CN111250078B

CN111250078B - MnOx @ Eu-CeOx low-temperature SCR flue gas denitration catalyst and preparation method and application thereof

Info

Publication number: CN111250078B
Application number: CN202010277922.2A
Authority: CN
Inventors: 喻成龙
Original assignee: Jiangxi Agricultural University
Current assignee: Jiangxi Agricultural University
Priority date: 2020-04-10
Filing date: 2020-04-10
Publication date: 2020-11-20
Anticipated expiration: 2040-04-10
Also published as: CN111250078A

Abstract

The invention discloses MnO_x@Eu‑CeO_xA low-temperature SCR flue gas denitration catalyst, a preparation method and application thereof. MnO prepared by hydrothermal method_xTaking the nano-rod as an inner core, and carrying out Eu-CeO by a modified chemical precipitation method_xThe precursor is wrapped in MnO_xThe outer layer of the nano-rod is roasted to prepare MnO with a core-shell structure_x@Eu‑CeO_xLow-temperature SCR flue gas denitration catalyst and prepared MnO_x@Eu‑CeO_xMnO in low-temperature SCR flue gas denitration catalyst_xNanorods and CeO_xAnd EuO_xThe molar mass ratio of (A) to (B) is 1: 0.4-1.2: 0.2-0.8. MnO of the invention_x@Eu‑CeO_xThe low-temperature SCR flue gas denitration catalyst has a core-shell structure, and the shell is a composite oxide shell, so that the redox capability of the active components and the interaction between the active components are greatly improved, and excellent NO is shown at 100-200 DEG C_xCatalytic reduction activity and low-temperature strong sulfur poisoning resistance.

Description

MnOx@Eu-CeOxLow-temperature SCR flue gas denitration catalyst and preparation method and application thereof

Technical Field

The invention belongs to the field of environmental protection and environmental catalysis, and particularly relates to MnO_x@Eu-CeO_xA low-temperature SCR flue gas denitration catalyst, a preparation method and application thereof.

Background

Nitrogen Oxides (NO)_x) Is one of the main atmospheric pollutants causing acid rain, photochemical smog and ozone layer damage, has serious harm to human health and ecological environment, and how to effectively control and reduce NO_xHas received attention from researchers in various countries. According to statistics, 70.9% of the discharge amount of nitrogen oxides in China in 2014 comes from the discharge of nitrogen oxides of industrial sources such as power, thermal power production and supply industries, wherein the discharge amount of the nitrogen oxides in thermal power plants accounts for 62.1% of the total discharge amount of the nitrogen oxides in industrial enterprises, and the nitrogen oxides are large households discharging the nitrogen oxides in China. Therefore, the control of the emission of nitrogen oxides from industrial sources, particularly in the power industry, is the key to the prevention and control of air pollution in China.

Among the numerous nitrogen oxide pollution control technologies, the Selective Catalytic Reduction (SCR) technology is the most widely used and technically mature technology for treating industrial source NO_xThe method of (1). And SCR technology for removing NO_xThe core of (A) is the good and bad performance of the catalyst, and the commercial vanadium-based catalyst (V) is adopted at present₂O₅-WO₃/TiO₂) The catalyst has excellent catalytic performance in a medium-temperature section (300-450 ℃), and the denitration device is arranged in front of the desulfurization and dust removal device in the temperature section, SO that the catalyst is at a high SO₂And high ash content environments. If the denitration device is placed in the desulfurization and dust removal device, the SO can be reduced₂And dust, but the flue gas temperature can be reduced to below 200 ℃, so that the energy consumption is avoided because the medium-temperature catalyst needs to reheat the flue gas, and the development of the low-temperature and high-efficiency non-vanadium denitration catalyst has very important significance for solving the problem.

