PROCESS OF SIMULTANEOUS PREPARATION OF CAPROLACTAM AND HEXAMETHYLENEDIAMINE

The invention concerns the simultaneous preparation of caprolactam and hexamethylene diamine from adipodinitrile, by the following steps: (a) the adipodinitrile is partially hydrogenated, producing a mixture substantially containing 6-aminocapronitrile, hexamethylene diamine, ammonia, adipodinitrile and hexamethylene imine (= "the mixture"); (b) the mixture obtained in step (a) is distilled, producing ammonia, as the forerunnings, and a residue I, in the presence of a compound A which is inert in the distillation conditions, the ammonia not being separated totally; (c) the residue I, substantially containing "the mixture", inert compound A and ammonia, the ammonia content being less than that of the mixture used in step (b), is subjected to a second distillation, producing a mixture of the inert compound A and ammonia, as the forerunnings, and a residue II; (d) the base II, substantially containing "the mixture" and inert compound A, is subjected to distillation in a third column, producing the inert compound A, as the forerunnings, and a residue III; (e) the base III, substantially containing "the mixture" and optionally an inert compound B, is subjected to distillation in a fourth column, producing forerunnings KP1, which substantially contain hexamethylene imine, optionally inert compound B and hexamethylene diamine, and a residue IV; (f) the forerunnings KP1 are subjected in a fifth column to distillation, producing forerunnings KP2, which substantially contain hexamethylene imine and optionally inert compound B, and a residue V, which substantially contains hexamethylene diamine with a degree of purity of at least 95 %, the forerunnings KP2 being fed to the third column or optionally only partially fed to the third column, and the rest being discarded; and (g) the residue IV, substantially containing 6-aminocapronitrile and adipodinitrile, is subjected in a sixth column to distillation, producing 6-aminocapronitrile with a degree of purity of at least 95 %, as forerunnings, and adiponitrile in the residue. The resultant 6-aminocapronitrile is cyclized to form caprolactam.