Method for selectively preparing azobenzene oxide or 1, 2-diphenyl hydrazine through nitrobenzene hydrogenation

Abstract

The invention discloses a method for selectively preparing azobenzene oxide or 1, 2-diphenylhydrazine through nitrobenzene hydrogenation, which comprises the following steps: adding a few-layer graphene coated Ni catalyst, alkali, nitrobenzene and a solvent into a polytetrafluoroethylene lining, ultrasonically mixing uniformly, filling the mixture into a reaction kettle, sealing, replacing air in the reaction kettle with hydrogen, and reacting for 2-4 hours; and controlling the temperature to 15-30 DEG C and reacting to obtain azobenzene oxide, or raising the temperature to 50-80 DEG C and reacting to obtain 1, 2-diphenylhydrazine. The few-layer graphene coated Ni catalyst is used for catalyzing nitrobenzene hydrogenation to prepare azobenzene oxide. The catalyst has the advantages of simple synthesis route, cheap and easily available raw materials, simple reaction conditions of the catalytic hydrogenation route, cheap and easily available nitrobenzene, and high economic benefit. The obtained few-layer graphene coated Ni catalyst has the advantages of mild reaction conditions, high product selectivity, easiness in separation and recovery, good cycling stability and the like when being used for catalyzing nitrobenzene hydrogenation to prepare azobenzene oxide or 1, 2-diphenyl hydrazine.

Description

Technical Field

[0001] The invention relates to the field of organic synthesis, and in particular to a method for selectively preparing oxyazobenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene. Background Art

[0002] Aromatic azoxy / azo compounds are important intermediates for the production of high-value chemical products such as dyes, pigments, food additives, liquid crystal materials and medicines. At present, the industrial production of aromatic azoxy / azo compounds usually adopts the scheme of oxidizing aromatic amines with strong oxidants. In contrast, the route of preparing aromatic azoxy / azo compounds by one-pot hydrogenation coupling using cheap and readily available nitroaromatics as substrates is more economical, efficient and environmentally friendly. However, the reduction of nitroaromatics involves a multi-step hydrogenation process, which will produce a series of intermediates such as nitrosoaromatics, hydroxylamine, azoxybenzene, azobenzene and hydrazine, and nitrosoaromatics and hydroxylamine are easily further hydrogenated to aniline, resulting in a decrease in the selectivity of the target product. Therefore, it has become an urgent problem to control the hydrogenation process of nitroaromatics with catalysts as the core to obtain aromatic azoxy / azo compounds with high selectivity.

[0003] In recent years, the development of catalysts for the selective hydrogenation of nitroaromatics to produce aromatic azoxy / azo compounds has focused on precious metal-based catalysts (see: ACS Catal., 10 (2020) 2837-2844, CN 101914036 A). In addition, in order to control the reaction path of nitroaromatic aromatic azoxy / azo compounds, reducing agents such as NaBH4, HCONH4, HCOOH, C3H7OH, N2H4·H2O, Zn, and Fe powder are quantitatively added to the reaction system. However, the use of precious metals and reducing agents will lead to cumbersome production and separation and recovery processes of target products, pushing up production costs (see: CN 111333550 A, CN 111875518 A, Mol. Catal. 2020, 490, 110943). Therefore, it is more valuable to develop non-precious metal-based catalysts and use cheap, readily available, green and environmentally friendly hydrogen as a hydrogen source to prepare aromatic azoxy / azo compounds with high selectivity.

