Details

Autor(en) / Beteiligte

• Heitmann, G.P.
• Dahlhoff, G.
• Niederer, J.P.M.
• Hölderich, W.F.

Titel

Active Sites of a [B]-ZSM-5 Zeolite Catalyst for the Beckmann Rearrangement of Cyclohexanone Oxime to Caprolactam

Ist Teil von

• Journal of catalysis, 2000-08, Vol.194 (1), p.122-129

Ort / Verlag

Amsterdam: Elsevier Inc

Erscheinungsjahr

2000

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• [B]-ZSM-5 is a very active and selective catalyst for the vapor-phase Beckmann rearrangement of cyclohexanone oxime to ϵ-caprolactam with high selectivities of up to 95% at 300°C and 100 mbar at complete initial conversion. The nature of the catalytically active sites on [B]-ZSM-5 was determined by investigating the influence of postsynthesis modifications, e.g., calcination under air, acid/base treatment, and hydrothermal treatment on the selectivity. Using FT-IR various hydroxyl groups and silanol nests on the surface of the [B]-ZSM-5 zeolites were found to be the active sites for the Beckmann rearrangement. Further investigations concerned the negative effect of adsorbed water on [B]-ZSM-5, which led to a decrease of its catalytic activity. This effect was shown to be reversible and could be explained with the hydration of boron oxide species on the surface. Experiments with as-synthesized and already calcined [B]-ZSM-5 showed the influence of the boron oxide species, which enhanced the conversion compared to the material without extraframework boron from 70% to 98%.