ESR study of paramagnetic species on reduced samples of molybdate catalysts

Abstract The ESR spectra of Mo(V) in reduced molybdenum catalysts have been studied. Samples with structures going from octahedral to tetrahedral through mixed coordination lead to ESR signals with axial or orthorhombic symmetry. The Mo(V) centers are mainly located in the bulk in Mo03 and in the sodium and potassium molybdates, while cadmium molybdate shows a higher surface reduction. The bulk and surface reducibility of the catalysts has been correlated with the oxidation mechanisms suggested for the catalysts investigated.