阅读说明：本技术 单原子Ag基催化剂及其制备和在催化氧化甲醛中的应用 (Monoatomic Ag-based catalyst, preparation thereof and application thereof in catalytic oxidation of formaldehyde ) 是由 关超阳 郭文雅 郎嘉良 赵刚 黄翟 于 2019-09-03 设计创作，主要内容包括：本发明具体涉及一种单原子Ag基催化剂及其制备和在催化氧化甲醛中的应用,所述单原子Ag基催化剂是通过以下方法制备：通过共沉淀法制备出Ag+/MnAl-LDH,然后将Ag+/MnAl-LDH在氢气气氛下高温焙烧,制得单原子Ag基催化剂。制得的单原子Ag基催化剂,活性组分Ag以原子级形式均匀分散在MnAl-LDO表面,能够实现在常温、无光条件下对甲醛的高效去除,将甲醛转化为完全无毒的二氧化碳和水。(The invention specifically relates to a monoatomic Ag-based catalyst, a preparation method thereof and application thereof in catalytic oxidation of formaldehyde, wherein the monoatomic Ag-based catalyst is prepared by the following method: preparing Ag +/MnAl-LDH by a coprecipitation method, and then roasting the Ag +/MnAl-LDH at high temperature in a hydrogen atmosphere to prepare the single-atom Ag-based catalyst. According to the prepared single-atom Ag-based catalyst, the active component Ag is uniformly dispersed on the surface of the MnAl-LDO in an atomic form, so that the formaldehyde can be efficiently removed under the conditions of normal temperature and no light, and the formaldehyde is converted into completely nontoxic carbon dioxide and water.)

1. A monoatomic Ag-based catalyst is composed of an active component Ag and a carrier, and is characterized in that the carrier is MnAl-LDO, and the active component Ag is uniformly dispersed on the surface of the MnAl-LDO in an atomic form.

2. The monoatomic Ag-based catalyst according to claim 1, wherein the molar ratio of Mn element to Al element is (2-4): 1.

3. The monoatomic Ag-based catalyst according to claim 1, wherein the Ag loading is 0.8 to 10%, and the particle size is 0.01 to 1 nm.

4. A method for preparing a monoatomic Ag-based catalyst according to any one of claims 1 to 3, comprising the steps of: preparing Ag +/MnAl-LDH by a coprecipitation method, and then roasting the Ag +/MnAl-LDH at high temperature in a hydrogen atmosphere to prepare the single-atom Ag-based catalyst.

5. The preparation method of claim 4, wherein the preparation method of Ag +/MnAl-LDH specifically comprises the following steps: and adding the precipitant solution into the mixed solution containing the manganese precursor, the aluminum precursor and the silver precursor under the conditions of room temperature and stirring, continuing stirring until the reaction is complete, crystallizing, washing to be neutral, and drying to obtain the Ag +/MnAl-LDH.

6. The preparation method according to claim 5, wherein the manganese precursor is a soluble salt of manganese, the aluminum precursor is a soluble salt of aluminum, the silver precursor is a soluble salt of silver, the total ion concentration of the mixed solution is 0.03-0.06mol/L, and the molar ratio of the manganese precursor to the aluminum precursor to the silver precursor is (2-4): 1: (0.02-0.4).

7. The method according to claim 5, wherein the precipitant is an alkaline substance, the precipitant solution has a concentration of 0.08 to 0.15mol/L, and the precipitant is mixed with a metal ion (Mn)²⁺+Al³⁺) In a molar ratio of (1-3): 1.

8. the method according to claim 5, wherein the crystallization temperature is 70-150 ℃ and the crystallization time is 8-16 h.

9. The preparation method as claimed in claim 4, wherein the calcination temperature is 300-500 ℃, the calcination time is 1-5h, and the temperature rise rate is 1-10 ℃/min.

10. Use of the monatomic Ag-based catalyst prepared according to the preparation method of any one of claims 4 to 9, characterized in that the monatomic Ag-based catalyst is used for converting formaldehyde into completely non-toxic carbon dioxide and water at room temperature in the absence of light.

