ISOLATON AND CHARACTERIZATION OF LIGNIN IN THE PRE-HYDROLYSIS LIQUOR OF KRAFT BASED DISSOLVING PULP PRODUCTION PROCESS

The separation of lignin from the pre-hydrolysis liquor (PILL) of dissolving pulp process will create new revenue for the dissolving pulp production process, and fits well with the integrated forest bio-refinery concept. Lignin will likely become a valuable source of renewable energy (e.g., biofuel,), and bio-materials (e.g. plastics, adhesives). In this study, lignin was isolated from the NIL by acidification with a weak H2SO4 solution, followed by purification through dissolving in a dioxane solution (9:1) and re-precipitation on diethyl ether. The characteristics of PHL lignin was compared with the dioxane lignin isolated from the hardwood (Maple, poplar and birch wood chips in the ratio of 7:2:1), which is the raw material for the dissolved pulp production. The thus obtained lignin samples were characterized by means of UV, FTIR, H-1-NMR spectroscopy, molecular weight determination, elemental and methoxyl analyses. The absorptivity of hardwood lignin was 10 L/(g.cm), while that of PHL lignin was 17.23 L/(g.cm). The presence of condensed structures in PHL lignin was observed as stronger band at 870 and 890cm(-1) in FTIR spectrum. The lignin isolated from the PHL has a low molecular weight, and a low methoxyl group per C-9 unit, in comparison with other lignin samples. H-1-NMR data indicates that a significant increase of phenolic hydroxyl content in the PHL lignin was observed as cleavage of aryl-ether bonds during the prehydrolysis process. Based on these results, it can be concluded that the isolated lignin from the PHL has potential value for the polymer industry.