Diffusion of octane in silicalite: A molecular dynamics study

Molecular dynamics simulations have been performed to study the diffusion of octane in silicalite. When hydrocarbons that are larger than C6 diffuse through this zeolite, the length of the molecule is such that diffusion through the sinusoidal channels becomes difficult. We have investigated the relative diffusivity through each channel and give an interpretation of the effect of temperature on this process. Simulations at 300 K show greater diffusivity in the sinusoidal channels, whereas at 450 K the straight channels show higher diffusion rates. When the temperature increases from 300 to 450 K, the diffusion coefficient in the straight channels increases by a factor of 5.2, whereas the coefficient in the sinusoidal channels increases by only 1.3. The trajectory plots also show larger diffusion paths through the straight channels at higher temperatures.