[0004] CN 101838219 A discloses a method for preparing 1,2-diphenylhydrazine by catalytic hydrogenation of nitrobenzene. Under optimal conditions, Raney nickel is used as a catalyst, anhydrous methanol is used as a solvent, 0.5 MPa hydrogen is used, sodium hydroxide is added, 0.1 MPa ammonia is introduced, and the reaction is carried out at room temperature for 12.0 h, and the yield of 1,2-diphenylhydrazine can reach 94%. CN 109928898 A discloses a method for green preparation of oxidized azo compounds using MOFs-derived magnetic nanoparticles as a recyclable catalyst. Using Co@CN as a catalyst, oxidized azobenzene is prepared by reduction in an alcohol solution, and the catalytically active component is a magnetic Co nanoparticle. CN 109603874 A discloses a copper-doped nitrogen-modified carbon material, its application, and a reaction method for oxidative coupling of aromatic amines to symmetrical / asymmetrical azobenzenes. Using modified Cu nanoparticles as catalytically active components, symmetrical / asymmetrical azobenzenes are prepared by oxidizing aromatic amines in an oxygen atmosphere, and the catalyst has strong universality for different substrates. Summary of the invention

[0005] The purpose of the present invention is to provide a method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene in view of the defects of the prior art.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene, characterized in that it comprises the following steps: adding a Ni catalyst wrapped in a few-layer graphene, a base, nitrobenzene and a solvent into a polytetrafluoroethylene liner, ultrasonically mixing them uniformly and then loading them into a reactor and sealing them, replacing the air in the reactor with hydrogen, controlling the temperature to 15-30°C for reaction to obtain azoxybenzene, or heating the temperature to 50-80°C for reaction to obtain 1,2-diphenylhydrazine.

[0007] Furthermore, the few-layer graphene-wrapped Ni catalyst is Ni particles wrapped inside the few-layer graphene, wherein the Ni particle size is 1 to 50 nanometers, the mass content is 5% to 90%, and the number of the few-layer graphene layers is 1 to 3 layers.

[0008] Furthermore, a few-layer graphene-wrapped Ni catalyst is prepared by using metal salt, organic amine and carbon source as raw materials through hydrothermal treatment to obtain a precursor, which is then calcined in a N2 atmosphere and then treated with a sulfuric acid solution.

[0009] Furthermore, the metal salt is one or a mixture of two or more of nickel acetate, nickel nitrate, nickel sulfate, and nickel chloride; the organic amine is one or a mixture of two or more of ethanolamine, urea, dicyandiamide, and hexamethylenetetramine; and the carbon source is one or a mixture of two or more of furfural, furfuryl alcohol, glycerol, glucose, fructose, and lactose.

[0010] Furthermore, the molar ratio of the metal salt, the organic amine, and the carbon source is 1:(0.5-2.0):(2.5-5.5).

[0011] Furthermore, the reaction conditions of the hydrothermal treatment are 100~180℃ for 2.0~24.0h; the calcination conditions are heating to 400~800℃ at 3.0~5.0℃ / min and maintaining for 2.0~8.0h; the concentration of the sulfuric acid solution is 0.1~2.0M, the temperature is 25~80℃, and the treatment time is 2.0~24.0h.

[0012] Furthermore, the dosage ratio of the oligolayer graphene-wrapped Ni catalyst: base: nitrobenzene: solvent is: (5.0~30 mg): (0.1~4.0 mmol): 0.5 mmol: 5.0 mL.

[0013] Furthermore, the base is potassium carbonate, sodium hydroxide, potassium hydroxide or sodium ethoxide.

[0014] Furthermore, the solvent is one or a mixture of two or more of water, methanol, ethanol, tetrahydrofuran and toluene.

[0015] Furthermore, the hydrogen pressure is 0.1~2.0 MPa, and the reaction time is 0.5~3.0 h.

[0016] The present invention adopts a few-layer graphene-wrapped Ni catalyst to catalyze nitrobenzene hydrogenation to prepare azobenzene oxide. The catalyst has a simple synthesis route, and the raw materials are cheap and readily available. The catalytic hydrogenation route has simple reaction conditions, simple operation, cheap and readily available nitrobenzene, and high economic benefits. The obtained few-layer graphene-wrapped Ni catalyst has the advantages of mild reaction conditions, high product selectivity, easy separation and recovery, good cycle stability, etc. in catalyzing nitrobenzene hydrogenation to prepare azobenzene oxide or 1,2-diphenylhydrazine. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is the XRD spectrum of the few-layer graphene-wrapped Ni catalyst prepared in Examples 1 to 4 of the present invention.

