Catalyst and method for preparing same, method for preparing arylamine compound

Abstract

The present application provides a catalyst and a preparation method thereof, and a method for preparing an aromatic amine compound, wherein the catalyst comprises a carbon carrier, platinum nanoparticles and metal oxide nanoparticles; the metal oxide nanoparticles are supported on the carbon carrier, and the platinum nanoparticles are supported on the metal oxide nanoparticles and / or the carbon carrier; and the catalyst further comprises an amine ligand which is adsorbed on the surface of the platinum nanoparticles. The catalyst of the present application can selectively catalyze the hydrogenation of an aromatic nitro compound into an aromatic amine compound, the conversion rate of the aromatic nitro compound is greater than 99.9%, the selectivity of the aromatic amine compound is greater than 99.9%, and the catalyst has excellent catalytic activity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of catalysts, in particular to a catalyst and a preparation method thereof, and a method for preparing an aromatic amine compound. BACKGROUND

[0002] A large number of daily necessities production processes involve catalytic hydrogenation processes, and the key to the catalytic reaction is the control of selectivity, which is directly related to the quality of the product. For example, aromatic amine compounds, more than 10 million tons of which are consumed in China every year, are mainly used for the production of medicines, spices, fertilizers, etc. Aromatic amine compounds are widely used, and the demand for products is different under various uses, so the types of products are very rich. Aromatic amine compounds are usually prepared by hydrogenation of aromatic nitro compounds. When there are multiple other reaction groups in addition to the nitro group in the aromatic nitro compound, it is generally difficult to obtain aromatic amine compounds with high yield. For example, p-aminostyrene is prepared by hydrogenation of p-nitrostyrene, at this time, there are two unsaturated functional groups (vinyl and nitro) on the benzene ring, and the two functional groups have high hydrogenation rates using conventional Pt / C, Pd / C, Ru / C catalysts, and the hydrogenation energy barrier of the vinyl group is lower than that of the nitro group, so it is difficult to obtain aminostyrene under the hydrogenation conditions using the commonly used catalysts. Similarly, when there are halogen, acetylene group, aldehyde group, carbonyl group, etc. on the benzene ring, conventional catalysts are still difficult to obtain satisfactory selectivity. It is very challenging and important to prepare a catalyst with high activity and high selectivity for the production of aromatic amine compounds from aromatic nitro compounds.

[0003] In addition to the control of selectivity, the durability and the resistance to poisoning of the catalyst are also very critical. Especially when the hydrogenation substrate or the reaction system contains S, N species, these species have very strong poisoning effect on the metal, which easily leads to catalyst deactivation. For example, the hydrogenation of 3-amino-4-nitro diphenyl sulfide to 3,4-diamino diphenyl sulfide is one of the important reactions for the preparation of fenbendazole drug. Due to the poisoning of the benzyl mercaptan to the metal, the catalyst hydrogenation method cannot be used in the industrial production of such arylamine products. At present, the industrial production can only use the stoichiometric reducing agent to reduce 3-amino-4-nitro diphenyl sulfide to prepare 3,4-diamino diphenyl sulfide, and the reducing agent can be hydrazine hydrate, Na2S and sodium borohydride. However, the preparation of these reducing agents involves multiple reaction processes, and some processes involve high temperature and high pressure conditions, which are high-pollution and high-energy-consumption reactions. Not only greatly increase the production cost, but also are not conducive to sustainable development. The conventional catalytic hydrogenation can be carried out under mild conditions, has the advantages of high hydrogen utilization rate, less by-products and easy separation of products, and meets the requirements of green chemistry. Therefore, it is of great significance to design a suitable catalyst to hydrogenate 3-amino-4-nitro diphenyl sulfide to 3,4-diamino diphenyl sulfide under mild conditions for the production of fenbendazole. The most critical thing among them is the resistance to sulfur poisoning, so the catalyst can also be used for other catalytic reactions that may poison the catalyst.

[0004] In summary, in the reduction of aromatic nitro compounds to aromatic amines, how to improve the conversion rate and selectivity, and avoid the poisoning of the catalyst by S, N, halogen and unsaturated groups is a technical problem to be solved at present. SUMMARY

[0005] In view of the above problems, the present application provides a catalyst and a preparation method thereof, and a method for preparing aromatic amine compounds, aiming to avoid catalyst poisoning while improving the conversion rate of aromatic nitro compounds and the selectivity of aromatic amine compounds.

[0006] In one aspect, the present application provides a catalyst, which comprises a carbon carrier, platinum nanoparticles and metal oxide nanoparticles; wherein the metal oxide nanoparticles are supported on the carbon carrier, and the platinum nanoparticles are supported on the metal oxide nanoparticles and / or the carbon carrier; the catalyst further comprises an amine ligand, and the amine ligand is adsorbed on the surface of the platinum nanoparticles.

[0007] In another aspect, the present application provides a method for preparing the above-mentioned catalyst, which comprises the following steps:

[0008] (1) dispersing a metal hydroxide and a carbon carrier in a first solvent, then rotary evaporation to dryness to obtain a solid phase, and calcining the solid phase to obtain a metal oxide / carbon carrier;

[0009] (2) dispersing the metal oxide / carbon carrier and the platinum precursor solution in a second solvent and stirring, separating out a solid phase, and then drying and roasting and reducing to obtain a Pt / metal oxide / carbon carrier;

[0010] (3) contacting the Pt / metal oxide / carbon carrier with an amine ligand to obtain the catalyst.

[0011] In still another aspect, the present application provides a method for preparing an arylamine compound, which comprises: mixing a catalyst, an aryl nitro compound and a reaction solvent, and performing a reaction in the presence of hydrogen to obtain an arylamine compound; wherein the catalyst is selected from the above-mentioned catalysts or is prepared by the above-mentioned method.

[0012] Advantages:

[0013] (1) The catalyst of the present application can be used for efficient catalysis under normal temperature and pressure or normal temperature and near normal pressure, has mild conditions, high activity and good stability, is conducive to reducing the operation difficulty and cost, and is conducive to industrialization development.

[0014] (2) The catalyst of the present application can selectively catalyze the hydrogenation of aryl nitro compounds to arylamine compounds, the conversion rate of aryl nitro compounds is greater than 99.9%, the selectivity of arylamine compounds is greater than 99.9%, and the catalyst has excellent catalytic activity.

[0015] (3) The catalyst of the present application can be used for the hydrogenation of S and N-containing aryl nitro compounds such as 3-amino-4-nitro diphenyl sulfide, has the ability to resist poisoning for S and N-containing reactants, has high yield, and can be repeatedly used;

[0016] (4) The catalyst of the present application can maintain an activity reduction of not more than 20% in a cycle test of at least 10 times for 0.5 h in a single reaction, has significant stability, is conducive to reducing the reaction cost and promoting the industrialization of products;

[0017] (5) The catalyst of the present application uses hydrogen as a reducing agent for the hydrogenation of aryl nitro compounds to prepare arylamine compounds, compared with hydrazine hydrate, sodium borohydride, Na2S and other reducing agents, hydrogen is easy to obtain and low in price, which is conducive to reducing the cost and promoting the industrialization development.

