JPS6021583B2 - Caprolactam manufacturing method - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing caprolactam.

Specifically, the present invention relates to a method for producing highly pure caprolactam in high yield from cyclohexanone oxime. As a method for producing prolactam from cyclohexanone oxime, a method comprising the following steps is known.

■ Cyclohexanone oxime in the presence of fuming sulfuric acid,
Beckmann rearrangement is carried out at an acidity of 50 to 60% and a temperature of 70 to 130°C, or after Beckmann rearrangement is carried out at a temperature of 70 to 100°C, the rearrangement reaction product is heat-treated to a temperature of 130 to 200°C. (See Publication No. 42-6723) Step (1) Neutralize the reaction mixture in the above step using an alkali such as ammonia, and then extract or neutralize using an organic solvent such as benzene. Extraction/separation process in which caprolactam is extracted using an acidic organic solvent such as phenol and separated into an organic solvent phase containing caprolactam and an aqueous solution phase; The organic solvent is removed to obtain crude caprolactam. Organic solvent removal step: ■ Crude caprolactam is purified by distillation.

Distillation process to obtain lactams. In the distillation step (2) in the caprolactam production method as described above, the main distillate, energetic prolactam, is obtained, and low-boiling crab fraction, high-boiling crab fraction, and pot grains are discharged.

The low-boiling fraction and high-boiling fraction contain impurities and have high permanganate values (PZ and PM), but the main component is caprolactam, and the total amount of the low-boiling fraction and high-boiling fraction is , usually in an amount of 7% or more by weight based on crude caprolactam, so discarding these amounts to a large loss.

To recover caprolactam from such low-boiling and high-boiling crab components, it is possible to carry out recovery distillation, but if a small amount of caprolactam with impurities is obtained by recovery distillation, the amount recovered can be increased. However, there are still considerable amounts of loose fabrics, commercial materials and pot residues in the recovery distillation, which must be discarded, and the effect of reducing losses is small.

There is also a known purification method in which caprolactam containing impurities is heated with fuming sulfuric acid, neutralized, extracted and separated, and then distilled. A considerable amount of low-boiling materials, high-grade materials, and pot residues that are discharged during the process have to be disposed of.

Moreover, the number of operations required increased, and this was not industrially satisfactory. The present inventors have conducted intensive research to obtain high-yield, high-purity caprolactam in the caprolactam manufacturing method described above, and have discovered that the low-boiling fractions and/or high-boiling fractions discharged in the distillation process (①) When the sea bream crab fraction is recycled to the Beckmann rearrangement or the heat treatment step of the Beckmann rearrangement reactant in (2) above, the low-boiling crab fraction and/or the high-boiling fraction having a large permanganate value may also be recycled. regardless of,
Deterioration in the quality of the obtained prolactam, low boiling fraction,
High distillate fraction and pot residue do not increase, and most of the circulated low-boiling crab fraction and/or high-boiling crab fraction can be obtained as energetic prolactam, so the yield of energetic prolactam can be greatly increased. The present invention was completed based on the knowledge that it is possible to raise the

That is, the purpose of the present invention is to industrially advantageously produce caprolactam, and the purpose is to subject cyclohexanone oxime to Beckmann rearrangement in the presence of fuming sulfuric acid, or to carry out the rearrangement and then rearrange it after completion of the rearrangement. A reaction mixture containing caprolactam is obtained by further heat treatment, caprolactam is separated from the reaction mixture as an organic solvent solution by organic solvent extraction, and the organic solvent is removed from the organic solvent solution to obtain crude caprolactam. In a caprolactam production method in which energetic prolactam is obtained by distillation from caprolactam, the low-boiling fraction and/or high-boiling fraction in the above distillation is recycled to the Beckmann rearrangement step or the heat treatment step after the Beckmann rearrangement is completed. This is achieved by

The present invention will be explained in detail below.

The Beckmann rearrangement of the present invention is carried out by converting cyclohexanone oxime into cyclohexanone oxime in the presence of fuming sulfuric acid with an acidity of 60 to
80-130qo at 60%, preferably 85-120qo
It is carried out at a temperature of about 300 ℃.

