A Comparative Study of Structural, Acidic and Hydrophilic Properties of Sn−BEA with Ti−BEA Using Periodic Density Functional Theory

Abstract

Periodic density functional theory has been employed to characterize the differences in the structural, Lewis acidic and hydrophilic properties of Sn-BEA and Ti-BEA. We show that the incorporation of Sn increases the Lewis acidity of BEA compared to the incorporation of Ti. Hence, the present work gives insight into the role of Sn in increasing the efficiency of the oxidation reactions. The results also justify that the percentage of Sn substituted in BEA is less than Ti. The structural analysis shows that the first coordination shell of Sn is larger than that of Ti. However, the second coordination of both sites remains the same. The water adsorption properties of these substituted zeolites are quantified. Moreover, we explain the higher Lewis acidity of Sn than the Ti site on the basis of the Fukui functions and charge population analysis.

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 .…”

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

“…Li et al (15) came to an analogous conclusion when a similar Lewis acid strength order of Ti < Zr ≤ Sn was found when computationally evaluating COE-4 (delaminated FER topology) zeolites using probe molecule adsorption energies. Although several theoretical studies have been conducted on the topic (16,17), few comprehensive experimental studies quantify Lewis acidity across different heteroatoms. To this end, Gunther et al, using magic angle spinning (MAS) nuclear magnetic resonance (NMR) of 15 N pyridine adsorbed on M-Beta zeolites, found that the experimentally observed 15 N chemical shift provides a scale for Lewis acidity that correlates well with Mulliken electronegativities and pyridine adsorption energies, as seen in Figure 2 (W.R. Gunther, V.K.…”

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

“…These catalytic materials are expected to exhibit the hydrophobic nature as water present is responsible in poisoning the active site. Discrepancy in calculation of the adsorption energy of water molecule on Sn-and Ti-BEA zeolite is already reported by us in our earlier study [34]. We next analyze the convergence of total energy and the desired properties dependent on it as a function of plane wave cut-off.…”

“…There are nine distinct crystallographically defined T-sites. We adopt the structure of BEA from our earlier theoretical study [34] and incorporate the Sn-and Ti-atoms at T2 and T1 sites [42], respectively. The interaction of H 2 O molecule at the active site is very important since it gives rise to geometric perturbations and energetic differences.…”

“…Several studies describe the structural and energetic features of these systems [23][24][25][26][27]. Structural details of Sn/Ti-BEA-complexes, their cohesive energies, interaction energies along with reactivity are well studied in the literature [22,[28][29][30][31][32][33][34]. This system is an appropriate example as it features a rigid and flexible framework with a simultaneous presence of two types of bonding, a covalent one e.g.…”