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 NH_{3} technical Fe catalysts promoted by Al_{2}O_{3} and K_{2}O at 400°-450° and 1 atm. pressure and H_{2}:N_{2} ratios of 0.5 up to 8.5, the rate constants are k=1.04X10^{3} at 400° and 7.78 at 450°. The rate of formation of NH_{3} is given by v=k_{1}P_{N2} (P^{3}_{H2}/P^{2}_{HN3})a with a=0.5. The determining factor in the forward process is the rate of activated adsorption on the N_{2}-free surface. For the reverse process, the rate of NH_{3} desorption is the rate-determining factor. For the complete process, the equation dP_{NH3}/dt=k_{1}(P_{N2}P^{1.5}_{H2}/P_{NH3})-k_{2}(P_{NH3}/P^{1.5}_{H2}) holds both for the experimental data of Temkin and Pyzhev and for those of other authors. The apparent energy of activation for NH_{3} formation is ~14 cal. and for decomposition ~40 cal. per mol. |