WO2023060920A1

WO2023060920A1 - Palladium monatomic catalyst, preparation method therefor, and application thereof in suzuki coupling reaction

Info

Publication number: WO2023060920A1
Application number: PCT/CN2022/098182
Authority: WO
Inventors: 乔波涛; 郭亚琳; 闵祥婷; 江训柱; 张涛
Original assignee: 中国科学院大连化学物理研究所
Priority date: 2021-10-15
Filing date: 2022-06-10
Publication date: 2023-04-20
Also published as: CN113750993A; CN113750993B

Abstract

The present invention relates to the technical field of catalysts, and relates to a magnesium oxide-loaded palladium monatomic catalyst, a preparation method therefor, and an application thereof in Suzuki coupling reaction. Metal active component palladium is dispersed on a carrier magnesium oxide in a monatomic form by using an impregnation method, the palladium monatomic catalyst of which the palladium monatomic loading amount is 0.01-5% of the total mass of the catalyst is obtained by roasting, and the preparation method is simple, convenient, safe, green, environment-friendly, and suitable for large-scale production. The obtained palladium monatomic catalyst has excellent catalytic performance on various Suzuki coupling reaction raw materials, has the remarkable advantages such as a high precious metal atom utilization rate, good stability, and low costs, and has good application prospects.

Description

A kind of palladium single atom catalyst and preparation method thereof and application in Suzuki coupling reaction

technical field

The invention belongs to the technical field of catalysts, and in particular relates to the preparation of a magnesium oxide-supported palladium single-atom catalyst and its application in Suzuki coupling reactions.

Background technique

The Suzuki coupling reaction is a cross-coupling reaction between organoborides and organohalides, and is a general-purpose method for efficiently forming carbon-carbon bond compounds. The reaction substrate is usually an electrophile such as an aryl halide, and a stable nucleophile such as an alkyl group or an aryl boron. The reaction process is simple and no toxic by-products are produced, and the reaction is widely used in the fields of natural products, pharmaceuticals, polymer materials, and chemicals.

At present, nickel-based, copper-based, iron-based, palladium-based and other catalysts are mainly used for the Suzuki coupling reaction. Chinese patent CN101830763B invented a nickel-based catalyst, which has a good catalytic effect on various Suzuki coupling reaction substrates, and has good stability and low cost; however, the preparation process of the catalyst is complicated and not suitable for large-scale production. And CN102086179B realizes the coupling reaction of bromide including inactive bromide by using metal iron salt as catalyst, which is difficult to realize by other catalysts, and catalyst and ligand are stable and easy to get; but the reaction conditions are relatively harsh, and the solvent Most of them are not friendly to the environment.

Among the many metal catalysts, palladium-based catalysts are usually the most active and widely used, including homogeneous palladium catalysts and heterogeneous palladium catalysts. The homogeneous palladium catalyst and the reaction substrate are in the same phase, the substrate is more likely to contact the active center, the reaction rate is fast, and the product selectivity is high, but the stability in the catalytic medium is poor, the catalyst is not easy to recycle, the cost is high, and the solvent environment is not good. Friendliness and so on restrict its mass production. However, heterogeneous palladium catalysts are easy to separate, high temperature resistant, and have a long life, but there are problems such as insufficient catalytic activity, harsh reaction conditions, and poor cycle stability. Therefore, it is a great challenge to design and prepare a new type of stable heterogeneous palladium catalyst to realize its high-efficiency catalysis in green solvents and under mild conditions.

Contents of the invention

The object of the present invention is to provide a palladium single-atom catalyst supported by magnesium oxide and a preparation method thereof. The prepared catalyst is used for the Suzuki coupling reaction and is an efficient and stable method for realizing carbon-carbon coupling. The preparation process of the catalyst is simple and easy for large-scale production. It has low noble metal palladium loading, extremely high (~100%) palladium atom utilization rate, and can catalyze the Suzuki coupling reaction with high activity and high selectivity. At the same time, the reaction process is environmentally friendly, the catalyst is stable and easy to recycle.

