Co3o4-based supported catalyst, preparation method and application thereof

Abstract

The application provides a preparation method of a Co3O4-based supported catalyst, and comprises the following steps: S1, dissolving cobalt acetylacetonate and cetyltrimethylammonium bromide in a mixed solution of ethylene glycol and deionized water, performing a hydrothermal reaction, performing centrifugal drying, and then calcining at 300-320 DEG C for 3h at a temperature increasing rate of 2-5 DEG C per minute ‑1 to obtain 2D Co3O4; S2, dissolving La(NO3)3.6H2O and urea in deionized water, adding the 2D Co3O4, uniformly stirring, and then performing a hydrothermal reaction, performing centrifugal drying, and then calcining at 400-600 DEG C for 2-4h at a temperature increasing rate of 3-5 DEG C per minute ‑1 to obtain a 2D Co3O4 / La2O2CO3 catalyst. The catalyst provided by the application is rich in active sites, has high catalytic activity and good thermal stability, can be used for catalytic combustion of low-concentration methane, and the preparation method provided by the application is simple and efficient, and is suitable for popularization and use.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of atmospheric governance, and relates to a Co3O4-based supported catalyst, a preparation method and application thereof, in particular to the application of the Co3O4-based supported catalyst in catalytic combustion of low-concentration methane. BACKGROUND

[0002] In the new development period of the world today, climate and environmental governance has become an important part of building a community with a shared future for mankind. Among the harmful chemical pollutants that deteriorate air quality, volatile organic compounds (VOCs) are important precursors of the troposphere ozone and make a great contribution to the process of generating ozone through photochemical reaction. In addition, VOCs can react with NOx / SO2 under the condition of atmospheric environmental ultraviolet radiation to produce secondary aerosols, ozone and photochemical smog, and have characteristics such as easy diffusion, toxicity and volatility, which can cause serious damage to the ecological environment and human health. Compared with organic compounds in VOCs, CH4 molecules have four completely identical and symmetrical C-H bonds, and each C-H bond has extremely high bond energy (439 kJ·mol -1 ), which makes it difficult to activate CH4 molecules. Theoretical calculations show that when the concentration of CH4 is 3000-5000 ppm, the ignition temperature of non-catalytic direct combustion is about 1300-1400℃, and higher temperature is required for complete oxidation, which also makes the catalytic reaction of CH4, especially the catalytic oxidation of low-concentration CH4, a probe reaction in the process of catalytic degradation of VOCs. According to the actual working conditions and environmental conditions, the treatment methods of VOCs can be divided into many kinds, among which the catalytic oxidation method can completely oxidize pollutants to CO2, H2O and harmless by-products at a relatively low temperature, and this method has the advantages of high efficiency, long service life and no secondary pollution, etc. It is considered as one of the effective and relatively mature methods for treating methane, and has become a research hotspot at present.

[0003] Spinel metal oxides have special crystal structure, which can provide a large number of oxygen vacancies, and are beneficial to methane activation, so they become a research focus of methane catalysts. Among them, Co3O4-based catalysts are concerned because of their strong morphology controllability, incomplete filling of three-dimensional orbit, high conversion of cobalt ions and fast redox cycle. Chen et al. synthesized Co3O4 nanocrystals with different morphologies by hydrothermal method, which all showed excellent catalytic activity for methane combustion reaction, but the thermal stability and sintering resistance of the catalysts had certain limitations. Therefore, a large number of researchers use metal oxides as carriers to optimize the stability of Co ions and the overall structural stability of the catalyst by loading Co3O4 oxide and metal oxide, so as to obtain excellent catalytic performance and structural stability. Bai Yanli et al. prepared Co3O4 / Al2O3 with different loading amounts, and found that the Co3O4 / Al2O3 with a loading amount of 40% had the best catalytic activity and thermal stability. Feng et al. used SmMn2O5 with strong thermal stability as a carrier to prepare Co3O4 / SmMn2O5 catalyst, and Co3O4 / SmMn2O5-50% had the best catalytic performance and the oxygen migration rate was greatly enhanced. The thermal stability and catalytic life of the supported catalysts are improved, but the combination of the excellent C-H activation ability of Co3O4 and the oxygen storage capacity of its carrier and the deep mineralization ability of pollutants still needs to be improved. SUMMARY

[0004] The purpose of the present application is to solve the problems of low-temperature activity, high cost and complicated preparation of non-noble metal supported catalysts, and to provide a Co3O4-based supported catalyst with rich active sites, high catalytic activity and good thermal stability for low-concentration methane catalytic combustion. The preparation method of the present application is simple and efficient.

