Ternary manganese-based denitration catalyst as well as preparation method and application thereof

Abstract

The invention relates to a ternary manganese-based denitration catalyst as well as a preparation method and application thereof, which can be applied to the technical fields of environmental catalysis and air pollution control. The catalyst has a wide active window and high water and sulfur resistance, and in addition, due to combination of samarium, the oxidation-reduction capacity of the catalyst is improved, so that the denitration selectivity of the catalyst is improved. The denitration catalyst can be used for eliminating NOx in exhaust gas discharged by fixed sources such as coal-fired power plants, building material kilns and metal smelting and mobile sources such as diesel vehicles.

Description

Technical Field

[0001] The present invention relates to a ternary manganese-based denitration catalyst for selective catalytic reduction (SCR) of NO by ammonia x and its preparation method and use. The denitration catalyst is applicable to the elimination of NO in the exhaust gases discharged from stationary sources such as coal-fired power plants, building material kilns, and metal smelting, as well as mobile sources such as diesel vehicles x and belongs to the technical field of environmental catalytic purification Background Technique

[0002] NO x As a main air pollutant, it not only causes environmental problems such as acid rain and photochemical smog, but also poses a serious threat to human health. Therefore, how to effectively eliminate NO x has become a research hotspot in the field of environmental catalysis. At present, the NH3-SCR technology is one of the most widely used and effective denitration technologies in industrial applications, and its core technology is the research and development of high-performance catalysts. Currently, the industrialized NH3-SCR catalysts generally use TiO2 as the carrier and V2O5 and WO3 as the active components. This catalyst has good catalytic performance in the range of 320-400 °C. However, this catalyst still has the following problems: the temperature window of the catalyst is narrow, while the temperature of industrial boiler flue gas and diesel vehicle exhaust gas fluctuates greatly. When the temperature is lower than 300 °C, the denitration activity of the catalyst is low; the carrier TiO2 is prone to phase change at high temperature, transforming from anatase type to rutile type, resulting in a significant decrease in the activity of the catalyst; the active component V2O5 has biological toxicity, increasing the cost of treating waste catalysts. Therefore, the research and development of efficient and environmentally friendly NH3-SCR catalysts is of great environmental significance for the control of NO x

[0003] Manganese-based catalysts have been attracting much attention in the field of low-temperature denitration due to their good low-temperature activity. Tang Xiaolong et al. found that the valence states of manganese oxides synthesized by different methods are different, and their denitration effects are also different. The influence of the valence state of manganese oxides in the SCR reaction is also relatively complex. Generally, it is considered that high-valence manganese ions are more likely to undergo electron transfer, generate L acid sites while undergoing redox reactions, thereby promoting the adsorption and activation of ammonia. However, high-valence oxides will also bring more side reactions, reducing their selectivity. In addition, manganese oxide catalysts have always been lacking in sulfur resistance. Tang Xiaolong et al. prepared MnO by redox coprecipitation method x ​-SnO2 oxide. Experiments have found that the Mn-Sn solid solution has excellent low-temperature SCR activity and a wide temperature window, and the introduction of Sn does not significantly improve the poor sulfur resistance of the manganese-based catalyst. Gao Fengyu et al. synthesized a CrMn2O4 catalyst with a spinel structure by the citric acid method and found that the combination of Cr and Mn can improve its sulfur resistance, but the low-temperature activity will also be sacrificed with the introduction of Cr. Therefore, it is necessary to prepare a new non-vanadium denitration catalyst with good performance for NO x removal, while having a wide temperature window and good sulfur and water resistance. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite catalyst with a simple preparation process and high efficiency for NH3-SCR denitration, as well as its preparation method and application.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] On the one hand, the present invention provides a ternary manganese-based denitration catalyst, and the composition of the ternary manganese-based denitration catalyst is expressed as SmO x / MnFeO x (x ranges from 1 to 4, and x satisfies valence balancing), wherein, according to the molar ratio, the ratio of samarium to manganese and iron is 5-15:100.

[0007] On the other hand, the present invention also provides a preparation method of a ternary manganese-based denitration catalyst, and the method includes the following steps: synthesizing manganese-iron oxide as a precursor by the hydrothermal method, then performing impregnation treatment with a soluble samarium salt, and obtaining the ternary manganese-based denitration catalyst through calcination.

[0008] Specifically, the preparation method includes the following steps:

[0009] (1) Prepare aqueous solutions containing soluble manganese salt, soluble iron salt, surfactant, soluble samarium salt, and HF respectively;

[0010] (2) Take the soluble manganese salt and soluble iron salt solutions obtained in step (1), stir and mix them in a water bath, add a surfactant, and then add a precipitating agent and continue to stir in the water bath to obtain a mixed solution, and perform a hydrothermal reaction;

[0011] (3) After the reaction is completed, cool down, filter by suction, wash, and dry to obtain MnFeO x ;

[0012] (4) Grind MnFeO x and add it to the samarium salt solution, and at the same time add HF as a framework etching agent and stir to prepare a slurry;

[0013] (5) Dry the slurry obtained in step (4), and then calcine it in a muffle furnace to obtain a ternary manganese-based catalyst.

