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 $\hbox{Fe}^{3+}$ species in the amorphous silica phase. At higher loading additional aggregated forms of iron oxide exist. Isolated $\hbox{Fe}^{3+}$ species in the silica matrix imply Brønsted acidity resulting in selective formation of ethylene, whereas $\hbox{FeO}_{\rm x}$ clusters catalyze formation of ethylene and aldehyde.