Oxygen-rich low-temperature co-SCR denitration catalyst, preparation method and application thereof

Abstract

The application belongs to the technical field of denitration catalysts, and discloses an oxygen-rich low-temperature CO-SCR denitration catalyst with high denitration efficiency under oxygen-rich and low-temperature conditions, and a preparation method and application thereof. The preparation method comprises the following steps: (1) dissolving paramagnetic active component precursors, auxiliary catalytic component precursors, carrier precursors and complexing agents in a solvent to uniformly mix to obtain a precursor solution; (2) adjusting the pH value of the precursor solution, and converting the solution into a sol under the condition of heating and stirring, and then standing and aging to form a wet gel; (3) placing the wet gel in a magnetic field environment, and performing drying treatment under the action of the magnetic field to obtain a dry gel; and (4) performing calcination treatment on the dry gel, and first performing first-stage heat treatment by introducing an inert atmosphere during the calcination process, and then switching to weak oxidizing atmosphere to perform second-stage heat treatment, and cooling to room temperature to obtain the oxygen-rich low-temperature CO-SCR denitration catalyst.

Description

Technical Field

[0001] This invention relates to the technical field of denitrification catalysts, and more specifically, to oxygen-enriched low-temperature CO-SCR denitrification catalysts, their preparation methods, and applications. Background Technology

[0002] With the rapid development of the global economy and the accelerating pace of industrialization, environmental pollution problems are becoming increasingly serious. Nitrogen oxides (NOx) x NO and carbon monoxide (CO) are major air pollutants that have attracted widespread attention. x Not only is NO a key component of acid rain and photochemical smog, but it also poses a serious threat to human health. Carbon monoxide is a toxic gas, and long-term exposure can lead to respiratory and cardiovascular diseases. Therefore, developing efficient purification technologies to reduce NO is crucial. x CO emissions have become an important research direction in the field of environmental protection.

[0003] Currently, selective catalytic reduction (SCR) technology is the main method for removing NO. x The mainstream technology is SCR. Traditional SCR catalysts are usually based on vanadium-titanium or zeolite-based materials, using ammonia as a reducing agent. However, this traditional NH3-SCR technology has obvious limitations: first, under high temperature and complex flue gas conditions, the catalyst has a narrow activity window and poor tolerance to SO2 and H2O; second, ammonia itself is corrosive and toxic, and "ammonia escape" is prone to occur during use, causing secondary pollution. In contrast, CO-SCR technology uses CO, a pollutant already present in the flue gas, as a reducing agent to reduce NO. x This not only avoids the problem of ammonia escape, but also removes two pollutants at the same time, achieving "waste treatment with waste", and has great application potential.

[0004] However, existing CO-SCR catalysts still have significant shortcomings in practical applications. Under oxygen-rich conditions, CO tends to react with oxygen rather than reduce NO, resulting in low denitrification efficiency. More importantly, traditional preparation processes limit catalyst performance: during conventional drying, the capillary pressure generated by solvent evaporation easily leads to the collapse of the gel skeleton, causing migration and severe aggregation of active components, reducing the dispersion of active sites; while conventional air-atmosphere calcination can remove organic matter, the strong oxidizing environment can over-oxidize metal ions, leading to a large loss of crucial oxygen vacancies; if only an inert atmosphere is used for calcination, it is difficult to completely remove organic residues, leading to carbon poisoning. Therefore, existing catalysts struggle to balance high dispersion and abundant oxygen vacancies, resulting in poor denitrification efficiency under oxygen-rich and low-temperature conditions. Summary of the Invention

[0005] The technical problem to be solved by this invention is to provide an oxygen-enriched low-temperature CO-SCR denitrification catalyst that still has high denitrification efficiency under oxygen-enriched and low-temperature conditions, as well as its preparation method and application. The technical solution is as follows:

[0006] The preparation method of oxygen-enriched low-temperature CO-SCR denitration catalyst includes the following steps:

[0007] (1) Dissolve the paramagnetic active component precursor, the co-catalytic component precursor, the support precursor and the complexing agent in a solvent and mix them evenly to obtain a precursor solution;

[0008] (2) Adjust the pH value of the precursor solution, and under heating and stirring conditions, transform the solution into a sol, and then let it stand and age to form a wet gel;

[0009] (3) The wet gel is placed in a magnetic field environment and dried under the action of the magnetic field to obtain a dry gel;

[0010] (4) The dry gel is calcined. During the calcination process, an inert atmosphere is first introduced for the first stage of heat treatment, and then a weak oxidizing atmosphere is switched for the second stage of heat treatment. After cooling to room temperature, an oxygen-rich low-temperature CO-SCR denitrification catalyst is obtained.