[0018] (6) The catalyst of the present application still has high activity for the catalytic hydrogenation of aryl nitro compounds to arylamine compounds under the condition of low Pt dosage (the molar ratio of Pt in the catalyst to the reaction substrate aryl nitro compound can be as low as 1:1000). BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1is a transmission electron microscope (TEM) characterization graph of the NH3-Pt / Fe2O3 / C catalyst obtained in Example 1;

[0020] Figure 2 is a powder X-ray diffraction (XRD) characterization graph of the NH3-Pt / Fe2O3 / C catalyst obtained in Example 1;

[0021] Figure 3 is a Fourier transform infrared spectroscopy (FTIR) characterization graph of the NH3-Pt / Fe2O3 / C catalyst obtained in Example 1;

[0022] Figure 4 is a representative scanning transmission electron microscope (STEM) and energy dispersive spectroscopy (STEM-EDS) elemental distribution characterization graph of the NH3-Pt / Fe2O3 / C catalyst obtained in Example 1;

[0023] Figure 5 is an X-ray photoelectron spectroscopy (XPS) characterization graph of the Pt element in the NH3-Pt / Fe2O3 / C catalyst obtained in Example 1;

[0024] Figure 6 is an X-ray photoelectron spectroscopy (XPS) characterization graph of the Fe element in the NH3-Pt / Fe2O3 / C catalyst obtained in Example 1;

[0025] Figure 7 is a graph of the conversion rate and selectivity of selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene over the NH3-Pt / Fe2O3 / C catalyst obtained in Example 1 over time;

[0026] Figure 8 is a graph of the conversion rate of selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene over the four catalysts in Comparative Examples 16-19 over time;

[0027] Figure 9 is a graph of the selectivity of selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene over the four catalysts in Comparative Examples 16-19 over time. DETAILED DESCRIPTION

[0028] The present application will be further described by the accompanying drawings and examples. Through these descriptions, the features and advantages of the present application will become more apparent.

[0029] In the present application, the term "room temperature" means ambient temperature, in some embodiments 15-40°C, in some embodiments 20-35°C, and in some embodiments 25-30°C;

[0030] In the present application, the term "loading" or "loading amount" means the percentage of the mass of an active component such as an active metal in the total mass of a catalyst;

[0031] In the present application, the term "and / or" should be understood as meaning either one of the options or a combination of any two or more of the options;

[0032] In the present application, the term "wt%" means mass percentage;

[0033] In the present application, the term "vol%" means volume percentage;

[0034] In the present application, the term "rpm" means revolutions per minute of the rotor;

[0035] In the present application, the term "Pt / Fe2O3 / C" means Fe2O3 is supported on a C carrier, and Pt is supported on the Fe2O3 and / or the C carrier;

[0036] In the present application, the term "NH3-Pt / Fe2O3 / C" means Fe2O3 is supported on a C carrier, and Pt is supported on the Fe2O3 and / or the C carrier, and NH3 is adsorbed on the surface of Pt.

[0037] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Although various aspects of implementations can be presented in terms of methods, one should appreciate that such implementations can also be implemented as appropriate with any number of computer-readable storage media storing instructions for execution on a computer or other processing device, and that the execution of the sequences of instructions stored on the computer-readable storage media can produce the processes described herein.

[0038] Moreover, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as there is no conflict.

[0039] In a first aspect, the present application provides a catalyst, comprising a carbon carrier, platinum nanoparticles, and metal oxide nanoparticles; the metal oxide nanoparticles are supported on the carbon carrier, and the platinum nanoparticles are supported on the metal oxide nanoparticles and / or the carbon carrier; the catalyst further comprises an amine ligand, and the amine ligand is adsorbed on the surface of the platinum nanoparticles.

[0040] It should be noted that the catalyst described above is a catalyst for selectively catalyzing the generation of arylamine compounds from aryl nitro compounds. Firstly, in the catalyst of the present application, the metal oxide nanoparticles are supported on the carbon carrier as active components, instead of being used as a carrier; secondly, the amine ligand is present on the surface of the platinum nanoparticles, which protects the catalytic active sites of Pt inside the amine ligand.

[0041] In the above-mentioned catalyst of the present application, the amine ligand is adsorbed on the surface of the platinum nanoparticles, preventing direct hydrogenation of aromatic nitro compounds such as nitrostyrene on Pt, but not affecting the activation of H2 molecules on Pt, because the H2 molecules, being small in size, can pass through the amine ligand to contact the platinum nanoparticles. The catalyst has metal oxide nanoparticles supported on the carbon carrier, and hydrogen is oxidized to active hydrogen intermediates on Pt as a reducing agent, and the nitro group in the aromatic nitro compound is catalytically reduced with the active hydrogen intermediates on the metal oxide nanoparticles. Since the metal oxide nanoparticles can only catalyze the reduction of the nitro group, but not the reduction of unsaturated groups such as double bonds, triple bonds, etc., the catalyst has good selective hydrogenation performance.

[0042] In addition, because the amine ligand is located on the surface of the platinum nanoparticles, it prevents the occurrence of side reactions of halogen, hydroxyl, aldehyde, carbonyl, etc. contained in Pt-catalyzed aromatic nitro compounds such as halogenated aromatic nitro compounds, hydroxyl aromatic nitro compounds, aldehyde aromatic nitro compounds, carbonyl aromatic nitro compounds, etc.; in addition, when amino aromatic nitro compounds, mercapto aromatic nitro compounds, etc. contain N, S, etc., the presence of the amine ligand also prevents the poisoning of the platinum nanoparticles by N, S, etc., so that the conversion rate and selectivity of the catalyst of the present application are significantly improved when catalyzing the hydrogenation reduction of aromatic nitro compounds to aromatic amine compounds.

[0043] As a preferred embodiment of the positional relationship of the several particles in the catalyst of the present application, the metal oxide nanoparticles are supported on the carbon carrier, a part of the platinum nanoparticles are supported on the metal oxide nanoparticles, and another part of the platinum nanoparticles are supported on the carbon carrier, and at least part of the platinum nanoparticles and the metal oxide nanoparticles are in contact, so that the activated particles after the activation of H2 on the platinum nanoparticles can quickly contact the aromatic nitro compound on the metal oxide nanoparticles to catalytically reduce the nitro group to generate aromatic amine compounds.

[0044] In one embodiment of the above-mentioned catalyst of the present application, the amine ligand is selected from one or more of NH3, methylamine, ethylamine, butylamine, ethylenediamine, propylenediamine, and butylenediamine, and is preferably NH3.

[0045] It should be noted that the above-mentioned amine ligand can be well modified or adsorbed on the surface of the platinum nanoparticles by coordination bond or coordination action, so that the active sites of the platinum nanoparticles are shielded or protected to some extent, and the active sites of the metal oxide nanoparticles are in an exposed state, thereby better realizing the high conversion rate and high selectivity of catalyzing the aromatic nitro compound to the aromatic amine compound. When the amine ligand is preferably NH3, the amine ligand modification process is more convenient and easier to operate, and the selective activity of the catalyst is also higher.

[0046] In another embodiment of the catalyst described above in this invention, the metal oxide nanoparticles are selected from one or more of Fe2O3, TiO2, Co3O4, CeO2, SnO2 and In2O3, preferably Fe2O3, and more preferably γ-Fe2O3;

[0047] The particle size of the metal oxide nanoparticles is less than or equal to 20 nm, and the particle size is preferably 5 to 10 nm.

[0048] It should be noted that the aforementioned metal oxide nanoparticles can effectively synergize with platinum nanoparticles, and by controlling the particle size of the metal oxide nanoparticles as described above, the catalyst can convert aromatic nitro compounds into aromatic amine compounds with higher selectivity. Fe2O3 is particularly widely available, low in cost, and highly active; therefore, Fe2O3 is the preferred metal oxide nanoparticle.

[0049] In one embodiment of the catalyst described above in this invention, the platinum nanoparticles include zero-valent platinum and / or positive-valent platinum, and the particle size of the platinum nanoparticles is less than or equal to 20 nm, preferably 5 to 10 nm.

[0050] It should be noted that platinum nanoparticles can be partially or entirely composed of zero-valent platinum. Controlling the smaller particle size of platinum nanoparticles can better catalyze the conversion of H2 into active units that can directly undergo hydrogenation reactions with nitro groups in aromatic nitro compounds.

