Molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as well as preparation method and application thereof

Abstract

The invention discloses a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as well as a preparation method and application of the molybdenum-manganese composite metal oxide catalyst, and relates to the technical field of catalysts. According to the technical scheme, ammonium metavanadate, oxalic acid, ammonium metatungstate and titanium dioxide are mixed to prepare turbid liquid, the turbid liquid is heated in a water bath, stirred and evaporated until the turbid liquid is solidified, and a vanadium-tungsten-titanium composite oxide precursor is prepared after drying and calcination; the preparation method comprises the following steps: dissolving manganese salt and ammonium molybdate in formamide, carrying out ultrasonic treatment to form a uniform solution, mixing the solution with the vanadium-tungsten-titanium composite oxide precursor powder, carrying out heat preservation and stirring, and finally drying and calcining to prepare the molybdenum-manganese metal diatom vanadium-tungsten-titanium composite oxide catalyst. The molybdenum-manganese composite metal oxide catalyst provided by the invention can realize efficient catalytic reduction of NO2 to form N2 and H2O at a low temperature of 200 DEG C, and the conversion rate of NO2 in a temperature interval of 200-400 DEG C is higher than 85%; and meanwhile, the N2 selectivity is kept close to that of a V2O5-WO3 / TiO2 catalyst.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2, and a preparation method and application thereof. Background Art

[0002] Gas boiler exhaust contains a large amount of nitrogen oxides (NO x ), of which NO2 accounts for more than 50%, forming a large amount of yellow smoke. The commercial ammonia selective catalytic reduction catalyst (V2O5-WO3 / TiO2) has the problem of slow NO2 reaction rate for high-concentration NO2 purification, and cannot effectively inhibit the generation of yellow smoke. At the same time, the exhaust temperature of gas boilers is low (<300℃), and the denitrification activity of V2O5-WO3 / TiO2 is low. The above has become an important bottleneck restricting the development of high-concentration NO2 purification technology.

[0003] At present, modification with transition metals (manganese, molybdenum, iron, cobalt, copper, cerium, etc.) is an effective means to improve the low-temperature catalytic activity of V2O5-WO3 / TiO2 catalysts. Its functions include introducing acidic sites to enhance reactant adsorption, providing electron-rich sites to enhance the ability to capture gas-phase oxygen molecules, and separating acid cycle and redox cycle reaction sites to enhance catalytic activity. However, how to effectively construct metal diatoms is the key to preparing efficient NO2 purification catalysts. Summary of the invention

[0004] The technical problem to be solved by the present invention is: to overcome the shortcomings of the prior art and provide a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 and its preparation method and application, which can realize efficient catalytic reduction of NO2 to form N2 and H2O under low temperature conditions of 200°C, and the NO2 conversion rate is higher than 85% in the temperature range of 200-400°C; at the same time, the N2 selectivity is maintained similar to that of the V2O5-WO3 / TiO2 catalyst.

[0005] The technical solution of the present invention is:

[0006] In a first aspect, the present invention provides a method for preparing a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2, comprising the following steps:

[0007] S1: mixing titanium dioxide powder and deionized water to prepare titanium dioxide slurry;

[0008] S2: dissolving ammonium metavanadate and ammonium metatungstate in oxalic acid, adding deionized water and stirring until all dissolved, and then adding the obtained solution to the titanium dioxide slurry in step S1;

[0009] S3: heating the mixed solution of step S2 in a water bath, stirring and evaporating the mixed solution until agglomerates, and then taking it out and drying it to obtain a vanadium-tungsten-titanium composite oxide precursor;

[0010] S4: grinding the vanadium-tungsten-titanium composite oxide precursor into powder and calcining it, and then taking it out after naturally cooling to room temperature;

[0011] S5: dissolving manganese salt and ammonium molybdate in formamide and ultrasonically treating the solution, then mixing the obtained solution with vanadium tungsten titanium composite oxide precursor powder, stirring the mixture continuously under heat preservation conditions, and then transferring the mixture to a rotary evaporator for dehydration and drying to obtain a metal diatomic vanadium tungsten titanium composite oxide precursor;

[0012] S6: drying the metal diatomic vanadium tungsten titanium composite oxide precursor, taking it out, grinding it and calcining it, and taking it out after naturally cooling it to room temperature to obtain a molybdenum manganese composite metal oxide catalyst.

