Preparation method and application of MXene-based low-temperature denitrification catalyst

Abstract

The invention discloses a preparation method and application of a MXene-based low-temperature denitration catalyst, and relates to the technical field of denitration catalysts. The invention uses a MXene / transition metal composite material obtained by Lewis acid molten salt etching and ammonia water soaking as a catalyst carrier material, potassium permanganate as an oxidant and a manganese source, and an acid as a reaction catalyst. Under the protection of high-purity nitrogen, a low-temperature denitration catalyst of manganese and other metal mixed oxides is prepared by heating and stirring the reaction, and the catalyst is uniformly loaded on the surface of the MXene carrier. The layered structure and chemical activity of the MXene carrier provide sufficient specific surface area and reaction sites for the dispersion and fixation of the mixed oxide catalyst. The MXene-based low-temperature denitration catalyst prepared by the invention has a simple synthesis process, high yield, and is green and environmentally friendly. The catalyst shows high denitration activity in the low-temperature selective catalytic reduction of nitrogen oxides, and thus has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of denitration catalysts, and in particular to a preparation method and application of a MXene-based low-temperature denitration catalyst. Background Art

[0002] At present, under aerobic conditions, the selective catalytic reduction reaction (SCR) with ammonia (NH3) as a reducing agent is one of the most widely used technologies among many nitrogen oxide elimination and control technologies. The core of this technology is the denitrification catalyst. In recent years, low-temperature NH3-SCR technology with potential industrial application value and significant energy-saving benefits has been widely studied. The key factors affecting the industrial application of low-temperature NH3-SCR denitrification technology are its poor catalyst selectivity, low reaction activity and weak resistance to H2O and SO2. The efficient preparation method and active components of low-temperature denitrification catalysts have been extensively and deeply studied at home and abroad. Manganese oxide has good low-temperature denitrification activity and has the advantages of low cost, low toxicity and environmental protection, so it has become a hot topic of research. In addition, the selection of catalyst carrier materials and the doping of transition metal oxides are effective methods to improve the low-temperature activity and anti-poisoning performance of manganese-based catalysts.

[0003] MXenes are a new type of two-dimensional transition metal carbon / nitride or carbonitride, which is composed of M n+1 AX n Phase material (MAX phase) is obtained by peeling off a single layer or thin layer of nanosheets. The unique two-dimensional layered structure, large specific surface area, and excellent electrical conductivity, mechanical stability, and magnetic properties have made MXenes quickly become a research hotspot, and have been widely used in many fields such as energy storage, catalysis, and adsorption. In 2019, scientists discovered that Ti3AlC2 can react with ZnCl2 molten salt in ZnCl2 molten salt, and thus proposed a new Lewis acid molten salt method. It can be seen from this that MXene with halogen end groups can be synthesized by molten salt or halogen-containing organic etchant, and the preparation of MXene by molten salt method does not cause pollution, which is a technology very suitable for industrial production.

[0004] Manganese-based catalysts are a hot topic in the research of low-temperature SCR denitrification technology. In recent years, researchers from various countries have reported a lot on them. Its main types can be divided into supported Mn-based catalysts and non-supported Mn-based catalysts. Supported Mn-based catalysts are prepared by loading active components on certain carriers to obtain a larger specific surface area and higher activity. Patent application number 202010419201.0 discloses a manganese-based ultra-low temperature denitrification catalyst powder and a preparation method thereof, using manganese oxide, iron oxide and a large amount of rare earth element oxides as active substances, and titanium oxide as a carrier. Patent application number 202110615740.6 discloses a MnO2 nanowire low-temperature denitrification catalyst based on a mesh TiO2 carrier. Although the low temperature avoids the use of rare earth elements and reduces production costs, the use of a single catalyst active component makes the low-temperature activity and anti-poisoning performance not very ideal. Up to now, there are few related technologies for preparing low-temperature denitrification catalysts using MXene as a carrier. Summary of the invention

[0005] The purpose of the present invention is to provide a preparation method and application of a MXene-based low-temperature denitration catalyst to solve the problems of low activity and complex preparation methods of existing low-temperature denitration catalysts mentioned in the above technical background.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a MXene-based low-temperature denitration catalyst comprises the following steps: firstly, using a MXene / transition metal composite material obtained by Lewis acid molten salt etching and ammonia water soaking as a catalyst carrier; then using potassium permanganate as an oxidant and a manganese source, and an acid as a reaction catalyst; and under the protection of high-purity nitrogen, heating and stirring the reaction to obtain a mixed oxide of manganese and other metals; and finally filtering, washing and drying to obtain a MXene-based low-temperature denitration catalyst.

