Preparation method of m-dibutylaminophenol

Abstract

The invention discloses a preparation method of m-dibutylaminophenol, and relates to the technical field of carbocyclic compound preparation, the m-dibutylaminophenol comprises the following raw materials: 2-chlorophenol, 2, 6-di-tert-butyl-4-methylphenol, zinc chloride, tetrabutylammonium bromide, sodium amide, potassium tert-butoxide, an activated 3A molecular sieve, di-n-butylamine and triethylamine; according to the invention, 2-chlorophenol is used as a core reaction substrate, the structure arrangement of ortho-position chlorine atoms and hydroxyl is highly adaptive, hydrogen chloride can be accurately removed under the action of strong alkali to generate a benzyne intermediate, and a stable benzene ring skeleton is provided for a target product; through the synergistic effect of the activated 3A molecular sieve, the 2, 6-di-tert-butyl-4-methylphenol and the potassium tert-butoxide, the total impurity content is greatly reduced, the product purity and color are remarkably optimized, and the synchronous improvement of the reaction efficiency and the product quality is realized.

Description

Technical Field

[0001] This invention relates to the field of carbocyclic compound preparation technology, and in particular to a method for preparing m-dibutylaminophenol. Background Technology

[0002] m-Dibutylaminophenol is an aminophenol compound with a specific structure. Its main value lies in its use as a chemical intermediate, especially in the polymer materials industry, where it is used to manufacture antioxidants and other auxiliaries.

[0003] m-Dibutylaminophenol has the following drawbacks: limited chemical stability, resulting in insufficient performance consistency in relevant application systems; its synthesis process often involves complex steps and low reaction selectivity, leading to low product yield and further increasing production costs. Based on this, the present invention provides a method for preparing m-dibutylaminophenol. Summary of the Invention

[0004] The main objective of this invention is to provide a product with high stability and purity of m-dibutylaminophenol, which is applied in a method for preparing m-dibutylaminophenol.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a method for preparing m-dibutylaminophenol, characterized by comprising the following raw materials: 127.3-129.9 parts of 2-chlorophenol, 2-2.4 parts of 2,6-di-tert-butyl-4-methylphenol, 3.7-4.5 parts of zinc chloride, 14.5-17.7 parts of tetrabutylammonium bromide, 67.3-71.1 parts of sodium amino acid, 10.1-12.3 parts of potassium tert-butoxide, 45-55 parts of activated 3A molecular sieve, 217-239.8 parts of di-n-butylamine, and 18.2-22.2 parts of triethylamine;

[0007] The preparation of the m-dibutylaminophenol includes the following steps:

[0008] Step 1. Add 2-chlorophenol, anhydrous ethanol, and 2,6-di-tert-butyl-4-methylphenol to a reaction vessel and stir. Set the water bath temperature to 30-40℃ and the stirring speed to 500 rpm. Stir for 5-8 minutes, then stop heating and allow the reaction vessel to cool naturally to 25℃ to obtain a 2-chlorophenol solution. Add zinc chloride and anhydrous ethanol to a new reaction vessel and stir at 400 rpm for 3 minutes to obtain a zinc chloride solution.

[0009] Step 2. Cool the activated 3A molecular sieve to 25°C in a desiccator, add it to the reaction vessel, close the lid, and purge with nitrogen for 15 minutes. Add liquid ammonia and stir at 200 rpm. Lower the reaction vessel temperature to -33°C. Add sodium amide and potassium tert-butoxide in 7 portions, stirring at 150-200 rpm, with 1.5-minute intervals between each addition. Add tetrabutylammonium bromide and stir at 200 rpm for 30 minutes. Using a constant pressure funnel, add 2-chlorophenol solution to the reaction vessel while stirring at a dropping rate of 5-6 mL / min. Maintain the reaction vessel temperature between -25°C and -20°C at 200 rpm. After the 2-chlorophenol solution has been completely added... The temperature was increased to -15℃ at a rate of 8℃ / h, and stirred for 1 hour. Zinc chloride solution was added to the reaction vessel using a constant pressure funnel and stirred at a dropping rate of 2mL / min and a stirring speed of 200rpm. Di-n-butylamine and triethylamine were added and stirred, and the stirring speed was increased to 450rpm for 75 minutes. The temperature was increased to -5℃ at a rate of 8℃ / h and stirred for 2.5-3 hours. The stirring speed was adjusted to 100rpm. The reaction vessel was allowed to heat up naturally to 20-25℃ and stirred for 4-6 hours. Concentrated hydrochloric acid was added dropwise to the reaction vessel using a constant pressure funnel and stirred. The water bath temperature was set to 20-25℃ and the stirring speed was increased to 600rpm. The addition of concentrated hydrochloric acid was stopped and the mixture was stirred for 30 minutes to obtain the crude product.

