FeO controls the sintering of iron-based oxygen carriers in chemical looping CO2 conversion

Abstract

Enhancement of sintering resistance is key to the application of iron-based oxygen carriers in chemical looping CO2 conversion processes. This drives research to seek the origin of iron oxide sintering during redox cycling. Herein, we explored it by using a Fe2O3 material on a stable ZrO2 support, based on a thermodynamic analysis and time-resolved in-situ X-ray diffraction characterization. Sintering of iron oxide particles originates from the formation of FeO as intermediate during reduction. A prolonged FeO presence leads to more severe sintering. Although quite counter-intuitive, increasing the reaction temperature can mitigate sintering as it shortens the transition time between FeO and Fe phases. These findings provide important insight for the rational design of iron-based oxygen carriers, as well as for the optimization of operating conditions to resist sintering in chemical looping processes.