In order to achieve the above object, the technical scheme that the present invention takes is:

One aspect of the present invention provides a palladium-based single-atom catalyst supported by magnesia. The catalyst includes a magnesia support and active metal palladium, and the active metal palladium is dispersed on the support in the form of a single atom.

In the above technical solution, further, the loading amount of the active metal target is 0.01%-5% of the total mass of the catalyst.

Another aspect of the present invention provides a kind of preparation method of above-mentioned catalyst, adopts impregnation method to prepare described catalyst, comprises the following steps:

1) Add the palladium metal precursor into deionized water to obtain solution I, and mix well;

2) Immersing the magnesium oxide support in the solution I obtained in step 1) to obtain solution II; the mass ratio of the magnesium oxide support, deionized water, and metal palladium is 1: (1-10): (0.0001-0.05) ;

3) drying the solution II obtained in step 2), the drying temperature is 40-200°C, and the drying time is 1-24h to obtain the product;

4) The product obtained in step 3) is calcined in air, the calcining time is 1-24 h, and the calcining temperature is 100-800° C. to obtain a palladium-based single-atom catalyst supported on magnesium oxide.

In the above technical solution, further, the palladium metal precursor is one or more of palladium nitrate, palladium chloride, tetraammine palladium chloride, tetraammine palladium nitrate, and sodium chloropalladate.

In the above technical solution, further, the carrier is dried magnesium oxide, the size of which is 5-500nm, and the drying temperature is 60-500°C.

Another aspect of the present invention provides an application of the above-mentioned catalyst in the Suzuki coupling reaction.

In the above technical scheme, further, organic borides and organic halogen compounds are used as reaction substrates, supported palladium catalysts are used as catalysts, and the reaction is carried out in a glass reaction tube, the reaction temperature range is 30-150 ° C, and the atmospheric pressure air atmosphere, The solvent is water or a non-toxic organic solvent, which can efficiently generate coupling products.

In the above technical scheme, further, the non-toxic organic solvent is ethanol.

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

The invention adopts an impregnation method to prepare the catalyst, and the preparation method has a simple process flow, is easy to operate, and is suitable for large-scale production.

The supported palladium single-atom catalyst of the present invention has the characteristics of lower noble metal loading and high utilization rate of metal atoms (~100%), and can effectively catalyze the occurrence of coupling reaction under milder conditions when applied to the Suzuki coupling reaction. It has the advantages of high activity, high selectivity, stable catalyst and easy recovery.

In addition, the reaction process is environmentally friendly, and the technical and economic effects are remarkable, which is favorable for popularization.

Description of drawings

Fig. 1 is palladium supported catalyst XRD pattern;

Fig. 2 is the palladium single-atom catalyst electron micrograph that embodiment 1 makes;

Fig. 3 is the electron micrograph of the palladium nanoparticle catalyst that comparative example 1 makes;

Fig. 4 is the cycle stability evaluation result of the palladium single-atom catalyst prepared in Example 1 in the Suzuki coupling reaction.

Detailed ways

The present invention will be described in detail through specific examples below, but these examples do not limit the content of the present invention. At the same time, the embodiment only provides some conditions for realizing this purpose, but it does not mean that these conditions must be met to achieve this purpose.

Example 1

1) Dissolve the Pd(NO ₃ ) ₂ (NH ₃ ) ₄ precursor in water so that the mass fraction is 10%, add 0.25 mL of the precursor solution to 5 mL of deionized water, and stir evenly with a glass rod;

2) Take 2g of magnesium oxide carrier with a size of about 50nm dried at 200°C and add it to the above solution, stir evenly, and impregnate;

3) drying the product obtained in step 2) in an oven at 80°C for 10 hours;

4) The product obtained in step 3) was calcined at 600° C. for 3 h in an air atmosphere with a heating rate of 5° C./min. After natural cooling, a sample was taken out and designated as CAT-1.

Characterized by X-ray powder diffraction (XRD), the results are shown in Figure 1, and no obvious characteristic diffraction peaks of metal palladium were found, indicating that the dispersion of palladium particles is relatively high.

Further characterization by electron microscope, Figure 2 is the spherical aberration electron microscope image of the catalyst, it can be clearly seen from Figure 2 that palladium is anchored on the carrier magnesium oxide in the form of a single atom, and the part in the circle in Figure 2 is a single atom of palladium.

