Investigation of the distribution of acidity in zeolites by temperature-programmed desorption of probe molecules. I. Dealuminated mordenites

Synthesis and Physicochemical Characterization of ZSM-5 Metallosilicate Zeolites Prepared by Isomorphous Substitution Process

“…However, this band did not develop in the spectrum of ZSM-5. Finally, in the study [28], it was concluded that the decrease of the extent of dealumination results in an increase of the strength of the Brønsted sites. Evidently, the stepwise heating of the M/ZSM-5 samples provide the largest desorption peaks strength of acid sites, in contrast to the individual desorption peaks for pure ZSM-5.…”

Effect of regeneration temperature and time on the activity of HUSY and HZSM5 zeolites during the catalytic pyrolysis of polyethylene

“…Two peaks centred at 54 and 0 ppm, can be observed, that correspond to tetrahedral coordinated Al atoms placed inside the framework and to extra-framework Al in an octahedral coordination, respectively [23,24]. Extra-framework Al behaves as weak Lewis acid sites [25]. Comparing areas of both peaks, an increase in extra-framework with respect to intra-framework aluminum can be observed in the zeolite LD-Z-900, so distribution of acid sites changes with the regeneration at 900 8C.…”

Heterogeneous Catalysis and Solid Catalysts

“…The integral area of the desorption peak gives the total acid site density, and the position of the peak maximum provides the activation energy of desorption (which may be close or identical to the heat of adsorption), which can be considered to be a measure of the acid strength. This approach has been applied for investigations of H forms of zeolites using ammonia as the probe [336], [337]. However, discrimination between Lewis and Brønsted acid sites is again only possible with the assistance of, e.g., vibrational spectroscopy.…”