CO2 methanation over nickel-CeO2 catalyst supported on Al2O3: Different impregnation strategies and Ni-Ce ratios

Methanation of CO2 was studied over Ni-CeO2-based catalysts supported on Al2O3 prepared by two different strategies: simultaneous and successive impregnation. The CeO2 addition modifies the interaction of Ni with the support, improving the CO2 conversion and the selectivity to CH4. The catalyst synthesized by simultaneous impregnation of NiO and CeO2 was more active than the catalyst synthesized by successive impregnation. This behavior was associated with the contribution of both oxygen vacancies and Ni-O-Ce solid solution at the surface, inducing a superior reducibility and more labile moderate basic sites. Microstructural analysis confirms the proximity of Ni nanoparticles and CeO2 nanocrystallites, improving the extension of the Ni-CeO2 interface and the activity of the catalyst. The optimal composition of the Ni-CeO2based catalysts was established by testing several catalysts with Ni and Ce contents between 10 and 30 wt% and 10 to 20 wt%, respectively, prepared by simultaneous impregnation. An excellent catalytic performance was obtained for the catalyst with 15 wt% Ni and 15 wt% Ce supported on Al2O3, with high stability after 90 h at 375 °C. The catalytic behavior was explained by the high density of moderate basic sites and the fine-tuning of the Ni-CeO2 interactions.