Preparation method of p-aminophenol

Abstract

The invention discloses a preparation method of p-aminophenol. The preparation method comprises the following steps: S1, synthesizing a Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst; s2, the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst catalyzes NaBH4 to reduce p-nitrophenol to prepare p-aminophenol. The catalyst used in the preparation method is excellent in catalytic performance and can be recycled; according to the preparation method, high-pressure equipment is prevented from being used for charging hydrogen, so that the operation risk is reduced; the preparation method avoids using a noble metal catalyst, and is low in cost; good application prospects are realized.

Description

Technical Field

[0001] The invention relates to the technical field of p-aminophenol preparation, and in particular to a method for preparing p-aminophenol. Background Art

[0002] p-Aminophenol is a widely used fine organic chemical intermediate in my country. In the dye industry, it is used to synthesize weak acid yellow 6G, weak acid yellow 5G, sulphur blue 3R, sulphur blue CV, sulphur brilliant green GB, and sulphur red brown B3R. In the pharmaceutical industry, it is used to synthesize paracetamol and clofibrate. It is also used in the preparation of developers, antioxidants, and additives. There are many methods for producing p-aminophenol, including the nitrobenzene method and the p-nitrophenol method.

[0003] The reaction mechanism for the catalytic hydrogenation of nitrobenzene to produce p-aminophenol is generally believed to involve the initial adsorption of nitrobenzene and hydrogen on the catalyst surface. Hydrogen molecules are activated to produce active hydrogen atoms, which then react with nitrobenzene to form phenylhydroxylamine. Phenylhydroxylamine undergoes a Bamberger rearrangement catalyzed by a protic acid to produce p-aminophenol. Currently, the industry primarily uses precious metals such as palladium and platinum as catalysts to catalyze the hydrogenation of nitrobenzene to produce p-aminophenol in a 10% to 20% sulfuric acid solution. This method is costly and requires high-pressure equipment to charge the hydrogen, which carries operational risks.

[0004] The catalytic hydrogenation of p-nitrophenol to p-aminophenol is primarily based on precious metal catalysts supported by Al₂O₃, SiO₂, TiO₂, or activated carbon. However, their high cost significantly limits their widespread application. Some catalysts use transition metals, such as Co₃O₄ nanoparticles, but their catalytic performance has been less than satisfactory. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention aims to provide a method for preparing p-aminophenol, which solves the problems of high cost and potential safety hazards in the preparation of p-aminophenol by catalytic hydrogenation.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing p-aminophenol comprises the following steps:

[0008] S1, synthesis of Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst;

[0009] S2, Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst catalyzes NaBH4 to reduce p-nitrophenol to prepare p-aminophenol.

[0010] Further, the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst described in S1 is prepared by the following steps:

[0011] Dissolve CoCl2·6H2O and anhydrous sodium acetate in ethylene glycol solution, add nitrogen-doped magnetic carbon nanotubes and soak for 10 - 12 h, then react at a constant temperature of 180 - 200 °C for 10 - 12 h. After the reaction ends, wash the sample with absolute ethanol and deionized water and dry it to obtain the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst.

[0012] Further, the mass ratio of CoCl2·6H2O, anhydrous sodium acetate and nitrogen-doped magnetic carbon nanotubes is 10:1:0.4 - 1.

[0013] Further, the nitrogen-doped magnetic carbon nanotubes are prepared by the following steps:

[0014] Ultrasonically dissolve metal salt FeCl3·6H2O in absolute ethanol, then add melamine and ultrasonically disperse to obtain a uniform suspension; continuously stir the suspension at 70 - 75 °C until the ethanol completely volatilizes to obtain a precursor; dry and grind the precursor, then place it in a tubular furnace filled with Ar gas and pyrolyze it at high temperature according to the heating program to obtain nitrogen-doped magnetic carbon nanotubes.

[0015] Further, the molar ratio of FeCl3·6H2O and melamine is 1∶2.

[0016] Further, the heating program of the tubular furnace is: raise the furnace temperature to 650 - 850 °C at a rate of 3 °C / min and hold for 2 h.

[0017] Further, the steps of the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst described in S2 catalyzing the reduction of p-nitrophenol by NaBH4 to obtain p-aminophenol are as follows:

[0018] S21. Prepare a mixed solution of p-nitrophenol and sodium borohydride;

[0019] S22. Add the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst to the mixed solution and react at 25 °C to obtain p-aminophenol.

[0020] Further, the specific steps of S21 are: respectively take 2 mL of p-nitrophenol solution with a concentration of 1.75×10 -4 mol / L and 2.1 - 3.5 mL of NaBH4 solution with a concentration of 0.05 mol / L to obtain a mixed solution; the molar ratio of NaBH4 to p-nitrophenol is 300 - 500:1.

