JPH0832671B2 - Method for producing high-purity suberonitrile - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing suberonitrile from 1,6-dichlorohexane and sodium cyanide.

Suberonitrile is useful in the fields of organic chemistry and biochemistry as an intermediate for the production of agricultural drugs, dicarboxylic acids, diamines and the like.

(Prior Art) Japanese Patent Application Laid-Open No. 61-12222 discloses a method for producing suberonitrile.
No. 58 was reacted with 1,6-hexanediol and hydrogen iodide or an iodide of an alkali metal to obtain 1,6-diiodohexane as a cyanating agent such as sodium cyanide, potassium cyanide and hydrocyanic acid. There is a method of reacting. In this method, crude suberonitrile is extracted with a hydrophobic organic solvent such as ether, chloroform, ethyl acetate or the like, washed with water, and distilled under reduced pressure to obtain suberonitrile having a purity of 98% or more.

(Problems to be Solved by the Invention) (R _{1 to} R ₄ represent an alkyl group having 3 to 10 carbon atoms, which may be the same or different from each other), in the presence of a phase transfer catalyst represented by 1,6-dichlorohexane and blue. A method for producing suberonitrile by reacting an aqueous solution of sodium chloride was invented.

According to this method, the reaction product liquid is separated into an oil phase and an aqueous phase by using a phase transfer catalyst, and in the oil phase, the catalyst and suberonitrile and a small amount of unreacted 1,6-dichlorohexane react with each other. It contains a body of 1-cyano-6-chlorohexane (hereinafter referred to as mononitrile), and the aqueous phase contains NaCl as a reaction product and a small amount of unreacted soda blue.

The product suberonitrile is obtained by distilling this oil phase liquid. Distillation of crude suberonitrile is performed under reduced pressure of 10 to 15 Torr to avoid pyrolysis of suberonitrile.
Distillation is carried out at a temperature below ℃. Distillation purification generally employs a method of first removing low-boiling substances, then taking out purified suberonitrile, and removing high-boiling substances as a bottom residue. In this distillation method, there is a problem in that tetrabutylammonium bromide or the like which is the phase transfer catalyst is partially decomposed into tributylamine or the like by heating and is mixed in the product suberonitrile to impair the quality.

(Means for Solving Problems) As a result of diligent studies to solve the above problems in purifying suberonitrile, the inventors have found that the conventional batch distillation method, that is, the first distillation column To remove the low boiling point in the second distillation column, instead of removing the high boiling point in the second distillation column, first remove the high boiling point in the first distillation column, then remove the low boiling point in the second distillation column By doing so, it is found that tributylamine produced by decomposition of tetrabutylammonium bromide or the like by heating in the first distillation column is removed as a low boiling substance in the second distillation column, and high-purity suberonitrile is obtained. Invented.

That is, the present invention has the general formula (R _{1 to} R ₄ represent an alkyl group having 3 to 10 carbon atoms, which may be the same or different from each other), in the presence of a phase transfer catalyst represented by 1,6-dichlorohexane and blue. When producing a suberonitrile by distilling the crude suberonitrile solution obtained by reacting the sodium hydroxide aqueous solution, two distillation columns are provided, first, the high boiling substance containing the catalyst is removed in the first distillation column, and then the second boiling column is removed. A method for producing high-purity suberonitrile characterized by removing unreacted 1,6-dichlorohexane in a double distillation column.

Examples of the phase transfer catalyst used in the present invention include tetrapropylammonium bromide and tetrabutylammonium bromide. Tetrabutylammonium bromide is particularly preferable.

Aqueous soda blue solution has an industrial concentration of 30
A ~ 35% aqueous solution can be used as it is, or the concentration can be lowered if necessary.

In the present invention, the amount of soda cyanide used is a theoretical amount of 2.0% of the molar ratio of soda soda to 1,6-dichlorohexane.
On the other hand, it is preferable that the amount is slightly excessive to about 2.1 to 2.6.
If this molar ratio is too low, the yield will be low and the loss of 1,6-dichlorohexane will be large. Also, if this molar ratio is too high, CN ions will remain in the wastewater, increasing the cost of wastewater treatment.

The amount of tetrabutylammonium bromide used is 1,6
-1.5-10 g, preferably 1.5-6.5 g, per mol of dichlorohexane. If the amount of tetrabutylammonium bromide or the like used is too small, the yield will be low, and if it is large, the load of the next purification step will be large.

The reaction temperature is 80 to 140 ° C, preferably 90 to 110 ° C.
If the reaction temperature is low, the reaction does not proceed, and if it is too high, it causes coloring or polymerization.

