Micron sheet rare earth-based denitration and chlorobenzene removal catalyst as well as preparation method and application thereof

Abstract

The invention discloses a micron-sheet rare-earth-based denitration and chlorobenzene removal catalyst as well as a preparation method and application thereof. The catalyst takes micron-sheet reduced graphene oxide as a carrier, a composite oxide of cerium oxide and vanadium oxide as an active component and a hexahydrotriazinyl covalent organic framework as an active site protective agent; on the basis of the mass of the carrier, the mass percentage of the active component is 5-10%, and the mass percentage of the active site protective agent is 1-5%. The catalyst synthesized by the method has the advantages of high specific surface area, difficult deposition of ammonium bisulfate, long service life, stable activity and the like, and can realize the target of low-temperature denitration and chlorobenzene removal in the non-electric industry.

Description

Technical Field

[0001] The present invention relates to a micron-sheet rare earth-based denitrification and dechlorobenzene catalyst, a preparation method thereof, and an application thereof, belonging to the field of air pollution control. Background Art

[0002] With the shift of the focus of air pollution control in China from the power industry to the non-power industries (such as steel, cement, glass, waste incineration, etc.), the problem of pollutant emissions in the non-power industries has become increasingly prominent. According to statistics, the non-power industries contribute more than 75% of the national emissions of NO x , SO 2 and particulate matter. Among them, the NO x emissions in the flue gas of steel sintering account for more than 50% of the total steel emissions.

[0003] The flue gas components in the non-power industries are complex and have the following characteristics: (1) Low temperature and high humidity: For example, the temperature of the flue gas of steel sintering is as low as 80-180°C, and the moisture content is 7%-13%; (2) Coexistence of multiple pollutants: It contains high concentrations of SO 2 , HCl, heavy metals, and chlorobenzene, etc., which are likely to cause catalyst poisoning and blockage. Traditional denitrification technologies (such as SNCR) are difficult to meet the strict standards, while the SCR technology needs to overcome problems such as insufficient low-temperature activity and weak anti-poisoning ability. At present, researchers at home and abroad have improved the redox ability and sulfur resistance of the catalyst by doping transition metals (Ce, Fe, Zr) or rare earth elements (such as La), and neutralized SO 3 by injecting an alkaline absorbent (such as Na salt), or designed acidic sites on the catalyst surface to inhibit the formation of ammonium bisulfate. For the low-temperature removal of VOCs such as chlorobenzene, a combined process of SCR and catalytic oxidation is adopted. For example, a denitrification catalyst (such as MnO x -CeO 2 ) and a VOCs oxidation catalyst (such as Pt / Al 2 O 3 ) are arranged in layers to achieve the synchronous removal of NO x and chlorobenzene. Therefore, the development of a denitrification and dechlorobenzene catalyst with both low-temperature activity, anti-poisoning property, and long service life is an important requirement and research trend for the non-power industries to achieve ultra-low emissions at present. Summary of the Invention

[0004] The object of the present invention is to propose a micron-sheet rare earth-based denitrification and dechlorobenzene catalyst, a preparation method thereof, and an application thereof in view of the current situation and existing problems of the treatment of complex flue gas in the existing non-power industries.

[0005] A micron-sheet rare earth-based denitrification and dechlorobenzene catalyst, which uses micron-sheet reduced graphene oxide as a carrier, a composite oxide of cerium oxide and vanadium oxide as an active component, and hexahydrotriazine-based covalent organic framework as an active site protector, and is prepared by a bubble template method-solvothermal growth method-impregnation calcination method; wherein, based on the mass of the carrier, the mass percentage content of the active component is 5-10%, and the mass ratio of cerium oxide to vanadium oxide in the active component is 1:(0.5-2).

