Preparation method and application of supported cobaltosic oxide catalyst

Abstract

The invention relates to a preparation method and application of a supported cobaltosic oxide catalyst, and the preparation method comprises the following steps: 1) dissolving a cobalt source and a carrier precursor in ethanol and water, adding 2-methylimidazole, stirring, standing, aging, and drying to obtain ZIF-67-based precipitate; and 2) carrying out primary roasting on the ZIF-67-based precipitate in a reducing atmosphere and carrying out secondary roasting in an oxidizing atmosphere in sequence to obtain the supported cobaltosic oxide catalyst, and applying the supported cobaltosic oxide catalyst to the reaction of catalyzing propane to generate carbon dioxide and water. Compared with the prior art, the method for preparing the supported cobaltosic oxide catalyst based on the ZIF-67 not only simplifies the preparation process and reduces the cost, but also remarkably improves the performance of the catalyst, and has important practical significance for improving the efficiency and economical efficiency of a VOCs catalytic oxidation technology; the preparation method provides a new and efficient solution for the development of a VOCs catalytic oxidation technology, and is expected to realize more environment-friendly and more economical VOCs treatment in industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental engineering and catalytic chemistry, in particular to the technical field of catalytic oxidation of volatile organic compounds (VOCs), and relates to a preparation method and application of a supported cobalt tetroxide catalyst, and specifically to a preparation method of a supported cobalt tetroxide catalyst based on ZIF-67 and using the catalyst to catalyze the reaction of propane to generate carbon dioxide and water. Background Art

[0002] In the field of catalytic oxidation of VOCs, cobalt oxide (Co3O4) has attracted widespread attention due to its excellent catalytic performance. However, pure Co3O4 catalysts tend to agglomerate under high temperature conditions, resulting in decreased activity. In contrast, supported Co3O4 catalysts exhibit stronger resistance to sintering and deactivation. Nevertheless, the interfacial interaction between Co3O4 and the carrier oxide may weaken its activity and stability in the complete oxidation reaction of VOCs. Traditional preparation methods rely on precious metal doping and material post-treatment techniques to optimize the interaction between cobalt and carrier oxides, but these methods are not only cumbersome in preparation process but also costly. Summary of the invention

[0003] The purpose of the present invention is to overcome the above problems, provide an innovative preparation method, specifically provide a preparation method for preparing a supported cobalt oxide catalyst based on ZIF-67, for improving the efficiency of VOCs catalytic oxidation and reducing related costs. The core of the preparation method is to use cobalt-based metal organic framework (MOFs) ZIF-67 as a cobalt source precursor, by introducing a precursor of a carrier (such as SiO2 or γ-Al2O3) during the synthesis of ZIF-67, and then through a reduction-oxidation heat treatment process, prepare a supported Co3O4 catalyst (ZIF-67 derived catalyst) with high activity and stability. Therefore, the preparation method of the present invention not only simplifies the preparation process, reduces costs, but also improves the performance of the catalyst.

[0004] The purpose of the present invention can be achieved by the following technical solutions:

[0005] The present invention provides a method for preparing a supported cobalt oxide catalyst, which forms a supported cobalt oxide catalyst by in-situ means, increases the specific surface area of ​​the catalyst, and improves the catalytic activity and stability. The preparation method comprises the following steps:

[0006] 1) dissolving a cobalt source and a carrier precursor in ethanol and water, adding 2-methylimidazole, stirring, standing and aging, and drying to obtain a ZIF-67-based precipitate;

[0007] 2) The ZIF-67-based precipitate is calcined once in a reducing atmosphere and then calcined twice in an oxidizing atmosphere to obtain a supported cobalt tetroxide catalyst.

[0008] Further, in step 1), the cobalt source is cobalt nitrate, and the carrier precursor is selected from any one of tetraethyl orthosilicate (TEOS), aluminum nitrate or pseudo-boehmite (Al2O3·H2O). The carrier precursor plays a role in redispersing the nanoparticles to form a silicon dioxide or aluminum oxide supported cobalt tetraoxide catalyst.

[0009] Furthermore, in step 1), the volume ratio of ethanol to water is 1:1.

[0010] Furthermore, in step 1), the molar concentration of the cobalt nitrate in the mixed solution of ethanol and water is 0.006-0.062 mol / L.

