Denitration catalyst and preparation method thereof

Abstract

The invention belongs to the technical field of environment-friendly catalysts, and particularly relates to a denitration catalyst and a preparation method thereof. The denitration catalyst comprises an MOF carrier, a manganese-containing oxide loaded on the MOF carrier, a first doping element and a second doping element, the molar ratio of the manganese element to the first doping element on the MOF carrier is 1: (0.1-0.3), and the molar ratio of the manganese element to the second doping element on the MOF carrier is 1: (0.05-0.15); the first doping element comprises Ce and / or La, and the second doping element comprises Fe and / or Co. The denitration catalyst disclosed by the invention has the beneficial effects that the denitration catalyst disclosed by the invention takes the MOF (ZIF-8 at-UiO-66) with the core-shell structure as a carrier and the manganese oxide as an active component, and Ce (La) and Fe (Co) are adopted for multi-element doping modification; the obtained catalyst has high NOx conversion rate (98% or above) and high N2 selectivity (99% or above) in the low-temperature interval of 150-250 DEG C, can still keep the denitration efficiency of 90% or above under the harsh condition of containing 100 ppm of SO2 and 10% of H2O, and is suitable for efficient denitration treatment of low-temperature flue gas of a thermal power generating unit.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of environmental protection catalysts, and particularly relates to a denitration catalyst and a preparation method thereof. BACKGROUND

[0002] With the increasingly stringent environmental protection requirements, flue gas treatment of thermal power units is developing towards low temperature. The traditional vanadium-titanium catalyst has excellent denitration performance in the range of 300-400 DEG C, but its activity significantly decreases in low-temperature flue gas (150-250 DEG C) under low load of the unit, and it has the problem of vanadium biological toxicity. Although the manganese-based catalyst shows good potential in the low-temperature section, it faces challenges such as narrow activity temperature window, poor resistance to sulfur and water, and low N2 selectivity in practical application. The existing research improves through single element doping or simple carrier loading, but the effect is limited, and it is difficult to maintain long-term stability under complex flue gas conditions. When MOF is used as a carrier for denitration catalyst, a single MOF (such as ZIF-8, UiO-66) or simple physical mixing is usually used, and the pore environment and controllable metal nodes of the MOF material cannot be fully utilized. Although the existing technology designs a core-shell MOF, the Zn / Co component does not match the target reaction for CO2 conversion reaction, and the targeted design for sulfur and water resistance is not involved. Therefore, it is a technical problem to be solved in the field to develop a manganese-based denitration catalyst with excellent low-temperature activity, high N2 selectivity and strong anti-poisoning ability. SUMMARY

[0003] The application provides a denitration catalyst and a preparation method thereof, and aims to solve the problem of rapid performance degradation of the existing denitration catalyst in a complex flue gas environment.

[0004] The application provides a denitration catalyst in a first aspect, which comprises a MOF carrier, a manganese-containing oxide supported on the MOF carrier, a first doping element and a second doping element. The molar ratio of manganese element to the first doping element on the MOF carrier is 1:(0.1-0.3), and the molar ratio of manganese element to the second doping element on the MOF carrier is 1:(0.05-0.15). The first doping element comprises Ce and / or La, and the second doping element comprises Fe and / or Co.

[0005] The denitration catalyst described in the application uses a core-shell structure MOF (ZIF-8@UiO-66) as a carrier, manganese oxide as an active component, and Ce(La) and Fe(Co) for multi-element doping modification; and the obtained catalyst has high NO xThe conversion rate is more than 98%, the N2 selectivity is more than 99%, the denitration efficiency is more than 90% under harsh conditions containing 100 ppm SO2 and 10% H2O, and the denitration catalyst is suitable for high-efficiency denitration treatment of low-temperature flue gas of a thermal power unit.

[0006] According to some embodiments of the denitration catalyst, the MOF carrier is a core-shell structure MOF carrier.

[0007] According to some embodiments of the denitration catalyst, the specific surface area of the MOF carrier is 800-1500 m 2 / g, and the pore volume of the MOF carrier is 0.5-1.2 cm 3 / g.

[0008] According to some embodiments of the denitration catalyst, the core layer of the MOF carrier is ZIF-8, and the shell layer of the MOF carrier is UiO-66.

