A denitration catalyst and a method for preparing the denitration catalyst by coupling waste biomass with vanadium-titanium magnetite

Abstract

The application discloses a denitration catalyst and a method for preparing the denitration catalyst by coupling waste biomass with vanadium-titanium magnetite. The method for preparing the denitration catalyst comprises the following steps: performing two-stage grinding treatment of activation grinding and nanometer grinding on the vanadium-titanium magnetite to obtain material 1; performing pyrolysis treatment on the biomass raw material to obtain material 2; and mixing the material 1 and the material 2 with water to perform slurry preparation, and then performing stirring, drying and compression molding on the obtained slurry in sequence, so that the denitration catalyst is obtained. The method uses the vanadium-titanium magnetite as a raw material, performs the activation grinding and nanometer grinding treatment to construct surface microcracks and crystal lattice defects, realizes the size refinement of the variable valence metal compound particles containing iron, vanadium and titanium in the vanadium-titanium magnetite, greatly improves the catalytic activity, uses the biomass carbon as a carrier to provide abundant attachment sites for the catalyst active substances, and utilizes the CH volatile substances left by the biomass to strengthen the reduction of NOx, so that the sintering flue gas is subjected to the ultra-low-temperature and high-efficiency denitration.

Description

Technical Field

[0001] This invention relates to a denitrification catalyst, particularly to an ultra-low temperature denitrification catalyst for sintering flue gas, and also to a method for preparing a denitrification catalyst by coupling vanadium-titanium magnetite with waste biomass, belonging to the sintering industry in the field of iron and steel metallurgy. Background Technology

[0002] Industrial emissions of nitrogen oxides (NOx) are a major cause of acid rain, photochemical smog, and ozone layer depletion, posing a serious threat to the human environment. Iron ore sintering is a primary source of NOx emissions from the steel industry, with NOx concentrations in flue gas reaching 400–600 mg / Nm³. 3 These emissions account for 50% of the total emissions from the steel industry. my country's "Opinions on Promoting the Implementation of Ultra-Low Emissions in the Steel Industry," issued in 2019, stipulates that the hourly average concentration of nitrogen oxides in sintering machine flue gas should not exceed 50 mg / Nm³. 3 Most sintering plants need to add high-efficiency denitrification technology to meet ultra-low emission standards. Therefore, efficient denitrification of sintering flue gas is of great significance for the green and sustainable development of the steel industry.

[0003] Selective catalytic reduction (SCR) is a widely used end-of-pipe flue gas denitrification technology due to its mature technology and high denitrification efficiency. The core of SCR denitrification technology is the catalyst, which mainly includes two categories: precious metals and metal oxides. Precious metal catalysts, developed in the 1970s and first used for NOx reduction, are prepared by supporting platinum (Pt), palladium (Pd), rhodium (Rh), lutetium (Lu), and gold (Au) on supports such as ion-exchange zeolites or activated carbon. While precious metal catalysts exhibit good low-temperature activity, they are very expensive and suffer from drawbacks such as a narrow activity temperature window, susceptibility to oxygen inhibition and sulfur poisoning, and numerous side reactions (generating large amounts of N2O), causing secondary pollution and reducing denitrification efficiency. Metal oxide catalysts mainly include V2O5, Fe2O3, MnOx, CuO, and CeO2. These oxides possess abundant variable valence states, giving them good redox capabilities and catalytic activity. However, the suitable denitrification temperature window for current oxide removal catalysts is higher than 180℃, requiring the flue gas to be heated before denitrification, which requires a large amount of additional fuel gas and increases the cost of end-of-pipe flue gas denitrification. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the first objective of this invention is to provide a denitrification catalyst with ultra-low temperature (<160℃) catalytic denitrification function, which can better meet the denitrification process of sintering flue gas, eliminate the need to heat the flue gas, reduce fuel consumption, and lower the cost of flue gas denitrification.

[0005] The second objective of this invention is to provide a method for preparing a denitrification catalyst. This method uses vanadium-titanium magnetite and biomass raw materials as raw materials, which is low in cost and simple in preparation steps, thus facilitating industrial production. The prepared denitrification catalyst has ultra-low temperature catalytic denitrification function (<160℃), which has significant advantages over existing denitrification catalysts.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing a denitrification catalyst by coupling vanadium-titanium magnetite with waste biomass, comprising the following steps: 1) performing two-stage grinding treatment of vanadium-titanium magnetite by activation grinding and nano-grinding to obtain material ①; 2) performing pyrolysis treatment on biomass raw materials to obtain material ②; 3) mixing material ① and material ② with water to form a slurry, and then sequentially stirring, drying and pressing the resulting slurry into shape to obtain the final product.

