A systematic study on (WO₃)₃ clusters as a model catalyst was performed by the experimental techniques temperature-programmed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS), as well as by density functional theory (DFT) calculations. The model catalyst was prepared by deposition of (WO₃)₃ vapor onto the well-characterized oxide surfaces TiO₂(110) and FeO(111)/Pt(111) in ultra-high vacuum. A series of aliphatic alcohols from methanol to t-butanol were used to identify various partial oxidation channels such as dehydration, dehydrogenation, and alcohol condensation. Our results indicate that the active sites are Lewis acidic tungstyl (W=O) groups where RO-H heterolytically dissociates into alkoxy (RO-) and hydroxyl (HO-). The alkoxy bound to W⁶⁺ undergoes further reactions into alkene, aldehyde, and ether. Dehydration is found to be the dominant channel for secondary and tertiary alcohols, while the other channels compete with dehydration in the oxidation of primary alcohols. The reaction mechanism for each reaction channel is discussed based on DFT calculations.

The research described in this presentation was performed in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory.