High-temperature-resistant high-activity mesoporous cerium-based denitration catalyst as well as preparation method and application thereof

Abstract

The invention discloses a high-temperature-resistant high-activity mesoporous cerium-based denitration catalyst as well as a preparation method and application thereof, belongs to the technical field of environment-friendly catalytic materials, and is suitable for efficiently removing nitrogen oxides (NOx) in industrial flue gas. The preparation method comprises the following steps: uniformly mixing a surfactant with a cerium source, an aluminum source and a phosphorus source or introducing other metal sources (such as tungsten and zirconium) in a volatile organic solvent to form sol through a solvent evaporation induced self-assembly (EISA) technology, and carrying out volatilization drying and high-temperature calcination to obtain the composite oxide catalyst with a mesoporous structure, the specific surface area being 150-230 m < 2 > / g and the pore diameter being 1-10 nm. Compared with a traditional cerium-based denitration catalyst, by introducing elements such as Al and P and an EISA one-step process, the high-temperature stability and the specific surface area of the catalyst are remarkably improved, the problems that a conventional catalyst is easy to sinter, the preparation process is complex and the like are solved, and the cerium-based denitration catalyst is suitable for the field of industrial flue gas denitration and has a wide application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of environmental protection catalytic materials, and particularly relates to a high-temperature resistant and highly active mesoporous cerium-based denitration catalyst, a preparation method thereof, and an application thereof in the efficient removal of nitrogen oxides (NO x ) in industrial flue gas. Background Art

[0002] Nitrogen oxides (NO x ) generated by fossil fuel combustion are one of the main air pollutants. They can not only damage the human respiratory system but even cause cell carcinogenesis. Excessive nitrogen oxides in the air can not only form nitric acid-type acid rain and deposit on surface water, causing eutrophication of water bodies, but also induce a series of environmental problems such as haze and ozone. Selective catalytic reduction technology (NH3-SCR) is an effective means to eliminate nitrogen oxides. Using conventional vanadium-tungsten-titanium-based denitration catalysts cannot meet the NO x emission standards specified by the industry, and there are also problems such as the toxicity of vanadium, narrow active window, and poor high-temperature stability. Therefore, it is urgent to develop new environmentally friendly non-vanadium-based denitration catalysts.

[0003] CeO2 has been widely studied due to its good oxygen storage and release capacity and excellent redox performance. During the Ce 3+ , Ce 4+ redox cycle, it can generate highly mobile free electrons, forming a sufficient number of oxygen free radicals and active oxygen vacancies. Moreover, China has rich reserves of rare earth resources. Therefore, Ce-based catalysts are one of the rare earth-based denitration catalysts with the greatest development potential in China in the future. However, the main existing problems are as follows: The specific surface area of conventional cerium-based catalysts is low (usually <50 m 2 / g), resulting in insufficient exposure of active sites. In addition, at high temperatures (>600 °C), cerium-based materials are prone to sintering and agglomeration of active components, leading to a decrease in activity (in CN112844374A, the activity of the cerium-based catalyst decreased by 40% after calcination at 700 °C). Therefore, improving the specific surface area and high-temperature resistance of cerium-based catalysts is a scientific problem that researchers are jointly concerned about.

[0004] The EISA method, also known as the solvent evaporation-induced self-assembly method, is an improved sol-gel method and is widely used in the preparation of mesoporous materials. Since the solvents used in this method are usually polar solvents with relatively high volatility such as ethanol, the hydrolysis and polycondensation degree of inorganic precursors is very low, which is conducive to self-assembly at the organic-inorganic interface. Compared with the conventional aqueous phase synthesis method, the EISA method is more simple and fast.

[0005] There have been relevant patents and literature reports on cerium-based denitration catalysts at home and abroad.

