Flue gas multi-pollutant catalyst with nanosheet-sphere hierarchical structure as well as preparation method and application of flue gas multi-pollutant catalyst

Abstract

The invention relates to the technical field of industrial flue gas pollution control, in particular to a flue gas multi-pollutant catalyst with a nanosheet-sphere hierarchical structure as well as a preparation method and application of the flue gas multi-pollutant catalyst. The catalyst comprises a carrier and an active component loaded on the carrier, the carrier comprises a Ti3C2MXene nanosheet, the active component comprises cobalt nanoparticles doped with N and S, and the catalyst has a nanosheet-sphere hierarchical structure. The preparation method comprises the following steps: mixing two-dimensional flaky Ti3C2MXene with cobalt salt, thiourea dioxide and a solvent, carrying out a hydrothermal reaction, and washing and drying an obtained solid product to obtain the Ti3C2MXene / cobalt dioxide composite material. The catalyst is simple in preparation process, has a nanosheet-sphere hierarchical structure, is large in specific surface area and multiple in active sites, can efficiently catalyze and oxidize Hg < 0 >, CO and NO in flue gas at the same time, can realize integrated cooperative control of multiple pollutants, shortens the flue gas purification process and reduces the purification cost.

Description

Technical Field

[0001] The present invention relates to the technical field of industrial flue gas pollution control, and in particular, to a flue gas multi-pollutant catalyst with a nano-sheet-sphere hierarchical structure, a preparation method thereof, and an application thereof. Background Art

[0002] Flue gas emitted from industrial sources such as coal-fired power plants and metal smelting contains a large amount of harmful substances such as elemental mercury (Hg 0 ), carbon monoxide (CO), and nitric oxide (NO). Hg 0 has high volatility, persistence, and bioaccumulation, and can be transported over long distances through the atmosphere, polluting the global ecological environment and posing a threat to the human nervous system and immune system. Incomplete combustion of fossil fuels produces CO. Especially in specific industries where CO is used as a reducing agent for metal smelting (such as iron and steel smelting, lead-zinc-copper smelting, etc.), a large amount of CO is generated and emitted through flue gas. CO is extremely easy to combine with hemoglobin, causing harm to the human body and being one of the main pollutants indirectly leading to global warming. An increase in the concentration of NO in the atmosphere can lead to the generation of photochemical smog, ozone layer depletion, and nitric acid-type acid rain, bringing serious harm to the natural environment and human production and life. Therefore, it is necessary to control Hg 0 , CO, and NO emitted from flue gas.

[0003] Control methods for Hg 0 , CO, and NO in industrial flue gas include adsorption method, absorption method, catalytic oxidation method, etc. Mercury removal by adsorption is to adsorb Hg 0 onto the surface of the adsorbent through physical or chemical action, and then the adsorbent is captured by the existing dust removal device and recycled; mercury removal by catalytic oxidation is to oxidize Hg 0 to Hg 2+ , and the soluble Hg 2+ is then removed by a wet purification device. The removal of CO mainly relies on catalytic oxidation to oxidize it into non-toxic and harmless CO2. The removal of NO in flue gas mainly includes selective catalytic reduction (NH3-SCR), selective non-catalytic reduction (NH3-SNCR), and oxidation-absorption method. In the SCR and SNCR methods, NO is reduced to N2; in the oxidation-absorption method, strong oxidants such as O3, H2O2, and HClO3 are used to oxidize NO to NO2, which is then absorbed by the solution and converted into nitrate for removal from the flue gas.