[0051] In one embodiment of the catalyst described above, based on the mass of the catalyst, the loading of the platinum nanoparticles is 0.1 to 10 wt%, the loading of the metal oxide nanoparticles is 5 to 30 wt%, and the amine ligand is saturatedly covered on the surface of the platinum nanoparticles.

[0052] It should be noted that, based on the mass of the catalyst, the loading of platinum nanoparticles can specifically be 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, etc., and the loading of metal oxide nanoparticles can specifically be 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, 11 wt%, 12 wt%, 15 wt%, 20 wt%, 22 wt%, 25 wt%, 28 wt%, etc. Saturated coverage of the platinum nanoparticle surface by amine ligands means that the entire surface of the platinum nanoparticles is covered by amine ligands, or in other words, the amine ligands completely encapsulate the surface of the platinum nanoparticles. In the catalyst of this invention, by controlling the loading of platinum nanoparticles and metal oxide nanoparticles as described above, and simultaneously saturating the surface of the platinum nanoparticles with amine ligands, the above components can better exert their effects, and the catalyst can selectively hydrogenate aromatic nitro compounds with higher conversion rates and selectivity.

[0053] In another embodiment of the above-mentioned catalyst of the present application, the carbon support is selected from one of conductive carbon black, carbon nanotube, graphene and porous carbon, preferably carbon nanotube.

[0054] It should be noted that by selecting the above-mentioned support, the metal oxide nanoparticles and platinum nanoparticles can be well loaded and exert their functions. When the support is preferably carbon nanotube, the co-loading of platinum nanoparticles and metal oxide nanoparticles can be better achieved, the metal particles can be better dispersed, agglomeration can be avoided, and the activity of the catalyst can be higher.

[0055] In a second aspect, the present application provides a method for preparing the above-mentioned catalyst, comprising the following steps:

[0056] (1) dispersing the metal hydroxide and the carbon support in a first solvent, then rotary evaporation to dryness to obtain a solid phase, calcining the solid phase to obtain a metal oxide / carbon support;

[0057] (2) dispersing the metal oxide / carbon support and a platinum precursor solution in a second solvent and stirring, separating the solid phase, then drying and roasting reduction to obtain a Pt / metal oxide / carbon support;

[0058] (3) contacting the Pt / metal oxide / carbon support with an amine ligand to obtain the catalyst.

[0059] It should be noted that in step (1), the metal hydroxide is first loaded onto the carbon support, and then the metal hydroxide is converted into metal oxide by calcination to obtain a carbon support loaded with metal oxide, i.e. a metal oxide / carbon support. In step (2), the method for loading Pt can use methods such as impregnation and sol-gel method, for example, the metal oxide / carbon support and the platinum precursor solution are dispersed in a second solvent and stirred, so that the platinum is well dispersed and loaded onto the carbon support and / or the metal oxide.

[0060] In an embodiment of the above-mentioned method of the present application, the first solvent and the second solvent are each independently selected from one or more of water, methanol and ethanol.

[0061] It should be noted that the use of the above-mentioned solvents is beneficial to improve the dispersibility of the metal oxide nanoparticles and platinum nanoparticles, and can better catalyze the conversion of aromatic nitro compounds into aromatic amine compounds.

[0062] In another embodiment of the above-mentioned method of the present application, the metal hydroxide and the carbon support are dispersed in the first solvent in step (1) according to the following ratio:

[0063] The mass ratio of the metal hydroxide to the carbon carrier is 1:(5-20), and the ratio of the mass of the carbon carrier to the volume of the first solvent is (2-5) g:30 mL;

[0064] The metal hydroxide is prepared by the following method:

[0065] The water-soluble metal salt is dissolved in water, and an alkali solution is added dropwise under stirring to obtain a metal hydroxide precipitate.

[0066] It should be noted that the metal precursor in the preparation of the metal hydroxide can be selected from one or more of ferric chloride, ferric nitrate, ferrous sulfate, titanium chloride, cobalt nitrate, cobalt chloride, cerium nitrate, tin chloride, indium chloride, etc. The metal hydroxide prepared based on the above method is loaded according to the method of step (1) and under the above quantity relationship, and the metal oxide after calcination can be loaded on the carbon carrier with small nanoparticle size and good dispersibility.

[0067] In one embodiment of the above method of the present application, the calcination in step (1) is performed at 200-500°C for 2-5 h.

[0068] Further, the calcination temperature in step (1) can be specifically 250°C, 300°C, 350°C, 400°C, 450°C, etc. By controlling the calcination temperature and time as above, the metal hydroxide loaded can be well converted into metal oxide.

[0069] In another embodiment of the above method of the present application, the platinum precursor in step (2) is selected from one or more of potassium chloroplatinate, platinum chloride, platinum nitrate, platinum acetate, ethylenediamine platinum, and acetylacetone platinum, and the concentration of the platinum precursor solution is 0.01-0.1 mol / L.

[0070] The calcination reduction in step (2) is performed in a hydrogen-argon mixed atmosphere at 200-300°C for 1-10 h.

[0071] Further, the calcination reduction temperature in step (2) can be specifically 250°C, the hydrogen content in the hydrogen-argon mixed atmosphere can be 2-10 vol%, specifically 3 vol%, 4 vol%, 6 vol%, 7 vol%, etc., and the reduction time can be specifically 2 h, 3 h, 4 h, 5 h, etc. By controlling the calcination reduction temperature, atmosphere, and time as above, the platinum substance loaded can be converted into platinum element. The platinum precursor solution with the above concentration is dispersed in the second solvent together with the metal oxide / carbon carrier and stirred, which can enable the platinum to be loaded with small particle size and good dispersibility.

[0072] In another embodiment of the above method of the present application, the molar ratio of the amine ligand to Pt in the Pt / metal oxide / carbon carrier in step (3) is greater than or equal to 10:1.

[0073] The method of contacting the Pt / metal oxide / carbon support with the amine ligand in step (3) comprises:

[0074] When the amine ligand is a gas, the amine ligand is introduced into a closed container in which the Pt / metal oxide / carbon support is placed and left to stand; or, when the amine ligand is a liquid and / or a solid, the amine ligand is dissolved in ethanol to obtain an amine ligand solution, the amine ligand solution and the Pt / metal oxide / carbon support are mixed and then subjected to ultrasonic treatment, and then the remaining solution is removed.

[0075] It should be noted that the molar ratio of the amine ligand to Pt in the Pt / metal oxide / carbon support is greater than or equal to 10:1 in step (3), so that the amine ligand can be saturated on the surface of the platinum nanoparticles, so that the catalyst has high selectivity. The amine ligand in the gas, liquid or solid phase is contacted with the Pt / metal oxide / carbon support in the above-mentioned manner, which can make the amine ligand in different phases well adsorbed on the surface of the platinum nanoparticles.

[0076] In a third aspect, the present application provides a method for preparing an arylamine compound, which comprises: mixing a catalyst, an aryl nitro compound and a reaction solvent, and reacting in the presence of hydrogen to obtain an arylamine compound; wherein the catalyst is selected from the above-mentioned catalyst or prepared by the above-mentioned method.

[0077] It should be noted that the above-mentioned catalyst or the catalyst prepared by the above-mentioned method has significantly improved conversion rate and selectivity when used to catalyze the hydrogenation reduction of aryl nitro compounds to arylamine compounds.

[0078] In an embodiment of the method for preparing an arylamine compound of the present application, the aryl nitro compound has the following structural formula:

[0079]

[0080] (R1) m represents that m H on the ring are replaced by m same or different R1, and each R1 is independently C1-C6 alkyl, C2-C6 alkenyl, C2-C6 alkynyl, C1-C5 aldehyde group, thiol, phenylthiol, halogen, hydroxyl or -COR4;

[0081] m is 0, 1, 2, 3, 4 or 5;

[0082] (R2) n represents that n H on the ring are replaced by n R2, and R2 is -NO2 or -NH2;

[0083] n is 0, 1, 2, 3, 4 or 5;

[0084] and 0≤m+n≤5;

[0085] R4 is selected from C1-C3 alkyl.

