Development of a transferable guest-host force field for adsorption of hydrocarbons in zeolites - I. Reinvestigation of alkane adsorption in silicalite by grand canonical Monte Carlo simulation

Grand canonical Monte Carlo simulation of several linear and branched alkanes adsorption in silicalite-1 zeolite has been performed using the anisotropic united atoms AUA-4 potential that had been developed earlier by Ungerer and co-workers to predict several bulk equilibrium properties of various hydrocarbons (P. Ungerer, C. Beauvais, J. Delhommelle, A. Boutin, B. Rousseau and A. H. Fuchs, J. Chem. Phys., 2000, 112, 5499). The zeolite potential parameters for the CH2 and CH3 groups were optimized using butane experimental adsorption data only. The use of combination rules enabled to predict the adsorption properties of other alkanes (methane, ethane, propane, butane, isobutane, pentane, 2-methylbutane, hexane, 2-methylpentane, heptane, 2-methylhexane, octane, and nonane) without any further readjustment of the force field parameters. In the temperature range 277 to 374 K a good agreement was found between simulation and experiments, as well as with the previous simulations results of Smit and coworkers. The effectiveness of the transferability of the present force field is demonstrated by the fact that adsorption properties of CH4 and other molecules containing a CH group were successfully predicted, although these groups were not introduced in the fitting procedure.