H-MOR: Density functional investigation for the relative strength of Brønsted acid sites and dynamics simulation of NH 3 protonation–deprotonation

Abstract

The adsorption energies of NH 3 at different positions in acidic mordenite, viz., main channel, side pocket, and double four-membered rings, are investigated using periodic density functional theory method. Furthermore, for the first time, the dynamic behavior of NH 3 interacting with Brønsted acid site in the main channel has been monitored. The results reveal that the adsorption energies of ammonia on Brønsted acid sites in the main channel (T 4, T 2, and T 1) are higher than that in the side pocket (T 3). Consequently, the strength of Brønsted acid sites follows the same order. Ammonia dynamics results show that the protons are in continuous transfer, where NH 3 acts as a bridge for transferring protons in between ammonium ion and framework oxygen ions.