A coce / ac@siO2 catalyst for low-temperature oxidation of co and reduction of no and a preparation method and application thereof

Abstract

The application relates to a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO and a preparation method and application thereof, and belongs to the technical field of flue gas purification. The application constructs an AC@SiO2 double-carrier structure with AC (coconut shell activated carbon) as a core and SiO2 as a shell, and CoO x and CeO y are loaded on the AC@SiO2 to form a CoCe / AC@SiO2 catalyst, the total mass of Co and Ce elements in the active component accounts for 2-4% of the AC, the mole amount of Co accounts for 20-80% of the total mole amount of Co and Ce, which is 100%. The SiO2 is coated on the AC through an ethanol activation pretreatment-impregnation method-Joule flash rapid activation-plasma surface treatment, and then Co and Ce are loaded on the AC@SiO2 through an impregnation method-steam synergistic calcination activation method to realize synchronous removal of CO and NO at low temperature. The application constructs a bifunctional catalyst by taking AC as a skeleton structure and a reactant enrichment platform, taking the SiO2 layer to regulate the microenvironment of the active center and the mass transfer of the reactant, and taking Co and Ce reaction sites, realizes coupling of two reactions of CO catalytic oxidation and NO catalytic reduction, and efficiently removes CO and NO and is environment-friendly and pollution-free.

Description

Technical Field

[0001] This invention relates to a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, its preparation method and application, belonging to the field of flue gas purification technology. Background Technology

[0002] Currently, efforts are underway to eliminate NO from sintering flue gas. x Commonly used technologies for CO and NO removal include CO selective catalytic reduction of NO (CO-SCR) and CO selective catalytic oxidation (CO-SCO). Among these, CO-SCR technology can separate CO and NO. x Simultaneous removal and conversion of CO2 and N2, while CO-SCO is suitable for treating low-concentration CO, boasting advantages such as low reaction temperature and high oxidation efficiency, making it one of the most economical and efficient emission reduction technologies. If CO-SCR and CO-SCO technologies can be applied synergistically, waste-to-waste treatment can be achieved, eliminating secondary pollution.

[0003] To achieve the synergistic application of CO-SCR and CO-SCO technologies, it is necessary to develop technologies that combine NO... x This composite catalyst exhibits dual functionalities of selective reduction and CO catalytic oxidation, and its structure includes a porous support and highly efficient active components. Activated carbon (AC) is used in the field of environmental catalysis for the removal of NO. x Activated carbon is the most widely used carrier material for CO, SO2, and VOCs. It boasts advantages such as low cost, flexible operating conditions, high specific surface area, and well-developed pore structure. In particular, coconut shell-based activated carbon, with its unique honeycomb pore structure and excellent adsorption performance, has demonstrated outstanding performance in the treatment of multiple pollutants in industrial flue gas and has become the preferred carrier for industrial applications. However, unmodified activated carbon is limited by micropore mass transfer resistance and insufficient surface active sites, resulting in poor dispersion of active metals and unsatisfactory CO and NO removal effects. Summary of the Invention

[0004] Low-temperature NO removal using existing activated carbon-supported metal active components x It has poor activity with CO and is less effective against NO. x To address the problems of low CO removal rates, this invention provides a CoCe / AC@SiO2 catalyst for low-temperature CO oxidation and NO reduction, along with its preparation method and application. Using inexpensive coconut shell activated carbon (AC) as a carrier, SiO2 is coated onto AC through ethanol activation pretreatment, impregnation, Joule flash rapid activation, and plasma surface treatment. Co and Ce are then loaded onto AC@SiO2 via impregnation and steam co-calcination activation to obtain the CoCe / AC@SiO2 catalyst, achieving simultaneous CO and NO removal at 100-250℃. This solves the problem of low-temperature NO removal from existing flue gas methods. x It has poor activity with CO and is less effective against NO. xThis invention addresses issues such as low CO removal rates. The CoCe / AC@SiO2 catalyst utilizes AC as a framework structure and reactant enrichment platform, and SiO2 layers to regulate the microenvironment of the active center and reactant mass transfer. It constructs a bifunctional catalyst by integrating Co and Ce reaction sites, achieving the coupling of CO catalytic oxidation and NO catalytic reduction. This not only efficiently removes both CO and NO simultaneously but is also environmentally friendly and pollution-free.

[0005] A method for preparing a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, wherein the CoCe / AC@SiO2 catalyst has a dual-support structure of AC@SiO2 with coconut shell activated carbon (AC) as the core and SiO2 as the shell, and the active component is CoO2. x and CeO y A CoCe / AC@SiO2 catalyst is formed on the surface of the AC@SiO2 dual-support structure. The total mass of Co and Ce elements in the active component accounts for 2-4% of AC. With the total molar amount of Co and Ce as 100%, the molar amount of Co accounts for 20%-80%.

