High-activity denitration catalyst and preparation method thereof
By doping vanadium oxide into cerium-based catalysts, a highly exposed crystalline catalytic material with a coupled structure of single atoms and nanoparticles is formed, which solves the problem of narrow temperature window of existing denitrification catalysts and achieves efficient denitrification at both low and high temperatures.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHINA CITY ENVIRONMENT PROTECTION ENGINEERING LIMITED COMPANY
- Filing Date
- 2024-02-28
- Publication Date
- 2026-07-24
AI Technical Summary
Existing denitrification catalysts have a narrow temperature window and cannot simultaneously meet the denitrification requirements in both high-temperature and low-temperature regions, especially exhibiting poor denitrification performance in low-temperature regions.
By doping vanadium oxide into cerium-based catalysts, a synergistic catalytic effect between single atoms and nanoparticles is formed, and a highly exposed crystal plane-anchored single-atom coupled catalytic material is prepared. Combined with VOx nanoparticle loading, the denitrification activity at low and high temperatures is improved.
It achieves high-efficiency denitrification performance over a wide temperature range, exhibiting excellent catalytic activity at low temperatures and maintaining good catalytic performance at high temperatures, providing a highly efficient catalytic solution for industrial exhaust gas purification.
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Figure CN118162126B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of flue gas pollution control technology, specifically relating to a highly active denitrification catalyst and its preparation method. Background Technology
[0002] Nitrogen oxides (NO) x NO is one of the major air pollutants in my country. x Excessive emissions cause a series of environmental problems, including ozone layer depletion, photochemical smog, haze, and acid rain. These problems not only damage socio-economic development and ecosystems but also seriously affect human health and daily life. In recent years, selective catalytic reduction (SCR) denitrification technology has been widely used in flue gas denitrification. Among them, selective catalytic reduction (NH3-SCR) technology using NH3 as a reducing agent is a promising denitrification technology for removing NO from industrial exhaust gases. x One of the most effective methods. Currently, the most widely used commercial catalysts in industrial applications are mainly V2O5-MoO3 / WO3-TiO2, with a relatively high temperature range of 300-400℃. However, after actual industrial flue gas passes through bag filters for dust removal and desulfurization, the temperature drop is relatively low. Existing high-temperature denitrification catalysts have poor denitrification performance in the low-temperature range and cannot meet the denitrification requirements. Therefore, there is an urgent need to develop efficient low-temperature denitrification catalysts for flue gas emission reduction.
[0003] Cerium-based (CeO2) catalysts possess abundant electronic defects, resulting in high oxygen storage / release capacity (OSC) and strong redox properties, which can enhance low-temperature catalytic activity. Therefore, Ce-based catalysts have become a research hotspot in the field of low-temperature denitrification, and composite cerium-based catalysts exhibit even superior catalytic performance. In recent years, the influence of crystal facet engineering or morphology control on catalytic performance has attracted widespread attention. Morphology and crystal facet effects play important roles in regulating the anti-poisoning properties of CeO2, improving low-temperature activity, and influencing surface oxygen vacancy concentration and acidic sites. Various CeO2 nanomaterials with different morphologies and exposed crystal faces, such as nanocubes, nanorods, nanospheres, nanosheets, and nanooctahedrons, have been synthesized using different methods. By doping and controlling the exposed crystal faces to modulate the electronic configuration of the material, the SCR activity of the denitrification catalyst can be effectively improved. Summary of the Invention
[0004] The purpose of this invention is to overcome the problem that existing denitrification catalysts have a narrow temperature window and cannot simultaneously meet the denitrification requirements in high and low temperature regions.
[0005] Therefore, the present invention provides a method for preparing a highly active denitrification catalyst, comprising the following steps:
[0006] (1) Dissolve vanadium salt in oxalic acid solution, and add cerium salt solution dropwise to obtain a mixed salt solution;
[0007] (2) Add alkali solution dropwise to the mixed salt solution until the pH of the solution reaches 8-12, then stop adding the solution and continue stirring and reacting to obtain a mixed slurry.
[0008] (3) The mixed slurry is filtered, washed, dried, crushed and calcined to obtain calcined powder;
[0009] (4) Weigh a certain amount of oxalic acid and vanadium salt, dissolve them in water, add the sample after calcination in step (3), and stir to react.
[0010] (5) After the reaction is completed, the sample is dried, crushed and calcined to obtain a highly active denitrification catalyst.