[0006] CN117654559A discloses a rare earth-based hollow nanotube denitration catalyst and its preparation method. This method first synthesizes a TiO2-Al2O3 hollow nanotube support through a microfluidic electrospinning technique, then impregnates the active components and promoter precursors and fixes the elements by adding a reducing agent, and finally obtains the finished catalyst through calcination. This catalyst uses the TiO2-Al2O3 hollow nanotube as the support, rare earth oxides as the active components, and MoO3 as the promoter, with a large specific surface area, high conversion rate, and excellent denitration effect in the high, medium, and low temperature ranges. However, this preparation process is complex and costly, and it is not suitable for large-scale production.

[0007] CN116726907A discloses a wide temperature window mesoporous cerium-based composite oxide denitration catalyst and its preparation method. This method first constructs a cerium-based inorganic-organic hybrid material through an induced self-assembly method, and then obtains a novel mesoporous cerium-based composite oxide catalyst through high-temperature heat treatment. The crystal form of this composite oxide catalyst is the perovskite-type titanium dioxide structure, and the cerium-based active components and tungsten and aluminum promoter components are amorphous structures. The catalyst preparation process is simple and the cost is relatively low, but the application value of this catalyst in high-temperature resistance has not been reflected.

[0008] CN112844374A discloses a Mn-Ce-Ti oxide aerogel denitration catalyst and its preparation method. A Mn-Ce-Ti oxide aerogel denitration catalyst with a large specific surface area, pore diameter, and pore volume is prepared by using the sol-gel method and supercritical drying technology. This catalyst has finer crystal grains, effectively promotes the electron transfer between manganese, cerium, and titanium metal oxides, thereby enhancing the catalytic reduction ability and surface acidity of the catalyst, and making it have good low-temperature activity and sulfur and water resistance. However, the preparation process of this method is relatively complex, and the introduction of the Mn component will cause the high-temperature stability of the catalyst to decline.

[0009] CN108837820A discloses a Ce-NbO x / Mesoporous titanium dioxide high-efficiency denitration catalyst and its preparation method. The active component Ce-NbO is loaded on the mesoporous TiO2 support by the sol-gel method x to form a composite denitration catalyst. The catalytic activity of this catalyst is optimized by adjusting the components, but its high-temperature resistance performance has not been reflected, and it is difficult to meet the actual requirements for the removal of fixed-source NO x in coal-fired power plants.

[0010] CN106984301A discloses an ordered mesoporous structure manganese-cerium-titanium catalyst, a preparation method thereof and uses thereof. By using a solvent evaporation-induced self-assembly synthesis method and using a triblock copolymer as a template agent, Mn / Ce active substances are assembled and introduced into the pore walls of a TiO2 support to prepare an ordered mesoporous structure manganese-cerium-titanium catalyst. This catalyst has high dispersion of active components, good pore permeability, stable order and a large specific surface area. However, the high temperature resistance of this catalyst is not mentioned.

[0011] Appl.Catal.B:Environ.2017,203:199(Applied Catalysis B:Environment,Efficient NH 3- SCR removal of NO x with highly ordered mesoporous WO3(χ)-CeO2atlow temperatures) In the literature, ordered mesoporous SiO2 (KIT-6) is used as a hard template, and a mesoporous cerium-based composite oxide is prepared by a nanocasting method, and the active temperature window is 200-350 °C. However, this method requires multiple impregnations and template removal, the preparation process is complex, the process is cumbersome, and the high temperature stability window needs to be further improved. J.Rare.Earth.2022,40:1232(Journal of Rare Earths,Revealing active species of CePO4catalyst forselective catalytic reduction of NO x with NH3) In the literature, it is revealed that the CePO4 catalyst has good high temperature stability (<600 °C) and SCR catalytic activity. However, after calcination at a higher temperature (800 °C) for 2 h, the activity is completely lost and cannot meet the requirements of higher industrial temperatures.

