The diffusion of carbon dioxide in NaX and NaY Faujasite systems was investigated by combining quasi-elastic neutron scattering and molecular dynamics methods. The experimentally evaluated diffusivity increased with loading whereas the simulated self-diffusivity decreased. This general behaviour was in good agreement with that previously reported for various gases in similar zeolite systems. It was also shown that the corrected diffusivity exhibited a significant concentration dependence. At low loadings, the activation energies for diffusion derived from quasi-elastic neutron scattering and molecular dynamics simulation agreed. They increased from NaY to NaX due to a stronger interaction between the CO2 molecules and the extra-framework cations. Extrapolation of the transport and self-diffusivities to zero coverage revealed a good agreement between experiment and simulation.

Diffusion of CO2 in NaY and NaX Faujasite Systems: Quasi-Elastic Neutron Scattering Experiments and Molecular Dynamics Simulations. Plant, D., Jobic, H., Llewellyn, P., Maurin, G.: European Physical Journal - Special Topics, 2007, 141[1], 127-32