[0006] A preparation method of the above catalyst, and the preparation method of the catalyst is as follows:

[0007] (1) Preparation of reduced graphene oxide micron-sheets by the bubble template method

[0008] Add a surfactant to a low-concentration graphene oxide solution and mix evenly to obtain a mixed solution. Then, introduce nitrogen to crosslink and solidify graphene oxide on the surface of the bubbles. After crosslinking and solidification, place the mixed solution in liquid nitrogen for freezing, and then freeze-dry the frozen solution to obtain a graphene oxide film. Finally, place the graphene oxide film in a reducing agent solution for water bath reduction. After water bath reduction, wash and vacuum dry in sequence to obtain reduced graphene oxide micron-sheets;

[0009] (2) Coupling of hexahydrotriazine-based covalent organic framework by the solvothermal growth method

[0010] Weigh hexahydrotriazine and terephthalic acid and dissolve them in N,N-dimethylformamide. Then add the reduced graphene oxide micron-sheets prepared in step (1) to form a mixed solution. Then place the mixed solution in a hydrothermal reaction kettle, introduce nitrogen to remove air, and then carry out a hydrothermal reaction. After the hydrothermal reaction, filter and vacuum dry to obtain a reduced graphene oxide micron-sheet carrier coupled with a hexahydrotriazine-based covalent organic framework;

[0011] (3) Preparation of the catalyst by the impregnation calcination method

[0012] Weigh cerium salt, vanadium salt, citric acid monohydrate, sodium oxalate, deionized water and the reduced graphene oxide micron-sheet carrier coupled with a hexahydrotriazine-based covalent organic framework prepared in step (2), mix them evenly, place them in a hydrothermal reaction kettle for hydrothermal reaction. After the reaction, filter and dry, and then place them in an atmosphere furnace and introduce nitrogen for low-temperature calcination to obtain a micron-sheet rare earth-based denitrification and dechlorobenzene catalyst.

[0013] In the technical solution of the present invention: in step (1), the preparation method of the low-concentration graphene oxide solution is to add deionized water to the graphene oxide dispersion to form a low-concentration graphene oxide slurry, and then perform ultrasonic treatment in an ice bath. After centrifugation, a uniformly dispersed low-concentration graphene oxide solution is obtained; wherein, the specification of the graphene oxide dispersion is the aqueous dispersion of TCI-G0557, its concentration is 10 mg / mL, the concentration of the low-concentration graphene oxide slurry is 2-5 mg / mL, the power of the ultrasonic treatment is 200-400 W, and the time of the ultrasonic treatment is 2-4 h.

[0014] In the technical solution of the present invention: the surfactant described in step (1) is sodium dodecyl sulfate, and the mass ratio of the surfactant to the low-concentration graphene oxide solution is 1:(40-80).

[0015] In the technical solution of the present invention: the inner diameter of the microporous gas diffuser described in step (1) is 0.2-1.0 mm, the rate of nitrogen gas introduction is 10-30 mL / min, the temperature of crosslinking and curing is 20-40 °C, the time of crosslinking and curing is 1-2 h, the mass ratio of the mixed solution to liquid nitrogen is 1:(30-50), and the time of freezing in liquid nitrogen is 20-40 min.

[0016] In the technical solution of the present invention: the temperature of freeze-drying in step (1) is -40 to -50 °C, the temperature of vacuum drying is 20-30 °C, the time of both freeze-drying and vacuum drying is 24-48 h, the reducing agent solution is a hydrazine hydrate solution with a mass concentration of 40-60%, the mass ratio of the graphene oxide film to the reducing agent solution is 1:(30-50), the temperature of water bath reduction is 70-90 °C, and the time of water bath reduction is 6-18 h.

[0017] In the technical solution of the present invention: the mass ratio of hexahydrotriazine, terephthalic acid, N,N-dimethylformamide and reduced graphene oxide micro-sheets in step (2) is 1:(1-2):(500-1000):(40-80), the temperature of the hydrothermal reaction is 160-180 °C, the time of the hydrothermal reaction is 36-72 h, the temperature of vacuum drying is 30-40 °C, and the time of vacuum drying is 24-48 h.

[0018] In the technical solution of the present invention: the cerium salt in step (3) is cerium chloride or cerium nitrate hexahydrate, the vanadium salt is ammonium metavanadate, the mass ratio of the cerium salt, citric acid monohydrate, sodium oxalate and deionized water is 1:(2-4):(0.5-1):(500-600), and the mass ratio of the cerium salt to the reduced graphene oxide micro-sheet carrier-coupled hexahydrotriazine-based covalent organic framework is 0.05-0.2:1-3;

[0019] The temperature of the hydrothermal reaction is 140 - 160 °C, the time of the hydrothermal reaction is 2 - 4 h, the temperature of drying is 80 - 100 °C, the time of drying is 3 - 6 h, the rate of nitrogen introduction is 20 - 40 mL / min, the temperature of low-temperature calcination is 300 - 350 °C, and the time of low-temperature calcination is 4 - 8 h.

