Micron sheet rare earth-based denitration and dechlorination benzene catalyst, preparation method and application thereof

Abstract

The application discloses a microparticle rare earth-based denitration and dechlorobenzene catalyst, a preparation method and application thereof, and belongs to the field of catalysts. The catalyst takes microparticle 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 protective agent. The mass percentage of the active component is 5-10% and the mass percentage of the active site protective agent is 1-5% based on the mass of the carrier. The catalyst synthesized by the method has the advantages of high specific surface area, difficulty in ammonium bisulfate deposition, long service life, stable activity and the like, and can realize the target of low-temperature denitration and dechlorobenzene in non-electricity industries.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of micron sheet rare earth-based denitration dechlorine benzene catalyst and its preparation method and application, belong to atmospheric pollution control field. BACKGROUND

[0002] With the focus of China's air pollution control from power industry to non-electricity industry (steel, cement, glass, waste incineration, etc.), the problem of pollutant emission of non-electricity industry is increasingly prominent. According to statistics, non-electricity industry contributes more than 75% of NO x , SO2 and particulate emission in China, among which the NO x emission in steel sintering flue gas accounts for more than 50% of total steel emission.

[0003] Non-electricity industry flue gas is complex, with the following characteristics: (1) low temperature and high humidity: such as steel sintering flue gas temperature is as low as 80-180℃, moisture content is 7%-13%; (2) multiple pollutants coexist: containing high concentration of SO2, HCl, heavy metals and chlorobenzene, etc., which is easy to cause catalyst poisoning and blockage. Traditional denitration technology (such as SNCR) is difficult to meet the stringent standard, while SCR technology needs to overcome the problems of low temperature activity, weak anti-poisoning ability, etc. At present, researchers at home and abroad improve the oxidation-reduction capacity and sulfur resistance of catalyst by doping transition metals (Ce, Fe, Zr) or rare earth elements (such as La), and neutralize SO3 by spraying alkaline absorbent (such as Na salt), or design catalyst surface acidic sites to inhibit the generation of ammonium bisulfate. For the low-temperature removal of chlorobenzene and other VOCs, SCR and catalytic oxidation combined process is adopted, such as layering denitration catalyst (such as MnO x -CeO2) and VOCs oxidation catalyst (such as Pt / Al2O3), to realize simultaneous removal of NO x and chlorobenzene. Therefore, it is an important demand and research trend to develop denitration dechlorobenzene catalyst with low temperature activity, anti-poisoning and long service life for non-electricity industry to achieve ultra-low emission. SUMMARY

[0004] The present application aims at the current situation and existing problems of complex flue gas disposal in non-electricity industry, and proposes a kind of micron sheet rare earth-based denitration dechlorobenzene catalyst and its preparation method and application.

[0005] A kind of micron sheet rare earth-based denitration dechlorobenzene catalyst, the catalyst uses micron sheet reduced graphene oxide as carrier, uses composite oxide of cerium oxide and vanadium oxide as active component, uses hexahydrotriazine-based covalent organic framework as active site protective agent, and is prepared by bubble template method-solvent thermal growth method-dipping calcination method;Among them, the mass percentage content of active component is 5-10% based on the mass of carrier, and the mass ratio of cerium oxide and vanadium oxide in active component is 1: (0.5-2).

[0006] A preparation method of the above-mentioned catalyst, which is as follows:

[0007] (1) Preparation of reduced graphene oxide microsheet by bubble template method

[0008] The surfactant is added to the low-concentration graphene oxide solution to obtain a mixed solution, then nitrogen is introduced to crosslink and solidify the graphene oxide on the surface of the bubbles, after crosslinking and solidification, the mixed solution is frozen in liquid nitrogen, then the frozen solution is freeze-dried to obtain a graphene oxide film, finally the graphene oxide film is placed in a reducing agent solution for water bath reduction, after water bath reduction, washing and vacuum drying are sequentially performed, and the reduced graphene oxide microsheet is obtained.

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

[0010] The hexahydrotriazine and terephthalic acid are weighed and dissolved in N,N-dimethylformamide, then the reduced graphene oxide microsheet prepared in step (1) is added to form a mixed solution, the mixed solution is then placed in a hydrothermal reaction kettle, nitrogen is introduced to remove air, and then hydrothermal reaction is performed, after hydrothermal reaction, filtration and vacuum drying are performed to obtain the reduced graphene oxide microsheet carrier coupled with the hexahydrotriazine-based covalent organic framework.

