(600a) Mixed-Conductor Supported Ferrites for Chemical Looping Conversion of Methane

The chemical looping strategy represents a promising option for carbon dioxide capture from fossil fuels. The chemical looping processes utilize solid oxygen carriers to indirectly convert carbonaceous fuels to concentrated CO₂ and carbon free products via redox reactions. Due to its low cost and abundance, iron oxide is a desirable option as an oxygen carrier. The challenge for iron oxide based oxygen carriers resides in their low activity for methane and solid fuel conversions. Our recent studies have indicated that mixed ionic and electronic conducting (MIEC) oxides, when used as the “support”, can significantly enhance the redox activity of ferrite based oxygen carriers. In the current study, ferrite based oxygen carriers supported with various MIEC perovskites are synthesized. The redox activities of these oxygen carriers are evaluated using a thermogravimetric analyzer (TGA) with H₂ and CH₄ as the reducing gases. The phase structures of these samples, before and after redox reactions, are determined using X-ray diffraction (XRD) and the morphologies of the samples are characterized by SEM. The results confirm the high redox activity of the MIEC supported ferrites. A general correlation between the mixed conductivity of the support and the redox activity of the oxygen carriers are observed. Long term redox reactions and microscopic/spectroscopic characterizations are also carried out to determine relationships between support composition/structure and the long term stability of the ferrite-based oxygen carriers.