Rare earth lanthanum doped manganese-based composite oxide catalyst as well as preparation method and application thereof
By using rare earth lanthanum-doped manganese-based composite oxide catalysts, the problem of deactivation of manganese-based oxides under high humidity conditions was solved, achieving efficient and stable ozone decomposition.
Patent Information
- Application Number
- CN202511245352.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-02
- Publication Date
- 2025-11-28
AI Technical Summary
Existing manganese-based oxide catalysts are susceptible to deactivation by water molecules during long-term operation, leading to a decrease in ozone decomposition efficiency and difficulty in maintaining stability in high humidity environments.
A rare-earth lanthanum-doped manganese-based composite oxide catalyst is used. By controlling the content of oxygen vacancies and manganese defect sites, combined with a specific contact angle design, competitive adsorption of water molecules is prevented, thereby improving the catalyst's resistance to moisture and its ability to decompose ozone.
Under high humidity conditions, the catalyst maintains a high ozone decomposition efficiency. With an initial concentration of 60-200 ppm, humidity of 0-90%, space velocity of 60,000-240,000 h⁻¹, particle size of 40-60 mesh, and reaction temperature of room temperature, the decomposition efficiency can reach 85%-95%, which significantly improves the stability of the catalyst.
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Figure CN121016733A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a kind of ozone catalytic decomposition catalytic material and its preparation method and application under normal temperature humid environment, belong to gas pollution control field. BACKGROUND
[0002] In recent years, with the rapid development of economy and global industrialization, ground ozone pollution has become a serious problem. Short-term or long-term exposure to ozone environment can cause respiratory diseases, such as asthma, cardiopulmonary disease, cardiovascular disease and even premature death. Therefore, it is urgent to develop safe, efficient and economical ozone elimination methods. At present, heterogeneous catalytic decomposition has become the most promising method due to its high efficiency, low cost and feasibility at room temperature, which has attracted widespread attention. Among various catalysts, manganese-based oxides show relatively high ozone decomposition performance due to their variable valence, diverse morphology, rich surface oxygen vacancies and adjustable phase. Balancing the concentration of [MnO4] tetrahedral and oxygen vacancies in Hausmannite for higher ozone purification [J]. Separation and Purification Technology, 2025, 365 article reports that by adjusting the concentration of [MnO4] tetrahedral structure and oxygen vacancies in manganese oxide, the long-term activity of ozone catalytic decomposition in high humidity environment is improved. By gradually reducing Mn3O4 in hydrogen condition, the ratio of surface oxygen vacancies and tetrahedral structure is optimized while maintaining the spinel structure, realizing the synergistic effect of two kinds of active sites, and significantly improving the stability and efficiency of the catalyst. Transition metal doped cryotolerance-type manganese oxide catalysts for ozone decomposition [J]. Applied Catalysis B: Environmental, 2017, 201:503-510 article reports that replacing K in potassium manganese oxide (OMS-2) structure with Ce 3+ + and Mn 4+ , can increase Mn 3+ The abundance of oxygen vacancies is beneficial for ozone decomposition. The aforementioned studies have all revealed the crucial role of manganese-based oxides in ozone catalysis. However, manganese oxides inevitably suffer severe deactivation during long-term operation, mainly due to the occupation of active sites by water or oxygen-containing intermediates during ozone decomposition. On the one hand, water molecules compete with ozone for adsorption, leading to the occupation of active sites. On the other hand, water may adhere to the catalyst surface and form a dense water film, severely hindering the contact between ozone and the catalytic active centers. Therefore, there is an urgent need to develop a strategy for high activity and long-term stability to ensure that manganese-based catalysts are unaffected by harsh environments. Summary of the Invention
[0003] In view of the current severe ozone pollution situation and the current state of ozone catalyst research, this invention provides rare earth-doped manganese-based oxides, their preparation methods, and applications. The rare earth-doped manganese-based composite oxides prepared by this method have a high content of oxygen vacancies and abundant manganese defect sites, as well as strong redox properties. These high oxygen vacancy content and strong redox properties enable rapid adsorption and decomposition of ozone.
[0004] To achieve this objective, the present invention adopts the following technical solution:
[0005] A rare-earth lanthanum-doped manganese-based composite oxide catalyst is disclosed. The catalyst is a lanthanum-doped manganese-based composite oxide composed of manganese trioxide and manganese pentaoxide, with manganese pentaoxide comprising 10-30% of the composite oxide. The contact angle between the manganese-based composite oxide and water is 30-50°. This specific contact angle prevents competitive adsorption of water and facilitates the participation of water molecules in the ozone decomposition reaction, thereby improving the catalyst's moisture resistance.