[0011] Specifically, in step (1) above, the vanadium salt includes one or more of ammonium metavanadate, vanadium oxalate, and vanadium oxalate; the cerium salt includes one or more of cerium nitrate, cerium sulfate, ammonium cerium nitrate, and cerium chloride.
[0012] Specifically, in step (1) above, the vanadium oxide doping amount is controlled to be 0-3%.
[0013] Specifically, the alkaline solution in step (2) above includes one or more of the following: sodium carbonate solution, potassium carbonate solution, sodium hydroxide solution, and ammonia water.
[0014] Specifically, step (2) above involves adding alkali solution dropwise to the mixed salt solution at 40-80℃ until the solution pH reaches 8-12, stopping the addition, continuing to stir for 4-8 hours, and then reacting at 80-220℃ for 8-24 hours.
[0015] Specifically, in step (3) above, the roasting temperature is 400-600℃ and the roasting time is 4-10h.
[0016] Specifically, in step (4) above, the vanadium oxide loading is controlled to be 0-3%.
[0017] Specifically, after adding the calcined powder in step (4) above, stir and react at 40-80℃ for 2-4 hours.
[0018] Specifically, in step (5) above, the calcination temperature is 400-600℃ and the calcination time is 4-10h.
[0019] Compared with the prior art, the present invention has the following advantages and beneficial effects:
[0020] The method for preparing this highly active denitration catalyst provided by the present invention involves designing and screening the formulation to dope V species into CeO2 with different exposed morphologies to form V single atoms, while simultaneously loading VO on the surface. xNanoparticles form a synergistic catalytic effect between single atoms and nanoparticles. The resulting highly exposed crystal-faceted anchored single-atom coupled catalytic material provides sufficient adsorption sites for reactants and enhances the activation efficiency of reactants and the conversion efficiency of intermediate species. It achieves excellent low-temperature denitrification activity while maintaining good high-temperature denitrification activity, providing highly efficient catalytic performance for the purification of industrial exhaust gases. This is of great significance in helping the steel industry achieve ultra-low emissions.
[0021] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description
[0022] Figure 1 This is the SCR activity test result in Example 3 of the present invention. Detailed Implementation
[0023] The technical solutions of the present invention will be clearly and completely described below with reference to embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Although representative embodiments of the present invention have been described in detail, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.
[0024] This invention provides a method for preparing a highly active denitration catalyst, comprising the following steps:
[0025] (1) Weigh a certain amount of cerium salt and dissolve it in deionized water. Stir for 0.5-3 hours until it is completely dissolved and set aside for later use. The cerium salt includes one or more of cerium nitrate, cerium sulfate, cerium ammonium nitrate, and cerium chloride.
[0026] Weigh a certain amount of oxalic acid and dissolve it in deionized water, then add a certain amount of vanadium salt and stir for 0.5-3 hours to ensure complete dissolution. Control the vanadium oxide doping amount to 0-3%, preferably 0.1-3%. After complete dissolution, slowly add the above cerium salt solution dropwise and stir for 0.5-3 hours to mix evenly to obtain a mixed salt solution.
[0027] The vanadium salt includes one or more of ammonium metavanadate, vanadium oxalate, and vanadium oxalate oxyacetate.
[0028] (2) Weigh a certain amount of alkali and dissolve it in deionized water. Stir for 0.5-3 hours to ensure complete dissolution, and prepare a 0.5-2 mol / L solution. The alkali solution includes one or more of sodium carbonate solution, potassium carbonate solution, sodium hydroxide solution, and ammonia solution.
[0029] Place the mixed salt solution in a water bath at 40-80℃, then add 0.5-2 mol / L alkali solution dropwise until the pH of the solution reaches 8-12. Stop adding the solution and continue stirring at 40-80℃ for 4-8 hours. Then transfer the slurry to a polytetrafluoroethylene liner and place it at 80-220℃ for 8-24 hours to obtain the mixed slurry.
[0030] (3) The mixed slurry was filtered and washed until the pH of the filtrate was 7. The filter cake was placed in an oven at 60-120℃ for 6-12 hours to dry the moisture. The dried filter cake was then ground and calcined in a muffle furnace at 400-600℃ under an oxygen atmosphere for 4-10 hours to obtain the calcined sample. The sample morphology included nanorods, nanospheres, nanosheets, and nanooctahedrons.