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

[0012] The cerium salt, vanadium salt, citric acid monohydrate, sodium oxalate, deionized water and the reduced graphene oxide microsheet carrier coupled with the hexahydrotriazine-based covalent organic framework prepared in step (2) are mixed uniformly, placed in a hydrothermal reaction kettle for hydrothermal reaction, filtered and dried after the reaction is completed, then placed in an atmosphere furnace for low-temperature calcination by introducing nitrogen, and the microsheet rare earth-based denitration and dechlorination catalyst is prepared.

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

[0014] In the technical scheme of the present application: in step (1), the surfactant 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 scheme of the present application: the inner diameter of the microporous gas diffuser in step (1) is 0.2-1.0 mm, the rate of nitrogen gas input is 10-30 mL / min, the cross-linking and curing temperature is 20-40 DEG C, the cross-linking and curing time is 1-2 h, the mass ratio of the mixed solution to liquid nitrogen is 1:(30-50), and the freezing time in liquid nitrogen is 20-40 min.

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

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

[0018] In the technical scheme of the present application: 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, monohydrated citric acid, 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 microsheet carrier coupled hexahydrotriazine-based covalent organic framework is 0.05-0.2:1-3.

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

[0020] In the technical scheme of the present application: the above-mentioned catalyst is applied in low-temperature denitration and dechlorination of benzene in non-electricity industry.

[0021] In the technical scheme of the present application: the above-mentioned non-electricity industry specifically refers to steel sintering and dry cement industry.

[0022] The catalyst activity evaluation experiment condition of the application: 1 mL of catalyst with 20-40 meshes is poured into a quartz tube with an inner diameter of 6 mm, and is fixed with quartz wool and iron wire, the quartz tube is placed in a tube furnace, and the actual temperature of the catalytic reaction is adjusted by controlling the heating temperature of the tube furnace. The gas composition: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), chlorobenzene (400 ppm), SO2 (200 ppm), the rest is N2, the total gas flow is 500 mL / min, the temperature is controlled at 120-240 DEG C, and each 30 DEG C stays stable for 30 min, the chlorobenzene concentration is determined by gas chromatography, and the NO concentration is determined by a flue gas analyzer, the dechlorobenzene efficiency and the denitration efficiency of the catalyst in the temperature range of 150-240 DEG C are all higher than 90%, and the denitration efficiency of the catalyst does not decrease obviously within 24 hours of operation.

[0023] Beneficial effects:

[0024] (1) In the application, the reduced graphene oxide microparticle is prepared by the bubble template method, the bubbles formed by the microporous gas diffuser serve as a dynamic soft template, the interface self-assembly effect guides the adsorption and cross-linking of the graphene oxide on the surface of the bubbles due to the electrostatic effect or van der Waals force, and the surface active agent sodium dodecyl sulfate can reduce the gas-liquid interfacial tension and promote the uniform spreading of the GO sheet on the surface of the bubbles. The reduced graphene oxide microparticle has high specific surface area and excellent electron transmission capacity, so it can enhance the redox performance of the active site, improve the low-temperature catalytic activity, and adsorb part of the ammonium bisulfate deposited on the surface of the catalyst, so as to avoid the coverage of the active site, thereby guaranteeing the long-term operation capacity of the catalyst.

[0025] (2) In the application, the solvent thermal growth method is coupled with the hexahydrotriazine-based covalent organic framework, which can utilize the high specific surface area of the hexahydrotriazine-based covalent organic framework to adsorb the ammonium bisulfate deposited on the surface of the catalyst, thereby avoiding the adsorption of the active site to the ammonium bisulfate and protecting the active site. The hexahydrotriazine-based covalent organic framework has high temperature resistance, and compared with general COFs materials, it is more suitable for the low-temperature denitration and dechlorobenzene reaction process.

[0026] (3) In the application, sodium oxalate promotes the uniform growth of the cerium-vanadium composite oxide active site on the surface of the carrier in the hydrothermal process, enhances the electron transmission performance between the active site and the carrier, and the cerium oxide and vanadium oxide both have excellent redox performance, thereby effectively guaranteeing the low-temperature activity of the catalyst.

[0027] (4) The catalyst prepared in the present application has a microsheet structure, and the surface uniformly loads active sites, which can promote sufficient contact between the active sites and the reaction gas, and can also utilize the larger contact angle to avoid the deposition of ammonium bisulfate on the surface of the catalyst, and a small amount of deposition of ammonium bisulfate can also be adsorbed by the high specific surface area of the reduced graphene oxide and hexahydrotriazine-based covalent organic framework, thereby ensuring the sulfur poisoning resistance of the catalyst.