[0011] Furthermore, in step 1), when the carrier precursor is tetraethyl orthosilicate, the molar ratio of the cobalt element in the cobalt source to the silicon element in tetraethyl orthosilicate is (0.085-0.767):1, and when the carrier precursor is aluminum nitrate or pseudo-boehmite, the molar ratio of the cobalt element in the cobalt source to the aluminum element in aluminum nitrate or pseudo-boehmite is (0.030-0.274):1.

[0012] Furthermore, in step 1), the molar ratio of the 2-methylimidazole to the cobalt element in the cobalt source is (2:1)-(8:1).

[0013] Further, in step 1), the stirring time is 10-15 hours, and the static aging time is 10-15 hours. Preferably, the stirring time is 12 hours, and the static aging time is 12 hours.

[0014] Furthermore, in step 1), during the drying, the drying temperature is 70-85°C and the drying time is 10-15 hours. Preferably, during the drying, the drying temperature is 80°C and the drying time is 12 hours.

[0015] Furthermore, in step 2), in the first calcination, the calcination temperature is 550-650°C, and the calcination time is 2-3h; in the second calcination, the calcination temperature is 250-350°C, and the calcination time is 2-3h; the reducing atmosphere is a mixed gas of hydrogen and argon, wherein the concentration of hydrogen is 5vol%, and the oxidizing atmosphere is air.

[0016] Further preferably, in step 2), in the first calcination, the calcination temperature is 600° C. and the calcination time is 2 h; in the second calcination, the calcination temperature is 300° C. and the calcination time is 2 h.

[0017] Furthermore, in step 2), when the carrier precursor is tetraethyl orthosilicate, the supported cobalt oxide catalyst is a high-efficiency silica-supported cobalt oxide (ZIF-Co-Si) catalyst; when the catalyst is the carrier precursor is aluminum nitrate or pseudo-boehmite, the supported cobalt oxide catalyst is a high-efficiency alumina-supported cobalt oxide (ZIF-Co-Al-AN) catalyst or a high-efficiency alumina-supported cobalt oxide (ZIF-Co-Al-AH) catalyst.

[0018] A second aspect of the present invention provides an application of a supported cobalt oxide catalyst, wherein the supported cobalt oxide catalyst is used to catalyze the reaction of propane to generate carbon dioxide and water.

[0019] The preparation method of the present invention simultaneously synthesizes precursors of ZIF-67 and carrier silica (or γ-alumina), and controls the crystallization rate by regulating the addition order of cobalt source, TEOS or 2-methylimidazole and other preparation details (reduction temperature, oxidation temperature, etc.), and orderly synthesizes a supported cobalt oxide catalyst supported by the carrier silica (or γ-alumina). The supported cobalt oxide catalyst obtained by the preparation method of the present invention exhibits high activity and stability. The method is essentially to regulate the direct interface effect between cobalt and carrier silica (or γ-alumina), thereby improving the activity and stability of the supported cobalt oxide catalyst.

[0020] Compared with the prior art, the present invention has the following characteristics:

[0021] 1) The present invention prepares a supported Co3O4 catalyst with high activity and stability by introducing a carrier precursor during the synthesis of ZIF-67 and then performing a reduction-oxidation heat treatment process;

[0022] 2) The present invention uses ZIF-67 as a cobalt source precursor. Due to its unique structure and properties, it can effectively anchor metal particles during the subsequent heat treatment process to prevent sintering at high temperatures, and can significantly improve the interface interaction problem between Co3O4 and the carrier oxide, thereby improving the activity and thermal stability of the catalyst;

[0023] 3) The preparation method of the present invention makes the preparation process of the catalyst more integrated, simplifies the traditional multi-step preparation process, simplifies the preparation process, and reduces costs;

[0024] 4) The present invention uses a precisely controlled reduction-oxidation heat treatment process to enable the carbon matrix formed by the supported Co3O4 catalyst during the heat treatment process to anchor the metal particles, preventing them from forming inert species with the carrier, thereby improving the activity and stability of the catalyst. For example, when γ-Al2O3 is used as a carrier (the carrier precursor is aluminum nitrate or pseudo-boehmite), traditional Co3O4 is easy to react with γ-Al2O3 to generate inert species CoAl2O4, thereby reducing the activity of the catalyst. The preparation method using ZIF-67 as a precursor can effectively avoid this problem;

