NATURE, STRENGTH, AND CONCENTRATION OF ACID SITES OF ERIONITE-RICH ZEOLITE-T DETERMINED BY AMMONIA IR SPECTROSCOPY

HNaK-containing T zeolites with different proton content were synthesi zed. Subsequently, the samples were characterized by i.r. spectroscopy and temperature-programmed desorption of ammonia. Besides the direct observation of the acid OH groups, ammonia was used as the probe molec ule to determine the nature, strength, and concentration of the acid s ites. The nature of the acid sites was identified by the different fre quencies for ionically bound ammonia (Bronsted sites) and coordinative ly bound ammonia (Lewis sites). The different Bronsted sites were char acterized by coupling of ammonia-i.r. spectroscopy with a desorption p rocedure. The temperature-programmed desorption of ammonia was applied as an opportunity for comparison to obtain exact information about th e concentration of the different acid sites observed by ammonia-i.r. s pectroscopy.