ISSN:
1572-8943
Keywords:
desorption energy distributions
;
EEM calculations
;
far-infrared spectroscopy
;
Na+-ion exchanged zeolites of different types
;
temperature-programmed desorption (TPD)
;
water adsorption
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract We have investigated the interaction of water with Na+-ion exchanged zeolites of different structures (LTA, FAU, ERI, MOR and MFI) by means of temperature-programmed desorption (TPD). The non-isothermal desorption of water shows, depending on the zeolite type, differently structured desorption profiles. In every case the profiles have, however, two main ranges. Using a regularization method, desorption energy distribution functions have been calculated. The desorption energy distributions between 42–60 kJ mol−1, which can be attributed to a non-specific interaction of water, show two clearly distinguished energy ranges. The water desorption behaviour of this range correlates with the electronegativity of the zeolites and the average charge of the lattice oxygen atoms calculated by means of the electronegativity equalization method (EEM). The part of the desorption energy distributions in the range of 60–90 kJ mol−1, reflecting interactions of water with Na+ cations, shows two more or less pronounced maxima. In agreement with vibrational spectroscopic studies in the far infrared region, it may be concluded that all samples under study possess at least two different cation sites.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01987483
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