Study of the dry reforming of methane and ethanol using Rh catalysts supported on doped alumina

Abstract

Various MxOy–Al2O3 oxides (M=Zr, Mg, Ni, Ce, La), prepared by a sol–gel method, were used as supports for rhodium catalysts in methane and ethanol dry reforming. After calcination, the Rh/MxOy–Al2O3 catalysts present BET surface areas between 85 and 208m2g−1. For the CH4 dry reforming, the highest yields in hydrogen are obtained in the following ranking: Rh/NiO–Al2O3>Rh/Al2O3>Rh/MgO–Al2O3≈Rh/CeO2–Al2O3>Rh/ZrO2–Al2O3>Rh/La2O3–Al2O3, not very different from the one for ethanol dry reforming at 800°C which is: Rh/NiO–Al2O3≫Rh/Al2O3≈Rh/MgO–Al2O3≈Rh/CeO2–Al2O3>Rh/ZrO2–Al2O3≈Rh/La2O3–Al2O3, although the reaction temperature is different. For the two reactions, the best catalyst is Rh/NiO–Al2O3 even if it deactivates during the reaction due to carbon deposition. This high activity may be explained by both the presence of the NiAl2O4 spinel phase, avoiding the deactivation of rhodium by migration in alumina, and the high dispersion of Rh favored by the presence of nickel particles at the support surface. Moreover, Ni particles on the support surface also contribute to the activity as demonstrated by the high hydrogen yield obtained in the presence of NiO–Al2O3, which is similar to the one obtained with Rh/Al2O3.