Technical Field

The invention belongs to the technical field of catalyst synthesis, and particularly relates to a monoatomic Ag-based catalyst, a preparation method thereof and application thereof in catalytic oxidation of formaldehyde.

Background

Formaldehyde is a main air pollutant with high toxicity in a vehicle or a room, and the formaldehyde can stimulate eyes, nasal cavities and respiratory tracts to cause anaphylactic reaction when contacting the formaldehyde for a short time; prolonged exposure to formaldehyde increases the likelihood of leukemia, nasopharyngeal carcinoma, breast cancer, and death. The world health organization international agency for the study of cancer has defined formaldehyde as a class of carcinogens. Therefore, how to remove formaldehyde in the car or the room with high efficiency is necessary.

The currently common method for removing formaldehyde pollutants in air comprises the following steps: adsorption, photocatalytic, plasma, catalytic oxidation, and the like. The catalytic oxidation method is to oxidize formaldehyde into harmless carbon dioxide and water by utilizing the oxidability of a catalyst, can thoroughly remove formaldehyde without causing secondary pollution, and is widely concerned and researched by people.

The noble metal Ag catalyst shows excellent catalytic performance in the formaldehyde catalytic degradation reaction. However, the catalyst used at present is mainly prepared by loading the active component silver on the active carbon by an impregnation method and then reducing the active component silver at high temperature. The catalyst prepared by the method has the advantages that the active component Ag is unevenly dispersed on the active carbon carrier, and the function of the active component is difficult to play.

Hydrotalcite (LDH), also known as layered double hydroxide, is An anionic layered microporous structure material with a chemical general formula of [ M2+1-xM3+ x (OH)2] x + (An-) x/n.yH 2O, wherein M2+ and M3+ are divalent and trivalent metal cations, respectively, and are located on a main body laminate; an-is An interlayer anion; x is the molar ratio of M2+/(M2+ + M3 +); y is the number of interlayer water molecules. The LDH crystal structure has lattice energy minimum effect and lattice orientation effect, and metal ions are uniformly distributed on the laminated plate in a certain mode to form a specific composition and structure. LDH is roasted to remove interlayer water and anions to form metal composite oxide (LDO), and the LDO has high specific surface area and adsorption performance and is an excellent carrier of the catalyst.

The monatomic catalyst is a novel catalyst, is based on metal active components at the atomic level, and has great advantages in the aspects of maximizing the number of active sites, enhancing the selectivity of target products, improving the inherent catalytic activity and reducing the consumption of noble metals.

At present, no report about the application of the monoatomic Ag-based catalyst taking LDO as a carrier to formaldehyde catalytic degradation is available.

Disclosure of Invention

The catalyst prepared by the method has firm combination between the active component Ag and a MnAl-LDO carrier, and the active component Ag is uniformly dispersed on the MnAl-LDO carrier in an atomic form, so that the efficient removal of formaldehyde can be realized under the conditions of normal temperature and no light, and the formaldehyde is converted into completely nontoxic carbon dioxide and water.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a monoatomic Ag-based catalyst consists of an active component Ag and a carrier, and is characterized in that the carrier is MnAl-LDO, and the active component Ag is uniformly dispersed on the surface of the MnAl-LDO in an atomic form.

Preferably, in the monoatomic Ag-based catalyst, the molar ratio of the Mn element to the Al element is (2-4): 1.

Preferably, in the monoatomic Ag-based catalyst, the Ag loading amount is 0.8-10%, and the particle size is 0.01-1 nm.

The preparation method of the monoatomic Ag-based catalyst comprises the following steps: preparing Ag +/MnAl-LDH by a coprecipitation method, and then roasting the Ag +/MnAl-LDH at high temperature in a hydrogen atmosphere to prepare the single-atom Ag-based catalyst.

Preferably, the preparation method of the Ag +/MnAl-LDH specifically comprises the following steps: and adding the precipitant solution into the mixed solution containing the manganese precursor, the aluminum precursor and the silver precursor under the conditions of room temperature and stirring, continuing stirring until the reaction is complete, crystallizing, washing to be neutral, and drying to obtain the Ag +/MnAl-LDH.

