Synthesis of furfural from xylan in γ-valerolactone/molten salt hydrate biphasic system

Herein, we reported a facile and efficient process for synthesis of furfural (FAL) from xylan in biphasic system. The excellent performance of more than 99.9% conversion of xylan with 77.22 mol% yield of FAL was obtained at 140 °C for 2 h. Notably, γ-valerolactone (GVL) was selected as the organic phase which played a key role in extracting and preserving the product FAL. Furthermore, a self-prepared molten salt hydrate (LiCl·3H2O) was designed as the water phase which conducted as both the solvent and catalyst. Besides, a proposed mechanism for the process is also investigated, especially on the pathways for the isomerization of xylose catalyzed by Al2(SO4)3 and LiCl·3H2O, respectively. Moreover, density functional theory (DTF) calculations were implemented to get insights into the total activation free energy of xylose isomerization to xylulose under different solvent ratios. Both of the catalyst and biphasic system could be recycled by simple steps, accompanying with more than 73.0 mol% of FAL yield obtained after three retrievals, which sheds lights on facile and efficient industrial production of FAL from corncob and lignocellulosic biomass.