to Fe3O4 occurs at lower temperatures of around 300 °C while the reduction to Fe 0 is shifted to significantly higher temperatures between 800 °C and 1000 °C. In addition, a peak broadening occurs at high temperatures. The peak broadening and the high reduction temperature are related to small particle sizes at lower loadings and stronger interactions between the Fe particles and the support favoring the formation of iron aluminates. To ensure complete reduction of the iron catalysts and to maintain the same reduction procedure in all three cases, the reduction temperature was set to 900 °C. The calcined catalyst (a) shows α-Al2O3 reflexes (gray) and Fe2O3 reflexes (red) with lower intensity. The intensity of Fe2O3 reflexes increases with increasing Fe loading. No other iron oxide species were observed. After reduction at 900 °C all Fe2O3 reflexes disappear and the diffraction pattern of Fe 0 becomes visible (orange), indicating complete reduction. The reflexes of Fe2O3, α-Al2O3 as well as Fe 0 are in good agreement with literature data. Figure : a) XRD measurements of the calcined catalysts with 1 wt%, 5 wt% and 10 wt% Fe-Loading. b) XRD measurements of the reduced catalysts with 1 wt%, 5 wt% and 10 wt% Fe-Loading.