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

dPNH3/dt=k1(PN2P1.5H2/PNH3)-k2(PNH3/P1.5H2)

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.