Adsorption of Aromatic from Alkane/Aromatic Mixtures by NaY Zeolite

The adsorption of liquid aromatic/alkane mixtures on NaY (Si/Al 2.43) has been investigated using a batch technique. The adsorption of aromatics (benzene and toluene) from hexane, heptanes and octane was measured at room temperature. Already at low concentrations, the aromatics were selectively adsorbed on NaY from their binary mixture with an alkane. In NaY zeolite, benzene and toluene are preferentially adsorbed over C6, C7 and C8 n-alkanes (benzene/n-C6 and toluene/C6 selectivity as high as 1000), because benzene and toluene have a higher heat of adsorption and pack more efficiently in the NaY super cages. Results for aromatics are consistent with specific interaction of its pi electrons with Na atoms on the zeolite surface. These interactions increase the heat of adsorption for aromatics with NaY zeolite. Also, the interaction of n-alkanes with active sites on the surface indicates the heat of adsorption is lower than that for aromatics.