[0006] The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO includes the following specific steps: (1) Coconut shell activated carbon AC was washed with deionized water, placed in a water bath at 60~80℃ for ultrasonic treatment for 2~4h, solid-liquid separation was performed, and dried to obtain pretreated coconut shell activated carbon AC. (2) The pretreated coconut shell activated carbon AC was added to an ethanol solution for surface activation treatment, solid-liquid separation, and drying to obtain activated coconut shell activated carbon C2H5OH / AC; (3) Add activated coconut shell activated carbon C2H5OH / AC to SiO2 solution, ultrasonically impregnate at 80~90℃ for 2~4h, then let stand at room temperature for 24~36h, and vacuum dry to obtain AC@SiO2 precursor; (4) The AC@SiO2 precursor is placed in a Joule thermal flash evaporation device and heated to 1600~1700℃ for Joule thermal flash evaporation treatment to activate AC@SiO2 at high temperature. Then, the AC@SiO2 catalyst is obtained by plasma surface treatment. (5) Add the AC@SiO2 catalyst to a cerium nitrate-cobalt nitrate mixed solution, ultrasonically impregnate at 80~90℃ for 2~4h, then let it stand at room temperature for 24~36h, and vacuum dry to obtain CoCe / AC@SiO2 precursor; (6) The CoCe / AC@SiO2 precursor is heated at a constant rate to 500~600℃ and activated by steam for 30~40min to obtain the CoCe / AC@SiO2 catalyst.

[0007] Preferably, the surface activation treatment in step (2) is carried out at a temperature of 80~90℃ for 2~4h.

[0008] Preferably, the concentration of the SiO2 solution in step (3) is 0.5~0.8 mol / L, and the mass ratio of SiO2 to coconut shell activated carbon AC in step (1) is 3%~5%.

[0009] Preferably, the peak voltage of the Joule heat flash treatment in step (4) is 200~300V, the instantaneous current is 300~400A, and the time is 500~600ms.

[0010] Preferably, in step (4), the plasma surface treatment power is 300~400W, the time is 20~30min, and the plasma discharge gas is a hydrogen-nitrogen mixture.

[0011] More preferably, the volume of hydrogen in the hydrogen-nitrogen mixture is 10-20%, and the flow rate of the hydrogen-nitrogen mixture is 13-15 ml / min.

[0012] Preferably, in step (5), the concentration of cerium nitrate in the cobalt nitrate-cerium nitrate mixed solution is 0.05~0.09 mol / L, and the concentration of cobalt nitrate is 0.025~0.075 mol / L.

[0013] Preferably, the steam introduction rate in step (6) is 35~39 ml / min.

[0014] The CoCe / AC@SiO2 catalyst of this invention can be used for low-temperature catalytic removal of CO and NO from flue gas, with a catalytic removal temperature of 100~250℃.

[0015] The present invention provides a method for testing the CO and NO removal performance of the CoCe / AC@SiO2 catalyst: (1) N2 was introduced to purge the CoCe / AC@SiO2 catalyst, while the temperature of the CO+NO removal fixed-bed reactor was raised to 100℃. (2) The mixed flue gas (simulated gas) from which CO and NO are to be removed is fed into a fixed-bed reactor, and the reaction temperature is controlled at 100-250℃. The NO flow rate in the mixed flue gas (simulated gas) from which CO and NO are to be removed is 2.4 ml·min. -1 (2.4×10 3 ppm), O2 volume concentration 10% (volume ratio), CO flow rate 4 ml·min -1 (4×10 3 ppm), the total flow rate of the mixed gas is 1000 ml·min -1 (1×10 6(ppm), N2 is the equilibrium gas. In the flue gas, CO + NO will oxidize CO to CO2 and reduce NO to N2 gas under the action of different CoCe / AC@SiO2 catalysts. (3) Before and after the process of removing CO+NO from the flue gas by different CoCe / AC@SiO2 catalysts, the flue gas analyzer recorded the various components in the flue gas and calculated the efficiency of CO+NO removal. (4) The gas after the reaction is released into the atmosphere after the unreacted CO and NO are absorbed by the limestone solution.

[0016] The principle of using the CoCe / AC@SiO2 catalyst of this invention for the low-temperature catalytic removal of CO and NO from flue gas is as follows: This invention encapsulates SiO2 onto AC via ethanol activation pretreatment, impregnation, Joule flash rapid activation, and plasma surface treatment. Then, Co and Ce are loaded onto AC@SiO2 via impregnation and steam synergistic calcination activation to prepare a CoCe / AC@SiO2 catalyst for CO oxidation and NO reduction.

[0017] Pretreatment of coconut shell activated carbon with an ethanol-water solution can enhance the performance of the support through a dual effect of hydroxylation modification and pore regulation: the polar functional groups introduced by ethanol molecules on the activated carbon surface can form strong coordination bonds with metal active components, inhibiting the migration and aggregation of metal particles during high-temperature reactions, and significantly enhancing the catalyst's anti-sintering ability and stability; simultaneously, the ethanol etching effect can precisely regulate the pore structure of activated carbon, forming a microenvironment suitable for the transport of carbon intermediates, and the surface functional groups can also serve as anchoring sites for carbon species, greatly improving the selectivity of carbon-based reactions. This pretreatment process requires no special equipment, is compatible with various carbon-based supports, and provides broad adaptability of active sites for different catalytic systems.

[0018] When loading Co and Ce elements using the equal-volume impregnation method, a highly dispersed loading of active components can be achieved through a stepwise impregnation-calcination process. Moreover, this process is simple to operate and can be mass-produced with only conventional equipment, significantly reducing the cost of catalyst preparation.

