Molecular dynamics simulations were used to study the diffusion of octane in silicalite. When hydrocarbons that were larger than C6 diffused through this zeolite, the length of the molecule was such that diffusion through the sinusoidal channels became difficult. An investigation was made of the relative diffusivity through each channel and an interpretation of the effect of temperature on this process was given. Simulations at 300K revealed greater diffusivity in the sinusoidal channels whereas, at 450K, the straight channels exhibited higher diffusion rates. When the temperature was increased from 300 to 450K, the diffusion coefficient in the straight channels increased by a factor of 5.2, whereas the coefficient in the sinusoidal channels increased by only 1.3. Trajectory plots also revealed larger diffusion paths through the straight channels at higher temperatures.

Diffusion of Octane in Silicalite: a Molecular Dynamics Study. N.Raj, G.Sastre, C.R.A.Catlow: Journal of Physical Chemistry B, 1999, 103[50], 11007-15