Thermocatalytic CO2 hydrogenation to high-yield ethanol and C3‒C5 alcohols over promoted Fe-based catalysts

Rb-promoted CuZnFe catalysts enable efficient CO 2 hydrogenation with high ethanol selectivity and space-time-yield (STY), while effectively suppressing methanation, offering a promising route for renewable fuel production using green H 2 . Direct catalytic hydrogenation is an effective approach for CO 2 utilization to produce ethanol and higher alcohols (HA), but developing non-precious metal catalysts with high activity and selectivity remains a major challenge. In this study, we report the development of a highly efficient 4wt%Rb/25wt%Cu-25wt%Zn-50wt%Fe catalyst, synthesized via the co-precipitation method, for the selective hydrogenation of CO 2 to ethanol and HA in a continuous flow fixed-bed reactor. The catalyst delivers an ethanol space-time yield (STY) of 4.4 mmol g cat −1 h −1 with 48.8% ethanol selectivity in the gas phase, while the condensed liquid fraction exhibits a maximum C 2+ OH selectivity of 85.3% under 20 bar (H 2 /CO 2 = 3) in the temperature range of 200–300 °C over 16–19 h. The superior catalytic performance is attributed to the optimized Rb loading, which enhances structural stability, preserves crystallinity, and mitigates Cu leaching. The Rb-promoting effect on C–C coupling arises from the synergistic interactions among Rb-Cu-Fe, as well as Rb-Cu-Zn. This synergy facilitates the formation of CH 3 CH 2 O*, CH 3 COO*, and CH 3 CHO* species on Rb/Cu-Fe 5 C 2 and Rb/CuZn sites. Notably, the 4%Rb/CuZnFe catalyst exhibits the most significant modifications in its electronic environment, likely due to changes in oxygen vacancies and altered metal-oxygen interactions upon Rb incorporation. Furthermore, the 4% Rb content plays a critical role in maintaining an optimal balance between catalyst basicity and oxygen vacancies, effectively enhancing CO 2 activation while suppressing side reactions. These findings underscore the potential of Rb-modified CuZnFe catalysts for efficient CO 2 hydrogenation to HA, offering a promising avenue for sustainable chemical production.