A method for photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine
Patent Information
- Application Number
- CN202611322752.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-28
- Publication Date
- 2026-11-03
AI Technical Summary
In existing technologies, the selective production yield of N-phenylhydroxylamine is low, and traditional metal reduction methods lead to environmental pollution.
A carbon nitride photocatalyst with surface-modified cyano and methyl groups was prepared by annealing melamine and trithiocyanate in ethanol and then reacting it with a thioacetamide solution via hydrothermal reaction. This photocatalyst was used to react with nitrobenzene, hydrazine hydrate and isopropanol under visible light to achieve highly selective reduction of nitrobenzene.
The photocatalyst achieves highly selective reduction of nitrobenzene to N-phenylhydroxylamine under mild reaction conditions, with a product selectivity of around 90%. The photocatalyst is simple to prepare, suitable for mass production, and has an apparent quantum efficiency of up to 4%. The performance of the photocatalyst is superior to that of other methods.
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Abstract
Description
Technical Field
[0001] This invention relates to the fields of photocatalysis and organic synthesis technology, specifically to a method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine. Background Technology
[0002] N-Phenylated hydroxylamine is a very important organic synthesis intermediate. Its application value stems from its unique molecular structure, which contains both NH and OH hydrogen donor sites, endowing it with excellent reactivity. Its reactivity is highly dependent on the pH environment of the system. Under acidic conditions, it readily undergoes rearrangement to form p-aminophenol; under alkaline conditions, it readily undergoes condensation reactions to form azo derivatives. Therefore, highly selective preparation of N-phenylhydroxylamine usually requires strict control of reaction conditions.
[0003] Industrially, nitrobenzene is mainly produced by the reduction of nitrobenzene with zinc powder. This process generates a large amount of metal waste, leading to environmental damage. Using photocatalysis to hydrogenate nitrobenzene to N-phenylhydroxylamine aligns with current green chemistry development principles. However, due to the numerous intermediates involved in this reaction and the involvement of multiple electron-proton transfers, the selective formation of N-phenylhydroxylamine places extremely high demands on the reaction system design. Therefore, a new, highly efficient photocatalyst is urgently needed. Summary of the Invention
[0004] To address the aforementioned technical problems, the present invention aims to provide a method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine, thereby solving the problem of low selective yield of existing N-phenylhydroxylamine production.
[0005] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A method for preparing a catalyst for the photocatalytic selective reduction of nitrobenzene to N-phenylhydroxylamine is provided, comprising the following steps: (1) Melamine and cyanuric acid were stirred evenly in ethanol, dried, and then annealed to obtain a light yellow product; (2) The light yellow product obtained in step (1) is mixed with thioacetamide solution, and then subjected to hydrothermal reaction. The yellow precipitate is then recovered, washed, and dried to obtain a photocatalytic selective reduction catalyst for the preparation of N-phenylhydroxylamine from nitrobenzene.
[0006] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, in step (1), the mass ratio of melamine to thiocyanate is 2.5:7.5.
[0007] Furthermore, in step (1), the sample is annealed at 550°C for 4 hours.
[0008] Furthermore, annealing was carried out at a heating rate of 3 °C / min.
[0009] Furthermore, in step (2), the mass-to-volume ratio of the light yellow product to the thioacetamide solution is 0.5 g: 50 mL. Furthermore, the concentration of the thioacetamide solution is 0.25 mol / L.
[0010] Furthermore, in step (2), the hydrothermal reaction is carried out at 160°C for 10 hours.
[0011] Furthermore, in step (2), ethanol is used for washing.
[0012] Furthermore, in step (2), the product is dried at 60°C for 10 hours.
[0013] The present invention also provides a photocatalytic selective reduction catalyst for the preparation of N-phenylhydroxylamine by the above method.
[0014] The present invention also provides the application of the above-mentioned photocatalytic selective reduction catalyst for nitrobenzene to N-phenylhydroxylamine in the photocatalytic selective reduction of nitrobenzene to N-phenylhydroxylamine.
