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 (table 23). 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. G.Sastre, C.R.A.Catlow, A.Corma: Journal of Physical Chemistry B, 1999, 103[25], 5187-96

Table 23

Diffusion Coefficients for Benzene and Propylene in MCM-22