Molybdenum Oxide Supported on Hydroxyapatite-Encapsulated γ-Fe2O3: A Novel Magnetically Recyclable Catalyst for Olefin Epoxidation

Hydroxyapatite-encapsulated magnetic γ-Fe2O3 (HAP-γ-Fe2O3) was synthesized and used as catalyst support. Molybdenum oxide nanoparticles were supported on HAP-γ-Fe2O3 by incipient wetness impregnation (MoOx/HAP-γ-Fe2O3). High-resolution transmission electron microscopy characterization demonstrated the formation of γ-Fe2O3 nanocrystallites with a mean diameter of 1–3 nm within the HAP matrix. The molybdenum oxide dispersed on the surface of HAP-γ-Fe2O3 showed good catalytic activities for the epoxidation of various olefins with tert-butyl hydroperoxide as oxidant. The magnetism of MoOx/HAP-γ-Fe2O3 provided a convenient route for the separation of the catalyst from the reaction mixture by a magnet. The catalyst was recycled at least five times without appreciable loss of catalytic activity.