Preparation method of micro-spherical low-temperature ferromanganese-based SCR (Selective Catalytic Reduction) catalyst and catalyst
The preparation of microspherical low-temperature ferromanganese-based SCR catalysts by solvothermal method has solved the problems of poor biotoxicity and low-temperature activity of vanadium-based catalysts in the prior art, and achieved the effect of high-efficiency low-temperature SCR activity and wide temperature window of the ferromanganese-based catalysts.
Patent Information
- Application Number
- CN202510250286.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-04
- Publication Date
- 2025-06-06
AI Technical Summary
In the prior art, vanadium-based catalysts have problems of poor biotoxicity and low-temperature activity, and the sulfur resistance of the ferromanganese-based catalysts is insufficient, making it difficult to adapt to the low-temperature operating conditions of the sintering machine flue gas.
The microspherical low-temperature ferromanganese-based SCR catalyst was prepared by solvothermal method. The complexation of the high-coordination solvent in the mixture of glycerol and ethanol and the metal precursor was promoted to the directional aggregation of nanoparticles and form a microsphere structure.
The prepared microspherical ferromanganese-based catalyst has better low-temperature SCR activity and a wide active temperature window, adapting to more variable reaction temperatures, and the rough surface microspheric morphology provides a larger specific surface area and active sites.
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Figure CN120094600A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the field of catalyst technology, and in particular to a method for preparing a micro-spherical low-temperature manganese iron-based SCR catalyst and a micro-spherical low-temperature manganese iron-based SCR catalyst. Background Art
[0002] Nitrogen oxides (NOx) are one of the main air pollutants produced by the combustion of fossil fuels, mainly including nitric oxide (NO) and nitrogen dioxide (NO2). They not only cause adverse effects on the human body, such as throat irritation, chest tightness, nausea and headache, but also lead to environmental problems such as acid rain, haze, photochemical smog, and greenhouse gas emissions. Therefore, it is urgent to effectively control NOx emissions. Ammonia selective catalytic reduction of NOx (NH3-SCR) technology has many advantages and is considered to be the most mature and effective method to reduce NOx emissions.
[0003] The key to NH3-SCR technology is the catalyst, among which vanadium-based catalysts have become the most commonly used catalysts in NOx emission control due to their excellent resistance to water and sulfur poisoning and low price. However, vanadium itself is biologically toxic and has poor low-temperature activity. The flue gas temperature (120℃~300℃) emitted by the sintering machine does not match the optimal operating temperature window (240~400℃) of the vanadium-based catalyst. An external heat source is also required to increase the flue gas temperature, which in turn increases the operating cost. Manganese-based, iron-based and cerium-based oxides are currently the three most representative non-vanadium oxide catalysts. MnOx has excellent low-temperature SCR activity due to its variable valence state and high-mobility lattice oxygen, but its poor sulfur resistance limits its practical application. Iron-based catalysts exhibit lower low-temperature SCR performance and stronger sulfur resistance. Modification of pure MnOx with iron can effectively widen the temperature window and improve sulfur resistance. In addition, studies have shown that the microscopic morphology of the catalyst has a regulatory effect on its catalytic activity. Therefore, it is of great significance to prepare manganese iron denitrification catalysts with specific microscopic morphology.
[0004] The methods reported so far for preparing denitration catalysts mainly include: coprecipitation method, sol-gel method, impregnation method, hydrothermal method, etc. However, the denitration catalysts obtained by these methods are mainly nanoparticles, which are prone to agglomeration under high-temperature calcination and high-temperature working conditions, which is not conducive to their catalytic application. In order to overcome this problem, researchers have prepared denitration catalysts with different morphologies by regulating the preparation conditions. For example, Liu et al. successfully prepared a new MnOx-CeO2 catalyst with a shell-in-shell microsphere structure by a one-step hydrothermal method. The catalyst has higher redox performance and more acid sites, and the unique structure provides an excellent way for gas transport. Zhang et al. synthesized a nanocage-structured MnxCo3-xO4 catalyst. The hollow and porous structural characteristics of the catalyst provide a larger surface area and more active sites, which can better adsorb and activate the reaction gas.
[0005] Therefore, in view of the above shortcomings, it is necessary to provide a technical solution to overcome or at least alleviate at least one of the above defects of the prior art. Summary of the invention
[0006] The technical problem to be solved by the present application is to provide a method for preparing a micro-spherical low-temperature manganese iron-based SCR catalyst in view of the defects in the prior art.
