EHMO STUDIES OF CHEMISORBED DIOXYGEN SPECIES ON NA2O AND K2O AND OF THEIR INTERACTION WITH CH4 AND CH3-RADICAL
- 化学化工－已发表论文 
With an improved EHMO method, three modes (flat-lying, vertical, and inclined insertion) for adsorption and activation of dioxygen on (100), (110) and (111) surfaces of Na2O and of K2O have been examined, and the interaction of these dioxygen adspecies with CH4 and with CH3 . (radical) from gas phase has been investigated. The results indicate that both oxides tend to form less charged adspecies of dioxygen, with the flat-lying adsorption on (110) surface most favorable energetically. All these chemisorbed dioxygen species are capable of interacting effectively with CH4 and abstracting one hydrogen atom from the CH4 molecule and their tendencies to reassociate with CH3 . , which would easily lead to deep oxidation of the fragments of hydrocarbons, are enhanced with increasing negative charges on them. In comparison with Na2O, K2O has a little stronger tendency to stabilize less charged dioxygen adspecies; this has a close relation with the known experimental fact that K+ showed better promoting effect than Na+ in improving C2-selectivity in methane oxidative coupling (MOC).