[0021] Further, the catalyst dosage in S22 is to add 1 - 2 mg of catalyst to 0.105 - 0.175 mmol of NaBH4.

[0022] Advantages of the present invention:

[0023] (1) The present invention uses Co3O4 / nitrogen-doped magnetic carbon nanotubes as a catalyst to catalytically reduce p-nitrophenol to prepare p-aminophenol. The nitrogen-doped magnetic carbon nanotubes have a high specific surface area and a unique tubular structure. As a carrier, Co3O4 can be uniformly dispersed on its surface or inside, improving the dispersion and stability of the catalyst. Due to the coordination effect between the nitrogen-doped magnetic carbon nanotubes and Co ions, Co3O4 can be anchored on the nitrogen-doped magnetic carbon nanotubes, making Co3O4 not easily fall off or break during the catalytic process. The nitrogen-doped magnetic carbon nanotubes have good electron conductivity, which can improve the conductivity of the Co3O4 catalyst and increase the catalytic reaction rate.

[0024] (2) The catalyst used in the present invention not only has excellent catalytic performance but is also easy to recycle. The present invention avoids using high-pressure equipment to fill hydrogen, reducing the operation risk. The present invention avoids using precious metals and uses the transition metal oxide Co3O4 with a simple preparation method and low price, having good application prospects. Specific embodiments

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0026] Example 1

[0027] This example provides a method for preparing p-aminophenol, including the following steps:

[0028] S1. Synthesize Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst:

[0029] S11. Ultrasonically dissolve 10 mL of 1×10 -3 mol / L FeCl3·6H2O in 60 mL of absolute ethanol, then add 2.5 mg of melamine and ultrasonically disperse to obtain a uniform suspension. Stir the suspension at 70 °C until the ethanol completely evaporates to obtain a precursor. After drying and grinding the precursor, place it in a tubular furnace filled with Ar gas and raise the furnace temperature to 750 °C at a rate of 3 °C / min, and keep it at this temperature for 2 h for high-temperature calcination and pyrolysis to obtain nitrogen-doped magnetic carbon nanotubes;

[0030] S12. Dissolve 10 g of CoCl2·6H2O and 1 g of anhydrous sodium acetate in 50 mL of ethylene glycol solution. Add 0.4 g of nitrogen-doped magnetic carbon nanotubes and soak for 12 h. Then transfer them to a high-pressure reactor and react at a constant temperature of 200 °C for 10 h. After the reaction, wash the sample with absolute ethanol and deionized water and dry it to obtain the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst;

[0031] S2. The Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst catalyzes the reduction of p-nitrophenol by NaBH4 to obtain p-aminophenol:

[0032] S21. Prepare a mixed solution of p-nitrophenol and sodium borohydride. The specific steps are as follows: Take 2 mL of a p-nitrophenol solution with a concentration of 1.75×10 -4 mol / L and 2.1 mL of a NaBH4 solution with a concentration of 0.05 mol / L to obtain a mixed solution; at this time, the molar ratio of NaBH4 to p-nitrophenol is 300:1;

[0033] S22. Add 1 mg of the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst to the mixed solution and react at 25 °C to obtain p-aminophenol.

[0034] Example 2

[0035] Compared with Example 1, the difference in this example is that "0.4 g of nitrogen-doped magnetic carbon nanotubes" in S12 is changed to "0.6 g of nitrogen-doped magnetic carbon nanotubes"; the other raw materials and the preparation process are the same as those in Example 1.

[0036] Example 3

[0037] Compared with Example 1, the difference in this example is that "0.4 g of nitrogen-doped magnetic carbon nanotubes" in S12 is changed to "0.8 g of nitrogen-doped magnetic carbon nanotubes"; the other raw materials and the preparation process are the same as those in Example 1.

[0038] Example 4

[0039] Compared with Example 1, the difference in this example is that "0.4 g of nitrogen-doped magnetic carbon nanotubes" in S12 is changed to "1 g of nitrogen-doped magnetic carbon nanotubes"; the other raw materials and the preparation process are the same as those in Example 1.

[0040] Example 5

[0041] Compared with Example 4, the difference in this example is that "2.1 mL of a NaBH4 solution with a concentration of 0.05 mol / L" in S21 is changed to "2.8 mL of a NaBH4 solution with a concentration of 0.05 mol / L", and at this time, the molar ratio of NaBH4 to p-nitrophenol is 400:1; the other raw materials and the preparation process are the same as those in Example 4.

[0042] Example 6

[0043] Compared with Example 4, the difference in this example is that the "2.1 mL of 0.05 mol / L NaBH4 solution" in S21 is changed to "3.5 mL of 0.05 mol / L NaBH4 solution". At this time, the molar ratio of NaBH4 to p-nitrophenol is 500:1; the other raw materials and the preparation process are the same as those in Example 4.

