A study was made of the behavior of benzene molecules in the pure siliceous MCM-22 analogue, ITQ-1. The diffusion coefficients did not exhibit any obvious differences, when using either a rigid zeolite framework or a flexible one. This implied that the flexibility of the zeolite framework did not introduce marked effects into the simulation results. From the molecular dynamics trajectories, it was found that the diffusion and migration of benzene occurred mainly in 12MW cavities. A high activation energy was required for one sorbate molecule to migrate from one 12MW cavity to another nearby 12MW cavity via the 10MW windows. The diffusion characteristics of the benzene molecules indicated that a pair of benzene molecules in S1 and S2 sites produced a relatively strong π-π stacking force and that the motions between two benzene molecules near to S1 and S2 sites would maintain their synergistic status in order to make the system remain in a state of optimal energy.

Diffusion of Benzene in MCM-22 Zeolite: a Molecular Dynamics Study. T.Hou, L.Zhu, X.Xu, M.Ji, X.Ye: Acta Physico-Chimica Sinica, 2000, 16[8], 707