[0011] As a further improvement to the above preparation method: in step (1): the paramagnetic active component precursor is at least one of the nitrate, acetate or sulfate of cobalt, manganese, iron, copper or nickel; the co-catalytic component precursor is at least one of the nitrates of cerium, lanthanum, praseodymium, neodymium, magnesium, calcium or potassium; the support precursor is at least one of the alkoxide or inorganic salt of titanium, silicon, aluminum or zirconium; the complexing agent is at least one of citric acid, oxalic acid or EDTA; and the solvent is deionized water and / or anhydrous ethanol.

[0012] As a further improvement to the above preparation method: the mass ratio of the oxides of metal ions in the paramagnetic active component precursor, the co-catalytic component precursor, and the support precursor is (5-25):(1-15):(60-94); the total molar concentration of all metal ions in the precursor solution is 0.5-2.0 mol / L; and the molar ratio of all metal ions to complexing agent in the precursor solution is 1:(1-5).

[0013] As a further improvement to the above preparation method: in step (2), the pH of the precursor solution is adjusted to 2-5, the heating temperature is 80-100℃, and the standing aging time is 12-48 hours.

[0014] As a further improvement to the above preparation method: in step (3), the magnetic field environment is generated by a permanent magnet array consisting of several neodymium iron boron permanent magnets arranged in a manner with opposite polarities; the permanent magnet array is fixed to the outside of a container containing wet gel, so that the magnetic field lines pass through the wet gel, and the magnetic field strength is controlled by adjusting the distance between the neodymium iron boron permanent magnets and the container.

[0015] As a further improvement to the above preparation method: the magnetic induction intensity of the magnetic field environment is 0.5-1.5T; the drying temperature is 80-100℃; and the drying time is 10-24 hours.

[0016] As a further improvement to the above preparation method: in step (4): the inert atmosphere is at least one of nitrogen, argon and helium, the first stage heat treatment is to heat from room temperature to 500-600℃ at a heating rate of 2-5℃ / min and hold for 2-4 hours; the weak oxidizing atmosphere is a mixture of oxygen and inert gas, the oxygen content is 0.5-5 vol%, the second stage heat treatment is to continue to hold for 1-3 hours.

[0017] As a further improvement to the above preparation method, it also includes hydrophobic and anaerobic modification treatment of the catalyst surface obtained in step (4): the catalyst is placed in a vapor deposition furnace of trichloromethylsilane or hexamethyldisilazane and treated at 180-220°C for 1-3 hours.

[0018] The oxygen-enriched low-temperature CO-SCR denitration catalyst was prepared by the above-described preparation method.

[0019] The flue gas purification method uses the oxygen-enriched low-temperature CO-SCR denitrification catalyst prepared by the above method to convert NOx and CO in the flue gas into N2 and CO2, respectively.

[0020] The advantages of the oxygen-enriched low-temperature CO-SCR denitration catalyst, its preparation method, and its application of the present invention are as follows:

[0021] (1) This invention utilizes the response characteristics of paramagnetic active components (such as Co, Mn, Fe, Cu, etc.) to magnetic fields to introduce a magnetic field environment during the drying stage of the wet gel. During the process of solvent evaporation leading to gel network shrinkage, the magnetic field force induces paramagnetic metal ions, effectively counteracting the disordered migration and aggregation of active components caused by capillary tension during conventional drying. The magnetic field induces the active components to exhibit an ordered microscopic arrangement along the direction of magnetic field lines, making the active sites highly uniformly dispersed on the surface of the support and within the pores, thereby significantly increasing the active specific surface area of ​​the catalyst and significantly improving the denitrification efficiency of the catalyst under low-temperature conditions.

