Kinetics and mechanism of NH3 synthesis over Fe(100) and K/Fe(100) model catalysts

In this investigation kinetics and mechanism of NH3 synthesis over Fe(100) and K/Fe(100) model catalysts have been studied. In this context, adsorption kinetics of both N2/Fe (100) and H2/Fe (100)systems is initially investigated. By using statistical mechanic approach, we have determined the adsorption coefficient for N2 and H2 molecules as well as transition probability of different states of adsorption and dissociation of the reactants molecules. The effect of surface catalyst temperature on the reaction rate (TOF) is studied under different reactant partial pressures. The mechanism of NH3 synthesis is suggested based on LH surface reactions model. According to the obtained results, activation energy for the reaction over Fe (100) and K/Fe(100) (for θk=0.1ML) was determined 19.6 and 11.1 kcal/mole, respectively. The order of reaction on both catalysts with respect to PN2 and PH2 was unity and negative, respectively. Based on our data analysis, the NH3 synthesis obeys Temkin isotherm.