[0005] To achieve the above purpose, the technical scheme used by the present application is as follows:

[0006] The present application provides a preparation method of a Co3O4-based supported catalyst, comprising the following steps:

[0007] S1, 2D Co3O4 preparation: dissolve cobalt acetylacetonate and cetyltrimethylammonium bromide in a mixed solution of ethylene glycol and deionized water, and perform hydrothermal reaction at 180-200℃ for 48h, centrifugal dry, and calcine at 300-320℃ for 3h with a heating rate of 2-5℃·min-1 to obtain 2D Co3O4; -1

[0008] ​S2, preparation of S2D Co3O4 / La2O2CO3 catalyst: after La(NO3)3.6H2O and urea are dissolved in deionized water, 2D Co3O4 prepared in step S1 is added, stirring is uniformly conducted, then hydrothermal reaction is conducted, after centrifugal drying, calcination is conducted at 400-600℃ for 2-4h, the temperature increasing rate is 3-5℃·min -1 , to obtain 2D Co3O4 / La2O2CO3 catalyst.

[0009] As preferred, in step S2, the hydrothermal reaction is specifically: hydrothermal reaction is conducted at 180-230℃ for 5-6h.

[0010] As preferred, in step S2, the hydrothermal reaction is specifically: hydrothermal reaction is conducted at 230℃ for 6h.

[0011] As preferred, in step S2, the molar ratio of La(NO3)3.6H2O to urea is 1:(3-6).

[0012] As preferred, in step S2, the molar ratio of La(NO3)3.6H2O to 2D Co3O4 is 1:(0.2-2).

[0013] As preferred, in step S2, the molar ratio of La(NO3)3.6H2O to 2D Co3O4 is 1:(1-2), preferably the molar ratio of La(NO3)3.6H2O to 2D Co3O4 is 1:1.

[0014] As preferred, in step S2, calcination is conducted at 500℃ for 3h, the temperature increasing rate is 3℃·min -1 .

[0015] The application further provides a Co3O4-based supported catalyst prepared by the above method.

[0016] The application further provides application of the above Co3O4-based supported catalyst in catalyzing methane combustion.

[0017] As preferred, the concentration of the methane is ≥1%.

[0018] The Co3O4-based supported catalyst of the application has rich active sites, high catalytic activity and good thermal stability, can be used for catalytic combustion of low-concentration (1%) methane, and the preparation method of the application is simple and efficient, and is suitable for popularization and use. BRIEF DESCRIPTION OF DRAWINGS

[0019] The accompanying drawings are included to provide a further understanding of the application, and constitute a part of the specification, and are used together with embodiments of the application to explain the application, and do not constitute a limitation on the application. In the drawings:

[0020] Figure 1 TEM image of 2D Co3O4 catalyst prepared in step 1 of Example 1.

[0021] Figure 2 TEM image of 2D Co3O4 catalyst prepared in step 1 of Example 1.

[0022] Figure 3 TEM image of 2D Co3O4 / La2O2CO3 prepared in step 2 of Example 1.

[0023] Figure 4 Catalyst activity under different hydrothermal conditions.

[0024] Figure 5 Comparison of CH4 catalysis effect of different catalysts.

[0025] Figure 6 O2-TPD spectrum of different catalysts.

[0026] Figures 7-10 TG-DTG of different catalysts. DETAILED DESCRIPTION

[0027] The following examples facilitate a better understanding of the present application, but do not limit the present application. In the following examples, the experimental methods are conventional methods, unless otherwise specified. In the following examples, the experimental materials are purchased from conventional biochemical reagent companies, unless otherwise specified. In the following examples, quantitative tests are set up with three repeated experiments, and the results are averaged.

