Application of magnetic iron nickel spinel in catalytic hydrogenation of aryl nitro compounds to prepare aryl amine compounds

Abstract

The application belongs to the technical field of organic synthesis, and particularly relates to application of magnetic iron-nickel spinel NiFe2O4 as a catalyst for preparing an aromatic amine compound from an aromatic nitro compound. The application finds that the iron-nickel spinel NiFe2O4 can be used as a catalyst to synthesize an aromatic amine compound from an aromatic nitro compound by catalytic hydrogenation, with hydrogen as a reducing agent. The iron-nickel spinel NiFe2O4 catalyst is prepared from iron salt and nickel salt as precursors, through a simple co-precipitation method to synthesize a nickel-iron composite oxide, and then reduced by CO. The application finds that the activity of CO as a reducing gas is much higher than that of H2, CH4, NH3 and CO2, which is innovative. The NiFe2O4 catalyst has magnetism, can be easily recycled by an external magnetic field, and reduces the cost of industrial application. Hydrogen is used as a reducing agent, and the hydrogen reaction pressure is low (0.5 MPa), which reduces the safety hazards of the hydrogenation process. The above production process is simple, the catalytic cost is low, the yield is high, and the process is easy to industrialize.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to the application of magnetic iron-nickel spinel NiFe2O4 as a catalyst for the preparation of aromatic amine compounds from aromatic nitro compounds. Technical Background

[0002] Aromatic amines are very important amine compounds, generally obtained by reducing aromatic nitro compounds with reducing agents, and are important intermediates in industrial production. They are mainly used in MDI, dye industry, rubber vulcanization accelerators, pharmaceuticals, pesticides, and organic intermediates. In addition, aniline itself can be used as a black dye, and its derivative methyl orange can be used as an indicator in acid-base titrations. Recently, with the application of some aromatic amine compounds in the medical anticancer field, and their role as a major raw material for MDI production, aromatic amine compounds have shown significant market development potential.

[0003] There are generally three traditional methods for synthesizing aromatic amine compounds: 1. Iron powder reduction method: using aromatic nitro compounds as raw materials, iron powder is used for reduction, and the reaction solution is neutralized, washed, and distilled to obtain the finished product. 2. Hydrogenation reduction method: nitrobenzene is subjected to gas-phase hydrogenation reduction in a fluidized bed vessel in the presence of a Raney-Ni or active Cu catalyst, and the reaction product is obtained by condensation and vacuum distillation. 3. Phenol ammonolysis: gas-phase ammonolysis and liquid-phase ammonolysis methods are used. However, due to the instability and low efficiency of the catalyst, difficulty in preservation, and the large amount of waste liquid generated during the reaction process, its industrial development has been restricted (see Appl. Catal. Benviron., 2018, Vol. 227, pp. 386-408; Chin. J. Catal., 2018, Vol. 39, pp. 79-87; Nature Commun., 2022, Vol. 13, pp. 723). In recent years, chemists have discovered that some modified heterogeneous catalysts can be used to directly catalyze the reduction of aromatic nitro compounds to aromatic amines in the presence of a reducing agent, which is also a highly efficient method. Reported studies have used metals such as Fe, Co, Ni, and Cu as catalysts for the reduction of aromatic nitro compounds, with reducing agents including CH3OH, NaBH4, CH3CH2COOH, and H2. However, the preparation of these catalysts is complex or costly (see *Angew. Chem. Int. Ed.*, 2016, Vol. 55, No. 25, 7081-7085). Therefore, finding a method with high conversion, high selectivity, and low pollution to produce aromatic amines, utilizing environmentally friendly and inexpensive reducing agents such as H2, is of significant practical importance. Reported advances in the reduction of aromatic nitro compounds using Ni-based catalysts include: a Ni@C catalyst obtained by solvation pyrolysis of nickel nitrate and BC in DMF, using H2 as a reducing agent, selectively catalyzing the synthesis of aniline from nitrobenzene at relatively high temperatures (see *ACS. Catal.*, 2023, 3224-3241); and a series of pyrolytic iron-based catalysts designed and prepared by pulverizing a mixture of MIL-88d and melamine, using H2 as a reducing agent to reduce nitrobenzene to aniline (see *Inorg. Chem.*, 2019, Vol. 58, 9469-9475). Furthermore, it has recently been discovered that Ni3C colloids formed in oleylamine can reduce nitrobenzene to aniline as a catalyst under H2 conditions (see *Catal. Sci. Technol.*, 2022, Vol. 12, 4572–4583). However, the above catalysts all have problems such as complex preparation processes and harsh reaction conditions. In order to solve the problems of the above catalysts, it is of great significance to develop an economical, environmentally friendly and efficient synthesis process for aromatic amine compounds.