[0009] According to some embodiments of the denitration catalyst, the loading amount of the manganese-containing oxide in the denitration catalyst is 5-15 wt%.

[0010] The second aspect of the present application provides a preparation method of the denitration catalyst according to the first aspect of the present application, comprising the following steps: (1) mixing a MOF carrier solution with a manganese-containing salt solution and a first doping element-containing salt solution, and sequentially performing first aging and filtration treatment after the mixing is completed; (2) mixing the filtered precipitate obtained in step (1) with a second doping element-containing salt solution, and sequentially performing second aging and filtration treatment after the mixing is completed; (3) performing heat treatment on the filtered precipitate obtained in step (2) to obtain the denitration catalyst.

[0011] According to some embodiments of the preparation method of the denitration catalyst, in step (1), the concentration of the MOF carrier solution is 0.01-0.15 g / ml.

[0012] According to some embodiments of the preparation method of the denitration catalyst, the concentration of the manganese-containing salt in the mixed solution of the manganese-containing salt and the first doping element-containing salt is 0.1-0.5 mol / L.

[0013] According to some embodiments of the preparation method of the denitration catalyst, the concentration of the first doping element-containing salt in the mixed solution of the manganese-containing salt and the first doping element-containing salt is 0.02-0.15 mol / L.

[0014] According to some embodiments of the preparation method of the denitration catalyst, the volume ratio of the MOF carrier solution to the solution containing the manganese-containing salt and the first doping element-containing salt is 1: (1-5).

[0015] According to some embodiments of the preparation method of the denitration catalyst, the temperature of the first mixing is 30-50℃, and the time of the first mixing is 4-8h.

[0016] According to some embodiments of the preparation method of the denitration catalyst, the temperature of the first aging is 35-45℃, and the time of the first aging is 5-7h.

[0017] According to some embodiments of the preparation method of the denitration catalyst, the concentration of the second doping element-containing salt in the solution containing the second doping element-containing salt is 0.05-0.2mol / L.

[0018] According to some embodiments of the preparation method of the denitration catalyst, in step (2), the mass ratio of the precipitate to the solution containing the second doping element-containing salt is 1: (10-20).

[0019] According to some embodiments of the preparation method of the denitration catalyst, the temperature of the second mixing is 20-30℃, and the time of the second mixing is 2-4h.

[0020] According to some embodiments of the preparation method of the denitration catalyst, the temperature of the second aging is 20-30℃, and the time of the second aging is 10-13h.

[0021] According to some embodiments of the preparation method of the denitration catalyst, in step (3), the obtained filtered precipitate is dried and then subjected to heat treatment.

[0022] According to some embodiments of the preparation method of the denitration catalyst, the temperature of the drying is 70-90℃, and the time of the drying is 10-15h.

[0023] According to some embodiments of the preparation method of the denitration catalyst, the heat treatment is heating to 280-320℃ at a heating rate of 1-3℃ / min under a nitrogen atmosphere, holding for 0.8-1.2h; and then heating to 400-500℃ at a heating rate of 0.8-1.2℃ / min, holding for 1.5-2.5h.

[0024] The third aspect of the present application provides a use of the denitration catalyst of the first aspect of the present application or the denitration catalyst obtained by the preparation method of the second aspect of the present application in the catalysis of nitrogen oxides in air pollution control.

[0025] According to some embodiments of the application, the activity temperature of the denitration catalyst is 150-250°C.

[0026] The beneficial effects of the present application include that the denitration catalyst described in the present application uses a core-shell structure MOF (ZIF-8@UiO-66) as a carrier, manganese oxide as an active component, and Ce(La) and Fe(Co) for multi-element doping modification; the obtained catalyst has high NO x conversion rate (98% or more) and high N2 selectivity (99% or more), and can still maintain a denitration efficiency of 90% or more under harsh conditions containing 100 ppm SO2 and 10% H2O, and is suitable for efficient denitration treatment of low-temperature flue gas of a thermal power unit. DETAILED DESCRIPTION

[0027] The embodiments of the present application are described in detail below, and the examples of the embodiments are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0028] In the present application, the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like mean that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the person skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0029] The embodiments of the present application provide a denitration catalyst, comprising a MOF carrier, a manganese oxide-containing material loaded on the MOF carrier, a first doping element and a second doping element. The molar ratio of the manganese element and the first doping element on the MOF carrier is 1:(0.1-0.3), for example, 0.1:1, 0.2:1, 0.25:1, 0.26:1, 0.3:1, etc., and the molar ratio of the manganese element and the second doping element on the MOF carrier is 1:(0.05-0.15); for example, 0.05:1, 0.06:1, 0.08:1, 0.12:1, 0.15:1, etc.

