Abstract: | This study goal was to estimate the potential of some industrial lignins (isolated lignins). The use of different chemical characterization methods specific for lignocelluloses has allowed an estimation of polymeric and aromatic composition of studied materials, especially with the determination of lignins contents (ADL and KLASON), with guaiacyl and syringyl monomers from uncondensed lignins quantified by thioacidolysis. The distributions of monomers have been proved to be a function of the starting materials type. P-hydroxybenzoic, vanillic and syringic acids, even they are easy liberated in alkaline medium, it can't be considered aromatic aldehydes precursors. In concordance with these results, the aldehydes can be considered precursors for correspondent acids, which can be formed by oxidative treatment. It can be observed that Kraft lignins from gymnosperms (Kraft and Indulin AT) contain mainly G units incorporated in P-O-4 structures and vanillin, in the same measure. Hydrolytic lignin (sugar cane origin) is formed principal, by p-coumaric acid and S monomers. The organosoluble lignins are constituted both G units and S units, which can be explained by the type of starting material (dycotyledonous angiosperms). |