Mobility of chromium in inorganic oxides Spectroscopic fingerprinting of oxidation states and coordination environments

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Bert M. Weckhuysen, Bart Schoofs and Robert A. Schoonheydt


Abstract

The mobility of Crn+ in inorganic oxides has been investigated by combined diffuse reflectance (DR)–EPR spectroscopies as a function of the Cr oxidation state, the type of inorganic oxide (silica, alumina and mordenite) and the environmental conditions (hydrated and dehydrated state). Crn+ ions are mobile under hydrated and dehydrated conditions and Crn+ preferentially migrates from silica to alumina and, to a lesser extent, to mordenite, although only a small amount of migration of Crn+ is observed from alumina to mordenite and vice versa. The observed preference sequences are discussed in relation to the properties of the inorganic oxides.


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