Non-noble metal catalysts and methods for their preparation and catalytic transfer hydrogenation of aromatic nitro compounds to produce aromatic amines

Abstract

The application provides a non-noble metal catalyst and a preparation method and a method for preparing aromatic amines by catalytic transfer hydrogenation reduction of aromatic nitro compounds, and relates to the technical fields of catalysis and organic synthesis. The non-noble metal catalyst provided by the application comprises carbon cloth and iron trioxide loaded on the carbon cloth. The application provides application of the non-noble metal catalyst in preparation of aromatic amines by catalytic transfer hydrogenation reduction of aromatic nitro compounds. The catalyst is used in preparation of aromatic amines by catalytic transfer hydrogenation reduction of aromatic nitro compounds, and high-pressure environment is not needed, the condition is mild, reduction of different aromatic nitro compound substrates can be realized, and the catalyst has the characteristics of high catalytic activity, high selectivity and recyclability. The results of examples show that when the catalyst is used in preparation of aromatic amines by catalytic transfer hydrogenation reduction of aromatic nitro compounds, the conversion rate of the aromatic nitro compounds is 85-95%, and the selectivity of the corresponding product aromatic amines is 90-98%.

Description

Non-precious metal catalysts and their preparation methods, and methods for the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines. Technical Field

[0001] This invention relates to the fields of catalysis and organic synthesis technology, and in particular to a non-precious metal catalyst, its preparation, and a method for the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines. Background Technology

[0002] Hydrogenation of aromatic nitro compounds is an important class of catalytic reactions, and its products, aromatic amine compounds (aromatic amines), are key intermediates in the manufacture of pharmaceuticals, pesticides, dyes, and pigments.

[0003] Industrially, the preparation of aromatic amines often involves reacting reducing agents such as iron powder and zinc powder with acids. However, this method generates large amounts of waste acid and residues, polluting the environment and hindering green development. Catalytic reduction using supported metal catalysts eliminates the need for large amounts of acid and offers high reaction yields and selectivity. CN113019393A discloses a platinum nanocatalyst, its preparation method, and a method for the selective hydrogenation synthesis of aromatic amines from aromatic nitro compounds. This method involves feeding aromatic nitro compounds, a supported metal catalyst—a platinum nanocatalyst—and a solvent into a reaction vessel, and then performing catalytic hydrogenation reduction under high-pressure conditions with added hydrogen to obtain the corresponding aromatic amine compounds. This method boasts high conversion and selectivity and is pollution-free. However, the platinum nanocatalyst used in this method requires the use of precious metals, resulting in high preparation costs and a complex process, making it unsuitable for industrial production. Furthermore, the reaction requires high pressure and flammable hydrogen, posing a certain degree of danger. Summary of the Invention

[0004] In view of this, the object of the present invention is to provide a non-precious metal catalyst, its preparation, and a method for the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines. The non-precious metal catalyst provided by the present invention can catalytically transfer hydrogenate aromatic nitro compounds, and has high catalytic activity and selectivity, and low cost.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] The present invention provides a non-precious metal catalyst comprising carbon cloth and ferric oxide supported on the carbon cloth, wherein the ferric oxide has a size of 4 to 7 μm.

[0007] This invention provides a method for preparing the non-precious metal catalyst described in the above technical solution, comprising the following steps:

[0008] The non-precious metal catalyst is obtained by mixing carbon cloth with an aqueous solution of ferric nitrate and carrying out a hydrothermal reaction.

[0009] Preferably, the carbon cloth is pretreated before being mixed with the ferric nitrate aqueous solution, the pretreatment including:

[0010] After cleaning, the carbon cloth is placed in nitric acid for hydrothermal treatment; the mass fraction of the nitric acid is 30-40%, the temperature of the hydrothermal treatment is 130-150℃, and the time is 4-6 hours.

[0011] Preferably, the concentration of the ferric nitrate aqueous solution is 0.0625–0.125 mol / L.

[0012] Preferably, the hydrothermal reaction is carried out at a temperature of 140–180°C for 4–6 hours.

[0013] This invention provides the application of the non-precious metal catalyst described in the above technical solutions or the non-precious metal catalyst prepared by the above technical solutions in the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines.

