JPS60199873A - Recovery of epsilon-caprolactam - Google Patents

Abstract

PURPOSE:The aqueous solution of epsilon-caprolactam which is formed as a by- product, when 11-cyanoundecanoic acid is produced, is concentrated, the oily layer is extracted, then distilled, combined with sulfuric acid, neutralized with aqueous ammonia, extracted with an organic solvent and distilled to give the titled compound of high purity. CONSTITUTION:In the recovery of high-purity epsilon-caprolactam from the epsilon-caprolactam aqueous solution which is obtained as a by-product, on the production of 11-cyanoundecanoic acid by pyrolysis of 1,1-peroxydicyclohexylamine, the aqueous solution is concentrated to separate into the caprolactam oil phase and aqueous ammonium sulfate phase and the epsilon-caprolactam oil phase is extracted with an organic solvent. Then, the extract is fractionated into the solvent and crude epsilon-caprolactam, then the crude caprolactam is combined with fuming sulfuric acid and they are kept at 90-150 deg.C. The mixture is neutralized with aqueous ammonia, extracted with an organic solvent, finally the extract is distilled to give epsilon-caprolactam of high purity. USE:It can be used as a starting substance for nylon.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for producing 12-aminododecanoic acid (hereinafter referred to as ADA), which is a 12-nylon monomer, comprising:
1.1-peroxydicyclohexylamine (hereinafter referred to as PX
Thermal decomposition of 11-cyanoundecanoic acid (referred to as A) produces 11-cyanoundecanoic acid (
The present invention relates to a method for recovering high-purity ε-caprolactam from an aqueous ε-caprolactam solution produced as a by-product during the production of CUA (hereinafter referred to as CUA).

A method has been proposed for separating CUA, cyclohexanone, and ε-caprolactam from a CUA melt produced by thermal decomposition of PXA (see Japanese Patent Publication No. 57-25029). However, the ε-caprolactam obtained by this method is a dilute solution of several wt% ε-caprolactam, and in addition to inorganic substances such as ammonium sulfate, it has 5 to 12 carbon atoms produced during thermal decomposition.
It contains many types of impurities that are different from conventional methods for producing chain and cyclic lactams, such as amides and carboxylic acids. For this reason, it has hitherto been difficult to efficiently recover high-purity ε-cabrolactam that can be used as a raw material for nylon for textiles from this dilute solution of ε-cabrolactam.

As a result of further investigation, the inventor found that this ε-turn 7
We were able to find a method for recovering high-yield and highly pure ε-Kab L+lactam from an aqueous lactam solution.

That is, the present invention provides C1,1Δ by thermal decomposition of PXA.
Method G for recovering high-purity ε-caprolactam from an aqueous ε-caprolactam solution produced as a by-product during the production of ε-caprolactam. In the second step, the ε-caprolactam Urawa is extracted with an organic solvent, and in the 31st culm, the extract is distilled to distill off the solvent and crude ε-caprolactam. In the fourth step, the crude ε-caprolactam is treated with sulfuric acid. Alternatively, add fuming sulfuric acid so that the acid concentration in terms of sulfuric acid in the mixed solution is 50 to 55 wt%, maintain the temperature at 90 to 150°C, neutralize with ammonium water in the fifth stage, and then In the 7th step, the extract is extracted with an organic solvent, and in the 7th step, the extract is distilled to obtain high-purity ε-
The present invention relates to a method for recovering ε-caprolactam, which is characterized by distilling Kabji2-lactam.

The ε-caprolactam used in the method of the present invention is l]χA
obtained along with the main product CUΔ in the thermal decomposition of
For every kg of PXAI, 0.10 to 0.20 kg is produced as a by-product.

This by-product ε-caprolactam is obtained as an aqueous solution of several wt% ε-caprolactam, and in addition to ammonium sulfate, it contains chain and cyclic acids such as amides and carboxylic acids centered on carbon i8 to 12 produced during thermal decomposition. Contains many types of impurities that are different from conventional manufacturing methods.

Next, each step of the method of the present invention will be explained.

(First step) In the concentration of ε-caprolactam aqueous solution, ε is added to the oil phase.
- In order to improve the yield of caprolactam, the concentration of ammonium sulfate in the aqueous phase is 20-4Qwt%, preferably 30-40wt%.
Adjust the concentration so that it is %. At this time, a portion of the separated aqueous phase may be recycled to facilitate concentration.

Furthermore, ammonium sulfate can be recovered from the extracted aqueous phase by crystallization.

(Second step) Impurities are removed as an extraction residue by extracting the ε-caprolactam oil phase with an organic solvent such as toluene or Hensen. At this time, if the pH of the oil phase is adjusted to 7 or higher using a base such as ammonia, the extraction efficiency will be improved.

