Selective Production of H₂ from Ethanol at Low Temperatures over Rh/ZrO₂–CeO₂ Catalysts

A series of Rh catalysts on various supports (Al₂O₃, MgAl₂O₄, ZrO₂, and ZrO₂–CeO₂) have been applied to H₂ production from the ethanol steam reforming reaction. In terms of ethanol conversion at low temperatures (below 450 °C) with 1wt% Rh catalysts, the activity decreases in the order: Rh/ZrO₂–CeO₂ > Rh/Al₂O₃ > Rh/MgAl₂O₄ > Rh/ZrO₂. Support plays a very important role on product selectivity at low temperatures (below 450 °C). Acidic or basic supports favor ethanol dehydration, while ethanol dehydrogenation is favored over neutral supports at low temperatures. The Rh/ZrO₂–CeO₂ catalyst exhibits the highest CO₂ selectivity up to 550 °C, which is due to the highest water gas shift (WGS) activity at low temperatures. Among the catalysts evaluated in this study, the 2wt% Rh/ZrO₂–CeO₂ catalyst exhibited the highest H₂ yield at 450 °C, which is possibly due to the high oxygen storage capacity of ZrO₂–CeO₂ resulting in efficient transfer of mobile oxygen species from the H₂O molecule to the reaction intermediate.