Synthesis, structural features, and reactivity of Fe-Mn mixed oxides prepared by microemulsion

Iron-manganese mixed oxides have been prepared by the microemulsion (MEM) technique, obtaining solids displaying homogeneously distributed Fe-Mn phases. For the sake of comparison similar samples prepared by different techniques have been studied. Magnetization measurements reveal that the extension of the Fe-Mn interaction was enhanced in the samples prepared by microemulsion and so was the sample homogeneity. The average size of the oxide particles prepared by microemulsion lies in the nanometer range, displaying also a narrow particle size distribution. A certain degree of manganese surface enrichment was observed for all samples and overall in those containing a larger amount of Mn, irrespective of the preparation method as revealed by X-ray photoelectron spectroscopy. Selected solids were used as catalyst precursors for the Fischer-Tropsch reaction. Mn promotion led to an enhancement of the olefin-to-paraffin ratio in the samples over which Fe-Mn interaction developed.