[0015] The present invention also provides a method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine, using the above-mentioned photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine catalyst as the catalyst.
[0016] Furthermore, nitrobenzene, hydrazine hydrate, isopropanol, and the above-mentioned photocatalytic selective reduction catalyst for nitrobenzene to prepare N-phenylhydroxylamine are mixed, and the hydrogenation reaction of nitrobenzene to prepare N-phenylhydroxylamine is carried out under visible light irradiation and argon atmosphere.
[0017] Furthermore, the mass-to-volume ratio of the catalyst for the photocatalytic selective reduction of nitrobenzene to N-phenylhydroxylamine and isopropanol is 10-50 mg: 1.5-50 mL.
[0018] Furthermore, the mass-to-volume ratio of the catalyst for the photocatalytic selective reduction of nitrobenzene to N-phenylhydroxylamine and isopropanol was 30 mg: 1.5 mL.
[0019] Furthermore, the light intensity is 0.1-0.3 W / cm². 2 .
[0020] Furthermore, the light intensity is 0.3 W / cm². 2 .
[0021] Furthermore, the molar volume ratio of nitrobenzene to isopropanol is 0.03-1 mmol: 1.5-50 mL.
[0022] Furthermore, the molar volume ratio of nitrobenzene to isopropanol is 0.03 mmol: 1.5 mL.
[0023] Furthermore, the molar ratio of nitrobenzene to hydrazine hydrate is 1:1-30.
[0024] Furthermore, the molar ratio of nitrobenzene to hydrazine hydrate is 1:20.
[0025] The present invention has the following beneficial effects: 1. Based on the traditional metal reduction of nitrobenzene to prepare N-phenylhydroxylamine, this invention innovatively introduces carbon nitride to absorb light and convert it into high-energy electrons and holes. The synergistic effect of the surface-modified cyano and methyl groups promotes the separation of photogenerated charges and the adsorption of nitrobenzene molecules, thereby selectively reducing nitrobenzene to N-phenylhydroxylamine.
[0026] 2. This invention can achieve highly selective reduction of nitrobenzene to N-phenylhydroxylamine under mild reaction conditions, and the product selectivity is basically unaffected in substrate scale-up tests.
[0027] 3. Under visible light irradiation, this invention uses carbon nitride co-modified with methyl and cyano groups as a photocatalyst and hydrazine hydrate as a hydrogen source to achieve highly efficient and selective conversion of nitrobenzene to N-phenylhydroxylamine under low temperature and normal pressure conditions. The selectivity of the main product N-phenylhydroxylamine is about 90%. The photocatalyst preparation method is simple and suitable for mass production.
[0028] 4. The method for the efficient and highly selective conversion of nitrobenzene to N-phenylhydroxylamine driven by visible light provided by the present invention achieves highly selective generation of N-phenylhydroxylamine under near room temperature and normal pressure conditions by modifying the surface of carbon nitride with synergistic modification of cyano and methyl groups, and controlling the amount of reducing agent hydrazine hydrate, the amount of photocatalyst, and the intensity of incident light. The apparent quantum efficiency of this process can reach 4% under 460 nm blue light. Attached Figure Description
[0029] Figure 1 SEM images of the four catalysts in Example 1 and Comparative Examples 1-3; Figure 2 The IR spectra of the four catalysts in Example 1 and Comparative Examples 1-3 are shown below. Figure 3 The XRD patterns are of the four catalysts in Example 1 and Comparative Examples 1-3; Figure 4 For the four catalysts in Example 1 and Comparative Examples 1-3 13 C solid-state NMR spectrum; Figure 5 The graphs show the performance evaluation of the four catalysts in Example 1 and Comparative Examples 1-3. Figure 6 The effects of hydrazine hydrate feed amount on nitrobenzene conversion rate and product selectivity in Examples 1-8; Figure 7The effects of photocatalyst dosage on nitrobenzene conversion and product selectivity in Examples 1 and 9-10; Figure 8 The effects of incident light intensity on nitrobenzene conversion and product selectivity in Examples 1 and 11-14; Figure 9 The relationship between apparent quantum efficiency and incident light wavelength is shown in Examples 1 and 15-17; Figure 10 The reaction kinetics curve for the conversion of nitrobenzene to N-phenylhydroxylamine in Example 1 is shown. Figure 11 The performance data for the CCN-cy catalyst in Example 1 after 5 cycles are as follows; Figure 12 The reaction kinetics curve for the conversion of nitrobenzene to N-phenylhydroxylamine in Example 18 is shown. Detailed Implementation
[0030] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.
