JPS6133819B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying α-amino-ε-caprolactam.

α-Amino-ε-caprolactam is known to be a useful raw material for the synthesis of the essential amino acid lysine and other compounds;
- When caprolactam is used as a raw material for lysine synthesis, particularly highly purified α-amino-ε-caprolactam is required. Based on this request, the inventors of the present invention conducted extensive studies to determine whether there is a method for obtaining extremely high purity α-amino-ε-caprolactam, and found that During this process, a unique behavior not seen in other solvents occurs, in which one molecule of α-amino-ε-caprolactam and one molecule of chloroform form an isolable crystalline adduct, and chloroform is further separated and removed from the adduct. The present inventors have discovered that it is easy to purify α-amino-ε-caprolactam, and have utilized this fact to accomplish the present invention, which purifies α-amino-ε-caprolactam to a high degree of purity.

Therefore, the object of the present invention is to obtain crude α-amino-ε-
Effectively removes impurities in caprolactam. The object of the present invention is to establish a new purification method capable of obtaining highly pure α-amino-ε-caprolactam.

The purpose was to isolate the crystalline adduct of α-amino-ε-caprolactam and chloroform by contacting the crude α-amino-ε-caprolactam with chloroform and then to separate it by crystallization, and then to isolate the crystalline adduct of α-amino-ε-caprolactam and chloroform from the adduct. This is achieved by separating and removing chloroform.

The method of the present invention will be specifically described below.

Crude α-amino-ε- used in the present invention
Caprolactam may be obtained by any method. Moreover, it may be obtained by any process. Therefore, a reaction mixture obtained by Beckman rearrangement of 2-aminocyclohexanone oxime, a reaction mixture obtained by neutralizing it, or α-amino-ε-caprolactam obtained by semi-purifying them, etc. can be used. . Chloroform is added to this and brought into contact with α-amino-ε-caprolactam. During this contact, it is necessary that the α-amino-ε-caprolactam be present in free form.

Therefore, when using the reaction mixture obtained by Beckmann rearrangement as crude α-amino-ε-caprolactam, it is necessary to neutralize it with an alkali such as ammonia in order to convert it into a free form of α-amino-ε-caprolactam. be. The amount of chloroform in this case can be arbitrarily determined depending on the types and component ratios of the components contained in the composition, as well as the operating temperature.
In the step of separating the adduct of amino-ε-caprolactam and chloroform out of the system, it is preferable to use the adduct in an amount of at least 1 to 3 times the molar amount of α-amino-ε-caprolactam in the composition.

The temperature for producing the adduct of α-amino-ε-caprolactam and chloroform from the composition ranges from 0° C. to the boiling point of chloroform. Furthermore, when separating the formed crystalline adduct out of the system, it is necessary to operate at a temperature of 30° C. or lower due to the physical properties of the adduct.

When producing an adduct, a contact time of 15 minutes or more between α-amino-ε-caprolactam and chloroform in the above temperature range is sufficient.

Next, the thus obtained crystalline α-amino-ε
−Adduct of caprolactam and chloroform α−
Separate into amino-ε-caprolactam and chloroform. In this case, the separation method is not particularly limited; for example, a method in which the adduct is placed in a high vacuum system at room temperature to volatilize chloroform, or a method in which α-amino-ε-caprolactam has low solubility and chloroform A method for eluting and removing chloroform by contacting it with a solvent that easily dissolves chloroform, and a method for eluting and removing chloroform by contacting it with a solvent that easily dissolves α-amino-ε-caprolactam. Many methods can be applied, such as a method of dissolving and separating .alpha.-amino-.epsilon.-caprolactam, and in any case, the operation can be performed at room temperature depending on the properties of the adduct, and conditions can be selected that will not impure α-amino-ε-caprolactam.

In this way, in the method of the present invention, an adduct crystal of α-amino-ε-caprolactam and chloroform is selectively formed from a system coexisting with impurities, and when the adduct is separated, the impurity remains dissolved in chloroform. α-amino-ε-
Caprolactam is highly purified, and α-amino-ε-caprolactam is completely purified in the step of removing chloroform from the adduct.

The effects of the present invention will be demonstrated below using Examples.

Example 1 α-Amino-ε-caprolactam 12.8g (0.10g
42.0 g of a Beckman rearrangement reaction product of 2-aminocyclohexanone oxime containing
35.7 g (0.3 mol) was placed in a 200 ml three-necked glass flask equipped with a stirrer, reflux condenser, and thermometer.The inner solution was heated in a hot water bath to bring the temperature to 40
After stirring for 15 minutes while maintaining the temperature at °C, the entire volume of the internal solution was transferred to a separating funnel, and the chloroform layer was separated.