The surface modification of nanoparticles has formed a research field and pushed the research of nanomaterials to a new stage. The significance of the research on the field of nanoparticle surface modification lies in that more nanoparticles can be modified on the surface, the basic physicochemical effect of the nanoparticles can be deeply known, and the application range of the nanoparticles can be expanded. The structural uniqueness and designability of the core-shell structure material and the cooperativity of all components enable the core-shell structure material to show excellent performance in the fields of environmental protection, electrochemistry, energy, petrochemical industry and the like. When the catalyst is applied to the low-temperature SCR reaction process, the special performance of the core-shell structure catalyst is mainly reflected in that the shell layer has a strong protection effect on the core and has a regulation and modification function on the core.

The manganese-based catalyst has higher low-temperature catalytic activity in the application of low-temperature selective catalytic reduction. However, the Mn-based catalyst has poor sulfur poisoning resistance. Accordingly, the invention uses MnO_xThe nano-rod is used as a core, and MnO with a composite shell is designed and synthesized_x@Eu-CeO_xThe low-temperature SCR flue gas denitration catalyst has excellent low-temperature SCR performance and strong poisoning resistance.

Disclosure of Invention

To overcome the deficiencies of the prior art, the present invention provides MnO_x@Eu-CeO_xA low-temperature SCR flue gas denitration catalyst, a preparation method and application thereof.

The invention is realized by the following technical scheme.

MnO_x@Eu-CeO_xPreparation method of low-temperature SCR flue gas denitration catalyst and low-temperature SCR flue gas denitration catalystCharacterized in that the preparation method firstly carries out hydrothermal synthesis to obtain MnO with high activity_xNanorods with MnO_xTaking the nano-rod as a core, and carrying out Eu-CeO by a modified chemical precipitation method_xWrapping to MnO_xThe outer layer of the nano-rod is roasted to prepare MnO_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst, MnO_x@Eu-CeO_xMnO in low-temperature SCR flue gas denitration catalyst_xNanorods and CeO_xAnd EuO_xThe molar mass ratio of (A) to (B) is 1: 0.4-1.2: 0.2-0.8.

Further, the preparation method comprises the following steps:

（1）MnO_xpreparing the nano-rods: 1.2156 g of KMnO₄The resulting solution was dissolved in 157.4 mL of deionized water with stirring. After dissolution, hydrochloric acid with a certain concentration is added, stirring is continued, and finally the volume is determined to 160 mL. Transferring the solution into a 200 mL reaction kettle, heating to 140 ℃, and reacting for a certain time. Naturally cooling to room temperature, taking out the product, washing the product to be neutral, and drying at 80 ℃ to obtain a powdery solid product.

（2）MnO_x@Eu-CeO_xThe preparation of (1): a certain amount of MnO_xAdding nanorod powder into absolute ethyl alcohol, performing ultrasonic treatment, stirring and dispersing uniformly, then sequentially adding a hexamethylenetetramine solution, a cerium nitrate hexahydrate solution and a europium nitrate hexahydrate solution, controlling the adding rates of the three solutions, performing reaction under the heating and stirring of a water bath, washing and drying a reaction product, roasting, and cooling to room temperature to finally obtain the MnO_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst.

Wherein the hydrochloric acid in the step (1) is a 37 wt% HCl solution, the dosage is 2.0-3.0 mL, and the reaction time is 6-24 h; the drying is carried out for 6-24 h at the temperature of 80 ℃.

Preferably, in the step (1), the dosage of the hydrochloric acid is 2.6 mL.

Preferably, in the step (1), the reaction time is 12 h; the drying is carried out for 12h at 80 ℃.

In the step (2), the amount of the absolute ethyl alcohol is 40-80 mL; the using amount of the manganese oxide is 0.7-2.5 g; the molar ratio of the hexamethylenetetramine to the cerium nitrate hexahydrate to the europium nitrate hexahydrate is 0.6-1.9: 2.5-10: 0.8-3.4; the adding sequence of the hexamethylene tetramine, the cerium nitrate hexahydrate and the europium nitrate hexahydrate is that a hexamethylene tetramine solution is added firstly, and then a cerium nitrate hexahydrate solution and a europium nitrate hexahydrate solution are added simultaneously. Controlling the adding rate of the hexamethylenetetramine solution, the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution to be 0.05 mL/min-2 mL/min; the temperature of the water bath heating is 70-80 ℃; the reaction time is 2-4 h; the drying is carried out for 8-12 h at the temperature of 70-80 ℃; the roasting is carried out for 2-4 h at the temperature rising rate of 0.5-1.5 ℃/min to 400-600 ℃ in the air atmosphere.

