Continuous Furfural Hydrogenolysis into 2-Methylfuran and 2-Methyltetrahydrofuran over Cu/γ–Al₂O₃ with ReOx and WOx as Catalyst Boosters

Cu/Al2O3 catalysts, enhanced with ReOx and WOx 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 ReOx and WOx 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/CuOx across all of the Cu-containing catalysts, whereas the valence states of Re0/ReOx and WOx 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 ReOx and WOx 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.