Synthesis and Characterization of Ru/Al2O3 Nanocatalyst for Ammonia Synthesis

Ru/Al2O3 catalysts were prepared by conventional incipient wetness impregnation as well as colloid deposition of RuCl3 precursor via in situ reduction with ethylene glycol (polyol) method on alumina support. The samples were characterized by TEM, XRD and TPR techniques. The catalytic performance tests were carried out in a fixed-bed micro-reactor under different operating conditions. Ethylene glycol as the reducing agent in the polyol method produced well-dispersed and uniform ruthenium nanoparticles with an average diameter of 7 nm supported on Al2O3. In conventional method, however, reduction by hydrogen resulted in considerably larger particles with average size of 12 nm. The Ru/Al2O3 catalyst prepared by polyol method exhibited three-fold higher activity in ammonia synthesis compared to the catalyst prepared by conventional method. The turnover frequency ratio of ammonia synthesis of polyol to conventional catalyst was estimated to be 2.1 at 450 degrees C implying the reaction is structure-sensitive over Ru-based catalysts.