[0014] In the present invention, the aqueous solution of soluble manganese and iron salts in step (1) is selected from one or more of ferric chloride, ferric nitrate, manganese acetate, and manganese nitrate, and its concentration is 0.3 - 0.6 mol / L.

[0015] In the present invention, the surfactant is selected from CTAB, and after adding the surfactant in step (2), its mass concentration in the mixed solution is 1% - 2%.

[0016] The soluble samarium salt is selected from one or more of samarium nitrate and samarium sulfate; the concentration of the aqueous solution of the soluble samarium salt is 1.0 - 3.0 mol / L.

[0017] In the present invention, in the soluble manganese salt and soluble iron salt solutions in step (2), the molar ratio of Mn to Fe is 2 - 3:1, and the precipitant is selected from one or more of urea and ammonium carbonate. Based on the total molar amount of manganese and iron elements being 1 mole, the addition amount of the precipitant is 0.83 - 1.7 mol.

[0018] In the present invention, the temperature of the hydrothermal reaction in step (2) is 40 - 80 °C, and the time of the hydrothermal reaction is 30 - 60 minutes.

[0019] In the present invention, the temperature after cooling in step (3) is preferably 20 - 35 °C. The suction filtration is carried out in a Buchner funnel, and the pore size of the filter paper used for the suction filtration is 0.2 - 0.5 microns; the washing solvent is selected from one or more of deionized water and methanol, and the number of washing times is not particularly limited, preferably 1 - 5 times; the drying process is carried out in a constant-temperature oven, the drying temperature is 80 - 120 °C, and the drying time is 12 - 24 hours.

[0020] In the present invention, the particle size after grinding in step (4) is 200 - 500 microns; based on the total molar amount of manganese and iron elements being 1 mole, in terms of the molar amount of samarium, the addition amount of the samarium salt is 0.05 - 0.15 mol; the stirring temperature is 50 - 70 °C, and the stirring time is 3 - 6 hours.

[0021] In the present invention, after adding HF in step (4), the concentration of HF in the solution is 0.1 - 0.3 mol / L.

[0022] In the present invention, the drying temperature in step (5) is 90 - 120 °C, the drying time is 12 - 24 hours, the calcination temperature is 400 - 600 °C, and the calcination time is 3 - 8 hours.

[0023] On the other hand, the present invention provides an application of a ternary manganese-based denitration catalyst in denitration.

[0024] Compared with the prior art, the present invention has the following advantages and outstanding effects: it does not use the toxic active component V2O5, and through the synergistic catalysis between metals, it broadens the active temperature window of the catalyst, improves the thermal stability of the catalyst, enables the catalyst to have good sulfur and water resistance, and realizes high-efficiency environmental protection and energy conservation in denitration applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 . The catalyst reduces NO x conversion rate DETAILED DESCRIPTION OF THE INVENTION

[0026] Raw materials and sources:

[0027] The chemicals used in the present invention: iron(III) nitrate nonahydrate, iron(III) chloride hexahydrate, manganese(II) acetate tetrahydrate, manganese(II) sulfate monohydrate, samarium(III) nitrate hexahydrate, samarium(III) sulfate nonahydrate, hydrofluoric acid (1%), cetyltrimethylammonium bromide, polyethylene glycol, urea, ammonium carbonate, etc. are all from Macklin Reagent Company.

[0028] Performance testing:

[0029] Denitration activity test: Different gases are mixed under the control of mass flow meters to form simulated flue gas. The flue gas flow rate in this experiment is 300 ml / min. The specific gas composition is as follows: 500 ppm NO, 500 ppm NH3, 5% O2, 5% H2O, 50 ppm SO2, and nitrogen is used as the balance gas. The flue gas enters the adsorption reaction system, passes through the catalyst bed to complete the SCR reaction, and the tail gas is simply treated (NH3) and then enters the flue gas analyzer (analysis system). The core of this test system is the flue gas analyzer, and the KM-9106 flue gas analyzer of Kane Company in the UK is used in this laboratory. Nitrogen selectivity test: Different gases are mixed under the control of mass flow meters to form simulated flue gas. The flue gas flow rate in this experiment is 300 ml / min. The specific gas composition is as follows: 500 ppm NO, 500 ppm NH3, 5% O2, and nitrogen is used as the balance gas. The flue gas enters the adsorption reaction system, passes through the catalyst bed to complete the SCR reaction, and the tail gas enters the infrared test. The GAS-MET Fourier transform infrared gas analyzer is used for test analysis. The calculation formula is as follows:

[0030] The denitration activity calculation formula is as follows:

[0031]

[0032]

[0033] In the formula, [NO x ​in Indicates NO x Concentration before entering the denitration catalyst, [NO x out Indicates NO x Concentration leaving the denitration catalyst; [NH3] in and [NH3] out Indicates the concentrations of NH3 entering and leaving the denitration catalyst;

[0034] [N2O] out Indicates the concentration of N2O leaving the denitration catalyst.

