Acidity and location of cations (H+, Na+) in HEMT and NaEMT determined using benzene adsorption

Abstract

Infrared spectroscopy is used to characterize the hydroxyls of HEMT and the interactions with benzene of these hydroxyls and of Na⁺ cations in NaEMT. Benzene adsorption studies reveal that HEMT is a stronger solid acid than HY or HSAPO-37 and that ca. 55–65% of the theoretical protons are still present after evacuation at 773 K. The changes with loading of the CH out-of-plane vibration of the adsorbed benzene give access to the number of interaction sites (H⁺ or Na⁺). In NaEMT all the cations are accessible to benzene. This may result from Na⁺ ion migration towards the large cages in the presence of the aromatic.