Spectroscopic and catalytic studies on Snsb oxide catalysts

Abstract Spectroscopy studies of the surface of Snsb oxide catalysts has been investigated by the X-ray photoelectronic method, and by Emission Spectroscopic study of the non -homogeneous structure of Snsb oxide catalysts using a Laser microsensor. In the first method, it has been found that the surface of Snsb oxide catalysts accumulates Sb, which accounts for their high selectivity in partial oxidation of olefin. In the second method Snsb oxide catalyst with different ratios of their compounds, and promoted with alkali metal compounds were used; for each catalyst we determined the concentration of elements in both dark and bright fields. It has been found that their structure is nonhomogeneous due to the nonuniform distribution of Sn and Sb cations and with increased Sn/Sb ratio, the intensity of Sb lines in both dark and bright field decreases, whereas that of Sn lines increases. These structural defects observed upon introducing an alkali metal compound into Snsb oxide catalyst, seem to be one of the reasons for the change in its catalystic properties in the partial oxidation of iso-butylene catalysed by reduced Snsb oxide catalyst. The results illustrated that the decreased total activity and increased selectivity of an Snsb oxide catalyst are due to its decreasing activity in deep oxidation caused by surface reduction and the blocking of its centers responsible for deep oxidation.