[0008] Specifically, the following steps are included:

[0009] (1) Titanium aluminum carbide (Ti3AlC2), sodium chloride, potassium chloride, and transition metal chloride are weighed in a mass ratio of 1:1-10:1-10:1-10, respectively, and placed in a mortar to be fully ground and mixed for 0.1-10 hours, and then a layer of sodium chloride and potassium chloride mixture is spread on the surface to isolate the air, and finally transferred to an ark and placed in a tube furnace, and directly heated from room temperature to 400-900°C at a temperature program of 1-20°C / min in an air atmosphere, and kept warm for 0.5-48 hours. After the reaction is completed, the obtained product is transferred to a beaker and soaked in a certain amount of ammonia solution for 1-10 days, and finally separated, washed and dried to obtain a MXene / transition metal composite material carrier;

[0010] (2) placing the MXene / transition metal composite material obtained by Lewis acid molten salt etching in a beaker, then adding a certain amount of deionized water and 0-10% acid and ultrasonically mixing at room temperature for 0.1-10 hours until a uniform dispersion is formed;

[0011] (3) Weigh a certain amount of potassium permanganate solid, add it to the mixture of step (2), and continue to stir and mix at room temperature for 0.1 to 24 hours after passing high-purity nitrogen gas, until a uniformly dispersed mixed solution is formed;

[0012] (4) heating the mixed solution in step (2) to 30-100° C. and reacting at this temperature for 0.1-24 hours;

[0013] (5) The reactant in step (3) is cooled and filtered, rinsed with water and ethanol until the filtrate is colorless, and then the filtered product is placed in a vacuum drying oven at 50 to 120° C. for drying to obtain MXene-based low-temperature denitration catalysts with different catalyst loadings.

[0014] Preferably, the transition metal chloride in step (1) includes but is not limited to any one or more of cobalt chloride, copper chloride and ferric chloride.

[0015] Preferably, in step (1), the drying temperature is 50-100° C. and the drying time is 12-24 h.

[0016] Preferably, the concentration of the MXene / transition metal composite material in step (2) is 2-20 mg / mL.

[0017] Preferably, the molar ratio of potassium permanganate to the MXene / transition metal composite material in step (3) is between 1:0.1 and 1:10.

[0018] Preferably, the stirring speed in step (3) is 50-500 r / min.

[0019] Preferably, the vacuum drying time in step (5) is 12-24 hours.

[0020] Another object of the present invention is to provide an application of the MXene-based low-temperature denitration catalyst prepared by the above preparation method in denitration, specifically, in the low-temperature selective catalytic reduction of nitrogen oxides in industrial exhaust gas.

[0021] Beneficial effects of the present invention:

[0022] 1. Using MXene as a catalyst carrier, its unique two-dimensional layered structure, large specific surface area, and excellent conductivity, mechanical stability, and magnetic properties are conducive to the dispersion and synergistic effect of active components on its surface, thereby promoting the low-temperature denitrification performance of the catalyst.

[0023] 2. Compared with the conventional preparation technology of binary manganese-based denitrification catalyst, the present invention uses MXene / transition metal composite material prepared by molten salt method as carrier material, potassium permanganate as oxidant and manganese source, and obtains binary manganese-based denitrification catalyst by heating and stirring. The whole synthesis process is simple, green and environmentally friendly, and has good industrial application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described below in conjunction with the accompanying drawings.

[0025] Figure 1 SEM images of the MXene-based low-temperature deNOx catalysts according to the embodiments of the present invention: A, Co / MXene; B, Mn-CoOx / MXene.

