Supported Ru catalysts show an exceptionally high catalytic activity and selectivity for the selective methanation of CO (down to &lt;100 ppm) in the presence of large amounts of CO2 (≥ 15%). This makes them attractive candidates for the ultra-purification of H2 for low temperature fuel cells via the Selective CO Methanation (SelMeth). Moreover, this reaction is an ideal case for studying the catalytic performance of Ru catalysts in hydrogenation reactions. Previously it has been established that the selectivity for CO methanation on Ru catalysts is in mainly determined by the Ru particle size, and increases as the Ru nanoparticle size decreases.[1,2] The activity, on the other hand, was found to depend sensitively on the nature of the oxide support.[3] From the comparison of isostructural Ru catalysts (i.e., similar Ru loading, particle size, and surface area) with different support materials we demonstrated that Ru/TiO2 is significantly more active compared to catalysts based on non or hardly reducible oxides (Al2O3, ZrO2, zeolite).[3] The deactivation, however, is more pronounced on these Ru/TiO2 catalysts. Based on time resolved operando XAFS and FTIR measurements in combination with high resolution electron microscopy (HR-TEM), we discuss the origin of deactivation of highly active Ru/TiO2 in the SelMeth. We will in particular try to separate the effects due to structural changes, e.g., changes in Ru particle size / shape and effects caused by the formation of poisoning surface species under reaction conditions. For a more general insight into the origin of deactivation on Ru catalysts, the stability of the isostructural Ru/Al2O3 in comparison to Ru/TiO2 will also be discussed.

Deactivation of supported Ru catalysts during the selective CO methanation (SelMeth): Separating structural and adlayer effects

253rd National Meeting (2017)

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