Simultaneous production of furfural, bromomethyl furfural and high-quality lignin from lignocellulosic biomass in a biphasic process involving molten salt hydrate

This study is to present an effective biphasic process for converting lignocellulosic biomass to high-value furan-based chemicals (primarily furfural from pentoses and bromomethyl furfural (BMF) from hexoses) and high-quality lignin under moderated conditions at 100-130 °C within 3 h. The biphasic system consists of an aqueous phase of molten salt hydrate, in which cellulose and hemicellulose in the biomass are converted to BMF and furfural, respectively, without pretreatment and an organic phase of extraction solvent, into which the produced furan products in the aqueous phase are immediately extracted to avoid undesirable condensation of the products to humins. Meanwhile, lignin in the biomass is extensively depolymerized during the reaction and separated as a residue from the system. The process was robust to handle different types of biomass including corn stover, switchgrass, aspen, poplar and Douglas fir. Under the investigated optimal conditions, the maximum molar yields of furfural and BMF were 69% and 85%, respectively. The lignin was preliminarily characterized by means of NMR, GPC, and FTIR to understand the nature of the lignin for co-product development.