[0022] (2) This invention innovatively adopts a segmented calcination strategy of "high-temperature inert atmosphere carbonization / reduction - weak oxidizing atmosphere stabilization". In the first stage, the process is carried out at high temperature in an inert atmosphere. The reducing atmosphere generated by the decomposition of complexing agents (such as citric acid) in the precursor, combined with the high-temperature environment, induces the distortion of the metal oxide lattice and generates a large number of oxygen vacancy defects. Then, the process is switched to a weak oxidizing atmosphere with low oxygen concentration. This not only removes residual carbon deposits, but also stabilizes the surface active species in a valence state that is conducive to the CO-SCR reaction, preventing the healing of oxygen vacancies due to excessive oxidation. This rich oxygen vacancy structure greatly promotes the adsorption and activation of reactant molecules and the flow of lattice oxygen, and reduces the reaction activation energy.

[0023] (3) The ordered dry gel structure formed by magnetic field drying in this invention provides a good skeletal foundation for subsequent calcination. Under the action of the magnetic field, a closer contact interface is formed between the active component and the support precursor. This contact is transformed into a stronger metal-support interaction (SMSI) in the subsequent segmented calcination, which not only locks in the active species and prevents them from sintering at high temperatures or during long-term operation, but also improves the redox cycle stability of the catalyst, enabling it to maintain high NO efficiency even in an oxygen-rich environment. x Conversion rate.

[0024] (4) Preferably, the present invention can also perform hydrophobic-hydrophilic modification treatment, grafting silicon-containing hydrophobic groups (such as methyl groups) onto the catalyst surface. The resulting hydrophobic barrier not only physically blocks the contact between water vapor and active sites and inhibits the competitive adsorption of water molecules on reactive active sites, but also reduces the adhesion and deposition of sulfur poisoning products such as ammonium bisulfate on the catalyst surface to a certain extent. Combined with the high dispersibility and rich pore structure of the catalyst itself, the catalyst still exhibits excellent anti-poisoning ability and long life characteristics under complex flue gas conditions containing water vapor and SO2.

[0025] The embodiments of the invention provided in this specification will be further described below with reference to the accompanying drawings and specific embodiments. Additional aspects and advantages of the embodiments of the invention provided in this specification will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the embodiments of the invention provided in this specification. Attached Figure Description

[0026] The accompanying drawings, which form part of the embodiments of the invention provided in this specification, are used to aid in understanding the embodiments of the invention provided in this specification. The content provided in the drawings and the related descriptions in the embodiments of the invention provided in this specification can be used to explain the embodiments of the invention provided in this specification, but do not constitute an undue limitation on the embodiments of the invention provided in this specification. In the drawings:

[0027] Figure 1This is a diagram of the catalytic performance testing device of the present invention.

[0028] Figure 2 The nitrogen adsorption-desorption isotherm of the oxygen-enriched low-temperature CO-SCR denitrification catalyst of Example 1 of the present invention.

[0029] Figure 3 The image shows the BJH pore size distribution curve of the oxygen-enriched low-temperature CO-SCR denitrification catalyst of Example 1 of this invention. Detailed Implementation

[0030] The embodiments of the invention provided in this specification will now be clearly and completely described in conjunction with the accompanying drawings. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. Before describing the embodiments of the invention provided in this specification in conjunction with the accompanying drawings, it should be particularly noted that:

[0031] The technical solutions and features provided in the embodiments of the invention provided in this specification, including the following description, can be combined with each other without conflict.

[0032] Furthermore, the embodiments of the inventions provided in this specification mentioned below are generally only a portion of the embodiments of the inventions provided in this specification, and not all of them. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the inventions provided in this specification without creative effort should fall within the scope of protection of the embodiments of the inventions provided in this specification.

[0033] Regarding the terminology and units in the embodiments of the invention provided in this specification: The terms "comprising," "including," "having," and any variations thereof in the description, claims, and related parts of the embodiments of the invention provided in this specification are intended to cover non-exclusive inclusion. Furthermore, other relevant terms and units in the embodiments of the invention provided in this specification can be reasonably interpreted based on the relevant content of the embodiments of the invention provided in this specification.

[0034] Example 1

[0035] The preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this embodiment includes the following steps:

[0036] (1) Cobalt nitrate and manganese nitrate (molar ratio of cobalt ions to manganese ions is 1:1) were selected as paramagnetic active component precursors, cerium nitrate and lanthanum nitrate (molar ratio of cerium ions to lanthanum ions is 1:1) were selected as co-catalytic component precursors, tetrabutyl titanate was selected as carrier precursor, and citric acid was selected as complexing agent. The above three precursors and complexing agent were dissolved together in deionized water and mixed evenly to obtain a precursor solution. The mass ratio of the paramagnetic active component precursor, co-catalytic component precursor, and carrier precursor converted into metal ion oxides was 15:8:80. The total molar concentration of all metal ions in the precursor solution was controlled at 1 mol / L, and the molar ratio of all metal ions to complexing agent was 1:3.

