Rational design of Ni-sepiolite catalysts: Impact of incorporation method and metal loading on CO2 methanation efficiency

The influence of Ni incorporation methods and metal loading on sepiolite-based catalysts for the CO 2 methanation reaction was investigated. Catalysts synthesized via precipitation exhibited a Ni phase strongly interacting with a partially folded sepiolite structure, as revealed by ²⁹Si-NMR and TPR analyses, distinct from those obtained by incipient wetness impregnation. The precipitation method resulted in catalysts with enhanced reducibility and a fourfold increase in Ni 0 surface area, as confirmed by XPS and H 2 -chemisorption measurements, which correlated with higher CO 2 conversion and CH 4 selectivity observed. Among the precipitation-based catalysts, the one with 20 wt% Ni loading exhibited the optimal balance between Ni⁰ surface area (13.6 m² g CAT −1 ) and catalytic performance (0.233 mol CH 4 g CAT −1 h −1 , at 400 °C). Stability tests demonstrated that this catalyst maintained a steady CH 4 yield over 24 h of continuous operation. • Incipient wetness impregnation and precipitation for Ni incorporation were compared. • Precipitation yields a semi-folded sepiolite structure, as shown by 29 Si NMR. • Precipitation led to catalysts with higher reducibility and Ni 0 surface area. • The 20 Ni wt% catalyst optimized the Ni 0 surface area and the catalytic results. • The optimum catalyst kept a constant CH 4 yield after 24-hour long stability tests.