Active Sites of a [B]-ZSM-5 Zeolite Catalyst for the Beckmann Rearrangement of Cyclohexanone Oxime to Caprolactam
[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...
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Published in | Journal of catalysis Vol. 194; no. 1; pp. 122 - 129 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Amsterdam
Elsevier Inc
15.08.2000
Elsevier |
Subjects | |
Online Access | Get full text |
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Summary: | [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%. |
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ISSN: | 0021-9517 1090-2694 |
DOI: | 10.1006/jcat.2000.2928 |