[0010] Step 3. Filter the crude product, wash with cold ethanol, recrystallize, filter, cool and crystallize, wash the refined product and vacuum dry to obtain m-dibutylaminophenol.

[0011] 2-Chlorophenol has a purity of 98-99.5% and a moisture content of ≤0.1%.

[0012] The sodium amide has a purity of 94-96% and a moisture content of ≤0.05%.

[0013] Potassium tert-butoxide is an anhydrous powder with a purity of 97-99%.

[0014] The purity of tetrabutylammonium bromide is 98-99.5%;

[0015] The purity of di-n-butylamine is 97-99%, and the moisture content is ≤0.1%.

[0016] The triethylamine has a purity of 98-99.5% and a moisture content of ≤0.1%.

[0017] Zinc chloride is anhydrous, with a moisture content of ≤0.05%.

[0018] The purity of 2,6-di-tert-butyl-4-methylphenol is 98-99.5%;

[0019] The particle size of activated 3A molecular sieves is 1-3 mm;

[0020] Liquid ammonia purity ≥ 99.5%;

[0021] Further, in step 1, 2-chlorophenol, anhydrous ethanol and 2,6-di-tert-butyl-4-methylphenol are added to the reaction vessel and stirred, and the mass ratio of 2,6-di-tert-butyl-4-methylphenol to anhydrous ethanol is 1:35.88.

[0022] Furthermore, in step 1, zinc chloride and anhydrous ethanol are placed in a new reaction vessel and stirred, with a mass ratio of zinc chloride to anhydrous ethanol of 1:1.92.

[0023] Furthermore, in step 2, the mass concentration of concentrated hydrochloric acid is 37%, and concentrated hydrochloric acid is added to adjust the pH to 1-2.

[0024] Furthermore, in step 2, the 3A molecular sieve is activated by placing it in a muffle furnace, setting the heating rate to 5°C / min, heating it to 300°C, and holding it at that temperature for 4 hours to obtain activated 3A molecular sieve.

[0025] Furthermore, in step 3, the crude product is filtered under vacuum at a set vacuum level of -0.095 MPa for 10 minutes.

[0026] The cold ethanol washing is performed by washing three times with cold anhydrous ethanol at 0-5℃, followed by filtration for 4-6 minutes.

[0027] Further, in step 3, recrystallization involves adding anhydrous ethanol and stirring, setting the stirring speed to 300 rpm, the temperature to 78°C, and refluxing for 30 minutes.

[0028] The mass ratio of the washed crude product to anhydrous ethanol is 1:1.4-1.6.

[0029] Furthermore, in step 3, a polytetrafluoroethylene (PTFE) filter membrane with a pore size of 4.5 μm is used for filtration. The PTFE filter membrane is soaked in anhydrous ethanol at 60-70°C for 5 minutes beforehand.

[0030] Further, in step 3, the cooling crystallization is carried out by adding distilled water and stirring at 200 rpm for 5-10 minutes, cooling to 0°C at a cooling rate of 2°C / h, and letting it stand for 7.5-8.5 hours.

[0031] Furthermore, in step 3, the refined product is washed and vacuum dried. The refined product is washed twice with a mixture of 0-5°C cold ethanol and water, cooled and crystallized, and then filtered for 5 minutes after washing.

[0032] The volume ratio of the cold ethanol to water is 1:1;

[0033] The vacuum drying process is set at a vacuum level of -0.098 MPa, a drying temperature of 40°C, and a drying time of 6 hours.

