Tandem reductive hydroformylation: A mechanism for selective synthesis of straight-chain α-alcohols by CO2 hydrogenation

Abstract

The direct conversion of CO2 into linear α-alcohols (C3+ alcohol) in high yields is challenging because of the complexity arising from multiple competitive reactions. No studies have yet elucidated why CO2 hydrogenation preferentially produces straight-chain C3+ alcohols rather than branched alcohols over metal oxide catalysts. In this study, we propose a new insight into the existence of tandem reductive hydroformylation as a mechanism for enhancing linear alcohol formation. We demonstrated a Na-promoted bimetallic Cu and Fe catalyst (Na–CuFe) that generated a C3+ alcohol-rich product (36.3 % of total products, 72.2 % of total alcohols) at a CO2 conversion of 14.2 %. The Na–CuFe catalyst developed Cu and Fe5C2 for the reverse water gas shift (RWGS) and Fischer–Tropsch synthesis (FTS) sites, respectively. The low Fe content resulted in the development of a Cu–Fe5C2 active interface. Operando in situ investigation demonstrated high CO owing to active RWGS reaction boosted chain growth for C3+ alcohols. Density functional theory (DFT) simulation indicated the preferred CHO insertion over CO for C–C coupling. Thus, the Cu–Fe5C2 interface promotes the hydroformylation of on-site-generated intermediate via FTS and subsequent reduction of C3+ aldehydes to their corresponding C3+ alcohols.