Spinel oxide catalyst derived from MOFs and preparation method thereof

Abstract

The invention discloses a spinel oxide catalyst derived from MOFs and a preparation method thereof, and belongs to a catalyst preparation technology, and the method comprises the following steps: firstly synthesizing an organic framework material of a metal, then introducing a precursor of another metal through an impregnation method, and then drying and roasting to obtain the spinel catalyst. The method is suitable for preparing any spinel type composite oxide, and the spinel type composite oxide catalyst prepared by the method has a high specific surface area and a strong synergistic effect among metal atoms, and can remarkably improve the molecular catalytic oxidation performance of atmospheric pollutants. The method is simple and feasible, and can be applied on a large scale.

Description

Technical Field

[0001] The present invention belongs to the technology of catalyst preparation, and specifically relates to a spinel oxide catalyst derived from MOFs and a preparation method thereof. Background Art

[0002] Volatile organic compounds (VOCs) are one of the main sources of air pollution. Emitted VOCs not only have a serious impact on human health, but also pollute the atmospheric environment, producing photochemical smog, causing ozone layer damage and poisoning of animals and plants and other serious consequences. Among the many end-of-pipe treatment technologies for air pollutants, catalytic combustion technology is considered to be one of the most effective means. It can not only achieve low-temperature elimination of VOCs to obtain pure carbon dioxide and water, but also achieve energy recovery. Efficient and stable catalysts are the core of this technology.

[0003] Non-precious metal catalysts have poor low-temperature activity, but they are abundant and cheap, and have the prospect of large-scale application. Therefore, it is imperative to improve the catalytic activity of non-precious metal oxides. Among them, spinel-type composite oxide (structural formula AB2O4) catalysts have become one of the most promising combustion catalysts due to their easily regulated chemical structure. There are many factors that affect the performance of spinel catalysts, such as specific surface area, elemental composition, morphology, surface defects, etc. Increasing the specific surface area is one of the effective strategies to improve catalytic efficiency.

[0004] When the traditional precipitation method is used to prepare spinel oxide catalysts, different solubility products of different metals will result in different metal depositions, and the dispersion of different metal atoms in the prepared catalyst is poor.

[0005] In recent years, metal-organic frameworks (MOFs) have attracted widespread attention in the research of nanocatalytic materials due to their huge surface area, rich microporous structure and controllable structure. Summary of the invention

[0006] In order to prepare a catalyst with better catalytic performance, the present invention proposes a spinel oxide catalyst derived from MOFs and a preparation method thereof. Compared with the precipitation method, the MOFs derivation method of the present invention enables the ligand to coordinate with different metals to achieve fusion between atoms, and the distribution of elements is more uniform, which enhances the synergistic effect between metal atoms, and at the same time, the specific surface area is improved to a certain extent, and the catalytic performance is improved.

[0007] A method for preparing a spinel oxide catalyst derived from MOFs, comprising the following steps:

[0008] First, an organic framework material of metal B is synthesized, and then a precursor of metal A is introduced by an impregnation method. The spinel catalyst is obtained after drying and calcination. The prepared spinel catalyst has an AB2O4 structure.

[0009] Furthermore, the A position is a divalent transition metal element ion, which is any one of Mn, Co, Fe, Zn, and Ni; the B position is a trivalent metal element ion, which is any one of Mn, Co, and Fe.

[0010] Furthermore, the organic framework material of metal B is synthesized by a solvent method or a liquid phase diffusion method.

[0011] Further, the synthesis raw materials of the metal B organic framework material include a precursor of metal B, a ligand and a solvent C;

[0012] The precursor of metal B is one of nitrate, chlorate and acetate; the ligand is imidazole or benzoic acid; and the solvent C is water, methanol or N,N-dimethylformamide.

[0013] The precursor and ligand of metal B are dissolved in solvent C, stirred evenly at room temperature, and then transferred to a hydrothermal kettle, kept in an oven for a period of time, filtered, washed, and dried in a vacuum oven after natural cooling to obtain a metal B organic framework material.