Preferably, in the preparation method of Ag +/MnAl-LDH, the manganese precursor is soluble salt of manganese.

Preferably, in the preparation method of Ag +/MnAl-LDH, the aluminum precursor is soluble salt of aluminum.

Preferably, in the preparation method of Ag +/MnAl-LDH, the silver precursor is a soluble salt of silver.

Preferably, in the preparation method of Ag +/MnAl-LDH, the total ion concentration of the mixed solution is 0.03-0.06mol/L, wherein the molar ratio of the manganese precursor to the aluminum precursor to the silver precursor is (2-4): 1: (0.02-0.4).

Preferably, in the preparation method of Ag +/MnAl-LDH, the precipitant is an alkaline substance.

Preferably, in the preparation method of Ag +/MnAl-LDH, the concentration of the precipitant solution is 0.08-0.15mol/L, and the precipitant is mixed with metal ions (Mn)²⁺+Al³⁺) In a molar ratio of (1-3): 1.

preferably, in the preparation method of Ag +/MnAl-LDH, the stirring speed is 1000-.

Preferably, in the preparation method of Ag +/MnAl-LDH, the crystallization temperature is 70-150 ℃, and the crystallization time is 8-16 h.

Preferably, in the preparation method of the Ag +/MnAl-LDH, the drying temperature is 70-150 ℃, and the drying time is 6-24 h.

Preferably, in the preparation method of the monoatomic Ag-based catalyst, the calcination temperature is 300-500 ℃, the calcination time is 1-5h, and the temperature rise speed is 1-10 ℃/min.

The single-atom Ag-based catalyst can be used for formaldehyde catalytic oxidation reaction to remove formaldehyde. The single-atom Ag-based catalyst can convert formaldehyde into completely nontoxic carbon dioxide and water at normal temperature under the condition of no light.

Compared with the prior art, the preparation method is simple, environment-friendly, low in cost and high in industrial application value, the active component Ag of the catalyst is firmly combined with the MgAl-LDO carrier, the active component Ag is uniformly dispersed on the MgAl-LDO carrier in an atomic form, the loading capacity of the active component Ag is 0.8-10%, the formaldehyde can be efficiently removed under the conditions of normal temperature and no light, and the formaldehyde is converted into completely nontoxic carbon dioxide and water; after the operation for 200 hours, the formaldehyde catalytic degradation capability of the catalyst is only slightly reduced, and the catalyst has stable performance.

1. Ag +/MnAl-LDH (manganese-aluminum layered composite hydroxide containing silver ions, which consists of manganese-aluminum layered composite hydroxide and silver ions adsorbed on the manganese-aluminum layered composite hydroxide) is prepared by a coprecipitation method, and due to the lattice positioning effect of the LDH, the components can be uniformly distributed, so that the Ag + is kept highly and uniformly dispersed in the MnAl-LDH.

2. And roasting the Ag +/MnAl-LDH at high temperature in a hydrogen atmosphere, so that interlayer water and anions of the MnAl-LDH are removed to form MnAl-LDO, and simultaneously, the Ag + is reduced into metal Ag in situ. The MnAl-LDO has higher specific surface area and adsorption performance and is a good carrier of the catalyst, and meanwhile, the memory effect of the MnAl-LDO enables the layer plate confinement effect generated along with the partial recovery of the layered structure in the process of loading the active component Ag by the MnAl-LDO to effectively prevent the active component Ag from aggregating and growing, so that the Ag is dispersed on the MnAl-LDO in an atomic form.

3. The atomic-grade Ag has high atom utilization rate, and has strong interaction with the carrier, particularly the synergistic effect with Mn element, so that the Ag realizes high-efficiency removal of formaldehyde at the same time of low load.

4. In the whole preparation reaction process, the synthesis steps of the catalyst are greatly simplified by a coprecipitation method and high-temperature roasting in a hydrogen atmosphere; no toxic and harmful by-products are generated, the environment is protected, the cost is low, and the method has industrial application value.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

The single-atom Ag-based catalyst consists of an active component Ag and a carrier, and is characterized in that the carrier is MnAl-LDO, and the active component Ag is uniformly dispersed on the surface of the MnAl-LDO in an atomic form.