[0030] The first doping element includes Ce and / or La, and the second doping element includes Fe and / or Co.

[0031] The denitration catalyst described in the application adopts a ternary synergistic active site design of Mn, Ce (La), and Fe (Co). The Ce / La elements can regulate oxygen vacancies and redox performance, and the Fe / Co elements can enhance surface acidity. The two form a synergistic effect with Mn, achieving comprehensive improvement of catalyst performance.

[0032] The denitration catalyst described in the application selects Ce or La as the first doping element, and controls the molar ratio of Ce or La to Mn to be (0.1-0.3):1. This ratio is the key to achieving excellent low-temperature activity and high N2 selectivity. 3+ / Ce 4+ and Mn 3+ / Mn 4+ are two important redox pairs. Under this ratio, the Ce species can effectively interact with the Mn species, promoting the migration and circulation of electrons within the catalyst. This not only increases the proportion of Mn 3+ in the valence state distribution, which is more conducive to the SCR reaction, but also induces the generation of a large number of chemisorbed oxygen (active oxygen) and oxygen vacancies on the catalyst surface.

[0033] If the ratio of the two is less than 0.1, the adjustment effect is limited, and the oxygen vacancy concentration is insufficient, so the low-temperature activity is not significantly improved. If the ratio of the two is higher than 0.3, excessive Ce species may cover part of the Mn active sites or form inert CeO2 agglomerates on the surface, which actually reduces the overall activity of the catalyst per unit mass. The ratio of (0.1-0.3):1 ensures that the Ce element can fully play its role as an “electron promoter” and “oxygen pump”, and will not significantly negatively affect the number of active sites.

[0034] The introduction of Ce or La can inhibit the excessive oxidation of NH3. In the SCR reaction, if NH3 is excessively oxidized, it will generate byproduct N2O, resulting in a decrease in N2 selectivity. The Ce species promotes the standard SCR reaction (4NH3+4NO+O2→4N2+6H2O) by regulating the types and reaction paths of active oxygen, thereby significantly improving N2 selectivity. Under this optimized ratio, the guiding effect of Ce on the reaction path is optimal, ensuring that high N2 selectivity can still be maintained within a wide temperature range, especially at >250°C.

[0035] Selecting Fe or Co as the second doping element and controlling the molar ratio of Fe or Co to Mn to be (0.05-0.15):1 is based on its role as a “structure promoter” and “acid enhancer”. This ratio is the essence of synergistically improving water and sulfur resistance and stable activity.

[0036] Fe and Co are typical Lewis acid site providers. Their introduction significantly increases the number and strength of acidic sites on the catalyst surface. These acidic sites have a stronger adsorption capacity for NH3 molecules. In the presence of water vapor, H2O competes with NH3 for adsorption on the catalyst surface. Stronger surface acidity means stronger adsorption of NH3, thus effectively resisting competitive adsorption deactivation caused by H2O molecules. SO2 can also adsorb onto the basic sites of the catalyst to form sulfate. The increase in Fe / Co reduces the number of basic sites on the surface, while the introduced acidic sites have a weaker adsorption capacity for SO2. More importantly, the presence of Fe species is thought to promote the decomposition of existing sulfate species on the surface that lead to deactivation, thus exhibiting a certain degree of self-regeneration capability.

