A process for the preparation of 4,4'-diaminodiphenyl ether

Abstract

The application discloses a method for preparing 4,4'-diamino diphenyl ether. The method uses 4,4'-dinitrodiphenyl ether as an initial raw material, and 4,4'-diamino diphenyl ether is prepared through catalytic hydrogenation reduction of the loaded catalyst; in the preparation of the catalyst, the dispersion of the metal active component on the carrier is improved without using a surfactant by means of a membrane dispersion micro-reactor, the metal consumption is reduced, the loaded structure is integrally formed, and the continuous production of the catalyst precursor is realized. The preparation process is more green and efficient, and is applied to the hydrogenation reduction of 4,4'-dinitrodiphenyl ether under mild reaction conditions, and excellent performance is shown, and the production cost is reduced.

Description

Technical Field

[0001] This invention relates to a method for synthesizing 4,4'-diaminodiphenyl ether, an important chemical raw material, and particularly to a method for preparing 4,4'-diaminodiphenyl ether using 4,4'-dinitrodiphenyl ether as a substrate and its catalyst. Background Technology

[0002] 4,4'-Diaminodiphenyl ether is a high-value-added fine chemical intermediate that can be used to synthesize engineering plastics such as polyimide and other high-temperature resistant polymers. It can also serve as a raw material and crosslinking agent for the synthesis of high-performance heat-resistant epoxy resins and polyurethanes, and can replace benzidine, which has carcinogenic effects, in the production of azo dyes and reactive dyes. Currently, the main method for producing 4,4'-diaminodiphenyl ether is the reduction of 4,4'-dinitrodiphenyl ether. Reduction methods are divided into chemical reduction and catalytic hydrogenation. Chemical reduction methods mainly include iron powder reduction, hydrazine hydrate reduction, and sodium sulfide reduction. Catalytic hydrogenation uses hydrogen as a reducing agent, reducing the substrate under the action of a hydrogenation catalyst. Compared with chemical reduction, catalytic hydrogenation has the advantages of simpler synthesis process, higher product purity, and less waste.

[0003] Currently, the catalysts used in catalytic hydrogenation mainly fall into two categories: one uses precious metal catalysts such as Pt and Pd, but their high price significantly impacts production costs; the other uses skeletal nickel catalysts, which, while inexpensive, are difficult to store and pose safety hazards such as flammability and explosiveness. To prepare 4,4'-diaminodiphenyl ether more efficiently and at a lower cost, researchers have investigated hydrogenation catalysts. Patent CN108906101 synthesized a catalyst using nitrogen-doped activated carbon as a support and nickel or iron as the active metal via an impregnation method. However, the support preparation requires high-pressure reactors at 100-200℃, placing high demands on equipment. Patent CN110639553 synthesized an iron-cobalt composite carbon-copper catalyst for the hydrogenation preparation of 4,4'-diaminodiphenyl ether, but the synthesis of the support involved the use of the surfactant polyethylene glycol, with calcination temperatures as high as 800-900℃ and a calcination atmosphere consisting of nitrogen and water vapor, making the preparation process complex.

[0004] In summary, the hydrogenation reduction synthesis of 4,4'-diaminodiphenyl ether using 4,4'-dinitrodiphenyl ether as a raw material under the action of a heterogeneous non-precious metal catalyst is a green and sustainable process route. Therefore, it is of great significance to develop a heterogeneous non-precious metal catalyst system with simple preparation process, no surfactant use, and high hydrogenation activity, and to apply it to the preparation of 4,4'-diaminodiphenyl ether. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing 4,4'-diaminodiphenyl ether. This method uses 4,4'-dinitrodiphenyl ether as the initial raw material, which is then catalytically hydrogenated and reduced to obtain 4,4'-diaminodiphenyl ether. This invention also provides a method for preparing a supported catalyst, which utilizes a membrane dispersion microreactor to improve the dispersion of the metal active component on the support without the use of surfactants, reducing the amount of metal used. The supported structure is integrally formed, and continuous production of the catalyst precursor is achieved, making the preparation process more green and efficient. This catalyst, applied under mild reaction conditions to the hydrogenation reduction of 4,4'-dinitrodiphenyl ether, exhibits excellent performance in the reaction and reduces production costs.

