A method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene

Abstract

The application discloses a method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene, which comprises the following steps: adding an oligolayer graphene wrapped Ni catalyst, an alkali, nitrobenzene and a solvent into a polytetrafluoroethylene lining, uniformly mixing by ultrasonic and then sealing into a reaction kettle, replacing the air in the reaction kettle with hydrogen, controlling the temperature to 15-30 DEG C to prepare azoxybenzene, or increasing the temperature to 50-80 DEG C to prepare 1,2-diphenylhydrazine. The oligolayer graphene wrapped Ni catalyst is applied to catalyze the hydrogenation of nitrobenzene to prepare azoxybenzene. The catalyst has the advantages of simple synthesis route, cheap and easily available raw materials, simple reaction condition, easy operation, cheap and easily available nitrobenzene and high economic benefit. The obtained oligolayer graphene wrapped Ni catalyst has the advantages of mild reaction condition, high selectivity to products, easy separation and recovery and good cycle stability in the preparation of azoxybenzene or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of organic synthesis, in particular to a method for selectively preparing azoxybenzene or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene. BACKGROUND

[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. Currently, the industrial production of aromatic azoxy / azo compounds usually adopts the scheme of oxidizing aromatic amines with strong oxidants. In contrast, the route of one-pot hydrogenation coupling to prepare aromatic azoxy / azo compounds from cheap and readily available nitroarenes is more economical, efficient and environmentally friendly. However, the reduction of nitroarenes involves a multi-step hydrogenation process, which produces a series of intermediates such as nitrosoarenes, hydroxylamines, azoxybenzene, azobenzene and hydrazine, and nitrosoarenes and hydroxylamines are easily further hydrogenated to anilines, resulting in a decrease in the selectivity of the target product. Therefore, controlling the hydrogenation process of nitroarenes with catalysts to obtain aromatic azoxy / azo compounds with high selectivity has become a problem to be solved.

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

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

[0005] The purpose of the present application is to overcome the defects of the prior art and provide a method for selectively preparing azobenzene or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme: a method for selectively preparing azobenzene or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene, characterized by comprising the following steps: adding oligolayer graphene-wrapped Ni catalyst, base, nitrobenzene and solvent into a polytetrafluoroethylene liner, mixing uniformly by ultrasonic and then sealing in a reaction kettle, replacing the air in the reaction kettle with hydrogen, controlling the temperature to 15-30 DEG C to prepare azobenzene, or increasing the temperature to 50-80 DEG C to prepare 1,2-diphenylhydrazine.

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

[0008] Further, the oligolayer graphene-wrapped Ni catalyst is prepared by using metal salt, organic amine and carbon source as raw materials, hydrothermal treatment to obtain a precursor, calcining the precursor in N2 atmosphere, and then treating with sulfuric acid solution.

[0009] Further, 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] Further, 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] Further, the reaction conditions of the hydrothermal treatment are 100-180 ℃ for 2.0-24.0 h; the conditions of the calcination are 3.0-5.0 ℃ / min to 400-800 ℃, keeping for 2.0-8.0 h; the concentration of the sulfuric acid solution is 0.1-2.0 M, the temperature is 25-80 ℃, and the treatment time is 2.0-24.0 h.

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

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

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

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

[0016] The oligolayer graphene wrapped Ni catalyst is used for catalyzing the hydrogenation of nitrobenzene to prepare azoxybenzene. The catalyst has the advantages of simple synthesis route, cheap and easily available raw materials, simple reaction conditions, easy operation, cheap and easily available nitrobenzene, high economic benefit, mild reaction conditions, high selectivity to the product, easy separation and recovery, good cycle stability and the like. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Fig. 1 is an XRD spectrum of the oligolayer graphene wrapped Ni catalyst prepared in Examples 1-4 of the present application.

[0018] Figure 2 Fig. 2 is a transmission electron microscope (TEM) photo of the oligolayer graphene wrapped Ni catalyst prepared in Examples 1-4 of the present application.

[0019] Figure 3 Fig. 3 is a high-resolution TEM photo of the oligolayer graphene wrapped Ni catalyst prepared in Examples 1-4 of the present application.

