Preparation of CeO2 / Fe-SA and N-alkylation application of amine

Abstract

The invention relates to preparation of CeO2 / Fe-SA and application of N-alkylation of amine, and discloses a preparation method of a monatomic iron catalyst and application of the monatomic iron catalyst in the aspect of N-alkylation of amine. During preparation, cerium oxide is taken as a carrier, and a metal iron source is successfully loaded in a monatomic form by adopting a surface oxidation-reduction method. The synthesis method conforms to the green chemistry concept, is pollution-free, simple to operate, low in cost and easy to popularize, and can effectively control the loading capacity of single atoms. The monatomic iron catalyst disclosed by the invention can be used for N-alkylation reaction of amine, has high activity, is easy to recover, and has good catalytic activity and long catalytic life.

Description

Technical Field

[0001] The present disclosure belongs to the field of catalytic technology, and particularly relates to a preparation method of a single-atom iron catalyst and its application in the N-alkylation reaction of amines. Background Art

[0002] The statements herein only provide background information related to the present disclosure and do not necessarily constitute prior art.

[0003] Amines and amine derivatives are the most basic and important organic nitrogen compounds because they can serve as starting materials for the preparation of other nitrogen-containing organic compounds. To meet specific synthetic needs, various methods with stronger selectivity, higher efficiency, and atom economy have been developed to synthesize different amines and amine derivatives. The N-alkylation reaction of amines / amines with alcohols as alkylating agents is a relatively environmentally friendly alternative method, not only because relatively high atom efficiency can be achieved by generating water as the only by-product, but also because alcohols are more readily available, more stable, less toxic, easier to store and handle, and less costly.

[0004] Due to the high activity of transition metal catalysts in alcohol activation and the great potential in dehydration alkylation reactions, progress has been made using traditional homogeneous metal catalysts such as Ru, Ir, Fe, Co, Mn, etc. Among them, iron has significant advantages compared with precious metals because it is the second most abundant metal in the earth's crust. Various iron salts and iron complexes are commercially available on a large scale or are easily synthesized. In addition, iron compounds are relatively non-toxic. Contrary to artificial precious metal catalysts, iron is an essential key element involved in various biological systems. For example, in metalloproteins used for the transport or metabolism of small molecules (oxygen, nitrogen, methane, etc.). Due to the easy change of oxidation state and unique Lewis acid characteristics, iron catalysts have been widely used in addition, substitution, cycloaddition, hydrogenation, reduction, and oxidative coupling reactions. Therefore, iron-based catalysts are ideal catalysts for carrying out N-alkylation reactions.

[0005] Some inherent problems of homogeneous catalysts, such as expensive ligands, limited reusability, and difficulty in product separation, pose great challenges to their further application. In order to discover more efficient and economical catalysts in this process, we have paid particular attention to the possibility of using single-atom catalysts (SACs) for the N-alkylation of amines. Single-atom catalysts have the advantages of both homogeneous and heterogeneous catalysts and are helpful for solving the above problems. Summary of the Invention

[0006] The purpose of the present disclosure is to provide a preparation method of a single-atom iron catalyst and its application in the N-alkylation reaction of amines. The reaction has mild reaction conditions, the catalyst is easy to separate, can be recycled, and has excellent cycle stability.

[0007] The technical solution adopted by the present disclosure to solve the above problems is as follows: A preparation method of a single-atom iron catalyst for the N-alkylation reaction of amines, comprising the following steps:

[0008] 1) Dispersing a cerium oxide support in deionized water to form a mixed solution, and then adding an iron source to the mixed solution to react Ce on the surface of CeO2 4+ with the iron source.

[0009] 2) After reacting for a period of time, separating the iron source from the solution, and obtaining CeO2 / Fe-SA after evaporating the solvent.

[0010] Preferably, the iron source in step 1) is elemental iron.

[0011] Preferably, the reaction method in step 1) is not limited to stirring, ultrasonic treatment, and oscillation.

