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

• Published in: ChemPlusChem (Weinheim, Germany) Germany), 2021-06, Vol.86 (6), p.889-903
• Main Authors: Gac, Wojciech, Zawadzki, Witold, Rotko, Marek, Greluk, Magdalena, Słowik, Grzegorz, Pennemann, Helmut, Neuberg, Stefan, Zapf, Ralf, Kolb, Gunther
• Format: Article
• Language: English
• Subjects: biogas; carbon dioxide methanation; heterogeneous catalysis; microchannel reactors; nickel
• ISSN: 2192-6506; 2192-6506
• DOI: 10.1002/cplu.202100196

Direct methanation of CO2 over ceria‐ and alumina‐supported nickel catalysts in the feed stream containing methane and traces of H2S 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 H2S into the feed stream led to the fast drop of CO2 conversion and CH4 selectivity; higher durability (20 %) was observed for Al2O3 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. The high resistance of ceria‐ and alumina‐supported nickel catalysts for sintering and coking in the direct methanation of CO2 in model biogas streams using packed‐bed and microchannel microreactors is reported. Higher activity at low temperatures was observed for the ceria‐supported catalyst (19 wt% Ni). At high temperatures, in the presence of methane and especially sulphur compounds in the feed stream, it lost its favourable properties in favour of alumina‐supported catalysts, especially those with a high Ni content (37 wt% Ni).