[0034] The present invention has the following beneficial effects:

[0035] 1. In this invention, by adding 2-chlorophenol as the core reaction substrate, the structural arrangement of its ortho-chlorine atom and hydroxyl group is highly compatible. Under the action of strong alkali, hydrogen chloride can be precisely removed to generate a benzene-yne ​​intermediate, providing a stable benzene ring skeleton for the target product. This raw material is readily available in the industry, can be purified to high purity through simple distillation, has easily controllable moisture content, stable chemical properties, low side reaction rate, and moderate cost, which is fully compatible with the core requirements of large-scale production for raw materials.

[0036] 2. In this invention, the added sodium amino acid exhibits extremely strong deprotonation activity, enabling it to efficiently catalyze the removal of hydrogen chloride from 2-chlorophenol in a liquid ammonia system, rapidly generating a highly active benzylene intermediate. The reaction exhibits outstanding selectivity, preventing excessive degradation of the raw materials. Its powdered form facilitates batch feeding control, and its good compatibility with liquid ammonia ensures uniform alkalinity in the reaction system, avoiding side reactions caused by localized overheating. The ammonia generated after the reaction can be recovered along with the liquid ammonia, leaving no harmful residues and minimally impacting subsequent purification processes, aligning with green production principles. Furthermore, it synergistically works with potassium tert-butoxide and tetrabutylammonium bromide. Sodium amino acid provides a strong alkaline environment, potassium tert-butoxide stabilizes the intermediate, and tetrabutylammonium bromide improves phase contact. These three elements form a synergistic system of strong base, stabilizer, and phase transfer catalyst, solving the problem of numerous side reactions caused by a single strong base and overcoming the rate bottleneck due to insufficient phase interface contact, thus improving product yield.

[0037] 3. In this invention, by activating 3A molecular sieve, 2,6-di-tert-butyl-4-methylphenol, and potassium tert-butoxide in synergy, the 3A molecular sieve selectively adsorbs trace amounts of moisture in the system, blocking the generation pathway of hydrolysis impurities at the source; the antioxidant preferentially reacts with trace amounts of oxygen in the system, preventing the highly reactive benzyne intermediate from being oxidized and degraded; potassium tert-butoxide, with its suitable alkalinity and unique steric hindrance, competitively adsorbs the active sites of benzyne, effectively preventing its self-polymerization. The synergistic effect of the three comprehensively covers the three core side reactions of hydrolysis, oxidation, and polymerization, solving the pain point of existing technologies where a single protection method cannot cover multiple types of side reactions, resulting in a significant reduction in total impurity content, significant optimization of product purity and color, and simultaneous improvement in reaction efficiency and product quality. Detailed Implementation

[0038] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0039] It should be noted that all raw materials used in the following experiments are commercially available.

[0040] Example 1: A method for preparing m-dibutylaminophenol, characterized by comprising the following raw materials: 127.3 parts 2-chlorophenol, 2 parts 2,6-di-tert-butyl-4-methylphenol, 3.7 parts zinc chloride, 14.5 parts tetrabutylammonium bromide, 67.3 parts sodium amino, 10.1 parts potassium tert-butoxide, 45 parts activated 3A molecular sieve, 217 parts di-n-butylamine, and 18.2 parts triethylamine;

[0041] The preparation of the m-dibutylaminophenol includes the following steps:

[0042] Step 1. Add 2-chlorophenol, anhydrous ethanol, and 2,6-di-tert-butyl-4-methylphenol to a reaction vessel and stir. Set the water bath temperature to 30-40℃ and the stirring speed to 500 rpm. Stir for 5-8 minutes, then stop heating and allow the reaction vessel to cool naturally to 25℃ to obtain a 2-chlorophenol solution. Add zinc chloride and anhydrous ethanol to a new reaction vessel and stir at 400 rpm for 3 minutes to obtain a zinc chloride solution.

