Catalytic dehydration of d-xylose to 2-furfuraldehyde in the presence of Zr-(W,Al) mixed oxides. Tracing by-products using two-dimensional gas chromatography-time-of-flight mass spectrometry
Zirconium-tungsten mixed oxides (ZrW) are effective catalysts in the aqueous-phase dehydration of d-xylose to 2-furfuraldehyde (Fur), at 170 °C. The texture and acid properties of ZrW materials were modified to enhance Fur yields. The catalysts prepared by co-condensation without a templating agent (ZrW(X), X = NO3, Cl; X is related to the type of zirconium precursor) possess relatively low specific surface area and amounts of accessible acid sites, leading to a modest Fur yield of ca. 35% at 99% conversion. The use of a templating agent in the preparation of mesoporous ZrW (ZrW-MP) increased considerably the specific surface area and the amount of accessible acid sites, which resulted in enhanced Fur yields (42%) reached at comparable conversions. Further improvements in Fur yields at high conversions were accomplished by introducing aluminium in the catalyst preparation procedure to give ZrAlW-MP (51% yield at 98% conversion). Fairly good catalytic results were also obtained in the case of the ZrAlW-MP catalyst, using solely water as solvent (46% yield at 93% conversion). A study of the identification of the reaction by-products by two-dimensional gas chromatography (GC × GC) combined with time-of-flight mass spectrometry (ToFMS) was carried out. âº Zr–W mixed oxides are solid acid catalysts in the aqueous phase dehydration of xylose into furfural. âº The texture and acid properties of Zr–W mixed oxides can be modified to enhance furfural yields. âº Catalyst preparation using a surfactant template and doping with Al enhances surface area and acidity. âº Identification of the water-soluble reaction by-products by SPME/GC × GC–ToFMS analyses.