Ordered mesoporous Co₃O₄-Al₂O₃ bimetal oxides for CO₂ hydrogenation to synthetic natural gas: Effects of surface Al₂O₃ distribution

The highly ordered mesoporous structures of Co₃O₄-Al₂O₃ mixed metal oxide, prepared by using a hard template of the mesoporous KIT-6, revealed a higher catalytic activity and stability for CO₂ hydrogenation to synthetic methane at an optimal surface Al content with ∼6 wt% (m-CoAl(1)). The higher CO₂ conversion (42.5%) and CH₄ selectivity (96.7%) were attributed to the adjusted surface hydrophobicity with optimal amount of spinel CoAl₂O₄ phases, where the CoAl₂O₄ phases mainly acted as structural stabilizing components in the ordered mesoporous Co₃O₄-Al₂O₃ matrices by suppressing the aggregations of Co₃O₄ nanoparticles as well as by generating more hydrophobic surfaces. At an optimal surface Al₂O₃ content (m-CoAl(1)), the stronger interactions of Co₃O₄-Al₂O₃ were selectively formed with the help of an optimal amount of the spinel CoAl₂O₄ phases, which further enhanced the surface hydrophobicity and oxygen vacant sites to effectively suppress competitive adsorption of water formed by CO₂ hydrogenation.