[0025] 5) The preparation method based on ZIF-67 proposed in the present invention not only simplifies the preparation process and reduces the cost, but also significantly improves the performance of the catalyst, which has important practical significance for improving the efficiency and economy of VOCs catalytic oxidation technology. This preparation method provides a new and efficient solution for the development of VOCs catalytic oxidation technology, and is expected to achieve more environmentally friendly and economical VOCs treatment in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 XRD patterns of n ZIF-Co-Si (n=50, 40, 30, 20, 10) catalysts prepared in Examples 1-5 and ZIF-Co@Si catalysts prepared in Comparative Examples;

[0027] Figure 2 The activity diagram of the n ZIF-Co-Si catalyst prepared in Examples 1-5 and the ZIF-Co@Si catalyst prepared in Comparative Example for complete oxidation of propane;

[0028] Figure 3 The cyclic stability of the 50ZIF-Co-Si catalyst prepared in Example 1 for complete oxidation of propane;

[0029] Figure 4 The cyclic stability of the 40ZIF-Co-Si catalyst prepared in Example 2 for complete oxidation of propane;

[0030] Figure 5 The cyclic stability of the 30ZIF-Co-Si catalyst prepared in Example 3 for complete oxidation of propane;

[0031] Figure 6 The cyclic stability of the 20ZIF-Co-Si catalyst prepared in Example 4 for complete oxidation of propane;

[0032] Figure 7 The cyclic stability of the 10ZIF-Co-Si catalyst prepared in Example 5 for complete oxidation of propane;

[0033] Figure 8 The cyclic stability of the ZIF-Co@Si catalyst prepared in the comparative example for complete oxidation of propane;

[0034] Fig. 9 The continuous stability of the 50ZIF-Co-Si catalyst prepared in Example 1 for complete oxidation of propane;

[0035] Fig.10 The effect of water vapor on the propane oxidation performance of the 50ZIF-Co-Si catalyst prepared in Example 1;

[0036] Fig.11 XRD patterns of ZIF-Co-Al-AN prepared in Example 6 and aZIF-Co-Al-AH (a=30, 20, 10, 5) catalysts prepared in Examples 7-10;

[0037] Fig.12 The activity diagram of the ZIF-Co-Al-AN prepared in Example 6 and the aZIF-Co-Al-AH catalysts prepared in Examples 7-10 for complete oxidation of propane;

[0038] Fig.13 The cyclic stability of the 30ZIF-Co-Al-AN catalyst prepared in Example 6 for complete oxidation of propane;

[0039] Fig.14 The cyclic stability of the 30ZIF-Co-Al-AH catalyst prepared in Example 7 for complete oxidation of propane;

[0040] Fig.15 The cyclic stability of the 20ZIF-Co-Al-AH catalyst prepared in Example 8 for complete oxidation of propane;

[0041] Fig.16 The cyclic stability of the 10ZIF-Co-Al-AH catalyst prepared in Example 9 for complete oxidation of propane;

[0042] Fig.17 The cyclic stability of the 5ZIF-Co-Al-AH catalyst prepared in Example 10 for complete oxidation of propane;

[0043] Fig.18 The continuous stability of the 20ZIF-Co-Al-AH catalyst prepared in Example 8 for complete oxidation of propane;

[0044] Fig.19 The effect of water vapor on the propane oxidation performance of the 20ZIF-Co-Al-AH catalyst prepared in Example 8. DETAILED DESCRIPTION

[0045] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0046] The following are more detailed implementation cases, which further illustrate the technical solutions of the present invention and the technical effects that can be obtained.

[0047] In the following examples, unless otherwise specified, raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0048] In the following examples, unless otherwise specified, the processing temperature is room temperature.

[0049] Embodiment 1:

[0050] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0051] S1: Weigh 3.6 g Co(NO3)2·6H2O and 3.67 ml TEOS and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0052] S2: Add 8.124 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0053] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt tetroxide catalyst, recorded as 50ZIF-Co-Si catalyst.

[0054] Embodiment 2:

[0055] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0056] S1: Weigh 2.4 g Co(NO3)2·6H2O and 3.67 ml TEOS and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0057] S2: Add 5.416 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0058] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt tetroxide catalyst, recorded as 40ZIF-Co-Si catalyst.