[0007] This invention uses vanadium-titanium magnetite and biomass raw materials to prepare a denitrification catalyst. The vanadium-titanium magnetite undergoes a two-stage grinding process involving activation milling and nanomilling. This process not only induces micro-cracks, lattice distortions, or lattice defects on the surface of the iron-, vanadium-, and titanium-containing variable-valence metal compound particles in the vanadium-titanium magnetite, significantly enhancing the catalytic activity of these compounds, but also refines the particle size of these compounds to the micro- and nano-scale. This facilitates the efficient dissociation of these catalytically active variable-valence metal compounds from inert gangue components such as aluminum and silicon, thereby exposing more... The biomass material has numerous highly active catalytic reaction sites, which is beneficial for low-temperature catalytic reduction and degradation of NOx. The biomass raw material undergoes pyrolysis, and the thermal decomposition and volatilization of organic components in the biomass raw material creates a rich porous structure, providing a supporting matrix for surface-activated and micro / nano-sized vanadium-titanium magnetite particles. At the same time, the biochar still contains a certain proportion of organic components, which can provide CH components with excellent reduction performance for NOx reduction. Therefore, when vanadium-titanium magnetite particles are combined with biochar, the two play a synergistic role in catalytic NOx reduction, thus preparing a product with low-temperature (<160℃) catalytic denitrification function, realizing the high-value utilization of low-value-added metal mineral resources and waste biomass resources.

[0008] As a preferred embodiment, the vanadium-titanium magnetite contains at least 0.6% vanadium and at least 4% titanium by mass. If the vanadium and / or titanium content in the vanadium-titanium magnetite is too low, the amount of vanadium and titanium catalytically active components it can provide will be insufficient, which is not conducive to the catalyst fully exerting its low-temperature catalytic denitrification activity.

[0009] As a preferred embodiment, the activation mill employs a high-energy ball mill, a high-pressure roller mill, or a planetary ball mill. Pretreatment of vanadium-titanium magnetite using high-pressure roller milling, high-energy ball milling, or planetary ball milling induces microcracks, lattice distortions, or lattice defects on the surface of the iron-, vanadium-, and titanium-containing variable-valence metal compound particles within the vanadium-titanium magnetite. This significantly enhances the catalytic activity of the iron-, vanadium-, and titanium-containing variable-valence metal chemicals within the vanadium-titanium magnetite.

[0010] As a preferred embodiment, the nanomill employs a micro-nano grinding method. Micro-nano grinding of vanadium-titanium magnetite primarily reduces the particle size of the activated vanadium-titanium magnetite while fully exposing the active components encapsulated in the gangue minerals. This micro-nano fine grinding not only refines the particle size of variable-valence metal chemicals such as iron, vanadium, and titanium to the micro-nano level, improving their uniform dispersion on the activated carbon surface, but also enables efficient dissociation of catalytically active variable-valence metal chemicals such as iron, vanadium, and titanium from inert gangue components such as aluminum and silicon. This provides more highly active catalytic reaction sites for low-temperature catalytic NOx reduction and degradation.

[0011] As a preferred embodiment, the specific surface area of ​​the material ① is 30-100 cm². 2 / g, with over 95% of the mass being -10μm particles and at least 50% being -1μm particles. Vanadium-titanium magnetite that has undergone two-stage grinding not only has a smaller particle size but also an increased number of catalytically active sites, leading to enhanced catalytic activity.

[0012] As a preferred embodiment, the biomass raw material includes at least one of corn stalks, rice straw, wheat straw, cotton stalks, rice husks, sugarcane bagasse, and sawdust. The preferred biomass raw material is waste biomass, which is low in cost and can generate high added value.

