A catalyst for the selective reduction of nitroaromatic compounds and its use

Abstract

The application discloses a catalyst for selectively reducing nitroaromatic compounds and application thereof. The application adopts a nitrogen-doped mesoporous carbon material loaded with ruthenium metal as a heterogeneous catalyst to catalyze the reduction of nitroaromatic compounds to obtain arylamine compounds. The method has a wide applicable range of substrates, and has a remarkable reduction effect on important pharmaceutical reaction intermediate molecules, and can achieve a yield of 99%. The reaction can be carried out under mild conditions of temperature and hydrogen pressure, the heterogeneous catalyst can be recycled and recovered, and the reaction process is green and environmentally friendly. The catalyst prepared by the application has a high specific surface area and a large pore volume, ordered mesoporous channels and super-small metal particle sizes, and can be reused for more than five times without obvious activity attenuation.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous catalytic organic synthesis, specifically relating to a method for selectively reducing nitroaromatic compounds using a ruthenium metal catalyst supported on a nitrogen-doped mesoporous carbon material. Background Technology

[0002] In organic synthesis, amines are important intermediates for producing other compounds. Therefore, the hydrogenation of nitroaromatics to obtain functionalized aromatic amines is crucial in the dye and pharmaceutical industries, especially for nitroaromatics with certain unsaturated functional groups. Traditional methods for synthesizing aromatic amines include reduction methods such as metal extraction, electrolysis, and hydrazine hydrate. However, these methods are energy-intensive, require highly corrosion-resistant equipment, and cause significant environmental pollution, and have been gradually replaced by catalytic hydrogenation. In catalytic hydrogenation, homogeneous catalysts exhibit high chemoselectivity, but typically require additional ligands or additives, which are difficult to separate from the reaction system after the reaction, and the metal components used are also difficult to recover. Heterogeneous catalysts, compared to homogeneous catalysts, offer advantages such as ease of separation and recyclability, making them more economically valuable.

[0003] Currently, there is a lack of heterogeneous catalysts that are highly active, highly selective, have good cycle stability, and operate under mild reaction conditions. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a catalyst for the selective reduction of nitroaromatic compounds and its application. This invention utilizes nitrogen-doped mesoporous carbon supported on ruthenium metal as a heterogeneous catalyst, enabling the selective reduction of nitroaromatic compounds containing unsaturated groups to aromatic amines under mild conditions. The reaction exhibits high conversion rate, high selectivity, and good cycle stability, and shows promise as a feasible approach for industrial catalysis.

[0005] The technical solution provided by this invention is as follows:

[0006] In a first aspect, the present invention provides a method for preparing a nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst, comprising the following steps:

[0007] (1) A mixture of ruthenium chloride aqueous solution, tryptophan and mesoporous silica template SBA-15-OH with silanol groups on the pore surface was dispersed in an ethanol-water mixed solvent and stirred evenly.

[0008] (2) The product is obtained by solvent evaporation, heating and calcination to remove template agent SBA-15-OH, followed by washing, drying and grinding.

[0009] Furthermore, in step (1), the ratio of ruthenium chloride, tryptophan and SBA-15-OH is 0.05-0.2 mmol: 0.8-3.2 g: 1-2 g.

[0010] Furthermore, in step (2), the heating and roasting are carried out in an argon atmosphere, and the roasting temperature is 500-900℃.

[0011] In a second aspect, the present invention provides a nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst, which is prepared by the method described in the first aspect.

[0012] Furthermore, in the catalyst, the size of the ruthenium metal particles is less than 5 nm, and the mass fraction is 0.1-20 wt%. Preferably, the mass fraction is 1-5 wt%.

[0013] Thirdly, the present invention provides the application of the catalyst described in the second aspect in the selective reduction of nitroaromatic compounds, comprising the following steps:

[0014] (1) Mix the nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst, nitroaromatic compound and solvent.

[0015] (2) Place it in a high-pressure reactor and fill it with hydrogen gas, and stir it magnetically at room temperature or under heating conditions to carry out the reaction;

[0016] (3) The product after the reaction is recovered to obtain aromatic amine compounds.

[0017] Furthermore, in step (1), the molar ratio of ruthenium atoms to nitroaromatic compounds in the nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst is 0.01-10:100, and the molar ratio of nitroaromatic compounds to solvent is 1g:10-200mL.

[0018] Furthermore, in step (1), the nitroaromatic compound is a substituted product of nitrobenzene, and the substituent contains at least one electron-withdrawing group or at least one electron-donating group; the electron-withdrawing group includes –C≡N, –C=O, –Cl, –Br, –I, –F, –C=C–, and the electron-donating group includes –CH3, –NH3, –O–CH3.