[0028] The Co3O4-based supported catalyst material provided by the present application is composed of 2D Co3O4 and La2O2CO3 oxides, and is obtained by a chemical hydrothermal process and adjusting the component addition ratio to obtain an optimal 2D Co3O4 / La2O2CO3 supported catalyst.

[0029] The preparation method of the Co3O4-based supported catalyst material of the present application is as follows:

[0030] 1. Preparation of 2D Co3O4 catalyst

[0031] The one-step hydrothermal synthesis method is used for preparation, and the detailed preparation process is as follows:

[0032] Weigh 0.0016 mol-0.0017 mol of cobalt acetylacetonate (Co(acac)3) and 0.006 mol of cetyltrimethylammonium bromide (CTAB), and dissolve them sequentially in a mixture of 60 mL of ethylene glycol and 11 mL of deionized water. After stirring continuously for 25-35 min, the mixture is ultrasonically cleaned. The homogeneous solution is then transferred to the inner liner of a high-pressure reactor and subjected to a hydrothermal reaction at 180-200℃ in an electric heating oven for 48 h. The hydrothermally treated solution is then poured into centrifuge tubes and centrifuged. The precipitate is then washed alternately with deionized water and anhydrous ethanol and centrifuged again. The centrifuged precipitate is then frozen in a freeze dryer for 24 h, followed by drying for another 24 h. Finally, the ground sample is calcined in a muffle furnace at 300-320℃ for 3 h, with a heating rate of 2-5℃·min. -1 2D Co3O4 catalyst was obtained.

[0033] Hexadecyltrimethylammonium bromide (CTAB) is a cationic surfactant that acts as a template agent to induce material growth, lowering the energy in a specific direction and facilitating oriented growth. The size and shape of the catalyst can be controlled during synthesis. In this experiment, it contributes to the formation of ultrathin 2D Co3O4.

[0034] 2. Preparation of a series of 2D Co3O4 / La2O2CO3 catalysts with different loadings

[0035] 2D Co3O4 / La2O2CO3 samples were prepared using a one-step hydrothermal synthesis method. The detailed preparation process is as follows:

[0036] 0.005 mol of the metal precursor nitrate La(NO3)3·6H2O and 0.010 mol–0.030 mol of urea were dissolved in 17.5 mL of deionized water and sonicated to form a homogeneous solution. The solution was then stirred in a stirrer at room temperature for 25–35 min. 0.001–0.010 mol of the 2D precursor prepared in step 1 was added… The Co3O4 catalyst was slowly added to the stirred solution, and stirring was continued for 25-35 minutes. The solution was then poured into a 50 mL polyethylene-lined high-pressure reactor and hydrothermally heated at 180-230℃ for 5-6 hours. After cooling to room temperature, Buchner filtration was performed, followed by washing several times with deionized water and anhydrous ethanol. The precipitate was then placed in an electrically heated forced-air drying oven for drying. There were no specific requirements for the drying temperature and time, as long as the water in the precipitate was removed relatively completely. For example, drying at 60-90℃ for 6-12 hours was sufficient. After drying, the sample was ground and calcined in a muffle furnace at 400-600℃ for 2-4 hours, with a heating rate of 3-5℃·min. -1 A series of 2DCo3O4 / La2O2CO3 catalysts with different loadings were obtained.

[0037] The reaction equations for the above reactions are as follows:

[0038] H2O→H + +OH -

[0039] CO(NH2)2+H2O→NH2COONH4, NH2COONH4+H2→(NH4)2CO3

[0040] (NH4)2CO3→2NH3+CO2+H2O

[0041] La 3+ +OH - →La(OH)3

[0042] La(OH)3 + CO2 → LaCO3(OH) + H2O

[0043] Co 2+ +OH - →Co(OH)2Co(OH)2+O2→Co3O4+H2O

[0044] LaCO3(OH)→La2O2CO3+CO2+H2O

[0045] In the above reaction, urea needs to be in excess to ensure that La(NO3)3·6H2O reacts completely. Preferably, the molar amount of urea is 3-6 times that of La(NO3)3·6H2O.

