In situ simultaneous synchrotron powder diffraction and mass spectrometry study of methane anaerobic combustion on iron-oxide-based oxygen carrier

Reduction of iron oxide/CeO₂ solid due to methane anaerobic combustion has been studied using in situ time-resolved synchrotron X-ray powder diffraction and mass spectrometry measurements. All the chemical reactions involved in the process have been mapped. Rietveld profile fitting analysis has given a quantitative estimation of the different phases at every step of the reaction. The reaction temperature has been estimated using thermal expansion of both Fe₂O₃ and CeO₂. From the structural parameters of CeO₂ it has been possible to claim that CeO₂ participates in the reduction process by transforming into a reduced CeO_x form. The number, x, of O atoms per formula unit has been estimated by measuring the percentage variation of the unit-cell parameters.