[0012] In summary, the preparation methods of cerium-based denitration catalysts at home and abroad mainly improve the catalytic activity by modulating the components and structural design, but there are problems such as complex preparation processes and high costs. At the same time, the catalytic activity after high temperature treatment is not ideal, and the problem of agglomeration of active sites caused by sintering and the decline of catalytic activity has not been solved. Summary of the Invention

[0013] The purpose of the present invention is to provide a high temperature resistant and highly active mesoporous cerium-based denitration catalyst, a preparation method thereof and an application in the efficient removal of nitrogen oxides (NO x ) in industrial flue gas. By introducing aluminum and phosphorus elements and combining the mesoporous confinement effect, the present invention solves the problems of high temperature deactivation, low specific surface area and complex preparation process of traditional cerium-based catalysts.

[0014] A preparation method of a high-temperature resistant and highly active mesoporous cerium-based denitration catalyst according to the present invention comprises the following steps:

[0015] (1) Dissolve a surfactant in a volatile organic solvent and stir until uniformly dispersed to obtain solution A; the surfactant concentration is 3-5 wt%, the surfactant is one of non-ionic, cationic, anionic, and amphoteric surfactants, and the organic solvent is one of absolute ethanol, acetonitrile, acetone, methanol, propanol, or tetrahydrofuran;

[0016] Among them, the non-ionic surfactant is one of F108, F127, P123, F98, B50-6600, Brij35, Brij56, Brij58, Brij76, Brij78; the cationic surfactant is one of cetyltrimethylammonium bromide and octadecyltrimethylammonium chloride; the anionic surfactant is sodium hexadecylsulfonate; the amphoteric surfactant is polyoxyethylene alkylammonium;

[0017] (2) Add a cerium source, an aluminum source, a phosphorus source, and a tungsten source or a zirconium source to solution A obtained in step (1), and continuously stir to form a homogeneous sol; the cerium source is cerium nitrate, cerium chloride, cerium acetate, or ammonium cerium nitrate; the aluminum source is aluminum chloride, aluminum nitrate, aluminum isopropoxide, or aluminum sec-butoxide; the phosphorus source is phosphoric acid, pyrophosphoric acid, or phosphorus trichloride; the tungsten source is ammonium tungstate; the zirconium source is zirconium nitrate, zirconium oxychloride, or zirconium isopropoxide; the molar ratio of the aluminum source to the cerium source is 0.5-3:1, the molar ratio of the phosphorus source to the cerium source is 0.5-3:1, and the tungsten source or zirconium source is 0-25% of the mass of the cerium source;

[0018] (3) Transfer the homogeneous sol obtained in step (2) to a petri dish, and volatilize and dry it at 20-50 °C for 2-5 days to form a film, obtaining a solid precursor; the film thickness is 0.1-2 mm, and the humidity of the volatilization and drying environment is 20-60% RH;

[0019] (4) Calcinate the solid precursor obtained in step (3) step by step in an air atmosphere to remove the surfactant, obtaining the high-temperature resistant and highly active mesoporous cerium-based NH3-SCR catalyst; the step-by-step calcination is to first heat up to 200-350 °C at a heating rate of 1-2 °C / min and calcine for 2-4 h, and then heat up to 400-500 °C at a heating rate of 3-5 °C / min and calcine for 1-3 h.

[0020] Structural characterization of the high-temperature resistant and highly active mesoporous cerium-based denitration catalyst:

[0021] The present invention prepares a high-temperature resistant and highly active mesoporous cerium-based NH3-SCR catalyst by the EISA strategy, with a composition of Ce-Al-P-O, Ce-W-Al-P-O, or Ce-Zr-Al-P-O, having a mesoporous structure, asFigure 1 and Figure 2 As shown, the specific surface area is 150 - 230 m 2 / g, and the pore diameter is 1 - 10 nm. The catalyst is nanoparticles with a particle size of 1 - 10 nm, and is uniformly distributed in the mesoporous structure framework. No agglomeration and growth are observed after high-temperature calcination. After calcination at 800 °C for 2 hours, the NO x conversion rate ≥ 80% in the temperature range of 300 - 600 °C, and it still has a mesoporous structure.