[0007] In order to solve the above technical problems, the present application provides a method for preparing a micro-spherical low-temperature manganese iron-based SCR catalyst, and the method for preparing a micro-spherical low-temperature manganese iron-based SCR catalyst comprises:
[0008] Obtain a mixture of glycerol and ethanol;
[0009] Adding a manganese-containing precursor, an iron-containing precursor and an auxiliary agent-containing precursor into a mixed solution of glycerol and ethanol and stirring until dissolved, thereby obtaining a first mixed solution;
[0010] The first mixed solution is transferred to a reaction kettle and reacted at 140-200° C. for 8-16 hours to obtain a first precipitate;
[0011] The first precipitate is filtered, washed, dried, and then placed in a muffle furnace in an air environment for calcination at 350-500° C. to obtain a micro-spherical low-temperature manganese-iron-based SCR catalyst.
[0012] Optionally, the manganese content in the manganese-containing precursor is 1 to 99 wt %;
[0013] The iron content in the iron-containing precursor is 99-1 wt %.
[0014] Optionally, the iron-containing precursor is one of ferric chloride and cerium nitrate.
[0015] Optionally, the manganese-containing precursor is one of manganese nitrate and manganese acetate.
[0016] Optionally, the reaction is carried out in a reactor at a reaction temperature of 120 to 180°C; the drying is carried out in an oven at a drying temperature of 60 to 120°C and a drying time of 10 to 15 hours; the calcination is carried out in a muffle furnace at a calcination temperature of 300 to 600°C and a calcination time of 2 to 8 hours.
[0017] Optionally, the ratio of glycerol to ethanol in the glycerol and ethanol mixture is between 6-8.
[0018] Optionally, the ratio of manganese to iron in the microspherical low-temperature manganese-iron-based SCR catalyst is 3:1.
[0019] The present application also provides a micro-spherical low-temperature manganese iron-based SCR catalyst, wherein the micro-spherical low-temperature manganese iron-based SCR catalyst is prepared by the micro-spherical low-temperature manganese iron-based SCR catalyst preparation method as described above.
[0020] The method for preparing the micro-spherical low-temperature manganese iron-based SCR catalyst of the present application has the following beneficial effects:
[0021] (1) The MnaFebOx prepared by this method is in the form of microspheres with a diameter of 1 to 1.3 μm and relatively uniform size. The solvothermal method is used to promote the hydrolysis and self-assembly process of the metal precursor in a high temperature and high pressure environment. The added organic solvent can adjust the polarity and viscosity of the solution, and can also adjust the crystal growth rate through coordination ability, promote the directional aggregation of nanoparticles, and form a microsphere structure. Specifically, glycerol is a high coordination ability solvent containing three hydroxyl groups, which can form [Mn(C3H8O3)x]2+ and [Fe(C3H8O3)y]3+ complexes with Mn2+ / Fe3+. Ethanol reduces the polarity of the system to promote micelle self-assembly, reduce the solvent viscosity, and thus increase the mass transfer rate.
[0022] (2) This method does not use a template agent during the preparation process, which is green and environmentally friendly;
[0023] (3) The preparation process of this method is a common solvent thermal synthesis method, which has a simple preparation process, is easy to operate, and is easy to mass produce. Specifically, the synthesized microspheres have a rough and loose surface, which can provide a larger specific surface area, thereby exposing more acid sites and active sites, thereby promoting the SCR reaction. Activity tests show that the catalyst with microsphere morphology has better low-temperature SCR performance than the catalyst with ordinary nanoparticle morphology, with T50 reduced from 120°C to 50°C, and has a wider active temperature window, which can adapt to more variable reaction temperatures. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Schematic diagram of a process for preparing a micro-spherical low-temperature manganese iron-based SCR catalyst in one embodiment of the present application;
[0025] Figure 2 NH3-SCR activity curves of samples prepared in Example 1, Comparative Example 1 and Comparative Example 2;
[0026] Figure 3 This is the SEM image of the sample prepared in Example 1 of the present application. DETAILED DESCRIPTION
[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.
