tert-Butanol intervention enables chemoselective conversion of xylose to furfuryl alcohol over heteropolyacids

Both the solvent and catalyst play important roles in the chemoselective transformation of biomass-related compounds to fine chemicals and fuels. We report herein an innovative catalytic strategy for the direct valorization of xylose without external H2 producing high yield of furfuryl alcohol (FA), which is a versatile platform molecule. The solvent tert-butanol served not only as a precursor of the hydrogen honor, but also as a shield to facilitate xylose dehydration and inhibit the polymerization and decomposition reactions of FA. Commercial H4SiW12O40 was found to work as a multifunctional catalyst during the cascade conversion and had good reusability. The underlying catalytic mechanism revealed that the Brønsted and Lewis acid sites co-existed cooperatively to catalyze the xylose dehydration step and the active metal site of W atom adsorbed the hydrogen proton for the transfer hydrogenation of furfural to FA. After the incorporation of the formic acid as a supplemental hydrogen source, an unprecedented FA yield of 90% could be accomplished in a batch reactor under mild conditions. The kinetic behavior describing the conversion of xylose to FA was investigated to monitor the process. The estimated activation energies for xylose dehydration, furfural hydrogenation, and FA decomposition were 85.1, 78.8, and 101.1 kJ mol−1, respectively. This study opens a new avenue for the selective production of FA from hemicellulose-derived pentose in a green and straightforward manner.