[0022] Performance evaluation of high-temperature resistant and highly active mesoporous cerium-based denitration catalyst:

[0023] 1) Evaluation method: The performance evaluation of the selective catalytic reduction of NO by the catalyst is carried out on a fixed-bed reactor. The reaction gas composition is 1000 ppm NO, 1000 ppm NH3 and 5% volume fraction of O2, with Ar as the balance gas. The GHSV (gas hourly space velocity) range is adjusted to 10000 - 480000 h –1 by controlling the gas flow rate and the sample loading amount, and the NH3-SCR reaction temperature range is 100 - 600 °C. The reactants are analyzed online by mass spectrometry (QIC 20). The mass spectrometry analyzes the gas concentration by detecting the characteristics of the gas: 30 (NO x : NO + NO2), N2 (28), 46 (NO2), 32 (O2), 17 or 15 (NH3) (the numbers represent the mass-to-charge ratio m / z, and in addition, m / z = 17 (NH3, main fragment) or m / z = 15 (NH3, minor fragment)). The denitrification activity is evaluated by the conversion rate of NO. The NO x conversion rate = (1 - [NO x outlet / [NO x inlet) * 100%, where NO x = NO + NO2. The NH3 conversion rate (XNH3) = (1 - [NH3]outlet / [NH3]inlet) * 100%, and the N2 selectivity = [N2]outlet / ([N2]outlet + [N2O]outlet) * 100%. [NO x outlet and [NO x inlet refer to the NO x concentrations at the outlet and inlet of the reactor respectively.

[0024] 2) Evaluation results: In the temperature range of 300 - 600 °C, the NO conversion rate of the sample (CAT1-5) is greater than 80%; after the sample is calcined at 800 °C for 2 hours, the NO conversion rate is still not less than 80%, while the sample without Al (Ce-P-O) has no activity after being calcined at 800 °C for 2 hours. Thus, it can be seen that the catalyst exhibits good catalytic performance and high-temperature resistance.

[0025] In summary, the present invention has the following advantages over the prior art:

[0026] 1. The main active component of the calcined catalyst is CeO2. Through the Ce 3+ →Ce 4+ redox cycle process, highly mobile free electrons are generated, forming a sufficient number of oxygen free radicals and active oxygen vacancies; Al2O3 as an additive can promote charge transfer, effectively improve the redox ability of the catalyst, thereby promoting the oxidation of NO to NO2 under high-temperature conditions and improving the "fast SCR" reaction efficiency. Using phosphoric acid as an acidic additive can further reduce the CeO2 crystal grain size and enhance the surface acidity of the catalyst, significantly improving the adsorption capacity of NH3 species on the catalyst surface. The synergistic effect of each component promotes the adsorption and activation of reactants, ultimately achieving the purpose of improving the high-temperature catalytic activity;

[0027] 2. Through the mesoporous framework confinement method, not only can the highly dispersed cerium-based nanoparticles be achieved to provide more reaction active sites, but the mesoporous channels can also effectively increase the collision frequency and diffusion of reactant molecules, making the catalytic reaction more complete;

[0028] 3. Al doping forms Ce-O-Al bonds, inhibiting the migration of CeO2 crystal grains at high temperatures; at the same time, the mesoporous phosphate structure has good structural stability and framework confinement effect, which can improve the thermal stability of the catalyst and reduce the damage of sintering to active sites;

[0029] 4. The EISA preparation method has simple process and cheap raw materials. The pore structure regulation and functional component composite are completed synchronously in one step, reducing 3-4 steps compared with the conventional nano-casting method. This enables elements such as cerium, aluminum, and phosphorus to be evenly and stably distributed in the solid solution composite oxide structure, significantly improving the high-temperature stability and specific surface area of the catalyst, solving problems such as easy sintering and complex preparation process of conventional catalysts, and being applicable to the field of industrial flue gas denitrification, with broad application prospects and practical value. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 FIG. is the TEM image of the catalyst prepared in Example 1 of the present invention, showing that the catalyst CAT-1 has a clear mesoporous structure, uniform pore wall thickness, and the nanoparticles are dispersed without aggregation.

