DE1543099C - Process for the reductive dimerization of acrylonitrile to adipic acid dinitrile - Google Patents

Description

1 2

The invention relates to the reductive dimerization reduction vessel the aqueous reaction medium

from acrylonitrile to adipic dinitrile. Mix with the acrylonitrile and on the other

The reductive dimerization of acrylonitrile to side an aqueous solution of an alkali metal or

Adipic acid dinitrile was already used by Knunyants and alkaline earth metal compounds in the electrolytic cell

Vyazankin (Bulletin of the Academy of Science of the 5. When current flows through the cell

U.S.S.R., 1967, pp. 253-255). amalgam is formed, and the mercury

During the reductive dimerization of acrylonitrile to the cathode, cations are removed from the cell Adipic acid dinitrile is effectively transferred in an aqueous medium by means of a to the reduction vessel. The react alkali metal or alkaline earth metal amalgams. The medium is withdrawn from the reduction vessel Relatively large io passes in the reaction medium and after the organic reaction quantities have been separated off of inorganic compounds fed back into the electrolytic cell as reaction products, tion products of the amalgam. The removal of these to provide amalgam-forming metal there. When Inorganic compounds are not always easily absorbed by the aqueous medium in the cell executable. It has now been found that the problem of alkali metal or alkaline earth metal ions has been exhausted, disposal can be reduced by returning it to the reduction vessel, the consumed reaction medium using around there as a reaction medium for the reduction of a a mercury cathode is electrolyzed so that further amount of acrylonitrile can be reused the concentration of inorganic compounds will be.

is reduced and the medium for further, if necessary, the method described

Reductions is suitable. 20 can be performed continuously by using the

As a result, any reaction medium present in the reaction medium will continuously go out of the reduction medium expensive additives are not lost, and the vessel subtracts the product and unreacted In addition, alkali metal or alkaline earth metal starting material is separated off, the aqueous residue in metal cations from the reaction medium are returned to the electrolytic cell and finally won and can then in the form of mercury 25 the aqueous medium from the electrolytic cell amalgams can be reused. returned to the reduction vessel.

The present invention therefore relates to a process.

drive to the reductive dimerization of acrylonitrile voltage of the electrolysis cells for a continuous

to adipic dinitrile in an aqueous medium by means of working method suitable and not on the use

Alkali or alkaline earth amalgam, which thereby becomes a single cell, as described in the present description

is indicated that the organic reduction exercise is explained, limited.

products wholly or partly from the aqueous medium in the reductive dimerization of acrylonitrile separates, this using a mercury, the pH is preferably between 2 and 13, cathode electrolyzed and that formed in particular between 5 and 11, held. The pH alkaline or alkaline earth algam again to the hydro- 35 value can in various ways, z. B. by means of a dimerization of acrylonitrile used. Buffer solution, can be controlled. Suitable buffer

After electrolysis, the mercury cathode can contain salts of polybasic acids, if they are attached to alkali or alkaline earth metal such. B. phosphates, borates and carbonates. the has enriched, useful as an amalgam for the further pH value but can also be done by adding an acid, reductive dimerization can be used. Furthermore, hydrochloric acid, in particular, can be regulated. The salt can the acid separated in the reduction process can be continuously controlled with automatic control Amalgam can be conveniently fed as a cathode for work. Are hydrochloric acid and amalgam in stage are used in which the metal is reintroduced - the same reaction vessel, so happens is won; It is evident that this preferably denotes this in various places. With ver-subject The process forming the invention for 45 turning of hydrochloric acid will convert chlorine ions into the applied a continuous procedure, reaction medium is introduced so that the subsequent can, in which the reductive dimerization electrolysis to the formation of chlorine as a by-product separated amalgam as cathode for the re-leads to the anode.

Extraction of the metal is used, whereupon the acid can be added during the reaction

the amalgam in the further reductive dimeric 50 or with the reaction medium before the reaction

ization is used; in addition, this can be mixed if there is enough

aqueous reaction medium from the reductive dimeric pH control is achieved.

