CN115947660A - Preparation method of high-purity dimethyl cyclohexylamine - Google Patents

Abstract

The invention relates to the technical field of organic synthesis, and discloses a preparation method of high-purity dimethyl cyclohexylamine, which comprises the following steps: adding a catalyst and cyclohexanone into a reactor, replacing the reactants for three times by nitrogen and hydrogen, introducing dimethylamine with a technical amount, carrying out a hydrogen pressure reaction, adding a small amount of formaldehyde after hydrogen is not taken basically, and continuing the reaction until the raw material is less than 0.05 percent and the N-methylcyclohexylamine is less than 0.02 percent; after the product is qualified, filtering to remove the catalyst, and removing ammonia and water; then rectifying, adding a small amount of phosphoric acid before rectifying, fully refluxing for 2-3h, sampling and analyzing, wherein the cyclohexanol content is less than 0.02%, and then rectifying normally to obtain the high-content N, N-dimethylcyclohexylamine with the content of more than 99.9%. According to the invention, a small amount of auxiliary agent is added to the existing production device of N, N-dimethylcyclohexylamine, so that high-purity N, N-dimethylcyclohexylamine meeting the requirements of customers is produced, and the method is simple to operate, and meets the use requirements without increasing investment.

Description

A kind of preparation method of high-purity dimethylcyclohexylamine

technical field

The invention relates to the technical field of organic synthesis, in particular to a preparation method of high-purity dimethylcyclohexylamine.

Background technique

N, N-dimethylcyclohexylamine, English: N, N-dimethylcyclohexylamine, molecular formula: C8H17N, CAS number: 98-94-2;

N,N-Dimethylcyclohexylamine is mainly used in the polyurethane catalyst industry. It is a low-viscosity, moderately active amine catalyst that can catalyze both gelation and foaming. The gel reaction provides a relatively balanced catalytic performance and is mainly used as a gel catalyst. At present, it is widely used in refrigerator materials and board materials;

With the development of the polyurethane industry and the extension of the field, especially the promotion and application in the automotive field, customers have higher and higher requirements for the quality of polyurethane catalysts. With the development of the polyurethane industry, 99.9% of the products are required to pass normal distillation. The two impurities of N-methylcyclohexylamine and cyclohexanol cannot be removed, and the demand cannot be met.

Contents of the invention

The object of the present invention is to provide a kind of preparation method of high-purity dimethylcyclohexylamine, to solve existing in the prior art " cyclohexanone and dimethylamine hydrogenation prepare N, N-dimethylcyclohexylamine, Generally all contain the N-methylcyclohexylamine (boiling point 149 ℃) of about 0.2% in the crude product, the cyclohexanol (boiling point 160 ℃) of about 0.2%, N, N-dimethylcyclohexylamine boiling point 160 ℃, cannot The problem of obtaining >99.9% high-purity N,N-dimethylcyclohexylamine is removed by conventional rectification.

To achieve the above object, the present invention provides following technical scheme: a kind of preparation method of high-purity dimethylcyclohexylamine, is characterized in that, comprises the following steps:

Step (1): Add the catalyst and cyclohexanone into the reactor, replace with nitrogen and hydrogen three times each, pass in a technological amount of dimethylamine, raise the temperature to 70-100°C, start to pass in hydrogen, and control the pressure to 3.0-3.5 MPa, the reaction temperature is 140-150°C;

Step (2): After hydrogen consumption slows down, pump formaldehyde into water, maintain at 3.0-3.5MPa, react at a temperature of 140-150°C, and take samples until no hydrogen is consumed. Raw materials cyclohexanone <0.05%, N-methylcyclohexyl Amine < 0.02% is qualified, otherwise continue to keep warm until qualified;

Step (3): After passing the test, filter the catalyst, heat the mother liquor to remove excess dimethylamine, divide the generated water, and then add phosphorus-containing acid;

Step (4): The system is refluxed under normal pressure for 2-3 hours, and then sampling analysis shows that the cyclohexanol <0.02% is qualified, and the rectification is continued to obtain high-purity N,N-dimethylcyclohexylamine with a content >99.9%.

Preferably, the mass of said water formaldehyde accounts for 0.1-1% of the total weight of cyclohexanone and dimethylamine.

Preferably, the catalyst is one or a mixture of palladium carbon, platinum carbon, palladium aluminum catalyst, palladium calcium carbonate catalyst.

Preferably, the phosphorus-containing acid is one or a mixture of phosphoric acid, phosphorous acid and metaphosphoric acid.

Preferably, the mass ratio of the phosphorus-containing acid to the material after water separation is 0.01-0.1%.

Preferably, using existing distillation equipment, after deamination and water separation, acid is added to reflux at normal pressure for 2-3 hours at a temperature of 155-165°C.

