Ni-Si synergistically modified manganese-based catalyst as well as preparation method and application thereof

Abstract

The invention provides a Ni-Si synergistically modified manganese-based catalyst as well as a preparation method and application thereof. According to the invention, the Ni-Si synergistically modified manganese-based catalyst is obtained through a simple synthesis route. The nitrogen oxide / CO synergistic removal performance and the sulfur poisoning resistance of the manganese-based catalyst are effectively improved based on the synergistic effect of a metal doping regulation body structure and acidic oxide coating optimization surface properties. The reason is that d-d orbital hybridization between Mn and Ni induced by doping Ni changes d electron cloud distribution and bonding characteristics of Mn, so that the valence state of Mn and the Mn-O bond length are effectively regulated and controlled, a defect structure is stabilized, and generation of rich oxygen vacancies is promoted; in addition, through coating of a proper amount of SiO2, SO2 can be prevented from being adsorbed on the surface of the catalyst, internal active components are protected, and the characteristic that the active components are prone to sulfur poisoning at low temperature can be effectively relieved.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and environmental catalysis technology, and particularly relates to a Ni-Si synergistic modified manganese-based catalyst, its preparation method and application. Background Technology

[0002] With the rapid development of the world economy, air pollution has become increasingly severe, including a surge in emissions of harmful gases such as carbon monoxide (CO) and nitrogen oxides, posing a significant threat to the environment and human health. Nitrogen oxides and CO in flue gas are currently key pollutants requiring treatment, especially in industries such as steel sintering. Traditional NH3-SCR (Selective Catalytic Reduction) technology, which uses ammonia (NH3) as a reducing agent to convert nitrogen oxides in flue gas into harmless nitrogen and water under the action of a catalyst, and is currently the most widely used flue gas denitrification technology), exhibits significant limitations under low-temperature conditions. For example, when the emission temperature of sintering flue gas is below the applicable temperature window of vanadium-based catalysts, the catalyst activity is poor, and ammonium sulfate is easily generated, clogging the catalyst pores and leading to catalyst poisoning and deactivation. Furthermore, CO removal technology is still in its early stages, and its low-temperature removal efficiency urgently needs improvement; moreover, the sulfur resistance of catalysts often fails to meet practical application requirements. Therefore, developing low-temperature catalysts that can effectively remove nitrogen oxides and CO from low-temperature flue gas, while also possessing excellent sulfur resistance, is crucial for solving increasingly serious environmental problems.

[0003] In both SCR reactions and CO catalytic oxidation, the performance of the catalyst directly affects the overall pollutant removal efficiency of the system. Compared to other transition metals, manganese oxides have attracted much attention due to their low cost, diverse valence states, strong redox capabilities, and environmental friendliness. Mn-based composite oxide catalysts are considered to be the most promising catalysts for low-temperature NH3-SCR and have received widespread attention from researchers in recent years. However, there is still considerable room for improvement in their low-temperature SCR activity, stability, temperature window, and SO2 resistance.

[0004] Therefore, developing a novel, efficient, stable, and sulfur-resistant Mn-based composite oxide catalyst and applying it to the NH3-SCR field has significant theoretical research value and practical engineering implications. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a Ni-Si synergistic modified manganese-based catalyst, its preparation method, and its application.

[0006] The present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a method for preparing a Ni-Si synergistically modified manganese-based catalyst, comprising the following steps:

[0008] Urea, manganese source and nickel source were added to water to carry out a co-precipitation reaction. After the reaction product was dried, it was calcined once to obtain Ni-doped manganese-based oxide.

[0009] Ni-doped manganese-based oxides were dispersed in an alcohol solvent, alkali was added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate was added. The reaction was stirred and the reaction product was dried and then calcined a second time to obtain a Ni-doped / SiO2-coated synergistically modified manganese-based catalyst.

[0010] Preferably, the molar amount of manganese in the manganese source is a mol, the total molar amount of manganese in the manganese source and nickel in the nickel source is 1.0 mol, and the molar ratio of urea, manganese in the manganese source and nickel in the nickel source is 5:a:(1.0-a), where 0.3≤a≤0.7.

[0011] Preferably, urea, manganese source and nickel source are added to water to carry out a co-precipitation reaction, wherein the co-precipitation reaction temperature is 80~90℃ and the time is 7~9h.

[0012] Preferably, after drying the reaction product, it is calcined once, wherein the calcination temperature is 400~500℃, the time is 4~8h, and the heating rate is 5~10°C / min.

[0013] Preferably, Ni-doped manganese-based oxide is dispersed in an alcohol solvent, an alkali is added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate is added. The mixture is stirred to react, wherein the reaction temperature is 20-25°C and the reaction time is 10-12 hours.

[0014] Preferably, Ni-doped manganese-based oxide is dispersed in an alcohol solvent, an alkali is added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate is added. The mixture is stirred and reacted, and the reaction product is dried and then calcined a second time. The second calcination temperature is 450-600℃, the time is 3-5h, and the heating rate is 4-5°C / min.

