Process method for preparing p-phenylenediamine from nitrobenzene by one-pot method

Abstract

The invention relates to the technical field of organic chemical synthesis, in particular to a process method for preparing p-phenylenediamine from nitrobenzene through a one-pot method, and the process method comprises the following steps: S1, ammoniation reaction: under inert gas and in a solvent system, nitrobenzene and amino salt are subjected to ammoniation reaction under heating and pressurizing conditions, and a reaction solution is obtained after the reaction is finished; and S2, reduction reaction: adding a catalyst into the reaction liquid, introducing hydrogen to carry out hydrogenation reduction reaction, and after the reaction is finished, carrying out hydrolysis and post-treatment to obtain p-phenylenediamine. The amino salt is at least one of sodium amide, lithium amide and potassium amide. The ammonolysis reaction temperature is 120-180 DEG C, the ammonolysis reaction pressure is 3-8 Mpa, and the ammonolysis reaction time is 6-10 h. The process method is reasonable in route design, low in raw material cost, easy to obtain, high in conversion rate, high in atom utilization rate, simple to operate and capable of reducing loss, and has potential industrial application prospects.

Description

Technical Field

[0001] The present invention relates to a process for preparing p-phenylenediamine by a one-pot method from nitrobenzene, belonging to the technical field of organic chemical synthesis. Background Art

[0002] p-Phenylenediamine, abbreviated as p-PAD, is a white to light purplish red flaky crystal at room temperature and is easily oxidized to a purplish red or dark brown crystal when exposed to air. p-Phenylenediamine is an important chemical intermediate and is widely used in many fields such as dyes, rubber antioxidants, polymers, etc. p-Phenylenediamine is an intermediate for azo disperse dyes, direct dyes, acid dyes, sulfur dyes and fur dyes, and is an effective ingredient in hair dyes. It has a very strong affinity for keratin in hair; p-phenyleneterephthalamide (PPTA) prepared from p-phenylenediamine has wide applications in the fields of aerospace, military, etc. because of its advantages such as low density, high strength, good toughness, high temperature resistance, and easy processing and molding, such as bulletproof vests, tank armors, etc.; p-phenylenediamine rubber antioxidants also occupy an important position among rubber antioxidants. The antioxidant prepared from p-phenylenediamine is an efficient anti-ozone agent, a good antioxidant and anti-flex cracking agent, a chain-breaking inhibitor, and also a metal complexing agent, etc.; p-phenylenediamine can be used as an epoxy resin curing agent, which can significantly increase the glass transition temperature of the cured product. It can be seen from this that p-phenylenediamine is an important organic synthesis intermediate with wide application value.

[0003] At present, industrially, chlorobenzene is mainly used as the starting material, and p-phenylenediamine is obtained through processes such as mixed acid nitration, liquid ammonia ammonolysis, and hydrogenation reduction. For example: The patent application with publication number CN117486729A discloses a method for producing p-phenylenediamine and a production device, and p-phenylenediamine is prepared through steps such as adding liquid ammonia for amination, filtration, melting, dehydration, rectification, crystallization and secondary crystallization. The patent application with publication number CN112209836A discloses a method for preparing p-phenylenediamine, including reacting p-dichlorobenzene with ammonia in the presence of a copper catalyst and a ligand to obtain p-phenylenediamine. The patent application with publication number CN109336769A discloses a method for preparing p-phenylenediamine, using p-dichlorobenzene and ammonia water as raw materials, a copper salt as a catalyst, and adding a Mannich base as a ligand in the reaction system to prepare p-phenylenediamine.

[0004] However, in the existing preparation methods, a large amount of acidic wastewater is generated during the mixed acid nitration process, resulting in serious pollution; the liquid ammonia ammonolysis is carried out in a high-temperature and high-pressure system, with high safety risks. In addition, the halogen salt, as a by-product of ammonolysis, will cause serious environmental pollution. Therefore, developing a scientific, green, safe and efficient synthesis method and route is of great significance and value for the industrial preparation of p-phenylenediamine. Summary of the Invention

[0005] In view of the deficiencies existing in the prior art, the present invention provides a process for preparing p-phenylenediamine by one-pot method from nitrobenzene. The process route is reasonably designed, with low raw material cost and easy availability, high conversion rate, high atom utilization rate, simple operation, reduced losses, and has potential industrial application prospects.

[0006] The technical solution of the present invention to solve the above technical problems is as follows: A process for preparing p-phenylenediamine by one-pot method from nitrobenzene, and the process is as follows: S1. Amination reaction: Under an inert gas, in a solvent system, nitrobenzene and an amino salt are subjected to an amination reaction under heating and pressurization conditions, and a reaction solution is obtained after the reaction ends; S2. Reduction reaction: A catalyst is added to the reaction solution, and hydrogen is introduced for a hydrogenation reduction reaction. After the reaction ends, p-phenylenediamine is obtained through hydrolysis and post-treatment.

[0007] Further, in step S1, the solvent is at least one of toluene, chloroform, dichloromethane, benzene, xylene, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0008] Further, in step S1, the amino salt is at least one of sodium amide, lithium amide, and potassium amide.

[0009] Further, in step S1, the molar ratio of nitrobenzene to the amino salt is 1:(1.2 - 1.8).

[0010] Further, in step S1, the amination reaction temperature is 120 - 180 °C, the amination reaction pressure is 3 - 8 Mpa, and the amination reaction time is 6 - 10 h.

