Functionality of Wheat Straw Lignin Extracted in Organic Acid Media

Wheat straw lignin was extracted by the CIMV process using organic acid media at pilot plant scale. The product was analyzed by gel permeation chromatography (GPC), H-1 and C-13 NMR spectroscopy, infrared attenuated total reflectance-Fourier transform infrared analysis (ATR-FTIR), and gas chromatography (GC) to clarify its structure and functionality. In most cases, lignin was esterified before analysis. Control of the esterification was conducted via ATR-FTIR and NMR. GC analysis was used to quantify total hydroxyl group of lignin by saponification of propionylated lignin and was also used to quantify phenolic hydroxyl groups of lignin by amino-lysis of propionylated lignin. Acetylated lignin was analyzed by GPC. Carboxylic group of lignin was determined by pH metric titration. Lignin extracted from the CIMV process was observed as a low molecular weight polymer with a low polydispersity index and high free hydroxyl content. The potential of lignin as a natural polyphenol was confirmed by the analytical results obtained. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 491-501, 2011