DE1643604C - - Google Patents

Description

The invention relates to a process for the production of adipic dinitrile from the electrolytic hydiodimerization of acrylonitrile reaction gel obtained using an emulated catholyte.

It is known that adipic acid dinitrile by electrolytic hydrodimerization voi. Acrylonitrile produced can be, as in the llSA patent writings 3,193,480 and 3,193,481. Furthermore, a Process for the separation of adipic acid dinitrile from the catholyte in such processes in the U.S. Patent 3,193,477 and Dutch Patent 6,505,391.

In general, the catholyte consists in the elec trolyt'.scher. Hydrodimerization of acrylonitrile au *. Propionitrile, adipic dinitrile, ethylene cyanohydrin, biscyanoethyl ether, acrylonitrile oligomers (mainly 2-CyanäthyIadipinsäuredinitril) and the like., The be. electrolysis. Water, acrylonitrile, a supporting electrolyte and other additives.

It is used for the hydrodimensioning of acrylonitrile preferably an electrolysis cell is used, which is divided by a diaphragm that contains the catholyte separates from the anolyte. When a current is passed through the cell, however, generally find one Migration of water scions from the anolyte to the Catholytes instead. This is accompanied by a transfer of water into the catholyte. The passed over The amount of water is very substantial. Assuming that the conversion of acrylonitrile to adiponitrile Would be 100%, the yield of adipic acid dinitrile is 54 g / Faraday, while that transferred The amount of water is 10 to 50 g / Faraday.

In order to thus keep the electrolysis continuously over a longer period of time optimal composition of the catholyte to achieve good conversion to adipic dinitrile To do this, it is necessary to add water, propionitrile, ethylene cyanohydrin and acrylonitrile oligomers to the The electrolysis formed as by-products, separated from the catholyte and removed from the Dissipate reaction system, while at the same time adiponitrile is deposited as a product. It is also very desirable. Acrylonitrile, the conductive salt and other additives as much as possible for Regain reuse.

The relationships between the vapor pressures of these main components to be separated and their boiling points are given below:

Pressure, mm Hg C. 5 C. 760 150 15th C. C. 77.3 ° C 33 ° C _ C. - C. 97 ° C 52 ° C - C. - 100 ° C 6I ⁰ C 18 ^C C. - 222 ° C 164 ° C 110 ^c 140 ° - 240 ° C 168 ' 160 ° 25O ° C 178 ' 243 ° 270 '

Acrylonitrile

Propionitrile

water

Ethylene cyanohydrin

Adipin uredinitrile

ßUcytnithyl & thcr

2-Cyanathyladipinsäuredinitril

These individual components can be obtained by catholyte in this new process

Separable by distillation, however, result when it is obtained.

Separation and recovery Difficulties depending on the subject of the invention is accordingly a

according to the type and properties of the electrics for the production of adipic acid dinitrile irolysis used electrolyte salts. This enables the electrolytic hydrodimerization of

there are disadvantages, e.g. B. a disruption of the separating acrylonitrile using an emulsify ca

and purification processes, the need for the tholyte obtained reaction mixture that thereby

application of an increased number of rectification columns is characterized that one either

and an inevitable deterioration of the host λ j ,,. . .,. ^. -,. _Λ ,,, ι

h- ftlichkei ^Β a) from the catholyte (2) a portion of the acrylic

D- α w \ u ν. -Ui- uv, - u " ^1O nitrile and water (2S) by rectification

I Λ l NA P, Τ I TtZ IT T- ^Ζ , ^Β · ^abtr cnnt, the remaining soil product (8) in

the, in the USA.-Palentschnft 3193 477 and separates in the oil phase (11) and aqueous phase (10) and

Dutch patent 6 505 391 described adipic acid dinitrile from the oil phase (11) wins

Process, salts are, which have a high solution con-.

may have for acrylonitrile, e.g. B. arylsulfonates than 15 .. ",".. ...., "Conductive salts in the electrolyte used, and one was ^initially the ^b> achst the catholyte (2) directly through AbAnsicht that the desired ad .pinsäuredinitr.l only ^{sctzcn in eme oil} P ^{ha <e <4} and a waßnge can be obtained in high yield when the ^{phase (5) l} ™ ^nt · ~ ^{ne T cl1} ^ "" ^ ί vaßngen hase 6?. , concentration of acrylonitrile in Ka.holyt high overall ^e will hold ^{"lfernl" nd} ^ ^the remaining mixture of the two. Numerous efforts have been ^{"phases (4} * ^S) a) working up ^then accordingly directed · a process for separating A process flow diagram can be found on the Enui Adipinsäuredinitril from such solutions to develop the description, in contrast to the known processes is

