Tribocatalytic oxidation of ethylene in the rubbing of palladium against aluminum oxide

Friction experiments of palladium rubbed against aluminum oxide in ethylene/oxygen mixed atmosphere have been carried out. The complete oxidation of ethylene to carbon dioxide and water at room temperature was demonstrated. The evolution of carbon dioxide was initiated just after the start of friction; momentarily the pressure reached its equilibrium whereas water was produced gradually. On the other hand, by heating the palladium wire in the same partial pressure of both gases, carbon monoxide and hydrogen were generated at 600 K and above. By increasing oxygen partial pressure, carbon dioxide and water were produced. These results indicate that the ethylene oxidation activity on palladium catalyst is enhanced by the friction of catalyst. Two kinds of reactions, fast and slow, are attributed to near-contact and out-of-contact activities of friction surfaces. The near-contact reaction is governed by tribo-electron emission, whereas the out-of-contact activity is due to the generated nascent surface.