Preparation method and application of integral guanidyl palladium catalyst for cotton

Abstract

The invention discloses a preparation method and application of a monolithic guanidyl palladium catalyst for cotton. Firstly, an amino silane coupling agent is used for modifying the surface of cotton, and then dicyandiamide is used for conducting secondary modification on the surface of the cotton, so that the surface of the cotton is rich in biguanidyl groups. The biguanidyl functionalized cotton is used as a carrier to load palladium to be used as a Suzuki reaction catalyst. The catalyst prepared by the method has excellent catalytic performance and good adaptability to a substrate, and the catalytic performance is not obviously attenuated after the catalyst is recycled for 10 times.

Description

Technical Field

[0001] This invention belongs to the field of palladium catalyst technology, and particularly relates to a method for preparing an integral supported palladium catalyst, and applies the prepared catalyst to the Suzuki coupling reaction. Background Technology

[0002] Sustainable catalysts are a fundamental requirement for the development of green chemistry. Heterogeneous catalysts, characterized by high catalytic activity, long-term stability, and non-recyclability, are becoming increasingly important in organic chemistry. Heterogeneous catalysts are typically classified according to their catalyst supports, including silica, polymers, modified carbon nanotubes, metal-organic frameworks, and covalent organic frameworks. Monolithic catalysts offer advantages such as easy recovery, good structural tunability, and high catalytic stability. However, to date, these monolithic catalysts have suffered from low loading capacity, which limits their application in large-scale processes.

[0003] Patent CN109621949 reports a magnesium-aluminum layered double hydroxide (TLD) supported ultrafine palladium nanoparticle catalyst, which, when applied to the Suzuki coupling reaction, exhibits good catalytic performance and reusability. Patent CN115572316A discloses a palladium catalyst containing crown ether pincer ligands. Different nitrogen-crown ether groups are introduced onto the esterified phenyl-pyridine backbone to design and prepare pincer ligands with steric hindrance and enrichment effects. This catalyst exhibits high catalytic activity. CN102500418A discloses a magnetic bidentate imine palladium ligand catalyst, which can be separated under an external magnetic field. CN102091657A discloses a method for preparing and using a magnetic double carbene palladium ligand catalyst. There are few reports on monolithically supported palladium catalysts for fibers. Summary of the Invention

[0004] The purpose of this invention is to address the aforementioned problems by providing a method for preparing and applying a monolithic cotton guanidine palladium catalyst. This method uses widely available biomass fibers as a support and employs a simple chemical modification method to modify the fiber surface, preparing a catalyst suitable for Suzuki catalysis. The catalyst prepared by this method exhibits excellent catalytic performance, good substrate compatibility, and no significant performance degradation after 10 cycles.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] 1. A method for preparing a cotton-based monolithic guanidine-palladium catalyst, characterized by comprising the following steps:

[0007] Step (1) Add 5g of cotton to 100mL of anhydrous toluene in aminopropyltriethoxysilane (15mmol). The mixture is refluxed at 110℃ for 24 hours under nitrogen atmosphere. After cooling to room temperature, it is washed three times with acetone and dried under vacuum at 60℃ for 24 hours to obtain amino-functionalized cotton.

[0008] Step (2) Take 2g of the amino-functionalized cotton described in step (1) above and disperse it in 50mL of acetonitrile under a nitrogen atmosphere. Add 5mmol of dicyandiamine acetonitrile solution and reflux at 80℃ for 24 hours. After cooling to room temperature, wash three times with acetone and diethyl ether and dry under vacuum at 60℃ for 24 hours to obtain biguanide-functionalized cotton.

[0009] Step (3) Take the biguanide-functionalized cotton from step (2) above, load it with palladium using an equal-volume impregnation method, and dry it;

[0010] Step (4) involves reduction with a reducing agent and vacuum drying for 24 hours to obtain the final catalyst.

[0011] Further, the palladium salt described in step (3) is selected from palladium chloride, palladium acetate, and ammonium chloropalladate.

