Characterization of hemicelluloses and lignin released in two-stage organosolv and alkaline peroxide treatments from Populus euphratica

Two-stage treatments of dewaxed Populus euphratica with ethanol-H2O (60/40,v/v) under acid catalyst (0.2 N HCI) at 70degrees for 4 h and sequentially, with 2% H2O2 at pH 11.5 for 16 h, resulted in a dissolution of 72.8% of the original hemicelluloses and 72.3% of the original lignin, respectively. The degradation and oxidation of these lignins and hemicelluloses during the acidic organosolv pre-treatment and alkaline peroxide post-treatment were investigated. No significant oxidations of lignin and hemicelluloses were observed during the acidic organosolv pre-treatment, whereas the alkaline peroxide post-treatment led to substantial oxidation of the degraded lignin, but no oxidation of the released hemicelluloses. This suggested that lignin provides some protection for the hemicelluloses in dewaxed Pop Was euphratica against attack by alkaline peroxide. FT-IR and C-13-NMR studies of the degraded lignin samples further revealed that carboxyl groups were produced during the alkaline peroxide post-treatment.