Synthesis method of high-purity 2, 6-dichloro-4-aminophenol

Abstract

The invention belongs to the technical field of chemical synthesis, and provides a high-purity 2, 6-dichloro-4-aminophenol synthesis method, which comprises: A1, mixing paranitroaniline and a 20-35 wt% hydrochloric acid aqueous solution, heating, introducing chlorine gas, and carrying out a reaction to obtain 2, 6-dichloro-4-nitroaniline; a2, mixing the 2, 6-dichloro-4-nitroaniline with methylbenzene, so as to obtain a 2, 6-dichloro-4-nitroaniline solution; mixing sulfuric acid, purified water and a first catalyst to obtain liquid; a3, sulfuric acid and nitrososulfuric acid are mixed and cooled, a 2, 6-dichloro-4-nitroaniline solution is dropwise added, a diazonium solution is obtained, the temperature is increased, the diazonium solution is dropwise added into the liquid, and a 2, 6-dichloro-4-nitrophenol phase is obtained; and A4, adding the 2, 6-dichloro-4-nitrophenol, toluene and a second catalyst into the reaction kettle, introducing hydrogen, and carrying out hydrogenation reaction to obtain the 2, 6-dichloro-4-aminophenol. The synthesis method disclosed by the invention is simple, the used second catalyst can be recycled, the generation amount of three wastes is small, and the yield and the purity of the 2, 6-dichloro-4-aminophenol are high.

Description

Technical Field

[0001] The invention relates to the technical field of chemical synthesis, and in particular to a method for synthesizing high-purity 2,6-dichloro-4-aminophenol. Background Art

[0002] 2,6-Dichloro-4-aminophenol is an important organic chemical intermediate, widely used in the pesticide, pharmaceutical and dye industries. Especially in the pesticide field, it is a key intermediate for the synthesis of highly effective and low-toxic insecticides chlorpyrifos and hexaflumuron. With the increasing global requirements for environmental protection and the safety of pesticide use, the demand for high-purity synthesis methods of 2,6-dichloro-4-aminophenol is growing. In the synthesis process, in order to obtain high-purity products, the reaction conditions need to be precisely controlled, including the molar ratio of reactants, temperature, pressure, solvent selection, and the use of catalysts.

[0003] At present, there are two common methods for synthesizing 2,6-dichloro-4-aminophenol: 1) Using 2,6-dichlorophenol as the starting material, first nitrifying it with nitric acid, and then reducing it with hydrazine hydrate or catalytic hydrogenation to obtain 2,6-dichloro-4-aminophenol. However, the nitration reaction will generate isomers, and the purification of isomers is difficult; 2) Using 3,4,5-trichloronitrobenzene as the starting material, hydrolyzing the nitro para-chlorine to hydroxyl under alkaline conditions, and then nitro reduction to obtain 2,6-dichloro-4-aminophenol. However, the hydrolysis selectivity of 3,4,5-trichloronitrobenzene is not high. It can be seen that both methods have the problem of low purity.

[0004] Chinese patent CN 115141109 A discloses a method for synthesizing 2,6-dichloro-4-aminophenol, a key intermediate of hexaflumuron. The method comprises the following steps: S1. Phenol is mixed with acetone, and bisphenol A is synthesized under the action of an acidic catalyst; S2. Bisphenol A is subjected to chlorination and dehydroxylation to obtain 2,6-dichlorophenol; S3. 2,6-dichlorophenol is subjected to nitration to obtain 2,6-dichloro-4-nitrophenol; S4. 2,6-dichloro-4-nitrophenol is mixed with hydrazine hydrate, and reduced under the action of a palladium-carbon catalyst to obtain 2,6-dichloro-4-aminophenol. Although this invention solves the problem of purifying isomers generated by the nitration reaction, so that the product has a high yield and high purity, this method has a complicated process and uses a toxic reagent such as hydrazine hydrate, which is not conducive to popularization and production.