[0013] Preferably, in step S1, the particle size of the titanium dioxide powder is 30-40 nm, the physical phase is a single anatase phase, and the titanium dioxide concentration in the titanium dioxide slurry is 5-10 wt.%.

[0014] Preferably, in step S2, the molar ratio of ammonium metavanadate to oxalic acid is 0.5-0.6:1.

[0015] Preferably, in step S3, the water bath heating temperature is 75-85°C, the drying temperature is 100-120°C, and the drying time is 10-12h.

[0016] Preferably, in step S4, during calcination, the heating rate is 5-10°C / min, the calcination temperature is 500-550°C, and the calcination time is 4-6h.

[0017] Preferably, in step S5, the loading amount of manganese and molybdenum is 0.9-1wt.%, the mass ratio of the total mass of manganese salt and ammonium molybdate to formamide is 1:100-110, the insulation temperature is 85-90°C, and the rotary evaporation temperature is 70-80°C; the manganese salt is manganese nitrate or manganese acetate.

[0018] Preferably, in step S6, the drying temperature is 100-120°C, the drying time is 4-12h, the heating rate during calcination is 5-10°C / min, the calcination temperature is 500-550°C, and the calcination time is 5-6h.

[0019] Preferably, in step S6, in the obtained molybdenum-manganese composite metal oxide catalyst, vanadium accounts for 1.8-2wt.%, and tungsten accounts for 5-5.6wt.%.

[0020] In a second aspect, the present invention provides a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2, which is prepared by the above-mentioned method for preparing the molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2.

[0021] In a third aspect, the present invention provides an application of the above-mentioned molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2, wherein the reaction temperature of the molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 is 200-400°C when removing NO2.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] Compared with the commercial V2O5-WO3 / TiO2 catalyst, the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst prepared by the present invention can achieve efficient catalytic reduction of NO2 to form N2 and H2O at a low temperature of 200°C, and the NO2 conversion rate is higher than 85% in the temperature range of 200-400°C; at the same time, the N2 selectivity is similar to that of the V2O5-WO3 / TiO2 catalyst. The catalyst has low raw material cost and simple preparation process, and can be applied to the selective catalytic reduction of nitrogen oxides in gas turbines and industrial boilers with high-concentration NO2 emissions, and the catalytic activity meets the emission requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a test chart for evaluating the catalyst activity of Examples 1 and 2 of the present invention.

[0025] Figure 2 It is a test chart of catalyst activity evaluation of Example 1 of the present invention and Comparative Examples 1-8.

[0026] Figure 3 This is a catalyst stability test chart of Example 1 of the present invention.

[0027] Figure 4 It is a test chart of catalyst activity evaluation of Example 1 of the present invention and Comparative Example 9.

[0028] Figure 5 It is a test chart of catalyst activity evaluation of Example 1 of the present invention and Comparative Example 10.

[0029] Figure 6 It is a test chart for evaluating the catalyst activity of Example 1 of the present invention and Comparative Example 11.

[0030] Figure 7 It is a test chart for evaluating the catalyst activity of Example 1 of the present invention and Comparative Example 12. DETAILED DESCRIPTION

[0031] In order to enable persons skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention.

