ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Using extended Hückel wave functions, molecular electrostatic potentials (MEP's) have been calculated for several model clusters representative of zeolites of offretite type. The clusters studied, which are all made of a central unit comprising 2 AlO4 and 16 SiO4 tetrahedra, differ only by the relative positions of the Al-atoms occupying the same crystallographic sites (T2) within the zeolite framework. using the MEP values as a color-coded acidity index for the various clusters, three-dimensional representations of their molecular surfaces are generated as solid models on a performing computer graphics system. Important differences in acidity are predicted for the clusters which can he classified into two types according to the distribution of Al-atoms: the first one is characterized by nearly independent acid sites localized around the main channel of zeolite (Figs. 3 and 6) whereas the second one exhibits interacting acid sites located longitudinally along the channel of the same gmelinite cage (Figs. 4 and 5). The possible relationship between the structure of the clusters and their catalytic activity towards organic species is discussed.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19900730112