[0004] Chinese Patent Application No. 202111276250.4 discloses a cerium-silver-loaded catalytic adsorbent for flue gas mercury and nitrogen oxide removal, a preparation method thereof, and an application thereof. By loading silver nanoparticles and CeO2 on EVS-10 molecular sieve, Hg 0Adsorption / oxidation-adsorption and NO reduction are used to achieve synergistic denitrification and mercury removal from coal-fired flue gas. Patents with application numbers 202211378278.3, 202111530349.2, 202111273291.8, and 202011400350.9 also disclose technologies for the simultaneous removal of NO and Hg 0 in flue gas. Patents with application numbers 202210240607.1 and 202111086928.2 disclose methods for the catalytic oxidation of CO and NO, and the core lies in the preparation method and application of high-performance catalysts. Currently, most industrial applications and potential pollutant purification technologies are for the purification of single or two pollutants in synergy. Due to the different principles (oxidation or reduction) for the removal of different pollutants, the reduction of NO and Hg 0 as well as the oxidation of CO require the loading of multiple different active components to jointly exert a multifunctional effect. The catalyst composition is complex, the preparation process is cumbersome, and the cost is extremely high.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The first object of the present invention is to provide a catalyst, which has a nanosheet-sphere hierarchical structure, a large specific surface area, many active sites, and can simultaneously catalytically oxidize Hg 0 , CO, and NO in flue gas, and can achieve the integrated synergistic control of multiple pollutants such as Hg 0 , CO, and NO in flue gas, shortening the flue gas purification process, and solving the problems in the prior art that each pollutant needs to be treated separately, resulting in a complex pollution purification system, and the catalyst for the synergistic catalytic purification of multiple pollutants is complex and has poor economy.

[0007] The second object of the present invention is to provide a preparation method of the above-mentioned catalyst. This method has a simple preparation process, is easy to scale up production, and the prepared product has high purity and high yield.

[0008] The third object of the present invention is to provide an application of the above-mentioned catalyst in flue gas purification.

[0009] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0010] A catalyst includes a carrier and active components loaded on the carrier. The carrier includes Ti3C2MXene nanosheets, and the active components include cobalt nanoparticles doped with N and S. The catalyst has a nanosheet-sphere hierarchical structure, and the nanosheet-sphere hierarchical structure refers to a micron-scale spherical structure formed by the self-assembly of nanosheets loaded with nanoparticles.

[0011] A preparation method of the above-mentioned catalyst includes the following steps:

[0012] Mix two-dimensional sheet-like Ti3C2 MXene with a cobalt salt, thiourea dioxide, and a solvent, and conduct a hydrothermal reaction. The obtained solid product is washed and dried to obtain the catalyst.

[0013] Preferably, the mass ratio of the Ti3C2 MXene, the cobalt salt, and the thiourea dioxide is 1-5:15-22:15-20.

[0014] Preferably, the solvent includes a first solvent and a second solvent. The first solvent includes polyethylene glycol and / or ethylene glycol, and the second solvent includes water.

[0015] Preferably, the temperature of the hydrothermal reaction is 180-300 °C, and the time of the hydrothermal reaction is 8-13 h.

[0016] Preferably, the Ti3C2 MXene is obtained by etching aluminum carbide titanium with hydrofluoric acid.

[0017] Preferably, the temperature of the etching is 30-100 °C, and the time of the etching is 36-72 h.

[0018] Application of the catalyst described in the foregoing embodiments or the catalyst prepared by the preparation method of the catalyst described in any one of the foregoing embodiments in flue gas purification, for catalytically oxidizing Hg 0 , CO, and NO in the flue gas.

[0019] Preferably, the method for flue gas purification using the catalyst includes the following steps:

[0020] Load the catalyst into a reactor, and introduce the flue gas into the reactor for reaction.

[0021] Preferably, the temperature of the flue gas purification is 200-350 °C.

[0022] Preferably, the oxygen concentration in the flue gas is not less than 1%, the Hg 0 concentration is not higher than 1 mg / m 3 , the CO concentration is not higher than 10000 mg / m 3 , the NO concentration is not higher than 1000 mg / m 3 , and the SO2 concentration is not higher than 500 mg / m 3 .

