Beckmann rearrangement of cyclohexanone oxime over Silicalite-1: an FT-IR spectroscopic study

The study of cyclohexanone oxime (CEOX) adsorption and reaction into F-caprolactam (CPL) by FT-IR spectroscopy was performed with Silicalite-1 (S-1) as a catalyst. Information of both active sites and reaction mechanism of the Beckmann rearrangement was obtained. At low temperature the physical sorption of CEOX on/in S-1 is the most relevant phenomenon. The accessibility of the internal OH's to the reactant increases at higher temperatures due to an easier diffusion. At 200 degreesC CEOX molecules present inside the zeolite are in proximity of the most acidic OH groups of S-1, the OH nests. The co-operation of more than one OH site transforms CEOX into epsilon-CPL, allowing the right reactant-active site configuration and favouring the stabilisation of the intermediate. (C) 2003 Elsevier Science Inc. All rights reserved.