Snia Viscosa Societa Nazionale Industria Applicazioni Viscosa S.p.a.

Snia Viscosa S.p.a.

Domenico Astarita

Paolo Senni

Mario Catoni

A process for the purification of raw caprolactam obtained by extraction h alkylated phenols from its sulphuric solution, re-extraction with water, oxidation preferably with KMnO.sub.4, evaporation of water and distillation, comprises, before the oxidation treatment, a 'fast distillation', in the presence of an alkali. The oxidation is conducted at 0.degree.-80.degree. C. and at atmospheric pressure with 0.005-0.5% by weight of KMnO.sub.4. The amount of alkali (NaOH) used in the fast distillation is comprised between 0.05 and 0.5% by weight.

Process for the purification of raw caprolactam

A process for purifying caprolactame by continuous and/or discontinuous (or atch) vacuum distillation comprises a first stage fast vacuum distillation of the raw caprolactame possibly in the presence of an alkaline and/or alkaline-earth hydroxide, a second stage consisting of a vacuum rectification distillation of the caprolactame obtained in the first stage and a third stage consisting of the fast vacuum distillation of the caprolactame yielded from the second stage, in the presence of an alkaline and/or alkaline-earth hydroxide. The hydroxide amount in the third and possibly the first stage distillation as well varies from 0.05 to 5% preferably from 0.1% to 1%.

Process for the purification of caprolactame

A method for purifying raw caprolactam containing, as impurities, primary amides of the formula ##STR1## R being a hydrocarbon radical having 1-14 carbon atoms, and other by-products is described. 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, (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 phases, (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.

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Segni, Italy

Domenico Astarita