[0043] Step 2. Cool the activated 3A molecular sieve to 25°C in a desiccator, add it to the reaction vessel, close the lid, and purge with nitrogen for 15 minutes. Add liquid ammonia and stir at 200 rpm. Lower the reaction vessel temperature to -33°C. Add sodium amide and potassium tert-butoxide in 7 portions, stirring at 150-200 rpm, with 1.5-minute intervals between each addition. Add tetrabutylammonium bromide and stir at 200 rpm for 30 minutes. Using a constant pressure funnel, add 2-chlorophenol solution to the reaction vessel while stirring at a dropping rate of 5-6 mL / min. Maintain the reaction vessel temperature between -25°C and -20°C at 200 rpm. After the 2-chlorophenol solution has been completely added... The temperature was increased to -15℃ at a rate of 8℃ / h, and stirred for 1 hour. Zinc chloride solution was added to the reaction vessel using a constant pressure funnel and stirred at a dropping rate of 2mL / min and a stirring speed of 200rpm. Di-n-butylamine and triethylamine were added and stirred, and the stirring speed was increased to 450rpm for 75 minutes. The temperature was increased to -5℃ at a rate of 8℃ / h and stirred for 2.5-3 hours. The stirring speed was adjusted to 100rpm. The reaction vessel was allowed to heat up naturally to 20-25℃ and stirred for 4-6 hours. Concentrated hydrochloric acid was added dropwise to the reaction vessel using a constant pressure funnel and stirred. The water bath temperature was set to 20-25℃ and the stirring speed was increased to 600rpm. The addition of concentrated hydrochloric acid was stopped and the mixture was stirred for 30 minutes to obtain the crude product.

[0044] Step 3. Filter the crude product, wash with cold ethanol, recrystallize, filter, cool and crystallize, wash the refined product and vacuum dry to obtain m-dibutylaminophenol.

[0045] In step 1, 2-chlorophenol, anhydrous ethanol and 2,6-di-tert-butyl-4-methylphenol are added to the reaction vessel and stirred. The mass ratio of 2,6-di-tert-butyl-4-methylphenol to anhydrous ethanol is 1:35.88.

[0046] In step 1, zinc chloride and anhydrous ethanol are placed in a new reaction vessel and stirred. The mass ratio of zinc chloride to anhydrous ethanol is 1:1.92.

[0047] In step 2, the mass concentration of concentrated hydrochloric acid is 37%, and concentrated hydrochloric acid is added to adjust the pH to 1-2.

[0048] In step 2, the 3A molecular sieve is activated by placing it in a muffle furnace, setting the heating rate to 5℃ / min, heating it to 300℃, and holding it at that temperature for 4 hours to obtain activated 3A molecular sieve.

[0049] In step 3, the crude product is filtered under vacuum at a set vacuum level of -0.095 MPa for 10 minutes.

[0050] The cold ethanol washing is performed by washing three times with cold anhydrous ethanol at 0-5℃, followed by filtration for 4-6 minutes.

[0051] In step 3, recrystallization is carried out by adding anhydrous ethanol and stirring, setting the stirring speed to 300 rpm and the temperature to 78°C, and refluxing for 30 minutes.

[0052] The mass ratio of the washed crude product to anhydrous ethanol is 1:1.4-1.6.

[0053] In step 3, a polytetrafluoroethylene (PTFE) filter membrane with a pore size of 4.5 μm is used for filtration. The PTFE filter membrane is soaked in anhydrous ethanol at 60-70℃ for 5 minutes beforehand.

[0054] In step 3, the cooling crystallization is achieved by adding distilled water and stirring at 200 rpm for 5-10 minutes, cooling to 0°C at a cooling rate of 2°C / h, and then letting it stand for 7.5-8.5 hours.

[0055] In step 3, the product is washed and vacuum dried. The product is washed twice with a mixture of 0-5℃ cold ethanol and water, cooled and crystallized. After washing, it is filtered for 5 minutes.

[0056] The volume ratio of the cold ethanol to water is 1:1;

[0057] The vacuum drying process is set at a vacuum level of -0.098 MPa, a drying temperature of 40°C, and a drying time of 6 hours.

[0058] Example 2, a method for preparing m-dibutylaminophenol, characterized by comprising the following raw materials: 128.6 parts of 2-chlorophenol, 2.2 parts of 2,6-di-tert-butyl-4-methylphenol, 4.1 parts of zinc chloride, 16.1 parts of tetrabutylammonium bromide, 69.2 parts of sodium amino acid, 11.2 parts of potassium tert-butoxide, 50 parts of activated 3A molecular sieve, 228.4 parts of di-n-butylamine, and 20.2 parts of triethylamine;

[0059] The preparation of the m-dibutylaminophenol includes the following steps:

[0060] Step 1. Add 2-chlorophenol, anhydrous ethanol, and 2,6-di-tert-butyl-4-methylphenol to a reaction vessel and stir. Set the water bath temperature to 30-40℃ and the stirring speed to 500 rpm. Stir for 5-8 minutes, then stop heating and allow the reaction vessel to cool naturally to 25℃ to obtain a 2-chlorophenol solution. Add zinc chloride and anhydrous ethanol to a new reaction vessel and stir at 400 rpm for 3 minutes to obtain a zinc chloride solution.

