Barium promoted Ni/Sm 2 O 3 catalysts for enhanced CO 2 methanation.

Low temperature CO 2 methanation is a favorable pathway to achieve high selectivity to methane while increasing the stability of the catalysts. A Ba promoted Ni/Sm 2 O 3 catalyst was investigated for CO 2 methanation at atmospheric pressure with the temperature ranging from 200-450 °C. 5Ni-5Ba/Sm 2 O 3 showed significant enhancement of CO 2 conversion particularly at temperatures ≤ 300 °C compared to Ni/Sm 2 O 3 . Incorporation of Ba into 5Ni/Sm 2 O 3 improved the basicity of the catalysts and transformed the morphology of Sm 2 O 3 from random structure into uniform groundnut shape nanoparticles. The uniformity of Sm 2 O 3 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 Sm 2 O 3 under a reducing environment presumably via isomorphic substitution. The disappearance of a high temperature (∼600 °C) reduction peak in H 2 -TPR analysis revealed the reducibility of NiO following impregnation with Ba. However, further increasing the Ba loading to 15% formed BaNiO 3 -BaNiO 2.36 phases which consequently reduced the activity of the Ni-Ba/Sm 2 O 3 catalyst at low temperature. Ni was suggested to segregate from BaNiO 3 -BaNiO 2.36 at high temperature thus exhibiting comparable activity with Ni/Sm 2 O 3 at 450 °C.