[0006] A method for preparing the above-mentioned rare earth lanthanum-doped manganese-based composite oxide catalyst, the method comprising the following steps:
[0007] (1) Add lanthanum salt and manganese salt to a solvent and dissolve to obtain mixture 1;
[0008] (2) Add the precipitant to the solvent and dissolve it to obtain mixture 2;
[0009] (3) Slowly add the mixture 2 from step (2) to the mixture 1 from step (1), stir evenly and adjust the pH value to 10-11, and then stir continuously for 1-5 hours to obtain the mixture 3.
[0010] (4) Aging the mixture obtained in step (3) for 6-24 hours;
[0011] (5) Centrifuge, wash and dry the aged mixture from step (4) to obtain lanthanum-doped basic manganese carbonate precursor.
[0012] (6) The lanthanum-doped basic manganese carbonate precursor from step (5) is calcined to obtain the lanthanum-doped manganese-based composite oxide catalyst.
[0013] In the above preparation method: the lanthanum salt and manganese salt in step (1) are in the form of any one of nitrate, sulfate and chloride; the molar ratio of manganese salt and lanthanum salt is 1:0.01~1.
[0014] In the above preparation method, the solvents used in steps (1) and (2) are either deionized water or anhydrous ethanol.
[0015] In the above preparation method: the precipitant in step (2) is one or a mixture of sodium hydroxide and sodium carbonate.
[0016] In the above preparation method: the molar ratio of manganese salt to precipitant in step (3) is 1:9-15.
[0017] In the above preparation method: the aging temperature in step (4) is 10-120℃.
[0018] In the above preparation method: in step (6), the calcination is carried out by heating at 3-8℃ / min and calcining at 400-700℃ for 2-6 hours.
[0019] In the technical solution of this invention, the catalyst prepared by the above method is used for ozone decomposition.
[0020] This invention provides rare-earth-doped manganese-based oxide catalysts, their preparation methods, and applications. A lanthanum-doped basic manganese carbonate composite precursor is synthesized by gradient co-precipitation of rare-earth metal ions and active ions using various precipitants. This composite precursor is then subjected to high-temperature treatment to form a rare-earth lanthanum-doped manganese-based composite oxide with a specific crystal structure. This composite oxide is composed of lanthanum-doped manganese trioxide and manganese octaoxide. The rare-earth-doped manganese-based composite oxide possesses a high content of oxygen vacancies and abundant manganese defect sites, as well as strong redox properties. These high oxygen vacancy content and strong redox properties enable rapid adsorption and decomposition of ozone.
[0021] The lanthanum-doped manganese-based oxides synthesized in this invention are manganese trioxide and manganese pentaoxide. These composite oxides have a high specific surface area, a multi-level mesoporous-macroporous channel structure, a large number of oxygen vacancies and manganese vacancies, and interface defects.
[0022] The rare-earth-doped manganese oxide prepared in this invention is used for ozone catalytic decomposition, with an initial ozone concentration of 60-200 ppm, a humidity of 0-90%, and a space velocity of 60,000-240,000 h⁻¹. -1 The particle size is 40-60 mesh, and the reaction temperature is room temperature.
[0023] Beneficial effects:
[0024] The ozone decomposition catalyst obtained in this invention is a manganese trioxide phase, exhibiting excellent catalytic activity. At room temperature, it achieves 100% decomposition efficiency for high concentrations of ozone. It also maintains high decomposition efficiency even under high humidity conditions, with the conversion rate remaining at 80%-85% after several hours of reaction at 85%-95% humidity. Compared to single transition metal oxides, it demonstrates higher resistance to humidity. Attached Figure Description
[0025] Figure 1 This is the XRD pattern of Example 3.
[0026] Figure 2 The graphs show the activity evaluation of Examples 1-4 and Comparative Examples 1-3 under dry conditions.
[0027] Figure 3 The graphs show the activity evaluation of Examples 1-4 and Comparative Examples 1-3 under high humidity conditions. Detailed Implementation
[0028] The present invention will be further described below with reference to embodiments, but the scope of protection of the present invention is not limited thereto:
[0029] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.
[0030] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.
[0031] Example 1
[0032] Catalyst preparation
[0033] (1) Weigh 0.23g (0.5mmol) of lanthanum nitrate and 3.56g (10mmol) of manganese nitrate (the molar ratio of lanthanum salt to manganese salt is 0.05:1) and add them to 150ml of deionized water. Stir to obtain a clear solution.
