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 m(2)/g, consisting of cobalt oxide or cobalt carbide nanoparticles (5-10 nm) dispersed on gamma-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.