Bayer Aktiengesellschaft

Jurgen Schroter

Hans-Walter Brandt

Friedhelm Steffens

Kurt Bauer

Bernd-Ulrich Kaiser

Harry Danziger

Guido Rampart

With the extraction method, a material exchange column with an ordered packing 2a or 2b on the basis of a plurality of layers 3 stacked parallel to the column axis and making point contact with one another is used. The packing 2a, 2b is perfused by a continuous and a dispersed phase in a counter current. The packing has a very large specific surface area of at least 300 m.sup.2 /m.sup.3 of packing volume. At the periphery of the packing 2a, 2b, the two phase streams are re-circulated into the packing at regular intervals through a rim seal composed of an elastic material not wettable by the dispersed phase. The rim seal is placed round the packing in the form of an elastic tube or pipe and seals the intermediate space between the internal column wall and the packing. A further improvement in the separating capacity can be achieved if pulsating operation is adopted. The method is characterized, in particular, in that an approximately constant high separating capacity is achieved with a high throughput per unit area over a relatively large loading tolerance of the column.

Method of liquid-liquid extraction using material exchange columns

A process for the purification of a solution of .epsilon.-caprolactam in benzene, toluene or xylene by washing with a liquid, wherein the washing liquid is a solution of .epsilon.-caprolactam in water in a weight ratio of from 15 : 1 to 1 : 3, which is used in a quantity of from 5 to 20% by weight, based on the solution of caprolactam in benzene, toluene or xylene, and wherein there are several washing stages so that the equilibrium between the two solutions can be readjusted.

Purification of .epsilon.-caprolactam

Process for the separation or purification of heat-sensitive compounds by carrier-vapor distillation, wherein the superheated solvent vapor which is loaded with the compound to be distilled is cooled by treatment with condensed solvent in counter-current and the amount of condensed solvent is measured in such a manner that a saturated solution of the compound which is almost at boiling point is formed from the superheated, loaded vapor. The process being especially apted for separating or purifying 4-hydroxybenzaldehydes optionally substituted by one or more C.sub.1 -C.sub.4 -alkoxy groups.

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Krefeld, Germany

Jurgen Schroter