A preparation method of 3,4'-diaminodiphenyl ether

Abstract

The present invention relates to the technical field of chemical synthesis, and in particular to a preparation method of 3,4'-diaminodiphenyl ether, the preparation method being: m-dinitrobenzene is dissolved in alcohol, and selective hydrogenation is performed with a palladium catalyst in a high temperature and high pressure reactor; the product after selective hydrogenation is co-heated and refluxed with a strong alkali aqueous solution, a first solvent, and a phase transfer catalyst to obtain m-aminophenol salt. m-aminophenol salt, p-nitroiodobenzene, an alkali, and a second solvent are co-heated and reacted, and then 3-amino-4'-nitrodiphenyl ether is obtained by post-treatment; after 3-amino-4'-nitrodiphenyl ether is dissolved in alcohol, hydrogenation reduction is performed with a palladium catalyst, and then 3,4'-diaminodiphenyl ether is obtained by post-treatment purification. By using common m-dinitrobenzene as a raw material, m-nitroaniline is obtained by selective hydrogenation, and then m-aminophenol salt is prepared by m-nitroaniline, and then etherification reaction is performed, and the reaction yield is higher, the purity is better, and the side reaction is less.

Description

Technical Field

[0001] The invention relates to a method for preparing 3,4'-diaminodiphenyl ether, and belongs to the technical field of chemical synthesis. Background Art

[0002] 3,4'-Diaminodiphenyl ether is an important component in the chemical industry and has gradually been valued by people in recent years. 3,4'-Diaminodiphenyl ether is a white crystal with a unique smell. It is insoluble in water, but soluble in organic solvents such as ethanol and xylene. At room temperature, 3,4'-diaminodiphenyl ether has high stability and is not easily affected by light and heat. 3,4'-diaminodiphenyl ether can be used as an intermediate for polymer synthesis, such as for the synthesis of polyamide or other polymer compounds. In addition, 3,4'-diaminodiphenyl ether can also be used as a modified monomer to participate in the preparation of heterocyclic aromatic polyamide fibers. By introducing 3,4'-diaminodiphenyl ether into the molecular structure of heterocyclic aramid, the elongation can be greatly improved while maintaining the high tensile strength at break of heterocyclic aramid, and better composite properties can be achieved. This high-strength and high-elongation heterocyclic aromatic polyamide fiber has broad application prospects in the field of national defense and military industry, especially in the field of bulletproof and special rubber reinforcement.

[0003] Chinese patent application CN1485315A discloses a method for preparing 3,4'-diaminodiphenyl ether, wherein nitrodiphenyl ether is used as a raw material, hydrazine hydrate is used as a reducing agent, and a reduction reaction is carried out in the presence of a catalyst, thereby obtaining the 3,4'-diaminodiphenyl ether under a relatively low pressure, but hydrazine hydrate is highly toxic and is not suitable for large-scale use in industry. Chinese patent application CN1583713A discloses a manufacturing process for 3,4'-diaminodiphenyl ether, wherein m-aminophenol or m-nitrophenol is reacted to generate phenol sodium salt, which is then reacted with p-nitrochlorobenzene in an equimolar ratio to obtain 3-amino-4'-nitrodiphenyl ether or 3,4'-dinitrodiphenyl ether, and then 3,4'-diaminodiphenyl ether is obtained by hydrogen reduction or iron powder reduction. The raw materials m-aminophenol and m-nitrophenol used in this method are expensive, and reduction with iron powder will produce more three wastes. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing 3,4'-diaminodiphenyl ether. By using common m-dinitrobenzene as a raw material, m-nitroaniline is obtained by selective hydrogenation, and then m-aminophenol salt is prepared by the m-nitroaniline, and then an etherification reaction is carried out. The reaction yield is higher, the purity is better, the side reaction is less, the reaction is clean and green, the three wastes are less, and the method is suitable for industrial application.

[0005] The technical solution of the present invention to solve the above technical problem is as follows: a preparation method of 3,4'-diaminodiphenyl ether, the preparation method is:

[0006] S1. Selective hydrogenation of m-dinitrobenzene:

[0007] Dissolving m-dinitrobenzene in alcohol, and selectively hydrogenating it with a palladium catalyst in a high-temperature and high-pressure reactor to obtain m-nitroaniline;

[0008] S2. Preparation of m-aminophenol salt:

[0009] The m-nitroaniline product after the selective hydrogenation is refluxed with a strong base aqueous solution, a first solvent, and a phase transfer catalyst to obtain m-aminophenol salt;

[0010] S3, preparation of 3-amino-4'-nitrodiphenyl ether:

[0011] m-aminophenol salt, p-nitroiodobenzene, a base and a second solvent are co-heated to react, and then post-treated to obtain 3-amino-4'-nitrodiphenyl ether;

[0012] S4. Preparation of 3,4'-diaminodiphenyl ether:

[0013] After 3-amino-4'-nitrodiphenyl ether is dissolved in alcohol, it is hydrogenated and reduced using a palladium catalyst in a high-temperature and high-pressure reactor, and then post-processed and purified to obtain 3,4'-diaminodiphenyl ether.