For this reason it was in the previously known in the method according to the invention, the addition of a

Process required to convert the catholyte into an oil as the third component to the catholyte not required

phase and to separate into an aqueous phase by separating this into two phases, and the waste

Acrylonitrile and / or water and / or organic vaporization of the water from the aqueous phase can be used in

Solvents, e.g. B. methylene chloride, take place as the first stage of a single stage.

the separation of adipic acid dinitrile from the catholyte The reason for the possibility of such a simple one

is added to the catholyte. 30 mode of operation is made with reference to the previous

Since salts with high solubility are explained for acrylic processes, in which compounds

nitrile are used as conductive salts, also contains genes such as aryl sulfonates, the acrylonitrile and adipin

the oil phase, which in the above-mentioned first dinitrile infinitely with increasing concentration

Stage is obtained, a large amount of the conductive salt. able to resolve these connections, normal

It was therefore considered necessary to use the second form of electrolyte salts in a concentration of normal

If the conductive salt of the oil phase is used more than 30% more often. Through

tion can be removed with water, for example. Furthermore, use of an electrolyte of such a type in

It was considered necessary, as a third stage, the acrylonitrile could with the known high concentration

and propionitrile by distillation from the now process separating '- catholytes into two

separated from the conductive salt freed oil phase. 40 phases not caused by distillates. · Of the catholyte in the

It was also required to be in a separate state, such as that produced by electrolysis, and to be independent of the cows The water can be reached by removing the concentrated soil product, evaporate from the aqueous obtained in the first stage. The distillation therefore had to be independent after the gen phase to remove. Separation of the catholyte into the oil phase and the

In contrast to these known processes, the aqueous phase can be carried out, the processes which are the subject of the In contrast to this, it is also possible in the process according to German patent application P 1 618 066.8 and that of the invention when the from an oil phase is made in German Offenlegungsschriften 1618067 and 1618068 and an aqueous phase consisting of a catholyte in which the applicant is distilled adipic acid dinitrile in a lower state in the electrolysis and reduced yield than in the known processes, possible to produce the bottom product obtained. Deviating from the known process of separating in two phases, since the electrolyte salts in the chamber which the catholyte in the state of a solution tholyte compounds such as sulfates or halides, which hold, these new processes do not have a high dissolving power for acrylonitrile and it can be noted that the electrolysis using adipic dinitrile can be used, a catholyte is carried out which is kept in the state 55 Hs is essential in the process according to the invention to distill the mainly adipic dinitrile and acrylonitrile existing catholyte and contains the obtained, and an aqueous phase consists of separating the main bottom product into two phases, one containing water and a lei salt, the wall-free course of the process in close concentration of the Lcitsalzcs is less than 30 ° / ₀ 60 never depending on the type and the concentration ration.des and the concentration of acrylonitrile both in the conductive salt used, the degree of concentration oil phase aiü is also low in the aqueous phase, the bottom product and the separation temperature without the electrolyte having to be able to produce the in the method according to the invention to increase the solubility of the acrylonitrile in the catholyte. In contrast to the known processes, it is not

It is obvious that for the separation and 65 it is easy to remove the catholyte by adding acrylic

Purification of the adipic dinitrile one of the previously nitrile, water and / or organic solvents,

There are many known processes to separate completely different processes such as methylene chloride

is required to remove the adiponitrile from the advantages, e.g. B .:

5 6

1. The number of stages can be reduced and the temperature of the bottom product can be kept low the way of working becomes easier. can.

,.,. ,,. ·. ,. As mentioned above, the procedure

2. Acrylonitrile water and methylene chloride, the _{äß the invention} the bottom product that be in the catholyte. the known process, ₅ acrylonitrile rectification column is obtained, is set in two phases, then had to be _separated by distillation. _The separation of the bottom product can be separated and recovered in two lation. _{Phasen erfo,.} " _{This Fa} " _{mdem one the floor} . Since this operation is in the process according to the _product , _{“In general, however, an} invention may not be necessary. the amount of _effective separation can be achieved by removing the bottom of the liquid subjected to distillation _{by cooling; Conc} . must be greatly reduced. trations of the water and the dissolved in the oil phase

Since the oil phase and the aqueous phase in the case of Leitsatzes and the concentration of the in the aqueous

drive according to the invention jointly distilled phase of dissolved adipic acid dinitrile are reduced,

can be, there are the following advantages: The aqueous phase obtained here is in a catho-

compared to the known method: 15 lyt container recycled. The oil phase consists mainly

...,. ",., .. r,. λ, mainly from adipic acid dinitrile and water and

1. "The rectification to remove acrylic _{huh one Tei, the conductive salt.}

nitr.l and propionitr.l from the oil phase and the Da purified _{to a sufficiently high degree}

Rectification to remove the water from _Ad j _p j _nssaure dinitril directly by rectification

the aqueous phase can be obtained in a single recti _{ao of the obtained oil hasc k are the}

fiz.erko onne. The number of the _following required addition | _I do not necessarily need to

Stulen can thus be reduced. _{derljch As the example} , _{2 shows, the extra clions} .