[0032] Example 1

[0033] This example prepares a molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst, and the preparation method is as follows:

[0034] S1. Mix anatase titanium dioxide powder with a particle size range of 30-40 nm with deionized water at room temperature to form a turbid solution A with a concentration of 10 wt.%;

[0035] S2: ammonium metavanadate and oxalic acid are mixed in a molar ratio of 0.5:1 to prepare a solution, which is then mixed with ammonium metatungstate and added with deionized water and stirred until completely dissolved to form solution B. Turbid solution A and solution B are mixed and stirred for 3 hours;

[0036] S3: heating the mixed solution of step S2 in a water bath at 80° C. with stirring until solidified, and drying the solid at 100° C. for 12 hours to obtain a vanadium-tungsten-titanium composite oxide precursor;

[0037] S4: Grind the vanadium-tungsten-titanium composite oxide precursor into powder, transfer it into a muffle furnace and calcine it at 550°C in an air atmosphere for 4 hours at a heating rate of 5°C / min, and take it out after naturally cooling to room temperature;

[0038] S5: dissolving manganese nitrate and ammonium molybdate in a formamide solution, wherein the mass ratio of the total mass of manganese nitrate and ammonium molybdate to formamide is 1:100, followed by ultrasonic treatment for 20 minutes; adding vanadium tungsten titanium composite oxide precursor powder to the above solution, keeping warm and stirring in a 90°C water bath for 6 hours, and then transferring to a rotary evaporator for dehydration and drying at 70°C to obtain a molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide precursor;

[0039] S6 The molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide precursor is dried at 100°C for 12 hours and then ground into powder, transferred into a muffle furnace and calcined at 550°C in an air atmosphere for 5 hours with a heating rate of 5°C / min. After naturally cooling to room temperature, it is taken out to obtain the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst MoMn-VWTi, in which vanadium accounts for 2wt.%, tungsten accounts for 5wt.%, manganese accounts for 1wt.%, and molybdenum accounts for 1wt.%.

[0040] Example 2

[0041] This example prepares a molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst, and the preparation method is as follows:

[0042] S1. Mix anatase titanium dioxide powder with a particle size range of 30-40 nm with deionized water at room temperature to form a turbid solution A with a concentration of 10 wt.%;

[0043] S2: ammonium metavanadate and oxalic acid are mixed in a molar ratio of 0.5:1 to prepare a solution, which is then mixed with ammonium metatungstate and added with deionized water and stirred until completely dissolved to form solution B. Turbid solution A and solution B are mixed and stirred for 3 hours;

[0044] S3: heating the mixed solution of step S2 in a water bath at 75° C. and stirring until solidified, and drying the solid at 110° C. for 11 hours to obtain a vanadium-tungsten-titanium composite oxide precursor;

[0045] S4: Grind the vanadium-tungsten-titanium composite oxide precursor into powder, transfer it into a muffle furnace and calcine it in an air atmosphere at 530°C for 5 hours at a heating rate of 6°C / min, and take it out after naturally cooling to room temperature;

[0046] S5: dissolving manganese acetate and ammonium molybdate in a formamide solution, wherein the mass ratio of the total mass of manganese acetate and ammonium molybdate to formamide is 1:105, followed by ultrasonic treatment for 20 minutes; adding vanadium tungsten titanium composite oxide precursor powder to the above solution, keeping warm and stirring in a water bath at 88°C for 6 hours, and then transferring to a rotary evaporator for dehydration and drying at 75°C to obtain a molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide precursor;

[0047] S6 The molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide precursor is dried at 110°C for 10 hours and then ground into powder, transferred into a muffle furnace and calcined at 530°C in an air atmosphere for 5.5 hours with a heating rate of 6°C / min. After naturally cooling to room temperature, it is taken out to obtain the molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide catalyst MoMn-VWTi, in which vanadium accounts for 1.9wt.%, tungsten accounts for 5.2wt.%, manganese accounts for 0.95wt.%, and molybdenum accounts for 0.95wt.%.

