Selective C2+ alcohol synthesis by CO2 hydrogenation via a reaction-coupling strategy

Abstract

Higher alcohol synthesis (HAS) from non-petroleum carbon resources (a mixture of H₂ and CO₂) is an attractive but challenging research target. This reaction still suffers from poor higher alcohol (HA) selectivity due to the complexity in the reaction network and uncontrollability in C–C coupling. Herein, we employed a reaction-coupling strategy to achieve selective conversion of CO₂ to HAs over multifunctional catalysts composed of a HAS primary component (KCuFeZn) and CH₃OH/CO synthesis promoting component (e.g., CuZnAlZr, ZnZr, ZnCrAl). A linear correlation between HA STY over multifunctional catalysts and CH₃OH + CO yield over promoting components confirms the key role of extra CH_xO*/CO* species in HAS catalysis. After screening, an optimized multifunctional catalyst composed of 4.7KCuFeZn and CuZnAlZr in close proximity realizes nearly 2 times higher HA selectivity (CO-free, 33.0% versus 17.4%) and HA STY (84.0 mg g_KCFZ⁻¹ h⁻¹versus 42.1 mg g_KCFZ⁻¹ h⁻¹) than the sole 4.7KCFZ catalyst at the same space velocity on the basis of 4.7KCFZ. Notably, the close proximity of two components by mortar mixing gives >55% selectivity to high value-added C₂₊ products (HA and light olefins). It is found that the fast migration of CO*/CH_xO* species can improve HAS activity via the synergy of two components at the interfaces. Hopefully, this work would provide a promising avenue to improve HAS activity over a multifunctional catalyst affording multiple types of active sites via a reaction-coupling strategy.