Hydrogen by chemical looping reforming of ethanol: The effect of promoters on La2-xMxNiO4-λ (M = Ca, Sr and Ce) oxygen carriers

- Intelligent La2-xMxNiO4-λ OCs possess exceptional self-recovery ability.
- Ca addition promoted reducibility of Ni and regeneration ability of perovskite.
- The growth of perovskite particles is suppressed by the cycle of Ni ions.
- Activity and stability of La2-xCaxNiO4-λ for CLR were found to be high.

Chemical looping reforming (CLR) of ethanol is a novel method to produce hydrogen. It's vital to select an appropriate oxygen carrier (OC) with favorable catalytic activity and high stability for successive redox processes. In current research, the intelligent perovskites La2-xMxNiO4-λ (M = Ca, Sr and Ce) were used as OCs and prepared by co-precipitation method. The 'intelligence' was embodied in exceptional self-recovery ability of perovskite during oxidation stage of CLR process, which was confirmed by the movement that Ni ions escaped and regained back to original position during oxidation step. The experimental result indicated that the movement effectively restrained the growth of metallic Ni and resulted in high activity of OC during life-time service and aging. Furthermore, the influence of promoters doping on the regeneration characteristics of OCs was investigated by BET, TEM, XRD, ICP-OES, TG and a fixed-bed experiment. From the perspective of catalytic performance, the addition of promoter strongly improved the reducibility of OCs, and the optimal substitution is Ca. The LNO-Ca OC exhibited favorable reducibility of nickel ions, shorter 'dead time', higher yield of hydrogen, superior ethanol conversion, stronger anti-carbon ability and excellent reproducibility of perovskite during successive redox reactions.