Effect of potassium on the high pressure kinetics of ammonia synthesis over fused iron catalyst

Abstract

Measurements were performed of reaction rate in the process of ammonia synthesis (T=370–470°C) on doubly promoted (DP) (Al₂O₃, CaO) and triply promoted (TP) (K₂O, Al₂O₃, CaO) iron catalysts. The latter were obtained by impregnation of the reduced and subsequently passivated DP precursors with alcoholic solution of KOH. The studies were carried out under high total pressure (10 MPa) in a wide range of ammonia partial pressure in the gas phase: from 0.25 to about 7 bar. The results are shown to be authoritative for the so-called kinetic regime. The effect of the presence of K⁺ cations in the catalyst was the stronger, as the temperature of the reaction was the lower and, in particular, the ammonia pressure in the gas phase the higher. The obtained results are in good accordance with the results of Somorjai's studies on activity of iron single crystal surfaces both clean and covered with (K+O) adlayer.