Adsorption of Water and Aromatics in Faujasite Zeolites: A Molecular Simulation Study

Abstract

We report a molecular simulation study of the equilibrium adsorption of water and aromatics in zeolite faujasite NaY. The Monte Carlo simulation methodology used in this work allows the nonframework cations to redistribute upon adsorption of fluids. We indeed observe a cation redistribution in model NaY upon water adsorption. The same phenomenon is observed in presence of adsorbed xylene molecules in the framework. A very small amount of water (some 5% weight) leads to the observed cation redistribution. The consequence of this is a change by a factor of 4 in the adsorption selectivity of NaY in favor of p-xylene, when a mixture of m and p-xylene are exposed to the zeolite sample.

Modeling and simulation of a simulated moving bed for adsorptive para-xylene separation

“…Like other zeolites, the adsorption performance of this type of zeolite is very sensitive to water content [31]. Therefore, the water content was carefully controlled prior to the adsorption experiment.…”

Evaluation of various water models for simulation of adsorption in hydrophobic zeolites

“…The most popular model is Tip4p [26], which has been used by Beauvais et al [18] to describe the location of the sodium cations in FAU in the presence of water; by Di Lella et al [19] to calculate the adsorption isotherms and cation distribution in FAU and MFI; by Trzpit et al [20] and Yang et al [21] to study water diffusion in MFI or by Cailliez et al [22] to study the interaction of water with the possible defects of the zeolite MFI. Desbiens et al [11,23] computed adsorption isotherms in MFI with different partial charges for the framework atoms not only with the Tip4p water model [26], but also with the Tip5p [27], MSPC/E [28] and the polarisable DEC [29] model.…”

Water Condensation in Hydrophobic Nanopores

“…We used the semiempirical TIP4P potential for water, [18] which was recently shown to provide a fairly good description of the adsorption of water in faujasite zeolites. [7,19] The host/guest potential is of the "Kiselev type": [20,21] It contains a single effective Lennard-Jones term that acts between the oxygen atoms of the framework and the oxygen atoms of the guest water molecules, together with a coulombic term that acts between the partial charges of the silicon and oxygen atoms and those of the guest molecules. We used the Lennard-Jones parameters for the zeolite oxygen atoms obtained from our previous work on the adsorption of hydrocarbons in silicalite-1 [22] together with the LorentzBerthelot combining rules.…”