[0037] The incorporation of Fe or Co can form a more stable composite oxide structure with Mn-O-Ce, acting as a "structural support" to inhibit the sintering and loss of active components during the reaction process. The proportion of the second dopant element needs to be much lower than that of the first dopant element. This is because the main function of Fe / Co is "modification" and "enhancement," not to dominate the reaction. If the proportion is too high (e.g., close to the amount of Mn), the redox properties of Fe / Co itself (especially Co, which has strong oxidizing power for NH3) may become dominant, thereby destroying the inherent low-temperature high activity of the Mn-based catalyst and potentially exacerbating the non-selective oxidation of NH3, leading to a decrease in N2 selectivity. The relatively low ratio of (0.05-0.15):1 is sufficient to "anchor" in the Mn-O-Ce system and provide enough acidic sites to achieve synergistic enhancement, while not changing the low-temperature active nature of Mn as the core.

[0038] In some embodiments of this application, the MOF carrier is a core-shell MOF carrier.

[0039] In some embodiments of this application, the specific surface area of ​​the MOF carrier is 800-1500 m². 2 / g, for example 800m 2 / g, 1000m 2 / g、1200m 2 / g、1300m 2 / g, 1500m 2 / g, etc., the pore volume of the MOF support is 0.5-1.2 cm³. 3 / g; for example, 0.5cm 3 / g, 0.8cm 3 / g, 1.0cm 3 / g, 1.2cm 3 / g etc.

[0040] In some embodiments of the present application, the core layer of the MOF carrier is ZIF-8, and the shell layer of the MOF carrier is UiO-66. The MOF carrier of the present application ingeniously combines the advantages of high specific surface area of ZIF-8 and excellent hydrothermal stability of UiO-66, and the gradient transition layer effectively alleviates the interface lattice mismatch and enhances the stability of the carrier.

[0041] In some embodiments of the present application, the manganese-containing oxide includes one or more of MnO, Mn2O3 and MnO2.

[0042] In some embodiments of the present application, the loading amount of the manganese-containing oxide in the denitration catalyst is 5-15wt%, for example, 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 15wt% and the like.

[0043] The embodiments of the present application also provide a preparation method of the denitration catalyst of the first aspect of the present application, including the following steps: (1) first mixing a MOF carrier solution with a manganese-containing salt solution and a first doping element-containing salt solution, and after the mixing is completed, sequentially performing first aging and filtration treatment; (2) second mixing the filtered precipitate obtained in step (1) with a second doping element-containing salt solution, and after the mixing is completed, sequentially performing second aging and filtration treatment; (3) heat treating the filtered precipitate obtained in step (2) to obtain the denitration catalyst.

[0044] The denitration catalyst of the present application adopts a step-by-step impregnation loading mode, which ensures uniform distribution and firm anchoring of the active components on the carrier, and effectively prevents sintering and loss of the active components.

[0045] In some embodiments of the present application, in step (1), the concentration of the MOF carrier solution is 0.01-0.15g / ml; for example, 0.01g / ml, 0.05g / ml, 0.08g / ml, 0.1g / ml, 0.12g / ml, 0.15g / ml and the like.

[0046] In some embodiments of the present application, the concentration of the manganese-containing salt in the mixed solution of the manganese-containing salt and the first doping element-containing salt is 0.1-0.5mol / L; for example, 0.1mol / L, 0.2mol / L, 0.3mol / L, 0.5mol / L and the like.

[0047] In some embodiments of the present application, the concentration of the first doping element-containing salt in the mixed solution of the manganese-containing salt and the first doping element-containing salt is 0.02-0.15mol / L; for example, 0.02mol / L, 0.05mol / L, 0.06mol / L, 0.08mol / L, 0.12mol / L, 0.15mol / L and the like.

[0048] In some embodiments of the present application, the volume ratio of the MOF carrier solution to the solution containing the manganese-containing salt and the first dopant element-containing salt is 1:(1-5); for example, 1:1, 1:2, 1:3, 1:5, etc.

[0049] In some embodiments of the present application, the temperature of the first mixing is 30-50℃, for example, 30℃, 35℃, 43℃, 46℃, 50℃, etc., and the time of the first mixing is 4-8h; for example, 4h, 5h, 6h, 8h, etc.

[0050] In some embodiments of the present application, the temperature of the first aging is 35-45℃, for example, 35℃, 38℃, 40℃, 43℃, 45℃, etc., and the time of the first aging is 5-7h, for example, 5h, 6h, 7h, etc.

