Process for the preparation of -caprolactam

The invention relates to a process for the preparation of -caprolactam starting from 6-aminocaproic acid, 6-aminocaproamide, 6-aminocaproic ester, 6-aminocapronitrile, oligomers or polymers of these compounds or mixtures comprising at least two of these compounds. A process for the preparation of -caprolactam starting from 6-aminocaproic acid, 6-aminocaproamide, 6-aminocaproic ester, 6-aminocapronitrile, oligomers or polymers of these compounds or mixtures comprising at least two of these compounds, which process is performed in the presence of N-(5-carboxypentyl)- -caprolactam and/or derivative thereof in an amount of less than 50 wt. % and more than 0.1 wt. % (based on the total reaction mixture).