[0031] Example 1: A method for preparing a catalyst for the photocatalytic selective reduction of nitrobenzene to N-phenylhydroxylamine includes the following steps: (1) Melamine and cyanuric acid were stirred evenly in ethanol at a mass ratio of 2.5:7.5 and dried thoroughly to obtain a yellow mixture. The yellow mixture was then annealed at 550 °C at a heating rate of 3 °C / min for 4 h to obtain a light yellow product. (2) The light yellow product obtained in step (1) was mixed with thioacetamide solution (concentration of 0.25 mol / L) at a mass-volume ratio of 0.5 g: 50 mL. The mixture was then subjected to hydrothermal reaction at 160 °C for 10 h. After the solution cooled, the upper turbid solution was discarded, the yellow precipitate was recovered, and the solution was washed repeatedly with ethanol and dried at 60 °C for 10 h to obtain a photocatalytic selective reduction catalyst for the preparation of N-phenylhydroxylamine from nitrobenzene, named CCN-cy.
[0032] A method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine includes the following steps: Nitrobenzene (0.03 mmol, substrate), hydrazine hydrate (reducing agent, molar ratio to nitrobenzene 1:20), isopropanol (1.5 mL, solvent), and CCN-cy (30 mg, photocatalyst) were mixed and irradiated with visible light (light intensity 0.3 W / cm²). 2The hydrogenation of nitrobenzene to prepare N-phenylhydroxylamine was carried out at 60℃ under an argon atmosphere.
[0033] Examples 2-8: A method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine includes the following steps: Nitrobenzene (0.03 mmol, substrate), hydrazine hydrate (reducing agent) in molar ratios of 1:1, 1:2, 1:4, 1:6, 1:10, 1:15, and 1:30 to nitrobenzene, along with isopropanol (1.5 mL, solvent) and CCN-cy (30 mg, photocatalyst), were mixed and irradiated with visible light (0.3 W / cm²). 2 The reaction to prepare N-phenylhydroxylamine by hydrogenation of nitrobenzene was carried out at 60 °C under an argon atmosphere for 45 min.
[0034] Examples 9-10: A method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine includes the following steps: Nitrobenzene (0.03 mmol, substrate), hydrazine hydrate (reducing agent, molar ratio to nitrobenzene 1:20), isopropanol (1.5 mL, solvent), and CCN-cy (10 mg, 50 mg, photocatalyst) were mixed and irradiated with visible light (light intensity 0.3 W / cm²). 2 The reaction to prepare N-phenylhydroxylamine by hydrogenation of nitrobenzene was carried out at 60 °C under an argon atmosphere for 45 min.
[0035] Examples 11-14: A method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine includes the following steps: Nitrobenzene (0.03 mmol, substrate), hydrazine hydrate (reducing agent, molar ratio to nitrobenzene 1:20), isopropanol (1.5 mL, solvent), and CCN-cy (30 mg, photocatalyst) were mixed and irradiated with visible light (light intensity 0.1 W / cm²). 2 0.15W / cm 2 0.2 W / cm 2 0.25 W / cm 2 The reaction to prepare N-phenylhydroxylamine by hydrogenation of nitrobenzene was carried out at 60 °C under an argon atmosphere for 45 min.
