Aluminium substituted lanthanum based perovskite type oxides, non-stoichiometry and performance in methane partial oxidation by framework oxygen

A series of Rh-promoted La0.75Sr0.25(Fe0.80Co0.20)(1-x)AlxO3-δ (x = 0, 0.10, 0.25, 0.40, 0.60) samples were investigated as oxygen reservoirs for the conversion of CH4 to syngas at 873 K and 1 atm. Neutron powder diffraction studies revealed a decreasing rhombohedral distortion on increasing Al-content. XPS and TEM were employed to investigate surface chemistry and morphology of the Al = 0.25 sample. The influence of Al-substitution on the redox properties was studied by flowing titration whereas catalytic properties were studied by means of transient pulses of CH4 and O2, as well of 13CH4 and CO. The products (CO, H2, CO2 and H2O) of the reaction between CH4 and the studied oxides were successfully tuned by tailoring the redox properties of the reducible oxides through the Al-substitution.