[0015] Preferably, the mass-to-volume ratio of the Ni-doped manganese-based oxide to the alcohol solvent is (0.6~0.8) g:(40~50) mL;

[0016] The molar ratio of the Ni-doped manganese-based oxide to the tetraethyl orthosilicate in the alcohol solution containing tetraethyl orthosilicate is (0.6~0.8) g: 0.2 mmol;

[0017] The alcohol solution containing tetraethyl orthosilicate comprises tetraethyl orthosilicate and an alcohol solvent, wherein the molar volume ratio of tetraethyl orthosilicate to alcohol solvent is 0.2 mmol:(40~50) mL;

[0018] The alcohol solvent includes methanol or ethanol;

[0019] In the step of adding urea, manganese source and nickel source to water, the molar volume ratio of urea to water is (0.1~0.2) mol: 500 mL;

[0020] The manganese source is manganese acetate;

[0021] The nickel source is nickel acetate.

[0022] Preferably, the alkali includes any one of ammonia, sodium hydroxide solution, and potassium hydroxide solution.

[0023] Secondly, the present invention also provides a Ni-Si synergistic modified manganese-based catalyst, which is prepared by the preparation method described above.

[0024] Thirdly, the present invention also provides a Ni-Si synergistic modified manganese-based catalyst prepared by the preparation method described above, or the application of the Ni-Si synergistic modified manganese-based catalyst described above in the removal of CO and nitrogen oxides from flue gas.

[0025] The preparation method and application of the Ni-Si synergistic modified manganese-based catalyst of the present invention have the following advantages compared with the prior art:

[0026] 1. The preparation method of the Ni-Si synergistic modified manganese-based catalyst of the present invention includes the preparation of Ni-doped manganese-based oxide and the formation of a uniform SiO2 coating layer on the surface of the Ni-doped manganese-based oxide; the preparation principle of Ni-doped manganese-based oxide is as follows: a Mn-Ni composite precursor is generated through a co-precipitation reaction, and then converted into Ni-doped manganese-based oxide by calcination; a uniform SiO2 coating layer is formed on the surface of Ni-doped manganese-based oxide by a hydrolysis-condensation reaction of tetraethyl orthosilicate (TEOS) followed by a second calcination, thereby optimizing the surface properties of the catalyst to improve sulfur resistance; the core advantage of this catalyst stems from the synergistic effect of Ni doping and SiO2 coating, which respectively improve performance from two dimensions: "bulk activity" and "surface sulfur resistance": Ni doping (bulk regulation): through dd Orbital hybridization optimizes the Mn valence state and oxygen vacancies, enhancing the catalyst's adsorption and activation capabilities for nitrogen oxides while simultaneously strengthening CO oxidation activity, thus providing an active basis for the synergistic removal of nitrogen oxides and CO. SiO2 coating (surface protection): A SiO2 layer of appropriate thickness can physically block SO2 in the flue gas from contacting the internal Mn active sites, reducing the sulfation and loss of manganese oxide active components, thereby effectively improving the catalyst's sulfur resistance.

[0027] 2. This invention synthesizes a series of Ni-Si synergistically modified manganese-based catalysts Mn by adjusting the molar ratio of Mn / Ni and the coating amount of tetraethyl orthosilicate. a Ni 1-a O x @Si. Studies have found that when the molar ratio of Mn / Ni is 0.5:0.5 and the dosage of the modifier tetraethyl orthosilicate is 0.2 mmol, the resulting catalyst Mn 0.5 Ni 0.5 O x @Si exhibits the best catalytic oxidation performance in NH3-SCR under CO-containing environments. When the CO concentration in the gas is 1000 ppm, Mn... 0.5 Ni 0.5 O x The Si catalyst achieves a 90% NO conversion rate during oxidation, with a temperature range of 150-300°C, while the unmodified MnO... x The catalytic performance of the catalyst under the same conditions is far inferior to that of the modified catalyst. After introducing SO2 gas at a concentration of 100 ppm, Mn... 0.5 Ni 0.5 O x The stable synergistic removal effect of the Si catalyst verifies its synergistic removal reaction capability, indicating that SiO2 coating can effectively alleviate sulfur poisoning and significantly improve the catalyst's sulfur resistance. Compared with existing manganese-based catalysts, the manganese-based catalyst provided by this invention has higher low-temperature catalytic oxidation activity, better reaction stability, and stronger resistance to sulfur poisoning, making it suitable for the synergistic removal of nitrogen oxides / CO. This invention provides a theoretical basis and experimental support for developing nitrogen oxide / CO synergistic removal catalysts with good activity, high stability, and strong resistance to sulfur poisoning. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 The XRD patterns of the catalysts prepared in Example 1 and Comparative Examples 1-3 are shown below.

