Kinetic study on the effect of solvent in 'vapor-phase' Beckmann rearrangement of cyclohexanone oxime on silicalite-1

The effect of solvents in the 'vapor-phase' Beckmann rearrangement of cyclo hexanone oxime was studied on silicalite-1 catalyst through kinetic measure ments. Solvents with various polarities were examined for the reaction. It was found that ethanol, which has medium polarity, was effective in the for mation of epsilon-caprolactam. The rate of epsilon-caprolactam formation fi tted the Langmuir-type rate equation for the various solvents. This experim ental rate equation was explained by the reaction scheme where the desorpti on of epsilon-caprolactam caused by the attack of a solvent molecule was th e rate-determining step. IR measurements confirmed the desorption of epsilo n-caprolactam induced by the attack of the ethanol molecule. Ethanol and me thanol gave specific improvements in the yield of epsilon-caprolactam proba bly due to the effect of OH groups. However, alcohols with higher carbon nu mbers lowered the yield owing to their hydrophobic nature. Therefore, ethan ol and methanol are the most effective solvents for the 'vapor-phase' Beckm ann rearrangement of cyclohexanone oxime on silicalite-1. (C) 2000 Elsevier Science B.V. All rights reserved.