Partial oxidation of methane on NiO–MgO–ZrO2 catalysts

Catalysts containing mixtures of NiO, MgO and ZrO2 were synthesized by the polymerization method. They were characterized by X-ray diffraction (XRD), physisorption of N2 (BET), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES), and then tested in the partial oxidation of methane (POM) in the presence of air (2CH4:1O2) at 750 °C for 6 h. Among the ternary oxides, the catalyst with 40 mol% MgO showed the highest conversion rates in the catalytic processes, but also the highest carbon deposition values (48 mmol h−1). The greater the amount of NiO–MgO solid solution formed, the higher was the conversion rate of reactants (CH4), peaking at 40 mol% of MgO. Catalysts with lower Ni content on the surface achieved a high rate of CH4 conversion into synthesis gas (H2 + CO). The formation of more NiO–MgO solid solution seemed to inhibit the deactivation of Ni° during reaction. The values of the H2/CO product ratio were generally found to be slightly lower than stoichiometric.