Application of catalyst in preparation of arylamine by selective hydrogenation of aromatic nitro compound

Abstract

The invention belongs to the technical field of application of selective hydrogenation catalysts in industry, and relates to application of a catalyst in preparation of arylamine by selective hydrogenation of an aromatic nitro compound. The catalyst is applied to the selective hydrogenation reaction of the aromatic nitro compound; wherein the aromatic nitro compound is shown as a formula I, the catalyst takes inert oxide silicon oxide as a carrier, and the active component is Cu; wherein the content of the active component is 0.1-50wt%, and the average particle size of the loaded metal is 0.5-20nm. Compared with the existing industrial synthesis route of selective hydrogenation of the aromatic nitro compound, the method provided by the invention has the remarkable advantages of simple reaction process operation, cost saving and the like.

Description

Technical Field

[0001] This invention belongs to the field of selective hydrogenation catalyst application technology in industry, and relates to the application of a catalyst for the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines. Background Technology

[0002] The selective hydrogenation of aromatic nitro compounds to prepare corresponding aromatic amines is one of the most important reactions in the fine chemical industry, with wide applications in pesticides, pharmaceuticals, dyes, and polymers. However, when the reactant molecules contain various easily reducible groups such as C=C and C≡C, selectively reducing the nitro group while retaining other functional groups remains a significant challenge. Industrially, stoichiometric reducing agents such as Na₂S₂O₄, Fe, Zn, and Sn are generally used, but the reaction system generates a large amount of waste. To overcome this drawback, H₂ is used as a reducing agent, and Pt / C modified with PbO or H₃PO₂ is used as a catalyst. While this significantly improves the selectivity to the target product, the catalyst activity decreases, and hydroxylamine intermediates are generated during the reaction. Even very low concentrations of hydroxylamine species pose an explosion hazard. Studies have found that adding iron or alum salts to the above catalytic system can convert hydroxylamine intermediates into the target product, but a large amount of transition metal salts remain in the solution after the reaction, making subsequent treatment complex and resulting in poor economic efficiency and severe environmental pollution. Therefore, there is an urgent need for a catalyst that can achieve both high activity and high selectivity without the addition of any organic or inorganic additives for these types of reactions. To achieve this goal, extensive research has been conducted and different types of catalysts have been developed, including homogeneous catalysts and supported catalysts. Among them, supported metal catalysts have the characteristics of easy recovery, high efficiency and good stability, and have been widely used in environmental catalysis, fine chemicals, petrochemicals and other fields.

[0003] Many patents and documents describe supported Au and Pt noble catalysts for the selective hydrogenation of aromatic nitro compounds. Their activities vary depending on the support and preparation method.

[0004] The literature (Science 2006, 313, 332-334) first reported that supported gold catalysts (Au / TiO2, Au / Fe2O3) were used for the selective hydrogenation of aromatic nitro compounds to aniline. At 120 °C and H2 pressure of 0.9 MPa for 6 hours, Au / TiO2 showed a substrate conversion of 98.5% and an aniline selectivity of 95.9%.

[0005] Patent CN111135822A discloses the application of a supported, highly dispersed noble metal (one or more of ruthenium, rhodium, palladium, silver, iridium, platinum, and gold) catalyst in the selective reaction of aromatic nitro compounds. The catalyst uses a high specific surface area oxide as a support, and the content of the active component is 0.05-20%. This catalyst exhibits excellent activity, selectivity, and stability in the selective hydrogenation reaction of aromatic nitro compounds.

[0006] Patent CN114950532A discloses a catalyst for the synthesis of aromatic amines from nitro aromatic compounds and its preparation method. Boron nitride, which has a high specific surface area and contains defective nitrogen, is used as a support. Ruthenium and palladium (Ru and Pd) are used as active components. The strong metal-nitrogen coordination between the metal and the support anchors and disperses the active metal on the support surface. Utilizing the synergistic effect of ruthenium-palladium hydrogenation catalysis, the efficient and selective hydrogenation of nitro aromatic compounds into aromatic amines is achieved.

[0007] In the literature (Chinese Journal of Catalysis 2021, 42, 1530-1537), the authors found that there is a strong interaction between the active component and the support in Au / TiO2 catalysts. After being treated at 300℃, 400℃ and 500℃ under H2 atmosphere, the strong interaction between the active component and the support can increase the interface length of Au-TiO2, thereby enhancing the activity of selective hydrogenation reaction of aromatic nitro compounds.

