Enhancing higher alcohols selectivity in CO2 hydrogenation over FeCu catalysts via Mg modification

Abstract

CO₂ hydrogenation to higher alcohols (C₂₊OH) over FeCu-based catalysts offers a promising route for carbon recycling. However, challenges such as low carbon utilization efficiency and limited product selectivity still exist due to the complexity of the reaction network and unclear formation mechanisms. Herein, a series of Mg-modified FeCu-based catalysts (2Na/Fe₁Cu₂Mg_x) with varying Mg content were synthesized via co-precipitation method, and their catalytic performance of CO₂ hydrogenation to C₂₊OH were investigated. The introduction of an appropriate amount of Mg significantly reduced the particle size of active metals and enhanced the metal-metal interaction between Cu and Fe species, thus further facilitated the formation of a highly dispersed Cu-χ-Fe₅C₂ interface structure. Multiple advanced characterizations have demonstrated that Cu-χ- Fe₅C₂ well-defined interface improved the adsorption capacities for both CO₂ and CO, simultaneously promoting the synergistic coupling of CHₓ and CO intermediates for the highly selective formation of C₂₊OH products. The 2Na/Fe₁Cu₂Mg₁ catalyst achieved a C₂₊OH selectivity of 25.4 % and a space-time yield (STY) of 75.1 mg·g_cat^-¹ ·h^-¹ with CO₂ conversion of 32.6 % under 320 °C, 5.0 MPa. Remarkably, the STY further rose to 110.1 mg·g_cat^-¹ ·h^-¹ when the reaction temperature increased to 380 °C, with a CO₂ conversion reaching 55.4 % and CO selectivity reduced to just 6.7 %. This study elucidates the pivotal role of Mg in modulating catalyst structure and constructing efficient active interfaces, providing a new theoretical foundation and design strategy for the rational development of highly selective catalysts for CO₂ hydrogenation to higher alcohols.