Abstract
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.