Preferably, in the step (2), the dosage of the absolute ethyl alcohol is 60 mL.

Preferably, in the step (2), the amount of the manganese oxide is 1.14 g.

Preferably, in the step (2), the molar ratio of the hexamethylenetetramine to the cerium nitrate hexahydrate to the europium nitrate hexahydrate is 1.3: 5: 1.7.

preferably, in the step (2), the hexamethylenetetramine, the cerium nitrate hexahydrate and the europium nitrate hexahydrate are added in sequence, namely, the hexamethylenetetramine solution is added, and then the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution are added simultaneously. The adding rates of the hexamethylenetetramine solution, the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution are controlled to be 0.05 mL/min, 0.1 mL/min and 0.2 mL/min respectively.

Preferably, in the step (2), the temperature of the water bath heating is 75 ℃; the reaction time is preferably 2 hours, 3 hours and 4 hours.

Preferably, the drying in the step (2) is drying at 80 ℃ for 12 h; the roasting is carried out in the air atmosphere, the temperature is increased to a certain roasting temperature at the temperature increase rate of 1 ℃/min, and the roasting temperature is respectively 400 ℃, 500 ℃ and 600 ℃ preferentially. The roasting time is 2 hours.

The invention also discloses MnO prepared by the method_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst. Prepared MnO_x@Eu-CeO_xThe SCR activity is higher than 90% in a low-temperature range of 100-200 ℃. The invention also discloses MnO_x@Eu-CeO_xThe low-temperature SCR flue gas denitration catalyst is applied to a low-temperature SCR flue gas denitration system.

The invention uses MnO_xThe nano-rod is used as a core, and MnO with a composite shell is designed and synthesized_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst. MnO_x@Eu-CeO_xThe catalyst is characterized in that 1) strong interaction between Mn and Ce exists in the catalyst, so that the catalytic activity of the catalyst can be obviously improved; 2) two different rare earth metal oxides are present in the catalyst shell, the two rare earth metal oxides being paired with SO₂Has different adsorption reaction performance, SO that the adsorbent has strong SO resistance₂The poisoning performance is good, and Eu and Ce are uniformly distributed, so that the Eu and Ce have multiple protection effects on the inner core; 3) coating double rare earth metal oxide in MnO by adopting improved chemical precipitation method_xThe nanorod surface improves the dispersibility of active components and simultaneously improves the redox performance and surface acidity of the catalyst, so that the catalyst shows excellent NH at a low temperature stage (below 200℃)₃-SCR performance.

Drawings

FIG. 1 shows comparative example 1 (MnO) in the present invention_x) Comparative example 2 (Eu-CeO)_x/MnO_x) Example 1 (MnO)_x@Eu-CeO_x) XRD pattern of

FIG. 2 shows comparative example 1 (MnO) in the present invention_x) Comparative example 2 (Eu-CeO)_x/MnO_x) Example 1 (MnO)_x@Eu-CeO_x) XPS spectra of

FIG. 3 shows comparative example 1 (MnO) in the present invention_x) Comparative example 2 (Eu-CeO)_x/MnO_x) Example 1 (MnO)_x@Eu-CeO_x) HRTEM atlas of

Wherein a, b and c are MnO_x(ii) a d. e, f are Eu-CeO_x/MnO_x) (ii) a g. h, i are MnO_x@Eu-CeO_x

FIG. 4 shows example 1 (MnO) of the present invention_x@Eu-CeO_x) TEM surface scanning image of

The invention is further explained with reference to the drawings and the embodiments.