[0026] Figure 2 This is the XRD diagram of the MXene-based low-temperature deNOx catalyst according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The Fe / MXene carrier materials were all prepared by the following steps: 0.25g Ti3AlC2, 0.3g NaCl, 0.35g KCl, and 1.5g FeCl2·4H2O were weighed and placed in a mortar and ground thoroughly for 10 minutes, then transferred to an ark and a layer of 0.2g NaCl and 0.25g KCl molten salt was spread on it, and finally placed in a tubular furnace. Under an air atmosphere, the temperature was raised from room temperature to 750°C at a rate of 5°C / min, and kept at 750°C for 4h. After the reaction was completed, the obtained product was transferred to a beaker and added with 20mL of ammonia solution to soak for 5 days. Finally, the dissolved product was filtered and vacuum dried at 60°C to obtain a Fe / MXene carrier.

[0029] The Co / MXene carrier materials were all prepared by the following steps: 0.25g Ti3AlC2, 0.3g NaCl, 0.35g KCl, and 1.8g CoCl2·4H2O were weighed and placed in a mortar and ground thoroughly for 10 minutes, then transferred to an ark and a layer of 0.2g NaCl and 0.25g KCl molten salt was spread on it, and finally placed in a tubular furnace. Under an air atmosphere, the temperature was raised from room temperature to 750°C at a rate of 5°C / min, and kept at 750°C for 4h. After the reaction was completed, the obtained product was transferred to a beaker and added with 20mL of ammonia solution to soak for 5 days. Finally, the dissolved product was filtered and vacuum dried at 60°C to obtain a Co / MXene carrier.

[0030] The Cu / MXene carrier materials were all prepared by the following steps: 0.25 g Ti3AlC2, 0.3 g NaCl, 0.35 g KCl, and 1.5 g CuCl2·4H2O were weighed and placed in a mortar and ground thoroughly for 10 min, then transferred to an ark and a layer of 0.2 g NaCl and 0.25 g KCl molten salt was spread on it, and finally placed in a tubular furnace. Under an air atmosphere, the temperature was raised from room temperature to 750°C at a rate of 5°C / min, and kept at 750°C for 4 h. After the reaction was completed, the obtained product was transferred to a beaker and added with 20 mL of ammonia solution to soak for 5 days. Finally, the dissolved product was filtered and vacuum dried at 60°C to obtain a Cu / MXene carrier.

[0031] Example 1

[0032] Weigh 0.14 g of Co / MXene carrier, then add 20 mL of deionized water and perform ultrasonic treatment at room temperature for 0.5 h until a uniformly dispersed dispersion is formed; then add 0.08 g of potassium permanganate solid, and after passing high-purity nitrogen, continue stirring at room temperature for 0.5 h until a uniformly dispersed mixed solution is formed; heat the mixed solution obtained above to 70°C, and stir the reaction at a constant temperature for 0.5 h; after the reaction is cooled to room temperature, filter it with deionized water until the filtrate is colorless, and then place the filtered product in a vacuum drying oven at 80°C for drying to obtain a manganese-cobalt mixed oxide denitrification catalyst supported on the MXene carrier.

[0033] Example 2

[0034] Weigh 0.14 g of Co / MXene carrier, then add 20 mL of deionized water and 0.05 mL of nitric acid and perform ultrasonic treatment at room temperature for 0.5 h until a uniformly dispersed dispersion is formed; then add 0.08 g of potassium permanganate solid, and after passing high-purity nitrogen, continue stirring at room temperature for 0.5 h until a uniformly dispersed mixed solution is formed; heat the obtained mixed solution to 70 ° C, and stir the reaction at a constant temperature for 1 h; after the reaction is cooled to room temperature, filter it with deionized water until the filtrate is colorless, and then place the filtered product in a vacuum drying oven at 80 ° C for drying to obtain a manganese-cobalt mixed oxide denitrification catalyst supported on the MXene carrier.

