Impact of the local environment of Brønsted acid sites in ZSM-5 on the catalytic activity in n-pentane cracking

Autor:	Maricruz Sanchez-Sanchez, Takaaki Ikuno, Manuel Wagenhofer, Gary L. Haller, Robin Kolvenbach, Johannes A. Lercher, Stefan Schallmoser
Rok vydání:	2014
Předmět:	Pentane chemistry.chemical_compound Chemistry Pyridine Inorganic chemistry Lewis acids and bases Physical and Theoretical Chemistry ZSM-5 Zeolite Fluid catalytic cracking Brønsted–Lowry acid–base theory Catalysis
Zdroj:	Journal of Catalysis. 316:93-102
ISSN:	0021-9517
DOI:	10.1016/j.jcat.2014.05.004
Popis:	The impact of the zeolite Bronsted and Lewis acid site concentration on the catalytic cracking of alkanes was explored using n-pentane and H-ZSM-5 as examples. Rates normalized to strong Bronsted acid sites (i.e., the turnover frequencies, TOF) showed that the two samples with the highest Al content had much higher TOF than all other samples. This difference has been unequivocally linked to the presence of extra-lattice alumina. Post-treatment of the zeolites with ammonium hexafluorosilicate and static calcination was used to vary the concentration of extra-lattice alumina. After extraction of extra-lattice alumina from the samples with high TOF, all TOFs were identical. IR spectra of adsorbed pyridine and NH3, coupled with 27Al MAS NMR, showed that the overall enhanced activity is associated with tetrahedrally coordinated extra-lattice alumina in close proximity to strong Bronsted acid sites. The TOF of these sites is approximately 40-times higher than the TOF on normal Bronsted acid sites.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::f2a43e441b961b3d9fcb74b85a3a0552 https://doi.org/10.1016/j.jcat.2014.05.004 Zobrazit plný text záznamu Full Text from ScienceDirect