[0028] Therefore, the catalyst prepared in the present application not only has excellent low-temperature deNOx and dechlorobenzene performance, but also has good sulfur poisoning resistance, and the catalyst components are environmentally friendly, the preparation process is simple, the cost is low, the cost performance is high, and the catalyst has strong application and promotion value. BRIEF DESCRIPTION OF DRAWINGS

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

[0030] Figure 2 DeNOx efficiency graph of the catalyst prepared in Examples 1-3 and Comparative Examples 1-2;

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

[0032] Figure 4 DeNOx efficiency graph of the catalyst prepared in Examples 1 and Comparative Example 2 within 24 hours. DETAILED DESCRIPTION

[0033] The present application will be further described below in conjunction with examples, which are implemented on the premise of the technical scheme of the present application, and detailed implementation modes and specific operation processes are given, but the protection scope of the present application is not limited to the following examples.

[0034] Example 1

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

[0036] Take 400 g of graphene oxide dispersion solution with a concentration of 10 mg / mL and add 1600 g of deionized water to form a low-concentration graphene oxide slurry, then ultrasonic treatment in ice bath with power of 200 W for 4 h to obtain uniform dispersed low-concentration graphene oxide solution, then take 50 g of sodium dodecyl sulfate and add it to 2000 g of graphene oxide solution with a concentration of 2 mg / L, then magnetic stirring at a speed of 100 r / min, and 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 make graphene oxide crosslink and solidify on the surface of the gas bubbles for 1 h (the crosslinking and solidification temperature is 20℃), after crosslinking and solidification, the mixed solution (20 g of crosslinked and solidified mixed solution per batch) is placed in 600 g of liquid nitrogen for rapid freezing for 20 min, then the frozen solution is placed in a freeze dryer at-40℃ for 48 h to obtain a graphene oxide film, finally take 3 g of graphene oxide film and place it in a 90 g of 40% mass concentration of hydrazine hydrate solution in a 70℃ water bath for 18 h, after water bath reduction, use deionized water and anhydrous ethanol to clean three times respectively, and then vacuum dry at 20℃ for 48 h to obtain reduced graphene oxide microparticles;

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

[0038] Take 50 mg of hexahydrotriazine and 50 mg of terephthalic acid and dissolve them in 25 g of N,N-dimethylformamide, then take 2 g of reduced graphene oxide microparticle carrier coupled with hexahydrotriazine-based covalent organic framework 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 hydrothermal reaction at 160℃ for 72 h, after hydrothermal reaction, filter and vacuum dry at 30℃ for 48 h to obtain the reduced graphene oxide microparticle carrier coupled with hexahydrotriazine-based covalent organic framework;

[0039] (3) Catalyst prepared by impregnation and calcination

[0040] Take 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 reduced graphene oxide microparticle carrier coupled with hexahydrotriazine-based covalent organic framework prepared in step (2) and mix them uniformly, then place them in a hydrothermal reaction kettle and hydrothermal reaction at 140℃ for 4 h, after reaction, filter and dry in an oven at 80℃ for 6 h, then place them in a gas furnace and introduce nitrogen at a rate of 20 mL / min, and then calcine at 300℃ for 8 h under nitrogen atmosphere to obtain a microparticle rare earth-based denitration and dechlorination catalyst (the mass percentage content of active components is 5% based on the mass of the carrier, and the mass ratio of cerium oxide to vanadium oxide in the active components is 1:0.5, and the SEM image of the catalyst is shown in Figure 1 );

[0041] (4) Catalytic activity test

[0042] Take 20-40 mesh catalyst 1 mL, pour into the inner diameter of 6 mm quartz tube, with quartz wool and iron wire fixed, the quartz tube is placed in the tube furnace, by controlling the heating temperature of the tube furnace to adjust the actual temperature of the catalytic reaction. The gas composition: NO (500 ppm), NH3(500 ppm), O2(11 vol.%), chlorobenzene (400 ppm), SO2(200 ppm), the rest is N2, the total flow rate of the gas is 500 mL / min, the temperature is controlled at 120-240℃, each 30℃ stays stable for 30 min, the concentration of chlorobenzene is determined by gas chromatography, the concentration of NO is determined by smoke analyzer, the dechlorobenzene efficiency and denitration efficiency of the catalyst in the temperature range of 150-240℃ are both higher than 90%, and the denitration efficiency of the catalyst does not decrease significantly within 24 h at 180℃.