[0023] Preferably, the contact time between the flue gas and the catalyst is not less than 0.5 s.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The catalyst provided by the present invention has a nanosheet-sphere hierarchical structure. Nano cobalt clusters are uniformly distributed on MXene nanosheets, forming coordination bonds with N and S, which can regulate the intrinsic activity of the catalyst. Due to surface energy, volume energy, quantum size effect and other effects, numerous MXene nanosheets self-assemble into micron-scale spheres. This nanosheet-sphere hierarchical structure significantly increases the specific surface area and active site density of the catalyst, and can efficiently catalyze the oxidation of Hg 0 、CO and NO in flue gas, converting them into Hg 2 + 、CO2 and NO2 respectively, which is applicable to the synergistic removal of multiple pollutants in flue gas from coal-fired power plants and smelting industries, shortening the overall flue gas purification process and reducing the purification cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 SEM image of the catalyst prepared in Example 1 of the present invention;

[0028] Figure 2 TEM image of the catalyst prepared in Example 1 of the present invention;

[0029] Figure 3 Removal efficiency diagram of Hg 0 、CO and NO in flue gas by the catalyst in Example 1 of the present invention;

[0030] Figure 4 Removal efficiency diagram of Hg 0 、CO and NO in flue gas by the catalyst in Example 3 of the present invention at different temperatures;

[0031] Figure 5 Removal efficiency comparison diagram of Hg 0 、CO and NO in flue gas by the catalysts in Example 1, Comparative Example 1 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments not indicated by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0033] The first aspect of the present invention provides a catalyst, which includes a carrier and an active component supported on the carrier. The carrier includes Ti3C2 MXene nanosheets, and the active component includes cobalt nanoparticles doped with N and S (the main components of the cobalt nanoparticles are Co and Co3O4). This catalyst has a nanosheet-sphere hierarchical structure. Among them, the nanosheet-sphere hierarchical structure refers to a micron-scale spherical structure formed by the self-assembly of nanosheets loaded with nanoparticles; the sheet-sphere refers to the sphere formed by the self-assembly of nanosheets, and the hierarchical structure refers to nanoparticles (active components), nanosheets and microspheres; the particle size of the nanoparticles is about 0.2-0.4 nm, the average length of the nanosheets is about 200 nm, and the particle size of the microspheres is about 2-5 μm.

[0034] The catalyst provided by the present invention has a nanosheet-sphere hierarchical structure. Nano-scale Co clusters are uniformly distributed on the MXene nanosheets, forming coordination bonds with the doped N and S atoms to form a special configuration, which can adjust the properties such as the spin state and d-band center of metallic Co, and play a role in regulating the binding energy between the active center and reactants and intermediates, etc., and finally achieve the regulation of the intrinsic activity of the catalyst. Due to the effects of surface energy, volume energy, quantum size effect, etc., numerous MXene nanosheets self-assemble to form micron-scale spheres. This nanosheet-sphere hierarchical structure has a large specific surface area and more active sites, and can efficiently catalyze the oxidation of Hg0, CO, and NO in flue gas, and convert them into Hg 2+ , CO2 and NO2 respectively, and is suitable for the synergistic removal of multiple pollutants in the flue gas of coal-fired power plants and the smelting industry.

[0035] The second aspect of the present invention provides a preparation method of the catalyst described in the foregoing embodiment, including the following steps:

[0036] Mix two-dimensional sheet-like Ti3C2 MXene with cobalt salt, thiourea dioxide and a solvent, carry out a hydrothermal reaction, and the obtained solid product is washed and dried to obtain the catalyst, denoted as Co-N-S / NP@Ti3C2 MXene.

[0037] In the present invention, Ti3C2 MXene is used as the substrate, cobalt salt and thiourea dioxide are used as the main raw materials for hydrothermal reaction, so that the C-Ti bond in Ti3C2 MXene is broken to form Ti-Co bond and Ti-O bond, and thiourea dioxide decomposes to dope nitrogen and sulfur atoms and form coordination bonds with Co. The nanosheets self-assemble under high temperature and high pressure to form a micron-sized spherical Co-N-S / NP@Ti3C2 MXene catalyst.

