Preparation method of trans-4-aminocyclohexanol

Abstract

The invention relates to a trans-4-aminocyclohexanol preparation method, which specifically comprises: (1) adding p-acetamidophenol, an organic solvent and a catalyst to a reaction container, carrying out nitrogen displacement, introducing hydrogen, heating, carrying out a stirring reaction, filtering the catalyst after the reaction is completely carried out, concentrating the mother liquor, carrying out reduced pressure distillation, and recrystallizing to obtain a pure product of p-acetamidophenol; (2) adding the pure product of p-acetamido cyclohexanol obtained in the step (1), sodium hydroxide and water into a reactor, heating, stirring for reaction, concentrating, filtering, dissolving with dichloromethane for liquid separation, drying, concentrating, pulping and filtering to obtain trans-4-aminocyclohexanol; the catalyst in the step (1) is a palladium-carbon catalyst with the metal content of 5%. By introducing the palladium-carbon catalyst, the preparation method of the trans-4-aminocyclohexanol is good in stereoselectivity, the cis-trans isomer ratio of the intermediate p-acetamido cyclohexanol can reach 9: 91, and the obtained product is high in yield and good in purity.

Description

Technical Field

[0001] The present invention belongs to the field of organic synthetic chemistry, and particularly relates to a method for preparing trans-4-aminocyclohexanol. Background Art

[0002] Trans-4-aminocyclohexanol is an important intermediate for the preparation of ambroxol hydrochloride. The reported synthetic routes utilize the principle that trans-4-aminocyclohexanol can be separated from cis-trans isomers by hydrogenation or reaction with acetone to form a Schiff base. p-Acetamidophenol is hydrogenated under the condition of a catalyst, and the product is hydrolyzed with an alkali to obtain cis-trans mixed 4-aminocyclohexanol, which is then reacted with acetone and hydrolyzed and extracted to obtain trans-4-aminocyclohexanol, or the cis isomer is converted to the trans isomer under the condition of catalytic hydrogenation. However, the reactions all require relatively high temperatures and pressures, and there are many reaction steps. For example, Yang Jian. A new process for the synthesis of trans-4-aminocyclohexanol [J]. Fine Chemicals, 2000, 17 (2): 100-102. This article reports that in the first step, under the catalytic condition of Raney nickel, the reaction pressure is 9 Mpa and the reaction temperature is 170 °C. The cis-trans ratio of p-acetamidocyclohexanol obtained after hydrogenation of p-acetamidophenol is 27:70; Tang Xinyuan. Research and development of trans-4-aminocyclohexanol [J]. Hangzhou Chemical Industry. 2005, 35 (4): 18-19. This article reports that in the first step, under the catalytic condition of Raney nickel, the reaction pressure is 9 Mpa and the reaction temperature is 165 °C. The cis-trans ratio of p-acetamidocyclohexanol obtained after hydrogenation of p-acetamidophenol is 40:60, and the 4-aminocyclohexanol obtained by alkaline hydrolysis still needs to undergo a catalytic reaction to convert the cis isomer to the trans isomer, with complex operations and high energy consumption.

[0003] Now, a new process is proposed for preparation. Using p-acetamidophenol as a raw material, under the catalytic condition of a palladium-carbon catalyst, the reaction temperature is 90 °C and the pressure is only 2 Mpa. After hydrogenation, the cis-trans ratio of the obtained p-acetamidocyclohexanol can reach 9:91, and the cis-trans p-acetamidocyclohexanol is separated by crystallization method. The obtained trans-p-acetamidocyclohexanol can be directly hydrolyzed to obtain high-purity trans-4-aminocyclohexanol: Summary of the Invention

[0004] In view of the above technical problems, the present invention provides a method for preparing trans-4-aminocyclohexanol. Trans-4-aminocyclohexanol can be prepared by a simple preparation technique, while avoiding high-temperature and high-pressure reaction conditions, reducing reaction steps, and meeting the requirements of atom economy.

