Characterization of Metal-Loaded Zeolites

Zeolites can be ion-exchanged with cations or impregnated with various metals to modify their performance for use in applications such as separations, adsorption and catalysis. For example, faujasite zeolites exchanged with Na, Li, K, Ca, Rb, Cs, Mg, Sr, Ba, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ru, Pd, Ag, Cd, In, Pt, H, Pb, La, Ce, Nd, Gd, Dy and Yb have been made and studied due to their use in separation and catalysis [135]. The ability to determine the distributions of these cations in the zeolitic structure is one of the key parameters needed in understanding adsorption mechanisms and molecular selectivities. Little has compiled an excellent reference 

Martra and coworkers studied low-temperature CO and room-temperature CO2 adsorphon on Na- and Ba-exchanged X and Y zeolites [138]. They were able to determine from the CO adsorphon IR data that Ba ions located in the Sn sites in both X and Y zeolites exhibit higher Lewis acid strength compared to Na ions in the same sites. Furthermore, the Lewis acid shength of both Ba and Na ions was dependent on the framework aluminum content of the zeolite. Using CO2 as a probe, they found that subshtuhng Na with Ba caused a reduchon in the basicity of the framework oxygens in proximity to the cahons. 

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