Exploring the stability of Fe2O3-MgAl2O4 oxygen storage materials for CO production from CO2

Abstract The stability of Fe 2 O 3 -MgAl 2 O 4 oxygen storage materials (OSMs) was investigated over 1000 redox cycles using H 2 as reductant and CO 2 as oxidant. Three different materials, with a nominal Fe 2 O 3 amount of 10 wt%, 30 wt% and 50 wt%, were evaluated. Characterization techniques such as N 2 adsorption, XRD and STEM-EDX were applied to study the evolution of morphological and crystallographic properties. XRD results show that Fe is incorporated in the MgAl 2 O 4 lattice of the as prepared materials, yielding a Mg-Fe-Al-O spinel structure. After redox cycling, part of Fe still remains within the spinel. The results of redox cycling reveal superior properties for 10Fe 2 O 3 -MgAl 2 O 4 , exhibiting stability in terms of morphology and, with an average space-time yield of 700 mmol CO s −1 kg Fe −1 , the highest activity among the OSMs studied. However, 50Fe 2 O 3 -MgAl 2 O 4 performs best in terms of overall CO yield, i.e. 0.6 mol CO kg OSM −1 , more than twofold higher compared to 10Fe 2 O 3 -MgAl 2 O 4 and 30Fe 2 O 3 -MgAl 2 O 4 even after 1000 cycles. Deactivation through sintering occurs in all three materials, though to a lesser extent for 10Fe 2 O 3 -MgAl 2 O 4 . Phase transformation to a Mg x Fe 1-x O phase predominantly causes a loss of oxygen storage capacity in 30Fe 2 O 3 -MgAl 2 O 4 and 50Fe 2 O 3 -MgAl 2 O 4 .