[0005] A method for preparing trans-4-aminocyclohexanol specifically comprises the following steps: (1) Add paracetamol, organic solvent, and catalyst into a reaction vessel, displace with nitrogen, introduce hydrogen, heat, and stir for reaction. After the reaction is complete, filter the catalyst, concentrate the mother liquor, distill under reduced pressure, and recrystallize to obtain pure paracetamol cyclohexanol; (2) Add the pure paracetamol cyclohexanol obtained in step (1), sodium hydroxide, and water into a reactor, heat, stir for reaction, concentrate, filter, dissolve in dichloromethane and separate by liquid-liquid extraction, dry, concentrate, slurry, and filter to obtain trans-4-aminocyclohexanol; The catalyst in step (1) is a palladium-carbon catalyst with a metal content of 5%.

[0006] Preferably, the preparation method of the palladium-carbon catalyst is as follows: (1) Under the temperature condition of 110°C to 120°C, reflux activated carbon in nitric acid solution for 1h to 3h, wash, and dry; (2) At room temperature, immerse the activated carbon treated in step (1) in an ethanol aqueous solution for impregnation for 2h to 4h, filter to obtain a filter cake, wash, and slurry with pure water to obtain an activated carbon slurry; (3) Dissolve palladium chloride in hydrochloric acid solution to obtain a palladium chloride precursor solution; (4) Drop the palladium chloride precursor solution obtained in step (3) into the activated carbon slurry obtained in step (2) to obtain reaction system A, stir and impregnate for 3h to 5h, adjust the pH value to 8 - 9, filter to obtain a retentate; (5) Slurry the retentate obtained in step (4) with pure water to obtain a catalyst slurry; (6) Mix the catalyst slurry obtained in step (5) with an aqueous solution of sodium hypophosphite in alcohol, stir at 75°C to 85°C for 1h to 2h for reduction, wash until there is no residual chloride ion to obtain a palladium-carbon catalyst.

[0007] Preferably, the volume concentration of ethanol in the ethanol aqueous solution in step (2) is 20% - 30%; the amount of pure water in the pure water slurry in step (2) is 10 - 15 times the mass of the filter cake after washing in step (2); the pure water used for pure water slurry in step (5) is 5 - 10 times the retentate.

[0008] Preferably, the mass ratio of activated carbon to palladium chloride is 12:1.

[0009] Preferably, the proportion of sodium hypophosphite in the aqueous solution of sodium hypophosphite in alcohol in step (6) is 5%, and the ratio of alcohol to water in the aqueous solution of alcohol is 25:75; the addition amount of sodium hypophosphite is 3 times the mass of palladium element.

[0010] Preferably, the mass ratio of paracetamol to the organic solvent is 1:3.9 - 1:5; the mass ratio of paracetamol to the catalyst is 20:(1 - 0.6); the mass ratio of paracetamol to sodium hydroxide is 20:(9.04 - 11.7).

[0011] Preferably, in step (1), the organic solvent is methanol, cyclohexane or water; the organic solvent used for recrystallization is acetone or dichloromethane.

[0012] Preferably, in step (1), the temperature of the stirring reaction is 90°C and the pressure is 2 - 3 Mpa.

[0013] Preferably, in step (2), the heating temperature is 100°C and the stirring reaction time is 2 h.

[0014] Advantages of the present invention: (1) The process is simple and easy to implement, with low cost and high production efficiency; by introducing a palladium-carbon catalyst, the preparation method of trans-4-aminocyclohexanol has good stereoselectivity, the cis-trans isomer ratio of the intermediate paracetamido cyclohexanol can reach 9:91, and the obtained product has high yield and good purity; (2) For the preparation method of trans-4-aminocyclohexanol of the present invention, the reaction temperature is 90°C and the reaction pressure is 2 Mpa, avoiding the use of high temperature and high pressure conditions in the traditional preparation process, with high safety, suitable for large-scale production, and at the same time, the production process has less three wastes, and is green, efficient and environmentally friendly. Description of the drawings

[0015] Figure 1 1H NMR spectrum of trans-4-aminocyclohexanol prepared in Example 3. Detailed implementation manners

[0016] The present invention will be further described in detail below through examples, but the protection scope of the present invention is not limited to the content described.