In the monoatomic Ag-based catalyst, the molar ratio of the Mn element to the Al element is (2-4): 1.

In the single-atom Ag-based catalyst, the Ag loading amount is 0.8-10%, and the grain diameter is 0.01-1 nm.

The preparation method of the monoatomic silver-based catalyst comprises the following steps: preparing Ag +/MnAl-LDH by a coprecipitation method, and then roasting the Ag +/MnAl-LDH at high temperature in a hydrogen atmosphere to prepare the single-atom Ag-based catalyst.

The preparation method of the monoatomic Ag-based catalyst specifically comprises the following steps:

1. adding the precipitant solution into a mixed solution containing a manganese precursor, an aluminum precursor and a silver precursor at room temperature, continuing stirring until the reaction is complete after the addition is finished, crystallizing, washing to be neutral, and drying to obtain Ag +/MnAl-LDH;

the preparation method of the Ag +/MnAl-LDH specifically comprises the following steps: and adding the precipitant solution into the mixed solution containing the manganese precursor, the aluminum precursor and the silver precursor under the conditions of room temperature and stirring, continuing stirring until the reaction is complete, crystallizing, washing to be neutral, and drying to obtain the Ag +/MnAl-LDH.

In the preparation method of the Ag +/MnAl-LDH, the manganese precursor is soluble salt of manganese, such as one or a mixture of more than two of nitrate, sulfate and carbonate of manganese.

In the preparation method of the Ag +/MnAl-LDH, the aluminum precursor is soluble salt of aluminum, such as any one or a mixture of more than two of nitrate, sulfate and carbonate of aluminum.

In the preparation method of Ag +/MnAl-LDH, the silver precursor is a soluble salt of silver, such as one or a mixture of more than two of nitrate, sulfate and carbonate of silver.

In the preparation method of Ag +/MnAl-LDH, the solvent of the mixed solution is selected by the person skilled in the art, such as deionized water or C1-5 alcohol, or the mixture of at least two of the above.

In the preparation method of the Ag +/MnAl-LDH, the total ion concentration of the mixed solution is 0.03-0.06mol/L, wherein the molar ratio of the manganese precursor to the aluminum precursor to the silver precursor is (2-4): 1: (0.02-0.4).

In the preparation method of Ag +/MnAl-LDH, the precipitant is alkaline substance, such as any one of urea, sodium hydroxide and sodium carbonate or a mixture of at least two of the above substances.

In the preparation method of Ag +/MnAl-LDH, the solvent of the precipitant solution is selected by the person skilled in the art, such as deionized water or C1-5 alcohol, or a mixture of at least two of the above.

In the preparation method of the Ag +/MnAl-LDH, the concentration of the precipitant solution is 0.08-0.15mol/L, and the precipitant is mixed with metal ions (Mn)²⁺+Al³⁺) In a molar ratio of (1-3): 1.

in the preparation method of the Ag +/MnAl-LDH, the stirring speed is 1000-5000 r/min.

In the preparation method of the Ag +/MnAl-LDH, the crystallization temperature is 70-150 ℃, and the crystallization time is 8-16 h.

In the preparation method of the Ag +/MnAl-LDH, the drying temperature is 70-150 ℃, and the drying time is 6-24 h.

In the preparation method of the monoatomic silver-based catalyst, the roasting temperature is 300-.

The single-atom Ag-based catalyst can be used for formaldehyde catalytic oxidation reaction to remove formaldehyde. The single-atom Ag-based catalyst can convert formaldehyde into completely nontoxic carbon dioxide and water at normal temperature under the condition of no light.

The catalyst performance test adopts a 3-cube standard formaldehyde test chamber, the temperature in the chamber is 25 ℃, the relative humidity is 50RH, a pollution source formaldehyde solution is released by adopting an HY-JQ-1 generator of Dongguan ring instrument equipment Limited company, and the formaldehyde concentration in the chamber is monitored by adopting a British recording type formaldehyde detector PPM-HTV.

The following examples are provided to further illustrate the embodiments of the present invention and are not intended to limit the scope of the present invention.