Physico-Chemical Characterization of Lignin Isolated from Industrial Sources for Advanced Application

Lignin is generated in large quantities as by-products in pulping industries and biorefineries through various processes. Lignin is currently isolated from the by-products but its application is limited due to non-uniform structure and unique chemical reactivity. However, advanced pulping industries and biorefineries involve improvement of the value derived from their lignin-containing by-product by converting them into new, advanced and high-value added products. This endeavor not only improves resources but also return revenue to their operations. The important strategy in this research is the isolation of lignin from pulping industry and biorefinery by-products and its further conversion into advance products such as microspheres. The specific objective was to investigate the physico-chemical and thermal characteristics of isolated lignin as well as fundamental studies of lignin solubilization in different organic solvents for the synthesis of lignin microspheres. The physico-chemical properties and the thermal behavior of lignin samples were characterized by using different analytical and thermal techniques. The solubilities of lignin samples were determined in different organic solvents and compared with the computed solubility parameter. For synthesis of lignin microspheres, either lignin was modified to lignin acetate to improve its solubility or the the soluble part of lignin in organic solvent was used in the process. The results showed that the molecular structure, functional groups, molecular weight, glass transition temperature and onset decomposition temperature of isolated lignins depend on the extraction process and plant source. Solubilities of lignins isolated from different sources vary in different organic solvents. However, the solubility of lignin in organic solvents is not predictable due to poor correlation between the solubilities of lignins and their solubility parameters. Uniform lignin acetate microspheres were synthesized with a size of about 1 ?m and narrow size distribution by using dichloromethane independent on the lignin source. Ethyl acetate was found as an alternative organic solvent useful in preparing lignin microspheres, which has relatively lower toxicity to human and the environment than dichloromethane. Finally, uniform lignin microspheres were synthesized from solubilized parts of two industrial lignins (hardwood kraft and non-wood soda lignins) in ethyl acetate under controlled conditions which have not been reported before.