[0011] Further, in step S2, the catalyst is at least one of Raney Ni, Pd / C, and Zn.

[0012] Further, in step S2, the hydrogen pressure in the hydrogenation reduction reaction system is 1 - 3 MPa.

[0013] Further, in step S2, the hydrogenation reduction reaction temperature is 60 - 100 °C, and the hydrogenation reduction reaction time is 2 - 5 h.

[0014] Further, in step S2, the hydrolysis and post-treatment process is as follows: The reaction system cooled to room temperature is slowly added to cooling water for hydrolysis. After filtering out insoluble substances, the pH is adjusted to acidic. After standing and separating phases, the organic phase is extracted with acidic water, the aqueous phases are combined, then the pH is adjusted to alkaline, and finally, p-phenylenediamine product is obtained through evaporation crystallization and rectification purification.

[0015] Further, the pH range for adjusting to acidic is lower than 4, and the pH range for adjusting to alkaline is higher than 8.

[0016] The beneficial effects of the present invention are as follows: The process method of the present invention synthesizes p-phenylenediamine by a one-pot method. The intermediate does not need to be separated, the operation is simple, the discharge of three wastes is small, the labor intensity in the production process is reduced, and the loss in the process is reduced, and the material utilization rate is high. Under the preferred conditions, when no purification operation is carried out, the crude p-phenylenediamine with a purity of more than 97% and a yield of more than 95% can be directly obtained. After rectification and purification, a p-phenylenediamine product with a purity of more than 99% and an overall yield of more than 90% can be obtained.

[0017] The raw materials used in the process method of the present invention are cheap and easily available, and the whole process method has the advantages of low cost and environmental friendliness. Description of the Drawings

[0018] Figure 1 It is the GC spectrum of the crude p-phenylenediamine prepared in Example 1; Figure 2 It is the GC spectrum of the p-phenylenediamine product prepared in Example 1. Detailed Description of the Invention

[0019] The following makes a detailed description of the specific implementation manners of the present invention. The present invention can be implemented in many other ways different from those described herein. Those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific implementation manners and do not limit the present invention.

[0021] A process method for preparing p-phenylenediamine from nitrobenzene by a one-pot method, and the process method is as follows: S1. Ammoniation reaction: Under an inert gas, in a solvent system, nitrobenzene and an amino salt are subjected to an ammoniation reaction under heating and pressurization conditions, and a reaction solution is obtained after the reaction ends; S2. Reduction reaction: A catalyst is added to the reaction solution, and hydrogen is introduced for a hydrogenation reduction reaction. After the reaction ends, p-phenylenediamine is obtained through hydrolysis and post-treatment.

[0022] Specifically, in step S1, the solvent is at least one of toluene, chloroform, dichloromethane, benzene, xylene, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0023] The process method principle equation for preparing p-phenylenediamine by one-pot method from nitrobenzene is as follows: .

[0024] The reaction mechanism is as follows: .

[0025] Preferably, the solvent is toluene. When toluene is used as the solvent, it is more conducive to obtaining crude p-phenylenediamine with high purity by one-step method.

[0026] More specifically, the dosage of the solvent is 3-8 times the mass of nitrobenzene.

[0027] Specifically, in step S1, the amino salt is at least one of sodium amide, lithium amide, and potassium amide.

[0028] Preferably, in step S1, the amino salt is sodium amide.

[0029] Specifically, in step S1, the molar ratio of nitrobenzene to amino salt is 1:(1.2-1.8).

[0030] Specifically, in step S1, the ammoniation reaction temperature is 120-180 °C, the ammoniation reaction pressure is 3-8 Mpa, and the ammoniation reaction time is 6-10 h.

[0031] Specifically, in step S2, the catalyst is at least one of Raney Ni, Pd / C, and Zn.

[0032] Specifically, the dosage of the catalyst is 1%-10% of the mass of nitrobenzene.

[0033] Specifically, in step S2, the hydrogen pressure in the hydrogenation reduction reaction system is 1-3 MPa.

[0034] Specifically, in step S2, the hydrogenation reduction reaction temperature is 60-100 °C, and the hydrogenation reduction reaction time is 2-5 h.

[0035] Specifically, in step S2, the hydrolysis and post-treatment process is as follows: the reaction system cooled to room temperature is slowly added to cooling water for hydrolysis. After filtering out the insoluble substances, the pH is adjusted to acidic. After standing and separating the phases, the organic phase is extracted with acidic water, the aqueous phases are combined, then the pH is adjusted to alkaline, and finally p-phenylenediamine product is obtained through evaporation crystallization and rectification purification.

[0036] Specifically, the pH range for adjusting to acidic is lower than 4, and the pH range for adjusting to alkaline is higher than 8.

[0037] More specifically, in the embodiments of the present invention, an inorganic acid such as hydrochloric acid or sulfuric acid is used to adjust the pH to acidic, and the acidic water used in the extraction is an aqueous solution of an inorganic acid such as hydrochloric acid or sulfuric acid, and the pH is lower than 4; an alkali such as sodium hydroxide, potassium hydroxide, or ammonia water is used to adjust the pH to alkaline.

[0038] Example 1 Step 1: Add 300 mL of toluene, 0.5 mol of nitrobenzene, and 0.75 mol of sodium amide to the autoclave, tighten the lid, and keep the autoclave in a well-sealed state. 2 The air replacement was continued for more than 1 min, the feed port of the kettle cover was closed, the temperature was raised to 140°C, and the reaction was kept at this temperature for 8 h to put the reaction system in the best state for the amination reaction.

