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.