Location of Brønsted sites in deuterated L-zeolite: A combined neutron powder diffraction and computer modeling study

• Published in: Materials chemistry and physics 2023-10, Vol.308, p.128250, Article 128250
• Main Authors: Martucci, A., Precisvalle, N., Fois, E., Ardit, M., Beltrami, G., Pasti, L., Cescon, M., Suard, E., Tabacchi, G.
• Format: Article
• Language: English
• Subjects: Brønsted acid sites; Deuterium form; L-zeolite; Molecular dynamics; Neutron powder diffraction
• ISSN: 0254-0584
• DOI: 10.1016/j.matchemphys.2023.128250

In this work both concentration and location of Brønsted acid sites (BASs) in a deuterated L-zeolite were determined by combining neutron powder diffraction with ab-initio molecular dynamics modelling. From the structure refinement of the acidic L zeolite, two Brønsted acid sites were identified. The first one, D1, is on the framework oxygen O5 pointing toward the center of the 8-membered ring channel; the second one, D2, located in proximity of the framework oxygen O1 pointing toward the 12-membered ring channel running parallel to the c-axis. On the whole, ∼7.7 acid sites were located in the unit-cell, corresponding to 58% and 14% for D1 and D2, respectively. The average structure of the simulated D-LTL was in good agreement with the experimental structure. The modelling revealed that the D2 BAS shows a large degree of mobility, consistent with the high thermal factor associated with that atomic position. The D1 BAS showed a behaviour consistent with static disorder, while the D2 BAS was characterized by a significant degree of dynamical disorder. In addition to these findings, the study also revealed that the O1 BAS had a higher Brønsted base character compared to the average basicity of the framework oxygens of the 12-membered ring channels. [Display omitted] •Acid L zeolite studied combining neutron powder diffraction and computer modeling.•Two Brønsted acid sites (D1 and D2) were located on O5 and O1 framework oxygen atoms.•The average simulated structure was in good agreement with the experimental one.•D1 BAS showed static disorder, while D2 BAS significant dynamical disorder.