Structural characterization of potassium hydroxide liquor lignin and its application in biorefinery

The structural characteristics of the lignin from potassium hydroxide (KOH) liquor of jute stick ( Corchorus capsularis ) pulping were determined and compared with the isolated dioxane lignin from jute stick. The lignin structure was characterized by elemental, methoxyl group analysis, UV, FTIR, 1 H-NMR, 31 P-NMR, and 2D-NMR spectroscopy and molecular weight. 2D-NMR of both lignins isolated showed a predominance of β-O-4 aryl ether linkages. KOH pulping cleaved β-O-4 aryl ether linkage and increased phenolic hydroxyl group and reduced molecular weight. KOH lignin can replace 40% phenol in phenol-formaldehyde resin with satisfactory shear strength.