Aluminium triplets in dealuminated zeolites detected by 27Al NMR correlation spectroscopy

New insights into hierarchical metal-containing zeolites; synthesis and kinetic modelling of mesoporous gallium-containing ZSM-5 for propane aromatization

“…Table 2). not covalently bonded to the zeolite lattice, respectively [35]. However, 27 Al MAS NMR spectrum of mesoporous Ga0.35HZ80 obtained by alkaline treatment revealed that there was an increase in the extent of dealumination, as evidenced by the increase in the intensity of octahedral extra framework Al (near 0 ppm) and the appearance of additional peak centered at ca.…”

Influence of steam-calcination and acid leaching treatment on the VGO hydrocracking performance of faujasite zeolite

“…At the same time, structural defects developed, as indicated by the sharpening of the signal at 3739 cm −1 assigned to terminal Si-OH groups. Acid leaching mainly affects the intensity of the band at 3600 cm −1 for the zeolite hydrother- around 3600 cm −1 has been extensively discussed in literature, because it has been linked to the increased acidity usually observed in USY zeolites [23,44].…”

“…On the other hand, it is known that some EFAl species are important to enhance the intrinsic acidity in USY zeolites [19]. The improved cracking activity of USY zeolites is believed to be influenced by synergistic interactions between framework and cationic EFAl species [20], and this topic has been subject of active debate in literature [21][22][23]. Hydrothermal treatment also results in loss of crystallinity and the development of a secondary pore system, reducing mass transport limitations and offering the possibility to convert a larger fraction of the feedstock.…”

Preparation and characterization of hierarchical USY by post-treatment

“…The resonance peak at 60 ppm is assigned to framework tetra-coordinated Al (Al(IV) a ). The tail resonance peak at *50 ppm is marked as Al(IV) b , but its assignment is unclear [16,[25][26][27][28]: (1) distorted tetra-coordinated framework Al atoms, (2) penta-coordinated aluminum species, and (3) non-framework four-coordinated Al species. The resonance peak at *35 ppm is attributed to nonframework penta-coordinated Al species (Al(V)).…”