[0012] Further, the palladium loading in step (3) is 0.1wt%-1wt%, more preferably 0.5wt%-1wt%, and most preferably 0.8wt%-1wt%.

[0013] Furthermore, the reducing agent in step (4) is selected from NaBH4 or hydrazine hydrate, with NaBH4 being the most preferred.

[0014] Furthermore, the NaBH4 reduction conditions described in step (4) are stirring at room temperature for 24 hours.

[0015] The application of the cotton monolithic guanidine palladium catalyst prepared by the aforementioned method in the catalytic Suzuki coupling reaction.

[0016] The application method includes the following steps:

[0017] (a) Substrate A, substrate B, solvent, and base were added to the reaction vessel, and a catalyst with an appropriate loading was added. The mixture was stirred continuously at 80°C and reacted for 12 hours.

[0018] (b) Remove the catalyst, add ethyl acetate, and allow it to stand to separate into layers.

[0019] (c) Take the supernatant from step (b), add an internal standard, and measure the reaction yield using gas chromatography.

[0020] Further, in step (a), substrate A is a halobenzene with a functional group. The halobenzene can be iodobenzene, bromobenzene, or chlorobenzene. The functional group of the halobenzene can be acetyl, methyl, nitro, etc. Substrate B is phenylboronic acid with a functional group, wherein the functional group of the phenylboronic acid is methoxy, chloro, cyano, etc.

[0021] Further, the solvent in step (a) can be water, ethanol, a mixture of water and ethanol in different proportions, glycerol, tetrahydrofuran, n-hexane, or other solvents, and the solvent volume is 1–5 mL. The most preferred solvent is EtOH / H2O (v:v = 1:1).

[0022] Furthermore, the base in step (a) is an inorganic base or an organic base; wherein the inorganic base is potassium carbonate, sodium carbonate, cesium carbonate, etc.; and the organic base is triethylamine, pyridine, etc. Attached Figure Description

[0023] Figure 1 This is a flowchart of the preparation process of monolithic biguanide functionalized cotton catalyst. Specific Implementation

[0024] Preparation of monolithic guanidine-palladium catalysts from cotton

[0025] Example 1

[0026] 5 g of cotton was added to 100 mL of a homogeneous solution of anhydrous toluene in aminopropyltriethoxysilane (15 mmol). The mixture was refluxed at 110 °C for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the cotton was washed three times with acetone and dried under vacuum at 60 °C for 24 hours to obtain amino-functionalized cotton. 2 g of the above amino-functionalized cotton was dispersed in 50 mL of acetonitrile under a nitrogen atmosphere, and 5 mmol of a dicyandiamine solution in acetonitrile was added. The mixture was refluxed at 80 °C for 24 hours. After cooling to room temperature, the cotton was washed three times with acetone and diethyl ether and dried under vacuum at 60 °C for 24 hours to obtain biguanide-functionalized cotton. Palladium was loaded using an equal-volume impregnation method with a palladium loading of 1 wt%, and then reduced with NaBH4.

[0027] Example 2

[0028] 5 g of cotton was added to 100 mL of a homogeneous solution of anhydrous toluene in aminopropyltriethoxysilane (15 mmol). The mixture was refluxed at 110 °C for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the cotton was washed three times with acetone and dried under vacuum at 60 °C for 24 hours to obtain amino-functionalized cotton. 2 g of the amino-functionalized cotton was dispersed in 50 mL of acetonitrile under a nitrogen atmosphere, and 5 mmol of a dicyandiamine solution in acetonitrile was added. The mixture was refluxed at 80 °C for 24 hours. After cooling to room temperature, the cotton was washed three times with acetone and diethyl ether and dried under vacuum at 60 °C for 24 hours to obtain biguanide-functionalized cotton. Palladium was loaded using an equal-volume impregnation method with a palladium loading of 0.8 wt%, and then reduced with NaBH4.

