Abstract: Ni/Al2O3 catalyst was prepared by evaporation method. Ni/α-Al2O3 and Ni/γ-Al2O3 catalysts were prepared using traditional incipient wetness impregnation. Dry reforming of methane over the prepared catalysts and the commercial catalyst Z118Y for steam reforming of natural gas was investigated. Properties of the carbon species deposited on the surface of the catalysts were characterized by H2-temperature programmed reduction (H2-TPR), Brunauer-Emmett-Teller (BET) specific surface area analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetry-differential scanning calorimetry (TG-DSC), and temperature programmed hydrogenation (TPH). The results showed that there are three main carbon species on the surface of the catalysts, namely amorphous, filamentous, and graphitic carbon. In addition, the content of carbon deposited on these catalysts varied because of different structures and properties of alumina. Filamentous carbon (namely carbon nanotubes) was the main species deposited on catalysts Z118Y, Ni/Al2O3, and Ni/α-Al2O3 while the graphitic carbon species was dominant on the Ni/γ-Al2O3 catalyst. Furthermore, the particle size of nickel on the Ni/γ-Al2O3 catalyst was small (less than 15 nm) and narrowly distributed while it also showed a high dispersion of metallic nickel on the support. It is recognized that the high dispersion of nickel particles would not only decrease the deposition of carbon on the surface of the catalyst but also depress the growth of filamentous carbon effectively.

Key words: Nickel, Alumina, Dry reforming of methane, Deposited carbon, Species