OPTIMIZING EXTRACTION AND STRUCTURAL CHARACTERIZATION OF ORGANOSOLV LIGNIN FROM WHEAT STRAW

Organosolv lignin from wheat straw was isolated with 1,3-butanediol at different temperatures (100, 120, 140, 160 and 180 degrees C) for 3 h and at 180 degrees C for different time periods (1, 1.5, 2, 2.5 and 5 h), respectively. The yield of the lignin fractions was generally high, the highest yield could reach 76.6% of the original lignin content. The most striking characteristics of these lignin fractions were the almost complete absence of neutral sugars (0.87%) and their low molecular weights (1500-2520 g/mol) with narrow polydispersities. Results showed that the organosolv lignin fractions contained a small amount of non-condensed guaiacyl, syringyl and p-hydroxyphenyl units, and a higher proportion of syringyl units was detected in the lignin fraction with a prolongation of the treatment time. Moreover, C-13-NMRand 2D HSQC spectra showed that the process did not significantly change the typical structure of the lignin