Noncatalytic organic synthesis of epsilon-caprolactam and decomposition ofnylon 6 using supercritical water

Noncatalytic Beckmann rearrangement of cyclohexanone-oxime into epsilon -ca prolactam was confirmed to be significantly promoted near the critical temp erature in subcritical and supercritical water (scH(2)O). A high-pressure a nd high-temperature FT-IR was further used to study the reactivities, in wh ich it has been demonstrated that scH(2)O acts effectively in place of conv entional acid catalysts. The rate constant for the formation of epsilon -ca prolactam significantly increases as the temperature approaches the critica l temperature of H2O. Furthermore, in the flow-reaction system nylon 6 was successfully decomposed to epsilon -caprolactam in scH(2)O at 653 K and 25 MPa, in which the yield of epsilon -caprolactam reached 91% even in short r eaction times ranging from 6 to 7 min.