Integrated process for the co-production of bioethanol, furfural, and lignin nanoparticles from birch wood via acid hydrotropic fractionation

This study proposes an efficient biorefining strategy for co-producing of bioethanol, furfural, and lignin nanoparticles (LNPs) from birch wood based on acid hydrotropic fractionation. Birch was fractionated into glucan-rich washed water-insoluble solids (WIS) fraction and xylose-rich spent liquor (SL) fraction with a low p-toluenesulfonic acid (p-TsOH) concentration of 15% (w/v). The obtained WIS was utilized to produce 75.5 g/L ethanol (76.3% ethanol yield based on initial sugars in the enzymatic hydrolysate) through separate hydrolysis and fermentation. Meanwhile, the xylose-rich SL was concentrated and catalyzed by dehydration to produce furfural with tetrahydrofuran (THF) as a co-solvent. The furfural concentration of 27.3 g/L (78.2% theoretical yield) was achieved from the 3-fold concentrated SL (without lignin precipitation) with a 3:1 THF-SL ratio at 160 °C for 7 min. The enzymatic hydrolysis solid residue of WIS was further fractionated by p-TsOH to prepare LNPs with an average particle size of 37.4 nm. The mass balance showed that 6.5 t oven-dry birch wood produced 1.0 t ethanol, 0.61 t furfural and 0.63 t LNPs.