[0046] The loading is calculated as the molar percentage of 2D Co3O4 catalyst to La(NO3)3·6H2O.

[0047] When the calcination temperature in step 2 is higher than 600℃, the two-dimensional structure of Co3O4 will be destroyed, and it will not be able to exhibit a uniform crystal structure, thus exhibiting catalytic activity similar to that of commercial Co3O4.

[0048] Example 1

[0049] The preparation method of the Co3O4-based supported catalytic material of the present invention is as follows:

[0050] 1. Preparation of 2D Co3O4 catalyst

[0051] It is prepared by a one-step hydrothermal synthesis method. The detailed preparation process is as follows:

[0052] Weigh 0.0017 mol of cobalt acetylacetonate (Co(acac)3) and 0.006 mol of hexadecyltrimethylammonium bromide (CTAB), and dissolve them sequentially in a mixture of 60 mL of ethylene glycol and 11 mL of deionized water. Stir continuously for 30 min, then sonicate in an ultrasonic cleaner for 15 min. Transfer the homogenized solution to the inner liner of a high-pressure reactor and perform a hydrothermal reaction at 180℃ in an electric heating oven for 48 h. Pour the hydrothermally heated solution into centrifuge tubes and centrifuge at 4000 r / min for 10 min. Wash the precipitate alternately with deionized water and anhydrous ethanol, and centrifuge after each washing. Freeze the centrifuged precipitate in a freeze dryer for 24 h, then dry it for 24 h. Finally, calcine the ground sample in a muffle furnace at 320℃ for 3 h at a heating rate of 2℃·min. -1 2D Co3O4 catalyst was obtained.

[0053] Figure 1 This is a TEM image of the 2D Co3O4 catalyst prepared in step 1 of Example 1.

[0054] Depend on Figure 1 It can be seen that the obtained Co3O4 catalyst has a 2D structure.

[0055] 2. Preparation of 2D Co3O4 / La2O2CO3 catalyst

[0056] 2D Co3O4 / La2O2CO3 samples were prepared using a one-step hydrothermal synthesis method. The detailed preparation process is as follows:

[0057] 2.1875 g (0.005 mol) of the metal precursor nitrate La(NO3)3·6H2O and 1.515 g (0.0252 mol) of urea were dissolved in 17.5 mL of deionized water and sonicated to form a homogeneous solution. The solution was then stirred at room temperature for 30 min. 1.2165 g (0.005 mol) of the 2D Co3O4 catalyst prepared in step 1 was slowly added to the stirred solution, and stirring was continued for 30 min. The solution was poured into a 50 mL polyethylene-lined high-pressure reactor and hydrothermally heated at 230 °C for 6 h. After cooling to room temperature, the solution was subjected to Buchner filtration and washed several times with deionized water and anhydrous ethanol. The precipitate was placed in an electric heating oven and dried at 60 °C for 12 h. After drying, the sample was ground and calcined in a muffle furnace at 500 °C for 3 h at a heating rate of 3 °C·min. -1 A 2D Co3O4 / La2O2CO3 catalyst with a loading of 100% was obtained.

[0058] Figure 2 This is a TEM image of the 2D Co3O4 catalyst prepared in step 1 of Example 1.

[0059] Figure 3 The image shows a TEM image of the 2D Co3O4 / La2O2CO3 prepared in step 2 of Example 1.

[0060] Depend on Figure 2 and Figure 3 It can be seen that in the above preparation method, the main exposed crystal plane of the prepared 2D Co3O4 is the {311} crystal plane. However, after hydrothermal composite with La2O2CO3, the main exposed crystal plane of 2D Co3O4 changes to the {111} crystal plane, and the methane catalytic activity on the {111} crystal plane is higher. This is determined by the hydrothermal temperature, duration, filling degree, and subsequent calcination temperature in the preparation method. If the calcination temperature in step 2 is higher than 600℃, the two-dimensional structure of Co3O4 is destroyed, and it cannot exhibit a uniform crystal plane structure, thus exhibiting catalytic activity similar to commercial Co3O4.