[0039] Step 2: After the reactor is heated to 140°C, charge N 2 When the pressure in the reactor reaches 4 MPa, the raw materials react fully. When the pressure in the reactor exceeds 8 MPa, the pressure is released to 4 MPa in time. Repeat this operation until the pressure in the reactor no longer increases. At this time, the reaction is considered to be over, the reaction liquid is cooled to room temperature, and the N 2 .

[0040] Step 3: The reaction liquid obtained in the previous step is directly added with Raney Ni catalyst without treatment, the lid of the reactor is tightened, and the reactor is kept in a well-sealed state. 2 The air replacement lasts for more than 3 minutes, the feed port on the kettle cover is closed, the temperature is raised to 80°C, and the reaction is kept at this temperature for 3 hours to ensure that the reaction system is in the best state for the reduction reaction.

[0041] Step 4: After the reactor is heated to 80°C, fill it with H 2 When the pressure reaches 2MPa, the raw materials will react fully. When the pressure in the reactor is lower than 0.5MPa, add H 2 Repeat this operation until the pressure in the kettle stops decreasing. The reaction is considered complete at this time. The reaction liquid cools to room temperature and the H 2 , N 2 Replace the residual gas in the kettle.

[0042] Step 5: Slowly pour the reaction solution from the previous step into cooling water (500 g), stir thoroughly for hydrolysis, filter out insoluble matter, and recover the catalyst.

[0043] Step 6: The pH of the filtrate in the previous step is adjusted to 3.0, and the filtrate is allowed to stand for phase separation. The organic phase is extracted three times with acidic water with a pH of less than 4.0, and the aqueous phase is combined. The pH of the aqueous phase is adjusted to 9.0 again, and most of the water is removed by vacuum rotary evaporation or cooling. The white solid product is the crude p-phenylenediamine, and the purity of the GC detection can reach 97.2%. The GC detection spectrum is as follows: Figure 1 As shown, the yield is 97.8%; the GC chromatogram data of the crude p-phenylenediamine is shown in Table 1 below.

[0044] Table 1 GC Chromatographic Data of Crude p-Phenylenediamine

[0045] After rectifying and purifying the crude p-phenylenediamine, the purity detected by GC can reach 99.1%, and the GC detection spectrum is as shown in Figure 2 shown, and the yield is 92.6%. The GC chromatographic data of the purified p-phenylenediamine product are as shown in Table 2 below.

[0046] Table 2 GC Chromatographic Data of p-Phenylenediamine Product

[0047] Example 2 Step 1: Add 600 mL of toluene, 0.5 mol of nitrobenzene, and 0.6 mol of sodium amide to the autoclave, tighten the autoclave lid, and keep the autoclave in a good sealed state. Replace the air with N 2 for more than 1 min, close the charging port of the autoclave lid, heat up to 140 °C, and keep the reaction for 8 h to make the reaction system in the best state for the amination reaction.

[0048] Step 2: After the autoclave is heated up to 140 °C, fill it with N 2 to a pressure of 4 MPa to make the raw materials react fully. When the pressure in the autoclave exceeds 8 MPa, release the pressure to 4 MPa in time, and repeat this operation until the pressure in the autoclave no longer rises. At this time, the reaction is regarded as completed, and the reaction solution is cooled to room temperature, and the N 2 in the autoclave is discharged.

[0049] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step, tighten the autoclave lid, and keep the autoclave in a good sealed state. Replace the air with H 2 for more than 3 min, close the charging port of the autoclave lid, heat up to 80 °C, and keep the reaction for 3 h to make the reaction system in the best state for the reduction reaction.

[0050] Step 4: After the autoclave is heated up to 80 °C, fill it with H 2 to a pressure of 2 MPa to make the raw materials react fully. When the pressure in the autoclave is lower than 0.5 MPa, fill it with H 2 to 2 MPa in time, and repeat this operation until the pressure in the autoclave no longer decreases. At this time, the reaction is regarded as completed, and the reaction solution is cooled to room temperature, and the H 2 in the autoclave is discharged, and N 2 is used to replace the residual gas in the autoclave.

[0051] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooling water, stir it fully for hydrolysis, filter out the insoluble substances, and recover the catalyst.

[0052] Step 6: Adjust the pH of the filtrate from the previous step to 2. Let the filtrate stand for phase separation. Extract the organic phase with acidic water having a pH < 4.0 three times, and combine the aqueous phases. Then adjust the pH of the aqueous phase to 10. Remove most of the water by rotary evaporation under reduced pressure or after cooling, and a white solid product will precipitate, which is the crude product of p-phenylenediamine. The purity detected by GC can reach 97.3%, and the yield is 97.2%. Subject the crude p-phenylenediamine to rectification and purification, and the purity detected by GC can reach 99.0%, and the yield is 92.0%.

[0053] Example 3 Step 1: Add 900 mL of toluene, 5.0 mol of nitrobenzene, and 6 mol of sodium amide to an autoclave. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with N 2 for more than 1 minute, close the charging port of the autoclave lid, heat up to 140 °C, and keep the reaction for 8 hours to make the reaction system in the best state for the amination reaction.

