Porous lanthanum-cobalt-manganese composite oxide catalyst as well as preparation method and application thereof

Abstract

The invention relates to a porous lanthanum-cobalt-manganese composite oxide catalyst and a preparation method and application thereof, and belongs to the field of new materials. An organic-inorganic self-assembly method is adopted, phenolic resin is compounded with metal hydroxide in an in-situ polymerization mode, a metal-phenolic resin composite precursor is formed, a polymer network framework serves as a template agent, high-temperature roasting is carried out, and the porous lanthanum-cobalt-manganese composite oxide catalyst with the high specific surface area is obtained. The composite oxide catalyst is rich in surface defects and oxygen vacancies, so that the composite oxide catalyst has high-stability CO catalytic oxidation performance at a relatively low temperature.

Description

Technical Field

[0001] The invention relates to a porous lanthanum, cobalt and manganese composite oxide catalyst and a preparation method and application thereof, belonging to the field of new materials. Background Art

[0002] Carbon monoxide (CO), primarily derived from industrial waste and vehicle exhaust, is produced by the incomplete combustion of fossil fuels and is a significant component of atmospheric pollutants. Currently, catalytic oxidation technology is considered the simplest and most effective method for CO purification, with the catalyst being the key. Commonly used catalysts include precious metal catalysts and transition metal oxide catalysts.

[0003] Precious metal catalysts show significantly higher catalytic activity than transition metal oxide catalysts at lower temperatures, but due to the high price of precious metals (Pd, Au, Pt, etc.), it is difficult to apply them on a large scale. Compared with precious metal catalysts, transition metal oxide catalysts have the advantages of large raw material reserves, low price, and variety, such as Co3O4, CuO, MnO x Metal oxides such as 2,4-dioxane and 2,6-dioxane also have strong redox abilities and therefore exhibit good catalytic CO oxidation activity at lower temperatures. For example, Xie et al. reported in Nature, Low-temperature oxidation of CO catalyzed by Co3O4 nanorods, 2009, 9, 458, that nano-Co3O4 with specific crystal faces was prepared by thermal precipitation. The nano-Co3O4 exhibited high catalytic activity at low temperatures, but was significantly affected by humidity.

[0004] Research has found that metal-organic frameworks (MOFs) are porous crystalline materials composed of metals linked by organic ligands. They possess a highly ordered crystal structure, a diverse array of active sites, and adjustable morphologies, promoting the stable dispersion of active components and making them ideal precursors for metal oxide catalysts. Chinese invention patent 201610874791.X discloses a method for preparing a copper-cerium composite oxide material. By precisely controlling reaction conditions and calcining to remove organic ligands, a porous structure is achieved, increasing the material's specific surface area. However, during the high-temperature calcination of the MOF, the MOF collapses, making it impossible to maintain its porous structure. Furthermore, the low yield of MOFs and the high cost of the ligands limit their industrial application.

[0005] Therefore, the development of low-cost, high-performance porous composite oxide catalysts has become the research focus of CO catalytic oxidation reaction. Summary of the Invention

[0006] Based on the shortcomings of current non-precious metal catalytic CO oxidation catalysts, such as a small number of active sites, poor moisture resistance, and low stability, the present invention provides a porous lanthanum, cobalt, and manganese composite oxide catalyst and a preparation method. The composite oxide catalyst has a multi-level pore structure, a stable crystal structure, and a large number of oxygen vacancies. The composite oxide catalyst exhibits good catalytic CO oxidation performance and moisture resistance under relatively low temperature conditions. The preparation method is simple, low-cost, and has broad application prospects.