[0008] However, although noble metal catalysts such as Pt, Pd, Au, and Ru exhibit good catalytic activity and product selectivity for the selective hydrogenation of nitro aromatic compounds, their production costs are relatively high, and some reaction conditions require harsh temperatures, significantly limiting their industrial applications. Therefore, using inexpensive metals to replace noble metals for the directed synthesis of aniline is a promising strategy. Summary of the Invention

[0009] The purpose of this invention is to provide a supported metal catalyst, its preparation, and its application in the selective hydrogenation reaction of aromatic nitro compounds.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A catalyst is disclosed for the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines; the catalyst is used in the selective hydrogenation reaction of aromatic nitro compounds; wherein the aromatic nitro compound is as shown in Formula 1.

[0012]

[0013] In the formula, R is selected from C1-C6 alkenyl, C≡N, C1-C6 alkynyl, aldehyde, carbonyl, and phenolic hydroxyl groups;

[0014] The catalyst uses inert oxide silicon dioxide as a support and Cu as the active component; the content of the active component is 0.1-50 wt%, and the average particle size of the metal after loading is 0.5-20 nanometers.

[0015] The catalyst was prepared as follows:

[0016] 1) Dissolve the soluble precursor of the metal active component, and add it to the solvent under stirring to obtain a metal precursor solution, and make the pH of the solution between 9 and 12; wherein, the metal active component is Cu, and the metal concentration in the metal precursor solution is 0.1-100 g / L;

[0017] 2) The above metal precursor solution is stirred and the support is added and mixed. The solvent is then heated to evaporate until the solution pH is neutral. The precipitate is collected by filtration and calcined at 200-550℃ for 0.5-10 hours to obtain the supported metal catalyst precursor. The content of the metal active component is 1-40 wt%.

[0018] 3) The precursor is placed in a reducing atmosphere and pretreated at 200-600℃ for 10-300 minutes to obtain a catalyst that can be directly used for hydrogenation reaction.

[0019] The soluble precursor of the metal active component is one or more of copper chloride, copper nitrate, copper sulfate, copper acetate, copper acetylacetone, and copper-containing organic complexes.

[0020] The solvent for the soluble precursor of the dissolved metal active component is one or a mixture of two or more of the following: water, methanol, ethanol, isopropanol, acetone, etc.

[0021] The solvent is an inorganic and / or organic solvent.

[0022] The inorganic solvent is one or a mixture of any of the following: sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonia, sodium phosphate, sodium dihydrogen phosphate, or other weakly alkaline reagents; the organic reagent is one or a mixture of any of the following: ethanol, methanol, ethylene glycol, etc.

[0023] The reducing atmosphere is one or a mixture of several of He, Ar, N2, and H2.

[0024] The carrier is one or more of the following: silica, ordered mesoporous silica, or amorphous commercial silica gel, which have a large specific surface area, good thermal stability, and are relatively inexpensive.

[0025] The hydrogenation reaction involves loading the prepared catalyst, aromatic nitro compound, and solvent into a closed reaction vessel, whereby the aromatic nitro compound undergoes selective hydrogenation to prepare aromatic amines. After the reaction, the catalyst is collected by filtration and recycled. The molar ratio of the active component to the aromatic nitro compound in the catalyst is between 0.05 and 1.

[0026] The reaction is carried out in a closed reactor with an initial hydrogen pressure of 0.1-5 MPa, a reaction temperature of 60-180°C, and a reaction time of 0.5-24 hours.

[0027] The solvent is one or more of water, methanol, ethanol, toluene, tetrahydrofuran, and n-dodecane.

[0028] The preferred reaction temperature is 80-150℃, the preferred initial hydrogen pressure is 0.5-2 MPa, and the preferred reaction time is 0.5-12 hours.

[0029] The catalyst can be recycled at least twice without a significant decrease in conversion and selectivity, and it is easy to separate from the reaction solution.

[0030] The present invention has the following beneficial effects:

[0031] This invention relates to the application of a supported metal catalyst in the selective hydrogenation reaction of aromatic nitro compounds. The catalyst enables the directed hydrogenation of nitro functional groups to aromatic amines, exhibiting high substrate conversion of aromatic nitro compounds and aniline product selectivity. The active component in the catalyst is inexpensive, reducing the economic cost. Furthermore, the catalyst is easily recoverable and recyclable, the operation is simple, and the reaction conditions are relatively mild, demonstrating promising industrial application prospects. Specifically:

[0032] 1. The catalyst preparation method of this invention is simple, requires no addition of any co-catalyst, and the active component is an inexpensive metal element, while the support is an inexpensive and readily available inert oxide, silicon dioxide, which effectively reduces the economic cost of the catalyst.