[0034] (2) Weigh 2g of sodium hydroxide (50mmol) and 5.3g of sodium carbonate (50mmol) and add them to 100ml of deionized water. Stir to obtain a clear solution. (The molar ratio of manganese salt to precipitant is 1:10)
[0035] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 10.5 and stir for another 2 hours.
[0036] (4) Place the solution obtained in step (3) at 60°C for 12 hours to age.
[0037] (5) Centrifuge and wash the mixture after the reaction in step (4), and dry it in an oven at 80°C for 12 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0038] (6) The basic rare earth carbonate / metal salt composite precursor from step (5) is placed in a muffle furnace and calcined at 500°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide A.
[0039] Catalyst evaluation
[0040] Evaluation steps (1) Set up the catalyst evaluation device and connect the high-purity oxygen cylinder, gas flow meter, ozone generator, humidifying gas washing bottle, quartz glass reaction tube, ozone detector, and tail gas absorption bottle in sequence with silicone hose and steel pipe. (2) Turn on the high-purity oxygen cylinder, adjust the airflow to 0.25L / min, turn on the ozone generator and adjust the ozone concentration to about 200ppm.
[0041] (3) Load 50 mg of molded catalyst into the quartz glass reaction tube and compact both ends with quartz wool. After the gas flow stabilizes, switch the gas path to the pipeline containing the catalyst, start the reaction timer, and record the outlet ozone concentration periodically. Evaluation results: Under room temperature and dry conditions, the space velocity is 120,000 h⁻¹. -1 The catalyst maintained 100% activity after being exposed to ozone for 6 hours; however, when the relative humidity reached 90%, the catalyst activity decreased to 76% after being exposed to ozone for 6 hours.
[0042] Example 2
[0043] Catalyst preparation
[0044] (1) Weigh 0.43g (1mmol) of lanthanum nitrate and 3.56g (10mmol) of manganese nitrate (the molar ratio of lanthanum salt to manganese salt is 0.1:1) and add them to 150ml of deionized water. Stir to obtain a clear solution.
[0045] (2) Weigh 2g (50mmol) of sodium hydroxide and 5.3g (50mmol) of sodium carbonate and add them to 100ml of deionized water. Stir to obtain a clear solution. (The molar ratio of manganese salt to precipitant is 1:10)
[0046] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 10.2 and stir for another 4 hours.
[0047] (4) Place the solution obtained in step (3) at 80°C for 6 hours to age.
[0048] (5) Centrifuge, wash and dry the mixture after the reaction in step (4) in an 80°C oven for 15 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0049] (6) The basic rare earth carbonate / metal salt composite precursor from step (5) is placed in a muffle furnace and calcined at 700°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide B.
[0050] Catalyst evaluation
[0051] Evaluation steps: Same as in Example 1. Evaluation results: Under room temperature and dry conditions, the space velocity was 120,000 h⁻¹. -1 The catalyst maintained 100% activity after being exposed to ozone for 6 hours; however, when the relative humidity reached 90%, the catalyst activity decreased to 83.2% after being exposed to ozone for 6 hours.
[0052] Example 3
[0053] Catalyst preparation
[0054] (1) Weigh 0.65 g (1.5 mmol) of lanthanum nitrate and 3.56 g (10 mmol) of manganese nitrate (molar ratio of lanthanum salt to manganese salt is 0.15:1) and add them sequentially to 150 ml of deionized water. Stir to obtain a clear solution. (Molar ratio of manganese salt to precipitant is 1:10)
[0055] (2) Weigh 2g (50mmol) sodium hydroxide and 5.3g (50mmol) sodium carbonate and add them to 100ml of deionized water. Stir to obtain a clear solution.
[0056] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 11 and stir for another 2 hours.
[0057] (4) Place the solution obtained in step (3) at 60°C for 12 hours to age.
[0058] (5) Centrifuge, wash and dry the mixture after the reaction in step (4) in an 80°C oven for 18 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0059] (6) The basic rare earth carbonate / metal salt composite precursor from step (5) is placed in a muffle furnace and calcined at 600°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide C.
[0060] Catalyst evaluation
[0061] Evaluation steps: Same as in Example 1. Evaluation results: Under room temperature and dry conditions, the space velocity was 120,000 h⁻¹. -1The catalyst maintained 100% activity after being exposed to ozone for 6 hours; however, when the relative humidity reached 90%, the catalyst activity decreased to 89.6% after being exposed to ozone for 6 hours.
[0062] Example 4
[0063] Catalyst preparation
[0064] (1) Weigh 0.87g (2mmol) of lanthanum nitrate and 3.56g (10mmol) of manganese nitrate (the molar ratio of lanthanum salt to manganese salt is 0.2:1) and add them to 150ml of deionized water. Stir to obtain a clear solution.
