Patent ID: 7208632

Claim:
A method of separating a feed mixture comprising 6-aminocapronitrile (ACN) and hexamethylenediamine (HMD), comprising: introducing a feed mixture comprising ACN, tetrahydroazepine (THA) and HMD into a refined distillation column; and operating the refined distillation column under conditions such that: a refined column distillate comprising HMD is withdrawn from the refined distillation column; a refined column side draw comprising ACN, THA and low levels of dimers of ACN and HMD is withdrawn from the refined distillation column; and a refined column tails comprising ACN, THA and high levels of dimers of ACN and HMD is withdrawn from the refined distillation column, wherein the levels of dimers of ACN and HMD in the refined column tails substantially exceeds the level of dimers of ACN and HMD in the refined column side draw.