[0048] The catalysts prepared in Example 1 and Example 2 were tested for activity evaluation. The test conditions were: 500 ppm NO2, 500 ppm NH3, 5% O2, N2 as the balance gas, total flow rate of 200 mL / min, gas hourly space velocity (GHSV) of 60000 mL·g -1 ·h -1 .

[0049] The activity evaluation results of the catalysts prepared in Example 1 and Example 2 are as follows: Figure 1 As shown. Figure 1 It can be seen that the MoMn-VWTi catalyst prepared with manganese acetate as the manganese source has higher activity, and the NO2 conversion rate is above 92%.

[0050] Example 3

[0051] This example prepares a molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst, and the preparation method is as follows:

[0052] S1: Anatase titanium dioxide powder with a particle size range of 30-40 nm is mixed with deionized water at room temperature to form a turbid solution A with a concentration of 5 wt.%;

[0053] S2: ammonium metavanadate and oxalic acid are mixed in a molar ratio of 0.6:1 to prepare a solution, which is then mixed with ammonium metatungstate and added with deionized water and stirred until completely dissolved to form solution B. Turbid solution A and solution B are mixed and stirred for 3 hours;

[0054] S3: heating the mixed solution of step S2 in a water bath at 85° C. and stirring until solidified, and drying the solid at 120° C. for 10 h to obtain a vanadium-tungsten-titanium composite oxide precursor;

[0055] S4: Grind the vanadium-tungsten-titanium composite oxide precursor into powder, transfer it into a muffle furnace and calcine it at 500°C in air atmosphere for 6 hours at a heating rate of 10°C / min, and take it out after cooling naturally to room temperature;

[0056] S5: dissolving manganese nitrate and ammonium molybdate in a formamide solution, wherein the mass ratio of the total mass of manganese nitrate and ammonium molybdate to formamide is 1:110, followed by ultrasonic treatment for 20 minutes; adding vanadium tungsten titanium composite oxide precursor powder to the above solution, keeping warm and stirring in a water bath at 85°C for 6 hours, and then transferring to a rotary evaporator for dehydration and drying at 80°C to obtain a molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide precursor;

[0057] S6 The molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide precursor is dried at 120°C for 4 hours and then ground into powder, transferred into a muffle furnace and calcined at 500°C in an air atmosphere for 6 hours with a heating rate of 10°C / min. After naturally cooling to room temperature, it is taken out to obtain the molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide catalyst MoMn-VWTi, in which vanadium accounts for 1.8wt.%, tungsten accounts for 5.6wt.%, manganese accounts for 0.9wt.%, and molybdenum accounts for 0.9wt.%.

[0058] Example 4

[0059] This example prepares a molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst, and the preparation method is as follows:

[0060] S1: Anatase titanium dioxide powder with a particle size range of 30-40 nm is mixed with deionized water at room temperature to form a turbid solution A with a concentration of 8 wt.%;

[0061] S2: ammonium metavanadate and oxalic acid are mixed in a molar ratio of 0.5:1 to prepare a solution, which is then mixed with ammonium metatungstate and added with deionized water and stirred until completely dissolved to form solution B. Turbid solution A and solution B are mixed and stirred for 3 hours;

[0062] S3: heating the mixed solution of step S2 in a water bath at 75° C. with stirring until solidified, and drying the solid at 110° C. for 12 hours to obtain a vanadium-tungsten-titanium composite oxide precursor;

[0063] S4: Grind the vanadium-tungsten-titanium composite oxide precursor into powder, transfer it into a muffle furnace and calcine it in an air atmosphere at 540°C for 5 hours at a heating rate of 5°C / min, and take it out after naturally cooling to room temperature;

[0064] S5: dissolving manganese nitrate and ammonium molybdate in a formamide solution, wherein the mass ratio of the total mass of manganese nitrate and ammonium molybdate to formamide is 1:100, followed by ultrasonic treatment for 20 minutes; adding vanadium tungsten titanium composite oxide precursor powder to the above solution, keeping warm and stirring in a 90°C water bath for 6 hours, and then transferring to a rotary evaporator for dehydration and drying at 70°C to obtain a molybdenum manganese metal diatomic vanadium tungsten titanium composite oxide precursor;

