Low-temperature scr denitration catalyst and preparation method thereof

Abstract

The present application relates to a kind of low-temperature SCR denitration catalyst and its preparation method, belong to catalyst preparation technical field.The catalyst contains 10~20% active component, 50~70% carrier and 10~30% catalysis according to mass percentage.Mixing nano Al2O3 with diatomite when preparing, add aluminum nitrate to prepare composite carrier A;Again, noble metal is dissolved with Hf, Ta, Ho element in water, after impregnation carrier A calcination product B;Subsequently, preparation transition metal, acidic substance solution and CNDs dispersion liquid, mixed ultrasonic mixture C;Finally, B is impregnated in C, after drying, calcination, extrusion molding catalyst.The catalyst is high in denitration efficiency at low temperature, and excellent in sulfur resistance and water resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst preparation, and relates to a low-temperature SCR denitration catalyst and a preparation method thereof. BACKGROUND

[0002] In recent years, the SCR technology has become one of the most effective technologies for controlling NO x emission in actual flue gas treatment due to its high denitration performance and relatively mature process. Therefore, as the core of the SCR technology, the reasonable design and use of the denitration catalyst can effectively improve the denitration efficiency, enhance the stability, and reduce the production cost. However, the V2O5 / TiO2 catalyst currently used in the SCR can only be used in flue gas at 300 DEG C to 420 DEG C, and if the denitration is performed under the flue gas condition below 300 DEG C, serious oxidation sulfur poisoning and water poisoning, and alkali (alkaline earth) metal poisoning will occur, and the poisoning is irreversible. However, except for the coal-fired gas generator set, the basic flue gas temperature of most industrial kilns including the cement kiln, the steel ball sintering equipment, and the waste incinerator is generally lower than 150 DEG C, even lower than 120 DEG C, and the nitrogen oxide emission concentration has large fluctuation, and the emission temperature is low.

[0003] Therefore, for these specific industries, it is necessary to develop a new denitration technology suitable for low-temperature flue gas and improve the existing catalyst to improve the efficiency and adaptability at low temperature. SUMMARY

[0004] The application aims to provide a low-temperature SCR denitration catalyst and a preparation method thereof, which has high NO x conversion rate and good catalyst stability.

[0005] The application can be achieved by the following technical solutions.

[0006] A low-temperature SCR denitration catalyst, according to mass percentage, the catalyst comprises 10 to 20% of an active component, 50 to 70% of a carrier, and 10 to 30% of a catalytic aid,

[0007] The active component is formed by compounding a noble metal and a metal element, and the mass ratio of the two is 1: (10 to 15);

[0008] The carrier is formed by compounding nano Al2O3 and diatomite, and the mass ratio of the two is 1: (2 to 3);

[0009] The catalytic aid is formed by compounding a transition metal, an acidic substance, and a biomass carbon nanodot, and the mass ratio of the three is 5:1: (0.1 to 1).

[0010] Further, the noble metal in the active component is at least one of Rh and Pt.

[0011] Further, the metal element in the active component is at least one of Hf, Ta, Ho.

[0012] Further, the transition metal in the catalytic aid is at least one of Fe, Co, Ni, Cu.

[0013] Further, the acid substance in the catalytic aid is at least one of phosphoric acid, sulfuric acid or its salt.

[0014] A preparation method of a low-temperature SCR denitration catalyst, the specific process of the preparation method is as follows,

[0015] S1: Nanometer Al2O3 is mixed with diatomite according to a mass ratio, deionized water is added and stirred uniformly, the solid-liquid ratio is 1: (5-10), a slurry is formed, 1-3 wt% of aluminum nitrate is added to the slurry, stirring is performed for 1-3 h, standing is performed at 40-60°C for 12-24 h, and drying is performed at 80-120°C for 6-12 h after standing, to obtain a composite carrier A;