ization as an electrolyte for metal recovery The economy of the process can be increased by and as a reaction medium for the further reductive certain additives, whereby the out-dimerization can be used. In the case of such a volume of adipic dinitrile and the quantities of the method, one or more cells and the undesired by-products produced, such as reaction vessels, can be used. The method z. B. propionitrile or a polymer, reduced can be carried out, for example, in an apparatus. As additives it is possible to use salts which consist of a reduction zone which, in the aqueous medium, can produce organic cations which the aqueous reaction medium contains and the 60, in particular, alkylated cations. You from an electrolytic cell, which include an aqueous, inter alia, alkylammonium, Phos solution of alkali or alkaline earth metal ions ent- phonium and sulfonium salts, especially Tetrahalt, is separated by a mercury layer, the alkylammonium salts, such as. B. Tetraäthylammoniums as cathode for the electrolytic cell as well as chloride. The additives should be chosen as alkali or alkaline earth metal amalgam in the 65 that it works after separation of the organic reduction-reduction zone. products remain in the aqueous medium. When using such a device, they can remain in solution during the electrolysis and can then be reused on one side of the mercury layer without further separation

3 4

will. They must of course be protected against electrolysis. After the extraction, layers A and B will be removed

be constant. in each case to remove the remaining solvent

Other additives can also be present distilled, whereupon layer B is added to the anode vessel

- such as B. alcohol or solubilizer -, a second electrolytic cell similar to the first

if it is fed to the process neither in the reduction vessel 5. The reduction vessel of this second

still disturb in the mercury cell. A device can also contain a fresh filling of reac-

small amount of a polymerization inhibitor, such as tion participants, as they are for the first process

z. B. Ν, Ν-dimethyl-p-nitrosoaniline, added step (reductive dimerization) were used,

the. : ./-./: After an electric current has passed through for 2 hours

For the method according to the invention io of 4 A through the second cell is the content of the

Potassium and sodium amalgams as a special second reduction vessel with the formation of two

proven suitable. . . Layers A ₁ and B ₁ worked up as before. the

The separation of the organic reduction _{pro-layer B 1} becomes the anode vessel of the first cell

products can easily be added in a manner known per se, after the potassium hydroxide

z. B. by distillation or solution extraction the solution has been completely removed. the

Follow. The content of the anode vessel of the second cell is

You can also pull a cell for the electrolysis and use layer A from the first reduction

a flowing mercury cathode. tion stage brought together. This mixture will

A cell with a flowing mercury cathode by distilling off some of the water on the

is particularly useful when chlorine is formed exclusively by weight of the first reaction mixture

will. Then the concentration of the organic acrylonitrile is adjusted. This concentrate will be

Salts in the aqueous medium are reduced, so that the 59.9 g of acrylonitrile is added, and the mixture is in

aqueous medium with the possibly existing reduction vessel of the first device

Additives can be reused. brought to there with the out of the in the anode vessel

The invention is in the following amalgam produced on the basis of 25 phosphate solution

Embodiments explained in more detail. Reaction to come.

The product is isolated as indicated, and the

Example 1 both phosphate solutions are used for further reductions used. .

It is carried out with a device according to Example 1 of FIG. 30. The results are as follows: '

British Patent 1,067,783. The .

inner cylindrical vessel has a diameter first reduction

of 8 cm and a height of 15 cm and is the starting material (acrylonitrile). 59 9 g

ί Sf ^m ^ ^{bStand VOn l} f ™ ^m u ^B ° i ^{n deS & υ} Λ ^{6Γεη Recycled} Acrylonitrile ''.'.':'.'.'.': 41.4 g

Vessel, which consists of a cylindrical trough of 12 cm 35 ^ aj- ■ - j · · · ι ίο

Diameter and a height of 7 cm. In recovered adipic acid dinitrile 15.3 g

the inner vessel protrudes a strip anode made of platinum yield of adipic acid dinitrile, be

Foil 1 cm wide and 10 cm long. In the interior drew on the used acrylic

Reduction vessel, a mixture of 81 g of potassium t is ¹ ^ "! 81 ° / o

dihydrogen phosphate, 18 g potassium hydroxide, 45 g Te- 40 yield of adipic acid dinitrile, loading

traäthylammonium-p-toluenesulfonate, 150 g of water and pulled on current 95%

59.9 g of acrylonitrile, and in the outer, with the platinum. _D,.

anode-provided vessel containing an electrolytic cell ^Second reduction

represents, a 40 percent by weight aqueous (by means of the phosphate solution of the first reduction

Potassium hydroxide solution introduced. Amalgam generated again after 2 hours 45 tion)

Flow of an electric current of 4 A through the yield of adipic acid dinitrile, loading

the cell will extract the contents of the reduction vessel onto the used acrylic

Finally the mercury is deducted, and the nitrile. . 90 ° / ₀

Vessel is rinsed with water, the washing yield of 'adipic acid dinitrile', 'be'-

water added to the withdrawn reaction mixture so moved to stream 92 ° /

will. The mixture is used to remove the acrylic '"°

nitrile and part of the water is distilled. As a third reduction

Residue remains two liquid layers A and ( _only with recovered phosphate solutions)

