Chemical looping combustion (CLC) is a novel combustion method that uses oxygen from an oxygen carrier (OC), or metal oxide, to react with a fuel source and produce power/heat and a sequestration ready stream of carbon dioxide. It requires the use of a reactive, robust, inexpensive, and environmentally benign OC. As a result, synthetic OC development has gained interest to improve reactivity while maintaining chemical/physical stability.<br/><br/>A synergetic effect among Cu, Fe, and Mn mixed metal oxides has been demonstrated in previous studies to improve reactivity, however, identifying the bulk phases by X-ray diffraction (XRD) is very challenging due to peak overlaps. Phase identification is vital to understand the altruistic behavior of synthetic mixed metal oxide systems during reduction and oxidation cycles of CLC. In order to differentiate trimetallic copper iron manganese oxide, a systematic study of single, bi-, and trimetallic OCs undergoing simultaneous differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) during temperature programmed reductions in methane was conducted. A unique correlation between the heat flow and corresponding phase formation was identified for the trimetallic copper iron manganese OC. This is remarkable because traditional XRD analysis could not distinguish trimetallic copper iron manganese oxide due to overlapping peaks. In this study, simultaneous (DSC/TGA) performance data from corresponding single and bimetallic oxide systems did not correlate well with the performance data of trimetallic copper iron manganese oxide. As a result, a distinct trimetallic phase was observed from its unique thermochemical properties during reduction by methane. This unique phase formed in the trimetallic oxide system contributed to increased reactivity as demonstrated from the performance data. In addition to phase discovery, the thermochemical data also demonstrated the capability of trimetallic copper iron manganese oxide to promote auto-thermal operation during CLC due to the presence of an exothermic reaction during reduction. It is important to note that the single metal oxide DSC/TGA data exhibited thermochemical data that agreed with calculated heat of reaction data available in the literature and it is difficult to find thermochemical data for new phases formed in the trimetallic systems.

Investigation of unique phase formation for trimetallic copper iron manganese oxygen carrier

253rd National Meeting (2017)

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