[0031] (4) Weigh a certain amount of oxalic acid and vanadium salt and dissolve them in water. Stir for 0.5-3 hours to ensure complete dissolution. Control the vanadium oxide loading to be 0-3%, preferably 0.1-3%. Slowly add the calcined sample to the solution and stir the mixture at 40-80°C for 2-4 hours.
[0032] (5) After the reaction is complete, the sample is placed in an oven at 80-120℃ for 12-24 hours to dry it, then ground into powder, and calcined in a muffle furnace at 400-600℃ under an oxygen atmosphere for 4-10 hours to obtain a highly active crystal-anchored single-atom denitration catalyst. The denitration catalyst is pressed into tablets and sieved to make 20-100 mesh particles.
[0033] The effects of the highly active denitrification catalyst and its preparation method of the present invention will be studied through specific embodiments below.
[0034] Example 1:
[0035] This embodiment provides a highly active denitrification catalyst, which is prepared through the following steps.
[0036] 1. Weigh 25.23g of cerium nitrate and dissolve it in deionized water, stirring for 2 hours until completely dissolved.
[0037] 2. Weigh 0.21g of oxalic acid and dissolve it in deionized water. Then add 0.13g of ammonium metavanadate and stir for 1 hour to completely dissolve it, so that the vanadium oxide loading is 1%. After it is completely dissolved, slowly add it dropwise to the cerium nitrate solution and stir for 2 hours to mix it evenly.
[0038] 3. Weigh 40g of sodium hydroxide and dissolve it in deionized water. Stir for 1 hour to ensure complete dissolution and prepare a 1mol / L solution for later use.
[0039] 4. Place the prepared solution containing cerium nitrate and ammonium metavanadate in a 60°C water bath, and then add 1 mol / L sodium hydroxide solution dropwise until the pH of the solution reaches 10. Continue stirring in the 60°C water bath for 4 hours.
[0040] 5. Transfer the above slurry to a 250 mL polytetrafluoroethylene liner and react in an oven at 180°C for 12 h. Then filter and wash the reacted slurry until the pH of the filtrate is 7, and place the filter cake in an oven at 100°C for 12 h.
[0041] 6. Grind the dried filter cake into powder and calcine it in an oxygen atmosphere in a muffle furnace at 500℃ for 6 hours to obtain the desired 1V2O5@CeO2 nanospheres.
[0042] 7. Weigh 0.41g of oxalic acid and dissolve it in deionized water. Then add 0.27g of ammonium metavanadate and stir for 1 hour to completely dissolve it. Then slowly add 10g of the above-mentioned calcined powder and stir in a water bath at 60°C for 4 hours.
[0043] 8. After the reaction was completed, the sample was placed in a 100℃ oven for 12 hours to dry it. Then the filter cake was ground into powder and calcined in an oxygen atmosphere in a muffle furnace at 500℃ for 6 hours to obtain a highly active denitrification catalyst, labeled as 2V2O5 / 1V2O5@CeO2.
[0044] 9. Compress the highly active denitrification catalyst into tablets and sieve them to form 40-60 mesh particles for activity evaluation.
[0045] Example 2:
[0046] This embodiment provides a highly active denitrification catalyst, which is prepared through the following steps.
[0047] 1. Weigh 25.23g of cerium nitrate and dissolve it in deionized water, stirring for 2 hours until completely dissolved.
[0048] 2. Weigh 0.43g of oxalic acid and dissolve it in deionized water. Then add 0.27g of ammonium metavanadate and stir for 1 hour to completely dissolve it, so that the vanadium oxide loading is 2%. After it is completely dissolved, slowly add it dropwise to the cerium nitrate solution and stir for 2 hours to mix it evenly.
[0049] 3. Weigh 40g of sodium hydroxide and dissolve it in deionized water. Stir for 1 hour to ensure complete dissolution and prepare a 1mol / L solution for later use.
[0050] 4. Place the prepared solution containing cerium nitrate and ammonium metavanadate in a 60°C water bath, and then add 1 mol / L sodium hydroxide solution dropwise until the pH of the solution reaches 10. Continue stirring in the 60°C water bath for 4 hours.
[0051] 5. Transfer the above slurry to a 250 mL polytetrafluoroethylene liner and react in an oven at 180°C for 12 h. Then filter and wash the reacted slurry until the pH of the filtrate is 7, and place the filter cake in an oven at 100°C for 12 h.
