DE1089745B - Process for the preparation of mixtures of terephthalic acid dinitrile and benzonitrile - Google Patents

Description

Process for the preparation of mixtures from terephthalic acid dinitrile and benzonitrile It is known that aromatic nitriles can be obtained from aromatic salts Can produce sulfonic acids by heating with alkyl cyanides. Here arise Nitrites, which correspond to the sulfonic acid residues present in the starting material Have number of C N groups. This method is used, for example, to obtain Benzonitrile from salts of benzoimongsulfonic acid.

Surprisingly, it has now been found that it is possible to use ter (2phthalic acid nitrile in a mixture with benzonitrile dgdureh to produce that the alkali metal salts of 4enzalmonosulfonsäure in the presence of alkali cyanides and v911 ßehWerrnetalleyaniden to temperatures heated above 30.degree. C. and the nitriles are continuously distilled off.

Sodium cyanide is preferably used, which is inexpensive and gives particularly good yields.

Heavy metal gyanides are used for the method according to the invention especially compounds of the metals zinc, cadmium, mercury or iron in question. Both simple and complex cyanides, such as e.g. B. red and yellow Blood liquor salt, dipotassium zirnkeyanide or dipotassium cadmium cyanide can be used. Instead of the heavy metal cyanides, other compounds of these metals can also be used are used, which under the conditions used with alkali metal cyanides convert to heavy metal cyanides.

To achieve good yields, it is necessary to use 1 mol of the sulfonic acid Salt to use at least about 2 moles of alkali metal cyanide, advantageously about 0.2 Moles of the heavy metal cyanide are added. It is useful to have a larger one Use an excess of alkali metal cyanide. A significant improvement in the yield is also achieved if the reaction mixture in addition to the above-mentioned starting materials still graphite potassium is added as a catalyst.

The reaction of the invention is advantageous in the absence of Water carried out. Starting materials that contain water of crystallization, for example the yellow blood liquor salt, must be dehydrated. It is also recommended that the To mix starting materials intimately before the reaction, for example by joint Grinding can be done in a ball mill.

It is advantageous to use inert diluents for the starting materials mentioned to add with a large surface, z. B. bentonite, activated carbon, kieselguhr or fine-grained Sand. These additives prevent the reaction mixtures from sticking together applied high temperatures and facilitate the distillation of the volatile Reaction products. The starting materials mentioned are used to carry out the inventive Reaction heated to a temperature above 300 ° C. Generally give reaction temperatures from about 400 ° C the best yields. The heating is carried out in the manner that the nitriles formed can continuously distill off from the reaction mixture. It is useful in the production of low-volatility nitriles under reduced Pressure to work to facilitate the distillation of the reaction product and to avoid decomposition of the nitrile.

In addition to the dinitrile, the reaction product generally contains one more or less large amount of the corresponding mononitrile.

Working up these mixtures is easy. You can z. B. by fractional distillation take place. In some cases, e.g. B. in the case of terephthalic acid dinitrile, the separation from mononitrile can be carried out very easily due to the fact that the dinitrile is solid at room temperature and mixes with the liquid mononitrile does not mix. Example 1 A mixture of 20.0 g of sodium benzenesulfonate, 35.0 g Sodium cyanide, 5.0 g cadmium fluoride and 50.0 g activated bentonite was in a Retort with a capacity of 250 cm3 is filled and distilled dry until Nothing more condensed in the ice-cold receiver. The distillate became the fractionated Subjected to distillation in vacuo. 2.8 g of benzonitrile and 2.4 g of terephthalic acid dinitrile were obtained obtain.

The above example was repeated, but with the difference that in place of cadmium fluoride 5.0 g anhydrous zinc chloride was added as a catalyst. The yield of terephthalic acid dinitrile was in this case 1.8 g.

The same experiment was carried out with the addition of 5.0 g of mercury chloride - carried out in place of cadmium fluoride. There were 1.6 g of terephthalic acid dinitrile obtain.

Example 2 A mixture of 20.0 g of sodium benzenesulfonate, 35.0 g Sodium cyanide and 5.0 g of cadmium fluoride were ground in a ball mill and off distilled dry in a glass retort. By fractional distillation of the transferred 4.0 g of benzonitrile and 1.5 g of terephthalic acid dinitrile were obtained from the distillate. Example 13 A mixture of 20.0 g of sodium benzenesulfonate, 35.0 g of sodium cyanide, 5.0 g of cadmium fluoride and 5.0 g of graphite potassium were subjected to dry distillation. By fractionation of the distillate, 8.4 g of terephthalic acid dinitrile and 2.4 g of benzonitrile obtained. Example14 A mixture of 20.0 g of lithium benzenesulfonate, 35.0 g of sodium cyanide, 30.0 g of bentonite and 5.0 g of potassium cadmium cyanide was in one Roller autoclave heated to 450 ° C while flushing with nitrogen. The autoclave was about one rotatable glass joint connected to a cooler. The heating continued for so long until no more distillate passed over. The distillate obtained in the cooler consisted of 4.8 g of terephthalic acid dinitrile and 4.8 g of benzonitrile. Example s A mixture of 20.0 g of sodium benzenesulfonate, 20.0 g of sodium cyanide and 10.0 g of anhydrous Potassium ferrocyanide was extracted in the same manner as in Example 4 in a roller autoclave heated to 450 ° C until no more distillate passed over. From the distillate-- 1.8 g of terephthalic acid dinitrile could be isolated.

Example 16 20.0 g of sodium benzenesulfonate, 50.0 g of potassium cyanide and 5.0 g of potassium cadmium cyanide were intimately mixed by grinding and placed in a glass retort Clay 100 cms capacity in an air bath heated to about 400 ° C. The heating was up continued until nothing more condensed in the ice-cold receiver. The distillate was purified by steam distillation and then by fractional distillation decomposed in vacuo. There were 6.0 g of benzonitrile and 0.8 g terephthalic acid dinitrile obtained.

Claims (5)

PArEVTANJPRCCHE: 1. Process for the preparation of mixtures of terephthalic acid dinitrile and benzonitrile, characterized in that the alkali metal salts of benzene monosulfonic acid are used in the presence of alkyl and heavy metal cyanides, optionally with the addition of Graphite potassium, heated to temperatures above 300 ° C and the nitriles formed continuously distilled from the reaction mixture. 2. The method according to claim 1, characterized characterized in that compounds of the metals zinc, cadmium, Uses mercury or iron. 3: Method according to claim 1 and 2, characterized in that that such heavy metal salts are added to the reaction mixture instead of the heavy metal cyanides adds, which under the applied reaction conditions with alkali metal cyanide Implement heavy metal cyanide. 4. Procedure. according to claim 1 to 3, characterized in that that at least 2 moles of alkali metal cyanide are used for 1 mole of the sulfonic acid salt. 5. The method according to claim 1 to 4, characterized in that the heating in the presence of inert solids with a large surface area.