CO2 methanation on γ-Al2O3 nanoparticles from waste aluminium: Effect of Ba promoter on sulfur impurities

The inferior activity of gamma-Al2O3 (GAL1) from the waste aluminium for CO2 methanation was improved using Ba promoter. Ba promoted CO2 conversion to similar to 82% with 100% methane selectivity at 400 C-degrees (Ni-Ba/GAL1), compared to similar to 10% conversion without Ba (Ni/GAL1). Acid digestion of waste aluminium formed residual Al-2(SO4)(3) at similar to 0.5% atomic weight, forming the detrimental NiAl2O4 under reaction conditions. Ba inhibited NiAl2O4 formation by producing BaAl2O4, increasing Ni-Ba/gamma-Al2O3 stability for 50 h at 400 C-degrees. In-situ DRIFTS analysis revealed that NiAl(2)O(4 )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 Ni-degrees 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 gamma-Al2O3 catalytic activity expands its potential use as a catalyst for CO2 methanation.