Fractional characterization of ash-AQ lignin by successive extraction with organic solvents from oil palm EFB fibre

The ash-AQ lignin from the black liquor of oil palm empty fruit bunch was fractionated into four fractions by successive extraction with organic solvents of increasing hydrogen-bonding capacity. A comparison study of the lignin heterogeneity between the fractions was made in terms of fractional yield, content of associated polysaccharides, molecular weight, contents of carbonyl, phenolic hydroxyl, and aliphatic hydroxyl groups, and thermal stability. It was found that the content of carbonyl groups and the ratio of non-condensed syringyl/guaiacyl units decreased considerably with increasing molecular weight whereas the thermal stability increased. (C) 2000 Elsevier Science Ltd. All rights reserved.