[0014] Further, in step S1, the alcohol is at least one of methanol and ethanol;

[0015] When the meta-dinitrobenzene is dissolved in alcohol, the mass fraction of the meta-dinitrobenzene is 5%-30%.

[0016] Preferably, in step S1, the alcohol is methanol, and the selective hydrogenation using methanol has better solubility and better reactivity;

[0017] When the m-dinitrobenzene is dissolved in methanol, the mass fraction of the m-dinitrobenzene is 10%-20%. Under this condition, the reaction temperature is relatively low and the system pressure is low.

[0018] Further, in step S1, the reaction temperature is 50°C-120°C, the pressure is 1-3Mpa, and the reaction time is 6-8h;

[0019] The molar ratio of the meta-dinitrobenzene to the hydrogen is 1:(3.0-3.2).

[0020] Further, in step S2, the m-aminophenol salt is sodium m-aminophenol or potassium m-aminophenol, and the strong base is sodium hydroxide or potassium hydroxide;

[0021] The first solvent is at least one of toluene, xylene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, pyridine, acetonitrile, and ethylene glycol;

[0022] The phase transfer catalyst (PTC) is at least one of benzyltriethylammonium chloride (TEBA), tetrabutylammonium bromide, and 18-crown-6 ether.

[0023] Further, the molar ratio of the intermediate nitroaniline in step S2 to the strong base in step S2 is 1:(2.2-2.6);

[0024] In step S2, the mass concentration of the strong alkali aqueous solution is 10%-50%; the reaction time is 4-8h;

[0025] The phase transfer catalyst accounts for 1%-5% of the mass of the first solvent.

[0026] Further, in step S3, the base is at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and sodium bicarbonate;

[0027] The second solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile and ethylene glycol.

[0028] Preferably, in step S3, the base is potassium carbonate, which has a better reaction effect in the reaction. In a system with N,N-dimethylacetamide as a solvent, the etherification effect is good, the yield is high, and the side reactions are few.

[0029] Further, in step S3, the reaction temperature is 140°C-150°C, and the reaction time is 3-5h;

[0030] The molar ratio of the m-aminophenol salt to p-nitroiodobenzene and the base is (1-1.05):1:(1.2-1.5).

[0031] Further, in step S4, the alcohol is at least one of methanol and ethanol;

[0032] When the 3-amino-4'-nitrodiphenyl ether is dissolved in alcohol, the mass fraction of the 3-amino-4'-nitrodiphenyl ether is 5%-30%;

[0033] In step S4, the reaction temperature is 50°C-120°C, the pressure is 1-3Mpa, and the reaction time is 6-12h;

[0034] The molar ratio of the 3-amino-4'-nitrodiphenyl ether to hydrogen is 1:(3.1-3.5).

[0035] Furthermore, in step S1 and step S4, the palladium catalyst is at least one of Pd, Pd / C, Pd / BaSO4, Pd / diatomaceous earth, PdO2, and Ru-Pd / C.

[0036] Preferably, in step S1 and step S4, the palladium catalyst is Pd / C, which has a better hydrogenation effect and a shorter reaction time.

[0037] Further, in step S4, after the reaction is completed, 3,4'-diaminodiphenyl ether is obtained after solid-liquid separation and recrystallization;

[0038] The solvent used for the recrystallization is a mixed solvent of methanol and n-heptane, wherein the mass ratio of methanol to n-heptane is 1:(5.5-6.5).

[0039] The beneficial effects of the present invention are:

[0040] The preparation method of 3,4'-diaminodiphenyl ether of the present invention uses m-dinitrobenzene as a raw material, first performs selective hydrogenation to generate m-nitroaniline, then uses m-nitroaniline as a raw material, reacts with sodium hydroxide to generate m-aminophenolate, and the m-aminophenolate and p-nitroiodobenzene are subjected to etherification reaction in a strong polar aprotic solvent under base catalysis to generate 3-amino-4'-nitrodiphenyl ether, and then performs hydrogenation to finally generate 3,4'-diaminodiphenyl ether. The 3,4'-diaminodiphenyl ether synthesized by the method has the advantages of less side reactions, low cost, high yield and purity, and the purity of the product is not less than 99.5%.