In addition, when the rearrangement reaction product is heat-treated after Beckmann rearrangement, Beckmann rearrangement is 70 to 10 pi○, preferably 8 pi
Heat treatment is carried out at a temperature of about 0 to 10000
It is preferable to carry out the heating at a temperature of about 25° C. and higher than the Beckmann rearrangement temperature before the heat treatment. By employing such conditions, the caprolactam yield can be significantly improved compared to the known method in which heat treatment is performed at 130 to 20 pi.

After the Beckmann rearrangement or the heat treatment of the rearrangement reaction product after Beckmann rearrangement, each step of extracting caprolactam by organic solvent extraction, separation, removing the organic solvent, and obtaining caprolactam by distillation is performed in accordance with the above steps 1 to 1. This can be carried out according to a well-known method such as that described in (2). In the present invention, the low boiling point and/or high boiling point in the crude caprolactam distillation step (1) described above is subjected to the Beckman rearrangement step (2) or the heat treatment of the rearrangement reaction product after Beckman rearrangement. circulates.

The low-boiling fraction and/or the high-boiling fraction are heated to 80 to 130 oo in the presence of fuming sulfuric acid in the step of heat treatment of the Beckmann rearrangement or Beckmann rearrangement rearrangement reaction product.
It is preferably held at a temperature of about 90 to 120 oo for at least 10 minutes, preferably at least 3 minutes.

Usually, the heat treatment for the Beckmann rearrangement or the rearrangement reaction product after the Beckmann rearrangement is carried out for 10 minutes or more, so the low boiling fraction and/or the high boiling fraction are transferred to the Beckmann rearrangement reactor or to the Beckmann rearrangement reactant. It can be introduced from any arbitrary location, such as directly into the heat treatment vessels of these vessels, or it can be introduced into joint pipes such as raw materials to these vessels.

The low-purity fraction and/or the high-key fraction are obtained in the step of heat treatment of Beckmann rearrangement or Beckmann rearrangement reactant.
Since almost no acid is consumed, there is no need to increase the amount of fuming sulfuric acid used in order to circulate it.

When using the method of the present invention, the throughput increases by the amount of circulating low-boiling crab fraction and/or high-chicken fraction in all of the steps ① to ① above, so there is no need to change the equipment. In order to carry out the present invention, it is sufficient to operate by reducing the feed rate of raw materials by an amount corresponding to the circulating amount of low-boiling fractions and high-boiling fractions. If possible, the yield can be significantly increased using the same amount of raw material as without the above circulation. In either case, the operating conditions for the steps (1) to (2) do not need to be particularly different from those in the case where the circulation is not performed. The method of the present invention is extremely advantageous industrially because it is possible to obtain high-purity caprolactam in high yield without changing the conditions of each step in the production of caprolactam from cyclohexanone oxime. Since only the residue from the distillation process is used, this method is preferable from the standpoint of preventing pollution.

EXAMPLES The present invention will be specifically explained below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

In the examples, "parts" and "%" indicate "parts by weight" and "% by weight," respectively.

Moreover, permanganate values PZ and PM are values measured by the following method.

PZ: One sample of caprolactam was dissolved in 100 ml of water, a 0.01 molar aqueous solution of potassium permanganate was added thereto, and after 60 minutes, the absorbance of the skin at a wavelength of 41° was measured.

Displayed in %. PM: A solution of 100 μl of caprolactam sample dissolved in 8 mol of sulfuric acid 150 μl was titrated using a 0.01 mol aqueous solution of potassium permanganate to measure the amount of potassium permanganate consumed. Expressed as secretion/k9-caprolactam.
Example 1 Cyclohexanone oxime 31 containing 5.7% water
20kg/hr, 25% oleum 3900k9/hr and low boiling fraction 8 obtained by distillation of caprolactam as described below
Beckman rearrangement was carried out at 9°C and an average residence time of 1 hour while introducing 0k9/hr and high-boiling crab fraction 140kg/hr into the fly Azusa tank.

While introducing this dislocation anti-mixture into another pitching tank,
qo, and the heat treatment was performed at an average residence time of 2 hours. Add 12% ammonia water 11950k9 to the reaction mixture of the above step.
/hr and neutralized with 60q○, benzene 17370
Add k9/hr and perform extraction at 2 pi○, separate the layers and extract the benzene phase containing caprolactam at 20765k9/hr.
From this, extract the benzene to obtain crude caprolactam 3.
095 kg/hr was obtained.

