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Keywords:

  • Beckmann rearrangement;
  • ϵ-caprolactam;
  • conversion;
  • selectivity;
  • microstructured chemical system

Abstract

A microstructured chemical system, constructed with a microsieve dispersion mixer, a delay loop and a microhydrolyzer is designed to carry out the Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam. The system is operated with oleum as the dispersed phase, and cyclohexanone oxime n-octane solution as the continuous phase. The mixing performance, conversion of cyclohexanone oxime and selectivity to ϵ-caprolactam are investigated and the results show that the reaction can be very well controlled due to the formation of microdroplets ranging from 10–25 μm. Under optimized conditions, the reaction can be accomplished with a residence time less than 40 s, and the selectivity higher than 99%. A two-stage technology of low-temperature to induce reaction, and high-temperature to enhance reaction is developed, and the corresponding molar ratio of oleum to cyclohexanone oxime can be reduced to 0.8, which is much lower than the industrial value of 1.2. © 2011 American Institute of Chemical Engineers AIChE J, 2012