Multinuclear solid-state NMR characterization of the Bronsted/Lewis acid properties in the BP HAMS-1B (H-[B]-ZSM-5) borosilicate molecular sieve using adsorbed TMPO and TBPO probe molecules
authors Wiper, PV; Amelse, J; Mafra, L
nationality International
journal JOURNAL OF CATALYSIS
author keywords Borosilicate MEI zeolite; Acid properties; Probe molecules; Solid-state NMR
keywords BORON-SUBSTITUTED ZSM-5; ISOMORPHOUS SUBSTITUTION; P-31 NMR; TRIMETHYLPHOSPHINE OXIDE; THEORETICAL CALCULATION; DEHYDRATED ZEOLITE; CHEMICAL-SHIFT; SITES; SPECTROSCOPY; BORALITES
abstract The acid properties of a dehydrated borosilicate, HAMS-1B (H-[B]-ZSM-5), including the acid types, strengths, location, and quantities are investigated by means of trialkylphosphine oxides through multinuclear ID/2D MAS NMR experiments. B-11 DQF-STMAS combined with H-1 MAS NMR studies revealed B-OH and distinct Si-OH protons associated with trigonal boron. P-31 NMR spectra of TMPO-treated HAMS-1B reveal three Bronsted and three Lewis acid sites. We have found a number of limitations applying the TMPO/TBPO method to identify internal/external acidity. Therefore, we propose a new approach to unambiguously discriminate external/internal acid sites by treating a pore-free and pore-blocked HAMS-1B zeolite. This method provided unique structural insight regarding the identification of boron species/coordinations associated with Bronsted/Lewis acid sites. Additionally, ICP analysis in tandem with solid-state NMR enabled full assignment of the detected internal/external acid species and the study of their acid strength. Moreover, we identify the nature of TMPO complexes arising from Bronsted/Lewis interactions. (C) 2014 Elsevier Inc. All rights reserved.
publisher ACADEMIC PRESS INC ELSEVIER SCIENCE
issn 0021-9517
year published 2014
volume 316
beginning page 240
ending page 250
digital object identifier (doi) 10.1016/j.jcat.2014.05.017
web of science category Chemistry, Physical; Engineering, Chemical
subject category Chemistry; Engineering
unique article identifier WOS:000340853800024
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journal impact factor 7.888
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