Simulations were used to study the diffusion of a mixture of benzene and propylene in purely siliceous MWW (MCM-22), a zeolite which contained two separate channel systems: a 10-member ring sinusoid and a 12-member ring super-cage interconnected by 10-member ring windows system. The diffusion processes in each channel system of MWW at 650K were studied independently. It was found that, in order to obtain quantitative or semi-quantitative diffusion coefficients, the framework had to be optimized. A large diffusivity of propylene in both channel systems was observed, and especially in the super-cage system, whereas benzene was not seen to diffuse in either of the two channel systems, and only intracage mobility was seen in the super-cage voids. Positions of minimum energy were located in both channels. The diffusion of benzene in the super-cage system appeared to be temperature-activated. When the temperature was increased, intercage diffusion was expected to occur.

Diffusion of Benzene and Propylene in MCM-22 Zeolite. a Molecular Dynamics Study. Sastre, G., Catlow, C.R.A., Corma, A.: Journal of Physical Chemistry B, 1999, 103[25], 5187-96