[0061] Example 2

[0062] The preparation method of the Co3O4-based supported catalytic material of the present invention is as follows:

[0063] 1. Preparation of 2D Co3O4 catalyst

[0064] Weigh 0.0017 mol of cobalt acetylacetonate (Co(acac)3) and 0.006 mol of hexadecyltrimethylammonium bromide (CTAB), and dissolve them sequentially in a mixture of 60 mL of ethylene glycol and 11 mL of deionized water. Stir continuously for 30 min, then sonicate in an ultrasonic cleaner for 15 min. Transfer the homogenized solution to the inner liner of a high-pressure reactor and perform a hydrothermal reaction at 190℃ in an electric heating oven for 48 h. Pour the hydrothermally heated solution into centrifuge tubes and centrifuge at 4000 r / min for 10 min. Wash the precipitate alternately with deionized water and anhydrous ethanol, and centrifuge after each washing. Freeze the centrifuged precipitate in a freeze dryer for 24 h, then dry it for 24 h. Finally, calcine the ground sample in a muffle furnace at 300℃ for 3 h with a heating rate of 3℃·min. -1 2D Co3O4 catalyst was obtained.

[0065] 2. Preparation of 2D Co3O4 / La2O2CO3 catalyst

[0066] 2.1875 g (0.005 mol) of the metal precursor nitrate La(NO3)3·6H2O and 0.600 g (0.010 mol) of urea were dissolved in 17.5 mL of deionized water and sonicated to form a homogeneous solution. The solution was then stirred at room temperature for 25 min. 1.2165 g (0.005 mol) of the 2D Co3O4 catalyst prepared in step 1 was slowly added to the stirred solution, and stirring was continued for 35 min. The solution was poured into a 50 mL polyethylene-lined high-pressure reactor and hydrothermally heated at 230 °C for 6 h. After cooling to room temperature, the solution was subjected to Buchner filtration and washed several times with deionized water and anhydrous ethanol. The precipitate was placed in an electrically heated blast drying oven and dried at 90 °C for 6 h. After drying, the sample was ground and calcined in a muffle furnace at 600 °C for 2 h at a heating rate of 5 °C·min. -1 A 2D Co3O4 / La2O2CO3 catalyst with a loading of 100% was obtained.

[0067] Example 3

[0068] The preparation method of the Co3O4-based supported catalytic material of the present invention is as follows:

[0069] 1. Preparation of 2D Co3O4 catalyst

[0070] Weigh 0.0017 mol of cobalt acetylacetonate (Co(acac)3) and 0.006 mol of hexadecyltrimethylammonium bromide (CTAB), and dissolve them sequentially in a mixture of 60 mL of ethylene glycol and 11 mL of deionized water. Stir continuously for 30 min, then sonicate in an ultrasonic cleaner for 15 min. Transfer the homogenized solution to the inner liner of a high-pressure reactor and perform a hydrothermal reaction at 200℃ in an electric heating oven for 48 h. Pour the hydrothermally heated solution into centrifuge tubes and centrifuge at 4000 r / min for 10 min. Wash the precipitate alternately with deionized water and anhydrous ethanol, and centrifuge after each washing. Freeze the centrifuged precipitate in a freeze dryer for 24 h, then dry it for 24 h. Finally, calcine the ground sample in a muffle furnace at 310℃ for 3 h at a heating rate of 5℃·min. -1 2D Co3O4 catalyst was obtained.

[0071] 2. Preparation of 2D Co3O4 / La2O2CO3 catalyst

[0072] 2.1875 g (0.005 mol) of the metal precursor nitrate La(NO3)3·6H2O and 0.901 g (0.015 mol) of urea were dissolved in 17.5 mL of deionized water and sonicated to form a homogeneous solution. The solution was then stirred at room temperature for 35 min. 1.2165 g (0.005 mol) of the 2D Co3O4 catalyst prepared in step 1 was slowly added to the stirred solution, and stirring was continued for 25 min. The solution was poured into a 50 mL polyethylene-lined high-pressure reactor and hydrothermally heated at 180 °C for 5 h. After cooling to room temperature, the solution was subjected to Buchner filtration and washed several times with deionized water and anhydrous ethanol. The precipitate was placed in an electric heating oven and dried at 70 °C for 8 h. After drying, the sample was ground and calcined in a muffle furnace at 400 °C for 4 h at a heating rate of 4 °C·min. -1 A 2D Co3O4 / La2O2CO3 catalyst with a loading of 100% was obtained.

