Hydrogen Production from Ethanol over Rh–Pd/CeO₂ Catalysts

The work presents a study by temperature programmed desorption, in situ infra red spectroscopy and catalytic steam reforming of ethanol (SRE) over CeO₂ and the bimetallic Pd-Rh/CeO₂; comparison with the monometallic catalysts (Rh/CeO₂ and Pd/CeO₂) was also made for the steam reforming study. Comparing TPD of ethanol over CeO₂ and the bimetallic catalysts indicated two main differences: the direct oxidation route to acetate over CeO₂ is suppressed by the presence of the metal and the lowering of the dehydrogenation reaction temperature by about 100 K. In situ IR study indicated that the bimetallic catalyst breaks the carbon–carbon bond of ethanol at low temperature <400 K, as evidenced by the presence of adsorbed CO species. SRE over ½ wt.% Rh–½ wt.% Pd/CeO₂, at 770 K at realistic conditions showed that maximum conversion and selectivity could be achieved. This high activity considering the very small amounts of transition metals on CeO₂ is discussed in light of their electronic and geometric effects.