Water in homoionic and heteroionic mordenites: a calorimetric study. Part 1.—Alkali and alkaline earth metal forms

Abstract

Heats of immersion in liquid water of Na-Zeolon exchanged with alkali metal, alkaline earth, Ag+, T1+ and Pb2+ ions are reported. The levels of ion exchange of Zeolon are shown to depend markedly on the degree of hydration of the cations. The heat data show that the Li+, Ca*+, Mg2+ and Sr2+ ions are located in the main channels after the immersion process and that the magnitude of the heats are governed by the energy of solvation of the cations by the anhydrous lattice. Correlations between the heats and cationic radii are shown to exist and these correlations could be useful for interpolation purposes.

Na+/Mordenite Interaction Energy Determined by Thermally Stimulated Depolarization Current

“…The results reported in Table on MNa 1 compare favorably with the data given by Mortier, Tyburce, and Coughlan …”

“…The results reported in Table 2 on MNa 1 compare favorably with the data given by Mortier, 16 Tyburce, 20 and Coughlan. 21 Only one discrepancy is noticeable: there is a maximum of four sites I occupied by Na + per unit cell, whereas the simulation gives 4.5. This difference is likely to be related to the fitting approach.…”

Theoretical prediction of low-frequency vibrations of extra-framework cations in mordenite zeolites

“…We find that four cations are split equally between sites IV and VI in the main channels, and four are located on sites I in the small channels. It is thus apparent that our chosen (Si,Al) configuration is particularly judicious because it leads to a cation distribution close to those observed experimentally by X-ray diffraction 15,16 and dielectric relaxation spectroscopy. 17 In the same way, the location of Na + cations determined for a typical (Si,Al) mordenite lattice Si/Al ¼ 11 (see Fig.…”

“…These simulations were performed by selecting suitable pair potentials for describing the interactions within the whole system and demonstrated that both the distribution of the extra-framework cations and their interaction with the zeolite host lattice are strongly modified by varying these two parameters. These results were then compared with experimental data obtained by X-ray diffraction 15,16 and dielectric relaxation spectroscopy. 17,18 The quantitative agreement obtained between theory and experiment reinforced the validity of the potential model used, and leads us to extend this study to the dynamical properties of the extra-framework cations by applying the molecular dynamics technique.…”

Behavioural Change according to the Si/Al Ratio of Successive Na-Mordenites Observed through Their Dielectric Relaxation during Water Vapour Adsorption Process

“…Site I with octahedral coordination is stable and its geometry leaves a tight room for the cation to move about. Its occupancy brings about a blocking of the lateral cavities and isolation of the principal channels from each other [58].…”