[0041] In the preparation method of 3,4'-diaminodiphenyl ether of the present invention, p-nitroiodobenzene is used for etherification reaction, which has a shorter reaction time and better effect than p-chloronitrobenzene. The method of preparing 3,4'-diaminodiphenyl ether of the present invention has easy-to-obtain raw materials, clean and green reaction, less three wastes, and a higher conversion rate. DETAILED DESCRIPTION

[0042] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0044] A preparation method of 3,4'-diaminodiphenyl ether, the preparation method comprising:

[0045] S1. Selective hydrogenation of m-dinitrobenzene:

[0046] Dissolving m-dinitrobenzene in alcohol, and selectively hydrogenating it with a palladium catalyst in a high-temperature and high-pressure reactor to obtain m-nitroaniline;

[0047] S2. Preparation of m-aminophenol salt:

[0048] The m-nitroaniline product after the selective hydrogenation is refluxed with a strong base aqueous solution, a first solvent, and a phase transfer catalyst to obtain m-aminophenol salt;

[0049] S3, preparation of 3-amino-4'-nitrodiphenyl ether:

[0050] m-aminophenol salt, p-nitroiodobenzene, a base and a second solvent are co-heated to react, and then post-treated to obtain 3-amino-4'-nitrodiphenyl ether;

[0051] S4. Preparation of 3,4'-diaminodiphenyl ether:

[0052] After 3-amino-4'-nitrodiphenyl ether is dissolved in alcohol, it is hydrogenated and reduced using a palladium catalyst in a high-temperature and high-pressure reactor, and then post-processed and purified to obtain 3,4'-diaminodiphenyl ether.

[0053] Specifically, in step S1, the alcohol is at least one of methanol and ethanol;

[0054] When the meta-dinitrobenzene is dissolved in alcohol, the mass fraction of the meta-dinitrobenzene is 5%-30%.

[0055] Specifically, in step S1, the palladium catalyst is at least one of Pd, Pd / C, Pd / BaSO4, Pd / diatomaceous earth, PdO2, and Ru-Pd / C.

[0056] Preferably, methanol is used in the selective hydrogenation because of its better solubility and reactivity.

[0057] Preferably, the selective hydrogenation uses a palladium-carbon catalyst, which has a better hydrogenation effect and a shorter reaction time.

[0058] Preferably, during the hydrogenation process, using methanol to dissolve the raw material can better react with palladium carbon for hydrogenation. When the mass fraction of m-dinitrobenzene is 10%-20%, the reaction temperature is relatively low and the system pressure is low.

[0059] Specifically, in step S1, the reaction temperature is 50°C-120°C, the pressure is 1-3Mpa, and the reaction time is 6-8h;

[0060] The molar ratio of the meta-dinitrobenzene to the hydrogen is 1:(3.0-3.2).

[0061] Specifically, in step S2, the m-aminophenol salt is sodium m-aminophenol or potassium m-aminophenol, and the strong base is sodium hydroxide or potassium hydroxide;

[0062] The first solvent is at least one of toluene, xylene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, pyridine, acetonitrile, and ethylene glycol;

[0063] The phase transfer catalyst is at least one of benzyltriethylammonium chloride, tetrabutylammonium bromide and 18-crown-6 ether.

[0064] Specifically, the molar ratio of the intermediate nitroaniline in step S2 to the strong base in step S2 is 1:(2.2-2.6);

[0065] In step S2, the mass concentration of the strong alkali aqueous solution is 10%-50%; the reaction time is 4-8h;

[0066] The phase transfer catalyst accounts for 1%-5% of the mass of the first solvent.

[0067] More specifically, the m-aminophenol salt in the embodiment of the present invention is sodium m-aminophenol, and the strong alkali aqueous solution is a sodium hydroxide aqueous solution.

[0068] More specifically, in step S2, the concentration of the aqueous solution of sodium hydroxide should not be too high. Adding a certain organic solvent (the first solvent) can better dissolve the raw materials. The presence of a phase transfer catalyst can promote the reaction faster and better. The temperature required for the reaction should not be too high. A higher concentration of sodium hydroxide and a higher temperature will cause the reaction to produce "black material", affecting the reaction efficiency.

[0069] Specifically, in step S3, the base is at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and sodium bicarbonate;

[0070] The second solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile and ethylene glycol.