[0020] In the technical solution of the present invention: the above-mentioned catalyst is applied to the low-temperature denitrification and dechlorobenzene in the non-electric industry.

[0021] In the technical solution of the present invention: the above-mentioned non-electric industry specifically refers to the steel sintering and dry-process cement industries.

[0022] The experimental conditions for evaluating the activity of the catalyst of the present invention: Take 1 mL of the catalyst with a particle size of 20 - 40 meshes, pour it into a quartz tube with an inner diameter of 6 mm, fix it with quartz wool and wire mesh, place the quartz tube in a tube furnace, and adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. Inlet gas components: NO (500 ppm), NH 3 (500 ppm), O 2 (11 vol.%), chlorobenzene (400 ppm), SO 2 (200 ppm), and the rest is N 2 , the total gas flow rate is 500 mL / min, control the temperature at 120 - 240 °C, stay stable for 30 min at every 30 °C, use gas chromatography to measure the chlorobenzene concentration, and use a flue gas analyzer to measure the NO concentration. In the temperature range of 150 - 240 °C, the dechlorobenzene efficiency and denitrification efficiency of the catalyst are both higher than 90%, and the denitrification efficiency of the catalyst does not decrease significantly within 24 h of operation.

[0023] Beneficial effects:

[0024] (1) In the present invention, bubble template method is used to prepare reduced graphene oxide micro-sheets. The bubbles formed by the microporous gas diffuser serve as dynamic soft templates. Through interfacial self-assembly, graphene oxide is guided to adsorb and crosslink and solidify on the bubble surface due to electrostatic interaction or van der Waals force. Among them, sodium dodecyl sulfate as a surfactant can reduce the gas-liquid interfacial tension and promote the uniform spreading of GO sheets on the bubble surface. The reduced graphene oxide micro-sheets have both a high specific surface area and excellent electron transport ability. Therefore, during the low-temperature denitrification and dechlorobenzene reaction process, it can not only enhance the redox performance of the active sites and improve the low-temperature catalytic activity, but also adsorb part of the ammonium bisulfate deposited on the catalyst surface to avoid the coverage of the active sites, thus ensuring the long-term operation ability of the catalyst;

[0025] (2) In the present invention, the solvothermal growth method is used to couple with the hexahydrotriazine-based covalent organic framework. This can utilize the high specific surface area of the hexahydrotriazine-based covalent organic framework to adsorb ammonium bisulfate deposited on the catalyst surface, thereby avoiding the adsorption of ammonium bisulfate on the active sites and protecting the active sites. At the same time, the hexahydrotriazine-based covalent organic framework has a relatively high tolerance temperature and is more suitable for the low-temperature denitrification and dechlorobenzene reaction process compared with general COFs materials;

[0026] (3) In the present invention, sodium oxalate is used to promote the uniform growth of the active sites of the cerium-vanadium composite oxide on the carrier surface during the hydrothermal process, enhancing the electron transfer performance between the active sites and the carrier. Moreover, both cerium oxide and vanadium oxide have excellent redox performance, thus effectively ensuring the low-temperature activity of the catalyst;

[0027] (4) The catalyst prepared in the present invention has a microstructure presenting a micron-sheet structure, and the surface is uniformly loaded with active sites. This can not only promote the full contact between the active sites and the reaction gas, but also utilize its larger contact angle to avoid the deposition of ammonium bisulfate on the catalyst surface. And the deposition of a small amount of ammonium bisulfate can also be adsorbed by the high specific surface area of reduced graphene oxide and the hexahydrotriazine-based covalent organic framework, thereby ensuring the sulfur poisoning resistance performance of the catalyst.