[0073] Example 4: Optimization Experiment of the Co3O4-based Supported Catalytic Material of the Present Invention

[0074] To investigate the effects of hydrothermal loading conditions and the loading of Co3O4 active component (x%, x = 20, 40, 60, 80, 100, 200) on the Co3O4 / La2O2CO3 composite, this example uses methane catalytic performance as the evaluation index to test and screen the prepared catalysts. The catalytic activity of the Co3O4 / La2O2CO3 composite catalysts under different hydrothermal conditions and with different Co3O4 loadings was tested.

[0075] A series of 2D Co3O4 / La2O2CO3 catalysts were prepared by adjusting the hydrothermal temperature and loading to 20%-100% and according to the corresponding molar ratio.

[0076] Taking a loading of 100% Co3O4 / La2O2CO3 as an example:

[0077] 2.1875 g (0.005 mol) of the metal precursor nitrate La(NO)3·6H2O and 1.515 g (0.0252 mol) of urea were dissolved in 17.5 mL of deionized water and ultrasonically dispersed to form a uniformly dispersed solution. The solution was then stirred in a stirrer at room temperature for 30 min. 1.2162 g (0.005 mol, i.e., 100% loading) of the 2D precursor prepared in step 1 of Example 1 was then added. The Co3O4 catalyst was slowly added to the stirred solution, and stirring was continued for 30 min. The mixed dispersion was then placed in a high-pressure reactor for hydrothermal reaction. The hydrothermal reaction was divided into two groups: one at a hydrothermal temperature of 180℃ for 5 h, and the other at a hydrothermal temperature of 230℃ for 6 h. After cooling to room temperature, the resulting solution was subjected to Buchner filtration and washed several times with deionized water and anhydrous ethanol. The filtered sample was then placed in an electric heating drying oven and dried at 60℃ for 12 h. Finally, the dried sample was ground and calcined in a muffle furnace at 500℃ for 3 h, with a heating rate of 3℃·min. -1 Two groups of Co3O4 / La2O2CO3 samples with 100% loading were obtained.

[0078] The hydrothermal temperature was set at 230℃ and the hydrothermal time was set at 6h. Then, the amount of the 2D Co3O4 catalyst was adjusted to 0.001mol, 0.002mol, 0.003mol, 0.004mol, and 0.01mol, respectively. Co3O4 / La2O2CO3 samples with loadings of 20%, 40%, 60%, 80%, and 200% were prepared sequentially according to the above method.

[0079] The catalytic method for methane using the catalyst prepared in this invention is as follows:

[0080] The catalyst samples prepared in this invention were subjected to catalytic performance testing using an online methane catalysis evaluation device equipped with a CPR-6060 fixed reaction bed (Tianjin Xianquan Industry and Trade Development Co., Ltd.). The inner diameter of the fixed-bed quartz tube reactor was 6 mm. The catalyst particle size was strictly controlled to be 40-60 mesh using tools such as a tablet press, and the dosage of the sample to be tested was set at 0.5 mL. The reaction gas composition was 99% synthesis air and 1% methane, and the total flow rate of the reaction gas was 50 mL·min. -1 Airspeed is 6000 h -1 The inlet and outlet concentrations of methane were determined using a gas chromatograph (GC-7900, Shanghai, China) equipped with a TDX-01 molecular sieve column (2×3mm, 80 mesh, temperature set at 120℃) from Tianmei (Holdings) Co., Ltd., with the FID detector and injection port temperature both set to 150℃. The catalytic activity of the catalyst was determined by the temperatures at which methane conversion reached 50% and 90% (T0). 50 and T 90The evaluation is performed using the formula shown in equation (2-1):

[0081]

[0082] In the formula, Y represents the methane conversion rate, %.