[0020] Figure 4 Fig. 4 is a photo of the oligolayer graphene wrapped Ni catalyst prepared in Example 4 of the present application separated by a magnet.

[0021] Figure 5is a flow chart for preparing azoxybenzene and 1,2-diphenylhydrazine by hydrogenation of nitrobenzene. DETAILED DESCRIPTION

[0022] In order to better understand the technical scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present application.

[0023] It should be noted that the terms "comprising" and "having" and any variations thereof in the specification and claims of the present application and the above-described accompanying drawings are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device comprising a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0024] Embodiment 1

[0025] The present embodiment is a preparation method of an oligolayer graphene-wrapped Ni catalyst for catalyzing hydrogenation of nitrobenzene to prepare azoxybenzene or 1,2-diphenylhydrazine, specifically comprising the following steps.

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

[0027] (2) Place the obtained solution in a polytetrafluoroethylene hydrothermal kettle, seal it, and then place it in a 100 ℃ oven for hydrothermal treatment for 24.0 h. After the hydrothermal reaction is completed, centrifugally separate the obtained solid product, and place it in an 80 ℃ oven for drying for 12.0 h.

[0028] (3) Place the dried solid product obtained in (2) in a N2 atmosphere, heat it to 400 ℃ at a rate of 3.0 ℃ / min, and maintain it at 400 ℃ for 8.0 h.

[0029] (4) After calcination, the obtained sample is treated with 0.1 M hydrochloric acid at 25 ℃ for 24.0 h, and finally washed with deionized water and anhydrous ethanol, and dried at 80 ℃ to obtain the Ni@G-1 catalyst.

[0030] Embodiment 2

[0031] The present embodiment is a preparation method of an oligolayer graphene-wrapped Ni catalyst for catalyzing hydrogenation of nitrobenzene to prepare azoxybenzene or 1,2-diphenylhydrazine, specifically comprising the following steps.

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

[0033] (2) The obtained solution was placed in a polytetrafluoroethylene hydrothermal kettle, and after sealing, it was placed in a 150 ℃ oven for hydrothermal treatment for 18.0 h. After the hydrothermal reaction was completed, the obtained solid product was centrifuged and dried in an 80 ℃ oven for 12.0 h.

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

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

[0036] Example 3

[0037] The present embodiment is a preparation method of an oligolayer graphene-wrapped Ni catalyst for catalyzing the hydrogenation of nitrobenzene to produce azoxybenzene and 1,2-diphenylhydrazine, which specifically comprises the following steps.

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

[0039] (2) The obtained solution was placed in a polytetrafluoroethylene hydrothermal kettle, and after sealing, it was placed in a 170 ℃ oven for hydrothermal treatment for 10.0 h. After the hydrothermal reaction was completed, the obtained solid product was centrifuged and dried in an 80 ℃ oven for 12.0 h.

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

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

[0042] Example 4

[0043] The present embodiment is a preparation method of an oligolayer graphene-wrapped Ni catalyst for catalyzing the hydrogenation of nitrobenzene to produce azoxybenzene and 1,2-diphenylhydrazine, which specifically comprises the following steps.

[0044] (1) Respectively take 0.5 mmol of nickel chloride, 0.5 mmol of nickel nitrate, 3.5 mmol of hexamethylenetetramine and 7.0 mmol of lactose in 60 mL of deionized water, and stir to dissolve.

[0045] (2) The obtained solution was placed in a polytetrafluoroethylene hydrothermal kettle, and after sealing, it was placed in a 180 ℃ oven for hydrothermal treatment for 5.0 h. After the hydrothermal reaction was completed, the obtained solid product was centrifuged and placed in a 80 ℃ oven for drying for 12.0 h.

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

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

[0048] Figure 1 The XRD patterns of the catalysts Ni@G-1, Ni@G-2, Ni@G-3 and Ni@G-4 prepared in Examples 1-4 were prepared. From the figure, a broad peak around 26° appeared, indicating that the Ni@G had a graphite carbon structure. The diffraction peaks at 44.4°, 51.8° and 76.8° corresponded to the characteristic peaks of metallic nickel, indicating that the catalyst still had Ni remaining after being subjected to strong acid washing, and the Ni was in a metallic state.

