Experimental and molecular simulation studies of adsorption and diffusion of cyclic hydrocarbons in silicalite-1

The adsorption and diffusion of benzene, p-xylene, cyclohexane, cis- and trans-1,4-dimethylcyclohexane (c- and t-DMCH) in silicalite-1 zeolite have been investigated using the frequency response (FR) experimental method and the simulation techniques such as the canonical ensemble Monte Carlo simulation, the force field minimisation and dynamics. It has been found by the FR measurements that two independent fluxes of p-xylene exist in the two channels of silicalite-1 respectively at low loadings and low temperatures, while at high temperatures, only one single, pure diffusion process is observed. The diffusivity of benzene is slower than that of p-xylene and the saturated hydrocarbons diffuse much more slowly than their aromatic equivalents. As found with benzene and p-xylene, t-DMCH has been found to diffuse much more rapidly than cyclohexane. The c-DMCH, on the other hand, diffuses extremely slowly. The theoretical calculations give rational interpretations to these interesting experimental results. (C) 2002 Elsevier Science Inc. All rights reserved.