[0061] Step 2. Activate the 3A molecular sieve in a muffle furnace, setting the heating rate to 5℃ / min, heat to 300℃, and maintain activation at this temperature for 4 hours. Cool naturally to 25℃ in a desiccator, then add it to the reaction vessel. Close the vessel lid, purge with nitrogen for 15 minutes, add liquid ammonia and stir at 200 rpm. Reduce the reaction vessel temperature to -33℃, then add sodium amide and potassium tert-butoxide in 7 portions, stirring at 150-200 rpm with 1.5-minute intervals between each addition. Add tetrabutylammonium bromide and stir at 200 rpm for 30 minutes. Using a constant pressure funnel, add 2-chlorophenol solution to the reaction vessel at a dropping rate of 5-6 mL / min. Control the reaction vessel temperature between -25℃ and -20℃, and maintain a stirring speed of 200 rpm. After the 2-chlorophenol solution was added dropwise, the temperature was increased to -15°C at a rate of 8°C / h and stirred for 1 hour. Zinc chloride solution was added to the reaction vessel using a constant pressure funnel and stirred at a dropping rate of 2 mL / min and a stirring speed of 200 rpm. Di-n-butylamine and triethylamine were added and stirred, with the stirring speed increased to 450 rpm for 75 minutes. The temperature was increased to -5°C at a rate of 8°C / h and stirred for 2.5-3 hours. The stirring speed was adjusted to 100 rpm, and the reaction vessel was allowed to naturally heat to 20-25°C and stirred for 4-6 hours. Concentrated hydrochloric acid was added dropwise to the reaction vessel using a constant pressure funnel and stirred. The water bath temperature was set to 20-25°C and the stirring speed increased to 600 rpm. When the pH reached 1-2, the addition of concentrated hydrochloric acid was stopped, and the mixture was stirred for 30 minutes to obtain the crude product.

[0062] Step 3. Filter the crude product, wash with cold ethanol, recrystallize, filter, cool and crystallize, wash the refined product and vacuum dry to obtain m-dibutylaminophenol.

[0063] In step 1, 2-chlorophenol, anhydrous ethanol and 2,6-di-tert-butyl-4-methylphenol are added to the reaction vessel and stirred. The mass ratio of 2,6-di-tert-butyl-4-methylphenol to anhydrous ethanol is 1:35.88.

[0064] In step 1, zinc chloride and anhydrous ethanol are placed in a new reaction vessel and stirred. The mass ratio of zinc chloride to anhydrous ethanol is 1:1.92.

[0065] In step 2, the mass concentration of concentrated hydrochloric acid is 37%, and concentrated hydrochloric acid is added to adjust the pH to 1-2.

[0066] In step 2, the 3A molecular sieve is activated by placing it in a muffle furnace, setting the heating rate to 5℃ / min, heating it to 300℃, and holding it at that temperature for 4 hours to obtain activated 3A molecular sieve.

[0067] In step 3, the crude product is filtered under vacuum at a set vacuum level of -0.095 MPa for 10 minutes.

[0068] The cold ethanol washing is performed by washing three times with cold anhydrous ethanol at 0-5℃, followed by filtration for 4-6 minutes.

[0069] In step 3, recrystallization is carried out by adding anhydrous ethanol and stirring, setting the stirring speed to 300 rpm and the temperature to 78°C, and refluxing for 30 minutes.

[0070] The mass ratio of the washed crude product to anhydrous ethanol is 1:1.4-1.6.

[0071] In step 3, a polytetrafluoroethylene (PTFE) filter membrane with a pore size of 4.5 μm is used for filtration. The PTFE filter membrane is soaked in anhydrous ethanol at 60-70℃ for 5 minutes beforehand.