[0006] The technical solution of this invention is as follows:

[0007] A method for preparing 4,4'-diaminodiphenyl ether, the method comprising the following steps:

[0008] Hydrogen gas was introduced into a reactor containing 4,4'-dinitrodiphenyl ether (DNDPE), N,N-dimethylacetamide (DMAC) and a supported catalyst, and the reaction was carried out at 50-100°C for 20-800 min to produce 4,4'-diaminodiphenyl ether through a hydrogenation reduction reaction.

[0009] The mass ratio of 4,4'-dinitrodiphenyl ether to catalyst is 500-2:1; the molar ratio of DNDPE to DMAC is 1:3-15; and the hydrogen pressure is 1.0-3.5 MPa.

[0010] The supported catalyst comprises an active component and a support, wherein the support is silica, the active component is a main metal M1, or a combination of main metal M1 and metal M2; the molar ratio of the active component to silica is 1:1-15; and the molar ratio of main metal M1 to auxiliary metal M2 is 1-15:1.

[0011] The main metal M1 of the catalyst is Ni;

[0012] The catalyst's promoter M2 is Co, Cu, Fe, Zn, or Ce;

[0013] The method for preparing the supported catalyst includes the following steps:

[0014] Metal nitrate and tetraethyl silicate are dissolved in anhydrous ethanol to obtain dispersed phase solution A; NaOH is dissolved in distilled water to obtain continuous phase solution B; dispersed phase solution A and continuous phase solution B are introduced into a membrane dispersion microreactor at a flow rate ratio of 1:0.5-1.5, and then passed through a residence tube at 55-65℃ to produce a slurry; the slurry is centrifuged, the precipitate is collected, washed, dried, calcined in air at 300-500℃, and reduced in a hydrogen atmosphere at 400-600℃ to obtain the catalyst;

[0015] The total concentration of metal nitrates in dispersed phase solution A is 0.04-0.2 mol / L; the concentration of tetraethyl silicate is 0.1-1.5 mol / L.

[0016] The concentration of NaOH in the continuous phase solution B is 0.5-1.2 mol / L;

[0017] The residence tube is made of polytetrafluoroethylene with an inner diameter of 1.5-2.5 mm and a residence time of 1-5 min.

[0018] The total flow rate is 1 mL / min-20 mL / min. Solution A and solution B are mixed in a membrane dispersion microreactor. The preferred membrane dispersion reactor has a stainless steel microfiltration membrane with a pore size of 0.5-5 μm, a diameter of 6.5-100 mm, and a thickness of 1.3-20 mm.

[0019] The essential features of this invention are:

[0020] This invention utilizes a membrane dispersion microreactor for the continuous preparation of catalyst precursors. In the membrane dispersion microreactor, the cross-flow shearing of the dispersed phase by the microfiltration membrane enables uniform and rapid mixing of metal ions and tetraethyl silicate in the dispersed phase with hydroxide ions in the continuous phase, improving mixing and mass transfer efficiency. This allows for high dispersion of the active metal component on the support without the use of surfactants, thereby enhancing the catalyst's hydrogenation capacity.

[0021] In the heterogeneous Ni-Co bimetallic catalyst supported on silica with a supported structure used in this invention, the presence of silica provides acidic sites for the nitro hydrogenation reduction reaction, promoting the hydrogenation of the reactants. The mutual doping of the active components Ni and Co plays a synergistic role, enhancing the hydrogenation activity of the catalyst and promoting the conversion of intermediates.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention provides a method for synthesizing 4,4'-diaminodiphenyl ether from 4,4'-dinitrodiphenyl ether. The preferred catalytic reaction conditions in this invention are 50-100°C and 1 MPa H2 pressure. This method requires minimal equipment, is economically feasible, and generates minimal waste. The conversion rate of 4,4'-dinitrodiphenyl ether is 100%, and the yield of 4,4'-diaminodiphenyl ether is 99.09%.