2. Since in the process according to the invention a '"fe are omitted, but a combination of large amounts of water together with acrylonitrile nation of various stages, which is distilled below, if a type of water is written, can be even more advantageous, steam distillation acrylonitrile can thus from the removal of the L ^ itsalzes from the oil phase of the ölpUase can be very effectively achieved even at Piner soil by separation of the concentrated temperature to 120 ⁰ C at atmospheric pressure in the bottom product Acryinitril-Rckiifizierkolor.nc from 100th If on the other hand in the known with the help of an extraction with water or a ge-Verfahrcn the acrylonitrile by distillation of the 3o saturated aqueous acrylonitrile solution, which is about 7 is to be removed solely to oil phase, the 11 ° / ₀ acrylonitrile must contain.

Floor temperature 170 to 225 ° C at normal pressure B ^{ei de} n known methods, for. B. in the procedure

be. of Dutch patent 6 505 391, becomes the conductive salt

extracted from the oil phase with water before the

3. Since in the method according to the invention, the ₃₅ acrylonitrile is removed therefrom. In contrast, the bottom temperature during distillation of the acrylic _w j _r d of the invention, the Leitnitrils can be reduced in the method of and the acrylonitrile _sa i _zm j _t of water extracted from the oil phase, after together off with a large amount of water the acrylonitrile has been removed therefrom is. The Verde distilled is used as a polymerization inhibitor of the invention drive according to thus has the advantage, is effective for acrylonitrile, a polymerisation ₄₀ that the amount of _un des acrylonitrile sation to be treated oil phase low during the distillation d operational reliability is higher and that the baffle layer prevented. easy separation in the extraction according to the invention

4. The number of stages can be in which dangerous acrylic achieved while handled nitrile in the extraction with high responsiveness of an oil phase, dw contains a large Acrylnitnlmenge is, in the method of the invention ", in accordance ^{with wat, r} ß ^Rosse Difficulties by reducing the inclination. The process regulation and ^ s ExtrakUonsgemisches for emulsification result

control is therefore made easier. P ^iese ^ ™ "!» «? · ^{??? ™ 1 *» «« «? A} ^ « "" ^{the oil} P ^h **

mainly contains adipic dinitrile.

In the following description of the process, it is useful to set the extraction i> i to a counter

According to the invention, the rectification column will carry out the 50 stream multiple extractor. because here

for the common distillation of the oil phase and an oil phase that does not contain conductive salt, using

aqueous phase is used, for the sake of brevity, a small amount of water is obtained

referred to as "acrylonitrile rectifying column". That can. As countercurrent multiple extractors we.dei

Liquid distilled off from this column preferably consists of the usual systems used, ζ. Β

mainly made of acrylonitrile, water and propionitrile. 55 packed columns, multiple columns, spray towers

However, since it is undesirable that adiponitrile consisting of mixer and settling vessel unit

contained therein, it is convenient to use the rectifying and pulsing columns.

tion in such a way that the higher-boiling adipin- During the extraction, an oil phase, which is not used

acid dinilril cannot pass. Contains conductive salt, and an aqueous phase that there

The above-mentioned acrylonitrile rectifying 60 contains conductive salt. It is appropriate to use this

column can go into the acrylonitrile rectifier not only at normal pressure, but also the resulting aqueous phase

can also be operated under reduced pressure. column, as already mentioned.

The application of reduced pressure has inso- The mixing of ethylene cyanohydrin with the dei

fine advantages than the bottom product obtained without the adipic dinitrile obtained as product can durc Necessity of cooling in two phases separated 65 Use of an adipic acid dinilril stripping colon

can be and that undesirable side reactions (stripped) are prevented. This column diei

ζ. B. the hydrolysis of Adipinsäuredinitril and Acryl- to the Adipinsäuredinitril from the Bodenprodul

nilril, can be easily prevented because the temperature of the adipic dinitrile rec

to separate fizierkoloime and the conditions obtained in this way that the adipic acid

To feed the distillate directly into a separator, which separates the dinitrile as completely as possible from the bottom product.