[0071] More specifically, in the etherification reaction of sodium m-aminophenol and p-nitroiodobenzene, the choice of base has a significant effect on the reaction. Potassium carbonate has a better reaction effect in the reaction. In the system with N,N-dimethylacetamide as the solvent, the etherification effect is good, the yield is high, and the side reactions are few.

[0072] Specifically, in step S3, the reaction temperature is 140°C-150°C, and the reaction time is 3-5h;

[0073] The molar ratio of the m-aminophenol salt to p-nitroiodobenzene and the base is (1-1.05):1:(1.2-1.5).

[0074] Specifically, in step S4, the alcohol is at least one of methanol and ethanol;

[0075] When the 3-amino-4'-nitrodiphenyl ether is dissolved in alcohol, the mass fraction of the 3-amino-4'-nitrodiphenyl ether is 5%-30%;

[0076] In step S4, the reaction temperature is 50°C-120°C, the pressure is 1-3Mpa, and the reaction time is 6-12h;

[0077] The molar ratio of the 3-amino-4'-nitrodiphenyl ether to hydrogen is 1:(3.1-3.5).

[0078] More specifically, in the reductive amination reaction of 3-amino-4'-nitrodiphenyl ether with hydrogen, it is necessary to ensure a sufficient amount of hydrogen. Higher reaction temperature and pressure can better promote the reaction, reduce the occurrence of side reactions, and improve the reaction conversion rate and yield.

[0079] Specifically, in step S4, the palladium catalyst is at least one of Pd, Pd / C, Pd / BaSO4, Pd / diatomaceous earth, PdO2, and Ru-Pd / C.

[0080] Specifically, in step S4, after the reaction is completed, 3,4'-diaminodiphenyl ether is obtained after solid-liquid separation and recrystallization;

[0081] The solvent used for the recrystallization is a mixed solvent of methanol and n-heptane, wherein the mass ratio of methanol to n-heptane is 1:(5.5-6.5).

[0082] Example 1

[0083] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 151.2 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 96%.

[0084] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 100 mL of 10% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h, evaporate to dryness the toluene and water, leaving a dark brown solid in the flask.

[0085] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N,N-dimethylformamide into a flask containing sodium m-aminophenol and heat to 140°C for 3 h. After the reaction is completed, cool naturally to room temperature and add 750 mL of water. Stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 95%.

[0086] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99.1%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.5%, and the recrystallization yield is 98.6%.

[0087] Example 2

[0088] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 95.2 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 70°C, the hydrogen pressure to 1.5 MPa, and react for 6 hours. Cool to room temperature, add 40 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 95%.

[0089] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of industrial-grade xylene, add 0.97 g of tetrabutylammonium bromide, stir and heat to reflux, then add 66.7 mL of 15% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h. Evaporate the xylene and water to dryness, leaving a dark brown solid in the flask.

[0090] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: 24.9 g of p-nitroiodobenzene, 8.4 g of potassium hydroxide and 75 g of N,N-dimethylacetamide were added to a flask containing sodium m-aminophenol and heated to 145°C for 4 h. After the reaction was completed, the mixture was naturally cooled to room temperature and 750 mL of water was added. The mixture was stirred for 30 min, filtered and dried to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 97%.

[0091] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 130 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 70°C, the hydrogen pressure to 1.5 MPa, and react for 6 hours. Cool to room temperature, add 80 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 98%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.5%, and the recrystallization yield is 97.9%.

[0092] Example 3

[0093] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 67 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 30 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 97%.

[0094] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 mL of N-methylpyrrolidone, add 0.97 g of tetrabutylammonium bromide, stir and heat to reflux, then add 50 mL of 20% sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h. Evaporate N-methylpyrrolidone and water to dryness, leaving a dark brown solid in the flask.

[0095] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N-methylpyrrolidone into a flask containing sodium m-aminophenol, heat to 145°C and react for 4 h. After the reaction is completed, cool naturally to room temperature, add 750 mL of water, stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether with a yield of 99%.

[0096] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 92 g of methanol, and 0.94 g of palladium carbon, stir evenly, replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 50 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.7% and the recrystallization yield is 98%.

[0097] Example 4

[0098] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 50.4 g ethanol, and 0.94 g Pd / C, stir evenly, replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 30 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 97%.

[0099] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 mL of tetrahydrofuran, add 3.2 g of 18-crown-6 ether, stir and heat to reflux, then add 40 mL of 25% sodium hydroxide solution dropwise under reflux for 1 h. Allow to react for 4 h. Evaporate the tetrahydrofuran and water to dryness, leaving a dark brown solid in the flask.