[0037] (2) Adjust the pH of the precursor solution to 4, stir at 90°C until the solution turns into a sol, then stop stirring and let it stand for 24 hours to form a wet gel.

[0038] (3) Arrange two neodymium iron boron permanent magnets in a manner with opposite polarities (N pole to S pole) to form a permanent magnet array, and fix the permanent magnet array symmetrically on the outside of a beaker containing wet gel. Adjust the position of the neodymium iron boron permanent magnets so that the vertical projection surface of the neodymium iron boron permanent magnets covers the wet gel to ensure that the magnetic field lines pass through the wet gel uniformly. Adjust the distance between the neodymium iron boron permanent magnets and the beaker, and use a gaussmeter probe to insert into the center of the wet gel inside the beaker for real-time monitoring to construct a constant magnetic field environment with a central magnetic induction intensity of 1T; under the action of this magnetic field, place the wet gel in an environment of 90℃ to dry for 18 hours to obtain dry gel.

[0039] (4) Place the dry gel in a heating furnace, first introduce nitrogen as an inert atmosphere, heat from room temperature to 550°C at a heating rate of 3°C / min and keep it at that temperature for 3 hours for the first stage of heat treatment; then switch the atmosphere to a mixture of oxygen and inert gas with an oxygen content of 3 vol%, and continue to keep it at that temperature for 2 hours for the second stage of heat treatment. After cooling to room temperature, the catalyst base powder is obtained.

[0040] (5) The catalyst base powder obtained in the above steps is placed in a vapor deposition furnace of trichloromethylsilane or hexamethyldisilazane and treated at 200°C for 2 hours to finally obtain the finished oxygen-enriched low-temperature CO-SCR denitrification catalyst.

[0041] Figure 1 This is a diagram of the catalytic performance testing apparatus of the present invention. Figure 1 As shown, N2, NO, O2, and CO are mixed in a gas mixing bottle and then treated by a humidifier to obtain a mixed gas. The NO concentration in the mixed gas is 500 ppm (denoted as C). NOin The concentrations are: O2 20 vol%, CO 2500 ppm, H2O 6 vol%, and space velocity 5000 h⁻¹.-1 The mixed gas passed through a catalyst-filled reaction bed at a flow rate of 2.5 L / min, with reaction temperatures of 180℃ and 200℃. The NO concentration in the exhaust gas passing through the reaction bed was measured using an infrared flue gas analyzer and recorded as C. NOout Then, the formula "Denitrification efficiency = (1-C)" is used. NOout / C NOin The denitrification efficiency is calculated as 100% × 100%.

[0042] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 89.5% at 180℃ and 95.7% at 200℃.

[0043] Figure 2 This is the nitrogen adsorption-desorption isotherm of the oxygen-enriched low-temperature CO-SCR denitrification catalyst in this embodiment. Figure 3 This is the BJH pore size distribution curve of the oxygen-enriched low-temperature CO-SCR denitrification catalyst in this embodiment. Figure 2 As shown, the nitrogen adsorption-desorption isotherm of the catalyst is isotherm IV, exhibiting an H3-type hysteresis loop and a well-developed mesoporous structure. Figure 3 As shown, the pore size distribution of the catalyst is concentrated around 20 nm. The specific surface area of ​​the catalyst, calculated using the BET method, is 78.5 m². 2 / g, total pore volume is 0.4514cm³ 3 / g, with an average pore size of 21.8nm.

[0044] Example 2

[0045] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this example is different in that: cobalt nitrate is selected as the paramagnetic active component precursor, cerium nitrate is selected as the co-catalytic component precursor, tetraethyl orthosilicate is selected as the support precursor, and oxalic acid is selected as the complexing agent. The mass ratio of the paramagnetic active component precursor, the co-catalytic component precursor, and the support precursor converted into metal ion oxides is 5:1:60, and the molar ratio of all metal ions to complexing agent is 1:1.

[0046] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 86.4% at 180℃ and 93.5% at 200℃.

