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Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam in microreactors

AIChE Journal, volume 56, issue 5, pages 1297-1304

K. T. Zuidhof, M. H. J. M. de Croon, J. C. Schouten. Eindhoven University of Technology, Eindhoven, the Netherlands

Abstract
Selectivities are presented of the Beckmann rearrangement of cyclohexanone oxime to ε-caprolactam with oleum for various conditions in three microreactors, viz., Y-junction, interdigital, and split and recombine mixers, followed by a 50-cm long microchannel of 250 μm internal diameter. Cyclohexanone oxime is dissolved in cyclooctane, which is inert for oleum. The selectivity is measured in the temperature range of 80–132°C. The concentration range of caprolactam in the reaction mixture is 31–41 wt %, in oleum. The total volumetric flow rate is 0.4 ml/min, whereas the flow rate ratio of ε-caprolactam/oleum over cyclohexanone oxime/cyclooctane ranges from 0.3 to 3. The selectivities measured with the three microreactors are: 70–99+%, 93–99+%, and 95–99+%, respectively. High ε-caprolactam concentration (41 wt %), high temperature (110–132°C), and a ratio of free H2SO4 to SO3 of unity have a negative effect on the selectivity.

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