[0005] Therefore, there is an urgent need for a method for synthesizing high-purity 2,6-dichloro-4-aminophenol, which can not only achieve high-yield and high-purity synthesis of 2,6-dichloro-4-aminophenol, but also achieve the coordinated development of economic and environmental benefits. Summary of the invention

[0006] In view of the existing technical problems, the purpose of the present invention is to provide a method for synthesizing high-purity 2,6-dichloro-4-aminophenol. The synthesis method of the present invention has simple steps, and the target compound is synthesized through a series of chemical reaction steps of chlorination, diazotization, hydrolysis and hydrogenation reduction. At the same time, the second catalyst used in the present invention can be recycled and reused, and the amount of three wastes generated is small, so that the coordinated development of economic benefits and environmental benefits is achieved, and the yield and purity of 2,6-dichloro-4-aminophenol are high, and the application value is good.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for synthesizing high-purity 2,6-dichloro-4-aminophenol, comprising the following steps:

[0009] A1. P-nitroaniline and 20-35wt% aqueous hydrochloric acid solution were mixed, stirred, heated to 50-60°C, chlorine gas was continuously introduced for 5-6h, cooled, filtered, and the obtained solid was washed with water 2-3 times, then washed with 5-10wt% soda solution until neutral, and dried to obtain 2,6-dichloro-4-nitroaniline;

[0010] A2. The 2,6-dichloro-4-nitroaniline obtained in step A1 is mixed with toluene to obtain a 2,6-dichloro-4-nitroaniline solution for standby use; sulfuric acid, purified water and the first catalyst are mixed and stirred to obtain a liquid for standby use;

[0011] A3. Sulfuric acid and nitrosylsulfuric acid are mixed, stirred, cooled to 4-8°C, and the 2,6-dichloro-4-nitroaniline solution obtained in step A2 is added dropwise, the reaction temperature is controlled at 10-15°C, and the reaction is kept warm for 1-2h to obtain a diazo liquid, and the temperature is raised to 100-120°C, and the diazo liquid is added dropwise into the liquid obtained in step A2, and the addition time is controlled to 5-7h, and the reaction is continued at a temperature of 1-2h, cooled, and separated to obtain an upper liquid, which is a 2,6-dichloro-4-nitrophenol phase;

[0012] A4. The 2,6-dichloro-4-nitrophenol phase obtained in step A3 and the second catalyst are added to a reactor, replaced with nitrogen and hydrogen 2-3 times respectively, and then hydrogen is introduced, the pressure and temperature are controlled, a hydrogenation reaction is carried out, the reaction is filtered, cooled, filtered, and dried to obtain 2,6-dichloro-4-aminophenol.

[0013] The reaction mechanism and effects of the present invention are as follows:

[0014] 1. The present invention uses p-nitroaniline as the starting material, and synthesizes the target compound through a series of chemical reaction steps including chlorination, diazotization, hydrolysis and hydrogenation reduction. First, the chlorination step is used to form a chlorophenol structure. The applicant controls the mass ratio of p-nitroaniline and a 20-35wt% hydrochloric acid aqueous solution to improve the selectivity of the reaction; and then adjusts the temperature of the chlorination reaction to 50-60°C to avoid the reduction of the reaction selectivity caused by the chlorination reaction temperature being too high, because polychlorinated by-products are easily produced when chlorinated at a higher temperature; at the same time, this temperature range also avoids the situation where the reaction rate is too slow. Secondly, controlling the molar ratio of nitrosylsulfuric acid and 2,6-dichloro-4-nitroaniline in the diazotization reaction is beneficial to improving the purity of 2,6-dichloro-4-nitrophenol. Finally, the applicant uses a new second catalyst to obtain high-yield and high-purity 2,6-dichloro-4-aminophenol through hydrolysis and hydrogenation reduction reactions.

[0015] 2. The present invention synthesizes a highly efficient second catalyst, which has excellent catalytic stability and high selectivity, and can significantly reduce the occurrence of side reactions. In addition, the second catalyst is easy to recycle and reuse, and has a relatively broad application prospect.

[0016] The present invention successfully synthesizes a copper-containing MOF precursor by a hydrothermal method. In a nitrogen atmosphere, the organic ligand [1,1'-biphenyl]-2,2',4,4',6,6'-hexacarboxylic acid decomposes to produce reducing gas, so that copper nitrate trihydrate is self-reduced to copper and carbonized at a specific calcination temperature, which is beneficial to improving the particle size of copper particles and making them more dispersible. At the same time, copper is mainly responsible for promoting the adsorption and dissociation of hydrogen during the hydrogenation of 2,6-dichloro-4-nitrophenol, which can improve the catalytic activity. In addition, the metal precursor has a great influence on the adsorption performance of metal ions and the catalytic activity of the second catalyst. The present application selects chloropalladic acid as a precursor, which has good adsorption effect and good dispersibility compared with other metal precursors, and improves the selectivity of the second catalyst. The applicant further adds (3-aminopropyl)triethoxysilane to improve the activity of the second catalyst, thereby improving the reaction process of nitrobenzene hydrogenation reduction.