[0083] CO—The concentration of methane at the gas chromatograph inlet;

[0084] C1—The concentration of methane at the gas chromatograph outlet.

[0085] The corresponding catalytic activity test results are as follows: Figure 4 As shown in Table 1.

[0086] Figure 4 The graph shows the catalyst activity under different hydrothermal conditions.

[0087] Table 1. Catalyst T under different hydrothermal conditions and with x% Co3O4 / La2O2CO3Co3O4 composite catalyst 50 T 90 Data table

[0088]

[0089] from Figure 4 It can be seen that the catalytic activity of the catalyst varies under different hydrothermal temperatures and times. By comparing the catalytic performance of the catalysts, it can be found that although the differences in catalyst activity under different hydrothermal conditions are not significant, the hydrothermal conditions with a hydrothermal temperature of 230℃ and a hydrothermal time of 6 hours show a greater activity than those with a hydrothermal condition of 180℃ and 5 hours. 50 and T 90 The performance is improved by 10℃ and 16℃ respectively, making it more suitable for the external conditions of the preparation process of this type of catalyst.

[0090] In subsequent experiments investigating the optimal Co3O4 loading, the above-mentioned optimal hydrothermal conditions were used as a basis. As shown in Table 1, after coupling the two phases, when the Co3O4 component loading was below 60%, the Co3O4 activity was superior to the x% Co3O4 / La2O2CO3 catalyst. With increasing loading, the catalyst activity continuously improved, reaching its optimum at 100% loading. 50 and T 90 The catalyst activity was optimized at 400℃ and 469℃, respectively, representing a decrease of 60℃ and 40℃ compared to the Co3O4 catalyst, indicating effective performance optimization. However, at 200% loading, the catalyst activity slightly decreased again due to insufficient exposure of active sites caused by excessive loading between the two phases. In summary, Co3O4, as the active host, can effectively improve catalytic performance when its loading is increased to an appropriate proportion.

[0091] Example 5: Experimental study on the catalytic effect of the Co3O4-based supported catalytic material of the present invention on CH4.

[0092] The experiment was divided into six groups:

[0093] 1. Co3O4 group: Common commercial Co3O4 material (purchased from Shanghai E. En Chemical Technology Co., Ltd.)

[0094] 2. Co3O4 material / La2O2CO3 group: ordinary commercial Co3O4 material / La2O2CO3 catalyst, prepared according to the method in step 2 of Example 1 of this invention.

[0095] 3. Co3O4 material / La2O2CO3 physical mixture group: ordinary commercial Co3O4 material and La2O2CO3 are physically mixed evenly.

[0096] The preparation method of La2O2CO3 is as follows: 2.1875g of La(NO3)3·6H2O and 1.515g of urea are dissolved in 17.5mL of deionized water and ultrasonically mixed to form a homogeneous solution. The solution is then stirred in a stirrer for 30min. The mixed solution is placed in the inner liner of a high-pressure reactor lined with polyethylene and hydrothermally heated at 120℃ for 12h. After cooling to room temperature, the solution is filtered, washed, and dried. It is then calcined in a muffle furnace at 500℃ for 3h to obtain the La2O2CO3 sample.

[0097] Subsequently, the XRD data of Co3O4 / La2O2CO3 were analyzed and the content was calculated using Jade software. Equal amounts of commercial Co3O4 and prepared La2O2CO3 were weighed and mixed evenly.

[0098] 4. 2D Co3O4 group: 2D Co3O4 catalyst prepared in Example 1 of this invention.

[0099] 5. 40% 2D Co3O4 / La2O2CO3 group: The 2D Co3O4 catalyst prepared in Example 4 of this invention, with a 2D Co3O4 active component loading of 40%.

[0100] 6. 2D Co3O4 / La2O2CO3 group: 2D Co3O4 / La2O2CO3 catalyst prepared in Example 1 of this invention.

[0101] The experimental procedure for catalyzing CH4 using the above catalysts is the same as in Example 4.

[0102] The experimental results are shown in Figure 5 , Figure 6 And Table 2.

[0103] Figure 5A comparison chart showing the effects of different catalysts on CH4 catalysis.

[0104] Figure 6 The O2-TPD spectra are for different catalysts.

