ISOLATION AND CHARACTERISATION OF LIGNINS FROM DIFFERENT BLACK LIQUORS

摘要

Since the last 30 years lignin has been subjected to an intensive investigation due to its unique structure that makes it useful for many applications, including polymer synthesis, obtaining of value added chemicals or as an additive with interesting properties. In this work a series of 4 black liquors from different origin, including kraft liquor from pine (pinus radiata), soda liquors from flax (linum usitatissimum), this one using anthraquinone as catalyst, and grapevine (Vitis vinifera) vineshoot, and another one from wild tamarind (leucaena leucocephala) extracted by the organosolv Alcell method, have been subjected to chemical treatments in order to isolate different types of lignin. Subsequently, these lignins have been characterized using Fourier transform infrared spectroscopy (FT-IR) and ~1H-NMR to analyse the chemical structure, gel permeation chromatography (GPC) for determining molecular weight (MW) and molecular weight distribution (MWD) and thermogravimetric analysis (TGA) to analyse the thermal degradation. Results show that kraft pine lignin has higher molecular weight and hydroxyl groups' content than the other samples, what seems to be related to its higher content in guaiacyl-type units.