A kind of preparation method of high-purity dimethylcyclohexylamine that the present invention proposes, beneficial effect is:

1. The present invention converts N-methylcyclohexylamine into N,N-dimethylcyclohexylamine by adding water formaldehyde, and in addition, by adding a small amount of phosphorus-containing acid, reflux can dehydrate cyclohexanol molecules Generate high-boiling dicyclohexyl ether (boiling point 242.5°C), which can be removed by rectification;

2. The present invention adds a small amount of additives to the existing production equipment of N,N-dimethylcyclohexylamine to produce high-purity N,N-dimethylcyclohexylamine that meets customer needs, and has the advantages of simple operation , without increasing investment, to meet the needs of use.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides a technical scheme: a preparation method of high-purity dimethylcyclohexylamine, the reaction formula of which is:

Example 1:

S1. Add 4Kg palladium carbon and 1600Kg cyclohexanone into the reactor, replace with nitrogen and hydrogen at least three times, feed 955kg of dimethylamine, start stirring, raise the temperature to 80°C, feed hydrogen, control the pressure at 3.4-3.5MPa, The temperature is 145-150°C, after hydrogen consumption slows down, pump in 5kg of 37% water formaldehyde, continue the heat preservation and pressure reaction until basically no hydrogen consumption, sampling analysis, raw material cyclohexanone: 0.032%, N-methylcyclohexylamine: 0.012%. The material is cooled to 60°C, filtered, and the mother liquor is sent to the water separator for deamination to remove excess dimethylamine, and then the water in the lower layer is separated;

S2. Add 0.4kg of phosphoric acid to the upper material, raise the temperature to about 160°C, keep full reflux for 2 hours, take a sample and analyze, cyclohexanol: 0.012%, and then rectify to obtain 2050kg of 99.92% N,N-dimethylcyclohexylamine , yield 98.9%.

Example 2:

S1. Add 6Kg of palladium calcium carbonate and 1600Kg of cyclohexanone into the reactor, replace with nitrogen and hydrogen for at least three times, pass in 1000kg of dimethylamine, start stirring, raise the temperature to 80°C, pass in hydrogen, and control the pressure at 3.4-3.5MPa , temperature 145-150°C, after hydrogen consumption slows down, pump 3kg of 37% water formaldehyde, continue heat preservation and pressure reaction until basically no hydrogen consumption, sampling analysis, raw material cyclohexanone: 0.023%, N-methylcyclohexylamine : 0.015%. The material is cooled to 60°C, filtered, and the mother liquor is sent to the water separator for deamination to remove excess dimethylamine, and then the water in the lower layer is separated;

S2. Add 0.2kg of phosphorous acid to the upper layer material, raise the temperature to about 160°C, keep total reflux for 2 hours, take a sample and analyze, cyclohexanol: 0.011%, and then rectify to obtain 2040kg of 99.94% N,N-dimethylcyclohexyl Amine, yield 98.4%.

Example 3:

S1. Add 6Kg platinum carbon and 1600Kg cyclohexanone into the reactor, replace with nitrogen and hydrogen at least three times, feed 920kg of dimethylamine, start stirring, raise the temperature to 80°C, feed hydrogen, control the pressure at 3.0-3.1MPa, The temperature is 130-140°C, after hydrogen consumption slows down, pump in 10kg of 37% water formaldehyde, keep warm and pressurize to react until hydrogen consumption is almost gone, sampling analysis, raw material cyclohexanone: 0.03%, N-methylcyclohexylamine: 0.01 %. The material is cooled to 60°C, filtered, and the mother liquor is sent to the deammonization water separation tank to remove excess dimethylamine, and then the water in the lower layer is separated;

S2. Add 0.3kg of metaphosphoric acid to the upper layer material, raise the temperature to about 160°C, keep total reflux for 2 hours, take a sample and analyze, cyclohexanol: 0.014%, and then rectify to obtain 2052kg of 99.92% N,N-dimethylcyclohexyl Amine, yield 99%.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications and substitutions can be made to these embodiments without departing from the principle and spirit of the present invention. and modifications, the scope of the invention is defined by the appended claims and their equivalents.

Claims (6)

1. a preparation method of high-purity dimethylcyclohexylamine, is characterized in that, comprises the following steps: Step (1): Add the catalyst and cyclohexanone into the reactor, replace with nitrogen and hydrogen three times each, pass in a technological amount of dimethylamine, raise the temperature to 70-100°C, start to pass in hydrogen, and control the pressure to 3.0-3.5 MPa, the reaction temperature is 140-150°C; Step (2): After hydrogen consumption slows down, pump formaldehyde into water, maintain at 3.0-3.5MPa, react at a temperature of 140-150°C, and take samples until no hydrogen is consumed. Raw materials cyclohexanone <0.05%, N-methylcyclohexyl Amine < 0.02% is qualified, otherwise continue to keep warm until qualified; Step (3): After passing the test, filter the catalyst, heat the mother liquor to remove excess dimethylamine, divide the generated water, and then add phosphorus-containing acid; Step (4): The system is refluxed under normal pressure for 2-3 hours, and then sampling analysis shows that the cyclohexanol <0.02% is qualified, and the rectification is continued to obtain high-purity N,N-dimethylcyclohexylamine with a content >99.9%. 2. the preparation method of a kind of high-purity dimethylcyclohexylamine according to claim 1 is characterized in that: described water formaldehyde quality accounts for cyclohexanone and dimethylamine gross weight and is 0.1-1%. 3. the preparation method of a kind of high-purity dimethylcyclohexylamine according to claim 1 is characterized in that: described catalyzer is one or in palladium carbon, platinum carbon, palladium aluminum catalyst, palladium calcium carbonate catalyst A mixture of several. 4. the preparation method of a kind of high-purity dimethylcyclohexylamine according to claim 1 is characterized in that: the acid containing phosphorus is phosphoric acid, phosphorous acid, one or both mixtures in metaphosphoric acid . 5. The preparation method of a kind of high-purity dimethylcyclohexylamine according to claim 1, characterized in that: the mass ratio of the phosphorus-containing acid to the material after water separation is 0.01-0.1%. 6. the preparation method of a kind of high-purity dimethylcyclohexylamine according to claim 1, is characterized in that: utilize existing distillation unit, after deamination divides water, add acid normal pressure reflux 2-3h, temperature 155 ℃ -165°C.