[0019] By applying a high instantaneous current to the catalyst precursor using a pulsed power supply, ultrafast non-equilibrium activation is achieved through the Joule heating effect: the instantaneous high temperature causes the precursor to decompose rapidly, while simultaneously inhibiting the ordered arrangement of atoms, forming a large number of amorphous metal oxide phases, which significantly increases the specific surface area of ​​the material; the thermal stress generated during the rapid heating-cooling process can introduce high-density defect structures on the material surface, and these defects can serve as active centers for the catalytic reaction, significantly increasing the reaction rate; the metastable structure formed by flash activation can exist stably at room temperature for a long time, and can dynamically transform into a more active crystalline phase during the reaction, providing a guarantee for the long-term stability of catalytic performance.

[0020] Plasma is used to treat the surface of the catalyst, and the surface structure is regulated by bombardment of high-energy particles and etching of active species: high-energy electrons in the plasma can promote the valence state transformation of the metal active components and enhance the redox ability of the catalyst; at the same time, active oxygen species in the plasma can react with lattice oxygen on the catalyst surface to form a large number of oxygen vacancies, which significantly promotes the adsorption and activation of reactant molecules. After plasma treatment, the low-temperature activity of the catalyst is greatly improved, and it can still maintain high activity stability after long-term continuous reaction.

[0021] High-temperature treatment of catalysts using water vapor as an activator can construct a rich mesoporous structure through etching, while introducing hydroxyl functional groups to lower the adsorption energy barrier of reactant molecules and significantly improve the low-temperature activity of the catalyst. The reaction between water vapor and carbon species on the catalyst surface can form a carbon nanotube framework, which inhibits the migration and aggregation of metal particles in high-temperature reactions and enhances the catalyst's resistance to sintering. After activation, the number of active oxygen species on the catalyst surface is greatly increased, which can efficiently promote the conversion and removal of pollutants and exhibit excellent treatment efficiency in waste gas purification reactions.

[0022] The beneficial effects of this invention are: (1) The CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO of the present invention exhibits excellent synergistic removal activity of CO and NO in the low-temperature range of 100~250℃, which can solve the problem of low-temperature NO removal by existing activated carbon-supported metal active components. x It has poor activity with CO and is less effective against NO. x Problems such as low CO removal rate; (2) The present invention uses coconut shell activated carbon pretreated with ethanol as a support, which can significantly improve the catalyst’s anti-sintering ability, reaction stability and selectivity for reactions involving carbon intermediates. The process is simplified and applicable to a variety of support systems. The impregnation method can improve the dispersion of Co and Ce elements on the catalyst surface. The operation is simple and the equipment requirements are low. Joule flash evaporation rapid activation directly applies instantaneous high current to the catalyst precursor, which can create a large number of unique active structures with amorphous, high defect and metastable states. Plasma surface treatment can promote the transformation of the valence state of metal active components and generate more oxygen vacancies. Water vapor activation can significantly improve the low-temperature activity and stability of the catalyst, reduce the reaction temperature, optimize surface oxygen species, enhance anti-sintering ability and improve CO and NO removal efficiency. (3) This invention synergizes with CO-SCR (simultaneously removes CO and NO) x It can be converted into CO2 and N2) and CO-SCO (which treats low concentrations of CO, and has the characteristics of low reaction temperature and high oxidation rate), which can realize waste treatment and avoid secondary pollution. Attached Figure Description

[0023] Figure 1The graphs show the CO and NO removal curves of the CoCe / AC@SiO2 catalysts in Examples 1-3. Figure 2 SEM images of the CoCe / AC@SiO2 catalysts in Examples 1-3; Figure 3 The nitrogen adsorption-desorption curves of the CoCe / AC@SiO2 catalysts in Examples 1-3 are shown. Figure 4 XRD patterns of CoCe / AC@SiO2 catalysts in Examples 1-3; Figure 5 The images show the FTIR spectra of the CoCe / AC@SiO2 catalysts in Examples 1-3. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0025] In this embodiment of the invention, the catalytic reactor is a fixed-bed reactor, the water bubbler temperature is 27°C, the feed gas is preheated before entering the reactor, the reaction temperature is 100~250°C, the total gas flow rate is 1000 ml / min, and the GHSV is 30000 h⁻¹. -1 ; Simulated flue gas composition: NO flow rate 2.4 ml·min -1 (2.4×10 3 ppm), O2 volume concentration 10% (volume ratio), CO flow rate 4 ml·min -1 (4×10 3 (ppm), N2 is the balance gas, and the simulated flue gas is mixed and fed into the fixed bed reactor. The gas flow rate is controlled by a rotor flow meter. The purity of CO, NO, N2, and O2 used in this invention is 99.99%. The activity of the catalyst in removing CO and NO was evaluated using CO conversion and NO conversion rates, calculated as follows: (1) (2) In the formula: ------CO concentration at reactor inlet, ppm; -----Reactor outlet CO concentration, ppm; ------NO concentration at reactor inlet, ppm; -----NO concentration at reactor outlet, ppm; This invention relates to a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO. The catalyst has an AC@SiO2 dual-support structure with coconut shell activated carbon (AC) as the core and SiO2 as the shell. The active component is CoO2. x and CeO y A CoCe / AC@SiO2 catalyst is formed on the surface of the AC@SiO2 dual-support structure.