[0065] (2) Weigh 2g (50mmol) of sodium hydroxide and 5.3g (50mmol) of sodium carbonate and add them to 100ml of deionized water. Stir to obtain a clear solution. (The molar ratio of manganese salt to precipitant is 1:10)
[0066] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 10-11, and stir for another 2 hours.
[0067] (4) Place the solution obtained in step (3) at 100°C for 12 hours.
[0068] (5) Centrifuge, wash and dry the mixture after the reaction in step (4) in an 80°C oven for 12 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0069] (6) The basic rare earth carbonate / metal salt composite precursor from step (5) is placed in a muffle furnace and calcined at 700°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide D.
[0070] Catalyst evaluation
[0071] Evaluation steps: Same as in Example 1. Evaluation results: Under room temperature and dry conditions, the space velocity was 120,000 h⁻¹. -1 The catalyst maintained 100% activity after being exposed to ozone for 6 hours; however, when the relative humidity reached 90%, the catalyst activity decreased to 80.5% after being exposed to ozone for 6 hours.
[0072] Example 5
[0073] Catalyst preparation
[0074] (1) Weigh 1.30g (3mmol) of lanthanum nitrate and 3.56g (10mmol) of manganese nitrate (the molar ratio of lanthanum salt to manganese salt is 0.3:1) and add them to 150ml of deionized water. Stir to obtain a clear solution.
[0075] (2) Weigh 2g (50mmol) of sodium hydroxide and 5.3g (50mmol) of sodium carbonate and add them to 100ml of deionized water. Stir to obtain a clear solution. (The molar ratio of manganese salt to precipitant is 1:10)
[0076] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 10 and stir for another 2 hours.
[0077] (4) Place the solution obtained in step (3) at 20°C for 12 hours to age.
[0078] (5) Centrifuge, wash and dry the mixture after the reaction in step (4) in an 80°C oven for 12 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0079] (6) The basic rare earth carbonate / metal salt composite precursor from step (5) is placed in a muffle furnace and calcined at 600°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide D.
[0080] Catalyst evaluation
[0081] Evaluation steps: Same as in Example 1. Evaluation results: Under room temperature and dry conditions, the space velocity was 120,000 h⁻¹. -1 The catalyst maintained 100% activity after being exposed to ozone for 6 hours; however, when the relative humidity reached 90%, the catalyst activity decreased to 78.2% after being exposed to ozone for 6 hours.
[0082] Comparative Example 1:
[0083] Catalyst preparation
[0084] (1) Weigh 3.56g (10mmol) of manganese nitrate and add it to 150ml of deionized water. Stir to obtain a clear solution.
[0085] (2) Weigh 2g (50mmol) of sodium hydroxide and 5.3g (50mmol) of sodium carbonate and add them to 100ml of deionized water. Stir to obtain a clear solution. (The molar ratio of manganese salt to precipitant is 1:10)
[0086] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 11 and stir for another 2 hours.
[0087] (4) Place the solution obtained in step (3) at 60°C for 12 hours to age.
[0088] (5) Centrifuge, wash and dry the mixture after the reaction in step (4) in an 80°C oven for 12 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0089] (6) The metal salt precursor from step (5) is placed in a muffle furnace and calcined at 500°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide E.
[0090] Catalyst evaluation
[0091] Evaluation steps: Same as in Example 1. Evaluation results: Under room temperature and dry conditions, the space velocity was 120,000 h⁻¹. -1 The catalyst maintained 70% activity after 6 hours of ozone introduction; however, when the relative humidity reached 90%, the catalyst activity decreased to 30% after 6 hours of ozone introduction.
[0092] Comparative Example 2:
[0093] Catalyst preparation
[0094] (1) Weigh 0.43g (1mmol) of lanthanum nitrate and 3.56g (10mmol) of manganese nitrate (the molar ratio of lanthanum salt to manganese salt is 0.1:1) and add them to 150ml of isopropanol. Stir to obtain a clear solution.
[0095] (2) Weigh 2g (50mmol) of sodium hydroxide and 5.3g (50mmol) of sodium carbonate and add them to 100ml of deionized water. Stir to obtain a clear solution. (The molar ratio of manganese salt to precipitant is 1:10)
[0096] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 11 and stir for another 4 hours.
[0097] (4) Place the solution obtained in step (3) at 80°C for 6 hours to age.
