From Lignocellulosic Biomass to Furfural: Insight into the Active Species of a Silica‐Supported Tungsten Oxide Catalyst

Abstract

A sol–gel‐synthesized silica‐supported tungsten oxide catalyst that has Lewis acidity was characterized and employed as a solid acid catalyst in the synthesis of furfural directly from lignocellulosic biomass (isolated xylans and crop wastes). In a one‐pot method, 71 % furfural formation from isolated xylan was possible using a water/toluene (1:2 v/v) biphasic solvent system at 170 °C after 10 h over 10 wt % WO3/SiO2. The WO3/SiO2 catalyst in the selective conversion of pentosan from crop wastes (bagasse, wheat straw, and rice husk) yielded 72–87 % furfural under the optimum reaction conditions. Additionally, the catalyst presented excellent recyclability in at least eight runs after simple water washing. From the catalyst characterization studies, it was suggested that silicotungstic‐type acid species are anchored on the WO3/SiO2 catalyst that help to achieve a good catalytic activity.

Tungsten-Based Catalysts for Environmental Applications

“…At low loading (<5% W), there were virtually no Brønsted sites. Bhaumik et al developed silica-supported WO 3 and Ga 2 O 3 catalysts for lignocellulosic biomass to furfural processes [92]. Although the acidity was not characterized in detail, the authors of this work stated that Lewis sites are the most abundant acid sites on the catalysts.…”

Efficient conversion of fructose into 5-hydroxymethylfurfural over WO3/reduced graphene oxide catalysts

“…In addition, tungsten oxide (WO 3 ), as an acidic catalyst, had been used for biomass conversion. Prasenjit Bhaumik et al 29 reported silica-supported WO 3 as a solid acid catalyst in the synthesis of furfural, directly from lignocellulosic biomass. Yue Liu et al 30 reported that WO 3 catalyzed the conversion of cellulose into propylene glycol and ethylene glycol.…”

Conversion of Sugars and Biomass to Furans Using Heterogeneous Catalysts in Biphasic Solvent Systems

“…Hydrothermally stable, supported metal oxide catalysts have been used for efficient one‐pot furfural synthesis by Bhaumik and Dhepe in a toluene/H 2 O biphasic system, similar to the one‐pot method previously mentioned using H‐USY zeolite . Improving upon 54 % furfural obtained with H‐USY (170 °C; 6 h), the reaction system with sol‐gel‐synthesized, silica‐supported tungsten oxide catalysts yielded 71 % furfural (170 °C; 10 h) from isolated xylan.…”

“…Improving upon 54 % furfural obtained with H‐USY (170 °C; 6 h), the reaction system with sol‐gel‐synthesized, silica‐supported tungsten oxide catalysts yielded 71 % furfural (170 °C; 10 h) from isolated xylan. Pentosane from various crop wastes yielded 72–87 % furfural (170 °C; 8 h), which demonstrated the utility of the tungsten oxide catalysts …”