JPH0558624B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to 1,1'-peroxydichlorohexylamine (hereinafter sometimes abbreviated as "PXA").
from the thermal decomposition product of 11-cyanoundecanoic acid, ε
- Concerning a method for recovering caprolactam and cyclohexanone.

[Conventional technology]

A known method for obtaining 11-cyanoundecanoic acid, which is useful as a raw material intermediate for nylon 12, is to thermally decompose PXA. i.e. British Patent No.
No. 1198422 describes a method of thermally decomposing PXA at a high temperature of 300 to 1000℃, and Japanese Patent Publication No. 49-31969
The product was sprayed in small droplets in an inert gas atmosphere such as superheated steam maintained at 250-1000℃.
A method for heating PXA is described. However, in addition to 11-cyanoundecanoic acid, the thermal decomposition reaction products of PXA contain a considerable amount of byproducts such as ε-caprolactam, cyclohexanone, saturated and unsaturated carboxylic acids and nitriles, and cyclic imides. This thermal decomposition reaction product is usually colored brown to blackish brown.

Therefore, it contains a wide variety of by-products.
There has been a need for a method for recovering useful 11-cyanoundecanoic acid, ε-caprolactam, and cyclohexanone from thermal decomposition products of PXA with a relatively simple process and high yield. For example, JP-A-55-
No. 87767 describes a process of separating the thermal decomposition product of PXA into an oil layer mainly containing 11-cyanoundecanoic acid and cyclohexanone and an aqueous layer mainly containing ε-caprolactam and cyclohexanone, and a process in which the oil layer is extracted with water. It consists of a step of mixing the liquid with an aqueous layer, a step of concentrating this mixed liquid and then distilling it to obtain an ε-caprolactam fraction, and a step of crystallizing and separating the obtained ε-caprolactam fraction with toluene.
A method for recovering PXA pyrolysis products is described.

However, the aqueous layer containing ε-caprolactam contained a considerable amount of entrained cyclohexanone, and this cyclohexanone was not recovered.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for efficiently recovering cyclohexanone entrained in the aqueous layer in a method for recovering useful 11-cyanoundecanoic acid, ε-caprolactam, and cyclohexanone from the thermal decomposition products of PXA. .

[Means for solving problems]

The above object of the present invention is to (a) thermally decompose 1,1'-peroxydicyclohexylamine (PXA) at a high temperature and then quickly cool it, thereby thermally decomposing mainly 11-cyanoundecanoic acid, cyclohexanone and ε-caprolactam. (b) adjusting the PH value of the pyrolysis product to 4 or less; and (c) extracting the PH-adjusted pyrolysis product with water to contain ε-caprolactam and entrained cyclohexanone. water layer and
Separating into an oil layer containing 11-cyanoundecanoic acid, (d) heating the aqueous layer to evaporate and condense the accompanying cyclohexanone and water, and collect it,
Achieved by a method characterized by recovering condensed ε-caprolactam, and (e) then extracting the evaporated recovery liquid with an organic solvent capable of extracting cyclohexanone from the evaporation recovery liquid to recover cyclohexanone. be done.

Hereinafter, the method for recovering PXA pyrolysis products of the present invention will be described.
The steps will be explained step by step with reference to the flow sheet of the attached drawings. The drawings are made according to the method of the invention
The process of recovering PXA pyrolysis products is shown.

The PXA oil 1 is heated to a high temperature, preferably about 400 to 800°C, in the pyrolysis tower 3 to undergo pyrolysis. In one advantageous pyrolysis method, PXA is sprayed from the top of the pyrolysis tower with a heated inert gas, preferably superheated steam 2, and then superheated steam 2 is blown into the top of the pyrolysis tower to remove the PXA. A thermal decomposition reaction is achieved instantaneously in the gas phase by maintaining a predetermined temperature.

By immediately quenching the thermal decomposition reaction system, the 11-cyanoundecanoic acid contained therein,
Components such as cyclohexanone and ε-caprolactam are condensed and recovered. That is, cooling water 9 is directly added to the pyrolysis product obtained in the pyrolysis process, and approximately
Rapidly cool to a temperature below 250℃. Preferably, cooling water 9 is sprayed into the tower from a spray nozzle provided at the bottom of the pyrolysis tower 3 to condense the pyrolysis reaction product,
A condensed thermal decomposition liquid containing 11-cyanoundecanoic acid is taken out from the bottom of the column. 60℃ for cooling water 9
The following are used and the amount supplied is sufficient to immediately quench the pyrolysis reaction system to below about 250°C, preferably below about 130°C.

From the standpoint of economic efficiency, it is desirable that a portion 9 of the water extract taken out from the water extraction tower 4 described later be recycled as the cooling water 9 .

