Preparation method and application of confinement type manganese-cerium diatomic cluster millimeter sphere catalyst

Abstract

The invention provides a preparation method of a confinement type manganese-cerium diatomic cluster millimeter sphere catalyst. The preparation method comprises the following steps: firstly, preparing a millimeter-scale carrier by adopting a carrier pre-forming process; mn and Ce are used as active components and are dispersed on the carrier in the form of atomic clusters in a dipping and calcining manner, and the atomic clusters are confined around adjacent atoms in a mutual bonding manner, so that the agglomeration of atomic sites can be effectively prevented. The atom cluster active component is uniformly dispersed on the surface of the carrier, so that the utilization efficiency of the active component can be fully improved; the unique coordination environment of the manganese-cerium diatom cluster endows the catalyst with excellent and stable electron transfer capability, and continuous, long-time and efficient catalytic action can be realized; in addition, the millimeter-scale catalyst is convenient to recycle, is relatively high in cyclicity and economical efficiency, and has unique advantages in the aspect of industrial application.

Description

Technical Field

[0001] The present invention relates to the fields of catalysts, environmental remediation and deep purification of sewage and wastewater, and in particular to a preparation method and application of a confined manganese-cerium diatomic cluster millimeter sphere catalyst. Background Art

[0002] As a catalytic technology with high degree of automation and no secondary pollutants, ozone catalytic oxidation technology has the advantages of low cost, no need to add additional chemical reagents, low sludge yield, and eco-friendliness. It has great application potential in the field of environmental governance. Due to the selective oxidation of ozone, the oxidation rate of some pollutants, especially organic pollutants, is relatively slow, resulting in incomplete removal of pollutants. In order to promote the efficient decomposition of ozone to produce more ·OH, the existing technology introduces catalysts or activators to promote ozone oxidation decomposition. For example, various transition metal oxides (MnO2, TiO2, NiO, Co3O4, MoO3, Fe2O3, etc.) are often used as catalysts for catalytic ozone oxidation.

[0003] At present, the research on ozone oxidation catalysts is mostly focused on powder catalysts. However, powder catalysts are inconvenient to use continuously and difficult to recycle during actual use. To this end, technicians have developed integral catalysts that are convenient for continuous use and recycling; for example, patent CN 118454688 A, a porous integral ozone catalyst and its preparation and application, records that the powder materials are first mixed and granulated, low-temperature dried to remove moisture, and then high-temperature calcined to sinter the catalyst into shape. At the same time, the gas-producing components are used to generate a porous structure in situ, and a porous integral ozone catalyst is obtained after cooling. It is also stated that the catalyst can be used to catalyze the degradation of organic pollutants. However, the integral catalyst (manganese-based) in the prior art is prone to cause high-valent Mn in the catalytic process. 4+ Accumulation, the active sites cannot be restored to the reduced state in time, resulting in reduced sustainability of catalysis; for this reason, technicians have developed bimetallic or even multi-metallic integral catalysts, such as Mn / Mg / Ca / Fe / Ti / Ce and other metals, to solve the problem of reduced activity of manganese-based catalysts and thus reduced sustainability.

[0004] However, the current synthesis process of supported dual / multi-metal catalysts not only needs to avoid metal atom agglomeration and increase the loading amount, but also needs to accurately control the formation of dual / multi-atom sites on the support surface. Therefore, how to prepare dual / multi-atom catalysts with uniform metal atom distribution and stable catalytic performance has become a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing a confined manganese-cerium diatomic cluster millimeter sphere catalyst. On the basis of a manganese-based catalyst, metallic cerium is introduced to construct a synergistic active site to improve the catalytic effect of the catalyst. At the same time, in order to avoid the agglomeration of the two metal atoms of Mn and Ce, the present invention achieves precise control of the diatomic sites on the surface of the carrier by preforming the carrier first and then impregnating it, so that the metal atoms in the prepared catalyst are evenly distributed and the catalytic performance is stable, which can be effectively used to catalyze the degradation of water pollutants by ozone.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a confined manganese-cerium diatomic cluster millimeter sphere catalyst, comprising the following steps:

[0008] (1) performing a preforming treatment on the carrier to obtain a preformed carrier;

[0009] (2) subjecting the preformed support to a first calcination to obtain a calcined support;

[0010] (3) impregnating the calcined support in a mixed solution of a manganese (II) salt and a cerium (IV) salt to obtain an impregnated product;

[0011] (4) The impregnation product is dried and subjected to a second calcination to obtain the confined manganese-cerium diatomic cluster millimeter sphere catalyst.

[0012] Preferably, the carrier is one of red clay and Al2O3; and / or,

[0013] The size of the preformed carrier is 2-5 mm.

