Sm-promoted alumina supported Ru catalysts for ammonia synthesis: Effect of the preparation method and Sm promoter

Sm promoted Ru/Al2O3 catalysts were prepared by different preparation methods. The samples were characterized by XRF, TEM, CO chemisorption and H-2-TPD. It is found that chlorine-free Ru/Al2O3 catalyst could be prepared by precipitation method. The presence of residual chlorine restricted the adsorbed hydrogen, which corresponded to the desorption peak in the temperature range of 150 to 325 degrees C. The addition of Sm significantly decreased the amount of adsorbed hydrogen. Sm promoted the precipitated Ru/Al2O3 catalysts showed higher ammonia synthesis activities than those samples obtained by hydrogen treatment or hydrazine reduction. The activity of Sm promoted Ru/Al2O3 catalysts increased up to a certain value and then decreased with the increase in Sm loading. (C) 2010 Elsevier B.V. All rights reserved.