[0024] The catalyst used in this invention is synthesized using a membrane dispersion microreactor, which has the advantages of low metal consumption, high dispersion, integrally formed supported structure, and a green and simple preparation process. Furthermore, this catalyst can continuously prepare precursors, showing potential for large-scale production. Moreover, this catalyst exhibits excellent activity and stability in nitro-catalyzed hydrogenation reactions, demonstrating promising application prospects. Detailed Implementation

[0025] The synthetic route of this invention is shown below:

[0026]

[0027] The technical features of the present invention will be further illustrated below with reference to implementation examples:

[0028] Example 1: Preparation of 10-Ni-SiO2-400-500

[0029] A metal salt-tetraethyl silicate mixed solution was prepared by mixing 2.91 g Ni(NO3)2·6H2O (0.01 mol) and 2.08 g tetraethyl silicate (TEOS, 0.01 mol) in 100 mL of anhydrous ethanol. A 1 mol / L NaOH solution was prepared by dissolving 4 g NaOH (0.1 mol) in 100 mL of distilled water. Both solutions were fed separately into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm at a flow rate of 5 mL / min using a continuous feed pump. The membrane was then passed through a 6.4 m long polytetrafluoroethylene tube with an inner diameter of 2 mm in a 60 °C water bath to obtain a slurry. The slurry was centrifuged, the precipitate was collected, and washed sequentially with distilled water and ethanol. The solid was dried at 100 °C for 6 h, calcined in air at 400 °C for 4 h, and the resulting material was reduced in hydrogen at 500 °C for 3 h.

[0030] Examples 2-4: Preparation of 10-Ni-3SiO2-400-500, 10-Ni-5SiO2-400-500, 10-Ni-7SiO2-400-500, and 10-Ni-9SiO2-400-500

[0031] The other steps are the same as in Example 1, except that the amount of tetraethyl silicate is changed to 6.25g, 10.42g, 14.58g, and 18.75g, respectively. Finally, four different materials were obtained: 10-Ni-3SiO2-400-500, 10-Ni-5SiO2-400-500, 10-Ni-7SiO2-400-500, and 10-Ni-9SiO2-400-500 catalysts.

[0032] The catalyst is represented by R-xM1-yM2-zSiO2-ab, where R represents the total flow rate, M1 represents the main metal, M2 represents the auxiliary metal, x and y represent the proportions of M1 and M2 in the total metal molar amount in the catalyst, z represents the molar ratio of silicon dioxide to the total metal, a represents the catalyst calcination temperature, and b represents the catalyst reduction temperature.

[0033] Example 5: Preparation of 10-0.75Ni0.25Cu-5SiO2-400-500

[0034] 2.18 g Ni(NO3)2·6H2O (0.0075 mol), 0.61 g Cu(NO3)2·3H2O (0.0025 mol), and 10.4 g tetraethyl orthosilicate (TEOS, 0.05 mol) were dissolved in 100 mL of anhydrous ethanol and mixed thoroughly to prepare a metal salt-tetraethyl orthosilicate mixed solution. 4 g NaOH (0.1 mol) was dissolved in 100 mL of distilled water to prepare a 1 mol / L NaOH solution. Both solutions were fed separately into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm at a flow rate of 5 mL / min using a continuous feed pump. The slurry was then passed through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 6.4 m in a water bath at 60 °C. The slurry was centrifuged, the precipitate was collected, and washed successively with distilled water and ethanol. The solid was dried at 100°C for 6 hours, calcined in air at 400°C for 4 hours, and the resulting material was reduced in hydrogen at 500°C for 3 hours. Examples 6-9: Preparation of 10-0.75Ni0.25Cu-5SiO2-400-500, 10-0.75Ni0.25Zn-5SiO2-400-500, 10-0.75Ni0.25Fe-5SiO2-400-500, and 10-0.75Ni0.25Ce-5SiO2-400-500.

[0035] The other steps are the same as in Example 5, except that 0.61g Cu(NO3)2·3H2O is replaced with 0.73g Co(NO3)2·6H2O, 0.74g Zn(NO3)2·6H2O, 1.01g Fe(NO3)2·9H2O, and 1.08g Ce(NO3)2·6H2O (molar amounts remain unchanged). Finally, four different materials were obtained: 10-0.75Ni0.25Cu-5SiO2-400-500, 10-0.75Ni0.25Zn-5SiO2-400-500, 10-0.75Ni0.25Fe-5SiO2-400-500, and 10-0.75Ni0.25Ce-5SiO2-400-500 catalysts.