[0017] Example 1 A palladium-carbon catalyst used for preparing trans-4-aminocyclohexanol, and its preparation method is as follows: (1) Under the temperature condition of 110°C, 12 g of activated carbon is refluxed in 300 mL of nitric acid solution for 3 h, washed and dried; (2) Under the room temperature condition, the activated carbon treated in step (1) is immersed in an ethanol aqueous solution with an ethanol concentration of 30% for 2 h, filtered to obtain a filter cake, washed, and slurried with pure water 10 times the mass of the washed filter cake to obtain an activated carbon slurry; (3) 1 g of palladium chloride is dissolved in 80 mL of hydrochloric acid solution with a mass concentration of 0.8 mol / L to obtain a palladium chloride precursor solution; (4) The palladium chloride precursor solution obtained in step (3) was dropped into the activated carbon slurry obtained in step (2) to obtain reaction system A, stirred and impregnated for 3 h, the pH value was adjusted to 8, filtered, and the retentate was obtained; (5) The retentate obtained in step (4) was slurried with 10 times the mass of the retentate of pure water to obtain a catalyst slurry; (6) The catalyst slurry obtained in step (5) was mixed with an alcohol aqueous solution containing 5% of sodium hypophosphite, the ratio of alcohol to water in the alcohol aqueous solution was: 25:75, and the addition amount of sodium hypophosphite was 3 times the mass of palladium element. Reduction was carried out by stirring at 75 °C for 2 h, washed until there was no residual chloride ion, and a palladium-carbon catalyst was obtained.

[0018] Example 2 A method for preparing a palladium-carbon catalyst used for preparing trans-4-aminocyclohexanol is as follows: (1) At a temperature of 120 °C, 12 g of activated carbon was refluxed in 300 mL of nitric acid solution for 1 h, washed, and dried; (2) At room temperature, the activated carbon treated in step (1) was immersed in an ethanol aqueous solution with an ethanol concentration of 20% and impregnated for 4 h, filtered to obtain a filter cake, washed, and slurried with 15 times the mass of the washed filter cake of pure water to obtain an activated carbon slurry; (3) 1 g of palladium chloride was dissolved in 80 mL of hydrochloric acid solution with a mass concentration of 0.8 mol / L to obtain a palladium chloride precursor solution; (4) The palladium chloride precursor solution obtained in step (3) was dropped into the activated carbon slurry obtained in step (2) to obtain reaction system A, stirred and impregnated for 5 h, the pH value was adjusted to 9, filtered, and the retentate was obtained; (5) The retentate obtained in step (4) was slurried with 5 times the mass of the retentate of pure water to obtain a catalyst slurry; (6) The catalyst slurry obtained in step (5) was mixed with an alcohol aqueous solution containing 5% of sodium hypophosphite, the ratio of alcohol to water in the alcohol aqueous solution was: 25:75, the addition amount of sodium hypophosphite was 3 times the mass of palladium element, and reduction was carried out by stirring at 85 °C for 1 h, washed until there was no residual chloride ion, and a palladium-carbon catalyst was obtained.

[0019] Example 3 A method for preparing trans-4-aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p-acetaminophen, 100 mL of cyclohexane, and 1.0 g of the catalyst obtained in Example 2 into a 250 mL high-pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 3.0 Mpa, heat to 90 °C, and then stir the reaction. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis product to the trans product is 10:90. Add the obtained white solid to 500 mL of acetone for recrystallization to obtain 13.7 g of trans-acetaminocyclohexanol crystals; (2) Add the trans-acetaminocyclohexanol crystals obtained in step (1), 11 g of sodium hydroxide, and 70 mL of water into a 250 mL flask. Heat to 100 °C and then stir the reaction for 2 h. Concentrate the reaction solution to 30% of the original volume, and a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and then separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying, and concentrate it to nearly dry. Add 50 mL of n-hexane and slurry at -10 °C for 1 h. Filter to obtain 9.53 g of a white solid product with a yield of 95% and an overall yield of 63%. The 1H NMR spectrum of the trans-4-aminocyclohexanol prepared in this example is shown in Figure 1 .