[0028] Embodiment 1:
[0029] like Figure 1 The method for preparing the micro-spherical low-temperature manganese iron-based SCR catalyst shown includes:
[0030] Obtain a mixture of glycerol and ethanol;
[0031] Adding a manganese-containing precursor, an iron-containing precursor and an auxiliary agent-containing precursor into a mixed solution of glycerol and ethanol and stirring until dissolved, thereby obtaining a first mixed solution;
[0032] The first mixed solution is transferred to a reaction kettle and reacted at 140-200° C. for 8-16 hours to obtain a first precipitate;
[0033] The first precipitate is filtered, washed, dried, and then placed in a muffle furnace in an air environment for calcination at 350-500° C. to obtain a micro-spherical low-temperature manganese-iron-based SCR catalyst.
[0034] In this embodiment, the manganese content in the manganese-containing precursor is 1 to 99 wt %;
[0035] The iron content in the iron-containing precursor is 99-1 wt %.
[0036] In this embodiment, the iron-containing precursor is one of ferric chloride and cerium nitrate.
[0037] In this embodiment, the manganese-containing precursor is one of manganese nitrate and manganese acetate.
[0038] In this embodiment, the reaction is carried out in a reactor, and the reaction temperature is 120-180°C; the drying is carried out in an oven, and the drying temperature is 60-120°C, and the drying time is 10-15h; the calcination is carried out in a muffle furnace, and the calcination temperature is 300-600°C, and the calcination time is 2-8h.
[0039] The ratio of glycerol to ethanol in the glycerol and ethanol mixture is between 6 and 8.
[0040] The ratio of manganese to iron in the micro-spherical low-temperature manganese-iron-based SCR catalyst is 3:1.
[0041] The present application also provides a micro-spherical low-temperature manganese iron-based SCR catalyst, wherein the micro-spherical low-temperature manganese iron-based SCR catalyst is prepared by the micro-spherical low-temperature manganese iron-based SCR catalyst preparation method as described above.
[0042] Example 2 (solvothermal preparation of Mn 3 FeO x Microspheres
[0043] Solvothermal synthesis of Mn 3 FeO x Microspheres:
[0044] Weigh 10 ml of glycerol and 60 mL of ethanol, put them into the same container and stir evenly.
[0045] Add 1.86 mg of manganese nitrate tetrahydrate and 1 mg of ferric nitrate nonahydrate (the molar ratio of manganese to iron is Mn:Fe=3:1), and stir for 1 hour to fully dissolve;
[0046] The solution obtained in (2) was transferred to a hydrothermal reactor, and then transferred to a muffle furnace, and the temperature was increased from room temperature to 180°C at a rate of 5°C / min and kept constant for 12 h, and then washed with deionized water, dried in an oven at 110°C for 12 h, and calcined in a muffle furnace at 450°C for 4 h under air atmosphere to obtain the final sample, which was labeled as Mn 3 FeO x .
[0047] Example 3 (solvothermal method to prepare Mn 5 Fe 3 O x Microspheres
[0048] The Mn5Fe3Ox microspheres were synthesized by the same synthesis method as in Example 1, except that the molar ratio of manganese to iron during the preparation process was Mn:Fe=5:3.
[0049] Example 3 (solvothermal preparation of Mn 3 Fe 5 O x Microspheres
[0050] Mn was synthesized by the same synthesis method as in Example 1. 3 Fe 5 O x The difference is that the molar ratio of manganese to iron in the preparation process is Mn:Fe=3:5.
[0051] Comparative Example 1 (Preparation of Mn by Coprecipitation 3 FeO x -CP (coprecipitation is abbreviated as CP)
[0052] Synthesis of Mn by coprecipitation 3 FeO x Manganese nitrate tetrahydrate and ferric nitrate nonahydrate were dissolved in ethanol and stirred for 4 h. Excess ammonia water was added for coprecipitation reaction. The precipitate was aged overnight, washed, dried in an oven at 110 °C, and calcined in a muffle furnace at 450 °C for 4 h in an air atmosphere to obtain Mn 3 FeO x The catalyst Mn:Fe molar ratio is 3:1
[0053] Figure 2 The denitration efficiency curves of the samples prepared in Example 1, Example 2, Example 3, and Comparative Example 1 are shown in the figure. 3 FeO x The catalyst has the best low-temperature activity, with a NO conversion rate of more than 50% at 50°C. 5 Fe 3 O x and Mn 3 Fe 5 Ox compared to Mn 3 FeO x As the Mn content decreases, the low temperature activity gradually decreases. 3 FeO x -CP is not only less active at low temperatures than Mn with a MnFe ratio of 3:1. 3 FeO x , and the activity drops significantly at high temperatures of 270°C and above.
