In situ Mössbauer studies and simultaneous catalytic reactions of CO + H2 mixtures at 1 and 20 bars pressure to form olefins were carried out on Fe and Fe-Ru bimetallic catalysts prepared by impregnation of Cab-O-Sil® with a hexane solution of Fe3(CO)12 and a mixture of Fe3(CO)12 and Ru3(CO)12. Under reaction conditions the main component of the Mössbauer spectra(I.S. = 0.0 mm s-1 and Q.S. = 0.5 mm s-) can be assigned to the reacting species of surface carbon, which can be distinguished from χ-carbide which has also formed during the reaction. In the presence of ruthenium, the spectra are very similar to those measured on iron, but a large χ-carbide signal with hyperfine splitting cannot be detected. From the kinetic and in situ Mössbauer experiments carried out under different conditions, direct evidence was found for the formation of mobile, reactive carbon which participates in the production of olefins and higher hydrocarbons. It can be transformed either into other types of carbon, one of which is responsible for methane formation, or into that species responsible for catalyst deactivation. A possible mechanism is discussed in this paper.
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