[0020] Example 4 A method for preparing trans-4-aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p-acetaminophen, 100 mL of methanol, and 1.0 g of the catalyst obtained in Example 2 into a 250 mL high-pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 3.0 Mpa, heat to 90 °C, and then stir the reaction. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis product to the trans product is 15:85. Add the obtained white solid to 500 mL of acetone for recrystallization to obtain 11.3 g of trans-acetaminocyclohexanol crystals; (2) Add the trans-acetaminocyclohexanol crystals obtained in step (1), 9.04 g of sodium hydroxide, and 70 mL of water into a 250 mL flask. Heat to 100 °C and then stir the reaction for 2 h. Concentrate the reaction solution to 30% of the original volume, and a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and then separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying, and concentrate it to nearly dry. Add 50 mL of n-hexane and slurry at -10 °C for 1 h. Filter to obtain 7.95 g of a white solid product with a yield of 96% and an overall yield of 52%.

[0021] Example 5 A method for preparing trans-4-aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p-acetaminophen, 100 mL of water, and 1.0 g of the catalyst obtained in Example 2 to a 250 mL high-pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 3.0 Mpa, heat to 90 °C, then stir and react. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis product to the trans product is 9:91. Add the obtained white solid to 500 mL of acetone for recrystallization to obtain 14.7 g of trans-4-acetamidocyclohexanol crystals; (2) Add the trans-4-acetamidocyclohexanol crystals obtained in step (1), 11.7 g of sodium hydroxide, and 70 mL of water to a 250 mL flask. Heat to 100 °C and stir and react for 2 h. Concentrate the reaction solution to 30% of the original volume, a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and then separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying and concentrate to nearly dry. Add 50 mL of n-hexane and slurry at -10 °C for 1 h, then filter to obtain 10.2 g of a white solid product with a yield of 95% and an overall yield of 67%.

[0022] Example 6 A method for preparing trans-4-aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p-acetaminophen, 100 mL of water, and 0.6 g of the catalyst obtained in Example 2 to a 250 mL high-pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 3.0 Mpa, heat to 90 °C, then stir and react. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis product to the trans product is 9:91. Add the obtained white solid to 500 mL of acetone for recrystallization to obtain 14.7 g of trans-4-acetamidocyclohexanol crystals; (2) Add the trans-4-acetamidocyclohexanol crystals obtained in step (1), 11.7 g of sodium hydroxide, and 70 mL of water to a 250 mL flask. Heat to 100 °C and stir and react for 2 h. Concentrate the reaction solution to 30% of the original volume, a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and then separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying and concentrate to nearly dry. Add 50 mL of n-hexane and slurry at -10 °C for 1 h, then filter to obtain 10.2 g of a white solid product with a yield of 95% and an overall yield of 67%.

[0023] Example 7 A method for preparing trans-4-aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p - acetaminophen, 100 mL of water, and 0.6 g of the recycled palladium - carbon catalyst with a 5% palladium loading into a 250 mL high - pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 2.0 Mpa, heat to 90 °C, then stir and react. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis - product to the trans - product is 9:91. Add the obtained white solid to 500 mL of acetone for recrystallization to obtain 14.7 g of trans - p - acetaminocyclohexanol crystals; (2) Add the trans - p - acetaminocyclohexanol crystals obtained in step (1), 11.7 g of sodium hydroxide, and 70 mL of water into a 250 mL flask. Heat to 100 °C and stir and react for 2 h. Concentrate the reaction solution to 30% of the original volume, a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying and concentrate to near - dryness. Add 50 mL of n - hexane and slurry at - 10 °C for 1 h, then filter to obtain 10.2 g of a white solid product with a yield of 95% and an overall yield of 63%.

