Grand canonical Monte Carlo simulations of nonrigid molecules: Siting and segregation in silicalite zeolite

A method is described for performing grand canonical Monte Carlo simulation s of molecules with internal degrees of freedom. The approach is applied to adsorption of methanol and cyclohexane in the zeolite silicalite. Calculat ed adsorption isotherms and heats of adsorption compare well with experimen tal data from the literature. In addition, the simulations provide informat ion on preferential siting of molecules in the different pores of silicalit e. Binary adsorption results are also predicted for cyclohexane/methane, be nzene/methane, and benzene/cyclohexane mixtures. The siting preferences of the single components result in clear segregation effects for these binary systems. Benzene and cyclohexane display preferred siting in the channel in tersections, while methane adsorbs preferentially in the channels. In the c ase of benzene/cyclohexane, the cyclohexane adsorbs in the intersections an d the benzene is pushed to the zigzag channels.