[0030] Figure 2 Scanning electron microscope (SEM) images of the catalysts prepared in Example 1 and Comparative Examples 1-3;

[0031] Figure 3The graph shows the results of the nitrogen oxide / CO synergistic removal performance test of the catalysts prepared in Example 1 and Comparative Examples 1-3;

[0032] Figure 4 The catalyst Mn in Example 1 0.5 Ni 0.5 O x @Si NO conversion rate comparison chart at different CO concentrations and CO conversion rate comparison chart at different CO concentrations. Detailed Implementation

[0033] To facilitate understanding of the present invention, a more comprehensive description of the invention will be provided below in conjunction with specific embodiments. Preferred embodiments of the invention are given in the specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0034] The order in which the embodiments are described below is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of the invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0035] This invention provides a method for preparing a Ni-Si synergistically modified manganese-based catalyst, comprising the following steps:

[0036] S1. Urea, manganese source and nickel source are added to water to carry out co-precipitation reaction. After drying the reaction product, it is calcined once to obtain Ni-doped manganese-based oxide.

[0037] S2. Ni-doped manganese-based oxides are dispersed in an alcohol solvent, alkali is added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate is added. The reaction is stirred and the reaction product is dried and then calcined a second time to obtain a Ni-Si synergistically modified manganese-based catalyst.

[0038] The present invention discloses a method for preparing a Ni-Si synergistically modified manganese-based catalyst, comprising the preparation of Ni-doped manganese-based oxide and the formation of a uniform SiO2 coating layer on the surface of the Ni-doped manganese-based oxide. The preparation principle of the Ni-doped manganese-based oxide is as follows: a Mn-Ni composite precursor is generated through a co-precipitation reaction, which is then calcined to convert it into Ni-doped manganese-based oxide. A uniform SiO2 coating layer is formed on the surface of the Ni-doped manganese-based oxide through a hydrolysis-condensation reaction of tetraethyl orthosilicate (TEOS) followed by secondary calcination, thereby optimizing the catalyst surface properties and improving sulfur resistance. The core advantage of this catalyst stems from the synergistic effect of Ni doping and SiO2 coating, which respectively enhance performance from two dimensions: "bulk activity" and "surface sulfur resistance." Ni doping (bulk regulation): through dd... Orbital hybridization optimizes the Mn valence state and oxygen vacancies, enhancing the catalyst's adsorption and activation capabilities for nitrogen oxides while simultaneously strengthening CO oxidation activity, thus providing an active basis for the synergistic removal of nitrogen oxides and CO. SiO2 coating (surface protection): A SiO2 layer of appropriate thickness can physically block SO2 in the flue gas from contacting the internal Mn active sites, reducing the sulfation and loss of manganese oxide active components, thereby effectively improving the catalyst's sulfur resistance.

[0039] This invention effectively improves the nitrogen oxide / CO synergistic removal performance and sulfur poisoning resistance of manganese-based catalysts by leveraging the synergistic effect of metal doping to regulate the bulk structure and acidic oxide coating to optimize surface properties. This is because Ni doping induces dd orbital hybridization between Mn and Ni, altering the d electron cloud distribution and bonding characteristics of Mn. This not only effectively regulates the valence state of Mn and the Mn-O bond length but also stabilizes the defect structure, thereby promoting the generation of abundant oxygen vacancies. Furthermore, appropriate SiO2 coating prevents SO2 adsorption on the catalyst surface and protects the internal active components.

[0040] This invention provides a Ni-Si synergistically modified manganese-based catalyst via a simple synthetic route. This catalyst boasts advantages such as inexpensive and readily available materials, a simple, efficient, and economical preparation method, minimal equipment and instrument requirements, and high yield. Compared to traditional wet impregnation or single-pot hydrothermal methods, this invention more effectively achieves precise control and optimization of catalyst active sites and surface acidity. Through SiO2 coating, the catalyst effectively mitigates the susceptibility to sulfur poisoning of the active components at low temperatures.

[0041] In some embodiments, the molar amount of manganese in the manganese source is a mol, the total molar amount of manganese in the manganese source and nickel in the nickel source is 1.0 mol, and the molar ratio of urea, manganese in the manganese source and nickel in the nickel source is 5:a:(1.0-a), where 0.3≤a≤0.7.

[0042] In some embodiments, urea, manganese source and nickel source are added to water to carry out a coprecipitation reaction, wherein the coprecipitation reaction temperature is 80~90℃ and the time is 7~9h.

[0043] In some embodiments, the reaction product is dried and then calcined once. The calcination temperature is 400-500°C, the time is 4-8 hours, and the heating rate is 5-10°C / min. That is, after drying the reaction product, the temperature is raised from room temperature (20-25°C) to 400-500°C at 5-10°C / min and calcined for 4-8 hours, which is the first calcination.

[0044] In some embodiments, Ni-doped manganese-based oxides are dispersed in an alcohol solvent, an alkali is added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate is added. The mixture is stirred to react, wherein the reaction temperature is 20-25°C and the reaction time is 10-12 h.

[0045] In some embodiments, Ni-doped manganese-based oxides are dispersed in an alcohol solvent, an alkali is added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate is added. The mixture is stirred and reacted. The reaction product is dried and then subjected to a second calcination. The second calcination temperature is 450-600°C, the time is 3-5 h, and the heating rate is 4-5°C / min. That is, after drying the reaction product, the temperature is raised from room temperature (20-25°C) to 450-600°C at a rate of 4-5°C / min and calcined for 3-5 h, which is the second calcination.

