Inhibition strategies for phase separation of iron-based oxygen carriers in chemical looping gasification- enhanced oxygen transport efficiency through oxide-support interactions

Abstract

Chemical looping gasification partially oxidizes biomass to obtain high-quality syngas using oxygen carriers, emerging as a potential method to cope with energy shortages. However, the oxygen carriers were susceptible to deactivation due to phase separation caused by different migration rates between atoms. In this work, the phase deviation of the oxygen carrier is inhibited by enhancing the lattice oxygen activity. Typically, the NiFe-based oxygen carriers were used as active sites and Ce atoms were introduced to change the lattice structure of the oxygen carriers. Calculated by density functional theory (DFT), Ce atoms formed a strong bonding interaction (Ni-O-Ce) with Ni atoms, causing lattice distortion of NiFe oxygen carriers that promote the formation of oxygen vacancies. Therefore, the syngas yields were increased from 537 ml/g (NF) to 633 ml/g (NF@0.5Ce) and 615 ml/g (NF@1.5Ce) in the N2 atmosphere. The syngas yields were increased from 895 to 1101 ml/g (NF@0.5Ce) and 1186 ml/g (NF@1.5Ce) with steam atmosphere. During the 20-cycle experiments, the phase separation of NiFe-based oxygen carriers was effectively suppressed by the intervention of Ce atoms. Therefore, it is a feasible option to induce lattice distortion of active grains by introducing inert elements to suppress phase separation.