[0004] Traditional methods for preparing magnetic iron-nickel spinel include hydrothermal methods, sol-gel methods, and co-precipitation methods. These methods have certain safety risks, are time-consuming, and are not suitable for industrial production. The method used in this invention, however, involves reducing the nickel-iron composite oxide with reducing gases such as CO, H2, CH4, NH3, and CO2 to obtain the desired catalyst. This method is highly innovative (see *New J. Chem*, 2022, Vol. 6, pp. 13228), allows for mass production, and reduces industrial application costs. Summary of the Invention

[0005] This invention discovers that adding magnetic iron-nickel spinel NiFe2O4 as a catalyst to a reaction vessel can catalytically reduce aromatic nitro compounds to aromatic amine compounds. Therefore, this invention provides a novel, low-cost, green, and efficient method for preparing aromatic amine compounds. The method is simple, low-cost, safe, and has a high yield. Specifically, it includes the following:

[0006] Firstly, this invention provides a special catalyst: magnetic iron-nickel spinel NiFe₂O₄. The NiFe₂O₄ catalyst is prepared by synthesizing nickel-iron composite oxides from iron and nickel salt precursors using a simple co-precipitation method, followed by CO reduction. X-ray diffraction comparison images of magnetic iron-nickel spinel prepared under different atmospheres and standard magnetic iron-nickel spinel are shown below. Figure 1 As shown; the X-ray photoelectron spectrum of the target magnetic iron-nickel spinel reduced in a CO atmosphere at 450℃ is as follows. Figure 2 As shown.

[0007] Preferably, the catalyst preparation method includes the following steps:

[0008] (1) Preparation of iron-nickel spinel NiFe2O4: A certain ratio (2:1) of iron salt and nickel salt was added to a reactor containing deionized water (the ratio of deionized water to salt molars was 1L:1mol), and stirred to dissolve it completely. A precipitant (ammonia, sodium hydroxide solution, sodium carbonate solution, potassium hydroxide solution, potassium carbonate solution, etc.) was slowly added to the reactor until the pH was 8-10, and the stirring time was 20h.

[0009] (2) Filtering, washing, and drying;

[0010] (3) The desired catalyst is obtained by calcining and reducing with CO (calcination temperature is 100-600℃).

[0011] Preferably, the catalyst reducing gas is CO, H2, CH4, NH3, or CO2.

[0012] Preferably, the catalyst reducing gas is CO.

[0013] Preferably, the reduction temperature of the catalyst is 100-600℃.

[0014] Preferably, the reduction temperature of the catalyst is 200-500℃.

[0015] Preferably, the catalyst reduction temperature is 450°C.

[0016] Secondly, the present invention provides a method for preparing an aromatic amine compound, the method comprising: using an aromatic nitro compound represented by formula (I) as a raw material, using methanol or other solvents as a reaction solvent, using iron-nickel spinel as a catalyst, and using hydrogen as a reducing agent, and catalytically reducing the aromatic amine compound represented by formula (II) to synthesize the aromatic amine compound represented by formula (II), wherein the organic solvents include ethanol, methanol, toluene, acetonitrile, tetrahydrofuran, and DMF;

[0017]

[0018] R1-R5 are selected from any one of hydrogen, halogen, hydroxyl, sulfonic acid group, substituted or unsubstituted straight-chain or branched alkyl, alkoxy, carbonyl, alkenyl, alkynyl, substituted or unsubstituted aryl, amide, cyano, but are not limited to the above substituents.

