FTIR study of N2 and CO adsorption on H-D-FER

Abstract

Low temperature adsorption of N2 on an H-D-FER sample was studied by FTIR spectroscopy in order to obtain information on the acidity of the hydroxyl groups. Three kinds of zeolite bridging hydroxyls were clearly distinguished, at 3609, 3596 and 3555cm−1 (3614, 3600 and 3556cm−1 at 100K). The respective OD groups were observed at 2662, 2653 and 2623cm−1 (2666, 2656 and 2621cm−1 at 100K). Nitrogen affects first the highest-frequency hydroxyls and last, the lowest frequency ones. A shift of the OH modes between 90 and 111cm−1 was measured for the different hydroxyls (between 64 and 79cm−1 for the OD groups). Experiments on CO adsorption have shown that this molecule was not convenient for measuring the acidity of the bridging hydroxyls because the spectra are complicated as a result of Fermi resonance and solvatation effects.