[0038] The present invention is prepared by a hydrothermal method. The process is simple and convenient for batch production. The high temperature and high pressure environment provided by the hydrothermal method can promote the full dissolution and mutual reaction of solutes, and then precipitate crystals. The synthesized material has high purity, high yield and low energy consumption. The prepared catalyst has a nanosheet-sphere hierarchical structure, and this hierarchical structure significantly improves the specific surface area and active site density of the catalyst, and can efficiently catalytically oxidize Hg in flue gas. 0 , CO and NO, and convert the pollutants into Hg 2+ , CO2, NO2 respectively. The oxidation efficiency of Hg 0 , CO and NO in industrial flue gas can reach more than 90%, realizing the integrated and collaborative control of multiple pollutants, shortening the overall flue gas purification process, reducing the purification cost. The Hg 2+ , NO2 pollutants after catalytic oxidation can be removed by the subsequent installed wet flue gas purification device, and it is particularly suitable for enterprises such as coal-fired power plants and metal smelting industries equipped with wet flue gas purification devices such as wet desulfurization and dynamic wave scrubbing.

[0039] In some specific embodiments of the present invention, the cobalt salt is cobalt acetate, such as cobalt acetate tetrahydrate. Compared with other cobalt salts, the presence of acetate roots is beneficial to the dissolution of solutes in the solvent and improves the reaction effect.

[0040] In some specific embodiments of the present invention, the mass ratio of Ti3C2 MXene, cobalt salt and thiourea dioxide is 1-5:15-22:15-20. For example, it can be any value among 1:15:15, 1:15:20, 1:22:20, 3:15:15, 3:15:20, 3:22:20, 5:15:15, 5:20:20, 5:22:20 or the range value composed of any two of these values. The Ti3C2 MXene nanosheets act as a carrier in the system and also have a reduction effect. During the hydrothermal reaction, the C-Ti bonds in Ti3C2 MXene break to form Ti-Co bonds and Ti-O bonds. Nanoscale Co clusters are evenly distributed on the Ti3C2 MXene nanosheets. Then, numerous Ti3C2 MXene nanosheets form a micron-scale spherical structure under hydrothermal conditions. It is difficult to form a nanosheet-sphere hierarchical structure without Ti3C2 MXene, and too little amount of Ti3C2 MXene will also lead to a reduction in active sites, thus affecting the catalytic performance; too little amount of cobalt salt means less active component content, and too much amount of cobalt salt is prone to agglomeration, both of which will affect the catalytic effect; thiourea dioxide reacts with the cobalt salt in the system to play the role of N and S doping and reduction. Under hydrothermal conditions, thiourea dioxide decomposes, and N and S atoms form coordination bonds with Co to form a special configuration, which can adjust properties such as the spin state and d-band center of metallic Co, play a role in regulating the binding energy between the active center and reactants and intermediates, and ultimately achieve the regulation of the intrinsic activity of the catalyst; the lack of any one of the three or the imbalance in the ratio of the three will affect the catalytic performance of the product. Therefore, the amounts of the three need to be reasonably controlled.

[0041] In some specific embodiments of the present invention, the solvents used include a first solvent and a second solvent. The first solvent includes polyethylene glycol and / or ethylene glycol, and the second solvent includes water; for example, the solvent can be a mixed solution of polyethylene glycol and water, or a mixed solution of ethylene glycol and water; to avoid introducing impurities, preferably, the water used is deionized water.

[0042] In some specific embodiments of the present invention, the temperature of the hydrothermal reaction is 180-300 °C. For example, it can be any value among 180 °C, 200 °C, 220 °C, 250 °C, 280 °C, 300 °C or the range value composed of any two of these values; the time of the hydrothermal reaction is 8-13 h. For example, it can be any value among 8 h, 9 h, 10 h, 11 h, 12 h, 13 h or the range value composed of any two of these values. The hydrothermal conditions will affect the product structure. For example, when the hydrothermal temperature is too low, it is not sufficient to form a complete nanosheet-sphere hierarchical structure, which will lead to a decrease in catalytic performance. By controlling the hydrothermal conditions within the above range, it is beneficial to form a complete nanosheet-sphere hierarchical structure, and the removal efficiency of three pollutants, namely Hg 0 , CO and NO in industrial flue gas can all reach more than 90%.

[0043] In some specific embodiments of the present invention, the obtained solid product is washed with ethanol and / or deionized water.

[0044] Ti3C2 MXene can be obtained by purchase or by preparation; in some specific embodiments, the used Ti3C2 MXene is obtained by etching aluminum titanium carbide (Ti3AlC2) with hydrofluoric acid; specifically, it includes the following steps: immersing aluminum titanium carbide in a hydrofluoric acid solution, continuously stirring and heating for etching, and centrifugally washing the obtained solid until it is neutral to obtain.