[0028] Therefore, the catalyst prepared in the present invention not only has excellent low-temperature denitrification and dechlorobenzene performance, but also has good sulfur poisoning resistance performance. Moreover, the components of this catalyst are environmentally friendly, the preparation process is simple, the cost is relatively low, the cost performance is high, and it has strong application and promotion value. Description of the Drawings

[0029] Figure 1 SEM image of the catalyst prepared in Example 1;

[0030] Figure 2 Denitrification efficiency diagrams of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2;

[0031] Figure 3 Dechlorobenzene efficiency diagrams of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2;

[0032] Figure 4 Denitrification efficiency diagrams of the catalysts prepared in Example 1 and Comparative Example 2 within 24 hours. Detailed Embodiments

[0033] The following further illustrates the present invention in conjunction with embodiments. The embodiments are implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] (1) Preparation of reduced graphene oxide microsheets by the bubble template method

[0036] Weigh 400 g of graphene oxide dispersion with a concentration of 10 mg / mL and add 1600 g of deionized water to form a low-concentration graphene oxide slurry. Then, ultrasonically treat it in an ice bath at a power of 200 W for 4 h to obtain a uniformly dispersed low-concentration graphene oxide solution. Then, weigh 50 g of sodium dodecyl sulfate and add it to 2000 g of graphene oxide solution with a concentration of 2 mg / L, and then perform magnetic stirring at a rotation speed of 100 r / min. Nitrogen gas is introduced through a microporous gas diffuser (the inner diameter of the microporous gas diffuser is 0.2 mm) at a rate of 10 mL / min to crosslink and solidify graphene oxide on the bubble surface for 1 h (the temperature of crosslinking and solidifying is 20 °C). After crosslinking and solidifying, the mixed solution (20 g of the crosslinked and solidified mixed solution per batch) is placed in 600 g of liquid nitrogen in batches and quickly frozen for 20 min. Then, the frozen solution is placed in a freeze dryer and freeze-dried at -40 °C for 48 h to obtain a graphene oxide film. Finally, weigh 3 g of the graphene oxide film and place it in 90 g of hydrazine hydrate solution with a mass concentration of 40% and reduce it in a water bath at 70 °C for 18 h. After water bath reduction, it is washed three times with deionized water and absolute ethanol respectively, and then vacuum-dried at 20 °C for 48 h to obtain reduced graphene oxide microsheets;

[0037] (2) Solvothermal growth method coupled with hexaazatriphenylene-based covalent organic framework

[0038] Weigh 50 mg of hexaazatriphenylene and 50 mg of terephthalic acid and dissolve them in 25 g of N,N-dimethylformamide. Then, weigh 2 g of the reduced graphene oxide microsheets prepared in step (1) to form a mixed solution. Then, place the mixed solution in a hydrothermal reaction kettle, remove the air by introducing nitrogen gas, and perform a hydrothermal reaction at 160 °C for 72 h. After the hydrothermal reaction, filter and vacuum-dry at 30 °C for 48 h to obtain a reduced graphene oxide microsheet support coupled with a hexaazatriphenylene-based covalent organic framework;

[0039] (3) Preparation of catalyst by impregnation-calcination method

[0040] Weigh 95.5 mg of cerium chloride, 42.9 mg of ammonium metavanadate, 191 mg of citric acid monohydrate, 47.8 mg of sodium oxalate, 47.75 g of deionized water and 2 g of the reduced graphene oxide microsheet support coupled with a hexaazatriphenylene-based covalent organic framework prepared in step (2), mix them evenly, place them in a hydrothermal reaction kettle and perform a hydrothermal reaction at 140 °C for 4 h. After the reaction, filter and dry in an oven at 80 °C for 6 h. Then, place it in an atmosphere furnace and introduce nitrogen gas (the rate of introducing nitrogen gas is 20 mL / min) and perform low-temperature calcination at 300 °C for 8 h to obtain a microsheet rare earth-based denitrification and dechlorination benzene catalyst (based on the mass of the support, the mass percentage content of the active component is 5%, and the mass ratio of cerium oxide to vanadium oxide in the active component is 1:0.5. The SEM diagram of the catalyst is as Figure 1as shown;

[0041] (4) Catalytic activity test

[0042] Take 1 mL of the catalyst with a particle size of 20 - 40 mesh and pour it into a quartz tube with an inner diameter of 6 mm. Fix it with quartz wool and wire mesh. Place the quartz tube in a tube furnace and adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. Inlet gas components: NO (500 ppm), NH 3 (500 ppm), O 2 (11 vol.%), chlorobenzene (400 ppm), SO 2 (200 ppm), and the rest is N 2 . The total gas flow rate is 500 mL / min. Control the temperature at 120 - 240 °C and stay stable for 30 min at every 30 °C. Use gas chromatography to measure the concentration of chlorobenzene and a flue gas analyzer to measure the concentration of NO. In the temperature range of 150 - 240 °C, the dechlorobenzene efficiency and denitrification efficiency of the catalyst are both higher than 90%, and the denitrification efficiency of the catalyst does not decrease significantly within 24 h of operation at 180 °C.