[0046] In some embodiments, the mass-to-volume ratio of Ni-doped manganese-based oxide to alcohol solvent is (0.6~0.8) g:(40~50) mL;

[0047] The molar ratio of Ni-doped manganese-based oxide to tetraethyl orthosilicate in an alcoholic solution containing tetraethyl orthosilicate is (0.6~0.8) g: 0.2 mmol;

[0048] An alcoholic solution containing tetraethyl orthosilicate comprises tetraethyl orthosilicate and an alcohol solvent, wherein the molar volume ratio of tetraethyl orthosilicate to alcohol solvent is 0.2 mmol:(40~50) mL;

[0049] Alcohol solvents include methanol or ethanol;

[0050] In the step of adding urea, manganese source and nickel source to water, the molar volume ratio of urea to water is (0.1~0.2) mol: 500 mL.

[0051] In some embodiments, the alkali includes any one of ammonia, sodium hydroxide solution, and potassium hydroxide solution.

[0052] In some embodiments, urea, manganese source and nickel source are added to water to carry out a coprecipitation reaction. After the coprecipitation reaction is completed, the reaction product is washed three times by centrifugation with deionized water and ethanol, dried in an oven at 60~80°C for 10~15h, and calcined once to obtain Ni-doped manganese-based oxide.

[0053] In some embodiments, Ni-doped manganese-based oxides are dispersed in an alcohol solvent, an alkali is added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate is added. The mixture is stirred to react. After the reaction is complete, the reaction product is washed three times by centrifugation with deionized water and ethanol, dried in an oven at 60-80°C for 10-15 hours, and then calcined a second time to obtain Ni-doped manganese-based oxides.

[0054] In some embodiments, the molar ratio of urea, manganese in the manganese source, and nickel in the nickel source is 5:a:(1.0-a), where 0.3≤a≤0.7, and the mass molar ratio of Ni-doped manganese-based oxide to tetraethyl orthosilicate is (0.6~0.8) g:0.2 mmol. By adjusting the molar ratio of Mn / Ni and the coating amount of tetraethyl orthosilicate, a series of Ni-Si synergistically modified manganese-based catalysts Mn were synthesized. a Ni 1-a O x @Si. Studies have found that when the molar ratio of Mn / Ni is 0.5:0.5 and the dosage of silicon-based tetraethyl orthosilicate is 0.2 mmol, the resulting catalyst Mn 0.5 Ni 0.5 O x @Si exhibits the best catalytic oxidation performance in NH3-SCR under SO2-containing conditions. When the SO2 content in the gas is 100 ppm, Mn... 0.5 Ni 0.5 O x The Si catalyst achieves a 90% NO conversion rate during oxidation, with a temperature range of 150-300°C, while the unmodified MnO... x Under the same conditions, the catalytic performance of the catalyst was far inferior to that of the modified catalyst. The SiO2 coating effectively alleviated sulfur poisoning and significantly improved the catalyst's sulfur resistance. After the introduction of CO, Mn... 0.5 Ni 0.5 O x The stable synergistic removal effect of the Si catalyst verifies its synergistic removal capability. Compared with existing manganese-based catalysts, the manganese-based catalyst provided by this invention exhibits higher low-temperature catalytic oxidation activity, better reaction stability, and stronger resistance to sulfur poisoning, making it suitable for the synergistic removal of nitrogen oxides and CO. This invention provides a theoretical basis and experimental support for developing nitrogen oxide / CO synergistic removal catalysts with good activity, high stability, and strong resistance to sulfur poisoning.

[0055] Based on the same inventive concept, the present invention also provides a Ni-Si synergistic modified manganese-based catalyst, which is prepared by the preparation method described above.

[0056] Based on the same inventive concept, this invention also provides an application of the Ni-Si synergistic modified manganese-based catalyst prepared by the above-described preparation method, or the above-described Ni-Si synergistic modified manganese-based catalyst, in the removal of CO and nitrogen oxides from flue gas. This catalyst can be used for the synergistic removal of nitrogen oxides and CO from low-temperature flue gas (150~300℃), and is particularly suitable for flue gas environments containing SO2 (e.g., when the SO2 concentration is 100ppm, the NO conversion rate can still reach over 90%).

[0057] The following specific embodiments further illustrate the Ni-Si synergistic modification of manganese-based catalysts, their preparation methods, and applications. This section further explains the invention in conjunction with specific embodiments, but should not be construed as limiting the invention. Unless otherwise specified, the techniques used in the embodiments are conventional methods well known to those skilled in the art. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in the art.

[0058] Example 1

[0059] This embodiment provides a method for preparing a Ni-Si synergistically modified manganese-based catalyst, including the following steps:

[0060] S1. Dissolve urea, manganese acetate tetrahydrate and nickel acetate tetrahydrate in a molar ratio of 5:0.5:0.5 in 500 mL of deionized water at room temperature (25 °C) (wherein, the concentration of urea is 0.2 mol / L and the molar amount of urea is 0.1 mol) to obtain a homogeneous solution.

