DE1158076B - Process for the production of caprylic lactam - Google Patents

Description

GERMAN

PATENT OFFICE

B57675IVd / 12p

REGISTRATION DATE: 30 A P R I L 1960

NOTICE THE REGISTRATION AND ISSUE '

EDITORIAL: NOVEMBER 28, 1963

It is to rearrange from German Patent Specification 739,259, French Patent No. 893026 and the Journal of Polymer Science, Vol. 3 (1948), page 89, known cyclooctanone oxime with about 94 ^l% sulfuric acid in 75% yield in capryllactam . According to Helvetia Chimica Acta, vol. 16 (1933), p. 1326, capryllactam of insufficient purity is obtained in a maximum of 90% yield if cyclooctanone oxime is rearranged with 85% sulfuric acid at high temperature. The German Auslegeschrift 1 046 623 also describes a process according to which largely pure capryllactam is obtained in high yield from cyclooctanone oxime if the Beckmann rearrangement of the oxime is carried out in the presence of oleum and of substances such as methanol, ethanol, ethylhexanol, ethylene glycol, Benzene, phenol, tetrahydrofuran or cyclohexene. In the known processes, however, difficulties arise in the work-up, especially in the case of continuous operation, which are caused by low yields, additives or polymer formation.

It has now been found that a capryllactam of high purity and good yield can be obtained Beckmann rearrangement of cyclooctanone oxime by means of sulfuric acid at elevated temperature, if you use a cyclooctanone oxime with a water content below 1%, preferably below 0.3%, in the presence of a sulfuric acid whose concentration is between 98% and the concentration of a fuming sulfuric acid with a content of no more than 0.5% free sulfur trioxide is surrounded.

It is surprising that this process gives pure caprylic lactam in good yield, since it is pointed out in the German Auslegeschrift 1046 623 that during the rearrangement of cyclooctanone oxime even when using weak oleum, even with short residence times, the formation of insoluble oligomers and polymers occurs, which reduces the yield of caprylic lactam.

The cyclooctanone oxime which can be used as starting material for the process according to the invention can be prepared and dried according to the usual methods. Preferably one turns to Drying of moist oxime procedures involving only relatively small amounts of the oxime be heated to higher temperatures or where drying at room temperature or only moderately increased temperature on the solid or liquid cyclooctanone oxime using a desiccant Process for the production of caprylic lactam

Applicant:

Aniline & Soda Factory in Baden

Corporation,

Ludwigshafen / Rhine

Dr. Günther Rapp, Lake Jackson, Tex. (V. St. A.), has been named as the inventor

undertakes to exclude decomposition of the thermally unstable cyclooctanone oxime. For example the molten oxime can be dried continuously in a thin film evaporator at reduced pressure will.

For the rearrangement process according to the invention, for. B. 1 part dry cyclooctanone oxime 1 to 2, preferably used 1.5 parts of sulfuric acid, and the rearrangement is conducted at temperatures between 108 and 12O ⁰ C, preferably 111-113 ⁰ C, optionally carried out continuously. The reaction mixture can be worked up in a customary manner. According to the process according to the invention, a capryllactam of high purity is obtained in a yield of at least 95%, which in particular does not contain any oligomers and polymers or other by-products.

The parts mentioned in the following example are parts by weight.

example

In a reaction system filled with 100% sulfuric acid, which is equipped with a mixer and a residence tube that allows residence times of 10 to 30 minutes, are hourly 100 parts of molten cyclooctanone oxime, which in a thin film evaporator to a water content of less than 0.2% was dried, and 150 parts of 100% sulfuric acid continuously fed. The temperature in the reaction system and in the residence tube is kept at 112 ° C. That The reaction mixture flowing out of the residence tube is continuously at a temperature below 50 ° C neutralized. The neutralized reaction mixture is free from oligomers and polymers

; i 309 750/382

Caprylic lactams and contains less than 0.1 percent by weight cyclooctanone and less than 0.1 percent by weight Cyclooctanone oxime. It is extracted with benzene in the usual way. After the abortion of the benzene, the reaction product is distilled under reduced pressure. You get every hour 95.2 parts of caprylic lactam, a pure white, non-yellowing polycaprylic lactam during polymerization results.

Claims (1)

PATENT CLAIM: Process for the preparation of capryllactam by Beckmann rearrangement of cyclooctanone oxime by means of sulfuric acid at elevated temperature, characterized in that a cyclooctanone oxime with a water content below 1% in the presence of a sulfuric acid whose concentration is between 98% and the concentration of a fuming sulfuric acid with a content of at most 0.5% free sulfur trioxide lies, rearranged. Considered publications:
German Patent No. 753 046;
German patent application D 4335 IVo / 12p
(announced on November 15, 1951). © 309 750/382 11.63