Carbon covered Mg-Al hydrotalcite supported nanosized Ru catalysts for ammonia synthesis

Carbon covered hydrotalcite (CCHT) supported Ru catalysts with single (Cs or Ba) and double (Cs and Ba) promoters were prepared by two different methods viz., impregnation (IMP) and polyol reduction (PR) methods using ethylene glycol as solvent. The performance of the catalysts for ammonia synthesis was carried out in the temperature range of 523-698 K at atmospheric pressure. The following sequence with respect to the % NH3 (volume/volume) formation was observed; BaRuCCHT-IMP < BaRuCCHT-PR < CsBaRuCCHT-IMP < CsRuCCHT-IMP < CsRuCCHT-PR < CsBaRuCCHT-PR. XRD, TEM, N-2-adsorption, H-2-TPR, CO chemisorption and TPD of H-2 and CO2 techniques were used to investigate the physico-chemical properties of the catalysts and also to establish the reasons responsible for superior catalytic activity of CsBaRuCCHT-PR catalyst. The CO chemisorption and TEM studies revealed that CsBaRuCCHT-PR catalyst possessed the high active Ru metal surface area and small particle size. The highest activity of this catalyst could be attributed to high surface area, low particle size, high active surface metal (Ru) area, and strong Ru-CCHT interaction. (C) 2015 Elsevier B.V. All rights reserved.