A comprehensive assessment of ammonia synthesis reaction kinetics and rate equations

In this study, the ammonia formation analytical rate equations were described well at pressures from 107 to 320 atm and different flow rates. The surface adsorption and desorption of nitrogen over iron-type catalysts were investigated according to the reaction kinetics of ammonia synthesis. The kinetic reaction rate equations of Temkin & Pyzhev, Langmuir–Hinshelwood, Ozaki et al., and the power rate law predicted the behaviour of the system and evaluated closeness to the experimental data. The microkinetic model rate (I and II) results were compared with other analytical and experimental rate equations. All proposed models showed excellent fits with experimental data. This result implies that the rate equation correlates to the overall dissociation rate of adsorbed nitrogen and the equilibrium constant for all ammonia formation reaction steps. The Temkin & Pyzhev rate results showed deficiencies at low ammonia synthesis operating pressures. Also, the nitrogen partial pressure reaction order was highly influenced by the power rate law results. The rate results from microkinetic models I and II were nearly the same. In addition, the Ozaki et al. rate equation could be used to predict the ammonia synthesis rate. The rapid computation time of the ammonia synthesis rate requires a simple rate equation. Therefore, calculating the rate based on the Temkin & Pyzhev and power rate laws is appropriate for fitting experimental measurements.