[0043] Example 2

[0044] (1) Bubble template method for preparing reduced graphene oxide microsheet

[0045] Take 400 g of 10 mg / mL graphene oxide dispersion liquid and add 400 g of deionized water to form a low concentration graphene oxide slurry, then ultrasonic treatment in ice bath at 400 W power for 2 h to obtain uniform dispersion of low concentration graphene oxide solution, then take 10 g of sodium dodecyl sulfate and add 800 g of 5 mg / L graphene oxide solution, then magnetic stirring at 200 r / min, and pass nitrogen gas through the microporous gas diffuser (the inner diameter of the microporous gas diffuser is 1.0 mm) at a rate of 30 mL / min to make the graphene oxide crosslink and solidify on the surface of the bubbles for 2 h (the crosslinking and solidification temperature is 40℃), after crosslinking and solidification, the mixed solution (20 g of crosslinked and solidified mixed solution per batch) is placed in 1000 g of liquid nitrogen for rapid freezing for 40 min, then the frozen solution is placed in a freeze dryer at-50℃ for 24 h to obtain a graphene oxide film, finally take 3 g of graphene oxide film and place it in 150 g of 60% mass concentration of hydrazine hydrate solution in a 90℃ water bath for 6 h, after water bath reduction, use deionized water and anhydrous ethanol to clean three times respectively, then vacuum dry at 30℃ for 24 h to obtain reduced graphene oxide microsheet;

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

[0047] Take 25 mg of hexahydrotriazine and 50 mg of terephthalic acid and dissolve them in 25 g of N,N-dimethylformamide, then take 2 g of the reduced graphene oxide microsheet carrier coupled with hexahydrotriazine-based covalent organic framework prepared in step (1) to form a mixed solution, and then place the mixed solution in a hydrothermal reactor, introduce nitrogen to remove air, and then hydrothermal reaction at 180℃ for 36h, filter and vacuum dry at 40℃ for 24h to obtain the reduced graphene oxide microsheet carrier coupled with hexahydrotriazine-based covalent organic framework;

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

[0049] Take 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 microsheet carrier coupled with hexahydrotriazine-based covalent organic framework prepared in step (2) and mix them evenly, then place them in a hydrothermal reactor and hydrothermal reaction at 160℃ for 2h, then filter and dry in an oven at 100℃ for 3h, then place them in an atmosphere furnace and introduce nitrogen (the rate of nitrogen introduction is 40mL / min) and calcine at 350℃ for 4h to obtain the microsheet rare earth-based denitration and dechlorination catalyst (the mass percentage content of the active component is 10% based on the mass of the carrier, and the mass ratio of cerium oxide to vanadium oxide in the active component is 1:2).

[0050] (4) Catalytic activity test

[0051] Take 20-40 mesh catalyst 1 mL, pour into a quartz tube with an inner diameter of 6 mm, fix with quartz wool and iron wire, 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. The inlet gas components are: NO (500 ppm), NH3 (500 ppm), O2 (11 vol.%), chlorobenzene (400 ppm), SO2 (200 ppm), and the rest is N2, the total gas flow is 500 mL / min, the control temperature is 120-240℃, and each 30℃ stays stable for 30 min. The chlorobenzene concentration is measured by gas chromatography, and the NO concentration is measured by a flue gas analyzer. The dechlorobenzene efficiency and denitration efficiency of the catalyst in the temperature range of 150-240℃ are both higher than 90%.

[0052] Example 3

[0053] (1) Preparation of reduced graphene oxide microsheet by bubble template method

[0054] Take 400 g of graphene oxide dispersion solution with a concentration of 10 mg / mL and add 800 g of deionized water to form a low-concentration graphene oxide slurry, then ultrasonic treatment in ice bath with power of 300 W for 3 h to obtain uniform dispersed low-concentration graphene oxide solution, then take 24 g of sodium dodecyl sulfate and add it to 1200 g of graphene oxide solution with a concentration of 3.33 mg / L, then magnetic stirring at a speed of 150 r / min, and 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 make graphene oxide crosslink and solidify on the surface of the gas bubbles for 2 h (the crosslinking and solidification temperature is 30℃), after crosslinking and solidification, the mixed solution (20 g of crosslinked and solidified mixed solution per batch) is placed in 800 g of liquid nitrogen for rapid freezing for 40 min, then the frozen solution is placed in a freeze dryer and freeze dried at-50℃ for 36 h to obtain a graphene oxide film, finally take 3 g of graphene oxide film and place it in 120 g of 50% mass concentration hydrazine hydrate solution in a 80℃ water bath for 12 h, after water bath reduction, use deionized water and anhydrous ethanol to clean three times respectively, and then vacuum dry at 25℃ for 36 h to obtain reduced graphene oxide microparticles;