[0061] The homogeneous solution was placed in an oil bath and co-precipitated at 90°C for 8 hours. After natural cooling to room temperature, the reaction product was washed three times with deionized water and ethanol by centrifugation, dried in a 60°C oven for 10 hours, cooled to room temperature, and then heated to 400°C at a rate of 10°C / min and calcined for 6 hours to obtain Ni-doped manganese-based oxide (denoted as Mn). 0.5 Ni 0.5 O x );

[0062] S2, Take 0.6g of Mn from step S1 0.5 Ni 0.5 O x Dispersed in 40 mL of anhydrous ethanol, the mixture was uniformly dispersed using an ultrasonic cleaner for 40 min to obtain the first suspension.

[0063] Ammonia solution (20% by mass) was added to the first suspension, and the pH was adjusted to 10 to obtain the second suspension.

[0064] An ethanol solution containing 0.2 mmol tetraethyl orthosilicate (obtained by adding 0.2 mmol tetraethyl orthosilicate to 40 mL of anhydrous ethanol) was added dropwise to the second suspension. The mixture was stirred at room temperature for 12 h. After stirring, the reaction product was washed three times by centrifugation with deionized water and ethanol, dried in a 60°C oven for 10 h, cooled to room temperature, and then heated to 450°C at a rate of 5°C / min and calcined for 3 h to obtain a Ni-Si synergistically modified manganese-based catalyst (denoted as Mn). 0.5 Ni 0.5 O x @Si).

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing a Ni-doped manganese-based catalyst, comprising the following steps:

[0067] Urea, manganese acetate tetrahydrate, and nickel acetate tetrahydrate in a molar ratio of 5:0.5:0.5 were fully dissolved in 500 mL of deionized water at room temperature (25 °C) (wherein, the concentration of urea was 0.2 mol / L and the molar amount of urea was 0.1 mol) to obtain a homogeneous solution.

[0068] The homogeneous solution was placed in an oil bath and co-precipitated at 90°C for 8 hours. After natural cooling to room temperature, the reaction product was washed three times with deionized water and ethanol by centrifugation, dried in a 60°C oven for 10 hours, cooled to room temperature, and then heated to 400°C at a rate of 10°C / min and calcined for 6 hours to obtain Ni-doped manganese-based oxide, which is the Ni-doped manganese-based catalyst, denoted as Mn. 0.5 Ni 0.5 O x .

[0069] Following the method described in Comparative Example 1, the molar ratios of urea, manganese acetate tetrahydrate, and nickel acetate tetrahydrate were adjusted to 5:0.7:0.3 and 5:0.3:0.7, respectively. All other process parameters remained the same as in Comparative Example 1. Ni-doped manganese-based catalysts were thus prepared, denoted as Mn. 0.7 Ni 0.3 O x Mn 0.3 Ni 0.7 O x .

[0070] Comparative Example 2

[0071] This comparative example provides a method for preparing a manganese-based catalyst, comprising the following steps:

[0072] Urea and manganese acetate tetrahydrate in a molar ratio of 5:1 were fully dissolved in 500 mL of deionized water at room temperature (25 °C) (wherein, the concentration of urea was 0.2 mol / L and the molar amount of urea was 0.1 mol) to obtain a homogeneous solution.

[0073] The homogeneous solution was placed in an oil bath and co-precipitated at 90°C for 8 hours. After natural cooling to room temperature, the reaction product was washed three times with deionized water and ethanol by centrifugation, dried in a 60°C oven for 10 hours, cooled to room temperature, and then heated to 400°C at a rate of 10°C / min and calcined for 6 hours to obtain manganese-based oxide, which is the manganese-based catalyst, denoted as MnO. x .

[0074] Comparative Example 3

[0075] This comparative example provides a method for preparing a nickel-based catalyst, comprising the following steps:

[0076] Urea and nickel acetate tetrahydrate in a molar ratio of 5:1 were fully dissolved in 500 mL of deionized water at room temperature (25 °C) (wherein, the concentration of urea was 0.2 mol / L and the molar amount of urea was 0.1 mol) to obtain a homogeneous solution.

[0077] The homogeneous solution was placed in an oil bath and co-precipitated at 90°C for 8 hours. After natural cooling to room temperature, the reaction product was washed three times by centrifugation with deionized water and ethanol. It was then dried in a 60°C oven for 10 hours, cooled to room temperature, and then heated to 400°C at a rate of 10°C / min and calcined for 6 hours to obtain nickel-based oxide, which is the nickel-based catalyst, denoted as NiO.

[0078] Performance testing

[0079] The catalysts prepared in Example 1 and Comparative Examples 1-3 were characterized, and the results are as follows: Figure 1 As shown; Figure 1 Ni-0.5@Si represents the Mn prepared in Example 1. 0.5 Ni 0.5 O x @Si, Ni-1.0 represents NiO prepared in Comparative Example 3, and Ni-0.7 represents Mn prepared in Comparative Example 1. 0.3 Ni 0.7 O x Ni-0.5 represents the Mn prepared in Comparative Example 1. 0.5 Ni 0.5 O x Ni-0.3 represents the Mn prepared in Comparative Example 1. 0.7 Ni 0.3 O xMn-1.0 represents the MnO prepared in Comparative Example 2. x .