[0014] Preferably, the temperature of the first calcination is 550-650°C, the calcination time is 4-6h, and the heating rate is 4-6°C / min.

[0015] Preferably, the mass concentration of metal ions in the mixed solution of manganese (II) salt and cerium (IV) salt is 2-10wt%, and the atomic ratio of manganese to cerium in the mixed solution of manganese (II) salt and cerium (IV) salt is 7:3.

[0016] Preferably, the second calcination temperature is 550-650°C, the calcination time is 4-6h, and the heating rate is 4-6°C / min.

[0017] The present invention also provides a confined manganese-cerium diatomic cluster millimeter sphere catalyst prepared by any of the above preparation methods, wherein the atomic cluster size of the catalyst is preferably 1-5 nm.

[0018] Preferably, the valence states of manganese and cerium in the catalyst are 3+ and 4+.

[0019] Preferably, the manganese atoms and cerium atoms in the catalyst are confined around adjacent atoms in a mutually bonded manner, and the bond length of Mn-Ce is

[0020] The present invention also provides the use of the confined manganese-cerium diatomic cluster millimeter sphere catalyst prepared by any of the preparation methods described above in catalyzing ozone degradation of water pollutants; more preferably, the water pollutants can be difficult-to-degrade pollutants such as humic acid and fulvic acid.

[0021] In the prior art, manganese-based catalysts have excellent ozone catalytic activity and have been used to catalyze ozone degradation of pollutants in water bodies; for example, patent CN 118454688 A records a method for preparing a porous monolithic ozone catalyst and its application in catalyzing ozone degradation of organic pollutants (antibiotics). Although the use of manganese oxide and cerium oxide as catalyst active ingredients is disclosed in its oxide; however, the monolithic catalyst (manganese-based) adopts a preparation method of mixing metal oxide (solid) with silicon dioxide and gas-producing components for granulation during the preparation process. After synthesis, the agglomeration of metal atoms cannot be effectively avoided, the active ingredients are unevenly distributed, and the loading amount is also low. This application adopts a carrier preforming process to prepare a millimeter-level carrier; and Mn and Ce are used as active components and dispersed on the carrier in the form of atomic clusters by impregnation and calcination. The atomic clusters are confined around adjacent atoms by bonding with each other and firmly anchored on the carrier surface, which can effectively prevent the agglomeration of atomic sites. In the present invention, the atomic cluster active components are evenly dispersed on the carrier surface, which can fully improve the utilization efficiency of the active components; the unique coordination environment of the manganese-cerium diatomic cluster gives it excellent and stable electron transfer ability, which can achieve continuous, long-term and efficient catalytic effect; in addition, the millimeter-scale catalyst is easy to recycle and has strong recyclability and economy, and has unique advantages in industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a physical picture of the millimeter ball catalyst prepared in Example 1;

[0023] Figure 2 This is a spherical aberration electron microscope image of the millimeter-sphere catalyst prepared in Example 1;

[0024] Figure 3 The K-edge X-ray absorption near-spectral synchrotron radiation diagram of the metal Fourier transform of the millimeter-sphere catalyst prepared in Example 1;

[0025] Figure 4 is the LSV curve of the millimeter ball catalyst prepared in Example 1;

[0026] Figure 5 This is a diagram showing the catalytic effect of the millimeter-sphere catalyst prepared in Example 1. DETAILED DESCRIPTION

[0027] The present invention provides a method for preparing a confined manganese-cerium diatomic cluster millimeter sphere catalyst, comprising the following steps:

[0028] (1) performing a preforming treatment on the carrier to obtain a preformed carrier;

[0029] (2) subjecting the preformed support to a first calcination to obtain a calcined support;

[0030] (3) impregnating the calcined support in a mixed solution of a manganese (II) salt and a cerium (IV) salt to obtain an impregnated product;

[0031] (4) The impregnation product is dried and subjected to a second calcination to obtain the confined manganese-cerium diatomic cluster millimeter sphere catalyst.

[0032] In the present invention, unless otherwise specified, the substances used are all commercially available products well known to those skilled in the art or can be prepared by themselves according to known methods.

[0033] The present invention first preforms the carrier to obtain a preformed carrier. In the present invention, the carrier is preferably one of red clay and Al2O3; more preferably red clay; the size of the preformed carrier is preferably 2-5 mm. Using red clay as a catalyst carrier, millimeter-sized red clay particles can be prepared in the preforming stage, and the prepared catalyst is also millimeter-sized, which can facilitate the recycling of the catalyst, has good recyclability and economy, and has broad prospects for industrial application. Figure 1 The actual picture of the millimeter ball catalyst prepared by the present application is shown. It can be seen from the figure that the catalyst has uniform shape and particle size and can be effectively recovered (for example, by screening and washing). The present invention has no special limitation on the preforming method, for example, a disc granulator can be used for granulation.