[0045] In some specific embodiments of the present invention, the etching temperature is 30 - 100 °C. For example, it can be any value among 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, 80 °C, 90 °C, 100 °C or a range value composed of any two of these values; the etching time is 36 - 72 h. For example, it can be any value among 36 h, 42 h, 48 h, 54 h, 60 h, 66 h, 72 h or a range value composed of any two of these values.

[0046] The third aspect of the present invention provides an application of the catalyst described in the foregoing embodiments or the catalyst prepared by the preparation method of any one of the foregoing embodiments in flue gas purification, for catalytically oxidizing Hg in the flue gas 0 , CO and NO.

[0047] The catalyst prepared by the present invention can simultaneously catalytically oxidize multiple pollutants such as Hg 0 , CO and NO in the flue gas, oxidize them into Hg 2+ , CO2, NO2. The Hg 2+ , NO2 pollutants after catalytic oxidation can be removed by the subsequent installed wet flue gas purification device. Using the catalyst of the present invention for flue gas purification has the function of integrally removing multiple pollutants such as Hg 0 , CO and NO in the flue gas. Under suitable purification conditions, the removal rates of the three pollutants can all reach more than 96%, the purification effect is excellent, and it can shorten the overall purification process, reduce the flue gas purification cost, and is particularly suitable for enterprises with wet purification devices such as wet desulfurization and dynamic wave scrubbing installed in industries such as coal-fired power plants and metal smelting.

[0048] In some specific embodiments of the present invention, the method for flue gas purification using the above catalyst includes the following steps:

[0049] Loading the catalyst into a reactor, introducing the flue gas into the reactor for reaction, and oxidizing and removing Hg 0 , CO and NO in the flue gas.

[0050] In some specific embodiments of the present invention, the temperature for flue gas purification is 200 - 350 °C. For example, it can be any value among 200 °C, 220 °C, 250 °C, 280 °C, 300 °C, 320 °C, 350 °C or a range value composed of any two of these values; the catalyst has good structural stability and catalytic efficiency stability within the above temperature range. When purifying flue gas within the above temperature range, the removal efficiency of the three pollutants can all reach over 90%.

[0051] In some specific embodiments of the present invention, the oxygen concentration in the flue gas is not less than 1%, the Hg 0 concentration is not higher than 1 mg / m 3 , the CO concentration is not higher than 10000 mg / m 3 , the NO concentration is not higher than 1000 mg / m 3 , and the SO2 concentration is not higher than 500 mg / m 3 ; when the component content in the flue gas is within the above range and the catalyst of the present invention is used for purification, good purification effects can be obtained.

[0052] In some specific embodiments of the present invention, the contact time between the flue gas and the catalyst bed is not less than 0.5 s.

[0053] The following will describe in detail some embodiments of the present invention in combination with specific examples. The raw material substances used in the examples can be obtained through commercial purchase without special instructions.

[0054] Example 1

[0055] The preparation method of the Co - N - S / NP@Ti3C2 MXene catalyst in this example adopts the following steps:

[0056] Take 0.5 g of Ti3C2 MXene nanosheets, 2 g of cobalt acetate tetrahydrate, and 2 g of thiourea dioxide, dissolve them in 50 mL of a polyethylene glycol aqueous solution with a mass concentration of 50%, then place them in a reactor, seal the reactor and heat it to 200 °C. After reacting for 10 h, naturally cool it to room temperature. The obtained solid is washed three times with ethanol and deionized water in sequence, and after drying, the Co - N - S / NP@Ti3C2 MXene catalyst is obtained. After grinding it into powder, it is reserved for use.

[0057] Calculate the yield of the product according to the input amount of the raw materials and the output amount of the product. The ratio of the output amount of the product to the input amount of the raw materials is its yield, and the yield is 92.3%.

