Effects of rhodium catalyst support and particle size on dry reforming of methane at moderate temperatures

Dry reforming of methane at 400-600 degrees C was studied over Rh catalysts with different supports (SiO2, gamma-Al2O3, alpha-Al2O3, TiO2, ZrO2, CeO2, Y2O3, SiO2-Al2O3, SiO2-MgO, SiO2-TiO2), Rh particle sizes (1.5-15.6 nm), and acidic properties (acidic site density, 0.37-3.40 mmol g(-1)). Catalysts with a high density of strongly acidic sites (e.g., alpha-Al2O3, SiO2-MgO) showed low activity and gradually deactivated with time on stream; in contrast, catalysts with a low density of strongly acidic sites (e.g., TiO2, gamma-Al2O3) showed high, stable activity. Rh/SiO2-TiO2 showed the best performance, with H-2 and CO yields of 1.8% and 4.2% at 400 degrees C and yields 37.3% and 53.1% at 600 degrees C, respectively. Catalyst activity depended strongly on Rh particle size; specific activity increased with decreasing particle size, indicating that Rh-catalyzed dry reforming of methane is structure-sensitive. The support type influenced not only the dispersion and reducibility of the Rh particles but also the specific activity of the catalysts. CO temperature-programmed desorption and FT-IR suggested that electron-deficient Rh delta+ species were generated by electronic interactions between the Rh particles and the support, and the number of these species strongly influenced the overall catalytic activity.

Automated summary

This study investigated the dry reforming of methane over Rh catalysts with different supports, Rh particle sizes, and acidic properties. Catalysts with a high density of strongly acidic sites showed low activity and gradual deactivation, while those with a low density of strongly acidic sites exhibited high, stable activity. Rh/SiO2-TiO2 showed the best performance, with activity strongly dependent on Rh particle size and support type.