[0035] Example 3

[0036] Weigh 0.14 g of Co / MXene carrier, then add 20 mL of deionized water and 0.05 mL of nitric acid and perform ultrasonic treatment at room temperature for 0.5 h until a uniformly dispersed dispersion is formed; then add 0.08 g of potassium permanganate solid, and after passing high-purity nitrogen, continue stirring at room temperature for 0.5 h until a uniformly dispersed mixed solution is formed; heat the obtained mixed solution to 90 ° C, and stir the reaction at a constant temperature for 1 h; after the reaction is cooled to room temperature, filter it with deionized water until the filtrate is colorless, and then place the filtered product in a vacuum drying oven at 80 ° C for drying to obtain a manganese-cobalt mixed oxide denitrification catalyst supported on the MXene carrier.

[0037] Example 4

[0038] Weigh 0.14 g of Co / MXene carrier, then add 20 mL of deionized water and 0.4 mL of nitric acid and perform ultrasonic treatment at room temperature for 0.5 h until a uniformly dispersed dispersion is formed; then add 0.08 g of potassium permanganate solid, and after passing high-purity nitrogen, continue stirring at room temperature for 0.5 h until a uniformly dispersed mixed solution is formed; heat the obtained mixed solution to 70°C, and stir the reaction at a constant temperature for 0.5 h; after the reaction is cooled to room temperature, filter it with deionized water until the filtrate is colorless, and then place the filtered product in a vacuum drying oven at 80°C for drying to obtain a manganese-cobalt mixed oxide denitrification catalyst supported on the MXene carrier.

[0039] Example 5

[0040] Weigh 0.14 g of Co / MXene carrier, then add 20 mL of deionized water and 0.1 mL of nitric acid and perform ultrasonic treatment at room temperature for 0.5 h until a uniformly dispersed dispersion is formed; then add 0.08 g of potassium permanganate solid, and after passing high-purity nitrogen, continue stirring at room temperature for 0.5 h until a uniformly dispersed mixed solution is formed; stir the obtained mixed solution at room temperature for 0.5 h; after the reaction is cooled to room temperature, filter it with deionized water until the filtrate is colorless, and then place the filtered product in a vacuum drying oven at 60°C for drying to obtain a manganese-cobalt mixed oxide denitrification catalyst supported on the MXene carrier.

[0041] Example 6

[0042] Weigh 0.14 g of Fe / MXene carrier, then add 20 mL of deionized water and 0.05 mL of nitric acid and perform ultrasonic treatment at room temperature for 1 hour until a uniformly dispersed dispersion is formed; then add 0.08 g of potassium permanganate solid, and after passing high-purity nitrogen, continue stirring at room temperature for 1 hour until a uniformly dispersed mixed solution is formed; heat the obtained mixed solution to 70°C and stir at a constant temperature for 2 hours; after the reaction is cooled to room temperature, filter with deionized water until the filtrate is colorless, and then place the filtered product in a vacuum drying oven at 60°C for drying to obtain a manganese-iron mixed oxide denitrification catalyst supported on the MXene carrier.

[0043] Example 7

[0044] Weigh 0.14 g of Cu / MXene carrier, then add 20 mL of deionized water and perform ultrasonic treatment at room temperature for 1 hour until a uniformly dispersed dispersion is formed; then add 0.08 g of potassium permanganate solid, and after passing high-purity nitrogen, continue stirring at room temperature for 2 hours until a uniformly dispersed mixed solution is formed; heat the above-obtained mixed solution to 100°C, and stir the reaction at a constant temperature for 2 hours; after the reaction is cooled to room temperature, filter it with deionized water until the filtrate is colorless, and then place the filtered product in a vacuum drying oven at 60°C for drying to obtain a manganese-copper mixed oxide denitrification catalyst supported on a MXene carrier.

[0045] like Figure 1-Figure 2 Shown are the SEM image and XRD image of the MXene-based low-temperature deNOx catalyst of an embodiment of the present invention.