[0035] The technical solution of the present invention will be further described below in conjunction with embodiments:

[0036] Example 1: Preparation of 5% SmO x / MnFeO x Catalyst

[0037] a) Add 100 g of deionized water to a 200 ml beaker and stir on a magnetic stirrer. Weigh 0.01 mol of ferric nitrate nonahydrate and 0.02 mol of manganese acetate tetrahydrate and add them to the beaker in sequence. Then add 1 g of CTAB and keep stirring for 1 h;

[0038] b) Take the mixed solution of manganese acetate and ferric nitrate obtained in step a), stir and mix it in a water bath at 60 °C for 30 minutes to obtain a mixed solution. Then add 0.15 mol of urea and continue stirring in the water bath for 30 minutes;

[0039] c) Transfer the mixed solution obtained in step b) to a 150 ml hydrothermal reaction kettle, carry out hydrothermal reaction at 160 °C for 12 hours, and then cool to room temperature;

[0040] d) Take the reaction solution obtained in step c), carry out suction filtration and washing, and dry it at 110 °C for 12 hours to obtain

[0041] MnFeO x ;

[0042] e) Take 1.5 ml of 1.0 mol / L (0.0015 mol) samarium nitrate solution, add 1.0 ml of 0.1 mol / L HF, stir evenly in a water bath at 50 °C to obtain a mixed solution; take 2.3 g of the powder obtained in d) and add it to the mixed solution, and stir for 3 hours to prepare a slurry.

[0043] f) Dry the slurry prepared in step e) at 110 °C for 12 hours, and then calcine it in a muffle furnace at 400 °C for 6 hours to prepare 5% SmO x / MnFeO x Catalyst;

[0044] ​Example 2: 10% SmO x / MnFeO x Preparation of the catalyst

[0045] a) Add 100 g of deionized water to a 200 ml beaker and place it on a magnetic stirrer to stir. Weigh 0.01 mol of iron(III) nitrate nonahydrate and 0.02 mol of manganese(II) acetate tetrahydrate and add them to the beaker in sequence. Then add 1 g of CTAB and keep stirring for 1 h;

[0046] b) Take the mixed solution of manganese(II) acetate and iron(III) nitrate obtained in step a), stir and mix it in a water bath at 50 °C for 30 minutes to obtain a mixed solution. Subsequently, add 0.15 mol of urea and continue stirring in the water bath for 30 minutes;

[0047] c) Transfer the mixed solution obtained in step b) to a 150 ml hydrothermal reactor, carry out hydrothermal reaction at 160 °C for 12 hours, and then cool it to room temperature;

[0048] d) Take the reaction solution obtained in step c), filter it by suction, wash it, and dry it at 110 °C for 12 hours to obtain MnFeO x ;

[0049] e) Take 1.5 ml of 2.0 mol / L (0.003 mol) samarium nitrate solution, add 1.0 ml of 1% HF, and stir evenly in a water bath at 60 °C

[0050] to obtain a mixed solution; Take 2.3 g of the powder obtained in d) and add it to the mixed solution, stir for 3 hours to prepare a slurry.

[0051] f) Dry the slurry prepared in step e) at 110 °C for 12 hours, and then calcine it in a muffle furnace at 400 °C for 6 hours to prepare 10% SmO x / MnFeO x catalyst;

[0052] Example 3: 15% SmO x / MnFeO x Preparation of the catalyst

[0053] a) Add 100 g of deionized water to a 200 ml beaker and place it on a magnetic stirrer to stir. Weigh 0.01 mol of iron(III) nitrate nonahydrate and 0.02 mol of manganese(II) acetate tetrahydrate and add them to the beaker in sequence. Then add 1 g of CTAB and keep stirring for 1 h;

[0054] b) Take the mixed solution of manganese(II) acetate and iron(III) nitrate obtained in step a), stir and mix it in a water bath at 60 °C for 30 minutes to obtain a mixed solution. Subsequently, add 0.15 mol of urea and continue stirring in the water bath for 30 minutes;

[0055] c) Transfer the mixed solution obtained in step b) into a 150 ml hydrothermal reactor, carry out hydrothermal reaction at 160 °C for 12 hours, and then cool it to room temperature;

[0056] d) Take the reaction solution obtained in step c), carry out suction filtration and washing, and dry it at 110 °C for 12 hours to obtain MnFeO x ;

[0057] e) Take 1.5 ml of 3.0 mol / L (0.0045 mol) samarium nitrate solution, add 1.0 ml of 1% HF,

[0058] Stir evenly in a 50 °C water bath to obtain a mixed solution; take 2.3 g of the powder obtained in d) and add it to the mixed solution, and stir for 3 hours to prepare a slurry.