[0018] Figure 2 It is a transmission electron microscope photograph of the few-layer graphene-wrapped Ni catalyst prepared in Examples 1 to 4 of the present invention.

[0019] Figure 3 It is a high-resolution transmission electron microscope photograph of the few-layer graphene-wrapped Ni catalyst obtained in Examples 1 to 4 of the present invention.

[0020] Figure 4 This is a photograph of using a magnet to separate the few-layer graphene-wrapped Ni catalyst obtained in Example 4 of the present invention.

[0021] Figure 5It is a schematic diagram of the process of hydrogenating nitrobenzene to produce azobenzene oxide and 1,2-diphenylhydrazine. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0023] It should be noted that the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or apparatuses.

[0024] Example 1

[0025] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for catalyzing the hydrogenation of nitrobenzene to produce oxyazobenzene or 1,2-diphenylhydrazine, which specifically includes the following steps.

[0026] (1) Take 1.0 mmol nickel nitrate, 2.0 mmol ethanolamine, and 4.0 mmol glycerol in 60 mL deionized water and stir to dissolve.

[0027] (2) The obtained solution was placed in a polytetrafluoroethylene hydrothermal autoclave, sealed, and placed in a 100 °C oven for hydrothermal treatment for 24.0 h. After the hydrothermal reaction was completed, the obtained solid product was separated by centrifugation and placed in an 80 °C oven for drying for 12.0 h.

[0028] (3) The dried solid product obtained in (2) was placed in a N2 atmosphere, heated to 400°C at 3.0°C / min, and maintained for 8.0 h.

[0029] (4) The calcined sample was treated with 0.1 M hydrochloric acid at 25 °C for 24.0 h and finally washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain the Ni@G-1 catalyst.

[0030] Example 2

[0031] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for catalyzing the hydrogenation of nitrobenzene to produce oxyazobenzene or 1,2-diphenylhydrazine, which specifically includes the following steps.

[0032] (1) Take 1.0 mmol nickel sulfate hexahydrate, 2.5 mmol urea, 2.5 mmol glycerol and 2.5 mmol glucose in 60 mL deionized water and stir to dissolve.

[0033] (2) The obtained solution was placed in a polytetrafluoroethylene hydrothermal autoclave, sealed, and placed in a 150°C oven for hydrothermal treatment for 18.0 h. After the hydrothermal reaction was completed, the obtained solid product was separated by centrifugation and placed in an 80°C oven for drying for 12.0 h.

[0034] (3) The dried solid product obtained in (1) was placed in a N2 atmosphere, heated to 500°C at 3.0°C / min, and maintained for 6.0 h.

[0035] (4) The calcined sample was treated with 1.0 M hydrochloric acid at 50 °C for 18.0 h, washed with deionized water and anhydrous ethanol, and dried at 80 °C to obtain the Ni@G-2 catalyst.

[0036] Example 3

[0037] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for catalyzing the hydrogenation of nitrobenzene to produce oxyazobenzene and 1,2-diphenylhydrazine, which specifically includes the following steps.

[0038] (1) Weigh 1.0 mmol nickel acetate, 2.0 mmol urea, 1.0 mmol dicyandiamide, and 6.0 mmol fructose into 60 mL deionized water and stir to dissolve.

[0039] (2) The obtained solution was placed in a polytetrafluoroethylene hydrothermal autoclave, sealed, and placed in a 170 °C oven for hydrothermal treatment for 10.0 h. After the hydrothermal reaction was completed, the obtained solid product was separated by centrifugation and placed in an 80 °C oven for drying for 12.0 h.

[0040] (3) The dried solid product obtained in (1) was placed in a N2 atmosphere, heated to 600°C at 3.0°C / min, and maintained for 4.0 h.

