Noncatalytic organic synthesis of ε-caprolactam and decomposition of nylon 6 using supercritical water

Noncatalytic Beckmann rearrangement of cyclohexanone-oxime into epsilon -caprolactam was confirmed to be significantly promoted near the critical temperature in subcritical and supercritical water (scH(2)O). A high-pressure and high-temperature FT-IR was further used to study the reactivities, in which it has been demonstrated that scH(2)O acts effectively in place of conventional acid catalysts. The rate constant for the formation of epsilon -caprolactam significantly increases as the temperature approaches the critical 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 reaction times ranging from 6 to 7 min.