An absorption edge and extended X-ray absorption fine structure study of a dispersed manganese dioxide oxidation catalyst

Abstract

Variously treated samples of a low-cost MnO₂–SiO₂ catalyst designed in the first instance for the complete vapour-phase oxidation of hydrocarbon and other vapours in pollution-control applications have been examined. The EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near-edge structure) characteristics of samples deliberately activated, deactivated or thermally degraded, i.e. respectively oxidised, reduced or destroyed, are compared. The oxidation number or effective atomic charge of the manganese ion in these samples is identified, as are also changes in the Mn—O bond distances. For comparison and reference, analogous data from bulk manganese oxides of known stoichiometry were also measured and are briefly considered.