[0058] Example 2

[0059] The preparation method of the Co - N - S / NP@Ti3C2 MXene catalyst in this example adopts the following steps:

[0060] Take 50 g of Ti3C2 MXene nanosheets, 200 g of cobalt acetate tetrahydrate, and 200 g of thiourea dioxide, dissolve them in 5000 mL of an aqueous polyethylene glycol solution with a mass concentration of 50%, then place them in a reactor. Seal the reactor and heat it to 280 °C. After reacting for 8 hours, naturally cool it to room temperature. Take out the solid sample and rinse it three times repeatedly with ethanol and deionized water. After drying, obtain the Co-N-S / NP@Ti3C2 MXene catalyst, and grind it into powder for standby.

[0061] Calculate the yield of the product based on the input amount of raw materials and the output amount of the product. The ratio of the output amount of the product to the input amount of the raw materials is its yield, and the yield is 91.8%.

[0062] Example 3

[0063] The preparation method of the Co-N-S / NP@Ti3C2 MXene catalyst in this example adopts the following steps:

[0064] Take 500 g of Ti3C2 MXene nanosheets, 2 kg of cobalt acetate tetrahydrate, and 2 kg of thiourea dioxide, dissolve them in 50 L of an aqueous polyethylene glycol solution with a mass concentration of 50%, then place them in a reactor. Seal the reactor and heat it to 250 °C. After reacting for 10 hours, naturally cool it to room temperature. Take out the solid sample and rinse it three times repeatedly with ethanol and deionized water. After drying, obtain the Co-N-S / NP@Ti3C2 MXene catalyst, and grind it into powder for standby.

[0065] Calculate the yield of the product based on the input amount of raw materials and the output amount of the product. The ratio of the output amount of the product to the input amount of the raw materials is its yield, and the yield is 92.5%.

[0066] Example 4

[0067] The preparation method of the Co-N-S / NP@Ti3C2 MXene catalyst in this example adopts the following steps:

[0068] Take 30 g of Ti3C2 MXene nanosheets, 350 g of cobalt acetate tetrahydrate, and 280 g of thiourea dioxide, dissolve them in 6000 mL of an aqueous polyethylene glycol solution with a mass concentration of 50%, then place them in a reactor. Seal the reactor and heat it to 280 °C. After reacting for 8 hours, naturally cool it to room temperature. Take out the solid sample and rinse it three times repeatedly with ethanol and deionized water. After drying, obtain the Co-N-S / NP@Ti3C2 MXene catalyst, and grind it into powder for standby.

[0069] Calculate the yield of the product based on the input amount of the raw material and the output amount of the product. The ratio of the output amount of the product to the input amount of the raw material is its yield, and the yield is 92.5%.

[0070] Example 5

[0071] The preparation method of the Co-N-S / NP@Ti3C2 MXene catalyst in this example adopts the following steps:

[0072] Take 30 g of Ti3C2 MXene nanosheets, 300 g of cobalt acetate tetrahydrate, and 400 g of thiourea dioxide, dissolve them in 6000 mL of a polyethylene glycol aqueous solution with a mass concentration of 50%, then place them in a reactor, seal the reactor and heat it to 280 °C. After reacting for 8 hours, naturally cool it to room temperature, take out the solid sample and rinse it three times with ethanol and deionized water. After drying, obtain the Co-N-S / NP@Ti3C2 MXene catalyst, and grind it into powder for standby.

[0073] Calculate the yield of the product based on the input amount of the raw material and the output amount of the product. The ratio of the output amount of the product to the input amount of the raw material is its yield, and the yield is 90.1%.

[0074] Comparative Example 1

[0075] The preparation method of the Co-N-S / NP@Ti3C2 MXene catalyst in this comparative example adopts the following steps:

[0076] Take 0.5 g of Ti3C2 MXene nanosheets, 2 g of cobalt acetate tetrahydrate, and 2 g of thiourea dioxide, dissolve them in 50 mL of a polyethylene glycol aqueous solution with a mass concentration of 50%, then place them in a reactor, seal the reactor and heat it to 100 °C. After reacting for 10 hours, naturally cool it to room temperature, and wash the obtained solid three times with ethanol and deionized water in sequence. After drying, obtain the catalyst.