[0054] Step 2: After the autoclave is heated up to 140 °C, fill it with N 2 to a pressure of 4 MPa to allow the raw materials to react fully. When the pressure in the autoclave exceeds 8 MPa, release the pressure in time to 4 MPa, and repeat this operation until the pressure in the autoclave no longer rises. At this time, it is regarded as the end of the reaction. Let the reaction solution cool to room temperature, and discharge the N 2 in the autoclave.

[0055] Step 3: Without any treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with H 2 for more than 3 minutes, close the charging port of the autoclave lid, heat up to 80 °C, and keep the reaction for 3 hours to make the reaction system in the best state for the reduction reaction.

[0056] Step 4: After the autoclave is heated up to 80 °C, fill it with H 2 to a pressure of 2 MPa to allow the raw materials to react fully. When the pressure in the autoclave is lower than 0.5 MPa, fill it with H 2 to 2 MPa in time, and repeat this operation until the pressure in the autoclave no longer decreases. At this time, it is regarded as the end of the reaction. Let the reaction solution cool to room temperature, and discharge the H 2 , and use N 2 to displace the residual gas in the autoclave.

[0057] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooled water, stir well for hydrolysis, filter off the insoluble matter, and recover the catalyst.

[0058] Step 6: Adjust the pH of the filtrate from the previous step to 1.0. Let the filtrate stand for phase separation. Extract the organic phase three times with acidic water having a pH < 4.0, and combine the aqueous phases. Then adjust the pH of the aqueous phase to 8.5. After removing most of the water by rotary evaporation under reduced pressure or by cooling, a white solid product precipitates, which is the crude product of p-phenylenediamine. The purity detected by GC can reach 97.1%, and the yield is 97.0%. The crude p-phenylenediamine is purified by rectification, and the purity detected by GC can reach 99.1%, and the yield is 91.5%.

[0059] Example 4 Step 1: Add 600 mL of toluene, 0.5 mol of nitrobenzene, and 0.9 mol of potassium amide to an autoclave. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with N 2 for more than 1 minute, close the charging port of the autoclave lid, heat up to 180 °C, and keep the reaction for 6 hours to make the reaction system in the best state for the amination reaction.

[0060] Step 2: After the autoclave is heated up to 180 °C, fill it with N 2 to a pressure of 3 MPa to allow the raw materials to react fully. When the pressure in the autoclave exceeds 8 MPa, release the pressure in time to 3 MPa, and repeat this operation until the pressure in the autoclave no longer rises. At this time, the reaction is considered to be over. Let the reaction solution cool to room temperature and discharge the N 2 in the autoclave.

[0061] Step 3: Without treatment, directly add Pd / C catalyst to the reaction solution obtained in the previous step. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with H 2 for more than 3 minutes, close the charging port of the autoclave lid, heat up to 60 °C, and keep the reaction for 5 hours to make the reaction system in the best state for the reduction reaction.

[0062] Step 4: After the autoclave is heated up to 60 °C, fill it with H 2 to a pressure of 3 MPa to allow the raw materials to react fully. When the pressure in the autoclave is lower than 0.5 MPa, fill it with H 2 to 3 MPa in time, and repeat this operation until the pressure in the autoclave no longer decreases. At this time, the reaction is considered to be over. Let the reaction solution cool to room temperature and discharge the H 2 , and use N 2 to replace the residual gas in the autoclave.

[0063] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooled water, stir well for hydrolysis, filter off the insoluble matter, and recover the catalyst.

[0064] Step 6: Adjust the pH of the filtrate from the previous step to 2. Let the filtrate stand for phase separation. Extract the organic phase three times with acidic water having a pH < 4.0, and combine the aqueous phases. Then adjust the pH of the aqueous phase to 10. After removing most of the water by rotary evaporation under reduced pressure or after cooling, a white solid product, which is the crude product of p-phenylenediamine, will precipitate. The purity detected by GC can reach 97.5%, and the yield is 97.0%. Subject the crude p-phenylenediamine to rectification and purification, and the purity detected by GC can reach 99.1%, and the yield is 91.3%.

[0065] Example 5 Step 1: Add 600 mL of toluene, 0.5 mol of nitrobenzene, and 0.6 mol of lithium amide to an autoclave. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with N 2 for more than 1 min, close the charging port of the autoclave lid, heat up to 120 °C, and keep the reaction for 10 h to make the reaction system in the best state for the amination reaction.

[0066] Step 2: After the autoclave is heated up to 120 °C, fill it with N 2 to a pressure of 8 MPa to allow the raw materials to react fully. When the pressure in the autoclave exceeds 8 MPa, release the pressure in time to 8 MPa, and repeat this operation until the pressure in the autoclave no longer rises. At this time, it is regarded as the end of the reaction. Let the reaction solution cool to room temperature, and discharge the N 2 in the autoclave.

[0067] Step 3: Without treatment, directly add a Zn catalyst to the reaction solution obtained in the previous step. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with H 2 for more than 3 min, close the charging port of the autoclave lid, heat up to 100 °C, and keep the reaction for 2 h to make the reaction system in the best state for the reduction reaction.

[0068] Step 4: After the autoclave is heated up to 100 °C, fill it with H 2 to a pressure of 1 MPa to allow the raw materials to react fully. When the pressure in the autoclave is lower than 0.5 MPa, fill it with H 2 to 1 MPa in time, and repeat this operation until the pressure in the autoclave no longer decreases. At this time, it is regarded as the end of the reaction. Let the reaction solution cool to room temperature, and discharge the H 2 , and use N 2 to displace the residual gas in the autoclave.

