Prehydrolysis and organosolv delignification process for the recovery of hemicellulose and lignin from beech wood
Beechwood was fractionated using a two-stage process approach followed by enzymatic hydrolysis of the obtained pulp. Where most of the xylan was recovered by the prehydrolysis in the first stage, while the most lignin was recovered in the subsequent organosolv delignification. Close to 85.8 wt% of the original xylan was recovered (prehydrolysis: 150 °C, 90 min, and 20 mM H2SO4) compared to 8.9 wt% of the original xylan in case of organosolv, without the prehydrolysis stage (organosolv: 150 °C, 70 min, 50% w/w aqueous ethanol, and 20 mM H2SO4). Low severity prehydrolysis was found to enhance the lignin yield by organosolv delignification (the maximum lignin yield obtained was 82.7 wt% of the original lignin), which implies that the lignin recondensation was reduced during the prehydrolysis. Prehydrolysis substantially improved the enzymatic cellulose digestibility from 56.74 g/L, after organosolv without prehydrolysis to 86.75 g/L.