[0013] As a preferred embodiment, the pyrolysis treatment conditions are: under a protective atmosphere, at a temperature of 300–500°C, for 20–40 minutes. The protective atmosphere is nitrogen or an inert gas. Preferably, the pyrolysis treatment is carried out at medium to low temperatures, which not only facilitates the formation of a rich porous structure, providing a supporting matrix for surface activation and micro / nano-sized vanadium-titanium magnetite particles, but also ensures that the biochar still contains a certain proportion of reducible organic components, providing CH components with excellent reducing properties for NOx reduction. As a more preferred embodiment, the volatile matter content of the material ② is 10–20% by mass, and the specific surface area is 200–500 cm². 2 / g, porosity 50-70%, and the proportion of pores with a diameter <50μm is not less than 80%.

[0014] As a preferred embodiment, the mass percentage composition of material ① and material ② is 3-8%: 92-97%. If the proportion of material ① is too low, the loading of variable valence metal chemicals such as vanadium, titanium, and iron, which have catalytic effects, will be too low, making it difficult to fully exert their function of low-temperature catalytic denitrification. If the proportion of material ① is too high, it will cause blockage of the micro-nano pores of activated carbon, which is not conducive to the diffusion of NOx gas and ammonia reducing agent into the activated carbon carrier and the diffusion of N2 generated in the reaction outward, thus hindering the efficient progress of the catalytic denitrification reaction.

[0015] As a preferred embodiment, during the stirring process, the temperature is 50–80°C, the stirring rate is 100–200 r / min, and the time is 20–50 min. This appropriate stirring process ensures that the activated vanadium-titanium magnetite is fully adsorbed and loaded onto the surface of the biochar.

[0016] The present invention also provides a denitrification catalyst, which is obtained by the preparation method described above.

[0017] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0018] 1) The method of this invention involves a two-stage grinding process: activation grinding and nano-grinding, on vanadium-titanium magnetite. First, activation is performed using high-pressure roller milling and high-energy ball milling, which generates microcracks, lattice distortions, or lattice defects on the surface of the iron-, vanadium-, and titanium-containing variable-valence metal compound particles in the vanadium-titanium magnetite. This significantly enhances the catalytic activity of the iron-, vanadium-, and titanium-containing variable-valence metal chemicals in the vanadium-titanium magnetite. Then, the activated vanadium-titanium magnetite undergoes micro- and nano-fine grinding. This refines the particle size of the iron-, vanadium-, and titanium-containing variable-valence metal chemicals to the micro- and nano-level, improving their uniform dispersion on the activated carbon surface. Furthermore, it enables efficient dissociation of the catalytically active variable-valence metal chemical particles from inert gangue components such as aluminum and silicon, thereby providing more highly active catalytic reaction sites for low-temperature catalytic NOx reduction and degradation.

[0019] 2) The method of the present invention involves subjecting waste biomass to medium-low temperature heat treatment. On the one hand, the thermal decomposition and volatilization of organic components in the biomass creates a rich pore structure, providing a loading matrix for surface-activated and micro-nano vanadium-titanium magnetite particles. On the other hand, the biochar obtained by medium-low temperature heat treatment still contains a certain proportion of organic components, which can provide CH components with excellent reduction performance for NOx reduction.

[0020] 3) The method of this invention involves loading inexpensive vanadium-titanium magnetite, after surface activation and particle size refinement pretreatment, onto biochar obtained from the pyrolysis of waste biomass, thereby preparing a catalyst with low-temperature (<160℃) catalytic denitrification function. This achieves high-value utilization of low-value-added metal mineral resources and waste biomass resources. The lattice distortion effect of the vanadium-titanium magnetite activation mill pretreatment and the nano-size effect of the micro-nano mill pretreatment significantly improve its catalytic reaction performance, helping to reduce the activation energy required for NOx reduction. Furthermore, the residual CH component in biomass has better reduction reaction activity, and the strong reducing environment of NH3-CH complex formed by it and ammonia facilitates the high-speed reduction of NOx to N2 at lower temperatures.