[0059] f) Dry the slurry prepared in step e) at 110 °C for 12 hours, and then calcine it in a muffle furnace at 400 °C for 6 hours to prepare a 15% SmO x / MnFeO x catalyst.

[0060] Example 4: 10% SmO x / MnFeO x (a) Preparation of the catalyst

[0061] a) Add 100 g of deionized water to a 200 ml beaker and place it on a magnetic stirrer for stirring. Weigh 0.015 mol of ferric nitrate nonahydrate and 0.45 mol of manganese sulfate monohydrate and add them to the beaker in sequence, and then add 2 g of PEG, and keep stirring for 1 h;

[0062] b) Take the mixed solution of manganese acetate and ferric nitrate obtained in step a), stir and mix it in a 60 °C water bath for 30 minutes to obtain a mixed solution, and then add 0.15 mol of ammonium carbonate, and continue to stir in the water bath for 30 minutes;

[0063] c) Transfer the mixed solution obtained in step b) into a 150 ml hydrothermal reactor, carry out hydrothermal reaction at 170 °C for 18 hours, and then cool it to room temperature;

[0064] d) Take the reaction solution obtained in step c), carry out suction filtration and washing, and dry it at 110 °C for 12 hours to obtain MnFeO x ;

[0065] e) Take 1.5 ml of 2.0 mol / L (0.003 mol) samarium nitrate solution, add 2.0 ml of 1% HF, 50 °C

[0066] Stir evenly in a water bath to obtain a mixed solution; take 2.3 g of the powder obtained in d) and add it to the mixed solution, and stir for 4 hours to prepare a slurry.

[0067] f) Dry the slurry obtained in step e) at 110 °C for 12 hours, and then calcine it in a muffle furnace at 600 °C for 6 hours to obtain 10% SmO x / MnFeO x Catalyst (a).

[0068] Example 5: 10% SmO x / MnFeO x (b) Preparation of the catalyst

[0069] a) Add 100 g of deionized water to a 200 ml beaker and stir it on a magnetic stirrer. Weigh 0.02 mol of ferric chloride hexahydrate and 0.04 mol of manganese sulfate monohydrate and add them to the beaker in sequence. Then add 2 g of CTAB and keep stirring for 1 h;

[0070] b) Take the mixed solution of manganese acetate and ferric nitrate obtained in step a), stir and mix it in a 60 °C water bath for 30 minutes to obtain a mixed solution. Then add 0.15 mol of ammonium carbonate and continue stirring in the water bath for 30 minutes;

[0071] c) Transfer the mixed solution obtained in step b) to a 150 ml hydrothermal reaction kettle and carry out hydrothermal reaction at 165 °C

[0072] for 24 hours, and then cool it to room temperature;

[0073] d) Take the reaction solution obtained in step c), filter it by suction, wash it, and dry it at 110 °C for 12 hours to obtain MnFeO x ;

[0074] e) Take 1.5 ml of 2.0 mol / L (0.003 mol) samarium sulfate solution, add 2.0 ml of 1% HF, stir evenly in a 70 °C water bath to obtain a mixed solution; take 2.3 g of the powder obtained in d) and add it to the mixed solution, stir for 4 hours to prepare a slurry.

[0075] f) Dry the slurry obtained in step e) at 110 °C for 12 hours, and then calcine it in a muffle furnace at 500 °C for 6 hours to obtain 10% SmO x / MnFeO x

[0076] Catalyst (b).

[0077] Example 6: 10% SmO x / MnFeO x (c) Preparation of the catalyst

[0078] a) Add 100 g of deionized water to a 200 ml beaker and place it on a magnetic stirrer for stirring. Weigh 0.01 mol of iron(III) nitrate nonahydrate and 0.02 mol of manganese(II) sulfate monohydrate respectively and add them to the beaker in sequence. Then add 1 g of PEG and keep stirring for 1 h;

[0079] b) Take the mixed solution of manganese(II) acetate and iron(III) nitrate obtained in step a), stir and mix it in a 60 °C water bath for 30 minutes to obtain a mixed solution. Subsequently, add 0.15 mol of urea and continue stirring in the water bath for 30 minutes;

[0080] c) Transfer the mixed solution obtained in step b) to a 150 ml hydrothermal reaction kettle, carry out hydrothermal reaction at 160 °C for 12 hours, and then cool to room temperature;

[0081] d) Take the reaction solution obtained in step c), filter it by suction, wash it, and dry it at 110 °C for 12 hours to obtain

[0082] MnFeO x ;

[0083] e) Take 1.5 ml of 2.0 mol / L (0.003 mol) samarium sulfate solution and add 1.0 ml of 1% HF, stir evenly in a 60 °C water bath to obtain a mixed solution; Take 2.3 g of the powder obtained in d) and add it to the mixed solution, stir for 6 hours to prepare a slurry.

