Molecular Simulation of the Impact of Defects on Electrolyte Intrusion in Zeolites

Abstract

We have investigated through molecular simulation the intrusion of electrolytes in two representative pure-silica zeolites, silicalite-1 and chabazite, in which point defects were introduced in varying amounts. We distinguish between two types of defects, considering either "weak" or "strong" silanol nest defects, resulting in different hydration behavior. In presence of weak defects, the hydration process occurs through a homogeneous nucleation process, while with strong defects we observe an initial adsorption followed by a filling of the nanoporous volume at higher pressure. However, we show not only that electrolytes do not penetrate the zeolites, but these defects appears to have only marginal influence on the thermodynamic of electrolyte intrusion. While replacing pure water by the electrolyte solution shifts intrusion pressure towards higher values because of the drop of water saturation vapor pressure, an increase in hydrophilicity of the framework due to point defects has the opposite effect showing that controlling the amount of defects in zeolites is crucial for storage energy applications.

Calorimetric Heats of Intrusion of LiCl Aqueous Solutions in Hydrophobic MFI-Type Zeosil: Influence of the Concentration

“…It is therefore possible that the “MFI-type zeosil – LiCl solution” system shows a different behavior from the previously studied cases. However, they are in agreement with the recent work of de Izarra et al who did not observe by molecular simulation the penetration of NaCl electrolytes in the micropores of silicalite-1 and chabazite zeosils.…”