Non-Modified Faujasite-Type Zeolites

Stimulated by the enormous interest in appHcations of faujasite-type zeoHtes (X- and Y-type zeolites) in catalysis, the pioneering IR spectroscopic work was first almost exclusively carried out with synthetic faujasites. 

Finally, Szymanski et al. even advanced the idea of formation of only three-fold coordinated Al (or Si) through combination of two bridging OH groups under 

In 1965, Uytterhoeven et al. published their classic paper, where they investigated by IR the development of acid OH groups via deammoniation of the ammonium form of Y-type zeolites [205]. In-situ deammoniation of faujasite-type NH4-Y at elevated temperatures generated bands of hydroxy groups at about 3740,3670 and 3580 cm- (cf. Fig. 19). 

The two prominent bands at 3670 and 3580 cm were ascribed to acid OH groups, now usually called bridging OH groups or hydroxy groups and visualized as Br0nsted acid centers, since they were able to react with neutralizing bases such as NH3 (reversing deammoniation) or pyridine (cf. Sect. 5.5.2.6.2). The 

Jacobs and Uytterhoeven [380] confirmed in a systematic study the assignment of the HF band to OjH groups suggested by earlier reports [379,381-384]. 

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