A series of Rh catalysts on various supports (Al2O3, MgAl2O4, ZrO2, and ZrO2-CeO 2) 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 H 2 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.
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Acknowledgements This work was supported by Department of Energy’s Office of Hydrogen, Fuel Cells, and Infrastructure Technologies. Most of work was performed in the Environmental Molecular Science Laboratory, a national scientific user facility sponsored by the U.S. Department of Energy’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory in Richland, WA.
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