[0024] Example 8 A preparation method of trans - 4 - aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p - acetaminophen, 100 mL of water, and 1.0 g of the catalyst obtained in Example 2 into a 250 mL high - pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 2.0 Mpa, heat to 90 °C, then stir and react. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis - product to the trans - product is 9:91. Add the obtained white solid to 500 mL of acetone for recrystallization to obtain 14.7 g of trans - p - acetaminocyclohexanol crystals; (2) Add the trans - p - acetaminocyclohexanol crystals obtained in step (1), 11.7 g of sodium hydroxide, and 70 mL of water into a 250 mL flask. Heat to 100 °C and stir and react for 2 h. Concentrate the reaction solution to 30% of the original volume, a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying and concentrate to near - dryness. Add 50 mL of n - hexane and slurry at - 10 °C for 1 h, then filter to obtain 10.2 g of a white solid product with a yield of 95% and an overall yield of 67%.

[0025] Example 9 A preparation method of trans - 4 - aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p-acetaminophen, 100 mL of water, and 0.6 g of the catalyst obtained in Example 2 into a 250 mL high-pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 2.0 Mpa, heat to 90 °C, then stir and react. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis product to the trans product is 9:91. Add the obtained white solid to 500 mL of dichloromethane for recrystallization to obtain 14.2 g of trans-4-acetamidocyclohexanol crystals; (2) Add the trans-4-acetamidocyclohexanol crystals obtained in step (1), 11.3 g of sodium hydroxide, and 70 mL of water into a 250 mL flask. Heat to 100 °C and stir and react for 2 h. Concentrate the reaction solution to 30% of the original volume, and a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and then separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying, and concentrate it to nearly dry. Add 50 mL of n-hexane and slurry at -10 °C for 1 h. Filter to obtain 9.9 g of a white solid product with a yield of 95% and an overall yield of 63%.

[0026] Example 10 A preparation method of trans-4-aminocyclohexanol specifically includes the following steps: (1) Add 20 g of p-acetaminophen, 100 mL of water, and 0.6 g of the catalyst obtained in Example 2 into a 250 mL high-pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 2.0 Mpa, heat to 90 °C, then stir and react. After the reaction is completed as monitored by gas chromatography, filter the catalyst. Concentrate the mother liquor and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis product to the trans product is 9:91. Add the obtained white solid to 500 mL of recycled acetone for recrystallization to obtain 13.8 g of trans-4-acetamidocyclohexanol crystals; (2) Add the trans-4-acetamidocyclohexanol crystals obtained in step (1), 11.0 g of sodium hydroxide, and 70 mL of water into a 250 mL flask. Heat to 100 °C and stir and react for 2 h. Concentrate the reaction solution to 30% of the original volume, and a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and then separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying, and concentrate it to nearly dry. Add 50 mL of n-hexane and slurry at -10 °C for 1 h. Filter to obtain 9.6 g of a white solid product with a yield of 95% and an overall yield of 63%.

[0027] Example 11 A preparation method of trans-4-aminocyclohexanol specifically includes the following steps: (1) Add 20 g of paracetamol, 100 mL of water, and 0.6 g of the catalyst obtained in Example 2 into a 250 mL high-pressure hydrogenation autoclave. Replace the air with nitrogen, introduce hydrogen to 2.0 Mpa, heat to 90 °C, then stir and react. After the reaction is completed monitored by gas chromatography, filter the catalyst, concentrate the mother liquor, and perform vacuum distillation to obtain 20.2 g of a white solid product with a yield of 99%. The content ratio of the cis product to the trans product is 9:91. Add the obtained white solid to 500 mL of acetone for recrystallization to obtain 14.7 g of trans - p - acetylaminocyclohexanol crystals; (2) Add the trans - p - acetylaminocyclohexanol crystals obtained in step (1), 9.85 g of sodium hydroxide, and 70 mL of water into a 250 mL flask. Heat to 100 °C and stir and react for 2 h. Concentrate the reaction solution to 30% of the original volume, a large amount of solid will precipitate. Filter the solid, dissolve it with dichloromethane and then separate the layers. Collect the organic phase, dry it with anhydrous sodium sulfate, filter after drying, and concentrate to nearly dry. Add 50 mL of n - hexane and slurry at - 10 °C for 1 h. Filter to obtain 10.2 g of a white solid product with a yield of 95% and an overall yield of 67%.

