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We apply the kinetic Monte Carlo random walk model, with activation energies derived from a new zeolite-hydrocarbon potential energy surface (PES). An Arrhenius fit yields the apparent activation energy£ a= 41 kJ mol-1, as compared with the previously determined experimental values14—27 kJ mol-1. Minimum energy paths from the new PES demonstrate “cartwheel” and “skateboard” hopping mechanisms for benzene in Na-Y. Analysis of the results suggests that activation energies from long length scale diffusion measurements, eg pulsed field gradient NMR, should be interpreted as site-to-window activation energies, whereas those from short length scale experiments, eg spin—lattice relaxation NMR, correspond to intracage site-to-site activation energies.