Barium promoted Ni/SmO catalysts for enhanced CO methanation.

Low temperature CO methanation is a favorable pathway to achieve high selectivity to methane while increasing the stability of the catalysts. A Ba promoted Ni/SmO catalyst was investigated for CO methanation at atmospheric pressure with the temperature ranging from 200-450 °C. 5Ni-5Ba/SmO showed significant enhancement of CO conversion particularly at temperatures ≤ 300 °C compared to Ni/SmO. Incorporation of Ba into 5Ni/SmO improved the basicity of the catalysts and transformed the morphology of SmO from random structure into uniform groundnut shape nanoparticles. The uniformity of SmO created interparticle porosity that may be responsible for efficient heat transfer during a long catalytic reaction. Ba is also postulated to catalyze oxygen vacancy formation on SmO under a reducing environment presumably isomorphic substitution. The disappearance of a high temperature (∼600 °C) reduction peak in H-TPR analysis revealed the reducibility of NiO following impregnation with Ba. However, further increasing the Ba loading to 15% formed BaNiO-BaNiO phases which consequently reduced the activity of the Ni-Ba/SmO catalyst at low temperature. Ni was suggested to segregate from BaNiO-BaNiO at high temperature thus exhibiting comparable activity with Ni/SmO at 450 °C.