[0072] In step 3, the cooling crystallization is achieved by adding distilled water and stirring at 200 rpm for 5-10 minutes, cooling to 0°C at a cooling rate of 2°C / h, and then letting it stand for 7.5-8.5 hours.

[0073] In step 3, the product is washed and vacuum dried. The product is washed twice with a mixture of 0-5℃ cold ethanol and water, cooled and crystallized. After washing, it is filtered for 5 minutes.

[0074] The volume ratio of the cold ethanol to water is 1:1;

[0075] The vacuum drying process is set at a vacuum level of -0.098 MPa, a drying temperature of 40°C, and a drying time of 6 hours.

[0076] Example 3, a method for preparing m-dibutylaminophenol, characterized by comprising the following raw materials: 129.9 parts 2-chlorophenol, 2.4 parts 2,6-di-tert-butyl-4-methylphenol, 4.5 parts zinc chloride, 17.7 parts tetrabutylammonium bromide, 71.1 parts sodium amino acid, 12.3 parts potassium tert-butoxide, 55 parts activated 3A molecular sieve, 239.8 parts di-n-butylamine, and 22.2 parts triethylamine;

[0077] The preparation of the m-dibutylaminophenol includes the following steps:

[0078] Step 1. Add 2-chlorophenol, anhydrous ethanol, and 2,6-di-tert-butyl-4-methylphenol to a reaction vessel and stir. Set the water bath temperature to 30-40℃ and the stirring speed to 500 rpm. Stir for 5-8 minutes, then stop heating and allow the reaction vessel to cool naturally to 25℃ to obtain a 2-chlorophenol solution. Add zinc chloride and anhydrous ethanol to a new reaction vessel and stir at 400 rpm for 3 minutes to obtain a zinc chloride solution.

[0079] Step 2. Cool the activated 3A molecular sieve to 25°C in a desiccator, add it to the reaction vessel, close the lid, and purge with nitrogen for 15 minutes. Add liquid ammonia and stir at 200 rpm. Lower the reaction vessel temperature to -33°C. Add sodium amide and potassium tert-butoxide in 7 portions, stirring at 150-200 rpm, with 1.5-minute intervals between each addition. Add tetrabutylammonium bromide and stir at 200 rpm for 30 minutes. Using a constant pressure funnel, add 2-chlorophenol solution to the reaction vessel while stirring at a dropping rate of 5-6 mL / min. Maintain the reaction vessel temperature between -25°C and -20°C at 200 rpm. After the 2-chlorophenol solution has been completely added... The temperature was increased to -15℃ at a rate of 8℃ / h, and stirred for 1 hour. Zinc chloride solution was added to the reaction vessel using a constant pressure funnel and stirred at a dropping rate of 2mL / min and a stirring speed of 200rpm. Di-n-butylamine and triethylamine were added and stirred, and the stirring speed was increased to 450rpm for 75 minutes. The temperature was increased to -5℃ at a rate of 8℃ / h and stirred for 2.5-3 hours. The stirring speed was adjusted to 100rpm. The reaction vessel was allowed to heat up naturally to 20-25℃ and stirred for 4-6 hours. Concentrated hydrochloric acid was added dropwise to the reaction vessel using a constant pressure funnel and stirred. The water bath temperature was set to 20-25℃ and the stirring speed was increased to 600rpm. The addition of concentrated hydrochloric acid was stopped and the mixture was stirred for 30 minutes to obtain the crude product.

[0080] Step 3. Filter the crude product, wash with cold ethanol, recrystallize, filter, cool and crystallize, wash the refined product and vacuum dry to obtain m-dibutylaminophenol.

[0081] In step 1, 2-chlorophenol, anhydrous ethanol and 2,6-di-tert-butyl-4-methylphenol are added to the reaction vessel and stirred. The mass ratio of 2,6-di-tert-butyl-4-methylphenol to anhydrous ethanol is 1:35.88.

[0082] In step 1, zinc chloride and anhydrous ethanol are placed in a new reaction vessel and stirred. The mass ratio of zinc chloride to anhydrous ethanol is 1:1.92.

[0083] In step 2, the mass concentration of concentrated hydrochloric acid is 37%, and concentrated hydrochloric acid is added to adjust the pH to 1-2.