[0026] Example 1: In this example, the total mass of Co and Ce elements in the active components accounts for 2% of AC. Taking the total molar amount of Co and Ce as 100%, Co accounts for 20% and Ce accounts for 80%, denoted as Co. 0.2 Ce 0.8 / AC@SiO2 catalyst; A method for preparing a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, the specific steps of which are as follows: (1) Coconut shell activated carbon AC was washed with deionized water, placed in a water bath at 60°C for 2 hours for ultrasonic treatment, solid-liquid separation, and dried to obtain pretreated coconut shell activated carbon AC. (2) The pretreated coconut shell activated carbon AC was added to an ethanol solution and surface activated at 80°C for 2 hours. After solid-liquid separation and drying, activated coconut shell activated carbon C2H5OH / AC was obtained. (3) The activated coconut shell activated carbon C2H5OH / AC was added to a 0.5 mol / L SiO2 solution, ultrasonically impregnated at 80℃ for 2 h, then left to stand at room temperature for 24 h, and vacuum dried to obtain AC@SiO2 precursor; the mass ratio of SiO2 to the coconut shell activated carbon AC in step (1) was 3%; (4) The AC@SiO2 precursor was placed in a Joule flash evaporation device and heated to 1600℃ for Joule flash evaporation treatment to activate AC@SiO2 at a high temperature. The peak voltage of the Joule flash evaporation treatment was 200V, the instantaneous current was 300A, and the time was 500ms. Then, the AC@SiO2 catalyst was obtained by plasma surface treatment. The plasma surface treatment power was 300W, the time was 20min, and the plasma discharge gas was a hydrogen-nitrogen mixture (the volume of hydrogen in the hydrogen-nitrogen mixture was 10%, and the flow rate of the hydrogen-nitrogen mixture was 13ml / min). (5) The AC@SiO2 catalyst was added to a cerium nitrate-cobalt nitrate mixed solution (the concentration of cerium nitrate in the cerium nitrate-cobalt nitrate mixed solution was 0.09 mol / L and the concentration of cobalt nitrate was 0.025 mol / L), ultrasonically impregnated at 80℃ for 2 h, then placed at room temperature for 24 h, and vacuum dried to obtain Co. 0.2 Ce 0.8 / AC@SiO2 precursor; (6) Co 0.2 Ce 0.8 The / AC@SiO2 precursor was uniformly heated to 500℃, and activated by introducing water vapor at a rate of 35 ml / min for 30 min to obtain Co. 0.2 Ce 0.8 / AC@SiO2 catalyst; This embodiment describes the low-temperature oxidation of CO and reduction of NO using Co. 0.2 Ce 0.8 The / AC@SiO2 catalyst was used for CO+NO removal at 100~250℃, with a catalyst loading of 8g. Before the experiment, N2 was introduced into the fixed-bed reactor to purge other gases and avoid interference. Then, simulated CO+NO from flue gas was introduced for 1 hour to allow CO to be removed. 0.2 Ce 0.8 / AC@SiO2 catalyst adsorption saturates CO+NO, reducing experimental errors; The simulated total gas flow rate is 1000 ml / min, and the GHSV is 30000 h. -1 The NO flow rate was 2.4 ml·min -1 (2.4×10 3 ppm), O2 volume concentration 10% (volume ratio), CO flow rate 4 ml·min -1 (4×10 3 ppm), N2 is the equilibrium gas; the simulated gases are mixed in a mixing chamber and then fed into a fixed-bed reactor, where Co 0.2 Ce 0.8 Under the action of / AC@SiO2 catalyst, CO is oxidized to CO2 and NO is reduced to N2; the gas after the reaction is discharged into the atmosphere after the unreacted CO and NO are absorbed by limestone solution; the CO and NO concentrations at the inlet and outlet are detected by flue gas analyzer. Co 0.2 Ce 0.8 The CO+NO removal efficiency of the / AC@SiO2 catalyst is shown in Table 1 and... Figure 1 , Table 1 Co 0.2 Ce 0.8 / AC@SiO2 catalyst CO+NO removal efficiency

[0027] From Table 1 and Figure 1 It can be seen that Co 0.2 Ce 0.8 The / AC@SiO2 catalyst maintains CO and NO removal rates above 97% and 99%, respectively, at 100–250 °C. Figures 2-5Characterization indicates that Co and Ce have a synergistic effect; Ce maximally regulates oxygen species migration, Ce 3+ / Ce 4+ The dynamic transformation efficiently transfers electrons, accelerating the adsorption and activation of NO. Co dominates the redox cycle, lowering the energy barrier for catalytic CO oxidation. The synergistic effect of Co and Ce achieves efficient removal of CO and NO.

