Grand canonical Monte Carlo, molecular dynamics and kinetic Monte Carlo simulations were made of benzene diffusion, with particular focus on the loading dependence. A realistic representation of the structure of the sorbate-sorbent system was first obtained, based upon grand canonical Monte Carlo simulation. The latter clearly revealed the characteristics of the adsorption sites of the benzene-NaY system, and two types of preferred adsorbing sites for benzene molecules, SII and W, were identified. The structure was then used as a basis for kinetic Monte Carlo and molecular dynamics simulations. A comparative study of two different mechanisms underlying jump diffusion in the zeolite showed that the diffusivity values predicted by the kinetic Monte Carlo and molecular dynamics methods were fairly close to each other. This led to the conclusion that, for benzene diffusion in NaY, the SII→W→SII jumps of benzene molecules predominated, while W→W jumps did not occur. These findings provided further support for previous conclusions concerning the absence of W→W jumps in benzene diffusion in NaY.

Molecular Simulations of Adsorption and Diffusion Behaviors of Benzene Molecules in NaY Zeolite. Z.Zhang, H.Liu, J.Zhu, B.Chen, H.Tian, Z.He: Chinese Journal of Chemical Engineering, 2009, 17[4], 618-24