the adipic acid dinitrile rectifying column can be peeled off, even if the biscyanoethyl ether

te * and the lower-boiling components are thermally decomposed. As a result, there is

separates. 5 so obtained bottom product of adipic acid dinitrile

The stripping column obtained according to the invention by extraction, mainly of acrylonitrile oligoceine containing conductive salt, consists mainly of 2-cyanoethyladipinitrile as mainly of adipic dinitrile, but also contains component and a small amount of the remaining water and a small amount of acrylonitrile as low conductive salt, and the content components boiling on adipic dinitrile. In order to separate these, io in the withdrawn bottoms product is below about 10 ° / _0, the oil phase is introduced into a separator. held. ·

This separator works at a soil temperature. B. when

from 100 to 200 ⁰ C and a_ bubble pressure of 40 to drive the Dutch patent 6 505 391, which by

50 mm Hg. Here, ethylene cyanohydrin is withdrawn from an adipic dinitrile stripping column

by thermal decomposition of the by-product 15 vapors of an adipic dinitrile recitification column

Biscyanäthyläthers formed in the electrolysis are removed, the distillate of the column must be a

stands, distilled off at the same time. Since it is undesirable to add separators for low-boiling components

that the adipic dinitrile are discharged at the same time in order to remove the ethylene cyanohydrin,

a rectification process is recommended. and the bottom product of the separation must be recovered

The bottom product of the separator, in which the adipic dinitrile rectifying column

lower-boiling components are separated off, are given.

Although it consists mainly of adipic dinitrile, in contrast to this, the process according to FIG

however, it also contains impurities, the biscyane invention has the following advantages: The required

ethyl ether and oligomers of acrylonitrile (mainly the number of rectifying columns is lower

borrowed 2-Cyanäthyladipinsäuredinitril), the minor as »5 lower amount of lower-boiling components

products are formed during electrolysis. is mixed with the vapors of the column in which the

The adipic dinitrile has to be rectified by rectification, which is difficult to rectify adipic dinitrile.

be separated from the bottom product. If this is fected, the column can easily go under

Rectification can be held in a single rectification unit in a high vacuum, is to be made, the bottom product consists of 30 Since the vapors of the separator for lower

this column consists mainly of 2-cyanoethyl-adipin-boiling components mainly of water

acid dinitrile and biscyanoethyl ether. If the remainder exist and a lesser amount of materials,

amount of adipic acid dinitrile in the to be withdrawn as low-boiling and difficult to condense

Bottom product, for example, should be below 10 ¹ V ₀ , contain sizing acrylonitrile, the column can

the bottom product must be kept slightly under high vacuum at a temperature above 35, and the

220 ⁰ C kept under high vacuum below 5 mm Hg lower boiling components can be effective

will. At this high temperature and this will be removed.

The vapors from the acrylonitrile rectification column are

Biscyanithyläthers introduced to acrylonitrile and ethylene cyanogen in a propionitrile separator and that

hydrin instead, their mixing with the product to 40 propionitrile after rectification as a bottom product

is feared. withdrawn together with water.

The boiling point of adipic acid dinitrile is The vapors of the acrylonitrile rectification column are

180 ⁰ C at 25 mnvHg and 160 ° C at 10 mm Hg. To stand mainly from acrylonitrile, water, propio |

To solve the above problem, nitrile and ethylene cyanohydrin become. From this accumulate

two columns are used, namely one column for 45 water, propionitrile and ethylene cyanohydrin in the ca-

Rectification of adipic dinitrile (hereinafter called tholyte) so that it can be withdrawn from the system

as adipic dinitrile rectification column must bezeicfaiet). It is undesirable to have dax |

and an adipic dinitrile stripping column that stripped the acrylonitrile off, thereby removing the total

Adipic acid dinitrile exhaustively from the 2-cyanide is deteriorated in adipic acid dinitrile, separates ethyladipinitrile, which is the main one. As acrylonitrile has the lowest of these substances

component of the soil product. The distillate that has boiling point will be that of the acrylonitrile

accrues from the adipic acid dinitrile stripping column, rectification column vapors withdrawn to a pro

is fed to the separator for pionitrile separators described above, in which a soil pro

the lower-boiling components fed. duct, which is mainly made up of Wasseil

In the process according to the invention, there is therefore propionitrile and ethylene cyanohydrin

the bottom temperature of the adipic dinitrile recti contains little acrylonitrile.

fizierkolonne chosen so that the ethylene cyanohydrin, In contrast to this, in the known process

the by thermal decomposition of Biscyanäthyl- ren, in which the oil phase and the aqueous phase, dii

ether is formed, is not obtained at the top of the column by treating the catholyte

goes. The bottom temperature of Adipinsäuredinitril- 60 can not be distilled together, sowoli