[0069] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooled water and stir well for hydrolysis. Filter off the insoluble matter and recover the catalyst.

[0070] Step 6: Adjust the pH of the filtrate from the previous step to 2. Let the filtrate stand for phase separation. Extract the organic phase three times with acidic water having a pH < 4.0, and combine the aqueous phases. Then adjust the pH of the aqueous phase to 10. Remove most of the water by rotary evaporation under reduced pressure or after cooling, and a white solid product will precipitate, which is the crude p-phenylenediamine. The purity detected by GC can reach 97.4%, and the yield is 96.9%. Subject the crude p-phenylenediamine to rectification and purification, and the purity detected by GC can reach 99.0%, and the yield is 91.0%.

[0071] Example 6 Step 1: Add 300 mL of xylene, 0.5 mol of nitrobenzene, and 0.75 mol of sodium amide to an autoclave. Tighten the autoclave lid and keep the reaction kettle in a good sealed state. Replace the air with N 2 for more than 1 minute, close the feeding port of the autoclave lid, heat up to 140 °C, and keep the reaction for 8 hours to make the reaction system in the best state for the amination reaction.

[0072] Step 2: After the reaction kettle is heated up to 140 °C, fill it with N 2 until the pressure reaches 4 MPa to allow the raw materials to react fully. When the pressure in the reaction kettle exceeds 8 MPa, relieve the pressure to 4 MPa in a timely manner. Repeat this operation until the pressure in the kettle no longer rises. At this time, it is regarded as the end of the reaction. Let the reaction solution cool to room temperature and discharge the N 2 in the kettle.

[0073] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step. Tighten the autoclave lid and keep the reaction kettle in a good sealed state. Replace the air with H 2 for more than 3 minutes, close the feeding port of the autoclave lid, heat up to 80 °C, and keep the reaction for 3 hours to make the reaction system in the best state for the reduction reaction.

[0074] Step 4: After the reaction kettle is heated up to 80 °C, fill it with H 2 until the pressure reaches 2 MPa to allow the raw materials to react fully. When the pressure in the reaction kettle is lower than 0.5 MPa, fill it with H 2 to 2 MPa in a timely manner. Repeat this operation until the pressure in the kettle no longer decreases. At this time, it is regarded as the end of the reaction. Let the reaction solution cool to room temperature and discharge the H 2 , and use N 2 to displace the residual gas in the kettle.

[0075] Step 5: Slowly pour the reaction solution from the previous step into cool water (500 g), stir well for hydrolysis, filter off the insoluble matter, and recover the catalyst.

[0076] Step 6: Adjust the pH of the filtrate from the previous step to 3.0. Let the filtrate stand for phase separation. Extract the organic phase three times with acidic water having a pH < 4.0, and combine the aqueous phases. Then adjust the pH of the aqueous phase to 9.0. Remove most of the water by rotary evaporation under reduced pressure or after cooling, and a white solid product will precipitate, which is the crude p-phenylenediamine. The purity detected by GC can reach 77.1%, and the yield is 97.8%. Subject the crude p-phenylenediamine to rectification and purification, and the purity detected by GC can reach 99.1%, and the yield is 75%.

[0077] Example 7 Step 1: Add 300 mL of N,N-dimethylformamide, 0.5 mol of nitrobenzene, and 0.75 mol of sodium amide to the autoclave. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with N 2 for more than 1 min, close the charging port of the autoclave lid, heat up to 140 °C, and keep the reaction for 8 h to make the reaction system in the best state for the amination reaction.

[0078] Step 2: After the autoclave is heated up to 140 °C, fill it with N 2 until the pressure reaches 4 MPa to make the raw materials react fully. When the pressure in the autoclave exceeds 8 MPa, relieve the pressure to 4 MPa in time. Repeat this operation until the pressure in the autoclave no longer rises. At this time, the reaction is regarded as completed. Let the reaction solution cool to room temperature, and discharge the N 2 in the autoclave.

[0079] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with H 2 for more than 3 min, close the charging port of the autoclave lid, heat up to 80 °C, and keep the reaction for 3 h to make the reaction system in the best state for the reduction reaction.

[0080] Step 4: After the autoclave is heated up to 80 °C, fill it with H 2 until the pressure reaches 2 MPa to make the raw materials react fully. When the pressure in the autoclave is lower than 0.5 MPa, fill it with H 2 to 2 MPa in time. Repeat this operation until the pressure in the autoclave no longer decreases. At this time, the reaction is regarded as completed. Let the reaction solution cool to room temperature, and discharge the H 2 , and use N 2 to replace the residual gas in the autoclave.

[0081] Step 5: Slowly pour the reaction solution from the previous step into the cooling water (500 g), stir it well for hydrolysis, filter off the insoluble substances, and recover the catalyst.

[0082] Step 6: Adjust the pH of the filtrate from the previous step to 3.0. Let the filtrate stand for phase separation. Extract the organic phase three times with acidic water having pH < 4.0, and combine the aqueous phases. Then adjust the pH of the aqueous phase to 9.0. After removing most of the water by rotary evaporation under reduced pressure or after cooling, a white solid product precipitates, which is the crude product of p-phenylenediamine. The purity detected by GC can reach 75.8%, and the yield is 97.9%. Subject the crude p-phenylenediamine to rectification and purification, and the purity detected by GC can reach 99.0%, and the yield is 74.8%.