[0084] In step 2, the 3A molecular sieve is activated by placing it in a muffle furnace, setting the heating rate to 5℃ / min, heating it to 300℃, and holding it at that temperature for 4 hours to obtain activated 3A molecular sieve.

[0085] In step 3, the crude product is filtered under vacuum at a set vacuum level of -0.095 MPa for 10 minutes.

[0086] The cold ethanol washing is performed by washing three times with cold anhydrous ethanol at 0-5℃, followed by filtration for 4-6 minutes.

[0087] In step 3, recrystallization is carried out by adding anhydrous ethanol and stirring, setting the stirring speed to 300 rpm and the temperature to 78°C, and refluxing for 30 minutes.

[0088] The mass ratio of the washed crude product to anhydrous ethanol is 1:1.4-1.6.

[0089] In step 3, a polytetrafluoroethylene (PTFE) filter membrane with a pore size of 4.5 μm is used for filtration. The PTFE filter membrane is soaked in anhydrous ethanol at 60-70℃ for 5 minutes beforehand.

[0090] In step 3, the cooling crystallization is achieved by adding distilled water and stirring at 200 rpm for 5-10 minutes, cooling to 0°C at a cooling rate of 2°C / h, and then letting it stand for 7.5-8.5 hours.

[0091] In step 3, the product is washed and vacuum dried. The product is washed twice with a mixture of 0-5℃ cold ethanol and water, cooled and crystallized. After washing, it is filtered for 5 minutes.

[0092] The volume ratio of the cold ethanol to water is 1:1;

[0093] The vacuum drying process is set at a vacuum level of -0.098 MPa, a drying temperature of 40°C, and a drying time of 6 hours.

[0094] Comparative Example 1: The difference between this comparative example and Example 1 is that:

[0095] This comparative example does not contain 2,6-di-tert-butyl-4-methylphenol.

[0096] Comparative Example 2: The difference between this comparative example and Example 1 is that:

[0097] This comparative example does not contain triethylamine.

[0098] Comparative Example 3 differs from Example 1 in that:

[0099] This comparative example does not contain activated 3A molecular sieve.

[0100] Performance testing: The m-dibutylaminophenol prepared in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 were tested.

[0101] Performance testing: The relevant properties of the samples prepared by the method for preparing m-dibutylaminophenol provided in Examples 1-3 and Comparative Examples 1-3 were tested respectively, and the test data are recorded in Table 1 below:

[0102] Appearance Product purity (%) Moisture content (%) Example 1 No yellowing 99.7 0.47 Example 2 No yellowing 99.8 0.46 Example 3 No yellowing 99.6 0.44 Comparative Example 1 yellowish 98.2 0.53 Comparative Example 2 No yellowing 96.4 0.55 Comparative Example 3 No yellowing 98.4 0.68

[0103] Based on the above data, the following conclusions can be drawn:

[0104] (1) The appearance of Examples 1-3 is far superior to that of Comparative Examples 1-3. The key point is that the examples can preferentially react with trace amounts of oxygen in the system by adding 2,6-di-tert-butyl-4-methylphenol, which protects the highly active benzylene intermediate from being oxidized to generate quinone impurities, thereby reducing the content of such impurities and changing the appearance of the product from slightly yellowish in the traditional process to pure white.

[0105] (2) The purity of the products of Examples 1-3 is far superior to that of Comparative Examples 1-3. The key point is that the examples added triethylamine, whose three ethyl groups provide significant steric hindrance, which can occupy some of the active sites in the reaction system, preventing di-n-butylamine from performing secondary alkylation on the target product, thus reducing the polyalkylation impurities.

[0106] (3) The moisture content of Examples 1-3 is far superior to that of Comparative Examples 1-3. The key point is that the examples add activated 3A molecular sieves, whose pore size only allows water molecules to pass through, which can adsorb trace amounts of water in the reaction system to below 0.01%, thus inhibiting the generation of hydrolytic impurities from the source.

[0107] Through the above demonstrations, the present invention is significantly superior to the control group in terms of appearance, product purity and moisture content, thus verifying the advanced nature and rationality of the preparation process.