The pyrolysis oil (condensed liquid of pyrolysis products) taken out from the bottom of the pyrolysis tower is led to a PH adjustment tank 8, where an acid such as dilute sulfuric acid is added to adjust the PH value to 4 or less, preferably 2 to 2. Make it 3. This pH adjustment is effective in improving the separation of the water layer and oil layer in the water extraction tower 4 and completely preventing flooding.

The pyrolysis oil with adjusted pH is supplied to the water extraction column 4. In the water extraction tower 4, the pyrolysis oil is extracted with water,
It is separated into an aqueous layer containing ε-caprolactam and the accompanying cyclohexanone and an oil layer containing 11-cyanoundecanoic acid. The amount of extracted water is preferably selected so that the weight ratio of the water layer to the oil layer is 0.5 to 5, particularly 1 to 4. The oil layer 11 is taken out from the top of the column and led to a step (not shown) for recovering 11-cyanoundecanoic acid and the like. On the other hand, the aqueous layer (water extract) is taken out from the bottom of the tower, and a part of it is sent to the pyrolysis tower 3 as cooling water 9.
The remaining portion 12 is led to the evaporator 5.

In the evaporator 5, the water extract 12 containing ε-caprolactam and cyclohexanone is heated to evaporate water and cyclohexane. The heating temperature inside the evaporator 5 is 50 to 120°C. Since the evaporator 5 evaporates most of the supplied aqueous extract 12, it is desirable to employ a dual-effect can.

The evaporated water and cyclohexanone are condensed, and the resulting distillate 13 is led to the organic solvent extraction column 7. A portion of the distillate is preferably led to the top of the water extraction column 4 as extraction water 14 of pyrolysis oil.

The bottom liquid 15 taken out from the bottom of the evaporator 5 is ε-
It is a concentrated solution of caprolactam. This can liquid 15 is led to a separation tank 6 and separated into ε-caprolactam oil 16 and ammonium sulfate liquid 17.

The cyclohexanone-containing water 13 led to the upper part of the organic solvent extraction tower 7 comes into contact with an organic solvent, preferably toluene 18, supplied to the lower part of the tower to extract cyclohexanone. The extracted liquid 20 containing cyclohexanone can be circulated from the organic solvent extraction tower 7 to the PH adjustment tank 8 for pyrolysis oil, or can be led to a cyclohexanone recovery step (not shown). Note that the aqueous layer (bottom liquid) 19 separated from the bottom of the organic solvent extraction tower 7 may be purged for the sake of process balance.

A preferred embodiment of the PXA pyrolysis product recovery process of the present invention is characterized in that the water balance within the process is taken into consideration. That is, as described above, a part of the water layer taken out from the water extraction tower 4 is guided to the pyrolysis tower 3 as cooling water 9. Then, in consideration of the water amount balance with the superheated steam 2 supplied to the pyrolysis tower 3, an amount of water corresponding to the amount of the superheated steam 2 is discharged from the organic solvent extraction tower 7 as a bottom liquid 19 to the outside of the system. If the aqueous phase of the bottom liquid from the organic solvent extraction tower 7 were to be circulated as cooling water to the pyrolysis tower 3, the amount supplied to the evaporator 4 would increase, and the equipment cost would increase significantly.

〔Example〕

The present invention will be specifically described below with reference to Examples.

Example 1 PXA using an apparatus having the arrangement shown in Figure 1
The pyrolysis products were recovered.

Toluene solution containing 75% by weight of 1,1'-peroxydicyclohexylamine (PXA oil) at 30℃
from the spray nozzle installed at the top of the pyrolysis tower 3.
It was sprayed together with superheated steam 2 at 500°C at a rate of 800Kg/H. Immediately after spraying, superheated steam 2 at 750°C is blown in to maintain the temperature inside the pyrolysis tower at 480°C.
Thermal decomposition reaction was carried out instantaneously in the gas phase. The total amount of superheated steam supplied was 2.8t/H. After that, immediately 40
℃ cooling water 9 was sprayed at a rate of 6000 kg/h to rapidly cool the thermal decomposition reaction system to a temperature of 130° C. or lower.

As this cooling water 9, a part of the water extract taken out from the water extraction tower 4 was recycled and used.

The pyrolysis oil taken out from the bottom of the pyrolysis tower was led to a pH adjustment tank 8, the pH of which was adjusted to 2.5 with dilute sulfuric acid, and sent to the water extraction tower 4. At the top of the water extraction tower 4, an evaporator 5 is installed.
Part 14 of the distillate circulated from the distillate was introduced as extraction water at a rate of 3600 Kg/H. In the water extraction tower 4, valuable by-products (ε-caprolactam and accompanying cyclohexanone) in the pyrolysis oil are extracted and removed.
- 1500 kg/h of cyanoundecanoic acid oil was obtained.

