Boosting CO2 Methanation over Ni-based Catalysts via La-Al Mixed Oxide Synergy

Abstract

LaAlO3 demonstrated a pronounced mixed-oxide synergistic effect as a support for Ni-based catalysts in the CO₂ methanation reaction. Catalysts supported on LaAlO3 exhibited higher CH4 yields and turnover frequency (TOF) values than those supported on the individual oxides, La2O3 and Al2O3. This enhanced performance was attributed to the higher density of intermediate-strength basic sites and the lower apparent activation energies associated with the LaAlO3-supported catalysts. Among the tested formulations, the 15 wt.% Ni catalyst on LaAlO3 (15Ni/LaAlO3) showed the best performance, achieving 91% CO2 conversion and 99% CH4 selectivity at 350 °C under high space velocity conditions [10,000 mL (g cat·h-1)]. A comprehensive characterization using SEM-TEM, TPR, and H2-chemisorption, combined with a mechanistic assessment via time-resolved operando FT-IR spectroscopy, revealed that the catalyst's activity stems from a well-balanced distribution of moderate basic sites and high Ni0 surface availability. This combination favors the complete reduction of carbonated intermediates through a hydrogen-assisted associative pathway, with monodentate carbonate and Ni0 -CO identified as key intermediates. Additionally, 15Ni/LaAlO3 was evaluated for the first time in biogas upgrading. Using a model sweetened biogas mixture (60% CH4 – 40% CO2), the catalyst produced biomethane with 90.2% CH4 content after 24 hours of continuous operation, confirming its potential for sustainable energy applications.