[0083] Example 8 Step 1: Add 300 mL of N,N-dimethylacetamide, 0.5 mol of nitrobenzene, and 0.75 mol of sodium amide to an autoclave. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with N 2 for more than 1 minute, close the feeding port of the autoclave lid, heat up to 140 °C, and keep the reaction for 8 hours to make the reaction system in the best state for the amination reaction.

[0084] Step 2: After the autoclave is heated up to 140 °C, fill it with N 2 until the pressure reaches 4 MPa to allow the raw materials to react fully. When the pressure in the autoclave exceeds 8 MPa, relieve the pressure to 4 MPa in a timely manner. Repeat this operation until the pressure in the autoclave no longer rises. At this time, consider the reaction to be over. Let the reaction solution cool to room temperature, and discharge the N 2 .

[0085] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step. Tighten the autoclave lid and keep the autoclave in a good sealed state. Replace the air with H 2 for more than 3 minutes, close the feeding port of the autoclave lid, heat up to 80 °C, and keep the reaction for 3 hours to make the reaction system in the best state for the reduction reaction.

[0086] Step 4: After the autoclave is heated up to 80 °C, fill it with H 2 until the pressure reaches 2 MPa to allow the raw materials to react fully. When the pressure in the autoclave is lower than 0.5 MPa, fill it with H 2 to 2 MPa in a timely manner. Repeat this operation until the pressure in the autoclave no longer decreases. At this time, consider the reaction to be over. Let the reaction solution cool to room temperature, and discharge the H 2 , and use N 2 to displace the residual gas in the autoclave.

[0087] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooling water, stir well for hydrolysis, filter off the insoluble matter, and recover the catalyst.

[0088] Step 6: Adjust the pH of the filtrate from the previous step to 3.0. Let the filtrate stand for phase separation. The organic phase is extracted 3 times with acidic water having a pH < 4.0, and the aqueous phases are combined. The pH of the combined aqueous phase is then adjusted to 9.0. Most of the water is removed by rotary evaporation under reduced pressure or after cooling, and a white solid product precipitates, which is the crude p-phenylenediamine. The purity detected by GC can reach 76.3%, and the yield is 97.9%. The crude p-phenylenediamine is purified by rectification, and the purity detected by GC can reach 99.1%, and the yield is 75.2%.

[0089] From the experimental results of Examples 1 - 8 above, it can be seen that the process method of the present invention can achieve the one-pot synthesis of p-phenylenediamine. This method has significant advantages such as simple operation, low cost, low price and easy availability of raw materials. Moreover, from the data comparison of Examples 1, 6, 7, and 8, it can be seen that when toluene is used as the solvent, it is more conducive to obtaining p-phenylenediamine products with high yields and high purities.

[0090] Comparative Example 1 p-Phenylenediamine was prepared using the same method as in Example 1, except that: the ammoniation reaction pressure was reduced. The ammoniation reaction pressure in this Comparative Example 1 was 1 Mpa. The specific process is as follows: Step 1: Add 300 mL of toluene, 0.5 mol of nitrobenzene, and 0.75 mol of sodium amide to the autoclave, tighten the lid of the autoclave, and keep the reaction kettle in a good sealed state. Use N 2 to displace the air for more than 1 minute, close the charging port of the lid, heat up to 140 °C, and keep the reaction for 8 hours to make the reaction system in the best state for the amination reaction.

[0091] Step 2: After the reaction kettle is heated up to 140 °C, fill it with N 2 to a pressure of 1 MPa to make the raw materials react fully. When the pressure in the reaction kettle exceeds 3 MPa, release the pressure in time to 1 MPa. After reacting for 8 hours, the reaction solution is cooled to room temperature, and the N 2 in the kettle is discharged.

[0092] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step, tighten the lid of the autoclave, and keep the reaction kettle in a good sealed state. Use H 2 to displace the air for more than 3 minutes, close the charging port of the lid, heat up to 80 °C, and keep the reaction for 3 hours to make the reaction system in the best state for the reduction reaction.

[0093] Step 4: After the reaction kettle is heated up to 80 °C, fill it with H 2 to a pressure of 2 MPa to make the raw materials react fully. When the pressure in the reaction kettle is lower than 0.5 MPa, fill it with H 2 to 2 MPa in time, and repeat this operation until the pressure in the kettle no longer decreases. At this time, it is regarded as the end of the reaction. The reaction solution is cooled to room temperature, and the H 2 in the kettle is discharged., N 2 Replace the residual gas in the replacement kettle.

[0094] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooling water, stir well for hydrolysis, filter off the insoluble matter, and recover the catalyst.

[0095] Step 6: Adjust the pH of the filtrate from the previous step to 3.0, let the filtrate stand for phase separation, extract the organic phase 3 times with acidic water with pH < 4.0, and combine the aqueous phases. Then adjust the pH of the aqueous phase to 9.0, remove most of the water by rotary evaporation under reduced pressure or after cooling, and a white solid product will precipitate, which is the crude p-phenylenediamine. The purity detected by GC is 87%, and the yield is 60.5%; the crude p-phenylenediamine is purified by rectification, and the purity detected by GC can reach 99.0%, and the yield is 42.5%.

[0096] It can be seen from the comparison of the experimental results of Comparative Example 1 and Example 1 that if the ammoniation reaction pressure is reduced, the yield of the product will decrease significantly. Therefore, using the ammoniation reaction pressure described in the present invention is more conducive to obtaining p-phenylenediamine products with high yield and high purity.