[0036] Examples 15-17: A method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine includes the following steps: Nitrobenzene (0.03 mmol, substrate), hydrazine hydrate (reducing agent, molar ratio with nitrobenzene 1:20), isopropanol (1.5 mL, solvent), and CCN-cy (30 mg, photocatalyst) were mixed and the apparent quantum efficiency (AQE) was measured under illumination from blue (425-510 nm, emission center wavelength 459 nm), green (475-600 nm, emission center wavelength 525 nm), and red (585-655 nm, emission center wavelength 626 nm) light sources, respectively, with the light intensity controlled at 0.1 W / cm². 2 The hydrogenation of nitrobenzene to prepare N-phenylhydroxylamine was carried out at 60 °C under an argon atmosphere for 60 min.
[0037] Example 18: A method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine includes the following steps: Nitrobenzene (1 mmol, substrate), hydrazine hydrate (15 mmol, reducing agent), isopropanol (50 mL, solvent), and CCN-cy (300 mg, photocatalyst) were mixed and irradiated under visible light (simultaneous irradiation by three LEDs, each with a light intensity of 0.3 W / cm²). 2 The reaction to prepare N-phenylhydroxylamine by hydrogenation of nitrobenzene was carried out at 60℃ under an argon atmosphere for a total reaction time of 7 hours. Samples were taken at regular intervals during the reaction.
[0038] Comparative Example 1: A method for preparing a catalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine includes the following steps: 10 g of melamine was annealed at 550 °C for 4 h at a heating rate of 3 °C / min to obtain a light yellow product, which was named CN.
[0039] Comparative Example 2: A method for preparing a catalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine includes the following steps: 50 mL of 0.25 mol / L thioacetamide aqueous solution was hydrothermally heated with 0.5 g CN (Comparative Example 1) at 160 °C for 10 h. After the solution cooled, the upper turbid solution was discarded, the yellow precipitate was recovered, and the precipitate was washed repeatedly with ethanol. The final product was dried at 60 °C for 10 h to obtain the product, which was named CCN.
[0040] Comparative Example 3: A method for preparing a catalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine includes the following steps: Melamine and cyanuric acid were mixed in ethanol at a mass ratio of 2.5:7.5 and dried thoroughly to obtain a yellow mixture. The yellow mixture was then annealed at 550 °C at a heating rate of 3 °C / min for 4 h to obtain a light yellow product, named CN-cy.
[0041] Test case The following figures are interpreted as follows: Azo azobenzene, Azoxy azobenzene, NSB nitrosobenzene, ANL aniline, PHAN-phenylhydroxylamine, Conv conversion, and Yield yield.
[0042] I. The CCN-cy prepared in Example 1, the CN prepared in Comparative Example 1, the CCN prepared in Comparative Example 2, and the CN-cy prepared in Comparative Example 3 were subjected to SEM, IR, and XRD. 13 C solid-state NMR detection and performance evaluation results are shown in Figure 1-5 ( Figure 1 In the diagram, (a) represents CN, (b) represents CN-cy, (c) represents CCN, and (d) represents CCN-cy.
[0043] Depend on Figure 1 It can be seen that the CN prepared in Comparative Example 1 and the CN-cy prepared in Comparative Example 3 exhibit blocky morphology, the CCN prepared in Comparative Example 2 exhibits clustered stacking morphology, and the CCN-cy prepared in Example 1 exhibits lamellar stacking morphology.
[0044] Depend on Figure 2 It can be seen that the CCN-cy prepared in Example 1, the CN prepared in Comparative Example 1, the CCN prepared in Comparative Example 2, and the CN-cy prepared in Comparative Example 3 all maintain the typical heptazine ring structure framework vibration peaks of carbon nitride. The peaks of CCN and CCN-cy at 1465 and 2900 cm⁻¹ are also significant. - The significantly enhanced peak at ¹ indicates that alkyl groups were successfully introduced onto the carbon nitride surface. Meanwhile, a peak at approximately 2170 cm⁻¹ was observed in CN-cy. - The new peak at ¹ belongs to the asymmetric stretching vibration of the cyano group. This peak does not change significantly in CCN-cy, which means that the cyano group has been successfully preserved.
