Dry reforming of methane over sub-stoichiometric NiAl2O4-mediated Ni/Al2O3 catalysts

A series of Ni/Al2O3 catalysts were prepared from substoichiometric NiAl2O4 precursors (Ni/Al molar ratio between 0.5 and 0.05) were examined for the dry reforming of methane. The calcined spinel precursors and the corresponding reduced catalysts were characterised by N2 physisorption, X-ray fluorescence, X-ray diffraction, Raman spectroscopy, electronic microscopy coupled to elemental mapping, X-ray photoelectron spectroscopy and temperature-programmed techniques. Compared with the stoichiometric counterpart, nickel species present in Ni-deficient precursors were mostly in the form of a spinelic phase. After high-temperature reduction, narrow particle size distributions centred at 10 nm were obtained. The largest available nickel surface area (18 m2 g−1) was exhibited by the catalyst derived from the precursor with a Ni/Al of 0.15. The NiAl2O4-mediated catalysts, especially those with Ni/Al molar ratio in the 0.15–0.25 range, exhibited a notable performance at 90,000 h−1 and 650 °C. The optimal catalyst (14%wt.%Ni), with 93%CH4 and 80%CO2 conversions, was also able to operate for 200 h despite the significant formation of carbonaceous nanotubes (around 1gC gCAT-1) and were examined.