[0097] Comparative Example 2 p-Phenylenediamine was prepared by the same method as in Example 1, except that: the dosage ratio of sodium amide was increased. The molar ratio of nitrobenzene to sodium amide in this Comparative Example 2 was 1:3, and the specific process was as follows: Step 1: Add 300 mL of toluene, 0.5 mol of nitrobenzene, and 1.5 mol of sodium amide to the autoclave, tighten the autoclave lid, and keep the autoclave in a good sealed state. Use N 2 Replace the air for more than 1 min, close the charging port of the autoclave lid, heat up to 140 °C, and keep the reaction for 8 h to make the reaction system in the best state for the amination reaction.

[0098] Step 2: After the autoclave is heated up to 140 °C, fill it with N 2 to a pressure of 4 MPa to make the raw materials react fully. When the pressure in the autoclave exceeds 8 MPa, release the pressure to 4 MPa in time, and repeat this operation until the pressure in the autoclave no longer rises. At this time, it is regarded as the end of the reaction. Let the reaction solution cool to room temperature, and discharge the N 2 .

[0099] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step, tighten the autoclave lid, and keep the autoclave in a good sealed state. Use H 2 Replace the air for more than 3 min, close the charging port of the autoclave lid, heat up to 80 °C, and keep the reaction for 3 h to make the reaction system in the best state for the reduction reaction.

[0100] Step 4: After the autoclave is heated up to 80 °C, fill it with H 2Up to a pressure of 2 MPa to allow the raw materials to react fully. When the pressure in the reaction kettle is lower than 0.5 MPa, promptly fill it with H 2 up to 2 MPa. Repeat this operation until the pressure in the kettle no longer decreases. At this point, the reaction is considered complete. The reaction solution is cooled to room temperature, and the H 2 , N 2 in the kettle is replaced to displace the residual gas in the kettle.

[0101] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooling water, stir it thoroughly for hydrolysis, filter off the insoluble matter, and recover the catalyst.

[0102] Step 6: Adjust the pH of the filtrate from the previous step to 3.0. Let the filtrate stand for phase separation. The organic phase is extracted 3 times with acidic water having a pH < 4.0, and the aqueous phases are combined. The pH of the aqueous phase is then adjusted to 9.0, and most of the water is removed by rotary evaporation under reduced pressure or after cooling, and a white solid product precipitates, which is the crude product of p-phenylenediamine. The purity detected by GC is 89.2%, and the yield is 64.3%. After rectifying and purifying the crude p-phenylenediamine, the purity detected by GC can reach 99.0%, and the yield is 43.2%.

[0103] It can be seen from the comparison of the experimental results of Comparative Example 2 and Example 1 that if the dosage ratio of the amino salt is increased, side reactions will occur in the system (such as connecting amino groups at positions other than the para position on nitrobenzene), ultimately resulting in a decrease in the yield and purity of the product.

[0104] Comparative Example 3 p-Phenylenediamine was prepared using the same method as in Example 1, except that: the ammoniation reaction temperature was lowered. The ammoniation reaction temperature in this Comparative Example 3 was 100 °C, and the specific process was as follows: Step 1: Add 300 mL of toluene, 0.5 mol of nitrobenzene, and 0.75 mol of sodium amide to the autoclave, tighten the lid of the autoclave, and keep the autoclave in a good sealed state. Use N 2 to displace air for more than 1 minute, close the feeding port of the lid, heat up to 100 °C, and keep the reaction for 8 h to make the reaction system in the best state for the ammoniation reaction.

[0105] Step 2: After the reaction kettle is heated up to 100 °C, fill it with N 2 up to a pressure of 4 MPa to allow the raw materials to react fully. When the pressure in the reaction kettle exceeds 8 MPa, promptly release the pressure to 4 MPa. Repeat this operation. After reacting for 8 hours, the reaction solution is cooled to room temperature, and the N 2 in the kettle is discharged.

[0106] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step, tighten the lid of the autoclave, and keep the autoclave in a good sealed state. Use H 2Replace the air for more than 3 min, close the charging port of the kettle cover, heat up to 80 °C, and keep the temperature for reaction for 3 h to make the reaction system in the best state for the reduction reaction.

[0107] Step 4: After the reaction kettle is heated up to 80 °C, charge H 2 to a pressure of 2 MPa to make the raw materials react fully. When the pressure in the reaction kettle is lower than 0.5 MPa, charge H 2 to 2 MPa in time, and repeat this operation until the pressure in the kettle no longer decreases. At this time, the reaction is regarded as completed. The reaction solution is cooled to room temperature, and the H 2 in the kettle is discharged, and N 2 is used to replace the residual gas in the kettle.

[0108] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooling water, stir it well for hydrolysis, filter out the insoluble substances, and recover the catalyst.

[0109] Step 6: Adjust the pH of the filtrate from the previous step to 3.0. Let the filtrate stand for phase separation. The organic phase is extracted 3 times with acidic water with pH < 4.0, and the aqueous phases are combined. Then adjust the pH of the aqueous phase to 9.0, and remove most of the water by rotary evaporation under reduced pressure or after cooling, and a white solid product will precipitate, which is the crude product of p-phenylenediamine. The purity detected by GC is 92.3%, and the yield is 70.3%; the crude product of p-phenylenediamine is purified by rectification, and the purity detected by GC can reach 99.0%, and the yield is 62.0%.

