The iron location in FeSBA- 15 strongly influences the selectivity to dehydrogenation and dehydration in ethanol conversion. At low iron loading, Fe is present as isolated Fe3+ species in the amorphous silica phase. At higher loading additional aggregated forms of iron oxide exist. Isolated Fe3+ species in the silica matrix imply Bronsted acidity resulting in selective formation of ethylene, whereas FeOx clusters catalyze formation of ethylene and aldehyde.