Ethoxy Groups on ZrO₂, CuO, and CuO/ZrO₂ Studied by IR Spectroscopy

The formation, properties, decomposition and reactions of ethoxy groups on ZrO₂, CuO, and CuO/ZrO₂ were followed by IR spectroscopy. The reaction of ethanol with terminal Zr-OH groups leads to the formation of monodendate ethoxy groups (type I), whereas the reaction of ethanol with tribridged Zr-OH grups results in the formation of bidendate ethoxyls (type II). In both cases, water is produced. Ethoxy groups of type II were also formed on CuO. The type of the surface species detected after interaction of ethanol with CuO/ZrO₂ was the same as detected for both oxides (i.e., ZrO₂ and CuO) separately. This suggests that no new phase was formed in the mixed oxide system. At higher temperatures, ethoxy groups were oxidized forming acetate ions. Gaseous ethanol present in the cell was oxidized to acetaldehyde without the intermediacy of ethoxy groups.