Exploded Wood Lignins From Pinus Radiata Wood. 2. The Effect of So₂ Pretreatment on Structure

Abstract

The acetone soluble lignins of Pinus radiata wood, which had been steam exploded by the Australian Siropulper process, both with and without SO₂ pretreatment, have been examined by ¹³C NMR spectroscopy. The marked structural effects of SO₂ pretreatment are discussed. A brief comparison of the lignins from wood treated by the Siropulper and Canadian Iotech processes (without SO₂ pretreatment) is also presented.

The soluble lignins from exploded wood treated by either the Siropulper or the Iotech process are very similar in structure and in the relative abundances of structural units. In contrast, SO₂ pretreatment markedly changed relative abundances. β-0-4 linked units were more extensively modified and β-5 linked units, which were stable in the absence of SO₂ pretreatment, were also extensively modified. No sulphur incorporation was detected and some differences between the steam explosion treatment and acidic sulphite pulping are outlined.