Exsolved LaNiRuO 3 perovskite-based catalysts for CO 2 methanation reaction

Hydrogenation of CO 2 for methane formation is one of the thermodynamically favorable processes for reducing atmospheric CO 2 emissions. The present work demonstrates the synthesis and evaluation of LaNiRuO 3 perovskite-derived catalysts for CO 2 methanation in both supported and unsupported (bulk) forms. Specifically, two catalysts were prepared: (i) a Ru-substituted LaNiO 3 perovskite, LaNi 0.9 Ru 0.1 O 3 , with 10 at% Ru and (ii) a supported version (30% LaNi 0.9 Ru 0.1 O 3 /Al 2 O 3 ). The catalysts were synthesized through controlled reduction conditions, and they were thoroughly characterized, before and after the exsolution process, using XRD, TEM, XPS, BET, H 2 -TPR, and H 2 -TPD techniques. The characterization results indicated that the exsolved LaNi 0.9 Ru 0.1 O 3 /Al 2 O 3 catalyst formed small Ni particles (∼6 nm), resulting in better dispersion (18%) while maintaining a high surface area (141 m 2 g −1 ) and porosity. This catalyst demonstrated a 10% higher CO 2 conversion (77%) at a temperature lower by 50 °C ( i.e. 400 °C) than the exsolved bulk LaNi 0.9 Ru 0.1 O 3 perovskite. Both catalysts exhibited over 90% selectivity for CH 4 in the 250–450 °C range. The enhanced catalytic performance of the exsolved LaNi 0.9 Ru 0.1 O 3 /Al 2 O 3 catalyst was attributed to the small Ni particle size, better dispersion, and the alumina support's high surface area and basic properties, facilitating the adsorption and dissociation of H 2 and CO 2 . Further long-term stability tests at 400 °C and 25 000 mL g −1 h −1 (WHSV) over 54 h revealed that the exsolved LaNi 0.9 Ru 0.1 O 3 /Al 2 O 3 catalyst maintained a 70% CO 2 conversion, with the CH 4 yield and selectivity above 60% and 95%, respectively. Thus, supporting the perovskite catalyst on Al 2 O 3 demonstrated a pronounced effect on the CO 2 conversion rate and CH 4 selectivity at lower temperatures along with ensuring the stability of catalyst over extended periods.