[0014] Furthermore, the impregnation method is to disperse the organic framework material of metal B in solvent D, and then introduce a certain amount of precursor of metal A;

[0015] The molar ratio of the metal B to the metal A is 2:1; the solvent D is methanol or ethanol; and the precursor of the metal A is one of nitrate, chlorate and acetate.

[0016] Furthermore, the drying temperature is 60-90° C., the drying time is 6-24 hours, and the drying method is drying in a vacuum drying oven.

[0017] Furthermore, the calcination temperature is 400-600° C., and the calcination time is 3-6 hours.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention uses MOFs as precursors to synthesize nanomaterials with high specific surface area and can achieve mixing at the molecular atomic level, which has obvious advantages over catalysts prepared by traditional methods.

[0020] (2) Compared with the traditional precipitation method, the spinel-type composite oxide prepared by the present invention has a high specific surface area and exhibits high catalytic oxidation performance.

[0021] (3) The spinel-type composite oxide prepared by the present invention has strong redox ability and abundant surface oxygen vacancies, which greatly improves the catalytic performance.

[0022] (4) The raw materials of the present invention are widely available, the preparation process is simple and repeatable, and it can also be applied on a large scale, and has a high application prospect in the field of catalytic materials.

[0023] (5) The present invention is applicable to the preparation of any spinel-type composite oxide, has a high specific surface area, and strong synergistic effect between metal atoms, and can significantly improve the catalytic oxidation performance of atmospheric pollutant molecules (VOCs). BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the XRD pattern of the Co-Mn-MOF spinel oxide in Example 1. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is described in detail below through embodiments, but the protection scope of the present invention is not limited to the embodiments.

[0026] The present invention discloses a spinel oxide catalyst derived from MOFs and a preparation method. The preparation method of the present invention uses a metal organic framework compound (MOFs) as a sacrificial template to prepare a spinel composite oxide (AB2O4) catalyst. The method first synthesizes a metal organic framework material, then introduces a precursor of another metal by an impregnation method, and then obtains a spinel catalytic material by drying and calcining. The method is applicable to the preparation of any spinel composite oxide. The spinel composite oxide (AB2O4) catalyst prepared by the method has a high specific surface area and a strong synergistic effect between metal atoms, and can significantly improve the catalytic oxidation performance of atmospheric pollutant molecules (VOCs). The method is simple and feasible, and can also be applied on a large scale.

[0027] Example 1: Preparation of manganese-based spinel composite oxides using the method of the present invention

[0028] First, 0.2 mol Mn(NO3)2·4H2O and 0.1 mol C6H3(COOH)3 were weighed and dissolved in 60 mL methanol solution. After stirring at room temperature for 0.5 h, a uniform solution was formed and transferred to a 100 mL hydrothermal kettle. It was kept in a 120 ° C oven for 3 h, and after natural cooling, it was filtered, washed and placed in a 70 ° C vacuum oven for 12 h. The obtained powder material was then dispersed in 20 mL methanol solution, followed by the introduction of 0.1 mol Co(NO3)2·6H2O, and evaporated in a 70 ° C water bath. Finally, the scraped powder was placed in a muffle furnace at 450 ° C for 3 h to obtain CoMn2O4 spinel catalytic material (named Co-Mn-MOF).

[0029] Example 2: Preparation of manganese-based spinel composite oxides by precipitation method

[0030] First, prepare 50mL of 0.2M Mn(NO3)2, then add 20mL of ammonia solution (25wt%) to the above solution, and then add 25mL of 0.2M Co(NO3)2 solution after the addition is complete. Continue stirring at room temperature for 2h, then filter, wash and dry in an oven at 110℃ for 12h. Then place the obtained powder material in a muffle furnace at 450℃ for 3h. Obtain CoMn2O4 spinel catalytic material (named CoMn2O4-C).