[0031] Figure 2Small-angle XRD pattern of the catalyst prepared in Example 1 of the present invention after calcination; among them, Figure (1) is the small-angle XRD pattern after calcination at 500 °C, showing obvious diffraction peaks, indicating that the material has a mesoporous structure after calcination at 500 °C; Figure (2) is the small-angle XRD pattern after calcination at 800 °C, and there is still a diffraction peak at a small angle after calcination at 800 °C, indicating that the mesoporous structure is still retained after high-temperature treatment. It is confirmed that by using the EISA method and introducing Al and P elements, it is beneficial to improve the thermal stability of the prepared catalyst and maintain its high specific surface area, thus showing high-efficiency NH3-SCR denitration performance. Detailed implementation manners

[0032] The following further illustrates a high-temperature resistant and highly active mesoporous cerium-based denitration catalyst, its preparation method, and the NH3-SCR denitration and high-temperature resistant performance of the present invention through specific examples:

[0033] Example 1

[0034] Weigh 1.0 g of F108 and dissolve it in 30 g of absolute ethanol, stir for 0.5 hours until evenly dispersed to obtain Solution A. Then add 4 millimoles (mmol) of aluminum chloride (AlCl3), 4 millimoles (mmol) of cerium chloride (CeCl3), and 1.0 g of phosphoric acid (10 millimoles) to Solution A, and continue to stir for 5 hours to form a homogeneous sol. Transfer the reaction mother liquor to a petri dish, volatilize and dry it at 35 °C for 3 days to form a film, obtaining a solid precursor; the film thickness is 0.5 mm, and the humidity of the volatilization and drying environment is 40% RH; place the obtained solid precursor in a muffle furnace, first heat it to 300 °C at a heating rate of 1 °C / min and calcine for 3 h, and then heat it to 500 °C at a heating rate of 2 °C / min for calcination to obtain the catalyst denoted as CAT-1. The components and physicochemical properties of CAT-1 are shown in Table 1, the denitration efficiency is shown in Table 2, and the high-temperature resistant performance is shown in Table 3.

[0035] Example 2

[0036] Weigh 1.5 g of P123 and dissolve it in 30 g of absolute ethanol. Stir for 0.5 h until it is uniformly dispersed to obtain Solution A. Then add 4 mmol of aluminum chloride (AlCl3), 4 mmol of cerium chloride (CeCl3), and 1.0 g of phosphoric acid (10 mmol) to Solution A, and continue to stir for 5 h to form a homogeneous sol. Transfer the reaction mother liquor to a petri dish, and volatilize and dry it at 35 °C for 3 days to form a film, obtaining a solid precursor; the film thickness is 0.5 mm, and the humidity of the volatilization and drying environment is 40% RH; place the obtained solid precursor in a muffle furnace, first heat it to 300 °C at a heating rate of 1 °C / min and calcine for 3 h, then heat it to 500 °C at a heating rate of 2 °C / min and calcine to obtain a catalyst denoted as CAT-2. The components and physicochemical properties of CAT-2 are shown in Table 1, the denitrification efficiency is shown in Table 2, and the high-temperature resistance performance is shown in Table 3.