[0028] Example 2: In this example, the total mass of Co and Ce elements in the active components accounts for 2% of AC. Taking the total molar amount of Co and Ce as 100%, Co accounts for 50% of the molar amount, and Ce accounts for 50% of the molar amount, denoted as Co. 0.5 Ce 0.5 / AC@SiO2 catalyst; A method for preparing a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, the specific steps of which are as follows: (1) Coconut shell activated carbon AC was washed with deionized water, placed in a water bath at 70℃ for ultrasonic treatment for 3 hours, solid-liquid separation was performed, and dried to obtain pretreated coconut shell activated carbon AC. (2) The pretreated coconut shell activated carbon AC was added to an ethanol solution and surface activated at 85°C for 3 hours. After solid-liquid separation and drying, activated coconut shell activated carbon C2H5OH / AC was obtained. (3) The activated coconut shell activated carbon C2H5OH / AC was added to a SiO2 solution with a concentration of 0.6 mol / L, stirred and impregnated at 85℃ for 3 h, then placed at room temperature for 30 h, and vacuum dried to obtain AC@SiO2 precursor; the mass ratio of SiO2 to coconut shell activated carbon AC in step (1) was 4%; (4) The AC@SiO2 precursor was placed in a Joule flash evaporation device and heated to 1650℃ for Joule flash evaporation treatment to activate AC@SiO2 at a high temperature. The peak voltage of the Joule flash evaporation treatment was 250V, the instantaneous current was about 350A, and the time was 550ms. Then, the AC@SiO2 catalyst was obtained by plasma surface treatment. The plasma surface treatment power was 350W, the time was 25min, and the plasma discharge gas was a hydrogen-nitrogen mixture (the volume of hydrogen in the hydrogen-nitrogen mixture was 15%, and the flow rate of the hydrogen-nitrogen mixture was 14ml / min). (5) The AC@SiO2 catalyst was added to a cerium nitrate-cobalt nitrate mixed solution (the concentration of cerium nitrate in the cerium nitrate-cobalt nitrate mixed solution was 0.07 mol / L and the concentration of cobalt nitrate was 0.05 mol / L), ultrasonically impregnated at 85℃ for 3 h, then placed at room temperature for 30 h, and vacuum dried to obtain Co. 0.5 Ce 0.5 / AC@SiO2 precursor; (6) Co0.5 Ce 0.5 The / AC@SiO2 precursor was uniformly heated to 550℃, and activated by introducing water vapor at a rate of 36 ml / min for 35 min to obtain Co. 0.5 Ce 0.5 / AC@SiO2 catalyst; This embodiment describes the low-temperature oxidation of CO and reduction of NO using Co. 0.5 Ce 0.5 The / AC@SiO2 catalyst was used for CO+NO removal at 100~250℃, with a catalyst loading of 8g. Before the experiment, N2 was introduced into the fixed-bed reactor to purge other gases and avoid interference. Then, simulated CO+NO from flue gas was introduced for 1 hour to allow CO to be removed. 0.5 Ce 0.5 / AC@SiO2 catalyst adsorption saturates CO+NO, reducing experimental errors; The simulated total gas flow rate is 1000 ml / min, and the GHSV is 30000 h. -1 The NO flow rate was 2.4 ml / min. -1 (2.4×10 3 ppm), O2 volume concentration 10% (volume ratio), CO flow rate 4 ml·min⁻¹ (4 × 10⁻¹) 3 ppm), N2 is the equilibrium gas; the simulated gases are mixed in a mixing chamber and then fed into a fixed-bed reactor, where Co 0.5 Ce 0.5 Under the action of the AC@SiO2 catalyst, CO is oxidized to CO2 and NO is reduced to N2. The gas after the reaction is discharged into the atmosphere after the unreacted CO and NO are absorbed by the limestone solution. The CO and NO concentrations at the inlet and outlet are detected by a flue gas analyzer. Co 0.5 Ce 0.5 The CO+NO removal efficiency of the / AC@SiO2 catalyst is shown in Table 2. Figure 1 , Table 2 Co 0.5 Ce 0.5 / AC@SiO2 catalyst CO+NO removal efficiency

[0029] From Table 1 and Figure 1 It can be seen that Co 0.5 Ce 0.5 The / AC@SiO2 catalyst maintains CO and NO removal rates above 98% and 98%, respectively, at 100–250 °C. Figures 2-5Characterization revealed a well-developed pore structure and a large amount of metal oxides adhering to its surface, exhibiting a typical type IV adsorption isotherm curve. The hysteresis loop showed an H4 type, indicating that Co... 0.5 Ce 0.5 The / AC@SiO2 catalyst has many micropores and mesopores formed by its layered structure. Acidic oxygen-containing functional groups such as hydroxyl groups readily react with NO, promoting the SCR reaction and improving the conversion efficiency of CO and NO.

