Phase interactions in Mg-Ni-Al-O oxygen carriers for chemical looping applications

- Ni-Mg-Al-O oxygen carriers with equilibrium phase composition were synthesised by from layered double hydroxides precursors.
- The synthesised oxygen carriers showed excellent performance over 100 redox cycles.
- The phase compositions of the oxygen carriers underwent significant changes over the redox cycles.
- The phase segregation of the NiO-MgO solid solution lead to improved reactivity of the Ni2+ during reduction.

Chemical looping combustion offers a solution to achieve carbon capture with minimal energy penalty and significantly reduced NOx formation. The design and synthesis of oxygen carriers play an important role in the advancement of chemical looping combustion. In this investigation, Mg-Ni-Al-O oxygen carriers were synthesised using layered double hydroxides (LDH) as precursors, which facilitate molecular level dispersion of cations in the resulting oxide composites. The behaviour of the synthesised oxygen carriers over 100 chemical looping cycles was studied. The results confirmed the presence of two solid solutions systems: MgO-NiO and MgAl2O4-NiAl2O4, the compositions of which changed over cycles and determined the performance of the oxygen carriers.