53b.    SHULTZ, J. F., SELIGMAN, B., LECKY, J., AND ANDERSON, R. B.  Studies of the Fischer-Tropsch Synthesis.  XII.  Composition Changes of Nitrided Iron Catalysts During the Synthesis.  Jour. Am. Chem. Soc., vol. 74, 1952, pp. 637-640; Chem. Abs., vol. 46, 1952, p. 5,290.

                 Changes in the composition of nitrided Fe catalysts during use in the Fischer-Tropsch synthesis at 7.8 and 21.4 atm. operating pressure are described.  The e-nitrides are slowly converted to e-carbonitrides, the rate of replacement of N by C being somewhat more rapid at 21.4 than at 7.8 atm.  At the lower operating pressure, oxidation and deposition of elemental C proceed at a very slow rate, whereas at 21.4 atm. these reactions are considerably more rapid in some catalysts.  At the higher pressure, the type of structural promoter appears to be important in determining the rates of oxidation and of deposition of free C.  When used, nitrided catalysts are treated with H₂, the N is almost completely removed, whereas the C content is not greatly changed.  A part of the C appears either as Hägg carbide or cementite, depending upon the temperature of hydrogenation.