Hydrogen and Carbon Monoxide Production by Chemical Looping over Iron-Aluminium Oxides

H-2 and CO production from H2O and CO2 is investigated experimentally using a two-step chemical looping process based on the redox cycles of iron-alumina mixed oxides. The reduction of Fe3O4 in the first endothermic step is followed by the splitting of CO2 or H2O in a second exothermic step. The iron-aluminum oxides are more reactive with H2O than with CO2 in the range 650-750 degrees C. Insitu XRD shows that deactivation results from different processes: iron oxide sintering and the formation of spinel (FeAl2O4) with a lower oxygen-storage capacity. However, FeAl2O4 assumes the role of Al2O3 and mitigates the iron oxide sintering. Deactivation at 650 degrees C is governed predominantly by sintering, and the further loss of activity is caused by combined sintering and spinel formation. Spinel formation is more dominant at 750 degrees C. A mixed oxide of Fe2O3 and Al2O3 with a mass ratio of 70:30 was the most active and stable for H2O and CO2 splitting in chemical looping.