[0016] S2: The noble metal element and the metal element are mixed according to a mass ratio, and are dissolved in deionized water to obtain a mixed solution, the metal ion concentration of the mixed solution is 0.1-0.5 mol / L, the composite carrier A is immersed in the mixed solution, stirring is performed for 4-8 h, the solid-liquid ratio is 1:5, drying is performed at 60-100°C for 6-12 h after stirring is completed, and the dried solid product is calcined in an air atmosphere at 300-400°C for 2-4 h, to obtain a product B;

[0017] S3: The transition metal element is dissolved in water to obtain a transition metal solution with a concentration of 0.2-1.0 mol / L,

[0018] The acid substance is dissolved in water to obtain an acid substance solution with a concentration of 0.1-0.5 mol / L;

[0019] The biomass raw material is pyrolyzed in nitrogen, the pyrolysis product is oxidized by concentrated sulfuric acid, and a CNDs dispersion liquid is obtained after dialysis purification, the mass concentration of the CNDs dispersion liquid is 1%-5%;

[0020] The transition metal solution, the acid substance solution and the CNDs dispersion liquid are mixed according to a mass ratio, and ultrasonic treatment is performed for 10-30 min, to form a mixed liquid C;

[0021] S4: The product B is immersed in the mixed liquid C, the solid-liquid ratio is 1: (2-4), ultrasonic treatment is performed for 1-2 h, drying is performed at 80-120°C for 8-12 h after filtration, calcination is performed in a nitrogen atmosphere at 350-450°C for 3-6 h after drying, and the calcined product is extruded to form a catalyst.

[0022] Further, in the S3, the biomass raw material is straw powder, the nitrogen pyrolysis parameters are that the pyrolysis temperature is 400-600 DEG C, and the pyrolysis duration is 2-4 h.

[0023] Further, in the S3, the mass ratio of the pyrolysis product and concentrated sulfuric acid is 1:3, the oxidation temperature is 80 DEG C, and the duration is 3 h.

[0024] Further, in the S3, the dialysis purification parameters are that the dialysis is continuously performed for 24-48 h at room temperature in a dialysis bag with a molecular weight cut-off of 1000-3500 Da, and the deionized water is replaced every 3-6 h.

[0025] The low-temperature SCR denitration catalyst and the preparation method thereof provided by the application significantly improve the denitration efficiency, sulfur resistance and structural stability of the catalyst under low-temperature conditions through the composite design of the active component, the carrier and the catalytic aid and the synergistic optimization of specific process parameters.

[0026] The active component of the application is formed by compounding the noble metal and the metal elements Hf, Ta and Ho in a mass ratio of 1:10-15, which significantly enhances the low-temperature catalytic activity through the electronic synergy and active site complementary effect of the noble metal and Hf, Ta and Ho. The noble metal surface has excellent electron migration capacity, can preferentially adsorb and activate NO molecules, and promotes the oxidation of NO into NO2, which is a key step in the low-temperature SCR reaction. However, the noble metal alone is easy to be poisoned and inactivated due to the adsorption of sulfides or water vapor, therefore, the application introduces the metal elements Hf, Ta and Ho to solve this problem, in the application, the noble metal elements and Hf, Ta and Ho are introduced in the form of metal salts, the metal oxides of Hf, Ta and Ho can form an atomic-level interface with the noble metal due to their rich oxygen vacancies and strong oxygen storage capacity, and can adjust the electronic state of the noble metal through electronic interaction, thereby reducing its affinity for sulfur species and inhibiting the sulfur poisoning phenomenon. In addition, the surface acid sites of the Hf, Ta and Ho oxides can promote the adsorption and dissociation of NH3, and form a synergistic reaction path with the NO activation step of the noble metal, thereby accelerating the NO activation reaction. This composite active structure of the noble metal and Hf, Ta and Ho enables the catalyst to maintain a relatively high NO conversion rate in the low-temperature range of 150-250 DEG C. x

