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Return to Abstracts of Literature 1750-1999

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 1948.    KÖLBEL, H., ACKERMANN, P., JUZA, R., AND TENTSCHERT, H.  [Reaction Mechanism of the Fischer-Tropsch Synthesis.  II.  Investigation of Iron Catalysts in the Hydrogenation of Carbon Monoxide.]  Erdöl u. Kohle, vol. 2, 1949, pp. 278-285; Chem. Abs., vol. 43, 1949, p. 8117.

        Fe catalysts prepared from Fe (NO₃)₃, initially a-Fe₂O₃, promoted with Cu (0.001-0.16%), K₂CO₃ (0.0-0.25%), and BaCO₃ were investigated analytically, catalytically, magnetically, thermomagnetically, by means of X-rays, and by adsorption measurements.  It was found that the milder the treatment during preparation, the more imperfect the a-Fe₂O₃ lattice and the greater the surface development.  Promotion with Cu or alkali had no influence on the state of crystallization.  After exposure to synthesis, the catalyst consisted principally of magnetite (Fe₃O₄) and always contained Fe carbide.  No free Fe was present.  Whether Cu or K was built into the magnetite lattice could not be decided.  Below 5%, Cu could not be detected by means of X-ray analysis.  Above 5% it was present in the elementary state.  In active catalysts, the system Fe-C is a function of the original composition and the conditions of catalysis (CO-H₂).  A labile carbide (Curie temperature, 220°) appears initially during synthesis and is stable only to about 290°.  After longer synthesis exposure, a second thermally stable carbide (Curie temperature between that of cementite Fe₃C and that of Fe₂C) either replaces the first or is formed in addition.  High alkali content, with longer synthesis exposure favor the formation of Fe₂C (Curie temperature 250°) stable up to 400°.  Since even the most labile of the 3 carbides had virtually no influence on the catalyst activity, it is concluded that Fe carbide is not the important intermediary it was thought to be previously.  For confirmation, see abs. 2009.