Continuous Furfural Hydrogenolysis into 2‑Methylfuran and 2‑Methyltetrahydrofuran over Cu/γ–Al₂O₃ with ReO_x and WO_x as Catalyst Boosters

Cu/Al₂O₃ catalysts, enhanced with ReO_x and WO_x as catalyst boosters, were employed for the hydrogenolysis of furfural (FAL) into 2-methylfuran (2-MF) and 2-methyltetrahydrofuran (2-MTHF) within a continuous fixed-bed reactor. Comprehensive catalyst analyses revealed that the addition of ReO_x and WO_x onto Cu/Al₂O₃ catalysts resulted in reinforced metal–support interactions, while the acidity, in terms of both its strength and quantity, was influenced by these booster additions. Additionally, structural characterizations after H₂ reduction via X-ray diffraction, X-ray absorption near-edge structure, and X-ray photoelectron spectroscopy confirmed the coexistence of Cu in the forms of Cu⁰/CuO_x across all of the Cu-containing catalysts, whereas the valence states of Re⁰/ReO_x and WO_x were detected for the ReCuAl and WCuAl catalysts, respectively. Operating at a maximum temperature of 220 °C, the ReCuAl catalyst achieved the highest combined yields of 2-MF and 2-MTHF at 80.4%, with the WCuAl catalyst reaching 89.0%, in contrast to the lowest yields of 54.0% obtained with the CuAl catalyst. These results underscore the positive impact of ReO_x and WO_x additions on Cu/Al₂O₃ catalysts, in which the catalyst acidity, metal–support interactions, and coexistence of metallic and oxophilic sites influenced the hydrogenolysis process, leading to the enhanced production of 2-MF and 2-MTHF simultaneously from FAL.