Confirmation of the strongest nitriles-hydroxy groups interaction in the side pockets of mordenite zeolites

The adsorption/desorption of various nitriles on mordenite type zeolites ha s been studied by FTIR spectroscopy. The two different hydroxy groups prese nt in mordenite give rise to distinct interactions with nitriles as probe m olecules. As soon as the adsorbed nitrile is small enough to penetrate the side pockets and react with acid hydroxy groups located inside, a very stro ng interaction appears leading to a typical high frequency stretching vibra tion nu>(*) over bar * (CN)(HF). The present paper indicates that there is no proton transfer from the zeolite to the nitrile at room temperature. Suc h a high nu>(*) over bar * (CN) frequency is not due to a protonated form o f nitrile but to a very strong hydrogen bonding. A stronger interaction of nitriles with hydroxy groups located inside the side pockets than with thos e located in the main channels could be due to both confinement and solvent effects.