Chemical looping steam reforming of methane over Ce-doped perovskites

Abstract

Chemical looping steam reforming of methane (CL-SRM) has emerged as an attractive pathway on H2O splitting for H2 production. However, this process still faces a major challenge in efficiently producing H2 with high redox kinetics and yields. In this paper, the promoting effects of Ce3+ substitution into LaFeO3 redox catalysts on thermochemical H2O splitting as well as partial oxidation of methane are presented. An appropriate amount of Ce3+ substitution in A site of LaFeO3 (La0.5Ce0.5FeO3) promotes the lattice oxygen conversion rate in methane partial oxidation step and boosts the reaction kinetics in H2O splitting step by enhancing the surface water activation and lattice oxygen mobility of the perovskite. In the CL-SRM process, the perovskite is reduced into Fe0/(La0.5Ce0.5)2O3 and Fe0/(La0.5Ce0.5)O2-x phases in methane partial oxidation step and recovered to the original perovskite structure in H2O splitting step with simultaneous production of hydrogen, which maintains a reversible phase transformation during 100 redox cycles. As a result, the La0.5Ce0.5FeO3 achieves high stability with the superior performance for syngas and hydrogen production. These findings provide the fundamental understanding on the synergy between the catalytic sites and enhanced lattice oxygen mobility for the promotion of H2O activation and hydrogen productivity in chemical looping process.