[0007] The present invention adopts an in-situ polymerization composite method, using an in-situ formed phenolic resin as a template agent to in-situ composite with a metal hydroxide to prepare a metal-phenolic resin composite. The precursor forms an organic-inorganic composite material, and the metal is uniformly distributed in the phenolic resin network structure. The metal-phenolic resin composite is used as a precursor, and the phenolic resin undergoes carbonization and decomposition through high-temperature carbonization and pyrolysis to form a metal and carbon composite material. The carbon is then oxidized and decomposed through high-temperature calcination to produce a porous structure, thereby preparing a porous lanthanum, cobalt and manganese composite oxide. Due to the unique perovskite structure of the composite oxide, abundant oxygen vacancies are provided, thereby improving the stability and moisture resistance of the catalyst. The catalyst contains cobalt and manganese in the perovskite structure, has strong redox ability, and can exhibit efficient and stable catalytic CO oxidation performance at a relatively low reaction temperature.

[0008] A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst comprises the following steps: (1) Add a certain amount of lanthanum salt, cobalt salt and manganese salt to 30 mL of water, stir and disperse them evenly to obtain a mixed solution 1; (2) Add a certain amount of formaldehyde solution (mass concentration 35%) and phenol to 30 mL of ethanol, stir and dissolve to obtain mixed solution 2; (3) Add mixed solution 1 to mixed solution 2, stir and mix well to obtain mixed solution 3; (4) Add a certain amount of ammonia water to the mixed solution 3, adjust the pH value to 8-9, and carry out in situ polymerization for 25-50 hours; (5) centrifuging, washing, and drying the mixed solution after the reaction in step (4) to obtain a metal-phenolic resin composite precursor; (6) The metal-phenolic resin composite precursor of step (5) is pyrolyzed at high temperature under inert gas conditions for 1-5 hours, and then calcined under air atmosphere for 1-3 hours to obtain a porous lanthanum cobalt manganese composite oxide catalyst.

[0009] Preferably, the lanthanum salt in step (1) is lanthanum nitrate, the cobalt salt is cobalt nitrate, and the manganese salt is manganese nitrate.

[0010] Preferably, the molar ratio of the lanthanum salt, the cobalt salt and the manganese salt added in step (1) is 1: (0.3-0.7): (0.3-0.7).

[0011] Preferably, the molar ratio of phenol to formaldehyde in step (2) is 1:(2-5).

[0012] Preferably, the molar ratio of the total metals (lanthanum, cobalt, manganese) to phenol in the mixed solution 3 in step (3) is 1:(1-3).

[0013] The reaction temperature of the reactor in step (4) is preferably 80-100°C.

[0014] Preferably, the centrifugation condition in step (5) is 5000 rpm for 10 min; and the drying condition is 100° C. for 24 h.

[0015] Preferably, the high-temperature pyrolysis temperature of step (6) is 400-600°C, the pyrolysis atmosphere is nitrogen or argon, and the calcination temperature is 400-600°C.

[0016] The porous lanthanum cobalt manganese composite oxide catalyst LaCo prepared by the present invention is preferably x Mn 1-x In O3, x is 0.3-0.7.

[0017] The porous lanthanum, cobalt and manganese composite oxide prepared by the present invention has a unique perovskite structure, provides abundant oxygen vacancies, thereby improving the stability and moisture resistance of the catalyst. The catalyst contains cobalt and manganese in the perovskite structure and has strong redox ability.

[0018] The invention also discloses the application of the porous lanthanum-cobalt-manganese composite oxide catalyst in removing CO from the atmosphere.

[0019] The porous lanthanum cobalt manganese composite oxide catalyst of the present invention: CO catalytic reaction performance test conditions and parameters: initial CO concentration of 10000ppm, O2 concentration of 1-5%, humidity 5-8% H2O, space velocity: 30000h -1 , the particle size of the composite oxide is 20-40 mesh. Beneficial effects

