Structural Aspects of Lignins From Eucalyptus Regnans Wood Steam Exploded By the Iotech and Siropulper Processes

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Abstract
The lignins extractable by acetone from Eucalyptus regnans wood after steam explosion treatment by either the Canadian Iotech Process or the Australian Siropulper Process have been examined by 13C NMR spectroscopy. Comparison with MWL showed structural changes which are discussed, compared for the two processes and compared with those for another hardwood (aspen) and a softwood (Pinus radiata). IR, MW and elemental analysis data are also discussed. The structural changes resulting from the two processes are quite similar and dominated by .beta.-ether cleavage. The modified structures found in E. regnans lignin differ from those found in the lignins from P. radiata and aspen in the amount and variety of reduced side-chain groups and in the amount of demethylation of aromatic moieties. Structural changes include elimination of hydroxy-groups and formation of carbonyl groups, .alpha.,.beta.-unsaturation and carbon-carbon linkages.