Promotion of Ru or Ni on Alumina Catalysts with a Basic Metal for CO 2 Hydrogenation: Effect of the Type of Metal (Na, K, Ba).

Ru and Ni on alumina catalysts have been promoted with a 10 wt% of alkali metal (K or Na) or alkaline earth metal (Ba) and tested in CO 2 methanation. For the catalyst consisting of Ni and Ba, the variation of Ba loading while keeping Ni loading constant was studied. The promotion in terms of enhanced CH 4 yield was found only for the addition of barium to 15 wt% Ni/Al 2 O 3 . In contrast, K and Na addition increased the selectivity to CO while decreasing conversion. For the Ru-based catalyst series, no enhancement in conversion or CH 4 yield was attained by any of the alkaline metals. CO 2 temperature-programed desorption (CO 2 -TPD) revealed that the amount of chemisorbed CO 2 increased significantly after the addition of the base metal. The reactivity of CO x ad-species for each catalyst was assessed by temperature-programed surface reaction (TPSR). The characterization revealed that the performance in the Sabatier reaction was a result of the interplay between the amount of chemisorbed CO 2 and the reactivity of the COx ad-species, which was maximized for the (10%Ba)15%Ni/Al 2 O 3 catalyst.