCo / AC catalysts with different plasma surface treatment times were subjected to NO removal reaction at 100-250°C, and the catalyst loading amount was 8g. Before 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, NO in the simulated flue gas was introduced for 1h to allow low-temperature CO and NH3 to couple and remove NO to the A-site doped CeCo / AC catalyst to adsorb NO to saturation, thereby reducing experimental errors.

[0086] The total flow rate of simulated gas is 1000ml / min, and the GHSV is 30000h -1 , NO flow rate is 4 ml min -1 (4×10 3 ppm), O2 volume concentration is 1.5% (volume ratio), 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), N2 is the balance gas; after the simulated gas is mixed in the gas mixing box, it is sent to the fixed bed reactor, and under the action of the A-site doped CeCo / AC catalyst for low-temperature CO+NH3 coupling to remove NO, the mixed reductant of CO and NH3 reduces NO to N2. The gas after the reaction is discharged into the atmosphere after the unreacted NO, CO, and NH3 are absorbed by the limestone solution, and the NO concentration at the inlet and outlet is detected by a flue gas analyzer;

[0087] The NO removal efficiency of A-site doped CeCo / AC catalysts with different plasma surface treatment times is shown in Table 4.

[0088] Table 4 NO removal efficiency of A-site doped CeCo / AC catalysts with different plasma surface treatment times

[0089]

[0090]

[0091] It can be seen from Table 4 that under the same temperature conditions, the CO and NH3 coupling removal of NO activity of CeCo / AC (20,20) catalyst is the highest, and the CO and NH3 coupling removal of NO activity of CeCo / AC (10,10) catalyst is the lowest, indicating that plasma surface treatment can improve the NO removal efficiency of the catalyst, but too short plasma surface treatment time is not conducive to catalyst modification and hinders the SCR reaction.

[0092] 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 method for preparing a CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3, characterized in that: The A-site doping carrier of the CeCo / AC catalyst is a Co / AC catalyst, the A-site doping metal is Ce, the total mass of Co and the A-site doping metal Ce is 2-4% of the mass of the AC carrier, and the molar amount of Co accounts for 20-80% based on the total molar amount of Co and the A-site doping metal Ce as 100%; The specific steps of the preparation method are as follows: (1) The coconut shell activated carbon was washed with deionized water, then ultrasonically vibrated in a water bath at a temperature of 60 to 80° C. for 2 to 4 h, solid-liquid separation was performed, and the pretreated activated carbon AC was obtained by drying; (2) adding the pretreated activated carbon AC into HNO3 solution for surface oxidation activity treatment, then washing with deionized water until neutral, solid-liquid separation, and drying to obtain activated activated carbon HNO3 / AC; (3) adding activated carbon HNO3 / AC to a cobalt nitrate solution, immersing at a temperature of 60 to 80°C for 2 to 4 hours, standing at room temperature for 24 to 48 hours, and then vacuum drying to obtain a Co / AC precursor; (4) placing the Co / AC precursor in a microwave high temperature sintering furnace, uniformly heating the temperature to 450-470° C. and microwave vacuum sintering for 90-110 min, and then performing plasma surface treatment to obtain a Co / AC catalyst; (5) adding the Co / AC catalyst as the A-site doping carrier into a cerium nitrate solution, immersing at a temperature of 60 to 80° C. for 2 to 4 hours, standing at room temperature for 24 to 48 hours, and then vacuum drying to obtain a CeCo / AC precursor; (6) The CeCo / AC precursor is placed in a microwave high temperature sintering furnace, the temperature is uniformly raised to 450-470°C and microwave vacuum sintered for 90-110 min, and then the A-doped CeCo / AC catalyst is obtained by plasma surface treatment.

2. The method for preparing the CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3 according to claim 1, characterized in that: Step (2) The concentration of HNO3 solution is 4-6 mol / L, the temperature of surface oxidation activation treatment is 80-90°C, and the time is 2-3h.

3. The method for preparing the CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3 according to claim 1, characterized in that: The concentration of the cobalt nitrate solution in step (3) is 0.025-0.4 mol / L.

4. The method for preparing the CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3 according to claim 1, characterized in that: In step (4) and step (6), the microwave power is 2-4 KW, the plasma surface treatment power is 200-300 W, the time is 10-20 min, and the plasma discharge gas is a hydrogen-nitrogen mixed gas.

5. The method for preparing the CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3 according to claim 4, characterized in that: The volume ratio of hydrogen to nitrogen in the hydrogen-nitrogen mixed gas is 1-2:10, and the flow rate of the hydrogen-nitrogen mixed gas is 10-14 ml / min.

6. The method for preparing the CeCo / AC catalyst for coupling removal of NO by low-temperature CO and NH3 according to claim 1, characterized in that: The concentration of the cerium nitrate solution in step (5) is 0.05-0.1 mol / L.

7. Application of the CeCo / AC catalyst prepared by the preparation method according to any one of claims 1 to 6 in the coupling removal of NO by CO and NH3 at low temperature, characterized in that: The reducing gas is CO and NH3, and the temperature for removing NO is 100-250°C.

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