[0084] f) Dry the slurry prepared in step e) at 110 °C for 12 hours, and then calcine it in a muffle furnace at 400 °C for 6 hours to prepare 10% SmO x / MnFeO x (c) catalyst.

[0085] Comparative Example 1: Preparation of MnFeO x Catalyst

[0086] a) Add 100 g of deionized water to a 200 ml beaker and place it on a magnetic stirrer for stirring. Weigh 0.01 mol of iron(III) nitrate nonahydrate and 0.02 mol of manganese(II) acetate tetrahydrate respectively and add them to the beaker in sequence. Then add 1 g of CTAB and keep stirring for 1 h;

[0087] b) Take the mixed solution of manganese(II) acetate and iron(III) nitrate obtained in step a), stir and mix it in a 60 °C water bath for 30 minutes to obtain a mixed solution. Subsequently, add 0.15 mol of urea and continue stirring in the water bath for 30 minutes;

[0088] c) Transfer the mixed solution obtained in step b) to a 150 ml hydrothermal reaction kettle, at 160 °C

[0089] Carry out hydrothermal reaction for 12 hours, and then cool to room temperature;

[0090] (d) Take the reaction solution obtained in step (c), filter it by suction, wash it, and dry it at 110 °C for 12 hours to obtain MnFeO x ;

[0091] (e) Roast the dried powder obtained in step (d) in a muffle furnace at 400 °C for 6 hours to prepare the MnFeO x catalyst.

[0092] Comparative Example 2: 10% SmO x / MnFeO x (d) Preparation of the catalyst

[0093] (a) Add 100 g of deionized water to a 200 ml beaker, place it on a magnetic stirrer and stir. Weigh 0.01 mol of ferric nitrate nonahydrate and 0.02 mol of manganese acetate tetrahydrate and add them to the beaker in sequence. Then add 1 g of CTAB and keep stirring for 1 h;

[0094] (b) Take the mixed solution of manganese acetate and ferric nitrate obtained in step (a), stir and mix it in a 60 °C water bath for 30 minutes to obtain a mixed solution. Then add 0.15 mol of urea and continue to stir in the water bath for 30 minutes;

[0095] (c) Transfer the mixed solution obtained in step (b) to a 150 ml hydrothermal reaction kettle, carry out hydrothermal reaction at 160 °C for 12 hours, and then cool to room temperature;

[0096] (d) Take the reaction solution obtained in step (c), filter it by suction, wash it, and dry it at 110 °C for 12 hours to obtain

[0097] MnFeO x ;

[0098] (e) Take 1.5 ml of 2.0 mol / L (0.03 mol) samarium nitrate solution, add 1.0 ml of 1% HNO3, stir evenly in a 60 °C water bath to obtain a mixed solution; take 2.3 g of the powder obtained in (d) and add it to the mixed solution, stir for 3 hours to prepare a slurry.

[0099] (f) Dry the slurry prepared in step (e) at 110 °C for 12 hours, and then roast it in a muffle furnace at 400 °C for 6 hours to prepare 10% SmO x / MnFeO x catalyst (d).

[0100] Comparative Example 3: 10% SmMnFeO x (e) Preparation of the catalyst

[0101] a) Add 100 g of deionized water to a 200 ml beaker and place it on a magnetic stirrer for stirring. Weigh 0.01 mol of iron(III) nitrate nonahydrate and 0.02 mol of manganese(II) acetate tetrahydrate successively and add them to the beaker. Then add 1.5 ml

[0102] of 2.0 mol / L (0.03 mol) samarium nitrate solution, and then add 1 g of CTAB. Keep stirring for 1 h;

[0103] b) Take the mixed solution obtained in step a) and stir it in a water bath at 60 °C for 30 minutes to obtain a mixed solution. Then add 0.15 mol of urea and continue stirring in the water bath for 30 minutes;

[0104] c) Transfer the mixed solution obtained in step b) to a 150 ml hydrothermal reactor, carry out hydrothermal reaction at 160 °C for 12 hours, and then cool it to room temperature;

[0105] d) Take the reaction solution obtained in step c), filter it, wash it, and dry it at 110 °C for 12 hours to obtain

[0106] SmMnFeO x ;

[0107] e) Dry the slurry prepared in step d) at 110 °C for 12 hours, and then calcine it in a muffle furnace at 400 °C for 6 hours to prepare 10% SmMnFeO x (e) catalyst.