[0020] The present invention utilizes an in-situ polymerization composite method to composite a phenolic resin obtained by in-situ polymerization with a metal hydroxide to prepare a metal-phenolic resin composite. This metal-phenolic resin composite serves as a precursor. High-temperature carbonization and pyrolysis are then performed to carbonize and decompose the phenolic resin, forming a metal-carbon composite material. This composite material is then subjected to high-temperature calcination to oxidize and decompose the carbon, creating a porous structure and preparing a porous lanthanum, cobalt, and manganese composite oxide. The raw materials used are inexpensive, the synthesis and preparation process is simple, and the equipment requirements are minimal. This composite oxide catalyst has a unique perovskite-type structure and porous characteristics, exposing the active metals cobalt and manganese as well as a large number of oxygen vacancies. This allows for high catalytic activity at relatively low reaction temperatures (120-160°C). Furthermore, the perovskite structure exhibits high stability and moisture resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a scanning electron microscope image of the porous lanthanum, cobalt and manganese composite oxide catalyst prepared in Example 1; Figure 2 1-4 and Comparative Examples 1-3 show the CO removal efficiency of the catalysts prepared. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the embodiments, but the protection scope of the present invention is not limited thereto.

[0023] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0024] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are all commercially available unless otherwise specified. Example 1

[0025] A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst comprises: (1) Weigh 10 mmol of lanthanum nitrate, 5 mmol of cobalt nitrate, and 5 mmol of manganese nitrate into 30 mL of water and stir to disperse them evenly to obtain a mixed solution 1.

[0026] (2) Weigh 40 mmol of phenol and a formaldehyde solution (35 wt%) containing 80 mmol of formaldehyde, add them to 30 mL of ethanol, mix well, and obtain mixed solution 2.

[0027] (3) Adding the mixed solution 1 to the mixed solution 2, stirring and mixing uniformly, to obtain a mixed solution 3; wherein the molar ratio of the total metal (lanthanum, cobalt, manganese) to phenol is 1:2.

[0028] (4) Ammonia water was added to the mixture 3 to adjust the pH to 8, and then the mixture was reacted at 80°C for 48 hours, naturally cooled to room temperature, centrifuged at 5000 rpm for 10 minutes, washed, and dried at 100°C for 24 hours to obtain a metal-phenolic resin composite precursor.

[0029] (5) The metal-phenolic resin composite precursor was treated in a nitrogen atmosphere at 500 ° C for 3 hours, and then calcined in an air atmosphere at 500 ° C for 2 hours to obtain a porous lanthanum cobalt manganese composite oxide LaCo 0.5 Mn 0.5 O3.

[0030] After testing, the specific surface area is 81m 2 / g, the morphology of the catalyst is as follows Figure 1 shown.

[0031] (6) Testing porous LaCo 0.5 Mn 0.5 O3 CO removal performance: The initial concentration of CO in the simulated flue gas is 10000ppm, the O2 concentration is 2%, the humidity is 5% H2O, and the air velocity is 30000h -1 The CO removal efficiency is greater than 99.7% above 150°C. Figure 2 shown. Example 2

[0032] A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst comprises: (1) Weigh 10 mmol of lanthanum nitrate, 3 mmol of cobalt nitrate, and 7 mmol of manganese nitrate into 30 mL of water, stir and disperse them evenly to obtain a mixed solution 1.

[0033] (2) Weigh 30 mmol of phenol and a formaldehyde solution (35 wt%) containing 120 mmol of formaldehyde, add them to 30 mL of ethanol, mix well, and obtain mixed solution 2.

[0034] (3) Adding the mixed solution 1 to the mixed solution 2, stirring and mixing, and obtaining a mixed solution 3; wherein the molar ratio of the total metal (lanthanum, cobalt, manganese) to phenol is 1:1.5.

[0035] (4) Ammonia water was added to the mixture 3 to adjust the pH to 8, and then the mixture was reacted at 90°C for 30 hours, naturally cooled to room temperature, centrifuged at 5000 rpm for 10 minutes, washed, and dried at 100°C for 24 hours to obtain a metal-phenolic resin composite precursor.

[0036] (5) The metal-phenolic resin composite precursor was treated at 450 °C in a nitrogen atmosphere for 4 hours, and then calcined at 550 °C in an air atmosphere for 2 hours to obtain a porous lanthanum cobalt manganese composite oxide LaCo 0.3 Mn 0.7 O3, after testing, the specific surface area is 76m 2 / g.