[0019] Preferably, R1-R5 are selected from hydrogen, cyano, fluorine, chlorine, bromine, iodine, and aldehyde, respectively.

[0020] Preferably, the aromatic nitro compounds include: nitrobenzene, 4-nitrobenzenenitrile, 2-fluoronitrobenzene, 2-chloronitrobenzene, 4-chloronitrobenzene, 3-iodonitrobenzene, 2-bromonitrobenzene, 4-nitroacetophenone, 2-nitrofluorene, 2-nitrobiphenyl, 2-nitropyridine, etc.

[0021] Preferably, the ratio of the catalyst to the aromatic nitro compound is 5-100 g: 1 mol.

[0022] Preferably, the ratio of the catalyst to the aromatic nitro compound is 10-80 g: 1 mol.

[0023] Preferably, the ratio of the catalyst to the aromatic nitro compound is 15-50 g: 1 mol.

[0024] Preferably, the ratio of the catalyst to the aromatic nitro compound is 25g:1mol.

[0025] Preferably, the reaction solvent is methanol.

[0026] Preferably, the mass ratio of the reaction solvent to the aromatic nitro compound is 1-100:1.

[0027] Preferably, the mass ratio of the reaction solvent to the aromatic nitro compound is 5-50:1.

[0028] Preferably, the mass ratio of the reaction solvent to the aromatic nitro compound is 5-10:1.

[0029] Preferably, the mass ratio of the reaction solvent to the aromatic nitro compound is 6:1.

[0030] Preferably, the catalyst is an iron-nickel spinel catalyst.

[0031] Preferably, the method includes the following steps: adding an aromatic nitro compound and iron-nickel spinel NiFe2O4 into a reactor containing a solvent, introducing hydrogen gas at a pressure of 0.1-1.0 MPa, reacting at 80-150°C for 1-10 h, and then filtering, distilling, and recrystallizing to obtain an aromatic amine compound.

[0032] Preferably, the reaction pressure is 0.1-1.0 MPa.

[0033] Preferably, the reaction pressure is 0.5 MPa.

[0034] Preferably, the reaction pressure is 0.75 MPa.

[0035] Preferably, the reaction temperature is 80-150°C.

[0036] Preferably, the reaction temperature is 100°C.

[0037] Preferably, the reaction temperature is 105°C.

[0038] Preferably, the reaction time is 1-10 hours.

[0039] Preferably, the reaction time is 4 hours.

[0040] Preferably, the reaction time is 5 hours.

[0041] Preferably, the reaction time is 10 hours.

[0042] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0043] (1) This invention uses magnetic nickel-iron spinel NiFe2O4 as a catalyst, which has low commercial cost, high activity, good selectivity, and can be synthesized by a simple co-precipitation method, followed by CO reduction. Compared with traditional catalysts, this invention greatly simplifies the catalyst preparation process, significantly reduces catalyst cost, and provides excellent performance.

[0044] (2) This invention discovers that CO has a much higher activity than gases such as H2, CH4, NH3, and CO2, which is innovative.

[0045] (3) The magnetic iron-nickel spinel NiFe2O4 catalyst used in this invention is magnetic and can be easily recycled and reused by applying an external magnetic field. Furthermore, the aromatic nitro compounds used in the process are commonly used low-cost basic raw materials in industry, which reduces the cost of industrial applications.

[0046] (4) The present invention uses cheap and readily available hydrogen as a reducing agent. The hydrogen reaction pressure is low (0.5MPa), which reduces the safety hazards of the hydrogenation process and is easy to industrialize.