[0043] Example 2

[0044] (1) Preparation of reduced graphene oxide microsheets by the bubble template method

[0045] Weigh 400 g of graphene oxide dispersion with a concentration of 10 mg / mL and add 400 g of deionized water to form a low-concentration graphene oxide slurry. Then, ultrasonically treat it at a power of 400 W for 2 h in an ice bath to obtain a uniformly dispersed low-concentration graphene oxide solution. Then, weigh 10 g of sodium dodecyl sulfate and add it to 800 g of graphene oxide solution with a concentration of 5 mg / L, and then stir magnetically at a rotation speed of 200 r / min. Pass nitrogen gas (the rate of nitrogen gas passing is 30 mL / min) through a microporous gas diffuser (the inner diameter of the microporous gas diffuser is 1.0 mm) to crosslink and solidify graphene oxide on the surface of the bubbles for 2 h (the temperature of crosslinking and solidifying is 40 °C). After crosslinking and solidifying, divide the mixed solution into batches (20 g of the crosslinked and solidified mixed solution per batch) and quickly freeze it in 1000 g of liquid nitrogen for 40 min. Then, place the frozen solution in a freeze dryer and freeze-dry it at -50 °C for 24 h to obtain a graphene oxide film. Finally, weigh 3 g of the graphene oxide film and place it in 150 g of hydrazine hydrate solution with a mass concentration of 60% and reduce it in a water bath at 90 °C for 6 h. After water bath reduction, wash it three times with deionized water and anhydrous ethanol respectively, and then dry it in vacuum at 30 °C for 24 h to obtain reduced graphene oxide microsheets;

[0046] (2) Solvothermal growth method coupled with hexa-hydrotriazine-based covalent organic framework

[0047] Weigh 25 mg of hexahydrotriazine and 50 mg of terephthalic acid and dissolve them in 25 g of N,N-dimethylformamide. Then weigh 2 g of the reduced graphene oxide micro-sheets prepared in step (1) to form a mixed solution. Next, place the mixed solution in a hydrothermal reaction kettle, purge with nitrogen to remove air, and then carry out a hydrothermal reaction at 180 °C for 36 h. After the hydrothermal reaction, filter and vacuum dry at 40 °C for 24 h to obtain a reduced graphene oxide micro-sheet support coupled with a hexahydrotriazine-based covalent organic framework;

[0048] (3) Preparation of the catalyst by impregnation calcination method

[0049] Weigh 168.2 mg of cerium nitrate hexahydrate, 171.5 mg of ammonium metavanadate, 672.8 mg of citric acid monohydrate, 168.2 mg of sodium oxalate, 100.92 g of deionized water and 2 g of the reduced graphene oxide micro-sheet support coupled with a hexahydrotriazine-based covalent organic framework prepared in step (2), mix them evenly, place them in a hydrothermal reaction kettle, carry out a hydrothermal reaction at 160 °C for 2 h. After the reaction, filter and dry in an oven at 100 °C for 3 h, then place them in an atmosphere furnace, purge with nitrogen (the nitrogen purging rate is 40 mL / min), and carry out low-temperature calcination at 350 °C for 4 h to obtain a micro-sheet rare earth-based denitrification and dechlorobenzene catalyst (based on the mass of the support, the mass percentage of the active component is 10%, and the mass ratio of cerium oxide to vanadium oxide in the active component is 1:2);

[0050] (4) Catalytic activity test

[0051] Take 1 mL of the catalyst with a particle size of 20 - 40 mesh, pour it into a quartz tube with an inner diameter of 6 mm, fix it with quartz wool and wire mesh. Place the quartz tube in a tube furnace, and adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. Inlet components: NO (500 ppm), NH 3 (500 ppm), O 2 (11 vol.%), chlorobenzene (400 ppm), SO 2 (200 ppm), and the rest is N 2 , the total gas flow rate is 500 mL / min, control the temperature at 120 - 240 °C, stay stable for 30 min at every 30 °C. Use gas chromatography to measure the chlorobenzene concentration and a flue gas analyzer to measure the NO concentration. In the temperature range of 150 - 240 °C, the dechlorobenzene efficiency and denitrification efficiency of the catalyst are both higher than 90%.

