Adsorption in zeolites using mechanically embedded ONIOM clusters

Adsorption in zeolites using mechanically embedded ONIOM clusters.

We have explored mechanically embedded three-layer QM/QM/MM ONIOM models for computational studies of binding in Al-substituted zeolites. In all the models considered, the high-level-theory layer consists of the adsorbate molecule and of the framework atoms within the first two coordination spheres of the Al atom and is treated at the M06-2X/6-311G(2df,p) level. For simplicity, flexibility and ...

Enantioselective adsorption in achiral zeolites.

Zwitterionic versus canonical amino acids over the various defects in zeolites: A two-layer ONIOM calculation

Defects are often considered as the active sites for chemical reactions. Here a variety of defects in zeolites are used to stabilize zwitterionic glycine that is not self-stable in gas phase; in addition, effects of acidic strengths and zeolite channels on zwitterionic stabilization are demonstrated. Glycine zwitterions can be stabilized by all these defects and energetically prefer to canonica...

Proton Adsorption Selectivity of Zeolites in Aqueous Media: Effect of Si/Al Ratio of Zeolites.

In addition to their well-known uses as catalysts, zeolites are utilized to adsorb and remove various cations from aqueous system. The adsorption of the cations is ascribed to the negative charge of zeolites derived from isomorphous substitution of Si by Al. The amount of Na+ adsorption on 4A, X, Y, Na-P1 and mordenite type zeolites were determined in aqueous media, in a two-cation (Na+ and H+)...

Proton Adsorption Selectivity of Zeolites in Aqueous Media: Effect of Exchangeable Cation Species of Zeolites

The saturation of negative charges of zeolites by specific cations to modify their physicochemical and catalytic properties has broadened the applications of zeolites. The adsorption behavior of H+ to Li+, Na+, K+, Rb+ and Cs+-saturated Linde-type A, Na-P1, mordenite, X type and Y type zeolites was evaluated at different pH-pM, where pH-pM is equal to log {(M+)/(H+)} and M+ represents either Li...