Physical characterization of [formula omitted] model supported catalysts : I. Electron microscopic studies of reduction behavior

Abstract

The morphology of Fe TiO 2 model supported catalysts has been monitored using transmission electron microscopy following hydrogen reduction at progressively higher temperatures. Nucleation and growth of iron particles from an initially contiguous iron overlayer was observed in the temperature range 608 to 707 K. Following reduction at 773 K, the smaller iron crystallites (less than 10 nm in size) were observed to spread over or wet the support surface, and reduction at temperatures of 875 K or higher extended this spreading behavior to larger crystallites. In addition, reduction at these latter temperatures caused decreases in the average iron particle size and the amount of iron present on the support as distinct iron crystallites. This can be attributed to a diffuse spreading of iron over the support or a diffusion of iron into the support.