[0108] Comparative Example 4: Preparation of Sm-Mn-Fe / TiO2-0.1 catalyst

[0109] The raw materials are TiO2, Mn(CH3COO)2·4H2O, Fe(NO3)3·9H2O and Sm(NO3)3. The mass of the active components is calculated according to Sm2O3, MnO2 and Fe2O3. Weigh the raw materials according to 25% of the mass of the active components being the denitration catalyst (i.e., the total mass of TiO2 and the active components) and the molar ratio of Sm:Mn:Fe being 0.1:1:1.

[0110] a) Dissolve Mn(CH3COO)2·4H2O, Fe(NO3)3·9H2O and Sm(NO3)3·6H2O in 100 mL of distilled water at 60 °C, then add TiO2 and stir for 30 minutes. Then add 1.5 mol / L (NH4)2CO3 solution dropwise until the pH reaches 8.4, and then continue stirring for 2 h. Then filter, wash and dry to obtain the precipitate.

[0111] b) Under a flowing air atmosphere, calcine the precipitate at 450 °C for 2 h to obtain the denitration catalyst, which is named Sm-Mn-Fe / TiO2-0.1.

[0112] The performance test of the catalyst of the present invention will be described below in combination with application examples:

[0113] Application Example 1: The preparation method of the catalyst is the same as that of Example 1. 0.12 g of the catalyst (40 - 60 mesh) is placed in a fixed-bed reactor. The reaction gas composition is 0.05% NO, 0.05% NH3, 5% O2, and nitrogen is used as the balance gas. The flow rate of the reaction gas is 300 ml / min, and the space velocity is 106,000 h -1 . The active evaluation temperature range is 75 - 350 °C. At different temperatures, the conversion rate of the catalyst for reducing NO x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0114] Application Example 2: The preparation method of the catalyst is the same as that of Example 2. 0.12 g of the catalyst (40 - 60 mesh) is placed in a fixed-bed reactor. The reaction gas composition is 0.05% NO, 0.05% NH3, 5% O2, and nitrogen is used as the balance gas. The flow rate of the reaction gas is 300 ml / min, and the space velocity is 106,000 h -1 . The active evaluation temperature range is 75 - 350 °C. At different temperatures, the conversion rate of the catalyst for reducing NO x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0115] Application Example 3: The preparation method of the catalyst is the same as that of Example 3. 0.12 g of the catalyst (40 - 60 mesh) is placed in a fixed-bed reactor. The reaction gas composition is 0.05% NO, 0.05% NH3, 5% O2, and nitrogen is used as the balance gas. The flow rate of the reaction gas is 300 ml / min, and the space velocity is 106,000 h -1 . The active evaluation temperature range is 75 - 350 °C. At different temperatures, the conversion rate of the catalyst for reducing NO x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0116] Application Example 4: The preparation method of the catalyst is the same as that of Example 4. 0.12 g of the catalyst (40 - 60 mesh) is placed in a fixed-bed reactor. The reaction gas composition is 0.05% NO, 0.05% NH3, 5% O2, and nitrogen is used as the balance gas. The flow rate of the reaction gas is 300 ml / min, and the space velocity is 106,000 h -1 . The active evaluation temperature range is 75 - 350 °C. At different temperatures, the conversion rate of the catalyst for reducing NO x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0117] Application Example 5: The preparation method of the catalyst was the same as that in Example 5. 0.12 g of the catalyst (40 - 60 mesh) was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, with nitrogen as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106,000 h -1 The temperature range for activity evaluation was 75 - 350 °C. At different temperatures, the conversion rate of NO reduced by the catalyst x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0118] Application Example 6: The preparation method of the catalyst was the same as that in Example 6. 0.12 g of the catalyst (40 - 60 mesh) was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, with nitrogen as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106,000 h -1 The temperature range for activity evaluation was 75 - 350 °C. At different temperatures, the conversion rate of NO reduced by the catalyst x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0119] Application Example 7: The preparation method of the catalyst was the same as that in Comparative Example 1. 0.12 g of the catalyst (40 - 60 mesh) was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, with nitrogen as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106,000 h -1 The temperature range for activity evaluation was 75 - 350 °C. At different temperatures, the conversion rate of NO reduced by the catalyst x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0120] Application Example 8: The preparation method of the catalyst was the same as that in Comparative Example 2. 0.12 g of the catalyst (40 - 60 mesh) was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, with nitrogen as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106,000 h -1 The temperature range for activity evaluation was 75 - 350 °C. At different temperatures, the conversion rate of NO reduced by the catalyst x is shown in Table 1, and the selectivity of the catalyst is shown in Table 2.