[0036] Example 10: Preparation of 10-0.5Ni0.5Co-5SiO2400-500

[0037] 1.45 g Ni(NO3)2·6H2O (0.005 mol), 1.46 g Co(NO3)2·6H2O (0.005 mol), and 10.4 g tetraethyl orthosilicate (TEOS, 0.05 mol) were dissolved in 100 mL of anhydrous ethanol and mixed thoroughly to prepare a metal salt-tetraethyl orthosilicate mixed solution. 4 g NaOH (0.1 mol) was dissolved in 100 mL of distilled water to prepare a 1 mol / L NaOH solution. Both solutions were fed separately at a flow rate of 5 mL / min into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm. The slurry was then obtained by passing the slurry through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 6.4 m in a water bath at 60 °C. The slurry was centrifuged, the precipitate was collected, and the precipitate was washed successively with distilled water and ethanol. The solid was dried at 100°C for 6 hours, calcined in air at 400°C for 4 hours, and the resulting material was reduced in hydrogen at 500°C for 3 hours.

[0038] Examples 11-14: Preparation of 10-0.83Ni0.17Co-5SiO2-400-500, 10-0.875Ni0.125Co-5SiO2-400-500, 10-0.9Ni0.1Co-5SiO2-400-500, and 10-0.92Ni0.08Co-5SiO2-400-500

[0039] The other steps are the same as in Example 10, except that the amounts of Ni(NO3)2·6H2O are 2.42g, 2.54g, 2.62g, and 2.66g, respectively, and the amounts of Co(NO3)2·6H2O are 0.49g, 0.36g, 0.29g, and 0.24g, respectively (the total molar amount of metal remains unchanged). Finally, four different materials were obtained: 10-0.83Ni0.17Co-5SiO2-400-500, 10-0.875Ni0.125Co-5SiO2-400-500, 10-0.9Ni0.1Co-5SiO2-400-500, and 10-0.92Ni0.08Co-5SiO2-400-500 catalysts.

[0040] Example 15: Preparation of 1-0.9Ni0.1Co-5SiO2-400-500

[0041] 2.62 g Ni(NO3)2·6H2O (0.009 mol), 0.29 g Co(NO3)2·6H2O (0.001 mol), and 10.4 g tetraethyl orthosilicate (TEOS, 0.05 mol) were dissolved in 100 mL of anhydrous ethanol and mixed thoroughly to prepare a metal salt-tetraethyl orthosilicate mixed solution. 4 g NaOH (0.1 mol) was dissolved in 100 mL of distilled water to prepare a 1 mol / L NaOH solution. Both solutions were fed separately into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm at a flow rate of 0.5 mL / min using a continuous feed pump. The slurry was then obtained by passing the slurry through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 3.2 m in a water bath at 60 °C. The slurry was centrifuged, the precipitate was collected, and washed successively with distilled water and ethanol. The solid was dried at 100°C for 6 hours, calcined in air at 400°C for 4 hours, and the resulting material was reduced in hydrogen at 500°C for 3 hours. Examples 16-21: 5-0.9Ni0.1Co-5SiO2-400-500, 7.5-0.9Ni0.1Co-5SiO 2: Preparation of -400-500, 12.5-0.9Ni0.1Co-5SiO2-400-500, 15-0.9Ni0.1Co-5SiO2-400-500, 17.5-0.9Ni0.1Co-5SiO2-400-500, and 20-0.9Ni0.1Co-5SiO2-400-500

[0042] The other steps are the same as in Example 15, except that the solution flow rate is changed to 2.5 mL / min, 3.75 mL / min, 6.25 mL / min, 7.5 mL / min, 8.75 mL / min, and 10 mL / min respectively (the residence time remains unchanged). Finally, six different materials were obtained: 5-0.9Ni0.1Co-5SiO2-400-500, 7.5-0.9Ni0.1Co-5SiO2-400-500, 12.5-0.9Ni0.1Co-5SiO2-400-500, 15-0.9Ni0.1Co-5SiO2-400-500, 17.5-0.9Ni0.1Co-5SiO2-400-500, and 20-0.9Ni0.1Co-5SiO2-400-500 catalysts.

