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

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.