Combining the Monte Carlo technique with (SI)-S-29 NMR spectroscopy: Simulations of cation locations in zeolites with various Si/Al ratios

For the first time, the monovalent cation positions in a zeolite, i.e., mor denite, with increasing SI/Al ratios are calculated from combination of Mon te Carlo techniques and Si-29 NMR spectroscopy. For each Si/Al ratio, a com bination of solid-state Si-29 NMR and Monte Carlo simulations is used and l eads to the proposal of a realistic structural model where the aluminum ato ms are distributed among the four possible crystallographic sites. Then, th e positions of the cations stabilizing the mordenite lattice are obtained b y using Monte Carlo simulated annealing. The populations of the sites occup ied by the cations and their variations with the Si/Al ratio predicted by t he model are in very good agreement with those measured by thermally stimul ated current spectroscopy on Na-mordenites.