Oxygen activity regulation over LaNiO3 perovskites by Ti substitution for chemical looping partial oxidation of methane

The oxygen species in oxygen carriers directly influence the reaction performance in chemical looping processes. This paper describes the relationship between oxygen species and performance in chemical looping partial oxidation of methane (CLPOM) over LaNi x Ti 1- x O 3- δ ( x  = 0, 0.25, 0.5, 0.75 and 1) perovskites . Due to the increase of Ti substitution, the predominate reaction during CLPOM gradually changes from complete oxidation to partial oxidation. Quasi in situ XPS characterization suggests that the relative concentration of nucleophilic lattice oxygen species for partial oxidation increases with Ti substitution, while the relative concentration of electrophilic adsorbed oxygen species for complete oxidation decreases. The moderate Ti substitution for LaNi 0.5 Ti 0.5 O 3- δ provides the suitable lattice oxygen activity for the methane partial oxidation. Moreover, LaNi 0.5 Ti 0.5 O 3- δ exhibits high cyclic stability in redox cycles. This work demonstrates that the regulation of oxygen species distribution and activity is feasible to tailor the reaction performance of oxygen carriers in chemical looping processes.