CO₂ methanation over alumina-supported cobalt oxide and carbide synthesized by reverse microemulsion method

High surface area alumina-supported cobalt oxides and carbides were synthesized using a one-pot reverse microemulsion method (followed by carburization for carbides). Two reverse microemulsion synthesis variations gave fine powders having specific surface areas ranging from 178−272 m²/g, consisting of cobalt oxide or cobalt carbide nanoparticles (5−10 nm) dispersed on γ-alumina (10−13 wt% cobalt loadings). The resulted materials were tested for CO₂ hydrogenation. Although all materials (two oxides and two carbides) were catalytically active, only cobalt carbides showed high selectivity to CH₄ formation (up to 99 %), while also being significantly more active and stable than corresponding cobalt oxides (up to 89 % CO₂ conversion for carbides). Investigation by in situ FTIR has shown significant differences in the reaction intermediates indicating different reaction mechanisms of CO₂ hydrogenation on cobalt oxide and cobalt carbide surfaces.