[0052] Example 3

[0053] (1) Preparation of reduced graphene oxide micro-sheets by the bubble template method

[0054] Weigh 400 g of graphene oxide dispersion with a concentration of 10 mg / mL, add 800 g of deionized water to form a low-concentration graphene oxide slurry, then ultrasonically treat it in an ice bath at a power of 300 W for 3 h to obtain a uniformly dispersed low-concentration graphene oxide solution. Then weigh 24 g of sodium dodecyl sulfate and add it to 1200 g of graphene oxide solution with a concentration of 3.33 mg / L, and then perform magnetic stirring at a rotation speed of 150 r / min. Nitrogen gas is introduced through a microporous gas diffuser (the inner diameter of the microporous gas diffuser is 0.5 mm) at a rate of 20 mL / min to crosslink and solidify graphene oxide on the surface of the bubbles for 2 h (the temperature of crosslinking and solidifying is 30 °C). After crosslinking and solidifying, the mixed solution (20 g of the crosslinked and solidified mixed solution per batch) is placed in 800 g of liquid nitrogen in batches and quickly frozen for 40 min. Then the frozen solution is placed in a freeze dryer and freeze-dried at -50 °C for 36 h to obtain a graphene oxide film. Finally, weigh 3 g of the graphene oxide film and place it in 120 g of hydrazine hydrate solution with a mass concentration of 50% and reduce it in a water bath at 80 °C for 12 h. After water bath reduction, it is washed three times with deionized water and absolute ethanol respectively, and then vacuum-dried at 25 °C for 36 h to obtain reduced graphene oxide micro-sheets;

[0055] (2) Solvothermal growth method coupled with hexaazatriphenylene-based covalent organic framework

[0056] Weigh 40 mg of hexaazatriphenylene and 60 mg of terephthalic acid and dissolve them in 24 g of N,N-dimethylformamide. Then weigh 2 g of the reduced graphene oxide micro-sheets prepared in step (1) to form a mixed solution. Then place the mixed solution in a hydrothermal reaction kettle, remove the air by introducing nitrogen gas, and perform hydrothermal reaction at 170 °C for 48 h. After hydrothermal reaction, filter and vacuum-dry at 35 °C for 36 h to obtain a reduced graphene oxide micro-sheet support coupled with hexaazatriphenylene-based covalent organic framework;

[0057] (3) Preparation of catalyst by impregnation and calcination method

[0058] Weigh 189.2 mg of cerium nitrate hexahydrate, 96.5 mg of ammonium metavanadate, 567.6 mg of citric acid monohydrate, 141.9 mg of sodium oxalate, 104.06 g of deionized water and 2 g of the reduced graphene oxide micro-sheet support coupled with hexaazatriphenylene-based covalent organic framework prepared in step (2), mix them evenly, place them in a hydrothermal reaction kettle, perform hydrothermal reaction at 150 °C for 3 h. After the reaction, filter and place it in an oven to dry at 90 °C for 4 h. Then place it in an atmosphere furnace, introduce nitrogen gas (the rate of introducing nitrogen gas is 30 mL / min), and perform low-temperature calcination at 320 °C for 6 h to obtain a micro-sheet rare earth-based denitrification and dechlorobenzene catalyst (based on the mass of the support, the mass percentage content of the active component is 7.5%, and the mass ratio of cerium oxide and vanadium oxide in the active component is 1:1);

[0059] (4) Catalytic activity test

[0060] Take 1 mL of the catalyst with a particle size of 20 - 40 mesh and pour it into a quartz tube with an inner diameter of 6 mm. Fix it with quartz wool and wire mesh. Place the quartz tube in a tube furnace, and adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. Inlet gas components: NO (500 ppm), NH 3 (500 ppm), O 2 (11 vol.%), chlorobenzene (400 ppm), SO 2 (200 ppm), and the rest is N 2 , with a total gas flow rate of 500 mL / min. Control the temperature at 120 - 240 °C, and stay stable for 30 min at every 30 °C. Use gas chromatography to measure the chlorobenzene concentration and a flue gas analyzer to measure the NO concentration. In the temperature range of 150 - 240 °C, the dechlorination efficiency and denitrification efficiency of the catalyst are both higher than 90%.