Claims

1. A method for preparing trans-4-aminocyclohexanol, characterized in that: The specific steps include: (1) Adding acetaminophenol, an organic solvent and a catalyst into a reaction vessel, replacing the atmosphere with nitrogen, introducing hydrogen, heating, stirring and reacting, filtering the catalyst after the reaction is complete, concentrating the mother liquor, performing vacuum distillation and recrystallization to obtain pure acetaminocyclohexanol; (2) adding the pure acetylaminocyclohexanol obtained in step (1), sodium hydroxide and water into a reactor, heating, stirring for reaction, concentrating, filtering, dissolving and separating the liquid with dichloromethane, drying, concentrating, beating and filtering to obtain trans-4-aminocyclohexanol; The catalyst in step (1) is a palladium-carbon catalyst with a metal content of 5%.

2. The method for preparing trans-4-aminocyclohexanol according to claim 1, characterized in that: The preparation method of the palladium-carbon catalyst is as follows: (1) Reflux the activated carbon in a nitric acid solution at 110°C to 120°C for 1h to 3h, wash, and dry; (2) Under room temperature, immersing the activated carbon treated in step (1) in an ethanol aqueous solution for 2 h to 4 h, filtering to obtain a filter cake, washing, and slurrying with pure water to obtain an activated carbon slurry; (3) dissolving palladium chloride in a hydrochloric acid solution to obtain a palladium chloride precursor solution; (4) adding the palladium chloride precursor solution obtained in step (3) dropwise to the activated carbon slurry obtained in step (2) to obtain a reaction system A, stirring and impregnating for 3 h to 5 h, adjusting the pH value to 8-9, filtering, and obtaining a retentate; (5) slurrying the retentate obtained in step (4) with pure water to obtain a catalyst slurry; (6) The catalyst slurry obtained in step (5) is mixed with an alcohol aqueous solution of sodium hypophosphite, and the mixture is stirred at 75° C. to 85° C. for 1 h to 2 h for reduction, and washed until no chloride ions remain, thereby obtaining a palladium carbon catalyst.

3. The method for preparing trans-4-aminocyclohexanol according to claim 2, characterized in that: The volume concentration of ethanol in the ethanol aqueous solution in step (2) is 20% to 30%; the amount of pure water in the pure water pulping in step (2) is 10 to 15 times the mass of the filter cake after washing in step (2); and the amount of pure water used for pure water pulping in step (5) is 5 to 10 times the mass of the retentate.

4. The method for preparing trans-4-aminocyclohexanol according to claim 3, characterized in that: The mass ratio of the activated carbon to palladium chloride is 12:

1.

5. The method for preparing trans-4-aminocyclohexanol according to claim 4, characterized in that: In step (6), the proportion of sodium hypophosphite in the alcohol aqueous solution of sodium hypophosphite is 5%, and the ratio of alcohol to water in the alcohol aqueous solution is 25:75; the amount of sodium hypophosphite added is 3 times the mass of the palladium element.

6. The method for preparing trans-4-aminocyclohexanol according to claim 1, characterized in that: The mass ratio of the acetaminophenol to the organic solvent is 1:3.9-1:5; the mass ratio of the acetaminophenol to the catalyst is 20:(1-0.6); and the mass ratio of the acetaminophenol to sodium hydroxide is 20:(9.04-11.7).

7. The method for preparing trans-4-aminocyclohexanol according to claim 6, characterized in that: The organic solvent in step (1) is methanol, cyclohexane or water; the organic solvent used for recrystallization is acetone or dichloromethane.

8. The method for preparing trans-4-aminocyclohexanol according to claim 1, characterized in that: The stirring reaction temperature in step (1) is 90° C. and the pressure is 2-3 MPa.

9. The method for preparing trans-4-aminocyclohexanol according to claim 1, characterized in that: The heating temperature in step (2) is 100° C. and the stirring reaction time is 2 h.

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