Monte Carlo simulations on adsorptions of benzene and xylenes in sodium-Y zeolites

The structures of benzene and C8 isomers (o-xylene, m-xylene, p-xylene) in NaY simulated by the canonical Monte Carlo method were in good agreement with the experimental data of the available neutron diffraction analysis. All these sorbed compounds are stacked through the aromatic pi-electron interaction on the cation of the SII site in the Sodium-Y. The experimental adsorption order (m-xylene > o-xylene > p-xylene) of xylene isomers in the faujasite was also in good agreement with the order obtained from calculated heats of adsorption. It was shown that the difference in the interaction between the 4-ring sites and the methyl groups of xylene caused the better adsorption of m-xylene compared to those of the others. From these results, our conclusion is that the adsorption of the C8 isomers in the faujasite can be explained by considering only the interaction between the zeolite framework and the adsorbate approximated as a rigid model. Moreover, this type of simulation proved to be very useful to understand the mechanism of the adsorption of aromatic compounds in zeolites like faujasites.