Properties of sodium ions in zeolite materials: FT-IR study of the low temperature adsorption of carbon monoxide

摘要

The low temperature adsorption of CO has been investigated on NaX (Si/Al a. r. = 1.3), NaY (Si/Al a. r. = 2.4), NaMOR (Si/Al a. r. = 6.5) and NaFER (Si/Al a. r. = 25) zeolites by FT-IR spectroscopy. For comparison CO adsorption has also been investigated on Na-silica-alumina. Bands assigned to CO C-bonded and O-bonded to Na+ ions have been observed and discussed. A correlation between the position of the band and the siting and coordination state of Na+ ions has been observed for C-bonded species. Some effect of the cavity has been envisaged for O-bonded species. Low frequency bands corresponding to quite stable species have also been found and assigned to carbon monoxide bonded to two cations. This suggests that CO may also probe couples of the nearest Na+ ions, that may act in adsorption.