DE1239303B - Process for the production of 1, 2-dicyancyclobutane - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

C 07 c

German class: 12 ο-25

Number: 1 239 303

File number: B 79788 IV b / 12 ο

Filing date: December 18, 1964

Open date: April 27, 1967

The invention relates to a process for the preparation of l ^ -Dicyancyclobutane by thermal dimerization of acrylonitrile.

In Journal of the American Chemical Society, vol. 71, 1949, p. 326, a process for the preparation of 1,2-dicyanecyclobutane by heating acrylonitrile to 195 to 304 ° C. in the presence of hydroquinone is described. The reaction times in this process are V2 to T ¹ Iz hours. The yields are low; they are a maximum of 50/0.

In the German interpretation documents 1081008, 1089 754 and 1103 330 disclose catalytic processes for the production of 1,2-dicyancyclobutane from Acrylonitrile described. Although high yields are achieved by this process, the conversions are are small. The processes have the disadvantage that under the disclosed reaction conditions long response times are required. In addition, the requirement for an inert gas atmosphere is one Difficulty.

The German Auslegeschrift 1146 051 describes a thermal process for the production of 1,2-dicyancyclobutane from acrylonitrile which is superior to the aforementioned process with regard to space-time yields. The dimer is obtained in yields of up to 95% in relatively short reaction times, although these high yields are only achieved with low conversions. The disadvantage is that one is forced to work in technically unusual vessel materials such as glass, silver or platinum, which is very difficult at reaction temperatures of 200 to 300 ° C. and pressures around 100 atmospheres. The reaction can only be carried out in stainless steel vessels if the process is carried out in the presence of water. In order to avoid water accumulation on the acrylonitrile in this case, a very specific pH value must be precisely maintained. The products of water attachment to acrylonitrile have the unpleasant property that they can only be separated from the dimeric acrylonitrile with difficulty. They boil in the same range as the cis-trans dimer mixture. The product obtained is therefore not very pure and cannot be used for many reactions. In addition, water addition reactions are inevitably coupled with poorer yields of acrylonitrile dimers. The separation of water also creates new problems. Another disadvantage of the process arises from the small amount of polyacrylonitrile which is obtained and which is insoluble in the reaction mixture, particularly in processes for production
of 1,2-dicyancyclobutane

Applicant:

Aniline & Soda Factory in Baden
Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Herbert Müller, Frankenthal;

Dr. Emil Scharf, Ludwigshafen / Rhine

continuous process execution, quickly leads to clogging of the apparatus.

The German Auslegeschrift 1146 051 recommends high autogenous acrylonitrile pressures apply, e.g. B. over 150 atm. (Under autogenous acrylonitrile printing, the pressure is understood, which corresponds to the vapor pressure or the partial pressure of the acrylonitrile at the dimerization temperature.) However, if acrylonitrile is heated in the presence of water until such a high If autogenous pressure is set, it is found that the addition of water to acrylonitrile is the main reaction will.

It has now been found that 1,2-dicyancyclobutane can be obtained by dimerizing acrylonitrile elevated temperature and under elevated pressure, optionally in the presence of a polymerization inhibitor, even at high conversion with high efficiency Booty is obtained if the acrylonitrile is added with an addition of 0.1 to 30 percent by weight, in particular from 15 to 20 percent by weight, of a carboxylic acid ester which is inert under the reaction conditions or an ester of an inorganic acid into a known dimerization temperature of 200 to Bringing in a pressure vessel heated to 400 ° C and rapidly cooling the reaction product after dimerization. There are no special purity requirements for the acrylonitrile; however, it should at least correspond to the quality of an industrially produced product, which is generally more than 99.4 per cent is pure. Substances how to stabilize them

709 577/373

of acrylonitrile, e.g. hydroquinone, ammonia or even water, do not interfere.

Practically all esters which are inert under the reaction conditions are suitable as ester additives. H, both organic acids and those inorganic acids, provided they are at the reaction temperature are persistent. Those esters, including acrylonitrile and dicyancyclobutane, are preferred solve the reaction conditions well and under the reaction conditions at least partially in liquid Phase.

