Reaction Mechanism and Catalytic Impact of Ni/CeO2–x Catalyst for Low-Temperature CO2 Methanation

Ni supported on calcined ceria nitrate catalyst is highly active and stable for low-temperature CO2 methanation reaction (CO2 conversion: 70% at 180 °C, 0.05 bar, and gas hourly space velocity (GHSV) of 14 400 L kg–1 h–1). We investigated CO2 adsorption and CO2 + H2 reaction on the surface of Ni/CeO2 and Ni/CeO2–x catalysts to examine the structure and strength of adsorbed species using diffuse reflection infrared Fourier transform spectroscopy (DRIFTS). At temperature of 180 °C, weakly adsorbed bridged carbonate was generated on the surface of CeO2–x support by new active sites of oxygen vacancies created by addition of H2. High reducibility of Ni/CeO2–x catalyst played an important role in increasing low-temperature CO2 methanation catalytic activity.