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

作者：Wiper Paul V; Amelse Jeffrey; Mafra Luis^*

来源：Journal of Catalysis, 2014, 316: 240-250.

DOI：10.1016/j.jcat.2014.05.017

• Borosilicate MEI zeolite
• Acid properties
• Probe molecules
• Solid-state NMR

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.

• 出版日期2014-7