NMR characterization of Bronsted acid sites in faujasitic zeolites with use of perdeuterated trimethylphosphine oxide.

The interactions of Bronsted acid sites of H-Y (FAU) with perdeuterated trimethylphosphine oxide (TMPO-d9) are studied with a set of high-resolution solid-state NMR experiments. Double- and triple-resonance MAS NMR techniques (such as CP, TRAPDOR, and REDOR) verify that the lines in the 31P MAS NMR spectrum are indeed from TMPO interacting with Bronsted acid sites. Replacement of acidic hydrogens in the sodalite cages with sodium cations results in the disappearance of one of the peaks, leading to final assignments of the resonances.