Distill this prolactam, PM5 ship/hr, P
I got Z bag% energy prolactam 2800k9/hr.

Yield based on raw material cyclohexanone oxime is 95.2
%Met. The low-boiling crab content is PM6 ['hr, PZI%
The yield was 80k9/hr, and the high-boiling fraction was 140k9/hr with PM260'/m2 and PZ62%, and these were circulated to the pseudo-entrainment tank of the Beckmann rearrangement.

In addition, the remaining pot capacity was 75k9'hr.

Comparative Example 1 Using the same cyclohexanone oxime (water content 5.7%) 3350k9/hr and 25% oleum 4180k9/hr as used in Example 1, the low-boiling fraction and high-boiling fraction obtained by distillation of crude caprolactam were without recirculating the minutes.
The other operations were performed in the same manner.

The PM of the obtained prolactam is 4'/k9, PZ
The yield was 84%, the yield was 2800 k9'hr, and the yield was 88.6% based on the starting material cyclohexanoxime.

In addition, the low boiling fraction is PM7 above/k9, PZI% and the yield is 80k9'hr, and the high key fraction is PM240 ['hr, PZI%].
At Z66%, the yield is 140k9/hr, and the pot residue is 70k9/hr.
It was hr. Combine the above low-grade fraction and high-boiling fraction,
Add 10 [9'hr] of 25% caustic soda aqueous solution to this,
When caprolactam was recovered and distilled, PM6's
/k9, PZ81% energetic prolactam 100kg/h
r is obtained, low boiling matter is 45k9/hr, and pot residue is 85k9
/hr. The total amount of seminal prolactam obtained from crude caprolactam distillation and recovery distillation was 2900k9
/hr, the yield was only 91.8% based on the raw material cyclohexanone oxime. Comparative Example 2 Instead of the recovery distillation of caprolactam in Comparative Example 1,
Low boiling crab fraction 80 [9/hr and high Shiji fraction 140XQ/hr
While introducing r and 5% oleum 304k9/hr into the rope azusa tank, heat treatment was performed at 110°C with an average residence time of 2 hours, and the heated product was neutralized with 12% aqueous ammonia and extracted with benzene. , when distillation was performed after removing penzene,
PM5'/hr, P rating 2% energy prolactam 140
k9/hr was obtained, the low fabric was 21 [9/hr, and the pot residue was 55 kg/hr.

The total amount of seminal prolactam obtained by distillation and recovery of crude caprolactam was 2 ok9/hr, and the yield was only 93.0% based on the raw material cyclohexanone oxime.

Example 2 Instead of introducing the low-boiling fraction and the high-boiling fraction into the rope azusa tank for Beckmann rearrangement in Example 1, the low-boiling fraction and the high-boiling fraction were added to the rearrangement reaction mixture after Beckmann rearrangement. The mixture was introduced into a rope frame tank for heat treatment, and the other operations were carried out in the same manner as in Example 1 to obtain 2800k9/hr of seminal prolactam containing ''ko of PM4 and PZ milk%.

Claims (1)

[Claims] 1. A reaction mixture containing caprolactam is obtained by subjecting cyclohexanone oxime to Beckmann rearrangement in the presence of fuming sulfuric acid, or by carrying out the rearrangement and further heat treatment after completion of the rearrangement, and from the reaction mixture an organic solvent is extracted. In the method for producing caprolactam, the caprolactam is separated as an organic solvent by extraction, the organic solvent is removed from the organic solvent solution to obtain crude caprolactam, and refined caprolactam is obtained from the crude caprolactam by distillation. A method for producing caprolactam, characterized in that a low-boiling fraction and/or a high-boiling fraction are recycled to the Beckmann rearrangement step or the heat treatment step after the Beckmann rearrangement is completed. 2 Perform Beckmann rearrangement at 70-100°C, then
The method for producing caprolactam according to claim 1, wherein the heat treatment is carried out at a temperature of 90 to 125°C and higher than the temperature of Beckmann rearrangement.