[0030] Example 3: In this example, the total mass of Co and Ce elements in the active components accounts for 2% of AC. Taking the total molar amount of Co and Ce as 100%, Co accounts for 80% and Ce accounts for 20%, denoted as Co. 0.8 Ce 0.2 / AC@SiO2 catalyst; A method for preparing a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, the specific steps of which are as follows: (1) Coconut shell activated carbon AC was washed with deionized water, placed in a water bath at 80℃ for ultrasonic treatment for 4 hours, solid-liquid separation was performed, and dried to obtain pretreated coconut shell activated carbon AC. (2) The pretreated coconut shell activated carbon AC was added to an ethanol solution and surface activated at 90°C for 4 hours. After solid-liquid separation and drying, activated coconut shell activated carbon C2H5OH / AC was obtained. (3) The activated coconut shell activated carbon C2H5OH / AC was added to a 0.7 mol / L SiO2 solution, stirred and impregnated at 90℃ for 4 h, then placed at room temperature for 36 h, and vacuum dried to obtain AC@SiO2 precursor; the mass ratio of SiO2 to the coconut shell activated carbon AC in step (1) was 5%; (4) The AC@SiO2 precursor was placed in a Joule flash evaporation device and heated to 1700℃ for Joule flash evaporation treatment to activate AC@SiO2 at high temperature. The peak voltage of the Joule flash evaporation treatment was 300V, the instantaneous current was about 400A, and the time was 600ms. Then, the AC@SiO2 catalyst was obtained by plasma surface treatment. The plasma surface treatment power was 400W, the time was 30min, and the plasma discharge gas was a hydrogen-nitrogen mixture (the volume of hydrogen in the hydrogen-nitrogen mixture was 20%, and the flow rate of the hydrogen-nitrogen mixture was 15ml / min). (5) The AC@SiO2 catalyst was added to a cerium nitrate-cobalt nitrate mixed solution (the concentration of cerium nitrate in the cerium nitrate-cobalt nitrate mixed solution was 0.05 mol / L and the concentration of cobalt nitrate was 0.075 mol / L), ultrasonically impregnated at 90℃ for 4 h, then placed at room temperature for 36 h, and vacuum dried to obtain Co. 0.8 Ce 0.2 / AC@SiO2 precursor; (6) Co 0.8 Ce 0.2 The / AC@SiO2 precursor was uniformly heated to 600℃, and activated by introducing water vapor at a rate of 37 ml / min for 40 min to obtain Co. 0.8 Ce 0.2 / AC@SiO2 catalyst; This embodiment describes the low-temperature oxidation of CO and reduction of NO using Co. 0.8 Ce 0.2 The / AC@SiO2 catalyst was used for NO removal at 100~250℃, with a catalyst loading of 8g. Before the experiment, N2 was introduced into the fixed-bed reactor to purge other gases and avoid interference. Then, CO+NO from simulated flue gas was introduced for 1 hour to allow CO to be removed. 0.8 Ce 0.2 / AC@SiO2 catalyst adsorption saturates CO+NO, reducing experimental errors; The simulated total gas flow rate is 1000 ml / min, and the GHSV is 30000 h. -1 The NO flow rate was 2.4 ml / min. -1 (2.4×10 3 ppm), O2 volume concentration 10% (volume ratio), CO flow rate 4 ml·min -1 (4×10 3 ppm), N2 is the equilibrium gas; the simulated gases are mixed in a mixing chamber and then fed into a fixed-bed reactor, where Co 0.8 Ce 0.2 Under the action of the AC@SiO2 catalyst, CO is oxidized to CO2 and NO is reduced to N2. The gas after the reaction is discharged into the atmosphere after the unreacted CO and NO are absorbed by the limestone solution. The CO and NO concentrations at the inlet and outlet are detected by a flue gas analyzer. Co 0.8 Ce 0.2 The CO+NO removal efficiency of the / AC@SiO2 catalyst is shown in Table 3. Figure 1 , Table 3 Co 0.8 Ce 0.2 / AC@SiO2 catalyst CO+NO removal efficiency

[0031] From Table 1 and Figure 1 It can be seen that Co 0.8 Ce 0.2 The / AC@SiO2 catalyst maintains CO and NO removal rates above 99% and 96%, respectively, at 100–250 °C. Figures 2-5Characterization results show that the catalyst generates more metal ion channels. The larger specific surface area and total pore volume not only provide a site for the uniform dispersion of metal oxides, but also provide more active sites for the removal of CO and NO, thereby improving the conversion rate of CO and NO.

