Rate-determining step in the NO _x reduction mechanism on BaY zeolites and the importance of long-range lattice effects

The mechanism of the NOx reduction reaction on BaNaY zeolite using acetic acid/acetate as a reductant has been explored using density functional theory. The elementary steps, the reaction intermediates, and the transition states were identified on a zeolite cluster consisting of 10 tetrahedral atoms (10T). The hydrogen abstraction reaction of acetic acid/ acetate was identified as the rate-determining elementary step at 473 K. The long-range electrostatic effect of the lattice on the rate-determining step was studied on expanded 24T, 30T, 34T, 40T, 44T, and 50T zeolite clusters. It was found that while acetate may be greatly stabilized on the expanded clusters with additional Na ⁺ cations and Al atoms, the stabilization of acetic acid is much less affected by the long-range lattice effect. The reaction barrier of the hydrogen abstraction reaction, on the other hand, is less sensitive to the long-range lattice effect. The results of this paper highlight the importance of long-range electrostatic effects on the modeling of "single-site" catalysts involving ionic species.