Iron-containing MCM-41 catalysts for Baeyer-Villiger oxidation of ketones using molecular oxygen and benzaldehyde

Iron(M)-containing mesoporous silica (MCM-41) with Fe contents up to 1.8 wt% have been prepared by direct hydrothermal synthesis (DHT) and template ion exchange (TIE) methods. Characterizations of these catalysts have been done by XRD, XPS, diffuse reflectance UV-vis, ESR, Mossbauer, and XAFS spectroscopies. Fe species in MCM-41 materials are tetrahedrally coordinated for the DHT method with Fe contents up to 1.1 wt% while those are mainly octahedrally coordinated for the TIE method. Among these catalysts, ferrisilicate and Fe2O3/Cab-O-Sil as references, Fe-MCM-41-DHT exhibited the highest catalytic activity for Baeyer-Villiger (B-V) oxidation of ketones using molecular oxygen and benzaldehyde. The prominent performance of the Fe-MCM-41-DHT could be ascribed to both tetrahedrally coordinated Fe 31 incorporated inside the framework of MCM-41 and its uniform nano-order mesopores allowing the access of bulky compounds to the active sites. Furthermore, this heterogeneous Fe catalyst was reusable without any appreciable loss in activity and selectivity. It has been confirmed by IR spectroscopy that the Fe-MCM-41-DHT catalyzed B-V reaction proceeded via coordination of carbonyl groups of ketone to Fe3+. (c) 2005 Elsevier B.V. All rights reserved.