[0100] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of dimethyl sulfoxide into a flask containing sodium m-aminophenol, heat to 145°C and react for 4-6 h. After the reaction is completed, cool naturally to room temperature, add 750 mL of water, stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether with a yield of 98.4%.

[0101] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 76.6 g of ethanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 30 g of ethanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 98.3%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.6%, and the recrystallization yield is 95%.

[0102] Example 5

[0103] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 50.4 g methanol, and 0.94 g Pd / BaSO4 and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 30 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 96%.

[0104] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 mL of tetrahydrofuran, add 3.2 g of 18-crown-6 ether, stir and heat to reflux, then add 33.4 mL of 30% sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h. Evaporate the tetrahydrofuran and water to dryness, leaving a dark brown solid in the flask.

[0105] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N,N-dimethylacetamide were added to a flask containing sodium m-aminophenol and heated to 145°C for 4 h. After the reaction was completed, the mixture was naturally cooled to room temperature and 750 mL of water was added. The mixture was stirred for 30 min, filtered and dried to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 98.8%.

[0106] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 76.6 g of methanol, and 0.94 g of Pd / BaSO4 and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 30 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 98%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.6%, and the recrystallization yield is 99.1%.

[0107] Example 6

[0108] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 50.4 g methanol, and 0.94 g Ru-Pd / C and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 30 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 93%.

[0109] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 mL of N,N-dimethylacetamide, add 3.2 g of 18-crown-6 ether, stir and heat to reflux, then add 33.4 mL of 30% sodium hydroxide solution dropwise under reflux for 1 h. Allow to react for 4 h, evaporate the water to dryness, and the flask will contain a dark brown liquid.

[0110] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: 24.9 g of p-nitroiodobenzene and 75 g of N,N-dimethylacetamide were added to a flask containing sodium m-aminophenol, and the mixture was heated to 145°C and reacted for 4 h. After the reaction was completed, the mixture was naturally cooled to room temperature, 750 mL of water was added, and the mixture was stirred for 30 min. The mixture was filtered and dried to obtain 3-amino-4'-nitrodiphenyl ether with a yield of 98%.

[0111] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 76.6 g of methanol, and 0.94 g of Ru-Pd / C and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 80°C, the hydrogen pressure to 1.8 MPa, and react for 6 hours. Cool to room temperature, add 30 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 98%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.7% and the recrystallization yield is 99%.

[0112] Example 7

[0113] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 319 g ethanol, and 0.94 g PdO2 and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 120°C, the hydrogen pressure to 3 MPa, and react for 6 hours. Cool to room temperature, add 50 g ethanol, stir evenly, filter, and recover the catalyst for reuse. Recover ethanol by rotary evaporation to obtain m-nitroaniline solid with a yield of 92.8%.

[0114] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 mL of tetrahydrofuran, add 0.69 g of tetrabutylammonium bromide, stir and heat to reflux, then add 20 mL of 50% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h. Evaporate the tetrahydrofuran and water to dryness, leaving a dark brown solid in the flask.

[0115] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: 26.1 g of p-nitroiodobenzene, 12.7 g of sodium carbonate and 75 g of N,N-dimethylacetamide were added to a flask containing sodium m-aminophenol and heated to 150°C for 5 h. After the reaction was completed, the mixture was cooled to room temperature naturally and 750 mL of water was added. The mixture was stirred for 30 min, filtered and dried to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 94%.

[0116] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 120°C, the hydrogen pressure to 3 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99.1%. Recrystallize with 0.5 times the mass of methanol and 3.25 times the mass of n-heptane. The gas phase detection purity is 99.5%, and the recrystallization yield is 98.4%.

[0117] Example 8

[0118] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 39.5 g methanol, and 0.94 g Pd and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 50°C, the hydrogen pressure to 1 MPa, and react for 8 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain m-nitroaniline solid with a yield of 93%.

[0119] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 50 mL of acetonitrile, add 2 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 40 mL of 25% aqueous sodium hydroxide solution dropwise under reflux for 1 h. Allow to react for 8 h. Evaporate tetrahydrofuran and water to dryness, leaving a dark brown solid in the flask.

[0120] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 25 g of p-nitroiodobenzene, 6.75 g of potassium hydroxide and 75 g of N-methylpyrrolidone into a flask containing sodium m-aminophenol, heat to 140°C and react for 5 h. After the reaction is completed, cool naturally to room temperature, add 750 mL of water, stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether with a yield of 94%.

[0121] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 50°C, the hydrogen pressure to 1 MPa, and react for 12 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99.1%. Recrystallize with 0.55 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.6%, and the recrystallization yield is 98.2%.