B. The top layer A consists mainly of. ,. ... .. .. .. ..,

an aqueous solution of tetraethylammonium 55 yield of adipic dinitrile, be

p-toluenesulfonate with most of the used acrylic

Reaction formed adipic dinitrile, while sauremtni yu / ₀

the lower layer mainly consists of an aqueous yield of adiponitrile, solution of potassium phosphate with small amounts drew on electricity 92%

of the quaternary salt and adipic dinitrile 60

consists. The two layers are separated from each other Example 2

separated, and layer A is diluted with water.

The two layers are then each chlorinated into the inner reduction vessel of the device

form extracted, whereupon the chloroform extracts are added according to Example 1, a mixture of 158 g of potassium

brought together and dried. Then 65 dihydrogen phosphate, 6 g potassium hydroxide, 60 g water

the solvent is distilled off. The residue obtained is 80.3 g of acrylonitrile and 240 g of a 25 weight

one a high-boiling product, from which one adipine percent aqueous solution of tetramethylammo-

acid dinitrile isolated by distillation in vacuo. nium hydroxide and one in the outer anode vessel

Claims (1)

5 6 40 weight percent potassium hydroxide solution. The results are as follows: brings. After flowing through one for AO minutes. Electric current of 16 A through the cell is ^{consoling reduction} the content of the reduction vessel excluding the starting material (acrylonitrile) 80.3 g Mercury withdrawn and the vessel with water 5 recovered acrylonitrile ... 47.7 g Rinsed out, the rinsing water with eggs removed Product (adipic acid dinitrile) 14.8 g drawn reaction mixture is mixed. The GE- . ^r . . . ... .. mix is used to remove acrylonitrile, propio- ·. Yield of adipic acid dinitrile, nitrile and some of the water is distilled. At the ^z ? 8 ^e . ^{n on the} used acrylic ^ Analysis found that the distillate was 47.7 g io ^{mtnl 46} / <· Contains acrylonitrile and 1.6 g propionitrile. The distillate yield of adipic acid dinitrile, tion residue is extracted with chloroform. The moved to electricity 69% The extract is dried and the solvent is subjected to 2nd reduction distilled off. The residue obtained is a high-boiling product, from which 14.4 g of adipic acid (using the from the phosphate solution of the first dinitrile obtained by distillation under reduced pressure, reduction of regenerated amalgam) will. The resulting distillation residue weighs, 'Yield of adipic dinitrile, be-1.6 g and, according to the gas analysis, contains on the used acrylic Liquid chromatography 0.4 g adipic acid dinitrile. nitrile 46% The yield obtained after extraction with chloroform as adipic acid dinitrile, aqueous Solution is drawn to the weight of the original draw on electricity 67% borrowed reaction mixture exclusively of acrylonitrile by distilling off part of the water Third reduction set and then into the outer anode vessel of a (only with recovered phosphate solutions) Second device introduced similar to the first. a ₅ Yield of adipic acid dinitrile, be The inner reduction vessel of this second device - _{on the used acrylic} . contains a fresh filling of reaction stellate nitrile 70 ° / as they are for the first step. '· · · · · · · · · ■ _ · · · ·· · · · · · · · / 0 (reductive dimerization) were used. According to the yield of adipic acid dinitrile, 40 minutes long flow of an electrical current 30 subjected to _64/0 Current of 16 A, the contents of the reduction vessel is worked up as described, whereupon the after extraction with chloroform and removal of the patent anorucb. Aqueous solution P · remaining in excess water is placed in the outer anode vessel of the first cell is brought after from this the potassium hydroxide process for the reductive dimerization of solution has been completely removed. The acrylonitrile to adipinitrile in aqueous The content of the outer vessel of the second cell becomes medium by means of alkali or alkaline earth amalgam, peeled off and mixed with 79.5 g of acrylonitrile. This is characterized by the fact that the Mixture is in the reduction vessel of the first cell 40 organic reduction products in whole or in part introduced to there with the separates from the aqueous medium in the anode part, this under Amalgam generated in the vessel's phosphate solution using a mercury cathode electrolytic to be implemented. The product is isolated and sated and the alkali or earth the two phosphate solutions are used again for the hydrodimerization of further alkali metal algam Reduction used. 45 acrylonitrile used.