Evaluation of the redox capability of manganese-titanium mixed oxides for thermochemical energy storage and chemical looping processes

Manganese oxides are capable of releasing molecular oxygen and regenerate in air under determined conditions. This fact makes these materials interesting for applications in different areas, such as thermochemical energy storage processes, oxygen production by chemical looping air separation (CLAS) or CO2 capture-oriented processes, namely chemical looping combustion (CLC) or chemical looping with oxygen uncoupling (CLOU). In this work, the potential to release molecular oxygen and regenerate in air of different manganese-titanium mixed oxides with mass fractions of titanium from 0 to 50%, were evaluated in a TGA apparatus. Besides, the reactivity of the mixed oxide samples to the main fuel gases (CO, H-2 and CH4) has been also evaluated. Consecutive redox cycles have been performed at different temperatures (850 and 940 degrees C) using nitrogen during reduction and air in oxidation. The oxygen transport capacity as well as the rate index for oxygen uncoupling and gas-solid reactions have been determined and compared to that found for other materials reported in literature. Moreover, solid phase identification in the different mixed oxide samples by XRD has been addressed in order to determine the oxygen release/regeneration mechanism. Results show a great potential of these materials as low-cost and environmentally friendly oxygen carriers.