[0051] In some embodiments of the present application, the MOF carrier is first dispersed in a solvent and subjected to ultrasonic treatment, and then impregnated in two steps, the first step being impregnation in a solution containing a manganese-containing salt and a first dopant element-containing salt, and the second step being impregnation in a solution containing a second dopant element-containing salt under ultrasonic assistance.

[0052] In some embodiments of the present application, the concentration of the second dopant element-containing salt in the solution containing the second dopant element-containing salt is 0.05-0.2mol / L, for example, 0.05mol / L, 0.08mol / L, 0.12mol / L, 0.16mol / L, 0.2mol / L, etc.

[0053] In some embodiments of the present application, in step (2), the mass ratio of the precipitate to the solution containing the second dopant element-containing salt is 1:(10-20), for example, 1:10, 1:12, 1:15, 1:18, 1:20, etc.

[0054] In some embodiments of the present application, the temperature of the second mixing is 20-30℃, and the time of the second mixing is 2-4h. In some embodiments of the present application, the temperature of the second aging is 20-30℃, for example, 20℃, 26℃, 30℃, etc., and the time of the second aging is 10-13h, for example, 10h, 12h, 13h, etc.

[0055] In some embodiments of the present application, in step (3), the obtained filtered precipitate is dried and then subjected to heat treatment.

[0056] In some embodiments of the present application, the temperature of the drying is 70-90℃, for example, 70℃, 75℃, 80℃, 90℃, etc., and the time of the drying is 10-15h, for example, 10h, 12h, 13h, 15h, etc.

[0057] In some embodiments of the present application, the heat treatment is heating to 280-320℃, for example 280℃, 300℃, 320℃, etc., at a heating rate of 1-3℃ / min under nitrogen atmosphere, holding for 0.8-1.2h, for example 0.8h, 1.0h, 1.2h, etc., then heating to 400-500℃, for example 400℃, 430℃, 460℃, 500℃, etc., at a heating rate of 0.8-1.2℃ / min, holding for 1.5-2.5h, for example 1.5h, 2h, 2.2h, 2.5h, etc.

[0058] The present application also provides a use of the denitration catalyst of the first aspect of the present application or the denitration catalyst prepared by the preparation method of the second aspect of the present application in the catalysis of nitrogen oxides in air pollution control. The denitration catalyst of the present application can achieve a NOx conversion rate of more than 98% at a low temperature of 180℃, a N2 selectivity of more than 99%, and a denitration efficiency of more than 92% after continuous operation for 4h under harsh conditions containing 100ppm SO2 and 10%H2O, showing excellent comprehensive anti-poisoning ability. x The present application also provides a use of the denitration catalyst of the first aspect of the present application or the denitration catalyst prepared by the preparation method of the second aspect of the present application in the catalysis of nitrogen oxides in air pollution control. The denitration catalyst of the present application can achieve a NOx conversion rate of more than 98% at a low temperature of 180℃, a N2 selectivity of more than 99%, and a denitration efficiency of more than 92% after continuous operation for 4h under harsh conditions containing 100ppm SO2 and 10%H2O, showing excellent comprehensive anti-poisoning ability.

[0059] In some embodiments of the present application, the activity temperature of the denitration catalyst is 150-250℃, for example 150℃, 180℃, 186℃, 197℃, 200℃, 220℃, 230℃, 250℃, etc.

[0060] The technical solutions of the present application are further described below in combination with specific embodiments.

