Synergistic benefits of ionic liquid and alkaline pretreatments of poplar wood. Part 2: characterization of lignin and hemicelluloses.

The effect of proposed integrated pretreatment on enzymatic hydrolysis of poplar wood has been reported in Part 1. Part 2 of this work investigated the detailed structural features of the isolated lignin and hemicellulosic fractions, which were obtained in high yields. The chemical structures of these polymer fractions obtained were compared with the corresponding alkaline lignin and hemicelluloses extracted from the raw material without ionic liquid (IL) pretreatment. The yields of alkaline lignin and hemicelluloses obviously increased after the IL pretreatment. No apparent degradation occurred for both lignin and hemicellulosic fractions during this integrated pretreatment process. The lignin fraction (RCEL), which obtained after the enzymatic hydrolysis, exhibited high percentages of β-O-4' aryl ether linkages and S/G ratio. It is believed that the high molecular weight and high purity hemicellulosic and lignin fractions obtained can serve as raw materials for the production of value-added products.