Diffusion of Isobutane in Silicalite: A Neutron Spin–Echo and Molecular Dynamics Simulation Study

Abstract

The diffusion of isobutane in silicalite was studied using neutron spin–echo (NSE) experiments and molecular dynamics (MD) simulations between 444 and 550 K. The experimental and simulated diffusion coefficients showed agreement well within an order of magnitude, as did the activation energies of diffusion which agreed to within 3.4 kJ mol–l (∼15%). Jump diffusion was observed by NSE with a jump distance of 10 A, also observed by the MD simulations showing that the residence time was spent in a small section of the sinusoidal channel, rather than the intersections between channels as reported in previous simulations. The level of sinusoidal trapping diminishes in the simulations with increasing temperature, where the isobutane develops isotropic diffusion through both channel systems, as observed by NSE experiments.