[0047] (5) The method described in this invention can catalytically reduce aromatic nitro compounds to the corresponding aromatic amine compounds with high selectivity. Attached Figure Description

[0048] Figure 1 X-ray diffraction comparison of magnetic iron-nickel spinel prepared under different atmospheres and standard magnetic iron-nickel spinel;

[0049] Figure 2 X-ray photoelectron spectrum of the target magnetic iron-nickel spinel reduced in a CO atmosphere at 450℃;

[0050] Figure 3 Mass spectrum of 3-iodoaniline synthesized by the method described in Example 8;

[0051] Figure 4 Mass spectrum of 2-aminophenylfluorene synthesized by the method described in Example 8;

[0052] Figure 5 Mass spectrum of 2-aminobiphenyl synthesized by the method described in Example 8;

[0053] Figure 6 Mass spectrum of 4-aminobenzonitrile synthesized by the method described in Example 8;

[0054] Figure 7 Mass spectrum of 4-aminoacetophenone synthesized by the method described in Example 8; Detailed Implementation

[0055] The present invention will be further described in detail below with reference to specific embodiments. The scope of protection of the present invention is not limited thereto. Unless otherwise specified, all raw materials used in the following embodiments can be purchased commercially.

[0056] Example 1: Synthesis of Aniline using Different Gas Reduction Catalysts

[0057] 1. Add 5g of iron-nickel spinel NiFe2O4-CO to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0058] 2. Add 5g of iron-nickel spinel NiFe2O4-CO2 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0059] 3. Add 5g of iron-nickel spinel NiFe2O4-CH4 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0060] 4. Add 5g of iron-nickel spinel NiFe2O4-NH3 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0061] 5. Add 5g of iron-nickel spinel NiFe2O4-H2 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0062] The yields of aniline obtained by the preparation methods described in 1-5 above were calculated, and the results are shown in Table 1 below:

[0063] Table 1. Process parameters and yield of aniline as described in Example 1

[0064]

[0065] The structural formula of the main product is shown in Formula 1 below. The results indicate that, using methanol as the reaction solvent, hydrogen as the reducing agent, iron-nickel spinel NiFe₂O₄ as the catalyst, and CO as the reducing roasting gas, the yield of aniline obtained from the reaction is as high as 100%.

[0066]

[0067]

[0068] Example 2: Preparation of catalysts at different CO reduction temperatures for the synthesis of aniline.

[0069] 1. Add 5g of iron-nickel spinel NiFe2O4-CO-200 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0070] 2. Add 5g of iron-nickel spinel NiFe2O4-CO-300 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0071] 3. Add 5g of iron-nickel spinel NiFe2O4-CO-350 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0072] 4. Add 5g of iron-nickel spinel NiFe2O4-CO-400 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0073] 5. Add 5g of iron-nickel spinel NiFe2O4-CO-450 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0074] 6. Add 5g of iron-nickel spinel NiFe2O4-CO-500 to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0075] The yields of aniline obtained by the preparation methods described in 1-6 above were calculated, and the results are shown in Table 2 below:

[0076] Table 2. Process parameters and yield of aniline as described in Example 2.

[0077]

[0078] The above results indicate that, using methanol as the reaction solvent, hydrogen as the reducing agent, and iron-nickel spinel NiFe2O4 as the catalyst, the yield of aniline obtained from the reaction is as high as 100% at a CO calcination reduction temperature of 450℃.

[0079] Example 3: Synthesis of aniline with different catalyst addition amounts

[0080] 1. Add 3g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0081] 2. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0082] 3. Add 7g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0083] 4. Add 10g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0084] 5. Add 12g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0085] The yields of aniline obtained by the preparation methods described in 1-5 above were calculated, and the results are shown in Table 3 below:

[0086] Table 3. Process parameters and yield of aniline as described in Example 3.

