2607.     PERRIN, M.  [Evolution of Activity of Fischer-Tropsch Catalysts.]  Compt. rend., vol. 224, 1947, pp. 342-343; Chem. Abs., vol. 41, 1947, p. 3739.

        Fischer and Meyer (abs. 988) observed that CO was completely hydrogenated to CH4 in the presence of a fresh catalyst.  Craxford (abs. 637) attributed the hydrogenation to metallic Co, and the synthesis of higher hydrocarbons to Co carbide.  Earlier it was observed that where the CO and H2 were diluted with CH4, condensable hydrocarbons were formed at once.  Now it has been found that N2 produces the same effect and, in general, lowering the partial pressure of CO and H2 inhibits the formation of CH4 almost completely.  Lowering of the synthesis temperature from 190° to 175°, as well as a reduction in the flow of the reactants, also reduces the necessary delay in the starting of the synthesis reaction.  These observations indicate that the initial production of CH4 is due to overheating the catalyst bed and that any method of preventing this temperature rise starts the hydrocarbon synthesis without the formation of excessive CH4.