Effects of zeolite channel walls and cation migration on N2O decomposition energies in Fe/ZSM-5

Density functional theory was used to compute minimum energy structures for surface intermediates involved in the catalytic decomposition of N2O over Fe/ZSM-5. The calculations were performed using a computational cluster containing only 5 tetrahedral zeolite atoms, and then repeated using a cluster with two full 10-membered zeolite rings. The differences between these two sets of calculations suggest that using a larger computational cluster allows the iron cation to occupy a site of higher coordination. This is accompanied by small changes in the computed values of Delta E for the five mechanistic reaction steps of N2O decomposition. Replicating the final geometry of the smaller cluster within the larger cluster indicated that longer-range interactions with the zeolite channel walls do not significantly affect the energies of the mechanistic steps studied. (c) 2006 Elsevier Inc. All rights reserved.