Adsorption and Reaction Behavior of Perfluoro-n-alkanes on Al2O3

The adsorption of perfluoro-n-pentane and perfluoro-n-hexane on gamma-Al2O3 at the solid/vapor interface has been studied by infrared spectroscopy and temperature-programed desorption (TPD). At ambient beam temperature perfluorocarbons are adsorbed as intact, unchanged molecules and undergo chemical transformations leading to the formation of adsorbed, unsaturated carboxylate species. With increasing temperature further reactions occur, finally resulting in deep oxidation of all adsorbed species (indicated by desorption of CO and CO2). These reactions are initiated by the formation of coordination bonds between perfluorocarbons and Lewis-acidic surface sites (coordinatively unsaturated cations) of Al2O3, followed by abstraction of fluorine from the adsorbed molecules. Copyright 1998 Academic Press.