Nickel on lanthanum-modified γ-Al₂O₃ oxygen carrier for CLC: Reactivity and stability

This study deals with the development of a lanthanum-modified Ni/La-γ-Al₂O₃ oxygen carrier suitable for a fluidized bed chemical-looping combustion (CLC) process. BET specific surface area analysis shows that the addition of La favors the thermal stability of γ-Al₂O₃ by preventing phase transformation. Temperature programmed characterization shows that the presence of La enhances the reducibility of the oxygen carrier by influencing the metal-support interactions helping the formation of reducible nickel species. Reactive characterization of the prepared oxygen carriers in a Chemical Reactor Engineering Center (CREC) fluidized Riser Simulator, using multiple reduction/oxidation cycles, demonstrates that the Ni/La-γ-Al₂O₃ particles display excellent reactivity and stability. The addition of La in the Ni/La-γ-Al₂O₃ influences the state of the surface minimizing the formation of nickel aluminate. It is argued that the addition of La also inhibits metal particle agglomeration by maintaining consistent metal dispersion during the cyclic oxidation/reduction processes.