Study on FTIR,1H and 13C NMR Characterization of Poplar I 214 Heartwood and Sapwood Lignins

Milled wood lignins (MWLs)extracted from poplar I 214Populus×euramericana(Dode) Guineir cv.'I 214' heartwood and sapwood were characterized by elemental analysis,FTIR, 1H and 13 C NMR spectroscopy.The results showed that the methoxyl content in heartwood lignin was 8.73% higher than that in sapwood lignin,and the C 9 empirical formula for heartwood lignin and sapwood lignin were C 9H 7 16 O 2 38 (OCH3) 1 99 and C 9H 8 61 O 2 73 (OCH3) 1 33,based on methoxyl and elemental analysis.The free aliphatic hydroxyl groups per C 9 unit (OH aliph) were 78.2% in total numbers of hydroxyl groups of heartwood lignin,and the free phenolic hydroxyl groups(OH ph)were 21.8%.The OH aliph were 79.2% and the OH ph were 20.8% in sapwood lignin.The hearwood lignin showed 55.5% guaiacyl units and 44.5% syringyl units in the aromatic region.The sapwood lignin showed 61 3% guaiacyl units and 38 7% syringyl units.The FTIR, 1H and 13 C NMR spectra showed both lignins belong to typical hardwood lignin. heartwood and sapwood were characterized by elemental analysis,FTIR, 1H and 13 C NMR spectroscopy.The results showed that the methoxyl content in heartwood lignin was 8.73% higher than that in sapwood lignin,and the C 9 empirical formula for heartwood lignin and sapwood lignin were C 9H 7 16 O 2 38 (OCH3) 1 99 and C 9H 8 61 O 2 73 (OCH3) 1 33,based on methoxyl and elemental analysis.The free aliphatic hydroxyl groups per C 9 unit (OH aliph) were 78.2% in total numbers of hydroxyl groups of heartwood lignin,and the free phenolic hydroxyl groups(OH ph)were 21.8%.The OH aliph were 79.2% and the OH ph were 20.8% in sapwood lignin.The hearwood lignin showed 55.5% guaiacyl units and 44.5% syringyl units in the aromatic region.The sapwood lignin showed 61.3% guaiacyl units and 38.7% syringyl units.The FTIR, 1H and 13 C NMR spectra showed both lignins belong to typical hardwood lignin.