Significant role of well-dispersed Fe²⁺ ions in the support of Ni catalysts in enhancing coking resistance during partial oxidation of methane

Coking is still a major cause of catalyst deactivation in catalytic methane reforming processes. In this work, doping the support of Ni/γ-Al₂O₃ catalysts with iron to provide redox functionality was found to significantly enhance coking resistance in methane partial oxidation. Catalysts with well-dispersed Fe³⁺ in the support, with Fe mass% in the range of 1.1–15.2 were prepared and tested in reactions at 700 °C. The catalyst with 3.2% Fe in the support showed negligible crystalline carbon at a coking rate of 9.0 × 10⁻⁶ g_cg⁻¹_catalysth⁻¹ compared with its Fe-free counterpart that showed a coking rate of 7.7 × 10⁻⁴ g_cg⁻¹_catalysth⁻¹. On the other hand, ≥10% Fe resulted in the formation of FeAl₂O₄ and Fe⁰ that promoted considerable coking. The unique influence of iron was referred to the role of the dispersed Fe²⁺, which is dominant upon reduction, in promoting a redox cycle that allow the oxidation and removal of carbon.