[0029] Example 3

[0030] 5 g of cotton was added to 100 mL of a homogeneous solution of anhydrous toluene in aminopropyltriethoxysilane (15 mmol). The mixture was refluxed at 110 °C for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the cotton was washed three times with acetone and dried under vacuum at 60 °C for 24 hours to obtain amino-functionalized cotton. 2 g of the above amino-functionalized cotton was dispersed in 50 mL of acetonitrile under a nitrogen atmosphere, and 5 mmol of a dicyandiamine solution in acetonitrile was added. The mixture was refluxed at 80 °C for 24 hours. After cooling to room temperature, the cotton was washed three times with acetone and diethyl ether and dried under vacuum at 60 °C for 24 hours to obtain biguanide-functionalized cotton. Palladium was loaded using an equal-volume impregnation method with a palladium loading of 0.6 wt%, and then reduced with NaBH4.

[0031] Example 4

[0032] 5 g of cotton was added to 100 mL of a homogeneous solution of anhydrous toluene in aminopropyltriethoxysilane (15 mmol). The mixture was refluxed at 110 °C for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the cotton was washed three times with acetone and dried under vacuum at 60 °C for 24 hours to obtain amino-functionalized cotton. 2 g of the amino-functionalized cotton was dispersed in 50 mL of acetonitrile under a nitrogen atmosphere, and 5 mmol of a dicyandiamine solution in acetonitrile was added. The mixture was refluxed at 80 °C for 24 hours. After cooling to room temperature, the cotton was washed three times with acetone and diethyl ether and dried under vacuum at 60 °C for 24 hours to obtain biguanide-functionalized cotton. Palladium was loaded using an equal-volume impregnation method with a palladium loading of 0.4 wt%, and then reduced with NaBH4.

[0033] Example 5

[0034] 5 g of cotton was added to 100 mL of a homogeneous solution of anhydrous toluene in aminopropyltriethoxysilane (15 mmol). The mixture was refluxed at 110 °C for 24 hours under a nitrogen atmosphere. After cooling to room temperature, the cotton was washed three times with acetone and dried under vacuum at 60 °C for 24 hours to obtain amino-functionalized cotton. 2 g of the amino-functionalized cotton was dispersed in 50 mL of acetonitrile under a nitrogen atmosphere, and 5 mmol of a dicyandiamine solution in acetonitrile was added. The mixture was refluxed at 80 °C for 24 hours. After cooling to room temperature, the cotton was washed three times with acetone and diethyl ether and dried under vacuum at 60 °C for 24 hours to obtain biguanide-functionalized cotton. Palladium was loaded using an equal-volume impregnation method with a palladium loading of 0.2 wt%, and then reduced with NaBH4.

[0035] Application of Palladium Nanoparticle Monolithic Biguanide Functionalized Cotton Catalyst

[0036] The application method of palladium nanoparticle-based monolithic biguanide functionalized cotton catalyst in the Suzuki reaction includes the following steps:

[0037] (a) Substrate A, substrate B, solvent, and base were added to the reaction vessel, and a catalyst with an appropriate loading was added. The mixture was stirred continuously at 80°C and reacted for 12 hours.

[0038] (b) Remove the catalyst, add ethyl acetate, and allow it to stand to separate into layers.

[0039] (c) Take the supernatant from step (b), add an internal standard, and measure the reaction yield using gas chromatography.

[0040] Example 6

[0041] The catalyst prepared in Example 2 was applied to the Suzuki reaction, and the performance of the catalyst was evaluated by screening the bases used. The performance of the catalyst is summarized in Table 1.

[0042] Table 1. Catalyst performance under different base conditions.

[0043]

[0044] Example 7

[0045] The catalysts prepared in Examples 1-5 were applied to the Suzuki reaction, and the loading of the catalysts was screened to evaluate their performance. The performance of the catalysts is summarized in Table 2.