[0037] (6) Testing porous LaCo 0.3 Mn 0.7 The CO removal performance of O3 is simulated with an initial CO concentration of 10,000 ppm and an O2 concentration of 5% in the flue gas; the humidity is 5% H2O, and the air velocity is 30,000 h -1 The CO removal efficiency is greater than 99.7% at temperatures above 140°C. Figure 2 shown. Example 3

[0038] A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst comprises: (1) Weigh 10 mmol of lanthanum nitrate, 4 mmol of cobalt nitrate, and 6 mmol of manganese nitrate into 30 mL of water, stir and disperse them evenly, and obtain a mixed solution 1.

[0039] (2) Weigh 60 mmol of phenol and a formaldehyde solution (35 wt%) containing 150 mmol of formaldehyde, add them to 30 mL of ethanol, mix well, and obtain mixed solution 2.

[0040] (3) Adding the mixed solution 1 to the mixed solution 2, stirring and mixing, and obtaining a mixed solution 3; wherein the molar ratio of the total metal (lanthanum, cobalt, manganese) to phenol is 1:3.

[0041] (4) Ammonia water was added to the mixture 3 to adjust the pH to 9, and then the mixture was reacted at 100°C for 25 hours, naturally cooled to room temperature, centrifuged at 5000 rpm for 10 minutes, washed, and dried at 100°C for 24 hours to obtain a metal-phenolic resin composite precursor.

[0042] (5) The metal-phenolic resin composite precursor was treated in an argon atmosphere at 600 ° C for 1 hour, and then calcined in an air atmosphere at 600 ° C for 1 hour to obtain a porous lanthanum cobalt manganese composite oxide LaCo 0.4 Mn 0.6 O3, after testing, the specific surface area is 69m 2 / g.

[0043] (6) Testing porous LaCo 0.4 Mn 0.6 The CO removal performance of O3 is simulated with an initial CO concentration of 10,000 ppm and an O2 concentration of 3% in the flue gas; the humidity is 5% H2O, and the air velocity is 30,000 h -1 The CO removal efficiency is greater than 99.2% at temperatures above 160°C. Figure 2 shown. Example 4

[0044] A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst comprises: (1) Weigh 10 mmol of lanthanum nitrate, 7 mmol of cobalt nitrate, and 3 mmol of manganese nitrate into 30 mL of water, stir and disperse them evenly to obtain a mixed solution 1.

[0045] (2) Weigh 20 mmol of phenol and a formaldehyde solution (35 wt%) containing 100 mmol of formaldehyde, add them to 30 mL of ethanol, mix well, and obtain mixed solution 2.

[0046] (3) Adding the mixed solution 1 to the mixed solution 2, stirring and mixing, and obtaining a mixed solution 3; wherein the molar ratio of the total metal (lanthanum, cobalt, manganese) to phenol is 1:1.

[0047] (4) Ammonia water was added to the mixture 3 to adjust the pH to 9, and then the mixture was reacted at 90°C for 50 hours, naturally cooled to room temperature, centrifuged at 5000 rpm for 10 minutes, washed, and dried at 100°C for 24 hours to obtain a metal-phenolic resin composite precursor.

[0048] (5) The metal-phenolic resin composite precursor was treated in a nitrogen atmosphere at 400 ° C for 5 hours, and then calcined in an air atmosphere at 400 ° C for 3 hours to obtain a porous lanthanum cobalt manganese composite oxide LaCo 0.7 Mn 0.3 O3, after testing, the specific surface area is 85m 2 / g.