[0032] Example 4: In this example, the total mass of Co and Ce elements in the active component accounts for 3% of AC. With the total molar amount of Co and Ce as 100%, the molar amount of Co accounts for 30% and the molar amount of Ce accounts for 70%, which is referred to as CoCe / AC@SiO2 catalyst. A method for preparing a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, the specific steps of which are as follows: (1) Coconut shell activated carbon AC was washed with deionized water, placed in a water bath at 65℃ for ultrasonic treatment for 2.5h, solid-liquid separation was performed, and dried to obtain pretreated coconut shell activated carbon AC. (2) The pretreated coconut shell activated carbon AC was added to an ethanol solution and surface activated at 83°C for 2.5 h. After solid-liquid separation and drying, activated coconut shell activated carbon C2H5OH / AC was obtained. (3) The activated coconut shell activated carbon C2H5OH / AC was added to a 0.55 mol / L SiO2 solution, stirred and impregnated at 83℃ for 2.5 h, then placed at room temperature for 27 h, and vacuum dried to obtain AC@SiO2 precursor; the mass ratio of SiO2 to coconut shell activated carbon AC in step (1) was 3.5%; (4) The AC@SiO2 precursor was placed in a Joule flash evaporation device and heated to 1630°C for Joule flash evaporation treatment to activate AC@SiO2 at a high temperature. The peak voltage of the Joule flash evaporation treatment was 230V, the instantaneous current was about 330A, and the time was 530ms. Then, the AC@SiO2 catalyst was obtained by plasma surface treatment. The plasma surface treatment power was 330W, the time was 23min, and the plasma discharge gas was a hydrogen-nitrogen mixture (the volume of hydrogen in the hydrogen-nitrogen mixture was 13%, and the flow rate of the hydrogen-nitrogen mixture was 13.5ml / min). (5) The AC@SiO2 catalyst was added to a cerium nitrate-cobalt nitrate mixed solution (the concentration of cerium nitrate in the cerium nitrate-cobalt nitrate mixed solution was 0.06 mol / L and the concentration of cobalt nitrate was 0.035 mol / L), ultrasonically impregnated at 83℃ for 2.5 h, then placed at room temperature for 27 h, and vacuum dried to obtain the CoCe / AC@SiO2 precursor; (6) The CoCe / AC@SiO2 precursor was heated to 530℃ at a constant rate and activated by passing water vapor at a rate of 38 ml / min for 33 min to obtain the CoCe / AC@SiO2 catalyst. In this embodiment, the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO was used to remove NO at 100~250℃, with a catalyst loading of 8g. Before the experiment, N2 was introduced into the fixed-bed reactor to remove other gases in the reactor and avoid interference from other gases. Then, CO+NO from simulated flue gas was introduced for 1 hour to saturate the CoCe / AC@SiO2 catalyst with CO+NO adsorption, thereby reducing experimental error. The simulated total gas flow rate is 1000 ml / min, and the GHSV is 30000 h. -1 The NO flow rate was 2.4 ml / min. -1 (2.4×10 3 ppm), O2 volume concentration 10% (volume ratio), CO flow rate 4 ml·min -1 (4×10 3 (ppm), N2 is the equilibrium gas; after the simulated gas is mixed in the mixing chamber, it is sent to the fixed bed reactor. Under the action of CoCe / AC@SiO2 catalyst, CO is oxidized to CO2 and NO is reduced to N2. The gas after the reaction is discharged into the atmosphere after the unreacted CO and NO are absorbed by the limestone solution. The CO and NO concentrations at the inlet and outlet are detected by the flue gas analyzer. The CO+NO removal efficiency of the CoCe / AC@SiO2 catalyst is shown in Table 4. Table 4. CO and NO removal efficiency of CoCe / AC@SiO2 catalyst

[0033] As shown in Table 4, the CO and NO removal rates of the CoCe / AC@SiO2 catalyst remained above 97% and 98% respectively at 100~250℃. The CoCe / AC@SiO2 catalyst has a large number of metal ion channels. The large specific surface area and total pore volume not only provide a site for uniform dispersion of metal oxides, but also provide more active sites for the removal of CO and NO, thereby improving the CO and NO conversion rate.

[0034] Example 5: In this example, the total mass of Co and Ce elements in the active component accounts for 4% of AC. With the total molar amount of Co and Ce as 100%, the molar amount of Co accounts for 70% and the molar amount of Ce accounts for 30%, which is referred to as CoCe / AC@SiO2 catalyst. A method for preparing a CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, the specific steps of which are as follows: (1) Coconut shell activated carbon AC was washed with deionized water, placed in a water bath at 75℃ for ultrasonic treatment for 3.5h, solid-liquid separation was performed, and dried to obtain pretreated coconut shell activated carbon AC. (2) The pretreated coconut shell activated carbon AC was added to an ethanol solution and surface activated at 88°C for 3.5 h. After solid-liquid separation and drying, activated coconut shell activated carbon C2H5OH / AC was obtained. (3) The activated coconut shell activated carbon C2H5OH / AC was added to a 0.65 mol / L SiO2 solution, stirred and impregnated at 88℃ for 3.5 h, then placed at room temperature for 33 h, and vacuum dried to obtain AC@SiO2 precursor; the mass ratio of SiO2 to coconut shell activated carbon AC in step (1) was 4.5%; (4) The AC@SiO2 precursor was placed in a Joule flash evaporation device and heated to 1680℃ for Joule flash evaporation treatment to activate AC@SiO2 at high temperature. The peak voltage of the Joule flash evaporation treatment was 280V, the instantaneous current was about 380A, and the time was 580ms. Then, the AC@SiO2 catalyst was obtained by plasma surface treatment. The plasma surface treatment power was 380W, the time was 28min, and the plasma discharge gas was a hydrogen-nitrogen mixture (the volume of hydrogen in the hydrogen-nitrogen mixture was 18%, and the flow rate of the hydrogen-nitrogen mixture was 14.5ml / min). (5) The AC@SiO2 catalyst was added to a cerium nitrate-cobalt nitrate mixed solution (the concentration of cerium nitrate in the cerium nitrate-cobalt nitrate mixed solution was 0.08 mol / L and the concentration of cobalt nitrate was 0.065 mol / L), ultrasonically impregnated at 88℃ for 3.5 h, then placed at room temperature for 33 h, and vacuum dried to obtain the CoCe / AC@SiO2 precursor; (6) The CoCe / AC@SiO2 precursor was heated to 580℃ at a constant rate and activated by passing water vapor at a rate of 39 ml / min for 38 min to obtain the CoCe / AC@SiO2 catalyst. In this embodiment, the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO was used to remove NO at 100~250℃, with a catalyst loading of 8g. Before the experiment, N2 was introduced into the fixed-bed reactor to remove other gases in the reactor and avoid interference from other gases. Then, CO+NO from simulated flue gas was introduced for 1 hour to saturate the CoCe / AC@SiO2 catalyst with CO+NO adsorption, thereby reducing experimental error. The simulated total gas flow rate is 1000 ml / min, and the GHSV is 30000 h. -1 The NO flow rate was 2.4 ml / min. -1 (2.4×10 3 ppm), O2 volume concentration 10% (volume ratio), CO flow rate 4 ml·min -1 (4×10 3(ppm), N2 is the equilibrium gas; after the simulated gas is mixed in the mixing chamber, it is sent to the fixed bed reactor. Under the action of CoCe / AC@SiO2 catalyst, CO is oxidized to CO2 and NO is reduced to N2. The gas after the reaction is discharged into the atmosphere after the unreacted CO and NO are absorbed by the limestone solution. The CO and NO concentrations at the inlet and outlet are detected by the flue gas analyzer. The CO+NO removal efficiency of the CoCe / AC@SiO2 catalyst is shown in Table 5. Table 5. CO and NO removal efficiency of CoCe / AC@SiO2 catalyst

