Direct Conversion of Carbon Dioxide to Methane over Ceria- and Alumina-Supported Nickel Catalysts for Biogas Valorization

Direct methanation of CO₂ over ceria- and alumina-supported nickel catalysts in the feed stream containing methane and traces of H₂ S is reported. Stability tests for 20 h at 350 and 600 °C with a packed-bed reactor showed high resistance of the catalysts to sintering processes. Higher conversion at 350 °C was observed for ceria supported nickel catalyst. Thermodynamic analysis indicated that CO₂ contained in biogas can be converted to methane without carbon formation under specific reaction conditions. An introduction of CH₄ to CO₂ -H₂ feed stream led to the decrease in CO₂ conversion and CH₄ selectivity. An introduction of the trace amounts of H₂ S into the feed stream led to the fast drop of CO₂ conversion and CH₄ selectivity; higher durability (20 %) was observed for Al₂ O₃ than CeO₂ supported catalysts. An improved performance of catalysts coated onto high-pressure microchannel microreactors for the direct CO₂ methanation reaction applying model biogas mixture was demonstrated.