14,800 kg of water 12 containing ε-caprolactam and accompanying cyclohexanone was extracted from the water extraction tower 4.
A portion of 6000 kg/H is sent to the pyrolysis tower 3 as cooling water 9 as described above, and the remaining
7800Kg/H was delivered to steam can (double effect can) 5.

The composition of Water 12 was as follows.

Substance concentration ε-caprolactamic acid 1.1% by weight Cyclohexanone 0.7 Water and others 98.2 The inside of the evaporator 5 was heated to 72°C. Can liquid 15 for 500
Kg/H ratio is taken out and guided to separation tank 6, ε-caprolactam oil 100Kg/H and sulfuric acid aqueous solution 400Kg/H
It was separated and recovered. The composition of the obtained ε-caprolactam oil was as follows.

Substance concentration ε-caprolactamic acid 4.5% by weight 11-cyanoundecanoic acid 0.5 〃 Cyclohexanoic acid 0.04 〃 Water and others 54.46 〃 The distillate from the evaporator 5 contains cyclohexanone. Of this distillate, 3600Kg/H is supplied to the water extraction column 4 as extracted water 14, and the remaining 370Kg/H
Kg/H was supplied to the toluene extraction column 7. In the toluene extraction tower 7, cyclohexanone was extracted with 550 kg/H of toluene 18. The extracted liquid 20 containing cyclohexanone is transferred to the PH adjustment tank 8 of pyrolysis oil.
circulated to. The tank liquid 19 from which cyclohexanone had been removed was purged out of the system.

〔Effect of the invention〕

According to the method of the present invention, useful 11-cyanoundecanoic acid, ε-caprolactam and cyclohexanone, particularly cyclohexanone entrained in the aqueous layer, can be very efficiently recovered from the thermal decomposition product of PXA.

In particular, if a water circulation system is adopted that takes into account the water balance within the process, the economic effectiveness of the recovery process will be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing the process for recovering PXA pyrolysis products of the present invention. 1: PXA oil, 2: superheated steam, 3: pyrolysis tower, 4: water extraction tower, 5: evaporator, 6: separation tank,
7: organic solvent extraction tower, 8: PH adjustment tank, 9: cooling water, 10: acid, 11: 11-cyanoundecanoic acid (oil layer), 12: water extract (aqueous layer), 13: distillate,
14: Extract water, 15: Can liquid (ε-caprolactam concentrate), 16: ε-caprolactam oil, 17:
Sulfuric acid aqueous solution, 18: organic solvent, 19: can liquid, 2
0: Extract containing cyclohexanone.

Claims (1)

[Scope of Claims] 1 (a) 1,1'-peroxydicyclohexylamine is thermally decomposed at high temperature and then rapidly cooled to produce a thermal decomposition product consisting mainly of 11-cyanoundecanoic acid, cyclohexanone and ε-caprolactam. (b) Adjust the PH value of the pyrolysis product to 4 or less; (c) Extract the pyrolysis product to be adjusted with water to ε
-separating into an aqueous layer containing caprolactam and the accompanying cyclohexanone and an oil layer containing 11-cyanoundecanoic acid; (d) heating the aqueous layer to evaporate and condense the entrained cyclohexanone and water and collect them; , recovering condensed ε-caprolactam, and (e) then extracting the evaporated recovery liquid with an organic solvent capable of extracting cyclohexanone from the evaporation recovery liquid to recover cyclohexanone. - A method for recovering peroxydicyclohexylamine thermal decomposition products. 2 (a) 1,1'-peroxydichlorohexylamine is thermally decomposed at high temperature and immediately quenched to produce a thermal decomposition product consisting mainly of 11-cyanoundecanoic acid, cyclohexanone and ε-caprolactam, (b ) Adjust the PH value of the pyrolysis product to 4 or less; (c) Extract the pyrolysis product to be PH-adjusted with water to
- separation into an aqueous layer containing caprolactam and accompanying cyclohexanone and an oil layer containing 11-cyanoundecanoic acid, and introducing a part of the aqueous layer to the thermal decomposition step (a) to rapidly cool the thermal decomposition product; (d) The aqueous layer is heated to recover the entrained cyclohexanone and water by evaporation and condensation, and the condensed ε-caprolactam is recovered. (e) Then, cyclohexanone is recovered from the evaporated and recovered liquid. The evaporated recovery liquid is extracted with an organic solvent capable of extracting cyclohexanone, and the cyclohexanone-containing extract extracted with the organic solvent is circulated to the PH adjustment step (b) of the pyrolysis product. 1. A method for recovering 1,1'-peroxydicyclohexylamine thermal decomposition products, which comprises combining with the decomposition products.