OXYGEN SPECIES FORMED ON DIFFERENT SURFACE SITES OF CAO BY DECOMPOSITION OF N2O AND THE REACTIVITY

Adsorbed oxygen species were appreciably formed on CaO by decomposition of N20. By temperature programmed desorption the activation energy of the desorption of oxygen was estimated to be 44-45 kcal/mol at amounts of adsorption below 0.15 μmol/m2CaO. It decreased rapidly with increased amounts of adsorbed oxygen species, staying at 31 kcal/mol above 0.5 μmol/m2CaO. Photoluminescence spectra of CaO suggested that adsorbed oxygen species were preferentially held on surface sites with low coordination number (coordination number of 4) at small amounts of adsorption whereas at large amounts of adsorption adsorbed oxygen species were mostly held on surface sites with high coordination number (coordination number of 5). The oxygen species formed on the former sites were more active than those formed on the latter sites for the oxidative dehydrogenation of ethane. Ethene was produced with high selectivity. © 1992.