[0061] Embodiment 1 A preparation method of a denitration catalyst, comprising the following steps: (1) Preparation of core-shell MOF carrier: 1.0g ZIF-8 core is dispersed in a 40ml methanol solution containing 0.5g 2-methylimidazole and 0.3g ZrCl3, and the UiO-66 shell layer is grown on the surface of the ZIF-8 by slow dropwise addition and 40℃ temperature control for 6h to form a core-shell structure with a gradient transition zone, and then centrifugation, washing and drying are performed to obtain a MOF carrier with a specific surface area of 1500m 2 / g, a pore volume of about 1.2 cm 3 / g, and a pore volume of about 1.2 cm (2) 6.89 g of the MOF carrier described above was weighed into 150 mL of anhydrous ethanol, and 300 W ultrasonic treatment was performed for 30 min to obtain an MOF carrier solution; 3.579 g of a manganese nitrate solution with a mass concentration of 50% and 0.434 g of cerium nitrate hexahydrate dissolved in 10 mL of water were obtained to form a mixed aqueous solution, and the mixed aqueous solution was added dropwise to the MOF carrier solution under stirring, and stirring was continued at 40°C for 4 h; after stirring was completed, aging was performed at 40°C for 6 h, and filtration was performed to obtain a filtered precipitate (the molar ratio of manganese elements and cerium elements in the filtered precipitate was 1:0.1); 0.202 g of iron nitrate nonahydrate was dissolved in 10 mL of an ethanol solution, and the solution was added dropwise to a container containing the filtered precipitate under intermittent ultrasonic conditions; after dropwise addition was completed, stirring was continued at 25°C for 2 h, and then aging was performed at 25°C for 12 h; filtration was performed to obtain a filtered precipitate (the molar ratio of manganese elements and iron elements in the filtered precipitate was 1:0.05); (3) The filtered precipitate obtained in step (2) was dried at 80°C for 12 h, and then, under a N2 atmosphere, the temperature was increased to 300°C at a rate of 2°C / min, and the temperature was maintained for 1 h; then, the temperature was increased to 450°C at a rate of 1°C / min, and the temperature was maintained for 2 h to obtain the denitration catalyst product.

[0062] Example 2 The difference between the preparation method of the denitration catalyst described in Example 2 and Example 1 is that, in the preparation process of the denitration catalyst described in Example 2, the molar ratio of manganese elements and the first doping element cerium on the MOF carrier is 1:0.2.

[0063] Example 3 The difference between the preparation method of the denitration catalyst described in Example 3 and Example 1 is that, in the preparation process of the denitration catalyst described in Example 3, the molar ratio of manganese elements and the first doping element cerium on the MOF carrier is 1:0.25.

[0064] Example 4 The difference between the preparation method of the denitration catalyst described in Example 4 and Example 1 is that, in the preparation process of the denitration catalyst described in Example 4, the molar ratio of manganese elements and the first doping element cerium on the MOF carrier is 1:0.3.

[0065] Example 5 The difference between the preparation method of the denitration catalyst described in Example 5 and Example 1 is that, in the preparation process of the denitration catalyst described in Example 5, the molar ratio of manganese elements and the second doping element Fe on the MOF carrier is 1:0.75.

[0066] Example 6 The preparation method of the denitration catalyst described in Example 6 is different from that of Example 1 only in that the molar ratio of manganese element to the second doping element Fe on the MOF carrier in the preparation process of the denitration catalyst described in Example 6 is 1:0.1.

[0067] Example 7 The preparation method of the denitration catalyst described in Example 7 is different from that of Example 1 only in that the molar ratio of manganese element to the second doping element Fe on the MOF carrier in the preparation process of the denitration catalyst described in Example 7 is 1:0.15.

[0068] Comparative Example 1 The preparation method of the denitration catalyst described in Comparative Example 1 is different from that of Example 1 only in that an Al2O3 carrier is used instead of an MOF carrier in the preparation process of the denitration catalyst described in Comparative Example 1.

[0069] Comparative Example 2 The preparation method of the denitration catalyst described in Comparative Example 2 is different from that of Example 1 only in that the way of loading manganese oxide and doping elements on the carrier in the preparation process of the denitration catalyst described in Comparative Example 2 is different.

