| Abstract | A series of nickel-magnesium mixed oxides (NiMg) of varying molar ratios, Ni₉Mg, Ni₂Mg, NiMg, NiMg₂ and NiMg₉, were synthesized using the co-precipitation technique. These materials were prepared as possible lower cost alternatives to Pd-based methane oxidation catalysts. The NiMg catalysts were characterized by means of X-ray diffraction (XRD), photoelectron spectroscopy (XPS) and H₂-temperature programmed reduction (H₂-TPR). Their activity for complete methane oxidation was investigated using temperature programmed oxidation. Ni₉Mg was found to be the most active catalyst of the series. Characterization results showed that most of the materials formed solid solutions of the NiₓMg₁₋ₓO type. The activity of the Ni₉Mg was attributed to its highest surface area and highest oxygen mobility. It was further tested and aged in simulated natural gas engine exhaust that contained 10 vol% water vapor. The results were compared to a reference 1 wt% Pd/Al₂O₃ methane oxidation catalyst tested under the same conditions. Ni₉Mg exhibited approximately 94% methane conversion after 40 h of aging which was higher than that of the Pd-based reference catalyst with methane conversion below 80% after only 16 h of aging. Ni₉Mg is thus proposed as a promising alternative to PGM-based catalysts for complete methane oxidation. |
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