Dry reforming of methane over supported Rh and Ru catalysts: Effect of the support (Al2O3, TiO2, ZrO2, YSZ) on the activity and reaction pathway.

The effect of Al 2 O 3 , TiO 2 , ZrO 2 and Yttria-Stabilized Zirconia (YSZ) supports on the activity of the dry reforming of CH 4 towards syngas production was investigated for Rh and Ru catalysts. Ruthenium-based catalysts were found to generally be more active than Rh leading H 2 /CO ratios close to unity above 700 °C. Methane conversion turnover frequency (TOF) over Rh catalysts becomes optimum for Rh/YSZ followed by Rh/TiO 2 and Rh/ZrO 2 , and finally Rh/Al 2 O 3 , which exhibited the lowest activity. The performance order is different for Ru catalysts, with TOF being increased in the order Ru/Al 2 O 3 <Ru/TiO 2 <Ru/YSZ < Ru/ZrO 2. Time-on-stream (TOS) stability tests showed that Rh/ZrO 2 is stable for 30 h, whereas Ru/ZrO 2 exhibits a slight decrease of both reactants' conversions. DRIFTS studies indicated that the reaction proceeds via a bifunctional mechanism involving both the metal and the support in the reaction pathway. The population and adsorption sites of produced carbonyls are strongly influenced by the metal-support combination determining the catalytic activity. [Display omitted] • DRM was studied over Rh and Ru supported on commercially available supports. • TOF of CH 4 conversion becomes optimum over Rh/YSZ and Ru/ZrO 2 catalysts. • 30 h time-on-stream stability was superior on Rh/ZrO 2 compared to Ru/ZrO 2. • DRIFTS revealed a bifunctional mechanism independently of the support used. • The population of linearly adsorbed carbonyls increases as DRM activity increases. [ABSTRACT FROM AUTHOR]