The reaction pressure is not particularly limited, but is usually atmospheric pressure. The reaction time is usually 0.5 to 8 hr, preferably 2 to 4 hr.

The reaction product liquid is cooled to room temperature to be separated into an upper oil phase liquid and a lower water phase liquid. The oil phase liquid contains suberonitrile as a product, mononitrile as a reaction intermediate and a catalyst, and high-purity suberonitrile is obtained by distilling this with two distillation columns. The first distillation column removes high boiling substances containing the catalyst, and the second distillation column removes low boiling substances.

In the first distillation column and the second distillation column, the liquid temperature is 200 ° C. or less in order to avoid thermal decomposition of suberonitrile as described above,
It is preferably 180 ° C or lower. Therefore, the pressure is 1 to 4
The pressure is 0 Torr, preferably 1 to 15 Torr. If the pressure is too high, the temperature at the bottom of the column rises and the suberonitrile decomposes, lowering the recovery rate. The pressure may be lower than this, but it is not economical because the distillation column becomes large. Each distillation column may be a plate column or a packed column, but the theoretical plate number may be 1 plate in the first distillation column and 5 to 50 plates, preferably 15 to 30 plates, depending on the distillation conditions. The reflux ratio is 0-5 in the first distillation column,
It is preferably 0-1 and in the second distillation column 5-20, preferably 5-10.

(Action and Effect) According to the present invention, high-purity suberonitrile can be obtained without mixing the product with tributylamine or the like produced by decomposition of tetrabutylammonium bromide or the like which is a phase transfer catalyst.

In this method, 1,6-dichlorohexane, which is industrially inexpensively obtained, is used as a raw material, and high-purity suberonitrile can be obtained by a very simple reaction step and purification step. Significant.

(Example) Next, the present invention will be specifically described with reference to examples. The comparative example is based on a conventional distillation purification method, that is, a method of removing low-boiling substances first, and then a method of removing high-boiling substances, which is compared with the examples according to the method of the present invention.

Example 1 Tetrabutylammonium bromide was used as a phase transfer catalyst, the molar ratio of sodium cyanide to 1,6-dichlorohexane was 2.1, and the catalyst amount was 3.3 g per mol of 1,6-dichlorohexane under normal pressure. After reacting for 4 hours at a reaction temperature of 110 ° C., 1000 g of crude suberonitrile liquid separated by cooling (suberonitrile concentration 84%) was subjected to simple distillation at a pressure of 10 Torr temperature of 180 ° C. to remove high boiling substances, and distillate 950 g (suberonitrile concentration of 87%). %) Was obtained. This distillate was placed in a distillation pot having a packing equivalent to 30 stages at the top, and the top pressure was 5 Torr (15 Tor in the pot).
r) Batch distillation was carried out at a reflux ratio of 5.0 to obtain 130 g of a low boiling distillate. The temperature at the time of this distillation is 53-160 ℃ at the top, 167-19 in the pot
It was 0 ° C. As a result, 820 g of purified suberonitrile having a purity of 99.0% or more was obtained, and tributylamine and butyl bromide were not detected in the purified suberonitrile.

Comparative Example 1 Crude suberonitrile liquid 10 obtained in the same manner as in Example 1
00g (suberonitrile concentration 83.0%) is the same as in Example 1 3
Batch distillation was performed using a distillation pot corresponding to 0 stage to obtain 110 g of a low boiling distillate. At this time, the reflux ratio was 5.0, the pressure was 2 Torr at the top and 10 Torr in the pot, and the temperature was 42 to 140 ° C at the top and 156 to 173 in the pot.
° C. 880 g of pot residual liquid obtained by this distillation (suberonitrile concentration 91.5%) was subjected to simple distillation at a pressure of 10 Torr and a temperature of 180 ° C to obtain 810 g of purified suberonitrile, the purity of which was 98.4% and tributylamine. 0.97
%, Butyl bromide 0.24% were detected.

Claims (1)

[Claims] 1. The general formula is (Wherein R _{1 to} R ₄ represent an alkyl group having 3 to 10 carbon atoms, and these may be the same or different from each other), in the presence of a phase transfer catalyst, 1,6-dichlorohexane and When producing a suberonitrile by distilling a crude suberonitrile solution obtained by reacting an aqueous solution of blue soda, two distillation columns are provided, and first, a high boiling substance containing the catalyst is removed in the first distillation column, and then, Method for producing high-purity suberonitrile characterized by removing low-boiling substances containing unreacted 1,6-dichlorohexane in a second distillation column