Selective methanation of CO over Ni/Al₂O₃ catalyst: Effects of preparation method and Ru addition

Four methods were adopted to prepare samples 20%NiO/Al₂O₃ with calcination fixed at 500 °C, which were then reduced into 20%Ni/Al₂O₃ and used as catalysts for reaction of selective methanation of CO in H₂-rich gas (CO-SMET). XRD and TPR measurements indicate that nickel aluminates were formed in the calcined samples and their formation was influenced by preparation methods. Higher temperatures were required to reduce the calcined samples more efficiently and to achieve a higher catalytic activity for CO-SMET. Among the four methods, the precipitation method using ammonium carbonate as precipitant produced the highest catalytic activity both for CO methanation and for CO₂ methanation after reduction at 800 °C for 2 h. The calcined sample 20%NiO/Al₂O₃ prepared with the method was therefore used as support and impregnated with Ru³⁺ solution. Ru addition promoted reduction of Ni²⁺ ions in the calcined sample even at the low temperatures of 400 °C and 500 °C. The catalyst 1%Ru-20%Ni/Al₂O₃ reduced at 500 °C thus had a superior performance, removing CO to ca. 30 ppm with a selectivity as high as 75% at reaction temperature of 220 °C.