[0059] Embodiment 3:

[0060] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0061] S1: Weigh 1.5 g Co(NO3)2·6H2O and 3.67 ml TEOS and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0062] S2: Add 3.385 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0063] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt oxide catalyst, recorded as 30ZIF-Co-Si catalyst.

[0064] Embodiment 4:

[0065] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0066] S1: Weigh 0.9 g Co(NO3)2·6H2O and 3.67 ml TEOS and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0067] S2: Add 2.031 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0068] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt tetroxide catalyst, recorded as 20ZIF-Co-Si catalyst.

[0069] Embodiment 5:

[0070] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0071] S1: Weigh 0.4 g Co(NO3)2·6H2O and 3.67 ml TEOS and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0072] S2: Add 0.903 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0073] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt tetroxide catalyst, recorded as 10ZIF-Co-Si catalyst.

[0074] Comparative Example:

[0075] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0076] S1: Dissolve 3.6 g Co(NO3)2·6H2O in 360 ml methanol, stir thoroughly, add 4.74 g 2-methylimidazole, stir for 12 h, centrifuge, wash repeatedly with methanol, and dry at 60 °C for 12 h to obtain ZIF-67;

[0077] S2: Dissolve 0.5 g ZIF-67 in 200 ml ethanol and 330 ml deionized water, stir thoroughly, add 2.5 g 2-methylimidazole, and sonicate for 30 min;

[0078] S3: Add 1.52 g CTAB (hexadecyl ammonium bromide) and 7 ml TEOS, stir for 30 min, let stand for aging for 24 h, centrifuge and wash the resulting solution, and dry it in a 60 °C oven for 12 h;

[0079] S4: The dried sample was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 h, and then calcined twice at 300°C in an air atmosphere for 2 h to obtain a supported cobalt tetroxide catalyst, which was recorded as ZIF-Co@Si catalyst.

[0080] Embodiment 6:

[0081] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0082] S1: Weigh 3.6 g Co(NO3)2·6H2O and 16.92 g Al(NO3)3·9H2O and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0083] S2: Add 8.124 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0084] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt tetroxide catalyst, which was recorded as 30ZIF-Co-Al-AN catalyst.

[0085] Embodiment 7:

[0086] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0087] S1: Weigh 3.6 g Co(NO3)2·6H2O and 2.7 g Al2O3·H2O and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0088] S2: Add 8.124 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0089] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt oxide catalyst, which was recorded as 30ZIF-Co-Al-AH catalyst.

[0090] Embodiment 8:

[0091] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0092] S1: Weigh 2.1 g Co(NO3)2·6H2O and 2.7 g Al2O3·H2O and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0093] S2: Add 4.739 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain ZIF-67 based precipitate;

[0094] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 h, and then calcined twice at 300°C in an air atmosphere for 2 h to obtain a supported cobalt tetroxide catalyst, recorded as 20ZIF-Co-Al-AH catalyst.

[0095] Embodiment 9:

[0096] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0097] S1: Weigh 0.9 g Co(NO3)2·6H2O and 2.7 g Al2O3·H2O and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0098] S2: Add 2.031 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0099] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 hours, and then calcined twice at 300°C in an air atmosphere for 2 hours to obtain a supported cobalt oxide catalyst, which was recorded as 10ZIF-Co-Al-AH catalyst.

[0100] Embodiment 10:

[0101] A method for preparing a supported cobalt oxide catalyst comprises the following steps:

[0102] S1: Weigh 0.4 g Co(NO3)2·6H2O and 2.7 g Al2O3·H2O and dissolve them in 200 ml ethanol and 200 ml deionized water, and sonicate for 30 min;

[0103] S2: Add 0.9 g of 2-methylimidazole, stir for 12 h, let stand for aging for 12 h, pour into a crystallization dish and dry at 80 °C for 12 h to obtain a ZIF-67-based precipitate;

[0104] S3: The ZIF-67-based precipitate was placed in a tubular furnace and calcined once at 600°C in a 5% hydrogen / argon atmosphere for 2 h, and then calcined twice at 300°C in an air atmosphere for 2 h to obtain a supported cobalt oxide catalyst, which was recorded as 5ZIF-Co-Al-AH catalyst.