Detailed Description

The invention provides MnO_x@Eu-CeO_xThe invention further discloses a low-temperature SCR flue gas denitration catalyst, a preparation method and an application thereof, and the invention is further explained by combining a specific embodiment. However, the embodiments of the present invention are not limited thereto, and may be performed with reference to conventional techniques if process parameters are not particularly noted.

Example 1

（1）MnO_xPreparing the nano-rods: 1.2156 g of KMnO₄The resulting solution was dissolved in 157.4 mL of deionized water with stirring. After dissolution, 2.6 mL of 37 wt% hydrochloric acid was added and the mixture was stirred until the volume was 160 mL. The solution was transferred to a 200 mL reactor and allowed to warm to 140 ℃ for 12 h. Naturally cooling to room temperature, taking out the product, washing the product to be neutral, and drying at 80 ℃ for 12h to obtain a powdery solid product.

（2）MnO_x@Eu-CeO_xThe preparation of (1): 1.14g of MnO_xAdding nanorod powder into 60 mL of absolute ethyl alcohol, performing ultrasonic treatment, uniformly stirring and dispersing, sequentially adding a hexamethylenetetramine solution, a cerium nitrate hexahydrate solution and a europium nitrate hexahydrate solution, controlling the adding rates of the three solutions, performing reaction for 3 hours under the heating and stirring of a 75-DEG C water bath (controlling the adding rates of the hexamethylenetetramine solution, the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution to be 0.1 mL/min preferentially respectively), and controlling the molar ratio of the three substances to be 1.3: 5: 1.7. washing a reaction product, drying at 80 ℃ for 12h, roasting at 500 ℃ for 3h, cooling to room temperature (the heating rate is 1.0 ℃/min), and finally obtaining the MnO_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst, wherein MnO_xNanorods and CeO_xAnd EuO_xThe molar mass ratio of (A) to (B) is 1: 0.8: 0.5.

Example 2

（1）MnO_xPreparing the nano-rods: 1.2156 g of KMnO₄The resulting solution was dissolved in 157.4 mL of deionized water with stirring. After dissolution, 2.0 mL of 37 wt% hydrochloric acid was added and the mixture was stirred until the volume was 160 mL. The solution was transferred to a 200 mL reactor and heated to 140 ℃ for 6 h. Naturally cooling to room temperature, taking out the product, washing the product to be neutral, and drying at 80 ℃ for 6 h to obtain a powdery solid product.

（2）MnO_x@Eu-CeO_xThe preparation of (1): adding 0.7g of MnO_xAdding nanorod powder into 40 mL of absolute ethyl alcohol, performing ultrasonic treatment, uniformly stirring and dispersing, sequentially adding a hexamethylenetetramine solution, a cerium nitrate hexahydrate solution and a europium nitrate hexahydrate solution, controlling the adding rates of the three solutions, performing reaction for 4 hours under the condition of heating and stirring in a water bath at 70 ℃ (controlling the adding rates of the hexamethylenetetramine solution, the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution to be 0.05 mL/min preferentially respectively), and controlling the molar ratio of the three substances to be 0.6:2.5: 0.8. Washing the reaction product, drying at 70 ℃ for 12h, roasting at 400 ℃ for 4h, cooling to room temperature (the heating rate is 0.5 ℃/min), and finally obtaining the MnO_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst, wherein MnO_xNanorods and CeO_xAnd EuO_xThe molar mass ratio of (A) to (B) is 1: 0.4: 0.2.

