Fe(CO)5, Fe3(CO)12 and [H Fe3(CO)11]− supported on Al2O3 or MgO exhibit after decomposition under CO + H2 a very high selectivity for low molecular weight olefins. Characterisation of the supported complexes before and after decomposition has been carried out using Ferromagnetic Resonance, Mössbauer Spectroscopy, Electron Microscopy and analysis of the gas phase. The behaviour of the precursor carbonyl depends on the water content of the support before impregnation: with dehydroxylated alumina and magnesia, thermal decomposition (T < 200°C) into superparamagnetic very small metal particles (q < 15 Å) occurs. Above 200°C, sintering to particles of higher sizes occurs to a certain extent. With hydroxylated alumina and magnesia, thermal decomposition leads to a mixture of superparamagnetic metallic particles and iron oxides. The oxidation of zerovalent icon is due to surface protons with evolution of hydrogen. The resulting high selectivities for low molecular weight olefins (ethylene, propylene) would result from the low particle sizes of metallic iron generated from zerovalent cluster carbonyls.
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films
- Materials Chemistry