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

[0056] Dissolve 40 mg of hexahydrotriazine and 60 mg of terephthalic acid in 24 g of N,N-dimethylformamide, then take 2 g of reduced graphene oxide microparticle carrier coupled with hexahydrotriazine-based covalent organic framework 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 hydrothermal reaction at 170℃ for 48 h, after hydrothermal reaction, filter and vacuum dry at 35℃ for 36 h to obtain the reduced graphene oxide microparticle carrier coupled with hexahydrotriazine-based covalent organic framework;

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

[0058] Mix 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 reduced graphene oxide microparticle carrier coupled with hexahydrotriazine-based covalent organic framework prepared in step (2) uniformly, place in a hydrothermal reaction kettle, hydrothermal reaction at 150℃ for 3 h, after reaction, filter and dry in an oven at 90℃ for 4 h, then place in a gas furnace and introduce nitrogen gas (the rate of nitrogen gas introduction is 30 mL / min) and calcine at 320℃ for 6 h to obtain a microparticle rare earth-based denitration and dechlorination catalyst (the mass percentage content of active component is 7.5% based on the mass of the carrier, and the mass ratio of cerium oxide to vanadium oxide in the active component is 1:1);

[0059] (4) Catalytic activity test

[0060] Take 20-40 mesh catalyst 1 mL, pour into the quartz tube with an inner diameter of 6 mm, fixed with quartz wool and iron wire, put the quartz tube in the tube furnace, adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. The gas composition is: NO (500 ppm), NH3(500 ppm), O2(11 vol.%), chlorobenzene (400 ppm), SO2(200 ppm), the rest is N2, the total gas flow is 500 mL / min, the control temperature is 120-240℃, each 30℃ stays stable for 30 min, the chlorobenzene concentration is determined by gas chromatography, the NO concentration is determined by flue gas analyzer, the dechlorobenzene efficiency and the denitration efficiency of the catalyst in the temperature range of 150-240℃ are both higher than 90%.

[0061] Comparative Example 1

[0062] (1) Catalyst preparation

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

[0064] Take 20-40 mesh catalyst 1 mL, pour into the quartz tube with an inner diameter of 6 mm, fixed with quartz wool and iron wire, put the quartz tube in the tube furnace, adjust the actual temperature of the catalytic reaction by controlling the heating temperature of the tube furnace. The gas composition is: NO (500 ppm), NH3(500 ppm), O2(11 vol.%), chlorobenzene (400 ppm), SO2(200 ppm), the rest is N2, the total gas flow is 500 mL / min, the control temperature is 120-240℃, each 30℃ stays stable for 30 min, the chlorobenzene concentration is determined by gas chromatography, the NO concentration is determined by flue gas analyzer, the dechlorobenzene efficiency and the denitration efficiency of the catalyst in the temperature range of 150-240℃ are both higher than 90%.

[0065] (3) Comparative effect

[0066] Compared with Example 2, the reduction of graphene oxide cannot form a micron sheet structure when nitrogen is not introduced by using a microporous gas diffuser during catalyst preparation. Although the purchased graphene oxide dispersion may be a nanosheet structure, the active component is difficult to be uniformly loaded on the surface of the nanosheet, and is easy to agglomerate, which leads to the dispersion of active sites cannot be maximized, thereby the catalytic activity is significantly reduced.

[0067] Comparative Example 2

[0068] (1) Catalyst preparation

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

[0070] Take 20-40 mesh catalyst 1 mL, pour into the inner diameter of 6 mm quartz tube, fixed with quartz wool and wire mesh, the quartz tube is placed in the tube furnace, by controlling the heating temperature of the tube furnace to adjust the actual temperature of the catalytic reaction. The gas composition: NO (500 ppm), NH3(500 ppm), O2(11 vol.%), chlorobenzene (400 ppm), SO2(200 ppm), the rest is N2, the total gas flow is 500 mL / min, the temperature is controlled at 120-240℃, each 30℃ stays stable for 30 min, the concentration of chlorobenzene is determined by gas chromatography, the concentration of NO is determined by smoke analyzer, the dechlorobenzene efficiency and denitration efficiency of the catalyst are both higher than 90% in the temperature range of 180-240℃, but the denitration efficiency of the catalyst gradually decreases within 24 h at 180℃;