[0087]

[0088] The above results indicate that when methanol is used as the reaction solvent, hydrogen as the reducing agent, iron-nickel spinel as the catalyst, and the ratio of methanol to aromatic nitro compounds is 25 g: 1 mol, the yield of aniline obtained from the reaction is as high as 98% or more.

[0089] Example 4: Synthesis of Aniline using Different Reaction Solvents

[0090] 1. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of ethanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0091] 2. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0092] 3. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of toluene, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0093] 4. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of tetrahydrofuran, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0094] The yields of aniline obtained by the preparation methods described in 1-4 above were calculated, and the results are shown in Table 4 below:

[0095] Table 4. Process parameters and yield of aniline as described in Example 4

[0096]

[0097] The above results indicate that the NiFe2O4-CO-450 catalyst can catalyze the synthesis of aniline from nitrobenzene using ethanol, methanol, toluene, or tetrahydrofuran as the reaction solvent; and that the yield of aniline obtained can reach up to 100% when methanol is used as the reaction solvent.

[0098] Example 5: Synthesis of aniline using different amounts of reaction solvent

[0099] 1. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 25g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0100] 2. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 50g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0101] 3. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0102] 4. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 100g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0103] 5. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 125g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0104] 6. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 150g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0105] The yields of aniline obtained by the preparation methods described in 1-6 above were calculated, and the results are shown in Table 5 below.

[0106] Table 5. Process parameters and yield of aniline as described in Example 5.

[0107]

[0108] The above results indicate that when methanol is used as the reaction solvent, hydrogen as the reducing agent, NiFe2O4-CO-450 as the catalyst, and the mass ratio of methanol to nitrobenzene is 6:1, the yield of aniline obtained from the reaction is as high as 90% or more.

[0109] Example 6: Synthesis of Aniline at Different Reaction Temperatures

[0110] 1. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 30℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0111] 2. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, heat to 50℃ and react for 4h, then filter, distill and recrystallize to obtain the product aniline.

[0112] 3. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 70℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0113] 4. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 80℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0114] 5. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0115] 6. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 130℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0116] 7. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 150℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0117] The yields of aniline obtained by the preparation methods described in 1-7 above were calculated, and the results are shown in Table 6 below:

[0118] Table 6. Process parameters and yield of aniline as described in Example 6

[0119]

[0120] The above results indicate that nitrobenzene can be catalytically synthesized into aniline at reaction temperatures of 30-150℃, using methanol as the reaction solvent, hydrogen as the reducing agent, and iron-nickel spinel as the catalyst. Furthermore, the yield of aniline obtained at reaction temperatures of 80-150℃ is consistently above 70%, and the yield reaches a maximum of 100% at a reaction temperature of 100℃. Example 7 describes the synthesis of aniline at different reaction times.

[0121] 1. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 2h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0122] 2. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0123] 3. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, and then heat to 100℃ and react for 6h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0124] 4. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 8h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0125] 5. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 10h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0126] The yields of aniline obtained by the preparation methods described in 1-5 above were calculated, and the results are shown in Table 7 below:

[0127] Table 7. Process parameters and yield of aniline as described in Example 7.

[0128]

[0129] The above results show that, with a reaction time of 1-10 h, methanol as the reaction solvent, hydrogen as the reducing agent, and iron-nickel spinel as the catalyst, nitrobenzene can be catalytically synthesized into aniline; at the same time, when the reaction time is 4-10 h, the yield of aniline obtained by the reaction is above 95%; and when the reaction time is 4 h, the yield of aniline obtained by the reaction can reach up to 100%.

[0130] Example 8: Synthesis of Aniline under Different Reaction Pressures

[0131] 1. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.1MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0132] 2. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.3MPa, and then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0133] 3. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.5MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0134] 4. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 0.75MPa, then heat to 100℃ and react for 4h. After filtration, distillation and recrystallization, the product aniline is obtained.

[0135] 5. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.7g of nitrobenzene and 75g of methanol, purge with hydrogen gas at 1.0MPa, heat to 100℃ and react for 4h. Then filter, distill and recrystallize to obtain the product aniline.

