Behavior of metallic iron catalysts during Fischer-Tropsch synthesis studied with Mössbauer spectroscopy, x-ray diffraction, carbon content determination, and reaction kinetic measurements

摘要: The conversion of unpromoted, unsupported metallic iron catalysts into carbides during Fischer-Tropsch synthesis (CO:H2:He = 1:1:3, 1 atm) was studied with Mossbauer spectroscopy, X-ray diffraction, carbon content analysis, and reaction kinetic measurements. From a comparison between experiments at different temperatures literature data, it is concluded that both conditions the nature catalyst determine combination will be formed. Investigation single-phase revealed diffraction pattern commonly ascribed to pseudohexagonal carbide Fe2C actually belongs ∈′-Fe2.2C. At 513 K lower, unknown iron-carbon species were found, referred as FexC. It believed FexC represents poorly defined structures α-Fe crystallographic carbide. behavior Fischer-Tropseh in more detail function time. found rate hydrocarbon formation initially low, passed through maximum, decreased thereupon, while started high rapidly. These results can understood consequence either competition bulk carbidization or relatively slow activation for hydrocarbons which plays no role. Deactivation caused by an excessive amount inactive surface catalyst.