Interaction of Methane with Calcium Ferrite in the Chemical Looping Partial Oxidation Application: Experimental and DFT Study

Experimental studies using mass spectroscopy, thermogravimetric analysis, in-situ x-ray diffraction (XRD), and theoretical density functional theory calculations were carried out to investigate the mechanism of methane partial oxidation over a CaFe2O4 oxygen carrier. The XRD analysis revealed the formation of the calcium ferrite phases during methane reduction occurred in the sequence CaFe2O4 □(→┴O^(2-) ) CaFe3O5 + Ca2Fe2O5 □(→┴O^(2-) ) FeO + Fe + CaO □(→┴O^(2-) ) Fe + CaO. Each of these phases were modeled using periodic density functional theory to study the activity of these phases for the reactivity with CH4, CO, and H2 along with the adsorbed surface species to help elucidate the effect that phase changes during reduction have on the chemical looping products CO and H2. Mass spectroscopic analysis revealed the formation of H2O and CO2 occurred prior to the formation of CO and H2, these products may be due to the removal of lattice oxygen bound in the discrete primary phase, which contributes to a sma...