[0037] Example 3

[0038] Weigh 1.0 g of F127 and dissolve it in 30 g of absolute ethanol. Stir for 0.5 h until it is uniformly dispersed to obtain Solution A. Then add 4 mmol of aluminum chloride (AlCl3), 4 mmol of cerium chloride (CeCl3), and 1.0 g of phosphoric acid (10 mmol) to Solution A, and continue to stir for 5 h to form a homogeneous sol. Transfer the reaction mother liquor to a petri dish, and volatilize and dry it at 35 °C for 3 days to form a film, obtaining a solid precursor; the film thickness is 0.5 mm, and the humidity of the volatilization and drying environment is 40% RH; place the obtained solid precursor in a muffle furnace, first heat it to 300 °C at a heating rate of 1 °C / min and calcine for 3 h, then heat it to 500 °C at a heating rate of 2 °C / min and calcine to obtain a catalyst denoted as CAT-3. The components and physicochemical properties of CAT-3 are shown in Table 1, the denitrification efficiency is shown in Table 2, and the high-temperature resistance performance is shown in Table 3.

[0039] Example 4

[0040] Weigh 1.5 g of F108 and dissolve it in 30 g of absolute ethanol. Stir for 0.5 h until evenly dispersed to obtain Solution A. Then add 4 mmol of aluminum chloride (AlCl3), 4 mmol of cerium chloride (CeCl3), 1.0 g of phosphoric acid (10 mmol), and 0.2 g of ammonium tungstate to Solution A, and continue stirring for 5 h to form a homogeneous sol. Transfer the reaction mother liquor to a petri dish and volatilize and dry it at 35 °C for 5 days to form a film, obtaining a solid precursor; the film thickness is 0.8 mm, and the humidity of the volatilization and drying environment is 40% RH; place the obtained solid precursor in a muffle furnace, first heat it to 300 °C at a heating rate of 1 °C / min and calcine for 3 h, then heat it to 500 °C at a heating rate of 2 °C / min and roast to obtain a catalyst denoted as CAT-4. The components and physicochemical properties of CAT-4 are shown in Table 1, the denitrification efficiency is shown in Table 2, and the high-temperature resistance performance is shown in Table 3.

[0041] Example 5

[0042] Weigh 1.5 g of F108 and dissolve it in 30 g of absolute ethanol. Stir for 0.5 h until evenly dispersed to obtain Solution A. Then add 4 mmol of aluminum chloride (AlCl3), 4 mmol of cerium chloride (CeCl3), 1.0 g of phosphoric acid (10 mmol), and 0.2 g of zirconium nitrate to Solution A, and continue stirring for 5 h to form a homogeneous sol. Transfer the reaction mother liquor to a petri dish and volatilize and dry it at 35 °C for 5 days to form a film, obtaining a solid precursor; the film thickness is 0.8 mm, and the humidity of the volatilization and drying environment is 40% RH; place the obtained solid precursor in a muffle furnace, first heat it to 300 °C at a heating rate of 1 °C / min and calcine for 3 h, then heat it to 500 °C at a heating rate of 2 °C / min and roast to obtain a catalyst denoted as CAT-5. The components and physicochemical properties of CAT-5 are shown in Table 1, the denitrification efficiency is shown in Table 2, and the high-temperature resistance performance is shown in Table 3.

[0043] Comparative Example 1

[0044] Weigh 1.0 g of F108 and dissolve it in 30 g of absolute ethanol. Stir for 0.5 h until evenly dispersed to obtain Solution A. Then add 4 mmol of cerium chloride (CeCl3) and 1.0 g of phosphoric acid (10 mmol) to Solution A, and continue stirring for 5 h to form a homogeneous sol. Transfer the reaction mother liquor to a petri dish and volatilize and dry it at 35 °C for 3 days to form a film, obtaining a solid precursor; the film thickness is 0.3 mm, and the humidity of the volatilization and drying environment is 40% RH; place the obtained solid precursor in a muffle furnace, first heat it to 300 °C at a heating rate of 1 °C / min and calcine for 3 h, then heat it to 500 °C at a heating rate of 2 °C / min and roast to obtain a catalyst denoted as DB-1. The components and physicochemical properties of DB-1 are shown in Table 1, the denitrification efficiency is shown in Table 2, and the high-temperature resistance performance is shown in Table 3.

