Preparation method and application of Co2P nano-catalyst

Abstract

The invention provides a preparation method of a Co2P nano-catalyst and application of the Co2P nano-catalyst in catalyzing synthesis of quinoxaline compounds, and relates to the technical field of doping materials and organic catalysis. The Co2P nano-catalyst is prepared by adopting a template sacrifice method, a mixture of melamine, cobalt phytate (PA-Co) and magnesium oxide is placed in a nitrogen atmosphere to be pyrolyzed, carbonization is completed, magnesium oxide of a carbonized product is washed away in an acetic acid solution, and the Co2P nano-catalyst is obtained. The preparation process is simple, non-toxic and easy to implement, and the catalyst has the characteristics of wide substrate range, good functional group tolerance, high yield, recyclability and the like in the synthesis of quinoxaline.

Description

Technical Field

[0001] The invention belongs to the technical field of catalyst material preparation, and specifically relates to a preparation method of a Co2P nanocatalyst and an application thereof in catalyzing the synthesis of quinoxalines. Background Art

[0002] Quinoxaline and its derivatives are an important class of N-heterocyclic compounds, characterized by a bicyclic system consisting of a benzene ring and a pyrazine ring. These compounds are widely used in the fields of natural products, drugs, organic semiconductors, optoelectronic materials, etc. Therefore, the synthesis of quinoxaline structures is of considerable significance.

[0003] Currently, many synthetic methods have been developed. Among them, the cyclization of alkynes with o-phenylenediamine to produce quinoxaline is considered to be the most economical due to its cost-effectiveness and readily available raw materials. Homogeneous catalysts such as Ru, Pd, Au, Cu and Co have attracted widespread attention due to their role in the synthesis of quinoxaline. Iodine- or bromine-mediated methods for the preparation of quinoxaline have also been reported. However, these methods usually require harsh conditions, including the use of precious metal catalysts, equivalent additives, large amounts of oxidants and long reaction times. These conditions result in poor functional group tolerance, low atomic efficiency, high production costs and environmental pollution, which limits their large-scale application in the industrial field. In response to the country's growing demand for green chemistry and sustainable development, people are increasingly interested in environmentally friendly and cost-effective non-precious metal catalysts. In addition, heterogeneous catalysts mainly use metal oxides to synthesize quinoxaline. There are few reports on nanocatalysts. However, nanocatalysts have surpassed traditional catalysts in many aspects and are considered to be the most promising catalysts in the future. Moreover, their high specific surface area and abundant active sites make them particularly valuable in various fields such as biofuels, organic synthesis, pharmaceuticals and fine chemicals.

[0004] Therefore, we developed a simple, recyclable, and highly active nanocatalyst for the synthesis of quinoxaline compounds. Summary of the invention

[0005] In view of the above technical problems, the purpose of the present invention is to provide a method for preparing a Co2P nanocatalyst and its application in the synthesis of quinoxaline compounds.

[0006] The present invention adopts a template sacrificial method to prepare a catalyst, a mixture of melamine, cobalt phytate (PA-Co) and magnesium oxide is placed in a nitrogen atmosphere for pyrolysis, carbonization is completed, and the product after carbonization is washed in an acetic acid solution to remove magnesium oxide, thereby obtaining a Co2P nanocatalyst. The preparation process is simple, non-toxic and easy to implement, and the catalyst has the characteristics of a wide substrate range, good functional group tolerance, high yield and recyclability in the synthesis of quinoxaline.

[0007] To achieve the above object, the present invention adopts the following technical solution: The preparation method of the Co2P nanocatalyst of the present invention comprises the following steps: S1, adding cobalt phytate, melamine and magnesium oxide to ethanol, stirring at room temperature for 8-12 hours, and removing the solvent to obtain Co-PA-N-MgO-X; The preparation method of cobalt phytate is as follows: adding cobalt acetate tetrahydrate into ethanol and stirring, then adding ethanol solution of phytic acid, reacting at 30-50° C. for 5-8 hours, filtering, and drying to obtain cobalt phytate (PA-Co); the molar ratio of cobalt acetate tetrahydrate to phytic acid is 6:1. The mass ratio of cobalt phytate, melamine, and magnesium oxide is 1.0-2.0:1:8.

[0008] S2. Pyrolyze Co-PA-N-MgO-X at 800-900 °C under nitrogen protection to obtain CoP@NC-MgO-X. The pyrolysis is performed by heating the temperature to 800-900 °C at a rate of 3 °C / min and then pyrolyzing for 1-3 hours.