[0034] After the carrier is obtained by preforming, the present invention performs a first calcination on the preformed carrier to obtain a calcined carrier. In the present invention, the temperature of the first calcination is preferably 550-650°C, more preferably 600°C; the calcination time is preferably 4-6h, more preferably 4h; the heating rate is preferably 4-6°C / min, more preferably 5°C / min; the purpose of the first calcination in the present application is mainly to fix the shape of the carrier through the sintering process to ensure its strength. The present invention has no special limitation on the atmosphere of the calcination, and it can be carried out in air.

[0035] After the carrier is calcined, the present invention immerses the calcined carrier in a mixed solution of manganese (II) salt and cerium (IV) salt to obtain an impregnated product. In the present invention, the mass concentration of metal ions in the mixed solution of manganese (II) salt and cerium (IV) salt is preferably 2-10wt%, and the atomic ratio of manganese to cerium in the mixed solution of manganese (II) salt and cerium (IV) salt is preferably 7:3. In the present invention, the manganese (II) salt refers to a +2-valent manganese salt, the cerium (IV) salt refers to a +4-valent cerium salt, and the mass concentration of metal ions in the mixed solution refers to the total mass concentration of the two metal ions; the present application limits the atomic ratio of manganese and cerium, because the applicant's experimental research found that the catalyst at this atomic ratio has the best catalytic performance.

[0036] After impregnation, the present invention continues to dry and calcine the impregnation product for the second time to obtain the confined manganese-cerium diatomic cluster millimeter sphere catalyst. In the present invention, the temperature of the second calcination is preferably 550-650°C, more preferably 600°C; the calcination time is preferably 4-6h, more preferably 4h; the heating rate is preferably 4-6°C / min, more preferably 5°C / min; the role of the second calcination in this application is different from the above-mentioned first calcination, and its main purpose is to convert the metal salt loaded on the carrier into a metal oxide through calcination, stimulate it to become an active component, and improve the catalytic activity of the catalyst. The present invention does not specifically limit the atmosphere of the calcination, and it can be carried out in air.

[0037] The present invention also provides a confined manganese-cerium diatomic cluster millimeter sphere catalyst prepared by any of the preparation methods described above, and the atomic cluster size of the catalyst is preferably 1-5nm. The catalysts in the prior art have the problem of large metal nanoparticle size and insufficient catalytic activity. The atomic cluster size of the atomic cluster catalyst prepared by the present application reaches 1-5nm, which fully improves the dispersibility of the bimetallic atomic clusters and the availability of active sites; and the distance between two adjacent metal atoms is very close, showing strong electronic interaction; multi-channel electron transfer circuits are formed between the atomic clusters, which strengthens the system's electron transfer performance, improves the catalytic effect, and ensures the catalyst's good catalytic activity. Figure 2 A shows that the atomic clusters in the millimeter ball catalyst prepared in the present application are tiny in size, reaching the nanometer level; Figure 2 B shows that the atomic clusters in the catalyst are evenly distributed without agglomeration.

[0038] In the present invention, the valence states of manganese and cerium in the catalyst are 3+ and 4+; in the present invention, the valence states of metallic manganese and cerium are both +3 and +4, that is, the valence state of manganese is +3 and +4, and the valence state of cerium is also +3 and +4; under this valence state, the electron transfer of the two metal oxides is stable and the activity is relatively high; the catalytic reaction can be carried out stably and continuously.

[0039] In the present invention, the manganese atoms and cerium atoms in the catalyst are confined around adjacent atoms in a mutually bonded manner, and the bond length of Mn-Ce is The bonding form of the two metal atoms in the present application effectively prevents the agglomeration of the atomic sites, ensures the uniformity of the distribution of the active ingredients on the carrier and increases the loading capacity. Figure 3 As shown, the metal Fourier transform K-edge X-ray absorption near-spectral synchrotron radiation diagram of the confined catalyst prepared in this application shows that the distance between two adjacent metal atoms is very close, and the Ce-Mn bond length is It exhibits strong electronic interactions; atomic clusters are confined around adjacent atoms by bonding with each other, which can greatly improve the stability of the catalyst.