[0014] This invention provides a method for the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines, comprising the following steps:

[0015] An aromatic nitro compound, a hydrogen donor, a solvent, and a catalyst are mixed and subjected to a catalytic transfer hydrogenation reduction reaction to obtain an aromatic amine; the hydrogen donor includes one or more of hydrazine hydrate, sodium borohydride, and ammonia borane; and the catalyst is a non-precious metal catalyst as described in the above technical solution or a non-precious metal catalyst prepared by the preparation method described in the above technical solution.

[0016] Preferably, the aromatic nitro compound is nitrobenzene or halogen-substituted nitrobenzene; the molar ratio of the aromatic nitro compound to the hydrogen donor is 1:(2-4), and the mass of the catalyst is 5-20% of the mass of the aromatic nitro compound.

[0017] Preferably, the solvent is methanol, ethanol, or water, and the mass of the aromatic nitro compound is 1 to 5% of the mass of the solvent.

[0018] Preferably, the temperature of the catalytic transfer hydrogenation reduction reaction is 70–85°C, and the time is 3–5 h.

[0019] This invention provides a non-precious metal catalyst comprising carbon cloth and ferric oxide supported on the carbon cloth, wherein the ferric oxide has a size of 4–7 μm. In this invention, the ferric oxide, as the active component, exhibits high dispersion on the carbon cloth and thus high catalytic activity; the carbon cloth, as the support, possesses strong selectivity and is suitable for supporting non-inert metal oxides.

[0020] This invention provides a method for preparing the non-precious metal catalyst described in the above technical solution. The preparation method provided by this invention has low cost, simple process, and high ferric oxide dispersion in the obtained catalyst.

[0021] This invention provides the application of the non-precious metal catalyst described in the above technical solutions or the non-precious metal catalyst prepared by the above preparation methods in the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines. Applying the non-precious metal catalyst provided by this invention to the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines eliminates the need for a high-pressure environment, provides mild conditions, enables the reduction of different aromatic nitro compound substrates, reduces side reactions, and improves the yield and selectivity of the target product, aromatic amines. Furthermore, the catalyst is low in cost and recyclable, making it suitable for the industrial production of catalytic transfer hydrogenation reduction of nitro compounds.

[0022] The results of the examples show that when the non-precious metal catalyst provided by the present invention is applied to the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines, the conversion rate of aromatic nitro compounds is 85-95%, and the selectivity of the corresponding product aromatic amine is 90-98%. Moreover, the catalyst can be recovered and reused, and still has high catalytic activity. Attached Figure Description

[0023] Figure 1 shows the XRD patterns of the pretreated carbon cloth and the prepared catalyst Fe2O3 / CC in the example.

[0024] Figure 2 shows the electron microscope (SEM) image of the carbon cloth after pretreatment (a) and the scanning electron microscope (SEM) image of the catalyst Fe2O3 / CC (b) in the example. Detailed Implementation

[0025] The present invention provides a non-precious metal catalyst comprising carbon cloth and ferric oxide supported on the carbon cloth, wherein the ferric oxide has a size of 4 to 7 μm.

[0026] In this invention, ferric oxide (Fe2O3) serves as the active component, exhibiting high dispersion on carbon cloth and thus high catalytic activity. The carbon cloth, acting as a support, possesses strong selectivity and is suitable for supporting non-inert metal oxides. In embodiments of this invention, the non-noble metal catalyst is represented as Fe2O3 / CC.

[0027] This invention provides a method for preparing the non-precious metal catalyst described in the above technical solution, comprising the following steps:

[0028] The non-precious metal catalyst is obtained by mixing carbon cloth with an aqueous solution of ferric nitrate and carrying out a hydrothermal reaction.

[0029] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known in the art.

[0030] This invention does not have any special requirements for the carbon cloth; any carbon cloth well-known to those skilled in the art can be used. Before mixing with the ferric nitrate aqueous solution, this invention preferably pre-treats the carbon cloth. The pre-treatment preferably includes: cleaning the carbon cloth and then immersing it in nitric acid for hydrothermal treatment. In this invention, the cleaning preferably involves sequentially immersing the carbon cloth in ethanol, acetone, and deionized water for ultrasonic treatment for 0.5 hours. The cleaning in this invention aims to remove oxides from the surface of the carbon cloth. This invention preferably immerses the cleaned carbon cloth in nitric acid for hydrothermal treatment. In this invention, the mass fraction of the nitric acid is preferably 30-40%, more preferably 35%, the hydrothermal treatment temperature is preferably 130-150°C, more preferably 140°C, and the time is preferably 4-6 hours, more preferably 5 hours. In this invention, the hydrothermal treatment thoroughly removes impurities from the carbon cloth, removing oxides, grease, or other contaminants from its surface. After the hydrothermal treatment, this invention preferably sequentially washes and dries the resulting carbon cloth; the washing preferably involves multiple rinsings with deionized water, and the drying temperature is preferably 60°C, with a drying time preferably 15 minutes.

