CO₂ hydrogenation to higher alcohols over K-promoted bimetallic Fe−in catalysts on a Ce−ZrO₂ support

Novel K-promoted bimetallic Fe- and In-based catalysts on a Ce− ZrO₂ support were prepared and tested for higher alcohol synthesis from CO₂ and hydrogen. The FeIn/Ce−ZrO₂ precursors with different Fe contents were characterized in detail, and well-dispersed Fe₂O₃ and In₂O₃ phases with oxygen vacancies were observed. The catalysts were tested in a continuous setup at extended times on stream (up to 100 h) at 300 °C, 10 MPa, a gas hourly space velocity of 4500 mL g⁻¹ h⁻¹, and a H₂/CO₂ ratio of 3. The effect of K loading, the pretreatment atmosphere, Fe/(Fe + In) molar ratios, and calcination temperature on CO₂ conversion and product selectivity were studied. Best performance with a CO₂ conversion of 29.6% and a higher alcohol selectivity of 28.7%, together with good stability, was obtained over a K-0.82-FeIn/Ce−ZrO₂_900 catalyst after activation under a CO atmosphere. These findings were rationalized by considering the effects of the individual catalyst components (K, Fe, and In) on catalyst performance. Surprisingly, the presence of calcined SiC, used as a diluent in the packed bed reactor, was shown to have a positive effect on catalyst performance and as such also is catalytically active. The best performance in terms of higher alcohol yield (8.5%) obtained in this work ranks in the top three of reports on CO₂ hydrogenation to higher alcohols in a continuous setup. Moreover, light olefins with 20.3% selectivity (6.0% yield) were coproduced over the optimized catalyst, which has a positive effect on the economic potential of the catalysts.