[0031] Example 3: Preparation of manganese-based spinel composite oxides using the method of the present invention

[0032] First, 0.2 mol Mn(NO3)2·4H2O and 0.1 mol C6H3(COOH)3 were weighed and dissolved in 60 mL methanol solution. After stirring at room temperature for 0.5 h, a uniform solution was formed and transferred to a 100 mL hydrothermal kettle. It was kept in a 120 ° C oven for 3 h, and after natural cooling, it was filtered, washed and placed in a 70 ° C vacuum oven for 12 h. The obtained powder material was then dispersed in 20 mL methanol solution, followed by the introduction of 0.1 mol Cu(NO3)2·4H2O and evaporated in a 70 ° C water bath. Finally, the scraped powder was placed in a muffle furnace at 450 ° C for 3 h to obtain the CuMn2O4 spinel catalytic material (named Cu-Mn-MOF).

[0033] Example 4: Preparation of manganese-based spinel composite oxides by precipitation method

[0034] First, prepare 50mL of 0.2M Mn(NO3)2, then add 20mL of ammonia solution (25wt%) to the above solution, and then add 25mL of 0.2M Cu(NO3)2 solution after the addition is complete. Continue stirring at room temperature for 2h, then filter, wash and dry in an oven at 110℃ for 12h. Then place the obtained powder material in a muffle furnace at 450℃ for 3h. Obtain CuMn2O4 spinel catalytic material (named CuMn2O4-C).

[0035] Example 5: Preparation of manganese-based spinel composite oxides using the method of the present invention

[0036] First, 0.2 mol Mn(NO3)2·4H2O and 0.1 mol C6H3(COOH)3 were weighed and dissolved in 60 mL methanol solution. After stirring at room temperature for 0.5 h, a uniform solution was formed and transferred to a 100 mL hydrothermal kettle. It was kept in a 120 ° C oven for 3 h, and after natural cooling, it was filtered, washed and placed in a 70 ° C vacuum oven for 12 h. The obtained powder material was then dispersed in 20 mL methanol solution, followed by the introduction of 0.1 mol Fe(NO3)2·9H2O, and evaporated in a 70 ° C water bath. Finally, the scraped powder was placed in a muffle furnace at 450 ° C for 3 h to obtain FeMn2O4 spinel catalytic material (named Fe-Mn-MOF).

[0037] Example 6: Preparation of manganese-based spinel composite oxides using the method of the present invention

[0038] First, 0.2 mol Mn(NO3)2·4H2O and 0.1 mol C6H3(COOH)3 were weighed and dissolved in 60 mL methanol solution. After stirring at room temperature for 0.5 h, a uniform solution was formed and transferred to a 100 mL hydrothermal kettle. It was kept in a 120 ° C oven for 3 h, and after natural cooling, it was filtered, washed and placed in a 70 ° C vacuum oven for 12 h. The obtained powder material was then dispersed in 20 mL methanol solution, followed by the introduction of 0.1 mol Ni(NO3)2·6H2O, and evaporated in a 70 ° C water bath. Finally, the scraped powder was placed in a muffle furnace at 450 ° C for 3 h to obtain CoMn2O4 spinel catalytic material (named Co-Mn-MOF).

[0039] Example 7: Preparation of manganese-based spinel composite oxides using the method of the present invention

[0040] First, 0.2 mol Mn(NO3)2·4H2O and 0.1 mol C6H3(COOH)3 were weighed and dissolved in 60 mL methanol solution. After stirring at room temperature for 0.5 h, a uniform solution was formed and transferred to a 100 mL hydrothermal kettle. It was kept in a 120 ° C oven for 3 h, and after natural cooling, it was filtered, washed and placed in a 70 ° C vacuum oven for 12 h. The obtained powder material was then dispersed in 20 mL methanol solution, followed by the introduction of 0.1 mol Zn(NO3)2·6H2O, and evaporated in a 70 ° C water bath. Finally, the scraped powder was placed in a muffle furnace at 450 ° C for 3 h to obtain a ZnMn2O4 spinel catalytic material (named Zn-Mn-MOF).