[0045] Comparative Example 2

[0046] Weigh 1.0 g of F108 and dissolve it in 30 g of absolute ethanol. Stir for 0.5 h until evenly dispersed to obtain Solution A. Then add 4 millimoles (mmol) of aluminum chloride (AlCl3), 4 millimoles (mmol) of cerium chloride (CeCl3), and 0.5 g of hydrochloric acid (0.2 M) to Solution A, and continue stirring for 5 h to form a homogeneous sol. Transfer the reaction mother liquor to a petri dish and volatilize and dry it at 35 °C for 3 days to form a film, obtaining a solid precursor; the film thickness is 0.5 mm, and the humidity of the volatilization and drying environment is 40% RH; place the obtained solid precursor in a muffle furnace, first heat it to 300 °C at a heating rate of 1 °C / min and calcine for 3 h, then heat it to 500 °C at a heating rate of 2 °C / min and calcine to obtain a catalyst denoted as DB-2. The components and physicochemical properties of DB-2 are shown in Table 1, the denitration efficiency is shown in Table 2, and the high-temperature resistance performance is shown in Table 3.

[0047] Table 1: Structural properties of the catalysts of Examples 1-5 and Comparative Examples 1-2

[0048] Item CAT-1 CAT-2 CAT-3 CAT-4 CAT-5 DB-1 DB-2 <![CDATA[Specific surface area (m 2 / g)]]> 185 220 205 190 175 98 82 Average pore diameter (nm) 7.2 6.7 6.3 6.2 6.8 7.5 6.9 Particle size (nm) 8.5 4.8 6.3 9.2 9.8 9.5 8.2

[0049] As can be seen from Table 1, the specific surface areas of the catalysts prepared in Examples 1-5 are much larger than those of Comparative Examples 1 and 2, and there are obvious differences in the pore sizes of CAT-1, CAT-2, and CAT-3. This technology can endow the catalyst with a large specific surface area while adjusting its pore size. Mesoporous framework confinement can effectively control the particle size of rare earth nanoparticles to be 1-10 nm.

[0050] Table 2: Denitration efficiency (%) of the catalysts of Examples 1-5 and Comparative Examples 1-2

[0051] Activation temperature (°C) CAT-1 CAT-2 CAT-3 CAT-4 CAT-5 DB-1 DB-2 260℃ 62 68 55 50 66 43 35 300℃ 80 81 82 82 80 49 10 370℃ 82 88 89 85 83 50 51 410℃ 90 92 95 90 92 65 55 450℃ 92 96 96 92 95 80 76 490℃ 93 98 98 98 96 82 85 530℃ 93 98 98 98 98 85 86 560℃ 92 95 98 98 98 85 86 600℃ 91 95 98 98 98 75 66

[0052] As can be seen from Table 2, the denitration efficiencies of the catalysts prepared in Examples 1-5 are better than those of Comparative Examples 1 and 2. In the temperature range of 300-600 °C, the denitration rate is greater than 80%. Under the condition of 600 °C, the denitration rates of CAT-1, CAT-2, CAT-3, CAT-4, and CAT-5 remain above 90%, showing good SCR performance. At the same time, it also shows that the introduction of phosphorus has a great influence on the denitration efficiency.

[0053] Table 3: Denitration efficiency (%) of the catalysts of Examples 1-5 and Comparative Examples 1-2 after withstanding high temperature of 800 °C

[0054] Time (h) CAT-1 CAT-2 CAT-3 CAT-4 CAT-5 DB-1 DB-2 2h 81 85 83 81 83 0 0

[0055] As can be seen from Table 3, the high-temperature resistance of the catalysts prepared in Examples 1-5 is better than that of Comparative Examples 1 and 2. After calcination at 800 °C for 2 h, the NO conversion rate is still not lower than 80%, and good catalytic activity is still maintained. This shows that the introduction of Al and P plays a key role in improving the high-temperature resistance of the cerium-based catalyst.

