Elucidation of metal and support effects during ethanol steam reforming over Ni and Rh based catalysts supported on (CeO2)-ZrO2-La2O3

Hydrogen production via steam reforming of biomass derived oxygenates is a promising environmental alternative to the use of fossil fuels. The ethanol steam reforming reaction is investigated over Ni and Rh based catalysts supported on ZrO2-La2O3 and CeO2-ZrO2-La2O3 mixed oxides, aiming at the elucidation of the role of the metal and the support in the reaction mechanism. Rh versus Ni is shown to be highly active and more selective with no methane production under all conditions studied. CeO2-ZrO2-La2O3 versus ZrO2-La2O3 is shown to promote efficiently the water gas shift reaction, enhancing hydrogen production substantially. Time on stream studies show that the catalysts on ceria containing supports are highly stable, whereas a gradual deactivation was more evident on the ZrO2-La2O3 supported catalysts. TPO analysis of spent catalysts revealed extremely low amounts of graphitic coke deposited on the Rh catalysts. On Ni, and particularly the ZrO2-La2O3 supported catalyst, larger peaks corresponding to both amorphous and graphitic coke were evident, amounting to higher coke production. The combined effects of metal and support make the catalysts on CeO2-ZrO2-La2O3 most suitable for the reaction, with Rh/CeO2-ZrO2-La2O3 showing particularly high activity, selectivity and stability, with minimal CH4 and CO production resulting at the highest H2 yield.