Tuning Lanthanum Promotion in Ni/CeO2 Catalysts for Hydrogen-Rich Syngas Production via Partial Oxidation of Methane

Partial oxidation of methane (POM) provides an efficient route to convert methane into hydrogen-rich syngas, with lower energy demands than conventional steam reforming. This work evaluates lanthanum promotion effects on the physicochemical properties and catalytic behaviour of Ni/CeO2 catalysts. A series of 5Ni + xLa/CeO2 catalysts with 0–2 wt.% La was synthesised by wetness impregnation and characterized using N2 adsorption–desorption, Raman spectroscopy, and cyclic H2-TPR–O2-TPO–H2-TPR analysis. The results proved that promoter La has a strong effect on the structure and surface chemistry of the Ni/CeO2 catalysts, as it modifies the CeO2 framework, encourages the formation of surface carbonate species, and changes Ni interaction with the support. These structural shifts are closely tied to the enhancement of the catalyst’s performance and stability during POM. Among the catalysts, 5Ni + 1.5La/CeO2 struck the best balance between textural properties and catalytic performance. At 600 °C and a GHSV of 14,400 mL h−1 gcat−1, the CH4 conversion reached about 57–59% and H2 yield reached 53–55% over 300 min on stream. It also led to more than 70% CH4 conversion and more than 65% H2 yield for 22 h at 600 °C and 7200 mL h−1 g_cat−1, showing sustainable hydrogen-rich syngas production during continuous operation. However, increasing the La loading to 2 wt.% strengthened the La–CeO2 interaction to the point of limiting the accessibility and dispersion of active sites, which lowered catalytic activity. Hence, these findings reveal that 1.5 wt.% La is the optimum loading, which balances support structure, metal–support interaction, surface chemistry, and active-site accessibility, and offers a practical strategy for producing more effective and stable Ni/CeO2 catalysts for hydrogen-rich syngas production via POM.