(392b) Molecular Screening of Alcohol Adsorption Onto Zeolite From Aqueous Solution

A methodology based on the combination of grand canonical Monte Carlo (GCMC) and expanded ensemble (EE) simulations has been used to study the adsorption of alcohols from dilute aqueous solution onto silicalite zeolite. The chemical potential of guest alcohol molecules in bulk aqueous solutions are calculated by the EE method, and the adsorption isotherms of the alcohols using GCMC simulations. This new approach results in adsorption isotherms that relate the loadings to external concentrations without using an equation of state, experimental data, or performing computationally expensive simulations such as two-phase Gibbs ensemble Monte Carlo (GEMC). Also, the method is “force-field consistent”, in that the same force field is used for the bulk fluid and the adsorption calculations, and the resulting isotherms can be directly compared with experimental data. We have established the validity of the new method by comparing the experimental data to our calculated adsorption isotherms on silicalite of methanol and ethanol, both from aqueous solution and from the vapor phase. Calculated heats of adsorption are also in good agreement with experimental data. In addition, these simulations provide molecular-level information on adsorption in the pores, such as the location of adsorption sites. This approach can be used to study the adsorption of any molecular species on any nanoporous adsorbent.