SSIE and Lattice Energy

The ranking of the reactivity of NaCl, KCl, RbCl, and CsCl in the HT regime of SSIE with NH4-ZSM-5, H-ZSM-5 and NH4-Y indicated above can be related to the lattice energy (El) of those salts. The lattice energies decrease in the same sequence as the peak temperatures. The following explanation may apply the lower the lattice energy, the lower the energy required to separate salt entities (most Hkely MCI molecules) from the salt crystalHtes (cf. Sect 7.2). This, in turn, reduces the temperature that must be appUed to make the solid-state reaction 

The relationship between the lattice energy and the reactivity for SSIE of metal compounds in mixtures with zeolites was generally confirmed by the work of Weitkamp and co-workers (cf. [44,45] and Sect. 5.3) concerning the systems of noble metal chlorides/hydrogen forms of zeolites. It should be noted, however, that such a relationship was not foimd in SSIE experiments with Mn oxides as compounds of the in-going cation [46]. 

The difference in the results of TPD of 1-propylamine from the BETA sample prior to and after SSIE indicated a 92.7% consumption of the Bronsted acid sites. 

When NaCl was employed instead of CsCl, in fact only 50 % of the protons were replaced by Na+. The reason for this different behavior of the systems 

CsCl/H,Na-BETA and NaCl/H,Na-BETA is not yet clear. However, Mavro-dinova observed that the rate and degree of SSIE were higher the larger the amount of admixed NaCl (compare the analogous behavior of the system CuCl/H-ZSM-5 Sect. 5.3.2). The XRD pattern showed that the crystal integrity was preserved. 

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