[0086] It is to be noted that the structure of the arylamine compound obtained by hydrogenation reduction of the above-mentioned aryl nitro compound can be shown as follows:

[0087]

[0088] R1, R4 are selected from the same groups as above; (R3) n represents that n H on the ring are replaced by n R3 respectively, wherein R3 is -NH2, and n is the same as above.

[0089] In another embodiment of the method for preparing arylamine compounds, the aryl nitro compound is selected from one or more of p-methyl nitrobenzene, o-methyl nitrobenzene, m-methyl nitrobenzene, p-ethyl nitrobenzene, p-tert-butyl nitrobenzene, p-dinitrobenzene, o-dinitrobenzene, m-dinitrobenzene, p-chloronitrobenzene, o-chloronitrobenzene, m-chloronitrobenzene, p-fluoronitrobenzene, o-fluoronitrobenzene, m-fluoronitrobenzene, p-bromonitrobenzene, o-bromonitrobenzene, m-bromonitrobenzene, p-iodonitrobenzene, o-iodonitrobenzene, m-iodonitrobenzene, p-nitrostyrene, o-nitrostyrene, p-nitrophenylacetylene, o-nitrophenylacetylene, p-hydroxynitrobenzene, o-hydroxynitrobenzene, p-nitrobenzaldehyde, p-nitroacetophenone, and 3-amino-4-nitro diphenyl sulfide.

[0090] Further, the product obtained by hydrogenation reduction of the above-mentioned aryl nitro compound corresponds to one or more of p-toluidine, o-toluidine, m-toluidine, p-ethyl aniline, p-tert-butyl aniline, p-diphenylamine, o-diphenylamine, m-diphenylamine, p-chloroaniline, o-chloroaniline, m-chloroaniline, p-fluoroaniline, o-fluoroaniline, m-fluoroaniline, p-bromoaniline, o-bromoaniline, m-bromoaniline, p-iodoaniline, o-iodoaniline, m-iodoaniline, p-aminostyrene, o-aminostyrene, p-aminophenylacetylene, o-aminophenylacetylene, p-hydroxyaniline, o-hydroxyaniline, p-aminobenzaldehyde, p-aminophenylacetophenone, and 3,4-diamino diphenyl sulfide.

[0091] In one embodiment of the method for preparing arylamine compounds, the reaction solvent is selected from one or more of water, methanol, ethanol, and isopropanol; the reaction is carried out at 30-80°C under a hydrogen pressure of 0.1-3.0 MPa for 0.5-50 h, preferably 0.5-5 h; and the molar ratio of platinum in the catalyst to the aryl nitro compound is 1:(50-5000), preferably 1:(50-1000).

[0092] Further, the temperature of the above reaction can be 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, etc., the reaction time can be 1h, 2h, 3h, 4h, 6h, 7h, 8h, 9h, 10h, 15h, 20h, etc., the hydrogen pressure can be 0.2MPa, 0.4MPa, 0.6MPa, 0.8MPa, 1.0MPa, 2.0MPa, etc., and the molar ratio of platinum element in the catalyst to the aromatic nitro compound in the feed can be 1:100, 1:200, 1:300, 1:400, 1:500, 1:600, 1:700, 1:800, 1:900, 1:1500, or 1:2000, etc.

[0093] In addition, the application can also provide the use of the above catalyst or the catalyst prepared by the above method in the selective catalytic preparation of aromatic amines from aromatic nitro compounds.

[0094] The application will be further described in detail by the following examples, but the application is not limited thereto. In the following examples, the experimental instruments and raw materials involved are commercially available products, unless otherwise specified.

[0095] The carbon nanotubes, carbon black, graphene and porous carbon used in the following examples were purchased from Shanghai Aldrin Biotech Co., Ltd.

[0096] Example 1: Preparation, structure characterization and use in the hydrogenation of aromatic nitro compounds of NH3-Pt / Fe2O3 / C catalyst with 1wt% Pt loading and 10wt% Fe2O3 loading and NH3 as ligand

[0097] 1. Preparation of the catalyst

[0098] (1) 0.81g of anhydrous ferric chloride was dissolved in 100mL of water in a 250mL beaker, and then 1M NaOH solution was added dropwise under stirring until the solution pH>9, and stirring was continued for 0.5h. The product was separated by centrifugation to obtain the precipitate Fe(OH)3, which was washed with water and re-dispersed in 30mL of water.

[0099] (2) 3.2g of carbon nanotubes was added to the above dispersion, and rotary evaporation was performed under negative pressure at 50℃ until dryness. The obtained solid material was placed in a crucible, and the crucible was placed in a muffle furnace, and the heating rate was set to 2℃ / min, and the temperature was raised to 300℃ and calcined for 3h, and then naturally cooled to room temperature.

[0100] (3) The product obtained by calcination was re-dispersed in 100 mL of water, 4 mL of 0.052 M potassium chloroplatinate solution was added, stirring was continued for 12 h, centrifugation, filtration, and vacuum drying at 60 °C. The dried material was placed in a crucible, which was placed in a tube furnace, and a hydrogen-argon mixture containing 5 vol% hydrogen was introduced at a flow rate of 50 mL / min. The heating rate was set to 2 °C / min, and the temperature was raised to 200 °C for 2 h of reduction reaction, and then naturally cooled to room temperature. The gas was turned off to obtain a Pt / Fe2O3 / C catalyst with a Pt loading of 1 wt% and a Fe2O3 loading of 10 wt%.

[0101] (4) Before the catalytic reaction, about 20 mg of Pt / Fe2O3 / C catalyst was placed in a 48 mL reaction container, and 0.1 MPa of NH3 was filled, and after standing for 20 min, an NH3-Pt / Fe2O3 / C catalyst was obtained

[0102] 2. Characterization of the above catalyst

[0103] TEM testing used a TECNAI F30 high-resolution transmission electron microscope. The acceleration voltage during testing was 300 kV.

[0104] XRD used an Ultima IV X-ray diffractometer from Japan Rigaku Company. The incident light of the instrument was Cu K ɑ X-ray The slit width was 0.5°, the working voltage was set to 40 kV, the working current was 15 mA, and the scanning speed was 10° / min.

[0105] XPS used a PHI Quantum-2000 photoelectron spectrometer. The X-ray source was Al K ɑ (1486.6 eV), the working voltage was 15 kV, the power was 35 W, the beam spot size was 200 μm, and the pressure of the vacuum system was 8 x 10 -9 torr.

[0106] Figure 1 The transmission electron microscope photo of the NH3-Pt / Fe2O3 / C catalyst showed that the iron oxide nanoparticles and Pt metal nanoparticles were uniformly dispersed on the surface of the carbon nanotube carrier, there were no large size particles, the particle size was very small (<7 nm), and the representative nanoparticles were marked with white circles in Figure 1 .

[0107] As can be seen from Figure 1 , the iron oxide nanoparticles are directly loaded on the surface of the carbon nanotube carrier, a part of the Pt metal nanoparticles are loaded on the surface of the carbon nanotube carrier, another part of the Pt metal nanoparticles are loaded on the iron oxide nanoparticles, and part of the iron oxide nanoparticles and the Pt metal nanoparticles are in contact.

[0108] Figure 2 is the powder X-ray diffraction spectrum of NH3-Pt / Fe2O3 / C catalyst, from which Figure 2 The diffraction peaks of γ-Fe2O3 and carbon carrier can be seen, and there is no diffraction peak of Pt metal nanoparticles, indicating that the loading of Pt metal nanoparticles is low and there is no existence of large particles.