[0080] from Figure 1 As can be seen, Ni-Si synergistic modification is beneficial to reducing the crystallinity of Mn2O3 in manganese-based oxide catalysts, weakening the bond energy of Mn-O bonds, and inhibiting the aggregation of Mn2O3 crystals.

[0081] Figure 2 Scanning electron microscope (SEM) images of the catalysts prepared in Examples 1 and Comparative Examples 1-3 are shown; where a) is the manganese-based catalyst MnO prepared in Comparative Example 2. x SEM images: b) is the SEM image of the nickel-based catalyst NiO prepared in Comparative Example 3; c) is the SEM image of the Mn prepared in Comparative Example 1. 0.3 Ni 0.7 O x The SEM image (d) shows the Mn prepared in Comparative Example 1. 0.5 Ni 0.5 O x SEM image, e) shows Mn prepared in Comparative Example 1. 0.7 Ni 0.3 O x SEM image, f) is the Mn prepared in Example 1. 0.5 Ni 0.5 O x SEM image of @Si.

[0082] By comparison Figure 2 It can be seen that Ni doping and SiO2 coating have a regulatory effect on the microstructure of manganese oxide materials. Comparing Comparative Example 1 with Comparative Examples 2 and 3, it can be found that the catalyst in Comparative Example 2 exhibits a large, smooth cylindrical shape, while the catalyst in Comparative Example 3 exhibits an irregular spherical shape with smaller particles. Furthermore, by comparing the Mn content in Comparative Example 1... 0.5 Ni 0.5 O x As can be seen from the catalyst in Comparative Example 2, Ni doping reduces the particle size of the catalyst. This is in contrast to the Mn catalyst in Comparative Example 1. 0.5 Ni 0.5 O x Catalyst and Mn in Example 1 0.5 Ni 0.5 O x As can be seen from the @Si catalyst, the particle size of the catalyst is further reduced and the morphology of the catalyst does not change significantly.

[0083] The catalysts prepared in Example 1 and Comparative Examples 1-3 were tested for their synergistic nitrogen oxide / CO removal performance. The test results are as follows: Figure 3 As shown in Figure 4, Figure 3 (a) represents Mn in Comparative Examples 1-30.3 Ni 0.7 O x Mn 0.5 Ni 0.5 O x Mn 0.7 Ni 0.3 O x MnO x A comparison of the catalytic performance of NiO catalysts with different proportions of manganese and nickel in NH3-SCR, (b) shows the catalytic performance of NiO catalysts with different proportions of manganese and nickel in Example 1, Comparative Example 2 and Comparative Example 1. 0.5 Ni 0.5 O x @Si (Mn in the figure) 0.5 Ni 0.5 @Si represents Mn 0.5 Ni 0.5 O x @Si), MnO x Mn 0.5 Ni 0.5 O x Comparison of the catalytic performance of three catalysts for NH3-SCR, (c) shows the Mn content in Example 1, Comparative Example 2, and Comparative Example 1. 0.5 Ni 0.5 O x @Si (Mn in the figure) 0.5 Ni 0.5 @Si represents Mn 0.5 Ni 0.5 O x @Si), MnO x Mn 0.5 Ni 0.5 O x A comparison of NO conversion rates for three catalysts at SO2=0 ppm and CO=1000 ppm, (d) shows the Mn content in Example 1, Comparative Example 2, and Comparative Example 1. 0.5 Ni 0.5 O x @Si (Mn in the figure) 0.5 Ni 0.5 @Si represents Mn 0.5 Ni 0.5 O x @Si), MnO x Mn 0.5 Ni 0.5 O x A comparison of CO conversion rates for the three catalysts at SO2 = 0 ppm and CO = 1000 ppm is shown in (e), where Mn is present in Example 1, Comparative Example 2, and Comparative Example 1. 0.5 Ni 0.5 O x @Si (Mn in the figure) 0.5Ni 0.5 @Si represents Mn 0.5 Ni 0.5 O x @Si), MnO x Mn 0.5 Ni 0.5 O x A comparison of NO conversion rates for three catalysts at SO2 = 100 ppm and CO = 1000 ppm is shown in (f), where Mn is present in Example 1, Comparative Example 2, and Comparative Example 1. 0.5 Ni 0.5 O x @Si (Mn in the figure) 0.5 Ni 0.5 @Si represents Mn 0.5 Ni 0.5 O x @Si), MnO x Mn 0.5 Ni 0.5 O x A comparison of CO conversion rates for three catalysts at SO2=100 ppm and CO=1000 ppm.

[0084] Figure 4 (a) is the catalyst Mn in Example 1. 0.5 Ni 0.5 O x @Si (Mn in the figure) 0.5 Ni 0.5 @Si represents Mn 0.5 Ni 0.5 O x (a) Comparison of NO conversion rates under different CO concentrations; (b) Catalyst Mn from Example 1. 0.5 Ni 0.5 O x @Si (Mn in the figure) 0.5 Ni 0.5 @Si represents Mn 0.5 Ni 0.5 O x @Si) Comparison of CO conversion rates at different CO concentrations.