[0031] In this invention, the concentration of the ferric nitrate aqueous solution is preferably 0.0625-0.125 mol / L. In an embodiment of this invention, the ferric nitrate aqueous solution is specifically prepared by adding 2.5-5 mmol Fe(NO3)3·9H2O to 40 mL of deionized water and stirring at room temperature for 0.5-1 h.

[0032] In this invention, the pretreated carbon cloth is preferably immersed in the ferric nitrate aqueous solution, and then transferred to a reaction vessel for hydrothermal reaction. This invention does not have specific requirements for the amount of the ferric nitrate aqueous solution, as long as it completely submerges the carbon cloth and does not exceed 80% of the reaction vessel's volume.

[0033] In this invention, the temperature of the hydrothermal reaction is preferably 140–180°C, more preferably 150–160°C, and the time is preferably 4–6 hours, more preferably 4–5 hours. During the hydrothermal reaction, ferric nitrate is converted to ferric hydroxide, and then to ferric oxide.

[0034] After the hydrothermal reaction is completed, the product is preferably removed and then washed and dried sequentially to obtain the non-precious metal catalyst. In this invention, the washing is preferably performed twice, alternating between water and ethanol; the drying temperature is preferably 60°C, and the drying time is preferably 2 hours.

[0035] The non-precious metal catalyst described in this invention is easy to prepare, has low preparation cost, and the active component Fe2O3 has good dispersibility.

[0036] This invention provides the application of the non-precious metal catalyst described in the above technical solutions or the non-precious metal catalyst prepared by the above preparation methods in the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines. Catalytic transfer hydrogenation is the hydrogenation or hydrogenolysis of hydrogen acceptor in the presence of a catalyst, using hydrazine hydrate, sodium borohydride, etc., as hydrogen donors. Applying the non-precious metal catalyst provided by this invention to the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines can reduce the environmental pollution caused by the reduction reaction of aromatic nitro compounds, and it does not require a high-pressure environment, providing mild conditions. It can achieve the reduction of different aromatic nitro compound substrates, reduce the occurrence of side reactions, and has the characteristics of high catalytic activity, high selectivity, and catalyst recyclability. In addition, it can reduce the cost of catalytic transfer hydrogenation reduction and has good prospects for industrial application.

[0037] This invention provides a method for the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines, comprising the following steps:

[0038] An aromatic nitro compound, a hydrogen donor, a solvent, and a catalyst are mixed and subjected to a catalytic transfer hydrogenation reduction reaction to obtain an aromatic amine; the hydrogen donor includes one or more of hydrazine hydrate, sodium borohydride, and ammonia borane; and the catalyst is a non-precious metal catalyst as described in the above technical solution or a non-precious metal catalyst prepared by the preparation method described in the above technical solution.

[0039] In this invention, the aromatic nitro compound is preferably nitrobenzene or halogen-substituted nitrobenzene, and the halogen-substituted nitrobenzene is preferably p-chloronitrobenzene or o-bromonitrobenzene. In this invention, the molar ratio of the aromatic nitro compound to the hydrogen donor is preferably 1:(2-4), more preferably 1:(3-4); the mass of the catalyst is preferably 5-20% of the mass of the aromatic nitro compound, more preferably 5-10%, and even more preferably 6-7.5%. In this invention, the solvent is preferably methanol, ethanol, or water, and the mass of the aromatic nitro compound is preferably 1-5% of the mass of the solvent, more preferably 1.5-2.5%.

[0040] In this invention, the preferred method for mixing the aromatic nitro compound, hydrogen donor, solvent and catalyst is to add the aromatic nitro compound and catalyst to the solvent, transfer the resulting mixture to a reaction vessel equipped with mechanical stirring, and then add the hydrogen donor thereto.

