3368.     TEMKIN, M., AND PYZHEV, V. [Kinetics of the Synthesis of Ammonia on Promoted Iron Catalysts.]  Jour. Phys. Chem. (U.S.S.R.), vol. 13, 1939, pp. 851-867; Chem. Abs., vol. 34, 1940, p. 6512.

        From experimental data on the synthesis and decomposition of NH3 technical Fe catalysts promoted by Al2O3 and K2O at 400-450 and 1 atm. pressure and H2:N2 ratios of 0.5 up to 8.5, the rate constants are k=1.04X103 at 400 and 7.78 at 450.  The rate of formation of NH3 is given by v=k1PN2 (P3H2/P2HN3)a with a=0.5.  The determining factor in the forward process is the rate of activated adsorption on the N2-free surface.  For the reverse process, the rate of NH3 desorption is the rate-determining factor.  For the complete process, the equation


holds both for the experimental data of Temkin and Pyzhev and for those of other authors.  The apparent energy of activation for NH3 formation is ~14 cal. and for decomposition ~40 cal. per mol.