Catalytically Active Sites for the Beckmann Rearrangement of Cyclohexanone Oxime to ε-Caprolactam

• Published in: Journal of catalysis Vol. 186; no. 1; pp. 12 - 19
• Main Authors: Heitmann, G.P., Dahlhoff, G., Hölderich, W.F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 15.08.1999; Elsevier
• Subjects: Catalysis; Catalysts: preparations and properties; Chemistry; Exact sciences and technology; General and physical chemistry; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry; Heterogeneous catalysis; Catalytic reaction; Beckmann rearrangement; Oxime; Catalytic site; Zeolite; Experimental study; Silica; Catalyst; Molecular sieve
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1006/jcat.1999.2552

The rearrangement of cyclohexanone oxime to ε-caprolactam was investigated over heterogeneous catalysts, especially over highly siliceous zeolites with a MFI structure. The aim of this work was to determine the active sites on these catalysts, rather than to optimize their catalytic performance. Amorphous silica and the silicalite-1 zeolite were chemically modified with aqueous acidic or basic solutions. Silicalite-1 was also treated hydrothermally at temperatures above 400°C. Catalytic reactions were carried out with the initial materials and their modifications in a fixed-bed reactor. Characterization of the catalyst with FT-IR, nitrogen sorption, and XRD revealed significant differences and gave important information about the active sites in the reaction. Silanol nests on the external surface of the highly siliceous ZSM-5 zeolite were most suitable for the Beckmann rearrangement.