Use of nitriles as probe molecules for the accessibility of the active sites and the detection of complex interactions in zeolites through IR spectroscopy

The results of infrared experiments performed on protonic zeolites (like H-FER, H-MFI, H-BEA, H-MOR and REY) and cationic zeolites such as Co–H-MOR, Li-MOR, Na-MOR, K-MOR, Cs-MOR, Na-X, Na-Y, are described. The nitrile probes AN = acetonitrile (ethanonitrile); PrN = propionitrile; IBN = isobutyronitrile (2-methyl-propionitrile); PN = pivalonitrile (2,2-dimethyl-propionitrile); DPPN = 2,2-diphenyl-propionitrile; BN = benzonitrile; oTN = ortho-toluonitrile, have been used in this study. Data have been obtained concerning the location of the protonic sites in the internal cavities and on the external surface; locations in different internal cavities of multipore structures have been discriminated. Analogously, the location of cations at the external surface versus the internal cavities may be distinguished. Complex interactions with more than one alkali cations have also been documented.