[0049] (6) Testing porous LaCo 0.7 Mn 0.3 The CO removal performance of O3 is simulated with an initial CO concentration of 10,000 ppm and an O2 concentration of 3% in the flue gas; the humidity is 8% H2O, and the air velocity is 30,000 h -1 The CO removal efficiency is greater than 99.7% at temperatures above 160°C. Figure 2 shown. Comparative Example 1

[0050] A method for preparing a catalyst, comprising: (1) Weigh 10 mmol of lanthanum nitrate, 5 mmol of cobalt nitrate, and 5 mmol of manganese nitrate into 30 mL of water and stir to disperse them evenly to obtain a mixed solution 1.

[0051] (2) Ammonia water was added to the mixture 1 to adjust the pH to 8, and then the mixture was reacted at 80°C for 48 hours, naturally cooled to room temperature, centrifuged at 5000 rpm for 10 minutes, washed, and dried at 100°C for 24 hours to obtain a metal precursor.

[0052] (3) The metal precursor was treated in a nitrogen atmosphere at 500 ° C for 3 hours, and then calcined in an air atmosphere at 500 ° C for 2 hours to obtain lanthanum cobalt manganese composite oxide LaCo 0.5 Mn 0.5 O3-NP, with a specific surface area of 12m 2 / g.

[0053] (4) LaCo was tested under the same conditions as in Example 1. 0.5 Mn 0.5 The CO removal performance of O3-NP was tested and found that the catalyst could only achieve the highest CO conversion rate of 94% at 200℃. Figure 2 shown. Comparative Example 2

[0054] A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst comprises: (1) Weigh 10 mmol of lanthanum nitrate, 5 mmol of cobalt nitrate, and 5 mmol of manganese nitrate into 30 mL of water, stir and disperse them evenly to obtain a mixed solution 1.

[0055] (2) Weigh 40 mmol of phenol and add it to 30 mL of ethanol. Mix well to obtain mixed solution 2.

[0056] (3) Add mixed solution 1 to mixed solution 2, stir and mix well to obtain mixed solution 3.

[0057] (4) Ammonia water was added to the mixture 3 to adjust the pH to 8, and then the mixture was reacted at 80°C for 48 hours, cooled naturally to room temperature, centrifuged at 5000 rpm for 10 minutes, washed, and dried at 100°C for 24 hours to obtain a composite precursor.

[0058] (5) The composite precursor was treated in a nitrogen atmosphere at 500 ° C for 3 hours, and then calcined in an air atmosphere at 500 ° C for 2 hours to obtain lanthanum cobalt manganese composite oxide LaCo 0.5 Mn 0.5 O3-NP, specific surface area of 32m 2 / g.

[0059] (6) LaCo was tested under the same conditions as in Example 1. 0.5 Mn 0.5 The CO removal performance of O3-NP has been tested and the CO removal efficiency can only reach 99.1% when the temperature reaches above 180℃. The CO removal efficiency of the catalyst is shown in the figure below. Figure 2 shown. Comparative Example 3

[0060] A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst comprises: (1) Weigh 10 mmol of lanthanum nitrate, 5 mmol of cobalt nitrate, and 5 mmol of manganese nitrate into 30 mL of water and stir to disperse them evenly to obtain a mixed solution 1.

[0061] (2) Weigh a formaldehyde solution (35 wt%) containing 80 mmol of formaldehyde and add it to 30 mL of ethanol. Mix well to obtain mixed solution 2.

[0062] (3) Add mixed solution 1 to mixed solution 2, stir and mix well to obtain mixed solution 3.

[0063] (4) Ammonia water was added to the mixture 3 to adjust the pH to 8, and then the mixture was reacted at 80°C for 48 hours, cooled naturally to room temperature, centrifuged at 5000 rpm for 10 minutes, washed, and dried at 100°C for 24 hours to obtain a composite precursor.

[0064] (5) The composite precursor was treated in a nitrogen atmosphere at 500 ° C for 3 hours, and then calcined in an air atmosphere at 500 ° C for 2 hours to obtain a porous lanthanum cobalt manganese composite oxide LaCo 0.5 Mn 0.5 O3, with a specific surface area of 25m 2 / g.