Suitable esters are, for example, those derived from alkane mono- or dicarboxylic acids, from benzene mono- or polycarboxylic acids or from aralkanecarboxylic acids on the one hand and from primary or secondary alkanols, alkanediols, alkanetriols or from phenols on the other hand, with either only the acid component or only the alcohol component may be polyfunctional. However, esters of inorganic acids, in particular weak inorganic acids, are also suitable. For example, the following can be used: formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid esters of methyl, ethyl, propyl, isopropyl, isobutyl or benzyl alcohol, succinic acid, glutaric acid, adipic acid ester, benzoic acid, phthalic acid, Isophthalic acid esters of the alcohols mentioned; Esters of polyfunctional alcohols, such as glycol, glycerine, to name but a few, can also be used with good success, and boric acid esters, e.g. B. trimethyl borate, triethyl borate. In general, suitably used such esters, which can be separated by distillation from the resulting 1,2-Dicyancyclobutan in a simple manner, that is, those whose boiling point is outside the range of about 270-320 ⁰ C at atmospheric pressure. However, if the 1,2-dicyancyclobutane is isolated from the reaction mixture by extraction, it is also possible to use esters with a boiling point in the range mentioned without further ado. Esters used with preference are, for example, alkane monocarboxylic acid esters with alkanols containing 1 to 20 carbon atoms in the acid radical and 1 to 20 carbon atoms in the alcohol radical, furthermore alkanedicarboxylic acid esters containing 2 to 10 carbon atoms in the acid radical and 1 to 20 carbon atoms in the alcohol radical, furthermore benzene monocarboxylic acid esters with 1 to 20 carbon atoms in the alcohol radical and benzene di and tricarboxylic acid esters with 1 to 20 carbon atoms in the alcohol radicals, the alcohol radicals in the latter not having to be uniform. Accordingly, compounds such as butyl benzyl phthalate can also be used successfully.

The dimerization takes place at temperatures of 5s 150 to 400 ° C, in particular between 250 and 350 ° C carried out. Thereby, there are autogenous pressures up to 1000 atü, in particular from 100 to 500 atü.

The dimerization is z. B. carried out in such a way that an acrylonitrile ester mixture introduced under pressure into a pressure vessel heated to the reaction temperature, in the case of discontinuous Operation in an autoclave, with continuous operation in a heated high-pressure pipe. the Residence time of the acrylonitrile-ester mixture is usually limited to 1 to ~ 150 minutes, preferably only 10 to 30 minutes. The dwell time is primarily determined by the temperature range in which work is to be carried out. Lower temperatures require longer residence times; at higher working temperatures shorter dwell times are used the end. Since the dimerization takes place exothermically, it may be necessary to provide cooling to keep the dimerization temperature range is not exceeded. To achieve good yields, it is advantageous to to rapidly cool the reaction mixture to a temperature below 200 ° C. after the reaction. One achieves this z. B. by quickly placing the contents of the autoclave in a water-cooled high pressure receiver brings.

All common materials are suitable for the pressure vessels; generally one will use prefer from steel vessels.

The reaction mixture is after cooling, for. B. worked up by distillation. You get a very pure (over 99%) 1,2-dicyancyclobutane. There is a cis-trans isomer mixture.

In the examples below, parts are parts by weight, unless stated otherwise. Parts by weight and volume are in the ratio of grams to cubic centimeters.

example 1

In a steel autoclave preheated to 275 ° C with an effective volume of 1000 parts by volume after displacement of the air with nitrogen from a storage vessel, a mixture of 100 parts Dibutyl phthalate and 600 parts of acrylonitrile, which contains 0.5 percent by weight of hydroquinone is stabilized, pressed. In the course of a minute, an initial maximum pressure of 350 atmospheres and a temperature of 275 ° C. Over the course of 15 minutes the pressure drops to 80 atü. The heat of reaction is dissipated via a cooling coil, whereby the temperature is not allowed to rise above 280 ° C. The reaction mixture is cooled rapidly A brownish colored reaction mixture is obtained, which is separated by distillation. As well as recovered Ester and acrylonitrile 95 parts of 1,2-dicyancyclobutane and 3 parts of residue are obtained, corresponding to a yield of 94.6% of theory l ^ -Dicyancyclobutane, with a m.p. ~ 41 ° C with a conversion of 16.5%. The isomer ratio trans; ice is 1: 1.12 and the purity is 99.8%.

