Continuous Furfural Hydrogenolysis into 2-Methylfuran and 2-Methyltetrahydrofuran over Cu/γ-Al<inf>2</inf>O<inf>3</inf> with ReO<inf>x</inf> and WO<inf>x</inf> as Catalyst Boosters

Abstract

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.