JPS63145261A - Production of 11-cyanoundecanoate - Google Patents

Abstract

PURPOSE:To deposit the titled ammonium salt, by thermally decomposing 1,1'- peroxydicyclohexylamine at a high temperature, quenching the resultant product, acidifying the quenched product, extracting the acidified product with water, separating the obtained extract into an aqueous layer and oily layer, adding aqueous ammonia to the oily layer, extracting and removing impurities. CONSTITUTION:1,1-Peroxydicyclohexylamine 1 is thermally decomposed in a thermal decomposition column 3, quenched with cooling water 23 and adjusted to pH <=4 in a pH adjusting vessel 9. The acidified product is then led to a water extraction column 4 and separated into an aqueous layer 12 containing epsilon-caprolactam and an oily layer 15 containing 11-cyanoundecanoic acid. The aqueous layer 12 is partially used as the cooling water 23. The oily layer 15 is mixed with a solution containing ammonia and water and led to an organic solvent extraction column 5 to convert the 11-cyanoundecanoic acid and isomers thereof into ammonium salts, which are then migrated into an aqueous layer 17. Cyclohexanone and other impurities are removed with an extracting organic solvent 13 and the aqueous layer 17 is successively led to crystallization vessels 6 and 8 to afford the aimed high-purity ammonium 11-cyanoundacanoate.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides ammonium 11-cyanoundecanoate from a thermal decomposition product of 1,1'-peroxydicyclohexylamine (hereinafter sometimes abbreviated as rPXAJ). Relating to a method for recovering salt.

[Conventional technology]

A method of thermally decomposing PXA is known as a method for obtaining 11-cyanoundecanoic acid, which is useful as a raw material intermediate for nylon 12. i.e. British Patent No. 1.198.42
No. 2 describes a method of thermally decomposing PXA at a high temperature of 300 to 1,000°C, and also
PXA was sprayed in droplets in an inert gas atmosphere such as heated steam held at 250-1000"C.
A method of heating is described.

However, 11-
In addition to cyanoundecanoic acid, it contains a considerable amount of by-products such as ε-caprolactam, cyclohexanone, saturated and unsaturated carboxylic acids and nitriles, and cyclic imides, and this thermal decomposition reaction product is usually brown to blackish-brown in color. It is colored in.

Therefore, there has been a need for a method for recovering useful 11-cyanoundecanoic acid from the thermal decomposition product of pxA containing such a wide variety of by-products in a relatively simple process and in high yield. For example, in Special Publication No. 60-26385, PXA
A step of dissolving the thermal decomposition reaction product in a mixed solvent of benzene, toluene or xylene and water, and separating the oil layer into an aqueous layer containing ε-caprolactam and an oil layer containing 11-cyanoundecanoic acid, and dissolving the oil layer with ammonia. A method is described that includes a step of extracting the 11-cyanoundecanoic acid ammonium salt by crystallization from the extract.

However, in the above method of crystallizing ammonium salt of 11-cyanoundecanoic acid from the extract obtained by extracting the oil layer with ammonia, it is difficult to perform the crystallization efficiently, and it is difficult to obtain high-purity 11-cyanoundecanoic acid. The problem was that salt was difficult to obtain.

[Problem that the invention seeks to solve]

An object of the present invention is to provide a method for efficiently recovering highly pure 11-cyanoundecanoate from a thermal decomposition product of PXA in a relatively simple process.

[Means for solving problems]

The above objects of the present invention are to (a) pyrolyze PXA at high temperature and immediately quench it to produce a pyrolysis product mainly containing 11-cyanoundecanoic acid, cyclohexanone and 1ε-caprolactam; The pH value of the pyrolysis product is adjusted to 4 or less, and the pyrolysis product to be adjusted (c)p)l is extracted with water, and an extract of water-soluble components including ε-caprolactam and 11-cyanoundecane are extracted. (d) After adding aqueous ammonia to the oil layer, impurities are extracted and removed from the oil layer with an extraction solvent, and (e) 11- from which the impurities have been removed by extraction. 11 from an aqueous solution containing ammonium cyanoundecanoate salt
- 1 characterized by precipitation of cyanoundecanoate
This is achieved by a method for producing 1-cyanoundecanoate.