[0047] Example 3

[0048] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this example is different in that: manganese nitrate is selected as the paramagnetic active component precursor, lanthanum nitrate is selected as the co-catalytic component precursor, aluminum isopropoxide is selected as the support precursor, and EDTA is selected as the complexing agent. The mass ratio of the paramagnetic active component precursor, the co-catalytic component precursor, and the support precursor converted into metal ion oxides is 25:15:94, and the molar ratio of all metal ions to complexing agent is 1:5.

[0049] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 85.8% at 180℃ and a denitrification efficiency of 92.8% at 200℃.

[0050] Example 4

[0051] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this example is different in that: cobalt nitrate and nickel nitrate (molar ratio of cobalt ions to nickel ions is 1:1) are selected as paramagnetic active component precursors, magnesium nitrate is selected as co-catalytic component precursor, aluminum nitrate is selected as support precursor, citric acid is selected as complexing agent, the mass ratio of the paramagnetic active component precursor, co-catalytic component precursor, and support precursor converted into metal ion oxides is 20:5:77, and the molar ratio of all metal ions to complexing agent is 1:4.

[0052] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 84.2% at 180℃ and a denitrification efficiency of 91.5% at 200℃.

[0053] Example 5

[0054] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this example is different in that: the magnetic induction intensity is 0.5T, and the wet gel is dried in an environment of 100°C for 10 hours to obtain the dry gel.

[0055] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 87.1% at 180℃ and a denitrification efficiency of 93.7% at 200℃.

[0056] Example 6

[0057] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this example is different in that: the magnetic induction intensity is 1.5T, and the wet gel is placed in an environment of 80°C for 24 hours to dry to obtain a dry gel.

[0058] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 87.6% at 180℃ and a denitrification efficiency of 94.3% at 200℃.

[0059] Example 7

[0060] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this example is different in that: the first stage of heat treatment is carried out by heating from room temperature to 500°C and holding for 4 hours; then the atmosphere is switched to a mixture of oxygen and inert gas with an oxygen content of 5 vol%, and the second stage of heat treatment is carried out by holding for 1 hour under a weak oxidizing atmosphere.

[0061] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 86.9% at 180℃ and a denitrification efficiency of 92.8% at 200℃.

[0062] Example 8

[0063] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitration catalyst in this example is different in that: the first stage of heat treatment is carried out by heating from room temperature to 600°C and holding for 2 hours; then the atmosphere is switched to a mixture of oxygen and inert gas with an oxygen content of 0.5 vol%, and the second stage of heat treatment is carried out by continuing to hold for 3 hours under a weak oxidizing atmosphere.

[0064] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 85.5% at 180℃ and a denitrification efficiency of 92.2% at 200℃.

[0065] Example 9

[0066] Compared with Example 1, the preparation method of the oxygen-enriched low-temperature CO-SCR denitrification catalyst in this example is different in that step (5) is not performed.

[0067] Tests showed that the oxygen-enriched low-temperature CO-SCR denitrification catalyst of this embodiment has a denitrification efficiency of 83.1% at 180℃ and 90.1% at 200℃.

[0068] Compare with Example 1

[0069] Compared with Example 1, the preparation method of CO-SCR denitration catalyst in this example is different in that: no magnetic field environment is applied in step (3), and ordinary drying method is used.

[0070] According to the test, the CO-SCR denitrification catalyst of this control example has a denitrification efficiency of 68.2% at 180℃ and a denitrification efficiency of 79.5% at 200℃.

[0071] Compare with Example 2

[0072] Compared with Example 1, the preparation method of CO-SCR denitration catalyst in this example is different in that the magnetic induction intensity 2T in step (3) is different.

[0073] The CO-SCR denitrification catalyst of this control example was tested and found to have a denitrification efficiency of 68.4% at 180℃ and 80.1% at 200℃.

[0074] Compare with Example 3

[0075] Compared with Example 1, the preparation method of CO-SCR denitration catalyst in this example is different in that only the first stage of heat treatment is performed in step (4).

[0076] According to the test, the CO-SCR denitrification catalyst of this control example has a denitrification efficiency of 50.5% at 180℃ and a denitrification efficiency of 66.2% at 200℃.

[0077] The examples of the oxygen-enriched low-temperature CO-SCR denitrification catalyst of the present invention are prepared by the preparation method of any one of the above examples.