[0041] (4) Finally, the calcined sample was treated with 1.5 M hydrochloric acid at 60 °C for 10.0 h. Finally, it was washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain the Ni@G-3 catalyst.

[0042] Example 4

[0043] This embodiment is a method for preparing a few-layer graphene-wrapped Ni catalyst for catalyzing the hydrogenation of nitrobenzene to produce oxyazobenzene and 1,2-diphenylhydrazine, which specifically includes the following steps.

[0044] (1) Weigh 0.5 mmol nickel chloride, 0.5 mmol nickel nitrate, 3.5 mmol hexamethylenetetramine and 7.0 mmol lactose respectively into 60 mL deionized water and stir to dissolve.

[0045] (2) The obtained solution was placed in a polytetrafluoroethylene hydrothermal autoclave, sealed, and placed in a 180°C oven for hydrothermal treatment for 5.0 h. After the hydrothermal reaction was completed, the obtained solid product was separated by centrifugation and placed in an 80°C oven for drying for 12.0 h.

[0046] (3) The dried solid product obtained in (1) was placed in a N2 atmosphere, heated to 700°C at 3.0°C / min, and maintained for 2.0 h.

[0047] (4) Finally, the calcined sample was treated with 2.0 M hydrochloric acid at 80 °C for 2.0 h. Finally, it was washed with deionized water and anhydrous ethanol and dried at 80 °C to obtain the Ni@G-4 catalyst.

[0048] Figure 1 XRD spectra of the catalysts Ni@G-1, Ni@G-2, Ni@G-3, and Ni@G-4 prepared in Examples 1 to 4. From the figure, it can be seen that the broad peak at about 26° indicates that Ni@G has a graphite carbon structure. The diffraction peaks at 44.4°, 51.8°, and 76.8° correspond to the characteristic peaks of metallic nickel, indicating that the catalyst still retains Ni after being washed with strong acid, and Ni is in a metallic state.

[0049] Figure 2 Transmission electron microscope photos of the catalysts Ni@G-1, Ni@G-2, Ni@G-3, and Ni@G-4 prepared in Examples 1 to 4. It can be seen from the figure that the four catalysts all present a flower cluster structure, and the Ni particles are evenly distributed therein.

[0050] Figure 3 High-resolution transmission electron microscopy photos of the catalysts Ni@G-1, Ni@G-2, Ni@G-3, and Ni@G-4 prepared in Examples 1 to 4. It can be seen from the figure that Ni in the four catalysts is wrapped by a few-layer graphene.

[0051] Figure 4 This is a photograph of a few-layer graphene-wrapped Ni catalyst prepared in Specific Example 4 of the present invention being separated using a magnet. As can be seen from the figure, the few-layer graphene-wrapped Ni catalyst involved in the present invention is magnetic and can be quickly separated by a magnet.

[0052] Example 5

[0053] This example is to use a few-layer graphene wrapped Ni catalyst to catalyze the hydrogenation of nitrobenzene to produce azobenzene oxide ( Figure 5 ), specifically including the following steps.

[0054] The few-layer graphene-wrapped Ni catalyst (Ni@G-1, Ni@G-2, Ni@G-3, Ni@G-4, 5.0-30 mg), base (one of potassium carbonate, sodium hydroxide, potassium hydroxide, sodium ethoxide, 0.1-4.0 mmol), nitrobenzene (0.5 mmol), solvent (one or a mixture of two or more of water, methanol, ethanol, tetrahydrofuran, toluene, 5.0 mL) were added to a 50 mL polytetrafluoroethylene liner, ultrasonically mixed and then placed in a reactor and sealed. After replacing the air in the reactor with hydrogen (0.1 MPa), the temperature was raised to the reaction temperature (25 °C) and the reaction was carried out for 0.5-2.0 h. After the reaction was completed, the catalyst was separated by a magnet and the product was analyzed by high performance liquid chromatography. Table 1 shows the catalytic activity of the few-layer graphene-wrapped Ni catalyst and the effects of different bases and solvents on the reaction.