Example 3

（1）MnO_xPreparing the nano-rods: 1.2156 g of KMnO₄Adding into 157.4 mL deionized water, stirring and dissolving; after dissolving, adding 3 mL of 37 wt% hydrochloric acid, continuing stirring, and finally metering to 160 mL; transferring the solution into a 200 mL reaction kettle, heating to 140 ℃, and reacting for 24 h; naturally cooling to room temperature, taking out the product, washing the product to be neutral, and drying at 80 ℃ for 24 h to obtain a powdery solid product;

（2）MnO_x@Eu-CeO_xthe preparation of (1): 2.5g of MnO_xAdding the nanorod powder into 80mL of absolute ethyl alcohol, performing ultrasonic treatment, stirring and dispersing uniformly, sequentially adding a hexamethylenetetramine solution, a cerium nitrate hexahydrate solution and a europium nitrate hexahydrate solution, controlling the adding rates of the three solutions, and adding the three solutions into a water bath at 80 DEG CThe reaction is carried out for 2h under thermal stirring (the adding rates of the hexamethylenetetramine solution, the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution are respectively controlled to be 0.2 mL/min preferentially), and meanwhile, the molar ratio of the three substances is controlled to be 1.9:10: 3.4. Washing a reaction product, drying at 80 ℃ for 6 h, roasting at 600 ℃ for 2h, and cooling to room temperature (the heating rate is 1.5 ℃/min), thereby finally obtaining the MnO_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst, wherein MnO_xNanorods and CeO_xAnd EuO_xThe molar mass ratio of (A) to (B) is 1: 1.2: 0.8.

Comparative example 1

MnO_xPreparing the nano-rods: 1.2156 g KMnO₄Adding into 157.4 mL deionized water, stirring and dissolving; after dissolving, adding 2.6 mL of 37 wt% hydrochloric acid, continuing stirring, and finally metering to 160 mL; the solution was transferred to a 200 mL reactor and allowed to warm to 140 ℃ for 12 h. Naturally cooling to room temperature, taking out a product, washing the product to be neutral, drying at 80 ℃ to obtain a powdery solid product, roasting the obtained solid product at 400 ℃ for 2h, cooling to room temperature to finally obtain the MnO_xA nanorod; the catalyst in this comparative example was uncoated pure MnO_xA nanorod catalyst.

Comparative example 2

Based on comparative example 1, Eu-CeO was prepared by a conventional impregnation method_x/MnO_xCatalyst sample, MnO corresponding to proportion 1_xThe nano-rod is dipped in the mixed solution of cerium nitrate and europium nitrate. The method comprises the following specific steps: dissolving a certain amount of cerous nitrate hexahydrate and europium nitrate hexahydrate in 80ml of deionized water, and adding 1.14g of MnO_xAnd stirring the nano rods at room temperature for 1 h. The molar ratio of Mn to Ce to Eu in the catalyst prepared by the impregnation method was the same as in example 1.

Comparative example 3

（1）MnO_xPreparing the nano-rods: 1.2156 g KMnO₄Adding into 157.4 mL deionized water, stirring and dissolving; after dissolving, adding 2.6 mL of 37 wt% hydrochloric acid, continuing stirring, and finally metering to 160 mL; the solution was transferred to a 200 mL reactor and allowed to warm to 140 ℃ for 12 h. Naturally cooling to roomTaking out the product, washing the product to be neutral, and drying at 80 ℃ to obtain a powdery solid product;

（2）MnO_x@CeO_xthe preparation of (1): a certain amount of MnO_xAdding nanorod powder into absolute ethyl alcohol, performing ultrasonic treatment, stirring and dispersing uniformly, sequentially adding a hexamine solution and a cerous nitrate hexahydrate solution, controlling the addition rate of the solutions, and reacting for 2 hours under the heating and stirring of a water bath at 75 ℃ (controlling the addition rates of the hexamine solution and the cerous nitrate hexahydrate solution to be 0.05 mL/min respectively and preferentially), and simultaneously controlling the molar ratio of the two substances to be 1.3: 5.0; washing and drying the reaction product, roasting at 400 ℃ for 2h, and cooling to room temperature to finally obtain the MnO_x@ CeO_xLow temperature SCR flue gas denitration catalyst.