[0121] Application Example 9: The preparation method of the catalyst was the same as that in Comparative Example 3. 0.12 g of the catalyst (40 - 60 mesh) was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, with nitrogen as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106,000 h -1。The active evaluation temperature range is 75 - 350 °C. At different temperatures, the catalyst reduces NO x conversion rates are shown in Table 1, and the catalyst selectivities are shown in Table 2.

[0122] Application Example 10: The preparation method of the catalyst is the same as that of Comparative Example 3. 0.12 g of the catalyst (40 - 60 mesh) is placed in a fixed-bed reactor. The reaction gas composition is 0.05% NO, 0.05% NH3, 5% O2, with nitrogen as the balance gas. The flow rate of the reaction gas is 300 ml / min, and the space velocity is 106,000 h -1 。The active evaluation temperature range is 75 - 350 °C. At different temperatures, the catalyst reduces NO x conversion rates are shown in Table 1, and the catalyst selectivities are shown in Table 2.

[0123] Table 1 Activity evaluation results of manganese-based denitration catalysts

[0124]

[0125]

[0126] Table 2 Selectivity evaluation results of manganese-based denitration catalysts

[0127]

[0128] For the MnFeO x catalyst, its optimal temperature point is 200 °C, the NO x conversion rate is 95%, and the temperature window is also relatively narrow. After 200 °C, the conversion rate decreases significantly. When Sm is introduced, the NO x conversion rate and temperature window are significantly improved, and the low-temperature activity is also better. Among them, the 10% SmO x / MnFeO x catalyst shows the best activity and relatively high selectivity, maintaining a conversion rate of over 90% in the range of 75 - 300 °C. As the Sm content continues to increase, its activity shows a deteriorating trend, possibly because the Sm on the catalyst surface gradually increases and agglomerates occur. It can be seen that the introduction of Sm significantly improves the selectivity of the catalyst. The Sm-Mn-Fe / TiO2-0.1 catalyst is a comparative sample involved in the literature. From the activity and selectivity results, it can be seen that the temperature window of the 10% SmO x / MnFeO x catalyst synthesized in the present invention is significantly wider, and the selectivity is also better than that of the comparative sample, which may be related to the spinel support used.

[0129] From the results of other comparative examples, it can be seen that when the metal ion concentration is increased, the activity of the synthesized product is not improved. This is because the increase in metal ion concentration is not conducive to the formation of the spinel structure. In addition, after changing the calcination temperature, the denitrification activities of the catalysts prepared at 500 and 600 °C are both lower than that at 400 °C, indicating that the calcination temperature may have a great influence on the structure or performance of the catalyst. According to the literature, Mn oxides may form different valence states at different calcination temperatures, thus affecting their SCR activity.

[0130] 10% SmMnFeO x (d) Nitric acid was used to replace hydrofluoric acid for etching treatment. Obviously, the treatment effect of HF is better. Treatment with HF can form more defective structures on the carrier surface, which is beneficial to the SCR reaction. 10% SmMnFeO x (e) The sample was synthesized by a one-step method. From the results, it can be seen that both the denitrification activity and N2 selectivity are significantly low. This may be because the Sm-Mn-Fe metal ions undergo hydrothermal reactions simultaneously, failing to form a stable structure but existing in the form of a solid solution, resulting in poor structure and low utilization rate of Sm atoms.

[0131] Next, for 10% SmO x / MnFeO x Catalyst Sm-Mn-Fe / TiO2-0.1 catalyst and MnFeO x were subjected to sulfur and water resistance tests, and the specific implementation is as follows:

[0132] Example 11: The preparation method of the catalyst was the same as that of Example 2. 0.12 g of the catalyst was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, 5% H2O, 50 ppm SO2, and nitrogen was used as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106,000 h -1 . The activity evaluation temperature was 150 °C, and the conversion rate of the catalyst for reducing NO x within 24 h is shown in Figure 1 .

[0133] Example 12: The preparation method of the catalyst was the same as that of Example 4. 0.12 g of the catalyst was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, 5% H2O, 50 ppm SO2, and nitrogen was used as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106000 h -1 . The activity evaluation temperature was 150 °C, and the conversion rate of the catalyst for reducing NO x within 24 h is shown in Figure 1 .

[0134] Example 13: The preparation method of the catalyst was the same as that of Comparative Example 4. 0.12 g of the catalyst was placed in a fixed-bed reactor. The reaction gas composition was 0.05% NO, 0.05% NH3, 5% O2, 5% H2O, 50 ppm SO2, and nitrogen was used as the balance gas. The flow rate of the reaction gas was 300 ml / min, and the space velocity was 106000 h -1 . The activity evaluation temperature was 150 °C, and the NO reduction rate of the catalyst within 24 h x is shown in Figure 1 .