Comparative example 1

The impregnation method in Example 1 is changed to the sodium borohydride reduction method. The key is to add sodium borohydride to reduce the palladium particles in the preparation process. When the palladium load is the same as in Example 1, the final catalyst obtained is mainly nanoparticles. The wood coupling reaction has low activity and poor selectivity. Comparative Example 1 and Example 1 together illustrate that the impregnation method of the present invention is the key to preparing a single-atom catalyst with high dispersion and high coupling reaction performance. Concrete preparation method comprises the following steps:

1) Dissolve the Pd(NO ₃ ) ₂ (NH ₃ ) ₄ precursor in water so that the mass fraction is 10%, add 0.25 mL of the precursor solution to 10 mL of deionized water, and stir vigorously;

2) Add 2 g of magnesium oxide carrier with a size of about 50 nm dried at 200°C to the above solution, and add 1 mg/mL sodium borohydride aqueous solution 10 mL dropwise under stirring at room temperature;

3) filter and wash the product obtained in step 2), and then take it out after drying in an oven at 80°C for 10 hours;

4) The product obtained in step 3) was calcined at 600° C. for 3 h in an air atmosphere with a heating rate of 5° C./min. After natural cooling, a sample was taken out and recorded as CAT-1-comparison.

Characterized by X-ray powder diffraction (XRD), as shown in Figure 1, no obvious metal palladium characteristic diffraction peaks are found, and Figure 3 is an electron microscope image of the catalyst, wherein palladium exists in the form of nanoparticles, and palladium nanoparticles are in the frame.

Example 2

1) Dissolve the Pd(NO ₃ ) ₂ (NH ₃ ) ₄ precursor in water so that its mass fraction is 15%, add 0.6 mL of the precursor solution to 3 mL of deionized water, and stir evenly with a glass rod;

2) Take 2g of magnesium oxide carrier with a size of about 200nm dried at 100°C and add it to the above solution, stir evenly, and impregnate;

3) drying the product obtained in step 2) in an oven at 60°C for 12 hours;

4) The product obtained in step 3) was calcined at 700° C. for 10 h in an air atmosphere with a heating rate of 10° C./min. After natural cooling, a sample was taken out and designated as CAT-2.

Example 3

1) Dissolve the PdCl ₂ (NH ₃ ) ₄ precursor in water so that the concentration of metal palladium is 2 mg/mL, add 1 mL of the precursor solution to 8 mL of deionized water, and stir evenly with a glass rod;

2) Take 2g of magnesium oxide carrier with a size of about 300nm dried at 300°C and add it to the above solution, stir evenly, and impregnate;

3) drying the product obtained in step 2) in an oven at 100°C for 8 hours;

4) The product obtained in step 3) was calcined at 500° C. for 8 hours in an air atmosphere with a heating rate of 10° C./min. After natural cooling, a sample was taken out and designated as CAT-3.

Example 4

1) Dissolve the PdCl ₂ (NH ₃ ) ₄ precursor in water so that the concentration of metal palladium is 2 mg/mL, add 4 mL of the precursor solution to 3 mL of deionized water, and stir evenly with a glass rod;

2) Add 10 g of magnesium oxide carrier with a size of about 50 nm dried at 200°C to the above solution, stir evenly, and impregnate;

3) drying the product obtained in step 2) in an oven at 120°C for 10 hours;

4) The product obtained in step 3) was calcined at 800° C. for 4 hours in an air atmosphere with a heating rate of 20° C./min. After natural cooling, a sample was taken out and designated as CAT-4.

Example 5

1) Dissolve the Na ₂ PdCl ₄ precursor in water so that the concentration of metal palladium is 9 mg/mL, add 1 mL of the precursor solution to 4 mL of deionized water, and stir evenly with a glass rod;

2) Take 3g of magnesium oxide carrier with a size of about 100nm dried at 300°C and add it to the above solution, stir evenly, and impregnate;

3) drying the product obtained in step 2) in an oven at 150°C for 10 hours;

4) The product obtained in step 3) was calcined at 400° C. for 16 hours in an air atmosphere with a heating rate of 10° C./min. After natural cooling, a sample was taken out and designated as CAT-5.