[0027] ​The carrier of this invention is prepared by composite of nano-Al2O3 and diatomaceous earth at a mass ratio of 1:2-3. Its hierarchical porous structure and synergistic surface chemical properties provide an ideal platform for efficient loading of active components and reaction mass transfer. Nano-Al2O3 possesses a high specific surface area and abundant surface hydroxyl groups, enabling it to chemically bond and stabilize noble metal-metal active components, preventing sintering deactivation during high-temperature calcination or reaction. However, single nano-Al2O3 is prone to crystal transformation under high-temperature hydrothermal conditions, such as the conversion of γ-Al2O3 to α-Al2O3, leading to a sharp drop in specific surface area. Therefore, this invention introduces diatomaceous earth. The introduction of diatomaceous earth, through its natural porous framework, forms an interpenetrating network with Al2O3 nanoparticles, not only suppressing the phase transformation of Al2O3 but also enhancing the overall compressive strength of the carrier through mechanical interlocking, ensuring the structural integrity of the catalyst under industrial flue gas flow rates. Furthermore, the SiO2 component in diatomaceous earth can form -Si-O-Al- bonds with Al2O3, further increasing the density of acidic sites on the surface and assisting the active component in the adsorption and activation of NH3. In the preparation process, the addition of aluminum nitrate is carried out through the hydrolysis of Al... 3+ The cross-linking reaction with the silanol groups on the diatomaceous earth surface strengthens the connection strength of the carrier skeleton. The static step promotes the slow dehydration of the colloid to form a uniform gel structure. The final dried composite carrier has a specific surface area of ​​180~250 m². 2 / g, pore volume 0.4~0.8cm 3 / g, laying the foundation for uniform loading of subsequent active components.

[0028] The catalyst promoter is composed of transition metals, acidic substances, and biomass carbon nanodots (CNDs) in a mass ratio of 5:1:0.1~1. It enhances the low-temperature activity and sulfur resistance of the catalyst through multi-dimensional effects of acid-base synergy, electron transfer, and spatial dispersion. In this invention, the transition metal is introduced in the form of a metal salt (such as Fe). 3+ Cu 2+ Transition metals can act as additional active sites in redox cycles. In low-temperature reaction pathways dominated by noble metal active components, transition metals assist in the activation of O2 and the conversion of intermediate products by accepting or releasing electrons. The introduction of acidic substances constructs Brønsted acid sites on the support surface, preferentially adsorbing NH3 molecules and promoting their dissociation into NH2. - Active intermediates, this process can significantly reduce NO x The activation energy of reduction reactions is particularly advantageous at low temperatures.

[0029] However, excessive introduction of acidic substances may lead to excessive acidity on the catalyst surface, causing excessive adsorption of NH3 and inhibiting reactant diffusion. Therefore, this invention introduces biomass CNDs to resolve this contradiction. The surface of CNDs is rich in functional groups such as carboxyl groups (-COOH) and hydroxyl groups (-OH), which can anchor transition metal ions and acidic substances through coordination, forming highly dispersed nanoscale composite active centers, preventing the aggregation of metal ions and uneven distribution of acidic substances. Furthermore, the π-π conjugated structure of CNDs possesses graphene-like electronic conductivity, acting as an electron channel to accelerate charge transfer between metals. CNDs transfer electrons required for the reduction of transition metals to Pt through their surface, maintaining the active state of the noble metal. The microporous structure of CNDs also provides diffusion channels for reactant molecules and forms a continuous hierarchical pore network with the macroporous structure of the support, further reducing mass transfer resistance.