[0041] Example 8: Preparation of manganese-based spinel composite oxides using the method of the present invention

[0042] First, 0.2 mol Mn(NO3)2·4H2O and 0.1 mol C6H3(COOH)3 were weighed and dissolved in 60 mL methanol solution. After stirring at room temperature for 0.5 h, a uniform solution was formed and transferred to a 100 mL hydrothermal kettle. It was kept in a 120 ° C oven for 3 h, and after natural cooling, it was filtered, washed and placed in a 70 ° C vacuum oven for 12 h. The obtained powder material was then dispersed in 20 mL methanol solution, followed by the introduction of 0.1 mol Co(NO3)2·6H2O, and evaporated in a 70 ° C water bath. Finally, the scraped powder was placed in a muffle furnace at 600 ° C for 3 h to obtain CoMn2O4 spinel catalytic material (named Co-Mn-MOF#).

[0043] Example 9: Toluene catalytic combustion performance test of manganese-based spinel catalytic material

[0044] The prepared manganese-based spinel catalytic material was subjected to a toluene catalytic combustion performance test under the following test conditions: 0.1 g manganese-based spinel catalytic material (catalyst), space velocity 48,000 h -1 , reaction temperature 100-350°C. The results are shown in the following table:

[0045] Table 1 Toluene catalytic combustion performance results of catalysts

[0046]

[0047]

[0048] Note: 10 , T 50 , T 90 The reaction temperatures correspond to the toluene conversion rates of 10%, 50% and 90% respectively; reaction conditions: catalyst 0.1

[0049] g, 1000ppm toluene, 20% oxygen, nitrogen as balance gas, reaction temperature: 100-350℃, space velocity 48,000h -1 .

[0050] It can be seen from the above table:

[0051] 1) Compared with the manganese-based spinel catalyst prepared by the traditional precipitation method, the catalytic activity of the catalyst prepared by metal organic ligand composite derivatization is significantly improved. This improvement in activity is attributed to the increase in specific surface area and the enhanced synergistic effect between metals;

[0052] 2) With Mn element as B-position, different A-position metals have different properties and different abilities to gain or lose electrons, which results in differences in catalytic activity. The Ni-Mn-MOF catalyst has the highest activity, while the Zn-Mn-MOF catalyst has the lowest activity.

[0053] As described above, although the present invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the present invention itself. Various changes in form and details may be made without departing from the spirit and scope of the present invention.

Claims

1. A method for preparing a spinel oxide catalyst derived from MOFs, characterized in that: First, an organic framework material of metal B is synthesized, and then a precursor of metal A is introduced by an impregnation method. The spinel catalyst is obtained after drying and calcination. The prepared spinel catalyst has an AB2O4 structure.

2. The preparation method according to claim 1, characterized in that: The A position is a divalent transition metal ion, which is any one of Mn, Co, Fe, Zn, and Ni; the B position is a trivalent metal ion, which is any one of Mn, Co, and Fe.

3. The preparation method according to claim 1, characterized in that: The organic framework material of metal B is synthesized by a solvent method or a liquid phase diffusion method.

4. The preparation method according to claim 2, characterized in that: The raw materials for synthesizing the metal B organic framework material include a precursor of metal B, a ligand and a solvent C; The precursor of metal B is one of nitrate, chlorate and acetate; The ligand is an imidazole or a benzoic acid; Solvent C is water, methanol or N,N-dimethylformamide.

5. The preparation method according to claim 2, characterized in that: The impregnation method is to disperse the organic framework material of metal B in solvent D and then introduce a certain amount of precursor of metal A; Solvent D is methanol or ethanol; The precursor of metal A is one of nitrate, chlorate and acetate.

6. The preparation method according to claim 2, characterized in that: The drying temperature is 60-90°C, the drying time is 6-24h, and the drying method is drying in a vacuum drying oven.

7. The preparation method according to claim 2, characterized in that: The calcination temperature is 400-600°C and the calcination time is 3-6h.

8. The spinel oxide catalyst prepared by the preparation method according to any one of claims 1 to 7.

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