[0052] 6. Grind the dried filter cake into powder and calcine it in an oxygen atmosphere in a muffle furnace at 500℃ for 6 hours to obtain the desired 2V2O5@CeO2 nanospheres.
[0053] 7. Weigh 0.21g of oxalic acid and dissolve it in deionized water. Then add 0.13g of ammonium metavanadate and stir for 1 hour to dissolve it completely. Then slowly add 10g of the above-mentioned calcined powder and stir in a water bath at 60°C for 4 hours.
[0054] 8. After the reaction was completed, the sample was placed in a 100℃ oven for 12 hours to dry it. Then the filter cake was ground into powder and calcined in an oxygen atmosphere in a muffle furnace at 500℃ for 6 hours to obtain a highly active denitrification catalyst, labeled as 1V2O5 / 2V2O5@CeO2.
[0055] 9. Compress the highly active denitrification catalyst into tablets and sieve them to form 40-60 mesh particles for activity evaluation.
[0056] Comparative Example 1:
[0057] This comparative example provides a catalyst in which V2O5 is completely coated on the outside of CeO2 nanospheres, prepared by the following steps.
[0058] 1. Weigh 25.23g of cerium nitrate and dissolve it in deionized water, stirring for 2 hours until completely dissolved.
[0059] 2. Weigh 40g of sodium hydroxide and dissolve it in deionized water. Stir for 1 hour to ensure complete dissolution and prepare a 1mol / L solution for later use.
[0060] 3. Place the prepared cerium nitrate solution in a 60°C water bath, and then add 1 mol / L sodium hydroxide solution dropwise until the pH of the solution reaches 10. Continue stirring in the 60°C water bath for 4 hours.
[0061] 4. Transfer the above slurry to a 250 mL polytetrafluoroethylene liner and react in an oven at 180°C for 12 h. Then filter and wash the reacted slurry until the pH of the filtrate is 7. Place the filter cake in an oven at 100°C for 12 h.
[0062] 5. Grind the dried filter cake into powder and calcine it in an oxygen atmosphere in a muffle furnace at 500℃ for 6 hours to obtain the desired CeO2 nanospheres.
[0063] 6. Weigh 0.65g of oxalic acid and dissolve it in deionized water. Then add 0.41g of ammonium metavanadate and stir for 1 hour to completely dissolve it. Then slowly add 10g of the above-mentioned calcined powder and stir in a water bath at 60°C for 4 hours.
[0064] 7. After the reaction was completed, the sample was placed in an oven at 100℃ for 12 hours to dry it. Then the filter cake was ground into powder and calcined in an oxygen atmosphere at 500℃ for 6 hours. The resulting catalyst was labeled as 3V2O5 / CeO2.
[0065] 8. Compress the catalyst into tablets and sieve them to make 40-60 mesh particles for activity evaluation.
[0066] Comparative Example 2:
[0067] This comparative example provides a catalyst in which all V2O5 is incorporated into CeO2, prepared by the following steps.
[0068] 1. Weigh 25.23g of cerium nitrate and dissolve it in deionized water, stirring for 2 hours until completely dissolved.
[0069] 2. Weigh 0.65g of oxalic acid and dissolve it in deionized water. Then add 0.41g of ammonium metavanadate and stir for 1 hour to completely dissolve it, so that the vanadium oxide loading is 3%. After it is completely dissolved, slowly add it dropwise to the cerium nitrate solution and stir for 2 hours to mix it evenly.
[0070] 3. Weigh 40g of sodium hydroxide and dissolve it in deionized water. Stir for 1 hour to ensure complete dissolution and prepare a 1mol / L solution for later use.
[0071] 4. Place the prepared solution containing cerium nitrate and ammonium metavanadate in a 60°C water bath, and then add 1 mol / L sodium hydroxide solution dropwise until the pH of the solution reaches 10. Continue stirring in the 60°C water bath for 4 hours.
[0072] 5. Transfer the above slurry to a 250 mL polytetrafluoroethylene liner and react in an oven at 180°C for 12 h. Then filter and wash the reacted slurry until the pH of the filtrate is 7, and place the filter cake in an oven at 100°C for 12 h.
[0073] 6. Grind the dried filter cake into powder and calcine it in an oxygen atmosphere in a muffle furnace at 500℃ for 6 hours. The resulting catalyst is denoted as 3V2O5@CeO2.