[0012] Preferably, the separation method of the single-atom iron catalyst after the reaction in step 2) is not limited, and any method that can separate the product can be applied.

[0013] More preferably, the metal iron single-atom loading amount on the CeO2 / Fe-SA catalyst is 1 wt% - 30 wt%.

[0014] Another object of the present disclosure is to provide an application of a single-atom iron catalyst in catalyzing the N-alkylation reaction of amines. Using CeO2 / Fe-SA as a catalyst, in an alkaline environment, the amine and alcohol react under atmospheric pressure conditions.

[0015] Specifically, it includes the following steps:

[0016] 1) Adding a CeO2 / Fe-SA catalyst, an amine, an alcohol, and an alkali source to a reaction flask.

[0017] 2) Reacting under atmospheric pressure at a temperature of 70 - 140 °C.

[0018] 3) Collecting the CeO2 / Fe-SA catalyst, washing it with ethyl acetate, and drying it for reuse.

[0019] Compared with the prior art, the advantages of the present disclosure are as follows:

[0020] (1) The single-atom iron catalyst of the present disclosure can solve the problem that it is difficult to separate the homogeneous catalyst from the raw materials and products. The preparation method of the present disclosure is a brand-new method, which conforms to the concept of green chemistry, has no pollution, is simple to operate, can be prepared in gram scale, can effectively control the single-atom loading amount, has low cost and is easy to promote.

[0021] (2)When the single-atom iron catalyst of the present disclosure is used in the N-alkylation reaction of amines, the conditions are mild, high yields are achieved under atmospheric pressure conditions, the catalyst is easy to recover, and good catalytic effects are maintained even after multiple uses. Description of the Drawings

[0022] The specification drawings forming a part of the present disclosure are used to provide a further understanding of the present disclosure. The schematic embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation of the present disclosure.

[0023] Figure 1 X-ray photoelectron spectroscopy of the Fe 2p orbital of the CeO2 / Fe-SA catalyst prepared in Example 1 of the present disclosure.

[0024] Figure 2 Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy AC-HAADF-STEM image of CeO2 / Fe-SA prepared in Example 1 of the present disclosure.

[0025] Figure 3 Synchrotron radiation data map of the CeO2 / Fe-SA catalyst prepared in Example 1 of the present disclosure.

[0026] Figure 4 Performance test results of the CeO2 / Fe-SA catalysts with different loadings for the catalytic N-alkylation reaction of aniline described in Application Example 1 of the present disclosure. Embodiments

[0027] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs.

[0028] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present disclosure. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0029] Example 1: Synthesis of CeO2 / Fe-SA Catalyst with a Loading of 16.89 wt%

[0030] (1)Weigh 100 mg of CeO2 in a beaker and add 100 mL of deionized water for ultrasonic dispersion.

[0031] (2)Under mechanical stirring, the uniformly dispersed CeO2 solution reacts with reduced iron powder.

[0032] After reacting for 24 h, the solution was separated from the reduced iron powder to obtain CeO2 / Fe-SA with a loading of 16.89 wt%.

[0033] Example 2: Synthesis of CeO2 / Fe-SA catalyst with a loading of 10.71 wt%

[0034] (1) Weighed 120 mg of CeO2 in a beaker, added 120 mL of deionized water, and carried out ultrasonic dispersion.

[0035] (2) Under ultrasonic conditions, the uniformly dispersed CeO2 solution reacted with the reduced iron powder.

[0036] (3) After reacting for 4 h, the solution was separated from the reduced iron powder to obtain CeO2 / Fe-SA with a loading of 10.71 wt%.

[0037] Example 3: Synthesis of CeO2 / Fe-SA catalyst with a loading of 7.56 wt%

[0038] (1) Weighed 100 mg of CeO2 in a beaker, added 100 mL of deionized water, and carried out ultrasonic dispersion.