[0049] Figure 2 The transmission electron micrographs of the catalysts Ni@G-1, Ni@G-2, Ni@G-3 and Ni@G-4 prepared in Examples 1-4 were prepared. From the figure, it can be seen that the four catalysts all presented a flower cluster structure, and the Ni particles were uniformly distributed therein.

[0050] Figure 3 The high-resolution transmission electron micrographs of the catalysts Ni@G-1, Ni@G-2, Ni@G-3 and Ni@G-4 prepared in Examples 1-4 were prepared. From the figure, it can be seen that the Ni in the four catalysts was in a state of being wrapped by few-layer graphene.

[0051] Figure 4 The photo of the few-layer graphene-wrapped Ni catalyst prepared in Example 4 of the application using a magnet for separation was prepared, and from the figure, it can be seen that the few-layer graphene-wrapped Ni catalyst involved in the application has magnetic properties and can be quickly separated by a magnet.

[0052] Example 5

[0053] This example is the application of the few-layer graphene-wrapped Ni catalyst to catalyze the hydrogenation of nitrobenzene to prepare azoxybenzene (Benzene Figure 5 ), which specifically includes the following steps.

[0054] The oligolayer 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, and the amount is 0.1-4.0 mmol), nitrobenzene (0.5 mmol), solvent (one of water, methanol, ethanol, tetrahydrofuran, toluene or a mixture of two or more, and the amount is 5.0 mL) are added into a 50 mL polytetrafluoroethylene liner, and then ultrasonic mixing is performed to obtain a uniform mixture, which is then sealed in a reaction kettle. After the air in the reaction kettle is replaced with hydrogen (0.1 MPa), the temperature is raised to the reaction temperature (25°C), and the reaction is carried out for 0.5-2.0 h. After the reaction is completed, the catalyst is separated by a magnet, and the product is analyzed by high performance liquid chromatography. Table 1 shows the catalytic activity of the oligolayer graphene wrapped Ni catalyst and the influence of different bases and solvents on the reaction.

[0055] Table 1

[0056]

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

[0058] Example 6

[0059] This example is a cyclic stability test of the oligolayer graphene wrapped Ni catalyst (Ni@G-4) for catalyzing the hydrogenation of nitrobenzene to azoxybenzene, which specifically includes the following steps.

[0060] 5.0 mg of the oligolayer graphene wrapped Ni catalyst (Ni@G-4), 2.0 mmol of sodium hydroxide, 0.5 mmol of nitrobenzene, 2.0 mL of water and 3.0 mL of ethanol are added into a 50 mL polytetrafluoroethylene liner, and then ultrasonic mixing is performed to obtain a uniform mixture, which is then sealed in a reaction kettle. After the air in the reaction kettle is replaced with hydrogen (0.1 MPa), the temperature is raised to the reaction temperature (25°C), and the reaction is carried out for 2.0 h. After the reaction is completed, the catalyst is separated by a magnet, and the product is analyzed by high performance liquid chromatography. Table 2 shows the cyclic stability of the oligolayer graphene wrapped Ni catalyst (Ni@G-4) for catalyzing the hydrogenation of nitrobenzene to azoxybenzene.

[0061] Table 2

[0062]

[0063] As shown in Table 2, Ni@G-4 exhibits superior catalytic activity and cyclic stability in the reaction of catalyzing hydrogenation of nitrobenzene to prepare azoxybenzene, and does not deactivate after ten cycles, and the selectivity to azoxybenzene remains >99%.

[0064] Example 7

[0065] This example is the application of oligolayer graphene-wrapped Ni catalyst to catalyze hydrogenation of nitrobenzene to prepare 1,2-diphenylhydrazine (Diphenylhydrazine, DPH), which specifically includes the following steps. Figure 5

[0066] 5.0 mg of oligolayer graphene-wrapped Ni catalyst (Ni@G-4), 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 a 50 mL polytetrafluoroethylene liner, and after ultrasonic mixing, they were sealed in a reaction kettle. After replacing the air in the reaction kettle 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 was completed, the catalyst was separated using a magnet, and the product was analyzed using high-performance liquid chromatography. Table 3 shows the effects of different amounts of base, hydrogen pressure, reaction temperature, and reaction time on the reaction of oligolayer graphene-wrapped Ni catalyst (Ni@G-4) catalyzing hydrogenation of nitrobenzene to prepare 1,2-diphenylhydrazine.

