AN XPS STUDY ON RUTHENIUM COMPOUNDS AND CATALYSTS

The binding energy (BE) of the relevant peaks of several ruthenium compounds have been measured with a monochromatic small spot XPS. The BE of the 3d5/2 level of ruthenium is in the range 279.91-282.88 eV. The variation of BE is due either to the variation of the oxidation state or to the different counter-ion. A series of catalysts with varying amounts of ruthenium supported on alumina and prepared using different precursors was also analyzed. The presence of more ruthenium species other than the metal was observed. On the basis of the values previously obtained on unsupported compounds, the species with higher BE were assigned to oxides. On all the samples prepared from RuCl3, an additional peak at a very high BE (283.79 eV) has been observed. This peak is related to the presence of chlorine on the surface: it is suggested that it is related to a charge transfer interaction. The influence of this species on the CO reactivity in the Fischer-Tropsch reaction is discussed.