In industrial adsorption processes carried out in liquid phase, charges are not always degassed before being injected and so they may contain dissolved oxygen that could induce undesired reactions responsible for premature adsorbent aging. To check this, we compared the reactivity of dodecen-1 in liquid phase at 150°C under air and under argon on two differently active solids, NaY and NaHY-6.7%. It shows that the oxidant atmosphere has a significant influence on the dodecen-1 reactivity. Oxygenated compounds are formed and irreversibly adsorbed on zeolite, leading to the filling of the porosity. This effect is more marked on the less active solid.