[0040] The present invention also provides the use of the confined manganese-cerium diatomic cluster millimeter sphere catalyst prepared by any of the above preparation methods in catalyzing ozone degradation of water pollutants; more preferably, the water pollutants can be humic acid, fulvic acid and other difficult-to-degrade pollutants. The method of the present invention can continuously catalyze ozone to produce active species to efficiently remove various pollutants in water, solving the problems of insufficient continuous catalytic performance and high regeneration cost of conventional ozone catalysts, and has broad application potential in the field of sewage and wastewater purification.

[0041] The technical solutions in the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Example 1

[0043] A method for preparing a confined manganese-cerium diatomic cluster millimeter sphere catalyst comprises the following steps:

[0044] (1) granulating the clay using a disc granulator to obtain preformed clay particles with a particle size of 2-5 mm;

[0045] (2) calcining the preformed clay particles at 600° C. in a static air atmosphere for 4 hours (the heating rate is controlled at 5° C. / min) to obtain calcined clay particles;

[0046] (3) Weighing 10 g of the calcined clay particles, immersing them in 20 mL of a 4 wt% manganese-cerium metal mixed solution (the molar ratio of Mn to Ce is fixed at 7:3); immersing for 24 h;

[0047] (4) The impregnated catalyst particles are placed in a 50°C oven and dried for 12 hours; the dried particle sample is calcined in a static air atmosphere at 600°C for 4 hours (heating rate of 5°C / min) to obtain the confined manganese-cerium diatomic cluster millimeter sphere catalyst of the present application.

[0048] Comparative Example 1

[0049] The difference between this comparative example and Example 1 is that the impregnating metal solution is a metal manganese salt solution of equal mass concentration.

[0050] Comparative Example 2

[0051] The difference between this comparative example and Example 1 is that the impregnating metal solution is a metal cerium salt solution of equal mass concentration.

[0052] Figure 4 The LSV curve of the atomic cluster electrocatalyst prepared in Example 1 is shown. Compared with the single metal atomic cluster catalysts prepared in Comparative Examples 1 and 2, the synthesized Mn and Ce diatomic atomic cluster catalysts form multi-channel electron transfer circuits between the atomic clusters, showing excellent electron transfer ability and improving the catalytic effect.

[0053] Figure 5 A diagram showing the catalytic effect of the confined millimeter-scale manganese-cerium atomic cluster catalyst prepared in Example 1 of the present application is shown. Figure 5 A is the effect diagram of degradation of fulvic acid model solution (concentration is 0.2g / L), Figure 5 B is the catalytic stability evaluation diagram. Figure 5 A shows that the confined millimeter-scale manganese-cerium atomic cluster catalyst exhibits excellent catalytic effect, and the TOC removal rate is more than 87.5% within 90 minutes; Figure 5 B shows that the stability of the confined millimeter-scale manganese-cerium atomic cluster catalyst is greatly improved compared with the control group. After repeated use for 5 times, the catalytic performance for fulvic acid is still more than 85%.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a confined manganese-cerium diatomic cluster millimeter sphere catalyst, comprising the following steps: (1) performing a preforming treatment on the carrier to obtain a preformed carrier; (2) subjecting the preformed support to a first calcination to obtain a calcined support; (3) impregnating the calcined support in a mixed solution of a manganese salt and a cerium salt to obtain an impregnated product; (4) The impregnation product is dried and subjected to a second calcination to obtain the confined manganese-cerium diatomic cluster millimeter sphere catalyst.

2. The preparation method according to claim 1, characterized in that: The carrier is one of red clay and Al2O3; and / or, The size of the preformed carrier is 2-5 mm.

3. The preparation method according to claim 1, characterized in that: The temperature of the first calcination is 550-650°C, the calcination time is 4-6h, and the heating rate is 4-6°C / min.

4. The preparation method according to claim 1, characterized in that: The mass concentration of metal ions in the mixed solution of manganese salt and cerium salt is 2-10wt%, and the atomic ratio of manganese to cerium in the mixed solution of manganese salt and cerium salt is 7:

3.

5. The preparation method according to claim 1, characterized in that: The second calcination temperature is 550-650°C, the calcination time is 4-6h, and the heating rate is 4-6°C / min.

6. The confined manganese-cerium diatomic cluster millimeter sphere catalyst prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The atomic cluster size of the catalyst is 1-5 nm.

7. The catalyst according to claim 6, characterized in that The valence states of manganese and cerium in the catalyst are 3+ and 4+.

8. The catalyst according to claim 6, characterized in that In the catalyst, the manganese atoms and cerium atoms are confined around adjacent atoms in a mutually bonded manner, and the bond length of Mn-Ce is 9. Use of the confined manganese-cerium diatomic cluster millimeter sphere catalyst prepared by the preparation method according to any one of claims 1 to 5 in catalytic ozone degradation of water pollutants.

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