Fabrication of bimetallic RuCu/HAP catalysts for the selective synthesis of C11 biofuel precursors from biomass-based 5-methylfurfural

Abstract

The synthesis of bis(5-methylfuran)methane (BMFM) from biomass-based 5-methylfurfural (5-MF), a vital fuel precursor, is crucial for biomass refining. However, selective BMFM production from 5-MF needs to suppress side reactions such as hydrogenolysis and decarbonylation. Therefore, direct hydrogenation of 5-MF into BMFM is very challenging in sustainable biomass valorization. In this study, we developed a bimetallic RuCu/hydroxyapatite (HAP) catalyst for selective synthesis of BMFM from 5-MF. The RuCu/HAP catalyst delivered a BMFM yield of 75.6% under mild reaction conditions (V_water : V_cyclohexane = 1 : 1, 4 MPa H₂, 100 °C, 4 h), significantly surpassing its monometallic counterparts (Ru/HAP: 28.7%; Cu/HAP: 0%). Furthermore, a 79% yield of C₁₁ straight-chain alkanes was obtained from BMFM through the hydrodeoxygenation (HDO) process. The systematic characterization revealed that Ru mediates hydrogenation steps via CO activation, while Cu orchestrates acid sites essential for self-condensation of 5-MFA. The synergistic interplay between metallic Ru and acidic Cu sites thereby enables simultaneous optimization of conversion efficiency and BMFM selectivity. These findings provide a practical and efficient route for converting lignocellulosic derivatives into renewable biofuels, particularly for sustainable aviation fuel applications.