Breaking the activity-selectivity trade-off of CO2 hydrogenation to light olefins.

Abstract

Catalytic hydrogenation of CO₂ to value-added fuels and chemicals is of great importance to carbon neutrality but suffers from an activity-selectivity trade-off, leading to limited catalytic performance. Herein, the ZnFeAlO₄ + SAPO-34 composite catalyst was designed, which can simultaneously achieve a CO₂ conversion of 42%, a CO selectivity of 50%, and a C₂-C₄⁼ selectivity of 83%, resulting in a C₂-C₄⁼ yield of almost 18%. This superior catalytic performance was found to be from the presence of unconventional electron-deficient tetrahedral Fe sites and electron-enriched octahedral Zn sites in the ZnFeAlO₄ spinel, which were active for the CO₂ deoxygenation to CO via the reverse water gas shift reaction, and CO hydrogenation to CH₃OH, respectively, leading to a route for CO₂ hydrogenation to C₂-C₄⁼, where the kinetics of CO₂ activation can be improved, the mass transfer of CO hydrogenation can be minimized, and the C₂-C₄⁼ selectivity can be enhanced via modifying the acid density of SAPO-34. Moreover, the spinel structure of ZnFeAlO₄ possessed a strong ability to stabilize the active Fe and Zn sites even at elevated temperatures, resulting in long-term stability of over 450 h for this process, exhibiting great potential for large-scale applications.