[0061] Comparative Example 1

[0062] (1) Catalyst preparation

[0063] Except that nitrogen is not introduced through a microporous gas diffuser during catalyst preparation, other conditions are the same as in Example 2; (2) Catalytic activity test

[0064] Take 1 mL of the catalyst with a particle size of 20 - 40 mesh and pour it into a quartz tube with an inner diameter of 6 mm. Fix it with quartz wool and wire mesh. Place the quartz tube in a tube furnace, and adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. Inlet gas components: NO (500 ppm), NH 3 (500 ppm), O 2 (11 vol.%), chlorobenzene (400 ppm), SO 2 (200 ppm), and the rest is N 2 , with a total gas flow rate of 500 mL / min. Control the temperature at 120 - 240 °C, and stay stable for 30 min at every 30 °C. Use gas chromatography to measure the chlorobenzene concentration and a flue gas analyzer to measure the NO concentration. In the temperature range of 180 °C, the dechlorination efficiency of the catalyst is 48.6% and the denitrification efficiency is 62.5%;

[0065] (3) Comparative effect

[0066] Compared with Example 2, when preparing the catalyst, nitrogen is not introduced through a microporous gas diffuser, and reduced graphene oxide cannot form a micron - sheet structure. Although the purchased graphene oxide dispersion may be in a nanosheet structure, it is difficult to uniformly disperse and load the active components on the surface of the nanosheets, and they are prone to agglomeration, resulting in the inability to maximize the dispersion of active sites, thus significantly reducing the catalytic activity.

[0067] Comparative Example 2

[0068] (1) Preparation of catalyst

[0069] Except that the hexahydrotriazine-based covalent organic framework is not coupled during the preparation of the catalyst, other conditions are the same as in Example 1; (2) Catalytic activity test

[0070] Take 1 mL of the catalyst with a particle size of 20 - 40 mesh and pour it into a quartz tube with an inner diameter of 6 mm. Fix it with quartz wool and wire mesh. Place the quartz tube in a tube furnace, and adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. Inlet gas components: NO (500 ppm), NH 3 (500 ppm), O 2 (11 vol.%), chlorobenzene (400 ppm), SO 2 (200 ppm), and the rest is N 2 , the total gas flow rate is 500 mL / min. Control the temperature at 120 - 240 °C, stay stable for 30 min at every 30 °C. Use gas chromatography to measure the chlorobenzene concentration and a flue gas analyzer to measure the NO concentration. The dechlorobenzene efficiency and denitrification efficiency of the catalyst are both higher than 90% in the temperature range of 180 - 240 °C, but the denitrification efficiency of the catalyst gradually decreases within 24 h of operation at 180 °C;

[0071] (3) Comparison effect

[0072] Compared with Example 1, when the hexahydrotriazine-based covalent organic framework is not coupled during the preparation of the catalyst, although the reduced graphene oxide micro-sheets can also adsorb part of the ammonium bisulfate, the overall specific surface area and the number of micro-pore structures of the catalyst will decrease, so that the active sites cannot be better protected from being covered by ammonium bisulfate. Therefore, although its initial catalytic activity is relatively high, its long-term activity will gradually decline.

Claims

1. A micron-sheet rare earth-based denitration and dechlorobenzene catalyst, characterized in that: The catalyst uses micron-sheet reduced graphene oxide as a carrier, a composite oxide of cerium oxide and vanadium oxide as an active component, and a hexahydrotriazine-based covalent organic framework as an active site protector. It is prepared by a bubble template method-solvothermal growth method-impregnation roasting method. The mass percentage of the active component is 5-10% based on the mass of the carrier, and the mass ratio of cerium oxide to vanadium oxide in the active component is 1:(0.5-2).