[0009] S3, the CoP@NC-MgO-X obtained in S2 is treated with an acetic acid solution to remove MgO to obtain a Co2P nanocatalyst, which is recorded as CoP@NCX. The treatment with the acetic acid solution is to use a 2 mol / L acetic acid solution for acid washing at room temperature for 8 to 10 h.

[0010] The present invention also provides an application of the Co2P nanocatalyst in the synthesis of quinoxaline compounds, which uses o-phenylenediamine and phenylacetylene or substituted phenylacetylene as raw materials, dimethyl sulfoxide as solvent, and reacts at 100-130°C for 5-12 h under the catalysis of the Co2P nanocatalyst to obtain quinoxaline or quinoxaline derivatives.

[0011] The structural formula of substituted phenylacetylene is: ; The structural formula of the quinoxaline derivative is: .

[0012] The molar ratio of o-phenylenediamine to phenylacetylene or substituted phenylacetylene is 1:3. The mass ratio of Co2P nanocatalyst to o-phenylenediamine is 1:1-1:2.

[0013] Beneficial effects of the present invention: 1. The preparation process of the Co2P nanocatalyst prepared by the present invention is simple, non-toxic and easy to implement; 2. Co2P nanocatalysts have a wide substrate range, good functional group tolerance, high yield and good recycling performance in the synthesis of quinoxaline and its derivatives. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a SEM image of CoP@NC-1.5 in an embodiment of the present invention.

[0015] Figure 2 is a TEM image of CoP@NC-1.5 in an embodiment of the present invention.

[0016] Figure 3 It is the C1s graph of CoP@NC-1.5 XPS in the embodiment of the present invention.

[0017] Figure 4 It is the N1s graph of CoP@NC-1.5 XPS in the embodiment of the present invention.

[0018] Figure 5 It is the P1s graph of CoP@NC-1.5 XPS in the embodiment of the present invention.

[0019] Figure 6 It is the Co2p diagram of CoP@NC-1.5 XPS in the embodiment of the present invention.

[0020] Figure 7 It is the EDS image of CoP@NC-1.5 in the embodiment of the present invention. DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0022] Example 1 Preparation of Co2P Nanocatalyst (1) Preparation of cobalt phytate: Cobalt (II) acetate tetrahydrate (60 mmol, 14.9 g) was added to ethanol (120 mL) and stirred at 40°C for 2 hours. Then, a 50% phytic acid (10 mmol, 13.2 g) solution in ethanol (40 mL) was slowly added to the reaction mixture and stirred at 40°C for 6 hours. The mixture was cooled to ambient temperature, filtered, and the filter cake was washed three times with ethanol (3 × 15 mL) and then dried to obtain cobalt phytate (PA-Co).

[0023] (2) Cobalt phytate (0.987 mmol, 1.0 g), melamine (7.94 mmol, 1.0 g), and magnesium oxide (198.5 mol, 8.0 g) were added to ethanol (60 mL) and stirred at room temperature for 10 hours. The ethanol was removed to obtain Co-PA-N-MgO-X. Then, Co-PA-N-MgO-X was heated to 800 °C in a nitrogen atmosphere at a rate of 3 °C / min and maintained at this temperature for 2 hours to complete the carbonization of the N-doped carbon material, which was recorded as CoP@NC-MgO-X. Subsequently, CoP@NC-MgO-X was acid-washed with 2 mol / L acetic acid solution (500 mL) for 9 h to remove MgO and obtain CoP@NC-1.0.

[0024] By changing the amount of cobalt phytate added to (1.48 mmol, 1.5 g) and keeping the rest unchanged, CoP@NC-1.5 was obtained; by changing the amount of cobalt phytate added to (1.97 mmol, 2.0 g) and keeping the rest unchanged, CoP@NC-2.0 was obtained.

[0025] Figure 1 : is a SEM image of CoP@NC-1.5 in an embodiment of the present invention. From the SEM image, we can see that the catalyst has an irregular pore structure.