[0109] Figure 3 is the in-situ infrared spectrum of NH3-Pt / Fe2O3 / C catalyst, the catalyst is placed in an in-situ cell, NH3 is introduced, and gaseous NH3 is purged with Ar, and infrared spectrum data is collected, Figure 3 the peak at 3210 cm -1 is the stretching vibration peak of adsorbed NH3, indicating that NH3 molecules are adsorbed on the catalyst, specifically, NH3 is adsorbed on the surface of Pt metal nanoparticles, and NH3 is coordinated with Pt metal nanoparticles.

[0110] Figure 4 is the scanning transmission electron microscope (STEM) image and energy dispersive spectrum (EDS) element distribution characterization result of NH3-Pt / Fe2O3 / C catalyst, indicating that Pt metal nanoparticles and γ-Fe2O3 nanoparticles are well dispersed on the surface of carbon nanotubes, and there is no existence of large size iron oxide particles or large size Pt particles.

[0111] Figure 5 is the X-ray photoelectron spectrum (XPS) of Pt element in NH3-Pt / Fe2O3 / C catalyst, proving that Pt metal nanoparticles are mainly zero-valent Pt element, indicating that Pt has been well reduced to metal state in the preparation process of the catalyst. From Figure 5 It can be seen that the binding energy of 4f of zero-valent platinum element is 69-72 eV and 73-75 eV, preferably 70.7 eV and 74.1 eV.

[0112] Figure 6 is the X-ray photoelectron spectrum (XPS) of Fe element in NH3-Pt / Fe2O3 / C catalyst, proving that Fe nanoparticles are mainly +3 valence iron element, indicating that the main component of iron oxide nanoparticles in the catalyst is Fe2O3.

[0113] 3. Selective catalytic preparation of p-aminostyrene from p-nitrostyrene

[0114] NH3-Pt / Fe2O3 / C catalyst (containing 1 μmol Pt) prepared in Example 1 was dispersed in 10 mL of ethanol, and 150 mg of p-nitrostyrene (1 mmol) was added, i.e. the molar ratio of the substrate p-nitrostyrene to Pt was 1000:1. The dispersion was introduced into a closed reaction vessel, which was purged of air by purging with H2, and was charged with 0.1 MPa of H2. The reaction vessel was then placed in a thermostatic water bath at 60°C, and the stirring rate was controlled at 800 rpm. At different times during the reaction, 100 μL of the reaction solution was taken out and analyzed by gas chromatography. The selectivity and conversion were then calculated according to the following formula:

[0115] Selectivity = amount of substance of p-aminostyrene ÷ (amount of substance of p-aminostyrene + amount of substance of p-aminoethylbenzene + amount of substance of p-nitroethylbenzene);

[0116] Conversion = (amount of substance of p-aminostyrene + amount of substance of p-aminoethylbenzene + amount of substance of p-nitroethylbenzene) ÷ (amount of substance of p-aminostyrene + amount of substance of p-aminoethylbenzene + amount of substance of p-nitroethylbenzene + amount of substance of p-nitrostyrene);

[0117] wherein p-aminostyrene is the target product, p-aminoethylbenzene and p-nitroethylbenzene are by-products, and p-nitrostyrene is the substrate, and the amounts of substance of the above components are obtained by gas chromatography peak area and integration.

[0118] The graph of the change of selectivity and conversion with time is shown in Figure 7 The p-nitrostyrene was completely converted into p-aminostyrene in 0.5 h at 60°C, and no by-products p-nitroethylbenzene or p-aminoethylbenzene were produced. The exposed Pt resulted in poor selectivity, and only when all the platinum nanoparticles were wrapped could a selectivity close to 100% be obtained, thus Figure 7 indicating that all the platinum nanoparticle surfaces were covered by the amine ligand, i.e. the platinum nanoparticle surfaces were saturatedly covered by the amine ligand, or in other words, the platinum nanoparticle surfaces were wrapped by the amine ligand.

[0119] 4. Investigation of the stability of the catalytic activity of the catalyst

[0120] The NH3-Pt / Fe2O3 / C catalyst prepared in Example 1 was tested by the above method for the selective catalysis of p-nitrostyrene to prepare p-aminostyrene for 10 cycles, and the reaction was carried out for 0.5 h each time. The conversion and selectivity of p-aminostyrene were detected each time, and the results are shown in Table 1. The catalyst did not show deactivation in the 10 cycles, further confirming its high stability.

[0121] Table 1

[0122] Cycling tests p-nitrostyrene conversion p-aminostyrene selectivity 1st ＞99.9％ ＞99.9％ 2nd ＞99.9％ ＞99.9％ 3rd ＞99.9％ ＞99.9％ 4th ＞99.9％ ＞99.9％ 5th ＞99.9％ ＞99.9％ 6th ＞99.9％ ＞99.9％ 7th ＞99.9％ ＞99.9％ 8th ＞99.9％ ＞99.9％ 9th ＞99.9％ ＞99.9％ 10th ＞99.9％ ＞99.9％

[0123] From the above, the catalyst provided by the present application can maintain the reaction substrate and Pt molar ratio of 1000 for at least 10 cycles, has significant catalytic selectivity and stability, and is conducive to reducing the reaction cost and promoting the industrialization of the product.

[0124] Examples 2-12: Activity investigation of catalysts with different Pt metal loadings

[0125] The catalyst was prepared according to the method of Example 1, except that:

[0126] The feeding amount of K2PtCl6 was adjusted to prepare NH3-Pt / Fe2O3 / C catalysts with Pt metal loadings of 0.1wt%, 0.5wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt% and 10wt%, respectively.

[0127] The prepared catalysts with different Pt metal loadings were respectively tested according to the method of Example 1 "selective catalytic preparation of p-aminostyrene from p-nitrostyrene", wherein the catalytic reaction time of the catalyst with a Pt metal loading less than 1wt% was extended to 2h. The results are shown in Table 2.

[0128] Table 2

[0129]

[0130]

[0131] From the above, the NH3-Pt / Fe2O3 / C catalyst with a Pt metal loading of 0.1-10wt% obtained by the present application can selectively catalyze the hydrogenation of p-nitrostyrene to p-aminostyrene, with a conversion rate of more than 99.9% and a selectivity of more than 99.9%.

[0132] Examples 13-17: Activity investigation of catalysts with different Fe2O3 metal oxide loadings

[0133] The catalyst was prepared according to the method of Example 1, except that:

[0134] The feeding amounts of FeCl3 and NaOH were adjusted to prepare NH3-Pt / Fe2O3 / C catalysts with Fe2O3 loadings of 5wt%, 15wt%, 20wt%, 25wt% and 30wt%, respectively.

[0135] The prepared catalysts with different Fe2O3 loadings were tested according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the reaction time of the catalysts with Fe2O3 loading less than 20 wt% was extended to 3 h, and the results are shown in Table 3.

[0136] Table 3

[0137]

[0138] As can be seen from the above, the NH3-Pt / Fe2O3 / C catalysts with Fe2O3 loadings of 5-30 wt% can selectively catalyze hydrogenation of p-nitrostyrene to p-aminostyrene, the conversion rate is greater than 99.9%, and the selectivity is greater than 99.9%.

[0139] Examples 18-22: Catalyst activity investigation using different kinds of metal oxide particles

[0140] The catalysts were prepared according to the method of Example 1, and the difference from Example 1 is that:

[0141] The metal oxide Fe2O3 was replaced by TiO2, Co3O4, CeO2, SnO2 and In2O3, respectively, to obtain NH3-Pt / TiO2 / C, NH3-Pt / Co3O4 / C, NH3-Pt / CeO2 / C, NH3-Pt / SnO2 / C or NH3-Pt / In2O3 / C, respectively.

