Role of promoters on highly active nano-Ru catalyst supported on Mg–Al hydrotalcite precursor for the synthesis of ammonia

Single (Ba) and double promoted (Ba and Cs) Ru catalysts supported on calcined Mg–Al hydrotalcite were prepared by polyol reduction method to investigate the role of promoters on catalytic activity for NH3 synthesis at atmospheric pressure. The activities of these catalysts were compared with those of their corresponding impregnated catalysts. All the catalysts were characterized by X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD) of CO2 to determine basicities of the catalyst, BET surface area and CO chemisorption studies to find out particle size and active metal area of Ru. The reaction rate on the double promoted Ru catalysts was found to be higher than single promoted one. The double promoted catalyst prepared by polyol method exhibited exceptionally high activity (0.76%, v/v) at 598 K among all the other catalysts studied. The higher activity was attributed to the availability of more number of basic sites due to the presence of both Cs and Ba promoters as observed from CO2 TPD and to the easily reducible Ru species, which was confirmed by TPR analysis.