Ammonia synthesis over different iron- and ruthenium-based catalysts was modelled with appropriate rate models, used for the simulation of the process under different configurations and conditions. The kinetic models have been simulated and validated against experimental data. A scaled up reactor has been designed, at first with a once through configuration. On this model reactor we performed a sensitivity analysis to optimise the reaction conditions. Then, the sizing of an ammonia separation unit and the optimisation of the recycle loop allowed to compare different possible configurations. A multibed catalytic reactor with intercooling was then designed, using the same catalyst or different catalyst types properly to maximise the ammonia productivity. In particular, Fe-based catalysts were followed by the Ru/C one, in order to push the ammonia productivity towards the equilibrium value. The goal of the work is the design of an ammonia synthesis loop which couples different catalysts towards the optimisation of productivity and cost of operation and installation.