[0105] The performance of each catalyst prepared in the above examples was tested:

[0106] The catalytic performance (activity, cyclic stability) of the n ZIF-Co-Si catalyst prepared in Examples 1-5, the ZIF-Co@Si catalyst prepared in the comparative example, and the aZIF-Co-Al-AN catalyst prepared in Examples 6-10 for complete oxidation of propane was tested in a fixed bed microreactor: the inner diameter of the quartz reaction tube was 4 mm, and the tube length was 400 mm. The catalyst dosage was 100 mg, and the catalyst was 40-60 mesh (0.2-0.4 mm). The simulated reaction gas was: 0.1 vol% C3H8, 18 vol% O2, with nitrogen as the balance gas. The gas flow rate was 50 mL / min, and the space velocity (GHSV) was 30000 mL / g cat h. The reaction temperature was monitored by a thermocouple placed in the catalyst bed, and the residence time at each temperature was 10 min. The tail gas carbon dioxide after the reaction was monitored online by chromatography, the chromatographic model was Varian GC-450, and the detectors were FID and TCD detectors. The reaction was carried out under programmed temperature conditions of 50-400 °C.

[0107] The continuous stability of propane complete oxidation was tested by introducing the 50ZIF-Co-Si catalyst prepared in Example 1 and the 20ZIF-Co-Al-AH catalyst prepared in Example 8 into the above device. The results are as follows: Fig. 9 and Fig.18 As shown, it can be seen that the two catalysts can still maintain the initial conversion rate (67%) without decay in the 100h continuous reaction test, showing good catalytic stability.

[0108] 10 vol% water vapor was introduced into the above device to replace the nitrogen with the same volume fraction, and the effect of water vapor on the propane oxidation performance of the 50ZIF-Co-Si catalyst prepared in Example 1 and the 20ZIF-Co-Al-AH catalyst prepared in Example 8 was tested. The results are as follows: Fig.10 and Fig.19 As shown in the figure, it can be seen that after the introduction of water vapor, the propane conversion rate of the catalyst decreased due to the competitive adsorption of H2O. When the water vapor was removed, the propane conversion rate increased again to the value before the addition of water vapor within 1 hour, indicating that H2O did not damage the catalyst. In the second cycle, the propane conversion rate still increased to the initial conversion rate after the second removal of water, indicating that the introduction of H2O only caused competitive adsorption and caused the catalyst activity to decrease, and did not damage the catalyst. 50ZIF-Co-Si and 20ZIF-Co-Al-AH catalysts have good water resistance.

[0109] Figure 1The XRD patterns of the n ZIF-Co-Si catalysts prepared in Examples 1-5 and the ZIF-Co@Si catalysts prepared in the comparative example, from which it can be seen that after calcination, the weak diffraction peaks of cobalt oxide replace the diffraction peaks of ZIF-67, indicating that the organic metal framework precursor is completely decomposed. There is a broad peak from amorphous silicon dioxide at around 2θ=25o, and Co exists in the Co3O4 crystalline phase (JCPDS PDF#76-1802). Compared with the comparative example ZIF-Co@SiO2, the n ZIF-Co-Si sample has a blue shift, which may be caused by the lattice defects caused by Si doping.

[0110] Figure 2-8 The activity diagram and cycle stability diagram of n ZIF-Co-Si catalyst and ZIF-Co@Si catalyst for complete oxidation of propane, Examples 1-4 all show catalytic activity that is better or equivalent to that of the comparative examples, especially 40ZIF-Co-Si in Example 2 shows the best catalytic activity, but the catalytic activity of 10ZIF-Co-Si in Example 5 is lower than that of the comparative example due to the low loading amount. Through the cycle stability, it was found that the activity of ZIF-Co@Si in the comparative example began to decline after the second cycle, and the activity dropped significantly after five cycles, mainly because Co3O4 agglomerated inside the SiO2 shell. After the second heating cycle began, the catalytic activity of the n ZIF-Co-Si catalyst of Examples 1-5 was significantly improved, and the catalytic effect after five cycles was still stronger than the first time, indicating that it has excellent cycle stability compared with the comparative example.

[0111] Fig.11 XRD patterns of ZIF-Co-Al-AN and ZIF-Co-Al-AH (a=30, 20, 10, 5) catalysts prepared in Examples 6-10. It can be seen from the figure that all samples mainly show the spinel diffraction peak of Co3O4 (JCPDS PDF#78-1970). Some samples show the diffraction peak of γ-Al2O3 (JCPDS PDF#77-0394) with low crystallinity. However, the crystallinity of all samples is poor, indicating that neither Al2O3 nor Co3O4 forms particularly large particles, but with the increase of Co loading, the crystallinity of Co3O4 gradually increases.

