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

Abstract

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.