Time‐Resolved In Situ MAS NMR Monitoring of the Nucleation and Growth of Zeolite BEA Catalysts under Hydrothermal Conditions

Abstract

Time-resolved C, Na, Al, and Si MAS NMR has been applied in situ for monitoring the hydrothermal synthesis of zeolite BEA. Isotopic labelling with Si and C isotopes has been used to follow the fate of siliceous species and structure directing agent (( CH -CH ) NOH). Two mechanistic pathways, namely solution-mediated and solid-solid hydrogel rearrangement have been distinguished for two synthesis procedures studied. The mechanisms of structure-directing behavior of TEA cations in two reaction pathways have been elucidated. The results show that multinuclear MAS NMR can serve as a superior tool for monitoring hydrothermal synthesis of various solids including zeolites, zeotypes, mesoporous materials, metal-organic frameworks and so on and for the design of novel outstanding materials for different applications.

Isolated Single‐Atom Ruthenium Anchored on Beta Zeolite as an Efficient Heterogeneous Catalyst for Styrene Epoxidation

“…Loading Ru onto the Beta zeolite support and hydrogenating the catalyst material at 473 K result in a disappearance of the Al 3+ hexa sites, as evidenced by the large drop in the intensity of the 0 ppm NMR signal (Figure 2c, inset). Concomitantly, the intensity of the 55 ppm NMR feature increases with the loading of Ru onto Beta zeolite, which suggests the interconversion of Al 3+ hexa and Al 3+ tetra [37] . The Ru loading on Beta zeolite apparently induced changes in the coordination number of Al.…”

“…55 ppm due to four‐coordinate framework aluminum (Al 3+ tetra ) and another signal at ca. 0 ppm owing to six‐coordinate framework aluminum (Al 3+ hexa ) were observable [35–38] . Loading Ru onto the Beta zeolite support and hydrogenating the catalyst material at 473 K result in a disappearance of the Al 3+ hexa sites, as evidenced by the large drop in the intensity of the 0 ppm NMR signal (Figure 2c, inset).…”

Supramolecular Organization in Confined Nanospaces

“…For zeolites, one prototypical case is 29 Si, sensitive to bond distances, angles, and next‐nearest‐neighbor environment: its usefulness in probing the Si/Al ordering in zeolites has been long recognized . Besides 29 Si, also 27 Al plays a key role in topical issues, like characterization of zeolitic acid sites, or nucleation and growth processes, while 33 P is especially relevant for aluminophosphates. Many other nuclei ( 1 H, 2 H, 13 C, 15 N, etc.)…”

Tracking the rearrangement of atomic configurations during the conversion of FAU zeolite to CHA zeolite

“…The reaction is generally mediated by amorphous aluminosilicates, [4][5][6][7][8] which makes the elucidation of the formation mechanism difficult. In situ analyses of zeolite formation [9][10][11][12][13][14][15] have been conducted to capture a detailed image of zeolite synthesis. Although these studies have deepened our understanding of the mechanism, the exact atomic rearrangement during this process is unknown, which makes it fundamentally challenging to link intermediate species with the formed zeolite structures.…”