Dealuminated H−Y Zeolites:  Relation between Physicochemical Properties and Catalytic Activity in Heptane and Decane Isomerization

Abstract

The acidity of a series of commercial dealuminated H−Y zeolites was studied by means of MAS NMR and XPS spectroscopy. 27Al MAS NMR has shown the presence of three types of Al in the dealuminated samples: framework tetrahedral Al, nonframework octahedral Al, and a third type of Al. As inferred from the framework Si/Al ratio obtained by 29Si MAS NMR spectra and from the evolution of the unit cell parameter determined by XRD, this third type of Al may be localized into the zeolite framework. XPS characterization of the samples in their acid form has allowed us to establish the relative concentration of Al at the outer surface of the particles. Upon adsorption of ammonia on the dealuminated zeolites, three types of acid sites have been evidenced by XPS. The analysis of the XPS data indicates that the strength of the acid sites associated with tetrahedral framework Al atoms is not influenced by the other types of Al. The catalytic results of heptane and decane hydroisomerization have evidenced that the acid sites of certain dealuminated H−Y zeolites may be very efficient. The information provided by MAS NMR, combined with the XPS results and literature data, has allowed us to partially elucidate the origin of the high activity of some dealuminated H−Y zeolites.

n-Hexadecane hydrocracking Single-Event MicroKinetics on Pt/H-beta

“…Both the structure of the zeolite pore network and the framework aluminium concentration may significantly affect the catalytic activity and/or selectivity towards isomer and cracked products [8][9][10][11][12][13][14]. Hydrocracking on faujasites occurs via an unconstrained reaction network and leads to a wide product distribution, while on zeolites with a narrower pore structure such as TON-type frameworks, the pore access for and the formation of bulky hydrocarbons is typically restricted by shape-selective effects.…”

Three-Dimensional Transmission Electron Microscopic Observations of Mesopores in Dealuminated Zeolite Y

“…[3,4] Recent works have focused on the design and synthesis of fluorescent oligonucleotides that exhibit an enhanced signal upon hybrid formation, [5±14] since these type of probes can be used in homogeneous, as well as heterogeneous, assays. The enhanced fluorescence has facilitated monitoring in vitro transcription, [15] ribozyme reaction, [16,17] and RNA folding. [18] Our research efforts have concentrated on the use of the sugar 2'-position as the site in the covalent attachment of several fluorophores.…”

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

“…For acid leached zeolites, the surface Si/Al increases, which implies removal of Al from the external surface region of the zeolite crystals. Al is assumed to be removed by dissolution of EFAl species and part of the remaining framework Al [33].…”

“…2, namely at 60, 30 and 0 ppm. The signals at 60 and 0 ppm are due to Al nuclei in tetrahedral and octahedral coordination environment, respectively [33][34][35]. The signal at 30 ppm is assigned to distorted tetrahedral or five-coordinated Al species [35][36][37].…”