The rectification column is therefore lower than the one acrylonitrile rectification column for removal d | Bottom temperature of the Adipinsäuredinitril-Abstreifko- Acrylnitriis from the oil phase as well as an evaporation

ton, and the Adipinsäuredinitrilgchalt the soil to evaporate the water from the aqueous Pha

products is held high. This soil product required The adipic acid dinilnil stripping column is pulled

leads. Propionitrile into the oil phase fiber. It's dating at

The adiponitrile stripping column is reciprocated known methods ear removal of Propi

visibly of the vacuum and the soil temperature under nitrile and water from the system necessary, <i |

i 643 604 _

^ ίο

Vapors of the acrylonitrile rectification column consist of a white and ethylene cyanohydrin, but contain no adipinter rectification for the separation of the acrylonitrile dinitrile. In a separator 9, the propionitrile is subjected to. At the same time a bottom product 8 after settling with or without rectification column is required to win the acrylonitrile cooling in an oil phase 11 is an aqueous phase and 10 from de "vapors separated from the water. 5 The aqueous phase 10 is withdrawn in the Katholytverdantpfer and a small amount of acrylic container 1. Since the oil phase 11 contains conductive salt contain an amount of nitrile, this phase is introduced into an extractor 12 to remove the conductive salt the following advantages: moderate, a continuously working countercurrent

lo multiple extractor 12 to be used. In this case

1. Since the number of rectification columns required, the oil phase 11 is abandoned at the foot of the column, is less. the investment costs are lower. while water or part of the saturated aqueous

, _ .. ,,. , _. , "Ι, ·., ·· !. Acrylonitrile solution32, which is contained in a cooler and

2. The process control and control is easier. separator 30 is obtained, and / or part 28 of the

is bottom product 27 of a Propionitrii separator 26

The bottom product of the propionitrile rectification agent dissolved as an extractant at the top of the column in the process according to the invention can be allocated. Both solutions are countercurrent be thrown after it is partially merged as an extraction. An oil phase 13, agent has been used in the gene extractor. which contains no conductive salt, at the top of the column and The top product of the column consists mainly of an aqueous solution 15 containing conductive salt at the foot made of acrylonitrile and water. After the condensation of the column withdrawn. The one containing the conductive salt it separates into two phases, of which a mainly aqueous solution 15 is introduced into the acrylonitrile rectifier mainly composed of acrylonitrile and the other mainly column 7.

consists of water. The oil phase 13, which is freed from the conductive salt, is mainly made of acrylonitrile

existing phase is for reuse in »5 separator 16 for low-boiling components returned to a catholyte container. The main-fed. In this column 16 are at the same time A phase consisting mainly of water can be found in the vapors 24 of an adipic acid dinitrile stripping column Recirculated extractor and introduced as extractant 22. From the separator 16 for lower be re-crvvcndct. boiling components becomes a distillate 17, the

For a better understanding of each of the above-mentioned stages, mainly composed of water, acrylonitrile and ethylene, a number of these cyanohydrates are subtracted overhead below. It is Steps described in connection with the figure, expediently, in the separator 16 for lower boiling points which is a flow sheet of a preferred embodiment components to carry out the rectification so represents form of the invention. Of course, the invention is that the distillate contains as little adipic acid dinitrile as possible The application does not apply to this specific embodiment. The distillate 17 is used as the feed solution 34 of the restricts. Acrylnüril rectifier column or as a feed solution

In a catholyte container 1, a catholyte 2 33 is fed to the propionitrile separator 26. If this held under such conditions that the oil phase uses distillate 17 as feed solution 34 or 33 and the aqueous phase is in the form of an emulsion. With will, depends mainly on the adipic acid or without additional treatments such as heating, 40 dinitnlmengc contained in the distillate 17. Centrifugation and filtration to separate the oil If the adipic dinitrile content of the distillate 17 phase of the aqueous phase in the catholyte 2 is low, this is preferably used as a feed solution this is fed to a catholyte separation container 3. used for the propionitrile separator. The oil phase 4 and the aqueous phase 5, which are here The bottom product 18 of the separator 16 for low

are separated, are combined and together a 45 lower-boiling component is fed to the adipic acid-acrylonitrile rectifying column 7. Dinitrile rectification column 19 is fed in here. The adipine is expedient, and part of the acid content in the separator 3 is withdrawn from the top of this column as a proteparent aqueous phase 6 into the catholyte container 1 product 28. That is to be returned at the foot of the column, that the amount of the solution that the bottom product 21 consists mainly of Acrylonitrile rectification container 7 is supplied, is 50 adiptnsäiaedinitril, biscyanäthytälher and 2-Cyanringer. However, as an important feature of the Erfin- athyladipinsäuredinitrü.

