Morphologic effect of CeO₂ on the catalytic performance of Ni/CeO₂ in CO methanation

CeO₂ supports with different morphologies (including spherical CeO₂-S, bud-shaped CeO₂-F, and polyhedral CeO₂-P) were synthesized and the supported Ni/CeO₂ catalysts were prepared by ammonia-water coordination impregnation method; the effect of CeO₂ morphology on the catalytic performance of Ni/CeO₂ in CO methanation was then investigated. The results indicate that CeO₂-S, CeO₂-F, and CeO₂-P supports are rather different in the exposed crystal planes and oxygen vacancies, which have a significant effect on the catalytic performance of Ni/CeO₂ in CO methanation. In particular, CeO₂-S has the most oxygen vacancies; for CO methanation over the Ni/CeO₂-S catalyst, the conversion of CO and selectivity to CH₄ at 350 ℃ reach 99.19% and 88.88%, respectively. After 10 h thermal stability test, the Ni/CeO₂-S catalyst displays lowest carbon deposit (2.5%); the selectivity to CH₄ over the Ni/CeO₂-S catalyst remains above 80%, which is 1.3 times of that over Ni/CeO₂-F and 17.6 times of that over Ni/CeO₂-P. The excellent catalytic performance of Ni/CeO₂-S may be ascribed to that CeO₂-S support has large surface area and mainly exposes the 111 crystal plane with a large amount of oxygen vacancies, which can enhance the interaction between the support and the active center and alleviate the carbon deposition.