| Abstract
| - Results of a comprehensive study on the chemical structure of lignin from plantation Eucalyptusglobulus Labill are presented. Lignin has been isolated by a modified mild acidolysis method andthoroughly characterized by functional group analysis, by a series of degradation techniques(nitrobenzene oxidation, permanganate oxidation, thioacidolysis, and Py−GC−MS), and 1H and 13CNMR spectroscopy. Plantation Eucalyptus globulus lignin was found to be of the S/G type with anextremely high proportion of syringyl (S) units (82−86%) and a minor proportion of p-hydrophenylpropane (H) units (roughly 2−3 mol %). Unknown C-6 substituted and 4-O-5‘ type syringylsubstructures represent about 65% of lignin “condensed” structures. Eucalypt lignin showed highabundance of β-O-4 (0.56/C6) structures and units linked by α-O-4 bonds (0.23/C6). The proportionof phenylcoumaran structures was relatively low (0.03/C6). Different kinds of β-β substructures (pino-/syringaresinol and isotaxiresinol types) in a total amount of 0.13/C6 were detected. ESI-MS analysisrevealed a wide molecular weight distribution of lignin with the center of gravity of mass distributionaround 2500 u. Keywords: Lignin;Eucalyptus globulus; functional group analysis; nitrobenzene oxidation;permanganate oxidation; thioacidolysis; analytical pyrolysis; ESIMS; 1H NMR spectroscopy; 13C NMRspectroscopy
|