[0021] 4) The method of the present invention uses vanadium-titanium magnetite and biomass raw materials as raw materials, which has a very low cost and simple preparation steps, which is conducive to industrial production. The prepared denitrification catalyst has the function of catalytic denitrification at ultra-low temperature (<160℃), which has obvious advantages over existing denitrification catalysts. Detailed Implementation

[0022] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The patent terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0024] Unless otherwise specified, the various reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0025] Example 1

[0026] Vanadium-titanium magnetite with a V content of 0.7% and a Ti content of 4.5% underwent a first-stage pretreatment using a high-energy ball mill (single grinding time 30 min, single feed rate 500 g, steel ball filling rate 35%, ball mill speed 30 r / min). Then, a second-stage pretreatment was performed using a micro / nano sand mill (single grinding time 10 min, feed rate 300 g, milling speed 1000 r / min), yielding a specific surface area of ​​40 cm². 2 Material ① with a volatile content of 97% -10μm and a specific surface area of ​​55% was obtained by carbonizing waste corn stalks at 350℃ for 20 min under Ar atmosphere to obtain a volatile content of 17% and a specific surface area of ​​210 cm³. 2Material ②, with a porosity of 55% and a pore size <50μm accounting for 85% of the total, was prepared by mixing material ① and material ② at a mass percentage of 4%:96% and then adding ultrapure water to form a suspension with a solid-liquid ratio of 1:3. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 100r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 15mm and a height of 25mm at room temperature. The catalytic denitrification effect of the cylindrical granular catalyst was then tested under simulated flue gas composition (O2 16%, N2 78%, CO2 6%) and temperature conditions of 150℃, with the ammonia-to-nitrogen ratio controlled at 0.9:1 and a space velocity of 3000m³ / g. 3 / (h·m 3 The denitrification efficiency can reach 81.5%, achieving efficient catalytic denitrification of sintering flue gas without the need for additional heating.

[0027] Example 2

[0028] Vanadium-titanium magnetite with a V content of 1.0% and a Ti content of 5.1% underwent a first-stage pretreatment using a high-energy ball mill (single grinding time 30 min, feed rate 500 g, steel ball filling rate 35%, ball mill speed 30 r / min). Then, a second-stage pretreatment was performed using a micro / nano sand mill (single grinding time 15 min, feed rate 300 g, milling speed 1000 r / min), yielding a specific surface area of ​​50 cm². 2 Material ① with a volatile content of 100% -10μm and a specific surface area of ​​64% ① was obtained by carbonizing waste corn stalks at 400℃ for 25 min under Ar atmosphere to obtain a volatile content of 14% and a specific surface area of ​​250 cm². 2 Material ②, with a porosity of 63% and a pore size <50μm accounting for 90% of the total, was prepared. Material ① and material ② were mixed at a mass percentage of 5%:95% and then dissolved in ultrapure water to form a suspension with a solid-liquid ratio of 1:4. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 120 r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 12 mm and a height of 20 mm at room temperature. The catalytic denitrification effect of the cylindrical granular catalyst was then tested under simulated flue gas composition (O2 16%, N2 78%, CO2 6%) and a temperature of 150℃, with the ammonia-to-nitrogen ratio controlled at 0.9:1 and a space velocity of 3000 m / s². 3 / (h·m 3 The denitrification efficiency can reach 86.5%, achieving efficient catalytic denitrification of sintering flue gas without the need for additional heating.

[0029] Example 3

[0030] Vanadium-titanium magnetite with a V content of 1.0% and a Ti content of 5.1% underwent a first-stage pretreatment using a high-pressure roller mill (30 min grinding time per cycle, 300 g feed rate, 35% steel ball filling rate, and 30 r / min mill speed). A second-stage pretreatment was then performed using a micro / nano sand mill (15 min grinding time per cycle, 300 g feed rate, and 1000 r / min mill speed), yielding a specific surface area of ​​65 cm². 2 Material ① with a volatile content of 100% and a -1μm content of 67% ①; waste corn stalks were carbonized at 400℃ for 25 min in an Ar atmosphere to obtain a volatile content of 14% and a specific surface area of ​​250 cm². 2 Material ②, with a porosity of 63% and a pore size <50μm accounting for 90% of the total, was prepared. Material ① and material ② were mixed at a mass percentage of 5%:95% and then dissolved in ultrapure water to form a suspension with a solid-liquid ratio of 1:4. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 120 r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 12 mm and a height of 20 mm at room temperature. The catalytic denitrification effect of the cylindrical granular catalyst was then tested under simulated flue gas composition (O2 16%, N2 78%, CO2 6%) and temperature conditions of 150℃, with the ammonia-to-nitrogen ratio controlled at 0.9:1 and a space velocity of 3000 m / s². 3 / (h·m 3 The denitrification efficiency can reach 90.3%, achieving efficient catalytic denitrification of sintering flue gas without the need for additional heating.

