Boosting Ethanol Production via Strategic CO Co-Feeding in CO2 Hydrogenation over Rh-Based Catalysts

Abstract

The catalytic hydrogenation of carbon dioxide (CO2) to ethanol is a highly promising reaction for carbon utilization and the production of renewable fuels and chemicals. Achieving high ethanol selectivity remains the biggest challenge in the field. Ethanol formation on rhodium (Rh)-based catalysts from CO2 hydrogenation relies on the carbon monoxide (CO) insertion pathway that is kinetically limited compared to the competing hydrogenation of methyl intermediates to methane. In this study, we demonstrate that adding CO to the CO2 hydrogenation reaction stream over colloidally synthesized Rh/Fe/Li–TiO2 catalysts can effectively overcome this limitation. This direct co-feeding strategy promotes C–C coupling and suppresses methanation, increasing ethanol selectivity 5-fold to 24% and boosting the space-time yield 6-fold with only a 15% CO cofeed (CO/(CO + CO2)). Under optimized, hydrogen-deficient conditions (H2/(CO + CO2)), the ethanol selectivity further increases to 32%. Our findings present an efficient, simplified pathway for upgrading CO2-rich streams into higher-value chemicals.