[0039] (2) Under oscillating conditions, the uniformly dispersed CeO2 solution reacted with the reduced iron powder.

[0040] (3) After reacting for 18 h, the solution was separated from the reduced iron powder to obtain CeO2 / Fe-SA with a loading of 7.56 wt%.

[0041] Example 4: Synthesis of CeO2 / Fe-SA catalyst with a loading of 3.42 wt%

[0042] (1) Weighed 200 mg of CeO2 in a beaker, added 200 mL of deionized water, and carried out ultrasonic dispersion.

[0043] (2) Under ultrasonic conditions, the uniformly dispersed CeO2 solution was transferred to an iron crucible for reaction.

[0044] (3) After reacting for 2 h, the solution was separated from the iron crucible to obtain CeO2 / Fe-SA with a loading of 3.42 wt%.

[0045] Example 5: Synthesis of CeO2 / Fe-SA catalyst with a loading of 1.07 wt%

[0046] (1) Weighed 150 mg of CeO2 in a beaker, added 150 mL of deionized water, and carried out ultrasonic dispersion.

[0047] (2) Under mechanical stirring conditions, transfer the uniformly dispersed CeO2 solution to an iron crucible for reaction.

[0048] (3) After reacting for 10 h, separate the solution from the iron crucible to obtain CeO2 / Fe-SA with a loading of 1.07 wt%.

[0049] Application Example 1:

[0050] Apply CeO2 / Fe-SA catalysts with different loadings to the aniline N-alkylation reaction to detect the catalytic performance of the CeO2 / Fe-SA catalysts. Specifically:

[0051] Apply the catalysts prepared in Examples 1-5 to the aniline N-alkylation reaction. The specific process is as follows:

[0052] Take 20 mg of the CeO2 / Fe-SA catalyst, 3 mmol of aniline, 6 mmol of benzyl alcohol, and 0.9 mmol of potassium hydroxide and add them to a 25 ml flask. Ultrasonically disperse them evenly. Subsequently, react at 105 °C. After reacting for 16 h, cool to room temperature. Dilute with ethyl acetate, centrifuge to separate the catalyst, and analyze the liquid product by gas chromatography to obtain the yield and conversion rate.

[0053] The above are only the preferred embodiments of the present disclosure and are not used to limit the present disclosure. Although the present disclosure has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present disclosure shall be included within the protection scope of the present disclosure.

Claims

1. A single-atom iron catalyst for the N-alkylation reaction of amines, which can be represented as CeO2 / Fe-SA (SA represents single atom).

2. A preparation method of a single-atom iron catalyst for the N-alkylation reaction of amines, characterized in that First, disperse CeO2 in water to form a mixed solution, and then add an iron source to the mixed solution for reaction. After the reaction, separate the iron source to obtain CeO2 / Fe-SA.

3. The preparation method of a single-atom iron catalyst for the N-alkylation reaction of amines according to claim 2, characterized in that The iron source is elemental iron.

4. The preparation method of a single-atom iron catalyst for the N-alkylation reaction of amines according to claim 2, characterized in that The reaction methods between CeO2 and iron include but are not limited to mechanical stirring, ultrasonic treatment, and oscillation.

5. The preparation method of a single-atom iron catalyst for the N-alkylation reaction of amines according to claim 2, characterized in that There is no limit to the separation method of the single-atom iron catalyst after the reaction, and any method that can separate the product can be applied.

6. The single-atom iron catalyst for the N-alkylation reaction of amines according to claim 2, characterized in that The iron loading in the single-atom iron catalyst is 1 wt% - 30 wt%.

7. An application of a single-atom iron catalyst for the N-alkylation reaction of amines, characterized in that Using CeO2 / Fe-SA as a catalyst, in an alkaline environment, amines and alcohols react under atmospheric pressure conditions.

8. The application of a single-atom iron catalyst for the N-alkylation reaction of amines according to claim 7, characterized in that The reaction temperature of amines and alcohols is 70 - 140 °C.

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