Copper-manganese oxide catalysts supported on alumina: Physicochemical features and catalytic performances in the aerobic oxidation of benzyl alcohol

We report the facile synthesis of alumina supported copper-manganese mixed oxide catalysts by a homogeneous deposition-precipitation method and the catalytic applications of these catalysts in the oxidation of benzyl alcohol using molecular oxygen. Benzyl alcohol conversion of ca. 90.9% was achieved with benzaldehyde as the main product. The catalyst can be recycled consecutively up to seven runs without appreciable loss of its activity and selectivity. Characterizations with X-ray diffraction, transmission electron microscopy, Raman, X-ray absorption spectroscopy, and hydrogen temperature-programmed reduction suggested the formation of a mixed oxide (Mn_1.5Cu _1.5O₄) microcrystalline phase after adding copper to the manganese supported on alumina. Such formation would account for the high catalytic performance. Calcination under high temperature decomposed this mixed oxide phase, resulting in a poor catalytic activity.