[0110] Comparative Example 4 p-Phenylenediamine was prepared by the same method as in Example 1, except that: the temperature of the ammoniation reaction was increased. The temperature of the ammoniation reaction in this Comparative Example 4 was 190 °C, and the specific process was as follows: Step 1: Add 300 mL of toluene, 0.5 mol of nitrobenzene, and 0.75 mol of sodium amide to the autoclave, tighten the kettle cover, and keep the reaction kettle in a good sealed state. Use N 2 to replace the air for more than 1 min, close the charging port of the kettle cover, heat up to 190 °C, and keep the temperature for reaction for 8 h to make the reaction system in the best state for the amination reaction.

[0111] Step 2: After the reaction kettle is heated up to 190 °C, charge N 2 to a pressure of 4 MPa to make the raw materials react fully. When the pressure in the reaction kettle exceeds 8 MPa, relieve the pressure to 4 MPa in time, and repeat this operation. After reacting for 8 hours, the reaction solution is cooled to room temperature, and the N 2 in the kettle is discharged.

[0112] Step 3: Without treatment, directly add Raney Ni catalyst to the reaction solution obtained in the previous step, tighten the kettle cover, and keep the reaction kettle in a good sealed state. Use H 2Replace the air for more than 3 min, close the charging port of the kettle cover, heat up to 80 °C, and keep the temperature for reaction for 3 h to make the reaction system in the best state for the reduction reaction.

[0113] Step 4: After the reaction kettle is heated up to 80 °C, fill it with H 2 to a pressure of 2 MPa to make the raw materials react fully. When the pressure in the reaction kettle is lower than 0.5 MPa, fill it with H 2 to 2 MPa in time. Repeat this operation until the pressure in the kettle no longer decreases. At this time, it is regarded as the end of the reaction. The reaction solution is cooled to room temperature, and the H 2 , N 2 in the kettle is replaced to remove the residual gas in the kettle.

[0114] Step 5: Slowly pour the reaction solution from the previous step into 500 g of cooling water, stir it well for hydrolysis, filter out the insoluble substances, and recover the catalyst.

[0115] Step 6: Adjust the pH of the filtrate from the previous step to 3.0. Let the filtrate stand for phase separation. The organic phase is extracted 3 times with acidic water with pH < 4.0, and the aqueous phases are combined. Then adjust the pH of the aqueous phase to 9.0, and remove most of the water by rotary evaporation under reduced pressure or after cooling, and a white solid product will precipitate, which is the crude product of p-phenylenediamine. The purity detected by GC is 91.4%, and the yield is 72.0%. After rectifying and purifying the crude product of p-phenylenediamine, the purity detected by GC can reach 99.0%, and the yield is 64.1%.

[0116] It can be seen from the comparison of the experimental results of Comparative Example 3, Comparative Example 4 and Example 1 that if the ammoniation reaction temperature is decreased or increased, the yield of the target product p-phenylenediamine will decrease. When the ammoniation reaction temperature is decreased, the ammoniation reaction is not completely converted, which ultimately leads to a decrease in the yield of p-phenylenediamine. When the ammoniation reaction temperature is increased, side reactions are likely to occur in the ammoniation reaction system, which ultimately leads to a decrease in the yield of the target product p-phenylenediamine. Therefore, adopting the ammoniation reaction temperature conditions described in the present invention is more conducive to obtaining p-phenylenediamine with high yield and high purity.

[0117] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of concise description, all possible combinations of the technical features in the above embodiments are not exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0118] For those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A process for preparing p-phenylenediamine from nitrobenzene in one pot, characterized in that: The process is as follows: S1. Amination reaction: Under an inert gas, in a solvent system, nitrobenzene and an amino salt undergo an amination reaction under heating and pressurization conditions, and a reaction liquid is obtained after the reaction is completed; S2, reduction reaction: A catalyst is added to the reaction solution, and hydrogen is introduced to carry out a hydrogenation reduction reaction. After the reaction is completed, p-phenylenediamine is obtained through hydrolysis and post-treatment.

2. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S1, the solvent is at least one of toluene, chloroform, dichloromethane, benzene, xylene, N,N-dimethylformamide, and N,N-dimethylacetamide.

3. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S1, the amino salt is at least one of sodium amide, lithium amide and potassium amide.

4. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S1, the molar ratio of nitrobenzene to amino salt is 1:(1.2-1.8).

5. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S1, the amination reaction temperature is 120-180° C., the amination reaction pressure is 3-8 MPa, and the amination reaction time is 6-10 h.

6. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S2, the catalyst is at least one of Raney Ni, Pd / C, and Zn.

7. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S2, the hydrogen pressure in the hydrogenation reduction reaction system is 1-3 MPa.

8. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S2, the hydrogenation reduction reaction temperature is 60-100° C., and the hydrogenation reduction reaction time is 2-5 h.

9. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 1, characterized in that: In step S2, the hydrolysis and post-treatment process is as follows: the reaction system cooled to room temperature is slowly added to cooling water for hydrolysis, the insoluble matter is filtered out and the pH is adjusted to acidic, after standing for phase separation, the organic phase is extracted with acidic water, the aqueous phases are combined, and then the pH is adjusted to alkaline, and finally the p-phenylenediamine product is obtained by evaporation, crystallization and distillation purification.

10. The process for preparing p-phenylenediamine from nitrobenzene in one pot according to claim 9, characterized in that: The pH is adjusted to an acidic pH range below 4 and an alkaline pH range above 8.

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