[0070] The specific operation steps include: (1) Preparation of core-shell MOF carrier: 1.0 g of ZIF-8 core is dispersed in a 40 mL methanol solution containing 0.5 g of 2-methylimidazole and 0.3 g of ZrCl3, and the UiO-66 shell layer is grown on the surface of ZIF-8 by slow dripping and 40°C temperature control for 6 h to form a core-shell structure with a gradient transition zone. After centrifugation, washing and drying, a MOF carrier with a specific surface area of 1500 m 2 / g, a pore volume of about 1.2 cm 3 / g, and a pore volume of about 1.2 cm (2) 0.4340 g of cerium nitrate hexahydrate and 3.579 g of 50% manganese nitrate solution, 0.202 g of iron nitrate nonahydrate were mixed and 60 mL of deionized water was added, and stirred uniformly to form a mixed solution, then the mixed solution was added dropwise into a mixed solution of 6 mL of 30% concentrated ammonia water and 54 mL of deionized water at a speed of 10 mL / min, and stirred while adding, after the addition was completed, the solution and the precipitate were allowed to stand for 10 h and then filtered to obtain the precipitate, then centrifuged and the precipitate was dried at a temperature of 90°C, then the dried precipitate was subjected to first calcination in a muffle furnace, wherein the temperature was raised at a rate of 5°C / min and calcined at 500°C for 4 h in the muffle furnace, at this time the molar ratio of Ce to Mn in the composite oxide powder obtained was 0.1:1; the calcined composite oxide was cooled to room temperature, 1.0 g of the calcined composite oxide powder was taken, then the composite oxide was placed in a ball mill and zirconium beads were used for ball milling, wherein the mass of the zirconium beads added was 10.0 g, the ball milling time was 3.0 h, and the ball milling speed was 450 revolutions / minute, to obtain a uniformly dispersed composite oxide MnOx powder after ball milling; (2) 0.1 g of the composite oxide powder after ball milling was taken and added to 1.0 g of the MOF carrier mixed with 100 mL of ethanol, then the mixed solution was ultrasonically dispersed for 30 minutes, and then the mixed solution was dried at 90°C, after which the dried mixture was sent into a muffle furnace for second calcination, the calcination temperature was 500°C, the temperature was raised at a rate of 5°C / min, and the calcination time was 4 h, thereby obtaining a denitration catalyst with a core-shell structure.

[0071] Catalytic performance research of the denitration catalysts described in Examples 1-7 and Comparative Examples 1-2 of the present application Research method: SCR activity evaluation was carried out on a fixed bed reactor, the reaction gas composition was: 500 ppm NO, 500 ppm NH3, 5% O2, 100 ppm SO2 (introduced when testing sulfur resistance), 10% H2O (introduced when testing water resistance), the balance was N2, the space velocity was 60000 h -1 . The results are shown in Table 1.

[0072] Table 1

[0073] As can be seen from Table 1, the denitration catalysts described in Examples 1-7 of the present application all have high activity and stability, which is due to the high specific surface area (800-1500 m 2 / g) and the gradient transition layer of the ZIF-8@UiO-66 core-shell structure. This structure promotes the high dispersion of the active components (Mn, Ce, Fe) and enhances the mass transfer efficiency.

[0074] Comparative Example 1 (Al2O3 support): Due to low specific surface area (typically < 300 m 2 / g) and lack of controllable pores, poor dispersion of active components leads to significant reduction of NO x conversion and N2 selectivity.

[0075] Comparative Example 2 (ball-milling-secondary calcination loading): The ball-milling process easily causes agglomeration of active components, and the secondary calcination can lead to sintering, resulting in decreased accessibility of active sites, thus the performance is lower than that of the DeNOx catalyst described in Example 1 of the present application.

[0076] Effect of doping element ratio From Examples 1-4 of the present application, it can be seen that: the introduction of Ce adjusts the valence state distribution of Mn by Ce 3+ / Ce 4+ oxidation and reduction pairs adjust the valence state distribution of Mn, increase the oxygen vacancy concentration, and thus improve the low-temperature activity. When the Mn:Ce molar ratio increases from 1:0.1 to 1:0.25 (Example 1→3), the NOx conversion gradually increases (92.5%→98.5%).

[0077] From Examples 1 and 5-7 of the present application, it can be seen that: Fe enhances the Lewis acidity of the catalyst surface, promotes NH3 adsorption, and improves the resistance to sulfur and water. When the Mn:Fe molar ratio increases from 1:0.05 to 1:0.075, the initial conversion under harsh conditions increases from 92.5% to 97.0%.

[0078] Stability mechanism: The gradient transition layer of the core-shell MOF support alleviates the structural collapse caused by thermal stress, and the doping elements (such as Fe) promote the decomposition of surface sulfate intermediates, preventing permanent poisoning of active sites. Comparative Examples 1-2 quickly deactivate under the action of SO2 / H2O due to the lack of this structure.