Example 2

As in Example 1, a preheated to 275 ° C is carried out Autoclave a mixture of 90 parts of ethyl acetate and 650 parts of acrylonitrile, stabilized with 0.5 percent by weight hydroquinone, pressed. The initial maximum pressure is 380 atü; he drops to 150 atmospheres in the course of 10 minutes. The temperature is kept at 275 ° C. by cooling. The autoclave is then rapidly cooled to room temperature. After opening you get a yellowish liquid. The reaction mixture is worked up by distillation. Next to Recovered acrylonitrile and ethyl acetate are 90 parts of l ^ -Dicyancyclobutane (Boiling range 100 to 117 ° C / 0.22 cm) as a fine, colorless, crystalline mass with a melting range from ~ 45 to 50 ° C. The purity is 99.4%; the isomer ratio cis: trans is given

1.2: 1, the conversion is 14%, the yield 97.5% of theory.

Example 3

As in Example 1, a mixture of 100 parts is placed in an autoclave preheated to 275 ° C Dimethyl adipate and 600 parts of acrylonitrile, containing 0.5 percent by weight of hydroquinone are stabilized, pressed. The initial pressure drops from 360 atmospheres to 170 atmospheres over the course of 15 minutes. The reaction temperature is kept at 275 ° C. by cooling. After that, the autoclave quickly becomes cooled and obtained a light brown liquid after opening. After separating off the ester and the unreacted acrylic by distillation nitriles 98 parts of l ^ -Dicyanocyclobutane are obtained. The conversion was 17.1%, the yield 95.4%.

Example 4

20th

As in Example 1, a preheated to 275 ° C is carried out Autoclave a mixture of 80 parts of glycol diacetate and 650 parts of acrylonitrile, the are stabilized with 0.5 weight percent hydroquinone, pressed. The pressure drops within 12 minutes from 340 atm to 80 atm. The heat of reaction is dissipated via a cooling coil. It is cooled rapidly and a yellow discharge is obtained after opening the autoclave. The distillative Working up the output gives 89 parts of 1,2-dicyanocyclobutane. The conversion is 14.5% that Yield 94.0%.

Example 5

As in Example 1, a preheated to 275 ° C is carried out Autoclave a mixture of 100 parts of tributyl borate and 600 parts of acrylonitrile, which are stabilized with 0.5 weight percent hydroquinone, pressed in. The initial pressure drops from 345 atmospheres to 90 atmospheres within 15 minutes. The heat of reaction is dissipated via a cooling coil. After 15 minutes, it is quickly cooled to room temperature and that after opening the autoclave resulting yellow reaction product worked up by distillation. There are 90 parts of 1,2-dicyanocyclobutane and 6 parts of residue are obtained, which corresponds to a conversion of 16% and a yield of 94%.

Example 6

In a steel autoclave with an effective volume of 1000 parts by volume, 100 parts Terephthalic acid dimethyl ester presented, and after displacement of the air by nitrogen is the Autoclave heated to 275 ° C. Now 650 parts of acrylonitrile, with 0.5 percent by weight Hydroquinone are stabilized, pressed in. The initial pressure of 300 atm falls over the course of 15 minutes down to 85 atm. The temperature is increased to 275 ° C. by dissipating the heat of reaction held. After 15 minutes, the mixture is rapidly cooled and, after opening the reactor, a yellow discharge obtain. The methyl terephthalate is filtered off with suction, the residue repeatedly with acrylonitrile washed out and the filtrate worked up by distillation. After the acrylonitrile has been separated off 102 parts of 1,2-dicyanocyclobutane and 6 parts of residue were obtained. The conversion is 16.5%, the yield 95%.

Claims (1)

Claim: Process for the production of 1,2-dicyancyclobutane by the dimerization of acrylonitrile at elevated temperature under elevated pressure, optionally in the presence of a polymerization inhibitor, characterized in that the acrylonitrile with an addition of 0.1 to 30 percent by weight, in particular from 15 to 20 percent by weight, one which is inert under the reaction conditions Carboxylic acid ester or an ester of an inorganic acid in a to the known dimerization temperature from 200 to 400 ° C heated pressure vessel introduces and after the dimerization the reaction product cools rapidly. Considered publications:
German interpretation document No. 1146 051. 709 577/373 4.67 © Bundesdruckerei Berlin