Abstract
Atomically dispersed gold supported on nanoscale ZnZrOx composite oxides was prepared and investigated in this work as a catalyst for the low-temperature ethanol dehydrogenation reactions. The composite ZnZrOx support disperses gold atomically and stabilizes it against growth much better than either of the neat oxides. Sequential ethanol conversion reactions to acetaldehyde and acetone take place on the Au/ZnZrOx catalysts within well-separated temperature windows over the range of tested temperatures (30-400 degrees C). ZnO modulates the acidity of the ZrO2 surface, and the extent of this was followed by isopropanol temperature-programmed desorption with online mass spectrometry (IPA-TPD/MS; and by diffuse reflectance UV-Vis-IR). Catalyst activity and selectivity were tested by temperature-programmed surface reaction (TPSR) and under steady-state reaction conditions. The work has demonstrated that ZnZrOx with optimized ZnO distribution preserves the active Au-O-x surface species under reaction conditions and suppresses undesired dehydration reactions. Addition of gold on the bare zirconia support passivates the acid sites catalyzing ethanol dehydration and introduces desired dehydrogenation sites at low temperatures (similar to 200 degrees C).