[0077] Comparative Example 2

[0078] The preparation method of the Co-N-S / NP@Ti3C2 MXene catalyst in this comparative example adopts the following steps:

[0079] Take 0.5 g of Ti3C2 MXene nanosheets, 15 g of cobalt acetate tetrahydrate, and 20 g of thiourea dioxide, dissolve them in 500 mL of a polyethylene glycol aqueous solution with a mass concentration of 50%, then place them in a reactor, seal the reactor and heat it to 200 °C. After reacting for 10 hours, naturally cool it to room temperature, and wash the obtained solid three times with ethanol and deionized water in sequence. After drying, obtain the catalyst.

[0080] Test Example

[0081] (1) Electron microscopy test

[0082] The catalysts prepared in each example were tested by SEM and TEM. Figure 1 Figure 4 is the scanning electron microscopy (SEM) image of the catalyst in Example 1. Figure 2 Figure 5 is the transmission electron microscopy (TEM) image of the catalyst in Example 1. The catalysts prepared by the method of the present invention are all micron-scale spherical structures formed by self-assembly of nanosheets, that is, they have a nanosheet-sphere hierarchical structure.

[0083] (2) Hg 0 Removal rate tests of CO and NO

[0084] The Co-N-S / NP@Ti3C2 MXene catalysts obtained from each example and each comparative example were respectively used to treat industrial flue gas containing Hg 0 , CO and NO. The content of Hg 0 in the simulated flue gas was 340 μg / m 3 , the content of CO was 2500 mg / m 3 , the content of NO was 400 mg / m 3 . The flue gas also contained 4% O2, 2% H2O, and the rest was nitrogen. The specific treatment process is as follows:

[0085] The above simulated flue gas was introduced into a reaction device containing 30 mg of Co-N-S / NP@Ti3C2 MXene catalyst at a flow rate of 150 mL / min. The contact time between the flue gas and the catalyst was 0.5 s, and the temperature was set at 250 °C. The purified exhaust gas was measured. The real-time concentrations of CO and NO were measured using a Testo 350 analyzer; the real-time concentration of Hg 0 in the exhaust gas was measured using a LUMEX mercury analyzer RA-915. After treatment with the catalysts in each example and each comparative example, the contents and removal rates of Hg 0 , CO and NO in the tail gas are shown in Table 1.

[0086] Table 1

[0087]

[0088] Figure 3 Figure 6 is the removal rate results of the catalyst in Example 1 for Hg 0 , CO and NO in the flue gas. Figure 5 Figure 7 is a comparison chart of the removal rate results of the catalysts in Example 1, Comparative Example 1, and Comparative Example 2 for Hg 0 , CO and NO in the flue gas. From the results in Table 1 and Figure 3 , Figure 5 , it can be seen that the catalysts prepared by the method of the present invention can simultaneously catalytically oxidize Hg 0 , CO and NO in the flue gas, and for Hg in the flue gas0 The removal rates of Hg, CO, and NO can all reach over 96%, enabling the integrated removal of multiple pollutants such as Hg, CO, and NO in flue gas. In contrast, in Comparative Example 1 and Comparative Example 2, the removal rates of the catalyst for Hg, CO, and NO are much lower than those in the examples. This is because the hydrothermal conditions in Comparative Example 1 are insufficient to form a complete nanosheet-sphere hierarchical structure, and in Comparative Example 2, the unbalanced ratio leads to a reduction in the active sites of the catalyst. This result verifies the important influence of the preparation parameters and conditions on the catalytic performance of the catalyst. 0 、CO and NO in the flue gas are much lower than those in the examples. This is because the hydrothermal conditions in Comparative Example 1 are insufficient to form a complete nanosheet-sphere hierarchical structure, and in Comparative Example 2, the unbalanced ratio leads to a reduction in the active sites of the catalyst. This result verifies the important influence of the preparation parameters and conditions on the catalytic performance of the catalyst. 0 、CO and NO are much lower than those in the examples. This is because the hydrothermal conditions in Comparative Example 1 are insufficient to form a complete nanosheet-sphere hierarchical structure, and in Comparative Example 2, the unbalanced ratio leads to a reduction in the active sites of the catalyst. This result verifies the important influence of the preparation parameters and conditions on the catalytic performance of the catalyst.