(Third step) The ε-caprolactam extract is distilled to recover the solvent and crude ε-caprolactam is distilled off, and high-boiling impurities are removed as distillation residue.

(Fourth step) This crude ε-caprolactam has a concentration of 50 to 55 wt% in terms of sulfuric acid in the mixed liquid, preferably 55 to [i Q w
Add sulfuric acid or fuming sulfuric acid to make 9 t%.
The temperature is maintained at 0 to 150'C1, preferably 120 to 14θC, to decompose impurities. If the concentration in terms of sulfuric acid is 5 Qwt% or less, the decomposition of impurities will be insufficient. True: 55wt%
Above this, decomposition of ε-caprolactam occurs. When the decomposition temperature is 90°C or less -C, the decomposition of impurities is insufficient and the purification effect is poor. Moreover, at temperatures above 150°C, the ε-caprolactam solution is lost and the yield decreases.

(Fifth step) Ammonium water is added to this acidic solution to neutralize it. Ammonium water concentration is 10
~14 wt% is preferred.

(Sixth step) This neutralized solution is extracted with an organic solvent such as Hensen or toluene, and decomposed impurities are removed together with ammonium sulfate water. Ammonium sulfate is also recovered from this ammonium sulfate solution by crystallization.

(Step 7) This extract is distilled to remove the solvent and to obtain high-purity ε
- Distilling caprolactam. The obtained high-purity ε-caprolactam has a permanganate value of 21,600 seconds or more,
Transmittance of 10wt% aqueous solution at 290nm is 95%
That's all.

In addition, permanganate value is pt! of 1g of sample. 7.0
The solution was dissolved in 100 ml of distilled water adjusted to 20° C., and a 1/100 normal permanganic acid solution was added thereto, and the number of seconds required for the solution to become the same color as the comparison solution was measured.

Comparative liquids are 0.3 g of cobalt chloride hexahydrate and 0.2 g of copper sulfate.
was dissolved in distilled water to make 100 ml and used.

Example 1 In the first step, a 1% ε-caprolactam aqueous solution was concentrated at normal pressure and 100°C until the ammonium sulfate concentration in the aqueous phase was 35 W +
, the concentration was adjusted so that it was %. The oil phase separated in the second step was neutralized with ammonia gas to adjust p II to 8, and then extracted using an extraction column with 3.1 g of toluene relative to the oil phase. In the third step, a small amount of caustic soda is added to the extract and distilled to remove 1-toluene, and then crude ε-caprolactam is distilled out. Fourth
In the process, fuming sulfuric acid was added to this crude i1Jε-caprolactam to make the acid concentration in terms of sulfuric acid in the mixture 57 wt%.
It stayed at 130°C for 2 hours. In the fifth step, this acid mixture is neutralized with ammonium water, and in the sixth step, this neutralized solution is extracted twice with twice the volume of Hensen. In the seventh step, after removing Hensen from this extract, 0.2 W of caustic soda was added.
t% was added and subjected to single distillation, and after distilling and removing 5 wt % of the initial distillation and U2, purified ε-caprolactam was distilled off as the main fraction, leaving 10 wt % as a high boiling point product. The quality of the obtained main fraction was such that the permanganate value was 21,600 seconds or more, and the transmittance at 290 nm was 98%.

Example 2 In the fourth step of the above operation, the concentration of sulfuric acid in the mixed liquid was set to 53
When expressed as wt%, the quality of the iM main fraction was that the permanganate value was 21,600 seconds or more, and the transmittance at 290 nm was 98%.

Example 3 In the fourth step of the procedure of Example 1, the temperature was brought to 100"C, and the quality of the main fraction obtained was such that the permanganate value was 21
The transmittance at 290 nm was 98% for 600 seconds or more.

Patent applicant Ube Industries Co., Ltd.

Claims (1)

[Claims] 1. In a method for recovering high-purity ε-caprolactam from an aqueous ε-caprolactam solution produced as a by-product during the production of II-cyanoundecanoic acid by thermal decomposition of 1-peroxydicyclohexylamine, the ε-caprolactam is recovered in the first step.
- The caprolactam aqueous solution is concentrated and separated into a C-caprolactam oil phase and an ammonium sulfate aqueous phase, and in the second step, the ε-caprolactam oil phase is extracted with an organic solvent, and in the third step, the extracted liquid is distilled to separate the solvent and crude oil. ε-caprolactam is distilled off, and in the fourth step, sulfuric acid or fuming sulfuric acid is added to the crude ε-caprolactam until the acid concentration in terms of sulfuric acid in the mixture is 50.
After adding it to ~55 wt% and keeping the temperature at 90 to 150 ° C, neutralized with ammonium water in the 5th step, extracted with an organic solvent in the 6th step, and extracted in the 7th step. A method for recovering ε-caprolactam characterized by distilling a liquid to distill out highly pure ε-caprolactam.