[0031] Example 4

[0032] Vanadium-titanium magnetite with a V content of 1.5% and a Ti content of 5.5% underwent a first-stage pretreatment using a high-pressure roller mill (single grinding time 40 min, feed rate 300 g, steel ball filling rate 35%, mill speed 30 r / min). Then, a second-stage pretreatment was performed using a micro / nano sand mill (single grinding time 20 min, feed rate 300 g, mill speed 1000 r / min), yielding a specific surface area of ​​85 cm². 2 Material ① with a volatile content of 11% and a specific surface area of ​​75% (g / g) and a -10μm content of 100% and a -1μm content of 75%; waste corn stalks were carbonized at 450℃ for 25 min in an Ar atmosphere to obtain a volatile content of 11% and a specific surface area of ​​279 cm². 2Material ②, with a porosity of 67% and a pore size <50μm accounting for 95% of the total, was prepared by mixing material ① and material ② at a mass percentage of 5%:95% and then adding ultrapure water to form a suspension with a solid-liquid ratio of 1:4. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 120r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 10mm and a height of 15mm at room temperature. The catalytic denitrification effect of the cylindrical granular catalyst was then tested under simulated flue gas composition (O2 16%, N2 78%, CO2 6%) and a temperature of 150℃, with the ammonia-to-nitrogen ratio controlled at 0.9:1 and a space velocity of 3000m⁻¹. 3 / (h·m 3 The denitrification efficiency can reach 94.0%, achieving efficient catalytic denitrification of sintering flue gas without the need for additional heating.

[0033] Comparative Example 1

[0034] Vanadium-titanium magnetite with a V content of 1.0% and a Ti content of 5.1% was selected as the material①; waste corn stalks were carbonized at 400℃ for 25 min in an Ar atmosphere to obtain a volatile matter content of 14% and a specific surface area of ​​250 cm³. 2 Material ②, with a porosity of 63% and a pore size <50μm accounting for 90% of the total, was prepared by mixing material ① and material ② at a mass percentage of 5%:95% and then adding ultrapure water to form a suspension with a solid-liquid ratio of 1:4. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 120r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 12mm and a height of 20mm at room temperature. The catalytic denitrification effect of the cylindrical granular catalyst was then tested under simulated flue gas composition (O2 16%, N2 78%, CO2 6%) and a temperature of 150℃, with the ammonia-to-nitrogen ratio controlled at 1:1 and a space velocity of 3000m³ / g. 3 / (h·m 3 The denitrification efficiency is 20.3%.

[0035] Comparative Example 2

[0036] Vanadium-titanium magnetite with a V content of 1.0% and a Ti content of 5.1% was selected as the material①; waste corn stalks were carbonized at 400℃ for 25 min in an Ar atmosphere to obtain a volatile matter content of 14% and a specific surface area of ​​250 cm³. 2Material ②, with a porosity of 63% and a pore size <50μm accounting for 90% of the total, was prepared by mixing material ① and material ② at a mass percentage of 5%:95% and then adding ultrapure water to form a suspension with a solid-liquid ratio of 1:4. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 120r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 12mm and a height of 20mm at room temperature. The cylindrical granular catalyst was then tested for catalytic denitrification effect under simulated flue gas composition conditions. An external heating source was used to raise the temperature of the sintering flue gas to 200℃. The flue gas composition was 16% O2, 78% N2, and 6% CO2, with an ammonia-to-nitrogen ratio controlled at 1:1 and a space velocity of 3000m. 3 / (h·m 3 The denitrification efficiency is 40.1%.

[0037] Comparative Example 3

[0038] Vanadium-titanium magnetite with a V content of 0.7% and a Ti content of 4.5% underwent a first-stage pretreatment using a high-energy ball mill (single grinding time 30 min, single feed rate 500 g, steel ball filling rate 35%, ball mill speed 30 r / min). Then, a second-stage pretreatment was performed using a micro / nano sand mill (single grinding time 10 min, feed rate 300 g, milling speed 1000 r / min), yielding a specific surface area of ​​40 cm². 2 Materials with a surface area of ​​300 cm³ / g, a -10μm content of 97%, and a -1μm content of 55% ①; 2 Commercial activated carbon with a porosity of 60% and a pore size <50μm accounting for 90% was selected. Materials ① and ② were mixed at a mass percentage of 4%:96% and then dissolved in ultrapure water to form a suspension with a solid-liquid ratio of 1:3. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 100r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 15mm and a height of 25mm at room temperature. The catalytic denitrification effect of the cylindrical granular catalyst was then tested under simulated flue gas composition (O2 16%, N2 78%, CO2 6%) and temperature conditions of 150℃, with the ammonia-to-nitrogen ratio controlled at 0.9:1 and a space velocity of 3000m³ / h. 3 / (h·m 3 The denitrification efficiency can reach 52.8%. Although it achieves catalytic denitrification of sintering flue gas without additional heating, its catalytic efficiency is significantly lower than that of Example 1.