[0135] It can be seen from the results that the 10% SmO x / MnFeO x catalyst had little activity loss after introducing H2O and SO2, and basically maintained a conversion rate of more than 96%. While the MnFeO x catalyst had acceptable activity change after initially adding only water, but the activity continued to decline rapidly after introducing SO2, and the final activity was only about 50%. It can be seen that the introduction of Sm improved the sulfur and water resistance of the Mn-Fe catalyst, and the appropriate amount of Sm could be evenly dispersed on the surface of the MnFeO x support, forming more new active sites. And this is inseparable from the role of HF in the impregnation process. HF has a certain erosion effect on the support surface, forming many surface defects or exposing more internal structures, which can make Sm better and more evenly combined with the support, and at the same time form more acidic centers, which is beneficial to the adsorption and activation process of reaction species.

[0136] In this invention, a series of SmO x / MnFeO x catalysts were prepared by hydrothermally synthesizing the Mn-Fe support and then impregnating different concentrations of Sm. The synthesized ternary manganese-based low-temperature denitration catalyst has excellent low-temperature activity and a wide temperature window, and at the same time has good sulfur and water resistance.

[0137] The synergistic effect between manganese and iron composite oxides significantly increased the Lewis acid sites and Bronsted acid sites on the catalyst surface, which was beneficial to the adsorption and activation of the reactant NH3. After impregnating samarium, the redox ability and denitration selectivity of the catalyst were improved. HF with a certain erosion effect on the support was introduced during the loading process, exposing more defects and internal structures of the support, which was beneficial to the combination of Sm and the support and the formation of a strong interaction, thus showing good denitration performance.

Claims

1. A ternary manganese-based denitration catalyst, characterized in that, The composition of the ternary manganese-based denitration catalyst is expressed as SmO x / MnFeO x , where the range of x is 1-4. According to the molar ratio, the ratio of samarium to manganese and iron is 5-15:

100.

2. The preparation method of the ternary manganese-based denitration catalyst according to claim 1, the method comprising the following steps: synthesizing manganese iron oxide as a precursor by a hydrothermal method, then impregnating with a soluble samarium salt, and obtaining the ternary manganese-based denitration catalyst through calcination.

3. The preparation method according to claim 2, characterized in that, The preparation method includes the following steps: (1) Prepare aqueous solutions containing a soluble manganese salt, a soluble iron salt, a surfactant, a soluble samarium salt, and HF respectively; (2) Take the soluble manganese salt and soluble iron salt solutions obtained in step (1), stir and mix them in a water bath, add a surfactant, then add a precipitant and continue to stir in a water bath to obtain a mixed solution, and carry out a hydrothermal reaction; (3) After the reaction is completed, cool down, perform suction filtration, washing, and drying to obtain MnFeO x ; (4) Add MnFeO x to the samarium salt solution after grinding, and at the same time add HF as a skeleton etchant and stir to obtain a slurry; (5) Dry the slurry prepared in step (4), and then calcine it in a muffle furnace to obtain the ternary manganese-based catalyst.

4. The preparation method according to claim 3, characterized in that, In the aqueous solutions of the soluble manganese and iron salts in step (1), the soluble manganese and iron salts are selected from one or more of iron chloride, iron nitrate, manganese acetate, and manganese nitrate, and the soluble samarium salt is selected from one or more of samarium nitrate and samarium sulfate.

5. The preparation method according to claim 3 or 4, characterized in that, In the soluble manganese salt and soluble iron salt solutions in step (2), the molar ratio of Mn to Fe is 2-3:1, and the precipitant is selected from one or more of urea and ammonium carbonate. Based on the total molar amount of manganese and iron elements being 1 mole, the addition amount of the precipitant is 0.83-1.7 mol.

6. The preparation method according to any one of claims 3-5, characterized in that, The temperature of the hydrothermal reaction in step (2) is 40-80°C, and the time of the hydrothermal reaction is 30-60 minutes; and / or, the temperature of drying in step (3) is 80-120°C, and the time of drying is 12-24 hours.

7. The preparation method according to any one of claims 3-6, characterized in that, In step (4), the particle size after grinding is 200-500 microns; based on the total molar amount of manganese and iron elements being 1 mole, in terms of the molar amount of samarium, the addition amount of the samarium salt is 0.05-0.15 mol; the temperature of the stirring is 50-70°C, and the time of the stirring is 3-6 hours.

8. The preparation method according to any one of claims 3 to 7, characterized in that, In step (5), the temperature of drying is 90-120°C, the time of drying is 12-24 hours, the temperature of calcination is 400-600°C, and the time of calcination is 3-8 hours.

9. The application of the ternary manganese-based denitration catalyst according to claim 1 or the ternary manganese-based denitration catalyst prepared by the preparation method according to any one of claims 2-8 in denitration.

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