[0085] Specifically, Figure 3 The reaction conditions for the tests in (a) and (b) were: NO concentration of 500 ppm, NH3 concentration of 500 ppm, O2 volume concentration of 5 vol.%, Ar as balance gas, total flow rate of mixed gas of 300 mL / min, and catalyst loading of 0.3 g.

[0086] Figure 3The reaction conditions for the tests in (c) and (d) were: NO concentration of 500 ppm, NH3 concentration of 500 ppm, CO concentration of 1000 ppm, O2 volume concentration of 5 vol.%, Ar as the equilibrium gas, total flow rate of mixed gas of 300 mL / min, and catalyst loading of 0.3 g.

[0087] Figure 3 The reaction conditions for the tests in (e) and (f) were: NO concentration of 500 ppm, NH3 concentration of 500 ppm, CO concentration of 1000 ppm, SO2 concentration of 100 ppm, O2 volume concentration of 5 vol.%, Ar as the balance gas, total flow rate of mixed gas of 300 mL / min, and catalyst loading of 0.3 g.

[0088] Figure 4 The reaction conditions for the tests in (a) and (b) were as follows: NO concentration was 500 ppm, NH3 concentration was 500 ppm, CO concentration was 0 ppm, 1000 ppm, 3000 ppm, and 5000 ppm, respectively, O2 volume concentration was 5 vol.%, Ar was used as the balance gas, the total flow rate of the mixed gas was 300 mL / min, and the catalyst loading was 0.3 g.

[0089] During the experiment, a programmed temperature-controlled reactor was used to control the catalyst bed temperature (temperature range: 50℃~350℃), and the inlet and outlet concentrations of the gas were detected using a flue gas analyzer.

[0090] Nitrogen oxide conversion rate (%) = (1)

[0091] In equation (1), This indicates the inlet gas concentration of nitrogen oxides in ppm. The concentration of nitrogen oxides (NO in this case) in the gas is expressed in ppm.

[0092] from Figure 3 As can be seen in (a), in Comparative Example 1, Mn 0.5 Ni 0.5 O x The catalyst exhibits good low-temperature activity and a wide temperature window in the denitrification reaction. Within the temperature window of 125°C to 300°C, the NO conversion rate is higher than 90%, and its denitrification performance is superior to that of MnO. x The catalyst indicates that Ni doping significantly improves the catalytic performance of manganese-based catalysts for NH3-SCR.

[0093] from Figure 3 As can be seen in (b), in Example 1, Mn 0.5 Ni 0.5 O xThe Si catalyst achieved a NO conversion rate of over 90% within a temperature window of 90°C to 300°C, realizing the low-temperature catalytic oxidation of NO. This indicates that the SiO2 coating further enhances the catalytic performance of the manganese-based catalyst in low-temperature NH3-SCR.

[0094] from Figure 3 As can be seen in (c), after the introduction of CO, MnO x The catalyst's reactivity decreased significantly in the high-temperature range because the CO oxidation reaction preempted the active sites required for the NH3-SCR reaction, while the Mn in Example 1... 0.5 Ni 0.5 O x The @Si catalyst, through synergistic modification by Ni doping and SiO2 coating, has a larger specific surface area, more oxygen vacancies, and stronger redox performance. Therefore, the catalytic performance of the catalyst in low-temperature NH3-SCR remains basically unchanged.

[0095] from Figure 3 As can be seen in (d), the three catalysts (Mn) were further investigated. 0.5 Ni 0.5 O x @Si,MnO x Mn 0.5 Ni 0.5 O x The catalytic oxidation activity of CO was investigated. The results showed that all catalysts exhibited excellent CO oxidation capabilities. With increasing reaction temperature, the CO conversion rate of all three catalysts increased rapidly, reaching nearly 100% complete conversion above 200°C. Notably, in the low-temperature region (100-175°C), pure MnO... x The catalytic activity is slightly lower than that of Mn. 0.5 Ni 0.5 O x and Mn 0.5 Ni 0.5 O x @Si indicates that Ni doping and SiO2 coating have a slight promoting effect on the low-temperature CO oxidation activity of the catalyst. From Figure 3 From (e, f), it can be seen that... Figure 3 When SO2 at a concentration of 100 ppm is introduced onto gases (c, d), the catalyst activity decreases in the following order: Mn 0.5 Ni 0.5 O x @Si>Mn 0.5 Ni 0.5 O x MnO xAfter coating with SiO2, the catalyst's sulfur resistance is further improved. This may be because the surface SiO2 hinders the direct contact between SO2 and the active component manganese oxide of the catalyst, reducing the reduction of the active component manganese oxide, and thus effectively improving the catalyst's sulfur resistance.

