Oxygen exchange between adsorbed oxygen and cesium-added zeolite X

Abstract Oxygen exchange between adsorbed oxygen and the zeolite X which contains cesium ions in excess of the ion-exchange capacity (cesium-added zeolite X) was studied by TPD of adsorbed 18 O 2 . The desorbed oxygen molecules were composed mainly of 18 O 2 and 16 O 2 ; the fraction of 18 O 16 O was small, indicating that a pair of oxygen atoms in the zeolite exchanges with an oxygen molecule. The retention of molecular identity of oxygen during the exchange, together with the ratio of 18 O/ 16 O in the desorbed oxygen, suggests the existence of the Cs 2 O particles in the zeolite cavities. A part of the surface layers of the Cs 2 O particles converts into the structures similar to those of the oxides such as Cs 2 O 2 , Cs 2 O 3 and Cs 2 O 4 when oxygen molecules are adsorbed. The catalytic activity of cesium-added zeolite X for 1-butene isomerization was completely poisoned by oxygen. The catalytically active species are concluded to be the Cs 2 O particles encapsulated in the zeolite cavities.