Structural, Electronic, and Bonding Properties of Zeolite Sn‐Beta: A Periodic Density Functional Theory Study

Abstract

Abstract:The structural, electronic and the bonding properties of the Sn-BEA are investigated by using the periodic density functional theory. Each of the 9 different T-sites in the BEA were substituted by the Sn atom and all the 9 geometries were completely optimized using the plane wave basis set in conjunction with the ultra-soft pseudopotential. On the basis of the structural and the electronic properties, it has been demonstrated that the substitution of the Sn atom in the BEA framework is an endothermic process and hence the incorporation of the Sn in the BEA is limited. The lowest unoccupied molecular orbitals (LUMO) energies have been used to characterize the Lewis acidity of each T-site. On the basis of the relative cohesive energy and the LUMO energy, T2 site is shown to be the most favorable site for the substitution of Sn atom in the BEA framework.

The Mechanism of Glucose Isomerization to Fructose over Sn‐BEA Zeolite: A Periodic Density Functional Theory Study

“…[33][34][35][36] Similar to previous studies, [37][38][39][40] the periodic model of BEA zeolite corresponded to polymorph A. [41] The optimized parameters of the tetragonal BEA unit cell were a = b = 12.657 and c = 26.396 .…”

“…To simulate Sn-BEA zeolite, a Sn atom was introduced at the T2 lattice position, that is, the thermodynamically preferred site for the isomorphous substitution. [37,40] The unit cell of the final model containing only perfectly tetrahedral lattice sites (model I, Sn sites (Si F O F ) 3 SnOH were constructed by partial lattice hydrolysis. [20,21] In this work, we considered two models for such defect sites, which differed in the size of the silanol nest neighboring the Sn center.…”

Lewis Acid Zeolites for Biomass Conversion: Perspectives and Challenges on Reactivity, Synthesis, and Stability

“…In addition, the relative substitution energies for different T-sites in the same topology are different enough thermodynamically to influence the distribution of metal centers. Computational (13,38) and extended X-ray absorption fine structure (EXAFS) spectroscopy studies (39) suggest that Sn preferentially occupies T-sites in the four-membered rings in Beta zeolites (Figure 3). These sites are designated as T1/T2 by Newsam…”

Influence of plane wave cut-off on structural and electronic properties in Sn-BEA and Ti-BEA zeolite water molecule interaction

“…In addition, zeolite beta (BEA) is a well known active catalyst for carrying out several organic reactions. Hence, the nature of its interaction, which is mainly weak attractive and coordinative, with several organic reagents and reaction media necessitates an understanding using such theoretical studies [20][21][22]. The incorporation of Ti-and Sn-at active sites (T-sites) finely tunes acidity and increases activity of the BEA (T-BEA).…”