[0112] Figure 12-17The activity diagram and cyclic stability spectrum of ZIF-Co-Al-AN and a ZIF-Co-Al-AH catalysts for complete oxidation of propane. It can be seen from the figure that compared with the ZIF-Co-Al-AN catalyst in Example 6 where the aluminum source is Al(NO3)3·9H2O, the 30ZIF-Co-Al-AH and 20ZIF-Co-Al-AH catalysts in Examples 7-8 where the aluminum source is Al2O3·H2O have higher oxidation activity for propane catalytic combustion, especially the 30ZIF-Co-Al-AH catalyst has the lowest complete oxidation temperature for propane catalytic combustion, showing the best catalytic activity, but the 10ZIF-Co-Al-AH and 5ZIF-Co-Al-AH in Examples 9-10 have a lower catalytic activity than that in Example 6 due to the low loading. Under the same conditions, five propane catalytic combustion cycle tests were carried out on the ZIF-Co-Al-AN and aZIF-Co-Al-AH catalysts. After five cycles of testing, the catalytic activity of the catalysts of all examples was improved, but the activity of the ZIF-Co-Al-AH catalysts of Examples 7-10 was significantly improved after the second cycle compared with the ZIF-Co-Al-AN catalyst in Example 6. In particular, the 20ZIF-Co-Al-AH catalyst had the largest improvement, showing excellent cycle stability.

[0113] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing a supported cobalt trioxide catalyst, characterized in that: The preparation method comprises the following steps: 1) dissolving a cobalt source and a carrier precursor in ethanol and water, adding 2-methylimidazole, stirring, standing and aging, and drying to obtain a ZIF-67-based precipitate; 2) The ZIF-67-based precipitate is calcined once in a reducing atmosphere and twice in an oxidizing atmosphere to obtain a supported cobalt tetroxide catalyst.

2. The method for preparing a supported cobalt trioxide catalyst according to claim 1, characterized in that: In step 1), the cobalt source is cobalt nitrate, and the carrier precursor is selected from any one of tetraethyl orthosilicate, aluminum nitrate or pseudo-boehmite.

3. The method for preparing a supported cobalt trioxide catalyst according to claim 2, characterized in that: In step 1), the volume ratio of ethanol to water is 1:

1.

4. The method for preparing a supported cobalt trioxide catalyst according to claim 2, characterized in that: In step 1), the molar concentration of cobalt nitrate in the mixed solution of ethanol and water is 0.006-0.062 mol / L.

5. The method for preparing a supported cobalt trioxide catalyst according to claim 2, characterized in that: In step 1), when the carrier precursor is tetraethyl orthosilicate, the molar ratio of the cobalt element in the cobalt source to the silicon element in tetraethyl orthosilicate is (0.085-0.767):1, and when the carrier precursor is aluminum nitrate or pseudo-boehmite, the molar ratio of the cobalt element in the cobalt source to the aluminum element in aluminum nitrate or pseudo-boehmite is (0.030-0.274):

1.

6. The method for preparing a supported cobalt trioxide catalyst according to claim 2, characterized in that: In step 1), the molar ratio of the 2-methylimidazole to the cobalt element in the cobalt source is (2:1)-(8:1).

7. The method for preparing a supported cobalt trioxide catalyst according to claim 2, characterized in that: In step 1), the stirring time is 10-15 hours, and the static aging time is 10-15 hours.

8. The method for preparing a supported cobalt trioxide catalyst according to claim 1, characterized in that: In step 1), during the drying, the drying temperature is 70-85° C. and the drying time is 10-15 hours.

9. The method for preparing a supported cobalt trioxide catalyst according to claim 1, characterized in that: In step 2), in the first calcination, the calcination temperature is 550-650°C and the calcination time is 2-3h; in the second calcination, the calcination temperature is 250-350°C and the calcination time is 2-3h; the reducing atmosphere is a mixed gas of hydrogen and argon, wherein the concentration of hydrogen is 5vol%, and the oxidizing atmosphere is air.

10. Use of a supported cobalt trioxide catalyst prepared by the preparation method according to any one of claims 1 to 9, characterized in that: The supported cobalt oxide catalyst is used for catalyzing the reaction of propane generating carbon dioxide and water.

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