[0079] Although the above examples have been shown and described, it can be understood that the above examples are exemplary and cannot be understood as limiting the present application, and the changes, modifications, replacements and variations of the above examples made by those of ordinary skill in the art are within the protection scope of the present application.

Claims

1. A denitration catalyst characterized by, Includes a MOF support, a manganese-containing oxide supported on the MOF support, a first dopant element, and a second dopant element; The molar ratio of manganese to the first dopant on the MOF support is 1:(0.1-0.3), and the molar ratio of manganese to the second dopant on the MOF support is 1:(0.05-0.15). The first doping element includes Ce and / or La, and the second doping element includes Fe and / or Co.

2. The de-NOx catalyst according to claim 1, characterized by, The MOF carrier is a core-shell structured MOF carrier; Preferably, the MOF support has a specific surface area comprised between 800 and 1500 m 2 / g, and a pore volume comprised between 0.5 and 1.2 cm 3 / g. Preferably, the core layer of the MOF vector is ZIF-8, and the shell layer of the MOF vector is UiO-66.

3. The de-NOx catalyst according to claim 1, characterized by, The loading of manganese oxides in the denitrification catalyst is 5-15 wt%.

4. The method for producing the de-NOx catalyst according to any one of claims 1 to 3, characterized by, Includes the following steps: (1) The MOF support solution is mixed with a solution containing manganese salt and a solution containing the first dopant element salt. After the mixing is completed, the first aging and filtration processes are carried out in sequence. (2) The filtered precipitate obtained in step (1) and the solution containing the second doped element salt are mixed for the second time. After the mixing is completed, the second aging and filtration processes are carried out in sequence. (3) The filtered precipitate obtained in step (2) is subjected to heat treatment to obtain the denitrification catalyst.

5. The method of claim 4, wherein the de-NOx catalyst is prepared by the steps of: preparing a slurry of the de-NOx catalyst; and drying the slurry. In step (1), the concentration of the MOF carrier solution is 0.01-0.15 g / ml; And / or, the concentration of manganese salt in the mixed solution containing manganese salt and the salt containing the first dopant element is 0.1-0.5 mol / L; And / or, the concentration of the first doping element salt in the mixed solution containing manganese salt and the first doping element salt is 0.02-0.15 mol / L; And / or, the volume ratio of the MOF support solution to the solution containing the manganese salt and the solution containing the first dopant element salt is 1:(1-5). And / or, the temperature of the first mixture is 30-50°C, and the time of the first mixture is 4-8 hours; And / or, the temperature of the first aging is 35-45℃, and the time of the first aging is 5-7h.

6. The method of claim 4, wherein the de-NOx catalyst is prepared by the steps of: preparing a slurry of the de-NOx catalyst; and drying the slurry. The concentration of the second doped element salt in the solution is 0.05-0.2 mol / L; And / or, in step (2), the mass ratio of the filtered precipitate to the solution containing the second doped element salt is 1:(10-20); And / or, the temperature of the second mixing is 20-30°C, and the time of the second mixing is 2-4 hours; And / or, the temperature of the second aging is 20-30°C, and the time of the second aging is 10-13 hours.

7. The method of claim 4, wherein the de-NOx catalyst is prepared by the steps of: preparing a slurry of the de-NOx catalyst; and drying the slurry. In step (3), the obtained filtered precipitate is dried and then subjected to heat treatment; Preferably, the drying temperature is 70-90℃ and the drying time is 10-15h.

8. The method for preparing the denitrification catalyst according to claim 4, characterized in that, The heat treatment is performed under a nitrogen atmosphere, heating to 280-320℃ at a heating rate of 1-3℃ / min and holding for 0.8-1.2h; then heating to 400-500℃ at a heating rate of 0.8-1.2℃ / min and holding for 1.5-2.5h.

9. The application of the denitrification catalyst according to any one of claims 1-3 or the denitrification catalyst obtained by the preparation method according to any one of claims 3-8 in the catalysis of nitrogen oxides in air pollution control.

10. The application according to claim 9, characterized in that, The denitrification catalyst has an activation temperature of 150-250℃.

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