RAMAN AND X-RAY-ABSORPTION STUDY OF SELENIUM INCORPORATED INTO THE CHANNELS OF MORDENITE - DEPENDENCE ON THE ION-EXCHANGE AND THE METHOD OFINCORPORATION

Influence of ion exchange and method of selenium incorporation into mo rdenite channels on the structure of incorporated selenium species are studied by Raman and X-ray absorption spectroscopy. It is shown that Se chains prepared by Se vapor adsorption are more regular than Se cha ins prepared by pressure injection of liquid Se. Concentration ratio b etween Se chains and Se-6 rings is found to be practically independent of the method of preparation but dependent on the type of cations in mordenite channels. Substitution of Na cations by larger monovalent ca tions leads to a decrease in Se chains concentration compared to Se-6 rings concentration and to an increase in average Se-Se bond length. X -ray absorption spectrum of M-Se for polarization of radiation perpend icular to the channels is shown to be determined mainly by Se-6 rings, and that for polarization parallel to the channels is a superposition of the absorption of chains and rings. Selenium incorporated into H-f orm of mordenite is found to be located not only in the original morde nite channels, but also in meso-channels organized due to partial dest ruction of the interchannel walls. (C)1998 Acta Metallurgica Inc.