Verfahren zur Trennung von w-Dodecalactam/Cyclo-dodecancarbonsäure/Schwefelsäure-Gemischen

The invention relates to a method of separating o -dodecalactam from the crude reaction product obtained by treating cyclododecacarboxylic acid with a nitrosylating agent in concentrated sulphuric acid or oleum, decarboxylating the nitrosocarboxylic acid to yield cyclododecanone oxime, and subjecting the latter to the Beckmann rearrangement. According to the invention, the resulting mixture of cyclododecacarboxylic acid, o -dodecalactam and sulphuric acid or oleum is diluted to a sulphuric acid concentration of less than 30% to precipitate a mixture of o -dodecalactam and cyclododecacarboxylic acid, and this mixture is treated with aqueous ammonia, preferably of a concentration below 15%, whereby the cyclododecacarboxylic acid dissolves and the o -dodecalactam remains. Alternatively, the original lactam-containing mixture may be treated with aqueous ammonia directly, whereby ammonium sulphate is obtained as a by-product. In either event, the ammonium cyclododecacarboxylate may be converted into cyclododecarboxylic acid for re-use by heating it to a temperature above 50 DEG C. in the dry state or in aqueous solution, preferably under reduced pressure. Examples are given. Specification 995,723 is referred to.