tion consists in the fact that the oil phase and the aqueous The bottom product 21 is an Adrpinsäure-

The catholyte phase is fed into an acrylonitrile rectifying dinitrile stripping column 22. It is appropriate to give up the column and be banded together, to remove the bottom product 23 from the column, and the cathoryte separating vessel 3 does not necessarily have to be raised after its adipic acid dinitrile content Required, but the Kathoiyt 2 can direct the to less than 10 · /. has been lowered. The bottom Acrylniiril rectifying column 7 are fed. product mainly consists of Acrytaitrilohgo-

In the Acrylonitrfl-RektinzJerkolonne 7 is also meres (mainly 2-cyanoethyl ether), Biscyanathyi the extract, d. H. an ether and conductive salt obtained in the extractor 12, which are not removed in the extractor Aqueous phase 15, which introduces the conductive salt. Has turned 60. The distillate 24 of adipic acid dinitrile In certain cases a distillate 34 is added to the stripping column 22 to the separator 16 for low a separator 1 * for components with lower boiling components, neateti supplied to Dk Dampfe 25 der Aarylnitrfl-Rektions & ierkokjnne '

The r \ opk> nitriKAbschekfcr 2 *; nig Führi..Voi falls through the acrylonitrile rear crater 7 When the vapors 25 are distilled off from the used «5 this separator becomes a liquid 27, the main Solution a bottoms product. The rectification consists of water, propionitrile and ethyl cyanohydride is made so that the transferred contains, deducted from Bodenptodukt. Because e * purpose Vapors 25 mainly from acrylonitrile, propionitrile is moderate, so that the soil product as little as possible

1 643

Contains acrylonitrile, the rectifloral will accordingly accomplished.

The vapors passing from the propionitrile separator 26 are condensed by cooling and in a cooler and separator 30 into an oil phase 31 consisting mainly of acrylonitrile and a mainly Aqueous phase 32 consisting of water separated. The oil phase 31 is the catholyte container 1 fed. The aqueous phase 32 is used as an extractant in the extractor 12.

The conductive salt in the catholyte used in the method according to the invention must be able to concentrated bottom product obtained by distillation of the oil phase and the aqueous phase Catholyte obtained is separated into two phases. Various supporting electrolytes can be used for this alone or used as a mixture, and the degree of concentration of the kaiholyte and the concentration of the conductive salt in the catholyte can be selected accordingly. As a Leitsake, which the aforementioned own * o Have shaft are preferably sulfates, halides, monomethyl sulfates and monoethyl sulfates used.

The pure charge potential of the cation of the conductive salt is preferably less than the potential at which the acrylonitrile is converted into adiponitrile will. Therefore, quaternary ammonium ions, Ammonium ions and alkali metal ions are preferred.

So that the electrolysis over a longer period of time in one remains stable state, an anionic polymerization inhibitor is preferably added, as in the German patents mentioned at the outset, or it is a known inhibitor of the Radical polymerization of acrylonitrile added.

In order to stabilize the emulsion from the oil phase and the aqueous phase in the catholyte, emulsifiers can be used animal, vegetable and various other synthetic viscous substances are added.

The concentration of the Lat salt in the catholyte is preferably less than 30%, since the conductivity of the catholyte in general its maximum in the concentration range of the conductive salt from 10 to 30 percent by weight reached in the aqueous phase and the aqueous Ftiase must be concentrated later. However, a concentration above 30% can also * 5 be applied.

The concentration of acrylonitrile in the catholyte and the ratio of the oil phase to the aqueous phase in the catholyte are selected as a function of the adipic acid dinitrile yield of the electrolysis, the conductivity of the emulsion and taking into account the fact that the amount of acrylate to be handled in the separation sand cleaning process is selected as possible be low soD. The optimal values depend on the type of guiding principle, but in general the acrylonitrile concentration in the oil phase is less than 50 * / * the acrylonitrile concentration in the aqueous phase is less than 5 * / * and the proportion of the oil phase in the catholyte is less than 50 * / «-

So

example 1

In an electrolysis, which is carried out according to the process shown in the flow diagram, eme came Emulsion as a catholyte for use, the aqueous phase and oil phase of which had the following composition:

Composition of the aqueous phase in the catholyte

Acrylonitrile?., 0%

Propionitrile 0.2 ° / ₀

Ethylene cyanohydrin traces

Adipic acid dinitrile 5.6%

Acrylonitrile oligomers 0.2%

Traces of biscyanoethyl ether

Water 74.0%

Conductive salt 18.0%

(Tetraethylammonium sulfate 16.0%

Hexamethylene diamine sulfate 2.0%)

pH 4

Composition of the oil phase in the catholyte

Acrylonitrile 23.2%

Propionitrile 2.1%

Ethylene cyanohydrin traces

Adipic acid dinitrile (Ί5.3%

AcTyl nitrile oligomers 2.7 "'"

Biscyanäthyläther 0.2 ":"

Water (<',.