Activity evaluation test

The catalysts prepared in the examples and the comparative examples are put in a quartz tube fixed bed reactor for activity evaluation under the condition of simulating flue gas in a laboratory, and NH is used₃The reducing gas is obtained by the following test conditions: NO and O₂The volume fractions of (A) and (B) are respectively 0.06% and 2.5%, the ammonia-nitrogen ratio is 1:1, Ar is balance gas, and the space velocity is 90,000h^-1. The gas analysis was performed using German Degraph 350 (NO-NO)₂-NO_xFlue gas analyzer), the denitration activity results of the catalysts prepared in examples and comparative examples are shown in table 1:

table 1 results of activity evaluation of examples and comparative examples

As can be seen from Table 1, the catalysts prepared in the examples all have good low-temperature SCR activity, wherein the low-temperature SCR activity of the example 1 is optimal, and nearly 100% of NO can be achieved at 100 DEG C_xAnd (4) conversion rate. Comparative example 1 pure MnO without coating of the Shell_xNanorod catalyst, which was subjected to SCR activity evaluation, and found that the low-temperature reduced NO of comparative example 1_xThe performance is obviously lower (50-175 ℃) than the SCR activity of the example 1, and the comparative example 2 adoptsEu-CeO prepared by traditional dipping method_x/MnO_xThe SCR activity of the catalyst samples was even worse than that of comparative example 1, further illustrating the use of an improved chemical precipitation process to encapsulate the double rare earth metal oxide in MnO_xThe nanorod surface improves the dispersibility of active components and simultaneously improves the redox performance and surface acidity of the catalyst, so that the catalyst shows excellent NH at a low temperature stage (below 200℃)₃-SCR performance.

Evaluation test for anti-poisoning

The catalysts prepared in the examples and the comparative examples are placed in a quartz tube fixed bed reactor for SO resistance under the condition of simulating flue gas in a laboratory₂Poisoning experiments with NH₃The reducing gas is obtained by the following test conditions: NO and O₂The volume fractions of (A) and (B) are respectively 0.06% and 2.5%, the ammonia-nitrogen ratio is 1:1, and SO is₂The volume fraction of (A) is 0.01 percent, Ar is balance gas, the reaction temperature is 200 ℃, and the space velocity is 90000 h^-1. The gas analysis was performed using German Degraph 350 (NO-NO)₂-NO_xSmoke analyzer), the results of the anti-poisoning test are shown in table 2:

table 2 sulfur resistance test of examples and comparative examples

As can be seen from table 2, the catalyst prepared in example 1 has strong sulfur poisoning resistance. High NO is still maintained under the condition of long-time sulfur-containing flue gas_xAnd (4) conversion rate.

As can be seen from FIG. 1, Eu-CeO in comparative example 2_x/MnO_xIs prepared by conventional impregnation methods (by preparing unfired MnO_xThe nano-rod is used as a carrier, and then is soaked in a cerium nitrate and europium nitrate solution overnight, and then is dried and roasted to prepare the nano-rod, wherein the Mn: ce: eu in the same ratio as in example 1), it is apparent that CeO is referred to in example 1₂The characteristic peak of (a) is clearly shifted towards high angles, which indicates that there is a clear strong interaction (Mn with Ce) in example 1.

As can be seen from fig. 2, the peak of XPS O1 s corresponding to example 1 is shifted in the binding energy direction, which indicates that a strong interaction is evident in example 1.

As can be seen from FIG. 3, the catalyst corresponding to example 1 is of a nano core-shell structure, the size is also in the nano range, the surface is rougher than that of comparative example 1, but the nano particles on the surface are uniformly distributed, but as can be seen from comparative example 2, the surface EuO is supported_xAnd CeO_xAre distributed unevenly and aggregation occurs. The impregnation method is not favorable for the dispersion of the catalytic component, the particle distribution on the surface of the prepared product is not uniform, and the aggregation phenomenon of large particles occurs.

FIG. 4 is a scanning TEM image of example 1, from which it can be seen that Mn is mainly distributed inside, Ce and Eu are distributed on the outer ring of the nanorod, and the distribution is uniform, which illustrates that the preparation method of the present invention improves the dispersibility of the active component, and at the same time, can confirm that the catalyst has an obvious core-shell structure.