[0044] Example 7

[0045] Compared with Example 5, the difference in this example is that the "1 mg of Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst" in S22 is changed to "1.5 mg of Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst"; the other raw materials and the preparation process are the same as those in Example 5.

[0046] Example 8

[0047] Compared with Example 5, the difference in this example is that the "1 mg of Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst" in S22 is changed to "2 mg of Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst"; the other raw materials and the preparation process are the same as those in Example 5.

[0048] Comparative Example 1

[0049] Compared with Example 1, the difference in this comparative example is that the "0.4 g of nitrogen-doped magnetic carbon nanotubes" in S12 is changed to "0.4 g of magnetic carbon nanotubes" to obtain the catalyst "Co3O4 / magnetic carbon nanotubes"; the other raw materials and the preparation process are the same as those in Example 1.

[0050] Comparative Example 2

[0051] Compared with Example 1, the difference in this comparative example is that "Co3O4" is prepared as the catalyst: 1 g of CoCl2·6H2O and 0.1 g of anhydrous sodium acetate are dissolved in 50 mL of ethylene glycol solution, transferred to a high-pressure reaction kettle, and reacted at a constant temperature of 200 °C for 10 h. After the reaction is completed, the sample is washed and dried with absolute ethanol and deionized water to obtain the Co3O4 catalyst; the other raw materials and the preparation process are the same as those in Example 1.

[0052] Comparative Example 3

[0053] This comparative example is different from Example 1 in that "nitrogen-doped magnetic carbon nanotubes" and "Co3O4" are directly mixed as the catalyst: 1 g of CoCl2·6H2O and 0.1 g of anhydrous sodium acetate are dissolved in 50 mL of ethylene glycol solution, transferred to a high-pressure reactor, and reacted at a constant temperature of 200 °C for 10 h. After the reaction is completed, the sample is washed with absolute ethanol and deionized water and dried to obtain Co3O4. The obtained Co3O4 and 0.4 g of nitrogen-doped magnetic carbon nanotubes are mixed evenly to obtain the catalyst. The preparation method of "nitrogen-doped magnetic carbon nanotubes" is the same as that in step S11 of Example 1; the remaining raw materials and preparation process are the same as those in Example 1.

[0054] The absorbance of the solution in the reaction system within a specific wavelength range (250 - 550 nm) is detected by a UV spectrophotometer to monitor the reaction process, and then the conversion rate of p-nitrophenol is calculated. The results are shown in Table 1.

[0055] Table 1

[0056] Conversion rate (%) 2 min 4 min 6 min Example 1 72.3 87.5 90.5 Example 2 73.4 88.1 91.5 Example 3 74.1 89.4 92.7 Example 4 75.1 90.5 93.6 Example 5 77.4 92.5 95.2 Example 6 76.2 91.3 94.1 Example 7 80.2 95.1 98.2 Example 8 83.5 97.3 100 Comparative Example 1 63.3 79.2 81.5 Comparative Example 2 0 0 0 Comparative Example 3 0 0 0

[0057] It can be obtained by comparing Example 1 with Example 4 that increasing the amount of nitrogen-doped magnetic carbon nanotubes in the catalyst is beneficial to improving the conversion rate of p-nitrophenol. The reason is that nitrogen-doped magnetic carbon nanotubes have a high specific surface area and a unique tubular structure. As a carrier, Co3O4 can be evenly dispersed on its surface or inside, improving the dispersion and stability of the catalyst; due to the coordination effect between nitrogen-doped magnetic carbon nanotubes and Co ions, Co3O4 can be anchored on the nitrogen-doped magnetic carbon nanotubes, making Co3O4 not easy to fall off or break during the catalytic process; nitrogen-doped magnetic carbon nanotubes have good electronic conductivity, which can improve the conductivity of the Co3O4 catalyst and increase the catalytic reaction rate.

[0058] It can be obtained by comparing Example 4 with Example 6 that appropriately increasing the molar ratio of NaBH4 to p-nitrophenol is beneficial to improving the conversion rate of p-nitrophenol, while excessive increase is not conducive to improving the conversion rate of p-nitrophenol; because H2 will be generated during the reduction of p-nitrophenol by NaBH4 to prepare p-aminophenol. The principle is that NaBH4 acts as a reducing agent and releases hydride ions (H - ), H -Attack the nitro group (-NO2) in p-nitrophenol to reduce it to an amino group (-NH2), generating p-aminophenol; at the same time, since the hydrogen element in NaBH4 increases from -1 to 0 (i.e., the valence state of H in H2), H2 will be generated as a by-product of the reaction; therefore, when the molar ratio of NaBH4 to p-nitrophenol increases, that is, the amount of NaBH4 is increased, the amount of H2 produced by hydrolysis and the conversion rate of p-nitrophenol increase sharply with the increase of the NaBH4 concentration. The solubility of H2 in water is small. If the amount of NaBH4 is increased excessively, the generated H2 will be adsorbed on the surface of the catalyst, reducing the catalytic efficiency.

