Promotion of CO2 methanation activity and CH4 selectivity at low temperatures over Ru/CeO2/Al2O3 catalysts

• CeO2 particles on Ru/30%CeO2/Al2O3 were small (6.5 nm) and dispersed highly on Al2O3.
• Partial surface reduction of CeO2 on Ru/CeO2/Al2O3 was promoted compared to Ru/CeO2.
• CeO2 on Ru catalysts promoted CO2 reduction to CO via formate species.
• CO methanation was improved over Ru/CeO2/Al2O3 compared to Ru/CeO2.
• Excellent activity of CO methanation over Ru/CeO2/Al2O3 led to high CH4 selectivity.

The effect of CeO2 loading amount of Ru/CeO2/Al2O3 on CO2 methanation activity and CH4 selectivity was studied. The CO2 reaction rate was increased by adding CeO2 to Ru/Al2O3, and the order of CO2 reaction rate at 250 °C is Ru/30%CeO2/Al2O3 > Ru/60%CeO2/Al2O3 > Ru/CeO2 > Ru/Al2O3. With a decrease in CeO2 loading of Ru/CeO2/Al2O3 from 98% to 30%, partial reduction of CeO2 surface was promoted and the specific surface area was enlarged. Furthermore, it was observed using FTIR technique that intermediates of CO2 methanation, such as formate and carbonate species, reacted with H2 faster over Ru/30%CeO2/Al2O3 and Ru/CeO2 than over Ru/Al2O3. These could result in the high CO2 reaction rate over CeO2-containing catalysts. As for the selectivity to CH4, Ru/30%CeO2/Al2O3 exhibited high CH4 selectivity compared with Ru/CeO2, due to prompt CO conversion into CH4 over Ru/30%CeO2/Al2O3.

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