| abstract |
Caprolactam and hexamethylenediamine are prepared simultaneously starting from adiponitrile by a process in which n (a) adiponitrile is partially hydrogenated to give a mixture containing essentially 6-aminocapronitrile, hexamethylenediamine, ammonia, adiponitrile and hexamethyleneimine, n (b) the mixture obtained in (a) is subjected to a distillation to give ammonia as the top product and a bottom product I, n (c) the bottom product I containing essentially 6-aminocapronitrile, hexamethylenediamine, adiponitrile, hexamethyleneimine, inert compound A and ammonia, the ammonia content being lower than that of the mixture used in stage (b), is subjected to a second distillation to give a mixture comprising the inert compound A and ammonia as the top product and a bottom product II, n (d) the bottom product II is subjected, in a third column, to a distillation to give the inert compound A as the top product and a bottom product III, n (e) the bottom product III is subjected, in a fourth column, to a distillation to give a top product KP1, containing essentially hexamethyleneimine and a bottom product IV, n (f) the top product KP1 is subjected, in a fifth column, to a distillation to give a top product KP2, which contains essentially hexamethyleneimine, and n (g) the bottom product IV containing essentially 6-aminocapronitrile and adiponitrile is subjected, in a sixth column, to a distillation to give 6-aminocapronitrile, n and the 6-aminocapronitrile thus obtained is then cyclized to give caprolactam. |