[0089] (3) Influence of flue gas treatment temperature

[0090] This experimental example also investigated the influence of the reaction temperature during the flue gas treatment process on the performance of the catalyst. The method was as follows: Using the catalyst prepared in Example 3, the content of Hg in the simulated flue gas was 340 μg / m 0 , the content of CO was 2500 mg / m 3 , the content of NO was 400 mg / m 3 , the flue gas also contained 4% O2 and 2% H2O, and the rest was nitrogen. At temperatures of 50°C, 100°C, 150°C, 200°C, 250°C, and 300°C respectively, the above simulated flue gas was introduced into a reaction device containing 30 mg of Co-N-S / NP@Ti3C2 MXene catalyst at a flow rate of 150 mL / min. The contact time between the flue gas and the catalyst was 0.5 s. The purified exhaust gas was measured, and a Testo 350 analyzer was used to measure the real-time concentrations of CO and NO; a LUMEX mercury analyzer RA-915 was used to measure the real-time concentration of Hg 3 in the exhaust gas. 0 in the exhaust gas.

[0091] The results are as Figure 4 shown. The catalyst shows good structural stability and catalytic efficiency stability at temperatures of 200 - 300°C. In this temperature range, the removal efficiency of the three pollutants can all reach over 90%, indicating that the catalyst prepared on a large scale can also be applied to the synergistic removal of flue gas pollutants.

[0092] Although the present invention has been illustrated and described with specific examples, it should be realized that the above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions described in the foregoing examples can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A catalyst, characterized in that The invention comprises a carrier and an active component loaded on the carrier, wherein the carrier comprises Ti3C2MXene nanosheets, the active component comprises cobalt nanoparticles doped with N and S, and the catalyst has a nanosheet-sphere hierarchical structure, wherein the nanosheet-sphere hierarchical structure refers to a micron-scale spherical structure formed by self-assembly of nanosheets loaded with nanoparticles.

2. The method for preparing the catalyst according to claim 1, characterized in that: The following steps are involved: The two-dimensional sheet-like Ti3C2MXene is mixed with cobalt salt, thiourea dioxide and a solvent, and a hydrothermal reaction is carried out. The obtained solid product is washed and dried to obtain the catalyst.

3. The method for preparing the catalyst according to claim 2, characterized in that: The mass ratio of the Ti3C2MXene, the cobalt salt and the thiourea dioxide is 1-5:15-22:15-20.

4. The method for preparing the catalyst according to claim 2, characterized in that: The solvent includes a first solvent and a second solvent, the first solvent includes polyethylene glycol and / or ethylene glycol, and the second solvent includes water.

5. The method for preparing the catalyst according to claim 2, characterized in that: The temperature of the hydrothermal reaction is 180-300° C., and the time of the hydrothermal reaction is 8-13 hours.

6. The method for preparing the catalyst according to claim 2, characterized in that: The Ti3C2MXene is obtained by etching aluminum carbide with hydrofluoric acid.

7. The method for preparing a catalyst according to claim 6, characterized in that: The etching temperature is 30-100° C., and the etching time is 36-72 hours.

8. Use of the catalyst according to claim 1 or the catalyst prepared by the method for preparing the catalyst according to any one of claims 2 to 7 in flue gas purification, characterized in that: Used for catalytic oxidation of Hg in the flue gas 0 , CO and NO.

9. The use according to claim 8, characterized in that: The method for flue gas purification using the catalyst comprises the following steps: The catalyst is loaded into a reactor, and the flue gas is introduced into the reactor for reaction.

10. The use according to claim 8 or 9, characterized in that: Contains at least one of the following characteristics: (1) The temperature of the flue gas purification is 200-350°C; (2) The oxygen concentration in the flue gas is not less than 1%, Hg 0 Concentration not higher than 1mg / m 3 、CO concentration is not higher than 10000mg / m 3 , NO concentration is not higher than 1000mg / m 3 , SO2 concentration is not higher than 500mg / m 3 ; (3) The contact time between the flue gas and the catalyst is not less than 0.5 s.

Images