Carbon dioxide reforming of methane over Ni incorporated into Ce-ZrO ₂ catalysts

A co-precipitation/digestion method was employed in a single step to prepare Ni-Ce-ZrO₂ catalysts useful for carbon dioxide reforming of methane. The loading amount of Ni and the ratio of CeO ₂ to ZrO₂ were systematically varied to optimize the co-precipitated Ni-Ce-ZrO₂ catalysts. The prepared catalysts were characterized by various physico-chemical characterization techniques such as XRD, BET surface area, hydrogen chemisorption, SEM, TPR and XPS. It was found that 15% Ni (w/w) co-precipitated with Ce_0.8Zr_0.2O₂ having cubic phase gave synthesis gas with CH₄ conversion more than 97% at 800 °C and such activity was maintained without significant loss during the reaction for 100 h. On the contrary, Ni-Ce-ZrO₂ having tetragonal phase (Ce_0.2Zr _0.8O₂) or mixed phase (Ce_0.8Zr _0.5O₂) deactivated during the reaction due to carbon formation. The enhanced catalytic activity and stability of the co-precipitated Ni-Ce_0.8Zr_0.2O₂ catalyst is attributed to a combination of the nano-crystalline nature of cubic Ce_0.8Zr_0.2O₂ support and the finely dispersed nano-sized NiO_x crystallites, resulting in the intimate contact between Ni and Ce_0.8Zr_0.2O ₂ particles.