[0136] The yields of aniline obtained by the preparation methods described in 1-5 above were calculated, and the results are shown in Table 8 below:

[0137] Table 8. Process parameters and yield of aniline as described in Example 8.

[0138]

[0139] The above results indicate that nitrobenzene can be catalytically synthesized into aniline under reaction pressures of 0.1-1.0 MPa, using methanol as the reaction solvent, hydrogen as the reducing agent, and iron-nickel spinel as the catalyst. Furthermore, the yield of aniline obtained under reaction pressures of 0.3-1.0 MPa is consistently above 70%, and the yield can reach up to 100% under a reaction pressure of 0.5 MPa.

[0140] Example 9: Synthesis of Aromatic Amine Compounds Using Different Aromatic Nitro Compounds

[0141] 1. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 14.1g of o-fluoronitrobenzene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 10h. After filtration, distillation, and recrystallization, obtain the product o-fluoroaniline. Its structural formula is shown in Formula 2 below.

[0142]

[0143] 2. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 15.8g of o-chloronitrobenzene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 4h. After filtration, distillation, and recrystallization, the product o-chloroaniline is obtained. Its structural formula is shown in Formula 3 below.

[0144]

[0145] 3. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 20.2g of o-bromonitrobenzene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 10h. After filtration, distillation, and recrystallization, the product o-bromoaniline is obtained. Its structural formula is shown in Formula 4 below.

[0146]

[0147] 4. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 15.8g of p-chloronitrobenzene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 4h. After filtration, distillation, and recrystallization, obtain the product p-chloroaniline. The structural formula is shown in Formula 5 below.

[0148]

[0149] 5. Add 5g of iron-nickel spinel to a 250mL reactor, then add 24.9g of m-iodonitrobenzene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 5 hours. After filtration, distillation, and recrystallization, obtain the product m-iodoaniline. The mass spectrum of the product is shown below. Figure 3 As shown, the structural formula is shown in Equation 6 below.

[0150]

[0151] 6. Add 5g of iron-nickel spinel to a 250mL reactor, then add 21.1g of 2-nitrofluorene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 10h. After filtration, distillation, and recrystallization, obtain the product 2-aminofluorene. The mass spectrum of the product is shown below. Figure 4As shown, the structural formula is shown in Equation 7 below.

[0152]

[0153] 7. Add 5g of iron-nickel spinel to a reactor with a volume of 250mL, then add 12.4g of 2-nitropyridine and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 10h. After filtration, distillation, and recrystallization, obtain the product 2-aminopyridine. Its structural formula is shown in Formula 8 below.

[0154]

[0155] 8. Add 5g of iron-nickel spinel to a 250mL reactor, then add 19.9g of 2-nitrobenzene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 10h. After filtration, distillation, and recrystallization, obtain the product 2-aminobiphenyl. The mass spectrum of the product is shown below. Figure 5 As shown, the structural formula is shown in Equation 9 below.

[0156]

[0157] 9. Add 5g of iron-nickel spinel to a 250mL reactor, then add 18.4g of 4-nitrobenzene and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 10h. After filtration, distillation, and recrystallization, obtain the product 4-aminobenzonitrile. The mass spectrum of the product is shown below. Figure 6 As shown, the structural formula is shown in Equation 10 below.

[0158]

[0159] 10. Add 5g of iron-nickel spinel to a 250mL reactor, then add 16.5g of 4-nitroacetophenone and 75g of methanol. Purge with hydrogen gas at 0.75MPa, then heat to 105℃ and react for 10h. After filtration, distillation, and recrystallization, obtain the product 4-aminoacetophenone. The mass spectrum of the product is shown below. Figure 7 As shown, the structural formula is shown in Equation 11 below.

[0160]

[0161] The yields of the aromatic amine compounds obtained by the preparation methods described in 1-10 above were calculated, and the results are shown in Table 9 below:

[0162] Table 9. Process parameters and product yield of the preparation method described in Example 9.