[0045] Depend on Figure 3 It can be seen that the CCN-cy prepared in Example 1, the CN prepared in Comparative Example 1, the CCN prepared in Comparative Example 2, and the CN-cy prepared in Comparative Example 3 all exhibit typical characteristic peaks of carbon nitride: diffraction peaks located at the (002) crystal plane at 27.5° and the (100) crystal plane at 12.7°, indicating that the heptaazine ring structural unit of carbon nitride can be well preserved after modification.
[0046] Depend on Figure 4It can be seen that the CCN-cy prepared in Example 1, the CN prepared in Comparative Example 1, the CCN prepared in Comparative Example 2, and the CN-cy prepared in Comparative Example 3 all exhibit two strong signals, located at 155.9 and 163.9 ppm, respectively, corresponding to C3N (C1) and C2N-NH in the carbon nitride framework. x (C2) proves that the main structure of carbon nitride remains intact after modification.
[0047] Depend on Figure 5 It can be seen that among the four samples, CCN-cy exhibited the best hydrogenation performance of nitrobenzene. After 45 min of reaction, the conversion rate of nitrobenzene reached 80.5%, and the selectivity of N-phenylhydroxylamine remained at 87.7%.
[0048] II. Hydrazine hydrate feeding ratio The conversion rates and products of nitrobenzene in Examples 1-8 were detected using high-performance liquid chromatography (HPLC) (ZORBAX SB-C18 column, 4.6 × 150 mm, mobile phase: a mixture of methanol and water). Results are shown below. Figure 6 .
[0049] Depend on Figure 6 It can be seen that the suitable molar ratio of nitrobenzene to hydrazine hydrate is 1:20.
[0050] III. Photocatalyst Dosage The conversion rate and products of nitrobenzene in Examples 1 and 9-10 were detected by high-performance liquid chromatography (HPLC) using a ZORBAX SB-C18 column (4.6 × 150 mm) and a mobile phase of a mixture of methanol and water. The results are shown in [Figure number missing]. Figure 7 .
[0051] Depend on Figure 7 It can be seen that the conversion rate of nitrobenzene is highest when the amount of CCN-cy is 30 mg. At this time, the yield of PHA also reaches its maximum value.
[0052] IV. Incident light intensity The conversion rate and products of nitrobenzene in Examples 1 and 11-14 were detected by high-performance liquid chromatography (HPLC) using a ZORBAX SB-C18 column (4.6 × 150 mm) and a mobile phase of a mixture of methanol and water. The results are shown in [Figure number missing]. Figure 8 .
[0053] Depend on Figure 8 It can be seen that the conversion rate of nitrobenzene on CCN-cy is directly related to the light intensity, and the conversion rate increases with the increase of light intensity.
[0054] V. Incident light wavelength The apparent quantum efficiency in Examples 15-17 was determined using high-performance liquid chromatography (HPLC) (ZORBAX SB-C18 column, 4.6 × 150 mm, mobile phase: a mixture of methanol and water). The results are shown below. Figure 9 .
[0055] Depend on Figure 9 It can be seen that the apparent quantum efficiency (AQE) of nitrobenzene conversion is in very good agreement with the CCN-cy UV-diffuse reflectance absorption spectrum, indicating that this is a photocatalytic reaction process. Under blue light, the AQE can reach 4%.
[0056] VI. Kinetic Curves of Example 1 The reaction kinetics of the conversion of nitrobenzene to N-phenylhydroxylamine in Example 1 were analyzed using high-performance liquid chromatography (HPLC) (ZORBAX SB-C18 column, 4.6 × 150 mm, mobile phase: a mixture of methanol and water). Results are shown below. Figure 10 .
