Dynamic Methane Partial Oxidation Using a Fe2O3@La_(0.8)Sr_(0.2)FeO_(3-δ) Core-Shell Redox Catalyst in the Absence of Gaseous Oxygen

摘要

Chemical looping reforming partially oxidizes methane into syngas through cyclic redox reactions of an active lattice-oxygen (O~(2-)) containing redox catalyst. The avoidance of direct contact between methane and steam and/or gaseous oxygen has the potential to eliminate the energy consumption for generating these oxidants, thereby increasing methane conversion efficiency. This article investigates redox catalysts comprised of iron oxide core covered with lanthanum strontium ferrite (LSF) shell. The iron oxide core serves as the primary source of latticeoxygen, whereas the LSF shell provides an active surface and facilitates O~(2-) and electron conductions. These core-shell materials have the promise to provide higher selectivity for methane conversion with lower solid circulation rates than traditional redox catalysts. Methane oxidation by this catalyst exhibits four distinct regions, i.e. deep oxidation; competing deep and selective oxidation; selective oxidation with autoactivation; and methane decomposition. Further investigations indicate that the evolution of “loose” lattice oxygen from the bulk contributes to deep oxidation, whereas reduced surface iron species are responsible for selective methane oxidation.