[0019] Furthermore, the substituents include –Cl, –Br, –I, –F, –C=CH2, –C≡N, C1~C2 alkyl, C1~C2 alkoxy, –COR 1 –R 2 C≡N,–SO2R 3 R 1 Selected from hydrogen, phenyl, C1-C2 alkyl or amino, R 2 Selected from phenyl or C1-C2 alkyl, R 3The amino group is selected from C1-C2 alkyl-substituted amino groups. Preferably, the substituent is selected from –Cl, –Br, –I, –F, –C=CH2, –CH3, –COH, –COPh, –O–CH3, –C≡N, –CH2C≡N or –SO2NHCH3.

[0020] Furthermore, in step (1), the solvent is one or a mixture of two or more of the following: water, ethanol, methanol, tetrahydrofuran, ethyl acetate, dichloromethane, acetonitrile, and cyclohexane.

[0021] Furthermore, in step (1), the reaction temperature is 0-200℃, the reaction pressure is 0.01-10MPa, and the reaction time is 0.01-200 hours. Preferably, the reaction pressure is 0.1-5MPa, and the reaction time is 0.1-20 hours.

[0022] Furthermore, in step (3), after the reaction is completed, the reaction solution can be filtered, extracted, and simply purified to obtain the aromatic amine product.

[0023] Furthermore, in step (3), after the reaction is complete, the catalyst can be washed, centrifuged, and dried for reuse.

[0024] The beneficial effects of this invention are:

[0025] 1) The heterogeneous nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst used in this invention is synthesized in a one-pot method. The synthesis process is simple, easy to operate, and can be industrialized for mass production. At the same time, the material has a regular and ordered mesoporous structure and a high specific surface area.

[0026] 2) The method for selectively reducing nitro aromatic compounds provided by this invention can selectively reduce nitro aromatic compounds containing unsaturated groups to aromatic amines under mild conditions. It can also selectively reduce the nitro group of 4-nitro-N-methylbenzyl sulfonamide, an important intermediate in pharmaceutical reactions, to the target amino product, achieving high conversion rate, high selectivity and good cycle stability. It is expected to become a feasible approach for industrial catalysis.

[0027] 3) The catalyst prepared by this invention has a high specific surface area and large pore volume, ordered mesoporous channels and ultra-small metal particle size, and can be reused more than five times without significant activity decay. Attached Figure Description

[0028] Figure 1 The image shows the X-ray diffraction pattern of the nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst prepared in Example 1.

[0029] Figure 2 This is a transmission electron microscope image of the nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst prepared in Example 1. Detailed Implementation

[0030] This invention provides a method for the selective reduction of nitroaromatic compounds and a catalyst thereof. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] Example 1

[0032] The steps for preparing nitrogen-doped mesoporous carbon-supported ruthenium metal catalysts are as follows:

[0033] 0.8-3.2 g of tryptophan was dissolved in 20 mL of ethanol and 20 mL of ultrapure water, and heated and stirred at 50-70 °C until completely dissolved. Then, 0.5-2 mL of a 0.1 mol / L ruthenium chloride aqueous solution and 1-2 g of SBA-15-OH template agent were added, and the mixture was stirred for 3 hours. The solvent was evaporated, and the sample was dried in an oven at 50-70 °C for 12-24 hours. The sample was then pyrolyzed at 500-900 °C in a tube furnace under an argon atmosphere at a heating rate of 1-10 °C / min. After cooling to room temperature, the SBA-15-OH template agent was removed with sodium hydroxide solution. The sample was then filtered, washed with water, and freeze-dried to obtain a nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst. The ruthenium metal particles had a size of less than 5 nm, a mass fraction of 1-5 wt%, and a specific surface area of ​​760 m². 2 / g, pore volume is 0.80cm³ 3 / g.

[0034] Figure 1 The image shows the X-ray diffraction pattern of the nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst. As can be seen from the image, the prepared nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst does not exhibit obvious ruthenium diffraction peaks, indicating that the ruthenium is uniformly distributed on the support and has a small particle size.

[0035] Figure 2 The image shows a transmission electron microscope (TEM) image of the nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst. As can be seen from the image, the prepared nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst completely replicates the mesoporous morphology of the template SBA-15-OH, with ruthenium metal uniformly distributed within the mesoporous channels and particle sizes around 2 nm.

[0036] Application Example 1

[0037]

[0038] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of p-chloronitrobenzene, and 1 mL of ultrapure water were added to a reaction tube and placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of p-chloronitrobenzene and the selectivity for p-chloroaniline both reached 99%.

[0039] Application Example 2

[0040]

[0041] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of p-fluoronitrobenzene, and 1 mL of ultrapure water were added to a reaction tube, which was then placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction was completed, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of p-fluoronitrobenzene and the selectivity for p-fluoroaniline both reached 99%.

[0042] Application Example 3

[0043]

[0044] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of p-bromonitrobenzene, and 1 mL of ultrapure water were added to a reaction tube, which was then placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of p-bromonitrobenzene and the selectivity for p-bromoaniline both reached 99%.