[0122] Comparative Example 1

[0123] The preparation process of this comparative example 1 is: directly using m-dinitrobenzene as a raw material to prepare sodium m-nitrophenolate, and then performing an etherification reaction to obtain 3,4'-dinitrodiphenyl ether. The specific preparation process is as follows:

[0124] (1) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 16.8 g of m-dinitrobenzene in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 100 mL of 10% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h. Evaporate toluene and water to dryness, leaving a dark brown solid in the flask.

[0125] (2) Preparation of 3,4'-dinitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene and 75 g of N,N-dimethylformamide into a flask containing sodium m-nitrophenolate, heat to 140 °C, and react for 3 h. After the reaction is completed, cool naturally to room temperature, add 750 mL of water, stir for 30 min, filter, and dry to obtain 3-amino-4'-nitrodiphenyl ether with a yield of 80%.

[0126] (3) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 91.6%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 98.5%, the gas phase purity of the second recrystallization is 99.3%, and the recrystallization yield is 88%.

[0127] From the above comparative example 1, it can be seen that: directly using m-dinitrobenzene as a raw material to prepare sodium m-nitrophenolate, and then performing an etherification reaction to obtain 3-amino-4'-nitrodiphenyl ether, the yield is low, only 80%, and the yield of 3,4'-diaminodiphenyl ether obtained after hydrogenation reduction is not high, and the purity is low during the first recrystallization, requiring a second recrystallization, and the recrystallization yield is only 88%. This shows that in Examples 1 to 8, selectively hydrogenating m-dinitrobenzene before reacting can effectively improve the reaction conversion rate and increase the yield.

[0128] Comparative Example 2

[0129] 3,4'-diaminodiphenyl ether was prepared by the same method as in Example 1, except that p-nitroiodobenzene in step (3) was replaced with p-nitrochlorobenzene. The specific preparation process is as follows:

[0130] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 151.2 g methanol, and 0.94 g palladium carbon, stir evenly, replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 96%.

[0131] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 100 mL of 10% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h, evaporate to dryness the toluene and water, leaving a dark brown solid in the flask.

[0132] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 15.8 g of p-nitrochlorobenzene and 75 g of N,N-dimethylformamide into a flask containing sodium m-aminophenol, heat to 140 °C, and react for 5 h. After the reaction is completed, cool naturally to room temperature, add 750 mL of water, stir for 30 min, filter, and dry to obtain 3-amino-4'-nitrodiphenyl ether with a yield of 90%.

[0133] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99.1%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 99.5%, and the recrystallization yield is 98.6%.

[0134] From the comparison of the experimental results of Example 1 and Comparative Example 1, it can be seen that the yield of p-nitroiodobenzene is significantly higher than that of p-nitrochlorobenzene, and the required reaction time is shorter. The main reason is that the electronegativity of iodine is smaller than that of chlorine, and the attraction to electrons is poorer, so that the carbon atom connected to iodine is more positively charged than the carbon atom connected to chlorine, making it easier for iodine atoms to leave, the reaction is easier to occur, the time required for the reaction is shorter, the yield is higher, and the reaction time is saved.

[0135] Comparative Example 3

[0136] 3,4'-diaminodiphenyl ether was prepared by the same method as in Example 1, except that the reaction pressure in step (1) of this comparative example 3 was 4 MPa (higher than the reaction pressure specified in the present invention). The specific preparation process is as follows:

[0137] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 151.2 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 4 MPa, and react for 6 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 94%.

[0138] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 100 mL of 10% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h, evaporate to dryness the toluene and water, leaving a dark brown solid in the flask.

[0139] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N,N-dimethylformamide into a flask containing sodium m-aminophenol and heat to 140°C for 3 h. After the reaction is completed, cool naturally to room temperature and add 750 mL of water. Stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 95%.

[0140] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99.1%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 97.2% and the recrystallization yield is 92%.

[0141] It can be seen from the experimental results of Example 1 and Comparative Example 3 that if the hydrogen pressure is too high during the selective hydrogenation of m-dinitrobenzene in step (1), the yield and purity of the final target product 3,4'-diaminodiphenyl ether will decrease, because excessively high hydrogen pressure will cause the reaction system to overheat and produce other by-products, resulting in a decrease in the reaction yield and purity.

[0142] Comparative Example 4

[0143] 3,4'-diaminodiphenyl ether was prepared by the same method as in Example 1, except that the reaction pressure in step (1) of this comparative example 4 was 0.7 MPa (lower than the reaction pressure specified in the present invention). The specific preparation process is as follows:

[0144] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 151.2 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 0.7 MPa, and react for 6 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 92%.