[0043] Example 22: Preparation of 10-0.9Ni0.1Co-5SiO2-300-500

[0044] 2.62 g Ni(NO3)2·6H2O (0.009 mol), 0.29 g Co(NO3)2·6H2O (0.001 mol), and 10.4 g tetraethyl orthosilicate (TEOS, 0.05 mol) were dissolved in 100 mL of anhydrous ethanol and mixed thoroughly to prepare a metal salt-tetraethyl orthosilicate mixed solution. 4 g NaOH (0.1 mol) was dissolved in 100 mL of distilled water to prepare a 1 mol / L NaOH solution. Both solutions were fed separately into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm at a flow rate of 5 mL / min using a continuous feed pump. The slurry was then obtained by passing the slurry through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 6.4 m in a water bath at 60 °C. The slurry was centrifuged, the precipitate was collected, and the precipitate was washed successively with distilled water and ethanol. The solid was dried at 100°C for 6 hours, calcined in air at 300°C for 4 hours, and the resulting material was reduced in hydrogen at 500°C for 3 hours.

[0045] Examples 23-25: Preparation of 10-0.9Ni0.1Co-5SiO2-350-500, 10-0.9Ni0.1Co-5SiO2-450-500, and 10-0.9Ni0.1Co-5SiO2-500-500

[0046] The other steps are the same as in Example 22, except that the calcination temperature in air is changed to 350℃, 450℃, and 500℃ respectively (the reduction temperature remains unchanged). Finally, three different materials were obtained: 10-0.9Ni0.1Co-5SiO2-350-500, 10-0.9Ni0.1Co-5SiO2-450-500, and 10-0.9Ni0.1Co-5SiO2-500-500 catalysts.

[0047] Example 26: Preparation of 10-0.9Ni0.1Co-5SiO2-400-400

[0048] 2.62 g Ni(NO3)2·6H2O (0.009 mol), 0.29 g Co(NO3)2·6H2O (0.001 mol), and 10.4 g tetraethyl orthosilicate (TEOS, 0.05 mol) were dissolved in 100 mL of anhydrous ethanol and mixed thoroughly to prepare a metal salt-tetraethyl orthosilicate mixed solution. 4 g NaOH (0.1 mol) was dissolved in 100 mL of distilled water to prepare a 1 mol / L NaOH solution. Both solutions were fed separately into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm at a flow rate of 5 mL / min using a continuous feed pump. The slurry was then obtained by passing the slurry through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 6.4 m in a water bath at 60 °C. The slurry was centrifuged, the precipitate was collected, and the precipitate was washed successively with distilled water and ethanol. The solid was dried at 100°C for 6 hours, calcined in air at 400°C for 4 hours, and the resulting material was reduced in hydrogen at 400°C for 3 hours.

[0049] Examples 27-29: Preparation of 10-0.9Ni0.1Co-5SiO2-400-450, 10-0.9Ni0.1Co-5SiO2-400-550, and 10-0.9Ni0.1Co-5SiO2-400-600

[0050] The other steps are the same as in Example 26, except that the reduction temperature in hydrogen is changed to 450℃, 550℃, and 600℃ respectively (the calcination temperature remains unchanged). Finally, three different materials were obtained: 10-0.9Ni0.1Co-5SiO2-400-450, 10-0.9Ni0.1Co-5SiO2-400-550, and 10-0.9Ni0.1Co-5SiO2-400-600 catalysts.

[0051] Example 30: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0052] The reaction was carried out in a 50 mL stainless steel reactor, with 0.065 g of the catalyst prepared in Examples 1-5, 1.3 g (5 mmol) of 4,4'-dinitrodiphenyl ether, and 2.2113 g (25 mmol) of N,N-dimethylacetamide added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2 and 100 °C with a stirring rate of 1500 rpm. After 30 min of reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 1.