[0017] In some embodiments, the mass ratio of p-nitroaniline to 20-35 wt % aqueous hydrochloric acid solution in step A1 is 1:(10-15).

[0018] In some embodiments, in step A2, the first catalyst is copper oxide or copper sulfate.

[0019] In some embodiments, the amount of the first catalyst used in step A2 is 8-15 wt % of 2,6-dichloro-4-nitroaniline.

[0020] In some embodiments, the mass ratio of 2,6-dichloro-4-nitroaniline to toluene in step A2 is 1:(3-4); the mass ratio of sulfuric acid, purified water and the first catalyst is 10:(8-10):1.

[0021] In some embodiments, the molar ratio of nitrosylsulfuric acid to 2,6-dichloro-4-nitroaniline in the 2,6-dichloro-4-nitroaniline solution in step A3 is (1.02-1.12):1.

[0022] Preferably, the molar ratio of nitrosylsulfuric acid to 2,6-dichloro-4-nitroaniline in the 2,6-dichloro-4-nitroaniline solution in step A3 is 1.06:1.

[0023] In some embodiments, the amount of the second catalyst used in step A4 is 1-3 wt % of the 2,6-dichloro-4-nitrophenol phase.

[0024] In some embodiments, the method for preparing the second catalyst in step A4 comprises the following steps:

[0025] S1. [1,1'-biphenyl]-2,2',4,4',6,6'-hexacarboxylic acid, N,N-dimethylformamide, and anhydrous ethanol are mixed and stirred to obtain solution 1; copper nitrate trihydrate and deionized water are mixed and stirred to obtain solution 2;

[0026] S2. Pour solution 1 obtained in step S1 into solution 2, stir, heat to 85-95°C, hydrothermally react for 16-20h, cool, centrifuge, wash, and dry to obtain a powder;

[0027] S3. Under a nitrogen atmosphere, the powder obtained in step S2 is carbonized and cooled to obtain a carrier;

[0028] S4. The carrier, methanol and (3-aminopropyl)triethoxysilane obtained in step S3 are mixed, ultrasonically dispersed, added to a 0.06-0.1 mol / L methanol solution of palladium chloride, immersed and stirred for 8-12 hours, and then a 0.5-1 mol / L methanol solution of sodium borohydride is added dropwise, stirred for 12-16 hours, filtered, washed, dried, and ground to obtain a second catalyst.

[0029] In some embodiments, the molar ratio of [1,1'-biphenyl]-2,2',4,4',6,6'-hexacarboxylic acid to copper nitrate trihydrate in step S1 is 1:(3.5-3.9).

[0030] In some embodiments, the ratio of the carrier, (3-aminopropyl)triethoxysilane, and the methanol solution of palladium chloride used in step S4 is 1 g: (0.4-0.6) mL: (5-9) mL.

[0031] In some embodiments, the specific conditions of the carbonization in step S3 are: heating to 450-650° C. at a heating rate of 4-8° C. / min, and maintaining the temperature for reaction and calcination for 2-3 hours.

[0032] In some embodiments, the conditions of the hydrogenation reaction in step A4 are: temperature 60-100° C., pressure 0.5-1.2 MPa.

[0033] Preferably, the conditions for the hydrogenation reaction in step A4 are: temperature 85° C., pressure 1.0 MPa.

[0034] In some embodiments, the yield of 2,6-dichloro-4-aminophenol is not less than 97%, and the purity is not less than 99%.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. The synthesis method of the present invention is simple, and the target compound is synthesized through a series of chemical reaction steps of chlorination, diazotization, hydrolysis and hydrogenation reduction. At the same time, the second catalyst used in the present invention can be recycled and reused, and the amount of three wastes generated is small, thereby achieving the coordinated development of economic benefits and environmental benefits. The yield of 2,6-dichloro-4-aminophenol is not less than 97%, the purity is not less than 99%, and the product has good market value.

[0037] 2. The present invention synthesizes a new type of second catalyst, which has good catalytic stability and high selectivity, effectively reduces the occurrence of side reactions, and the second catalyst is easy to recycle and reuse, and has a relatively broad application prospect.