[0030] In the preparation process of this invention, in step S2, a precursor solution of noble metals and Hf, Ta, and Ho is loaded onto a composite carrier using an equal-volume impregnation method. The matching control of stirring time and impregnation solution concentration ensures the uniform distribution of metal ions within the carrier pores. Subsequent calcination promotes the formation of highly dispersed metal-oxide composite particles of noble metals and Hf, Ta, and Ho elements. The anchoring effect of Hf, Ta, and Ho oxides on the noble metal particles significantly inhibits their high-temperature migration and aggregation. In step S3, biomass is pyrolyzed under nitrogen protection to form a carbonaceous precursor. Concentrated sulfuric acid oxidation introduces oxygen-containing functional groups onto the CNDs surface. Subsequent dialysis purification effectively removes unreacted sulfuric acid and small molecule fragments, ensuring the purity of the functional groups on the CNDs surface and the stability of the dispersion. The ultrasonic composite of transition metals, acidic substances, and CNDs promotes chemical bonding rather than simple physical mixing. For example, Fe... 3+ It forms a Fe-OOC-CNDs complex with the -COOH group of CNDs, while the PO4 group of H3PO4... 3- The catalyst forms a hydrogen bond network with the -OH group of CNDs. This strong interaction enables the catalyst to exist stably on the surface and in the pores of the support when it is subsequently loaded into product B. In step S4, calcination at 350~450℃ under nitrogen for 3~6 h promotes the reduction of the transition metal part to a lower valence state, enhancing its activation ability for NH3. On the other hand, the nitrogen atmosphere inhibits the excessive oxidation of CNDs, preserving its surface functional groups and conductivity.

[0031] The beneficial effects of this invention are:

[0032] (1) The noble metal-metal composite active component provides a high density of NO oxidation sites, acidic substances promote the adsorption and dissociation of NH3, and CNDs accelerate the transfer of electrons between metals. The three work synergistically to effectively enhance NO oxidation. x Conversion rate;

[0033] (2) The competitive adsorption of SO2 by Hf, Ta, and Ho oxides, the dispersion and isolation of sulfate by CNDs, and the acid catalytic decomposition of sulfur species by acidic substances work together to give the catalyst excellent sulfur resistance.

[0034] (3) The diatomaceous earth-Al2O3 composite support resists structural collapse under hydrothermal conditions through physical cross-linking. The bonding between CNDs and transition metals inhibits the migration and loss of active components. The acidic substances in the catalyst reinforce the surface structure of the support through chemical bonding, thereby making the catalyst more stable. Attached Figure Description

[0035] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0036] Figure 1 Examples and comparative examples of the present invention (NO) x Conversion rate data chart;

[0037] Figure 2 The figures show the sulfur resistance and water resistance data of the embodiments and comparative examples of the present invention.

[0038] Figure 3 The figures show the alkali resistance metal properties of the embodiments and comparative examples of the present invention.

[0039] Figure 4 The figures show the metallic properties of alkali-resistant earth in the embodiments and comparative examples of the present invention. Detailed Implementation

[0040] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0041] Example 1

[0042] Catalyst composition: The active component accounts for 15% of the total mass, of which the mass ratio of noble metal Pt to Hf is 1:10, the support accounts for 60% of the total mass, the mass ratio of nano Al2O3 to diatomaceous earth is 1:2, the catalyst promoter accounts for 25% of the total mass, and the mass ratio of transition metal Fe, acidic substance H3PO4 and biomass carbon nanodots is 5:1:0.1.

[0043] S1: Mix 10 g of nano Al2O3 with 20 g of diatomaceous earth, add 150 g of deionized water, stir to form a slurry, add 0.3 g of aluminum nitrate to the slurry, continue stirring for 2 h, let stand at 50℃ for 18 h, and then dry at 100℃ for 9 h to obtain porous composite carrier A.

[0044] S2: Dissolve 0.45 g Pt(NO3)2 and 1.5 g Hf(NO3)4 in 30 mL of deionized water, with a metal ion concentration of 0.25 mol / L;

[0045] 30 g of composite carrier A was impregnated in a mixed solution with a solid-liquid ratio of 1:5, stirred for 6 h, dried at 80 °C for 9 h, and calcined in air at 350 °C for 3 h to obtain product B, Pt-Hf / Al2O3-diatomite.

[0046] S3: Prepare a 0.4 mol / L Fe(NO3)3 solution by taking 20 mL of Fe(NO3)3 solution;

[0047] To prepare a 0.3 mol / L H3PO4 solution, take 4 mL of H3PO4 solution;

[0048] Straw powder was pyrolyzed in nitrogen at 500℃ for 3 h. The product was mixed with concentrated sulfuric acid at a mass ratio of 1:3 and oxidized at 80℃ for 3 h. The mixture was then dialyzed for 36 h using a dialysis bag with a molecular weight cutoff of 2000 Da to obtain a CNDs dispersion. 5 mL of the 3% CNDs dispersion was taken.

