• ϵ-Caprolactam;
  • Beckmann rearrangement;
  • Cyclooctane solution;
  • Internal recirculation


Beckmann rearrangement of cyclohexanone oxime dissolved in cyclooctane with oleum to ϵ-caprolactam was demonstrated in a microreactor setup with internal recirculation operated in continuous mode. The core of the setup comprised a 316 stainless-steel micromixer consisting of 17 split-and-recombine units connected to a delay loop, a 316 stainless-steel microchannel reactor with an internal diameter of 0.250 mm and a length of 0.50 m. At 100 °C, the conversion of cyclohexanone oxime was complete and the selectivity towards ϵ-caprolactam was approximately 99 %. The solvent cyclooctane reduces the observed purity of the produced oleum/ϵ-caprolactam. This reduction in purity might be a severe hurdle for usage of a solvent on the industrial scale in the Beckmann rearrangement of cyclohexanone oxime in oleum to ϵ-caprolactam.