Confinement effect on the interaction of hydroxy groups contained in the side pockets of H-mordenite with nitriles; a FT-IR study

Abstract

Adsorption of CD₃CN and CH₂ClCN was studied at room temperature on an H-mordenite (H-MOR) (Si:Al=10.7) sample by FT-IR spectroscopy. Study of both ν(OH) vibrations of the zeolite and ν(Câ–·N) frequencies of adsorbed species allowed differentiation of the interaction of nitriles with OH groups in the main channels and in the side pockets. Observed ν(Câ–·N) frequencies were compared to those of nitriles in variable H₀ solutions. It is concluded that protonated species are formed in side pockets while in the main channels only strongly H-bonded species occur. Results were confirmed using a pyridine-pretreated sample and a more bulky nitrile probe, CHCl₂CN. They were explained involving confinement effects in the side pockets.