[0041] In this invention, the temperature of the catalytic transfer hydrogenation reduction reaction is preferably 70-85°C, more preferably 70-80°C, and the time is preferably 3-5 h, more preferably 3.5-4.5 h.

[0042] After the catalytic transfer hydrogenation reduction reaction is completed, the present invention preferably filters the resulting reaction solution to obtain a catalyst and a filtrate. In the present invention, the catalyst can be recycled and the catalytic transfer hydrogenation reduction reaction can be repeated; after desolvation, the filtrate yields an aromatic amine, a product corresponding to an aromatic nitro compound.

[0043] In this invention, when the hydrogen donor is hydrazine hydrate, after the catalytic transfer hydrogenation reduction reaction, hydrazine hydrate is decomposed into H2 and N2, and the decomposition products are green and pollution-free.

[0044] In existing technologies, when using precious metal catalysts to catalyze nitro compounds, dehalogenation occurs when catalyzing halogen-containing nitro compounds, resulting in poor selectivity. However, this application uses the non-precious metal catalyst described above to catalytically transfer hydrogenate and reduce halogen-containing aromatic nitro compounds, which exhibits excellent selectivity.

[0045] To further illustrate the present invention, the following detailed descriptions, in conjunction with examples, of non-precious metal catalysts and their preparation methods, as well as methods for the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines, should not be construed as limiting the scope of protection of the present invention.

[0046] The catalysts used in the following examples are Fe2O3 / CC (Fe2O3 supported on carbon cloth), which were prepared according to the following methods:

[0047] Carbon cloth pretreatment: Cut the carbon cloth into 1cm×2cm pieces (0.1mm thick), and then place them in ethanol, acetone, and deionized water respectively for 0.5 hours of ultrasonic treatment to remove surface oxides. Then place them in a reaction vessel containing 35% nitric acid and hydrothermally heat at 140℃ for 5 hours. After the reaction is completed, rinse them several times with deionized water and then dry them in a vacuum oven at 60℃ for 15 minutes for later use.

[0048] Synthesis of Fe2O3 / CC: 2.5 mmol Fe(NO3)3·9H2O was added to 40 mL of deionized water and stirred at room temperature for 0.5 h to obtain an aqueous solution of ferric nitrate; the pretreated carbon cloth was then immersed in the aqueous solution of ferric nitrate and placed in a reaction vessel for hydrothermal reaction at 160 °C for 6 h. After the reaction vessel cooled to room temperature, the reactants were removed, washed twice alternately with water and ethanol, and then vacuum dried at 60 °C for 2 h to obtain the catalyst Fe2O3 / CC.

[0049] Figure 1 shows the XRD patterns of the pretreated carbon cloth (CC) and the prepared catalyst Fe2O3 / CC. It can be seen that the peaks near 33.2° and 35.8° of the catalyst belong to the characteristic diffraction patterns of Fe2O3, indicating that iron oxide is effectively loaded onto the carbon cloth.

[0050] Figure 2 shows the electron microscope (SEM) images of the pretreated carbon cloth (CC) (a) and the scanning electron microscope (SEM) image of the Fe2O3 / CC catalyst (b). The SEM images show that blocky iron oxide is highly dispersed on the surface of the support, with a size of 4–7 μm.

[0051] Example 1

[0052] 690 mg (5 mmol) of nitrobenzene and 50 mg of Fe₂O₃ / CC catalyst were added to 50 mL of ethanol (1.09 mol), and then transferred to a 250 mL reactor equipped with a mechanical stirrer. 1 g of hydrazine hydrate (20 mmol) was added. The mixture in the reactor was heated to 70 °C and maintained at this temperature for 3.5 h. After the reaction was complete, the catalyst was recovered by filtration, and the product aniline was obtained after solvent removal. Gas chromatography-mass spectrometry (GC-MS) analysis showed that the conversion rate of nitrobenzene was 95% and the selectivity of aniline was 98%.

[0053] Example 2

[0054] The experimental process of this embodiment is the same as that of Example 1, except that "nitrobenzene is replaced with an equal molar amount of p-chloronitrobenzene and the solvent ethanol is replaced with an equal volume of methanol". Other reaction conditions and experimental operations are the same as those of Example 1. The final product obtained is p-chloroaniline with a conversion rate of 90% for p-chloronitrobenzene and a selectivity of 90% for p-chloroaniline.