[0053] Table 1. Effect of nickel-silicon molar ratio on the reaction

[0054]

[0055] As can be seen from the data in Table 1, the hydrogenation performance of the catalyst gradually improves as the nickel-silicon molar ratio increases from 1:1 to 1:5; however, the hydrogenation performance of the catalyst decreases as the nickel-silicon molar ratio further increases, and the preferred nickel-silicon molar ratio is 1:5.

[0056] Example 31: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0057] The reaction was carried out in a 50 mL stainless steel reactor, with 0.065 g of the catalyst prepared in Examples 6-10, 1.3 g (5 mmol) of 4,4'-dinitrodiphenyl ether, and 2.2113 g (25 mmol) of N,N-dimethylacetamide added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2 and 100 °C with a stirring rate of 1500 rpm. After 30 min of reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 2.

[0058] Table 2. Effect of the second metal on the reaction.

[0059]

[0060] As shown in Table 2, the introduction of metals Cu, Zn, Fe, and Ce did not improve catalyst performance; instead, it weakened hydrogenation activity. However, the hydrogenation activity of the catalyst was improved when a second metal, Co, was added. Co is the preferred second metal component.

[0061] Example 32: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0062] The reaction was carried out in a 50 mL stainless steel reactor, with 0.065 g of the catalyst prepared in Examples 11-15, 1.3 g (5 mmol) of 4,4'-dinitrodiphenyl ether, and 2.2113 g (25 mmol) of N,N-dimethylacetamide added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2 and 100 °C with a stirring rate of 1500 rpm. After 20 min of reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 3.

[0063] Table 3 Effect of nickel-cobalt molar ratio on the reaction

[0064]

[0065]

[0066] As shown in Table 3, the synergistic effect between nickel and cobalt gradually increases as the nickel-cobalt molar ratio increases from 1:1 to 9:1, leading to a gradual improvement in the catalyst's hydrogenation activity. However, when the nickel-cobalt molar ratio is further increased to 11:1, the catalyst activity decreases, and a nickel-cobalt molar ratio of 9:1 is preferred.

[0067] Example 33: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0068] The reaction was carried out in a 50 mL stainless steel reactor, with 0.065 g of the catalyst prepared in Examples 16-19, 1.3 g (5 mmol) of 4,4'-dinitrodiphenyl ether, and 2.2113 g (25 mmol) of N,N-dimethylacetamide added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2 and 100 °C with a stirring rate of 1500 rpm. After 30 min of reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 4.

[0069] Table 4. Effect of total flow rate on the reaction

[0070]

[0071] As shown in Table 4, the catalyst exhibits poor hydrogenation performance at lower total flow rates. However, the hydrogenation activity significantly improves as the flow rate increases to 7.5 ml / min. Furthermore, the catalyst performance declines when the total flow rate reaches 12.5 ml / min; a total flow rate of 10 ml / min is preferred.

[0072] Example 34: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0073] The reaction was carried out in a 50 mL stainless steel reactor, with 0.065 g of the catalyst prepared in Examples 21-24, 1.3 g (5 mmol) of 4,4'-dinitrodiphenyl ether, and 2.2113 g (25 mmol) of N,N-dimethylacetamide added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2 and 80 °C with a stirring rate of 1500 rpm. After 30 min of reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 5.

[0074] Table 5 Effect of calcination temperature on the reaction

[0075]

[0076] As can be seen from the data in Table 5, the hydrogenation performance of the catalyst increases when the calcination temperature increases to 350℃; however, further increasing the calcination temperature to 450℃ reduces the catalytic performance of the catalyst, and the preferred calcination temperature is 400℃.

[0077] Example 35: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0078] The reaction was carried out in a 50 mL stainless steel reactor, with 0.065 g of the catalyst prepared in Examples 25-28, 1.3 g (5 mmol) of 4,4'-dinitrodiphenyl ether, and 2.2113 g (25 mmol) of N,N-dimethylacetamide added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2 and 80 °C with a stirring rate of 1500 rpm. After 30 min of reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 6.

