Anchoring Nanosized Iron Oxide into Ordered Mesoporous Alumina as Oxygen Carrier for Chemical Looping Dry Methane Reforming

Chemical looping dry methane reforming (CLDMR) is an emerging technology that facilitates CH4 conversion and CO2 utilization. The efficiency of the CLDMR process largely depends on the performance of oxygen carriers (OCs). This study incorporates iron oxide nanoparticles into mesoporous alumina via postcasting (Fe/MA) and direct-synthesis (Fe-MA). Isothermal CLDMR tests reveal that the Fe/MA OC prepared by postcasting exhibits higher reactivity during the initial 5 redox cycles compared to the directly synthesized Fe-MA OC. However, this trend reverses over the subsequent 15 cycles at both 900 and 850 °C. The initial high reactivity of Fe/MA is attributed to a compensation effect caused by iron oxide nanoparticles enriched near the pore entrances and exits. Unfortunately, these nanoparticles are prone to agglomeration and sintering, leading to a rapid decline in reactivity in later cycles. In contrast, the Fe-MA OC maintains high reactivity throughout all cycles, even at a lower temperature of 800 °C. Both types of OCs show high CO selectivity (98–99%). Nevertheless, the Fe-MA OC yields an H2/CO molar ratio closer to the theoretical value. Overall, the performance of the Fe-MA OC is comparable to or better than those reported in previous studies, demonstrating its promising potential for CLDMR applications.