High Entropy Catalysts for Synthesis of Biofuels (C7–C17) via the Adjustable Carbon Chain Increasing of Furfural (C5) at Mild Temperature

The number of carbon atoms is closely related to the properties of liquid fuels. As for furfural (FUR)-based biofuels, the regulation of carbon chain length is greatly significant to improve the quality. In this work, the C7–C17 fuel precursor has been successfully synthesized via the oxidative condensation processes of biomass-derived FUR with aliphatic alcohols. With the promotion of the MgLaFeMnCu high entropy catalyst (HECAT), the carbon chain increase of FUR is adjustable by changing the carbon number of aliphatic alcohols. Typically, 2-(furan-2-yl-methylene) butanal (FMB, C9) could be prepared from the reaction of furfural with n-butanol, in which a 99.7% conversion and 93.8% selectivity of FMB were obtained at 80 °C for 2 h. Especially, a 94.3% conversion of FUR with 95.1% selectivity of FMB could be achieved at room temperature for a suitable reaction time. Moreover, all the oxidative condensation reactions of FUR with C2–C12 alcohols have been successfully performed to generate the C7–C17 precursor in the presence of MgLaFeMnCu HECAT. Further investigations revealed that the occurrence of active O2–· species plays a crucial role during the oxidative condensation reactions. Meanwhile, the high activity of HECAT is attributed to the abundant oxygen vacancies, high surface area, and synergistic effects of the numerous metallic components.