[0059] It can be obtained by comparing Example 5, Example 7, and Example 8 that increasing the amount of the catalyst is beneficial to improving the conversion rate of p-nitrophenol.

[0060] It can be obtained by comparing Comparative Example 1 and Example 1 that the catalytic efficiency of the catalyst obtained by using nitrogen-doped magnetic carbon nanotubes as the carrier is higher than that obtained by using magnetic carbon nanotubes as the carrier because there is a coordination effect between nitrogen-doped magnetic carbon nanotubes and Co ions. Therefore, Co3O4 can be anchored on the nitrogen-doped magnetic carbon nanotubes, making Co3O4 not easily fall off or break during the catalytic process, thereby improving the catalytic efficiency.

[0061] It can be obtained by comparing Comparative Example 2, Comparative Example 3, and Example 1 that when using Co3O4 alone as the catalyst or directly mixing nitrogen-doped magnetic carbon nanotubes and Co3O4 as the catalyst, the conversion rate is 0 after reacting at 25°C for 6 min in the catalytic reduction of p-nitrophenol to prepare p-aminophenol, indicating that Co3O4 as the catalyst may require a higher reaction temperature and a longer reaction time; using the physical mixture of nitrogen-doped magnetic carbon nanotubes and Co3O4 as the catalyst does not significantly improve the catalytic efficiency of Co3O4, and it may also require a higher reaction temperature and a longer reaction time.

[0062] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0063] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing p-aminophenol, characterized in that, It includes the following steps: S1. Synthesize Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst; S2. Use the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst to catalyze the reduction of p-nitrophenol by NaBH4 to prepare p-aminophenol.

2. The preparation method of p-aminophenol according to claim 1, characterized in that, The Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst described in S1 is prepared by the following steps: Dissolve CoCl2·6H2O and anhydrous sodium acetate in an ethylene glycol solution, add nitrogen-doped magnetic carbon nanotubes and soak for 10 - 12 h, then carry out a constant-temperature reaction at 180 - 200 °C for 10 - 12 h. After the reaction ends, wash the sample with absolute ethanol and deionized water and dry it to obtain the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst.

3. The preparation method of p-aminophenol according to claim 2, characterized in that, The mass ratio of CoCl2·6H2O, anhydrous sodium acetate and nitrogen-doped magnetic carbon nanotubes is 10:1:0.4 - 1.

4. The preparation method of p-aminophenol according to claim 2, wherein, The nitrogen-doped magnetic carbon nanotubes are prepared by the following steps: Ultrasonically dissolve metal salt FeCl3·6H2O in absolute ethanol, then add melamine and ultrasonically disperse to obtain a uniform suspension; continuously stir the suspension at 70 - 75 °C until the ethanol completely evaporates to obtain a precursor; dry and grind the precursor, then place it in a tube furnace filled with Ar gas and pyrolyze it at high temperature according to the heating program to obtain nitrogen-doped magnetic carbon nanotubes.

5. The preparation method of p-aminophenol according to claim 4, characterized in that, The molar ratio of FeCl3·6H2O and melamine is 1∶2.

6. The preparation method of p-aminophenol according to claim 4, characterized in that, The heating program of the tube furnace is: raise the furnace temperature to 650 - 850 °C at a rate of 3 °C / min and keep it at this temperature for 2 h.

7. The preparation method of p-aminophenol according to claim 1, characterized in that, The steps for the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst described in S2 to catalyze the reduction of p-nitrophenol by NaBH4 to obtain p-aminophenol are: S21. Prepare a mixed solution of p-nitrophenol and NaBH4; S22. Add the Co3O4 / nitrogen-doped magnetic carbon nanotube catalyst to the mixed solution and react at 25 °C to obtain p-aminophenol.

8. The preparation method of p-aminophenol according to claim 7, characterized in that, The specific steps of S21 are as follows: respectively take 2 mL of p-nitrophenol solution with a concentration of 1.75×10 -4 mol / L and 2.1 - 3.5 mL of NaBH4 solution with a concentration of 0.05 mol / L to obtain a mixed solution; the molar ratio of NaBH4 to p-nitrophenol is 300 - 500:

1.

9. The preparation method of p-aminophenol according to claim 7, characterized in that, In S22, the catalyst dosage is 1 - 2 mg of catalyst added to 0.105 - 0.175 mmol of NaBH4.