Differentiation of Diverse Tetrapropylammonium Cations Occluded in MFI-Type Zeolites by 15N CP MAS NMR Spectroscopy
High resolution solid state 1H–15N CP MAS NMR spectroscopy was used to study the TPA+ species present in ZSM-5 samples and in silicalite prepared either in alkaline medium or in a non-alkaline fluoride medium. The resolution of the spectra recorded for the samples prepared in fluoride medium enabled to differentiate two types of TPA+, compensating or not the framework charge, both present in some of the solids.