[0098] (5) Centrifuge, wash and dry the mixture after the reaction in step (4) in an 80°C oven for 15 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0099] (6) The basic rare earth carbonate / metal salt composite precursor from step (5) is placed in a muffle furnace and calcined at 700°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide F.
[0100] Catalyst evaluation
[0101] Evaluation steps: Same as in Example 1. Evaluation results: Under room temperature and dry conditions, the space velocity was 120,000 h⁻¹. -1 The catalyst maintained 75% activity after 6 hours of ozone introduction; however, when the relative humidity reached 90%, the catalyst activity decreased to 45% after 6 hours of ozone introduction.
[0102] Comparative Example 3:
[0103] Catalyst preparation
[0104] (1) Weigh 0.43g (1mmol) of lanthanum nitrate and 3.56g (10mmol) of manganese nitrate (the molar ratio of lanthanum salt to manganese salt is 0.1:1) and add them to 150ml of deionized water. Stir to obtain a clear solution.
[0105] (2) Weigh 1 g (25 mmol) of sodium hydroxide and 2.4 g (25 mmol) of ammonium carbonate and add them to 100 ml of deionized water. Stir to obtain a clear solution. (The molar ratio of manganese salt to precipitant is 1:5)
[0106] (3) Add the solution obtained in step (2) to the solution obtained in step (1) and stir until homogeneous. Adjust the pH of the solution to 10.2 and stir for another 4 hours.
[0107] (4) The solution obtained in step (3) is aged at 80°C for 6 hours.
[0108] (5) Centrifuge, wash and dry the mixture after the reaction in step (4) in an 80°C oven for 15 hours to obtain the basic rare earth carbonate / metal salt composite precursor.
[0109] (6) The basic rare earth carbonate / metal salt composite precursor from step (5) is placed in a muffle furnace and calcined at 700°C for 5 hours at a heating rate of 5°C / min to obtain lanthanum-doped manganese-based oxide F.
[0110] Catalyst evaluation
[0111] Evaluation steps: Same as in Example 1. Evaluation results: Under room temperature and dry conditions, the space velocity was 120,000 h⁻¹. -1 The catalyst maintained 77% activity after 6 hours of ozone introduction; however, when the relative humidity reached 90%, the catalyst activity decreased to 37.5% after 6 hours of ozone introduction.
Claims
1. A rare earth lanthanum-doped manganese-based composite oxide catalyst, characterized in that: The catalyst is a lanthanum-doped manganese-based composite oxide, which is composed of manganese trioxide and manganese pentaoxide, with manganese pentaoxide accounting for 10-30% of the manganese-based composite oxide. The contact angle between the manganese-based composite oxide and water is 30-50°.
2. A method for preparing the rare earth lanthanum-doped manganese-based composite oxide catalyst according to claim 1, characterized in that, The method includes the following steps: (1) Add lanthanum salt and manganese salt to a solvent and dissolve to obtain mixture 1; (2) Add the precipitant to the solvent and dissolve it to obtain mixture 2; (3) Slowly add the mixture 2 from step (2) to the mixture 1 from step (1), stir evenly and adjust the pH value to 10-11, and then stir continuously for 1-5 hours to obtain the mixture 3. (4) Aging the mixture obtained in step (3) for 6-24 hours; (5) Centrifuge, wash and dry the aged mixture from step (4) to obtain lanthanum-doped basic manganese carbonate precursor. (6) The lanthanum-doped basic manganese carbonate precursor from step (5) is calcined to obtain the lanthanum-doped manganese-based composite oxide catalyst.
3. The method according to claim 2, characterized in that: The lanthanum salt and manganese salt mentioned in step (1) are in the form of any one of nitrate, sulfate and chloride; the molar ratio of manganese salt and lanthanum salt is 1:0.01 to 1.
4. The method according to claim 2, characterized in that: The solvents used in steps (1) and (2) are either deionized water or anhydrous ethanol.
5. The method according to claim 2, characterized in that: The precipitant mentioned in step (2) is one or a mixture of sodium hydroxide and sodium carbonate.
6. The method according to claim 2, characterized in that: In step (3), the molar ratio of manganese salt to precipitant is 1:9-15.
7. The method according to claim 2, characterized in that: The aging temperature in step (4) is 10-120℃.
8. The method according to claim 2, characterized in that: In step (6), the calcination is carried out by raising the temperature by 3-8℃ / min and calcining at 400-700℃ for 2-6 hours.
9. The catalyst prepared by the method of claim 2 is used for ozone decomposition.
10. The application according to claim 9, characterized in that, The initial ozone concentration is 60-200 ppm, the humidity is 0-90%, and the space velocity is 60,000-240,000 h⁻¹. -1 .