X-RAY PHOTOELECTRON-SPECTROSCOPY STUDIES OF SOLVATED METAL ATOM DISPERSED CATALYSTS - MONOMETALLIC IRON AND BIMETALLIC IRON COBALT PARTICLES ON ALUMINA

XPS studies of solvated metal atom dispersed (SMAD) catalysts coupled with detailed studies of reference compounds of iron metal, FeO, Fe2O3, Fe3O4, and FeOOH were carried out. It is shown that toluene-solvated iron atoms nucleate at surface OH groups of the A1203 catalyst support. The resultant iron oxide surface species served as nucleation sites for deposition of more iron atoms, leading to very small metallic iron clusters/particles. A thin oxide layer was detected on the particle surface that is believed to come from adventitious oxygen. When toluene-solvated cobalt and iron atoms were allowed to mix and nucleate together, iron reacted with and deposited on surface OH groups first. Then nucleation of Co and Fe occurred together on these surface iron oxide sites, with a slight excess of iron on the inside part of the particle. The iron oxide served as a gradient between the ionic support oxide and metallic iron/cobalt. Mössbauer spectroscopy confirmed the metallic nature of SMAD iron particles (unsupported). © 1990, American Chemical Society. All rights reserved.