[0039] Comparative Example 4

[0040] Vanadium-titanium magnetite with a V content of 0.7% and a Ti content of 4.5% underwent a first-stage pretreatment using a high-energy ball mill (single grinding time 30 min, feed rate 500 g, steel ball filling rate 35%, ball mill speed 30 r / min) to obtain a specific surface area of ​​20 cm². 2 Material ① with a volatile content of 78% -10μm and a specific surface area of ​​30% was obtained by carbonizing waste corn stalks at 350℃ for 20 min under Ar atmosphere to obtain a volatile content of 17% and a specific surface area of ​​210 cm³. 2 Material ②, with a porosity of 55% and a pore size <50μm accounting for 85% of the total, was prepared by mixing material ① and material ② at a mass percentage of 4%:96% and then adding ultrapure water to form a suspension with a solid-liquid ratio of 1:3. The suspension was stirred for 20 minutes at 50℃ and a stirring speed of 100r / min, then filtered, dried, and pressed into cylindrical granular catalyst particles with a diameter of 15mm and a height of 25mm at room temperature. The catalytic denitrification effect of the cylindrical granular catalyst was then tested under simulated flue gas composition (O2 16%, N2 78%, CO2 6%) and temperature conditions of 150℃, with the ammonia-to-nitrogen ratio controlled at 0.9:1 and a space velocity of 3000m³ / g. 3 / (h·m 3 The denitrification efficiency can reach 43.5%. Although it achieves catalytic denitrification of sintering flue gas without additional heating, its catalytic efficiency is significantly lower than that of Example 1.

Claims

1. A method for preparing a denitration catalyst from vanadium-titanium magnetite coupled waste biomass, characterized by comprising the following steps: The method comprises the following steps: ​ 1) performing two-stage grinding treatment of vanadium-titanium magnetite by activation grinding and nano grinding to obtain material ①; the mass percentage of -10 μm particle size of the material ① is more than 95%, and the mass percentage of -1 μm particle size is not less than 50%; the activation grinding adopts high-energy ball milling, high-pressure roller milling or planetary ball milling mode; the nano grinding adopts micro-nano grinding mode; 2) performing pyrolysis treatment on the biomass raw material to obtain material ②; the pyrolysis treatment is performed under the following conditions: under a protective atmosphere, at a temperature of 300-500 ℃, and heat preservation for 20-40 min; the mass percentage content of volatile matter of the material ② is 10-20%, the porosity is 50-70%, and the proportion of holes with a pore size of less than 50 μm is not less than 80%; 3) mixing the material ① and the material ② with water to perform sizing, and then performing stirring, drying and pressing in sequence to obtain the product.

2. The method for preparing a denitrification catalyst by coupling vanadium-titanium magnetite with waste biomass according to claim 1, characterized in that: The vanadium-titanium magnetite has a vanadium mass content of not less than 0.6% and a titanium mass content of not less than 4%.

3. The method for preparing a denitrification catalyst by coupling vanadium-titanium magnetite with waste biomass according to claim 1, characterized in that: The biomass raw material comprises at least one of corn straw, rice straw, wheat straw, cotton stalk, chaff, bagasse and sawdust.

4. The method according to claim 1, wherein the vanadium-titanium magnetite coupled waste biomass is used to prepare a denitration catalyst. The mass percentage composition of the material ① and the material ② is 3-8%:92-97%.

5. The method according to claim 1, wherein the vanadium-titanium magnetite coupled waste biomass is used to prepare a denitration catalyst. In the stirring process, the temperature is 50-80 ℃, the stirring rate is 100-200 r / min, and the time is 20-50 min. ​ 6. A de-NOx catalyst characterized by: The product is prepared by the method according to any one of claims 1-5.