Hereinafter, the method for producing 11-cyanoundecanoate of the present invention will be explained step by step with reference to the flow sheet of the attached drawings. The figure shows the process for obtaining 11-cyanoundecanoate from PXA according to the method of the invention.

The PXAI is heated to a high temperature in the pyrolysis column 3, preferably about 400
It is heated to ~800°C to undergo thermal decomposition. In one advantageous pyrolysis method, PXA is sprayed from the top of the pyrolysis column with a heated inert gas, preferably heated steam 2, and further heated steam 2 is blown into the top of the pyrolysis column,
PXA is maintained at a predetermined temperature to instantaneously achieve a thermal decomposition reaction in the gas phase.

The thermal decomposition reaction system is immediately quenched to condense and recover the components contained therein, such as 11-cyanoundecanoic acid, cyclohexanone, and ε-caprolactam.

That is, cooling water 23 is directly poured into the thermal decomposition product obtained in the thermal decomposition process to rapidly cool it to a temperature of about 250° C. or lower.

Preferably, cooling water 23 is sprayed into the tower from a spray nozzle provided at the bottom of the pyrolysis tower 3 to condense the pyrolysis reaction product, and the condensed pyrolysis containing 11-cyanoundecanoic acid is released from the bottom of the tower. Take out the liquid. 60℃ for cooling water 23
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 viewpoint of economical utility, the cooling water 23 is made of water extraction group 4 described later.
It is desirable to recycle a portion of the water extract extracted from the plant.

The pyrolysis oil (condensate of pyrolysis products) taken out from the bottom of the pyrolysis tower is led to a regulating tank 9, where it is heated with an acid such as dilute sulfuric acid.
0 to bring the pH value below 4, preferably between 2 and 3. This pH adjustment is effective in completely preventing flooding within the water extracting group 4.

The pyrolysis oil with adjusted pl+ is supplied to the water extraction tower 4.

In the water extraction tower 4, the pyrolysis oil is extracted with water 11 and separated into an aqueous layer 12 containing ε-caprolactam and an oil layer 15 containing 11-cyanoundecanoic acid. The amount of extracted water 11 is preferably selected so that the weight ratio of water layer 12 to oil layer 15 is 0.5 to 5, particularly 1 to 4.

The oil layer 15 is taken out from the top of the water extraction tower 4, mixed with a solution 18 containing ammonia and water, and then introduced into the organic solvent extraction tower 5. As the solution 18 containing ammonia and water, it is desirable to recycle and use a solution containing ammonia and water recovered from the mother liquor taken out from the crystallization tank 6. Oil layer 15
In addition to 11-cyanoundecanoic acid, some of its isomers (e.g., 7-cyanoundecanoic acid and 2-butyl-7-
11-cyanoundecanoic acid and its isomers become ammonium salts by reaction with ammonia, and are transferred into the aqueous layer 17 by extraction with the organic solvent 13. The concentration and amount of ammonia water are preferably adjusted to such an extent that the concentration of ammonium 11-cyanoundecanoate in the water layer 17 is 10 to 30% by weight, and the concentration of free ammonia is 1 to 20% by weight.

The extraction operation is preferably performed at a temperature of 30 to 70°C.

On the other hand, the aqueous extraction solution 12 taken out from the bottom of the water extraction tower 4
The accompanying cyclohexanone and ε-caprolactam are recovered.

An organic solvent for extraction, preferably toluene, is supplied to the lower part of the organic solvent extraction tower 5, and cyclohexanone and other impurities (for example,
Hexanenitrile, hexenenitrile) is extracted and removed. The amount of toluene supplied is 0.1 to 2 times (weight ratio) the amount of oil N15. The toluene extract 16 is taken out from the top of the extraction column 5, led to a cyclohexanone and toluene recovery step (not shown), and separated in one distillation.

-Aqueous solution 17 containing ammonium salt of 4,11-cyanoundecanoic acid and ammonium salts of its isomers is taken out from the bottom of extraction column 5, fed to crude 11-cyanoundecanoic acid crystallization tank 6, and purified by crystallization. . Although the crystallization can be carried out in one stage, it is preferable to carry out the crystallization in two stages as follows.