[0045] Application Example 4

[0046]

[0047] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of p-iodonitrobenzene, and 1 mL of ultrapure water were added to a reaction tube, which was then placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction was completed, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of p-iodonitrobenzene and the selectivity for p-iodoaniline both reached 99%.

[0048] Application Example 5

[0049]

[0050] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of p-methylnitrobenzene, and 1 mL of ultrapure water were added to a reaction tube, which was then placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of p-methylnitrobenzene and the selectivity for p-methylaniline both reached 99%.

[0051] Application Example 6

[0052]

[0053] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of 3-nitrostyrene, and 1 mL of ultrapure water were added to a reaction tube and placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of 3-nitrostyrene and the selectivity for 3-vinylaniline both reached 99%.

[0054] Application Example 7

[0055]

[0056] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of 4-nitrobenzophenone, and 1 mL of ultrapure water were added to a reaction tube and placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of 4-nitrobenzophenone and the selectivity for 4-aminobenzophenone both reached 99%.

[0057] Application Example 8

[0058]

[0059] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of p-nitrobenzene ether, and 1 mL of ultrapure water were added to a reaction tube, which was then placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 10 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of p-nitrobenzene ether and the selectivity for p-aminoanisole both reached 99%.

[0060] Application Example 9

[0061]

[0062] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of p-nitrobenzene, and 1 mL of ultrapure water were added to a reaction tube, which was then placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 20 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of p-nitrobenzene and the selectivity of p-aminobenzonitrile both reached 99%.

[0063] Application Example 10

[0064]

[0065] 10 mg of the catalyst prepared in Example 1, 0.2 mmol of 4-nitro-N-methylbenzylmethanesulfonamide, and 1 mL of ultrapure water were added to a reaction tube, which was then placed in a high-pressure reactor. Hydrogen gas at 10 bar was introduced, and this process was repeated six times to completely purge air. Finally, hydrogen gas at 10 bar was introduced, and the reaction was carried out at 25°C for 20 hours. After the reaction, the mixture was filtered and extracted with ethyl acetate. Gas chromatography analysis showed that the conversion rate of 4-nitro-N-methylbenzylmethanesulfonamide and the selectivity of 4-amino-N-methylbenzylmethanesulfonamide both reached 99%.

[0066] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the invention.

Claims

1. A method for preparing a nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst, characterized in that: Includes the following steps: (1) A mixture of ruthenium chloride aqueous solution, tryptophan and SBA-15-OH mesoporous silica template rich in silanol groups on the pore surface was dispersed in an ethanol-water mixed solvent and stirred evenly; the ratio of ruthenium chloride, tryptophan and SBA-15-OH was 0.05-0.2 mmol: 0.8-3.2 g: 1-2 g; (2) The template agent SBA-15-OH is removed by solvent evaporation, heating and calcination, and sodium hydroxide solution. Then it is washed, dried and ground to obtain the product.

2. The preparation method according to claim 1, characterized in that: In step (2), the heating and roasting are carried out in an argon atmosphere at a temperature of 500-900 °C.

3. A nitrogen-doped mesoporous carbon-supported ruthenium metal catalyst, characterized in that: Prepared using the method described in any one of claims 1-2.

4. The catalyst according to claim 3, characterized in that: In the catalyst, the size of the ruthenium metal particles is less than 5 nm, and the mass fraction is 0.1-20 wt%.

5. The application of the catalyst according to claim 3 or 4 in the selective reduction of nitroaromatic compounds, characterized in that, Includes the following steps: (1) The nitrogen-doped mesoporous carbon supported ruthenium metal catalyst, nitroaromatic compound and solvent are stirred and mixed; the nitroaromatic compound is a substituted product of nitrobenzene, and the substituent contains at least one electron-withdrawing group or at least one electron-donating group; the electron-withdrawing group includes –C≡N, –C=O, –Cl, –Br, –I, –F and –C=C–, and the electron-donating group includes –CH3, –NH2, –O–CH3; the molar ratio of ruthenium metal atoms to nitroaromatic compound in the nitrogen-doped mesoporous carbon supported ruthenium metal catalyst is 0.01-10:100; (2) Place it in a high-pressure reactor and fill it with hydrogen gas. Stir it magnetically at room temperature. The reaction pressure is 0.1-5 MPa and the reaction time is 0.1-20 hours. (3) The product after the reaction is recovered to obtain aromatic amine compounds.

6. The application according to claim 5, characterized in that: In step (1), the ratio of nitroaromatic compound to solvent is 1g:10-200mL.

7. The application according to claim 5, characterized in that: In step (1), the solvent is one or a mixture of two or more of the following: water, ethanol, methanol, tetrahydrofuran, ethyl acetate, dichloromethane, acetonitrile, and cyclohexane.

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