[0074] 7. Compress the catalyst into tablets and sieve them to make 40-60 mesh particles for activity evaluation.
[0075] Example 3:
[0076] This embodiment evaluates the SCR activity of the catalysts prepared in Examples 1-2 and Comparative Examples 1-2.
[0077] 0.25 g of catalyst was loaded into a quartz fixed-bed reactor (0.6 cm inner diameter), and the reaction gas was purged with 500 ppm NO, 500 ppm NH3, 5 vol% O2, and He (>99.999%) as a balance gas. The volume hourly space velocity (VHSV) was 100,000 h⁻¹. -1 Before activity testing, samples were pretreated for 1 hour in a He atmosphere (>99.999%) at 500℃. The reactor was continuously regulated using a temperature controller, with a heating rate of 2℃ / min during evaluation. The reactor temperature was monitored using thermocouples inserted into the catalyst bed, maintaining temperatures from 120 to 450℃, and data were collected after stabilizing at each temperature point for half an hour. Flue gas analysis was used to calculate the NO conversion rate. The NO conversion rates of the catalyst at different temperature points are shown below. Figure 1 .
[0078] Depend on Figure 1 It is known that the 3V2O5 / CeO2 formed by completely coating V2O5 onto CeO2 via impregnation exhibits relatively poor low-temperature NO conversion, with only 68% NO conversion at 180℃. While the catalyst formed by directly incorporating all V2O5 into CeO2 via a one-step hydrothermal method shows relatively excellent low-temperature activity (89% NO conversion at 180℃), its high-temperature activity drops significantly. However, the method provided in this application, which involves doping a portion of V2O5 into CeO2 to form nanoparticles and then coating a portion of V2O5 onto these nanoparticles to construct a composite structure of single-atom and nanoparticle coupling, not only demonstrates excellent low-temperature activity but also good high-temperature activity with a relatively wide temperature window. This indicates that the coupled structure of single atoms and nanoparticles can facilitate the adsorption and activation of reactants while also inhibiting the over-oxidation of NH3 species, thereby effectively improving the catalytic activity of the SCR reaction.
[0079] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.
Claims
1. A method for preparing a highly active denitration catalyst, characterized in that, Includes the following steps: (1) Dissolve vanadium salt in oxalic acid solution, and add cerium salt solution dropwise to obtain a mixed salt solution; (2) Add alkali solution dropwise to the mixed salt solution at 40-80℃ until the pH of the solution reaches 8-12, stop adding, continue stirring for 4-8h, and then react at 180-220℃ for 8-24h. (3) The mixed slurry is filtered, washed, dried, crushed and calcined to obtain the calcined sample; (4) Weigh a certain amount of oxalic acid and vanadium salt, dissolve them in water, add the sample after calcination in step (3), and stir to react; (5) After the reaction is completed, the sample is dried, crushed and calcined to obtain a highly active denitrification catalyst.
2. The method for preparing the highly active denitration catalyst as described in claim 1, characterized in that: In step (1), the vanadium salt includes one or more of ammonium metavanadate, vanadium oxalate, and vanadium oxalate; the cerium salt includes one or more of cerium nitrate, cerium sulfate, cerium ammonium nitrate, and cerium chloride.
3. The method for preparing the highly active denitrification catalyst as described in claim 1, characterized in that: In step (1), the vanadium oxide doping amount is controlled to be 0.1-3%.
4. The method for preparing the highly active denitration catalyst as described in claim 1, characterized in that: The alkaline solution in step (2) includes one or more of the following: sodium carbonate solution, potassium carbonate solution, sodium hydroxide solution, and ammonia water.
5. The method for preparing the highly active denitrification catalyst as described in claim 1, characterized in that: In step (3), the roasting temperature is 400-600℃ and the roasting time is 4-10h.
6. The method for preparing the highly active denitrification catalyst as described in claim 1, characterized in that: In step (4), the vanadium oxide loading is controlled to be 0.1-3%.
7. The method for preparing the highly active denitration catalyst as described in claim 1, characterized in that: After adding the calcined powder in step (4), stir and react at 40-80℃ for 2-4 hours.
8. The method for preparing the highly active denitration catalyst as described in claim 1, characterized in that: In step (5), the calcination temperature is 400-600℃ and the calcination time is 4-10h.
9. The highly active denitrification catalyst prepared by the preparation method according to any one of claims 1-8.