[0038] 3. The present invention strictly controls the reaction pressure and temperature to avoid a slow reaction rate leading to a decrease in yield. Further, the applicant increases the yield and purity of 2,6-dichloro-4-aminophenol by controlling the addition amount of the second catalyst and other additives. DETAILED DESCRIPTION

[0039] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0040] According to the ratios of the raw materials and the preparation methods specified in the following examples and comparative examples, 2,6-dichloro-4-aminophenol was synthesized.

[0041] In order to facilitate those skilled in the art to implement the present invention, the sources of some raw materials in the embodiments and comparative examples are described as follows:

[0042] Sulfuric acid: analytical grade;

[0043] Palladium carbon catalyst: purchased from Wuhan Jiyesheng Chemical Co., Ltd., model number JYS1541;

[0044] Other raw materials are not specially specified and can be purchased from the market.

[0045] Preparation Example 1

[0046] The preparation method of the second catalyst A comprises the following steps:

[0047] S1. 0.05 mol of [1,1'-biphenyl]-2,2',4,4',6,6'-hexacarboxylic acid, 200 mL of N,N-dimethylformamide, and 200 mL of anhydrous ethanol were mixed and stirred for 30 min to obtain solution 1; 0.185 mol of copper nitrate trihydrate and 200 mL of deionized water were mixed and stirred for 10 min to obtain solution 2;

[0048] S2. The solution 1 obtained in step S1 was poured into solution 2, stirred for 1 h, heated to 90 ° C, hydrothermally reacted for 18 h, cooled to room temperature, centrifuged, washed alternately with anhydrous ethanol and deionized water 3 times each, and dried at 100 ° C for 5 h to obtain a powder;

[0049] S3. The powder obtained in step S2 was carbonized in a tube furnace under a nitrogen atmosphere, heated to 550°C at a heating rate of 5°C / min, and calcined for 2.5h, and cooled to room temperature to obtain a carrier;

[0050] S4. 10 g of the carrier obtained in step S3, 150 mL of methanol, and 5 mL of (3-aminopropyl)triethoxysilane were mixed, ultrasonically dispersed for 30 min, added to 65 mL of 0.08 mol / L palladium chloride methanol solution, immersed and stirred for 10 h, and then 50 mL of 1 mol / L sodium borohydride methanol solution was added dropwise, stirred for 15 h, filtered, washed with deionized water 3 times, dried at 80 ° C to constant weight, and ground to obtain a second catalyst B.

[0051] Preparation Example 2

[0052] The preparation method of the second catalyst B is the same as that of Preparation Example 1, except that the amount of copper nitrate trihydrate added in step S1 is 0.165 mol.

[0053] Preparation Example 3

[0054] The preparation method of the second catalyst C is the same as that of Preparation Example 1, except that the amount of 0.08 mol / L methanol solution of palladium chloride added in step S4 is 48 mL.

[0055] Preparation Example 4

[0056] The preparation method of the second catalyst D is the same as that of Preparation Example 1, except that (3-aminopropyl)triethoxysilane is not added in step S4.

[0057] Example 1

[0058] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol comprises the following steps:

[0059] A1. 300 g of p-nitroaniline and 3750 g of a 28 wt % aqueous solution of hydrochloric acid were mixed, stirred for 1 h, heated to 55 ° C, chlorine gas was continuously introduced for 5.5 h, cooled to room temperature, filtered, and the solid was washed with water three times, then washed with 8 wt % aqueous sodium hydroxide solution until neutral, and dried at 80 ° C for 6 h to obtain 2,6-dichloro-4-nitroaniline;

[0060] A2. 100 g of 2,6-dichloro-4-nitroaniline obtained in step A1 was mixed with 350 g of toluene to form a solution to obtain a 2,6-dichloro-4-nitroaniline solution for standby use; 200 g of sulfuric acid, 180 g of purified water and 20 g of copper sulfate were mixed and stirred to obtain a liquid for standby use;

[0061] A3. Mix 240.5 g of sulfuric acid and 65 g of nitrosylsulfuric acid, stir for 1 h, cool to 6 ° C, add 450 g of the 2,6-dichloro-4-nitroaniline solution obtained in step A2, control the reaction temperature at 12 ° C, keep the reaction for 1.5 h, and obtain a diazo solution. Heat to 110 ° C, add the diazo solution dropwise into the 240 g liquid obtained in step S2, control the addition time for 6 h, continue to keep the reaction for 1.5 h, cool to room temperature, separate the layers, and obtain the upper layer, which is the 2,6-dichloro-4-nitrophenol phase;