[0079] Table 6 Effect of reduction temperature on the reaction

[0080]

[0081] As shown in Table 6, the hydrogenation performance of the catalyst gradually improves with increasing reduction temperature; however, when the reduction temperature is further increased to 550℃, the hydrogenation performance of the catalyst decreases significantly. The preferred reduction temperature is 500℃.

[0082] Example 36: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0083] The reaction was carried out in a 50 mL stainless steel reactor, with the catalyst prepared in Example 14, namely 10-0.9Ni0.1Co-5SiO2-400-500, 4,4'-dinitrodiphenyl ether (1.3 g, 5 mmol), and N,N-dimethylacetamide (2.2113 g, 25 mmol). Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2, 80 °C, and different catalyst amounts (0.065 g, 0.052 g, 0.039 g, 0.026 g, 0.013 g), with a stirring rate of 1500 rpm. After complete reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 7.

[0084] Table 7 Effect of catalyst dosage on the reaction

[0085]

[0086] As shown in Table 7, the reaction time gradually increases with decreasing catalyst dosage. Considering factors such as catalyst cost, energy consumption, and product yield, the optimal catalyst dosage is 0.026 g, which is 2% of the substrate mass.

[0087] Example 37: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0088] The reaction was carried out in a 50 mL stainless steel reactor, with the catalyst obtained in Example 14, 10-0.9Ni0.1Co-5SiO2-400-500 (0.026 g), 4,4'-dinitrodiphenyl ether (1.3 g, 5 mmol), and N,N-dimethylacetamide (2.2113 g, 25 mmol) added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at 3 MPa H2 and different temperatures (90 °C, 70 °C, 60 °C, 50 °C) at a stirring rate of 1500 rpm. After complete reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 8.

[0089] Table 8 Effect of reaction temperature on the reaction

[0090]

[0091] As can be seen from the data in Table 8, the reaction time gradually increases as the reaction temperature gradually decreases. Considering factors such as energy consumption and product yield, the optimal reaction temperature is 80℃.

[0092] Example 38: Hydrogenation reduction of 4,4'-dinitrodiphenyl ether

[0093] The reaction was carried out in a 50 mL stainless steel reactor, with the catalyst obtained in Example 14, 10-0.9Ni0.1Co-5SiO2-400-500 (0.026 g), 4,4'-dinitrodiphenyl ether (1.3 g, 5 mmol), and N,N-dimethylacetamide (2.2113 g, 25 mmol) added. Before the reaction, the reactor was purged five times with H2 to replace the gas. Hydrogenation reduction was carried out at different hydrogen pressures (2.5 MPa, 2 MPa, 1.5 MPa, 1 MPa) and 80 °C, with a stirring rate of 1500 rpm. After complete reaction, the reaction solution was filtered to remove the catalyst and analyzed by high-performance liquid chromatography (HPLC) using external standard method. The reaction results are shown in Table 9.

[0094] Table 9. Effect of hydrogen pressure on the reaction

[0095]

[0096] As shown in Table 9, the reaction time gradually increases as the hydrogen pressure decreases. However, a lower hydrogen pressure reduces the requirements on the equipment. Considering all factors, a hydrogen pressure of 1 MPa is preferred.