[0055] Table 1

[0056]

[0057] As shown in Table 1, using 5.0 mg Ni@G-4 as catalyst, 2.0 mmol sodium hydroxide as base auxiliary, 0.5 mmol nitrobenzene, 2.0 mL water and 3.0 mL ethanol as solvent, at 25 °C and 0.1 MPa hydrogen pressure for 2.0 h, the nitrobenzene conversion rate can reach 100%, and the selectivity for azoxybenzene can reach 99.1%.

[0058] Example 6

[0059] This embodiment is a cyclic stability test of catalyzing nitrobenzene hydrogenation to produce oxyazobenzene using a few-layer graphene-wrapped Ni catalyst (Ni@G-4), which specifically includes the following steps.

[0060] 5.0 mg of Ni catalyst (Ni@G-4) wrapped with few-layer graphene, 2.0 mmol of sodium hydroxide, nitrobenzene (0.5 mmol), 2.0 mL of water and 3.0 mL of ethanol were added to 50 mL of polytetrafluoroethylene liner, ultrasonically mixed and sealed in a reactor. After replacing the air in the reactor with hydrogen (0.1 MPa), the temperature was raised to the reaction temperature (25 °C) and the reaction was continued for 2.0 h. After the reaction, the catalyst was separated by a magnet, washed with ethanol three times and then directly used for the cycle test. The product was analyzed by high performance liquid chromatography. Table 2 shows the cycle stability of nitrobenzene hydrogenation to oxyazobenzene catalyzed by Ni catalyst (Ni@G-4) wrapped with few-layer graphene.

[0061] Table 2

[0062]

[0063] As shown in Table 2, Ni@G-4 exhibits excellent catalytic activity and cyclic stability in the catalytic hydrogenation of nitrobenzene to produce oxyazobenzene. It has not been deactivated after ten cycles, and the selectivity for oxyazobenzene has always remained at >99%.

[0064] Example 7

[0065] This example is to use a few-layer graphene wrapped Ni catalyst to catalyze the hydrogenation of nitrobenzene to produce 1,2-diphenylhydrazine ( Figure 5 ), specifically including the following steps.

[0066] 5.0 mg of Ni catalyst (Ni@G-4) wrapped with few-layer graphene, sodium hydroxide (2.0~4.0 mmol), nitrobenzene (0.5 mmol), and solvent (2.0 mL of water and 3.0 mL of ethanol) were added to 50 mL of polytetrafluoroethylene liner, ultrasonically mixed and then placed in a reactor and sealed. After replacing the air in the reactor with hydrogen (0.1~ 2.0 MPa), the temperature was raised to the reaction temperature (25~60 ℃) and the reaction was carried out for 2.0~3.0 h. After the reaction, the catalyst was separated by a magnet and the product was analyzed by high performance liquid chromatography. Table 3 shows the hydrogenation of nitrobenzene to 1,2-diphenylhydrazine catalyzed by Ni catalyst (Ni@G-4) wrapped with few-layer graphene and the effects of different alkali dosages, hydrogen pressures, reaction temperatures and reaction times on the reaction.

[0067] Table 3

[0068]

[0069] As shown in Table 3, using 5.0 mg Ni@G-4 as catalyst, 4.0 mmol sodium hydroxide as base auxiliary, 0.5 mmol nitrobenzene, 2.0 mL water and 3.0 mL ethanol as solvent, at 50 °C and 1.5 MPa hydrogen pressure for 3.0 h, the nitrobenzene conversion rate can reach 100%, and the selectivity for 1,2-diphenylhydrazine can reach 99.5%.

[0070] Example 8

[0071] This embodiment is a cyclic stability test of catalyzing nitrobenzene hydrogenation to 1,2-diphenylhydrazine using a few-layer graphene-wrapped Ni catalyst (Ni@G-4), which specifically includes the following steps.