[0055] Example 3

[0056] The experimental process of this embodiment is the same as that of Example 1, except that "nitrobenzene is replaced with an equal molar amount of o-bromonitrobenzene, and the solvent ethanol is replaced with an equal volume of methanol". Other reaction conditions and experimental operations are the same as those of Example 1. The final product obtained is o-bromoaniline, with a conversion rate of 86% for o-bromonitrobenzene and a selectivity of 95% for o-bromoaniline.

[0057] Example 4

[0058] The experimental process of this embodiment is the same as that of Example 1, except that "nitrobenzene is replaced with an equal molar amount of o-bromonitrobenzene, and the solvent ethanol is replaced with an equal volume of water". Other reaction conditions and experimental operations are the same as those of Example 1. The final product obtained is o-bromoaniline, with a conversion rate of 85% for o-bromonitrobenzene and a selectivity of 90% for o-bromoaniline.

[0059] Example 5

[0060] The experimental process of this embodiment is the same as that of Example 1, except that "hydrazine hydrate is replaced with an equal molar amount of sodium borohydride and the solvent ethanol is replaced with an equal volume of methanol". Other reaction conditions and experimental operations are the same as those of Example 1. The final product obtained is aniline, with a conversion rate of 93% for nitrobenzene and a selectivity of 95% for aniline.

[0061] Example 6

[0062] The experimental process of this embodiment is the same as that of Example 1, except that "hydrazine hydrate is replaced with an equal molar amount of ammonia borane and ethanol solvent is replaced with an equal volume of methanol". Other reaction conditions and experimental operations are the same as those of Example 1. The final product obtained is aniline, with a conversion rate of 90% for nitrobenzene and a selectivity of 92% for aniline.

[0063] Example 7

[0064] To verify the catalytic activity of the catalyst after use, the catalyst recovered by filtration in Example 1 was repeatedly used in the experiment to prepare aniline. The experimental conditions and procedures were the same as in Example 1. The experimental results were as follows: when the catalyst recovered by filtration in Example 1 was repeatedly used four times, the yields of aniline product were 91.3%, 90.1%, 87.2%, and 85.5%, respectively.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. The application of a non-precious metal catalyst in the catalytic transfer hydrogenation reduction of aromatic nitro compounds to prepare aromatic amines, wherein the non-precious metal catalyst comprises carbon cloth and ferric oxide supported on the carbon cloth, the ferric oxide having a size of 4~7 μm; the preparation method of the non-precious metal catalyst includes the following steps: The non-precious metal catalyst is obtained by mixing carbon cloth with an aqueous solution of ferric nitrate and carrying out a hydrothermal reaction.

2. The application according to claim 1, characterized in that, Before mixing with the ferric nitrate aqueous solution, the carbon cloth is pretreated. The pretreatment includes: cleaning the carbon cloth and then immersing it in nitric acid for hydrothermal treatment; the mass fraction of the nitric acid is 30-40%, the temperature of the hydrothermal treatment is 130-150℃, and the time is 4-6 hours.

3. The application according to claim 1, characterized in that, The concentration of the ferric nitrate aqueous solution is 0.0625~0.125 mol / L.

4. The application according to claim 1, characterized in that, The hydrothermal reaction is carried out at a temperature of 140~180℃ for 4~6 hours.

5. A method for preparing aromatic amines by catalytic transfer hydrogenation reduction of aromatic nitro compounds, characterized in that, Includes the following steps: An aromatic nitro compound, a hydrogen donor, a solvent, and a catalyst are mixed and subjected to a catalytic transfer hydrogenation reduction reaction to obtain an aromatic amine; the hydrogen donor includes one or more of hydrazine hydrate, sodium borohydride, and ammonia borane; and the catalyst is a non-precious metal catalyst used in any one of claims 1 to 4.

6. The method according to claim 5, characterized in that, The aromatic nitro compound is nitrobenzene or halogen-substituted nitrobenzene; the molar ratio of the aromatic nitro compound to the hydrogen donor is 1:(2~4), and the mass of the catalyst is 5~20% of the mass of the aromatic nitro compound.

7. The method according to claim 5, characterized in that, The solvent is methanol, ethanol or water, and the mass of the aromatic nitro compound is 1 to 5% of the mass of the solvent.

8. The method according to claim 5, characterized in that, The catalytic transfer hydrogenation reduction reaction is carried out at a temperature of 70-85°C for 3-5 hours.

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