[0097] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing 4,4'-diaminodiphenyl ether, characterized in that the method comprises the following steps: In a reactor containing 4,4'-dinitrodiphenyl ether (DNDPE), N,N-dimethylacetamide (DMAC) and a supported catalyst, hydrogen gas is introduced into the reactor and the reaction is carried out at 50-100 °C for 20-800 min, resulting in a hydrogenation reduction reaction to produce 4,4'-diaminodiphenyl ether. in, The mass ratio of 4,4'-dinitrodiphenyl ether to catalyst is 500-2:1; the molar ratio of DNDPE to DMAC is 1:3-15; and the hydrogen pressure is 1.0-3.5 MPa. The supported catalyst is prepared by one of the following five methods: Method 1: 2.91 g Ni(NO3)2·6H2O and 10.42 g tetraethyl silicate were mixed evenly in 100 mL of anhydrous ethanol to prepare a metal salt-tetraethyl silicate mixed solution; 4 g NaOH was dissolved in 100 mL of distilled water to prepare a 1 mol / L NaOH solution; the two solutions were fed into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm at a flow rate of 5 mL / min using a continuous feed pump; the slurry was then obtained by passing the membrane through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 6.4 m in a water bath at 60 ℃; the slurry was centrifuged, the precipitate was collected, and washed successively with distilled water and ethanol; the solid was dried at 100 ℃ for 6 h, calcined in air at 400 ℃ for 4 h, and the resulting material was reduced in hydrogen at 500 ℃ for 3 h; Alternatively, Method 2: Dissolve 2.54 g Ni(NO3)2·6H2O, 0.36 g Co(NO3)2·6H2O, and 10.4 g tetraethyl silicate in 100 mL of anhydrous ethanol and mix thoroughly to obtain a metal salt-tetraethyl silicate mixed solution; dissolve 4 g NaOH in 100 mL of distilled water to prepare a 1 mol / L NaOH solution; continuously feed the two solutions at a flow rate of 5 mL / min into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm, and then pass them through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 6.4 m in a water bath at 60 ℃ to obtain a slurry; centrifuge the slurry, collect the precipitate, wash it successively with distilled water and ethanol, dry the solid at 100 ℃ for 6 h, calcine it in air at 400 ℃ for 4 h, and reduce the obtained material in hydrogen at 500 ℃ for 3 h; Alternatively, Method 3: Dissolve 2.62 g Ni(NO3)2·6H2O, 0.29 g Co(NO3)2·6H2O, and 10.4 g tetraethyl silicate in 100 mL of anhydrous ethanol and mix thoroughly to obtain a metal salt-tetraethyl silicate mixed solution; dissolve 4 g NaOH in 100 mL of distilled water to prepare a 1 mol / L NaOH solution; continuously feed the two solutions at a flow rate of 5 mL / min into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm, and then pass them through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 6.4 m in a water bath at 60 ℃ to obtain a slurry; centrifuge the slurry, collect the precipitate, wash it successively with distilled water and ethanol, dry the solid at 100 ℃ for 6 h, calcine it in air at 400 ℃ for 4 h, and reduce the obtained material in hydrogen at 500 ℃ for 3 h; Alternatively, Method 4: Dissolve 2.62 g Ni(NO3)2·6H2O, 0.29 g Co(NO3)2·6H2O, and 10.4 g tetraethyl silicate in 100 mL of anhydrous ethanol and mix thoroughly to obtain a metal salt-tetraethyl silicate mixed solution; dissolve 4 g NaOH in 100 mL of distilled water to prepare a 1 mol / L NaOH solution; continuously feed the two solutions at a flow rate of 3.75 mL / min into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm, and then pass them through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 3.2 m in a water bath at 60 ℃ to obtain a slurry; centrifuge the slurry, collect the precipitate, wash it successively with distilled water and ethanol, dry the solid at 100 ℃ for 6 h, calcine it in air at 400 ℃ for 4 h, and reduce the obtained material in hydrogen at 500 ℃ for 3 h; Alternatively, Method 5: Dissolve 2.62 g Ni(NO3)2·6H2O, 0.29 g Co(NO3)2·6H2O, and 10.4 g tetraethyl silicate in 100 mL of anhydrous ethanol and mix thoroughly to obtain a metal salt-tetraethyl silicate mixed solution; dissolve 4 g NaOH in 100 mL of distilled water to prepare a 1 mol / L NaOH solution; continuously feed the two solutions at a flow rate of 6.25 mL / min into a membrane dispersion microreactor equipped with a stainless steel microfiltration membrane with a pore size of 1 μm, a diameter of 6.5 mm, and a thickness of 1.5 mm, and then pass them through a polytetrafluoroethylene tube with an inner diameter of 2 mm and a length of 3.2 m in a water bath at 60 ℃ to obtain a slurry; centrifuge the slurry, collect the precipitate, wash it successively with distilled water and ethanol, dry the solid at 100 ℃ for 6 h, calcine it in air at 400 ℃ for 4 h, and reduce the obtained material in hydrogen at 500 ℃ for 3 h.

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