RuO₂–Ru/Hβ zeolite catalyst for high-yield direct conversion of xylose to tetrahydrofurfuryl alcohol

Tetrahydrofurfuryl alcohol (THFOL), a valuable biomass-derived chemical, is an important precursor for producing linear diols and biodegradable solvents. Herein, we present the one-pot cascade conversion of xylose to THFOL over an Hβ zeolite-supported RuO₂–Ru (RuO₂–Ru/Hβ) catalyst. To elucidate the structure–property correlation of the RuO₂–Ru/Hβ catalyst and achieve a high THFOL yield via sequential isomerization, dehydration, and hydrogenation, several synthesis methods, namely incipient wetness impregnation, reductive deposition, activated reductive deposition, and post-oxidative activated reductive deposition (ARD-O) were used. The best catalytic performance was obtained over the RuO₂–Ru/Hβ-ARD-O catalyst. An almost complete conversion of xylose and a high THFOL yield of 61.8% were achieved after 1 h at 180 °C under an initial H₂ pressure of 3.0 MPa in tetrahydrofuran. In-depth analyses of the RuO₂–Ru/Hβ-ARD-O catalyst furfural (FFA)- and CO-probed diffuse reflectance infrared Fourier transform spectra indicated the formation of RuO₂ at the corner and edge sites of Ru nanoparticles. The direct conversion of FFA to THFOL at interfacial RuO₂–Ru sites without furfuryl alcohol (FOL) readsorption hindered the contact of FOL with the acidic support, which suppressed the formation of humin and other byproducts and led to a high THFOL yield.