1. 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
- Author
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Jeffrey Amelse, Luís Mafra, and Paul V. Wiper
- Subjects
Inorganic chemistry ,P-31 NMR ,chemistry.chemical_element ,Amorphous silica-alumina ,02 engineering and technology ,ISOMORPHOUS SUBSTITUTION ,010402 general chemistry ,Molecular sieve ,01 natural sciences ,Catalysis ,BORALITES ,Isomorphous substitution ,Lewis acids and bases ,Physical and Theoretical Chemistry ,Boron ,Zeolite ,chemistry.chemical_classification ,SITES ,SPECTROSCOPY ,Chemistry ,DEHYDRATED ZEOLITE ,THEORETICAL CALCULATION ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,BORON-SUBSTITUTED ZSM-5 ,TRIMETHYLPHOSPHINE OXIDE ,CHEMICAL-SHIFT ,Acid strength ,Crystallography ,Solid-state nuclear magnetic resonance ,0210 nano-technology - 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.
- Published
- 2014