NMR and IR studies of hydroxyl groups in CaNa and MgNa forms of zeolites A

Abstract

By measurement of MAS proton magnetic resonance and near-infrared spectra, the existence of bridging hydroxyl groups in MgNaA and CaNaA zeolites is excluded. The MAS proton magnetic resonance lines observed at 2.5–3 ppm for CaNaA and at 3.5 ppm for MgNaA (apart from the small contributions of “terminal” OH groups) and the corresponding bands at 4576 and 4525 cm −1 in the near-infrared spectra are attributed to hydroxyl groups attached to the exchangeable cations.