The influence of framework flexibility upon the adsorption and diffusion of methane in LTA zeolites was investigated using Monte Carlo and molecular dynamics simulations. The framework flexibility of the pure silica structure (ITQ-29), the sodium form (LTA-4A) and the sodium/calcium form (LTA-5A) were analyzed. Simulations were performed at 500K over the full loading range. It was found that the framework flexibility affected differently the adsorption and diffusion of methane. The effect of flexibility upon adsorption was small. The influence upon diffusion seemed however to be much larger, and strongly dependent upon three factors: the density and type of non-framework cations located in the LTA zeolite, the loading of methane in the structure, and especially the force field parameters used to model the framework.

Modeling Adsorption and Self-Diffusion of Methane in LTA Zeolites: the Influence of Framework Flexibility. A.García-Sánchez, D.Dubbeldam, S.Calero: Journal of Physical Chemistry C, 2010, 114[35], 15068-74