Selective oxidation of ethanol over Ag, Cu and Au nanoparticles supported on Li₂O/Γ-Al₂O₃

In an effort to verify a previous striking report that ethanol could be oxidized selectively to ethylene oxide, ethanol oxidation on Ag, Cu, or Au nanoparticles supported on Li₂O/γ-Al₂O₃ or γ-Al₂O₃ was examined between 100 and 400 °C. Ag and Cu catalysts were found to be highly selective to acetaldehyde (>95% on Ag below 325 °C and on Cu below 250 °C). On Au, selectivities to acetaldehyde were lower, with higher selectivity to ethyl acetate and acetic acid. No ethylene oxide was observed under any conditions. Our results, including selectivity variations among these metals, are consistent with previous studies of ethanol oxidation over coinage metals supported on γ-Al₂O₃, with no changes in primary product identity and minor changes in selectivity upon addition of Li₂O. Unfortunately, these results are in direct contradiction to previous work reporting the desirable direct conversion of ethanol to ethylene oxide on Ag, Cu, and Au on Li₂O/γ-Al₂O₃.