ISSN:
0142-2421
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Physics
Notes:
Chemisorption of ammonia on the acid sites located at the outer surface of dealuminated mordenites has been investigated by x-ray photoelectron spectroscopy. The N 1s level of chemisorbed ammonia results from the overlapping of three components occurring near 402.4, 400.5 and 399.1 eV. From the N 1s binding energy of NH4+- exchanged mordenite and values reported in the literature for pyridine adsorbed on Brönsted and Lewis acid sites, the components at 402.5 and 399.1 eV are assigned to ammonia in interaction with Si-OH-Al framework groups and with Lewis acid sites, respectively. Based on XPS N/Al ratios and infrared results, the component at 400.5 eV is attributed to ammonia chemisorbed on silanol groups. The surface concentration of the three types of acid sites is estimated from the decomposition of the N 1s peaks. Evidence for the presence of surface extra-framework Al in dealuminated mordenites is provided and the influence of these Al species on the outer surface acidity is discussed.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/sia.740210908