[0049] Mix the above solutions and sonicate for 20 minutes to form a homogeneous mixture C;

[0050] S4: 30 g of product B was impregnated in 75 mL of mixed solution C at a solid-liquid ratio of 1:2.5, sonicated for 1.5 h, filtered, dried at 100 °C for 10 h, calcined at 400 °C in nitrogen for 4.5 h, and extruded into shape at a pressure of 15 MPa to obtain the catalyst.

[0051] Example 2

[0052] Catalyst composition: The active component accounts for 18% of the total mass, of which the mass ratio of noble metal Rh to Ta is 1:37, the support accounts for 55% of the total mass, the mass ratio of nano Al2O3 to diatomaceous earth is 1:2.5, the catalyst promoter accounts for 27% of the total mass, and the mass ratio of transition metal Cu, acidic substance H2SO4 and biomass carbon nanodots is 5:1:0.5.

[0053] S1: Mix 8g of nano-Al2O3 with 20g of diatomaceous earth, add 196g of deionized water, stir to form a slurry, add 0.84g of aluminum nitrate to the slurry, continue stirring for 1 h, let stand at 60℃ for 24 h, and then dry at 110℃ for 10 h to obtain porous composite carrier A.

[0054] S2: Dissolve 0.3 g H3RhCl6·3H2O and 6.3 g TaCl5 in 24 mL of deionized water, with a metal ion concentration of 0.35 mol / L;

[0055] 28 g of composite carrier A was impregnated in a mixed solution with a solid-liquid ratio of 1:5, stirred for 7 h, dried at 90 °C for 8 h, and calcined at 380 °C in air for 3.5 h to obtain product B Rh-Ta / Al2O3-diatomite.

[0056] S3: Prepare a 0.8 mol / L Cu(NO3)2 solution by taking 25 mL of Cu(NO3)2 solution;

[0057] To prepare a 0.2 mol / L H2SO4 solution, take 5 mL of H2SO4 solution;

[0058] Straw powder was pyrolyzed in nitrogen at 600℃ for 2 h. The product was mixed with concentrated sulfuric acid at a mass ratio of 1:3 and oxidized at 80℃ for 3 h. The mixture was then dialyzed for 24 h using a dialysis bag with a molecular weight cutoff of 1000 Da to obtain a CNDs dispersion. 2 mL of the 5% CNDs dispersion was taken.

[0059] Mix the above solutions and sonicate for 30 minutes to form a homogeneous mixture C;

[0060] S4: 30 g of product B was impregnated in 105 mL of mixed solution C at a solid-liquid ratio of 1:3.5, sonicated for 2 h, filtered, dried at 90 °C for 12 h, calcined at 450 °C in nitrogen for 5 h, and extruded into shape at a pressure of 15 MPa to obtain the catalyst.

[0061] Example 3

[0062] Catalyst composition: The active component accounts for 20% of the total mass, of which the mass ratio of noble metal Pt to Ho is 1:15, the support accounts for 50% of the total mass, the mass ratio of nano Al2O3 to diatomaceous earth is 1:3, the catalyst promoter accounts for 30% of the total mass, and the mass ratio of transition metal Ni, acidic substance AlPO4 and biomass carbon nanodots is 5:1:1.

[0063] S1: Mix 10 g of nano Al2O3 with 30 g of diatomaceous earth, add 400 g of deionized water, stir to form a slurry, add 1.2 g of aluminum nitrate to the slurry, continue stirring for 1 h, let stand at 40℃ for 12 h, and then dry at 120℃ for 6 h to obtain porous composite carrier A.