Example 6

1) Dissolve the Na ₂ PdCl ₄ precursor in water so that the concentration of metal palladium is 3 mg/mL, add 0.5 mL of the precursor solution to 3 mL of deionized water, and stir evenly with a glass rod;

2) Take 5g of magnesium oxide carrier with a size of about 20nm dried at 250°C and add it to the above solution, stir evenly, and impregnate;

3) drying the product obtained in step 2) in an oven at 60°C for 14 hours;

4) The product obtained in step 3) was calcined at 600° C. for 10 hours in an air atmosphere with a heating rate of 15° C./min. After natural cooling, a sample was taken out and designated as CAT-6.

Example 7

The catalysts (Examples 1-6, Comparative Example 1) prepared above were evaluated in glass reaction tubes. Under normal air atmosphere, add palladium catalyst (2 mg), 4-bromobiphenyl (0.2 mmol), (4,4,5,5-tetramethyl-1,3,2-dioxo Borolan-2-yl)benzene (0.2mmol), potassium carbonate (1.0mmol), ethanol (3mL), deionized water (1mL), and heated in an oil bath to 80°C for 0.5 hours. Cool naturally to room temperature, and add internal standard mesitylene. The specific reaction results are shown in Table 1.

Table 1

Example 8

The performance of the catalyst prepared in Example 1 was evaluated in a glass reaction tube. Under normal air atmosphere, add palladium catalyst (2 mg), 4-bromobiphenyl (0.2 mmol), (4,4,5,5-tetramethyl-1,3,2-dioxo Borolan-2-yl)benzene (0.2 mmol), potassium carbonate (1.0 mmol), ethanol (3 mL), deionized water (1 mL), and heated in an oil bath to 80°C for 20 minutes. Cool naturally to room temperature, and add internal standard mesitylene. After the reaction, the catalyst was recovered and a cycle stability test was performed. As shown in Figure 4, the palladium single-atom catalyst has higher activity, product selectivity and reactant stability.

The above embodiments are only preferred embodiments of the present invention, and are not intended to limit the implementation. The protection scope of the present invention should be determined by the scope defined in the claims. On the basis of the above description, other changes or changes in different forms can also be made. Obvious changes or variations derived therefrom are still within the scope of protection of the present invention.

Claims

A magnesia-supported palladium-based single-atom catalyst is characterized in that: the catalyst includes a magnesia carrier and active metal palladium, and the active metal palladium is dispersed on the carrier in the form of a single atom.
The catalyst according to claim 1, characterized in that: the loading of the active metal target is 0.01-5% of the total mass of the catalyst.
A method for preparing the catalyst according to any one of claims 1-2, characterized in that: preparing the catalyst by impregnation method comprises the following steps:

1) Add the palladium metal precursor into deionized water to obtain solution I, and mix well;

2) Immersing the magnesium oxide support in the solution I obtained in step 1) to obtain solution II; the mass ratio of the magnesium oxide support, deionized water, and metal palladium is 1: (1-10): (0.0001-0.05) ;

3) drying the solution II obtained in step 2), the drying temperature is 40-200°C, and the drying time is 1-24h to obtain the product;

4) The product obtained in step 3) is calcined in air, the calcining time is 1-24 h, and the calcining temperature is 100-800° C. to obtain a palladium-based single-atom catalyst supported on magnesium oxide.
The preparation method according to claim 3, characterized in that: the palladium metal precursor is one of palladium nitrate, palladium chloride, tetraammine palladium chloride, tetraammine palladium nitrate, sodium chloropalladate or Two or more.
The preparation method according to claim 3, characterized in that: the carrier is dried magnesium oxide with a size of 5-500nm, and the drying temperature is 60-500°C.
An application of the catalyst described in any one of claims 1-2, characterized in that it is used for the Suzuki coupling reaction.
The application according to claim 6, characterized in that: the reaction substrate is an organoboride and an organohalogen compound, the reaction temperature is 30-150°C, and the reaction solvent is water or non-toxic organic solvent.