[0163]

[0164] The mass spectra of the main products in reactions 1-10 above are as follows: Figure 3-7 As shown above, the results indicate that using methanol as the reaction solvent, hydrogen as the reducing agent, and iron-nickel spinel as the catalyst, o-fluoronitrobenzene can be catalytically synthesized into o-fluoroaniline with a yield of 98%; o-chloronitrobenzene into o-chloroaniline with a yield of 96%; o-bromonitrobenzene into o-bromoaniline with a yield of 96%; p-chloronitrobenzene into p-chloroaniline with a yield of 100%; m-iodonitrobenzene into m-iodoaniline with a yield of 85%; 2-nitrofluorene into 2-aminofluorene with a yield of 100%; 2-nitropyridine into 2-aminopyridine with a yield of 100%; 2-nitrobiphenyl into 2-aminobiphenyl with a yield of 100%; 4-nitrobenzonitrile into 4-aminobenzonitrile with a yield of 89%; and 4-nitroacetophenone into 4-aminoacetophenone with a yield of 95%. Therefore, the method described in this invention can catalytically synthesize aromatic amine compounds from aromatic nitro compounds, and the yield of the target product is high.

[0165] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. The application of magnetic iron-nickel spinel NiFe2O4 as a catalyst for the hydrogenation of aromatic nitro compounds to prepare aromatic amine compounds, characterized in that: The iron-nickel spinel NiFe2O4 catalyst is prepared using iron and nickel salts as precursors via a simple co-precipitation method. This involves dissolving a certain proportion of iron and nickel salts in deionized water, slowly adding a certain concentration of alkaline solution until the pH is greater than 8, stirring for a certain time, and then filtering, washing, drying, and calcining the resulting precipitate before reduction with a reducing gas. The reducing gas is CO, and the reduction temperature is 100-450 ℃. The hydrogenation preparation of aromatic amine compounds uses the aromatic nitro compound shown in formula (I) as the raw material, methanol or other solvents as the reaction solvent, the iron-nickel spinel NiFe2O4 as the catalyst, and hydrogen as the reducing agent to catalyze the reduction reaction to synthesize the aromatic amine compound shown in formula (II). Other solvents include toluene, trifluorotoluene, tetrahydrofuran, ethanol, and acetonitrile. Equation (I) Equation (II); R1-R5 are selected from any one of hydrogen, halogen, hydroxyl, alkoxy, carbonyl, alkenyl, alkynyl, substituted or unsubstituted aryl, and cyano groups.

2. Use according to claim 1, wherein The CO reduction temperature is 450 °C.

3. The application as described in claim 1, characterized in that, The ratio of the catalyst to the aromatic nitro compound is 5-100 g:1 mol; the mass ratio of the reaction solvent to the aromatic nitro compound is 1-100:

1.

4. The application as described in claim 1, characterized in that, The aromatic nitro compounds include: nitrobenzene, 4-nitrobenzenenitrile, 2-fluoronitrobenzene, 2-chloronitrobenzene, 4-chloronitrobenzene, 3-iodonitrobenzene, 2-bromonitrobenzene, 4-nitroacetophenone, 2-nitrofluorene, and 2-nitrobiphenyl.

5. The application as described in claim 1 or 3, characterized in that, The application includes the following steps: adding aromatic nitro compounds and iron-nickel spinel NiFe2O4 into a reactor containing solvent, introducing hydrogen gas at a pressure of 0.1-1.0 MPa, reacting at 80-150℃ for 1-10 h, and then filtering, distilling, and recrystallizing to obtain aromatic amine compounds.

6. The application as described in claim 5, characterized in that, The catalyst to aromatic nitro compound is used in a ratio of 25 g to 1 mol; the reaction solvent to aromatic nitro compound is used in a mass ratio of 6:1; the hydrogen pressure is 0.5 MPa; the reaction temperature is 100 °C; and the reaction time is 4 h.

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