[0064] S2: Dissolve 0.75 g Pt(NH3)4(NO3)2 and 13.5 g Ho(NO3)3·6H2O in 50 mL of deionized water, with a metal ion concentration of 0.45 mol / L;

[0065] 40 g of composite carrier A was impregnated in a mixed solution with a solid-liquid ratio of 1:5, stirred for 8 h, dried at 100 °C for 6 h, and calcined in air at 400 °C for 2 h to obtain product B, Pt-Ho / Al2O3-diatomite.

[0066] S3: Prepare a 1 mol / L Ni(NO3)2·6H2O solution by taking 30 mL of Fe(NO3)3 solution;

[0067] To prepare a 0.5 mol / L AlPO4 solution, take 6 mL of AlPO4 solution;

[0068] Straw powder was pyrolyzed in nitrogen at 400℃ for 4 h. The product was mixed with concentrated sulfuric acid at a mass ratio of 1:3 and oxidized at 80℃ for 3 h. The mixture was then dialyzed for 48 h using a dialysis bag with a molecular weight cutoff of 3500 Da to obtain a CNDs dispersion. 30 mL of the 1% CNDs dispersion was taken.

[0069] Mix the above solutions and sonicate for 10 min to form a homogeneous mixture C;

[0070] S4: 35 g of product B was impregnated in 140 mL of mixed solution C at a solid-liquid ratio of 1:4, sonicated for 1 h, filtered, dried at 120 °C for 8 h, calcined at 350 °C in nitrogen for 6 h, and extruded into shape at a pressure of 15 MPa to obtain the catalyst.

[0071] Comparative Example 1

[0072] In this comparative example, no acidic substances were added during the preparation process, and the remaining steps were the same as in Example 1.

[0073] Comparative Example 2

[0074] In this comparative example, no biomass carbon nanodots were added during the preparation process, and the remaining steps were the same as in Example 1.

[0075] The denitrification catalysts of Examples 1-3 and Comparative Examples 1-2 of the present invention were subjected to performance testing and denitrification experiments. The test results are summarized in Table 1.

[0076] The performance testing methods are as follows:

[0077] (1) Denitrification efficiency determination: The simulated flue gas composition was NOx, NH3, O2 and N2, and the space velocity was 10000 h. -1 The NOx concentration was 1500 mg / m³. 3The NH3 / NOx molar ratio was 1:1.03, O2 concentration was 17%, and water content was 12%. The reaction temperature was controlled between 100 and 250°C. The flow rates of each gas were controlled by mass flow meters. Before entering the reactor, the gas was mixed in a gas mixer and then preheated in a preheater. The NOx concentrations at the inlet and outlet were measured by a flue gas analyzer. To eliminate the influence of other environmental factors, the system was tested after 60 minutes of stable operation. The test data are as follows: Figure 1 As shown.

[0078] (2) Determination of sulfur and water resistance: The simulated flue gas composition was NOx, NH3, SO2, H2O, O2 and N2, with a space velocity of 10000 h. -1 The NOx concentration was 1500 mg / m³. 3 NH3 / NOx molar ratio = 1:1.03, O2 concentration: 17%, SO2 concentration: 1000 mg / m³ 3 H2O content: 25 vol%; reaction temperature controlled at 120℃. Gas flow rates are controlled by mass flow meters. Before entering the reactor, the gas is mixed in a gas mixer and then preheated in a preheater. NOx concentrations at the inlet and outlet are measured by a flue gas analyzer. To eliminate the influence of surface adsorption, system data collection begins 30 minutes after stable operation. Test data are as follows: Figure 2 As shown.

[0079] (3) Determination of resistance to alkali metals and alkaline earth metals: Two test blocks were taken for each catalyst and placed in 2% potassium hydroxide + 2% sodium hydroxide solution and 2% calcium hydroxide + 2% magnesium hydroxide solution, respectively. After being placed at 100℃ for 72h, they were taken out and dried in a forced-air drying oven at 120℃ for 3h, and then calcined in a muffle furnace at 400℃ for 3h. They were then taken out and tested separately. The test conditions were: flue gas composition: NOx, NH3, O2 and N2, space velocity of 10000 h⁻¹. -1 The NOx concentration was 1500 mg / m³. 3 The NH3 / NOx molar ratio was 1:1.03, the O2 concentration was 17%, and the reaction temperature was controlled at 120℃. Test data are as follows: Figures 3-4 As shown.