[0065] (6) LaCo was tested under the same conditions as in Example 1. 0.5 Mn 0.5 The CO removal performance of O3-NP has been tested and the CO removal efficiency can only reach 99.3% when the temperature reaches above 190℃. The CO removal efficiency of the catalyst is shown in the figure below. Figure 2 shown.

[0066] The description herein is provided to enable one of ordinary skill in the art to implement or use the present disclosure. Various modifications to the present disclosure will be apparent to one of ordinary skill in the art, and the overall principles defined herein may be applied to other variations without departing from the scope of the present disclosure. Therefore, the present disclosure is not limited to the examples and designs described herein, but should be given the widest scope consistent with the principles and novel features disclosed herein.

[0067] Although one or more exemplary embodiments of the present disclosure have been described with reference to the drawings, persons skilled in the art will understand that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the following claims.

[0068] Although the present disclosure has been described in detail above using general descriptions and specific embodiments, it will be apparent to those skilled in the art that modifications or improvements may be made based on the embodiments of the present disclosure. Therefore, such modifications or improvements, as long as they do not depart from the spirit of the present disclosure, are within the scope of protection claimed by the present disclosure.

[0069] The foregoing is merely an excerpt from the disclosure, and these modifications may be made to the invention in light of the above detailed description. The terms used in the appended claims should not be construed to limit the invention to the specific embodiments disclosed in the specification. Rather, the scope of the invention is to be determined entirely by the appended claims, which are to be construed in accordance with established doctrines of claim interpretation.

Claims

1. A method for preparing a porous lanthanum-cobalt-manganese composite oxide catalyst, characterized in that: The following steps are involved: Add lanthanum salt, cobalt salt and manganese salt to 30 mL of water, stir and disperse evenly to obtain a mixed solution 1, wherein the molar ratio of the lanthanum salt, cobalt salt and manganese salt is 1:(0.3-0.7):(0.3-0.7); The formaldehyde solution and phenol were added to 30 mL of ethanol and stirred to dissolve to obtain a mixed solution 2, wherein the molar ratio of phenol to formaldehyde was 1:(2-5); Adding the mixed solution 1 to the mixed solution 2 and stirring to mix uniformly to obtain a mixed solution 3, wherein the molar ratio of the total metal (lanthanum, cobalt, manganese) to phenol is 1: (1-3); Add ammonia water to the mixed solution 3 to adjust the pH value to 8-9, and carry out in-situ polymerization for 25-50 hours; The mixed solution after the reaction in step (4) is centrifuged, washed, and dried to obtain a metal-phenolic resin composite precursor; The metal-phenolic resin composite precursor of step (5) is pyrolyzed at high temperature under inert gas conditions for 1-5 hours, and then calcined under air atmosphere for 1-3 hours to obtain a porous lanthanum cobalt manganese composite oxide catalyst.

2. The preparation method according to claim 1, wherein: The lanthanum salt in step (1) is lanthanum nitrate, the cobalt salt is cobalt nitrate, and the manganese salt is manganese nitrate.

3. The preparation method according to claim 1, wherein: The reaction temperature of step (4) is 80-100°C.

4. The preparation method according to claim 1, wherein: In step (5), the centrifugation condition is 5000 rpm for 10 min; and the drying condition is 100° C. for 24 h.

5. The preparation method according to claim 1, wherein: The high-temperature pyrolysis temperature of step (6) is 400-600°C, the pyrolysis atmosphere is nitrogen or argon; and the calcination temperature is 400-600°C.

6. A porous lanthanum, cobalt and manganese composite oxide catalyst prepared by the preparation method according to any one of claims 1 to 5.

7. The porous lanthanum, cobalt and manganese composite oxide catalyst according to claim 6, characterized in that: The porous lanthanum cobalt manganese composite oxide catalyst LaCo x Mn 1-x In O3, x is 0.3-0.

7.

8. Use of the porous lanthanum, cobalt and manganese composite oxide catalyst according to claim 6 in removing CO from the atmosphere.

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