In the crystallization tank 6, the crude ammonium 11-cyanoundecanoate aqueous solution is cooled to 0 to 20°C, particularly to 5 to 15°C, to precipitate crystals of ammonium 11-cyanoundecanoate. 7-cyanoundecanoic acid contained as an impurity,
Ammonium salts such as 2-butyl-7-diatzhebutanoic acid have high solubility and therefore remain in the mother liquor side. This mother liquor is taken out from the crystallization tank 6 and introduced into the distiller 24. It is preferable that the solution 18 containing ammonia and water is recovered from the distiller 24, mixed with the oil layer 15 taken out from the water extraction column 4, and circulated to the organic solvent extraction column 5. The remaining mother liquor 19 containing ammonium salts such as 7-cyanoundecanoic acid and 2-butyl-7-diachebutanoic acid is purged from the distiller 24 to outside the system.

Note that a centrifuge may be used, for example, to separate the mother liquor and the crystals of ammonium 11-cyanoundecanoate salt.

The crystals 20 of 11-cyanoundecanoic acid ammonium salt precipitated in the crystallization tank 6 are led to the dissolution tank 7, and dissolved in the mother liquor 23 taken out from the next purified 11-cyanoundecanoic acid ammonium salt crystallization tank 8. The solution 21 is taken out from the dissolution tank 7 and sent to the purified 11-cyanoundecanoic acid ammonium salt crystallization tank 8. The solution in the second crystallization tank 8 is about 0 to 3
By cooling to 0° C., especially 5 to 20° C., crystallization and purification are performed again to obtain white crystals 22 of purified ammonium salt of 11-cyanoundecanoic acid with high purity.

〔Example〕

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

Example 1 From PXA using an apparatus having the arrangement shown in FIG.
-Cyanoundecanoic acid was produced.

Toluene oil (PXA oil) containing 75% by weight of 1.1'-peroxydicyclohexylamine at 30°C was heated to 800 kg from a spray nozzle installed at the top of the pyrolysis tower 3.
g/H with superheated steam 2 at 500'C. Immediately after the spraying, superheated steam 2 at 750°C was blown in to maintain the temperature inside the thermal decomposition tower at 480°C, and a thermal decomposition reaction was instantaneously carried out in the gas phase. The total supply amount of superheated steam is 2
．． It was 8t/h. Immediately thereafter, cooling water 23 was sprayed at 6 rrr/H from a number of spray nozzles installed at the bottom of the tower.
The thermal decomposition reaction system was rapidly cooled to a temperature of 130° C. or lower. As this cooling water 23, a part of the filtrate extract taken out from the water extraction tower 4 was recycled and used.

Pyrolysis oil taken out from the bottom of the pyrolysis tower is pl + adjustment tank 9
The pH was adjusted to 2.5 with dilute sulfuric acid, and the mixture was sent to water extraction column 4. At the top of the water extraction tower 4, 3.600 g of extracted water is added.
It was introduced at a rate of kg/H. By-product valuables (ε-caprolactam) in the pyrolysis oil are extracted and removed in the water extraction tower 4,
11-cyanoundecanoic acid oil 1, 500 kg/H was obtained. The composition of this 11-cyanoundecanoic acid oil is shown in Table 1.

Table-1 11-Composition of cyanoundecanoic acid oil--
-----------1 (wt%) 11-cyanoundecanoic acid 20 cyclohexanone
127-cyanoundecanoic acid
1.32-butyl-7-diathebutanoic acid 0.6
Hexanenitrile 0.5Hexenenitrile 0.1Others
5.5 The extracted aqueous solution 12 taken out from the water extraction tower 4 is led to an evaporator (not shown), and ε-caprolactam can be recovered from the bottom of the evaporator.

The 11-cyanoundecanoic acid oil is mixed with 1900 kg/H of mother liquor (containing 4% Ammoev 6x) taken out from the crystallization tank 6 in the next crystallization step, and then supplied to the upper part of the organic solvent extraction tower 5. 700 kg / to the lower part of the extraction tower
13 of H toluene was fed. Cyclohexanone and other impurities in the 11-cyanoundecanoic acid oil were extracted and removed. The composition of the toluene extract is shown in Table 2.