[0145] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 100 mL of 10% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h, evaporate to dryness the toluene and water, leaving a dark brown solid in the flask.

[0146] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N,N-dimethylformamide into a flask containing sodium m-aminophenol and heat to 140°C for 3 h. After the reaction is completed, cool naturally to room temperature and add 750 mL of water. Stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 93%.

[0147] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 98%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 97.0% and the recrystallization yield is 90%.

[0148] It can be seen from the experimental results of Example 1 and Comparative Example 4 that if the hydrogen pressure is too low during the selective hydrogenation of m-dinitrobenzene in step (1), the yield and purity of the final target product 3,4'-diaminodiphenyl ether will decrease, because too low a hydrogen pressure will lead to incomplete reaction of the raw materials and residual raw materials, resulting in a decrease in the reaction yield and purity.

[0149] Comparative Example 5

[0150] 3,4'-diaminodiphenyl ether was prepared by the same method as in Example 1, except that a sodium hydroxide aqueous solution with a mass concentration of 60% (higher than the concentration of the strong alkali aqueous solution specified in the present invention) was used in step (2) of this comparative example 5. The specific preparation process is as follows:

[0151] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 151.2 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 96%.

[0152] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 16.6 mL of 60% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h. Evaporate the toluene and water to dryness, leaving a black solid in the flask.

[0153] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N,N-dimethylformamide into a flask containing sodium m-aminophenol and heat to 140°C for 3 h. After the reaction is completed, cool naturally to room temperature and add 750 mL of water. Stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 92%.

[0154] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 98%. Recrystallize with 0.5 times the mass of methanol and 3 times the mass of n-heptane. The gas phase detection purity is 96.5%, and the recrystallization yield is 94%.

[0155] It can be seen from the experimental results of Example 1 and Comparative Example 5 that if the concentration of the sodium hydroxide solution in step (2) is too high, the yield and purity of the final target product 3,4'-diaminodiphenyl ether will decrease, because too high a concentration of sodium hydroxide will lead to the generation of by-products, such as black char, which will reduce the yield and purity of the reaction.

[0156] Comparative Example 6

[0157] 3,4'-diaminodiphenyl ether was prepared by the same method as in Example 1, except that only n-heptane was used in the recrystallization in step (4) of this comparative example 6. The specific preparation process is as follows:

[0158] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 151.2 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 96%.

[0159] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 100 mL of 10% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h, evaporate to dryness the toluene and water, leaving a dark brown solid in the flask.

[0160] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N,N-dimethylformamide into a flask containing sodium m-aminophenol and heat to 140 °C for 3 h. After the reaction is completed, cool naturally to room temperature and add 750 mL of water. Stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether with a yield of 95%.

[0161] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99.1%. Recrystallize with 3.5 times n-heptane, the gas phase detection purity is 99.5%, and the recrystallization yield is 93%.

[0162] Comparative Example 7

[0163] 3,4'-diaminodiphenyl ether was prepared by the same method as in Example 1, except that only methanol was used in the recrystallization in step (4) of this comparative example 7. The specific preparation process is as follows:

[0164] (1) Selective hydrogenation of m-dinitrobenzene: In a high-temperature and high-pressure reactor, add 16.8 g m-dinitrobenzene, 151.2 g methanol, and 0.94 g palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 50 g methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 96%.

[0165] (2) Preparation of sodium m-aminophenol: In a 1 L three-necked round-bottom flask, dissolve 13.8 g of m-nitroaniline in 40 ml of toluene, add 0.69 g of benzyltriethylammonium chloride, stir and heat to reflux, then add 100 mL of 10% aqueous sodium hydroxide solution dropwise over 1 h. Allow to react for 4 h, evaporate to dryness the toluene and water, leaving a dark brown solid in the flask.

[0166] (3) Preparation of 3-amino-4'-nitrodiphenyl ether: Add 24.9 g of p-nitroiodobenzene, 20.7 g of potassium carbonate and 75 g of N,N-dimethylformamide into a flask containing sodium m-aminophenol and heat to 140°C for 3 h. After the reaction is completed, cool naturally to room temperature and add 750 mL of water. Stir for 30 min, filter and dry to obtain 3-amino-4'-nitrodiphenyl ether in a yield of 95%.