[0142] When the metal oxide is replaced by TiO2, Co3O4, CeO2, SnO2 and In2O3, respectively, the step (1) of catalyst preparation is based on titanium tetrachloride, cobalt nitrate, cerium nitrate, tin tetrachloride, indium nitrate and NaOH to prepare the hydroxide precipitate of the corresponding metal.

[0143] The prepared catalysts with different metal oxide particles were tested according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the reaction time was 0.5 h, and the results are shown in Table 4.

[0144] Table 4

[0145] Catalyst p-nitrostyrene conversion p-aminostyrene selectivity [NH3-Pt / TiO2 / C] ＞99.9％ ＞99.9％ [NH3-Pt / Co3O4 / C] ＞99.9％ ＞99.9％ [NH3-Pt / CeO2 / C] ＞99.9％ ＞99.9％ [NH3-Pt / SnO2 / C] ＞99.9％ ＞99.9％ [NH3-Pt / In2O3 / C] ＞99.9％ ＞99.9％

[0146] As can be seen from the above, the NH3-Pt / TiO2 / C, NH3-Pt / Co3O4 / C, NH3-Pt / CeO2 / C, NH3-Pt / SnO2 / C and NH3-Pt / In2O3 / C catalysts provided by the present application can selectively catalyze hydrogenation of p-nitrostyrene to p-aminostyrene, the conversion rate is greater than 99.9%, and the selectivity is greater than 99.9%, which has excellent catalytic activity.

[0147] Examples 23-25: Catalyst activity investigation using different carbon carriers

[0148] The catalyst was prepared according to the method of Example 1, except that:

[0149] The carrier carbon nanotubes were replaced with conductive carbon black, graphene or porous carbon, respectively, to obtain NH3-Pt / Fe2O3 / conductive carbon black, NH3-Pt / Fe2O3 / graphene and NH3-Pt / Fe2O3 / porous carbon catalysts, respectively.

[0150] The catalysts prepared with different carriers were tested according to the method of Example 1 for "selective catalytic preparation of p-aminostyrene from p-nitrostyrene", and the results obtained after 0.5 h of reaction are shown in Table 5.

[0151] Table 5

[0152] Catalyst p-nitrostyrene conversion p-aminostyrene selectivity [NH3-Pt / Fe203 / conductive carbon black] ＞99.9％ ＞99.9％ [NH3-Pt / Fe203 / graphene] ＞99.9％ ＞99.9％ [NH3-Pt / Fe2O3 / porous carbon] ＞99.9％ ＞99.9％

[0153] As can be seen from the above, the NH3-Pt / Fe2O3 / conductive carbon black, NH3-Pt / Fe2O3 / graphene and NH3-Pt / Fe2O3 / porous carbon catalysts provided by the present application can all selectively catalyze the hydrogenation of p-nitrostyrene to p-aminostyrene, with a conversion greater than 99.9% and a selectivity greater than 99.9%, and have excellent catalytic activity.

[0154] Examples 26-31

[0155] The catalyst was prepared according to the method of Example 1, except that:

[0156] The ligand NH3 in Example 1 was replaced with methylamine, ethylamine, butylamine, ethylenediamine, propylenediamine and butylenediamine, respectively, to obtain methylamine-Pt / Fe2O3 / C, ethylamine-Pt / Fe2O3 / C, butylamine-Pt / Fe2O3 / C, ethylenediamine-Pt / Fe2O3 / C, propylenediamine-Pt / Fe2O3 / C and butylenediamine-Pt / Fe2O3 / C.

[0157] The butylamine, ethylenediamine and propylenediamine were liquids, and the butylenediamine was crystalline. The liquid or crystalline amine ligand was first dissolved in 5 mL of ethanol, about 20 mg of the Pt / Fe2O3 / C catalyst obtained from step (3) was placed in a centrifuge tube, and the ethanol solution of the dissolved amine ligand (the molar ratio of the amine ligand to platinum in the Pt / Fe2O3 / C catalyst was the same as in Example 1) was added. After ultrasonic treatment for 10 min, the excess ligand solution was removed by centrifugation.

[0158] The catalysts prepared with different amine ligands were tested according to the method of "selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene" in Example 1, and the results are shown in Table 6.

[0159] Table 6

[0160]

[0161]

[0162] As can be seen from the above, the amine ligands described above can be used to selectively catalyze the hydrogenation of p-nitrostyrene to p-aminostyrene, with a conversion rate of greater than 99.9% and a selectivity of greater than 99.9%, and excellent catalytic activity.

[0163] Examples 32-33: Investigation of the reduction temperature in the preparation of the catalyst

[0164] The catalyst was prepared according to the method of Example 1, except that the following differences were made:

[0165] The temperature for reduction in step (3) in a hydrogen-argon mixture was changed from 200°C to 250°C or 300°C.

[0166] The catalysts prepared were tested according to the method of "selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene" in Example 1, and the results are shown in Table 7.

[0167] Table 7

[0168] Reduction temperature (°C) in preparation of catalyst p-nitrostyrene conversion p-aminostyrene selectivity 250℃ ＞99.9％ ＞99.9％ 300℃ ＞99.9％ ＞99.9％

[0169] As can be seen from Example 1, the NH3-Pt / Fe2O3 / C catalyst prepared in step (3) of the catalyst preparation at a reduction temperature of 200-300°C has the highest activity in the selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene, with a conversion rate of p-nitrostyrene of greater than 99.9% and a selectivity of p-aminostyrene of greater than 99.9% after 0.5h.

[0170] Test Example 1: Investigation of the activity and selectivity of the catalytic reaction using different solvents

[0171] Based on the catalyst prepared in Example 1, the catalyst was tested according to the method of "selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene" in Example 1, and the results are shown in Table 8. The difference from Example 1 is that the solvent used was changed from ethanol to methanol or isopropanol.

[0172] Table 8

[0173] Reaction solvent for catalytic reaction p-nitrostyrene conversion p-aminostyrene selectivity Methanol ＞99.9％ ＞99.9％ Isopropanol ＞99.9％ ＞99.9％

[0174] From the above, in addition to ethanol, the catalyst has good activity in catalyzing selective hydrogenation of p-nitrostyrene to p-aminostyrene in methanol or isopropyl alcohol, the conversion rate is greater than 99.9%, and the p-aminostyrene selectivity is greater than 99.9%.

[0175] Test Example 2: Activity and selectivity of catalytic reaction temperature

[0176] Based on the catalyst finally prepared in Example 1, the characterization test was carried out according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the reaction was 0.5 h. Different from Example 1:

[0177] The reaction temperature was changed from 60°C to 30°C, 40°C, 50°C, 70°C, 80°C, and the results are shown in Table 9.

[0178] Table 9

[0179] Solvent temperature (°C) in reaction p-nitrostyrene conversion p-aminostyrene selectivity 30 ＞99.9％ ＞99.9％ 40 ＞99.9％ ＞99.9％ 50 ＞99.9％ ＞99.9％ 70 ＞99.9％ ＞99.9％ 80 ＞99.9％ ＞99.9％

[0180] As can be seen from the above, the NH3-Pt / Fe2O3 / C catalyst prepared in Example 1 has higher reaction activity in the reaction of selective catalytic hydrogenation of p-nitrostyrene to p-aminostyrene, the conversion rate is greater than 99.9%, and the p-aminostyrene selectivity is greater than 99.9%.

[0181] Test Example 3: Investigation of the effect of hydrogen pressure on the activity of the catalytic reaction

[0182] Based on the catalyst finally prepared in Example 1, the characterization test was carried out according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the reaction was 0.5 h. Different from Example 1:

[0183] The pressure of the filled H2 was different, and was changed to 0.2 MPa, 0.4 MPa, 0.6 MPa, 0.8 MPa, 1.0 MPa, 2.0 MPa, and 3.0 MPa, respectively. The results are shown in Table 10.

