Extraction of Lignins Using a Modified Dioxane Method and an Ionic Liquid and Comparative Molecular Weight and Structural Studies by Chromatography and ??C NMR Spectroscopy, Techniques

In this study, lignins were extracted from three different plant species including poplar (populus nigra), cypress (Cupressus sempervirens), and bagasse (Gramineae Saccharum officinarum L.) by dioxane method and ionic liquid method and their molecular weight distributions (GPC) and their structural features (¹³C NMR) were compared to conclude which of lignins (DL or IL) is more unchanged and similar to the original lignin. The results indicate that there is considerable differences between dioxane lignins and ionic liquid lignins of three different species regarding average molecular weights (M¯n ). Meanwhile, ¹³C NMR spectroscopy, showed that dominant structural units of the three kind of lignins are phenyl propanes, and reveals the known differences between the lignins of hardwood, softwoods and non-woods. It seems that from this point of view, there are no considerable differences between dioxane lignins and ionic liquid lignins.