Conductive salt O.j ', · ,,

(Tetraethylammonium sulfate OJ 'V ₀

Hexamethylene diamine sulfate 0.2%)

The weight ratio of the aqueous phase to the oil phase in the catholyte was 75:25. Some of the catholyte was removed and, after allowing it to settle in the catholyte separator 3, separated into two layers. 3 parts of the oil phase and 1 part of the aqueous phase were mixed and added to the acrylonitrile rectifying column. The bottom temperature of this column 7 was kept at 110 ^° C. under normal pressure. The bottom product was stripped, cooled to 30 ⁰ C and separated by settling in the oil phase and the aqueous phase had the following compositions:

Composition of the oil phase

Acrylonitrile 0.1%

Propionitrile traces

Ethylene cyanohydrin traces

Adipic acid dininitrile 90.7%

Acrylonitrile oligomers 3.9%

Biscyanoethyl ether 0.2%

Water 3.8%

Conductive salt 1.2%

Composition of the aqueous phase

Acrylonitrile traces

Propionitrile traces

Ethylene cyanohydrin traces

Acrylonitrile oligomeric traces

Biscvanäthvläther traces

Adipic acid dinitrile 3.0%

Water 53%

Conductive salt 44 · /.

The aqueous phase was returned to the catholyte container and the oil phase was introduced into the continuous packed extraction column 12 working in countercurrent. At the head of the extra! tor, the saturated aqueous aa yl oil solution 3! those obtained in the cooler and separator 30 were abandoned from the extraction agent. The amount of drawn extraction cuts was a third! d Amount of the oil phase used from the head d

Extractor, an oil phase was withdrawn, which the had the following composition and contained little conductive salt:

Acrylonitrile 1.9%

Propionitrile traces

Ethylene cyanohydrin traces

Acrylonitrile oligomers 3.8%

Biscyanoethyl ether 0.2%

Water 3.9%

Conductive salt 0.02%

Adipic acid dinitrile 90.2%

The oil phase was in the separator 16 for lower boilers Components at a floor temperature of 15

180 ⁰ C and a bubble pressure of 40m! NHG rectified At the same time became the Destillat24

Adipic acid dinitrile stripping column 22 of the solution,

which was used in the separator 16, in an acrylonitrile amount of about one twentieth the amount of ao propionitrile rectified in the bladder to obtain a bottom product of the following composition:

Acrylonitrile traces

Propionitrile 10.3%

Ethylene cyanohydrin 0.2%

Adipic acid dinitrile traces

Water 89.5%

Example 2

In the process shown in the flow diagram, an emulsion was used as catholyte2, the consisted of an aqueous phase and an oil phase of the following composition:

Aqueous phase

g g g de

oil phase 13 used added. The Destiaat of the adipic acid dinitrile stripping column had the following to composition:

Ethylene cyanohydrin.
Adipic acid dinitrile ..
Acrylonitrile oligomers
Biscyanoethyl ether ...

water

Sodium sulfate

PH value

1.0%

Save

sense

3.0%

sense

86%

10%

oil phase

24% 12%

Tracks 56%

3%

0.1%

5.0% 0.005%

., Sense

Ethylene cyanohydrin 1.6%

Adipic acid dinitrile 40%

biscyanoethyl ether 7%

2-cyanoethylajipic acid dinitrile 50%

The weight ratio of aqueous phase to oil from the separator for low-boiling composite phase in the catholyte was 60:40. A part! of the cathonent A bottoms product 18 with the following lytes was removed and allowed to settle

separated in the catholyte separator 3. 4 parts of the oil phase and 1 part of the aqueous phase were mixed and introduced into the acrylonitrile rectification column 7. 35

Composition deducted:

Ethylene cyanohydrin 0.02%

Water 0.03%

Acrylonitrile 0.01%

Adipic acid twist 93.3%

Acrylonitrile oligomers ■ 6.0%

Biscyanäthj ether 0.6%

Conductive salt 0.03%

The bottom product was fed to the adipic dinitrile rectifying column 19, from which adipic dinitrile of a purity of more than 99.7% was obtained as a product. Simultaneously, a Bodenprcdukt the following composition was obtained at the bottom temperature of 200 ⁰ C and the bubble pressure of mm Hg:

Adipic acid dinitr ¹ 26%

Acrylonitrile oligomers 73%

Biscyanoethyl ether 0.7%

The column was maintained at a 7 Bocentemperatur of 108 ⁰ C and under atmospheric pressure. The bottom product formed in this column was drawn off, cooled to 40 ° C. and separated into the oil phase and the aqueous phase by settling, which had the following composition:

45

Acrylonitrile

Propionitrile

Ethylene cyanohydrin
Adipic acid dinitrile.
Acrylonitrile oligomers
Biscyanoethyl ether ...

Water ,

Sodium sulfate

oil phase

0.2% trace trace 89.0% 4.8% 0.15 x /. 5.7% 0.01%

Aqueous phase

Traces traces traces 0.16% traces traces 68% 32%

Bottoms 21 were in the adipic dinitrile stripping column 22 at a floor temperature

of 215 ° C and a bubble pressure of 4 mm Hg The aqueous phase was in the catholyte

Vaporized. ^ Here a bottom product 23 of the 55 was returned. The oil phase was taken directly to the separator 16 for lower-boiling components Bypassing the extractor shown in the flow diagram given because it contained little conductive salt. To Treatment of this phase in the Adipinsäuredinitril-60 rectifying column 19 and in the Adipinsäuredinitril-

received the following composition:

Adipic acid dinitrile 4.7 "/ 0

Acrylonitrile oligomers 93.1%

Biscyanoethyl ether 1.5%

Conductive salt 0.7 ° /

In the meantime, the distillate was 25 of the acrylonitrile rectifying column in the propionitrile separator 26 at a bottom temperature of 100 ° C. and normal pressure Stripping column 22 at the same bottom temperature and at the same pressure as in Example 1 was Obtained adipic dinitrile with a purity of more than 99.7%.

1 sheet of drawings

Claims (6)

Patent claims: 1. Process for the production of adipic acid dinitrile from the electrolytic hydrodimerization reaction mixture obtained from acrylonitrile using an emulsified catholyte, characterized in that one either a) part of the acrylonitrile from the catholyte (2) and separating the water (25) by rectification, the remaining bottom product (8) separates in oil phase (11) and aqueous phase (10) and adipic acid dinitrile from the oil phase (Jl) wins or b) first the catholyte (2) directly by settling into an oil phase (4) and an aqueous one Phase (5) separates, part of the aqueous Πase (6) is removed and the remaining mixture the two phases (4, 5) then accordingly a) worked up. 2. Method according to claim 1, characterized in that the aqueous phase (10) is separated off oil phase (11), the adipic acid dinitrile, Was ^ r and conductive salt en'häit. with water or one aqueous solution of acrylonitrile (14) and extracted the adiponitrile from the purified oil phase (13) wins. 3. The method according to claim 1 or 2, characterized in that one of the oil phase (Ii) The separated aqueous phase (10) is returned to the catholyte emulsion (1) and the adipic acid dinitrile. Oil phase (11, 13) containing water and Lt salt by distillation into one of water, Acrylonitrile and ethylene cyanohydrin existing overhead product (17) and an adipic acid dinitrile, Bottom product (18) containing biscyanoethyl ether and acrylonitrile oligomers separates from this Bottom product (18) separates pure adipic dinitrile (20) overhead by rectification, from the remaining bottom product (21), the adipic acid dinitrile, biscyanoethyl ether and acrylonitrile oligomers contains, separates a vapor fraction (24) and in the distillation of the oil phase (11) and the remaining acrylonitrile oligomers, biscyanoethyl ether and electrolyte salt residues containing Removes liquid as bottom product (23). 4. The method according to claim 3, characterized in that one part of it ^ it distillate (25) Water and acrylonitrile (29) distilled off over the head and propionitrile and water as ais Bottom product (27) withdraws and the other part of the distillate (29) cools and turns into an acrylonitrile phase (31), which is returned to the catholyte emulsion (1) and into a saturated one with acrylonitrile aqueous phase (32, 14), which is used to extract the oil phase (11), separates. 5. The method according to claim 3 or 4, characterized in that the entire distillate (25) by distillation in propionitrile ind water as the bottom product (27) and water and acrylonitrile as Top product (29), which is returned to the catholyte emulsion (1), separates. 6. Process according to Claims 3 to 5, characterized in that the top product (29) withdrawn water-acrylonitrile mixture cools and in the acrylonitrile phase (31) and in the with acrylonitrile saturated aqueous phase (32) separates.