| 摘要 |
<p>The present invention is directed to a method for purifying raw caprolactum containing, as impurities, primary amides of the formula (I) R being a hydrocarbon radical having 1-14 carbon atoms, and other by-products which are small amounts of aliphatic and aromatic cyclocarboxylic acids, epsilon-aminocapronic acid and unsaturated oxidable substances. The operations, carried out in the following order, consist in (a) treating a solution of raw caprolactam in a water insoluble organic solvent with water to extract most of the caprolactam in purified form, the concentration of raw caprolactam in the organic solvent being comprised between 2 and 12% by weight; (b) separating the aqueous caprolactam solution and isolating the caprolactam, (c) treating the remaining organic solution with mineral acid to cause the formation of two separate phases, the amount of mineral acid being from 0.02 to 0.2 parts by weight per part of raw caprolactam; (d) separating these phases into a heavy phase containing the mineral acid, dilution water and most of the amides and by-products and a light phase containing the organic solvent and any residual amides and by-products, and (e) preferably recycling the light phase to (a). Further object of the invention is the purified caprolactam thus obtained.</p> |