[0080] Table 1:

[0081]

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A low-temperature SCR denitration catalyst, characterized in that, By weight percentage, the catalyst comprises 10-20% active component, 50-70% support, and 10-30% catalytic promoter. The active component is formed by a combination of noble metals and metallic elements, with a mass ratio of 1:(10~15). The metal element in the active component is at least one of Hf, Ta, and Ho; The carrier is formed by nano-Al2O3 and diatomite in a mass ratio of 1:(2~3). The catalyst is composed of a transition metal, an acidic substance, and biomass carbon nanodots in a mass ratio of 5:1:(0.1~1). The specific process for preparing the catalyst is as follows: S1: Mix nano-Al2O3 with diatomaceous earth in a mass ratio, add deionized water and stir evenly, with a solid-liquid ratio of 1:(5~10) to form a slurry. Add 1~3 wt% aluminum nitrate to the slurry, stir for 1~3 h, let stand at 40~60℃ for 12~24 h, and dry at 80~120℃ for 6~12 h to obtain composite carrier A; S2: Mix the precious metal element with the metal element in a certain mass ratio, dissolve in deionized water to obtain a mixed solution with a metal ion concentration of 0.1~0.5 mol / L. Immerse the composite carrier A in the mixed solution and stir for 4~8 h with a solid-liquid ratio of 1:

5. After stirring, dry at 60~100℃ for 6~12 h. Calcine the dried solid product in air at 300~400℃ for 2~4 h to obtain product B. S3: Dissolve transition metal elements in water to obtain transition metal solutions with a concentration of 0.2~1.0 mol / L. Acidic substances are dissolved in water to obtain acidic solutions with a concentration of 0.1~0.5 mol / L; Biomass raw materials are pyrolyzed in nitrogen, and the pyrolysis products are oxidized with concentrated sulfuric acid and purified by dialysis to obtain a biomass carbon nanoparticle dispersion with a mass concentration of 1% to 5%. Mix the transition metal solution, acidic substance solution and biomass carbon nanoparticle dispersion according to the mass ratio, and sonicate for 10-30 minutes to form mixture C; S4: Impregnate product B in mixed solution C with a solid-liquid ratio of 1:(2~4), sonicate for 1~2 h, filter, dry at 80~120℃ for 8~12 h, calcine at 350~450℃ in a nitrogen atmosphere for 3~6 h, and extrude the calcined product to obtain the catalyst.

2. The low-temperature SCR denitration catalyst according to claim 1, characterized in that, The noble metal in the active component is at least one of Rh and Pt.

3. The low-temperature SCR denitration catalyst according to claim 1, characterized in that, The transition metal in the catalyst is at least one of Fe, Co, Ni, and Cu.

4. The low-temperature SCR denitration catalyst according to claim 1, characterized in that, The catalyst may contain at least one of the following acidic substances: phosphoric acid, sulfuric acid, or their salts.

5. The low-temperature SCR denitration catalyst according to claim 1, characterized in that, The biomass raw material in S3 is straw powder, and the nitrogen pyrolysis parameters are: pyrolysis temperature 400~600℃, pyrolysis time 2~4 h.

6. The low-temperature SCR denitration catalyst according to claim 1, characterized in that, In S3, the mass ratio of pyrolysis products to concentrated sulfuric acid is 1:3, the oxidation temperature is 80℃, and the time is 3h.

7. The low-temperature SCR denitration catalyst according to claim 1, characterized in that, The parameters for dialysis purification in S3 are as follows: continuous dialysis at room temperature for 24-48 hours in a dialysis bag with a molecular weight cutoff of 1000-3500 Da, with deionized water replaced every 3-6 hours.

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