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 of the acetate precursor solution, the [Mn(H 2 O) 6 ] 2+ complex interacts strongly with surface hydroxyls of the γ-Al 2 O 3 . Evidence was obtained that this anchoring reaction proceeds at a Mn/OH ) 1/2 ratio up to 4.5 wt % Mn loading, leading to a highly dispersed oxidic manganese layer. At higher loadings, the precursor complex is deposited on the surface concurrently. Upon drying at 383 K, part of the manganese is oxidized to higher oxidation states (Mn 3+ and Mn 4+ ), while a further increase in (average) oxidation state takes place upon calcination at 573 K. After calcination, the manganese species are present as a mixture of Mn 2+ , Mn 3+ , and Mn 4+ . At low loadings (<1 wt %), approximately equal amounts of these three oxidation states are present, whereas Mn 3+ becomes the predominant species at higher loadings. ESR reveals that at low loadings, almost all the manganese is present as isolated species, while at 4.5 wt % Mn loading, still more than 70% of the manganese is isolated. The decrease of the fraction of isolated manganese species at higher loadings is accompanied by a decreased selectivity toward N 2 production in the selective catalytic reduction of NO. The fraction Mn 2+ is present in an axially distorted octahedral coordination.

Low-Energy Ion Scattering (LEIS) was employed to study the surface of unsupported and silica-supported Cu/ZnO catalysts. It was shown that, by applying isotopic enrichment (63Cu and 68Zn), the copper and zinc signals can be separated. LEIS measurements showed a considerable amount of lead on the surface of the 63Cu/68ZnO catalyst. It was concluded that lead originated from the 68ZnO raw material and segregated during catalyst reduction to the surface. In contrast, no impurities were detected on the surface of the 63Cu/68ZnO/SiO2 catalyst. This seemingly contradictory observation was attributed to the higher degree of copper and zinc dispersion in the latter catalyst or interaction of lead with the support. It was shown previously, that catalytic activity of Cu/ZnO/SiO2 catalysts in methanol synthesis and ester hydrogenolysis is proportional with the reduction temperature applied (600−750 K). A depth profile of copper and zinc obtained for the high-temperature reduced silica-supported catalyst revealed that the surface was enriched in zinc, whereas copper was more abundant in layers beneath the surface. In the low-temperature reduced catalyst, the zinc enrichment was less prominent. These results suggest that the reduction at high-temperature results in segregation of zinc oxide to the surface.