| Summary: | Supported nickel catalysts were synthesized, characterized, and employed in the carbon oxides co-methanation process. Five NiO/CeO<sub>2</sub>-ZrO<sub>2</sub> mixed oxides, with the same Ni content and different Ce/Zr molar ratios, were prepared by the soft-template method. They were characterized through ICP-AES, N<sub>2</sub> adsorption, XRD, and TPR. Reduced Ni/CeO<sub>2</sub>-ZrO<sub>2</sub> catalysts were obtained by submitting the oxide systems to reduction treatment in H<sub>2</sub> at 400 °C. They were characterized by XRD, H<sub>2</sub>-TPD, and CO<sub>2</sub> adsorption microcalorimetry and their catalytic performances in the carbon oxides co-methanation were investigated. Catalytic tests were performed in a fixed-bed continuous-flow microreactor at atmospheric pressure. The effect of experimental conditions (reaction temperature, space velocity, reactants molar ratio) was also studied. Almost complete CO conversion was obtained on any catalyst, whereas CO<sub>2</sub> conversion was much lower and increased with Ce content, at least up to Ce/Zr = 1. The beneficial effect of the Ce content could be related to the increased NiO reducibility and to the higher ability to adsorb and activate CO<sub>2</sub>. However, at high Ce/Zr ratios, it is probably counterbalanced by an interplay of reactions involving CO and CO<sub>2</sub>.
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