Nanodispersed Fe Oxide Supported Catalysts with Tuned Properties

Catalysts comprising amorphous Fe2O3 nanoparticles dispersed on silica and silica−zirconia are presented. A molecular Fe precursor was grafted on the oxide support surface by an equilibrium−adsorption method. Afterward, calcination of the material produced amorphous Fe2O3 nanoparticles on the oxide support surface. The different nature of the oxide support (Si x Zr1- x O2, 0.715 < x < 1) imparted tunable electronic (studied by UV−vis diffuse reflectance spectroscopy), dimensional (studied by electron paramagnetic resonance spectroscopy, EPR), and redox (studied by thermal programmed reduction, TPR) properties to the samples, with following down toward their catalytic properties. The different support surfaces were covered by the iron oxide phase (from 5 to 10%), constituted of nanosized particles in a narrow size interval (between 2 and 9 nm, studied by EPR line shape and transmission electron microscopy, TEM, analyses). Homogeneous surface distribution was achieved in any case (studied by scanning electron micrographs coupled with energy dispersive X-ray spectroscopy, SEM-EDS). The precise arrangement and nuclearity of the iron oxide nanoparticles on the surface depended on the support nature. Besides, from Fe2O3 nanoaggregates (3d and 2d nanoparticles), the presence of isolated Fe3+ ions in strong interaction with the oxide support was revealed, the amount increasing with the zirconia content in the support.