Finally, it should be emphasized that the above-described preferred embodiments of the present invention are merely examples of implementations, rather than limitations, and that many variations and modifications of the invention are possible to those skilled in the art, without departing from the spirit and scope of the invention.

Claims

1.MnO_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized in that MnO with high activity is synthesized by hydrothermal method in the preparation method_xNanorods with MnO_xTaking the nano-rod as a core, and carrying out Eu-CeO by a modified chemical precipitation method_xCoating the precursor to MnO_xThe outer layer of the nano-rod is roasted to prepare MnO_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst, MnO_x@Eu-CeO_xMnO in low-temperature SCR flue gas denitration catalyst_xNanorods and CeO_xAnd EuO_xThe molar mass ratio of (A) to (B) is 1: 0.4-1.2: 0.2-0.8.

2. The MnO of claim 1_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized by comprising the following steps of:

（1）MnO_xpreparing the nano-rods: 1.2156 g of KMnO₄Adding into 157.4 mL deionized water, stirring and dissolving; after dissolving, adding hydrochloric acid, continuing stirring, and finally fixing the volume to 160 mL; transferring the solution into a 200 mL reaction kettle, and heating to 140 ℃ for reaction; naturally cooling to room temperature, taking out the product, washing the product to be neutral, and drying at 80 ℃ to obtain a powdery solid product;

（2）MnO_x@Eu-CeO_xthe preparation of (1): MnO of_xAdding nanorod powder into absolute ethyl alcohol, performing ultrasonic treatment, stirring and dispersing uniformly, then sequentially adding a hexamethylenetetramine solution, a cerium nitrate hexahydrate solution and a europium nitrate hexahydrate solution, controlling the adding rates of the three solutions, performing reaction under the heating and stirring of a water bath, washing and drying a reaction product, roasting, and cooling to room temperature to finally obtain the MnO_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst.

3. The MnO of claim 2_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized in that in the step (1), the hydrochloric acid is a 37 wt% HCl solution, the dosage of the HCl solution is 2.0-3.0 mL, and the reaction time is 6-24 h; the drying is carried out for 6-24 h at the temperature of 80 ℃.

4. The MnO of claim 2_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized in that in the step (2), the using amount of the absolute ethyl alcohol is 40-80 mL, and the using amount of the manganese oxide is 0.7-2.5 g.

5. The MnO of claim 2_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized in that in the step (2), the hexamine, the cerous nitrate hexahydrate and the nitre hexahydrateThe molar ratio of the acid europium is 0.6-1.9: 2.5-10: 0.8-3.4.

6. The MnO of claim 2_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized in that in the step (2), the adding sequence of the hexamethylenetetramine, the cerium nitrate hexahydrate and the europium nitrate hexahydrate is that the hexamethylenetetramine solution is added firstly, then the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution are added simultaneously, and the adding speed of the hexamethylenetetramine solution, the cerium nitrate hexahydrate solution and the europium nitrate hexahydrate solution is controlled to be 0.05 mL/min-2 mL/min.

7. The MnO of claim 2_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized in that in the step (2), the water bath heating temperature is 70-80 ℃; the reaction time is 2-4 h.

8. The MnO of claim 2_x@Eu-CeO_xThe preparation method of the low-temperature SCR flue gas denitration catalyst is characterized in that in the step (2), the drying is carried out for 8-12 hours at the temperature of 70-80 ℃; the roasting is carried out for 2-4 h at the temperature rising rate of 0.5-1.5 ℃/min to 400-600 ℃ in the air atmosphere.

9. MnO obtainable by the process according to any one of claims 1 to 8_x@Eu-CeO_xLow temperature SCR flue gas denitration catalyst.

10. The MnO of claim 9_x@Eu-CeO_xThe low-temperature SCR flue gas denitration catalyst is applied to a low-temperature SCR flue gas denitration system.