[0046] Table 2 Catalytic performance of different catalysts

[0047]

[0048] Example 8

[0049] The catalyst prepared in Example 2 was applied to the Suzuki reaction, and the performance of the catalyst was evaluated by screening the solvents used. The performance of the catalyst is summarized in Table 3.

[0050] Table 3 Catalytic performance using different solvents

[0051]

[0052] Example 9

[0053] Substrate expansion was carried out using the catalyst prepared in Example 2, and the performance is summarized below.

[0054]

Claims

1. A method for preparing a cotton-based monolithic guanidine-palladium catalyst, characterized in that, Includes the following steps: Step (1) Take 5g of cotton and add it to 100mL of anhydrous toluene in aminopropyltriethoxysilane (15mmol). The mixture is refluxed at 110℃ for 24 hours under nitrogen atmosphere. After cooling to room temperature, it is washed three times with acetone and dried under vacuum at 60℃ for 24 hours to obtain amino-functionalized cotton. Step (2) Take 2g of the amino-functionalized cotton described in step (1) above and disperse it in 50mL of acetonitrile under a nitrogen atmosphere. Add 5mmol of dicyandiamine acetonitrile solution and reflux at 80℃ for 24 hours. After cooling to room temperature, wash three times with acetone and diethyl ether and dry under vacuum at 60℃ for 24 hours to obtain biguanide-functionalized cotton. Step (3) Take the biguanide-functionalized cotton from step (2) above, load it with palladium using an equal-volume impregnation method, and dry it; Step (4) involves reduction with a reducing agent and vacuum drying for 24 hours to obtain the final catalyst.

2. The method for preparing a monolithic cotton guanidine-palladium catalyst according to claim 1, characterized in that, The palladium salt mentioned in step (3) is selected from palladium chloride, palladium acetate, and ammonium chloropalladium.

3. The method for preparing a monolithic guanidine-based palladium catalyst for cotton according to claim 1, characterized in that, The palladium loading in step (3) is 0.1wt%-1wt%, more preferably 0.5wt%-1wt%, and most preferably 0.8wt%-1wt%.

4. The method for preparing a monolithic cotton guanidine-palladium catalyst according to claim 1, characterized in that, The reducing agent in step (4) is selected from NaBH4 or hydrazine hydrate, with NaBH4 being the most preferred.

5. The method for preparing a monolithic cotton guanidine-palladium catalyst according to claim 1, characterized in that, The reduction conditions described in step (4) are stirring at room temperature for 24 hours.

6. The application of the cotton monolithic guanidine palladium catalyst prepared by the preparation method according to any one of claims 1-4 in the catalytic Suzuki coupling reaction.

7. The application as described in claim 6, characterized in that, The application method includes the following steps: (a) Add substrate A, substrate B, solvent, and base to the reaction vessel, add a catalyst with an appropriate loading, and stir continuously at 80°C for 12 h. (b) Remove the catalyst, add ethyl acetate, and allow it to stand to separate into layers; (c) Take the supernatant from step (b), add an internal standard, and measure the reaction yield using gas chromatography.

8. The application as described in claim 6, characterized in that, In step (1), substrate A is a halobenzene with a functional group, wherein the halobenzene can be iodobenzene, bromobenzene, or chlorobenzene, and the functional group of the halobenzene can be acetyl, methyl, nitro, etc.; substrate B is phenylboronic acid with a functional group, wherein the functional group of the phenylboronic acid can be methoxy, chloro, cyano, etc.

9. The application as described in claim 6, characterized in that, The solvent in step (1) is water, ethanol, a mixture of water and ethanol in different proportions, glycerol, tetrahydrofuran, n-hexane and other solvents, and the amount of solvent used is 1 to 5 mL.

10. The application as described in claim 6, characterized in that, The base in step (1) is an inorganic base or an organic base; the inorganic base is potassium carbonate, sodium carbonate, cesium carbonate, etc.; the organic base is triethylamine, pyridine, etc.

Images