| Summary: | A new spinelized Ni catalyst (Ni-UGSO) using Ni(NO<sub>3</sub>)<sub>2</sub>·6H<sub>2</sub>O as the Ni precursor was prepared according to a less material intensive protocol. The support of this catalyst is a negative-value mining residue, UpGraded Slag Oxide (UGSO), produced from a TiO<sub>2</sub> slag production unit. Applied to dry reforming of methane (DRM) at atmospheric pressure, T = 810 °C, space velocity of 3400 mL/(h·g) and molar CO<sub>2</sub>/CH<sub>4</sub> = 1.2, Ni-UGSO gives a stable over 168 h time-on-stream methane conversion of 92%. In this DRM reaction optimization study: (1) the best performance is obtained with the 10–13 wt% Ni load; (2) the Ni-UGSO catalysts obtained from two different batches of UGSO demonstrated equivalent performances despite their slight differences in composition; (3) the sulfur-poisoning resistance study shows that at up to 5.5 ppm no Ni-UGSO deactivation is observed. In steam reforming of methane (SRM), Ni-UGSO was tested at 900 °C and a molar ratio of H<sub>2</sub>O/CH<sub>4</sub> = 1.7. In this experimental range, CH<sub>4</sub> conversion rapidly reached 98% and remained stable over 168 h time-on-stream (TOS). The same stability is observed for H<sub>2</sub> and CO yields, at around 92% and 91%, respectively, while H<sub>2</sub>/CO was close to 3. In mixed (dry and steam) methane reforming using a ratio of H<sub>2</sub>O/CH<sub>4</sub> = 0.15 and CO<sub>2</sub>/CH<sub>4</sub> = 0.97 for 74 h and three reaction temperature levels (828 °C, 847 °C and 896 °C), CH<sub>4</sub> conversion remains stable; 80% at 828 °C (26 h), 85% at 847 °C (24 h) and 95% at 896 °C (24 h). All gaseous streams have been analyzed by gas chromatography. Both fresh and used catalysts are analyzed by scanning electron microscopy-electron dispersive X-ray spectroscopy (SEM-EDXS), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) coupled with mass spectroscopy (MS) and BET Specific surface. In the reducing environment of reforming, such catalytic activity is mainly attributed to (a) alloys such as FeNi, FeNi<sub>3</sub> and Fe<sub>3</sub>Ni<sub>2</sub> (reduction of NiFe<sub>2</sub>O<sub>4</sub>, FeNiAlO<sub>4</sub>) and (b) to the solid solution NiO-MgO. The latter is characterized by a molecular distribution of the catalytically active Ni phase while offering an environment that prevents C deposition due to its alkalinity.
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