Introduction Methane, a major source of greenhouse gases as well as a principal component of natural gas, has been converted to hydrogen through steam reforming in the form of a mixture with CO. To separate pure hydrogen, energy-consuming sub-processes are required. However, catalytic methane decomposition (CMD) produces pure hydrogen and carbon nano-materials without the generation of a gaseous by-product. In this study, the nickel-carbon core-shell catalyst was synthesized by the reduction of CO2 under 1 bar and 800 K. The prepared core-shell catalyst was used for CMD to produce pure hydrogen and carbon nanoonion through CMD. Moreover, the spent catalyst was regenerated by the oxidative elimination of carbon nanoonion with CO2. Result and Discussion Core-shell structure. The synthesized catalyst had the clear core-shell structure with the nickel particle core and the amorphous carbon shell. This amorphous shell can prevent the oxidation of nickel particle during preparation. According to the previously reported mechanism of CMD for producing carbon nanoonion, the active nickel particle can be deactivated when the particle is completely encapsulated by the coke from decomposition.2 However, the amorphous carbon shell helped the nickel core escape the enclosed carbon through the originally existed amorphous structure before being deactivated. The escaped nickel particle was re-used for CMD and then, the catalytic activity of the core-shell catalyst was increased. Cyclic process of CMD and CO2 regeneration. The catalytic activities of the core-shell catalyst to CMD and the oxidative regeneration by CO2 were consistently maintained during 15 cycles. Conclusions The core-shell catalyst synthesized from CO2 showed the unprecedented catalytic activity of CMD for producing high-purity hydrogen and CNO due to its characteristics; the absence of NiO and the core-shell structure. Moreover, the spent catalyst was successfully regenerated through the oxidative elimination of carbon by CO2 with the production of pure CO.

Catalytic methane decomposition and oxidative regeneration by CO2 over nickel-carbon core-shell catalyst

253rd National Meeting (2017)

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