[0184] Table 10

[0185] Hydrogen pressure (MPa) p-nitrostyrene conversion p-aminostyrene selectivity 0.2 ＞99.9％ ＞99.9％ 0.4 ＞99.9％ ＞99.9％ 0.6 ＞99.9％ ＞99.9％ 0.8 ＞99.9％ ＞99.9％ 1.0 ＞99.9％ ＞99.9％ 2.0 ＞99.9％ ＞99.9％ 3.0 ＞99.9％ ＞99.9％

[0186] As can be seen from Example 1, under the hydrogen pressure of 0.1-3.0 MPa in the container, the catalyst provided in Example 1 is used for reaction, p-nitrostyrene can be efficiently and selectively hydrogenated to p-aminostyrene, the conversion rate of p-nitrostyrene is greater than 99.9%, and the selectivity of p-aminostyrene is greater than 99.9%.

[0187] Test Example 4: Investigation of the activity of other reaction substrates

[0188] Take 20 mg of the catalyst prepared in Example 1, and perform the characterization test according to the method of "selective catalytic reduction of p-nitrostyrene to prepare p-aminostyrene" in Example 1, and the reaction is performed for 0.5 h.

[0189] The difference from Example 1 is that:

[0190] The difference from Example 1 is that:

[0191] Table 11

[0192]

[0193] As can be seen from the above, based on the catalyst prepared in Example 1, the above substrates can be selectively hydrogenated to the corresponding aromatic amine compounds, and the conversion rate is greater than 99.9%, and the aromatic amine compound selectivity is greater than 99.9%.

[0194] Comparative Examples 1-3: Catalyst activity investigation using different types of metal oxide particles

[0195] The catalyst is prepared according to the method of Example 1, and the difference from Example 1 is that:

[0196] The metal oxide Fe2O3 is replaced by SiO2, MgO and ZnO respectively to obtain NH3-Pt / SiO2 / C, NH3-Pt / MgO / C and NH3-Pt / ZnO / C catalysts.

[0197] When preparing the catalyst, when the metal oxide is SiO2, step (1) is not performed, and step (2) is directly performed based on the purchased SiO2sol; when the metal oxide is MgO, step (1) is changed to prepare magnesium hydroxide precipitate based on magnesium chloride and sodium carbonate; when the metal oxide is ZnO, step (1) is changed to prepare zinc hydroxide precipitate based on water-soluble zinc salt and NaOH.

[0198] The prepared metal oxide particles were subjected to characterization tests according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the results obtained after 0.5 h of reaction are shown in Table 12.

[0199] Table 12

[0200] Catalyst p-nitrostyrene conversion p-aminostyrene selectivity [NH3-Pt / SiO2 / C] 3.2％ ＞99.9％ [NH3-Pt / MgO / C] 5.6％ ＞99.9％ [NH3-Pt / ZnO / C] 2.7％ ＞99.9％

[0201] As can be seen from the above, the NH3-Pt / SiO2 / C, NH3-Pt / MgO / C and NH3-Pt / ZnO / C catalysts have lower activity.

[0202] Comparative Examples 4-5

[0203] The catalysts were prepared according to the method of Example 1, except that:

[0204] The ligand NH3 in Example 1 was replaced by propyl mercaptan and mercaptoethylamine, respectively, to obtain propyl mercaptan-Pt / Fe2O3 / C and mercaptoethylamine-Pt / Fe2O3 / C catalysts.

[0205] The propyl mercaptan and mercaptoethylamine are liquids, and the liquid amine ligands were introduced in the same way as the liquid ligands in Examples 26-31.

[0206] The prepared catalysts were subjected to characterization tests according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the results obtained after 0.5 h of reaction are shown in Table 13.

[0207] Table 13

[0208] Catalyst p-nitrostyrene conversion p-aminostyrene selectivity Propyl mercaptan-Pt / Fe2O3 / C ＜1％ ＞99.9％ Mercaptoethylamine-Pt / Fe2O3 / C ＜1％ ＞99.9％

[0209] As can be seen from the above, the propyl mercaptan-Pt / Fe2O3 / C and mercaptoethylamine-Pt / Fe2O3 / C catalysts have lower activity.

[0210] Comparative Examples 6-9: results of investigation of reduction temperature in preparation of catalysts

[0211] The catalysts were prepared according to the method of Example 1, except that:

[0212] The temperature for reduction in a hydrogen-argon mixture in step (3) was changed from 200°C to 100°C, 150°C, 350°C and 400°C, respectively.

[0213] The prepared catalysts were subjected to characterization tests according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the results obtained after 0.5 h of reaction are shown in Table 14.

[0214] Table 14

[0215] Reduction temperature (°C) in preparation of catalyst p-nitrostyrene conversion p-aminostyrene selectivity 100℃ ＜60％ ＞99.9％ 150℃ ＜60％ ＞99.9％ 350℃ ＜60％ ＞99.9％ 400℃ ＜60％ ＞99.9％

[0216] It can be seen that the NH3-Pt / Fe2O3 / C catalyst prepared at lower and higher reduction temperatures also has catalytic activity and good selectivity for selective hydrogenation of p-nitrostyrene to p-aminostyrene, and the relative activity is poor.

[0217] Comparative Examples 10-12: Activity and selectivity of catalytic reaction using different solvents

[0218] Based on the catalyst prepared in Example 1, the characterization test was carried out according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the reaction time was 0.5 h. Different from Example 1, the solvent used was changed from ethanol to acetonitrile, toluene or cyclohexane. The results are shown in Table 15.

[0219] Table 15

[0220] Reaction solvent for catalytic reaction p-nitrostyrene conversion p-aminostyrene selectivity Acetonitrile ＜5％ ＞99.9％ Toluene ＜5％ ＞99.9％ Cyclohexane ＜5％ ＞99.9％

[0221] As can be seen from the above, the catalyst has low activity for selective hydrogenation of p-nitrostyrene to p-aminostyrene in acetonitrile, toluene and cyclohexane.

[0222] Comparative Examples 13-15

[0223] Based on the catalyst prepared in Example 1, the characterization test was carried out according to the method of "selective catalytic preparation of p-aminostyrene from p-nitrostyrene" in Example 1, and the reaction time was 0.5 h. Different from Example 1,

[0224] the reaction temperature was changed from 60°C to 0°C, 10°C and 20°C. The results are shown in Table 16.

[0225] Table 16

[0226] Solvent temperature (°C) in reaction p-nitrostyrene conversion p-aminostyrene selectivity 0 ＜50％ ＞99.9％ 10 ＜50％ ＞99.9％ 20 ＜50％ ＞99.9％

[0227] As can be seen from the above, when the reaction temperature is 0-20°C, the reaction activity is low, and the conversion rate is less than 50%.

[0228] Comparative Examples 16-19

[0229] The NH3-Pt / Fe2O3 / C catalyst prepared in Example 1 includes Pt nanoparticles, iron oxide nanoparticles, NH3 ligand and carbon nanotubes. A catalyst is prepared by removing one component or two components other than the carbon nanotube carrier in Example 1, and catalysts NH3-Pt / C, Pt / Fe2O3 / C, Pt / C and Fe2O3 / C are obtained.

[0230] Comparative Example 16 was carried out according to steps (3) and (4) of Example 1, in step (3), the calcined product was re-dispersed in 100 mL of water instead of dispersing 3.2 g of carbon nanotubes in 100 mL of water, to obtain NH3-Pt / C;

[0231] Comparative Example 17 was carried out according to steps (1) to (3) of Example 1 to obtain Pt / Fe2O3 / C;

[0232] Comparative Example 18 was carried out according to step (3) of Example 1 only, the calcined product was re-dispersed in 100 mL of water instead of dispersing 3.2 g of carbon nanotubes in 100 mL of water, to obtain Pt / C;

[0233] Comparative Example 19 was carried out according to steps (1) and (2) of Example 1 to obtain Fe2O3 / C.