[0054] Figure 3 This is the SEM of the sample prepared in Example 1. From the figure, we can see that the sample prepared by the solvothermal method (Mn 3 FeO x ) presents a rough microsphere morphology with a diameter of 1 to 1.3 μm and is relatively uniform overall. 3 FeO x -CP is in the form of irregular nanoparticles, such as Figure 3 This shows that the microsphere morphology has an important effect on the Mn a Fe b O x NH 3 -SCR activity has a good promoting effect.
[0055] The specific parameters of the catalysts prepared by Examples 1, 2 and 3 are as follows:
[0056]
[0057] Experimental analysis:
[0058] The SCR performance evaluation of all catalysts was carried out in a fixed bed quartz reactor. The catalyst (40-60 mesh) was placed in a quartz tube with an inner diameter of 6 mm and placed in a resistance furnace with a controlled temperature range of 50-400°C. A Fourier transform infrared spectrometer (Nicolet IS50 FTIR) equipped with a gas cell was used to measure the NH 3 ,NO,N 2 O and NO 2 The total flow rate was 500 mL / min, [NO]: 1000 ppm, [NH 3 ]:1000ppm, [O 2 ]:10%, nitrogen is the balance gas.
[0059] Mn 3 FeO x It shows the best low-temperature activity. According to common sense, increasing the proportion of Mn should enhance the low-temperature performance of the catalyst (Mn has better low-temperature activity than Fe, but is easily deactivated at high temperatures). However, 5 Fe 3 O x It did not show stronger low-temperature activity, Mn 3 Fe 5 O x It showed worse low temperature activity. Therefore, 3 / 1 is the best Mn / Fe ratio for this denitrification catalyst.
[0060] Specifically, since the MnaFebOx prepared in the present application is in the form of microspheres with a diameter of 1 to 1.3 μm, the deactivation phenomenon that should occur at high temperatures in the prior art theoretically does not occur, so that the MnaFebOx prepared in the present application exhibits good low-temperature activity while not experiencing high-temperature deactivation.
[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims
1. A method for preparing a microspherical low-temperature manganese iron-based SCR catalyst, characterized in that: The method for preparing the micro-spherical low-temperature manganese iron-based SCR catalyst comprises: Obtain a mixture of glycerol and ethanol; Adding a manganese-containing precursor, an iron-containing precursor and an auxiliary agent-containing precursor into a mixed solution of glycerol and ethanol and stirring until dissolved, thereby obtaining a first mixed solution; The first mixed solution is transferred to a reaction kettle and reacted at 140-200° C. for 8-16 hours to obtain a first precipitate; The first precipitate is filtered, washed, dried, and then placed in a muffle furnace in an air environment for calcination at 350-500° C. to obtain a micro-spherical low-temperature manganese-iron-based SCR catalyst.
2. The method for preparing a microspherical low-temperature manganese iron-based SCR catalyst according to claim 1, characterized in that: The manganese content in the manganese-containing precursor is 1 to 99 wt%; The iron content in the iron-containing precursor is 99-1 wt %.
3. The method for preparing a microspherical low-temperature manganese iron-based SCR catalyst according to claim 2, characterized in that: The iron-containing precursor is one of ferric chloride and cerium nitrate.
4. The method for preparing a microspherical low-temperature manganese iron-based SCR catalyst according to claim 3, characterized in that: The manganese-containing precursor is one of manganese nitrate and manganese acetate.
5. The method for preparing a microspherical low-temperature manganese iron-based SCR catalyst according to claim 4, characterized in that: The reaction is carried out in a reactor at a temperature of 140 to 200° C.; the drying is carried out in an oven at a temperature of 60 to 120° C. and a drying time of 10 to 15 hours; the calcination is carried out in a muffle furnace at a temperature of 300 to 600° C. and a calcination time of 2 to 8 hours.
6. The method for preparing a microspherical low-temperature manganese iron-based SCR catalyst according to claim 5, characterized in that: The ratio of glycerol to ethanol in the glycerol and ethanol mixture is between 6 and 8.
7. The method for preparing a microspherical low-temperature manganese iron-based SCR catalyst according to claim 6, characterized in that: The ratio of manganese to iron in the micro-spherical low-temperature manganese-iron-based SCR catalyst is 3:
1.
8. A microspherical low-temperature manganese iron-based SCR catalyst, characterized in that: The microspherical low-temperature manganese iron-based SCR catalyst is prepared by the microspherical low-temperature manganese iron-based SCR catalyst preparation method according to any one of claims 1 to 7.