Characterization of Al2O3-Supported Manganese Oxides by Electron Spin Resonance and Diffuse Reflectance Spectroscopy

摘要: Alumina-supported manganese oxides, used as catalysts for the selective catalytic reduction of NO, were characterized by combined electron spin resonance and diffuse reflectance spectroscopies. Upon impregnation acetate precursor solution, [Mn(H2O)6]2+ complex interacts strongly with surface hydroxyls γ-Al2O3. Evidence was obtained that this anchoring reaction proceeds at a Mn/OH = 1/2 ratio up to 4.5 wt % Mn loading, leading highly dispersed oxidic layer. At higher loadings, is deposited on concurrently. drying 383 K, part oxidized oxidation states (Mn3+ Mn4+), while further increase in (average) state takes place upon calcination 573 K. After calcination, species are present mixture Mn2+, Mn3+, Mn4+. low loadings (<1 %), approximately equal amounts these three present, whereas Mn3+ becomes predominant loa...