Chloroform was evaporated from the separated chloroform layer so that 20.0 g of chloroform remained in the system, and the mixture was again transferred to the three-necked flask and slowly cooled from 40° C. to 5° C. while stirring to precipitate crystals.
19.4 g of crystals were separated and collected from the entire solution using a centrifuge.

This crystal has a melting point of 31°C, and when analyzed by gas chromatography, it is found to be 51.6% by weight of α-amino-ε-caprolactam and 48.4% by weight of chloroform, α-amino-ε-caprolactam:chloroform (molar ratio) = 1: It was 1.01.

Chloroform was evaporated from 15.0 g of the collected crystals at 25° C. under a reduced pressure of 10 mmHg, yielding 7.7 g of white crystals. The α-amino-ε-caprolactam analysis value of this crystal by gas chromatography was 99.7% by weight.

Example 2 α-amino-ε-caprolactam 12.8g (0.1
The pH of the Beckman rearrangement product of 2-aminocyclohexanone oxime containing (mol) was adjusted to 9.0 using the same procedure as in Example 1, and 35.7 g of chloroform
(0.3 mol) was transferred to the three-necked flask of Example 1,
After heating the internal organs to 40°C and stirring for 15 minutes, the chloroform layer was separated. A portion of this chloroform layer was placed in a 100 ml glass four-necked flask equipped with a stirrer, a thermometer, a dropping funnel, and a condenser for chloroform distillation, and the liquid temperature was maintained at 10°C in a cold water bath while stirring the contents. . While dropping the remaining chloroform layer from the dropping funnel, the inside was reduced in pressure through a condenser, and the chloroform was distilled off so that the composition of the internal solution was 1.8 moles of chloroform to 1 mole of α-amino-ε-caprolactam. Crystals precipitated. The total amount of crystals was taken out and separated using a centrifuge, and the amount of crystals was 19.2 g. The amount of α-amino-ε-caprolactam analyzed by gas chromatography was
51.6% by weight, and 48.4% by weight of chloroform.

15.0g of the collected crystals was added to 50% of cyclohexane.
After stirring well, the crystals and the solvent were separated to obtain 7.7 g of crystals. Analysis of the crystals by gas chromatography revealed that the purity of α-amino-ε-caprolactam was 99.6% by weight.

Example 3 Contains organic by-product impurities related to the Beckmann rearrangement reaction of 2-aminocyclohexanone oxime,
16.4 g (0.10 mol) of alkaline crude α-amino-ε-caprolactam with a purity of 78% by weight and 17.8 g (0.15 mol) of chloroform were placed in the three-necked flask of Example 1, and heated in a cold water bath. When stirred for 30 minutes while maintaining the temperature at 10°C, crystals precipitated. The total amount was taken out and separated using a centrifuge. 16.7 g of crystals were analyzed by gas chromatography and found to be 51.5% by weight of α-amino-ε-caprolactam and 48.5% by weight of chloroform.

When 15 ml of water is added to 15 g of the separated crystals, 2
It was separated into layers. The water layer was separated and the water was removed by drying under reduced pressure to obtain 7.7 g of crystals. When this crystal was analyzed by gas chromatography, α-amino-ε
- Caprolactam was 99.9% by weight.

Example 4 Crude α-amino-ε- synthesized by Beckman rearrangement reaction of 2-aminocyclohexanone oxime
Purity 97.8 purified by vacuum distillation of caprolactam
% α-amino-ε-caprolactam 13.1 g (α
-amino-ε-caprolactam (0.10 mol) and chloroform (15.5 g (0.13 mol)) were placed in the three-necked flask of Example 1, a small amount of ammonia gas was blown into the flask, and the flask was stirred at room temperature for 30 minutes. The entire amount was transferred to a beaker and cooled to 5°C in an ice water bath to precipitate crystals. 15.0g of the collected crystals were heated to 10mm at 25°C.
When chloroform is evaporated under reduced pressure of Hg, 7.7g
White crystals were obtained. This purified α-amino-ε
- The purity of caprolactam was 99.7%.

Claims (1)

[Claims] 1. After bringing crude α-amino-ε-caprolactam into contact with chloroform, a crystalline adduct of α-amino-ε-caprolactam and chloroform is isolated by crystallization separation, and then chloroform is removed from the adduct. A method for purifying α-amino-ε-caprolactam, which comprises separating and removing it.