[0072] 5.0 mg of Ni catalyst (Ni@G-4) wrapped with few-layer graphene, 4.0 mmol of sodium hydroxide, nitrobenzene (0.5 mmol), 2.0 mL of water and 3.0 mL of ethanol were added to 50 mL of polytetrafluoroethylene liner, ultrasonically mixed and then sealed in a reactor. After replacing the air in the reactor with hydrogen (1.5 MPa), the temperature was raised to the reaction temperature (50 °C) and the reaction was continued for 3.0 h. After the reaction was completed, the catalyst was separated by a magnet, washed three times with ethanol and then directly used for the cycle test. The product was analyzed by high performance liquid chromatography.

[0073] Table 4 shows the cyclic stability of nitrobenzene hydrogenation to oxyazobenzene catalyzed by the few-layer graphene-wrapped Ni catalyst (Ni@G-4).

[0074] Table 4

[0075]

[0076] As shown in Table 4, Ni@G-4 exhibits excellent catalytic activity and cyclic stability in the catalytic hydrogenation of nitrobenzene to produce 1,2-diphenylhydrazine. It has not been deactivated after ten cycles, and the selectivity for 1,2-diphenylhydrazine has always remained at >99%.

[0077] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene, characterized in that The method comprises the following steps: adding a Ni catalyst wrapped with a few-layer graphene, a base, nitrobenzene and a solvent into a polytetrafluoroethylene liner, uniformly mixing the mixture by ultrasonication, loading the mixture into a reaction kettle and sealing the reaction kettle, replacing the air in the reaction kettle with hydrogen, controlling the temperature to 15 to 30° C. to react and obtain oxyazobenzene, or raising the temperature to 50 to 80° C. to react and obtain 1,2-diphenylhydrazine.

2. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 1, characterized in that: The few-layer graphene-wrapped Ni catalyst is Ni particles wrapped inside the few-layer graphene, wherein the Ni particle size is 1 to 50 nanometers, the mass content is 5% to 90%, and the few-layer graphene has 1 to 3 layers.

3. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 2, characterized in that: The few-layer graphene-wrapped Ni catalyst is prepared by using metal salt, organic amine and carbon source as raw materials and hydrothermally treating the precursor, calcining the precursor in a N2 atmosphere and then treating the catalyst with a sulfuric acid solution.

4. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 3, characterized in that: The metal salt is one of nickel acetate, nickel nitrate, nickel sulfate, and nickel chloride, or a mixture of two or more thereof; the organic amine is one of ethanolamine, urea, dicyandiamide, and hexamethylenetetramine, or a mixture of two or more thereof; and the carbon source is one of furfural, furfuryl alcohol, glycerol, glucose, fructose, and lactose, or a mixture of two or more thereof.

5. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 3, characterized in that: The molar ratio of the metal salt, the organic amine and the carbon source is 1:(0.5-2.0):(2.5-5.5).

6. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 3, characterized in that: The reaction conditions of the hydrothermal treatment are 100-180°C for 2.0-24.0h; the calcination conditions are heating to 400-800°C at 3.0-5.0°C / min and maintaining for 2.0-8.0h; the concentration of the sulfuric acid solution is 0.1-2.0M, the temperature is 25-80°C, and the treatment time is 2.0-24.0h.

7. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 1, characterized in that: The dosage ratio of the few-layer graphene-wrapped Ni catalyst: base: nitrobenzene: solvent is: (5.0-30 mg): (0.1-4.0 mmol): 0.5 mmol: 5.0 mL.

8. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 1, characterized in that: The base is potassium carbonate, sodium hydroxide, potassium hydroxide or sodium ethoxide.

9. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 1, characterized in that: The solvent is one or a mixture of two or more of water, methanol, ethanol, tetrahydrofuran and toluene.

10. The method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenating nitrobenzene according to claim 1, characterized in that: The hydrogen pressure is 0.1-2.0 MPa, and the reaction time is 0.5-3.0 h.

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