Recovery and characterization of lignin from alkaline straw pulping black liquor: As feedstock for bio-oil research

Conversion of lignin derived from lignocellulosic biomass to bio-oil has the promising potential to significantly reduce petroleum dependence. For that purpose, it is necessary to search for a low-cost lignin source. In this study, lignin sample was separated from straw pulping black liquor by HCl-precipitation, followed by extraction with a mixture of dioxane and water. The content of lignin in the total black liquor solid reached up to 34.8%, determined by UV spectroscopy, and the yield could account for 74.4% of the total lignin composition. The structure of lignin was investigated by various spectroscopic techniques such as FTIR, H-1-NMR, XRD, and XPS. The structural analysis revealed that recovered lignin preserved basic lignin structure, but had relatively lower amount of -O-4 linkages. The molecular weights were studied through THF-eluted GPC showing that separated lignin had the low M-n, which was favorable for the full degradation process during conversion of lignin to bio-oil. Therefore, a feasible solution for effective utilization of lignin in straw pulping black liquor as feedstock for bio-oil was proposed in the study. (c) 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42057.