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

Direct methanation of CO ₂ over ceria- and alumina-supported nickel catalysts in the feed stream containing methane and traces of H ₂ 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 CO ₂ contained in biogas can be converted to methane without carbon formation under specific reaction conditions. An introduction of CH ₄ to CO ₂ -H ₂ feed stream led to the decrease in CO ₂ conversion and CH ₄ selectivity. An introduction of the trace amounts of H ₂ S into the feed stream led to the fast drop of CO ₂ conversion and CH ₄ selectivity; higher durability (20 %) was observed for Al ₂ O ₃ than CeO ₂ supported catalysts. An improved performance of catalysts coated onto high-pressure microchannel microreactors for the direct CO ₂ methanation reaction applying model biogas mixture was demonstrated.
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