Table 2 Composition of toluene extract 1 1 charcoal 1 part --- No.
0.10 Other impurities
7.5 Toluene 81.
96 toluene extract 16 is taken out from the top of the extraction column and subjected to a cyclohexanone and toluene recovery step (not shown).
sent to.

The aqueous solution 17 containing ammonium 11-cyanoundecanoate taken out from the extraction tower 5 is sent to the crude ammonium 11-cyanoundecanoate crystallization tank 6 and heated at 8° in the crystallization tank 6.
The mixture was cooled to C. to precipitate crystals of 11-cyanoundecanoic acid ammonium salt.

The mother liquor is taken out from the crystallization tank 6, and the ammonium salts of 7-cyanoundecanoic acid and 2-butyl-7-diashebutanoic acid contained therein are purged, and about 6% by weight of ammonia and water are recovered from the mother liquor by distillation. A solution 18 containing toluene and organic solvent was transferred to an organic solvent extraction tower 5. The precipitated crystals of 11-cyanoundecanoic acid ammonium salt are led to the melting tank 7, and the mother liquor 2 is taken out from the next second crystallization tank 8.
3 and dissolved. The obtained solution is transferred to the second crystallization tank (
The purified 11-cyanoundecanoic acid ammonium salt) was sent to 8, cooled to 12° C. in the same tank, and crystallized again to obtain 400 kg/I of highly purified purified 11-cyanoundecanoic acid ammonium salt (white crystals). The composition of the purified 11-cyanoundecanoic acid ammonium salt crystals obtained is shown in Table 3.

Margin table below-3 Ammonia 0.5 water
24.5ε-caprolactam 0.0 cyclohexanone
0.0 hexanenitrile
0.0hexenenitrile
0.0 [Effect of the Invention] According to the present invention, highly pure 11-cyanoundecanoic acid can be efficiently produced from PXA. In particular, according to the production method of the present invention, compared to the method described in Japanese Patent Publication No. 60-26385, the process of adjusting the pH of the PXA thermal decomposition product to 4 or less before extracting it with water is required. Instead of directly sending the water-extractable 11-cyanoundecanoic acid solution to the crystallization separation process, cyclohexanone and other impurities are first extracted and removed with an organic solvent such as toluene, and then ammonium 11-cyanoundecanoate is extracted with water. By sending the product to the crystallization separation process, the crystallization is performed very efficiently, and a product with high purity can be produced at a high yield.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing a process for producing 11-cyanoundecanoic acid from PXA according to the present invention. 1: PXA oil, 2: Superheated steam, 3: Thermal decomposition tower, 4: Water extraction group, 5: Organic solvent extraction tower, 6: Crude ammonium 11-cyanoundecanoate crystallization tank, 7: Dissolution tank, 8: Purification 11-Cyanoundecanoic acid ammonium crystallization tank, 9: PL + adjustment tank, lo: acid, 11: extraction water, 12: extraction aqueous solution, 13: extraction organic solvent,
15: oil layer, 16: organic solvent extract, 17: aqueous solution containing 11-cyanoundecanoic acid ammonium salt, 18: solution containing ammonia and water from crystallization tank 6, 19: mother liquor to be purged, 20: crystallize 11-Cyanoundecanoic acid ammonium salt crystal, 21: Solution of the same crystal, 22: Purified 11-cyanoundecanoic acid ammonium salt crystal, 23: Mother liquor from crystallization tank 8, 24: Distillation column.

Claims (1)

[Claims] 1, (a) 1,1'-peroxydicyclohexylamine is thermally decomposed at high temperature and then immediately quenched to produce mainly 11
-cyanoundecanoic acid, cyclohexanone and -ε-
producing a pyrolysis product containing caprolactam; (b) adjusting the pH value of the pyrolysis product to 4 or less; (c) extracting the pyrolysis product to be pH adjusted with water;
Separate into an aqueous layer containing caprolactam and an oil layer containing 11-cyanoundecanoic acid, (d) add aqueous ammonia to the oil layer, extract and remove impurities from the oil layer with an extraction solvent, and then (e ) From an aqueous solution containing 11-cyanoundecanoic acid ammonium salt from which impurities have been removed by extraction, 11-
A method for producing 11-cyanoundecanoate, which comprises precipitating ammonium cyanoundecanoate.