[0096] To investigate the effect of CO on the denitrification performance of the catalyst, in Figure 3 Based on gases (a, b), different concentrations of CO gas were introduced, from... Figure 4 As can be seen from (a), the presence of CO affects Mn 0.5 Ni 0.5 O x The @Si catalyst exhibited a significant inhibitory effect on the NH3-SCR activity, and this inhibitory effect intensified with increasing CO concentration. Specifically, as the CO concentration increased from 0 ppm to 5000 ppm, the catalyst's activity curve shifted towards the higher temperature range, resulting in a significant decrease in both its low-temperature activity (<175°C) and high-temperature activity (>275°C). This indicates that CO oxidation, as a competitive reaction, competes with the NH3-SCR reaction for active sites and / or reactive oxygen species on the catalyst surface. Under high CO concentrations, this competition intensifies, leading to a more significant inhibitory effect on NO conversion.

[0097] Figure 4 (b) shows the Mn content at different CO concentrations. 0.5 Ni 0.5 O x The CO catalytic oxidation performance of the @Si catalyst itself was examined. Interestingly, when the CO concentration increased from 1000 ppm to 3000 ppm, the CO conversion curves almost overlapped, indicating that the catalyst activity was very stable within this concentration range. However, when the CO concentration was further increased to 5000 ppm, the CO conversion rate showed a significant decrease throughout the entire test temperature range. This suggests that excess CO molecules strongly adsorbed and occupied the active sites of the catalyst, which in turn inhibited the adsorption and activation of another reactant—oxygen (O2), thus leading to a decrease in the overall reaction rate.

[0098] It is understood that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0099] The above are merely preferred embodiments of this application, and only specifically describe the technical principles of this application. These descriptions are only for explaining the principles of this application and should not be construed as limiting the scope of protection of this application in any way. Based on this explanation, any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application, as well as other specific embodiments of this application that can be conceived by those skilled in the art without creative effort, should be included within the scope of protection of this application.

Claims

1. A method for preparing a Ni-Si synergistically modified manganese-based catalyst, characterized in that, Includes the following steps: Urea, manganese source and nickel source were added to water to carry out a co-precipitation reaction. After the reaction product was dried, it was calcined once to obtain Ni-doped manganese-based oxide. Ni-doped manganese-based oxides were dispersed in an alcohol solvent, alkali was added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate was added. The reaction was stirred and the reaction product was dried and then calcined a second time to obtain a Ni-Si synergistically modified manganese-based catalyst.

2. The method for preparing the manganese-based catalyst according to claim 1, characterized in that, The molar amount of manganese in the manganese source is a mol, the total molar amount of manganese in the manganese source and nickel in the nickel source is 1.0 mol, and the molar ratio of urea, manganese in the manganese source and nickel in the nickel source is 5:a:(1.0-a), where 0.3≤a≤0.

7.

3. The method for preparing the manganese-based catalyst as described in claim 1, characterized in that, Urea, manganese source, and nickel source are added to water to carry out a coprecipitation reaction. The coprecipitation reaction temperature is 80~90℃ and the time is 7~9h.

4. The method for preparing the manganese-based catalyst as described in claim 1, characterized in that, After drying the reaction product, it is calcined once. The calcination temperature is 400~500℃, the time is 4~8h, and the heating rate is 5~10°C / min.

5. The method for preparing the manganese-based catalyst according to claim 1, characterized in that, Ni-doped manganese-based oxides were dispersed in an alcohol solvent, alkali was added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate was added. The mixture was stirred and reacted at a temperature of 20-25°C for 10-12 hours.

6. The method for preparing the manganese-based catalyst according to claim 1, characterized in that, Ni-doped manganese-based oxides were dispersed in an alcohol solvent, alkali was added to adjust the pH to 9-10, and then an alcohol solution containing tetraethyl orthosilicate was added. The mixture was stirred and reacted. The reaction product was dried and then calcined a second time. The second calcination temperature was 450-600℃, the time was 3-5h, and the heating rate was 4-5°C / min.

7. The method for preparing the manganese-based catalyst according to claim 1, characterized in that, The mass-to-volume ratio of the Ni-doped manganese-based oxide to the alcohol solvent is (0.6~0.8) g:(40~50) mL; The molar ratio of the Ni-doped manganese-based oxide to the tetraethyl orthosilicate in the alcohol solution containing tetraethyl orthosilicate is (0.6~0.8) g: 0.2 mmol; The alcohol solution containing tetraethyl orthosilicate comprises tetraethyl orthosilicate and an alcohol solvent, wherein the molar volume ratio of tetraethyl orthosilicate to alcohol solvent is 0.2 mmol:(40~50) mL; The alcohol solvent includes methanol or ethanol; In the step of adding urea, manganese source and nickel source to water, the molar volume ratio of urea to water is (0.1~0.2) mol: 500 mL; The manganese source is manganese acetate; The nickel source is nickel acetate.

8. The method for preparing the manganese-based catalyst according to claim 1, characterized in that, The alkali includes any one of ammonia water, sodium hydroxide solution, and potassium hydroxide solution.

9. A Ni-Si synergistically modified manganese-based catalyst, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 8.

10. The application of a Ni-Si synergistic modified manganese-based catalyst prepared by any one of the preparation methods described in claims 1 to 8, or the Ni-Si synergistic modified manganese-based catalyst described in claim 9, in the removal of CO and nitrogen oxides from flue gas.

Images