[0234] Then, the characterization tests were carried out according to the method "Selective catalytic reduction of p-nitrostyrene to prepare p-aminostyrene" of Example 1, and the reaction time was 0.5 h. The results are shown in Table 17.

[0235] Table 17

[0236] Catalyst p-nitrostyrene conversion p-aminostyrene selectivity [NH3-Pt / C] ＜10％ >99.9％ Pt / Fe203 / C ＞99.9％ ＜30％ Pt / C ＞99.9％ ＜30％ Fe2O3 / C ＜10％ >99.9％

[0237] The conversion rate and selectivity of the above catalysts in the above catalytic reaction as a function of time are shown in Figures Figure 8 and Figure 9 It can be seen that the reaction activity of NH3-Pt / C and Fe2O3 / C catalysts for the hydrogenation of p-nitrostyrene to prepare p-aminostyrene is low, and the conversion rate of p-nitrostyrene is less than 10%. The reaction selectivity of Pt / Fe2O3 / C and Pt / C catalysts for the hydrogenation of p-nitrostyrene to prepare p-aminostyrene is low, and the selectivity of p-aminostyrene is less than 30%.

[0238] The above describes the present application in combination with preferred embodiments, but these embodiments are only exemplary and are used for illustration only. On this basis, various substitutions and improvements can be made to the present application, and these all fall within the protection scope of the present application.

Claims

1. A catalyst comprising a carbon support, platinum nanoparticles, and metal oxide nanoparticles; wherein the metal oxide nanoparticles are supported on the carbon support, and the platinum nanoparticles are supported on the metal oxide nanoparticles, or the platinum nanoparticles are supported on both the metal oxide nanoparticles and the carbon support; the catalyst further comprises an NH3 ligand adsorbed on the surface of the platinum nanoparticles.

2. The catalyst according to claim 1, wherein the metal oxide nanoparticles are selected from one or more of Fe2O3, TiO2, Co3O4, CeO2, SnO2, and In2O3. The particle size of the metal oxide nanoparticles is less than or equal to 20 nm.

3. The catalyst according to claim 2, wherein the metal oxide nanoparticles are selected from Fe2O3.

4. The catalyst according to claim 3, wherein the metal oxide nanoparticles are selected from γ-Fe2O3.

5. The catalyst according to claim 1, wherein the platinum nanoparticles comprise zero-valent platinum and / or positive-valent platinum, and the particle size of the platinum nanoparticles is less than or equal to 20 nm.

6. The catalyst according to claim 1, wherein, based on the mass of the catalyst, the loading of the platinum nanoparticles is 0.1-10 wt%, the loading of the metal oxide nanoparticles is 5-30 wt%, and the NH3 ligand is saturatedly covering the surface of the platinum nanoparticles.

7. The catalyst according to claim 1, wherein the carbon support is selected from conductive carbon black, carbon nanotubes, graphene, and porous carbon.

8. The catalyst according to claim 7, wherein the carbon support is a carbon nanotube.

9. A method for preparing the catalyst according to any one of claims 1 to 8, comprising the following steps: (1) Disperse the metal hydroxide and carbon support in a first solvent, then evaporate to dryness to obtain a solid, and calcine the solid to obtain a metal oxide / carbon support; (2) The metal oxide / carbon support and platinum precursor solution are dispersed in a second solvent and stirred to separate the solid phase. Then, the solid phase is dried and calcined to obtain Pt / metal oxide / carbon support. (3) The Pt / metal oxide / carbon support is brought into contact with NH3 ligand to obtain the catalyst.

10. The method of claim 9, wherein the first solvent and the second solvent are each independently selected from one or more of water, methanol, and ethanol.

11. The method according to claim 9, wherein in step (1), the metal hydroxide and the carbon support are dispersed in the first solvent in the following proportions: The mass ratio of the metal hydroxide to the carbon support is 1:(5~20), and the mass ratio of the carbon support to the volume of the first solvent is (2~5) g:30 mL. The metal hydroxide was prepared by the following method: A water-soluble metal salt is dissolved in water, and an alkaline solution is added dropwise while stirring to obtain a metal hydroxide precipitate.

12. The method according to claim 9, wherein the calcination in step (1) is carried out at 200~500°C for 2~5 h.

13. The method according to claim 9, wherein the platinum precursor in step (2) is selected from one or more of potassium chloroplatinate, platinum chloride, platinum nitrate, platinum acetate, ethylenediamine platinum and platinum acetylacetonate, and the concentration of the platinum precursor solution is 0.01~0.1 mol / L; The calcination and reduction described in step (2) are carried out in a hydrogen-argon mixed atmosphere at 200-300°C for 1-10 h; The molar ratio of the NH3 ligand to the Pt in the Pt / metal oxide / carbon support in step (3) is greater than or equal to 10:1; The method for contacting the Pt / metal oxide / carbon support with the NH3 ligand in step (3) includes: When the NH3 ligand is a gas, the NH3 ligand is introduced into a sealed container containing the Pt / metal oxide / carbon support and allowed to stand.

14. A method for preparing aromatic amine compounds, comprising: A catalyst, an aromatic nitro compound, and a reaction solvent are mixed and reacted in the presence of hydrogen to obtain an aromatic amine compound; wherein the catalyst is selected from any one of the catalysts described in claims 1 to 8, or is prepared by any one of the methods described in claims 9 to 13.

15. The method according to claim 14, wherein the structural formula of the aromatic nitro compound is shown below: (R1) m This indicates that each of the m H atoms on the ring is independently replaced by m identical or different R1 atoms, and each R1 is independently C1~C6 alkyl, C2~C6 alkenyl, C2~C6 alkynyl, C1~C5 aldehyde, mercapto, phenylmercapto, halogen, hydroxyl or -COR4; m can be 0, 1, 2, 3, 4, or 5; (R2) n This indicates that each of the n H atoms on the ring is independently replaced by one of the n R2 atoms, where R2 is either -NO2 or -NH2; n is 0, 1, 2, 3, 4 or 5; And 0 ≤ m + n ≤ 5; R4 is selected from C1 to C3 alkyl groups.

16. The method according to claim 15, wherein the aromatic nitro compound is selected from one or more of p-methylnitrobenzene, o-methylnitrobenzene, m-methylnitrobenzene, p-ethylnitrobenzene, p-tert-butylnitrobenzene, p-dinitrobenzene, o-dinitrobenzene, m-dinitrobenzene, p-chloronitrobenzene, o-chloronitrobenzene, m-chloronitrobenzene, p-fluoronitrobenzene, o-fluoronitrobenzene, m-fluoronitrobenzene, p-bromonitrobenzene, o-bromonitrobenzene, m-bromonitrobenzene, p-iodonitrobenzene, o-iodonitrobenzene, m-iodonitrobenzene, p-nitrostyrene, o-nitrostyrene, p-nitrophenylacetylene, o-nitrophenylacetylene, p-hydroxynitrobenzene, o-hydroxynitrobenzene, p-nitrobenzaldehyde, p-nitroacetophenone, and 3-amino-4-nitrodiphenyl sulfide.

17. The method according to claim 14, wherein the reaction solvent is selected from one or more of water, methanol, ethanol and isopropanol; the reaction is carried out at 30-80°C and a hydrogen pressure of 0.1-3.0 MPa for 0.5-50 h; and the molar ratio of platinum to the aromatic nitro compound in the catalyst is 1:(50-5000).

18. The method according to claim 17, wherein the reaction is carried out at 30-80°C and a hydrogen pressure of 0.1-3.0 MPa for 0.5-5 h.

19. The method according to claim 17, wherein the molar ratio of platinum to the aromatic nitro compound in the catalyst is 1:(50~1000).

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