[0035] As shown in Table 5, the CO and NO removal rates of the CoCe / AC@SiO2 catalyst remained above 98% and 98% respectively at 100~250℃. The CoCe / AC@SiO2 catalyst has a large number of metal ion channels. The large specific surface area and total pore volume not only provide a site for uniform dispersion of metal oxides, but also provide more active sites for the removal of CO and NO, thereby improving the CO and NO conversion rate.

[0036] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO, characterized in that: The CoCe / AC@SiO2 catalyst has a dual-support structure of AC@SiO2 with coconut shell activated carbon (AC) as the core and SiO2 as the shell. The active component is CoO2. x and CeO y A CoCe / AC@SiO2 catalyst is formed on the surface of the AC@SiO2 dual-support structure. The total mass of Co and Ce elements in the active component accounts for 2-4% of AC. With the total molar amount of Co and Ce as 100%, the molar amount of Co accounts for 20-80%.

2. The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 1, characterized in that, The specific steps are as follows: (1) Coconut shell activated carbon AC was washed with deionized water, placed in a water bath at 60~80℃ for ultrasonic treatment for 2~4h, solid-liquid separation was performed, and dried to obtain pretreated coconut shell activated carbon AC. (2) The pretreated coconut shell activated carbon AC was added to an ethanol solution for surface activation treatment, solid-liquid separation, and drying to obtain activated coconut shell activated carbon C2H5OH / AC; (3) Add activated coconut shell activated carbon C2H5OH / AC to SiO2 solution, ultrasonically impregnate at 80~90℃ for 2~4h, then let stand at room temperature for 24~36h, and vacuum dry to obtain AC@SiO2 precursor; (4) The AC@SiO2 precursor is placed in a Joule thermal flash evaporation device and heated to 1600~1700℃ for Joule thermal flash evaporation treatment to activate AC@SiO2 at high temperature. Then, the AC@SiO2 catalyst is obtained by plasma surface treatment. (5) Add the AC@SiO2 catalyst to a cerium nitrate-cobalt nitrate mixed solution, ultrasonically impregnate at 80~90℃ for 2~4h, then let it stand at room temperature for 24~36h, and vacuum dry to obtain CoCe / AC@SiO2 precursor; (6) The CoCe / AC@SiO2 precursor is heated at a constant rate to 500~600℃ and activated by steam for 30~40min to obtain the CoCe / AC@SiO2 catalyst.

3. The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 2, characterized in that: The surface activation treatment in step (2) is carried out at a temperature of 80~90℃ for 2~4 hours.

4. The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 2, characterized in that: In step (3), the concentration of SiO2 solution is 0.5~0.8 mol / L, and the mass ratio of SiO2 to coconut shell activated carbon AC in step (1) is 3%~5%.

5. The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 2, characterized in that: Step (4) The peak voltage of the Joule flash evaporation device is 200~300V, the instantaneous current is 300~400A, and the time is 500~600ms.

6. The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 2, characterized in that: Step (4) The plasma surface treatment power is 300~400W, the time is 20~30min, and the plasma discharge gas is a hydrogen-nitrogen mixture.

7. The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 6, characterized in that: The volume of hydrogen in the hydrogen-nitrogen mixture is 10-20%, and the flow rate of the hydrogen-nitrogen mixture is 13-15 ml / min.

8. The preparation method of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 2, characterized in that: In step (5), the concentration of cerium nitrate in the cobalt nitrate-cerium nitrate mixed solution is 0.05~0.09 mol / L, and the concentration of cobalt nitrate is 0.025~0.075 mol / L.

9. The method for preparing the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO according to claim 2, characterized in that: Step (6) The water vapor rate is 35~39 ml / min.

10. The application of the CoCe / AC@SiO2 catalyst for low-temperature oxidation of CO and reduction of NO as described in claim 1 in the catalytic removal of CO and NO from flue gas, characterized in that: The temperature for catalytic removal is 100~250℃.

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