VIBRATIONAL SPECTROSCOPY OF THE GAS-SOLID INTERACTION BETWEEN ANHYDRIDE MOLECULES AND OXIDE-COVERED POLYCRYSTALLINE ZINC SUBSTRATE

The room-temperature interaction between anhydride-type molecules and oxide-covered zinc substrates has been studied using infrared reflecti on-absorption and high-resolution electron energy loss spectroscopies. Gas-solid interactions were carried out extensively for acetic anhydr ide on polycrystalline zinc substrate, either in-situ prepared, or ex- situ chemically prepared prior to its vacuum introduction. Vibrational spectroscopy revealed the formation of adsorbed carboxylate species i n both cases, accompanied by the consumption of surface hydroxyls, whi ch thus appeared to be the active sites in the adsorption process. How ever, other active surface sites were demonstrated on the ex-situ chem ically prepared substrates, namely zinc ions covered by carbonate spec ies which are easily displaced upon anhydride adsorption. The interact ion mechanism was found to be the same for the adsorption of maleic an d succinic anhydride on industrial zinc-covered substrates.