The inferior activity of ?-Al2O3 (GAL1) from the waste aluminium for CO2 methanation was improved using Ba promoter. Ba promoted CO2 conversion to ?82% with 100% methane selectivity at 400 C (Ni-Ba/GAL1), compared to ?10% conversion without Ba (Ni/GAL1). Acid digestion of waste aluminium formed residual Al2(SO4)3 at ?0.5% atomic weight, forming the detrimental NiAl2O4 under reaction conditions. Ba inhibited NiAl2O4 formation by producing BaAl2O4, increasing Ni-Ba/?-Al2O3 stability for 50 h at 400 C. In-situ DRIFTS analysis revealed that NiAl2O4 caused CO2 methanation via CO2 dissociation into CO, followed by high temperature hydrogenation to CH4. Ba promotes catalytic activity and stability of alumina with sulfur impurities by maintaining Nio oxidation states to catalyze CO2 hydrogenation to formate at low temperatures, producing a high methane yield. In addition to transforming waste aluminium into a valuable material, investigation on ?-Al2O3 catalytic activity expands its potential .....

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