Kinetics of reduction of supported nanoparticles of iron oxide

A series of catalysts prepared by dispersing iron oxide on supports of different nature and acidity has been studied. Silica (S) and silica-zirconia mixed oxides (SZ) with different ZrO2 content (from 5 to 45 mass%) were used as supports for the iron oxide phase which was deposited over them by an equilibrium-adsorption method. The red-ox properties of the Fe-catalysts were studied by temperature programmed reduction (TPR) technique. The two well defined and narrow TPR peaks observed could be associated with the reduction steps: I) Fe2O3 -> FeO and Fe2O3 -> Fe(0) (at ca. 400°C) and II) FeO -> Fe(0)(at ca. 800–900°C). The temperature of the second-step-peak increased with the zirconia content in the support, likely because of the stronger interaction of the iron oxide phase with the support. Activation parameters for the two step-reduction processes were obtained by a simple computation procedure applied to the TPR profiles.