[0078] An embodiment of the flue gas purification method of the present invention is an oxygen-enriched low-temperature CO-SCR denitrification catalyst prepared by any of the preparation methods described in the above embodiments, which removes NO from the flue gas. x CO is converted into N2 and CO2, respectively.

[0079] The embodiments of the invention provided in this specification have been described above. Those skilled in the art will be able to implement the embodiments of the invention provided in this specification based on these descriptions. All other preferred embodiments and implementations obtained by those skilled in the art based on the above description of the embodiments of the invention provided in this specification without inventive effort should fall within the protection scope of the embodiments of the invention provided in this specification.

Claims

1. A method for preparing an oxygen-enriched low-temperature CO-SCR denitration catalyst, characterized in that, Includes the following steps: (1) Dissolve the paramagnetic active component precursor, the co-catalytic component precursor, the support precursor and the complexing agent in a solvent and mix them evenly to obtain a precursor solution; (2) Adjust the pH value of the precursor solution, and under heating and stirring conditions, transform the solution into a sol, and then let it stand and age to form a wet gel; (3) The wet gel is placed in a magnetic field environment and dried under the action of the magnetic field to obtain a dry gel; wherein the magnetic induction intensity of the magnetic field environment is 0.5-1.5T; (4) The dry gel is calcined. During the calcination process, an inert atmosphere is first introduced for the first stage of heat treatment, and then a weak oxidizing atmosphere is switched for the second stage of heat treatment. After cooling to room temperature, an oxygen-rich low-temperature CO-SCR denitration catalyst is obtained. The weak oxidizing atmosphere is a mixture of oxygen and inert gas, and the oxygen content is 0.5-5 vol.

2. The preparation method according to claim 1, characterized in that: In step (1): The paramagnetic active component precursor is at least one of the following: nitrate, acetate, or sulfate of cobalt, manganese, iron, copper, and nickel. The precursor of the co-catalytic component is a nitrate of at least one of cerium, lanthanum, praseodymium, neodymium, magnesium, calcium, and potassium; The carrier precursor is an alkoxide or inorganic salt of at least one of titanium, silicon, aluminum or zirconium; The complexing agent is at least one of citric acid, oxalic acid, and EDTA; The solvent is deionized water and / or anhydrous ethanol.

3. The preparation method according to claim 1, characterized in that: The mass ratio of the oxides of metal ions in the paramagnetic active component precursor, the co-catalytic component precursor, and the support precursor is (5-25):(1-15):(60-94); The total molar concentration of all metal ions in the precursor solution is 0.5-2.0 mol / L; The molar ratio of all metal ions to complexing agent in the precursor solution is 1:(1-5).

4. The preparation method according to claim 1, characterized in that: In step (2), the pH of the precursor solution is adjusted to 2-5, the heating temperature is 80-100℃, and the aging time is 12-48 hours.

5. The preparation method according to claim 1, characterized in that: In step (3), the magnetic field environment is generated by an array of permanent magnets consisting of several neodymium iron boron permanent magnets arranged in opposite polarities. The array of permanent magnets is fixed to the outside of a container containing wet gel, so that the magnetic field lines pass through the wet gel. The magnetic field strength is controlled by adjusting the distance between the neodymium iron boron permanent magnets and the container.

6. The preparation method according to claim 1, characterized in that: In step (3), the drying temperature is 80-100℃ and the drying time is 10-24 hours.

7. The preparation method according to claim 1, characterized in that: In step (4): The inert atmosphere is at least one of nitrogen, argon, and helium. The first stage of heat treatment is to heat from room temperature to 500-600℃ at a heating rate of 2-5℃ / min and hold at that temperature for 2-4 hours. The second stage of heat treatment involves continuing to hold the temperature for 1-3 hours.

8. The preparation method according to claim 1, characterized in that: It also includes hydrophobic and anaerobic modification treatment of the catalyst surface obtained in step (4): the catalyst is placed in a vapor deposition furnace of trichloromethylsilane or hexamethyldisilazane and treated at 180-220°C for 1-3 hours.

9. An oxygen-enriched low-temperature CO-SCR denitrification catalyst, characterized in that: It is prepared by the preparation method according to any one of claims 1-8.

10. A method for purifying flue gas, characterized in that: The oxygen-enriched low-temperature CO-SCR denitrification catalyst prepared by the preparation method described in any one of claims 1-8 converts NOx and CO in flue gas into N2 and CO2, respectively.

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