Kinetic study of ammonia synthesis on a promoted Ru/C catalyst

A set of kinetic tests on a promoted Ru/C catalyst for ammonia synthesis has been carried out under industrially relevant reaction conditions (T= 370-460 DegC, P= 50-100 bar). The results have been elaborated by using some kinetic models either derived from literature or here-developed. The best results, as for fitting and consistency of the optimized parameters, were obtained by simply modifying the Temkin equation with the addn. of H2 and NH3 adsorption terms, to take into account their inhibiting effect on catalyst performance. Such an equation can be advantageously applied for better design and operation of ammonia synthesis reactors using Ru/C catalysts. The activation energy for the synthesis reaction was 23 kcal/mol, much lower than that previously found for Fe-based catalysts. From a practical point of view, it has been shown that the working pressure can be decreased, with the same plant productivity, by 40-50% when using the present Ru/C catalyst. Likewise, the ammonia concn. in the exit gas can be increased by about the same value if the working pressure is not decreased.