424a.    CAMPBELL, W. M. AND JOHNSTONE, H. F.  Reactions of Hydrogen and Carbon Monoxide in a Tubular Reaction With Iron-Copper Catalyst.  Ind. Eng. Chem., vol. 44, 1952, pp. 1,570-1,575; Chem. Abs., vol. 46, 1952, p. 8,349.

                   Some of the factors affecting the Fischer-Tropsch synthesis were studied in order to learn more about the reaction mechanism.  The reactor consisted of a porous alundum tube, impregnated with the catalyst, through which the gases flowed longitudinally.  Stable and reproducible Fe-Cu catalysts which produce CO₂ and hydrocarbons from synthesis gas at atmospheric pressure were developed.  When treated with steam and CO at 250° the activity of these catalysts increases.  At 280° the activity drops rapidly and eventually reaches a period of constant activity where the only products are CH₄, C₂H₄, C and CO₂.  The loss in activity due to H₂S poisoning is a linear function of the amount of S absorbed, and when about 0.5 atom of S/atom of metal is taken up the activity is 0.  Catalysts producing CO₂ are active for the water gas shift reaction.  Heating at 310° in the presence of H₂ and CO destroys the synthesis reaction activity, but does not change the shift reaction activity.  H₂S destroys the activity for both reactions.  The shift reaction activity of a H₂O producing catalyst can be increased by increasing the H₂ concentration in the feed gas.  These results are definite proof of the existence of 2 types of active centers.  1 for the shift reaction and the other for the synthesis reaction.  A dual reaction mechanism is proposed, by which paraffins are formed by Craxford’s mechanism, and olefins are formed by simply splitting the (CH₂)_n chain off the surface.  In a CO₂-producing catalyst, the metal active centers must be present in clusters principally.