[0033] 2. The catalyst of this invention has excellent catalytic reaction performance. During use, it has a strong ability to selectively hydrogenate nitro functional groups without the need to add any other reagents to inhibit the activation of other functional groups. Moreover, the catalyst has good substrate applicability for selective hydrogenation of aromatic nitro compounds containing multiple functional groups (e.g., aldehyde, ketone, halogenated functional groups, nitrile groups).

[0034] 3. The catalyst of this invention exhibits high activity and selectivity for the selective hydrogenation of nitro aromatic compounds, can be recycled multiple times without significant decrease in activity, and is easily separated from the reaction solution after reaction, making the operation simple.

[0035] In summary, this invention achieves efficient and highly selective conversion of aromatic nitro compounds to aniline. Compared with existing industrial catalyst systems, the supported metal catalyst provided by this invention is green, cost-effective, and has the potential for industrial application. Attached Figure Description

[0036] Figure 1 The image shows the XRD diffraction pattern of the catalyst prepared in Representative Example 2. Detailed Implementation

[0037] The present invention will now be described in detail through specific embodiments. It should be noted that these embodiments are merely examples and do not constitute any limitation on the nature and scope of the present invention. The present invention can be implemented as long as it meets the conditions set forth in the content section of this invention.

[0038] Example 1:

[0039] 1) Weigh 0.3774g of copper nitrate trihydrate and dissolve it in 20mL of deionized water. Stir for 15 minutes to ensure it is fully dissolved.

[0040] 2) Adjust the pH of the solution to 10 with ammonia water, continue stirring for 30 minutes, weigh 1g of pre-ground silica with a size of less than 100 mesh and add it to the above solution, continue stirring for 30 minutes;

[0041] 3) Stir and evaporate the solvent at 70°C until the solution pH is about 7. Filter, wash thoroughly with deionized water, dry at 80°C overnight, calcine at 500°C for 3 hours, and then cool to room temperature to obtain the catalyst.

[0042] Example 2:

[0043] 1) Weigh 0.5651g of copper nitrate trihydrate and dissolve it in 20mL of deionized water. Stir for 15 minutes to ensure it is fully dissolved.

[0044] 2) Adjust the pH of the solution to 10 with ammonia water, continue stirring for 30 minutes, weigh 1g of pre-ground silica with a size of less than 100 mesh and add it to the above solution, continue stirring for 30 minutes;

[0045] 3) Evaporate the solvent by stirring at 70℃ until the solution pH is approximately 7. Filter, wash thoroughly with deionized water, dry at 80℃ overnight, calcine at 500℃ for 3 hours, and then cool to room temperature to obtain the catalyst (see [link to catalyst]). Figure 1 ).

[0046] Depend on Figure 1 The absence of any characteristic diffraction peaks in the XRD pattern indicates that the active metal component in the prepared supported metal catalyst exists in a highly dispersed state within the catalyst.

[0047] Comparative Example 1:

[0048] 3-Aminopropyltriethoxysilane (APTES) modified silica support: 400 mL of ethanol was measured into a 500 mL three-necked flask using a graduated cylinder, and 20 g of APTES was added to prepare a solution. 8.00 g of pre-ground silica support was accurately weighed and added to the above solution. The three-necked flask was placed in a water bath and magnetically stirred, then refluxed at 80 °C for 24 hours. The solution was then filtered, washed with ethanol, and dried in an oven at 60 °C for 6 hours. The APTES-modified silica support was obtained.

[0049] At room temperature (~25℃), 5.23 mL (9.56 mg / mL) of HAuCl4 solution was added to a final volume of 20 mL with water. After stirring thoroughly, 1.0 g of APTES-modified silica support was added, and stirring continued for 30 minutes to allow HAuCl4 to adsorb onto the support surface. After filtration and washing, the solution was redispersed in 20 mL of 0.1 M NaBH4 aqueous solution. After stirring, the solution was filtered again and washed until no Cl- was detected by AgNO3. - The Au / SiO2 catalyst was obtained by drying at 80℃ for 10 hours and calcining at 500℃ for 6 hours.

[0050] Comparative Example 2:

[0051] At room temperature (~25℃), 0.001g of platinum acetylacetonate and 1.2mL of ethanol were ultrasonically mixed to form a solution, which was then impregnated with 0.5g of pre-ground silica support. The solution was dried at 60℃ overnight and calcined at 400℃ for 2 hours to obtain the Pt / SiO2 comparative catalyst.

[0052] Comparative Example 3:

[0053] Weigh 1g of ground SiO2 and dissolve 0.2078g of Ni(NO3)2·6H2O in 1.5g of deionized water. Add the dissolved nickel nitrate solution dropwise to the SiO2 powder, stir well, and dry in an oven at 80℃ for 6 hours. After drying, calcine in a muffle furnace at 500℃ for 6 hours. The calcined catalyst is denoted as Ni / SiO2.

