γ-Fe2O3 nanoparticle in NaY-zeolite matrix: Preparation, characterization, and heterogeneous catalytic epoxidation of olefins

Nano-sized crystals of maghemite iron oxide (γ-Fe2O3) were synthesized onto the surface of NaY-zeolite crystals by immobilizing a polynuclear iron complex [Fe4O2(O2CCH3)7(bpy)2](ClO4) (bpy = 2,2′-bipyridine) and subsequent calcination of the material in oxygen. Superparamagnetic γ-Fe2O3 particles with sizes ∼5 nm were formed on the surface of the zeolite matrix. The nano-composite, γ-Fe2O3@NaY has been subsequently subjected for thorough characterization with several spectroscopic techniques as well as magnetic and transmission electron microscopic measurements. This confirms the formation of maghemite nanoparticles on a NaY-zeolite surface. γ-Fe2O3@NaY shows a remarkable catalytic efficiency in epoxidation reactions with various olefins using tert-BuOOH as oxidant. Notably, styrene shows a remarkable high conversion (90%) as well as epoxide selectivity (95%) while trans-stilbene is completely converted to its oxide with tert-BuOOH over a γ-Fe2O3@NaY catalyst.