Synthesis of Ni-CeO₂ catalyst for the partial oxidation of methane using RF thermal plasma

Ni-CeO₂ catalysts with a nickel content of 50 mol% were prepared using RF thermal plasma, and their catalytic activities for methane partial oxidation were characterized. For the synthesis of Ni-CeO₂ catalysts, a precursor containing Ni (~5-μm diameter) and CeO₂ (~200-nm diameter) powders were heated simultaneously using an RF plasma at a power level of ~52 kVA and a powder feeding rate of ~120 g/h. From the X-ray diffraction data and transmission electron microscopy images, the precursor formed into high crystalline CeO₂ supports with nanosized Ni particles (< 50-nm diameter) on their surfaces. The catalytic performance was evaluated under atmospheric pressure at >500℃ and a CH₄:O₂ molar ratio of 2:1 with Ar diluent. Although the Ni content was high (~50 mol%), the experimental results reveal a methane conversion rate of >70%, selectivities of CO and H₂ greater than 90% and slight carbon coking during an on-stream test at 550℃ for 24 h. However, at 750℃, the on-stream test revealed the formation of filament-like carbons with an increased methane conversion rate over 90%.