[0065] S6 The molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide precursor is dried at 100°C for 12 hours and then ground into powder, transferred into a muffle furnace and calcined at 540°C in an air atmosphere for 5 hours with a heating rate of 5°C / min. After naturally cooling to room temperature, it is taken out to obtain the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst MoMn-VWTi, in which vanadium accounts for 2wt.%, tungsten accounts for 5wt.%, manganese accounts for 1wt.%, and molybdenum accounts for 1wt.%.

[0066] Comparative Example 1

[0067] The difference between Comparative Example 1 and Example 1 is that steps S5 and S6 are not performed to obtain a vanadium-tungsten-titanium composite oxide catalyst VWTi.

[0068] Comparative Example 2

[0069] The difference between Comparative Example 2 and Example 1 is that ammonium molybdate is not added in step S5, and the manganese metal atom vanadium tungsten titanium composite oxide catalyst Mn-VWTi is finally prepared.

[0070] Comparative Examples 3-8

[0071] The difference between Comparative Examples 3-8 and Example 1 is that the ammonium molybdate in step S5 of Example 1 is replaced by cerium, copper, cobalt, iron, zirconium and niobium in turn, and the prepared catalysts are cerium manganese metal diatomic vanadium tungsten titanium composite oxide catalyst CeMn-VWTi, copper manganese metal diatomic vanadium tungsten titanium composite oxide catalyst CuMn-VWTi, cobalt manganese metal diatomic vanadium tungsten titanium composite oxide catalyst CoMn-VWTi, iron manganese metal diatomic vanadium tungsten titanium composite oxide catalyst FeMn-VWTi, zirconium manganese metal diatomic vanadium tungsten titanium composite oxide catalyst ZrMn-VWTi, and niobium manganese metal diatomic vanadium tungsten titanium composite oxide catalyst NbMn-VWTi.

[0072] Comparative Example 9

[0073] The difference from Example 1 is that manganese accounts for 8 wt.% in the catalyst, and the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst MoMn (8%)-VWTi is finally prepared.

[0074] Comparative Example 10

[0075] The difference from Example 1 is that the molybdenum content in the catalyst is 10 wt.%, and the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst Mo (10%) Mn-VWTi is finally prepared.

[0076] Comparative Example 11

[0077] The difference from Example 1 is that in step S4, the calcination temperature is 800° C., and finally the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst MoMn-(VWTi-800) is prepared.

[0078] Comparative Example 12

[0079] The difference from Example 1 is that in step S6, the calcination temperature is 800°C, and finally the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst MoMn-VWTi-800 is prepared.

[0080] The activity evaluation test of the catalysts prepared in Example 1 and Comparative Examples 1-12 was carried out under the following test conditions: 600 ppm NO x (100ppm NO, 500ppm NO2), 600ppm NH3, 5% O2, N2 as balance gas, total flow rate 200mL / min, gas hourly space velocity (GHSV) 60000mL·g -1 ·h -1 .

[0081] The activity evaluation results of the catalysts prepared in Example 1 and Comparative Examples 1-12 are as follows: Figure 2 , 4 -7. Figure 2 It can be seen that in the temperature range of 200-400°C, the NO2 conversion rate of the molybdenum-manganese metal diatomic vanadium-tungsten-titanium composite oxide catalyst MoMn-VWTi of Example 1 can be maintained at more than 85%, which is better than the catalysts prepared in Comparative Examples 1-12.

[0082] The catalyst prepared in Example 1 was tested for stability under the following conditions: 600 ppm NO x (100ppm NO, 500ppm NO2), 600ppm NH3, 5% O2, N2 as balance gas, temperature 300℃, total flow rate 200mL / min, gas hourly space velocity (GHSV) 60000mL·g -1 ·h -1 .