[0046] Denitrification activity test

[0047] The denitration activity of the denitration catalyst in the embodiment was tested under the following test conditions: about 0.12 g of the above MXene-based denitration catalyst was weighed and filled into a reactor for denitration activity evaluation. The volume fractions of NO and NH3 were both 0.05%, the volume fraction of O2 was 5%, and the rest was N2. The gas flow rate was 180 mL min -1 , airspeed is about 50000h -1 After the airflow stabilized for 30 minutes, the NO conversion rate in the reaction temperature range of 100-180°C was measured using a German M60x flue gas analyzer. The test results are shown in the following table:

[0048]

[0049] The above specific implementation method part specifically introduces the analytical method involved in the present invention. It should be noted that the above introduction is only to help those skilled in the art better understand the method and ideas of the present invention, rather than limiting the relevant content. Without departing from the principle of the present invention, those skilled in the art may also make appropriate adjustments or modifications to the present invention, and the above adjustments and modifications shall also fall within the scope of protection of the present invention.

Claims

1. A method for preparing a MXene-based low-temperature denitration catalyst, characterized in that: First, the MXene / transition metal composite material obtained by Lewis acid molten salt etching and ammonia soaking is used as a catalyst carrier, and then potassium permanganate is used as an oxidant and manganese source, and acid is used as a catalyst for the reaction. Under the protection of high-purity nitrogen, a mixed oxide of manganese and other metals is obtained by heating and stirring the reaction, and finally a MXene-based low-temperature denitration catalyst is obtained after filtering, washing and drying. Specifically, the following steps are included: (1) Weigh titanium aluminum carbide, sodium chloride, potassium chloride, and transition metal chloride in a mass ratio of 1:1-10:1-10:1-10, place them in a mortar and grind them thoroughly for 0.1-10 h, then spread a layer of sodium chloride and potassium chloride mixture on the surface to isolate the air, finally transfer them to an ark and put them into a tube furnace, directly heat the temperature from room temperature to 400-900°C at a rate of 1-20°C / min in an air atmosphere, and keep the temperature for 0.5-48 h. After the reaction is completed, transfer the obtained product to a beaker and add a certain amount of ammonia solution to soak it for 1-10 days, and finally separate, wash and dry to obtain a MXene / transition metal composite material carrier; wherein the transition metal chloride is cobalt chloride, copper chloride or ferric chloride; (2) The MXene / transition metal composite material obtained by Lewis acid molten salt etching was placed in a beaker, and then 20 mL of deionized water and 0.05 mL of nitric acid were added and ultrasonically mixed at room temperature for 0.1 to 10 h until a uniform dispersion was formed; (3) Weigh a certain amount of potassium permanganate solid, add it to the mixture of step (2), and continue to stir and mix at room temperature for 0.1 to 24 h after passing high-purity nitrogen gas, until a uniformly dispersed mixed solution is formed; (4) heating the mixed solution in step (2) to 30-100°C and reacting at the constant temperature for 0.1-24 h; (5) The reactant in step (3) is cooled and filtered, rinsed with water and ethanol until the filtrate is colorless, and then the filtered product is placed in a vacuum drying oven at 50-120° C. for drying to obtain MXene-based low-temperature denitration catalysts with different catalyst loadings.

2. The method for preparing a MXene-based low-temperature denitration catalyst according to claim 1, characterized in that: In step (1), the drying temperature is 50-100°C and the drying time is 12-24h.

3. The method for preparing a MXene-based low-temperature denitration catalyst according to claim 1, characterized in that: The concentration of the MXene / transition metal composite material in step (2) is 2-20 mg / mL.

4. The method for preparing a MXene-based low-temperature denitration catalyst according to claim 1, characterized in that: The molar ratio of potassium permanganate to the MXene / transition metal composite material in step (3) is between 1:0.1 and 1:

10.

5. The method for preparing a MXene-based low-temperature denitration catalyst according to claim 1, characterized in that: The stirring speed in step (3) is 50-500 r / min.

6. The method for preparing a MXene-based low-temperature denitration catalyst according to claim 1, characterized in that: The vacuum drying time in step (5) is 12-24 hours.

7. Application of the MXene-based low-temperature denitration catalyst prepared according to the preparation method according to any one of claims 1 to 6 in denitration.

8. The use according to claim 7, characterized in that: Application in low-temperature selective catalytic reduction of nitrogen oxides in industrial exhaust gas.

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