[0062] A4. 60g of 2,6-dichloro-4-nitrophenol phase obtained in step A3 and 1.2g of the second catalyst A were added to the reactor, replaced with nitrogen and hydrogen three times respectively, and then hydrogen was introduced, the pressure was controlled to 1.0MPa, the temperature was 85°C, and the hydrogenation reaction was carried out for 6h, filtered, cooled to room temperature, filtered, and dried at 95°C to constant weight to obtain 2,6-dichloro-4-aminophenol.

[0063] Example 2

[0064] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol comprises the following steps:

[0065] A1. 300 g of p-nitroaniline and 4500 g of a 20 wt % aqueous solution of hydrochloric acid were mixed, stirred for 1 h, heated to 60 ° C, chlorine gas was continuously introduced for 5 h, cooled to room temperature, filtered, and the solid was washed with water three times, then washed with a 10 wt % aqueous solution of sodium hydroxide until neutral, and dried at 80 ° C for 6 h to obtain 2,6-dichloro-4-nitroaniline;

[0066] A2. 100 g of 2,6-dichloro-4-nitroaniline obtained in step A1 was mixed with 400 g of toluene to form a solution to obtain a 2,6-dichloro-4-nitroaniline solution for later use; 200 g of sulfuric acid, 200 g of purified water and 20 g of copper sulfate were mixed and stirred to obtain a liquid for later use;

[0067] A3. Mix 231.6 g of sulfuric acid and 62.6 g of nitrosylsulfuric acid, stir for 1 h, cool to 4 ° C, add 450 g of the 2,6-dichloro-4-nitroaniline solution obtained in step A2, control the reaction temperature at 10 ° C, keep the reaction for 2 h, obtain a diazo solution, heat to 100 ° C, add the diazo solution dropwise into the 168 g liquid obtained in step S2, control the addition time for 7 h, continue to keep the reaction for 2 h, cool to room temperature, separate the layers, and obtain the upper layer, which is the 2,6-dichloro-4-nitrophenol phase;

[0068] A4. 60g of 2,6-dichloro-4-nitrophenol phase obtained in step A3 and 0.6g of the second catalyst A were added to the reactor, replaced with nitrogen and hydrogen three times respectively, and then hydrogen was introduced, the pressure was controlled to 1.0MPa, the temperature was 85°C, and the hydrogenation reaction was carried out for 6h, filtered, cooled to room temperature, filtered, and dried at 95°C to constant weight to obtain 2,6-dichloro-4-aminophenol.

[0069] Example 3

[0070] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol comprises the following steps:

[0071] A1. 300 g of p-nitroaniline and 3000 g of a 35 wt % aqueous solution of hydrochloric acid were mixed, stirred for 1 h, heated to 50 ° C, chlorine gas was continuously introduced for 6 h, cooled to room temperature, filtered, and the solid was washed with water three times, then washed with a 5 wt % aqueous solution of sodium hydroxide until neutral, and dried at 80 ° C for 6 h to obtain 2,6-dichloro-4-nitroaniline;

[0072] A2. 100 g of 2,6-dichloro-4-nitroaniline obtained in step A1 was mixed with 300 g of toluene to form a solution to obtain a 2,6-dichloro-4-nitroaniline solution for later use; 200 g of sulfuric acid, 160 g of purified water and 20 g of copper sulfate were mixed and stirred to obtain a liquid for later use;

[0073] A3. Mix 254.2 g of sulfuric acid and 67.8 g of nitrosylsulfuric acid, stir for 1 h, cool to 8 ° C, add 450 g of the 2,6-dichloro-4-nitroaniline solution obtained in step A2, control the reaction temperature at 15 ° C, keep the reaction for 1 h, obtain a diazo solution, heat to 120 ° C, add the diazo solution dropwise into the 285 g of liquid obtained in step S2, control the addition time for 5 h, continue to keep the reaction for 1 h, cool to room temperature, separate the layers, and obtain the upper layer, which is the 2,6-dichloro-4-nitrophenol phase;

[0074] A4. 60g of 2,6-dichloro-4-nitrophenol phase obtained in step A3 and 1.8g of the second catalyst A were added to the reactor, replaced with nitrogen and hydrogen three times respectively, and then hydrogen was introduced, the pressure was controlled to 1.0MPa, the temperature was 85°C, and the hydrogenation reaction was carried out for 6h, filtered, cooled to room temperature, filtered, and dried at 95°C to constant weight to obtain 2,6-dichloro-4-aminophenol.