[0026] Figure 2 This is the TEM image of CoP@NC-1.5 in the embodiment of the present invention. From the TEM image, we can see that there are nanoparticles in the catalyst. Figure 3 This is the C1s graph of the CoP@NC-1.5 XPS in the embodiment of the present invention. From the C1s spectrum, we can conclude that there are three chemical environments of the carbon element in the catalyst, namely CC, CO and CN. Figure 4 This is the N1s graph of the CoP@NC-1.5 XPS in the embodiment of the present invention. From the N1s spectrum, we can conclude that there are three chemical environments of the nitrogen element in the catalyst, namely pyridinic-N, pyrrolic-N and nitrogen oxide. Figure 5 This is the P1s graph of the CoP@NC-1.5 XPS in the embodiment of the present invention. From the P1s spectrum, we can conclude that there are two chemical environments of phosphorus in the catalyst, namely phosphorus oxide and Co-P Figure 6 This is the Co2p graph of CoP@NC-1.5 XPS in the embodiment of the present invention. From the Co2p spectrum, we can conclude that the valence state of the cobalt element in the catalyst is between +2 and +3. Figure 7This is the EDS image of CoP@NC-1.5 in the embodiment of the present invention. From the EDS image, we can see that nitrogen and oxygen elements are evenly dispersed on the carbon carrier, and cobalt and phosphorus elements aggregate to form Co2P nanoparticles.

[0027] Example 2-14 Synthesis of quinoxaline using Co2P nanocatalyst 20 mg of CoP@NCX, 0.2 mmol of o-phenylenediamine, 0.6 mmol of phenylacetylene, and 5 mL of solvent were reacted at 80-130°C for 5-12 h to obtain quinoxaline. The specific reaction conditions and quinoxaline yields are shown in the following table: Example 15 Synthesis of Quinoxaline Derivatives Catalyzed by Co2P Nanocatalyst 20 mg of CoP@NC-1.5, 0.2 mmol of o-phenylenediamine, 0.6 mmol of different substituted phenylacetylene, 5 mL of dimethyl sulfoxide were reacted at 120 °C for 5 h to obtain quinoxaline derivatives with the following yields: Example 16 The catalyst was separated from the system after the reaction of Example 14 by centrifugation, washed three times with dimethyl sulfoxide, and vacuum dried for 2 h. Then, the recovered catalyst, 0.2 mmol of o-phenylenediamine, 0.6 mmol of phenylacetylene and 5 mL of dimethyl sulfoxide were reacted at 120 ° C for 5 h. After three recovery tests, the yield of quinoxaline was 45.6%.

Claims

1. A method for preparing a Co2P nanocatalyst, characterized in that: The following steps are involved: S1, adding cobalt phytate, melamine and magnesium oxide to ethanol, stirring at room temperature for 8-12 hours, and removing the solvent to obtain Co-PA-N-MgO-1.5; S2, pyrolyzing Co-PA-N-MgO-X at 800-900 °C under nitrogen protection to obtain CoP@NC-MgO-X; S3. The CoP@NC-MgO-X obtained in S2 is treated with an acetic acid solution to remove MgO to obtain a Co2P nanocatalyst, which is recorded as CoP@NCX.

2. The method for preparing the Co2P nanocatalyst according to claim 1, characterized in that: In S1, the preparation method of cobalt phytate is: adding cobalt acetate tetrahydrate to ethanol and stirring, then adding ethanol solution of phytic acid, reacting at 30-50° C. for 5-8 hours, filtering, and drying to obtain cobalt phytate (PA-Co); the molar ratio of cobalt acetate tetrahydrate to phytic acid is 6:

1.

3. The method for preparing the Co2P nanocatalyst according to claim 1, characterized in that: In S1, the mass ratio of cobalt phytate, melamine and magnesium oxide is 1.0-2.0:1:

8.

4. The method for preparing the Co2P nanocatalyst according to claim 1, characterized in that: In S2, the pyrolysis is performed by heating the temperature to 800-900 °C at 3 °C / min and then pyrolyzing for 1-3 hours.

5. The method for preparing the Co2P nanocatalyst according to claim 1, characterized in that: In S3, the treatment with acetic acid solution is to use 2 mol / L acetic acid solution for pickling at room temperature for 8 to 10 h.

6. Use of the Co2P nanocatalyst prepared by the method according to claim 1 in the synthesis of quinoxaline compounds, characterized in that: Using o-phenylenediamine and phenylacetylene or substituted phenylacetylene as raw materials and dimethyl sulfoxide as solvent, the reaction is carried out at 80-130°C for 5-12 h under the catalysis of Co2P nanocatalyst to obtain quinoxaline or quinoxaline derivatives; The structural formula of substituted phenylacetylene is: ; The structural formula of the quinoxaline derivative is: .

7. The use of the Co2P nanocatalyst in the synthesis of quinoxaline compounds according to claim 6, characterized in that: The molar ratio of o-phenylenediamine to phenylacetylene or substituted phenylacetylene is 1:

3.

8. The use of the Co2P nanocatalyst in the synthesis of quinoxaline compounds according to claim 6, characterized in that: The mass ratio of Co2P nanocatalyst to o-phenylenediamine is 1:1~1:2.

Images