(714g) Identification of Different Proton and Aluminum Species in H-ZSM5

The chemical shift is valuable information for understanding the structure and properties of proton species in H-ZSM5 zeolite. Here, H¹NMR and Al²⁷NMR of protonic and aluminum species in H-ZSM5 zeolite have been calculated using Density Functional Theory (DFT) calculations, through with we show that computed data are in good agreement with experimental solid-state NMR spectra and provide insights for the location and configuration of the protons. Different protonic species consist of silanol group (Si-OH), isolated Bronsted acid site (BAS), extra-framework aluminum (EFAl), and acidic OH groups in the proximity of extra framework aluminum (BAS/EFAl). In particular, we find that protonic chemical shift of single BAS depends on its locations; a tighter confinement normally leads to a higher chemical shift value. The calculated chemical structure of BAS/EFAl synergies may also indicate enhanced catalytic activity. We further show that Al²⁷NMR is dependent on the coordination number and the local environment and that the quadrupolar constant is greatly influenced by the geometrical symmetry. The combination of H¹NMR and Al²⁷NMR using DFT calculations thus helps characterize active sites in H-ZSM5 zeolite, as NMR spectra reveal fingerprint of the zeolite’s structure.