[0071] (3) Comparative effect

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

Claims

1. A microparticle rare earth-based denitration and dechlorination benzene catalyst, characterized in that: The catalyst uses reduced graphene oxide microsheet 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-solvent thermal growth method-impregnation calcination method; wherein, based on the mass of the carrier, the mass percentage 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). ​ 2. A process for the preparation of the catalyst of claim 1, characterized in that: The preparation method of the catalyst is as follows: (1) preparing reduced graphene oxide microsheet by a bubble template method The surface active agent is added to the low-concentration graphene oxide solution to mix uniformly to obtain a mixed solution, then nitrogen is introduced to crosslink and solidify the graphene oxide on the surface of the bubbles, after crosslinking and solidification, the mixed solution is frozen in liquid nitrogen, then the frozen solution is freeze-dried to obtain a graphene oxide film, finally the graphene oxide film is placed in a reducing agent solution for water bath reduction, after water bath reduction, washing and vacuum drying are sequentially performed, and the reduced graphene oxide microsheet is obtained; (2) coupling hexahydrotriazine-based covalent organic framework by a solvent thermal growth method hexahydrotriazine and terephthalic acid are dissolved in N,N-dimethylformamide, then the reduced graphene oxide microsheet prepared in step (1) is added to form a mixed solution, the mixed solution is placed in a hydrothermal reaction kettle, nitrogen is introduced to remove air, and then hydrothermal reaction is performed, after hydrothermal reaction, filtration and vacuum drying are performed to prepare the reduced graphene oxide microsheet carrier coupling hexahydrotriazine-based covalent organic framework; (3) preparing the catalyst by impregnation calcination method cerium salt, vanadium salt, citric acid monohydrate, sodium oxalate, deionized water and the reduced graphene oxide microsheet carrier coupling hexahydrotriazine-based covalent organic framework prepared in step (2) are mixed uniformly, placed in a hydrothermal reaction kettle for hydrothermal reaction, filtered and dried after reaction, then placed in a gas furnace for low-temperature calcination by introducing nitrogen, and the micron sheet rare earth-based denitration and dechlorination catalyst is prepared.

3. The method of claim 2, wherein: In step (1), the concentration of the low-concentration graphene oxide solution is 2-5 mg / mL, and the surface active agent is sodium dodecyl sulfate.

4. The method of claim 2, wherein: In step (1), the mass ratio of the surface active agent to the graphene oxide solution is 1:(40-80).

5. The method of claim 2, wherein: In step (1), the nitrogen is introduced by using a microporous gas diffuser with an inner diameter of 0.2-1.0 mm, and the nitrogen introduction rate is 10-30 mL / min; the crosslinking and solidification temperature is 20-40℃, and the crosslinking and solidification time is 1-2 h.

6. The method of claim 2, wherein: In step (1), the mass ratio of the mixed solution to liquid nitrogen is 1:(30-50), and the liquid nitrogen freezing time is 20-40 min; The freezing drying temperature is-40--50℃, and the freezing drying time 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 water bath reduction temperature is 70-90℃, the water bath reduction time is 6-18 h; the vacuum drying temperature is 20-30℃, and the vacuum drying time is 24-48 h.

7. The method of claim 2, wherein: The mass ratio of the hexahydrotriazine, terephthalic acid, N,N-dimethylformamide and reduced graphene oxide microsheet in step (2) is 1:(1~2):(500~1000):(40~80); The temperature of the hydrothermal reaction is 160~180℃, and the time of the hydrothermal reaction is 36~72h; the temperature of the vacuum drying is 30~40℃, and the time of the vacuum drying is 24~48h.

8. The method of claim 2, wherein: The cerium salt in step (3) is cerium chloride or cerium nitrate hexahydrate, and the vanadium salt is ammonium metavanadate; the mass ratio of the cerium salt, monohydrate citric acid, sodium oxalate and deionized water is 1:(2~4):(0.5~1):(500~600); The mass ratio of the cerium salt and the 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℃, the time of the hydrothermal reaction is 2~4h; the temperature of the drying is 80~100℃, the time of the drying is 3~6h; the rate of the nitrogen gas flowing in is 20~40mL / min, the temperature of the low-temperature calcination is 300~350℃, and the time of the low-temperature calcination is 4~8h.

9. The application of the catalyst in claim 1 in the low-temperature denitration and dechlorination of benzene in non-electricity industry.

10. Use according to claim 9, characterized in that, The non-electricity industry specifically refers to the steel sintering and dry cement industry.

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