[0167] (4) Preparation of 3,4'-diaminodiphenyl ether: In a high-temperature and high-pressure reactor, add 23.0 g of 3-amino-4'-nitrodiphenyl ether, 207 g of methanol, and 0.94 g of palladium carbon and stir evenly. Replace with hydrogen 2-3 times, set the temperature to 60°C, the hydrogen pressure to 1.2 MPa, and react for 6 hours. Cool to room temperature, add 100 g of methanol, stir evenly, filter, and recover the catalyst for reuse. Recover methanol by rotary evaporation to obtain a solid with a yield of 99.1%. Recrystallize with 3.5 times methanol, the gas phase detection purity is 99.6%, and the recrystallization yield is 90%.

[0168] It can be seen from the experimental results of Example 1 and Comparative Examples 6 and 7 that if a single solvent is used for recrystallization in step (4), the yield of the final target product 3,4'-diaminodiphenyl ether will be significantly reduced. Therefore, the use of the methanol and n-heptane mixed solvent defined in the present invention for recrystallization and purification is more conducive to obtaining a high yield and high purity target product.

[0169] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0170] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A method for preparing 3,4'-diaminodiphenyl ether, characterized in that: The preparation method is: S1. Selective hydrogenation of m-dinitrobenzene: Dissolving m-dinitrobenzene in alcohol, and selectively hydrogenating it with a palladium catalyst in a high-temperature and high-pressure reactor to obtain m-nitroaniline; S2. Preparation of m-aminophenol salt: The m-nitroaniline product after the selective hydrogenation is refluxed with a strong base aqueous solution, a first solvent, and a phase transfer catalyst to obtain m-aminophenol salt; S3, preparation of 3-amino-4'-nitrodiphenyl ether: m-aminophenol salt, p-nitroiodobenzene, a base and a second solvent are co-heated to react, and then post-treated to obtain 3-amino-4'-nitrodiphenyl ether; S4. Preparation of 3,4'-diaminodiphenyl ether: After 3-amino-4'-nitrodiphenyl ether is dissolved in alcohol, it is hydrogenated and reduced using a palladium catalyst in a high-temperature and high-pressure reactor, and then post-processed and purified to obtain 3,4'-diaminodiphenyl ether.

2. A method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S1, the alcohol is at least one of methanol and ethanol; When the meta-dinitrobenzene is dissolved in alcohol, the mass fraction of the meta-dinitrobenzene is 5%-30%.

3. A method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S1, the reaction temperature is 50°C-120°C, the pressure is 1-3Mpa, and the reaction time is 6-8h; The molar ratio of the meta-dinitrobenzene to the hydrogen is 1:(3.0-3.2).

4. The method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S2, the m-aminophenol salt is sodium m-aminophenol or potassium m-aminophenol, and the strong base is sodium hydroxide or potassium hydroxide; The first solvent is at least one of toluene, xylene, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, pyridine, acetonitrile, and ethylene glycol; The phase transfer catalyst is at least one of benzyltriethylammonium chloride, tetrabutylammonium bromide and 18-crown-6 ether.

5. The method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: The molar ratio of the intermediate nitroaniline in step S2 to the strong base in step S2 is 1:(2.2-2.6); In step S2, the mass concentration of the strong alkali aqueous solution is 10%-50%; the reaction time is 4-8h; The phase transfer catalyst accounts for 1%-5% of the mass of the first solvent.

6. The method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S3, the base is at least one of sodium hydroxide, potassium hydroxide, potassium carbonate, sodium carbonate, and sodium bicarbonate; The second solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile and ethylene glycol.

7. The method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S3, the reaction temperature is 140°C-150°C, and the reaction time is 3-5h; The molar ratio of the m-aminophenol salt to p-nitroiodobenzene and the base is (1-1.05):1:(1.2-1.5).

8. The method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S4, the alcohol is at least one of methanol and ethanol; When the 3-amino-4'-nitrodiphenyl ether is dissolved in alcohol, the mass fraction of the 3-amino-4'-nitrodiphenyl ether is 5%-30%; In step S4, the reaction temperature is 50°C-120°C, the pressure is 1-3Mpa, and the reaction time is 6-12h; The molar ratio of the 3-amino-4'-nitrodiphenyl ether to hydrogen is 1:(3.1-3.5).

9. The method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S1 and step S4, the palladium catalyst is at least one of Pd, Pd / C, Pd / BaSO4, Pd / diatomaceous earth, PdO2, and Ru-Pd / C.

10. The method for preparing 3,4'-diaminodiphenyl ether according to claim 1, characterized in that: In step S4, after the reaction is completed, 3,4'-diaminodiphenyl ether is obtained after solid-liquid separation and recrystallization; The solvent used for the recrystallization is a mixed solvent of methanol and n-heptane, wherein the mass ratio of methanol to n-heptane is 1:(5.5-6.5).