Claims

1. A method for preparing a high temperature resistant and highly active mesoporous cerium-based denitration catalyst, the steps of which are as follows: (1) dissolving a surfactant in a volatile organic solvent and stirring until uniformly dispersed to obtain a solution A; in the solution A, the concentration of the surfactant is 3 to 5 wt %; (2) adding a cerium source, an aluminum source, a phosphorus source, and a tungsten source or a zirconium source to the solution A obtained in step (1), and continuously stirring to form a uniform sol; wherein the molar ratio of the aluminum source to the cerium source is 0.5 to 3:1, the molar ratio of the phosphorus source to the cerium source is 0.5 to 3:1, and the tungsten source or the zirconium source is 0 to 25% of the mass of the cerium source; (3) transferring the uniform sol obtained in step (2) to a culture dish, volatilizing and drying at 20 to 50° C. for 2 to 5 days to form a film to obtain a solid precursor; (4) The solid precursor obtained in step (3) is calcined step by step in an air atmosphere to remove the surfactant, thereby obtaining the high temperature resistant and highly active mesoporous cerium-based NH3-SCR catalyst.

2. The method for preparing a high temperature resistant and highly active mesoporous cerium-based denitration catalyst according to claim 1, characterized in that: The surfactant in step (1) is one of nonionic, cationic, anionic and amphoteric surfactants, and the organic solvent is one of anhydrous ethanol, acetonitrile, acetone, methanol, propanol or tetrahydrofuran.

3. The method for preparing a high temperature resistant and highly active mesoporous cerium-based denitration catalyst according to claim 2, characterized in that: The nonionic surfactant is one of F108, F127, P123, F98, B50-6600, Brij35, Brij56, Brij58, Brij76, and Brij78; the cationic surfactant is one of hexadecyltrimethylammonium bromide and octadecyltrimethylammonium chloride; the anionic surfactant is sodium hexadecyl sulfonate; and the amphoteric surfactant is polyoxyethylene alkylammonium.

4. The method for preparing a high temperature resistant and highly active mesoporous cerium-based denitration catalyst according to claim 1, characterized in that: The cerium source in step (2) is cerium nitrate, cerium chloride, cerium acetate or ammonium cerium nitrate; the aluminum source is aluminum chloride, aluminum nitrate, aluminum isopropoxide or aluminum sec-butoxide; the phosphorus source is phosphoric acid, pyrophosphoric acid or phosphorus trichloride; the tungsten source is ammonium tungstate; and the zirconium source is zirconium nitrate, zirconium oxychloride or zirconium isopropoxide.

5. The method for preparing a high temperature resistant and highly active mesoporous cerium-based denitration catalyst according to claim 1, characterized in that: The film thickness in step (3) is 0.1-2 mm, and the ambient humidity for volatilization and drying is 20-60% RH.

6. The method for preparing a high temperature resistant and highly active mesoporous cerium-based denitration catalyst according to claim 1, characterized in that: The stepwise calcination in step (4) is firstly heating the temperature to 200-350°C at a heating rate of 1-2°C / min and calcining for 2-4h, and then heating the temperature to 400-500°C at a heating rate of 3-5°C / min and calcining for 1-3h.

7. A high temperature resistant and highly active mesoporous cerium-based denitration catalyst, characterized in that: The method is prepared by any one of claims 1 to 6.

8. A high temperature resistant and highly active mesoporous cerium-based denitration catalyst according to claim 7, characterized in that: The chemical composition of the catalyst is Ce-Al-PO, Ce-W-Al-PO or Ce-Zr-Al-PO, with a specific surface area of ​​150 to 230 m 2 / g, pore size 1~10nm.

9. Use of a high temperature resistant and highly active mesoporous cerium-based denitration catalyst as claimed in claim 7 or 8 in the efficient removal of nitrogen oxides in industrial flue gas.

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