DE1047784B - Process for the production of ª-caprolactam - Google Patents

Description

In technology, ε-caprolactam is mostly obtained by rearrangement of cyclohexanone oxime, which in turn, is produced starting from phenol via cyclohexanol and cyclohexanone or from nitrocyclohexane. It has also already been described, ε-caprolactam from ε-aminocaproamide or from its slightly alkaline cleavable lower acyl derivatives with the help of alkaline to gain reacting substances by heating to the decomposition temperature. As an alkaline accelerator z. B. sodium hydroxide, potassium hydroxide and sodium amide are used. The reaction preferably takes place in diluents, such as ditolyl ether or diphenylamine, or in alkaline melts, in particular melting of alkali salts of lower fatty acids. It can also be used in the presence of inert gases, z. B. nitrogen, to be worked.

It has now been found that ε-caprolactam can be obtained by heating ε-aminocaproic acid amide to the decomposition temperature in the presence of inert gases and solvents can advantageously be prepared in such a way that in the absence of alkaline-reacting decomposition accelerators is operated at pressures of 20 to 150 atmospheres.

Particularly suitable solvents are dioxane, tetrahydrofuran, ethanol or other low-boiling liquids. The main inert gas used is hydrogen or nitrogen. The reaction temperature is between 100 and 300 ° C, but advantageously between 180 and 23O ⁰ C.

It can be assumed that in addition to the reaction of the ring closure of aminocaproic acid amide to lactam under A second reaction occurs, namely the formation of ε-ε-iminodicaproamide, also with elimination of ammonia, but in contrast to the first reaction, from 2 molecules of ε-aminocaproamide.

The formation of ε-caprolactam is strongly preferred over the formation of ε-ε-iminocaproamide.

The formation of this secondary amino compound can be suppressed practically completely, if the Reaction mixture adds ammonia.

The reaction can be carried out continuously in a pressure tube in manner known per se, thereby to obtain yields of more than 95 ° / ₀ to ε-caprolactam.

The absence of alkaline reaction accelerators greatly facilitates the continuous operation.

Method of manufacture
of e-caprolactam

Applicant:
INVENTA AG

for research and patent exploitation,
Lucerne (Switzerland)

Representative: Dr.-Ing. Dr. jur. H. Mediger, patent attorney, and Dr. jur. P. Mediger, lawyer,

Munich 9, Aggensteinstr. 13th

Claimed priority:
Switzerland from April 4, 1955

Dr. Clau Berther, Chur,

and Dr. Johann Giesen, Haldenstein, Chur (Switzerland), have been named as the inventor

example 1

32.5 parts of ε-aminocaproic acid amide are dissolved in 300 parts of dioxane and kept under a hydrogen pressure of 50 atmospheres and 200 ° C. in the autoclave for 90 minutes. After cooling, the reaction mixture is filtered off from the iminodicaproic acid amide which has precipitated and the solution is evaporated. The residue is then distilled at 3 mm. The yield is 92 ° / ₀ of pure lactam (Kp. = ₃ mm 118 ° C) and 5 ° / ₀ Iminodicapronsäureamid. The implementation is quantitative.

Example 2

32.5 parts of ε-aminocaproamide are reacted under the same conditions as those given in Example 1. However, 40 parts of ammonia are added to the starting mixture. The conversion amounts to 82.1 ° / ₀ and the yield of pure lactam 95.2 ° / _0th Iminodicaproamide is only obtained in traces.

Example 3

32.5 parts of ε-aminocaproic acid amide are dissolved in 300 parts of dioxane and ^{kept at 220 °} C. for 60 minutes under a nitrogen pressure of 50 atmospheres. Here, 91.2 ° / ₀ pure lactam and 4 ° / ₀ Iminodicapronsäure obtained in 62.6% conversion.

Claims (2)

Patent claims: 1. Process for the production of ε-caprolactam by heating ε-aminocaproic acid amide Decomposition temperature in the presence of inert gases, preferably hydrogen or nitrogen and solution 809 727/454 3 4 means, characterized in that in the absence of 3. The method according to claim 1 and 2, characterized characterized by alkaline decomposition accelerators that with the addition of ammonia is worked at pressures of 20 to 150 atmospheres. will. 2. The method according to claim 1, characterized in 5 indicates that dioxane is used as the solvent I ⁿ considered publications: will. German patent specification No. 859 015. , © 80S727M54 12.58