Brønsted/Lewis Acid Synergy in Methanol-to-Aromatics Conversion on Ga-Modified ZSM-5 Zeolites, As Studied by Solid-State NMR Spectroscopy

Abstract

1H–71Ga internuclear spatial proximity/interaction between Brønsted acid site (BAS) and cationic Ga species (Lewis acid sites) in Ga-modified ZSM-5 zeolites, which leads to a synergic effect in the methanol-to-aromatics (MTA) conversion, was identified with solid-state NMR spectroscopy. The internuclear distance between BAS and Ga species was measured, which is similar to that of a neighboring BAS pair located in the six-membered rings of ZSM-5. The Brønsted acidity of the Ga-modified zeolite was considerably enhanced due to the synergic effect, and the synergic active sites were quantified by 1H–71Ga double-resonance solid-state NMR, which shows a correlation with the aromatics selectivity in the MTA reaction.