Stable Mixed Fe-Mn Oxides Supported on ZrO₂ Oxygen Carriers for Practical Utilization in CLC Processes

The objective of the research was to prepare Fe-based materials for use as oxygen carriers (OCs) and investigate their reactivity in terms of their applicability to energy systems. The performance of ZrO2 supported Fe-Mn oxide oxygen carriers with hydrogen/air in an innovative combustion technology known as chemical looping combustion (CLC) was analyzed. The influence of manganese addition (15–30 wt.%) on reactivity and other physical properties of oxygen carriers was discussed. Thermogravimetric analyses (TGA) were conducted to evaluate their performance. Multi-cycle tests were conducted in TGA with oxygen carriers utilizing gaseous fuel. The effect of redox cycle number and temperature on stability and oxygen transport capacity and redox reaction rate were also evaluated. Physical-chemical analysis such as phase composition was investigated by XRD, while morphology by SEM-EDS and surface area analyses were investigated by the BET method. For screening purposes, the reduction and oxidation were carried out from 800 °C to 1000 °C. Three-cycle TGA tests at the selected temperature range indicated that all novel oxygen carriers exhibited stable chemical looping combustion performance, apart from the reference material, i.e., Fe/Zr oxide. A stable reactivity of bimetallic OCs, together with complete H2 combustion without signs of FeMn/Zr oxide agglomeration, were proved. Oxidation reaction was significantly faster than the reduction reaction for all oxygen carriers. Furthermore, the obtained data indicated that the materials have a low cost of production, with superior reactivity towards hydrogen and air, making them perfect matching carriers for industrial applications for power generation