As one of the rate expressions of high pressure ammonia synthesis in which industrial iron catalyst is employed, Temkin's Eqs. (1) and (2) are well known, but neither of them satisfy the data published by other investigators. This has been pointed out by Emmett, Uchida, Comings and others.
The authors propose here some rate expressions, Eqs. (10) and (11) which they have obtained after examining all the data available. Eq. (10) is correspondent to the case where the rate-determining step is the dissociated adsorption of nitrogen molecule and the active site of catalyst is partly covered with atomic nitrogen, viz., in the Langmuir type adsorption.
Eq. (10) is for the data of doubly or triply promoted catalyst (Cf. Fig. 1), while Eqs. (14) and (15) are for the singly promoted (by Al₂O₃) catalyst. Eq. (10) is found to be of great practical use, because the constant Ka remains constant, regardless of the variety of temperature and the kinds of catalysts employed.