[0075] Example 4

[0076] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation method is the same as that of Example 1, except that an equal amount of a second catalyst B is used to replace a second catalyst A.

[0077] Example 5

[0078] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation manner is the same as that of Example 1, except that an equal amount of a second catalyst C is used to replace a second catalyst A.

[0079] Example 6

[0080] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation method is the same as that of Example 1, except that an equal amount of a second catalyst D is used to replace a second catalyst A.

[0081] Example 7

[0082] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation manner is the same as that of Example 1, except that the amount of 28wt% hydrochloric acid aqueous solution added in step A1 is 2700g.

[0083] Example 8

[0084] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation manner is the same as that of Example 1, except that the amount of liquid in step A3 is 140 g, that is, the amount of the first catalyst used is 7 wt % of 2,6-dichloro-4-nitroaniline.

[0085] Example 9

[0086] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation manner is the same as that of Example 1, except that the amount of nitrosylsulfuric acid added in step A3 is 70.6 g.

[0087] Example 10

[0088] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation manner is the same as that of Example 1, except that the amount of the second catalyst added in step A4 is 0.48 g.

[0089] Comparative Example 1

[0090] A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, the specific implementation method is the same as that of Example 1, except that an equal amount of a commercially available conventional palladium-carbon catalyst is used to replace the second catalyst A.

[0091] Effect evaluation:

[0092] The 2,6-dichloro-4-aminophenol prepared in the above Examples 1-10 and Comparative Example 1 was tested, and the product was measured and the purity was calculated using a high performance liquid chromatograph. The specific results are shown in Table 1.

[0093] Table 1

[0094] Serial number Yield / % purity / % Example 1 98.1 99.9 Example 2 97.2 99.5 Example 3 97.6 99.7 Example 4 95.9 97.4 Example 5 92.7 97.0 Example 6 91.7 96.5 Example 7 94.6 97.5 Example 8 94.3 97.2 Example 9 95.2 98.1 Example 10 92.1 97.4 Comparative Example 1 90.7 95.7

[0095] From the results in Table 1, it can be seen that the yield of 2,6-dichloro-4-aminophenol prepared and synthesized in Example 1-3 is not less than 97%, and the purity is not less than 99%.

[0096] Compared with Example 1, when preparing the second catalyst, Example 4-6 changes the molar ratio of [1,1'-biphenyl]-2,2',4,4',6,6'-hexacarboxylic acid and copper nitrate trihydrate, which affects the adsorption of metallic copper particles on the carrier and the catalytic activity, thereby reducing the yield and purity of the product; Example 5 changes the dosage ratio of the carrier, (3-aminopropyl)triethoxysilane, and methanol solution of palladium chloride, reduces the number of palladium particles, and weakens the catalytic activity and selectivity. Example 6 does not add (3-aminopropyl)triethoxysilane, and the reaction activity decreases. All of the above will further reduce the yield and purity of 2,6-dichloro-4-aminophenol.

[0097] In Example 7, the mass ratio of p-nitroaniline to 20-35 wt % hydrochloric acid aqueous solution was changed, and the selectivity of the reaction decreased, affecting the yield and purity of 2,6-dichloro-4-nitroaniline, and further affecting the yield and purity of 2,6-dichloro-4-aminophenol.

[0098] Example 8 changes the dosage of the first catalyst, and Example 9 changes the molar ratio of nitrosylsulfuric acid to 2,6-dichloro-4-nitroaniline, both of which affect the yield and purity of 2,6-dichloro-4-nitrophenol, thereby reducing the yield and purity of 2,6-dichloro-4-aminophenol.

[0099] In Example 10, the dosage of the second catalyst was changed, and the catalytic activity decreased, thereby reducing the yield and purity of 2,6-dichloro-4-aminophenol.

[0100] Compared with Example 1, Comparative Example 1 uses an equal amount of commercially available palladium-carbon catalyst to replace the second catalyst A, which has low catalytic activity, resulting in a decrease in the yield and purity of 2,6-dichloro-4-aminophenol.