[0108] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0109] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing m-dibutylaminophenol, characterized in that, The raw materials include the following components: 127.3-129.9 parts 2-chlorophenol, 2-2.4 parts 2,6-di-tert-butyl-4-methylphenol, 3.7-4.5 parts zinc chloride, 14.5-17.7 parts tetrabutylammonium bromide, 67.3-71.1 parts sodium amide, 10.1-12.3 parts potassium tert-butoxide, 45-55 parts activated 3A molecular sieve, 217-239.8 parts di-n-butylamine, and 18.2-22.2 parts triethylamine; The preparation of the m-dibutylaminophenol includes the following steps: Step 1. Add 2-chlorophenol, anhydrous ethanol and 2,6-di-tert-butyl-4-methylphenol to a reaction vessel and stir to obtain a 2-chlorophenol solution; add zinc chloride and anhydrous ethanol to a new reaction vessel and stir to obtain a zinc chloride solution; Step 2. Place the activated 3A molecular sieve in a desiccator and cool it to 25°C. Add it to the reaction vessel, close the lid, introduce nitrogen gas, add liquid ammonia and stir. When the temperature of the reaction vessel drops to -33°C, add sodium amino acid and potassium tert-butoxide in 7 batches, stirring each time with an interval of 1.5 minutes. Add tetrabutylammonium bromide and stir. Use a constant pressure funnel to add 2-chlorophenol solution to the reaction vessel and stir. Control the temperature at -15°C at a heating rate of 8°C / h and stir for 1 hour. Use a constant pressure funnel to add zinc chloride solution to the reaction vessel and stir. Add di-n-butylamine and triethylamine and stir. Control the temperature at -5°C at a heating rate of 8°C / h and stir. Stop heating and allow the reaction vessel to naturally heat up to 20-25°C. Stir. Use a constant pressure funnel to add concentrated hydrochloric acid to the reaction vessel and stir. Stop adding concentrated hydrochloric acid and obtain the crude product. Step 3. Filter the crude product, wash with cold ethanol, recrystallize, filter, cool and crystallize, wash the refined product and vacuum dry to obtain m-dibutylaminophenol.

2. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 1, 2-chlorophenol, anhydrous ethanol, and 2,6-di-tert-butyl-4-methylphenol are added to the reaction vessel and stirred. The mass ratio of 2,6-di-tert-butyl-4-methylphenol to anhydrous ethanol is 1:35.

88.

3. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 1, zinc chloride and anhydrous ethanol are placed in a new reaction vessel and stirred, with a mass ratio of zinc chloride to anhydrous ethanol of 1:1.

92.

4. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 2, the mass concentration of concentrated hydrochloric acid is 37%, and concentrated hydrochloric acid is added to adjust the pH to 1-2.

5. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 2, the 3A molecular sieve is activated by placing it in a muffle furnace, setting the heating rate to 5°C / min, heating it to 300°C, and holding it at that temperature for 4 hours to obtain activated 3A molecular sieve.

6. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 3, the crude product is filtered under vacuum at a set vacuum level of -0.095 MPa for 10 minutes. The cold ethanol washing is performed by washing three times with cold anhydrous ethanol at 0-5℃, followed by filtration for 4-6 minutes.

7. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 3, recrystallization is performed by adding anhydrous ethanol and stirring, setting the stirring speed to 300 rpm and the temperature to 78°C, and then refluxing and stirring for 30 minutes. The mass ratio of the washed crude product to anhydrous ethanol is 1:1.4-1.

6.

8. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 3, a polytetrafluoroethylene (PTFE) filter membrane with a pore size of 4.5 μm is used for filtration. The PTFE filter membrane is soaked in anhydrous ethanol at 60-70°C for 5 minutes beforehand.

9. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 3, the cooling crystallization is achieved by adding distilled water and stirring at 200 rpm for 5-10 minutes, cooling to 0°C at a cooling rate of 2°C / h, and then letting it stand for 7.5-8.5 hours.

10. The method for preparing m-dibutylaminophenol according to claim 1, characterized in that, In step 3, the product is washed and vacuum dried. The product is washed twice with a mixture of 0-5℃ cold ethanol and water, cooled and crystallized, and then filtered for 5 minutes after washing. The volume ratio of the cold ethanol to water is 1:1; The vacuum drying process is set at a vacuum level of -0.098 MPa, a drying temperature of 40°C, and a drying time of 6 hours.