ROOM TEMPERATURE INTERACTION OF CO WITH ALKALI-METAL CATIONS IN M-ZSM-5 ZEOLITES AS STUDIED BY JOINT FT-IR SPECTROSCOPY AND MICROCALORIMETRY

摘要

The interaction of CO with K-ZSM-5 zeolite has been studied at 303 K by means of FT-IR spectroscopy and adsorption microcalorimetry, and compared with previous results concerning CO adsorption on Li- and Na-ZSM-5 zeolites. In all three cases, IR spectroscopy indicates the presence of two M~+ sites, less distinguishable on Na-ZSM-5, and clearly observable on Li-ZSM-5 and K-ZSM-5 zeolites. The case of Li-ZSM-5 offers peculiar features, probably due to the smaller size of Li~+ ions. For the main species, the heat of adducts formation and the extinction coefficient of the corresponding IR absorption band have been determined.