[0101] The above is only a preferred embodiment of the present invention and does not constitute any form of limitation to the present application. Although the present application is disclosed as above in the preferred embodiment, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution.

Claims

1. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol, characterized in that: The following steps are included: A1. P-nitroaniline and 20-35wt% aqueous hydrochloric acid solution were mixed, stirred, heated to 50-60°C, chlorine gas was continuously introduced for 5-6h, cooled, filtered, and the obtained solid was washed with water 2-3 times, then washed with 5-10wt% soda solution until neutral, and dried to obtain 2,6-dichloro-4-nitroaniline; A2. The 2,6-dichloro-4-nitroaniline obtained in step A1 is mixed with toluene to obtain a 2,6-dichloro-4-nitroaniline solution for standby use; sulfuric acid, purified water and the first catalyst are mixed and stirred to obtain a liquid for standby use; A3. Sulfuric acid and nitrosylsulfuric acid are mixed, stirred, cooled to 4-8°C, and the 2,6-dichloro-4-nitroaniline solution obtained in step A2 is added dropwise, the reaction temperature is controlled at 10-15°C, and the reaction is kept warm for 1-2h to obtain a diazo liquid, and the temperature is raised to 100-120°C, and the diazo liquid is added dropwise into the liquid obtained in step A2, and the addition time is controlled to 5-7h, and the reaction is continued at a temperature of 1-2h, cooled, and separated to obtain an upper liquid, which is a 2,6-dichloro-4-nitrophenol phase; A4. The 2,6-dichloro-4-nitrophenol phase obtained in step A3 and the second catalyst are added to a reactor, replaced with nitrogen and hydrogen 2-3 times respectively, and then hydrogen is introduced, the pressure and temperature are controlled, a hydrogenation reaction is carried out, the reaction is filtered, cooled, filtered, and dried to obtain 2,6-dichloro-4-aminophenol.

2. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 1, characterized in that: The mass ratio of p-nitroaniline and 20-35wt% hydrochloric acid aqueous solution in step A1 is 1:(10-15).

3. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 1, characterized in that: In step A2, the first catalyst is copper oxide or copper sulfate.

4. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 1, characterized in that: In step A2, the amount of the first catalyst used is 8-15 wt % of 2,6-dichloro-4-nitroaniline.

5. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 1, characterized in that: The molar ratio of nitrosylsulfuric acid to 2,6-dichloro-4-nitroaniline in the 2,6-dichloro-4-nitroaniline solution in step A3 is (1.02-1.12):

1.

6. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 1, characterized in that: The amount of the second catalyst used in step A4 is 1-3 wt % of the 2,6-dichloro-4-nitrophenol phase.

7. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 1, characterized in that: The method for preparing the second catalyst in step A4 comprises the following steps: S1. [1,1'-biphenyl]-2,2',4,4',6,6'-hexacarboxylic acid, N,N-dimethylformamide, and anhydrous ethanol are mixed and stirred to obtain solution 1; copper nitrate trihydrate and deionized water are mixed and stirred to obtain solution 2; S2. Pour solution 1 obtained in step S1 into solution 2, stir, heat to 85-95°C, hydrothermally react for 16-20h, cool, centrifuge, wash, and dry to obtain a powder; S3. Under a nitrogen atmosphere, the powder obtained in step S2 is carbonized and cooled to obtain a carrier; S4. The carrier, methanol and (3-aminopropyl)triethoxysilane obtained in step S3 are mixed, ultrasonically dispersed, added to a 0.06-0.1 mol / L methanol solution of palladium chloride, immersed and stirred for 8-12 hours, and then a 0.5-1 mol / L methanol solution of sodium borohydride is added dropwise, stirred for 12-16 hours, filtered, washed, dried, and ground to obtain a second catalyst.

8. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 7, characterized in that: The molar ratio of [1,1'-biphenyl]-2,2',4,4',6,6'-hexacarboxylic acid to copper nitrate trihydrate in step S1 is 1:(3.5-3.9).

9. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to claim 7, characterized in that: In step S4, the usage ratio of the carrier, (3-aminopropyl)triethoxysilane, and the methanol solution of palladium chloride is 1 g: (0.4-0.6) mL: (5-9) mL.

10. A method for synthesizing high-purity 2,6-dichloro-4-aminophenol according to any one of claims 1 to 9, characterized in that: The yield of the 2,6-dichloro-4-aminophenol is not less than 97%, and the purity is not less than 99%.