[0105] Table 2. Catalytic activity, specific surface area, pore volume, pore size, and oxygen adsorption / desorption data of the samples.

[0106]

[0107] As shown in Table 2, firstly, the 2D Co3O4 of this invention has a much larger specific surface area than commercially available Co3O4 prepared by conventional methods. The specific surface area, pore volume, and pore size of the 2D Co3O4 catalyst of this invention are 62.65 m². 2 ·g -1 0.35cc·g -1 Compared to ordinary commercial Co3O4 materials, the physical characterization data, including 13.061nm, show a significant increase, with a 34-fold difference in specific surface area and a marked increase in the proportion of macropores.

[0108] Secondly, La2O2CO3 was chosen as the support for the composite with 2D Co3O4 because La2O2CO3 has excellent oxygen-donating properties. This was verified through temperature-programmed oxygen desorption (O2-TPD) experiments, which effectively determined the redox capacity of the catalyst. The O2-TPD spectra of 2D Co3O4 and the 2D Co3O4 / La2O2CO3 catalysts are shown below. Figure 6 As shown, the oxygen desorption data are listed in Table 2. Compared to the 2D Co3O4 catalyst, the 2D Co3O4 / La2O2CO3 catalyst can achieve higher adsorption oxygen at a lower temperature. This indicates that the oxygen adsorption capacity of the catalyst is improved after loading La2O2CO3, thereby enhancing the catalyst's methane catalytic performance.

[0109] Finally, when ordinary commercial Co3O4 material and La2O2CO3 prepared by hydrothermal method were physically mixed, the catalytic effect on methane was only slightly better than that of ordinary commercial Co3O4 material alone, and worse than that of other groups, indicating that simply mixing the two is not enough.

[0110] The thermal stability results of each catalyst of the present invention are shown in the figure. Figures 7-10 .

[0111] Figures 7-10 The images show the TG-DTG spectra of different catalysts.

[0112] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a Co3O4-based supported catalyst for the catalytic combustion of methane, characterized in that: Includes the following steps: Preparation of S1,2D Co3O4: Cobalt acetylacetonate and hexadecyltrimethylammonium bromide were dissolved in a mixed solution of ethylene glycol and deionized water, and subjected to a hydrothermal reaction at 180-200 °C for 48 h. After centrifugation and drying, the mixture was calcined at 300-320 °C for 3 h at a heating rate of 2-5 °C·min. -1 2D Co3O4 was obtained; Preparation of S2, 2D Co3O4 / La2O2CO3 catalyst: La(NO3)3·6H2O and urea were dissolved in deionized water, and then the 2D Co3O4 prepared in step S1 was added. After stirring evenly, a hydrothermal reaction was carried out. After centrifugation and drying, the catalyst was calcined at 400-600 ℃ for 2-4 h at a heating rate of 3-5 ℃·min. -1 The 2D Co3O4 / La2O2CO3 catalyst was obtained; the hydrothermal reaction was specifically carried out at 180-230 ℃ for 5-6 h. The molar ratio of La(NO3)3·6H2O to urea is 1:(3-6). The molar ratio of La(NO3)3·6H2O to 2D Co3O4 is 1:(0.2-2).

2. The preparation method according to claim 1, characterized in that: In step S2, the hydrothermal reaction specifically involves hydrothermal treatment at 230 °C for 6 h.

3. The preparation method according to claim 1, characterized in that: In step S2, the molar ratio of La(NO3)3·6H2O to 2DCo3O4 is 1:(1-2).

4. The preparation method according to claim 3, characterized in that: In step S2, the molar ratio of La(NO3)3·6H2O to 2DCo3O4 is 1:

1.

5. The preparation method according to claim 1, characterized in that: In step S2, calcination is carried out at 500 °C for 3 h, with a heating rate of 3 °C·min. -1 .

6. A Co3O4-based supported catalyst, which is prepared by the method according to any one of claims 1-5.

7. The application of the Co3O4-based supported catalyst according to claim 6 in the catalytic combustion of methane.

8. The application according to claim 7, characterized in that: The concentration of methane is ≥1%.

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