Combined oxides as oxygen carrier material for chemical-looping combustion with oxygen uncoupling

Oxygen-carrier materials for chemical-looping with oxygen uncoupling (CLOU) must be capable to take up and release gas-phase O2 at conditions relevant for generation of heat and power. In principle, the capability of a certain material to do so is determined by its thermodynamic properties. This paper provides an overview of the possibility to design feasible oxygen carrier materials from combined oxides, i.e. oxides with crystal structures that include several different cations. Relevant literature is reviewed and the thermodynamic properties and key characteristics of a few selected combined oxide systems are calculated and compared to experimental data. The general challenges and opportunities of the combined oxide concept are discussed. The focus is on materials with manganese as one of its components and the following families of compounds and solid solutions have been considered: (MnyFe1-y)Ox, (MnySi1-y)Ox, CaMnO3-δ,(NiyMn1-y)Ox, (MnyCu1-y)Ox and (MnyMg1-y)Ox.