Abstract
Uniform ruthenium nanoparticles with an average diameter of 5 nm were prepared by polyol method and then deposited on acidic (Al2O3) and basic (MgO) type of supports. After conditioning, the catalytic activity of the supported Ru nanoparticles was tested for ammonia synthesis. The present study revealed some very interesting features of the nano-sized Ru nanoparticles (i.e. Ru-nano/Al2O3) as compared with the conventional catalysts (Ru-conv/Al2O3). In contrast to the conventionally prepared catalysts (by impregnation), the morphology of the well-defined Ru nanoparticles on the support was independent of metal loading. Thus, the TOF values in the kinetic region were not affected by metal loading. It was observed also that, the catalytic activity of the Ru nanoparticles was little affected by the nature of the support. Due to the minimization of the metal-support interaction, the Ru-nano/Al2O3 catalyst exhibited high activity for ammonia synthesis. The maximum reaction rate over Ru-nano/Al2O3 was at least one order of magnitude higher (around 925 micro mol g-1 h-1) than the rate observed over conventional Ru/Al2O3 catalysts. The activation energies for ammonia formation over alumina and magnesia supported Ru nanoparticles were 107 and 77 kJ mol-1.
