CHARACTERIZATION OF FILAMENTOUS CARBON ON NI/MGO CATALYSTS BY HIGH-RESOLUTION ELECTRON-MICROSCOPY

High-resolution electron microscopy has been used to characterize the filamentous carbon deposits which are obtained during the steam-reforming of n-butane, as catalyzed by Ni supported on MgO. Lower reaction temperatures ( ∼ 400-500°C) resulted in partially graphitic filamentous fibers, with small crystals, identified as predominantly Ni, usually located at the fiber tip. Higher reaction temperatures ( ∼ 650-700°C) gave carbon tubes or shells with a more highly developed graphitic nature, while the microcrystals at the ends of the tubes, identified as mainly NiO, were typically encapsulated by several graphitic sheets. Overall, these results are further confirmation that the morphology of the carbon deposits, and their growth mechanism, is independent of the type of catalyst and the particular catalytic reaction. © 1990.