Enhanced performance of red mud oxygen carrier for chemical looping combustion via tandem reactions

Biomethane power generation, particularly chemical looping combustion technology, has garnered significant attention recently due to its ability to capture CO2 in situ. In this study, dual bed layers oxygen carriers (DBL) for chemical looping combustion of methane were designed. The LaFe0.93Ni0.07O3 oxygen carrier with excellent CH4 partial oxidation was applied in upper bed layer and low-cost red mud was located into lower bed layer. This tandem reaction showed much higher methane conversion (87.1 %) than that over the single oxygen carrier of red mud (33.9 %) and the mechanically mixed oxygen carrier of LaFe0.93Ni0.07O3 and red mud (77.7 %). In addition, the mechanically mixed sample showed a quick deactivation, with the methane conversion dropping 54.2 % after 40 redox cycles due to the encapsulation of the active LaFe0.93Ni0.07O3 by red mud, while the double bed system showed high stability in the long-term redox cycle. The limitedly increased crystallite size of LaFeO3, as well as completely replenished lattice oxygen, were responsible for superior activity and stability of DBL. This study provides a new strategy to improve the efficiency of chemical looping combustion of methane in fixed bed reactor by tandem reactions over different oxygen carriers with complementary functions in terms of activity and cost.