SIMULATED ANNEALING STUDY OF CATION DISTRIBUTION IN DEHYDRATED ZEOLITES

A simulated annealing method is employed to describe the cation distri bution in dehydrated zeolites. The cation distribution in faujasite-ty pe zeolites with 56 cations per unit cell as a function of temperature is simulated and the results are compared with that obtained by Van D un et al. [J.J. Van Dun, K. Dhaeze, W.J. Mortier and D.E.W.Vaughan, J. Phys. Chem. Solids, 50 (1989) 469] who used the Bragg-Williams approx imation and the quasi-chemical-equilibrium method in their statistical thermodynamical model. The Na-ion distribution in faujasite-type zeol ites can be accurately simulated through adjusting three parameters, i .e. e(I) - e(I) and e(II) - e(I), the site energy level differences be tween the cations on the different cation sites, and w, the repulsive energy between cations on adjacent sites I and I'. (C) 1997 Elsevier S cience B.V.