Systematic Isolation and Characterization of Regenerated Hemicellulose and Lignin from Soybean Feedstocks Using Ionic Liquids

The use of ionic liquids in biomass pretreatment for ethanol production has seen increased attention in recent years. In this work, 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-ethyl-3-methylimidazolium acetate ([Emim]Ac) were used to regenerate and recover significant amount of hemicellulose and lignin from soybean meal, flakes, and hulls. The regenerated lignin and hemicellulose were characterized using Fourier-transform infrared (FTIR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). For all three ionic liquids, the amount of regenerated hemicellulose and lignin ranged from approximately 6 to 12% and 8 to 19%, respectively. Lignin characteristic bands 1738.8, 1652.6, 1516.4, 1455.2, and 1174.9 cm−1 were identified in the FTIR spectrum. The regenerated hemicellulose showed the characteristic bands 1658.31, 1434.14, 1167.98, and 865.20 cm−1. The Py-GC/MS analysis of the regenerated lignin showed the characteristic grass lignin pyrolyzates phenol, 2-methoxyphenol, 4-methylphenol, 2-benzaldehyde, 2-methoxy-4-vinylphenol, phenol-2,6-dimethoxy, and ethylvanillin.