Unique Adsorption Properties Anionic Oxygens and Isolated Cations

Unique Adsorption Properties Anionic Oxygens and Isolated Cations [Pg.99]

Zeolites exhibit many unique adsorption properties, mainly because of their unique surface chemistry. The surface of the framework is essentially oxygen atoms, because Si and A1 are buried or recessed in the tetrahedra of oxygen atoms, so they are not exposed and cannot be accessed by adsorbate molecules. Also, the anionic oxygen atoms are much more polarizable [Pg.99]

Besides the anionic oxygen, cations are located at certain sites, and most of these sites are hidden or inaccessible to the adsorbate molecules. However, with molecules with permanent dipoles and quadruples, the interactions with these few exposed cations can dominate the total interaction potential. [Pg.100]

From Table V, the zeolite anion is more electronegative than F. Also shown in Table V are the electron occupancies in the 5s orbital of the Ag+ that is bonded to the anion. For a perfect anion, the Ag+ to which it is bonded should have an empty 5s orbital. Again, it is seen that Ag+ in AgZ has the lowest occupancy in its 5s orbital, indicating that the Z (i.e., zeolite framework anion) is the most electronegative anion. [Pg.100]

The strong anionic nature of the zeolite framework and the corresponding, strong cations are unique with zeolites. Furthermore, the cations and anions are not located closely to each other, which exert strong electric fields over the surface. [Pg.100]

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