The perturbation of surface species of zeolite HY by Xe has been studied with the use of in situ FT-IR spectroscopy. The Brönsted acid sites, characterized by a band at 3638 cm−1, are located in the zeolite super-cages, as suggested previously, while Brönsted
acid sites attributed to a 3545-cm−1 band are located in the small zeolite cages and are inaccessible to the Xe molecules. The Brönsted acid sites in the supercages are found to have a weaker acidity than those in the small cages. The data also indicate that pyridine
molecules are more strongly bonded to the super-cage Brönsted acid sites than are the NH3 molecules. This work is an example of the usefulness of liquid-nitrogen-temperature FT-IR techniques, coupled with multiple-scan data acquisition methods, for studying weak interactions
between Xe and zeolite surface species in detail. This work also shows how FT-IR spectroscopy can complement Xe-129 NMR spectroscopy in studies of the nature of zeolite surface species using Xe as a probe molecule.
Department of Chemistry, University of Utah, Salt Lake City, Utah 84112
Publication date: November 1, 1989
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