1949. KÖLBEL, H., AND LANGHEIM, R. [Reaction Mechanism of the Fischer-Tropsch Synthesis. III. Investigation of the Carbides Formed in the Hydrogenation of Carbon Monoxide on Iron Catalysts.] Erdöl u. Kohle, vol. 2, 1949, pp. 544-550; Chem. Abs., vol. 44, 1950, p. 3235.

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Literature Abstracts

Purpose of the work reported in this paper was to examine the carbide theory of CO hydrogenation and to explain the carbide found by thermalmagnetic examination on used Fe catalysts. Of further interest was the effect of the promoters of Fe catalyst, alkali and Cu, on carbide formation. A review of the work of other investigators on the formation of Fe carbides is presented. In the treatment of pure, paramagnetic γ-Fe₂O₃ with CO at 265° a carbide Fe₂C is obtained. Beside this there is a separation of elementary C. The stability of the Fe₃C, which results in a certain manner from the speed of hydrogenation of the carbide-C, depends upon the raw material and its previous history as well as upon the conditions surrounding its preparation. Alkali hastens the formation of carbide- and elementary C. Cu accelerates the formation of carbide- but exerts a negative effect on the formation of elementary C. It also hastens the reduction of the Fe catalyst in carbide formation and CO hydrogenation. In the presence of both alkali and Cu, the speed of formation of carbide- and of elementary C undergoes a further, quite considerable increase. The X-ray diagram of Fe₂C agrees well with that found by G. Hägg, and the Curie point lies at about 240°-250°. The formation of a well-defined carbide and the synthesis reaction are not 2 consecutive but 2 parallel occurring reactions, which have their common starting point in the activation of the CO, which in one case leads to carbide formation and in the other to hydrocarbons. Alkali catalyzes both reactions directly, Cu catalyzes indirectly through the acceleration of the reduction of Fe₂O₃.