[0083] The stability test results of the catalyst prepared in Example 1 are as follows: Figure 3 As shown. Figure 3 It can be seen that within 20 hours, the NO2 conversion rate of the MoMn-VWTi catalyst can be maintained at about 90.5%, and the N2 selectivity can be maintained at about 81.6%, indicating that the catalyst prepared in Example 1 has good stability.

Claims

1. A method for preparing a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2, characterized in that: The following steps are involved: S1: mixing titanium dioxide powder and deionized water to prepare titanium dioxide slurry; S2: dissolving ammonium metavanadate and ammonium metatungstate in oxalic acid, adding deionized water and stirring until all dissolved, and then adding the obtained solution to the titanium dioxide slurry in step S1; S3: heating the mixed solution of step S2 in a water bath, stirring and evaporating the mixed solution until agglomerates, and then taking it out and drying it to obtain a vanadium-tungsten-titanium composite oxide precursor; S4: grinding the vanadium-tungsten-titanium composite oxide precursor into powder and calcining it, and then taking it out after naturally cooling to room temperature; S5: dissolving manganese salt and ammonium molybdate in formamide and ultrasonically treating the solution, then mixing the obtained solution with vanadium tungsten titanium composite oxide precursor powder, stirring the mixture continuously under heat preservation conditions, and then transferring the mixture to a rotary evaporator for dehydration and drying to obtain a metal diatomic vanadium tungsten titanium composite oxide precursor; S6: drying the metal diatomic vanadium tungsten titanium composite oxide precursor, taking it out, grinding it and calcining it, and taking it out after naturally cooling it to room temperature to obtain a molybdenum manganese composite metal oxide catalyst.

2. The method for preparing a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as claimed in claim 1, characterized in that: In step S1, the particle size of the titanium dioxide powder is 30-40 nm, the physical phase is a single anatase phase, and the titanium dioxide concentration in the titanium dioxide slurry is 5-10 wt.%.

3. The method for preparing a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as claimed in claim 1, characterized in that: In step S2, the molar ratio of ammonium metavanadate to oxalic acid is 0.5-0.6:

1.

4. The method for preparing a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as claimed in claim 1, characterized in that: In step S3, the water bath heating temperature is 75-85°C, the drying temperature is 100-120°C, and the drying time is 10-12h.

5. The method for preparing a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as claimed in claim 1, characterized in that: In step S4, during calcination, the heating rate is 5-10°C / min, the calcination temperature is 500-550°C, and the calcination time is 4-6h.

6. The method for preparing the molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 according to claim 1, characterized in that: In step S5, the loading amount of manganese and molybdenum is 0.9-1wt.%, the mass ratio of the total mass of manganese salt and ammonium molybdate to formamide is 1:100-110, the insulation temperature is 85-90°C, and the rotary evaporation temperature is 70-80°C; the manganese salt is manganese nitrate or manganese acetate.

7. The method for preparing the molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 according to claim 1, characterized in that: In step S6, the drying temperature is 100-120°C, the drying time is 4-12h, the heating rate during calcination is 5-10°C / min, the calcination temperature is 500-550°C, and the calcination time is 5-6h.

8. The method for preparing the molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as claimed in claim 1, characterized in that: In step S6, in the obtained molybdenum-manganese composite metal oxide catalyst, vanadium accounts for 1.8-2wt.%, and tungsten accounts for 5-5.6wt.%.

9. A molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2, characterized in that: The catalyst is prepared by the method for preparing a molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 as described in any one of claims 1 to 8.

10. The use of the molybdenum-manganese composite metal oxide catalyst for efficient NO2 purification as claimed in claim 9, characterized in that: When the molybdenum-manganese composite metal oxide catalyst for efficiently purifying NO2 removes NO2, the reaction temperature is 200-400°C.

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