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High Resolution Image Download MS PowerPoint Slide The CO 2 methanation process in the presence of CO is a catalytic challenge toward the abatement of CO 2 emissions from industrial exhaust gases with the goal of producing CH 4 as a clean fuel. Herein, the CO x methanation mechanisms of a NiO-CeO 2 (Np) catalyst constituted by nickel oxide-cerium oxide nanoparticles with efficient operation under CO 2 and CO + CO 2 gas mixtures were addressed. In situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) analyses and 13 C 18 O 2 (49) pulse isotopic experiments reveal that solo CO 2 methanation and comethanation (CO + CO 2 ) present a common mechanism in which CO 2 is transformed into *CO, from where the reaction proceeds. According to our outputs, inlet CO interferes with the CO 2 methanation activity, delaying the reaction onset without selectivity impacts. Conversely, in the absence of CO 2, the solo CO methanation performance is remarkably limited with poor CH 4 selectivity. As demonstrated, the solo CO methanation mechanism is based on formates as key intermediates at low temperatures (<250 °C), while competitive CO 2 production takes place onward. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) analyses conducted in synchrotron revealed a higher degree of reduction in the catalyst when CO and H 2 are fed either alone or in combination with CO 2, attributed to the CO oxygen abstraction capacity from the CeO 2 phase. In the comethanation mixture, CO 2 and CO are balanced in oxidation–reduction processes, yielding the maximum CO x conversion, while in the solo CO methanation, reductive processes prevail, limiting the CH 4 formation.
Martínez‐López et al. (Sat,) studied this question.