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Aiming at a mechanistic understanding of the CO and CO 2 methanation reaction over supported Ru catalysts and the underlying physical reasons, we have investigated the methanation of CO and CO 2 over a Ru/zeolite and a Ru/Al 2 O 3 catalyst, in idealized and CO 2 -rich reformate gases by in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) measurements, employing quantitative steady-state isotope transient kinetik analysis (SSITKA) techniques. On the basis of the correlation between CO ad band intensity/CO ad coverage, CH 4,ad /HCO ad /formate band intensity, and the CH 4 formation rate under steady-state conditions, HCO ad is unambiguously identified as reaction intermediate species in the dominant reaction pathway for CO methanation on the Ru/Al 2 O 3 catalyst. On the Ru/zeolite such species could not be detected. CO 2 methanation proceeds via dissociation to CO ad, which is subsequently methanated. Formation and decomposition of surface formates plays only a minor role in the latter reaction, they rather act as spectator species.
Eckle et al. (Tue,) studied this question.