2. A method for preparing the catalyst according to claim 1, characterized in that: The preparation method of the catalyst is as follows: (1) Preparation of reduced graphene oxide microsheets by bubble template method A surfactant is added to a low-concentration graphene oxide solution and mixed to obtain a mixed solution, and then nitrogen is introduced to cross-link and solidify the graphene oxide on the surface of the bubbles, and after cross-linking and solidification, the mixed solution is placed in liquid nitrogen for freezing, and then the frozen solution is freeze-dried to obtain a graphene oxide film, and finally the graphene oxide film is placed in a reducing agent solution for water bath reduction, and after water bath reduction, it is washed and vacuum dried in sequence to obtain reduced graphene oxide microsheets; (2) Solvothermal growth method for coupling hexahydrotriazine-based covalent organic frameworks Dissolving hexahydrotriazine and terephthalic acid in N,N-dimethylformamide, then adding the reduced graphene oxide microsheet prepared in step (1) to form a mixed solution, placing the mixed solution in a hydrothermal reactor, introducing nitrogen to remove air and then performing a hydrothermal reaction, filtering after the hydrothermal reaction and vacuum drying to obtain a reduced graphene oxide microsheet carrier coupled with a hexahydrotriazine-based covalent organic framework; (3) Preparation of catalyst by impregnation and calcination method Weigh cerium salt, vanadium salt, monohydrated citric acid, sodium oxalate, deionized water and the reduced graphene oxide micron sheet carrier coupled with the hexahydrotriazine-based covalent organic framework obtained in step (2), mix them evenly, place them in a hydrothermal reactor for hydrothermal reaction, filter and dry them after the reaction, and then place them in an atmosphere furnace and introduce nitrogen for low-temperature calcination to obtain a micron sheet rare earth-based denitration and dechlorobenzene catalyst.

3. The preparation method according to claim 1, characterized in that: In step (1), the concentration of the low-concentration graphene oxide solution is 2-5 mg / mL, and the surfactant is sodium dodecyl sulfate.

4. The preparation method according to claim 2, characterized in that: In step (1), the mass ratio of the surfactant to the graphene oxide solution is 1:(40-80).

5. The preparation method according to claim 1, characterized in that: In step (1), nitrogen is introduced through a microporous gas diffuser with an inner diameter of 0.2 to 1.0 mm, and the rate of nitrogen introduction is 10 to 30 mL / min; the temperature for cross-linking and curing is 20 to 40° C., and the time for cross-linking and curing is 1 to 2 h.

6. The preparation method according to claim 2, characterized in that: In step (1), the mass ratio of the mixed solution to liquid nitrogen is 1:(30-50), and the freezing time in liquid nitrogen is 20-40 minutes; The freeze drying temperature is -40 to -50°C, and the freeze drying time is 24 to 48 hours; The reducing agent solution is a hydrazine hydrate solution with a mass concentration of 40-60%, the mass ratio of the graphene oxide film to the reducing agent solution is 1:(30-50), the temperature of the water bath reduction is 70-90°C, and the time of the water bath reduction is 6-18h; the temperature of the vacuum drying is 20-30°C, and the time of the vacuum drying is 24-48h.

7. The preparation method according to claim 2, characterized in that: The mass ratio of hexahydrotriazine, terephthalic acid, N,N-dimethylformamide and reduced graphene oxide microsheets described in step (2) is 1: (1-2): (500-1000): (40-80); The temperature of the hydrothermal reaction is 160-180° C., and the time of the hydrothermal reaction is 36-72 hours; the temperature of the vacuum drying is 30-40° C., and the time of the vacuum drying is 24-48 hours.

8. The preparation method according to claim 2, characterized in that: In step (3), the cerium salt is cerium chloride or cerium nitrate hexahydrate, and the vanadium salt is ammonium metavanadate; the mass ratio of the cerium salt, citric acid monohydrate, sodium oxalate, and deionized water is 1:(2-4):(0.5-1):(500-600); The mass ratio of cerium salt to reduced graphene oxide microsheet carrier coupled hexahydrotriazine-based covalent organic framework is 0.05-0.2:1-3; The temperature of the hydrothermal reaction is 140-160°C, and the time of the hydrothermal reaction is 2-4 hours; the temperature of the drying is 80-100°C, and the time of the drying is 3-6 hours; the rate of nitrogen introduction is 20-40 mL / min, the temperature of the low-temperature calcination is 300-350°C, and the time of the low-temperature calcination is 4-8 hours.

9. Use of the catalyst according to claim 1 in low-temperature denitration and dechlorobenzene removal in non-electricity industries.

10. The non-electricity industry described in claim 9 specifically refers to the steel sintering and dry process cement industries.

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