CHARACTERIZATION OF DISSOLVED LIGNINS IN 2-STAGE ORGANOSOLV DELIGNIFICATION OF WHEAT-STRAW

Wheat straw was pre-treated with 0.5 N NaOH at 75 degrees C for 2 h an d then post-delignified by 1.0 N H2SO4 catalyzed in ethanol-water (60/ 40, v/v) system at 75 degrees C for 2 h (Alkaline Pretreatment) or pre -hydrolyzed with 1.0 N H2SO4 for partial release of hemicelluloses at reflux temperature for 2 h and then post-delignified in organosolv pro cess (Acidic Pretreatment) through two-stage, respectively. Alkaline p retreatment yielded a higher release of lignin (51.2%) as compared to acidic pretreatment, in which 23.0% lignin was dissolved. On the other hand, acidic pretreatment appeared to be more effect on the rate of t he organosolv delignification during the following stage. The isolated alkali lignin LA, acid-soluble lignin and organosolv lignin fractions were characterized by UV, IR and C-13-NMR spectroscopy. The chemical composition of the four lignin fractions are reported.