[0054] Application Example 1:

[0055] The catalysts in Examples 1-2 and Comparative Examples 1-3 were all reduced with H2 before use. The reduction conditions were 400℃ H2 treatment for half an hour, followed by cooling to room temperature. The catalysts were then quickly removed and poured into a reaction tube containing 5 ml of reaction solution. The reaction solution was 0.05 M 3-nitrostyrene reaction solution (toluene as solvent, o-xylene as internal standard). The reaction conditions were 1 MPa H2, and the reaction temperature could be adjusted as needed. The specific experimental results are shown in the table below.

[0056] Table 1. Representative results of catalyst activity tests in the examples.

[0057]

[0058] As shown in Table 1, the catalyst obtained by the embodiments of the present invention using inexpensive specific metals at specific loadings for the catalytic hydrogenation of nitro groups in aromatic nitro compounds exhibits significantly superior activity. Furthermore, compared to commonly used precious metal catalysts such as gold and platinum, under the same silica support and reaction conditions, the catalyst of the present invention demonstrates superior activity and selectivity. Compared to commonly used Ni-based inexpensive metal catalysts, the catalyst of the present invention also exhibits significantly higher activity and selectivity. Moreover, the activity and selectivity of the catalyst of the present invention can be replicated at least twice.

Claims

1. An application of a catalyst for the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: Application of catalysts in the selective hydrogenation reaction of aromatic nitro compounds; wherein the aromatic nitro compounds are those shown in Formula 1. In the formula, R is selected from C1-C6 alkenyl, C≡N, C1-C6 alkynyl, aldehyde, carbonyl, and phenolic hydroxyl groups; The catalyst uses inert oxide silicon dioxide as a support and Cu as the active component; the content of the active component is 0.1-50 wt%, and the average particle size of the metal after loading is 0.5-20 nanometers.

2. The application of the catalyst according to claim 1 in the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The catalyst was prepared as follows: 1) Dissolve the soluble precursor of the metal active component, and add it to the solvent under stirring to obtain a metal precursor solution, and make the pH of the solution between 9 and 12; wherein, the metal active component is Cu, and the metal concentration in the metal precursor solution is 0.1-100 g / L; 2) The above metal precursor solution is stirred and the support is added and mixed. The solvent is then heated to evaporate until the solution pH is neutral. The precipitate is collected by filtration and calcined at 200-550℃ for 0.5-10 hours to obtain the supported metal catalyst precursor. The content of the metal active component is 1-40 wt%. 3) The precursor is placed in a reducing atmosphere and pretreated at 200-600℃ for 10-300 minutes to obtain a catalyst that can be directly used for hydrogenation reaction.

3. The application of the catalyst according to claim 2 in the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The soluble precursor of the metal active component is one or more of copper chloride, copper nitrate, copper sulfate, copper acetate, copper acetylacetone, and copper-containing organic complexes. The solvent for the soluble precursor of the dissolved metal active component is one or a mixture of two or more of the following: water, methanol, ethanol, isopropanol, acetone, etc. The solvent is an inorganic and / or organic solvent.

4. The application of the catalyst according to claim 3 for the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The inorganic solvent is one or a mixture of any of the following: sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonia, sodium phosphate, sodium dihydrogen phosphate, or other weakly alkaline reagents; the organic reagent is one or a mixture of any of the following: ethanol, methanol, ethylene glycol, etc.

5. The application of the catalyst according to claim 2 in the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The reducing atmosphere is one or a mixture of several of He, Ar, N2, and H2.

6. The application of the catalyst according to claim 2 in the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The carrier is one or more of the following: silica, ordered mesoporous silica, or amorphous commercial silica gel, which have a large specific surface area, good thermal stability, and are relatively inexpensive.

7. The application of the catalyst according to any one of claims 1-6 for the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The prepared catalyst, aromatic nitro compound, and solvent are loaded into a closed reaction vessel to selectively hydrogenate the aromatic nitro compound to prepare aromatic amines. After the reaction, the catalyst is collected by filtration and recycled. The molar ratio of the active component to the aromatic nitro compound in the catalyst is 0.05-1.

8. The application of the catalyst according to claim 7 in the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The reaction is carried out in a closed reactor with an initial hydrogen pressure of 0.1-5 MPa, a reaction temperature of 60-180°C, and a reaction time of 0.5-24 hours.

9. The application of the catalyst according to claim 7 in the selective hydrogenation of aromatic nitro compounds to prepare aromatic amines, characterized in that: The solvent is one or more of water, methanol, ethanol, toluene, tetrahydrofuran, and n-dodecane.

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