[0067] Table 3

[0068]

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

[0070] Example 8

[0071] This example is the cyclic stability test of oligolayer graphene-wrapped Ni catalyst (Ni@G-4) in the reaction of catalyzing hydrogenation of nitrobenzene to prepare 1,2-diphenylhydrazine, which specifically includes the following steps.

[0072] ​5.0 mg of oligolayer graphene-wrapped Ni catalyst (Ni@G-4), 4.0 mmol of sodium hydroxide, nitrobenzene (0.5 mmol), 2.0 mL of water and 3.0 mL of ethanol were added into a 50 mL polytetrafluoroethylene liner, and after ultrasonic mixing, they were sealed in a reaction kettle. After replacing the air in the reaction kettle with hydrogen (1.5 MPa), the temperature was raised to the reaction temperature (50 °C), and the reaction was carried out for 3.0 h. After the reaction was completed, the catalyst was separated using a magnet and washed with ethanol three times before being directly used for the recycling test. The product was analyzed using high-performance liquid chromatography.

[0073] Table 4 is the recycling stability of the oligolayer graphene-wrapped Ni catalyst (Ni@G-4) in the catalytic hydrogenation of nitrobenzene to prepare azoxybenzene.

[0074] Table 4

[0075]

[0076] As can be seen from Table 4, Ni@G-4 exhibits superior catalytic activity and recycling stability in the reaction of catalytic hydrogenation of nitrobenzene to prepare 1,2-diphenylhydrazine, and after being used for ten cycles, it does not deactivate, and the selectivity to 1,2-diphenylhydrazine remains >99%.

[0077] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene, characterized in that The method comprises the following steps: adding oligolayer graphene wrapped Ni catalyst, alkali, nitrobenzene and solvent into a polytetrafluoroethylene inner liner, mixing uniformly under ultrasonic, loading into a reaction kettle for sealing, replacing air in the reaction kettle with hydrogen, controlling temperature to 15-30 DEG C for reaction to prepare azobenzene or controlling temperature to 50-80 DEG C for reaction to prepare 1,2-diphenylhydrazine. The oligolayer graphene wrapped Ni catalyst is prepared by using metal salt, organic amine and carbon source as raw materials, and by hydrothermal treatment to obtain a precursor, and by calcining the precursor in a N2 atmosphere and then treating with a sulfuric acid solution. 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.

2. The process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene according to claim 1, characterized in that: The oligolayer graphene wrapped Ni catalyst is Ni particles wrapped in oligolayer graphene, wherein the size of the Ni particles is 1-50 nanometers, the mass content of the Ni particles is 5%-90%, and the number of layers of the oligolayer graphene is 1-3.

3. The process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene according to claim 1, 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).

4. The process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene according to claim 1, characterized in that: The reaction conditions of the hydrothermal treatment are 100-180 DEG C for 2.0-24.0 h; the calcination conditions are 3.0-5.0 DEG C / min to 400-800 DEG C, keeping for 2.0-8.0 h; the concentration of the sulfuric acid solution is 0.1-2.0 M, the temperature is 25-80 DEG C, and the treatment time is 2.0-24.0 h.

5. The process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene according to claim 1, characterized in that: The amount ratio of the oligolayer graphene wrapped Ni catalyst, the alkali, the nitrobenzene and the solvent is (5.0-30 mg): (0.1-4.0 mmol): 0.5 mmol: 5.0 mL.

6. The process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of nitrobenzene according to claim 1, characterized in that: The alkali is potassium carbonate, sodium hydroxide, potassium hydroxide or sodium ethoxide.

7. The process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of 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.

8. The process for the selective production of phenyl azo oxide or 1,2-diphenylhydrazine by hydrogenation of 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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