[0057] Depend on Figure 10 It can be seen that after 1 hour of reaction on the surface of CCN-cy catalyst, nitrobenzene has been completely converted, and after 3 hours of reaction, the selectivity of N-phenylhydroxylamine can still be maintained above 80%, and it will not undergo further coupling or conversion into aniline.
[0058] VII. Cyclic Stability The CCN-cy catalyst from Example 1 was recycled 5 times, with each reaction lasting 1 hour. The conversion rate of nitrobenzene and the product selectivity were measured, and the results are shown below. Figure 11 .
[0059] Depend on Figure 11 It can be seen that after five cycles of reaction, the CCN-cy catalyst still exhibits excellent performance.
[0060] VIII. Kinetic Curves of Example 18 The reaction kinetics of the conversion of nitrobenzene to N-phenylhydroxylamine in Example 18 were analyzed using high-performance liquid chromatography (HPLC) (ZORBAX SB-C18 column, 4.6 × 150 mm, mobile phase: a mixture of methanol and water). The results are shown in [Figure number missing]. Figure 12 .
[0061] Depend on Figure 12 It can be seen that, without optimized design, after 7 hours of reaction, the selectivity of N-phenylhydroxylamine can still be maintained at around 90% after nitrobenzene is completely converted.
[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing a catalyst for the photocatalytic selective reduction of nitrobenzene to N-phenylhydroxylamine, characterized in that, Includes the following steps: (1) Melamine and cyanuric acid were stirred evenly in ethanol, dried, and then annealed to obtain a light yellow product; (2) The light yellow product obtained in step (1) is mixed with thioacetamide solution, and then subjected to hydrothermal reaction. The yellow precipitate is then recovered, washed, and dried to obtain a photocatalytic selective reduction catalyst for the preparation of N-phenylhydroxylamine from nitrobenzene.
2. The method for preparing the photocatalytic selective reduction catalyst for N-phenylhydroxylamine according to claim 1, characterized in that, In step (1), the mass ratio of melamine to thiocyanate is 2.5:7.
5.
3. The method for preparing the photocatalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine according to claim 1, characterized in that, In step (1), the sample is annealed at 550°C for 4 hours.
4. The method for preparing the photocatalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine according to claim 1, characterized in that, In step (2), the mass-to-volume ratio of the light yellow product to the thioacetamide solution is 0.5 g: 50 mL.
5. The method for preparing the photocatalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine according to claim 1, characterized in that, In step (2), the hydrothermal reaction is carried out at 160℃ for 10 hours.
6. The photocatalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine prepared by the method according to any one of claims 1-5.
7. The application of the photocatalytic selective reduction catalyst for N-phenylhydroxylamine according to claim 6 in the photocatalytic selective reduction of nitrobenzene to N-phenylhydroxylamine.
8. A method for the photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine, characterized in that, The photocatalytic selective reduction catalyst for nitrobenzene to prepare N-phenylhydroxylamine as described in claim 6 is used as the catalyst.
9. The method for photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine according to claim 8, characterized in that, Nitrobenzene, hydrazine hydrate, isopropanol, and the photocatalytic selective reduction catalyst for nitrobenzene to N-phenylhydroxylamine as described in claim 6 are mixed, and the reaction for the hydrogenation of nitrobenzene to N-phenylhydroxylamine is carried out under visible light irradiation and an argon atmosphere.
10. The method for photocatalytic selective reduction of nitrobenzene to prepare N-phenylhydroxylamine according to claim 9, characterized in that, The mass-to-volume ratio of the photocatalyst for the selective reduction of nitrobenzene to N-phenylhydroxylamine and isopropanol is 10-50 mg: 1.5-50 mL; the light intensity is 0.1-0.3 W / cm². 2 The molar volume ratio of nitrobenzene to isopropanol is 0.03-1 mmol: 1.5-50 mL; the molar ratio of nitrobenzene to hydrazine hydrate is 1:1-30.