Vanadium-Promoted Low-Temperature and High-Efficiency CO2 Hydrogenation Catalysts Integrated with Metals Recovery Process: A Promising Carbon Emission Reduction Strategy

Converting spent aluminum-based catalysts into novel CO2 methanation catalysts represents a promising strategy for simultaneous waste valorization and greenhouse gas mitigation. However, achieving a high-value utilization of spent catalysts and efficient low-temperature CO2 methanation remains a significant challenge. This study reports the synthesis of high-performance carbon sequestration Ni-M/Al2O3 catalysts (M = Mn, Mo, Co, V) with high CO2 conversion and CH4 selectivity, derived from regenerated γ-phase alumina (γ-Al2O3) support obtained from spent catalysts. The associated active metals were recovered through selective leaching and subsequently incorporated via wet impregnation. Catalytic performance was evaluated in a fixed-bed reactor under atmospheric pressure, with the 20 wt % Ni-1 wt % V catalyst demonstrating optimal activity at 300 °C, achieving 92.95% CO2 conversion and CH4 yield peak. Mechanistic investigations revealed that V doping induces HCO* co-intermediates formation and shifts the reaction pathway from reverse water–gas shift to formate route, thereby reducing the rate-determining step barrier and facilitating methanation. This study establishes an effective green and sustainable approach for spent catalyst valorization while providing fundamental insights into V-promoted low-temperature CO2 methanation, offering significant implications for carbon reduction and energy transition technologies.